Discs, hard

McLafferty, F. W., and Stauffer, D. B. (1992). Registry of Mass Spectral Data, 5th ed. New York Wiley. Magnetic disc, hard disc, or CD-ROM, 220,000 spectra. 

A typical computer system might have three of four different storage media. For example, a personal computer system might have solid state memory, a floppy disc drive, a hard disc drive and a tape back-up unit. Solid state memory provides the high speeds for computations, the floppy disc is useful for swapping data and software, the hard disc provides fast, bulk storage, and the tape back-up unit is required because the hard disc is sealed in its box and its data is vulnerable to malfunction or operator error. It will be noted from Table 9.1 that optical storage systems seem to combine the best properties of floppy disc, hard disc and... 

It has not proved possible to develop general analytical hard-core models for liquid crystals, just as for nonnal liquids. Instead, computer simulations have played an important role in extending our understanding of the phase behaviour of hard particles. Frenkel and Mulder found that a system of hard ellipsoids can fonn a nematic phase for ratios L/D >2.5 (rods) or L/D <0.4 (discs) [73] however, such a system cannot fonn a smectic phase, as can be shown by a scaling... 

Phase Transitions in Non-additive Symmetric Hard Disc Fluids... 

Another example of phase transitions in two-dimensional systems with purely repulsive interaction is a system of hard discs (of diameter d) with particles of type A and particles of type B in volume V and interaction potential U U ri2) = oo for < 4,51 and zero otherwise, is the distance of two particles, j l, A, B] are their species and = d B = d, AB = d A- A/2). The total number of particles N = N A- Nb and the total volume V is fixed and thus the average density p = p d = Nd /V. Due to the additional repulsion between A and B type particles one can expect a phase separation into an -rich and a 5-rich fluid phase for large values of A > Ac. In a Gibbs ensemble Monte Carlo (GEMC) [192] simulation a system is simulated in two boxes with periodic boundary conditions, particles can be exchanged between the boxes and the volume of both boxes can... 

Freezing transitions have been examined in recent years by density functional methods [306-313]. Here we review the results [298] of a modification of the Ramakrishnan-Yussouff theory to the model fluid with Hamiltonian (Eq. (25)) a related study of phase transitions in a system of hard discs in two dimensions with Ising internal states which couple anti-ferromagnetically to their neighbors is shown in Ref. 304. First, a combined... 

The integrals are over the full two-dimensional volume F. For the classical contribution to the free energy /3/d([p]) the Ramakrishnan-Yussouff functional has been used in the form recently introduced by Ebner et al. [314] which is known to reproduce accurately the phase diagram of the Lennard-Jones system in three dimensions. In the classical part of the free energy functional, as an input the Ornstein-Zernike direct correlation function for the hard disc fluid is required. For the DFT calculations reported, the accurate and convenient analytic form due to Rosenfeld [315] has been used for this quantity. 

Adsorption of hard sphere fluid mixtures in disordered hard sphere matrices has not been studied profoundly and the accuracy of the ROZ-type theory in the description of the structure and thermodynamics of simple mixtures is difficult to discuss. Adsorption of mixtures consisting of argon with ethane and methane in a matrix mimicking silica xerogel has been simulated by Kaminsky and Monson [42,43] in the framework of the Lennard-Jones model. A comparison with experimentally measured properties has also been performed. However, we are not aware of similar studies for simpler hard sphere mixtures, but the work from our laboratory has focused on a two-dimensional partly quenched model of hard discs [44]. That makes it impossible to judge the accuracy of theoretical approaches even for simple binary mixtures in disordered microporous media. 

Usually special solids, such as nut shells, limestone, expanded perlite, etc., are added to the drilling muds to fill or clog rock fractures in the open hole of a well. Most of these lost circulation materials can shorten the life of pump parts. They are especially hard on valves and seats when they accumulate on the seats or between the valve body and the valve disc. 

Discs Discs of nickel electroformed on to mandrels bearing grooves modulated with recorded sound have been used for many years for stamping sound recording discs. This process has been adapted and refined for the manufacture of digital records, including video discs . Video disc stampers must be hard, stress-free, and flat to within 0.1 m results of a short investigation directed towards these requirements have been reported ". 

The microcomputer may also be interfaced with most types of electronic equipment used in the laboratory. This facilitates the collection and processing of the data, which may be stored on floppy or hard discs for later use. 

Goglia, P. R., Berkowitz, J., Hoehn, J., Xidis, A., and Stover, L., Diamond-Like Carbon Applications in High Density Hard Disc Recording Heads," Diamond Rel. Mat., Vol. 10, 2001, pp. 271-277. 

Magnetic hard discs are used in computers to store information in the form of magnetic bits on a ferromagnetic alloy film. To protect the magnetic medium, a hard carbon coating about... 

We performed SPEM studies on hard disc coupons covered with lubricant films of different types and thicknesses [70]. No evidence of dewetting was observed with films of submonolayer average thickness (17 A for Zdol and 14 A for Zdol-TX). Dewetting was observed, however, when the film thickness was above one monolayer. The stracture of these films during dewetting differs depending on the type of lubricant. 

Is this an Uncorrelated Hard-Disc Fluid In order to answer this question we compute a 2D CLD and test, whether the function is positive everywhere. In this case the equatorial streak can be considered pure particle scattering. 

Figure 8.37a shows the projected intensity100 as a function of the elongation of the material. The resulting 2D CLDs are presented in Fig. 8.37b. Equatorial streaks are observed from an elongation of e = 1.73. Only at this elongation there are some faint correlations among the microfibrils the CLD becomes slightly negative at r 8 nm. For higher elongation the structure in the fiber cross-section conforms to a hard-disc fluid.

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