合金元素及第二相对钨的影响

综述了活化烧结元素,合金化元素,杂质元素及化合物对钨合金组织和性能的影响,并对新型钨基合金及其复合材料的研究,开发提出了一些看法。     

基于数值模拟的印制电路板低透锡率焊盘焊接温度分析

部分印制电路板通孔焊盘与接地层连接,手工焊接过程中接地层散热严重,焊点透锡率不足。为解决此问题,通过ABAQUS软件计算多层印制板手工焊接普通焊盘、低透锡率焊盘的温度分布情况,分析整板预热对温度及透锡率的影响。分析结果显示,未预热状态下低透锡率焊盘的镀铜层散失热量约为普通焊盘孔的4倍,低透锡率焊盘孔非焊接面温度为125～126℃,远低于锡铅共晶焊料熔点(183℃);预热85、100、115℃情况下低透锡率焊盘非焊接面温度分别提高至171.5、179、187.5℃。模拟与实验结果表明,整板预热85～115℃可有效改善通孔焊盘透锡率、提高焊点服役可靠性。     

Plasma Niobium Surface Alloying of Pure Titanium and its Oxidation at 900 ℃

A niobium-modified layer on pure titanium surface was obtained by means of double glow plasma surface alloying technique. The modified layer was uniform, continuous, compact and well adhered to the substrate. The niobium composition in the modified layer decreased gradually from the surface to the substrate. The oxidation behavior of the niobium-modified layer was investigated and compared with the untreated surface at 900 ℃ for 100 h. Characterization of the layers was performed using X-ray diffraction and scanning electron microscope, respectively. The test results show that the oxidation behavior of pure titanium was improved by niobium alloying process. Niobium has a positive influence on the oxidation resistance.     

Effects of Atomic Oxygen Irradiation on Transparent Conductive Oxide Thin Films

作为一种功能薄膜,透明导电氧化物(TCO)薄膜在飞行器的抗原子氧(AO)涂层和太阳能电池领域有着巨大的应用价值。ZnO:Al(ZAO)和In2O3:Sn(ITO)薄膜是目前研究和应用最广泛的TCO。本文对ITO薄膜和ZAO薄膜进行了不同通量的AO辐照。通过对辐照前后样品的X射线衍射、扫描电镜及霍耳效应的表征及测试,研究了AO辐照对这两种TCO薄膜的结构、性能及电学特性的影响。研究表明AO辐照对ZAO薄膜表面有明显的侵蚀作用,但对其结构和导电性能没有明显影响。对于ITO薄膜,随着AO通量的增大,其载流子浓度逐渐下降从而导致了电阻率的提高,电阻率的最大变化达到了21.7%。     

Night-time total electron content enhancements at equatorial anomaly region in China

This paper presents small scale (duration ?1 h, ΔTEC ? 1TECU) night-time total electron content (TEC) enhancements observed at the equatorial anomaly region in China, for the first time. The data is from a GPS receiver chain established in 2005 by Institute of Center for Space Science and Applied Research, Chinese Academy of Sciences and a GPS receiver of International GPS Service (IGS), located between Fuzhou (26.1°N, 119.3°E) and Nanning (22.8°N, 108.3°E). Two other GPS observations of IGS taken at higher latitude were also used to investigate the localization of such phenomenon. The characteristics of the night-time TEC enhancement are examined with two case studies. The TEC increases about 1–3TECU, intermittently. While the night-time TEC enhancement mainly occurs at the equatorial anomaly region, it can be observed at middle latitude as well. The spatial size of the enhancement region is less than 5° in longitude. The primary statistical study shows that the TEC enhancement is more often observed in spring and autumn, but rarely in summer. It has no dependence on geomagnetic activity. The enhancement can occur both before and after midnight.     

The effect of total solar eclipse of October 3, 2005, on the total electron content over Europe

GPS observations from EUREF permanent GPS network were used to observe the response of TEC (Total Electron Content) to the total solar eclipse on October 3, 2005, under quiet geomagnetic conditions of the daytime ionosphere. The effect of the eclipse was detected in diurnal variations and more distinctly in the variations of TEC along individual satellite passes. The trough-like variations with a gradual decrease and followed by an increase of TEC at the time of the eclipse were observed over a large region. The depression of TEC amounted to 3–4 TECU. The maximum depression was observed over all stations located at the maximum path of the solar eclipse. The delay of a minimum level of TEC with respect to the maximum phase of the eclipse was about 20–30 min.     

RPC-MIP: the Mutual Impedance Probe of the Rosetta Plasma Consortium

The main objective of the Mutual Impedance Probe (MIP), part of the Rosetta Plasma Consortium (RPC), is to measure the electron density and temperature of Comet 67P/Churyumov-Gerasimenko’s coma, in particular inside the contact surface. Furthermore, MIP will determine the bulk velocity of the ionised outflowing atmosphere, define the spectral distribution of natural plasma waves, and monitor dust and gas activities around the nucleus. The MIP instrumentation consists of an electronics board for signal processing in the 7 kHz to 3.5 MHz range and a sensor unit of two receiving and two transmitting electrodes mounted on a 1-m long bar. In addition, the Langmuir probe of the RPC/LAP instrument that is at about 4 m from the MIP sensor can be used as a transmitter (in place of the MIP ones) and MIP as a receiver in order to have access to the density and temperature of plasmas at higher Debye lengths than those for which the MIP is originally designed.     

旋转对气膜冷却覆盖区域的影响

气膜冷却是应用于航空发动机上的冷却技术,旋转是影响气膜与主流掺混区域的重要因素.在旋转气膜外换热实验台上进行的平板气膜冷却实验对此问题进行了研究.与静止叶片相比,气膜出流在旋转叶片表面会发生展向偏离.在压力面,转速增加,气膜出流先向低旋转半径方向偏转,后向高旋转半径方向偏转;在吸力面,气膜出流向高旋转半径方向偏转.动量流量比固定,当密度比增加时,压力面气膜出流轨迹向低旋转半径方向偏转加剧;吸力面气膜出流轨迹向高旋转半径方向的偏转也增大.      

在MATLAB中模拟平稳随机过程

叙述了平稳随机过程理论的基本定义,以及运用实谱分解方法模拟平稳随机过程的原理.全面分析了在微型计算机上使用MATLAB软件模拟平稳随机过程的注意事项,包括:信号源的选取,仿真算法和相应参数的设置,由于功率谱密度的不同定义而需要进行相应的调整等3个方面.结合大气紊流和航空母舰在海上的随机运动的2个实例,给出了在MATLAB中模拟类似过程的方法,并对结果进行了检验.分析表明在MATLAB中能够较好地模拟平稳随机过程.      

电子束固化环氧树脂的引发和增长反应速率

对二苯基碘 鎓 六氟磷酸盐引发的环氧树脂电子束(EB)辐射固化反应动力学进行了研究,应用环氧树脂乙腈溶液推导出引发剂辐射分解速率常数和引发、增长反应速率.动力学研究结果表明,二苯基碘 鎓六氟磷酸盐引发剂经电子束辐射分解产生质子酸的过程是二级反应,在辐射反应过程中,环氧树脂体系的引发速率和增长速率分别迅速达到最大值后逐渐减小.