激光准直技术综述

本文概述了我国、英、美、联邦德国和苏联等国的激光准直技术的研究情况,针对目前激光准直仪存在的主要问题,介绍了国内外各种新的准直方法。这些方法都从不同的角度提高了激光准直仪的精度。在此基础上,本文还分析了激光准直技术研究的发展方向及其应用前景。     

激光熔覆制备金属间化合物抗冲蚀涂层

采用同轴送粉方法,激光熔覆制备了WC增强Ni3Al金属间化合物基复合涂层,通过试验,优化了工艺参数,对激光熔覆涂层的成分、组织和硬度进行了测试和分析.结果表明,激光熔覆涂层无裂纹和气孔,与基体形成良好的冶金结合,WC颗粒的添加显著提高了涂层硬度.     

用单片ROM改善码同步器的误码性能

即使滤波器是理想的,采用离散信号处理的前置滤波来抗干扰时,误码性能也要降低。用平均采样器即差分线性滤波器来处理从相关采样获得的统计值时,就会出现误码性能的降低。但是,用正交变换可以减弱已滤波的采样统计的从属性,从而使平均采样表现出近似最优性能。本文为对码同步器的判决产生不利影响的元件提供数学判据和一种替代的正交变换,这种变换通过增加一片 ROM 实现,可以应用于大多数的数字化码同步的设计。     

Potentials of manufacture and repair of nickel base turbine components used in aero engines and power plants by laser metal deposition and laser drilling

IntroductionExpensive turbine parts like HPT(HighPressure Turine)blades or vanes are replaced bynew parts in case of damage.For example theburn through of the inner side of a blade or vane(Figure 1)is a frequently appearing damage,which cannot be repaired…     

Astrobiologically interesting stars within 10 parsecs of the sun

The existence of life based on carbon chemistry and water oceans relies upon planetary properties, chiefly climate stability, and stellar properties, such as mass, age, metallicity, and galactic orbits. The latter can be well constrained with present knowledge. We present a detailed, up-to-date compilation of the atmospheric parameters, chemical composition, multiplicity, and degree of chromospheric activity for the astrobiologically interesting solar-type stars within 10 parsecs of the Sun. We determined their state of evolution, masses, ages, and space velocities, and produced an optimized list of candidates that merit serious scientific consideration by the future space-based interferometry probes aimed at directly detecting Earthsized extrasolar planets and seeking spectroscopic infrared biomarkers as evidence of photosynthetic life. The initially selected stars number 33 solar-type within the total population (excluding some incompleteness for late M-dwarfs) of 182 stars closer than 10 parsecs. A comprehensive and detailed data compilation for these objects is still lacking; a considerable amount of recent data has so far gone unexplored in this context. We present 13 objects as the nearest "biostars," after eliminating multiple stars, young, chromospherically active, hard x-ray- emitting stars, and low metallicity objects. Three of these "biostars"-- Zeta Tucanae, Beta Canum Venaticorum, and 61 Virginis -- closely reproduce most of the solar properties and are considered as premier targets. We show that approximately 7% of the nearby stars are optimally interesting targets for exobiology.     

Repair Welding of Casting Magnesium Alloys： A Review

Magnesium (Mg) alloys have broad application prospects in the fields of aerospace, national defense, and military industries, owing to their advantages of high specific strength and stiffness, good damping properties, and excellent castabilities. However, defects such as oxidation inclusions, shrinkage cavities and porosities, and hot cracks are readily generated in Mg alloy components, which seriously reduce the performance stability of the products. Related repair welding technologies for Mg alloys can greatly reduce the rejection rate and production cost, and exhibit significant value in scientific research and engineering application. In this review, the weldability of Mg alloys is introduced firstly according to their physical and chemical properties. Then, various repair welding technologies and pre-weld treatments applicable to Mg alloys are systematically summarized, and the effects of welding parameters as well as heat treatments on the microstructure and performance of the repaired joints are clarified. Finally, the existing problems and development trends of repair welding technologies for Mg alloys are summarized based on the actual engineering application requirements.     

基于冷备份多模冗余结构的BRAM自修复方法

随着现场可编程门阵列（FPGA）在空天电子系统中的广泛应用,受空间辐射恶劣环境影响,FPGA中重要的存储器电路BRAM,因采用SRAM技术极易发生位翻转故障,虽绝大部分情况表现为瞬时故障,但永久故障依然存在。针对BRAM自修复方法仅修复瞬时故障的现状,对能同时修复瞬时故障和永久故障的自修复方法进行研究,提出了一种冷备份多模冗余结构,用3个热备份模块和1个冷备份模块来构造BRAM,该结构可通过三模冗余刷新方法修复瞬时故障和冷备份替换方法修复永久故障。给出了整个BRAM自修复系统中各模块的电路结构和实现方法,实验验证了系统的自修复能力,并在可靠性、硬件资源和时间消耗3个方面,通过对比分析论证了自修复方法的有效性。     

Space Life Science of China in 2015

With the human space exploration activities, space life science is an emerging interdisciplinary and it covers a wide range of research. Based on our country's manned space station and recoverable satellite science experimental platform, the development of space life science research is very important to acquire new knowledge or new innovation in technology, to give further services to the human space exploration activities, to improve the national economic and social development. Based on present situation, both theoretical and applied researches were continuously performed in 2015. Here, we review and summarize the researches on space life sciences which were contributed by Chinese scientists.      

采用结构协方差矩阵的机载／天基雷达的空时自适应处理

本文表明有效地采用机载／天基（A/S）杂波协方差矩阵（CCM）的部分信息可以大大提高在杂波和干扰环境下块处理空／时自适应处理机（STAP）的收敛性能。CCM的部分知识以由机载雷达团体开发的简化通用杂波模型（GCM）为基础。设定一个参数的先验知识，该参数应是易于通过与这种模型相关的雷达平台可测的（但不一定准确）。这种GCM产生一种假定的CCM。用这种假定的CCM和热噪声协方差矩阵的精确知识一起形成STAP要用的未知干扰协方差矩阵的最大似然估值（MLE）。对利用先验杂波和热噪声协方差信息的这种新算法的评估采用两种杂波模型：1）失配的GCM，2）高保真的空军研究实验室STAP杂波模型。对于这两种杂波模型，这种新算法要大大好于（即收敛更快）采样矩阵求逆（SMI）和快速最大似然（FML）STAP算法，后一种模型仅用了热噪声协方差矩阵的信息。     

基于图像的测量方法在工业风洞跨声速流测量中的最新进展

风洞中非定常复杂流场的实验研究要求先进的测量技术.基于图像的测量技术中最重要的是测量平面流速度场、平面压强分布、模型位置和变形、模型温度以及定量的高速流可视化等技术.DLR(德国宇航研究院)对这些技术的应用包括从低速流到跨声速流、从增升装置到螺旋桨和旋翼、从弹射装置和水塔储水罐尾迹流旋涡到三角翼上涡破裂现象等的研究.由于跨声速风洞的特殊环境,将基于图像的测量技术用于跨声速流要求专门的技术开发和有经验的科学家.给出了DLR空气动力学和流动技术研究所将基于图像的测量技术应用于跨声速流研究的最新进展.