Thermal Noise in Amplitude Comparison Monopulse Systems

In this paper we consider the problem of estimation of angle of arrival in an Amplitude Comparison Monopulse antenna arrangement with the explicit inclusion of internally generated thermal, i.e., receiver, noise as an interference to the desired measurement. A pulsed type radar is assumed, and an ideal (i.e., point) radar target is postulated. This latter restriction is made so that consideration of the effects of target scintillation, glint, or other external random phenomena can be excluded from our treatment of the problem. In this context, a maximum likelihood analysis is made to determine the form of the estimate of angle of arrival, and the probability density function (pdf) of this quantity is computed. The form of the estimate is found to be a ratio of Gaussian variables quite like that used in conventional monopulse signal processing. The pdf obtained for the estimate is believed to be new, and it serves to emphasize the bias and indeterminate variance effects associated with this type of nonlinear signal processing. Some useful approximations to the pdf are discussed, and a unit of precision for the estimate is defined.     

Retrieval of a wind profile from the Galileo Probe telemetry signal

Ultrastable oscillators onboard the Galileo Probe and Orbiter will permit very accurate determinations of the frequency of the Probe's telemetry signal as the Probe descends from a pressure level of several hundred mb to a level of about 20 bars. Analysis of the time-varying frequency can provide, in principle, a unique and important definition of the vertical profile of the zonal wind speed in the Jovian atmosphere. In this paper, we develop a protocol for retrieving the zonal wind profile from the Doppler shift of the measured frequency; assess the impact of a wide range of error sources on the accuracy of the retrieved wind profile; and perform a number of simulations to illustrate our technique and to assess the likely accuracy of the retrieval.Because of unavoidably large uncertainties in the absolute frequencies of the oscillators, we use time-differenced frequencies in our analysis. Nevertheless, it is possible to recover absolute wind speeds as well as wind shears, since the Orbiter/Probe geometry changes significantly during the Probe relay link. We begin with the full relativistic Doppler shift equation. Through the use of power series expansions and a basis function representation of the wind profiles, we reduce the basic equation to a set of linear equations that can be solved with standard linear least-squares techniques.There are a very large number of instrumental and environmental factors that can introduce errors into the measured signal or to the recovery of zonal winds from the data. We provide estimates of the magnitudes of all these error sources and consider the degree to which they may be reduced by a posteriori information as well as the results of calibration tests. The most important error source is the a posteriori uncertainty in the Probe's entry longitude. The accuracy of the retrieved winds is also limited by errors in the Probe's descent velocity, as obtained from atmospheric parameters measured by several Probe experiments, and in the a posteriori knowledge of secular drifts in the oscillators' frequencies during the relay link, due, for example, to aging and radiation damage.Our simulations indicate that zonal winds may be retrieved from the Doppler data to an accuracy of several m s^-1. Therefore, it may be possible to discriminate among alternative models for the basic drive of the zonal winds, since they differ significantly in the implied zonal wind profile.     

论高校医院与全科医学

摘 要 保证高校教职工、大学生的身心健康，是高校医院义不容辞的责任。为此，应探索一条更适合高校实际情况的医疗模式。本文就高校医院应如何为师生员工提供全方位的医疗保健服务进行了初步探讨。     

用于复杂应力状态复合材料性能实验研究的双向加载试验机

介绍了一种用于复合材料板试样作双向加载试验的材料试验机,该试验机由计算机控制,可实现按比例的双向加载,可在4个应力象限內作不同形式的组合应力试验,最大拉伸载荷可达110kN,最大压缩栽荷可达170kN。该试验机的研制成功为复合材料强度理论的研究提供了有利的条件。     

一类多变量MRAC算法的研究

本文应用超稳定性理论证明了由Sobel和Bar—kana等提出的多变量模型参考自适应算法。直接得到了自适应控制信号u_p并且推出了一种δ——校正算法。     

基于建构主义学习理论的CAI系统设计原则

本文论述了以建构主义学习理论为理论基础的CAI系统设计开发的一般性原则。     

我国太阳能应用的可行性分析

本文针对我国推广使用绿色环保能源太阳能的可行性进行了探讨，文章首先介绍了太阳能的产生机制，分析了我国太阳能资源的能量总量和分布情况，讨论了直接利用太阳能的二种途径：光热转换和光电转换，并具体讨论了光热转换和光电转换所涉及的实际技术，具体包括：用于采集太阳能并进行光热转换的集热器、辅助热动力系统、太阳能供暖、太阳能制冷、太阳能热力发电、太阳光发电，介绍了国内外使用太阳能的现状和发展趋势，并对我国地域广大且太阳能资源丰富的西部地区的太阳能开发利用的可行性进行了分析。     

改革英语阅读课堂模式初探

阅读课是一门实践课，而在传统的阅读课教学模式中，教师处于中心位置，重知识传授，轻能力培养。为改变这种状况，尝试探索新的课堂模式，以泛读带动精读，让学生在阅读中亲自感悟阅读技巧，教师的主要任务是给与必要的指导。     

O形密封圈在锥面密封中的结构设计与计算

介绍在两个互相配合的锥面上使用0形密封圈的结构设计与计算。     

US–Russian cooperation in human spaceflight: assessing the impacts

How far the broad security, political and economic goals behind the USA's invitation to Russia to participate in the International Space Station have been achieved is assessed in this synthesis of the views of a range of experts in Russian affairs and US foreign and national security policy. The article covers the impacts of cooperation on the Russian aerospace industrial base, on nonproliferation issues and on overall US–Russian relations. Various themes are identified—such as Russian ambivalence over embracing Western norms—and while the experts agreed on certain subjects, there was no overall unanimity.