The positioning system is the part of the waterjet machine that moves the waterjet nozzle. The more accurately the nozzle can be positioned, the more precisely you can make parts.
Although not every application calls for high precision, having a precise machine means that you do not have to turn down high tolerance work, and that you can often eliminate secondary processes. With modern waterjets, it is entirely possible to make parts with a precision of better than ±0.003″ (0.076 mm). Also considered here are features that are important for best surface finish.
An X-Y positioning system with the bellows removed, showing precision gearing
Most waterjet machines uses an X-Y positioning system, meaning the nozzle moves up-and-down and back-and-forth. In general, the positioning system is not a wear item on a waterjet, as long as you take care to keep it clean and properly lubricated.
The more accurate your machine is, the more jobs you are capable of taking. Some machines can easily make parts in the ±0.002″ (0.05 mm) range, and with a little effort, do even better. This can be important if you want to compliment or compete with wire EDM, or milling. It can also be important if you want to reduce the number of secondary operations on parts you make. If you can make the part within tolerance on a single machine, then you can reduce your costs and increase profits by avoiding secondary operations.
Each manufacturer has a different way of stating accuracy. Find out what they are talking about. Here are some things to look for:
Positioning accuracy vs. final part accuracy
Just because a machine positions within 0.001″ (0.025 mm), does not mean that your final parts will be within 0.001″ (0.025 mm). Final part accuracy is a function of many variables including material, thickness, positioning accuracy, feed rate, controller, nozzle setup, machine vibrations, operator skill, and much more. While positioning accuracy is necessary for final part accuracy, it is not the only factor.
Dynamic vs. static measurements of positioning accuracy
Was the positioning accuracy measured by moving the machine, then coming to a complete stop, then measuring (static positioning accuracy)? Or was the machine measured while it was moving (dynamic positioning accuracy)? Many machines will position well at rest, but at speed it is more difficult. Be sure to ask how well the machine tracks position at higher speeds, such as 150 inches/min (38 cm/min)? At slow speeds you don’t get the same servo following errors that you do at higher speeds.
Repeatability is a key factor in obtaining precision. If you make five of the same part in different places on the machine, do the parts come out the same? Have your sales person do some tests while you watch, if possible. It is important to watch your test parts being made, to insure that they are not making a lot of your parts, and then only showing you the one that came out best.
Depending on the part you are machining, some waterjets are capable of accuracies as close as ±0.0005″ (0.013 mm). But this is only under certain rare conditions, specifically using a thin material and careful setup by an advanced user. If a manufacturer claimed such high precision, they would get themselves into a lot of trouble with a new user who just bought a machine, and is cutting something where such precision is impossible. For this reason, most manufacturers have found that it is better to quote something more reasonable that covers a typical user making typical parts. In other words, they are cautious when quoting tolerances.
On the other hand, some manufacturers, in order to gain a selling advantage, are a little less cautious when quoting precision. Therefore, you will find that there is a wide variation in actual part precision, but a less wide variation in claimed precision by manufacturers.
You watch parts being made on the machine, then measure the results. Do not run “canned” parts, where the sales person has had time to tweak the program. Create parts from scratch, that you draw at the controller from an idea in your head. This will not only give you a better idea of how the machine is programmed, but it will also help show you what kind of real world tolerances you can expect.
Protection from dirt, dust, and moisture
The bearings and drive mechanism of the X-Y positioning system are precision equipment. Attached to a waterjet, they are in an environment where there is a lot of abrasive, which can destroy that precision. Moisture is also not good on the inner components of your machine. How easy is the machine to keep clean? Are there spots for dirt to collect? Look for fully sealed X-Y guides and ball screws to eliminate the risk of abrasive contamination of precision surfaces. Bellows should not have horizontal “pleats” that can trap dirt and abrasive material and cause bellow failure. Also look for other places where dirt and moisture might cause problems. If you are buying a used machine, be careful of dirt in expensive places.
You probably don’t need to go very fast (more than 50 inches per minute or 1.3 meters per minute) if you are using the machine for abrasivejet machining. For nearly all parts, you will be limited by how fast the machine cuts, rather than the speed of the positioning system. Only if you do a lot of pure waterjet cutting, or cutting of extremely thin material, will maximum speed be important.
Waterjet machines come in a variety of sizes, and most machines are measured by the size of the “table,” where the material sits. This is usually larger than the machining area, as the nozzle can’t travel all the way to the edge of the table. The catcher tank is sized to fit the table. When purchasing a waterjet, one thing you will have to decide is the size of the table.
The ideal abrasive waterjet shop would have several small machines, one medium sized one, and one large one, running two or more nozzles. However, if you are only buying one machine, then the choice is not as clear, and depends a lot on the kind of work you currently do, and the kind of work you want to get into.
Big machines are more expensive to purchase and operate, but you are not limited in the size of a part you can make without indexing it.
Small machines are less expensive to purchase and operate, and are small enough that it is more fun to use the machine. It is more convenient to use the machine for smaller jobs, and for “machinist” type work. For small parts, you can be more profitable, because you are not trying to pay for a big machine.
There is no good answer to this, however, so ultimately it is up to you. Keep in mind, however, that most sales people would rather sell a big machine than a small machine, because that is where they make the most money. When purchasing a machine, you need to determine how you will be making the most money.
Table size and nozzle travel
You will pay more for a bigger table, bigger tables tend to be less accurate, and bigger tables take up a lot of space. You also need to have more work for the machine to pay for it. Smaller tables can often work with the occasional big piece of material with a little setup, so you might not miss out on as much work as you think. If you are a production or fabrication shop, where you do a lot of work with huge sheets of material, then you should look at the bigger tables
Rule of thumb
The table should be sized to easily hold stock material of standard sizes and the nozzle travel should be great enough to cut at least 1″ or 2″ (2.5 or 5 cm) greater than standard-sized material. For example, a machine shop generally using 2′ x 4′ (60 cm x 120 cm) stock material should have a nozzle travel of at least 26″ x 50″ (66 cm x 127 cm) and a fabrication shop using 4′ x 8′ (60 cm x 240 cm) material should have a nozzle travel of at least 50″ x 98″ (66 cm x 250 cm). This gives you a little room to move, fixture, and clamp material to the table.
Here are some measurable things to consider regarding tank and size:
How much space does the entire machine take up? Don’t forget ceiling requirements. Will it fit in your shop?
What is the biggest cut you can make without having to move the material?
What is the biggest sheet of material you can fit in the machine, yet still cut submerged? Cutting with the material submerged is much quieter and cleaner than cutting in the open.
What is the biggest sheet of material you can cut by feeding the material through the machine? Can you feed the material through the machine? In some cases this dimension may be that the biggest material you can machine is equal to the width of the machine in one dimension, and infinity in the other.
Be sure to think about other factors such as how you will load and unload the material, how will you pull the finished parts from the machine, and are there things in the way such as bellows that might get damaged in the process.
Cutting with the material submerged greatly reduces noise and splash from the tank. This is important if you are operating in a machine shop environment, and don’t want to make a mess or have to wear hearing protection. Here are some things to consider:
How fast does the water level raise / lower?
It should be possible to raise or lower the level of water on the cutting surface by at least one inch per second (2.5 cm/sec) to insure rapid and convenient operation. Otherwise, you spend a lot of time waiting for the water to rise instead of making parts.
What is the deepest you can submerge?
For good noise and splash protection you will want the water level at least 0.5″ (10 mm) from the top of the material. It is even nicer to raise the water level up to 2″ (5 cm) above the material being machined for maximum noise and splash protection. Some people prefer to cut without submerging so that they can watch that the nozzle does not break on loose material. This is unnecessary if your nozzle is properly protected, and you program your paths with collision avoidance in mind.
Material handling and fixturing
You want to consider how you will get material into your machine, which will depend on how large the table is. Questions to ask about material handling and fixturing include:
What is the biggest piece of material you can fit submerged in the machine?
Remember that this will be smaller than the largest piece of material you can fit on the table. Make sure you can fit a standard size sheet of the material you work with the most.
What if your material is bigger than the table?
If the material you want to cut is larger than the table, can you put the material on top of the machine, or are there guards in the way?
What is the actual cutting envelope of the machine?
The cutting area of the machine is usually smaller than the table size, and it can be further reduced by some accessories you may purchase.
How does the cutting envelope compare with standard material sizes?
If the cutting envelope is smaller than your standard material size, you may not be able to use as much of the material as you want. One of the advantages of waterjets is that you can use most of the material, because of the small kerf and small sideways forces.
What options do you have for fixturing your material?
How will you make sure that your material doesn’t move during machining? Most fixturing with waterjets involves clamping the material, so make sure that there are places where you can attach clamps.
How rigid is the table? This affects the accuracy of the final part. Is the positioning system connected to the tank or separate? If they are separate, you may find that the two systems move independently of each other, and therefore, the part you are cutting also moves independently of the machine. If they are not rigidly attached, then a forklift driving by, or the machine’s motion itself could cause vibration marks on your parts. This will result in a less precise part with worse edge quality.
Also check the rigidity of the nozzle attachment to the table. It does not have to be super rigid, as the cutting forces exerted by the jet are not very strong, but it should not move easily either, or it may be pulled by the high pressure tubing. Relative vibrations between nozzle and part are a common source of fine errors when trying to achieve maximum precision with some machines.
What happens to spent material and water? Some systems have optional tank clean-out systems, or you may have to shovel the tank out by hand. Shoveling by hand is a lot cheaper than an automatic clean out system, but finding volunteers can be difficult.
There are also some after market clean-out systems available.
As long as you are not cutting toxic materials, your waste water can be sent down the drain, although you can recycle it if you want. If you are cutting toxic materials, you will need to have a water recycling system and a way to dispose of your waste garnet, as it will be contaminated with small pieces of the material.
Water recycling is sometimes useful in areas where water/sewer is expensive, or if you are cutting hazardous materials regularly. You don’t have to get a water recycling system from the same place you get your waterjet, however.
Material is supported in the tank by a system of slats, typically spaced about 1″ (2.5 cm) apart. With time, the slats will get cut by the nozzle and need to be replaced. You should look for material support slats that can be quickly changed on an individual basis as needed or removed completely for simple installation of special holding fixtures.
Can the machine be easily moved to a new location?
Some machines are easy to move with a forklift, while others (especially big ones) may require significant effort, rebuilding, and calibrating. This may or may not be important depending on how often you re-arrange or move your shop or whether you ever intend to sell the machine.
Choosing a nozzle doesn’t just happen when you purchase your waterjet machine. You can also purchase new nozzles throughout the life of your waterjet, as technology advances and newer and better nozzles come out. Regardless of the technology, however, there are still some basic features to look for.
Look for a precision nozzle assembly with fixed alignment jewel orifice and mixing tube. It should be possible to change or exchange either an abrasivejet nozzle or a pure waterjet nozzle in under five minutes without special tools. It should be possible to completely overhaul a nozzle in less than 15 minutes.
Mixing tube guard
Check that the nozzle has a mixing tube guard that protects the mixing tube from side impacts that can happen if the operator accidentally runs the nozzle into the side of piece of material stock. Many nozzles expose the mixing tube out where they are easily broken. The mixing tube is delicate, so make sure its protected.
Mixing tube protectors will also reduce the amount of splash as well, especially during piercing. You can always remove the protector for special needs, but having the protector will save you a lot of money and frustration.
Mixing tube life
Mixing tube life is quoted differently by every manufacturer. Most manufacturers use the same mixing tube material from Boride, and thus they wear at similar rates. Mixing tubes are like drill bits: when is a drill bit worn out? That depends on what you are using it for. If you are using it for precision machining, then it is considered worn out earlier. For rough work, you can say it lasts longer. Mixing tube life is strongly affected by water quality .
Mixing tube size
Longer mixing tubes give slightly better focus, and perhaps last a little longer. Smaller inside diameters give slightly faster cutting, and more precision, but wear a little quicker. Thicker mixing tubes are less likely to break when they hit something.
Mixing tube diameter
Smaller mixing tube diameters offer greater precision, reduced taper, and reduced kerf. They also do not require much pumping power, because they are typically used with a correspondingly smaller jewel. However, they do not cut as quickly as larger ones connected to larger pumps.
Diamond, ruby, and sapphire jewels
Most jewels used in waterjets are made from rubies, because they are relatively cheap and relatively durable. Rubies and sapphires are the same thing, except that rubies have a slight impurity that makes them red. Diamond jewels usually last longer but are more expensive.
You typically replace the jewel at the same time you replace a mixing tube, and the cheap rubies work well. If you don’t like replacing your jewel, you can use a diamond jewel. This should not make or break a buying decision, because most manufacturers offer the option of either jewel type (as well as the after-market). Water quality significantly affects jewel life. With clean water, jewels and mixing tubes last longer.
With the high pressures created by waterjets, making sure the jewel is accurately aligned can dramatically affect wear on the mixing tube and cutting efficiency. Most nozzles are pre aligned, but some require that you do it manually. If your jewel doesn’t align well, then you will wear your mixing tube out prematurely because the water is hitting the side of the tube instead of shooting straight down it. Also, you will not cut as effectively.
Besides nozzle design in general, one thing that can cause jewel misalignment is accumulated minerals caused by poor water quality. The accumulated materials will change the geometry of the jewel, and disturb the jet. Another thing that can cause jewel misalignment is dirt under the jewel, which can occur when rebuilding the nozzle. Always do your nozzle rebuilds in a clean environment, and clean the items you are rebuilding to avoid this kind of problem. Likewise, if you rebuild something upstream, such as the pump, you should remove the nozzle and flush the system, to insure no upstream debris can damage or plug the jewel.
Running multiple nozzles is a reasonable way to increase productivity without buying a second machine. You will need a large pump, or several small pumps to operate multiple nozzles at once. Then, simply mount your nozzles next to each other on the same machine. There is some risk, however, that a nozzle clog or snag on one nozzle can ruin all the parts underneath the other nozzles.
Note that when running multiple nozzles, some precision is lost because of the inability to compensate for tool wear exactly over both nozzles, but in most applications it’s still possible to get good precision.
If you are doing lots of the same part over and over, you can produce more at once with multiple heads. Many high production waterjet shops cut with multiple cutting heads, and most job and machine shops use a single head.
Some manufacturers offer a “MiniJet” nozzle, which is a nozzle with a smaller jewel and mixing tube that can produce a very thin cut, as thing as 0.020″ (0.5 mm). These MiniJet nozzles are good for cutting very small pieces, where the tiny cut allows intricate features to be cut, such as for jewelry. They are also good when cutting expensive material or precious metals where you want to preserve as much of the material as possible.
Because the waterjet stream is narrower, they will cut slower than a standard nozzle. Still, many machine shops find it useful to keep a MiniJet nozzle handy for specialty work.
The abrasive feed system makes sure that there is a steady flow of abrasive to the nozzle where it is mixed with the water. Flow rates are typically about a pound a minute (0.5 kg/min). You have some choices in types of hoppers for your waterjet machine.
If you do long runs of cutting, you will probably want a hopper that gives you lots of time by holding a lot of abrasive. Hoppers with capacities of 300 lb to 600 lb (135 to 275 kg) are pretty common, and are a good option to invest in.
Eventually your will get a mixing tube clog and water will shoot back into your abrasive system. Look for a design that doesn’t make you empty your hopper if water backs up the abrasive line.
If you like to adjust and tune your system, then you might want to change abrasive types for certain materials. This is not necessary for most machine shops, but if you do glass, or other non-metallic materials, then you may want to machine with a finer or softer abrasive. In that case, you’ll want to have an abrasive feed system that makes it easy to use other types of abrasives.
Similarly, you may want to be able to adjust abrasive flow rates to get the best machining for different materials. Some feed systems have a single flow rate, while others let you adjust the flow rate as desired.
The basic abrasive feed system designs are discussed below.
Hopper next to nozzle
Having the hopper next to the nozzle is sometimes called a “mini hopper.” In this case, there is a metering device underneath the hopper that opens up to allow gravity to drop the abrasive through an orifice and into the abrasive tube.
Mini hopper mounted on positioning system to feed abrasive to nozzle
- Fast abrasive delivery to nozzle
- Easy to change abrasive types
- Very accurate and consistent abrasive flow
- You can see the abrasive level easily
- Low capacity and must be refilled often
- You need to be able to reach the hopper to refill it; if it needs refilling in the middle of making a part, you might have to interrupt machining to refill it
The common application of this design is for shops that do lots of single piece production, and don’t do long runs.
Bulk abrasive hopper fed from floor
In this case, suction from the nozzle is used to draw abrasive from a large abrasive tank on the floor that is typically pressurized with air into the nozzle.
A bulk abrasive hopper
- Easy to load in the abrasive, even from heavy bags (no need to lift up the bags)
- Very high capacity that will last many hours before refill is needed
- No warning before abrasive runs out
- Typically the abrasive metering is not very accurate or consistent
- More expensive
- Harder to change abrasive types, unless you have more than one hopper where you can switch abrasive feed tubes
- If water goes up abrasive tube (as in case of nozzle plug), then you may have to empty several hundred pounds of abrasive (depending on system)
- To add abrasive, you have to first depressurize the system. This can be awkward if you need to do this while the machine is cutting, unless you also have a second small hopper to act as a buffer to give you time to fill.
A combination of mini hopper and bulk hopper
In this setup the larger hopper feeds the smaller hopper located next to the nozzle.
This design generally offers the best of both worlds, specifically:
- The small gravity fed hopper provides an even and precise abrasive flow rate
- Provides faster response of abrasive delivery, which is essential for piercing brittle materials
- Provides early warning, should the larger abrasive hopper run out.
- Depending on the design, it can make it easy to change abrasive types for special purposes
- Depending on the design, it can make it easy to change the abrasive flow rate for special purposes
- Costs the most money
The “brain” of a waterjet machine is called the controller because it controls the high-pressure water pump, the abrasive flow, and the movement of the nozzle. Unlike older machine tools which are controlled by humans, waterjets are controlled by computers because of the complicated nature of the waterjet stream.
The software running on the controller is extremely important. You should look at your programming options thoroughly before purchasing a system. Make sure that you like the included software, and also make sure that you have other programming options available. Can you import files from AutoCAD, MasterCAM, Adobe Illustrator, and other popular CAD / CAM / Drawing packages?
Watch out for proprietary software with unpublished file formats to store your CAD data, or tool path files. If you decide later on that you don’t like the software that comes with the system, it is nice to be able to export the data to a different CAD package. You may also want to use some other third party software for nesting, gear generation, or other special shape generation.
Also watch out for software that you must pay lots of money to upgrade, or pay money for extra seats (each computer the software is installed on is called a “seat”). Often, it is to your advantage to run the software on several computers. Perhaps one seat on the machine, one or two in the office, and another seat at home, or on your laptop. It is of course also to your advantage to run recent software with all the latest features and bug fixes.
You should also ask about maintenance and upgrade fees for the controller software. These hidden costs can be large, and upgrading software is something you will want to do at least once per year because of the rapid developments in this area, and for simple bug fixes.
Choosing a good controller, then, is a key decision when purchasing a waterjet. You want to make sure that the controller does its job well, and that it’s easy for you to use. Following are a number of factors you should look at when choosing a controller.
Jet behavior compensation
The waterjet stream exhibits chaotic behavior—it’s difficult to accurately predict what it’s going to do, especially when the nozzle is moving. Not only is the stream lagging behind the nozzle, but it’s also bouncing off the material you are machining.
Older waterjet systems required you to set “feed rates” (how quickly the nozzle moved across the material). Most modern waterjets calculate these for you automatically and provide precise control of the nozzle. Still, there are differences in how well controllers compensate for jet behavior.
You should look for a motion control or programming system that calculates optimized nozzle travel speeds and speed variations based on the materials and shapes being machined prior to cutting the part. This type of control is critical to controlling wash-out and irregularity at corners and around curves. For ultra-precise machining, the control system should be capable of setting different speeds at very fine intervals, especially around curves and corners.
The controller should at a minimum compensate for the following
As the nozzle moves forward, the jet lags behind it. The faster the nozzle moves, the more the jet lags behind. This becomes even more complicated when the nozzle moves around corners as the jet can move outwards (bouncing off the walls of the cut more) and even cut into the corner itself. The controller should also “look ahead” on the toolpath, so that it can compensate for features that are coming up, such as corners, and slow down as needed.
Kick-back when accelerating out of a corner
As the nozzle moves out of a corner, it’s possible for the jet to bounce off the walls of the corner just cut, gouging them out. This is called “kick-back” and is controlled by adjusting the nozzle speed when exiting the corner.
Kerf width (Tool offset)
The kerf width refers to the amount of material removed by the waterjet stream. The width of your cutting stream will vary from nozzle to nozzle, and as a result of wear. Virtually any controller should compensate for this, typically by letting you enter a value that you’ve measured.
The controller should automatically predict and compensate for taper, typically by either slowing the cutting rate down or by tilting the nozzle.
The controller may use other optimizations the controller does for you to improve speed or precision such as automatic corner passing, corner looping, and automatic pierce assignments.
How the machine pierces materials is important. Ideally the controller should offer a full range of piercing methods to deal with different situations.
Automatic dual pressure support
Your high-pressure water pump may support dual pressure, but that does little good if the controller doesn’t. Make sure that your controller will automatically switch the pump pressure for piercing. Otherwise, you will either not be able to use dual-pressure piercing, or you will be forced into the awkward condition of having to pre-pierce all the holes at low pressure, then cut at high pressure.
Error mapping and compensation
It is possible to compensate for low-grade components through software by using techniques such as “error mapping”. Error mapping can also be used to gain an extra measure of precision from an already high precision machine. Can you adjust the machine for a stretched ball screw? Do you need mapping? Is the machine in question constructed with cheap components, and compensated for through mapping?
Depending on construction of the machine, this feature may or may not be necessary, although even on a precisely constructed machine, it is possible to get an order of magnitude greater precision with error mapping. Therefore, there are really two different applications for it:
- Making a very low cost machine that is still reasonably precise. The biggest flaw to this strategy is that you need to perform the error mapping, which in itself is fairly expensive to do, and often needs to be done more than once. This is a complex solution to a problem that in many cases could be much better solved with precision components to begin with.
- Making a precise machine more precise. If you have a machine that is already as precise as you can make it mechanically, then error mapping can increase precision by a factor of ten. Once you get to a certain level of precision in positioning accuracy, however, many other effects of waterjet machining will dominate, and additional positioning accuracy is pretty much useless except for someone doing something highly specialized such as researching cutting models
User interface issues
The interaction between you and the controller software is called the “user interface,” and it should be easy for you to understand how it works. To some extent, this is a matter of personal preference—some people like a very visual user interface, while others like lots of text. While you won’t become an expert after a few minutes of working with it, you should feel comfortable and commands should make sense and work the way you think they should.
Try drawing a part from scratch. Don’t watch a “canned” demonstration of a memorized part. Is it easy to make just one part, and does it turn out good the first try—or do you have to make a part, then adjust your program , then make another part?
Does the programming system have automated features to speed up common processes such as tool path creation and geometry fixing?
If the programming system makes the tool path for you, can you override what it did, if you don’t like what it did? This may be quite important for collision avoidance. Probably more so than for other machines such as lasers where parts that are cut can simply fall under the table, and not pose a collision hazard. In waterjet machining, the parts will tend to tip on the supports, and present collision hazards. Falling into the tank is not desirable for various reasons—especially the fact that the blast from the nozzle may cut up the part as it falls.
Part creation options
Look at the options available for creating parts, since this is a key activity in running your waterjet. Most controllers include software for drawing parts and preparing them for creation on the waterjet. Making parts on a waterjet requires some special adjustments, such as surface finish and hole drilling, so you’ll probably need to use the controller software for at least part of this.
You may also want to use software from other companies with your waterjet. If you are already familiar with a CAD / CAM package, check that the controller can import those files and work with them. Again, try it out. Don’t rely on assurances that it will work–people who have worked with computers for years don’t believe anything until they see it work.
No single nesting software package will suit everyone’s unique needs. There are many widely varied nesting software packages out there, and they each have their strengths and weaknesses for a given task. Nesting software ranges from about $1000 to over $25,000, depending on capability. Be sure to check upgrade prices for this software.
- Does the company that makes your abrasivejet publish their file formats publicly?
If not, then you may not have many choices of nesting software, and may be locked into whatever package the manufacturer of your machine has to offer. This is not necessarily bad, but you will not have much choice in the matter.
- Do you need to output files to your other machines?
If so, make sure that the nesting software you get can post to your other machines as well. Some nesting software can post only to lasers and waterjets and other “beam cutting” tools, while other nesting software can also do punch presses and other tools.
- Do you intend to nest a single part over and over to fill a sheet of material, as in a production environment?
Or will you instead start with a piece of material, then fill it up with a wide variety of different parts?
The answer to this question will mean a huge difference in price of the nesting software. Most waterjet users cut the same part over and over, and don’t fill sheets with all sorts of different shaped parts. Therefore, think about this carefully before purchasing the more expensive nesting software options.
You may want to wait until you have your machine for a few months, then decide if you need nesting software, and what features you really need.
If you are an OMAX Customer, be sure to read the “nesting software buyers guide” in the OMAX Interactive Reference.
Software for scanning is useful for converting artwork from a scanned image or photograph into a vector CAD file. If you are planning on doing artwork, or reverse-engineering parts, you may want to see what kind of image tracing capabilities come with your machine. There are also third party software options in this regard such as Cutting Shop from Arbor Image, Adobe Illustrator, and others. Look for “Raster To Vector” software with your favorite search engine for other options.
Things go wrong, even with waterjet machining and you should consider how well the controller can recover if your mixing tube clogs or breaks.
How easy is it to save the part? Look for user specified machine home or “Zero” positions. Also look for the ability to stop in the middle of a cut, and backup, then resume, and the ability to quickly jump to a specific spot on the path. Find out how to recover, should the power go out in the middle of machining a $5000 part.


Transfer printing enhanced by new laser-driven shape memory effect
A unique transfer printing approach detailed in Assistant Professor Seok Kim’s paper, “Laser-Driven Shape Memory Effect for Transfer Printing Combining Parallelism with Individual Object Control,” was published last week in the journal Advanced Materials Technologies. His graduate student Jeffrey Eisenhaure is first author on the paper.
“Transfer printing, a method using polymeric stamps to transfer micro-objects, has been demonstrated either as a parallel process with high throughput, or as a low throughput process allowing individual manipulation of micro-objects—but not both simultaneously,” Kim said. “So it has been challenging to claim that transfer printing-based microassembly is a highly flexible and scalable, manufacturing process.”
To address this challenge, Kim and Eisenhaure presented a unique transfer printing approach which enables arbitrary pattern transfer from an array of micro-objects via localized control of adhesion. The technique relies on thermally induced shape change of shape memory polymer (SMP) stamp arrays with carbon black-composite shape memory polymer (CBSMP) microstructuring.
In this process, heat is first delivered globally by a resistive heater, facilitating parallel micro-object pickup, then locally by laser illumination absorbed within the CBSMP during printing. This enables precise and selective micro-object release with packing density limited only by the spot size of the accompanying laser system.
This work, along with Kim’s “micro-LEGO” manufacturing techniques, serves as a foundation to make transfer printing-based assembly one of the common micro-manufacturing methods, enabling microsystems with higher performance or new functionalities, with relevance not only to microelectromechanical systems (MEMS) but also to electronics, photonics, and other areas.
Kim is a leading scientist in advanced transfer printing and transfer printing-based microassembly. His work on multiple-material assembly, called “micro-LEGO,” was recently published by Scientific Reports. He joined the MechSE department as an assistant professor in 2011. He earned a bachelor’s degree in mechanical engineering in 2000 from Pohang University of Science and Technology (South Korea), a master’s degree in mechanical and aerospace engineering in 2005 from UCLA, and a PhD in mechanical engineering in 2009 from Carnegie Mellon University.
Eisenhaure received his bachelor’s degree in chemical engineering in 2007 from the University of Massachusetts Amherst.


Waterjets can make parts to very tight tolerances and today some machines can create parts with a tolerance of as small as ± 0.001″ (0.025 mm), although ±0.002″ (0.05 mm) is perhaps more realistic in most cases. Achieving these tolerances requires an understanding of the factors that affect precision waterjet machining.
Obtainable tolerances vary greatly from manufacturer to manufacturer. Most of this variation comes from differences in controller technology, and some of the variation comes from machine construction. Over the years, progress has been made in improving the ability of waterjets to achieve high tolerances. A machine from 1990 was capable of tolerances of 0.060″ to 0.010″ (1.5 mm to 0.25 mm), between 10 and 60 times higher than today’s machines.
Positioning accuracy vs. tolerance
Positioning accuracy refers to how precisely the abrasivejet head can be positioned on the X-Y cutting table, and specifically how reproducible that positioning is. Being able to precisely position the cutting head is an important first step to achieving high tolerances, but it’s only the first step.
When purchasing a machine, be sure measure parts that come off the machine you are going to buy. Some manufacturers stretch the truth a bit when quoting tolerances, or they quote the positioning accuracy of the mechanics of the machine, which does not necessarily translate into the cutting accuracy in the final parts.
A machine that can position the cutting head to within 0.001″ (0.025 mm) might still produce parts accurate to only 0.005″ (0.12 mm).
What affects precision?
There are a number of factors that affect the tolerances that can be achieved on a part. Some of these are easier to control than others.
The hardness of the material affects how precisely you can machine it. Harder materials typically exhibit less taper, and taper is a big factor in determining what kind of tolerances you can hold. You can compensate for taper by adjusting the cutting speed or tilting the cutting head opposite of the taper direction. See Introduction to tilting.
As the material gets thicker, it becomes more difficult to control the behavior of the jet as it exits out the bottom. This will cause blow-out in the corners, and more taper around curves. Material thickness also affects both the amount and the type of taper. Materials thinner than 1/8″ (3 mm) tend to exhibit V-shaped taper, while very thick material can show barrel-taper.
Obviously, the more precisely you can position the jet, the more precisely you can machine the part. Generally speaking, though, it is much easier to find precise tables, than it is to find machines that can make precise parts.
Stability of table
Vibrations between the motion system and the material, poor velocity control, and other sudden variances in conditions can cause blemishes in the part (often called witness marks), as shown in a severe case below.
Witness marks on a part
The hardware that is out there varies greatly in stability and susceptibility to vibrations. If the cutting head vibrates relative to the part you are cutting, then your part will be uneven. Witness marks can also be caused by poor fixturing of the material.
Control of the abrasive jet
A precise machine starts with a precise table, but it is the control of the jet that brings the precision to the part. A key factor in precision is software—not hardware. This is also true for cutting speed. Good software can increase cutting speeds dramatically. This is because it is only through sophisticated software that the machine can compensate for a “floppy tool” made from a stream of water, air, and abrasive.
Waterjet machining has certain built-in limitations to tolerance. While you can compensate for them to some extent, they will limit the precision of your final parts. Following is a discussion of the major areas that limit precision with waterjet machining.
Also note that “precision” is a relative term–waterjets can create parts with a tolerance of as small as ± 0.001″ (0.025 mm), although ±0.002″ (0.05 mm) is perhaps more realistic in most cases.
Because the waterjet is a “floppy tool,” it tends to wander as you are machining. On straight line cutting, this translates into a “lag” as shown in this illustration:
Note that the jet lags behind the moving nozzle
This lag can usually be ignored when cutting in a straight line, but becomes critical when near a corner. As the jet approaches a corner, it becomes necessary to slow the motion down so the bottom of the jet can catch up to the top, and be perpendicular to your material. If you don’t slow down, you will have an ugly corner indeed.
If you accelerate quickly when coming out of a corner, the jet will kick back, and mar your part.
Most modern waterjet controllers compensate for this behavior automatically. The difference between manufacturers is the extent to which their software accurately models the behavior of the jet. Some software does a better job than others.
The important thing if you already own a waterjet is to make sure you take advantage of software updates offered by the manufacturer. These updates can incorporate newer models, which can improve the accuracy of your waterjet without changing any of the hardware.
Abrasive jets have a tool width that typically ranges between 0.020″ (0.5mm) and 0.040″ (1.0mm), depending on the mixing tube diameter. As you slow down to make a nice corner, the kerf grows slightly. The amount it grows is a function of how much you slowed down, while the amount you must slow down by is a function of your material thickness. In other words, the thicker the material, the harder it is to get precision in the corners.
Most controllers compensate for kerf width automatically, but don’t fully compensate for the kerf growing as a function of speed.
Kerf width depends on the nozzle you are using. With low horsepower pumps, you have a narrower kerf. With high horsepower pumps, you have a larger kerf.
Pure waterjets have a smaller kerf than abrasivjets.
Taper is the difference between the top profile of the cut verses the bottom profile. As the waterjet stream rapidly erodes the material, it may do so unevenly, resulting in an uneven edge, similar to a canyon formed by a stream. For more information on taper, see All about taper.
Taper prevents your part from having a straight edge and will affect precision. For maximum precision, you should invest in a tilting jet head to eliminate taper.
Lead-in and Lead-out
It takes time, and distance, to pierce the material before you can begin making the part. This section of the tool path is called the “lead-in” (at the beginning of the part), and a “lead-out” at the end of the part, where the cutting continues while the water pressure is reduced. The size of the lead-in and lead-out will depend on the thickness and type of material, as you need to wait for the bottom of the jet (where the jet exits the material), which will lag more in thicker materials.
Even with a lead-in and lead-out, it is difficult, and often impossible to avoid a small witness mark in your final part.
The precision of the positioning system sets a practical limit on how precisely you can make parts. If the machine positions the head to a precision of 0.001″ (0.025 mm), then that is the limit to the precision of your final part.


What is abscess? What are the causes, symptoms and types of abscess? Information on abscess treatment.
Abscess; a localized collection of pus caused by bacteria, fungi, or parasites that have gained access to solid tissue.
Most abscesses are caused by pusforming (pyogenic) bacteria. These bacteria include staphylococci, streptococci, gonococci, and meningococci. They liberate toxins that destroy cells, increase the local acidity, and cause the capillaries to dilate. White blood cells (leukocytes) then can pass through the dilated capillary walls. These white cells liquefy dead tissue, resulting in a cavity containing pus. Pus consists of living and dead bacteria, fragments of destroyed tissue, some white cells, and fluid given off fromcells. When an abscess occurs, monocytes (certain white cells) are mobilized to eliminate the dead cells and bacteria by a process known as phagocytosis. Other cells combine with newly formed capillaries and other elements to form a wall to delimit the abscess. The size of the abscess is determined by the number and virulence of the bacteria and also by the resistance of the host.
Symptoms. The chief signs of an abscess are swelling, pain, heat, and redness. Swelling is the result of the accumulation of fluid, serum, and other substances given off by the cells. Pain is attributed to increased tension that exerts pressure on local sensory nerve endings. Heat and redness are due to the engorgement of blood vessels. When the pain is severe, a fifth sign may appear: interference with the normal functioning of the organ or organism. Fever and a general feeling of malaise may also occur. Other complaints vary with the location of the abscess.
Types of Abscesses:
Various names are applied to abscesses according to the causal agent and the location of the abscess.
Brain abscesses may result from different types of bacteria carried from an original site of infection in the ear, nasal passages, lung, or heart. The majority of brain abscesses come from middle ear infections and occur in the area of the cerebellum. However, an abscess may develop in any part of the brain.
An abscess around the tonsil (peritonsillar abscess) sometimes develops as a complication of streptococcal tonsillitis. Also known as quinsy sore throat, it may produce pus that spreads to form another abscess behind the pharynx (retropharyngeal abscess).
A lung abscess is usually caused by the aspiration of infected material. This may follow surgery in which a general anesthesia has been used, or it may result from an infected blood clot or from some types of bacterial pneumonia. When the abscess erodes a major part of the bronchial tube, the patient coughs up large amounts of pus. If the abscess remains untreated, pus may develop in the cavity around the lungs (pleural cavity), causing empyema.
Abscesses of the kidney are usually the result of infections spreading up from the bladder; they may also result from bacteria carried in the blood from a carbuncle or from an inflammation of the lining of the heart (endocarditis).
Abscesses of the fiver may be caused by bacteria in the veins, arteries, and ducts entering the liver. The portal vein, which drains the intestinal tract and goes to the liver, is responsible for most abscesses of the fiver. An example is the amoebic abscess, a common complication of amoebic dysentery.
Ovarian abscesses often are associated with an infection of the fallopian tube on the same side. In such a case, the term “tubo-ovarian abscess” is employed.
The general treatment for an abscess is the surgical evacuation and drainage of the abscess and the administration of antimicrobial drugs to combat infection. Small abscesses may undergo complete resolution without drainage, while larger abscesses may continue to accumulate pus until the abscess breaks.
When uncontrolled, bacteria from abscesses may get into the blood stream and cause abscesses to appear in distant organs.
***This article is for informational purposes only. It is not a doctor warning or recommendation.


In the any industry that requires the use of heavy industrial equipment, safety is paramount. Every day work crews risk injury when handling these machines, so every effort should be made to keep work sites as safe as possible. Through safety courses, various certifications, ANSI and OSHA requirements, and better-developed equipment, manufacturers and the industries using such machinery strive to provide safer working conditions for workers. This is further supported by the development of new technology in radio remote controls for the operation of a boom and crane.
Boom trucks have been operated in a number of different ways ever since being developed. Control usually is from either inside the vehicle or from external controls on the chassis. Both of these arrangements can leave operators exposed to certain risks, such as a malfunctioning boom, the dropping of heavy items, unbalanced vehicles that tip over, or even accidental electrocution. It is an unfortunate part of the job, sometimes simply unavoidable when working with machinery that handles such large loads.
With all risk factors in mind, boom truck technology has advanced to remote radio-controlled operation. Such distant control greatly increases job site safety by removing operators and all other workers from the immediate operating area of these machines. In case of an accident such as dropping a load, tipping over, or a boom malfunction, the worst damage should be the loss of the equipment or the load being lifted while human lives are protected. Remote control offers the ability to operate multiple ton units with precision, without the associated risks that have caused serious injuries and even deaths in the past.
Unfortunately, the remote operation of such heavy machinery is not foolproof, having had its share of problems. Depending on the device that is used, its radio frequency and the job site location can cause interference between the operator and the device which is a notable concern and an additional safety issue.
There has been some advancement in the use of military-developed, spread-spectrum radio frequencies and remote devices designed to alleviate such problems. Radio signals from these devices move faster than other types of radio frequencies, which makes the other types unable to interfere with this device’s signal. With a higher safety record and more proven effectiveness in preventing radio interference, equipment manufacturers are beginning to look toward the exclusive use of such technology. The biggest concern is that these types of radio remote controls will greatly increase vehicle production costs due to the inclusion of such a high-tech component. There is some controversy over whether or not larger manufacturers will regularly use this newer, more sophisticated radio technology making such units more expensive.
As remote controls on boom trucks become a more standard feature, many of the larger vehicle manufacturers are in favor of this newer, more advanced technology as the best way to ensure work crew safety. There is still much discussion to occur about both the pros and cons of standardizing a more expensive remote control technology and how to bring the cost down without sacrificing safety. Yes, protection from harm can occur with boom truck remote radio-controlled handling and be beneficial – so long as the cost doesn’t significantly increase as well!


Use of biogas
Use of biogas to produce electric or thermal energy
The by-product of anaerobic treatment is a high-energy biogas which can be combusted in its own boiler room or possibly fed to the central boiler in the factory.
With larger volumes of biogas produced it is advantageous to install a cogeneration unit. It can provide a combined use of biogas for electricity and heat generation. By cleaning your wastewater you will get clean, environmentally friendly energy that will help you reduce your operating costs.
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Chemicals serve many functions in hydraulic fracturing. From limiting the growth of bacteria to preventing corrosion of the well casing, chemicals are needed to insure that the fracturing job is effective and efficient.
Why Chemicals Are Used
Given today's technology, chemicals must be used in hydraulic fracturing to ensure the producing formation is effectively treated. The chart shown below depicts generic hydraulic fracturing chemical usage including the types of chemicals, their uses in the process and the result of their use.
As previously noted, chemicals perform many functions in a hydraulic fracturing job. Although there are dozens to hundreds of chemicals which could be used as additives, there are a limited number which are routinely used in hydraulic fracturing. The following is a list of the chemicals used most often. This chart is sorted alphabetically by the Product Function to make it easier for you to compare to the fracturing records .


The Importance of Chelated Minerals
The human body needs minerals for various important functions within the body. Normally, this can be provided by a balanced diet; however, the standard modern diet is often lacking in some of the most important minerals.
This is mostly due to overly processed food and depleted soil, making it difficult to get the optimal daily intake. In addition, people who have a dairy intolerance may not get enough calcium.
Mineral supplements are often recommended to help maintain optimal mineral levels in the body. But how do you know which ones to choose when there are several different forms of minerals on the market. Today’s post will cover chelated minerals and the benefits of this form of mineral.
Definition of Chelate
Chelate comes from the Greek word for “claw,” and in the supplement world, this refers to how organic compounds are attached to a minerals. Chelation is a specific binding process that binds inorganic minerals with organic compounds to provide more stability and bioavailability. When you are comparing the different mineral supplements on the market, it’s important to keep in mind that this process is used for better absorption, which is the main benefit of taking chelated minerals.
The complete ring structure of chelated minerals also increases stability. That stability reduces the chances of negative reactions with fat-soluble vitamins and other minerals. Therefore, the added stability is an important component of increasing the absorption rate in a few different ways.
Absorption of minerals is a common issue because any nutrient that reaches the upper GI tract is not absorbed very well. That’s why mineral supplements need greater bioavailability. Many mineral supplements are taken from inorganic sources or mineral salts, which are poorly assimilated and have low bioavailability. While citric acid is a chelating agent that improves the absorption of minerals, it does not form a complete ring.
When you take a product that contains various minerals, it is also important that each mineral comes in the chelated form. For example, Miracle Choice Chelated Minerals advanced chelation enhances absorption.
Why our bodies require Chelated Minerals:
In order to maintain and regulate necessary body functions it is vital that minerals become a staple in our lives. Chelated Minerals are necessary for the nervous system, normalizing the heartbeat, improving the brain and mental abilities, fighting fatigue, and increasing energy, electrolyte balance and aiding the metabolic process.
Chelated Minerals are the building blocks to the life of every cell in our bodies. They are pivotal components of many life-supporting systems and contain over 74+ organic minerals and other nutrients associated with blood, enzymes, hormones, oxygen transport and cellular activities.


Android Analog clock and Digital clock example
The android.widget.AnalogClock and android.widget.DigitalClock classes provides the functionality to display analog and digital clocks.
Android analog and digital clocks are used to show time in android application.
Android AnalogClock is the subclass of View class.
Android DigitalClock is the subclass of TextView class. Since Android API level 17, it is deprecated. You are recommended to use TextClock Instead.
The AnalogClock was deprecated in API level 23. This widget is no longer supported. Instead if you want to use AnalogClock in your application you need to hard code. It does not appear in API level 27 to drag from palette.
Note: Analog and Digital clocks cannot be used to change the time of the device. To do so, you need to use DatePicker and TimePicker.
In android, you need to drag analog and digital clocks from the pallet to display analog and digital clocks.
Now, drag the analog and digital clocks, now the xml file will look like this.
We have not write any code here.
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Recently, in Singapore a case of Monkeypox virus has been reported. It is worrying news for all East South Asian countries because a first case has reported in this region.The disease mostly occurring in Central and West Asia. Singapore health ministry is taking serious step after that and the Nigerian citizen has been isolate from society.
Monkeypox virus is followed by a rashes that forms blisters and crests on skin and swelling. During attacked of virus fever and body toughness felt by patients. Its symptoms are appear similar to chickenpox but it may not reason of patients death like chickenpox. Monkeypox mainly attacks on DNA through which its grow all the body
According to World Health Organization(WHO) ,Monkeypox virus is zoonotic virus ,which mostly transmitted to people from various animals such as rodents and primates but has limited spread through human-to-human transmission. There is no specific treatment or vaccine available although prior smallpox vaccination highly effective in preventing Monkeypox as well.
Human Monkeypox was first identified in 1970 in the Democratic Republic of Congo in the region where smallpox was eliminated in 1968. Since then,majority of cases reported in rural,rainforest regions of Congo Basin and Western Africa. In spring of 2003, Monkeypox case were confirmed in the United State America, It was first reported occurrence of the disease outside of the African continent.
Why its called Monkeypox? Its is the virus.It was first identified in 1958 amoung the laboratory along the body of Monkey after that its called ‘Monkeypox’. Most of case are reported in Nigeria in several years.
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The technology of broiler farming mainly focuses on breeding and feeding management in order to improve the production capacity of broiler chickens and raise the efficiency of breeding, thereby increasing the overall income of the farm.
1. Choose high-quality and high-yielding broiler breeders.
Select breeder breeds that are suitable for local growth conditions and have high yield performance, strong disease resistance and can produce high-quality offspring to purify breeders and prevent vertical spread of diseases.
2 Strictly select young birds
Chicks must be hatched from 52-65 grams of breeding eggs, and the same batch of chicks should be from the same parent flock. The chicks have good feathers, clean and shiny. The umbilicus healed well without infection, and the feathers around the anus were dry. He is agile and lively, struggling forcefully in his hands, and his chicken feet are as shiny as wax.
Three temperature is one of the main factors in the brooding stage, and the appropriate temperature can bring the maximum benefit of the feed.
Too low temperature can easily cause respiratory disease and death of chickens. The first week of brooding in winter and spring is generally controlled at 35℃～36℃, and then lowered by 2℃～3℃ every week. Second, according to the reaction of chickens, this is also a problem that farmers should pay attention to. When the temperature is too low, the chickens will be sharp. It is called a pile. When the temperature is too high, the chickens are scattered and panting. The chickens are evenly distributed when the temperature is right. You can also use a combination of thermometer and senses to judge whether the temperature is suitable.
4. Fresh air in the chicken house can prevent respiratory diseases.
Harmful gases or dust in the air can affect the health of chickens and even cause death. The anaerobic bacteria in the chicken house decompose manure and nitrogen-containing organic matter to produce ammonia. When the ammonia concentration in the chicken house is 15×10-6, people feel uncomfortable. In addition, when the coal stove is used for heat preservation, a large amount of carbon monoxide and carbon dioxide are produced , Hydrogen sulfide and other harmful gases, so you should ventilate without reducing the normal room temperature to reduce the content of harmful gases and dust in the chicken house.
5. Special attention should be paid to the drying and cleaning of litter when raising broilers.
During the brooding period, it is best to use horizontal raising on the Internet, so that the chickens and manure are separated to reduce diseases; the temperature of the medium and large chickens should be thickened to increase the temperature below 18 ℃.
Sixth, the density should not be too high
Excessive density will cause unbalanced growth of chickens and increase of harmful gases in the air. Especially in spring, when humidity is high, chickens are susceptible to E. coli, coccidia, staphylococcus, etc., and can accelerate the epidemic. Therefore, broilers should generally be controlled at about 10 per square meter.
Seven reduce stress response.
Excessive voices, group transfers, vaccination, sudden weather changes, and feed conversion are bad stimuli to chickens and can often cause disease. Avoid unnecessary catching and disturbing as much as possible during the feeding period. Anti-stress drugs can be used for prevention before transfer to groups and vaccination; take care of the cold stress caused by the drop in temperature.


Bloom argued there are six levels of domain expertise, and his concern was that education systems at the time were rooted firmly on knowledge, the lowest level. (…) The objectives are a hierarchy showing your ability with a specific domain. Informally you can think of them like this…
- Knowledge — The ability to recite lists, rules, formulas, specific facts.
- Comprehension — The ability to understand the reasoning behind said rules/facts, and translate and re-state where necessary
- Application — The ability to apply acquired knowledge in new situations to produce solutions
- Analysis — The ability to recognize patterns, question reasoning, distinguish facts from inferences.
- Synthesis — The ability create new knowledge, methods, formulas, based analysis of problems.
- Evaluation — The ability to create multiple solutions and select the most effective in a given situation
Des on the contrast blog


Introduction The website is a means of rapidly locating information on the economic costs of soil erosion. Soil erosion is a form of soil degradation on agricultural land.
Paul Bowles in the medina of Tangier, Morocco in An inveterate traveler, composer and writer, Paul Bowles was a truly remarkable figure whose life and work embodied and responded to major impulses of the twentieth century.
His life would be of considerable interest even had he not produced numerous musical scores, four novels, more than sixty short stories, many travel pieces, an unrevealing autobiography and dozens of translations of stories by Moroccan storytellers.
Burroughs, Allen Ginsberg and Patricia Highsmith. Man is adrift in an endless existential quest to Essay about soil erosion together meaning in an increasingly chaotic, ugly, barbaric, horrifying world. Taprobane island sustained only minor damage from the tsunami disaster that occurred on December 26, Bowles fondly remembers his mother reading Poe to him in his early years, while he chiefly remembered his father, a dentist, as a strict disciplinarian.
In his autobiography, Bowles recounts hearing his grandmother tell him that his father had tried to kill him when he was a baby, by leaving him virtually naked in a basket by an open window in the dead of winter. True or not, these impressions and feelings certainly had a profound effect on the artist as a young man and can be felt on occasion in his writing.
Bowles began drawing maps and spinning fictions in notebooks when he was quite young.
In his late teens Bowles enrolled in the University of Virginia, conscious that Edgar Allan Poe had studied there nearly a century earlier.
Thus began a life of travel and expatriation that places him in a long tradition of American writers such as James Fenimore Cooper, Henry James, Gertrude Stein, Edith Wharton and so many others. After this first, short visit to Europe, Bowles returned to New York where he met the composer Henry Cowell who referred him to Aaron Copland for studies in composition.
When Copland announced plans to go to Europe, Bowles was quick to follow. While in Paris the young Bowles, impeccably dressed and boyishly charming, found that doors opened easily before him.
Among those he called upon was Gertrude Stein, who had set up residence in Paris two decades earlier and lived, with her lover Alice B. Toklas, on rue de Fleurus.
Erosion of soil by water is quite significant and takes place chiefly in two ways (a) Sheet erosion, (b) Gully erosion. (a) Sheet movement of water causes sheet erosion and depends on the velocity and quantity of pronounced surface runoff and the erodability of the soil itself. A biographical essay on Paul Bowles' life as a composer, writer, translator and traveler by Allen Hibbard. Paul Bowles left the United States in and lived 52 years as an expatriate in Tangier, Morocco, where Paul Bowles wrote novels, short stories and travel articles, in addition to doing translations of Moroccan writers and storytellers. In this essay I intend to give facts and discuss the effects and causes on these topics and discuss the solutions being carried out to improve the conditions.
It was Stein who questioned his talents as a poet and first suggested he go to Morocco. Bowles could hardly have imagined that his first visit to Africa with Copland, inwould lead to such a long-term relationship with that continent.
In North Africa Bowles found a place where magic, storytelling, djenoun geniesthe power of the curse and a kind of primitive spirit were alive and vibrant. Throughout the thirties and the early forties Bowles lived nomadically, using New York a city for which he often expressed his disdainas a base.
During this time he did a considerable amount of composing. His early compositions include: In Bowles met Jane Auer, whom he married the following year.Discuss on the impact of land clearance and reclamation for residential and urban infra-structural development on the environment.
With the high rate of urbanization and industrialization, land clearance and reclamation are the general practices to satisfy the demands for lands for development. Severe soil erosion brought about by animals overgrazing and vegetation being cleared in Kenya.
(Reproduced by permission of. Essay on Soil Erosion and The Erosion of Civilizations - Soil erosion began with the dawn of agriculture, when people abandoned their hunter-gatherer lifestyles and began using the land for intensive agriculture, thus removing the protective vegetation cover .
Soil erosion has arguably the greatest impact on the agricultural sector. The part which is removed during soil erosion is the topsoil. Topsoil contains the majority of the soil’s nutrients, organic matter and pesticides, so this would obviously pose a problem to farmers who rely on the soil for their yearly income.
In this essay I intend to give facts and discuss the effects and causes on these topics and discuss the solutions being carried out to improve the conditions.
A biographical essay on Paul Bowles' life as a composer, writer, translator and traveler by Allen Hibbard. Paul Bowles left the United States in and lived 52 years as an expatriate in Tangier, Morocco, where Paul Bowles wrote novels, short stories and travel articles, in addition to doing translations of Moroccan writers and storytellers.


Magellanic Penguins at Punta Tombo National Reserve, Patagonia, Argentina
Puerto Madryn is the gateway to Peninsula Valdes in central eastern Patagonia, knowns as the best place to observe large marine life in their natural habitat. It is also the gateway to the Punto Tombo Natural Reserve, home to the largest colony of Magelan penguins in South America. I have seen whales but not penguins, so Porto Tombo it was.
We drove about 2 h south of Puerto Madryn along the coast hoping to see the thousands of Magelanic penguins who return to the shores of Patagonia every year. From September until the end of March the penguins spend their time picking their partners, mating, laying eggs, incubate their eggs, raising the chicks and preparing for the trip north to Brazil. Penguins mate for life and can live more than 30 years together.
The reserve is rather remote and the last 50 km or so are gravel roads so be prepared for some dust and rough patches, although over all the road is good. Be sure to fill up your tank as there are no gas stations within a convenient distance.
The natural reserve land was previously a private ranch (estancia) and was donated to the Chubut province by the owner in the 1970s. The large tract of land is home to various wildlife and en route we saw many alpacas (similar to llamas but smaller) roaming the fields safe from human predators.
The penguin reserve is regulated and you cannot just go wandering as you please. You enter through the ranger’s station and then follow a path, about a kilometer long, leading to the beach observation point. You begin to see penguins right away, they often seek shelter and shade below the footbridges along the path and in their burrows.
Magellan penguins are named after the explorer Ferdinand Magellan who first spotted the species in 1520. They are about 30″ tall with tuxedo-like black back and white chest. Chicks are softer brown on the back and white on the front. Before laying the eggs they dig a burrow in the ground, often under a thorny bush, and the female lays her two eggs in the security of the shelter. The male stands guard by the burrow to protect the female but there is a division of labour as they take turns hatching the eggs and going out into the sea nearby to feed on fish and replenish body fat. They trade places every week or 10 days and while they remain on hatching duty they do not eat at all. Incubation continues for about 40 days and when the chicks hatch they remain in the burrows for another month until their waterproof feathers develop. One thing that surprised me was the lack of snow and the heat. Don’t penguins love the cold? Apparently not, Magellanic penguins hatch their eggs where temperatures remain over 20ºC.
On land penguins have no natural predators to worry about, but at sea they are preyed upon by seals and killer whales and unfortunately, some of them do not return to their burrows. Their biggest threat though cones from oil spills and decline of sea life on which they feed.
Each year the penguins return to Punta Tombo to the same burrow they dug before. The male arrive earlier to make sure their burrow hasn’t been snapped up by some lazy penguin who prefers not to dig their own. Once the female arrives, she connects with her mate through his call.
We were lucky to have the colony still in the reserve as the season for hatching and raising the young was coming to an end. It was a remarkable to see them waddle clumsily on land and swim with such grace and efficiency in the water. Unphased by our presence they did not seem to mind us and we could get close although never left the marked path. They seem to tolerate the hundreds of tourists that flock to the area, and people were quite respectful of their presence and kept their distance.
It was a special experience, a new one for me and one I would like to repeat when opportunity arises.


The art of constructing buildings and making streets and sidewalks has been width us since the days of the Egyptians. While the technology used today to make concrete has certainly changed for the better, the Egyptians, Greeks, Romans used baking ovens where they mixed clay with straw and other earthen material to formulate material that was later used for construction. Today’s concrete and cement mixers look so much different than their earlier counterparts. When you talk of cement mixers, most people envision the huge cement rotating drums that are mounted on large construction trucks that speed to and fro construction sites.
Sometimes, cement mixers trucks are also known as concrete mixer trucks. While cement and concrete are actually different, people refer to them interchangeably. Concrete mixers use specialized technology that mixes sand, gravel, water and some chemicals to form cement which is a gooey substance that is used to make sidewalks and road paths.
These mixers are very convenient. In the past, people used to mix the concrete and cement themselves and this was not always very efficient because it was slow. The hand mixed cement mixers did not always do a good job. This was because of the time element and the composition element. The cement was then packed into wheel barrows then ferried to the construction site. But cement mixers have changed all this and are a much better option. They save time and encourage efficiency because the cement can be processed and mixed at the same time while the truck is on the way to the construction site.
Cement began being part of road construction in the 1800s and all this was brought about by the motor revolution which caused many cars to be manufactured. Then in the 1920s automobiles became more widespread and so did concrete mixers.
In the 1970s, there were some concerns raised by environmentalists regarding cement mixers and there were technological modifications made in order to ensure that the concrete mixers were environment. Today, the concrete mixers, use safer materials, emit less toxins, are skid resistant and are also more or less weather resistant. The 18-wheeler trucks have also been modified to support cement and transportation of that cement to and fro the construction site.
Today, over 90% of the roads in the United States are constructed using cement. The trucks can be bought from the regular car dealers that sell ordinary cars. Companies like Ford, Fiat, Mercedes Benz all have truck divisions which sell cement trucks. If you wanted to purchase a truck you also might want to look online. If your budget is shoe-string then the best place to look for a concrete mixer truck is online where someone may be selling a used truck. eBay also stocks good deals when it comes to cement trucks and the price is also affordable because eBay allows buyers to bid on the products.


A couple months ago, some of our friends did something called Whole 30. It’s an eating program that helps you break bad habits and cravings, and identifies any food sensitivities that might be causing you digestive issues. It emphasizes eating foods with few ingredients and nothing processed, so that means a lot of meat, veggies, fruit, and nuts. They said it was great so we’ve been thinking about doing it for a while. I eat a lot of fruit and vegetables anyway, so that part wouldn’t be hard, but no chocolate or baked goods (no sugar allowed!) would be tough.
We haven’t quite gotten started but have looked into it and are planning to make it happen soon. There are tons of materials out there about the program, including a version of the four page introduction in Spanish. I was excited to see this because it means that the Whole 30 people are inclusive and want to reach a wide audience, and also because it meant I got to practice my Spanish. I read through it and enjoyed understanding familiar content along with encountering some new words and phrases.
For example, the intro included the phrase “alergias estacionales.” “Alergias” is of course a cognate (allergies), so that part was easy, but at first I wasn’t sure what “estacionales” meant. I broke down the word into a more basic form that I might recognize, “estacion,” and was pretty sure that meant “season.” I googled it and saw that I was correct. Thus, the phrase “alergias estacionales” is “seasonal allergies.” Using previous knowledge and contextual information, I was able to acquire a new phrase. I am an allergy sufferer so I have a tangible experience to tie this phrase to, which will help it endure in my mind.
When encountering new words in a language, making associations with real life things (visualization, memories, etc.) can be an effective way to remember them. If you can connect the language with something you’ve actually seen, done, or experienced, it is more likely to be truly integrated into your knowledge. After all, the purpose of language is sharing information about reality: ourselves, the world around us, and all the things it contains.
Learning Spanish food vocabulary is an area where this is fairly easy to do. Since I read the introduction to Whole 30 in Spanish, throughout the 30 day program I will be able to think about what I’m doing in Spanish. I have (at least some of) the vocabulary and phrases I need to conceptualize and reflect on what’s going on in my actual life, and that is powerful for language acquisition. We eat at least three times a day so food is a regular part of our lives. It is also a multi-sensory experience – sight, smell, taste, touch, perhaps even hearing something cooking – which makes for excellent learning material because it gives your brain multiple points of association to grab on to. Try cooking a traditional Argentinian dish or ordering Peruvian food for lunch when you’re at work to really connect the food with what you’re learning.
If you want to acquire Spanish, integrate it into your real life. For a great way to immerse yourself in authentic Spanish, download Pars Omni Spanish Voices for free today and get access to native spoken Spanish right from your computer.


A Useful Guide On How To Remove Fluoride From Water
Do you know how to remove fluoride from water? If not, you are the right place to learn the easy tips on it. People are conscious enough about the controversy surrounding fluoridation of the drinking water. This is a way to get the drinking water without fluoride.
Moreover, I have got some other water purification methods that do not remove fluoride from drinking water. Now, read the article on how to remove fluoride from water to know how to do it.
Why is there Fluoride in My Water?
Some communities develop naturally occurring fluoride in drinking water systems for the supposed link of low cases of cavity and fluoride. Remember that they’re doing it for their benefit.
This thing has gone through a system known as water fluoridation. At first, drinking water passes through government-owned filtration systems before reaching your taps or other sources.
There, they make water clean and portable. They also add a controlled amount of fluoride in water before going to the residential areas. In this way, you end up your fluoridated water.
This is the only system by which you get fluoride from drinking water. Some companies produce and sell fluoride water in bottles which approaches their filtration systems.
The appearance of water doesn’t change at all. This water is also drinkable. You are doing more harm instead of satisfying your thirst.
Why is Fluoride Bad?
Now the question, is fluoride beneficial or harmful to you? For some particular situations, it may be. The condition becomes somewhat realistic if there is fluoridation in drinking water. So what is the utility of fluoride?
The only threat you face from fluoridation is ‘fluorosis’. It is a condition where enamel of the teeth changes radically for a huge amount of fluoride inside the body.
You find no enamel in your teeth what you get just now. It affects the teeth and helps to grow. So we can say fluoride is a medical condition which affects children.
If there is fluorosis on your teeth, the developing teeth become discolored. There is un-removable ‘stain or brown’ and yellow color on teeth. Though you brush your teeth many times, there is still stain. So fluoride is terrible for health. It is an example of fluorosis.
Although you intake fluoride from the toothpaste, the dangers of fluoride may not enter into your bloodstream.
Now the question, is fluoride toxic if someone takes it through toothpaste? It remains in your teeth though you spit it out. Here is the place where you are supposed to be.
Though you let it enter your bloodstream, your body will be benefited little. Moreover, you will suffer from the side effect of fluoride. It may seem that consuming pimple cream with phosphate fluoride. This implies that it is for your face not for your stomach.
Luckily your kidney works more to get rid of fluoride danger catches in your body. But there is a limit to what they can do.
Fortunately, you can be got rid of about half amount that you digest within few days. If you consume more fluoride, there is the possibility of fluorosis. This is the evidence that affects your thyroid gland.
Side effects of Fluoride in drinking water
The exact amount of fluoride is beneficial for dental health. On the other way, an excess amount of fluoride is harmful to teeth. It causes dental fluorosis.
More fluoride weakens bones and ligaments. Moreover, it creates a problem for the nervous system.
The Fluoridealert.org reports that people having clinical signs of fluorosis may suffer from significant symptoms like overt osteoarthritis and chronic joint pain.
There has a suggested amount of fluoride level. A higher level may happen where fluoride is easily detected. Laura Pressley, Ph.D. is an anti-fluoridation advocate.
He tells Waterlogic publication that Texas has a higher natural level of calcium fluoride for geology and oil deposits.
If there is the high level of fluoride in your country or state water, it will be better removing them from the drinking water. Removing it may be a good thing for the benefit of your health.
Why remove fluoride from your water?
For a long time, people think fluoride is a toxic substance. Therefore, fluoride is being used as rodenticides or pesticides.
So the Food and Drug Administration now found that the toothpaste carries a poison warning and should contact the poison controlling centers if used for brushing.
The excessive use of fluoride is the reason for painful bone disease. It also causes discoloration of your teeth which is popularly known as dental fluorosis.
For a long time, exposure to fluoride may cause chronic ailments like bone fragility, arthritis, glucose intolerance, dental fluorosis, gastrointestinal distress, and possibly cardiovascular syndrome plus certain kinds of cancer.
Ways to remove fluoride from water
Distillation can remove anything from the water. By the help of distiller, you may remove fluoride. The distillation system is energy and time-consuming. Distillation makes the water lifeless and empty.
So after distillation, you need to add salt or minerals to the water. You need to think about the energetically enhancing distilled water. For more, you can see the chapter 11 and 12 consequently.
Reverse Osmosis is a kind of normal osmotic process. It depends on the semipermeable membrane or on the pressure of water to remove contaminants. The RO has the power to remove 90 to 95 % of contaminants from water.
The RO membrane caught the contaminants and flushed away by the flow of the water. The method need 2 to 4 gallons of water to make one gallon of RO water. The efficiency of RO system can be reduced for the lots of contaminants found in the source water.
RO can remove various kinds of a pollutant from the water. A quality RO system can remove VOCs, hard water minerals, heavy metals, and some other contaminants.
The hard contaminants can reduce the lifespan of the RO system. The adding of salt and the reintroduction of the life force is a must to bring RO system back to the normal position.
Fluoride invites activated alumina that contains a big surface area. It has an array of the tunnel-like pores. So alumina is being greatly used to remove fluoride at present.
If the setting is very perfect, it can remove up to 98% of fluoride along with arsenic. Challenges are in great number.
As the system works with an ion exchange method, the water remains in contact with the media for a long time. The media can hold a lot of fluorides. The flow rate is ¼ gallon/ minute is great for absorbing fluoride.
The other problem of activated alumina is that the media is saturated with the fluoride depending on the fluoride in the water and the amount of media to the system. The other problem is that aluminum is released into the treated water.
There are lots of claims that the filter can remove fluoride utilizing activated alumina. The demerits are that all the system to function for a short time before being saturated. The other demerit is that it does not slow the flow rate to give time for adsorption.
How to remove fluoride from water
Only some system works better than they claim. Unless the flow rate is slow or unless you clean the activated alumina, or recharged or replace the activated alumina will not do the desired function.
There are many tanks typed fluoride removal systems on the market. They can do a good performance for a long time for backwashing and frequent topping off or the recharging cycle. The systems are applied to remove fluoride from water. Many people think it is fluoride problem.
The reason for this is the environment. For backwash, you may use the caustic chemicals. At the time of replacing the tanks, you will see lots of arsenic, mercury, fluoride, lead, and cadmium.
Bone-Char Carbon is being used for centuries to take out naturally happening fluoride from water. It attracts fluoride like the bones attract fluoride to the body.
There is a porous matrix to the bone and rich in surface ions. They may be replaced by fluoride or other contaminants that appear with fluoride. The bone char has an unbelievable power to remove contaminants.
The BC carbon can remove fluoride up to 90% from water. The efficiency can be accelerated by adding pre-filters.
The pre-filters remove contaminants and other metals before exposure to BC carbon. BC works great with little pH, and it cannot do its function with hard water.
The medium is being used greatly to incorporate with lots of systems where cartridges are used as media.
There are some problems with it. The Bone Char is said to be an organic medium. Medical grade bone char is clean bone char no doubt.
Simple Steps to Reduce Fluoride Exposure
You have already known that excess amount of fluoride is dangerous for health. Therefore it is a must that you reduce exposure to chemicals. It doesn’t mean that you have to cut fluoride in your drinking water.
Using non-fluoride toothpaste
It is easy to say but difficult to do. Most commercial toothpaste contain fluoride. You can get fluoride-free toothpaste for using at home with little efforts. If you are using commercial toothpaste, don’t allow your children swallow it.
Processed foods contain more fluoride. So try to avoid this food as much as you can. Eat natural food more than processed food. At the same time, you should avoid fruit juices, soft drinks, and canned stews/soups. If you consume more processed foods, there is more possibility of eating more fluoride.
Asking your dentist about fluoride gels
Many dentists suggest using fluoride gels to care for oral health problems. It also resists cavities. But do you know these gels have higher cavity risk? Try to understand why your dentist is suggesting these gels for treating cavities.
Cutting back on tea
This is very difficult to express thought it is a must. Black and green tea contain top levels of fluoride. It means that this is time to consume less beverage. The reason is that tea absorbs chemicals.
Buying only organic grapes and grape products
Many vineyards in the USA apply cryolite. It is a pesticide which contains fluoride. It means that all wines, grapes, and grape juices have a higher risk of cryolite containing chemicals. There was no danger of fluoride exposure in organic grape products.
Avoiding non-stick cookware
Non-stick pots and frying pans are Teflon coated. Teflon is a coat which contains fluoride. If foods come in contact with Teflon, there is a possibility of chemical leaching into the food.
Follow this instruction closely. Then you will be able to reduce the possibilities of health problem from fluoride.
All things can develop your health. You must think about the effect of at last. The final key is willingness and discipline to offer a change.
How To Remove Fluoride From Water Naturally
Though all of us have the desire to remove fluoride from water along with fancy purification systems, we cannot buy the system. The natural method of removing fluoride is cheap, safe and very effective.
A very credible discovery has undergone by the researchers of the University of Rajasthan. The researchers covered 75 mg of Holy Basil leaves in 100 ml of water which included above 7.4 parts per million of fluoride.
Subsequent absorbing the leaves in water for eight hours, they found that the fluoride reduces 1.1 parts per million. The World Health Organization admits that the safe level of fluoride in your drinking water is from 0.5 to 1 parts per million.
What’s the Tulsi Plant?
Tulsi is using for a long time in Ayurveda medicines as thinking the main medicinal plant which has a great healing power. Its stems and leaves both are very useful in preparing the medicine.
The plant is most reverent and sacred herbs in India. There are lots of things in tulsi such as acid, oleanolic, carvacrol, ursolic acid, Linalool, romantic acid, eugenol and some other active compounds which have been proven very useful for health. It exhibits antiseptic, analgesic, antifungal, antibacterial and aphrodisiac properties.
The Tulsi plant has powerful anti-inflammatory and antioxidant properties. The plants also being used as a remedy for coughs, fevers, bronchitis, colds, cures rheumatism, malaria, arthritis, diabetes, relieves spasms and insect repellant.
For medical purposes, both dried powder and fresh leaves prepared from the tulsi plant are being used as infusions, herbal teas, and tinctures. Tulsi tea holds a big amount of antioxidant and nutrient substance, takes out toxins out of the body, improves digestion, develops immunity, relieves colds and stress has warming and calming effects. Therefore it is wise not to spend more money for removing fluoride from water.
How fluoridation works
Definitely, you have learnt on how fluoridation works so far. Fluoride acts by binding with the tooth enamel that is made up of hydroxyapatite, a crystal made of phosphorus, calcium, oxygen, and hydrogen by the view of the American Scientist. By altering the hydroxyl molecule on hydroxylapatite, fluoride aids teeth to be constructed more resistant to the attack of acid bacteria.
Surely, how fluoride aids are protecting teeth and how much it saves them is not clear well. The result of the thesis is that fluoride works topically at the beginning level when fluoride-rich toothpaste is used for the teeth.
Tooth decay, if keeps untreated, may be the cause of serious health hazard like infections which may spread to the jaw. In the United States, tooth decay has wonderfully declined as fluoridation started, view of the CDC.
Moreover, tooth decay also turned down in other countries which do not fluoridate, view of the World Health Organization (WHO).


Although much has been written on the history of the requirement of proof of crimes beyond a reasonable doubt, this is the first study to probe the history of its civil counterpart, proof by a preponderance of the evidence. It turns out that the criminal standard did not diverge from a preexisting civil standard, but vice versa. Only in the late eighteenth century, after lawyers and judges began speaking of proof beyond a reasonable doubt, did references to the preponderance standard begin to appear. Moreover, U.S. judges did not start to instruct juries about the preponderance standard until the mid-nineteenth century, and English judges not until after that. The article explores these developments and their causes with the help of published trial transcripts and newspaper reports that have only recently become accessible. The history thus revealed casts a new light on two subjects that have aroused much scholarly attention during the last few years: the fact that European civil law systems do not proclaim differing standards for civil and criminal proceedings; and the questionable policy foundations on which the preponderance standard rests.
The Surprising History of the Preponderance Standard of Civil Proof,
67 Fla. L. Rev.
Available at: https://scholarship.law.ufl.edu/flr/vol67/iss5/2


HOLLOW CROWN PARSNIP (Pastinaca sativa) is an American heirloom dating to the 1820s, The thick, tapering white roots are manageable size -- they grow 12" long x 2"-3" thick. Parsnips are one of those home garden treasures - you almost never see them at the green grocers, and when you do they are usually kind of tired and sad looking. These are hollow-crowned, so one interesting use of them is to carve into root-flutes, which will delight any children in your sphere! The flavor is mild and sweet (the seeds even smell sweet), more so if gathered after first frost. Excellent storage type. 110 days. 100 seeds.
ABOUT PARSNIPS: Long-ignored in modern home vegetable gardens, parsnips are one of the most valuable food crops you can grow. Cultivated since antiquity (Roman Emperor Tiberius was so fond of them he imported them from the Rhineland), butwith little attention paid to selection until the 19th Century. Parsnips can be used in soups (Holland), to make beer (Ireland), wine (France) marmalade (Spain) or just enjoyed as a you would any sweet and delicious root vegetable, boiling and eaten with butter; mashed, formed into cakes, dipped in flour and sauteed; thinly sliced in salads or, my favorite, roasted with other roots such as carrots and potatoes. They are also favored by livestock - pigs and horses in particular love them.
MEDICINAL: Historically, parsnips have been recommended since Pliny's day for a variety of ailments. Culpepper said they were good as a diuretic and for flatulence.
GROWING TIPS: Easy to grow provided you prepare the soil well, digging deeply and removing any debris or rocks that will interfere with growth. Strong soil is preferred to sandy as the enormous roots do need that support. Seed sown in February will be ready by September, or adjust for your calendar. They can be dug through the winter, and then not completely harvested until you are ready to sow again the following February. Sow 1" deep, droping 3 seeds together every 8" with rows 15" apart. Once seedlings emerge and get two sets of leaves, thin to the strongest of the three and keep hoed until harvest.


annual basis in many situations, but could be feasible during summer low flows
Fiala and Vasata (1982)
when symptoms of eutrophication are most extreme.
also note that maintenance of aerobic conditions in the siltation basin is
essential to phosphorus removal, presumably because iron and/or calcium
plexation of phosphorus may be involved and because anaerobic reservoir sedi-
ments may release phosphorus at high rates and thus reduce the efficiency of
In deep preimpoundment basins, maintenance of aerobic conditions
might require artificial circulation.
In some areas, dry dams have been constructed to aid in flood control.
These dams may be particularly effective in silt and nutrient control as well,
since they receive and store the "first-flush" runoff, a portion of the
graph that can be heavily loaded with pollutants.
Prereservoir phosphorus removal
Wahnbach Reservoir (Federal Republic of Germany) was impounded in 1957.
Within 10 years, treatment of the water for drinking purposes became very
expensive, and organic compounds excreted into the water by algae were forming
precursors for the development of trihalomethanes.
Phosphorus was shown to be
the limiting element, and nutrient budget studies showed that more than
50 percent of it came from diffuse or
sources on the watershed,
making sufficient diversion nearly impossible. A smaller reservoir
to serve as a floodwater retention basin and a phosphorus elimi-
nation plant (PEP) were built at the upper end of the main reservoir.
After detention in the smaller reservoir, water is pumped into the PEP
and treated with F e
to precipitate phosphorus, followed by a
electrolyte to form large
The water is then filtered through layers of
activated carbon, hydroanthracite, and quartz sand. The plant can handle up
, and about 95 to 99 percent of phosphorus-containing compounds
Output concentration to the main reservoir averaged 4
over 2 years.
Also, the PEP has high removal (99 percent) of colifonn
bacteria, chlorophyll, and turbidity, and lesser removal of chemical oxygen
demand (77 percent) and dissolved organic carbon (58 percent).
state of the reservoir is now nearly oligotrophic.
Detailed descriptions of
the PEP at Wahnbach Reservoir are provided by Bernhardt (1980, 1981).
have not been reported.