The Internet is increasingly being used as basic infrastructure for a variety of services. A high-performance server system is the key to the success of all these Internet services. However, the explosive growth of Internet has resulted in heavy demands being placed on Internet servers and has raised great concerns in terms of performance, scalability and availability of the associated services. A monolithic server hosting a service is usually not sufficient to handle these challenges. Distributed server architecture, consisting of multiple heterogeneous computers that appears as a single high performance system, has proven a successful and cost effective alternative to meet these challenges. Consequently, more and more Internet service providers run their service on a cluster of servers, and this trend is accelerating. The distributed server architecture is only an insufficient answer to the challenges faced by Internet service providers today. This thesis presents an integrated system for supporting scalable and highly reliable Internet services on the distributed server architecture. This system is composed consists of two major parts: Server Load Balancer and Distributed Server management System. The server load balancer can intelligently route the incoming requests to the appropriate server node. The Java-based management system can relieve administrator¡¥s burden on managing such a distributed server system. With these mechanisms, we can provide an integrated system to consolidate a group of heterogeneous computers to be a powerful, adaptive, reliable Internet server system.

This paper is to investigate the impact of temperature sensitivity to the load profiles of power system by artificial neural networks (ANN). The load survey study is performed to derive the typical load patterns of the residential, commercial, and industrial customers respectively. By executing the training process of customer power consumption and temperature, the ANN model is created to derive the temperature sensitivity of power consumption for each customer class, which is then used to solve the impact of temperature rise to system power profiles. According to the system load composition and temperature sensitivity of power consumption by each customer class, the hourly increase of system power loading due to 1¢J temperature rise is solved. To study the temperature effect to the system reliability, the ¡§IEEE Reliability Test System¡¨ is selected as test system for power system reliability analysis. Based on the temperature sensitivity of power consumption for each customer class and load composition of each load bus. The power demand is updated with the temperature rise. The temperature sensitivity of commercial customers is very significant because of the high air conditioner loading. When the system load composition is most composed of commercial customers, the power demand are due to temperature rise will have very critical impact to system reliability. On the other hand, the tempearture rise will have less impact of reliability analysis for the system which serves high percentage of industrial customers. It is concluded that the research of temperature sensitivity on power consumption can provide important information for system reliability analysis. Better substation planning and system capacity expansion can be obtained to meet system reliability criterion by taking into account the temperature effect to system loading.

none

Management decisions in complex industrial facilities usually consider both the economic and environmental aspects of the plant's performance. For nuclear power plants (NPPs), safety is also a very substantial issue. The objectives of this dissertation are to develop and demonstrate a novel useful conceptual model that could be used to allocate maintenance funds for a nuclear power plant in such a way as to meet all specified safety requirements and objectives, while achieving a high degree of economic performance. The model is based on the general theory that the reliability of a plant at any time is a function of its initial reliability and the maintenance history of the individual plant components (Smith, 1997). Such a model can assist in evaluating strategic management decisions regarding allocation of funds for nuclear power plant maintenance. It could be used as a simulation tool; various scenarios could be studied to answer "what if" questions. Simulations of this type will allow a better understanding of the relationship between maintenance, economic performance, and safety, and consequently will lead to better decision making. The novelty of this model is tied to the intimate relationship that it develops between maintenance activities at a nuclear plant, and their relationship to prescribed safety requirements and to the economic performance of that plant.

Modern power systems are now stepping into the post-restructuring era, in which utility industries as well as ISOs (Independent System Operators) are involved. Attention needs to be paid to the reliability study of power systems by both the utility companies and the ISOs. An uninterrupted and high quality power is required for the sustainable development of a technological society. Power system blackouts generally result from cascading outages. Protection system hidden failures remain dormant when everything is normal and are exposed as a result of other system disturbances. This dissertation provides new methods for power system vulnerability analysis including protection failures. Both adequacy and security aspects are included. The power system vulnerability analysis covers the following issues: 1) Protection system failure analysis and modeling based on protection failure features; 2) New methodology for reliability evaluation to incorporate protection system failure modes; and, 3) Application of variance reduction techniques and evaluation. A new model of current-carrying component paired with its associated protection system has been proposed. The model differentiates two protection failure modes, and it is the foundation of the proposed research. Detailed stochastic features of system contingencies and corresponding responses are considered. Both adequacy and security reliability indices are computed. Moreover, a new reliability index ISV (Integrated System Vulnerability) is introduced to represent the integrated reliability performance with consideration of protection system failures. According to these indices, we can locate the weakest point or link in a power system. The whole analysis procedure is based on a non-sequential Monte Carlo simulation method. In reliability analysis, especially with Monte Carlo simulation, computation time is a function not only of a large number of simulations, but also time-consuming system state evaluation, such as OPF (Optimal Power Flow) and stability assessment. Theoretical and practical analysis is conducted for the application of variance reduction techniques. The dissertation also proposes a comprehensive approach for a TTC (Total Transfer Capability) calculation with consideration of thermal, voltage and transient stability limits. Both steady state and dynamic security assessments are included in the process of obtaining total transfer capability. Particularly, the effect of FACTS (Flexible AC Transmission Systems) devices on TTC is examined. FACTS devices have been shown to have both positive and negative effects on system stability depending on their location. Furthermore, this dissertation proposes a probabilistic method which gives a new framework for analyzing total transfer capability with actual operational conditions.

Reliability assessment is of primary importance in designing and planning distribution systems that operate in an economic manner with minimal interruption of customer loads. With the advances in renewable energy sources, Distributed Generation (DG), is forecasted to increase in distribution networks. The study of reliability evaluation of such networks is a relatively new area. This research presents a new methodology that can be used to analyze the reliability of such distribution systems and can be applied in preliminary planning studies for such systems. The method uses a sequential Monte Carlo simulation of the distribution system’s stochastic model to generate the operating behavior and combines that with a path augmenting Max flow algorithm to evaluate the load status for each state change of operation in the system. Overall system and load point reliability indices such as hourly loss of load, frequency of loss of load and expected energy unserved can be computed using this technique. On addition of DG in standby mode of operation at specific locations in the network, the reliability indices can be compared for different scenarios and strategies for placement of DG and their capacities can be determined using this methodology.

Nowadays, web services have been widely utilized on the Internet. The communication of organizations becomes much easier; thanks to the advances of computer and communication technologies and the inexpensive cost, and the integration of applications within and across business organizations is a trend. In general, there are two approaches in composing web services inside or outside an organization: orchestration and choreography. Previous work in the web service selection is usually based on orchestration model and focuses on the interest of a single party. However, in many application scenarios, business goals are achieved by pair-wise interactions among a set of WSs, and there is no single entity that is in charge of selecting web service for each task. Each web service can autonomously perform web service selection. By autonomy, we maintain that each WS is aware of only its partner web services. In such a choreographic environment, we study the kind of information that each web service should provide to its partner web services and how each web service should perform web service selection so as to maximize the chance of successfully accomplish a business goal. The proposed approach is evaluated by simulating 10,000 execution sequences of the target WS and assumed a fixed operation reliability for each delegation. The experimental results show that our proposed method is close to centralized method and better than other two selection methods, namely random and view-based-propagation-free.

Thesis (M. Sc.)--University of Alberta, 2009. / Title from PDF file main screen (viewed on Nov. 27, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science in Engineering Management, Department of Mechanical Engineering, University of Alberta." Includes bibliographical references.

Thesis (Ph.D.), Memorial University of Newfoundland, 2000. / Bibliography: leaves 174-178.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.