Development and performance evaluation of tropospheric scintillation model on Ku-band satellite link over Akure,Nigeria

Existing amplitude scintillation prediction models often perform less satisfactorily when deployed outside the regions where they were formulated. This necessitates the need to evaluate the performance of scintillation models developed in one region using data data from other regions while documenting their relative errors. Due to its variation with elevation angle, frequency, other link parameters and meteorological factors, we employed three years (January 2016 to December 2018) of concurrently measured satellite radio beacons and tropospheric weather parameters to develop a location-based amplitude scintillation prediction model over the Earth-space path of Akure (7.17^oN, 5.18^oE), South-western Nigeria. The satellite beacon measurement used Tektronix Y400 NetTek Analyzer at 1 s integration time while meteorological parameters, namely; temperature, pressure and relative humidity were measured using Davis Vantage Vue weather station at 1 min integration time. Comparative study of the model’s performance with nine (9) existing scintillation prediction models indicates that the best and worst performing models, in terms of root mean square error (RMSE), are the Statistical Temperature and Refractivity (STN) and direct physical and statistical prediction (DPSP) models with values 11.48 and 51.03 respectively. Also, worst month analysis indicates that April, with respective enhancement and fade values of 0.88 and 0.90 dB for 0.01% exceedance, is the overall worst calendar month for amplitude scintillation.     

任意波发生器静态特性的评价

介绍了任意波发生器的主要静态特性指标、校准方法及实现过程。通过一组实验．获得了实际校准结果，并对校准中需要注意的问题进行了讨论。所述方法涉及的静态特性内容比较全面。具有足够的测量准确度、分辨力和稳定性。可用于任意波发生器的静态指标评价和计量。     

飞机选型的模糊评判

本文把模糊数学的模糊变换原理用于购买新机型的评判。给出了各评判指标的定义和隶属度:并按 Saatz 的二元对比标度确定各指标的重要度;以及模糊变换的计算方法和应用举例。     

历经十年寿命试验的消旋天线机构轴承的可靠性分析

解决了一个计算可靠性问题的特例。分析了消旋天线机构轴承历经10年寿命试验的可靠性问题。并给出了轴承在不同可靠寿命要求下的可靠度(对应不同置信度)。     

液冷头盔致冷效能的医学研究

在45℃高温条件下,应用液冷头盔给10名被试者的头颈部致冷,散热效能较高,可带走安静时30.9％～48.3％的代谢产热。降低身体的热蓄积,减少出汗,减慢心率、直肠温度和皮肤温度的上升速率。对头颈部致冷可降低身体的热紧张度50％～70％,明显改善对温热的舒适感觉。同时表明,致冷液温、流量及液流走向,对致冷效能均有显著影响。为液冷头盔及致冷装置的设计,提供了医学实验依据。     

变轨发动机不等量截尾试验可靠度评估

对于可靠度要求极高和任务时间以小时计的变轨发动机来说，目前广泛采用以铌合金为材料并喷涂以抗高温氧化涂层方案的推力室，这一类发动机在方案试验阶段结束后的研制试验中往往只出现截尾试验的结果。给出了不等量截尾试验结果的可靠度评估方案。     

The development of a Russian communication satellite of small class, operating in the geostationary and high-elliptical orbits

In 1994-1995 Lavochkin Association (Russia) together with the other enterprises in accordance with technical requirements of the Russian Space agency, developed a new Russian communication satellite of a small class that will operate in both the geostationary (GSO) and high-elliptical (HEO) orbits. This satellite may be injected into operational orbits using a SOYUZ-2 launch vehicle (LV) and a FREGAT upper stage (US) from Plesetsk and Baykonur space launch sites (SLS).The main reason for creating such a satellite was to decrease the cost of the support and development of the Russian communication geostationary satellites group.Russian satellites Horizont, Express, Ekran and Gals, which operate in GSO, are the basis of the space segment for communications, radio and TV broadcasting. All of these satellites are injected into GSO by the PROTON LV. PROTON is a launch vehicle of a heavy class. The use of a middle class LV instead of a heavy class will allow to reduce considerably the launch cost. The change of a heavy class LV to a LV of middle class determined one economic reason for this project. Besides, the opportunity to launch S/C into GSO from Russian Plesetsk SLS increases the independence of Russia in the domain of space communications, despite the presence of the contract with Kazachstan about the rent of Baykonur SLS. Finally, use of small satellites with a rather small number of transponders is more effective than the use of big satellites. It will allow also to increase a satellite group (by the launch of additional satellites) precisely in accordance to the development of the ground segment.     

威布尔型产品的可靠性评估方法研究

在简要介绍极大拟然和小概率原理的基础上，针对威布尔型产品特征寿命的求取方法在各种文献中没有介绍、经典的双威布尔型串并联系统的可靠性评估方法既繁琐又不精确等情况，详细论述了如何运用威布尔型单机产品的可靠性试验样本求取其特征寿命，如何运用等效折合的方法求取威布尔型串并联系统的可靠性置信下限，最后对某威布尔型发动机系统的可靠性进行了评估,取得了较理想的结果。     

纤维缠绕复合材料层间质量声-超声无损评价

叙述了用声－超声进行复合材料危害性缺陷无损评价的研究，认为，声－超声信号在试样厚度上产生纵不皮共振，使得频谱能量集中在某些频率点附近，而声波又以切波的形式由发射换能器传向接收换能器，可用声－超声谱峰的位置来无损评价纤维缠绕增强型复合材料的层间结合质量。实验结果表明这一参量对纤维增强型合材料中的分层或紧贴型分层比较灵敏。     

并行工程及其在航空电子产品研制中的应用

 概述了并行工程的运行特性,介绍了并行工程在空管应答机研制中的应用并分析了在缩短开发周期、提高产品质量、降低研制成本和改进售后服务方面的成效,总结了应用推广并行工程的经验与体会。