Dissertations / Theses on the topic 'PhD output'

This dissertation focuses on the production of knowledge that contributes to economic growth through the accumulation of human capital and technological change. More specifically, I look at the proclivity and effectiveness of different types of universities and colleges to send individuals on to pursue a doctoral degree in science or engineering (S&E) and how PhD attainment relates to characteristics of students who attend these institutions and the faculty who teach at these institutions. A tobit estimation is employed to test for institution effects, the effect of student and faculty characteristics, and also the impact of economic factors. To partially control for selection, survey results from the Higher Education Research Institute (HERI) are used to determine students’ desire for a PhD when entering and exiting college. I find that student and faculty characteristics matter, as do economic variables. Unobservable and/or un-measureable characteristics affecting PhD output, which differ systematically by type of institution, however, remain even after controlling for the aforementioned variables. Based on the analysis in this dissertation, I conclude that much of what are typically regarded as tier effects on PhD output are in fact due to the selective matching between students and their undergraduate institutions. By adding measures for selective matching and proxies for individual opportunities, we see that ability, faculty characteristics and accomplishments, and peer effects maintain significant, positive effects on rates of PhD output. Finally, rates vary not only by institution type, but also by field.

A new heuristic method to improve the I/O pad assignment for the sea-of-gates placement algorithm "PROUD" is proposed. In PROUD, the preplaced I/O pads are used as the boundary conditions in solving sparse linear equations to obtain the optimal module placement. Due to the total wire length determined by the module positions is the strong function of the preplaced I/O pad positions, the optimization of the I/O pad circular order and their assignment to the physical locations on the chip are attempted in the thesis. The proposed I/O pad assignment program is used as a predecessor of PROUD. The results have revealed excellent improvement.

Thesis (M.S.)--Southern Illinois University Carbondale, 2006.<br>"Department of Mechanical Engineering and Energy Processes." Includes bibliographical references (leaves 210-220). Also available online.

Cette thèse contribue au développement des recherches dans le domaine du Pronostic et Health Management : gestion de l’état de santé des systèmes complexes. Dans un contexte de management opérationnel et de sûreté de fonctionnement des systèmes, nous proposons d’étudier comment la modélisation par un Modèle Graphique Probabiliste Dynamique (MGPD) permet le diagnostic de l’état de santé courant d’un système, le pronostic de cet état et de l’évolution des dégradations, ainsi que l’estimation de sa durée de vie résiduelle en fonction de ses conditions opérationnelles. La dégradation des composants est en général inconnue et nécessite un arrêt du système pour être observée. Cependant, cela est difficile, voire impossible, durant l’exploitation du système. Néanmoins, un ensemble de grandeurs observables sur le système ou le composant peut caractériser le niveau de dégradation et faciliter l’estimation de la durée de vie résiduelle du composant et du système. Les MGPD offrent une approche adaptée à la modélisation de l’évolution de l’état de santé des systèmes et des composants. Nous étendons la modélisation classique des modèles de la famille des HMM vers les IOHMM pour permettre une propagation temporelle de l’incertitude afin de résoudre le problème de pronostic de l’état de santé et de l’estimation de la durée de vie résiduelle. Cette recherche comprend l’extension des algorithmes d’apprentissage et d’inférence appliqués aussi bien dans le cas d’un composant que pour un système structuré. Cette thèse a pour but de contribuer à lever les verrous scientifiques suivants : - Considérer l'état de santé du système par un modèle stochastique et apprendre les paramètres du modèle à partir des mesures disponibles sur le système. - Établir un diagnostic de l’état de santé du système et le pronostic de son évolution en intégrant plusieurs conditions opérationnelles. - Estimer la durée de vie résiduelle des composants et des systèmes structurés (série, parallèle) à partir de ses composants. L’enjeu est majeur, car le pronostic de la dégradation des composants du système permet de définir des stratégies soit de pilotage soit de maintenance par rapport à la durée de vie résiduelle du système. Cela permet la réduction de la probabilité d’occurrence d’un arrêt pour cause de dysfonctionnement du système, soit en ajustant la vitesse de dégradation pour s’accorder à un plan de maintenance préventif, soit en planifiant les interventions de maintenance de manière proactive<br>This thesis contributes to prognosis and health management for assessing health condition of complex systems. In the context of operational management and operational safety of systems, we propose to investigate how Dynamic Probabilistic Graphical Modelling (DPGM) can be used to diagnose the current health state of systems, prognostic the future health state, and the evolution of degradation, as well as estimate its remaining useful life based on its operating conditions. System degradation is generally unknown and requires shutting down the system to be observed. However, this is difficult or even impossible during system operation. Though, a set of observable quantities on a system or component can characterise the level of degradation and help to estimate the remaining useful life of components and systems. The DPGM provides an approach suitable for modelling the evolution of the health state of systems and components. The aim of this thesis is to transpose and capitalize on the experience of these previous works in a prognostic context on the basis of a more efficient DPGM taking into account the available knowledge on the system. We extend the classical HMM family models to the IOHMM to allow the time propagation of uncertainty to address prognostic problems. This research includes the extension of learning and inference algorithms. Variants of the HMM model are proposed to incorporate the operating environment into the prognosis. The aim of this thesis is to contribute to solving the following scientific locks: - Considering the state of health whatever the complexity of the system by a stochastic model and learning the model parameters from the available measurements on the system. - Establish a diagnosis of the state of health of the system and the prognosis of its evolution by integrating several operational conditions. - Estimate the remaining useful life of components and structured systems with series and parallel components. This is a major challenge because the prognosis of the degradation of system components makes it possible to define strategies for either control or maintenance in relation to the residual life of the system. This allows the reduction of the probability of occurrence of a shutdown due to a system malfunction either by adjusting the degradation speed to fit in with a preventive maintenance plan or by proactively planning maintenance interventions

碩士<br>國立臺灣大學<br>電機工程學研究所<br>87<br>A high-speed CMOS serial link transceiver is proposed. This transceiver uses parallelism to overcome the intrinsic gate speed limitation of CMOS technology. The parallelism used by the transmitter is the multiplexing-at-output-pad technique. The one used by the receiver is the oversampling technique. For the oversampling technique, we design an active sampling circuit which has larger SNR than a passive sampling circuit. A new data recovery algorithm which has fast tracking rate is proposed. In addition, we will present a general architecture of a high resolution multi-phase clock generator which is the crucial building block for the oversampling receiver. Finally, a test-chip is implemented for 2.5Gb/s data rate and the simulated results are shown.

The empirical relations between the nominal money stock and output implied by two classes of equilibrium rational expecations business cycle models are examined. The two classes are the monetary business cycle (MBC) model, which relies on monetary shocks as the source of business cycles, and the real business cycle (RBC) model, which relies on real shocks The neutrality of monetary policy in the MBC model is a debated issue in the literature. It is demonstrated, however, that the MBC model implies that observed movements in money should be uncorrelated with output regardless of the neutrality issue. This result implies that the existing empirical studies that find a significant relation between observed money and output conclusively reject the MBC model Money and output are correlated in the RBC model because of the endogenous response of money to current and expected future real shocks that, in turn, are the fundamental causes of output fluctuations. The untested hypothesis of the RBC model is that money and output are uncorrelated once the effects of current and expected future real shocks have been controlled. Use of a vector of measurable real shocks and the rational expectations assumption allows tests of this hypothesis to be designed. Execution of these tests reveals that the vector of measurable real shocks can explain the majority of postwar U.S. output variation. However, money remains significant in explaining output variation after controlling for current and expected future real shocks. Therefore, the RBC model is also rejected as an explanation for the correlation between money and output<br>acase@tulane.edu

The desire to find useful information by abstracting a user's profile from user data is in great demand in a lot of fields today. An algorithm or method is needed to be able to get the profile of a user online and realtime. Trying to solve the problem, we study the biological structure and psychological behavior of human cognitive system. Parameter estimation is the key but estimation in this domain is challenging. In order to allow the parameters to be tracked automatically, we develop a new technique using sliding mode control observer design. Our approach is to trace the output switching time, model internal dynamics in a persistent way while driving the estimation error to approach zero. The performance of the proposed observer has robust reaction to disturbance. It is easy and efficient to implement since the information it requires is easy to access. It can facilitate solving profile identification problems in a variety of domains. Using sliding mode observer, it makes possible the construction of a system that observes closely human interest individually. Its unique cognition oriented paradigm, proven theories, and supporting architecture allows for continuously adaptive monitoring and updating the current information<br>acase@tulane.edu

The retina is a sensory tissue that converts optical images into neural signals known as light responses. Light responses are transmitted from photoreceptors to bipolar cells to retinal ganglion cells (RGCs) in parallel pathways specific for either light increments or light decrements. This improves vision by doubling the retina’s dynamic range and increasing contrast sensitivity. Research has shown that Off pathways, which are sensitive to light decrements, are likely modulated by the activity of metabotropic glutamate receptor 6 (mGluR6) receptors, cannabinoid 1 receptors (CB1Rs), and γ-aminobutyric acid C (GABAC) receptors. In this dissertation, I investigate how these neurotransmitter receptors modulate Off responses in the retina by performing whole-cell recordings of mouse RGCs. On bipolar cells express mGluR6 receptors, a type of glutamate receptor that hyperpolarizes bipolar cells when bound to glutamate. Previous research has shown that these receptors modulate Off responses under dark adaptation, but effects under light adaptation were unclear. My research has shown that mGluR6 receptor agonist DL-2-amino-4-phosphonobutyric acid (APB) decreases light-evoked Off responses under light adaptation by disrupting dopaminergic transmission between amacrine cells and Off bipolar cells. CB1Rs are localized to many cell types including cone and bipolar cell axon terminals, each of which release glutamate. Research primarily in brain has shown that cannabinoid receptor activation prevents neurotransmitter release from the presynapse. This has led to the hypothesis that CB1R activation would decrease glutamate release in Off pathways and attenuate Off responses. My research shows that CB1R agonists differentially modulate Off responses. Based on my results, I suggest that CB1R agonists increase light-evoked Off responses in one population of RGCs by reducing GABA transmission between GABAergic amacrine cells and Off bipolar cells. GABAergic amacrine cells feed back onto bipolar cell axon terminals that express GABAC receptors. Previous research has shown that GABAC receptor antagonist (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid (TPMPA) alters On responses, but effects on Off responses are unclear. I show that TPMPA modulates kinetics of both On and Off responses recorded from On-Off RGCs. All together, the results in this dissertation indicate that mGluR6 receptors, CB1Rs, and GABAC receptors modulate Off responses, and therefore vision.<br>acase@tulane.edu

Speech is the tool humans use to communicate that sets us apart from any other species. It is a complex interplay between the motor speech system of the speaker and the auditory system of the listener. Self-monitoring uses what one hears to help monitor what one says by way of an automatic feedback loop. We tested the theory that humans are selectively adaptive to acoustic stimuli that contain speech-like frequencies. In Study One, we measured speech output changes given speech versus noise masks during a naming task. Results showed that noise containing speech-similar frequencies (broadband, 0.0--20 kHz; bandpassed, 0.05--4.5 kHz; high-notched, 8.0--11.5 kHz removed) elicited significant changes in the acoustic features of the speech output, while noise with speech-similar frequencies removed (low-notched, 0.5--4.5 kHz removed) did not. In Study Two, we measured duration matching accuracy, and speech output changes given speech and noise masks during a novel duration matching task. Participants matched /a/, /f/, and noise at 300 ms, 550 ms, and 800 ms lengths in quiet, speech (/a/, /i/), broadband noise, and /f/-frequency shaped noise masks. Findings showed that it was more difficult to duration match /a/ given a speech versus a noise mask. In addition, there were different error patterns between speech and noise; speech targets were overshot with error greatest at 550 ms, while noise targets were undershot with error increasing as target length increased. Collectively, results support the theory that self-monitoring in humans is selectively affected by frequencies within the speech range and that a specialized module exists for processing speech information<br>acase@tulane.edu

碩士<br>國立成功大學<br>光電科學與工程研究所<br>97<br>In this study, we demonstrated GaN-based light-emitting diodes(LEDs) with non-alloyed metal contacts on n-GaN and transparent contact layer(TCL), which was indium tin oxide and/or gallium-doped zinc oxide, to serve as the n-type electrode and the p-type electrode, respectively. The TCLs had rough surface with mesh structure. Besides, photolithography process was applied to form micro-pillar waveguide at the periphery of LEDs to enhance the light extraction efficiency. The result will be discussed in detail in this thesis. In this study, the non-alloyed metal contacts including Cr/Au and Ag/Cr/Au were used to serves as electrodes and reflectors at the same time. The conventional electrode pad (Cr/Au) and the reflective electrode pad (Ag/Cr/Au) deposited on n-GaN layer can exhibit Ohmic characteristics on n-GaN. The specific contact resistance(ρ_c) was as low as ~�Q10^(-4)Ω-cm^2. The non-alloyed metal contacts(Ag/Cr/Au) used in the present experimental blue LEDs also play the role of reflector to prevent the emitted light from absorption by the opaque electrode pads(Cr/Au) with low reflectivity. The experiments implemented by the above-mentioned schemes exhibited a marked enhancement in light-extraction efficiency, and their electrical properties were comparable with the conventional LEDs. With an injection current of 20mA, the light output power of the ITO/mesh GZO LEDs can be markedly improved by 20.6% of magnitude as compared to the conventional ITO/planar GZO LEDs. Furthermore, the enhancement can be boosted to 32.9% if the Cr/Au electrode pads were replace by the reflective Ag/Cr/Au electrode pads. The same experiment were also performed to GaN-based LEDs with different sizes which chip size was 575×250 μm^2. With an injection current of 20mA, the light output power of the ITO/mesh GZO LEDs can be markedly improved by 20.9% of magnitude as compared to the conventional ITO/planar GZO LEDs. Similarly, the enhancement can be further boosted like the technique was used in the LEDs with chip size of 300×300 μm^2. The enhancement in light output power was as high as 29.4% of magnitude if the Cr/Au electrode pads were replace by the reflective Ag/Cr/Au electrode pads. In order to further increase the light output power, micro-pillar waveguides at the periphery of LEDs were implemented. As a result, the light output power is boosted to 38.6%. In summary, we had demonstrated GaN-based LEDs with micro-pillar waveguides, reflective pads and roughed TCL. The light output power of the LEDs could be enhanced about 38.6% of magnitude, and the operation voltage of the LEDs had just a slightly increase of 0.1~0.15v as compared to the conventional LEDs.

Thesis (Ph.D.)--State University of New York at Buffalo, 2006.<br>Title from PDF title page (viewed on Feb. 28, 2007) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Titus, Albert H. Includes bibliographical references.

Thesis (M.S.)--State University of New York at Buffalo, 2006.<br>Title from PDF title page (viewed on Mar. 21, 2007) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Lenker, James. Includes bibliographical references.

Bottom sediments of the Upper Barataria Basin and the Mississippi River-Gulf Outlet estuarine complexes consist predominantly of silty clays and clayey silts derived from the erosion of the St. Bernard lobe of the Mississippi River delta. Montmorillonite dominates the sediment clay mineralogy and reflects the influence of the Mississippi River Basin The acid-leachable concentrations of fourteen trace metals were determined for 284 bottom sediment and 44 core interval samples by plasma emission. The areal metal distribution is controlled predominantly by the bottom sediment texture and mineralogy and is significantly correlated with smaller grain-size sediments, carbon content, and aluminum and iron content. Ba, Cd, Pb, and Zn are the least correlatable and may reflect the greatest anthropogenic influence. Sediments have greater mean metal content than Florida and Texas estuarine sediments, generally due to their finer grain size, lack of CaCO3, and higher clay, iron, and carbon content Concentrations of As, Ba, Cd, Pb, V and Zn, elevated relative to basinwide means, were detected from sediments associated with oil and gas drilling and production, sandblasting, dredging, and stormwater and industrial discharges. Average metal contents were comparable to other Gulf Coast estuaries and below the lowest effect level sediment quality guidelines from compiled biological assessments. Biological effects from metal concentrations comparable to those found would be expected to be rare Elutriate testing designed to simulate sediment disruptions similar to dredging operations or major storm events were performed on the most highly contaminated sediments. Results indicate the release of metals into the water column, but at concentrations below the Louisiana Ambient Water Quality Criteria. Sediments displayed an inherent capacity to remove the released metals from the water column upon return to original conditions Sediment accumulation rates were determined from four cores using 210Pb geochronology. Compaction corrected accumulation rates varied from 0.1 to 0.28 cm/yr and were comparable to observed rates from Louisiana estuaries. Within Lake Salvador core intervals, concentrations of As, Ba, Cr, Cd, Pb, and Zn have increased by 10% to 30% in sediments accumulated within the last 50 years, though little variation was noted from sediments accumulated during the 1800's<br>acase@tulane.edu

Thesis (M.A.)--State University of New York at Buffalo, 2008.<br>Title from PDF title page (viewed on Sept. 04, 2008) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Pendergast, David R., Duffey, Michael E. Includes bibliographical references.

Thesis (M.S.)--State University of New York at Buffalo, 2008.<br>Title from PDF title page (viewed on Jan. 15, 2009) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Briner, Jason Includes bibliographical references.