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Kashyap, Mukesh. "Decision support to avoid collapses in structural refurbishment projects". Thesis, Loughborough University, 2007. https://dspace.lboro.ac.uk/2134/34410.
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Safety management to avoid collapses during structural refurbishments of buildings has been of great concern to site professionals and management involved in structural refurbishments. The problems hindering safety in refurbishment projects were identified as: process bottlenecks, absence of a structured refurbishment process and limitations in the use of decision support tools. The aim of the research was to develop a Safety-Integrated Refurbishment Process Model (RPM) and establish its viability as the basis for a Decision Support System (DSS) to avoid structural collapses in refurbishment projects.
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Wintels, Werner. "Synoptic energetics of planetary-scale collapses of available potential energy". Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84450.
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We identify physical processes and localized atmospheric structures that modulate the global-scale atmospheric available potential energy (APE). A 1979--95 time series of Northern Hemisphere APE is derived from the National Centers for Environmental Prediction (NCEP) reanalysis. We discern an average three-day cycle in the APE depletion rate dA/dt with a time series of intraseasonal (1.6--180-day) fluctuations. Synoptic-scale APE depletion events are falls and subsequent rises in dA/dt, and are classified as APE collapses when exceeding climatologically-derived thresholds of APE fall and dA/dt. Three associated regional baroclinic waves are observed. West Pacific warm surges (Type A) accompany cyclogenesis over Japan, anticyclogenesis over the west-central North Pacific, and shallow East Asian cold surges. Bering warm surges (Type B) comprise intense southerly flow across the Bering Strait, cyclogenesis near the Kamchatka Peninsula, and intense anticyclogenesis over Alaska. Atlantic Canada warm surges (Type C) include onshore warm flow and eastern North American storm tracks.January/February 1989 brought the largest vacillation- and synoptic-scale APE collapses of the study period. A pronounced Madden-Julian Oscillation (MJO) modulated equatorial convection over the Indian Ocean during the APE build-up. The initial APE collapse coincided with Type A development and intensifying MJO convection shifting to the West Pacific warm pool, which was prominent because of the 1988--89 La Nina. Extensive large-scale ascent amplified the thermally direct Hadley cell circulation, with descent strong over East Asia. The second collapse was associated with Type B development characterized by a record-breaking Alaska anticyclone.
Factors explaining lacking precision in energy budget calculations include missing o values above 100 hPa, limited representation of subgrid processes, and limited temporal resolution of diurnal convection over tropical landmasses.
Correlation analysis shows baroclinic conversion (diabatic generation) accounting for 80% (20%) of vacillation-scale dA/dt fluctuations. Baroclinic conversion contributes considerably (69%) to the synoptic variability only during synoptic-scale APE collapses (23 January to 4 February), illustrating the prominence of resolvable baroclinic processes during these periods.
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Yuan, Xiaoping. "Extensional collapses in the overpressured frictional upper crust based on limit analysis". Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEE009/document.
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Dans ce manuscrit nous développons l'approche cinématique 2D du calcul à la rupture pour examinerles effondrements en extension (ou failles normales) de la croûte supérieure cassante qui résultent desurpressions de fluides. Les sujets d'intérêt liés à la déformation en extension sont (1) les roles de lapression des fluides, des processus de surface, et des propriétés des matériaux et des failles sur lastabilité des structures d'extension; (2) la formation de failles normales à faible pendage et de failleslistriques; (3) la distribution de la déformation au dessus d'un glissement à faible pendage; et (4)l'influence de l'adoucissement mécanique des failles et des processus de sédimentation sur cettedistribution.Cette approche mécanique est vérifiée par la théorie du prisme critique de Coulomb, et la généralise pour étudier la topographie complexe de la péninsule de Mejillones dans le Nord du Chili. Cetteapproche est aussi appliquée à l'instabilité gravitaire dans le delta du Niger en reliant les structurescompressives en bas de pente aux structure extensives en amont par un détachement profond. Nousprédisons des surpressions de fluides beaucoup plus élevée que celles obtenues par application duprisme de Coulomb. Enfin, cette méthodologie est appliquée à l'étude de la forme de failles normalesreliant un détachement profond à la surface. Dans le cas du delta du Niger, nous montrons que lesfailles à faible pendage et les failles listriques impliquent que la profondeur de rétention des fluides estfaible. La version séquentielle de l'analyse limite ouvre de nouvelles voies pour suivre l'évolutionstructurale dans le temps du jeu sur les failles normales. Les simulations montrent en particulier qu'unefaille normale tourne vers des pendage plus faibles au fur et à mesure de la dénudation du mur, formantune région qui passe du mur au toit de la faille active en rotation. La prédiction de cette région estillustrée par des expériences analogiques et des exemples de terrainThis manuscript develops a 2D kinematic approach of Limit Analysis to examine the extensionalfailures in the brittle, upper crust resulting from fluid overpressures and normal faulting. There aremany interesting topics related to the extensional deformation such as (1) the roles of fluid pressure,topographic process, material and fault properties on the stability of extensional structures; (2) theformation of low-angle and listric normal fault; (3) the deformation pattern due to slip on a low-anglefault; and (4) the influence of fault softening and sedimentation processes on this deformation pattern.This mechanical approach applied to wedge prototypes is validated by the critical Coulomb wedge(CCW) theory, and it generalizes the CCW theory to investigate the complex topography on theMejillones peninsula, Northern Chile. Additionally, this approach is also applied to investigate gravityinstability of Niger Delta by linking down-slope compressional to up-slope extensional failures througha deep detachment. We predict much higher fluid overpressures than that of the CCW theory. Finally,this Limit Analysis methodology is applied to investigate the shape of normal fault linking a lowdetachment to the surface. The application to Niger Delta implies that the formation of very low-angleand strongly listric faults results from a shallow fluid-retention depth. The sequential version of LimitAnalysis opens new ways to envision the structural evolution through time resulting from normalfaulting. The simulations show that the normal fault rotates during extension, forming a region of Footto-Hanging Wall (FHW) where the material in the footwall is sheared upon entering the hanging wall.The creation of the FHW region is illustrated by sandbox experiments and field examples
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Arcangeli, Daniele. "Scenarios of lateral collapses of the Vavilov seamount in the central Tyrrhenian sea". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18134/.
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The strong EW asymmetry observed for the Vavilov seamount could be the result of an ancient collapse from its western flank. Two scenarios for the pre-collapse morphology of the seamount are built up by reshaping the western flank of Vavilov and modelling it as the eastern one. In scenario 1 the detached mass is assumed to slide down on the present bathymetry, i.e. the sliding surface outside the detachment niche is identified with the today’s abyssal plane to the west of Vavilov. Instead, in scenario 2 it is assumed that the difference between the depth of the western (less deep) and eastern (deeper) abyssal planes is due to the deposition and subsequent reworking of the collapsed material. Therefore, in scenario 2 the identified deposit is removed from the present bathymetry, while the western flank is reshaped approximately like in scenario~1.
The motion of the landslide is simulated by the model UBO-BLOCK2, developed by the Tsunami Research Team of the University of Bologna, that treats it as a grid of blocks sliding under the effect of friction, drag forces and interaction forces. The influence of various parameters on the model's output is discussed for simulations that regard scenario 1. For scenario 2, the agreement between the hypothesised deposit and the one computed through the simulations is used to tune the model parameters, and in particular the sea bottom friction coefficient, that is the one that most affects the landslide motion.
The conclusion of the thesis is that scenario 2 supports reasonably well the hypothesis that the Vavilov seamount experienced a collapse of the western flank, that the collapsed material filled the western abyssal plane causing an average decrease of the sea floor depth by hundreds of meters, that most of the material accumulated not too far from the feet of the Vavilov’s seamount, which is consistent with the available seismic lines.
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Khan, Muhammad Abbas. "Detection of collapses and communicating with inaccessible areas in underground coal mines using WSN". Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2016. https://ro.ecu.edu.au/theses/1782.
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Wireless sensor networks (WSN) are used in underground mines to monitor concentration of gases, temperature, and humidity. A WSN deployed in underground mines can also be used for localisation of miners and for detecting collapses. Underground coal mines consist of long and narrow tunnels, several hundred metres beneath the surface of earth. These tunnels can be several kilometres long, with the width and height of these tunnels being no more than a few metres. A WSN in underground coal mine is an example of a chain type wireless sensor network (CWSN). CWSNs are special types of WSNs in which sensor nodes are placed along an elongated geographical area with the nodes forming a chain topology. In CWSNs, their shape dictates network design. Unlike other large scale WSN, there is only one path for data transfer in CWSNs. Hence the probability of network getting broken in disjoint sections, due to node failures, is much higher in CWSNs compared to other large scale WSNs. Disjoint sections are two sections of the same network which are out of the communication range of each other. When the network is broken into two or more disjoint sections, the sink node loses connectivity with parts of the network and hence some areas are left unmonitored despite having functional sensor nodes.
In the first contribution chapter of this thesis, we design a distributed connectivity restoration algorithm for generic chain-type wireless sensor networks. We usemovable relay nodes to restore connectivity in the network. Our algorithm strivesto move a minimum number of relay nodes while only requiring local knowledge ofthe network. In the second contribution chapter, we consider the scenario of collapses occurring in underground coal mines. We design an algorithm for detecting collapses in chapter four. A collapse may leave parts of the mine inaccessible and unmonitored. A collapse will also break WSN into two or more disjoint sections which are physically separated by the collapse consisting of soil and rock. We investigate the propagation characteristics of EM waves through soil and rock. We determine the factors on which communication range of EM waves through soil depends on. We propose special movable relay nodes which use low frequency and high power transmitters to communicate through a collapsed area of the mine, restoring connectivity in the WSN. We design an algorithm to restore connectivity through collapsed areas of the underground mine tunnels using these special movable relay nodes. Communicating with inaccessible area of the mine will help locate miners which may be trapped in that section and will enable the network to monitor the inaccessible area of the mine.
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Alston, Sylvia, i n/a. "Where meaning collapses: a creative exploration of the role of humour and laughter in trauma". University of Canberra. Professional Communication, 2009. http://erl.canberra.edu.au./public/adt-AUC20091215.114305.
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The thesis consists of a full-length novel and an exegesis that examines the ways in which humour can be used to restore the symbolic order and serve as a means of regaining control, thus allowing those involved in the most disturbing, painful and challenging situations to feel less powerless.
The research component of the thesis involved critical reading, fieldwork, observations, and personal interviews. The texts examined include works by Michael Billig, Henri Bergson and Julia Kristeva, in particular her reference to the act of laughing at the abject as a kind of horrified 'apocalyptic laughter', a compulsion to confront that which repels (Kristeva 1982, pp. 204-206). As part of the fieldwork, I completed training to become a Laughter Club leader. Laughter Clubs are based on the notion that laughter, even fake laughter, is beneficial. This concept is explored in more detail in the exegesis. The fieldwork also included training in laughter-generating activities for students and staff at two local primary schools. The observational component, which involved the Australian War Memorial, the 'Reveries: Photography and Mortality' exhibition, Norwood Crematorium and the children's garden and babies' rose garden at the Gungahlin cemetery, enabled me to examine images and memories of death as well as the responses of other visitors. The final component of my research involved personal interviews. The participants in these interviews were drawn from a diverse range of fields including: volunteers at a local hospice, hospital clowns, general practitioners, cancer survivors and their carers, a psychiatrist, nurses, a paramedic, a police officer, a hospital teacher and bereaved parents.
The findings from this research provided the framework for the creative piece, a novel set in present-day Canberra. The story begins one autumn evening when thirteen-year-old Sam is found unconscious and bleeding from a head wound. By the time Maggie, Sam's widowed mother, arrives at the hospital, Sam has regained consciousness. His x-rays show a large mass in his brain and he is kept in for further tests. The results confirm that Sam has an inoperable tumour. Maggie and Sam rely on humour in their interactions both with each other and with other people as a means of maintaining that 'baseline of social control' (Kristeva 1982, p. 99), staying on the edge of what Kristeva refers to as the place 'where meaning collapses' (p. 2).
Humour is their anchor, enabling them to maintain a grip on their new normality. And, as if having a dying child isn't enough to cope with, Maggie is being pursued by a handsome and slightly younger man.
Both the findings in my exegesis, and the creative work they led to, suggest that although there has been an enormous amount of research undertaken over the previous thirty or so years, there is no conclusive proof that humour can be closely correlated with health. At best, humour can provide a means of controlling that which would otherwise be outside our control.
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Hoyte, Catherine, i n/a. "An Australian Mirage". Griffith University. School of Arts, Media and Culture, 2004. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20040719.103628.
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This thesis contains a detailed academic analysis of the complete rise and fall of Christopher Skase and his Qintex group mirage. It uses David Harvey's 'Condition of Postmodernity' to locate the collapse within the Australian political economic context of the period (1974-1989). It does so in order to answer questions about why and how the mirage developed, why and how it failed, and why Skase became the scapegoat for the Australian corporate excesses of the 1980s. I take a multi-disciplinary approach and consider corporate collapse, corporate regulation and the role of accounting, and corporate deviance.
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Senac, Geoffrey. "Automatic load shedding scheme and the integration of new capacitors’ controller in the South-West region of France to mitigate large scale voltage collapses". Thesis, KTH, Elektriska energisystem, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-153666.
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Since the modern world is totally dependent on electricity, it is necessary to ensure that electrical power is generated and transmitted to end users with minimum interruptions. Given the importance of electricity for the operation of our society, it is really important to fill continuously good safety conditions. This policy must handle two major areas: reducing the risk of occurrence of a crisis and its management if a very constraining disturbance happens. This master’s thesis is mainly focused on this last point. With the continuous increasing of consumption and the high investment costs, it becomes more complicated to ensure good safety margins, since the network is exploited closer to its limits. A recent study demonstrates that the South-West region of France was prone to voltage collapses after very severe faults and as a result the need of an under-voltage load shedding in this region was evokated. In parallel, to ensure the voltage stability, RTE (Réseau de Transport d’Electricité - Electricity Transmission Network) has invested also in equipments such as capacitors and static reactive power compensators. With newly installation of compensation means on the network, the necessity to develop a new device called SMACC (Système avancé pour le contrôle de lacompensation - Advanced system for the control of the compensation) capable of handling more efficiently the control of these batteries of capacitors has been highlighted. Ultimately the thesis focuses also on the new HVDC (High-voltage direct current) line between France and Spain. This line is a key for long-term voltage stability study, since itincreases the exchange capacity between France and Spain, and has the ability to provide or absorb reactive power to the network.
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Ånäs, Kristoffer. "The Significance of Giant Flank Collapses on Magma Ascent in the NE Rift Zone of Tenerife, Canary Islands: A Structural Modelling and Diffusion Approach". Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-438578.
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On the volcanic ocean island Tenerife in the Canary archipelago, several giant flank collapses haveoccurred over the last one million years. The link between the lateral collapses and the resultingvolcanism in the rift zones is not fully understood and was investigated within the framework of thisproject. A field survey along the north eastern rift zone on Tenerife was performed, where dyke intrusionstructural data was collected to analyse the exact distribution of dykes in the area. To determine themagma ascent rate, diffusion analysis of major elements in olivine crystals was conducted incollaboration with ETH Zürich. Additionally, analogue gelatine model experiments were performed toimprove the understanding of the processes that reconfigure linear rift zones to triaxial or multiaxial riftzones. Injections of fluid into the gelatine ridges produced fractures which mainly were linear andfollowed the along strike direction. Position A’ in the centre of the unstable section, produced the mostdiverse injection patterns and had a roughly 30 % higher acceleration compared to position A, positionedat the border of the unstable section. From the results of the diffusion modelling of Mg in olivinephenocrysts an ascent rate of the magma was calculated to an average ascent velocity of 10.4–14.0 km/h.This is extremely fast and suggests that the Orotava collapse is strongly connected to the formation ofankaramite dykes in the area as a result of sudden decrease in the lithostatic pressure.På vulkanön Teneriffa i den kanariska övärlden har flera jättelika skred skett. Kopplingen mellan dessaskred och vulkanismen i sprickzonerna på ön har undersökts inom ramen för detta arbete. Enfältundersökning genomfördes längs den nordöstra sprickzonen på Teneriffa, där data ommagmagångarnas orientering och läge insamlades. För att bestämma hur snabbt magman steg till ytan,genomfördes diffusionsanalys av Mg i olivinkristaller från ankaramitgångar i samarbete med ETH iZürich. Utöver det utfördes även experiment med analoga gelatinmodeller för att förbättra förståelsenför de processer som förändrar linjära riftzoner till treaxliga eller fleraxliga riftzoner. Injiceringen avvätskan i gelatinmodellerna producerade sprickor som i huvudsak var linjära och följde strykriktningenpå riftzonen. Position A’, i mitten av den instabila sektorn i modellen gav högst variation avinjiceringarna och hade omkring 30 % högre acceleration jämfört med position A placerad i kanten avden instabila sektorn. Baserat på resultatet av diffusionsmodelleringen kunde en uppstigningshastighetför magman beräknas till en medelhastighet på 10,4–14,0 km/h. Detta är extremt snabbt och visar attkollapsen av Orotava är starkt kopplad till bildningen av ankaramitgångar i området som ett resultat aven plötslig minskning av det litostatiska trycket.
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Clowney, Patrick. "Colossal Collapses| An Analysis of 11 Department of Defense Acquisition Program Management Factors that Influence Department of Defense Acquisition Program Termination Using Relative Importance Weight and Chi-squared Distribution". Thesis, The George Washington University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10150142.
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The United States Department of Defense (DoD) loses billions of dollars annually on cancelled or failed acquisition programs. Several DoD acquisition studies, Office of Management and Budget Studies, Government Accountability Office Reports, as well as other studies highlight the disturbing fact, of a plethora of programs that fail to meet full operational requirement capabilities, and therefore, are eventually cancelled. In these cases, the DoD loses billions of investment dollars without any return. Scholars, program managers, and systems engineers posit that there are a host of factors that influence whether a program is cancelled or allowed to continue. They include, but are not limited to political pressures, cost overruns, schedule overruns, and performance shortfalls.
The research here aims to add to the body of knowledge of systems engineering, program management, and the factors that influence acquisition program terminations within the United States Department of Defense (DoD). Specifically, this research surveyed the United States DoD acquisition program managers, defense industry program managers, and defense industry consultants, to evaluate and analyze the key program factors that influence DoD acquisition program terminations. The research also conducted a comparison of different attributes that would lead to project failure amongst various groups. This research used relatively important weight calculations and a chi-squared distribution analysis in order to compare the differences between DoD acquisition program managers, defense industry program managers, and defense industry consultants, with regards to the factors that lead to DoD acquisition program terminations. This research aims to further answer several interrelated research questions, in order to identify the factors that have the greatest influence on program and project cancellation from the expert’s perspective, and capture any significant differences between DoD program managers, DoD industry personnel, and DoD consultants. The research questions include the following:
1) Are there any statistically significant differences between what DoD program managers, DoD industry personnel, and DoD consultants personnel think influence program cancellation? 2) Are there statistically significant differences of the various DoD acquisition program factors between what DoD program managers, DoD industry personnel, and DoD consultants personnel think influence program cancellation?
An exhaustive literature review identified 11 critical factors that were associated with program management for examination. For this study, the examination and methodology used were the Relative Importance Weight technique, to analyze the attributes and factors. RIW methodology consisted of conducting a survey to identify and evaluate the relative importance of the signi?cant factors influencing program termination. Respondents of this survey included the following groups: 1) DoD program and project managers, 2) DoD Industry personnel, and 3) DoD consultants. The outcomes of this research serve three primary purposes: 1) identify the Relative Importance Weight of DoD acquisition program factors that influence program termination, 2) fulfill a system’s engineering and program management’s knowledge gap, by understanding and identifying the most critical factors within the unique DoD acquisition program management system, and 3) serve as a spring board for future research for DoD program management. The results of this research indicate that a statistically significant difference does not exist between the three groups with relative importance of 11 program management factors.
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Lans, Benjamin. "Genèse des systèmes karstiques de Gironde (Entre-deux-mers et Graves) : role de la "fantômisation" et du potentiel hydrodynamique dans les calcaires oligocènes, crétacés et miocènes". Thesis, Bordeaux 3, 2014. http://www.theses.fr/2014BOR30058.
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Cette thèse a pour objet d’appliquer le nouveau paradigme de la fantômisation en Gironde (France), principalement aux calcaires tertiaires, et secondairement aux calcaires crétacés. La fantômisation transforme, par des processus vraisemblablement biochimiques, la roche saine en roche poreuse, en conservant le volume initial. On parle alors d’altération isovolumique ou « géoporose ». L’intérêt de la Gironde est de comporter de vastes étendues carbonatées plus ou moins karstifiées, dont l’Entre-deux-Mers et ses nombreuses grottes. Les calcaires de l’Oligocène inférieur montrent en carrière des phénomènes d’altération qui peuvent servir de modèle pour expliquer la genèse des cavités locales. L’intérêt de cette région est de présenter différents stades évolutifs de karstification par fantômisation, en fonction du potentiel hydrodynamique. On observe tous les stades en zone de plaine et de bas plateau : - des systèmes karstiques incipients, en phase de formation, situés en rive gauche de la Garonne, en zone de battement de nappe phréatique ; - des systèmes karstiques jeunes, en zone dénoyée, de type perte-résurgence, en Entre-deux-Mers ; - des systèmes karstiques complexes impliquant plusieurs étages calcaires fantômisés, du Crétacé supérieur à l’Oligocène et au Miocène, au sud de la Gironde ; - des paléokarsts du Pléistocène moyen probable, fossilisés par des sédiments ; - des paléokarsts précoces, correspondant à une phase préliminaire de sédimentation dans des zones fantômisées, récemment exondées par abaissement relatif du niveau phréatique (surrection). Tous ces stades d’évolution de la karstification permettent de bâtir en Gironde un modèle de spéléogenèse en fonction du paramètre hydrodynamique, qui commande l’évacuation mécanique de l’altérite. Ce nouveau regard sur la spéléogenèse offre l’occasion de mieux comprendre le fonctionnement des sources de rive gauche, qui présentent des débits réguliers très tamponnés. Le pompage des eaux souterraines, depuis plus de 30 ans, provoque un rabattement de la nappe phréatique, qui pourrait expliquer localement certains effondrements et l’assèchement de plusieurs sources. Ces aspects de génie civil montrent l’intérêt de cette problématique à la frontière recherche fondamentale / recherche appliquée. En effet, l’alimentation en eau de l’agglomération bordelaise provient exclusivement des terrains cénozoïques, et en particulier de l’OligocèneThe aim to this PhD thesis is to apply the new ghost-rock alteration paradigm to the Gironde (SW France), first to tertiary limestone, then secondarily to cretaceous limestone. The ghost-rock alteration transforms, probably by biochemical processes, the unweathered rock to porous rock, keeping its original volume. This is also called isovolumic alteration or "geoporosis". The interest of the Gironde is that it presents large carbonated areas, more or less karstified, especially the Entre-deux-Mers limestone plateau and its numerous caves. In quarries, the limestone from early Oligocene shows alteration phenomena that can be used as a model to explain the genesis of local caves. The advantage of this area is to present different evolutionary stages of karstification by ghost-rock alteration, depending on the hydrodynamic potential. We can observe all the stages in plains and low plateau areas: - Incipient karstic systems, in genesis phase, situated on the left bank of the Garonne river, in the groundwater table variation level; - Young karstic systems in dewatered areas, lost-resurgence type, in the Entre-deux-Mers; - Complex karstic systems formed by several limestone layers, affected by ghost-rock alteration, from late Cretaceous to Oligocene and Miocene, in the south of the Gironde; - Palaeokarsts probably dating from middle Pleistocene, clogged with sediment; - Early palaeokarsts, corresponding to a preliminary phase of sedimentation into ghost-rock altered areas, recently dewatered by a relative lowering of the water table (uplift) . All these stages of karstic evolution in Gironde help us to build a speleogenesis model, based on hydrodynamic parameters controlling the mechanical removal of the alterite. This new look at the speleogenesis is an opportunity to better understand the functioning of the sources situated on the left bank, which have regular and highly buffered flows. The pumping of groundwater for more than 30 years, causing a lowering of the water table, could explain some local collapses and depletion of several sources. These aspects of civil engineering show the importance of this issue at the limit of fundamental / applied research. Indeed, the drinking water of Bordeaux agglomeration is provided exclusively from cenozoic grounds, and in particular oligocene limestone
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Feuer, Mia. "Collapse". VCU Scholars Compass, 2009. http://scholarscompass.vcu.edu/etd/1820.
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Through large sculptural works that are often caricatures of representational objects, my work explores the complicated moments and tangled histories of childhood Jewish schooling in Winnipeg and travels to Israel and Palestine as an adult. My thesis exhibition Collapse, as well as most of my graduate work, examines my investigation through manmade constructions that control and restrict or unite and connect the movement of others. Sculptures about a destroyed bridge’s imagined longing for exotic places, a giant onion serving as a resuscitation mechanism against tear gas or a construction crane to Armageddon are some examples of work that explore the poetry I find in dichotomies, and serve as a series of recollections that negotiate experiences beyond full understanding.
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Normann, Andrew J. "Twice Collapsed". Bowling Green State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1428515708.
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Constan, Lea. "On Collapse". Thesis, Konstfack, Textil, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:konstfack:diva-7802.
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This project is an active exploration of subjectivities through the medium of weaving. In a narrative illustrated with woven works, the emotional trajectory of this person of mixed cultural background through Swedish society is described. First, the work is contextualized in terms of the larger politico-cultural-discursive context, entitled the outside. It is then positioned in terms of the individual context, the inside, largely dramatized as the developments in the art of western tapestry in the past century. This culminates in the final works, three of which are presented in the final exhibition. They are entitled monads, the etymology of which, in Greek, relates to the words one, alone, or singularity. Each is a conceptual microcosm proposing a different light distribution scheme. They are imprints of alternative actualizing tendencies. There could only be one; at the end of the experiment, Schrodinger’s cat is either dead or alive. The collapse involves the very structure of the ground, and is therefore embedded directly into the weave structure. But remember, each act of observation is an irreversible disturbance to the system. In the interpretation of the primary emanation arises difference, but in which direction will the pendulum swing, and on what forces does its motion hinge? Do subjectivities follow the locality assumption? Do you produce subjectivities or do they produce you?
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Croudace, Katherine Margaret. "Relativistic cosmological collapse". Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627524.
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Huber, Sacha. "Economic Theories of Collapse". St. Gallen, 2008. http://www.biblio.unisg.ch/org/biblio/edoc.nsf/wwwDisplayIdentifier/06612162001/$FILE/06612162001.pdf.
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Ochsendorf, John Allen. "Collapse of masonry structures". Thesis, University of Cambridge, 2002. https://www.repository.cam.ac.uk/handle/1810/244820.
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This dissertation examines the collapse of masonry structures in response to large support displacements and horizontal ground accelerations. There are two main classes of masonry structure: arches that thrust, and supporting elements, such as walls and buttresses, which resist the thrust. This dissertation analyses the safety of arches and buttresses and identifies the resulting collapse mechanisms due to support displacements or horizontal accelerations. In particular, this research investigates the stability of a masonry arch supported on buttresses and the conditions necessary for collapse to occur. Engineers are frequently asked to determine the safety of masonry structures that have been severely distorted over the years, often due to subsidence or other long-term movements in the foundations, and this dissertation provides guidance in the assessment of such structures. The resistance of masonry buttresses to high-level horizontal loads is examined. In the case of failure due to overturning, a fracture will develop in the masonry, significantly reducing the resistance of the buttress. The capacity is further reduced by outward leaning of the buttresses, a common source of distress for masonry structures due to movements in the supporting foundations. Based on these considerations, new measures of safety are proposed for buttresses under horizontal loading. Outward leaning of the buttresses increases the span of the arch or vault. Spreading supports will cause large deformations in the arch, which increase the horizontal thrust of the arch and may lead to collapse. In addition, lateral ground accelerations can cause the collapse of arches. The influence of seismic action can be approximated to first order by equivalent static analysis to determine the initial collapse mechanism. These problems are analysed for circular masonry arches, and the collapse conditions are identified for various geometries. The findings are combined to investigate the stability of the masonry arch supported on buttresses. The safety of the system is examined by studying the influence of imposed displacements. As the buttresses lean, the thrust of the vault increases and the resistance of the buttress decreases. The collapse mechanisms are identified for both the static case of leaning buttresses and the dynamic case of horizontal acceleration. This analysis illustrates that the arch will collapse and the buttresses will remain standing in most cases. Based on these considerations, new methods are proposed for assessing the safety of masonry structures and determining the influence of future movements on the stability of existing masonry structures.
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Tziannaros, M. "Modelling bladder-collapse flow". Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1317813/.
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The thesis is concerned with the modelling of urinary motion during bladder collapse and is mathematically based. The bladder model as a collapsing vessel is developed as a step towards complementing use of nomograms. Urine motion inside is taken as unsteady flow of incompressible fluid, while the dimensions and collapse rate of the vessel are prescribed using data which is close to realistic biological values. Evolutions of velocities, volume ow rates and effects of the collapse rate are examined. An introduction is made which includes lower urinary tract urodynamics as well as the unique feature that the bladder changes shape and size substantially compared with other vessels. An investigation of simple two-dimensional shapes takes place in chapter two, along with limiting cases for thin vessels. Chapter three analyses simple axisymmetric shapes especially the sphere because of its relevance in addition to its fundamental nature. Development of a numerical scheme is addressed in the next chapter to tackle more complex shapes through the boundary element method and an iterative finite difference scheme with emphasis on flexibility of approach. An extension to more advanced structures of the vessel is constructed in chapter five by means of a concise boundary condition and shape definition. Chapter six takes the work a step further as the approach is applied to axisymmetric configurations. While in an appendix, an extension to implement full viscous effects is then inspected. Finally, further work is discussed in the conclusion.
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Skinfill, Craig Ernest. "Electromagnetism in Gravitational Collapse". BYU ScholarsArchive, 2005. https://scholarsarchive.byu.edu/etd/349.
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A numerical approach to including electromagnetism with general relativity is developed using GRAXI as a starting point. We develop a mathematical model describing electromagnetism coupled to a scalar field in an evolving axisymmetric spacetime. As there are numerous formulations of electromagnetism, we evalute different formulations in a limited flat space case. The full curved space system is then developed, using the flat case as a guide to implementing electromagnetism. This model is then implemented using GRAXI as a code base.
20
Papapietro, Luca. "Gravitational collapse and Hawking radiation". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/17999/.
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This thesis is organized as follows:
In chapter 1 the theory of a massless scalar field in curved spacetime is introduced. Furthermore the Bogolubov transformation are discussed.
In chapter 2 the Hawking effect is derived with the necessary approximations. Then it is briefly mentioned the problem of the information loss paradox
In chapter 3 the contribution of the Hawking radiation to the bi-dimensional stress energy tensor is analyzed.
In chapter 4 a generic model of gravitational collapse is analyzed with emphasis on the quantum effects. Then we restrict to the case of the collapse of a thin shell, and the accuracy of the Unruh state approximation is examined.
In chapter 5 the proposals that the emission of pre-Hawking radiation could prevent the formation of an event horizon for a collapsing object are analyzed.
In chapter 6 the arguments which aim to disprove the possibility that pre-Hawking radiation could prevent the formation of a black hole are discussed. Then is questioned the existence of pre-Hawking radiation.
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Skinfill, Craig Ernest. "Electromagnetism in axisymmetric gravitational collapse /". Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1152.pdf.
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Omukai, Kazuyuki. "Protostellar Collapse with Various Metallicities". 京都大学 (Kyoto University), 2000. http://hdl.handle.net/2433/181102.
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Aguilar-Martinez, Silvestre. "Critical collapse of Newtonian fluids". Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/54754.
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This thesis constitutes a numerical study concerning the dynamics of an inviscid
fluid subject to Newtonian gravity. Type-II critical phenomena has been previously measured in gravitational collapse simulations of isothermal-gas-spheres in Newtonian gravity. Our first objective was to extend this work by applying the more general polytropic-gas equation-of-state to the spherically symmetric fluid. We showed that under generic conditions of critical collapse, the polytropic gas allows for scale-invariant solutions. These solutions display self-similarity of the first kind with non-linear scaling between the space and time variables. One of these solutions was identified as the critical solution in critical collapse simulations. Such solution was found to have a single unstable mode with a Lyapunov exponent whose value depends on the polytropic index (Γ) from the equation of state. We argued that this behavior constitutes evidence of type-II critical phenomena with a transition from type-II to type-I behavior occurring at Γ ≥ 6/5. Thus, the polytropic gas exhibits both types of critical behavior. These phenomena was investigated dynamically and also from perturbation analysis. In the second phase of the project we extended the hydrodynamic model to treat
axi-symmetric gravitational collapse. This allowed us to study the effect of angular momentum on the critical solution. As previously predicted, infinitesimal initial rotation introduces a non-spherical, unstable axial mode into the dynamics. The measured scaling behavior of the specific angular momentum of the collapsed core agrees with the predicted growth rate (Lyapunov exponent) of the axial perturbation. This two-mode linear regime modifies the scaling laws via the introduction of universal functions that depend on the two-parameter family of initial data. The predicted universality of these functions was confirmed through careful measurements of the collapsed mass and its angular momentum near the collapse threshold. A two-parameter space survey reveals a universal behavior of the order-parameters, with no mass-gap even in the presence of finite initial rotation. The behavior changes slightly beyond some initial rotation threshold. The results then, can be interpreted as an intermediate convergence to a non-spherical self-similar critical solution with a single unstable mode.Science, Faculty of
Physics and Astronomy, Department of
Graduate
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Akbarian, Kaljahi Arman. "Numerical studies in gravitational collapse". Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/56287.
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In the first part of this thesis, we solve the coupled Einstein-Vlasov system in spherical symmetry using direct numerical integration of the Vlasov equation in phase space. Focusing on the case of massless particles we study critical phenomena in the model, finding strong evidence for generic type I behaviour at the black hole threshold that parallels what has previously been observed in the massive sector. For differing families of initial data we find distinct critical solutions, so there is no universality of the critical configuration itself. However we find indications of at least a weak universality in the lifetime scaling exponent, which is yet to be understood. Additionally, we clarify the role that angular momentum plays in the critical behaviour in the massless case. The second part focuses on type II critical collapse. Using the critical collapse of a massless scalar field in spherical symmetry as a test case, we study a generalization of the BSSN formulation due to Brown that is suited for use with curvilinear coordinates. We adopt standard dynamical gauge choices, including 1+log slicing and a shift that is either zero or evolved by a Gamma-driver condition. With both choices of shift we are able to evolve sufficiently close to the black hole threshold to 1) unambiguously identify the discrete self-similarity of the critical solution, 2) determine an echoing exponent consistent with previous calculations, and 3) measure a mass scaling exponent, also in accord with prior computations. Our results can be viewed as an encouraging first step towards the use of hyperbolic formulations in more generic type II scenarios, including the as yet unresolved problem of critical collapse of axisymmetric gravitational waves. In the last part, we present simulations of nonlinear evolutions of pure gravity waves. We describe a new G-BSSN code in axial symmetry that is capable of evolving a pure vacuum content in a strong gravity regime for both Teukolsky and Brill initial data. We provide strong evidence for the accuracy of the numerical solver. Our results suggest that the G-BSSN is promising for type II critical phenomena studies.Science, Faculty of
Physics and Astronomy, Department of
Graduate
25
Herbauts, Isabelle Manon. "Causal wave function collapse model". Thesis, Queen Mary, University of London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427988.
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Back, Trevor. "Ionisation induced collapse of minihaloes". Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7608.
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The first stars, galaxies and black holes in the universe produced large quantities of ionising UV radiation; forming H II regions in the neutral gas before the Epoch of Reionisation (EoR). These ionisation fronts will have come into contact with overdensities in the surrounding Intergalactic Medium (IGM), including haloes which were in the process of collapse. Previous studies have shown that the feedback processes on these secondary haloes can either disrupt the gas, or induce further cooling from the formation of molecular hydrogen. The ionising source will eventually die and create a defunct H II region, which expands into the surrounding neutral IGM. Minihaloes at the edge of these defunct H II regions are particularly susceptible to positive feedback due to not having been photoevaporated like their counterparts further inside the ionised volume. In this thesis, numerical simulations of minihaloes at the edges of H II regions formed by the first luminous objects before the EoR are presented. A methodology of including secondary ionisations from high energy photons is also implemented into the radiation hydrodynamical code ZEUS-RT. The interaction of differing spectral index sources with minihaloes including secondary ionisation is discussed. The secondary ionisations show the greatest effect for hard spectral sources with a large fraction of high energy photons; where a decrease in photoheating and an increase in ionisation rate is found at the outer reaches of the ionisation front (I-front). The increased ionisation rate lowers the optical depth of the gas for subsequent photons, and thus reduces the trapping of I-fronts in high densities found in the minihalo cores. The ratio of the free electron fraction to the temperature in the core of the minihaloes is found to constrain the resulting evolution. A high ratio is correlated with the creation of molecular hydrogen, which can then induce further cooling and the collapse of the system.A large parameter suite of 3780 two-dimensional minihalo models utilising radiative hydrodynamical simulations with 12 species and a coupled reaction network, including H2 cooling, HD cooling, Lyman-Werner radiation and secondary ionisation is performed. The parameter space includes: the spectral index representing different sources such as quasars or galaxies, the mass of the minihaloes from 105 - 106 Mʘ, the redshift of ionisation from z ~ 10 - 30, and other factors which denote the position of the minihalo relative to the boundary of the H II region. Minihaloes with average core densities of n0 = 2 - 10 cm-3 show almost unanimous positive feedback, while the majority of minihaloes under this average density are disrupted. Minihaloes with core densities above this value generally would have collapsed in isolation anyway, but are found to not be delayed by the I-front. The H2 fraction in the minihalo gas is also increased in models with no blowout by factors between 2 - 100 times that of an isolated minihalo. This is especially significant for lower redshift, z ≤ 15, minihaloes. Finally, a parameter suite of larger 106 - 107 Mʘ minihaloes results in the creation of self-gravitating clumps of gas moving out of the dark matter potential. The gas core is compressed by the I-front, enriched with molecular hydrogen, and ejected by the pressure front after the source dies. These "baryon bullets" could be progenitors of primordial globular clusters found in the haloes of galaxies today. Properties such as old stellar populations and the lack of dark matter haloes can be explained by this radiative ejection method. The dynamical nature of these interacting systems and diversity of subsequent evolution suggest that minihaloes less than 108 Mʘ are important in the early formation history of the universe, and in determining the constraining parameters of the EoR. The feedback mechanisms investigated, and secondary ionisation physics, should be included in astrophysical simulations and analytical calculations determining the evolution of the universe at this critical epoch.
27
Eldridge, J. J. "Progenitors of core-collapse supernovae". Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598804.
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The progenitors of core-collapse supernovae are stars with an initial mass greater than about 8M⊙. Understanding the evolution of these stars is necessary to comprehend the evolution and differences between supernovae. We have constructed new and unique opacity tables to increase model accuracy during the latest stages of stellar evolution. We have investigated how initial mass, initial composition and mass loss affects the progenitors and their populations. There are many prescriptions for mass loss. Different research groups use their preferred rates. We have compared 12 different prescriptions and determined which provides the best fit to observations. We use our preferred mass-loss scheme to make suggestions as to the source of the differences between supernova types from our progenitor models. Binary evolution is considered in order to search for low luminosity SN progenitors and progenitor types not possible from single stars. Removal of the hydrogen envelope is more common and we find quite different hydrogen deficient SN progenitors. We discuss the implications of our binary models for ultra-luminous X-ray sources and gamma-ray bursts. We present an estimation of the mass distribution for black holes at various metallicities showing that massive black holes are not formed until very low metallicities. Finally we combine the single star and binary results to determine their relative populations and compare to observations. However it is not possible to draw many firm conclusions because of the uncertainty in observations to date.
28
Agelidis, Nicholas. "Collapse of stringer-stiffened cylinders". Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37384.
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Langroudi, Arya Assadi. "Micromechanics of collapse in loess". Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5284/.
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Soil collapse is amongst one of the most significant ground related hazards. A collapsible soil, in particular loess, typically has an open-structure and collapse occurs when as a consequence of the addition of water and/or load the particles rearrange to form a more dense fabric. Collapse leads to a suite of problems for buildings and infrastructures built on or in collapsing soil. Treatment to mitigate collapse often involves in densification. However, such approaches have been reported not always effective enough to combat the problem. This stems from a lack of understanding of soils’ geochemistry and structure, the result of which is an oversimplification of complex geotechnical and geological interactions. An important example of such limited knowledge is the increasing evidence of restoration of the collapsing structure upon wetting-drying cycles, which is widely ignored in the current compaction practice. This research aims to first identifying collapse micro-mechanisms in fine-grained soils, examining the contribution of a handful of soil constituents in collapsibility, and finally developing a practical tool for ground engineers to evaluate the efficiency of the current compaction practice for systematically classified fine-grained soils, and to take modified/novel earthwork approaches where the current practice fails to fully remove the collapse risk.
30
Hamadé, Rufus Salah. "Critical phenomena in gravitational collapse". Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624941.
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Shieh, Jinn-An. "Film collapse in elastohydrodynamic lubrication /". The Ohio State University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487760357820679.
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Wood, Curtis James. "PROGRESSIVE COLLAPSE OF FRAME BUILDINGS". The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1543244236847612.
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Stephen, David Ojonimi. "Progressive collapse assessment of structures". Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/17769/.
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The collapse of buildings over the last century as a result of abnormal loads has renewed interest in the field of structural engineering. Key events such as the disproportionate collapse of the Ronan Point building in London, the collapse of the Alfred Murray Building and the World Trade Centre are structural failures that have triggered more research into progressive collapse. Consequently, new design guidelines around the globe with a prescriptive recommendation for improving structural integrity based on tying force provision have been developed. However, in existing design guidelines and codes throughout the world, there is a lack of a codified modelling technique for progressive collapse. As a result of this limitation, researchers adopt different methods. Generally, during the progressive collapse, structural members experiencing significant displacements and rotations, while the beam-column connections are subjected to large tensile forces not envisaged at the conventional design phase. Hence, this study presents an assessment of the effect of column removal time, the modelling techniques and the susceptibility of simple connections designed to Eurocode 3 Part: 1-8 to progressive collapse. A computationally efficient approach and column removal time for progressive collapse assessment are proposed. The findings show that a braced framed system is likely to exhibit at least 35% progressive collapse when compared with a moment resisting frame system using the joint displacement and rotation criteria. Furthermore, the research shows that the UK tie provision in EN1991-1-7 underestimates the magnitude of the catenary force developed under the progressive collapse scenario. Consequently, the connection is disposed to progressive collapse with the shear force in the column and catenary action in the beam as the critical internal forces. Based on this assessment, five times the tensile force specified in EC3 for tensile force connection design checks is recommended. Shear force in the column and catenary force action in the beam are the internal governing forces that determine the maximum dynamic amplification factor of a simple connection. The work provides evidence that the tie beam-column web connection at the corner column is more critical under progressive collapse scenario as compared with the primary beam. Column web failure in yielding is attributed to the large catenary force developed in the tie beam connected to the web of the column.
34
Yeh, Wei-Ming. "Pattern collapse in lithographic nanostructures: quantifying photoresist nanostructure behavior and novel methods for collapse mitigation". Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47696.
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The Microelectronics industry has continuously pushed the limit of critical dimensions to sub-20 nm. One of the challenges is pattern collapse, caused by unbalanced capillary forces during the final rinse and drying process. The use of surfactants offers a convenient method to reduce capillary forces but causes another deformation issue. This thesis work focuses on alternative approaches that are compatible with lithographic processes to mitigate pattern collapse. First, an e-beam lithography pattern with a series of varying line and space widths has been specifically designed in order to quantitatively study pattern collapse behavior. This pattern generates increasing stress in the pairs of resist lines as one moves across the pattern array and eventually a sufficiently small space value (critical space, S1c) is reached in each array such that the stress applied to the resist exceeds the critical stress (σc) required for pattern bending and subsequently feature deformation and collapse occurrs. The patterns we designed allow us to qualitatively and quantitatively study pattern collapse and obtain consistent, reproducible results.
In the first part of the thesis work, a quick surface crosslink (called a reactive rinse) that involves the strengthening of the resist using crosslinking via carbodiimide chemistry while the resist structures are still in their wet state, has been developed and demonstrated. This technique provides efficient and significant improvement on the pattern collapse issue. In the second part of the thesis work, a triethoxysilane compound, vinyl ether silane (VE), has been successfully synthesized. It can be used to modify the silicon or silicon nitride substrates and form a covalent bond with the resist film instead of manipulating the surface energies using common HMDS. Compared to traditional Hexamethyldisilazane (HMDS) vapor primed surfaces, the implementation of the VE adhesion promoter resulted in a significant improvement in the adhesion and resistance to adhesion based pattern collapse failure in small sub-60 nm resist features. In the third part of the thesis work, the effect of drying rates and drying methods has been systematically studied. SEM analysis and critical stress results showed that fast drying appear to reduce the resist collapse. The line pair orientations in each pattern array with respect to the wafer radius reveal an apparent effect of fluid flow and centrifugal forces on collapse. Finally, a comprehensive pattern collapse model that incorporates adhesion based pattern failure and elastoplastic deformation-based failure, and dimensionally dependent resist modulus properties has been developed. This model provides such an excellent prediction of the experimental data and supports the idea that this level of combined adhesion-failure and elastoplastic-failure based pattern collapse modeling, where one explicitly considers the dimensionally dependent mechanical properties of the resist can be quantitatively predictive and useful for understanding the pattern collapse behavior of polymeric nanostructures.
35
Wang, Pengyu. "Collapsed variational inference for computational linguistics". Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:13c08f60-1441-4ea5-b52f-7ffd0d7a744f.
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Bayesian modelling is a natural fit for tasks in computational linguistics, since it can provide interpretable structures, useful prior controls, and coherent management of uncertainty. However, exact Bayesian inference is intractable for many models of practical interest. Developing both accurate and efficient approximate Bayesian inference algorithms remains a fundamental challenge, especially for the field of computational linguistics where datasets are large and growing and models consist of complex latent structures. Collapsed variational inference (CVI) is an important milestone that combines the efficiency of variational inference (VI) and the accuracy of Markov chain Monte Carlo (MCMC) (Teh et al., 2006). However, its previous applications were limited to bag-of-words models whose hidden variables are conditionally independent given the parameters, whereas in computational linguistics, the hidden variable dependencies are crucial for modelling the underlying syntactic and semantic relations. To enlarge the application domain of CVI as well as to address the above Bayesian inference challenge, we investigate the applications of collapsed variational inference to computational linguistics. In this thesis, our contributions are three-fold. First, we solve a number of inference challenges arising from the hidden variable dependencies and derive a set of new CVI algorithms for the two ubiquitous and foundational models in computational linguistics, namely hidden Markov models (HMMs) and probabilistic context free grammars. We also propose CVI for hierarchical Dirichlet process (HDP) HMMs that are Bayesian nonparametric extensions of HMMs. Second, along the way we propose a set of novel algorithmic techniques, which are generally applicable to a wide variety of probabilistic graphical models in the conjugate exponential family and computational linguistic models using non-conjugate HDP constructions. Therefore, our work represents one step in bridging the gap between increasingly richer Bayesian models in computational linguistics and recent advances in approximate Bayesian inference. Third, we empirically evaluate our proposed CVI algorithms and their stochastic versions in a range of computational linguistic tasks, such as part-of-speech induction, grammar induction and many others. Experimental results consistently demonstrate that, using our techniques for handling the hidden variable dependencies, the empirical advantages of both VI and MCMC can be combined in a much larger domain of CVI applications.
36
Malavolti, Carlotta. "The collapse of the Twin Towers". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/3278/.
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37
Ohashi, Seiju. "Gravitational Collapse in the Lovelock Theory". 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/175111.
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38
To, Kenneth Chi-Wan. "Intracellular mechanisms underlying growth cone collapse". Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31697.
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During the course of development, expression of attractive and inhibitory guidance cues play a pivotal role in the pathfinding decisions of a growing neuron. In addition, injury-induced recapitulation of their expression, particularly inhibitory cues, likely influences the course of axonal regeneration, thus providing a rationale for the intense focus in this area of research. Though significant progress has been made, it remains poorly described what signaling cascades, and in what combination, are involved during inhibitory-cue induced growth cone collapse. Therefore, to further understand why neurons are repelled or inhibited by certain cues, the aim of this thesis is to identify the underlying intracellular mechanisms regulating growth cone collapse induced by inhibitory cues. Using a novel anti-invasive compound called Motuporamine C(MotC), I have characterized in chapter 2 its effects as a regulator of neuronal outgrowth. I found that MotC was a robust stimulator of growth cone collapse leading to a cessation of neurite growth. This was partially mediated through Rho-ROCK signaling, a pathway involved in regulating actin dynamics. Based on this partial response, I hypothesized that other signal transduction pathways were involved. I addressed this in chapter 3 by identifying calcium-activated calpain, a protease well-characterized in playing a role in adhesion regulation, was also activated during MotC-induced growth cone collapse. Furthermore, I show that concurrent inhibition of both Rho-ROCK and calpain pathways are necessary for maximum attenuation of the MotC-mediated collapse response. Since these results were identified using an organic molecule not endogenously expressed in vertebrate organisms, I hypothesized in chapter 4 that similar pathways would be activated in response to a physiological in vivo guidance cue. Using the inhibitory cue Semaphorin 5B (Sema5B), I found in addition to the activation of calpain, the phosphatase calcineurin was also involved in mediating Sema5B-induced growth cone collapse. Moreover, it is the combination of calpain- and calcineurin-mediated pathways that is required for evoking maximal growth cone collapse and that cross-talk between these two effector molecules occurs. These results are of particular interest since previously it was proposed by Gomez and Zheng (2006) that calpain and calcineurin signaling cascades were parallel pathways. Taken together, my findings show that different inhibitory cues activate multiple intracellular pathways that appear to impinge on different aspects of the intracellular machinery regulating motility. The combinatorial activation of these pathways is necessary for mediating maximal growth cone collapsing effects. Moreover, the elucidation of common signaling cascades between inhibitory cues to induce growth cone collapse may eventually provide novel targets for the development of new therapeutic strategies to promote functional recovery following neuronal injury.Medicine, Faculty of
Graduate
39
Smit, Job Martijn. "Neutrino transport in core-collapse supernovae". [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 1998. http://dare.uva.nl/document/91897.
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Ahmadi-Nedushan, Behrooz 1966. "Progressive collapse analysis of offshore platforms". Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22639.
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This thesis presents a study of the ultimate strength capacity of two offshore platforms located in the Gulf of Mexico. The objective of the study was to validate existing non-linear finite element models for estimating the loads and strength of offshore platforms.From August 24 to 26 1992, hurricane Andrew moved through the Gulf of Mexico with sustained winds of 140 miles per hour. Thirty-six major platforms suffered significant damage, of these, ten were completely toppled and twenty-six were leaning significantly or had significant topside damage.
Structures "H" and "K" were bridge-connected platforms, located in the ST151 field of the South Timbalier area of the Gulf of Mexico, platform "H" collapsed during Andrew, while "K" survived undamaged. They were both designed, fabricated, and installed in the early 1960's.
A push-over analysis, using the program USFOS was used to estimate the ultimate strength of the two structures in three direction: end-on, diagonal and broadside.
In the first series of analyses, all the primary members such as legs, vertical and horizontal braces, piles, soil, conductors and deck structure were precisely defined with appropriate finite elements as well as secondary members such as conductors guides barge bumpers. In the second series of analyses it was assumed that there was no horizontal or vertical movements at the level of the mudmat. In the third series of analysis the model used in the first series of analysis was modified by increasing stiffness and resistance of the piles 10 times. Finally a fourth model was investigated in which the soil resistance of the mud-level horizontal members is modelled. (Abstract shortened by UMI.)
41
Fasia, Alexandra. "Spectroscopic study of core-collapse supernovae". Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313777.
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Veal, Andrew Richard. "Models of polymer adsorption and collapse". Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277107.
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Flint, Graeme. "Fire induced collapse of tall buildings". Thesis, University of Edinburgh, 2005. http://hdl.handle.net/1842/1172.
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This research was designed to investigate possible mechanisms that fires could initiate that might lead to collapse of a tall building of similar design to the WTC Towers. It was not designed to be a forensic study and no initial damage was applied to the structure. The effects of fire on long span, truss based floor systems was investigated both locally and globally using finite element models.
44
Dove, Christopher John. "Explicit wavefunction collapse and quantum measurement". Thesis, Durham University, 1996. http://etheses.dur.ac.uk/5187/.
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In this thesis, we are concerned with models of explicit wavefunction collapse as a possible solution to the measurement problem of quantum mechanics. We examine the models where collapse is to near-position eigenstates, originally introduced by Ghirardi, Rimini and Weber in 1986, where the wavefunction is spontaneously localized at random times. Subsequent models where some of the problems of the GRW model are solved, are discussed, for both sudden localization and continuous localization processes. We comment briefly on the possible origins of collapse. The consequences of possible wavefunction collapse on the operation of quantum computers are described. Finally, we look at an attempt to describe the collapse process in a Lorentz-invariant manner.
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Crockett, R. M. "The progenitors of core-collapse supernovae". Thesis, Queen's University Belfast, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517262.
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Holland, M. R. "Canopy collapse of dried pea crops". Thesis, University of Edinburgh, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305741.
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Park, Jong-Chan. "Bending collapse behaviourof top-hat tubes". Thesis, University of Liverpool, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398576.
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Onoufriou, Andriani. "Collapse of damaged ring stiffened cylinders". Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/47537.
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Dai, Lei Ph D. Massachusetts Institute of Technology. "Spatio-temporal dynamics before population collapse". Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/95869.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references.
Theory predicts that the approach of catastrophic thresholds in natural systems may result in an increasingly slow recovery from small perturbations, a phenomenon called critical slowing down. In this thesis, we used replicate laboratory populations of the budding yeast Saccharomyces cerevisiae for direct observation of critical slowing down in spatio-temporal dynamics before population collapse. In the first project, we mapped the bifurcation diagram experimentally and found that the populations became more vulnerable to disturbance closer to the tipping point. Fluctuations of population density increased in size and timescale near the tipping point, in agreement with the theory. In the second project, we used spatially extended yeast populations to evaluate early warning signals based on spatio-temporal fluctuations. We found that indicators based on fluctuations increased before collapse of connected populations; however, the magnitude of increase was smaller than that observed in isolated populations, as local variation is reduced by dispersal. Furthermore, we propose a generic indicator based on deterministic spatial patterns, recovery length. In our experiments, recovery length increased substantially before population collapse, suggesting that the spatial scale of recovery can provide a warning signal before tipping points in spatially extended systems. In the third project, we characterized how different environmental drivers influence the dynamics of yeast populations. We compared the performance of early warning signals across multiple deteriorating environments. We found that the varying performance is determined by how a system responds to changes in a specific driver, which can be captured by a relation between stability and resilience. Furthermore, we demonstrated that the positive correlation between stability and resilience, as the essential assumption of indicators based on critical slowing down, can break down when multiple environmental drivers are changed simultaneously.
by Lei Dai.
Ph. D.
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Hrousis, Constantine Athanasios 1970. "Computational modeling of asthmatic airway collapse". Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/32692.
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