Suction caissons are a foundation system for offshore structures which offer a number of advantages over traditional piled foundations. In particular, due to the method of installation used, they are well suited for deep-water applications. The suction caisson consists of an open ended cylindrical shell, which is installed below the seabed in a sequence which consists of two loading phases. The caisson is first installed part way under self weight, with the installation being completed by lowering the pressure within the cylinder and thus allowing the ambient water pressure to force the caisson into the ground. This thesis examines a number of structural issues which result from the form of the caisson — essentially a thin walled cylinder — and the interaction of the caisson with the surrounding soil during installation. To do this, variational analysis and nonlinear finite element analysis are employed to examine the buckling and collapse behaviour of these cylinders. In particular, two issues are considered; the influence of the open end, and the interaction between the cylinder and soil on the buckling and collapse loads. First, the behaviour of open ended cylinders is considered, where the boundary condition at the open end is allowed to vary continuously from completely free to pinned, by the use of a variable lateral spring. This lateral spring restraint may be considered to represent the intermediate restraint provided by a ring stiffener which is not fully effective. The effect of various combinations of boundary conditions is accounted for by the use of a multiplier on the lower bound to the buckling load of a cylinder with classical supports. The variable spring at the open end may also be considered to be an initial, simple representation of the effect of soil restraint on the buckling load. More complex representations of the soil restraint are also considered. A nondimensional factor is proposed to account for the influence of this spring on the buckling load. One combination of boundary conditions, where the upper end of the caisson is pinned, and the lower end free (referred to as a PF boundary condition), is found to have buckling and collapse behaviour which is unusual for cylindrical shells. Buckling loads for such shells are much lower than would be found for cylinders with more typical boundary conditions, and of similar dimensions. More unusually however, PF cylinders are shown to have positive postbuckling strength. The behaviour is found to be a result of the large flexibility which results from the low restraint provided by the PF boundary conditions. This is shown by continuously decreasing the flexibility of the cylinder, by increasing the axial restraint at the pinned end. It is shown that this results in a large increase in buckling load, and a return to more usual levels of imperfection sensitivity. In particular, with an intermediate level of axial restraint, buckling loads and imperfection sensitivity are intermediate between those of PF shells with no, and with full, axial restraint. Overall however, collapse loads for PF cylinders with no additional restraint are well below those of cylinders with stiffer boundary conditions, for equal geometries. Eigenvalue buckling of cylinders fully and partially embedded in an elastic material are examined, and two analytical solutions are proposed. One of these is an extension of a method previously proposed by Seide (1962), for core filled cylinders, to pin ended cylinders which have support from both a core and a surrounding material. The second method represents the elastic support as a two parameter foundation. While more approximate than the first method, this method allows for the examination of a wider range of boundary conditions, and of partial embedment. It is found that the buckling load of the shell/soil system decreases as the embedment ratio decreases. Collapse of fully and partially embedded cylinders is also examined, using nonlinear finite element analysis. The influence of plasticity in the soil is also considered. For cylinders with small imperfections, it is found that the collapse load shows a large increase over that of the same cylinder with no soil support. However, as the size of initial geometric imperfections increases, it is found that the collapse load rapidly approaches that of the unsupported cylinder. In particular, in weak soils the gain in strength over the unsupported shell may be minimal. The exception to this is again PF cylinders. As these have relatively low collapse loads, even very weak soils are able to offer an increase in collapse load over the unsupported case. Finally, a summary of these results is provided in the form of guidance for design of such structures.

This thesis investigates the capabilities of the Collapse Prediction Relay (CPR-D) and also investigates the use of system identification for detection of oscillatory instability. Both the CPR-D and system identification are based on system measurements and do not require modelling of the power system. Measurement based stability monitors can help to avoid instability and blackouts, in cases where the available system model can not predict instability. The CPR-D uses frequency patterns in voltage oscillation to detect system instability. The relay is based on non-linear dynamics Theory. If a collapse is predicted, measures could be taken to prevent a blackout. The relay was tested using the output of simulators and was later installed in a substation. The data from laboratory tests and site installations is analysed enabling a detailed evaluation of the CPR-D.Oscillatory instability can be detected by monitoring the damping ratio of oscillations in the power system. Poor damping indicates a smaller stability margin. Subspace identification is used to estimate damping ratios. The method is tested under different conditions and using several power system models. The results show that using several measurements gives more accurate estimates and requires shorter data windows. A selection method for measurements is proposed in the thesis.

[pt] O problema de estabilidade de tensão está intimamente ligado à falta de recursos e questões ambientais que limitam a expansão do sistema de transmissão. Esta realidade em conjunto com o crescimento da carga submete os sistemas elétricos a carregamentos pesados, podendo levar a situações de colapso de tensão. O desenvolvimento de métodos para avaliação do carregamento da rede de transmissão tornou-se necessário e imprescindível para que se possa entender o funcionamento do sistema nestas condições e possibilitar a sua operação de modo correto. Em relatório de força-tarefa internacional está explicitada a necessidade de uma ferramenta computacional capaz de verificar a eficácia das ações de controle de tensão na operação do sistema elétrico em tempo-real. Com esse objetivo, foi desenvolvida uma ferramenta computacional com base no sistema linearizado das equações de fluxo de carga, e de todas as outras equações de controles e limites, julgadas pertinentes, para avaliação do efeito das ações de controle de tensão. Determinase uma matriz de sensibilidade [VCS], voltage control sensitivity matrix, através da qual se pode estabelecer a relação existente entre as tensões controladas e as grandezas controladoras. Os elementos diagonais relacionam a grandeza controladora de cada equipamento com a respectiva tensão controlada. A análise do sinal desses elementos estabelece se uma determinada ação de controle será adequada ou não, isto é, se terá efeito esperado ou oposto. Os elementos fora da diagonal representam a interdependência existente entre os equipamentos controladores de tensão. A matriz de sensibilidade também permite que ações de controle de tensão sejam calculadas com o objetivo de mover um ponto de operação inadequado, ou que esteja suscetível à inadequacidade do controle de tensão, colocando-os em um ponto de operação seguro, onde ações operativas de controle de tensão tenham o efeito esperado. Os resultados da avaliação do método desenvolvido e aplicado a sistemas-teste e reais foram qualitativamente coerentes com aqueles obtidos pela resolução (analítica, iterativa por Newton ou iterativa continuada) das equações de fluxo de carga, validando a proposta. A dimensão da matriz [VCS] é proporcional ao número de barras com tensão controlada em análise. Esta matriz não é esparsa e então, quando utilizada para representar o controle de tensão realizado por um número elevado de equipamentos controladores, sua análise direta pode se tornar complexa. Portanto, uma análise baseada nos autovalores e autovetores associados à matriz [VCS] é aplicada objetivando identificar barras de tensão controlada com efeito reverso, ocorrendo de modo contrário ao esperado, e a existência de controles conflitantes. Buscam-se autovalores negativos, nulos ou próximos de zero. A localização das barras com problemas se dá através do exame dos autovetores e fatores de participação associados a esses autovalores. O cálculo e a análise da matriz de sensibilidade dos controles de tensão são executados de forma extremamente rápida e, portanto, o esforço computacional não impede que a ferramenta desenvolvida possa ser usada durante a operação em tempo-real. / [en] The voltage stability problem has been associated with environment questions and lack of financial resources for transmission system expansion. This reality together with the load growth makes the electrical system to be subject of heavy loadings, what can lead to situations of voltage collapse. The development of methods for evaluation of transmission network loading became necessary and indispensable in order to correct operation of the system under heavy loading conditions. In an international force-task report it is stated the need for analytical tools capable of verifying the voltage control action adequacy in the real-time operation. This work reports the development of a computation tool able to evaluate the effect of voltage control actions on the voltage itself. It is based the linearized load flow equations, including control and limit equations judged pertinent. The tool establishes a sensitive matrix, named [VCS] for voltage control sensitivity matrix, that relates the controlling variables and the controlled voltages. Through the analysis of the sign of each diagonal element, it is possible to know whether a specific control action is adequate or not. Moreover, the off-diagonal elements represent the interdependence among the voltage controller devices of the power system under analysis. The sensitivity matrix also allows the calculation of control actions necessary to move the operating point from an unstable area, or near by, to a secure operating region where all voltage control actions would have the expected effect. The results obtained with the voltage control sensitivity matrix applied on real and test-systems was qualitatively coherent with those calculated by analytical, iteractive by Newton-Raphson and/or continuationiteractive solution of power flow equations, validating the proposed method. The [VCS] dimension is proportional to the number of buses with controlled voltage in the system area under analysis. The matrix is not sparse and when there are a large number of voltage control equipments, its immediate analysis may be complex. Therefore, an analysis based on eigenvalues and eigenvectors associated with [VCS] matrix is used in order to identify voltage control action with opposite effect. In this case, the analysis is focused on negative eigenvalues. The identification of conflicting controls existence of any system area under analysis is a by-product. The voltage control sensitivity matrix computation and analysis are performed extremely fast. Therefore, the computational effort does not constrain its use in real-time operation.

Kim, Straub, and Keyes introduced the statistical temperature molecular dynamics (STMD) algorithm to overcome broken ergodicity by sampling a non­-Boltzmann flat energy histogram as noted in Kim, Straub, and Keyes, Phys. Rev. Lett. 97: 050601 (2007). Canonical averages are calculated via reweighting to the desired temperature. While STMD is promising, its application has been almost entirely to simple or model systems. In this dissertation the implementation of STMD into the biosimulation package CHARMM is used to simulate the methionine enkephalin pentamer peptide with a methione terminal cap in a droplet of CHARMM TIP3P water molecules. Chain thermodynamics is analyzed from the novel perspective of the statistical temperature as a function of potential energy, $TS(U), automatically generated by STMD. Both the minimum in the slope of $TS(U), and the peak in the heat capacity as a function of temperature, calculated via reweighting, indicate a collapse transition at Tθ ≈ 253K. Distributions of dihedral angles are obtained as a function of temperature. Rotamer regions found in the literature are reproduced, along with unique regions not found previously, including with advanced algorithms, indicating the power of STMD enhanced sampling.

The seismic design maps on ASCE 7-05, International Building Code- 2006/2009, assumed uniform hazard ground motion with 2% probability of exceedance in 50 years for the entire conterminous U.S. But, Luco et al in 2007 pointed out that as uncertainties in collapse capacity exists in structures, an adjustment on uniform hazard ground motion was proposed to develop new seismic design maps. Thus, risk-targeted ground motion with 1% probability collapse in 50 years is adopted on ASCE 7-10. Even though these seismic design maps are developed for buildings, performance-based bridge design is done using same maps. Because significance difference lies on design procedure of buildings and bridges this thesis suggests some adjustment should be made on uncertainty in the collapse capacity(β) when using for bridge design. This research is done in 3 cities of U.S— San Francisco, New Madrid and New York. Hazard curve is drawn using 2008 version of USGS hazard maps and risk- targeted ground motion is calculated using equation given by Luco et al adjusting the uncertainty in collapse capacity(β) to be 0.9 for bridge design instead of 0.8 as used for buildings. The result is compared with existing result from ASCE 7-10, which uses β=0.6. The sample design response spectrum for site classes A, B, C and D is computed for all 3 cities using equations given in ASCE 7-10 for all β. The design response spectrum curves are analyzed to concluded that adjustment on uncertainty in collapse capacity should be done on ASCE 7-10 seismic design maps to be used for performance-based bridge design.

Magnetic resonance (MR) is a highly versatile technique with great potential for use in industrial applications; from the in situ study of unit operations to the optimisation of product properties. This thesis, concerned with the latter, is divided into two parts. Firstly, dynamic MR is applied to characterise the flow behaviour, or rheology, of process fluids. Such characterisation is typically performed using conventional rheometry methods operating offline, with an online, or inline, method sought for process control and optimisation. Until recently, MR was an unlikely choice for this application due to the requirement of high-field MR hardware. However, recent developments in low-field MR hardware mean that the potential of MR in such applications can now be realised. Since the implementation of MR flow imaging is challenging on low-field MR hardware, two new approaches to MR rheometry are described using pulsed field gradient (PFG) MR. A cumulant analysis of the PFG MR signal is first used to characterise the rheology of model power-law fluids, namely xanthan gum-in-water solutions, accurate to within 5% of conventional rheometry, the data being acquired in only 6% of the time required when using MR flow imaging. The second approach utilises a Bayesian analysis of the PFG MR signal to characterise the rheology of model Herschel--Bulkley fluids, namely Carbopol 940-in-water solutions; data are acquired in only 12% of the time required for analysis using MR flow imaging. The suitability of the Bayesian MR approach to study process fluids is demonstrated through experimental study on an alumina-in-acetic acid slurry used by Johnson Matthey. Secondly, MR imaging is used to provide insights into the origins and mechanisms of colloidal gel collapse. Many industrial products are colloidal gels, a space-spanning network of attractive particles with a yield stress. Colloidal gels are, however, known to undergo gravitational collapse after a latency period, thus limiting the shelf-life of products. This remains poorly understood, with a more detailed understanding of both fundamental interest and practical importance. To this end, MR imaging is applied offline to investigate the phase behaviour of colloidal gels. In particular, a comparison of the simulated and experimental phase diagrams suggests gravitational gel collapse to be gravity-driven. Furthermore, measurement of the colloid volume fraction using MR imaging indicates the formation of clusters of colloids at the top of the samples. Whether such clusters initiate gravitational gel collapse is yield stress-dependent; the gravitational stress exerted by a cluster must be sufficient to yield the colloidal gel.

abstract: This dissertation discusses the Cournot competition and competitions in the exploitation of common pool resources and its extension to the tragedy of the commons. I address these models by using potential games and inquire how these models reflect the real competitions for provisions of environmental resources. The Cournot models are dependent upon how many firms there are so that the resultant Cournot-Nash equilibrium is dependent upon the number of firms in oligopoly. But many studies do not take into account how the resultant Cournot-Nash equilibrium is sensitive to the change of the number of firms. Potential games can find out the outcome when the number of firms changes in addition to providing the "traditional" Cournot-Nash equilibrium when the number of firms is fixed. Hence, I use potential games to fill the gaps that exist in the studies of competitions in oligopoly and common pool resources and extend our knowledge in these topics. In specific, one of the rational conclusions from the Cournot model is that a firm's best policy is to split into separate firms. In real life, we usually witness the other way around; i.e., several firms attempt to merge and enjoy the monopoly profit by restricting the amount of output and raising the price. I aim to solve this conundrum by using potential games. I also clarify, within the Cournot competition model, how regulatory intervention in the management of environmental pollution externalities affects the equilibrium number of polluters. In addition, the tragedy of the commons is the term widely used to describe the overexploitation of open-access common-pool resources. Open-access encourages potential resource users to continue to enter the resource up to the point where rents are exhausted. The resulting level of resource use is higher than is socially optimal, and in extreme cases can lead to the collapse of the resource and the communities that may depend on it. In this paper I use the concept of potential games to evaluate the relation between the cost of resource use and the equilibrium number of resource users in open access regimes. I find that costs of access and costs of production are sufficient to determine the equilibrium number of resource users, and that there is in fact a continuum between Cournot competition and the tragedy of the commons. I note that the various common pool resource management regimes identified in the empirical literature are associated with particular cost structures, and hence that this may be the mechanism that determines the number of resource users accessing the resource. / Dissertation/Thesis / Doctoral Dissertation Applied Mathematics for the Life and Social Sciences 2017

Orientador: José Augusto de Lollo / Banca: Leandro Eugenio Silva da Cerri / Banca: Wilson Manzoli Júnior / Resumo: O colapso de solos é um fenômeno típico de solos altamente porosos quando saturados, induzindo recalques significativos em fundações de obras civis, comprometendo total ou parcialmente estas obras. Tal fenômeno é bastante comum nos solos arenosos que ocorrem em boa parcela do Estado de São Paulo e em particular na cidade de Ilha Solteira. A grande disseminação de processos de colapso de solos em todo o Estado faz com que seu estudo seja imprescindível para o entendimento das variáveis que os condicionam e dos fatores que os desencadeiam. A proposta deste trabalho foi caracterizar o processo de colapso de solos na área urbana de Ilha Solteira, em termos de sua ocorrência, condicionantes, mecanismos e conseqüências, com o objetivo de avaliar e representar cartograficamente o risco de ocorrência deste processo. Os estudos mostraram que na área estudada a associação do comportamento natural do solo com problemas em obras de infra-estrutura urbana (redes de água e esgoto) induz uma situação de alta suscetibilidade de ocorrência de colapso de solos, o que pode ser notado pela disseminação de ocorrências por toda a área. A avaliação do risco de colapso de solos permitiu classificá-lo em alto, médio e baixo grau. As informações obtidas na avaliação de risco fundamentam a elaboração de medidas para eliminar ou reduzir os riscos instalados e ainda para evitar a instalação de novas áreas de risco. O resultado final foi a elaboração de uma carta de cadastramento de risco de colapso de solos e, a partir desta, a elaboração de uma carta de zoneamento de risco, constituindo-se em importantes ferramentas para projetos e obras de ocupação, além de fornecerem subsídios para elaboração de planos de seguro de edificações. A metodologia utilizada para avaliação e representação de risco de colapso de solos poderá ser aplicada em estudos nos bairros mais... (Resumo completo, clicar acesso eletrônico abaixo). / Abstract: Soil collapse is a characteristic process in porous soils when saturated and produce large settlements in civil engineering foundations. This process is very common in typical fine sand soils present in State of São Paulo large areas, thus Ilha Solteira region. Due this process has affected large areas of São Paulo State the study of soils with collapsible behavior is very important to understand variables that cause or are responsible for the process. This work proposed to characterize the process of soil collapse (events, causes, mechanisms, consequences) in the Ilha Solteira urban area, purposing to evaluate and to present the risk of soil collapse on a chart. Studies showed that in the Ilha Solteira city the association of natural behavior of soil with problems in urban infrastructure works (water and sewage pipes) characterize a situation of high susceptibility of soil collapse, which can be observed by dissemination of occurrences by total area. The evaluation of soil collapse risk permitted to classify it in high, medium and small degree. Information gained in this risk evaluation is important for take the necessary steps for reduce, eliminate or avoid the problem of soil collapse. The final result was the representation of the soil collapse risk on cadastre and zoning charts, which constitute on important tool for adopting construction guidelines, besides to provide subsidies for elaboration of edifications insurance. Respecting locals specifications, the methodology utilized for evaluation and representation of risk of soil collapse can be applied in studies in other areas with similar problems. / Mestre

[pt] Este trabalho apresenta um estudo do comportamento mecânico, em especial nas características de resistência, de um solo laterítico submetido à contaminação de licores cáusticos a diferentes concentrações. O programa experimental envolveu ensaios de caracterização, ensaios químicos, difração de raios-X, microscopia eletrônica de varredura e ensaios triaxiais com diferentes valores de concentrações cáusticas. Propriedades mecânicas foram determinadas mediante a execução de ensaios triaxiais CID a diferentes concentrações cáusticas, assim como as interações físico- químicas que foram determinadas mediante ensaios químicos de pH, capacidade de troca catiônica e ataque sulfúrico. Os resultados do programa experimental demonstraram uma acentuada variação de volume do solo, a qual está ligada à presença dos licores cáusticos e, por outro lado, também indicaram que os parâmetros de resistência ao cisalhamento do solo são pouco afetados pelos licores cáusticos. / [en] This work presents the results of a laboratory study on the effects of infiltration of a caustic liqueur on the stress- strain- strength behavior of a sandy lateritic soil. The experimental program consisted of general characterization,chemicals tests, X-ray diffraction analysis, electron microscopy and triaxial tests using the caustic liqueur at different concentrations.Mechanic and hydraulic properties were obtained performing triaxial CID tests with different caustic concentrations. Physical- chemical interactions were evaluated through of determination of pH, cation exchange capacity and sulfuric attack tests. The results obtained showed that soil suffers large volume changes under percolation of the liqueur, with these changes being a function of the caustic concentration, on the other hand, the shear strength parameters are little affected by the liqueur.

Made available in DSpace on 2014-06-11T19:22:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-23Bitstream added on 2014-06-13T20:09:48Z : No. of bitstreams: 1 martins_lfb_me_bauru.pdf: 963421 bytes, checksum: 7c1f9175f040c64a63fdf8db9f7a10a1 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho foi feita uma análise comparativa entre diferentes escolhas dos pontos utilizados pelo método look ahead na estimação do ponto de máximo carregamento de um sistema elétrico de potência. O Fluxo de Cargo Continuado é utilizado na geração dos pontos de operação utilizados pelo método look ahead e para servir como referência na comparação entre os resultados previstos e o ponto de máximo carregamento real. Uma vez que a exatidão dessa estimativa é fortemente afetada pela escolha desses pontos, o FCC é modificado para fornecer pontos mais adequados para o bom funcionamento do método look ahead. A metodologia proposta é aplicada ao sistema IEEE de 300 barras, os resultados obtidos mostram o seu bom funcionamento / Here we did a comparative analysis between different choices of the points used by the look ahead method for estimating maximum loading point of a power system. The Continued Power Flow (CPF) is used in the generation of operating points used by the look ahead method and to serve as a reference in comparison between the predicted results and the real maximum loading point. Since the accurancy of this estimative is strongly affected by choicen of these points, the CPF is modified to provide the most appropriate for the proper functioning of the method look ahead. The proposed methodology system is applied to IEEE 300 buses, the results have shown its good functioning