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Latorre, Malcolm. "The Physical Axon : Modeling, Simulation and Electrode Evaluation". Doctoral thesis, Linköpings universitet, Avdelningen för medicinsk teknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-138587.
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Electrodes are used in medicine for detection of biological signals and for stimulating tissue, e.g. in deep brain stimulation (DBS). For both applications, an understanding of the functioning of the electrode, and its interface and interaction with the target tissue involved is necessary. To date, there is no standardized method for medical electrode evaluation that allows transferability of acquired data. In this thesis, a physical axon (Paxon) potential generator was developed as a device to facilitate standardized comparisons of different electrodes. The Paxon generates repeatable, tuneable and physiological-like action potentials from a peripheral nerve. It consists of a testbed comprising 40 software controlled 20 μm gold wires embedded in resin, each wire mimicking a node of Ranvier. ECG surface Ag-AgCl electrodes were systematically tested with the Paxon. The results showed small variations in orientation (rotation) and position (relative to axon position) which directly impact the acquired signal. Other electrode types including DBS electrodes can also be evaluated with the Paxon. A theoretical comparison of a single cable neuronal model with an alternative established double cable neuron model was completed. The output with regards to DBS was implemented to comparing the models. These models were configured to investigate electrode stimulation activity, and in turn to assess the activation distance by DBS for changes in axon diameter (1.5-10 μm), pulse shape (rectangular biphasic and rectangular, triangular and sinus monophasic) and drive strength (1-5 V or mA). As both models present similar activation distances, sensitivity to input shape and computational time, the neuron model selection for DBS could be based on model complexity and axon diameter flexibility. An application of the in-house neuron model for multiple DBS lead designs, in a patient-specific simulation study, was completed. Assessments based on the electric field along multiple sample planes of axons support previous findings that a fixed electric field isolevel is sufficient for assessments of tissue activation distances for a predefined axon diameter and pulse width in DBS.Elektroder används inom sjukvården, både för att mäta biologiska signaler, t.ex. hjärtats aktivitet med EKG, eller för att stimulera vävnad, t.ex. vid djup hjärnstimulering (DBS). För båda användningsområdena är det viktigt med en grundläggande förståelse av elektrodens interaktion med vävnaden. Det finns ingen standardiserad metod för att utvärdera medicinsk elektroders dataöverföringsfunktion. I den här avhandlingen presenteras en metod för att underlätta elektrodtestning. En hårdvarumodell av ett axon (Paxon) har utvecklats. Paxon kan programmeras för att efterlikna repeterbara aktionspotentialer från en perifer nerv. Längs axonet finns 40 noder, vilka var och en består av en tunn (20 μm) guldtråd inbäddad i harts och därefter kopplad till elektronik. Denna testbädd har använts för att undersöka EKG elektroders egenskaper. EKG elektroderna visade på variationer i orientering och position i relation till Paxon. Detta har en direkt inverkan på den registrerade signalen. Även andra elektrotyper kan testas i Paxon, t.ex. DBS elektroder. En teoretisk jämförelse mellan två neuronmodeller med olika komplexitet, anpassade för användning vid DBS studier, har utförts. Modellerna konfigurerades för att studera inverkan på aktiveringsavstånd från olika axondiametrar, stimulationspuls och stimulationsstyrka. Då båda modellerna visade likvärdiga aktiveringsavstånd och beräkningstid så förordas den enklare neuronmodellen för DBS simuleringar. En enklare modell kan lättare introduceras i klinisk verksamhet. Simuleringarna stöder tidigare resultat som visat att det elektriska fältet är en bra parameter för presentation av resultat vid simulering av DBS. Metoden exemplifieras vid simulering av aktiveringsavstånd och elektriska fältets utbredning för olika typer av DBS elektroder i en patient-specifik studie.
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Sjöstedt, Carl-Johan. "Modeling and Simulation of Physical Systems in a Mechatronic Context". Doctoral thesis, KTH, Maskinkonstruktion (Avd.), 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10522.
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This thesis gives different views on the modeling and simulation of physical systems, especially together with embedded systems, forming mechatronic systems. The main considered application domain is automotive. One motivation behind the work is to find suitable representations of physical systems to be used in an architectural description language for automotive embedded systems, EAST-ADL2, which is implemented as a UML2 profile, and uses concepts from both UML and SysML. As a part of the thesis, several languages and tools are investigated, including bond graphs, MATLAB/Simulink, Ptolemy II, Modelica, MATLAB/Simscape and SysML. For SysML, the modeling of continuous-time systems and how it relates to MATLAB/Simulink and Modelica is evaluated. A case study of an electric power assisted steering is modeled to show the differences, the similarities and the usage of the above mentioned languages and tools. To be able to classify the tools and languages, five realization levels were developed: Physical modeling models Constraint models Continuous causal models Discretized models Discretized models with solver and platform implementation By using these realization levels, models, tools and modeling languages can be classified, and transformations between them can be set up and analyzed. As a result, a method to describe the simulation behavior of a MATLAB/Simulink model has been developed using SysML activity diagrams as an approach to achieve integrated system models. Another result is an evaluation of the parametric diagrams of SysML for continuous-time modeling, which shows that they do not enable “physical modeling”, i.e. modeling the topology of the system and getting the underlying equations out of this topology. By including physical ports and physical connectors to SysML internal block diagrams, this could be solved. The comparison also shows many similarities between the languages. The results led to a more detailed investigation on conjugate variables, such as force and velocity, and electric current and voltage, and how these are treated in various languages. The thesis also includes two industrial case studies: one of a twin-screw compressor, and one of a simulation environment for automotive fuel-cell systems. Conclusions are drawn from these models, referring to the realization levels.QC 20100810
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Esmael, Muzeyen Hassen. "Modeling Basic Physical Links in Acumen". Thesis, Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-18119.
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Simulation is the process of computing a behavior determined by a given model of a system of interest. Modeling is the process of creating a model that formally describes a given class of system. Modeling and simulation can be used to quickly and cheaply study and understand new technologies. Today, a wide range of systems are simulated using different tools. However, converting models into simulation codes can still be difficult and time consuming. In this thesis, we study how a new modeling and simulation language called Acumen can be used to model basic physical links. This language is aimed at bridging the gap between modeling and simulation. We focus on basic physical links as an interesting type of system to model and simulate. We also focus on comparing Acumen to MATLAB and Simulink. The types of links we consider include models of an RC low-pass filter, Amplitude Modulation, Frequency Modulation, Amplitude Shift Keying, Phase Shift Keying and Frequency Shift Keying systems. Each of these examples is modeled in Acumen, MATLAB and Simulink. We find that, for the most part, Acumen allows us to naturally express a wide range of modulation techniques mentioned above. When compared to MATLAB ad Simulink, we find that Acumen is simple language to understand. Acumen codes are described in a more natural way. Simplicity is the biggest advantage of Acumen.
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Cozza, Dario. "Modeling and physical studies of kesterite solar cells". Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4302.
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Ce travail de thèse porte sur la modélisation et la simulation numérique de cellules solaires à base de kësterite (CZTSé, CZTS) dans le but d’étudier leurs mécanismes physiques et d’améliorer la conception de ces dispositifs. Les kësterites sont une classe de matériaux que l’on peut déposer en couches minces et qui sont constitués d’éléments abondants sur Terre et donc à faible coût. Deux modèles numériques pour les cellules solaires CZTSe et CZTS sont proposés. Des simulations 1D et 2D sont réalisées: le logiciel SCAPS est utilisé pour étudier l’impact des couches de molybdène et de MoSe2, présents au contact arrière des cellules solaires CZTSe. Nous étudions également les propriétés idéales de couches d’interface alternatives qui pourraient remplacer le MoSe2 pour améliorer les performances des cellules solaires. La méthode des matrices de transfert (TMM) et le logiciel SCAPS sont utilisés conjointement pour effectuer des simulations optoélectroniques dans le but d’optimiser l’épaisseur du buffer (CdS) et le TCO (Transparent Conductive Oxide) afin de maximiser le courant de court-circuit (JSC ) des cellules solaires. Enfin Silvaco est utilisé pour réaliser des simulations 2D des joints de grains (GBs) du CZTSe présents à l’intérieur des absorbeurs polycristallins de la kësterite. Pour ce faire, des caractérisations KPFM sont effectuées dans le but de trouver des corrélations possibles entre les pertes de rendement et l'activité électrique des GBsThis thesis deals with modeling and simulations of kesterite solar cells with the aim of studying their physical mechanisms and improving the design of the devices. Synthetic kesterites are thin film materials made of cheap/earth-abundant elements. Two numerical models for a Cu2ZnSnSe4 (CZTSe) and a Cu2ZnSnS4 (CZTS) solar cell are proposed. The provided values of the material parameters, for all the layers of the solar cell, are obtained either from comparisons/analysis of data found in literature or, in some cases, from direct measurements. 1D and 2D simulations are performed: the software SCAPS is used to study the impact of the Molybdenum and the MoSe2 layers, present at the back contact of CZTSe solar cells. We investigate also the ideal properties of alternative interfacial layers that could replace the MoSe2 layer to improve the device performances. The transfer matrix method (TMM) and SCAPS are employed together to perform optoelectronic simulations with the aim of optimizing the thickness of the buffer (CdS) and the window (ITO) layers in order to maximize the short circuit current (JSC ) of the device. Finally Silvaco is used to perform 2D simulations of the CZTSe grain boundaries (GBs) present inside the polycrystalline kesterite absorbers. For the latter work, experimental Kelvin probe force microscopy (KPFM) characterizations are performed in order to find possible correlations between the performance losses and the electrical activity of the GBs
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Sjöstedt, Carl-Johan. "Modeling and simulation of physical systems in a mechatronic context /". Stockholm : Skolan för indutstriell teknik och managemnet, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10522.
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Du, Dongping. "Physical-Statistical Modeling and Optimization of Cardiovascular Systems". Scholar Commons, 2002. http://scholarcommons.usf.edu/etd/5875.
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Heart disease remains the No.1 leading cause of death in U.S. and in the world. To improve cardiac care services, there is an urgent need of developing early diagnosis of heart diseases and optimal intervention strategies. As such, it calls upon a better understanding of the pathology of heart diseases.
Computer simulation and modeling have been widely applied to overcome many practical and ethical limitations in in-vivo, ex-vivo, and whole-animal experiments. Computer experiments provide physiologists and cardiologists an indispensable tool to characterize, model and analyze cardiac function both in healthy and in diseased heart. Most importantly, simulation modeling empowers the analysis of causal relationships of cardiac dysfunction from ion channels to the whole heart, which physical experiments alone cannot achieve.
Growing evidences show that aberrant glycosylation have dramatic influence on cardiac and neuronal function. Variable but modest reduction in glycosylation among congenital disorders of glycosylation (CDG) subtypes has multi-system effects leading to a high infant mortality rate. In addition, CDG in all young patients tends to cause Atrial Fibrillation (AF), i.e., the most common sustained cardiac arrhythmia. The mortality rate from AF has been increasing in the past two decades. Due to the increasing healthcare burden of AF, studying the AF mechanisms and developing optimal ablation strategies are now urgently needed.
Very little is known about how glycosylation modulates cardiac electrical signaling. It is also a significant challenge to experimentally connect the changes at one organizational level (e.g.,electrical conduction among cardiac tissue) to measured changes at another organizational level (e.g., ion channels). In this study, we integrate the data from in vitro experiments with in-silico models to simulate the effects of reduced glycosylation on the gating kinetics of cardiac ion channel, i.e., hERG channels, Na+ channels, K+ channels, and to predict the glycosylation modulation dynamics in individual cardiac cells and tissues.
The complex gating kinetics of Na+ channels is modeled with a 9-state Markov model that have voltage-dependent transition rates of exponential forms. The model calibration is quite a challenge as the Markov model is non-linear, non-convex, ill-posed, and has a large parametric space. We developed a new metamodel-based simulation optimization approach for calibrating the model with the in-vitro experimental data. This proposed algorithm is shown to be efficient in learning the Markov model of Na+ model. Moreover, it can be easily transformed and applied to many other optimization problems in computer modeling.
In addition, the understanding of AF initiation and maintenance has remained sketchy at best. One salient problem is the inability to interpret intracardiac recordings, which prevents us from reconstructing the rhythmic mechanisms for AF, due to multiple wavelets' circulating, clashing and continuously changing direction in the atria. We are designing computer experiments to simulate the single/multiple activations on atrial tissues and the corresponding intra-cardiac signals. This research will create a novel computer-aided decision support tool to optimize AF ablation procedures.
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Sadeghi, Reineh Maryam. "Physical Modeling and Simulation Analysis of an Advanced Automotive Racing Shock Absorber using the 1D Simulation Tool AMESim". Thesis, Linköpings universitet, Fluida och mekatroniska system, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-92146.
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Shock absorbers are crucial components of a vehicle’s chassis responsible for the trade-off between stability, handling, and passenger comfort. The aim of the thesis is to investigate the physical behavior of an advanced automotive racing shock absorber, known as TTR, developed by Öhlins Racing AB. This goal is achieved by developing a detailed lumped parameter numerical model of the entire TTR suspension in the advanced 1D simulation tool, AMESim. The shock absorber is mainly composed of the main cylinder with through-rod piston design and the gas reservoir located at the low pressure hydraulic line, which connects the compression and rebound sides. The mentioned sides are identical in terms of the components which are a High Speed Adjuster, a Low Speed Adjuster, and a check valve mounted in parallel. The adjusters are special hydraulic valves, which can be modified in terms of flow metering characteristics by means of external accessible screws. Adjustment is done in a series of discrete numbers called ‘clicks’. A fixed orifice and a spring-loaded poppet valve are responsible for controlling the piston low and high speed regions respectively. The developed AMESim numerical model is capable of capturing the physics behind the real shock absorber damping characteristics, under both static and dynamic conditions. The model is developed mainly using the standard AMESim mechanical, hydraulic and hydraulic component design libraries and allows discovering the impact of each single hydraulic component on the TTR overall behavior. In particular, the 1D model is presented in two levels of progressive physical complexity in order to improve the dynamic damping characteristics. Several physical phenomena are considered, such as the hydraulics volumes pressure dynamics, the contribution of external spring and pressure forces to the dynamic balance of the moving elements, the static and viscous frictions, and the elastic deformations induced by solid boundaries pressure. In this thesis, progressive model validation with different types of measurements is as well presented, covering the individual hydraulic components models as well as the entire shock absorber model. The measurements have been performed on the flow benches and dynamometers available at the Öhlins Racing measurements laboratory. These comparisons, deeply discussed in the thesis, allow discovering the impact of specific physical effects on the low and high speed hydraulic valves static performance and on the shock absorber dynamic behavior. Numerical results show good agreement, especially at low and medium frequencies and symmetric ‘click’ adjustments on compression and rebound sides. Further model development is necessary in the other areas, for example by considering more complex models of the valve dynamics and fluid flow patterns, i.e. flow forces, together with more advanced models of the sealing elements viscous friction, and thermal effects. Finally, the AMESim environments offered a good level of flexibility in designing the TTR hydro-mechanical system, by allowing the user to choose between different levels of model complexity.
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San, Omer. "Multiscale Modeling and Simulation of Turbulent Geophysical Flows". Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/28031.
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The accurate and efficient numerical simulation of geophysical flows is of great interest in numerical weather prediction and climate modeling as well as in numerous critical areas and industries, such as agriculture, construction, tourism, transportation, weather-related disaster management, and sustainable energy technologies. Oceanic and atmospheric flows display an enormous range of temporal and spatial scales, from seconds to decades and from centimeters to thousands of kilometers, respectively. Scale interactions, both spatial and temporal, are the dominant feature of all aspects of general circulation models in geophysical fluid dynamics. In this thesis, to decrease the cost for these geophysical flow computations, several types of multiscale methods were systematically developed and tested for a variety of physical settings including barotropic and stratified wind-driven large scale ocean circulation models, decaying and forced two-dimensional turbulence simulations, as well as several benchmark incompressible flow problems in two and three dimensions. The new models proposed here are based on two classes of modern multiscale methods: (i) interpolation based approaches in the context of the multigrid/multiresolution methodologies, and (ii) deconvolution based spatial filtering approaches in the context of large eddy simulation techniques. In the first case, we developed a coarse-grid projection method that uses simple interpolation schemes to go between the two components of the problem, in which the solution algorithms have different levels of complexity. In the second case, the use of approximate deconvolution closure modeling strategies was implemented for large eddy simulations of large-scale turbulent geophysical flows. The numerical assessment of these approaches showed that both the coarse-grid projection and approximate deconvolution methods could represent viable tools for computing more realistic turbulent geophysical flows that provide significant increases in accuracy and computational efficiency over conventional methods.Ph. D.
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Shen, Wensheng. "Computer Simulation and Modeling of Physical and Biological Processes using Partial Differential Equations". UKnowledge, 2007. http://uknowledge.uky.edu/gradschool_diss/501.
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Scientific research in areas of physics, chemistry, and biology traditionally depends purely on experimental and theoretical methods. Recently numerical simulation is emerging as the third way of science discovery beyond the experimental and theoretical approaches. This work describes some general procedures in numerical computation, and presents several applications of numerical modeling in bioheat transfer and biomechanics, jet diffusion flame, and bio-molecular interactions of proteins in blood circulation.
A three-dimensional (3D) multilayer model based on the skin physical structure is developed to investigate the transient thermal response of human skin subject to external heating. The temperature distribution of the skin is modeled by a bioheat transfer equation. Different from existing models, the current model includes water evaporation and diffusion, where the rate of water evaporation is determined based on the theory of laminar boundary layer. The time-dependent equation is discretized using the Crank-Nicolson scheme. The large sparse linear system resulted from discretizing the governing partial differential equation is solved by GMRES solver.
The jet diffusion flame is simulated by fluid flow and chemical reaction. The second-order backward Euler scheme is applied for the time dependent Navier-Stokes equation. Central difference is used for diffusion terms to achieve better accuracy, and a monotonicity-preserving upwind difference is used for convective ones. The coupled nonlinear system is solved via the damped Newton's method. The Newton Jacobian matrix is formed numerically, and resulting linear system is ill-conditioned and is solved by Bi-CGSTAB with the Gauss-Seidel preconditioner.
A novel convection-diffusion-reaction model is introduced to simulate fibroblast growth factor (FGF-2) binding to cell surface molecules of receptor and heparan sulfate proteoglycan and MAP kinase signaling under flow condition. The model includes three parts: the flow of media using compressible Navier-Stokes equation, the transport of FGF-2 using convection-diffusion transport equation, and the local binding and signaling by chemical kinetics. The whole model consists of a set of coupled nonlinear partial differential equations (PDEs) and a set of coupled nonlinear ordinary differential equations (ODEs). To solve the time-dependent PDE system we use second order implicit Euler method by finite volume discretization. The ODE system is stiff and is solved by an ODE solver VODE using backward differencing formulation (BDF). Findings from this study have implications with regard to regulation of heparin-binding growth factors in circulation.
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REN, QIANGGUO. "A BDI AGENT BASED FRAMEWORK FOR MODELING AND SIMULATION OF CYBER PHYSICAL SYSTEMS". Master's thesis, Temple University Libraries, 2011. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/213130.
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Electrical and Computer EngineeringM.S.E.E.
Cyber-physical systems refer to a new generation of synergy systems with integrated computational and physical processes which interact with one other. The development and simulation of cyber-physical systems (CPSs) are obstructed by the complexity of the subsystems of which they are comprised, fundamental differences in the operation of cyber and physical elements, significant correlative dependencies among the elements, and operation in dynamic and open environments. The Multiple Belief-Desire-Intention (BDI) agent system (BDI multi-agent system) is a promising choice for overcoming these challenges, since it offers a natural way to decompose complex systems or large scale problems into decentralized, autonomous, interacting, more or less intelligent entities. In particular, BDI agents have the ability to interact with, and expand the capabilities of, the physical world through computation, communication, and control. A BDI agent has its philosophical grounds on intentionality and practical reasoning, and it is natural to combine a philosophical model of human practical reasoning with the physical operation and any cyber infrastructure. In this thesis, we introduce the BDI Model, discuss implementations of BDI agents from an ideal theoretical perspective as well as from a more practical perspective, and show how they can be used to bridge the cyber infrastructure and the physical operation using the framework. We then strengthen the framework's performance using the state-of-the-art parallel computing architecture and eventually propose a BDI agent based software framework to enable the efficient modeling and simulation of heterogeneous CPS systems in an integrated manner.
Temple University--Theses
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Broome, John D. "Simulation Modeling of Karst Aquifer Conduit Evolution and Relations to Climate". TopSCHOLAR®, 2008. http://digitalcommons.wku.edu/theses/36.
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ABSTRACT Karst regions of the world that receive relatively similar amounts of precipitation display a wide variety of landscapes. It has been suggested (Groves and Meiman, 2005) that climates exhibiting larger discrete storm events have more dissolving power and consequently higher rates of conduit growth than climates with more uniform precipitation distributions. To study this concept, a computer program “Cave Growth” was developed that modeled the growth of a cross-section of a cave passage under dynamic flow and chemical conditions. A series of 46 simulation datasets were created to represent different climatic conditions. These simulations had the same total annual discharge, but demonstrated a range of flow distributions quantified by use of a gamma distribution index, along with two special theoretical cases.
After simulating a year of conduit growth for each of the various flow distributions in a series of model runs, and repeating these sets of simulations for three different passage cross-section geometries, it was evident that the annual temporal distribution of flow did indeed impact the amount of cave growth. However, an increase in the “storminess” of the climate did not simply equate to more dissolution and thus conduit growth. Rather, the quantity and duration of surface contact between water and the conduit walls combined with dissolution rates to affect the total growth. The amount of wetted perimeter (contact between fluid and passage floor/walls) generated by specific conduit to capacity were shown to be very effective at growing the cave. Above this level, the dissolving power of additional water was essentially wasted. This investigation suggests that the maximum amount of passage flow levels depended upon the shape of the passage. Flow conditions that filled the growth occurs under flow conditions that result in the most wetted perimeter for the longest period of time at the highest dissolution rate.
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Pandey, Anup. "Modeling and Simulation of Amorphous Materials". Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1479377563495893.
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Cheng, Jingjing. "Shaken baby syndrome : simulation via computational and physical modelling". Thesis, University of Sheffield, 2008. http://etheses.whiterose.ac.uk/6116/.
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The terms "abusive head injury" and "shaken baby syndrome" refer to a unique pattern of non-accidental traumatic injury occurring in children that many clinicians and researchers have good reason to believe is caused by violent shaking. Typical injuries include subdural haemorrhage, retinal haemorrhage as well as tears to cortical bridging veins. A major paradox is that the injuries induced by a shaking event are much more severe than those caused by even violent single - impact head trauma, despite the relatively low accelerations in shaking. Infants younger than 6 months are significantly more vulnerable to the shaken baby syndrome than older infants and children, and one possible explanation is given that the softness of the infant brain and compliant skull structure allows violent motions to be set up (Cheng et al. 2005). These new mechanisms, could have an important role in explaining the basic mechanics of shaken baby syndrome. Several models of infant head have been created with the optimized anatomical detail and accurate constitutive material properties from literature. The driving input to these models is derived from data generated in our research programme at the Transport Research Laboratory (TRL) (Brudenell 2000) with the theory of kinematics rigid body reconstruction. Numerical simulations are applied by using the finite element system LS-DYNA, and the consequences have been correlated with clinically observed damage in infant victims, and the brain skull boundary condition is investigated via the fluid structure interaction (FSI) method. A shaking testing apparatus has been custom designed with computer aided design methodology (CAD), and is manufactured and assembled in the workshop. The driving of the rig is able to apply stable, repetitive linear motion within the range of accuracy and magnitude of human shaking. An experimental model has been constructed and mounted on the rig with important structures consisting of brain, cerebrospinal fluid (CSF), skull and infantile membrane. The system validates the computational modelling by demonstrating the relative motion of the continuum system within the transparent skull replica. The research, as a first exploration in this area, contributes to the study of the infant abusive head injury, and is able to draw the data together in a discussion of the implications for the mechanics of the shaken baby syndrome.
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Buxton, Robert Charles. "Direct simulation Monte Carlo modelling of physical vapour deposition". Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426851.
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Dixon, Christopher Mark. "Modelling and simulation of physical processes occuring in circuit breakers". Thesis, University of Liverpool, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.544370.
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Goldsmith, Cory Scott. "Analytical Modeling and Numerical Simulations of Time Delays in Attosecond Streaking of One- and Two-Photon Ionization". Thesis, University of Colorado at Boulder, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10978194.
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The generation of attosecond-duration (1 as = 10–18 s) coherent light through the process of high-order harmonic generation has opened the perspective for probing fundamental processes, such as photoionization, on the natural timescale of electron dynamics in matter. One probing technique is the attosecond streaking method, in which the momentum of the photoelectron is measured as a function of the time delay between the ionizing, attosecond extreme ultraviolet (XUV) pulse, and a weak, femtosecond near-infrared (NIR) pulse which streaks the momentum of the photoelectron, known as a streaking trace. The observed trace contains time information about the photoionization process in the form of a time offset to the vector potential of the streaking field, known as the streaking time delay. Theoretical simulations show that for one-photon ionization this time delay is accumulated by the photoelectron in the continuum when propagating away from the parent ion, whereas for resonant two-photon ionization there exists an additional absorption delay which depends on the properties of the XUV pulse. In this thesis, we use both analytical techniques and numerical simulations to study the contributions of the total time delay observed in streaking, and further explore applications of the streaking time delay to gain insights into the electron dynamics. We first derive an analytical formula for the streaking time delay in one-photon ionization. The predictions based on the model formula, which can be performed within seconds of computation time, are in good agreement with those of computationally extensive numerical simulations.
We demonstrate that the analytical formula not only allows deeper insight into the nature of the time delay, but also offers the opportunity to effectively analyze other theoretical interpretations and potential effects, such as the effect of a chirp in the ionizing attosecond pulse on the time delay measurement. We then apply time-dependent perturbation theory to derive an analytical formula for the absorption delay in resonant two-photon ionization. We use the analytical formula to demonstrate how the absorption delay can be controlled further by the attosecond pulse duration and central frequency in case of an isolated resonance. Furthermore, we show how multiple resonances within the bandwidth of the ionizing pulses as well as the streaking field influence the absorption delay in model systems as well as simple atoms and molecules. We conclude by exploring the option to apply isolated elliptically polarized attosecond pulses to obtain sub-attosecond temporal information via the observation of photoelectron angular distributions as a function of the ellipticity of the pulse.
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García, Iturbe Selma L. "Simulation of physical and chemical processes in reservoirs: Two case studies". Thesis, University of North Texas, 2005. https://digital.library.unt.edu/ark:/67531/metadc4968/.
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Managing water quality aspects requires the use of integrative tools that allow a holistic approach to this problem. Water quality models coupled to hydrodynamic models are these tools. This study presents the application of the water quality model WASP coupled to the hydrodynamic model DYNHYD for two distinct reservoirs: Lake Texoma and Tocoma Reservoir. Modeling the former included simulations of water velocities, water level, and four chemical and physical compounds: chlorides, dissolved oxygen (DO), biochemical oxygen demand (BOD), and total suspended solids (TSS); and validation of the results by comparing with observed values during March - May, 1997. The latter is still under project status and the simulation was performed in a prospective way. The analysis included simulations of water velocities under current and for expected conditions, DO and BOD. Both models, DYNHYD and WASP, fitted pretty well to observed conditions for Lake Texoma and for where Tocoma Reservoir has been planned. Considering management and decision support purposes, the role of boundary and loading conditions also was tested. For Lake Texoma, controlling boundary conditions for chlorides is a determinant factor for water quality of the system. However, DO and TSS in the reservoir are governed by additional process besides the condition of the boundary. Estimated loadings for this system did not provided significant effects, even though the allocation of a load for chlorides resulted in significant changes in the trend for expected chloride concentrations at the Washita River Arm of Lake Texoma. For Tocoma Reservoir, the expected concentration of DO all over the reservoir is going to driven by boundary conditions, as well as by the management of autochthonous BOD loadings provided by vegetation decomposition. These two factors will be determinant for the resulting water quality of the future reservoir.
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Ivchenko, Dmitrii. "Modeling and design of a physical vapor deposition process assisted by thermal plasma (PS-PVD)". Thesis, Limoges, 2018. http://www.theses.fr/2018LIMO0099/document.
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Le procédé de dépôt physique en phase vapeur assisté par plasma thermique (PS-PVD) consiste à évaporer le matériau sous forme de poudre à l’aide d’un jet de plasma d’arc soufflé pour produire des dépôts de structures variées obtenus par condensation de la vapeur et/ou dépôt des nano-agrégats. Dans le procédé de PS-PVD classique, l’intégralité du traitement du matériau est réalisée dans une enceinte sous faible pression, ce qui limite les phénomènes d’évaporation ou nécessite d’utiliser des torches de puissance importante. Dans ce travail, une extension du procédé de PS-PVD conventionnel à un procédé à deux enceintes est proposée puis explorée par voie de modélisation et de simulation numérique : la poudre est évaporée dans une enceinte haute pression (105 Pa) reliée par une tuyère de détente à une enceinte de dépôt basse pression (100 ou 1 000 Pa), permettant une évaporation énergétiquement plus efficace de poudre de Zircone Yttriée de granulométrie élevée, tout en utilisant des torches de puissance raisonnable. L’érosion et le colmatage de la tuyère de détente peuvent limiter la faisabilité d’un tel système. Aussi, par la mise en oeuvre de modèles numériques de mécaniquedes fluides et basé sur la théorie cinétique de la nucléation et de la croissance d’agrégats, on montre que, par l’ajustement des dimensions du système et des paramètres opératoires ces deux problèmes peuvent être contournés ou minimisés. En particulier, l’angle de divergence de la tuyère de détente est optimisé pour diminuer le risque de colmatage et obtenir le jet et le dépôt les plus uniformes possibles à l'aide des modèles susmentionnés, associés à un modèle DSMC (Monte-Carlo) du flux de gaz plasmagène raréfié. Pour une pression de 100 Pa, les résultats montrent que la barrière thermique serait formée par condensation de vapeur alors que pour 1 000 Pa, elle serait majoritairement formée par dépôt de nano-agrégatsPlasma Spray Physical Vapor Deposition (PS-PVD) aims to substantially evaporate material in powder form by means of a DC plasma jet to produce coatings with various microstructures built by vapor condensation and/or by deposition of nanoclusters. In the conventional PS-PVD process, all the material treatment takes place in a medium vacuum atmosphere, limiting the evaporation process or requiring very high-power torches. In the present work, an extension of conventional PS-PVD process as a two-chamber process is proposed and investigated by means of numerical modeling: the powder is vaporized in a high pressure chamber (105 Pa) connected to the low pressure (100 or 1,000 Pa) deposition chamber by an expansion nozzle, allowing more energetically efficient evaporation of coarse YSZ powders using relatively low power plasma torches. Expansion nozzle erosion and clogging can obstruct the feasibility of such a system. In the present work, through the use of computational fluid dynamics, kinetic nucleation theory and cluster growth equations it is shown through careful adjustment of system dimensions and operating parameters both problems can be avoided or minimized. Divergence angle of the expansion nozzle is optimized to decrease the clogging risk and to reach the most uniform coating and spray characteristics using the aforementioned approaches linked with a DSMC model of the rarefied plasma gas flow. Results show that for 100 Pa, the thermal barrier coating would be mainly built from vapor deposition unlike 1,000 Pa for which it is mainly built by cluster deposition
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Villa, A. "Three dimensional geophysical modeling : from physics to numerical simulation". Doctoral thesis, Università degli Studi di Milano, 2010. http://hdl.handle.net/2434/148440.
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The main objective of this thesis is to provide a comprehensive numerical tool for the three-dimensional simulation of sedimentary basins. We have used a volume averaging technique to obtain a couple of basin-scale mathematical models. We have used some innovative numerical techniques to deal with such models. A multi-fluid implicit tracking technique is developed and integrated with a Stokes solver that is robust with respect to the variations of the coefficients. The movement of the basin boundaries and the evolution of the faults are treated with an Ale and a Finite Volume scheme respectively. Also some mesh refinement methods are used to guarantee a sufficient accuracy. The numerical experiments show a good qualitative agreement with the measured geometry of the sedimentary layers.
(Pubblicata - vedi http://hdl.handle.net/2434/148441)
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Paradise, Richard A. "Modeling and simulation of the physical layer of the single channel ground and airborne radio system (SINCGARS)". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Jun%5FParadise.pdf.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 2005.Thesis Advisor(s): Frank Kragh, Herschel H. Loomis. Includes bibliographical references (p. 55-56). Also available online.
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Aguilera, Miguel. "Semantic and Physical Modeling and Simulation of Multi-Domain Energy Systems: Gas Turbines and Electrical Power Networks". Thesis, KTH, Elkraftteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-214532.
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The ITEA3 OpenCPS (Open Cyber-Physical System Model-Driven CertifiedDevelopment) project focuses on interoperability between the Modelica/UnifiedModeling Language (UML)/Functional Mock-up Interface (FMI) standards, improved(co-)simulation execution speed, and verified code generation. The project aims to developa modeling and simulation framework for cyber-physical and multi-domain systems. Oneof the main use cases for the framework, is the multi-domain equation-based modelingand simulation of detailed gas turbine power plants (including the explicit equation-basedmodeling of turbomachinery dynamics) and the electrical power grid.In this work, UML class diagrams based on the Common Information Model (CIM)standard are used to describe the semantics of the electrical power grid. An extension basedon the standard ISO 15926 has been proposed to derive the multi-domain semanticsrequired by the models that integrate the electrical power grid with the detailed gas turbinedynamics.Furthermore, the multi-domain physical modeling and simulation Modelica language hasbeen employed to create the equation-based models of the use case of this project. Acomparative analysis between the Single-Domain and Multi-Domain model responses hasbeen performed both in time and frequency. The results show some interesting differencesbetween the turbine dynamics representation of the commonly used GGOV1 standardmodel and the less simplified model of a gas turbine.Finally, the models from each domain can be exchanged between two differentstakeholders by means of Functional Mock-Up Units (FMUs), defined by the FMIstandard. Promising test results were obtained with different simulation tools that supportthe standard, which demonstrates the feasibility of exchanging unambiguous multi-domainmodels with a detailed gas turbine representation. This shows the potential of the FMIstandard for manufacturers to exchange equation-based multi-domain models, while at thesame time protecting their intellectual property.Projektet ITEA3 OpenCPS (Öppen, certifierad modelldriven utveckling för cyberfysiskasystem) fokuserar på interoperabilitet mellan standarderna för Modelica, Unified ModelingLanguage (UML) och Functional Mock-up Interface (FMI), förbättring av tidsåtgångenför (sam-)simulering, samt verifierad kodgenerering. Projektet syftar till att utveckla enplattform för modellering och simulering av cyberfysiska system och system somrepresenteras av olika sorters fysikaliska modeller (eng. multi-domain modeling). Ett av defrämsta användningsområdena för plattformen är ekvationsbaserad modellering ochsimulering av detaljerade gasturbinmodeller i elkraftverk (inklusive explicitekvationsbaserad modellering av dynamiken mellan termiska och roterande komponenter)som är sammankopplade med kraftsystemet.I detta examenarbete används klassdiagram i UML baserade på standarden för CommonInformation Model (CIM) och komponentdiagram från SysML för att beskrivakraftsystemet. En utvidgning baserat på ISO 15926-standarden föreslås för att härledasemantiken för modeller som integrerar både kraftsystemet och detaljerad dynamik förgasturbiner.Vidare så har Modelica, ett språk för modellering och simulering av olikartade fysikaliskasystem, utnyttjats för att skapa ekvationsbaserade modeller som utvecklats i detta projekt.En komparativ analys har genomförts för en detaljerad modell med termodynamik och enförenklad modell genom undersökning av både frekvenssvar och tidssimuleringar.Resultaten visar att skillnader uppstår mellan den detaljerade modellen och den ikraftsystemsammanhang allmänt använda modellen GGOV1, vilket kan förklaras medförenklingar i den snareSlutligen kan modeller från olika fysikaliska domäner utbytas mellan intressenter med s.k.Functional Mock-Up Units (FMU-enheter), som definieras av FMI-standarden. Lovanderesultat uppnåddes med simuleringsverktyg som stöder FMI-standarden vilket visarmöjligheten till ett otvetydigt utbyte av detaljerade gasturbinmodeller och elkraftsmodeller.Detta visar potentialen i FMI-standarden för modellutbyte mellan olikamodelleringsdomäner, vilket skulle kunna låta tillverkare att dela ekvationsbaserademodeller utan att ge upp immateriella tillgångar.
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Song, Hanbing. "Rhythmogenic and Premotor Functions of Dbx1 Interneurons in the Pre-Bötzinger Complex and Reticular Formation: Modeling and Simulation Studies". W&M ScholarWorks, 2016. https://scholarworks.wm.edu/etd/1499449835.
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Breathing in mammals depends on rhythms that originate from the preBötzinger complex (preBötC) of the ventral medulla and a network of brainstem and spinal premotor neurons. The rhythm-generating core of the preBötC, as well as some premotor circuits, consists of interneurons derived from Dbx1-expressing precursors but the structure and function of these networks remain incompletely understood. We previously developed a cell-specific detection and laser ablation system to interrogate respiratory network structure and function in a slice model of breathing that retains the preBötC, premotor circuits, and the respiratory related hypoglossal (XII) motor nucleus such that in spontaneously rhythmic slices, cumulative ablation of Dbx1 preBötC neurons decreased XII motor output by half after only a few cell deletions, and then decelerated and terminated rhythmic function altogether as the tally increased. In contrast, cumulatively deleting Dbx1 premotor neurons decreased XII motor output monotonically, but did not affect frequency nor stop functionality regardless of the ablation tally. This dissertation presents several network modeling and cellular modeling studies that would further our understanding of how respiratory rhythm is generated and transmitted to the XII motor nucleus. First, we propose that cumulative deletions of Dbx1 preBötC neurons preclude rhythm by diminishing the amount of excitatory inward current or disturbing the process of recurrent excitation rather than structurally breaking down the topological network. Second, we establish a feasible configuration for neural circuits including an Erdős-Rényi preBötC network and a small-world reticular premotor network with interconnections following an anti-preferential attachment rule, which is the only configuration that produces consistent outcomes with previous experimental benchmarks. Furthermore, since the performance of neuronal network simulations is, to some extent, affected by the nature of the cellular model, we aim to develop a more realistic cellular model based on the one we adopted in previous network studies, which would account for some recent experimental findings on rhythmogenic preBötC neurons.
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Ding, Xiangyang. "Physically-based Simulation of Tornadoes". Thesis, University of Waterloo, 2005. http://hdl.handle.net/10012/1200.
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In this physically-based tornado simulation, the tornado-scale approach techniques are applied to simulate the tornado formation environment. The three-dimensional Navier-Stokes equations for incompressible viscous fluid flows are used to model the tornado dynamics. The boundary conditions applied in this simulation lead to rotating and uplifting flow movement as found in real tornadoes and tornado research literatures. Moreover, a particle system is incorporated with the model equation solutions to model the irregular tornado shapes. Also, together with appropriate boundary conditions, varied particle control schemes produce tornadoes with different shapes. Furthermore, a modified metaball scheme is used to smooth the density distribution. Texture mapping, antialising, animation and volume rendering are applied to produce realistic visual results. The rendering algorithm is implemented in OpenGL.
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Santhanam, Anand. "MODELING, SIMULATION, AND VISUALIZATION OF 3D LUNG DYNAMICS". Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3824.
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Medical simulation has facilitated the understanding of complex biological phenomenon through its inherent explanatory power. It is a critical component for planning clinical interventions and analyzing its effect on a human subject. The success of medical simulation is evidenced by the fact that over one third of all medical schools in the United States augment their teaching curricula using patient simulators. Medical simulators present combat medics and emergency providers with video-based descriptions of patient symptoms along with step-by-step instructions on clinical procedures that alleviate the patient's condition. Recent advances in clinical imaging technology have led to an effective medical visualization by coupling medical simulations with patient-specific anatomical models and their physically and physiologically realistic organ deformation. 3D physically-based deformable lung models obtained from a human subject are tools for representing regional lung structure and function analysis. Static imaging techniques such as Magnetic Resonance Imaging (MRI), Chest x-rays, and Computed Tomography (CT) are conventionally used to estimate the extent of pulmonary disease and to establish available courses for clinical intervention. The predictive accuracy and evaluative strength of the static imaging techniques may be augmented by improved computer technologies and graphical rendering techniques that can transform these static images into dynamic representations of subject specific organ deformations. By creating physically based 3D simulation and visualization, 3D deformable models obtained from subject-specific lung images will better represent lung structure and function. Variations in overall lung deformations may indicate tissue pathologies, thus 3D visualization of functioning lungs may also provide a visual tool to current diagnostic methods. The feasibility of medical visualization using static 3D lungs as an effective tool for endotracheal intubation was previously shown using Augmented Reality (AR) based techniques in one of the several research efforts at the Optical Diagnostics and Applications Laboratory (ODALAB). This research effort also shed light on the potential usage of coupling such medical visualization with dynamic 3D lungs. The purpose of this dissertation is to develop 3D deformable lung models, which are developed from subject-specific high resolution CT data and can be visualized using the AR based environment. A review of the literature illustrates that the techniques for modeling real-time 3D lung dynamics can be roughly grouped into two categories: Geometrically-based and Physically-based. Additional classifications would include considering a 3D lung model as either a volumetric or surface model, modeling the lungs as either a single-compartment or a multi-compartment, modeling either the air-blood interaction or the air-blood-tissue interaction, and considering either a normal or pathophysical behavior of lungs. Validating the simulated lung dynamics is a complex problem and has been previously approached by tracking a set of landmarks on the CT images. An area that needs to be explored is the relationship between the choice of the deformation method for the 3D lung dynamics and its visualization framework. Constraints on the choice of the deformation method and the 3D model resolution arise from the visualization framework. Such constraints of our interest are the real-time requirement and the level of interaction required with the 3D lung models. The work presented here discusses a framework that facilitates a physics-based and physiology-based deformation of a single-compartment surface lung model that maintains the frame-rate requirements of the visualization system. The framework presented here is part of several research efforts at ODALab for developing an AR based medical visualization framework. The framework consists of 3 components, (i) modeling the Pressure-Volume (PV) relation, (ii) modeling the lung deformation using a Green's function based deformation operator, and (iii) optimizing the deformation using state-of-art Graphics Processing Units (GPU). The validation of the results obtained in the first two modeling steps is also discussed for normal human subjects. Disease states such as Pneumothorax and lung tumors are modeled using the proposed deformation method. Additionally, a method to synchronize the instantiations of the deformation across a network is also discussed.Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Computer Science
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Khare, Neeraj Prasad. "Predictive Modeling of Metal-Catalyzed Polyolefin Processes". Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/11065.
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This dissertation describes the essential modeling components and techniques for building comprehensive polymer process models for metal-catalyzed polyolefin processes. The significance of this work is that it presents a comprehensive approach to polymer process modeling applied to large-scale commercial processes. Most researchers focus only on polymerization mechanisms and reaction kinetics, and neglect physical properties and phase equilibrium. Both physical properties and phase equilibrium play key roles in the accuracy and robustness of a model.
This work presents the fundamental principles and practical guidelines used to develop and validate both steady-state and dynamic simulation models for two large-scale commercial processes involving the Ziegler-Natta polymerization to produce high-density polyethylene (HDPE) and polypropylene (PP). It also provides a model for the solution polymerization of ethylene using a metallocene catalyst. Existing modeling efforts do not include physical properties or phase equilibrium in their calculations. These omissions undermine the accuracy and predictive power of the models.
The forward chapters of the dissertation discuss the fundamental concepts we consider in polymer process modeling. These include physical and thermodynamic properties, phase equilibrium, and polymerization kinetics. The later chapters provide the modeling applications described above.Ph. D.
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Rozier, David. "Qualitative modelling and simulation of physical systems for a diagnostic purpose". Thesis, De Montfort University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391563.
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Sasse, Hugh Granville. "Enhancing numerical modelling efficiency for electromagnetic simulation of physical layer components". Thesis, De Montfort University, 2010. http://hdl.handle.net/2086/4406.
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The purpose of this thesis is to present solutions to overcome several key difficulties that limit the application of numerical modelling in communication cable design and analysis. In particular, specific limiting factors are that simulations are time consuming, and the process of comparison requires skill and is poorly defined and understood. When much of the process of design consists of optimisation of performance within a well defined domain, the use of artificial intelligence techniques may reduce or remove the need for human interaction in the design process. The automation of human processes allows round-the-clock operation at a faster throughput. Achieving a speedup would permit greater exploration of the possible designs, improving understanding of the domain. This thesis presents work that relates to three facets of the efficiency of numerical modelling: minimizing simulation execution time, controlling optimization processes and quantifying comparisons of results. These topics are of interest because simulation times for most problems of interest run into tens of hours. The design process for most systems being modelled may be considered an optimisation process in so far as the design is improved based upon a comparison of the test results with a specification. Development of software to automate this process permits the improvements to continue outside working hours, and produces decisions unaffected by the psychological state of a human operator. Improved performance of simulation tools would facilitate exploration of more variations on a design, which would improve understanding of the problem domain, promoting a virtuous circle of design. The minimization of execution time was achieved through the development of a Parallel TLM Solver which did not use specialized hardware or a dedicated network. Its design was novel because it was intended to operate on a network of heterogeneous machines in a manner which was fault tolerant, and included a means to reduce vulnerability of simulated data without encryption. Optimisation processes were controlled by genetic algorithms and particle swarm optimisation which were novel applications in communication cable design. The work extended the range of cable parameters, reducing conductor diameters for twisted pair cables, and reducing optical coverage of screens for a given shielding effectiveness. Work on the comparison of results introduced ―Colour maps‖ as a way of displaying three scalar variables over a two-dimensional surface, and comparisons were quantified by extending 1D Feature Selective Validation (FSV) to two dimensions, using an ellipse shaped filter, in such a way that it could be extended to higher dimensions. In so doing, some problems with FSV were detected, and suggestions for overcoming these presented: such as the special case of zero valued DC signals. A re-description of Feature Selective Validation, using Jacobians and tensors is proposed, in order to facilitate its implementation in higher dimensional spaces.
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CHEN, YUKAI. "Modelling and simulation of non-functional properties in cyber-physical systems". Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2709320.
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Cyber Physical Systems (CPS) have emerged as one of the most important academic and industrial research topics. These systems bridge the cyber world of computing and communications with the physical world. This intimate coupling between the cyber and physical manifests itself from the nano-world to large-scale systems. The CPS will transform how humans interact with and control the physical world around us. As a very promising research field, there are a variety of questions need to be solved, at different layers of the architecture and for different aspects of systems design, to trigger and to ease the integration of the physical and cyber worlds. Therefore, the next challenge facing the EDA community is to develop methods and also tools for CPS design. However, CPS as a tightly integrated system with computation and physical components, currently available EDA methods and tools are not equipped to handle such integrated modelling and simulation. To address this issue, there is a demand for developing appropriate EDA methods and tools to satisfy the need for an integrated modelling of the dynamics of the physical systems and the computational platforms.
Because CPS include heterogeneous components, even the simulation of their functionality represents already a significant challenge, since these components imply different time scales and accuracies, and interactions among different domains. However, the assessment of functionality is not the only dimension to be considered. Since CPS combine heterogeneous domains, other metrics must be considered to ensure their correct operations, such as power consumption, thermal behaviour or reliability. Modelling and monitoring of these properties in isolation is not a new problem. Power, thermal and reliability analysis have been studied since two decades in traditional EDA field, unfortunately, no current design methodology can simultaneously master all non-functional aspects of CPS. This dissertation aims at bridging this gap focusing on integration-aware solutions to different non-functional aspects of CPS by proposing a novel multi-layer, bus-centric single modelling and simulation framework. Multi-layer because it is structured hierarchically, with each property corresponding to a simulation layer; Bus-centric in that each property is simulated by adopting a specific virtual bus, which conveys and elaborates property information, used to derive property-specific status of the overall system.
This dissertation focuses on three main non-functional properties: power, temperature and reliability, in the form of aging. Concerning power property, firstly, a unified model of a power source that is applicable to any power scale, and that can be derived solely from data contained in the specification is proposed; then we propose a novel methodology that bring the traditional analysis of Energy Storage Devices (ESDs) in the time domain move to frequency domain, a circuit equivalent battery model account for load variations is also proposed. Based on the proposed novel battery model, we propose an optimal battery-aware scheduling policy for two kinds of CPS, namely, a multi-sensor IoT device and unmanned aerial vehicle delivery system. Moreover, since the ESDs of a CPS also need recharging when it finishes discharging phase, and the charging protocol strongly affects the performance of ESDs, we introduce an optimal charging protocol to reduce the battery aging effects while keep high Quality of Service (QoS) of the battery powered devices.
In terms of temperature, since the existing methods rely on the co-simulation with an external thermal simulator, we devise one built-in thermal simulator in our proposed simulation framework. For achieving concurrent co-simulation with others non-functional properties in our proposed framework, we implement the standard RC equivalent circuit thermal simulator into a SystemC-AMS platform, we get comparable thermal simulation results to the existing simulators, yet with much better performance.
With regard to aging, in order to keep the same simulation speed with other non-functional properties, the existing transistor-level and gate-level methods for investigating the aging, specifically, the aging due to Negative-bias temperature instability (NBTI) of the microprocessor are inadequate, therefore, we propose a novel empirical system-level NBTI aging macro-model of microprocessor, we also propose one methodology that conducts characterization on different architectures and with various synthesis constraints allows to yield lower and upper bounds of NBTI aging of any embedded cores without knowing its net-list.
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Cao, Di. "Physically Based Simulation of Various Fabrics with Multi-Level Modeling". The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1492519984871715.
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Shams, Es-haghi Siamak. "Modeling and Simulation of Diffusion in Evaporating Polymer Solutions". University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1430492857.
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Younis, Mohammad Ibrahim. "Modeling and Simulation of Microelectromechanical Systems in Multi-Physics Fields". Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/11202.
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The first objective of this dissertation is to present hybrid numerical-analytical approaches and reduced-order models to simulate microelectromechanical systems (MEMS) in multi-physics fields. These include electric actuation (AC and DC), squeeze-film damping, thermoelastic damping, and structural forces. The second objective is to investigate MEMS phenomena, such as squeeze-film damping and dynamic pull-in, and use the latter to design a novel RF-MEMS switch.
In the first part of the dissertation, we introduce a new approach to the modeling and simulation of flexible microstructures under the coupled effects of squeeze-film damping, electrostatic actuation, and mechanical forces. The new approach utilizes the compressible Reynolds equation coupled with the equation governing the plate deflection. The model accounts for the slip condition of the flow at very low pressures. Perturbation methods are used to derive an analytical expression for the pressure distribution in terms of the structural mode shapes. This expression is substituted into the plate equation, which is solved in turn using a finite-element method for the structural mode shapes, the pressure distributions, the natural frequencies, and the quality factors. We apply the new approach to a variety of rectangular and circular plates and present the final expressions for the pressure distributions and quality factors. We extend the approach to microplates actuated by large electrostatic forces. For this case, we present a low-order model, which reduces significantly the cost of simulation.
The model utilizes the nonlinear Euler-Bernoulli beam equation, the von K´arm´an plate equations, and the compressible Reynolds equation.
The second topic of the dissertation is thermoelastic damping. We present a model and analytical expressions for thermoelastic damping in microplates. We solve the heat equation for the thermal flux across the microplate, in terms of the structural mode shapes, and hence decouple the thermal equation from the plate equation. We utilize a perturbation method to derive an analytical expression for the quality factor of a microplate with general boundary conditions under electrostatic loading and residual stresses in terms of its structural mode shapes. We present results for microplates with various boundary conditions.
In the final part of the dissertation, we present a dynamic analysis and simulation of MEMS resonators and novel RF MEMS switches employing resonant microbeams. We first study microbeams excited near their fundamental natural frequencies (primary-resonance excitation). We investigate the dynamic pull-in instability and formulate safety criteria for the design of MEMS sensors and RF filters. We also utilize this phenomenon to design a low-voltage RF MEMS switch actuated with a combined DC and AC loading. Then, we simulate the dynamics of microbeams excited near half their fundamental natural frequencies (superharmonic excitation) and twice their fundamental natural frequencies (subharmonic excitation). For the superharmonic case, we present results showing the effect of varying the DC bias, the damping, and the AC excitation amplitude on the frequency-response curves. For the subharmonic case, we show that if the magnitude of the AC forcing exceeds the threshold activating the subharmonic resonance, all frequency-response curves will reach pull-in.Ph. D.
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Rosa, José Manuel Nunes de Brito. "Behavioral modeling of the NB-IoT downlink physical layer". Master's thesis, Universidade de Aveiro, 2018. http://hdl.handle.net/10773/23530.
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Mestrado em Engenharia Eletrónica e TelecomunicaçõesThe Internet of Things (IoT) paradigm de nes a fully connected network of devices enabling new forms of interaction between users and devices. The constant growth of these networks, as well as an increasing demand for more reliable, low bit rate and massive communication data ows lead to the emergence of new technologies and set of standards, such as, the Low Power Wide Area Networks (LPWAN). In June 2016, 3GPP, the consortium responsible for LTE development and standardization, released a new licensed band based standard, named Narrow Band (NB) IoT. NB-IoT was designed based on the same principles of other LPWAN standards, providing better coverage and additionally an easier integration on existing cellular systems. In this dissertation a study on the NB-IoT Physical Layer is presented along with an open source behavioral implementation in MATLAB of the downlink transmission and reception chains. The system generates and recovers one radio frame successfully performings procedures such as MIB and SIB1-N extracting along with scheduling and recovering data scheduled through control channels by higher layer paramenters. The project models and executes the downlink transmission (eNodeB) and reception (terminal) PHYs either in a pure simulation environment using di erent channel models, as well as integrated with an USRP software de ned radio device for co-simulation. The simulation and co-simulation results are presented evaluating the transmission's quality and performance of the implemented Zero Forcing equalizer.
O paradigma da Internet of Things (IoT) define uma rede interligada de dispositivos que permite o surgimento de novas formas de interacção entre utilizadores e dispositivos. O constante crescimento destas redes assim como a crescente demanda por uma fiabilidade maior, bit rates mais baixos e circulação massiva de informação insurgiu o aparecimento de novas tecnologias tais como as Low Power Wide Area Networks (LPWAN). Em Junho de 2016 a 3GPP, o órgão responsável pelo LTE, lançou um novo standard para bandas licenciadas o Narrowband (NB) -IoT. O NB-IoT foi desenhado com base nos mesmos princípios que as outras LPWAN com o acréscimo de uma maior cobertura assim como uma mais fácil integração em sistemas celulares existentes. Nesta dissertação aborda-se um estudo da sua camada física (PHY Layer) juntamente com uma implementação comportamental open source em Matlab das cadeias de transmissão e recepção em downlink. O projecto modela e executa transmissões em downlink (eNodeB) e sua recepcção (terminal) tanto em ambiente simulado como integrado com um dispositivo de software defined radio, USRP, para validação laboratorial. Os resultados obtidos tanto de simulação como co-simulação são apresentados avaliando a qualidade de transmissão assim como o comportamento do equalizador Zero Forcing implementado.
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Söderqvist, Hampus. "Modeling and simulation of particle dynamics in microfluidic channels". Thesis, Umeå universitet, Institutionen för fysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-137473.
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Wing, Allison A. "Physical mechanisms controlling self-aggregation of convection in idealized numerical modeling simulations". Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90606.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2014.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 141-146).
The ubiquity of cloud clusters and their role in modulating radiative cooling and the moisture distribution underlines the importance of understanding how and why tropical convection organizes. In this work, the fundamental mechanism underlying the self-aggregation of convection is explored using a cloud resolving model. The objective is to identify and quantify the interactions between the environment and the convection that allow the convection to spontaneously organize into a single cluster. Specifically, the System for Atmospheric Modeling is used to perform 3-d cloud system resolving simulations of radiative-convective equilibrium in a non-rotating framework, with interactive radiation and surface fluxes and fixed sea surface temperature. Self-aggregation only occurs at sea surface temperatures above a certain threshold. As the system evolves to an aggregated state, there are large changes to domain averaged quantities important to climate, such as radiative fluxes and moisture. Notably, self-aggregation begins as a dry patch that expands, eventually forcing all the convection into a single clump. Thus, when examining the initiation of self-aggregation, we focus on processes that can amplify this initial dry patch. Sensitivity tests suggest that wind-dependent surface fluxes and interactive longwave radiative fluxes are important for permitting self-aggregation. A novel method is introduced to quantify the magnitudes of the various feedbacks that control self-aggregation within the framework of the budget for the spatial variance of column - integrated frozen moist static energy. The absorption of shortwave radiation by atmospheric water vapor is found to be a key positive feedback in the evolution of aggregation. In addition, there is a positive wind speed - surface flux feedback whose role is to counteract a negative air-sea enthalpy disequilibrium - surface flux feedback. The longwave radiation - water vapor feedback transitions from positive to negative in the early and intermediate stages of aggregation. The long-wave radiation - cloud feedback is the dominant positive feedback that maintains the aggregated state once it develops. Importantly, the mechanisms that maintain the aggregated state are distinct from those that instigate the evolution of self-aggregation. These results and those of a companion study suggest that the temperature dependence of self-aggregation enters through the longwave feedback term.
by Allison A. Wing.
Ph. D.
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Hedberg, Vilhelm. "Evaluation of Hair Modeling, Simulation and Rendering Algorithms for a VFX Hair Modeling System". Thesis, Linköpings universitet, Medie- och Informationsteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-65592.
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Creating realistic virtual hair consists of several major areas: creating the geometry, moving the hair strands realistically and rendering the hair. In this thesis, a background survey covering each one of these areas is given. A node-based, procedural hair system is presented, which utilizes the capabilities of modern GPUs. The hair system is implemented as a plugin for Autodesk Maya, and a user interface is developed to allow the user to control the various parameters. A number of nodes are developed to create effects such as clumping, noise and frizz. The proposed system can easily handle a variety of hairstyles, and pre-renders the result in real-time using a local shading model.
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Alzoubi, Khawla Ali. "NANO-ELECTRO-MECHANICAL SWITCH (NEMS) FOR ULTRA-LOW POWER PORTABLE EMBEDDED SYSTEM APPLICATIONS: ANALYSIS, DESIGN, MODELING, AND CIRCUIT SIMULATION". Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1278511770.
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Natsupakpong, Suriya. "Physically Based Modeling and Simulation for Virtual Environment based Surgical Training". Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1259182314.
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Ertugay, Kivanc. "Gis-based Stochastic Modeling Of Physical Accessibility By Using Floating Car Data And Monte Carlo Simulations". Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613777/index.pdf.
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The term physical accessibility has widely been used by geographers, economists and urban planners and basically reflects the relative ease of access to/from several urban/rural services by considering various travelling costs. Numerous accessibility measures, ranging from simple to sophisticated, can be found in the GIS based accessibility modeling literature. However, whether simple or sophisticated, one of the fundamental shortcomings of the current GIS-based accessibility measures is that they are generally calculated from a fixed catchment area boundary based on constant traveling costs such as Euclidian (bird-flight) distance costs or transportation network-based average speed costs (e.g. 50 km/h for main streets and 30 km/h for local streets, etc.). Although such deterministic approaches are widely used in GIS-based accessibility modeling literature, they are not realistic, especially due to highly variable speeds in road segments and uncertainty in the accuracy and reliability of the accessibility measures. Therefore, this dissertation provides a new stochastic methodology for GIS-based accessibility modeling process by using GPS-based floating car data and Monte Carlo Simulation (MCS) that could handle variations in traveling costs and consider all possible catchment area boundaries, instead of one average or maximum fixed catchment area boundary. The main contribution of the research is thatthe proposed physical accessibility modeling could handle uncertainties in transportation costs, create significant improvement on accuracy and reliability of accessibility measures in terms of catchment area boundaries and support decision makers who are supposed to deal with accessibility, location/allocation and service/catchment area related issues. The proposed stochastic methodology is implemented to a case study on medical emergency service accessibility, in Eskisehir, Turkey and the results of the deterministic and stochastic accessibility models are compared. The main focus of the case study is not to evaluate a specific accessibility condition in a detailed manner but to provide a methodological discussion and comparison between the deterministic and stochastic accessibility modeling process. With the implementation to a case study, it is shown that
the results of the proposed methodology are more realistic than the conventional deterministic approaches.
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Nakao, Megumi. "Cardiac surgery simulation with active interaction and adaptive physics-based modeling". 京都大学 (Kyoto University), 2003. http://hdl.handle.net/2433/148777.
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Shen, Luming. "Multi-scale modeling and simulation of multi-physics in film delamination /". free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p3144456.
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Liao, Poyuan. "Design and simulation of a terahertz sensor using finite element modeling". Thesis, Monterey, California : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Dec/09Dec%5FLiao.pdf.
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Thesis (M.S. in Applied Physics)--Naval Postgraduate School, December 2009.Thesis Advisor(s): Karunasiri, Gamani; Grbovic, Dragoslav. "December 2009." Description based on title screen as viewed on January 26, 2010. Author(s) subject terms: THz, terahertz, bi-material, micro-cantilever, microbolometer, QCL, quantum cascade laser, MEMS, detection, focal plane array, NETD Includes bibliographical references (p. 35-36). Also available in print.
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Jun, Jong Brian. "A Visual Simulation Life-Cycle Of The Queston Physician Network". Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/10030.
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This research develops a discrete-event simulation model of the Queston Physician Network using the Visual Simulation Environment (VSE), an object-oriented simulation software program. The Queston Physician Network, a subsidiary of Biological & Popular Culture, Inc., attempts to centralize the administrative, financial, and telecommunication needs of a network of primary care physicians located throughout the United States. The VSE, running on the NeXTSTEP operating system, is a discrete event simulation software package with the capability to tackle the complexities associated with such a network design. The advantages of VSE over other simulation languages include its visualization of objects, domain independence, and object-oriented design and modeling.
The objective of the Queston simulation model is to addresses the performance capabilities of the physician network operationally centralized in the Queston Information Center. Additionally, the model could be used to analyze a physician-patient encounter of a generic clinic to identify recommended staffing and scheduling schemes.
Object-oriented programming allows the objects in the model to be instantiated at the time of execution. This feature permits the creation of one flexible generic clinic that can be reused to produce several identical clinics at program execution. In this model, one generic, family practice clinic and the Queston Information Center are created. Input data provided by both medical experts and a time study are used. Verification and validation techniques are applied in all phases of the modeling effort. Results using different configurations are presented and recommendations for future research are discussedMaster of Science
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Doyle, Carolyn. "Computer Modeling and Simulation of Ground Beef and Lettuce Handling for Hamburgers at a Typical Fast-Food Restaurant". Digital Commons @ East Tennessee State University, 2002. https://dc.etsu.edu/etd/728.
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Numerous Escherichia coli O157:H7 outbreaks have been associated with fast food restaurants. This research created a computer model and simulation with the Micrografx computer software program Process™ for the safe handling of ground beef patties and lettuce in a typical fast food restaurant.
A reference facility was visited to obtain a text description of the flow of food. To create the model, a process diagram was made that graphically represented the series of steps that were taken from the arrival of products to the delivery of the cooked and assembled product to the consumer. A process model was created when the steps in the process diagram was assigned behaviors. The final phase was process simulation.
The simulation results indicated the model was representative of a typical fast-food restaurant. The model was then used successfully to simulate three potential breakdowns of the food safety system that could lead to a foodborne illness outbreak.
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Campos, Luiza Cintra. "Modelling and simulation of the biological and physical processes of slow sand filtration". Thesis, University College London (University of London), 2002. http://discovery.ucl.ac.uk/43778/.
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Slow sand filtration (SSF) is the earliest form of engineered potable water treatment and remains one of the most efficient processes for improving the physical, biological and chemical quality of water. However, whilst widely used throughout the world, knowledge of the filtration mechanisms remains limited. This is important in understanding and managing the processes that are responsible for gradually blocking the filter reducing its operational life and filtration efficiency. The objective of this thesis was to develop a mechanistic simulation model of the fundamental physico-chemical and biological processes responsible for the filtration mechanisms operating in slow sand filters. The model solves a set of equations describing schmutzdecke development above the sand and microbial biomass growth within the sand. The model assumes that the schmutzdecke layer contributes to the water purification process and its growth is described as linear function in relation to time. The dynamic interactions between the principal groups of microorganisms including: algae, bacteria and protozoa, were modelled using Monod-type kinetic equations. The filtration performance of the filter media was defined in the model by the removal of particulate material from water and was represented by a combination of headloss and filtration coefficient functions. The model was calibrated and verified using data from full and pilot plant-scale SSF operated by Thames Water Utilities Ltd. Simulation results showed that interstitial biomass was the smallest part of the bulk specific deposit in both covered and uncovered filters. However, microbial dynamics played an important role in the filtration performance. Schmutzdecke development had a major influence on the operation of uncovered filters and was responsible for the significant increase of headloss observed during operation. The model provides a representation of the fundamental nature of SSF processes and could form the basis of an operational management system to optimise SSF.
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Fors, Jonathan. "Modeling and OpenFOAM simulation of streamers in transformer oil". Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-80932.
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Electric breakdown in power transformers is preceded by pre-breakdown events such as streamers. The understanding of these phenomena is important in order to optimize liquid insulation systems. Earlier works have derived a model that describes streamers in transformer oil and utilized a finite element method to produce numerical solutions. This research investigates the consequences of changing the numerical method to a finite volume-based solver implemented in OpenFOAM. Using a standardized needle-sphere geometry, a number of oil and voltage combinations were simulated, and the results are for the most part similar to those produced by the previous method. In cases with differing results the change is attributed to the more stable numerical performance of the OpenFOAM solver. A proof of concept for the extension of the simulation from a two-dimensional axial symmetry to three dimensions is also presented.Elektriska genomslag i högspänningstransformatorer föregås av bildandet av elektriskt ledande kanaler som kallas streamers. En god förståelse av detta fenomen är viktigt vid konstruktionen av oljebaserad elektrisk isolation. Tidigare forskning i ämnet har tagit fram en modell för fortplantningen av streamers. Denna modell har sedan lösts numeriskt av ett beräkningsverktyg baserat på finita elementmetoden. I denna uppsats undersöks konsekvenserna av att byta metod till finita volymsmetoden genom att implementera en lösare i OpenFOAM. En standardiserad nål-sfär-geometri har ställts upp och ett flertal kombinationer av oljor och spänningar har simulerats. De flesta resultaten visar god överensstämmande med tidigare forskning medan resultat som avviker har tillskrivits de goda numeriska egenskaperna hos OpenFOAM-lösaren. En ny typ av simulering har även genomförts där simulationen utökas från en tvådimensionell axisymmetrisk geometri til tre dimensioner.
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Lucas, Bruce. "Fundamental Modeling of Solid-State Polymerization Process Systems for Polyesters and Polyamides". Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/29378.
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The dissertation describes and assembles the building blocks for sound and accurate models for solid-state polymerization process systems of condensation polymers, particularly poly(ethylene terephthalate) and nylon-6. The work centers on an approach for modeling commercial-scale, as opposed to laboratory-scale, systems. The focus is not solely on coupled polymerization and diffusion, but extends to crystallization, physical properties, and phase equilibrium, which all enhance the robustness of the complete model.
There are three applications demonstrating the utility of the model for a variety of real, industrial plant operations. One of the validated simulation models is for commercial production of three different grades of solid-state PET. There are also validated simulation models for the industrial leaching and solid-state polymerization of nylon-6 covering a range of operating conditions. The results of these studies justify our mixing-cell modeling approach as well as the inclusion of all relevant fundamental concepts.
The first several chapters discuss in detail the engineering fundamentals that we must consider for modeling these polymerization process systems. These include physical properties, phase equilibrium, crystallization, diffusion, polymerization, and additional modeling considerations. The last two chapters cover the modeling applications.Ph. D.
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Minamoto, Yuki. "Physical aspects and modelling of turbulent MILD combustion". Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/245204.
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Moderate or Intense Low-oxygen Dilution (MILD) combustion is one of combustion technologies which can improve efficiency and reduce emissions simultaneously. This combustion type is characterised by the highly preheated reactant temperature and the relatively small temperature rise during combustion due to the intense dilution of the reactant mixture. These unique combustion conditions give MILD combustion very attractive features such as high combustion efficiency, reduction of pollutant emissions, attenuation of combustion instabilities and flexibility of the flow field. However, our understanding of MILD combustion is not enough to employ the MILD combustion technology further for modern combustion devices. In this thesis, Direct Numerical Simulation (DNS) has been carried out for turbulent MILD combustion under four MILD and classical premixed conditions. A two-phase strategy is employed in the DNS to include the effect of imperfect mixing between fresh and exhaust gases before intense chemical reactions start. In the simulated instantaneous MILD reaction rate fields, both thin and distributed reaction zones are observed. Thin reaction zones having flamelet like characteristics propagate until colliding with other thin reaction zones to produce distributed reaction zones. Also, the effect of such interacting reaction zones on scalar gradient has to be taken into account in flamelet approaches. Morphological features of MILD reaction zones are investigated by employing Minkowski functionals and shapefinders. Although a few local reaction zones are classified as thin shape, the majority of local reaction zones have pancake or tube-like shapes. The representative scales computed by the shapefinders also show a typical volume where intense reactions appear. Given high temperature and existence of radicals in the diluted reactants, both reaction dominated and flame-propagation dominated regions are locally observed. These two phenomena are closely entangled under a high dilution condition. The favourable conditions for these phenomena are investigated by focusing on scalar fluxes and reaction rate. A conditional Probability Density Function (PDF) is proposed to investigate flamelet/non-flamelet characteristics of MILD combustion. The PDF can be obtained by both numerically and experimentally. The PDF shows that MILD combustion still has the direct relationship between reaction rate and scalar gradient, although the tendency is statistically weak due to the distributed nature of MILD reaction zones. Finally, based on the physical aspects of MILD combustion explained in this work, a representative model reactor for MILD combustion is developed. The model reactor is also used in conjunction with the presumed PDF for a mean and filtered reaction rate closure. The results show a good agreement between the modelled reaction rate and the DNS results.
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Vedin, Jörgen. "Numerical modeling of auroral processes". Doctoral thesis, Umeå University, Physics, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1117.
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One of the most conspicuous problems in space physics for the last decades has been to theoretically describe how the large parallel electric fields on auroral field lines can be generated. There is strong observational evidence of such electric fields, and stationary theory supports the need for electric fields accelerating electrons to the ionosphere where they generate auroras. However, dynamic models have not been able to reproduce these electric fields. This thesis sheds some light on this incompatibility and shows that the missing ingredient in previous dynamic models is a correct description of the electron temperature. As the electrons accelerate towards the ionosphere, their velocity along the magnetic field line will increase. In the converging magnetic field lines, the mirror force will convert much of the parallel velocity into perpendicular velocity. The result of the acceleration and mirroring will be a velocity distribution with a significantly higher temperature in the auroral acceleration region than above. The enhanced temperature corresponds to strong electron pressure gradients that balance the parallel electric fields. Thus, in regions with electron acceleration along converging magnetic field lines, the electron temperature increase is a fundamental process and must be included in any model that aims to describe the build up of parallel electric fields. The development of such a model has been hampered by the difficulty to describe the temperature variation. This thesis shows that a local equation of state cannot be used, but the electron temperature variations must be descibed as a nonlocal response to the state of the auroral flux tube. The nonlocal response can be accomplished by the particle-fluid model presented in this thesis. This new dynamic model is a combination of a fluid model and a Particle-In-Cell (PIC) model and results in large parallel electric fields consistent with in-situ observations.
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Wang, Shihu. "Computer Simulation and Mathematical Modeling of Reversibly Associated Polymers". Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1275488088.
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Pinska, Adrianna. "Addition of flexible linkers to GPU-accelerated coarse-grained simulations of protein-protein docking". Thesis, Faculty of Science, 2019. http://pubs.cs.uct.ac.za/archive/00001307/.
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Multiprotein complexes are responsible for many vital cellular functions, and understanding their formation has many applications in medical research. Computer simulation has become a valuable tool in the study of biochemical processes, but simulation of large molecular structures such as proteins on a useful scale is computationally expensive. A compromise must be made between the level of detail at which a simulation can be performed, the size of the structures which can be modelled and the time scale of the simulation. Techniques which can be used to reduce the cost of such simulations include the use of coarse-grained models and parallelisation of the code. Parallelisation has recently been made more accessible by the advent of Graphics Processing Units (GPUs), a consumer technology which has become an affordable alternative to more specialised parallel hardware.
We extend an existing implementation of a Monte Carlo protein-protein docking simulation using the Kim and Hummer coarse-grained protein model [1] on a heterogeneous GPU-CPU architecture [2]. This implementation has achieved a significant speed-up over previous serial implementations as a result of the efficient parallelisation of its expensive non-bonded potential energy calculation on the GPU.
Our contribution is the addition of the optional capability for modelling flexible linkers between rigid domains of a single protein. We implement additional Monte Carlo mutations to allow for movement of residues within linkers, and for movement of domains connected by a linker with respect to each other. We also add potential terms for pseudo-bonds, pseudo-angles
and pseudo-torsions between residues to the potential calculation, and include additional residue pairs in the non-bonded potential sum. Our flexible linker code has been tested, validated and benchmarked. We find that the implementation is correct, and that the addition of the linkers does not significantly impact the performance of the simulation.
This modification may be used to enable fast simulation of the interaction between component proteins in a multiprotein complex, in configurations which are constrained to preserve particular linkages between the proteins. We demonstrate this utility with a series of simulations of diubiquitin chains, comparing the structure of chains formed through all known linkages between two ubiquitin monomers. We find reasonable agreement between our simulated structures and experimental data on the characteristics of diubiquitin chains in solution.