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Shim, Jaesool. "Modeling and simulation of non linear electrophoresis." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Dissertations/Fall2007/j_shim_121407.pdf.
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Fogarty, Joseph C. "High Dimensional Non-Linear Optimization of Molecular Models." Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5618.
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Molecular models allow computer simulations to predict the microscopic properties of macroscopic systems. Molecular modeling can also provide a fully understood test system for the application of theoretical methods. The power of a model lies in the accuracy of the parameter values which govern its mathematical behavior. In this work, a new software, called ParOpt, for general high dimensional non-linear optimization will be presented. The software provides a very general framework for the optimization of a wide variety of parameter sets. The software is especially powerful when applied to the difficult task of molecular model parameter optimization. Three applications of the ParOpt software, and the Nelder-Mead algorithm implemented within it, are presented: a coarse-grained (CG) water--ion model, a model for the determination of lipid bilayer structure via the interpretation of scattering data, and a reactive molecular dynamics (ReaxFF) model for oxygen and hydrogen. Each problem presents specific difficulties. The power and generality of the ParOpt software is illustrated by the successful optimization of such a diverse set of problems.
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Argoti, Caicedo Alvaro Andres. "Linear and non-linear mechanistic modeling and simulation of the formation of carbon adsorbents." Diss., Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/279.
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Atie, Elie. "Modeling of high electromagnetic field confinement metamaterials for both linear and non-linear applications." Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2044/document.
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Notre recherche porte sur la réponse optique des nanostructures et nous sommes certainement intéressés à la modélisation de ces structures afin d'améliorer le confinement de la lumière. Ce confinement est un des paramètres qui conduisent à l'exaltation des effets optique linéaires et non linéaires, simultanément. Notre travail est divisé en deux sections, qui présentent deux effets optiques diffèrents basées sur le confinement des champs à l’intérieur du structure. Dans la première section, la réponse optique d’une nano-antenne à ouverture en forme de nœud papillon (BNA : Bowtie nano-aperture) sera étudiée en fonction de l’indice de réfraction du milieu. L’étude discute la variation de la longueur d’onde de résonance ainsi que l’intensité du champ confiné au milieu du gap de la BNA en fonction de la distance qui sépare l’antenne d’un substrat placé en face. L’étude prend le cas d’une BNA gravée au bout d’une fibre optique métallisée. Une étude numérique complète a été réalisée par des simulations numériques basées sur la méthode des différences finies FDTD-3D (Finite Difference Time Domaine – Three dimension). Le code utilisé est développé au sein du département d’Optique de l’Institut FEMTO-ST. Notre modèle numérique décrits bien la géométrie de l’antenne ainsi que la pointe. De même les propriétés optiques de la couche métallique de la sonde sont bien décrites à travers un modèle de dispersion (model de Drude). Une étude expérimentale a été réalisée en plus pour une validation des résultats collecte théoriquement, l’étude a considéré le cas de deux BNA avec des paramètres géométrique différents, néanmoins les résultats obtenues se correspond fortement aux résultats obtenues numériquement. Dans la deuxième partie, l'effet électro-optique des nanostructures sera étudié. L’effet électro-optique ou effet Pockels consiste d’une variation linéaire de l'indice de réfraction d'un milieu non-linéaire en fonction d'un champ électrique extérieur. Cependant, la variation est reliée au tenseur de susceptibilité non linéaire du deuxième ordre, ainsi, cette effet ce produit seulement dans les matériaux non-centrosymétrique. Dans notre étude les nanostructures sont fabrique avec le Niobate de Lithium (LN) qui est considéré comme le plus avantageux diélectrique pour l’exaltation des effets non linéaire grâce à ces propriétés (acousto-optique, électro-optique, piézoélectrique …). L’étude est complétée numériquement garce a des simulations basées sur la FDTD en tenant compte de la polarisation du champ. Au début, une validation de l’utilisation de la FDTD pour estimer l’effet électro-optique intrinsèque du LN a été achevée, l’étude considère un milieu homogène (pas de confinement des champs dans le milieu) qui a pour indice de réfraction celle du LN. Pour des structure qui présentes un confinement du champ plusieurs approximation ont été suggère dans cette partie. En outre, nous présentons un nouveau modèle auto-cohérent dans lequel la variation de l'indice de réfraction est modifiée au cours de la simulation. Plusieurs structure ont été discutés (réflecteur de Bragg, structure à cavité et 2D cristal photonique) qui présentent des facteurs de confinement différents. Une étude comparative entre les différentes méthodes, montre que la différence entre les résultats de chaque hypothèse devient plus important proportionnellement au facteur de confinementOur research is concerned with the optical response of nano-structures by modeling them in order to enhance the confinement of light in these structures, which leads to the exaltation of linear and nonlinear optical effects.Our work is divided into two sections, which are based on the enhancement of the electric field inside the structure. In the first section, we study the optical properties of a Bowtie Nano-aperture, BNA, as a function of the refractive index of the surrounding medium. The study discusses the variation of the resonance wavelength and the intensity of the enhanced field in the gap of the BNA as a function of the distance from a sample placed in front of our BNA. The BNA is engraved at the apex of a metallic coated fiber tip. In this section a theoretical study was achieved using the Finite Difference Time Domain method FDTD in which we implement a Drude dispersion model to faithfully describe the optical properties of metals. In addition, a validating experimental study was achieved and a high accordance between both results is recorded.In the second section, the electro optical effect of nano-structures is studied. Electro-optical effect or Pockels effect is the variation of the refractive index of a nonlinear media as a function of an applied external electric field. The electro-optical effect is a linear variation of the media refractive index. However it is also related to the second order nonlinear susceptibility tensor, thus it becomes a nonlinear effect that only occurs in non-centrosymetric material. In our study we chose the case of a nano-structure fabricated with Lithium Niobate. Lithium Niobate is widely used in photonic applications due to its electro-optical, acousto-optical and nonlinear optical properties. We present a theoretical study of the electro-optical effects using the FDTD simulation method. We started by approving the ability to use the FDTD to calculate the refractive index variation in bulk Lithium Niobate then we suggest different approximations to estimate the refractive index variation when the light is confined inside the structure. In addition we suggest a new self-consistent method in which the variation of the refractive index is modified during the simulation. The study shows a comparison between different assumptions (used in previous research) and the self-consistent method for various structures, like Bragg reflectors, cavity structures and 2D photonic crystals. The study shows that the difference between the results of each assumption becomes greater when the optical confinement in the structure becomes more important
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Engel, James Economics Australian School of Business UNSW. "Studies of non-linear features in the business cycle." Publisher:University of New South Wales. Economics, 2008. http://handle.unsw.edu.au/1959.4/42960.
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Writers on the business cycle often emphasize that non-linear models are needed to account for certain of its features. Thus it is often said that either the asymmetry of the duration of business cycle expansions and contractions or the variability of these quantities demand a non-linear model. Such comments are rarely made precise however and mostly consist of references to such assertions from the past. Thus the asymmetry in the cycle is mostly accompanied by references to Keynes (1936) and Burns and Mitchell (1946). But these authors were looking at what we call today the classical cycle i.e. movements in the level of GDP, and so the fact that there are long expansions and short contractions can arise simply due to the presence of long-run growth in the economy, and it is not obvious that it has much to do with non-linearity. This thesis aims to introduce various statistics that can be used to characterise the specific shape of the non-linearity observed in macroeconomic time series. Chapter 2 introduces a range of statistics and presents the dating algorithm used in this thesis, which is based on the BBQ algorithm of Harding and Pagan (2002). Chapter 3 tests the adequacy of linear models versus the SETAR model of van Dijk and Franses(2003) and the bounceback model of Kim, Morley and Piger (2005) in capturing observed non-linear features of the data. Chapter 4 extends this work by examining the three state Markov model of Hamilton (1989), again using the ??bounce-back?? model of Kim C., Morley, J. and J. Piger, (2005), and the more complicated ??tension?? model of DeJong, D., Dharmarajan, H., Liesenfeld, R. and Richard, J., (2005). Chapter 4 also extends Chapter 3 by estimating the above mentioned models on US GDP, Australian non-farm GDP, US investment and Australian dwellings investment. They are then simulated in order to gauge the cycle properties. Chapter 5 analyses the business cycle implications of two related multivariate dynamic factor models presented in papers by Kim and Piger (2001, 2002). Finally Chapter 6 concludes.
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SPINOLA, ALEXANDRE DE LIMA. "MODELING AND NON LINEAR CONTROL OF A GROUND VEHICLENULLS STEERING." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=5109@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORModelagem e Controle Não Linear de um Veículo Terrestre sobre Suspensão descreve um estudo em dinâmica veicular no qual inicialmente apresenta-se um modelo analítico para representar a geração de forças longitudinais e laterais no contato do pneu com o solo. Em seguida é desenvolvido, para um automóvel de passeio terrestre sobre suspensão, um modelo não linear de 4 graus de liberdade (velocidades longitudinal, lateral, de guinada e de rolagem), e a sua linearização. Expande-se esse modelo para um de 8 graus de liberdade, no qual inclui-se o movimento de rotação axial de cada uma das quatro rodas, e consideram-se os movimentos do veículo somente no plano, sem efeitos de pitch ou bounce, mas apresentando alguma relação de distribuição de cargas devido ao roll. Descrevem-se ainda modelos em Grafos de Ligação para os três dinâmicas de um veículo terrestre (longitudinal, lateral e vertical) e seus acoplamentos, visando futuras análises mais detalhadas desse sistema. Todos os modelos em malha aberta são validados através simulações computacionais em diversas condições típicas de operação. Na segunda parte desse trabalho é apresentada a estratégia proposta para o tratamento do problema de controle direcional do veículo em uma manobra qualquer, empregando a metodologia da linearização por realimentação, tendo como base o modelo linear de 4 graus de liberdade. São analisados os resultados encontrados através de simulação computacional para a malha fechada com diferentes combinações de parâmetros, empregando os modelos não lineares de 4 e 8 graus de liberdade. Conclui-se discutindo a possibilidade de generalização deste procedimento para diferentes aplicações em Dinâmica Veicular.
Modeling and Non Linear Control of a Ground Vehicle's Steering describles a study in vehicle dynamics, which presents an analytic model representing the generation of longitudinal and lateral forces at the contact patch between tire and ground. Next it is developed, for a typical passenger car, a non-linear model with four degrees of freedom (longitudinal, lateral, yaw and roll velocities), and its linearization. This model is then expanded to another one with eight degrees of freedom, which includes the axial rotation of each one of the four wheels, and considers the vehicle's movement only at a known plane, whithoud pitch and bounce effects, but including some load distribution among the wheels, due to roll. Computational simulation in varius typical operation condition validate all open loop models. The second part of this work presents the proposed strategy for directional control of a vehicle at any type of manoeuvre, using the feedback linearization methodology, directly applied to the linear four degrees of freedom model. Theresults obtained trhough computational simulation for a closed loop model with different parameters are analysed using both nonlinear four and eight degrees of freedom models. The possibility of generalizing this procedure to distinct applications in Vehicle Dynamics is, then, discussed.
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Rozite, Liva. "Non-linear behavior of bio-based composite : characterization and modeling." Licentiate thesis, Luleå tekniska universitet, Materialvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18691.
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The development and application of bio-based composite materials have been frequently studied. Most of the work is done on quasi-static performance of these materials. However, these composites are highly non-linear therefore there is need for investigation of their viscelastic and viscoplastic behavior. This thesis is dealing with characterization and modeling of behavior of bio-based composite. The effect of temperature and relative humidity on mechanical behavior of natural fiber reinforced bio-based matrix composites subjected to tensile loading was investigated. Composites with different natural fibers (flax, viscose) and bio-based matrices (PLA, Lignin) were studied. Elastic modulus, the nonlinear tensile stress-strain curves and failure were analyzed showing that all materials are temperature sensitive. The nonlinearity was evaluated by studying modulus degradation as well as development of viscoelastic and viscoplastic strains as a function of applied load. The time-dependent phenomena were investigated in short term creep and strain recovery tests at several high stress levels. These tests demonstrated significantly higher viscoplastic strain in lignin than PLA based composites. Both, viscoelastic and viscoplastic strains are larger at higher relative humidity. The observed nonlinearity was attributed to microdamage, viscoelastic and viscoplastic response suggesting Schapery’s type of model for viscoelasticilty and Zapas’ model for viscoplasticity. PLA and lignin based flax fiber composites have been analyzed in order to obtain parameters needed for model. It was found that in PLA based composites after loading at stress levels below the maximum possible the elastic modulus is not affected and, therefore, damage does not need to be included in the material model. The modulus reduction in lignin based composites in tension starts before the maximum in stress-strain curve is reached and it can be as large as 50%. With increasing relative humidity these effects are slightly magnified. It appears that there is no region of linear viscoelasticity for PLA based composites. Nonlinear elasticity, viscoelasticity and viscoplasticity are equally responsible for observed nonlinearity in tensile tests.Godkänd; 2012; 20120416 (livroz); LICENTIATSEMINARIUM Ämnesområde: Polymera konstruktionsmaterial/Polymeric Composite Materials Examinator: Professor Roberts Joffe, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: Professor Markus Stommel, Universität des Saarlandes, Saarbrücken, Deutschland Tid: Tisdag den 22 maj 2012 kl 09.00 Plats: E231, Luleå tekniska universitet
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Booth, Eric Jason. "Progress and Challenges in Non-Linear Constitutive Modeling for Composite Material." Thesis, Montana State University, 2007. http://etd.lib.montana.edu/etd/2007/booth/BoothE0507.pdf.
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In this paper is outlined a technique for determining the non-linear constitutive properties of an orthrotropic laminated material such as a fiber reinforced composite. The Characterization of Composites is difficult because of the anisotropic stiffness properties of the material and also because of the complex manner in which they accumulate internal damage and eventually fail. Presented here are techniques for determining the mechanical properties of a material by solving what is known as the Inverse Problem. In such a problem, the response of a material system to an external stimulus is measured, then, this information is used to divine the corresponding material properties of that system. Progress in solving the Inverse Problem for Non-Linear Material Properties is presented as well as challenges that remain.
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Swensen, Ingrid. "Modeling and Non-linear Control of Gel Breaking in Drilling Operations." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for teknisk kybernetikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-25754.
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As the petrolium operators are drilling deeper and more complicated well paths, extreme downhole presure variations during drilling operations may cause damage to equipment. This may in addition result in production restrictions and increased cost. Therefore, the main purpose of this project was to develop a non-linear control structure to stabilize the downhole pressure, such that the pressure never exceeds the $\pm$ 2 bar limit when the mud pump was started. Mud pump startup is one of the main reasons for increased pressure. Mud at rest will, after some time, start the process of gelling. When the system is set to motion again, a considerable amount of force is therefore required to break the gel. In order to achieve pressure stabilization, a controller was implemented on the mud pump. This controller included two proportional controllers, one monitored the downhole pressure, while the other used the calculated structure of the mud as an input parameter, meaning that the gelling was taken into account. The effects from a controlled back pressure pump were also assessed. Incorporating automatic contol on the mud pump resulted in a downhole pressure that remained within the $\pm$ 2 bar boundaries. The pump was able to provide the desired flow rate in a reasonable amount of time. This is because the pump decreased the flow only when the downhole pressure increased at an excessive rate, giving the gelled mud more time to brake.Throughout the project, the back pressure pump was implemented as a constant flow rate. A test scenario where the back pressure pump was a subject of automatic control showed a slight improvement with regards to downhole pressure stabilization, as well as a more stable choke valve opening. Automatic back pressure control might result in improved startup and shutdown timing. With two controllers, one on the choke valve and one on the mud pump, a more stable mud break-down process can be achieved. This can lead to several economic advantages such as time saved when returning to reference flow rate, less wear on the choke valve, as well as fewer operators needed to handle the mud pump.
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Segatta, Francesco <1989>. "Modeling Photoinduced Events and Non-linear Spectroscopy in Complex Multichromophoric Systems." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amsdottorato.unibo.it/8469/1/Segatta_Francesco_tesi.pdf.
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What are the processes activated by light when it impinges on a sample of light- sensitive molecules in mutual interaction? How can this information be accessed from both the experimental and theoretical sides? This work is aimed at answering at these specific questions. In order to accomplish this goal, we use state-of-the-art computational methods and develop novel theoretical approaches for investigating static and dynamical properties of networks of interacting molecular organic chromophores, and compute their spectroscopy. We focus in particular on the simulation of non-linear time-resolved techniques, such as the pump-probe and the two dimensional electronic spectroscopy. These approaches have been proven to be fundamental tools to track the system photoinduced dynamics with extremely high time and spectral resolution and disentangle contributions from different system components. We conclude that the synergic combination of “independent” results from accurate quantum chemical calculations and detailed spectroscopic experiments is the way to reach a reliable map of the activated energy transfer processes and to gain new physical insights into the system properties.
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Hughes, Jonathan L. "Applications of Stability Analysis to Nonlinear Discrete Dynamical Systems Modeling Interactions." VCU Scholars Compass, 2015. http://scholarscompass.vcu.edu/etd/3819.
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Many of the phenomena studied in the natural and social sciences are governed by processes which are discrete and nonlinear in nature, while the most highly developed and commonly used mathematical models are linear and continuous. There are significant differences between the discrete and the continuous, the nonlinear and the linear cases, and the development of mathematical models which exhibit the discrete, nonlinear properties occurring in nature and society is critical to future scientific progress. This thesis presents the basic theory of discrete dynamical systems and stability analysis and explores several applications of this theory to nonlinear systems which model interactions involving economic agents and biological populations. In particular we will explore the stability properties of equilibria associated with inter-species and intergenerational population dynamics in biology and market price and agent composition dynamics in economics.
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Sundaram, Sathish Kumar. "Extending VHDL-AMS to support non-linear frequency based modeling and simulation." Cincinnati, Ohio : University of Cincinnati, 2005. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1108503739.
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Gurkan, Niyazi Ersan. "Non-linear Mathematical Modeling Of Gear Rotor Bearing Systems Including Bearing Clearance." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606798/index.pdf.
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ABSTRACT
NON-LINEAR MATHEMATICAL MODELING
OF GEAR-ROTOR-BEARING SYSTEMS
INCLUDING BEARING CLEARANCE
GÜRKAN, Niyazi Ersan M.S. Department of Mechanical Engineering Supervisor: Prof. Dr. H. Nevzat Ö
ZGÜ
VEN November 2005, 130 pages In this study, a non-linear mathematical model of gear-rotor systems which consists of elastic shafts on elastic bearings with clearance and coupled by a non-linear gear mesh interface is developed. The mathematical model and the software (NLGRD 2.0) developed in a previous study is extended to include the non-linear effects due to bearing clearances by using non-linear bearing models. The model developed combines the versatility of using finite element method and the rigorous treatment of non-linear effect of backlash and bearing clearances on the dynamics of the system. The software uses the output of Load Distribution Program (LDP), which computes loaded static transmission error and mesh compliance for the contact points of a typical mesh cycle, as input. Although non-varying mesh compliance is assumed in the model, the excitation effect of time varying mesh stiffness is indirectly included through the loaded static transmission error, which is taken as a displacement input into the system. Previous computer program which was written in Fortran 77 is rewritten by using MatLAB 7.0 and named as NLGRD (Non-Linear Geared Rotor Dynamics) Version 3.0. The program is highly flexible and open to further developments. The program calculates dynamic to static load ratio, dynamic transmission error, forces and displacements at bearings. The mathematical model suggested and the code (NLGRD version 3.0) are validated by comparing the numerical results obtained from the model suggested with experimental data available in literature. The results are also compared with those of previously developed non-linear models. The effects of different system parameters such as bearing stiffness, bearing clearance and backlash on the gears are investigated. The emphasis is placed on the interaction of clearances in bearings with other system parameters.
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Hardy, Joseph T. 1978. "Injection compression modeling of non-linear positive temperature coefficient circuit protection devices." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/30315.
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Thesis (S.M. and S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (leaf 72).
Polymeric self-resettable circuit protection devices have been manufactured for many years with an extrusion based process. These devices add negligible resistance to a circuit at normal power operating conditions but increases in resistance by several orders of magnitude at a pre-determined level of power in order to protect the circuit from over- current or over-voltage conditions. After the electrical surge stops, and power returns to a normal level, the resistance of the device drops, and the circuit may resume its normal operation. These devices are used in computers, cell-phones, and other consumer and industrial electronic devices where normal fuses are not convenient or practical. The current manufacturing process extrudes long sheets of 2-mm thick polymer lined with 0.05-mm thick foil on both sides. This foil-polymer-foil structure, called plaque, is punched into 13 mm x 8 mm x 2 mm rectangles, called chips. The chips undergo heat treatment and radioactive cross-linking steps before wire leads are soldered onto them for easy electrical connection to either test or circuit boards. Though effective, this process produces more waste and remains less flexible than an injection-compression (IC) molding process. With this new process, devices are made individually in a multi- cavity mold, skipping the punching and soldering steps. This thesis explores IC molding and its benefits and drawbacks for manufacturing circuit protection devices. IC molded devices were manufactured, tested, and compared to standard devices, produced by the extrusion process, in the areas of physical and electrical performance.
(cont.) Budget considerations prevented the study of individually IC molded devices and instead a 150 mm x 75 mm mold cavity was used to create an IC molded plaque from which chips could be punched and wire leads attached. In this way, any electrical variations across the IC molded plaque, produced by flow or thermal properties of the new process, could be studied with electrical tests, and physical variations across the IC molded plaque could be examined with a peel test. Cycle life data and data comparing device resistance to device temperature show that the new manufacturing process has potential to create equal or better performing devices than the existing extrusion process.
by Joseph T. Hardy.
S.M.and S.B.
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SUNDARAM, SATHISH KUMAR. "EXTENDING VHDL-AMS TO SUPPORT NON-LINEAR FREQUENCY-BASED MODELING AND SIMULATION." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1108503739.
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Anand, Chaoba Nikkie. "Internet traffic modeling and forecasting using non-linear time series model GARCH." Thesis, Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/2229.
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Albanna, Ahmad. "HARMONIC MODELING AND SIMULATION OF NON-LINEAR PWM INVERTERS IN DISTRIBUTED GENERATION SYSTEMS." OpenSIUC, 2010. https://opensiuc.lib.siu.edu/dissertations/243.
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The research presented in this dissertation primarily focuses on providing analytical frequency-domain equations that use the system and controller parameters to accurately characterize the power conversion harmonics resulting from the deployment of hysteresis current-controlled inverters within the ac network. In addition, the ac and dc harmonic interactions under both ideal system conditions (constant dc excitation and pure sinusoidal ac voltages) and non-ideal system conditions (harmonic terms are added to the dc and ac sources) are derived for the fixed- and variable-band hysteresis current control. The spectral characteristics, such as frequency orders, spectral magnitude and bandwidth, are given in terms of line and control parameters, a development not only useful in analyzing the harmonic output sensitivity to line and controller parameter variations, but also in filter and system design. Various simulation studies compared results obtained from the developed models to those obtained from the Fourier analysis of MATLAB/Simulink output with very good agreement. The developed models proved their reliability and improved numerical efficiency in harmonic studies compared to those performed using time-domain simulations.
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Post, Katharina. "A System of Non-linear Partial Differential Equations Modeling Chemotaxis with Sensitivity Functions." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 1999. http://dx.doi.org/10.18452/14365.
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Wir betrachten ein System nichtlinearer parabolischer partieller Differentialgleichungen zur Modellierung des biologischen Phänomens Chemotaxis, das unter anderem in Aggregationsprozessen in Lebenszyklen bestimmter Einzeller eine wichtige Rolle spielt. Unser Chemotaxismodell benutzt Sensitivitäts funktionen, die die vorkommenden biologischen Prozesse genauer spezifizieren. Trotz der durch die Sensitivitätsfunktionen eingebrachten, zusätzlichen Nichtlinearitäten in den Gleichungen erhalten wir zeitlich globale Existenz von Lösungen für verschiedene biologisch realistische Klassen von Sensitivitätsfunktionen und können unter unterschiedlichen Bedingungen an die Systemdaten Konvergenz der Lösungen zu trivialen und nicht-trivialen stationären Punkten beweisen.We consider a system of non-linear parabolic partial differential equations modeling chemotaxis, a biological phenomenon which plays a crucial role in aggregation processes in the life cycle of certain unicellular organisms. Our chemotaxis model introduces sensitivity functions which help describe the biological processes more accurately. In spite of the additional non-linearities introduced by the sensitivity functions into the equations, we obtain global existence of solutions for different classes of biologically realistic sensitivity functions and can prove convergence of the solutions to trivial and non-trivial steady states.
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Blumenthal, Kinsey Megan. "Predicting Spatial Variability of Soil Organic Carbon in Delmarva Bays." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/73692.
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Agricultural productivity, ecosystem health, and wetland restoration rely on soil organic carbon (SOC) as vital for microbial activity and plant health. This study assessed: (1) accuracy of topographic-based non-linear models for predicting SOC; and (2) the effect of analytic strategies and soil condition on performance of spectral-based models for predicting SOC. SOC data came from 28 agriculturally converted Delmarva Bays sampled down to 1 meter. R2 was used as an indicator of model performance. For topographic-based modeling, correlation coefficients and condition indices reduced 50 terrain-related values to three datasets of 16, 11, and 7 variables. Five types of non-linear models were examined: Generalized Linear Mondel (GLM) ridge, GLM LASSO, Generalized Additive Model (GAM) non-penalized, GAM cubic splice, and partial least-squares regression. Carbon stocks varied widely, 50 to 219 Mg/ha, with the average around 93 Mg/ha. Topography shared a weak relationship to SOC with most attributes showing a correlation coefficient less than 0.3. GLM ridge and both GAMs achieved moderate accuracy at least once, usually using the 16 or 11 variable datasets. GAMs consistently performed the best. Prior to carbon analysis, hyperspectral signatures were recorded for the topmost soil horizons under different conditions: moist unground, dry unground, and dry ground. Twenty-four math treatment and smoothing technique combinations were run on each hyperspectral dataset. R2 varied greatly within datasets depending on analytic strategy, but all datasets returned an R2 greater than 0.9 at least twice. Moist unground soil models outperformed the others when comparing the best models among datasets.Master of Science
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Katri, Patricia. "Modeling the Transmission Dynamics of the Dengue Virus." Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_dissertations/417.
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Dengue (pronounced den'guee) Fever (DF) and Dengue Hemorrhagic Fever (DHF), collectively known as "dengue," are mosquito-borne, potentially mortal, flu-like viral diseases that affect humans worldwide. Transmitted to humans by the bite of an infected mosquito, dengue is caused by any one of four serotypes, or antigen-specific viruses. In this thesis, both the spatial and temporal dynamics of dengue transmission are investigated. Different chapters present new models while building on themes of previous chapters. In Chapter 2, we explore the temporal dynamics of dengue viral transmission by presenting and analyzing an ODE model that combines an SIR human host- with a multi-stage SI mosquito vector transmission system. In the case where the juvenile populations are at carrying capacity, juvenile mosquito mortality rates are sufficiently small to be absorbed by juvenile maturation rates, and no humans die from dengue, both the analysis and numerical simulations demonstrate that an epidemic will persist if the oviposition rate is greater than the adult mosquito death rate. In Chapter 3, we present and analyze a non-autonomous, non-linear ODE system that incorporates seasonality into the modeling of the transmission of the dengue virus. We derive conditions for the existence of a threshold parameter, the basic reproductive ratio, denoting the expected number of secondary cases produced by a typically infective individual. In Chapter 4, we present and analyze a non-linear system of coupled reaction-diffusion equations modeling the virus' spatial spread. In formulating our model, we seek to establish the existence of traveling wave solutions and to calculate spread rates for the spatial dissemination of the disease. We determine that the epidemic wave speed increases as average annual, and in our case, winter, temperatures increase. In Chapter 5, we present and analyze an ODE model that incorporates two serotypes of the dengue virus and allows for the possibility of both primary and secondary infections with each serotype. We obtain an analytical expression for the basic reproductive number, R_0, that defines it as the maximum of the reproduction numbers for each strain/serotype of the virus. In each chapter, numerical simulations are conducted to support the analytical conclusions.
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Ahmed, Syed Iftekhar. "A new approach for modeling the non-linear one dimensional consolidation behaviour of tailings." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44810.
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The management of tailings largely depends on its consolidation behaviour. Extensive works on this sector have been performed as it plays a significant role in economic and environmental considerations of a tailings management facility. To resolve these issues, consolidation theories had been developed for one, two or three dimensional condition with numerical solutions for soft soils like tailings which behave differently from natural soils. Eventually, large strain consolidation tests have experienced at its advance level for precise determination of experimental data because non-linear behaviour of compressibility and hydraulic conductivity fits to a wide range of functions. This non-unique behaviour of tailings is believed to be an aftermath of the combination of flocculation, sedimentation, consolidation, segregation, deposition, freeze-thaw and desiccation phenomena. Similarly, a consequence of several factors combined called “apparent over-consolidation” is a mystery to the tailings industry and the reasons for this occurrence are not fully understood. It is believed to be the result of the combination of several contributing factors at low effective stresses. Previously, it was assumed that tailings are normally consolidated or consolidating under the load of mounting deposited materials and numerical modeling had been performed by different researchers based on this assumption. However, the apparent compressibility behaviour of tailings was noticed for different types of tailings at a wide range of solids content and various types of testing procedures. Conducting statistical analysis, a new compressibility function, one of the forms of Weibull distribution, is proposed to fit the void ratio-effective stress relationship considering pre-consolidation behaviour. A fully implicit model was developed by introducing that proposed compressibility equation to predict the tailings long term consolidation behaviour. A case study was performed for different types of tailings to predict the consolidation behaviour followed by the sensitivity analysis of the developed model. Significant effects of apparent consolidation have been observed on void ratio, effective stress, excess pore water pressure and tailings settlement for a period of 50 years. The major outcome of this study is the consideration of apparent over-consolidation behaviour during the early stage of the deposition helps to formulate the model more precisely.
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Soufian, Majeed. "Hard and soft computing techniques for non-linear modeling and control with industrial applications." Thesis, Manchester Metropolitan University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273053.
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Karra, Kiran. "Modeling and Analysis of Non-Linear Dependencies using Copulas, with Applications to Machine Learning." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/85110.
Full textAbstract:
Many machine learning (ML) techniques rely on probability, random variables, and stochastic modeling. Although statistics pervades this field, there is a large disconnect between the copula modeling and the machine learning communities. Copulas are stochastic models that capture the full dependence structure between random variables and allow flexible modeling of multivariate joint distributions. Elidan was the first to recognize this disconnect, and introduced copula based models to the ML community that demonstrated magnitudes of order better performance than the non copula-based models Elidan [2013]. However, the limitation of these is that they are only applicable for continuous random variables and real world data is often naturally modeled jointly as continuous and discrete. This report details our work in bridging this gap of modeling and analyzing data that is jointly continuous and discrete using copulas.
Our first research contribution details modeling of jointly continuous and discrete random variables using the copula framework with Bayesian networks, termed Hybrid Copula Bayesian Networks (HCBN) [Karra and Mili, 2016], a continuation of Elidan’s work on Copula Bayesian Networks Elidan [2010]. In this work, we extend the theorems proved by Neslehov ˇ a [2007] from bivariate ´ to multivariate copulas with discrete and continuous marginal distributions. Using the multivariate copula with discrete and continuous marginal distributions as a theoretical basis, we construct an HCBN that can model all possible permutations of discrete and continuous random variables for parent and child nodes, unlike the popular conditional linear Gaussian network model. Finally, we demonstrate on numerous synthetic datasets and a real life dataset that our HCBN compares favorably, from a modeling and flexibility viewpoint, to other hybrid models including the conditional linear Gaussian and the mixture of truncated exponentials models.
Our second research contribution then deals with the analysis side, and discusses how one may use copulas for exploratory data analysis. To this end, we introduce a nonparametric copulabased index for detecting the strength and monotonicity structure of linear and nonlinear statistical dependence between pairs of random variables or stochastic signals. Our index, termed Copula Index for Detecting Dependence and Monotonicity (CIM), satisfies several desirable properties of measures of association, including Renyi’s properties, the data processing inequality (DPI), and ´ consequently self-equitability. Synthetic data simulations reveal that the statistical power of CIM compares favorably to other state-of-the-art measures of association that are proven to satisfy the DPI. Simulation results with real-world data reveal CIM’s unique ability to detect the monotonicity structure among stochastic signals to find interesting dependencies in large datasets. Additionally, simulations show that CIM shows favorable performance to estimators of mutual information when discovering Markov network structure.
Our third research contribution deals with how to assess an estimator’s performance, in the scenario where multiple estimates of the strength of association between random variables need to be rank ordered. More specifically, we introduce a new property of estimators of the strength of statistical association, which helps characterize how well an estimator will perform in scenarios where dependencies between continuous and discrete random variables need to be rank ordered. The new property, termed the estimator response curve, is easily computable and provides a marginal distribution agnostic way to assess an estimator’s performance. It overcomes notable drawbacks of current metrics of assessment, including statistical power, bias, and consistency. We utilize the estimator response curve to test various measures of the strength of association that satisfy the data processing inequality (DPI), and show that the CIM estimator’s performance compares favorably to kNN, vME, AP, and HMI estimators of mutual information. The estimators which were identified to be suboptimal, according to the estimator response curve, perform worse than the more optimal estimators when tested with real-world data from four different areas of science, all with varying dimensionalities and sizes.Ph. D.
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Puida, Mantas. "Computer modeling of structural innovations in biosensors." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20090917_095917-45818.
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Biosensor mathematical and computer modeling is an important task for the development of new biosensors and for the improvement of the existing ones. Objects of this study are mathematical and numerical models which describe operation of novel lipase activity assessment biosensors and theoretical biosensor with controllable permeability membrane. Specific aims of this thesis are to identify what mathematical and numerical models are best suited for modeling specific lipase activity assessment biosensors and to identify what parameters of operation are specific for biosensor with controllable membrane. Also to identify the conditions which would reveal the positive and negative features of controllable membrane. It was discovered that in the case of lipase activity assessment biosensor the classic mathematical model should be extended with a non-linear term (in respect to substrate). Also, it was discovered that biosensor with controllable membrane would be useful in cases when biosensor cannot be physically removed from the operating environment, but still needs to be reconfigured for operation in the kinetic or diffusion mode.Matematinis ir skaitinis biojutiklių modeliavimas yra svarbus uždavinys, kuriant naujus ir tobulinant esamus biojutiklius. Disertacijos tyrimo objektas – matematiniai bei skaitiniai modeliai, aprašantys naujoviškų lipazės aktyvumo nustatymo biojutiklių bei teorinio biojutiklio, padengto valdoma membrana, veikimą. Tyrimo tikslai – nustatyti, kokie matematiniai ir skaitiniai modeliai geriausiai tinka lipazės aktyvumo nustatymo biojutikliams aprašyti, taip pat nustatyti, kokiais parametrais pasižymėtų biojutiklis, turintis valdomą membraną, kokiomis sąlygomis išryškėtų jo privalumai ir trūkumai. Nustatyta, kad lipazės aktyvumo matavimo biojutiklio modeliavimui klasikinį modelį reikia papildyti netiesiniu nariu. Biojutiklis su valdoma membrana pasiteisintų, jei fiziškai neištraukiant jutiklio iš darbinės aplinkos, reikėtų perjunginėti jo darbo režimą iš difuzinio į kinetinį ir atvirkščiai.
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Pieraccini, Luca. "Shear behaviour of reinforced cconcrete slab under concentrated load: an investigation through non-linear and sequentially linear analysis." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/5902/.
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English:
The assessment of safety in existing bridges and viaducts led the Ministry of Public Works of the Netherlands to finance a specific campaing aimed at the study of the response of the elements of these infrastructures. Therefore, this activity is focused on the investigation of the behaviour of reinforced concrete slabs under concentrated loads, adopting finite element modeling and comparison with experimental results.
These elements are characterized by shear behaviour and crisi, whose modeling is, from a computational point of view, a hard challeng, due to the brittle behavior combined with three-dimensional effects.
The numerical modeling of the failure is studied through Sequentially Linear Analysis (SLA), an alternative Finite Element method, with respect to traditional incremental and iterative approaches. The comparison between the two different numerical techniques represents one of the first works and comparisons in a three-dimensional environment. It's carried out adopting one of the experimental test executed on reinforced concrete slabs as well.
The advantage of the SLA is to avoid the well known problems of convergence of typical non-linear analysis, by directly specifying a damage increment, in terms of reduction of stiffness and resistance in particular finite element, instead of load or displacement increasing on the whole structure
.
For the first time, particular attention has been paid to specific aspects of the slabs, like an accurate constraints modeling and sensitivity of the solution with respect to the mesh density. This detailed analysis with respect to the main parameters proofed a strong influence of the tensile fracture energy, mesh density and chosen model on the solution in terms of force-displacement diagram, distribution of the crack patterns and shear failure mode.
The SLA showed a great potential, but it requires a further developments for what regards two aspects of modeling: load conditions (constant and proportional loads) and softening behaviour of brittle materials (like concrete) in the three-dimensional field, in order to widen its horizons in these new contexts of study.
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Ahmed, Khaled I. E. "Finite element modeling of non-linear structural response of transmission towers including bolted joint slippage." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31507.
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Slippage of bolted joints plays an important role in the behavior of transmission tower
structures under various loading. Two main types of bolted joints are commonly used in
towers; column-to-column and beam-to-column joints. The effect of slippage of the bolted
joints on the behavior of transmission towers was previously analyzed using two approximate
models; instantaneous and continuous joint slippage models. The previously proposed models
of joint slippage implied that joint slippage has little effect on a transmission tower load
carrying capacity. These models have also shown that deflections of towers due to slippage
are very small compared to the overall deformation. These studies have considered on)y
beam-to-column joints, ignoring column-to-column joints. The previous models based on the
above assumptions and models based on rigid joint behavior were not able to capture the
response of transmission towers under considerable differential settlements caused by frost
heave.
In this thesis, two common bolted joint types used in transmission tower structure are
analyzed and discussed based on a series of full-size tower joint experiments conducted at the
University of Manitoba. It is observed that joints stiffness properties such as equivalent
modulus of elasticity, yield strength and fracture strength are much lower than that of the
connected members. The experimental results also show that previously reported
instantaneous and continuous joint slippage models do not accurately simulate the behavior of
bolted joints. Two finite element models are proposed in this thesis to simulate the slippage of the two
main joint types; column-to-column (type-A joints) and beam-to-column (type-C joints).
Stiffness matrices of the new joint finite elements are established with the aid of the
experimental data. An elastic geometrically nonlinear finite element code is developed using
Fortran 90 to analyze the 3-D response of transmission tower structures taking into account the
effect of joint slippage. A graphical user interface based on Visual Basic is attached to the
finite element code to allow practicing engineers to input all data, build the tower finite
element model and display the tower response in an efficient and convenient manner.
The response of a 2-D tower substructure and a 3-D full-scale tower used by Manitoba
Hydro is analyzed by using the finite element code. The numerical study shows that slippage
of beam-to-column and column-to-column joints have significant effects on the tower load
carrying capacity. Column-to-column joint slippage shows the most significant impact on the
transmission tower behavior by either reducing the tower load carrying capacity or
significantly increasing the tower deflection under working loads. On the other hand, joint
slippage has a positive effect on the tower response under frost heave induced displacements
as substantial redistribution of tower member forces takes place due to joint slippage and
actual member forces are much lower than those predicted by standard structural analysis
software based on the rigid joint assumption or simplified slippage models.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Pablos, Rabano Alejandro. "Modeling of a PMSynRel stator with concentrated windings using FEM and non-linear reluctance networks." Thesis, KTH, Elektrisk energiomvandling, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-124543.
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Permanent magnets synchronous reluctance (PMSynRel) motors are attractive due to their high torque density and because a lower quantity of permanent magnets is necessary in comparison with other permanent magnet machines. This thesis deals with the analysis of PMSynRel machines using a finite element method (FEM) and reluctance networks. First, a PMSynRel machine model is built in order to carry out simulations using a finite element method package. The effect of different design parameters such as the combination of the number of poles and slots, the number of flux barriers or the number of magnets can be studied since the implementation provides the possibility to change those variables. Next, a reluctance networks model, aimed to enable lower computation times than corresponding finite element models, is implemented for analysing the flux density distributions along the air gap of the machine disregarding the magnetic influence of the rotor. Finally, the results are compared with FEM simulations. It is concluded that the agreement reached is satisfactory in most of the cases analysed.
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Rivera, Alejandro. "Non-Linear Finite Element Method Simulation and Modeling of the Cold and Hot Rolling Processes." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/31035.
Full textAbstract:
A nonlinear finite element model of the hot and cold rolling processes has been developed for flat rolling stock with rectangular cross section. This model can be used to analyze the flat rolling of cold and hot steel rectangular strips under a series of different parameters, providing the rolling designer with a tool that he can use to understand the behavior of the steel as it flows through the different passes.
The models developed, take into account all of the non-linearities present in the rolling problem: material, geometric, boundary, and heat transfer. A coupled thermal-mechanical analysis approach is used to account for the coupling between the mechanical and thermal phenomena resulting from the pressure-dependent thermal contact resistance between the steel slab and the steel rolls.
The model predicts the equivalent stress, equivalent plastic strain, maximum strain rate, equivalent total strain, slab temperature increase, increase in roll temperature, strip length increase, slab thickness % reduction (draft), and stripâ s velocity increase, for both the cold and hot rolling processes. The FE model results are an improvement over the results obtained through the classical theory of rolling. The model also demonstrates the role that contact, plastic heat generation and friction generated heat plays in the rolling process.
The analysis performed shows that the steel in cold rolling can be accurately modeled using the elastic-plastic (solid Prandtl-Reuss) formulation, with a von Mises yield surface, the Praguer kinematic hardening rule, and the Ramberg-Osgood hardening material model. The FE models also demonstrate that the steel in hot rolling can be modeled using the rigid-viscoplastic (flow Levy-Mises) formulation, with a von Mises yield surface, and Shidaâ s material model for high temperature steel where the flow stress is a function of the strain, strain rate, and the temperature.
Other important contributions of this work are the demonstration that in cold rolling, plane sections do not remain plane as the classic theory of rolling assumes. As a consequence, the actual displacements, velocity, and stress distributions in the workpiece are compared to and shown to be an improvement over the distributions derived from the classical theory. Finally, the stress distribution in the rolls during the cold rolling process is found, and shown to be analogous to the stress distribution of the Hertz contact problem.Master of Science
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Roslyakova, Irina [Verfasser], Holger [Gutachter] Dette, and Ingo [Gutachter] Steinbach. "Modeling thermodynamical properties by segmented non-linear regression / Irina Roslyakova ; Gutachter: Holger Dette, Ingo Steinbach." Bochum : Ruhr-Universität Bochum, 2017. http://d-nb.info/1140222953/34.
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Norgren, Karin. "Evaluation of Robust Model Building Tools to Improve the Efficiency of Non-linear Mixed Effect Model Building Workflows." Thesis, Uppsala universitet, Institutionen för farmaci, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-451801.
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Population PK models aim to describe the change in drug concentration over time for a specific population. The populations in population PK modelling often refer to subjects in a clinical trial of a potential drug candidate. Population PK models are frequently described by non-linear mixed effect (NLME) models, that including both random and fixed effect components. The fixed effect components 𝜽 (THETA) portray typical parameter values in the population while the random effects components 𝜼 (ETA) allow for the incorporation of inter-individual variability (IIV) on the typical population value. The IIVs are therefore an important element of NLME models, but the estimation of the IIVs can be time consuming and become a limiting factor for more complex models. Linear approximation of the IIV’s has been suggested as a way to reduce the estimation time whilst maintaining robustness. The aim of this project was to evaluate and compare the estimation time and robustness of the IIVs for the linear approximation of parameter estimation errors in NLME models compared to those estimated in non-linear models. Population PK NLME models were developed for two datasets of phenobarbital and moxonidine. The datasets contained different levels of complexity such as number of subjects, datapoints and route of administration. The models were developed within R-studio using the assembler and Pharmpy packages and evaluated in NONMEM 7.5. Based on the objective function values (OFVs), obtained in the model building processes, selected models were linearised using Pearl speaks NONMEM (PsN). The estimated 𝜀′𝑠 and run-time of the linearised models were compared to their non-linearized counterparts. For all the models a reduction in run-time could be observed but with a slight variation in the estimations between the linearised and non-linearised models. The biggest run time reduction was seen in the oral transit compartment models for moxonidine with a 3100-fold reduction in estimation time. The estimation time reduction displayed could more quickly provide valuable information regarding the chosen error models of more complex models and while parameters estimated may not be identical to the non-linearised models, they should be sufficient during the model building phase.
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Farajollahi, Meisam. "Fabrication and non-linear modeling of conducting polymer-based actuators : toward catheter and tactile display applications." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/58649.
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The low voltage operation and relatively high strain response of conducting polymer actuators have made their use in different applications of great interest. In this thesis, modeling and characterization of the chemoelectromechanical behaviour of the linear freestanding and bending trilayer conducting polymer-based actuators are presented. In the modeling approach, a combination of state space representation and a two-dimensional RC transmission line was employed to develop the time domain model. Electrical and ionic conductivities and also Young’s modulus versus oxidation state were measured and incorporated into the model. Significant changes in conductivity and Young’s modulus make using a non-linear model necessary for accurate modeling. Implementation of the non-linear functions for electrical and mechanical properties in the model is one of the major advantages of the modeling approach. Capability of the model to predict the linear strain and radius of curvature for bending trilayer actuators versus time and position with good agreement with experiments are shown in this thesis. Voltage drop along the length of the film, away from the attachment point and the variation in electrical conductivity with state of charge along this length necessitated the use of a 2D non-linear model to obtain effective predictions of response for the film dimension used.
Tubular actuators using conducting polymers as the active material for a catheter application are developed. Laser micromachining to pattern the actuators is demonstrated. A 0.95 mm diameter device is shown to achieve a 22 mm radius of curvature under activation of 2 V. A closed form beam bending model for trilayer actuators with tubular and rectangular cross sections is derived. These formulations predict the radius of curvature as a function of applied voltage and free strain considering different Young’s modulus for conducting polymer layers. This derivation is also useful for other multilayer actuators.
The force generated by trilayer actuators is an important parameter which is investigated in this work. Mathematical derivation and simulations are employed to determine this parameter. Some solutions and their effects on force generated by trilayer actuators are presented to show how the force can be enhanced for tactile interface application.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Zou, Yuanshu. "Robustifying a Non-Linear Model using Wavelets: A Bayesian Approach with an Application to Pharmacokinetics Modeling." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1378197606.
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Ernest, II Charles. "Benefits of Non-Linear Mixed Effect Modeling and Optimal Design : Pre-Clinical and Clinical Study Applications." Doctoral thesis, Uppsala universitet, Institutionen för farmaceutisk biovetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-209247.
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Despite the growing promise of pharmaceutical research, inferior experimentation or interpretation of data can inhibit breakthrough molecules from finding their way out of research institutions and reaching patients. This thesis provides evidence that better characterization of pre-clinical and clinical data can be accomplished using non-linear mixed effect modeling (NLMEM) and more effective experiments can be conducted using optimal design (OD). To demonstrate applicability of NLMEM and OD in pre-clinical applications, in vitro ligand binding studies were examined. NLMEMs were used to evaluate precision and accuracy of ligand binding parameter estimation from different ligand binding experiments using sequential (NLR) and simultaneous non-linear regression (SNLR). SNLR provided superior resolution of parameter estimation in both precision and accuracy compared to NLR. OD of these ligand binding experiments for one and two binding site systems including commonly encountered experimental errors was performed. OD was employed using D- and ED-optimality. OD demonstrated that reducing the number of samples, measurement times, and separate ligand concentrations provides robust parameter estimation and more efficient and cost effective experimentation. To demonstrate applicability of NLMEM and OD in clinical applications, a phase advanced sleep study formed the basis of this investigation. A mixed-effect Markov-chain model based on transition probabilities as multinomial logistic functions using polysomnography data in phase advanced subjects was developed and compared the sleep architecture between this population and insomniac patients. The NLMEM was sufficiently robust for describing the data characteristics in phase advanced subjects, and in contrast to aggregated clinical endpoints, which provide an overall assessment of sleep behavior over the night, described the dynamic behavior of the sleep process. OD of a dichotomous, non-homogeneous, Markov-chain phase advanced sleep NLMEM was performed using D-optimality by computing the Fisher Information Matrix for each Markov component. The D-optimal designs improved the precision of parameter estimates leading to more efficient designs by optimizing the doses and the number of subjects in each dose group. This thesis provides examples how studies in drug development can be optimized using NLMEM and OD. This provides a tool than can lower the cost and increase the overall efficiency of drug development.My name should be listed as "Charles Steven Ernest II" on cover.
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Huber, Florian, and Katrin Rabitsch. "Exchange rate dynamics and monetary policy - Evidence from a non-linear DSGE-VAR approach." WU Vienna University of Economics and Business, 2019. http://epub.wu.ac.at/7210/1/wp295.pdf.
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In this paper, we reconsider the question how monetary policy influences exchange rate dynamics. To this end, a vector autoregressive (VAR) model is combined with a two-country dynamic stochastic general equilibrium (DSGE) model. Instead of focusing exclusively on how monetary policy shocks affect the level of exchange rates, we also analyze how they impact exchange rate volatility. Since exchange rate volatility is not observed, we estimate it alongside the remaining quantities in the model. Our findings can be summarized as follows. Contractionary monetary policy shocks lead to an appreciation of the home currency, with exchange rate responses in the short-run typically undershooting their long-run level of appreciation. They also lead to an increase in exchange rate volatility. Historical and forecast error variance decompositions indicate that monetary policy shocks explain an appreciable amount of exchange rate movements and the corresponding volatility.Series: Department of Economics Working Paper Series
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Sakoske, George Emil. "Non-linear flow, fracture, mechanical quenching, and computer modeling of a glass cylinder pressed between parallel plates." Case Western Reserve University School of Graduate Studies / OhioLINK, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=case1056478895.
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Pihlgren, Pontus. "Design of Class Structures and Inter Class Communication Interface : Computer Methods used in Non-linear Mixed Effects Modeling." Thesis, Uppsala University, Department of Information Technology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-89279.
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The field of pharmacokinetics and pharmacodynamics describes the interactionbetween drugs and the human body from the time the drug is absorbed in the blood stream, distributed in the body, metabolized and finally excreted. The behavior can be described with nonlinear mixed effects models. NONMEM is a software for estimating parameters of such models and simulation of data. This thesis describes the design of Perl-speaks-NONMEM (PsN) which is a software framework for control of different aspects of NONMEM such as creating input, performing execution and output interpretation and presentation. The framework aims to simplify implementation of a range of statistical tools not featured in NONMEM. PsN includes the Bootstrap for measuring statistical accuracy and precision, the Case Deletion Diagnostics (CDD) for identifying influential individuals in medical studies and the Log Likelihood Profiling (LLP) for estimating asymmetrical confidence intervals for parameter estimates. PsN interfaces with various GRID systems: Sun Grid Engine, Plattform LSF and openMosix to enable parallel execution of NONMEM instances. The implementation of PsN was aided with custom built tools for generating class definitions, constructors and from UML diagrams. PsN also provides a set of command line interface tools that simplify usage for researchers without programming experience.
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Simon, Alban. "Non linear internal waves modeling of their influence on acoustic mode energy fluctuations and characterization using SAR systems." Thesis, Monterey, Calif. : Naval Postgraduate School, 2007. http://bosun.nps.edu/uhtbin/hyperion-image.exe/07Dec%5FSimon.pdf.
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Thesis (M.S. in Physical Oceanography and M.S. in Meteorology)--Naval Postgraduate School, December 2007.Thesis Advisor(s): Colosi, John A. ; Durkee, Philip A. "December 2007." Description based on title screen as viewed on January 18, 2008. Includes bibliographical references (p. 89-93). Also available in print.
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Al-Mohssen, Husain Ali 1977. "Chemical vapor deposition modeling using direct simulation Monte Carlo with non-linear chemistry and level set profile evolution." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/89933.
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Voskuilen, Chelsea E. "Modeling Confidence and Response Time in Associative Recognition: A Single Process Explanation of Non-Linear z-ROC Functions." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1338294529.
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Vappou, Jonathan. "Biomechanical study of brain tissue : In vivo approach using magnetic resonance elastography and modeling of non linear properties." Université Louis Pasteur (Strasbourg) (1971-2008), 2007. http://www.theses.fr/2007STR13221.
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Porumamilla, Hemanth. "Modeling, analysis and non-linear control of a novel pneumatic semi-active vibration isolator a concept validation study /." [Ames, Iowa : Iowa State University], 2007.
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Krak, Michael David. "Step-response of discontinuous non-linear torsional systems: Experimental and parameter estimation studies." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1460981012.
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Ferretti, Manuel. "Non-linear mechanics of generalized continua and applications to composite materials." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0100.
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La microstructure des matériaux constitue un outil essentiel pour optimiser les propriétés mécaniques des structures et ainsi améliorer leurs performances. Ce manuscrit est organisé comme suit : - Dans le chapitre 1 nous introduisons les aspects généraux de la mécanique des renforts fibreux.- Dans le chapitre 2 nous rappelons certains concepts fondamentaux concernant la mécanique des milieux continus classiques et les théories de deuxième gradient.- Dans le chapitre 3 nous nous proposons de présenter une première modélisation des renforts fibreux de composites en mettant en place des modèles numériques discrets. Dans un deuxième moment nous introduisons une modélisation continue de deuxième gradient et nous montrons que les termes d’ordre supérieur permettent une description satisfaisante des effets de flexion locale sur-cités.- Dans le chapitre 4 on particularise le cadre général de la mécanique des milieux continus introduit dans le chapitre 2 au cas particulier des milieux continus 2D. - Dans le chapitre 5 nous introduisons une hypothèse cinématique forte sur les déformations ad- missibles, en supposant que les mèches du renfort considéré sont inextensibles. Une méthode numérique permettant de montrer certaines solutions concernant le cas du bias extension test est codée en Mathematica et les résultats obtenus sont discutésGeneralized continuum theories may be good candidates to model micro-structured materials in a more appropriate way (both in the static and dynamic regime) since they are able to account for the description of the macroscopic manifestation of the presence of microstructure in a rather simplified way. The present manuscript is organized as follows: In chapter 1 a general description of fibrous composite reinforcements is given, with particular attention to the introduction of standard experimental tests which are used to characterize the micro- and macro-structural mechanical properties of such materials. In chapter 2 some fundamental issues concerning classical continuum mechanical models are recalled. Moreover, second gradient continuum models are introduced and discussed by means of the Principle of Virtual Work. Since the applications targeted in this manuscript are limited to static cases, we refrain here to treat the more general case including inertia effects. In chapter 3 we start analyzing some discrete and continuum models for the description of the mechanical behavior of 2D woven composites. At this stage of the manuscript, we want to show how some discrete numerical simulations allowed us to unveil some very special deformation modes related to the effect of the local bending of fibers on the overall macroscopic deformation of fibrous composite reinforcements. Such discrete simulations showed rather clearly that microscopic bending of the fibers cannot be neglected when considering the deformation of fibrous composite reinforcements. For this reason, we subsequently introduced a continuum model which is able to account for such microstructure-related effects by means of second gradient terms appearing in the strain energy density. In chapter 4 we reduce the general continuum mechanical framework introduced in Chapter 2 to the particular case of 2D continua. We put a strong accent on the geometric interpretation of second gradient deformation measures which are seen to be directly related to the in-plane curvatures of suitable coordinate lines. Such coordinate lines will be interpreted in the next chapters are the yarns of the considered 2D woven composite, so acquiring a direct physical sense. In chapter 5 we introduce a strong kinematical hypothesis on the admissible deformations, assuming that the yarns composing the woven reinforcements are inextensible. Such assumption allows us to build-up a simplified first gradient model for the behavior of 2D woven reinforcements which is still representative of their mechanical behavior. A constrained least Action principle is proposed and the associated integral Euler-Lagrange equations are presented. A numerical method allowing to show some solutions concerning the case of bias extension test is implemented in Mathematica and the obtained results are discussed
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Harihara, Ramachandra Sharma. "Modeling of Scheduling Algorithms with Alternative Process Plans in an Optimization Programming Language." Ohio University / OhioLINK, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1108045192.
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Törnqvist, Oskar. "Black-Box Modeling of the Air Mass-Flow Through the Compressor in A Scania Diesel Engine." Thesis, Linköping University, Department of Electrical Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-52125.
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Stricter emission legislation for heavy trucks in combination with the customers demand on low fuel consumption has resulted in intensive technical development of engines and their control systems. To control all these new solutions it is desirable to have reliable models for important control variables. One of them is the air mass-flow, which is important when controlling the amount of recirculated exhaust gases in the EGR system and to make sure that the air to fuel ratio is correct in the cylinders. The purpose with this thesis was to use system identification theory to develop a model for the air mass-flow through the compressor. First linear black-box models were developed without any knowledge of the physics behind. The collected data was preprocessed to work in the modeling procedure and then models with one or more inputs where built according to the ARX model structure. To further improve the models performance, non-linear regressors was developed from physical relations for the air mass-flow and used to form grey-box models of the air mass-flow.In conclusion, the performance was evaluated through comparing the estimated air mass-flow from the best model with the estimate that an extended Kalman filter together with a physical model produced.
Hårdare utsläppskrav för tunga lastbilar i kombination med kundernas efterfrågan på låg bränsleförbrukning har resulterat i en intensiv utveckling av motorer och deras kontrollsystem. För att kunna styra alla dessa nya lösningar är det nödvändigt att ha tillförlitliga modeller över viktiga kontrollvariabler. En av dessa är luftmassflödet som är viktig när man ska kontrollera den mängd avgaser som återcirkuleras i EGR-systemet och för att se till att kvoten mellan luft och bränsle är korrekt i motorns cylindrar. Syftet med det här examensarbetet var att använda systemidentifiering för att ta fram en modell över luftmassflödet förbi kompressorn. Först togs linjära svartboxmodeller fram utan att ta med någon kunskap om den bakomliggande fysiken. Insamlade data förbehandlades för att passa in i modelleringsproceduren och efter det skapades i enlighet med ARX-modellstrukturen modeller med en eller flera insignaler. För att ytterligare förbättra modellernas prestanda togs icke-linjära regressorer fram med hjälp av fysikaliska relationer för luftmassflödet. Dessa användes sedan för att skapa gråboxmodeller av luftmassflödet. Avslutningsvis utvärderades prestandan genom att det estimerade luftmassflödet från den bästa modellen jämfördes med det estimat som ett utökat kalmanfilter tillsammans med fysikaliska ekvationer genererade.
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Shen, Jue. "Quantization Effects Analysis on Phase Noise and Implementation of ALL Digital Phase Locked-Loop." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-37212.
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With the advancement of CMOS process and fabrication, it has been a trend to maximize digital design while minimize analog correspondents in mixed-signal system designs. So is the case for PLL. PLL has always been a traditional mixed-signal system limited by analog part performance. Around 2000, there emerged ADPLL of which all the blocks besides oscillator are implemented in digital circuits. There have been successful examples in application of Bluetooth, and it is moving to improve results for application of WiMax and ad-hoc frequency hopping communication link. Based on the theoretic and measurement results of existing materials, ADPLL has shown advantages such as fast time-to-market, low area, low cost and better system integration; but it also showed disadvantages in frequency resolution and phase noise, etc. Also this new topic still opens questions in many researching points important to PLL such as tracking behavior and quantization effect. In this thesis, a non-linear phase domain model for all digital phase-locked loop (ADPLL) was established and validated. Based on that, we analyzed that ADPLL phase noise prediction derived from traditional linear quantization model became inaccurate in non-linear cases because its probability density of quantization error did not meet the premise assumption of linear model. The phenomena of bandwidth expansion and in-band phase noise decreasing peculiar to integer-N ADPLL were demonstrated and explained by matlab and verilog behavior level simulation test bench. The expression of threshold quantization step was defined and derived as the method to distinguish whether an integer-N ADPLL was in non-linear cases or not, and the results conformed to those of matlab simulation. A simplified approximation model for non-linear integer-N ADPLL with noise sources was established to predict in-band phase noise, and the trends of the results conformed to those of matlab simulation. Other basic analysis serving for the conclusions above covered: ADPLL loop dynamics, traditional linear theory and its quantitative limitations and numerical analysis of random number. Finally, a present measurement setup was demonstrated and the results were analyzed for future work.
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Hosseini, Kordkheili Seyed. "A new continuum based non-linear finite element formulation for modeling of dynamic response of deep water riser behavior." Thesis, Brunel University, 2009. http://bura.brunel.ac.uk/handle/2438/4068.
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The principal objective of this investigation is to develop a nonlinear continuum based finite element formulation to examine dynamic response of flexible riser structures with large displacement and large rotation. Updated Lagrangian incremental approach together with the 2nd Piola-Kirchhoff stress tensor and the Green-Lagrange strain tensor is employed to derive the nonlinear finite element formulation. The 2nd Piola-Kirchhoff stress and the Green-Lagrange strain tensors are energy conjugates. These two Lagrangian tensors are not affected by rigid body rotations. Thus, they are used to describe the equilibrium equation of the body independent of rigid rotations. While the current configuration in Updated Lagrangian incremental approach is unknown, the resulting equation becomes strongly nonlinear and has to be modified to a linearized form. The main contribution of this work is to obtain a modified linearization method during development of incremental Updated Lagrangian formulation for large displacement and large rotation analysis of riser structures. For this purpose, the Green-Lagrange strain and the 2nd Piola-Kirchhoff stress tensors are decomposed into two second-order six termed functions of through-thethickness parameters. This decomposition makes it possible to explicitly account for the nonlinearities in the direction along the riser thickness, as well. It is noted that using this linearization scheme avoids inaccuracies normally associated with other linearization schemes. The effects of buoyancy force, riser-seabed interaction as well as steady-state current loading are considered in the finite element solution for riser structure response. An efficient riser problem fluid-solid interaction Algorithm is also developed to maintain the quality of the mesh in the vicinity of the riser surface during riser and fluid mesh movements. To avoid distortions in the fluid mesh two different approaches are proposed to modify fluid mesh movement governing elasticity equation matrices values; 1) taking the element volume into account 2) taking both element volume and distance between riser centre and element centre into account. The formulation has been implemented in a nonlinear finite element code and the results are compared with those obtained from other schemes reported in the literature.
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Allen, Andy. "Analytic element modeling of the High Plains Aquifer: non-linear model optimization using Levenberg-Marquardt and particle swarm algorithms." Thesis, Kansas State University, 2012. http://hdl.handle.net/2097/14103.
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Master of ScienceDepartment of Civil Engineering
David R. Steward
Accurate modeling of the High Plains Aquifer depends on the availability of good data that represents and quantities properties and processes occurring within the aquifer. Thanks to many previous studies there is a wealth of good data available for the High Plains Aquifer but one key component, groundwater-surface water interaction locations and rates, is generally missing. Without these values accurate modeling of the High Plains Aquifer is very difficult to achieve. This thesis presents methods for simplifying the modeling of the High Plains Aquifer using a sloping base method and then applying mathematical optimization techniques to locate and quantify points of groundwater-surface water interaction. The High Plains Aquifer has a base that slopes gently from west to east and is approximated using a one-dimensional stepping base model. The model was run under steady-state predevelopment conditions using readily available GIS data representing aquifer properties such as hydraulic conductivity, bedrock elevation, recharge, and the predevelopment water level. The Levenberg-Marquardt and particle swarm algorithms were implemented to minimize error in the model. The algorithms reduced model error by finding locations in the aquifer of potential groundwater-surface water interaction and then determining the rate of groundwater to surface water exchange at those points that allowed for the best match between the measured predevelopment water level and the simulated water level. Results from the model indicate that groundwater-surface water interaction plays an important role in the overall water balance in the High Plains Aquifer. Findings from the model show strong groundwater-surface water interaction occurring in the northern basin of the aquifer where the water table is relatively shallow and there are many surface water features. In the central and southern basins the interaction is primarily limited to river valleys. Most rivers have baseflow that is a net sink from groundwater.
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Mauff, Katya. "Multivariate muti-level non-linear mixed-effect models and their application to the modeling of drug-concentration time curves." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10719.
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This thesis discusses the techniques involved in the fitting of nonlinear mixed effect (NLME) models. In particular, it looks at the application of these techniques to the analysis of concentration-time data for the aforementioned antimalarial compounds, and details the necessary extensions to the basic modeling process that were required in order to accommodate multiple responses and multiple observation phases (pregnant and postpartum).
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Puida, Mantas. "Kompiuterinis struktūrinių inovacijų biojutikliuose modeliavimas." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20090917_095908-48267.
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Matematinis ir skaitinis biojutiklių modeliavimas yra svarbus uždavinys, kuriant naujus ir tobulinant esamus biojutiklius. Disertacijos tyrimo objektas – matematiniai bei skaitiniai modeliai, aprašantys naujoviškų lipazės aktyvumo nustatymo biojutiklių bei teorinio biojutiklio, padengto valdoma membrana, veikimą. Tyrimo tikslai – nustatyti, kokie matematiniai ir skaitiniai modeliai geriausiai tinka lipazės aktyvumo nustatymo biojutikliams aprašyti, taip pat nustatyti, kokiais parametrais pasižymėtų biojutiklis, turintis valdomą membraną, kokiomis sąlygomis išryškėtų jo privalumai ir trūkumai. Nustatyta, kad lipazės aktyvumo matavimo biojutiklio modeliavimui klasikinį modelį reikia papildyti netiesiniu nariu. Biojutiklis su valdoma membrana pasiteisintų, jei fiziškai neištraukiant jutiklio iš darbinės aplinkos, reikėtų perjunginėti jo darbo režimą iš difuzinio į kinetinį ir atvirkščiai.Biosensor mathematical and computer modeling is an important task for the development of new biosensors and for the improvement of the existing ones. Objects of this study are mathematical and numerical models which describe operation of novel lipase activity assessment biosensors and theoretical biosensor with controllable permeability membrane. Specific aims of this thesis are to identify what mathematical and numerical models are best suited for modeling specific lipase activity assessment biosensors and to identify what parameters of operation are specific for biosensor with controllable membrane. Also to identify the conditions which would reveal the positive and negative features of controllable membrane. It was discovered that in the case of lipase activity assessment biosensor the classic mathematical model should be extended with a non-linear term (in respect to substrate). Also, it was discovered that biosensor with controllable membrane would be useful in cases when biosensor cannot be physically removed from the operating environment, but still needs to be reconfigured for operation in the kinetic or diffusion mode.