Spectrum efficiency sub-carrier and energy efficiency power allocation for downlink multi-user CoMP in multi-cell system

Coordinated multi-point transmission/reception （CoMP） was proposed currently as an effective technology to improve cell-edge throughput in next-generation wireless systems. Most of the existing work discussed clustering methods mostly to maximize the edge user throughput while neglecting the problem of energy efficiency, such as those algorithm clustering base stations （BSs） of better channel condition and BSs of worse channel condition together. In addition, BSs usually increase the transmit power to achieve higher throughput without any considering of interference caused to other users, that may result in energy waste. The authors focus on the throughput maximizing problem while fully considering energy saving problem in CoMP systems. A coefficient is defined to describe the fitness of clusters. Then a sub-carrier allocation algorithm with clustering method is put forward for CoMP downlink, which can save the transmit power of BS and increase the throughput. Furthermore a power allocation scheme is proposed based on non-cooperation game; in which the transmit power is decreased by BSs generally to reach the Nash equation （NE）. Simulation shows that the proposed sub-carrier allocation scheme and power allocation algorithm are better than the existing ones on users＇ throughput while consumes much less energy.     

6061-T6铝合金高速高功率CO_2激光填丝焊接性的研究

为实现6061-T6铝合金薄板的高速高功率CO2激光填丝焊接,选用了ER4043,ER5356两种焊丝进行了焊接性试验。利用鱼骨状试样对两种焊丝的激光焊接铝合金6061-T6的热裂纹敏感性进行了分析;利用金相显微镜、扫描电镜、显微硬度计以及万能材料试验机分析了焊接接头的组织与性能。研究结果表明,与填充ER5356焊丝相比,填充ER4043焊丝的焊接接头热裂纹敏感性较低,焊接速度可达6 m/min。焊缝主要是柱状晶、等轴晶及少量树枝晶,显微硬度在60~80 HV,拉伸强度可达240~262 MPa,弯曲性能良好。     

电子信息机房UPS供电方式的选择

文中介绍了常用的UPS系统供电方式,通过对各种UPS供电方式的系统效率、设备投资、容错性能、可用性、装机占地面积及承重的比较,为用户提供在不同类型的电子信息机房选择UPS系统的建议。     

基于Simulink＆DSP Blockset功率谱估计的仿真实现

Matlab／DSP Blockset／Estimation库提供了对输入信号进行功率谱分析的各种模块。在Simulink图形化的交互环境下,用户只需用鼠标拖动Estimation库中的功率谱估计模块,便能迅速地进行信号的功率谱估计的仿真。     

Traffic‐aware downlink power allocation in multiuser OFDM system

Multiuser orthogonal frequency division multiplexing (OFDM) is a promising technology to achieve high uplink/downlink (DL) capacities in the next generation broadband wireless networks such as WiMAX (Worldwide Interoperability for Microwave Access). In this paper, we investigate the DL adaptive power allocation (APA) in multiuser OFDM system from the perspective of cross‐layer design. Specifically, we formulate APA as an optimization problem with the traffic profile of each user asit a priori knowledge. To solve the optimization problem, we develop a fairness‐constrained optimal prioritized effective throughput (PET) strategy and the corresponding iterative algorithms, aiming at balancing the prioritized effective throughput and the linear or logarithmic user satisfaction‐based fairness. Simulation results show that our proposed APA optimization approach can achieve satisfying performance. Copyright © 2011 John Wiley & Sons, Ltd.     

FTU技术在张掖市农网建设中的应用分析

在时张掖市农村电网改造和农电负荷变化情况调查的基础上,基于柔性输电理论,为提高农网供电质量和供电可靠性,分析了在张掖市农网中适时采用FTU技术的必要性及可行性。采用FTU技术建立配电设备与馈线主站之间的通信,获取配电系统运行控制及管理所需数据,执行主站给出的对配电设备的控制调节指令,实现提高供电质量和供电可靠性,降低电能损耗,提高设备利用率,减少维护费用,节省总投资的效果。实现正常情况下的优化配网运行和故障时的自动判别和自动隔离故障区以及恢复非故障区供电。为今后张掖市农网的进一步改造提出决策依据。     

Power output fluctuations in large scale pv plants: One year observations with one second resolution and a derived analytic model

The variable nature of the irradiance can produce significant fluctuations in the power generated by large grid‐connected photovoltaic (PV) plants. Experimental 1 s data were collected throughout a year from six PV plants, 18 MWp in total. Then, the dependence of short (below 10 min) power fluctuation on PV plant size has been investigated. The analysis focuses on the study of fluctuation frequency as well as the maximum fluctuation value registered. An analytic model able to describe the frequency of a given fluctuation for a certain day is proposed. Copyright © 2010 John Wiley & Sons, Ltd.     

A Compact Broadband PHEMT MMIC Power Amplifier for K through Ka-band Applications

A compact and broadband MMIC power amplifier operating from 18 GHz to 35 GHz is developed for K- through Ka-band applications implementing a rigorous electromagnetic (EM) simulation of closely spaced matching networks. The EM simulation results in a compact chip size as small as 2.16 mm × 2.0 mm and isolations of less than -25 dB up to 40 GHz between neighboring distributed structures. The two-stage balanced power amplifier fabricated using a 0.25 µm AlGaAs/InGaAs/GaAs PHEMT technology has an average gain of 11 dB, return losses less than -10 dB, and P1 dB above 20.5 dBm from 18 GHz to 35 GHz. This compact and broadband MMIC power amplifier is suited for power amplifiers for most K through Ka-band communication systems such as the FSS, LMDS, and ITS.     

Optimum Uplink Power/Rate Control for Minimum Delay in CDMA Networks

We derive a new joint power and rate control rule with which we can minimize the mean transmission delay in CDMA networks for a given mean transmission power. We show that it is optimal to respectively control the power inverse‐linearly and the rate linearly to the square root of channel gain while maintaining the signal‐to‐interference ratio at a constant. We also show that the proposed joint power/rate control rule achieves excellent performance results in terms of the probability of the instantaneous delay being within a target delay against one‐dimensional control schemes.     

论电网工程造价控制的问题与对策

我国的电网工程造价控制经过多年的发展,已经取得了长足的进步,然而还存在一些问题,致使电网工程造价控制水平受到了一定的制约。文中探讨了电网工程造价控制中存在的问题,并提出了一些意见和对策。