Power Stretch

Thus, theoretically obtained asymptotic behavior (77) concurs with the phenomenological power-stretched exponential law (25). Using (78), it is possible to ascertain the relationship between the structural parameters a, ft, sm and the phenomenological fitting parameters v, p, zm as follows ... 

The response of a sinusoidal stress signal applied to a material will depend on the viscoelastic nature of that material, hence a sample of spring steel will be almost totally elastic, whereas a tub of grease or honey will be predominantly viscous. Hooke s "True theory of elasticity" said. The power of any spring is in the same proportion with the tension thereof, i.e. if one power stretch will bend it one space, two will bend it two. three will bend it three and so forth." Hence force F = A(A.v). where delta v is the displacement. Euler refined this to include the cross-sectional area A and the original length Z, but it was not until about 1800 that Thomas Young published it more widely as ... 

Moisture and high relative humidity next to the skin cause discomfort. Polartec Power Stretch keeps the skin dry through three complementary mechanisms ... 

When the sweat reaches the outside of the fabric, it spreads out to many times its original surface area, enabling it to dry at least two times faster than cotton. Polartec power-stretch product offers a four-way stretch material that is highly breathable and keeps the user s skin dry when sweating occurs and thus feels comfortable as next-to-skin material in sportswear. It is claimed to have high wind and abrasion resistance and is machine washable. 

The requirements of seam extension can vary dramatically with the product application that is, comfort stretch (up to 30%) for casual garments and performance wear and support garments can exhibit extensions of more than 100%— power stretch. 

This is an extension of the open width processing principles in combination with causticisation. The fabric construction should be devised so that there is space to allow yam crimp to develop. Causticisation will cause the crimp development and impart a memory which together with the fibre s high modulus and resilience will allow stretch with high degrees of recovery, equal to that achievable with elastane containing fabrics. It should be borne in mind though, that this is a comfort stretch rather than the power stretch associated with elastomerics. 

Muscle strains most often occur as a result of powerful stretching when the muscle is contracted. This typically occurs during an eccentric contraction, when the muscle is being lengthened as it activates (Zarins and Ciullo 1983). In these cases, there is... 

A larger value for the stretch force constant Kj. leads to a greater tendency for the bond to remain at its equilibrium distance rg Higher powers of r - rg, giving cubic, quartic, or higher terms are also common. A Morse function might also be employed. 

The CO2 laser is a near-infrared gas laser capable of very high power and with an efficiency of about 20 per cent. CO2 has three normal modes of vibration Vj, the symmetric stretch, V2, the bending vibration, and V3, the antisymmetric stretch, with symmetry species (t+, ti , and (7+, and fundamental vibration wavenumbers of 1354, 673, and 2396 cm, respectively. Figure 9.16 shows some of the vibrational levels, the numbering of which is explained in footnote 4 of Chapter 4 (page 93), which are involved in the laser action. This occurs principally in the 3q22 transition, at about 10.6 pm, but may also be induced in the 3oli transition, at about 9.6 pm. 

Most extmded latex fibers are double covered with hard yams in order to overcome deficiencies of the bare threads such as abrasiveness, color, low power, and lack of dyeabiUty. During covering, the elastic thread is wrapped under stretch which prevents its return to original length when the stretch force is removed thus the fiber operates farther on the stress—strain curve to take advantage of its higher elastic power. Covered mbber fibers are commonly found in narrow fabrics, braids, surgical hosiery, and strip lace. 

Manually adjusted screw or ratchet take-ups that adjust the position of the tail pulley to control belt tension can be used on relatively short, light duty conveyors. Automatic take-ups are used on conveyors over about 25 to 30 m long. The most common is the weighted automatic gravity take-up (see Fig. la). Other types of automatic take-ups have hydrauHc or pneumatic powered devices to adjust a snub pulley position and maintain a constant belt tension. The requited take-up movement varies according to the characteristics of the belt constmction and the belt length. Typically, take-up movements for pHed belts are 2% to 3% of the center distance between head and tail pulley, and about 0.5% for steel cable belts. The take-up movements requited for soHd woven belts are usually shorter because of the lower elastic stretch. Take-up requirements for a particular situation should be confirmed by the belt manufacturer. 

Electrochemical corrosion protection of the internal surfaces of reaction vessels, tanks, pipes and conveyor equipment in the chemical, power and petroleum industries is usually carried out in the presence of strongly corrosive media. The range stretches from drinking water through more or less contaminated river, brackish and seawater frequently used for cooling, to reactive solutions such as caustic soda, acids and salt solutions. 

Fig, 23-1 Limiting length of a parallel insulated stretch of pipe with capacitive interference by a 50-Hz, three-phase overhead power line with a nominal voltage >110 kV [2]. 

For assessing a close proximity situation with oblique sections, a map drawn to scale is necessary that shows the tracks of the interfering high-voltage power line or the stretch of electric railway line and the pipeline that is interfered with. 

The austenitic structure can be strengthened by cold work, and high strengths, still with adequate ductility, can be obtained by cold rolling, drawing or stretching. The power requirement for such strengthening... 

The linearity of L with N is maintained at the theta point. Relative to Eq. 5, the chains have shrunk by a factor of (a/d),/3 but the linear variation indicates that the chains are still distorted at the theta point and characteristic dimensions do not shrink through a series of decreasing power laws as do free chains [29-31]. Experimentally, Auroy [25] has produced evidence for this linearity even in poor solvents. Pincus [32] has recently applied this type of analysis to tethered polyelectrolyte chains, where the electrostatic interactions can produce even stronger stretching effects than those that have been discussed for good solvents. Tethered polyelectrolytes have also been studied by others [33-35],... 

Here, the chains are expected to be stretched, as indicated by the 2/3-power dependence of L on N, but less strongly than in solvent. The experimental evidence available to examine this argument is discussed in the section on block copolymer melts. 

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