Thermal distortion analysis of a deployable parabolic reflector

A thermal distortion analysis of the ATS-6 Satellite parabolic reflector was performed using NASTRAN level 15.1. The same NASTRAN finite element method was used to conduct a one g static load analysis and a dynamic analysis of the reflector. In addition, a parametric study was made to determine which parameters had the greatest effect on the thermal distortions. The method used to model the construction of the reflector is described and the results of the analyses are presented

Constructions of skew-tolerant and skew-detecting codes

The paradigm of skew-tolerant parallel asynchronous communication was introduced by Blaum and Bruck (see ibid., vol. 39, 1993) along with constructions for codes that can tolerate or detect skew. Some of these constructions were improved by Khachatrian (1991). In this paper these constructions are improved upon further, and the authors prove that the new constructions are, in a certain sense, optimal

Sentencing the Mentally Retarded to Death: An Eighth Amendment Analysis

Today, on death rows across the United States, sit a number of men with the minds of children. These people are mentally retarded. Typical of these individuals is Limmie Arthur, who currently is imprisoned at Central Correctional Institution in Columbia, South Carolina. Although Arthur is twenty-eight years old, all the mental health professionals who have evaluated him, including employees of the South Carolina Department of Corrections, agree he has the mental capacity of approximately a 10-year-old child. Arthur was convicted and sentenced to death for the murder of a neighbor. At his first trial, his court appointed attorneys did not present any evidence regarding Mr. Arthur\u27s mental retardation. Neither the first jury that sentenced Limmie Arthur to death nor the attorneys who represented him in that proceeding knew he was mentally disabled. After his death sentence was reversed by the South Carolina Supreme Court on other grounds, we became involved in the case. A routine psychological assessment revealed Limmie Arthur was mentally retarded. At his second trial, conducted before a judge sitting without a jury, extensive evidence regarding Arthur\u27s mental retardation was presented. After deliberating for approximately one hour, the trial judge sentenced Arthur to death. We suspected that the evidence regarding Arthur\u27s mental retardation may have been misunderstood and that our client may have been sentenced to die not in spite of the fact he was mentally disabled but rather because he was mentally retarded. We immediately filed a motion for reconsideration and reduction of sentence. A hearing was conducted in conjunction with this motion several weeks later to determine whether the execution of any mentally retarded person is inconsistent with the eighth amendment to the United States Constitution. The court, however, refused to modify its prior ruling. Limmie Arthur\u27s case demonstrates in dramatic fashion the current failure of the American criminal justice system to adequately weigh mental retardation in the capital sentencing process. Whether a mentally retarded person such as Limmie Arthur should be sentenced to death is not a proper issue to be resolved by juries and judges on a case-by-case basis. After first describing what it means to be a person with mental retardation, this article will demonstrate that mental retardation is a significant and devastating mental impairment which reduces a mentally retarded person\u27s moral blameworthiness to a level different in kind from other nonretarded persons accused of murder. Thus, the current procedures governing the imposition of the death penalty are inadequate to ensure mental retardation is given the weight it deserves in the sentencing process. Furthermore, this article will attempt to articulate the reasons the death penalty is never an appropriate sentence when imposed upon a person with mental retardation and, thus, constitutes cruel and unusual punishment in violation of the eighth amendment. Finally, this article will set forth the reasons why mental retardation is a mitigating factor that deserves great weight in the capital sentencing process, and therefore, unique procedural protections are necessary in a case involving a mentally retarded defendant

Sentencing the Mentally Retarded to Death: An Eighth Amendment Analysis

Today, on death rows across the United States, sit a number of men with the minds of children. These people are mentally retarded. Typical of these individuals is Limmie Arthur, who currently is imprisoned at Central Correctional Institution in Columbia, South Carolina. Although Arthur is twenty-eight years old, all the mental health professionals who have evaluated him, including employees of the South Carolina Department of Corrections, agree he has the mental capacity of approximately a 10-year-old child. Arthur was convicted and sentenced to death for the murder of a neighbor. At his first trial, his court appointed attorneys did not present any evidence regarding Mr. Arthur\u27s mental retardation. Neither the first jury that sentenced Limmie Arthur to death nor the attorneys who represented him in that proceeding knew he was mentally disabled. After his death sentence was reversed by the South Carolina Supreme Court on other grounds, we became involved in the case. A routine psychological assessment revealed Limmie Arthur was mentally retarded. At his second trial, conducted before a judge sitting without a jury, extensive evidence regarding Arthur\u27s mental retardation was presented. After deliberating for approximately one hour, the trial judge sentenced Arthur to death. We suspected that the evidence regarding Arthur\u27s mental retardation may have been misunderstood and that our client may have been sentenced to die not in spite of the fact he was mentally disabled but rather because he was mentally retarded. We immediately filed a motion for reconsideration and reduction of sentence. A hearing was conducted in conjunction with this motion several weeks later to determine whether the execution of any mentally retarded person is inconsistent with the eighth amendment to the United States Constitution. The court, however, refused to modify its prior ruling. Limmie Arthur\u27s case demonstrates in dramatic fashion the current failure of the American criminal justice system to adequately weigh mental retardation in the capital sentencing process. Whether a mentally retarded person such as Limmie Arthur should be sentenced to death is not a proper issue to be resolved by juries and judges on a case-by-case basis. After first describing what it means to be a person with mental retardation, this article will demonstrate that mental retardation is a significant and devastating mental impairment which reduces a mentally retarded person\u27s moral blameworthiness to a level different in kind from other nonretarded persons accused of murder. Thus, the current procedures governing the imposition of the death penalty are inadequate to ensure mental retardation is given the weight it deserves in the sentencing process. Furthermore, this article will attempt to articulate the reasons the death penalty is never an appropriate sentence when imposed upon a person with mental retardation and, thus, constitutes cruel and unusual punishment in violation of the eighth amendment. Finally, this article will set forth the reasons why mental retardation is a mitigating factor that deserves great weight in the capital sentencing process, and therefore, unique procedural protections are necessary in a case involving a mentally retarded defendant

New interactions in the dark sector mediated by dark energy

Cosmological observations have revealed the existence of a dark matter sector, which is commonly assumed to be made up of one particle species only. However, this sector might be more complicated than we currently believe: there might be more than one dark matter species (for example, two components of cold dark matter or a mixture of hot and cold dark matter) and there may be new interactions between these particles. In this paper we study the possibility of multiple dark matter species and interactions mediated by a dark energy field. We study both the background and the perturbation evolution in these scenarios. We find that the background evolution of a system of multiple dark matter particles (with constant couplings) mimics a single fluid with a time-varying coupling parameter. However, this is no longer true on the perturbative level. We study the case of attractive and repulsive forces as well as a mixture of cold and hot dark matter particles

Vacuum Cherenkov radiation and bremsstrahlung from disformal couplings

The simplest way to modify gravity is to extend the gravitational sector to include an additional scalar degree of freedom. The most general metric that can be built in such a theory includes disformal terms, so that standard model fields move on a metric which is the sum of the space time metric and a tensor constructed from first derivatives of the scalar. In such a theory gravitational waves and photons can propagate at different speeds, and these can in turn be different from the maximum speed limit for matter particles. In this work we show that disformal couplings can cause charged particles to emit Cherenkov radiation and bremsstrahlung apparently in vacuum, depending on the background evolution of the scalar field. We discuss the implications of this for observations of cosmic rays, and the constraints that arise for models of dark energy with disformal couplings

Slow roll inflation in the presence of a dark energy coupling

In models of coupled dark energy, in which a dark energy scalar field couples to other matter components, it is natural to expect a coupling to the inflaton as well. We explore the consequences of such a coupling in the context of single-field slow-roll inflation. Assuming an exponential potential for the quintessence field we show that the coupling to the inflaton causes the quintessence field to be attracted toward the minimum of the effective potential. If the coupling is large enough, the field is heavy and is located at the minimum. We show how this affects the expansion rate and the slow-roll of the inflaton field, and therefore the primordial perturbations generated during inflation. We further show that the coupling has an important impact on the processes of reheating and preheating