卫星导航增强技术

精度、连续性、可用性、完好性,是评价全球卫星导航系统(GNSS)及用户接收机设备性能的四项基本指标。其中,精度是指GNSS的定位和授时精确度,完好性是指GNSS定位和授时输出结果的可信度。没有完好性保证的GNSS定位和授时技术无法成为众多应用领域的主导航手段,尤其是那些与经济、财产、生命相关的应用领域(如航空导航、航海导航、武器制导、交通执法、不停车收费、气象探空、电力授时等),对GNSS的精度和完好性提出了较高要求,这些要求超出了GNSS基本系统的服务能力,因此需要在GNSS基本系统的基础上,建设专门的增强系统,以提高用户设备的精度和完好性,从而满足特定用户的使用需求。欧美等国针对GPS在航空、航海领域的应用,建设了多套GPS增强系统,中国针对BDS基本系统,建设了北斗地基增强系统。在分析GNSS精度和完好性指标的基础上,介绍GNSS增强系统和技术。     

抗H2S毒化的载体催化元件

载体催化元件是最为常用的矿下瓦斯浓度检测器件，它灵敏度较高，线性度好，可精确地检测瓦斯浓度。为了克服其容易H2S中毒的缺点，采用并改进了现有的防中毒方法，明显地提高了元件的抗中毒能力。     

Experimental and numerical simulations of idealized aircraft cabin flows

Two different generic cabin configurations, deduced from the passenger cabin and the sleeping bunk of a modern mega liner, have been investigated numerically by means of Reynolds-averaged Navier–Stokes (RANS) computations and experimentally by particle image velocimetry (PIV) as well as thermography. In order to study the flow of fresh air in the vicinity of the luggage compartment, a cabin mock-up which represents the region above the passengers to the luggage compartment has been built. Additionally, a single person sleeping bunk of the crew rest compartments was considered. Comparisons between computations and measurements show a good agreement. They further indicate that higher order low Reynolds number turbulence models are suited best to predict the complex 3D-cabin airflow with separation.     

A new efficient technology of aerodynamic design based on CFD driven optimization

This paper describes a new technology of aerodynamic design based on CFD driven constrained optimization to minimum drag. Within an aircraft development project we focus on the aerodynamic design of wings and show how the design process has been advanced with the new capabilities achieved through the use of the recently developed in-house optimization tool OPTIMAS. The optimization method of the present work is based on the use of Genetic Algorithms and accurate full Navier–Stokes drag prediction. The results include a variety of optimization cases for aerodynamic design of transport-type aircrafts.     

AMF phasing—A precise control of the ignition timing of AKM for reduction of the injection error

This paper deals with a new concept, named “AMF Phasing”, which intends to minimize the effect of injection error that would result during apogee motor firing (AMF) of the spinning spacecraft. The characteristic of velocity increment error is derived analytically, based on the disturbed spinning motion during AMF. In order to precisely estimate the amount of fuel required for post-AMF orbital correction maneuvers, a probability model is proposed which estimates the total injection error probability combining the dominant error factors, i.e. pre-AMF attitude determination error and velocity increment error during AMF.It is shown that a substantial saving in fuel normally consumed for post-AMF can be expected, when the resultant velocity increment error contribution, which otherwise would be randomly directed in inertial space, is controlled so that it appears in the direction of local right ascension by igniting AKM at the proper instant (AMF Phasing). The procedure for AMF phasing, using a Sun pulse as a reference signal for the ignition timing is described in this paper. It was actually applied for GMS-2, Japan's second Geostationary Meteorological Satellite (HIMAWARI-II). The HIMAWARI-II post-AMF orbit determination shows that AMF Phasing worked successfully and it is concluded that a substantial fuel saving was achieved.     

Electrical power distribution on space based radar satellites

The radar payload on a space-based radar (SBR) satellite could require tens of kilowatts of power distributed to many small loads over a large area. This poses special problems for the power distribution and control system (PDCS). A study that examined the power requirements of an SBR spacecraft is reported. A baseline prime power system, generating about 30 kW, was derived. The proposed distribution network would transmit 240 V at 20 kHz. The voltage would be downconverted in one converter for about 100 transmit/receive modules. The design considerations are discussed, and the baseline PDCS is described     

循环电载荷下大功率LED金引线疲劳断裂寿命预测

随着大功率发光二极管（LED）在照明领域的普及与广泛应用,可靠性逐渐成为研究的重点。大功率LED封装器件中金引线疲劳断裂失效一直是制约其可靠性的重要因素。通过针对大功率LED封装器件中的金引线力学仿真与功率循环试验相结合的方法,首先确定循环电载荷条件下该型LED的主要失效原因为金引线疲劳断裂,其次提出基于电流加速模型的加速因子提取方法和基于应变幅值的Coffin-Manson解析寿命预测方法,最终完成对LED金引线疲劳断裂寿命的预测和试验验证。研究结果表明:所提方法具有较高的寿命预测精度,可以满足大功率LED封装器件可靠性快速、准确评估的要求。      

航天器AIT中心空气霉菌特性研究

通过对中国3个地区的航天器AIT厂房内空气中霉菌进行采集,利用培养法得到纯化菌株53株,通过ITS测序鉴定分属8个属,进一步对这些霉菌的特性进行研究,发现青霉属和曲霉属内不同菌株间的菌落径向生长速率差异较大,研究同时显示不同种属霉菌对消毒剂PHMB的敏感性差异非常大,这些差异将加剧微生物防护与控制的难度。     

金属材料微裂纹取向与超声波和频非线性效应

针对非线性超声无损检测金属材料微裂纹取向角度的问题,开展了微裂纹取向与超声波的和频非线性效应研究,建立了超声和频非线性特征系数与微裂纹取向角度的关系模型。理论和有限元仿真实验结果表明,随着微裂纹取向角度的逐渐增大,超声和频非线性特征系数与微裂纹取向角度之间呈现明显的正相关趋势,而且相比二次非线性特征系数,和频非线性特征系数对微裂纹取向检测更为敏感。同时,从超声波平均能流密度（即声强）的角度出发,计算可知和频分量声强会随着微裂纹取向角度的增大而增大,而二次谐波声强基本不会发生变化,同时和频分量声强占比相比于二次谐波声强占比也得到了明显提高。超声波声强计算结果与仿真计算结果趋势基本一致,证明了理论模型的正确性。通过实验验证了模型的有效性,为金属材料微裂纹取向的检测提供了一种有效的手段。      

基于双层K近邻算法航站楼短时客流量预测

航站楼离港客流量在短时期内呈现准周期性规律变化,易受航班计划、天气等多种因素影响,表现出复杂的非线性特点。为了实现航站楼短时客流量的准确预测,在传统K近邻（KNN）算法基础上增加了航班计划状态模式匹配方法,以航班计划包含的多维属性作为特征选取相似历史运营日作为预测基准向量,建立基于航站楼短时客流量预测的双层K近邻模型。通过实例分析,与ARIMA模型和传统K近邻模型等进行比较,证明双层K近邻模型预测误差更小,精度更高,模型拟合度相对传统K近邻模型提高了8%~10%,为航站楼短时客流量精确预测提供了一种新的解决思路。