螺柱焊机电气控制系统的设计与功能优化

为了实现大直径螺柱焊的自动化,提出了一种基于三菱可编程控制器MELSEC IQ-F驱动伺服电机驱动系统以及气动装置的自动化螺柱焊系统,在详细分析螺柱焊确定自动焊接的过程,给出系统整体实现方案.给出了三台PLC控制11台伺服电机的的拓扑图.给出单工位工作时的系统的动作顺序图,提供了一个良好的操作界面.经实际运行证明设计可行.针对焊接中弧偏吹现象、焊缝受材料及外界干扰等现象,采取齿型双铜极来实现左右电极接触面相等,提升焊接效果,加装软橡胶实现自动纠正接触面不平等情况,产品经厂家使用证明,焊接的产品达到了企业的要求,极大的提升了焊接的质量和工作效率.     

认知Mesh网络的动态分层图路由模型及路由策略

该文提出了在认知无线电Mesh网络环境下的动态分层图路由模型,该模型将节点感知范围内的信道可用性用两状态离散时间马尔可夫链建模,建立认知无线电Mesh网络拓扑和连通性的动态模型。基于该模型提出了一种跨层设计的动态接口分配方案。仿真结果表明,动态分层图模型在适应接入频谱的动态变化和描述认知无线电Mesh网络的拓扑结构方面,表现出比静态分层图模型更加优异的性能。     

Performance analysis of microcell/macrocell with reuse partitioning in TDMA‐based cellular systems

System capacity and grade of service (GoS) are both important for the rapid growth of cellular communication services. In this paper, we propose a two‐tier TDMA‐based cellular system with macrocell overlaid on microcell clusters by implementing fixed channel assignment (FCA) scheme and fixed reuse partitioning (FRP) scheme in microcell layer and macrocell layer, respectively, named FCA–FRP overlay scheme. Improvement can be achieved in both system capacity and GoS. Theoretical analysis based on the overlay scheme without overflow and with overflow is first presented. It shows that the simulation results are agreed with the analytical results. Then, simulation results, obtained from the overlay scheme with and without overflow, show that the performance in terms of the call blocking probability, the call dropping probability and system capacity of such a system can be greatly improved compared with a conventional one‐tier cellular system deployed with FCA or FRP scheme. Copyright © 2008 John Wiley & Sons, Ltd.     

Shared partial path protection in WDM networks with shared risk link groups

For 100% shared risk link group (SRLG) failure protection, conventional full path protection has to satisfy SRLG-disjoint constraints, i.e., its working path and backup path cannot go though the same SRLG. With the increase of size and number of SRLGs, capacity efficiency of conventional shared full path protection becomes poorer due to SRLG-disjoint constraints and the blocking probability becomes much higher due to severe traps. To solve these problems, we present a partial path protection scheme where SRLG-disjoint backup paths may only cover part of the working path. Full path protection becomes a special case of partial path protection, in which the backup path covers the full working path. By choosing the most survivable partial backup path as backup path, we can make the impact of SRLG failures as low as possible and accept as many as possible connection requests. Assuming every SRLG has the same probability to fail, we present a heuristic algorithm to find the most survivable partial backup path by choosing full path protection first, iteratively computing partial backup paths and choosing the most survivable one. The benefit of this heuristic algorithm is that it can find the optimal results within less iteration. Analytical and simulation results show that, compared to conventional full path protection, our proposed scheme can significantly reduce blocking probability with little sacrifice on survivability. The proposed scheme is very useful particularly when the network contains a lot of SRLGs and the blocking probability of conventional full path protection becomes too high.

稀疏波长变换网络性能分析与研究

文章对动态业务模型下的稀疏波长变换网络性能进行了分析与研究，对波分复用（WDM）网络中引入波长变换器后的网络性能进行了系统的仿真，分析了波长变换器数量、波长变换器位置、波长变换范围以及路由波长算法等因素对网络性能的影响。     

X波段同轴腔多注速调管的研究

开展了具有同轴谐振腔互作用电路和双模工作杆控电子枪的X波段同轴腔双模多注速调管的研究工作.结合数值计算和冷测实验,对工作于TM₃₁₀高次模的同轴谐振腔模式分布和特性参数进行研究,获得了可满足多注速调管要求的谐振腔特性阻抗和良好的模式稳定性.采用具有双控制极的新型杆控多注电子枪及电子光学系统,可使多注速调管具有双模的新工作特性,通过数值模拟获得了优化的几何参数和具有良好层流性和波动性的空心多电子注.对采用6个电子注和5个谐振腔的X波段多注速调管进行了注波互作用大信号计算,结果表明当电子注电压为21.5kV,脉冲电流为14.4A时,可在30MHz频带范围内获得的100kW左右的脉冲输出功率,互作用效率大于30%,增益大于36dB.     

协同项目多目标任务分配优化算法

在协同项目中，伙伴企业间的任务分配问题直接影响到项目的整体获益。针对这一问题，以费用最小和承担企业数最少为目标，并充分考虑了任务之间的紧密关联关系，提出了一个有效的任务分配启发式算法，并进行了实例验证，给出了对算法的评价。     

Enhanced efficiency and frequency assignment by optimizing the base stations location in a mobile radio network

Most mobile radio networks have been planned based on the classical cellular concept. However, alternative planning strategies that lead to more efficient network configurations are necessary due to the fact that the traffic density is generally far from constant throughout the service area, making necessary the relocation of base stations inside the traffic hotspots. If the traffic is characterized in a discrete way, the optimization of base stations location resembles vector quantization, a well-known problem in signal processing. In this paper, we use this analogy to propose a mobile radio network planning algorithm. Simulation results show that higher trunking efficiency as well as improved frequency assignment can be obtained if an existing mobile radio network is redesigned using the presented strategy. Raúl Chávez-Santiago was born in Oaxaca City, Mexico. He obtained the B.Sc. degree in communications and electronics engineering in 1997 from the School of Mechanical and Electrical Engineering (ESIME-IPN), and the M.Sc. degree in electrical engineering in 2001 from the Center of Research and Advanced Studies of the National Polytechnic Institute (CINVESTAV-IPN) in Mexico City. He has professional experience as Computer Networking Engineer, and Research and Teaching Assistant. Currently, he is completing his studies toward the Ph.D. degree at Ben-Gurion University (BGU) of the Negev, Israel. In 2002, he received the URSI Young Scientist Award. His main research interests are the optimal planning of radio communication networks, the electromagnetic compatibility of terrestrial and satellite radio systems, and the efficient use of the radio spectrum. He is an IEEE and IEICE student member, and a URSI radio scientist. Avi Raymond was born in Yavne, Israel. He received the B.Sc. and M.Sc. degrees in electrical engineering from Ben-Gurion University (BGU) of the Negev in 2000 and 2005, respectively. He worked for two years in a communication company in the field of Telephony and Broadband Services. He also worked as a Research Assistant in the communications laboratory at BGU. He currently works at Elta Electronic Industries Ltd. as System Engineer and pursues studies toward a second M.Sc. degree in systems engineering at the Technion Institute of Technology, Haifa, Israel. His research interests are the optimization algorithms for frequency assignment in cellular networks. Vladimir Lyandres was born in 1944, in Vologda, Russia. He received the M.Sc. degree in communications engineering in 1966 and the Ph.D. degree in communications theory in 1972 from the State University of Telecommunications (SUT), Saint Petersburg, Russia. He was with SUT until 1990 holding a position of Senior Scientific Associate and working on research and development of digital transmission systems, modeling of radio communication channels and algorithms of frequency planning for broadcasting and cellular systems. Since 1991 he holds a position of Researcher at the communications laboratory and Professor at the Department of Electrical and Computer Engineering, Ben-Gurion University (BGU) of the Negev, Israel. His research interests include synthesis of Markov models, combinatorial optimization, and adaptive power loading. He is a senior member of IEEE and member of IEICE.     

Range Assignment for Biconnectivity and k-Edge Connectivity in Wireless Ad Hoc Networks

Depending on whether bidirectional links or unidirectional links are used for communications, the network topology under a given range assignment is either an undirected graph referred to as the bidirectional topology, or a directed graph referred to as the unidirectional topology. The Min-Power Bidirectional (resp., Unidirectional) k-Node Connectivity problem seeks a range assignment of minimum total power subject to the constraint that the produced bidirectional (resp. unidirectional) topology is k-vertex connected. Similarly, the Min-Power Bidirectional (resp., Unidirectional) k-Edge Connectivity problem seeks a range assignment of minimum total power subject to the constraint the produced bidirectional (resp., unidirectional) topology is k-edge connected. The Min-Power Bidirectional Biconnectivity problem and the Min-Power Bidirectional Edge-Biconnectivity problem have been studied by Lloyd et al. [23]. They show that range assignment based the approximation algorithm of Khuller and Raghavachari [18], which we refer to as Algorithm KR, has an approximation ratio of at most 2(2 – 2/n)(2 + 1/n) for Min-Power Bidirectional Biconnectivity, and range assignment based on the approximation algorithm of Khuller and Vishkin [19], which we refer to as Algorithm KV, has an approximation ratio of at most 8(1 – 1/n) for Min-Power Bidirectional Edge-Biconnectivity. In this paper, we first establish the NP-hardness of Min-Power Bidirectional (Edge-) Biconnectivity. Then we show that Algorithm KR has an approximation ratio of at most 4 for both Min-Power Bidirectional Biconnectivity and Min-Power Unidirectional Biconnectivity, and Algorithm KV has an approximation ratio of at most 2k for both Min-Power Bidirectional k-Edge Connectivity and Min-Power Unidirectional k-Edge Connectivity. We also propose a new simple constant-approximation algorithm for both Min-Power Bidirectional Biconnectivity and Min-Power Unidirectional Biconnectivity. This new algorithm applies only to Euclidean instances, but is best suited for distributed implementation. A preliminary version of this work appeared in the proceedings of the 2nd International Conference on AD-HOC Network and Wireless (Adhoc-Now 2003). Research performed in part while visiting the Max-Plank-Institut fur Informatik. Gruia Calinescu is an Assistant Professor of Computer Science at the Illinois Institute of Technology since 2000. He held postdoc or visiting researcher positions at DIMACS, University of Waterloo, and Max-Plank Institut fur Informatik. Gruia has a Diploma from University of Bucharest and a Ph.D. from Georgia Insitute of Technology. His research interests are in the area of algorithms. Peng-Jun Wan has joined the Computer Science Department at Illinois Institute of Technology in 1997 and has been an Associate Professor since 2004. He received his Ph.D. in Computer Science from University of Minnesota in 1997, M.S. in Operations Research and Control Theory from Chinese Academy of Science in 1993, and B.S. in Applied Mathematics from Tsinghua University in 1990. His research interests include optical networks and wireless networks.     

Analysis of bandwidth allocation algorithms for wireless personal area networks

A major issue in the design and operation of ad hoc networks is sharing the common spectrum among links in the same geographic area. Bandwidth allocation, to optimize the performance of networks in which each station can converse with at most a single neighbor at a time, has been recently studied in the context of Bluetooth Personal Area Networks. There, centralized and distributed, capacity assignment heuristics were developed, with applicability to a variety of ad hoc networks. Yet, no guarantees on the performance of these heuristics have been provided. In this paper, we extend these heuristics such that they can operate with general convex objective functions. Then, we present our analytic results regarding these heuristics. Specifically, we show that they are β-approximation (β<2) algorithms. Moreover, we show that even though the distributed and centralized algorithms allocate capacity in a different manner, both algorithms converge to the same results. Finally, we present numerical results that demonstrate the performance of the algorithms. Randeep Bhatia received the Ph.D. degree in Computer Science from University of Maryland, the M.S. degree in Mathematics and Computer Science from University of Illinois at Chicago and the B.Tech. degree in Computer Science and Engineering from Indian Institute of Technology, Delhi. He is currently with the High Speed Networks Research Department at Bell Labs, Lucent technologies, working on network design, traffic engineering and scheduling algorithms. His current research interests are in the area of QoS for multimedia services in wireless data networks. Adrian Segall received the B.Sc. and M.Sc. degrees in electrical engineering from the Technion, Israel Institute of Technology in 1965 and 1971, respectively, and the Ph.D. degree in electrical engineering with a minor in statistics from Stanford University in 1973. After serving active duty in the Israel Defense Forces, he joined in 1968 the Scientific Department of Israel’s Ministry of Defense. From 1973 to 1974 he was a Research Engineer at System Control Inc., Palo Alto, CA and a Lecturer at Stanford University. From 1974 to 1976 he was an Assistant Professor of Electrical Engineering and Computer Science at the Massachusetts Institute of Technology. From 1987 to 1998 he was on the faculty of the Department of Computer Science at the Technion. He is presently Benjamin Professor of Computer-Communication Networks in the Department of Electrical Engineering, Technion, Israel Institute of Technology. From 1982 to 1984 he was on leave with the IBM T.J.Watson Research Center, Yorktown Heights, NY. He held visiting positions with IBM, AT&T and Lucent Bell Labs. His current research interests are in the area of optical networks, wireless, sensor and ad-hoc networks. Dr. Segall is an IEEE Fellow and has served in the past as Editor for Computer Communication Theory of the IEEE Transactions on Communications, Editor for the IEEE Information Theory Society Newsletter and Senior Editor for the IEEE Journal on Selected Areas in Communications. He was selected as an IEEE delegate to the 1975 IEEE-USSR Information Theory Workshop, and is the recipient of the 1981 Miriam and Ray Klein Award for Outstanding Research and of the 1990 Taub Award in Computer Science. Gil Zussman received the B.Sc. degree in Industrial Engineering and Management and the B.A. degree in Economics (both summa cum laude) from the Technion—Israel Institute of Technology in 1995. He received the M.Sc. degree (summa cum laude) in Operations Research from Tel-Aviv University in 1999 and the Ph.D. degree in Electrical Engineering from the Technion—Israel Institute of Technology in 2004. Between 1995 and 1998, he served as an engineer in the Israel Defense Forces. He is currently a Postdoctoral Associate in the Laboratory for Information and Decision Systems in MIT. His current research interests are in the area of ad hoc and sensor networks. In particular, he is interested in energy efficient protocols, medium access control protocols, and personal area networks. Gil received the Knesset (Israeli Parliament) Award for distinguished students, the Best Student Paper Award at the IFIP-TC6 Networking 2002 Conference, and the IEEE Communications Magazine Best Paper Award at the OPNETWORK 2002 Conference. In 2004 he received the Marie Curie Outgoing International Fellowship and the Fulbright Fellowship.