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Dissertationen zum Thema „System collapse“
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1
Al-Ashwal, Natheer Ali Mohammed. „Power system oscillatory instability and collapse prediction“. Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/power-system-oscillatory-instability-and-collapse-prediction(18ffc3fa-9b1b-40c6-b614-d757eb641046).html.
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This thesis investigates the capabilities of the Collapse Prediction Relay (CPR-D) and also investigates the use of system identification for detection of oscillatory instability. Both the CPR-D and system identification are based on system measurements and do not require modelling of the power system. Measurement based stability monitors can help to avoid instability and blackouts, in cases where the available system model can not predict instability. The CPR-D uses frequency patterns in voltage oscillation to detect system instability. The relay is based on non-linear dynamics Theory. If a collapse is predicted, measures could be taken to prevent a blackout. The relay was tested using the output of simulators and was later installed in a substation. The data from laboratory tests and site installations is analysed enabling a detailed evaluation of the CPR-D.Oscillatory instability can be detected by monitoring the damping ratio of oscillations in the power system. Poor damping indicates a smaller stability margin. Subspace identification is used to estimate damping ratios. The method is tested under different conditions and using several power system models. The results show that using several measurements gives more accurate estimates and requires shorter data windows. A selection method for measurements is proposed in the thesis.
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Marticello, Daniel Nicholas Jr. „Complexity within the Air Force acquisition system gaining insight from a theory of collapse“. Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/70825.
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Thesis (S.M. in Engineering and Management)--Massachusetts Institute of Technology, Engineering Systems Division, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 122-129).
Joseph Tainter's theory of societal collapse is applied in an examination of the U.S. Air Force's aircraft acquisition system in order to gain insight into the enterprise's lagging performance. Theories of collapse at both the societal level and the organizational level are reviewed. Tainter's interrelationship between increasing system complexity and diminishing marginal returns is highlighted as especially relevant to the performance of the Air Force aircraft acquisition enterprise. Using Tainter's theory as a framework, evidence is gathered leading to the conclusions that the Air Force aircraft acquisition enterprise is highly complex and as a result is experiencing diminishing marginal returns. Tainter's framework is then also used to explain why past attempts to reform the enterprise have fallen short of their goals. Previous reform efforts, in the form of reorganizations and senior leader initiatives, have been ineffectual beyond the short term because they fail to reduce the underlying level of complexity within the enterprise. The use of workarounds by stakeholders within the enterprise are shown to be efforts to increase marginal returns and avoid overcomplexity. The primary implication of viewing the Air Force aircraft acquisition enterprise through the lens of Tainter's theory of collapse is that in order to be effective, any effort undertaken to improve the performance of the enterprise must reduce the overall level of complexity within the system. Additional insights include the use of current workarounds as leading indicators of complexity or overly burdensome processes. Lastly, senior acquisition leaders should be prepared should a collapse of the enterprise occur. A vision of a much less complex enterprise should be advocated.
by Daniel Nicholas Marticello Jr.
S.M.in Engineering and Management
3
Ambrus, Marcel. „How long does it take until a quantum system reemerges after gravitational collapse? /“. [S.l.] : [s.n.], 2004. http://www.zb.unibe.ch/download/eldiss/04ambrus_m.pdf.
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Manona, Cecil W., und presented at an ISER Seminar March 1995 Paper. „The collapse of the 'tribal authority' system and the rise of civic organisations“. Rhodes University, Institute of Social and Economic Research, 1995. http://hdl.handle.net/10962/2454.
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The paper examines the performance of a local ('tribal') authority which existed in the Keiskammahoek district up to 1993 and accounts for the rise of civic organisations which challenged tribal authorities virtually everywhere in the former Ciskei. It suggests that the problems of this local authority which included inefficiency, corruption and lack of democracy were manifestations of the limitations of the Black Authorities Act of 1951 which attempted to revive traditional authority in the rural areas in south Africa even though this was incompatible with political developments in many other African states, particularly in a period during which the process of decolonisation was at its peak.Digitised by Rhodes University Library on behalf of the Institute of Social and Economic Research (ISER)
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Gotoda, Takeshi. „Anomalous enstrophy dissipation via triple collapse of point vortices in a Euler-Poincare system“. 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225379.
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Rasch, Sebastian [Verfasser]. „Resilience, collapse and reorganization of a rangeland socio-ecological system in South Africa / Sebastian Rasch“. Bonn : Universitäts- und Landesbibliothek Bonn, 2016. http://d-nb.info/1107541727/34.
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Beeravolu, Nagendrakumar. „Predicting Voltage Abnormality Using Power System Dynamics“. ScholarWorks@UNO, 2013. http://scholarworks.uno.edu/td/1722.
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The purpose of this dissertation is to analyze dynamic behavior of a stressed power system and to correlate the dynamic responses to a near future system voltage abnormality. It is postulated that the dynamic response of a stressed power system in a short period of time-in seconds-contains sufficient information that will allow prediction of voltage abnormality in future time-in minutes. The PSSE dynamics simulator is used to study the dynamics of the IEEE 39 Bus equivalent test system. To correlate dynamic behavior to system voltage abnormality, this research utilizes two different pattern recognition methods one being algorithmic method known as Regularized Least Square Classification (RLSC) pattern recognition and the other being a statistical method known as Classification and Regression Tree (CART). Dynamics of a stressed test system is captured by introducing numerous contingencies, by driving the system to the point of abnormal operation, and by identifying those simulated contingencies that cause system voltage abnormality.
Normal and abnormal voltage cases are simulated using the PSSE dynamics tool. The results of simulation from PSSE dynamics will be divided into two sets of training and testing set data. Each of the two sets of data includes both normal and abnormal voltage cases that are used for development and validation of a discriminator. This research uses stressed system simulation results to train two RLSC and CART pattern recognition models using the training set obtained from the dynamic simulation data. After the training phase, the trained pattern recognition algorithm will be validated using the remainder of data obtained from simulation of the stressed system. This process will determine the prominent features and parameters in the process of classification of normal and abnormal voltage cases from dynamic simulation data.
Each of the algorithmic or statistical pattern recognition methods have their advantages and disadvantages and it is the intention of this dissertation to use them only to find correlations between the dynamic behavior of a stressed system in response to severe contingencies and the outcome of the system behavior in a few minutes into the future.
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Di, Palma Debora. „Progressive collapse of concrete structures during construction phase: analysis and measures for risk reduction“. Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
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Shoring systems are used as temporary support for structures under construction and their primary function is to support and transmit various types of loads. To optimize this phase it has been developed a technique known as Clearing or partial Striking; it consists in removing a percentage of shores few days after the casting such that the load is redistributed between the slab and the remaining shores. In this way the shores removed in one floor can be used to start building the upper one. It is thus really important to conceive the process in a proper way assuring that the whole system is able to support the loads acting on it. This is the reason for which there is a prudent need to understand which conditions lead to the collapse of shoring systems and what measures can impounded in the design process to mitigate the risk of failure.
The aim of this thesis is to perform a progressive collapse analysis, during the construction phase of the building, by instantly removing one or several primary load bearing elements and analyzing the structure’s remaining capability to absorb the damage. The analysis have been performed varying load conditions and slab thicknesses and, once the results from standard shores cases have been obtained, calculations with load limiters have been performed. The entire study has been developed with finite elements by means of ANSYS APDL starting from a FE model developed by Alvarado (2010). The important aspect of this investigation has been the risk reduction of progressive collapse, in particular it has been analyzed the behavior performed by the structure when enhanced support systems are used.
Along with the finite element study it has been taken part in a experimental study aimed at analyze the load transmission in enhanced shoring system.
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Dyanat, Mohsen. „The emergence of the new subordinate system in southwest and central Asia after the collapse of the USSR“. Thesis, University of Exeter, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284621.
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Kuraev, Alexey. „Internationalization of Higher Education in Russia: Collapse or Perpetuation of the Soviet System? A Historical and Conceptual Study“. Thesis, Boston College, 2014. http://hdl.handle.net/2345/3799.
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Thesis advisor: Philip G. AltbachThis study traces the policy and implementation of internationalization in the Russian higher education system from 1917 to the present. The analysis suggests that international academic policy has been applied by the Russian state continuously, though with radically differing emphasis and mechanisms, through the last hundred years. Chapter One presents the research questions, design and methodology of the study. Chapter Two reviews scholarly literature related to academic internationalization and situates this definition within the context of Russian higher education. Chapters 3-5 explore the role of international activities in Russian higher education during the seventy years of the Soviet era. Trends in Soviet academic international policy related to three major historical periods are discussed in this section: a) the initial Bolshevik program for global academic reform; b) Sovietization of higher education in the countries of Communist Bloc; and c) East-West international academic competition during the Cold War period. Chapters 6-7 address the role of internationalization in the reformation of Russian higher education during the last two decades of Post-Soviet period. This section examines the extent and likely outcomes of these changes. This research demonstrates that Russian higher education has had a continuous international aspect, though organized differently than Western structures. The analysis also suggests that key organizational components of the Soviet administrative system still exist in the current Russian higher education structure. The current implementation of internationalization presents Russian academics with an opportunity to enforce academic professionalism and promote their status as global academics. At the same time, however, state organization and governing administration principles of Russian higher education continue to reduce academics to functional executors of state directives and deliverers of vocational training. In this way, internationalization serves as a critical nexus for the collision of traditional administrative structures with the new aspirations of Russian academics
Thesis (PhD) — Boston College, 2014
Submitted to: Boston College. Lynch School of Education
Discipline: Educational Leadership and Higher Education
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Pendar, Hodjat. „The mechanical linkage of abdominal movements and the respiratory system in beetles“. Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/72865.
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Abdominal pumping is a well-known behavior in insects, thought to function largely in respiratory processes. In particular, the abdominal pump is considered to produce ventilation of air in the tracheal system, but the mechanistic link between abdominal movement and flow of air is not well understood. In this thesis, we explore the relationship between the abdominal pump and ventilation of air using pupal and adult forms of the darkling beetle Zophobas morio.
First, we investigated the mechanical linkage between abdominal pumping and active ventilation in pupae by simultaneously measuring abdominal movement, hemolymph pressure, CO2 emission, and deformation of tracheal tubes. This study revealed that pupae with low metabolic rates do indeed exhibit tracheal compression, which is coincident with abdominal pumping and pressure pulsation. However, more than 63% of the abdominal pumps and associated pressure pulsations did not lead to tracheal compression. This result can be explained by the status of the spiracles; when the system is closed, little compression in the tracheae can occur. Therefore, we conclude that abdominal pumping in insects does not necessarily lead to ventilation and may serve other functions, such as producing hemolymph flow for circulation.
Insects have an open circulatory system, with flow driven largely by the small dorsal vessel. Within the open coelom, hemolymph pressure should be mostly uniform, suggesting that abdominal pumping does not produce hemolymph flows within the main body cavity. We tested this assumption by simultaneously measuring hemolymph pressure in different locations in the coelom. Within the abdomen and thorax, hemolymph pressure is nearly uniform, as expected. However, hemolymph pressures are significantly different between the abdomen and thorax. This suggests that the coelom is compartmentalized, and that abdominal pumping can induce hemolymph flow within the coelom.
Throughout these experiments, we faced a common difficulty inherent to flow-through respirometry systems: they are incapable of providing direct, instantaneous measurement of gas concentration. Previous methods are not able to reconstitute the rapid dynamical changes in respiratory signals that are required for precise temporal analysis. Therefore, we developed two new methods to accurately recover instantaneous gas exchange signals, based on new models of the impulse response of the system. These methods enabled us to accurately recover fast- changing respiratory signals with a higher fidelity than previously possible. Using these methods, we demonstrate the synchronization of respiratory data with other physiologically relevant signals, such as pressure and abdominal movement.
This research was supported by NSF grant #0938047 and the Virginia Tech Institute for Critical Technology and Applied Science (ICTAS).Ph. D.
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Olajubutu, Michael Olaolu. „Utilizing microprocessor based relays as predictive tools to mitigate voltage instability problems that stem from the fast voltage collapse and delayed voltage recovery phenomena“. Auburn, Ala., 2007. http://repo.lib.auburn.edu/07M%20Theses/OLAJUBUTU_MICHAEL_35.pdf.
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Motono, Eiichi. „Chinese-British commercial conflicts in Shanghai and the collapse of the merchant-control system in late Qing China, 1860-1906“. Thesis, University of Oxford, 1994. http://ora.ox.ac.uk/objects/uuid:27ae2da8-a15b-40e1-a0b2-bc33fc8ecbaa.
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During the 1860s, Chinese merchants reestablished their commercial organizations which are recorded as Guilds (hanghui) in the sources compiled under the guidance of the Qing local government officials. From the decade until the end of the 1880s, English sources emphasized the solidarity of the commercial organizations of Chinese merchants and their superiority to the British mercantile community in the commercial conflicts in which they were engaged. However, from the 1890s, English sources ceased to complain the strength of the commercial organizations of Chinese merchants, and, at the same time, Chinese sources emphasized the existence of a crisis in which Chinese merchants were losing their solidarity. Moreover, the Qing local government officials endeavoured to maintain their control over the commercial organizations of Chinese merchants, an attempt which led to the birth of Chinese chambers of commerce in the early twentieth century. Former studies, which dealt with the superiority of the Chinese merchants' organizations to the British mercantile firms in the 1860s and the 1870s, or the birth of the Chinese bourgeoisie and the activities of their commercial organizations in the early twentieth century, have not been able to reveal what happened in the commercial organizations of the Chinese merchants during the late nineteenth century. The solidarity of the Chinese merchant organizations was maintained by the rule that no one could claim the privilege of doing business without paying the Lijin tax imposed upon it, and the collapse of their solidarity began with when some Chinese compradors and merchants found it possible to do their business without keeping this rule by means of cooperating British mercantile firms, who enjoyed key privi- leges under the Treaties as regards non-payment of the Lijin tax and investment on the basis of limited liability. By intensively analyzing three commercial conflicts between prominent Chinese merchant organizations and British mercantile firms that took place in Shanghai between the end of the 1870s and the end of the 1880s, this study reveals how, and under what conditions some Chinese compradors and merchants could do their business without observing the afore-mentioned rule governing the Chinese merchants' organizations, what happened when British mercantile people became aware what their compradors or cooperative Chinese merchants had doing behind their back, and how these developments contributed to the end of the old-style merchant class, and the beginning of a bourgeoisie. By bringing these facts to the surface for analysis, this study shows a little known aspect of the Chinese society and tries on the basis to re-evaluate an aspect of concept of "China's response to the Western impact."
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Flores, Solano Francisco Xavier. „Influence of the Gravity System on the Seismic Performance of Special Steel Moment Frames“. Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/73143.
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This study investigates the influence of the gravity load resisting system on the collapse performance of Special Steel Moment Frames (SMFs). The influence was quantified using the FEMA P-695 methodology. The buildings used for this study were a 2-, 4- and 8-story SMFs taken from the ATC76-1 project where their collapse performance was already evaluated without the gravity system. The main work of this dissertation has been divided in two parts. The first part studies the influence of the gravity system when it is incorporated explicitly as part of the lateral resisting system. Aspects of the gravity frame that were investigated include the contribution of stiffness and strength of beam to column connections, and the location of splices in the gravity columns. Moreover, this research investigates the potential for the development of inelastic deformations in the gravity columns, and the effect of such deformations on structural response. The results show that gravity connections and gravity column's continuity profoundly affect the computed response and collapse probability. The inelastic behavior in gravity columns has a less important effect but should be included in the analysis.
The second part of the investigation looks more in depth at the role of the gravity columns on the collapse performance of SMFs. Using the 2-, 4- and 8-story SMFs, the gravity columns are incorporated using the approach where all the gravity columns are lumped into one elastic, pinned at the base and continuous element. The approach is first validated by checking different aspects such as: strength of gravity connections to induce yielding into gravity columns, difference between the explicit and lumping column approach, and required gravity column's splices to provide continuity. The stiffness of the element representing the gravity columns was varied in order to find the influence of the gravity columns. At the end of the study it was found that they have a significant influence on the collapse performance of SMFs, especially on taller structures like the 8-story model. Moreover it was concluded that an adequate stiffness of the gravity columns could be found by performing nonlinear static pushover analysis.Ph. D.
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Pavlick, Bay. „A fuzzy logic based controller to provide end-to-end congestion control for streaming media applications“. [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001253.
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Alkema, Nike Kristin. „A historical institutionalist explanation for the party change : the contingent collapse of the Democrazia Cristiana and the path dependent political diaspora of Catholics in the Italian party system“. Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543732.
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Guimarães, Márcia Barbosa da Costa. „A ocupação pré-colonial da região dos Lagos, RJ: sistema de assentamento e relações intersocietais entre grupos sambaquianos e grupos ceramistas Tupinambá e da tradição Una“. Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/71/71131/tde-05092007-111015/.
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A pesquisa teve por objetivo compreender o sistema de assentamento dos grupos sambaquianos que ocuparam o Complexo Lagunar de Saquarema entre 6.600-1.500 anos cal BP. Tendo por base o pressuposto de que o estudo da continuidade e da mudança é fundamental para o desenvolvimento de estudos regionais, foi construído um modelo onde dois fatores, mudança ambiental e contato intersocietal, influenciaram o processo de transformação sociocultural verificado entre os grupos sambaquianos. Assim, embora partilhassem traços comuns, o que lhes permitia manter um caráter identitário - podendo esse ser vislumbrado num sistema de assentamento onde as relações sociais se davam em função da laguna de Saquarema - os grupos sambaquianos apresentavam diferenças entre si, resultado de um longo processo adaptativo. A gradual mudança na disponibilidade de recursos malacológicos acabou por resultar no fortalecimento de um grupo sobre outro. Os melhores adaptados, representados pelos ocupantes dos sambaquis de Saquarema e da Pontinha, tiveram contato com grupos ceramistas relacionados à tradição Una, ocupantes do sítio Ilha dos Macacos. Tal contato pôde ser verificado através do aparato tecnológico (predomínio absoluto dos artefatos de lascamento), pela adoção de novas práticas funerárias (cremação, manipulação de ossos humanos) e pela concomitância das ocupações. Assim, por volta de 2.000 anos cal AP, esse contato, somado a um processo que já vinha se desenvolvendo no interior do sistema, marcou o início do colapso da sociedade sambaquiana no Complexo Lagunar de Saquarema.This research aimed contributing to the understanding of the settlement pattern of sambaqui dwellers who occupied the Saquarema lagoonar system (Rio de Janeiro State, Brazil) between 6600 and 1500 cal years BP. It considers the premise that studies of continuity and change are the base to the development of regional synthesis. The model developed presumes that two factors, environmental change and intersocietary contact, have influenced the processes of sociocultural change in the sambaqui society. From this point of view, it is suggested that, although sambaqui people shared common characteristics that allowed them to keep an identity, sambaqui groups presented differences between each other, which resulted from a long adaptative process. This identitary character may be recognized in their settlement pattern, in which social relationships were established in relation with the Saquarema Lagoon. However, gradual changes in the availability of malacological resources induced the reinforcement of some groups over the others. Better-adapted groups, represented by the occupants of sambaquis Saquarema and Pontinha, have established contacts with ceramists related to Una tradition, who occupied Ilha dos Macacos. This contact is attested by the characteristics of the technological apparatus (absolute predominance of flaked artifacts), by the adoption of new funerary practices (cremation, manipulation of human bones) and by the concomitance of occupations. Around 2000 cal years BP, this contact, associated to a process that had already been developing inside the sambaqui system, marked the beginning of the collapse of the sambaqui society in the Saquarema lagoonar system.
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Knutsson, Elias. „Drones – a tool of escalation or de-escalation in conflicts?“ Thesis, Försvarshögskolan, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:fhs:diva-9985.
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The use of drones in conflicts is under development and is increasing rapidly. The first real drone warfare was seen in Pakistan in the War on Terrorism in 2004. Between officials and scientists, there are divided opinions about whether the drone strikes can increase terrorism or cause the collapse of organizations. The purpose of this thesis is to examine how the effectiveness of drones, in terms of precision and lethality, can be seen to escalate or de-escalate a conflict. The aim is to explore whether two existing theories about air power can explain the case of killing the Iranian general, Qasem Soleimani, in 2020. As a qualitative case study, the approach results in favor of Pape´s theory over Warden´s. Pape says that decapitation is more likely to escalate a conflict, which confirms this case. Other explanations in his theory are the absence of unexpected political effects and the overthrow of government. Though Wardens theory shows some aspects of de-escalation, the conclusion is that Soleimani was not the center of gravity that was meant to cause system collapse. Further research is required since the findings cannot identify any escalating or de-escalating effects within the Quds Force.
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Hagerfors, Erika, und Emelie Lagrosen. „Riskanalyskartor i GIS över tsunamidrabbade områden vid ett skredscenario av vulkanen Cumbre Vieja på La Palma, Kanarieöarna“. Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-296215.
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På Kanarieön La Palma finns sprickzonen och vulkanen Cumbre Vieja. Under ett vulkanutbrott år 1949 bildades ett förkastningssystem längs vulkanens västra sida som skulle kunna vara ett förstadium till en framtida kollaps av vulkanen. Denna kollaps skulle kunna leda till bildandet av en tsunami när kollapsmaterial rasar ner i havet likt ett jordskred. Tsunamin kan komma att spridas över stora delar av Atlanten och i olika grad påverka de omkringliggande kontinenterna. Det finns olika teorier om hur stort jordskredet kommer att bli och om det kommer att ske successivt eller kollapsa som en enda enhet. I detta arbete studeras fyra kollapsscenarier med volymer av 20 km3, 40 km3, 80 km3 och 450 km3 närmare. Utifrån dessa volymer skapas riskanalyskartor i GIS över ön Teneriffa och New Yorks storstadsområde som visar hur långt över land tsunamin når vid de olika kollapsscenarierna. Dessa kartor jämförs sedan med markanvändningskartor över Teneriffa och New Yorks storstadsområde. Trots att tsunamivågen kan bli mycket hög vid Teneriffas kust kommer stora delar av ön att undkomma tsunamin, vilket bl.a. beror på öns höga höjd över havet. Då de flesta byggnader är belägna vid kusten innebär det att många människor ändå riskerar att drabbas. New Yorks storstadsområde är istället lågt beläget, vilket bidrar till att många kustnära områden kommer att drabbas trots att våghöjden har avtagit väsentligt. Då detta område är mycket tätbefolkat kan en tsunami därför leda till en stor påverkan.On the Canary Island La Palma there is a volcanic ridge called Cumbre Vieja. During an eruption in 1949 a fault system was formed along the western flank of the volcano that can be an early stage of a future flank collapse of Cumbre Vieja. During this collapse a large volume of rock material will fall into the ocean like a landslide, which could lead to the formation of a tsunami. The tsunami could spread over large parts of the Atlantic Ocean and to varying extent affect the surrounding continents. There are different theories of how big the landslide will be and if it will collapse gradually or as a coherent block. In this study four collapse scenarios with different volumes, 20 km3, 40 km3, 80 km3 and 450 km3, are studied more closely. Based on these volumes, vulnerability maps are created in GIS covering the island Tenerife and the New York metropolitan area. The maps show the land reach of the tsunami for each of the collapse scenarios. These maps are thereafter compared with land use maps over Tenerife and the New York metropolitan area. Despite the high amplitude of the tsunami wave at the coast of Tenerife, large parts of the island will remain unaffected by the tsunami. This is due to, among other things, the high altitude of the island. However, most buildings are located along the coast, which means that many people are at risk. The New York metropolitan area has, on the other hand, low altitude which is one explanation why many coastal areas will be affected despite the significant decrease in tsunami wave height. A tsunami would have a major impact due to these areas being densely populated.
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Al-Hinai, Amer. „Voltage collapse prediction for interconnected power systems“. Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1639.
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Thesis (M.S.)--West Virginia University, 2000.Title from document title page. Document formatted into pages; contains xii, 94 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 66-67).
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Cao, Ngoc-Tuyen. „Apport de la Surveillance Microsismique en Champ Proche pour la détection de Mécanismes et Signes Précurseurs aux Instabilités Gravitaires : Surveillance expérimentale d'une Cavité Saline en exploitation : Cas du site de Cerville-Buissoncourt“. Thesis, Vandoeuvre-les-Nancy, INPL, 2011. http://www.theses.fr/2011INPL107N/document.
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L'étude des signes précurseurs d'un effondrement brutal au-dessus de cavités souterraines, dont le recouvrement est caractérisé par la présence d'un banc massif et raide, est un problème majeur pour la sécurité publique. Aussi, pour progresser dans la compréhension et l'évolution des mécanismes mis en jeu, une cavité saline, située dans le NE de la France, a été suivie en temps réel, entre 2004 et 2009, jusqu'à son effondrement. Celle-ci a été exploitée par dissolution, jusqu'à atteindre une dimension critique (de l'ordre de 180 m) sous un recouvrement de 180 m, armé d'un banc raide de Dolomie situé à 120 m de profondeur.Un système de mesures multi-paramètres haute résolution visait à caractériser les signes précurseurs ainsi qu'à suivre l'effondrement lui-même. Il comprenait des dispositifs à la fois géotechniques et géophysiques, dont des mesures de nivellement de surface et un réseau permanent d'écoute microsismique. Ce dernier, dont les données font l'objet principal de cette thèse, était constitué de neuf sondes équipées de géophones 40 Hz (5 unidirectionnels et 4 tridirectionnels), réparties autour et à l'aplomb de la cavité, dont une dans le banc raide.L'évolution de la cavité a été marquée par deux épisodes majeurs d'activité microsismique :- au printemps 2008, la reprise de la dissolution dans la cavité a engendré l'apparition de crises répétées avec plusieurs milliers d'événements en quelques jours, traduisant un changement de régime microsismique, marqueur de l'instabilité de la cavité ;- en février 2009, suite à ces observations, l'exploitant a décidé de provoquer l'effondrement, par le rabattement intensif de saumure dans la cavité. Pendant les trois jours d'opération, plus de 30000 événements ont été enregistrés (sur 60000 depuis 2004).L'étude de la signature des événements apporte des renseignements essentiels pour la surveillance opérationnelle et la discrimination de ces deux périodes. En particulier, alors que les valeurs maximales atteintes en amplitude, énergie au capteur et fréquence fondamentale apparente, sont assez stables au cours des crises, les sauts marqués durant l'effondrement, permettent de présumer de son imminence. L'évolution de la distribution des microséismes en termes d'énergie libérée et d'occurrence, calculée de manière similaire à la loi de Gutenberg-Richter, bien que souvent difficile à interpréter, a pu être associée à des hausses du niveau piézométrique, ainsi qu'à de petites accélérations de l'affaissement mesuré en surface. Pendant la période d'effondrement, le nombre d'événements microsismiques augmente en suivant une loi en puissance.La localisation des microséismes a nécessité la mise en place d'une stratégie adaptée pour garantir la qualité et l'homogénéité des résultats (sélection des enregistrements, calibrage, étude paramétrique).Cependant, l'utilisation d'un modèle de vitesse constant sur toute la période s'est révélé impossible, compte tenu de l'évolution rapide et permanente du milieu. Il a donc été entrepris d'établir des modèles de vitesse différents en fonction des périodes d'évolution de la cavité.Les distributions spatio-temporelles des foyers ainsi localisés montrent l'existence de structures préférentielles de rupture et souligne le rôle majeur du banc raide.Croisées avec les autres mesures acquises sur le site, ces résultats ont permis d'établir un scénario probable d'évolution de la cavité et de proposer quelques recommandations pour la surveillance opérationnelleThe study of the precursory signs of a brutal collapse above underground caverns, with an overburden characterized by the presence of a massive and stiff bench, is a major problem for public safety. Thus, to progress in the comprehension and the evolution of the concerned mechanisms, a salt cavern, located in the NE France, was monitored in real-time, since 2004 to 2009, until its collapse. This cavern was mined by solution, until reaching its critical dimension (about 180 m) under a covering of 180 m thick, armed with a stiff Dolomite bench located at 120 m of depth.A multi-parameter high resolution monitoring system aimed at characterizing the precursory signs and following collapse itself. It included both geotechnical and geophysical devices as surface leveling measurements and a permanent microseismic network. This one, which data are the principal subject of this thesis, consisted in nine probes equipped with 40 Hz geophones (5 1D and 4 3D), distributed around and directly below the cavern, including one located in the stiff bench.The evolution of the cavern was marked by two major episodes of microseismic activity:- at the beginning of spring 2008, the dissolution restart in the cavern which caused repeated crisis with several thousand events in a few days, this represent a change in the microseismic regime and marked the cavern instability;- in February 2009, following these observations, the owner decided to trigger the collapse by intensive brine pumping in the cavern. During the three days of the operation, more than 30,000 events were recorded (against 60,000 since 2004).The study of the event signature provides essential information for operational monitoring and the discrimination of these two periods. Particularly, while maximal values reached in amplitude, energy and apparent fundamental frequency are quite stable during the 2008 episodes, the rises of this values are important during the collapse period (prior to the peak of activity), allowed us to suppose its imminence. The evolution of the microseism distribution in terms of energy released and occurrence, calculated similarly to the Gutenberg-Richter law, although often difficult to interpret, has been associated with piezometric level rises, and with small accelerations of surface subsidence. During the collapse, the microseismic activity acceleration follows a power law.Microseisms location required the establishment of an appropriate strategy to ensure the quality and the consistency of the results (record selection, calibration, parametric analysis). However, the use of a constant velocity model over all the period was impossible due to the fast and permanent evolution of the environment. Thus, several models were used, according to the a priori known cavern evolution.The event spatiotemporal distributions, thus located, revealed the existence of preferential failure structures and highlight the role of the stiff bench, located at 120 m depth
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Georgakopoulos, Phillip J. (Phillip John) 1982. „An overview of progressive collapse in structural systems“. Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/31117.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005.Includes bibliographical references (leaves 54-55).
It has become evident recently that abnormal loads need to be considered in the design of structures so that progressive collapse can be prevented. Building collapses such as the Ronan Point, Alfred P. Murrah, and World Trade Center have shown the catastrophic nature of progressive collapse and with an increasing trend towards more terrorist action in the future, it is clear structural design must include progressive collapse mitigation. The most critical abnormal loadings that have potential to cause progressive failure are blast and impact. These loads are impulsive and dynamic in nature with the potential to induce destructive forces, and to further complicate matters is the random nature of occurrence which makes it difficult to predict adequate levels of design. Much research has been conducted over the past several decades, but to this day very little standardized language has been published to help designers create progressive collapse resistant structures. What is known is that robust structures can be built economically by following a general design philosophy of redundancy, ductility, and overall structural integrity. Reinforced concrete structures are especially well suited for resisting progressive collapse by specifying steel reinforcement detailing such as continuous top and bottom reinforcement, close spacing of stirrups, strategic locations of splices, continuous reinforcement through joints, and designing slabs for two-way action. Steel structures have good ductility, but connection detailing is usually the weakest point and requires special design, such as the use of the SidePlate (tm) connection.
(cont.) Regardless of the type of material used, the design should strive for a uniform, regular layout of the structural system with limited span lengths and close spacing of beams and columns. Perimeter defense systems should be employed as this decreases the threat of an abnormal loading. Since there has been little consideration of extreme loadings, existing structures may be inadequate and require retrofit. Although more difficult, it is possible to achieve improved progressive collapse resistance through the use of externally applied retrofits, such as concrete encasement or the application of composite polymer materials.
by Phillip J. Georgakopoulos.
M.Eng.
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Hawkins, Nigel Trevor. „On-line reactive power management in electric power systems“. Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363434.
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Santos, Carlisson Junior Ramos dos. „Método rápido para avaliação da margem de estabilidade de tensão considerando os limites de potência reativa dos geradores“. Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/18/18154/tde-06042009-152456/.
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A análise de estabilidade de tensão em tempo real exige o cálculo periódico da margem de estabilidade para um número grande de contingências. Isto motiva o desenvolvimento de técnicas rápidas para determinação da margem de estabilidade de tensão adequadas aos requisitos da operação em tempo real. Neste trabalho utiliza-se uma técnica rápida, denominada Look-Ahead, para estimar a margem de carregamento do sistema de potência. O método explora a propriedade quadrática da curva (\'lâmbda\'-V) , próximo ao ponto de bifurcação, e utiliza a informação de dois fluxos de potência e do vetor tangente para estimar com boa precisão o ponto de máximo carregamento (PMC) do sistema de potência. O método Look-Ahead estima o PMC do sistema de potência sem considerar as violações dos limites de potência reativa dos geradores. Este trabalho propõe uma nova metodologia para estimar o valor de carregamento no qual ocorre violação dos limites de potência reativa dos geradores do sistema. Essa técnica é baseada na característica aproximadamente quadrática da curva (Q-\'lâmbda\'). A metodologia proposta é mais rápida, em comparação com o fluxo de potência continuado, e calcula o PMC considerando as violações dos limites de reativos dos geradores. A eficácia do método proposto é comprovada por intermédio de vários testes com um sistema obtido a partir de uma redução do sistema sul sudeste brasileiro.Real time voltage stability analysis requires the periodic calculation of the stability margin for a large number of contingencies. This requirement motivates the development of fast techniques to determine stability margin that are suitable for real time operation. This work uses a fast technique called Look-Ahead, to estimate power system loading margin. The method exploits the fact that close to the bifurcation point, the (\'lâmbda\'-V) curve has quadratic property, which enables a good loading margin estimate. It also uses the information of the tangent vector and two power flow results to estimate, with good precision, the power systems maximum loading point (MLP), the voltage profile at the MLP as well as the loading values for which voltage limits are violated. The Look-Ahead method estimates the power system MLP without considering generators reactive power limit violations. This dissertation proposes a new methodology to estimate the loading value at the points where generator reactive power limits are reached. This technique is based on nearly quadratic characteristic curve (Q-\'lâmbda\'). The proposed methodology is faster in comparison with continuation power flow and computes the MLP considering the violation of reactive limits of generators. To prove the effectiveness of the proposed method, several tests using the reduced brazilian south and southeast system were performed.
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Lomas, Mark Richard. „An investigation of voltage collapse phenomena in power systems“. Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266016.
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Lignos, Dimitrios. „Sidesway collapse of deteriorating structural systems under seismic excitations /“. May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Wilson, Jonathan P. „Non-linear dynamics and power systems“. Thesis, University of Bath, 2000. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341136.
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Hemmerlin-Kohler, Sophie. „Estimation et agrégation des puissances actives et réactives absorbées par les charges consommatrices d'un réseau en régime perturbé“. Grenoble INPG, 1993. https://hal.archives-ouvertes.fr/tel-02010571.
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Les réseaux électriques sont des systèmes complexes dont l'étude requiert l'utilisation de moyens de simulation numérique importants. Certains régimes perturbés tels que ceux qui précèdent et succèdent à un écoulement de tension, sont fortement conditionnés par le comportement des charges consommatrices. Si la modélisation des composants du réseau, est devenue assez précise, il n'en est pas encore de même pour des charges, vues comme des ensembles agrégés. L'étude a consisté à établir les modèles élémentaires de diverses charges rentrées couramment dans les réseaux, ainsi que les modèles de leurs équivalents agrégés. Deux types de charges ont été considérés. D'une part les charges dites "passives", généralement non linéaires (éclairage), d'autre part les charges dites "actives", que sont essentiellement les moteurs asynchrones fonctionnant en régime dynamique lent, de caractère électromécanique. Dans tous les cas, les modèles proposés permettent d'obtenir les puissances active et réactive absorbées par des charges é lé Dentaires et agrégées, en fonction des variations importantes de tension et/ou de fréquence apparaissant lors des incidents de réseauxThe complexity of power Systems requires the use of signifîcant numerical simulations. Some supply system disturbances, like those before and after a voltage collapse, are strongly conditioned by the loads' behaviour. In spite of an improved accuracy conceming the field of power system components modelîing, the accuracy of load aggregation needs to be further developped. This study has consisted in the élaboration of usual basic and aggregate loads models. Two kinds of loads hâve been considered : on the one hand, usually non-linear loads called "passive" (lighting), on the other hand so-called "active" loads which are essentially induction motors working under an electromechanical dynamic. In ail the cases, the proposed models allow the obtention of active and reactive power absorbed by basic or aggregate loads. Thèse powers' models dépend upon large voltage and/or frequency déviations which can occur during large power system disturbances
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Bahari, Iskandar. „Collapse, revival and decoherence of entanglement in two qubits systems“. Thesis, University of York, 2018. http://etheses.whiterose.ac.uk/20491/.
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We extend study of the Jaynes-Cummings model involving a pair of identical two-level atoms (or qubits) interacting with a single mode quantised field. We investigate the effects of replacing the radiation field mode with a ‘big spin’, comprising a collection of N qubits, or spin-1/2 particles. We demonstrate the similarities of this set-up to the qubits-field model in terms of the qubits state probability, occurrence of attractor states, generation of Schr ̈odinger cat state, and in particular the collapse and revival of the entanglement between the two qubits in the qubit subsystem. We extend our analysis by taking into account a decoherence effect due to qubit imperfections. We study two cases of ‘error’ in the system for both the field mode and ‘big spin’ cases. In the first part, we consider the case of systems with non-resonance frequencies, and secondly we let the systems evolve with a difference in the dipole interaction strengths of the two qubits. We average over the errors in both of these parameters with distributions of varying width. We demonstrate the effects of such error modeling in both the field mode and the ‘big spin’ scenarios. We discover that increasing the width of the ‘error’ distribution increases suppression of the coherent dynamics of the coupled system, including the collapse and revival of the entanglement between the qubits. We also find out that the decoherence effects are more significant in the system with difference in the coupling strength as opposed to the nonresonance case that has higher robustness against errors. At the end of the study, we investigate the qubit-big spin system with a modest value of N to identify the smallest size of the big spin that exhibits the important events in such interacting model.
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Bahadornejad, Momen. „On-line local load measurement based voltage instability prediction“. Queensland University of Technology, 2005. http://eprints.qut.edu.au/16187/.
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Voltage instability is a major concern in operation of power systems and it is well known that voltage instability and collapse have led to blackout or abnormally low voltages in a significant part of the power system. Consequently, tracking the proximity of the power system to an insecure voltage condition has become an important element of any protection and control scheme. The expected time until instability is a critical aspect. There are a few energy management systems including voltage stability analysis function in the real-time environment of control centres, these are based on assumptions (such as off-line models of the system loads) that may lead the system to an insecure operation and/or poor utilization of the resources. Voltage instability is driven by the load dynamics, and investigations have shown that load restoration due to the on-load tap changer (OLTC) action is the main cause of the voltage instability. However, the aggregate loads seen from bulk power delivery transformers are still the most uncertain power system components, due to the uncertainty of the participation of individual loads and shortcomings of the present approaches in the load modeling. In order to develop and implement a true on-line voltage stability analysis method, the on-line accurate modeling of the higher voltage (supply system) and the lower voltage level (aggregate load) based on the local measurements is required. In this research, using the changes in the load bus measured voltage and current, novel methods are developed to estimate the supply system equivalent and to identify load parameters. Random changes in the load voltage and current are processed to estimate the supply system Thevenin impedance and the composite load components are identified in a peeling process using the load bus data changes during a large disturbance in the system. The results are then used to anticipate a possible long-term voltage instability caused by the on-load tap changer operation following the disturbance. Work on the standard test system is provided to validate the proposed methods. The findings in this research are expected to provide a better understanding of the load dynamics role in the voltage stability, and improve the reliability and economy of the system operation by making it possible to decrease uncertainty in security margins and determine accurately the transfer limits.
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Navarro-Perez, Rogelio. „Voltage collapse proximity assessment for the operational planning of power systems“. Thesis, Imperial College London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241887.
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Angeles, Antolin Linan Maria. „Effects of load modelling on Voltage Impasse Regions (VIR)“. Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-254416.
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Voltage Impasse Region (VIR) is a phenomenon in power systemswhose dynamics are describe by a set of Differential AlgebraicEquations (DAE). VIR denotes a state-space area where voltagecausality is lost, i.e. the Jacobian of the algebraic part of DAEis singular. In a Time Domain Simulation (TDS) once system trajectoriesenter VIR, TDS experiences non-convergence of the solution.Then, there is no reason to continue with the simulation. Thisis why it is important to understand the mechanisms that introduceVIR. It is known that VIR appears in relation to static, non-linearload models. However, it remained unknown what the cumulativeeffect of several static, non-linear loads would be.This master thesis has further expanded the concept of VIRby carrying out a structured study on how the load modelling affectsVIR. For this purpose, this thesis proposes a quasi-dynamicmethodology to map VIR in the relative rotor angle space. Themethodology introduces a new discrete index called Voltage ImpasseRegion Flag (VIRflag), which allows to determine if the algebraicequations of DAE are solvable or not and, thus, to locate VIR.A test system is used to test the proposed quasi-dynamic approach.The VIRflag was first used to map VIR for various load combinations.Then, the relationship between TDS non-convergence issuesand the intersection of a trajectory with VIR is examined toverify the proposed methodology.The proposed method has been proved to be efficient in the determinationof VIR regardless of the number of non-linear loads inthe power system. Among the static exponential load models, theConstant Power (CP) load component has been identified as theone with the largest influence on VIR appearance and shape. TheConstant Current (CC) loads induce ”smaller" VIR areas and theConstant Impedance (CI) load can only alter the shape of VIR inthe presence of non-linear load models.VIR (Voltage Impasse Regions) är ett fenomen i kraftsystem varsdynamiska förlöp beskrivs av differential-algebraiska ekvationer(DAE). VIR betecknar ett område i tillståndsrummet där går förlorad,dvs Jakobianen av den algebraiska delen av DAE är singulärI tidsdomän-simuleringar (TDS) när en trajektoria träffar VIR,konvergerar TDS inte till en lösning. Då finns ingen anledning attfortsätta med simuleringen. Därför är det viktigt att förstå mekanismernasom introducerar VIR. Det är känt att VIR är relateradetill statiska, icke-linjära lastmodeller. Det var dock okänt vadden kumulativa effekten av flera statiska, icke-linjära belastningarskulle vara.Denna uppsats har vidareutvecklat begreppet VIR genom attgenomföra en strukturerad studie om hur lastmodellering påverkarVIR. För detta ändamål föreslår denna avhandling en kvasidynamiskmetod för att kartlägga VIR i det relativa rotorvinkelrummet.Metoden introducerar ett nytt diskret index som heterVoltage Impasse Region Flag (VIRflag), vilket gör det möjligt attbestämma om den algebraiska delen av DAE är lösbar eller inteoch därmed lokalisera VIR. Ett används för att testa det föreslagnakvasi-dynamiska tillvägagångssättet. VIRflag användes först för attkartlägga VIR för olika belastningskombinationer. Därefter granskasförhållandet mellan konvergensproblem i TDS och korsningenmellan en trajektoria och VIR för att verifiera den föreslagna metoden.Den föreslagna metoden har visat sig vara effektiv vid bestämningav VIR, oberoende av antalet icke-linjära belastningar. Bland destatiska exponentiella belastningsmodellerna har konstanteffektlast(CP) haridentifierats som den som har störst inflytande påVIR;s form. Den konstantströmlasten (CC) inducerar mindre"VIRområdenoch konstantimpedanslasten (CI) kan endast ändra formenav VIR i närvaro av icke-linjära belastningsmodeller.
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Rodrigues, Roberio Paulino. „O colapso da URSS: um estudo das causas“. Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/8/8137/tde-11072007-112541/.
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Investiga as causas históricas, políticas, sociais e econômicas que mais contribuíram para o colapso e desaparecimento da União Soviética em 1991. Como um esforço de reinterpretação do fenômeno, desde a gênese até o esgotamento da URSS, apóia-se em análises e dados de alguns dos mais conhecidos especialistas no assunto. Considera que um conjunto de elementos se combinou para tal desfecho. Aponta como causas principais: a) o atraso material e cultural da velha Rússia para iniciar a construção do socialismo; b) o isolamento da Revolução Russa, fruto, entre outros fatores, do reformismo político que paralisou a classe operária no Ocidente; c) as agressões militares que a URSS sofreu, com suas imensas perdas humanas e os custos insuportáveis de defesa, derivados da ameaça permanente que vinha do exterior, que contribuíram para exauri-la economicamente; d) a natureza ditatorial do sistema político, como elemento central, que se pôde acelerar a industrialização e a modernização em uma primeira fase, trouxe imensos prejuízos humanos por outro e funcionou a partir de certo ponto no tempo como uma trava à continuidade do desenvolvimento da economia e da sociedade; e) o esgotamento do modelo extensivo de crescimento na virada para os anos 70, a desaceleração econômica que chega à estagnação no início dos anos 80 e o acentuado atraso tecnológico em relação ao mundo capitalista, verificado já na década de 70; f) As grandes transformações sociais, culturais e comportamentais ocorridas no mundo e na URSS, a Revolução da Informação e as mobilizações democráticas em todo Leste Europeu, que erodiram as fundações do sistema soviético; g) A Perestroika, que como programa de reformas acelerou a democratização do regime político, levando à desagregação do velho mecanismo burocrático de planejamento e gestão estatais da economia, o que por sua vez gerou caos; h) As mobilizações nacionalistas e a ofensiva restauracionista selaram a desagregação do sistema soviético. O processo final que levou ao colapso da URSS parece mais uma combinação de progressivas revoluções ou mobilizações democráticas - que em muito se assemelham às revoluções burguesas, já que suas bandeiras e demandas não diferem muito daquelas levantadas nas revoluções de 1789 e 1848 - com a implosão de um sistema político debilitado e ultrapassado, onde já não cabiam as forças produtivas e sociais que dentro dele se desenvolviamThe major historical, political, social and economic reasons contributing to the collapse as well as the disintegration of the USSR in 1991 are the core aspects scrutinized in this study. In an effort to make sense of the phenomenon from a different perspective, departing from the genesis to the collapse of the USSR, data analyzed by some of the most renowned researchers has been used as a theoretical basis. In this sense, such an outcome is attributed to a series of combined factors. Not only the material and cultural backwardness of slow-tochange Russia in order to set up socialism, but also the consequent isolation of the Russian Revolution, a result - amongst other factors - of the political conventionalism that paralyzed the Western working class, are two of the main explanations pointed out. A third aspect equally relevant refers to the military attacks that Russia had to cope with, not to mention its huge human losses and the unbearable defense costs - a consequence of permanent external threats -, thus impoverishing the country. On top of that, there is - as a crucial component - the double-edged essence of the dictatorial political system for, if on one hand, it speeds up both industrialization and modernization, on the other hand, it also accounts for huge human losses, thus representing - from a given moment - an obstacle to the continuing economic and social development. A fifth chain of events worth highlighting is the failure of the extensive economic development pattern at the turn of the seventies, followed by the economic deceleration, almost on the verge of stagnation in the eighties, not to mention the conspicuous technological delay when compared to the capitalist world, where it had been in evidence since the seventies. In addition to this, the huge social, cultural and behavioral changes - which took place in the world as well as in the USSR, followed by both the Information Revolution and democratic mobilizations throughout Eastern Europe - undermined the foundations of the Soviet system. Furthermore, while the Perestroika - as a restructuring program - became the catalyst for dismantling the conservative bureaucratic structures of government led planning and management, on the other hand, it also accelerated the democratization of the political government, which produced chaos. Last but by no means least, the nationalist mobilizations allied to the restoration offensive determined the downfall of the Soviet system. By and large, the final process responsible for the collapse of the USSR resembles more a combination of consecutive revolutions or a series of democratic mobilization - very similar to the bourgeois revolutions in many aspects given that its causes and demands do not differ substantially from the ones arisen in the 1789 and 1848 revolutions, - with the dismantling of a debilitated and outdated political system, since productive and social forces in full development in its interior could not fit into such a structure anylonger
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Mukhedkar, Radnya A. „Flexible alternating current transmission systems for the prevention of voltage collapse in electrical power systems“. Thesis, University of the West of England, Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252564.
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Hui, Ka Chun. „Voltage collapse indicators for on-line voltage security monitoring in power systems“. Thesis, Imperial College London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313312.
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Mohammed, Mahmoud M. Jr. „Development of intelligent systems for evaluating voltage profile and collapse under contingency operation“. Diss., Kansas State University, 2011. http://hdl.handle.net/2097/8408.
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Doctor of PhilosophyDepartment of Electrical and Computer Engineering
Shelli K. Starrett
Monitoring and control of modern power systems have become very complex tasks due to the interconnection of power grids. These large-scale power grids confront system operators with a huge set of system inputs and control parameters. This work develops and compares intelligent systems-based algorithms which may be considered by power system operators or planners to help manage, process, and evaluate large amounts of data due to varying conditions within the system. The methods can be used to provide assistance in making operational control and planning decisions for the system in a timely manner. The effectiveness of the proposed algorithms is tested and validated on four different power systems. First, Artificial Neural Network (ANN) models are developed and compared for two different voltage collapse indices and utilizing two different-sized sets of inputs. The ANNs monitor and evaluate the voltage profile of a system and generate intelligent conclusions regarding the status of the system from a voltage stability perspective. A feature reduction technique, based on the analysis of generated data, is used to decrease the number of inputs fed to the ANN, decreasing the number of physical quantities that need to be measured. The major contribution of this work is the development of four different algorithms to control the VAR resources in a system. Four different objectives were also considered in this part of the work, namely: minimization of the number of control changes needed, minimization of the system power losses, minimization of the system's voltage deviations, and consideration of the computational time required. Each of the algorithms is iterative in nature and is designed to take advantage of a method of decoupling the load flow Jacobian matrix to decrease the time needed per iteration. The methods use sensitivity information derived from the load flow Jacobian and augmented with equations relating the desired control and dependent variables. The heuristic-sensitivity based method is compared to two GA-based methods using two different objective functions. In addition, a FL algorithm is added to the heuristic-sensitivity algorithm and compared to a PS-based algorithm. The last part of this dissertation presents the use of one of the GA-based algorithms to identify the size of shunt capacitor necessary to enhance the voltage profile of a system. A method is presented for utilizing contingency cases with this algorithm to determine required capacitor size.
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Wang, Zihao. „Conceptualization and design of a future chest drainage canister“. Thesis, Umeå universitet, Designhögskolan vid Umeå universitet, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-125683.
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Changsha city in Hunan province, China. Place: Changsha Center Hospital, Hunan province. City Area: 11,819 square kilometers City population: 714.66 million I watched the whole process of chest drainage surgery, introduced by Yang Jicheng, who is a thoracic surgeon attending doctor at this capital. During the field research in China, I also had research opportunity of chest drainage management, mostly performed by nurses, where I found out lots of design opportunities about the Chong canister, which was the most popular chest drainage canister used all over the China Then I went back to Umea, Sweden, met Fredrik Homner who is a thoracic surgery doctor working in Norrlands University Hospital for almost 30 years. I told him what I saw in China and we exchanged lots of opinion about chest drainage. I realized that Chinese chest drainage patients were suffering unnecessary pain from outmoded equipment, which in Sweden they had already updated since 20 years ago. Whit help of Fredrik Holmner, I had opportunity to watch the whole process of pulmonary resection and endoscope technical, the focus of this process was the insertion of chest drainage tube at the end of this 5 hours surgery. After I had seen so many materials related to chest drainage, I found out my design focus, which was the Maquet Oasis Drain, that had been recognized as the most advanced chest drainage equipment in the world and had been widely used in Europe and United States.
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Tezcan, Tolga. „State space collapse in many-server diffusion limits of parallel server systems and applications“. Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-07022006-162830/.
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Thesis (Ph. D.)--Industrial and Systems Engineering, Georgia Institute of Technology, 2007.Jiangang Dai, Committee Co-Chair ; Amy Ward, Committee Co-Chair ; Anton Kleywegt, Committee Member ; Ron Billings, Committee Member ; Mor Armony, Committee Member.
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Vignjevic, R. „A simplified simulation of the combined bending/torsion collapse of thin walled beams in the explicit DYNA3D code“. Thesis, Cranfield University, 1993. http://dspace.lib.cranfield.ac.uk/handle/1826/11110.
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Chevalier, Samuel. „Using Real Time Statistical Data To Improve Long Term Voltage Stability In Stochastic Power Systems“. ScholarWorks @ UVM, 2016. http://scholarworks.uvm.edu/graddis/637.
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In order to optimize limited infrastructure, many power systems are frequently operated close to critical, or bifurcation, points. While operating close to such critical points can be economically advantageous, doing so increases the probability of a blackout. With the continued deployment of Phasor Measurement Units (PMUs), high sample rate data are dramatically increasing the real time observability of the power grids. Prior research has shown that the statistics of these data can provide useful information regarding network stability and associated bifurcation proximity. Currently, it is not common practice for transmission and distribution control centers to leverage the higher order statistical properties of PMU data. If grid operators have the tools to determine when these statistics warrant control action, though, then the otherwise unused statistical data present in PMU streams can be transformed into actionable information.
In order to address this problem, we present two methods that aim to gauge and improve system stability using the statistics of PMU data. The first method shows how sensitivity factors associated with the spectral analysis of the reduced power flow Jacobian can be used to weight and filter incoming PMU data. We do so by demonstrating how the derived participation factors directly
predict the relative strength of bus voltage variances throughout a system. The second method leverages an analytical solver to determine a range of "critical" bus voltage variances. The monitoring and testing of raw statistical data in a highly observable load pocket of a large system are then used to reveal when control actions are needed to mitigate the risk of voltage collapse. A simple reactive power controller is then implemented that pushes the stability of the system back to a stable operating paradigm. Full order dynamic time domain simulations are used in order to test this method on both the IEEE 39 bus system and the 2383 bus Polish system. We also compare this method to two other, more conventional, controllers. The first relies on voltage magnitude signals, and the second depends only on local control of a reactive power resource. This comparison illustrates how the use of statistical information from PMU measurements can substantially improve
the performance of voltage collapse mitigation methods.
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Beeravolu, Nagendrakumar. „Pattern Recognition of Power Systems Voltage Stability Using Real Time Simulations“. ScholarWorks@UNO, 2010. http://scholarworks.uno.edu/td/1279.
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The basic idea deals with detecting the voltage collapse ahead of time to provide the operators a lead time for remedial actions and for possible prevention of blackouts. To detect cases of voltage collapse, we shall create methods using pattern recognition in conjunction with real time simulation of case studies and shall develop heuristic methods for separating voltage stable cases from voltage unstable cases that result in response to system contingencies and faults. Using Real Time Simulator in Entergy-UNO Power & Energy Research Laboratory, we shall simulate several contingencies on IEEE 39-Bus Test System and compile the results in two categories of stable and unstable voltage cases. The second stage of the proposed work mainly deals with the study of different patterns of voltage using artificial neural networks. The final stage deals with the training of the controllers in order to detect stability of power system in advance.
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Oyarce, Alejandro. „Electrode degradation in proton exchange membrane fuel cells“. Doctoral thesis, KTH, Tillämpad elektrokemi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-133437.
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The topic of this thesis is the degradation of fuel cell electrodes in proton exchange membrane fuel cells (PEMFCs). In particular, the degradation associated with localized fuel starvation, which is often encountered during start-ups and shut-downs (SUs/SDs) of PEMFCs. At SU/SD, O2 and H2 usually coexist in the anode compartment. This situation forces the opposite electrode, i.e. the cathode, to very high potentials, resulting in the corrosion of the carbon supporting the catalyst, referred to as carbon corrosion. The aim of this thesis has been to develop methods, materials and strategies to address the issues associated to carbon corrosion in PEMFC.The extent of catalyst degradation is commonly evaluated determining the electrochemically active surface area (ECSA) of fuel cell electrode. Therefore, it was considered important to study the effect of RH, temperature and type of accelerated degradation test (ADT) on the ECSA. Low RH decreases the ECSA of the electrode, attributed to re-structuring the ionomer and loss of contact with the catalyst.In the search for more durable supports, we evaluated different accelerated degradation tests (ADTs) for carbon corrosion. Potentiostatic holds at 1.2 V vs. RHE were found to be too mild. Potentiostatic holds at 1.4 V vs. RHE were found to induce a large degree of reversibility, also attributed to ionomer re-structuring. Triangle-wave potential cycling was found to irreversibly degrade the electrode within a reasonable amount of time, closely simulating SU/SD conditions.Corrosion of carbon-based supports not only degrades the catalyst by lowering the ECSA, but also has a profound effect on the electrode morphology. Decreased electrode porosity, increased agglomerate size and ionomer enrichment all contribute to the degradation of the mass-transport properties of the cathode. Graphitized carbon fibers were found to be 5 times more corrosion resistant than conventional carbons, primarily attributed to their lower surface area. Furthermore, fibers were found to better maintain the integrity of the electrode morphology, generally showing less degradation of the mass-transport losses. Different system strategies for shut-down were evaluated. Not doing anything to the fuel cell during shut-downs is detrimental for the fuel cell. O2 consumption with a load and H2 purge of the cathode were found to give around 100 times lower degradation rates compared to not doing anything and almost 10 times lower degradation rate than a simple air purge of the anode. Finally, in-situ measurements of contact resistance showed that the contact resistance between GDL and BPP is highly dynamic and changes with operating conditions.Denna doktorsavhandling behandlar degraderingen av polymerelektrolytbränslecellselektroder. polymerelektrolytbränslecellselektroder. Den handlar särskilt om nedbrytningen av elektroden kopplad till en degraderingsmekanism som heter ”localized fuel starvation” oftast närvarande vid uppstart och nedstängning av bränslecellen. Vid start och stopp kan syrgas och vätgas förekomma samtidigt i anoden. Detta leder till väldigt höga elektrodpotentialer i katoden. Resultatet av detta är att kolbaserade katalysatorbärare korroderar och att bränslecellens livslängd förkortas. Målet med avhandlingen har varit att utveckla metoder, material och strategier för att både öka förståelsen av denna degraderingsmekanism och för att maximera katalysatorbärarens livslängd.Ett vanligt tillvägagångsätt för att bestämma graden av katalysatorns degradering är genom mätning av den elektrokemiskt aktiva ytan hos bränslecellselektroderna. I denna avhandling har dessutom effekten av temperatur och relativ fukthalt studerats. Låga fukthalter minskar den aktiva ytan hos elektroden, vilket sannolikt orsakas av en omstrukturering av jonomeren och av kontaktförlust mellan jonomer och katalysator.Olika accelererade degraderingstester för kolkorrosion har använts. Potentiostatiska tester vid 1.2 V mot RHE visade sig vara för milda. Potentiostatiska tester vid 1.4 V mot RHE visade sig däremot medföra en hög grad av reversibilitet, som också den tros vara orsakad av en omstrukturering av jonomeren. Cykling av elektrodpotentialen degraderade istället elektroden irreversibelt, inom rimlig tid och kunde väldigt nära simulera förhållandena vid uppstart och nedstängning.Korrosionen av katalysatorbäraren medför degradering av katalysatorn och har också en stor inverkan på elektrodens morfologi. En minskad elektrodporositet, en ökad agglomeratstorlek och en anrikning av jonomeren gör att elektrodens masstransportegenskaper försämras. Grafitiska kolfibrer visade sig vara mer resistenta mot kolkorrosion än konventionella kol, främst p.g.a. deras låga ytarea. Grafitiska kolfibrer visade också en förmåga att bättre bibehålla elektrodens morfologi efter accelererade tester, vilket resulterade i lägre masstransportförluster.Olika systemstrategier för nedstängning jämfördes. Att inte göra något under nedstängning är mycket skadligt för bränslecellen. Förbrukning av syre med en last och spolning av katoden med vätgas visade 100 gånger lägre degraderingshastighet av bränslecellsprestanda jämfört med att inte göra något alls och 10 gånger lägre degraderingshastighet jämfört med spolning av anoden med luft. In-situ kontaktresistansmätningar visade att kontaktresistansen mellan bipolära plattor och GDL är dynamisk och kan ändras beroende på driftförhållandena.
QC 20131104
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Cindi, Brian Msizi. „3-D Seismic structural interpretation : insights to thrust faulting and paleo-stress field distribution in the deep offshore Orange Basin, South Africa“. University of the Western Cape, 2016. http://hdl.handle.net/11394/5548.
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>Magister Scientiae - MScThe Orange Basin provides exceptional 3-D structures of folds and faults generated during soft-sediment slumping and deformation which is progressive in nature. 3-D seismic and structural evaluation techniques have been used to understand the geometric architecture of the gravity collapse structures. The location of the seismic surveyed area is approximately 370 km northwest of the Port of Saldanha. The interpretation of gravitational tectonics indicate significant amount of deformation that is not accounted for in the imaged thrust belt structure. The Study area covers 8200 square kilometre (km²) of the total 130 000 km² area of the Orange Basin offshore South Africa. The south parts of the Study area are largely featureless towards the shelf area. The north has chaotic seismic facies as the result of an increase in thrust faults in seismic facies 2. Episodic gravitational collapse system of the Orange Basin margin characterizes the late Cretaceous post-rift evolution. This Study area shows that implications of stress field and thrust faulting to the thickness change by gravity collapse systems are not only the result of geological processes such as rapid sedimentation, margin uplift and subsidence, but also could have occurred as the result of the possible meteorite impact. These processes caused gravitational potential energy contrast and created gravity collapse features that are observed between 3000-4500ms TWT intervals in the seismic data.
Shell Exploration & Production Company
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Caswell, Joseph M. „THE POTENTIAL ROLE OF CONSCIOUSNESS IN THE COLLAPSE OF RANDOM PHYSICAL SYSTEMS: A QUANTITATIVE BIOPHYSICAL INVESTIGATION OF COGNITIVE INTENTION“. Thesis, Laurentian University of Sudbury, 2014. https://zone.biblio.laurentian.ca/dspace/handle/10219/2202.
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Decades of research into the anomalous phenomenon of consciousness-correlated collapse of random systems has supported the contention that human intention appears capable of eliciting significant deviations within these external systems. The following series of experiments was conducted in order to identify potential physical factors which might play a role in the consciousness-correlated effects on a random event generator device. Transcerebral application of a specific physiologically-patterned electromagnetic field was found to enhance the occurrence of this consciousness-mediated interaction. Furthermore, immersing the test area in electromagnetic ‘noise’ appears to interfere with the apparent effects of intention. Subsequent analyses were conducted in order to examine the potential contributions of gravitational sources on this phenomenon. Cerebral biophoton emission was also examined which determined that biophotons are related to the output of a proximal random event generator within both time and frequency domains. This initial series of experiments revealed a seemingly integral temporal component in this form of experiment which occurs at approximately 2 minutes into the test phase. Finally, space weather factors were examined for potential associations with the random event generator phenomenon which revealed a number of significant relationships that may contribute to this process. An artificial neural network was then constructed in order to predict values of geomagnetic activity for future experiments. These results may be among the first to quantitatively identify the probable energies and physical parameters associated with successful consciousness-mediated non-local interaction with an external system.
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Judd, Johnn P. „Multi-hazard performance of steel moment frame buildings with collapse prevention systems in the central and eastern United States“. Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/73509.
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This dissertation discusses the potential for using a conventional main lateral-force resisting system, combined with the reserve strength in the gravity framing, and or auxiliary collapse-inhibiting mechanisms deployed throughout the building, or enhanced shear tab connections, to provide adequate serviceability performance and collapse safety for seismic and wind hazards in the central and eastern United States. While the proposed concept is likely applicable to building structures of all materials, the focus of this study is on structural steel-frame buildings using either non-ductile moment frames with fully-restrained flange welded connections not specifically detailed for seismic resistance, or ductile moment frames with reduced beam section connections designed for moderate seismic demands.
The research shows that collapse prevention systems were effective at reducing the conditional probability of seismic collapse during Maximum Considered Earthquake (MCE) level ground motions, and at lowering the seismic and wind collapse risk of a building with moment frames not specifically detailed for seismic resistance. Reserve lateral strength in gravity framing, including the shear tab connections was a significant factor. The pattern of collapse prevention component failure depended on the type of loading, archetype building, and type of collapse prevention system, but most story collapse mechanisms formed in the lower stories of the building. Collapse prevention devices usually did not change the story failure mechanism of the building. Collapse prevention systems with energy dissipation devices contributed to a significant reduction in both repair cost and downtime. Resilience contour plots showed that reserve lateral strength in the gravity framing was effective at reducing recovery time, but less effective at reducing the associated economic losses. A conventional lateral force resisting system or a collapse prevention system with a highly ductile moment frame would be required for regions of higher seismicity or exposed to high hurricane wind speeds, but buildings with collapse prevention systems were adequate for many regions in the central and eastern United States.Ph. D.
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Keskin, Mehmet B. „Continuation Power Flow And Voltage Stability In Power Systems“. Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608718/index.pdf.
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This thesis investigates an important power system phenomenon, voltage stability, by using continuation power flow method. Voltage collapse scenario is presented which can be a serious result of voltage instability and the parameters that affect voltage collapse are discussed.
In analyzing power system voltage stability, continuation power flow method is utilized which consists of successive load flows. This method is applied to a sample test system and Turkish Power System and load-voltage curves for several buses are obtained.
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Slovenec, Derek. „Multi-Hazard Assessment and Performance-Based Design of Facade Systems including Building Frame Interaction“. Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1560187143941942.
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Brosius, Logan Robert Thomas. „On the Rise of China, The Reconfiguration of Global Power, and the Collapse of the Modern Liberal Order“. Kent State University Honors College / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1453337681.
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Mukhopadhyay, Shayok. „Robust forward invariant sets for nonlinear systems“. Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52311.
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The process of quantifying the robustness of a given nonlinear system is not necessarily trivial. If the dynamics of the system in question are not sufficiently involved, then a tight estimate of a bound on system performance may be obtained. As the dynamics of the system concerned become more and more involved, it is often found that using the results existing in the literature provides a very conservative bound on system performance. Therefore, the motivation for this work is to develop a general method to obtain a less conservative estimate of a bound on system performance, compared to the results already available in literature. The scope of this work is limited to two dimensions at present. Note that working in a two dimensional space does not necessarily make the objective easily achievable. This is because quantifying the robustness of a general nonlinear system perturbed by disturbances can very easily become intractable, even on a space with dimension as low as two.
The primary contribution of this work is a computational algorithm, the points generated by which are conjectured to lie on the boundary of the smallest robust forward invariant set for a given nonlinear system. A well known path-planning algorithm, available in existing literature, is leveraged to make the algorithm developed computationally efficient.
If the system dynamics are not accurately known, then the above computed approximation of an invariant set may cease to be invariant over the given finite time interval for which the computed set is expected to be invariant. Therefore, the secondary contribution of this work is an algorithm monitoring a computed approximation of an invariant set. It is shown that for a certain type of systems, this secondary monitoring algorithm can be used to detect that a computed approximation of an invariant set is about to cease to be invariant, even if the primary algorithm computed the set based on an unsophisticated dynamical model of a system under consideration.
The work related to computing approximations of invariant sets is tested mainly with the curve tracking problem in two dimensions. The algorithm monitoring whether a computed approximation of an invariant set is about to cease to be invariant is inspired by work related to detecting Lithium-ion (Li-ion) battery terminal voltage collapse detection.
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Qin, Wenyi. „Many server queueing models with heterogeneous servers and parameter uncertainty with customer contact centre applications“. Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/33167.
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In this thesis, we study the queueing systems with heterogeneous servers and service rate uncertainty under the Halfin-Whitt heavy traffic regime. First, we analyse many server queues with abandonments when service rates are i.i.d. random variables. We derive a diffusion approximation using a novel method. The diffusion has a random drift, and hence depending on the realisations of service rates, the system can be in Quality Driven (QD), Efficiency Driven (ED) or Quality-Efficiency-Driven (QED) regime. When the system is under QD or QED regime, the abandonments are negligible in the fluid limit, but when it is under ED regime, the probability of abandonment will converge to a non-zero value. We then analyse the optimal staffing levels to balance holding costs with staffing costs combining these three regimes. We also analyse how the variance of service rates influence abandonment rate. Next, we focus on the state space collapse (SSC) phenomenon. We prove that under some assumptions, the system process will collapse to a lower dimensional process without losing essential information. We first formulate a general method to prove SSC results inside pools for heavy traffic systems using the hydrodynamic limit idea. Then we work on the SSC in multi-class queueing networks under the Halfin-Whitt heavy traffic when service rates are i.i.d. random variables within pools. For such systems, exact analysis provides limited insight on the general properties. Alternatively, asymptotic analysis by diffusion approximation proves to be effective. Further, limit theorems, which state the diffusively scaled system process weakly converges to a diffusion process, are usually the central part in such asymptotic analysis. The SSC result is key to proving such a limit. We conclude by giving examples on how SSC is applied to the analysis of systems.