Antenna-array pattern nulling using a differential evolution algorithm

A new method based on the differential evolution (DE) algorithm is proposed for antenna-array pattern synthesis with prescribed nulls. The array excitation amplitudes are the only controlling parameters, and the objectives are to synthesize array patterns with nulls imposed on directions of interferences while keeping the sidelobe levels (SLLs) below prescribed levels. Many factors such as the excitation dynamic range ratio, null depth level, null width, and SLLs are taken into account in the synthesis. Simulation results of several typical problems are compared with published results to illustrate the effectiveness of the proposed method. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 57–63, 2004.     

电分标准工作曲线的推导与实践研究

本文根据人眼视觉特性、孟塞尔方程及彩色复制理论,并结合实际工艺路线和工艺条件,推导出标准阶调复制曲线和标准电分工作曲线。它与德国Hell公司所绘的电分标准工作曲线基本一致。并做到了各工序有数据,有质量标准,使平印制版做到有规可循。     

Perspective:Societally connected multimedia across cultures

The advance of the Internet in the past decade has radically changed the way people communicate and col- laborate with each other. Physical distance is no more a barrier in online social networks, but cultural differences (at the individual, community, as well as societal levels) still govern human-human interactions and must be con- sidered and leveraged in the online world. The rapid de-ployment of high-speed Internet allows humans to interact using a rich set of multimedia data such as texts, pictures, and videos. This position paper proposes to define a new research area called ’connected multimedia’, which is the study of a collection of research issues of the super-area social media that receive little attention in the literature. By connected multimedia, we mean the study of the social and technical interactions among users, multimedia data, and devices across cultures and explicitly exploiting the cultural differences. We justify why it is necessary to bring attention to this new research area and what benefits of this new research area may bring to the broader scientific research community and the humanity.     

利用“球化效应”激光扫描制备球形Ti粉的研究

利用“球化效应”，在SLS设备上探索将异形Ti粉转化为高性能球形粉末的可行途径。通过系统地改变激光功率、扫描速度，以及选取合适的激光扫描间距，探明了形成“球化效应”的工艺条件，并在激光功率为600W，扫描速度为30mm／s时，获得了较为理想的球形Ti粉。通过对球化过程进行理论分析，得出了选取激光扫描制备球形Ti粉工艺参数的准则。     

矿区土壤重金属Cd高光谱建模与模型适应性分析

以粤北南岭某矿区土壤为研究对象,采用传统采样检测方法分析土壤重金属含量.借助ASD FieldSpec 4型便携式高光谱仪测量土壤光谱反射率,将土壤反射率经过卷积平滑后进行8种数据变换,分析9种光谱数据指标与镉(Cd)含量的相关性.采用偏最小二乘和随机森林方法,结合Pearson相关系数分别建立9种光谱数据指标的土壤重金属Cd含量的高光谱反演模型.并对其预测能力进行评价,实现了局地尺度上土壤重金属Cd含量反演,探究了不同Cd浓度区间对建模精度的影响.结果表明:通过不同的数据变换方式可以有效消除基线,去除背景干扰并提高光谱数据与Cd的相关性.其中一阶微分变换效果最为理想;偏最小二乘(Partial Least Squares Regression,PLSR)与随机森林(Random Forest Regression,RF)均能不同程度预测Cd含量,其中采用一阶微分结合随机森林(FD-RF)方法所建模型具备较高可靠性,R2超过0.80;当样本浓度平均值变化超过40％时,建立的模型预测能力降低.该研究方法可以作为土壤重金属Cd检测的手段,研究结果可以为土壤重金属高光谱反演提供方法和理论支持.     

三维薄膜型FLNG储舱晃荡载荷的数值仿真

针对浮式液化天然气(Floating Liquefied Natural Gas,FLNG)船大型储舱内的液体晃荡问题,分别以薄膜型储舱的1∶20模型及原型为研究对象,采用CFD仿真方法分析百年一遇生存海况下液舱内晃荡载荷的基本规律和危险工况.结果表明:在真实海况下,现有FLNG储舱设计中的晃荡冲击载荷主要来源于船体纵向运动,可能出现的最大冲击载荷约为0.4 MPa,主要发生在纵舱壁与横向隔水舱的拐角位置,危险载液率为20%~30%及90%.     

中文信息处理的词法问题——以句本位语法图解树库构建为背景

该文对比了句本位语法图解树库与中文信息处理现行词法规范在分词单位和词类标注两方面的差异,指出目前自动词法分析与句法分析的若干脱节之处,梳理了图解树库中关于临时造词、惯用语等特殊结构的标注策略和语言学理据,并探讨了“依句辨品”和“指称化”等汉语词类相关理论在中文信息处理中的实现方式。     

捷克锻造技术的发展概况

本文介绍捷克在锻压技术方面的发展情况,主要叙述科研机构与研究开发的业务范围、生产厂家与生产的主要设备以及今后的发展目标。