Dissertations / Theses on the topic 'SEMK model'
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Chakkingal, Anoop. "Réglage de la sélectivité de la synthèse Fischer-Tropsch : aperçu de la modélisation microcinétique et de l'apprentissage automatique." Electronic Thesis or Diss., Centrale Lille Institut, 2022. http://www.theses.fr/2022CLIL0015.
Striving towards a circular economy has led to the re-investigation of many existing processes, with the target of developing more sustainable variants. In our present economy, plastics form an important and omnipresent material affecting our daily lives. They are inexpensive, durable, corrosion resistant, and light weight leading to their use in a wide variety of applications.Within the plastic chemical recycling scheme, Fischer-Tropsch synthesis (FTS) could play a key role as the syngas feedstock that is converted in it, can be generated via the gasification of the considered plastics. This syngas is then chemo-catalytically converted into hydrocarbons such as paraffins and light olefins. Typical FTS catalysts are based on supported cobalt or iron species.Among the mechanistic kinetic models, the comprehensive variant based on the Single Event MicroKinetics (SEMK) concept has been widely applied in the field of oligomerization, autoxidative curing, etc. and has proven to be a versatile tool to simulate Fischer-Tropsch synthesis. However, developing mechanistic models for every chemical engineering challenge is not always feasible due to their complexity and the in-depth knowledge required to build such models.A detailed evaluation on the potential of using machine learning approaches to match the performance of results obtained using the Single-Event MicroKinetic model was carried out. Initially, the focus was on a single dominant output scenario (methane selective catalyst). The current work thus shows that more widely applied techniques in data science can now be applied for systematic analysis and interpretation of kinetic data. Similar analysis using experimental data can also help experimenters in their preliminary analysis, to detect hidden trends in the data, and thus to identify importance features. After gaining confidence on the investigated interpretation techniques, for the FTS reaction with single dominant output, a similar investigation on the potential of iron based catalysts with enhanced light olefin selectivity is carried out next
Dhurandhar, Amit. "Semi-analytical method for analyzing models and model selection measures." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0024733.
Yu, Fu. "On statistical analysis of vehicle time-headways using mixed distribution models." Thesis, University of Dundee, 2014. https://discovery.dundee.ac.uk/en/studentTheses/d101df63-b7db-45b6-8a03-365b64345e6b.
Goes, Adriano Almeida 1978. "Modelo de propagação empírico para sistemas RFID passivo = Emprirical propagation model for RFID passive systems." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/261045.
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: Resultados de campanhas de medição realizadas visando o desenvolvimento de uma fer-ramenta para o projeto, implantação e análise de sistemas de RFID são mostrados nesse traba-lho. Particularmente, a perda de percurso de rádio a partir de um leitor de RFID até um TAG, e de volta para o leitor é caracterizada na banda 915 MHz, para diferentes distâncias de separação leitor-TAG, alturas de TAG e de antena do leitor. Vários cenários de propagação foram considerados, incluindo ambientes exteriores e in-teriores, para os quais foi colhido um extenso número medidas. Os dados de campo são, então, comparados a uma versão melhorada do modelo clássico perda caminho 2-ray, ajustada para incluir também os padrões de radiação da antena não omnidirecionais no leitor. Além disso, foi investigado, por meio da análise de medidas de campo, o efeito da mobi-lidade do TAG no sinal recebido no leitor. Para a coleta das medidas, foi construído um aparato composto de uma esteira de velocidade controlada, onde foram instalados TAGs de teste. Os resultados de medida mostraram que a mobilidade do TAG provoca uma diminuição do valor médio e um aumento da variância do sinal recebido no leitor. Essa atenuação extra e a variância do sinal não são fortemente afetadas pelo valor da velocidade. Por fim, esses efeitos de propagação são incorporados em um modelo matemático, que pode ser utilizado para a simulação e planejamento de sistemas RFID
Abstract: Results of measurement campaigns carried out aiming at the development of a tool for design, deployment, and analysis of RFID systems are shown. Particularly, the radio path loss from an RFID reader towards the test TAG and back to the reader is characterized at the 915 MHz band. The path loss is estimated based on the received signal strength measured at the reader, for different reader¿TAG separation distances and different antenna TAG heights. Several propagation scenarios have been considered, including outdoor and indoor environments for which an extensive number of typical real manufacturing plants have been chosen. The field data are then compared to a proposed novel, improved version of the classical 2-ray path loss model, adjusted to include non-omnidirectional antenna radiation patterns at the reader. In addition, the effect of TAG mobility in the received signal at the reader was also investigated, by means of field measurements. To collect the field measurements, an apparatus was designed and constructed, consisting of a mat of controlled speed, on which test TAGs were installed. The results showed that TAG mobility decreases the average value increases the variance of the received signal at the reader. This extra attenuation and the increased variance of the signal are not strongly affected by the value of speed. Finally, these two effects are incorporated into a mathematical model that can be used for simulation and planning of RFID systems
Doutorado
Telecomunicações e Telemática
Doutor em Engenharia Elétrica
Nwi-Mozu, Isaac. "Robustness of Semi-Parametric Survival Model: Simulation Studies and Application to Clinical Data." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/etd/3618.
Pouliot, George. "A Variable Resolution Nonhydrostatic Global Atmospheric Semi-implicit Semi-Lagrangian Model." NCSU, 2000. http://www.lib.ncsu.edu/theses/available/etd-20000403-180910.
ABSTRACTPOULIOT, GEORGE. A Variable Resolution Nonhydrostatic Global Atmospheric Semi-implicit Semi-Lagrangian Model. (Under the direction of Dr. Fredrick H.M. Semazzi.)The objective of this project is to develop a variable-resolution finite difference adiabatic global nonhydrostatic semi-implicit semi-Lagrangian (SISL) model based on the fully compressible nonhydrostatic atmospheric equations. To achieve this goal, a three-dimensional variable resolution dynamical core was developed and tested.The main characteristics of the dynamical core can be summarized as follows: Spherical coordinates were used in a global domain. A hydrostatic/nonhydrostatic switch was incorporated into the dynamical equations to use the fully compressible atmospheric equations. A generalized horizontal variable resolution grid was developed and incorporated into the model. For a variable resolution grid, in contrast to a uniform resolution grid, the order of accuracy of finite difference approximations is formally lost but remains close to the order of accuracy associated with the uniform resolution grid provided the grid stretching is not too significant. The SISL numerical scheme was implemented for the fully compressible set of equations. In addition, the generalized minimum residual (GMRES) method with restart and preconditioner was used to solve the three-dimensional elliptic equation derived from the discretized system of equations. The three-dimensional momentum equation was integrated in vector-form to incorporate the metric terms in the calculations of the trajectories. Using global re-analysis data for a specific test case, the model was compared to similar SISL models previously developed. Reasonable agreement between the model and the other independently developed models was obtained. The Held-Suarez test for dynamical cores was used for a long integration and the model was successfully integrated for up to 1200 days. Idealized topography was used to test the variable resolution component of the model. Nonhydrostatic effects were simulated at grid spacings of 400 meters with idealized topography and uniform flow. Using a high-resolution topographic data set and the variable resolution grid, sets of experiments with increasing resolution were performed over specific regions of interest. Using realistic initial conditions derived from re-analysis fields, nonhydrostatic effects were significant for grid spacings on the order of 0.1 degrees with orographic forcing. If the model code was adapted for use in a message passing interface (MPI) on a parallel supercomputer today, it was estimated that a global grid spacing of 0.1 degrees would be achievable for a global model. In this case, nonhydrostatic effects would be significant for most areas.A variable resolution grid in a global model provides a unified and flexible approach to many climate and numerical weather prediction problems. The ability to configure the model from very fine to very coarse resolutions allows for the simulation of atmospheric phenomena at different scales using the same code. We have developed a dynamical core illustrating the feasibility of using a variable resolution in a global model.
Silva, Marcelo Ferreira da. "Densidade espectral para o modelo de Anderson de duas impurezas sem correlação eletrônica." Universidade de São Paulo, 1998. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-07052014-145918/.
This work calculates analytically and numerically the spectral density for the two impurity uncorrelated Anderson model (U = O). Our results serve as an initial step towards understanding models with electronic correlation. The studied model describes the interaction between conduction-band electrons of a metal and localized magnetic impurities. The simplification U = O turns the Hamiltonian quadratic, allowing us to split it into two parts: one involving only even operators (even channel), the other involving odd operators (odd channel). Each term has a form differing a little from that for the Resonant Level Hamiltonian. Our results include analytic diagonalization as well as numerical calculations using the method of the Renormalization Group, adapted for the two impurity case. The traditional tridiagonalization method imposes particle-hole symmetry, while our treatment preserves the energy dependence of the coupling, between the impurities and the conduction-band, and consequently, the natural asymmetry of the model. The simplicity of the Hamiltonian allowed us to (1) identify characteristics of the model that affect adversely the acuracy of the numeric calculation and (2) find a way to surround such difficulties. The results here found helped the development of the calculation of the spectral density of the correlated model, developed simultaneously in our research group.
Ramos, Luís Roberto. "Propriedades termodinâmicas do Modelo de Falicov-Kimball de duas impurezas sem spin." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-03062014-103216/.
In this work, we study the Falicov-Kimball model with two localized spinless impurities hybridized with conduction electrons of a host metal, therefore, valence fluctuation is intrinsic to the model. The conduction states are also electrostatically scattered whenever a charge is present em the local levels of the impurities. The study was realized computing thermodynamics properties of the model, more specifically, we analyze the temperature dependent specific heat end charge susceptibility for many different parameters of the model. The Numerical Renormalization Group with two discretization parameters is used to obtain the spectrum of the model, from what the thermodynamics is obtained. We discuss the importance of going beyond the usual approximation that projects all moment at the Fermi Level. We begun our study of the thermodynamical properties analyzing values of the parameters space, where the model becomes quadratic (that is, where hybridization or Coulomb scattering are absent), and thus simple interpretations of the data are possible. We verified, for example, that for non-zero hybridization, the system shows Fermi liquid behavior at low temperature. The Wilson ratio, defined here with the charge susceptibility instead of magnetic one, has the universal value R = 1, whenever the hybridization is present. For some choices of the model parameters the model behaviors like heavy fermion.
Wendler, Tim Glenn. "Algebraic Semi-Classical Model for Reaction Dynamics." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/5755.
Bulla, Jan. "Application of Hidden Markov and Hidden Semi-Markov Models to Financial Time Series." Doctoral thesis, [S.l. : s.n.], 2006. http://swbplus.bsz-bw.de/bsz260867136inh.pdf.
Preacher, Kristopher J. "The Role of Model Complexity in the Evaluation of Structural Equation Models." The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1054130634.
Santos, Douglas Gomes dos. "Estimação de volatilidade em séries financeiras : modelos aditivos semi-paramétricos e GARCH." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2008. http://hdl.handle.net/10183/14892.
Volatility estimation and forecasting are very important matters for the financial markets. Themes like risk and uncertainty in modern economic theory have encouraged the search for methods that allow for the modeling of time varying variances. The main objective of this dissertation is to compare global and local regressions in terms of their capacity to extract the volatility of Ibovespa and Standard and Poor 500 indexes. To achieve this aim, parametric GARCH and semiparametric additive models estimation and forecasting are performed. The first ones, traditionally applied in the estimation of conditional second moments, have their capacity suggested in many papers. The second ones provide high flexibility and visually informative descriptions of the relationships between the variables, like asymmetries and nonlinearities. Therefore, testing the last ones´ performance against the acknowledged parametric structures is an appropriate investigation. Comparisons are made in selected periods of high volatility in the international financial market (crisis), measuring the models´ performance inside and outside sample. The results that were found suggest the capacity of semiparametric models to estimate and forecast the Indexes returns´ volatility at the analyzed moments.
Bond, S. A. "Dynamic models of semi-variance." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596758.
Bush, Christopher A. "Semi-parametric Bayesian linear models /." The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487856076417948.
Brefeld, Ulf. "Semi-supervised structured prediction models." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2008. http://dx.doi.org/10.18452/15748.
Learning mappings between arbitrary structured input and output variables is a fundamental problem in machine learning. It covers many natural learning tasks and challenges the standard model of learning a mapping from independently drawn instances to a small set of labels. Potential applications include classification with a class taxonomy, named entity recognition, and natural language parsing. In these structured domains, labeled training instances are generally expensive to obtain while unlabeled inputs are readily available and inexpensive. This thesis deals with semi-supervised learning of discriminative models for structured output variables. The analytical techniques and algorithms of classical semi-supervised learning are lifted to the structured setting. Several approaches based on different assumptions of the data are presented. Co-learning, for instance, maximizes the agreement among multiple hypotheses while transductive approaches rely on an implicit cluster assumption. Furthermore, in the framework of this dissertation, a case study on email batch detection in message streams is presented. The involved tasks exhibit an inherent cluster structure and the presented solution exploits the streaming nature of the data. The different approaches are developed into semi-supervised structured prediction models and efficient optimization strategies thereof are presented. The novel algorithms generalize state-of-the-art approaches in structural learning such as structural support vector machines. Empirical results show that the semi-supervised algorithms lead to significantly lower error rates than their fully supervised counterparts in many application areas, including multi-class classification, named entity recognition, and natural language parsing.
Vasconcelos, Julio Cezar Souza. "Modelo linear parcial generalizado simétrico." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/11/11134/tde-26072017-105153/.
In this work we propose the symmetric generalized partial linear model, based on the generalized partial linear models and symmetric linear models, that is, the response variable follows a distribution that belongs to the symmetric distribution family, considering a linear predictor that has a parametric and a non-parametric component. Some distributions that belong to this class are distributions: Normal, t-Student, Power Exponential, Slash and Hyperbolic among others. A brief review of the concepts used throughout the work was presented, namely: residual analysis, local influence, smoothing parameter, spline, cubic spline, natural cubic spline and backfitting algorithm, among others. In addition, a brief theory of GAMLSS models is presented (generalized additive models for position, scale and shape). The models were adjusted using the package gamlss available in the free R software. The model selection was based on the Akaike criterion (AIC). Finally, an application is presented based on a set of real data from Chile\'s financial area.
Le, Roux Daniel Y. "A semi-Lagrangian finite element barotropic ocean model." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ44492.pdf.
White, P. D. "Semi-synthetic model studies related to cytochrome c." Thesis, University of Exeter, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378247.
Malsiner-Walli, Gertraud, Paul Hofmarcher, and Bettina Grün. "Semi-parametric Regression under Model Uncertainty: Economic Applications." Wiley, 2019. http://dx.doi.org/10.1111/obes.12294.
NUNES, THIAGO RIBEIRO. "A MODEL FOR EXPLORATION OF SEMI-STRUCTURED DATASETS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2017. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=32904@1.
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PROGRAMA DE EXCELENCIA ACADEMICA
Tarefas de exploração de informação são reconhecidas por possuir características tais como alta complexidade, falta de conhecimento do usuário sobre o domínio da tarefa e incertezas sobre as estratégias de solução. O estado-da-arte em exploração de dados inclui uma variedade de modelos e ferramentas baseadas em diferentes paradigmas de interação, como por exemplo, busca por palavras-chave, busca facetada e orientação-a-conjuntos. Não obstante os muitos avanços das últimas décadas, a falta de uma abordagem formal do processo de exploração, juntamente com a falta de uma adoção mais pragmática do princípio de separação-de-responsabilidades no design dessas ferramentas são a causa de muitas limitações. Dentre as limitações, essa tese aborda a falta de expressividade, caracterizada por restrições na gama de estratégias de solução possíveis, e dificuldades de análise e comparação entre as ferramentas propostas. A partir desta observação, o presente trabalho propõe um modelo formal de ações e processos de exploração, uma nova abordagem para o projeto de ferramentas de exploração e uma ferramenta que generaliza o estado-da-arte em exploração de informação. As avaliações do modelo, realizadas por meio de estudos de caso, análises e comparações o estado-da-arte, corroboram a utilidade da abordagem.
Information exploration processes are usually recognized by their inherent complexity, lack of knowledge and uncertainty, concerning both the domain and the solution strategies. Even though there has been much work on the development of computational systems supporting exploration tasks, such as faceted search and set-oriented interfaces, the lack of a formal understanding of the exploration process and the absence of a proper separation of concerns approach in the design phase is the cause of many expressivity issues and serious limitations. This work proposes a novel design approach of exploration tools based on a formal framework for representing exploration actions and processes. Moreover, we present a new exploration system that generalizes the majority of the state-of-the art exploration tools. The evaluation of the proposed framework is guided by case studies and comparisons with state-of-the-art tools. The results show the relevance of our approach both for the design of new exploration tools with higher expressiveness, and formal assessments and comparisons between different tools.
Sirbone, Fabio Renato Camargo. "Modelagem semi-empírica de compressores herméticos alternativos." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/18/18147/tde-18072007-111535/.
In the present work is applied a semi-empirical method that uses a non-linear optimization technique for determination of the volumetric and combined efficiencies of hermetic reciprocating compressor. Relations to approximately estimate the mass flow and the electric power of the compressor are also proposed. All these compressor characteristics are calculated through physical model relations, used in the optimization calculations. The method is implemented in the EES (Engineering Equation Solver) software and is based on the works of Jahing (1999) and Jahing et al. (2000). In the method, four experimental measurements of the mass flow and electric power are enough to determine the fitting parameters of the model. This procedure allows the generation of satisfactory compressor maps without the necessity of a higher number of experimental data, as in the case of norm ARI 540 application. The results obtained with the model can be used for the design of new compressors.
Torrent, Hudson da Silva. "Estimação não-paramétrica e semi-paramétrica de fronteiras de produção." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2010. http://hdl.handle.net/10183/25786.
There exists a large and growing literature on the specification and estimation of production frontiers and therefore efficiency of production units. In this thesis we focus on deterministic production frontier models, which are based on the assumption that all observed data lie in the technological set. Among the existing statistical models and estimators for deterministic frontiers, a promising approach is that of Martins-Filho and Yao (2007). They propose an estimation procedure that consists of three stages. Their estimator is fairly easy to implement as it involves standard nonparametric procedures. In addition, it has a number of desirable characteristics vis-a-vis traditional deterministic frontier estimators as DEA and FDH. In this thesis we propose three papers that improve the model proposed in Martins-Filho and Yao (2007). In the first paper we improve their estimation procedure by adopting a variant of the local exponential smoothing proposed in Ziegelmann (2002). Our estimator is shown to be consistent and asymptotically normal. In addition, due to local exponential smoothing, potential negativity of conditional variance functions that may hinder the use of Martins-Filho and Yao's estimator is avoided. In the second paper we propose a novel method for estimating production frontiers in only two stages. (Continue). There we show that we can eliminate the second stage of Martins-Filho and Yao as well as of our first paper, where estimation of the same frontier model requires three stages under different versions for the second stage. We study asymptotic properties showing consistency andNirtnin, asymptotic normality of our proposed estimator under standard assumptions. In the third paper we propose a semiparametric variation of the frontier model studied in the second paper. We rewrite that model allowing for estimating the production frontier and efficiency of production units in a multiple input context without suffering the curse of dimensionality. Our approach places that model within the framework of additive models based on assumptions regarding the way inputs combine in production. In particular, we consider the cases of additive and multiplicative inputs, which are widely considered in economic theory and applications. Monte Carlo studies are performed in all papers to shed light on the finite sample properties of the proposed estimators. Furthermore a real data study is carried out in all papers, from which we rank efficiency within a sample of USA Law Enforcement agencies using USA crime data.
Umsrithong, Anake. "Deterministic and Stochastic Semi-Empirical Transient Tire Models." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/26270.
Ph. D.
Santos, Franciane Mendonça dos. "Modelagem concentrada e semi-distribuída para simulação de vazão, produção de sedimentos e de contaminantes em bacias hidrográficas do interior de São Paulo." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/18/18139/tde-26112018-145857/.
The lack of hydrological data in Brazil is a recurrent problem in many regions, especially in hydrometric data, sediment yield and water quality. The research by simplified models has increased in the last decades, however, the estimation of hydrossedimentological data from these more sophisticated models demands many variables, which must be adjusted for each natural system, which makes it difficult to apply. At times it is necessary to respond quickly without much precision in the results, in these situations, simpler models with few parameters can be the solution. The objective of this research is to evaluate different modelling tools used estimate streamflow, sediments yield and nutrients loads values, and namely to compare the results obtained from a physically-based distributed hydrological model (SWAT) with the results from a lumped hydrological, the Soil Conservation Service (SCS-CN) and the Generalized Watershed Loading Function (GWLF) model. Both models use the curve number (CN) concept, determined from land use, soil hydrologic group and antecedent soil moisture conditions and were run with a daily time step. We are particularly interested in understanding under which conditions the use of each model is to be recommended, namely when does the addition effort required to run the distributed model leads to effective better results. The input variables and parameters of the lumped model are assumed constant throughout the watershed, while the SWAT model performs the hydrological analysis at a small unit level, designated as hydrological response units (HRUs), and integrates the results at a sub-basin level. In relation to the flow simulation, the results of the two models were highly influenced by the rainfall data, indicating that, possibly, faults or measurement errors could have negatively influenced the results. Therefore, it was proposed to apply the distributed model with high-resolution grids of daily precipitation to verify the efficiency of its results when compared to rainfall data. For simulation of sediment, nitrogen and phosphorus, SWAT performs a more detailed simulation and thus provides slightly better results. The use of the SWAT was also extended to simulate the influence of reservoir, in order to verify the potentiality of the model, in relation to the simulation. The models also were used to identify which are potential impacts of the ongoing land use changes. The scenarios were: I - Current scenario, II - trend scenario, with the increase of urban land and replacement of the exposed soil and part of the native forest by agricultural use; III - desirable scenario complements the trend urban growth with the replacement of exposed soil and part of the agricultural use by reforestation. The methodologies were applied on two watersheds located in the Southeast of Brazil. The first one is the Jacaré-Guaçu river basin, included in the Water Resources Management Unit 13 (UGRHI-13), upstream of Cruzes river confluence, with an area of 1934 km2. The second watershed is the Atibaia River Basin, a part of Water Resources Management Unit 5 (UGRHI-5). It has an area of 2817.88 km2 and covers municipalities of the states of São Paulo and Minas Gerais.
Das, Sourav. "Models of semi-systematic visual search." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1181250703/.
Trommershäuser, Julia. "A semi-microscopic model of synaptic transmission and plasticity." [S.l.] : [s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=963474626.
Bhattacharjee, Binita 1976. "Kinetic model reduction using integer and semi-infinite programming." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/30062.
MIT Science Library copy in pages.
Also issued in pages.
Includes bibliographical references (leaves 147-155).
In this work an optimization-based approach to kinetic model reduction was studied with a view to generating reduced-model libaries for reacting-flow simulations. A linear integer formulation of the reaction elimination problem was developed in order to allow the model reduction problem to be solved cheaply and robustly to guaranteed global optimality. When compared with three other conventional reaction-elimination methods, only the integer-programming approach consistently identified the smallest reduced model which satisfies user-specified accuracy criteria. The proposed reaction elimination formulation was solved to generate model libraries for both, homogeneous combustion systems, and 2-D laminar flames. Good agreement was observed between the reaction trajectories predicted by the full mechanism and the reduced model library. For kinetic mechanisms having many more reactions than species, the computational speedup associated with reaction elimination was found to scale linearly with the size of the derived reduced model. Speedup factors of 4-90 were obtained for a variety of different mechanisms and reaction conditions. The integer-programming based reduction approach was tested successfully on large-scale mechanisms comprising up to [approximately] 2500 reactions. The problem of identifying optimal (maximum) ranges of validity for point-reduced kinetic models was also investigated. A number of different formulations for the range problem were proposed, all of which were shown to be variants of a standard semi-infinite program (SIP). Conventional algorithms for nonlinear semi-infinite programs are essentially all lower-bounding methods which cannot guarantee the feasibility of an incumbent at finite termination.
(cont.) Thus, they cannot be used to identify rigorous ranges of validity for reduced kinetic models. In the second part of this thesis, inclusion functions were used to develop an inner approximation method which generates a convergent series of feasible upper bounds on the minimum value of a smooth, non-linear semi-infinite program. The inclusion-constrained reformulation approach was applied successfully to a number of test problems in the SIP literature. The new upper-bounding approach was then combined with existing lower-bounding methods in a branch-and-bound framework which allows smooth nonlinear semi-infinite programs to be solved finitely to [epsilon]-optimality. The branch-and-bound algorithm was also tested on a number of small literature examples. In the final chapter of the thesis, extensions of the existing algorithm and code to solve practical engineering problems, including the range identification problem, were considered.
by Binita Bhattacharjee.
Ph.D.
Mockelman, Jeffrey A. (Jeffrey Alan). "Semi-analytical model of ionization oscillations in Hall thrusters." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98810.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 107-108).
This thesis presents efforts to better understand the breathing-mode oscillation within Hall thrusters. These oscillations have been present and accepted within Hall thrusters for decades, but recent interest in the oscillation has occurred partly due to a possible connection between wall erosion and the oscillations. The first part of this thesis details a steady model of the ionization region in a Hall thruster that finds existence criteria for the steady solution under the hypothesis that the steady limits match the smooth sonic passage limits. Operation outside these limits would correspond to unsteady behavior which could result in either a periodic oscillatory behavior or plume extinguishment. To distinguish between periodic behavior and thruster extinguishment, an unsteady model of the ionization region is developed, but this model falls short of its goal. The transient model, however, is still useful for observation of the periodic nature of an oscillating Hall thruster. Next, an anode depletion model for Hall thrusters is formulated. This model explores one of the causes of thruster extinguishment, when the plasma cannot reach the anode. Finally, a new method for performing Boron Nitride erosion measurements is discussed and preliminary results are presented. This method imbeds Lithium ions into Boron Nitride. The depth of the Lithium can be measured before and after erosion or deposition to give a net erosion or accumulation measurement.
by Jeffrey A. Mockelman.
S.M.
Hong, Jiazheng. "A Semi-Analytical Load Distribution Model of Spline Joints." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1426110670.
Clertant, Matthieu. "Semi-parametric bayesian model, applications in dose finding studies." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066230/document.
Phase I clinical trials is an area in which statisticians have much to contribute. For over 30 years, this field has benefited from increasing interest on the part of statisticians and clinicians alike and several methods have been proposed to manage the sequential inclusion of patients to a study. The main purpose is to evaluate the occurrence of dose limiting toxicities for a selected group of patients with, typically, life threatening disease. The goal is to maximize the potential for therapeutic success in a situation where toxic side effects are inevitable and increase with increasing dose. From a range of given doses, we aim to determine the dose with a rate of toxicity as close as possible to some threshold chosen by the investigators. This dose is called the MTD (maximum tolerated dose). The standard situation is where we have a finite range of doses ordered with respect to the probability of toxicity at each dose. In this thesis we introduce a very general approach to modeling the problem - SPM (semi-parametric methods) - and these include a large class of methods. The viewpoint of SPM allows us to see things in, arguably, more relevant terms and to provide answers to questions such as asymptotic behavior. What kind of behavior should we be aiming for? For instance, can we consistently estimate the MTD? How, and under which conditions? Different parametrizations of SPM are considered and studied theoretically and via simulations. The obtained performances are comparable, and often better, to those of currently established methods. We extend the findings to the case of partial ordering in which more than one drug is under study and we do not necessarily know how all drug pairs are ordered. The SPM model structure leans on a hierarchical set-up whereby certain parameters are linearly constrained. The theoretical aspects of this structure are outlined for the case of distributions with discrete support. In this setting the great majority of laws can be easily considered and this enables us to avoid over restrictive specifications than can results in poor behavior
Nobrega, Karliane Fernandes. "A interpreta??o sem?ntica dos auxiliares modais poder, precisar e dever: uma abordagem da sem?ntica cognitiva." Universidade Federal do Rio Grande do Norte, 2007. http://repositorio.ufrn.br:8080/jspui/handle/123456789/16359.
Apresentamos, neste trabalho, com base na sem?ntica cognitiva, uma an?lise do significado, em contexto, dos auxiliares modais poder, precisar e dever. Analisamos 120 textos produzidos por candidatos ao vestibular e por alunos do ensino fundamental, como resposta da quest?o n?mero tr?s da prova discursiva de L?ngua Portuguesa do vestibular 2005 da UFRN, que pede aos candidatos para explicitar a diferen?a de sentido entre tr?s frases, observando o uso desses tr?s verbos. Consideramos que um item lexical n?o ? incorporado a uma representa??o ling??stica sem?ntica fixa, limitada e ?nica, mas antes, ? ligado a uma representa??o ling??stica sem?ntica flex?vel e aberta que prov? acesso a muitas concep??es e sistemas conceituais dependente de cada contexto determinado. Com base em seu significado, um item lexical evoca um grupo de dom?nios cognitivos, que por sua vez, apresentam um determinado conte?do conceitual. Isto implica em afirmar que a rede de significados lexicais vai variar conforme o conhecimento de mundo de cada um (LANGACKER, 2000). A relev?ncia deste trabalho ? proporcionar uma contribui??o para a descri??o sem?ntica do portugu?s
We present, in this work, based on cognitive semantics, an analysis of the meaning in context of the modal auxiliaries can, need and must. We analysed 120 texts produced by applicants for university entrance examinations and primary school students as answer to question number three of the Portuguese Language discursive test, in the entrance examinations for UFRN, that asked the candidates to explicit the difference in meaning between three sentences, observing the use of those three verbs. We consider that a lexical item is not incorporated by a steady semantic structure, limited and unique, but instead, it is linked to an open and flexible linguistic semantic representation that provides access to many conceptions and conceptual systems depending on each determined context. Based on its meaning, a lexical item evokes a group of cognitive domains, which present a determined conceptual content. This makes possible to affirm that the net of lexical meanings will vary according to the world knowledge each one has (LANGACKER, 2000). The relevance of this work is provide a understanding of the semantic decription of portuguese
Huss, Anders. "Hybrid Model Approach to Appliance Load Disaggregation : Expressive appliance modelling by combining convolutional neural networks and hidden semi Markov models." Thesis, KTH, Skolan för datavetenskap och kommunikation (CSC), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-179200.
Den ökande energikonsumtionen är en stor utmaning för en hållbar utveckling. Bostäder står för en stor del av vår totala elförbrukning och är en sektor där det påvisats stor potential för besparingar. Non Intrusive Load Monitoring (NILM), dvs. härledning av hushållsapparaters individuella elförbrukning utifrån ett hushålls totala elförbrukning, är en tilltalande metod för att fortlöpande ge detaljerad information om elförbrukningen till hushåll. Detta utgör ett underlag för medvetna beslut och kan bidraga med incitament för hushåll att minska sin miljöpåverakan och sina elkostnader. För att åstadkomma detta måste precisa och tillförlitliga algoritmer för el-disaggregering utvecklas. Denna masteruppsats föreslår ett nytt angreppssätt till el-disaggregeringsproblemet, inspirerat av ledande metoder inom taligenkänning. Tidigare angreppsätt inom NILM (i frekvensområdet
Odstrčil, Aleš. "Semi-aktivní tlumicí jednotka vozidla." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417417.
Kosuri, Durga Renuka. "Direct Biocontrol of a Simulated Anthropomorphic Computer Finger Model Using SEMG." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1147468452.
Kyncl, Jaroslav. "Semi-lexical heads in Czech modal structures." Thesis, University of Wolverhampton, 2008. http://hdl.handle.net/2436/33738.
Chen, Chunxia. "Semi-parametric estimation in Tobit regression models." Kansas State University, 2013. http://hdl.handle.net/2097/15300.
Department of Statistics
Weixing Song
In the classical Tobit regression model, the regression error term is often assumed to have a zero mean normal distribution with unknown variance, and the regression function is assumed to be linear. If the normality assumption is violated, then the commonly used maximum likelihood estimate becomes inconsistent. Moreover, the likelihood function will be very complicated if the regression function is nonlinear even the error density is normal, which makes the maximum likelihood estimation procedure hard to implement. In the full nonparametric setup when both the regression function and the distribution of the error term [epsilon] are unknown, some nonparametric estimators for the regression function has been proposed. Although the assumption of knowing the distribution is strict, it is a widely adopted assumption in Tobit regression literature, and is also confirmed by many empirical studies conducted in the econometric research. In fact, a majority of the relevant research assumes that [epsilon] possesses a normal distribution with mean 0 and unknown standard deviation. In this report, we will try to develop a semi-parametric estimation procedure for the regression function by assuming that the error term follows a distribution from a class of 0-mean symmetric location and scale family. A minimum distance estimation procedure for estimating the parameters in the regression function when it has a specified parametric form is also constructed. Compare with the existing semiparametric and nonparametric methods in the literature, our method would be more efficient in that more information, in particular the knowledge of the distribution of [epsilon], is used. Moreover, the computation is relative inexpensive. Given lots of application does assume that [epsilon] has normal or other known distribution, the current work no doubt provides some more practical tools for statistical inference in Tobit regression model.
Delgado, Carlos Alberto Cardozo. "Semi-parametric generalized log-gamma regression models." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/45/45133/tde-15032018-185352/.
O objetivo central do trabalho é proporcionar ferramentas estatísticas para modelos de regressão semiparamétricos quando os erros seguem distribução log-gamma generalizada na presença de observações censuradas ou não censuradas. A estimação paramétrica e não paramétrica são realizadas através dos procedimentos Newton - Raphson, escore de Fisher e Backfitting (Gauss - Seidel). As propriedades assintóticas dos estimadores de máxima verossimilhança penalizada são estudadas em forma analítica, bem como através de simulações. Alguns procedimentos de diagnóstico são desenvolvidos, tais como resíduos tipo componente do desvio e resíduo quantílico, bem como medidas de influ\\^encia local sob alguns esquemas usuais de perturbação. Todos procedimentos do presente trabalho são implementados no ambiente computacional R, o pacote sglg é desenvolvido, assim como algumas aplicações a dados reais são apresentadas.
Huamán, René Negrón. "On integrable deformations of semi-symmetric space sigma-models." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-06112018-011344/.
Nesta tese revisamos alguns aspectos das deformações de Yang-Baxter de modelos sigma em espaços semi-simétricos. Damos uma breve revisão do modelo sigma de supercordas e, em seguida, oferecemos uma introdução ao método de deformação de Yang-Baxter. Em seguida, mostramos como obter uma deformação integrável do modelo sigma híbrido. Além disso, mostramos que o dual gravitacional da teoria ABJM beta-deformada pode ser obtida como uma deformação de Yang-Baxter. Isso é feito selecionando-se uma combinação conveniente de geradores de Cartan para construir uma matriz r Abeliana satisfazendo a equação clássica de Yang-Baxter.
Gupta, Vivek. "Probability of SLA Violation for Semi-Markov Availability." Ohio University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1235610777.
Sabbir, Md Mainul Hasan. "Accuracy of semi-infinite diffusion theory to estimate tissue hemodynamics in layered slab models." Miami University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=miami1627383040154061.
Kat, Cor-Jacques. "Suspension forces on a tri-axle air suspended semi-trailer." Diss., Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-06242009-153546/.
Johannessen, Irene. "Thrust allocation in semi-submersible rig using model predictive control." Thesis, Norwegian University of Science and Technology, Department of Engineering Cybernetics, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-8843.
A thrust allocation system is used to determine how the desired forces, computed by a high level control sytem, can be distributed among the thrusters. The main goal of the thrust allocation is to obtain the desired force, but other objectives can also be included. Such secondary goals can be to minimize fuel consumption, keep wear and tear of the thruster to a minimum and avoid overloading the power systems. The thrust allocation should also take forbidden sectors and actuator rate constraints into account. It is essential to safe operation that the allocation system provides a solution, and provides the solution in time. In this thesis MPC (Model predictive control) is suggested as a method to solve the control allocation problem for CyberRig I (a scaled model of a semi-submersible drilling unit). 3 MPC algorithms are simulated in matlab, and the most complete are chosen for on-line implementation. The algorithm is based on an extended thrust formulation, and allows for rotatable thrusters. The cost function penalizes change in thust magnitude and in the azimuth angle. Forbidden sector constraints and rate constrains, both for thrust magnitude and angle, are implemented. It is shown in simulations that the MPC algorithm performs well in comparison with an existing quasi-static method. Its main benefit over the quasi-static method is the ability to handle constraints. The cost of using MPC is increased computational efforts.
Allison, Anne-Marie E. "Analytical investigation of a semi-empirical flow-induced vibration model." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0014/NQ31170.pdf.
Hagi-Bishow, Mohamed. "Assessment of LEACHM-C model for semi-arid saline irrigation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0007/MQ44178.pdf.
Ford, D. C. "A semi-empirical model of the spectra of dusty galaxies." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599112.
Almeida, Ricardo Carvalho de. "Simulation of atmospheric frontogenesis with a semi-Lagrangian numerical model." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/28536.
Hamzat, Kadri Obafemi. "A semi-mechanistic model based on oil expression from groundnuts." Thesis, Cranfield University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333986.
Zhang, Longyu. "A QoE Model to Evaluate Semi-Transparent Augmented-Reality System." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/38833.
Bryson, Louise Kay. "An erosion and sediment delivery model for semi-arid catchments." Thesis, Rhodes University, 2016. http://hdl.handle.net/10962/2892.
Prenzel, Oliver. "Process model for the development of semi-autonomous service robots." Aachen Shaker, 2009. http://d-nb.info/996919937/04.