通用模拟示波器故障的分析与诊断

本文将通用模拟示波器电路分成五部分，总结和分析了每一部分电路故障可能引起的几种异常显示，给出了每一部分电路故障诊断方法及在相应电路中出现故障的常见器件，对有些故障与故障现象之间的因果关系做了进一步分析。     

液压能源管路系统振动主动控制的理论研究

对飞机液压能源管路系统的振动问题进行了探讨.提出一种基于振动主动控制(VAC)技术对飞机液压能源管路系统进行消振的方法,在手段上采用压电/压电致伸技术,以压电陶瓷(PZT)作为作动器,具有驱动力大、响应频率高和体积小等优点;控制方法上采用参数寻优的控制策略,它能始终能根据外界干扰因素的变化来调整控制参数.经过理论分析和仿真验证,证明其具有良好的自适应性和鲁棒性,在变转速和变负载情况下始终能保持最佳的消振效果.     

Ionospheric F2-Layer critical frequency retrieved from COSMIC radio occultation: A statistical comparison with measurements from a meridional ionosonde chain over Southeast Asia

In this paper, we compared the F2-Layer critical frequency (foF2) derived from FORMOSAT-3/COSMIC radio occultation (RO) and ionosondes at Chiang Mai, Chumphon and Kototabang during the years 2008–2015 to evaluate the performance of COSMIC RO over Southeast Asia region. The results show that the time development of foF2 values derived from COSMIC RO generally agrees well with those from ionosonde measurements. However, the differences between the foF2 derived from COSMIC RO and that derived from ionosonde observations display latitudinal dependence. COSMIC RO tends to underestimate foF2 at Chiang Mai and Kototabang, which is near to the north EIA crest and the south one, respectively, while a little overestimate foF2 at Chumphon, which is close to the geomagnetic equator. COSMIC RO agrees best with ionosonde at Chumphon and worst at Chiang Mai. At each ionosonde station, the quality of COSMIC RO data degrades with the increase of solar activity. In addition, at the station Chiang Mai and Kototabang, COSMIC RO performs better in summer than in equinox and winter. Furthermore, the differences in foF2 derived from COSMIC RO and that from ionosonde measurements vary with local time, i.e., the differences in foF2 are generally smaller at night and larger in noontime when equatorial ionization anomaly (EIA) is well developed.     

中国当务之急应转变负利率

我国目前利率水平低于CPI涨幅,处于负利率状态,负利率正在使居民的消费能力下降,财富缩水,扭曲资本的市场化配置功能,加剧通货膨胀预期,更造成社会资金一定程度的错配,助长资产泡沫。通过分析负利率的成因和负面影响,提出可提高定期存款利率、稳定物价和转变经济增长模式来消除负利率。     

基于CCSDS标准的航天器上行遥控链路 协议体系与可靠性技术

针对航天测控领域中上行遥控业务的协议体系选择与可靠性设计问题,在对我国现行国军标技术指标要求与现有航天测控系统天地基遥控技术特点进行归纳梳理的基础上,基于空间段信息传输无线链路特点与CCSDS(Consultative Committee for Space Data Systems,空间数据系统咨询委员会)标准规范,研究给出了适用于我国航天测控任务的空间段遥控协议体系与可靠性措施,利用梳理统计方法对上行遥控体制进行了数学建模分析,并与CCSDS给出的应用算例进行了对比分析.分析结果表明,所涉及的上行遥控体制与CCSDS标准规范的工作效能基本相当,能够满足我国航天任务上行遥控任务使用需求.     

基于RANS/LES混合方法的分离流动模拟

飞行器在大迎角、快速俯仰机动时,流场中含有大尺度、非定常的涡结构,传统雷诺平均Navier-Stokes （RANS）模型不能准确模拟流场结构,根据国际上相关研究的发展趋势,需要采用混合RANS/大涡模拟（LES）模型来对复杂分离流动进行准确模拟。本文对基于分区混合与湍流尺度混合的双重RANS/LES混合计算模型进行发展与应用。通过典型简化模型的静、动态湍流大分离流动,测试和验证所采用的脱体涡模拟（DES）类方法,重点研究改进的延迟DES （IDDES）模型在动态问题应用中的正确性和有效性,并对所采用的数值模拟方法和相应的计算软件的可靠性、鲁棒性以及精度进行了考核验证。典型算例包括超声速圆柱底部流动、跨声速方腔流动、NACA0015机翼深失速分离涡模拟等。计算表明：发展的IDDES类混合计算模型可有效解决对数层不匹配的问题;对于定态非定常分离流动,DES、DDES、IDDES等模型计算结果差别不大,随着流动的非定常特性增强,IDDES模型的优势逐渐显现;对于动态非定常分离流动,则需要采用IDDES类模型。     

运动的核弹比静止的核弹威力小?——多普勒效应、红移、光行差和动体的质能当量关系

证明爱因斯坦立足于光速不变假设和长度收缩假设的洛伦茨变换未能正确地解释多普勒效应、红移和光行差现象;他也未能给出正确的动体的质能当量关系.作者立足于完全符合相对性原理的伽利略变换,成功地解决了上述问题.     

Singularity analysis for single gimbal control moment gyroscope system using space expansion method

Control Moment Gyroscope (CMG) is an effective candidate for agile satellites and large spacecraft attitude control because of its powerful torque amplification capability. The most serious situation, however, in using CMG is the inherent geometric singularity problem, where there’s no torque output along a particular direction. Space expansion method has been proposed in this work for the singularity analysis. Based on inverse mapping transformation, an expanded Jacobian matrix which is a full rank square matrix is obtained. The singular angle sets of the 3-parallel cluster and pyramid cluster are distinguished using space expansion method. An effective hybrid steering strategy, able to deal with the elliptic singularity, is further proposed. Simulation results demonstrate the excellent performance of the proposed steering logic compared to the generalized singular robust logic and pseudo inverse logic in terms of energy consumption and torque error.     

航空维修多媒体辅助培训

阐述了MCBT开发的必要性、主要优点、发展前景和面临的主要问题,提出了使全行业尽快了解和重视这一工作,加强MCBT的开发步伐,促进航空维修及其培训水平的快速提高的看法.     

基于放大因子与Spalart-Allmaras湍流模型的转捩预测

为了验证放大因子输运方程与Spalart-Allmaras(S-A)湍流模型耦合对转捩现象的模拟精度,选取Schubauer and Klebanoff(S-K)平板、S809低速翼型、30p30n多段翼型以及复杂的三维HiLiftPW-1构型进行自由转捩计算,并将计算结果与实验进行比较分析,其中针对S809算例,还与Langtry-Menter(L-M)转捩模型进行了比较.算例结果表明:放大因子输运方程与S-A湍流模型的耦合能够较好的捕捉转捩位置以及转捩发展过程,对分离泡诱导的转捩的模拟相比L-M转捩模型更精确,转捩位置的捕捉精度提升了10%;对比实验,多段翼转捩位置的捕捉误差最大为6.5%;针对三维高升力增升构型,以实验作为参考,全湍流计算与考虑边界层转捩的对比显示考虑边界层转捩能够更加精确的模拟气动力系数,升力和表面摩擦阻力系数的模拟精度精度提升1%.