湍流参数对风扇宽频噪声预测影响

对于现代先进涡扇发动机,占比越来越大的风扇/压气机宽频噪声成为亟需解决的问题。基于三维风扇声源模型,开展了湍流输入参数对宽频噪声预测影响的研究。结果表明:后传声功率级比前传声功率级普遍高5 dB左右;当湍流参数增大时,也会较大幅度改变前传和后传的声功率级,但对频谱形状影响较小;声功率级随湍流积分尺度增大而减小,随背景湍流速度、中心线湍流速度、湍流宽度增大而增大,其中背景湍流速度对宽频噪声影响最大。发现湍流参数通过作用于上洗速度谱来影响宽频噪声预测结果。      

100KV直流标准高压源介绍

输出电压在１０ｋＶ以上的电压源，大多数都是直接用于耐压试验、Ｘ光机电源或其它高压试验装置。其准确度，稳定度指标都很低，一般不能用它对仪器仪表进行检定。本文所介绍的标准高压源，由于应用了许多先进的设计思想、设计线路以及诸如通过光纤直接传递模拟信号控制高压输出等关键技术，使其最终达到了输出电压１０～１０５ｋＶ，２４ｈ稳定度２×１０￣（－５），准确度优于１×１０￣（－４）。同时采用７位数字调节输出，非常符合一般检定人员的操作习惯，可直接用于１０～１００ｋＶ的标准仪表、分压器的检定。     

四频激光陀螺腔体材料及元件

本文介绍了激光陀螺的工作原理及四频激光陀螺的特点。对四频激光陀螺的稳定性与所使用的材料和元件作了论述。     

实战天基激光武器系统设计的技术需求分析

本文系根据美国天基激光武器采购能力和结构研究 (A&AS)项目综述的一篇技术报告。文中分析了空军和导弹防御组织 (BMDO)发展天基激光武器 (SBL)所采取的现行技术途径以及为使实战SBL系统投入战场使用所必需的技术需求。A&AS项目确认了需要大力改进当前技术能力的几个重要技术领域 :发展大型展开式光学系统 ,提高波阵面控制和振动控制能力 ,增加激光器功率。最后讨论了还需改进的远程目标捕获、跟踪和指向控制技术 ,空间飞行器的共性技术 ,建模和仿真 ,以及地面试验技术。     

Cleaning space debris with a space-based laser system

High-energy pulsed laser radiation may be the most feasible means to mitigate the threat of collision of a space station or other valuable space assets with orbital debris in the size range of 1–10 cm. Under laser irradiation, part of the debris material is ablated and provides an impulse to the debris particle. Proper direction of the impulse vector either deflects the object trajectory or forces the debris on a trajectory through the upper atmosphere, where it burns up. Most research concentrates on ground-based laser systems but pays little attention to space-based laser systems.There are drawbacks of a ground-based laser system in cleaning space debris. Therefore the placement of a laser system in space is proposed and investigated. Under assumed conditions,the elimination process of space debris is analyzed. Several factors such as laser repetition frequency, relative movement between the laser and debris, and inclination of debris particles which may exercise influence to the elimination effects are discussed. A project of a space-based laser system is proposed according to the numerical results of a computer study. The proposed laser system can eliminate debris of 1–10 cm and succeed in protecting a space station.     

面向太阳系边际探测的激光通信方案研究

针对我国太阳系边际探测任务需求,提出了利用激光链路进行对地高速信息传输的方案。梳理了深空激光通信的国外发展现状,分析了太阳系边际探测任务的激光链路特点和约束条件,给出了飞行激光终端和激光地面站的初步方案和主要参数,进行了链路预算和影响因素分析,并对我国未来太阳系边际探测任务激光通信的发展进行展望,为我国太阳系边际探测任务的激光通信论证与实施提供参考。     

Fatigue behavior of direct laser deposited Ti-6.5Al-2Zr-1Mo-1V titanium alloy and its life distribution model

The present work aims to investigate the fatigue behavior of Direct Laser Deposition (DLD) Ti-6.5Al-2Zr-1Mo-1V titanium alloy under constant amplitude stress. 22 pieces of DLD Ti-6.5Al-2Zr-1Mo-1V titanium alloy standard cylinder specimens were tested under a stress level of 800?MPa with a stress ratio of 0.06. Fatigue fractography and fatigue life data were obtained. Through the fracture surface analysis, the specimens were divided into two categories in accordance with the location of crack initiation and defect types. Comparison of fatigue life and behavior between two specimen types was given, which was followed by a discussion about the impact of defect type, size and position on the fatigue life of the specimen. The fatigue test results also show a large variation of fatigue life. To illustrate the statistical characteristics of the fatigue life, probabilistic analysis was performed, and a novel bimodal lognormal model was established. The model has a good fit with the experimental data and can reduce the scatter of the fatigue life significantly.     

激光陀螺吸气剂的测试方法研究

激光陀螺谐振腔内部的工作气体纯度直接影响陀螺的光功率输出,吸气剂作为激光陀螺内部维持气体纯度的关键部件,是决定激光陀螺光功率长期稳定性的关键因素。针对激光陀螺对吸气剂的使用需求,提出了一种含振动冲击筛选与质谱检测等手段相结合的综合检测方法,并通过实验对吸气剂的结构强度、吸气性能与激活条件进行了分析。实验结果表明,该方法能够有效地判断某种吸气剂选型是否满足激光陀螺的使用要求,为激光陀螺吸气剂的选择提供指导。     

Spin motion determination of the Envisat satellite through laser ranging measurements from a single pass measured by a single station

The Satellite Laser Ranging (SLR) technology is used to accurately determine the position of space objects equipped with so-called retro-reflectors or retro-reflector arrays (RRA). This type of measurement allows to measure the range to the spacecraft with high precision, which leads to determination of very accurate orbits for these targets. Non-active spacecraft, which are not attitude controlled any longer, tend to start to spin or tumble under influence of the external and internal torques and forces.If the return signal is measured for a non-spherical non-active rotating object, the signal in the range residuals with respect to the reference orbit is more complex. For rotating objects the return signal shows an oscillating pattern or patterns caused by the RRA moving around the satellite’s centre of mass. This behaviour is projected onto the radial component measured by the SLR.In our work, we demonstrate how the SLR ranging technique from one sensor to a satellite equipped with a RRA can be used to precisely determine its spin motion during one passage. Multiple SLR measurements of one target over time allow to accurately monitor spin motion changes which can be further used for attitude predictions. We show our solutions of the spin motion determined for the non-active ESA satellite Envisat obtained from measurements acquired during years 2013–2015 by the Zimmerwald SLR station, Switzerland. All the necessary parameters are defined for our own so-called point-like model which describes the motion of a point in space around the satellite centre of mass.     

复杂装备研制项目的风险源识别

大型复杂装备研制项目高风险与参研单位多的特点使得研制过程中风险传导时有发生。针对风险传导要素风险源的识别问题,提出了一种基于关联规则(AR)与决策实验室分析法(DEMATEL)的风险源识别方法。该方法从数据挖掘的角度,先求解出风险类型与风险因素的关联规则,再求解出风险源之间的影响程度,最后通过DEMATEL得到各风险源相关参数。并且对某参研单位数据库中某阶段的数据用此方法完成了风险源的识别,识别结果显示了各风险类型对应的风险源以及易导致研制项目发生风险传导的风险源。