Types of Linings

As in crystals, defects in liquid crystals can be classified as point, line or wall defects. Dislocations are a feature of liquid crystal phases where tliere is translational order, since tliese are line defects in tliis lattice order. Unlike crystals, tliere is a type of line defect unique to liquid crystals tenned disclination [39]. A disclination is a discontinuity of orientation of tire director field. 

Lined vessels are used for many applications. Any type of lining can be used in an ASME Code vessel, provided it is compatible with the metal of the vessel and the contents. Glass, rubber, plastics, rare metals, and ceramics are a few types. The hning may be installed separately, or if a metal is used, it may be in the rorm of clad plate. The cladding on plate can sometimes be considered as a stress-carrying part of the vessel. 

In the first case, if we had considered a safe line length of 250 km, this would become 500 km for a symmetrical line. Figure 24.18 illustrates such a condition. Depending upon the length and type of line, a line length compensation may be required. Most transmission lines are seen to be within permissible lengths and only a few may require such a compensation. Nevertheless, it may be worth reducing the phase displacement between E, and to less than 15° electrical, to further iinprove the quality and stability level of power transmission. 

The other major defects in solids occupy much more volume in the lattice of a crystal and are refeiTed to as line defects. There are two types of line defects, the edge and screw defects which are also known as dislocations. These play an important part, primarily, in the plastic non-Hookeian extension of metals under a tensile stress. This process causes the translation of dislocations in the direction of the plastic extension. Dislocations become mobile in solids at elevated temperamres due to the diffusive place exchange of atoms with vacancies at the core, a process described as dislocation climb. The direction of climb is such that the vacancies move along any stress gradient, such as that around an inclusion of oxide in a metal, or when a metal is placed under compression. 

The two types of lines on a flowsheet are (1) those representing outlines and details of equipment, instruments, etc., and (2) those representing pipe carrying process or utility liquids, solids, or vapors and electrical or instrument connections. The latter must be distinguished among tliemselves as suggested by Figure 1-21. 

Three types of lines are used in fluid power systems pipe (rigid), tubing (semi-rigid), and hoses (flexible). A number of factors are considered when the type of line is selected for a particular application. These factors include the type of fluid, the required system pressure, and the location of the system. For example, heavy pipe might be used for a large, stationary system, but comparatively lightweight tubing must be used in mobile applications. Flexible hose is required in installations where units must be free to move relative to each other. 

The simplest type of line defect is the edge dislocation, which consists of an extra half plane of atoms in the crystal, as illustrated schematically in Fig. 20.30a edge dislocations are often denoted by 1 if the extra half plane ab is above the plane sp, or by T if it is below. 

The second type of line defect is the screw dislocation, which is rather less easy to visualise. Consider, however, a block of material, half of which is sheared one interatomic distance with respect to the other half, as shown in Fig. 20.306. The line cdthen constitutes a screw dislocation the arrangement of atoms around a screw dislocation is shown in Fig. 20.30c. 

The intensity of the EPR resonance absorption is a measure of the number of paramagnetic centres present [346], while the type of line observed and the measured g factor are indications of the interactions of the paramagnetic particles and of their distribution within the matrix. Such spectra are much more sensitive to changes in crystal field and atomic orientations than X-ray diffraction and are not dependent upon crystallinity [347]. The nature of the paramagnetic particles may be discerned from the superfine structure of the spectrum. 

Fig. 16. The yield Xg of the product Q of the slower reaction of a set of two competitive parallel reactions in a fed batch reactor plotted vs. impeller speed (in /s). The experimental data are due to Bourne and Yu (1991) the crosses refer to feeding reactant A at the top of the vessel, while the diamonds refer to feeding more closely to the impeller. The various types of lines refer to simulations as specified in the legend. Reproduced with permission from R. A. Bakker (1996).

When transferring fuel and fuel additives from storage to the pump and to its final point of use, different types of lines and hoses are utilized. Mild steel, stainless steel, and cross-linked polyethylene hose are the typical materials of construction used. These materials withstand the temperature and environmental extremes of outdoor installation and are compatible with fuels and most additives. 

Figure 1. Dependence of the interaction energies for the linear and T-shaped configurations as r bond increases. Dot-dashed, solid, dotted, long-dashed type of lines correspond to r= 2.19, 2.28, 2.37 and 2.46 A, respectively...

The second type of line defect, the screw dislocation, occurs when the Burger s vector is parallel to the dislocation line (OC in Figure 1.33). This type of defect is called a screw dislocation because the atomic structure that results is similar to a screw. The Burger s vector for a screw dislocation is constructed in the same fashion as with the edge dislocation. When a line defect has both an edge and screw dislocation... 

Low frequency spectra of liquids are notably deficient of any structure, and it has long been hoped that a technique would be discovered that provides the same type of line narrowing enjoyed in echo-based electronic and NMR spectroscopy. Tanimura and Mukamel observed that such a technique was possible, and proposed a two-time interval, fifth-order Raman pulse sequence capable of distinguishing, for example, inhomogeneous and homogeneous contributions to the lineshape.[4] The pulse sequence, shown in Fig. 1, is simply an extension of conventional time-domain third-order Raman-based methods. At the... 

Where in Fig. 6.3 two curves are drawn with the same type of line, the upper curve describes the free — free transitions of the collisional pair, and the lower one the bound — free contributions. Asymptotically, at high frequencies, the bound — free contributions amount to only about 1% of the free — free components. At the lower frequencies, however, the bound — free components are relatively more significant. In fact, the bound — free components which must be superimposed with the free — free components to obtain the spectral function, Eq. 6.54, affect the shapes of the profiles near the line centers. We note that the quadrupole-induced components 0223, 2023 do not feature a bound — bound spectrum, but the less important overlap components 0221, 2021 do. However, absorption due to this overlap component is insignificant, a few percent of the total absorption. 

This table is essentially self-explanatory. Each plane that is perpendicular to the page is shown by a line drawn where it intersects the page. The type of line shows the type of plane. When the plane is in or parallel to the page it is shown by a pair of lines, without arrowheads for a simple mirror and with one or more arrowheads (or an additional arrow ) to indicate the direction of a glide operation. To show the height of a plane above the base of the cell, its fractional distance will be given. 

The ledge has zero dislocation character. A detailed discussion of the topological basis of these different types of line defects is given by Sutton and Balluffi [2]. 

The T2 relaxation times of 50 /rsec and 40 msec given in the preceding discussion correspond to line half-widths of 6.4 kHz and 8 Hz, respectively. Whipple et al. (265) concluded that the line widths of several hundred Hz which are obtained in practice must be due to bulk magnetic susceptibility effects. This type of line broadening is removable by MAS (273) and they were the first to obtain high resolution spectra with linewidths similar to those expected from the T2 values. 

Continuation of this process quickly becomes dreadfully complicated because of the severe overlap of signals. Many of the correlations have been drawn in with different types of lines for each of the different residues in the expanded view. The reader is invited to trace some of these correlations but cautioned to be wary of frustration. 

For = 90°, this ratio is 1 and we see all four lines equally in each row (16 peaks in all in the crosspeak, Fig. 9.33, lower left). For = 35°, the ratio is 0.1 (1 to 10) lines 3 and 4 are only 10% of the intensity of lines 1 and 2 (eight intense peaks in all in the crosspeak, Fig. 9.33 lower right). Some people use a 45° pulse ( COSY-45 ), for a ratio of 0.17 (1 to 5.8). As we make smaller, we pay a price in overall intensity since both types of line are multiplied by sin2 although the ratio gets better as the overall sensitivity goes down. This analysis illustrates the power of product operators as well as the need to look ahead and anticipate which terms will be important to avoid an explosion of complexity. 

Pourbaix diagrams are plots of (reversible) potential vs. pH for elements in pure water. They consist of regions of stability defined by lines as borders. Three types of lines exist on Pourbaix diagrams. Horizontal lines describe reactions that are dependent only on potential (e.g., Fe = Fe2+ + 2e ). Vertical lines describe reactions that are dependent only on pH (e.g., Fe2+ + 20H = Fe(OH)2). Angled lines correspond to reactions that depend on both potential and pH (e.g., 02 + 4H+ + 4e = 2H20). 

Figure 10 -pH diagram for Cu showing all three types of lines along with the effects of dissolved copper concentration. 

A reversible minor displacive transformation of tetrahedral atoms can reduce the symmetry of the ZSM-5 framework to monoclinic, and thus make the appearance of the additional lines in the powder pattern possible. The observation of this type of line splitting in XRD patterns of ZSM-5 thus provides insights into subtle framework motions. 

Liquid Type of line Optimum pressure gradient, ( Pm)opt. Pa/ Ti Velocity limit, m/s... 

Fig. 14. Absorbance-concentration curves obtained with aqueous lithium solutions. Note the difference in sensitivities depending on the type of line source (from reference (M3) by courtesy Perkin-Elmer Corporation).

This asymmetry provides a clear and simple criterion for differentiating between the two types of line broadening. It can be explained in the following way. Following excitation by the first pulse, the coherent polarizations of the subsystems (of an inhomogeneous system) assume their natural frequencies... 

This is what accounts for the discrete values of frequency v in emission spectra of atoms. Absorption spectra are correspondingly associated with the annihilation of a photon of the same energy and concomitant excitation of the atom from En to Em Fig. 1.9 is a schematic representation of the processes of absorption and emission of photons by atoms. Absorption and emission processes occur at the same set frequencies, as is shown by the two types of line spectra in Fig. 1.7. 

Figure 1.7 Continuous spectrum and two types of line spectra. From http // cseplO.phys.utk.edu/astr162/lect/light/absorption.html...

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