Discrete fibers

Discrete fibers (also known as chopped fibers) are short-length fibers (a few centimeters) which are generally randomly oriented. They are 

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Paper consists of sheet materials that are comprised of bonded small discrete fibers. The fibers usually are ceUulosic in nature and are held together by hydrogen bonds (see Cellulose). The fibers are formed into a sheet on a fine screen from a dilute water suspension. The word paper is derived from papyms, a sheet made in ancient times by pressing together very thin strips of an Egyptian reed Cjperuspapyrus) (1). 

Correct answer = C. The parasympathetic system maintains essential bodily functions, such as vision, movement of food, and urination. It uses acetylcholine, not norepinephrine, as a neurotransmitter, and discharges as discrete fibers that are activated separately. The postganglionic fibers of the parasympathetic system are short compared to the sympathetic division. The adrenal medulla is under control of the sympathetic system. 

Equation 20.1 assumes that anisotropic fillers such as fibers or platelets are all aligned in the direction of tensile deformation. If the orientation distribution differs from this transversely isotropic alignment, the composite modulus would be obtained in the three principal axis directions by orientational averaging. This equation (along with other equations which are not listed here), when combined with orientational averaging, can thus provide an estimate of the reinforcement expected from any orientational distribution of discrete fibers or platelets. 

J. R. Burt, and K. A. Szabo, Methods of making floor tile and wall covering from extruded hot recycled vinil thermoplastic membrane having discrete fibers ramdomly dispersed therein, Patent US5560797 (1995). 

Carpet waste disposed of in landfills each year is about 2-3 million tons in the US A and about 4-6 million tons per year worldwide. Reinforcements of concrete and soil with discrete fibers are proven technologies to enhance the performance of these materials. Because of the vast amount of concrete and soil involved in... 

High level of automation possible Discrete fiber orientations possible Large, oversized, complex and integral structures possible Reduced bonding and assembly efforts... 

Carnaby, G.A., Postle, R. (1991), Discrete fiber versus continuum models in the mechanics of staple yarns, Jom-nal of Applied Polymer Science Applied Polymer Symposium, 47, pp. 341-354... 

The rheology of liquid crystal polymers was reviewed by Wissbrun. A more recent review is from 1996, ° particularly Chapter 4 by Cogswell and Wissbrunn, which makes the point that LCP changes the rules which govern the balance between ease of processing and service performance compared to conventional thermoplastics reinforced by the addition of discrete fiber fillers. These reviews describe the essential features of the usual response of thermotropic polymers to shear, namely shear-thinning. 

Fibrillated Fibers. Instead of extmding cellulose acetate into a continuous fiber, discrete, pulp-like agglomerates of fine, individual fibrils, called fibrets or fibrids, can be produced by rapid precipitation with an attenuating coagulation fluid. The individual fibers have diameters of 0.5 to 5.0 ]lni and lengths of 20 to 200 )Jm (Fig. 10). The surface area of the fibrillated fibers are about 20 m /g, about 60—80 times that of standard textile fibers. These materials are very hydrophilic an 85% moisture content has the appearance of a dry soHd (72). One appHcation is in a paper stmcture where their fine fiber size and branched stmcture allows mechanical entrapment of small particles. The fibers can also be loaded with particles to enhance some desired performance such as enhanced opacity for papers. When filled with metal particles it was suggested they be used as a radar screen in aerial warfare (73). 

High performance composites may be laminates wherein veils of carbon fiber ate treated with an epoxy resin, stacked up to the desired final product thickness, and then laminated together under heat and pressure (see Composite materials Carbon and graphite fibers). Simply mixing together carbon or glass fibers and polymeric resins to form a reinforced plastic leads to a composite material, but this is not a laminate if not constmcted from discrete phes. 

Dip coating is very commonly used for coating continuous objects that are not flat, such as fibers, and for irregularly shaped discrete objects. Tears or drops of coating at the bottom of dip coated articles may be removed by electrostatic attraction as the article is moved along a conveyor. 

Fiber and Karplus [38] presented an effective set of numerical methods for computing the reaction paths based on this approximation. First the path is discretized—it is expressed as a chain of intermediate configurations of the system rj,. The line integrals of Fq. (19) are then written as... 

Muscle biopsy is usually undertaken to confirm the provisional clinical diagnosis. Because the skin lesions normally precede those in muscle, biopsies of muscle taken early may show little abnormality. Inflammatory foci may be scanty or absent and muscle fiber diameters may be normal. However typical biopsies show discrete foci of inflammatory cells, with a predominance of B-lymphocytes (see Figure 18). These cells are situated in perimysial connective tissue rather than in the en-domysium and are often also perivascular in location. Muscle fiber necrosis occurs in JDM but muscle fibers do not appear to be the primary target of the disordered immune process. Rather, it is the micro vasculature of the muscle which appears to degenerate first and muscle necrosis is preceded by capillary necrosis, detectable at the ultrastructural level. 

Extruders play a key role in many conversions processes we use them to melt solid polymers and pump the resulting molten material to a die or a mold. After the molten polymer has been molded to the desired shape, it is cooled to form a solid product. We can feed the output of an extruder to continuous forming processes to create films, pipes, and fibers. Alternatively, we can employ discontinuous molding processes to create discrete items, such as soda bottles, lenses for single use cameras, or bathtubs. 

Because the terminal ganglia are located within the innervated tissue, there is typically little divergence in the parasympathetic system compared to the sympathetic system. In many organs, the ratio of preganglionic fibers to postganglionic fibers is 1 1. Therefore, the effects of the parasympathetic system tend to be more discrete and localized, with only specific tissues stimulated at any given moment, compared to the sympathetic system in which a more diffuse discharge is possible. 

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