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As technology shrinks new types of defects are being discovered and new fault models are being created for those defects. Transition delay and path delay fault models are two such models that have been created, but they still fall short in that they are unable to obtain a high test coverage of smaller delay defects; these defects can cause functional behavior to fail and also indicate potential reliability issues. The first part of this dissertation addresses these problems by presenting an enhanced timing-based delay fault testing technique that incorporates the use of standard delay ATPG, along with timing information gathered from standard static timing analysis. Utilizing delay fault patterns typically increases the test data volume by 3-5X when compared to stuck-at patterns. Combined with the increase in test data volume associated with the increase in gate count that typically accompanies the miniaturization of technology, this adds up to a very large increase in test data volume that directly affect test time and thus the manufacturing cost. The second part of this dissertation presents a technique for improving test compression and reducing test data volume by using multiple expansion ratios while determining the configuration of the scan chains for each of the expansion ratios using a dependency analysis procedure that accounts for structural dependencies as well as free variable dependencies to improve the probability of detecting faults. Finally, this dissertation addresses the problem of unknown values (X’s) in the output response data corrupting the data and degrading the performance of the output response compactor and thus the overall amount of test compression. Four techniques are presented that focus on handling response data with large percentages of X’s. The first uses X-canceling MISR architecture that is based on deterministically observing scan cells, and the second is a hybrid approach that combines a simple X-masking scheme with the X-canceling MISR for further gains in test compression. The third and fourth techniques revolve around reiterative LFSR X-masking, which take advantage of LFSR-encoded masks that can be reused for multiple scan slices in novel ways. / text

M. Tech. Electrical Engineering.. / Wireless mesh networks (WMNs) have become a better alternative for extending wireless Local Area Networks (WLANs) to provide network coverage up to the furthest of far flung rural areas. This has been implemented by using a meshed backbone network interconnecting the mesh access points (MAPs) that manage each of the WLANs, thus providing a vital mode complimentary to the wireless infrastructure-based networks. The benefits of WMN deployments, however, come with certain challenges e.g., power management. Due to the limited availability of power in typical rural areas in Africa, this dissertation presents an energy efficient localized distributed topology control algorithm to efficiently manage power consumption at the backbone of the wireless mesh networks. The goal is to extend these networks’ lifetimes, as well as improve on throughput. The focus of the project is on the application of the WMNs in rural areas in Africa and in remote urban areas where the mesh nodes are mostly powered by exhaustible power sources like wet-cells or diesel controlled power generators and hence, are considered power constrained. The proposed algorithm uses the propagation models and the concept of relay region to obtain an optimal transmission power per node. It further applies a topology management protocol framework to limit the average number of neighbours per node, which helps to reduce internodes interferences during communication. The performance of the algorithm is validated through extensive simulations in the Network Simulator (NS-2) environment. The results are further compared to those of the conventional IEEE 802.11b mesh network, without transmission power control. It is shown that with a reduction in per node transmission power via topology control it is possible to reduce the total energy consumption in the overall network. It is further shown that this reduction may lead to poor performance in capacity. Hence, it is important to ensure a proper balance in the transmit power to obtain a balance in energy efficiency as well as in throughput.

M. Tech. Electrical Engineering. / Discusses the transport of real time data in WMNs as a challenging problem. The main cause of this problem is transport layer protocols. These protocols have traditionally been used successfully for wired networks. However, their raw implementation in wireless networks has proven to be inefficient, since wireless channels are characterized by a higher Bit Error Rate (BER), Packet Loss Rate (PLR), interference, bandwidth limitations and mobility when compared to wired network channels. Thus, for the efficient transport of real time video in WMNs, transport protocols need to be adapted to be adapted to wireless networks since they were not originally developed for this application.

published_or_final_version / abstract / toc / Physics / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / toc / Industrial and Manufacturing Systems Engineering / Doctoral / Doctor of Philosophy

No description available.

This study describes first and second year university physics students' understanding and reasoning of the concepts, angular speed and angular acceleration. The analysis was based on student responses to various tasks presented to them during one hour long interviews. These responses were characterized from a phenomeno graphic research perspective developed by Marton (1981) and his colleagues at Gothenburg University in Sweden. The findings of the study are described by categories of description and by categories of reasoning. Categories of description characterize; students' conceptualizations of angular speed from different frames of reference, and the ways in which students make comparisons of the angular speeds of two objects. Categories of reasoning characterize the ways in which students were thought to reason about the concepts of angular speed and angular acceleration in several task settings. Interpretation of these findings are discussed with reference to the role a typical introductory physics textbook may have had in shaping the way in which students think about these angular kinematic concepts. Finally, instructional implications and directions for future research are given.

Interaction with mobile devices suffers from a number of shortcomings, most of which are linked to the small size of screens. Artificial tactile feedback promises to be particularly well suited to the mobile interaction context. To be practical, tactile transducers for mobile devices must be small and light, and yet be capable of displaying a rich set of expressive stimuli. This thesis introduces a tactile transducer for mobile interaction that is capable of distributed skin stimulation on the fingertip. The transducer works on a principle that was first investigated because of its potential application to the display of Braille. A preliminary study was conducted on an earlier version of the transducer. It concluded that subjects were able to identify simple Braille characters with a high rate of success. Then, a complete re-design of the transducer addressed the goal of integration in a handheld prototype for mobile interaction. The resulting device comprises a liquid crystal graphic display co-located with the miniature, low-power, distributed tactile transducer. Next, it was needed to measure the perceptual differences between the stimuli that the device could display. Our experiences with one evaluation approach raised questions relating to the methodology for data collection. Therefore, an analysis of the process was carried out using a stimulus set obtained with the device. By means of multidimensional scaling analysis, both the perceptual parameters forming the stimuli space and the evaluation technique were validated. Finally, two experiments were carried out with the objective to develop new mobile interactions paradigms that combined visual and tactile feedback. Both experiments modeled a list scrolling task on the device. The first experiment found a marginal improvement in performance when tactile feedback was employed. It also came at a higher attentional cost dedicated to operating the device. For the second experiment, the scrolling paradigm and the tactile feedback were improved. This lead to a decrease in the reliance on vision when tactile feedback was enabled. Results showed a 28% decrease in the number of key presses that controlled the visibility state of the scroll list.

This thesis is concerned with the design and implementation of radio frequency (RF) power amplifiers and micro-electromechanical systems---namely MEMS varactors. This is driven by the many wireless communication systems which are constantly moving towards increased integration, better signal quality, and longer battery life. / The power amplifier consumes most of the power in a receiver/transmitter system (transceiver), and its output signal is directly transmitted by the antenna without further modification. Thus, optimizing the PA for low power consumption, increased linearity, and compact integration is highly desirable. / Micro-electromechanical systems enable new levels of performance in radio-frequency integrated circuits, which are not readily available via conventional IC technologies. They are good candidates to replace lossy, low Q-factor off-chip components, which have traditionally been used to implement matching networks or output resonator tanks in class AB, class F, or class E power amplifiers. The MEMS technologies also make possible the use of new architectures, with the possibility of flexible re-configurability and tunability for multi-band and/or multi-standard applications. / The major effort of this thesis is focused on the design and fabrication of an RF frequency class AB power amplifier in the SiGe BiCMOS 5HP technology, with the capability of being tuned with external MEMS varactors. The latter necessitated the exploration of wide-tuning range MEMS variable capacitors, with prototypes designed and fabricated in the Metal-MUMPS process. / An attempt is made to integrate the power amplifier chip and the MEMS die in the same package to provide active tuning of the power amplifier matching network, in order to keep the efficiency of the PA constant for different input power levels and load conditions. / Detailed simulation and measurement results for all circuits and MEMS devices are reported and discussed.