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Zhou, Xiaobin. "Mathematical and Physical Simulations of BOF Converters." Doctoral thesis, KTH, Tillämpad processmetallurgi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-175462.
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The purpose of this study is to develop mathematical models to explore the mixing and its related phenomena in converter bath. Specifically, first, a mathematical model of a physical model converter, which was scaled down to 1/6th of a 30 t vessel, was developed in this study. A number of parameters were studied and their effects on the mixing time were recorded in a top blown converter. Second, a mathematical model for a combined top-bottom blown was built to investigate the optimization process. Then, a side tuyere was introduced in the combined top-bottom blown converter and its effects on the mixing and wall shear stress were studied. Moreover, based on the above results, the kinetic energy transfer phenomena in a real converter were investigated by applying the mathematical models. A simplified model, in which the calculation region was reduced to save calculation compared to simulations of the whole region of the converter, was used in the mathematical simulation. In addition, this method was also used in the simulation of real converters. This approach makes it possible to simulate the Laval nozzle flow jet and the cavity separately when using different turbulence models. In the top blown converter model, a comparison between the physical model and the mathematical model showed a good relative difference of 2.5% and 6.1% for the cavity depth and radius, respectively. In addition, the predicted mixing time showed a good relative difference of 2.8% in comparison to the experimental data. In an optimization of a combined top-bottom blown converter, a new bottom tuyere scheme with an asymmetrical configuration was found to be one of the best cases with respect to a decreased mixing time in the bath. An industrial investigation showed that the application effects of the new tuyere scheme yield a better stirring condition in the bath compared to the original case. Furthermore, the results indicated that the mixing time for a combined top-bottom-side blown converter was decreased profoundly compared to a conventional combined top-bottom blown converter. It was found that the side wall shear stress is increased by introducing side blowing, especially in the region near the side blowing plume. For a 100 t converter in real, the fundamental aspects of kinetic energy transfer from a top and bottom gas to the bath were explored. The analyses revealed that the energy transfer is less efficient when the top lance height is lowered or the flowrate is increased in the top blowing operations. However, an inverse trend was found. Namely, that the kinetic energy transfer is increased when the bottom flowrate is increased in the current bottom blowing operations. In addition, the slag on top of the bath is found to dissipate 6.6%, 9.4% and 11.2% for the slag masses 5, 9 and 15 t compared to the case without slag on top of the surface of the bath, respectively.<br><p>QC 20151015</p>
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Machekhin, Yu P. "Measurement of non physical quantities." Thesis, XXI IMEKO World Congress, Prague, Czech Republic, 2015. http://openarchive.nure.ua/handle/document/8669.
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The work focused on the development of measurement methods in non-physical areas of human activity. Analyzed not technical activities of a person lying in the fields of social, biological, economic and other areas where no standards or measurement procedures, built on mathematical and physical models. It is shown that for measuring physical quantities it is necessary to use methods that provide measurements and processing of measurement results. Implementation of measurements of physical quantities for which there are no reference values, is possible only in the case when a connection is established between the test value and operating parameters, which is in the nature of the scales. The basis of these scales are measured intervals of time during which the dynamic system is returned to a stable state.
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Böhm, Ulrike, Gesche Pospiech, Hermann Körndle, and Susanne Narciss. "Physicists use mathematics to describe physical principles an mathematicians use physical phenomena to illustrate mathematical formula - Do they really mean the same?" Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-82341.
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Matthews, Amanda. "A Mathematical Model for Anti-Malarial Drug Resistance." VCU Scholars Compass, 2009. http://scholarscompass.vcu.edu/etd/1721.
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Despite the array of medical advances of our modern day society, infectious diseases still plague millions of people worldwide. Malaria, in particular, causes substantial suffering and death throughout both developed and developing countries. Aside from the socioeconomic challenges presented by the disease's prevalence in impoverished nations, one of the major difficulties scientists have encountered while attempting to eradicate the disease is the parasite's ability to become resistant to new drugs and methods of treatment. In an effort to better understand the dynamics of malaria, we analyze a mathematical model that accounts for both the treatment aspect as well as the drug resistance that accompanies it. Simulations demonstrating the effects of treatment rates and the level of resistance are studied and discussed in hopes of shedding additional light on the characteristics of this devastating epidemic.
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Paul-Michael, Salomonsky. "A Mathematical System for Human Implantable Wound Model Studies." VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/3187.
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Dermal wound healing involves a myriad of highly regulated and sophisticated mechanisms, which are coordinated and carried out via several specialized cell types. The dominant players involved in this process include platelets, neutrophils, macrophages and fibroblasts. These cells play a vital role in the repair of the wound by orchestrating tasks such as forming a fibrin clot to stanch blood flow, removing foreign organisms and cellular debris, depositing new collagen matrix and establishing the contractile forces which eventually bridge the void caused by the initial infraction.\\[5pt] \indent Our current understanding of these mechanisms has been primarily based upon animal models. Unfortunately, these models lack insight into pathologic conditions, which plague human beings, such as keloid scar or chronic ulcer formation. Consequently, investigators have proposed a number of {\it in vivo} techniques to study wound repair in humans in order to overcome this barrier. One approach, which has been devised to increase our level of understanding of these chronic conditions, involves the cutaneous placement of a small cylindrical structure within the appendage of a human test subject.\\[5pt] \indent Researches have designed a variety of these implantable structures to examine different aspects of wound healing in both healthy subjects and individuals that experience some trauma related condition. In each case, several implants are surgically positioned at multiple locations under sterile conditions. These structures are later removed at distinct time intervals at which point they are histologically analyzed and biochemically assayed to deduce the presence of biological markers involved in the repair process. Implantable structures used in this way are often referred to as Human Implantable Models or Systems.\\[5pt] \indent Clinical studies with implantable models open up tremendous opportunities in fields such as biomathematics because they provide an experimentally controlled setting that aids in the development and validation of mathematical models. Furthermore, experiments carried out with implants greatly simplify the mathematics required to describe the repair process because they minimize the modeling of complex features associated with healing such as wound geometry and the evolution of contractile forces.\\[5pt] \indent In this work, we present a notional mathematical model, which accounts for two fundamental processes involved in the repair of an acute dermal wound. These processes include the inflammatory response and fibroplasia. Our system describes each of these events through the time evolution of four primary species or variables. These include the density of initial damage, inflammatory cells, fibroblasts and deposition of new collagen matrix. Since it is difficult to populate the equations of our model with coefficients that have been empirically derived, we fit these constants by carrying out a large number of simulations until there is reasonable agreement between the time response of the variables of our system and those reported by the literature for normal healing. Once a suitable choice of parameters has been made, we then compare simulation results with data obtained from clinical investigations. While more data is desired, we have a promising first step toward describing the primary events of wound repair within the confines of an implantable system.
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Sen, Sagar. "A model-driven approach to design engineered physical systems /." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101173.
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The constant growth in complexity of engineered physical (electrical, mechanical etc.) systems has led to the development of software tools to store and reuse design knowledge to simplify the creation of such systems. Models that encode structure and behaviour of components in the system are currently being developed based on the techniques prescribed by Model Driven Engineering (MDE). We use MDE concepts to develop appropriate modelling formalisms to allow creation of models of a target Engineered Physical System ( EPS) at different levels of abstraction. Each level of abstraction presents a certain view of the EPS to a domain expert in the development team. For instance, a high-level view is suitable for a person in a managerial role. An engineer who deals with the same system at a lower level of abstraction develops a model using idealized physical components. A physicist's concern is the physical meaningfulness of the model. The physicist's model verifies if the model prescribed by the manager via the engineer adheres to the laws of conservation of energy and momentum. Finally, a mathematician or a computer scientist obtains a solution to the constrained equations imposed by the dynamical system by solving it analytically or numerically. This model usually takes the form of a set of Differential Algebraic Equations provided by the physicist.<br>We design model transformations to transform models from a high-level modelling language to lower-level language. We present visual Graph Grammar rules to perform these transformations. We start with a high-level representation of the physical system which is a model in the High-level Physical System Model modelling language. This model is transformed in subsequent steps to a set of trajectories that describe the state of the physical system over time. We show that this hierarchy of transformations to encode knowledge about physical systems drastically reduces design space size at the high-level of abstraction. We search the space of an example EPS using a design heuristic based randomized algorithm to determine the speedup in search due to reduction in the number of design variables.
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Sumner, Neil R. "Calibration of a conceptual rainfall-runoff model using simulated annealing." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 1995. https://ro.ecu.edu.au/theses/1169.
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Simulated annealing (Kirkpatrick et al, 1983) is used to estimate the parameters of a mathematical model that predicts the water yield from a catchment. The calibration problem involves finding the global minimum of a multivariate function that has many extraneous local minima, a situation in which conventional optimisation methods are ineffective. The objective function which quantifies discrepancies between the computed and observed streamflows must be carefully selected to satisfy the least square assumptions. Several published simulated annealing algorithms have been implemented, tested and evaluated using standard test functions. Appropriate cooling schedules are found for each algorithm and test function investigated. The number of function evaluations required to find the minimum is compared to published results for the test functions using either simulated annealing and other global optimisation methods. A new simulated annealing algorithm based on the Hooke and Jeeves (1961) pattern search method is developed and compared with existing algorithms from the literature.
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Bhaskar, Ankush. "Physical understanding and mathematical modeling of geomagnetic field variations during disturbed magnetosphere-ionosphere system." Thesis, Indian Institute of Geomagnetism (IIG), 2016. http://localhost:8080/xmlui/handle/123456789/885.
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A thesis submitted to the University of Mumbai for the Ph.D.(Science) degree in physics under the guidance of Dr. Geeta Vichare<br>The thesis concludes with the following list of major conclusions drawn from the entire study.
• The effect of IMF Bz turnings observed in the equatorial geomagnetic field vari ations indicates that the magnitude of northward Bz does not have the influence on the equatorial ionosphere whereas, the response signatures are mainly con trolled by the magnitudes of southward Bz during both northward and southward
turnings.
• The equivalent current vectors reveal a clockwise (anticlockwise) ionospheric cur rent loop in the afternoon (morning) sector during the main impulse (MI) of the negative pressure impulse (SI−). This indicates an ionospheric twin-cell-vortex current system (DP2) due to field-aligned currents (FACs) associated with the
dusk-to-dawn convection electric field during the MI of the SI−.
• The stochastic variations of EEJ and Sq are in a cross-talk with a net flow of information from EEJ to Sq station for data having time resolutions between 30-120 min. This suggests that the variations in the magnetic field of EEJ are reflected in Sq, indicating EEJ and Sq are coupled systems.
• The physical processes responsible for the geomagnetic storms and Forbush de creases are different, even though they originate due to common interplanetary disturbance like ICMEs and CIRs. For geomagnetic storms, reconnection is the major process whereas, FDs are mainly caused by inhibited diffusion of cosmic
rays into the ICMEs due to enhanced IMF and Vsw. It is observed that expan sion of ICME contributes in early recovery phase whereas the gradual variation of solar wind speed beyond ICME boundaries is responsible for the long duration of FD recovery.
• The developed artificial neural networks are capable in forecasting global SYMH, ASYH indices and locally observed geomagnetic field variations in Indian sector about an hour before, provided the real-time upstream solar wind data is available.
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Anderson, Evelyn Carole. "Anumerical model for the estimation of solar radiation on rugged terrain /." The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487259125218402.
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Brook, Sapoty, and mikewood@deakin edu au. "A physical theory of organisation and consequent neural model of spatio-temporal pattern acquisition." Deakin University. School of Architecture and Engineering, 1987. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20050825.121850.
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A neurone model (the FORMON) is proposed which provides a mathematical explanation for a range of psychological phenomena and has potential in Artificial Intelligence applications. A general definition of organisation in terms of entropy and information is formulated. The concept of microcodes is introduced to describe the physical nature of organisation.
Spatio-temporal pattern acquisition and processing functions attributable to individual neurones are reviewed. The criterion for self-organisation in a neurone is determined as the maximisation of mutual organisation. A feedback control system is proposed to satisfy this criterion and provide an integrated long-term memory of spatio-temporal pattern. This pattern acquisition system is shown to be applicable to dendritic pattern recognition and axonal pattern generation. Provision is also made for adaptation, short-term memory and operant learning.
An electro-chemical model of transmission and processing of neural signals is outlined to provide the pattern acquisition functions of the Formon model. A transverse magnetic mode of electrotonic propagation is postulated in addition to the transverse electromagnetic mode.
Configurations of the Formon are categorised in terms of possible pattern processing functions. Connective architectures are proposed as self-organising models of acquisitive semantic and syntactic networks.
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Racheal, Cooper. "Analysis of Mathematical Models of the Human Lung." VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/3289.
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The processes of lung ventilation and perfusion, diffusion, and gas transport make up the system of breathing and tissue oxygenation. Here, we present several mathematical formulations of the essential processes that contribute to breathing. These models aid in our understanding and analysis of this complex system and can be used to form treatments for patients on ventilators. With the right analysis and treatment options, patients can be helped and money can be saved. We conclude with the formulation of a mathematical model for the exchange of gasses in the body based on basic reaction kinetics.
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Lee, Jeffrey K. "A model for solving the capacitated facility location with multiple feasible facility sizes and an evaluation of a microcomputer based solution method." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/24358.
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Thomas, Brian Gordon. "Investigation of panel crack formation in steel ingots using mathematical and physical models." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25980.
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An investigation of panel crack formation in steel ingots was undertaken
to improve understanding of the mechanisms by which they develop and to evaluate possible solutions to the problem. The investigation revealed that two distinct types of panel cracks, both of which are partly caused by intermediate-temperature embrittlement of steel involving aluminum nitride precipitation, operate under different mechanisms. Isothermal, physical modelling experiments were conducted to determine the flow patterns, velocity profiles and flame geometry in a bottom-fired soaking pit and the resultant effects on heat transfer. An investigation involving comparison with analytical solutions determined the optimum numerical method to employ for the mathematical modelling of complex, two-dimensional, transient, heat-conduction problems. This method was formulated to calculate the temperature distribution in a steel ingot during the various processing stages from initial casting up to rolling and was verified with industrial measurements. A transient, elasto-visco-plastic, thermal-stress model employing the finite-element method was formulated, developed and verified using analytical solutions. Based on the temperatures calculated by the finite-element, heat-transfer model as input data, the transient, internal stress state of the ingot was calculated, taking into account the effects of phase-transformation volume changes and kinetics, creep, and temperature-dependent mechanical property behavior. The simulated stress histories were found to be directly linked to the progress of the phase-transformation front and were used to clarify the role of stress generation in panel crack formation. Finally, the results of a metallurgical investigation of steel ingot samples containing off-corner panel cracks were synthesized with the results of the physical and mathematical models to determine mechanisms and to suggest solutions for the formation of both mid-face and off-corner panel cracks. Mid-face panel cracks are apparently formed during air cooling when the mid-face surface is between the Ar₁ and 500 °C. Off-corner panel cracks appear to initiate internally during the early stages of reheating, but do not propagate to the surface until air cooling after removal from the soaking pit.<br>Applied Science, Faculty of<br>Mining Engineering, Keevil Institute of<br>Graduate
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Schmidtt, David Marmolejo. "Two loop super-WZNW model with reductions to supersymmetric and fermionic integrable models/." São Paulo, 2009. http://hdl.handle.net/11449/132737.
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Orientador: José Francisco Gomes<br>Banca: Luiz Agostinho Ferreira<br>Banca: Francesco Toppan<br>Banca: Marco Aurélio Cattacin Kneipp<br>Banca: Clisthenis Ponce Constantinidis<br>Resumo: Nessa tese se constrói o funcional de ação dos modelos de Toda supersimétricos afins e se deduzem as transformações de supersimétria dos modelos desde o ponto de vista de fluxos de simetria Fermionicos. A integrabilidade é definida em termos de um problema de fatorização de Riemann-Hilbert estendido que unifica parâmetros de evolução Abelianos e não Abelianos. Se introduzem modelos integráveis puramente Fermionicos definidos em supercosets onde toda a parte Bosonica é completamente eliminada. Vários exemplos são considerados<br>Abstract: In this thesis we construct the action functional for the supersymmetric affine Toda models and deduce the supersymmetry transformations of the models from the point of view of Fermionic symmetry flows. The underlying Integrability is defined in terms of an extended Riemann-Hilbert factorization problem which unifies Abelian and non-Abelian evolution parameters. We also introduce purely Fermionic Integrable models defined on supercosets where the Bosonic part is completely eliminated. Several examples are consider<br>Doutor
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Wan, Iat-meng, and 溫日明. "Physical characterization of dewatered sewage sludge for landfilling." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31220034.
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Pant, Sudeep Raj. "Mathematical and physical modelling of crack growth near free boundaries in compression." University of Western Australia. School of Civil and Resource Engineering, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0139.
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[Truncated abstract] The fracture of brittle materials in uniaxial compression is a complex process with the development of cracks generated from initial defects. The fracture mechanism and pattern of crack growth can be altered considerably by the presence of a free surface. In proximity of a free surface, initially stable cracks that require an increase in the load to maintain the crack growth can become unstable such that the crack growth maintains itself without requiring further increase in the load. This leads to a sudden relief of accumulated energy and, in some cases, to catastrophic failures. In the cases of rock and rock mass fracturing, this mechanism manifests itself as skin rockbursts and borehole breakouts or as various non-catastrophic forms of failure, e.g. spalling. Hence, the study of crack-boundary interaction is important in further understanding of such failures especially for the purpose of applications to resource engineering. Two major factors control the effect of the free boundary: the distance from the crack and the boundary shape. Both these factors as well as the effect of the initial defect and the material structure are investigated in this thesis. Three types of boundary shapes - rectilinear, convex and concave - are considered. Two types of initial defects - a circular pore and inclined shear cracks are investigated in homogeneous casting resin, microheterogeneous cement mixes and specially fabricated granulate material. The preexisting defects are artificially introduced in the physical model by the method of inclusion and are found to successfully replicate the feature of pre-existing defects in terms of load-deformation response to the applied external load. It is observed that the possibility of crack growth and the onset of unstable crack growth are affected by the type of initial defect, inclination of the initial crack, the boundary shape and the location of the initial defect with respect to the boundary. The initial defects are located at either the centre or edge of the sample. The stresses required for the wing crack initiation and the onset of unstable crack growth is highest for the initial cracks inclined at 35° to the compression axis, lowest at 45° and subsequently increases towards 60° for all the boundary shapes and crack locations. In the case of convex boundary, the stress of wing crack initiation and the stress of unstable crack growth are lower than for the case of rectilinear and concave boundary for all the crack inclinations and crack locations. The crack growth from a pre-existing crack in a sample with concave boundary is stable, requiring stress increase for each increment of crack growth. The stress of unstable crack growth for the crack situated at the edge of the boundary is lower than the crack located at the centre of the sample for all the crack inclinations and boundary shapes.
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Iwuanyanwu, Paul Nnanyereugo. "Pre-service science teachers’ conceptual and procedural difficulties in solving mathematical problems in physical science." Thesis, University of the Western Cape, 2014. http://hdl.handle.net/11394/4002.
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>Magister Scientiae - MSc<br>Students frequently leave first-year physical science classes with a dual set of physical laws in mind- the equations to be applied to qualitative problems and the entrenched set of concepts, many erroneous, to be applied to qualitative, descriptive, or explanatory problems. It is in this sense that the emphasis of this study is on ‘change’ rather than acquisition. Thus, a blend of theoretical framework was considered according to the aim of the study. Of immediate relevance in this regard within the “constructivist paradigm” are: Posner, Strike, Hewson and Gertzog’s (1982) conceptual change theory and the revised Bloom’s Taxonomy. Moreover, the very shift or restructuring of existing knowledge, concepts or schemata is what distinguishes conceptual change from other types of learning, and provides students with a more fruitful conceptual framework to solve problems, explain phenomena, and function in the world (Biemans & Simons, 1999; Davis, 2011). A quasi-experimental design was adopted to explore pre-service teachers’ conceptual and procedural difficulties in solving mathematical problems in physical science. Sixteen second and third year pre-service teachers in one of the historically black universities in the Western Cape, South Africa, participated in the study. Two inseparable concepts of basic mechanics, work-energy concepts were taught and used for data collection. Data were collected using questionnaires, Physical Science Achievement Test (PSAT), Multiple Reflective Questions (MRQ) and an interview. An explicit problem solving strategy (IDEAL strategy versus maths-in-science instructional model) was taught in the intervention sessions for duration of three weeks to the experimental group (E-group). IDEAL strategy placed emphasis on drill and practice heuristics that helped the pre-service teachers’ (E-group) understanding of problem-solving. Reinforcing heuristics of this IDEAL strategy include breaking a complex problem into sub-problems. Defining and representing problem (e.g. devising a plan-using Free-Body-Diagram) was part of the exploring possible strategies of the IDEAL. More details on IDEAL strategy are discussed in Chapter 3. The same work-energy concepts were taught to the control group (C-group) using lecture-demonstration method. A technique (i.e. revised taxonomy table for knowledge and cognitive process dimension) was used to categorize and analyse the level of difficulties for each item tested (e.g. D1 = minor difficulty, D2 = major difficulty, and D3 = atypical difficulty
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Garrett, Susan R. "A mathematical model for the detection of deep space objects." Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/90970.
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The problem of detecting deep space objects with certain probabilities was investigated. A mathematical model was then developed from given problem specifications that deals with the trade-off of various parameters involved in the detection problem.
A software package that allows the user to input data interactively was written to implement the model. The completed program as well as an analysis of the tested results are included.<br>M.S.
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Ho, Yanfang. "Group theoretical analysis of in-shell interaction in atoms." Scholarly Commons, 1985. https://scholarlycommons.pacific.edu/uop_etds/487.
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A group theoretic approach to Layzer's 1/2 expansion method is explored. In part this builds on earlier work of Wulfman(2), of Moshinsky et al(l4), and of Sinanoglu, Herrick(lS), and Kellman (16) on second row atoms.
I investigate atoms with electrons in the 3s-3p-3d shell and find:
1. Wulfman's constant of motion accurately predicts configuration mixing for systems with two to eight electrons in the 3s-3p subshell.
2. The same constant of motion accurately predicts configuration mixing for systems with two electrons in the 3s-3p-3d shell.
3. It accurately predicts configuration mixing in systems of high angular momentum L and of high spin angular momentum S containing three electrons in the 3s-3p-3d shell, but gives less accurate results when L and S are both small.
I also show how effective nuclear charges may be calculated by a group theoretical approach. In addition I explore several new methods for expressing electron repulsion operators in terms of operators of the 80(4,2) dynamical group of one - electron atoms.
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Park, Soojin. "Modelling soil-landform continuum on a three-dimensional hillslope." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670238.
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Brooks, Jeremy. "A Singular Perturbation Approach to the Fitzhugh-Nagumo PDE for Modeling Cardiac Action Potentials." Digital Commons @ East Tennessee State University, 2011. https://dc.etsu.edu/honors/152.
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The study of cardiac action potentials has many medical applications. Dr. Dennis Noble first used mathematical models to study cardiac action potentials in the 1960s. We begin our study of cardiac action potentials with one form of the Fitzhugh-Nagumo partial differential equation. We use the non-classical method to produce a closed form solution for the decoupled Fitzhugh Nagumo equation. Using voltage recording data of action potentials in a cardiac myocyte and in purkinje fibers, we estimate parameter values for the closed form solution with standard linear and non-linear regression methods. Results are limited, thus leading us to perturb the solution to obtain a better fit. We turn to singular perturbation theory to justify our pole-based approach. Finally, we test our model on independent action potential data sets to evaluate our model and to draw conclusions on how our model can be applied.
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Li, Xun. "Physical systems for the active control of transformer noise." Title page, contents and abstract only, 2000. http://hdl.handle.net/2440/37964.
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Traditional means of controlling sound radiated by electrical power transformers involve the construction of large expensive barriers or full enclosures, which cause maintainability and cooling problems. One promising alternative is to use active noise control to cancel the noise. This thesis is concerned with one of the many problems which need to be investigated to develop a practical active noise cancellation system for transformers. This work, in particular, is concerned with the physical system design which includes the selection of the control source types and the evaluation of the near-field sensing strategies. Loudspeakers have been widely used in the past as an acoustic source for canceling transformer noise. The principal disadvantage of using loudspeakers is that to achieve global noise control, a large number, driven by a multi-channel controller, are required. However, if large panels are used in place of loudspeakers as control sources, it is possible that the number of the control sources and complexity of the controller could be reduced substantially. In addition to reducing the number of control sources and simplifying their application, panel sound sources could also overcome some disadvantages of the loudspeakers, such as limited life and deterioration due to the weather. Thus, part of the work described in this thesis is concerned with the development of a resonant curved panel with a backing cavity as an acoustic type source. The advantages of using a curved panel rather than a flat panel are twofold: first a curved panel is more easily excited by the extensional motion of the piezoelectric patch actuators; and second, it is more difficult to adjust the resonance frequencies of the efficient modes of a flat panel than of a curved panel. The analytical models for the design of the panel cavity systems have been developed. As an example, a resonant curved panel with a backing cavity system was constructed and the sound radiation of the system was measured. Results show that a resonant panel-cavity sound source could be used as an alternative to a number of loudspeakers for active cancellation of electric power transformer noise. Due to the advantages of using the vibration type control sources, two types of vibration control sources (inertial electrodynamic shakers and piezoelectric patch actuators) were considered and the mechanical output of the inertial shakers has been compared with that of the piezoelectric actuators. In contrast with the piezoelectric actuators, the resonance frequencies of the inertial shakers can be tuned to the frequencies of interest using simple tuning procedures, so that the output efficiency of the shakers can be increased. The output performance was evaluated for two types of actuators by measuring the structural response of either a panel or a transformer when excited by the actuators at half their rated voltage input. Results demonstrated that a much larger output amplitude at the frequency of interest can be achieved by the tuned inertial type actuators. Two near-field sensing strategies, the minimization of the sum of the sound intensities and the minimization of the sum of the squared sound pressures, have been studied. A quadratic expression was derived for the minimization of the sum of the sound intensities in the near-field. To evaluate the control performances achieved using both sensing strategies, a flat-panel was modelled with a harmonic point force disturbance and several point force control sources. Simulation results show that the control performance could be improved by minimizing the sum of the sound intensities in the hydrodynamic near-field, provided that a very large number of error sensors were used, otherwise better results were achieved using near-field squared pressure sensing. Both sensing strategies were used to predict the noise reductions that resulted for the active noise control of a small transformer in the laboratory environment and for a large electrical power transformer on site. To optimize the locations of the control sources (for the large transformer on site) and the locations of the error sensors (for the small transformer in the laboratory environment), a genetic algorithm (GA), which is an evolutionary optimization technique, was employed as a search procedure to optimize the control source and error sensor locations. The results showed that the control source locations and/or the error sensor locations must be optimized to achieve the maximum sound reduction for either error sensing strategy, especially for the sound intensity minimization; otherwise, the sound field level may increase after control due to the character of the cost function (the sum of the sound intensities). The simulation results were experimentally validated for the small transformer in the laboratory environment. Due to the limitation of the number of controller channels, the control performance was only evaluated for squared pressure minimization. The results demonstrated that for the case of 8 control sources and 8 error sensors, at 100 Hz, an average sound pressure reduction of 15.8 dB was achieved when evaluated at 528 monitoring locations at 0.25 m intervals on a surface that surrounded the transformer.<br>Thesis (Ph.D.)--Engineering (Department of Mechanical Engineering), 2000.
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Bouraoui, Faycal. "Development of a continuous, physically-based distributed parameter, nonpoint source model." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-10192006-115604/.
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Dasci, Abdullah. "Discrete and continuous models for production-distribution systems." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37625.
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This thesis presents a series of integrated models for simultaneous optimization of location, capacity, product range, and production technology decisions in production-distribution systems. The interactions between these decisions can be significant. This thesis draws its motivation from these interactions. In order to benefit from the capital and/or employment subsidies, preferential tax rates, and free trade zones provided by governments, firms need to take the interdependencies between their location, capacity and technology decisions into account. These decisions could be further complicated due to varying scale and scope economies inherent in different production technologies.<br>The models proposed in this thesis are based on two fundamentally different but equally central approaches. The first approach builds on traditionally popular integer programming formulation in facility location theory, in which two such models presented in this thesis. The first one assumes that there are a number of dedicated production technologies for each product whereas, the second one assumes that a set of flexible technologies is also present. Analytical properties of the models are described, which lead to the development of exact and heuristic solution procedures. Results of several sets of computational experiments are also reported. The second approach is based on continuous approximation (also known as continuum mechanics), which has not been used to its potential in the literature. The third model in this thesis is proposed for a system with single product. It is based on the use of continuous functions in representing spatial distribution of cost parameters and decision variables. In this model, the focus is to compute the service regions leaving the precise plant locations to a subsequent analysis. This model lends itself to closed form solutions and allows derivation of a number of insights on the impact of several cost factors on facility design decisions. Then, it is utilized in an analytical framework to analyze several plant focus decisions of firms in a multi-product environment. The closed form solution is used to analyze several product and market focus strategies, which have provided several insights into more sophisticated plant focus decisions and into the impact of different production technologies on these decisions.
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O'Neil, Nicole. "An Agent Based Model of Tumor Growth and Response to Radiotherapy." VCU Scholars Compass, 2012. http://scholarscompass.vcu.edu/etd/2831.
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An agent based model was developed to examine the growth of a tumor in a healthy cell population. Response to radiation and impact of mutation and bystander effects were studied. In the growth model, the cancer cells proliferated outward becoming invasive. The mass of cancer cells developed a necrotic core. Various treatment protocols of radiation were compared. Timing of treatments was critical to the success of therapy. The event of mutation was rare. When mutation occurred, either unsuccessful treatment or re-growth could result. Multiple rounds of radiation potentially led to increased mutation. Low levels of the bystander effect had little impact on the overall behavior of the system when considered alone and in combination with mutation. Higher levels of bystander effect and increased affected area resulted in significant cell death. Increasing the radius of the bystander effect in combination with mutation resulted in large numbers of mutation and unsuccessful treatment.
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Hillmer, Kiekebusch Ingrid Andrea. "Scales of interactions between physical processes, primary producers and nutrients in aquatic ecosystems." University of Western Australia. Centre for Water Research, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0177.
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[Truncated abstract] Estimating internal biogeochemical fluxes is essential to the understanding of the dynamic of aquatic ecosystems. Different ecological approaches have been used to gain insight into the internal cycling, but success has been limited. A critical point is the identification of the characteristic scales of patterns and the underlying processes affecting the behaviour of biological and chemical species. Failing to capture these scales leads to misinterpretation of field and numerical data. In this study, key aspects in the design of ecological surveys are identified to ensure that the internal biogeochemical processes are well represented. In the first part of this thesis, a 1D reaction-diffusion-advection equation is used to investigate the formation of patterns and relevant time and spatial scales. This is used to define an approach for the determination of a critical domain size that allows differentiation of the role of local and internal cycling from advective fluxes across the open boundaries in a shallow coastal ecosystem. By using a 3D numerical model, in conjunction with an extensive field data set, it is shown that domain sizes must be larger than this critical value in order to capture the patterns generated within the system. For smaller domains, transport processes control the evolution of the system across the boundaries misleading the interpretation of the internal ecological dynamics. The study of the influence of boundary fluxes on ecological patchiness was motivated by the need to define the size of the domain necessary for the assessment of the impact of a sewage outflow on a coastal regime. The quantification of biogeochemical processes has proven to be difficult to achieve especially under conditions of high spatial and temporal hydrodynamic and biogeochemical variability. In the second part of this thesis, a Lagrangian experimental design is employed to estimate biogeochemical rate coefficients in situ. A set of four drogues and a cross-transect sampling design is used to capture the patchy distribution of phytoplankton and nutrient species, and high transport and mixing rates. ... Total chlorophyll from both models shows similar behavior when the variability in the 3D model, expressed as Chlamax/Chlamin, is low. When Chlamax/Chlamin is high, the difference between the biomass predicted by the two models reaches 30% due to the generation of localised patches. Comparison of the 1D and 3D results highlights the need of using models that are able to resolve the spatial complexity to some extent, as the use of averaged properties may produce misleading results. This is especially important in the presence of patches with differential physiological and biogeochemical characteristics, and nonlinear processes, in which case biomass average is not necessarily linearly related to the averaged environment.
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de, la Puente Alejandro M. "Kaon photoproduction of the proton: contribution of higher angular momentum and energy resonances to the cross-section and polarization asymmetries through an effective Lagrangian model." FIU Digital Commons, 2008. http://digitalcommons.fiu.edu/etd/3014.
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The differential cross-section and polarization observables in the process γ + p --> K++ Λ are studied within an isobaric approach that includes resonances with total angular momentum J ≤ 5/2 over a center of mass energy range from W = 1.6 GeV to W=2.6 GeV. The model is used to fit recent experimental data as a function of the coupling products at the photon and strong vertices for the well established low energy resonances, as well as the total decay width for the high energy less well-established resonances.
The model employed in this study is based on an effective hadronic lagrangian using a tree-level approximation. The model uses Feynman diagrammatic techniques to extract the interaction vertices at a first order level in perturbation theory.
To extract the coupling strength products involved in the reaction, a X2- minimization technique is used to fit experimental data. The results suggests that both differential cross-section and double polarization observables need to be fit simultaneously to obtain an accurate description of the data. In addition, it was found that while resonances with angular momentum J= 5/2 do not couple strongly to the KΛ channel, higher energy states with J = 3/2 do couple strongly to the KΛ channel and are highly relevant for an accurate description of the data at energies beyond 1.9 GeV.
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Kaspi, Yohai. "Turbulent convection in the anelastic rotating sphere : a model for the circulation on the giant planets." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45780.
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Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2008.<br>Includes bibliographical references (p. 207-221).<br>This thesis studies the dynamics of a rotating compressible gas sphere, driven by internal convection, as a model for the dynamics on the giant planets. We develop a new general circulation model for the Jovian atmosphere, based on the MITgcm dynamical core augmenting the nonhydrostatic model. The grid extends deep into the planet's interior allowing the model to compute the dynamics of a whole sphere of gas rather than a spherical shell (including the strong variations in gravity and the equation of state). Different from most previous 3D convection models, this model is anelastic rather than Boussinesq and thereby incorporates the full density variation of the planet. We show that the density gradients caused by convection drive the system away from an isentropic and therefore barotropic state as previously assumed, leading to significant baroclinic shear. This shear is concentrated mainly in the upper levels and associated with baroclinic compressibility effects. The interior flow organizes in large cyclonically rotating columnar eddies parallel to the rotation axis, which drive upgradient angular momentum eddy fluxes, generating the observed equatorial superrotation. Heat fluxes align with the axis of rotation, contributing to the observed flat meridional emission. We show the transition from weak convection cases with symmetric spiraling columnar modes similar to those found in previous analytic linear theory, to more turbulent cases which exhibit similar, though less regular and solely cyclonic, convection columns which manifest on the surface in the form of waves embedded within the superrotation. We develop a mechanical understanding of this system and scaling laws by studying simpler configurations and the dependence on physical properties such as the rotation period, bottom boundary location and forcing structure. These columnar cyclonic structures propagate eastward, driven by dynamics similar to that of a Rossby wave except that the restoring planetary vorticity gradient is in the opposite direction, due to the spherical geometry in the interior.<br>(cont.) We further study these interior dynamics using a simplified barotropic annulus model, which shows that the planetary vorticity radial variation causes the eddy angular momentum flux divergence, which drives the superrotating equatorial flow. In addition we study the interaction of the interior dynamics with a stable exterior weather layer, using a quasigeostrophic two layer channel model on a beta plane, where the columnar interior is therefore represented by a negative beta effect. We find that baroclinic instability of even a weak shear can drive strong, stable multiple zonal jets. For this model we find an analytic nonlinear solution, truncated to one growing mode, that exhibits a multiple jet meridional structure, driven by the nonlinear interaction between the eddies. Finally, given the density field from our 3D convection model we derive the high order gravitational spectra of Jupiter, which is a measurable quantity for the upcoming JUNO mission to Jupiter.<br>by Yohai Kaspi.<br>Ph.D.
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Desatová, Martina. "Numerické modelování proudění v bezpečnostním přelivu vybraného vodního díla." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2020. http://www.nusl.cz/ntk/nusl-409714.
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This thesis deals with mathematical modelling of water flow through the safety object. It explains the principle of mathematical modelling and its laws. There is also present-ed the mathematical models used by numerical modelling. The results of mathemati-cal model Koryčany are included in this thesis compared with hydraulic calculations and physical model.
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García, Iturbe Selma L. "Simulation of physical and chemical processes in reservoirs: Two case studies." Thesis, University of North Texas, 2005. https://digital.library.unt.edu/ark:/67531/metadc4968/.
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Managing water quality aspects requires the use of integrative tools that allow a holistic approach to this problem. Water quality models coupled to hydrodynamic models are these tools. This study presents the application of the water quality model WASP coupled to the hydrodynamic model DYNHYD for two distinct reservoirs: Lake Texoma and Tocoma Reservoir. Modeling the former included simulations of water velocities, water level, and four chemical and physical compounds: chlorides, dissolved oxygen (DO), biochemical oxygen demand (BOD), and total suspended solids (TSS); and validation of the results by comparing with observed values during March - May, 1997. The latter is still under project status and the simulation was performed in a prospective way. The analysis included simulations of water velocities under current and for expected conditions, DO and BOD. Both models, DYNHYD and WASP, fitted pretty well to observed conditions for Lake Texoma and for where Tocoma Reservoir has been planned. Considering management and decision support purposes, the role of boundary and loading conditions also was tested. For Lake Texoma, controlling boundary conditions for chlorides is a determinant factor for water quality of the system. However, DO and TSS in the reservoir are governed by additional process besides the condition of the boundary. Estimated loadings for this system did not provided significant effects, even though the allocation of a load for chlorides resulted in significant changes in the trend for expected chloride concentrations at the Washita River Arm of Lake Texoma. For Tocoma Reservoir, the expected concentration of DO all over the reservoir is going to driven by boundary conditions, as well as by the management of autochthonous BOD loadings provided by vegetation decomposition. These two factors will be determinant for the resulting water quality of the future reservoir.
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Osei, Ofosuhene. "Level Crossing Times in Mathematical Finance." Digital Commons @ East Tennessee State University, 2013. https://dc.etsu.edu/etd/1126.
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Level crossing times and their applications in finance are of importance, given certain threshold levels that represent the "desirable" or "sell" values of a stock. In this thesis, we make use of Wald's lemmas and various deep results from renewal theory, in the context of finance, in modelling the growth of a portfolio of stocks. Several models are employed .
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Leos, Zamorategui Arturo. "On the interface between physical systems and mathematical models : study of first-passage properties of fractional interfaces and large deviations in kinetically constrained models." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC183/document.
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La thèse décrit les propriétés d’équilibre et hors d’équilibre de modèles mathématiques stochastiques de systèmes physiques. À l’aide de simulations numériques, on étudie les fluctuations des différentes quantités mais on s’interesse aussi aux grands déviations dans certains systèmes. La première partie de la thèse se concentre sur l’étude des interfaces rugueuses observées dans des processus de croissance. Ces interfaces sont simulées avec des nouvelles techniques de programmation en parallèle qui nous permettent d’accéder à des systèmes de très grande taille. D’une part, on discute le cas diffusif, représenté par l’équation d’Edward-Wilkinson dans des interfaces périodiques, pour lequel on obtient une solution exacte de l’équation discrète dans l’espace de Fourier. Avec cette solution on déduit le facteur de structure associé aux amplitudes des modes et l’expression exacte est comparée avec les valeurs numériques. De plus, on fait le lien entre les propriétés de premier passage des interfaces et le mouvement Brownien. On mesure la distribution des longueurs des intervalles et on compare les résultats avec une version modifiée du théorème de Sparre-Andersen. D’autre part, on étudie le cas général qui inclut les cas sous-diffusif et superdiffusif avec des conditions de bord périodiques. On étudie pour ces interfaces fractionnaires des propriétés de premier passage liées aux zéros des interfaces. Dans l’état stationnaire, on étudie également les premiers cumulants et propriétés d’échellement de la longueur des intervalles et de la densité de zéros. De plus, on mesure la largeur typique de l’interface et ses propriétés d’échellement. Finalement, on analyse le comportement de ces observables dans les interfaces hors d’équilibre et on discute leur dépendance en la taille du système. On discute également les conditions de stabilité des solutions del’équation discrète, importantes pour les simulations des interfaces. Dans une deuxième partie, on étude la transition de phase dynamique dans des modèles cinétiquement contraints afin d’étudier la transition vitreuse observée dans des verres structuraux. Pour un modèle en dimension un, on étudie la géométrie spatio-temporelle des bulles d’inactivité qui caractérisent les hétérogénéités dynamiques observées dans les verres. On trouve que les directions spatiales et temporelles des bulles ne sont pas liées par un comportement diffusif. En contraste, on confirme l’échellement de l’aire et d’autres quantités attendues pour un système, a priori diffusif. De plus, grâce à la théorie des grandes déviations et l’algorithme de clonage, on identifie la transition de phase dynamique dans des systèmes en deux dimensions spatiales. D’abord on mesure l’énergie libre dynamique pour différentes valeurs du paramètre λ. Après, on conjecture des valeurs critiques λ c = Σ/K, avec Σ la tension surface d’une ı̂le de sites actifs entourée par des sites inactifs dans un modèle effectif et K l’activité moyenne du système, pour laquelle la transition de phase a lieu dans la limite de taille infinie. En mesurant l’activité du système et le nombre d’occupation, on observe la dépendance de ces observables avec la taille des systèmes étudiés loin de la transition. Finalement, on mesure la propagation du front des sites actifs dans tout les systèmes. Pour l’un des systèmes étudiés, on identifie une vitesse balistique du front qui nous permet d’observer la transition de phase d’un point de vue dynamique<br>This thesis investigates both equilibrium and nonequilibrium properties of mathematical stochastic models that as a representation of physical systems. By means of extensive numerical simulations we study mean quantities and their fluctuations. Nonetheless, in some systems we are interested also in large deviations. The first part of the thesis focuses on the study of rough interfaces observed in growth processes. These interfaces are simulated with state-of-the-art simulations based on parallel computing which allow us to study very large systems. On the one hand, we discuss the diffusive case given by the Edward-Wilkinson equation in periodic interfaces. For the discrete version of such an equation, we obtain an analytic solution in Fourier space. Fur-ther, we derive an exact expression of the structure factor related with the modes amplitudes describing the interface and compare it with the numerical values. Moreover, using a mapping between stationary interfaces and the Brownian motion, we relate the distribution of the intervals generated by the zeros of the interface with the first-passage distribution given by a the Sparre-Andersen theorem in the case of the Brownian motion. As a generalization of the results obtained in the diffusive case, we study a linear Langevin equation with a Riesz-Feller fractional Laplacian of order z used to simulate sub- and super-diffusive interfaces. In this general case, we identify three regimes based on the scaling behaviour of the cumulants of the intervallengths, the density of zeros and the width of the interface. Finally, we study the evolution in time of some of the observables introduced before. In the second part of the thesis, we study the dynamical phase transition in kinetically constrained models (KCMs) in order to get some insight on the glass transition observed in structural glasses. In a one-dimensional KCM we study the geometry of the bubbles of inactivity in space-time for systems at different temperatures. We find that the spatial length of the bubbles does not scale diffusively with its temporal duration. In contrast, we confirm a vidiffusive behaviour for other quantities studied. Further, by means of large deviation theory and cloning algorithms, we identify the dynamical phase transition in two-dimensional systems. To start with, we measure numerically the dynamical free energy both by measuring the largest eigenvalue of the evolution operator,for small systems, and via the cloning algorithm, for larger systems. We conjecture a value λ c = Σ/K, with Σ the surface tensionof a bubble of activity surrounded by a sea of inactive sites in an effective interfacial model and K the mean activity of the system, for each of the systems studied. For the activity of the system and the occupation number we discuss their scaling properties far from the phase transition. Starting from an empty system subject to different boundary conditions, we investigate the front propagation of active sites. We argue that the phase transition in this case can be identified by the abrupt slowing-down of the front. This is done by measuring the ballistic speed of the front in the simplest case studied. Finally, we propose an effective model following the Feynman-Kac formula for a moving front.-proprietés de premier passage, interface rugueuse, diffusion fractionnaire , système hors d'équilibre, transition de phase dynamique, modèle cinétiquement contraint, grandes déviations.-first-passage properties, rough interface, fractional diffusion, out-of-equilibrium system, dynamical phase transition, kinetically constrained model, large deviations
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Pihnastyi, O. M. "Statistical two-level model of the production process." Thesis, Apostrophe, 2011. http://repository.kpi.kharkov.ua/handle/KhPI-Press/42134.
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The mathematical model of economical-manufacturing systems with mass production output was constructed. The state of any production system at any time moment is usually given as a point in two-dimensional phase space. The distribution function for the base product is input, and the equation, being analogous to the kinetic equation in Physics, is put down. Both the engineering-production and the generative functions were determined. The closed system of equations for the distribution function moment was put down in the zero approximation. For the closed system of equations of the manufacturing system’s macroscopic state was obtained. The conditions of manufacturing systems stable operating were written down. The connection between the surplus and the pace of base products motion lengthwise the technological chain was shown. The manufacturing process’ disturbed state system of equations for the particular case of the stability theory (the case of one zero roots of the system’s characteristic equation) was considered.
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Lee, Haksu. "Development and performance analysis of a physically based hydrological model incorporating the effects of subgrid heterogeneity." University of Western Australia. School of Environmental Systems Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0129.
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[Truncated abstract] The balance equations of mass and momentum, defined at the scale of what has been defined as a Representative Elementary Watershed (REW) has been proposed by Reggiani et al. (1998, 1999). While it has been acknowledged that the REW approach and the associated balance equations can be the basis for the development of a new generation of distributed physically based hydrological models, four building blocks have been identified as necessary to transform the REW approach into, at the very least least, a workable modelling framework beyond the theoretical achievements. These are: 1) the development of reasonable closure relations for the mass exchange fluxes within and between various REW sub-regions that effectively parameterize the effects of sub-REW heterogeneity of climatic and landscape properties, 2) the design of numerical algorithms capable of generating numerical solutions of the REW-scale balance equations composed of a set of coupled ordinary differential and algebraic equations for the number of REWs constituting a study catchment and the sub-regions within the REWs, 3) applications of the resulting numerical model to real catchments to assess its performance in the prediction of any specified hydrological variables, and 4) the assessment of the model reliability through estimation of model predictive uncertainty and parameter uncertainty. This thesis is aimed at making substantial progress in developing each of these building blocks. Chapter 1 presents the background and motivation for the thesis, while Chapter 2 summarizes its main contributions. Chapter 3 presents a description of the closure problem that the REW approach faces, and presents and implements various approaches to develop closure relations needed for the completeness of balance equations of the REW approach. ... In addition, Chapter 4 also shows an initial application of CREW to a small catchment, Susannah Brook in the south-west of Western Australia. Chapter 5 presents the application of CREW to two meso-scale catchments in Australia, namely Collie and Howard Springs, located in contrasting climates. Chapter 6 presents results of the estimation of predictive uncertainty and parameter sensitivity through the application of CREW to two catchments in Australia, namely Susannah Brook and Howard Springs, by using the Generalized Likelihood Uncertainty Estimation (GLUE) methodology. Finally, Chapter 7 presents recommendations for future work for the further advancement of the REW approach. Through these exercises this PhD thesis has successfully transformed the REW-scale coupled balance equations derived by Reggiani et al. (1998, 1999) into a new, well tested numerical model blueprint for the development and implementation of distributed, physically based models applicable at the catchment, or REW scale.
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Sima, Adam. "Accounting for Model Uncertainty in Linear Mixed-Effects Models." VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/2950.
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Standard statistical decision-making tools, such as inference, confidence intervals and forecasting, are contingent on the assumption that the statistical model used in the analysis is the true model. In linear mixed-effect models, ignoring model uncertainty results in an underestimation of the residual variance, contributing to hypothesis tests that demonstrate larger than nominal Type-I errors and confidence intervals with smaller than nominal coverage probabilities. A novel utilization of the generalized degrees of freedom developed by Zhang et al. (2012) is used to adjust the estimate of the residual variance for model uncertainty. Additionally, the general global linear approximation is extended to linear mixed-effect models to adjust the standard errors of the parameter estimates for model uncertainty. Both of these methods use a perturbation method for estimation, where random noise is added to the response variable and, conditional on the observed responses, the corresponding estimate is calculated. A simulation study demonstrates that when the proposed methodologies are utilized, both the variance and standard errors are inflated for model uncertainty. However, when a data-driven strategy is employed, the proposed methodologies show limited usefulness. These methods are evaluated with a trial assessing the performance of cervical traction in the treatment of cervical radiculopathy.
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Беда, Іван Микитович, Иван Никитич Беда, Ivan Mykytovych Beda та О. М. Молошний. "Застосування визначеного інтеграла до задач природознавства". Thesis, Вид-во СумДУ, 2010. http://essuir.sumdu.edu.ua/handle/123456789/6115.
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Rosen, Mary Ellen Furner. "Mean Square Displacement for a Discrete Centroid Model of Cell Motion and a Mathematical Analysis of Focal Adhesion Lifetimes and Their Effect on Cell Motility." BYU ScholarsArchive, 2021. https://scholarsarchive.byu.edu/etd/8780.
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One of the characteristics that distinguishes living things from non-living things is motility. On the cellular level, the motility or non-motility of different types of cells can be life building, life-saving or life-threatening. A thorough study of cell motion is needed to help understand the underlying mechanisms that enhance or prohibit cell motion. We introduce a discrete centroid model of cell motion in the context of a generalized random walk. We find an approximation for the theoretical mean square displacement (MSD) that uses a subset of the state space to estimate the MSD for the entire space. We give some intuition as to why this is an unexpectedly good estimate. A lower and upper bound for the MSD is also given. We extend the centroid model to an ODE model and use it to analyze the distribution of focal adhesion (FA) lifetimes gathered from experimental data. We found that in all but one case a unimodal, non-symmetric gamma distribution is a good match for the experimental data. We use a detach-rate function in the ODE model to determine how long a FA will persist before it detaches. A detach-rate function that is dependent on both force and time produces distributions with a best fit gamma curve that closely matches the data. Using the data gathered from the matching simulations, we calculate both the cell speed and mean FA lifetime and compare them. Where available, we also compare this relationship to that of the experimental data and find that the simulation reasonably matches it in most cases. In both the simulations and experimental data, the cell speed and mean FA lifetime are related, with longer mean lifetimes being indicative of slower speeds. We suspect that one of the main predictors of cell speed for migrating cells is the distribution of the FA lifetimes.
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Bienen, Britta. "Three-dimensional physical and numerical modelling of jack-up structures on sand." University of Western Australia. School of Civil and Resource Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0208.
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Mobile offshore jack-up drilling rigs are not custom-designed for a particular location but rated for typical operating characteristics, like water depths. They may be deployed at a number of different sites during their design life. Under the current guidelines, the jack-up is required to be assessed for its suitability for each new proposed location, assuming environmental loading conditions due to wind, waves and current corresponding to a 50-year return period storm applicable to the site. Traditionally, these assessments have been performed in two dimensions, simplifying the jack-up to a plane frame and the loading conditions to be in-plane with the rig's 'axis of symmetry'. This thesis introduces a computer program, named SOS_3D, for the fluid-structure-soil interaction analysis of jack-up response in three dimensions. Extensive experimental series have been performed to provide evidence for the generalisation of the foundationsoil interaction model to general six degree-of-freedom loading conditions and its applicability to load paths and stress levels relevant to jack-up spudcans. These experiments included (1) 1g single footing tests, (2) centrifuge single footing tests and (3) centrifuge model jack-up tests. The latter tests highlighted differences in response and mode of failure depending on the loading direction of the jack-up and re-iterated the importance of three-dimensional modelling. The numerical program SOS_3D introduced early in this thesis was shown to represent a useful tool for the prediction of jack-up behaviour under general combined loading in three dimensions. It provided reasonably good, conservative predictions of the experimentally measured jack-up behaviour.
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Holinka, Matouš. "Numerické modelování proudění v bezpečnostním objektu vodního díla." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265709.
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This thesis deals with the solution of numerical modeling. Consequently problems associated with the flow of the water over spillway of the specific water structure. In this case numerical modeling means modeling of fluid movement, which is described by mathematical means. Especially nowadays, when a lot of spillways need to be recalculated, whether it meets the capacity demands, or there is no need to tackle reconstruction. With today's software capabilities there is a wide range of commercial and freeware resources. The numerical model, compared to physical model is less accurate which is, on the otherhand, physical model is usually financially and time-consuming. The following work simulates the behavior of water on the edge of the spillway, in the trough and then behind the trough. The result is a comparison of the water depth in the trough calculated by the numerical and the physical model.
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Winegar, Matthew Bryston. "Extending the Abstract Data Model." Digital Commons @ East Tennessee State University, 2005. https://dc.etsu.edu/etd/1007.
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The Abstract Data Model (ADM) was developed by Sanderson [19] to model and predict semantic loss in data translation between computer languages. In this work, the ADM was applied to eight languages that were not considered as part of the original work. Some of the languages were found to support semantic features, such as the restriction semantics for inheritance found in languages like XML Schemas and Java, which could not be represented in the ADM. A proposal was made to extend the ADM to support these semantic features, and the requirements and implications of implementing that proposal were considered.
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Schmidt, Piet O. "Origins of Effective Charge of Multivalent Ions at a Membrane/Water Interface and Distribution of 2,3,4,5-Tetrachlorophenol in a Membrane Model System." PDXScholar, 1995. https://pdxscholar.library.pdx.edu/open_access_etds/5049.
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Biological cells and subcellular organelles are surrounded by membranes to form compartments performing specialized functions. Adsorption or partitioning of biologically active compounds into the membrane is the first step in the process of modification of cell function. This work is concerned with the problem of distribution of charged molecules between water and electrically charged membrane surface and between water and octanol. Part I of this thesis is focused on the electrostatic interactions taking place between charges on the membrane and ions present in the aqueous region of the membrane/water interface. The objective was to explore theoretically the origin of anomalous behavior of Ruthenium Red (RuR), a positively charged hexavalent ion. It was discovered in studies of RuR adsorption to negatively charged membranes that within the framework of the Gouy-Chapman theory of the membrane/water interface, RuR behaves as an ion with effective charge less than its physical charge. Moreover, the effective charge was found to be dependent on the density of electric charge at the membrane surface. Two theoretical models of the interfacial region were examined: the Rod Model and the Maximum Density Model. The Rod Model takes into account steric constraints imposed on RuR at the vicinity of the membrane surface. The Maximum Density Model attempts to account for non-ideal behavior by including repulsive interactions. These theoretical studies illustrate the consequences of finite size and ion-ion interactions of adsorption of large molecular ions to electrically charged membrane surfaces. Part II is an experimental study whose objective was to determine the partition coefficient of the negatively charged 2,3,4,5-tetrachlorophenol (TeCP) between water and octanol. The study was based on spectrophotometric measurements of the equilibrium concentrations of TeCP in water and octanol as a function of pH. The octanol/water partition coefficient for both the non-ionized and ionized species of TeCP were determined. It was found that the partition coefficient of ionized TeCP to lipid membrane is about 400 times greater than that for octanol. This result supports the hypothesis that the octanol/water partition coefficient of ionized chlorophenols cannot be used for predicting their distribution between water and lipid-bilayercontaining elements of the environment.
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Osta, Iman M. "From Physical Model To Proof For Understanding Via DGS:Interplay Among Environments." Proceedings of the tenth International Conference Models in Developing Mathematics Education. - Dresden : Hochschule für Technik und Wirtschaft, 2009. - S. 464 - 468, 2012. https://slub.qucosa.de/id/qucosa%3A1798.
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The widespread use of Dynamic Geometry Software (DGS) is raising many interesting questions and discussions as to the necessity, usefulness and meaning of proof in school mathematics. With these questions in mind, a didactical sequence on the topic “Conics” was developed in a teacher education course tailored for pre-service secondary math methods course. The idea of the didactical sequence is to introduce “Conics” using a concrete manipulative approach (paper folding) then an explorative DGS-based construction activity embedding the need for a proof. For that purpose, the DGS software serves as an intermediary tool, used to bridge the gap between the
physical model and the formal symbolic system of proof. The paper will present an analysis of participants’ geometric thinking strategies, featuring proof as an embedded process in geometric construction situations.
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Qi, Songyun. "Dynamics from an equilibrium lattice model of a microemulsion." Scholarly Commons, 1999. https://scholarlycommons.pacific.edu/uop_etds/526.
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A 3D lattice model of three-component microemulsion employed previously to describe the equilibrium phase behavior has been extended to investigate the nonequilibrium dynamics of such system. The model is based on "Dynamical Monte Carlo" simulations which apply a coarse-grained velocity field onto a conventional Monte Carlo lattice, so as to represent realistically interactions between particles, and which permits the observation of time-dependent behavior. The results for viscosity are obtained by applying the velocity gradient onto the system. The simulations are performed over a range of shear rates and temperatures. Compared to the oil-rich (water-rich) phase, the microemulsion phase shows a typical (non-Newtonian) behavior and considerably lower viscosity at a given temperature. Both phases exhibit the characteristic viscosity decrease with an increase in temperature. The velocity auto-correlation function of a microemulsion phase is found to follow a Kohlrausch-Wiliams-Watts (KWW) stretched-exponential law, rather than a simple exponential decay. The stretched exponent is related to the normal, inhibited and enhanced diffusion behaviors of the system.
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Dray, Alyssa W. "A Multistage Incidence Estimation Model for Diseases with Differential Mortality." Scholarship @ Claremont, 2010. https://scholarship.claremont.edu/hmc_theses/21.
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According to theWorld Health Organization, surgically removable cataract remains the leading cause of blindness worldwide. In sub-Saharan Africa, cataract surgical rate targets should ideally be set based on cataract incidence (the number of new cataracts developed each year). Unfortunately, the longitudinal studies necessary to measure incidence have not yet been feasible in these areas. Our research instead proposes a method for estimating incidence based on available cataract prevalence data. We extend a method proposed by Podgor and Leske (1986) to estimate age-specific incidence from age-specific prevalence in single diseases with differential mortality. A two-stage disease extension is created in order to differentiate between unilateral cataract and bilateral cataract. The new model, along with a numerical simulation method to generate confidence intervals, is implemented in the statistical programming language R. The model is then applied to Rapid Assessment of Avoidable Blindness survey data from parts of Eritrea, The Gambia, Kenya (two regions), Mali, Rwanda and Tanzania. Our results suggest significant geographic variations in cataract incidence, a hypothesis to be further investigated as the RAAB survey expands and improves. We also show how the model can be further extended to model any n-stage progressive disease with differential mortality. to model any n-stage progressive disease with differential mortality.
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Vereen, Kalimah. "An SCIR Model of Meningococcal Meningitis." VCU Scholars Compass, 2008. http://scholarscompass.vcu.edu/etd/710.
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A model for meningitis is developed by adding a class of carriers to the basic SIR model. This model is used to analyze the impact a vaccination program can have on the health of the population of epidemic prone countries. Analysis of the model shows the local stability of the disease free equilibrium, the existence of an endemic equilibrium and computation of the reproduction number, ℜ0 . Using a MATLAB program we simulate a time course of the model using parameters gathered from the World Health Organization. The numerical solution demonstrates that our reproduction number was correct. We thenconcluded that a high infection transmission rate requires a high vaccine rate.
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Schuerg, Frank. "Fractal geometry of iso-surfaces of a passive scalar in a turbulent boundary layer." Thesis, Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04082004-180358/unrestricted/schuerg%5ffrank%5f200312%5fms.pdf.
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Osta, Iman M. "From Physical Model To Proof For Understanding Via DGS: Interplay Among Environments." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-80806.
Full textAbstract:
The widespread use of Dynamic Geometry Software (DGS) is raising many interesting questions and discussions as to the necessity, usefulness and meaning of proof in school mathematics. With these questions in mind, a didactical sequence on the topic “Conics” was developed in a teacher education course tailored for pre-service secondary math methods course. The idea of the didactical sequence is to introduce “Conics” using a concrete manipulative approach (paper folding) then an explorative DGS-based construction activity embedding the need for a proof. For that purpose, the DGS software serves as an intermediary tool, used to bridge the gap between the
physical model and the formal symbolic system of proof. The paper will present an analysis of participants’ geometric thinking strategies, featuring proof as an embedded process in geometric construction situations.
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Zhao, Yajing. "Chaotic Model Prediction with Machine Learning." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8419.
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Chaos theory is a branch of modern mathematics concerning the non-linear dynamic systems that are highly sensitive to their initial states. It has extensive real-world applications, such as weather forecasting and stock market prediction. The Lorenz system, defined by three ordinary differential equations (ODEs), is one of the simplest and most popular chaotic models. Historically research has focused on understanding the Lorenz system's mathematical characteristics and dynamical evolution including the inherent chaotic features it possesses. In this thesis, we take a data-driven approach and propose the task of predicting future states of the chaotic system from limited observations. We explore two directions, answering two distinct fundamental questions of the system based on how informed we are about the underlying model. When we know the data is generated by the Lorenz System with unknown parameters, our task becomes parameter estimation (a white-box problem), or the ``inverse'' problem. When we know nothing about the underlying model (a black-box problem), our task becomes sequence prediction. We propose two algorithms for the white-box problem: Markov-Chain-Monte-Carlo (MCMC) and a Multi-Layer-Perceptron (MLP). Specially, we propose to use the Metropolis-Hastings (MH) algorithm with an additional random walk to avoid the sampler being trapped into local energy wells. The MH algorithm achieves moderate success in predicting the $\rho$ value from the data, but fails at the other two parameters. Our simple MLP model is able to attain high accuracy in terms of the $l_2$ distance between the prediction and ground truth for $\rho$ as well, but also fails to converge satisfactorily for the remaining parameters. We use a Recurrent Neural Network (RNN) to tackle the black-box problem. We implement and experiment with several RNN architectures including Elman RNN, LSTM, and GRU and demonstrate the relative strengths and weaknesses of each of these methods. Our results demonstrate the promising role of machine learning and modern statistical data science methods in the study of chaotic dynamic systems. The code for all of our experiments can be found on \url{https://github.com/Yajing-Zhao/}
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Carias, Rui Manuel Roteiro. "A mathematical model to determine strategic options for a firm using time based financial accounting and physics equations." Thesis, University of South Africa, 2007. http://hdl.handle.net/10500/55.
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Executive Summary
This report uses modified physics and the basic business relationship equations to describe the business system. The
physics - business equations are derived using conformal mapping, while thermodynamic and kinematic relationships
are further developed and related before being applied to a business situation. The system developed has general
applicability to business and can be used for strategic competitive positioning, amongst other postulated uses.
The main purpose of this project is to build on existing work in the area of process modeling and strategy formulation to
define a quantitative management tool that will effectively enable the formulation of a generic framework, to measure
the effects of various strategic options using time based financial management and physics models.
The main aims of this research project are to provide an evaluative summary of the existing literature on the
applications of process modeling and physics to business limited in scope to competitive strategic planning through a
literature review of existing business models and the subsequent development of a mathematical model based on
kinematics and thermodynamics for strategic formulation.
From the literature review derive a mathematical framework relating business and physics based on an indirect
relationship of physical laws to business models based on existing knowledge. Further explain why the derived model
has applications to business, and derive a non-rigorous mathematical proof thereof. From these equations make
recommendations on how this model can be utilised as a tool to assist in strategy formulation. Thereafter provide
statistical proof that the model is applicable to a defined set of companies and show by means of applications how to
determine optimal strategies using the model.
The main objectives of the research project are to utilise the quantitative tool to determine where a company is, and
where it should position itself in future to optimise its competitive position. Further, the framework must be developed
into a strategic tool that would allow for the fast turnaround in the implementation of strategy, and the ability to quickly
predict necessary changes in direction.
The statistical hypothesis tested asks if it is possible to relate the laws of physics to business and use the resultant
mathematical framework to analyse a firm’s competitive position in an industry and position it accordingly.
From the derived equations a mathematical model to determine strategic options for a firm using time based financial
accounting principles and physics equations can be formulated and used to find profitable options for a firm. By
implication the model can be applied to strategic positioning of the firm. Unfortunately there is no work in the literature
reviews to build this study on and much of it is built from first principles. This leads to complex mathematical
relationships, which may prove difficult to follow.
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Monette, Liza. "Numerical simulations of nucleation and growth phenomena." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=64053.
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