Energy-optimal base station density in cellular access networks with sleep modes

Sleep modes are widely accepted as an effective technique for energy-efficient networking: by adequately putting to sleep and waking up network resources according to traffic demands, a proportionality between energy consumption and network utilization can be approached, with important reductions in energy consumption. Previous studies have investigated and evaluated sleep modes for wireless access networks, computing variable percentages of energy savings. In this paper we characterize the maximum energy saving that can be achieved in a cellular wireless access network under a given performance constraint. In particular, our approach allows the derivation of realistic estimates of the energy-optimal density of base stations corresponding to a given user density, under a fixed performance constraint. Our results allow different sleep mode proposals to be measured against the maximum theoretically achievable improvement. We show, through numerical evaluation, the possible energy savings in today’s networks, and we further demonstrate that even with the development of highly energy-efficient hardware, a holistic approach incorporating system level techniques is essential to achieving maximum energy efficiency.     

Intelligent Information‐Centric Networking routing scheme under imprecise information

Information‐Centric Networking (ICN) has been accepted to overcome some weaknesses of the current Internet architecture, showing that “what is being exchanged” is more important than “who are exchanging information.” Given the inadequate considerations on Quality of Service (QoS) and energy saving in ICN routing, we propose in this paper a routing algorithm to enhance the two aspects. At first, on one hand, Cauchy distribution is used as a fuzzy model to evaluate users' QoS requirements, such as bandwidth, delay, and error rate; on the other hand, we formulate energy saving problem to evaluate the green quality of routing algorithm. Then, we design a link selection approach by considering QoS and energy saving, which belongs to a multi‐objective decision problem resolved by intelligent drops algorithm. Finally, we implement the proposed algorithm and compare it with the famous adaptive forwarding mechanism in terms of some significant metrics, and the experimental results reveal that the proposed algorithm is more efficient.     

Factors involved in associations between Facebook use and college adjustment: Social competence,perceived usefulness,and use patterns

Although previous research has investigated widespread use of social media, especially Facebook, by youth attending college, the conditions under which these media foster adjustment to college remain unclear. This study tested a model illuminating pathways linking social competence to college adjustment via students’ perceptions about the usefulness of Facebook and ways in which they used the medium. Self-report survey data from 321 college students (M age = 20.09; 58% female; 84% Caucasian) attending a major Midwestern university supported the proposed model, indicating that higher social competence could foster or impede college adjustment, depending upon how it was related to beliefs about the usefulness of different Facebook functions and how these perceptions, in turn, were associated with patterns of Facebook use. Findings underscore the importance of considering connections among personal attributes, perception of media effectiveness, and media behaviors in assessing the implications of social media for users’ psychosocial well-being.     

无源性理论在永磁同步电动机混沌控制中的应用

永磁同步电动机在一定的工作条件下呈现出混沌运动，根据无源性网络理论，设计电动机混沌动力学模型的控制器，将混沌系统等效为无源系统，消除系统中的混沌运动，降低系统自激振动的危害，实现混沌系统的快速稳定。     

Self-Organized Monitoring in Ad-Hoc Networks

We propose in this paper a self-organized monitoring architecture for mobile ad-hoc networks based on a selective scheme where subsets of nodes are managed. These nodes are determined based on their network behavior in order to favor subsets of well-connected nodes. The key idea is to relax the requirements of the management plane, and to use these manageable subsets to monitor the performance of the overall network. We therefore propose a new performance metric to be monitored, in order to estimate the capability of ad-hoc nodes to communicate end-to-end in the network. Extensive simulations show how different parameters affect this metric.     

GPRS无线DDN系统与应用

介绍基于GPRS网络无线DDN系统的构成、组网以及在电力系统的应用，同时对传输包长度、效率、时延等参数进行分析。     

同步电动机改型设计

对同步电动机从400V改为6000V过程中的几个问题通过实例进行分析说明,可供同步电机的改型设计参考。     

具有大电流输出能力的开关电源

本文介绍大电流输出的开关电源芯片MAX1623的特点，设计原理和典型应用电路。     

Cross-Layering Approaches in Wireless Ad Hoc Networks

Wireless ad hoc networks are temporary formed, infrastructureless networks. Due to the unstable channel conditions and network connectivity, their characteristics impose serious challenges in front of network designers. The layering approach to network design does not fit the ad hoc environment well. Therefore, various cross-layering approaches, where protocol layers actively interact, exchange inherent layer information and fine tune their parameters according to the network status are becoming increasingly popular. This paper presents an in-depth analysis of the latest cross-layering approaches for wireless ad hoc networks supported by several examples. A special emphasis is put on the link and network layer related cross-layer designs. Several link adaptation and efficient service discovery schemes are elaborated through analytical and simulation studies. Their performance shows the potentials of the cross-layering for boosting system characteristics in wireless ad hoc networks. Liljana Gavrilovska currently holds a position of full professor at Faculty of Electrical Engineering, University “St. Cyril and Metodij” – Skopje, Macedonia. She is chief of Telecommunications Laboratory and teaches undergraduate courses in telecommunication networks, data transmission and switching and traffic theory, and graduate courses in wireless, mobile and personal networks, teletraffic engineering and planning, and broadband multiservices networks. In 2000 she joined the Center for PersonKommunikation, Aalborg University, Denmark, as a visiting professor and during 2001--2002 she held a position of associate research professor at the same university. Currently she holds a part-time position of associated research professor with Center for Teleinfrastructur (CTIF). Prof. Gavrilovska was involved in several EU (ACTS ASAP, IST PACWOMAN, MAGNET, TEMPUS) and national/international projects. She published numerous conference and journal papers and participated in several workshops. At the moment she is working on the book “Ad Hoc Networking Towards Seamless Communications” together with prof. R. Prasad. Her research interests include wireless and personal area networks, ad hoc networking, networking protocols, traffic analysis, QoS, and optimization techniques. She is a senior member of IEEE and serves as a Chair of Macedonian Communication Chapter.     

烟气轮机长周期高负荷运行的途径和方法

北京燕山分公司2000kt/a催化裂化装置的烟气轮机机组,在投运的几年内,存在电仪故障多、气轮机轴振动大及回收率低等一系列问题。通过技术攻关及操作优化,烟气轮机的轴振动值最大不超过70μm,发电量提高至13000kW·h以上,每年停机检修的时间可控制在15天以内,全年的净收效益将达到5460万元,每年可提高效益1620万元。与装置同步运转率由2004年的87%提高到96%,显著提高了经济效益和社会效益。