串联型MPPT空间电源系统稳定性技术

串联型最大功率点跟踪(MPPT)空间电源系统存在母线电压振荡或跌落等不稳定现象,文章以MPPT不调节母线电源拓扑为研究对象,建立了系统等效电路模型,通过小信号等效分析、状态空间方程特征根求解等手段,分别对MPPT控制域及电压控制域下电源系统的稳定性进行了分析.结果表明,在太阳电池阵及阵列功率调节器特性曲线一定的条件下,通过对二者间电感、电容参数合理配置,可以保证系统稳定.在MATLAB/SIMULINK中搭建了串联型MPPT不调节母线电源系统仿真模型并进行实例仿真,仿真结果验证了理论分析的正确性.     

Comparison of topside electron density computed by ionospheric models and plasma density observed by DMSP satellites

Electron density obtained by IRI (topside options NeQuick and IRI-Corr) and NeQuick models in their standard versions have been compared with plasma density values measured by F13 and F15 DMSP satellites for years of different solar activities. A statistical study of the differences between modeled and experimental data has been carried out to investigate each model performance.     

高能束流加工技术的应用及发展

针对高能束焊接、高能束快速成形及高能束表面加工等三个方面进行讨论,概述并归纳当前的技术现状及应用,结合现代航空技术对制造工艺提出的新要求,阐述高能束流加工技术在航空制造中的发展趋势。     

基于PC/104总线的飞机电源产品综合测试系统

详细介绍了一套基于PC／104总线和虚拟仪器技术的飞机电源产品综合测试系统的功能和软硬件实现原理。阐述了测试系统的设计原理，最后结合整个系统设计介绍了在LabVIEW环境下测试系统软件的设计和实现。     

毫米波国家功率基准及其国际关键比对

文章介绍了一种基于热敏电阻功率座的对称双线结构的矩形波导微量热计的设计和传递标准有效效率计算方法。给出了功率基准热电堆测量曲线及该频段毫米波功率传递标准量值结果。这种新的微量热计将作为我国毫米波功率基准,它将我国的毫米波功率测量能力提高到了75GHz。国际比对是国际多边证书互认的基础,是我国产品进入国际市场准入的质量认证基础,国际关键比对是比对活动中的核心活动。文章介绍了我国参加毫米波WR-22（33GHz-50GHz）国际关键比对情况。     

无速度传感器永磁同步电机直接转矩控制系统

详细阐述了零矢量在永磁直接转矩控制系统中的作用，指出如果合理应用零矢量，不仅能使永磁电机(PMSM)的DTC系统正常运行，而且能减少转矩脉动的频率和改善系统的性能。还研究了PMSM的DTC系统的无速度传感器技术，构建了包含零矢量在内的无速度传感器PMSM的DTC系统，仿真和实验都证明了理论的正确性。在无速度传感器的条件下，PMSM的DTC系统实现了宽范围调速，调速比达到了1：100。     

多电飞机电力系统及其关键技术

多电飞机将机载二次能源逐步统一为电能,有效提高了飞机的燃油经济性、可靠性和维护性,已成为航空科技发展的重要方向。作为机载二次能源系统的核心,电力系统在多电飞机发展过程中起到了关键支撑作用。电力系统及其关键技术的创新发展是实现飞机综合性能提升和全局优化的必要基础。本文从多电飞机的基本概念与特点出发,分析对比了典型多电飞机的电力系统架构,在此基础上系统地总结了支撑多电飞机电力系统发展的关键技术,讨论了未来多电飞机电力系统高压、直流和智能化的发展趋势。     

Water surface temperature estimation from Landsat 7 ETM+ thermal infrared data using the generalized single-channel method: Case study of Embalse del Río Tercero (Córdoba,Argentina)

Monitoring of warm distribution in water is fundamental to understand the performance and functioning of reservoirs and lakes. Surface water temperature is a key parameter in the physics of aquatic systems processes since it is closely related to the energy fluxes through the water–atmosphere interface. Remote sensing applied to water quality studies in inland waterbodies is a powerful tool that can provide additional information difficult to achieve by other means. The combination of good real-time coverage, spatial resolution and free availability of data makes Landsat system a proper alternative. Many papers have developed algorithms to retrieve surface temperature (principally, land surface temperature) from at-sensor and surface emissivity data. The aim of this study is to apply the single-channel generalized method (SCGM) developed by Jiménez-Muñoz and Sobrino (2003) for the estimation of water surface temperature from Landsat 7 ETM+ thermal bands. We consider a constant water emissivity value (0.9885) and we compare the results with radiative transfer classic method (RTM).     

Global empirical models of the density peak height and of the equivalent scale height for quiet conditions

Monthly average electron density profiles have been calculated from hourly electron density N(h) recorded in 26 digisonde stations distributed worldwide encompassing the time interval 1998–2006. The ionospheric electron density peak height of the F2 region, hmF2, and the effective scale height at the hmF2, Hm, deduced from average profiles have been analyzed to obtain the quiet-time behavior and have been analytically modeled by the spherical harmonic analysis (SH) technique using the modip latitude as the coordinate of the reference system. The coefficients of the SH models of hmF2 and Hm are bounded to the solar activity, and the temporal and seasonal variations are considered by Fourier expansion of the coefficients. The SH models provide a tool to predict hmF2 and Hm located anywhere in the range of latitudes between of 70°N and 70°S and at any time. The SH analytical model for hmF2 improves the fit to the observations by 10% in average compared to the IRI prediction, and it might improve the IRI prediction of hmF2 by more than 30% at high and low latitudes. The analytical model for Hm predicts the quiet behavior of the effective scale height with accuracy better than 15% in average which enables to obtain a good estimation of vertical profiles. These results could be useful to estimate information for the topside profile formulation.     

The statistical treatment implemented to obtain the planetary protection bioburdens for the Mars Science Laboratory mission

NASA Planetary Protection Policy requires that Category IV missions such as those going to the surface of Mars include detailed assessment and documentation of the bioburden on the spacecraft at launch. In the prior missions to Mars, the approaches used to estimate the bioburden could easily be conservative without penalizing the project because spacecraft elements such as the descent and landing stages had relatively small surface areas and volumes. With the advent of a large spacecraft such as Mars Science Laboratory (MSL), it became necessary for a modified—still conservative but more pragmatic—statistical treatment be used to obtain the standard deviations and the bioburden densities at about the 99.9% confidence limits. This article describes both the Gaussian and Poisson statistics that were implemented to analyze the bioburden data from the MSL spacecraft prior to launch. The standard deviations were weighted by the areas sampled with each swab or wipe. Some typical cases are given and discussed.