Дисертації: "Mathematical model of tire"

1

Straka, Tomáš. "Matematické modely pneumatik." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-449788.

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This master‘s thesis describes problematics of mathematical models of tires for computer simulations. The goal of this thesis is to depict currently used models of tires and to compare them. Thesis describes brush type models, Fiala, Magic Formula (Pacejka), FTire, UA-Gim, 521 and DELFT. Those models are compared to each other by simulations carried out in software MSC ADAMS Car. The results are shown in figures with commentary and evaluation. This thesis serves as introduction to problematics of currently used mathematical models of tire in computer simulations.

2

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.

QC 20151015

3

Kim, Taejung 1969. "Time-optimal CNC tool paths : a mathematical model of machining." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8861.

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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.
Includes bibliographical references (p. 181-188).
Free-form surface machining is a fundamental but time-consuming process in modern manufacturing. The central question we ask in this thesis is how to reduce the time that it takes for a 5-axis CNC (Computer Numerical Control) milling machine to sweep an entire free-form surface in its finishing stage. We formulate a non-classical variational time-optimization problem defined on a 2-dimensional manifold subject to both equality and inequality constraints. The machining time is the cost functional in this optimization problem. We seek for a preferable vector field on a surface to obtain skeletal information on the toolpaths. This framework is more amenable to the techniques of continuum mechanics and differential geometry rather than to path generation and conventional CAD/CAM (Computer Aided Design and Manufacturing) theory. After the formulation, this thesis derives the necessary conditions for optimality. We decompose the problem into a series of optimization problems defined on 1-dimensional streamlines of the vector field and, as a result, simplify the problem significantly. The anisotropy in kinematic performance has a practical importance in high-speed machining. The greedy scheme, which this thesis implements for a parallel hexapod machine tool, uses the anisotropy for finding a preferable vector field.
(cont.) Numerical integration places tool paths along its integral curves. The gaps between two neighboring toolpaths are controlled so that the surface can be machined within a specified tolerance. A conservation law together with the characteristic theory for partial differential equations comes into play in finding appropriately-spaced toolpaths, avoiding unnecessarily-overlapping areas. Since the greedy scheme is based on a local approximation and does not search for the global optimum, it is necessary to judge how well the greedy paths perform. We develop an approximation theory and use it to economically evaluate the performance advantage of the greedy paths over other standard schemes. In this thesis, we achieved the following two objectives: laying down the theoretical basis for surface machining and finding a practical solution for the machining problem. Future work will address solving the optimization problem in a stricter sense.
by Taejung Kim.
Ph.D.

4

Daukste, Liene. "Mathematical Modelling of Cancer Cell Population Dynamics." Thesis, University of Canterbury. Department of Mathematics and Statistics, 2012. http://hdl.handle.net/10092/10057.

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Mathematical models, that depict the dynamics of a cancer cell population growing out of the human body (in vitro) in unconstrained microenvironment conditions, are considered in this thesis. Cancer cells in vitro grow and divide much faster than cancer cells in the human body, therefore, the effects of various cancer treatments applied to them can be identified much faster. These cell populations, when not exposed to any cancer treatment, exhibit exponential growth that we refer to as the balanced exponential growth (BEG) state. This observation has led to several effective methods of estimating parameters that thereafter are not required to be determined experimentally. We present derivation of the age-structured model and its theoretical analysis of the existence of the solution. Furthermore, we have obtained the condition for BEG existence using the Perron-Frobenius theorem. A mathematical description of the cell-cycle control is shown for one-compartment and two-compartment populations, where a compartment refers to a cell population consisting of cells that exhibit similar kinetic properties. We have incorporated into our mathematical model the required growing/aging times in each phase of the cell cycle for the biological viability. Moreover, we have derived analytical formulae for vital parameters in cancer research, such as population doubling time, the average cell-cycle age, and the average removal age from all phases, which we argue is the average cell-cycle time of the population. An estimate of the average cell-cycle time is of a particular interest for biologists and clinicians, and for patient survival prognoses as it is considered that short cell-cycle times correlate with poor survival prognoses for patients. Applications of our mathematical model to experimental data have been shown. First, we have derived algebraic expressions to determine the population doubling time from single experimental observation as an alternative to empirically constructed growth curve. This result is applicable to various types of cancer cell lines. One option to extend this model would be to derive the cell cycle time from a single experimental measurement. Second, we have applied our mathematical model to interpret and derive dynamic-depicting parameters of five melanoma cell lines exposed to radiotherapy. The mathematical result suggests there are shortcomings in the experimental methods and provides an insight into the cancer cell population dynamics during post radiotherapy. Finally, a mathematical model depicting a theoretical cancer cell population that comprises two sub-populations with different kinetic properties is presented to describe the transition of a primary culture to a cell line cell population.

5

Yip, Wai San. "Model updating in real-time optimization /." *McMaster only, 2002.

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6

McCloud, Nadine. "Model misspecification theory and applications /." Diss., Online access via UMI:, 2008.

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7

Tang, Philip Kwok Fan. "Stochastic Hydrologic Modeling in Real Time Using a Deterministic Model (Streamflow Synthesis and Reservoir Regulation Model), Time Series Model, and Kalman Filter." PDXScholar, 1991. https://pdxscholar.library.pdx.edu/open_access_etds/4580.

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The basic concepts of hydrologic forecasting using the Streamflow Synthesis And Reservoir Regulation Model of the U.S. Army Corps of Engineers, auto-regressive-moving-average time series models (including Greens' functions, inverse functions, auto covariance Functions, and model estimation algorithm), and the Kalman filter (including state space modeling, system uncertainty, and filter algorithm), were explored. A computational experiment was conducted in which the Kalman filter was applied to update Mehama local basin model (Mehama is a 227 sq. miles watershed located on the North Santiam River near Salem, Oregon.), a typical SSARR basin model, to streamflow measurements as they became available in simulated real time. Among the candidate AR and ARMA models, an ARMA(l,l) time series model was selected as the best-fit model to represent the residual of the basin model. It was used to augment the streamflow forecasts created by the local basin model in simulated real time. Despite the limitations imposed by the quality of the moisture input forecast and the design and calibration of the basin model, the experiment shows that the new stochastic methods are effective in significantly improving the flood forecast accuracy of the SSARR model.

8

Kang, Joonyun. "Time domain mathematical model for six-degree-of-freedom motion in a wave." Thesis, University of Strathclyde, 2009. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21999.

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In this thesis a novel controller for providing greater flexibility of operation of wind turbines known as the Power Adjusting Controller (PAC) is presented. The controller takes the form of an augmentation to a wind turbine’s full envelope controller, allowing it to be applied to any horizontal axis, pitch regulated, variable speed wind turbine. Conventional wind turbine control seeks to maximise the power output of a wind turbine whilst minimising the loads on the turbine, controlling on the error in generator speed via demands to the blade pitch actuator and generator torque actuator. The PAC uses additions to the full envelope controller inputs and outputs to alter the power output of the turbine by an additional input value ∆P. It is ensured that the operation of the full envelope controller is not compromised by the PAC. Testing of the PAC using lumped parameter models of wind turbines and full aero-elastic models makes clear a requirement for a wind speed estimator within the PAC that incorporates the effects of dynamic inflow. A novel wind speed estimator that accounts for dynamic inflow by redefining blade element momentum theory solely in terms of the dynamics at the rotor is therefore developed and incorporated into the PAC. Limits are designed to ensure that the operating point of a wind turbine with the PAC is kept within a safe operational envelope, and a system of flags and sub-flags is developed to allow easy integration of the PAC into a hierarchical wind farm control structure. The effect of using the PAC on the wind turbine loads is investigated, with the ultimate loads introduced by operation of the PAC found to be within the range of normal operating loads and the impact of prolonged reduction of the power output found to reduce the lifetime damage equivalent loads in most cases.

9

Despain, Lynnae. "A Mathematical Model of Amoeboid Cell Motion as a Continuous-Time Markov Process." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5671.

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Understanding cell motion facilitates the understanding of many biological processes such as wound healing and cancer growth. Constructing mathematical models that replicate amoeboid cell motion can help us understand and make predictions about real-world cell movement. We review a force-based model of cell motion that considers a cell as a nucleus and several adhesion sites connected to the nucleus by springs. In this model, the cell moves as the adhesion sites attach to and detach from a substrate. This model is then reformulated as a random process that tracks the attachment characteristic (attached or detached) of each adhesion site, the location of each adhesion site, and the centroid of the attached sites. It is shown that this random process is a continuous-time jump-type Markov process and that the sub-process that counts the number of attached adhesion sites is also a Markov process with an attracting invariant distribution. Under certain hypotheses, we derive a formula for the velocity of the expected location of the centroid.

10

Wang, Xiang, and 王翔. "Model order reduction of time-delay systems with variational analysis." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B46604236.

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11

張立茜 and Liqian Zhang. "Optimal H2 model reduction for dynamic systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31241372.

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12

Cheung, Ka-chun, and 張家俊. "Optimal asset allocation problems under the discrete-time regime-switching model." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B31311234.

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13

Wu, Sha. "Mathematical Model of Glucose-Insulin Metabolism and Model Predictive Glycemic Control for Critically Ill Patients Considering Time Variability of Insulin Sensitivity." Kyoto University, 2020. http://hdl.handle.net/2433/259047.

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14

Mwelwa, Elenestina Mutekenya. "The application of the monthly time step Pitman rainfall-runoff model to the Kafue River basin of Zambia." Thesis, Rhodes University, 2005. http://hdl.handle.net/10962/d1006171.

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This thesis presents a discussion on the study undertaken in the application of the monthly time step Pitman rainfall-runoff model to the Kafue River basin. The study constituted one of the initial steps in the capacity building and expansion of the application of hydrologic models in the southern African region for water resources assessment, one of the core areas of the Southern African FRIEND project (Flow Regimes from International Experimental Network Data). The research process was undertaken in four major stages, each stage working towards achieving the research objectives. The first stage was the preparation of spatial data which included the selection and delineation of sub-catchments and inclusion of spatial features required to run the Pitman model and transferring the spatial data into SPATSIM. The second stage was the preparation of input data, mainly rainfall, streamflow, evaporation, and water abstraction data. This information was then imported into SPATSIM, which was able to assist in the further preparation of data by assessment of the input data quality, linking of observed flows and spatial interpolation of point rainfall data to average catchment rainfall in readiness for running and calibration of the model. The third stage was the running and calibration of the Pitman model. Use was made of both the automatic calibration facility, as well as manual calibration by means of the time series graph display and analysis facility of SPATSIM. Model calibration was used to obtain the best fit and an acceptable correlation between the simulated and the observed flows and to obtain simulation parameter sets for sub-catchments and regions within the Kafue catchment. The fourth stage was the analysis and evaluation of the model results. This included verification of results over different time periods and validation and testing of parameter transfers to other catchments. This stage also included the evaluation of SPATSIM as a tool for applying the model and as a database for the processing and storage of water resources data. The study’s output includes: A comprehensive database of hydrometeorological, physical catchment characteristics, landuse and water abstraction information for the Kafue basin; calibrated Pitman model parameters for the sub-catchments within the Kafue basin; recommendations for future work and data collection programmes for the application of the model. The study has also built capacity by facilitating training and exposure to rainfall-runoff models (specifically the Pitman model) and associated software, SPATSIM. In addition, the dissemination of the results of this study will serve as an effective way of raising awareness on the application of the Pitman model and the use of the SPATSIM software within Zambia and the region. The overall Pitman model results were found to be satisfactory and the calibrated model is able to reproduce the observed spatial and temporal variations in streamflow characteristics in the Kafue River basin.

15

Boguta, Maria. "A New Space-Time Model for Interacting Agents in the Financial Market." Thesis, Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-3180.

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In this thesis we present a new space-time model of interacting agents in the financial market. It is a combination of the Curie-Weiss model and a model introduced by Järpe. We investigate properties such as the critical temperature and magnetization of the system. The distribution of the Hamiltonian function is obtained and a hypothesis test of independence is derived. The results are illustrated in an example based on real data.

16

Camp, Nicholas Julian. "A model for the time dependent behaviour of rock joints." Master's thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/21138.

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This thesis is a theoretical investigation into the time-dependent behaviour of rock joints. Much of the research work that has been conducted to date in the area of finite element analysis has been involved with the development of special elements to deal with these discontinuities. A comprehensive literature survey is undertaken highlighting some of the significant contributions to the modelling of joints. It is then shown how internal variables can be used to model discontinuities in the rock mass. A finite element formulation is described resulting in a system of equations which can easily be adapted to cope with various constitutive behaviours on the discontinuities. In particular, a viscoplastic relationship; which uses a homogeneous, hyperbolic yield function is adopted. The viscoplastic relationship can be used for both time-dependent (creep) or quasi-static (elasto-plastic) problems. Time-dependent behaviour requires a time integration scheme and therefore a generalised explicit/implicit scheme is chosen. The resulting numerical algorithms are all implemented in the finite element program, NOSTRUM. Various examples are presented to illustrate certain features of both the formulation and the numerical algorithm. Jointed rock beams and a jointed infinite rock mass are modelled assuming plane strain conditions. Reasons are proposed to explain the predicted behaviour. The results of the analysis shows that the internal variable formulation successfully models time-dependent joint movements in a continuous media. The method gives good, qualitative results which agree with observations in deep level mines. It is recommended that quantitative mine observations be used to calibrate the model so that usable predictions of joint movement can be made. This would enable any new developments to be implemented in the model. Further work on implicit methods might allow greater modelling flexibility by reducing computer run times.

17

Ryberg, Albin. "Optimisation of hauling schedules and passing bay locations in underground mines using a time-discrete mathematical model." Thesis, Linköpings universitet, Optimeringslära, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-169826.

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The ambition of this project is to contribute to the development of optimisation techniques for underground mining. This resulted in a mathematical model to optimise a type of underground transportation system called the ramp. The ramp is a tunnel from the underground mining areas which trucks use to transport material up to the surface. We consider the case where the ramp only fits one truck at a time and it therefore needs passing bays where trucks can meet. We were inspired by an article which optimised the positions of the passing bays and the schedule for the trucks, during a certain time period. We extended that work by proposing a new mathematical model that can handle a more general and complex mine. The result from optimally solving the model gives the positioning of the passing bays and a schedule which completes a number of trips down and up the ramp as quickly as possible. The model can be used both for long-term and short-term planning. The long-term planning regards the positions of the passing bays. The model can therefore be used before the passing bays are constructed to gain insights about where to place them. The short-term planning is about finding an optimal trip schedule given the placement of the passing bays. The model can therefore also be used to provide a haulage schedule for an upcoming time period.

18

Rodriguez, Javier A. "Capacity expansion and capital investment decisions using the Economic Investment Time Model : a case oriented approach /." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-07292009-090518/.

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19

Kim, Deokmin. "Mathematical and historical dynamics of modern economy : an application to the Korean economy." Thesis, Paris 1, 2017. http://www.theses.fr/2017PA01E036/document.

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Il est essentiel d’étudier la dynamique non linéaire en mathématiques et nous permet d’interpréter des phénomènes aussi irréguliers et imprévisibles à la suite de processus déterministes, et non de simples erreurs ou chances statistiques.La dynamique du système est une méthodologie ainsi qu’une méthode pour implémenter des mouvements dynamiques non linéaires. Par ces deux méthodes,nous capturons la crise dans les cycles économiques et testons l’accumulation de capital, et les changements techniques dans le cadre du modèle Macro Stock Management et les appliquons à ceux de l’économie sud-coréenne. Divers outils d’analyse des séries chronologiques sont utilisés pour estimer les effets de l’investissement sur les taux de profit et les effets de l’inégalité salariale et de la dette des consommateurs sur la demande intérieure depuis la crise financière mondiale de 2008. Le Structural Vector Auto-Regressive model impose des restrictions à long terme ou à court terme sur le système VAR, il utilise pour distinguer deux variables avec des caractéristiques similaires. Perron (1989) fait valoir que les tests de racine unitaire traditionnels tels que le test Augmenté Dickey-Fuller sont susceptibles de ne pas détecter la stationnarité ou la non stationnarité des données si elles ont des ruptures structurelles. Zivot et Andrews(1992) et Lumsdaine et Papell (1997) proposent le modèle de test racine unitaire avec ruptures structurelles endogènes. Le test Gregory-Hansen fournit des informations sur une rupture structurelle dans un test de co-intégration. Le modèle ARDL (Auto Regressive Distributed Lags) est utilisé pour capturer les relations à long terme entre les variables
It is essential to study nonlinear dynamics in mathematics, and it gives us room to interpret such irregular and unpredictable phenomena as a result of deterministic processes, not mere statistical errors or chances. System dynamics is a methodology as well as a method to implement nonlinear dynamic movements.By these two methods, we capture the crisis in the business cycles and test capital accumulation, and technical changes within the framework of the Macro Stock Management model and apply them to those of the Korean economy. In the latter part of this study, various time series analysis tools are used to estimate the effects of investment on the rates of profit and the effects of wage inequality and consumers’ debt on domestic demand since the global financial crisis of2008. Because the Structural Vector Auto-Regressive (SVAR) model impose on the long run or short run restrictions on the VAR system, it uses to distinguish two variables with similar characteristics, such as the after-tax rate of profit and the rate of profit after payment of interests and dividends excluding taxes (the after-payment rate of profit). Perron (1989) argues that the traditional unit root tests such as the Augmented Dickey-Fuller test are likely to fail to detect the stationarity or non-stationarity of the data if it has structural breaks. Zivot and Andrews (1992) and Lumsdaine and Papell (1997) propose the unit root test of the time series data with a single or two breaks in the time series. The Gregory-Hansen test provides information about a structural break in a cointegration test. The Auto Regressive Distributed Lags (ARDL) model is used to capture long-run relationships between variables

20

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. .

21

Wang, Qing, and 王卿. "Model reduction for dynamic systems with time delays: a linear matrix inequality approach." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B38645439.

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22

Kallblad, Sigrid Linnea. "Topics in portfolio choice : qualitative properties, time consistency and investment under model uncertainty." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:3593bc59-594e-4feb-a20a-c18b75c9b8bc.

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The study of expected utility maximization in continuous-time stochastic market models dates back to the seminal work of Merton 1969 and has since been central to the area of Mathematical Finance. The associated stochastic optimization problems have been extensively studied. The problem formulation relies on two strong underlying assumptions: the ability to specify the underpinning market model and the knowledge of the investor's risk preferences. However, neither of these inputs is easily available, if at all. Resulting issues have attracted continuous attention and prompted very active and diverse lines of research. This thesis seeks to contribute towards this literature and questions related to both of the above issues are studied. Specifically, we study the implications of certain qualitative properties of the utility function; we introduce, and study various aspects of, the notion of robust forward investment criteria; and we study the investment problem associated with risk- and ambiguity-averse preference criteria defined in terms of quasiconcave utility functionals.

23

Zheng, Tingting. "Mathematical modeling of soil erosion by rainfall and shallow overland flow." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/9144.

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New analytical and numerical solutions are developed to both the kinematic approximation to the St Venant equations and the Hairsine-Rose (HR) soil erosion model in order to gain a better physical understanding of soil erosion and sediment transport in shallow overland flow. The HR model is unique amongst physically based erosion models in that it is the only one that: considers the entire distribution of the soil s sediment size classes, considers the development of a layer of deposited non-cohesive sediment having different characteristics to the original underlying cohesive soil and considers separately the erosion processes of rainfall detachment, runoff entrainment and gravitational deposition. The method of characteristics and the method of lines were used to develop both the analytical and numerical solutions respectively. These solutions were obtained for boundary and initial conditions typical of those used in laboratory flume experiments along with physically realistic constant and time dependent excess rainfall rates. Depending on the boundary and initial conditions, interesting new solutions of the kinematic wave equation containing expansion waves, travelling shocks as well as solutions which split into an upslope and downslope drying profiles were found. Numerical solutions of the HR model were applied to the experimental flume data of Polyakov and Nearing (2003) obtained under flow conditions which periodically cycled between net erosion and net deposition conditions. While excellent agreement was found with suspended sediment data, the analysis suggested that an additional transport mechanisms, traditionally not included in soil erosion models, was occurring. While the inclusion of bed-load transport improved the ii overall model prediction, it was still not sufficient. Subsequent asymptotic analysis then showed that the interaction of the flow with an evolving bed morphology was in fact far more important than bed load transport. A very interesting finding from this work showed that the traditional criterion of validating sediment transport model based solely on suspended sediment data was not sufficient as reliable predictions could be obtained even when important transport mechanisms were neglected. Experimental plots of sediment discharge or suspended sediment concentration against water discharge in overland flow have been shown to contain significant hysteresis between the falling and rising limbs of the discharge hydrograph. In the final Chapter, the numerical solution developed for the complete system of soil erosion and kinematic flow was used to show that it was possible for the HR model to simulate three of the four hysteresis loops identified in the literature. Counter clock-wise loops, clock-wise loops and figure 8 loops could all be produced as a result of starting with different initial conditions, being mi(x; 0) = 0, mi(x; 0) = pimt and mi(x; 0) = 0:5pimt respectively. This is the first time that these types of hysteresis loops have been produced by any erosion model. The generation of these hysteresis loops are physically explainable in terms of sediment availability and is consistent with data obtained on the field scale.

24

Casas, Villalba Isabel. "Statistical inference in continuous-time models with short-range and/or long-range dependence." University of Western Australia. School of Mathematics and Statistics, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0133.

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The aim of this thesis is to estimate the volatility function of continuoustime stochastic models. The estimation of the volatility of the following wellknown international stock market indexes is presented as an application: Dow Jones Industrial Average, Standard and Poor’s 500, NIKKEI 225, CAC 40, DAX 30, FTSE 100 and IBEX 35. This estimation is studied from two different perspectives: a) assuming that the volatility of the stock market indexes displays shortrange dependence (SRD), and b) extending the previous model for processes with longrange dependence (LRD), intermediaterange dependence (IRD) or SRD. Under the efficient market hypothesis (EMH), the compatibility of the Vasicek, the CIR, the Anh and Gao, and the CKLS models with the stock market indexes is being tested. Nonparametric techniques are presented to test the affinity of these parametric volatility functions with the volatility observed from the data. Under the assumption of possible statistical patterns in the volatility process, a new estimation procedure based on the Whittle estimation is proposed. This procedure is theoretically and empirically proven. In addition, its application to the stock market indexes provides interesting results.

25

Hetrick, Todd M. "Development and Validation of a Modified Clean Agent Draining Model for Total Flooding Fire Suppression Systems." Digital WPI, 2009. https://digitalcommons.wpi.edu/etd-theses/121.

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This project analyzes the validity of theoretical models used to predict the duration (hold time) for which a halon-replacement suppression agent will remain within a protected enclosure. Two current models and one new formulation are investigated; the sharp descending interface model (as applied in NFPA 2001, Annex C), the wide descending interface model (implemented in ISO 14520.1, Annex E), and the thick descending interface model (introduced herein). The thick interface model develops the characteristic thickness as an additional input parameter. Experimental data from 34 full-scale tests designed to characterize the discharge and draining dynamics of seven clean extinguishing agents (CEA) is used to assess model validity. For purposes of model validation the characteristic thickness is regressed from the experimental data although further work may be required to establish the independence of this parameter to other system design and environmental variables. Results show that the wide and sharp interface models' validity is highly sensitive to the threshold of agent concentration decay being modeled; whereas the thick interface prediction method demonstrates increased robustness at any modeled threshold. When the hold time is defined as a 15% decay in agent concentration, experimentally obtained hold time values are roughly 10% shorter than sharp interface predictions, 60% longer than wide interface predictions, and 30% longer than the thick interface model predicts.

26

Cigánek, Jan. "Metoda konečných prvků v časové oblasti a její aplikace." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-233673.

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Disertační práce se zabývá modelováním dispersních materiálů metodou konečných prvků v časové oblasti. V práci jsem navrhl matematický model zahrnující dispersní modely a aplikoval jsem na něj metodu konečných prvků. Pozornost jsem věnoval třem nejvíce používaným dispersním modelům. Jedná se o Debyeho model, Lorentzův model a Drudův model. Dále jsem se zabýval technikami implementace těchto dispersních modelů. Techniky jsem zabudoval do metody konečných prvků. Navíc jsem vyvinul novou metodu založenou na technice digitální filtrace. Funkčnost vyvinutých metod a technik jsem ověřil na řadě testovacích příkladů. Diskutoval jsem dosažené výsledky a navrhuji jejich možná vylepšení.

27

Milan, Milotić. "Uticaj procesnih parametara na pirolizu i gasifikaciju otpadnih automobilskih pneumatika." Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2015. http://www.cris.uns.ac.rs/record.jsf?recordId=93324&source=NDLTD&language=en.

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U disertaciji je prikazan matematički modelgasifikacije otpadnih automobilskih pneumatika.Modelom je istražen uticaj količine ubačenog vazduhai vodene pare u gasifikator i temperatura gasifikacijena prinos gasovitih produkata. Numerička proceduraje riješena Newton-Raphson metodom a brojnevrijednosti molskih udjela gasovitih komponenata uravnotežnoj mješavini dobijene su korišćenjemprogramskog jezika C.U drugom dijelu disertacije prikazano jeeksperimentalno ispitivanje pirolize otpadnihautomobilskih pneumatika. Eksperimentalni rezultatiukazuju da na prinos gasa, odnosno na prinos čvrstog(koksnog) ostatka značajno utiču parametri: veličinačestice otpadne gume, temperatura pirolize i brzinazagrijavanja uzorka.
The dissertation presents a mathematical model ofgasification of waste automotive tires. The modelexamined the impact of the amount of the loaded air andwater vapor in the gasifier and gasification temperatureto yield gaseous products. The numerical procedure isresolved Newton-Raphson method and the numericalvalues of mole portions of gaseous components in theequilibrium mixture obtained using the programminglanguage C.In the second part of the thesis is shownexperimentally testing pyrolysis of waste automotivetires. Experimental results indicate that the yield of gas,or to yield a solid (coke) significantly affect the rest of theparameters: the size of the particles of waste rubberpyrolysis temperature and heating rate of the sample.

28

Imam, Bisher 1960. "Evaluation of disaggregation model in arid land stream flow generation." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277033.

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A Disaggregation model was tested for arid land stream flow generating. The test was performed on data from Black River, near Fort Apache, Arizona. The model was tested in terms of preserving the relevant historical statistics on both monthly and daily levels, the monthly time series were disaggregated to a random observation of their daily components and the daily components were then reaggregated to yield monthly values. A computer model (DSGN) was developed to perform the model implementation. The model was written and executed on the Macintosh plus personal computer Data from two months were studied; the October data represented the low flow season, while the April data represented the high flow season. Twenty five years of data for each month was used. The generated data for the two months was compared with the historical data.

29

Tinari, Paul D. D. "It is possible to use some of the basic equations of mathematical physics to model time and space varying sociological phenomena. Thèse annexe." Doctoral thesis, Universite Libre de Bruxelles, 1989. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/213238.

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30

Rodríguez, Iván. "Bayesian analysis for Cox's proportional hazard model with error effect and applications to accelerated life testing data." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2007. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.

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31

Lee, Hojong. "Identification of Tire Dynamics Based on Intelligent Tire." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/88829.

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Sensor-embedded tires, known as intelligent tires, have been widely studied because they are believed to provide reliable and crucial information on tire-road contact characteristics e.g., slip, forces and deformation of tires. Vehicle control systems such as ABS and VSP (Vehicle Stability Program) can be enhanced by leveraging this information since control algorithms can be updated based on directly measured parameters from intelligent tire rather than estimated parameters based on complex vehicle dynamics and on-board sensor measurements. Moreover, it is also expected that intelligent tires can be utilized for the purpose of the analysis of tire characteristics, taking into consideration that the measurements from the sensors inside the tire would contain considerable information on tire behavior in the real driving scenarios. In this study, estimation methods for the tire-road contact features by utilizing intelligent tires are investigated. Also, it was discussed how to identify key tire parameters based on the fusion technology of intelligent tire and tire modeling. To achieve goals, extensive literature reviews on the estimation methods using the intelligent tire system was conducted at first. Strain-based intelligent tires were introduced and tested in the laboratory for this research. Based on the literature review and test results, estimation methods for diverse tire-road contact characteristics such as slippages and contact forces have been proposed. These estimation methods can be grouped into two categories: statistical regressions and model based methods. For statistical regressions, synthetic regressors were proposed for the estimation of contact parameters such as contact lengths, rough contact shapes, test loads and slip angles. In the model-based method, the brush type tire model was incorporated into the estimation process to predict lateral forces. Estimated parameters using suggested methods agreed well with measured values in the laboratory environment. By utilizing sensor measurements from intelligent tires, the tire physical characteristics related to in-plane dynamics of the tire, such as stiffness of the belt and sidewall, contact pressure distribution and internal damping, were identified based on the combination of strain measurements and a flexible ring tire model. The radial deformation of the tread band was directly obtained from strain measurements based on the strain-deformation relationship. Tire parameters were identified by fitting the radial deformations from the flexible ring model to those derived from strain measurements. This approach removed the complex and repeated procedure to satisfy the contact3 constraints between the tread and the road surface in the traditional ring model. For tires with different specifications, identification using the suggested method was conducted and their results are compared with results from conventional methods and tests, which shows good agreements. This approach is available for the tire standing still or rolling at low speeds. For tires rolling at high speeds, advanced tire model was implemented and associated with strain measurements to estimate dynamic stiffness, internal damping effects as well as dynamic pressure distributions. Strains were measured for a specific tire under various test conditions to be used in suggested identification methods. After estimating key tire parameters step by step, dynamic pressure distributions was finally estimated and used to update the estimation algorithm for lateral forces. This updated estimation method predicted lateral forces more accurately than the conventional method. Overall, this research will serve as a stepping stone for developing a new generation of intelligent tire capable of monitoring physical tire characteristics as well as providing parameters for enhanced vehicle controls.
PHD

32

Coroneo, Laura. "Essays on modelling and forecasting financial time series." Doctoral thesis, Universite Libre de Bruxelles, 2009. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210284.

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This thesis is composed of three chapters which propose some novel approaches to model and forecast financial time series. The first chapter focuses on high frequency financial returns and proposes a quantile regression approach to model their intraday seasonality and dynamics. The second chapter deals with the problem of forecasting the yield curve including large datasets of macroeconomics information. While the last chapter addresses the issue of modelling the term structure of interest rates.

The first chapter investigates the distribution of high frequency financial returns, with special emphasis on the intraday seasonality. Using quantile regression, I show the expansions and shrinks of the probability law through the day for three years of 15 minutes sampled stock returns. Returns are more dispersed and less concentrated around the median at the hours near the opening and closing. I provide intraday value at risk assessments and I show how it adapts to changes of dispersion over the day. The tests performed on the out-of-sample forecasts of the value at risk show that the model is able to provide good risk assessments and to outperform standard Gaussian and Student’s t GARCH models.

The second chapter shows that macroeconomic indicators are helpful in forecasting the yield curve. I incorporate a large number of macroeconomic predictors within the Nelson and Siegel (1987) model for the yield curve, which can be cast in a common factor model representation. Rather than including macroeconomic variables as additional factors, I use them to extract the Nelson and Siegel factors. Estimation is performed by EM algorithm and Kalman filter using a data set composed by 17 yields and 118 macro variables. Results show that incorporating large macroeconomic information improves the accuracy of out-of-sample yield forecasts at medium and long horizons.

The third chapter statistically tests whether the Nelson and Siegel (1987) yield curve model is arbitrage-free. Theoretically, the Nelson-Siegel model does not ensure the absence of arbitrage opportunities. Still, central banks and public wealth managers rely heavily on it. Using a non-parametric resampling technique and zero-coupon yield curve data from the US market, I find that the no-arbitrage parameters are not statistically different from those obtained from the Nelson and Siegel model, at a 95 percent confidence level. I therefore conclude that the Nelson and Siegel yield curve model is compatible with arbitrage-freeness.

Doctorat en Sciences économiques et de gestion
info:eu-repo/semantics/nonPublished

33

Liebermann, Joëlle. "Essays in real-time forecasting." Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209644.

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This thesis contains three essays in the field of real-time econometrics, and more particularly

forecasting.

The issue of using data as available in real-time to forecasters, policymakers or financial

markets is an important one which has only recently been taken on board in the empirical

literature. Data available and used in real-time are preliminary and differ from ex-post

revised data, and given that data revisions may be quite substantial, the use of latest

available instead of real-time can substantially affect empirical findings (see, among others,

Croushore’s (2011) survey). Furthermore, as variables are released on different dates

and with varying degrees of publication lags, in order not to disregard timely information,

datasets are characterized by the so-called “ragged-edge”structure problem. Hence, special

econometric frameworks, such as developed by Giannone, Reichlin and Small (2008) must

be used.

The first Chapter, “The impact of macroeconomic news on bond yields: (in)stabilities over

time and relative importance”, studies the reaction of U.S. Treasury bond yields to real-time

market-based news in the daily flow of macroeconomic releases which provide most of the

relevant information on their fundamentals, i.e. the state of the economy and inflation. We

find that yields react systematically to a set of news consisting of the soft data, which have

very short publication lags, and the most timely hard data, with the employment report

being the most important release. However, sub-samples evidence reveals that parameter

instability in terms of absolute and relative size of yields response to news, as well as

significance, is present. Especially, the often cited dominance to markets of the employment

report has been evolving over time, as the size of the yields reaction to it was steadily

increasing. Moreover, over the recent crisis period there has been an overall switch in the

relative importance of soft and hard data compared to the pre-crisis period, with the latter

becoming more important even if less timely, and the scope of hard data to which markets

react has increased and is more balanced as less concentrated on the employment report.

Markets have become more reactive to news over the recent crisis period, particularly to

hard data. This is a consequence of the fact that in periods of high uncertainty (bad state),

markets starve for information and attach a higher value to the marginal information content

of these news releases.

The second and third Chapters focus on the real-time ability of models to now-and-forecast

in a data-rich environment. It uses an econometric framework, that can deal with large

panels that have a “ragged-edge”structure, and to evaluate the models in real-time, we

constructed a database of vintages for US variables reproducing the exact information that

was available to a real-time forecaster.

The second Chapter, “Real-time nowcasting of GDP: a factor model versus professional

forecasters”, performs a fully real-time nowcasting (forecasting) exercise of US real GDP

growth using Giannone, Reichlin and Smalls (2008), henceforth (GRS), dynamic factor

model (DFM) framework which enables to handle large unbalanced datasets as available

in real-time. We track the daily evolution throughout the current and next quarter of the

model nowcasting performance. Similarly to GRS’s pseudo real-time results, we find that

the precision of the nowcasts increases with information releases. Moreover, the Survey of

Professional Forecasters does not carry additional information with respect to the model,

suggesting that the often cited superiority of the former, attributable to judgment, is weak

over our sample. As one moves forward along the real-time data flow, the continuous

updating of the model provides a more precise estimate of current quarter GDP growth and

the Survey of Professional Forecasters becomes stale. These results are robust to the recent

recession period.

The last Chapter, “Real-time forecasting in a data-rich environment”, evaluates the ability

of different models, to forecast key real and nominal U.S. monthly macroeconomic variables

in a data-rich environment and from the perspective of a real-time forecaster. Among

the approaches used to forecast in a data-rich environment, we use pooling of bi-variate

forecasts which is an indirect way to exploit large cross-section and the directly pooling of

information using a high-dimensional model (DFM and Bayesian VAR). Furthermore forecasts

combination schemes are used, to overcome the choice of model specification faced by

the practitioner (e.g. which criteria to use to select the parametrization of the model), as

we seek for evidence regarding the performance of a model that is robust across specifications/

combination schemes. Our findings show that predictability of the real variables is

confined over the recent recession/crisis period. This in line with the findings of D’Agostino

and Giannone (2012) over an earlier period, that gains in relative performance of models

using large datasets over univariate models are driven by downturn periods which are characterized

by higher comovements. These results are robust to the combination schemes

or models used. A point worth mentioning is that for nowcasting GDP exploiting crosssectional

information along the real-time data flow also helps over the end of the great moderation period. Since this is a quarterly aggregate proxying the state of the economy,

monthly variables carry information content for GDP. But similarly to the findings for the

monthly variables, predictability, as measured by the gains relative to the naive random

walk model, is higher during crisis/recession period than during tranquil times. Regarding

inflation, results are stable across time, but predictability is mainly found at nowcasting

and forecasting one-month ahead, with the BVAR standing out at nowcasting. The results

show that the forecasting gains at these short horizons stem mainly from exploiting timely

information. The results also show that direct pooling of information using a high dimensional

model (DFM or BVAR) which takes into account the cross-correlation between the

variables and efficiently deals with the “ragged-edge”structure of the dataset, yields more

accurate forecasts than the indirect pooling of bi-variate forecasts/models.
Doctorat en Sciences économiques et de gestion
info:eu-repo/semantics/nonPublished

34

Milroy, Scott P. "A three-dimensional biophysical model of light, nutrient, and grazing controls on phytoplankton competition affecting red tide maintenance on the west Florida shelf." [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002068.

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35

He, Rui. "Systematic Tire Testing and Model Parameterization for Tire Traction on Soft Soil." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/104386.

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Tire performance over soft soil influences the performance of off-road vehicles on soft soil, as the tire is the only force transmitting element between the off-road vehicles and soil during the vehicle operation. One aspect of the tire performance over soft soil is the tire tractive performance on soft soil, and it attracts the attention of vehicle and geotechnical engineers. The vehicle engineer is interested in the tire tractive performance on soft soil because it is related to vehicle mobility and energy efficiency; the geotechnical engineer is concerned about the soil compaction, brought about by the tire traffic, which accompanies the tire tractive performance on soft soil. In order to improve the vehicle mobility and energy efficiency over soft soil and mitigate the soil compaction, it's essential to develop an in-depth understanding of tire tractive performance on soft soil. This study has enhanced the understanding of tire tractive performance on soft soil and promoted the development of terramechanics and tire model parameterization method through experimental tests. The experimental tests consisted of static tire deflection tests, static tire-soil tests, soil properties tests, and dynamic tire-soil tests. The series of tests (test program) presented herein produced parameterization and validation data that can be used in tire off-road traction dynamics modeling and terramechanics modeling. The 225/60R16 97S Uniroyal (Michelin) Standard Reference Test Tire (SRTT) and loamy sand were chosen to be studied in the test program. The tests included the quantification or/and measurement of soil properties of the test soil, pre-traffic soil condition, the pressure distribution in the tire contact patch, tire off-road tractive performance, and post-traffic soil compaction. The influence of operational parameters, e.g., tire inflation pressure, tire normal load, tire slip ratio, initial soil compaction, or the number of passes, on the measurement data of tire performance parameters or soil response parameters was also analyzed. New methods of the rolling radius estimation for a tire on soft soil and of the 3-D rut reconstruction were developed. A multi-pass effect phenomenon, different from any previously observed phenomenon in the available existing literature, was discovered. The test data was fed into optimization programs for the parameterization of the Bekker's model, a modified Bekker's model, the Magic Formula tire model, and a bulk density estimation model. The modified Bekker's model accounts for the slip sinkage effect which the original Bekker's pressure-sinkage model doesn't. The Magic Formula tire model was adapted to account for the combined influence of tire inflation pressure and initial soil compaction on the tire tractive performance and validated by the test data. The parameterization methods presented herein are new effective terramechanics model parameterization methods, can capture tire-soil interaction which the conventional parameterization methods such as the plate-sinkage test and shear test (not using a tire as the shear tool) cannot sufficiently, and hence can be used to develop tire off-road dynamics models that are heavily based on terramechanics models. This study has been partially supported by the U.S. Army Engineer Research and Development Center (ERDC) and by the Terramechanics, Multibody, and Vehicle (TMVS) Laboratory at Virginia Tech.
Doctor of Philosophy
Big differences exist between a tire moving in on-road conditions, such as asphalt lanes, and a tire moving in off-road conditions, such as soft soil. For example, for passenger cars commonly driven on asphalt lanes, normally, the tire inflation pressure is suggested to be between 30 and 35 psi; very low inflation pressure is also not suggested. By contrast, for off-road vehicles operated on soft soil, low inflation pressure is recommended for their tires; the inflation pressure of a tractor tire can be as low as 12 psi, for the sake of low post-traffic soil compaction and better tire traction. Besides, unlike the research on tire on-road dynamics, the research on off-road dynamics is still immature, while the physics behind the off-road dynamics could be more complex than the on-road dynamics. In this dissertation, experimental tests were completed to study the factors influencing tire tractive performance and soil behavior, and model parameterization methods were developed for a better prediction of tire off-road dynamics models. Tire or vehicle manufacturers can use the research results or methods presented in this dissertation to offer suggestions for the tire or vehicle operation on soft soil in order to maximize the tractive performance and minimize the post-traffic soil compaction.

36

Yang, Xiaozhe. "Vehicle Routing Problem with Time Windows and Driving/Working Time Restrictions." Ohio University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1227621524.

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37

Kazemi, Omid. "Comprehensive Tire Model For Multibody Simulations." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/338760.

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Tires serve as important components of wheeled vehicles and their analytical modeling has drawn the attention of many researches in the past decades. A high-resolution finite element (FE) tire model contains detailed structural and material characteristics of a tire that exhibit degrees-of-freedom (DoF) in the order of 10⁵ or greater. However, such high-resolution models in their full detail are not practically applicable in multibody dynamic analysis of vehicles and a reduction in their order becomes necessary. In this research different formulations to construct condensed FE tire models suitable for multibody simulations are developed and their characteristics are discussed. In addition, two new and novel forms of substructuring are presented that aim at isolating the contact region of a tire without the need for keeping the boundary DoF which otherwise remain in the reduced system in the standard substructuring procedures. The new substructuring methods provide a great tool in constructing condensed FE tire models with much less total number of DoF compared to cases where a standard substructuring is used. In order to increase the computational efficiency of the condensed FE tire models even further, the possibility of model condensation in the contact region is studied. This research also addresses the applicability of available friction models into the condensed FE tire models. Different formulations of a condensed tire model presented in this research are used to construct several computational models. These models are utilized to simulate certain scenarios and the results are discussed.

38

Molisani, Leonardo Rafael. "A Coupled Tire Structure-Acoustic Cavity Model." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/11187.

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Recent experimental results have shown that the vibration induced by the tire air cavity resonance is transmitted into the vehicle cabin and may be responsible for significant interior noise. The tire acoustic cavity is excited by the road surface through the contact patch on the rotating tire. The effect of the cavity resonance is that results in significant forces developed at the vehicle's spindle, which in turn drives the vehicle's interior acoustic field. This tire-cavity interaction phenomenon is analytically investigated by modeling the fully coupled tire-cavity systems. The tire is modeled as an annular shell structure in contact with the road surface. The rotating contact patch is used as a forcing function in the coupled tire-cavity governing equation of motion. The contact patch is defined as a prescribed deformation that in turn is expanded in its Fourier components. The response of the tire is then separated into static (i.e. static deformation induced by the contact patch) and dynamic components due to inertial effects. The coupled system of equations is solved analytically in order to obtain the tire acoustic and structural responses. The model provides valuable physical insight into the patch-tire-acoustic interaction phenomenon. The influence of the acoustic cavity resonance on the spindles forces is shown to be very important. Therefore, the tire cavity resonance effect must be reduced in order to control the tire contribution to the vehicle interior. The analysis and modeling of two feasible approaches to control the tire acoustic cavity resonances are proposed and investigated. The first approach is the incorporation of secondary acoustic cavities to detune and damp out the main tire cavity resonance. The second approach is the addition of damping directly into the tire cavity. The techniques presented in this dissertation to suppress the adverse effects of the acoustic cavity in the tire response, i.e. forces at the spindle, show to be very effective and can be easily applied in practice.
Ph. D.

39

Meister, Kadri. "On Methods for Real Time Sampling and Distributions in Sampling." Doctoral thesis, Umeå : Univ, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-415.

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40

Conte, Francesco. "Expanding the brush tire model for energy studies." Thesis, KTH, Fordonsdynamik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-164284.

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Considering the more and more important issues concerning the climate changes and the global warming, the automotive industry is paying more and more attention to vehicle concepts with full electric or partly electric propulsion systems. The introduction of electric power sources allow the designers to implement more advanced motion control systems in vehicle, such as active suspensions. An example of this concept is the Autonomous corner module (ACM), designed by S. Zetterström. The ACM is a modular based suspension system that includes all features of wheel control, such as control of steering, wheel torque and camber individually, using electric actuators. With a good control strategy it is believed that is it possible to reduce the fuel consumption and/or increase the handling properties of the vehicle. In particular, camber angle has a significant effect on vehicle handling. However, very few efforts have been done in order to analyse its effects on tire dissipated energy. The aim of this study is to develop a new tire model, having as starting point the simple Brush Tire model, in order to analyse the tire behaviour, in terms of forces generated and energy dissipated, for different dynamic situations. In order to reach this scope, the characteristic equations of the rubber material are implemented in a 3D Multi-Line brush tire model. In this way the energy dissipated, thus the rolling resistance force, can be studied and analysed, considering also the tire geometry. From the results of this work it is possible to assert that the angular parameters (e.g. camber angle) affect the power losses in rolling tires, as well as the tire geometry influences their rolling resistance. Thus, using a good control strategy, it is possible to reduce the power losses in tires.

41

Sams, Thomas A. "A New Analytical Tire Model For Determining The Effect of Damping Foam on Tire/Vehicle Vibration." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1552062613909176.

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42

IVERSON, ARTHUR EVAN. "THE MATHEMATICAL MODELING OF TIME-DEPENDENT PHOTOCONDUCTIVE PHENOMENA IN SEMICONDUCTORS." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184068.

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This dissertation presents results pertaining to the mathematical modeling of semiconductor photoconductors and includes the formulation, analysis, and solution of photoconductive device model equations. The fundamental semiconductor device equations of continuity and transport are derived for the case of a material which contains a large density of deep-level impurities. Electron and hole trapping on deep-level impurities is accounted for by trapping-kinetics rate equations. The coupling between carrier drift and the electric field is completed through Poisson's equation. Simple, nonlinear model equations are presented for bulk-material response based on the dynamics of electron and hole trapping and recombination on deep-level impurities. The characteristics of the solution to these model equations are observed to depend strongly on the excitation intensity. These model equations qualitatively reproduce observed experimental behavior of an iron-doped indium phosphide photoconductor. A theory of the effect of deep-level centers on the generation-recombination noise and responsivity of an intrinsic photoconductor is presented. It is shown that the deep-level centers can influence the generation-recombination noise and responsivity in three main ways: (i) they can shorten the bulk carrier lifetime by Schockley-Read-Hall recombination; (ii) for some values of the capture cross sections, deep-level densities, and temperature, the deep-level centers can trap a significant fraction of the photogenerated minority carriers. This trapping reduces the effective minority carrier mobility and diffusivity and thus reduces the effect of carrier sweep out on both generation noise and responsivity; (iii) the deep-level centers add a new thermal noise source, which results from fluctuations between bound and free carriers. The strength of this new noise source decreases with decreasing temperature at a slower rate than band-to-band thermal generation-recombination noise. Photoconductive device model equations based on time-dependent, convective/diffusive transport equations are presented. The system of model equations is solved numerically with boundary conditions that represent ideal ohmic contacts. Computed results are presented for different photoconductor lengths and bias voltages with spatially uniform, rectangular light-pulse illumination.

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Björnberg, Jakob Erik. "Graphical representations of Ising and Potts models : stochastic geometry of the quantum Ising model and the space-time Potts model." Thesis, University of Cambridge, 2010. https://www.repository.cam.ac.uk/handle/1810/224774.

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Statistical physics seeks to explain macroscopic properties of matter in terms of microscopic interactions. Of particular interest is the phenomenon of phase transition: the sudden changes in macroscopic properties as external conditions are varied. Two models in particular are of great interest to mathematicians, namely the Ising model of a magnet and the percolation model of a porous solid. These models in turn are part of the unifying framework of the random-cluster representation, a model for random graphs which was first studied by Fortuin and Kasteleyn in the 1970's. The random-cluster representation has proved extremely useful in proving important facts about the Ising model and similar models. In this work we study the corresponding graphical framework for two related models. The first model is the transverse field quantum Ising model, an extension of the original Ising model which was introduced by Lieb, Schultz and Mattis in the 1960's. The second model is the space-time percolation process, which is closely related to the contact model for the spread of disease. In Chapter 2 we define the appropriate 'space-time' random-cluster model and explore a range of useful probabilistic techniques for studying it. The space-time Potts model emerges as a natural generalization of the quantum Ising model. The basic properties of the phase transitions in these models are treated in this chapter, such as the fact that there is at most one unbounded fk-cluster, and the resulting lower bound on the critical value in Z. In Chapter 3 we develop an alternative graphical representation of the quantum Ising model, called the random-parity representation. This representation is based on the random-current representation of the classical Ising model, and allows us to study in much greater detail the phase transition and critical behaviour. A major aim of this chapter is to prove sharpness of the phase transition in the quantum Ising model - a central issue in the theory - and to establish bounds on some critical exponents. We address these issues by using the random-parity representation to establish certain differential inequalities, integration of which give the results. In Chapter 4 we explore some consequences and possible extensions of the results established in Chapters 2 and 3. For example, we determine the critical point for the quantum Ising model in Z and in 'star-like' geometries.

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Frey, Norman W. "Development of a rigid ring tire model and comparison among various tire models for ride comfort simulations." Connect to this title online, 2009.

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Bian, Ning. "Model-based tire road friction estimation for passenger vehicles." Düsseldorf VDI-Verl, 2007. http://d-nb.info/997346825/04.

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Siramdasu, Yaswanth. "Discrete Tire Model Application for Vehicle Dynamics Performance Enhancement." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/74394.

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Tires are the most influential component of the vehicle as they constitute the only contact between the vehicle and the road and have to generate and transmit forces necessary for the driver to control the vehicle. The demand for the tire models are increasing due to the need to study the variations of force generation mechanisms due to various variables such as load, pressure, speed, and road surface irregularities. Another need from the vehicle manufactures is the study of potential incompatibilities associated with safety systems such as Anti-lock Braking System (ABS) and Electronic Stability Control (ESC) and tires. For vehicle dynamic simulations pertaining to the design of safety systems such as ABS, ESC and ride controllers, an accurate and computationally efficient tire model is required. As these control algorithms become more advanced, they require accurate and extended validity in the range of frequencies required to cover dynamic response due to short wavelength road disturbances, braking and steering torque variations. Major thrust has been provided by the tire industry to develop simulation models that accurately predict the dynamic response of tires without the use of computationally intensive tools such as FEA. The objectives of this research are • To develop, implement and validate a rigid ring tire model and a simulation tool to assist both tire designers and the automotive industry in analyzing the effects of tire belt vibrations, road disturbances, and high frequency brake and steering torque variations on the handling, braking, and ride performances of the vehicle. • To further enhance the tire model by considering dynamic stiffness changes and temperature dependent friction properties. • To develop, and implement novel control algorithms for braking, stability, and ride performance improvements of the vehicle
Ph. D.

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Liu, Xin. "Fast exponential time integration scheme and extrapolation method for pricing option with jump diffusions." Thesis, University of Macau, 2010. http://umaclib3.umac.mo/record=b2148264.

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Sadeghi, Parastoo School of Electrical Engineering And Telecommunications UNSW. "Modelling, information capacity, and estimation of time-varying channels in mobile communication systems." Awarded by:University of New South Wales. School of Electrical Engineering And Telecommunications, 2006. http://handle.unsw.edu.au/1959.4/32310.

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In the first part of this thesis, the information capacity of time-varying fading channels is analysed using finite-state Markov channel (FSMC) models. Both fading channel amplitude and fading channel phase are modelled as finite-state Markov processes. The effect of the number of fading channel gain partitions on the capacity is studied (from 2 to 128 partitions). It is observed that the FSMC capacity is saturated when the number of fading channel gain partitions is larger than 4 to 8 times the number of channel input levels. The rapid FSMC capacity saturation with a small number of fading channel gain partitions can be used for the design of computationally simple receivers, with a negligible loss in the capacity. Furthermore, the effect of fading channel memory order on the capacity is studied (from first- to fourth-order). It is observed that low-order FSMC models can provide higher capacity estimates for fading channels than high-order FSMC models, especially when channel states are poorly observable in the presence of channel noise. To explain the effect of memory order on the FSMC capacity, the capacities of high-order and low-order FSMC models are analytically compared. It is shown that the capacity difference is caused by two factors: 1) the channel entropy difference, and 2) the channel observability difference between the high-order and low-order FSMC models. Due to the existence of the second factor, the capacity of high-order FSMC models can be lower than the capacity of low-order FSMC models. Two sufficient conditions are proven to predict when the low-order FSMC capacity is higher or lower than the high-order FSMC capacity. In the second part of this thesis, a new implicit (blind) channel estimation method in time- varying fading channels is proposed. The information source emits bits ???0??? and ???1??? with unequal probabilities. The unbalanced source distribution is used as a priori known signal structure at the receiver for channel estimation. Compared to pilot-symbol-assisted channel estimation, the proposed channel estimation technique can achieve a superior receiver bit error rate performance, especially at low signal to noise ratio conditions.

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Kilminster, Devin. "Modelling dynamical systems via behaviour criteria." University of Western Australia. Dept. of Mathematics and Statistics, 2002. http://theses.library.uwa.edu.au/adt-WU2003.0029.

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An important part of the study of dynamical systems is the fitting of models to time-series data. That is, given the data, a series of observations taken from a (not fully understood) system of interest, we would like to specify a model, a mathematical system which generates a sequence of “simulated” observations. Our aim is to obtain a “good” model — one that is in agreement with the data. We would like this agreement to be quantitative — not merely qualitative. The major subject of this thesis is the question of what good quantitative agreement means. Most approaches to this question could be described as “predictionist”. In the predictionist approach one builds models by attempting to answer the question, “given that the system is now here, where will it be next?” The quality of the model is judged by the degree to which the states of the model and the original system agree in the near future, conditioned on the present state of the model agreeing with that of the original system. Equivalently, the model is judged on its ability to make good short-term predictions on the original system. The main claim of this thesis is that prediction is often not the most appropriate criterion to apply when fitting models. We show, for example, that one can have models that, while able to make good predictions, have long term (or free-running) behaviour bearing little resemblance to that exhibited in the original time-series. We would hope to be able to use our models for a wide range of purposes other than just prediction — certainly we would like our models to exhibit good free-running behaviour. This thesis advocates a “behaviourist” approach, in which the criterion for a good model is that its long-term behaviour matches that exhibited by the data. We suggest that the behaviourist approach enjoys a certain robustness over the predictionist approaches. We show that good predictors can often be very poorly behaved, and suggest that well behaved models cannot perform too badly at the task of prediction. The thesis begins by comparing the predictionist and behaviourist approaches in the context of a number of simplified model-building problems. It then presents a simple theory for the understanding of the differences between the two approaches. Effective methods for the construction of well-behaved models are presented. Finally, these methods are applied to two real-world problems — modelling of the response of a voltage-clamped squid “giant” axon, and modelling of the “yearly sunspot number”.

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Borovičková, Michaela. "Fantomový přípravek pro perfusní zobrazování." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2012. http://www.nusl.cz/ntk/nusl-219731.

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This work focuses on issues relating to the perfusion analysis. The aim of this work is to perform experimental measurements of the phantom and then evaluate the perfusion curves. This curves are used to himation of perfusion hemodynamic parameters, which indicates important informatik about monitoring area. All processes associated with the designation and evaluation are performed in a program named Matlab. The output of work is a system that provides the reader into the problem of perfusion analysis and allows him to understand and know what is the meaning od analysis, what demands are placed on the evaluation and what is the result of this perfusion analysis.

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