基于P89LPC936单片机的锂离子电池组智能充电机设计

为实现对不同标称电压的锂离子电池组的智能充电和容量检测,设计了一种基于P89LPC936单片机的智能充电机,充电控制电路采用IR2181S高低端边缘驱动器实现自动选择充电,能对电池进行快速充电和常规充电,利用电子负载对电池进行恒流放电,并检测电池电压,根据电流积分法计算容量,以此判断电池的老化程度。实验结果表明,该充电机能对标称电压为25.2 V和14.4 V的锂离子电池组实现1 h快速充电和容量检测,测试精度达到了99.8%。     

基于LabWindows/CVI的舵机负载模拟系统设计

基于为地面半物理仿真提供模拟工作状态的需要,针对舵机负载环境的特点,采用分布式控制结构,对舵机负载模拟系统进行设计。基于LabWindows/CVI开发环境,采用多媒体定时器与多线程技术,完成了对上位机与下位机软件系统的设计。基于结构不变性原理,设计了前馈补偿环节,成功抑制了控制过程中产生的多余力,保证了系统的控制精度。结合实践证明,该舵机负载模拟系统在试验中工作良好,动态响应误差不大于5%,控制效果及各项指标均达到了设计要求。     

船舶电力系统断电预防控制的研究

针对船舶电力系统的短路,接地故障、过载、有功或无功负载共享等系统故障引起的全网断电问题,利用一种新的基于观测器的快速减负荷系统,设计了一种负载转矩限制控制器。利用船舶推进器模型建立被控对象的数学模型;引入全波傅式测频算法,并实时的测得电网的频率;最后针对船舶推进器转矩控制进行仿真和分析。仿真结果显示,当观测器测得的频率低于某一限定的频率时,负载转矩限制控制器快速的减少推进器的转矩。     

证券分析师业绩预测和投资评级准确性实证分析

本文以国内证券分析师业的业绩预测和投资评级为研究对象,从投资评级的准确性、投资建议赢利性、业绩预测误差及其来源等几个方面进行了实证分析。研究结果表明,证券分析师的投资建议无论是在短期还是中长期均不能产生显著的超额收益,业绩预测误差是导致投资评级失误的原因之一,而业绩预测误差主要源于分析师对公司层面信息的错误判断。     

Yield condition for circular cylindrical shells made of a fiber-reinforced composite

A yield condition is obtained for circular cylindrical shells made of a definite class of fiber-reinforced composite material whose components possess plastic properties. It is shown that, in the plane of generalized stresses — the axial bending moment and the circumferential force (when the axial force is absent) — the yield curve consists of two linear and four curvilinear sections. By approximating the curvilinear sections, we get a piecewise linear yield condition described by a hexagon in the plane indicated. The nonlinear equations and the corresponding piecewise linear equations of the yield condition for particular cases are given in the form of tables. In solving specific boundary-value problems, we consider a circular cylindrical shell simply supported at its ends and loaded with a uniform internal pressure, for which the load-carrying capacity is determined in relation to the mechanical properties of composite components and some characteristic geometrical parameters. The results of numerical calculations are represented in the form of graphs. __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 5, pp. 655–666, September–October, 2006.     

“神舟”四号中的空间环境研究

空间环境 ,特别是日地空间环境是人类航天活动关系极为密切的环境 .文章以“神舟”四号为背景 ,概要介绍了为“神舟”四号飞船所作的空间环境安全保障服务 ,包括在“神舟”四号飞船上进行的空间环境探测、空间环境分布及变化规律的研究、空间环境对人类航天活动及“神舟”飞船的影响 (空间环境效应 ) ,以及为保障“神舟”飞船发射安全、正常运行、顺利返回所作的空间环境预报等 .此外 ,概要评述了国内外上述研究领域的研究现状与进展     

基于AR(n)模型的卡尔曼滤波模型

考虑到对于处于不同位置的变形监测点,由于它们所处的位置不同,各种环境因素对它们的影响及影响程度也不同,作者预置数个AR(n)模型,通过计算比较,选择剩余标准差最小的AR(n)模型作为初选模型,再将初选的AR(n)模型的模型参数看作包含有动态噪声的状态向量,建立卡尔曼滤波模型.实例分析表明,采用这种方法能够提高模型的拟合精度和预测精度.     

大规模边界元分析的子域并行算法及其工程应用

为了扩大边界元多域分析的计算规模,对边界元子域并行算法进行了研究,针对不同的使用情况研制了不同的算法。算法引入分块技术以解决内存不足的矛盾,引入选主元或局部选主元技术以提高数值稳定性。特别是发展了多机一域算法,可以灵活解决不均匀子域划分的负载平衡问题。数值试验结果和实际工程应用都表明算法是有效的。     

Wavelength-Conversion-Based Protocols for Single-Hop Photonic Networks with Bursty Traffic

WDM star networks using fixed lasers and tunable optical filters are favored by the current state-of-the-art in technology over the other WDM star architectural forms. However, networks of this architectural form suffer from low efficiency when the offered traffic is bursty. Under bursty traffic conditions, it is probable that some wavelengths are idle, while some other wavelengths are overloaded. Therefore, the overall network performance is degraded. In this paper, a new MAC protocol which is capable of operating efficiently under bursty traffic conditions is introduced. According to the proposed protocol an array of tunable wavelength converters is placed at the network hub in order to uniformly distribute the incoming packets to the available wavelengths. In this way, the load is balanced between the wavelengths and consequently, the network performance is improved. The performance of the proposed protocol is studied via analytical and simulation results which indicate that a WDM Star network operating under this protocol achieves a high throughput-delay performance under both bursty and non-bursty traffic conditions.