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作者： Saunders, Shelly Ross, Margaret Staples, Geoff Wellington, Sean Faculty of Technology Southampton Solent University East Park Terrace Southampton Hampshire SO14 ORD United Kingdom ACE Group Global Insurance and Reinsurance Company United Kingdom Southampton Institute United Kingdom Department of Software Quality Southampton Solent University United Kingdom BCS BCS Council Quality Specialist Group BCSWomen Specialist Group BCS Ethics Expert Panel BCS Quality Specialist Group BCS TickIT Committee Royal Statistical Society Faculty of Technology Southampton Solent University United Kingdom Institution of Electrical Engineering

Web Services technologies and their supporting collection of de facto standards are now reaching the point of maturity where they are appearing in production software systems. Service Oriented Architectures (SOAs) using Web Services as an enabling technology are also being discussed widely in the IT press. However, despite the numerous and real advantages of these architectural patterns there are still many software quality challenges that remain unresolved. This is particularly true as we consider more advanced architectures that exploit the technology to its maximum advantage: utility computing and on-demand service discovery and composition, grid computing and multi-agent systems will only become pervasive once the software quality challenges of real-world industrial applications have been addressed. In this paper potential quality issues such as performance, reliability and availability are addressed in terms of the quality assurances that might need to be provided to consumers of services. Proposed XML-based Service Level Agreement (SLA) languages are reviewed as a means of providing these quality assurances in machine-readable ways. We also discuss how SLAs might be automatically negotiated to enable automated, on-demand service discovery and composition. The next section of this paper addresses quality issues from a service provider's perspective. The providers of such services will need to ensure that SLA commitments are met and this poses interesting problems in terms of application management. Network quality of service is currently addressed through such means as IntServ and DiffServ. Research proposals to introduce similar techniques at an application level are described. From the service consumer's perspective, interesting research proposals for proactively ensuring that good quality of service is obtained are also reviewed. These could be particularly important for creating confidence, from a consumer's perspective, in these architectures. Finally, the

关键词： Web services

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BlueGene/L Failure Analysis and Prediction Models

BlueGene/L Failure Analysis and Prediction Models

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International Conference on Dependable Systems and Networks (DSN)

作者： Yinglung Liang Yanyong Zhang A. Sivasubramaniam M. Jette R. Sahoo Electrical & Computer Engineering Department Rutgers University USA Computational Resource Management Group Lawrence Livemore National Laboratory USA Computer Science & Engineering Department Pennslyvania State University USA Exploratory Systems Software Department IBM Thomas J. Watson Research Center USA

The growing computational and storage needs of several scientific applications mandate the deployment of extreme-scale parallel machines, such as IBM's BlueGene/L which can accommodate as many as 128 K processors. One of the challenges when designing and deploying these systems in a production setting is the need to take failure occurrences, whether it be in the hardware or in the software, into account. Earlier work has shown that conventional runtime fault-tolerant techniques such as periodic checkpointing are not effective to the emerging systems. Instead, the ability to predict failure occurrences can help develop more effective checkpointing strategies. Failure prediction has long been regarded as a challenging research problem, mainly due to the lack of realistic failure data from actual production systems. In this study, we have collected RAS event logs from BlueGene/L over a period of more than 100 days. We have investigated the characteristics of fatal failure events, as well as the correlation between fatal events and non-fatal events. Based on the observations, we have developed three simple yet effective failure prediction methods, which can predict around 80% of the memory and network failures, and 47% of the application I/O failures

关键词： Failure analysis Predictive models Production systems Checkpointing Concurrent computing Parallel machines Hardware Runtime Fault tolerant systems Prediction methods

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Fault-Tolerant Multilevel Converter Topology

Fault-Tolerant Multilevel Converter Topology

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IEEE International Symposium on Industrial Electronics (ISIE)

作者： Salvador Ceballos Josep Pou Igor Gabiola Jose Luis Villate Jordi Zaragoza Dushan Boroyevich ROBOTIKER Energy Unit Tecnalia Technological Corporation Basque Spain Power Quality and Renewable Energy (QuPER) Research Group Department of Electronic Engineering Technical University of Catalonia Catalonia Spain Department of Electrical and Computer Engineering Center for Power Electronics Systems (CPES) Virginia Technology VA USA

This paper presents a modified topology of the neutral-point-clamped converter. The main change consists on adding a fourth leg, which is based on the flying-capacitor converter structure. The aim of this additional leg is to provide fault tolerance to the converter. Furthermore, during normal operation mode, this leg is able to provide a stiff neutral voltage. Consequently, the low-frequency voltage oscillations that appear in the neutral point of the standard three-level topology for some operation conditions no longer exist. As a result, the modulation strategy of the three main legs of the converter does not have to take care of voltage balance, and it can be design to achieve optimal output voltage waveforms, as well as to improve efficiency of the converter. Some simulation results are presented to show viability of this approach under both, normal operation mode and fault event. Experimental results are expected to include in the final paper.

关键词： Fault tolerance Leg Capacitors Switches Sampling methods Voltage control Circuit topology Diodes Frequency Network topology

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Enabling Self-Managing Applications using Model-based Online Control Strategies

Enabling Self-Managing Applications using Model-based Online...

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International Conference on Autonomic Computing (ICAC)

作者： V. Bhat M. Parashar Hua Liu M. Khandekar N. Kandasamy S. Abdelwahed TASSL Rutgers University Piscataway NJ USA TASSL Rutgers University Piscataway NJ Xerox Innovation Group Webster NY USA Electrical and Computer Engineering Department Drexel University Philadelphia PA USA Institute for Software Integrated Systems Nashville TN USA

The increasing heterogeneity, dynamism and uncertainty of emerging DCE (Distributed Computing Environment) systems imply that an application must be able to detect and adapt to changes in its state, its requirements and the state of the system to meet its desired QoS constraints. As system and application scales increase, ad hoc heuristic-based approaches to application adaptation and self-management quickly become insufficient. This paper builds on the Accord programming system for rule-based self-management and extends it with model-based control and optimization strategies. This paper also presents the development of a self-managing data streaming service based on online control using Accord. This service is part of a Grid-based fusion simulation workflow consisting of long-running simulations, executing on remote supercomputing sites and generating several terabytes of data, which must then be streamed over a wide-area network for live analysis and visualization. The self-managing data streaming service minimize data streaming overheads on the simulations, adapt to dynamic network bandwidth and prevent data loss. An evaluation of the service demonstrating its feasibility is presented.

关键词： Application software quality of service Distributed computing Uncertainty Analytical models Mesh generation Grid computing Runtime Technological innovation Electronic mail

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μFUP: A software development process for embedded systems

μFUP: A software development process for embedded systems

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Dagstuhl-Workshop MBEES: Modellbasierte Entwicklung eingebetteter Systeme - Workshop on Model-Based Development of Embedded Systems, MBEES 2005

作者： Geiger, Leif Siedhof, Jörg Zündorf, Albert University of Kassel Software Engineering Research Group Department of Computer Science and Electrical Engineering Wilhelmshöher Allee 73 34121 Kassel Germany

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OO model based programming of PLCs

OO model based programming of PLCs

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Dagstuhl-Workshop MBEES: Modellbasierte Entwicklung eingebetteter Systeme - Workshop on Model-Based Development of Embedded Systems, MBEES 2005

作者： Zündorf, Albert Geiger, Leif Siedhof, Jörg University of Kassel Software Engineering Research Group Department of Computer Science and Electrical Engineering Wilhelmshöher Allee 73 34121 Kassel Germany

This paper shows an example how object oriented models may be implemented even on a PLC device. This enables us to exploit the tremendous advantages of object oriented concepts even in the field of embedded systems. Safety concerns are addressed by limiting the maximal number of objects per type and by wrapping each use of a pointer within a null pointer check. These advantages are paid by additional memory and runtime consumption. However, we claim that the development process is shortened and that time-to-market and maintenance efforts are significantly improved. Finally one gains the flexibility provided e.g. by the use of design patterns. The structured text example of this paper have been derived manually from our OO model, as a feasibility study. The code has been employed on a PLC controlling our LEGO carousel storage, successfully. The automatic generation of structured text from an OO model through our CASE tool Fujaba is current work at University of Paderborn, cf [EGSW04].

关键词： Embedded systems

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Effects of normal weather conditions on interruptions in distribution systems

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International Journal of Power and Energy Systems 2005年第1期25卷 54-61页

作者： Domijan Jr., A. Matavalam, R.K. Montenegro, A. Wilcox, W.S. Joo, Y.S. Delforn, L. Diaz, J.R. Davis, L. D'Agostini, J. Florida Power Affiliates and PQ Laboratory Dept. of Electrical and Computer Engineering University of Florida Gainesville FL 32611 United States Florida Power and Light Company 9250 West Flagler Street Miami FL 33174 United States Electrical Engineering Faculty University of Florida Florida Power Affiliates and Power Quality Laboratory Florida Power Affiliates and Power Quality Laboratory University of Florida Department of Electrical Engineering UPV Statistics Department University of Florida University of Florida Florida Power and Light FPL Group IEEE Power Engineering Society Reliability Engineering Group

Power disturbances are a major concern in a power distribution system because of economic and customer satisfaction losses. Among many the causes of power disturbances, weather plays a vital role. Hence, it is important to gain an understanding of the effects of normal weather conditions on power distribution interruptions. This article shows that normal weather conditions do have an effect on the frequency of power distribution interruptions. Normal weather conditions refers to weather conditions that are not extreme (e.g., tornadoes, storms, lightning, hurricanes) but rather are common in everyday life, including but not limited to temperature, rain, wind, relative humidity, and pressure. The authors explain the different steps in analyzing the normal weather impact, from weather and interruption data collection to obtaining significant results. A Poisson regression model is also performed to determine the significance of several weather variables and the relative magnitude of the contributions of each variable to the total number of daily outages.

关键词： Weather modification

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Harmonic modeling and simulation considerations for interharmonic limits in the revised IEEE Standard 519-1992

Harmonic modeling and simulation considerations for interhar...

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2005 IEEE Power engineering Society General Meeting

作者： Halpin, S. Mark IEEE Department of Electrical and Computer Engineering Auburn University AL 36849 United States IEEE PES IAS PES Task Force Power Quality Subcommittee Harmonics Working Group Power System Engineering Committee Department of Electrical and Computer Engineering Auburn University

ISBN: (纸本)078039156X

One of the major differences in the revised IEEE Std 519 and the 1992 version will be the inclusion of interharmonic limits. These limits will likely be based on voltage fluctuation considerations below the second harmonic and will be consistent with even-order harmonics for frequencies above the second harmonic. Much is known about equipment modeling for frequencies above the power frequency, but significant work is needed to address modeling and simulation issues near or below the power frequency. Because voltage fluctuations can become problematic at very low levels, it is necessary to obtain greater accuracy in results than is often the case in harmonic studies. There is, therefore, a clear need for improvement in models and simulation techniques for lower frequencies. © 2005 IEEE.

关键词： Second harmonic generation

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Enhancement of Carrier-Based Modulation Strategies for Multilevel Converters

Enhancement of Carrier-Based Modulation Strategies for Multi...

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Annual IEEE Conference on Power Electronics Specialists (PESC)

作者： J. Pou P. Rodriguez J. Zaragoza V. Sala C. Jaen D. Boroyevich Departments of Electronic and Electrical Engineering Power Quality and Renewable Energy (QuPER) Research Group Technical University of Catalonia Spain Departments of Electronic and Electrical Engineering Research Group Terrassa Catalonia SPAIN Department of Electrical and Computer Engineering Center for Power Electronics Systems (CPES) Virginia Polytechnic Institute and State University Blacksburg VA USA Department of Electrical and Computer Engineering Center for Power Electronics Systems (CPES) Blacksburg VA USA

Carrier-based modulation strategies can be improved by inclusion of zero sequences in the modulation signals. In this paper, the modulation signals of a three-level neutral-point-clamped converter are modified to achieve maximum benefit of the DC-link voltage, and to help achieve voltage balance between the DC-link capacitors. The proposed strategy is obtained from the analysis of space-vector modulation patterns. Therefore, compared to standard sinusoidal PWM, 15% larger amplitudes of the output voltage fundamentals, better voltage-balancing performance, and lower switching frequencies in the devices can all be achieved. Furthermore, implementation of this modulation technique in a digital-signal processor is much easier than space-vector modulation, and also lowers processing time requirements. Efficiency of the modulation algorithm is verified by simulation and experiment

关键词： Voltage Pulse width modulation Support vector machines Capacitors Digital modulation Pulse width modulation converters Pattern analysis Switching frequency Sampling methods Field programmable gate arrays

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Fast-processing modulation strategy for the neutral-point-clamped converter with total elimination of the low-frequency voltage oscillations in the neutral point

Fast-processing modulation strategy for the neutral-point-cl...

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Annual Conference of Industrial Electronics Society

作者： J. Pou P. Rodriguez V. Sala J. Zaragoza R. Burgos D. Boroyevich Power Quality and Renewable Energy (QuPER) Research Group Departments of Electronic and Electrical Engineering Technical University of Catalonia Catalonia Spain Center for Power Electronics Systems (CPES) Department of Electrical and Computer Engineering Virginia Polytechnic Institute Virginia Tech State University VA USA

This paper presents a novel modulation strategy for the neutral-point-clamped converter. This strategy overcomes one of the main problems of this converter, which is the low-frequency voltage oscillation that appears in the neutral point under some operating conditions. The proposed modulation strategy can completely remove this oscillation for all the operating points and for any kind of loads, even unbalanced and nonlinear loads. The algorithm is based on a carrier-based PWM. Nevertheless, it can generate the maximum output voltage amplitudes attainable under linear modulation, such as space-vector modulation. Furthermore, this technique can be implemented with a very simple algorithm, and hence can be processed very quickly. A control loop for balancing the voltages on the DC-link capacitors is also proposed. This balancing strategy is designed so that it does not increase the switching frequencies of the devices when it is applied to the converter. The proposed modulation technique is verified by simulation and experiment

关键词： Pulse width modulation Capacitors Voltage control Amplitude modulation Switching frequency Topology Power quality Renewable energy resources Power electronics Switching converters

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