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Troller, Joakim Brendjord. "Compression Capacity of Timber Sills Loaded Perpendicular to the Grain : Ultimate Limit State (ULS) and Serviceability Limit State (SLS)." Thesis, Norges Teknisk-Naturvitenskapelige Universitet, Institutt for bygg, anlegg og transport, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-27225.
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The purpose of this thesis is to derive a new model to calculate the compression capacity of timber loaded perpendicular to the grain in Ultimate Limit State (ULS). The different parameters included in the capacity formulas, are found by various compression test conducted at the Department of Structural Engineering (KT) during the spring of 2014. Some of the parameters have been determined directly from data collected from the compression machine, while others required the usage of optical measuring techniques. It was derived two different models for calculating the compression capacity perpendicular to the grain in this thesis. The first model is based on the strain field generated in the wood, and the second on the total energy required to reach a defined fracture criterion.The two models give some variation in the carrying capacity, compared to the values calculated with the current regulations in Eurocode 5 part 1-1. For smaller loading lengths the current regulations gives a capacity that is quite high, compared to the new models derived in this thesis. This is because the current model has rules that allows the applied load to be distributed over an effective area, which can lead to a carrying surface that is twice the size of the actual loading surface. When the loading length are getting larger, the new models will stabilize towards values of the capacity that is similar or larger to the ones found with the current regulations. It has also been derived a model for calculating in Serviceability Limit State (SLS), which provides the opportunity to determine the desired deformations in a connection based on own preferences.
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Dunne, Helen P. "Finite element limit analysis of offshore foundations on clay." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:ba9c9beb-e055-4f46-a9f9-b2d10bd292b7.
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Capacity analysis is a common preliminary step in the design of offshore foundations. Inaccuracies in traditional capacity analysis methods, and the advancement of numerical modelling capabilities, have increasingly led designers to optimise foundations using more complex methods. In this thesis, the ultimate limit state capacity of a range of foundation types is investigated using finite element limit analysis. Novel three-dimensional finite element limit analysis software is benchmarked against analytical solutions and conventional displacement finite element analysis. It is then used to find lower and upper bounds of foundation capacity, with adaptive mesh refinement used to reduce the bound gap over successive iterations of the solution. Rigid foundations subjected to short term loading on clay soil are analysed. The undrained soil is modelled as a rigid--plastic von Mises material, and attention is given to modelling any normal and/or shear stress limits at the foundation/soil interface. Shallow foundations, suction anchor foundations, and hybrid mudmat/pile foundations are considered. Realistic six degree-of-freedom load combinations are applied and results are reported in the form of normalised design charts, and tables, that are suitable for use in preliminary design. Relationships between loading combinations and failure mechanisms are also explored. A number of case studies based on authentic foundation designs are analysed. The results suggest that finite element limit analysis could provide an attractive alternative to displacement finite element analysis for preliminary foundation design calculations.
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Kucuk, Sinan. "A Comparative Investigation Of Heat Transfer Capacity Limits Of Heat Pipes." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12609125/index.pdf.
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Heat pipe is a passive two phase device capable of transferring large rates of heat with a minimal temperature drop. It is a sealed tube with a wick structure lined in it and with a working fluid inside the tube. It consists of three parts: an evaporator, a condenser and an adiabatic section. The heat pipes are widely used in electronics cooling and spacecraft applications. Although they can transfer large rate of heat in a short range, they have operating limits, namely: the capillary limit, the viscous limit, the entrainment limit, the sonic limit and the boiling limit. These limits determine the heat transfer capacity of the heat pipe. The properties of the working fluid, the structure of the wick, the orientation of the pipe, the length and the diameter of the tube etc. are the parameters that affect the limits. In this study, an analytical 1-D heat pipe model is formed and a computer code is prepared in order to analyze the effects of the parameters on the heat transfer capacity of a heat pipe. Water, Ammonia and Mercury are investigated as working fluids for different operating temperature ranges. The software is tested for a typical application for each working fluid.
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Perninge, Magnus. "A Stochastic Control Approach to Include Transfer Limits in Power System Operation." Doctoral thesis, KTH, Elektriska energisystem, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-41986.
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The main function of the power grid is to transfer electric energy from generating facilities to consumers. To have a reliable and economical supply of electricity, large amounts of electric energy often have to be transferred over long distances. The transmission system has a limited capacity to transfer electric power, called the transfer capacity. Severe system failures may follow if the transfer capacity is reached during operation. Due to uncertainties, such as the random failure of system components, the transfer capacity for the near future is not readily determinable. Also, due to market principles, and reaction times and ramp rates of production facilities, power flow control is not fully flexible. Therefore, a transfer limit, which is below the transfer capacity, is decided and preventative actions are taken when the transfer reaches this limit. In this thesis an approach to deciding an optimal strategy for power flow control through activation of regulating bids on the regulating power market is outlined. This approach leads to an optimal definition of transfer limits as the boundary between the domain where no bid should be activated and the domains where bids should be activated. The approach is based on weighing the expected cost from system failures against the production cost. This leads to a stochastic impulse control problem for a Markov process in continuous time. The proposed method is a novel approach to decide transfer limits in power system operation. The method is tested in a case study on the IEEE 39 bus system, that shows promising results. In addition to deciding optimal transfer limits, it is also investigated how the transfer capacity can be enhanced by controlling components in the power system to increase stability.QC 20111010
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Lima, Severino Cesário de. "Desempenho fiscal da dívida dos grandes municípios brasileiros." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/12/12136/tde-01022012-174857/.
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Com a promulgação da Lei de Responsabilidade Fiscal (LRF), foram instituídas as regras de disciplina fiscal com o objetivo de reduzir o déficit público e estabilizar o montante da dívida pública em relação ao Produto Interno Bruto (PIB). Essas regras de disciplina fiscal compõem as restrições orçamentárias rígidas (hard budget constraint), destacando-se a exigência do orçamento equilibrado, o limite legal do endividamento, a destinação da dívida para investimentos e o controle indireto da dívida por meio do limite de despesas com pessoal. Todavia, dentre essas regras, os gestores dos grandes Municípios brasileiros alegam que o limite legal de endividamento de 1,2 da Receita Corrente Líquida (RCL) fixado pelo Senado Federal é inadequado, pois é único para todos os governos locais sem apresentar tratamento diferenciado aos grandes Municípios que possuem profundas diferenças em termos de população, renda e receita. Nesse contexto, é extremamente importante avaliar o desempenho fiscal da dívida dos grandes Municípios brasileiros, tendo como foco o nível de endividamento segundo os recursos potenciais desses governos locais e das restrições orçamentárias instituídas pela LRF. Assim, esta tese tem como objetivo central medir e explicar o desempenho do nível da dívida dos grandes Municípios brasileiros em função dos recursos potenciais para servir à dívida e dos mecanismos de restrições orçamentárias. Para tanto, foram considerados, no estudo, todos os grandes Municípios acima de 500.000 habitantes. Para medir o desempenho do nível da dívida, foi utilizada a análise envoltória de dados (DEA) em painel, denominada de DEA Dinâmica DSBM (Dinamic Slacks Based Model) com dados de 2000 a 2008, considerando como input o nível da dívida, como variável carryover o resultado primário e como outputs variáveis representativas dos recursos potenciais do Município: PIB, valor das propriedades e tamanho populacional. O desempenho do nível da dívida obtido com o DEA DSBM foi explicado pelas regras de disciplina fiscal com o uso da regressão GEE (Generalized Estimating Equations). Os resultados não rejeitaram as hipóteses de que o limite de despesas com pessoal e a destinação da dívida para investimentos são responsáveis para garantir o desempenho do nível da dívida dos grandes Municípios brasileiros. Os resultados rejeitaram a hipótese do equilíbrio orçamentário corrente influenciar positivamente o desempenho da dívida, contudo, considerando que para o cumprimento dessa regra fiscal é necessário observar as demais regras testadas, confirmou-se a tese de que os mecanismos de restrições orçamentárias provocam efeitos positivos no nível da dívida dos grandes Municípios brasileiros. Esses achados veem acentuar e eficácia da LRF no controle do endividamento público. Por outro lado, os dados revelaram que as transferências voluntárias, por representarem ajuda financeira implícita, atuam como uma força contrária ao desempenho do nível da dívida, flexibilizando as restrições orçamentárias, conforme prevê a hipótese do soft budget constraint (restrição orçamentária flexível). Considerando a relevância da regra fiscal do limite de endividamento no contexto das restrições orçamentárias, o estudo investigou se o limite fixado pelo Senado Federal reflete os recursos potenciais dos grandes Municípios. Os resultados revelaram, contrariamente ao esperado, que o limite legal é bastante elevado para esses Municípios, exceto para São Paulo e Rio de Janeiro, cuja capacidade de endividamento, segundo seus recursos potenciais, conduz a um limite médio de 0,35 da RCL. Contudo, para os Municípios de São Paulo e Rio de Janeiro o limite legal deveria ser bem maior que o instituído pelo Senado Federal, respectivamente, 1,84 e 1,64 da RCL, haja vista o considerável tamanho populacional desses Municípios, o significativo fluxo de riqueza expresso pelo PIB e a expressiva riqueza da comunidade representada pelo valor das propriedades. Acredita-se que esse estudo tenha contribuído para uma reflexão da dívida pública, apresentando uma metodologia que auxilie no avanço de estudos nessa área.With the promulgation of the Fiscal Responsibility Law (FRL) some rules for fiscal discipline were set in order to reduce the public deficit and stabilize the public debt relative to Gross National Product (GDP). These rules compound the hard budget constraint, highlighting the balanced-budget requirement, the legal limit of indebtedness, the allocation of debt for investments and indirect control of debt through the limit of personnel expenses. However, among these rules, managers of large municipalities in Brazil claim that the legal limit of indebtedness of 1.2 over the Net Current Revenue (NCR) set by the Senate is inadequate because it is unique for all local governments without giving special treatment to major municipalities that have sound differences in terms of population, income and revenue. In this context, it is extremely important to assess the fiscal performance of the debt of major Brazilian cities, focusing on the level of debt according to the potential resources of local governments and budget constraints imposed by the FRL. So, this thesis has as principal purpose to measure and explain the performance of the debt level of the major Brazilian municipalities in terms of potential resources and mechanisms of budget constraints. To do that, we considered in the study all the larger municipalities over 500,000 inhabitants. In order to measure the performance of the debt level we used Data Envelopment Analysis (DEA) in a panel of data, called Dynamic DEA DSBM (Slacks Based Dynamic Model) with data from 2000 to 2008, considering the debt level as input, the primary result as carryover variable and as output variables that represent the potential resources of the City: GDP, property values and population size. The performance of the debt level achieved using DEA DSBM was explained by the rules of fiscal discipline using GEE regression (Generalized Estimating Equations). The results did not reject the hypothesis that the limit of personnel expenses and the allocation of debt for investments are responsible for ensuring the performance of the debt level of the major Brazilian municipalities. The results rejected the hypothesis of the current balanced budget to positively influence the performance of debt, however, considering that to obey this rule it\'s necessary to observe the further rules tested, we confirmed the thesis that the mechanisms of budget constraints cause positive effects on the debt level of large Brazilian municipalities. These findings intensified the efficacy of the FRL in the control of public debt. On the other hand, the data revealed that voluntary transfers, which represent implicit financial aid, act as a counterforce to the performance level of debt, weakening the budget constraints, as predicted by the hypothesis of soft budget constraint. Considering the importance of the fiscal rule of debt limit in the context of hard budget constraints mechanism, this study investigated whether the limit set by the Senate reflects the potential resources of the major Brazilian cities. The results showed, contrary to the expectations, that the legal limit is quite high for large municipalities, except for São Paulo and Rio de Janeiro, because the debt capacity of these municipalities, according to its potential resources, leads to an average limit of 0.35 of the NCR. However, for the municipalities of São Paulo and Rio de Janeiro the legal limit should be much larger than that established by the Senate, respectively, 1.84 and 1.64 of the NCR, because of the considerable size of population, the significant flow of wealth expressed by the GDP and the considerable wealth of the community represented by the property values. We believed this study has contributed to a reflection of the public debt and introducing a methodology to assist in the progress of studies in this area.
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Andersson, Andreas. "Capacity assessment of arch bridges with backfill : Case of the old Årsta railway bridge." Doctoral thesis, KTH, Bro- och stålbyggnad, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-32827.
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The work presented in this thesis comprises the assessment of existing arch bridges with overlying backfill. The main objective is to estimate the load carrying capacity in ultimate limit state analysis. A case study of the old Årsta railway bridge is presented, serving as both the initiation and a direct application of the present research. The demand from the bridge owner is to extend the service life of the bridge by 50 years and increase the allowable axle load from 22.5 to 25 metric tonnes. The performed analyses show a great scatter in estimated load carrying capacity, depending on a large number of parameters. One of the factors of main impact is the backfill material, which may result a significant increase in load carrying capacity due to the interaction with the arch barrel. Based on theoretical analyses, extensive conditional assessments and the demand from the bridge owner, it was decided that the bridge needed to be strengthened. The author, in close collaboration with both the bridge owner and the persons performing the conditional assessment, performed the development of a suitable strengthening. The analyses showed a pronounced three-dimensional behaviour, calling for a design using non-linear finite element methods. Due to demands on full operability during strengthening, a scheme was developed to attenuate any decrease in load carrying capacity. The strengthening was accepted by the bridge owner and is currently under construction. It is planned to be finalised in 2012. The application of field measurements to determine the structural manner of action under serviceability loads are presented and have shown to be successful. Measured strain of the arch barrel due to passing train has been performed, both before, during and after strengthening. The results serve as input for model calibration and verification of the developed strengthening methods. The interaction of the backfill was not readily verified on the studied bridge and the strengthening was based on the assumption that both the backfill and the spandrel walls contributed as dead weight only. The finite element models are benchmarked using available experimental results in the literature, comprising masonry arch bridges with backfill loaded until failure. Good agreement is generally found if accounting for full interaction with the backfill. Similarly, accounting for the backfill as dead weight only, often results in a decrease in load carrying capacity by a factor 2 to 3. Still, several factors show a high impact on the estimated load carrying capacity, of which many are difficult to accurately assess. This suggests a conservative approach, although partial interaction of the backfill may still increase the load carrying capacity significantly.Arbetet i föreliggande avhandling omfattar analyser av befintliga bågbroar med ovanliggande fyllning. Huvudsyftet är att uppskatta bärförmågan i brottgränstillstånd. En fallstudie av gamla Årstabron redovisas, vilken utgör både initieringen och en direkt tillämpning av föreliggande forskning. Kravet från broförvaltaren är att öka brons livslängd med 50 år, samtidigt som axellasten ska ökas från nuvarande 22.5 ton till 25 ton. Utförda analyser visar på stor spridning i uppskattad bärförmåga, beroende på ett stort antal parametrar. En av de främsta faktorerna är fyllningens egenskaper, vilken kan resultera i en markant ökning av bärförmågan p.g.a. samverkan med bågen. Baserat på teoretiska analyser, tillståndsbedömningar och krav från broförvaltaren beslutades att bron skulle förstärkas. En förstärkningsmetod har utvecklats i nära samarbete med broförvaltaren och personer som tidigare utfört tillståndsbedömningarna. Analyserna visar ett utpräglat tredimensionellt beteende, vilket har föranlett användandet av icke-linjära finita elementmetoder. Krav på full trafik under samtliga förstärkningsarbeten har resulterat i att dessa utförs enligt en föreskriven ordning, som ska reducera minskning i bärförmåga under samtliga etapper. Förstärkningsförslaget godkändes av Banverket och är för närvarande under byggnation. Enligt plan ska dessa slutföras under 2012. Fältmätningar har använts för att bestämma det statiska verkningssättet under brukslaster, vilket visas ge goda resultat. Resulterande töjningar från passerande tåg har uppmäts i bågen, både före, under och efter förstärkning. Resultaten har använts både för att kalibrera beräkningsmodeller och att verifiera utförda förstärkningar. Samverkan mellan båge och fyllning har inte kunnat verifierats för den aktuella bron och de utvecklade förstärkningarna baseras på en modell där både fyllning och sidomurar endast utgör yttre verkande last. De framtagna finita element modellerna har jämförts med experimentella resultat från litteraturen, omfattande tegelvalvsbroar med ovanliggande fyllning belastade till brott. Generellt erhålls god överensstämmelse om full samverkan mellan båge och fyllning antas. Om fyllningen istället endast betraktas som yttre last, minskar lastkapaciteten ofta med en faktor 2 till 3. Fortfarande uppvisar ett antal faktorer stor inverkan på bärförmågan, vilka ofta är svåra att med säkerhet bestämma. Ett konservativt betraktningssätt rekommenderas, även om delvis samverkan med fyllningen fortfarande kan öka bärförmågan avsevärt.
QC 20110426
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Chen, Zhijian. "Capacity limits and length limits in immediate recall : a reconciliation /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p1422917.
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Strömgren, Per. "Modelling of Traffic Performance for Swedish Roads and Motorways." Doctoral thesis, KTH, Transportplanering, ekonomi och teknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-185930.
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This thesis consists of five scientific articles oriented towards capacity. Managing capacity constraints with associated delays is a big issue at new design as well as at trimming existing traffic facilities. In larger Swedish cities these challenges have become more and more important as a result of growing traffic demand due to rapid population increase.Models for estimating capacity and delay are available, but not many are calibrated for Swedish conditions due to the high effort required. This thesis documents development and calibration of new models for motorway links, entry and exit lanes and weaving areas and an developed space-time model with the ability to calculate queue length, delay, etc.The first article is focused on identifying weaknesses in the former Swedish capacity method for motorways, and development of new models overcoming these shortcomings. The development includes new models for jam density at queue, capacity in weaving areas and fundamental flow-density relationships for 15 different highway types for inclusion in the new Swedish capacity manual.The second article describes the development of a Swedish motorway space-time model to estimate travel times and queues in oversaturated conditions based on the American FREEVAL model in Highway Capacity Manual 2010 (HCM 2010). Calibration and validation of the model has been performed with data from the Motorway Control System (MCS) in Stockholm. A good correspondence was obtained for most cases, but further calibration and validation efforts are required for entry and exit lanes.The third article describes further development of the intersection model in the Swedish microscopic model “Rural Traffic Simulator (RuTSim). This is a continuation of the work documented in the author’s licentiate thesis published in 2002. The development focused on simulation of intersections using a new concept on lane use not included in the old RuTSim model. The model describes Swedish rural intersections with flared approaches providing a non-discreet lane use due to vehicle types in queue. New data for calibration and validation data was also generated. The validation results showed good correspondence between simulated and empirical delay results. The new intersection model is now implemented in RuTSim, providing new tools for estimation of capacity, delay and queue length already included in Swedish guidelines and capacity manuals/software (Capcal).The fourth article describes the development of a new capacity model for roadwork zones. Focus is on the resulting capacity of one lane due to several reduction factors. These factors include impacts of closed road shoulders, reduction of number of lanes, diversion of traffic to the opposite carriageway, commuting traffic, length of work zone, lane width and type of road work. The first two correction factors were successfully validated in a full-scale test on the E6 motorway in Gothenburg.The fifth article describes development and implementation of a new harmonization algorithm for MCS systems on motorways designed to increase bottleneck capacity and throughput. Two different models were developed, one of which was implemented in the existing MCS system on E4 Södertäljevägen south of Stockholm. Full-scale trials were carried out with a model based on trigger levels in terms of flow. The second model based on the difference in the variance of speed during two following time periods was tested offline also with very good results.QC 20160429
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Lipowczan, Martin. "Inverzní analýza spolehlivosti předpjatého mostu." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-372071.
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The proposed diploma thesis deals with the application of methodology and tools of inverse analysis for design of selected structural parameters using a fully probabilistic analysis to determine the level of its reliability. The method based on artificial neural networks is used to approximate the inverse function. The inverse analysis was carried out in two ways that differs in the method of obtaining reliability indicators. The structure analyzed in this work was an existing bridge. The year of construction is estimated approximately between the years 1955 to 1960. The bridge is located close to the Uherský Ostroh. It is a one-piece concrete slab made of MPD3 and MPD4 girders post-tensioned by tendons. Based on the 2006 and 2007 diagnostic surveys, laboratory tests, normative regulations and recommendations and, last but not least, sensitivity analyses, an inverse design of selected design parameters was performed for required limit states. Various load levels, different alternatives of design parameters and different neural network structures were studied.
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Velecká, Renata. "Statické řešení založení novostavby horského hotelu." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226922.
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Master's thesis deals with design and static solution of foundation slab of mountain hotel. Two calculation versions are made – simplified („inverse ceiling“) and calculation using software RF-SOILIN. This thesis also includes a comparison of both results. Reinforcement is designed for more accurate internal forces and the assessment of structure is performed according to the 1st limit state of capacity.
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Dorji, Jigme. "Strength and serviceability assessment of aged masonry arch bridges." Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/213050/1/Jigme_Dorji_Thesis.pdf.
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This thesis investigated strength and serviceability of aged masonry arch bridges which exist in rail track networks in Australia. The method is based on the measurement of structural responses under operating loads and experimental tests. Two typical bridges were investigated for Australian Rail and Track Corporation Ltd (ARTC) and found that the bridges are safe against the operating loads, despite having undergone aging phenomenon.
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Chatzinotas, Symeon. "Information-theoretic capacity limits in multi-cell joint processing systems." Thesis, University of Surrey, 2009. http://epubs.surrey.ac.uk/842899/.
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Multicell Joint Processing has emerged as a new paradigm of cooperative communications, which aims at pushing the capacity limits of cellular systems by eliminating inter-cell interference. Its operation is based on the concept of Base Station cooperation, which is enabled through wideband error-free low-latency links to a central signal processor. This processor is responsible for jointly encoding or decoding the signals, which are transmitted to or received from the User Terminals of the cellular system. The rationale behind this cooperation is that spatially distributed Base Stations are able to act as multiple antennas of a single universal transceiver, which servers the entire cellular system. In this context, the objective is to determine the capacity performance of a multicell joint processing system under the limitations imposed by a practical cellular channel. Towards this end, a comprehensive cellular channel model is proposed, which accommodates continuous path loss functions, distributed User Terminals, multiple antennas and correlated flat fading. Focusing on the uplink channel, the per-cell sum-rate capacity is determined using asymptotic analysis and the derived closed-forms are verified through Monte Carlo simulations. The core of the analysis is based on free probability and random matrix theory, which provide the mathematical tools for studying the asymptotic eigenvalue distribution of the channel matrix. Based on this setting, it is observed that multicell processing effectively removes the interference-limited behavior of conventional cellular systems, since increasing the system power always results in higher capacity. The exact sum-rate capacity depends on the total received power across the system, which is determined by the user distribution, the cell density and the path loss. Including multiple antennas at the Base Stations results in a linear capacity scaling, whereas multiple antennas at the User Terminals do not provide a capacity enhancement. Similarly, antenna correlation at the Base Station side degrades the capacity, while correlation at the User Terminal has no effect. Furthermore, the distribution of the sum-rate capacity across individual User Terminal rates is investigated in terms of fairness. It is observed that by first decoding strong-channel User Terminals, rate fairness is promoted, but equal rate sharing can only be achieved by employing power control in parallel with heuristic user ordering. Focusing on the downlink channel, the per-cell sum-rate capacity is evaluated using duality principles and the individual user rates are calculated considering channel-dependent and random encoding orders. More specifically, three types of power allocations are considered: a) optimal power allocation with system power constraint as an upper bound, b) optimal power allocation with the more appropriate per-cell power constraint and c) uniform power allocation in the dual uplink domain. In this context, it is shown that the upper bound calculated considering a system power constraint is tight for the considered range of cellular parameters and it can be utilized to closely estimate the realistic downlink capacity of a per-cell power constrained system. Furthermore, the downlink user rate vectors are greatly affected by the employed encoding order. More specifically, by considering a user ordering which favours the deep-fade User Terminals, the fairness over the downlink rates can be promoted, while uniform power allocation favours user rate fairness on the expense of the sum-rate capacity.
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Ain-Ul-Aisha, FNU. "Fundamental Limits of Poisson Channels in Visible Light Communications." Digital WPI, 2017. https://digitalcommons.wpi.edu/etd-dissertations/475.
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Visible Light Communications (VLC) has recently emerged as a viable solution for solving the spectrum shortage problem. The idea is to use artificial light sources as medium to communicate with portable devices. In particular, the light sources can be switched on and off with a very high-frequency corresponding to 1s and 0s of digital communication. The high-frequency on-off switching can be detected by electronic devices but not the human eyes, and hence will not affect the light sources' illumination functions. In VLC, if a receiver is equipped with photodiodes that count the number of arriving photons, the channels can be modeled as Poisson channels. Unlike Gaussian channels that are suitable for radio spectrum and have been intensively investigated, Poisson channels are more challenging and are not that well understood. The goal of this thesis is to characterize the fundamental limits of various Poisson channels that models different scenarios in VLC. We first focus on single user Poisson fading channels with time-varying background lights. Our model is motivated by indoor optical wireless communication systems, in which the noise level is affected by the strength of the background light. We study both the single-input single-output (SISO) and the multiple-input and multiple-output (MIMO) channels. For each channel, we consider scenarios with and without delay constraints. For the case without a delay constraint, we characterize the optimal power allocation scheme that maximizes the ergodic capacity. For the case with a strict delay constraint, we characterize the optimal power allocation scheme that minimizes the outage probability. We then extend the study to the multi-user Poisson channels and analyze the sum-rate capacity of two-user Poisson multiple access channels (MAC). We first characterize the sum-rate capacity of the non-symmetric Poisson MAC when each transmitter has a single antenna. We show that, for certain channel parameters, it is optimal for a single-user to transmit to achieve the sum-rate capacity. This is in sharp contrast to the Gaussian MAC, in which both users must transmit, either simultaneously or at different times, in order to achieve the sum-rate capacity. We then characterize the sum-rate capacity of the Poisson MAC with multiple antennas at each transmitter. By converting a non-convex optimization problem with a large number of variables into a non-convex optimization problem with two variables, we show that the sum-rate capacity of the Poisson MAC with multiple transmit antennas is equivalent to a properly constructed Poisson MAC with a single antenna at each transmitter. We further analyze the sum-rate capacity of two-user Poisson MIMO multiple-access channels (MAC), when both the transmitters and the receiver are equipped with multiple antennas. We first characterize the sum-rate capacity of the Poisson MAC when each transmitter has a single antenna and the receiver has multiple antennas. We show that similar to Poisson MISO-MAC channels, for certain channel parameters, it is optimal for a single user to transmit to achieve the sum-rate capacity, and for certain channel parameters, it is optimal for both users to transmit. We then characterize the sum-rate capacity of the channel where both the transmitters and the receiver are equipped with multiple antennas. We show that the sum-rate capacity of the Poisson MAC with multiple transmit antennas is equivalent to a properly constructed Poisson MAC with a single antenna at each transmitter.
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Teklemariam, Daniel Mekonnen, and Bennie Hamunzala. "Design of Thick Concrete Beams : Using Non-Linear FEM." Thesis, KTH, Bro- och stålbyggnad, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-189141.
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The experimental studies performed on the behaviour of very thick concrete beams subjected to static loads have revealed that the shear mechanisms play an important role in the overall response and failure behaviour. The aim of this thesis is to recommend suitable design methods for thick concrete beams subjected to off-centre static concentrated load according Eurocode 2 by using non-linear finite element analysis (NLFEA). To achieve this task, Abaqus/Explicit has been used by employing constitutive material models to capture the material non-linearity and stiffness degradation of concrete. Concrete damaged plasticity model and perfect plasticity model has been used for concrete and steel respectively. Three dilation angles (30º, 38º and 45º) and fracture energy from FIB 1990 (76 N/m) and FIB 2010 (142 N/m) has been used to investigate their influence on the finite element model. The dilation angle of 38º and FIB 2010 fracture energy was adopted as the suitable choice that reasonably matched with the experimental results. In verifying and calibrating the finite element model, the experimental results of the thick reinforced concrete beam conducted by the American Concrete Institute have been used. Three design approaches in the ultimate and serviceability limit state according to Eurocode 2 recommendations have been used namely; the beam method, strut and tie method and shell element method. Using the reinforcement detailing of the hand calculations of beam method and strut and tie method and linear finite element analysis of shell element method, non-linear finite element models have been pre-processed and analysed in Abaqus/Explicit. During the post-processing, the results have been interpreted and compared between the three design methods. The results under consideration are hand-calculated load at 0.3 mm crack width, FE-load at 0.3 mm crack width, amount of reinforcement and FE-failure load. The comparison of the results between the three design approaches (beam method, strut and tie method and shell element method) indicates that strut and tie method is better design approach, because it is relatively economic with regards to the quantity of reinforcement bars, has the higher load capacity and has a higher load at crack width of 0.3 mm crack width.De experimentella studier som utförts på tjocka betongbalkar som utsätts för statisk last har visat att skjuvning spelar en viktig roll i brottmekanismen. Syftet med detta examensarbete är att rekommendera lämpliga dimensioneringsmetoder för tjock betongbalkar utsatt for statisk koncentrerad last enligt Eurokod 2 med hjälp av ickelinjära finita element metod. Abaqus/Explicit användes genom att utnyttja konstitutiva materialmodeller för att fånga materialens icke-linjäritet och minskad styvhet. Tre dilatationsvinklar (30°, 38° och 45°) och två brottenergi från FIB 1990 (76 N/m) och FIB 2010 (142 N/m) tillämpas för att kontrollera deras inverkan på FE-modellerna. Dilatationsvinkel med 38° och FIB 2010 med högre brottenergi valdes i de icke-linjära finita elementanalyserna. Kontroll av FE-modellerna är baserad på ”American Concret Institutes” experimentella resultat på de tjocka betongbalkarna. Handberäkningar av tjocka betongbalkar har utförts i brott- och bruksgränstillstånd med tre dimensioneringsmetoder i Eurokod 2 nämligen balk metoden, fackverksmetoden och linjära-FE skalelementmetoden. Jämförelse har gjorts för de olika dimensioneringsmetoderna, genom att använda de armeringsdetaljer av handberäkningar i de verifierade och kalibrerade icke linjära FE-modellerna i Abaqus/Explicit. Resultaten i fråga är last för 0.3 mm handberäknad sprikvidd, FE-last för 0.3 mm sprikvidd, armeringsmängd och FE-brottlast. Jämförelse av resultaten mellan de tre dimensioneringsmetoder (balkmetod, fackverksmetod och skalelementmetod) visar att fackverksmetod är bättre design metod, eftersom det är relativt ekonomiskt med avseende på armeringsmängd, har högre lastkapacitet och last på 0.3 mm sprickvidd.
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Ranjbar, Mohammad. "Optimal Signaling Strategies and Fundamental Limits of Next-Generation Energy-Efficient Wireless Networks." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1564677171677636.
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Camilleri, Marguerite. "Environmental capacity for Malta : living within limits in a small island state." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621340.
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Mazzotti, Sofia. "Equilibri nel modello di Cournot quando esistono limiti di capacità produttiva." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13564/.
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L'obiettivo di questa tesi è quello di applicare alcune nozioni tipiche dei sistemi dinamici discreti a una situazione economica. Si considerano vari casi di oligopolio, secondo il modello di Cournot, e si osserva che un sistema di n competitori inizia a essere instabile con l'aumentare di n. Si approfondisce poi il caso di un duopolio simmetrico in cui i competitori hanno limitate capacità produttive. Se ne studiano i punti di equilibrio e la loro stabilità e, considerando la funzione di reazione, si osserva che le variazioni degli attrattori prodotte da cambiamenti dei parametri nella funzione dei costi sono dovute alle border-collision bifurcations, cioè all'urto di tali attrattori con le discontinuità della funzione di reazione. Si danno in ultimo alcuni strumenti per trovare i bacini di attrazione.
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Bugetti, Maria Novella <1980>. "L'amministrazione di sostegno tra tutela della persona e limiti di capacità." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/97/.
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Pollock, Tony Steven, and tony pollock@nicta com au. "On Limits of Multi-Antenna Wireless Communications in Spatially Selective Channels." The Australian National University. Research School of Information Sciences and Engineering, 2003. http://thesis.anu.edu.au./public/adt-ANU20050418.143712.
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Multiple-Input Multiple-Output (MIMO) communications systems using multiantenna arrays simultaneously during transmission and reception have generated significant interest in recent years. Theoretical work in the mid 1990?s showed the potential for significant capacity increases in wireless channels via spatial multiplexing with sparse antenna arrays and rich scattering environments. However, in reality the capacity is significantly reduced when the antennas are placed close together, or the scattering environment is sparse, causing the signals received by different antennas to become correlated, corresponding to a reduction of the effective number of sub-channels between transmit and receive antennas. By introducing the previously ignored spatial aspects, namely the antenna array geometry and the scattering environment, into a novel channel model new bounds and fundamental limitations to MIMO capacity are derived for spatially constrained, or spatially selective, channels. A theoretically derived capacity saturation point is shown to exist for spatially selective MIMO channels, at which there is no capacity growth with increasing numbers of antennas. Furthermore, it is shown that this saturation point is dependent on the shape, size and orientation of the spatial volumes containing the antenna arrays along with the properties of the scattering environment. This result leads to the definition of an intrinsic capacity between separate spatial volumes in a continuous scattering environment, which is an upper limit to communication between the volumes that can not be increased with increasing numbers of antennas within. It is shown that there exists a fundamental limit to the information theoretic capacity between two continuous volumes in space, where using antenna arrays is simply one choice of implementation of a more general spatial signal processing underlying all wireless communication systems.
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Beirami, Ahmad. "Network compression via network memory: fundamental performance limits." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53448.
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The amount of information that is churned out daily around the world is staggering, and hence, future technological advancements are contingent upon development of scalable acquisition, inference, and communication mechanisms for this massive data. This Ph.D. dissertation draws upon mathematical tools from information theory and statistics to understand the fundamental performance limits of universal compression of this massive data at the packet level using universal compression just above layer 3 of the network when the intermediate network nodes are enabled with the capability of memorizing the previous traffic. Universality of compression imposes an inevitable redundancy (overhead) to the compression performance of universal codes, which is due to the learning of the unknown source statistics. In this work, the previous asymptotic results about the redundancy of universal compression are generalized to consider the performance of universal compression at the finite-length regime (that is applicable to small network packets). Further, network compression via memory is proposed as a compression-based solution for the compression of relatively small network packets whenever the network nodes (i.e., the encoder and the decoder) are equipped with memory and have access to massive amounts of previous communication. In a nutshell, network compression via memory learns the patterns and statistics of the payloads of the packets and uses it for compression and reduction of the traffic. Network compression via memory, with the cost of increasing the computational overhead in the network nodes, significantly reduces the transmission cost in the network. This leads to huge performance improvement as the cost of transmitting one bit is by far greater than the cost of processing it.
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Soriguera, Francesc, Irene Martínez, Marcel Sala, and Mónica Menénde. "Effects of low speed limits on freeway traffic flow." Elsevier, 2017. https://publish.fid-move.qucosa.de/id/qucosa%3A72818.
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Recent years have seen a renewed interest in Variable Speed Limit (VSL) strategies. New opportunities for VSL as a freeway metering mechanism or a homogenization scheme to reduce speed differences and lane changing maneuvers are being explored. This paper examines both the macroscopic and microscopic effects of different speed limits on a traffic stream, especially when adopting low speed limits. To that end, data from a VSL experiment carried out on a freeway in Spain are used. Data include vehicle counts, speeds and occupancy per lane, as well as lane changing rates for three days, each with a different fixed speed limit (80 km/h, 60 km/h, and 40 km/h). Results reveal some of the mechanisms through which VSL affects traffic performance, specifically the flow and speed distribution across lanes, as well as the ensuing lane changing maneuvers. It is confirmed that the lower the speed limit, the higher the occupancy to achieve a given flow. This result has been observed even for relatively high flows and low speed limits. For instance, a stable flow of 1942 veh/h/lane has been measured with the 40 km/h speed limit in force. The corresponding occupancy was 33%, doubling the typical occupancy for this flow in the absence of speed limits. This means that VSL strategies aiming to restrict the mainline flow on a freeway by using low speed limits will need to be applied carefully, avoiding conditions as the ones presented here, where speed limits have a reduced ability to limit flows. On the other hand, VSL strategies trying to get the most from the increased vehicle storage capacity of freeways under low speed limits might be rather promising. Additionally, results show that lower speed limits increase the speed differences across lanes for moderate demands. This, in turn, also increases the lane changing rate. This means that VSL strategies aiming to homogenize traffic and reduce lane changing activity might not be successful when adopting such low speed limits. In contrast, lower speed limits widen the range of flows under uniform lane flow distributions, so that, even for moderate to low demands, the under-utilization of any lane is avoided. These findings are useful for the development of better traffic models that are able to emulate these effects. Moreover, they are crucial for the implementation and assessment of VSL strategies and other traffic control algorithms.
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Basak, Chandramallika. "Capacity limits of the focus of attention and dynamics of the focus switch cost in the working memory." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2005. http://wwwlib.umi.com/cr/syr/main.
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Le, Anh Duc. "Fundamental Limits of Communication Channels under Non-Gaussian Interference." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1469011496.
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Kacem, Ahmed. "Etude de la capacité limite de déformation dans le procédé de relevage de bord par expansion." Phd thesis, Université de Bretagne Sud, 2013. http://tel.archives-ouvertes.fr/tel-00840726.
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Le procédé de soyage qui consiste à réaliser un relevage du bord dans un trou préalablement poinçonné ou percé a été étudié sur deux tôles en aluminium A1050-H14 et A6061-O. Une caractérisation mécanique a été effectuée en utilisant des essais de traction et de cisaillement (monotone et cyclique). En bénéficiant des résultats de cette caractérisation, des modèles éléments finis 2D et 3D de soyage ont été développés en utilisant des critères de plasticité isotrope et anisotrope (Hill 1948). Ces modèles ont été améliorés par la technique de remaillage et la prise en compte de l'endommagement en utilisant un modèle non couplé puis un modèle couplé. Des outils de presse ont été également conçus, fabriqués et exploités pour mener des expérimentations destinées principalement à valider les résultats numériques.
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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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Nancey, Alain. "Capacité portante des fondations superficielles sous sollicitations sismiques." Phd thesis, Grenoble 1, 1992. http://tel.archives-ouvertes.fr/tel-00783443.
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Ce mémoire montre la construction de modèles de calcul, pour l'étude de la capacité portante des fondations superficielles soumises à des sollicitations sismiques. La première partie examine la règlementation française (Règles PSG9) et ses évolutions (Recommandations AFPS90), dans le-domaine de la protection parasismique. A partir des données sismologiques et géotechniques concernant le site particulier de Mexico, le second chapitre fournit les paramètres sismiques de la modélisalion. La troisième partie propose le remplacement des effets dynamiques du séisme par des efforts pseudo-statiques équivalents à l'utilisation de l'Analyse Limite, pour déterminer les chargements de rupture, en supposant un comportement rigide-plastique du sol. Les différentes approches sont rappelées ici. La quatrième partie présente les résultats obtenus par les trois méthodes suivantes: une approche statique élastique, un calcul utilisant des lignes de rupture circulaires, un calcul cinématique faisant intervenir une méthode de résolution par éléments finis. L'influence des paramètres de dimension des modèles (L,H,B) est particulièrement mise en évidence. Enfin, une cinquième partie est consacrée au calcul du déplacement permanent résultant d'une secousse sismique. Deux lypes de méthodes sont présentés, supposant toutes un comportement rigide-plastique les premières ne considèrent, comme effet du séisme, qu'une surcharge temporaire au niveau de l'ouvrage, les dernières déterminent le déplacement, à partir d'un accélérogramme artificiel et de coefficients sismiques appliqués à l'ensemble sol-fondation.
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Svoboda, Petr. "Nosná železobetonová konstrukce bytového domu." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226746.
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The main purpose of thesis is a static solution of load bearing reinforced concrete structure of flat house. The work contains an assessment of waterproof concrete building. The object is built under the groundwater level. Supporting structures are concrete slab, walls and columns. An assessment of these structures is realized in terms of first critical state- carrying capacity and second limit state- limitation of crack widths.
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Ferencz, Balázs. "Nosná železobetonová konstrukce objektu administrativní budovy." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226920.
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The Master’s thesis is focused on the analysis and design of selected members of load-bearing structure of an administration building according to the ultimate limit states (ULS) and seviceability limit states (SLS). The calculation and the analysis was supported by design software SCIA ENGINEER 2012. Structural analysis deals with the design of the reinforced concrete (RC) flat slab above the 4rd strorey which is particularly supported by RC columns and particularly lies on RC walls. Furthermore, the Master’s thesis contains analysis of some selected columns of last three storeys, column of lowest storey, construction of stairway between 4rd and 5th storeys. The work beside this deals with the calculation and design of foundation of the object. The rest parts of the load-bearing structure are not solved in the Master’s thesis.
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Kacem, Ahmed. "Étude de la capacité limite de déformation dans les procédés de mise en forme par déformation locale." Lorient, 2013. http://www.theses.fr/2013LORIS288.
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Cette thèse s’inscrit dans le cadre de la recherche d’une bonne maîtrise expérimentale et théorique en vue de déterminer la capacité limite de déformation de la tôle dans les procédés de mise en forme par relevage du bord. Le procédé de relevage du bord d’un trou est pris comme sujet pour développer la méthodologie d’analyse. L’étude a été menée sur deux tôles en aluminium A1050-H14 et A6061-O. Une caractérisation mécanique a été effectuée en utilisant des essais de traction et de cisaillement. Des modèles éléments finis ont été développés en utilisant des critères de plasticité isotrope et anisotrope. Ces modèles ont été améliorés par la prise en compte de l’endommagement. Des expérimentations ont été réalisées pour valider les résultats numériques. Dans une première partie, un intérêt a été porté à la maîtrise technologique du procédé en analysant l’effet de taux de réduction sur le procédé de relevage du bord d’un trou. Une méthodologie a été mise au point pour distinguer deux conditions de relevage : avec ou sans laminage. L’étude s’est ensuite orientée vers la quantification de l’effet des différentes hypothèses de l’anisotropie de la tôle. L’accent a été mis sur la qualité de la prédiction numérique de quelques paramètres. Ensuite, le travail a été focalisé sur l’identification de la capacité limite de déformation d’un bord relevé. Un critère macroscopique d’initiation de rupture avec une approche non couplée a été adopté pour la prédiction de l’ampleur de l’endommagement. Enfin, on s’est intéressé à la caractérisation de l’endommagement dans un bord relevé en utilisant le modèle d’endommagement couplé de Gurson-Tvergaard-NeedlemanThis thesis deals with the experimental and numerical investigations of the limits of the flanging process arising from material failure. The methodology developed in this study was applied particularly to the stretch flanging process of a hole in sheet metal called the hole-flanging process. The materials studied are made of A1050-H14 and A6061-O aluminium alloys. Mechanical characterizations have been performed through uniaxial tensile and shear tests. An elasticplastic finite element models based on isotropic and anisotropic yield criteria were developed. These models were enhanced by the integration of the damage in simulation. Experiments were conducted to verify the reliability of the developed finite element models. First, the effect of the clearance thickness ratio on the hole-flanging process was studied. A methodology was made to distinguish two conditions of the process: hole-flanging with and without ironing. Then, the effect of material anisotropy assumptions on the predictive accuracy of finite element simulations of the hole-flanging process was quantified. The study was then focused on the determination of the limits of hole-flanging process arising from material failure. For that purpose, a fracture criterion was calibrated and used in simulations to predict the damage of the flange. Finally, the damage occurrence in flanged edge was characterized by using the coupled approach of Gurson-Tvergaard-Needleman
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Hamlaoui, Madani. "Capacité portante des fondations superficielles pour géomateriaux avec modèles plastiques non associés." Thesis, Lille 1, 2015. http://www.theses.fr/2015LIL10146.
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En plasticité associée c’est-à-dire avec la loi de normalité, la solution analytique de Prandtl-Hill donne la charge limite exacte d’un poinçon sur un massif semi-infini de fondation avec le critère de Mohr-Coulomb. Or, il est reconnu expérimentalement que les sols ont un comportement plastique non associé, ce qui signifie qu’en réalité la valeur de la charge limite n’est qu’une estimation.On se propose dans ce travail de combler ce manque en abordant le problème de la capacité portante d’une fondation superficielle lorsque la loi de plasticité est non associée. Sur la base des simulations numériques et d’une extension de l’analyse limite aux matériaux à lois non associées par l’approche du bipotentiel, de Saxcé (1992), on propose une solution analytique approchée par une méthode variationnelle et on la compare à la formule de Drescher et Detournay (1993) et aux résultats numériquesIn associated plasticity, i.e. with the normality law, Prandtl-Hill analytical solution gives the exact limit load of a punch on a semi-infinite massive of foundation with Mohr-Coulomb model. However, it is experimentally recognized that geomaterial shave a non-associated behavior, what means that in reality the value of the limit load is only an estimation.In this work, it is proposed to fill this lack in addressing the problem of the bearing capacity of a shallow foundation, when the low of plasticity is no-associated. On the basis of numerical simulations and an extension of the limit analysis method to materials with non-associated laws by the bipotential approach, de Saxcé (1992), we proposed an approximated analytical solution by a variational method and we compared to Drescher-Detournay formula (1993) and numerical results
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Kliegl, Reinhold. "Kognitive Plastizität und altersbedingte Grenzen am Beispiel des Erwerbs einer Gedächtnistechnik." Universität Potsdam, 1989. http://opus.kobv.de/ubp/volltexte/2009/4032/.
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Die Bedeutung kognitiver Entwicklungskapazität (Plastizität) und ihrer altersabhängigen Grenzen für Theorien kognitiven Alters wird thematisiert. Für kognitive Basisprozesse wird erwartet, daß die durch Training umgesetzte Entwicklungskapazität älterer Menschen zwar ausreicht, die Ausgangsleistung junger Erwachsener zu übertreffen, daß aber aufgrund altersbedingter Grenzen der Entwicklungskapazität nur sehr wenige ältere Erwachsene das Leistungsniveau trainierter junger Erwachsener erreichen werden. Am Beispiel eines Gedächtnistrainingsprogrammes zur Erhöhung der Merkfähigkeit für Wortlisten werden zwei Forschungsstrategien vorgestellt: (a) das Training von sehr leistungsfähigen älteren Erwachsenen und (b) Längsschnitt-Einzelfall-Studien. Die experimentellen Befunde bestätigten die theoretischen Erwartungen. Zwar waren die Leistungen der besten älteren Erwachsenen etwa doppelt so hoch wie die untrainierter junger Erwachsener, aber die durch das Training aufgedeckten Altersverluste konnten auch in bis zu 75 weiteren Übungsstunden nicht behoben werden.The relevance of developmental reserve capacity (plasticity) and associated age-related limits for theories of cognitive aging is discussed. For basic cognitive mechanisms, older adults' developmental reserve capacity is expected to be sufficient to surpass young adults' baseline performance. Aging-related limits of this reserve, however, will allow only very few older adults to achieve levels of performance characteristic of trained young adults. Two research strategies (designed to engineer a mnemonic skill for serial recall of words) are described: (a) training of positively selected, mentally very fit older adults and (b) longitudinal single case studies. Experimental results were in agreement with the theoretical expectations. The best older adults scored about twice as high as untrained young adults but even with up to 75 additional experimental sessions the age difference generated by the cognitive intervention was not overcome.
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Vielmo, Alexandro Luiz. "LIMITE SUPERIOR DA RETENÇÃO DA ÁGUA NO SOLO: MÉTODO DE CAMPO E MÉTODO DE ESTIMATIVA." Universidade Federal de Santa Maria, 2008. http://repositorio.ufsm.br/handle/1/7494.
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The superior limit of water retention in soil, also known as field capacity, still is motive of discussion and research inside the academic community. This happens because the
variability of soils determines the alternation of results obtained by all methods that were performed. The need of accuracy, quickness of results, and test cost are the factors that point which method should be used. The recommendation for the determination of field capacity is that it must be performed in situ ; however, due to its slow process, the method has been performed in labs. The present work was developed using data available in literature, compiled in such a way to create a database about the subject studied. A
comparative analysis between the volumetric humidity values, obtained through field experiments and the volumetric humidity values estimated by the proposed methodology,
and also using the different adjustment models of the water retention curve in soil. In order to establish the comparison, a regression analysis between the values of field capacity was
performed using the many procedures in attempt to obtain the correlation coefficient (r) and the Wilmont concordance index (c). From the results obtained in this work it is possible to conclude that the evaluation of the proposed methodology the estimative of field capacity
concerning an inflection of the retention curve when modeled by a third-degree polynomial presented performance in the class outstanding and very good in 66.5% of the cases and
classes of performance very weak 16,6% and extremely bad in about 16,6% of the cases. The applied methodology did not present consistent results for the different sources of data
used and in a general way, the best foundO limite superior da retenção de água no solo, também conhecido como capacidade de campo, ainda é motivo de discussão e pesquisa entre a comunidade acadêmica, pois a variabilidade dos solos determina a variação nos resultados obtidos em todos os métodos utilizados. A necessidade de acurácia, rapidez dos resultados e custo do teste é que determinam qual método deve ser utilizado. A recomendação para a determinação da capacidade de campo é de que seja realizada "in situ"; entretanto, devido ao processo ser moroso, essa tem sido realizada em laboratório. O presente trabalho foi desenvolvido utilizando dados disponíveis na literatura, reunidos de modo a formarem um banco de dados sobre o assunto em estudo. Foi feito uma análise comparativa entre os valores de umidade volumétrica, obtidos através dos experimentos no campo e os valores da umidade volumétrica estimados com a metodologia proposta e utilizando os diferentes modelos de ajuste da curva de retenção da água no solo. Para realizar a comparação foi feita analise de regressão entre os valores da capacidade de campo pelos diferentes procedimentos com o objetivo de obter o coeficiente de correlação (r) e o índice de concordância de Wilmont (c), A partir dos resultados encontrados neste trabalho concluiu-se que a avaliação da metodologia proposta, para a estimativa da capacidade de campo em função do ponto de inflexão da curva de retenção, quando modelada por um polinômio de 3° grau, apresentou classe de desempenho ótimo e muito bom (66.5%), muito fraco (16,6%) e péssimo (16,6%). A metodologia aplicada não apresentou resultados consistentes para as diferentes fontes de dados utilizadas, sendo que de maneira geral, os melhores desempenhos encontrados foram para as curvas de retenção determinadas a campo, com exceção de solos de dunas de areia.
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Muler, González Vanessa. "Furthering social exchange theory in the study of resident impact perceptions: three approximations to the limits to tourism growth." Doctoral thesis, Universitat de Girona, 2020. http://hdl.handle.net/10803/672160.
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This thesis links the limits of tourism growth and social exchange theory (SET) through tourism impacts perceptions of residents. SET has been the most widely used theory to explain the perceptions by residents of tourism since their participation in tourism can be understood as an exchange in which they receive benefits in exchange for costs. In its entirety, this thesis explains the limits of tourism growth through the language of SET and aims to confirm certain aspects of the combination of both. Firstly, it confirms that the indicators of the limits of tourism growth do not necessarily coincide with those of SET since the perceptions of residents may be positive while they are reluctant to accept more tourists. Secondly, four social exchange relationships are identified which pair costs and benefits. These relationships have specific links to the limits of tourism growth which suggests that exchanges that involve limited resources may affect social carrying capacity. And finally, it characterizes the role that values play in the exchange system as perceived by residents. It is noted that residents do not only refer to values typical of tourism growth but also the opposite, those of degrowth, and that the latter have an impact on the way residents perceive tourists and the limits of tourism growthLa tesis vincula els límits del creixement turístic i la teoria d’intercanvi social (TIS) mitjançant les percepcions d’impactes turístics dels residents de l’àrea d’estudi. La TIS ha estat la teoria més utilitzada per explicar les percepcions dels residents ja que la participació d’aquests en el turisme es pot entendre com un intercanvi en el qual els residents reben uns beneficis a canvi de suportar uns costos. En la seva totalitat, aquesta tesi explica els límits del creixement turístic mitjançant el llenguatge d’aquesta teoria i té per objectiu confirmar certs aspectes de la combinació d’ambdues teories (límits del creixement turístic i TIS). En primer lloc, confirma que els indicadors dels límits del creixement turístic no necessàriament coincideixen amb els de la TIS, ja que les percepcions positives del residents no es corresponen amb una voluntat d’acceptar més turistes. En segon lloc, s’identifiquen quatre relacions d’intercanvi social en les quals es vinculen costos i beneficis des de la perspectiva del residents. Aquestes relacions tenen vinculacions específiques amb els límits del creixement turístic, el que suggereix que els intercanvis que afecten recursos limitats poden afectar la capacitat de càrrega social. Finalment, es caracteritza el rol que tenen els valors en el sistema d’ intercanvi tal i com el perceben els residents. Es constata que els residents no només fan referència a valors propis del creixement turístic sinó també valors contraris, de decreixement, i que aquests últims incideixen en la manera en que perceben als turistes i els límits del creixement turístic
Programa de Doctorat Interuniversitari en Turisme
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Agdestein, Sofie Døving. "Operating Room Scheduling Problem : Considering the uncertain arrivals of the emergency patients and the capacity limits of the pre-op and post-op facilities." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for industriell økonomi og teknologiledelse, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-20960.
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This thesis proposes a solution approach to the operating room scheduling problem (ORSP) with two types of demand for surgery: known elective demand and uncertain emergency demand. The ORSP consists of scheduling elective surgeries to an operating room and a time period, while minimizing costs. The uncertainty regarding emergency patient arrivals and the capacity constraints of the pre-op and post-op facilities are taken into account. The problem is modeled using multi-stage stochastic programming, and the dynamics of the emergency patient arrival process are shown using a scenario tree structure. Two types of recourse decisions are allowed in each stage; a scheduled elective patient may be postponed one time period (type 1), or the operating room can be changed for the elective patient within the same time period (type 2). In addition, the emergency patients arriving must be allocated rooms in each stage. The model is implemented in XpressMP. Two heuristics are applied to the model: fix and relax and an improvement algorithm. The computational study shows that including the uncertainty by using the multi-stage model presented is beneficial for problems represented by up to 8 scenarios. The model performs the best when only allowing recourse decisions of type 1. For the test instances used, including the pre-op and post-op capacity constraints seem to be of a small value.
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Nissan, Albania. "Evaluation of Variable Speed Limits : Empirical Evidence and Simulation Analysis of Stockholm’s Motorway Control System." Doctoral thesis, KTH, Trafik och Logistik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-13200.
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Variable Speed Limits (VSL) are often used to improve traffic conditions on congested motorways. VSL can be implemented as mandatory or advisory. The objective of the thesis isto study in detail the effectiveness of VSL. The focus is on both, design parameters and conditions under which VSL are most effective. The MCS system on the E4 motorway inStockholm is used as a case study. The evaluation was conducted using empirical methods (including aggregate data from microwave sensors and other sources, and disaggregate data from a mobile study), and microscopic traffic simulation. The empirical analysis is based on before and after VSL data, including evaluation of individual measures of performance, and multivariate analysis in the form of the fundamental diagram, and speed-density relationships. The results from the empirical study are mixed with an indication that driver behavior has a strong impact on the effectiveness of the system. The microscopic traffic simulation analysis included the development of a platform for testing VSL and more generally motorway control strategies. The simulation platform was calibrated and validated with the empirical data and includes in addition to VSL, and Automatic Incident Detection (AID) system, the ALINEA ramp metering algorithm. The test-platform allows the testing of different control strategies and various combinations of control strategies, under different scenarios and in a controlled environment. The results from the simulation study indicate that driver compliance is an important factor and VSL performance quickly deteriorates as compliance rate drops. Hence, VSL should be implemented as mandatory instead of advisory. In addition, mandatory VSL can be effective both, under incident and moderately congested conditions. A combined VSL and ramp metering strategy can be most effective in reducing travel time, improving traffic conditions on the motorway. Furthermore, the results indicate that such a strategy also has the least impact on the flows entering the motorway from the ramps.QC20100630
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Cavalcante, Valberg Barbosa. "Evaluation of the limits and restrictions of the state fund to combat poverty in the state of Cearà - FECOP a particular case." Universidade Federal do CearÃ, 2013. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=10605.
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Secretaria do Planejamento e GestÃoRESUMO Este à um tema relacionado ao Fundo de Combate à Pobreza do Estado do Cearà â FECOP, instituÃdo pela Lei Complementar n 37, de 26 de novembro de 2003, regulamentado pelo Decreto Estadual n 27.379, que busca dar suporte para as aÃÃes de polÃticas pÃblicas na superaÃÃo da pobreza no Estado do CearÃ, em duas vertentes na mudanÃa estrutural e nos processos de polÃticas compensatÃrias, que envolvem todas as aÃÃes das secretarias estaduais do Cearà no combate à pobreza, e o projeto proposto busca situar como problemÃtica se està polÃtica pÃblica esta realmente reduzindo a pobreza no Estado cearense, e qual a sua natureza de atuaÃÃo, no perÃodo de 2004 a 2010, no contexto do quadro neoliberal e da mundializaÃÃo do capitalismo financeiro, como elementos constitutivos da reproduÃÃo ampliada da pobreza, de forma generalizada em todos os paÃses em desenvolvimento, dentro de uma inclusÃo injusta da globalizaÃÃo capitalista. O objetivo principal deste estudo à avaliar, bem como examinar e reflexivamente a implementaÃÃo, as concepÃÃes, os princÃpios e os resultados alcanÃados do FECOP, com relaÃÃo ao comportamento dos Ãndices referentes à pobreza extrema e da pobreza, no perÃodo hà pouco mencionado, de maneira diferenciada e mais abrangente do que a variÃvel explicativa dominante utilizada e focada apenas na insuficiÃncia de renda.
ABSTRACT The design of the proposed study to be described is a theme related to the Fund to Combat Poverty in the State of Cearà â FECOP, which was established by complementary Law No. 37, dated November 26, 2003 and regulated by State Decree 27379, which seeks to support the actions of public policies in overcoming poverty in the State of CearÃ, in two-pronged in the structural change and the processes of compensatory policies, that involve all actions of state departments of Cearà in fighting poverty, and the proposed project seeks to put as problematic if this public policy is really reducing poverty in the State of CearÃ, and what is its nature of operations in the period from 2004 to 2010, set against the backdrop Neo-Liberal and globalization of financial capitalism, as constituent elements of the expanded reproduction of poverty so widespread throughout developing countries, within an unfair inclusion of capitalist globalization. The main objective of this study is to evaluate, analyze critically and reflectively the implementation, concepts, principles and achievements of FECOP, regarding the behavior of the indices related to extreme poverty and poverty in the aforementioned period, in a differently and more comprehensive than the dominant explanatory variable used and focused only on insufficient income.
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Parrish, Bradley K. "Affordable Housing in the Florida Keys: Providing Affordable Units Within the Limits of Local Growth Management Regulations." Cincinnati, Ohio : University of Cincinnati, 2007. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1188344427.
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Thesis (Master of Community Planning)--University of Cincinnati, 2007.Advisor: Xinhao Wang. Title from electronic thesis title page (viewed Feb. 6, 2008). Includes abstract. Keywords: affordable; housing; affordable housing; Florida Keys; Growth Management; ROGO; Residential Rate of Growth Ordinance; Rate of Growth Ordinance; hurricane evacuation; FKCCS; florida keys carrying capacity study; community planning thesis; planning thesis. Includes bibliographical references.
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Housset, Johann. "Variations de croissance et capacité d’adaptation des populations marginales fragmentées d’arbres des zones boréo-montagnardes, en réponse aux changements climatiques." Thesis, Paris, EPHE, 2015. http://www.theses.fr/2015EPHE3041/document.
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Cette thèse a pour objectif de déterminer le devenir des populations marginales d’arbres boréo-montagnards dans le contexte des changements climatiques. La réponse dendroclimatique et la structure génétique des espèces sont analysées conjointement sur des gradients incluant les zones de distributions continues et marginales. Les deux modèles biologiques choisis sont le thuya occidental en limite nordique (forêt boréale canadienne) et le pin cembro en limite occidentale (Alpes). Les hypothèses suivantes ont été testées : le réchauffement climatique au cours du XXe siècle a entrainé une augmentation de croissance ; la variabilité de croissance est reliée à la structure génétique aux niveaux intra- et inter-populationnels. Une baisse de croissance du thuya a été observée après 1980 en zone marginale, qui serait liée à une limitation par la sécheresse. Pour les deux espèces, les relations climat-croissance étaient essentiellement modulées par le volume des précipitations, mais également par des variables édaphiques et par la taille des arbres. L’existence d’un lien significatif entre la structure génétique et certaines variables climatiques laisse néanmoins espérer un potentiel d'adaptation génétique, dont l’ampleur dépendra de la diversité génétique disponible pour la sélection naturelle. Par ailleurs, le synchronisme de croissance entre les arbres était à la fois influencé par la diversité génétique intra-populationnelle et par le volume des précipitations. En conclusion, il apparaît très difficile de distinguer les effets du climat et de la génétique sur la croissance des arbres étudiésThis thesis aims to assess the fate of marginal populations, in the context of climate change, for boreo-mountain tree species. The dendroclimatic response and the genetic structure of the species are jointly analyzed on gradients including both the continuous and the marginal distribution zones. Two biological models have been chosen for this research, white cedar at its northern limit (boreal forest) and stone pine at its western limit (temperate mountain forest). The following hypotheses were tested: global warming during the twentieth century has led to increased growth; growth variability is related to the genetic structure at the intra- and inter-population levels. A decline in cedar growth was observed after 1980 in marginal zone, which could be linked to drought constraints on growth. For both species, climate-growth relationships were essentially modulated by the amount of precipitation, but also by soil and tree-size variables. The existence of a significant link between genetic structure and some climatic variables still leaves some hope for a genetic adaptation potential, which magnitude will depend on the genetic diversity available for natural selection. The growth synchronicity between the trees was both influenced by the intra-population genetic diversity and the amount of precipitation. In conclusion, it is very difficult to disentangle the effects of climate and genetics on the growth of the studied trees
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Vincent, Hugues. "Développement d'un modèle de calcul de la capacité ultime d'éléments de structure (3D) en béton armé, basé sur la théorie du calcul à la rupture." Thesis, Paris Est, 2018. http://www.theses.fr/2018PESC1038/document.
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Pour l’évaluation de la résistance ultime des ouvrages l’ingénieur de génie civil fait appel à différentes méthodes plus ou moins empiriques, dont de nombreuses manuelles, du fait de la lourdeur excessive des méthodes par éléments finis non-linéaires mises en œuvre dans les logiciels de calcul à sa disposition. Le calcul à la rupture, théorisé par J. Salençon, indique la voie de méthodes rigoureuses, tout à fait adaptées à cette problématique, mais dont la mise en œuvre systématique dans un logiciel a longtemps buté sur l’absence de méthodes numériques efficaces. Ce verrou de mathématique numérique a été levé récemment (Algorithme de point intérieur).Dans ce contexte l’objectif de la présente thèse est de mettre au point les méthodes permettant d’analyser, au moyen du calcul à la rupture, la capacité ultime d’éléments en béton armé tridimensionnels. Les deux approches du calcul à la rupture, que sont les approches statique et cinématiques, seront mises en œuvre numériquement sous la forme d’un problème d’optimisation résolu à l’aide d’un solveur mathématique dans le cadre de la programmation semi définie positive (SDP).Une large partie du travail sera consacré à la modélisation des différents matériaux constituant le béton armé. Le choix du critère pour modéliser la résistance du béton sera discuté, tout comme la méthode pour prendre en compte le renforcement. La méthode d’homogénéisation sera utilisée dans le cas de renforcement périodique et une adaptation de cette méthode sera utilisée dans le cas de renforts isolés. Enfin, les capacités et le potentiel de l’outil développé et mis en œuvre au cours de cette thèse seront exposés au travers d’exemples d’application sur des structures massivesTo evaluate the load bearing capacity of structures, civil engineers often make use of empirical methods, which are often manuals, instead of nonlinear finite element methods available in existing civil engineering softwares, which are long to process and difficult to handle. Yield design (or limit analysis) approach, formalized by J. Salençon, is a rigorous method to evaluate the capacity of structures and can be used to answer the question of structural failure. It was, yet, not possible to take advantage of these theoretical methods due to the lack of efficient numerical methods. Recent progress in this field and notably in interior point algorithms allows one to rethink this opportunity. Therefore, the main objective of this thesis is to develop a numerical model, based on the yield design approach, to evaluate the ultimate capacity of massive (3D) reinforced concrete structural elements. Both static and kinematic approaches are implemented and expressed as an optimization problem that can be solved by a mathematical optimization solver in the framework of Semi-Definite Programming (SDP).A large part of this work is on modelling the resistance of the different components of the reinforced concrete composite material. The modelling assumptions taken to model the resistance of concrete are discussed. And the method used to model reinforcement is also questioned. The homogenization method is used to model periodic reinforcement and an adaptation of this technique is developed for isolated rebars. To conclude this work, a last part is dedicated to illustrate the power and potentialities of the numerical tool developed during this PhD thesis through various examples of massive structures
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Štramberský, Martin. "Návrh předpjaté nádrže." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226967.
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The matter of this diploma thesis is a static storage tank for petroleum substances, the study of a solution for appropriate shape of shell and its effort to dihedral for roofing, and the study of effect of the storage of inner roofs walls of the tank to the size of the internal forces. The internal walls are carried out by the method of finite elements in the engineering program Scia Engineering 2013 and on the basis of it, designing of the framing sections of the tank. There is a calculation part of the lower horizontal bias wreaths of the shell and internal supporting wall. All the components are assessed on the 1st limit state of the load-bearing capacity and the 2nd limit state of the application (emergence cracks, limiting voltage in the concrete and a prestressing steel). The existing external wall is assessed only on the marginal status load of carrying capacity. The part of diploma thesis is also drawing documentation, accompanying report and technical report. The goal of the diploma thesis was to design the tank without an occurrence of the cracks in the concrete so as the vertical wall was prestressing only in the horizontal direction and the optimal proposal roof tanks as an addition.
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Khan, Inamullah. "Etude expérimentale de la corrosion en béton armé." Thesis, Toulouse, INSA, 2012. http://www.theses.fr/2012ISAT0043/document.
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Les objectifs de la thèse sont d’étudier l’influence de la pré-fissuration sur le développement de la corrosion des armatures du béton armé, les corrélations entre les pertes de section d’armatures dues à la corrosion et la fissuration du béton d’enrobage en résultant et l'effet de la corrosion sur les propriétés mécaniques des structures en béton armé soumis à un environnement salin. Les essais ont été réalisées pour étudier les différentes propriétés mécaniques comme la résistance à la flexion, la résistance au cisaillement, etc. Le travail expérimental est constitué de deux parties: dans la première partie des petits échantillons annulaires en mortier ont été testés afin d'observer l'effet des fissures sur la corrosion. Les résultats montrent que quelque soit l’ouverture des fissures, la corrosion démarre en fond de fissure et se propage le long de l’interface acier-béton endommagée en fond de fissure par la création de la fissure. Dans la deuxième partie, une étude approfondie a été réalisée sur une poutre en béton armé qui a été corrodée dans un environnement salin pendant 26 ans et une poutre non corrodée de même âge pour mieux comprendre l'effet de la corrosion sur les propriétés mécaniques (flexion, cisaillement , propriétés mécaniques de l’acier corrodé) d’éléments en béton armé. Un nouveau modèle a été proposé pour la relation entre la largeur des fissures de corrosion et la perte de section d'acierThe thesis aims to study the effect of corrosion on the mechanical properties of reinforced concrete reinforced concrete structures in chloride environment. Experiments were carried out in order to investigate the different mechanical properties such as bending strength, shear strength etc. The experimental work consists of two parts; in the first part small annular cement sand mortar samples were tested in order to observe the effect of cracks on corrosion. Results show that cracks whatever their width allows the corrosion onset at bottom of cracks and along the steel-concrete interface damaged zone caused by the creation of cracks. In the second part an extensive study was carried out on a 26-year-old corroded reinforced concrete beam and a non-corroded of same age in order to better understand the effect of corrosion on reinforced concrete members in flexion and shear. Impact of corrosion on the mechanical properties of steel in reinforced concrete was studied. A new model was proposed for the relationship between corrosion cracks width and loss of steel cross-section
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Matušíková, Anna. "Navrhování konstrukcí s FRP výztuží." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2012. http://www.nusl.cz/ntk/nusl-225478.
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This diploma thesis presents available FRP software for calculating load bearing capacity of the structures reinforced with FRP and compares them between each other. Furthermore theory and algorithm of my own software is presented here. Load bearing capacity of structures which are reinforced with non-metallic reinforcement and loaded by combination of normal force and bending moment can be solved by my programme. Effects of high temperatures on the concrete structures can be included in the calculation. In the second part of the thesis is calculated load-bearing capacity and deflection of the real beam reinforced with FRP reinforcement and load-bearing capacity of member with FRP reinforcement with effect of elevated temperature. This has been done using my software. Comparison of results from hand calculation and laboratory load-bearing testing is done at the end. This laboratory testing was accomplished by Institute of Concrete and Mansory Structures at our faculty.
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Dang, Vu Hiep. "Phases d'initiation et de propagation de la corrosion des armatures du béton armé fissuré en environnement carbonique ou salin." Thesis, Toulouse, INSA, 2013. http://www.theses.fr/2013ISAT0039/document.
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Cette thèse s’intéresse à l’étude la corrosion des armatures du béton armé à la fois sur les conditions de son initiation et de sa propagation mais également sur ses conséquences à long terme sur le fonctionnement en service des ouvrages.Le démarrage d’une étude à long terme sur les conditions de l’initiation et de la propagation de la corrosion en ambiance saline est présenté et les premiers résultats confirment l’initiation précoce de la corrosion mais montrent que l’influence des fissures sur la propagation dépend des conditions de leur exposition et de l’enrobage.Une étude a été réalisée sur la carbonatation en présences de fissures et sur ses conséquences sur l’initiation et la propagation de la corrosion. Des échantillons annulaires de mortier renforcé par une armature HA ont été fissurés. Les résultats ont montrés que quelque soit l’ouverture des fissures mécaniques, il y a une carbonatation des lèvres de la fissure et de l’interface acier-béton. Après exposition à des cycles d’humidification séchage, la corrosion se développe tout le long de l’armature mais avec une épaisseur plus importante en sous-face de l’armature ou la qualité de l’interface est moins bonne. Les résultats montrent que les fissures de corrosion induites par le développement de la couche de rouille prennent naissance à partir des micro-fissures dues à l’endommagement mécanique. Ce résultat est cohérent avec le développement des fissures de corrosion observées dans la partie sur l’initiation et la propagation de la corrosion en ambiance saline.Une autre partie de la thèse est consacrée à l’étude des propriétés mécaniques résiduelles de poutres en béton armé corrodées par 26 à 28 années de conservation majoritairement sous charge de flexion en ambiance saline.On s’intéresse d’abord au comportement en traction simple des aciers corrodés. La corrosion induite par les chlorures conduit à des piqûres de géométries très diverses qui rendent difficile l’évaluation de la section résiduelle d’acier. Cependant, il apparait que la contrainte effective de plasticité est peu affectée, la contrainte ultime est légèrement augmentée significative d’un écrouissage plus important après corrosion et surtout l’élongation à rupture est drastiquement réduite par la présence des piqures de corrosion.L’effet de la corrosion des armatures sur le comportement en flexion est ensuite étudié. La corrosion se traduit par un changement du mode de rupture, de l’écrasement du béton comprimé après une phase de plastification des aciers à la rupture fragile et brutale des armatures tendues après corrosion. La diminution de la capacité portante est proportionnelle à la perte de section d’acier dans les sections les plus sollicitées. La perte de ductilité ou diminution de la flèche à rupture des poutres en béton armé est très importante et pourrait remettre ne cause la sécurité dans le fonctionnement des éléments corrodés.L’effet de la corrosion sur la résistance à l’effort tranchant est ensuite étudié. Pour ce faire des éléments courts (poutres épaisses) sont testés en flexion simple. Les résultats montrent que la corrosion peut conduire à des changements de fonctionnement mécanique mais que la résistance vis-à-vis de l’effort tranchant est globalement peu affectée par la corrosion des armatures longitudinales ou des cadres d’effort tranchant. La complexité des phénomènes mis en jeu sur des éléments courts et l’importance des bielles de béton comprimées dans les effets d’arc peuvent expliquer ces résultats. Par ailleurs, la capacité d’ancrage des armatures droites corrodées apparait très largement supérieure à celle attendue compte tenu de la présence des fissures de corrosion et des prévisions issues de la littérature. Le confinement dû à l’appui et le fait que la corrosion naturelle n’affecte pas tout le périmètre des barres d’armatures peuvent expliquer ces résultats surprenantsThis thesis aims to study the reinforcement corrosion embedded in reinforced concrete structures on both initiation and propagation of corrosion and its long-term consequences on the service life of structures. Firstly, a long-term study on the conditions for the initiation and propagation of corrosion in saline environment is presented and the first results confirm the early initiation of corrosion, but shows that the influence of pre-cracks on the propagation of corrosion depends on their conditions of exposure and concrete cover thickness. A study was conducted in carbon dioxide condition with presence of cracks to examine its impact on the initiation and propagation of corrosion. The results showed that whatever the mechanical crack opening, the crack edge and the steel-concrete interface were carbonated. Carbonation of the steel-concrete interface is likely to be due to mechanical damage induced by loading and stress transfer from the steel to mortar when creating cracks. This damage is also caused by the presence of internal micro-cracks around the steel bar. Following exposure to wetting-drying cycles, corrosion develops throughout the reinforcement but with a greater thickness of rust layer on the underside of the reinforcement where the quality of the interface is weaker. The results showed that the corrosion cracking induced by the development of rust layer arises from internal micro-cracks due to mechanical damage. This result is consistent with the development of corrosion cracks observed previously in saline environment. Another part of the thesis is to study the residual mechanical properties of corroded reinforced concrete beams of 26-28 years exposed to a saline environment under bending load. The behavior of single tensile steel corroded extracted from these corroded beams is studied. It is very difficult to know the true stress of tensile steels corroded "naturally" in concrete contaminated by exposure to chlorides. Indeed, the corrosion induced by chlorides leads to create corrosion pits with various geometries that make it difficult to determine accurately the residual steel cross-section. However, it appears that the true yield stress is unaffected, the true ultimate stress is slightly increased by corrosion but the total elongation at failure is drastically reduced by the presence of pitting corrosion. The effect of reinforcement corrosion on flexural behavior is then studied. The corrosion resulted in a change in failure mode, from concrete crushing in compression after yielding of tensile steel to brittle failure of tension reinforcement. The decrease of the load bearing capacity is proportional to the loss of steel section in the mid-span section. The loss of ductility or decrease in deflection at failure of reinforced concrete beams is very important and could be the limiting factor for the service life of corroded RC structures. It appears that the change in ductility of corroded reinforced concrete beam is correlated with the change in ductility of the steel due to corrosion. The effect of corrosion on the shear behavior is then studied. To make this, the short-shear span beams (deep beams) were tested under three point bending until failure. The results showed that corrosion can lead to changes in mechanical behavior but load bearing capacity of deep beams is generally unaffected by corrosion of longitudinal reinforcement and stirrups. These results can be explained by a coupled behavior between arch action and beam action leading to change in load transfer mechanism and failure mode. In addition, the capacity of straight end anchorage of corroded reinforcement appears to be very much higher than expected despite the presence of corrosion cracks. Concrete confinement effect due to the end support reaction and the “natural” corrosion condition which do not lead to a homogeneous damage all around perimeter of re-bars may explain these surprising results
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Abgrall, Cédric. "Allocation de ressources dans les réseaux sans fil denses." Phd thesis, Télécom ParisTech, 2010. http://pastel.archives-ouvertes.fr/pastel-00581776.
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Cette thèse s'intéresse au problème de gestion de l'interférence co-canal dans les réseaux de communications sans fil. Tout d'abord nous abordons les systèmes de communications coopératives et étudions le compromis entre les bienfaits et les méfaits de la coopération. Plus un message est redondé via les relais, meilleure en est son décodage, mais plus la redondance interfère avec les destinations voisines et en affectent les performances. Nous proposons ainsi de coordonner et d'adapter l'allocation des ressources et l'activation de la coopération dans des cellules voisines aux variations temporelles, spatiales et fréquentielles du contexte courant de communication. Nous proposons ensuite un classificateur d'interférence à trois régimes dont le but est d'estimer l'interférence co-canal perçue par une destination sur une bande afin d'adapter le traitement de l'interférence à la nature temps-variable du canal de transmission et ainsi améliorer le décodage en réception. Ce classificateur est finalement combiné à de l'optimisation sous contraintes de QoS afin de dériver des algorithmes de contrôle de puissance. Une approche centralisée et une approche distribuée sont proposées et toutes deux cherchent à minimiser la puissance de transmission sous respect des contraintes de QoS, et ce quel que soit le scénario de transmission. Nos résultats de simulations montrent que notre approche adaptative permet de réduire notablement le budget de puissance sans affecter la fiabilité de la transmission.
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Wilkinson, Timothy James. "The Plastic Behaviour of Cold-Formed Rectangular Hollow Sections." University of Sydney. Department of Civil Engineering, 2000. http://hdl.handle.net/2123/843.
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The aim of this thesis is to assess the suitability of cold-formed rectangular hollow sections (RHS) for plastic design. The project involved an extensive range of tests on cold-formed Grade C350 and Grade C450 (DuraGal) RHS beams, joints and frames. A large number of finite element analyses was also carried out on models of RHS beams. The conclusion is that cold- formed RHS can be used in plastic design, but stricter element slenderness (b/t) limits and consideration of the connections, are required. Further research, particularly into the effect of axial compression on element slenderness limits, is required before changes to current design rules can be finalised. Bending tests were performed on cold-formed RHS to examine the web and flange slenderness required to maintain the plastic moment for a large enough rotation suitable for plastic design. The major conclusions of the beam tests were: (i) Some sections which are classified as Compact or Class 1 by current steel design specifications do not maintain plastic rotations considered sufficient for plastic design. (ii) The current design philosophy, in which flange and web slenderness limits are independent, is inappropriate. An interaction formula is required, and simple formulations are proposed for RHS. Connection tests were performed on various types of knee joints in RHS, suitable for the column - rafter connection in a portal frame. The connection types investigated were welded stiffened and unstiffened rigid knee connections, bolted plate knee joints, and welded and bolted internal sleeve knee joints, for use in RHS portal frames. The ability of the connections to act as plastic hinges in a portal frame was investigated. The most important finding of the joint tests was the unexpected fracture of the cold-formed welded connections under opening moment before significant plastic rotations occurred. The use of an internal sleeve moved the plastic hinge in the connection away from the connection centre- line thus eliminating the need for the weld between the RHS, or the RHS and the stiffening plate, to carry the majority of the load. The internal sleeve connections were capable of sustaining the plastic moment for large rotations considered suitable for plastic design. Tests on pinned-base portal frames were also performed. There were three separate tests, with two different ratios of vertical to horizontal point loads, simulating gravity and horizontal wind loads. Two grades of steel were used for comparison. The aims of the tests were to examine if a plastic collapse mechanism could form in a cold-formed RHS frame, and to investigate if plastic design was suitable for such frames. In each frame, two regions of highly concentrated curvature were observed before the onset of local buckling, which indicated the formation of plastic hinges and a plastic collapse mechanism. An advanced plastic zone structural analysis which accounted for second order effects, material non-linearity and member imperfections slightly overestimated the strength of the frames. The analysis slightly underestimated the deflections, and hence the magnitude of the second order effects. A second order plastic zone analysis, which did not account for the effects of structural imperfections, provided the best estimates of the strengths of the frames, but also underestimated the deflections. While cold-formed RHS did not satisfy the material ductility requirements specified for plastic design in some current steel design standards, plastic hinges and plastic collapse mechanisms formed. This suggests that the restriction on plastic design for cold-formed RHS based on insufficient material ductility is unnecessary, provided that the connections are suitable for plastic hinge formation, if required. A large number of finite element analyses were performed to simulate the bending tests summarised above, and to examine various parameters not studied in the experimental investigation. To simulate the experimental rotation capacity of the RHS beams, a sinusoidally varying longitudinal local imperfection was prescribed. The finite element analysis determined similar trends as observed experimentally, namely that the rotation capacity depended on both the web slenderness and flange slenderness, and that for a given section aspect ratio, the relationship between web slenderness and rotation capacity was non-linear. The main finding of the finite element study was that the size of the imperfections had an unexpectedly large influence on the rotation capacity. Larger imperfections were required in the more slender sections to simulate the experimental results. There should be further investigation into the effect of varying material properties on rotation capacity.
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Chan, Teck-Wai. "Proximity-to-separation based energy function control strategy for power system stability." Thesis, Queensland University of Technology, 2003. https://eprints.qut.edu.au/15840/1/Teck-Wai_Chan_Thesis.pdf.
Full textAbstract:
The issue of angle instability has been widely discussed in the power engineering literature. Many control techniques have been proposed to provide the complementary synchronizing and damping torques through generators and/or network connected power apparatus such as FACTs, braking resistors and DC links. The synchronizing torque component keeps all generators in synchronism while damping torque reduces oscillations and returns the power system to its pre-fault operating condition. One of the main factors limiting the transfer capacity of the electrical transmission network is the separation of the power system at weak links which can be understood by analogy with a large spring-mass system. However, this weak-links related problem is not dealt with in existing control designs because it is non-trivial during transient period to determine credible weak links in a large power system which may consist of hundreds of strong and weak links. The difficulty of identifying weak links has limited the performance of existing controls when it comes to the synchronization of generators and damping of oscillations. Such circumstances also restrict the operation of power systems close to its transient stability limits. These considerations have led to the primary research question in this thesis, "To what extent can the synchronization of generators and damping of oscillations be maximized to fully extend the transient stability limits of power systems and to improve the transfer capacity of the network?" With the recent advances in power electronics technology, the extension of transfer capacity is becoming more readily achievable. Complementary to the use of power electronics technology to improve transfer capacity, this research develops an improved control strategy by examining the dynamics of the modes of separation associated with the strong and weak links of the reduced transmission network. The theoretical framework of the control strategy is based on Energy Decomposition and Unstable Equilibrium Points. This thesis recognizes that under extreme loadings of the transmission network containing strong and weak links, weak-links are most likely to dictate the transient stability limits of the power system. We conclude that in order to fully extend the transient stability limits of power system while maximizing the value of control resources, it is crucial for the control strategy to aim its control effort at the energy component that is most likely to cause a separation. The improvement in the synchronization amongst generators remains the most important step in the improvement of the transfer capacity of the power system network.
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Chan, Teck-Wai. "Proximity-to-Separation Based Energy Function Control Strategy for Power System Stability." Queensland University of Technology, 2003. http://eprints.qut.edu.au/15840/.
Full textAbstract:
The issue of angle instability has been widely discussed in the power engineering literature. Many control techniques have been proposed to provide the complementary synchronizing and damping torques through generators and/or network connected power apparatus such as FACTs, braking resistors and DC links. The synchronizing torque component keeps all generators in synchronism while damping torque reduces oscillations and returns the power system to its pre-fault operating condition. One of the main factors limiting the transfer capacity of the electrical transmission network is the separation of the power system at weak links which can be understood by analogy with a large spring-mass system. However, this weak-links related problem is not dealt with in existing control designs because it is non-trivial during transient period to determine credible weak links in a large power system which may consist of hundreds of strong and weak links. The difficulty of identifying weak links has limited the performance of existing controls when it comes to the synchronization of generators and damping of oscillations. Such circumstances also restrict the operation of power systems close to its transient stability limits. These considerations have led to the primary research question in this thesis, "To what extent can the synchronization of generators and damping of oscillations be maximized to fully extend the transient stability limits of power systems and to improve the transfer capacity of the network?" With the recent advances in power electronics technology, the extension of transfer capacity is becoming more readily achievable. Complementary to the use of power electronics technology to improve transfer capacity, this research develops an improved control strategy by examining the dynamics of the modes of separation associated with the strong and weak links of the reduced transmission network. The theoretical framework of the control strategy is based on Energy Decomposition and Unstable Equilibrium Points. This thesis recognizes that under extreme loadings of the transmission network containing strong and weak links, weak-links are most likely to dictate the transient stability limits of the power system. We conclude that in order to fully extend the transient stability limits of power system while maximizing the value of control resources, it is crucial for the control strategy to aim its control effort at the energy component that is most likely to cause a separation. The improvement in the synchronization amongst generators remains the most important step in the improvement of the transfer capacity of the power system network.
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Calvente, René Matias. "Méthodologie de contrôle en place des micropieux à partir d'essais dynamiques." Thesis, Clermont-Ferrand 2, 2014. http://www.theses.fr/2014CLF22471/document.
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L’état de l’art réalisé dans le cadre de ce travail a permis d’identifier une grande variété de techniques de réalisation de micropieux avec des comportements effort-déformation difficiles à prédire. Quant aux méthodes de contrôle, du point de vue de l’intégrité il existe deux méthodes développées pour les pieux lesquelles ne sont pas toujours applicables aux cas de micropieux ; et du point de vue du contrôle du comportement mécanique, il existe un essai assez utilisé pour le contrôle de micropieux : l’essai d’arrachement. Cet essai est facile à réaliser et à interpréter, cependant il est onéreux (long temps d’essai) et difficile à mettre en place. Un autre type d’essai, utilisé dans le contrôle de fondations profondes, est l’essai de chargement dynamique. La recherche bibliographique a permis d’identifier les avantages et inconvénients de ce type d’essai adaptés et déjà validés dans le contrôle de pieux. Nous avons donc proposé une nouvelle méthodologie basée sur des essais de chargement dynamique à faible contrainte nécessitant des énergies de battage beaucoup moins importantes que dans les essais de chargement dynamique classiques. Le protocole et dispositif d’essai de la méthodologie ont été calibrés et validés à partir de simulations numériques afin notamment de justifier les choix de l’énergie d’impact, de la masse du marteau et de l’amortisseur à utiliser. Les observations numériques sont ensuite vérifiées expérimentalement sur des micropieux à échelle réelle mis en place dans un site expérimental développé dans le cadre de ce projet. La méthodologie de contrôle en place de la résistance en service de micropieux développée, c’est une méthode originale simple à réaliser, facile à mettre en oeuvre et d’interprétation immédiate. Elle a été validée aussi dans le cas de micropieux à échelle réelle en conditions maitrisées dans le site expérimental et non maitrisées dans trois chantiers réels de micropieux. Finalement, le progrès dans les recherches, a permis le développement d’une méthodologie de contrôle de la résistance limite de micropieux. Pour cela nous proposons d’utiliser un modèle analytique de prédiction du comportement effort-déformation alimenté par les résultats de l’essai de chargement dynamique à faible déformation et d’un essai complémentaire de reconnaissance des paramètres à la rupture du sol. L´objectif de ce développement est de proposer une prédiction de la résistance limite du micropieux testé sans compromettre son intégrité. L’application de la méthodologie a montré qu’elle donne des résultats très proches de ceux observés dans les essais statiquesThe review of the state-of-the-art of micropiles produced as part of this work allows to identify a wide variety of construction methodologies which have a stress-strain behavior difficult to predict. As for the testing methods, there are methods for assessing the condition of piles or shafts but they are not always applicable to the micropiles; and in terms of the control of mechanical behavior, the most used load testing micropile is the uplift static load test. The static load test is easy to perform and interpret, however the reaction system is cumbersome and slow to erect, therefore this test is time and cost consuming. Another type of test that can be used in the control of deep foundations is the dynamic load testing. The literature review helped to identify the advantages and disadvantages of this type of test that has been adapted and validated in control of pile behavior. The new methodology proposed in this work is based on low-strain dynamic test requiring a smaller impact energy than a high-strain dynamic test. The testing protocol and loading device of the methodology have been calibrated and validated by numerical simulations in order to justify the choice of the impact energy, the weight of hammer and the cushion that will be used. The numerical observations are then verified by experiences in full-scale micropiles installed in an experimental site developed as part of this project. The developed in situ control methodology of the resistance in service of micropiles is an original method, easy to carry out, simple to execute and with an immediate interpretation. This methodology has been validated on full-scale micropiles in contained conditions and also in uncontained conditions in three real projects of micropiles. Finally, the advances in the investigations have led to develop a methodology for control the micropile’s ultimate resistance. We propose to use an analytical model for predicting the stress-strain behavior, which must be supplied with the results of the low-strain dynamic micropile test and of a complementary geotechnical test in order to examine the parameter of soil failure. The goal of this development is to provide a method for predict the micropile’s ultimate resistance without compromising its integrity. The results of the application of the new method to the experimental micropiles are in close agreement with the results observed in the static load test
La revisión del estado del arte en relación a micropilotes, realizada en este trabajo, ha permitido identificar una gran variedad de técnicas de construcción, donde la predicción de sus comportamientos mecánicos, es una tarea difícil de realizar. Con respecto a los métodos de control, desde el punto de vista de la integridad, existen actualmente métodos no siempre aplicables a los micropilotes, y desde el punto de vista del control del comportamiento mecánico, el ensayo más utilizado es el ensayo de arrancamiento. El ensayo de arrancamiento es de fácil realización e interpretación, sin embargo es oneroso, por su larga duración y la necesidad de disponer de equipos muy pesados.Otro tipo de ensayo, que es utilizado para el control de fundaciones profundas en general, es el ensayo de carga dinámica, cuyas ventajas y desventajas han sido identificadas en la investigación bibliográfica.La nueva metodología propuesta, motivo de este trabajo, está basada en los ensayos de carga dinámica a baja deformación, donde se necesita una energía de impacto mucho menos importante que en el caso de los ensayos clásicos de carga dinámica.El protocolo de la metodología y su dispositivo de ensayo han sido calibrados y validados a partir de simulaciones numéricas con el fin de, principalmente, justificar la elección de la energía de impacto, de la masa del martillo y del amortiguador a utilizar. Las observaciones numéricas han sido, luego, verificadas experimentalmente sobre micropilotes a escala real, instalados en un sitio experimental desarrollado en el marco de este proyecto.La metodología de control in situ, de la resistencia en servicio de micropilotes, desarrollada en este trabajo, es un método original, simple de realizar, con un sistema fácil de instalar y de interpretación inmediata. Ella ha sido validada, en el caso de micropilotes a escala real en condiciones controladas en el sitio experimental, y no controladas en el caso de tres proyectos reales.Además, el avance en las investigaciones, dio lugar al desarrollo de una metodología de control de la resistencia límite de micropilotes. Para ello proponemos utilizar un modelo analítico de predicción del comportamiento esfuerzo-deformación alimentado por resultados del ensayo de carga dinámica a baja deformación y de un ensayo complementario de reconocimiento de los parámetros de ruptura del suelo. El objetivo de este desarrollo es de proponer un método de predicción de la resistencia límite de micropilotes sin comprometer su integridad. La aplicación de la metodología ha mostrado que los resultados son muy cercanos a los observados en los ensayos de carga estática
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"Capacity Limit, Link Scheduling and Power Control in Wireless Networks." Doctoral diss., 2013. http://hdl.handle.net/2286/R.I.18780.
Full textAbstract:
abstract: The rapid advancement of wireless technology has instigated the broad deployment of wireless networks. Different types of networks have been developed, including wireless sensor networks, mobile ad hoc networks, wireless local area networks, and cellular networks. These networks have different structures and applications, and require different control algorithms. The focus of this thesis is to design scheduling and power control algorithms in wireless networks, and analyze their performances. In this thesis, we first study the multicast capacity of wireless ad hoc networks. Gupta and Kumar studied the scaling law of the unicast capacity of wireless ad hoc networks. They derived the order of the unicast throughput, as the number of nodes in the network goes to infinity. In our work, we characterize the scaling of the multicast capacity of large-scale MANETs under a delay constraint D. We first derive an upper bound on the multicast throughput, and then propose a lower bound on the multicast capacity by proposing a joint coding-scheduling algorithm that achieves a throughput within logarithmic factor of the upper bound. We then study the power control problem in ad-hoc wireless networks. We propose a distributed power control algorithm based on the Gibbs sampler, and prove that the algorithm is throughput optimal. Finally, we consider the scheduling algorithm in collocated wireless networks with flow-level dynamics. Specifically, we study the delay performance of workload-based scheduling algorithm with SRPT as a tie-breaking rule. We demonstrate the superior flow-level delay performance of the proposed algorithm using simulations.Dissertation/Thesis
Ph.D. Electrical Engineering 2013
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CHENG, CHUN-YEN, and 鄭俊煙. "Upper bound limit analysis for the bearing capacity of shallow foundation on slope." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/29391553793382615666.
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