Nb/α-Ti3Al体系的互扩散行为

采用反应扩散偶的方法,研究了Nb元素在α-Ti₃Al中的扩散行为.反应扩散偶经过120 h扩散退火,在高温(1 573 K)下生成了均匀的β-(Ti,Nb)扩散层;低温(1 273,1 423 K)下生成不均匀的扩散区,相组成为Ti₃Al(Nb),β-(Ti,Nb)及Nb₂Al.采用Dayananda方法计算了体系的扩散系数,即根据一个扩散偶的浓度分布曲线计算体系的扩散系数.采用平均扩散系数来表征体系的扩散系数,得出扩散模型和相关扩散机理.结果表明:Ti和Al的主扩散系数比Nb的主扩散系数大5个数量级;Ti的主扩散系数约是Al的2倍.Nb通过占据Ti的空位进行扩散,Nb的掺入阻碍了Ti元素扩散,从而提高了α-Ti₃Al体系的高温抗氧化性能.     

基于小型三坐标测量机的机械研究

从三坐标测量机的实际设计出发,通过对小型三坐标测量机的机械分析和实验,对三坐标测量机的设计提供理论基础的分析和可行的思路。     

2.5维编织复合材料弹性性能的理论研究

以2.5维编织复合材料细观几何结构的深入研究为基础,详细分析了其单元体模型。采用圆形纤维束截面和经纱沿正弦曲线分布的假设,建立了基于刚度平均的2.5维编织复合材料弹性性能分析预报模型,并采用M atlab编程用于计算该类材料的力学性能。在材料经向纱线密度不变的情况下,预测了弹性性能随纬向纱线密度的变化规律。通过理论计算结果与实验值对比,验证了该方法的正确性。     

FY-3卫星积雪监测产品概述及在遥感服务中的应用

介绍了风云三号(FY-3)气象卫星主要成像传感器及其积雪监测产品情况,FY-3卫星利用其1级数据能反演积雪覆盖、积雪深度、雪水当量等多种积雪监测参数和产品。卫星可见光-近红外传感器提供积雪覆盖监测信息,微波成像传感器提供积雪深度、雪水当量监测信息。针对防灾减灾以及应对气候变化分别给出积雪监测产品的遥感服务应用。结合国内外积雪遥感监测技术的发展趋势,提出利用FY-3卫星进行积雪监测的未来前景。FY-3卫星积雪监测产品在防灾减灾和应对气候变化方面能为遥感部门提供客观、可靠、全面、及时的参考信息。     

GMRT monitoring of Cyg X-1 and Cyg X-3

We present the results of low frequency radio observations of the X-ray binaries, Cygnus X-1 and Cygnus X-3, during different X-ray states. The low frequency observations were made for the first time for these sources at 0.61 and 1.28 GHz using the Giant Meter-wave Radio Telescope (GMRT) between 2003 and 2004. Both Cyg X-1 and Cyg X-3 are highly variable at low radio frequencies. We also compare our data with the observations at 15 GHz conducted by the Ryle telescope. Spectral turnover is seen for both the sources below 2 GHz. The data suggest that the change in the radio flux density in both the sources is correlated to the X-ray hardness ratio and follows a similar behavior pattern.     

快速凝固Ti3Al基合金相变的X—射线衍射分析

利用Ｘ－射线衍射分析研究了快速凝固Ｔｉ－２５Ａｌ－１０Ｎｂ－３Ｖ－１Ｍｏ合金回火的转变过程，结果表明，依照回火温度的不同，快速凝固合金中的亚稳β＿０相将产生不同的转变。在６００～８００℃之间回火时，亚稳β＿０相转变为Ｏ相；８１０℃回火时，合金的显微组织由Ｏ＋α＿２＋β＿０相组成；而９５０℃回火的合金的显微组织则为α＿２＋β＿０相，回火Ｏ相的晶格常数与Ｏ相形成温度有关。     

YE3系列(IP23)设计参数的分析和测试验证

YE3系列(IP23)三相异步电动机在整体结构上做了全新的设计,直接影响了电动机各种设计参数的选取。对杂散损耗、机械损耗以及气隙等设计值的选取作了对比分析,并结合样机测试数据来验证取值的合理性。     

Higher order ionospheric error correction in BDS precise orbit determination

The ionospheric error affects the accuracy of the Global Navigation Satellite Systems observation and precise orbit determination. Usually, only the first order ionospheric error is considered, which can be eliminated by the ionospheric-free linear combination observation. But the remaining higher order ionospheric error will affect the accuracy of observations and their applications. In this paper, the influence of the higher order ionospheric error have been studied by using the International Geomagnetic Reference Field 13 and the Global Ionosphere Maps model produced by the Center for Orbit Determination in Europe. Focus on ionospheric error, the experiment of paper at doy 302 in 2019, which show that the second order ionospheric error impacting BeiDou Navigation Satellite System (BDS) B1I and B3I observation is 6.3569 mm and 11.8484 mm, respectively. Whereas, the third order ionospheric error impacting BDS B1I and B3I observation is 0.1734 mm and 0.3977 mm, respectively. Due to the current measurement accuracy of BDS carrier-phase observation can reach 2 mm, the influence of high order ionospheric error on observation should be considered. For BDS precise orbit determination, the orbit overlapping results are indicated that its orbit accuracy can be improved approximately 5 mm with the higher order ionospheric error correction, which is also in agreement with the results of Satellite Laser Ranging in this work.     

印刷锡膏工艺参数的优化

印刷锡膏是表面组装生产中的第一道工序,也是最关键的工序,在表面组装生产中60%一70%的焊接缺陷与锡膏的印刷有关.本文将讨论与锡膏印刷有关的问题,包括锡膏参数和印刷机(特别是与刮刀有关的)参数,并对这些参数进行优化,以达到最好的锡膏涂布效果.     

飞机重量平衡手册的编制探究

初步研究了飞机重量平衡手册的编制规章依据、编写规范和编写方法,通过对ATA2200及S1000D相关标准的研究,为我国民机重量平衡手册的编制提出建议。