Material characteristic properties parameters

The prevalently used waveguides are optical fibres. Fibre technology is standard in the UV to near-IR, but also some fibres for light transport in the mid-IR have been developed. An overview of different IR fibre materials and their characteristic performance parameters is given in Table 1. More details can be found in a number of reviews focused on the material properties of IR transmitting optical fibres26 31. For some applications, as an alternative to optical fibres also hollow waveguides may be used. 

At high temperatures, ferroelectric materials transform to the paraelectric state (where dipoles are randomly oriented), ferromagnetic materials to the paramagnetic state, and ferroelastic materials to the twin-free normal state. The transitions are characterized through order parameters (Rao Rao, 1978). These order parameters are characteristic properties parametrized in such a way that the resulting quantity is unity for the ferroic state at a temperature sufficiently below the transition temperature, and is zero in the nonferroic phase beyond the transition temperature. Polarization, magnetization and strain are the proper order parameters for the ferroelectric. 

We interrupt the procedure to ask some important questions concerning (1) the determination of the characteristic geometric parameter, (2) the setting of all relevant material properties, and (3) the taking into account the gravitational acceleration. 

A complete description of the viscoelastic properties of a material requires information over very long times. To supplement creep and stress relaxation measurements which are limited by experimental limitations, experiments are therefore performed in which an oscillating stress or strain is applied to the specimen. These constitute an important class of experiments for studying the viscoelastic behavior of polymeric solids. In addition to elastic modulus, it is possible to measure by these methods the viscous behavior of the material in terms of characteristic damping parameters. 

For the mathematical description of the component transport through a porous membrane there are two modeling approaches common. The first is the so-called extended Pick model (EFM), which can be applied to describe the transport of diluted, nonadsorbable gases in mesoporous membrane materials at low pressure (Veldsink et al., 1995 Papavassiliou et al., 1997 Al-Juaied et al., 2001). The second, the more general dusty gas model, is based on the Stefan-Maxwell approach for multicomponent diffusion (Mason et al., 1967 Krishna and WesseUngh, 2000). Both models require knowledge of the above-mentioned membrane properties (e.g.. Bo, c/t). Because for a specific membrane material these parameters are a priori not predictable, they have to be determined experimentally. Typical membrane materials and characteristic transport parameters used in this work are Hsted in Table 5.1. 

Elasticity is one of the most characteristic properties of polymer fluids. To date, this parameter has been largely overlooked. Thus, the elastic material function may lead, under high shear-rates (e.g. injection) to a loss of energy and to material defects. A measure of the storable elastic energy is the storage modulus G (G" = loss modulus). The ratio G"/G indicates whether a body is mainly elastic or viscous. 

The mechanical properties of the weldline zone can be influenced by the material characteristics and by the processing conditions. In practical terms, the freedom one has to improve the weldline strength by changing processing parameters, such as the melt and mold temperatures, to favor chain diffusion is limited (polymer degradation and longer cycle time) [4]. 

The characterization of solid particles, most of which are, in practice, irregular in shape, is usually made by analysing the particle size (the measure of size most relevant to the particle property which is under investigation) and its distribution. Other characteristic properties of the solid material may be included in the measure of size determined, for example Stokes diameter combines size, density and shape all in one parameter, they can be characterized separately if necessary. British Standard BS2955 attempts to define shape qualitatively a quantitative measure of particle shape can be obtained indirectly by analysing two or more measures of particle size and looking at different shape coefficients that relate to those sizes. 

Nonwovens are one of the fastest growing textile sectors with diverse applications. These applications have an extensive list, ranging from baby diapers to high performance geotextiles. The essential requirements of these applications are good understanding of the raw material characteristics and process parameters in order to achieve the desired product properties. 

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