The Cluster Spatio-Temporal Analysis of Field Fluctuations (STAFF) Experiment

The Spatio-Temporal Analysis of Field Fluctuations (STAFF) experiment is one of five experiments which together comprise the Wave Experiment Consortium (WEC). STAFF consists of a three-axis search coil magnetometer to measure magnetic fluctuations at frequencies up to 4 kHz, and a spectrum analyser to calculate in near-real time aboard the spacecraft, the complete auto- and cross-spectral matrices using the three magnetic and two electric components of the electromagnetic field. The magnetic waveform at frequencies below either 10 Hz or 180 Hz is also transmitted. The sensitivity of the search coil is adapted to the phenomena theo be studied: the values 3 × 10^-3 nT Hz^-1/2 and 3 × 10^-5 nT Hz^-1/2 are achieved respectively at 1 Hz and 100 Hz. The dynamic range of the STAFF instruments is about 96 dB in both waveform and spectral power, so as to allow the study of waves near plasma boundaries. Scientific objectives of the STAFF investigations, particularly those requiring four point measurements, are discussed. Methods by which the wave data will be characterised are described with emphasis on those specific to four-point measurements, including the use of the Field Energy Distribution function.     

顾及多路径误差改正的GNSS大坝形变监测研究

在GPS短基线相对定位中,可以根据多路径误差周期约为1天的重复性特点建立误差模型,采用坐标域或观测值域滤波的方法进行多路径误差改正.北斗系统由GEO、IGSO和MEO三种卫星类型组成,其中MEO卫星类型接近7天的轨道周期与GEO和IGSO约为1天的轨道周期差异较大,因此对北斗观测值进行多路径误差改正时只能采用观测值域滤波方法.本文以某水库大坝形变监测网为例,对GPS和BDS观测值分别建立多路径误差模型,根据各自卫星轨道周期进行多路径误差改正,结果表明经改正后大坝形变监测精度有较大提高.     

航天器资源约束的时间拓扑排序处理方法

针对航天器自主任务规划中的资源受限、约束复杂、活动并行等问题,提出了基于时间拓扑排序的航天器资源计算方法。考虑规划结果中资源产生及消耗,采用资源约束网络模型表示规划中动作的资源需求。通过分析资源变化与动作执行时间的关系,在资源处理过程中对资源约束网络的资源突变时刻进行拓扑排序,优化了流量推进路径的选择过程,时间复杂度为O(n 2 )。数值仿真结果表明,算法提高了规划过程中资源处理的效率。     

航天器零推进剂姿态机动启发式规划方法

针对零推进剂姿态机动约束耦合,导致规划效率低的问题,提出一种基于约束评价启发式的差分进化算法.基于零推进剂姿态机动约束分析,在规划空间中建立约束评价函数,对航天器约束和控制力矩陀螺约束进行解耦分类处理.设计基于约束评价函数的启发式策略,用于改进差分进化算法的种群变异,主动控制规划进程,引导零推进剂姿态机动规划序列满足多...     

新型含铜催化剂对RDX／HTPB推进剂燃速影响的研究

用热分析方法筛选出两含铜催化剂对ＲＤＸ／ＨＴＰＢ推进剂进行了配方试验研究，采用声发射法测定４－８ＭＰａ条件下药条燃速，由实验结果可看出：这两种新型含铜催化剂对提高燃速，降低燃速压强指数有明显效果；燃速提高４２％，压强指数降低１４％，经适当组合，可进一步提高燃速，降低燃速压强指数。     

Radiation analysis for manned missions to the Jupiter system.

An analysis for manned missions targeted to the Jovian system has been performed in the framework of the NASA RASC (Revolutionary Aerospace Systems Concepts) program on Human Exploration beyond Mars. The missions were targeted to the Jupiter satellite Callisto. The mission analysis has been divided into three main phases, namely the interplanetary cruise, the Jupiter orbital insertion, and the surface landing and exploration phases. The interplanetary phase is based on departure from the Earth-Moon L1 point. Interplanetary trajectories based on the use of different propulsion systems have been considered, with resulting overall cruise phase duration varying between two and five years. The Jupiter-approach and the orbital insertion trajectories are considered in detail, with the spacecraft crossing the Jupiter radiation belts and staying around the landing target. In the surface exploration phase the stay on the Callisto surface is considered. The satellite surface composition has been modeled based on the most recent results from the GALILEO spacecraft. In the transport computations the surface backscattering has been duly taken into account. Particle transport has been performed with the HZETRN heavy ion code for hadrons and with an in-house developed transport code for electrons and bremsstrahlung photons. The obtained doses have been compared to dose exposure limits.     

SPRI: simulator of polarimetric radar images

Simulator of polarimetric radar images (SPRI) consists of a suite of image processing programs for producing realistic millimeter-wave (MMW) radar images artificially on a workstation. The heart of the simulation approach is a polarimetric Rayleigh clutter simulator coupled to a clutter database. The simulator produces high resolution single-look polarimetric images. Hard targets can then be embedded into this clutter map, and the resultant image can be degraded in resolution, number of looks, polarization, etc. to match that which would be observed by a real sensor. Examples of simulated images, and comparisons of these simulations to actual images, are presented. The MMW Clutter Database is the most comprehensive to-date database of over 3500 Mueller matrices for many kinds of terrestrial clutter measured at 35 and 95 GHz, many of which are at incidence angles close to grazing. The database can be accessed via a World Wide Web flexible interface that enables data to be combined in new and unique ways specified by the user, and displayed in either tabular or graphical format. The structure and access procedure to the database are described     

弹性飞机平衡的阵风外载荷计算与分析

连续紊流是适航规范中阵风载荷分析必须考虑的一种阵风模型,但其引起的阵风载荷在飞机结构设计中的应用一直存在困难.在平稳随机过程的假设下,基于von Karman连续紊流功率谱模型和线性系统连续紊流响应的功率谱方法,使用载荷累加法获得外载荷形式的阵风载荷.在此基础上,通过引入载荷响应的相关性推导并建立了一种生成多组连续紊流平衡外载荷分布的方法.垂向连续紊流情况下的算例结果表明:连续紊流外载荷分布是全机平衡的.平衡的外载荷分布可通过机动飞行载荷分析中的载荷包线方法识别载荷设计情况,从而应用于飞机结构的强度分析与设计.     

基于CWT-CNN的齿轮箱运行故障状态识别

针对传统故障诊断中提取的特征不具有自适应能力、很难匹配特定故障的问题,提出了一种基于连续小波变换(CWT)和二维卷积神经网络(CNN)的齿轮箱故障诊断方法.该方法对齿轮箱故障振动信号采用连续小波变换构造其时频图,以其为输入构建卷积神经网络模型,通过多层卷积池化形成深层分布式故障特征表达.利用反向传播算法调整网络各层的结...