Preparation of transmission electron microscopy cross-section specimens of crack tips using focused ion beam milling

The preparation of transmission electron microscope (TEM) thin foil specimens from metal alloys containing cracks is usually thwarted by the difficulty in preventing preferential erosion of material along the flanks and at the tips of cracks. Recent developments in focused ion beam (FIB) micromachining methods have the potential to overcome this inherent problem. In this article we describe the development of new procedures, one using FIB alone and the other using a combination of FIB with more conventional ion milling to generate TEM specimens that largely retain the microstructural information at stress corrosion cracks in austentic alloys. Examples of corrosion product phase identification and interfacial segregation are included to verify that detailed information is not destroyed by ion bombardment during specimen preparation.     

电缆地层测试取样模式研究

稠油、低渗透性、高压差等疑难地层及其取样纯度和泵抽时间是电缆地层测试目前面临的主要问题.应用斯伦贝谢公司研制的聚焦探针,改进传统探针的取样模式,在很大程度上解决了这些问题.以多口井的成功应用为基础,分析研究聚焦探针的取样模式和技术特性,总结其应用效果和适用范围,并提出合理化建议,对电缆地层测试技术在中国的应用和发展具有...     

M盆地淡水地层油层电性标准研究

M盆地 L区地层水为淡水类型 ,各井随埋深的不同及钻井泥浆性能的不同 ,油、水电性识别极为困难。油、水层二者间的各种电阻率的交叉范围很大 ,应用经典的确定某一电阻率值的方法或 RL Ld- RMSF L等关系不可能建立其有效的图版。自然电位曲线是主要反映泥浆滤液与地层水关系的电测曲线 ,自然电位异常幅度值ΔVSP亦与地层电阻率有关。根据自然电位电性原理 ,对 M盆地 L区试油层的 RLL d-ΔVSP的关系进行了研究。研究表明 ,油、水层在 RL Ld-ΔVSP图版上具有明显的界面 ,利用界面方程可对 M盆地 L区油、水层进行有效的判别 ,具有极为重要的应用价值     

数字滤波技术在电阻率测井仪器中的应用探讨

以微球测井仪为例建立了对采集数据作数字滤波处理的数学模型,并进行了仿真研究.其结果表明,与传统模拟处理方法相比,数字滤波器不仅能有效减少硬件,而且更因其阶数高、幅频特性更理想、无温度漂移、处理精度和可靠性较高,从而提高了数据处理的质量,其处理速度也能够满足测井实时性的要求.此方法对其它电阻率仪器也可适用.     

微球形聚焦测井仪技术改造

介绍油田普遍使用的一种测井方法－微球形聚焦测井。它用于测量地层冲洗带电阻率。文中还介绍了微球形聚焦测井仪在使用过程中所出现问题解决的措施,并提出了在测井仪器选用中的一种思路－强强联合。经技术改造后的仪器,在现场应用,取得Ｒｘｏ、Ｒｍｃ,ｄＨ三条全优曲线,取得较好的效果。     

少道叠加在海上高分辨率地震资料处理中的应用

受原始记录远道频率低于近道频率、动校拉伸、速度误差等因素的影响 ,满覆盖叠加降低了地震剖面的分辨率。文中讨论了少道叠加方法 ,对少道叠加和满覆盖叠加的结果做了分析和对比 ,认为少道叠加既可以保护高频信息 ,又可以压制随机噪音。少道叠加技术的关键在于消除叠前道集中的随机噪音和多次波 ,提高叠前资料信噪比。少道叠加技术在实际资料处理中见到了明显的效果。     

面向水环境监测的无线传感网络协作波束形成远距离传输优化方法

在无线传感网络技术应用于水环境的自主监测过程中,无线传感网络限制的传输距离成为制约其发展的主要问题之一。针对当前水环境监测及无线传感网络远距离传输存在的问题,提出了基于改进的高斯骨架差分进化的波束合成远距离传输优化方法。首先根据远距离传输要求建立优化模型,该模型不仅考虑接收节点方向协作波束的主瓣增益,还考虑了旁瓣对其他非接收方向的干扰问题;然后提出了改进高斯骨架差分优化方法,该方法在交叉过程中增加对旁瓣幅值的判断,加速了节点功率优化的收敛速度。实验对比和验证分析结果表明,该方法在不同主瓣增益要求条件下最小旁瓣增益性能比典型优化算法提升了6.8%~10.2%,比随机优化方法提升了31.8%~35.4%,不仅能够满足实际要求,而且能够有效减少对其他非接收方向的干扰,为实现水环境监测远距离传输提供了有效的理论和技术支撑。     

Online ice crystal size measurements during sorbet freezing by means of the focused beam reflectance measurement (FBRM) technology. Influence of operating conditions

In ice cream and sorbet manufacturing small ice crystals are desired to deliver a product with a smooth texture and good palatability. This research studied the influence of the operating conditions on the ice crystal size and the draw temperature of the sorbet during the freezing process. The evolution of ice crystal size was tracked with the focused beam reflectance measurement (FBRM) technique, which uses an in situ sensor that makes it possible to monitor online the chord length distribution (CLD) of ice crystals in sorbets containing up to 40% of ice. The refrigerant fluid temperature had the most significant influence on the mean ice crystal chord length, followed by the dasher speed, whereas the mix flow rate had no significant influence. A decrease in the refrigerant fluid temperature led to a reduction in ice crystal size, due to the growth of more small ice crystals left behind on the scraped wall from previous scrapings. Increasing the dasher speed slightly reduced the mean ice crystal chord length, due to the production of new small ice nuclei by secondary nucleation. For a given refrigerant fluid temperature and dasher speed, low mix flow rates resulted in lower draw temperatures, due to the fact that the product remains in contact with the freezer wall longer. High dasher speeds warmed the product slightly, due to the dissipation of frictional energy in the product, the effect of which was in part moderated by the improvement in the heat transfer coefficient between the product and the freezer wall.     

基于2阶锥规划的雷达干扰宽带数字波束形成优化设计

针对现有宽带数字波束形成方法在雷达干扰技术领域的工程应用中存在适用信号单一、干扰效果差、实现难度高等缺点,采用一种基于2阶锥规划(SOCP)理论的雷达干扰宽带数字波束形成方法,在波束形成器的每个阵元通道各自使用1个对应的宽带有限长单位冲激响应滤波器对待发射宽带干扰信号进行整体幅相调制。为获得最佳滤波器系数,采用线性约束最小功率准则对波束形成器进行设计及优化。通过消除旁瓣约束式的频率依赖性,并将滤波器系数求解问题的解析形式转化为相应的SOCP形式,降低了优化难度。仿真结果表明,该方法可以较好地解决相应约束条件下雷达干扰宽带数字波束形成优化设计问题。     

On Downlink Beamforming Methods: Capacity and Error Probability Performance

In space-division multiple access (SDMA), different beamforming or space-domain precoding techniques can be applied. We investigate two different space-domain precoding methods, the maximum capacity (MC) and the minimum mean square error (MMSE) precoders, for the downlink channel. It is shown that the MMSE precoding, which is practically implementable, can provide a reasonable performance in terms of the capacity and error probability, while the MC precoding is not practical (although it is optimum in terms of the capacity). Space-domain precoding methods are also applied to code-division multiple access (CDMA) systems.This work was supported by the HY-SDR Research Center at Hanyang University, Seoul, Korea, under the ITRC Program of MIC, Korea.Jinho Choi was born in Seoul, Korea. He recieved the B.E. degree (magna cum laude) in electronics engineering from Sogang University in 1989 and the M.S.E. and Ph.D. degree in electrical engineering from the Korea Advanced Institute of Science and Technology in 1991 and 1994, respectively. Currently he is a Senior Lecturer in the School of Electrical Engineering and Telecommunications,University of New South Wales, Australia. Dr. Choi received the 1999 Best Paper Award of Signal Processing from EURASIP.Seungwon Choi received the B.S. degree from Hanyang University, Seoul, Korea, in 1980 and the M.S. degree from Seoul National University, Seoul, in 1982, both the electronic engineering. He received the M.S. degree in computer engineering in 1985 and the Ph.D degree in electrical engineering in 1988 from Syracuse University, Syracuse, NY.From 1982 to 1984, he was with LG Electronics Co. Ltd., Seoul, where he helped developed the 8-mm camcorder system. From 1988 to 1989, he was with the Department of Electrical and Computer Engineering, Syracuse University, as an Assistant Professor. In 1989, he joined the Electronics and Telecommunications Research Institute, daejeon, Korea, where he developed the adaptive algorithm for real-time application in secure telephone systems. From 1990 to 1992, he was with yhe Communication Research Laboratory, Tokyo, Japan, as a science and Technology Agency Fellow, developing adaptive antenna array system and adaptive equalizing filters for applications in land-mobile communications. He joined Hanyang University, Seoul, in 1992 as an Assistant Professor. He is a Professor in the School of Electrical and Computer Engineering, Hanyang University. His research interests include digital communications and adaptive signal processing with a recent focus on the real-time implementation of smart antenna system for 3G mobile communication system.