The electric power industry is undergoing a restructuring process. The major goals of the change of the industry structure are to motivate competition, reduce costs and improve the service quality for consumers. In the meantime, it is also important for the new structure to maintain system reliability. Power system reliability is comprised of two basic components, adequacy and security. In terms of the time frame, power system reliability can mean short-term reliability or long-term reliability. Short-term reliability is more a security issue while long-term reliability focuses more on the issue of adequacy. This dissertation presents techniques to address some security issues associated with short-term reliability and some adequacy issues related to long-term reliability in deregulated power systems. Short-term reliability is for operational purposes and is mainly concerned with security. Thus the way energy is dispatched and the actions the system operator takes to remedy an insecure system state such as transmission congestion are important to shortterm reliability. Our studies on short-term reliability are therefore focused on these two aspects. We first investigate the formulation of the auction-based dispatch by the law of supply and demand. Then we develop efficient algorithms to solve the auction-based dispatch with different types of bidding functions. Finally we propose a new Optimal Power Flow (OPF) method based on sensitivity factors and the technique of aggregation to manage congestion, which results from the auction-based dispatch. The algorithms and the new OPF method proposed here are much faster and more efficient than the conventional algorithms and methods. With regard to long-term reliability, the major issues are adequacy and its improvement. Our research thus is focused on these two aspects. First, we develop a probabilistic methodology to assess composite power system long-term reliability with both adequacy and security included by using the sequential Monte Carlo simulation method. We then investigate new ways to improve composite power system adequacy in the long-term. Specifically, we propose to use Flexible AC Transmission Systems (FACTS) such as Thyristor Controlled Series Capacitor (TCSC), Static Var Compensator (SVC) and Thyristor Controlled Phase Angle Regulator (TCPAR) to enhance reliability.

Fault tolerant control can accommodate the component faults in a control system such as sensors, actuators, plants, etc. This dissertation presents two fault tolerant control schemes to accommodate the failures of power amplifiers and sensors in a magnetic suspension system. The homopolar magnetic bearings are biased by permanent magnets to reduce the energy consumption. One control scheme is to adjust system parameters by swapping current distribution matrices for magnetic bearings and weighting gain matrices for sensor arrays, but maintain the MIMO-based control law invariant before and after the faults. Current distribution matrices are evaluated based on the set of poles (power amplifier plus coil) that have failed and the requirements for uncoupled force/voltage control, linearity, and specified force/voltage gains to be unaffected by the failure. Weighting gain matrices are evaluated based on the set of sensors that have failed and the requirements for uncoupling x1 and x2 sensing, runout reduction, and voltage/displacement gains to be unaffected by the failure. The other control scheme is to adjust the feedback gains on-line or off-line, but the current distribution matrices are invariant before and after the faults. Simulation results have demonstrated the fault tolerant operation by these two control schemes.

Marine energy is a renewable source that has not been exploited widely. Fetching the off-shore marine energy requires a lot of investments, thus, maximizing the power delivered by the marine current system is important. Marine current power generation may be limited during certain periods due to weather situation and far distance power transmission that makes failure rate arise and repair time long. In this thesis, using marine current speed recorded at Taiwan coastline, we analyze the reliability and not-delivery energy indices of different off-shore power collection topologies and transmission system by using fault tree analysis and network reduction method. Model parameter uncertainty effects on the system reliability are studied and economic assessments of these configurations are also conducted.

Web services have emerged as a de facto standard for encapsulating services within or across organization boundaries. Various proposals have been made to compose Web services into workflow so as to meet the goal previously unaccomplished by a single entity. This thesis intends to investigate the Web services-based workflow access control problem. It starts by analyzing the various access control constraints proposed in the literatures and presenting three primitive constructs that are capable of specify these constraints. It then proposes a Web service selection approach that dynamically chooses a performer for each task in the workflow, not only to satisfy all access control constraints currently but also to increase the chance of completing the entire process in the future. The proposed approach is evaluated using synthetic data and is shown to result in the execution that is less likely to violate any specified access control constraints.

Solder bump is used to connect organic substrate with chip to form Flip Chip package. Comparing to wire bond package, the path is reduced so the electrical performance is much better. Due to the environmental concern, eutectic bump is replaced by lead-free bump gradually. Meanwhile, since wafer technology is improved from 55 nm to 40 nm, the material for dielectric layers is also changed so the material for the package need to revised to meet the characteristic of wafer. Now the laser grooving is adopted before blade sawing to accommodate the brittleness of new 40nm wafer. Also, one extra polyimide is added in the wafer fabrication to reinforce the robustness of the circuit. The stress inside the lead-free bump can be reduced by optimizing the temperature of the reflow process and the speed of cooling. Different UBM structure is also reviewed to find out its affect on the strength of bump and low-K circuit so the failure mode of bump can be predicted. The selection of underfill need to be well considered so, the warpage of package can be reduced, the maximum protection of bump and low-K circuit can be achieved, and the process is easier to control. (The four underfills are reviewed) The reliability test is utilized to decide the best bump composition, the structure of UBM, the selection of underfills and the process parameter. By adding the laser grooving in the wafer sawing process, the chance of crack on die low-K layer is reduced during the reliability test. As for the UBM structure, the POU is better than RPI to reduce the crack of die low-K layer. The result is verified on the package with no underfill by Temperature cycle. Last, the matching of SnCu0.7 bump with SAC305 C4 pad has the best result. During the research, the variance of CTE for the core of substrate contributes less warpage of package, comparing to the difference of Tg for underfills. The adhesion of underfills varies and the underfill UA9 has the best result. The flip chip package with underfill UA9 can passes TCB1000. The optimization of UBM structure for lead-free bump is researched and discussed. Composition of the lead-free bump, process parameter, and cost, those factors are also studied.

<p>This thesis deals with the reliability and life-time ofelectronic components and ways to determine these factors.Plastic encapsulated and open test circuits were assessed atdifferent humidity and temperature conditions. From the resultsan acceleration factor could be derived using the Arrheniusrelation. This factor is used to determine failure rates atdifferent drift conditions under accelerated test conditions. Aformula for the factor containing both relative humidity andtemperature could be established and was found to hold also formeasurements published by others.</p><p>Electrostatic discharge (ESD) transients were studiedexperimentally and by simulation with good agreement. A verysensitive method to detect latent failures of two kinds wasintroduced by nonlinearity measurements utilizing the thirdharmonic of a test signal. The ESD-susceptibility dependence ondesign and technology is shown and can be used to improvebuilt-in reliability.</p><p>Influences in the performance of semiconductor devices fromdefects like fixed charges and ions were interpreted for thefirst time by simulation using a 2D- finite element componentprogram. Significant results gave an application to a MOSFETdevice showing parameter derating, especially the change of thethreshold value. A short description of later development insimulation methods with new, more powerful tools improvingcomponent performance and reliability is given.</p><p>Charged thin films of Teflon, so called<i>electrets</i>, are used as microphone membranes. Theelectret voltage is a suitable reliability factor. Fromexperimental results a mathematical relation including thetemperature was established for the rate of decay of theelectret voltage with time. A method to charge the electretswith radioactive sources is outlined and described in apatent.</p><p>Finally an attempt was done to analyze the reliability ofthin film circuits by mathematical methods. Bell Labsintroduced<i>RC</i>-feedback filters realized in tantalum thin filmtechnology. The phase shift of the filter is about π or180°. A mathematical apparatus was developed to calculatethe change in frequency and attenuation from small componentvariations in resistors and capacitors. First and higher ordercorrections were derived, using expansion by the Taylor seriesfor the higher order.</p><p><b>Keywords:</b>reliability, failure mechanism, accelerationtests, ESD, latent failure, plastic encapsulation, electret,thin film</p>

<p>The main goal in this thesis is to select and test Forward Error Correction (FEC) schemes suitable for network video transmission over RTP/UDP. There is a general concern in communication networks which is to achieve a tradeoff between reliable transmission and the delay that it takes. Our purpose is to look for techniques that improve the reliability while the realtime delay constraints are fulfilled. In order to achieve it, the FEC techniques focus on recovering the packet losses that come up along any transmission. The FEC schemes that we have selected are Parity Check algorithm, ReedSolomon (RS) codes and a Convolutional code. Simulations are performed to test the different schemes.</p><p>The results obtained show that the RS codes are the more powerful schemes in terms of recovery capabilities. However they can not be deployed for every configuration since they go beyond the delay threshold. On the other hand, despite of the Parity Check codes being the less efficient in terms of error recovery, they show a reasonable low delay. Therefore, depending on the packet loss probability that we are working with, we may chose one or other of the different schemes. To summarize, this thesis includes a theoretical background, a thorough analysis of the FEC schemes chosen, simulation results, conclusions and proposed future work.</p>

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 113-116). Also available in electronic version. Access restricted to campus users.

Thesis (M. Phil.)--University of Hong Kong, 1980.

Background: Several field-based team sports contain repeated, maximal effort sprints with varying rest lengths in between. This puts high demands on athletes’ metabolic and neuromuscular systems. Testing the anaerobic capacity of athletes is essential to improve and evaluate the progression. One test being utilised for assessing anaerobic capacity is the 300-yard shuttle run test. The test is field-based with stopwatches as the sole equipment. However, the test has not been properly tested for reliability.   Aim: The aim of this bachelor thesis was therefore to investigate the reliability of the 300-yard shuttle run test. Methods: The study was performed with a test-retest method and included a familiarisation meeting, test session and retest session.  Test subjects performed the 300-yard shuttle run test at two different occasions with seven or fourteen days in between. The intraclass correlation coefficient (ICC) and 95% confidence interval (CI) was utilised to quantify the reliability. An ICC&gt;0.8 was considered acceptable. Results: 17 American football players participated in the study (median age 20, min. =18, max. =38 y; median weight 83, min. =67, max. =133 kg; median height 184, min. =169, max. =194 cm). The ICC for the test-retest was 0.97 (95% CI  0.91-0.99). Conclusion: Based on the results of this study 300-yard shuttle test is proposed as a test providing reliable results.