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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Entwicklung einer Niederenergie-Implantationskammer mit einem neuartigen Bremslinsensystem

Borany, Johannes von, Teichert, Jochen January 2001 (has links)
In diesem Report wird eine Niederenergie-Implantationskammer (NEI-Kammer) beschrieben, die im Forschungszentrum Rossendorf entwickelt und aufgebaut wurde. Die Kammer ermöglicht es, die Implantation von Ionen bei niedrigen Energien (< 30 keV) mit einer Implantationsanlage für mittlere Energien durchzuführen. In der Kammer werden der Ionenstrahl, den der Implanter liefert, auf die erwünschte niedrige Energie abgebremst. Dazu wird ein elektrostatisches Bremslinsensystem eingesetzt, das auf einem neuartigen Prinzip basiert. Das System besteht aus einer Sammellinse und einer Zerstreuungslinse, wobei die Öffnungsfehler beider Linsen entgegengesetzte Vorzeichen besitzen und sich gegenseitig kompensieren. Dadurch ist es möglich, Wafer gebräuchlicher Größe bei geringer Energie mit hoher Dosishomogenität zu implantieren. Die NEI-Kammer ist insbesondere für Forschungseinrichtungen eine vorteilhafte Lösung, da sie eine wesentlich kostengünstigere und flexiblere Alternative zur Anschaffung einer Niederenergie-Implantationsanlage darstellt.
22

Affective and Autonomic Responses to Erotic Images among Young Women with and without Sexual Difficulties

De Pesa, Natasha 01 January 2015 (has links)
Existing models of female sexual dysfunction (FSD) are broad and do not provide information about how to improve existing interventions. The purpose of the current study is to extend the empirical application of a disgust model of FSD (de Jong, van Overveld, & Borg, 2013) to a population of young women reporting difficulties with sexual desire and/or arousal and related distress. Sixty college-aged females participated in the study and were placed into two groups based upon their reports of sexual functioning and sexual distress: a control group (i.e., no sexual difficulties or distress) and a clinical group (i.e., difficulties with sexual desire and/or arousal and accompanying distress). Participants were attached to physiological equipment and shown images displaying neutral, positive, disgusting, and erotic content. It was hypothesized that the clinical group would show more evidence of disgust (via affective and autonomic responses) than the control group. Consistent with hypotheses, no group differences were found in any of the affective or autonomic measures during presentation of the neutral, positive, or disgust images. Group differences during presentation of the erotic images (i.e., in facial EMG, heart rate, and self-report affective ratings) and follow-up analyses provided preliminary evidence for generalizing the disgust model of female sexual dysfunction beyond disorders of sexual pain, at least among some women. Exploratory analyses implicated a relationship between a history of sexual victimization and self-report disgust ratings of erotic images. Future research should further explore these relationships in order to shed more light on how disgust-based mechanisms impact the onset and maintenance of female sexual dysfunction.
23

Exploiting the Biologic Ability of Carbon Dioxide to Manipulate Cerebral Blood Flow in Order To Prevent Mild Traumatic Brain Injury

Reeder, Evan January 2022 (has links)
No description available.
24

Modeling and Analysis of Crankshaft Energy Harvesting for Vehicle Fuel Economy Improvement

Grimm, Benjamin Mihuta 19 July 2012 (has links)
No description available.
25

Extern träningsbelastning för ett fotbollslag i Damallsvenskan : Analyser av försäsongsträning

Ek, Oskar January 2021 (has links)
Bakgrund: Damfotboll har vuxit kraftigt senaste åren. Spelares externa belastning monitoreras med utrustning bestående av global positioning system, accelerometer och pulsband. Variablerna total distans, höghastighetslöpning och accelerationer/decelerationer har beskrivits som relevanta mått för att monitorera den externa belastningen för fotbollsspelare. Syfte: Att undersöka den externa belastningen i samband med träning, samt dess fluktuationer över tre mesocykler, för ett fotbollslag i Damallsvenskan under försäsongsträning, med fokus på variablerna total distans, high speed running och accelerationer/decelerationer.Metod: 15 utespelare inkluderades och försäsongsträningen delades in i tre mesocykler med 14 pass vardera. Between- och within subject-analyser utfördes med fokus på total distans, höghastighetslöpning samt accelerationer/decelerationer.Resultat: Resultatet visade en ökning av respektive variabel mellan mesocykel ett och två, följt av en minskning mellan två och tre. En tydlig minskning av höghastighetslöpning under mesocykel tre noterades. Between subjects-analysen visade lägre absoluta värden och variation än within subjects-analysen. Stora variationer i spelares externa belastning förelåg. Slutsats: Damfotbollsspelares externa belastning varierade kraftigt vid undersökning av total distans, höghastighetslöpning och accelerationer/decelerationer i samband med försäongsträning. Enligt en blockperiodisering, misslyckades i upprätthållandet av intensitet i sista mesocykeln. / Background: Womens’ football has grown rapidly. An increased use of tracking devices in football research has been shown, where total distance, high speed running and accelerations/decelerations stand out as important variables to track.Aim: To investigate external load, and its fluctuations over three mesocycles, for a team of elite female footballers during pre-season training.Method: A between- and within subject-analysis of 15 players from a team in Damallsvenskan, looking at total distance, high speed running and accelerations/decelerations, was conducted. Training sessions were divided into three mesocycles where comparisons were made.Results: Results showed an increase of each variable between mesocycle one and two, followed by a decrease in all variables between mesocycle two and three in both analyses. A decrease in high speed running during mesocycle three was prevalent. Between-subjects analysis showed slightly lower absolute values and slightly less variation than the within- subject analysis. Both analyses showed a big between- and within-players variation. Conclusion: Female footballers’ external load during pre-season training sessions were shown to display big variation looking at total distance, high speed running and accelerations/decelerations. Following a block periodisation model, the final mesocycle before season start failed in adequately maintaining intensity during tapering.
26

Statistical and Behavioral Modeling of Driver Behavior on Signalized Intersection Approaches

Amer, Ahmed 12 January 2011 (has links)
The onset of a yellow indication is typically associated with the risk of vehicle crashes resulting from dilemma-zone and red-light-running problems. Such risk of vehicle crashes is greater for high-speed signalized intersection approaches. The research presented in this dissertation develops statistical as well as behavioral frameworks for modeling driver behavior while approaching high-speed signalized intersection approaches at the onset of a yellow indication. The analysis in this dissertation utilizes two sources of data. The main source is a new dataset that was collected as part of this research effort during the summer of 2008. This experiment includes two instructed speeds; 72.4 km/h (45 mph) with 1727 approaching trials (687 running and 1040 stopping), and 88.5 km/h (55 mph) with 1727 approaching trials (625 running and 1102 stopping). The complementary source is an existing dataset that was collected earlier in the spring of 2005 on the Virginia Smart Road facility. This dataset includes a total of 1186 yellow approaching trials (441 running and 745 stopping). The adopted analysis approach comprises four major parts that fulfill the objectives of this dissertation. The first part is concerned with the characterization of different driver behavioral attributes, including driver yellow/red light running behavior, driver stop-run decisions, driver perception-reaction times (PRT), and driver deceleration levels. The characterization of these attributes involves analysis of variance (ANOVA) and frequency distribution analyses, as well as the calibration of statistical models. The second part of the dissertation introduces a novel approach for computing the clearance interval duration that explicitly accounts for the reliability of the design (probability that drivers do not encounter a dilemma zone). Lookup tables are developed to assist practitioners in the design of yellow timings that reflects the stochastic nature of driver PRT and deceleration levels. An extension of the proposed approach is presented that can be integrated with the IntelliDriveSM initiative. Furthermore, the third part of the dissertation develops an agent-based Bayesian statistics approach to capture the stochastic nature of the driver stop-run decision. The Bayesian model parameters are calibrated using the Markov Chain Monte Carlo (MCMC) slice procedure implemented within the MATLAB® software. In addition, two procedures for the Bayesian model application are illustrated; namely Cascaded regression and Cholesky decomposition. Both procedures are demonstrated to produce replications that are consistent with the Bayesian model realizations, and capture the parameter correlations without the need to store the set of parameter realizations. The proposed Bayesian approach is ideal for modeling multi-agent systems in which each agent has its own unique set of parameters. Finally, the fourth part of the dissertation introduces and validates a state-of-the-art behavioral modeling framework that can be used as a tool to simulate driver behavior after the onset of a yellow indication until he/she reaches the intersection stop line. The behavioral model is able to track dilemma zone drivers and update the information available to them every time step until they reach a final decision. It is anticipated that this behavioral model will be implemented in microscopic traffic simulation software to enhance the modeling of driver behavior as they approach signalized intersections. / Ph. D.
27

Morphological and mechanical characterization of the human liver to improve a finite element model / Caractérisation morphologique et mécanique du foie humain en vue de l’amélioration d’un modèle éléments finis

Chenel, Audrey 03 December 2018 (has links)
Lors des accidents de la route, les lésions de l’abdomen mettent des vies en jeu et nécessitent un traitement médical long et coûteux. Il est important d’offrir une meilleure prévention des lésions abdominales traumatiques. Des modèles numériques de corps humain ont été développés afin de comprendre les mécanismes lésionnels. L’objectif de cette thèse est de contribuer au développement d’un modèle numérique de foie humain pour la prédiction de lésions hépatiques en cas de choc.Dans un premier temps, une caractérisation morphologique du foie a été réalisée sur 78 scanners et a mis en évidence l’existence de 4 morphotypes. Ensuite, des expérimentations ont mis en évidence l’influence de la pressurisation des vaisseaux sur la déformation de la capsule et ont permis d’identifier la déformation à rupture locale lors d’un choc.Enfin, les modèles numériques des 4 morphotypes identifiés ont été construits pour simuler les essais de décélération réalisés dans la partie expérimentale. / In road accidents, lesions of the abdomen are life-threatening, and require a long and expensive medical treatment. It is important to offer a better prevention of traumatic abdominal injuries. Numerical models of the human body have been developed to understand the mechanisms of injury. The aim of this thesis is to contribute to the development of a numerical model of human liver for the prediction of liver lesions in case of shock.First, a morphological characterization of the liver was performed on 78 healthy patient scanners and highlight the existence of 4 morphotypes.Then, experiments were carried out to highlight the influence of this pressurization of the vessels on the strain state of the Glisson capsule and to identify the local ultimate strain during an impact.Finally, the numerical models of the 4 identified morphotypes were constructed and used to simulate the deceleration tests performed in the experimental part.
28

Comportamento dos motoristas em interseções semaforizadas / Driver behavior at signalized intersections

Colella, Diogo Artur Tocacelli 29 February 2008 (has links)
Esta pesquisa caracterizou o comportamento de motoristas em interseções semaforizadas sob três aspectos: (1) reação frente à mudança do verde para o amarelo; (2) comportamento durante a desaceleração para parar; e (3) comportamento durante a saída do cruzamento semaforizado. Os dados foram coletados em uma interseção localizada em pista de testes no Virginia Tech Transportation Institute, nos EUA. A amostra foi composta por 60 motoristas voluntários igualmente divididos em função do gênero; dos quais 32 tinham idade inferior a 65 anos (\"jovens\"). Foram investigados efeitos da idade, do gênero e da declividade da via sobre as seguintes situações: tomada de decisão entre parar ou prosseguir no amarelo; posição de parada em relação à faixa de retenção; tempo de percepção e reação (TPR) para frenagem e partida do cruzamento; efeito de zonas de opção e de dilema; taxa de desaceleração para parada na interseção; e taxa de aceleração para partida da interseção. As análises indicaram que: (1) os motoristas mais jovens invadiram mais a faixa de retenção que os idosos; (2) mulheres apresentam maiores TPR para decidir partir da interseção; e (3) o TPR é menor no declive tanto para a decisão de frear quanto para a partida do cruzamento. As taxas de desaceleração não apresentaram influência dos fatores avaliados. Por outro lado, constatou-se que a aceleração foi afetada pelo fator declividade. Como resultado final da pesquisa, foram propostos modelos, em função do tempo, que exprimem a desaceleração/aceleração usada pelos motoristas ao frear/acelerar. Foram propostos modelos para o motorista médio e para motoristas desagregados em três grupos em função da agressividade. / The objective of this research was to characterize driver behavior at signalized intersections according to three aspects: (1) reaction at the onset of the amber phase; (2) behavior during the deceleration to stop at the signal; and (3) behavior during the acceleration to leave the intersection at the onset of the green. The data were collected at a signalized intersection on a private highway, at the Virginia Tech Transportation Institute, in the USA. The sample consisted of 60 volunteer drivers, equally divided by gender. The sample was divided into two age groups: younger drivers (age was less than 65) and older drivers. Effects of gender, age group and roadway grade were investigated for the following aspects: decision making at the onset of amber; final stopping position with relation to the stop line; perception/reaction times (PRT) at the onset of the amber and the green lights; effects of dilemma and option zones; and deceleration and acceleration rates used by the drivers. The analyses suggest that: (1) younger drivers tend to stop farther past the stop line, compared to older drivers; (2) women have longer PRT at the onset of the green; and (3) PRT are shorter on downgrade at the onset of both amber and green lights. The observed deceleration rates were not affected by gender, age group or roadway grade. Acceleration rates were found to be influenced by the grade. A set of models that express the acceleration/deceleration rates as a function of time were proposed to represent the average behavior observed for drivers in the sample. Specific models were also proposed for aggressive, non-aggressive and intermediate drivers.
29

Lean blowout and its robust sensing in swirl combustors

Bompelly, Ravi K. 11 January 2013 (has links)
Lean combustion is increasingly employed in both ground-based gas turbines and aircraft engines for minimizing NOx emissions. Operating under lean conditions increases the risk of Lean Blowout (LBO). Thus LBO proximity sensors, combined with appropriate blowout prevention systems, have the potential to improve the performance of engines. In previous studies, atmospheric pressure, swirl flames near LBO have been observed to exhibit partial extinction and re-ignition events called LBO precursors. Detecting these precursor events in optical and acoustic signals with simple non-intrusive sensors provided a measure of LBO proximity. This thesis examines robust LBO margin sensing approaches, by exploring LBO precursors in the presence of combustion dynamics and for combustor operating conditions that are more representative of practical combustors, i.e., elevated pressure and preheat temperature operation. To this end, two combustors were used: a gas-fueled, atmospheric pressure combustor that exhibits pronounced combustion dynamics under a wide range of lean conditions, and a low NOx emission liquid-fueled lean direct injection (LDI) combustor, operating at elevated pressure and preheat temperature. In the gas-fueled combustor, flame extinction and re-ignition LBO precursor events were observed in the presence of strong combustion dynamics, and were similar to those observed in dynamically stable conditions. However, the signature of the events in the raw optical signals have different characteristics under various operating conditions. Low-pass filtering and a single threshold-based event detection algorithm provided robust precursor sensing, regardless of the type or level of dynamic instability. The same algorithm provides robust event detection in the LDI combustor, which also exhibits low level dynamic oscillations. Compared to the gas-fueled combustor, the LDI events have weaker signatures, much shorter durations, but considerably higher occurrence rates. The disparity in precursor durations is due to a flame mode switch that occurs during precursors in the gas-fueled combustor, which is absent in the LDI combustor. Acoustic sensing was also investigated in both the combustors. Low-pass filtering is required to reveal a precursor signature under dynamically unstable conditions in the gas-fueled combustor. On the other hand in the LDI combustor, neither the raw signals nor the low-pass filtered signals reveal precursor events. The failure of acoustic sensing is attributed in part to the lower heat release variations, and the similarity in time scales for the precursors and dynamic oscillations in the LDI combustor. In addition, the impact of acoustic reflections from combustor boundaries and transducer placement was addressed by modeling reflections in a one-dimensional combustor geometry with an impedance jump caused by the flame. Implementing LBO margin sensors in gas turbine engines can potentially improve time response during deceleration transients by allowing lower operating margins. Occurrence of precursor events under transient operating conditions was examined with a statistical approach. For example, the rate at which the fuel-air ratio can be safely reduced might be limited by the requirement that at least one precursor occurs before blowout. The statistics governing the probability of a precursor event occurring during some time interval was shown to be reasonably modeled by Poisson statistics. A method has been developed to select a lower operating margin when LBO proximity sensors are employed, such that the lowered margin case provides a similar reliability in preventing LBO as the standard approach utilizing a more restrictive operating margin. Illustrative improvements in transient response and reliabilities in preventing LBO are presented for a model turbofan engine. In addition, an event-based, active LBO control approach for deceleration transients is also demonstrated in the engine simulation.
30

Comportamento dos motoristas em interseções semaforizadas / Driver behavior at signalized intersections

Diogo Artur Tocacelli Colella 29 February 2008 (has links)
Esta pesquisa caracterizou o comportamento de motoristas em interseções semaforizadas sob três aspectos: (1) reação frente à mudança do verde para o amarelo; (2) comportamento durante a desaceleração para parar; e (3) comportamento durante a saída do cruzamento semaforizado. Os dados foram coletados em uma interseção localizada em pista de testes no Virginia Tech Transportation Institute, nos EUA. A amostra foi composta por 60 motoristas voluntários igualmente divididos em função do gênero; dos quais 32 tinham idade inferior a 65 anos (\"jovens\"). Foram investigados efeitos da idade, do gênero e da declividade da via sobre as seguintes situações: tomada de decisão entre parar ou prosseguir no amarelo; posição de parada em relação à faixa de retenção; tempo de percepção e reação (TPR) para frenagem e partida do cruzamento; efeito de zonas de opção e de dilema; taxa de desaceleração para parada na interseção; e taxa de aceleração para partida da interseção. As análises indicaram que: (1) os motoristas mais jovens invadiram mais a faixa de retenção que os idosos; (2) mulheres apresentam maiores TPR para decidir partir da interseção; e (3) o TPR é menor no declive tanto para a decisão de frear quanto para a partida do cruzamento. As taxas de desaceleração não apresentaram influência dos fatores avaliados. Por outro lado, constatou-se que a aceleração foi afetada pelo fator declividade. Como resultado final da pesquisa, foram propostos modelos, em função do tempo, que exprimem a desaceleração/aceleração usada pelos motoristas ao frear/acelerar. Foram propostos modelos para o motorista médio e para motoristas desagregados em três grupos em função da agressividade. / The objective of this research was to characterize driver behavior at signalized intersections according to three aspects: (1) reaction at the onset of the amber phase; (2) behavior during the deceleration to stop at the signal; and (3) behavior during the acceleration to leave the intersection at the onset of the green. The data were collected at a signalized intersection on a private highway, at the Virginia Tech Transportation Institute, in the USA. The sample consisted of 60 volunteer drivers, equally divided by gender. The sample was divided into two age groups: younger drivers (age was less than 65) and older drivers. Effects of gender, age group and roadway grade were investigated for the following aspects: decision making at the onset of amber; final stopping position with relation to the stop line; perception/reaction times (PRT) at the onset of the amber and the green lights; effects of dilemma and option zones; and deceleration and acceleration rates used by the drivers. The analyses suggest that: (1) younger drivers tend to stop farther past the stop line, compared to older drivers; (2) women have longer PRT at the onset of the green; and (3) PRT are shorter on downgrade at the onset of both amber and green lights. The observed deceleration rates were not affected by gender, age group or roadway grade. Acceleration rates were found to be influenced by the grade. A set of models that express the acceleration/deceleration rates as a function of time were proposed to represent the average behavior observed for drivers in the sample. Specific models were also proposed for aggressive, non-aggressive and intermediate drivers.

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