Day Of The Dead

Anthropolog

Providing More Effective and Efficient Casino RFPs

The proliferation of gaming has required governmental entities to become more efficient in the selection of new gaming operators. The Request for Proposal (RFP) process has become the accepted method for selecting operators in new jurisdictions. However, the development of this process has been, and continues to be, evolving; more recent RFPs have learned from the mistakes made in earlier ones. The authors discuss how to make the RFP process more effective and efficient by analyzing the mistakes made in previous RFPs. They provide recommendations on how to structure the initial RFP and about what information should be contained in all RFPs

Self-consistent determination of the perpendicular strain profile of implanted Si by analysis of x-ray rocking curves

Results of a determination of strain perpendicular to the surface and of the damage in (100) Si single crystals irradiated by 250-keV Ar+ ions at 77 K are presented. Double-crystal x-ray diffraction and dynamical x-ray diffraction theory are used. Trial strain and damage distributions were guided by transmission electron microscope observations and Monte Carlo simulation of ion energy deposition. The perpendicular strain and damage profiles, determined after sequentially removing thin layers of Ar+-implanted Si, were shown to be self-consistent, proving the uniqueness of the deconvolution. Agreement between calculated and experimental rocking curves is obtained with strain and damage distributions which closely follow the shape of the trim simulations from the maximum damage to the end of the ion range but fall off more rapidly than the simulation curve near the surface. Comparison of the trim simulation and the strain profile of Ar+-implanted Si reveals the importance of annealing during and after implantation and the role of complex defects in the final residual strain distribution

Temperature Dependent Viscous Drag in Close-packed Metals

The influence of viscous drag on dislocation motion in close-packed metals is examined. Three experimental measurements of the viscous drag are discussed, i.e. internal friction, strain rate versus stress, and stress-time-displacement measurements. Experimental results of each of these methods are compared. Theories of dislocation-phonon and dislocation-electron interactions leading to viscous drag are briefly described. The experimentally-determined dislocation drag coefficient is qualitatively in agreement with the predictions of damping through dislocation-phonon interactions. It is concluded that additional theoretical work is needed for a quantitative comparison of theory and experiment. Additional experimental work to determine the temperature dependence of the drag coefficient below 66°K is needed to resolve discrepancies in different theories of the dislocation-electron interaction

On the measurement of dislocation damping forces at high dislocation velocity

In direct mobility experiments in single crystals, dislocation velocity is studied as a function of stress by the application of short-duration stress pulses. The stress pulse consists of a loading wave, followed microseconds later, by an unloading wave. At high velocities, dislocation inertia effects become important if the dislocation damping force is a decreasing function of dislocation velocity. In general, the magnitude of this force can be determined only if the relative velocity between the applied stress wave and the dislocation is considered

Experimental Measurement of the Drag Coefficient

The drag coefficient is related to the dissipative viscous force which acts on a dislocation in motion, The magnitude of the drag coefficient for a dislocation of known Burgers vector is determined by measurement of the viscous force at a known dislocation velocity, or by measurement of the energy dissipation brought about by the viscous force. We discuss here these measurements and explore the special conditions which make possible the determination of the drag coefficient

An experimental study of the mobility of edge dislocations in pure copper single crystals

The velocity of edge dislocations in 99.999% pure copper crystals has been measured as a function of stress at temperatures from 66°K to 373°K by means of a torsion technique. The range of resolved shear stress was 0 to 15 megadynes/cm^2 for seven temperatures (66°K, 74°K, 83°K, 123°K, 173°K, 296°K, 373°K). Dislocation mobility is characterized by two distinct features: (a) relatively high velocity at low stress (maximum velocities of about 9000 cm/see were realized at low temperatures), and (b) increasing velocity with decreasing temperature at constant stress. The relation between dislocation velocity and resolved shear stress is: v=v_0(τ_r)/τ_0)^n, where v is the dislocation velocity at resolved shear stress τ_r, v_o is a constant velocity chosen equal to 2000 cm/sec, τ_0 is the resolved shear stress required to maintain velocity v_0, and n is the mobility coefficient. The experimental results indicate that τ_0 decreases from 16.3 × 10^6 to 3.3 × 10^6 dynes/cm^2 and n increases from about 0.9 to 1.1 as the temperature is lowered from 296°K to 66°K. The experimental dislocation behaviour is qualitatively consistent with an interpretation on the basis of phonon drag

Comments on the Measurement of Dislocation Mobility and the Drag Due to Phonons and Electrons

Experimental methods for the measurement of intrinsic interactions between moving dislocations and the crystal lattice are considered. It is emphasized that the stress pulse method is applicable at stress levels greater than about twice the static flow stress, while internal friction experiments may be used to explore the interaction at very low stress levels and small dislocation velocities. Recent results of low temperature stress pulse measurements in Cu are presented. The interactions deduced from measurements between 4.2°K and 400°K in some FCC metals are compared to theoretical predictions. Suggestions are made for future theoretical and experimental work on unresolved aspects of the intrinsic interactions