Physical shape

The physical shape of fibers affects their appearance, luster, hand and feel, cohesiveness, and many other properties. The shape of fibers can be examined both in longitudinal and cross-sectional directions. The simplest longitudinal shape of fibers is straight. But many natural polymer fibers, such as cotton and wool, have crimp longitudinal shape. Synthetic nanofiber fibers can be made to have straight, crimp, coiled, or spiral shape. 

The cross-sectional shape of fibers is more complex. Many natural polymer fibers have unique cross-sectional shapes. For example, the cross-section of dry cotton is kidney-shaped, while that of degummed silk is nearly a triangle. These cross-sectional shapes are controlled by genetic codes, and human has limited influence. However, the cross-sectional shapes of synthetic polymer flbers, inorganic flbers, and nanofibers can be manipulated by controlling the fiber formation processes. The cross-sectional shapes of these fibers range from circular to oval, triangular, dog bone, trilobal or multilobal, hollow, etc. 

Compared with fibers with other types of cross-sections, circular fibers have the smallest surface area, and can pack closely together into yams, composites, or other stractures. Circular fibers often are lustrous and have soft and smooth handle. On the other hand, dog bone-shaped and flat cross-section fibers have a harsher, less smooth feel. Trilobal and multilobal fibers exhibit an increased luster and have excellent ability to obscure the object placed beneath them because they can reflect the light not only from the surface but also from one lobe to another. Hollow fibers have low packing density and provide greater bulk with less weight. In addihon, hollow fibers have high absorbency due to their large surface area. 

In addition to the longitudinal and cross-sectional shapes, the surface structure of fibers varies. Mat r fibers have smooth and even contour. However, some fibers are rough, uneven, or have unique surface features. For example, wool fibers are covered with many scales that make them cling closely together. 

The mass density or density of a material is its mass per imit volume  

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Dry chlorine reacts with most metals combustively depending on temperature alurninum, arsenic, gold, mercury, selenium, teUerium, and tin react with dry CI2 in gaseous or Hquid form at ordinary temperatures carbon steel ignites at about 250°C depending on the physical shape and titanium reacts violendy with dry chlorine. Wet chlorine is very reactive because of the hydrochloric acid and hypochlorous acid (see eq. 37). Metals stable to wet chlorine include platinum, silver, tantalum, and titanium. Tantalum is the most stable to both dry and wet chlorine. 

Dump lime is a physical shape of quicklime, derived from vertical kilns. 

The heat produced by the reaction of a pyrolant is dependent on various physicochemical properties, such as the chemical nature of the fuel and oxidizer, the fractions in which they are mixed, and their physical shapes and sizes. Metal particles are commonly used as fuel components of pyrolants. When a metal particle is oxidized by gaseous oxidizer fragments, an oxide layer is formed that coats the particle. If the melting point of the oxide layer is higher than that of the metal particle, the metal oxide layer prevents further supply of the oxidizer fragments to the metal, and so the oxidation remains incomplete. If, however, the melting point of the oxide layer is lower than that of the metal particle, the oxide layer is easily removed and the oxidation reaction can continue. 

Fig. 12.17 shows a typical set of afterburning flame photographs obtained when a nitropolymer propellant without a plume suppressant is burned in a combustion chamber and the combustion products are expelled through an exhaust nozzle into the ambient air. The physical shape of the luminous flame is altered significantly by variation of the expansion ratio of the nozzle. The temperature of the combustion products at the nozzle exit decreases and the flow velocity at the nozzle exit increases with increasing e at constant chamber pressure. 

Without considering radiogenic growth, effectively we are considering a non-radiogenic isotope such as Ar. Two effective shapes, plane sheet and solid sphere, are considered here. The effective shape is not necessarily the physical shape diffusive anisotropy must also be considered in determining the effective shape (Section 3.2.11 and Figure 3-13). 

In contrast to y-rays and x-rays, the electron beam can be steered relatively easily, thus allowing irradiation of a variety of physical shapes. 

Experienced firefighters have realized the necessity of staying in top physical shape, and for years many... 

Fig. 57a. A typical multilayered cloth made cf potassium tartaric amide 31b at pH 5. Its observed physical shape is fortuitous. (Negative stain, uranyl acetate 1%). b Freeze-etching erf a similar multilayer made of the sodium salt 31a. At higher magnification (below), the bilayer profiles become visible (Pt/C shadowed), c Fiber pattern of 31a. (Negative stain, uranyl acetate 1%). d Digitized area of the fiber bundle taken from (c). e Fourier transform of the input image from (d), as obtained by calculating the reciprocal space frequencies (x-y exchanged). Two intense spots yield a periodical pattern of 38.78 A [376]...

The process is very fast, clean and can be controlled with much precision. There is no permanent radioactivity since the machine can be switched off. In contrast to y-rays and x-rays, the electron beam can be steered relatively easily, thus allowing irradiation of a variety of physical shapes. 

There are three general types of oilfield separators presently available, based on the physical shape of the containing vessel vertical, horizontal and spherical. Each have their place in oilfield gas and liquid separation. 

For a solid material chemical assay, level of impurities and its physical characteristics, such as specific density, bulk density, particle size distribution and the like are included. This physical shape information is required to assure that adequate processing and material handling operations will be provided. 

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