Three components, gain analysis, tolerance analysis in-depth, and a brief non- linearity analysis, are presented. In the first component, the effects of an Erbium doped waveguide amplifier in a microring are investigated using a time domain simulation. Methods to simulate the gain versus average input signal power in the microring are studied, given that it has a long lifetime compared to the short delay time of the microring. The methods are based on the dependence of the gain on the power of the signal being fed to the ring. An algorithm is proposed to perform a thorough tolerance analysis on any optical circuit with respect to any optical parameter. The algorithm, based on Monte Carlo Simulation, is implemented on a complex optical circuit that is designed to obtain a bandpass filter response of given specifications. It is also tested on similar designs for a comparative study between them. The parameters and the structure of the designs used for the analysis are presented in detail. The results are presented in terms of the yield with respect to the parameter being varied, against their tolerance value. Algorithms for studying the effects of two types of non-linearities are presented. The Kerr nonlinearity and the two-photon absorption are included in the bandpass filter designs used for the tolerance analysis. The algorithms are based on the power circulating in different regions of the circuit under consideration. The variation in the original response because of the loss due to nonlinearity is observed and analyzed for different power levels of the input signal.

The rapidly increasing expansion and popularity of the Internet makes more and more users accept web service type. The web server with single server architecture is no longer satisfying a large number of user requests. The web cluster architecture becomes another batter solution. In our previous work, our laboratory has implemented a prototype of layer7 web switch, which provides content-aware land balancing. We also designed and implemented a management system to provide a easy way for system configuration. With the increasing of web technologies, most of web sites supply ¡§session-aware¡¨ service type. The session is that clients and servers that wish to exchange state information to place HTTP requests and responses within a lager context. In this paper, we propose a session-aware management in the web cluster. Base on our management system, we design a fault tolerance and QoS policy with session to improve performance and reliability of our web cluster system.

In this thesis, a novel fiber structure with advantages of high coupling efficiency, long working distance and better alignment tolerance has been presented. In this structure, the front-end of the singe-mode fiber (SMF) was spliced a graded-index fiber (GIF) with 50£gm core diameter. A hyperbolic-shaped lens was fabricated in the front-end of GIF. This novel fiber structure can increase the coupling efficiency of SMF effectively by using the wavefront-transfer characteristic of hyperbolic-shaped lens and the focusing characteristic of GIF. According to the simulation results, the optimized length of the GIF was 1160£gm. This novel fiber structure can reach to the coupling efficiency of 77% and working distance of 16£gm when the output power of laser diode was operated at 10mW and the radius curvature of lensed fiber was 12.74£gm. The lateral and longitudinal alignment tolerances of this fiber were 0.8£gm and 1.3£gm, respectively. In comparison with the conventional SMF lens, this novel fiber structure has longer working distance and better fiber alignment tolerance. Therefore, this structure can increase the package yield and reduce the fabrication cost for the application of laser module package.

With shrinking feature size and growing integration density in the Deep Sub- Micron (DSM) technologies, the global buses are fast becoming the "weakest-links" in VLSI design. They have large delays and are error-prone. Especially, in system-onchip (SoC) designs, where parallel interconnects run over large distances, they pose difficult research and design problems. This work presents an approach for evaluating the data carrying capacity of such wires. The method treats the delay and reliability in interconnects from an information theoretic perspective. The results point to an optimal frequency of operation for a given bus dimension for maximum data transfer rate. Moreover, this optimal frequency is higher than that achieved by present day designs which accommodate the worst case delays. This work also proposes several novel ways to approach this optimal data transfer rate in practical designs.From the analysis of signal propagation delay in long wires, it is seen that the signal delay distribution has a long tail, meaning that most signals arrive at the output much faster than the worst case delay. Using communication theory, these "good" signals arriving early can be used to predict/correct the "few" signals that arrive late. In addition to this correction based on prediction, the approaches use coding techniques to eliminate high delay cases to generate a higher transmission rate. The work also extends communication theoretic approaches to other areas of VLSI design. Parity groups are generated based on low output delay correlation to add redundancy in combinatorial circuits. This redundancy is used to increase the frequency of operation and/or reduce the energy consumption while improving the overall reliability of the circuit.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002. / Includes bibliographical references (leaves 118-119). Also available in electronic version. Access restricted to campus users.

To effectively minimize biofilms, which are prevalent in chlorinated drinking water distribution systems, the effect of biofilm age on antimicrobial tolerance and resistance must be investigated. It was our hypothesis that antimicrobial tolerance emerges quickly during biofilm development and that both antimicrobial tolerance and resistance increase as the biofilm ages. We further hypothesized that antimicrobial tolerance and resistance vary among the individual community members. In this study, young and mature biofilms of Pseudomonas aeruginosa, a model biofilm organism, were grown and exposed to antimicrobial agents in several different treatments. Results showed that the increased antimicrobial tolerance of intact biofilms compared to planktonic cells arises early (i.e., within hours) in biofilm development. The short-term tolerance of resuspended mature biofilm cells to antimicrobial agents peaked at a biofilm age of 14 days and subsequently declined; the peak and decline in antimicrobial tolerance may be related to periodic detachment events in the biofilm. The antimicrobial resistance of resuspended mature biofilm cells continuously exposed to antimicrobial agents increased with biofilm age. Furthermore, individual members in mature biofilm communities exhibited variation in antimicrobial tolerance, thereby highlighting divergence of the biofilm community from the original parent strain.

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The finding that the performance of a response during periods of drug exposure facilitates the development of tolerance to the effects of the drug on that response is commonly referred to as contingent drug tolerance. Contingent tolerance is typically demonstrated in before-and-after design experiments. One group of subjects receives drug before the performance of the criterion response (drug-before-test condition) and a second group of subjects receives drug after the performance of the criterion response (the drug-after-test condition). The usual finding is that substantial tolerance develops in the drug-before-test condition, but no tolerance whatsoever develops in the drug-after-test condition. Such demonstrations of contingent tolerance have led to the drug-effect theory of tolerance: the theory that tolerance to a particular drug effect is an adaptive response to the experience of that particular drug effect. The purpose of this thesis was to clarify the relation between drug exposure, drug effects, and the development of tolerance. Several experiments have demonstrated that no tolerance whatsoever develops to anticonvulsant drug effects if convulsive stimulation is administered prior to each drug injection (drug-after-test condition), rather than afterwards (drug-before-test condition). Be that as it may, a different experimental design was used in Experiments 1 and 2 to show that small amounts of tolerance develop in the absence of concurrent convulsive stimulation. Rats that received either 3 intraperitoneal injections of diazepam (5.0 mg/kg) per day for 10 days (Experiment 1) or 1 gastric intubation of ethanol (5 g/kg) for 21 days (Experiment 2) were significantly more tolerant than vehicle controls; however, the tolerance could be detected only by a sensitive savings measure. The purpose of Experiment 3 was to test a novel interpretation for the inconsistency between Experiments 1 and 2 on the one hand and the repeated failure to observe tolerance to anticonvulsant drugs following drug exposure without concurrent convulsive stimulation in the drug-after-test condition of before-and-after experiments on the other. This hypothesis is that small amounts of tolerance do develop following each drug injection in the drug-after-test condition but that it is dissipated the next day by the convulsive activity experienced in the absence of the drug. To test this hypothesis, one group of amygdala-kindled rats received 15 diazepam injections (2.5 mg/kg) each before a convulsive stimulation, one group received 15 diazepam injections each after a convulsive stimulation, one group received 15 diazepam injections with no convulsive stimulation, and one group received 15 vehicle injections either with or without convulsive stimulations. The drug-before-stimulation rats developed substantial tolerance as has been frequently reported, and the hypothesis was confirmed by the finding that the drug-only rats developed tolerance significantly faster than the rats in the drug-afterstimulation group and the rats in the vehicle-control group. The results of these experiments make two important points. First, tolerance develops following drug exposure even when the criterion response is not performed during drug exposure —albeit substantially less than when it is performed. Presumably, this is because a few of the neural circuits that are active during a convulsion are spontaneously active following the drug administration. Second, the reason why the subjects in the drug-after condition display no evidence of tolerance is because the drug-free performance of the criterion response prior to each drug exposure causes any tolerance that has developed to dissipate.

The semiconductor technology development empowers fabrication of extremelycomplex integrated circuits (ICs) that may contain billions of transistors. Suchhigh integration density enables designing an entire system onto a single chip,commonly referred to as a System-on-Chip (SoC). In order to boost performance,it is increasingly common to design SoCs that contain a number of processors, socalled multi-processor system-on-chips (MPSoCs).While on one hand, recent semiconductor technologies enable fabrication ofdevices such as MPSoCs which provide high performance, on the other hand thereis a drawback that these devices are becoming increasingly susceptible to faults.These faults may occur due to escapes from manufacturing test, aging effects orenvironmental impacts. When present in a system, faults may disrupt functionalityand can cause incorrect system operation. Therefore, it is very importantwhen designing systems to consider methods to tolerate potential faults. To copewith faults, there is a need of fault handling which implies automatic detection,identification and recovery from faults which may occur during the system’s operation.This work is about the design and implementation of a fault handling methodsfor an MPSoC. A fault aware Resource Manager (RM) is designed and implementedto obtain correct system operation and maximize the system’s throughputin the presence of faults. The RM has the responsibility of scheduling jobs to availableresources, collecting fault states from resources in the system and performingfault handling tasks, based on fault states. The RM is also employed in multipleexperiments in order to study its behavior in different situations.