改进残存比率法

1.问题的提出 从使用过程得到的故障统计资料常有信息丢失现象,用这种样本进行产品可靠性分析时,残存比率法是有效的工具,并已在实践中得到广泛应用。然而,用文献介绍的公式计算的残存比率和可靠度与真值有较大出入,当删除样品数较大时偏差尤其明显。本文的目的是力图找到发生这种偏差的原因和纠正偏差的方法,使残存比率法更加完善。     

机动目标的逆合成孔径雷达成像

 逆合成孔径雷达(ISAR)和合成孔径雷达 (SAR)都是利用目标 (场景)与雷达的相对运动,提高横向分辨率,实现对目标 (场景 )的成像。SAR的运动方是雷达平台,可控制作平稳飞行,且用仪器测校其偏离误差;ISAR的运动方通常是非合作目标,运动不受控制,且难以精确测量。当目标作机动飞行时,以目标作固定基准,雷达等效地在空间形成流形复杂的逆合成孔径 (阵列 ),对这种情况下成像的问题进行了系统的研究。     

The Coma of Comet 9P/Tempel 1

As comet 9P/Tempel 1 approaches the Sun in 2004–2005, a temporary atmosphere, or “coma,” will form, composed of molecules and dust expelled from the nucleus as its component icy volatiles sublimate. Driven mainly by water ice sublimation at surface temperatures T > 200 K, this coma is a gravitationally unbound atmosphere in free adiabatic expansion. Near the nucleus (≤ 10² km), it is in collisional equilibrium, at larger distances (≥10⁴ km) it is in free molecular flow. Ultimately the coma components are swept into the comet’s plasma and dust tails or simply dissipate into interplanetary space. Clues to the nature of the cometary nucleus are contained in the chemistry and physics of the coma, as well as with its variability with time, orbital position, and heliocentric distance. The DI instrument payload includes CCD cameras with broadband filters covering the optical spectrum, allowing for sensitive measurement of dust in the comet’s coma, and a number of narrowband filters for studying the spatial distribution of several gas species. DI also carries the first near-infrared spectrometer to a comet flyby since the VEGA mission to Halley in 1986. This spectrograph will allow detection of gas emission lines from the coma in unprecedented detail. Here we discuss the current state of understanding of the 9P/Tempel 1 coma, our expectations for the measurements DI will obtain, and the predicted hazards that the coma presents for the spacecraft. An erratum to this article is available at .     

合成射流与横向主流作用的流场数值分析

建立了将合成射流激励器腔体、出口喉道、外部流场作为单连域计算处理的吹/吸型边界模型。在此基础上,对横向主流偏转角及上下壁面压力变化进行了讨论。计算结果表明,激励器布置位置是影响主流偏转角的重要因素,在主流通道内侧,激励器与主流出口之间的上下壁面压力差较大。文中还对两种不同模式下合成射流对主流的控制效果做了比较。     

主动流动控制实验台及测量系统

本文介绍了合成射流机理实验台及测量系统的建立、功能、技术指标和可以开展的工作，并介绍了部分实验结果。     

赣江吴城段底质Cu元素垂直污染分布研究

为建立鄱阳湖水域沉积物中重金属的相关研究方法,了解重金属污染物的迁移规律,并探讨底泥中重金属的垂直分布特征,采用底质柱状采样器通过临水垂直插管法采集鄱阳湖流域赣江吴城段的底质样品,利用微波消解—AS-990型原子吸收分析体系对柱状样中不同深度的样品进行重金属Cu含量的测定。结果显示,柱状样垂直方向和年代分布中Cu含量呈锯齿型分布。重金属垂直分布与年代变化相一致,是因为年代分布与底泥沉积厚度之间的关系主要由沉积率所决定。     

机载聚束式合成孔径雷达的成象处理设计

针对机载聚束式合成孔径雷达工作模式可在小目标范围内实现高分辨力成象的特点，提出了一种以解线性调频技术为核心的，适于聚束式ＳＡＲ成象的灵活高效的信号处理方法和流程。     

单通道SAR实现ATI动目标检测的新方法

研究了采用单通道合成孔径雷达(SAR,Synthetic Aperture Radar)多视沿航迹向干涉(ATI,Along Track Interferometry)实现地面慢速运动目标指示的检测方法.分析了该方法所需的步骤,即利用重叠或不重叠的窗构造子视,对子视分别成像,相位误差校正并求干涉.关于其中起关键作用的相位误差校正步骤,提出了利用信号子空间投影进行相位配准的补偿方法.借助该鲁棒的自适应方法可以从某种程度上解决子图像间的去相关问题,降低相位随机性的影响,从2幅子视图像的干涉相位图上敏锐地检测到运动目标.通过仿真实验,验证了该方法可以有效地从强杂波中检测动目标,为单通道SAR实现地面运动目标指示(GMTI,Ground Moving Target Indication)、扩展已有SAR系统功能提供可靠的途径.      

SYNTHETIC STRESS LIFE TESTING OF MECHATRONIC PRODUCTS UNDER VARIABLE STRESS SPECTRUM

Mechatronic products usually endure the variable stress spectrum when they operate in certain operational condition and environmental condition, which obey the Weibull distribution. In accordance with the features of mechatronic product, this paper analyzes the failure mode, its corresponding sensitive stress and the design principles of life testing profiles. Based on the above analyses, this paper presents a synthetic stress life testing method based on the hybrid Weibull distribution and its statistical method under variable stress spectrum to evaluate the reliability and life indices of mechatronic products. Because the mechatronic products have many characteristics such as high price, long life and small testing samples, the synthetic stress life testing method under variable load spectrum can simulate the real various spectra, decrease the life testing time and reduce the testing samples. So it is effective to carry out the life testing to mechatronic products. The application results of hydraulic pumps indicate that this method can easily handle the experimental data under variable amplitude spectrum, obtain the high precision parameters point estimation and confidence interval estimation and reduce the testing cost greatly.     

分布仿真中视景数据库的构造

详细介绍了视景数据库的构造过程,讨论了构造过程中等距网格和三角形不规则网格两种地形模型的优缺点,文化特征物与地形的三种整合方法和多种细节层次的表示等关键技术,然后阐述了视景调度的算法及其与构造的关系,最后给出在DVENET中实现的一个例子并就视景数据库现在存在的问题及将来的解决方案进行了讨论.