Dissertations / Theses on the topic 'Dynamic field'
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1
Chapman, Craig K. "Coarsening dynamical systems : dynamic scaling, universality and mean-field theories." Thesis, University of Glasgow, 2012. http://theses.gla.ac.uk/3255/.
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We study three distinct coarsening dynamical systems (CDS) and probe the underlying scaling laws and universal scaling functions. We employ a variety of computational methods to discover and analyse these intrinsic statistical objects. We consider mean-field type models, similar in nature to those used in the seminal work of Lifshitz, Slyozov and Wagner (LSW theory), and statistical information is then derived from these models. We first consider a simple particle model where each particle possesses a continuous positive parameter, called mass, which itself determines the particle’s velocity through a prescribed law of motion. The varying speeds of particles, caused by their differing masses, causes collisions to take place, in which the colliding particles then merge into a single particle while conserving mass. We computationally discover the presence of scaling laws of the characteristic scale (mean mass) and universal scaling functions for the distribution of particle mass for a family of power-law motion rules. We show that in the limit as the power-law exponent approaches infinity, this family of models approaches a probabilistic min-driven model. This min-driven model is then analysed through a mean-field type model, which yields a prediction of the universal scaling function. We also consider the conserved Kuramoto-Sivashinsky (CKS) equation and provide, in particular, a critique of the effective dynamics derived by Politi and ben-Avraham. We consider several different numerical methods for solving the CKS equation, both on fixed and adaptive grids, before settling on an implicit-explicit hybrid scheme. We then show, through a series of detailed numerical simulations of both the CKS equation and the proposed dynamics, that their particular reduction to a length-based CDS does not capture the effective dynamics of the CKS equation. Finally, we consider a faceted CDS derived from a one-dimensional geometric partial differential equation. Unusually, an obvious one-point mean-field theory for this CDS is not present. As a result, we consider the two-point distribution of facet lengths. We derive a mean-field evolution equation governing the two-point distribution, which serves as a two-dimensional generalisation of the LSW theory. Through consideration of the two-point theory, we subsequently derive a non-trivial one-point sub-model which we analytically solve. Our predicted one-point distribution bears a significant resemblance to the LSW distribution and stands in reasonable agreement with the underlying faceted CDS.
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Stoupis, James D. "Dynamic testing of loss of field protection." Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-08292008-063410/.
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Ambrose, Joseph Paul. "Dynamic field theory applied to fMRI signal analysis." Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/2035.
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In the field of cognitive neuroscience, there is a need for theory-based approaches to fMRI data analysis. The dynamic neural field model-based approach has been developing to meet this demand. This dissertation describes my contributions to this approach. The methods and tools were demonstrated through a case study experiment on response selection and inhibition. The experiment was analyzed via both the standard behavioral approach and the new model-based method, and the two methods were compared head to head. The methods were quantitatively comparable at the individual-level of the analysis. At the group level, the model-based method reveals distinct functional networks localized in the brain. This validates the dynamic neural field model-based approach in general as well as my recent contributions.
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Guest, A. R. "The dynamic breakage of Kimberlite in the near field /." [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18507.pdf.
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Monson, Peter A. "Dynamic mean field theory for fluids in mesoporous materials." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184643.
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Cook, Steven Charles. "Dynamic Near Field Communication Pairing For Wireless Sensor Networks." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3737.
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Wireless sensor network (WSN) nodes communicate securely using pre-installed cryptographic keys. Although key pre-installation makes nodes less expensive, the technical process of installing keys prevents average users from deploying and controlling their own WSNs. Wireless pairing enables users to set up WSNs without pre-installing keys, but current pairing techniques introduce numerous concerns regarding security, hardware expense, and usability. This thesis introduces dynamic Near Field Communication (NFC) pairing, a new pairing technique designed for WSNs. This pairing overcomes the limitations of both key pre-installation and current pairing techniques. Dynamic NFC pairing is as secure as using pre-installed keys, requires only inexpensive NFC hardware, and is easy to use since the user simply holds nodes close together to add them to a network. A sample application shows the power of dynamic NFC pairing. The user adds sensors and actuators to a WSN by holding each node close to a central node or network coordinator. Data readings stream instantly from each sensor to a web page where the user may view data as well as click buttons to cause events to occur on the actuators. This happens quickly and securely without exposing the user to the complexity of cryptographic keys.
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Gorman, Geoffrey Allen. "Field deployable dynamic lighting system for turbid water imaging." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68945.
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Thesis (S.M.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), September 2011."September 2011." "©2011"--P. 2. Cataloged from PDF version of thesis.
Includes bibliographical references (p. 97-101).
The ocean depths provide an ever changing and complex imaging environment. As scientists and researches strive to document and study more remote and optically challenging areas, specifically scatter-limited environments. There is a requirement for new illumination systems that improve both image quality and increase imaging distance. One of the most constraining optical properties to underwater image quality are scattering caused by ocean chemistry and entrained organic material. By reducing the size of the scatter interaction volume, one can immediately improve both the focus (forward scatter limited) and contrast (backscatter limited) of underwater images. This thesis describes a relatively simple, cost-effective and field-deployable low-power dynamic lighting system that minimizes the scatter interaction volume with both subjective and quantifiable improvements in imaging performance.
by Geoffrey Allen Gorman.
S.M.
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Monson, Peter A. "Dynamic mean field theory for fluids in mesoporous materials." Diffusion fundamentals 16 (2011) 13, S. 1-2, 2011. https://ul.qucosa.de/id/qucosa%3A13742.
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Wray, Thomas. "Developments in dynamic field gradient focusing : microfluidics and integration." Thesis, University of Liverpool, 2012. http://livrepository.liverpool.ac.uk/7973/.
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Advances in modern science require the development of more robust and improved systems for electroseparations in chromatography. In response, the progress of a new analytical platform is discussed. DFGF (Dynamic Field Gradient Focusing) is a separation technique, first described in 1998, which exploits the differences in electrophoretic mobility and hydrodynamic area of analytes to result in separation. This is achieved by taking a channel and applying a hydrodynamic flow in one direction and a counteracting electric field gradient acting in the opposite direction, resulting in analytes reaching a focal point according to their electrophoretic mobility. Work through this project has seen innovations to improve existing DFGF devices, including the design and manufacture of a novel packing material, while developing the latest DFGF system. This incorporates a microfluidic separation channel, eliminating the need for packing material or monolith. The new microfluidic device also features whole-on-column UV detection. Improvements through the developments of this device are discussed, most notably the utilisation of a new rapid prototyping technique. Examples of applications undertaken with the new device are demonstrated including novel samples and integration with mass spectrometry and 2D-HPLC.
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Lomp, Oliver [Verfasser]. "Cognitive object recognition based on dynamic field theory / Oliver Lomp." München : Verlag Dr. Hut, 2017. http://d-nb.info/1140977741/34.
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Jin, Donghyun. "Dynamic ON-resistance in high voltage GaN field-effect-transistors." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/91108.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references.
Recently, the development of energy efficient electrical power management systems has received considerable interest due to its potential to realize significant energy savings for the world. With current Si-based power electronics system being matured, GaN Field-Effect-Transistors have emerged as a disruptive technology with great potential that arises from the outstanding material properties of GaN. However, in spite of great progress in GaN device fabrication, electrical reliability and a number of unique anomalies of GaN remain key challenges that prevent the wide deployment of this technology. In particular, the dynamic ON-resistance (RON), in which the RON of the transistor remains high for a certain period of time after a high-voltage OFF-ON switching event, is a critical concern. This phenomenon greatly affects the efficiency of electrical power management circuits based on GaN power transistors. This thesis investigates in depth this important issue. Firstly, we have developed a new dynamic RON measurement methodology which can observe dynamic RON transients after OFF-to-ON switching events over many decades in time. We have experimentally demonstrated this technique on GaN-on-SiC high-voltage HEMTs (High-Electron- Mobility-Transistors). The possible origin of the mechanisms responsible for dynamic RON in these devices has been postulated. Through our new technique, the impact of high-power stress on dynamic RON has been investigated as well. The results emphasize the importance of studying dynamic RON characteristics over very short time scale when conducting reliability studies of GaN transistors. Secondly, high-voltage GaN-on-Si MIS (Metal-Insulator-Semiconductor) HEMTs designed for > 600 V switching operation have been investigated. Excessive electron trapping leading to total current collapse has been observed. We have carried out an extensive characterization of this phenomenon and we have proposed "Zener trapping" as the responsible mechanism. In this view, electron trapping takes place inside the AlGaN/GaN heterostructure through a tunneling process under high-electric-field. The understanding derived here suggests that this effect can be mitigated through attention to defect control during epitaxial growth and appropriate design of the field plate structure of the device. Our findings in this thesis provide a path to achieve high performance GaN power transistors with minimum dynamic RON effects.
by Donghyun Jin.
Ph. D.
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Haw, Matthew James. "Boudica & field notes towards a dynamic film-poem form." Thesis, Lancaster University, 2017. http://eprints.lancs.ac.uk/124994/.
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The thesis comprises an original, book-length sequence of poems, Boudica, and a film-poem of the same name. Boudica engages in a topographical mediation on East Anglia, specifically the landscapes of Norfolk and north Suffolk. The subject of the sequence is Boudica, a young woman trapped within a stifling suburban upbringing and her dead-end job at the pub in her village. Structured in four parts, the poem explores her adolescent ennui, her ambivalence towards place and her small acts of existential rebellion against this condition. The verse itself is constructed of images from cinema and after cinema, images bound to the physicality of cinema. Poet and narrator are allowed access to the viewfinder: lines, images, and stanzas attempt to frame themselves within the logic of cinematography, a logic which asks that the poet’s eye becomes the camera lens, exploiting cinema and ekphrasis by projecting meaning without making it explicit. The film is composed of images which have been suggested by the lyrics, the cinematic sequencing of these images has then dictated the order in which the lyrics appear in the collection. The thematic and structural links between the film and the sequence of poems are the subject of the supporting reflective essay. This paper explores my practice-led methodology and approach to the making of Boudica, offering key definitions with regards to ekphrasis and the hybrid film-poem form. It explores dynamic points of intersection between film and poetry in Boudica as well as case studies in recent writing and practice on ekphrasis, poetry and cinema.
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Omatuku, Emmanuel Ngongo. "Phase field modeling of dynamic brittle fracture at finite strains." Master's thesis, Faculty of Engineering and the Built Environment, 2019. http://hdl.handle.net/11427/30172.
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Fracture is the total or partial separation of an initially intact body through the propagation of one or several cracks. Computational methods for fracture mechanics are becoming increasingly important in dealing with the nucleation and propagation of these cracks. One method is the phase field approach, which approximates sharp crack discontinuities with a continuous scalar field, the so-called phase field. The latter represents the smooth transition between the intact and broken material phases. The evolution of the phase field due to external loads describes the fracture process. An original length scale is used to govern the diffusive approximation of sharp cracks. This method further employs a degradation function to account for the loss of the material stiffness during fracture by linking the phase field to the body’s bulk energy. To prevent the development of unrealistic crack patterns and interpenetration of crack faces under compression, this study uses the anisotropic split of the bulk energy, as proposed by Amor et al. [5], to model the different fracture behavior in tension, shear and compression. This research is part of a larger project aimed at the modeling of Antarctic sea ice dynamics. One aspect of this project is the modeling of the gradual break-up of the consolidated ice during spring. As a first step, this study reviews a phase field model used for dynamic brittle fracture at finite strains. Subsequently, this model is implemented into the in-house finite element software SESKA to solve the benchmark tension and shear tests on a single-edge notched block. The implementation adopts the so-called monolithic scheme, which computes the displacement and phase field solutions simultaneously, with a Newmark time integration scheme. The results of the solved problems demonstrate the capabilities of the implemented dynamic phase field model to capture the nucleation and propagation of cracks. They further confirm that the choice of length-scale and mesh size influences the solutions. In this regard, a small value of the length-scale converges to the sharp crack topology and yields a larger stress value. On the other hand, a large length-scale parameter combined with a too coarse mesh size can yield unrealistic results.
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Liang, Jiachao. "Dynamic Contrast Enhanced Magnetic Resonance Imaging at High and Ultra-high Fields." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1228327344.
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Guo, Jiuhao, and 郭九昊. "Velocity field measurement of a scroll vortex intake flow." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B48079881.
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A scroll vortex intake is a hydraulic structure that transfers water stably from one
elevation to a lower one by generating a swirling vortex flow down a vertical drop-
shaft. Scroll vortex intakes are applied widely in water supply, stormwater drainage
and sewerage systems. For a good engineering design, a sufficiently large and stable
air core needs to be maintained within the dropshaft. Although a number of the-
oretical and experimental investigations have been conducted, the understanding
and predictions of the vortex flow is still far from complete due to a lack of de-
tailed velocity field and air core measurements. This study aims to achieve a better
understanding of the scroll vortex intake flow. The hydraulic theory of scroll vortex
intake is revisited and detailed measurements of air core and velocity field of the
vortex flow is conducted.
A 1:15 physical model of a scroll vortex intake has been designed according
to dynamic Froude similitude and constructed. Experiments have been conducted
to measure the head-discharge relation. Piezometric head and air core size are
measured at the throat of the vortex flow. Velocity fields are measured using Laser
Doppler Anemometry (LDA).
The measurements show that the vortex flow in the chamber resembles a free
vortex and the circulation is approximately equal to that at the inlet to chamber.
The chamber flow is not affected by the bottom boundary effect at bottom above
a depth of the order of the dropshaft diameter. The throat section of the vor-
tex flow is located slightly below the chamber bottom and within the bellmouth
at the entrance to dropshaft. For the vortex flow in and downstream of the bell-
mouth, the tangential velocity distribution can be described by a Rankine vortex
(combination of forced and free vortex); the transition from forced to free vortex
occurs at around the middle of the vortex flow layer. The pressure is positive for
all locations and all discharges. Due to viscous effect, the maximum circulation is
found to be lower than the inlet circulation. Consistent with the free vortex theory,
the vertical velocity in the dropshaft is approximately constant. By accounting for
the loss of circulation between chamber inlet and the dropshaft, a new 1D theory
is proposed. Unlike previous models, the new theory gives good predictions of
head-discharge relation and minimum air core size without the need of physically
unrealistic assumptions.
This study has revealed the structure of a scroll vortex intake flow for the first
time. Characteristic flow features of the scroll vortex intake have been elucidated.
The findings have helped to explain and resolve the long-standing discrepancies
between the theoretical predictions of three representative 1D hydraulic theories.
The vortex flow measurements also provide a basis for the development of a new
theory and the validation of 3D numerical models.published_or_final_version
Civil Engineering
Master
Master of Philosophy
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Lamoureux, Julien. "Modeling and reduction of dynamic power in field-programmable gate arrays." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/414.
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Field-Programmable Gate Arrays (FPGAs) are one of the most popular platforms for implementing digital circuits. Their main advantages include the ability to be (re)programmed in the field, a shorter time-to-market, and lower non-recurring engineering costs. This programmability, however, is afforded through a significant amount of additional circuitry, which makes FPGAs significantly slower and less power-efficient compared to Application Specific Integrated Circuits (ASICs).
This thesis investigates three aspects of low-power FPGA design: switching activity estimation, switching activity minimization, and low-power FPGA clock network design. In our investigation of switching activity estimation, we compare new and existing techniques to determine which are most appropriate in the context of FPGAs. Specifically, we compare how each technique affects the accuracy of FPGA power models and the ability of power-aware CAD tools to minimize power. We then present a new publicly available activity estimation tool called ACE-2.0 that incorporates the most appropriate techniques. Using activities estimated byACE-2.0, power estimates and power savings were both within 1% of results obtained using simulated activities. Moreover, the new tool was 69 and 7.2 times faster than circuit simulation for combinational and sequential circuits, respectively.
In our investigation of switching activity minimization, we propose a technique for reducing power in FPGAs by minimizing unnecessary transitions called glitches. The technique involves adding programmable delay elements at inputs of the logic elements of the FPGA to align the arrival times, thereby preventing new glitches from being generated. On average, the proposed technique eliminates 87% of the glitching, which reduces overall FPGA power by17%. The added circuitry increases the overall FPGA area by 6% and critical-path delay by less than 1%.
Finally, in our investigation of low-power FPGA clock networks, we examine the tradeoff between the power consumption of FPGA clock networks and the cost of the constraints they impose on FPGA CAD tools. Specifically, we present a parameterized framework for describing FPGA clock networks, we describe new clock-aware placement techniques, and we perform an empirical study to examine how the clock network parameters affect the overall power consumption of FPGAs. The results show that the techniques used to produce a legal placement can have a significant influence on power and delay. On average, circuits placed using the most effective techniques dissipate 9.9% less energy and were 2.4% faster than circuits placed using the least effective techniques. Moreover, the results show that the architecture of the clock network is also important. On average, FPGAs with an efficient clock network were up to12.5% more energy efficient and 7.2% faster than other FPGAs.
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Bur, Christian. "Selectivity Enhancement of Gas Sensitive Field Effect Transistors by Dynamic Operation." Doctoral thesis, Linköpings universitet, Tillämpad sensorvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-114670.
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Gas sensitive field effect transistors based on silicon carbide, SiC-FETs, have been applied to various applications mainly in the area of exhaust and combustion monitoring. So far, these sensors have normally been operated at constant temperatures and adaptations to specific applications have been done by material and transducer platform optimization. In this thesis, the methodology of dynamic operation for selectivity enhancement is systematically developed for SiC-FETs. Temperature cycling, which is well known for metal oxide gas sensors, is transferred to SiC-FETs. Additionally, gate bias modulation is introduced increasing the performance further. The multi-dimensional sensor data are evaluated by use of pattern recognition mainly based on multivariate statistics. Different strategies for feature selection, crossvalidation, and classification methods are studied. After developing the methodology of dynamic operation, i.e., applying the virtual multi-sensor approach on SiC-FETs, the concept is validated by two different case studies under laboratory conditions: Discrimination of typical exhaust gases and quantification of nitrogen oxides in a varying background is presented. Additionally, discrimination and quantification of volatile organic compounds in the low parts-perbillion range for indoor air quality applications is demonstrated. The selectivity of SiC-FETs is enhanced further by combining temperature and gate bias cycled operation. Stability is increased by extended training.Gaskänsliga fält-effekt-transistorer baserade på halvledarmaterialet kiselkarbid (SiC-FET) har redan framgångsrikt använts för olika tillämpningar främst inom området för avgas- och förbränningsövervakning. Normalt har dessa sensorer använts vid konstant temperatur och anpassning till specifika tillämpningar har gjorts av material och sensor optimering. I denna avhandling har metoden för dynamisk modulering systematiskt utvecklats för att ökaselektiviteten av SiC-FETs. Temperatur-cykling är en välkänd metod för metalloxidsensorer och har nu tillämpats på SiC-FETs för första gången. Likaså har den pålagda gatepotentialen varierats. Mönsterigenkänningsmetoder baserade på multivariat statistik används för att utvärdera multi-dimensionella sensordata. Olika strategier för urval, korsvalidering och klassificering av okända uppgifter studeras. Efter att metodiken för dynamiska mätmetoder har beskrivits i detalj, verifieras strategin av virtuella-multisensorer genom två tester under laboratorieförhållanden. Detta visas av exemplet med separering av typiska avgaser och bestämning av koncentrationen av kväveoxider i varierande gasblandningar. Vidare har ett test genomförts där flyktiga organiska föreningar identifieras och kvantifieras för att bestämma kvaliteten på inomhusluft. Dessutom kan man öka selektiviteten av sensorerna genom att kombinera modulering av temperatur och gate-potential.
Gassensitive Feldeffekt-Transistoren basierend auf Siliziumkarbid (SiC-FET) werden überwiegend für die Abgasmessung eingesetzt. Üblicherweise werden diese Sensoren bei konstanter Temperatur betrieben. Durch die Auswahl geeigneter Materialien sowie durch die Modifikation der Sensoren können diese für verschiedene Anwendungen optimiert werden. In der vorliegenden Dissertation wird die Methodik einer dynamischen Betriebsweise zur Selektivitätssteigerung systematisch weiterentwickelt. Temperaturmodulation ist ein bewährtes Verfahren für Halbleitergassensoren, das hier auf SiC-FETs übertragen wird. In ähnlicher Weise wird auch das Gate-Potential zyklisch variiert. Mustererkennungsverfahren basierend auf multivariater Statistik werden eingesetzt, um die mehrdimensionalen Messdaten auszuwerten. Verschiedene Verfahren zur Merkmalsauswahl, Kreuzvalidierung und Klassifikation unbekannter Daten werden untersucht. Nachdem die Methodik ausführlich dargelegt wurde, wird der Ansatz des virtuellen Multisensors anhand zweier Anwendungen unter Laborbedingungen verifiziert. Dies wird am Beispiel der Konzentrationsbestimmung von Stickoxiden in variierenden Gasgemischen gezeigt. Zudem werden flüchtige organische Verbindungen im niedrigen ppb-Bereich zur Bestimmung der Innenraumluftqualität erkannt und quantifiziert. Die Selektivität kann durch die Kombination von Temperatur- und Potentialmodulation weiter gesteigert und Drifteinflüsse durch erweitertes Training kompensiert werden.
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Poole, Michael Stephen. "Improved equipment and techniques for dynamic shimming in high field MRI." Thesis, University of Nottingham, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.445686.
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Xu, Zhibing. "Statistical Modeling and Predictions Based on Field Data and Dynamic Covariates." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/51130.
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Reliability analysis plays an important role in keeping manufacturers in a competitive position. It can be applied in many areas such as warranty predictions, maintenance scheduling, spare parts provisioning, and risk assessment. This dissertation focuses on statistical modeling and predictions based on lifetime data, degradation data, and recurrent event data. The datasets used in this dissertation come from the field, and have complicated structures. The dissertation consists of three main chapters, in addition to Chapter 1 which is the introduction chapter, and Chapter 5 which is the general conclusion chapter. Chapter 2 consists of the traditional time-to-failure data analysis. We propose a statistical method to address the failure data from an appliance used at home with the consideration of retirement times and delayed reporting time. We also develop a prediction method based on the proposed model. Using the information of retirement-time distribution and delayed reporting time, the predictions are more accurate and useful in the decision making. In Chapter 3, we introduce a nonlinear mixed-effects general path model to incorporate dynamic covariates into degradation data analysis. Dynamic covariates include time-varying environmental variables and usage condition. The shapes of the effect functions of covariates may be constrained to be, for example, monotonically increasing (i.e., higher temperature is likely to cause more damage). Incorporating dynamic covariates with shape restrictions is challenging. A modified alternative algorithm and the corresponding prediction method are proposed. In Chapter 4, we introduce a multi-level trend-renewal process (MTRP) model to describe component-level events in multi-level repairable systems. In particular, we consider two-level repairable systems in which events can occur at the subsystem level, or the component (within the subsystem) level. The main goal is to develop a method for estimation of model parameters and a procedure for prediction of the future replacement events at component level with the consideration of the effects from the subsystem replacement events. To explain unit-to-unit variability, time-dependent covariates as well as random effects are introduced into the heterogeneous MTRP model (HMTRP). A Metropolis-within-Gibbs algorithm is used to estimate the unknown parameters in the HMTRP model. The proposed method is illustrated by a simulated dataset.Ph. D.
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Loget, Gabriel. "Electric field-generated asymmetric reactivity : from materials science to dynamic systems." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14572/document.
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L’électrochimie bipolaire est un phénomène générant une réactivité asymétrique à la surface d’objets conducteurs, sans contact électrique direct. Ce concept est basé sur le fait que lorsqu’un objet conducteur est localisé dans un champ électrique, il se polarise. Par conséquent, une différence de potentiel est générée entre ses deux extrémités, et peut être utilisée pour induire des réactions redox localisées. Dans cette thèse, l’utilisation de l’électrochimie bipolaire pour la science des matériaux et pour la locomotion d’objets est présentée.Jusqu’à présent, la plupart des méthodes ou procédés utilisés pour générer des objets asymétriques,appelés aussi objets « Janus », nécessitent l’introduction d’une interface pour briser la symétrie. Nous avons développé une nouvelle approche basée sur l’électrodéposition bipolaire pour générerce type d’objet en grande quantité. Grâce à cette technologie différents matériaux tels que des métaux, des polymères et des semi‐conducteurs ont pu être déposés sur diverses particulesconductrices. Il a été aussi démontré que l’électrochimie bipolaire pouvait être utilisée pour lamicrostructuration de substrats conducteurs.Nous avons induit des mouvements à des objets conducteurs en exploitant le phénomèned’électrochimie bipolaire. Certains objets Janus synthétisés par l’approche précédente ont pu être utilisés comme micronageurs. La brisure de symétrie qui est générée par l’électrochimie bipolaire peut être aussi utilisée directement pour générer un mouvement de particules isotropes. En employant ce concept, nous avons pu provoquer des mouvements de translation, rotation et lévitation pour des particules de carbones ou métalliquesThe phenomenon of bipolar electrochemistry generates an asymmetric reactivity on the surface ofconductive objects in a wireless manner. This concept is based on the fact that when a conducingobject is placed in an electric field, it gets polarized. Consequently, a potential difference appearsbetween its two extremities, that can be used to drive localized redox reactions. In the presentthesis, bipolar electrochemistry was used for material science and the locomotion of objects.So far, the majority of methods and processes used for the generation of asymmetric objects, alsocalled “Janus” objects, is based on using interfaces to break the symmetry. We developed a newapproach based on bipolar electrodeposition for generating this type of objects in the bulk. Using thistechnology, various materials like metals, polymers and semiconductors could be deposited ondifferent types of conducting particles. We also showed that bipolar electrochemistry can be used forthe microstructuration of conducting substrates.Motion generation by bipolar electrochemistry has also been demonstrated. Some of the Janusobjects synthesized by the previous approach can be used as microswimmers. The asymmetricreactivity that is induced by bipolar electrochemistry can also be used directly to generate motion ofnon‐hybrid objects. With this concept we induced translations, rotations and levitations of carbonand metal particles
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Proffitt, Donnie E. II. "EXPERIMENTAL INVESTIGATION TO INFORM OPTIMAL CONFIGURATIONS FOR DYNAMIC NEAR-FIELD PASSIVE UHF RFID SYSTEMS." UKnowledge, 2013. http://uknowledge.uky.edu/me_etds/29.
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RFID has been characterized as a “disruptive technology” that has the potential to revolutionize numerous key sectors. A key advantage of passive RFID applications is the ability to wirelessly transmit automatic identification and related information using very little power. This paper presents an experimental investigation to inform the optimal configuration for programming passive ultra-high frequency (UHF) RFID media in dynamic applications. Dynamic programming solutions must be designed around the tag’s functionality, the physical programming configuration and environment. In this investigation, we present a methodology to determine an optimal configuration to maximize the systems programming efficiency for dynamic applications.
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Weiss, Céline. "A dynamic view on strategic management Where and how system dynamics can contribute to a long-established field /." St. Gallen, 2009. http://www.biblio.unisg.ch/org/biblio/edoc.nsf/wwwDisplayIdentifier/01655182002/$FILE/01655182002.pdf.
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Prince, Robert T. "Evaluation of Field Tests Performed on an Aluminum Deck Bridge." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36719.
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Studies have shown that over 30 percent of the bridges in the United States are structurally deficient, and/or over 50 years old. The majority of the highway bridges have reinforced concrete decks supported on steel or concrete girders. Over the years, weathering and deicing chemicals have caused spalling of the concrete surrounding the reinforcing steel, deteriorating many bridges to levels that often result in closure. Repairing or reconstructing the reinforced concrete deck to meet current design specifications is often not possible or feasible, and at times seems illogical due to the possibility of reoccurrence. Because of reinforced concrete's downfalls, there is a move toward alternative materials and designs for bridge deck replacements. In particular, Reynolds Metals Company has lead the movement toward the use of a shop-extruded aluminum deck system known as ALUMADECKTM.
The purpose of this research is to evaluate data collected from full-scale testing under test truck loading of an in-service ALUMADECK bridge system. The bridge is known as the Little Buffalo Creek Bridge and is located in Mecklenburg County, VA. The topics researched from the load tests are the composite action amongst the deck and supporting members, the load distribution amongst supporting members, the dynamic load allowance for supporting members, and the developed deck stresses due to test truck loads. Evaluations of the research topics include comparisons to the methods employed in the design calculations provided by VDOT and to those of the American Association of State Highway and Transportation Officials (AASHTO) design specifications.Master of Science
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Pyekh, Yury B. "Dynamic terrain following: nvCPD scanning technique improvement." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34826.
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There is a large number of measurement techniques that is used for a surface inspection and a
characterization of different types of materials. One of these techniques is a contact potential
difference (CPD) scanning technique. In this project a non-vibrating contact potential difference
(nvCPD) method is utilized to measure a work function and a topographical structure of a sample
surface. A sample is mounted on a spindle that rotates at high speed. A nvCPD sensor detects
work-function variations during movement above the sample surface. There are certain factors that
create difficulties during the measurement process. A nonplanar sample surface, the spindle wobble
and an incline of a mounted sample impede the safe (without impacting the surface) scanning at a
close distance. The goal of this thesis was to implement a height sensor as a feedback device to
dynamically control and adjust a CPD sensor flying height. Since a CPD signal is inversely
proportional to the flying height, minimization of this height will enhance the signal magnitude, the
signal-to-noise ratio and the resolution of measurements.
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Testud, Frederik [Verfasser], and Jürgen [Akademischer Betreuer] Hennig. "Dynamic magnetic field estimation for magnetic resonance imaging = Dynamische Magnetfeldmessung für Magnetresonanztomographie." Freiburg : Universität, 2013. http://d-nb.info/1123478422/34.
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Parris, Matthew. "OPTIMIZING DYNAMIC LOGIC REALIZATIONS FOR PARTIAL RECONFIGURATION OF FIELD PROGRAMMABLE GATE ARRAYS." Master's thesis, University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4128.
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Many digital logic applications can take advantage of the reconfiguration capability of Field Programmable Gate Arrays (FPGAs) to dynamically patch design flaws, recover from faults, or time-multiplex between functions. Partial reconfiguration is the process by which a user modifies one or more modules residing on the FPGA device independently of the others. Partial Reconfiguration reduces the granularity of reconfiguration to be a set of columns or rectangular region of the device. Decreasing the granularity of reconfiguration results in reduced configuration filesizes and, thus, reduced configuration times. When compared to one bitstream of a non-partial reconfiguration implementation, smaller modules resulting in smaller bitstream filesizes allow an FPGA to implement many more hardware configurations with greater speed under similar storage requirements. To realize the benefits of partial reconfiguration in a wider range of applications, this thesis begins with a survey of FPGA fault-handling methods, which are compared using performance-based metrics. Performance analysis of the Genetic Algorithm (GA) Offline Recovery method is investigated and candidate solutions provided by the GA are partitioned by age to improve its efficiency. Parameters of this aging technique are optimized to increase the occurrence rate of complete repairs. Continuing the discussion of partial reconfiguration, the thesis develops a case-study application that implements one partial reconfiguration module to demonstrate the functionality and benefits of time multiplexing and reveal the improved efficiencies of the latest large-capacity FPGA architectures. The number of active partial reconfiguration modules implemented on a single FPGA device is increased from one to eight to implement a dynamic video-processing architecture for Discrete Cosine Transform and Motion Estimation functions to demonstrate a 55-fold reduction in bitstream storage requirements thus improving partial reconfiguration capability.M.S.Cp.E.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Computer Engineering MSCpE
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Schlueter, Alexander [Verfasser], and Charlotte [Akademischer Betreuer] Kuhn. "Phase Field Modeling of Dynamic Brittle Fracture / Alexander Schlueter ; Betreuer: Charlotte Kuhn." Kaiserslautern : Technische Universität Kaiserslautern, 2018. http://d-nb.info/116213397X/34.
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Liu, Yang. "Light field rendering of under-sampled dynamic scenes by a plane sweep /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2004. http://uclibs.org/PID/11984.
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Johnson, Jeffrey S. "A dynamic neural field model of visual working memory and change detection." Diss., University of Iowa, 2008. http://ir.uiowa.edu/etd/12.
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Rattana, Prapanporn. "Mean-field-like approximations for stochastic processes on weighted and dynamic networks." Thesis, University of Sussex, 2015. http://sro.sussex.ac.uk/id/eprint/56600/.
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The explicit use of networks in modelling stochastic processes such as epidemic dynamics has revolutionised research into understanding the impact of contact pattern properties, such as degree heterogeneity, preferential mixing, clustering, weighted and dynamic linkages, on how epidemics invade, spread and how to best control them. In this thesis, I worked on mean-field approximations of stochastic processes on networks with particular focus on weighted and dynamic networks. I mostly used low dimensional ordinary differential equation (ODE) models and explicit network-based stochastic simulations to model and analyse how epidemics become established and spread in weighted and dynamic networks. I begin with a paper presenting the susceptible-infected-susceptible/recovered (SIS, SIR) epidemic models on static weighted networks with different link weight distributions. This work extends the pairwise model paradigm to weighted networks and gives excellent agreement with simulations. The basic reproductive ratio, R0, is formulated for SIR dynamics. The effects of link weight distribution on R0 and on the spread of the disease are investigated in detail. This work is followed by a second paper, which considers weighted networks in which the nodal degree and weights are not independent. Moreover, two approximate models are explored: (i) the pairwise model and (ii) the edge-based compartmental model. These are used to derive important epidemic descriptors, including early growth rate, final epidemic size, basic reproductive ratio and epidemic dynamics. Whilst the first two papers concentrate on static networks, the third paper focuses on dynamic networks, where links can be activated and/or deleted and this process can evolve together with the epidemic dynamics. We consider an adaptive network with a link rewiring process constrained by spatial proximity. This model couples SIS dynamics with that of the network and it investigates the impact of rewiring on the network structure and disease die-out induced by the rewiring process. The fourth paper shows that the generalised master equations approach works well for networks with low degree heterogeneity but it fails to capture networks with modest or high degree heterogeneity. In particular, we show that a recently proposed generalisation performs poorly, except for networks with low heterogeneity and high average degree.
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Yaqub, Hashim. "Reducing head mounted display VR sickness through dynamic field of view constriction." Thesis, University of Bath, 2018. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.761035.
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Although virtual reality (VR) head-mounted displays (HMD) have been in use since the mid-1960s, the surge in public awareness and access to VR had spurred an increased interest in all industries to investigate the potential of VR as an interaction modality associated with high subjective presence. Many challenges need to be addressed through the disciplined application of research methods, especially combating VR sickness, if this potential is to be realised. This Engineering Doctorate thesis reports a series of investigations within the context of real-world development with a partner company (BMT Defence Service, a naval engineering consultant). The primary interest of the thesis is in the potential of VR for developing cases and uses for this technology in training. The target modality of training was a portable set-up, i.e. sitting down with a laptop, HMD and a game controller. This set up would prove beneficial for providing axillary training to personnel who are not always able to receive regular on-board training. It would also prepare people for situations which are difficult to simulate in real-world conditions. Example cases included familiarisation, line of sight tests, hazard recognition and evacuation procedures. An initial study of VR HMD experience in training scenario highlighted VR sickness as a key limiting factor for usability thus focusing the research on identifying and reducing the factors which induce VR sickness. Prior research suggest that static field of view restrictions could help but only at the cost of loss of presence. There were no reported studies of the effects of restricting the field of view dynamically thus this thesis presents two investigations of dynamic Field of View (FOV) constriction triggered by movement in a virtual space. It was hypothesised that a reduction in FOV reduced the induction of VR sickness. The problem with doing so however was that it may negatively influence presence as the change in FOV could distract the user. This thesis reports the development of a method for adjusting FOV to reduce simulator VR without loss of presence. Two dynamic FOV constriction studies are reported. The first failed to demonstrate a clear effect but subjective user reports suggested methodological and experiential issues in its design. Meanwhile, research into a similar method was published at the 3DUI Symposium at IEEE VR 2016. Fernandes \& Feiner (2016) \cite{DynamicFOV_Feiner16}, who demonstrated that dynamic FOV constriction can reduce VR sickness without compromising presence. However, their work used interaction scenarios with normal walking in an unchallenging virtual environment. Users were not subject to the types of motion which literature suggests are most likely to induce sickness. Consequently, the second DFOV constriction study tested VR sickness reduction in more discomforting situations via involuntary movements and animations on the virtual character and camera. Many of these animations and movements are typical in first-person applications and yet are absent from VR applications. These include for example head-bobbing, falling animations, stumbling, and forward rolls. The aim was to test whether DFOV constriction could allow VR developers to include such facets in future development. It showed that extreme movements still generate VR sickness, despite the use of DFOV constriction, but subjective reports suggest some users appear to benefit. Further research is recommended on introducing user control to the extent of DFOV manipulation. The thesis concludes with an evaluation of the state-of-the-art in DFOV constriction as a general approach to immersive VR interactions, including how the human vestibular system may limit DFOV effectiveness as a means of controlling VR sickness.
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Singh, Gurpreet. "Dynamic Thermal Field-Induced Directed Self-Assembly of Block Copolymer Thin Films." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1372120753.
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Deogekar, Sai Sharad. "A Computational Study of Dynamic Brittle Fracture Using the Phase-Field Method." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439455086.
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Wahlstedt, Linnéa. "Dynamic Knowledge Integration : A field study of an Information Systems Development Project." Doctoral thesis, Linköpings universitet, Företagsekonomi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-102595.
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Current research on knowledge integration offers valuable structural analyses of factors that influence knowledge integration, performance outcomes, and knowledge integration mechanisms. Less attention has been paid to how knowledge integration is carried out over time in cross-functional development projects. This thesis is based on a year-long field study of an Information Systems Development Project. The study shows how the knowledge integration process was repeatedly interrupted by different problems that could not be resolved by merely relying on integration mechanisms that were imposed by the top management. Instead, a bottom-up dynamic evolved where the project members and participating project managers managed to reestablish coordination and knowledge integration through the invention of different ‘collective heuristics’. A novel model of Dynamic Knowledge Integration is presented which claims that knowledge integration contains two interplaying processes; one consisting of different knowledge integration mechanisms and activities, and one consisting of the collective heuristics that were invented and employed when unexpected problems emerged. In general, this research argues that knowledge integration can be understood as a dynamic process, of which both knowledge integration mechanisms and collective heuristics constitute core elements.Aktuell forskning inom området kunskapsintegration erbjuder värdefulla strukturella analyser av påverkansfaktorer, prestationsutfall och mekanismer för kunskapsintegration. Mindre uppmärksamhet har riktats mot att förstå hur kunskapsintegration åstadkoms över tid i tvärfunktionella utvecklingsprojekt. Avhandlingen bygger på en ett år lång fältstudie av ett informationssystemutvecklingsprojekt. Studien visade att kunskapsintegrationsprocessen ideligen avbröts av olika problem som inte kunde lösas med de integrationsmekanismer som den högsta ledningen infört. Istället utvecklades en ”underifrån-dynamik” där projektmedlemmarna och de deltagande projektledarna lyckades återställa koordinering och kunskapsintegration genom skapandet av olika ”kollektiva heuristiker”. En ny modell för Dynamisk Kunskapsintegration presenteras som visar att kunskapsintegration inrymmer två samverkande processer; en som består av olika mekanismer och aktiviteter för kunskapsintegration och en som består av de kollektiva heuristikerna som uppfanns och användes när oväntade problem uppstod. Mer generellt visar denna forskning hur kunskapsintegration kan förstås som en process i vilken mekanismer och heuristiker utgör centrala element som båda behövs för att förklara processens dynamiska karaktär.
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Chen, Rui. "Dynamic optimal control for distress large financial networks and Mean field systems with jumps Optimal connectivity for a large financial network Mean Field BSDEs and Global Dynamic Risk Measures." Thesis, Paris Sciences et Lettres (ComUE), 2019. https://portail.bu.dauphine.fr/fileviewer/index.php?doc=2019PSLED042.
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Cette thèse propose des modèles et des méthodes pour étudier le contrôle du risque dans de larges systèmes financiers. Nous proposons dans une première partie une approche structurelle : nous considérons un système financier représenté comme un réseau d’institutions connectées entre elles par des interactions stratégiques sources de financement mais également par des interactions qui les exposent à un risque de contagion de défaut. La nouveauté de notre approche réside dans le fait que ces deux types d’interaction interfèrent. Nous proposons des nouvelles notions d’équilibre pour ces systèmes et étudions la connectivité optimale du réseau et le risque systémique associé. Dans une deuxième partie, nous introduisons des mesures de risque systémique définies par des équations différentielles stochastiques rétrogrades dirigées par des opérateurs à champ moyen et étudions des problèmes d’arrêt optimal associés. La dernière partie aborde des questions de liquidation optimale de portefeuillesThis thesis presents models and methodologies to understand the control of systemic risk in large systems. We propose two approaches. The first one is structural : a financial system is represented as a network of institutions. They have strategic interactions as well as direct interactions through linkages in a contagion process. The novelty of our approach is that these two types of interactions are intertwined themselves and we propose new notions of equilibria for such games and analyze the systemic risk emerging in equilibrium. The second approach is a reduced form.We model the dynamics of regulatory capital using a mean field operator : required capital depends on the standalone risk but also on the evolution of the capital of all other banks in the system. In this model, required capital is a dynamic risk measure and is represented as a the solution of a mean-field BDSE with jumps. We show a novel dual representation theorem. In the context of meanfield BSDEs the representation gives yield to a stochastic discount factor and a worst-case probability measure that encompasses the overall interactions in the system. We also solve the optimal stopping problem of dynamic risk measure by connecting it to the solution of reflected meanfield BSDE with jumps. Finally, We provide a comprehensive model for the order book dynamics and optimal Market making strategy appeared in liquidity risk problems
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Koh, Shannon Computer Science & Engineering Faculty of Engineering UNSW. "Generating the communication infrastracture for module-based dynamic reconfiguration of FPGas." Publisher:University of New South Wales. Computer Science & Engineering, 2008. http://handle.unsw.edu.au/1959.4/41418.
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Current approaches to supporting module-based FPGA reconfiguration focus on various aspects and sub-problems in the area but do not combine to form a coherent, top-down methodology that factors low-level device parameters into every step of the design flow. This thesis proposes such a top-down methodology from application specification to low-level implementation, centered around examining the problem of generating a point-to-point communications infrastructure to support the changing interfaces of dynamically placed modules. Low-level implementation parameters are considered at every stage to ensure that area, timing and budget constraints of the application are met. The approach advocates the regular layout of modules surrounded by a wiring harness supporting the communications for those modules, and thus provides an advanced understanding of how to implement the "fixed wiring harness" model of reconfigurable computing proposed by Brebner. Results have shown that compared to flattened net lists the regularity of the layout does not impose significant overheads on critical path delays. At high communication densities it can even result in lower delays. The core of the methodology is an infrastructure generation process that allocates modules to slots and merges configuration graphs to form wiring harnesses that support the communications for these merged configurations. This thesis suggests methods and evaluates algorithms for configuration graph merging so as to reduce run-time reconfiguration overheads. Initial experiments with a greedy merging algorithm performed on an optical flow application resulted in a substantial reduction of 64% in reconfiguration time. The effects of graph merging with the initial greedy algorithm and an improved dynamic programming algorithm were explored for a range of device sizes and architectural parameters. Results show that configuration merging using the greedy method results in significant reductions to the reconfiguration delay. The dynamic programming algorithm provides consistent improvements above and beyond the savings provided by the greedy method. In addition, a strong correlation was identified between the quality of front-end design activities such as partitioning and the effectiveness of back-end implementations. The methodology is integrated into the Xilinx commercial tool flow for partial reconfiguration, and is effective for implementing applications for module-based FPGA reconfiguration where the modules and their communications requirements are known at design time. It also allows a system designer to consider alternate device sizes and parameters until a set is found that satisfies the application constraints.
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Hardyniec, Andrew B. "Dynamic Testing and Modeling of a Superelevated Skewed Highway Bridge." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/34806.
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Created in response to the aging infrastructure in the United States, the Long Term Bridge Performance Program (LTBPP) under the Federal Highway Administration (FHWA) proposes to assess the long-term performance of representative bridges through nondestructive evaluation (NDE) techniques and visual inspection. For consistency, a set of guidelines is needed to define the procedures for testing each bridge. The NDE techniques involve dynamic testing, and the protocol for this testing has yet to be finalized.
To evaluate the dynamic testing guidelines, a 103 ft single-span, simply supported highway bridge was dynamically tested. The test bridge was characterized by a skew of 34° and superelevation around 4%. Forced vibration testing involved an impact hammer with accelerometers measuring the response. Resonant frequencies were identified from the data by picking peaks from the magnitudes of the frequency response functions (FRF). Eleven modes were identified with frequencies ranging from 2.75 Hz to 22.5 Hz. Mode shapes associated with each mode were constructed using the imaginary components of the FRFs. The half-power bandwidth method was used to estimate the damping for each mode, with values ranging from 1% to 5% of critical damping.
Finite element (FE) models of the bridge were constructed in the commercial FE software Abaqus. The effects of adding and removing superelevation and skew, varying mesh refinement, and changing boundary conditions on modal parameters were thoroughly investigated. FE models were compared to the experimental results by directly comparing frequencies and using the modal assurance criterion to compare mode shapes. Support conditions of the actual structure were bounded using the results of the comparison.
Much insight was gained about forced vibration testing as applied to a full-scale bridge. The spectral resolution of the data proved to limit the accuracy and confidence of detecting closely-spaced modes and calculating damping estimates. Also, a more controlled method of exciting the structure was desired, such as using a shaker with a known input. Resonant frequencies of the FE models were sensitive to changes in boundary conditions, with some frequencies doubling. Both changes in boundary conditions and including skew and superelevation noticeably affected the mode shapes. When compared to the experimental results, the models with idealized roller and pin boundary conditions provided the best correlations based on resonant frequencies and mode shapes.Master of Science
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Tong, Xianqiao. "Real-time Prediction of Dynamic Systems Based on Computer Modeling." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/47361.
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This dissertation proposes a novel computer modeling (DTFLOP modeling) technique to predict the real-time behavior of dynamic systems. The proposed DTFLOP modeling classifies the computation into the sequential computation, which is conducted on the CPU, and the parallel computation, which is performed on the GPU and formulates the data transmission between the CPU and the GPU using the parameters of the memory access speed and the floating point operations to be carried out on the CPU and the GPU by relating the calculation rate respectively. With the help of the proposed DTFLOP modeling it is possible to estimate the time cost for computing the model that represents a dynamic system given a certain computer. The proposed DTFLOP modeling can be utilized as a general method to analyze the computation of a model related to a dynamic system and two real life systems are selected to demonstrate its performance, the cooperative autonomous vehicle system and the full-field measurement system.
For the cooperative autonomous vehicle system a novel parallel grid-based RBE technique is firstly proposed. The formulations are derived by identifying the parallel computation in the prediction and correction processes of the RBE. A belief fusion technique, which fuses not only the observation information but also the target motion information, has hen been proposed. The proposed DTFLOP modeling is validated using the proposed parallel grid-based RBE technique with the GPU implementation by comparing the estimated time cost with the actual time cost of the parallel grid-based RBE. The superiority of the proposed parallel grid-based RBE technique is investigated by a number of numerical examples in comparison with the conventional grid-based RBE technique. The belief fusion technique is examined by a simulated target search and rescue test and it is observed to maintain more information of the target compared with the conventional observation fusion technique and eventually leads to the better performance of the target search and rescue.
For the full-field measurement system a novel parallel DCT full-field measurement technique for measuring the displacement and strain field on the deformed surface of a structure is proposed. The proposed parallel DCT full-field measurement technique measures the displacement and strain field by tracking the centroids of the marked dots on the deformed surface. It identifies and develops the parallel computation in the image analysis and the field estimation processes and then is implemented into the GPU to accelerate the conventional full-field measurement techniques. The detail strategy of the GPU implementation is also developed and presented. The corresponding software package, which also includes a graphic user interface, and the hardware system consist of two digital cameras, LED lights and adjustable support legs to accommodate indoor or outdoor experimental environments are proposed. The proposed DTFLOP modeling is applied to the proposed parallel DCT full-field measurement technique to estimate its performance and the well match with the actual performance demonstrates the DTFLOP modeling. A number of both simulated and real experiments, including the tensile, compressive and bending experiments in the laboratory and outdoor environments, are performed to validate and demonstrate the proposed parallel DCT full-field measurement technique.Ph. D.
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Schneegans, Sebastian [Verfasser], Gregor [Akademischer Betreuer] Schöner, and Laurenz [Akademischer Betreuer] Wiskott. "Dynamic field theory of visuospatial cognition / Sebastian Schneegans. Gutachter: Gregor Schöner ; Laurenz Wiskott." Bochum : Ruhr-Universität Bochum, 2016. http://d-nb.info/1081246669/34.
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Bur, Christian [Verfasser]. "Selectivity Enhancement of Gas Sensitive Field Effect Transistors by Dynamic Operation / Christian Bur." Aachen : Shaker, 2015. http://d-nb.info/1075437172/34.
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Smagina, Zana. "Dynamic amplification for moving vehicle loads on buried pipes : Evaluation of field-tests." Thesis, KTH, Bro- och stålbyggnad, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-36801.
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Alam, Mohammad Faridul. "A dynamic hybrid RANS/LES modeling methodology for turbulent/transitional flow field prediction." Thesis, Mississippi State University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3603414.
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A dynamic hybrid Reynolds-averaged Navier-Stokes (RANS)-Large Eddy Simulation (LES) modeling framework has been investigated and further developed to improve the Computational Fluid Dynamics (CFD) prediction of turbulent flow features along with laminar-to-turbulent transitional phenomena. In recent years, the use of hybrid RANS/LES (HRL) models has become more common in CFD simulations, since HRL models offer more accuracy than RANS in regions of flow separation at a reduced cost relative to LES in attached boundary layers. The first part of this research includes evaluation and validation of a dynamic HRL (DHRL) model that aims to address issues regarding the RANS-to-LES zonal transition and explicit grid dependence, both of which are inherent to most current HRL models. Simulations of two test cases—flow over a backward facing step and flow over a wing with leading-edge ice accretion—were performed to assess the potential of the DHRL model for predicting turbulent features involved in mainly unsteady separated flow. The DHRL simulation results are compared with experimental data, along with the computational results for other HRL and RANS models. In summary, these comparisons demonstrate that the DHRL framework does address many of the weaknesses inherent in most current HRL models.
Although HRL models are widely used in turbulent flow simulations, they have limitations for transitional flow predictions. Most HRL models include a fully turbulent RANS component for attached boundary layer regions. The small number of HRL models that do include transition-sensitive RANS models have issues related to the RANS model itself and to the zonal transition between RANS and LES. In order to address those issues, a new transition-sensitive HRL modeling methodology has been developed that includes the DHRL methodology and a physics-based transition-sensitive RANS model. The feasibility of the transition-sensitive dynamic HRL (TDHRL) model has been investigated by performing numerical simulations of the flows over a circular cylinder and a PAK-B airfoil. Comparisons with experimental data along with computational results from other HRL and RANS models illustrate the potential of TDHRL model for accurately capturing the physics of complex transitional flow phenomena.
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García, Daza Fabián Alonso. "Coarse-Grained Mean-Field Simulations of Surfactant Micelles: Static and Dynamic Equilibrium Properties." Doctoral thesis, Universitat Rovira i Virgili, 2016. http://hdl.handle.net/10803/396177.
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Les molècules de surfactants estan compostes per seccions hidrofíliques i hidrofòbiques del qual les interaccions
oposades amb el medi solvent deriven en un comportament particular on, a una concentració de surfactant coneguda
com la concentració crítica micel·lar (CMC), els surfactants s'associen en micel·les. No obstant això, malgrat el gran
nombre de treballs de simulació, experimentals i teòrics, sembla estar encara incomplet l'enteniment a nivell
microscòpic de l'acte assemblage de surfactants en agregats micelars. A la recerca d'un millor enteniment del procés
de micelización i el seu impacte en propietats microscòpiques i macroscòpiques, aquest treball fa servir el mètode
single-chain mean-field (SCMF) per a un grup de sistemes de surfactants representats per una sèrie de models de
grans. En particular, el treball aborda: (i) l'estudi de propietats estàtiques d'equilibri per a diferents sistemes de
surfactants i l'anàlisi de desviacions experimentals de propietats d'equilibri per surfactants gemini del qual les escales
de longitud disminueixen la possibilitat de ser estudiats pels mètodes de simulació usuals, i, (ii) el desenvolupament
d'una versió dinàmica del SCMF per obtenir propietats dinàmiques en equilibri que ens permetin estudiar el fenomen
d'intercanvi cinètic en sistemes micelars.Las moléculas de surfactantes están compuestas por secciones hidrofílicas e hidrofóbicas cuyas interacciones opuestas con el medio solvente derivan en un comportamiento particular donde, a una concentración de surfactante conocida como la concentración crítica micelar (CMC), los surfactants se asocian en micelas. No obstante, a pesar del gran número de trabajos de simulación, experimentales y teóricos, parece estar aún incompleto el entendimiento a nivel microscópico del auto ensamblaje de surfactantes en agregados micelares. En busca de un mejor entendimiento del proceso de micelización y su impacto en propiedades microscópicas y macroscópicas, este trabajo usa el método single-chain mean-field (SCMF) para un grupo de sistemas de surfactantes representados por una serie de modelos de granos. En particular, el trabajo aborda: (i) el estudio de propiedades estáticas de equilibrio para diferentes sistemas de surfactantes y el análisis de desviaciones experimentales de propiedades de equilibrio para surfactantes gemini cuyas escalas de longitud disminuyen la posibilidad de ser estudiados por los métodos de simulación usuales, y, (ii) el desarrollo de una versión dinámica del SCMF para obtener propiedades dinámicas en equilibrio que nos permitan estudiar el fenómeno de intercambio cinético en sistemas micelares.
Surfactants molecules are composed by hydrophilic and hydrophobic moieties whose opposite interactions with the solvent medium result in a particular behavior where, at a surfactant concentration known as the critical micelle concentration (CMC), the surfactants self-associate into micelles. However, despite the wide number of simulation, experimental and theoretical works, microscopic understanding of the self-assembly of surfactants into micellar aggregates seems to be still incomplete. Looking for a deep knowledge of the micellization process and its impact on microscopic and macroscopic properties, this work is aimed to use the single-chain mean-field (SCMF) theory for a diverse set of surfactant systems represented by a series of coarse-grained models. In particular, the work coverages the following: (i) the study of static equilibrium properties of different surfactant systems and the analysis of experimental deviations of equilibrium properties for gemini surfactant systems whose length scales decrease the possibility of being studied by regular simulation methods, and, (ii) development of a dynamic version of the SCMF scheme, to obtain dynamic equilibrium properties that enable us to study kinetics exchange phenomena in micellar systems.
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Diewald, Felix [Verfasser], and Ralf [Akademischer Betreuer] Müller. "Phase Field Modeling of Static and Dynamic Wetting / Felix Diewald ; Betreuer: Ralf Müller." Kaiserslautern : Technische Universität Kaiserslautern, 2020. http://d-nb.info/1205314733/34.
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Heitzman, Michael Thomas Chicone Carmen Charles. "A free boundary gas dynamic model as a two-body field theory problem." Diss., Columbia, Mo. : University of Missouri--Columbia, 2009. http://hdl.handle.net/10355/7017.
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Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 26, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Professor Carmen Chicone. Vita. Includes bibliographical references.
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Inati, Souheil James 1971. "Dynamic nuclear polarization and electron spin resonance in paramagnetic solids at high field." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/17474.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 1999.Includes bibliographical references (p. 155-161).
Recent advances in high resolution solid state nuclear magnetic resonance spectroscopy have permitted the detailed structural study of large biological systems. The feasibility of many of these experiments is limited by the inherently low sensitivity of solid state NMR, and the implementation of complex multi-dimensional homo- and hetero-nuclear recoupling pulse sequences has been restricted to small model compounds. The primary focus of this thesis is the description of investigations of dynamic nuclear polarization (DNP) at high magnetic field as a means of improving the signal to noise in solid state NMR spectroscopy. DNP transfers the large polarization of unpaired electron spins to nuclei in a process involving sample irradiation at or near the electronic Larmor frequency. Large signal enhancements have been achieved in a nitroxide doped frozen aqueous solution at 5T. The relevant relaxation times governing the transfer process have been measured via the application of various high frequency pulsed electron paramagnetic resonance (EPR) techniques, and a model incorporating cross-relaxation is used to explain the results. It is shown that the electronic and nuclear spin dynamics are consistent with the thermal mixing mechanism of polarization transfer. The high frequency (139.5 GHz, 5T) EPR spectrometer used to perform these experiments is described in detail and several other advancements in the application of high power, high frequency microwave technology to magnetic resonance are also discussed.
by Souheil James Inati.
Ph.D.
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Hedric, Andrew C. "Dynamic Behaviors of Historical Wrought Iron Truss Bridges – a Field Testing Case Study." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc822751/.
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Civil infrastructure throughout the world serves as main arteries for commerce and transportation, commonly forming the backbone of many societies. Bridges have been and remain a crucial part of the success of these civil networks. However, the crucial elements have been built over centuries and have been subject to generations of use. Many current bridges have outlived their intended service life or have been retrofitted to carry additional loads over their original design. A large number of these historic bridges are still in everyday use and their condition needs to be monitored for public safety. Transportation infrastructure authorities have implemented various inspection and management programs throughout the world, mainly visual inspections. However, careful visual inspections can provide valuable information but it has limitations in that it provides no actual stress-strain information to determine structural soundness. Structural Health Monitoring (SHM) has been a growing area of research as officials need to asses and triage the aging infrastructure with methods that provide measurable response information to determine the health of the structure. A rapid improvement in technology has allowed researchers to start using new sensors and algorithms to understand the structural parameters of tested structures due to known and unknown loading scenarios. One of the most promising methods involves the use of wireless sensor nodes to measure structural responses to loads in real time. The structural responses can be processed to help understand the modal parameters, determine the health of the structure, and potentially identify damage. For example, modal parameters of structures are typically used when designing the lateral system of a structure. A better understanding of these parameters can lead to better and more efficient designs. Usually engineers rely on a finite element analysis to identify these parameters. By observing the actual parameters displayed during field testing, the theoretical FE models can be validated for accuracy. This paper will present the field testing of a historic wrought iron truss bridge, in a case study, to establish a repeatable procedure to be used as reference for the testing of other similar structures.
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Lonsbury, Cody. "QUASI-MAGNETOSTATIC FIELD MODELING OF SHIPS IN THE PRESENCE OF DYNAMIC SEA WAVES." UKnowledge, 2016. http://uknowledge.uky.edu/ece_etds/85.
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Mechanical stresses placed on ferromagnetic materials while under the influence of a magnetic field are known to cause changes to the permanent magnetization of the material. Modeling this phenomenon is vital to the safety of ocean faring ships. In this thesis, a quasi-strip theory method of computing the nonlinear wave induced motion of a ship is developed, and the fluid pressure on the surface of the hull is used to determine the mechanical stresses. An existing magnetostatic volume integral equation code is used to evaluate the effects of the ship motion and hull stresses. The resulting changes in the magnetic field for various ship forms are presented to demonstrate the effects of given sea states.
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Kallam, Ramachandra. "Accelerated Frame Data Relocation on Xilinx Field Programmable Gate Array." DigitalCommons@USU, 2010. https://digitalcommons.usu.edu/etd/655.
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Emerging reconfiguration techniques that include partial dynamic reconfiguration and partial bitstream relocation have been addressed in the past in order to expose the flexibility of field programmable gate array at runtime. Partial bitstream relocation is a technique used to target a partial bitstream of a partial reconfigurable region (PRR) onto other identical reconfigurable regions inside an FPGA, while partial dynamic reconfiguration is used to target a single reconfigurable region. Prior works in this domain aim to minimize "relocation time" with the help of on-chip or on-line processing. In this thesis, a novel PRR-PRR relocation algorithm is proposed and implemented both in software and hardware. Dedicated hardware architecture, called the accelerated relocation circuit (ARC), is designed and presented for fast relocation. An analytical model is also proposed to evaluate the performance of the PRR-PRR relocation algorithm and highlight the speed-up obtained by the proposed hardware implementation. ARC has been tested on two categories of designs: dynamically scalable systolic array designs and fault tolerant designs. It has been compared against the software implementation of the algorithm, BiRF, hardware architecture for bitstream relocation, and a software solution for bitstream relocation. An average speed-up of 153x for ARC over BiRF is observed, with the additional advantage of not storing any bitstreams, thus saving invaluable block random access memory (BRAMs). Accuracy of proposed analytical model was found to be more than 95% for all the test cases.
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Vaidya, Varun, and Kushal Bheemesh. "Adaptive Warning Field System." Thesis, Högskolan i Halmstad, CAISR Centrum för tillämpade intelligenta system (IS-lab), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-35312.
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This thesis is based on the work carried out in the field of safety systems for Autonomous Guided Vehicles(AGV). With autonomous vehicles being more prominent today, safe traversing of these is a major concern. The same is true for AGVs working in industry environment like forklift trucks etc. Our work applies to industrial robots. The method described here is developed by closely following an algorithm developed for safe traversing of a robot using a warning field. The report describes the literature review with work related to the safe traversing, path planning and collision avoidance in robots. The next part is dedicated to describing the methodology of implementation of the Adaptive Warning Field Method and the Dynamic Window Approach. The evaluation of the Adaptive Warning Method with the previous developed Warning Field Methods is done and test cases are designed to test the working of the designed method. Vrep simulation environment and Industrial data is used to run a simulation of the robot using the method developed in this work. We find that the method performs better compared to the previous methods in the designed scenarios. Lastly we conclude the report with the future work that can be carried out to improve and extend the algorithm.