An optimal equivalent subchannel algorithm for low voltage power line communication system

According to the low voltage power line channel features,combined with adaptive bit loading and power allocation algorithm,an optimal equivalent subchannel algorithm is proposed.Under the condition of fixed amount of transmitted bits and the minimum transmitted power model,impact of optimal equivalent subchannel on the system performance is studied.The optimization algorithm sorts subchannels with similar transmission features into groups,thus the signaling load can be reduced,and the spectrum can be better used.The simulation results show that system can get lower bit error rate(BER) by adopting optimal equivalent subchannel algorithm.     

Blind estimation of IQ imbalance withnull subcarriers for OFDM systems

Orthogonal frequency division multiplexing (OFDM) is sensitive to the in-phase and quadrature-phase (IQ) imbalance induced by the direct conversion architectures. A compensation scheme of IQ imbalance exploiting null subcarriers in OFDM symbols is presented. The proposed algorithm is with high bandwidth utilization because the training symbols are not required. The effect of IQ imbalance on OFDM systems is studied, and the mirror relationship between the FFT of a sequence and that of its conjugate is employed to estimate and compensate the IQ imbalance. This method can be applied to multiple input multiple output (MIMO) OFDM systems with space time block code (STBC). Performance analysis shows that the proposed algorithm is asymptotically unbiased. The variance is inversely proportional to the number of OFDM symbols, null subcarriers, the SNR and the channel frequency response, and proportional to the IQ imbalance. Simulation results demonstrate that this scheme can obtain almost the optimal bit error rate (BER).     

Novel channel estimation algorithm for OFDM/TDM over fast fading channels

For the shortage of tracking ability against fast fading channel of the existing pilot structures and channel estimation algorithms in OFDM combined with time division multiplexing (OFDM/TDM) system, an improved channel estimation algorithm is proposed. The channel transfer functions are obtained by estimating the channel properties with two adjacent time domain multiplexing (TDM) pilot sequences, while the channel state information of the OFDM/TDM symbols is obtained with interpolation Combined with frequency domain equalization based on minimum mean square error (MMSE-FDE), the proposed algorithm can significantly compensate the path loss over fast fading channels. Simulation results show that, compared with the existing channel estimation algorithms, the proposed algorithm can achieve better performance, which is not only capable of dealing with slow fading channels, but also has a better tracking ability against fast fading channels with the same data transmission efficiency.     

Adaptive bit allocation algorithm in an orphogonal frequency division multiplexing system of cognitive radio

An orphogonal frequency division multiplexing(OFDM) based cognitive radio architecture was designed to meet the transmission requirements of a cognitive radio system. After finishing the allocation of subtransmission, and keeping BER within the limit that ensures service quality, an adaptive bit allocation method was proposed to allocate the bit and energy of subtransmission dynamically. The total power for launching needed reached its minimum (or SNR per bit reached its maximum). Compared with the fixed bit allocation method, the proposed method is simpler, decreases the system transmission power, and has better BER performance.     

Research on a Novel Inverter of VSC

In order to improve waveform performance of light HVDC system, a lot of switches which operate in high frequency are used, which causes large switching losses and results high cost. A new Buck type voltage source converter(BVSC) is proposed. The new BVSC comprises a dual-buck converter and a three-phase inverter operating in grid frequency. Only two high frequency switches are used, which results good output waveform performance. In order to reduce the high frequency switching losses, a novel improved double-frequency Buck type voltage source converter(DBVSC) is also proposed. An additional dual-Buck converter is added to the BVSC, the added dual-Buck converter deals with the fundamental power that operates in low frequency, and BVSC only deals with harmonic power that operates in high frequency. The output waveform is enhanced and the switching losses are reduced in DBVSC, and the power rating is also increased. The DBVSC is very suitable for large power rating application. The one cycle control theory is adopted to control the proposed DBVSC with analog circuit, which is very simple. The proposed DBVSC and control method are verified by simulation.     

Allocation Rule in Life-cycle Assessment Inventory of MSW''sIncineration System

The allocation MSW disposal measure, which would occupy large quantity of land, cannot meet the need of the development of the urban area and economics and the great yielding of MSW. The author gets the conclusion that the nost suitable disposal measure for MSW is incineration. The allocation and the life cycle evaluation are both focused on.The principles and influencing factors of the allocation in relation to these systems are discussed in detail. A conclusion is that the factors of economic and envronment policy are more important than technique.     

前混合磨料射流磨料速度测试的新方法

前混合磨料射流超强的打击力主要是由高速磨料群提供的,因此,磨料速度测试是磨料打击力分布规律等研究的基础。针对传统研究方法的不足之处,笔者提出采用PIV技术结合自主编程设计的磨料中心识别程序,实现非接触式测试手段下磨料速度测试实验研究,并利用该方法简要分析了喷嘴结构对磨料速度的影响。结果表明,在一定范围内增加直线段长度有利于提高喷嘴出口处磨料的速度,表明在喷嘴直线段末端磨料依然处于明显的加速状态;增加收敛段长度对提高喷嘴出口处磨料速度有一定的作用,但磨料速度增幅不大;收敛角较大时,液相在收敛段前半段加速缓慢而在后半段过于剧烈,因磨料颗粒加速滞后于液相的原因导致喷嘴出口处磨料速度降低。     

Outage probability and power allocation in cognitive relay networks under imperfect channel state information

Considering the interference introduced by primary user, the outage probability of cognitive relay networks under imperfect channel state information is analyzed based, on the relay selection for the maximum channel gain. In addition, the mathematical optimization model of maximizing the spectrum efficiency under the interference constraint of primary user and the QoS requirement of cognitive user is proposed for cognitive relay networks. Then, the optimal solution of the model is obtained with the Lagrangian method. The proposed scheme improves the spectrum efficiency of cognitive relay networks on the premise of guaranteeing the transmission performance of primary user. Simulation results show that the proposed power allocation scheme improves the system performance compared with the traditional equal power allocation scheme. Meanwhile, it indicates that the approximate spectrum efficiency can be obtained under the perfect channel state and the imperfect channel state. Under the imperfect channel state, the feedback information and the complexity of implementation will be reduced, which is beneficial to the engineering application.     

Introduction: Environmental conflict in the Asia‐Pacific

Abstract: The literature on environmental conflict has expanded greatly over the past 10 years, yet most of the cases and theory have been from a Western, Northern, and developed world context. This volume concentrates on cases of current conflict and its management from Asian and Pacific nations. This paper presents a brief literature review of the nature of environmental conflict and highlights some of the key authors who have featured. Their conclusions are summarised into four key suppositions; a) Environmental conflict is a result of scarcity and represents social struggles against uneven usage and allocation of resources; b) Environmental conflict reflects poor performance by governments in developing complex public policy; c) Environmental conflict involves the issues of power and rights; d) Environmental conflict is an inevitable consequence of development and can be constructive.     

电源分配网络阻抗分析及去耦电容优化

高速印制板电源分配网络（power delivery networks,PDN）受电电源端口具有瞬时电流大、目标阻抗小的特点。针对任意形状电源板的阻抗问题,提出一种基于解析式与有限差分法的互补模型,并在此基础上结合粒子群算法实现多个受电电源端口的阻抗优化。通过Matlab仿真,发现互补模型的结果与全波有限元法的基本吻合,计算时间则大幅缩短。测量结果表明,优化后实验板的多个受电电源端口阻抗均满足各自的目标值要求。     

Parameter design and simulation for animproved direct current side active power filter

Considering the characteristics of the dc side series active power filter (APF) that the output voltage cannot be adjusted and the control circuit is complex , an improved single phase dc series APF topology is proposed. The improvement of the new circuit topology and fundamental working principle are analyzed. Following the circuit power factor pre regulator principle, the designing method for the main circuit parameters is given. The voltage ring and the current ring are designed by using the zero pole method. The main circuit power switch is controlled with the same frequencies, while the control circuit was simplified further. Compared with the paralleled APF, the main circuit of topology structure is simplified and the number of the active switches is reduced, which show low input current harmonics, high power factor, large voltage output adjustment range and low cost. The simulation results prove that the proposed topology is correct and reliable.     

Joint Parameters Estimation for CDMA Signals

In wireless communications,mobiles emit signals that arrive at a receiver with multiple paths,each with its own direction of arrival(DOA),path delay,fading,and Doppler shift frequency,which influence the quality of communication seriously.These parameters should be taken into account in array signal processing.Based on CDMA signal,a novel Space-Time approach is proposed to estimation the DOA,time delay,and the Doppler shift frequency.Because utilize special signal model about space-time-frequency of mobile communications.The proposed algorithm has simpler structure and high quality of division.The simulation results show the feasibility and effectiveness of the method.     

An electromagnetic interference design of a high speed image acquisition system on DM642

A novel design is presented to defend against electromagnetic interference (EMI) in a high speed data acquisition system. Problems that affect signal integrity (SI) in high speed image acquisition systems, such as reflection, crosstalk and ground bounce, are deeply analyzed in a manner consistent with transmission line theory. The results can theoretically inform EMI design of important networks, including system power, ground, clocks, high speed wires and decoupling capacitors. Experiments simulating print circuit board(PCB) reflection and EMI on high speed signal wires between DM642 and SDRAM are conducted. The power and ground should be placed separately in different layers. The clock lines passing through holes should be as few as possible. The signal lines should be as close to the same length as possible. The results show that amplitude of the signal overshoot is less than 0.7 V and the EMI amplitude is within the federal communications commission(FCC) standard.     

Bit Allocation Algorithm OFDM Systems Based for Low Voltage Network Transmitted Efficiency

Selfadaptation OFDM is suitable for the low voltage network.To satisfy the request of high speed communication in low voltage network,this paper studies a bit allocation algorithm for low voltage network OFDM systems based transmitted efficiency.And compared with the fix modulate OFDM and fix power OFDM,this algorithm can allocate the power and modulate flexibly and increase the speed.It is very appropriate for the low voltage network application.     

Dual mode AC DC AC converter for contactless power transfer system

A new type AC DC AC converter which can work in Buck or Boost mode is proposed in order to overcome the deficiencies of the primary circuit of the traditional contactless power transfer system. Through switching this two modes and turning the duty cycles of the switches, not only the resonant current amplitude of the primary resonant current can be controlled to be constant against a wide range variation of input voltage, but also the problems, such as surge current, high cost, complex control etc., caused by the DC filter and DC/DC converter in a traditional CPT system are effectively eliminated. The topology and operation principle of the proposed converter have been analyzed. The corresponding control strategy has been presented and verified by simulation results.     

雨久花种群开花期生殖株构件表型可塑性及生长分析

采用大样本取样野外实地测定方法,对丹东地区雨久花种群生殖株的数量性状和生殖分配规律进行了分析。结果表明,在开花期,雨久花种群单个生殖株植株高度和花序长分别为(91.59±7.96)cm和(11.10±2.46)cm,花数为(68.47±18.52)个;生殖株生物量、根生物量、茎生物量、叶生物量和花序生物量分别为(9.97±4.13)g、(1.21±0.66)g、(6.36±2.91)g、(1.35±0.76)g和(1.05±0.51)g。花期雨久花种群生殖株变异系数以叶生物量最大,为56.41%;其次为根生物量54.14%;株高最小,为4.87%,各数量性状具有较大的表型可塑性。雨久花种群生殖株表型可塑性遵循着规律性,即随着株高的增加,花序长和花数量呈幂函数增加,根生物量和花序生物量呈直线增加;花序生物量与总生物量之间不存在相关的函数关系。     

Simple and High Performance Timing Synchronization in OFDM System

One ML timing offset estimation method for orthogonal frequency-division multiplexing(OFDM) systems is presented.The performance of our timing offset estimator are compared to that of H.Minn's estimator in terms of estimator variance error in both AWGN channel and multipath fading channel. Because no performance floor exists under high SNR condition,the new estimator can get more accurate estimation result with low computational complexity even under multipath fading environment.     

Reliability Evaluation Model of Composite Generation and Transmission System Incorporating FACTS Devices

The utilization of Flexible AC Transimssion System(FACTS)technology has significant impact on power system reliability performance.Series FACTS devices such as Thyristor Controlled Phase Shifting Transformers(TCPSTs) and Thyristor Controlled Series Compensators(TCSCs) can change the natural allocation of the power flow and effectively alleviate transmission congestion.Parallel FACTS devices such as Static Var Compensators(SVCs)can provide reactive power support and maintain voltage stability.So it is important to quantitatively evaluate their benefits to the power system reliability.The traditional models of the composite generation and transmission system reliability evaluation are mainly focused on conventional generation and transmission facilities.This paper researches the power flow model of TCPST and TCSC,and then presents the optimal load shedding model incorporating TCPSTs,TCSCs and SVCs and effectively incorporates them into the reliability evaluation model.The proposed method is tested on the RBTS and the obtained results show that the system reliability can be improved effectually by FACTS devices.     

Performance Analysis of Anti-CW Interference in MC-CDMA Systems

The multicarrier-code division multiple access (MC-CDMA),which is the combination of direct sequence CDMA (DS-CDMA) and orthogonal frequency division multiplexing (OFDM) techniques, offers various advantages over single-carrier CDMA system. Some of the advantages are that MC-CDMA systems possess can remove the intersymbol interference (ISI) and enhance narrow-band interference suppression capabilities. So the MC-CDMA technique becomes a focus in the field of mobile communication. The authors introduce the typical MC-CDMA system model, discuss the decision statisticalvariable in Rayleigh fading channel included the CW interference, and give the expressions of probability of error in uplink. An approach is proposed with Modified Equal Gain Combining (MEGC) to decrease the effect of CW interference. Theoretical analysis and numerical results show that the anti-CW interference performance of MC-CDMA system can be improved used the MEGC approach.     

Managing the hinterland beyond: Two ideal‐type strategies of economic development for small island territories

Abstract: Rarely does one come across critical analysis which looks at islands as the strategic and candid promoters of a role as political and economic usufructuaries over external resources. This paper is premised on the proposition that a small territory is especially obliged to use extra‐territorial resources as its hinterland for economic success. Such resources extend over a whole range of goods and services and include access to investment, welfare, security, stable currency, international relations, specialised labour power, transfers, markets and higher education. The MIRAB syndrome is one way of articulating this condition. This paper proposes a second cluster of features that are, or can be, deployed by small territories in a manner somewhat different from MIRAB; this second cluster has a more proactive policy orientation and a disposition towards carving out procedural and jurisdictional powers. It is thus proposed to consider a small territory's engagement with the external hinterland as a position on a sliding scale, a strategic mix of options located between two distinct development trajectories, of which MIRAB is one and the PROFIT model the other.