47,798 research outputs found

    The Temptation and Fall of Original Understanding

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    Review of: The Tempting of America: The Political Seduction of the Law, by Robert H. Bork (Free Press, 1990

    Beyond social engineering: A strategy for fostering institutional creativity in developing country river basins

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    Challenges in Managing the New Diverse Labor Force

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    Among the purposes of this chapter is (1) to examine past and present statuses of demographic groups who earlier suffered discrimination in employment but who today are legally protected. Our purpose is then (2) to appraise the issue of perceptions of fairness and equality, and next (3) to discuss problems still existing in the labor market in achieving “equality” under the law. Finally (4) we will offer some proposals for meeting still existing shortcomings. Because space requirements prohibit a discussion of all these groups, we are focusing on two of the largest: women and African-Americans

    Transition stages of Rayleigh–Taylor instability between miscible fluids

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    Direct numerical simulations (DNS) are presented of three-dimensional, Rayleigh–Taylor instability (RTI) between two incompressible, miscible fluids, with a 3:1 density ratio. Periodic boundary conditions are imposed in the horizontal directions of a rectangular domain, with no-slip top and bottom walls. Solutions are obtained for the Navier–Stokes equations, augmented by a species transport-diffusion equation, with various initial perturbations. The DNS achieved outer-scale Reynolds numbers, based on mixing-zone height and its rate of growth, in excess of 3000. Initial growth is diffusive and independent of the initial perturbations. The onset of nonlinear growth is not predicted by available linear-stability theory. Following the diffusive-growth stage, growth rates are found to depend on the initial perturbations, up to the end of the simulations. Mixing is found to be even more sensitive to initial conditions than growth rates. Taylor microscales and Reynolds numbers are anisotropic throughout the simulations. Improved collapse of many statistics is achieved if the height of the mixing zone, rather than time, is used as the scaling or progress variable. Mixing has dynamical consequences for this flow, since it is driven by the action of the imposed acceleration field on local density differences

    Radiocarbon analysis of modern skeletal remains to determine year of birth and death: a case study

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    To aid in the development of a biological profile for human remains found in Collyhurst, Manchester, England we undertook 14C analysis of tooth enamel, tooth collagen and bone collagen on behalf of Greater Manchester Police. On the basis of the analyses of the teeth, we concluded that the person was born between 1950 and 1954 while on the basis of our analyses of cortical and trabecular bone we estimated the year of death to be between 1969 and 1974. This would make the maximum age range around 15 to 24 years. Analyses of the dentition and other skeletal parameters can eliminate the younger part of the range so an age of around 18 to 24 years at death would seem most likely. The δ13C and δ15N values for the bone collagen were higher than would be expected for someone subsisting on a purely terrestrial diet, implying some consumption of marine resources which could lead to reduced 14C activities. Taking any potential marine effect into account could reduce this age range to around 18 to 21 years

    Inflatable device for installing strain gage bridges

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    Methods and devices for installing in a tubular shaft multiple strain gages are disclosed with focus on a method and a device for pneumatically forcing strain gages into seated engagement with the internal surfaces of a tubular shaft in an installation of multiple strain gages in a tubular shaft. The strain gages or other electron devices are seated in a template-like component which is wrapped about a pneumatically expansible body. The component is inserted into a shaft and the body is pneumatically expanded after a suitable adhesive was applied to the surfaces

    A Generalized Method for Automatic Downhand and Wirefeed Control of a Welding Robot and Positioner

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    A generalized method for controlling a six degree-of-freedom (DOF) robot and a two DOF positioner used for arc welding operations is described. The welding path is defined in the part reference frame, and robot/positioner joint angles of the equivalent eight DOF serial linkage are determined via an iterative solution. Three algorithms are presented: the first solution controls motion of the eight DOF mechanism such that proper torch motion is achieved while minimizing the sum-of-squares of joint displacements; the second algorithm adds two constraint equations to achieve torch control while maintaining part orientation so that welding occurs in the downhand position; and the third algorithm adds the ability to control the proper orientation of a wire feed mechanism used in gas tungsten arc (GTA) welding operations. A verification of these algorithms is given using ROBOSIM, a NASA developed computer graphic simulation software package design for robot systems development

    Real time flight simulation methodology

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    An example sensitivity study is presented to demonstrate how a digital autopilot designer could make a decision on minimum sampling rate for computer specification. It consists of comparing the simulated step response of an existing analog autopilot and its associated aircraft dynamics to the digital version operating at various sampling frequencies and specifying a sampling frequency that results in an acceptable change in relative stability. In general, the zero order hold introduces phase lag which will increase overshoot and settling time. It should be noted that this solution is for substituting a digital autopilot for a continuous autopilot. A complete redesign could result in results which more closely resemble the continuous results or which conform better to original design goals

    Non-compliance with randomised allocation and missing outcome data in randomised controlled trials evaluating surgical interventions : a systematic review

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    Acknowledgements JAC held MRC training (reference number: G0601938) and methodology (reference number: G1002292) fellowships while this research was undertaken. The Health Services Research Unit is core funded by the Chief Scientist Office of the Scottish Government Health and Social Care Directorates. The authors accept full responsibility for this manuscript.Peer reviewedPublisher PD
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