钛合金熔模精铸氧化锆陶瓷型壳／金属界面反应研究

通过实际浇注和真空扩散连接分别制取了钛／型壳界面，借助ＳＥＭ、ＥＰＭＡ和显微硬度仪等分析测试手段对所得界面进行了深入研究，初步提出了以Ｚｒ、Ｏ元素向钛基体内的扩散为主导的界面反应机制。实验结果表明，界面反应并非在整个界面上均衡推进，而是在浓度、温度、能量起伏、以及陶瓷颗粒位向适宜的区域优先发生界面反应     

Solar activity dependence of total electron content derived from GPS observations over Mbarara

Vertical total electron content (VTEC) observed at Mbarara (geographic co-ordinates: 0.60°S, 30.74°E; geomagnetic coordinates: 10.22°S, 102.36°E), Uganda, for the period 2001–2009 have been used to study the diurnal, seasonal and solar activity variations. The daily values of the 10.7 cm radio flux (F_10.7) and sunspot number (R) were used to represent Solar Extreme Ultraviolet Variability (EUV). VTEC is generally higher during high solar activity period for all the seasons and increases from 0600 h LT and reaches its maximum value within 1400 h–1500 h LT. All analysed linear and quadratic fits demonstrate positive VTEC-F_10.7 and positive VTEC-R correlation, with all fits at 0000 h and 1400 h LT being significant with a confidence level of 95% when both linear and quadratic models are used. All the fits at 0600 h LT are insignificant with a confidence level of 95%. Generally, over Mbarara, quadratic fit shows that VTEC saturates during all seasons for F_10.7 more than 200 units and R more than 150 units. The result of this study can be used to improve the International Reference Ionosphere (IRI) prediction of TEC around the equatorial region of the African sector.     

Propagation of non-linear ion-sound pulses in dusty plasma waveguides

There are a lot of objects in space associated with dusty plasma inclusions. Such inclusions may bear a prolonged shape and behave as waveguides for ion-sound waves. In the case of space plasmas, the dust particles can possess both negative charge, due to electron attachment, and positive one, due to photoionization. In this paper the propagation of linear and non-linear ion-sound wave pulses in the dusty plasma waveguides, possessing positive charge, is studied. It has been demonstrated that non-linear dynamics of baseband pulse propagation in plasma waveguide possesses essentially non-solitonic behavior. Namely, propagation of a long ion-sound pulse leads to an excitation of a shock-like wave but not a stable localized nonlinear pulse. Also, when a Korteveg–de Vries (KdV) soliton is incident onto the dusty plasma waveguide, some part of the soliton energy is captured by the waveguide and transformed into a multi-pulse structure. Additionally, an interaction of dusty plasma inclusions with KdV soliton can lead to the occurrence of transverse instabilities of the soliton and its eventual destruction.     

On small active region filaments,fibrils and surges

High resolution Hα images and magnetograms (0.2 arc s) of an active region were obtained in alternating time series at 42 s cadences using the Swedish 1-m Solar Telescope on 2004 August 21. The Hα filtergrams reveal an active region filament and surges consisting of thread-like structures which have widths similar to the widths of chromospheric fibrils, both recorded down to the resolution limit in the best images. All observed structures in the active region appear highly dynamic. Fibrils show counterstreaming strongly resembling the counterstreaming threads in filaments.     

X线乳腺图像中微钙化检测的快速排除无病变区域法

介绍一种通过去除数字化乳腺x线照片中的无病变区域（TNR）间接地获取感兴趣区域（ROI）的方法。该方法可通过3个步骤来实现：（1）将图像划分为若干个不重合的相等大小块，并为每块计算5个特征；（2）通过域值法进行粗分析，排除肯定不含有病变的块；（3）使用代价敏感的支持向量分类器作更精细的分析，以进一步排除肯定不含有病变的块。在真实的数字化X线乳腺照片上的实验表明：该方法可以有效地去除高达81．71％的无病变区域。     

Microphysics of Magnetic Reconnection

Magnetic reconnection is a universal phenomenon where energy is efficiently converted from the magnetic field to charged particles as a result of global magnetic topology changes during which earlier separated plasma regions become magnetically connected. While the reconnection affects large volumes in space most of the topology changes and of the energization occur within small localized regions. Regions of special importance are the X-region and the separatrix region. The understanding of the microphysics of these regions is crucial for the overall understanding of the reconnection. The Earth magnetosphere is the best environment where the details of these regions can be studied in situ. We summarize their main properties and discuss recent spacecraft observations.     

圆柱度误差最小区域评定方法述评

本文简介圆柱度误差评定的常用数学模型，并对用最小区域法评定圆柱度误差的几种近似方法及其优缺点展开讨论。     

平板上钝缘舵在超声速绕流中的三维分离特性研究

对于平板上的直立钝缘舵在M_∞=1.79、2.04和2.50的条件下,研究了该平板干扰区中的三维分离特性。着重讨论了钝缘直径、舵面迎角和来流马赫数对主分离线位置和形状的影响。分析了该类三维分离在性态上更强地依赖于无粘流动特性。此外,还对分离区内的二次分离发展过程和形态进行了初步讨论。     

多等级区域侦察弹性星座设计方法

针对传统侦察星座目标单一、弹性低的问题，提出了多等级区域侦察弹性星座的设计方法。该方法将星座设计过程按区域等级信息分为多个子星座逐步设计，直到整体星座对所有的区域性能满足设计要求。以区域被划分为3个等级为例，首先对星座设计需求、设计指标及设计步骤进行了分析。其次推导了地面最低分辨率和轨道高度的关系并确定了不同子星座的轨道高度。最后考虑轨道倾角、一箭多星发射、光照和升交点漂移同步约束，构建基础星座、子星座1和子星座2的优化模型。最终设计星座为3层混合星座，共8个轨道面和70颗卫星，星座对各等级区域的最大重访时间分别为10937s，12241s和17437s，弹性指数为2213%，2420%和6361%。结果表明该方法设计的星座可实现对区域覆盖和弹性分级的设计要求，证明了方法的有效性。对比Walker星座设计方法，在同等设计要求下，Walker星座所需卫星数为156颗，多等级区域侦察弹性星座所需卫星数远低于Walker星座，结果进一步证明了该星座设计方法的优越性。     

Injection of 40-kHz-modulated electron beam from the satellite: II. Excitation of electrostatic and whistler waves

Beam-plasma interaction effects are studied during the active space experiment with electron and Xe-ion beam injections in an ionospheric plasma. Permanent 40-kHz-modulated electron beam injection occurs simultaneously with a xenon-ion beam injected by the Hall-type plasma thruster operating in a square-pulse mode (100/50 s for a job/pause duration). The unusual behavior of the background charged particle fluxes and wave activity stimulated during the beam-plasma interaction have been registered by the scientific instruments onboard Intercosmos-25 station (IK-25) and Magion-3 subsatellite. The longitudinal and electromagnetic wave instabilities and their mutual relationship are considered in order to explain the observed effects. The excitation of electrostatic waves by the electron injection has been considered for different resonance conditions near the linear stability boundary. Beam-driven electromagnetic instability is responsible for the backward-propagating whistler waves excited via cyclotron resonance. Competition of these two beam instabilities is one of the subjects of the present study.