Modeling effective properties of chiral composites

After a brief overview of the concepts of electromagnetic chirality and wave propagation in chiral media, this paper deals with the field of microwave-chiral-material modeling. First, studies regarding the scattering of single-chiral or non-chiral elements with different shapes (various designs of helices, Ω-shaped scatterers, wires, and loops) are presented. Results of the backscattered field given by different computer codes are compared. Comparisons among analytical, numerical, and experimental results are also reported. Second, the case of a collection of chiral inclusions is treated. A review of different methods, developed to estimate average properties of helix-loaded materials, is given. Modeling of the effective properties of a chiral slab, such as the rotation angle, ellipticity, permittivity, and permeability, is explored. Reflection and transmission coefficients, evaluated by various methods, are compared with each other, and with measurements. Limitations of the models, possible improvements, and new directions for research are also described. Finally, applications of such composites to the design of radar-absorbing materials are addressed     

Intelligent robotics in manufacturing, service, and rehabilitation:an overview

Advances in intelligent robotics are resulting in a new generation of programmable, sensory-interactive, computer-controlled machines capable of operating with human supervision or autonomously from sensed information. The design and integration of these machines require knowledge of actuators, control, mechanisms, mobility, programming, and sensors. The application of intelligent robotic technologies can increase the productivity, safety, and the quality of life for people in a wide range of tasks for land, space, and undersea environments. This paper provides an overview of developments of intelligent robotics to manufacturing systems, robotic aids for the disabled, and service. The references highlight advances in robot control, sensor integration, mechanical hands, manufacturing automation, walking machines, and powered prostheses     

微波处理菘蓝种子的子叶发育与生物光子辐射的相关性

比较研究不同时间长度的微波辐照菘蓝种子对种子萌发率、淀粉酶活性、转氨酶活性、蛋白酶活性、蛋白质含量、游离氨基酸含量、总DNA含量、子叶发育状况及其生物光子辐射强度的影响.采用微波辐射浸泡3h的菘蓝(Isatis ind igotica Fort)种子.与对照相比,四种处理均能不同程度提高菘蓝种子萌发率、淀粉酶活性、转氨酶活性、蛋白酶活性,促进蛋白质、游离氨基酸、DNA合成,促进子叶发育,提高了生物光子辐射强度.低剂量微波辐射能提高种子生理生化代谢机能,促进种子萌发和幼苗生长发育,研究发现8 s微波预处理效果最为显著.     

无人机SAR/MTI侦察技术中若干问题的探讨

本文介绍了国外无人机SAR／MTI雷达研究现状和发展方向,列举了X、Ka,Ku三种频段SAR／MTI雷达主要技术指标,重点从工程实现的角度对SAR／MTI雷达技术中若干问题进行了探讨,包括无人机、SAR的成像模式和MTI兼容技术、频段选择、SAR成像实时数据的传输方式、惯导系统、最后讨论了成像算法。     

TD-LTE多频、分层组网的业务连续性研究

本文基于提升LTE多频、分层网下用户的业务感知,使用MR(测量报告)、扫频、切换性能等多维数据,全面评估异频共站小区、异频邻区的覆盖连续性和切换点,设定异频测量、切换参数,开展了多频网驻留策略、频间业务连续性、异频切换算法等多方面的研究,减少不必要的异频测量和切换、合理均衡各频段小区的业务承载,通过海量的MR数据,自动判别覆盖连续性、自动设定异频测量门限、自动计算异频邻区间的切换偏置,改善边缘用户的频繁重选导致手机接入感知下降、续航能力降低等问题。     

TCG架构下的证明问题研究及进展

证明问题是可信计算的核心问题之一.TCG架构下的证明问题解决方案由于可扩展性差、不灵活、容易暴露平台隐私以及性能低,正在成为可信计算的应用、推广和普及的瓶颈,严重地阻碍了可信计算在更广的范围内进行延伸和拓展.介绍了证明的基本概念并给出形式化定义,详细阐述了三元和四元证明系统的基本架构及工作机制,并指出平台身份证明采用了“推”式四元证明系统,而平台配置证明仍然采用三元证明系统.分析了当前对TCG架构下的平台身份证明、平台环境状态配置信息证明以及平台动态环境状态（运行时环境状态）证明等三个方面开展的研究工作,并对这些工作进行了总结.结合已有的研究成果,探讨了TCG架构下的证明问题的研究方向及其面临的挑战.     

事件科普营销模式探究

从事件的视角看科普,已形成了社会公共事件、社会热点事件、社会突发事件等社会事件中嵌入科普的应急科普模式。但从科普的视角看事件,应急科普模式只是依托事件展开科普的组成部分,结合事件营销和科普营销的已有研究基础,本文提出事件科普营销模式,界定其依借公益性、聚焦性和危机性事件的内涵和依附性、新闻性、策划性三个特征,并从科学技术渗透疆常生活、资源整合、投入产出效率等角度论述其兴起的内在依据,并提出借势方式和造势方式下的四种路径。     

基于TM影像光谱指数的棉花病害严重度估测

通过获取多时相试验区TM影像和大田同步调查棉花黄萎病,将TM影像光谱指数与病害严重度进行相关分析,建立棉花病害严重度估测模型.结果表明:随着病害严重度的增加,TM影像光谱指数B2,B4,SATVI,OSAVI,MSAVI,TSAVI,SVNSWI,SNSWIa,SNSWIb,SVNI,DNSIa,DNSIb,NDSWI...     

新媒体时代传统媒体战略转型与融合发展路径研究

2014年,注定以“媒体融合元年”为标志写入中国新闻发展史。在新一代信息技术支撑下,推动传统媒体和新媒体融合发展,既是技术问题,又是战略任务,必将对未来的媒体形态和格局产生深远影响。新媒体带来新思维,新思维带来新变革。作为媒体人,只有以改革创新精神迎接变革,加快媒体在理念、体制、技术、内容、运营等多个方面的融合,为民众提供更高效、更实时、更接地气的媒体内容,才能在这场变革中引领时代潮流,走出特色的科学发展之路,最终形成立体多样、融合发展的现代传播体系。     

环氧塑封料中填充剂的作用和发展

环氧塑封料占据整个半导体封装市场的90％左右,而填充剂含量占环氧塑封料的60％～90％,因此填充剂的性能直接影响环氧塑封料的加工性能、机械性能、导热性能和半导体器件的封装工艺性能、导热性能、可靠性能等。另外,当今社会电子技术日新月异,集成电路正向着超大规模、超高速、高密度、大功率、多功能、绿色环保化的方向发展,因此对环氧塑封料的性能要求愈来愈高,相应的填充剂性能也有了许多新的要求,并且也出现了许多新型填充剂。文中详细地介绍了环氧塑封料中填充剂的作用,各种填充剂对环氧塑封料和封装器件的性能影响以及环氧塑封料中填充剂的分类和发展。     

物联网发展现状研究

在介绍物联网概念的基础上,首先简单说明了物联网的体系架构,阐述了射频识别、无线传感网络、无线通讯、人工智能等物联网关键技术,然后对当前美国、欧盟、日本、韩国、中国等世界各国物联网发展战略进行概述,重点阐述物联网领域主要的标准化组织及其已经形成的物联网相关标准,对物联网的应用现状进行了归纳,对应用前景进行了展望,最后对物联网领域下一步亟待开展的相关工作进行说明。     

High-Reliability Low-Ag-Content Sn-Ag-Cu Solder Joints for Electronics Applications

Sn-Ag-Cu (SAC) alloy is currently recognized as the standard lead-free solder alloy for packaging of interconnects in the electronics industry, and high- Ag-content SAC alloys are the most popular choice. However, this choice has been encumbered by the fragility of the solder joints that has been observed in drop testing as well as the high cost of the Ag itself. Therefore, low-Ag-content SAC alloy was considered as a solution for both issues. However, this approach may compromise the thermal-cycling performance of the solders. Therefore, to enhance the thermal-cycling reliability of low-Ag-content SAC alloys without sacrificing their drop-impact performance, alloying elements such as Mn, Ce, Ti, Bi, In, Sb, Ni, Zn, Al, Fe, and Co were selected as additions to these alloys. However, research reports related to these modified SAC alloys are limited. To address this paucity, the present study reviews the effect of these minor alloying elements on the solder joint reliability of low-Ag-content SAC alloys in terms of thermal cycling and drop impact. Addition of Mn, Ce, Bi, and Ni to low-Ag-content SAC solder effectively improves the thermal-cycling reliability of joints without sacrificing the drop-impact performance. Taking into consideration the improvement in the bulk alloy microstructure and mechanical properties, wetting properties, and growth suppression of the interface intermetallic compound (IMC) layers, addition of Ti, In, Sb, Zn, Al, Fe, and Co to low-Ag-content SAC solder has the potential to improve the thermal-cycling reliability of joints without sacrificing the drop-impact performance. Consequently, further investigations of both thermal-cycling and drop reliability of these modified solder joints must be carried out in future work.     

软件无线电电台的计算机仿真

分析了软件无线电的分层结构,设计了一种软件无线电电台模型,其射频段参数、信道模型、调制方式和信源编码方式等可编程控制。建立了一种软件无线电电台的计算机仿真平台,进行了计算机仿真,验证了软件无线电的一些重要思想和技术。针对AM,SSB,FM,OOK,PSK,QPSK,MSK,FSK,16QAM九种信号,仿真结果表明,在载波频率、调制方式、信道模型等可以根据需要设置的环境下,电台的收发都能达到预期效果。当接收信号的信噪比为20 dB,AM与SSB调制度为0.8,FM的调频指数为3、数字调制的传速率都为2000 b/s时,载波频率的平均检测误差不大于2%,平均调制类型识别正确率不低于96%,模拟调制的平均失真率小于3%,数字调制的平均误码率小于10-5。     

偏振成像技术的研究进展及应用

偏振成像技术的优势是把信息量从3个自由度,即光强、光谱和空间,扩充到7个自由度,包括光强、光谱、空间、偏振度、偏振方位角、偏振椭率和旋转方向,这种观测信息量的丰富有利于提高对研究目标探测的精确度。本文首先介绍在近几十年内偏振成像技术在国内外的研究进展,其次介绍偏振技术在军事及民用领域的典型应用,最后对我国在偏振成像技术方面存在的问题给出合理的建议。     

物联网搜索技术综述

随着物联网的普及和发展,物联网搜索是摆在学术界和工业界面前迫切需要解决的问题,物联网搜索因此成为当前的一个研究热点。面对越来越多的传感器以及它们所产生的数据,只有结合智能的物联网搜索,才能体现这些数据的生命力。与传统的Baidu、Google、Bing、Yahoo等搜索引擎不同,物联网搜索从搜索对象、物理网数据的特点（大规模的、实时变化的、高度动态的、异构的、复杂的安全环境等）到物联网搜索的架构均与传统互联网不同,这导致了物联网搜所面临的挑战将更大。由此,阐述了物联网搜索的概念、特点、相关技术,对现有的典型系统和算法进行了比较性总结,分析了目前研究中存在的问题和挑战,并展望了其未来的发展方向。     

Engineering Automotive Software

The amount of software in cars grows exponentially. Driving forces of this development are the availability of cheaper and more powerful hardware, as well as the demand for innovation through new functionality. The rapidly growing significance of software and software-based functionality is at the root of various challenges in the automotive industries. These concern their organization, definition of key competencies, processes, methods, tools, models, product structures, division of labor, logistics, maintenance, and long-term strategies. This paper pinpoints the idiosyncrasies of the domain, characterizes the essentials of automotive software, and discusses the challenges of automotive software engineering     

智慧城市概念辨析

物联网已列入国家发展战略,智慧城市的发展目标是推动整个城市的繁荣,推动民生,并通过物联网的建设,扶持和带动整个物联网产业的发展,带动整个社会的进步。本文针对智慧城市的起因、定义、内涵、内在动力、价值、建设难点、与物联网的关系以及运营商对其的探索等内容进行详细的阐述。     

Pervasive intelligent endogenous 6G wireless systems: Prospects,theories and key technologies

The worldwide large-scale commercial deployment of 5G has commenced in 2020 for supporting enhanced Mobile BroadBand (eMBB), ultra-Reliable and Low-Latency Communications (uRLLC), and massive Machine-Type Communications (mMTC) services. Nevertheless, the upsurge of Artificial Intelligence (AI)-powered applications, the developmental law of one-decade-one-generation of wireless communications and the inherent limitations of 5G have also been spurring the industry and academia to dedicate their efforts to the research of future 6G wireless systems. 6G will be a disruptive, pervasive, intelligent, and endogenous wireless system, which will revolutionize all walks of life and accelerate the transformation and innovation of the global society. In this paper, we present a forward-looking, comprehensive and in-depth analysis and technical identification of 6G. Specifically, we firstly introduce the fundamental theories of 6G in terms of potential requirements. Then, we focus our attention on the discussion of promising key technologies in terms of spectrum, air interface, delay, access, energy consumption, coverage, AI, electromagnetism, interaction, etc.     

CompactPCI总线技术及系统设计

CompactPCI总线具有高总线带宽、高性能、支持热插拔，满足高速度、高性能尤其是复杂控制算法并要求可视化操作的应用场合的功能需求。首先，对CompactPCI总线技术在扩展性、封装和连接、被动式背板、热插拔和高性能等方面的技术特点。然后对其核心技术——热插拔技术做了简要的介绍，并在此基础上，对CompactPCI系统设计的相关问题进行了详细的论述。最后指出CompactPCI总线技术在工业、热力、石化、冶金、交通、现代通讯、核能、航空、航天、军事等领域具有广阔的应用前景。