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189,046 | I am working on a space exploration and combat game, and I can create galaxies, nebulas, solar systems, and load and unload them procedurally as needed. Meaning the stars that the player can see are exactly where they are. I have a coordinate system set up with meter-precision, meaning it's sufficient to map quite several galaxies, but also tiny missiles.
For now, I created a galaxy with 10.000.000 solar systems, and my SQLite database reached 5gb. It takes ~30 minutes to generate it, and I notice a slow-down as the size of the database increases in loading times. I did a lot of optimization, and while everything is running fine and well now, I seek to reach 200-300m solar systems if possible. The database would be stored locally on the user's drive, rather than downloaded from a server. I use a GlobalX/Y/Z (int64) and LocalX/Y/Z (double) for coordinates, and only the GlobalX/Y/Z is used to find large objects like stars and planets (I also use multiple chunk systems).
[Elite Dangerous manages to store the data of 400 *billion*](https://elite-dangerous.fandom.com/wiki/Galaxy) solar systems and has no issues with loading times, somehow. How can they display many stars in the background? How do they manage to store a lot more data than I already do?
For now, my data is quite minimalistic and comparatively minuscule in number, but they must have quite a lot of data for each stellar object even. What technical "tricks" can I employ to solve this problem in my game? | 2021/02/10 | [
"https://gamedev.stackexchange.com/questions/189046",
"https://gamedev.stackexchange.com",
"https://gamedev.stackexchange.com/users/117840/"
] | The trick Elite likely uses is that they don't pre-generate the whole galaxy and store it in a database. They likely generate most of the galaxy at runtime when it is needed.
I would do this using a pseudorandom but deterministic algorithm which can generate the properties of every object in the galaxy at runtime just from its position.
So when a player zooms into a section of the galaxy, then the galaxy chunk generation algorithm is run, which takes the chunk coordinates as input and outputs a list of stars with position, color and size. Same input always results in the same output, so when another player zooms into the same chunk later, they get the same results. You might have different algorithms for different zoom levels which each take the output of the previous algorithm into account and add more detail to it. So the algorithm on the lowest zoom factor only generates the largest stars (so you can quickly generate a view which shows the whole galaxy at once), and the closer the player zooms into any part of the galaxy, the more additional small stars get generated in that area.
Then, when the player clicks on any of these stars to zoom into its star system, the star system generation algorithm is run. Its input are color, size and galactic position of the star. Its output is a list of planets with their types, sizes and orbital parameters. It too is a deterministic algorithm so it always generates the same planets for the same star.
And then you can do the same thing with planet surfaces, cities on the planet surfaces, houses in those cities and rooms in those houses. So you end up with a galaxy with a level of detail which would take an exorbitant amount of data to store all at once. But you don't need to store it all, because any of that data can be re-calculated on demand.
A really neat tool for procedural generation algorithms like that are noise pattern algorithms like [Simplex Noise](https://en.wikipedia.org/wiki/Simplex_noise) or [Worley Noise](https://en.wikipedia.org/wiki/Worley_noise). You can sample them at arbitrary locations to get reproducible results. Another are standard pseudorandom number generators which can be initialized with a seed value and then always generate the same sequence of numbers for the same seed value.
All you really need to store in a database is data which can not actually be re-generated on demand:
* Parts of the galaxy which you want to design by hand
* Changes to the galaxy which are the result of player actions
First you check if any such datasets exist in your database for the requested data, and when they don't, you generate the data using the algorithms.
\_\_
Now you just need to come up with algorithms which generate interesting and varied results and then with game mechanics which provide an engaging and interesting game experience which benefits from all that content variety. I am looking forward to playing what you will come up with. | In addition to the points that have been made about not actually generating all the data there's another factor: You can't actually draw 10,000,000 stars. Nobody has a display that can handle it. Therefore, there's no need to have 10,000,000 stars loaded.
Select X, Y, Brightness, Color, ID from StarTable Where X > CurrentX - 200ly And X < CurrentX + 200ly And Y > CurrentY - 200ly And Y < CurrentY + 200ly.
Select X, Y, Brightness, Color, ID from BrightStarTable Where X > CurrentX - 2000ly And X < CurrentX + 2000ly And Y > CurrentY - 2000ly And Y < CurrentY + 2000ly.
That will be a tiny fraction of your total stars, but it is sufficient to draw anything you can see out the window of your starship. I would store all the details on the stars in a separate table accessed by the StarID as you only need those details when examining a particular star.
You can cut the loaded data down even more by having a DimStarTable with an even shorter query range. Most stars will be in this table.
Another option also comes to mind: Define a new variable: Sector. Sector = (int)(x/100ly) + (int)(y/100ly) \* 10000. You load the sector you are in and the 8 adjoining sectors. The select would run faster. (Likewise, the bright star table would have 1000ly sectors.) |
189,046 | I am working on a space exploration and combat game, and I can create galaxies, nebulas, solar systems, and load and unload them procedurally as needed. Meaning the stars that the player can see are exactly where they are. I have a coordinate system set up with meter-precision, meaning it's sufficient to map quite several galaxies, but also tiny missiles.
For now, I created a galaxy with 10.000.000 solar systems, and my SQLite database reached 5gb. It takes ~30 minutes to generate it, and I notice a slow-down as the size of the database increases in loading times. I did a lot of optimization, and while everything is running fine and well now, I seek to reach 200-300m solar systems if possible. The database would be stored locally on the user's drive, rather than downloaded from a server. I use a GlobalX/Y/Z (int64) and LocalX/Y/Z (double) for coordinates, and only the GlobalX/Y/Z is used to find large objects like stars and planets (I also use multiple chunk systems).
[Elite Dangerous manages to store the data of 400 *billion*](https://elite-dangerous.fandom.com/wiki/Galaxy) solar systems and has no issues with loading times, somehow. How can they display many stars in the background? How do they manage to store a lot more data than I already do?
For now, my data is quite minimalistic and comparatively minuscule in number, but they must have quite a lot of data for each stellar object even. What technical "tricks" can I employ to solve this problem in my game? | 2021/02/10 | [
"https://gamedev.stackexchange.com/questions/189046",
"https://gamedev.stackexchange.com",
"https://gamedev.stackexchange.com/users/117840/"
] | The trick Elite likely uses is that they don't pre-generate the whole galaxy and store it in a database. They likely generate most of the galaxy at runtime when it is needed.
I would do this using a pseudorandom but deterministic algorithm which can generate the properties of every object in the galaxy at runtime just from its position.
So when a player zooms into a section of the galaxy, then the galaxy chunk generation algorithm is run, which takes the chunk coordinates as input and outputs a list of stars with position, color and size. Same input always results in the same output, so when another player zooms into the same chunk later, they get the same results. You might have different algorithms for different zoom levels which each take the output of the previous algorithm into account and add more detail to it. So the algorithm on the lowest zoom factor only generates the largest stars (so you can quickly generate a view which shows the whole galaxy at once), and the closer the player zooms into any part of the galaxy, the more additional small stars get generated in that area.
Then, when the player clicks on any of these stars to zoom into its star system, the star system generation algorithm is run. Its input are color, size and galactic position of the star. Its output is a list of planets with their types, sizes and orbital parameters. It too is a deterministic algorithm so it always generates the same planets for the same star.
And then you can do the same thing with planet surfaces, cities on the planet surfaces, houses in those cities and rooms in those houses. So you end up with a galaxy with a level of detail which would take an exorbitant amount of data to store all at once. But you don't need to store it all, because any of that data can be re-calculated on demand.
A really neat tool for procedural generation algorithms like that are noise pattern algorithms like [Simplex Noise](https://en.wikipedia.org/wiki/Simplex_noise) or [Worley Noise](https://en.wikipedia.org/wiki/Worley_noise). You can sample them at arbitrary locations to get reproducible results. Another are standard pseudorandom number generators which can be initialized with a seed value and then always generate the same sequence of numbers for the same seed value.
All you really need to store in a database is data which can not actually be re-generated on demand:
* Parts of the galaxy which you want to design by hand
* Changes to the galaxy which are the result of player actions
First you check if any such datasets exist in your database for the requested data, and when they don't, you generate the data using the algorithms.
\_\_
Now you just need to come up with algorithms which generate interesting and varied results and then with game mechanics which provide an engaging and interesting game experience which benefits from all that content variety. I am looking forward to playing what you will come up with. | Philipp already gave a great answer, but I'll address your question about how Elite Dangerous operates their database.
>
> Elite Dangerous manages to store the data of 400 billion solar systems and has no issues with loading times, somehow. How can they display many stars in the background? How do they manage to store a lot more data than I already do?
>
>
>
1. Elite Dangerous stores the star map data that isn't procedurally generated on a server, not locally. They presumably have one or more very powerful servers, optimized for big data, with the database always loaded and running. When the player scrolls around the map or visits a new star system, the game client sends a request to the server, the server queries relevant data from the database and sends it back to the game client. Because the database is on a server, it could potentially be many terabytes in size without causing any issues for the players. They probably have very big and expensive servers developed over years by backend specialists, so this approach is unlikely to be feasible for an indie team.
2. Elite Dangerous absolutely has loading times, they just cleverly mask it with in-game mechanics. This is educated guesswork, but based on my play experience I think it works like this:
1. When you activate the hyperdrive, there's a progress bar while the hyperdrive warms up. I think this is the stage when the game client sends the request for data for the system you're about to jump to. Occasionally, this takes much longer than normal for no explicable reason - probably because the server was slow to respond to the query.
2. During the actual hyperspace jump, the game is loading/procedurally generating the next star system, including the background skybox, based on the data it received from the server. The animation you see of your ship hurtling through hyperspace is just a very fancy loading screen. |
189,046 | I am working on a space exploration and combat game, and I can create galaxies, nebulas, solar systems, and load and unload them procedurally as needed. Meaning the stars that the player can see are exactly where they are. I have a coordinate system set up with meter-precision, meaning it's sufficient to map quite several galaxies, but also tiny missiles.
For now, I created a galaxy with 10.000.000 solar systems, and my SQLite database reached 5gb. It takes ~30 minutes to generate it, and I notice a slow-down as the size of the database increases in loading times. I did a lot of optimization, and while everything is running fine and well now, I seek to reach 200-300m solar systems if possible. The database would be stored locally on the user's drive, rather than downloaded from a server. I use a GlobalX/Y/Z (int64) and LocalX/Y/Z (double) for coordinates, and only the GlobalX/Y/Z is used to find large objects like stars and planets (I also use multiple chunk systems).
[Elite Dangerous manages to store the data of 400 *billion*](https://elite-dangerous.fandom.com/wiki/Galaxy) solar systems and has no issues with loading times, somehow. How can they display many stars in the background? How do they manage to store a lot more data than I already do?
For now, my data is quite minimalistic and comparatively minuscule in number, but they must have quite a lot of data for each stellar object even. What technical "tricks" can I employ to solve this problem in my game? | 2021/02/10 | [
"https://gamedev.stackexchange.com/questions/189046",
"https://gamedev.stackexchange.com",
"https://gamedev.stackexchange.com/users/117840/"
] | In addition to the points that have been made about not actually generating all the data there's another factor: You can't actually draw 10,000,000 stars. Nobody has a display that can handle it. Therefore, there's no need to have 10,000,000 stars loaded.
Select X, Y, Brightness, Color, ID from StarTable Where X > CurrentX - 200ly And X < CurrentX + 200ly And Y > CurrentY - 200ly And Y < CurrentY + 200ly.
Select X, Y, Brightness, Color, ID from BrightStarTable Where X > CurrentX - 2000ly And X < CurrentX + 2000ly And Y > CurrentY - 2000ly And Y < CurrentY + 2000ly.
That will be a tiny fraction of your total stars, but it is sufficient to draw anything you can see out the window of your starship. I would store all the details on the stars in a separate table accessed by the StarID as you only need those details when examining a particular star.
You can cut the loaded data down even more by having a DimStarTable with an even shorter query range. Most stars will be in this table.
Another option also comes to mind: Define a new variable: Sector. Sector = (int)(x/100ly) + (int)(y/100ly) \* 10000. You load the sector you are in and the 8 adjoining sectors. The select would run faster. (Likewise, the bright star table would have 1000ly sectors.) | If you have a deterministic algorithm that uses a seed, like how PRNG's work, you can store almost nothing and generate the star's positions on the fly, only keeping those that you currently need. Think how demoscene demos work. |
189,046 | I am working on a space exploration and combat game, and I can create galaxies, nebulas, solar systems, and load and unload them procedurally as needed. Meaning the stars that the player can see are exactly where they are. I have a coordinate system set up with meter-precision, meaning it's sufficient to map quite several galaxies, but also tiny missiles.
For now, I created a galaxy with 10.000.000 solar systems, and my SQLite database reached 5gb. It takes ~30 minutes to generate it, and I notice a slow-down as the size of the database increases in loading times. I did a lot of optimization, and while everything is running fine and well now, I seek to reach 200-300m solar systems if possible. The database would be stored locally on the user's drive, rather than downloaded from a server. I use a GlobalX/Y/Z (int64) and LocalX/Y/Z (double) for coordinates, and only the GlobalX/Y/Z is used to find large objects like stars and planets (I also use multiple chunk systems).
[Elite Dangerous manages to store the data of 400 *billion*](https://elite-dangerous.fandom.com/wiki/Galaxy) solar systems and has no issues with loading times, somehow. How can they display many stars in the background? How do they manage to store a lot more data than I already do?
For now, my data is quite minimalistic and comparatively minuscule in number, but they must have quite a lot of data for each stellar object even. What technical "tricks" can I employ to solve this problem in my game? | 2021/02/10 | [
"https://gamedev.stackexchange.com/questions/189046",
"https://gamedev.stackexchange.com",
"https://gamedev.stackexchange.com/users/117840/"
] | Philipp already gave a great answer, but I'll address your question about how Elite Dangerous operates their database.
>
> Elite Dangerous manages to store the data of 400 billion solar systems and has no issues with loading times, somehow. How can they display many stars in the background? How do they manage to store a lot more data than I already do?
>
>
>
1. Elite Dangerous stores the star map data that isn't procedurally generated on a server, not locally. They presumably have one or more very powerful servers, optimized for big data, with the database always loaded and running. When the player scrolls around the map or visits a new star system, the game client sends a request to the server, the server queries relevant data from the database and sends it back to the game client. Because the database is on a server, it could potentially be many terabytes in size without causing any issues for the players. They probably have very big and expensive servers developed over years by backend specialists, so this approach is unlikely to be feasible for an indie team.
2. Elite Dangerous absolutely has loading times, they just cleverly mask it with in-game mechanics. This is educated guesswork, but based on my play experience I think it works like this:
1. When you activate the hyperdrive, there's a progress bar while the hyperdrive warms up. I think this is the stage when the game client sends the request for data for the system you're about to jump to. Occasionally, this takes much longer than normal for no explicable reason - probably because the server was slow to respond to the query.
2. During the actual hyperspace jump, the game is loading/procedurally generating the next star system, including the background skybox, based on the data it received from the server. The animation you see of your ship hurtling through hyperspace is just a very fancy loading screen. | If you have a deterministic algorithm that uses a seed, like how PRNG's work, you can store almost nothing and generate the star's positions on the fly, only keeping those that you currently need. Think how demoscene demos work. |
189,046 | I am working on a space exploration and combat game, and I can create galaxies, nebulas, solar systems, and load and unload them procedurally as needed. Meaning the stars that the player can see are exactly where they are. I have a coordinate system set up with meter-precision, meaning it's sufficient to map quite several galaxies, but also tiny missiles.
For now, I created a galaxy with 10.000.000 solar systems, and my SQLite database reached 5gb. It takes ~30 minutes to generate it, and I notice a slow-down as the size of the database increases in loading times. I did a lot of optimization, and while everything is running fine and well now, I seek to reach 200-300m solar systems if possible. The database would be stored locally on the user's drive, rather than downloaded from a server. I use a GlobalX/Y/Z (int64) and LocalX/Y/Z (double) for coordinates, and only the GlobalX/Y/Z is used to find large objects like stars and planets (I also use multiple chunk systems).
[Elite Dangerous manages to store the data of 400 *billion*](https://elite-dangerous.fandom.com/wiki/Galaxy) solar systems and has no issues with loading times, somehow. How can they display many stars in the background? How do they manage to store a lot more data than I already do?
For now, my data is quite minimalistic and comparatively minuscule in number, but they must have quite a lot of data for each stellar object even. What technical "tricks" can I employ to solve this problem in my game? | 2021/02/10 | [
"https://gamedev.stackexchange.com/questions/189046",
"https://gamedev.stackexchange.com",
"https://gamedev.stackexchange.com/users/117840/"
] | In addition to the points that have been made about not actually generating all the data there's another factor: You can't actually draw 10,000,000 stars. Nobody has a display that can handle it. Therefore, there's no need to have 10,000,000 stars loaded.
Select X, Y, Brightness, Color, ID from StarTable Where X > CurrentX - 200ly And X < CurrentX + 200ly And Y > CurrentY - 200ly And Y < CurrentY + 200ly.
Select X, Y, Brightness, Color, ID from BrightStarTable Where X > CurrentX - 2000ly And X < CurrentX + 2000ly And Y > CurrentY - 2000ly And Y < CurrentY + 2000ly.
That will be a tiny fraction of your total stars, but it is sufficient to draw anything you can see out the window of your starship. I would store all the details on the stars in a separate table accessed by the StarID as you only need those details when examining a particular star.
You can cut the loaded data down even more by having a DimStarTable with an even shorter query range. Most stars will be in this table.
Another option also comes to mind: Define a new variable: Sector. Sector = (int)(x/100ly) + (int)(y/100ly) \* 10000. You load the sector you are in and the 8 adjoining sectors. The select would run faster. (Likewise, the bright star table would have 1000ly sectors.) | Philipp already gave a great answer, but I'll address your question about how Elite Dangerous operates their database.
>
> Elite Dangerous manages to store the data of 400 billion solar systems and has no issues with loading times, somehow. How can they display many stars in the background? How do they manage to store a lot more data than I already do?
>
>
>
1. Elite Dangerous stores the star map data that isn't procedurally generated on a server, not locally. They presumably have one or more very powerful servers, optimized for big data, with the database always loaded and running. When the player scrolls around the map or visits a new star system, the game client sends a request to the server, the server queries relevant data from the database and sends it back to the game client. Because the database is on a server, it could potentially be many terabytes in size without causing any issues for the players. They probably have very big and expensive servers developed over years by backend specialists, so this approach is unlikely to be feasible for an indie team.
2. Elite Dangerous absolutely has loading times, they just cleverly mask it with in-game mechanics. This is educated guesswork, but based on my play experience I think it works like this:
1. When you activate the hyperdrive, there's a progress bar while the hyperdrive warms up. I think this is the stage when the game client sends the request for data for the system you're about to jump to. Occasionally, this takes much longer than normal for no explicable reason - probably because the server was slow to respond to the query.
2. During the actual hyperspace jump, the game is loading/procedurally generating the next star system, including the background skybox, based on the data it received from the server. The animation you see of your ship hurtling through hyperspace is just a very fancy loading screen. |
2,401,517 | I want to schedule the email with asp.net and C# code.
what is basic idea or code for schedule email? | 2010/03/08 | [
"https://Stackoverflow.com/questions/2401517",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/285041/"
] | Try just writing a simple console app that sends the email and using Windows Task Scheduler to run it when you need it. Sending an email is a pretty standard task, like Will said, there are plenty of similar questions pertaining to it on here already, but if you have a look at the [System.Net.Mail](http://msdn.microsoft.com/en-us/library/system.net.mail.aspx) namespace, that should get you started. | You could have a table in SQL called mailToBeSent or something like that...and each time you want to schedule an email, insert an email into that table with all the appropriate data elements (subject, to, cc, body etc), and most importantly have a field for date/time to be sent, and have a SQL job run every 5/10/15 minutes or whatever you choose, and check that table for mail that needs to be sent...send the message, and delete the record on success.
I know someone who uses this setup and it works beautifully. Unfortunately I don't have his code, but a few google searches for each piece of the process might prove fruitful.
Here's a start: <http://www.google.com/search?&q=how+to+use+sql+job+table+to+send+emails>
The first set of links look good. If you start down this road and need some more help let us know. |
2,401,517 | I want to schedule the email with asp.net and C# code.
what is basic idea or code for schedule email? | 2010/03/08 | [
"https://Stackoverflow.com/questions/2401517",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/285041/"
] | Try just writing a simple console app that sends the email and using Windows Task Scheduler to run it when you need it. Sending an email is a pretty standard task, like Will said, there are plenty of similar questions pertaining to it on here already, but if you have a look at the [System.Net.Mail](http://msdn.microsoft.com/en-us/library/system.net.mail.aspx) namespace, that should get you started. | The most simple way to differ the sending of email is to schedule a task in the windows scheduled tasks tool.
This task is a simple call to a vbs file.
This vbs file open an url from your web application.
Behind this url, put a webpage that do your scheduled work inside the app, in this case, the sending of emails.
It doesn't need windows service, just a simple vbs.
The called page is in your app, so no need to do some extra work to interface data or treatment outside of the web app.
Hope this will help,
Regards,
Pierre. |
2,401,517 | I want to schedule the email with asp.net and C# code.
what is basic idea or code for schedule email? | 2010/03/08 | [
"https://Stackoverflow.com/questions/2401517",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/285041/"
] | Use a scheduler perhaps? [Quartz.NET](http://quartznet.sourceforge.net/) is a pretty decent one.
I assume you already know how to send a mail, so just schedule a new job, and roll with it. | Try just writing a simple console app that sends the email and using Windows Task Scheduler to run it when you need it. Sending an email is a pretty standard task, like Will said, there are plenty of similar questions pertaining to it on here already, but if you have a look at the [System.Net.Mail](http://msdn.microsoft.com/en-us/library/system.net.mail.aspx) namespace, that should get you started. |
2,401,517 | I want to schedule the email with asp.net and C# code.
what is basic idea or code for schedule email? | 2010/03/08 | [
"https://Stackoverflow.com/questions/2401517",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/285041/"
] | You could have a database table EmailSchedule(ID, SendTo, Subject, MessageBody, SendDateTime)
When you want to schedule an email to be sent, write to the table.
Then have a process that runs every x minutes and sends all emails where SendDateTime <= Now | You could have a table in SQL called mailToBeSent or something like that...and each time you want to schedule an email, insert an email into that table with all the appropriate data elements (subject, to, cc, body etc), and most importantly have a field for date/time to be sent, and have a SQL job run every 5/10/15 minutes or whatever you choose, and check that table for mail that needs to be sent...send the message, and delete the record on success.
I know someone who uses this setup and it works beautifully. Unfortunately I don't have his code, but a few google searches for each piece of the process might prove fruitful.
Here's a start: <http://www.google.com/search?&q=how+to+use+sql+job+table+to+send+emails>
The first set of links look good. If you start down this road and need some more help let us know. |
2,401,517 | I want to schedule the email with asp.net and C# code.
what is basic idea or code for schedule email? | 2010/03/08 | [
"https://Stackoverflow.com/questions/2401517",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/285041/"
] | You could have a database table EmailSchedule(ID, SendTo, Subject, MessageBody, SendDateTime)
When you want to schedule an email to be sent, write to the table.
Then have a process that runs every x minutes and sends all emails where SendDateTime <= Now | The most simple way to differ the sending of email is to schedule a task in the windows scheduled tasks tool.
This task is a simple call to a vbs file.
This vbs file open an url from your web application.
Behind this url, put a webpage that do your scheduled work inside the app, in this case, the sending of emails.
It doesn't need windows service, just a simple vbs.
The called page is in your app, so no need to do some extra work to interface data or treatment outside of the web app.
Hope this will help,
Regards,
Pierre. |
2,401,517 | I want to schedule the email with asp.net and C# code.
what is basic idea or code for schedule email? | 2010/03/08 | [
"https://Stackoverflow.com/questions/2401517",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/285041/"
] | Use a scheduler perhaps? [Quartz.NET](http://quartznet.sourceforge.net/) is a pretty decent one.
I assume you already know how to send a mail, so just schedule a new job, and roll with it. | You could have a database table EmailSchedule(ID, SendTo, Subject, MessageBody, SendDateTime)
When you want to schedule an email to be sent, write to the table.
Then have a process that runs every x minutes and sends all emails where SendDateTime <= Now |
2,401,517 | I want to schedule the email with asp.net and C# code.
what is basic idea or code for schedule email? | 2010/03/08 | [
"https://Stackoverflow.com/questions/2401517",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/285041/"
] | The most simple way to differ the sending of email is to schedule a task in the windows scheduled tasks tool.
This task is a simple call to a vbs file.
This vbs file open an url from your web application.
Behind this url, put a webpage that do your scheduled work inside the app, in this case, the sending of emails.
It doesn't need windows service, just a simple vbs.
The called page is in your app, so no need to do some extra work to interface data or treatment outside of the web app.
Hope this will help,
Regards,
Pierre. | You could have a table in SQL called mailToBeSent or something like that...and each time you want to schedule an email, insert an email into that table with all the appropriate data elements (subject, to, cc, body etc), and most importantly have a field for date/time to be sent, and have a SQL job run every 5/10/15 minutes or whatever you choose, and check that table for mail that needs to be sent...send the message, and delete the record on success.
I know someone who uses this setup and it works beautifully. Unfortunately I don't have his code, but a few google searches for each piece of the process might prove fruitful.
Here's a start: <http://www.google.com/search?&q=how+to+use+sql+job+table+to+send+emails>
The first set of links look good. If you start down this road and need some more help let us know. |
2,401,517 | I want to schedule the email with asp.net and C# code.
what is basic idea or code for schedule email? | 2010/03/08 | [
"https://Stackoverflow.com/questions/2401517",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/285041/"
] | Use a scheduler perhaps? [Quartz.NET](http://quartznet.sourceforge.net/) is a pretty decent one.
I assume you already know how to send a mail, so just schedule a new job, and roll with it. | You could have a table in SQL called mailToBeSent or something like that...and each time you want to schedule an email, insert an email into that table with all the appropriate data elements (subject, to, cc, body etc), and most importantly have a field for date/time to be sent, and have a SQL job run every 5/10/15 minutes or whatever you choose, and check that table for mail that needs to be sent...send the message, and delete the record on success.
I know someone who uses this setup and it works beautifully. Unfortunately I don't have his code, but a few google searches for each piece of the process might prove fruitful.
Here's a start: <http://www.google.com/search?&q=how+to+use+sql+job+table+to+send+emails>
The first set of links look good. If you start down this road and need some more help let us know. |
2,401,517 | I want to schedule the email with asp.net and C# code.
what is basic idea or code for schedule email? | 2010/03/08 | [
"https://Stackoverflow.com/questions/2401517",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/285041/"
] | Use a scheduler perhaps? [Quartz.NET](http://quartznet.sourceforge.net/) is a pretty decent one.
I assume you already know how to send a mail, so just schedule a new job, and roll with it. | The most simple way to differ the sending of email is to schedule a task in the windows scheduled tasks tool.
This task is a simple call to a vbs file.
This vbs file open an url from your web application.
Behind this url, put a webpage that do your scheduled work inside the app, in this case, the sending of emails.
It doesn't need windows service, just a simple vbs.
The called page is in your app, so no need to do some extra work to interface data or treatment outside of the web app.
Hope this will help,
Regards,
Pierre. |
78,306 | As I'm teaching General Biology to my college students, I realized that I don't fully understand how a 3-P nucleotide like ATP is broken down to be incorporated into DNA during replication. **How does this work??**
In other words, what is the actual mechanism/reaction pathway for the following:
[](https://i.stack.imgur.com/6MGmz.jpg)
**What I know:**
I understand that ATP is typically hydrolyzed to become dephosphorylated in other contexts. I also understand that a phosphate of one nucleotide is bonded to a deoxyribose of an adjacent nucleotide via dehydration synthesis from the joining of their hydroxyl groups to form DNA.
However, I cannot seem to find a good resource (online or in any of my [admittedly simple] general bio textbooks) that demonstrate how exactly both of these reactions take place during replication...
I'm assuming that DNA polymerase is taking advantage of the released phosphates from ATP (and the appropriate forms of GTP, CTP, TTP) to become activated?
**Overall, what does this whole process look like on a chemical/molecular level?**
I'd love a visual (especially a video) if you could provide such a resource in addition to a thorough explanation of what's going on here. | 2018/10/19 | [
"https://biology.stackexchange.com/questions/78306",
"https://biology.stackexchange.com",
"https://biology.stackexchange.com/users/16866/"
] | I found [this paper](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3047511/), which goes very deep into the molecular details of the individual steps of this reaction and also discusses how this is coupled to nucleotide selectivity.
The 'basic' details about the reaction (quoted from [this section](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3047511/#S5title), which also has a nice figure):
>
> The polymerization reaction proceeds by a simple nucleophilic attack
> of the 3'OH of the primer on the α-phosphate of the incoming dNTP
> followed by the elimination of pyrophosphate [...] The reaction uses a
> "two metal ion" mechanism in which metal ion A activates the 3'OH as a
> metal hydroxide while both metals A and B stabilizes the developing
> negative charge on the α-phosphate in the transition state.
>
>
>
The metal ions are Magnesium (Mg$^{2+}$) and are properly positioned by the enzyme structure and some additional amino acid side chains also help with the activation of the reaction. | **Apologia**
The answer given by @Nicolai is essentially correct (and I have upvoted it). However I feel that the question embodies certain mistaken assumptions that should be challenged so that naïve readers of the question are not misled in to accepting them. (I refer to these below as ‘problems’.) I also feel that illustrations — not included in the answer provided by @Nicolai — are needed in this respect.)
**Supporting authority**
I have used a [2016 paper in Science by Gao and Wang](http://science.sciencemag.org/content/352/6291/1334.full) as my authority, quoting from it and reproducing part of one of its figures for those who have not library access to this journal. The authors actually propound a ‘three-metal ion’ mechanism, rather than the ‘two-metal ion’ mechanism mentioned by @Nicolai. This, however does not affect the basic points I am making, although it serves to illustrate that the details of the enzyme mechanism are of a complexity that is unsuitable for teaching at an introductory level.
Here are two key frames from Fig. 1 of that paper:
[](https://i.stack.imgur.com/Ot6sM.jpg)
**Problem 1**
>
> “I'm assuming that DNA polymerase is taking advantage of the released phosphates from ATP (and the appropriate forms of GTP, CTP, TTP) to become activated?”
>
>
>
An enzyme is not ‘activated’ by the products of the reaction it catalyses. The binding of the substrate may result in a conformation change that results in more favourable state for catalysis — and which might be referred to as ‘activation’‡ in a discussion of that topic; but the use of that word can only confuse at the level at which the current question is asked. This is because one of the key concepts in enzyme catalysis is *‘activation energy’* — the energy required to achieve the *transition state*. Activation energy refers to the activation of the reactants — not the enzyme. To quote from the paper:
>
> Enzymes increase the rate of chemical reactions, which is thought to occur by a reduction in the activation energy required to reach the transition state (Fig. 1A)
>
>
>
Chemical reactions which result in a decrease in (Gibbs) Free Energy (the ‘Energy’ axis in Fig. 1A) are thermodynamically favourable. They occur slowly because they proceed through a transition state of higher energy. The role of an enzyme catalyst is to lower the energy to get to that transition state (the activation energy). As the figure shows, this reaction is thermodynamically favourable. The released pyrophosphate has no function, except to be hydrolysed by pyrophosphatases to prevent the polymerization being reversed.
**Problem 2**
It is unclear what the arrow at the left of the figure in the question (from the α-phosphate of the dNTP to the primer OH) is meant to represent†. Normally one would assume that this would be an electron, however here this does not make sense. As @Nicolai says
>
> “…reaction proceeds by a simple nucleophilic attack of the 3'OH of the primer on the α-phosphate of the incoming dNTP”
>
>
>
i.e. the arrow should be *from* the oxygen electrons of the OH *to* the nucleophilic phosphate. This is shown in Fig. 1B (where the nascent DNA chain is on the left and the dNTP on the right). The latter figure actually shows the transition state, which allows one to see in a general way how this could be of lower energy than for the uncatalysed non-enzymic reaction. It is stabilized by the two metal ions (Mg2+), which themselves are held in the appropriate position by acidic side-chains at the active site of the enzyme.
**Footnotes**
‡As @user1136 points out, the expression ‘enzyme activation’ is also used to describe action of positive allosteric effectors — small molecules that increase the activity of the active site by a structural change initiated by their binding at a site distal from the active site — the allosteric site. This is a further potential cause of confusion as it has no relevance here.
†In a comment, the poster writes “The arrow in the… picture… represents conceptual movement of molecules and not ‘real-world’ chemical interactions”. If this is what was intended (I am not familiar with the source), in my opinion the authors should have used a different style of arrow (e.g. a wider one, ➡︎ rather than ➛, and *not* drawn it from the phosphate to the OH. It betrays a lack of either knowledge or concern for chemical conventions, and is particularly misleading for the student who wishes to understand biology at a chemical level. I find it inexcusable in a publisher with a reputation like that of Benjamin. |
4,845,736 | I recently had a homework question where we were supposed to work with a chess board, and place a number of queens on the board.
The question was trivial in terms of difficulty, but what I wanted to ask was this:
Should I just make a boolean 2-D array and change every position that contains a queen to 1 or should I make a private class to represent a queen, that has x and y coordinates as instance variables?
This might not seem very important or pressing, but I'm using Java and it kinda gets to the core of the concept of OO programming. If we never use the modular capabilities of Java, then why use Java at all? We might as well have written the same thing in C or Python.
Which would be more appropriate in general do you think? I would appreciate it if you could restrict your answers to ones that are backed by reason, as opposed to opinions or personal preferences. | 2011/01/30 | [
"https://Stackoverflow.com/questions/4845736",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/384108/"
] | In this case having a 2D array of Queens (separate class but without containing x,y coordinates) or booleans (indicating either a presence or absence of a queen) should be the correct choice.
The reasoning is as follows:
* Queens as such do not have a position. You should design your objects (POJOs) independently of where they will be used and include as class members only properties that are relevant to them on their own.
* The positioning data has nothing to do with the queens and should be separated from them. Put in simpler terms, it is not a queens' job to take care of her position, but rather that of an external party (player, program, whatever). This is called **separation of responsibilities**.
* Most algorithms that you would like to use will be more difficult to implement and very hard to read and follow logically. Simple iterations of the board would be made impossible (or useless, at the least).
You will have to clearly define the role of each object in your system in order to be able to design it in a way that's both extensible & easy to work with. Not having a good idea of what exactly each object will be doing might lead to a wrong decision somewhere along the path, which itself will lead to more bad decisions down the road that deal with it until it becomes so bloated with hacks and workarounds that you would decide to start over :) | >
> Should I just make a boolean 2-D array
> and change every position that
> contains a queen to 1 or should I make
> a private class to represent a queen,
> that has x and y coordinates as
> instance variables?
>
>
>
This is really two questions:
1. Should I store the queens' positions inside a single 2D array, or should I store the x/y coordinates for each queen?
2. Should I use a simple datastructure, or a class to hold this data?
The answer to 1. is, as pointed out by the other answers: It depends. Use the data structure that is easiest for the algorithms you need.
The answer to 2. is: Yes, I would always wrap the data structure (whichever you use, the list of coordinates or the array) in a class. Even if the class may sound trivial, if you use a class, it will be immediately apparent that you are storing positions. If you just use a 2D array, people will have to wonder what it does. Plus, you can have suitable methods in the class, enforce invariants (e.g. <10 queens) etc. ... all the OO goodness :-). |
4,845,736 | I recently had a homework question where we were supposed to work with a chess board, and place a number of queens on the board.
The question was trivial in terms of difficulty, but what I wanted to ask was this:
Should I just make a boolean 2-D array and change every position that contains a queen to 1 or should I make a private class to represent a queen, that has x and y coordinates as instance variables?
This might not seem very important or pressing, but I'm using Java and it kinda gets to the core of the concept of OO programming. If we never use the modular capabilities of Java, then why use Java at all? We might as well have written the same thing in C or Python.
Which would be more appropriate in general do you think? I would appreciate it if you could restrict your answers to ones that are backed by reason, as opposed to opinions or personal preferences. | 2011/01/30 | [
"https://Stackoverflow.com/questions/4845736",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/384108/"
] | >
> Should I just make a boolean 2-D array
> and change every position that
> contains a queen to 1 or should I make
> a private class to represent a queen,
> that has x and y coordinates as
> instance variables?
>
>
>
It depends on your needs. If, for example, you need to iterate over board and check each square in order to define if there is a queen I would pick the first approach, but if you have only two or three queens and make decisions depending on their mutual disposition storing coordinates as a field of a class Queen would be a better idea as for me.
>
> This might not seem very important or
> pressing, but I'm using Java and it
> kinda gets to the core of the concept
> of OO programming. If we never use the
> modular capabilities of Java, then why
> use Java at all? We might as well have
> written the same thing in C or Python.
>
>
>
Having the ability to use OOP does not imply that it's always the best solution, sometimes creating a separate class instead of using primitive types will just complicate things and make your code harder to support. | In this case having a 2D array of Queens (separate class but without containing x,y coordinates) or booleans (indicating either a presence or absence of a queen) should be the correct choice.
The reasoning is as follows:
* Queens as such do not have a position. You should design your objects (POJOs) independently of where they will be used and include as class members only properties that are relevant to them on their own.
* The positioning data has nothing to do with the queens and should be separated from them. Put in simpler terms, it is not a queens' job to take care of her position, but rather that of an external party (player, program, whatever). This is called **separation of responsibilities**.
* Most algorithms that you would like to use will be more difficult to implement and very hard to read and follow logically. Simple iterations of the board would be made impossible (or useless, at the least).
You will have to clearly define the role of each object in your system in order to be able to design it in a way that's both extensible & easy to work with. Not having a good idea of what exactly each object will be doing might lead to a wrong decision somewhere along the path, which itself will lead to more bad decisions down the road that deal with it until it becomes so bloated with hacks and workarounds that you would decide to start over :) |
4,845,736 | I recently had a homework question where we were supposed to work with a chess board, and place a number of queens on the board.
The question was trivial in terms of difficulty, but what I wanted to ask was this:
Should I just make a boolean 2-D array and change every position that contains a queen to 1 or should I make a private class to represent a queen, that has x and y coordinates as instance variables?
This might not seem very important or pressing, but I'm using Java and it kinda gets to the core of the concept of OO programming. If we never use the modular capabilities of Java, then why use Java at all? We might as well have written the same thing in C or Python.
Which would be more appropriate in general do you think? I would appreciate it if you could restrict your answers to ones that are backed by reason, as opposed to opinions or personal preferences. | 2011/01/30 | [
"https://Stackoverflow.com/questions/4845736",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/384108/"
] | >
> Should I just make a boolean 2-D array and change every position that contains a queen to 1 or should I make a private class to represent a queen, that has x and y coordinates as instance variables?
>
>
>
There is no single general answer to such questions. Either one can be suitable in specific situations, solving specific problems.
>
> If we never use the modular capabilities of Java, then why use Java at all? We might as well have written the same thing in C or Python.
>
>
>
The fact that Java is an OO language does not mean we *must* define and use classes and objects for every piece of data we need to represent.
If I understand your question correctly, you are asking about an implementation detail. Object oriented programming is not so much concerned about the specific implementation details as it is concerned about *encapsulating* those implementation details behind a suitable interface which represents some important domain concept well. Hence clients of the class need not know nor think about its implementation details, only about the higher level abstraction represented by an interface. | >
> Should I just make a boolean 2-D array
> and change every position that
> contains a queen to 1 or should I make
> a private class to represent a queen,
> that has x and y coordinates as
> instance variables?
>
>
>
It depends on your needs. If, for example, you need to iterate over board and check each square in order to define if there is a queen I would pick the first approach, but if you have only two or three queens and make decisions depending on their mutual disposition storing coordinates as a field of a class Queen would be a better idea as for me.
>
> This might not seem very important or
> pressing, but I'm using Java and it
> kinda gets to the core of the concept
> of OO programming. If we never use the
> modular capabilities of Java, then why
> use Java at all? We might as well have
> written the same thing in C or Python.
>
>
>
Having the ability to use OOP does not imply that it's always the best solution, sometimes creating a separate class instead of using primitive types will just complicate things and make your code harder to support. |
4,845,736 | I recently had a homework question where we were supposed to work with a chess board, and place a number of queens on the board.
The question was trivial in terms of difficulty, but what I wanted to ask was this:
Should I just make a boolean 2-D array and change every position that contains a queen to 1 or should I make a private class to represent a queen, that has x and y coordinates as instance variables?
This might not seem very important or pressing, but I'm using Java and it kinda gets to the core of the concept of OO programming. If we never use the modular capabilities of Java, then why use Java at all? We might as well have written the same thing in C or Python.
Which would be more appropriate in general do you think? I would appreciate it if you could restrict your answers to ones that are backed by reason, as opposed to opinions or personal preferences. | 2011/01/30 | [
"https://Stackoverflow.com/questions/4845736",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/384108/"
] | >
> Should I just make a boolean 2-D array and change every position that contains a queen to 1 or should I make a private class to represent a queen, that has x and y coordinates as instance variables?
>
>
>
There is no single general answer to such questions. Either one can be suitable in specific situations, solving specific problems.
>
> If we never use the modular capabilities of Java, then why use Java at all? We might as well have written the same thing in C or Python.
>
>
>
The fact that Java is an OO language does not mean we *must* define and use classes and objects for every piece of data we need to represent.
If I understand your question correctly, you are asking about an implementation detail. Object oriented programming is not so much concerned about the specific implementation details as it is concerned about *encapsulating* those implementation details behind a suitable interface which represents some important domain concept well. Hence clients of the class need not know nor think about its implementation details, only about the higher level abstraction represented by an interface. | >
> Should I just make a boolean 2-D array
> and change every position that
> contains a queen to 1 or should I make
> a private class to represent a queen,
> that has x and y coordinates as
> instance variables?
>
>
>
This is really two questions:
1. Should I store the queens' positions inside a single 2D array, or should I store the x/y coordinates for each queen?
2. Should I use a simple datastructure, or a class to hold this data?
The answer to 1. is, as pointed out by the other answers: It depends. Use the data structure that is easiest for the algorithms you need.
The answer to 2. is: Yes, I would always wrap the data structure (whichever you use, the list of coordinates or the array) in a class. Even if the class may sound trivial, if you use a class, it will be immediately apparent that you are storing positions. If you just use a 2D array, people will have to wonder what it does. Plus, you can have suitable methods in the class, enforce invariants (e.g. <10 queens) etc. ... all the OO goodness :-). |
4,845,736 | I recently had a homework question where we were supposed to work with a chess board, and place a number of queens on the board.
The question was trivial in terms of difficulty, but what I wanted to ask was this:
Should I just make a boolean 2-D array and change every position that contains a queen to 1 or should I make a private class to represent a queen, that has x and y coordinates as instance variables?
This might not seem very important or pressing, but I'm using Java and it kinda gets to the core of the concept of OO programming. If we never use the modular capabilities of Java, then why use Java at all? We might as well have written the same thing in C or Python.
Which would be more appropriate in general do you think? I would appreciate it if you could restrict your answers to ones that are backed by reason, as opposed to opinions or personal preferences. | 2011/01/30 | [
"https://Stackoverflow.com/questions/4845736",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/384108/"
] | >
> Should I just make a boolean 2-D array and change every position that contains a queen to 1 or should I make a private class to represent a queen, that has x and y coordinates as instance variables?
>
>
>
There is no single general answer to such questions. Either one can be suitable in specific situations, solving specific problems.
>
> If we never use the modular capabilities of Java, then why use Java at all? We might as well have written the same thing in C or Python.
>
>
>
The fact that Java is an OO language does not mean we *must* define and use classes and objects for every piece of data we need to represent.
If I understand your question correctly, you are asking about an implementation detail. Object oriented programming is not so much concerned about the specific implementation details as it is concerned about *encapsulating* those implementation details behind a suitable interface which represents some important domain concept well. Hence clients of the class need not know nor think about its implementation details, only about the higher level abstraction represented by an interface. | In this case having a 2D array of Queens (separate class but without containing x,y coordinates) or booleans (indicating either a presence or absence of a queen) should be the correct choice.
The reasoning is as follows:
* Queens as such do not have a position. You should design your objects (POJOs) independently of where they will be used and include as class members only properties that are relevant to them on their own.
* The positioning data has nothing to do with the queens and should be separated from them. Put in simpler terms, it is not a queens' job to take care of her position, but rather that of an external party (player, program, whatever). This is called **separation of responsibilities**.
* Most algorithms that you would like to use will be more difficult to implement and very hard to read and follow logically. Simple iterations of the board would be made impossible (or useless, at the least).
You will have to clearly define the role of each object in your system in order to be able to design it in a way that's both extensible & easy to work with. Not having a good idea of what exactly each object will be doing might lead to a wrong decision somewhere along the path, which itself will lead to more bad decisions down the road that deal with it until it becomes so bloated with hacks and workarounds that you would decide to start over :) |
4,845,736 | I recently had a homework question where we were supposed to work with a chess board, and place a number of queens on the board.
The question was trivial in terms of difficulty, but what I wanted to ask was this:
Should I just make a boolean 2-D array and change every position that contains a queen to 1 or should I make a private class to represent a queen, that has x and y coordinates as instance variables?
This might not seem very important or pressing, but I'm using Java and it kinda gets to the core of the concept of OO programming. If we never use the modular capabilities of Java, then why use Java at all? We might as well have written the same thing in C or Python.
Which would be more appropriate in general do you think? I would appreciate it if you could restrict your answers to ones that are backed by reason, as opposed to opinions or personal preferences. | 2011/01/30 | [
"https://Stackoverflow.com/questions/4845736",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/384108/"
] | >
> Should I just make a boolean 2-D array
> and change every position that
> contains a queen to 1 or should I make
> a private class to represent a queen,
> that has x and y coordinates as
> instance variables?
>
>
>
It depends on your needs. If, for example, you need to iterate over board and check each square in order to define if there is a queen I would pick the first approach, but if you have only two or three queens and make decisions depending on their mutual disposition storing coordinates as a field of a class Queen would be a better idea as for me.
>
> This might not seem very important or
> pressing, but I'm using Java and it
> kinda gets to the core of the concept
> of OO programming. If we never use the
> modular capabilities of Java, then why
> use Java at all? We might as well have
> written the same thing in C or Python.
>
>
>
Having the ability to use OOP does not imply that it's always the best solution, sometimes creating a separate class instead of using primitive types will just complicate things and make your code harder to support. | You could adequately represent the **state** of the board using either of the methods you have described. The most *appropriate* method to use will depend on the desired **behavior** of the system, which we haven't been told. |
4,845,736 | I recently had a homework question where we were supposed to work with a chess board, and place a number of queens on the board.
The question was trivial in terms of difficulty, but what I wanted to ask was this:
Should I just make a boolean 2-D array and change every position that contains a queen to 1 or should I make a private class to represent a queen, that has x and y coordinates as instance variables?
This might not seem very important or pressing, but I'm using Java and it kinda gets to the core of the concept of OO programming. If we never use the modular capabilities of Java, then why use Java at all? We might as well have written the same thing in C or Python.
Which would be more appropriate in general do you think? I would appreciate it if you could restrict your answers to ones that are backed by reason, as opposed to opinions or personal preferences. | 2011/01/30 | [
"https://Stackoverflow.com/questions/4845736",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/384108/"
] | >
> Should I just make a boolean 2-D array
> and change every position that
> contains a queen to 1 or should I make
> a private class to represent a queen,
> that has x and y coordinates as
> instance variables?
>
>
>
It depends on your needs. If, for example, you need to iterate over board and check each square in order to define if there is a queen I would pick the first approach, but if you have only two or three queens and make decisions depending on their mutual disposition storing coordinates as a field of a class Queen would be a better idea as for me.
>
> This might not seem very important or
> pressing, but I'm using Java and it
> kinda gets to the core of the concept
> of OO programming. If we never use the
> modular capabilities of Java, then why
> use Java at all? We might as well have
> written the same thing in C or Python.
>
>
>
Having the ability to use OOP does not imply that it's always the best solution, sometimes creating a separate class instead of using primitive types will just complicate things and make your code harder to support. | >
> Should I just make a boolean 2-D array
> and change every position that
> contains a queen to 1 or should I make
> a private class to represent a queen,
> that has x and y coordinates as
> instance variables?
>
>
>
This is really two questions:
1. Should I store the queens' positions inside a single 2D array, or should I store the x/y coordinates for each queen?
2. Should I use a simple datastructure, or a class to hold this data?
The answer to 1. is, as pointed out by the other answers: It depends. Use the data structure that is easiest for the algorithms you need.
The answer to 2. is: Yes, I would always wrap the data structure (whichever you use, the list of coordinates or the array) in a class. Even if the class may sound trivial, if you use a class, it will be immediately apparent that you are storing positions. If you just use a 2D array, people will have to wonder what it does. Plus, you can have suitable methods in the class, enforce invariants (e.g. <10 queens) etc. ... all the OO goodness :-). |
4,845,736 | I recently had a homework question where we were supposed to work with a chess board, and place a number of queens on the board.
The question was trivial in terms of difficulty, but what I wanted to ask was this:
Should I just make a boolean 2-D array and change every position that contains a queen to 1 or should I make a private class to represent a queen, that has x and y coordinates as instance variables?
This might not seem very important or pressing, but I'm using Java and it kinda gets to the core of the concept of OO programming. If we never use the modular capabilities of Java, then why use Java at all? We might as well have written the same thing in C or Python.
Which would be more appropriate in general do you think? I would appreciate it if you could restrict your answers to ones that are backed by reason, as opposed to opinions or personal preferences. | 2011/01/30 | [
"https://Stackoverflow.com/questions/4845736",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/384108/"
] | I know you don't want an opinion but I'm going to give you one anyway: there is no general case. The art of software design lies in being able to make the appropriate choice in data and code structure depending on the specifics of the application. OO languages give you a more expressive palette to design with, but there are no hard and fast rules that apply in every situation.
So, that's the opinion. Now, to your specific example. A question I might ask myself is: What's more useful? An individual piece knowing where it is on the board, or the board knowing where each piece is? If you don't have a separate notion of a board, i.e. in the form of a 2D array that contains pieces, then you're going to have to ask every piece where it is everytime you need to do something with a piece. This is perhaps fine if you only have a couple of pieces, but it gets inefficient the more pieces you have.
Conversely if, let's say, you have a very large chessboard - 500x500 - and only a couple of pieces on it, then a 2D array would be very inefficient, so a sparse data structure would likely be better.
Another way to look at it: if you have more the one piece then they're going to be held in a data structure of some kind, perhaps an array, or a 2D array, or a linked list, or an array of linked lists, or whatever. What data structure are you going to choose, and why? | You could adequately represent the **state** of the board using either of the methods you have described. The most *appropriate* method to use will depend on the desired **behavior** of the system, which we haven't been told. |
4,845,736 | I recently had a homework question where we were supposed to work with a chess board, and place a number of queens on the board.
The question was trivial in terms of difficulty, but what I wanted to ask was this:
Should I just make a boolean 2-D array and change every position that contains a queen to 1 or should I make a private class to represent a queen, that has x and y coordinates as instance variables?
This might not seem very important or pressing, but I'm using Java and it kinda gets to the core of the concept of OO programming. If we never use the modular capabilities of Java, then why use Java at all? We might as well have written the same thing in C or Python.
Which would be more appropriate in general do you think? I would appreciate it if you could restrict your answers to ones that are backed by reason, as opposed to opinions or personal preferences. | 2011/01/30 | [
"https://Stackoverflow.com/questions/4845736",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/384108/"
] | >
> Should I just make a boolean 2-D array
> and change every position that
> contains a queen to 1 or should I make
> a private class to represent a queen,
> that has x and y coordinates as
> instance variables?
>
>
>
It depends on your needs. If, for example, you need to iterate over board and check each square in order to define if there is a queen I would pick the first approach, but if you have only two or three queens and make decisions depending on their mutual disposition storing coordinates as a field of a class Queen would be a better idea as for me.
>
> This might not seem very important or
> pressing, but I'm using Java and it
> kinda gets to the core of the concept
> of OO programming. If we never use the
> modular capabilities of Java, then why
> use Java at all? We might as well have
> written the same thing in C or Python.
>
>
>
Having the ability to use OOP does not imply that it's always the best solution, sometimes creating a separate class instead of using primitive types will just complicate things and make your code harder to support. | I know you don't want an opinion but I'm going to give you one anyway: there is no general case. The art of software design lies in being able to make the appropriate choice in data and code structure depending on the specifics of the application. OO languages give you a more expressive palette to design with, but there are no hard and fast rules that apply in every situation.
So, that's the opinion. Now, to your specific example. A question I might ask myself is: What's more useful? An individual piece knowing where it is on the board, or the board knowing where each piece is? If you don't have a separate notion of a board, i.e. in the form of a 2D array that contains pieces, then you're going to have to ask every piece where it is everytime you need to do something with a piece. This is perhaps fine if you only have a couple of pieces, but it gets inefficient the more pieces you have.
Conversely if, let's say, you have a very large chessboard - 500x500 - and only a couple of pieces on it, then a 2D array would be very inefficient, so a sparse data structure would likely be better.
Another way to look at it: if you have more the one piece then they're going to be held in a data structure of some kind, perhaps an array, or a 2D array, or a linked list, or an array of linked lists, or whatever. What data structure are you going to choose, and why? |
4,845,736 | I recently had a homework question where we were supposed to work with a chess board, and place a number of queens on the board.
The question was trivial in terms of difficulty, but what I wanted to ask was this:
Should I just make a boolean 2-D array and change every position that contains a queen to 1 or should I make a private class to represent a queen, that has x and y coordinates as instance variables?
This might not seem very important or pressing, but I'm using Java and it kinda gets to the core of the concept of OO programming. If we never use the modular capabilities of Java, then why use Java at all? We might as well have written the same thing in C or Python.
Which would be more appropriate in general do you think? I would appreciate it if you could restrict your answers to ones that are backed by reason, as opposed to opinions or personal preferences. | 2011/01/30 | [
"https://Stackoverflow.com/questions/4845736",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/384108/"
] | >
> Should I just make a boolean 2-D array and change every position that contains a queen to 1 or should I make a private class to represent a queen, that has x and y coordinates as instance variables?
>
>
>
There is no single general answer to such questions. Either one can be suitable in specific situations, solving specific problems.
>
> If we never use the modular capabilities of Java, then why use Java at all? We might as well have written the same thing in C or Python.
>
>
>
The fact that Java is an OO language does not mean we *must* define and use classes and objects for every piece of data we need to represent.
If I understand your question correctly, you are asking about an implementation detail. Object oriented programming is not so much concerned about the specific implementation details as it is concerned about *encapsulating* those implementation details behind a suitable interface which represents some important domain concept well. Hence clients of the class need not know nor think about its implementation details, only about the higher level abstraction represented by an interface. | You could adequately represent the **state** of the board using either of the methods you have described. The most *appropriate* method to use will depend on the desired **behavior** of the system, which we haven't been told. |
10,370,571 | I'm new to xcode .I want to autoplay a sound when I open the app . I put the code in viewDidLoad but when I open other view and go back the sound play again .how can fix this problem ?? | 2012/04/29 | [
"https://Stackoverflow.com/questions/10370571",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/1363398/"
] | I just bumped into this feature by accident but looking up to see if I figure how to get to it. it looked like it popped up when I started typing after having launched eclipse without focusing on any particular view... more to come as soon as I find out for sure.
EDIT: Apparently when you first launch Eclipse the focus is on the "Quick Action" search box on the top right of the tool bar and that's where you can start typing command names for it to list and let you pick in good Sublime Text style. Not sure how to shortcut into the box other than clicking it, but apparently there's the feature.
EDIT#2: <http://www.vogella.com/tutorials/EclipseShortcuts/article.html#shortcuts_overview> describes Ctrl+3 as being the shortcut to get there, on the Mac it translates to Cmd+3. | I haven't been able to find anything, so I have started on developing my own plugin. |
305,482 | I'm trying to find a word or short description for someone who...
* ...May well wave their arms and legs around, but not in a clumsy, clowny way, not randomly, not without a purpose.
* ...Is not afraid of getting attention from physical expressions, but may not actively seek it either.
* ...Generally likes to move his\her body around, with no sports activities or physical tasks involved.
Some examples of the movement I'm talking about:
* Dancing, especially without music or being the only one dancing around other people.
* Stretching arms and legs far and wide while not alone.
* Literally jumping around for being in a good mood (I'm talking about grown ups)
* Likes to use the whole body to impersonate something or someone, when explaining or telling a story.
These people are usually extroverts, but 'extrovert' has way too broad meaning. | 2016/02/10 | [
"https://english.stackexchange.com/questions/305482",
"https://english.stackexchange.com",
"https://english.stackexchange.com/users/117018/"
] | **[animated](http://www.merriam-webster.com/dictionary/animated)**
>
> full of movement and activity
>
>
>
or (although it's not as broadly usable as animated)
**[gesticulator](http://www.thefreedictionary.com/gesticulator)**
one who gesticulates, where gesticulate means
>
> To say or express by gestures.
>
>
> | Physically talkative, demonstrative personality, even perhaps in Don Quixote's sense. |
119,378 | The thing is, I am confused whether the word *selfish* itself can be used without expressing a negative connotation. I am a bit biased about it since I believe that by using this word it automatically implies that a third party will be affected by the action.
The thesaurus provides *self-interested*, *self-seeking*, *egoistic*; *illiberal*, *parsimonious*, and *stingy* as its synonyms; and I am aware that some can be used in a positive manner. For example self-seeking doesn't necessarily mean I am affecting someone else.
In other words, will everyone who hears *selfish* automatically perceive a negative meaning for the preceding action?
Could there be a better word that could express a similar meaning without being negative? | 2013/07/16 | [
"https://english.stackexchange.com/questions/119378",
"https://english.stackexchange.com",
"https://english.stackexchange.com/users/21503/"
] | Ayn Rand wrote a book called *The Virtue of Selfishness*.
As an Objectivist, she espouses [rational selfishness](http://aynrandlexicon.com/lexicon/selfishness.html).
That page says
>
> In popular usage, the word “selfishness” is a synonym of evil; the image it conjures is of a murderous brute who tramples over piles of corpses to achieve his own ends, who cares for no living being and pursues nothing but the gratification of the mindless whims of any immediate moment.
>
>
> Yet the exact meaning and dictionary definition of the word “selfishness” is: concern with one’s own interests.
>
>
>
The connotations of *selfishness* outweigh its denotation. To express yourself without a lot of hand-waving, try qualifying it with *rational selfishness, enlightened self-interest,* or simply *self-interest*. | I think if you use the phrase 'self-focused' you might be able to get away with it. It doesn't sound quite as bad as the other examples you have provided. |
119,378 | The thing is, I am confused whether the word *selfish* itself can be used without expressing a negative connotation. I am a bit biased about it since I believe that by using this word it automatically implies that a third party will be affected by the action.
The thesaurus provides *self-interested*, *self-seeking*, *egoistic*; *illiberal*, *parsimonious*, and *stingy* as its synonyms; and I am aware that some can be used in a positive manner. For example self-seeking doesn't necessarily mean I am affecting someone else.
In other words, will everyone who hears *selfish* automatically perceive a negative meaning for the preceding action?
Could there be a better word that could express a similar meaning without being negative? | 2013/07/16 | [
"https://english.stackexchange.com/questions/119378",
"https://english.stackexchange.com",
"https://english.stackexchange.com/users/21503/"
] | I think if you use the phrase 'self-focused' you might be able to get away with it. It doesn't sound quite as bad as the other examples you have provided. | My mileage varies from that of the OP. For me, "self-seeking" is always negative, morally worse than "selfish". It implies actively doing something against the welfare of someone else, not just having a bad attitude deep inside.
Although I am absolutely not a Randian, I have possibly congruent issues with the word "selfish" from my own experience: having suffered from the sort of person who would say, "You're being very selfish for not bringing me a cup of tea (before I ask for one!)" To me, "selfishness" *may* mean doing what I want and am entitled to in place of doing what *you* want and are not entitled to. People use accusations of selfishness to be selfish! Abusus non tollit usum, of course, but still.
As for "self-centered", I have always had problems understanding it. I live (even am trapped) in *my* body, how can I possibly be centered anywhere else? One is surely self-centered in the sense that one is necessarily the centre of one's own universe but one may still act according to the Categorical Imperative or whatever other ethical system floats one's boat. IOW, being "self-centered" doesn't mean that you have to be *nasty*.
My own preferred term for what the bad guys do is **predation**. They are treating us as *food*. |
119,378 | The thing is, I am confused whether the word *selfish* itself can be used without expressing a negative connotation. I am a bit biased about it since I believe that by using this word it automatically implies that a third party will be affected by the action.
The thesaurus provides *self-interested*, *self-seeking*, *egoistic*; *illiberal*, *parsimonious*, and *stingy* as its synonyms; and I am aware that some can be used in a positive manner. For example self-seeking doesn't necessarily mean I am affecting someone else.
In other words, will everyone who hears *selfish* automatically perceive a negative meaning for the preceding action?
Could there be a better word that could express a similar meaning without being negative? | 2013/07/16 | [
"https://english.stackexchange.com/questions/119378",
"https://english.stackexchange.com",
"https://english.stackexchange.com/users/21503/"
] | I think if you use the phrase 'self-focused' you might be able to get away with it. It doesn't sound quite as bad as the other examples you have provided. | **Ambition** is related and can be positive, but it's not quite the same thing, and in the wrong context it could be seen negatively.
>
> [**ambition**](http://www.merriam-webster.com/dictionary/ambition) - an ardent desire for rank, fame, or power
>
>
> |
119,378 | The thing is, I am confused whether the word *selfish* itself can be used without expressing a negative connotation. I am a bit biased about it since I believe that by using this word it automatically implies that a third party will be affected by the action.
The thesaurus provides *self-interested*, *self-seeking*, *egoistic*; *illiberal*, *parsimonious*, and *stingy* as its synonyms; and I am aware that some can be used in a positive manner. For example self-seeking doesn't necessarily mean I am affecting someone else.
In other words, will everyone who hears *selfish* automatically perceive a negative meaning for the preceding action?
Could there be a better word that could express a similar meaning without being negative? | 2013/07/16 | [
"https://english.stackexchange.com/questions/119378",
"https://english.stackexchange.com",
"https://english.stackexchange.com/users/21503/"
] | Ayn Rand wrote a book called *The Virtue of Selfishness*.
As an Objectivist, she espouses [rational selfishness](http://aynrandlexicon.com/lexicon/selfishness.html).
That page says
>
> In popular usage, the word “selfishness” is a synonym of evil; the image it conjures is of a murderous brute who tramples over piles of corpses to achieve his own ends, who cares for no living being and pursues nothing but the gratification of the mindless whims of any immediate moment.
>
>
> Yet the exact meaning and dictionary definition of the word “selfishness” is: concern with one’s own interests.
>
>
>
The connotations of *selfishness* outweigh its denotation. To express yourself without a lot of hand-waving, try qualifying it with *rational selfishness, enlightened self-interest,* or simply *self-interest*. | Self-preservation
-----------------
>
> Self-preservation is the first responsibility — *Margaret Anderson*
>
>
> |
119,378 | The thing is, I am confused whether the word *selfish* itself can be used without expressing a negative connotation. I am a bit biased about it since I believe that by using this word it automatically implies that a third party will be affected by the action.
The thesaurus provides *self-interested*, *self-seeking*, *egoistic*; *illiberal*, *parsimonious*, and *stingy* as its synonyms; and I am aware that some can be used in a positive manner. For example self-seeking doesn't necessarily mean I am affecting someone else.
In other words, will everyone who hears *selfish* automatically perceive a negative meaning for the preceding action?
Could there be a better word that could express a similar meaning without being negative? | 2013/07/16 | [
"https://english.stackexchange.com/questions/119378",
"https://english.stackexchange.com",
"https://english.stackexchange.com/users/21503/"
] | Self-preservation
-----------------
>
> Self-preservation is the first responsibility — *Margaret Anderson*
>
>
> | My mileage varies from that of the OP. For me, "self-seeking" is always negative, morally worse than "selfish". It implies actively doing something against the welfare of someone else, not just having a bad attitude deep inside.
Although I am absolutely not a Randian, I have possibly congruent issues with the word "selfish" from my own experience: having suffered from the sort of person who would say, "You're being very selfish for not bringing me a cup of tea (before I ask for one!)" To me, "selfishness" *may* mean doing what I want and am entitled to in place of doing what *you* want and are not entitled to. People use accusations of selfishness to be selfish! Abusus non tollit usum, of course, but still.
As for "self-centered", I have always had problems understanding it. I live (even am trapped) in *my* body, how can I possibly be centered anywhere else? One is surely self-centered in the sense that one is necessarily the centre of one's own universe but one may still act according to the Categorical Imperative or whatever other ethical system floats one's boat. IOW, being "self-centered" doesn't mean that you have to be *nasty*.
My own preferred term for what the bad guys do is **predation**. They are treating us as *food*. |
119,378 | The thing is, I am confused whether the word *selfish* itself can be used without expressing a negative connotation. I am a bit biased about it since I believe that by using this word it automatically implies that a third party will be affected by the action.
The thesaurus provides *self-interested*, *self-seeking*, *egoistic*; *illiberal*, *parsimonious*, and *stingy* as its synonyms; and I am aware that some can be used in a positive manner. For example self-seeking doesn't necessarily mean I am affecting someone else.
In other words, will everyone who hears *selfish* automatically perceive a negative meaning for the preceding action?
Could there be a better word that could express a similar meaning without being negative? | 2013/07/16 | [
"https://english.stackexchange.com/questions/119378",
"https://english.stackexchange.com",
"https://english.stackexchange.com/users/21503/"
] | I think if you use the phrase 'self-focused' you might be able to get away with it. It doesn't sound quite as bad as the other examples you have provided. | There certainly is potential for selfishness to be positive but it is complicated and more about context than semantics or philosophy! I work with the very elderly, in the cohort of 28 I work with I have 3 centenarians, 6 who might be centenarians in 2020, a few youngsters paddling around in sub 90 zone and the rest all nonagenarians. That is a bloody long time to have to be grateful to people and their support of your physical and/or mental frailty.
I gallop elders off on trips to/ rendezvous with family/friends at, art galleries, museums, sporting venues, cafes, woods, farms, pubs, restaurants, rural shows, concerts, trails etc. In response to their thanks I claim to be using them to have an excuse to have a good time myself and get out of of my work place and their home, 'totally selfish really'. In the normal home based routine I claim (and actually do have) a very low boredom threshold - we do not get stuck into a bingo / sing song rut. Instead I work on the basis that if I am bored, my crew will be bored too.
At this point we become collaborators, they do not have to feel 'grateful', I am no longer a do-gooder, they know they provide the excuse and I provide the imagination and drive, between us we subvert the status quo and have a rollicking good time! My 'selfishness' empowers people to no longer just be lovingly carried burdens but people with the power to gift me and us pleasure.
Selfish in the right, possibly ironic context can be good. Which then opens the whole subject of irony and the British v American sense of humour? |
119,378 | The thing is, I am confused whether the word *selfish* itself can be used without expressing a negative connotation. I am a bit biased about it since I believe that by using this word it automatically implies that a third party will be affected by the action.
The thesaurus provides *self-interested*, *self-seeking*, *egoistic*; *illiberal*, *parsimonious*, and *stingy* as its synonyms; and I am aware that some can be used in a positive manner. For example self-seeking doesn't necessarily mean I am affecting someone else.
In other words, will everyone who hears *selfish* automatically perceive a negative meaning for the preceding action?
Could there be a better word that could express a similar meaning without being negative? | 2013/07/16 | [
"https://english.stackexchange.com/questions/119378",
"https://english.stackexchange.com",
"https://english.stackexchange.com/users/21503/"
] | Self-preservation
-----------------
>
> Self-preservation is the first responsibility — *Margaret Anderson*
>
>
> | **Ambition** is related and can be positive, but it's not quite the same thing, and in the wrong context it could be seen negatively.
>
> [**ambition**](http://www.merriam-webster.com/dictionary/ambition) - an ardent desire for rank, fame, or power
>
>
> |
119,378 | The thing is, I am confused whether the word *selfish* itself can be used without expressing a negative connotation. I am a bit biased about it since I believe that by using this word it automatically implies that a third party will be affected by the action.
The thesaurus provides *self-interested*, *self-seeking*, *egoistic*; *illiberal*, *parsimonious*, and *stingy* as its synonyms; and I am aware that some can be used in a positive manner. For example self-seeking doesn't necessarily mean I am affecting someone else.
In other words, will everyone who hears *selfish* automatically perceive a negative meaning for the preceding action?
Could there be a better word that could express a similar meaning without being negative? | 2013/07/16 | [
"https://english.stackexchange.com/questions/119378",
"https://english.stackexchange.com",
"https://english.stackexchange.com/users/21503/"
] | Ayn Rand wrote a book called *The Virtue of Selfishness*.
As an Objectivist, she espouses [rational selfishness](http://aynrandlexicon.com/lexicon/selfishness.html).
That page says
>
> In popular usage, the word “selfishness” is a synonym of evil; the image it conjures is of a murderous brute who tramples over piles of corpses to achieve his own ends, who cares for no living being and pursues nothing but the gratification of the mindless whims of any immediate moment.
>
>
> Yet the exact meaning and dictionary definition of the word “selfishness” is: concern with one’s own interests.
>
>
>
The connotations of *selfishness* outweigh its denotation. To express yourself without a lot of hand-waving, try qualifying it with *rational selfishness, enlightened self-interest,* or simply *self-interest*. | My mileage varies from that of the OP. For me, "self-seeking" is always negative, morally worse than "selfish". It implies actively doing something against the welfare of someone else, not just having a bad attitude deep inside.
Although I am absolutely not a Randian, I have possibly congruent issues with the word "selfish" from my own experience: having suffered from the sort of person who would say, "You're being very selfish for not bringing me a cup of tea (before I ask for one!)" To me, "selfishness" *may* mean doing what I want and am entitled to in place of doing what *you* want and are not entitled to. People use accusations of selfishness to be selfish! Abusus non tollit usum, of course, but still.
As for "self-centered", I have always had problems understanding it. I live (even am trapped) in *my* body, how can I possibly be centered anywhere else? One is surely self-centered in the sense that one is necessarily the centre of one's own universe but one may still act according to the Categorical Imperative or whatever other ethical system floats one's boat. IOW, being "self-centered" doesn't mean that you have to be *nasty*.
My own preferred term for what the bad guys do is **predation**. They are treating us as *food*. |
119,378 | The thing is, I am confused whether the word *selfish* itself can be used without expressing a negative connotation. I am a bit biased about it since I believe that by using this word it automatically implies that a third party will be affected by the action.
The thesaurus provides *self-interested*, *self-seeking*, *egoistic*; *illiberal*, *parsimonious*, and *stingy* as its synonyms; and I am aware that some can be used in a positive manner. For example self-seeking doesn't necessarily mean I am affecting someone else.
In other words, will everyone who hears *selfish* automatically perceive a negative meaning for the preceding action?
Could there be a better word that could express a similar meaning without being negative? | 2013/07/16 | [
"https://english.stackexchange.com/questions/119378",
"https://english.stackexchange.com",
"https://english.stackexchange.com/users/21503/"
] | There certainly is potential for selfishness to be positive but it is complicated and more about context than semantics or philosophy! I work with the very elderly, in the cohort of 28 I work with I have 3 centenarians, 6 who might be centenarians in 2020, a few youngsters paddling around in sub 90 zone and the rest all nonagenarians. That is a bloody long time to have to be grateful to people and their support of your physical and/or mental frailty.
I gallop elders off on trips to/ rendezvous with family/friends at, art galleries, museums, sporting venues, cafes, woods, farms, pubs, restaurants, rural shows, concerts, trails etc. In response to their thanks I claim to be using them to have an excuse to have a good time myself and get out of of my work place and their home, 'totally selfish really'. In the normal home based routine I claim (and actually do have) a very low boredom threshold - we do not get stuck into a bingo / sing song rut. Instead I work on the basis that if I am bored, my crew will be bored too.
At this point we become collaborators, they do not have to feel 'grateful', I am no longer a do-gooder, they know they provide the excuse and I provide the imagination and drive, between us we subvert the status quo and have a rollicking good time! My 'selfishness' empowers people to no longer just be lovingly carried burdens but people with the power to gift me and us pleasure.
Selfish in the right, possibly ironic context can be good. Which then opens the whole subject of irony and the British v American sense of humour? | **Ambition** is related and can be positive, but it's not quite the same thing, and in the wrong context it could be seen negatively.
>
> [**ambition**](http://www.merriam-webster.com/dictionary/ambition) - an ardent desire for rank, fame, or power
>
>
> |
119,378 | The thing is, I am confused whether the word *selfish* itself can be used without expressing a negative connotation. I am a bit biased about it since I believe that by using this word it automatically implies that a third party will be affected by the action.
The thesaurus provides *self-interested*, *self-seeking*, *egoistic*; *illiberal*, *parsimonious*, and *stingy* as its synonyms; and I am aware that some can be used in a positive manner. For example self-seeking doesn't necessarily mean I am affecting someone else.
In other words, will everyone who hears *selfish* automatically perceive a negative meaning for the preceding action?
Could there be a better word that could express a similar meaning without being negative? | 2013/07/16 | [
"https://english.stackexchange.com/questions/119378",
"https://english.stackexchange.com",
"https://english.stackexchange.com/users/21503/"
] | Self-preservation
-----------------
>
> Self-preservation is the first responsibility — *Margaret Anderson*
>
>
> | There certainly is potential for selfishness to be positive but it is complicated and more about context than semantics or philosophy! I work with the very elderly, in the cohort of 28 I work with I have 3 centenarians, 6 who might be centenarians in 2020, a few youngsters paddling around in sub 90 zone and the rest all nonagenarians. That is a bloody long time to have to be grateful to people and their support of your physical and/or mental frailty.
I gallop elders off on trips to/ rendezvous with family/friends at, art galleries, museums, sporting venues, cafes, woods, farms, pubs, restaurants, rural shows, concerts, trails etc. In response to their thanks I claim to be using them to have an excuse to have a good time myself and get out of of my work place and their home, 'totally selfish really'. In the normal home based routine I claim (and actually do have) a very low boredom threshold - we do not get stuck into a bingo / sing song rut. Instead I work on the basis that if I am bored, my crew will be bored too.
At this point we become collaborators, they do not have to feel 'grateful', I am no longer a do-gooder, they know they provide the excuse and I provide the imagination and drive, between us we subvert the status quo and have a rollicking good time! My 'selfishness' empowers people to no longer just be lovingly carried burdens but people with the power to gift me and us pleasure.
Selfish in the right, possibly ironic context can be good. Which then opens the whole subject of irony and the British v American sense of humour? |
24,203 | One way how to look at refraction by a dielectric medium like water or glass is that (phase) velocity of light decreases because it is the wavelength rather than the frequency of the light which changes.
I have read somewhere (but can't recall where) that the frequency must remain the same because otherwise principle of causality would be broken. Is that true? | 2012/04/22 | [
"https://physics.stackexchange.com/questions/24203",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/7786/"
] | The EM field must remain continuous at the air/water boundary. This can only happen if the frequency stays the same. If the frequency changed there would be a discontinuity oscillating at the difference in the frequencies. | I haven't heard that explanation before, but I imagine that the argument might go something like this. The amplitude of a plane light wave at a frequency *ω* varies like sin(*ωt*). Roughly speaking, when it encounters a medium, the disturbance in the electric field perturbs the electron clouds of the atoms in the medium and makes them oscillate, also at frequency *ω*. The moving charges, in turn, create a disturbance in the electric field, again at frequency *ω*, which becomes part of the propagating wave.
If the frequencies weren't the same, then the charges wouldn't be *following* the electric field; they'd be off doing their own thing. How would they even be supposed to know that the original wave was a sinusoid with a well-defined frequency? Suppose the frequency in the medium *ω*₁ was higher than *ω*, then at time *t* = 0 both the amplitude of the electric field and the perturbation of the electron cloud might start increasing from 0. However, the electron cloud would reach its peak *earlier* and start decreasing, whereas the electric field that was supposed to be driving it wouldn't start decreasing yet! I suppose that could be argued to violate causality.
However, this argument is rubbish; in practice, the response of the medium to an electric field is not linear, and other frequencies are generated when a light wave propagates through a medium. |
24,203 | One way how to look at refraction by a dielectric medium like water or glass is that (phase) velocity of light decreases because it is the wavelength rather than the frequency of the light which changes.
I have read somewhere (but can't recall where) that the frequency must remain the same because otherwise principle of causality would be broken. Is that true? | 2012/04/22 | [
"https://physics.stackexchange.com/questions/24203",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/7786/"
] | Your question extends well beyond electromagnetic phenomena to waves in general. For example, when sound (a pressure wave, which is arguably a lot simpler than an EM wave) moves from air to water, it too undergoes a change in wavelength while retaining the same frequency.
So why in general are wavelengths mutable but frequencies invariant when waves of any type travel between media that change their propagation speed?
It's actually pretty straightforward: It's the only way to keep one wave from "getting ahead" of itself and ending up in the future.
Think of wave cycles as clocks that just happen to be moving, as in those sinusoidal diagrams where you get a sinusoidal wave by projecting a point rotating around a circle onto a moving line. An observer at a distance will see this clock keeping a certain time, say 60 cycles per second, at it travels.
If some segment of that clock then inexplicably started moving at 120 cycles per second, it would literally pull ahead of the other segments in time, counting out new seconds twice as fast as before.
So, while it's unusual to express such issues in terms of causality, there certainly is an aspect of the need for time measurements to stay constant, and that aspect of the situation for any wave does require simple changes in medium *not* to result in changes of frequency.
With all that said, here are two important qualifiers:
(1) You can always create a new clock frequency based on the old one. If you happen to own a green laser pointer, it internally contains a frequency doubler that takes every half wavelength of an infrared laser and converts it to a full wavelength of green light. This does no violate causality for the same reason that adding a second hand to an old-fashioned analog clock does not violate causality: You are simply adding a finer level of measurement to time by breaking up the earlier cycles into smaller ones that still fit within (and do not get ahead of) the larger, earlier cycles.
(2) The trickier point, and one that leads to some interesting issues, is that wave frequencies do change when frames are in motion relative to each other. Such changes are called Doppler shifts: Waves originating in a source that is moving towards the observer, such as the sounds of an approaching ambulance, are perceived as having a higher frequencies than expected, while than waves originated by a source moving away from the observer, such as the ambulance after it has passed by, are perceived as having lower frequencies than expected. That's why I said "an observer at a distance" earlier, so as to avoid immediate consideration of these relative motion effects.
This brings up an interesting point relative to your question: Why don't Doppler shifts undermine causality? Wouldn't the approaching ambulance in effect have a faster "sound clock" than the the one that is moving away from the observer, and so be moving more quickly into the future than an ambulance that has already passed?
The simple and not-very-satisfying answer is that the causality rule I mentioned earlier only applies locally, that is, because sound in the air is in direct contact with sound in the water, the sound in one or the other cannot begin vibrating faster without creating a contradiction at the interface between the two.
That's correct, but again, it's not a terribly satisfying answer. The problem is that once you get into your head a vision of the physical ambulance speaker diaphragms vibrating faster enough to give that higher-pitched sound, it become hard not to wonder whether the entire entire ambulance, including the clocks within it, might not also be "vibrating faster" than you are as long as the ambulance is approaching. We of course know from direct experience when driving and riding in vehicles that this is not the case, since we don't wind up at Grandma's house sooner just because of the Doppler effect makes the vibrations of our voices during the trip sound higher pitched from Grandma's perspective -- assuming Grandma has very, very good hearing! However, some sort of conceptual reconciliation does seem to be needed.
So, let's look at that vibrating speaker diaphragm issue in particular: Does the diagram vibrate faster? Grandma, being a former astrophysicist and have in here possession a particularly find long-range telescope capable of detecting even minute vibrations, watches you travel from her high mountaintop abode. (By all accounts, you have an interesting Grandma.) She observes voice and other vibrations in your vehicle and detects *no* discernible difference from the rates she expects. Yet when she looks at the reading from her equally sophisticated super-sized very-long-distance parabolic microphone (don't say anything bad about Granny while traveling), she hears a higher frequency that does *not* match what she sees in the telescope!
So what in the world is going on here? How can *both* observations be correct?
The trick is that I haven't told you about all of Grandma's data yet. Very shortly after you begin your trip (there is a very small but detectable speed-of-light delay), Grandma sees you begin to move in her direction. With light, that motion seems to be very close to the time she sees, undetectably close with ordinary instruments in fact.
However, she does *not* hear you yet! In fact, a good portion of you journey is over before her microphone picks up any sound at all -- and when it does, it is the sound of the *start* of your journey, much delayed. From that point on the sound plays out as if on fast forward. Remarkably, this accelerated rate works out to be just fast enough to compensate for the lost gap in time, so that by the time you get to Grandma's house, the reality portrayed by light and the reality portrayed by sound are once again in synch, at least as far as human eyes and ears are concerned. Causality is saved, because everything that appeared to be happening *faster* than normal time was in fact just a sort of delayed recording of events that had already happened.
(You can witness this same effect yourself by having someone at the far end of a football field clap very loudly -- cymbals work better! -- and noticing that you *see* them clap before you *hear* them clap. This is exactly the kind of delay Grandma sees with her instruments, only larger and with Doppler effects added.)
What is happening in cases like this, then, is that the "message" conveyed by sound waves is being "bunched up" (technical term) into a shorter sequence that does not arrive until a bit later, leaving a gap of silence.
A useful analysis technique is to analyze the extreme cases of such phenomena, since these often give you a better feel for where the interesting parts are. In this case, imagine driving (or more realistically, flying) towards Grandma's house at just under the speed of sound. What happens then? Well, think about it: It's a horse race, with sound just barely winning and just barely arriving before you do. So, for almost the entire journey, Grandma hears only silence while watching (with some trepidation one would imagine) you fly towards her house at several hundred kilometers per seconds. Only at the very end does she get a burst of sound that represents your *entire* trip towards her house, hugely Doppler shifted so that for example your voices would be in the extreme ranges of ultrasound.
Now with that I'll end, but leave a bit of a tickler for an issue that is beyond the scope of your question.
I mentioned that Grandma, with her very good optical telescope, actually did see a bit of delay in getting images, since of course light is very fast, but not *infinitely* fast. Does that mean that there is a still faster "instantaneous" reality lurking behind the speed of light, one in which all events are exactly synchronized and the light is only giving the appearance of some delay? After all, Doppler effects apply to light too. They are for example the cause the red shift seen in the spectral lines of galaxies that are moving away from us at very high speeds.
So, is the time delay caused by the finite speed of light also an illusion?
Here's the surprising answer: no. A fellow named Einstein notices that in the case of light, there is some kind of absolute cosmic limit going on, and from some early experiments he postulated a very weird idea: Light *always* to travel at the velocity c, or about 300,000 km/s, *no matter how you are moving*. From this simple postulate and [one other](https://physics.stackexchange.com/questions/23991/special-relativity-and-e-mc2/24074#24074) (physics doesn't change when you are moving), he constructed the entire fabric of the special theory of relativity, for which he later received a certain amount of notoriety... :)
Now, here's what interesting about that in the context of your question: For the special case of light, motion *does* have a real impact on clock speeds! That is, you really can construct cases where, with the proper combination of speed and acceleration, you can make one system slower *in reality* than another. This is not abstraction, since for example if you have ever used a GPS navigation system, the proper location of your vehicles *requires* that the slowing of time due to relativity effects (speed and some others from gravity) be taken into account.
Very roughly, here's why: Since nothing travels faster than the speed of light c, all of the parts of you and the machinery around you must also interact with each other no faster than the speed of light. That means there can be no greater or "absolute" time standard by which to measure their motions; whatever light does, that becomes the final and *only* meaningful result. Play that idea out against the postulates I just mentioned, and you find that fast motion sort of "sucks out" or makes unavailable a large chunk of the available light velocity needed for your internal systems to move quickly. If you travel at almost exactly c, almost nothing is left of the internal fraction of c needed for atoms to vibrate and clocks to update. As observed by someone else outside of your domain, your time seems to slow to a crawl.
Yet another mystery lurks there, however, since that "just a crawl" analysis applies in *both* directions -- that's why they call it relativity!
But again, that's another story, and I think it's time to draw this answer to a close. | The EM field must remain continuous at the air/water boundary. This can only happen if the frequency stays the same. If the frequency changed there would be a discontinuity oscillating at the difference in the frequencies. |
24,203 | One way how to look at refraction by a dielectric medium like water or glass is that (phase) velocity of light decreases because it is the wavelength rather than the frequency of the light which changes.
I have read somewhere (but can't recall where) that the frequency must remain the same because otherwise principle of causality would be broken. Is that true? | 2012/04/22 | [
"https://physics.stackexchange.com/questions/24203",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/7786/"
] | The EM field must remain continuous at the air/water boundary. This can only happen if the frequency stays the same. If the frequency changed there would be a discontinuity oscillating at the difference in the frequencies. | Here is a tutorial paper on causality and attenuation in classical EM. <http://mesoscopic.mines.edu/~jscales/causality.pdf> The theory applies to any linear response law, but many (famous) EM texts get this wrong or don't explain it well. This was published in the European journal is Physics. Our audience is advanced undergrads and grad students. The physical explanation is easy to understand but the ramifications can be subtle. Keep in mind that in the space-time domain Maxwell's equations are purely real and causality requires response functions such as the electric susceptibility to be non-local. This can be swept under the rug in the Fourier domain, but at some peril for students. |
24,203 | One way how to look at refraction by a dielectric medium like water or glass is that (phase) velocity of light decreases because it is the wavelength rather than the frequency of the light which changes.
I have read somewhere (but can't recall where) that the frequency must remain the same because otherwise principle of causality would be broken. Is that true? | 2012/04/22 | [
"https://physics.stackexchange.com/questions/24203",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/7786/"
] | The conservation of frequency is just the conservation of energy, since $$E=h\nu.$$ | I haven't heard that explanation before, but I imagine that the argument might go something like this. The amplitude of a plane light wave at a frequency *ω* varies like sin(*ωt*). Roughly speaking, when it encounters a medium, the disturbance in the electric field perturbs the electron clouds of the atoms in the medium and makes them oscillate, also at frequency *ω*. The moving charges, in turn, create a disturbance in the electric field, again at frequency *ω*, which becomes part of the propagating wave.
If the frequencies weren't the same, then the charges wouldn't be *following* the electric field; they'd be off doing their own thing. How would they even be supposed to know that the original wave was a sinusoid with a well-defined frequency? Suppose the frequency in the medium *ω*₁ was higher than *ω*, then at time *t* = 0 both the amplitude of the electric field and the perturbation of the electron cloud might start increasing from 0. However, the electron cloud would reach its peak *earlier* and start decreasing, whereas the electric field that was supposed to be driving it wouldn't start decreasing yet! I suppose that could be argued to violate causality.
However, this argument is rubbish; in practice, the response of the medium to an electric field is not linear, and other frequencies are generated when a light wave propagates through a medium. |
24,203 | One way how to look at refraction by a dielectric medium like water or glass is that (phase) velocity of light decreases because it is the wavelength rather than the frequency of the light which changes.
I have read somewhere (but can't recall where) that the frequency must remain the same because otherwise principle of causality would be broken. Is that true? | 2012/04/22 | [
"https://physics.stackexchange.com/questions/24203",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/7786/"
] | Your question extends well beyond electromagnetic phenomena to waves in general. For example, when sound (a pressure wave, which is arguably a lot simpler than an EM wave) moves from air to water, it too undergoes a change in wavelength while retaining the same frequency.
So why in general are wavelengths mutable but frequencies invariant when waves of any type travel between media that change their propagation speed?
It's actually pretty straightforward: It's the only way to keep one wave from "getting ahead" of itself and ending up in the future.
Think of wave cycles as clocks that just happen to be moving, as in those sinusoidal diagrams where you get a sinusoidal wave by projecting a point rotating around a circle onto a moving line. An observer at a distance will see this clock keeping a certain time, say 60 cycles per second, at it travels.
If some segment of that clock then inexplicably started moving at 120 cycles per second, it would literally pull ahead of the other segments in time, counting out new seconds twice as fast as before.
So, while it's unusual to express such issues in terms of causality, there certainly is an aspect of the need for time measurements to stay constant, and that aspect of the situation for any wave does require simple changes in medium *not* to result in changes of frequency.
With all that said, here are two important qualifiers:
(1) You can always create a new clock frequency based on the old one. If you happen to own a green laser pointer, it internally contains a frequency doubler that takes every half wavelength of an infrared laser and converts it to a full wavelength of green light. This does no violate causality for the same reason that adding a second hand to an old-fashioned analog clock does not violate causality: You are simply adding a finer level of measurement to time by breaking up the earlier cycles into smaller ones that still fit within (and do not get ahead of) the larger, earlier cycles.
(2) The trickier point, and one that leads to some interesting issues, is that wave frequencies do change when frames are in motion relative to each other. Such changes are called Doppler shifts: Waves originating in a source that is moving towards the observer, such as the sounds of an approaching ambulance, are perceived as having a higher frequencies than expected, while than waves originated by a source moving away from the observer, such as the ambulance after it has passed by, are perceived as having lower frequencies than expected. That's why I said "an observer at a distance" earlier, so as to avoid immediate consideration of these relative motion effects.
This brings up an interesting point relative to your question: Why don't Doppler shifts undermine causality? Wouldn't the approaching ambulance in effect have a faster "sound clock" than the the one that is moving away from the observer, and so be moving more quickly into the future than an ambulance that has already passed?
The simple and not-very-satisfying answer is that the causality rule I mentioned earlier only applies locally, that is, because sound in the air is in direct contact with sound in the water, the sound in one or the other cannot begin vibrating faster without creating a contradiction at the interface between the two.
That's correct, but again, it's not a terribly satisfying answer. The problem is that once you get into your head a vision of the physical ambulance speaker diaphragms vibrating faster enough to give that higher-pitched sound, it become hard not to wonder whether the entire entire ambulance, including the clocks within it, might not also be "vibrating faster" than you are as long as the ambulance is approaching. We of course know from direct experience when driving and riding in vehicles that this is not the case, since we don't wind up at Grandma's house sooner just because of the Doppler effect makes the vibrations of our voices during the trip sound higher pitched from Grandma's perspective -- assuming Grandma has very, very good hearing! However, some sort of conceptual reconciliation does seem to be needed.
So, let's look at that vibrating speaker diaphragm issue in particular: Does the diagram vibrate faster? Grandma, being a former astrophysicist and have in here possession a particularly find long-range telescope capable of detecting even minute vibrations, watches you travel from her high mountaintop abode. (By all accounts, you have an interesting Grandma.) She observes voice and other vibrations in your vehicle and detects *no* discernible difference from the rates she expects. Yet when she looks at the reading from her equally sophisticated super-sized very-long-distance parabolic microphone (don't say anything bad about Granny while traveling), she hears a higher frequency that does *not* match what she sees in the telescope!
So what in the world is going on here? How can *both* observations be correct?
The trick is that I haven't told you about all of Grandma's data yet. Very shortly after you begin your trip (there is a very small but detectable speed-of-light delay), Grandma sees you begin to move in her direction. With light, that motion seems to be very close to the time she sees, undetectably close with ordinary instruments in fact.
However, she does *not* hear you yet! In fact, a good portion of you journey is over before her microphone picks up any sound at all -- and when it does, it is the sound of the *start* of your journey, much delayed. From that point on the sound plays out as if on fast forward. Remarkably, this accelerated rate works out to be just fast enough to compensate for the lost gap in time, so that by the time you get to Grandma's house, the reality portrayed by light and the reality portrayed by sound are once again in synch, at least as far as human eyes and ears are concerned. Causality is saved, because everything that appeared to be happening *faster* than normal time was in fact just a sort of delayed recording of events that had already happened.
(You can witness this same effect yourself by having someone at the far end of a football field clap very loudly -- cymbals work better! -- and noticing that you *see* them clap before you *hear* them clap. This is exactly the kind of delay Grandma sees with her instruments, only larger and with Doppler effects added.)
What is happening in cases like this, then, is that the "message" conveyed by sound waves is being "bunched up" (technical term) into a shorter sequence that does not arrive until a bit later, leaving a gap of silence.
A useful analysis technique is to analyze the extreme cases of such phenomena, since these often give you a better feel for where the interesting parts are. In this case, imagine driving (or more realistically, flying) towards Grandma's house at just under the speed of sound. What happens then? Well, think about it: It's a horse race, with sound just barely winning and just barely arriving before you do. So, for almost the entire journey, Grandma hears only silence while watching (with some trepidation one would imagine) you fly towards her house at several hundred kilometers per seconds. Only at the very end does she get a burst of sound that represents your *entire* trip towards her house, hugely Doppler shifted so that for example your voices would be in the extreme ranges of ultrasound.
Now with that I'll end, but leave a bit of a tickler for an issue that is beyond the scope of your question.
I mentioned that Grandma, with her very good optical telescope, actually did see a bit of delay in getting images, since of course light is very fast, but not *infinitely* fast. Does that mean that there is a still faster "instantaneous" reality lurking behind the speed of light, one in which all events are exactly synchronized and the light is only giving the appearance of some delay? After all, Doppler effects apply to light too. They are for example the cause the red shift seen in the spectral lines of galaxies that are moving away from us at very high speeds.
So, is the time delay caused by the finite speed of light also an illusion?
Here's the surprising answer: no. A fellow named Einstein notices that in the case of light, there is some kind of absolute cosmic limit going on, and from some early experiments he postulated a very weird idea: Light *always* to travel at the velocity c, or about 300,000 km/s, *no matter how you are moving*. From this simple postulate and [one other](https://physics.stackexchange.com/questions/23991/special-relativity-and-e-mc2/24074#24074) (physics doesn't change when you are moving), he constructed the entire fabric of the special theory of relativity, for which he later received a certain amount of notoriety... :)
Now, here's what interesting about that in the context of your question: For the special case of light, motion *does* have a real impact on clock speeds! That is, you really can construct cases where, with the proper combination of speed and acceleration, you can make one system slower *in reality* than another. This is not abstraction, since for example if you have ever used a GPS navigation system, the proper location of your vehicles *requires* that the slowing of time due to relativity effects (speed and some others from gravity) be taken into account.
Very roughly, here's why: Since nothing travels faster than the speed of light c, all of the parts of you and the machinery around you must also interact with each other no faster than the speed of light. That means there can be no greater or "absolute" time standard by which to measure their motions; whatever light does, that becomes the final and *only* meaningful result. Play that idea out against the postulates I just mentioned, and you find that fast motion sort of "sucks out" or makes unavailable a large chunk of the available light velocity needed for your internal systems to move quickly. If you travel at almost exactly c, almost nothing is left of the internal fraction of c needed for atoms to vibrate and clocks to update. As observed by someone else outside of your domain, your time seems to slow to a crawl.
Yet another mystery lurks there, however, since that "just a crawl" analysis applies in *both* directions -- that's why they call it relativity!
But again, that's another story, and I think it's time to draw this answer to a close. | I haven't heard that explanation before, but I imagine that the argument might go something like this. The amplitude of a plane light wave at a frequency *ω* varies like sin(*ωt*). Roughly speaking, when it encounters a medium, the disturbance in the electric field perturbs the electron clouds of the atoms in the medium and makes them oscillate, also at frequency *ω*. The moving charges, in turn, create a disturbance in the electric field, again at frequency *ω*, which becomes part of the propagating wave.
If the frequencies weren't the same, then the charges wouldn't be *following* the electric field; they'd be off doing their own thing. How would they even be supposed to know that the original wave was a sinusoid with a well-defined frequency? Suppose the frequency in the medium *ω*₁ was higher than *ω*, then at time *t* = 0 both the amplitude of the electric field and the perturbation of the electron cloud might start increasing from 0. However, the electron cloud would reach its peak *earlier* and start decreasing, whereas the electric field that was supposed to be driving it wouldn't start decreasing yet! I suppose that could be argued to violate causality.
However, this argument is rubbish; in practice, the response of the medium to an electric field is not linear, and other frequencies are generated when a light wave propagates through a medium. |
24,203 | One way how to look at refraction by a dielectric medium like water or glass is that (phase) velocity of light decreases because it is the wavelength rather than the frequency of the light which changes.
I have read somewhere (but can't recall where) that the frequency must remain the same because otherwise principle of causality would be broken. Is that true? | 2012/04/22 | [
"https://physics.stackexchange.com/questions/24203",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/7786/"
] | Your question extends well beyond electromagnetic phenomena to waves in general. For example, when sound (a pressure wave, which is arguably a lot simpler than an EM wave) moves from air to water, it too undergoes a change in wavelength while retaining the same frequency.
So why in general are wavelengths mutable but frequencies invariant when waves of any type travel between media that change their propagation speed?
It's actually pretty straightforward: It's the only way to keep one wave from "getting ahead" of itself and ending up in the future.
Think of wave cycles as clocks that just happen to be moving, as in those sinusoidal diagrams where you get a sinusoidal wave by projecting a point rotating around a circle onto a moving line. An observer at a distance will see this clock keeping a certain time, say 60 cycles per second, at it travels.
If some segment of that clock then inexplicably started moving at 120 cycles per second, it would literally pull ahead of the other segments in time, counting out new seconds twice as fast as before.
So, while it's unusual to express such issues in terms of causality, there certainly is an aspect of the need for time measurements to stay constant, and that aspect of the situation for any wave does require simple changes in medium *not* to result in changes of frequency.
With all that said, here are two important qualifiers:
(1) You can always create a new clock frequency based on the old one. If you happen to own a green laser pointer, it internally contains a frequency doubler that takes every half wavelength of an infrared laser and converts it to a full wavelength of green light. This does no violate causality for the same reason that adding a second hand to an old-fashioned analog clock does not violate causality: You are simply adding a finer level of measurement to time by breaking up the earlier cycles into smaller ones that still fit within (and do not get ahead of) the larger, earlier cycles.
(2) The trickier point, and one that leads to some interesting issues, is that wave frequencies do change when frames are in motion relative to each other. Such changes are called Doppler shifts: Waves originating in a source that is moving towards the observer, such as the sounds of an approaching ambulance, are perceived as having a higher frequencies than expected, while than waves originated by a source moving away from the observer, such as the ambulance after it has passed by, are perceived as having lower frequencies than expected. That's why I said "an observer at a distance" earlier, so as to avoid immediate consideration of these relative motion effects.
This brings up an interesting point relative to your question: Why don't Doppler shifts undermine causality? Wouldn't the approaching ambulance in effect have a faster "sound clock" than the the one that is moving away from the observer, and so be moving more quickly into the future than an ambulance that has already passed?
The simple and not-very-satisfying answer is that the causality rule I mentioned earlier only applies locally, that is, because sound in the air is in direct contact with sound in the water, the sound in one or the other cannot begin vibrating faster without creating a contradiction at the interface between the two.
That's correct, but again, it's not a terribly satisfying answer. The problem is that once you get into your head a vision of the physical ambulance speaker diaphragms vibrating faster enough to give that higher-pitched sound, it become hard not to wonder whether the entire entire ambulance, including the clocks within it, might not also be "vibrating faster" than you are as long as the ambulance is approaching. We of course know from direct experience when driving and riding in vehicles that this is not the case, since we don't wind up at Grandma's house sooner just because of the Doppler effect makes the vibrations of our voices during the trip sound higher pitched from Grandma's perspective -- assuming Grandma has very, very good hearing! However, some sort of conceptual reconciliation does seem to be needed.
So, let's look at that vibrating speaker diaphragm issue in particular: Does the diagram vibrate faster? Grandma, being a former astrophysicist and have in here possession a particularly find long-range telescope capable of detecting even minute vibrations, watches you travel from her high mountaintop abode. (By all accounts, you have an interesting Grandma.) She observes voice and other vibrations in your vehicle and detects *no* discernible difference from the rates she expects. Yet when she looks at the reading from her equally sophisticated super-sized very-long-distance parabolic microphone (don't say anything bad about Granny while traveling), she hears a higher frequency that does *not* match what she sees in the telescope!
So what in the world is going on here? How can *both* observations be correct?
The trick is that I haven't told you about all of Grandma's data yet. Very shortly after you begin your trip (there is a very small but detectable speed-of-light delay), Grandma sees you begin to move in her direction. With light, that motion seems to be very close to the time she sees, undetectably close with ordinary instruments in fact.
However, she does *not* hear you yet! In fact, a good portion of you journey is over before her microphone picks up any sound at all -- and when it does, it is the sound of the *start* of your journey, much delayed. From that point on the sound plays out as if on fast forward. Remarkably, this accelerated rate works out to be just fast enough to compensate for the lost gap in time, so that by the time you get to Grandma's house, the reality portrayed by light and the reality portrayed by sound are once again in synch, at least as far as human eyes and ears are concerned. Causality is saved, because everything that appeared to be happening *faster* than normal time was in fact just a sort of delayed recording of events that had already happened.
(You can witness this same effect yourself by having someone at the far end of a football field clap very loudly -- cymbals work better! -- and noticing that you *see* them clap before you *hear* them clap. This is exactly the kind of delay Grandma sees with her instruments, only larger and with Doppler effects added.)
What is happening in cases like this, then, is that the "message" conveyed by sound waves is being "bunched up" (technical term) into a shorter sequence that does not arrive until a bit later, leaving a gap of silence.
A useful analysis technique is to analyze the extreme cases of such phenomena, since these often give you a better feel for where the interesting parts are. In this case, imagine driving (or more realistically, flying) towards Grandma's house at just under the speed of sound. What happens then? Well, think about it: It's a horse race, with sound just barely winning and just barely arriving before you do. So, for almost the entire journey, Grandma hears only silence while watching (with some trepidation one would imagine) you fly towards her house at several hundred kilometers per seconds. Only at the very end does she get a burst of sound that represents your *entire* trip towards her house, hugely Doppler shifted so that for example your voices would be in the extreme ranges of ultrasound.
Now with that I'll end, but leave a bit of a tickler for an issue that is beyond the scope of your question.
I mentioned that Grandma, with her very good optical telescope, actually did see a bit of delay in getting images, since of course light is very fast, but not *infinitely* fast. Does that mean that there is a still faster "instantaneous" reality lurking behind the speed of light, one in which all events are exactly synchronized and the light is only giving the appearance of some delay? After all, Doppler effects apply to light too. They are for example the cause the red shift seen in the spectral lines of galaxies that are moving away from us at very high speeds.
So, is the time delay caused by the finite speed of light also an illusion?
Here's the surprising answer: no. A fellow named Einstein notices that in the case of light, there is some kind of absolute cosmic limit going on, and from some early experiments he postulated a very weird idea: Light *always* to travel at the velocity c, or about 300,000 km/s, *no matter how you are moving*. From this simple postulate and [one other](https://physics.stackexchange.com/questions/23991/special-relativity-and-e-mc2/24074#24074) (physics doesn't change when you are moving), he constructed the entire fabric of the special theory of relativity, for which he later received a certain amount of notoriety... :)
Now, here's what interesting about that in the context of your question: For the special case of light, motion *does* have a real impact on clock speeds! That is, you really can construct cases where, with the proper combination of speed and acceleration, you can make one system slower *in reality* than another. This is not abstraction, since for example if you have ever used a GPS navigation system, the proper location of your vehicles *requires* that the slowing of time due to relativity effects (speed and some others from gravity) be taken into account.
Very roughly, here's why: Since nothing travels faster than the speed of light c, all of the parts of you and the machinery around you must also interact with each other no faster than the speed of light. That means there can be no greater or "absolute" time standard by which to measure their motions; whatever light does, that becomes the final and *only* meaningful result. Play that idea out against the postulates I just mentioned, and you find that fast motion sort of "sucks out" or makes unavailable a large chunk of the available light velocity needed for your internal systems to move quickly. If you travel at almost exactly c, almost nothing is left of the internal fraction of c needed for atoms to vibrate and clocks to update. As observed by someone else outside of your domain, your time seems to slow to a crawl.
Yet another mystery lurks there, however, since that "just a crawl" analysis applies in *both* directions -- that's why they call it relativity!
But again, that's another story, and I think it's time to draw this answer to a close. | The conservation of frequency is just the conservation of energy, since $$E=h\nu.$$ |
24,203 | One way how to look at refraction by a dielectric medium like water or glass is that (phase) velocity of light decreases because it is the wavelength rather than the frequency of the light which changes.
I have read somewhere (but can't recall where) that the frequency must remain the same because otherwise principle of causality would be broken. Is that true? | 2012/04/22 | [
"https://physics.stackexchange.com/questions/24203",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/7786/"
] | The conservation of frequency is just the conservation of energy, since $$E=h\nu.$$ | Here is a tutorial paper on causality and attenuation in classical EM. <http://mesoscopic.mines.edu/~jscales/causality.pdf> The theory applies to any linear response law, but many (famous) EM texts get this wrong or don't explain it well. This was published in the European journal is Physics. Our audience is advanced undergrads and grad students. The physical explanation is easy to understand but the ramifications can be subtle. Keep in mind that in the space-time domain Maxwell's equations are purely real and causality requires response functions such as the electric susceptibility to be non-local. This can be swept under the rug in the Fourier domain, but at some peril for students. |
24,203 | One way how to look at refraction by a dielectric medium like water or glass is that (phase) velocity of light decreases because it is the wavelength rather than the frequency of the light which changes.
I have read somewhere (but can't recall where) that the frequency must remain the same because otherwise principle of causality would be broken. Is that true? | 2012/04/22 | [
"https://physics.stackexchange.com/questions/24203",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/7786/"
] | Your question extends well beyond electromagnetic phenomena to waves in general. For example, when sound (a pressure wave, which is arguably a lot simpler than an EM wave) moves from air to water, it too undergoes a change in wavelength while retaining the same frequency.
So why in general are wavelengths mutable but frequencies invariant when waves of any type travel between media that change their propagation speed?
It's actually pretty straightforward: It's the only way to keep one wave from "getting ahead" of itself and ending up in the future.
Think of wave cycles as clocks that just happen to be moving, as in those sinusoidal diagrams where you get a sinusoidal wave by projecting a point rotating around a circle onto a moving line. An observer at a distance will see this clock keeping a certain time, say 60 cycles per second, at it travels.
If some segment of that clock then inexplicably started moving at 120 cycles per second, it would literally pull ahead of the other segments in time, counting out new seconds twice as fast as before.
So, while it's unusual to express such issues in terms of causality, there certainly is an aspect of the need for time measurements to stay constant, and that aspect of the situation for any wave does require simple changes in medium *not* to result in changes of frequency.
With all that said, here are two important qualifiers:
(1) You can always create a new clock frequency based on the old one. If you happen to own a green laser pointer, it internally contains a frequency doubler that takes every half wavelength of an infrared laser and converts it to a full wavelength of green light. This does no violate causality for the same reason that adding a second hand to an old-fashioned analog clock does not violate causality: You are simply adding a finer level of measurement to time by breaking up the earlier cycles into smaller ones that still fit within (and do not get ahead of) the larger, earlier cycles.
(2) The trickier point, and one that leads to some interesting issues, is that wave frequencies do change when frames are in motion relative to each other. Such changes are called Doppler shifts: Waves originating in a source that is moving towards the observer, such as the sounds of an approaching ambulance, are perceived as having a higher frequencies than expected, while than waves originated by a source moving away from the observer, such as the ambulance after it has passed by, are perceived as having lower frequencies than expected. That's why I said "an observer at a distance" earlier, so as to avoid immediate consideration of these relative motion effects.
This brings up an interesting point relative to your question: Why don't Doppler shifts undermine causality? Wouldn't the approaching ambulance in effect have a faster "sound clock" than the the one that is moving away from the observer, and so be moving more quickly into the future than an ambulance that has already passed?
The simple and not-very-satisfying answer is that the causality rule I mentioned earlier only applies locally, that is, because sound in the air is in direct contact with sound in the water, the sound in one or the other cannot begin vibrating faster without creating a contradiction at the interface between the two.
That's correct, but again, it's not a terribly satisfying answer. The problem is that once you get into your head a vision of the physical ambulance speaker diaphragms vibrating faster enough to give that higher-pitched sound, it become hard not to wonder whether the entire entire ambulance, including the clocks within it, might not also be "vibrating faster" than you are as long as the ambulance is approaching. We of course know from direct experience when driving and riding in vehicles that this is not the case, since we don't wind up at Grandma's house sooner just because of the Doppler effect makes the vibrations of our voices during the trip sound higher pitched from Grandma's perspective -- assuming Grandma has very, very good hearing! However, some sort of conceptual reconciliation does seem to be needed.
So, let's look at that vibrating speaker diaphragm issue in particular: Does the diagram vibrate faster? Grandma, being a former astrophysicist and have in here possession a particularly find long-range telescope capable of detecting even minute vibrations, watches you travel from her high mountaintop abode. (By all accounts, you have an interesting Grandma.) She observes voice and other vibrations in your vehicle and detects *no* discernible difference from the rates she expects. Yet when she looks at the reading from her equally sophisticated super-sized very-long-distance parabolic microphone (don't say anything bad about Granny while traveling), she hears a higher frequency that does *not* match what she sees in the telescope!
So what in the world is going on here? How can *both* observations be correct?
The trick is that I haven't told you about all of Grandma's data yet. Very shortly after you begin your trip (there is a very small but detectable speed-of-light delay), Grandma sees you begin to move in her direction. With light, that motion seems to be very close to the time she sees, undetectably close with ordinary instruments in fact.
However, she does *not* hear you yet! In fact, a good portion of you journey is over before her microphone picks up any sound at all -- and when it does, it is the sound of the *start* of your journey, much delayed. From that point on the sound plays out as if on fast forward. Remarkably, this accelerated rate works out to be just fast enough to compensate for the lost gap in time, so that by the time you get to Grandma's house, the reality portrayed by light and the reality portrayed by sound are once again in synch, at least as far as human eyes and ears are concerned. Causality is saved, because everything that appeared to be happening *faster* than normal time was in fact just a sort of delayed recording of events that had already happened.
(You can witness this same effect yourself by having someone at the far end of a football field clap very loudly -- cymbals work better! -- and noticing that you *see* them clap before you *hear* them clap. This is exactly the kind of delay Grandma sees with her instruments, only larger and with Doppler effects added.)
What is happening in cases like this, then, is that the "message" conveyed by sound waves is being "bunched up" (technical term) into a shorter sequence that does not arrive until a bit later, leaving a gap of silence.
A useful analysis technique is to analyze the extreme cases of such phenomena, since these often give you a better feel for where the interesting parts are. In this case, imagine driving (or more realistically, flying) towards Grandma's house at just under the speed of sound. What happens then? Well, think about it: It's a horse race, with sound just barely winning and just barely arriving before you do. So, for almost the entire journey, Grandma hears only silence while watching (with some trepidation one would imagine) you fly towards her house at several hundred kilometers per seconds. Only at the very end does she get a burst of sound that represents your *entire* trip towards her house, hugely Doppler shifted so that for example your voices would be in the extreme ranges of ultrasound.
Now with that I'll end, but leave a bit of a tickler for an issue that is beyond the scope of your question.
I mentioned that Grandma, with her very good optical telescope, actually did see a bit of delay in getting images, since of course light is very fast, but not *infinitely* fast. Does that mean that there is a still faster "instantaneous" reality lurking behind the speed of light, one in which all events are exactly synchronized and the light is only giving the appearance of some delay? After all, Doppler effects apply to light too. They are for example the cause the red shift seen in the spectral lines of galaxies that are moving away from us at very high speeds.
So, is the time delay caused by the finite speed of light also an illusion?
Here's the surprising answer: no. A fellow named Einstein notices that in the case of light, there is some kind of absolute cosmic limit going on, and from some early experiments he postulated a very weird idea: Light *always* to travel at the velocity c, or about 300,000 km/s, *no matter how you are moving*. From this simple postulate and [one other](https://physics.stackexchange.com/questions/23991/special-relativity-and-e-mc2/24074#24074) (physics doesn't change when you are moving), he constructed the entire fabric of the special theory of relativity, for which he later received a certain amount of notoriety... :)
Now, here's what interesting about that in the context of your question: For the special case of light, motion *does* have a real impact on clock speeds! That is, you really can construct cases where, with the proper combination of speed and acceleration, you can make one system slower *in reality* than another. This is not abstraction, since for example if you have ever used a GPS navigation system, the proper location of your vehicles *requires* that the slowing of time due to relativity effects (speed and some others from gravity) be taken into account.
Very roughly, here's why: Since nothing travels faster than the speed of light c, all of the parts of you and the machinery around you must also interact with each other no faster than the speed of light. That means there can be no greater or "absolute" time standard by which to measure their motions; whatever light does, that becomes the final and *only* meaningful result. Play that idea out against the postulates I just mentioned, and you find that fast motion sort of "sucks out" or makes unavailable a large chunk of the available light velocity needed for your internal systems to move quickly. If you travel at almost exactly c, almost nothing is left of the internal fraction of c needed for atoms to vibrate and clocks to update. As observed by someone else outside of your domain, your time seems to slow to a crawl.
Yet another mystery lurks there, however, since that "just a crawl" analysis applies in *both* directions -- that's why they call it relativity!
But again, that's another story, and I think it's time to draw this answer to a close. | Here is a tutorial paper on causality and attenuation in classical EM. <http://mesoscopic.mines.edu/~jscales/causality.pdf> The theory applies to any linear response law, but many (famous) EM texts get this wrong or don't explain it well. This was published in the European journal is Physics. Our audience is advanced undergrads and grad students. The physical explanation is easy to understand but the ramifications can be subtle. Keep in mind that in the space-time domain Maxwell's equations are purely real and causality requires response functions such as the electric susceptibility to be non-local. This can be swept under the rug in the Fourier domain, but at some peril for students. |
86,171 | So, I've tried all the standard methods. Checked the outlet, which is screw directly into the lath(yeah, is that even up to code?!). Magnet doesn't work, I've got a rare earth magnet, and the plaster is apparently too think to pick it up(it's about an inch thick, so this doesn't make sense). I though to use the window as a base, but from the center line of where a stud would be at the edge of the window, 16 inches from there, there is no stud(I drilled it).
I'm losing my mind on this. | 2016/03/09 | [
"https://diy.stackexchange.com/questions/86171",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/51214/"
] | Digital Voltmeters are very high impedance and can read voltage on a circuit without loading it down. That is how they are designed.
The 40vac you are detecting on one side of the duplex breaker, with the other side turned on, is a static voltage induced on the conductor due to its proximity with another energized conductor. (This is basically how transformers work. One conductor wrapped tightly around another conductor transfers energy into the secondary conductor.) This 40 volts would disappear if you attached a load on the conductor.
This is one time when solenoid style voltmeters are superior since they load the circuit down and the static voltage disappears since it doesn't have enough power to actuate the solenoid.
The 1.45vac detected when they are both turned off is the same effect only very much diminished. Voltage induced by energized conductors nearby.
If you have a solenoid style or a regular voltmeter instead of a DMM then use that to take your readings.
Good luck! | I believe you've accidentally discovered **a pressing and immediate safety problem** you need to fix ASAP. You have a miswired MWBC (*multi-wire branch circuit*) which overloads the neutral wire.
It is very common to wire the disposal and dishwasher as an MWBC - each gets *an opposing pole* of "hot" and they share the neutral. Since they are opposite poles, if both loads are at max, they "cancel each other out" and the neutral handles nothing at all. Very slick. But if they're on the same pole, the neutral handles twice its capacity - danger!
As ArchonOSX points out, that residual voltage is just induced from parallel wires. The 1.45 volts is from being parallel to other wires for a short distance. The 40V indicates a much longer distance - suggesting it's an MWBC run in the same Romex.
How do I know the danger condition exists? Look at your breakers. You have a Square D "Homelite" (HOM) panel - it's the consumer-grade Square D product. You have oddball breakers and this confused your electrician. Let's start at the beginning.
[](https://i.stack.imgur.com/B4kWW.jpg)
Here is what a normal 1-pole breaker looks like. Note it has 1 switch and operates 1 circuit. It is bulky and takes a lot of space. Actually it takes ***one space*** in the panel.
[](https://i.stack.imgur.com/YBs3I.jpg)
Now here's what a 2-pole breaker looks like. It's twice the width - and that's very important! As you know, USA electricity is 240V across its 2 poles, with "neutral" in the middle - 120V from pole to neutral. Panels are designed with a "zigzag" so every other ***space*** is on an opposite pole. A 2-pole breaker like this is guaranteed to be on opposite poles, so 240v across them. Works for stoves and dryers, and it's exactly what you need for an MWBC.
[](https://i.stack.imgur.com/kOZ60.jpg)
OK, but with big houses, panels fill up fast. As a workaround to that problem, they make "tandem" circuit breakers like this which cram 2 circuits into one ***space***. You have a panel full of these. This is legit, but since it occupies one ***space***, it only has access to one *pole*. Both circuits are on the same pole.
Now look at your photo, with the dishwasher and disposal turned off. They are on a tandem, both on the same pole. If they are an MWBC sharing a neutral, that's the bad thing!
How to fix this? First find out if they are an MWBC. Look and see if they share a neutral - check either in the kitchen (one hot being red and the other black is a major clue) or pull the panel cover off and see if there's a red, black, white and bare heading into the same Romex. You can also measure voltage between the dishwasher "hot" and the disposal "hot" - if the difference is 240 volts, the MWBC is wired correctly, if it's 0 volts, it is dangerous.
If it is defective, you have a bigger problem still. Your electrician may have made this mistake more than once. I would search the panel for any other mistakes, particularly with MWBCs.
To fix it, the cheap way is to simply rearrange wires so the MWBC hots are on opposite poles (breakers in adjacent ***spaces***). The right way is to follow th National Electrical Code, which as of 2008 requires\*\* a 2-pole breaker for MWBCs, which also assures the two hots are on opposite poles, preventing this common mistake. On a busy panel like this, how do you find the room? Like this.
[](https://i.stack.imgur.com/hwHdf.jpg)
[Here's the product link for that](http://amzn.to/1R5tkvY). Notice it takes 2 ***spaces***, assuring opposite poles, and gives a tied 2-pole circuit (for your MWBC) in the center, and two single circuits on the outside (for whatever else you displaced.) Like all these breakers, you can get them in a variety of amperages to suit. |
15,478 | I understand that the first BLAST yields almost the same results as blastp. The second time the iterated blast generates different results as it uses different matrix based on our first result.
But I don't understand how exactly the second matrix is generated. | 2014/03/04 | [
"https://biology.stackexchange.com/questions/15478",
"https://biology.stackexchange.com",
"https://biology.stackexchange.com/users/3615/"
] | Ignoring for the moment the question of politics, let's consider the various definitions of the term "invasive species" that are in use. Colautti and MacIsaac write in their discussion of invasive species terminology ([1](http://www.esf.edu/efb/parry/502_reading/colautti2004.pdf)):
>
> The greatest confusion [among the discussed ecological terms]
> surrounds the common term ‘invasive’ and its various derivatives
> (Richardson et al., 2000a). Explicit or implicit definitions for
> ‘invasive’ include: (1) a synonym for ‘nonindigenous’ (e.g. Goodwin et
> al., 1999; Radford &Cousens, 2000); (2) an adjective for native or
> nonindigenous species (NIS) that have colonized natural areas (e.g.
> Burke & Grime, 1996); (3) discrimination of NIS established in
> cultivated habitats (as ‘noninvasive’) from those established in
> natural habitats (e.g. Reichard & Hamilton, 1997); (4) NIS that are
> widespread (e.g. van Clef & Stiles, 2001); or (5) widespread NIS that
> have adverse effects on the invaded habitat (e.g. Davis & Thompson,
> 2000; Mack et al., 2000).
>
>
>
Note that except for #2, all the definitions require that the species is a nonindigenous (non-native) species in the area under consideration. Therefore, while humans may be considered to have been an invasive species for much of our species history, under most definitions of the term **we no longer qualify because** except in a few places (mainly the arctic, antarctic and marine environments, where human presence is minimal) **we are now a native species.**
See also <http://www.smithsonianmag.com/science-nature/are-humans-an-invasive-species-42999965/?no-ist> | I don't think there is a good answer.
1. Many people and organisations do not even consider Homo sapiens when making such lists. Why? Because we have been for millennia a narcissistic species (think about religious narrative). This is similar to non-scientifically talking about animals. Homo sapiens is usually implicitly excluded from considerations.
2. Although Homo sapiens is present on all continents apart from Antarctica, Homo as a genus has been present for millions of years in Eurasia. Homo erectus has been there particularly long. Homo sapiens has outcompeted these species.
3. Ecosystems do change. Whether or not Homo sapiens is sufficiently long to be a native species is not a well posed question. Any answer would depend on arbitrary cutoffs. For instance if the first migration of Homo sapiens to Americas happened 14k years ago and it took 20 years per generation, then Americas are populated *only* for 700 generations. Is it a lot or is it little?
4. However, there are places in the world (mostly islands) where Homo sapiens settled very recently. Mauritius was first settled in 1638. And it is clear that since then many bird species (not only the famous dodo) went extinct and most of the area was converted from forests to sugar cane fields and towns. So yes, in this case there is no doubt the migration was recent and that it drastically changed the ecosystem, therefore it fulfils the definition.
5. Pragmatism. Probably the most important of it. We define invasive species for a reason: to give them a negative connotation and possibly plan a future removal. Doing these actions against humans are completely different from the legal point.
To sum up: a external observer would classify humans as an invasive species in at least some regions (Mauritius) and not in other (Africa south of Sahara). But people don't classify themselves as such because of political, moral, legal and pragmatic reasons. |
549,065 | I am absolutely confused about trying to calculate circumference. And I do not mean using the math formula, I mean back in old days when people had very primitive tools, and had to make the discoveries.
In order to create a circle you can take a long strip of paper and try to fold it into a circle. By knowing paper's length you can know circumference. However how would you go about putting the piece of paper into perfect circle to measure the diameter? No matter what you do you might be just a millimeter off while trying to measure the diameter.
Now let's say you take a compass and draw a circle. You will be able to easily measure the diameter, however you will not be able to fold a strip of paper into a perfect circle, again it might be just a millimeter off.
Third way I can think of they used is to first draw a square inside and outside of the circle you draw with compass. Then you changes it into pentagon, then hexagon and so forth and use math to try to find the circumference. But again I think it does not allow you to calculate with perfect precision (no calculators, primitive age).
Due to that no matter what you do you will not be able to perfectly derive formulas to calculate circumference if given diameter or vice versa. So how exactly did the people derive these formulas and make perfect circles with all the values know and discover pi?
Sorry I tried searching but didn't find anything. I would really love to know the answer. | 2013/11/02 | [
"https://math.stackexchange.com/questions/549065",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/22529/"
] | As to your assumption that they would never be able to shape it perfectly into a circle, suppose you had a circular block of wood. You cut a piece of paper slightly longer than the circumference, wrapped it around the wood, and drew a line on the paper using the circle as a guideline. Now you measure the length of the line. This would be trickier than it sounds, but it would be possible with the material they had, and would be very accurate. | The question asked is related, I guess, to that of the Portolan Charts and how they could have been drawn so accurately. It was not just a matter in those days of just 'taking' a compass rose. They had to draw one. And there was no square paper or spreadsheet programs. My answer would be that it is because of the amazing regularity of the 'behavior'of numbers that they found their way.
I have watched the building of a traditional house in an African country, which started out by fixing a pole in the ground. To that pole was attached another pole, with a ring at one end, which fit just around the central pole, while the other end was used to measure the distance of the (mud) bricks to the central pole. After one layer of bricks had been laid, the pole was placed on a support of one brick high, etc., which shows the use of the radius to the circumference. |
16,653,180 | I need some help. I've few MySQL queries and I need to "translate" it into ElasticSearch syntax.
There are different kind of querys, easy "selects", and others with Join's that I think it's not possible to translate it.
What is best thing I can do?
Regards. | 2013/05/20 | [
"https://Stackoverflow.com/questions/16653180",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/1728678/"
] | The best thing I can recommend is read up about ElasticSearch and rethink the whole thing. Usually when modelling data for a search engine/NOSQL is not the same as modelling it for a RDB. Understanding the concept is my best advice here. No quick fix.
Books and sources I recommend.
[ElasticSearch Server](https://rads.stackoverflow.com/amzn/click/com/1849518440)
[NoSQL Distilled](https://rads.stackoverflow.com/amzn/click/com/0321826620)
[ElasticSearch.org](http://elasticsearch.org)
Hope that helps you on the way. But like I said no real quick fix or translation table to do what you want. | The SQL data mapping to ElasticSearch can be done easily with:
1.Proper Data Modelling by de-normalization based on your query requirements
2.If still want have relationships without re-indexing then Parent-Child Realtionship
<https://www.elastic.co/guide/en/elasticsearch/guide/current/parent-child.html>
Thanks,
Vishu |
10,443,596 | I'm using the Asana API and the "opt\_expand=." option when reading all the tasks in a project. It returns me a lot of information but not the tags. Is there a way to read the tags associated with a task? | 2012/05/04 | [
"https://Stackoverflow.com/questions/10443596",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/184164/"
] | (I work for Asana)
The API does not expose tags yet, but it is high on our list of features to add. | Asana's API now has Tag support (added June 19, 2012) <https://asana.com/developers/api-reference/tags> |
27,243,850 | Is it possible to use material design themes for versions below Android 5.0?
According to [this link](https://developer.android.com/design/material/index.html), it is not the case:
>
> Material design is a comprehensive guide for visual, motion, and
> interaction design across platforms and devices. Android now includes
> support for material design apps. To use material design in your
> Android apps, follow the guidelines defined in the material design
> specification and use the new components and functionality available
> in Android 5.0 (API level 21) and above.
>
>
> | 2014/12/02 | [
"https://Stackoverflow.com/questions/27243850",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/4314611/"
] | You can use the support library to have some of features in older versions as well as mentioned in below link:-
<https://developer.android.com/training/material/compatibility.html>
also as mentioned below you can visit this link as well:-
<http://android-developers.blogspot.in/2014/10/appcompat-v21-material-design-for-pre.html> | You can use AppCompat as stated here: <http://android-developers.blogspot.com/2014/10/appcompat-v21-material-design-for-pre.html>
Everything you are asking for is in that link. cheers :) |
27,243,850 | Is it possible to use material design themes for versions below Android 5.0?
According to [this link](https://developer.android.com/design/material/index.html), it is not the case:
>
> Material design is a comprehensive guide for visual, motion, and
> interaction design across platforms and devices. Android now includes
> support for material design apps. To use material design in your
> Android apps, follow the guidelines defined in the material design
> specification and use the new components and functionality available
> in Android 5.0 (API level 21) and above.
>
>
> | 2014/12/02 | [
"https://Stackoverflow.com/questions/27243850",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/4314611/"
] | You can use the support library to have some of features in older versions as well as mentioned in below link:-
<https://developer.android.com/training/material/compatibility.html>
also as mentioned below you can visit this link as well:-
<http://android-developers.blogspot.in/2014/10/appcompat-v21-material-design-for-pre.html> | Yes it is possible to use material design themes below android 5.0. U can follow this link to see backward compatibility [link](https://developer.android.com/training/material/compatibility.html)
and to learn more about material design use this
[link](https://developer.android.com/training/material/get-started.html) |
27,243,850 | Is it possible to use material design themes for versions below Android 5.0?
According to [this link](https://developer.android.com/design/material/index.html), it is not the case:
>
> Material design is a comprehensive guide for visual, motion, and
> interaction design across platforms and devices. Android now includes
> support for material design apps. To use material design in your
> Android apps, follow the guidelines defined in the material design
> specification and use the new components and functionality available
> in Android 5.0 (API level 21) and above.
>
>
> | 2014/12/02 | [
"https://Stackoverflow.com/questions/27243850",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/4314611/"
] | You can use the support library to have some of features in older versions as well as mentioned in below link:-
<https://developer.android.com/training/material/compatibility.html>
also as mentioned below you can visit this link as well:-
<http://android-developers.blogspot.in/2014/10/appcompat-v21-material-design-for-pre.html> | Use AppCompat lib as stated in other comments and
One of the best examples of using material compatibility is.
<https://github.com/tekinarslan/AndroidMaterialDesignToolbar> |
54,412 | According to [Impact Nottingham](https://impactnottingham.com/2023/02/east-palestine-ohio-exploring-the-worst-environmental-disaster-in-the-history-of-the-usa/):
>
> East Palestine, Ohio: Exploring The Worst Environmental Disaster in
> the History of the USA
>
>
> On 3rd February 2023, a freight train carrying various potentially
> hazardous chemicals derailed in the town of East Palestine in Ohio,
> USA. This tragic environmental disaster is causing the residents of
> East Palestine to fear for their safety, as well as that of the town’s
> water and air. Thomas Martin explores the aftermath of the event, and
> solutions to prevent incidents like in the future.
>
>
>
A similar notion is echoed by [activist Erin Brockovich](https://thehill.com/homenews/state-watch/3871176-erin-brockovich-east-palestine-a-disaster-like-one-ive-never-seen/):
>
> Environmental activist Erin Brockovich has called the derailment of a
> train carrying hazardous chemicals in East Palestine, Ohio, earlier
> this month a disaster “like one I’ve never seen.”
>
>
> Brockovich, who discovered that groundwater contamination from Pacific
> Gas and Electric Company was sickening residents in the small town of
> Hinkley, Calif., in the 1990s, told “CNN This Morning” that the East
> Palestine incident feels reminiscent of the disastrous Hinkley case.
>
>
>
Is it true that the [East Palestine train derailment](https://en.wikipedia.org/wiki/2023_Ohio_train_derailment) can be considered the "worst environmental disaster in US history"? | 2023/02/24 | [
"https://skeptics.stackexchange.com/questions/54412",
"https://skeptics.stackexchange.com",
"https://skeptics.stackexchange.com/users/23144/"
] | It certainly was a nasty disaster, but the worst environmental disaster in US history? That is extremely dubious. That claim is just newsies and others wanting to get top headlines. Think back to the [Exxon Valdez oil spill](https://darrp.noaa.gov/oil-spills/exxon-valdez), the [Three Mile Island disaster](https://en.wikipedia.org/wiki/Three_Mile_Island_accident), the [Dust Bowl](https://houstonpbs.pbslearningmedia.org/resource/ecological-disaster-ken-burns-dust-bowl/ken-burns-the-dust-bowl/), [Love Canal](https://cumulis.epa.gov/supercpad/SiteProfiles/index.cfm?fuseaction=second.cleanup&id=0201290), the [BP Deepwater Horizon oil spill](https://www.epa.gov/enforcement/deepwater-horizon-bp-gulf-mexico-oil-spill), and the list goes on and on. We won't know the full extent of the damage from the East Palestine train derailment for years. To immediately call it the worst environmental disaster in US history is at best premature, and more likely is plain old headline-grabbing newsiness. | While it is somewhat a matter of opinion what disaster was worst, there are clear examples that were much worse. I'll just mention one.
The 1944 liquefied natural gas tank [explosion](https://Cleveland%20East%20Ohio%20Gas%20explosion), also in Ohio:
About 131 dead.
79 houses and 2 factories destroyed.
[](https://i.stack.imgur.com/YSTJ7.jpg)
[Image source](https://www.cleveland.com/metro/2014/10/east_ohio_gas_explosion_70_yea.html) |
54,412 | According to [Impact Nottingham](https://impactnottingham.com/2023/02/east-palestine-ohio-exploring-the-worst-environmental-disaster-in-the-history-of-the-usa/):
>
> East Palestine, Ohio: Exploring The Worst Environmental Disaster in
> the History of the USA
>
>
> On 3rd February 2023, a freight train carrying various potentially
> hazardous chemicals derailed in the town of East Palestine in Ohio,
> USA. This tragic environmental disaster is causing the residents of
> East Palestine to fear for their safety, as well as that of the town’s
> water and air. Thomas Martin explores the aftermath of the event, and
> solutions to prevent incidents like in the future.
>
>
>
A similar notion is echoed by [activist Erin Brockovich](https://thehill.com/homenews/state-watch/3871176-erin-brockovich-east-palestine-a-disaster-like-one-ive-never-seen/):
>
> Environmental activist Erin Brockovich has called the derailment of a
> train carrying hazardous chemicals in East Palestine, Ohio, earlier
> this month a disaster “like one I’ve never seen.”
>
>
> Brockovich, who discovered that groundwater contamination from Pacific
> Gas and Electric Company was sickening residents in the small town of
> Hinkley, Calif., in the 1990s, told “CNN This Morning” that the East
> Palestine incident feels reminiscent of the disastrous Hinkley case.
>
>
>
Is it true that the [East Palestine train derailment](https://en.wikipedia.org/wiki/2023_Ohio_train_derailment) can be considered the "worst environmental disaster in US history"? | 2023/02/24 | [
"https://skeptics.stackexchange.com/questions/54412",
"https://skeptics.stackexchange.com",
"https://skeptics.stackexchange.com/users/23144/"
] | It certainly was a nasty disaster, but the worst environmental disaster in US history? That is extremely dubious. That claim is just newsies and others wanting to get top headlines. Think back to the [Exxon Valdez oil spill](https://darrp.noaa.gov/oil-spills/exxon-valdez), the [Three Mile Island disaster](https://en.wikipedia.org/wiki/Three_Mile_Island_accident), the [Dust Bowl](https://houstonpbs.pbslearningmedia.org/resource/ecological-disaster-ken-burns-dust-bowl/ken-burns-the-dust-bowl/), [Love Canal](https://cumulis.epa.gov/supercpad/SiteProfiles/index.cfm?fuseaction=second.cleanup&id=0201290), the [BP Deepwater Horizon oil spill](https://www.epa.gov/enforcement/deepwater-horizon-bp-gulf-mexico-oil-spill), and the list goes on and on. We won't know the full extent of the damage from the East Palestine train derailment for years. To immediately call it the worst environmental disaster in US history is at best premature, and more likely is plain old headline-grabbing newsiness. | Apparently not by number of animals killed either.
The estimate I [found](https://eu.usatoday.com/story/news/nation/2023/02/24/east-palestine-train-derailment-fish-animal-deaths/11337404002/) for East Palestine is 43,000 animals killed, mostly minnows.
In comparison, the Deepwater Horizon spill killed [some](https://www.fisheries.noaa.gov/national/marine-life-distress/sea-turtles-dolphins-and-whales-10-years-after-deepwater-horizon-oil#:%7E:text=An%20estimated%204%2C900%E2%80%937%2C600%20large,on%20sea%20turtle%20nesting%20beaches.) "56,000–166,000 small juvenile sea turtles" and smaller number of other animals.
(And yeah, some other press headlines declared DH the ["biggest"](https://www.vice.com/en/article/884z93/the-biggest-environmental-disaster-in-us-history-never-really-ended) or ["worst"](https://www.deccanherald.com/content/75657/oil-spill-worst-environmental-disaster.html) environmental disaster in US history, FWTW. DH also features at #2 (behind the Nevada Test Site) in a certain [listicle](https://owlcation.com/stem/-Ten-Worst-Man-Made-Environmental-Disasters-in-American-History), but like with many such pieces, there's no clear criteria given for the ranking.)
OTOH, a CNN piece title "The Gulf spill: America's worst environmental disaster?" [says](http://edition.cnn.com/2010/US/08/05/gulf.worst.disaster/index.html):
>
> Disasters are hard to rank and tricky to compare, historians say, but they cite several calamities that rival or surpass the [DH] Gulf oil spill in terms of lives lost or affected.
>
>
> In 1889, for example, a poorly maintained dam collapsed, sending a wall of water crashing through Johnstown, Pennsylvania. The flood killed over 2,200 people and destroyed 1,600 homes.
>
>
> Historians also cite what happened in blue-collar community of Love Canal, New York, which was built atop more than 20,000 tons of chemical waste and linked to high rates of cancer and birth defects. Hundreds of families were ultimately forced to flee.
>
>
> In terms of permanently disrupting a way of life for the largest number of Americans, historians say, nothing compares to the 1930s Dust Bowl, a slow-motion disaster sparked by years of shortsighted farming practices and serious drought. Native grasses across the country's heartland were torn up, leaving little to hold the topsoil in place. When the winds kicked up, dust storms turning the sky black could be seen as far away as New York City. About 2.5 million people fled the Dust Bowl in one of the largest migrations in U.S. history. Families abandoned countless farms. That devastated the region's agriculture economy. [...]
>
>
> In 1910 and 1911, though, more oil spilled onto land in California as a result of the Lakeview Gusher, the consequence of a 1910 well explosion in California's Central Valley. Nearly 380 million gallons are believed to have spilled over nearly a year and a half. That spill, though, directly affected relatively few people and had "a less complicated ecological impact," [Brian Black, an environmental historian at Penn State] said.
>
>
> Fewer people may have been affected by Love Canal than by the Gulf spill, but petroleum is "not quite as corruptive as the toxins were at Love Canal," Black said; chemicals and radioactive materials can pose a potentially greater long term risk.
>
>
> The bottom line: it's tough to rank environmental calamities.
>
>
> "We can't appreciate the magnitude of (some disasters) until their results and implications have had time to play out," Black said.
>
>
> |
54,412 | According to [Impact Nottingham](https://impactnottingham.com/2023/02/east-palestine-ohio-exploring-the-worst-environmental-disaster-in-the-history-of-the-usa/):
>
> East Palestine, Ohio: Exploring The Worst Environmental Disaster in
> the History of the USA
>
>
> On 3rd February 2023, a freight train carrying various potentially
> hazardous chemicals derailed in the town of East Palestine in Ohio,
> USA. This tragic environmental disaster is causing the residents of
> East Palestine to fear for their safety, as well as that of the town’s
> water and air. Thomas Martin explores the aftermath of the event, and
> solutions to prevent incidents like in the future.
>
>
>
A similar notion is echoed by [activist Erin Brockovich](https://thehill.com/homenews/state-watch/3871176-erin-brockovich-east-palestine-a-disaster-like-one-ive-never-seen/):
>
> Environmental activist Erin Brockovich has called the derailment of a
> train carrying hazardous chemicals in East Palestine, Ohio, earlier
> this month a disaster “like one I’ve never seen.”
>
>
> Brockovich, who discovered that groundwater contamination from Pacific
> Gas and Electric Company was sickening residents in the small town of
> Hinkley, Calif., in the 1990s, told “CNN This Morning” that the East
> Palestine incident feels reminiscent of the disastrous Hinkley case.
>
>
>
Is it true that the [East Palestine train derailment](https://en.wikipedia.org/wiki/2023_Ohio_train_derailment) can be considered the "worst environmental disaster in US history"? | 2023/02/24 | [
"https://skeptics.stackexchange.com/questions/54412",
"https://skeptics.stackexchange.com",
"https://skeptics.stackexchange.com/users/23144/"
] | I'm just going to use Wikipedia for this because the claim is obviously hyperbole.
This is East Palestine:
<https://en.wikipedia.org/wiki/2023_Ohio_train_derailment>
>
> Of the 51 derailed cars, 11 of them were tank cars which dumped 100,000 gallons of hazardous materials, including vinyl chloride, benzene residue, and butyl acrylate.
>
>
>
Approximately 100 tons of hazardous material was released in a town of 5000 people. So far, no casualties.
This is Love Canal:
<https://en.wikipedia.org/wiki/Love_Canal>
>
> During the 1940s, the canal was purchased by Hooker Chemical Company, which used the site to dump 19,800 t (19,500 long tons; 21,800 short tons) of chemical byproducts from the manufacturing of dyes, perfumes, and solvents for rubber and synthetic resins.
>
>
>
Approximately 20000 tons of hazardous material was released in a city of 50000 people. Three thousand people lived directly on a hazardous waste landfill including a school with hundreds of children. Extensively documented health effects.
This is Buffalo Creek:
<https://en.wikipedia.org/wiki/Buffalo_Creek_flood>
>
> The resulting flood unleashed approximately 132 million US gallons (500,000 cubic metres; 500 million litres) of black waste water, cresting over 30 feet (9.1 m) high, upon the residents of 16 coal towns along Buffalo Creek Hollow. Out of a population of 5,000 people, 125 were killed,[5] 1,121 were injured, and over 4,000 were left homeless
>
>
>
I don't even think East Palestine is the worst currently ongoing environmental disaster in the United States, either in impact or potential scope. I could provide probably hundreds of counterexamples in addition to these two. | While it is somewhat a matter of opinion what disaster was worst, there are clear examples that were much worse. I'll just mention one.
The 1944 liquefied natural gas tank [explosion](https://Cleveland%20East%20Ohio%20Gas%20explosion), also in Ohio:
About 131 dead.
79 houses and 2 factories destroyed.
[](https://i.stack.imgur.com/YSTJ7.jpg)
[Image source](https://www.cleveland.com/metro/2014/10/east_ohio_gas_explosion_70_yea.html) |
54,412 | According to [Impact Nottingham](https://impactnottingham.com/2023/02/east-palestine-ohio-exploring-the-worst-environmental-disaster-in-the-history-of-the-usa/):
>
> East Palestine, Ohio: Exploring The Worst Environmental Disaster in
> the History of the USA
>
>
> On 3rd February 2023, a freight train carrying various potentially
> hazardous chemicals derailed in the town of East Palestine in Ohio,
> USA. This tragic environmental disaster is causing the residents of
> East Palestine to fear for their safety, as well as that of the town’s
> water and air. Thomas Martin explores the aftermath of the event, and
> solutions to prevent incidents like in the future.
>
>
>
A similar notion is echoed by [activist Erin Brockovich](https://thehill.com/homenews/state-watch/3871176-erin-brockovich-east-palestine-a-disaster-like-one-ive-never-seen/):
>
> Environmental activist Erin Brockovich has called the derailment of a
> train carrying hazardous chemicals in East Palestine, Ohio, earlier
> this month a disaster “like one I’ve never seen.”
>
>
> Brockovich, who discovered that groundwater contamination from Pacific
> Gas and Electric Company was sickening residents in the small town of
> Hinkley, Calif., in the 1990s, told “CNN This Morning” that the East
> Palestine incident feels reminiscent of the disastrous Hinkley case.
>
>
>
Is it true that the [East Palestine train derailment](https://en.wikipedia.org/wiki/2023_Ohio_train_derailment) can be considered the "worst environmental disaster in US history"? | 2023/02/24 | [
"https://skeptics.stackexchange.com/questions/54412",
"https://skeptics.stackexchange.com",
"https://skeptics.stackexchange.com/users/23144/"
] | I'm just going to use Wikipedia for this because the claim is obviously hyperbole.
This is East Palestine:
<https://en.wikipedia.org/wiki/2023_Ohio_train_derailment>
>
> Of the 51 derailed cars, 11 of them were tank cars which dumped 100,000 gallons of hazardous materials, including vinyl chloride, benzene residue, and butyl acrylate.
>
>
>
Approximately 100 tons of hazardous material was released in a town of 5000 people. So far, no casualties.
This is Love Canal:
<https://en.wikipedia.org/wiki/Love_Canal>
>
> During the 1940s, the canal was purchased by Hooker Chemical Company, which used the site to dump 19,800 t (19,500 long tons; 21,800 short tons) of chemical byproducts from the manufacturing of dyes, perfumes, and solvents for rubber and synthetic resins.
>
>
>
Approximately 20000 tons of hazardous material was released in a city of 50000 people. Three thousand people lived directly on a hazardous waste landfill including a school with hundreds of children. Extensively documented health effects.
This is Buffalo Creek:
<https://en.wikipedia.org/wiki/Buffalo_Creek_flood>
>
> The resulting flood unleashed approximately 132 million US gallons (500,000 cubic metres; 500 million litres) of black waste water, cresting over 30 feet (9.1 m) high, upon the residents of 16 coal towns along Buffalo Creek Hollow. Out of a population of 5,000 people, 125 were killed,[5] 1,121 were injured, and over 4,000 were left homeless
>
>
>
I don't even think East Palestine is the worst currently ongoing environmental disaster in the United States, either in impact or potential scope. I could provide probably hundreds of counterexamples in addition to these two. | Apparently not by number of animals killed either.
The estimate I [found](https://eu.usatoday.com/story/news/nation/2023/02/24/east-palestine-train-derailment-fish-animal-deaths/11337404002/) for East Palestine is 43,000 animals killed, mostly minnows.
In comparison, the Deepwater Horizon spill killed [some](https://www.fisheries.noaa.gov/national/marine-life-distress/sea-turtles-dolphins-and-whales-10-years-after-deepwater-horizon-oil#:%7E:text=An%20estimated%204%2C900%E2%80%937%2C600%20large,on%20sea%20turtle%20nesting%20beaches.) "56,000–166,000 small juvenile sea turtles" and smaller number of other animals.
(And yeah, some other press headlines declared DH the ["biggest"](https://www.vice.com/en/article/884z93/the-biggest-environmental-disaster-in-us-history-never-really-ended) or ["worst"](https://www.deccanherald.com/content/75657/oil-spill-worst-environmental-disaster.html) environmental disaster in US history, FWTW. DH also features at #2 (behind the Nevada Test Site) in a certain [listicle](https://owlcation.com/stem/-Ten-Worst-Man-Made-Environmental-Disasters-in-American-History), but like with many such pieces, there's no clear criteria given for the ranking.)
OTOH, a CNN piece title "The Gulf spill: America's worst environmental disaster?" [says](http://edition.cnn.com/2010/US/08/05/gulf.worst.disaster/index.html):
>
> Disasters are hard to rank and tricky to compare, historians say, but they cite several calamities that rival or surpass the [DH] Gulf oil spill in terms of lives lost or affected.
>
>
> In 1889, for example, a poorly maintained dam collapsed, sending a wall of water crashing through Johnstown, Pennsylvania. The flood killed over 2,200 people and destroyed 1,600 homes.
>
>
> Historians also cite what happened in blue-collar community of Love Canal, New York, which was built atop more than 20,000 tons of chemical waste and linked to high rates of cancer and birth defects. Hundreds of families were ultimately forced to flee.
>
>
> In terms of permanently disrupting a way of life for the largest number of Americans, historians say, nothing compares to the 1930s Dust Bowl, a slow-motion disaster sparked by years of shortsighted farming practices and serious drought. Native grasses across the country's heartland were torn up, leaving little to hold the topsoil in place. When the winds kicked up, dust storms turning the sky black could be seen as far away as New York City. About 2.5 million people fled the Dust Bowl in one of the largest migrations in U.S. history. Families abandoned countless farms. That devastated the region's agriculture economy. [...]
>
>
> In 1910 and 1911, though, more oil spilled onto land in California as a result of the Lakeview Gusher, the consequence of a 1910 well explosion in California's Central Valley. Nearly 380 million gallons are believed to have spilled over nearly a year and a half. That spill, though, directly affected relatively few people and had "a less complicated ecological impact," [Brian Black, an environmental historian at Penn State] said.
>
>
> Fewer people may have been affected by Love Canal than by the Gulf spill, but petroleum is "not quite as corruptive as the toxins were at Love Canal," Black said; chemicals and radioactive materials can pose a potentially greater long term risk.
>
>
> The bottom line: it's tough to rank environmental calamities.
>
>
> "We can't appreciate the magnitude of (some disasters) until their results and implications have had time to play out," Black said.
>
>
> |
54,412 | According to [Impact Nottingham](https://impactnottingham.com/2023/02/east-palestine-ohio-exploring-the-worst-environmental-disaster-in-the-history-of-the-usa/):
>
> East Palestine, Ohio: Exploring The Worst Environmental Disaster in
> the History of the USA
>
>
> On 3rd February 2023, a freight train carrying various potentially
> hazardous chemicals derailed in the town of East Palestine in Ohio,
> USA. This tragic environmental disaster is causing the residents of
> East Palestine to fear for their safety, as well as that of the town’s
> water and air. Thomas Martin explores the aftermath of the event, and
> solutions to prevent incidents like in the future.
>
>
>
A similar notion is echoed by [activist Erin Brockovich](https://thehill.com/homenews/state-watch/3871176-erin-brockovich-east-palestine-a-disaster-like-one-ive-never-seen/):
>
> Environmental activist Erin Brockovich has called the derailment of a
> train carrying hazardous chemicals in East Palestine, Ohio, earlier
> this month a disaster “like one I’ve never seen.”
>
>
> Brockovich, who discovered that groundwater contamination from Pacific
> Gas and Electric Company was sickening residents in the small town of
> Hinkley, Calif., in the 1990s, told “CNN This Morning” that the East
> Palestine incident feels reminiscent of the disastrous Hinkley case.
>
>
>
Is it true that the [East Palestine train derailment](https://en.wikipedia.org/wiki/2023_Ohio_train_derailment) can be considered the "worst environmental disaster in US history"? | 2023/02/24 | [
"https://skeptics.stackexchange.com/questions/54412",
"https://skeptics.stackexchange.com",
"https://skeptics.stackexchange.com/users/23144/"
] | Apparently not by number of animals killed either.
The estimate I [found](https://eu.usatoday.com/story/news/nation/2023/02/24/east-palestine-train-derailment-fish-animal-deaths/11337404002/) for East Palestine is 43,000 animals killed, mostly minnows.
In comparison, the Deepwater Horizon spill killed [some](https://www.fisheries.noaa.gov/national/marine-life-distress/sea-turtles-dolphins-and-whales-10-years-after-deepwater-horizon-oil#:%7E:text=An%20estimated%204%2C900%E2%80%937%2C600%20large,on%20sea%20turtle%20nesting%20beaches.) "56,000–166,000 small juvenile sea turtles" and smaller number of other animals.
(And yeah, some other press headlines declared DH the ["biggest"](https://www.vice.com/en/article/884z93/the-biggest-environmental-disaster-in-us-history-never-really-ended) or ["worst"](https://www.deccanherald.com/content/75657/oil-spill-worst-environmental-disaster.html) environmental disaster in US history, FWTW. DH also features at #2 (behind the Nevada Test Site) in a certain [listicle](https://owlcation.com/stem/-Ten-Worst-Man-Made-Environmental-Disasters-in-American-History), but like with many such pieces, there's no clear criteria given for the ranking.)
OTOH, a CNN piece title "The Gulf spill: America's worst environmental disaster?" [says](http://edition.cnn.com/2010/US/08/05/gulf.worst.disaster/index.html):
>
> Disasters are hard to rank and tricky to compare, historians say, but they cite several calamities that rival or surpass the [DH] Gulf oil spill in terms of lives lost or affected.
>
>
> In 1889, for example, a poorly maintained dam collapsed, sending a wall of water crashing through Johnstown, Pennsylvania. The flood killed over 2,200 people and destroyed 1,600 homes.
>
>
> Historians also cite what happened in blue-collar community of Love Canal, New York, which was built atop more than 20,000 tons of chemical waste and linked to high rates of cancer and birth defects. Hundreds of families were ultimately forced to flee.
>
>
> In terms of permanently disrupting a way of life for the largest number of Americans, historians say, nothing compares to the 1930s Dust Bowl, a slow-motion disaster sparked by years of shortsighted farming practices and serious drought. Native grasses across the country's heartland were torn up, leaving little to hold the topsoil in place. When the winds kicked up, dust storms turning the sky black could be seen as far away as New York City. About 2.5 million people fled the Dust Bowl in one of the largest migrations in U.S. history. Families abandoned countless farms. That devastated the region's agriculture economy. [...]
>
>
> In 1910 and 1911, though, more oil spilled onto land in California as a result of the Lakeview Gusher, the consequence of a 1910 well explosion in California's Central Valley. Nearly 380 million gallons are believed to have spilled over nearly a year and a half. That spill, though, directly affected relatively few people and had "a less complicated ecological impact," [Brian Black, an environmental historian at Penn State] said.
>
>
> Fewer people may have been affected by Love Canal than by the Gulf spill, but petroleum is "not quite as corruptive as the toxins were at Love Canal," Black said; chemicals and radioactive materials can pose a potentially greater long term risk.
>
>
> The bottom line: it's tough to rank environmental calamities.
>
>
> "We can't appreciate the magnitude of (some disasters) until their results and implications have had time to play out," Black said.
>
>
> | While it is somewhat a matter of opinion what disaster was worst, there are clear examples that were much worse. I'll just mention one.
The 1944 liquefied natural gas tank [explosion](https://Cleveland%20East%20Ohio%20Gas%20explosion), also in Ohio:
About 131 dead.
79 houses and 2 factories destroyed.
[](https://i.stack.imgur.com/YSTJ7.jpg)
[Image source](https://www.cleveland.com/metro/2014/10/east_ohio_gas_explosion_70_yea.html) |
26,946 | I'm really a total newbie to this, so excuse the basicness (?) of the question.
I have a default installation of Windows Server 2003, and I want to test an e-mailing application.
1. **What's the process for setting up an SMTP server on that box?** Does Windows Server 2003 provide one, or can I install a free one? Which one?
2. I want to test my app in terms of delivering the e-mail to the SMTP server, but I don't actually need the e-mails to go out. **Is there a way to have the SMTP server behave as it normally would, except just don't send out the e-mails?**
cheers
andy | 2009/06/17 | [
"https://serverfault.com/questions/26946",
"https://serverfault.com",
"https://serverfault.com/users/39171/"
] | 1. As Matt alluded to, use the "Manage Your Server" screen to add the SMTP role as per [these instructions](http://www.ilopia.com/Articles/WindowsServer2003/EmailServer.aspx).
2. You could use Windows Firewall on that server to block all outgoing traffic over port 25. Better yet, block all outbound port 25 traffic from your server's IP address at the gateway's firewall. This keeps you from crippling the server's network connection completely.
You could read up a bit on SMTP security on Windows Server 2003 with the following Microsoft KB Article 324285 (sorry, you'll have to find that one on your own; Server Fault only allows new users to post one URL per post). That article shows that you can grant or deny access to the SMTP virtual server based on IP addresses. This could be yet another alternative way of restricting mail flow to only those few places that you want to allow. | You can setup the Windows Server 2003 with the Mail Server role. It comes with Windows, so in a sense it is free (as in you already paid for it).
If you give the server a bad gateway ip then it cannot send any emails, and you can check everything you need to on your LAN.
Being new be very careful. I would check heavily into security for Windows Server 2003 especially in regards to email. This could make an excellent vector of attack against you. |
2,203,906 | I've been using the MVP pattern for a while with ASP.NET. I've stuck to the defined pattern of raising presenter events from the view.
It has struck me that I could expose methods in the presenter that the view could call directly.
Technically, using direct methods calls would require less code. The other benefit is that I tend to share presenters across multiple views that offer similar functionality. This means that sometimes some of the event handlers are forced to be registered in a view, only to comply with the shared presenter's interface, but then are not used in that particular view at all.
A example of this would be a diary view, that in one view allows you to cancel an appointment, and in another it doesn't. The rest of the presenter events for loading the data, and saving an appointment are used in both. I don't want to write two separate presenters that almost offer the same functionality.
I'd like to hear what others think who are actively using MVP. Are there any reasons you can think of why direct method calls from the view to the presenter are bad in MVP? | 2010/02/04 | [
"https://Stackoverflow.com/questions/2203906",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/119624/"
] | I use direct method calls, and don't see any worhtwhile reason to be defining events on the presenter. What you are using with events is called I believe "Observing Presenter" style. It does offer complete decoupling of View from Presenter, but with added complexity. | If your view calls the presenter directly, then it would be tightly coupled like in mvc. I don't understand why some frameworks take this approach as opposed to raising events on the view. |
2,203,906 | I've been using the MVP pattern for a while with ASP.NET. I've stuck to the defined pattern of raising presenter events from the view.
It has struck me that I could expose methods in the presenter that the view could call directly.
Technically, using direct methods calls would require less code. The other benefit is that I tend to share presenters across multiple views that offer similar functionality. This means that sometimes some of the event handlers are forced to be registered in a view, only to comply with the shared presenter's interface, but then are not used in that particular view at all.
A example of this would be a diary view, that in one view allows you to cancel an appointment, and in another it doesn't. The rest of the presenter events for loading the data, and saving an appointment are used in both. I don't want to write two separate presenters that almost offer the same functionality.
I'd like to hear what others think who are actively using MVP. Are there any reasons you can think of why direct method calls from the view to the presenter are bad in MVP? | 2010/02/04 | [
"https://Stackoverflow.com/questions/2203906",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/119624/"
] | I use direct method calls, and don't see any worhtwhile reason to be defining events on the presenter. What you are using with events is called I believe "Observing Presenter" style. It does offer complete decoupling of View from Presenter, but with added complexity. | We can write an interface which contains all methods that we want to call from view. Presenter will implement this interface. We can then pass instance of this interface to view, and view can call methods on this interface. This will reduce coupling between two. |
35,701 | I have a number of projects that could benefit from JavaScript. I've seen a lot of "Oh, you can use JavaScript for that!", but little detail about how and where that's done. Does the script live on a server somewhere or is it just embeded with a cut-and-paste via the "edit HTML source" button?
Looking for some guidance on the best place within the sites/farms from which to run scripting. | 2012/05/08 | [
"https://sharepoint.stackexchange.com/questions/35701",
"https://sharepoint.stackexchange.com",
"https://sharepoint.stackexchange.com/users/7360/"
] | The best approach is to create a Scripts document library, preferably with versioning enabled to store your JavaScript files. Then on the pages you'd like to use them, add a Content Editor web part to the page and use the link box to point to your javascript files. | Here are a couple resources you may find useful:
[The SharePoint & jQuery Guide](http://sharepointhillbilly.com/Lists/Posts/Post.aspx?ID=16)
[SharePoint Client-Side Development with the JSOM and jQuery](https://vimeo.com/29124752) |
35,701 | I have a number of projects that could benefit from JavaScript. I've seen a lot of "Oh, you can use JavaScript for that!", but little detail about how and where that's done. Does the script live on a server somewhere or is it just embeded with a cut-and-paste via the "edit HTML source" button?
Looking for some guidance on the best place within the sites/farms from which to run scripting. | 2012/05/08 | [
"https://sharepoint.stackexchange.com/questions/35701",
"https://sharepoint.stackexchange.com",
"https://sharepoint.stackexchange.com/users/7360/"
] | Technically, the scripts can reside anywhere as long as the users have read access to them.
In practice, client side solutions usually have a short lifecycle, and you'll certainly want to place them in a location that you can easily update. A good option is the Style Library within a site collection, which has the added benefit of caching the files. If you have internet access, you could also consider using a CDN to call popular files (like jQuery.js).
On the pages themselves, you can add the scripts to either the master page or via a Web Part, depending on the scope of your customization. Here are some explanations from my blog if you use Web Parts:
<http://blog.pathtosharepoint.com/2010/10/27/about-scripts-web-parts-and-urban-myths/>
[Update] I just came across this fresh article:
<http://techtrainingnotes.blogspot.com/2012/05/adding-javascript-and-css-to-sharepoint.html>
Note that the above links only show some basics. There are several more ways to include scripts, especially if you work with Master pages. | The best approach is to create a Scripts document library, preferably with versioning enabled to store your JavaScript files. Then on the pages you'd like to use them, add a Content Editor web part to the page and use the link box to point to your javascript files. |
35,701 | I have a number of projects that could benefit from JavaScript. I've seen a lot of "Oh, you can use JavaScript for that!", but little detail about how and where that's done. Does the script live on a server somewhere or is it just embeded with a cut-and-paste via the "edit HTML source" button?
Looking for some guidance on the best place within the sites/farms from which to run scripting. | 2012/05/08 | [
"https://sharepoint.stackexchange.com/questions/35701",
"https://sharepoint.stackexchange.com",
"https://sharepoint.stackexchange.com/users/7360/"
] | There are several ways to add JavaScript to SharePoint. You could add directly or reference it into the masterpage, page layout, code behind etc.. The script lives always on a server, because it serves it.
Keep in mind that JavaScript is different language to learn and can be very powerful. Therefor I recommend learning it:
<http://www.codecademy.com> (Nice website where you can learn the fundamentals)
<https://developer.mozilla.org/en/JavaScript/Guide> (Very comprehensive information)
Besides learning the language it's recommended to place JavaScript into files, so you can reuse and manage your code. The **Style Library** is a good place for the \*.js files, also such as for the style sheets (css). Besides learning JavaScript I would also recommend to have a look at jQuery. | Here are a couple resources you may find useful:
[The SharePoint & jQuery Guide](http://sharepointhillbilly.com/Lists/Posts/Post.aspx?ID=16)
[SharePoint Client-Side Development with the JSOM and jQuery](https://vimeo.com/29124752) |
35,701 | I have a number of projects that could benefit from JavaScript. I've seen a lot of "Oh, you can use JavaScript for that!", but little detail about how and where that's done. Does the script live on a server somewhere or is it just embeded with a cut-and-paste via the "edit HTML source" button?
Looking for some guidance on the best place within the sites/farms from which to run scripting. | 2012/05/08 | [
"https://sharepoint.stackexchange.com/questions/35701",
"https://sharepoint.stackexchange.com",
"https://sharepoint.stackexchange.com/users/7360/"
] | Technically, the scripts can reside anywhere as long as the users have read access to them.
In practice, client side solutions usually have a short lifecycle, and you'll certainly want to place them in a location that you can easily update. A good option is the Style Library within a site collection, which has the added benefit of caching the files. If you have internet access, you could also consider using a CDN to call popular files (like jQuery.js).
On the pages themselves, you can add the scripts to either the master page or via a Web Part, depending on the scope of your customization. Here are some explanations from my blog if you use Web Parts:
<http://blog.pathtosharepoint.com/2010/10/27/about-scripts-web-parts-and-urban-myths/>
[Update] I just came across this fresh article:
<http://techtrainingnotes.blogspot.com/2012/05/adding-javascript-and-css-to-sharepoint.html>
Note that the above links only show some basics. There are several more ways to include scripts, especially if you work with Master pages. | There are several ways to add JavaScript to SharePoint. You could add directly or reference it into the masterpage, page layout, code behind etc.. The script lives always on a server, because it serves it.
Keep in mind that JavaScript is different language to learn and can be very powerful. Therefor I recommend learning it:
<http://www.codecademy.com> (Nice website where you can learn the fundamentals)
<https://developer.mozilla.org/en/JavaScript/Guide> (Very comprehensive information)
Besides learning the language it's recommended to place JavaScript into files, so you can reuse and manage your code. The **Style Library** is a good place for the \*.js files, also such as for the style sheets (css). Besides learning JavaScript I would also recommend to have a look at jQuery. |
35,701 | I have a number of projects that could benefit from JavaScript. I've seen a lot of "Oh, you can use JavaScript for that!", but little detail about how and where that's done. Does the script live on a server somewhere or is it just embeded with a cut-and-paste via the "edit HTML source" button?
Looking for some guidance on the best place within the sites/farms from which to run scripting. | 2012/05/08 | [
"https://sharepoint.stackexchange.com/questions/35701",
"https://sharepoint.stackexchange.com",
"https://sharepoint.stackexchange.com/users/7360/"
] | Technically, the scripts can reside anywhere as long as the users have read access to them.
In practice, client side solutions usually have a short lifecycle, and you'll certainly want to place them in a location that you can easily update. A good option is the Style Library within a site collection, which has the added benefit of caching the files. If you have internet access, you could also consider using a CDN to call popular files (like jQuery.js).
On the pages themselves, you can add the scripts to either the master page or via a Web Part, depending on the scope of your customization. Here are some explanations from my blog if you use Web Parts:
<http://blog.pathtosharepoint.com/2010/10/27/about-scripts-web-parts-and-urban-myths/>
[Update] I just came across this fresh article:
<http://techtrainingnotes.blogspot.com/2012/05/adding-javascript-and-css-to-sharepoint.html>
Note that the above links only show some basics. There are several more ways to include scripts, especially if you work with Master pages. | Here are a couple resources you may find useful:
[The SharePoint & jQuery Guide](http://sharepointhillbilly.com/Lists/Posts/Post.aspx?ID=16)
[SharePoint Client-Side Development with the JSOM and jQuery](https://vimeo.com/29124752) |
13,861,128 | Basically I create dump file:
1. Under debug : VC10 Debug->Save dump as...
2. Under release: Procexp->right click -> Save dump -> Create Full Dump...
Via 1, I can open the dump file with VC10 (symbol path, Debug source file all setup properly), I can see all the stack information with source code as well as the value of all variable .
Via 2, I can open the dump file with VC10 (symbol path, Debug source file all setup properly), I can see all the stack information with source code **BUT** values of all variable are not there.
Even if I put the local variable into Debug Watch window,it says Error: Symbol "xxx" not found.
How should I fix this for 2?
**How did my setup the dump debugging?**
**For symbol path:**
Action->Set symbol paths -> add pdb path for Debug & Release folder for my project as well as using Microsoft Symbol Servers.
**For Debug Source path:**
Dump project solution -> Property-> Debug Source Files -> Add my project file folder
BTW: For the same dump file, I have also used WinDbg and I can see all the stack information as well(after setting symbol and source path correctly).
Thanks | 2012/12/13 | [
"https://Stackoverflow.com/questions/13861128",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/833538/"
] | A debug build is a build that ensures you'll get the best possible debugging experience. Looking at local variables is not a problem.
A release build turns on the code optimizer. It does *many* things to your code, but definitely the first victim are local variables. They may get entirely removed or stored in CPU registers. If you really do need to know the value of such a local variable then you typically need to look at the machine code to figure out what cpu register stores it. This will however never work if this is in code that's buried down the stack trace, the value would have been pushed onto the stack somewhere. Finding out where is next to impossible.
Debugging optimized code is hard, no two ways about it. Get the bugs out with the debug build, Hail Mary on the release build. | Thanks for all the nice inputs but I think I have found the reason myself today!
**Reason**: It was a build issue,some components the exe need to use have not been build properly !
**Note**: In my case "*mini dump*" 7M and "*full dump*" 112M does the same job, both created from procexp. And once I load them in VS I have access to:
1. All the stack information
2. All the variable information
3. It pinpoints to the exactly location once I switch stack to my code
from kernel32.dll!\_UnhandleExceptionFiler.
So essentially as long as you set up VC10 like I did above & below, you should be fine:
**For symbol path:**
Action->Set symbol paths -> add pdb path for Debug & Release folder for my project as well as using Microsoft Symbol Servers.
**For Debug Source path:**
Dump project solution -> Property-> Debug Source Files -> Add my project file folder |
67,432 | My understanding is that Masters and PhD students often need to TA -- even if they're already research assistants to a professor.
I'm a first year undergraduate who took courses heavily TA-reliant last semester. My impression is that my TAs (oh they were helpful people) don't really get much out of TAing. The job just covers some of their costs and their tuition.
Sure, you may learn a bit about teaching others, but I doubt that you may learn much after three weeks of doing so. Many of the users on this site were once or are TAs. Do you agree with my view?
If TAing is really a necessary evil, are there better ways to fund your education? | 2016/04/22 | [
"https://academia.stackexchange.com/questions/67432",
"https://academia.stackexchange.com",
"https://academia.stackexchange.com/users/52075/"
] | It may be necessary; some universities require students to TA even if they have other sources of funding. It need not be evil. It depends on your attitude (do you want to help students learn?) and which faculty you are working with (Do they care if you help students? Do they care if you learn something yourself?). Unfortunately you usually do not get to chose who you work with. TAs (and also faculty) should receive training in how to teach, but may not.
There are many other ways to fund education, some of which pay better than being a TA, and some of which are more prestigious. They all have limited supply. | I understand that it might often be thought that one learns little more after TA'ing for a few weeks, or a year, or a few years.
However, I strongly disagree. I have seen no cases where anyone came to a profound understanding of the psychology of 18/20-year-olds even after years of dealing with them. Nor understanding the complicated, self-contradictory goals of lower-division mathematics. Nor... Many research-oriented people in math never do quite catch on, although the norm is an uneasy truce with the seemingly-ineffable realities.
I truly think that until one can nearly-effortlessly do a bit (of course, hours within some limits...) of TA'ing, one has not understood the situation of academic mathematicians, and does not understand the job itself. (The "research" aspect has its own invidious pitfalls, but/and these are fairly different, perhaps opposite, from those of TA'ing.) |
67,432 | My understanding is that Masters and PhD students often need to TA -- even if they're already research assistants to a professor.
I'm a first year undergraduate who took courses heavily TA-reliant last semester. My impression is that my TAs (oh they were helpful people) don't really get much out of TAing. The job just covers some of their costs and their tuition.
Sure, you may learn a bit about teaching others, but I doubt that you may learn much after three weeks of doing so. Many of the users on this site were once or are TAs. Do you agree with my view?
If TAing is really a necessary evil, are there better ways to fund your education? | 2016/04/22 | [
"https://academia.stackexchange.com/questions/67432",
"https://academia.stackexchange.com",
"https://academia.stackexchange.com/users/52075/"
] | It may be necessary; some universities require students to TA even if they have other sources of funding. It need not be evil. It depends on your attitude (do you want to help students learn?) and which faculty you are working with (Do they care if you help students? Do they care if you learn something yourself?). Unfortunately you usually do not get to chose who you work with. TAs (and also faculty) should receive training in how to teach, but may not.
There are many other ways to fund education, some of which pay better than being a TA, and some of which are more prestigious. They all have limited supply. | Sometimes? Here's my notion of when it's evil: When a department admits a ton of graduate students it has no particular inclination to mentor much less graduate because without a steady stream of TAs it can't keep its undergrad classrooms staffed. Been there, did that, burned out.
For Ph.D candidates intending to teach, TAships are not intrinsically evil; well-run (not a guarantee, sadly), they are straight-up job training. |
67,432 | My understanding is that Masters and PhD students often need to TA -- even if they're already research assistants to a professor.
I'm a first year undergraduate who took courses heavily TA-reliant last semester. My impression is that my TAs (oh they were helpful people) don't really get much out of TAing. The job just covers some of their costs and their tuition.
Sure, you may learn a bit about teaching others, but I doubt that you may learn much after three weeks of doing so. Many of the users on this site were once or are TAs. Do you agree with my view?
If TAing is really a necessary evil, are there better ways to fund your education? | 2016/04/22 | [
"https://academia.stackexchange.com/questions/67432",
"https://academia.stackexchange.com",
"https://academia.stackexchange.com/users/52075/"
] | It may be necessary; some universities require students to TA even if they have other sources of funding. It need not be evil. It depends on your attitude (do you want to help students learn?) and which faculty you are working with (Do they care if you help students? Do they care if you learn something yourself?). Unfortunately you usually do not get to chose who you work with. TAs (and also faculty) should receive training in how to teach, but may not.
There are many other ways to fund education, some of which pay better than being a TA, and some of which are more prestigious. They all have limited supply. | I think TAing helps in evolving a graduate student's character. Teaches him/her how to plan courses, interact with students and enhance public speaking/presentation skills. Its the another road "step" into academia (other than research). Perhaps that why it is necessary in many schools even for those appointed with full research funding.
What I don't like about the current system is that TAs tend to teach the same course over and over again! It gets boring and many loses motivation. Also, there can be many grey and shady areas between professors and TAs/graders. For instance, professors asking TAs to do the bulk of the work, being available for extra office hours, write exams, update notes etc. In such cases, TAs tend to agree to these things "most can't even say No!". |
67,432 | My understanding is that Masters and PhD students often need to TA -- even if they're already research assistants to a professor.
I'm a first year undergraduate who took courses heavily TA-reliant last semester. My impression is that my TAs (oh they were helpful people) don't really get much out of TAing. The job just covers some of their costs and their tuition.
Sure, you may learn a bit about teaching others, but I doubt that you may learn much after three weeks of doing so. Many of the users on this site were once or are TAs. Do you agree with my view?
If TAing is really a necessary evil, are there better ways to fund your education? | 2016/04/22 | [
"https://academia.stackexchange.com/questions/67432",
"https://academia.stackexchange.com",
"https://academia.stackexchange.com/users/52075/"
] | I understand that it might often be thought that one learns little more after TA'ing for a few weeks, or a year, or a few years.
However, I strongly disagree. I have seen no cases where anyone came to a profound understanding of the psychology of 18/20-year-olds even after years of dealing with them. Nor understanding the complicated, self-contradictory goals of lower-division mathematics. Nor... Many research-oriented people in math never do quite catch on, although the norm is an uneasy truce with the seemingly-ineffable realities.
I truly think that until one can nearly-effortlessly do a bit (of course, hours within some limits...) of TA'ing, one has not understood the situation of academic mathematicians, and does not understand the job itself. (The "research" aspect has its own invidious pitfalls, but/and these are fairly different, perhaps opposite, from those of TA'ing.) | I think TAing helps in evolving a graduate student's character. Teaches him/her how to plan courses, interact with students and enhance public speaking/presentation skills. Its the another road "step" into academia (other than research). Perhaps that why it is necessary in many schools even for those appointed with full research funding.
What I don't like about the current system is that TAs tend to teach the same course over and over again! It gets boring and many loses motivation. Also, there can be many grey and shady areas between professors and TAs/graders. For instance, professors asking TAs to do the bulk of the work, being available for extra office hours, write exams, update notes etc. In such cases, TAs tend to agree to these things "most can't even say No!". |
67,432 | My understanding is that Masters and PhD students often need to TA -- even if they're already research assistants to a professor.
I'm a first year undergraduate who took courses heavily TA-reliant last semester. My impression is that my TAs (oh they were helpful people) don't really get much out of TAing. The job just covers some of their costs and their tuition.
Sure, you may learn a bit about teaching others, but I doubt that you may learn much after three weeks of doing so. Many of the users on this site were once or are TAs. Do you agree with my view?
If TAing is really a necessary evil, are there better ways to fund your education? | 2016/04/22 | [
"https://academia.stackexchange.com/questions/67432",
"https://academia.stackexchange.com",
"https://academia.stackexchange.com/users/52075/"
] | Sometimes? Here's my notion of when it's evil: When a department admits a ton of graduate students it has no particular inclination to mentor much less graduate because without a steady stream of TAs it can't keep its undergrad classrooms staffed. Been there, did that, burned out.
For Ph.D candidates intending to teach, TAships are not intrinsically evil; well-run (not a guarantee, sadly), they are straight-up job training. | I think TAing helps in evolving a graduate student's character. Teaches him/her how to plan courses, interact with students and enhance public speaking/presentation skills. Its the another road "step" into academia (other than research). Perhaps that why it is necessary in many schools even for those appointed with full research funding.
What I don't like about the current system is that TAs tend to teach the same course over and over again! It gets boring and many loses motivation. Also, there can be many grey and shady areas between professors and TAs/graders. For instance, professors asking TAs to do the bulk of the work, being available for extra office hours, write exams, update notes etc. In such cases, TAs tend to agree to these things "most can't even say No!". |
1,474 | As you might know, Preview has a lossy rotation feature.
Could you please recommend a tool that allows images rotation in a lossless way? | 2010/09/12 | [
"https://apple.stackexchange.com/questions/1474",
"https://apple.stackexchange.com",
"https://apple.stackexchange.com/users/725/"
] | The only true lossless rotation for images would be a file format that allows you to save the image in its original format, and then specify what angle it will be rotated to when displayed on screen.
One program which can do this is [InkScape](http://inkscape.org/download/). It will allow you to [import](http://tavmjong.free.fr/INKSCAPE/MANUAL/html/File-Import.html) (and embed) an image, and then rotate it. You can then rotate the image to any angle, as many times as you like without causing any loss of quality. | I’m not sure what you mean by “loussy rotation feature” but you can always try other more advanced graphic suites like:
[Acorn](http://flyingmeat.com/acorn/) (Has a free more limited version that could be enough)
[Pixelmator](http://www.pixelmator.com/)
[The Father of All… Photoshop](http://www.photoshop.com/)
For what is worth, I don’t think Preview has a loussy rotation feature. If you rotate an image and then rotate it back, the result is the same as before any rotation; loussy would be if pixels were lost in the rotation to a point where going back to the exact same image could not be possible. |
1,474 | As you might know, Preview has a lossy rotation feature.
Could you please recommend a tool that allows images rotation in a lossless way? | 2010/09/12 | [
"https://apple.stackexchange.com/questions/1474",
"https://apple.stackexchange.com",
"https://apple.stackexchange.com/users/725/"
] | The only true lossless rotation for images would be a file format that allows you to save the image in its original format, and then specify what angle it will be rotated to when displayed on screen.
One program which can do this is [InkScape](http://inkscape.org/download/). It will allow you to [import](http://tavmjong.free.fr/INKSCAPE/MANUAL/html/File-Import.html) (and embed) an image, and then rotate it. You can then rotate the image to any angle, as many times as you like without causing any loss of quality. | I use [wine](http://braumeister.org/formula/wine) (and [XQuartz](http://xquartz.macosforge.org/trac/wiki)) and [IrfanView](http://www.irfanview.com/).
 |
89,451 | The company I work for has a contract with a consulting firm to manage ERP functions. This relationship with the consulting firm has been ongoing for at least five years. Over that time, we've always had one specific consultant that is assigned to our account. Most of our dealings with the consulting firm is done through this individual. We work closely with them to solve problems and complete tasks.
I've only been with the company for three years, but over time I've noticed that our lead consultant speaks slower and slower. He will pause after every two or three words, take a moment, give me a long drawn out "uhhhhhmmmm" before continuing for another two or three words, rinse and repeat. This makes communication very slow and frustrating for everyone involved. I know this because our staff discusses it from time to time. For the most part, I've just put up with it. I assume it's likely a medical disability or some speech impediment.
This creates a major problem for me. I have full responsibility to assign tasks for the consulting firm and to sign their invoices. I've noticed that perhaps we do not receive the full benefit of their services, and their work has been a bit under par. I'm not exaggerating when I say a sentence that I could say in perhaps 4 to 5 seconds could literally take our lead consultant 75 to 90 seconds to say. Their rate is almost 200 USD/hr. Before, my frustration just came from my impatience and this slowing me down, having to talk to him for much longer that I think is appropriate. But now I'm starting to get emotional when I see the amount of time it takes for them to do something and how much I'm paying for him to stammer and say "umm" for 80% of the time.
Normally I feel like I can suppress my frustration pretty well, but this morning I lashed out a bit while on the phone with him. I said "C'mon man, get it out, I've got things to do". I felt ugly, and I'm not proud of that, but it's obvious to me now that this is a much bigger issue than I thought and something needs to be done.
My question is, what are my options? Is there something wrong with me? Do I need to learn more patience? Should I talk to him? Ensure that he is getting speech therapy that they need? Should I have the consulting firm adjust their rate to accommodate the time difference? Should I discuss with the consulting firm and request a new consultant? Should I cancel the contract and move on to a new consulting firm?
**Update**: I apologized later that same morning in a private face to face discussion. | 2017/04/19 | [
"https://workplace.stackexchange.com/questions/89451",
"https://workplace.stackexchange.com",
"https://workplace.stackexchange.com/users/27494/"
] | It would probably help to generally discuss it with the consulting firm, in a way as positive as possible. I assume you don't want to get him fired, but you need some positive change of the situation.
You are of course in no position to require to know about his medical details. If you don't feel close enough to talk to this person themselves about the problem, then you should not feel entitled to suggest any type of therapy (they might already get).
In the end, you are paying for his time. If you do not feel you get your money's worth anymore, you need this to be discussed, even if it is based on a disability.
Lashing out for sure is not going to help the situation. In case it is a speech impairment the pressure and stress might very well make it worse.
Consider the time you worked with him. Has his insight been valuable to you? What is the reason you and your colleagues have put up with the problem so far? Then you might not want to loose that.
Discuss different ways of communication, and potentially a lower billing for time spent with vocal communication (but probably not for his general work).
If there is no reason to put up with it, you are of course free to request a different consultant or change the firm completely. | You can do one of two, possibly three things.
1. Apologise to the account manager and put up with the slow speech.
2. Ask the firm for a new account manager.
3. Cut ties and find a new firm to work with.
***It's not your fault you got impatient but you probably shouldn't have lashed out like you did, but it's also not their fault either***. You have work to get done and you may be against deadlines however they might have developed an issue with their speech in which case can't be helped and they might be trying their best.
*On the flip side they may just be bored and not interested in the work or conversation and not putting any effort into what they're doing, in which case you may want to find a new account manager or new firm*. It's up to you what you want to do with this situation really, whatever you feel happy doing.
You could talk to the account manager and apologise and talk it through and explain your stance on the situation but I'd advise against it because there's too many variables for that to potentially work out well for the both of you without wires being crossed and it turning into negativity.
Assess the situation right now and decide if this company is worth working with and whether you'd benefit from a new account manager or talking it through with the current one to resolve the situation between the two of you. |
8,268 | We have a page where a user can see a list of products. This list is quite large, so initially, we don't show the list. The user can enter a search term, click 'search', and the correct products are shown.
Sometimes, a user will want to see all products.
How would you best implement this? Any popular examples?
Options we have:
* user can enter an empty search term en click 'search' (might not be as intuitive)
* a seperate button 'show all' (which clutters the UI more) | 2011/06/17 | [
"https://ux.stackexchange.com/questions/8268",
"https://ux.stackexchange.com",
"https://ux.stackexchange.com/users/6045/"
] | You've kind of given a clue to the answer in the question - **Sometimes** a user will want to see all products.
Don't bother the user with making them think about whether they want to see all the results even before they've done the search and before they know how many results you are talking about.
Only when you have displayed some results, do you then want the user to be able to decide if/how they want to refine the search.
If there's only a few results, then don't even show the 'Show all' button. If there's lots of results (as you suggest there is in this instance) then show a manageable number and indicate how many out of the total are being displayed. At this point you can show the 'show all' button.
If the result is very very big you maybe don't want to give the option to 'show all' at all (unmanageable).
Once the user has an idea of the number shown and the total number, (and maybe of how paginated pages this corresponds to) they have the required information to be able to answer the question '*Do I want to see all the results at once - or is it more manageable to look at a page at a time?*'.
Ideally, like eBay and some Amazon pages, you can also give an option to specify how many items can appear on each page - make this setting remembered between sessions if possible as it would automatically provide the 'number of items that the user is comfortable viewing at once'.
For a great example (and not just in **my** opinion), see www.JohnLewis.com - eg searching for sofas <http://bit.ly/kUSAaR>
JohnLewis were ranked top in the 2010 Ecommerce Usability for high street retailers (report here <http://bit.ly/lAiZcp>) | I'm kind of with Archie, but it depends on the purpose of the list. If the user knows - before they search - that they want to see all the items, give them the option of a button then. Or default all items to shown and allow the user to filter (as opposed to search - same thing technically, but slightly different connotation linguistically).
Alternatively, I would suggest just having a button that is shown once search results are on display. I'd imagine (well, speaking from experience) that - depending on the context of the list - people will probably try to search and maybe only invoke the "Show All" if they don't initially find what they're looking for. |
8,268 | We have a page where a user can see a list of products. This list is quite large, so initially, we don't show the list. The user can enter a search term, click 'search', and the correct products are shown.
Sometimes, a user will want to see all products.
How would you best implement this? Any popular examples?
Options we have:
* user can enter an empty search term en click 'search' (might not be as intuitive)
* a seperate button 'show all' (which clutters the UI more) | 2011/06/17 | [
"https://ux.stackexchange.com/questions/8268",
"https://ux.stackexchange.com",
"https://ux.stackexchange.com/users/6045/"
] | You've kind of given a clue to the answer in the question - **Sometimes** a user will want to see all products.
Don't bother the user with making them think about whether they want to see all the results even before they've done the search and before they know how many results you are talking about.
Only when you have displayed some results, do you then want the user to be able to decide if/how they want to refine the search.
If there's only a few results, then don't even show the 'Show all' button. If there's lots of results (as you suggest there is in this instance) then show a manageable number and indicate how many out of the total are being displayed. At this point you can show the 'show all' button.
If the result is very very big you maybe don't want to give the option to 'show all' at all (unmanageable).
Once the user has an idea of the number shown and the total number, (and maybe of how paginated pages this corresponds to) they have the required information to be able to answer the question '*Do I want to see all the results at once - or is it more manageable to look at a page at a time?*'.
Ideally, like eBay and some Amazon pages, you can also give an option to specify how many items can appear on each page - make this setting remembered between sessions if possible as it would automatically provide the 'number of items that the user is comfortable viewing at once'.
For a great example (and not just in **my** opinion), see www.JohnLewis.com - eg searching for sofas <http://bit.ly/kUSAaR>
JohnLewis were ranked top in the 2010 Ecommerce Usability for high street retailers (report here <http://bit.ly/lAiZcp>) | I reckon you may be looking for some sort of "faceted search" where what you initially show the user is e.g. "Latest products". The user can then change the search filter by selecting "All products" etc. A bit like the left-hand side panel on the Google results page, showing "The web" or "Pages from ..." (click "More search tools" to see more examples) |
191,039 | In deploying to a new (Solaris 9) environment recently, one of the steps was to copy a set of files and directories to their new location and then to apply the group UID bit (using "chmod -R g+s") to all files in the directory tree giving a mode of -rwxr-s--- to everything. The result was that none of our shell scripts would execute unless they were individually opened and re-saved. I should add that we had earlier set g+s on the target parent folder prior to copying files; this had set the initial mode on all the new directories to drwxr-s--- but the files had a mode of -rwxr-x---
Having eventually discovered which step caused the problem, we were able to cut out that step and proceed.
I would like, however, to understand what the "s" bit means when applied to directories and files, in the hope that this will explain why we had the problem in the first place. | 2008/10/10 | [
"https://Stackoverflow.com/questions/191039",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/26790/"
] | Here is very handy explanation of SGID (chmod g+s): <http://www.linuxnix.com/sgid-set-sgid-linuxunix/>
>
> SGID (Set Group ID up on execution) is a special type of file
> permissions given to a file/folder. Normally in Linux/Unix when a
> program runs, it inherits access permissions from the logged in user.
> SGID is defined as giving temporary permissions to a user to run a
> program/file with the permissions of the file group permissions to
> become member of that group to execute the file. In simple words users
> will get file Group’s permissions when executing a
> Folder/file/program/command.
>
>
> | When you need to use it: Fix SVN file ownership issue when you use svn+ssh. Somebody told me it only happens on BDB, but I had such issue in FSFS storage too. Basically when you want to keep the ownership of child files inside a directory consistent when there are other users writing stuff on it, you would have to use u+s/g+s. |
191,039 | In deploying to a new (Solaris 9) environment recently, one of the steps was to copy a set of files and directories to their new location and then to apply the group UID bit (using "chmod -R g+s") to all files in the directory tree giving a mode of -rwxr-s--- to everything. The result was that none of our shell scripts would execute unless they were individually opened and re-saved. I should add that we had earlier set g+s on the target parent folder prior to copying files; this had set the initial mode on all the new directories to drwxr-s--- but the files had a mode of -rwxr-x---
Having eventually discovered which step caused the problem, we were able to cut out that step and proceed.
I would like, however, to understand what the "s" bit means when applied to directories and files, in the hope that this will explain why we had the problem in the first place. | 2008/10/10 | [
"https://Stackoverflow.com/questions/191039",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/26790/"
] | For executable files, this means that when the file is executed, it is executed as the group that owns the file, not the group of the user executing the file.
This is useful if you want users to be able to assume the permissions of a particular group just for running one command.
However, it is also a security risk as it is allowing users to elevate their permissions. You have to know that the scripts with this bit set aren't going to do anything that would let users abuse these extra permissions. | When you need to use it: Fix SVN file ownership issue when you use svn+ssh. Somebody told me it only happens on BDB, but I had such issue in FSFS storage too. Basically when you want to keep the ownership of child files inside a directory consistent when there are other users writing stuff on it, you would have to use u+s/g+s. |
191,039 | In deploying to a new (Solaris 9) environment recently, one of the steps was to copy a set of files and directories to their new location and then to apply the group UID bit (using "chmod -R g+s") to all files in the directory tree giving a mode of -rwxr-s--- to everything. The result was that none of our shell scripts would execute unless they were individually opened and re-saved. I should add that we had earlier set g+s on the target parent folder prior to copying files; this had set the initial mode on all the new directories to drwxr-s--- but the files had a mode of -rwxr-x---
Having eventually discovered which step caused the problem, we were able to cut out that step and proceed.
I would like, however, to understand what the "s" bit means when applied to directories and files, in the hope that this will explain why we had the problem in the first place. | 2008/10/10 | [
"https://Stackoverflow.com/questions/191039",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/26790/"
] | Setting directories g+s makes all new files created in said directory have their group set to the directory's group.
This can actually be really handy for collaborative purposes if you have the umask set so that files have group write by default.
Note: This is the way it works in Linux, it could work completely differently in Solaris. | When you need to use it: Fix SVN file ownership issue when you use svn+ssh. Somebody told me it only happens on BDB, but I had such issue in FSFS storage too. Basically when you want to keep the ownership of child files inside a directory consistent when there are other users writing stuff on it, you would have to use u+s/g+s. |
191,039 | In deploying to a new (Solaris 9) environment recently, one of the steps was to copy a set of files and directories to their new location and then to apply the group UID bit (using "chmod -R g+s") to all files in the directory tree giving a mode of -rwxr-s--- to everything. The result was that none of our shell scripts would execute unless they were individually opened and re-saved. I should add that we had earlier set g+s on the target parent folder prior to copying files; this had set the initial mode on all the new directories to drwxr-s--- but the files had a mode of -rwxr-x---
Having eventually discovered which step caused the problem, we were able to cut out that step and proceed.
I would like, however, to understand what the "s" bit means when applied to directories and files, in the hope that this will explain why we had the problem in the first place. | 2008/10/10 | [
"https://Stackoverflow.com/questions/191039",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/26790/"
] | Setting directories g+s makes all new files created in said directory have their group set to the directory's group.
This can actually be really handy for collaborative purposes if you have the umask set so that files have group write by default.
Note: This is the way it works in Linux, it could work completely differently in Solaris. | For files it means that the file is executed as the group that owns the file, not the group user that executes the file belongs to. It is usable when you want to allow user to do something which for which he does not have the privilege. For example, for one DBMS I use, it is common to allow everybody to backup databases. Although only the 'dbms' group has read/write access to database file, the backup program has g+s set to allow anyone to access the database through it, but not directly.
For directories, it means that newly created directories will be owned by the group that owns the directory, not the group user that created the file belongs to. A good example for this is web space of sourceforge.net project. Imagine 3 developers maintaining the project website. Now, if one of them creates a file, only he can write to it (by default). To work around this, all users on the same project are in the same group as well, and directory has rws privilege for that group, so whoever creates the file, it gets created as readable and writable to the group. |
191,039 | In deploying to a new (Solaris 9) environment recently, one of the steps was to copy a set of files and directories to their new location and then to apply the group UID bit (using "chmod -R g+s") to all files in the directory tree giving a mode of -rwxr-s--- to everything. The result was that none of our shell scripts would execute unless they were individually opened and re-saved. I should add that we had earlier set g+s on the target parent folder prior to copying files; this had set the initial mode on all the new directories to drwxr-s--- but the files had a mode of -rwxr-x---
Having eventually discovered which step caused the problem, we were able to cut out that step and proceed.
I would like, however, to understand what the "s" bit means when applied to directories and files, in the hope that this will explain why we had the problem in the first place. | 2008/10/10 | [
"https://Stackoverflow.com/questions/191039",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/26790/"
] | For executable files, this means that when the file is executed, it is executed as the group that owns the file, not the group of the user executing the file.
This is useful if you want users to be able to assume the permissions of a particular group just for running one command.
However, it is also a security risk as it is allowing users to elevate their permissions. You have to know that the scripts with this bit set aren't going to do anything that would let users abuse these extra permissions. | More information about setuid and setgid [here](http://en.wikipedia.org/wiki/File_system_permissions#Additional_Permissions) |
191,039 | In deploying to a new (Solaris 9) environment recently, one of the steps was to copy a set of files and directories to their new location and then to apply the group UID bit (using "chmod -R g+s") to all files in the directory tree giving a mode of -rwxr-s--- to everything. The result was that none of our shell scripts would execute unless they were individually opened and re-saved. I should add that we had earlier set g+s on the target parent folder prior to copying files; this had set the initial mode on all the new directories to drwxr-s--- but the files had a mode of -rwxr-x---
Having eventually discovered which step caused the problem, we were able to cut out that step and proceed.
I would like, however, to understand what the "s" bit means when applied to directories and files, in the hope that this will explain why we had the problem in the first place. | 2008/10/10 | [
"https://Stackoverflow.com/questions/191039",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/26790/"
] | For files it means that the file is executed as the group that owns the file, not the group user that executes the file belongs to. It is usable when you want to allow user to do something which for which he does not have the privilege. For example, for one DBMS I use, it is common to allow everybody to backup databases. Although only the 'dbms' group has read/write access to database file, the backup program has g+s set to allow anyone to access the database through it, but not directly.
For directories, it means that newly created directories will be owned by the group that owns the directory, not the group user that created the file belongs to. A good example for this is web space of sourceforge.net project. Imagine 3 developers maintaining the project website. Now, if one of them creates a file, only he can write to it (by default). To work around this, all users on the same project are in the same group as well, and directory has rws privilege for that group, so whoever creates the file, it gets created as readable and writable to the group. | More information about setuid and setgid [here](http://en.wikipedia.org/wiki/File_system_permissions#Additional_Permissions) |
191,039 | In deploying to a new (Solaris 9) environment recently, one of the steps was to copy a set of files and directories to their new location and then to apply the group UID bit (using "chmod -R g+s") to all files in the directory tree giving a mode of -rwxr-s--- to everything. The result was that none of our shell scripts would execute unless they were individually opened and re-saved. I should add that we had earlier set g+s on the target parent folder prior to copying files; this had set the initial mode on all the new directories to drwxr-s--- but the files had a mode of -rwxr-x---
Having eventually discovered which step caused the problem, we were able to cut out that step and proceed.
I would like, however, to understand what the "s" bit means when applied to directories and files, in the hope that this will explain why we had the problem in the first place. | 2008/10/10 | [
"https://Stackoverflow.com/questions/191039",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/26790/"
] | For executable files, this means that when the file is executed, it is executed as the group that owns the file, not the group of the user executing the file.
This is useful if you want users to be able to assume the permissions of a particular group just for running one command.
However, it is also a security risk as it is allowing users to elevate their permissions. You have to know that the scripts with this bit set aren't going to do anything that would let users abuse these extra permissions. | For files it means that the file is executed as the group that owns the file, not the group user that executes the file belongs to. It is usable when you want to allow user to do something which for which he does not have the privilege. For example, for one DBMS I use, it is common to allow everybody to backup databases. Although only the 'dbms' group has read/write access to database file, the backup program has g+s set to allow anyone to access the database through it, but not directly.
For directories, it means that newly created directories will be owned by the group that owns the directory, not the group user that created the file belongs to. A good example for this is web space of sourceforge.net project. Imagine 3 developers maintaining the project website. Now, if one of them creates a file, only he can write to it (by default). To work around this, all users on the same project are in the same group as well, and directory has rws privilege for that group, so whoever creates the file, it gets created as readable and writable to the group. |
191,039 | In deploying to a new (Solaris 9) environment recently, one of the steps was to copy a set of files and directories to their new location and then to apply the group UID bit (using "chmod -R g+s") to all files in the directory tree giving a mode of -rwxr-s--- to everything. The result was that none of our shell scripts would execute unless they were individually opened and re-saved. I should add that we had earlier set g+s on the target parent folder prior to copying files; this had set the initial mode on all the new directories to drwxr-s--- but the files had a mode of -rwxr-x---
Having eventually discovered which step caused the problem, we were able to cut out that step and proceed.
I would like, however, to understand what the "s" bit means when applied to directories and files, in the hope that this will explain why we had the problem in the first place. | 2008/10/10 | [
"https://Stackoverflow.com/questions/191039",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/26790/"
] | For files it means that the file is executed as the group that owns the file, not the group user that executes the file belongs to. It is usable when you want to allow user to do something which for which he does not have the privilege. For example, for one DBMS I use, it is common to allow everybody to backup databases. Although only the 'dbms' group has read/write access to database file, the backup program has g+s set to allow anyone to access the database through it, but not directly.
For directories, it means that newly created directories will be owned by the group that owns the directory, not the group user that created the file belongs to. A good example for this is web space of sourceforge.net project. Imagine 3 developers maintaining the project website. Now, if one of them creates a file, only he can write to it (by default). To work around this, all users on the same project are in the same group as well, and directory has rws privilege for that group, so whoever creates the file, it gets created as readable and writable to the group. | To expand on your specific problem a little, it has already been noted that sgid executables can cause problems by granting users permissions they don't normally have. While this is an issue for any executable, it creates a potentially-exploitable race condition in the case of scripts (specifically meaning "files which execute by means of an external interpreter identified by a #! at the beginning of the file") which can be used to execute any arbitrary code with the script's permissions.
Unix deriviatives have implemented a number of schemes over the years which are aimed at mitigating or eliminating this vulnerability, most of which have included some form of prohibiting the execution of suid or sgid scripts entirely or requiring you to jump through a few hoops to enable it (usually on a script-by-script basis). One such scheme would be the cause of your inability to run the scripts after turning on their sgid flag. |
134,462 | I have a concrete floor and I made two holes to bolt a 1/4"-thick steel plate. The problem is that the steel plates haven't been drilled yet.
How can I determine where the holes will be drilled in the steel plates so they match the holes in the concrete?
[](https://i.stack.imgur.com/1Kt5n.png) | 2018/03/13 | [
"https://diy.stackexchange.com/questions/134462",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/53603/"
] | Since nobody else has mentioned it, I'll add another option that I've used in the past for spacing holes.
1. Put some paint on the floor around the holes.
2. While the paint is still wet, place the metal plate on the floor.
When you remove the metal plate from the floor, the wet paint will have transferred to the plate but will leave two spots behind where the holes were. Mark those spots, clean up the wet paint, and drill.
This also works great for spacing screw holes for handles on cabinets & drawers although I would usually use lipstick for those instead of paint. | An alternative to Mark's idea would be to use plexiglass. Lay that down and mark either the center of the holes or the holes themselves. Drill through the plexiglass, make sure the holes are aligned properly, and then use that as a template to drill holes in the steel.
I would have added this as a comment under his answer but I don't have 50 reputation yet. |
134,462 | I have a concrete floor and I made two holes to bolt a 1/4"-thick steel plate. The problem is that the steel plates haven't been drilled yet.
How can I determine where the holes will be drilled in the steel plates so they match the holes in the concrete?
[](https://i.stack.imgur.com/1Kt5n.png) | 2018/03/13 | [
"https://diy.stackexchange.com/questions/134462",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/53603/"
] | Do you really need to use the holes drilled in the concrete?
If not, pick another pair to be drilled far enough from the original ones. Make the hoes in the metal sheet first, put the sheet in position, secure it from movement and mark the spots or drill through the holes in the concrete.
Another point to be taken is how much the holes shall be coaxial. If the misfit can be in order of milimeters you can measure the position with a scale. If it must fit perfectly, two extra holes are a good tradeoff. | An alternative to Mark's idea would be to use plexiglass. Lay that down and mark either the center of the holes or the holes themselves. Drill through the plexiglass, make sure the holes are aligned properly, and then use that as a template to drill holes in the steel.
I would have added this as a comment under his answer but I don't have 50 reputation yet. |
134,462 | I have a concrete floor and I made two holes to bolt a 1/4"-thick steel plate. The problem is that the steel plates haven't been drilled yet.
How can I determine where the holes will be drilled in the steel plates so they match the holes in the concrete?
[](https://i.stack.imgur.com/1Kt5n.png) | 2018/03/13 | [
"https://diy.stackexchange.com/questions/134462",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/53603/"
] | The usual methods are:
1. Careful measurement. Really this doesn't need to be that precise, you are not looking for a press-fit between bolts and clearance holes.
If it goes wrong, just elongate a hole into a slot using whatever tools you have to hand (e.g. a round file, clapped-out old Bridgeport, ...) - Remember: "A grinder *file/filler* and paint make me the welder machinist I ain't".
2. Put pointy or painty things into the holes then press the steel plate down in place to mark it. In the dead-tree-carcass world there are things called "dowel pins" used for this kind of thing. | If you have a laserpointer (or 2) "hang them" (they should not move around of course) above if possible so they point down vertically into the center of the hole(s). Put the steelplate in position and the laser marks the spot(s). |
134,462 | I have a concrete floor and I made two holes to bolt a 1/4"-thick steel plate. The problem is that the steel plates haven't been drilled yet.
How can I determine where the holes will be drilled in the steel plates so they match the holes in the concrete?
[](https://i.stack.imgur.com/1Kt5n.png) | 2018/03/13 | [
"https://diy.stackexchange.com/questions/134462",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/53603/"
] | The usual methods are:
1. Careful measurement. Really this doesn't need to be that precise, you are not looking for a press-fit between bolts and clearance holes.
If it goes wrong, just elongate a hole into a slot using whatever tools you have to hand (e.g. a round file, clapped-out old Bridgeport, ...) - Remember: "A grinder *file/filler* and paint make me the welder machinist I ain't".
2. Put pointy or painty things into the holes then press the steel plate down in place to mark it. In the dead-tree-carcass world there are things called "dowel pins" used for this kind of thing. | The **hole spacing** is more important than the location of the holes on the metal plate. Therefore, working off of option 1 from @RedGrittyBrick, this is the approach I would take using a wax pencil or marker and a carpenter's square.
(1) On one edge of the plate mark a (rough) centerline.
(2) Align this edge of the plate to the holes in the concrete, with the centerline mark (roughly) centered between the holes, and **carefully mark the center of each hole on the edge of the plate**. You should now have 3 marks on the edge of the plate.
(3) **Carefully transfer the outer marks** as two lines across the steel plate using a square.
(4) Mark a line perpendicular to these two lines and (roughly) on center on the plate. You should have three lines on the steel plate. **The intersection of the three lines marks the center of the two holes to be drilled.**
Repeat the entire procedure if you have multiple pre-drilled locations. *Don't assume that other holes in other places in the concrete are equally spaced or centered.* |
134,462 | I have a concrete floor and I made two holes to bolt a 1/4"-thick steel plate. The problem is that the steel plates haven't been drilled yet.
How can I determine where the holes will be drilled in the steel plates so they match the holes in the concrete?
[](https://i.stack.imgur.com/1Kt5n.png) | 2018/03/13 | [
"https://diy.stackexchange.com/questions/134462",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/53603/"
] | The usual methods are:
1. Careful measurement. Really this doesn't need to be that precise, you are not looking for a press-fit between bolts and clearance holes.
If it goes wrong, just elongate a hole into a slot using whatever tools you have to hand (e.g. a round file, clapped-out old Bridgeport, ...) - Remember: "A grinder *file/filler* and paint make me the welder machinist I ain't".
2. Put pointy or painty things into the holes then press the steel plate down in place to mark it. In the dead-tree-carcass world there are things called "dowel pins" used for this kind of thing. | Do you really need to use the holes drilled in the concrete?
If not, pick another pair to be drilled far enough from the original ones. Make the hoes in the metal sheet first, put the sheet in position, secure it from movement and mark the spots or drill through the holes in the concrete.
Another point to be taken is how much the holes shall be coaxial. If the misfit can be in order of milimeters you can measure the position with a scale. If it must fit perfectly, two extra holes are a good tradeoff. |
134,462 | I have a concrete floor and I made two holes to bolt a 1/4"-thick steel plate. The problem is that the steel plates haven't been drilled yet.
How can I determine where the holes will be drilled in the steel plates so they match the holes in the concrete?
[](https://i.stack.imgur.com/1Kt5n.png) | 2018/03/13 | [
"https://diy.stackexchange.com/questions/134462",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/53603/"
] | Lay the steel plate on the concrete where you want it. Draw a line around it. Cut a piece of paper to the same size as the steel plate. Place it on the concrete in the same position as the marked outline. Locate the concrete holes by gently pressing down where you think they are (tracing paper makes this even easier). Poke a hole through the paper at the center of each hole. Place the paper on top of the steel plate, and mark the centers of the holes. | I like Mark's answer best (create a paper template and mark the holes) but another technique came to mind.
Take a straightedge and a construction pencil.
- Mark the centerline of the two holes longer than your steel plate.
- Mark a line perpendicular, on each hole, wider than your plate.
- Put the plate down, use your straightedge and the marks to locate the hole centers.
[hmm. similar but different to Stanwoods solution which I did not see at first] |
134,462 | I have a concrete floor and I made two holes to bolt a 1/4"-thick steel plate. The problem is that the steel plates haven't been drilled yet.
How can I determine where the holes will be drilled in the steel plates so they match the holes in the concrete?
[](https://i.stack.imgur.com/1Kt5n.png) | 2018/03/13 | [
"https://diy.stackexchange.com/questions/134462",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/53603/"
] | If you have a laserpointer (or 2) "hang them" (they should not move around of course) above if possible so they point down vertically into the center of the hole(s). Put the steelplate in position and the laser marks the spot(s). | Tape one side of a piece of paper onto the concrete and trace the holes, then put the steel plate under the piece of paper and center punch the holes onto the steel plate. |
134,462 | I have a concrete floor and I made two holes to bolt a 1/4"-thick steel plate. The problem is that the steel plates haven't been drilled yet.
How can I determine where the holes will be drilled in the steel plates so they match the holes in the concrete?
[](https://i.stack.imgur.com/1Kt5n.png) | 2018/03/13 | [
"https://diy.stackexchange.com/questions/134462",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/53603/"
] | The usual methods are:
1. Careful measurement. Really this doesn't need to be that precise, you are not looking for a press-fit between bolts and clearance holes.
If it goes wrong, just elongate a hole into a slot using whatever tools you have to hand (e.g. a round file, clapped-out old Bridgeport, ...) - Remember: "A grinder *file/filler* and paint make me the welder machinist I ain't".
2. Put pointy or painty things into the holes then press the steel plate down in place to mark it. In the dead-tree-carcass world there are things called "dowel pins" used for this kind of thing. | Since nobody else has mentioned it, I'll add another option that I've used in the past for spacing holes.
1. Put some paint on the floor around the holes.
2. While the paint is still wet, place the metal plate on the floor.
When you remove the metal plate from the floor, the wet paint will have transferred to the plate but will leave two spots behind where the holes were. Mark those spots, clean up the wet paint, and drill.
This also works great for spacing screw holes for handles on cabinets & drawers although I would usually use lipstick for those instead of paint. |
134,462 | I have a concrete floor and I made two holes to bolt a 1/4"-thick steel plate. The problem is that the steel plates haven't been drilled yet.
How can I determine where the holes will be drilled in the steel plates so they match the holes in the concrete?
[](https://i.stack.imgur.com/1Kt5n.png) | 2018/03/13 | [
"https://diy.stackexchange.com/questions/134462",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/53603/"
] | I like Mark's answer best (create a paper template and mark the holes) but another technique came to mind.
Take a straightedge and a construction pencil.
- Mark the centerline of the two holes longer than your steel plate.
- Mark a line perpendicular, on each hole, wider than your plate.
- Put the plate down, use your straightedge and the marks to locate the hole centers.
[hmm. similar but different to Stanwoods solution which I did not see at first] | You need something with a slot in it, the same width as the bolts intended to go in the holes. Pass one bolt through, run a nut down and finger-tighten in place. Pass other bolt through, run a nut down it and tighten until you can slide the bolt easily along the slot. Now you have a gauge. Put your fixed bolt in one hole, slide the other along a slot until the bolt drops into the other hole. Tighten the nut with your fingers. Now the bolts are the correct distance apart.
Remove gauge from the concrete and use it indicate where to drill on the steel. |
134,462 | I have a concrete floor and I made two holes to bolt a 1/4"-thick steel plate. The problem is that the steel plates haven't been drilled yet.
How can I determine where the holes will be drilled in the steel plates so they match the holes in the concrete?
[](https://i.stack.imgur.com/1Kt5n.png) | 2018/03/13 | [
"https://diy.stackexchange.com/questions/134462",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/53603/"
] | The **hole spacing** is more important than the location of the holes on the metal plate. Therefore, working off of option 1 from @RedGrittyBrick, this is the approach I would take using a wax pencil or marker and a carpenter's square.
(1) On one edge of the plate mark a (rough) centerline.
(2) Align this edge of the plate to the holes in the concrete, with the centerline mark (roughly) centered between the holes, and **carefully mark the center of each hole on the edge of the plate**. You should now have 3 marks on the edge of the plate.
(3) **Carefully transfer the outer marks** as two lines across the steel plate using a square.
(4) Mark a line perpendicular to these two lines and (roughly) on center on the plate. You should have three lines on the steel plate. **The intersection of the three lines marks the center of the two holes to be drilled.**
Repeat the entire procedure if you have multiple pre-drilled locations. *Don't assume that other holes in other places in the concrete are equally spaced or centered.* | Do you really need to use the holes drilled in the concrete?
If not, pick another pair to be drilled far enough from the original ones. Make the hoes in the metal sheet first, put the sheet in position, secure it from movement and mark the spots or drill through the holes in the concrete.
Another point to be taken is how much the holes shall be coaxial. If the misfit can be in order of milimeters you can measure the position with a scale. If it must fit perfectly, two extra holes are a good tradeoff. |
34,729 | If a plane can already autoland and stay aligned while roll-out by itself, on a CAT-3 ILS-Approach, I asked why there is no auto-takeoff-function on todays autopilots.
Because it should be technically possible and much safer than a hand flown takeoff.
* For the technic:
When on the runway, the pilot presses an auto-take-off button. The plane stays aligned by following a normal CAT-3 Localizer. Takeoff-Thrust is made with autothrottle. At Vr, the plane rotates by itself, smoothly,and activates VNAV and LNAV and follows the SID. It is also possible to implement a live wind sensor to dynamically update V-Speeds.
* For safety:
In case of an emergency during take-off, a computer take-off would be more safer. The plane knows the speed and runway length. So in case of an emergency, it knows if it's below V1 and also if the available runway length is sufficient for a safe rejected take-off. A computer always has a lower reaction time than humans and they can response faster. A computer can immediately decide wether to take off or reject based on lots of live data. A (rejected) take-off performed by a computer should be times safer.
So, why has an autotake-off-function not been developed yet? And what arguments would speak against an auto-take-off function?
--
There is not an answer to my question here: [On modern commercial airliners, how much of the flight could be fully taken care of by the auto pilot?](https://aviation.stackexchange.com/questions/2866/on-modern-commercial-airliners-how-much-of-the-flight-could-be-fully-taken-care) as stated below. I want to know what reasons, if there are any, speak against auto-take-off. | 2017/01/17 | [
"https://aviation.stackexchange.com/questions/34729",
"https://aviation.stackexchange.com",
"https://aviation.stackexchange.com/users/12629/"
] | With some refinement and programming, the technology is easily there, sure; it just needs a few million dollars of design and certification costs for very little benefit.
The main reason we have autolands is because it saves airlines money, by allowing the plane to land safely in minimal visibility instead of diverting to another airport. Aircraft taking off don't have this problem as they can do it in just about zero visibility. If there is no commercial incentive, the reality is it is not going to happen. Only when pilots are considered surplus to requirements will this ability be developed in earnest.
There could be an argument made that it should be done for safety's sake, but I don't buy it. Pilot errors made on the takeoff run, resulting in an accident are incredibly rare. Maybe an auto takeoff could prevent a few tailstrikes but I can't see much more benefit.
Whenever you introduce something new you have to think long and hard about the ramifications of it. There's a whole discussion to be had on how rejected takeoffs would work - generally speaking, you do not want automation doing something that the pilots aren't expecting. It is sometimes better to take an issue into the air than take the risk of a high-speed RTO even under V1, how will the computer judge that when there are few hard and fast rules for it? **Do you trust the *human* programmers to account for every single scenario?** Then there's pilot competency, how do they keep their skills up when they could go months without flying the aircraft? If they are in the habit of delegating their decision making to the computer, will they be able to handle the heat in that career-defining moment when the computer fails and it's all on them? | It is perfectly possible- in a very limited sense and has been demonstrated in aircraft like Global Hawk (not a commercial airliner, but it can be done here). The problem is what to do when the unexpected happens.
Technically, it is possible- you can set the TOGA thrust and set rotation speed and let the aircraft do the take-off, but the problem is, that's about it. What will the aircraft do when someone else decides to crash the runway? It has to detect, decide and act appropriately- which increases the system complexity multiple times due to the sensors required (you are already asking for a radar to detect obstacles; the sensor count will go up, not down).
Safety wise, the issue is, the aircraft can react to *known* problems. What will it do when something that's not in its library occurs? Unlike human pilots, they cannot experiment and compare notes with the other crew and come to a decision. That computers are better and safer than humans is based on the belief that it has access to all data and is programmed to do the correct thing- which is not true always.
Another important thing during takeoff is that the flight crew is in constant communication with the ATC; by far this is the most complex part in the actual take-off barring something unexpected. Computers are not capable of doing it right now. Also, they have to respond to emergencies- both internal (system failure etc) and external (changing ATC instructions, traffic etc).
Also, what will you do when the computer decides to reboot itself in the middle of the takeoff procedure? |
11,922 | I see at least a few credit unions offering these savings-secured loans. I can kinda see the advantage to taking a loan against a CD with penalties for breaking, but share and savings accounts have me confused on why you'd pay that.
So, **why might people take out a loan secured by liquid savings?** | 2011/11/05 | [
"https://money.stackexchange.com/questions/11922",
"https://money.stackexchange.com",
"https://money.stackexchange.com/users/2410/"
] | The purpose of taking a "secured loan" is to build credit. This might be done by someone who had a bad stain on their credit history such as a bankruptcy or foreclosure, or possibly by someone just out of school (presumably with few or no student loans),and no credit history. Not everyone needs to, or should do this, however.
The advantage for a borrower is that s/he gets to create a record of repaying a loan that will partly mitigate the bad credit history. The advantage for the bank is that it is "no risk," because the savings account is the security for the loan. That would make it willing to "lend" to a bad credit risk. | I can see that building credit is a valid reason. I would also suggest another scenario, when you have locked up money in long-term savings, with a substantial penalty for early withdrawal. If you suddenly needed money then you might save money by borrowing against the long-term deposit rather than pay the penalties. This is especially true if you needed the money only for a short time. |
55,275 | I want to express my great satisfaction of this person. Are there any differences between the two sentences?
>
> This shows a great sense of responsibility which is **deeply**
> appreciated.
>
>
> This shows a great sense of responsibility which is **dearly**
> appreciated.
>
>
> | 2012/01/19 | [
"https://english.stackexchange.com/questions/55275",
"https://english.stackexchange.com",
"https://english.stackexchange.com/users/17205/"
] | Being a possible collocation of *appreciate*, "deeply appreciated" would be more suitable. *Dearly*, on the other hand, will also intensify the meaning of appreciate by adding a sense of "very much". | There's a *deep* difference between the two.
Something *deeply* appreciated is *profoundly* or *thoroughly* approved.
Something *dearly* appreciated is done so with *fondness* or *affection*, which is not the sentiment you want to convey in this case. |
11,619,296 | I made the command line helloworld project and it worked. When I try to build from XCode the option to build a "Cordova-Based" application is not there. This picture is what it supposed to show. I don't have the icon. I went through install like the wiki says, Xcode was closed, then I tried the helloworld, success:), and the New Project Cordova-Based... crap, really...
What I should see
and what I do see.
 | 2012/07/23 | [
"https://Stackoverflow.com/questions/11619296",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/314836/"
] | I ran the 1.9 installer and it showed up in Xcode. | this option was deleted in Cordova 2.xx
you must use the command lines
<http://docs.phonegap.com/en/edge/guide_command-line_index.md.html#Command-Line%20Usage> |
323,468 | I recently did a backup of a FAT32 disk which contained a lot of diverse data. It contains many media files, many big binary files, and as usual with FAT32, it has all kinds of odd (but potentially important) permissions for all of these different files. The whole directory of this backup weighs in at a few hundred GB. I would like to have a compressed archive of this backup, but I have a few requirements from whatever archival utility that I use:
* It needs to preserve extended attributes
* It needs to preserve timestamps
* It needs to preserve permissions
* I would like for it to preserve as much metadata as possible
I know that there are many different archiving utilities which fit at least some of my needs, but I would like to know of one which fits them all. I.e., which one can maintain the most metadata and also (preferably) has a good compression ratio for a diverse data set. | 2018/04/24 | [
"https://apple.stackexchange.com/questions/323468",
"https://apple.stackexchange.com",
"https://apple.stackexchange.com/users/79496/"
] | Do the Home Screen Layout Reset:
Settings -> General -> Reset -> Reset Home Screen Layout -> Reset Home Screen
Hope this will others also.
[Source](https://ios.gadgethacks.com/how-to/find-missing-apps-your-iphone-0184187/) | This happened to me and I finally found the app where I had embedded it two folders deep. Remember that home screens can have folders within folders. |
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