The objective of the research presented in this thesis was to investigate the effects of wearout processes on the performance and reliability of CMOS bistable circuits. The main wearout process affecting reliability of submicron MOS devices was identified as hot-carrier stress (and the resulting degradation in circuit performance). The effect of hot-carrier degradation on the resolving time leading to metastability of the bistable circuits also have been investigated. Hot-carrier degradation was identified as a major reliability concern for CMOS bistable circuits designed using submicron technologies. The major hot-carrier effects are the impact ionisation of hot- carriers in the channel of a MOS device and the resulting substrate current and gate current generation. The substrate current has been used as the monitor for the hot-carrier stress and have developed a substrate current model based on existing models that have been extended to incorporate additional effects for submicron devices. The optimisation of the substrate current model led to the development of degradation and life-time models. These are presented in the thesis. A number of bistable circuits designed using 0.7 micron CMOS technology design rules were selected for the substrate current model analysis. The circuits were simulated using a set of optimised SPICE model parameters and the stress factors on each device was evaluated using the substrate current model implemented as a post processor to the SPICE simulation. Model parameters for each device in the bistable were degraded according to the stress experienced and simulated again to determine the degradation in characteristic timing parameters for a predetermined stress period. A comparative study of the effect of degradation on characteristic timing parameters for a number of latch circuits was carried out. The life-times of the bistables were determined using the life-time model. The bistable circuits were found to enter a metastable state under critical timing conditions. The effect of hot-carrier stress induced degradation on the metastable state operation of the bistables were analysed. Based on the analysis of the hot-carrier degradation effects on the latch circuits, techniques are suggested to reduce hot-carrier stress and to improve circuit life-time. Modifications for improving hot- carrier reliability were incorporated into all the bistable circuits which were re-simulated to determine the improvement in life-time and reliability of the circuits under hot-carrier stress. The improved circuits were degraded based on the new stress factors and the degradation effects on the critical timing parameters evaluated and these were compared with those before the modifications. The improvements in the life-time and the reliability of the selected bistable circuits were quantified. It has been demonstrated that the hot-carrier reliability for all the selected bistable circuits can be improved by design techniques to reduce the stress on identified critically stressed devices.

Electrical reliability assurance is a very important aspect of electrical power systems; significant consideration should be given to reliability at both the planning and operation stage of power systems. A decrease in reliability levels can lead to enormous economic losses, especially for certain industrial facilities, and utilities could be penalized for violation of the mandatory reliability standards. Besides the traditional methods for electrical reliability enhancement, it is highly recommended to consider the adoption of innovative technologies, such as the integration of Distributed Generation (DG) units into the electrical network, especially those which are based on renewable energy source (wind and photovoltaic). Distributed Generation technologies can be beneficial to the electrical distribution system performance. However, these pose certain technical challenges to the reliable operation of the system. In this work, we also focus on the micro-grid operation security during islanding mode of operation in the presence of DG units. In this thesis, the unique aspects of reliability evaluation for an electrical distribution system has been performed using system-independent analytical expressions, considering probabilistic load and DG unit modeling, under different scenarios including dispatchable and renewable DG units with reasonable penetration levels. Further, a modified adequacy formulation has been adopted during the islanding mode of operation in order to consider micro-grid load correlation and an additional load curtailment level introduced in this work. The extra curtailment is needed to ensure adequate technical constraints and allow successful micro-grid operation, when the dispatchable DG units rating in a micro-grid is less than a defined percentage of the micro-grid peak load at time of islanding. Afterwards, during islanding, a second load curtailment level is adopted as needed to ensure service continuity under different operational conditions. A distribution test system is considered, and accordingly reliability indices are evaluated for both the worst case load scenario (islanding occurs at peak load), and for a realistic case (islanding might occur at any load level). Further, Expected Energy Not Served is evaluated. In conclusion, the impacts of DG units and islanded operation of micro-grids have been analyzed for the enhancement of the overall reliability of the distribution system and the successful islanding mode of operational conditions.

Commonly in clinical settings, the patients posture is visually evaluated by the clinician using anatomical landmark references. However, this measurement is subjective and not quantifiable. Photogrammetry to assess posture was thought to be a possible good clinical alternative to the other methods because it is non-invasive, quantifiable, and less expensive. However, more tests were needed to determine its validity. This study tested the reliability and the validity of five angles measuring craniocervical posture using photogrammetry. Radiographs and photographs of the craniocervical posture of 39 healthy-female subjects were taken in a standardized sagittal standing position. Markers were placed on the back of the subjects neck and ear. A second photograph and radiograph was taken 1 week later using 21 of the 39 subjects to test reliability. The angles were analyzed using Alcimage software. Intraclass-correlation coefficient and standard error of measurement was used to test the reliability. Concurrent validity was tested using Pearson correlation and regression analysis. Discriminant analysis was used to test the discriminant validity. Sensitivity/specificity and predicted values were also calculated. The results showed that photogrammetry ICC values were good to excellent when assessed by 2 raters (ICC=0.89-0.99). The posture of the subjects was reproducible when tested using radiographs (ICC=0.89-0.98). One rater was reliable in reattaching the markers (ICC=0.71-0.91) and precise in locating the reference spinous processes (87.8%). Craniovertebral angle (CVA) appeared to be valid in measuring the position of the head in relation to the cervical spine (r=0.84) and to be able discriminate subjects with aligned posture, slight forward head posture (SFHP), and forward head posture (FHP) assessed by 1 rater (84.6% correctly classified). Cervical inclination angle (CIA) appears to be valid in discriminating subjects with aligned and FHP (86% and 88% respectively) but moderate to predict the cervical spine inclination. The cervical lordosis angles were not able to discriminate postures and predict the cervical lordosis. CVA and CIA were able to detect postural differences through the sensitivity/specificity and predicted values analysis. This study supports the validation of CVA and CIA to assess craniocervical posture which may improve the ability of the clinician to detect and quantify craniocervical postural alterations. / Rehabilitation Science

国立情報学研究所で電子化したコンテンツを使用している。

国立情報学研究所で電子化したコンテンツを使用している。

Thesis (M.S.)--University of Hawaii at Manoa, 2007. / Includes bibliographical references (leaves 32-33). / viii, 39 leaves, bound ill. 29 cm

To be effective, applications such as streaming multimedia require both a more stable and more reliable service than the default best effort service from the underlying computer network. To guarantee steady data transmission despite the unpredictability of the network, a single reserved path for each traffic flow is used. However, a single dedicated path suffers from single link failures. To allow for continuous service inexpensively, unreserved backup paths are used in this thesis. While there are no wasted resources using unreserved backup paths, recovery from a failure may not be perfect. Thus, a goal for this approach is to design algorithms that compute backup paths to mask the failure for all traffic, and failing that, to maximize the number of flows that can be unaffected by the failure. Although algorithms are carefully designed with the goal to provide perfect recovery, when using only unreserved backup paths, re-routing of all affected flows, at the same service quality as before the failure, may not be possible under some conditions, particularly when the network was already fully loaded prior to the failure. Alternate strategies that trade off service quality for continuous traffic flow to minimize the effects of the failure on traffic should be considered. In addition, the actual backup path calculation can be problematic because finding backup paths that can provide good service often requires a large amount of information regarding the traffic present in the network, so much that the overhead can be prohibitive. Thus, algorithms are developed with trade-offs between good performance and communication overhead. In this thesis, a family of algorithms is designed such that as a whole, inexpensive, scalable, and effective performance can be obtained after a failure. Simulations are done to study the trade-offs between performance and scalability and between soft and hard service guarantees. Simulation results show that some algorithms in this thesis yield competitive or better performance even at lower overhead. The more reliable service provided by unreserved backup paths allows for better performance by current applications inexpensively, and provides the groundwork to expand the computer network for future services and applications.

Thesis (M.S.)--State University of New York at Binghamton, Industrial and Systems Engineering Department, 2006. / Includes bibliographical references.

Project report (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Abstract. Includes bibliographical references (leaves 72-75). Also available via the Internet.

Thesis (M.S.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains ix, 130 p. : ill. Includes abstract.