一种通用电子式互感器数字接口的研究与实现

电子式电流/电压互感器(ETA/ETV)与继保设备的合并单元(MU)的数字接口一直没有明确的规范,为方便ETA/ETV与各厂家的MU接口,考察了国内电力设备二次厂家MU的数字输入输出格式后提出了一种通用的电子式互感器与MU的数字接口方法。该方法采用复杂可编程逻辑器件(CPLD)作为核心处理器件,能够方便地实现各种数字输出的ETA/ETV与MU的接口。接口转换系统与四方公司MU的配合实验结果验证了接口方法和系统软硬件设计的正确性,可以运用在实际的一次互感器和二次设备接口的场合。     

Fast iterative WSVT algorithm in WNN minimization problem for multiuser massive MIMO channel estimation

In this paper, channel estimation for multiuser massive MIMO system is addressed for the scenario, where the number of scatterers is small compared to the base station antennas and single antenna users in the cell. If the number of scatterers is limited, then the corresponding angle of arrivals are finite. Moreover, if all the users share the same angle of arrivals, then the correlation among the channel vector increases. Thus, the high‐dimensional channel is approximated to the low‐rank matrix. This rank minimization problem is formulated as the weighted nuclear norm problem and is estimated using iterative weighted singular value thresholding (IWSVT) algorithm. To increase the convergence rate, fast IWSVT algorithm is proposed and the performance is measured based on mean square error and uplink and downlink achievable sum‐rate. The simulation study shows that the proposed weighted nuclear norm minimization method with fast IWSVT algorithm performs better than the conventional least square and the nuclear norm minimization method for various finite scatterers in different signal‐to‐noise ratio levels.     

Unfolding of cytochrome c immobilized on self-assembled monolayers. An electrochemical study

The electron transfer (ET) process of progressively unfolded bovine cytochrome c immobilized on different self-assembled monolayers (SAMs) was investigated. Insight is gained on the role of the SAM surface on the functionality of the partially unfolded and non-native forms of the adsorbed protein. Direct electrochemical measurements were performed on cytochrome c adsorbed on mercaptopyridine (MP) and mixed 11-mercapto-1-undecanoic acid/11-mercapto-1-undecanol (MUA/MU) at varying temperature, in the presence of urea as unfolding agent. Under strongly unfolding conditions, a non-native form of cytochrome c, in which the methionine ligand is replaced by a histidine, was observed on both MP and MUA/MU SAMs. The E°′ of the native form, in which the haem is axially coordinated by methionine and histidine, slightly shifts to negative values upon increasing urea concentration. However, the non-native bis-histidinate species shows a much lower E°′ value (by approximately 0.4 V) which is by far enthalpic in origin and largely determined by axial ligand swapping. Analysis of the reduction enthalpies and entropies and of the ET rate constants indicate that the nature of the SAM (hydrophilic or anionic) results in changes in the conformational rearrangement of the cytochrome c under unfolding conditions.     

Analysis of minimum transmit sum power and scheduling power gain for multi‐user MIMO‐OFDM networks with rate constraints

Minimum transmit sum power (MTSP) is of high theoretical and practical value in multi‐user rate‐constrained systems; it is, however, quite difficult to be numerically characterized in complex channels for the prohibitively high computational power required. In this paper, we present a computationally efficient method to approximate the MTSP in multi‐user multiple‐input multiple‐output orthogonal frequency division multiplexing (MU‐MIMO‐OFDM) wireless networks. Specifically, we propose both lower and upper bounds of the MTSP, which are asymptotically accurate in the limit of large K, the number of users. Then, we develop two iterative water‐filling algorithms to numerically solve the proposed bounds. These algorithms are with low complexity, that is, linear in K, and therefore enable the analysis of MTSP in complex channels even if K is large. Numerical results demonstrate the effectiveness of the bounds in approximating the MTSP and the high computational efficiency of the proposed iterative water‐filling algorithms. With the proposed bounds, we further numerically study scheduling power gain (SPG), which is defined as MTSP reduction achieved by scheduling resources over multiple channel blocks in time domain. We simulate the SPG in different wireless environments defined in Third Generation Partnership Project spatial channel extended model and find insignificant SPG in some cases, indicating that the benefit from scheduling over multiple channel blocks is limited and simply allocating resources within the present channel is sufficient. Our analysis on the MTSP and SPG provides guidelines on the design of resource schedulers in MU‐MIMO‐OFDM networks. Copyright © 2014 John Wiley & Sons, Ltd.     

三小区多用户MIMO系统中干扰对齐优化算法

针对三小区多用户MIMO干扰信道系统,通过一个启发性例子,联合设计发射预编码矩阵和接收赋形矩阵,给出基于特征向量闭式解的干扰对齐优化算法,相比已有干扰对齐算法,用户端可使用更少的天线资源获得相同的自由度性能,且只需本小区内用户协作共享信道信息;并归纳出普适场景下系统配置与可达自由度之间的关系：设定每个小区中的基站配置M根天线和K个用户,用户配置N根天线,各个基站对本小区中每个用户都发送d个数据流,当M=N≥2 Kd时,所提算法总共可获得3 Kd个自由度。所提算法可以完全消除小区间干扰和用户间干扰,相比传统的正交化干扰抑制算法,系统容量得到了明显地提升。     

Defense against primary user emulation attacks from the secondary user throughput perspective

The maximization of Secondary user (SU) throughput has been studied extensively in honest cooperative spectrum sensing (CSS). However, when primary user emulation attacks (PUEAs) are launched, the model of CSS changes. This also necessitates the redesigning of the SU throughput maximisation scheme. In this paper, such redesigning of the SU throughput maximisation scheme under PUEAs has been carried out. Our objective is to suppress the damages caused by the PUEAs on the SU throughput. To serve this purpose, an optimally weighted CSS has been proposed. The optimal weights are obtained by maximising the SU throughput while protecting the primary user (PU) from interference in a network facing the PUEAs. Considering the significance of simplicity and speed in CSS, we apply the Nelder Mead Simplex Algorithm to solve the problem. The experiments carried out endorse the effectiveness of the proposed scheme compared to the existing combination schemes.     

EPSON MU110-II型9针式打印机的控制器开发

介绍了基于EPSON公司的MU110-II型9针针式打印机控制器的设计过程。该控制器CPU选用MCS-51单片机控制,包括数据输入、数据传输、字库及步进电机4个功能模块,通过软件驱动能控制打印机完成各种方式的打印动作。     

应用于iSCSI的TOE技术分析

由于现有的计算机处理能力跟不上网络的高速发展，使众多的网络服务器以及存储设备为处理TCP/IP而不堪重负，于是TOE(TCP IP offload engine)技术被提上了日程。该文分析了基于TOE的iSCSI for initiator的实现。     

数字化变电站的电压互感器配置和电压切换

简要介绍了常规变电站中电压互感器的配置及电压切换。提出了在开发电子式电压电流互感器后,在数字化变电站中如何配置电子式电压互感器,以及如何进行电压切换等问题。还提出了几种电压互感器的配置方案,并对方案进行了比较,提出了数字化变电站中电压切换的方案。     

智能化变电站二次侧电能计量系统计量误差分析及现场检测方法

针对智能化变电站模拟量输入式合并单元的电能计量系统误差超差问题,构建了智能化变电站二次侧电能计量模拟系统及其检测平台。在电压合并单元、电流合并单元、数字化电能表均满足检测规范要求的前提下,分析可能造成电能计量误差的因素,开展电能计量误差的影响测试,最终确定了影响电能计量误差的关键因素及其影响程度,并提出了智能化变电站二次侧电能计量系统现场测试检测平台,从而解决其计量误差超差问题。