Thesis (M.S.)--California Polytechnic State University, 2008. / Mode of access: Internet. Title from PDF title page, viewed on March 26, 2009. Major professor: Dennis Derickson, Ph.D. "Presented to the Electrical Engineering Department Faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the Master of Science degree in Electrical Engineering." "December 2008." Includes bibliographical references (p. 93-94). Will also be available on microfiche.

Thesis (M.S.)--Rochester Institute of Technology, 1981. / Typescript. Includes bibliographical references.

Thesis supervisor: Mona K. Garvin. Includes bibliographic references (p. 55-57).

Indiana University-Purdue University Indianapolis (IUPUI) / Background: Erosive tooth wear (ETW) is the loss of tooth substance due to chemo-mechanical action unrelated to bacteria. ETW affects approximately 46 percent of children/adolescents and 80 percent of adults in the U.S. Visual examination indices are available for the clinical assessment of ETW. Although useful, they are subjective and heavily based on the clinical experience of the examiner. Some quantitative techniques have been proposed and used for clinically assessing erosive tooth wear, including quantitative light-induced fluorescence, ultrasonic measurement, and more recently, polarization-sensitive optical coherence tomography (PS-OCT). Objective: The objective of this study was to explore the ability of PS-OCT to objectively measure erosive tooth wear on occlusal surfaces. Method: This study was conducted in two phases. In the first phase, 10 sound extracted human lower first premolars were selected and then exposed to tooth wear simulation gradually. PS-OCT and micro computed tomography (μ-CT) were used to evaluate enamel thickness of those premolars at the buccal cusp tip during the simulation. In phase 2, 40 extracted human lower first premolars with different severity levels of ETW on occlusal surfaces were selected based on the Basic Erosive Wear Examination (BEWE) index. A total of 10 teeth (n =10) were selected for each BEWE score (0/1/2/3). PS-OCT and μ-CT were used to evaluate the enamel thickness at the highest point on the occlusal surface. Results: There was good agreement between PS-OCT and μ-CT in both phases (phase 1: 0.89 and phase 2: 0.97) with no significant difference between PS-OCT and μ-CT. Conclusion: This result shows the potential of PS-OCT as reliable method for measuring enamel thickness and monitoring tooth wear progression on the occlusal surface

No description available.

Use of proxy caches in the World Wide Web is beneficial to the end user, network administrator, and server administrator since it reduces the amount of redundant traffic that circulates through the network. In addition, end users get quicker access to documents that are cached. However, the use of proxies introduces additional issues that need to be addressed. In particular, there is growing concern over how to maintain cache consistency and coherency among cached versions of documents. The existing consistency protocols used in the Web are proving to be insufficient to meet the growing needs of the Internet population. For example, too many messages sent over the network are due to caches guessing when their copy is inconsistent. One option is to apply the cache coherence strategies already in use for many other distributed systems, such as parallel computers. However, these methods are not satisfactory for the World Wide Web due to its larger size and more diverse access patterns. Many decisions must be made when exploring World Wide Web coherency, such as whether to provide consistency at the proxy level (client pull) or to allow the server to handle it (server push). What trade offs are inherent for each of these decisions? The relevant usage of any method strongly depends upon the conditions of the network (e.g., document types that are frequently requested or the state of the network load) and the resources available (e.g., disk space and type of cache available). Version 1.1 of HTTP is the first protocol version to give explicit rules for consistency on the Web. Many proposed algorithms require changes to HTTP/1.1. However, this is not necessary to provide a suitable solution. One goal of this dissertation is to study the characteristics of document retrieval and modification to determine their effect on proposed consistency mechanisms. A set of effective consistency policies is identified from the investigation. The main objective of this dissertation is to use these findings to design and implement a consistency algorithm that provides improved performance over the current mechanisms proposed in the literature. Optimistically, we want an algorithm that provides strong consistency. However, we do not want to further degrade the network or cause undue burden on the server to gain this advantage. We propose a system based on the notion of soft-state and based on server push. In this system, the proxy would have some influence on what state information is maintained at the server (spatial consideration) as well as how long to maintain the information (temporal consideration). We perform a benchmark study of the performance of the new algorithm in comparison with existing proposed algorithms. Our results show that the Synchronous Nodes for Consistency (SINC) framework provides an average of 20% control message savings by limiting how much polling occurs with the current Web cache consistency mechanism, Adaptive Client Polling. In addition, the algorithm shows 30% savings on state space overhead at the server by limiting the amount of per-proxy and per-document state information required at the server. / Ph. D.

Phase Synchrony (PS) and coherence analyses of stochastic time series - tools to discover brain tissue pathways traveled by electrical signals - are considered for the specific purpose of processing of the electroencephalogram (EEG). We propose the Phase Synchrony Processor (PSP), as a tool for implementing phase synchrony analysis, and examine its properties on the basis of known signals. Long observation times and wide filter bandwidths can decrease bias in PS estimates. The value of PS is affected by the difference in frequency of the sequences being analyzed and can be related to that frequency difference by the periodic sinc function. PS analysis of the EEG shows that the average PS is higher - for a number of electrode pairs - for non-ADHD than for ADHD participants. The difference is more pronounced in the δ rhythm (0-3 Hz) and in the γ rhythm (30-50 Hz) PS. The Euclidean classifier with electrode masking yields 66 % correct classification on average for ADHD and non-ADHD subjects using the δ and γ1 rhythms. We observed that the average γ1 rhythm PS is higher for the eyes closed condition than for the eyes open condition. The latter may potentially be used for vigilance monitoring. The Euclidean discriminator with electrode masking shows an average percentage of correct classification of 78 % between the eyes open and eyes closed subject conditions. We develop a model for a pair of EEG electrodes and a model-based MS coherence estimator aimed at processing short (i.e. 20 samples) EEG frames. We verify that EEG sequences can be modeled as AR(3) processes degraded by additive white noise with an average SNR of approximately 11-12 dB. Application of the MS coherence estimator to the EEG suggests that MS coherence is generally higher for non-ADHD individuals than for ADHD participants when evaluated for the θ rhythm of EEG. Also, MS coherence is consistently higher for ADHD subjects than for the majority of non-ADHD individuals when computed for the low end of the δ rhythm (i.e. below 1 Hz). ADHD produces more measurable effects in the frontal lobe EEG and for participants performing attention intensive tasks. / Ph. D.

The implementation of multiple processors on a single chip has been made possible with advancements in process technology. The benefits of having multiple cores on a single chip bring with it a new set of constraints for maintaining fast and consistent memory accesses. Cache coherence protocols are needed to maintain the consistency of shared memory on individual caches. Current cache coherency protocols are either snoop based, which is not scalable but provides fast access for small number of cores, or directory based, which involves a directory that acts as the ordering point providing scalability with relatively slower access. Our focus is on improving the memory access time of the scalable directory protocol. We have observed that most memory requests follow a pattern where in one of the processors, which we will dub the Producer, repeatedly writes to a particular memory location. A subset of the remaining cores, which we will dub the Consumers, repeatedly read the data from that same memory location. In our implementation we utilize this relationship to provide direct cache to cache transfers and minimize the access time by avoiding the indirection through the directory. We move the directory temporarily to the Producer node so that the consumer can directly request the producer for the cache line. Our technique improves the memory access time by 13 percent and reduces network traffic by 30 percent over standard directory coherence protocol with very little area overhead.

Neste trabalho foram estudadas algumas formas de relação entre séries temporais multivariadas. Discutiu-se, inicialmente, a função de coerência, uma função análoga a função de correlação(que é dada no domínio do tempo) calculada no domínio da freqüência. Foram estudadas também as funções de coerência parcial e coerência parcial direcionada. A função de coerência parcial mede a relação entre duas componentes de uma série multivariada, isolados os efeitos de outra série. Em linhas gerais, a Coerência Parcial Direcionada pode ser interpredata como a decomposição da coerência parcial a partir de modelos autoregressivos multivariados. Esse conceito pode ser interpretado como uma representação do conceito de causalidade de Granger no domínio da freqüência. Finalmente, foram aplicadas as funções acima em dois conjuntos de dados: um modelo VAR(1) trivariado simulado e dados de medições de eletroencefalograma. / In this work we studied relationships between multivariate time series. We discussed the coherence function, a function similar to the correlation function(calculated in time domain) in frequency domain. Next, we discussed partial coherence and partial directed coherence. The partial coherence measures the relationship between two components of a multivariate time series, after removing the influence of another time series. Generally, the partial directed coherence can be interpreted as the decompositioin of the partial coherence from multivariate autoregressive models. We can interpret this function as a representation of the Granger causality concept in frequency domain. Finally, we applied these concepts in two situations: a simulated VAR(1) model and an electroencefalogram database.

<p>Optical coherence tomography (OCT) is a non-invasive optical imaging modality that provides micron-scale resolution of tissue micro-structure over depth ranges of several millimeters. This imaging technique has had a profound effect on the field of ophthalmology, wherein it has become the standard of care for the diagnosis of many retinal pathologies. Applications of OCT in the anterior eye, as well as for imaging of coronary arteries and the gastro-intestinal tract, have also shown promise, but have not yet achieved widespread clinical use.</p><p>The usable imaging depth of OCT systems is most often limited by one of three factors: optical attenuation, inherent imaging range, or depth-of-focus. The first of these, optical attenuation, stems from the limitation that OCT only detects singly-scattered light. Thus, beyond a certain penetration depth into turbid media, essentially all of the incident light will have been multiply scattered, and can no longer be used for OCT imaging. For many applications (especially retinal imaging), optical attenuation is the most restrictive of the three imaging depth limitations. However, for some applications, especially anterior segment, cardiovascular (catheter-based) and GI (endoscopic) imaging, the usable imaging depth is often not limited by optical attenuation, but rather by the inherent imaging depth of the OCT systems. This inherent imaging depth, which is specific to only Fourier Domain OCT, arises due to two factors: sensitivity fall-off and the complex conjugate ambiguity. Finally, due to the trade-off between lateral resolution and axial depth-of-focus inherent in diffractive optical systems, additional depth limitations sometimes arises in either high lateral resolution or extended depth OCT imaging systems. The depth-of-focus limitation is most apparent in applications such as adaptive optics (AO-) OCT imaging of the retina, and extended depth imaging of the ocular anterior segment.</p><p>In this dissertation, techniques for extending the imaging range of OCT systems are developed. These techniques include the use of a high spectral purity swept source laser in a full-field OCT system, as well as the use of a peculiar phenomenon known as coherence revival to resolve the complex conjugate ambiguity in swept source OCT. In addition, a technique for extending the depth of focus of OCT systems by using a polarization-encoded, dual-focus sample arm is demonstrated. Along the way, other related advances are also presented, including the development of techniques to reduce crosstalk and speckle artifacts in full-field OCT, and the use of fast optical switches to increase the imaging speed of certain low-duty cycle swept source OCT systems. Finally, the clinical utility of these techniques is demonstrated by combining them to demonstrate high-speed, high resolution, extended-depth imaging of both the anterior and posterior eye simultaneously and in vivo.</p> / Dissertation