3,081 research outputs found

    Investigation to define the propagation characteristics of a finite amplitude acoustic pressure wave Final report

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    Aerodynamic noise generation by finite amplitude pressure wave propagation through entropy producing region

    Investigation to define the propagation characteristics of a finite amplitude acoustic pressure wave

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    A theoretical analysis of the propagation characteristics of a finite amplitude pressure wave is presented. The analysis attempts to study the contribution of entropy-producing regions to the mechanism of aerodynamic noise generation. It results in a nonlinear convective wave equation in terms of entropy and a thermodynamic 'J' function. A direct analogy between the derived governing equation and those used in classical literature is obtained. An idealization of the processes considered permits the uncoupling of the equations of motion with a consequent construction of an acoustic analogy treating shock wave emission of finite amplitude acoustic waves. An engineering approach is reflected in the concept of an extended plug nozzle whose function is to facilitate aerodynamic noise attenuation by modifying the entropy-producing regions

    Ab initio parametrised model of strain-dependent solubility of H in alpha-iron

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    The calculated effects of interstitial hydrogen on the elastic properties of alpha-iron from our earlier work are used to describe the H interactions with homogeneous strain fields using ab initio methods. In particular we calculate the H solublility in Fe subject to hydrostatic, uniaxial, and shear strain. For comparison, these interactions are parametrised successfully using a simple model with parameters entirely derived from ab initio methods. The results are used to predict the solubility of H in spatially-varying elastic strain fields, representative of realistic dislocations outside their core. We find a strong directional dependence of the H-dislocation interaction, leading to strong attraction of H by the axial strain components of edge dislocations and by screw dislocations oriented along the critical slip direction. We further find a H concentration enhancement around dislocation cores, consistent with experimental observations.Comment: part 2/2 from splitting of 1009.3784 (first part was 1102.0187), minor changes from previous version

    A whole-bark method of rearing Dryocoetes Confusus SW.

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    On piezophase effects in mechanically loaded atomic scale Josephson junctions

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    The response of an intrinsic Josephson contact to externally applied stress is considered within the framework of the dislocation-induced atomic scale Josephson effect. The predicted quasi-periodic (Fraunhofer-like)stress-strain and stress-current patterns should manifest themselves for experimentally accessible values of applied stresses in intrinsically defected (e.g.,twinned) crystals.Comment: REVTEX (epsf style), 2 EPS figure

    Critical Dynamics of Burst Instabilities in the Portevin-Le Chatelier Effect

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    We investigate the Portevin-Le Chatelier effect (PLC), by compressing Al-Mg alloys in a very large deformation range, and interpret the results from the viewpoint of phase transitions and critical phenomena. The system undergoes two dynamical phase transitions between intermittent (or "jerky") and "laminar" plastic dynamic phases. Near these two dynamic critical points, the order parameter 1/\tau of the PLC effect exhibits large fluctuations, and "critical slowing down" (i.e., the number Ď„\tau of bursts, or plastic instabilities, per unit time slows down considerably).Comment: the published 4-page version is in the PRL web sit

    Life on Death Row

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    The purpose of this chapter is to examine the general conditions for those living on death row in the United States. This examination involves the various restrictions of freedom outside of cell, size and conditions in cells, allowances on personal property, and limits on food and recreation. Special attention is given to discussing the unique relationships that often develop between correctional officers and death row inmates. These relationships are explored through the phenomena of “Hustling” (i.e., any actions taken by an inmate to generate revenue, power, or control over their environment). This type of behavior often is used as a coping mechanism for death row inmates as they deal with their living environment and potential fate. An interesting aspect of this behavior is that it can also serve as a coping mechanism for correctional officers working through the unique demands placed on those working with condemned inmates
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