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Dynamic Performance of a Wind Generation System with Thyristor Controlled Capacitor Compensation
Get PDFA dynamic model of a variable speed cage machine wind generation unit, including wind profile, wind turbine, induction generator, local load and transmission line connecting the grid is developed. The steady state as well as the dynamic performance of the wind energy system is explored. The performance of the system under wind gust conditions has been studied and the amount of transient injection to the grid investigated. A stabilizing control scheme which minimizes the transient injection through a thyristor controlled variable capacitance at the generator terminal is explored. PI controller with optimized gain settings is included in the control loop. The ‘optimal’ parameters of the PI controller are obtained through a pole-placement technique. The PI controlled variable capacitance strategy has demonstrated very good damping profile for the wind turbine-generator power system
A Web Searching Guide: Internet Search Engines & Autonomous Interface Agents Collaboration
Get PDFThe Internet represents the biggest communication media and its dimension increases every day. This continuous growth of information makes the Internet more and more interesting, but also the task of finding selected information becomes more complex and hard. Finding exactly what a user needs is not always an easy task: for example common search engines provide thousands of links for every search. Obviously not all these links are related to what the user really needs. In this paper, we present a Collaborative Autonomous Interface Agent (CAIA) that collaborates with the Internet search engines and supports the user in finding exactly the information consistent with his/her interest. A system has been designed, fully implemented and tested. The testing results shows a big improvement in the relevancy of the retrieved links and of the user’s satisfaction by using CAIA+Google compared to using only Google
COLLABORATIVE MULTI-AGENT-BASED E-COMMERCE FRAMEWORK
Get PDFSoftware agents offer a promise to change electronic commerce trading by helping traders to purchase products based on their interests and preferences. E-commerce systems are increasingly recognizing the importance of giving additional value to customers by providing customized transactional experiences. We believe that increased support for collaboration is a logical next step in the evolution of the e-commerce systems. The main goal here is to create a collaborative multi-agent based e-commerce framework that allows autonomy, pro-activity, and personalization including an intelligent mall agent, a seller agent, and a buyer agent with their independent profiles. The basic idea is to get a fully qualified broker that can intelligently identify the buyer’s needs based on standard parameters that are given to help alleviate the problems of finding interest items. The proposed framework aims to giving meaningful responses to meaningful requests and to delivering appropriate items to people who need it, when they need it, in a manner that meets their interests. To demonstrate the proposed framework a prototype is implemented and tested
Packet Reservation Multiple Access (PRMA) with Random Contention
Get PDFPacket reservation multiple access (PRMA) can be considered as a merge of slotted ALOHA protocol and time division multiple access (TDMA) protocol. Independent terminals transmit packets to base station by contending to access an available time slots. A terminal that succeeds in reserving a certain time slot keeps on this reservation for transmitting its subsequent packets. Speech activity detection is used in PRMA to improve system capacity. In this work we propose a simpler contention mechanism that does not depend on a predetermined permission probability as in the original PRMA. In the new method, terminals select the contention slot uniformly from the pool of remaining free slots in the current frame. We evaluate the performance of the new contention mechanism in terms of various metrics including maximum number of carried voice calls and packet delays for a given acceptable drop rate of voice packets. We show that the new mechanism is superior to that of the original PRMA for loaded systems and is expected to be insensitive for traffic source burstiness
ICS 343: Fundamentals of Computer Networks (3-3-4)
Get PDFJunior Level Course Syllabus on Computer Network
Performance Analysis and Comparison of Interrupt-Handling Schemes in Gigabit Networks
Get PDFInterrupt processing can be a major bottleneck in the end-to-end performance of Gigabit networks. The performance of Gigabit network end hosts or servers can be severely degraded due to interrupt overhead caused by heavy incoming traffic. In particular, excessive latency and significant degradation in system throughput can be encountered. Also, user applications may livelock as the CPU power gets mostly consumed by interrupt handling and protocol processing. A number of interrupt handling schemes has been proposed and employed to mitigate the interrupt overhead and improve OS performance. Among the most popular interrupt handling schemes are normal interruption, polling, interrupt coalescing, and disabling and enabling of interrupts. In previous work, we presented a preliminary analytical study and models of normal interruption and interrupt coalescing. In this article, we extend our analysis and modeling to include polling and the scheme of interrupt disabling and enabling. For polling, we study both pure (or FreeBSD-style) polling and Linux NAPI polling. The performances for all these schemes are compared using both mathematical analysis and discrete-event simulation. The performance is studied in terms of three key performance indictors: throughput, system latency, and the residual CPU bandwidth available for user applications. As opposed to our previous work, we consider not only Poisson traffic, but also bursty traffic with empirical packet size distribution. Our analysis and simulation work gives insight into predicting the system performance and behavior when employing a certain interrupt handling scheme. It is concluded that no single interrupt handling scheme outperforms all other schemes under all traffic conditions. Based on obtained results, we propose and discuss a novel hybrid scheme of interrupt disabling-enabling and pure polling in order to attain peak performance under low and heavy traffic loads
Research Article A Unified Approach to BER Analysis of Synchronous Downlink CDMA Systems with Random Signature Sequences in Fading Channels with Known Channel Phase
No full textA detailed analysis of the multiple access interference (MAI) for synchronous downlink CDMA systems is carried out for BPSK signals with random signature sequences in Nakagami-m fading environment with known channel phase. This analysis presents a unified approach as Nakagami-m fading is a general fading distribution that includes the Rayleigh, the one-sided Gaussian, the Nakagami-q, and the Rice distributions as special cases. Consequently, new explicit closed-form expressions for the probability density function (pdf ) of MAI and MAI plus noise are derived for Nakagami-m, Rayleigh, one-sided Gaussian, Nakagami-q, and Rician fading. Moreover, optimum coherent reception using maximum likelihood (ML) criterion is investigated based on the derived statistics of MAI plus noise and expressions for probability of bit error are obtained for these fading environments. Furthermore, a standard Gaussian approximation (SGA) is also developed for these fading environments to compare the performance of optimum receivers. Finally, extensive simulation work is carried out and shows that the theoretical predictions are very well substantiated