Disk-shaped

The physics of ultrasound is well known and widely described in many publications. Recording amplitudes from model reflectors at different depths by Dr. Josef Krautkramer in 1959 led to the DGS-diagram Echo amplitudes from disk shaped reflectors of different sizes were... 

The measuren.cnts are performed on a sample made from Inconell IN 718 placed at our disposal by Me oren- und Turbinen-Union Miinchen GmbH (MTU). The sample is of disk shape and has a curved side and a flat side, see also fig. 6. On the curved side MTU had detected a segregation reaching to the surface but with unknown depth. It had been detected by segregation etching and its existence was confirmed by eddy current testing. Both methods are successful only in such a special case where the segregation extends to the surface. 

Figure 4.6 The growth of disk-shaped crystals, (a) All crystals have been nucleated simultaneously. All crystals have the same radius rt after an elapsed time t. (b) Nucleation is sporadic. Crystal A has had enough time to reach point X, while B has not, although both originate in the same ring a distance r from x.

Depending on the method of data read-out, respectively read-in/read-out, two systems are distinguished mechanooptical systems with usually disk-shaped media (optical disks), and purely optical systems with card-shaped media without moving parts (optical memory cards). 

Compared to photographic films, BR is handicapped due to its very low light sensitivity. Also, as a possible material for disk-shaped digital optical information storage, BR does not offer an advantage over estabUshed magnetooptical materials ia spite of its higher line resolutioa, because ia both cases... 

High demands are placed on the substrate material of disk-shaped optical data storage devices regarding the optical, physical, chemical, mechanical, and thermal properties. In addition to these physical parameters, they have to meet special requirements regarding optical purity of the material, processing characteristics, and especially in mass production, economic characteristics (costs, processing). The question of recyclabiUty must also be tackled. 

Discotic Phases. Molecules which are disk-shaped rather than elongated also form thermotropic Hquid crystal phases. Usually these molecules have aromatic cores and six lateral substituents, although the predominance of six lateral substituents is solely historical molecules with four lateral substituents also can form Hquid crystal phases. Although the flatness of these molecules creates a steric effect promoting alignment of the normal to the disks, the fact that disordered side chains are also necessary for the formation of these phases (as is often the case for Hquid crystallinity in elongated molecules) should not be ignored. 

Disk-shaped molecules based on a metal atom possess discotic Hquid crystal phases. An example is octasubstituted metaHophthalocyanine. FiaaHy, metallomesogens which combine both rod-like and disk-like features iato a single molecule adopt the biaxial nematic phase. In addition to there being a preferred direction for orientation of the longest molecular axis as is tme for the nematic phase, perpendicular to this direction is another preferred direction for orientation of the shortest molecular axis (12). NonmetaHomesogens which combine both rod- and disk-like features iato a single molecule also adopt a biaxial nematic phase, but at least ia one case the amount of biaxiaHty is very small (15). 

Shape anisotropy is related to the magnetostatic energy of a magnet. A needle-shaped sample tends to line the atomic moments along the needle axis and a disk-shaped sample tends to line these moments parallel to the disk surface. 

Particle shape is also important. Disk-shaped as well as cylindrical-shaped conductors have a high response because large induced current loops are formed. Small randomly shaped conductors, such as those present in cmshed slag, also respond favorably. Sphere-shaped particles generate small-current loops, however, and do not have a high response. Multiple-current loops occur in conductors that have irregular bends, producing counteractive forces that tend to nullify each other. 

The basic single-angle interval light-scattering method caimot accurately measure individual red blood cell or platelet volumes, but it can provide MCV and MPV. Red cells are bi-concave disks, and platelets ate rod to disk shaped Scattering intensities depend on the orientation in the flow cell. 

Configurations of interest are those using disk-shaped samples cut from crystals in orientations that permit plane waves of uniaxial strain to propagate through their thickness when a uniform load is applied to their face. When the diameter of the disk is sufficiently large in comparison to its thick-... 

FIG. 16 Phase diagram of fluid vesicles as a function of pressure increment p and bending rigidity A. Solid lines denote first-order transitions, dotted lines compressibility maxima. The transition between the prolate vesicles and the stomatocytes shows strong hysteresis efifects, as indicated by the error bars. Dashed line (squares) indicates a transition from metastable prolate to metastable disk-shaped vesicles. (From Gompper and KroU 1995 [243]. Copyright 1995 APS.)... 

Yoshitome et al. (Y2) examined mass transfer from single samples of benzoic acid suspended in an air-water bubble-column. Spherical, cylindrical, and disk-shaped samples of diameters from 25 to 75 mm were used,... 

In the nucleosome, the DNA is supercoiled in a left-handed helix over the surface of the disk-shaped histone octamer (Figure 36-2). The majority of core histone proteins interact with the DNA on the inside of the supercoil without protruding, though the amino terminal tails of all the histones probably protrude outside of this structure and are available for regulatory covalent modifications (see Table 36-1). 

One of the attractive features of SECM is that the UME tip response is based on well-established electrochemical principles, making the technique quantitative. This aspect of SECM can be illustrated by considering the case of simple diffusion-limited electrolysis at an amperometric disk-shaped tip. When the tip is positioned a long way from the target... 

All the simulations reported in this chapter relate to a disk-shaped UME, characterized by RG = 10, which is typical of the probes used in SECM experiments and for most previous theoretical treatments. 

Assuming that the orifice is disk-shaped, one can calculate the steady-state diffusion-limiting current to a pipette from Eq. (1). However, current values about three times higher than expected from Eq. (1) were measured for interfacial IT [18] and ET [5]. The following empirical equation for the limiting current at a pipette electrode was proposed [18bj ... 

Thus the time during which the transport process attains the steady state depends strongly on the radius of the sphere r0. The steady state is connected with the dimensions of the surface to which diffusion transport takes place and does, in fact, not depend much on its shape. Diffusion to a semispherical surface located on an impermeable planar surface occurs in the same way as to a spherical surface in infinite space. The properties of diffusion to a disk-shaped surface located in an impermeable plane are not very different. The material flux is inversely proportional to the radius of the surface and the time during which stationary concentration distribution is attained decreases with the square of the disk radius. This is especially important for application of microelectrodes (see page 292). 

Another typical example of inhomogeneity in rheometry is the oxidation of a polymer in a rotational rheometer in which a disk-shaped sample is held between metal fixtures. The oxygen enters the sample through the free surface (at the outer diameter) and diffuses radially inwards. The result is a radial gradient in properties which changes with time. If the reaction with oxygen results in... 

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