Volume 2 Issue 2
Authors: Ahmad M. Assad; Morad Abdelaziz; Mostafa I. Marei
Abstract: The clamped-type multilevel inverters, which include Neutral Point Clamped (NPC) and Flying Capacitor (FC) inverters, are very attractive topologies for implementing shunt Active Power Filters (APF) in medium and high power networks. This paper presents a simple and adaptive control algorithm for a three-level current-controlled NPC-based APF. The proposed control algorithm employs three independent ADAptive LINEar combiners (ADALINE) modules to provide fast, accurate, and adaptive harmonic tracking. Two Proportional Integral (PI) controllers are implemented to generate the necessary reference current components for regulating the neutral point potential and the dc-side voltage, simultaneously. Furthermore, the proposed control algorithm is expanded for the control of the FC-based APF by replacing the Neutral Point (NP) potential controller with a modified dual band hysteresis current control (HCC) to regulate the voltage of the clamping capacitors using the redundant switching states. Simulation results are provided to evaluate the performance the two proposed multifunction control algorithms. The results expose the adaptive and accurate compensation of the load harmonics as well as the fast regulation of the voltages across the dc-side capacitors under normal and dynamic conditions.
Keywords: Active Power Filter; Flying Capacitor Multilevel Inverter; Harmonics Compensation; Neutral Point Clamped Inverter
Authors: Wenhua Yu; Xiaoling Yang; Lihong Zhang
Abstract: Parallel Finite Difference Time Domain (FDTD) method has been studied for a long time due to the expensive computation and huge memory needed for its application. In this paper, we introduce a novel hardware acceleration technique based on Vector Arithmetic Logic Unit (VALU) built in a regular CPU for parallel FDTD simulation with Convolutional Perfect Matched Layer (CPML) absorbing boundary condition (ABC). We discuss the acceleration effect for the FDTD method using SSE and AVX instructions and give an implementation on PC. We developed three types of code: code developed by C language, code accelerated by SSE instructions and code accelerated by AVX instructions. We analyse the radiation character of two models of dipole antenna and rectangle micro strip patch antenna using the accelerated code and present the results of a performance study of the FDTD algorithm on Intel 2nd core i5 2320 (quad core) named Sandy Bridge. The results show that we can improve the performance of FDTD algorithm using SSE and AVX instructions.
Keywords: FDTD; VALU; SIMD; SSE; AVX; Acceleration
Authors: Bingbing Xia; Yue Zhang; Yanfang Jing; Li Liu
Abstract: Mobile Ad hoc Networks (MANETs) consist of a collection of wireless mobile devices dynamically forming a temporary network without the use of any existing network infrastructure or centralized administration. File sharing is a popular used application, which has important status in MANETs. File sharing in MANETs is mainly based on Peer-to-Peer (P2P) network. And a P2P file sharing system generally consists of a search algorithm and a file transfer protocol in which search algorithm attracts a lot of attention. In this paper, we overview and analyze the recently researches about file sharing algorithms. We categorize them into four categories: the DHT-based methods, flooding-based methods, advertisement-based methods and social-based methods according to different searching method. We present a comprehensive up to date survey of these methods. Furthermore, we analyze some challenging issues which inspire the future work.
Keywords: Peer-to-peer Network; Mobile Ad hoc Network; DHT; Flooding; Advertisement; Social Network
Authors: Oleg A. Gorbachev; Vsevolod B. Ivanov; Dmitry.V. Khazanov; Andrey A.Kholmogorov
Abstract: Earlier authors presented the first own results of research of positioning errors in radio navigation systems. They were received at specialized observation stations of Irkutsk Branch of Moscow State Technical University of Civil Aviation. This article is devoted to more detailed consideration of time variations of consumers’ positioning errors. The found features can be used for increase of accuracy of positioning.
Keywords: Satellite Radio Navigation; PPP; Positioning Error; Ionosphere; Total Electron Content; Ionospheric Correction