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|---|---|---|---|---|---|
56,075,283 | I'm trying to make a program that can be able to make a search request on most websites such as YouTube, ESPN, My university course timetable etc...
I have looked online for various solutions but many of them point to simply adding your search query at the end of the url you are "getting", but that doesn't seem to work with all websites some of them don't update their URL's when you manually make a search, while many others might give each and every URL a unique 'id'. Would it be possible to scrape a search bar from any website and then specifying a search query and entering it? Is there a function for that? | 2019/05/10 | [
"https://Stackoverflow.com/questions/56075283",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/10402319/"
] | You need to Use Selenium Instance to do that. You can not achieve it using BeautifulSoup or requests. | It's possible to use a text-based web browser and automate the search with a script. Then you can download the site you get from this browser and scrape it with BeautifulSoup or something else. |
74,871 | What is the difference between *mostest* and *most*?
Can they be used interchangeably? | 2012/07/17 | [
"https://english.stackexchange.com/questions/74871",
"https://english.stackexchange.com",
"https://english.stackexchange.com/users/8278/"
] | *Mostest* is not an accepted word, though it is [in some dictionaries](http://dictionary.reference.com/browse/mostest) listed as slang. *Most* is already in superlative form, so adding *-est* is redundant and ungrammatical. It was popularized, however, in the saying (intentionally ungrammatical, to convey a sense of crude common sense): "getting thar fustest with the mostest".
However, unless you want to appear illiterate, or crack a questionable pun, you should always use *most*, never *mostest*. | The only context in which it is acceptable to use the word "mostest" is immediately after the words "I love you the". "Bestest" is also acceptable in this context (and no other). |
74,871 | What is the difference between *mostest* and *most*?
Can they be used interchangeably? | 2012/07/17 | [
"https://english.stackexchange.com/questions/74871",
"https://english.stackexchange.com",
"https://english.stackexchange.com/users/8278/"
] | *Mostest* is not an accepted word, though it is [in some dictionaries](http://dictionary.reference.com/browse/mostest) listed as slang. *Most* is already in superlative form, so adding *-est* is redundant and ungrammatical. It was popularized, however, in the saying (intentionally ungrammatical, to convey a sense of crude common sense): "getting thar fustest with the mostest".
However, unless you want to appear illiterate, or crack a questionable pun, you should always use *most*, never *mostest*. | *Mostest* sounds silly, like saying *betterer* or even *more betterer*. You would (should!) only do this for deliberate comedic effect (as Leigh Francis does in the guise of Keith Lemon). It's certainly out of place in any kind of formal setting.
The correct comparative is *more* and the correct superlative is *most*. There's no need to add another *-est* suffix. |
56,211 | I'm currently running a small to medium sized network consisting of approx. 40 workstations and 30 servers (both physical and virtual) consisting of various versions of Windows 2000, XP, 2003, and a single Thecus N5200 Pro. My current backup solution consists of Backup Exec 11D and an HP Storageworks DAT72 tape drive. Backups are done nightly and are currently at 54 GB although there is an additional 100 GB that I would like to add on to that job. The job is not incremental or differential, it is a straight backup of everything to a single tape. Wednesday's tape is taken off-site for 3 months after which it is returned and archived permanently. Thursdays tape is archived on-site for 3 months. Monday, Tuesday, and Friday's tapes are reused each week. Backups are not done Saturday or Sunday because employees have weekends off and very little changes occur during this time.
I would like to rebuild this backup solution in terms of more storage volume and less human intervention. These two items have led me to research [HP's StorageWorks 1/8 G2 Tape Autoloader](http://h10010.www1.hp.com/wwpc/us/en/en/WF05a/12169-304612-82176-82176-82176-3319912.html).
My question is: If we were to go with the G2 (using LTO-3 tapes initially), what changes would you make to my current backup solution? This could involve reducing the number of tapes ($$), incremental or differential backup job, ease of restoration, permanent storage, temporary off-site storage. The size of the backup job would start at 154 GB and would not exceed 400 GB for at least 3-4 years at the earliest.
If you have a solution that involves different technology/approach please feel free to post as I am interested in all possible solutions to this problem. | 2009/08/19 | [
"https://serverfault.com/questions/56211",
"https://serverfault.com",
"https://serverfault.com/users/9884/"
] | Much as online backup may be tempting in your scenario, I would seriously urge you to fully research the viability of doing a full server restore from such a backup before making a decision about it. Also consider the times you need to make a one-off emergency full backup, e.g. before installing a new service pack.
The HP unit looks good, and while I don't have direct experience with their kit I have heard enough good things to satisfy me that you won't go too far wrong with it.
I'm fond of Overland kit myself, and while they're not really aimed at your level, something like their new ArcVault 12 might be an alternative option worth considering: <http://www.overlandstorage.com/US/products/arcvault12.html>
Now, about your strategy. If time windows, tape space and tape budget allow it, you could just do a full every night. It simplifies the whole setup for you, as you can restore from a single backup set without any fooling around. If you can't do this (and I'll assume it's not feasible), go for a nightly differential so that you have a max of 2 backup sets (last full and last diff) to go back to. Never go incremental, it's just too much hassle.
With LTO3 and differentials you can aim for one tape per week. So configure your weekly full to overwrite and your nights diffs to append, set an overwrite protection of however long you want to keep data for, and do the calculations from there. Using a proper tape library like the Overland can automate the whole thing for you, which is very nice.
Above all, my usual advice on backups to keep it simple and boring, avoid exotic seeming solutions, and try to retain some manual element in it applies also. | As I am sure you are aware -- incremental and differential backups are a trade off. You gain faster overall backups with less data on tape, however restorations are more complex and slower. Incremental backups have always struck me as "RAID 0 for backups" and I avoid them.
**Tape/Nearline Hybrid**
Based on your current use, I might suggest reviewing the benefits of a full backup to tape on a Monday (so the tape can still be archived for 3 months, and then permanently stored), and then each day doing an incremental to nearline storage. Since your M/Tu/Fri tapes are recycled and possibly dont leave the site -- replacing that with nearline disk storage could reduce the complexity considerably.
**Cloud Backup**
Based on your bandwidth, recovery requirements, and data change rate -- an online backup solution can be rather appealing. They typically do a one-time full backup, and then take incremental and compile them such that you can restore from a single point in time and you are none-the-wiser they were pulling incrementals the entire time. |
279,237 | I'm making the switch from Maya to Blender, but one thing that I couldn't find is to assign a hotkey to hide and unhide an armature in the viewport. I don't like the visual clutter and as an animator I just want to make a pose and see it without all the controls of the rig.
So far I managed to find this, but now I need to assign it to a hotkey.
bpy.context.space\_data.show\_object\_select\_armature = False
bpy.context.space\_data.show\_object\_select\_armature = True
Cheers!
Edwin | 2022/11/15 | [
"https://blender.stackexchange.com/questions/279237",
"https://blender.stackexchange.com",
"https://blender.stackexchange.com/users/157808/"
] | It is really easy. Apply emission shader with either a color or texture as the color input. Also enable the Bloom in the render properties for getting your desired effect
[](https://i.stack.imgur.com/7IYgL.png)
[](https://i.stack.imgur.com/CHIfj.png)
[EDIT 1 - Emission along the edges]:
====================================
Simple again. Just assign a different material to the faces along the edges. For this to be done I did a loop cut on the faces of the cube along the edges and assigned them the emission material. For other faces that are not emitting they have the regular principled bsdf material
Output you need
---------------
[](https://i.stack.imgur.com/I0iJh.png)
Mesh editing necessary - cut along the edges to make them polygons/faces
------------------------------------------------------------------------
[](https://i.stack.imgur.com/heFGD.png)
Add different material to non-emitting interior faces
-----------------------------------------------------
[](https://i.stack.imgur.com/ilLuS.png) | I can see 2 effects: Glare and bokeh, but the bokeh stays still. You can do both in the *Compositor*, but you can activate the *Bloom* effect in Eevee, which will give you the glare effect. As for the bokeh, create some grey bubble on a white background, like that:
[](https://i.stack.imgur.com/SF7uR.jpg)
Then in the *Compositor* mix the image with the rendered image through a *Mix Shader* in *Divide* mode:
[](https://i.stack.imgur.com/clbV8.jpg) |
30,236,170 | I know there are lot of questions and answers are available like this but since 2 days I tried to figure out this issue and not got any success.
I have added the below listed frameworks in my projects,
libSqlite3.dylib
AddressBook.framework
AssetsLibrary.framework
AVFoundation.framework
CoreMotion.framework
MediaPlayer.framework
but not getting any success
 | 2015/05/14 | [
"https://Stackoverflow.com/questions/30236170",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/3090578/"
] | This library AssetsLibrary.framework in Step 3, is not included in your project, that's why you are getting this error.
Try these:
You need to add the AssetsLibrary framework to the “Link Binary With Libraries” build phase of your target.
Try cleaning your project using Command+Shift+K and adding the required frameworks again. Hope it will start working
Copy files into your project but forgot to check the target to add the files to. To resolve: Open the Build Phases for the correct target, expand Compile Sources and add the missing .m files.
Another cause, may be:
You include a static library that is built for another architecture like i386, the simulator on your host machine. To resolve:
If you have multiple library files from your libraries vendor to include in the project you need to include the one for the simulator (i386) and the one for the device (armv7 for example). | Missing library or missing .m file
Check and add:
TargetSettings -> Build Phases -> Compile Sources -> add your .m class -> Build and Run |
30,236,170 | I know there are lot of questions and answers are available like this but since 2 days I tried to figure out this issue and not got any success.
I have added the below listed frameworks in my projects,
libSqlite3.dylib
AddressBook.framework
AssetsLibrary.framework
AVFoundation.framework
CoreMotion.framework
MediaPlayer.framework
but not getting any success
 | 2015/05/14 | [
"https://Stackoverflow.com/questions/30236170",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/3090578/"
] | I think you've copied the Frameworks into your project, rather than just linking to them, so they only contain the library compiled for device. Xcode will normally locate the Simulator version of the framework for you.
Delete any of the .framework folders in your project and Finder, then follow Step 6 of this tutorial with the frameworks you listed in your original post: <http://quickblox.com/developers/IOS-how-to-connect-Quickblox-framework#Framework> | Missing library or missing .m file
Check and add:
TargetSettings -> Build Phases -> Compile Sources -> add your .m class -> Build and Run |
167,015 | My already accepted internship at an IT-company was canceled. The reason they mentioned to me were that almost all employees of the department I was supposed to work in are currently in home-office and there would be nobody around to tutor me.
They said they would be happy to repropose their offer once back to normal office-work, probably in 2021.
My question: Should I tell them that I would be willing to do my internship remotely as well in case the head of the department agrees, and ask them if they would consider such a scenario? Or should I remain silent, wait for next year and proceed as proposed? Would asking put them off somehow?
*Update:*
On Monday I suggested the option of a remote internship and as expected, they have already thought about it and had some concerns. But to my surprise after HR spoke with the head of the department and their concerns got resolved , they were willing to give it a try under additional regulations/requirements :) Thanks again for your thoughts on this one! | 2020/11/19 | [
"https://workplace.stackexchange.com/questions/167015",
"https://workplace.stackexchange.com",
"https://workplace.stackexchange.com/users/122668/"
] | >
> Would asking put them off somehow?
>
>
>
There is very little/no harm in asking but expect a polite no after which either accept the next year opportunity or go and search for another internship (or do both).
As of why: training junior employees is just not something that generally works well remotely (at least in my 20 years of almost-exclusively remote experience) as it takes the already hard and expensive takes of training them and then cranks the difficulty up by few notches by removing the personal contact from the equation. It can be done, sure, but most companies are not equipped and trained to do it correctly. | >
> Should I tell them that I would be willing to do my internship
> remotely as well in case the head of the department agrees, and ask
> them if they would consider such a scenario?
>
>
>
It's perfectly reasonable to suggest that option.
It's unlikely to succeed however, since if that was something the company would consider, they would have offered that choice to you first.
Still, if you don't ask you won't know, and I can't see how it would cause problems just to ask. |
117,835 | Does a mortgaged home purchase impact your federal U.S. tax return in any way? | 2019/12/10 | [
"https://money.stackexchange.com/questions/117835",
"https://money.stackexchange.com",
"https://money.stackexchange.com/users/92200/"
] | In the US you can take a standard deduction or itemize your deductions. Mortgage interest and property tax tips the scales in favor of itemizing deductions for many people. So the answer to your question is, it depends. If the sum of your itemized deductions exceeds the standard deduction then you pay less federal income tax by itemizing your deductions. If you wouldn't itemize deductions if not for mortgage interest and property tax then buying a house would impact your federal tax return favorably.
Since the standard deduction was recently increased and the state and local tax deduction was capped in 2018, fewer people benefit from itemizing and the benefit is reduced among those that still do. The impact of the tax law varies by state, since some have much higher property tax than others.
There have been federal first-time home buyer credits in the past, but not presently. | In a comment, you clarified that you were specifically asking about a *first* house:
>
> I was hoping for a more cohesive overview of what tax elements come into play for a new homeowner
>
>
>
At the federal level, there are no tax benefits to buying your *first* house. You get the same benefits as anyone else who owns a house with a mortgage. This has been a change from the days when the Housing and Economic Recovery Act offered a tax credit to first time buyers from 2008 through 2010. Some people who may wonder about a first time home buyers tax credit may be remembering that program.
However, some states have [specific programs or tax benefits](https://www.nerdwallet.com/blog/mortgages/first-time-home-buyer-programs-by-state/) for first time buyers. Some of these programs can essentially trickle up to your federal return. It's hard to describe if this applies for you or not, because we don't know your state.
Some of those state programs operate as tax credits, but in other cases the link to your taxes is indirect (i.e. some programs will subsidize your down payment with additional cash if you meet certain criteria, which is effectively tax-free money in the year in which you buy your home). |
208,246 | We have a website; which, till now had only HTML pages. Now we are redeveloping it in ASP .Net.
This means that all the .html pages will be changed to .aspx extension. The problem is, there are a lot of external references to these pages, and we dont want to go and chage each and every link to aspx right away.
Is there any way to redirect a link to .html pages to .aspx pages? For example, is there any way that the server checks the file specified, finds out that it links to .html page and automatically opens the .aspx page? | 2008/10/16 | [
"https://Stackoverflow.com/questions/208246",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/6621/"
] | if you do some sort of url rewriting you can have all the links stay the same and just serve up the aspx pages, request for index.html gets mapped to index.aspx
here's what ms says about asp.net url rewriting:
<http://msdn.microsoft.com/en-us/library/ms972974.aspx> | Here's how we handled a similar situation.
1. Setup IIS to map html extension to ASP.Net instead of handling it directly.
2. In the HttpApplication.BeginRequest handler see if the request is being made for a html file that has been migrated to aspx if so then serve out the aspx page instead by redirecting the response.
3. In case the html fiile hasn't been mapped yet just serve out the static html file. |
208,246 | We have a website; which, till now had only HTML pages. Now we are redeveloping it in ASP .Net.
This means that all the .html pages will be changed to .aspx extension. The problem is, there are a lot of external references to these pages, and we dont want to go and chage each and every link to aspx right away.
Is there any way to redirect a link to .html pages to .aspx pages? For example, is there any way that the server checks the file specified, finds out that it links to .html page and automatically opens the .aspx page? | 2008/10/16 | [
"https://Stackoverflow.com/questions/208246",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/6621/"
] | if you do some sort of url rewriting you can have all the links stay the same and just serve up the aspx pages, request for index.html gets mapped to index.aspx
here's what ms says about asp.net url rewriting:
<http://msdn.microsoft.com/en-us/library/ms972974.aspx> | Like stusmith touched on, you should not let your underlying technology be exposed (and certainly not mandate) what your URIs look like. The best way is as mentioned to not show any extensions at all, but in the current situation maybe it is possible to configure the system in such a way that .html files are acted upon as if they were .aspx?
I don't know the first thing about .NET but I assume that this is possible without having to go through too many hoops.
The second best approach is to rewrite the URIs, but that requires extra work for the server (not much, but it adds up).
(Don't redirect with a meta refresh. Every other solution is better.) |
208,246 | We have a website; which, till now had only HTML pages. Now we are redeveloping it in ASP .Net.
This means that all the .html pages will be changed to .aspx extension. The problem is, there are a lot of external references to these pages, and we dont want to go and chage each and every link to aspx right away.
Is there any way to redirect a link to .html pages to .aspx pages? For example, is there any way that the server checks the file specified, finds out that it links to .html page and automatically opens the .aspx page? | 2008/10/16 | [
"https://Stackoverflow.com/questions/208246",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/6621/"
] | if you do some sort of url rewriting you can have all the links stay the same and just serve up the aspx pages, request for index.html gets mapped to index.aspx
here's what ms says about asp.net url rewriting:
<http://msdn.microsoft.com/en-us/library/ms972974.aspx> | You might want to look into the ASP.NET System.Web.Routing namespace, which was added in .NET 3.5 SP1 I believe:
<http://blogs.msdn.com/mikeormond/archive/2008/05/14/using-asp-net-routing-independent-of-mvc.aspx>
<http://msdn.microsoft.com/en-us/library/system.web.routing.aspx> |
208,246 | We have a website; which, till now had only HTML pages. Now we are redeveloping it in ASP .Net.
This means that all the .html pages will be changed to .aspx extension. The problem is, there are a lot of external references to these pages, and we dont want to go and chage each and every link to aspx right away.
Is there any way to redirect a link to .html pages to .aspx pages? For example, is there any way that the server checks the file specified, finds out that it links to .html page and automatically opens the .aspx page? | 2008/10/16 | [
"https://Stackoverflow.com/questions/208246",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/6621/"
] | I would take this opportunity to leave extensions (.html, .aspx, etc) behind.
For all our major websites we now use a custom mapping system, whereby a virtual page URI is mapped to a specific .aspx (or.html) page. This has a few benefits:
* Your visitors see "nicer" URIs;
* You're free to re-organise your site as you see fit, behind the scenes, without breaking existing incoming links;
* You can use dynamic virtual URIs, eg instead of /Product.aspx?p=Blah, you can use /Products/Blah
We have our own custom system, but I believe ASP.NET MVC now has this feature built-in.
(If you go down this route, you can add legacy mappings for .html URIs that point to your new .aspx pages). | Here's how we handled a similar situation.
1. Setup IIS to map html extension to ASP.Net instead of handling it directly.
2. In the HttpApplication.BeginRequest handler see if the request is being made for a html file that has been migrated to aspx if so then serve out the aspx page instead by redirecting the response.
3. In case the html fiile hasn't been mapped yet just serve out the static html file. |
208,246 | We have a website; which, till now had only HTML pages. Now we are redeveloping it in ASP .Net.
This means that all the .html pages will be changed to .aspx extension. The problem is, there are a lot of external references to these pages, and we dont want to go and chage each and every link to aspx right away.
Is there any way to redirect a link to .html pages to .aspx pages? For example, is there any way that the server checks the file specified, finds out that it links to .html page and automatically opens the .aspx page? | 2008/10/16 | [
"https://Stackoverflow.com/questions/208246",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/6621/"
] | I would take this opportunity to leave extensions (.html, .aspx, etc) behind.
For all our major websites we now use a custom mapping system, whereby a virtual page URI is mapped to a specific .aspx (or.html) page. This has a few benefits:
* Your visitors see "nicer" URIs;
* You're free to re-organise your site as you see fit, behind the scenes, without breaking existing incoming links;
* You can use dynamic virtual URIs, eg instead of /Product.aspx?p=Blah, you can use /Products/Blah
We have our own custom system, but I believe ASP.NET MVC now has this feature built-in.
(If you go down this route, you can add legacy mappings for .html URIs that point to your new .aspx pages). | Like stusmith touched on, you should not let your underlying technology be exposed (and certainly not mandate) what your URIs look like. The best way is as mentioned to not show any extensions at all, but in the current situation maybe it is possible to configure the system in such a way that .html files are acted upon as if they were .aspx?
I don't know the first thing about .NET but I assume that this is possible without having to go through too many hoops.
The second best approach is to rewrite the URIs, but that requires extra work for the server (not much, but it adds up).
(Don't redirect with a meta refresh. Every other solution is better.) |
208,246 | We have a website; which, till now had only HTML pages. Now we are redeveloping it in ASP .Net.
This means that all the .html pages will be changed to .aspx extension. The problem is, there are a lot of external references to these pages, and we dont want to go and chage each and every link to aspx right away.
Is there any way to redirect a link to .html pages to .aspx pages? For example, is there any way that the server checks the file specified, finds out that it links to .html page and automatically opens the .aspx page? | 2008/10/16 | [
"https://Stackoverflow.com/questions/208246",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/6621/"
] | I would take this opportunity to leave extensions (.html, .aspx, etc) behind.
For all our major websites we now use a custom mapping system, whereby a virtual page URI is mapped to a specific .aspx (or.html) page. This has a few benefits:
* Your visitors see "nicer" URIs;
* You're free to re-organise your site as you see fit, behind the scenes, without breaking existing incoming links;
* You can use dynamic virtual URIs, eg instead of /Product.aspx?p=Blah, you can use /Products/Blah
We have our own custom system, but I believe ASP.NET MVC now has this feature built-in.
(If you go down this route, you can add legacy mappings for .html URIs that point to your new .aspx pages). | You might want to look into the ASP.NET System.Web.Routing namespace, which was added in .NET 3.5 SP1 I believe:
<http://blogs.msdn.com/mikeormond/archive/2008/05/14/using-asp-net-routing-independent-of-mvc.aspx>
<http://msdn.microsoft.com/en-us/library/system.web.routing.aspx> |
208,246 | We have a website; which, till now had only HTML pages. Now we are redeveloping it in ASP .Net.
This means that all the .html pages will be changed to .aspx extension. The problem is, there are a lot of external references to these pages, and we dont want to go and chage each and every link to aspx right away.
Is there any way to redirect a link to .html pages to .aspx pages? For example, is there any way that the server checks the file specified, finds out that it links to .html page and automatically opens the .aspx page? | 2008/10/16 | [
"https://Stackoverflow.com/questions/208246",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/6621/"
] | You might want to look into the ASP.NET System.Web.Routing namespace, which was added in .NET 3.5 SP1 I believe:
<http://blogs.msdn.com/mikeormond/archive/2008/05/14/using-asp-net-routing-independent-of-mvc.aspx>
<http://msdn.microsoft.com/en-us/library/system.web.routing.aspx> | Here's how we handled a similar situation.
1. Setup IIS to map html extension to ASP.Net instead of handling it directly.
2. In the HttpApplication.BeginRequest handler see if the request is being made for a html file that has been migrated to aspx if so then serve out the aspx page instead by redirecting the response.
3. In case the html fiile hasn't been mapped yet just serve out the static html file. |
208,246 | We have a website; which, till now had only HTML pages. Now we are redeveloping it in ASP .Net.
This means that all the .html pages will be changed to .aspx extension. The problem is, there are a lot of external references to these pages, and we dont want to go and chage each and every link to aspx right away.
Is there any way to redirect a link to .html pages to .aspx pages? For example, is there any way that the server checks the file specified, finds out that it links to .html page and automatically opens the .aspx page? | 2008/10/16 | [
"https://Stackoverflow.com/questions/208246",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/6621/"
] | You might want to look into the ASP.NET System.Web.Routing namespace, which was added in .NET 3.5 SP1 I believe:
<http://blogs.msdn.com/mikeormond/archive/2008/05/14/using-asp-net-routing-independent-of-mvc.aspx>
<http://msdn.microsoft.com/en-us/library/system.web.routing.aspx> | Like stusmith touched on, you should not let your underlying technology be exposed (and certainly not mandate) what your URIs look like. The best way is as mentioned to not show any extensions at all, but in the current situation maybe it is possible to configure the system in such a way that .html files are acted upon as if they were .aspx?
I don't know the first thing about .NET but I assume that this is possible without having to go through too many hoops.
The second best approach is to rewrite the URIs, but that requires extra work for the server (not much, but it adds up).
(Don't redirect with a meta refresh. Every other solution is better.) |
64,722 | I just finished *R-2800: P&W's Dependable Masterpiece* and noticed there's no mention of a pump for crankcase ventilation. Is this handled by the oil scavenge pumps? | 2019/05/24 | [
"https://aviation.stackexchange.com/questions/64722",
"https://aviation.stackexchange.com",
"https://aviation.stackexchange.com/users/36532/"
] | Centrifugal compressors only produce a more compact engine at low mass flow, which means low thrust.
The amount of thrust an engine can produce is proportional to its intake area times exhaust velocity. Increasing the latter is undesirable, as energy and thus fuel consumption is proportional to velocity *squared*. So engine designers target mass flow to gain more thrust, not more velocity.
Since they are 3D structures, in a basic solid design (that you'd find in early jets and small modern turbines), the volume of a centrifugal compressor grows in *cubic proportion* to its diameter, while frontal area, which limits its mass flow and thus its thrust, increases only as diameter *squared*. This creates a cube-square law.
Large real-life parts are filled with lightening and cooling channels, so the *mass-to-area* law is more complex. Still, it cannot eliminate the volume effect entirely. The end result is that the mass of centrifugal compressors grows considerably faster than their mass flow.
At the highest power levels, centrifugal compressors become prohibitively heavy even for fixed powerplant machinery, where durability otherwise trumps weight, so the largest base load powerplants run all-axial. With axial compressors, the flat design with a short air flow path allows mass to only grow in direct proportion to mass flow, and very powerful engines can be built within reasonable dimensions.
It's not pure cube-square law in either case, but it's something like k1\*massflow^[2.5, 2.8] for centrifugal versus k2\*massflow^[2.2, 2.4] for axial, where k2>k1, giving centrifugal compressors some advantage in small sizes. Centrifugals are also much cheaper to produce (at least small ones).
High-performance engines, such as those in commercial aircraft, also need to pack more thrust into the smallest cross-section they can, while maintaining efficiency, so as to reduce drag and also fit under the wings, enabling heavier jets. Axial compressors offer a lot more intake area for any given cross-section - thus more thrust.
The smallest jets, where thrust requirements are small and the engine's cross-section is very small compared to the fuselage, can afford the extra diameter of a centrifugal or diagonal flow compressor. Yes, it's the same cube-square law (also reduced somewhat in practice) that keeps the *engine cross-section* to *total cross-section* ratio increasing as aircraft go up in size. Small centrifugal compressors are simpler, easier to build, and more robust than small axial ones.
So in every industry, as power grows, there is a crossover point from centrifugal to axial. For aircraft where drag is critical, it's just above small bizjets, mobile ground and helicopter turbines stay centrifugal or mixed up to a few MW, and in the tens of megawatts even fixed powerplants switch from axial/centrifugal to all-axial.
Engines close to that crossover point typically combine axial and centrifugal stages. Newer diagonal compressors are in-between and quite good, offering an even more tailored compromise. | Axial turbine engines take up a lot of space...lengthwise. Centrifugal compressors are shorter and wider, and are very often used in turboprop and turboshaft engines, for instance the Rolls Royce Dart is a single axis turboprop engine. The photo demonstrates the compactness of the engine...lengthwise.
[](https://i.stack.imgur.com/UIh5b.png).
>
> Can you create a centrifugal air pump that pushes as much air as a axial jet engine.
>
>
>
Yes you can. It will have two main issues:
1. The losses in the centrifugal compressors will be higher than for an axial configuration reaching the same compression ratio.
2. Part of the frontal area cannot be used for airflow.
>
> What are the main disadvantages of centrifugal air engines from the standard axial engines.
>
>
>
Centrifugal compressors:
* Are slightly less efficient than axial compressors (for a given compression ratio).
* Expel the airflow perpendicular to free stream, so that if multiple stages are required the airflow must be guided into quite a bendy pathway, with additional negative impact on efficiency.
* Result in an engine with a larger frontal area.
Advantages are:
* Centrifugal compressors achieve higher compression ratios than axial compressors - per stage. Compression ratios of 4 - 6, while an axial stage can only do 1.4 - 1.6.
* They are of a more robust and often less costly construction.
Larger engines (high mass flow, high compression ratio and minimal frontal area) use axial compressors almost exclusively: the internal losses are lowest. Centrifugal compressors are used for design cases where other factors than efficiency are of interest, such as cost and limitation of length for helicopter turboshafts.
An example of the use of a centrifugal compressor in a turbofan engine is the [Garrett AiResearch ATF3](https://en.wikipedia.org/wiki/Garrett_ATF3). A 3-shaft engine, with the fan on shaft 1, five axial stages on shaft 2, and a centrifugal stage on shaft 3.
[](https://i.stack.imgur.com/1gFfy.png)
[Picture source](https://www.flightglobalimages.com/cutaways/aeroengines-jet-cutaways/garrett-airesearch-atf3-cutaway-poster-1569707.html)
The hot exhaust stream is deflected back into the fan bypass, which cools it down and results in a low IR signature. This engine is used in the Dassault Falcon. Note that there is no principal technical difficulty to scale this engine up to A380 level, other than the decreased efficiency due to the multiple deflections in the airstream. The wider frontal area is not a problem in the compressor part, and the total compression ratio increases a lot using this final stage.
As in the ATF3, centrifugal compressors are often combined with an axial stage, which pre-whirls the air stream into the centrifugal compressor and increases both efficiency and max compression ratio per single stage, as compared to a flat single stage.
[](https://i.stack.imgur.com/Z6KAK.png) |
64,722 | I just finished *R-2800: P&W's Dependable Masterpiece* and noticed there's no mention of a pump for crankcase ventilation. Is this handled by the oil scavenge pumps? | 2019/05/24 | [
"https://aviation.stackexchange.com/questions/64722",
"https://aviation.stackexchange.com",
"https://aviation.stackexchange.com/users/36532/"
] | Axial turbine engines take up a lot of space...lengthwise. Centrifugal compressors are shorter and wider, and are very often used in turboprop and turboshaft engines, for instance the Rolls Royce Dart is a single axis turboprop engine. The photo demonstrates the compactness of the engine...lengthwise.
[](https://i.stack.imgur.com/UIh5b.png).
>
> Can you create a centrifugal air pump that pushes as much air as a axial jet engine.
>
>
>
Yes you can. It will have two main issues:
1. The losses in the centrifugal compressors will be higher than for an axial configuration reaching the same compression ratio.
2. Part of the frontal area cannot be used for airflow.
>
> What are the main disadvantages of centrifugal air engines from the standard axial engines.
>
>
>
Centrifugal compressors:
* Are slightly less efficient than axial compressors (for a given compression ratio).
* Expel the airflow perpendicular to free stream, so that if multiple stages are required the airflow must be guided into quite a bendy pathway, with additional negative impact on efficiency.
* Result in an engine with a larger frontal area.
Advantages are:
* Centrifugal compressors achieve higher compression ratios than axial compressors - per stage. Compression ratios of 4 - 6, while an axial stage can only do 1.4 - 1.6.
* They are of a more robust and often less costly construction.
Larger engines (high mass flow, high compression ratio and minimal frontal area) use axial compressors almost exclusively: the internal losses are lowest. Centrifugal compressors are used for design cases where other factors than efficiency are of interest, such as cost and limitation of length for helicopter turboshafts.
An example of the use of a centrifugal compressor in a turbofan engine is the [Garrett AiResearch ATF3](https://en.wikipedia.org/wiki/Garrett_ATF3). A 3-shaft engine, with the fan on shaft 1, five axial stages on shaft 2, and a centrifugal stage on shaft 3.
[](https://i.stack.imgur.com/1gFfy.png)
[Picture source](https://www.flightglobalimages.com/cutaways/aeroengines-jet-cutaways/garrett-airesearch-atf3-cutaway-poster-1569707.html)
The hot exhaust stream is deflected back into the fan bypass, which cools it down and results in a low IR signature. This engine is used in the Dassault Falcon. Note that there is no principal technical difficulty to scale this engine up to A380 level, other than the decreased efficiency due to the multiple deflections in the airstream. The wider frontal area is not a problem in the compressor part, and the total compression ratio increases a lot using this final stage.
As in the ATF3, centrifugal compressors are often combined with an axial stage, which pre-whirls the air stream into the centrifugal compressor and increases both efficiency and max compression ratio per single stage, as compared to a flat single stage.
[](https://i.stack.imgur.com/Z6KAK.png) | While a centrifugal compressor can acheive greater compression than a *single* compressor stage in an axial flow engine, the axial flow design allows for multiple compressor stages, achieving higher overall compression of the air and consequently greater efficiency. Centrifugal flow jet engines are, however, tough and reliable. |
64,722 | I just finished *R-2800: P&W's Dependable Masterpiece* and noticed there's no mention of a pump for crankcase ventilation. Is this handled by the oil scavenge pumps? | 2019/05/24 | [
"https://aviation.stackexchange.com/questions/64722",
"https://aviation.stackexchange.com",
"https://aviation.stackexchange.com/users/36532/"
] | Axial turbine engines take up a lot of space...lengthwise. Centrifugal compressors are shorter and wider, and are very often used in turboprop and turboshaft engines, for instance the Rolls Royce Dart is a single axis turboprop engine. The photo demonstrates the compactness of the engine...lengthwise.
[](https://i.stack.imgur.com/UIh5b.png).
>
> Can you create a centrifugal air pump that pushes as much air as a axial jet engine.
>
>
>
Yes you can. It will have two main issues:
1. The losses in the centrifugal compressors will be higher than for an axial configuration reaching the same compression ratio.
2. Part of the frontal area cannot be used for airflow.
>
> What are the main disadvantages of centrifugal air engines from the standard axial engines.
>
>
>
Centrifugal compressors:
* Are slightly less efficient than axial compressors (for a given compression ratio).
* Expel the airflow perpendicular to free stream, so that if multiple stages are required the airflow must be guided into quite a bendy pathway, with additional negative impact on efficiency.
* Result in an engine with a larger frontal area.
Advantages are:
* Centrifugal compressors achieve higher compression ratios than axial compressors - per stage. Compression ratios of 4 - 6, while an axial stage can only do 1.4 - 1.6.
* They are of a more robust and often less costly construction.
Larger engines (high mass flow, high compression ratio and minimal frontal area) use axial compressors almost exclusively: the internal losses are lowest. Centrifugal compressors are used for design cases where other factors than efficiency are of interest, such as cost and limitation of length for helicopter turboshafts.
An example of the use of a centrifugal compressor in a turbofan engine is the [Garrett AiResearch ATF3](https://en.wikipedia.org/wiki/Garrett_ATF3). A 3-shaft engine, with the fan on shaft 1, five axial stages on shaft 2, and a centrifugal stage on shaft 3.
[](https://i.stack.imgur.com/1gFfy.png)
[Picture source](https://www.flightglobalimages.com/cutaways/aeroengines-jet-cutaways/garrett-airesearch-atf3-cutaway-poster-1569707.html)
The hot exhaust stream is deflected back into the fan bypass, which cools it down and results in a low IR signature. This engine is used in the Dassault Falcon. Note that there is no principal technical difficulty to scale this engine up to A380 level, other than the decreased efficiency due to the multiple deflections in the airstream. The wider frontal area is not a problem in the compressor part, and the total compression ratio increases a lot using this final stage.
As in the ATF3, centrifugal compressors are often combined with an axial stage, which pre-whirls the air stream into the centrifugal compressor and increases both efficiency and max compression ratio per single stage, as compared to a flat single stage.
[](https://i.stack.imgur.com/Z6KAK.png) | All existing centrifugal-compressor aircraft engines have been turbojets or turboprops.
Aside from their low power compared with modern turbofans (the Rolls-Royce Dart mentioned in another answer produced about 1 MW, compared with 50MW for a modern large turbofan engine core) the larger diameter of a centrifugal compressor would make it hard to design an efficient turbofan, by restricting the area of the fan duct.
Increasing the outer diameter of the fan blades to enlarge the bypass duct is not a practical option, since it is limited by the ground clearance of the aircraft. Trying to avoid that issue with very large diameter tail-mounted engines would just create a different set of design problems. |
64,722 | I just finished *R-2800: P&W's Dependable Masterpiece* and noticed there's no mention of a pump for crankcase ventilation. Is this handled by the oil scavenge pumps? | 2019/05/24 | [
"https://aviation.stackexchange.com/questions/64722",
"https://aviation.stackexchange.com",
"https://aviation.stackexchange.com/users/36532/"
] | Axial turbine engines take up a lot of space...lengthwise. Centrifugal compressors are shorter and wider, and are very often used in turboprop and turboshaft engines, for instance the Rolls Royce Dart is a single axis turboprop engine. The photo demonstrates the compactness of the engine...lengthwise.
[](https://i.stack.imgur.com/UIh5b.png).
>
> Can you create a centrifugal air pump that pushes as much air as a axial jet engine.
>
>
>
Yes you can. It will have two main issues:
1. The losses in the centrifugal compressors will be higher than for an axial configuration reaching the same compression ratio.
2. Part of the frontal area cannot be used for airflow.
>
> What are the main disadvantages of centrifugal air engines from the standard axial engines.
>
>
>
Centrifugal compressors:
* Are slightly less efficient than axial compressors (for a given compression ratio).
* Expel the airflow perpendicular to free stream, so that if multiple stages are required the airflow must be guided into quite a bendy pathway, with additional negative impact on efficiency.
* Result in an engine with a larger frontal area.
Advantages are:
* Centrifugal compressors achieve higher compression ratios than axial compressors - per stage. Compression ratios of 4 - 6, while an axial stage can only do 1.4 - 1.6.
* They are of a more robust and often less costly construction.
Larger engines (high mass flow, high compression ratio and minimal frontal area) use axial compressors almost exclusively: the internal losses are lowest. Centrifugal compressors are used for design cases where other factors than efficiency are of interest, such as cost and limitation of length for helicopter turboshafts.
An example of the use of a centrifugal compressor in a turbofan engine is the [Garrett AiResearch ATF3](https://en.wikipedia.org/wiki/Garrett_ATF3). A 3-shaft engine, with the fan on shaft 1, five axial stages on shaft 2, and a centrifugal stage on shaft 3.
[](https://i.stack.imgur.com/1gFfy.png)
[Picture source](https://www.flightglobalimages.com/cutaways/aeroengines-jet-cutaways/garrett-airesearch-atf3-cutaway-poster-1569707.html)
The hot exhaust stream is deflected back into the fan bypass, which cools it down and results in a low IR signature. This engine is used in the Dassault Falcon. Note that there is no principal technical difficulty to scale this engine up to A380 level, other than the decreased efficiency due to the multiple deflections in the airstream. The wider frontal area is not a problem in the compressor part, and the total compression ratio increases a lot using this final stage.
As in the ATF3, centrifugal compressors are often combined with an axial stage, which pre-whirls the air stream into the centrifugal compressor and increases both efficiency and max compression ratio per single stage, as compared to a flat single stage.
[](https://i.stack.imgur.com/Z6KAK.png) | Centrifugal compressors are limited by the size and sharp angle of the diffuser duct that has to straighten out the outward flowing air flow from the impeller compressor and reroute it back to the combustion chambers. This restricts the amount of air that can flow through this engine. Axial flow engines are straight through design and don't have this limitation. |
64,722 | I just finished *R-2800: P&W's Dependable Masterpiece* and noticed there's no mention of a pump for crankcase ventilation. Is this handled by the oil scavenge pumps? | 2019/05/24 | [
"https://aviation.stackexchange.com/questions/64722",
"https://aviation.stackexchange.com",
"https://aviation.stackexchange.com/users/36532/"
] | Centrifugal compressors only produce a more compact engine at low mass flow, which means low thrust.
The amount of thrust an engine can produce is proportional to its intake area times exhaust velocity. Increasing the latter is undesirable, as energy and thus fuel consumption is proportional to velocity *squared*. So engine designers target mass flow to gain more thrust, not more velocity.
Since they are 3D structures, in a basic solid design (that you'd find in early jets and small modern turbines), the volume of a centrifugal compressor grows in *cubic proportion* to its diameter, while frontal area, which limits its mass flow and thus its thrust, increases only as diameter *squared*. This creates a cube-square law.
Large real-life parts are filled with lightening and cooling channels, so the *mass-to-area* law is more complex. Still, it cannot eliminate the volume effect entirely. The end result is that the mass of centrifugal compressors grows considerably faster than their mass flow.
At the highest power levels, centrifugal compressors become prohibitively heavy even for fixed powerplant machinery, where durability otherwise trumps weight, so the largest base load powerplants run all-axial. With axial compressors, the flat design with a short air flow path allows mass to only grow in direct proportion to mass flow, and very powerful engines can be built within reasonable dimensions.
It's not pure cube-square law in either case, but it's something like k1\*massflow^[2.5, 2.8] for centrifugal versus k2\*massflow^[2.2, 2.4] for axial, where k2>k1, giving centrifugal compressors some advantage in small sizes. Centrifugals are also much cheaper to produce (at least small ones).
High-performance engines, such as those in commercial aircraft, also need to pack more thrust into the smallest cross-section they can, while maintaining efficiency, so as to reduce drag and also fit under the wings, enabling heavier jets. Axial compressors offer a lot more intake area for any given cross-section - thus more thrust.
The smallest jets, where thrust requirements are small and the engine's cross-section is very small compared to the fuselage, can afford the extra diameter of a centrifugal or diagonal flow compressor. Yes, it's the same cube-square law (also reduced somewhat in practice) that keeps the *engine cross-section* to *total cross-section* ratio increasing as aircraft go up in size. Small centrifugal compressors are simpler, easier to build, and more robust than small axial ones.
So in every industry, as power grows, there is a crossover point from centrifugal to axial. For aircraft where drag is critical, it's just above small bizjets, mobile ground and helicopter turbines stay centrifugal or mixed up to a few MW, and in the tens of megawatts even fixed powerplants switch from axial/centrifugal to all-axial.
Engines close to that crossover point typically combine axial and centrifugal stages. Newer diagonal compressors are in-between and quite good, offering an even more tailored compromise. | While a centrifugal compressor can acheive greater compression than a *single* compressor stage in an axial flow engine, the axial flow design allows for multiple compressor stages, achieving higher overall compression of the air and consequently greater efficiency. Centrifugal flow jet engines are, however, tough and reliable. |
64,722 | I just finished *R-2800: P&W's Dependable Masterpiece* and noticed there's no mention of a pump for crankcase ventilation. Is this handled by the oil scavenge pumps? | 2019/05/24 | [
"https://aviation.stackexchange.com/questions/64722",
"https://aviation.stackexchange.com",
"https://aviation.stackexchange.com/users/36532/"
] | Centrifugal compressors only produce a more compact engine at low mass flow, which means low thrust.
The amount of thrust an engine can produce is proportional to its intake area times exhaust velocity. Increasing the latter is undesirable, as energy and thus fuel consumption is proportional to velocity *squared*. So engine designers target mass flow to gain more thrust, not more velocity.
Since they are 3D structures, in a basic solid design (that you'd find in early jets and small modern turbines), the volume of a centrifugal compressor grows in *cubic proportion* to its diameter, while frontal area, which limits its mass flow and thus its thrust, increases only as diameter *squared*. This creates a cube-square law.
Large real-life parts are filled with lightening and cooling channels, so the *mass-to-area* law is more complex. Still, it cannot eliminate the volume effect entirely. The end result is that the mass of centrifugal compressors grows considerably faster than their mass flow.
At the highest power levels, centrifugal compressors become prohibitively heavy even for fixed powerplant machinery, where durability otherwise trumps weight, so the largest base load powerplants run all-axial. With axial compressors, the flat design with a short air flow path allows mass to only grow in direct proportion to mass flow, and very powerful engines can be built within reasonable dimensions.
It's not pure cube-square law in either case, but it's something like k1\*massflow^[2.5, 2.8] for centrifugal versus k2\*massflow^[2.2, 2.4] for axial, where k2>k1, giving centrifugal compressors some advantage in small sizes. Centrifugals are also much cheaper to produce (at least small ones).
High-performance engines, such as those in commercial aircraft, also need to pack more thrust into the smallest cross-section they can, while maintaining efficiency, so as to reduce drag and also fit under the wings, enabling heavier jets. Axial compressors offer a lot more intake area for any given cross-section - thus more thrust.
The smallest jets, where thrust requirements are small and the engine's cross-section is very small compared to the fuselage, can afford the extra diameter of a centrifugal or diagonal flow compressor. Yes, it's the same cube-square law (also reduced somewhat in practice) that keeps the *engine cross-section* to *total cross-section* ratio increasing as aircraft go up in size. Small centrifugal compressors are simpler, easier to build, and more robust than small axial ones.
So in every industry, as power grows, there is a crossover point from centrifugal to axial. For aircraft where drag is critical, it's just above small bizjets, mobile ground and helicopter turbines stay centrifugal or mixed up to a few MW, and in the tens of megawatts even fixed powerplants switch from axial/centrifugal to all-axial.
Engines close to that crossover point typically combine axial and centrifugal stages. Newer diagonal compressors are in-between and quite good, offering an even more tailored compromise. | All existing centrifugal-compressor aircraft engines have been turbojets or turboprops.
Aside from their low power compared with modern turbofans (the Rolls-Royce Dart mentioned in another answer produced about 1 MW, compared with 50MW for a modern large turbofan engine core) the larger diameter of a centrifugal compressor would make it hard to design an efficient turbofan, by restricting the area of the fan duct.
Increasing the outer diameter of the fan blades to enlarge the bypass duct is not a practical option, since it is limited by the ground clearance of the aircraft. Trying to avoid that issue with very large diameter tail-mounted engines would just create a different set of design problems. |
64,722 | I just finished *R-2800: P&W's Dependable Masterpiece* and noticed there's no mention of a pump for crankcase ventilation. Is this handled by the oil scavenge pumps? | 2019/05/24 | [
"https://aviation.stackexchange.com/questions/64722",
"https://aviation.stackexchange.com",
"https://aviation.stackexchange.com/users/36532/"
] | Centrifugal compressors only produce a more compact engine at low mass flow, which means low thrust.
The amount of thrust an engine can produce is proportional to its intake area times exhaust velocity. Increasing the latter is undesirable, as energy and thus fuel consumption is proportional to velocity *squared*. So engine designers target mass flow to gain more thrust, not more velocity.
Since they are 3D structures, in a basic solid design (that you'd find in early jets and small modern turbines), the volume of a centrifugal compressor grows in *cubic proportion* to its diameter, while frontal area, which limits its mass flow and thus its thrust, increases only as diameter *squared*. This creates a cube-square law.
Large real-life parts are filled with lightening and cooling channels, so the *mass-to-area* law is more complex. Still, it cannot eliminate the volume effect entirely. The end result is that the mass of centrifugal compressors grows considerably faster than their mass flow.
At the highest power levels, centrifugal compressors become prohibitively heavy even for fixed powerplant machinery, where durability otherwise trumps weight, so the largest base load powerplants run all-axial. With axial compressors, the flat design with a short air flow path allows mass to only grow in direct proportion to mass flow, and very powerful engines can be built within reasonable dimensions.
It's not pure cube-square law in either case, but it's something like k1\*massflow^[2.5, 2.8] for centrifugal versus k2\*massflow^[2.2, 2.4] for axial, where k2>k1, giving centrifugal compressors some advantage in small sizes. Centrifugals are also much cheaper to produce (at least small ones).
High-performance engines, such as those in commercial aircraft, also need to pack more thrust into the smallest cross-section they can, while maintaining efficiency, so as to reduce drag and also fit under the wings, enabling heavier jets. Axial compressors offer a lot more intake area for any given cross-section - thus more thrust.
The smallest jets, where thrust requirements are small and the engine's cross-section is very small compared to the fuselage, can afford the extra diameter of a centrifugal or diagonal flow compressor. Yes, it's the same cube-square law (also reduced somewhat in practice) that keeps the *engine cross-section* to *total cross-section* ratio increasing as aircraft go up in size. Small centrifugal compressors are simpler, easier to build, and more robust than small axial ones.
So in every industry, as power grows, there is a crossover point from centrifugal to axial. For aircraft where drag is critical, it's just above small bizjets, mobile ground and helicopter turbines stay centrifugal or mixed up to a few MW, and in the tens of megawatts even fixed powerplants switch from axial/centrifugal to all-axial.
Engines close to that crossover point typically combine axial and centrifugal stages. Newer diagonal compressors are in-between and quite good, offering an even more tailored compromise. | Centrifugal compressors are limited by the size and sharp angle of the diffuser duct that has to straighten out the outward flowing air flow from the impeller compressor and reroute it back to the combustion chambers. This restricts the amount of air that can flow through this engine. Axial flow engines are straight through design and don't have this limitation. |
64,722 | I just finished *R-2800: P&W's Dependable Masterpiece* and noticed there's no mention of a pump for crankcase ventilation. Is this handled by the oil scavenge pumps? | 2019/05/24 | [
"https://aviation.stackexchange.com/questions/64722",
"https://aviation.stackexchange.com",
"https://aviation.stackexchange.com/users/36532/"
] | While a centrifugal compressor can acheive greater compression than a *single* compressor stage in an axial flow engine, the axial flow design allows for multiple compressor stages, achieving higher overall compression of the air and consequently greater efficiency. Centrifugal flow jet engines are, however, tough and reliable. | All existing centrifugal-compressor aircraft engines have been turbojets or turboprops.
Aside from their low power compared with modern turbofans (the Rolls-Royce Dart mentioned in another answer produced about 1 MW, compared with 50MW for a modern large turbofan engine core) the larger diameter of a centrifugal compressor would make it hard to design an efficient turbofan, by restricting the area of the fan duct.
Increasing the outer diameter of the fan blades to enlarge the bypass duct is not a practical option, since it is limited by the ground clearance of the aircraft. Trying to avoid that issue with very large diameter tail-mounted engines would just create a different set of design problems. |
64,722 | I just finished *R-2800: P&W's Dependable Masterpiece* and noticed there's no mention of a pump for crankcase ventilation. Is this handled by the oil scavenge pumps? | 2019/05/24 | [
"https://aviation.stackexchange.com/questions/64722",
"https://aviation.stackexchange.com",
"https://aviation.stackexchange.com/users/36532/"
] | While a centrifugal compressor can acheive greater compression than a *single* compressor stage in an axial flow engine, the axial flow design allows for multiple compressor stages, achieving higher overall compression of the air and consequently greater efficiency. Centrifugal flow jet engines are, however, tough and reliable. | Centrifugal compressors are limited by the size and sharp angle of the diffuser duct that has to straighten out the outward flowing air flow from the impeller compressor and reroute it back to the combustion chambers. This restricts the amount of air that can flow through this engine. Axial flow engines are straight through design and don't have this limitation. |
64,722 | I just finished *R-2800: P&W's Dependable Masterpiece* and noticed there's no mention of a pump for crankcase ventilation. Is this handled by the oil scavenge pumps? | 2019/05/24 | [
"https://aviation.stackexchange.com/questions/64722",
"https://aviation.stackexchange.com",
"https://aviation.stackexchange.com/users/36532/"
] | Centrifugal compressors are limited by the size and sharp angle of the diffuser duct that has to straighten out the outward flowing air flow from the impeller compressor and reroute it back to the combustion chambers. This restricts the amount of air that can flow through this engine. Axial flow engines are straight through design and don't have this limitation. | All existing centrifugal-compressor aircraft engines have been turbojets or turboprops.
Aside from their low power compared with modern turbofans (the Rolls-Royce Dart mentioned in another answer produced about 1 MW, compared with 50MW for a modern large turbofan engine core) the larger diameter of a centrifugal compressor would make it hard to design an efficient turbofan, by restricting the area of the fan duct.
Increasing the outer diameter of the fan blades to enlarge the bypass duct is not a practical option, since it is limited by the ground clearance of the aircraft. Trying to avoid that issue with very large diameter tail-mounted engines would just create a different set of design problems. |
139,719 | I bought a Kitchenaid KDFE104D to replace an older Kitchenaid dishwasher. I never had any issues with the older dishwasher but eventually it died. I bought this one since I had a good experience with Kitchenaid.
First couple months all was fine but then dishwasher developed a disgusting egg smell. After research I found out that this was sulphur smell coming from sewer system.
I live in Boston area and my house is built in 1940. It has a septic system. I do not have a garbage disposal and I am extremely clean.
Here is what I tried:
1. Cleaned the sink, poured baking soda+ vinegar+hot water multiple times
2. I checked dishwasher filter, it is clean
3. I ran the dishwasher empty in very hot water with baking soda
4. I added baking soda and vinegar to loads
5. I tried smaller loads
6. I wash in extra long and extra hot cycle
7. I always rinse before i put dishes
8. I rewashed multiple times to get rid of the smell
9. I keep the DW door open and if it is smelling put baking soda and spray with vinegar
10. I remove dishes immediately after they are washed
So far nothing worked! Sometimes dishes don't smell immediately but when I use them I can smell them.
Often times dishwasher is smelling like sewer when it is empty so I am sure it is not because of dirty dishes.
It is so so so frustrating. I have no idea what else to do. Any other ideas?
Here is the under-sink plumbing:
[](https://i.stack.imgur.com/QVruI.jpg)[](https://i.stack.imgur.com/Z4nel.jpg)[](https://i.stack.imgur.com/O3U60.jpg)
I added more pictures of the sink side:
<https://ibb.co/df6bTJ>
<https://ibb.co/fqekNd>
<https://ibb.co/itNuFy>
<https://ibb.co/fY1bTJ> | 2018/05/29 | [
"https://diy.stackexchange.com/questions/139719",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/86223/"
] | From the description, this sounds like one of my favorite topics - dishwasher air gaps/high loops. However, from the picture it looks like the dishwasher drain hose goes up high. But since I can't see it come down, and since I know that if it is NOT installed correctly you are likely to have a problem, here goes:
The dishwasher drain normally requires an **air gap**. Traditionally, this would be a hose up to a corner of the sink into a little plastic/metal gadget referred to as the air gap. This would literally provide an air gap as the water would come out of the hose and through the air back down into another hose which would connect to the disposal or to the sink trap. Many recent (now on the order of at least 20 years, but not sure how long) models allow for a **high loop** configuration. In this setup, the hose loops up as high as possible - preferably up to just underneath the counter - and then loops back down to output into the disposal or the sink trap. This effectively provides an air gap as the water can only come back up through the high loop and back into the dishwasher if the sink were to fill up to the same height, which would hopefully be an extremely rare event. Even in such a case, the water would still not backflow into the water main (which would be a real safety issue) unless the water input to the dishwasher were open at the same time (i.e., dishwasher starting a cycle). So it is safe & effective and approved in many, but not all, areas.
There are two likely problems related to the high loop/air gap:
1 - The dishwasher hose is **not mounted high enough** - either installed incorrectly or was installed correctly but fell down. In this case any time the sink fills up even a little bit, or the disposal clogs a little so that it can't drain as fast as the dishwasher is trying to send out the waste water, dirty water can flow backwards into the dishwasher. Even if you can't see dirty water, this can cause quite a stink.
2 - The end of the dishwasher hose is going into the drain pipe **after the trap**. In this case, despite having the high hose, which provides an air gap to prevent backflow, sewer gas could go back through the hose to the dishwasher because it would not be blocked by the water in the trap.
If you can't figure this out, see if you can (a) get a picture of the highest point of the hose so we can see how high it is relative to the sink and (b) a picture of the hose where it attaches to the drain pipes. One or both of those may already be in the pictures you posted, but I can't tell because of the shadows. | My Kitchen Aid dishwasher has a foul smell sometimes. I don't rinse my dishes. I tried everything. Mine was coming from food build up on the bottom edge of the door. Open the door and wipe off the bottom edge, the seal down there was gross on mine. This solved my problem. |
139,719 | I bought a Kitchenaid KDFE104D to replace an older Kitchenaid dishwasher. I never had any issues with the older dishwasher but eventually it died. I bought this one since I had a good experience with Kitchenaid.
First couple months all was fine but then dishwasher developed a disgusting egg smell. After research I found out that this was sulphur smell coming from sewer system.
I live in Boston area and my house is built in 1940. It has a septic system. I do not have a garbage disposal and I am extremely clean.
Here is what I tried:
1. Cleaned the sink, poured baking soda+ vinegar+hot water multiple times
2. I checked dishwasher filter, it is clean
3. I ran the dishwasher empty in very hot water with baking soda
4. I added baking soda and vinegar to loads
5. I tried smaller loads
6. I wash in extra long and extra hot cycle
7. I always rinse before i put dishes
8. I rewashed multiple times to get rid of the smell
9. I keep the DW door open and if it is smelling put baking soda and spray with vinegar
10. I remove dishes immediately after they are washed
So far nothing worked! Sometimes dishes don't smell immediately but when I use them I can smell them.
Often times dishwasher is smelling like sewer when it is empty so I am sure it is not because of dirty dishes.
It is so so so frustrating. I have no idea what else to do. Any other ideas?
Here is the under-sink plumbing:
[](https://i.stack.imgur.com/QVruI.jpg)[](https://i.stack.imgur.com/Z4nel.jpg)[](https://i.stack.imgur.com/O3U60.jpg)
I added more pictures of the sink side:
<https://ibb.co/df6bTJ>
<https://ibb.co/fqekNd>
<https://ibb.co/itNuFy>
<https://ibb.co/fY1bTJ> | 2018/05/29 | [
"https://diy.stackexchange.com/questions/139719",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/86223/"
] | From the description, this sounds like one of my favorite topics - dishwasher air gaps/high loops. However, from the picture it looks like the dishwasher drain hose goes up high. But since I can't see it come down, and since I know that if it is NOT installed correctly you are likely to have a problem, here goes:
The dishwasher drain normally requires an **air gap**. Traditionally, this would be a hose up to a corner of the sink into a little plastic/metal gadget referred to as the air gap. This would literally provide an air gap as the water would come out of the hose and through the air back down into another hose which would connect to the disposal or to the sink trap. Many recent (now on the order of at least 20 years, but not sure how long) models allow for a **high loop** configuration. In this setup, the hose loops up as high as possible - preferably up to just underneath the counter - and then loops back down to output into the disposal or the sink trap. This effectively provides an air gap as the water can only come back up through the high loop and back into the dishwasher if the sink were to fill up to the same height, which would hopefully be an extremely rare event. Even in such a case, the water would still not backflow into the water main (which would be a real safety issue) unless the water input to the dishwasher were open at the same time (i.e., dishwasher starting a cycle). So it is safe & effective and approved in many, but not all, areas.
There are two likely problems related to the high loop/air gap:
1 - The dishwasher hose is **not mounted high enough** - either installed incorrectly or was installed correctly but fell down. In this case any time the sink fills up even a little bit, or the disposal clogs a little so that it can't drain as fast as the dishwasher is trying to send out the waste water, dirty water can flow backwards into the dishwasher. Even if you can't see dirty water, this can cause quite a stink.
2 - The end of the dishwasher hose is going into the drain pipe **after the trap**. In this case, despite having the high hose, which provides an air gap to prevent backflow, sewer gas could go back through the hose to the dishwasher because it would not be blocked by the water in the trap.
If you can't figure this out, see if you can (a) get a picture of the highest point of the hose so we can see how high it is relative to the sink and (b) a picture of the hose where it attaches to the drain pipes. One or both of those may already be in the pictures you posted, but I can't tell because of the shadows. | Do you smell sulfer in your shower too? Hot water heaters are often a source of silver smell.
This is from <https://www.corroprotec.com/rotten-egg-smell/?gclid=CjwKCAiApNSABhAlEiwANuR9YBMCVqxTMTUdOi-sj72Uo4aK_zwGvhKcSoBPB8NkZqWyZ1Wp5cwKkBoCATgQAvD_BwE>
What Causes The Rotten Egg Smell
Although there are several reasons why you have rotten egg smell in your hot water, the most common cause is the sulfur bacteria in the hot water tank. They feed on sulfur and produce hydrogen sulfide gas as waste. When the gas dissolves in the water, it gives it that characteristic odor of spoiled eggs.
Another less common cause is the chemical reaction between your water which has high levels of magnesium content and the magnesium anode in the tank. In some cases, the chemical reaction can be stopped by removing the anode rod. However, we don't recommend that since the water heater won't have any protection against corrosion.
Stops Rotten Egg Smell in Hot Water
How to Stop The Rotten Egg Smell
No matter what causes this rotten egg smell in your water, the best thing to do is to replace the magnesium anode with a Corro-Protec anode.
The Corro-Protec anode will solve the rotten |
139,719 | I bought a Kitchenaid KDFE104D to replace an older Kitchenaid dishwasher. I never had any issues with the older dishwasher but eventually it died. I bought this one since I had a good experience with Kitchenaid.
First couple months all was fine but then dishwasher developed a disgusting egg smell. After research I found out that this was sulphur smell coming from sewer system.
I live in Boston area and my house is built in 1940. It has a septic system. I do not have a garbage disposal and I am extremely clean.
Here is what I tried:
1. Cleaned the sink, poured baking soda+ vinegar+hot water multiple times
2. I checked dishwasher filter, it is clean
3. I ran the dishwasher empty in very hot water with baking soda
4. I added baking soda and vinegar to loads
5. I tried smaller loads
6. I wash in extra long and extra hot cycle
7. I always rinse before i put dishes
8. I rewashed multiple times to get rid of the smell
9. I keep the DW door open and if it is smelling put baking soda and spray with vinegar
10. I remove dishes immediately after they are washed
So far nothing worked! Sometimes dishes don't smell immediately but when I use them I can smell them.
Often times dishwasher is smelling like sewer when it is empty so I am sure it is not because of dirty dishes.
It is so so so frustrating. I have no idea what else to do. Any other ideas?
Here is the under-sink plumbing:
[](https://i.stack.imgur.com/QVruI.jpg)[](https://i.stack.imgur.com/Z4nel.jpg)[](https://i.stack.imgur.com/O3U60.jpg)
I added more pictures of the sink side:
<https://ibb.co/df6bTJ>
<https://ibb.co/fqekNd>
<https://ibb.co/itNuFy>
<https://ibb.co/fY1bTJ> | 2018/05/29 | [
"https://diy.stackexchange.com/questions/139719",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/86223/"
] | From the description, this sounds like one of my favorite topics - dishwasher air gaps/high loops. However, from the picture it looks like the dishwasher drain hose goes up high. But since I can't see it come down, and since I know that if it is NOT installed correctly you are likely to have a problem, here goes:
The dishwasher drain normally requires an **air gap**. Traditionally, this would be a hose up to a corner of the sink into a little plastic/metal gadget referred to as the air gap. This would literally provide an air gap as the water would come out of the hose and through the air back down into another hose which would connect to the disposal or to the sink trap. Many recent (now on the order of at least 20 years, but not sure how long) models allow for a **high loop** configuration. In this setup, the hose loops up as high as possible - preferably up to just underneath the counter - and then loops back down to output into the disposal or the sink trap. This effectively provides an air gap as the water can only come back up through the high loop and back into the dishwasher if the sink were to fill up to the same height, which would hopefully be an extremely rare event. Even in such a case, the water would still not backflow into the water main (which would be a real safety issue) unless the water input to the dishwasher were open at the same time (i.e., dishwasher starting a cycle). So it is safe & effective and approved in many, but not all, areas.
There are two likely problems related to the high loop/air gap:
1 - The dishwasher hose is **not mounted high enough** - either installed incorrectly or was installed correctly but fell down. In this case any time the sink fills up even a little bit, or the disposal clogs a little so that it can't drain as fast as the dishwasher is trying to send out the waste water, dirty water can flow backwards into the dishwasher. Even if you can't see dirty water, this can cause quite a stink.
2 - The end of the dishwasher hose is going into the drain pipe **after the trap**. In this case, despite having the high hose, which provides an air gap to prevent backflow, sewer gas could go back through the hose to the dishwasher because it would not be blocked by the water in the trap.
If you can't figure this out, see if you can (a) get a picture of the highest point of the hose so we can see how high it is relative to the sink and (b) a picture of the hose where it attaches to the drain pipes. One or both of those may already be in the pictures you posted, but I can't tell because of the shadows. | Indeed, an aluminum or zinc anode rod replacement in the water heater would be the solution if the smell is linked to water anywhere else in the house. |
139,719 | I bought a Kitchenaid KDFE104D to replace an older Kitchenaid dishwasher. I never had any issues with the older dishwasher but eventually it died. I bought this one since I had a good experience with Kitchenaid.
First couple months all was fine but then dishwasher developed a disgusting egg smell. After research I found out that this was sulphur smell coming from sewer system.
I live in Boston area and my house is built in 1940. It has a septic system. I do not have a garbage disposal and I am extremely clean.
Here is what I tried:
1. Cleaned the sink, poured baking soda+ vinegar+hot water multiple times
2. I checked dishwasher filter, it is clean
3. I ran the dishwasher empty in very hot water with baking soda
4. I added baking soda and vinegar to loads
5. I tried smaller loads
6. I wash in extra long and extra hot cycle
7. I always rinse before i put dishes
8. I rewashed multiple times to get rid of the smell
9. I keep the DW door open and if it is smelling put baking soda and spray with vinegar
10. I remove dishes immediately after they are washed
So far nothing worked! Sometimes dishes don't smell immediately but when I use them I can smell them.
Often times dishwasher is smelling like sewer when it is empty so I am sure it is not because of dirty dishes.
It is so so so frustrating. I have no idea what else to do. Any other ideas?
Here is the under-sink plumbing:
[](https://i.stack.imgur.com/QVruI.jpg)[](https://i.stack.imgur.com/Z4nel.jpg)[](https://i.stack.imgur.com/O3U60.jpg)
I added more pictures of the sink side:
<https://ibb.co/df6bTJ>
<https://ibb.co/fqekNd>
<https://ibb.co/itNuFy>
<https://ibb.co/fY1bTJ> | 2018/05/29 | [
"https://diy.stackexchange.com/questions/139719",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/86223/"
] | My Kitchen Aid dishwasher has a foul smell sometimes. I don't rinse my dishes. I tried everything. Mine was coming from food build up on the bottom edge of the door. Open the door and wipe off the bottom edge, the seal down there was gross on mine. This solved my problem. | Indeed, an aluminum or zinc anode rod replacement in the water heater would be the solution if the smell is linked to water anywhere else in the house. |
139,719 | I bought a Kitchenaid KDFE104D to replace an older Kitchenaid dishwasher. I never had any issues with the older dishwasher but eventually it died. I bought this one since I had a good experience with Kitchenaid.
First couple months all was fine but then dishwasher developed a disgusting egg smell. After research I found out that this was sulphur smell coming from sewer system.
I live in Boston area and my house is built in 1940. It has a septic system. I do not have a garbage disposal and I am extremely clean.
Here is what I tried:
1. Cleaned the sink, poured baking soda+ vinegar+hot water multiple times
2. I checked dishwasher filter, it is clean
3. I ran the dishwasher empty in very hot water with baking soda
4. I added baking soda and vinegar to loads
5. I tried smaller loads
6. I wash in extra long and extra hot cycle
7. I always rinse before i put dishes
8. I rewashed multiple times to get rid of the smell
9. I keep the DW door open and if it is smelling put baking soda and spray with vinegar
10. I remove dishes immediately after they are washed
So far nothing worked! Sometimes dishes don't smell immediately but when I use them I can smell them.
Often times dishwasher is smelling like sewer when it is empty so I am sure it is not because of dirty dishes.
It is so so so frustrating. I have no idea what else to do. Any other ideas?
Here is the under-sink plumbing:
[](https://i.stack.imgur.com/QVruI.jpg)[](https://i.stack.imgur.com/Z4nel.jpg)[](https://i.stack.imgur.com/O3U60.jpg)
I added more pictures of the sink side:
<https://ibb.co/df6bTJ>
<https://ibb.co/fqekNd>
<https://ibb.co/itNuFy>
<https://ibb.co/fY1bTJ> | 2018/05/29 | [
"https://diy.stackexchange.com/questions/139719",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/86223/"
] | Do you smell sulfer in your shower too? Hot water heaters are often a source of silver smell.
This is from <https://www.corroprotec.com/rotten-egg-smell/?gclid=CjwKCAiApNSABhAlEiwANuR9YBMCVqxTMTUdOi-sj72Uo4aK_zwGvhKcSoBPB8NkZqWyZ1Wp5cwKkBoCATgQAvD_BwE>
What Causes The Rotten Egg Smell
Although there are several reasons why you have rotten egg smell in your hot water, the most common cause is the sulfur bacteria in the hot water tank. They feed on sulfur and produce hydrogen sulfide gas as waste. When the gas dissolves in the water, it gives it that characteristic odor of spoiled eggs.
Another less common cause is the chemical reaction between your water which has high levels of magnesium content and the magnesium anode in the tank. In some cases, the chemical reaction can be stopped by removing the anode rod. However, we don't recommend that since the water heater won't have any protection against corrosion.
Stops Rotten Egg Smell in Hot Water
How to Stop The Rotten Egg Smell
No matter what causes this rotten egg smell in your water, the best thing to do is to replace the magnesium anode with a Corro-Protec anode.
The Corro-Protec anode will solve the rotten | Indeed, an aluminum or zinc anode rod replacement in the water heater would be the solution if the smell is linked to water anywhere else in the house. |
119,659 | I'm trying to register a new App ID inside iTunes connect web site, but when I've filled out the details and hit continue, it just comes up "Loading" and stays like that, any ideas? | 2014/02/02 | [
"https://apple.stackexchange.com/questions/119659",
"https://apple.stackexchange.com",
"https://apple.stackexchange.com/users/63085/"
] | Just for anyone else with the same issue. I tried another browser and it worked fine, so it's some kind of browser issue. | This happened to me one time too. I would check my internet connection first. Internet connection problem is something that happens frequently. After that i would go over all the information that you provided and see if there is a mistake somewhere. |
119,659 | I'm trying to register a new App ID inside iTunes connect web site, but when I've filled out the details and hit continue, it just comes up "Loading" and stays like that, any ideas? | 2014/02/02 | [
"https://apple.stackexchange.com/questions/119659",
"https://apple.stackexchange.com",
"https://apple.stackexchange.com/users/63085/"
] | This was happening to me because I was using Safari "Private mode". When I turned back to "Non Private Mode" the problem was solved | This happened to me one time too. I would check my internet connection first. Internet connection problem is something that happens frequently. After that i would go over all the information that you provided and see if there is a mistake somewhere. |
119,659 | I'm trying to register a new App ID inside iTunes connect web site, but when I've filled out the details and hit continue, it just comes up "Loading" and stays like that, any ideas? | 2014/02/02 | [
"https://apple.stackexchange.com/questions/119659",
"https://apple.stackexchange.com",
"https://apple.stackexchange.com/users/63085/"
] | I had AdBlock Plus and Ghostery running. Disabling both allowed it to work for me. | This happened to me one time too. I would check my internet connection first. Internet connection problem is something that happens frequently. After that i would go over all the information that you provided and see if there is a mistake somewhere. |
119,659 | I'm trying to register a new App ID inside iTunes connect web site, but when I've filled out the details and hit continue, it just comes up "Loading" and stays like that, any ideas? | 2014/02/02 | [
"https://apple.stackexchange.com/questions/119659",
"https://apple.stackexchange.com",
"https://apple.stackexchange.com/users/63085/"
] | Just for anyone else with the same issue. I tried another browser and it worked fine, so it's some kind of browser issue. | This was happening to me because I was using Safari "Private mode". When I turned back to "Non Private Mode" the problem was solved |
119,659 | I'm trying to register a new App ID inside iTunes connect web site, but when I've filled out the details and hit continue, it just comes up "Loading" and stays like that, any ideas? | 2014/02/02 | [
"https://apple.stackexchange.com/questions/119659",
"https://apple.stackexchange.com",
"https://apple.stackexchange.com/users/63085/"
] | Just for anyone else with the same issue. I tried another browser and it worked fine, so it's some kind of browser issue. | I had AdBlock Plus and Ghostery running. Disabling both allowed it to work for me. |
58,807,476 | Does redis update the key value and ttl if I set the **same** key value and ttl again before the current ttl expires? When I do so, it doesn't seem to do anything, and the keys expire after the previous set timeout.
The code is pretty simple - write the same keys in redis over and over again with the same value and same ttl - but looks like I should be getting the key and setting the new ttl value instead. Is this the case? | 2019/11/11 | [
"https://Stackoverflow.com/questions/58807476",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/2213141/"
] | It will update the value and the TTL.
[](https://i.stack.imgur.com/IbjFu.png) | Does redis update the key value and ttl if I set the same key value and ttl again before the current ttl expires?
->**yes, it definitely update** new ttl and value for the key |
5,286,560 | I understand basic binary logic and how to do basic addition, subtraction etc. I get that each of the characters in this text is just a binary number representing a number in a charset. The numbers dont really mean anything to the computer. I'm confused however as to how a computer works out that a number is greater than another. what does it do at the bit level? | 2011/03/13 | [
"https://Stackoverflow.com/questions/5286560",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/195674/"
] | It subtracts one from the other and sees if the result is less than 0 (by checking the highest-order bit, which is 1 on a number less than 0 since computers use 2's complement notation).
<http://academic.evergreen.edu/projects/biophysics/technotes/program/2s_comp.htm> | It substracts the two numbers and checks if the result is positive, negative (highest bit - aka "the minus bit" is set), or zero. |
5,286,560 | I understand basic binary logic and how to do basic addition, subtraction etc. I get that each of the characters in this text is just a binary number representing a number in a charset. The numbers dont really mean anything to the computer. I'm confused however as to how a computer works out that a number is greater than another. what does it do at the bit level? | 2011/03/13 | [
"https://Stackoverflow.com/questions/5286560",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/195674/"
] | If you have two numbers, you can compare each bit, from most significant to least significant, using a 1-bit comparator gate:
Of course n-bit comparator gates exist and are described further [here](http://www.electronics-tutorials.ws/combination/comb_8.html). | It substracts the two numbers and checks if the result is positive, negative (highest bit - aka "the minus bit" is set), or zero. |
5,286,560 | I understand basic binary logic and how to do basic addition, subtraction etc. I get that each of the characters in this text is just a binary number representing a number in a charset. The numbers dont really mean anything to the computer. I'm confused however as to how a computer works out that a number is greater than another. what does it do at the bit level? | 2011/03/13 | [
"https://Stackoverflow.com/questions/5286560",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/195674/"
] | It subtracts one from the other and sees if the result is less than 0 (by checking the highest-order bit, which is 1 on a number less than 0 since computers use 2's complement notation).
<http://academic.evergreen.edu/projects/biophysics/technotes/program/2s_comp.htm> | Within the processor, often there will be microcode to do operations, using hardwired options, such as add/subtract, that is already there.
So, to do a comparison of an integer the microcode can just do a subtraction, and based on the result determine if one is greater than the other.
Microcode is basically just low-level programs that will be called by assembly, to make it look like there are more commands than is actually hardwired on the processor.
You may find this useful:
<http://www.osdata.com/topic/language/asm/intarith.htm> |
5,286,560 | I understand basic binary logic and how to do basic addition, subtraction etc. I get that each of the characters in this text is just a binary number representing a number in a charset. The numbers dont really mean anything to the computer. I'm confused however as to how a computer works out that a number is greater than another. what does it do at the bit level? | 2011/03/13 | [
"https://Stackoverflow.com/questions/5286560",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/195674/"
] | If you have two numbers, you can compare each bit, from most significant to least significant, using a 1-bit comparator gate:
Of course n-bit comparator gates exist and are described further [here](http://www.electronics-tutorials.ws/combination/comb_8.html). | It subtracts one from the other and sees if the result is less than 0 (by checking the highest-order bit, which is 1 on a number less than 0 since computers use 2's complement notation).
<http://academic.evergreen.edu/projects/biophysics/technotes/program/2s_comp.htm> |
5,286,560 | I understand basic binary logic and how to do basic addition, subtraction etc. I get that each of the characters in this text is just a binary number representing a number in a charset. The numbers dont really mean anything to the computer. I'm confused however as to how a computer works out that a number is greater than another. what does it do at the bit level? | 2011/03/13 | [
"https://Stackoverflow.com/questions/5286560",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/195674/"
] | It subtracts one from the other and sees if the result is less than 0 (by checking the highest-order bit, which is 1 on a number less than 0 since computers use 2's complement notation).
<http://academic.evergreen.edu/projects/biophysics/technotes/program/2s_comp.htm> | I guess it does a bitwise comparison of two numbers from the most significant bit to the least significant bit, and when they differ, the number with the bit set to "1" is the greater.
In a Big-endian architecture, the comparison of the following Bytes:
A: 0010 1101
B: 0010 1010
would result in A being greatest than B for its 6th bit (from the left) is set to one, while the precedent bits are equal to B.
But this is just a quick theoretic answer, with no concerns about floating point numbers and negative numbers. |
5,286,560 | I understand basic binary logic and how to do basic addition, subtraction etc. I get that each of the characters in this text is just a binary number representing a number in a charset. The numbers dont really mean anything to the computer. I'm confused however as to how a computer works out that a number is greater than another. what does it do at the bit level? | 2011/03/13 | [
"https://Stackoverflow.com/questions/5286560",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/195674/"
] | If you have two numbers, you can compare each bit, from most significant to least significant, using a 1-bit comparator gate:
Of course n-bit comparator gates exist and are described further [here](http://www.electronics-tutorials.ws/combination/comb_8.html). | Within the processor, often there will be microcode to do operations, using hardwired options, such as add/subtract, that is already there.
So, to do a comparison of an integer the microcode can just do a subtraction, and based on the result determine if one is greater than the other.
Microcode is basically just low-level programs that will be called by assembly, to make it look like there are more commands than is actually hardwired on the processor.
You may find this useful:
<http://www.osdata.com/topic/language/asm/intarith.htm> |
5,286,560 | I understand basic binary logic and how to do basic addition, subtraction etc. I get that each of the characters in this text is just a binary number representing a number in a charset. The numbers dont really mean anything to the computer. I'm confused however as to how a computer works out that a number is greater than another. what does it do at the bit level? | 2011/03/13 | [
"https://Stackoverflow.com/questions/5286560",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/195674/"
] | If you have two numbers, you can compare each bit, from most significant to least significant, using a 1-bit comparator gate:
Of course n-bit comparator gates exist and are described further [here](http://www.electronics-tutorials.ws/combination/comb_8.html). | I guess it does a bitwise comparison of two numbers from the most significant bit to the least significant bit, and when they differ, the number with the bit set to "1" is the greater.
In a Big-endian architecture, the comparison of the following Bytes:
A: 0010 1101
B: 0010 1010
would result in A being greatest than B for its 6th bit (from the left) is set to one, while the precedent bits are equal to B.
But this is just a quick theoretic answer, with no concerns about floating point numbers and negative numbers. |
34,186,191 | I have two developer account. I created app from first developer account with certain name. App is not yet submitted for review, it is in initial development phase.
Now we thought creating app from another developer account will be more appropriate. Problem is that, now it is not allowing me to use the same name. It says "The App Name you entered has already been used". Which is fine, because it is used in another account.
But I went ahead and renamed my app from earlier account. Still it is not allowing me to use original name from second developer account.
1) Does it take some time to put app name back into pool?
2) I don't see the delete option in the first dev account, so that I can try to delete the app. | 2015/12/09 | [
"https://Stackoverflow.com/questions/34186191",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/3749559/"
] | If renaming the previous app to something completely random does not work, you can try this:
When you create the new app, instead of selecting "English" as primary language, select "UK English" (or anything else, really). The unicity is per language, and local variations are counted as separate languages. | First off, once you register the app name, no matter if in development or release, that App name will from now on be taken. Now to your question, you have two options here.
A) You could transfer the app to your second account
B) You could delete the app (not recommended)
A) If you transfer the app, you basically give the ownership to another account. To do this, simply follow the steps listed by apple [here](https://developer.apple.com/library/ios/documentation/LanguagesUtilities/Conceptual/iTunesConnect_Guide/Chapters/TransferringAndDeletingApps.html).
B) This option is not recommended as once you remove it in this account you will never be able to reuse the identifier or the App name. If you want to go ahead and delete the app, follow this [tutorial](https://developer.apple.com/library/ios/documentation/LanguagesUtilities/Conceptual/iTunesConnect_Guide/Chapters/TransferringAndDeletingApps.html) again provided by Apple.
Lastly, you can try to simply rename your app. I am not sure if that will work as I have never tried it myself, but nothing speaks against it. Simply open your app in iTunes Connect and then change the display name. This should again offer the old name into the pool of available names.
Hope that helps, Julian |
34,186,191 | I have two developer account. I created app from first developer account with certain name. App is not yet submitted for review, it is in initial development phase.
Now we thought creating app from another developer account will be more appropriate. Problem is that, now it is not allowing me to use the same name. It says "The App Name you entered has already been used". Which is fine, because it is used in another account.
But I went ahead and renamed my app from earlier account. Still it is not allowing me to use original name from second developer account.
1) Does it take some time to put app name back into pool?
2) I don't see the delete option in the first dev account, so that I can try to delete the app. | 2015/12/09 | [
"https://Stackoverflow.com/questions/34186191",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/3749559/"
] | First off, once you register the app name, no matter if in development or release, that App name will from now on be taken. Now to your question, you have two options here.
A) You could transfer the app to your second account
B) You could delete the app (not recommended)
A) If you transfer the app, you basically give the ownership to another account. To do this, simply follow the steps listed by apple [here](https://developer.apple.com/library/ios/documentation/LanguagesUtilities/Conceptual/iTunesConnect_Guide/Chapters/TransferringAndDeletingApps.html).
B) This option is not recommended as once you remove it in this account you will never be able to reuse the identifier or the App name. If you want to go ahead and delete the app, follow this [tutorial](https://developer.apple.com/library/ios/documentation/LanguagesUtilities/Conceptual/iTunesConnect_Guide/Chapters/TransferringAndDeletingApps.html) again provided by Apple.
Lastly, you can try to simply rename your app. I am not sure if that will work as I have never tried it myself, but nothing speaks against it. Simply open your app in iTunes Connect and then change the display name. This should again offer the old name into the pool of available names.
Hope that helps, Julian | Renaming the app actually worked for me:
1. Go to your iTunes connect account that contains the app you want to 'deprecate'
2. Select the app, go to App Information
3. Rename the app in Localizable Information, click save
Now sign into your other iTunes connect account and try to create the app. |
34,186,191 | I have two developer account. I created app from first developer account with certain name. App is not yet submitted for review, it is in initial development phase.
Now we thought creating app from another developer account will be more appropriate. Problem is that, now it is not allowing me to use the same name. It says "The App Name you entered has already been used". Which is fine, because it is used in another account.
But I went ahead and renamed my app from earlier account. Still it is not allowing me to use original name from second developer account.
1) Does it take some time to put app name back into pool?
2) I don't see the delete option in the first dev account, so that I can try to delete the app. | 2015/12/09 | [
"https://Stackoverflow.com/questions/34186191",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/3749559/"
] | If renaming the previous app to something completely random does not work, you can try this:
When you create the new app, instead of selecting "English" as primary language, select "UK English" (or anything else, really). The unicity is per language, and local variations are counted as separate languages. | Renaming the app actually worked for me:
1. Go to your iTunes connect account that contains the app you want to 'deprecate'
2. Select the app, go to App Information
3. Rename the app in Localizable Information, click save
Now sign into your other iTunes connect account and try to create the app. |
3,210 | Let's say Alice wants to send Bob some coins. Bob needs to tell Alice where to send them, so he sends his address to Alice. How does Bob send this address so that Alice knows that the address she is receiving is indeed Bob's address and not an Eve's (an eavesdropper) who wants to steal the coins? | 2012/03/18 | [
"https://bitcoin.stackexchange.com/questions/3210",
"https://bitcoin.stackexchange.com",
"https://bitcoin.stackexchange.com/users/1185/"
] | Bitcoin doesn't currently provide any protection against that. Alice and Bob will need to make sure that their communication channel is secure. | The #bitcoin-otc marketplace uses GPG authentication to protect against this very situation.
Because irc nicknames are vulnerable to manipulation, the task of first authenticating with the channel's bot helps to ensure that the communications are truly from the intended trading partner.
* <http://wiki.bitcoin-otc.com/wiki/OTC_Rating_System>
This is just one method to address this subject. There are many options. |
3,210 | Let's say Alice wants to send Bob some coins. Bob needs to tell Alice where to send them, so he sends his address to Alice. How does Bob send this address so that Alice knows that the address she is receiving is indeed Bob's address and not an Eve's (an eavesdropper) who wants to steal the coins? | 2012/03/18 | [
"https://bitcoin.stackexchange.com/questions/3210",
"https://bitcoin.stackexchange.com",
"https://bitcoin.stackexchange.com/users/1185/"
] | The problem itself is not Bitcoin-specific per se. It's a matter of being able to verify the sender of some data. Bitcoin addresses are only designed to be immune to typos (they contain a checksum), but otherwise the protocol does nothing.
One can, however, do a couple things to make sure a proper address is sent and received:
* One can use a vanity address that is hard to generate and clearly is related to the situation. Using 1Bob... would not be the best choice, but 1BobEveryman..., or 1ThankYouAlice... can be better (examples chosen for clarity, normally you'd be using base 58 alphabet). Generally, if it takes more than a couple minutes to generate an address you know it either came from the original sender, or someone deliberately wanted to steal Bob's identity (by spending a lot of time beforehand generating the address).
* One can try checking the history of the address in the [Bitcoin Block Explorer](http://blockexplorer.com/). If the address has been used a couple times, it is less likely it will be fake. Being Eve I probably wouldn't want to use the same address for scamming people more than once, and generating a history of transactions would take some time.
* One can ask Bob to provide his Bitcoin address wrapped in Bob's digital signature. The main problem with this is securing Bob's signature in the first place, which is basically the same problem as we are solving right now.
* One can look for address received on the internet. A lot of people have a habit of including the Bitcoin address they use in places like forum signatures, their websites and the like.
* If Alice knows Bob, they might decide on using some information only they would know to create an ECDSA keypair and use that for transmitting Bitcoins. Such information might be for example be the movie they saw when they first met, some information from the school they attended and so forth. Generally, something that they remember and would be hard to find out. Alice can use that as the private seed of the keypair, generate the public address to send the Bitcoins to, and make the transfer. Bob then would have to repeat the same process and withdraw Bitcoins on their end. The main problem with this approach is whether Bob an Alice know each other beforehand and trust themselves with handling private keys.
* When all else fails, one can always meet Bob in person and get their address that way.
All in all, there are many ways to prevent a man in the middle attack in the descried scenario. | Bitcoin doesn't currently provide any protection against that. Alice and Bob will need to make sure that their communication channel is secure. |
3,210 | Let's say Alice wants to send Bob some coins. Bob needs to tell Alice where to send them, so he sends his address to Alice. How does Bob send this address so that Alice knows that the address she is receiving is indeed Bob's address and not an Eve's (an eavesdropper) who wants to steal the coins? | 2012/03/18 | [
"https://bitcoin.stackexchange.com/questions/3210",
"https://bitcoin.stackexchange.com",
"https://bitcoin.stackexchange.com/users/1185/"
] | Bitcoin doesn't currently provide any protection against that. Alice and Bob will need to make sure that their communication channel is secure. | If Alice met Bob through his website, <https://bobbysox.com/>, then she can be pretty sure that the address Bob displays on his site is real, so long as Bob's SSL certificate is verified successfully. For Eve to play woman-in-the-middle she would have to somehow get hold of a certificate for bobbysox.com, or Alice's browser will alert her to the fact that there's a problem with the secure connection. (Whether Alice takes any notice is another matter).
That's often how Bitcoin addresses are passed from merchant to buyer, via secure socket layer web connections.
Note: interestingly, when I click on that link I just made up, I see a warning: "The site's security certificate is not trusted!" |
3,210 | Let's say Alice wants to send Bob some coins. Bob needs to tell Alice where to send them, so he sends his address to Alice. How does Bob send this address so that Alice knows that the address she is receiving is indeed Bob's address and not an Eve's (an eavesdropper) who wants to steal the coins? | 2012/03/18 | [
"https://bitcoin.stackexchange.com/questions/3210",
"https://bitcoin.stackexchange.com",
"https://bitcoin.stackexchange.com/users/1185/"
] | The problem itself is not Bitcoin-specific per se. It's a matter of being able to verify the sender of some data. Bitcoin addresses are only designed to be immune to typos (they contain a checksum), but otherwise the protocol does nothing.
One can, however, do a couple things to make sure a proper address is sent and received:
* One can use a vanity address that is hard to generate and clearly is related to the situation. Using 1Bob... would not be the best choice, but 1BobEveryman..., or 1ThankYouAlice... can be better (examples chosen for clarity, normally you'd be using base 58 alphabet). Generally, if it takes more than a couple minutes to generate an address you know it either came from the original sender, or someone deliberately wanted to steal Bob's identity (by spending a lot of time beforehand generating the address).
* One can try checking the history of the address in the [Bitcoin Block Explorer](http://blockexplorer.com/). If the address has been used a couple times, it is less likely it will be fake. Being Eve I probably wouldn't want to use the same address for scamming people more than once, and generating a history of transactions would take some time.
* One can ask Bob to provide his Bitcoin address wrapped in Bob's digital signature. The main problem with this is securing Bob's signature in the first place, which is basically the same problem as we are solving right now.
* One can look for address received on the internet. A lot of people have a habit of including the Bitcoin address they use in places like forum signatures, their websites and the like.
* If Alice knows Bob, they might decide on using some information only they would know to create an ECDSA keypair and use that for transmitting Bitcoins. Such information might be for example be the movie they saw when they first met, some information from the school they attended and so forth. Generally, something that they remember and would be hard to find out. Alice can use that as the private seed of the keypair, generate the public address to send the Bitcoins to, and make the transfer. Bob then would have to repeat the same process and withdraw Bitcoins on their end. The main problem with this approach is whether Bob an Alice know each other beforehand and trust themselves with handling private keys.
* When all else fails, one can always meet Bob in person and get their address that way.
All in all, there are many ways to prevent a man in the middle attack in the descried scenario. | The #bitcoin-otc marketplace uses GPG authentication to protect against this very situation.
Because irc nicknames are vulnerable to manipulation, the task of first authenticating with the channel's bot helps to ensure that the communications are truly from the intended trading partner.
* <http://wiki.bitcoin-otc.com/wiki/OTC_Rating_System>
This is just one method to address this subject. There are many options. |
3,210 | Let's say Alice wants to send Bob some coins. Bob needs to tell Alice where to send them, so he sends his address to Alice. How does Bob send this address so that Alice knows that the address she is receiving is indeed Bob's address and not an Eve's (an eavesdropper) who wants to steal the coins? | 2012/03/18 | [
"https://bitcoin.stackexchange.com/questions/3210",
"https://bitcoin.stackexchange.com",
"https://bitcoin.stackexchange.com/users/1185/"
] | The problem itself is not Bitcoin-specific per se. It's a matter of being able to verify the sender of some data. Bitcoin addresses are only designed to be immune to typos (they contain a checksum), but otherwise the protocol does nothing.
One can, however, do a couple things to make sure a proper address is sent and received:
* One can use a vanity address that is hard to generate and clearly is related to the situation. Using 1Bob... would not be the best choice, but 1BobEveryman..., or 1ThankYouAlice... can be better (examples chosen for clarity, normally you'd be using base 58 alphabet). Generally, if it takes more than a couple minutes to generate an address you know it either came from the original sender, or someone deliberately wanted to steal Bob's identity (by spending a lot of time beforehand generating the address).
* One can try checking the history of the address in the [Bitcoin Block Explorer](http://blockexplorer.com/). If the address has been used a couple times, it is less likely it will be fake. Being Eve I probably wouldn't want to use the same address for scamming people more than once, and generating a history of transactions would take some time.
* One can ask Bob to provide his Bitcoin address wrapped in Bob's digital signature. The main problem with this is securing Bob's signature in the first place, which is basically the same problem as we are solving right now.
* One can look for address received on the internet. A lot of people have a habit of including the Bitcoin address they use in places like forum signatures, their websites and the like.
* If Alice knows Bob, they might decide on using some information only they would know to create an ECDSA keypair and use that for transmitting Bitcoins. Such information might be for example be the movie they saw when they first met, some information from the school they attended and so forth. Generally, something that they remember and would be hard to find out. Alice can use that as the private seed of the keypair, generate the public address to send the Bitcoins to, and make the transfer. Bob then would have to repeat the same process and withdraw Bitcoins on their end. The main problem with this approach is whether Bob an Alice know each other beforehand and trust themselves with handling private keys.
* When all else fails, one can always meet Bob in person and get their address that way.
All in all, there are many ways to prevent a man in the middle attack in the descried scenario. | If Alice met Bob through his website, <https://bobbysox.com/>, then she can be pretty sure that the address Bob displays on his site is real, so long as Bob's SSL certificate is verified successfully. For Eve to play woman-in-the-middle she would have to somehow get hold of a certificate for bobbysox.com, or Alice's browser will alert her to the fact that there's a problem with the secure connection. (Whether Alice takes any notice is another matter).
That's often how Bitcoin addresses are passed from merchant to buyer, via secure socket layer web connections.
Note: interestingly, when I click on that link I just made up, I see a warning: "The site's security certificate is not trusted!" |
4,501 | There are a set of winter tires on there already, but I'm not worried about getting paint or rust remover on the tires -- I've ordered some new tires already (going studded this year) and will be getting rid of the ones I have.
How vigilant should I be with rust? Is it enough to wipe it down and clean it up with chemicals or do I need to get out the Dremel tool and sand my way down to clean metal before painting? How many coats of paint should I use? | 2012/10/13 | [
"https://mechanics.stackexchange.com/questions/4501",
"https://mechanics.stackexchange.com",
"https://mechanics.stackexchange.com/users/2302/"
] | I think it depends on how bad the rust patches are. If it's just surface rust, I'd clean up the rust with a wire brush and some sand paper and treat the remaining rust with chemical rust remover or converter, then repaint the wheel.
If there is significantly deep rust on the rim that goes deep enough to warrant grinding out, I'd be a bit careful or would just get a replacement rim as I wouldn't want to run the risk that the rim has been weakened. That said, I don't think I've seen that sort of rust on a steel rim that wasn't a several decades old and used in a very damp/salty environment, and even then it's pretty rare. | With rust you really need to grind down to bare metal, then use rust-resist paint as your first layer, covered with a couple more layers of paint to protect that undercoat (depending on how hard-wearing the paint is) otherwise it will just spread. |
70,941 | Scenario 1:
Artist B buys a line image of a cat licenced on a stock image website by Artist A. (licence terms-free to distribute, modify but must credit original artist).
Artist B colours it and then places it on a creative commons clipart website without crediting the original artist. (Image can be used free for commercial use except merchandising, no accreditation required).
Person C uses Artist B's image from the clipart website without the knowledge of Artist A.
Is Person C infringing on Person A's copyright by using B's image? Is Person B allowed to post their image on the clipart website?
Scenario 2
Artist B uses Artist A's clipart to make their own version of the animal. They place this on a creative commons stock site-(free for commercial, no attribution required).
Artist C uses Artist B's version in their own work, publishes and later finds that Artist B based their work on A's clipart. Artist A cannot be located and the work is only visible on a couple of free for personal use clipart websites. The work seems to be an orphan work. It cannot be ascertained if Artist B has permission to make the derivative. What is the legal position of Artist C (assuming no fair use/fair dealings)?
Thanks | 2021/08/19 | [
"https://law.stackexchange.com/questions/70941",
"https://law.stackexchange.com",
"https://law.stackexchange.com/users/39573/"
] | In both scenarios B is infringement on A's copyright by failing to comply with the license terms (no attribution). B therefore cannot grant the rights that B's posting claims to grant. C may not use B's work in reliance on B's license, since B did not have the rights to grant. A could issue a takedown against B's work or C's work, 9or could sue either for infringement. However, since C acted in good faith, damages awarded to A against C would probably be minimal, and most artists in A's position would not sue C.
Note that since C's work is also directly derivative of A's, C can probably comply with A's license simply by providing proper attribution to A. At that point, C would be in compliance, not infringing, and there would be no case against c for currant actions. In theory there could be a suit against C for past infringement, but this would be unlikely in practice unless there had been significant provable economic damage. | In scenario 1, Artist C is violating Artist A's copyright conditions. He might be requested to remove his work from the public domain if A finds out. However he's unlikely to be sued directly, because the actual copyright infringement was done by Artist B, who didn't hold on to A's license and *deliberately* used an incompatible license for his derivative work. C was acting in good faith. B might even be liable for any damage done to C (i.e. missed income).
Scenario 2 isn't different, except that now C found out himself that B had been violating A's copyright/license terms. C's work still is technically violating A's copyright, but again he should probably sue B for the copyright violation. |
2,287 | How much the pitch (horizontal orientation) can differ from the angle of attack? I am trying to understand the claim that "angle of attack indicator was unfortunately not available", contributing to problems during Air France [Flight 447](http://en.wikipedia.org/wiki/Air_France_Flight_447). [Attitude indicator](http://en.wikipedia.org/wiki/Attitude_indicator) most likely was available? | 2014/03/14 | [
"https://aviation.stackexchange.com/questions/2287",
"https://aviation.stackexchange.com",
"https://aviation.stackexchange.com/users/917/"
] | The angle of attack is the angle between the wing (wing chord to be precise) and the direction of travel (undisturbed airflow). The angle of pitch is the angle between the main body axis and the horizon. The difference can theoretically be any angle, but during normal flight it will be limited to about 15 degrees.
The reason that the angle of attack sensor was inoperative was due to low airspeed. Below 60 knot IAS the indication is unreliable and therefore the indicator is inhibited. This also inhibits the stall warning. This lead to the confusing situation that lowering the nose to correct the stall increased the airspeed beyond 60 knots, thereby reactivating the stall warning. | It can be. Remember that the angle of attack is the angle between the chord line of the airfoil and the relative wind. Imagine if the plane is level with the horizon with zero airpseed. It will fall straight down, putting the angle of attack close to 90 degrees with the pitch close to zero.
That said, during normal flight it's not likely that pitch and angle of attack will be excessively different. But honestly the two aren't closely related: You can exceed the critical angle of attack and stall at any pitch, bank, or yaw angle. |
2,287 | How much the pitch (horizontal orientation) can differ from the angle of attack? I am trying to understand the claim that "angle of attack indicator was unfortunately not available", contributing to problems during Air France [Flight 447](http://en.wikipedia.org/wiki/Air_France_Flight_447). [Attitude indicator](http://en.wikipedia.org/wiki/Attitude_indicator) most likely was available? | 2014/03/14 | [
"https://aviation.stackexchange.com/questions/2287",
"https://aviation.stackexchange.com",
"https://aviation.stackexchange.com/users/917/"
] | It can be. Remember that the angle of attack is the angle between the chord line of the airfoil and the relative wind. Imagine if the plane is level with the horizon with zero airpseed. It will fall straight down, putting the angle of attack close to 90 degrees with the pitch close to zero.
That said, during normal flight it's not likely that pitch and angle of attack will be excessively different. But honestly the two aren't closely related: You can exceed the critical angle of attack and stall at any pitch, bank, or yaw angle. | [](https://i.stack.imgur.com/muxDg.png)
Just before the ground impact
Just watch [this video](https://www.youtube.com/watch?v=keCnK4kh65U) of a looping gone bad during a flight display. [At 1:30](https://youtu.be/keCnK4kh65U?t=90) into the video it becomes painfully obvious by how much both can diverge in extreme situations *(shown above).*
The flight path angle is the difference between pitch attitude and angle of attack. If pitch attitude and angle of attack would be equal, the airplane could only fly straight ahead at the same altitude. Once it climbs, it has to increase pitch attitude at constant angle of attack. With enough thrust or speed, both can be 90° apart.
Now consider flying inverted: Both are almost 180° apart.
In a dive, again the difference will become large because the flight path angle takes on negative values.
The more fun it makes to fly an aircraft, the more both angles diverge. Only [boring aircraft](http://en.wikipedia.org/wiki/Airliner) will keep both of them at similar, low values. |
2,287 | How much the pitch (horizontal orientation) can differ from the angle of attack? I am trying to understand the claim that "angle of attack indicator was unfortunately not available", contributing to problems during Air France [Flight 447](http://en.wikipedia.org/wiki/Air_France_Flight_447). [Attitude indicator](http://en.wikipedia.org/wiki/Attitude_indicator) most likely was available? | 2014/03/14 | [
"https://aviation.stackexchange.com/questions/2287",
"https://aviation.stackexchange.com",
"https://aviation.stackexchange.com/users/917/"
] | It can be. Remember that the angle of attack is the angle between the chord line of the airfoil and the relative wind. Imagine if the plane is level with the horizon with zero airpseed. It will fall straight down, putting the angle of attack close to 90 degrees with the pitch close to zero.
That said, during normal flight it's not likely that pitch and angle of attack will be excessively different. But honestly the two aren't closely related: You can exceed the critical angle of attack and stall at any pitch, bank, or yaw angle. | Just want to add the image.
Angle of attack is relative to the direction of relative wind (which is equivalently relative to the direction the plane is going, if in still air and the angle of incidence = 0, i.e. the wing is mounted parallel to the longitudinal axis of the plane), while pitch is relative to the horizontal axis. Angle of attack depends on the pitch, current velocity of the aircraft and the wind. They can be different.
Angle of attack is important to the aerodynamics (amount of lift, drag, etc.), while pitch tells you the aircraft's orientation relative to the ground.
[Image source](http://www.aeroskytech.com/english/firstnotions/anglesen.png)
Assumptions for the image: still air and angle of incidence is 0.
 |
2,287 | How much the pitch (horizontal orientation) can differ from the angle of attack? I am trying to understand the claim that "angle of attack indicator was unfortunately not available", contributing to problems during Air France [Flight 447](http://en.wikipedia.org/wiki/Air_France_Flight_447). [Attitude indicator](http://en.wikipedia.org/wiki/Attitude_indicator) most likely was available? | 2014/03/14 | [
"https://aviation.stackexchange.com/questions/2287",
"https://aviation.stackexchange.com",
"https://aviation.stackexchange.com/users/917/"
] | It can be. Remember that the angle of attack is the angle between the chord line of the airfoil and the relative wind. Imagine if the plane is level with the horizon with zero airpseed. It will fall straight down, putting the angle of attack close to 90 degrees with the pitch close to zero.
That said, during normal flight it's not likely that pitch and angle of attack will be excessively different. But honestly the two aren't closely related: You can exceed the critical angle of attack and stall at any pitch, bank, or yaw angle. | >
> How much the pitch (horizontal orientation) can differ from the angle
> of attack?
>
>
>
270 degrees appears to be the maximum angle that the pitch attitude can differ from the angle-of-attack.
Some examples of extreme differences between pitch attitude and angle-of-attack:
* Jet fighter or aerobatic airplane or aerobatic glider in a prolonged vertical climb. (May be a steady-state situation or the aircraft may even be gaining airspeed or it may just be a "zoom" climb where airspeed is exchanged for altitude; obviously only the latter is possible with the glider.) For simplicity assume a symmetrical airfoil. Pitch attitude is 90 degrees, angle-of-attack is zero degrees, for a difference of 90 degrees.
* Now the throttle (if present) is pulled back to drop the engine power to zero, but the nose is kept pointing straight up until the aircraft starts to tailslide backwards. Pitch attitude is still 90 degrees, but angle-of-attack is now 180 degrees, for a difference of 90 degrees.
* Now imagine the tailsliding aircraft experiences a slight variation in angle-of-attack-- perhaps due to a horizontal wind gust striking the aircraft-- that changes the direction of the relative airflow by one degree, so that the relative airflow is aimed slightly toward the top surface of the wing, rather than aimed directly at the trailing edge. Now the angle-of-attack has changed from 180 degrees (which also could be called minus 180 degrees) to minus 179 degrees. Now the difference between angle-of-attack and pitch attitude is 269 degrees.
* Flat spin with flight path approximating a vertical descent. Angle-of-attack may be close to 90 degrees, but pitch attitude may be close to zero degrees. Actually on the retreating wing it would seem the angle-of-attack may go beyond 90 degrees (wing actually moving backwards relative to the airmass, so the local airflow comes partly from behind), in which case the difference between angle-of-attack of that wing, and pitch attitude of the aircraft, would also go beyond 90 degrees. |
2,287 | How much the pitch (horizontal orientation) can differ from the angle of attack? I am trying to understand the claim that "angle of attack indicator was unfortunately not available", contributing to problems during Air France [Flight 447](http://en.wikipedia.org/wiki/Air_France_Flight_447). [Attitude indicator](http://en.wikipedia.org/wiki/Attitude_indicator) most likely was available? | 2014/03/14 | [
"https://aviation.stackexchange.com/questions/2287",
"https://aviation.stackexchange.com",
"https://aviation.stackexchange.com/users/917/"
] | The angle of attack is the angle between the wing (wing chord to be precise) and the direction of travel (undisturbed airflow). The angle of pitch is the angle between the main body axis and the horizon. The difference can theoretically be any angle, but during normal flight it will be limited to about 15 degrees.
The reason that the angle of attack sensor was inoperative was due to low airspeed. Below 60 knot IAS the indication is unreliable and therefore the indicator is inhibited. This also inhibits the stall warning. This lead to the confusing situation that lowering the nose to correct the stall increased the airspeed beyond 60 knots, thereby reactivating the stall warning. | [](https://i.stack.imgur.com/muxDg.png)
Just before the ground impact
Just watch [this video](https://www.youtube.com/watch?v=keCnK4kh65U) of a looping gone bad during a flight display. [At 1:30](https://youtu.be/keCnK4kh65U?t=90) into the video it becomes painfully obvious by how much both can diverge in extreme situations *(shown above).*
The flight path angle is the difference between pitch attitude and angle of attack. If pitch attitude and angle of attack would be equal, the airplane could only fly straight ahead at the same altitude. Once it climbs, it has to increase pitch attitude at constant angle of attack. With enough thrust or speed, both can be 90° apart.
Now consider flying inverted: Both are almost 180° apart.
In a dive, again the difference will become large because the flight path angle takes on negative values.
The more fun it makes to fly an aircraft, the more both angles diverge. Only [boring aircraft](http://en.wikipedia.org/wiki/Airliner) will keep both of them at similar, low values. |
2,287 | How much the pitch (horizontal orientation) can differ from the angle of attack? I am trying to understand the claim that "angle of attack indicator was unfortunately not available", contributing to problems during Air France [Flight 447](http://en.wikipedia.org/wiki/Air_France_Flight_447). [Attitude indicator](http://en.wikipedia.org/wiki/Attitude_indicator) most likely was available? | 2014/03/14 | [
"https://aviation.stackexchange.com/questions/2287",
"https://aviation.stackexchange.com",
"https://aviation.stackexchange.com/users/917/"
] | The angle of attack is the angle between the wing (wing chord to be precise) and the direction of travel (undisturbed airflow). The angle of pitch is the angle between the main body axis and the horizon. The difference can theoretically be any angle, but during normal flight it will be limited to about 15 degrees.
The reason that the angle of attack sensor was inoperative was due to low airspeed. Below 60 knot IAS the indication is unreliable and therefore the indicator is inhibited. This also inhibits the stall warning. This lead to the confusing situation that lowering the nose to correct the stall increased the airspeed beyond 60 knots, thereby reactivating the stall warning. | Just want to add the image.
Angle of attack is relative to the direction of relative wind (which is equivalently relative to the direction the plane is going, if in still air and the angle of incidence = 0, i.e. the wing is mounted parallel to the longitudinal axis of the plane), while pitch is relative to the horizontal axis. Angle of attack depends on the pitch, current velocity of the aircraft and the wind. They can be different.
Angle of attack is important to the aerodynamics (amount of lift, drag, etc.), while pitch tells you the aircraft's orientation relative to the ground.
[Image source](http://www.aeroskytech.com/english/firstnotions/anglesen.png)
Assumptions for the image: still air and angle of incidence is 0.
 |
2,287 | How much the pitch (horizontal orientation) can differ from the angle of attack? I am trying to understand the claim that "angle of attack indicator was unfortunately not available", contributing to problems during Air France [Flight 447](http://en.wikipedia.org/wiki/Air_France_Flight_447). [Attitude indicator](http://en.wikipedia.org/wiki/Attitude_indicator) most likely was available? | 2014/03/14 | [
"https://aviation.stackexchange.com/questions/2287",
"https://aviation.stackexchange.com",
"https://aviation.stackexchange.com/users/917/"
] | The angle of attack is the angle between the wing (wing chord to be precise) and the direction of travel (undisturbed airflow). The angle of pitch is the angle between the main body axis and the horizon. The difference can theoretically be any angle, but during normal flight it will be limited to about 15 degrees.
The reason that the angle of attack sensor was inoperative was due to low airspeed. Below 60 knot IAS the indication is unreliable and therefore the indicator is inhibited. This also inhibits the stall warning. This lead to the confusing situation that lowering the nose to correct the stall increased the airspeed beyond 60 knots, thereby reactivating the stall warning. | >
> How much the pitch (horizontal orientation) can differ from the angle
> of attack?
>
>
>
270 degrees appears to be the maximum angle that the pitch attitude can differ from the angle-of-attack.
Some examples of extreme differences between pitch attitude and angle-of-attack:
* Jet fighter or aerobatic airplane or aerobatic glider in a prolonged vertical climb. (May be a steady-state situation or the aircraft may even be gaining airspeed or it may just be a "zoom" climb where airspeed is exchanged for altitude; obviously only the latter is possible with the glider.) For simplicity assume a symmetrical airfoil. Pitch attitude is 90 degrees, angle-of-attack is zero degrees, for a difference of 90 degrees.
* Now the throttle (if present) is pulled back to drop the engine power to zero, but the nose is kept pointing straight up until the aircraft starts to tailslide backwards. Pitch attitude is still 90 degrees, but angle-of-attack is now 180 degrees, for a difference of 90 degrees.
* Now imagine the tailsliding aircraft experiences a slight variation in angle-of-attack-- perhaps due to a horizontal wind gust striking the aircraft-- that changes the direction of the relative airflow by one degree, so that the relative airflow is aimed slightly toward the top surface of the wing, rather than aimed directly at the trailing edge. Now the angle-of-attack has changed from 180 degrees (which also could be called minus 180 degrees) to minus 179 degrees. Now the difference between angle-of-attack and pitch attitude is 269 degrees.
* Flat spin with flight path approximating a vertical descent. Angle-of-attack may be close to 90 degrees, but pitch attitude may be close to zero degrees. Actually on the retreating wing it would seem the angle-of-attack may go beyond 90 degrees (wing actually moving backwards relative to the airmass, so the local airflow comes partly from behind), in which case the difference between angle-of-attack of that wing, and pitch attitude of the aircraft, would also go beyond 90 degrees. |
2,287 | How much the pitch (horizontal orientation) can differ from the angle of attack? I am trying to understand the claim that "angle of attack indicator was unfortunately not available", contributing to problems during Air France [Flight 447](http://en.wikipedia.org/wiki/Air_France_Flight_447). [Attitude indicator](http://en.wikipedia.org/wiki/Attitude_indicator) most likely was available? | 2014/03/14 | [
"https://aviation.stackexchange.com/questions/2287",
"https://aviation.stackexchange.com",
"https://aviation.stackexchange.com/users/917/"
] | Just want to add the image.
Angle of attack is relative to the direction of relative wind (which is equivalently relative to the direction the plane is going, if in still air and the angle of incidence = 0, i.e. the wing is mounted parallel to the longitudinal axis of the plane), while pitch is relative to the horizontal axis. Angle of attack depends on the pitch, current velocity of the aircraft and the wind. They can be different.
Angle of attack is important to the aerodynamics (amount of lift, drag, etc.), while pitch tells you the aircraft's orientation relative to the ground.
[Image source](http://www.aeroskytech.com/english/firstnotions/anglesen.png)
Assumptions for the image: still air and angle of incidence is 0.
 | [](https://i.stack.imgur.com/muxDg.png)
Just before the ground impact
Just watch [this video](https://www.youtube.com/watch?v=keCnK4kh65U) of a looping gone bad during a flight display. [At 1:30](https://youtu.be/keCnK4kh65U?t=90) into the video it becomes painfully obvious by how much both can diverge in extreme situations *(shown above).*
The flight path angle is the difference between pitch attitude and angle of attack. If pitch attitude and angle of attack would be equal, the airplane could only fly straight ahead at the same altitude. Once it climbs, it has to increase pitch attitude at constant angle of attack. With enough thrust or speed, both can be 90° apart.
Now consider flying inverted: Both are almost 180° apart.
In a dive, again the difference will become large because the flight path angle takes on negative values.
The more fun it makes to fly an aircraft, the more both angles diverge. Only [boring aircraft](http://en.wikipedia.org/wiki/Airliner) will keep both of them at similar, low values. |
2,287 | How much the pitch (horizontal orientation) can differ from the angle of attack? I am trying to understand the claim that "angle of attack indicator was unfortunately not available", contributing to problems during Air France [Flight 447](http://en.wikipedia.org/wiki/Air_France_Flight_447). [Attitude indicator](http://en.wikipedia.org/wiki/Attitude_indicator) most likely was available? | 2014/03/14 | [
"https://aviation.stackexchange.com/questions/2287",
"https://aviation.stackexchange.com",
"https://aviation.stackexchange.com/users/917/"
] | [](https://i.stack.imgur.com/muxDg.png)
Just before the ground impact
Just watch [this video](https://www.youtube.com/watch?v=keCnK4kh65U) of a looping gone bad during a flight display. [At 1:30](https://youtu.be/keCnK4kh65U?t=90) into the video it becomes painfully obvious by how much both can diverge in extreme situations *(shown above).*
The flight path angle is the difference between pitch attitude and angle of attack. If pitch attitude and angle of attack would be equal, the airplane could only fly straight ahead at the same altitude. Once it climbs, it has to increase pitch attitude at constant angle of attack. With enough thrust or speed, both can be 90° apart.
Now consider flying inverted: Both are almost 180° apart.
In a dive, again the difference will become large because the flight path angle takes on negative values.
The more fun it makes to fly an aircraft, the more both angles diverge. Only [boring aircraft](http://en.wikipedia.org/wiki/Airliner) will keep both of them at similar, low values. | >
> How much the pitch (horizontal orientation) can differ from the angle
> of attack?
>
>
>
270 degrees appears to be the maximum angle that the pitch attitude can differ from the angle-of-attack.
Some examples of extreme differences between pitch attitude and angle-of-attack:
* Jet fighter or aerobatic airplane or aerobatic glider in a prolonged vertical climb. (May be a steady-state situation or the aircraft may even be gaining airspeed or it may just be a "zoom" climb where airspeed is exchanged for altitude; obviously only the latter is possible with the glider.) For simplicity assume a symmetrical airfoil. Pitch attitude is 90 degrees, angle-of-attack is zero degrees, for a difference of 90 degrees.
* Now the throttle (if present) is pulled back to drop the engine power to zero, but the nose is kept pointing straight up until the aircraft starts to tailslide backwards. Pitch attitude is still 90 degrees, but angle-of-attack is now 180 degrees, for a difference of 90 degrees.
* Now imagine the tailsliding aircraft experiences a slight variation in angle-of-attack-- perhaps due to a horizontal wind gust striking the aircraft-- that changes the direction of the relative airflow by one degree, so that the relative airflow is aimed slightly toward the top surface of the wing, rather than aimed directly at the trailing edge. Now the angle-of-attack has changed from 180 degrees (which also could be called minus 180 degrees) to minus 179 degrees. Now the difference between angle-of-attack and pitch attitude is 269 degrees.
* Flat spin with flight path approximating a vertical descent. Angle-of-attack may be close to 90 degrees, but pitch attitude may be close to zero degrees. Actually on the retreating wing it would seem the angle-of-attack may go beyond 90 degrees (wing actually moving backwards relative to the airmass, so the local airflow comes partly from behind), in which case the difference between angle-of-attack of that wing, and pitch attitude of the aircraft, would also go beyond 90 degrees. |
2,287 | How much the pitch (horizontal orientation) can differ from the angle of attack? I am trying to understand the claim that "angle of attack indicator was unfortunately not available", contributing to problems during Air France [Flight 447](http://en.wikipedia.org/wiki/Air_France_Flight_447). [Attitude indicator](http://en.wikipedia.org/wiki/Attitude_indicator) most likely was available? | 2014/03/14 | [
"https://aviation.stackexchange.com/questions/2287",
"https://aviation.stackexchange.com",
"https://aviation.stackexchange.com/users/917/"
] | Just want to add the image.
Angle of attack is relative to the direction of relative wind (which is equivalently relative to the direction the plane is going, if in still air and the angle of incidence = 0, i.e. the wing is mounted parallel to the longitudinal axis of the plane), while pitch is relative to the horizontal axis. Angle of attack depends on the pitch, current velocity of the aircraft and the wind. They can be different.
Angle of attack is important to the aerodynamics (amount of lift, drag, etc.), while pitch tells you the aircraft's orientation relative to the ground.
[Image source](http://www.aeroskytech.com/english/firstnotions/anglesen.png)
Assumptions for the image: still air and angle of incidence is 0.
 | >
> How much the pitch (horizontal orientation) can differ from the angle
> of attack?
>
>
>
270 degrees appears to be the maximum angle that the pitch attitude can differ from the angle-of-attack.
Some examples of extreme differences between pitch attitude and angle-of-attack:
* Jet fighter or aerobatic airplane or aerobatic glider in a prolonged vertical climb. (May be a steady-state situation or the aircraft may even be gaining airspeed or it may just be a "zoom" climb where airspeed is exchanged for altitude; obviously only the latter is possible with the glider.) For simplicity assume a symmetrical airfoil. Pitch attitude is 90 degrees, angle-of-attack is zero degrees, for a difference of 90 degrees.
* Now the throttle (if present) is pulled back to drop the engine power to zero, but the nose is kept pointing straight up until the aircraft starts to tailslide backwards. Pitch attitude is still 90 degrees, but angle-of-attack is now 180 degrees, for a difference of 90 degrees.
* Now imagine the tailsliding aircraft experiences a slight variation in angle-of-attack-- perhaps due to a horizontal wind gust striking the aircraft-- that changes the direction of the relative airflow by one degree, so that the relative airflow is aimed slightly toward the top surface of the wing, rather than aimed directly at the trailing edge. Now the angle-of-attack has changed from 180 degrees (which also could be called minus 180 degrees) to minus 179 degrees. Now the difference between angle-of-attack and pitch attitude is 269 degrees.
* Flat spin with flight path approximating a vertical descent. Angle-of-attack may be close to 90 degrees, but pitch attitude may be close to zero degrees. Actually on the retreating wing it would seem the angle-of-attack may go beyond 90 degrees (wing actually moving backwards relative to the airmass, so the local airflow comes partly from behind), in which case the difference between angle-of-attack of that wing, and pitch attitude of the aircraft, would also go beyond 90 degrees. |
196,469 | Sometimes I can't see which clause fits the best. What "check-up" could be done to make sure which one is the right one?
For example,
**1) He will do anything that is needed. or He will do anything what is needed.**
**2) They always ignore that is so obvious. or They always ignore what is so obvious.**
**3) All that I have is yours. or All what I have is yours.**
My take is the correct ones are 1) that 2) that 3) what/that???
But I am not sure. I think it has to do something with different types or dependent clauses, but I don't know how to go about them in this case. Any suggestions?
Here is an interesting example
How do I know what I think, until I see what I say? VERSUS How do I know that I think, until I see what I say?
I think both are correct meaning two different things. | 2014/09/15 | [
"https://english.stackexchange.com/questions/196469",
"https://english.stackexchange.com",
"https://english.stackexchange.com/users/28753/"
] | ***That* and *Which***
Relative clauses with *which* or *that* usually modify nouns. The end result is that the original noun becomes one big Noun Phrase and functions just like a large noun.
* Do you remember the **volcano** ***[which erupted whilst we were on holiday]***?
Here we see the noun *volcano* being modified by *which ... holiday*. The whole Noun Phrase *the volcano which erupted whilst we were on holiday* has the function of Direct Object of the verb *remember*.
Notice that it is the word *which* that is the subject of *which erupted whilst we were on holiday* - not the word *volcano*. Rather, the word *volcano* is the ***antecedent*** for the pronoun *which*. This means that we interpret *which* within the clause through the word *volcano* which comes before it. In normal relative clauses, the pronoun *which* always has an antecedent. The relative word *that*, also appears in clauses in front of which there is some kind of noun as an antecedent:
* Do you remember the **volcano *[that erupted whilst we were on holiday]***?
So in both of these types of relatives clause we have an antecedent noun, which helps us interpret another element in the embedded relative clause.
***What***
If we compare the following sentences we''ll see that there's a very specific difference in relative clauses with *what*:
* **The things that** she did were thoughtful and useful.
* **The things which** she did were thoughtful and useful.
* **What** she did was thoughtful and useful.
or
* I liked **the thing(s) which** she did.
* I liked **the thing(s) that** she did.
* I liked **what** she did.
The big difference is that, as you can see, there's no antecedent noun for the relative clauses with *what*. The relative clauses with *which/that* all have *the things* as an antecedent. *What* takes the place of both the antecedent as well as the relative word.
**The Examples**
With regard to the Original Poster's examples:
>
> * 1) He will do **anything** ***\_*** is needed.
>
>
>
Here we see that there is an antecedent noun phrase, *anything*. Therefore we need to use *that* or *which*:
* *He'll do anything that's needed*.
[However, if we removed the noun phrase *anything* completely, then we could use *what*:
* He'll do what's needed.]
>
> * 2) They always ignore ***\_*** is so obvious.
>
>
>
Here there is no antecedent noun so we have to use *what*:
* They always ignore what's so obvious.
>
> * 3) **All** ***\_*** I have is yours.
>
>
>
Here we find an antecedent noun, the pronoun *all*. We cannot therefore use *what*, but must use *that* instead. We could use *which* but when the antecedent is a pronoun like this it is often better to use *that*.
* All that I have is yours.
Regarding the Original Poster's last unnumbered example, consider the following:
>
> I know what I think.
>
>
> I know that I think.
>
>
>
The first sentence has a relative clause, *what I think* as a direct object. Within the relative clause itself, the object of *think* is understood as the item *what*.
The second sentence however does not have a relative clause. We know this is the case because there is no antecedent for *that*. The clause following *know* is a declarative content clause. The sentence has the same structure as *I know that Yetis exist* or *I know that you like cheese.*
In the second example,the clause *that I think* is the complement of the verb *know*. The verb *think* here has no object. The word *that* is a marker showing that the following clause is subordinate. In fact we can remove *that* entirely from the sentence and it will still be grammatical and still have the same meaning:
* I know I think. Or at least I believe I do.
**Conclusion**
To sum up, if there is an antecedent noun in the main clause then *that* or *which* appears at the front of the relative clause. We find *what* when there is no antecedent.
*Hope this is helpful!* | *That* always needs to refer to another word or clause in the context, *what* doesn't have to do that.
*What* is also used to form questions: what do you think? You don't ask "that do you think?"
A simple "trick" I use myself is that you can usually replace "what" by "that which" without changing the meaning:
1) He will do anything that is needed. or He will do anything what is needed.
*That* refers to *anything*. "He will do anything that which is needed" makes no sense. So, *that* is correct.
Note that without *anything*, *what* would be correct:
He will do what is needed; he will do *that which* is needed.
2) They always ignore that is so obvious. or They always ignore what is so obvious.
*That* does not refer to anything in the sentence. They ignore *that which* is obvious, so *what* is correct.
3) All that I have is yours. or All what I have is yours.
*That* refers to *all*. *All that which* makes no sense, so *that* is correct. Again, without *all*, it would be *What I have is yours*.
You last sentence is interesting:
>
> How do I know that I think?
>
>
>
That refers to *I think*, the action of thinking. So you wonder how you can know that you actually perform the act of thinking. One could say that question is answered by the fact you ask the question!
>
> How do I know what I think?
>
>
>
*What* can be replaced by "that which", you don't wonder *if* you think, but (about) *what* you think. Normally this version is the one you mean.
Note: as Janus Bahs Jacquet mentions, to make things a little less clear, in some dialects, *what* can be used instead of *that* in sentences like your first one. In that case, the important thing is , be consistent. |
32,483,001 | I'm using MySQL Workbench on a 64bit/Win 8.1 machine to trying to connect to an Azure MySQL service, but everytime I get the following error:
>
> Lost connection to MySQL server at 'reading authorization packet', system error:0
>
>
>
I followed many tutorial found ever the internet, and I also tried to disable temporarely the firewall: most of them says that the only needed parameters are:
* hostname (the one given in Azure portal/MyDB/Properties)
* username (the one given in Azure portal/MyDB/Properties)
* (optional) password (to store in vault)
I tried also using different connection methods (Standard TCP/IP and Local socket/pipe, as suggested [here](https://stackoverflow.com/questions/16129399/mysql-workbench-cannot-connect-to-database-server)) but nothing.
Can help? | 2015/09/09 | [
"https://Stackoverflow.com/questions/32483001",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/5278185/"
] | I was not able to recreate your issue. Here are the steps that I tried with a MySQL database created thru the Azure portal.
1. Open MySql Workbench.
2. Setup new connection with the following settings.
3. Hostname: HOSTNAME
4. Port: PORT
5. Username: USERNAME
6. Pasword: PASSWORD
7. Database: DATABASE NAME
8. Test Connection > Succeeded.
The settings above came from portal.azure.com > MyDatabase > All settings.
One suggestion is to contact ClearDB support. You can login to ClearDB from your database's Azure dashboard by clicking on Manage Database. From there you can go to Support and log a support incident. | I was also struggling with a similar issue, as I was not able to connect my MySQL workbench with Azure VM that's running MySQL.
I've contacted the Azure support to help me out after trying it for 3-4 hrs.
They suggested me to go into network security group of that VM, and add 3306 or whatever port that your MySQL is running on our Azure to the inbound and outbound list and add the exception as All.
It helped me to connect MySQL workbench with Azure VM with MySQL on it. |
32,229 | Just as the title says in your own opinion list the top 10 apps i should install after a fresh ubuntu install. Please i need as many responses as possible(apps, tweaks, update etc) | 2011/03/27 | [
"https://askubuntu.com/questions/32229",
"https://askubuntu.com",
"https://askubuntu.com/users/12846/"
] | 1. Fix the buttons (move them to the right or reverse them)
2. Install Gnome-do
3. Install Docky
4. Re-theme
5. Activate ufw firewall
6. Install Kubuntu desktop (nice to have both options)
...
1. Make a backup copy of all your installed applications using Synaptic and store it offline. It makes rebuilding a machine much easier next time (you end up having 3 steps instead of 10+) | [OMG!Ubuntu's Guide](http://www.omgubuntu.co.uk/2010/10/10-things-to-do-after-installing-ubuntu-10-10-maverick-meerkat/)
>
> So you’ve downloaded Ubuntu 10.10, made yourself a freshly minted copy and installed it with haste. Now what?
>
>
> Here is our guide to the top 10 post-install must-do’s that will help ensure you get off to a marvellous start with the Maverick Meerkat.
>
>
> |
72,931 | So I would like to get Clarks M3 hydraulic disc brake set but the only size available is 180mm but i am not sure what to measure to see if this will fit my carrera vengeance ltd edition 16 inch frame bike. Many thanks. | 2020/10/24 | [
"https://bicycles.stackexchange.com/questions/72931",
"https://bicycles.stackexchange.com",
"https://bicycles.stackexchange.com/users/53483/"
] | As long as the kit includes the correct caliper mount adaptors, it will be fine. You can buy them separately if you need to.
It looks like bike has post mount fork and IS on the frame so it's likely you will need to buy at least one of those in addition to the kit. | Start by measuring the diameter of your current disc. If it is 180, the change will be very easy.
If you have 160, I'd keep trying (to find that size). In a quick search I did just now searching "Clarks M3 hydraulic disc brake set" the first result I got was a 160mm set. There was a run on bike parts for a while, but I think that is slowly winding down. If you need and want the 160 set, I bet you'll find it.
May I ask why you want that set in particular? Nothing wrong with it, and there is nothing wrong with liking a product just because you like it. I have my preferences for sure. Its just that there are so many choices out there.
The question may come up, if you have 160 now, is it OK to move up to 180. You could, with different adapters for the calipers. However, this will create more braking forces that translate into the fork and frame. It would probably be fine, but I'd check with someone at Carrera or your LBS to be sure that those extra forces won't damage the frame. I am not familiar enough with Carrera to say confidently. |
72,931 | So I would like to get Clarks M3 hydraulic disc brake set but the only size available is 180mm but i am not sure what to measure to see if this will fit my carrera vengeance ltd edition 16 inch frame bike. Many thanks. | 2020/10/24 | [
"https://bicycles.stackexchange.com/questions/72931",
"https://bicycles.stackexchange.com",
"https://bicycles.stackexchange.com/users/53483/"
] | As long as the kit includes the correct caliper mount adaptors, it will be fine. You can buy them separately if you need to.
It looks like bike has post mount fork and IS on the frame so it's likely you will need to buy at least one of those in addition to the kit. | the 'Limited Edition' seems to date back at least a decade in various specs, so the question is hard to answer
looking at the one on the current Halfords website it has an SR Suntour XCM30 fork of some unknown MY and mechanical disc brakes
<https://www.halfords.com/bikes/mountain-bikes/carrera-vengeance-limited-edition-mens-mountain-bike---xs-s-m-l-xl-frames-216878.html>
this 10 year old version
<http://web.archive.org/web/20110414134431/http://www.halfords.com/webapp/wcs/stores/servlet/ProductMobileDisplay?catalogId=10151&storeId=10001&productId=786835&categoryId=165499&langId=-1>
had
RockShox Dart 1 forks with 100mm travel and pre-load adjustment
Shimano 24 speed gearing with Alivio rear mech, great for hill climbing
New Shimano BR-M445 hydraulic disc brakes provide strong and powerful braking performance
Generally speaking disc brakes used to mount with something called 'International Standard' and since about 2007 this switched almost exclusively to 'Post Mount'. In earlier years before IS there were proprietary manufacturer-specific fittings as well. In recent years we now have 'flat mount', which is supposed to look better on road bikes and now appears on MTBs as well.
Chances are you have Post Mount, but you'd need to look at the fork AND the rear disc brake to see that.
According to Clarks, it is PM & IS compatible
<http://www.clarkscyclesystems.com/product-range/brake-systems/hydraulic-disc-brakes/m3-hydraulic-brake.html?att_color=40&attr_diameter=229&attr_wheel_option=224>
It looks like the brake is natively PM, and has an IS adapter supplied.
One issue is that you are buying a set <https://www.chainreactioncycles.com/clarks-m3-hydraulic-disc-brake-set/rp-prod162155>
This comprises rotors and brakes. However it's very possible that your rotors attach to your bike using 'centerlock'. These ones are 'six bolt'.
Compare centerlock
[](https://i.stack.imgur.com/eNiFq.png)
If you have centerlock now, then six bolt won't be a good purchase, because it will need an expensive adapter to fit your bike, and it's just generally a bad idea
In addition, you can check rotor wear with a caliper, but unless they are worn, these are fairly basic discs that likely won't be an upgrade on what you have fitted already
If they are rusty or worn out AND you have six-bolt rotors already, then that's not a problem.
As far as 180mm vs 160mm goes, the size of your current rotors will be marked on them. Whatever you have now is fine. If it's bigger then you'd need to check the specs for the fork. A fork might not be rated for 180mm. In addition, the fork will have a native brake size, typically 160mm, so if you fit a 180mm rotor, then you will need to fit the brake with an adapter for 160mm to 180mm. Here's the Clarks model
[](https://i.stack.imgur.com/0jcMY.jpg)
You would need to check if you have the adapter with the 180mm set, or if you have 180mm brakes fitted already then re-use it. Either way the adapter is no big deal, but it's something to consider.
Otherwise when buying hydraulic brakes you'd typically focus on lever design. For MTBing a lot of people like short levers for 1-finger braking, which adds control. For touring longer levers are common. I am not quite sure what lever design is on the M3, but it looks unusual, so you might like to review that aspect.
Also, if you remove the brake calipers from the bike (without disconnecting the hose), which should just require an Allen key, then you can review the model number, etc. to find the current specs and what adapter, if any is fitted. This will help with your purchase. And check the rotors at the same time - marked diameter and centerlock vs six bolt. |
8,629,480 | On the official page I see the android-sdk\_r16-linux.tgz but I can not found some lower versions from the android skd. Any ideas how can I download some lower version ? | 2011/12/25 | [
"https://Stackoverflow.com/questions/8629480",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/706780/"
] | I don't know why you would want to do this (bug fixes and improvement happen with newer releases and you wont be able to build to a target of Android 3.0+), but:
Windows: <http://dl.google.com/android/installer_r12-windows.exe>
Linux: <http://dl.google.com/android/android-sdk_r12-linux_x86.tgz>
<http://dl.google.com/android/android-sdk_r14-linux.tgz>
(the oldest I can find is r12)
OSX: <http://dl.google.com/android/android-sdk_r14-macosx.zip>
(oldest I found is r14)
So, hopefully you are using Windows and then you're in luck.
Hope that helps! Really, though, I would reconsider your motivation to use an outdated plugin. | SDK download is just a starter kit, actual platform is downloaded from the Android SDK manager in Eclipse. You can download the version you want by choosing the appropriate checkbox |
8,629,480 | On the official page I see the android-sdk\_r16-linux.tgz but I can not found some lower versions from the android skd. Any ideas how can I download some lower version ? | 2011/12/25 | [
"https://Stackoverflow.com/questions/8629480",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/706780/"
] | I don't know why you would want to do this (bug fixes and improvement happen with newer releases and you wont be able to build to a target of Android 3.0+), but:
Windows: <http://dl.google.com/android/installer_r12-windows.exe>
Linux: <http://dl.google.com/android/android-sdk_r12-linux_x86.tgz>
<http://dl.google.com/android/android-sdk_r14-linux.tgz>
(the oldest I can find is r12)
OSX: <http://dl.google.com/android/android-sdk_r14-macosx.zip>
(oldest I found is r14)
So, hopefully you are using Windows and then you're in luck.
Hope that helps! Really, though, I would reconsider your motivation to use an outdated plugin. | Thanks to TryTryAgain's lead, I was able to find the right filename for the r12 SDK for linux:
<http://dl.google.com/android/android-sdk_r12-linux_x86.tgz> |
877,106 | I have somewhat of an interesting problem that might not have a solution, but it never hurts to ask. I am trying to find my Windows 8 Activation key that came with the operating system when it was pre-installed on my Microsoft Surface Pro (first generation).
Last week I went ahead and upgraded to Windows 10 Technical Preview on the surface tablet, however now I am trying to revert and re-install windows 8. I assume that when I try to do this I will need to provide an activation key.
Does anyone know if this is possible? I downloaded a program (<https://www.magicaljellybean.com/keyfinder/>) and it shows my Windows 10 CD Key, but would that be the same as my old Windows 8 activation key?
Let me know if you guys have any ideas - thanks!
Will | 2015/02/12 | [
"https://superuser.com/questions/877106",
"https://superuser.com",
"https://superuser.com/users/418278/"
] | Your product key is contained in the ACPI table SLIC. It's human-readable there. If you use the correct install media, it should be automatically detected and entered, no need for you to do anything. | Nirsoft's *ProduKey*, <http://www.nirsoft.net/utils/product_cd_key_viewer.html>, might be of help. Also, is there a sticker on the Surface Pro or its packaging, if you still have it, with the key? |
877,106 | I have somewhat of an interesting problem that might not have a solution, but it never hurts to ask. I am trying to find my Windows 8 Activation key that came with the operating system when it was pre-installed on my Microsoft Surface Pro (first generation).
Last week I went ahead and upgraded to Windows 10 Technical Preview on the surface tablet, however now I am trying to revert and re-install windows 8. I assume that when I try to do this I will need to provide an activation key.
Does anyone know if this is possible? I downloaded a program (<https://www.magicaljellybean.com/keyfinder/>) and it shows my Windows 10 CD Key, but would that be the same as my old Windows 8 activation key?
Let me know if you guys have any ideas - thanks!
Will | 2015/02/12 | [
"https://superuser.com/questions/877106",
"https://superuser.com",
"https://superuser.com/users/418278/"
] | Your product key is contained in the ACPI table SLIC. It's human-readable there. If you use the correct install media, it should be automatically detected and entered, no need for you to do anything. | You can simply use the "rollback option" that appears after you restart your computer. I've tried it before and it reverted my Windows 10 install to Windows 8.1 with no problems.
Also, my current Windows 10 Tech Preview serial is the same as my original Windows 8.1 license key, and I assume this is the same for everybody who has upgraded their systems through Windows Update (not with a complete ISO and clean install). If [the program provided by @DrMoishe Pippik](http://www.nirsoft.net/utils/product_cd_key_viewer.html) doesn't work, you may want to use [Speccy Portable](https://www.piriform.com/speccy/download/portable) to write it down somewhere before doing the rollback:
 |
877,106 | I have somewhat of an interesting problem that might not have a solution, but it never hurts to ask. I am trying to find my Windows 8 Activation key that came with the operating system when it was pre-installed on my Microsoft Surface Pro (first generation).
Last week I went ahead and upgraded to Windows 10 Technical Preview on the surface tablet, however now I am trying to revert and re-install windows 8. I assume that when I try to do this I will need to provide an activation key.
Does anyone know if this is possible? I downloaded a program (<https://www.magicaljellybean.com/keyfinder/>) and it shows my Windows 10 CD Key, but would that be the same as my old Windows 8 activation key?
Let me know if you guys have any ideas - thanks!
Will | 2015/02/12 | [
"https://superuser.com/questions/877106",
"https://superuser.com",
"https://superuser.com/users/418278/"
] | Your product key is contained in the ACPI table SLIC. It's human-readable there. If you use the correct install media, it should be automatically detected and entered, no need for you to do anything. | Most keyfinders will pull your Windows product key and your Internet Explorer key. If you've lost your Win 7/8 key and you don't have a label or the label is destroyed, you can try using your Internet Explorer key. I've found that the IE key is always the same as your Windows key, but for some reason, upgrading to Windows 10 doesn't change the key over when you pull it with a keyfinder.
Edit: for use in the case that you have passed the one-month rollback period and your physical key media is destroyed. |
88,121 | I am a US citizen and a resident of Thailand. My Thai wife and I are planning on travelling to France for three weeks for our honeymoon. We just held the social wedding ceremony, but haven't applied for our marriage certificate with the local district office yet.
She is employed by a multinational company in Bangkok, but I'm afraid her salary might not be high enough to meet minimum visa requirements.
Will the fact that she is married to a US national be taken into account when applying for a Schengen visa? | 2017/02/15 | [
"https://travel.stackexchange.com/questions/88121",
"https://travel.stackexchange.com",
"https://travel.stackexchange.com/users/57426/"
] | If she had been a US resident, she would've been deemed a lower-risk traveller, although the same procedure would be in place.
But no, she should provide the exact same documentation as "ordinarily" stipulated, and needs to meet the exact same requirements.
Submit as much proof as you can that you as a couple will have enough money to spend on your honeymoon without engaging in illegal employment, and she should be fine. | Unfortunately no. The fact that she is married to an American (who has visa free entry to Schengen states) has no effect on her Schengen visa application. Even if she were a Permanent Resident of the USA, which she is not yet, it wouldn't have any effect. Your privileges do not transfer to your spouse.
She would still have to satisfy the requirements for a Schengen visa that a typical Thai citizen has to satisfy. |
88,121 | I am a US citizen and a resident of Thailand. My Thai wife and I are planning on travelling to France for three weeks for our honeymoon. We just held the social wedding ceremony, but haven't applied for our marriage certificate with the local district office yet.
She is employed by a multinational company in Bangkok, but I'm afraid her salary might not be high enough to meet minimum visa requirements.
Will the fact that she is married to a US national be taken into account when applying for a Schengen visa? | 2017/02/15 | [
"https://travel.stackexchange.com/questions/88121",
"https://travel.stackexchange.com",
"https://travel.stackexchange.com/users/57426/"
] | Formally, it will not make a difference that she is married to a US citizen. Practically, it will most likely give her a great advantage, as the consular officer ultimately will evaluate her ability to finance the trip and her willingness to leave the Schengen area after having being granted entry.
Assuming that the consulate considers your relationship genuine (it may actually be a problem if you don't have an official marriage certificate yet):
* It will not be an issue that your wife herself has not the financial means to pay for the trip if you have. It will be a relatively common situation that married couples apply for a visa for common travel and only one part has a sufficient income or financial means to pay for und justify the cost of travel. You might be required to sign an affidavit to declare your liability for any costs incurred during travel.
* I would also assume that being married to a non-EEA citizen will be an advantage. After all, you yourself cannot stay indefinitely in the EEA, so her willingness to stay together with you after the trip, is likely to reduce the risk of her overstaying illegaly (without you). | Unfortunately no. The fact that she is married to an American (who has visa free entry to Schengen states) has no effect on her Schengen visa application. Even if she were a Permanent Resident of the USA, which she is not yet, it wouldn't have any effect. Your privileges do not transfer to your spouse.
She would still have to satisfy the requirements for a Schengen visa that a typical Thai citizen has to satisfy. |
88,121 | I am a US citizen and a resident of Thailand. My Thai wife and I are planning on travelling to France for three weeks for our honeymoon. We just held the social wedding ceremony, but haven't applied for our marriage certificate with the local district office yet.
She is employed by a multinational company in Bangkok, but I'm afraid her salary might not be high enough to meet minimum visa requirements.
Will the fact that she is married to a US national be taken into account when applying for a Schengen visa? | 2017/02/15 | [
"https://travel.stackexchange.com/questions/88121",
"https://travel.stackexchange.com",
"https://travel.stackexchange.com/users/57426/"
] | If she had been a US resident, she would've been deemed a lower-risk traveller, although the same procedure would be in place.
But no, she should provide the exact same documentation as "ordinarily" stipulated, and needs to meet the exact same requirements.
Submit as much proof as you can that you as a couple will have enough money to spend on your honeymoon without engaging in illegal employment, and she should be fine. | Formally, it will not make a difference that she is married to a US citizen. Practically, it will most likely give her a great advantage, as the consular officer ultimately will evaluate her ability to finance the trip and her willingness to leave the Schengen area after having being granted entry.
Assuming that the consulate considers your relationship genuine (it may actually be a problem if you don't have an official marriage certificate yet):
* It will not be an issue that your wife herself has not the financial means to pay for the trip if you have. It will be a relatively common situation that married couples apply for a visa for common travel and only one part has a sufficient income or financial means to pay for und justify the cost of travel. You might be required to sign an affidavit to declare your liability for any costs incurred during travel.
* I would also assume that being married to a non-EEA citizen will be an advantage. After all, you yourself cannot stay indefinitely in the EEA, so her willingness to stay together with you after the trip, is likely to reduce the risk of her overstaying illegaly (without you). |
79,949 | Scenario:
A stored procedure receives from code a DateTime with, let's say DateTime.Now value, as a datetime parameter.
The stored procedure needs to store only the date part of the datetime on the row, but preserving all date related arithmetics for, to say, do searches over time intervals and doing reports based on dates.
I know there is a couple of ways, but what is the better having in mind performance and wasted space? | 2008/09/17 | [
"https://Stackoverflow.com/questions/79949",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/6359/"
] | Business Logic should be handled outside of the proc. The procs jobs should be to save the data passed to it. If the requirment is to only store Date and not time, then the BL/DL should pass in DateTime.Now\*\*.Date\*\* (or the equiv...basically the Date part of your DateTime object).
If you can't control the code for some reason, there's always convert(varchar(10), @YOURDATETIME, 101) | store the date with time = midnight
EDIT: i was assuming MS SQL Server |
79,949 | Scenario:
A stored procedure receives from code a DateTime with, let's say DateTime.Now value, as a datetime parameter.
The stored procedure needs to store only the date part of the datetime on the row, but preserving all date related arithmetics for, to say, do searches over time intervals and doing reports based on dates.
I know there is a couple of ways, but what is the better having in mind performance and wasted space? | 2008/09/17 | [
"https://Stackoverflow.com/questions/79949",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/6359/"
] | Business Logic should be handled outside of the proc. The procs jobs should be to save the data passed to it. If the requirment is to only store Date and not time, then the BL/DL should pass in DateTime.Now\*\*.Date\*\* (or the equiv...basically the Date part of your DateTime object).
If you can't control the code for some reason, there's always convert(varchar(10), @YOURDATETIME, 101) | Essentially you're only going to store the Date part of your DateTime object. This means regardless of how you wish to handle querying the data the Date returned will always be set to 00:00:00.
Time related functions are useless in this scenario (even though your original DateTime object uses them) as your database drops this info.
Date related arithmetics will still apply though you will have to assume a time of midnight for each date returned from the database. |
79,949 | Scenario:
A stored procedure receives from code a DateTime with, let's say DateTime.Now value, as a datetime parameter.
The stored procedure needs to store only the date part of the datetime on the row, but preserving all date related arithmetics for, to say, do searches over time intervals and doing reports based on dates.
I know there is a couple of ways, but what is the better having in mind performance and wasted space? | 2008/09/17 | [
"https://Stackoverflow.com/questions/79949",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/6359/"
] | Business Logic should be handled outside of the proc. The procs jobs should be to save the data passed to it. If the requirment is to only store Date and not time, then the BL/DL should pass in DateTime.Now\*\*.Date\*\* (or the equiv...basically the Date part of your DateTime object).
If you can't control the code for some reason, there's always convert(varchar(10), @YOURDATETIME, 101) | SQL Server 2008 has a date only type (DATE) that does not store the time. Consider upgrading.
<http://www.sqlteam.com/article/using-the-date-data-type-in-sql-server-2008> |
79,949 | Scenario:
A stored procedure receives from code a DateTime with, let's say DateTime.Now value, as a datetime parameter.
The stored procedure needs to store only the date part of the datetime on the row, but preserving all date related arithmetics for, to say, do searches over time intervals and doing reports based on dates.
I know there is a couple of ways, but what is the better having in mind performance and wasted space? | 2008/09/17 | [
"https://Stackoverflow.com/questions/79949",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/6359/"
] | Business Logic should be handled outside of the proc. The procs jobs should be to save the data passed to it. If the requirment is to only store Date and not time, then the BL/DL should pass in DateTime.Now\*\*.Date\*\* (or the equiv...basically the Date part of your DateTime object).
If you can't control the code for some reason, there's always convert(varchar(10), @YOURDATETIME, 101) | If you're working on Oracle, inside your stored procedure use the TRUNC function on the datetime. This will return ONLY the date portion. |
680,963 | For example, whenever someone tries to go to `apple.com`, I want them to go to another website, but just when someone connects to my Wi-Fi. Maybe by using dnsmasq? Please don't be afraid to ask for clarification. | 2013/11/26 | [
"https://superuser.com/questions/680963",
"https://superuser.com",
"https://superuser.com/users/277178/"
] | You can open this chrome URL in new tabs to have multiple instances of the Library open:
chrome://browser/content/places/places.xul
and can view the tabs side-by-side with the [Tile Tabs](https://addons.mozilla.org/en-US/firefox/addon/tile-tabs/) extension. | Having the Bookmarks Sidebar and the Manage Bookmarks facilities open at the same time is the only way I've found to more easily move bookmarks around. I've posted to user groups and looked at all the addons and this seems to be the answer.
Some things like selecting multiple bookmarks work differently in the sidebar versus the Manage Bookmarks library. Just a few differences I've had to adjust my approach for, are (BTW I've looked many times but haven't found any article that addresses what the differences are or explain *why* there are differences):
Manage Bookmarks - can select multiple folders or bookmarks.
Sidebar - can only select one folder or bookmark.
Manage Bookmarks - can delete folders or bookmarks with the delete key.
Sidebar - have to right-click and use the dropdown menu.
Manage Bookmarks - does not show separators.
Sidebar - separators are visible.
I almost always use Manage Bookmarks as the "move from" list bc I can select multiples. The Sidebar is also clumsy when dragging bookmarks from one folder to another. |
92,284 | I do not know much about tensors. So I wonder:
Is it possible to explain [general relativity](http://en.wikipedia.org/wiki/General_relativity) without tensors?
I have some understanding of special relativity.
I also have some understanding about differential equations and matrices. | 2014/01/03 | [
"https://physics.stackexchange.com/questions/92284",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/12204/"
] | John Baez does just that on his site, [The Meaning of Einstein's Equation](http://math.ucr.edu/home/baez/einstein/). Here, he gives an easily readable explanation of Einstein's equation and derives some of it's consequences, even Newton's inverse square law. The abstract:
>
> This is a brief introduction to general relativity, designed for both
> students and teachers of the subject. While there are many excellent
> expositions of general relativity, few adequately explain the
> geometrical meaning of the basic equation of the theory: Einstein's
> equation. Here we give a simple formulation of this equation in terms
> of the motion of freely falling test particles. We also sketch some of
> the consequences of this formulation and explain how it is equivalent
> to the usual one in terms of tensors. Finally, we include an annotated
> bibliography of books, articles and websites suitable for the student
> of relativity.
>
>
> | This has been mentioned before in some of the other answers but let me just expand on it. Einstein's Field equation is a tensor equation relating the curvature of space-time to the distribution of energy and momentum. Feynman states in his lectures on physics (vol 2 chapter 42) that the field equation is equivalent to the statement that the scalar curvature of space (not space-time) at any point is proportional to the energy density at that point, and this must be true for any local inertial observer. (As you know from special relativity, two observers with different velocities disagree on measurements of space/time and momentum/energy, so Feynman's condition means different things to different observers.)
It can be shown that Feynman's statement is equivalent to the field equation (mathematically they both imply each other), so in that sense you can state General Relativity in a way which avoids the use of tensors, but the problem comes when you want to calculate anything. For example, working out what the field equation implies for the space-time curvature around a spherical star is relatively straightforward, but working out what Feynman's condition implies in the same situation is very complicated (I know because I tried... and failed).
Like most mathematical tools, tensors take some getting used to but eventually make your life easier. The question you need to answer is how deep do you want to go into General Relativity? If it's more than a passing acquaintence then learning tensors will save you time in the long run. |
92,284 | I do not know much about tensors. So I wonder:
Is it possible to explain [general relativity](http://en.wikipedia.org/wiki/General_relativity) without tensors?
I have some understanding of special relativity.
I also have some understanding about differential equations and matrices. | 2014/01/03 | [
"https://physics.stackexchange.com/questions/92284",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/12204/"
] | Of course it can be. But then, instead of a single object which incorporates certain parameters (for example, a metric tensor), which has a very useful properties, you are going to work with 16 (!) parameters (which are tensor elements), each having relations with other tensor elements. It is also more convenient to express energy, momentum in tensor formalism.
It's naive to think that those who work with general relativity use the hard way. So it happens, that tensor formalism is most likely the most easy one. | John Baez does just that on his site, [The Meaning of Einstein's Equation](http://math.ucr.edu/home/baez/einstein/). Here, he gives an easily readable explanation of Einstein's equation and derives some of it's consequences, even Newton's inverse square law. The abstract:
>
> This is a brief introduction to general relativity, designed for both
> students and teachers of the subject. While there are many excellent
> expositions of general relativity, few adequately explain the
> geometrical meaning of the basic equation of the theory: Einstein's
> equation. Here we give a simple formulation of this equation in terms
> of the motion of freely falling test particles. We also sketch some of
> the consequences of this formulation and explain how it is equivalent
> to the usual one in terms of tensors. Finally, we include an annotated
> bibliography of books, articles and websites suitable for the student
> of relativity.
>
>
> |
92,284 | I do not know much about tensors. So I wonder:
Is it possible to explain [general relativity](http://en.wikipedia.org/wiki/General_relativity) without tensors?
I have some understanding of special relativity.
I also have some understanding about differential equations and matrices. | 2014/01/03 | [
"https://physics.stackexchange.com/questions/92284",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/12204/"
] | I suggest this book: [A Most Incomprehensible Thing](http://rads.stackoverflow.com/amzn/click/0957389442). It assumes very little math background and does a good job introducing you to tensors and GR. | Einstein (The meaning of Relativity) and Feynman (available in audio
from a CalTech lecture from his Lectures in Physics) went a long ways
but I think if you want to understand it which means working some with it
the answer is: No. |
92,284 | I do not know much about tensors. So I wonder:
Is it possible to explain [general relativity](http://en.wikipedia.org/wiki/General_relativity) without tensors?
I have some understanding of special relativity.
I also have some understanding about differential equations and matrices. | 2014/01/03 | [
"https://physics.stackexchange.com/questions/92284",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/12204/"
] | John Baez does just that on his site, [The Meaning of Einstein's Equation](http://math.ucr.edu/home/baez/einstein/). Here, he gives an easily readable explanation of Einstein's equation and derives some of it's consequences, even Newton's inverse square law. The abstract:
>
> This is a brief introduction to general relativity, designed for both
> students and teachers of the subject. While there are many excellent
> expositions of general relativity, few adequately explain the
> geometrical meaning of the basic equation of the theory: Einstein's
> equation. Here we give a simple formulation of this equation in terms
> of the motion of freely falling test particles. We also sketch some of
> the consequences of this formulation and explain how it is equivalent
> to the usual one in terms of tensors. Finally, we include an annotated
> bibliography of books, articles and websites suitable for the student
> of relativity.
>
>
> | Einstein (The meaning of Relativity) and Feynman (available in audio
from a CalTech lecture from his Lectures in Physics) went a long ways
but I think if you want to understand it which means working some with it
the answer is: No. |
92,284 | I do not know much about tensors. So I wonder:
Is it possible to explain [general relativity](http://en.wikipedia.org/wiki/General_relativity) without tensors?
I have some understanding of special relativity.
I also have some understanding about differential equations and matrices. | 2014/01/03 | [
"https://physics.stackexchange.com/questions/92284",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/12204/"
] | I suggest this book: [A Most Incomprehensible Thing](http://rads.stackoverflow.com/amzn/click/0957389442). It assumes very little math background and does a good job introducing you to tensors and GR. | This has been mentioned before in some of the other answers but let me just expand on it. Einstein's Field equation is a tensor equation relating the curvature of space-time to the distribution of energy and momentum. Feynman states in his lectures on physics (vol 2 chapter 42) that the field equation is equivalent to the statement that the scalar curvature of space (not space-time) at any point is proportional to the energy density at that point, and this must be true for any local inertial observer. (As you know from special relativity, two observers with different velocities disagree on measurements of space/time and momentum/energy, so Feynman's condition means different things to different observers.)
It can be shown that Feynman's statement is equivalent to the field equation (mathematically they both imply each other), so in that sense you can state General Relativity in a way which avoids the use of tensors, but the problem comes when you want to calculate anything. For example, working out what the field equation implies for the space-time curvature around a spherical star is relatively straightforward, but working out what Feynman's condition implies in the same situation is very complicated (I know because I tried... and failed).
Like most mathematical tools, tensors take some getting used to but eventually make your life easier. The question you need to answer is how deep do you want to go into General Relativity? If it's more than a passing acquaintence then learning tensors will save you time in the long run. |
92,284 | I do not know much about tensors. So I wonder:
Is it possible to explain [general relativity](http://en.wikipedia.org/wiki/General_relativity) without tensors?
I have some understanding of special relativity.
I also have some understanding about differential equations and matrices. | 2014/01/03 | [
"https://physics.stackexchange.com/questions/92284",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/12204/"
] | Of course it can be. But then, instead of a single object which incorporates certain parameters (for example, a metric tensor), which has a very useful properties, you are going to work with 16 (!) parameters (which are tensor elements), each having relations with other tensor elements. It is also more convenient to express energy, momentum in tensor formalism.
It's naive to think that those who work with general relativity use the hard way. So it happens, that tensor formalism is most likely the most easy one. | I suggest this book: [A Most Incomprehensible Thing](http://rads.stackoverflow.com/amzn/click/0957389442). It assumes very little math background and does a good job introducing you to tensors and GR. |
92,284 | I do not know much about tensors. So I wonder:
Is it possible to explain [general relativity](http://en.wikipedia.org/wiki/General_relativity) without tensors?
I have some understanding of special relativity.
I also have some understanding about differential equations and matrices. | 2014/01/03 | [
"https://physics.stackexchange.com/questions/92284",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/12204/"
] | Of course it can be. But then, instead of a single object which incorporates certain parameters (for example, a metric tensor), which has a very useful properties, you are going to work with 16 (!) parameters (which are tensor elements), each having relations with other tensor elements. It is also more convenient to express energy, momentum in tensor formalism.
It's naive to think that those who work with general relativity use the hard way. So it happens, that tensor formalism is most likely the most easy one. | Einstein (The meaning of Relativity) and Feynman (available in audio
from a CalTech lecture from his Lectures in Physics) went a long ways
but I think if you want to understand it which means working some with it
the answer is: No. |
4,954 | Suppose John Doe is facing criminal prosecution in Florida. He raises a 4th Amendment issue, and the Florida Supreme Court grants him relief. At this point, the state of Florida can appeal to the US Supreme Court, and the US Supreme Court can, if it chooses, review the judgment of the Florida Supreme Court.
What puzzles me is this: at this point, there is no federal harm to either party. True, the Florida Supreme Court might have used an erroneous federal constitutional theory to tie the hands of the Florida Attorney General, but nothing in the US Constitution says they can't do that.
What is the justification that prevents this from being considered an abstract question? | 2015/11/03 | [
"https://law.stackexchange.com/questions/4954",
"https://law.stackexchange.com",
"https://law.stackexchange.com/users/-1/"
] | The Supremacy Clause.
U.S. Constitution, Article VI, Clause 2:
>
> This Constitution, and the Laws of the United States which shall be made in pursuance thereof; and all treaties made, or which shall be made, under the authority of the United States, shall be the supreme law of the land; and **the judges in every state shall be bound thereby, anything in the constitution or laws of any state to the contrary notwithstanding.** [emphasis mine]
>
>
>
This is also known as the "Supremacy Clause" of the U.S. Constitution. It prevents any law of any state from acting contrary to the federal constitution. A comment correctly cites multiple cases that use this clause, in part, as the basis for SCOTUS' authority to review State Supreme Court decisions.
So in your hypothetical, the federal issue in play is the clarity of the federal constitution which supersedes state law. | Losing on an interpretation of the federal constitution creates a federal case or controversy. |
105,310 | [My proposal, App Stores](http://area51.stackexchange.com/proposals/30702?tab=ontopic&phase=definition#tab-top) has 62 followers. According to the sidebar, it needs 5 on topic and 5 off topic to move on to the next stage. There are 33 sample questions, including more than enough of both kinds. What am I missing? | 2011/09/07 | [
"https://meta.stackexchange.com/questions/105310",
"https://meta.stackexchange.com",
"https://meta.stackexchange.com/users/142875/"
] | Yeah the rule for qualifying on-topic/off-topic questions is
>
> Each question needs 20 on-topic/off-topic votes, and 4 times as many on-topic/off-topic as off-topic/on-topic votes`.
>
>
>
You can find it by hovering over the question counts under the proposal status in the sidebar. It's also in the [Area 51 FAQ](http://area51.stackexchange.com/faq) | What are you missing? Voters.
In order for a question to count as one of the 10 you need, a question has to have at least X\* votes of a specific type.
\*I believe this number to be *around* 20. Looking at a few other proposals in the commit phase, their examples *mostly* have >20 votes(I found a few with 18&19). No examples in your proposal have >15. |
2,132 | A friend of mine (an old scuba instructor to be honest) told me that a too slow ascent is unsafe because it increases the time you stay at higher depths.
I think I have a good understanding of decompression algorithms (especially VPM and RGBM) and a good mathematical background, so I can roughly say that the risk of decompression sickness is a function of a derivative of pressure. In other words, the slower the better; if the ascent speed where near to zero, the risk would be near to zero too.
Am I wrong? Could my friend's theory be considered true at some point in the history of scuba diving? | 2013/01/21 | [
"https://sports.stackexchange.com/questions/2132",
"https://sports.stackexchange.com",
"https://sports.stackexchange.com/users/1038/"
] | It does lower the risk of decompression sickness, but let's take an extreme example. Let's try for 1 foot every 2 minute. You are changing the dynamics of a typical ascent table, which are usually made for the 30ft/min (1 foot every 2 seconds) ascent rate. You are taking 60 times as long to ascend, so you are spending longer times at deeper depths, which does cause the build-up of more nitrogen, etc. However, as long as you're not going ridiculously slow, I think the difference is negligble in the grand scheme of things (remember, most numbers are worst-case scenarios anyways, as it takes you X time to actually get to your depth, you're not at 60 feet immediately, etc. etc.) Safety static stops (usually at 15 feet) are also recommended. | Yes slow ascent can be more unsave.
It is proven to accent faster for a bit and make stops will me far more effective to decompress then to just assent slowly all the way.
This is because:
2) Building up less gas at depth.
1) Doing an more optimal decompression.
To put it in an example:
Say you make a deep dive. your tissues take up gas because of the pressure difference between your tissues and the surrounding pressure. ( I'm sure you already knew that )
There are fast and slow tissues. ( onces that take on gas quick and onces that take on gas slow )
Staying longer at depth you build up more gas in the tissues ( Saturate )
So as you ascent you actually still are building up more gas in your (slow) tissues.
While ascending your tissues become over saturated and you start to desaturate ( 'decompress' )
There is a point where the decompression is optimal ( larges pressure difference between your over saturated tissues and surroundings so gas exchange speeds up but not that large to cause dangerous bubbles to apear )
For this reason I do stops every dive ( even a shallow dive on nitrox I make stops of 1 minute )
The more effective you decompress the better you come out the water and the less change you'll have to a DCS.
Also stopping every dive trains you to stay at one depth to do those stops more safely.
For more info also check out this [wiki](http://en.wikipedia.org/wiki/Decompression_%28diving%29) about decompression |
2,132 | A friend of mine (an old scuba instructor to be honest) told me that a too slow ascent is unsafe because it increases the time you stay at higher depths.
I think I have a good understanding of decompression algorithms (especially VPM and RGBM) and a good mathematical background, so I can roughly say that the risk of decompression sickness is a function of a derivative of pressure. In other words, the slower the better; if the ascent speed where near to zero, the risk would be near to zero too.
Am I wrong? Could my friend's theory be considered true at some point in the history of scuba diving? | 2013/01/21 | [
"https://sports.stackexchange.com/questions/2132",
"https://sports.stackexchange.com",
"https://sports.stackexchange.com/users/1038/"
] | It does lower the risk of decompression sickness, but let's take an extreme example. Let's try for 1 foot every 2 minute. You are changing the dynamics of a typical ascent table, which are usually made for the 30ft/min (1 foot every 2 seconds) ascent rate. You are taking 60 times as long to ascend, so you are spending longer times at deeper depths, which does cause the build-up of more nitrogen, etc. However, as long as you're not going ridiculously slow, I think the difference is negligble in the grand scheme of things (remember, most numbers are worst-case scenarios anyways, as it takes you X time to actually get to your depth, you're not at 60 feet immediately, etc. etc.) Safety static stops (usually at 15 feet) are also recommended. | Lets be practical, for a too slow ascent rate to be dangerous it has to be so slow that you would basically not even be ascending.
A fast ascent rate creates way more problems than a slow ascent. If you ascent too fast you increase chance of DCS & AGE and the faster you ascent the harder it becomes to control your ascent rate.
Do people know where our ascent rates come from? 60feet/min or 18m/min ? It was becuase the US Navy wanted their divers to come up as fast as possible (and still be safe). The commercial divers used to do 10feet/min or 3m/min.
And rates where increased not necessarily because slower was unsafe, but because the sooner someone is out the water the better, so we keep trying to find the fastest way to get people out safely. Not for recreational use, but commercial and military.
=============================
**Historical ascent rates:**
Historical guidelines as to rates of ascent are pertinent. In the 19th century, for example, the French physiologist Paul Bert in 1878 quoted rates of 3 feet per minute and the English physiologist John Scott Haldane in 1907 recommended ascent rates between 5 and 30 feet (1.5 and 9 meters) per minute. From 1920-1957, rates of 25 feet (7.5 meters) per minute were recommended. Then in 1958, Cdr. Francis Douglas Fane of the U.S. Navy West Coast Underwater Demolition Team wanted rates for his frogmen of 100 feet (30 meters) per minute or faster.
Here is interesting article on safety stops and ascend rates.
<http://www.daneurope.org/c/document_library/get_file?folderId=13501&name=DLFE-133.pdf> |
2,132 | A friend of mine (an old scuba instructor to be honest) told me that a too slow ascent is unsafe because it increases the time you stay at higher depths.
I think I have a good understanding of decompression algorithms (especially VPM and RGBM) and a good mathematical background, so I can roughly say that the risk of decompression sickness is a function of a derivative of pressure. In other words, the slower the better; if the ascent speed where near to zero, the risk would be near to zero too.
Am I wrong? Could my friend's theory be considered true at some point in the history of scuba diving? | 2013/01/21 | [
"https://sports.stackexchange.com/questions/2132",
"https://sports.stackexchange.com",
"https://sports.stackexchange.com/users/1038/"
] | Lets be practical, for a too slow ascent rate to be dangerous it has to be so slow that you would basically not even be ascending.
A fast ascent rate creates way more problems than a slow ascent. If you ascent too fast you increase chance of DCS & AGE and the faster you ascent the harder it becomes to control your ascent rate.
Do people know where our ascent rates come from? 60feet/min or 18m/min ? It was becuase the US Navy wanted their divers to come up as fast as possible (and still be safe). The commercial divers used to do 10feet/min or 3m/min.
And rates where increased not necessarily because slower was unsafe, but because the sooner someone is out the water the better, so we keep trying to find the fastest way to get people out safely. Not for recreational use, but commercial and military.
=============================
**Historical ascent rates:**
Historical guidelines as to rates of ascent are pertinent. In the 19th century, for example, the French physiologist Paul Bert in 1878 quoted rates of 3 feet per minute and the English physiologist John Scott Haldane in 1907 recommended ascent rates between 5 and 30 feet (1.5 and 9 meters) per minute. From 1920-1957, rates of 25 feet (7.5 meters) per minute were recommended. Then in 1958, Cdr. Francis Douglas Fane of the U.S. Navy West Coast Underwater Demolition Team wanted rates for his frogmen of 100 feet (30 meters) per minute or faster.
Here is interesting article on safety stops and ascend rates.
<http://www.daneurope.org/c/document_library/get_file?folderId=13501&name=DLFE-133.pdf> | Yes slow ascent can be more unsave.
It is proven to accent faster for a bit and make stops will me far more effective to decompress then to just assent slowly all the way.
This is because:
2) Building up less gas at depth.
1) Doing an more optimal decompression.
To put it in an example:
Say you make a deep dive. your tissues take up gas because of the pressure difference between your tissues and the surrounding pressure. ( I'm sure you already knew that )
There are fast and slow tissues. ( onces that take on gas quick and onces that take on gas slow )
Staying longer at depth you build up more gas in the tissues ( Saturate )
So as you ascent you actually still are building up more gas in your (slow) tissues.
While ascending your tissues become over saturated and you start to desaturate ( 'decompress' )
There is a point where the decompression is optimal ( larges pressure difference between your over saturated tissues and surroundings so gas exchange speeds up but not that large to cause dangerous bubbles to apear )
For this reason I do stops every dive ( even a shallow dive on nitrox I make stops of 1 minute )
The more effective you decompress the better you come out the water and the less change you'll have to a DCS.
Also stopping every dive trains you to stay at one depth to do those stops more safely.
For more info also check out this [wiki](http://en.wikipedia.org/wiki/Decompression_%28diving%29) about decompression |
44,773,214 | I have a very simple nodejs application that accepts json data (1KB approx.) via POST request body. The response is sent back immediately to the client and the json is posted asynchronously to an Apache Kafka queue. The number of simultaneous requests can go as high as 10000 per second which we are simulating using Apache Jmeter running on three different machines. The target is to achieve an average throughput of less than one second with no failed requests.
On a 4 core machine, the app handles upto 4015 requests per second without any failures. However since the target is 10000 requests per second, we deployed the node app in a clustered environment.
Both clustering in the same machine and clustering between two different machines (as described [here](http://cjihrig.com/blog/scaling-node-js-applications/)) were implemented. Nginx was used as a load balancer to round robin the incoming requests between the two node instances. We expected a significant improvement in the throughput (like documented [here](http://stackabuse.com/setting-up-a-node-js-cluster/)) but the results were on the contrary.
The number of successful requests dropped to around 3100 requests per second.
My questions are:
1. What could have gone wrong in the clustered approach?
2. Is this even the right way to increase the throughput of Node application?
3. We also did a similar exercise with a java web application in Tomcat container and it performed as expected 4000 requests with a
single instance and around 5000 successful requests in a cluster
with two instances. This is in contradiction to our belief that
nodejs performs better than a Tomcat. Is tomcat generally better
because of its thread per request model?
Thanks a lot in advance. | 2017/06/27 | [
"https://Stackoverflow.com/questions/44773214",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/2322475/"
] | Per your request, I'll put my comments into an answer:
Clustering is generally the right approach, but whether or not it helps depends upon where your bottleneck is. You will need to do some measuring and some experiments to determine that. If you are CPU-bound and running on a multi-core computer, then clustering should help significantly. I wonder if your bottleneck is something besides CPU such as networking or other shared I/O or even Nginx? If that's the case, then you need to fix that before you would see the benefits of clustering.
>
> Is tomcat generally better because of its thread per request model?
>
>
>
No. That's not a good generalization. If you are CPU-bound, then threading can help (and so can clustering with nodejs). But, if you are I/O bound, then threads are often more expensive than async I/O like nodejs because of the resource overhead of the threads themselves and the overhead of context switching between threads. Many apps are I/O bound which is one of the reasons node.js can be a very good choice for server design.
>
> I forgot to mention that for http, we are using express instead of the native http provided by node. Hope it does not introduce an overhead to the request handling?
>
>
>
Express is very efficient and should not be the source of any of your issues. | As jfriend said , you need to find the bottlenecks ,
one thing you can try is to reduce the bandwith/throughput by using sockets to pass the json and especially this library <https://github.com/uNetworking/uWebSockets>.
The main reason for that is that an http request is significantly heavier than a socket connection.
Good Example : <https://webcheerz.com/one-million-requests-per-second-node-js/>
lastly you can also compress the json via (http gzip) or a third party module.
work on the weight ^^
Hope it helps! |
18,836 | Most of the people follow the 3rd precept of lay buddhism without knowing the actual meaning of it. Personally, even I don't know the actual meaning of it. Most of the people including me understand it as, "not practicing adultery outside marriage". But I know there's more than that. I simply don't know what.
Can you give a clear answer for this two questions.
* What is the actual meaning of the 3rd precept?
* What does it(the 3rd precept) say about "fornication"? | 2017/01/06 | [
"https://buddhism.stackexchange.com/questions/18836",
"https://buddhism.stackexchange.com",
"https://buddhism.stackexchange.com/users/10606/"
] | There are four conditions for wrong conduct in sexual pleasures.
1. There must be a man or woman with whom it is improper to
have sexual intercourse.
2. There must be intention to have sexual intercourse with such a
person.
3. Action must be taken to have such an intercourse.
4. There must be enjoyment from contact of the sexual organs.
With reference to the first condition, there are twenty kinds of
women with whom men should have no sexual relations. They can
be divided into three groups, namely:
* women under the
guardianship of parents, family members, relatives and authorities
charged with their care;
* married or betrothed women;
* bhikkhunis and religious women observing the Holy Life.
For all women,
* a man forbidden by tradition or
* under religious rules
is prohibited as a partner.
If someone is an unwilling partner, who is drugged or forced to
have sexual intercourse under threat of violence or coercion,
conditions (2) and (4) exclude them from having violated the precept.
Source: [FIVE PRECEPTS (PACASILA)](https://www.urbandharma.org/pdf/PDF_BuddhismCourse/11_%20Five%20Precepts.pdf) - urbandharma.org
It is also sexual misconduct when one engages a partner at an inappropriate time, such as when a woman is pregnant, or when she is nursing. It is unethical to take the mother away from the baby for sex. It is also misconduct to have sex at inappropriate places, such as at places of worship.
Source: [The Third Precept: Abstain from Sexual Misconduct](https://snfwrenms.wordpress.com/2011/12/28/the-second-precept-abstain-from-stealing/)
Also it is sometimes considered [Poya](https://en.wikipedia.org/wiki/Poya) / [Uposatha](https://en.wikipedia.org/wiki/Uposatha) is in appropriate time to have sex.
In addition, outside the bedroom is considered an inappropriate place in some interpretations.
---
As for the question about fornication: if the partner belongs to a category you should not have sex with, then you break the precept. | The 3rd precept was spoken by the Buddha at a time in social/cultural history where it was a social/cultural norm for parents to arrange the marriage of their children. The Sigalovada Sutta advocates this is a duty of parents towards their children. Therefore, the 3rd precept should be considered in this social context. In other words, the 3rd precept when literally read may be inadequate for modern Western society/culture. |
18,836 | Most of the people follow the 3rd precept of lay buddhism without knowing the actual meaning of it. Personally, even I don't know the actual meaning of it. Most of the people including me understand it as, "not practicing adultery outside marriage". But I know there's more than that. I simply don't know what.
Can you give a clear answer for this two questions.
* What is the actual meaning of the 3rd precept?
* What does it(the 3rd precept) say about "fornication"? | 2017/01/06 | [
"https://buddhism.stackexchange.com/questions/18836",
"https://buddhism.stackexchange.com",
"https://buddhism.stackexchange.com/users/10606/"
] | There are four conditions for wrong conduct in sexual pleasures.
1. There must be a man or woman with whom it is improper to
have sexual intercourse.
2. There must be intention to have sexual intercourse with such a
person.
3. Action must be taken to have such an intercourse.
4. There must be enjoyment from contact of the sexual organs.
With reference to the first condition, there are twenty kinds of
women with whom men should have no sexual relations. They can
be divided into three groups, namely:
* women under the
guardianship of parents, family members, relatives and authorities
charged with their care;
* married or betrothed women;
* bhikkhunis and religious women observing the Holy Life.
For all women,
* a man forbidden by tradition or
* under religious rules
is prohibited as a partner.
If someone is an unwilling partner, who is drugged or forced to
have sexual intercourse under threat of violence or coercion,
conditions (2) and (4) exclude them from having violated the precept.
Source: [FIVE PRECEPTS (PACASILA)](https://www.urbandharma.org/pdf/PDF_BuddhismCourse/11_%20Five%20Precepts.pdf) - urbandharma.org
It is also sexual misconduct when one engages a partner at an inappropriate time, such as when a woman is pregnant, or when she is nursing. It is unethical to take the mother away from the baby for sex. It is also misconduct to have sex at inappropriate places, such as at places of worship.
Source: [The Third Precept: Abstain from Sexual Misconduct](https://snfwrenms.wordpress.com/2011/12/28/the-second-precept-abstain-from-stealing/)
Also it is sometimes considered [Poya](https://en.wikipedia.org/wiki/Poya) / [Uposatha](https://en.wikipedia.org/wiki/Uposatha) is in appropriate time to have sex.
In addition, outside the bedroom is considered an inappropriate place in some interpretations.
---
As for the question about fornication: if the partner belongs to a category you should not have sex with, then you break the precept. | Precepts are originally designed for monks. So, a monk would totally abstain from sex. However, for the laity Buddha simply said that the average person should avoid sexual misbehavior. Sexual misbehavior is simply sexual conduct which is socially unacceptable. One example is adultery. Another might be beastiality. Another might be homosexuality. It largely depends on the culture. |
18,836 | Most of the people follow the 3rd precept of lay buddhism without knowing the actual meaning of it. Personally, even I don't know the actual meaning of it. Most of the people including me understand it as, "not practicing adultery outside marriage". But I know there's more than that. I simply don't know what.
Can you give a clear answer for this two questions.
* What is the actual meaning of the 3rd precept?
* What does it(the 3rd precept) say about "fornication"? | 2017/01/06 | [
"https://buddhism.stackexchange.com/questions/18836",
"https://buddhism.stackexchange.com",
"https://buddhism.stackexchange.com/users/10606/"
] | Precepts are originally designed for monks. So, a monk would totally abstain from sex. However, for the laity Buddha simply said that the average person should avoid sexual misbehavior. Sexual misbehavior is simply sexual conduct which is socially unacceptable. One example is adultery. Another might be beastiality. Another might be homosexuality. It largely depends on the culture. | The 3rd precept was spoken by the Buddha at a time in social/cultural history where it was a social/cultural norm for parents to arrange the marriage of their children. The Sigalovada Sutta advocates this is a duty of parents towards their children. Therefore, the 3rd precept should be considered in this social context. In other words, the 3rd precept when literally read may be inadequate for modern Western society/culture. |
1,655 | For example, let's say I have a friend sprinting a 50m distance and that friend wants me to time the race, but I don't have a stopwatch so I have to count "manually". Can I count while simultaneously thinking about how she'll do and while wondering what I'm going to have for dinner? | 2012/09/17 | [
"https://cogsci.stackexchange.com/questions/1655",
"https://cogsci.stackexchange.com",
"https://cogsci.stackexchange.com/users/1150/"
] | Parallel processes are often studied in a so called ['dual task' paradigm](http://en.wikipedia.org/wiki/Dual-task_paradigm), where participants are drawing a picture and reciting a poem or, as in your example, counting and thinking about other things.
Often this method is used to demonstrate limits in attention and find insights into how the brain works (in a serial versus parallel manner). Training is an important factor in this question. It has been shown that with a sufficient amount of training a lot of tasks can be done parallel very well - so if you sit there long enough and automize the counting the rest will follow. | I have to partly disagree with schultem here-- he is right that the dual task paradigm is used to study multitasking, but the idea that we can truly do two cognitive tasks at the same time is still contentious. In particular, the opposing view might say that we can't really do two cognitive processes at the same time, but we are in fact switching between the two tasks very rapidly. To make a an analogy, consider a computer with a single-core CPU: although behaviorally it seems like you are running multiple processes at the same time, all applications still depend on a single bottleneck.
One of the most well studied experimental paradigms for this domain is called the '[psychological refractory period](http://en.wikipedia.org/wiki/Psychological_refractory_period)', or PRP effect, which shows over [2,700 hits on google scholar](http://scholar.google.com/scholar?q=%22psychological%20refractory%20period%22&btnG=&hl=en&as_sdt=0,44).
A typical PRP task has the subject perform two reaction time tasks. For instance, he may have to hit a button with his right hand in response to a high pitched tone, and hit a button with his left hand in response to a low pitched tone. At the same time, he performs another concurrent task-- e.g., saying "blue" in response to a blue stimulus, and "green" in response to a green stimulus. By altering the stimulus onset asynchrony (SOA) (that is, the time from the start of the tone to the start of the visual stimuli), we can examine what operations people are able to perform in parallel.
Each task can be broken down into three components: perceptual analysis, response selection (cognitive), and response processing. A prominent theory emerging from the results of many PRP tasks is that we are able to truly do two operations in parallel if they require different modes: for instance, we can do perceptual analysis of a visual stimuli and auditory tone at the same time, and we can make a manual and vocal response at the same time, however we cannot do two response selections at the same time because they essentially require the same cognitive resources (single bottleneck).
This image from wikipedia describes what I'm talking about. The response selection from the second task must wait for the response selection from the first task to finish before it begins. The result is that, at short SOA, the total time taken to respond to both stimuli is the same-- as long as perceptual analysis of the second task ends before the response selection from the first task.
So in sum, yes, it might be possible to do the two tasks you are talking about in parallel, especially with practice. But on a more fundamental level, you may really just be doing very rapid multitasking. If you're interested in this theory, you may also want to read about [threaded cognition](http://scholar.google.com/scholar?hl=en&q=threaded%20cognition&btnG=&as_sdt=1,44&as_sdtp=), which demonstrates this effect for complex tasks. |
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