天基雷达观测空间碎片的研究现状及关键技术分析

文章针对空间碎片观测中尚未得到确切观测数据的危险碎片的观测需求,综合分析了国内外的研究水平和现状,对天基雷达观测的需求和关键技术开展研究,提出了天基空间碎片观测有三个关键技术需要解决,即如何确定雷达工作体制和平台轨道以提高观测效率,如何有效探测尺度只有几个毫米-几个厘米的细小目标,如何对观测到的空间碎片进行分类和精确定轨。     

复杂背景下磨粒显微图像分割

针对DMAS系统中复杂背景下磨粒图像的自动分割问题，根据磨粒图像的相关特征，充分利用领域知识，基于图像分割和边界跟踪的思想，选取了适合磨粒图像分割的最大类间方差阈值法，并结合腐蚀、膨胀等图像处理技术，实现了复杂背景下磨粒图像的有效分割和目标提取。最后算例表明了本方法的简洁有效性。本文研究将对进一步展开磨粒识别和机械设备故障诊断研究工作提供前提和依据。     

应用微机校定三相变压器的联结组及标号

三相变压的联结组标号对其正常运行极为重要，必须校定，而目前变还缺少全面快捷的校定方法和设备。本文介绍采用微机系统来实现联结组桔的校定，首先把四类联结组差别区分开，然后分析指出同一类联结组中，除有六种正序标号外，存在六种逆序标号，提出用新的筛选法能简捷地判别校定同一类的十二种标号，当微机系统进行实际测试时，必须考虑电源电压三相不对称程序的影响，故经数学推导得出用实测计算值代替理想计算值作判别比较的基     

测量数据部分丢失的非线性系统迭代学习控制

研究非线性离散系统的迭代学习控制．利用并行分配补偿方法(PDC)确定非线性系统的T-S模型,把非线性模型特换为局部线性模型。假定数据丢失的概率已知,采用满足Bernoulli分布的序列来描述测量数据的丢失,研究具有测量数据部分丢失的线性离散系统的迭代学习控制器的设计。结合T-S模型设计了数据丢失的迭代学习控制器,所设计的迭代学习控制器具有期望收敛特性和二次型性能指标。仿真结果表明了该设计方法的有效性。     

降低陶瓷与陶瓷或金属连接温度的技术

为降低陶瓷与陶瓷或金属的连接温度，目前采用的连接方法有过渡液相扩散连接、兰固态连接、机械连接、粘接、铟封和陶瓷表面低温改性后低温钎焊等。本文从上述连接方法的原理设计、连接材料设计与制备、接头性能及各自的优缺点等方面综述了陶瓷与陶瓷或金属低温连接研究的现状。     

渐近展开匹配法在跨音速钝头薄翼型绕流分析中的应用

一、引言 众所周知,钝头翼型的头部区域对均匀来流的扰动不再是小量,该处流动不符合小扰动假设。因此,由跨音速小扰动方程得出的解在头部区域失效。本文将流场分为外部解区,内外解区及头部附近的内内解区（见图1）。     

三连杆平面欠驱动机械臂系统的最优运动规划

研究了在两固定端点之间运动的三连杆平面欠驱动机械臂的最优运动规划问题.该机械臂有两个受驱动的移动关节,而第三个关节是一个既无驱动器又无制动器的被动关节.施加在自由运动连杆上的动力学约束是一个二阶非完整约束.通过坐标和输入变换,系统的状态和输入变量被表示为子状态变量的高阶导数形式;通过这些新的子状态变量,将一个受约束的动力学优化问题变成一个无约束的优化问题.利用变分法原理,推导出满足优化问题的必要条件.给出了PPR型平面欠驱动机械臂最优运动规划的数值算例.      

A biophysical model for estimating the frequency of radiation-induced mutations resulting from chromosomal translocations.

Gene mutations can be induced by radiation as a result of chromosomal translocations. A biophysical model is developed to estimate the frequency of this type of mutation induced by low-LET radiation. Mutations resulting from translocations are assumed to be formed by misrejoining of two DNA double strand breaks (DSB), one within the gene and one on a different chromosome. The chromosome containing the gene is assumed to occupy a spherical territory and does not overlap spatially with other chromosomes. Misrejoining between two DSB can occur only if the two DSB are closer than an interaction distance at the time of their induction. Applying the model to mutations of the hprt gene induced in G0 human lymphocyte cells by low-LET radiation, it is calculated that mutations resulting from translocations account for about 14% of the total mutations. The value of the interaction distance is determined to be 0.6 micrometers by comparing with the observed frequency of translocations in the X-chromosome.     

Measurements of upper atmosphere wind and temperature from meteorological rocket experiments during winter 1979

This institute conducted a series of meteorological rocket experiments for the upper-atmospheric sounding in the winter of 1979. Within the overlap altitude range with balloon flights, a comparison of the results with the standard radiosonde data indicated that the rocket-borne system was reliable. The measurements from foru rocket flights for the region between 20 and 30 km showed a degree of compatibility to each other while those for above 30 km differed considerably from one another. At low latitude, the temperature profiles in the winter stratosphere in general showed a reasonably good agreement with the U.S. Standard Atmospheric Supplements, 1966 (USSAS 66). A temperature of 2–24°C lower than the USSAS 66, however, was recorded in the lower mesosphere. Above 30 km the maximum diurnal variation in temperature was 9°C or so. In the winter, the wind profile showed the westerlies and the maximum wind velocity of 92.1 Msec^?1 was obtained from these experiments at the height of 60 km.     

Design optimization for asymmetrical ZVS-PWM zeta converter

In this paper, a new soft-switching Zeta converter with an asymmetrical pulsewidth modulation (PWM) control is proposed. The proposed Zeta converter has the features of constant frequency operation, zero voltage switching (ZVS), and low voltage stress on the active switches. Moreover, it can achieve high power density, high efficiency, low switching loss, and low component count, which make converter operation at low to medium power level feasible. Operational principle of the Zeta converter is presented in detail, and a specific example is designed and implemented to verify its feasibility.