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1
PUSCEDDU, MATTEO. "Valutazione degli aggiustamenti cardiocircolatori durante apnea statica e dinamica in apneisti d'elitè mediante l'uso di un dispositivo portatile". Doctoral thesis, Università degli Studi di Cagliari, 2014. http://hdl.handle.net/11584/266480.
Testo completoAbstract (sommario):
Aim: Considering that sympathetic activation is induced by exercise, it is reasonable to assume that hemodynamic adjustments to exercise act in opposition to those elicited by the diving response. However, cardiovascular measurements have never been performed during underwater dynamic apnoea (DA), and this hypothesis remains speculative.
Methods: Data concerning heart rate (HR), stroke volume (SV) and cardiac output (CO) during static apnoea (SA) and DA were collected from 12 elite divers by means of an impedance cardiograph adapted to the underwater environment. Mean arterial pressure (MBP), systemic vascular resistance (SVR) and arterial oxygen saturation (SaO2) were also assessed.
Five trials were performed by the divers: head-out immersion during normal breathing (test A); 3 min of SA immersed at the surface (B) and at 3 m depth (C); DA till exhaustion immersed at the surface (D) and at 3 m depth (E).
Results: Both B and C conditions led to bradycardia (_17%) compared to A and also induced a decrement in SV (_8%) and in CO (_25%), while MBP was maintained because of an increase in SVR. A significant MBP increment (+11%) was detected only during tests D and E, when a SaO2
drop was also present, whereas HR, SV and CO remained unchanged.
Conclusion: We concluded that typical diving response was present only during SA, while sympathetic activation was induced by exercise during DA, which partially obscured the effects of the diving response.
2
Allinger, Jérémie. "Etude des différents facteurs influençant la perte de cοnnaissance chez l'apnéïste". Electronic Thesis or Diss., Normandie, 2024. http://www.theses.fr/2024NORMR081.
Testo completoAbstract (sommario):
Ce travail de thèse proposait d’étudier les facteurs influençant la perte de connaissance chez les apnéistes. Dans un premier temps, nous avons étudié la prévalence des accidents en apnée compétitive en fonction de la discipline d’apnée pratiquée (étude 1) puis tenté d’établir s’il existait un profil particulièrement à risque pour la syncope chez les apnéistes experts (étude 2). Dans un second temps, nous avons analysé l’impact cognitif d’une série d’apnées maximales chez des apnéistes experts ainsi qu’après une séance d’apnée habituelle chez des apnéistes amateurs (études 3 et 4). Par ailleurs, une attention particulière a été portée à la quantification et à la gestion de la charge d’entraînement en apnée en situation écologique (étude 4). Enfin, les réponses hémodynamiques et d’oxygénation cérébrale des apnéistes novices ont été comparées lors d’apnées statiques et dynamiques (étude 5). Les syncopes restent relativement fréquentes (3,31 % des accidents), avec un risque deux fois plus élevé pour les disciplines sans palme. Certains apnéistes avec une capacité à réaliser de longues apnées ont tendance à prendre plus de risques, notamment chez les compétiteurs expérimentés masculins. Cela pourrait être en lien avec une exposition répétée à l’hypoxie puisque nous avons montré qu’une série d’apnées maximales affecte directement les fonctions cognitives, peu importe le niveau d’entraînement. Toutefois, chez les non-experts, une seule séance d'apnée dans un cadre non compétitif n’a pas révélé de déficits cognitifs notables, ce qui suggère que ces altérations dépendent probablement de l'intensité, la fréquence des apnées et donc de la dose hypoxique. Cette dose hypoxique semble dépendre également du type d’apnée : statique ou dynamique. Ainsi, bien que l'apnée statique bénéficie de mécanismes compensatoires plus efficaces, l'apnée dynamique, en raison de l'effort musculaire accru, induit une hypoxie plus rapide mettant davantage à l'épreuve les mécanismes de protection cérébrale. Il semble donc intéressant d’utiliser des outils pour quantifier la charge d’entraînement des apnéistes afin de mieux évaluer la dose hypoxique induite et, à terme, de limiter les risques de syncopes pour prévenir les éventuelles futures altérations cognitives. Ces travaux ouvrent la voie à de futures recherches sur les adaptations à l’hypoxie induite par l’apnée dans le cadre sportif et médical, tout en appelant à une meilleure gestion des risques liés à la pratiqueThe aim of this thesis was to study the factors influencing loss of consciousness in freedivers. Firstly, we studied the prevalence of accidents in competitive freediving as a function of the freediving discipline practised (study 1) and then attempted to establish whether there was a particularly high-risk profile for syncope among expert freedivers (study 2). Secondly, we analysed the cognitive impact of a series of maximal apneas in expert freedivers and after a regular freediving session in amateur freedivers (studies 3 and 4). In addition, particular attention was paid to the quantification and management of apnea training load in ecological situations (study 4). Finally, the haemodynamic and cerebral oxygenation responses of novice freedivers were compared during static and dynamic apneas (study 5). Syncope remains relatively frequent (3.31% of accidents), with a risk twice as high for disciplines without fins. Certain freedivers with the ability to perform long apneas tend to take more risks, particularly among experienced male competitors. This could be linked to repeated exposure to hypoxia, since we have shown that a series of maximal apneas directly affects cognitive functions, regardless of the level of training. However, in non-experts, a single apnea session in a non-competitive setting did not reveal any notable cognitive deficits, which suggests that these alterations probably depend on the intensity and frequency of apneas and therefore on the hypoxic dose. This hypoxic dose also seems to depend on the type of apnoea: static or dynamic. Thus, although static apnoea benefits from more effective compensatory mechanisms, dynamic apnoea, because of the increased muscular effort, induces more rapid hypoxia, putting the brain's protective mechanisms to a greater test. It therefore seems worthwhile to use tools to quantify the training load of freedivers in order to better assess the hypoxic dose induced and, ultimately, to limit the risks of syncope in order to prevent future cognitive impairment. This work paves the way for future research into adaptations to hypoxia induced by apnoea in sports and medical settings, while calling for better management of the risks associated with practice
3
Yaghi, Anas H. "Static and dynamic brittle fracture". Thesis, University of Nottingham, 1993. http://eprints.nottingham.ac.uk/11786/.
Testo completoAbstract (sommario):
The project examined the static and dynamic fracture mechanics of brittle materials. Destructive testing was performed on brittle, elastic, isotropic and homogeneous epoxy resin specimens made of Araldite CT-200 with Hardener HT-907. Three types of specimen were investigated, namely the three point bend (3PB) beam, the compact mixed-mode (CMM) specimen and the pressure tube. The 3PB and CMM specimens contained both narrow notches and real cracks. The pressure tubes included semi-circular notches. The real cracks were obtained by controlled fatiguing. The research involved the evaluation of the static mode-I and mode-II real and apparent critical stress intensity factors. The fracture surfaces and the phenomenon of crack branching were studied. The dynamic mode-I stress intensity factor was obtained at the inception of crack instability and also at branching. The concept of the existence of a unique relationship between the dynamic stress intensity factor and the instantaneous crack velocity was addressed. The possibility of modelling cracks in structural components by using cast shim notches in epoxy resin was discussed. The modelling of the static behaviour was proposed to be accurate and relatively easy. The dynamic behaviour would be approximately modelled; therefore suggestions on how to improve the dynamic modelling of propagating cracks were recommended, paying particular attention to the branching process and the instantaneous crack velocity. In addition to the experimental work, finite element analysis was conducted for the 3PB and CMM specimens containing narrow notches. It was shown that the specific geometry and loading conditions were unimportant and that the loading was conveniently characterised by the stress intensity factors for an equivalent crack. A method was devised which provided a relatively cheap and efficient means of determining stress concentration factors for what might appear to be complex geometries and loading conditions.
4
Rushton, Matthew V. "Static and dynamic type systems". Diss., Connect to the thesis Connect to the thesis, 2004. http://hdl.handle.net/10066/1483.
Testo completo
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Birdi, Bhavneet Kaur. "A Study of Dynamic + Static Space". Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/33577.
Testo completoAbstract (sommario):
Architecture and dance are both able to communicate through a language of rhythm and choreography. The fluidity and balance of a dancer as an artistic endeavor can be an inspiration, to develop analogous architectural forms as a kind of transcribed motions of the dance.
A dancer''s movements and pauses can be interpreted as dynamic and static architectural moments. Dynamic space suggests to be active, and continuous, while static aims to be passive, tranquil and defined.
A proposal for an Art Center consisting of theater and a studio space serves as a vehicle to explore formally the spatial components inspired by dance. In the proposal, the theater embodies the active expression of motion. This provides a dynamic architectural space through two concentric curved enclosures that expand and contract horizontally and vertically. In contrast, the studios form a static shell, promoting a serene environment where the architecture frames the dancer''s activity.
The duality of dynamic and static architectural space in the work is a primary framework. The dynamic expresses the kinetic nature of architectural elements in space; in contrast, the static reveals the potential of a precisely measured room to achieve a balanced harmony when juxtaposed together.Master of Architecture
6
Knüsel, Philipp. "Dynamic neuronal representations of static sensory stimuli /". Zürich : ETH, 2006. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=16660.
Testo completo
7
Vöcking, Berthold. "Static and dynamic data Management in networks /". Paderborn : HNI, 1998. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=008668511&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
Testo completo
8
Silvera-Munoz, Raul E. "Static instruction scheduling for dynamic issue processors". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0003/MQ44107.pdf.
Testo completo
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Li, Li Min. "Static and dynamic properties of epileptogenic lesions". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0035/NQ64604.pdf.
Testo completo
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Silvera, Muñoz Raúl E. "Static instruction scheduling for dynamic issue processors". Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20237.
Testo completoAbstract (sommario):
This thesis presents a novel approach to the instruction scheduling problem for dynamic issue processors. Our approach aims at generating an instruction sequence with a low register pressure and a high level of Instruction-Level Parallelism (ILP) exploitable by the dynamic issue mechanism of the processor. Our objective is to improve the performance of the program by taking advantage of the out-of-order execution and register renaming mechanisms of the processor to reduce the amount of spill code introduced by the register allocator.Our approach uses a traditional ILP scheduler to generate an initial schedule for the program, and then reorders its instructions to reduce the register pressure of the program. This reordering is performed carefully. to ensure that the dynamic issue mechanism of the processor is able to exploit from the reordered sequence as much parallelism as available on the original schedule.
We have proposed an approximate method to determine, for a given instruction sequence and a given instruction schedule, whether a particular dynamic issue superscalar processor can exploit from the sequence as much ILP as present in the schedule. (Abstract shortened by UMI.)
11
Li, Li Min 1964. "Static and dynamic properties of epileptogenic lesions". Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36638.
Testo completoAbstract (sommario):
A series of studies were undertaken with the aim of assessing the static and dynamic profiles of the most common types of epileptogenic lesions: hippocampal sclerosis and cortical developmental malformations. Neuronal metabolic dysfunction measured by proton magnetic resonance spectroscopic imaging (1H-MRSI) overlaps the structural lesion displayed by magnetic resonance imaging (MRI), The extent of neuronal metabolic dysfunction, however, tends to be wider than the MRI-visible lesion and may reflect the intrinsic nature and extent of the original epileptogenic damage. In addition, neuronal metabolic dysfunction and synchronized neuronal firing often coincide spatially and vary together in intensity possibly reflecting the severity of the epileptogenic process.Non-foreign tissue lesional, temporal lobe epilepsy (TLE) syndrome is a heterogeneous condition, which displays a spectrum of neuronal damage. The different patterns of neuronal damage measured by MRI volumetry (MRIVol) and 1H-MRSI enable accurate probabilistic prediction of TLE lateralization and discrimination of TLE from extra-TLE. Furthermore, both MRIVol and 1H-MRSI have a prognostic value in surgical TLE patients, which can be used to streamline surgical candidates.
The neuronal damage is present in the early stages of the epileptogenic process in patients with localization related epilepsy. This process is dynamic and shows a slow progressive neuronal loss and dysfunction in TLE patients, which is not related to seizure burden. Neuronal metabolic dysfunction, lesions, spikes, cognitive decline, and psychiatric disorders are part of the epileptogenic process. These different domains parallel each other in a given time, although their pathophysiological processes are distinct. Thus seizures and neuronal damage co-exist but are not causally related.
Normalization of neuronal metabolic function is seen in post-operative seizure-free patients, with a recovery half time of six months. However, the process of neuronal recovery does not occur in patients who are seizure-free due to antiepileptic medication. The epileptogenic process causes disruption of normal neuronal network and in order to reverse this disruption the epileptogenic area must be isolated or resected surgically. The epileptic state is a translation in time of the activity of the epileptogenic process. Seizures, stereotyped behavioral manifestations, are the hallmark of the epileptogenic process, Absence of seizures, however, does not reflect inactivity of the epileptogenic process, Neuronal damage as measured by NAA/Cr can serve as a surrogate marker of the epileptogenic state.
12
Sedaghat, Yasaman. "Combined static-dynamic deformations with haptic rendering". Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=106565.
Testo completoAbstract (sommario):
We present a real-time, physically based simulation method for animating high-resolution elastic deformations with a focus on haptic interaction. To achieve interactive rates without losing accuracy, the reduced material stiffness matrix is precomputed by removing the equations that correspond to the internal nodes of the system. In addition, we employ linear modal analysis to precompute the natural vibration modes of the system. We introduce a deformation-coupling technique in order to achieve the reduced dynamic behaviour while keeping the high-resolution local deformations. During real-time simulation, the high-spatial-frequency static deformations are coupled with the low-spatial-frequency dynamics, by projecting the reduced coordinate deformations onto an orthogonal basis constructed from natural vibration modes. To explore the implications of the coupling system, we describe different integration techniques to time-step the reduced dynamic solution in addition to evaluating the force feedback. Moreover, we show how we handle multiple contact points for non-sticky materials. To improve the contact-handling procedure, we employ our sliding technique to include friction. We compare our proposed method to the previously existing techniques in terms of run-time complexity and deformation properties using 3D meshes embedded in finite elements.Nous présentons une méthode de simulation temps réel conforme aux lois de la physique pour animer des déformations élastiques à haute résolution, tout en portant une attention particulière aux interactions haptiques. Pour obtenir un résultat permettant une interaction temps réel sans perte de précision, la matrice réduite de rigidité du matériau est précalculée en excluant les équations correspondant aux noeuds internes du système. De plus, nous avons recours à l'analyse modale linéaire pour pré-calculer les modes de vibration naturelle du système. Nous proposons une technique de couplage des déformations afin d'obtenir le comportement à dynamique réduite recherché tout en préservant les propriétés des déformations locales à haute résolution. Lors de la simulation temps réel, les déformations statiques à haute fréquence spatiale sont couplées à la dynamique spatiale réduite à basse fréquence en projetant les déformations en coordonnées réduites sur une base orthogonale construite à partir des modes de vibration naturelle. Afin d'explorer l'impact du système de couplage, nous décrivons différentes techniques d'intégration pour avancer la solution de dynamique réduite dans le temps tout en évaluant le retour de force haptique. De plus, nous détaillons notre approche pour la gestion de points de contact multiples pour des matériaux non-adhésifs ainsi que notre méthode pour la gestion du glissement. Nous comparons la méthode que nous avançons aux techniques existantes en termes de complexité du temps d'exécution et en termes des propriétés de déformation, et ce en utilisant un maillage 3D intégré à un système à éléments finis.
13
Winkler, B. "Static and dynamic models of mineral energetics". Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385893.
Testo completo
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Griffiths, Peter Robert. "Static and Dynamic Components of Droplet Friction". Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4897.
Testo completoAbstract (sommario):
As digital microfluidics has continued to mature since its advent in the early 1980's, an increase in new and novel applications of this technology have been developed. However, even as this technology has become more common place, a consensus on the physics and force models of the motion of the contact line between the fluid, substrate, and ambient has not been reached. This uncertainty along with the dependence of the droplet geometry on the force to cause its motion has directed much of the research at specific geometries and droplet actuation methods.
The goal of this thesis is to help characterize the components of the friction force which opposes droplet motion as a one dimensional system model based upon simple system parameters independent from the actuation method. To this end, the force opposing the motion of a droplet under a thin rectangular glass cover slip was measured for varying cover slip dimensions (widths, length), gap height between the cover slip and substrate, and bulk droplet velocity. The stiffness of the droplet before droplet motion began, the force at which the motion initiated, and the steady-state force opposing the droplet motion were measured. The data was then correlated to hypothesized equations and compared to simple models accounting for the forces due to the contact angle hysteresis, contact line friction, and viscous losses.
It was found that the stiffness, breakaway force, and steady-state force of the droplet could be correlated to with an error standard deviation of 8 %, 14%, and 10 % respectively. Much of the error was due to an unexpected height dependence for the breakaway and steady-state forces and testing error associated with the velocity. The models for the stiffness and breakaway force over predicted the results by 36% and 16% respectively. During testing,
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stability issues with the cover slip were observed and simple dye testing was conducted to visualize the droplet flow field.
15
Friesecke, Gero. "Static and dynamic problems in nonlinear mechanics". Thesis, Heriot-Watt University, 1993. http://hdl.handle.net/10399/1458.
Testo completo
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Kennedy, Graeme J. "Static and dynamic aspects of angle perception". Thesis, Glasgow Caledonian University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443161.
Testo completo
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Andreadou, Anna. "Some static and dynamic finite elastic deformations". Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.352956.
Testo completo
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Wilkie, J. "Static and dynamic optimisation with marine applications". Thesis, University of Strathclyde, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382414.
Testo completo
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Heaton, N. J. "Static and dynamic properties of liquid crystals". Thesis, University of Southampton, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375364.
Testo completo
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Hirst, Anthony John. "Adaptive evolution in static and dynamic environments". Thesis, Open University, 1998. http://oro.open.ac.uk/57869/.
Testo completoAbstract (sommario):
This thesis provides a framework for describing a canonical evolutionary system. Populations of individuals are envisaged as traversing a search space structured by genetic and developmental operators under the influence of selection. Selection acts on individuals' phenotypic expressions, guiding the population over an evaluation landscape, which describes an idealised evaluation surface over the phenotypic space. The corresponding valuation landscape describes evaluations over the genotypic space and may be transformed by within generation adaptive (learning) or maladaptive (fault induction) local search. Populations subjected to particular genetic and selection operators are claimed to evolve towards a region of the valuation landscape with a characteristic local ruggedness, as given by the runtime operator correlation coefficient. This corresponds to the view of evolution discovering an evolutionarily stable population, or quasi-species, held in a state of dynamic equilibrium by the operator set and evaluation function. This is demonstrated by genetic algorithm experiments using the NK landscapes and a novel, evolvable evaluation function, The Tower of Babel. In fluctuating environments of varying temporal ruggedness, different operator sets are correspondingly more or less adapted. Quantitative genetics analyses of populations in sinusoidally fluctuating conditions are shown to describe certain well known electronic filters. This observation suggests the notion of Evolutionary Signal Processing. Genetic algorithm experiments in which a population tracks a sinusoidally fluctuating optimum support this view. Using a self-adaptive mutation rate, it is possible to tune the evolutionary filter to the environmental frequency. For a time varying frequency, the mutation rate reacts accordingly. With local search, the valuation landscape is transformed through temporal smoothing. By coevolving modifier genes for individual learning and the rate at which the benefits may be directly transmitted to the next generation, the relative adaptedness of individual learning and cultural inheritance according to the rate of environmental change is demonstrated.
21
PASQUETTI, EDUARDO. "STATIC AND DYNAMIC STABILITY OF GUYED TOWERS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=3709@1.
Testo completoAbstract (sommario):
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOTorres estaiadas são, em geral, estruturas bastante leves e esbeltas e que apresentam comportamento eminentemente não - linear. Assim, a análise de sua estabilidade sob cargas estáticas e dinâmicas é essencial para se ter um projeto econômico e seguro. Neste trabalho estuda-se a estabilidade estática e dinâmica de um modelo plano de torre estaiada. Especial atenção é dada à modelagem dos estais, que são modelados como elementos de mola (linear ou não -linear) ou como cabos inextensíveis. Faz-se, com base no princípio da energia potencial mínima, um estudo da carga crítica e do caminho pós-crítico. Um estudo paramétrico minucioso permite analisar a influência dos diversos parâmetros físicos e geométricos na estabilidade da torre e chegar às melhores configurações para os estais. Na análise dinâmica atenção especial é dada ao estudo paramétrico da freqüência natural. Com base nos resultados da análise estática, analisa-se também o comportamento global da torre em vibração livre e forçada. Em virtude das não linearidades, verifica-se que a torre pode apresentar diversos comportamentos típicos de sistemas não -lineares tais como saltos, bifurcações de período e caos.
Guyed towers are in general very light and slender structures and their behavior under static and dynamic loads is eminently nonlinear. Thus the analysis of its stability under static and dynamic loads is an essential step in obtaining an economic and safe project. In this work the static and dynamic stability analysis of a plain model of a guyed tower is studied. Special attention is given to the modeling of the stays; here they are modeled as spring elements (linear or nonlinear) or as inextensible cables. A study of the critical load and the postcritical nonlinear equilibrium paths is conducted based on the principle of the minimum potential energy A detailed parametric analysis is performed to identify the influence of the physical and geometric parameters of the system on the stability of the tower. This allows one to choose the best configurations for the stays. In the dynamic analysis special attention is given to the parametric study of the system natural frequencies. Based on the results of the static analysis, the global behavior of the tower under free and forced vibration is also analyzed. Due to the inherent nonlinearities, the tower may present dynamic responses typical of nonlinear systems such as jumps, period bifurcations and chaos.
22
Leo, John 1964. "Dynamic process creation in a static model". Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/14038.
Testo completo
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Varvarigos, Emmanouel A. "Static and dynamic communication in parallel computing". Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/12868.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1992.Includes bibliographical references (p. 186-191).
by Emmanouel A. Varvarigos.
Ph.D.
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Siegkas, Petros. "Static and dynamic performance of Ti foams". Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:68938d12-d104-4637-8b08-d1c126ddca84.
Testo completoAbstract (sommario):
Titanium (Ti) foams of different densities 1622-4100 Kgm-3 made by a powder sintering technique were studied as to their structural and mechanical properties. The foams were tested under static and dynamic loading. The material was tested quasi statically and dynamically under strain rates in the range of 0.001-2500 s-1 and under different loading modes. It was found that strain rate sensitivity is more pronounced in lower density foams. Experiments were complimented by virtual testing. Based on the Voronoi tessellations a computational method was developed to generate stochastic foam geometries. Statistical control was applied to produce geometries with the microstructural characteristics of the tested material. The generated structures were numerically tested under different loading modes and strain rates. Voronoi polyhedrals were used to form the porosity network of the open cell foams. The virtually generated foams replicated the geometrical features of the experimentally tested material. Meshes for finite element simulations were produced. Existing material models were used for the parent material behaviour (sintered Ti) and calibrated to experiments. The virtual foam geometries of different densities were numerically tested quasi statically under uniaxial, biaxial and triaxial loading modes in order to investigate their macroscopic behaviour. Dynamic loading was also applied for compression. Strain rate sensitive and insensitive models were used for the parent material model in order to examine the influence of geometry and material strain rate sensitivity under high rates of deformation. It was found that inertial effects can enhance the strain rate sensitivity for low density foams and numerical predictions for the generated foam geometries were in very good agreement with experimental results. Power laws were established in scaling material properties with density. The study includes: 1. Information on the material behaviour and data for macroscopically modelling this type of foams for a range of densities and under different strain rates. 2. A proposed method for virtually generating foam geometries at a microscopic scale and examine the effect of geometrical characteristics on the macroscopic behaviour of foams.
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Saltos, Atiencia Ramiro Javier. "Soft-clustering in static and dynamic environments". Tesis, Universidad de Chile, 2016. http://repositorio.uchile.cl/handle/2250/142058.
Testo completoAbstract (sommario):
Doctor en Sistemas de IngenieríaEn la actualidad, el entorno macro y micro económico en el cual op eran las empresas está cambiando constantemente y a gran velo cidad. Esto se deb e princip almente al auge de las nuevas tecnologías, la revolución de la información y la gran facilidad con la que ahora p o demos comu nicarnos con cualquier parte d el mundo. Debido a la gran canti dad de información que está siendo generada segundo tras segundo, junto con la facilidad con la que se puede acceder a ella, la minería de datos y la investigación de op eracion es se han convertido en una de las herramientas más imp ortantes para desarrollar sistemas de ap oyo a la toma de decisiones en to dos los niveles. La imp ortancia del traba jo conjunto de ambas disciplinas radica en la faci lidad relativa con la que extraen cono cimiento de enormes bases de datos y la utilizan para optimizar los pro cesos organizacionales relevantes. En particular, para la min ería de datos, estos hechos h an provo cado qu e las bases de datos sean dinámicas, es decir, el nà omero de datos disponibles crece cada segundo haciendo que tiempo de vida útil de los modelos se reduzca, haciendo necesario actualizarlos periódicamente de tal forma que encajen con la realidad actual. Lo anterior demanda el desarrollo de nuevos algoritmos que sean capaces de manejar este tipo de cambios, lo cual ha ido ganando importancia en los últimos años. Adicionalmente, la incertidumbre, ambigüedad e imprecisión presentes en los problemas de la vida real son factores muy importantes a considerar cuando se desarrollan diferentes algoritmos de minería de datos. La forma más común de lidiar con la incertidumbre viene dada por la teoría de probabilidad, sin embargo, la ambigüedad e imprecisión han sido dejadas de lado hasta la aparición de nuevas formas de tratarlas; dos de las cuales son la teoría de conjuntos " fuzzy" y "rough." Con las ideas anteriores en mente, en esta tesis, un algoritmo clásico de clustering basado en support vectors es estudiado profundamente y extendido a una versión rough-fuzzy con el fin de darle la habilidad de manejar la ambigüedad e imprecisión presente en el mundo real. Luego de esto, este novedoso algoritmo de soft-computing es generalizado a una versión dinámica siendo capaz de procesar bases de datos que reciben nueva información con el paso del tiempo. Finalmente, utilizando como base estos dos algoritmos, un método de detección de outliers es propuesto como una de las múltiples posibles aplicaciones que resultan de esta investigación. En cada capítulo, los experimentos computacionales, resultados y discusión son provistos enfatizando la contribución que este trabajo de investigación tiene para la sociedad señalando los futuros desarrollos y posibles campos de aplicación
26
VITICCHIE', ALESSIO. "Software Attestation with Static and Dynamic Techniques". Doctoral thesis, Politecnico di Torino, 2019. http://hdl.handle.net/11583/2749160.
Testo completo
27
Perez, Demydenko Camilo. "Static and dynamic disorder in nanocrystalline materials". Doctoral thesis, Università degli studi di Trento, 2019. https://hdl.handle.net/11572/368145.
Testo completoAbstract (sommario):
Peak profiles in X-ray Diffraction (XRD) patterns from nanocrystalline materials are affected by static and dynamic disorder which is specific of the size and shape of the nanocrystalline domains. Owing to their intrinsic differences, the two types of disorder can be separated, providing independent information from the modelling of the XRD patterns. In the present thesis a model for the static strain created by the nanoparticle surface is proposed. The model is built within the frame of the Whole Powder Pattern Modelling (WPPM) approach for XRD line profile analysis, developed at the University of Trento in the past 20 years. The WPPM approach is decribed in details. Based on a complex Fourier Transform of the diffraction profiles, the model leads to general equations to be used with the WPPM approach to represent the distorted atomic configuration with respect to the reference bulk one. The model was also implemented in TOPAS, a commercial and very popular software, developing a specific macro allowing a larger community of users to benefit of this new opportunity of studying nanocrystalline materials. The thesis work also extended to a more traditional and general description of strain
broadening of XRD peak profiles, involving invariant forms under the Laue group symmetry operations of the material under study. As for the dynamic strain, the fundamentals of the Thermal Diffuse Scattering (TDS) contribution to the peak profiles are reviewed. Starting from the original work
of B.E. Warren, the theory is generalized to account for surface effects, leading to a particular model developed recently at the University of Trento. This model was thoroughly reviewed and corrected. To test the model a parallel computer code in C was written, exploiting Molecular Dynamics simulations for obtaining reliable and independent estimates of static and dynamic disorder in nanocrystals.
28
Perez, Demydenko Camilo. "Static and dynamic disorder in nanocrystalline materials". Doctoral thesis, University of Trento, 2019. http://eprints-phd.biblio.unitn.it/3636/1/CAMILO_PEREZ_DEMYDENKO_thesis_PhD.pdf.
Testo completoAbstract (sommario):
Peak profiles in X-ray Diffraction (XRD) patterns from nanocrystalline materials are affected by static and dynamic disorder which is specific of the size and shape of the nanocrystalline domains. Owing to their intrinsic differences, the two types of disorder can be separated, providing independent information from the modelling of the XRD patterns. In the present thesis a model for the static strain created by the nanoparticle surface is proposed. The model is built within the frame of the Whole Powder Pattern Modelling (WPPM) approach for XRD line profile analysis, developed at the University of Trento in the past 20 years. The WPPM approach is decribed in details. Based on a complex Fourier Transform of the diffraction profiles, the model leads to general equations to be used with the WPPM approach to represent the distorted atomic configuration with respect to the reference bulk one. The model was also implemented in TOPAS, a commercial and very popular software, developing a specific macro allowing a larger community of users to benefit of this new opportunity of studying nanocrystalline materials. The thesis work also extended to a more traditional and general description of strain
broadening of XRD peak profiles, involving invariant forms under the Laue group symmetry operations of the material under study. As for the dynamic strain, the fundamentals of the Thermal Diffuse Scattering (TDS) contribution to the peak profiles are reviewed. Starting from the original work
of B.E. Warren, the theory is generalized to account for surface effects, leading to a particular model developed recently at the University of Trento. This model was thoroughly reviewed and corrected. To test the model a parallel computer code in C was written, exploiting Molecular Dynamics simulations for obtaining reliable and independent estimates of static and dynamic disorder in nanocrystals.
29
Lehtosalo, Jukka Antero. "Adapting dynamic object-oriented languages to mixed dynamic and static typing". Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708510.
Testo completo
30
Rebello, Gayle, e n/a. "Measuring dynamic hamstring flexibility: Dynamic versus static stretching in the warm-up". University of Canberra. School of Health Sciences, 2006. http://erl.canberra.edu.au./public/adt-AUC20070618.095511.
Testo completoAbstract (sommario):
The main purpose of this study was to compare the acute effects of static and dynamic stretching
in the warm-up, on hamstring flexibility using a reliable set-up for measurement.
Static and dynamic flexibility was measured using five modifications of the Straight Leg Raise
(SLR) test to measure hip flexion range of motion (ROM). In the first part of the study (n = 33)
hamstring flexibility was measured using a Static-passive, Static-active, Dynamic-supine and
Dynamic-standing tests. The results of this study were used to calculate reliability statistics and
to compare the various static and dynamic flexibility tests. There was a significant difference
between Static-passive (SPH) and the Dynamic-supine (DSUH) tests (p less than .05).
This was followed by an intervention study (n = 12) where participants were randomly assigned
to three intervention treatments of 225 seconds on separate days: No stretching (Treatment I),
Static stretching (Treatment 2) and Dynamic stretching (Treatment 3) in a cross-over study
design. Static stretching had no impact on dynamic hamstring flexibility; however, dynamic
stretching improved dynamic flexibility while simultaneously increasing static flexibility. This
has implications for the specificity of stretching in sport.
31
PONTES, BRUNO DO CARMO. "STATIC AND DYNAMIC SIMULATION FOR THE VOLTAGE CONTROL BY LTC AND STATIC VOLTAGE COMPENSATOR". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2008. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=13043@1.
Testo completoAbstract (sommario):
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROO tema abordado neste trabalho é a observação e análise, em regime permanente e dinâmico, da ocorrência de um fenômeno que já foi observado em condições reais de operação do sistema elétrico brasileiro, que é a relação oposta à usual entre a grandeza controlada e a grandeza controladora. Nestes caso, mesmo que haja margem de recursos para manter a tensão controlada, ela não é útil. Por exemplo, uma diminuição na relação de transformação num transformador de tapes variáveis, com intuito de aumentar a tensão controlada acaba por reduzí-la, até que os limites de troca de tapes sejam atingidos ou o sistema entre em colapso. Para demonstrar a existência do problema, foram executadas simulações, em regime permanente e dinâmico, e verificado o efeito do controle de tensão por um transformador com tapes variáveis e por compensadores estáticos de potência reativa, situações corriqueiras de um sistema de potência. Foram demonstradas situações em que foi possível verificar a mudança da região de operação. Para a análise em regime permanente foi utilizado um algoritmo de fluxo de carga, e para a análise dinâmica, uma simulação no domínio do tempo. Nas simulações envolvendo transformadores de tapes variáveis, foi possível verificar a existência o efeito reverso da ação de controle de tensão nas análises estática e dinâmica. Nas simulações utilizando o compensador estático de potência reativa houve divergência entre os resultados das duas análises.
This work presents the observation and analysis, in steady state and dynamic performance, of the phenomenon already observed in real operation conditions of the Brazilian Electric System, which is the opposite relationship between the controlled value and the target value. In this case, even if the resources have margin to keep the voltage controlled, this is not useful. For example, the reduction in the turn ratio on load tap changer transformer, with the aim of increase in the controlled voltage, result in its reduction, until the tap changer limit is reached or the system is led to the collapse. To demonstrate the existence of this problem, steady state and dynamic performance simulations were done, and the voltage control effect by on load tap changer transformer and static var compensator , current situations in a power system. Several situations where is possible verify the operation region changing was demonstrated. For steady state analysis was used a load flow algorithm and, for the dynamic analysis, a time domain simulation. In the simulations with on load tap changer transformer, it was possible to verify the existence of the reverse effect of the voltage control action in the static and dynamic analysis. In the simulations using static var compensator, a divergence was found between the results in the two analyses.
32
Grimsmo, Nils. "Dynamic indexes vs. static hierarchies for substring search". Thesis, Norwegian University of Science and Technology, Department of Computer and Information Science, 2005. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9225.
Testo completoAbstract (sommario):
This report explores the problem of substring search in a dynamic document set. The operations supported are document inclusion, document removal and queries. This is a well explored field for word indexes, but not for substring indexes. The contributions of this report is the exploration of a multi-document dynamic suffix tree (MDST), which is compared with using a hierarchy of static indexes using suffix arrays. Only memory resident data structures are explored. The concept of a ``generalised suffix tree'', indexing a static set of strings, is used in bioinformatics. The implemented data structure adds online document inclusion, update and removal, linear on the single document size. Various models for the hierarchy of static indexes is explored, some which of give faster update, and some faster search. For the static suffix arrays, the BPR cite{SS05} construction algorithm is used, which is the fastest known. This algorithm is about 3-4 times faster than the implemented suffix tree construction. Two tricks for speeding up search and hit reporting in the suffix array are also explored: Using a start index for the binary search, and a direct map of global addresses to document IDs and local addresses. The tests show that the MDST is much faster than the hierarchic indexes when the index freshness requirement is absolute, and the documents are small. The tree uses about three times as much memory as the suffix arrays. When there is a large number of hits, the suffix arrays are slightly faster on reporting hits, as there they have better memory locality. If you have enough primary memory, the MDST seems to be the best choice in general.
33
Erdal, Feride. "Web Market Analysis: Static, Dynamic And Content Evaluation". Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614694/index.pdf.
Testo completoAbstract (sommario):
Importance of web services increases as the technology improves and the need for the challenging e-commerce strategies increases. This thesis focuses on web market analysis of web sites by evaluating from the perspectives of static, dynamic and content. Firstly, web site evaluation methods and web analytic tools are introduced. Then evaluation methodology is described from three perspectives. Finally, results obtained from the evaluation of 113 web sites are presented as well as their correlations.
34
Mallakunta, Narendra. "Static and dynamic analysis of rectangular sandwich plates". Thesis, University of Ottawa (Canada), 1990. http://hdl.handle.net/10393/5984.
Testo completoAbstract (sommario):
The static and dynamic characteristics of homogeneous rectangular plates and rectangular sandwich plates are studied by the finite element method using a 8-node isoparametric rectangular element. A computer code utilizing the finite element method is developed to generate solutions for the static and dynamic analysis of homogeneous plates and sandwich plates for conditions of plane stress, plane strain, bending, and combined stress and bending for small deformation problems only. However, in this work, the scope is limited to bending problems only. Further, only the values for the center deflection are generated, in the static analysis, even though the code has the capability to generate the various stress components. In the dynamic analysis, the natural frequency and the associated mode shapes are determined. The boundary conditions are taken as free, simply supported, clamped edge constraints and their combinations. Uniformly distributed loads, concentrated loads or a combination of both can be applied. This study concentrates on free vibration problems in the case of the dynamic analysis. The effect of considering non-uniform shear distribution in the core of the sandwich plate is studied for both the static and dynamic analysis. The impact of considering two different orders of numerical integration is also studied. (Abstract shortened by UMI.)
35
Zhan, H. J. "Static and dynamic analysis of toroidal LPG tanks". Thesis, University of Ottawa (Canada), 2008. http://hdl.handle.net/10393/27611.
Testo completoAbstract (sommario):
Liquefied petroleum gas (LPG) is considered clean, safe and cheap, offering a viable alternative to conventional fuels. Nowadays, the use of LPG as a fuel source in motor vehicles is steadily increasing. The LPG tanks in motor vehicles can be of toroidal shape. The toroidal LPG tanks are generally of non-circular cross-section, and may be supported at points, lines or patches on the surface. Among the mechanical properties of interest for toroidal LPG tanks are the static behavior under internal pressure, the vibration characteristics, the buckling and collapse loads, and the properties under impact loading arising from accident conditions.
In the current work, a shell-theory finite element analysis is carried out of toroidal LPG tanks, with non-circular cross-section. The analysis serves to determine the natural frequencies, the buckling and collapse pressures, and the deformation of impacted tanks. The differential quadrature method is used as an alternate means in the vibration analysis. A variety of support conditions are considered, including lines of support at the inner and outer equators of the tank. For validation, comparison is made with previously published results for stress, vibration and buckling of circular and elliptical toroidal shells, and impact deformation of spherical and cylindrical shells. Finally, a parametric study is carried out to determine the influence on the natural frequency, buckling and collapse pressures, and the deformation of the impacted tanks, of shell size, shell thickness, material properties, and support conditions.
36
Wahba, Yohanna M. F. "Static and dynamic analyses of guyed antenna towers". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0008/NQ52445.pdf.
Testo completo
37
Nandurkar, Kuldeep Pandurang. "Static and Dynamic Behavior of Stress Coated Membranes". Thesis, Montana State University, 2006. http://etd.lib.montana.edu/etd/2006/nandurkar/NandurkarK0806.pdf.
Testo completoAbstract (sommario):
Large space mirrors need to be made of ultra-lightweight materials (membranes) that have very low densities and high flexibility (compliance) for packaging. A coating application necessary for optical reflectivity may also impart to these ultra-lightweight materials a desired shape and to help maintain that shape in the harsh environment of space. When a coating is applied on the membrane substrate, stresses develop in the coating due to atomistic processes. These stresses are fundamental to the final shape of the substrate. Coatings applied to the substrate in order to maintain a particular shape are known as the 'stress coating prescription'. As there is no way one could directly measure stresses in the coatings experimentally, in this work it will be explained how finite element analysis (FEA) was used in estimating stresses in the coatings. This work mainly comprises static pressuredeflection tests (bulge tests) on the coated and uncoated membranes, and a comparison of the experimental results to FEA findings in order to estimate the stresses in the coatings. Before FEA results are matched with the experimental results, an analytical solution to the problem in hand will be derived. Uncertainties due to variation in coating thicknesses and difficulties in coating process have led to various uncertainties in this work, and these uncertainties are also discussed. The ability to use changes in vibration frequency as a measure of coating stress is also investigated.
38
Eng, David 1978. "Combining static and dynamic data in code visualization". Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=78356.
Testo completoAbstract (sommario):
The task of developing, tuning, and debugging compiler optimizations is a difficult one which can be facilitated by software visualization. There are many characteristics of the code which must be considered when studying the kinds of optimizations which can be performed. These characteristics can include large amounts of data which would be difficult to inspect without the appropriate tools. Both static data collected at compile-time and dynamic runtime data can reveal opportunities for optimization and affect code transformations. In order to expose the behavior of such complex systems, visualizations should include as much information as possible and accommodate the different sources from which this information is acquired.This thesis presents a visualization framework designed to address these issues. The framework is based on a new, extensible language called JIL which provides a common format for encapsulating intermediate representations and associating them with compile-time and runtime data. We present new contributions which extend existing compiler and profiling frameworks, allowing them to export the intermediate languages, analysis results, and code metadata they collect as JIL documents. Visualization interfaces can then combine the JIL data from separate tools, exposing both static and dynamic characteristics of the underlying code. We present such an interface in the form of a new web-based visualizer, allowing JIL documents to be visualized online in a portable, customizable interface.
39
Davies, Timothy J. "Static, dynamic and fatigue characteristics of helical cables". Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/10916.
Testo completoAbstract (sommario):
Extensive parametric studies have been carried out, using the orthotropic sheet theoretical model of Hobbs and Raoof, on a wide range of spiral strand constructions, with outside diameters, d, and lay angles, a, in the practical ranges, 16.4 mm ≤ d ≤ 184 mm, and 11 ≤ α ≤24 , respectively. The effects of an external hydrostatic pressure on certain structural characteristics of sealed spiral strands, used in deep water applications, have also been studied in some detail, for water depths ranging from 0 m to 2000 m. The results, based on such theoretical parametric studies, have, for example, been used to refute claims by Jolicoeur that, by a simple modification, a significant improvement to the original orthotropic sheet model of Hobbs and Raoof , had been found. In addition, using such studies, axial fatigue life design S-N curves have been developed, which cater for the effects of an externally applied hydrostatic pressure on sheathed spiral strands. Simple (hand-based) formulations have also been developed for estimating the maximum frictional axial and torsional hysteresis along with ,the associated axial load range/mean axial load, and range of twist/2, respectively, at which they occur, relating to both, the in-air conditions and also when a sheathed spiral strand is subjected to an external hydrostatic pressure. The previously reported work of Raoof and his associates, in connection with the response of helical cables (spiral strands and/or wire ropes) to impact loading, has been extended to include the development of closed-form solutions for predicting the extensional-torsional wave speeds and displacements, in axially preloaded helical cables, experiencing a half-sine type of impact loading at one end, with the other end fixed. The influence of the lay angle on the response of a spiral strand to three different (i.e. unit-step, triangular and half-sine) forms of impact loading functions, has also been analysed, with much emphasis placed on the practical implications of the final results in connection with non-destructive methods of wire fracture detection under service conditions.
40
Melas, Dimitris. "Optimal investment decisions in static and dynamic environments". Thesis, London School of Economics and Political Science (University of London), 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.551337.
Testo completoAbstract (sommario):
This thesis addresses three optimisation problems. The first problem concerns static portfolio optimization. Empirical evidence suggests that asset dynamics can be characterised by a multifactor representation of asset returns. In this context, investors can capture the premium or hedge the risk associated with a particular factor through factor-mimicking portfolios. We examine different methods for constructing optimal factor-mimicking portfolios. We provide analytical considerations in the construction of factor-mimicking portfolios, along with empirical evidence. Also, we illustrate potential practical applications of factor-mimicking portfolios in the institutional investment process. The second problem addresses continuous time optimal consumption and investment for an agent investing in a complete arbitrage-free market consisting of several risky assets and a bank account. In particular, we consider a general model in which the agent's preferences exhibit a linear habit formation pattern that captures the effect of past consumption on current utility. Using duality methods, we establish the existence of an optimal consumption and investment strategy. We also prove that the optimal portfolio consumption pair can be expressed in terms of the solution to the Hamilton-Jacobi-Bellman equation that the problem's value function satisfies. The third problem concerns a general one-dimensional lro diffusion which must be maintained within an externally specified bounded interval by means of an impulse control process. We minimise a long-term average criterion that penalises deviations of the state process from a given nominal point within this region as well as the use of impulsive control effort. We solve the resulting optimisation problem and we provide an explicit optimal control strategy under general assumptions. The model that we study is motivated by several applications, including the problem of determining an optimal central bank intervention strategy aiming at the control of an exchange rate or an inflation rate, as well as the problem of designing optimal contribution policies in defined benefit pension plans.
41
O'Connor, J. P. F. "The static and dynamic analysis of arch dams". Thesis, University of Bradford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371484.
Testo completo
42
FERREIRA, LUIS FERNANDO. "STATIC AND DYNAMIC SIMULATION FOR GENERATOR VOLTAGE CONTROL". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2006. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=9454@1.
Testo completoAbstract (sommario):
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOO problema tratado nesta dissertação é a relação oposta entre a tensão de excitação de geradores e compensadores síncronos e a tensão controlada, quando o sistema de transmissão da área encontra-se muito carregado. Neste caso, a capacidade nominal de um gerador / compensador não seria útil para manter a tensão controlada. Devido à relação oposta, uma maior excitação da máquina iria abaixar a tensão controlada. O controle automático iria continuar agindo, abaixando ainda mais a tensão. Este mecanismo pode levar o sistema ao colapso e foi verificado em ponto de operação real do sistema brasileiro. Esse fenômeno ocorre quando a injeção de potência na rede de transmissão ou distribuição é elevada. Com o advento da geração distribuída, co-geração e produtores independentes, usualmente conectados à rede existente em níveis de tensão mais baixas, têm-se observado ocorrências do fenômeno. O objetivo do trabalho é então entender melhor as situações operativas reais que levam à ocorrência do fenômeno, principalmente quando existem vários equipamentos de controle de tensão ao redor do gerador em análise. A abordagem do problema baseou-se na verificação do comportamento do gerador / compensador como dispositivo de controle de tensão, no domínio do tempo e em regime permanente. Avaliaram-se as ações de controle do mesmo a partir de sete tipos de análise distintas para pontos de operação na região normal e anormal da curva SV. A real existência do fenômeno foi comprovada através de algumas destas análises. Porém, conclui-se que nem todas as formas de análise no domínio do tempo fazem uma avaliação completa do fenômeno. Dentre essas, estão a análise dinâmica agregada e a análise dinâmica agregada sob influência dos equipamentos de controle de tensão, que para pontos de operação na região anormal da curva SV não responderam em concordância com os outros tipos de análise.
The problem addressed in this research is the opposite relationship between the , synchronous generator / compensator excitation voltage and the controlled voltage when nearby network is heavily loaded. In this situation, the nominal capacity of a generator / compensator would not keep the voltage controlled. Due to the opposite relationship, the higher the excitation voltage the lower is the controlled voltage. So, the automatic control would continue acting lowering the voltage. This mechanism, verified in a real operational point of the Brazilian Electric System, can lead the system to collapse. This phenomenon occurs when the power injection into the network is high. It is prone to occur in the new scenario of distributed generation connected to already existing low voltage networks. The objective of this work is to understand the actual operative situations that lead to the occurrence of the phenomenon, mainly when there are several voltage control devices nearby the generator. The analysis of the problem was based on the verification of the generator behaviour as a voltage control device, in time domain simulation and in steady state. The control actions were evaluated from seven different ways for operating points in the normal and the abnormal region of the SV curve. The actual existence of the phenomenon was proven through some of these analyses. However, some of the time domain simulations did not evaluated the phenomenon completely. Among them, the aggregated dynamic analysis and the aggregated dynamic analysis under influence of other voltage control devices have not got the expected responses for the abnormal region of the SV curve, in comparison with other analysis.
43
Huang, Xuejiao. "Meshless investigation for nonlocal elasticity : static and dynamic". Thesis, Queen Mary, University of London, 2017. http://qmro.qmul.ac.uk/xmlui/handle/123456789/24643.
Testo completoAbstract (sommario):
The numerical treatment of nonlocal problems, which taking into account material microstructures, by means of meshless approaches is promising due to its efficiency in addressing integropartial differential equations. This thesis focuses on the investigation of meshless methods to nonlocal elasticity. Firstly, mathematical constructions of meshless shape functions are introduced and their properties are discussed. Shape functions based upon different radial basis function (RBF) approximations are implemented and solutions are compared. Interpolation errors of different meshless shape functions are examined. Secondly, the Point Collocation Method (PCM), which is a strong-form meshless method, and the Local Integral Equation Method (LIEM) that bases on the weak-form, are presented. RBF approximations are employed both in PCM and LIEM. The influences of support domains, different kinds of RBFs and free parameters are studied in PCM. While in LIEM, analytical forms of integrals, which is new in meshless method, is addressed. And, the number of straight lines that enclose the local integral domain as well as the integral radius are analyzed. Several examples are conducted to demonstrate the accuracy of PCM and LIEM. Besides, comparisons are made with Abaqus solutions. Then, PCM and LIEM are applied to nonlocal elastostatics based on the Eringen's model. Formulations of both methods are reported in the nonlocal frame. Numerical examples are presented and comparisons between solutions obtained from both methods are made, validating the accuracy and effectiveness of meshless methods for solving static nonlocal problems. Simultaneously, the influence of characteristic length and portion factors are investigated. Finally, LIEM is employed to solve nonlocal elastodynamic problems. The Laplace transform method and the time-domain technique are implemented in LIEM respectively as the time marching schemes. Numerical solutions of both approaches are compared, showing reasonable agreements. The influence of characteristic length and portion factors are investigated in nonlocal dynamic cases as well.
44
Attwood, Julia Patton. "Static and dynamic properties of polyethylene fibre composites". Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709355.
Testo completo
45
Balas, Benjamin J. (Benjamin John). "Learning about dynamic objects and recognizing static form". Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39004.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 2007.Includes bibliographical references.
The effects of observed object motion on object perception are examined in two sets of studies. The first section of the thesis provides a thorough examination of various untested aspects of the basic "temporal association" hypothesis, which suggests that object motion provides a principled basis for linking distinct images together if they appear within small time intervals. Using familiar and unfamiliar objects undergoing various forms of non-rigid motion, I ask how well this simple hypothesis predicts behavior in change detection and categorization tasks. The results favor a modified version of the hypothesis which operates over a population of units, such that increases in generalization also produce increases in image sensitivity. The observed effects of long-term knowledge concerning object appearance and expected patterns of motion also force additional modifications of the initial hypothesis to incorporate interactions between learned predictions and recent experience. Specifically, the tendency to alter patterns of generalization following dynamic exposure appears to be contingent on the stability of the direction of movement through appearance space.
(cont.) Consistent with this expanded model, performance in our categorization task appears to depend heavily on whether or not a coherent direction of movement through appearance space can be determined across both categories to be learned. In the second section of the thesis, I report the results of two parametric analyses of image encoding following dynamic exposure. In each case, I ask how the movement of an object up to the presentation of particular image affects an observers' ability to accurately recall that image. Novel, rigidly rotating objects are used in both cases to characterize the influence of appearance dynamics on short and long-term image encoding. In both cases, I find that local appearance change over time exerts a powerful influence on encoding, suggesting that both immediate percepts and visual memory are modulated by the recent past. The result is a complex picture of dynamic object perception that goes far beyond the basic principle of object motion as a tool for learning invariant recognition.
by Benjamin J. Balas.
Ph.D.
46
Singer, Neil C. "Utilizing dynamic and static stability to orient parts". Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15316.
Testo completoAbstract (sommario):
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1985.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.
Bibliography: leaves 141-143.
by Neil C. Singer.
M.S.
47
Hinchley, Sarah L. "Static and dynamic effects of sterically demanding ligands". Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/15028.
Testo completoAbstract (sommario):
This thesis is concerned with the determination of the gas-phase structures of large, asymmetric, sterically crowded molecules, with bulky alkyl ligands. Gas-phase electron diffraction is the best fluid phase technique available for the determination of structure. However, the many assumptions needed to refine these sterically encumbered molecules made complete structural determination impossible. In these cases, other fluid phase experimental data are called upon to fill in the structural detail, the main ones being liquid crystal nuclear magnetic resonance (LCNMR) and microwave spectroscopy. However, for the kind of systems under study in this thesis, it is not possible to collect data from these types of experiment. The combination of gas-phase electron diffraction data and ab initio calculations, called the SARACEN method, has overcome these problems. It has opened up the possibility of studying compounds previously beyond our capabilities. Advances in computational power mean that we can now calculate the structures of larger molecules with ~ 70 atoms to reasonable accuracy, and that our computers can now refine experimental structures up to 100 atoms in size. Previously, the SARACEN method has been applied to smaller systems of ~20 atoms. In this thesis, the method has been applied to much larger systems and many interesting features of the ligands, the effects they have on each other and the overall structures of molecules have been revealed. A series of disilanes with increasing steric bulk have been studied: 1,2-di-tert-butyltetrachlorodisilane, 1,1,2-tri-tert-butyldisilane, and 1,1,2,2-tetra-tert-butyldisilane. The structural results are surprising. The three-coordinate systems of tri(tert-butyl)sulfurtriimide and bis(trichlorosilyl)tert-butylphosphine have also been studied. Finally, the very unusual bis[bis(trimethylsily)methyl]phosphine and arsine radicals and the related dimers in the crystalline phase have been studied. Detailed analysis of the steric crowding of the solid structures has revealed the interesting new concept of ligands as energy reservoirs, which facilitate bond dissociation in the dimer.
48
Mercier, Joseph Alexander. "Static and dynamic properties of semiconductor laser arrays". Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392368.
Testo completo
49
Quartermain, Brian. "Static and dynamic pre-stressing of metal discs". Thesis, Sheffield Hallam University, 1985. http://shura.shu.ac.uk/20257/.
Testo completoAbstract (sommario):
In order to develop a technique of controlled prestressing of metal components, mild steel discs were dynamically loaded using explosives. Subsequently, mild steel discs of similar dimensions were loaded statically. The following loading conditions were studied:(i) at fixed radius and varying load (ii) at varying radial positions and fixed load (iii) at constant load and fixed radius but varying outer diameter of disc (dynamic tests only).For the dynamically loaded discs, residual radial stresses have been obtained by an experimental technique, based on strain gauge readings, which permitted the estimation of the residual stresses at the incremental radius of the successively cut sections of the discs for both outer and inner sections. Further analysis of the experimental results has produced values for the residual radial and hoop stress at radii close to the explosive loading radius. Correlation from results obtained from the statically loaded discs was provided by strain gauges fixed at varying fixed radii on each-loaded disc. The experimental analysis for the statically loaded discs was of simpler form than that required for the dynamically loaded discs. In order to establish the validity of the method for estimating the residual radial stresses, certain other experimental measurements have been made viz: planedeformation, hardness, microstructural examination and buckling tests. A theoretical model based on plastic deformation of the loaded annulus has been developed which requires an estimation of the energy transferred from the loading ring or annulus to the surface of the disc. In the majority of cases, agreement between experimental and theoretical values of residual radial and hoop stress have been found in both magnitude and sign. A further theoretical approach was applied using finite element technique to validate the equivalent stress values obtained from the experimental results of the statically loaded discs. Comparison of the results again showed good agreement in magnitude and sign.
50
Khalizeva, A. G. "Static and dynamic analysis of impulse gas seal". Thesis, Сумський державний університет, 2014. http://essuir.sumdu.edu.ua/handle/123456789/34841.
Testo completoAbstract (sommario):
Impulse seal is the type of non-contacting seal. Work of seal is based on the creation of a high-frequency pulse pressure in handling the cells. In this case it receives the name of pulsed compaction. It consists of an axially movable ring, closed chambers, a rotating wear band and radial feeders.
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