Characteristics and Compression

Solid materials, by virtue of their response to applied mechanical force, can be classified under the following three heads (Fig. 4) (36)  

Elastic Any change in shape is completely reversible, and the material returns to its original shape upon release of applied stress. 

Plastic Permanent change in the shape of a material due to applied stress, e.g., MCC, corn starch, and sodium chloride. 

Brittle Rapid propagation of a crack throughout the material on application of stress, e.g., sucrose, mannitol, sodium citrate, lactose, and dicalcium phosphate. 

The predisposition of a material to deform in a particular manner depends on its lattice structure, in particular whether weakly bonded lattice planes are inherently present. In definite terms, most of the materials cannot be classified distinctly into individual categories. Pharmaceuticals exhibit all three characteristics, with one of them being the predominant response, thus making it difficult to clearly demarcate the property favorable for compressibility. 

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Capacity can vary depending on breaking characteristics and compression strength of each installed horsepower, size of feed, rate of feed, type of fall, and proper operating conditions. 

The quality of a compressed tablet is determined by material fill characteristics and compression behavior. During compression, the rate at which tablets can be produced can be limited due to non-uniform material fill characteristics. Pending successful and reproducible material fill (die fill), the powder mass must form a coherent compact that stays intact upon ejection out of the die. Therefore, tablet press performance can be limited due to poor fill characteristics and/or poor compression behavior. 

Other Fiber Deformations. Deformations such as bending, torsion, shear, and compression are of practical importance in textile apphcations. Bending and twisting of yams, both influential in the development of bulk and stretch in filament yams, are also important in the production of staple yams. Bending characteristics are important in cmsh resistance in carpets. Bending and shear are factors that influence the hand and drape of apparel fabrics, whereas compression influences the recovery of fabrics after such processes as winding. 

The foundation of shock-compression science is based upon observations and analyses of the mechanical responses of solid samples to shock-loading pulses. Although the resulting mechanical framework is necessary, there is no reason to believe that a sufficiently complete scientific picture can be based on mechanical considerations alone. Nevertheless, the base of our knowledge rests here, and it is essential to recognize its characteristics, and critically examine the work. 

The fundamental characteristics of compression are the same for centrifugal and reciprocating compressors. The manner in which these fundamentals are interpreted must be adapted to the particular machine type and operating characteristics, and this accounts for the difference in design procedures. 

Velocity and Attenuation of the Pressure Waves. The velocity and attenuation of the mud pulses or waves have been studied theoretically and experimentally. The velocity depends on the mud weight, mud compressibility, and on the drillpipe characteristics, and varies from 4920 ft/s for a light water-base mud to 3,940 ft/s for a heavy water-base mud. An oil-base mud velocity will vary from 3,940 ft/s for a light mud to 3,280 ft/s for a heavy mud. 

Morini Gl, Lorenzini M, Salvigini S (2006) Friction characteristics of compressible gas flows in micro-tubes. Exp. Thermal and Fluid Science 30 733-744 Mudawar 1 (2001) Assessment of high-heat-flux thermal management schemes. IEEE CPT Trans 24 122-141... 

The physicochemical characteristics of the active ingredient in relation to the dosage form and the suitability for its intended purpose was discussed in several EPARs, particularly relating to the solubility characteristics and absorption from the gut. The compression characteristics were also mentioned in some EPARs. The possible effects of different polymorphs or evidence that only a single polymorph is used are addressed as appropriate. Different amorphous or crystalline forms are also discussed. Where affecting the dosage form, selection properties such as unpleasant taste or smell are mentioned. 

Grolmes, M. A., and H. K. Fauske, 1969, Propagation Characteristics of Compression and Rarefaction Pressure Pulses in One-Component Vapor-Liquid Mixtures, Nuclear Eng. Design 77 137-142. (3) Grolmes, M. A., and H. K. Fauske, 1970, Modeling of Sodium Expulsion of Freon-11, ASME Paper 70-HT-24, Fluids Engineering Heat Transfer and Lubrication Conf., Detroit, MI. (4)... 

It is not surprising, therefore, that this dynamic technique was chosen to provide information on chiral interactions in compressed films. Given that these stereochemically differentiated systems may have dramatically different HI A isotherm characteristics, and hence different packing arrangements, it is plausible that their flow properties are stereochemically differentiated as well. 

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