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Sieber, Jan. "Longitudinal dynamics of semiconductor lasers." Doctoral thesis, [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963267795.
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Kliment, Linda K. "Dynamics of longitudinal wake vortices." Diss., Wichita State University, 2009. http://hdl.handle.net/10057/2554.
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In the present study, the mid-field vortex wake is investigated. For the most part, the results focus on the motion of a pair of co-rotating vortices prior to merger, both in and out of ground effect. However, in order to verify the experimental and computational methods, results for single vortices, counter-rotating pairs, and complex wakes are also presented. A method is presented which allows measurement of the time dependent motion of vortex filaments. This optical method interferes minimally with the wake and allows recording of vortex location and time-dependent motion. From the position and time information recorded, extraction of the amplitudes of motion, core motion, spiraling behavior, vortex strengths, and the principal planes of motion is possible.
First, a single vortex is studied in order to establish a basis for comparison. The dye remains in the core and the motion of a single vortex is shown to exhibit a growth in amplitude with increasing downstream distance and strength. The core motion is shown to be minimal, remaining smaller that one core diameter. In addition, when the single vortex is forced to oscillate at a given frequency, the dye still remains in the core, even though the amplitudes of motion are large. The forcing frequency is identified easily against the background noise. Two four-vortex cases are then presented. The first case consists of filaments that spiral while in the second they scatter. These results are consistent with those shown in literature and show that the experimental method can be used for analyzing complex wakes. Pairs of unforced, co-rotating filaments are studied outside of ground effect. Many cases are presented, some for nearly equal strengths and others in which one vortex is much stronger than the other. As in the single-vortex case, the amplitudes of motion are shown to increase as the downstream distance becomes greater. The constant rate of spiraling is shown to increase as the vortex strength increases and vortex span decreases. Vortex span either remains constant or decreases with downstream distance depending on the vortex separation distance. The motion of the center of spiraling is shown to be minimal, similar to the motion of the vortex core in the single-vortex cases. The filaments are shown to sometimes oscillate along preferred directions, which is inconsistent with a theoretical model developed in 1975. A few cases are also presented in which the merger location is analyzed. However, these are visual investigations only, since it is not possible to obtain quantitative data for such cases with the experimental method available. The behavior of co-rotating vortices in the presence of forcing functions is then presented. The results are compared to the theoretical model developed in 1975 and those published after 2002. However, a direct comparison with analytical results is not possible due to the large scatter in the experimental data. Regardless, the experimental results show that the forced corotating vortices do have an unstable oscillatory motion with growing amplitude. The preferred direction of motion implies the presence of stationary waves. These results contradict those of the analytical model developed in 1975 but agree in nature with those published more recently. Ground effect is then considered for counter-rotating vortices, because there is a wealth of information on this topic in the literature. When counter-rotating vortices are near a ground plane, a lateral drift as well as a rebounding behavior is present. The counter-rotating vortices are shown to have a preferred direction of motion which tends to become parallel to the ground plane. The motion is also shown to have increasing amplitude, although this quantity is slightly reduced by the presence of the ground plane. In addition, ground roughness in the form of streamwise ridges has no affect on the vortex trajectories, within the range of downstream distances observable in these experiments. After comparing the results to those in literature, it is concluded that the experimental method is valid and can be used to study co-rotating vortices in ground effect.
Literature lacks information on co-rotating vortices in ground effect. The results in this document show that co-rotating vortices in ground effect have a lateral drift as well as a rebound similar to those of counter-rotating pairs. The resulting motion is similar to that of leapfrogging vortex rings. Preferred directions of motion are present, although no trend can be established. In addition, the amplitudes of motion are reduced slightly by the presence of the ground, just as they are for the counter-rotating vortices. Due to the lack of information on co-rotating vortices in ground effect in the current literature, a comparison is impossible. Therefore, two simple computation efforts are undertaken in order to verify some of the flow features. Using a two-dimensional viscous analysis, limited to laminar flow, it is shown that when co-rotating vortices are placed near a stationary wall, a boundary layer forms on the surface and separates. The secondary vortex released by boundary layer separation leads to rebounding of the primary vortices. In addition to affecting the trajectory, the no-slip boundary also affects the time to vortex merger as well as leading to an elongation of the vorticity contours. Furthermore, this analysis demonstrates that making the strengths of the two vortices differ slightly does not affect the spiraling rate, surface boundary layer separation, or rebound. A second inviscid model is also used to study cases consisting of two vortices of unequal strengths. Having unequal strengths does affect the lateral drift of corotating vortices in ground effect. Also, the center of spiraling shifts towards the stronger vortex. However, the inviscid model shows that the vortex span is unaffected by difference in strengths.Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering
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Harris, John Richardson. "Longitudinal dynamics of an intense electron beam." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/2906.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2005.Thesis research directed by: Electrical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Koscielniak, S. R. "Longitudinal beam dynamics studies on the ISIS synchrotron." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379845.
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Haider, Muhammad Rezaul. "Longitudinal Thermal and Solute Dynamics in Regulated Rivers." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/6870.
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Dam releases increase river stage and can reverse groundwater movement into and out of the river. As the flood, thermal, and solute waves travel downstream in a regulated river, the size of the waves is anticipated to be affected both by river processes and exchanges with near river groundwater. This study established a modeling framework to quantify the influences of the groundwater exchanges on the temperatures and solute concentration dynamics along regulated rivers. The wave properties, volume of exchanges, conservative solute mass exchanges, and heat energy exchanges were calculated as a function of time and distance downstream. Results show that the temperature and solute concentrations are influenced by the arrival of flood waves. Groundwater exchanges were found to affect temperatures along the river with a minimal effect on solute concentration. These findings provide insight regarding the influences of hydropeaking occurring in a large fraction of rivers in the world which has important implications for water quality and the ecology of regulated rivers.
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Hamersma, H. A. (Herman Adendorff). "Longitudinal vehicle dynamics control for improved vehicle safety." Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/40829.
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An autonomous vehicle is a vehicle that is capable of navigating and driving with no human intervention whatsoever through the utilization of various sensors and positioning systems. The possible applications of autonomous vehicles are widespread, ranging from the aerospace industry to the mining and military sectors where the exposure of human operators to the operating conditions is hazardous to their health and safety. Automobile accidents have become the leading cause of death in certain segments of the world population. Removing the human driver from the decision-making process through automation may result in significantly safer highways. Although full autonomy may be the ultimate goal, there is huge scope for systems that aid the driver in decision making or systems that take over from the driver under conditions where the human driver fails.
The aim of the longitudinal control system to be implemented on the Land Rover test vehicle in this study is to improve the vehicle’s safety by controlling the vehicle’s longitudinal behaviour. A common problem with sports-utility-vehicles is the low rollover threshold, due to a high centre of gravity. Rather than modifying the vehicle to increase the rollover threshold, the aim of the control system presented here is to prevent the vehicle from exceeding speeds that would cause the vehicle to reach its rollover threshold.
In order to develop a control system that autonomously controls the longitudinal degree of freedom, a model of the test vehicle (a 1997 Land Rover Defender 110 Wagon) was developed in MSC.ADAMS/View and validated experimentally. The model accurately captures the response of the test vehicle to supply forces as generated by the engine and demand forces applied through drag, braking and engine braking. Furthermore, the model has been validated experimentally to provide reliable simulation results for lateral and vertical dynamics.
The control system was developed by generating a reference speed that the vehicle must track. This reference speed was formulated by taking into account the vehicle’s limits due to lateral acceleration, combined lateral and longitudinal acceleration and the vehicle’s performance capabilities. The control system generates the desired throttle pedal position, hydraulic pressure in the brake lines, clutch position and gear selection as output. The MSC.ADAMS\View model of the test vehicle was used to evaluate the performance of the control system on various racetracks of which the GPS coordinates were available. The simulation results indicate that the control system performs as expected.
Finally, the control system was implemented on the test vehicle and the performance was evaluated by conducting field tests in the form of a severe double lane change manoeuvre. The results of the field tests indicated that the control system limited the acceleration vector of the vehicle’s centre of gravity to prescribed limits, as predicted by the simulation results.Dissertation (MEng)--University of Pretoria, 2013.
gm2014
Mechanical and Aeronautical Engineering
unrestricted
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Tian, Kai. "Study of longitudinal dynamics in space-charge dominated beams." College Park, Md.: University of Maryland, 2008. http://hdl.handle.net/1903/8063.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2008.Thesis research directed by: Dept. of Electrical and Computer Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Zhang, Elizabeth Y. "Microinvasive probes for the longitudinal interrogation of neural dynamics." Thesis, Massachusetts Institute of Technology, 2018. https://hdl.handle.net/1721.1/121645.
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This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 91-99).
Chronically implantable probes are critical to investigating the neural dynamics of functions such as learning, motivation, and movement control over the extended timescales at which they develop. Proven functional lifetimes of over a year are also necessary for eventual clinical use in human patients to help monitor and treat certain neurological diseases. Existing electrochemical probes experience signal degradation and have not been reported to remain viable after 4 months of implantation. Chronic inflammatory and foreign body responses due to large implanted device size and mechanical mismatch are believed to be major contributors to signal degradation. In the first half of this thesis, I present the design of parylene-coated carbon fiber electrodes for electrochemical measurements that reduces implanted footprint by 2 orders of magnitude and flexural rigidity by 3 orders of magnitude compared to state-of-art electrochemical probes.
The parylene-coated carbon fiber electrodes induced minimal chronic inflammatory responses that were not significantly distinguishable from unpenetrated control tissue. The novel microinvasive probes demonstrated stable subsecond measurement of extracellular dopamine neurochemicals for over 1 year. The second half of this thesis explores the effect of axial vibration during probe implantation to reduce experienced insertion forces. The greater compliance of microinvasive probes often preclude their successful implantation, particularly in deep brain regions. Current approaches temporarily encase probes in larger and stiffer guide tubes, for example, but these methods induce undesirable acute trauma that compromise long-term measurement performance. Dynamic implantation was found to significantly reduce in vitro insertion forces and significantly reduce acute in vivo tissue trauma hen compared to conventional static implantation.
The extended chronic functionality of the parylene-coated carbon fiber electrodes and the reduced insertion forces generated during dynamic implantation enable future study of neuroplastic functions and the progression of neurodegenerative diseases in awake and behaving animals, and the findings further advance microinvasive probes towards clinical human use.
by Elizabeth Y. Zhang.
M. Eng.
M.Eng. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
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Adhynugraha, Muhammad Ilham. "Longitudinal dynamics of wing in ground effect craft in waves." Thesis, Cranfield University, 2017. http://dspace.lib.cranfield.ac.uk/handle/1826/13095.
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An assessment of the longitudinal motion of a hybrid configuration called the aerodynamically alleviated marine vehicle (AAMV) with the presence of waves, is demonstrated in the thesis. The development of this type of vehicle requires a mathematical framework to characterise its dynamics with the influence of external forces due to the waves’ motion. An overview of the effect of waves towards the models of dynamics developed for wing in ground effect (WIGE) craft and high-speed marine vehicles (planing craft) is carried out. However, the overview only leads to a finding that the longitudinal stability of a lifting surface over wavy ground effect is not entirely established. Taking this fact into account, the analysis of the model is proposed for a WIGE craft configuration. A simplification is adopted considering heave motion only in the modelling of oscillation. The simplification is made to thoroughly capture the effect of oscillation toward dynamic stability of the vehicle. To support the model verification, a numerical simulation followed by a semi-empirical design method was adopted to produce aerodynamic data, both in two-dimensional and three-dimensional domains, respectively. The results show that the combination of underpinning parameters, i.e. ride height, frequency and amplitude of oscillation, remarkably influence the aerodynamics. The characteristics in aerodynamics affect the production of stability derivatives and eventually stability behaviour of the chosen configuration. Some patterns in the results are identified but there also some data that show the peculiarity. Thus further investigation is needed.
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Dassanayake, Achala Viomy. "Machining dynamics and stability analysis in longitudinal turning involving workpiece whirling." Thesis, [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1817.
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Zeni, Daniel. "Longitudinal dynamics modeling and handling qualities of a conventional jet aircraft." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8530/.
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Un noto centro di ricerca europea ha recentemente modificato un jet convenzionale di classe CS-25 in una piattaforma scientifica. Durante il processo di certificazione delle modifiche, l’impatto delle stesse sulle prestazioni è stato studiato in modo esaustivo. Per lo studio delle qualità di volo, i piloti collaudatori hanno sviluppato una procedura di certificazione ad hoc che consiste in test qualitativi separati della stabilità longitudinale, laterale e direzionale.
L’obiettivo della tesi è analizzare i dati di volo, registrati durante i test di collaudo, con l'obiettivo di estrarre informazioni di carattere quantitativo circa la stabilità longitudinale del velivolo modificato. In primo luogo sono state analizzate tre diverse modifiche apportate all’aeromobile e successivamente i risultati sono stati messi a confronto per capirne l’influenza sulle qualità di volo dell’aeromobile. Le derivate aerodinamiche sono state stimate utilizzando la cosiddetta “identificazione dei parametri”, che mira a replicare le variabili registrate durante i test di volo, variando un dato insieme di coefficienti all’interno del modello linearizzato della dinamica dell’aeromobile. L'identificazione del modo di corto periodo ha consentito l'estrazione dei suoi parametri caratteristici, quali il rapporto di smorzamento e la frequenza naturale. La procedura ha consentito inoltre di calcolare il cosiddetto “Control Anticipation Parameter” (CAP), parametro caratterizzante delle qualità di volo di un aeroplano. I risultati ottenuti sono stati messi a confronto con i requisiti prescritti dalla normativa MIL-STD-1797-A, risultando conformi al livello più alto di qualità di volo.
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Raffington, Laurel. "Socioeconomic disparities in children’s cognitive development: Longitudinal dynamics and stress mechanisms." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/19217.
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Individuelle Unterschiede in der kognitiven Entwicklung von Kindern korrelieren mit ihrem sozioökonomischen Status (engl. socioeconomic status, SES). Allerdings hat die bisherige Forschung längsschnittliche Dynamiken meist ignoriert. Des Weiteren sind die Mechanismen, die zu SES–bedingten Diskrepanzen in der kognitiven Entwicklung führen, weitgehend unbekannt. Gemäß einer Hypothese ist es die Dysregulation der Sekretion des Stresshormons Cortisol die SES Unterschiede vermittelt, da niedriger SES robust mit höherem chronischen Stress assoziiert.
Die vorliegende Dissertation weist im Längsschnitt nach, dass Veränderungen im Familieneinkommen die kognitive Entwicklung von armen Kindern im späteren Kindesalter vorhersagen (Studie I). Bemerkenswerterweise wirkt kindliche Kognition auch auf Veränderungen im elterlichen Einkommen, was auf bisher vernachlässigte bidirektionale Familiendynamiken hinweist. Zudem liefert die Dissertation querschnittliche empirische Evidenz für die Hypothese, dass ein stressbezogener Mechanismus in SES–bedingten Unterschieden kognitiver Entwicklung involviert ist. Höherer Stress und ein geringeres Einkommen waren beide mit Anzeichen des Hypocortisolismus in Kindern charakterisiert (Studie II und III). Außerdem gab es Hinweise, dass kognitive Kontrolle vor den Effekten von Stress schützen könnte (Studie II). Schließlich zeigt die Dissertation erstmalig, dass hyporeaktive Cortisolprofile in Reaktion auf akuten Stress in ärmeren Kindern mit deren niedrigerer Gedächtnisleistung assoziiert ist (Studie III). Beachtenswert ist, dass Ergebnisse dieser Dissertation nicht auf Umwelt oder genetisch vermittelte Kausalität schließen lassen. In zukünftigen Interventionsstudien sollte weiter untersucht werden, ob Interventionen die Einkommensgewinne stärken, Stress reduzieren oder die Reaktion von Kindern auf akuten Stress verbessern, kognitive Unterschiede im Zusammenhang mit SES verringern.Individual differences in cognitive development in childhood vary along gradients of socioeconomic status (SES). Yet, research has largely ignored longitudinal dynamics, despite evidence that SES, especially income, also changes over time. Furthermore, fairly little is known about the mechanisms by which SES explains cognitive disparities. Lower SES environments are marked by high chronic stress exposure, which has led to the hypothesis that dysregulation of the stress response system resulting in altered cortisol secretion mediates disparities in cognition. This dissertation provides longitudinal evidence for the notion that family income gains and losses predict poor children’s cognitive development throughout later childhood (Paper I). Remarkably, children’s cognition also predicts their parents’ earning ability, indicating previously neglected bidirectional family dynamics. Moreover, this dissertation provides cross–sectional evidence for a stress mechanism involved in SES disparities of cognitive functioning. Both higher stress and lower income are associated with patterns of hypocortisolism in middle childhood (Paper II & III). Further, cognitive control skills may buffer against the embedding of stress exposure in diurnal cortisol secretion (Paper II). Lastly, cortisol hyporeactivity to stress found in low–income children is uniquely associated with their lower memory performance. Notably, this dissertation does not warrant environmentally– or genetically–mediated assumptions of causality. Future intervention studies should continue to explore whether facilitating family income gains, reducing stress exposure, normalizing cortisol secretion, or improving children’s stress coping by training cognitive control alleviates SES–related disparities in cognition.
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Heffernan, Matthew Evan Bevly David M. "Simulation, estimation, and experimentation of vehicle longitudinal dynamics that effect fuel economy." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Summer/Theses/HEFFERNAN_MATTHEW_41.pdf.
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Lee, Changheon. "Dynamics of Advice Network and Knowledge Contribution: A Longitudinal Social Network Analysis." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/243117.
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Online communities have become an increasingly popular channel for social interaction, enabling knowledge and opinion sharing across a board range of topics and contexts. Their viability and sustainability depends largely on contributions from community members in terms of time, resources, and knowledge. However, how individuals' knowledge contribution behavior changes over time and what network structural characteristics influence individuals' contribution behavior is not well understood. This study investigates "co-evolution" of social networks (i.e. advice network) and knowledge contribution behavior thorough a lens of social selection and social influence mechanism. This study are particularly interested in examining the dynamics of the advice network ties and the knowledge contribution behavior in the context of virtual financial communities in which people voluntarily participate to exchanges investing-related information. Unlike popular friendship-based online social networks, virtual financial communities in this study enables members to construct their own advice network by adding, maintaining, or terminating advice ties. Changes in network ties are referred to as social selection, while changes in individuals' behavior in response to the current network position are referred to as social influence. Dynamic network modeling is applied to investigate effects of social selection and influence separately and then examine the interplay between social selection and behavioral influence. Examination of such effects both separately and simultaneously requires a longitudinal data that capture dynamic changes in both the advice ties and the behavior under study.
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Wagner, Simon John, and simonjwagner@gmail com. "DERAILMENT RISK ASSESSMENT." Central Queensland University. Engineering, 2004. http://library-resources.cqu.edu.au./thesis/adt-QCQU/public/adt-QCQU20060720.100637.
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There is a large quantity of literature available on longitudinal train dynamics and
risk assessment but nothing that combines these two topics. This thesis is focused at
assessing derailment risks developed due to longitudinal train dynamics. A key
focus of this thesis is to identify strategies that can be field implemented to correctly
manage these risks. This thesis quantifies derailment risk and allows a datum for
comparison. A derailment risk assessment on longitudinal train dynamics was
studied for a 107 vehicle train consist travelling along the Monto and North Coast
Lines in Queensland, Australia. The train consisted of 103 wagons and 4
locomotives with locomotives positioned in groups of two in lead and mid train
positions. The wagons were empty hopper wagons on a track gauge of 1067mm.
The scenarios studied include: the effect of longitudinal impacts on wagon dynamics
in transition curves; and the effects of longitudinal steady forces on wagon dynamics
on curves. Simulation software packages VAMPIRE and CRE-LTS were used.
The effects of longitudinal impacts from in-train forces on wagon dynamics in curves
were studied using longitudinal train simulation and detailed wagon dynamics
simulation. In-train force impacts were produced using a train control action. The
resulting worst-case in-train forces resulting from these simulations were applied to
the coupler pin of the wagon dynamics simulation model. The wagon model was
used to study the effect of these in-train forces when applied in curves and transitions
at an angle to the wagon longitudinal axis. The effects of different levels of coupler
impact forces resulting from different levels of coupling slack were also studied.
Maximum values for wheel unloading and L/V ratio for various curve radii and
coupler slack conditions were identified. The results demonstrated that the
derailment criteria for wheel unloading could be exceeded for a coupler slack of
50mm and 75mm on sharper curves, up to 400m radii.
A detailed study of the effect of steady in-train forces on wagon dynamics on curves
also was completed. Steady in-train forces were applied to a three wagon model
using VAMPIRE. Maximum and minimum values of wheel unloading and L/V ratio
were identified to demonstrate the level of vehicle stability for each scenario. The
results allowed the worse cases of wheel unloading and L/V ratio to be studied in
detail.
Probability density functions were constructed for the occurrence of longitudinal
forces and coupler angles for the Monto and North Coast Lines. Data was simulated
for a coupler slack of 25, 50 and 75mm and force characteristics were further
classified into the occurrences of impact and non-impact forces. These probability
density functions were analysed for each track section to investigate the effects of
coupler slack, track topography and gradient on wagon dynamics. The possible
wagon instability in each of these scenarios was then assessed to give a measure of
the potential consequences of the event. Risk assessment techniques were used to
categorise levels of risk based on the consequences and likelihood of each event. It
was found that for the train configuration simulated, the Monto Line has a higher
derailment risk than the North Coast Line for many of the scenarios studies in this
thesis. For a coupler slack of 25mm no derailment risks were identified, 50mm
coupler slack derailment risks were only identified on the Monto track and the
majority of derailment risks were identified for a 75mm coupler slack.
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Hawley, Lance. "Longitudinal dynamics of the therapy process during and following brief treatment for depression." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102983.
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Given the pervasive, debilitating nature of major depressive disorder, a large body of clinical research has evaluated the efficacy of short-term treatments for depression. Researchers have attempted to understand the complex mechanism of therapeutic change by examining treatment response, which is typically defined as the extent of symptom change between the intake and termination sessions. However, this approach fails to recognize that therapy is a non-linear, dynamic longitudinal process. An alternative approach involves analysis of longitudinal repeated measures process and outcome indicators in order to examine change both during treatment as well as following treatment. In order to evaluate dynamic, longitudinal hypotheses, it is necessary to use an appropriate analytical framework. A structural modelling technique termed Latent Difference Score Analysis (LDS) is well suited for this purpose, allowing for evaluation of longitudinal growth within a time series, while also considering multivariate relationships and determinants.The purpose of this research was to evaluate established theories of depression vulnerability as well as theories of psychotherapy process, both during and following depression treatment. The research described in Chapter 2 examined several theories of the longitudinal relationship between depression and perfectionism during depression treatment, while considering the role of the therapeutic alliance. Longitudinal LDS analyses supported a "personality vulnerability" model of depression, in which perfectionism predicted the subsequent rate of depression change throughout treatment. Results indicate that patients with high levels of perfectionism experience less reduction in their depression scores throughout treatment. Furthermore, the strength of the therapeutic alliance significantly predicted the rate of change in personality vulnerability throughout therapy. The research described in Chapter 3 examined several theories of the longitudinal relationship between depression and stress following treatment termination. Results supported a "stress reactivity" model, in which stressful events led to elevations in the rate of depression change following therapy. Multigroup LDS analysis indicated that stress reactivity only occurred for patients who had been treated with medication, and not for those who had received psychotherapy.
These findings have several implications. First, comprehensive analyses of treatment efficacy can move beyond symptom reduction by examining mechanisms underlying treatment response using an appropriate statistical framework. The first paper demonstrates that an efficient route to symptom reduction involves establishing an adequate therapeutic alliance in order to target personality vulnerability. The second paper demonstrates that importance of evaluating treatment efficacy by considering whether a treatment leads to enduring change. Specifically, results indicate that the enduring effects of psychotherapy (in comparison to medication treatments) following treatment termination involves increased resiliency to stressful life events.
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Dorais, Stephanie. "The Dynamics Of Resilience In A Centering Meditation: A Longitudinal Randomized Controlled Trial." W&M ScholarWorks, 2021. https://scholarworks.wm.edu/etd/1627407477.
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In use for centuries across nations, meditation is still one of the widely used interventions to promote holistic health. Despite its large research base, many forms of meditation in use still have yet to be subject to empirical research. Centering prayer has been an established contemplative practice since the third century and has recently gained popularity at the turn of the last century. Individuals practiced centering to find stillness and, through the stillness, their inner strength. Due to its lack of empirical evidence, centering practice has primarily remained in religious or contemplative circles outside instead of counseling treatment. Furthermore, it is almost entirely out of the young adult population's knowledge, a generation that has increasingly identified with spirituality over the years. Due to this potential match with the population and other stated needs of the college counseling field for complementary and alternative forms of treatment, the present study aims to test the effectiveness of a centering prayer meditation on resilience in the college population. Further, it seeks to examine the temporal dynamics of resilience during this intervention over four weeks. To address this goal, I conducted a longitudinal randomized controlled trial where university students (n = 150) joined at random a treatment group or a control group. Each group took assessments measuring their resilience, hope, mindfulness, spiritual transcendence, and stress at three points in time with equal intervals of two weeks (T1, T2, and T3). Also, they took a brief assessment of hope every morning and every evening for the duration of the study. At the onset of the study, participants in the treatment group received a brief online introductory training to centering meditation. Afterward, the study procedure requested them to practice centering for 10 minutes every morning and every evening for the study duration. After meditation, they completed their brief assessments of hope, while the control group completed them at the same time without the meditation. This study used two research methods from temporal dynamics, including growth curve modeling and time series analysis. The growth curve model indicated a statistically significant difference in resilience over four weeks between the treatment and control group (p < .05). The 4-week treatment had approximately a moderate within-group effect on the treatment group (d = .48). A subsequent growth curve model indicated that hope was a significant explanatory variable (p < .05) and within-subject mediator (p < .01) of resilience over time. Based on the hypothesis of this effect of hope on resilience, the study included a time series analysis analyzing the bi-daily levels of hope between the treatment group and control group. Using an ARIMA modeling procedure, the analysis detected that the treatment group had an ARIMA (1, 1, 0) model, indicating a statistically significant increasing trend in hope and autocorrelation to aid in forecasting, p < .000. The model accounted for 56% of the variance in hope while controlling for the trend in the data (stationary R2 = .56). As expected, the control group did not have an increasing trend in hope, but it showed a forecastable model through its AR(1) and MA (1), p <.000. Lastly, the study explored how other psychosocial properties of resilience such as mindfulness, stress, and spiritual transcendence could affect the trajectory of resilience over time. A growth curve model indicated that each variable had a statistically significant fixed effect on resilience over time, p < .05. Time served as a statistically significant random effect in the models of stress and spiritual transcendence, p < .000. Discussion of limitations and implications for counseling practice and research will follow.
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Xu, Lei. "Magnetization Dynamics at Elevated Temperatures." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/311342.
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The area of ultrafast (sub-nanosecond) magnetization dynamics of ferromagnetic elements and thin films, usually driven by a strong femtosecond laser pulse, has experienced intense research interest. In this dissertation, laser-induced demagnetization is theoretically studied by taking into account interactions among electrons, spins, and lattice. We propose a microscopic approach under the three temperature framework and derive the equations that govern the demagnetization at arbitrary temperatures.To address the question of magnetization reversal at high temperatures, the conventional Landau-Lifshitz equation is obviously unsatisfactory, since it fails to describe the longitudinal relaxation. So by using the equation of motion for the quantum density matrix within the instantaneous local relaxation time approximation, we propose an effective equation that is capable of addressing magnetization dynamics for a wide range of temperatures. The longitudinal and transverse relaxations are analyzed, magnetization reversal processes near Curie temperatures is also studied. Furthermore, we compared our derived Self-consistent Bloch equation and Landau-Lifshitz-Bloch equation in detail. Finally, the demagnetzation dynamics for ferromagnetic and ferrimagnetic alloys is studied by solving the Self-consistent Bloch equation.
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Eckert, Jony Javorski 1988. "Análise comparativa entre os métodos de cálculo da dinâmica longitudinal em veículos." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264392.
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Orientador: Franco Giuseppe DediniDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Dinâmica veicular é o estudo das interações entre o veículo, condutor e o ambiente bem como as reações de carga, sendo esta dividida em 3 grandes áreas: dinâmica longitudinal, vertical e lateral. Existem variações entre os métodos propostos pela literatura para o cálculo da dinâmica longitudinal do veículo, sendo que o objetivo deste trabalho é, por meio de simulações, compararem os resultados obtidos pelas diversas metodologias. Por meio de um modelo gerado com auxílio do programa de análise dinâmica de multicorpos Adams®, juntamente com o Simulink Matlab®, foram implementados os métodos de cálculo propostos pela literatura de forma a simular o comportamento de um veículo em função de uma demanda de potência gerada por meio do padrão de velocidades imposto pelos ciclos das normas brasileiras NBR6601 e NBR7024. Os resultados encontrados foram comparados por meio da correlação linear entre as curvas de torque resultantes do modelo dinâmico, possibilitando uma avaliação entre os resultados encontrados pelos diferentes métodos. Também foram avaliados o consumo de combustível, a influência da variação da massa do veículo e da estratégia de condução no comportamento dinâmico do veículo, bem como modelos complementares referentes a veículos híbridos e o efeito da adição de um modelo de embreagem no conjunto simulado
Abstract: Vehicular dynamics is the study of interactions between vehicle, driver and load reactions. The vehicular dynamics is divided into three areas: longitudinal, vertical and lateral. There are variations between the methods proposed in the literature to calculate the longitudinal dynamics of the vehicle. The purpose of this study is, through simulations; compare the results obtained by different methods. By means of a model generated by Adams® (Software of Multibody Dynamics Analysis) together with Simulink Matlab® were implemented the calculation methods proposed by literature to simulate the behavior of a vehicle according to a power demand resulting from the default speeds cycles required by Brazilian Standards NBR6601 and NBR7024. The results were compared using linear correlation between the couple curves resulting from the dynamic model, allowing an evaluation of the results reported by different methods. Were also evaluated: the fuel consumption and the influence of the mass vehicle variation, the driving strategy in the vehicle dynamic behavior, some complementary models of hybrid vehicles and the effect of add a clutch model
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica
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Islam, Zeenath Ul. "Statistical modelling and analysis of the infection dynamics of PRRSV in vivo infections." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/29513.
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Porcine reproductive and respiratory syndrome (PRRS) is one of the most economically significant viral diseases facing the global swine industry. Viraemia profiles of PRRS virus challenged pigs reflect the severity and progression of infection within the host and provide crucial information for subsequent control measures. In this thesis we analyse the largest longitudinal PRRS viraemia dataset from an in-vivo experiment, and corresponding immune measures in the form of cytokine data and neutralising antibodies. In the PRRS Host Genetic Consortium (PHGC) trials, pigs were challenged with one of two PRRSV isolates (NVSL and KS06, respectively). In Chapter 2 we derive a statistical description of the temporal changes in viraemia and determine the influence of diverse factors (e.g. PRRSV strain, pig genetic background, resistance genotype, etc.) on viraemia profiles. The well-established methodology of linear mixed modelling with a repeated measures model and fitting a linearized Wood’s function, a gamma-type function, is applied to the viraemia dataset. The virus isolate had a significant impact on the viraemia profiles which was captured by statistically significant differences in model parameters via both statistical methods. The more virulent NVSL isolate had higher early viraemia predictions and a faster rate of decline than KS06. In line with previous studies the WUR “resistance” genotype, associated with lower AUC viraemia found in previous studies, also resulted in lower viraemia predictions in the statistical models. The typical time trends of the viraemia profiles were a rise to a peak followed by a period of decline with dynamics and magnitude influenced by the virus isolate. Both uni and bimodal viraemia profiles were observed. The Wood’s model appeared a suitable candidate model for the data associated with uni-modal profiles and captured the time trends concisely in only three model parameters which also had a biological relevance. Overall the best fitting Wood’s model (y=atbe-ct) was when there was a random effect in Wood’s parameters b and c. Bimodal profiles significantly reduced the model fit, particularly in the later phase of infection resulting in large model residuals. However bimodal profiles did not impact upon the significance of the differences between the LSM repeated measures estimates nor the LSM linearized Wood’s model parameter estimates. The longitudinal viraemia measures from the PRRSV challenge experiment revealed substantial differences in the viraemia profiles between hosts infected with the same PRRSV challenge dose, pointing to considerable variation in the host response to PRRSV infections. In Chapter 3 we provide a suitable mathematical description of all viraemia profiles with biologically meaningful parameters for quantitative analysis of profile characteristics. The Wood’s function and a biphasic extended Wood’s function were fit to the individual profiles using Bayesian inference with a likelihood framework in Chapter 3. Using maximum likelihood inference and numerous fit criteria, we established that the broad spectrum of viraemia trends could be adequately represented by either uni-or biphasic Wood’s functions. Three viraemic categories emerged: cleared (uni-modal and below detection within 42 days post infection(dpi)), persistent (transient experimental persistence over 42 dpi) and rebound (biphasic within 42 dpi). The convenient biological interpretation of the model parameters estimates, allowed us not only to quantify inter-host variation, but also to establish common viraemia curve characteristics and their predictability. The convenient biological interpretation of the model parameters estimates, allowed us not only to quantify inter-host variation, but also to establish common viraemia curve characteristics and their predictability, which were utilized in subsequent quantitative genetic analyses to identify genomic regions associated with these new resistance traits. The Bayesian approach for curve fitting in Chapter 3 led to better model fits than the classical linear mixed models approach of Chapter 2. Furthermore in Chapter 4 we explored the association between the observed PRRS viraemia profile characteristics and the corresponding measures of the immune response in the form of: neutralising antibody (nAb) cross protection data and longitudinal cytokine profiles. Statistical analysis of the profile characteristics revealed that persistent profiles were distinguishable already within the first 21 dpi, whereas it is not possible to predict the onset of viraemia rebound. Analysis of the neutralizing antibody (nAb) data indicated that there was a ubiquitous strong response to the homologous PRRSV challenge, but high variability in the range of cross-protection of the nAbs. Persistent pigs were found to have a significantly higher nAb cross-protectivity than pigs that either cleared viraemia or experienced rebound within 42 dpi. We determined the typical features and time trends of each cytokine profile, examined the associations between cytokines, and characterised the cytokine response. A stronger association was found in the direction of cytokines driving the ensuing viraemia characteristics as opposed to vice versa. It was found that viraemia class differences were best captured in the anti-viral cytokine IFNA and also the chemokine CCL2, furthermore these key cytokines were the most strongly associated with viraemia measures. The breadth of the cytokine responsiveness was associated with viral profile class and genetic background but not the WUR genotype. The statistical categorization of pigs from each PHGC trial through model fitting provides a critical basis for the generation of new desirable host phenotypes, and of potential use in the genetic selection of pigs with favourable infection traits. Our study provides novel insights into the nature and degree of variation of hosts’ responses to infection as well as new informative traits for subsequent genetic and modelling studies.
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Bohman, Love. "Director Interlocking and Firm Ownership : Longitudinal Studies of 1- and 3-Mode Network Dynamics." Doctoral thesis, Stockholms universitet, Sociologiska institutionen, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-36774.
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This thesis is based on three empirical studies of the director interlock network among Swedish firms listed on the Stockholm Stock Exchange, focusing on its consequences for firm behavior and its association with ownership structures. Director interlocks are created when directors serve on, and hence interlock, several boards. Director interlocks aggregate to a social network that not only connects most firms into a single component, but are, more essentially, also shown to affect firm behavior. The introductory chapter contains a review of the director interlock research as well as some suggestions for future research directions. Study I is an examination of the importance of director interlock relations for stock repurchases. Using parametric survival analysis, it is demonstrated that the decision to repurchase stocks is dependent on both the firms’ economic settings and their director interlocks. Study II examines the network impact on recruitment of new board members in the network of firms, directors, and owners. Using simulations, it is shown that directors with personal contact with a director and/or owner of the recruiting firm have a substantially increased probability of being recruited to the focal board. Study III examines the association between ownership and director interlocks. Re-analyses of the same network examined in Study II show that multiple director assignments are highly dependent on ownership interlocks. The three studies exemplify the real-world consequences of board interlocks and field a new understanding of the mechanisms behind their formation. Furthermore, the association between the director and ownership interlocks suggests that the ownership network (co-)produces some of the phenomena that have been attributed to the director network. These results underscore the need for further examination of director interlocks to bring the owners back into the analysis.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript.
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Martin, de Holan Pablo. "The dynamics of knowledge in international strategic alliances : a longitudinal study of service firms." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37775.
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This thesis studies the notion of knowledge in business firms, and in particular the concept of knowledge mobilization, understood as the mechanisms used by organizations to apply, transfer and retain knowledge about cause and effect relationships. As a theoretical framework, we use here a derivative of the resource based view of the firm called the knowledge based view. This theory is used to understand and analyze how service organizations in international strategic alliances developed and refined their knowledge base.Methodologically, this thesis utilizes a qualitative, longitudinal perspective, based on several cases of organizations in similar structural context but whose results after a few years of operation show large variances. The findings of this work show that the usefulness of knowledge for business firm (its value), is highly dependent on the life-cycle of the organization. Also, the types of knowledge mobilized varied also according to position in the life-cycle. Whereas younger, inexperienced organizations sought to transfer and develop knowledge, older organizations tried to prevent knowledge from dissipating. All these findings contribute to the creation of a contingent, evolutionary view of knowledge in business firms. In addition, the notion of knowledge consolidation (or effortful activities needed to maintain a piece of knowledge in the organization) is developed, and evidence is presented to support it.
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Lyons, David J. "Context and complexity : a longitudinal study of motivational dynamics among South Korean university students." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6711/.
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This thesis reports on a longitudinal qualitative study of the L2 motivational systems of a group of South Korean university students. The study adopts a complex dynamics system approach to the collection and analysis of data, and develops an original three-level model of context to investigate the interaction of elements within the learners’ motivational systems and to track how these interactions led to perceptible changes in these systems over the course of the research. The study highlights the complex, dynamic nature of L2 motivation and the necessity of including context as a key part of the L2 motivational system. It further calls into question traditional conceptions of autonomy in the field and the general applicability of some current concepts in L2 motivation. In addition, it emphasizes the importance of non-quantitative approaches in illuminating the motivational processes at work within individuals. On the basis of these findings, the thesis calls for the general incorporation of complexity perspectives in L2 motivation research and for language pedagogy to incorporate the insights gained from such studies to enhance the classroom environments and learners’ investment in language learning.
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Acton, Bryan Patrick. "Working in Harmony: The Impact of Personality on the Short- and Long-Run Dynamics of Team Cohesion." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/78138.
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Team cohesion represents arguably the most studied team construct as it has been consistently shown to be associated with improved performance. However, although cohesion is now understood to be an emergent state—as it develops over a team's life cycle—research has yet to uncover the dynamic nature of cohesion. The current study was designed to particularly test the impact of team personality composition both on the initial status of cohesion, and on changes in cohesion over time. 80 newly formed teams performed a highly interdependent team task, and team cohesion was measured over six time points. Personality was measured prior to the task and calculated at the team level, as both an average and a variability score. After performing longitudinal hierarchical linear modeling, results indicated that team personality impacts cohesion differently at initial status and over time. In particular, higher team agreeableness predicted greater slopes of cohesion, but not initial cohesion levels. Also, higher extraversion predicted greater initial status of cohesion, but not greater slopes. These results present important boundary conditions for understanding the role of team personality composition on team cohesion.Master of Science
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Chou, Hsin-Hui. "Technological changes and business network dynamics : a longitudinal perspective from the optical recording media industry." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/technological-changes-and-business-network-dynamics-a-longitudinal-perspective-from-the-optical-recording-media-industry(6b61e609-5686-456c-b067-fd26286247f1).html.
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In the past thirty years, the IMP Group's Interaction and Network Approach has gained its increasing popularity in researching economic behaviours among resource-dependent business actors through relational linkages (Håkansson et al., 2004; Turnbull et al., 1996). Within network research, understanding the dynamics in business networks, in which interfirm relationships are regarded as crucial constituents, has been of particular interest (Johnston et al., 2006; Möller and Halinen, 1999). Moreover, technology has been identified as an important component driving the evolution of a business network, where technological change may bring about positive and negative effects on the relationships embedded in this network, and consequently, results in network dynamics (Afuah, 2000; Christensen, 1997; Håkansson and Waluszewski, 2002b; Lundgren, 1995). A perspective of resource interaction (e.g. Håkansson et al., 2009) suggests that technological change needs to be treated as a process rather than a critical event. However the nature of this process as well as how it impacts on the configuration of a technology-based business net and on dynamics of relationships constituting this net remains under-examined.Based on qualitative research methods, a longitudinal single-case study is chosen to conduct an empirical investigation in the optical recording media industry, in order to address the above research problems. To facilitate the data collection, a focal net perspective and an input-process-output model are employed. The focal net under study is characterised as a value-creating and technology-bundled business net. A total of 72 interviews were carried out in three stages and with the focal actor, its customers, suppliers and a complementor. The empirical data allows the research to reconstruct the evolution of the focal business net, which covers a time-span of more than 10 years from 1998 to 2008, and in which major technological change has taken place three times, from CD-R to DVD-/+R, DVD Double Layer and HD/Blu-ray technologies. In the development of the optical recording technology, the focal net has experienced four net reconfigurations in which radical changes of relationships as well as disturbance in resource interaction are observed. Based on the case study result, empirical observations are offered and new insights into the process of the arrival of technological change and net reconfiguration and relationship dynamics affected by this technological arrival are developed. Moreover, theoretical contribution, managerial implications, limitations and future research directions are provided.
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Pereira, Danilo Carlos. "Dinamica não linear e controle de uma aeronave em voo longitudinal." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265379.
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Orientadores: Jose Manoel Balthazar, Paulo R. G. KurkaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Neste trabalho analisou-se a dinâmica não linear de uma aeronave em vôo longitudinal. Efetuou-se a análise do comportamento bifurcacional da aeronave F-8 ¿Cruzader¿. Na análise bifurcacional foi estudado o comportamento topológico desta aeronave tomando-se dois parâmetros de controle: a deflexão do profundor e a alteração da massa da referida aeronave. Ante a pesquisa desenvolvida, foi proposto um projeto de controle linear ótimo com o objetivo de estabilizar as oscilações do ângulo de ataque, considerando-se regiões criticas do comportamento não linear da aeronave. Adicionalmente, incluiu-se no modelo matemático a variação da velocidade longitudinal da aeronave, visto tratar-se de simulações numéricas em um túnel de vento virtual
Abstract: In this work it was analyzed the non linear dynamic of an aircraft taken onto longitudinal flight. It was done analysis of the bifurcacional behavior of the aircraft F-8 ¿Cruzader¿. In the bifurcational analysis was studied the topological behavior of this aircraft taken into account two parameters of control: the deflection of the elevator and the alteration of the mass of the related aircraft. In the face of the developed research, an optimum linear control project was proposed with the objective of stabilizing the oscillations of the angle-of-attack. Additionally, the variation of the longitudinal speed of the aircraft was included in the mathematic model in order to simulate the oscillatory movement of the aircraft considered, in a tunnel of virtual wind
Doutorado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica
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Bland, Simon Nicholas. "Plasma dynamics in aluminium wire array Z-pinch implosions." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342345.
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Handoko, Yunendar Aryo, and yunendar@inka web id. "INVESTIGATION OF THE DYNAMICS OF RAILWAY BOGIES SUBJECTED TO TRACTION / BRAKING TORQUE." Central Queensland University. Centre for Railway Engineering, 2006. http://library-resources.cqu.edu.au./thesis/adt-QCQU/public/adt-QCQU20070209.101959.
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The limitations of current simulation packages in addressing the true longitudinal behaviour of railway bogie dynamics during braking/traction has prompted the development of a Rail Bogie Dynamics (RBD) program in this thesis. The RBD program offers novel features for the calculation of the speed profile as a function of the brake torque as well as explicitly determining wheelset angular velocity. With such capability, the speed profile is no longer treated as an input calculated as a priori as required by most of the current simulation systems. The RBD program has been developed using a formulation that includes the wheelset pitch degree of freedom explicitly with a coordinate reference system that is fixed in space and time. The formulation has made the simulation of the bogie dynamics during braking/traction possible in a natural way using the brake/traction torque as the input and the resulting speed profile as the output without any need for working out the speed profile as a priori. Consequently, severe dynamics during braking such as the wheelset skid and the onset of wheel climb derailment can be modelled and critical parameters investigated using the RBD program. The RBD program has been validated, where possible, through a series of simulations using a commercial software package (VAMPIRE). For cases which cannot be simulated by VAMPIRE such as the wheelset skid, a novel experimental program has been designed and commissioned in the Heavy Testing Laboratory of the Central Queensland University as reported in this thesis. One of the possible applications of the RBD program in examining the effect of asymmetric brake shoe force in bogies equipped with one-side push brake shoe arrangement is illustrated in this thesis. It is believed that the model and RBD program will have significant benefit in understanding the true longitudinal behaviour of wagons in suburban passenger trains that operate under braking/ traction torques for most of their travel. Similar studies will also be useful to freight train wagon dynamics during entry and exit of speed restriction zones and tight curves.
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Sorgenfrei, Florian [Verfasser]. "Time-Resolved Jitter-Free Experiments at FLASH: From Longitudinal Coherence Studies to Nonlinear Dynamics / Florian Sorgenfrei." München : Verlag Dr. Hut, 2013. http://d-nb.info/1042308047/34.
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Torchinsky, Darius H. "Optical study of shear and longitudinal acoustic waves and complex relaxation dynamics of glass forming liquids." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45440.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2008.Includes bibliographical references (p. 259-277).
The spectroscopic technique Impulsive Stimulated Scattering (ISS) was refined and used to study the complex structural relaxation dynamics of glass forming liquids, allowing both empirical modeling and testing of the predictions of the mode-coupling theory (MCT). Longitudinal and shear acoustic waves throughout much of the MHz frequency range, time-dependent thermal expansion on nanosecond and microsecond scales, and slower thermal diffusion were all monitored in real time. The data were used to construct complex longitudinal modulus spectra spanning from, 30 kHZ to 3 GHz, and complex shear modulus spectra from - 10 MHz to 1 GHz. In the liquid tetramethyl tetraphenyl trisiloxane, experiments which verified timetemperature superposition of its relaxation dynamics permitted construction of a master plot of scaled relaxation spectra in the entire temperature range studied. MCT predictions of power-law frequency dependencies of the high and low frequency wings of the loss modulus yielded a high-frequency exponent parameter in good agreement with the width of the non-exponential relaxation kinetics. The low-frequency exponent did not agree with the predicted value. In triphenyl phosphite, measurements of the measured shear relaxation spectrum over two decades in frequency revealed that it does not match the previously measured longitudinal spectrum, suggesting that different underlying degrees of freedom contribute to shear and compressional relaxation. Measurement of shear wave propagation as a function of temperature lent credence to the dominance of the temperature dependence of the transport by the instantaneous shear modulus. These measurements also call into question other relationships drawn between glass mechanical behavior and the supercooled liquid fragility. In work conducted collaboratively, the ISS technique was employed in singles hot measurements of liquid benzene under conditions of shock loading. The results indicate that benzene remains in a liquid state for at least 200 ns after the shock's arrival. ISS was also used to characterize both the thermal transport and mechanical properties of nanofluids.
(cont.) Finally, results of ISS acoustic measurements of thin films and their relationship with the study of glass forming liquids are briefly discussed.
by Darius H. Torchinsky.
Ph.D.
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Vaillant, Julia. "Imbricated dynamics in times of fragile growth : individuals, families and household businesses in Madagascar, 1995-2005." Thesis, Paris 9, 2012. http://www.theses.fr/2012PA090068.
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Dans les pays en développement, l'imbrication des activités économiques au sein du ménage rend la mesure de la dynamique des revenus complexe, en particulier lorsque les périodes étudiées sont longues. Le contexte choisi est celui de la décennie 1995-2005 à Madagascar, une période particulièrement intéressante puisqu'il s'agit du premier épisode de croissance soutenue et quasi-ininterrompue depuis l'indépendance du pays en 1960. En utilisant des données collectées auprès de ménages ruraux et urbains et d'entreprises du secteur informel, en coupe et en panel, les trois chapitres étudient chacun un aspect particulier du problème de mesure la dynamique de la pauvreté sur longue période dans un contexte d'imbrication forte des unités productives et des ménages. Le premier chapitre examine la dynamique du secteur informel à Antananarivo en tenant compte de sa nature très hétérogène. Le deuxième mesure l'écart de performance entre les unités de production dirigées par des femmes et celles dirigées par des hommes. Il teste l’existence d’effets différenciés selon le genre des normes de partage et d’allocation des tâches au sein du ménage sur l’efficience technique des entreprises. Le troisième chapitre discute l’opportunité de suivre des migrants dans les enquêtes longitudinales. L’étude des micro-entreprises doit tenir compte de leur environnement familial et social, pour prendre la pleine mesure des contraintes qui pèsent sur elles. Des recherches sur le comportement et la rationalité économique des ménages urbains apparaissent nécessaire. En l'absence de données longitudinales, la principale limite du travail réside dans l'impossibilité de décrire la démographie des entreprises informelles dans le temps. Il semble indispensable d’imaginer des dispositifs de collectes de données innovants permettant de suivre ces unités de production dans le tempsIn developing countries, the complex interdependence of households, individuals and businesses makes the measurement of welfare dynamics challenging, especially over a long period, because economic activities are predominantly embedded in households. The context we have chosen, Madagascar between 1995 and 2005, is particularly interesting because it corresponds to an unprecedented period of growth interrupted only by a recession in 2002 due to a political crisis. Using urban, rural, cross-sectional and panel data, the three essays presented attempt to shed light on various aspects of welfare dynamics over a long period in Madagascar, with a special focus on the imbrication of productive activities, households and individuals. The first essay studies informal sector dynamics in Antananarivo with a special attention on its heterogeneous nature. The second measures the extent of the gender performance gap among informal entrepreneurs and explores the existence of gender-differentiated effects of sharing norms and the allocation of tasks within the household on the technical efficiency of enterprises. Finally, the third essay is a methodological contribution on the relevance of tracking movers in panel data collection in rural areas. Studying microenterprises within their family and social environment is necessary to fully grasp the constraints on productive activities. More research is necessary on the behavior and economic rationality of urban households. The lack of panel data on informal businesses limits what can be said on their demography, especially over a long period. There is a pressing need for innovative data collection devices which follow these production units over time
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Granberg, Nils. "The dynamics of second language learning : a longitudinal and qualitative study of an adult's learning of Swedish." Doctoral thesis, Umeå universitet, Litteraturvetenskap och nordiska språk, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-59857.
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An often discussed issue in the field of second language learning is the influence and importance of individual differences, IDs, such as motivation, personality, previous learning experiences and learning strategies. It has been claimed that IDs form a complex system in the learner, but little consensus has been reached as regards definitions of constructs or their relative importance. Taking the individual learner as a starting-point, this dissertation attempts to demonstrate the complexity of individual differences in the single learner by adopting an in-depth holistic approach. For this purpose a longitudinal case study was designed to follow the learning process of a young Greek woman's acquisition of Swedish during a ten-month intensive course in Sweden. The study is mainly based on self-report and personal diaries, which have been interpreted and analysed qualitatively. The learning process is extensively described and changes in, for example, strategy use, life situation and learning progress are illustrated. There are indeed many complex factors which have the potential to influence learning. In this particular case, seven factors are indicated as having had a positive influence: previous language learning experiences (especially as regards learning strategies), long-term motivation, metalinguistic awareness, social contacts with L2 speakers, access to English as a mediating language, access to a strict and intensive Swedish course, and a well-needed learning break in the middle of the studies. Negative factors were largely of an emotional nature, especially a period of liminality which created feelings of not belonging, of being betwixt and between. It is suggested that IDs form a dynamic variable system in the learner. All the IDs are present in the learner, but they seem to change both in substance over time and in importance for the learner at different times in the learning process. Furthermore, IDs appear to be interconnected in a complex and dynamic way. The results of this study strongly emphasise the importance of both an holistic and a longitudinal approach to IDs in second language learning.digitalisering@umu
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Heigoldt, Matthias [Verfasser], and Stefan [Akademischer Betreuer] Karsch. "Temporal dynamics of the longitudinal bunch profile in a laser wakefield accelerator / Matthias Heigoldt ; Betreuer: Stefan Karsch." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2017. http://d-nb.info/1136270981/34.
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Klein, Marit [Verfasser]. "Optics Calculations and Simulations of Longitudinal Beam Dynamics for the Low-α Mode at ANKA / Marit Klein." München : Verlag Dr. Hut, 2012. http://d-nb.info/1028784295/34.
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Gasparini, Ricardo Ferreira. "Dinâmica longitudinal de veículos pesados = forças resistivas e outros fatores de influência no consumo de combustível." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264373.
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Orientador: Franco Giuseppe DediniDissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: O principal objetivo deste trabalho é estudar a interação de veículos comerciais com o meio e a influência de suas características dinâmicas no consumo de combustível. O primeiro passo é o levantamento dos parâmetros influentes na modelagem para o desempenho veicular, seja este baseado em métodos de energia, seja baseado em métodos de forças. As relações do veículo com o ambiente serão tratadas como aspectos influentes e incluídas no modelo de desempenho. As simulações e a modelagem final foram implementadas no programa GTDrive, software comercial. Conhecendo essas interações entre veículo e meio, e a influência destas interações no consumo de combustível, deseja-se propor uma nova abordagem no desenvolvimento de projetos automotivos para futuras aplicações em veículos comerciais, visando a redução do consumo de combustível no Brasil
Abstract: The main focus of this work is the study of interaction between commercial vehicle and the environment and also the influence of their dynamic characteristics in the fuel consumption. The first step of this work is to analyze the types of vehicle dynamic modeling based on energy and based on forces (Newton). The relationship between the vehicle and it.senvironment will be considered as influent aspects and should be included into vehicle dynamic modeling. By understanding this relationships and their influence in the fuel consumption it is possible to propose an approach to develop new automotive projects for future commercial vehicle applications focus on fuel consumption and taking into account the Brazilian reality
Mestrado
Dinâmica
Mestre em Engenharia Automobilistica
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Leclercq-Samson, Adeline. "Estimation dans les modèles non-linéaires à effets mixtes : extensions de l'algorithme SAEM pour l'analyse de la dynamique virale sous traitement anti-VIH." Paris 6, 2006. http://www.theses.fr/2006PA066536.
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Zhang, Hancheng. "SYNTHESIZING COOPERATIVE ADAPTIVE CRUISE CONTROL WITH SHARED AUTONOMY." OpenSIUC, 2019. https://opensiuc.lib.siu.edu/theses/2542.
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In this thesis, we present research on synthesizing autonomous driving with shared autonomy using Unity Engine. Adaptive Cruise Control (ACC) is considered as level 1 autonomous vehicle, which has been studied by academia and commercialized by industry. Cooperative Adaptive Cruise Control (CACC) system is an expansion of ACC, in which communication is set up between members to share driving information. Shared autonomy is a subject about human-computer interactivities. In our research, we developed a highly customizable 3D environment. We can simulate various driving scenarios and analyze the performance of different driving methods from human driving to CACC. The result of simulation proves the safety and efficiency of CACC, and the project also provides a potential of assisting the improvement of autonomous vehicles.
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Long, Jacob Andrew. "Time Dynamics and Stability of Political Identity and Political Communication." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595519865595447.
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Liere, Diederik Willem van. "Network horizon and the dynamics of network positions a multi-method multi-level longitudinal study of interfirm networks /." [Rotterdam] : Rotterdam : Erasmus Research Institute of Management (ERIM), Erasmus University Rotterdam ; Erasmus University [Host], 2007. http://hdl.handle.net/1765/10181.
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Lohano, Hari Ram. "Agricultural Growth and Poverty Dynamics in Rural Pakistan : A Longitudinal Survey in Sindh Province (1987/88 - 2004/05)." Thesis, University of Bath, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.507773.
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Tsourides, Kleovoulos (Kleovoulos Leo). "Visually grounded virtual accelerometers : a longitudinal video investigation of dyadic bodily dynamics around the time of word acquisition." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/65179.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2010.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 105-110).
Human movement encodes information about internal states and goals. When these goals involve dyadic interactions, such as in language acquisition, the nature of the movement and proximity become representative, allowing parts of our internal states to manifest. We propose an approach called Visually Grounded Virtual Accelerometers (VGVA), to aid with ecologically-valid video analysis investigations, involving humans during dyadic interactions. Utilizing the Human Speechome (HSP) [1] video corpus database, we examine a dyadic interaction paradigm taken from the caregiver-child ecology, during language acquisition. We proceed to characterize human interaction in a video cross-modally; by visually detecting and assessing the child's bodily dynamics in a video, grounded on the caregiver's bodily dynamics of the same video and the related HSP speech transcriptions [2]. Potential applications include analyzing a child's language acquisition, establishing longitudinal diagnostic means for child developmental disorders and generally establishing a metric of effective human communication on dyadic interactions under a video surveillance system. In this thesis, we examine word-learning transcribed video episodes before and after the age of the word's acquisition (AOA). As auditory stimulus is uttered from the caregiver, points along the VGVA tracked sequences corresponding to the onset and post-onset of the child-caregiver bodily responses, are used to longitudinally mark and characterize episodes of word learning. We report a systematic shift in terms of caregiver-child synchrony in motion and turning behavior, tied to exposures of the target word around the time the child begins to understand and thus respond to instances of the spoken word. The systematic shift, diminishes gradually after the age of word acquisition (AOA).
by Kleovoulos (Leo) Tsourides.
S.M.
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Chen, Ren. "Bayesian Inference on Mixed-effects Models with Skewed Distributions for HIV longitudinal Data." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4298.
Full textAbstract:
Statistical models have greatly improved our understanding of the pathogenesis of HIV-1 infection
and guided for the treatment of AIDS patients and evaluation of antiretroviral (ARV) therapies.
Although various statistical modeling and analysis methods have been applied for estimating the
parameters of HIV dynamics via mixed-effects models, a common assumption of distribution is
normal for random errors and random-effects. This assumption may lack the robustness against
departures from normality so may lead misleading or biased inference. Moreover, some covariates
such as CD4 cell count may be often measured with substantial errors. Bivariate clustered
(correlated) data are also commonly encountered in HIV dynamic studies, in which the data set particularly
exhibits skewness and heavy tails. In the literature, there has been considerable interest in,
via tangible computation methods, comparing different proposed models related to HIV dynamics,
accommodating skewness (in univariate) and covariate measurement errors, or considering skewness
in multivariate outcomes observed in longitudinal studies. However, there have been limited
studies that address these issues simultaneously.
One way to incorporate skewness is to use a more general distribution family that can provide
flexibility in distributional assumptions of random-effects and model random errors to produce robust
parameter estimates. In this research, we developed Bayesian hierarchical models in which the
skewness was incorporated by using skew-elliptical (SE) distribution and all of the inferences were
carried out through Bayesian approach via Markov chain Monte Carlo (MCMC). Two real data set
from HIV/AIDS clinical trial were used to illustrate the proposed models and methods.
This dissertation explored three topics. First, with an SE distribution assumption, we compared
models with different time-varying viral decay rate functions. The effect of skewness on the model
fitting was also evaluated. The associations between the estimated decay rates based on the best
fitted model and clinical related variables such as baseline HIV viral load, CD4 cell count and longterm
response status were also evaluated. Second, by jointly modeling via a Bayesian approach,
we simultaneously addressed the issues of outcome with skewness and a covariate process with measurement errors. We also investigated how estimated parameters were changed under linear,
nonlinear and semiparametric mixed-effects models. Third, in order to accommodate individual
clustering within subjects as well as the correlation between bivariate measurements such as CD4
and CD8 cell count measured during the ARV therapies, bivariate linear mixed-effects models with
skewed distributions were investigated. Extended underlying normality assumption with SE distribution
assumption was proposed. The impacts of different distributions in SE family on the model
fit were also evaluated and compared.
Real data sets from AIDS clinical trial studies were used to illustrate the proposed methodologies
based on the three topics and compare various potential models with different distribution
specifications. The results may be important for HIV/AIDS studies in providing guidance to better
understand the virologic responses to antiretroviral treatment. Although this research is motivated
by HIV/AIDS studies, the basic concepts of the methods developed here can have generally broader
applications in other fields as long as the relevant technical specifications are met. In addition, the
proposed methods can be easily implemented by using the publicly available WinBUGS package,
and this makes our approach quite accessible to practicing statisticians in the fields.
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Hardenbicker, Paulin [Verfasser], Markus [Akademischer Betreuer] Weitere, Thomas [Gutachter] Berendonk, and Helmut [Gutachter] Hillebrand. "Phytoplankton dynamics in two large rivers: : long-term trends, longitudinal dynamics and potential impacts of climate change / Paulin Hardenbicker ; Gutachter: Thomas Berendonk, Helmut Hillebrand ; Betreuer: Markus Weitere." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://d-nb.info/1154680002/34.
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Hardenbicker, Paulin [Verfasser], Markus [Akademischer Betreuer] Weitere, Thomas U. [Gutachter] Berendonk, and Helmut [Gutachter] Hillebrand. "Phytoplankton dynamics in two large rivers: : long-term trends, longitudinal dynamics and potential impacts of climate change / Paulin Hardenbicker ; Gutachter: Thomas Berendonk, Helmut Hillebrand ; Betreuer: Markus Weitere." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-147859.
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Peterson, Samuel. "Why Can’t We Be Friends? Exploring Short-term Peer Selection and Peer Influence Dynamics Using Longitudinal Social Network Analysis." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1505124845051989.
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Kim, Mihyun Esther. "A study on pulsation in Runehamar Tunnel fire tests with forced longitudinal ventilation." Link to electronic thesis, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-100506-112551/.
Full textAbstract:
Thesis (M.S.) -- Worcester Polytechnic Institute.Keywords: pulsation; FDS; fire dynamics simulator; oscillation; fluctuation; tunnel fire; forced ventilation. Includes bibliographical references (p.65-66).
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Ahmad, Husain Abdulrahman. "Dynamic Braking Control for Accurate Train Braking Distance Estimation under Different Operating Conditions." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/19322.
Full textAbstract:
The application of Model Reference Adaptive Control (MRAC) for train dynamic braking is investigated in order to control dynamic braking forces while remaining within the allowable adhesion and coupler forces. This control method can accurately determine the train braking distance. One of the critical factors in Positive Train Control (PTC) is accurately estimating train braking distance under different operating conditions. Accurate estimation of the braking distance will allow trains to be spaced closer together, with reasonable confidence that they will stop without causing a collision. This study develops a dynamic model of a train consist based on a multibody formulation of railcars, trucks (bogies), and suspensions. The study includes the derivation of the mathematical model and the results of a numerical study in Matlab. A three-railcar model is used for performing a parametric study to evaluate how various elements will affect the train stopping distance from an initial speed. Parameters that can be varied in the model include initial train speed, railcar weight, wheel-rail interface condition, and dynamic braking force. Other parameters included in the model are aerodynamic drag forces and air brake forces. An MRAC system is developed to control the amount of current through traction motors under various wheel/rail adhesion conditions while braking. Minimizing the braking distance of a train requires the dynamic braking forces to be maximized within the available wheel/rail adhesion. Excessively large dynamic braking can cause wheel lockup that can damage the wheels and rail. Excessive braking forces can also cause large buff loads at the couplers. For DC traction motors, an MRAC system is used to control the current supplied to the traction motors. This motor current is directly proportional to the dynamic braking force. In addition, the MRAC system is also used to control the train speed by controlling the synchronous speed of the AC traction motors. The goal of both control systems for DC and AC traction motors is to apply maximum available dynamic braking while avoiding wheel lockup and high coupler forces. The results of the study indicate that the MRAC system significantly improves braking distance while maintaining better wheel/rail adhesion and coupler dynamics during braking. Furthermore, according to this study, the braking distance can be accurately estimated when MRAC is used. The robustness of the MRAC system with respect to different parameters is investigated, and the results show an acceptable robust response behavior.
Ph. D.
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Raffington, Laurel [Verfasser], Ulman [Gutachter] Lindenberger, Christine [Gutachter] Heim, and Kimberly [Gutachter] Noble. "Socioeconomic disparities in children’s cognitive development: Longitudinal dynamics and stress mechanisms / Laurel Raffington ; Gutachter: Ulman Lindenberger, Christine Heim, Kimberly Noble." Berlin : Humboldt-Universität zu Berlin, 2018. http://d-nb.info/1182540996/34.
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Raffington, Laurel [Verfasser], Ulman Gutachter] Lindenberger, Christine [Gutachter] [Heim, and Kimberly [Gutachter] Noble. "Socioeconomic disparities in children’s cognitive development: Longitudinal dynamics and stress mechanisms / Laurel Raffington ; Gutachter: Ulman Lindenberger, Christine Heim, Kimberly Noble." Berlin : Humboldt-Universität zu Berlin, 2018. http://d-nb.info/1182540996/34.
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Blimbaum, Jordan Matthew. "Finite element analysis of acoustic wave transverse to longitudinal coupling during transverse combustion instability." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44757.
Full textAbstract:
Velocity-coupled combustion instability is a major issue facing lean combustor design in modern gas turbine applications. In this study, we analyze the complex acoustic field excited by a transverse acoustic mode in an annular combustor. This work is motivated by the need to understand the various velocity disturbance mechanisms present in the flame region during a transverse instability event. Recent simulation and experimental studies have shown that much of the flame response during these transverse instabilities may be due to the longitudinal motion induced by the fluctuating pressure field above the nozzles. This transverse to longitudinal coupling has been discussed in previous work, but in this work it is given a robust acoustic treatment via computational methods in order to verify the mechanisms by which these two motions couple.
We will provide an in-depth discussion of this coupling mechanism and propose a parameter, Rz, also referred to as the Impedance Ratio, in order to compare the pressure/velocity relationship at the nozzle outlet to quasi one-dimensional theoretical acoustic approximations. A three-dimensional inviscid simulation was developed to simulate transversely propagating acoustic pressure waves, based on an earlier experiment designed to measure these effects. Modifications to this geometry have been made to account for lack of viscosity in the pure acoustic simulation and are discussed.
Results from this study show that transverse acoustic pressure excites significant axial motion in and around the nozzle over a large range of frequencies. Furthermore, the development of Rz offers a defined physical parameter through which to reference this important velocity-coupled instability mechanism. Therefore, this study offers an in-depth and quantifiable understanding of the instability mechanism caused by transversely propagating acoustic waves across a combustor inlet, which can be applied to greatly improve annular combustor design in future low-emissions gas turbine engines.