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Kernan, Martin Richard. "Predicting surface water critical loads at the catchment scale." Thesis, University College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298825.
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Current applications of the critical loads concept are geared primarily towards targeting emission control strategies at a national and international level. In the UK maps of critical loads for freshwaters are available at 10km2 resolution based on a single representative site in each grid square. These maps do not take variations of water chemistry within mapping units into account and are therefore of limited use for application to non-mapped sites. This thesis describes the development of an empirical statistical model, which uses nationally available secondary data, to predict freshwater critical loads for catchments lacking the appropriate water chemistry information. A calibration exercise using data from 78 catchments throughout Scotland is described. Water chemistry for each catchment has been determined and each catchment is characterised according to a number of attributes. Multivariate statistical analysis of these data shows clear relationships between catchment attributes and water chemistry and between water chemistry and diatom critical load. The key variables which explain most of the variation in critical load relate to soil, geology and land use within the catchment. Using these variables (as predictors) in a regression analysis diatom critical load could be predicted across a broad gradient of sensitivity (R2adj = c. 0.8). The predictive power of the model was maintained when different combinations of explanatory variables were used. This accords the model a degree of flexibility in that model paramaterisation can be geared towards availability of secondary data. There are limitations with the model. These relate to the nature of the predictor variables and the ability of the model to predict critical loads for more sensitive sites. Nevertheless the ability of the model to differentiate between sensitive and non-sensitive sites offers considerable scope for environmental managers to undertake national inventories of catchment sensitivity and specific assessments of individual catchments.
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BURGOS, RODRIGO BIRD. "EVALUATION OF CRITICAL LOADS AND INITIAL POST-BUCKLING BEHAVIOR OF PORTAL FRAMES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2005. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=6714@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICONesta dissertação estuda-se a flambagem e o comportamento pós-crítico inicial de pórticos planos através da formulação de elementos finitos com graus de liberdade adicionais para posterior implementação no programa de análise FTOOL. Realizaram-se análises linearizadas para a determinação das cargas críticas clássicas e modos de flambagem de colunas com diferentes condições de contorno. Em um segundo momento, realizaram-se testes numéricos no sentido de prever a estabilidade do caminho pós-crítico (sensibilidade a imperfeições) de algumas estruturas cujos resultados analíticos são conhecidos. Finalmente, criaram- se alguns exemplos no FTOOL para comprovar a sua eficácia na obtenção de cargas críticas e avaliação do comportamento pós-crítico inicial de pórticos planos. Utilizou-se o pórtico de Roorda como exemplo para a detecção da sensibilidade a imperfeições, devido à sua simplicidade e ao conhecimento dos seus resultados analíticos.
The buckling and post-buckling behavior of portal frames are studied by the formulation of finite elements with additional degrees of freedom in order to implement a new routine for obtaining critical loads in FTOOL, a structural analysis educational interactive system. Linearized analyses were performed in order to obtain critical loads and buckling modes for columns with different boundary conditions. Later, numerical tests were done in order to predict the stability of the post- critical path (sensitivity to imperfections) of some structures which analytical results are known. Finally, some examples were modeled in FTOOL to verify its accuracy in obtaining critical loads of portal frames. Roorda s frame was used as an example for the detection of the sensitivity to imperfections, based on its simplicity and knowledge of its analytical results.
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MacPhee, Kirsty Potts. "Hydrochemistry, soil chemistry and critical loads of selected upland moorland catchments, Scotland." Thesis, University of Aberdeen, 1997. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU094086.
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This thesis presents precipitation, streamwater and soil chemistry from three upland catchments in Scotland situated upon granite parent material and receiving different deposition loadings. Marine ions are identified as important components of precipitation and streamwater at the two coastal sites (Bealach and Cardoon) and lesser importance at the inland site (Allt a'Mharcaidh). Similar ratios of Na:Ca:Mg in precipitation and streamwater indicate the importance of catchment hydrology and organic soils in controlling streamwater chemistry. Input/output budgets indicate SO4-S and H+ loss from the Cardoon (a region of high acid deposition inputs) compared with the other two less polluted sites which exhibit SO4-S and H + retention. The SO4-S loss from the Cardoon is also associated with a high DOC flux in streamwater. In all three catchments differences were found between published critical load values and those calculated as part of this study. Seasonal and annual variations in critical loads for freshwaters at all sites indicate sampling for the national mapping exercise does not reflect the most acid-sensitive periods. Streamwater was also more sensitive than standing waters, with lower critical load values. Soil critical load values were lower than published soil critical load values as well as freshwater critical loads calculated in this study. Inclusion of marine-derived base-cations in PROFILE calculations of soil critical loads increased values markedly (1 keq ha-1yr -1) at the 2 coastal sites. Soil critical load varied little between horizons, suggesting that the identification of hydrologically important mineral horizon was not important. Lowest critical load values for freshwaters were controlled by the organic horizons which are not considered in PROFILE calculations. The implications of the omission of organic horizons from critical load calculations for soil in upland catchments are discussed and the use of critical loads at a catchment based level addressed.
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Smith, Carol M. S. "Assessment of critical loads of acidity for selected U.K. upland organic soils." Thesis, University of Aberdeen, 1993. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU555089.
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The use of critical loads of acidity to quantify damage to sensitive components of terrestrial and aquatic ecosystems has developed rapidly over the last decade. While much work has focused on defining damage to forested ecosystems, surface waters and groundwaters, there has been little work done on defining critical loads of acidity for ombrotrophic and minerotrophic peat. This thesis presents a modelling approach to quantify damage to ombrotrophic peat ecosystems, since such damage can result in a decline in both surface water quality and the ability of peat to act as an absorbent to aerial pollutants. Initial investigations were concerned with the factors which could be included in investigations of critical loads of N and acidity to the surface organic horizons of forest and moorland soils. The modelling approach was then developed from a series of laboratory-based simulation experiments to investigate the effect of contents of H&'43 , Ca2&'43 and Mg2&'43 in rainfall upon the chemistry of the peat ion exchange complex. The basic tenet of the modelling approach was that ion exchange equilibria for peat is rapid, mineral input to the surface of ombrotrophic peat from mineral weathering is negligible and that atmospheric inputs of wet and dry deposition will dominate the peat chemistry. These simulation experiments provided peat pH values resulting from equilibration with the simulated rainfall. By combining these with databases of atmospheric depositon for the U.K., critical loads of acidity and the present day peat pH were calculated and mapped. The critical load values for peat thus obtained were incorporated in the U.K. Critical Load mapping program, which was used to support the on-going European negotiations of emission reduction within the United Nations Convention on Long-range Transboundary Air Pollution (U.N. E.C.E. C.L.T.A.P.).
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Gustafson, David J. "Utilizing an energy management system with distributed resources to manage critical loads and reduce energy costs." Thesis, Monterey, California: Naval Postgraduate School, 2014. http://hdl.handle.net/10945/43921.
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Approved for public release; distribution is unlimitedEnergy security is critical to the DOD and can be achieved using different methods, but for DOD installations cost effectiveness must be taken into consideration when evaluating energy security goals. Energy Storage Systems (ESSs) have a wide range of associated technologies as well as large differences in cost and capabilities. This study examines the cost effectiveness of utilizing an ESS to perform peak shaving with an Energy Management System (EMS). An EMS used with an ESS can perform several functions that can be beneficial to the grid. These functions include peak shaving, conducting power factor correction, matching critical load to most efficient distributed resource, and islanding a system during commercial grid disruption. While utilizing an ESS within a microgrid allows several benefits, to include peak shaving, the ability to utilize photovoltaic arrays during islanding, and power factor correction, the implementation of the ESS by itself is likely to prove cost prohibitive. The DOD requires energy projects to have net savings over the life cycle of the project and in areas without high differential between peak power and off-peak power, this goal will be difficult to achieve.
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Kennedy, Fiona M. "Soil mineral weathering rates and critical loads of sulphur at six forested sites in the UK." Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363834.
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Rapp, Lars. "Critical loads of acid deposition for surface water : exploring existing models and a potential alternative for Sweden /." Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 2001. http://epsilon.slu.se/avh/2001/91-576-6091-3.pdf.
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Schlutow, Angela, and Thomas Scheuschner. "Ökologische Belastungsgrenzen - Aktualisierung und Präzisierung der Erfassung von ökologischen Belastungsgrenzen und ihrer Überschreitungen im Freistaat Sachsen – Fortschreibung der Critical Loads/Level- Untersuchungen bis 2006." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1242142532199-71513.
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Mit dem Critical Loads/Levels-Konzept wurde ein europäischer Ansatz verwirklicht, der einerseits die Notwendigkeit zur Verminderung des Eintrags von Luftschadstoffen verdeutlicht, andererseits die Beurteilung des Erfolgs von Luftreinhaltemaßnahmen erlaubt. Im vorliegenden Heft werden für Sachsen die Überschreitungen der ökologischen Belastungsgrenzen hinsichtlich des Säure- und Stickstoffeintrages für die Rezeptoren Wald und naturnahe waldfreie Ökosysteme dargestellt. Diese liegen für den Zeitraum 1990 - 2006 im Landesplanungsmaßstab (1:200.000) vor. Danach sind viele sächsische Ökosysteme einer ernst zu nehmenden kritischen Belastung insbesondere durch oxidierte und reduzierte Stickstoffverbindungen aus der Atmosphäre ausgesetzt. Das vorliegende Heft richtet sich insbesondere an Institutionen, die an Planungen im Landes-, Regional- und lokalen Maßstab beteiligt sind, aber auch an Naturschutzverbände, Eigentümer und Nutzer des Waldes sowie Forschungseinrichtungen und die interessierte Öffentlichkeit.
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Feroze, Hassan. "Multi-Agent Systems in Microgrids: Design and Implementation." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/34687.
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The security and resiliency of electric power supply to serve critical facilities are of high importance in todayâ s world. Instead of building large electric power grids and high capacity transmission lines, an intelligent microgrid (or smart grid) can be considered as a promising power supply alternative. In recent years, multi-agent systems have been proposed to provide intelligent energy control and management systems in microgrids. Multi-agent systems offer their inherent benefits of flexibility, extensibility, autonomy, reduced maintenance and more. The implementation of a control network based on multi-agent systems that is capable of making intelligent decisions on behalf of the user has become an area of intense research.
Many previous works have proposed multi-agent system architectures that deal with buying and selling of energy within a microgrid and algorithms for auction systems. The others proposed frameworks for multi-agent systems that could be further developed for real life control of microgrid systems. However, most proposed methods ignore the process of sharing energy resources among multiple distinct sets of prioritized loads. It is important to study a scenario that emphasizes on supporting critical loads during outages based on the userâ s preferences and limited capacity. The situation becomes further appealing when an excess DER capacity after supplying critical loads is allocated to support non-critical loads that belong to multiple users. The previous works also ignore the study of dynamic interactions between the agents and the physical systems. It is important to study the interaction and time delay when an agent issues a control signal to control a physical device in a microgrid and when the command is executed. Agents must be able to respond to the information sensed from the external environment quickly enough to manage the microgrid in a timely fashion. The ability of agents to disconnect the microgrid during emergencies should also be studied. These issues are identified as knowledge gaps that are of focus in this thesis.
The objective of this research is to design, develop and implement a multi-agent system that enables real-time management of a microgrid. These include securing critical loads and supporting non-critical loads belonging to various owners with the distributed energy resource that has limited capacity during outages.
The system under study consists of physical (microgrid) and cyber elements (multi-agent system). The cyber part or the multi-agent system is of primary focus of this work. The microgrid simulation has been implemented in Matlab/Simulink. It is a simplified distribution circuit that consists of one distributed energy resources (DER), loads and the main grid power supply. For the multi-agent system implementation, various open source agent building toolkits are compared to identify the most suitable agent toolkit for implementation in the proposed multi-agent system. The agent architecture is then designed by dividing overall goal of the system into several smaller tasks and assigning them to each agent. The implementation of multi-agent system was completed by identifying Roles (Role Modeling) and Responsibilities (Social and Domain Responsibilities) of agents in the system, and modeling the Knowledge (Facts), rules and ontology for the agents. Finally, both microgrid simulation and multi-agent system are connected together via TCP/IP using external java programming and a third party TCP server in the Matlab/Simulink environment.
In summary, the multi-agent system is designed, developed and implemented in several simulation test cases. It is expected that this work will provide an insight into the design and development of a multi-agent system, as well as serving as a basis for practical implementation of an agent-based technology in a microgrid environment. Furthermore, the work also contributes to new design schemes to increase multi-agent systemâ s intelligence. In particular, these include control algorithms for intelligently managing the limited supply from a DER during emergencies to secure critical loads, and at the same time supporting non-critical loads when the users need the most.Master of Science
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Darestani, Mostafa Yousefi. "Response of concrete pavements under moving vehicular loads and environmental effects." Queensland University of Technology, 2007. http://eprints.qut.edu.au/16662/.
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The need for modern transportation systems together with the high demand for sustainable pavements under applied loads have led to a great deal of research on concrete pavements worldwide. Development of finite element techniques enabled researchers to analyse the concrete pavement under a combination of axle group loadings and environmental effects. Consequently, mechanistic approaches for designing of concrete pavements were developed based on results of finite element analyses. However, unpredictable failure modes of concrete pavements associated with expensive maintenance and rehabilitation costs have led to the use of empiricalmechanistic approach in concrete pavement design. Despite progressive knowledge of concrete pavement behaviour under applied loads, concrete pavements still suffer from deterioration due to crack initiation and propagation, indicating the need for further research. Cracks can be related to fatigue of the concrete and/or erosion of materials in sub-layers. Although longitudinal, midedge and corner cracks are the most common damage modes in concrete pavements, Austroads method for concrete pavement design was developed based on traditional mid-edge bottom-up transverse cracking introduced by Packard and Tayabji (1985). Research presented in this thesis aims to address the most common fatigue related distresses in concrete pavements. It uses comprehensive finite element models and analyses to determine the structural behaviour of concrete pavements under vehicular loads and environmental effects. Results of this research are supported by laboratory tests and an experimental field test. Results of this research indicate that the induced tensile stresses within the concrete pavement are significantly affected by vehicle speed, differential temperature gradient and loss of moisture content. Subsequently, the interaction between the above mentioned factors and concrete damage modes are discussed. Typical dynamic amplifications of different axle groups are presented. A new fatigue test setup is also developed to take into consideration effects of pavement curvature on fatigue life of the concrete. Ultimately, results of the research presented in this thesis are employed to develop a new guide for designing concrete pavements with zero maintenance of fatigue damage.
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Malan, Andreas Dawid. "Critical normal traffic loading for flexure of bridges according to TMH7." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80013.
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Thesis (MScEng)--Stellenbosch University, 2013.ENGLISH ABSTRACT: Different types of live loading due to traffic may act on bridges. The focus of this study is on normal traffic loading according to the South African specification of TMH7. Heavy vehicles are not included in normal traffic loading. TMH7 represents the code of practice for the design of highway bridges and culverts in South Africa. The aim of the study is to provide an insight into the flexural analysis of skew bridges, under the effects of normal traffic loading. The need for the study arose since the specification of TMH7 does not explicitly specify application patterns for normal traffic loading. Only the intensity of normal traffic loading is specified and it should be applied to yield the most adverse effects. For these reasons, a set of so-called standard application patterns are investigated and developed through the course of this study. The envelope of the values from the standard application patterns are compared to the most adverse application pattern for flexural effects in certain design regions of the bridge deck. Flexure, as in the context of this study, translates into the bending and twisting of the bridge deck under loads. A number of numerical experiments are performed for typical single span and multi-span continuous carriageways, where the standard application patterns are compared to the most adverse application patterns. The results from the numerical experiments are documented and compared as the angle of skew of the bridge deck increases in plan-view. For this purpose, the development of effective and specialized software was necessary. It was found that the set of standard application patterns can be used as a preliminary approximation for the most adverse effects of normal traffic loading, for specific flexural resultants in certain design regions of a bridge deck. However, for a large number of secondary flexural effects, the set of standard application patterns did not represent a good approximation for the most adverse values.
AFRIKAANSE OPSOMMING: Verskillende tipes lewendige belasting, as gevolg van verkeer, kan op brûe inwerk. Die fokus van die studie is op normale verkeers-belasting volgens die Suid-Afrikaanse spesifikasie van TMH7. Swaar-voertuie word nie ingesluit by normale verkeers-belasting nie. TMH7 verteenwoordig die kode vir die ontwerp van padbrûe en duikers in Suid-Afrika. Die doel van die studie is om insig te verskaf in die buig-analise van skewe brûe, as gevolg van die werking van normale verkeers-belasting. Die rede vir hierdie studie ontstaan aangesien die spesifikasie van TMH7 nie eksplisiet aanwendingspatrone vir normale verkeers-belasting voorskryf nie. Slegs die intensiteit van normale verkeersbelasting word voorgeskryf en dit moet aangewend word om die negatiefste effekte te verkry. Vir hierdie redes word 'n versameling van sogenaamde standaard aanwendings-patrone deur die loop van die studie ondersoek en ontwikkel. Die omhullings-kurwe van die waardes wat deur die standaard patrone gelewer word, word vergelyk met die waarde van die aanwendings-patroon wat die negatiefste buig-effek in sekere ontwerp-areas van die brugdek veroorsaak. Buig-effekte, soos van toepassing op hierdie studie, verwys na buig en wring van die brugdek as gevolg van belastings. 'n Aantal numeriese eksperimente, vir enkel-span sowel as multi-span deurlopende brugdekke, word uitgevoer en die standaard aanwendings-patrone word vergelyk met die aanwendings-patrone wat die negatiefste waardes lewer. Die resultate van die numeriese eksperimente word gedokumenteer en vergelyk soos die hoek van skeefheid van die brugdek in plan-aansig toeneem. Vir hierdie doel is die ontwikkeling van effektiewe en gespesialiseerde sagteware dus nodig. Daar is gevind dat die standaard aanwendings-patrone, vir spesifieke buig-resultante in sekere ontwerp-areas van die brugdek, as 'n voorlopige benadering vir die negatiefste effekte van normale verkeers-belasting gebruik kan word. Dit was egter verder gevind dat vir 'n groot aantal sekondêre buig-effkte, die versameling standaard aanwendings-patrone nie as 'n goeie benadering vir die negatiefste waardes dien nie.
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Kargarmoakhar, Ramtin. "Large-Scale Testing to Study the Effects of Critical Parameters on the Aerodynamic Behavior of Long Span Bridges." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/1857.
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Long-span bridges are flexible and therefore are sensitive to wind induced effects. One way to improve the stability of long span bridges against flutter is to use cross-sections that involve twin side-by-side decks. However, this can amplify responses due to vortex induced oscillations.
Wind tunnel testing is a well-established practice to evaluate the stability of bridges against wind loads. In order to study the response of the prototype in laboratory, dynamic similarity requirements should be satisfied. One of the parameters that is normally violated in wind tunnel testing is Reynolds number. In this dissertation, the effects of Reynolds number on the aerodynamics of a double deck bridge were evaluated by measuring fluctuating forces on a motionless sectional model of a bridge at different wind speeds representing different Reynolds regimes. Also, the efficacy of vortex mitigation devices was evaluated at different Reynolds number regimes.
One other parameter that is frequently ignored in wind tunnel studies is the correct simulation of turbulence characteristics. Due to the difficulties in simulating flow with large turbulence length scale on a sectional model, wind tunnel tests are often performed in smooth flow as a conservative approach. The validity of simplifying assumptions in calculation of buffeting loads, as the direct impact of turbulence, needs to be verified for twin deck bridges. The effects of turbulence characteristics were investigated by testing sectional models of a twin deck bridge under two different turbulent flow conditions.
Not only the flow properties play an important role on the aerodynamic response of the bridge, but also the geometry of the cross section shape is expected to have significant effects. In this dissertation, the effects of deck details, such as width of the gap between the twin decks, and traffic barriers on the aerodynamic characteristics of a twin deck bridge were investigated, particularly on the vortex shedding forces with the aim of clarifying how these shape details can alter the wind induced responses.
Finally, a summary of the issues that are involved in designing a dynamic test rig for high Reynolds number tests is given, using the studied cross section as an example.
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Strengbom, Joachim. "Nitrogen, parasites and plants : key interactions in boreal forest ecosystems." Doctoral thesis, Umeå universitet, Ekologi och geovetenskap, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-111110.
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In the work described in this thesis I studied how increases in nitrogen (N) inputs may affect plant community structure in boreal forest understorey vegetation. These phenomena were investigated in N fertilization experiments and along a national N deposition gradient. After five years of N additions, large changes in understorey vegetation composition were observed in the fertilization study. In plots that received 50 kg N ha'1 year"1 (N2), the abundance of the dominant species, Vaccinium myrtillus, decreased on average by 32 %. No decrease was observed in control plots during the same period. In contrast, the grass Deschampsia flexuosa responded positively to increased N input, being on average more than five times as abundant in the N2 treatments as in controls. Also an increase was seen in the incidence of disease caused by the parasitic fungus Valdensia heterodoxa on leaves of V. myrtillus following N additions. The parasite was on average nearly twice as abundant in N2 plots than in control plots. This could be explained by increased N concentrations in host plant tissue. Disease incidence also increased following experimental additions of glutamine to leaf surfaces of V. myrtillus, suggesting a causal connection between plant N concentration and performance of the fungus. The parasite also played a key role in the observed changes in understorey species composition. D. flexuosa was more abundant in patches in which V. myrtillus was severely affected by V heterodoxa. This suggests that V heterodoxa mediates the increased abundance of D. flexuosa following increased N additions. The fungus mediates changes in the composition of understorey vegetation mainly by increasing light availability via premature leaf loss of V. myrtillus. The incidence of disease due to the parasite was on average higher in large than in smaller N-treated plots, indicating that the response to N fertilization is spatially scale dependent. This shows that using small plot sizes in experiments that simulate changed environmental conditions may be problematic, as important interactions may be underestimated. Comparison of the occurrence of understorey species between regions with different rates of N deposition revealed that the occurrence of the two dwarf shrubs V. myrtillus and V. vitis- idaea was lower in regions with high N deposition compared to regions with low deposition. The opposite pattern was found for V heterodoxa. This is consistent with expectations from N fertilization experiments. For D. flexuosa no differences in occurrence were found between the different regions investigated. The effects on vegetation and mycorrhizal fungi observed following N additions were also found to be long lasting. Nine years after termination of the fertilization, no signs of recovery were detected, and nearly 50 years after termination characteristic signs of N fertilization were found among bryophytes and mycorrhizal fungi. This suggests that the time needed for re-establishment of the original biota following N-induced changes may be substantial.Diss. (sammanfattning) Umeå : Umeå universitet, 2002, härtill 5 uppsatser
digitalisering@umu
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Freitas, Alexandre Alves de. "Situações críticas no projeto de edifícios de concreto armado submetidos a ações de construção." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-18042005-182719/.
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O presente trabalho consiste no estudo das ações construtivas e seus efeitos em edifícios de concreto armado. Para a avaliação desses efeitos é aplicado o método das estruturas primárias em pavimentos de edifícios, verificando-se os estados limites durante a sua construção. São considerados edifícios com diferentes subsistemas horizontais, alterando-se o sistema de escoramento e o ciclo de construção. As condições de construção são comparadas com aquelas usualmente empregadas no projeto estrutural que considera o edifício submetido às ações finais e com resistência do concreto aos 28 dias, buscando evidenciar as que são críticas. A partir dos resultados obtidos na pesquisa conclui-se que a situação usual de projeto está a favor da segurança para sistemas estruturais semelhantes aos apresentados e nas situações construtivas adotadas.The present work deals with the structural effects of construction loads on reinforced concrete buildings. The evaluation of those effects is carried out on building floors with the method of the primary structures, including the verification of all limit states during the construction phase. Alternative structural systems are considered for buildings, varying the formwork and the construction cycle. The usual structural design, which considers the building subjected to the total loads and concrete with the age of 28 days, is compared with the design base on the construction conditions, searching for the critical ones. From the results it is apparent that the usual structural design is safe for structural systems and construction conditions similar to those considered in this work.
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Maghsoodi, Soheib. "Thermo-mechanical behavior of soil-structure interface under monotonic and cyclic loads in the context of energy geostructures." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0031.
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L'incorporation d'échangeurs de chaleur dans des géostructures conventionnelles comme les pieux peut extraire la chaleur du sol à des fins de chauffage et l'injecter dans le sol à des fins de refroidissement. Ces dernières années, des recherches ont été menées à l'échelle réelle et en laboratoire pour étudier l'effet de la température sur le comportement géotechnique de ces géostructures énergétiques ainsi que sur le sol environnant. En effet, ces géostructures énergétiques peuvent être soumises à des charges mécaniques cycliques et a des variations thermiques tout au long de leur durée de vie. L'objectif de cette étude était d'approfondir la compréhension du comportement du contact sable/argile-structure sous des charges thermomécaniques complexes. Un dispositif de cisaillement direct à température contrôlée permettant d'effectuer des essais monotones et cycliques à charge normale constante ou à rigidité normale constante a été mis au point. La réponse de l'interface aux effets thermiques sur le comportement mécanique des sols et l'interface sol-structure a été étudiée. Le sable de Fontainebleau et l'argile kaolin ont été utilisés comme substituts pour les sols sableux et argileux. Les résultats ont montré que les variations thermiques appliquées ont un effet négligeable sur la résistance au cisaillement de l'interface entre le sable et la structure du sol. Dans les échantillons d'argile, l'augmentation de la température a augmenté la cohésion et par conséquent la résistance au cisaillement, en raison de la contraction thermique pendant le chauffage. L'adhérence de l'interface argile-structure était inférieure à la cohésion des échantillons d'argile. Pour étudier les effets de la charge mécanique cyclique sur l'interface argile-structure à différentes températures, des essais de cisaillement direct monotone et cyclique à volume équivalent non drainé ont été réalisés sur l'interface argile-argile et argile-structure à différentes températures. Les résultats ont montré que le nombre de cycles jusqu'à la rupture pour l'essai d'interface argile-structure était inférieur à celui du cas argile-argile dans la même gamme de rapports de contraintes de cisaillement cycliques et moyennes. L'augmentation de la température a réduit le taux d'accumulation des contraintes et le nombre de cycles jusqu'à la rupture a été multiplié par 2 ou 3. Le taux de dégradation (paramètre de dégradation, t) a diminué de 16% avec un chauffage de 22 à 60 °C pour les différents rapports de contrainte cyclique testés. Un modèle d'interface sol-structure non isotherme basé sur la théorie de l'état critique a ensuite été développé. Le modèle non isotherme prend en compte l'effet de la température sur le taux de vide de l'interface avant le cisaillement. Le modèle est capable de saisir l'effet de la température sur l'interface sol-structure dans des conditions de charge normale constante et de rigidité normale constante pour les interfaces sableuses et argileuses. Les paramètres supplémentaires ont des significations physiques et peuvent être déterminés à partir d'essais classiques en laboratoire. La formulation est en bon accord avec les résultats expérimentaux et les principales tendances sont correctement reproduitesIncorporation of heat exchangers in conventional geostructures like piles can extract the heat from the soil for heating purposes and inject it to the soil for cooling purposes. In recent years, research has been conducted at full and laboratory scale to investigate the effect of temperature on the geotechnical behavior of these energy geostructures as well as on the surrounding soil. Indeed, these energy geostructures can be subjected to cyclic mechanical loads and thermal variations throughout their lifetime. The aim of this study was to deepen the understanding regarding the behavior of sand/clay-structure contact under complex thermo-mechanical loads. A temperature-controlled direct shear device to perform monotonic and cyclic constant normal load or constant normal stiffness tests was developed. The response of the interface to the thermal effects on the mechanical behaviour of soils and soil-structure interface was investigated. Fontainebleau sand and kaolin clay were used as proxies for sandy and clayey soils. The results showed that the applied thermal variations have a negligible effect on the shear strength of the sand and sand-structure interface. In clay samples the temperature increase, increased the cohesion and consequently the shear strength, due to thermal contraction during heating. The adhesion of the clay-structure interface, was less than the cohesion of the clay samples. To investigate the mechanical cyclic load effects on the clay-structure interface at different temperatures, monotonic and cyclic constant-volume equivalent-undrained direct shear tests were performed on clay-clay and clay-structure interface at different temperatures. The results showed that, the number of cycles to failure for the clay-structure interface test was lower than that for the clay-clay case in the same range of cyclic and average shear stress ratios. Increasing the temperature, decreased the rate of strain accumulation and the number of cycles to failure increased by 2-3 times. The rate of degradation (degradation parameter, t) decreased by 16% with heating from 22 to 60oC for the different cyclic stress ratios tested. A non-isothermal soil-structure interface model based on critical state theory was then developed. The non-isothermal model takes into account the effect of temperature on the void ratio of interface prior to shearing. The model is capable to capture the effect of temperature on soil-structure interface under constant normal load and constant normal stiffness conditions for both sandy and clayey interfaces. The additional parameters have physical meanings and can be determined from classical laboratory tests. The formulation is in good agreement with the experimental results and the main trends are properly reproduced
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Jansson, Fredrik, and Nils Nilsson. "Buckling of End-Bearing Retaining Walls in Clay." Thesis, KTH, Jord- och bergmekanik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-229808.
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The design of back-anchored retaining walls in Sweden has traditionally not included global elastic instability of the retaining wall as a possible failure mode. Eurocode 3 part 5 (SS-EN 1993-5) requires design of steel structural members for retaining walls to assess the risk of buckling if the normal force exceeds 4 % of the critical buckling load of the retaining wall. The geological conditions in Eastern Sweden are characterized by the intersection of very hard Precambrian rock and very soft Holocene clays. Thus often ground anchors anchored in rock at a 30-50 degree angle to the vertical plane are used to support retaining walls, resulting in a very high utilization of the ground anchor and a significant normal force in the retaining wall. The threshold value for buckling risk is consequently frequently exceeded and the specific failure mode, of global buckling, is often limiting the use of the structural members in practical design. The buckling load can either be calculated using Euler’s second or third buckling mode, or by modelling the soil-structure interaction by a suitable model. Since no such model is specified in the code, the aim of this thesis was to develop a model which takes into account the stabilizing effect of the soil for the calculation of the buckling force and to model the soil-structure interaction with a beam-spring model connected to Winkler springs. The model simulations show that the soil has a significant influence on the critical load, especially when the retaining wall base is driven to depths greater than 2 meters below excavation depth. The model simulations suggest that higher utilization, with up to 4 times greater critical load, of the steel members is possible for some specific cases and an idealized design factor is also elaborated.Dimensioneringen av bakåtförankrade spontväggar har traditionellt sett i Sverige inte tagit hänsyn till risken för global knäckning. I och med införandet av Eurokod 3 kapitel 5 (SS-EN 1993-5) som styrande dokument vid dimensionering av sponter måste risken för knäckning nu mera beaktas när normalkraften överstiger 4 % av den kritiska knäckningslasten. De geologiska förhållandena i de östra delarna av Sverige, med lösa leror som täcker hårt berg, leder till att bakåtförankrade sponter med brant lutande stag ofta används. Detta leder till en hög utnyttjandegrad av ankaret och också stora normalkrafter i sponten, vilket leder till att knäckning ofta blir dimensionerande brottmod för sponten. Metoden för att beräkna knäckningslasten kan enligt SS-EN 1993-5 göras med Eulers andra eller tredje knäckningsfall eller med en modell som tar hänsyn till jordens stabiliserande effekt. Idag finns ingen sådan numerisk modell att hitta i litteraturen, varför målet med detta arbete har varit att finna en lämplig modell för att ta hänsyn till jordens inverkan vid bestämning av knäckningslasten. För att modellera samverkan mellan jorden och sponten användes en balkmodell med Winkler fjädrar. Simuleringarna visar att jorden har en signifikant inverkan på den kritiska knäckningslasten, särskilt när nedslagsdjupet är större än 2 meter. Flera simulerade geometrier har gett drygt fyra gånger högre knäcklast jämfört med den knäcklast som erhålls om SS-EN 1993-5 följs. Om jorden tas hänsyn till i dimensioneringen av en spont skulle således slankare konstruktioner kunna användas.
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Zak, Susan K. "Estimating uncertainty of critical load models." Thesis, Lancaster University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274231.
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Rizzetto, Simon. "Prédiction de la sensibilité biogéochimique et écologique des écosystèmes forestiers français aux dépôts atmosphériques azotés dans un contexte de changement global." Phd thesis, Toulouse, INPT, 2017. http://oatao.univ-toulouse.fr/19558/1/Rizzetto.pdf.
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Depuis des décennies, les dépôts atmosphériques azotés sont connus pour agir de manière sévère sur le fonctionnement des écosystèmes forestiers. Ils influent en effet la biogéochimie du sol, l’équilibre des éléments nutritifs et, en conséquence, la croissance des espèces végétales, la biodiversité végétale de sous-étage et plus globalement la santé des forêts. Dans le cadre de la convention internationale de Genève visant à limiter la pollution atmosphérique transfrontalière à longue distance, le concept de « Charges Critiques », défini à la fin des années 1980, a été retenu comme outil permettant d’évaluer la sensibilité d’un écosystème aux contaminants. Il permet d’estimer la quantité maximale de polluants atmosphériques acceptable par l’écosystème avant apparition de conséquences néfastes à son fonctionnement. De plus, en raison de l’impact des changements globaux sur les processus biogéochimiques régissant le fonctionnement des écosystèmes, l’influence des dépôts atmosphériques et du changement climatique doit être considéré de manière simultanée pour évaluer l’évolution de l’état des écosystèmes au cours du temps. Dès lors l’enjeu majeur est de pouvoir prédire l’effet combiné de ces facteurs sur les écosystèmes forestiers français. C’est l’objectif de ce travail de thèse. Des modèles dynamiques couplés biogéochimiques – écologiques, tels que les modèles ForSAFE-VEG ou PROPS, ou écologiques (basés sur la base de données EcoPlant) ont été développés ou adaptés à ces fins, et appliqués à différentes échelles locale, régionale et nationale, selon différents scénarios de dépôts et climatiques. L’application et la calibration du modèle couplé ForSAFE-VEG sur des placettes forestières permanentes du réseau RENECOFOR ont permis de prédire l’évolution de la composition biogéochimique de la solution du sol et en cascade de la composition floristique de trois sites, sous différents scénarios de dépôts atmosphériques et de changement climatique. Les principales évolutions des sites sont liées à leurs caractéristiques stationnelles. Si le changement climatique joue un rôle prédominant sur la réponse des espèces, les écosystèmes oligotrophes restent sensibles aux dépôts de N. A court terme, l’effet combiné des dépôts et du changement climatique sur le long terme est modulé par les effets de la gestion forestière. L’extrapolation du modèle couplé à plus large échelle nécessite une continuité dans la disponibilité des données d’entrée et de calibration de la réponse des espèces. Les données et scénarios de changement climatiques ont été complétés et actualisés à l’aide du modèle SAFRAN et des nouveaux scénarios RCP régionalisés. La calibration de la réponse des espèces végétales à l’échelle de la France a été réalisée à partir des mesures de la base de données phytoécologiques EcoPlant, par le développement de modèles de distribution d’espèces (SDM), en intégrant simultanément des variables climatiques, édaphiques, d’énergie et de nutrition. Le couplage entre le modèle ForSAFE et les SDM assure une modélisation robuste à l’échelle du territoire de la réponse des écosystèmes forestiers dans le temps, calibrée pour les conditions pédoclimatiques françaises. La modélisation des charges critiques d’acidité, d’eutrophisation et de biodiversité sur l’ensemble des sites RENECOFOR et la totalité des écosystèmes forestiers français montre des sensibilités variées aux dépôts de soufre et d’azote en fonction des écosystèmes, avec parmi les plus sensibles les Landes, la Sologne et le Massif Central. Des indices de qualité des habitats (HSi) ont été calculés à l’échelle de tous les écosystèmes par le modèle PROPS et les SDM. La sélection des espèces représentatives reste primordiale car elle conditionne la valeur finale de HSi. Ce paramètre est l’un des plus sensibles à prendre en compte dans la modélisation. Il est à mettre en relation avec les objectifs de protection des écosystèmes voulus par les gestionnaires.
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Giardina, Ronald Joseph Jr. "General Nonlinear-Material Elasticity in Classical One-Dimensional Solid Mechanics." ScholarWorks@UNO, 2019. https://scholarworks.uno.edu/td/2666.
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We will create a class of generalized ellipses and explore their ability to define a distance on a space and generate continuous, periodic functions. Connections between these continuous, periodic functions and the generalizations of trigonometric functions known in the literature shall be established along with connections between these generalized ellipses and some spectrahedral projections onto the plane, more specifically the well-known multifocal ellipses. The superellipse, or Lam\'{e} curve, will be a special case of the generalized ellipse. Applications of these generalized ellipses shall be explored with regards to some one-dimensional systems of classical mechanics. We will adopt the Ramberg-Osgood relation for stress and strain ubiquitous in engineering mechanics and define a general internal bending moment for which this expression, and several others, are special cases. We will then apply this general bending moment to some one-dimensional Euler beam-columns along with the continuous, periodic functions we developed with regard to the generalized ellipse. This will allow us to construct new solutions for critical buckling loads of Euler columns and deflections of beam-columns under very general engineering material requirements without some of the usual assumptions associated with the Ramberg-Osgood relation.
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Davis, Marion Denise. "Is working memory load a critical factor in distractor processing?" Thesis, University of Canterbury. Psychology, 2007. http://hdl.handle.net/10092/1403.
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To achieve goal-orientated behaviour, selective attention is often needed to filter out irrelevant information. Past research has shown that working memory (WM) plays a critical role in selective attention, with high WM load leading to more distractor interference than low WM load. However, because WM load is usually manipulated by requiring participants to hold in memory either one or several digits that were presented simultaneously while performing a selective attention task, the extent of attentional focus was not controlled. The present study examined the effect of WM load on distractor inhibition while keeping attentional focus constant by presenting one digit (low load condition) or six digits (high load condition) sequentially. The participants in the high-load condition demonstrated greater distractor interference than the participants in the low-load condition, suggesting that WM load influences distractor inhibition even when the extent of attentional focus was controlled. This result provides converging evidence to Lavie's (1995, 2005) load theory of attention and cognitive control.
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Ranade, Ashutosh M. "Load Rating for the Critical Components of Ironton-Russell Bridge." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1504782535042068.
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Brickley, Gary. "Physiological and metabolic responses to continuous and intermittent exercise using the critical power concept." Thesis, University of Brighton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302290.
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Kuylenstierna, Johan Carl Ivar. "Assessment of ecosystem sensitivity to acidic deposition : critical load estimates, detriment and damage." Thesis, University of York, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385220.
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Igwemezie, Chibuzo John Paul. "A critical analysis of electricity distribution processes in Nigeria : a management perspective (2005 – 2015)." University of the Western cape, 2016. http://hdl.handle.net/11394/5567.
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Masters in Public Administration - MPANigeria has been experiencing challenges in the distribution of power to the whole country in the past decades. As a result, more than half of Nigeria's population is affected by the ineffectiveness of the distribution of electricity which lowers their standard of living. As the country's power sector experienced a steady growth after its independence in 1960, it was anticipated at the time that, at that rate of growth and development, most of Nigeria should have been electrified by now. However, challenges in the distribution of electricity have persisted and this has negatively affected the economy and living standard of the country. From the management perspective, this research looks at the situation of the distribution of electricity in Nigeria from the year 2005 to 2015. Specifically, it will analyses management challenges affecting the distribution of electricity in the country. It is well documented how Nigeria is currently facing an electricity crisis despite all the government efforts to provide adequate power to the citizens. In the distribution of electricity in Nigeria, the research will look at how the planning of the organization is been done so as to ensure effective power delivery to the country. The research will further look at how the management manages the organization and how it is being controlled for effective power distribution. In this research, I shall use qualitative and quantitative research techniques. Secondary qualitative and quantitative data will be used in carrying out this research. Published books, journals, newspaper articles, and government policies shall be critically examined in order to produce a well-informed report. Before the research is conducted, the appropriate consent from the University of the Western Cape will be sought to ensure that all protocols are strictly adhered to.
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Oliveira, Yuri Calil Loures de. "Alimentação de cargas hospitalares críticas utilizando conversores estáticos." Universidade Federal de Juiz de Fora, 2016. https://repositorio.ufjf.br/jspui/handle/ufjf/1398.
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CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico
Esta dissertação apresenta um estudo de estratégias de alimentação de cargas hospitalares críticas utilizando conversores estáticos de energia. As cargas hospitalares escolhidas foram os equipamentos de raio x, tomografia computadorizada e ressonância magnética, sendo comparadas as seguintes formas de integração à rede: (i) estrutura com um retificador trifásico conectado à rede e três inversores monofásicos conectados às cargas ou (ii) estrutura com três retificadores monofásicos conectados à rede e três inversores monofásicos conectados às cargas. Por questões de patente, houve dificuldade em se encontrar os circuitos de front-end das fontes de alimentação das cargas hospitalares. Logo, as mesmas foram construídas dentro do ambiente de simulação do software PSIM utilizando dados de medição obtidos na literatura. O controle dos retificadores trifásico e monofásico foi realizados utilizando duas malhas de controle em cascata, com a malha interna controlando a corrente consumida da rede e a malha externa regulando a tensão no barramento CC. Para os três inversores monofásicos de saída foram implementados os controles PI RES e PI SRF visando uma comparação quanto ao desempenho. Como forma de validar o modelo matemático do sistema e o algoritmo de controle, foram feitas simulações utilizando o software PSIM. A análise feita comprovou que os resultados de simulação se mostraram coerentes com a modelagem matemática do sistema.
This master thesis presents a study about feeding strategies of critical hospital loads through power static converters. The chosen hospital loads were the x ray equipment, the computed tomography and the magnetic resonance. The following forms of grid integration were compared: (i) structure with a three-phase rectifier connected to the network and three single-phase inverters connected to the loads or (ii) structure with three single-phase rectifiers connected to the network and three single-phase inverters connected to the loads. Due to patent issues, it was difficult to find the front-end circuits for power supplies of hospital loads. Therefore, the loads were implemented in PSIM software environment using measurement data obtained from literature. The control of three-phase and single-phase rectifiers was implemented using two cascaded control loops, with the inner loop controlling the current drawn from the network and the outer loop regulating the DC bus voltage. For the single-phase inverter, PI RES and PI SRF controls were implemented, targeting a comparison in terms of performance. In order to validate the mathematical model of the system and the control algorithm, simulations were performed using the PSIM software. The analysis showed that the simulation results were consistent with the mathematical modeling of the system.
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Alkan, Olsson Johanna. "Setting limits in nature and the metabolism of knowledge : the case of the critical load concept /." Linköping : Univ, 2003. http://www.bibl.liu.se/liupubl/disp/disp2003/arts274s.pdf.
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Lockwood, Sarah E. "A Critical View of Contemporary Environmentalism: Pushing for Grassroots Struggle and Hope during an Era of Escalating Catastrophe." Scholarship @ Claremont, 2016. http://scholarship.claremont.edu/scripps_theses/745.
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Curtis, Christopher James. "An assessment of the representation of moorland nitrogen sinks in static critical load models for freshwater acidity." Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397251.
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RINDER, MARIA M. "Three-Dimensional Dynamic Biomechanical Model for Lifting and Lowering Activities: Systematic Review, Critical Appraisal and Model Development." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1179430261.
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Erguner, Kamil. "Analytical Examination Of Performance Limits For Shear Critical Reinforced Concrete Columns." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12611220/index.pdf.
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Most of the older reinforced concrete (RC) buildings have columns that are deficient
when the current code requirements are considered. Therefore, performance of the columns
determines the performance of the structure under the effects of earthquake induced lateral
loads. It is recognized that no provision is proposed in TEC2007 to estimate the failure type
called flexure-shear. Behavior of columns having probability of failing in flexure-shear
failure mode is mostly underestimated by TEC2007 procedures. In addition, failure type
classification of columns performed according to the linear and nonlinear procedures of
TEC2007 needs to be examined with respect to the test results to cover all failure types
including flexure-shear failure in order to lead the engineers develop economical and
realistic retrofit solutions.
In this study, different methods are explored to obtain reliable estimates for the
performance of code deficient shear critical RC columns. Special considerations are given to
Axial-Shear-Flexure interaction (ASFI) approach due to its mechanical background.
After examination of different approaches, ASFI method with proposed
modifications was selected as the most reliable model and lateral load-displacement analyses
were performed on a database of shear critical columns. Findings were compared with the
estimations of the nonlinear procedure given in Turkish Earthquake Code (TEC2007) for
database columns. In addition, drift capacity equations and simplified safe drift capacity
equations are proposed in light of statistical studies on the selected column specimens.
In the last part of the study, performance evaluation of columns according to
nonlinear procedures of FEMA 356, TEC2007, ASCE/SEI 41 update supplement, and
EUROCODE 8 were conducted.
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Oztop, Celal. "Beforehand Obtaining A Safety Operation Condition By Using Daily Load Curves In Transient Stability And Graphical Software For Transient Stability Applications." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/2/12606457/index.pdf.
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ABSTRACT
In this thesis, relationship between two most important transient stability indices, critical clearing time and generator rotor angle is examined for one machine-infinite bus system and then extended to the multimachine case and is observed to be linear.
By using the linear relationship between critical clearing time and generator rotor angle and utilizing the daily load curve, a new preventive method is proposed. The aim of this method is to make all critical clearing times longer than the relay and circuit breaker combination operation time. In the proposed method, desired critical clearing times are obtained by using on line system data and daily load curves. Then desired values are adjusted by generators output rescheduling and terminals voltage control
Visual computer language is used for graphical and numerical solutions. Comprehension of one machine infinite bus system and multimachine system transient stability become easier.
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Govender, Dharshini. "Economic empowerment through business loans - A critical look at credit protection law for small, micro and medium enterprises in South Africa and Australia." Master's thesis, Faculty of Law, 2019. http://hdl.handle.net/11427/31436.
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a) Overview
The question to be answered in this dissertation is whether the National Credit Act 34 of 2005 (the NCA), promotes or impedes the sustainable growth of the South African economy. This question will be answered through exploring the importance of the contribution made by small, micro and medium enterprises (SMMEs) to the economy. This research question is premised on the findings in structural change theory of development economics.1 This theory advances the view that for a developing country to obtain sustainable growth of its economy there needs to be a decline in the number of microenterprises over a period of years and an increase in the number small and medium enterprises (SMEs). 2 This dissertation interrogates whether the NCA supports this kind of sustainable growth of the South African economy. The hypothesis proposes that the NCA impedes the sustainable economic development of South Africa. In support of this, I have examined the NCA and the protection that it affords to SMEs in South Africa. Specifically, I have examined the extent to which the NCA permits lending to SMEs by financiers, in contrast to the permission given to financiers to lend to microenterprises. In addition, I have examined the extent to which the NCA protects SME borrowers in cases where the SME qualifies for a loan, so bringing it within the provisions of NCA. This is then contrasted with the protection extended by the provisions of the NCA to microenterprises. In this investigation, I have undertaken a review of case law in South Africa to substantiate my view that the NCA inhibits sustainable growth of the South African economy. The decisions raise some important considerations, including problems caused by the concept of separate legal personality of juristic persons run by an individual in the context of borrowing, the extent to which credit guarantees offered by these individual owners should be legally enforceable and the ambiguity of developmental loans envisaged by the NCA. To address these problems, I have looked to foreign jurisprudence, especially the legal protection offered to SMEs in Australia when taking out a loan. A comparison between South African law and Australian law suggests how access to credit by SMEs and microenterprises can be improved to ensure sustainable economic growth of the economy.
b) Research Methodology
A doctrinal, desktop-based research method is used. The main documentary data analysed to answer the research question is primary legislation, specifically the NCA and the Usury Act 73 of 1968. Secondary sources, such as commentaries and publications by various researchers will be explored. Further documentary data will include empirical data collected in secondary sources. Other persuasive legal texts will be utilised, such as the Australian Securities and Investments Commission Act 2001 (Cth) (the ASIC), The Australian National Consumer Credit Protection Act 2009 (the ACCPA) as well as the Australian Code of Banking Practice (the COBP)
c) Limitations to the Study
The main limitation to this dissertation has been determining the exact number of SMMEs that exist in South Africa. Studies so far undertaken have used different methodologies and research strategies and their objectives may have differed to the objectives of this paper.3 Despite the growing amount of literature and research that is being conducted regarding SMMEs, there is still very little known about them. This is largely a result of the high number of unregistered SMMEs that exist. A further limitation on the research is that each survey contains different definitions of small, micro and medium business. For example, the South African General Entrepreneurial Monitor (GEM) measures different types of entrepreneurship and not the number of businesses to enable international comparisons. In contrast the department of trade and industry’s (DTI) definition of small business is used to determine the number of small businesses in South Africa; and this is the definition used in the National Small Business Act 102 of 1996 (the Small Business Act).
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Barreto, Mateus Neves 1989. "Uma abordagem para a previsão de carga crítica do sistema elétrico brasileiro = An approach for critical load forecasting of brasilian power system." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259923.
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Orientadores: Takaaki Ohishi, Ricardo Menezes SalgadoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: O Sistema Elétrico Brasileiro abastece cerca de 97% da demanda de energia nacional. Frente ao extenso território brasileiro, necessita-se de um sistema de transmissão de larga escala, devido as grandes distâncias entre as gerações, das hidroelétricas, e a principal concentração da demanda, no Sudeste brasileiro. Para garantir segurança e economia da operação do Sistema Elétrico Brasileiro são realizadas análises da operação do sistema de geração e transmissão frente às condições de cargas críticas. A ideia é preparar o sistema para suportar as condições mais severas de carga. A curva de carga crítica é calculada para cada mês com discretização horária (ou menor). A mesma é composta pela carga mínima observada num dado mês no período da primeira a oitava hora, e pela carga máxima observada no mês para as horas restantes. Utilizando históricos de demanda pertencentes aos agentes do Setor Elétrico Brasil, foi possível criar um histórico de cinco anos, 60 meses, de curvas de carga crítica. Esses dados foram disponibilizados pelo Operador Nacional do Sistema Elétrico Brasileiro ¿ ONS, em conjunto com o desenvolvimento de um projeto de pesquisa, através de um sistema de suporte a decisão nomeado SysPrev. Nesta dissertação são propostos três modelos para realizar a previsão da curva de carga crítica. Dois modelos utilizam Redes Neurais Artificiais e um modelo utiliza Suavização Exponencial de Holt-Winters (HW). Os resultados obtidos por todos os modelos foram satisfatórios. O modelo de Suavização Exponencial se destacou perante os outros dois modelos atingindo erros médios absolutos próximos a 3%. Esses resultados justificam-se devido às séries históricas de curvas de carga crítica possuírem características de tendência e sazonalidade e o modelo de HW ser projetado especificamente para séries temporais com estas características
Abstract: The Brazilian Power System supplies around 97 % of national energy demand. By reason of the broad Brazilian territory, it requires a transmission system of large scale, due to the large distances between the generations of hydropower and the main concentration of demand that stay in southeastern of Brazil. To ensure security and economy of operation of the Brazilian Electric System are performed analyzes the operation of generation and transmission system due to the conditions of critical loads. The idea is to prepare the system to resist the harshest load conditions. The curve of critical load is calculated for each month with hourly discretization (or less). It's made with the minimum load observed in a given month between the first to eighth hour, and to maximum load observed in the month for the rest of hours. Using the demand agents¿ history belonging to the Brazilian Power System, it was possible to create a record of five years, 60 months, of curves of critical load. These datas were available by the National Operator of the Brazilian Power System as part of the development of a research project, made available by a decision support system named SysPrev. This dissertation proposed three models to perform the forecasting of the critical load curve. Two models using Artificial Neural Networks and one model using Exponential Smoothing Holt-Winters (HW). The results obtained by all the models were satisfactory. The exponential smoothing model stood out against the other two models, this having absolute average errors near 3%. These results are justified due to the historical series of curves of critical load has characteristics of trend and seasonality and the HW model is specifically designed for time series with such characteristics
Mestrado
Engenharia de Computação
Mestre em Engenharia Elétrica
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Pignatiello, Grant Alan. "The Relationships Among Self-Regulation, Cognitive Load, Decision Support, and Decision Making Readiness in Surrogate Decision Makers for the Critically Ill." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1528453527097319.
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Boggs, Joshua Thomas. "The Performance and Behavior of Deck-to-Girder Connections for the Sandwich Plate System (SPS) in Bridge Deck Applications." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/32998.
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An innovative approach to possible construction or rehabilitation of bridge decks can be found in a bridge construction system called the Sandwich Plate System (SPS). The technology developed and patented by Intelligent Engineering Canada Limited in conjunction with an industry partner, Elastogran GmbH, a member of BASF, may be an effective alternative to traditional bridge rehabilitation techniques.
Although the systemâ s behavior has been studied the connection of the SPS deck to the supporting girders has not been investigated. Two types of connection are presented in this research. The use of a bent plate welded to the SPS deck and subsequently bolted to the supporting girder utilizing slip-critical connections has been utilized in the construction of a SPS bridge. A proposed SPS bridge system utilizes the top flange of the supporting girder welded directly to the SPS deck as the deck-to-girder connection.
The fatigue performance of a deck-to-girder connection utilizing a bent plate welded to the deck and bolted to the supporting girder using slip-critical connections was tested in the Virginia Tech Materials and Structures Laboratory. The testing concluded that the fatigue performance of the welded and bolted bent plate connection was limited by the weld details and no slip occurred in the slip-critical connections. Finite element modeling of the two types of deck-to-girder connections was also used to determine influence of the connections on the local and global behavior of a SPS bridge system. A comparison of the different connection details showed that the connection utilizing the flange welded directly to the SPS deck significantly reduces the stresses at location of the welds in the connections, but the connection type has a limited influence on the global behavior of a SPS bridge.
Master of Science
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Phasha, Manteng Ruth. "A critical analysis of the implications of commissioner South African Revenue Service v Brummeria Renaissance (Pty) Ltd on the taxation of the benefits of interest-free shareholders' loans." Diss., University of Pretoria, 2009. http://hdl.handle.net/2263/23892.
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The ruling by the Supreme Court of Appeal in Commissioner South African Revenue Service v Brummeria Renaissance (Pty) Ltd on 13 September 2007 added to and amended South African case law regarding the critical definition of ‘gross income’ in the Income Tax Act 58 of 1962. The court diverged from the existing precedent – set in Stander v Commissioner for Inland Revenue – that receipts that “could not be converted into cash and could not be transferred to anyone else” are not taxable. In Commissioner South African Revenue Service v Brummeria Renaissance (Pty) Ltd the court ruled that what is key is that the benefit has an ascertainable monetary value. Accordingly, the benefits of interest-free loans can be valued – using the weighted prime overdraft interest rate – and can be taxed. This decision has been the subject of much debate, centring on the aptness of the amended view of ‘gross income’, the quid pro quo principle discussed in the judgement, the valuation method, and the implications of these for taxpayers. The purpose of this study is to present arguments and additional information to this continued debate, looking particularly at the impact of Commissioner South African Revenue Service v Brummeria Renaissance (Pty) Ltd on interest-free shareholders’ loans, without attempting to provide a definitive answer to this debate. This non-empirical study explores the topic through a review of literature, with the sources cited being mainly published public articles, tax text books and conference papers retrieved from the internet. CopyrightDissertation (MCom)--University of Pretoria, 2010.
Taxation
unrestricted
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Arpaci, Erdogan. "Analysis Of Sinusoidal And Helical Buckling Of Drill String In Horizontal Wells Using Finite Element Method." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12611003/index.pdf.
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The number of horizontal wells is increasing rapidly in all over the world with the growth of new technological developments. During horizontal well drilling, much more complex problems occur when compared with vertical well drilling, such as decrease in load transfer to the bit, tubular failure, tubular fatigue and tubular lock-up. This makes selection of appropriate tubular and making the right drill string design more important. As the total compression load on the horizontal section increases, the behavior of the tubular changes from straight to sinusoidal buckling, and if the total compression load continues to increase the behavior of the tubular changes to helical buckling. Determination of critical buckling loads with finite element method (FEM) in horizontal wells is the main objective of this study. Initially, a computer program (ANSYS) that uses FEM is employed to simulate different tubular and well conditions. Four different pipe sizes, four different wellbore sizes and three different torque values are used to model the cases. Critical buckling load values corresponding to significant variables are collected from these simulated cases. The results are classified into different buckling modes according to the applied weight on bit values and the main properties of the simulated model, such as modulus of elasticity, moment of inertia of tubular cross section, weight per unit length of tubular and radial clearance between the wellbore and the tubular. Then, the boundary equations between the buckling modes are obtained. The equations developed in this thesis by simulating the cases for the specific tubular sizes are used to make a comparison between the critical buckling load values from the models in the literature and this work. It is observed that the results of this work fit with literature models as the tubular size increases. The influence of torque on critical buckling load values is investigated. It is observed that torque has a slight effect on critical buckling load values. Also the applicability of ANSYS for buckling problems was revealed by comparing the ANSYS results with the literature models’
results and the experimental study in the literature.
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Strahin, Brandon L. "WEAR AND CORROSION RESISTANT TRIBOLOGICAL SURFACE TREATMENTS FOR TITANIUM ALLOYS: EVALUATION OF COMPLIMENTARY AND SUPPLEMENTARY DUPLEX TREATMENT PROCESSES." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555110923128525.
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Gai, Guodong. "Modeling of water sprays effects on premixed hydrogen-air explosion, turbulence and shock waves Modeling pressure loads during a premixed hydrogen combustion in the presence of water spray Numerical study on laminar flame velocity of hydrogen-air combustion under water spray effects Modeling of particle cloud dispersion in compressible gas flows with shock waves A new formulation of a spray dispersion model for particle/droplet-laden flows subjected to shock waves Particles-induced turbulence: a critical review of physical concepts, numerical modelings and experimental investigation A new methodology for modeling turbulence induced 1 by a particle-laden flow using a mechanistic model." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMIR14.
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Cette thèse de doctorat est dédiée au développement de modèles physiques pour l’étude des systèmes d’aspersion de gouttelettes d’eau en milieu réactif d’hydrogène-air pré-mélangée dans les centrales nucléaires. Des modèles d’ordre réduit sont développés pour décrire l’évaporation des gouttelettes d’eau dans la flamme, la dispersion des nuages de particules après le passage des ondes de choc et l’évolution de l’échelle caractéristiques de turbulence avec la présence d’un jet d’eau. Une nouvelle méthodologie est proposée pour évaluer les effets de l’évaporation par l’aspersion sur la propagation de la flamme d’hydrogène turbulente à l’intérieur d’un volume fermé et un modèle simple est développé pour la quantification de la décélération de la vitesse laminaire avec l’évaporation des gouttelettes à l’intérieur de la flamme. Également, un modèle analytique est proposé pour la prédiction de la dispersion de nuage de particule après le passage d’une onde de choc en s’appuyant sur le one-way formalisme avec une extension afin de prédire l’apparition d’un pic de densité du nombre de particules en utilisant le two-way formalisme. En ce qui concerne la modulation de la turbulence induite par les particules, un modèle simple est utilisé pour l’estimation des échelles intégrales de la turbulence induites par l’injection de nuage des particules. Ces modèles numériques développés peuvent être couplés pour être mis en œuvre dans les simulations numériques à grande échelle de l’effet du système d’aspersion sur les explosions accidentelles d’hydrogène dans les centrales nucléairesThis PhD dissertation is dedicated to develop simple models to investigate the effect of water spray system on the premixed hydrogen-air combustion in the nuclear power plants. Specific simple models are developed to describe the water droplet evaporation in the flame, particle cloud dispersion after the shock wave passage, and turbulence length scale evolution with the presence of a water spray. A methodology is proposed to evaluate the spray evaporation effects on the propagation of the turbulent hydrogen flame inside a closed volume and a simple model is developed for the quantification of the laminar velocity deceleration with the droplets evaporation inside the flame. An analytical model is proposed for the prediction of particle cloud dispersion after the shock passage in the one-way formalism and another analytical model is dedicated to describe the spray-shock interaction mechanism and predict the appearance of a particle number density peak using the two-way formalism. A review of the important criteria and physical modelings related to the particle-induced turbulence modulation is given and a mechanistic model is used for the estimation of the turbulent integral length scales induced by the injection of particle clouds. These developed numerical models can be coupled to implement in the large-scale numerical simulations of the spray system effects on the accidental hydrogen explosions in the nuclear power plants
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Barik, Tapas Kumar. "Modern Adaptive Protection and Control Techniques for Enhancing Distribution Grid Resiliency." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/103644.
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Power distribution systems have underwent a lot of significant changes in the last two
decades. Wide-scale integration of Distributed Energy Resources (DERs) have made the
distribution grid more resilient to abnormal conditions and severe weather induced outages.
These DERs enhance the reliability of the system to bounce back from an abnormal situation
rather quickly. However, the conventional notion of a radial system with unidirectional
power flow does not hold true due to the addition of these DERs. Bidirectional power flow
has challenged the conventional protection schemes in place. The most notable effects on
the protection schemes can be seen in the field of islanding or Loss of Mains(LOM) detection
and general fault identification and isolation. Adaptive protection schemes are needed to
properly resolve these issues. Although, previous works in this field have dealt with this
situation, a more comprehensive approach needs to be taken considering multiple topologies
for developing adaptive protection schemes. The most common protective devices widely
deployed in the distribution system such as overcurrent relays, reverse power relays at Point
of Common Coupling(PCC), fuses, reclosers and feeder breakers need to studied in implementing
these schemes.
The work presented in this dissertation deals with simulation based and analytical approaches
to tackle the issues of islanding and adaptive protection schemes. First we propose a multiprinciple
passive islanding detection technique which relies on local PCC measurements, thus
reducing the need of additional infrastructure and still ensuring limited Non Detection Zone
(NDZ). The next step to islanding detection would be to sustain a islanded distribution
system in order to reduce the restoration time and still supply power to critical loads. Such
an approach to maintain generator load balance upon islanding detection is studied next by
appropriate shedding of non-critical and low priority critical loads based upon voltage sensitivity
analysis. Thereafter, adaptive protection schemes considering limited communication
dependency is studied with properly assigning relay settings in directional overcurrent relays
(DOCRs), which are one of the most widely deployed protective devices in distribution
systems by catering to multiple topologies and contingencies. A simulation based technique
is discussed first and then an analytical approach to solve the conventional optimal relay
coordination problem using Mixed Integer Linear Programming (MILP) with the usage of
multiple setting groups is studied. All these approaches make the distribution more robust
and resilient to system faults and ensure proper fault identification and isolation, ensuring
overall safety of system.Doctor of Philosophy
With widespread integration of inverter-based distributed energy resources (DERs) in the distribution grid, the conventional protection and control schemes no longer hold valid. The necessity of an adaptive protection scheme increases as the DER penetration in the system increases. Apart from this, changes in system topology and variability in DER generation, also change the fault current availability in the system in real-time. Hence, the protection schemes should be able to adapt to these variations and modify their settings for proper selectivity and sensitivity towards faults in the system, especially in systems with high penetration of DERs. These protection schemes need to be modified in order to properly identify and isolate faults in the network as well as correctly identify Loss of Mains (LOM) or islanding phenomenon. Special attention is needed to plan the next course of action after the islanding occurrence. Additionally, the protective devices in distribution system should be utilized to their maximum capability to create an adaptive and smart protection system. This document elaborately explains the research work pertaining to these areas.
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Khamisi, Ali. "Stability of Tubular Steel Structures : Buckling and Lateral Torsional Buckling." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0172.
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Ce sujet est d’actualité suite à une évolution rapide des types de conception de structures élancées utilisées dans les installations provisoires. C’est seulement depuis une vingtaine d’années que ces structures sont préfabriquées en cadres multidirectionnels (de sections tubulaires en acier ou en aluminium). Ces structures sont légères et leur stabilité réside seulement dans les raideurs internes au niveau des files de montants et au niveau horizontal par les planchers ainsi que dans les liaisons avec l’ouvrage. Ce travail concerne l’étude des instabilités (flambement-déversement) en tenant compte de différents types d’imperfections. De nouvelles courbes de flambement ainsi que les facteurs d’imperfection associés sont proposés dans cette thèse. Ces courbes sont obtenues en imposant une déformée initiale représentant les défauts géométriques et mécaniques (contraintes résiduelles). Les résultats expérimentaux confrontés avec les prévisions théoriques de l’Eurocode 3 montrent que les valeurs des imperfections figurant dans la littérature sont extrêmement exagérées. Les valeurs préconisées dans ce travail pourraient présenter un certain intérêt pour une modification éventuelle des courbes européennes de flambement pour ce type de structure. En ce qui concerne l’instabilité latérale, une méthodologie originale d’essais en vraie grandeur de poutres à treillis formés d’éléments tubulaires a été également mise au point. Le système de chargement à « roues libres » développé permet de libérer le point d’application de l’effort dès le début de l’instabilité. Cette technique conduit à des mesures plus précises du moment critique de déversementThis subject becomes topical following a rapid evolution of design procedures for slender structures used widely in the temporary installations. Only through the last twenty years that these structures are prefabricated of multidirectional frames (steel or aluminium tubular sections). These structures are lightweight and their stability lies only in the internal stiffness at rows of posts and horizontally by the planking as well as the links with the building. This work concerns the study of instabilities (buckling - lateral torsional buckling) taking into account different types of imperfections. New buckling curves and the associated imperfection factors are proposed in this thesis. These curves are obtained by imposing an initial deformed representing the geometrical and mechanical defects (residual stress). The experimental results were confronted with theoretical predictions of Eurocode 3 which show that the values of the imperfections in the literature are extremely exaggerated. The values advocated in this work could be of interest for a possible adjustment of the European buckling curves for this type of structure. Regarding the lateral instability, an original methodology in real scale tests of trusses consist of tubular elements was also developed. The developed loading system of "free wheels" allows releasing the point of application of the force from the beginning of instability. This technique leads to more accurate measurements of the critical lateral torsional buckling moment
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Schwarzak, Susann, Maciej Kryza, Marek Błaś, Mariusz Szymanowski, Małgorzata Werner, Mieczysław Sobik, Krzysztof Migała, et al. "Klimaprojektionen, Luftverschmutzung und Belastungsgrenzen von Ökosystemen: Klimawandel, Luftverschmutzung und ökologische Belastungsgrenzen von Ökosystemen im polnisch-sächsischen Grenzraum." Sächsisches Landesamt für Umwelt, Landwirtschaft und Geologie (LfULG), 2014. https://slub.qucosa.de/id/qucosa%3A71620.
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Im Rahmen des regionalen Klimaprojektes KLAPS werden Klimawandel, Luftverschmutzung und ökologische Belastungsgrenzen im polnisch-sächsischen Grenzraum untersucht.
Mit dem vorliegenden Bericht liegt eine umfassende Analyse über die zukünftig mögliche klimatische und lufthygienische Entwicklung bis zum Jahr 2100 vor. Aufbauend auf den projizierten Klima- und Emissionsszenarien werden sowohl die Entwicklung als auch Überschreitung von Belastungsgrenzen von Ökosystemen (Critical Load) dargestellt.
Redaktionsschluss: 30.10.2014
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Sylla, Ibrahima. "high loaded anaerobic mesophilic digestion of sewage sludge : An evaluation of the critical organic loading rate and hydraulic retention time for the anaerobic digestion process at Käppala Wastewater Treatment Plant (WWTP)." Thesis, Mälardalens högskola, Framtidens energi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-52406.
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Käppala wastewater treatment plant (WWTP) has, during a few years, observed an increase in organic loading rate (OLR) in the mesophilic anaerobic digester R100, due to an increased load to the WWTP. The digestion of primary sludge at Käppala WWTP is today high loaded, with a high organic loading rate (OLR) and low hydraulic retention time (HRT). This study aims to evaluate the effect of the maximum OLR and the minimum HRT for the anaerobic digestion of sewage sludge and to investigate further actions that can be taken into consideration in case of process problems in the digestion. The study consists of (a) a practical laboratory experiment of 6 pilot-scale reactors to investigate how the process stability is affected when the OLR increases and the HRT decreases. (b) A mass balance calculation based on the energy potential in the feeding sludge and the digested sludge. (c) A study of the filterability of the digested sludge. (d) The construction of a forecasting model in Excel, to predict when digester R100 will reach its maximum OLR and minimum HRT. The result of the study shows that the maximum OLR for Käppala conditions is 4.9 g VS dm-3 d-1, meaning that R100 will reach its maximum organic load around the year 2031. An OLR of 4.5-4.9 and an HRT of 12 days is optimal for R100, according to the present study. Keeping the anaerobic digestion process in balance is vital when it comes to the outcome of energy in the anaerobic digestion process. Pushing the process to produce more gas can become counterproductive since a high OLR can lead to process imbalance, which in turn leads to low biogas production. Imbalance in the digestion process can occur fast; therefore, the margin for overload in the anaerobic digestion process must be significant. The methane concentration in the converted biogas and the pH level in the reactor are the best stability parameters for the conditions at Käppala. Ammonia is the less efficient stability parameter since it did not predict or detect any instability during the experimental process. Furthermore, the OLR and HRT have a significant impact on the needed quantity for dewatering polymer. The higher digestion of organic material in the sludge, the bigger the need for the polymer to take care of the rest material.
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Gärdeklint, Sylla Ibrahima Sory. "HIGH LOADED ANAEROBIC MESOPHILIC DIGESTION OF SEWAGE SLUDGE : An evaluation of the critical organic loading rate and hydraulic retention time for the anaerobic digestion process at Käppala Wastewater Treatment Plant (WWTP)." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-52283.
Full textAbstract:
Käppala wastewater treatment plant (WWTP) has, during a few years, observed an increase in organic loading rate (OLR) in the mesophilic anaerobic digester R100, due to an increased load to the WWTP. The digestion of primary sludge at Käppala WWTP is today high loaded, with a high organic loading rate (OLR) and low hydraulic retention time (HRT). This study aims to evaluate the effect of the maximum OLR and the minimum HRT for the anaerobic digestion of sewage sludge and to investigate further actions that can be taken into consideration in case of process problems in the digestion. The study consists of (a) a practical laboratory experiment of 6 pilot-scale reactors to investigate how the process stability is affected when the OLR increases and the HRT decreases. (b) A mass balance calculation based on the energy potential in the feeding sludge and the digested sludge. (c) A study of the filterability of the digested sludge. (d) The construction of a forecasting model in Excel, to predict when digester R100 will reach its maximum OLR and minimum HRT. The result of the study shows that the maximum OLR for Käppala conditions is 4.9 g VS dm-3 d-1, meaning that R100 will reach its maximum organic load around the year 2031. An OLR of 4.5-4.9 and an HRT of 12 days is optimal for R100, according to the present study. Keeping the anaerobic digestion process in balance is vital when it comes to the outcome of energy in the anaerobic digestion process. Pushing the process to produce more gas can become counterproductive since a high OLR can lead to process imbalance, which in turn leads to low biogas production. Imbalance in the digestion process can occur fast; therefore, the margin for overload in the anaerobic digestion process must be significant. The methane concentration in the converted biogas and the pH level in the reactor are the best stability parameters for the conditions at Käppala. Ammonia is the less efficient stability parameter since it did not predict or detect any instability during the experimental process. Furthermore, the OLR and HRT have a significant impact on the needed quantity for dewatering polymer. The higher digestion of organic material in the sludge, the bigger the need for the polymer to take care of the rest material.
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Nguyen, Thanh Truong. "Numerical modeling and buckling analysis of inflatable structures." Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10123.
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L’objectif principal de cette thèse est de modéliser en flambement des poutres pressurisées en tissu souple homogène orthotrope (THO) composite. La première partie détaille les études expérimentales qui ont été menées sur des poutres gonflables à certain niveaux de pression afin de caractériser les propriétés mécaniques du matériau et le comportement en flambement de la structure. Dans une deuxième partie, une approche analytique a été envisagée afin d’étudier le flambement ainsi que le comportement d’une poutre gonflable orthotrope. Un modèle 3D gonflables poutre orthotrope basé sur la cinématique de Timoshenko a été présenté brièvement. La charge critique a été étudiée pour différents cas de charge avec différentes conditions aux limites. Les résultats ont été confrontés aux résultats théoriques disponibles. Pour vérifier la limite de validité des résultats, la charge d’apparition des plis a également fait l’objet d’une étude pour chacun des cas. La dernière partie est consacrée à une étude linéaire et à une analyse non-linéaire du flambement de la poutre gonflable en THO composite. Le modèle éléments finis (MEF) établi ici implique un élément poutre de Timoshenko à trois-nœuds avec une continuité de type C0. Un test de convergence du maillage sur la force critique de la poutre a été réalisé par la résolution du problème aux valeurs propres. En outre, un MEF non-linéaire a été développé en utilisant la procédure itérative de quasi-Newton avec incréments de chargement adaptatif permettant le tracé pas à pas de la réponse charge-déflexion de la poutre. Les résultats ont été validés à partir d’un certain niveau de pression par des résultats expérimentaux et numériquesThe main goals of this thesis are to modeling and to perform the buckling study of inflatable beams made from homogeneous orthotropic woven fabric (HOWF) composite. Three main scenarios were investigated in this thesis. The first is the experimental studies which were performed on HOWF inflatable beam in various inflation pressures for characterizing the orthotropic mechanical properties and buckling behaviors of the beam. In the second scenario, an analytical approach was considered to study the buckling and the behavior of an inflatable orthotropic beam. A 3D inflatable orthotropic beam model based on the Timoshenko's kinematics was briefly introduced: the nonlinearities (finite rotation, follower forces) were included in this model. The results were compared with theoretical results available in the literature. To check the limit of validity of the results, the wrinkling load was also presented in every case. The last scenario is devoted to the linear eigen and non-linear buckling analysis of inflatable beam made of HOWF. The finite element (FE) model established here involves a three-noded Timoshenko beam element with C0-type continuity for the transverse displacement and quadratic shape functions for the bending rotation and the axial displacement. In the linear buckling analysis, a mesh convergence test on the beam critical load was carried out by solving the linearized eigenvalue problem. In addition, a nonlinear FE model was developed by using the quasi-Newton iteration with adaptive load stepping for tracing load-deflection response of the beam. The results were validated from a certain pressure level by experimental and thin-shell FE results
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Ross, Annie Elizabeth. "Wrongful Convictions as a Result of Public Defender Representation." Digital Commons @ East Tennessee State University, 2010. https://dc.etsu.edu/etd/1761.
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Our criminal justice system works very hard to prevent criminals from harming other individuals; however, unfortunately mistakes happen. One wrongful conviction is one too many. There are multiple factors that can be assumed to be the cause of wrongful convictions. However, due to the lack of directly related research, the determents are not well established. The following research addresses wrongful convictions as a result of public defender representation. Through the process of theory construction, the research uses critical race theory and social disorganization theory to show the relationship between court appointed representation and wrongful convictions. A new theory is also established that is referred to as the partial load reduction theory. This theory establishes the relationship that exists between wrongful convictions and public defender representation and provides solutions as well as new avenues for future research.
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Arakelian, Vivian Maria. "Estudo dos ajustes cardiorrespiratórios e metabólicos durante o exercício resistidos em jovens e idosos - proposta de avaliação da carga crítica no Leg Press 45º." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/82/82131/tde-20072012-153709/.
Full textAbstract:
O treinamento físico resistido tem sido enfaticamente incentivado, proporcionando efeitos favoráveis na força e endurance muscular, na função cardiovascular, metabolismo e na redução do risco cardiovascular. No entanto, é escassa a literatura sobre os ajustes cardiovasculares, ventilatórios e metabólicos no exercício resistido na população idosa. Além disso, pouco é sabido sobre tais ajustes na carga crítica (CC), a qual demarcaria a transição do exercício moderado para o exercício intenso nesta modalidade de exercício. Dessa forma, os objetivos deste trabalho são: avaliar o comportamento das respostas cardiovasculares, respiratórias e metabólicas durante o exercício físico resistido (Leg Press 45º) em diferentes intensidades, bem como determinar a intensidade da CC e ainda nessa intensidade comparar as respostas da freqüência cardíaca (FC), pressão arterial sistólica (PAS), ventilação (VE), consumo de oxigênio (\'VO IND.2\'), produção de dióxido de carbono (\'VCO IND.2\'), quociente respiratório (QR), percepção subjetiva de esforço (PSE) e lactato sangüíneo ([Lac]) obtidas durante exercício entre dois grupos (jovens e idosos). Participaram deste estudo 28 indivíduos do sexo masculino, sendo 15 jovens e 13 idosos, aparentemente saudáveis, sendo que a média de idade dos jovens foi de 22,7 ± 2,5 anos, massa média de 77,6 ± 10,2 kg e estatura média de 180,0 ± 10,0 cm e nos idosos a média de idade foi de 68,6 ± 4,0 anos, massa média de 76,7 ± 7,5 kg e estatura média de 170,0 ± 1,0 cm, não etilistas, não tabagistas, e sem distúrbios cardiorrespiratórios, neurológicos, metabólicos e articulares. Durante todos os procedimentos foram monitoradas PA, FC e eletrocardiograma nas derivações MC5, DII e V2 modificadas, sendo que foram realizados: teste de 1RM em exercício resistido no Leg Press 45º; teste de esforço físico dinâmico resistido com diferentes percentuais de 1RM, testados de acordo para obtenção da carga crítica, pela regressão linear dos pontos apurados na construção do gráfico: carga X inverso do tempo (tempo = duração do exercício até a fadiga). Com relação ao tempo de execução e o número de repetições não houve diferenças entre os grupos (p = 0,25 e p = 0,49; respectivamente); para a FC e PAS, temos para o grupo jovem uma resposta exacerbada da FC comparada aos idosos durante exercício (p<0,0001), sendo que o comportamento da PAS revela-se de modo contrário, havendo assim uma resposta mais acentuado para o grupo idoso (p<0,0197). A [Lac] foi maior em jovens na intensidade da CC (p = 0,0014), bem como o valor de PSE (0,00021). Para os parâmetros ventilatórios (VE, \'VO IND.2\' e \'VCO IND.2\') temos maiores valores para o grupo jovem também na fase de exercício para diferentes intensidades, principalmente na CC (p<0,0001, para as três variáveis). Além disso, foi possível determinar a carga crítica para ambos os grupos, sendo que essa foi em torno de 38% 1RM (p = 0,22). Dessa forma, esse foi o primeiro estudo que avaliou e comparou as respostas fisiológicas entre jovens e idosos em diferentes intensidades da RM, no exercício de Leg Press 45º, assim como na CC.The resistance training has been strongly encouraged, providing favorable effects on muscular strength and endurance, cardiovascular function, metabolism and cardiovascular risk reduction. However, there is little literature about the cardiovascular, ventilation and metabolic responses in resistance exercise in the elderly. Moreover, little is known about such adjustments in the critical load (CL), which indicates the transition of moderate to intense exercise in this type of exercise. Thus, the objectives of this study are: To evaluate the cardiovascular, respiratory and metabolic changes during resistance exercise (leg press 45º) at different intensities and to determine the intensity of the CL and even that intensity to compare the responses of heart rate (HR), systolic blood pressure (SBP), ventilation (VE), oxygen consumption (\'VO IND.2\'), production of carbon dioxide (\'VCO IND.2\'), respiratory quotient (RQ), perceived exertion (PSE) and blood lactate ([Lac]) obtained during exercise between two groups (young and old). Participated in this study 28 males, 15 young and 13 elderly, apparently healthy, with an average age of the young was 22.7 ± 2.5 years, mean weight 77.6 ± 10.2 kg and mean height of 180.0 ± 10.0 cm, and in the elderly the average age was 68.6 ± 4.0 years, mean weight 76.7 ± 7.5 kg and mean height of 170.0 ± 1.0 cm, non-alcoholic non-smoker, and without cardio-respiratory, neurological, metabolic and joints disorders. During all procedures were monitored BP, HR and ECG at MC5, DII and V2 modified, and were carried out: 1RM resistance exercise on the leg press at 45º; exercise stress test dynamic resistance with different percentages of 1RM tested agreement for obtaining the critical load, the linear regression of the points made during the construction of the graph: load X reverse of time (time = duration of exercise until fatigue). Regarding the execution time and number of repetitions no differences between the groups (p = 0.25 and p = 0.49, respectively) for the HR and SBP, we have exacerbated response of HR for a young group compared to elderly, during exercise (p < 0.0001), and the SBP appears to be so contrary, so there is more pronounced for the elderly group (p < 0.0197). The [Lac] was greater in young people in the CC intensity (p = 0.0014), as well as the value of PSE (0.00021). For the ventilatory parameters (VE, \'VO IND.2\' and \'VCO IND.2\') have higher values in the young group also during the exercise for different intensities, mainly in the CC (p < 0.0001 for the three variables). Furthermore, it was possible to determine the CL for both groups, and this was around 38% 1RM (p = 0.22). Thus, this was the first study that evaluated and compared the physiological responses between young and old in different intensities of 1RM in the exercise of Leg Press 45º, as in CL.
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Lavalle, Laura Vanessa Araque. "Estudo da interação solo-concreto das estacas escavadas do campo experimental de Araquari." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/163427.
Full textAbstract:
Procurando diminuir as incertezas a respeito do comportamento de estacas em perfis arenosos, desenvolveu-se um campo experimental localizado em Araquari-SC, conduzido pela Universidade Federal do Rio Grande do Sul, no qual foram executados (a) ensaios de campo para definir as condições geotécnicas do solo, (b) estacas escavadas e hélice continua e (c) provas de carga estática nos elementos estruturais. O presente trabalho tem como objetivo estudar as variáveis que intervêm no mecanismo de transferência de carga ao solo. Mediante ensaios de laboratório, caracterizou-se o solo presente no campo experimental, definiram-se os parâmetros de resistência, mineralogia, forma, distribuição e tamanho das partículas, para serem usadas na retro análise do coeficiente de pressão de solo (ks) das provas de carga. Para esta finalidade foram analisados os resultados medidos em estacas escavadas executadas com bentonita e polímero. A retro análise foi realizada através do método beta (β), abordagem que permite a obtenção da capacidade lateral das estacas construídas em perfis arenosos, baseado nas tensões verticais, no coeficiente de pressão de solo e no ângulo de atrito da interface solo-estaca. Devido à interação entre as partículas do solo e concreto da estaca, estas são mobilizadas a elevados níveis de deformações, o ângulo de atrito da interface é considerado próximo ao ângulo de atrito no estado crítico da areia. O solo presente no campo experimental corresponde a areia fina com lentes de silte. Assim, os parâmetros de resistência definidos foram o ângulo de atrito no estado crítico e de pico com valores de 33,0° e 33,4° respetivamente. O ângulo no estado crítico foi utilizado na retro análise das provas de carga e como resultado foi obtido o ks, para posteriormente ser comparado ao coeficiente de empuxo no repouso (k0). Os resultados mostraram que com a profundidade o valor ks aproxima-se ao valor de k0, apresentado uma relação de ks/k0 próxima a unidade. Conclui-se que, o mecanismo de transferência de carga entre o solo e a estaca pode ser avaliado em função das tensões iniciais do depósito, expressas a partir de k0 estimado com base nos ensaios de laboratório.In order to reduce the uncertainties regarding the behavior of piles in sandy profiles, an experimental field was developed by the Federal University of Rio Grande do Sul in Araquari-SC, where were executed (a) field tests to define soil geotechnical conditions, (b) bored and continuous flight auger piles and (c) static load tests on the structural elements. The aim of this research was to study the variables that intervene in the soil load transfer mechanism. The soil at the experimental field was characterized by laboratory tests, and parameters of resistance, mineralogy, particle shape, distribution and size were obtained for use in the back analysis of the soil pressure coefficient (ks) of the load tests. For this purpose, were analyzed the results measured on bored piles executed with bentonite and polymer. The back analysis was made using the beta method (β), which allows to estimate the lateral capacity of the piles constructed in sandy profiles, based on vertical stresses, soil pressure coefficient and friction angle of the soil-pile interface. Due to the interaction between the soil particles and the pile concrete, the first are mobilized at high deformation levels, the friction angle of the interface is considered close to the friction angle in the sand critical state. The soil present in the experimental field corresponds to fine sand with silt lenses. Thus, the resistance parameters defined were the critical state and peak friction angle with values of 33.0 ° and 33.4 ° respectively. The critical state angle was used in the back analysis of the load tests, and as a result the ks was obtained, to be subsequently compared to the at rest lateral earth pressure coefficient (k0). The results showed that, with depth, the value ks approaches the value of k0, with a relation of ks / k0 close to unity. It is concluded that the load transfer mechanism between the soil and the pile can be evaluated as a function of the initial stresses of the deposit, expressed from an estimated k0 based on the laboratory tests.
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Piloto, P. A. G. "Análise experimental e numérica do comportamento de estruturas metálicas sujeitas à acção do fogo." Doctoral thesis, Universidade do Porto, Faculdade de Engenharia, 2001. http://hdl.handle.net/10198/2093.
Full textAbstract:
Neste trabalho é apresentado um estudo sobre o efeito da acção do fogo em estruturas
metálicas, tendo sido elaborado um estudo numérico e experimental de um fenómeno de instabilidade
estrutural relativo à encurvadura lateral torsional de vigas a elevadas temperaturas. Foram efectuados
ensaios destrutivos em vários perfis com vista à determinação da carga limite resistente ou de colapso.
O efeito do fogo, como elemento activo e prejudicial à resistência do elemento estrutural, foi
determinado tendo-se verificado uma substancial diminuição das capacidades resistentes, devendo por
isso as acções serem convenientemente determinadas e analisadas.
No âmbito deste trabalho foram ainda estudadas as acções em estruturas sujeitas à acção do
fogo, a variação das propriedades mecânicas e térmicas do aço com a temperatura e o comportamento
não linear geométrico e material da estrutura.
Tendo como objectivo o desenvolvimento de ensaios experimentais em vigas de perfil
comercial, foi elaborada a candidatura de um projecto de Investigação e Desenvolvimento, intitulado
“Lateral Buckling of Steel Beams Under Fire Conditions”, financiado pelo Ministério da Ciência e da
Tecnologia, o que tornou possível a constituição de todo o equipamento que serviu de base a este
trabalho. Neste caso construiu-se um “setup” com as vertentes térmica e estrutural necessárias para
ensaiar estruturas em situação acidental de incêndio.
Paralelamente foram desenvolvidos vários ensaios numéricos do fenómeno de encurvadura
lateral a elevadas temperaturas com um programa de análise não linear geométrica e material, como são
exemplo os programas SAFIR, ANSYS e Cosmos/M, os quais permitiram validar os restantes
resultados e justificar a necessidade da revisão de algumas formulas simplificadas que o Eurocódigo 3
apresenta, nomeadamente as que dizem respeito à determinação da resistência de vigas à encurvadura
lateral, em situação de incêndio.
No final é apresentada a validação de uma proposta de cálculo simples para verificação de elementos estruturais à encurvadura, que se propõe em alternativa à proposta apresentada pelo Eurocódigo 3. In this thesis a numerical and experimental validation of the lateral torsional buckling
phenomenon of steel I beams under fire conditions is presented. A set of experimental destructive tests
were made in several I beams profiles for the buckling moment resistance determination.
The fire effect as an active element may produce a severe reduction in structural strength. The
numerical simulation of this phenomenon was done by means of a finite element code with non linear
material and geometrical behaviour, based on elevated and constant temperatures.
The structural actions under fire conditions, the material behaviour regarding its mechanical
and thermal properties variation with temperature and the non linear behaviour of structures were also
studied..
Having in mind the development of experimental tests in the commercial profiles IPE100, a
research project “ Lateral Buckling of Steel I Beams Under Fire Condition” has been financed by the
Science and Technology Portuguese Ministry, helping us to build a thermal and structural set up for this
propose.
In parallel, several numerical simulations had been done by means of the material and
geometrical non linear finite element code SAFIR, as well as, with other commercial codes, ANSYS
and CosmosM. This lead us to the justification and the needed of reviewing some simple formulas in
Eurocode regarding the lateral buckling behaviour of structures under fire conditions.
Finally a validation of a new proposal for a simple model in lateral torsional buckling under fire conditions is presented, different from that used in Eurocode, that seams to give unsafe results.
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Morais, Danielly Luz Araújo de. "Análise estática não-linear de cascas conoidais." Universidade Federal de Goiás, 2017. http://repositorio.bc.ufg.br/tede/handle/tede/7875.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
In the analytical study of conoidal shallow shells, one has the difficulty in analytically representing their displacement fields. In this way a numerical analysis, such as the Finite Element Method (MEF), has been used in the study of this type of structure. In this work, a static analysis of conoidal shallow shells from curved parabolic or cylindrical edges of linear, homogeneous and isotropic elastic material is performed, subjected to a transversal uniformly load distributed along the surface. With the thin-plate formulation derived from Kirchhoff's hypotheses and the theory developed by Marguerre for thin shells, the non-linear equilibrium equations that govern the behavior of the conoidal shell were determined, considering that this is a plate with an initial displacement. A linear parametric analysis of the critical loads and of buckling modes through the MEF is performed using ABAQUS 6.11® program, varying the contour and height conditions of the curved edges. Analytically, a complexity of the components of the buckling mode displacement fields of a given geometry is evaluated by its decomposition into double Fourier series. With the non-linear analysis via MEF, the non-linear equilibrium trajectories of the displacements are obtained and the first non-linear loading limit points are obtained. Nonlinear parabolic or cylindrical geometric parabolic geometry trajectories with describable supports at their four edges are also compared, evaluating how the geometric non-linearities influence the modes of the displacement fields during loading. Finally, a non-linear parametric analysis of the influence of the variation of the curved edge heights on the equilibrium trajectories of the membrane stresses and resulting from internal moments of the conoidal shell is carried out. It is verified, with this work, that linear analyzes can underestimate, or overestimate, the nonlinear behavior of the conoid. As the parametric analysis influences the behavior of the conoid in front of the load, either in the linear analysis, resulting in different critical loads and modes of buckling, or in the nonlinear analysis, resulting in differentiated limits loads and nonlinear equilibrium trajectories of the displacements and membrane stresses and moments.
No estudo analítico de cascas conoidais abatidas, tem-se a dificuldade de representar analiticamente os seus campos de deslocamentos. Dessa forma a análise numérica, como por exemplo, via Método dos Elementos Finitos (MEF), vem sendo utilizada no estudo desse tipo de estrutura. Neste trabalho, elabora-se uma análise estática de cascas conoidais abatidas de bordas curvas parabólicas, ou cilíndricas, de material elástico linear, homogêneo e isotrópico, submetidas a um carregamento transversal uniformemente distribuído ao longo da superfície. Com a formulação para placas finas derivada das hipóteses de Kirchhoff e a teoria desenvolvida por Marguerre para cascas finas, determinam-se as equações não-lineares de equilíbrio que regem o comportamento da casca conoidal, considerando que esta seja uma placa com um deslocamento inicial. Faz-se uma análise paramétrica linear das cargas críticas e modos de flambagem através do MEF utilizando o programa ABAQUS 6.11®, variando-se as condições de contorno e altura das bordas curvas. Avalia-se, analiticamente, a complexidade das componentes dos campos de deslocamentos do modo de flambagem de uma dada geometria através de sua decomposição em séries duplas de Fourier. Com a análise não-linear via MEF, obtêm-se as trajetórias não-lineares de equilíbrio dos deslocamentos da casca e obtêm-se os primeiros pontos limites de carregamento não-lineares. Comparam-se também as trajetórias não-lineares de equilíbrio de conóides de geometrias parabólicas, ou cilíndricas, com apoios indeslocáveis em suas quatro bordas, avaliando como as não-linearidades geométricas influenciam nos modos dos campos de deslocamentos durante o carregamento. Por fim, efetua-se uma análise paramétrica não-linear da influência da variação das alturas das bordas curvas nas trajetórias de equilíbrio dos esforços de membrana e resultantes de momentos internos dos conóides. Verifica-se, com este trabalho, que análises lineares podem subestimar, ou superestimar, o comportamento não-linear do conóide. Sendo que a análise paramétrica influencia o comportamento do conóide frente ao carregamento, seja no âmbito da análise linear, resultando em diferentes cargas críticas e modos de flambagem, seja na análise não-linear, resultando em cargas limites e trajetórias não-lineares de equilíbrio dos deslocamentos e dos esforços de membrana e momentos, diferenciados.