Various Uses of the Most Popular Rounds

With a long and varied past, .44 shells remain the most used selection with several genres. This particular bullet can be utilized with a lot of distinctive guns, like revolvers along with rifles. Countless sportsmen opt for 44 Magnum rounds because of its effectiveness in relation to different types of animals including medium to much larger creatures. The item’s pitfall for hunting is how heavy it is in addition to precision limitations at rather long ranges. such characteristics are actually precisely what render bulk 44 Mag ammo an absolute necessity among rifle clubs and also safety buffs. The mass and proportions mean a great deal of strength along with speed upon near scope, meaning it is really an ideal bullet meant for heading off those people that mean to actually do harm. Dabblers or competition shooters view this type of ammunition perfect for improving their skills at their shooting range due to its length related obstacles. Because of its adaptability and level of popularity, 44 Magnum bullets can be difficult to find at a local level; consequently, any individual in search of 44 Magnum ammo for sale may well find better results on the web when compared to their particular area firearms dealers. This method can help hobbyists, sportsmen and also protectors of their families similarly acquire the armaments they demand regardless of the sorts of guns they decide to use.

Durable TV Stands

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TV stands and for that matter audio racks, media storage, speaker stands and almost all components of home theater furniture, are available in wood, steel, and glass. Some are also available in clear or tinted acrylic. When setting up your home theater you need to locate those that are built to last, unless you plan to replace the furniture every couple of years.

For wooden stands, solid wood is the best, though not the only choice, for durable material. Take your pick from hardwoods, softwoods, wood veneer, and engineered woods. Hardwood is premium wood. In hardwood, you have a choice of maple, oak, teak, cherry, mahogany, and ebony. These are generally harder to work, more attractive, and more expensive.

Softwoods include pine, spruce, cedar, redwood, and fir. Though the name might suggest, these are not necessarily softer. All solid wood, whether hardwood or softwood, have a strong decorative appeal in their grain, which looks elegant and can last a lifetime and more. Wood veneer is another popular material for making stands. It looks as good as solid wood, but is much cheaper. It is made up of thin strips of real wood glues to a substrate, which makes it cheaper than solid woods.

Engineered woods are made from mill waste, wood scraps and other materials that would otherwise be discarded as trash. The mill waste and wood scrap is glued and bonded into sheets. These products are environmentally friendly and recycled. They reduce the need for tree cutting and in many ways are better than solid wood because they cost less and do not warp. TV stands made from engineered wood are not as durable as those made from solid wood, but with a little care and upkeep can last for decades.

Metal stands come in aluminum, brass, and stainless steel, which is the predominant material in the market. Unlike the other metals, stainless steel does not rust or tarnish. It takes chrome plating as well as powder coating very well, which means that it is available in a variety of attractive finishes. It can be worked into an overwhelming variety of sleek, creative and innovative designs with ease. A modern stand made of steel goes well with your high-tech audio and video systems, and lasts very long.

Glass is of three types. Regular glass, also known as ‘annealed glass’, shatters into large shards with razor sharp edges, and is not suitable for furniture. Heat-treated or ‘toughened’ glass is much stronger than annealed glass. Glass that is treated with chemicals and heat, known as ‘tempered glass’, is many times stronger than annealed glass. When broken, it forms small cube-like pieces instead of sharp-edged shards, and is therefore much safer than annealed glass. stands, speaker stands, audio stands etc made of tempered glass can last long but need careful handling. You need to be extra careful while cleaning or moving them.

Serenitylivingstores strives to assist people in making informed decisions on furnishing their homes. He writes for http://www.tv-stands-shop.com/, an online shop for TV stands and other furniture.

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Blown Film Extrusion Introduction

Blown Film Extrusion Introduction
Blown film extrusion is a technology that is the most common method to make plastic films, especially for the packaging industry. The process involves extruding a tube of molten polymer through a die and inflating to several times its initial diameter to form a thin film bubble. This bubble is then collapsed and used as a lay-flat film or can be made into bags. Usually polyethylene is used with this process, and other materials can be used as blends with these polymers. A diagram of a polyethylene chain is shown in Figure 1 to the right.
Background Theory on Polymers

In the cooling step of blown film extrusion, the amorphous, transparent melt crystallizes to form a translucent, hazy, or opaque film. The point where opacity begins in the bubble is known as the frost line. 
Fig 1: Model of polytheylene chain frompolyethylene Wikipedia article.The frost line height is controlled by several parameters: the air flow, film speed, and temperature difference between the film and the surroundings. Properties of the film, such as tensile strength, flexural strength, toughness, and optical properties, drastically change depending on the orientation of the molecules. As the transverse or hoop direction properties increase, the machine or longitudinal direction properties decrease. For instance, if all the molecules were aligned in the machine direction, it would be easy to tear the film in that direction, and very difficult in the transverse direction.

The Film Blowing machine Process

Fig 2: Schematic of set-up from User:J.Chiang.

Typically, blown film extrusion is carried out vertically upwards, however horizontal and downward extrusion processes are now becoming more common. Figure 2 shows a schematic of the set-up for blown film extrusion. This procedure consists of four main steps: The polymer material starts in a pellet form, which are successively compacted and melted to form a continuous, viscous liquid. This molten plastic is then forced, or extruded, through an annular die. Air is injected through a hole in the center of the die, and the pressure causes the extruded melt to expand into a bubble. The air entering the bubble replaces air leaving it, so that even and constant pressure is maintained to ensure uniform thickness of the film. The bubble is pulled continually upwards from the die and a cooling ring blows air onto the film. The film can also be cooled from the inside using internal bubble cooling. This reduces the temperature inside the bubble, while maintaining the bubble diameter. After solidification at the frost line, the film moves into a set of nip rollers which collapse the bubble and flatten it into two flat film layers. The puller rolls pull the film onto windup rollers. The film passes through idler rolls during this process to ensure that there is uniform tension in the film. Between the nip rollers and the windup rollers, the film may pass through a treatment centre, depending on the application. During this stage, the film may be slit to form one or two films, or surface treated. Advantages Blown film generally has a better balance of mechanical properties than cast or extruded films because it is drawn in both the transverse and machine directions. Mechanical properties of the thin film include tensile and flexural strength, and toughness. The nearly uniform properties in both directions allow for maximum toughness in the film.
Blown film extrusion can be used to make one large film, two smaller ones, or tubes that can be made into bags. Also, one die can make many different widths and sizes without significant trimming. This high level of flexibility in the process leads to less scrap material and higher productivity. Blown films also require lower melting temperatures than cast extrusion. Measured at the die opening, the temperature of cast film is about 220 C, where as the temperature of blown film is about 135 C. Furthermore, the cost of the equipment is approximately 50% of a cast line.

Blown Film Extrusion Disadvantages Blown film has a less effective cooling process than flat film. Flat film cooling is done by means of chill rolls or water, which have significantly higher specific heat capacities than the air that is used in the blown film cooling process. The higher specific heat capacity allows the substance to absorb more heat with less change in the substance temperature. Compared to cast film, blown film has a more complicated and less accurate method to control film thickness; cast film has a thickness variation of 1 to 2% versus the 3 to 4% for blown film. The resins used for casting typically have a lower melt flow index, which is the amount of polymer that can be forced through a standard die in 10 minutes according to a standard procedure. The melt flow index for cast film is about 5.0 g/10 min where as for blown film it is about 1.0 g/10 min. Consequently, the production rates for cast film are higher: cast film lines can reach production rates of up to 300m/min where as blown film lines are usually less than half this value. And finally, cast film has better optical properties, including transparency, haze, and gloss.

Common Problems Air entrapment between film layers and rollers – this may cause film scratching or wrinkling, or processing problems when winding up the film due to reduced friction. Possible solutions to this is using a vacuum to remove entrapped air or by using winding rolls with a diamond shaped groove in the rubber cover to increase surface area and decrease amount of entrapped air in the film. Large output fluctuations from the die – this causes thickness variations, and can be prevented by keeping the extruder clean and by using more consistently shaped pellets in the extruder. Melt fractures – these appear as roughness or wavy lines on the film surface, and can be eliminated by lowering the viscosity of the polymer melt. This can be done by increasing the melting temperature or by adding an internal lubricant to the material composition. Thickness variations in the film – this can be avoided by centering the die in the extrusion line before every run, adjusting the air speed of the cooling system, or by using heated die lips. Die lines on the surface of the film – this defect reduces the aesthetic appeal of the film, reduces optical properties, and weakens mechanical properties such as tear strength. This can usually be avoided by routinely cleaning the inner surfaces of the die and by refinishing scratched or roughened flow surfaces. Gels – these defects are small, hard globules encapsulated in the film or stuck on the film surface and reduce the aesthetic appeal of the film and cause stress concentration points which may result in premature failure. These are caused by overheating to the point of polymer degradation in the die, and can therefore be avoided by cleaning the inner surfaces of the die on a regular basis. Optimization of the Process Coextrusion One way to improve the line efficiency of blown film extrusion is to implement coextrusion. This is the process of extruding two or more materials simultaneously through a single die. The orifices in the die are arranged such that the layers merge together before cooling. This process saves time because it extrudes two or more layers at the same time, and it provides a method with fewer steps to produce multilayer films. The production rate for a coextruded multilayer film of three layers is about 65m/min, and the production rate for a single layer of blown film is about 130m/min. Thus, in order to produce 10 000m of a three layer multilayer film, it would take almost 4 hours using a single layer blown film process, and only 2 and a half hours using the coextrusion process. Furthermore, the film produced from the single layer process would require an extra step to glue the layers together using some sort of adhesive. Coextrusion is the least expensive means of producing layered films and the coextrusion system is capable of quick changeovers to minimize production line down time.

Minimizing the Melt Temperature
The efficiency of blown film extrusion can be improved by minimizing the temperature of the polymer melt. Reduction of the melt temperature causes the melt to require less heating in the extruder. Normal extrusion conditions have a melting temperature at about 190 C despite the fact that the temperature of the melt only needs to be about 135 C. However, it is not always practical to decrease the melting temperature by that much. By decreasing the melt temperature 2 to 20 C, the motor load can be decreased by about 1 to 10%. Furthermore, reduction of the melt temperature causes less need for cooling, so there is a reduced use of the cooling system. Moreover, removing heat from the bubble is usually the rate-limiting factor in this extrusion process, so by having less heat in the polymer to remove, the rate of the process can be increased, thus yielding higher productivity. A way to maintain the melt temperature at a minimum is to choose an extruder that is matched to the specific processing conditions, such as the material of the melt, pressure, and throughput.

Heated Extrusion Die Lips
Typically, solutions to melt fractures involve decreasing the output or increasing the melt temperature to decrease the shear stress in the extruder. Both of these methods are not ideal because they both reduce the efficiency of the blown film line. Heated extrusion die lips can solve this problem. This targeted heating method allows for film extruders to be run at higher production rates with narrower die gaps while eliminating melt fractures. Direct heat is applied to the surface of the polymer melt as it exits the die so that viscosity is reduced. Therefore, melt fractures, which are caused when trying to extrude too much of the polymer at one time, will no longer act as a limiting factor to increasing the production rate. Furthermore, heated die lips use less energy than increasing the melting temperature because only the surface of the melt is heated and not the bulk of the liquid. Another benefit of using heated die lips is that thickness variations can be controlled by adding heat to certain areas along the die circumference to make the film at that position thinner. This would ensure that no excess material is used.
Determine how much energy each of these processes can save per given volume of material. 

Above article from www.appropedia.org

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Makeup for HDTV: Looking Your Best on TV

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The purpose for all makeup is to enhance your best features and minimize your flaws. Unlike television of old, high definition television does not require the thick pancake makeup, dark contouring or dramatic applications. Nor will everyday street makeup create flawless looking skin.

A professional makeup artist, studied in HDTV, can tailor your approach guided by your coloring and bone structure. For personal application, the following is a guideline to the products and application techniques you will need before you appear on HDTV.

Men and women alike require a foundation, concealer and blush/bronzer for any HDTV appearance. Women (and some men) will also need eye makeup and lip color.

Aptly named, the foundation selected for on air appearance is the single most important element in creating a pleasing look.

The allover face makeup used in HDTV differs from daywear. Even the most flawless complexions should not attempt to go barefaced. Makeup for HDTV should cover the entire face, neck, hands and any other exposed skin. Attempting spot application will appear just as that…spots!

The two formulations of makeup to date which best serve HDTV are airbrush and mineral powders.

Airbrush makeup is the choice of most professional television makeup artists. The coverage is complete and flawless. Applying airbrush makeup requires a compressor-like machine. Makeup is applied in seconds, evenly and completely. Tiny molecules of either water based, alcohol, polymer, or silicone based foundation is sprayed through a medium to fine airbrush nozzle onto the skin.

Complete airbrush systems with a low pressure compressor (about 10 psi) range in price from $120US to $1,000US or more.

Television anchors, hosts or frequent TV guests would benefit from this investment. Use takes a little practice, but it is easy to master. The flawless appearance pays for itself.

“Airbrush” makeup in an aerosol can is available at many price ranges. This make-up works quite well for occasional application. However, following manufacturer’s instructions to apply to the hand and then to the face can lead to streaking. Direct spraying on to the face is not recommended by most manufacturers, or by this author. This product is inexpensive, and can produce acceptable results.

Airbrush makeup can correct flaws, hide tattoos and cover rosacea, port wine and similar skin blemishes.

The other option for HDTV quality foundation is mineral powders. This is the easiest makeup to master for amateur application. Skin tone shades are applied via a kabuki brush, a stub handled thickly bristled brush.

Application involves buffing the powder into the skin, which creates a soft matte appearance. Shine on HDTV is glaring, distracting, and reminiscent of the flop sweats on Broadcast News.

The actual application uses a surprisingly small amount of powder to achieve coverage. Minor to moderate skin imperfections can be hidden without creating a chalky appearance.

The only caution in selecting a mineral powder makeup is the mica content. Mica is a light reflector, and can create unflattering reflections on the skin. Test any mineral powder under a strong light or in bright sunlight. If the powder appears to “sparkle”, choose another brand with less reflectivity.

Poorly applied makeup is a distraction (remember Al Gore’s imitation Reagan makeup during the first George W. Bush presidential debate?)

Adjusting the makeup formulation and application before standing in from of a high definition camera can create the appearance you need to allow your message to be heard.

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