Dissertations / Theses on the topic 'Forward modeling'
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Singh, Saransh. "Application of Forward Modeling to Materials Characterization." Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/1009.
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The four pillars of material science and engineering namely structure, processing, properties and performance form the so-called material paradigm. At the heart of the material paradigm is materials characterization, which is used to measure and identify the relationships. Materials Characterization typically reconstructing the conditions giving rise to a measurement, a classic inverse problem. The solutions of these inverse problems are under or over determined and not unique. The solutions of these inverse problems can be greatly improved if accurate forward models exist for these characterization experiments. In this thesis, we will be focusing of developing forward models for electron diffraction modalities. Specifically, four different forward models for electron diffraction, namely the Electron Backscatter Diffraction, Electron Channeling Patterns, Precession Electron Diffraction and Transmission kikuchi Diffraction modalities are presented. Further, these forward models are applied to important materials characterization problems, including diffraction pattern indexing using the dictionary approach and forward model based orientation refinement. Finally, a novel pole figure inversion algorithm using the cubochoric representation and model based iterative reconstruction is also presented.
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Tighe, Jan Elizabeth. "Modeling and analysis of cellular CDMA forward Channel /." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2001. http://handle.dtic.mil/100.2/ADA391598.
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Dissertation (M.S. in Applied Mathematics and Ph.D. in Electrical Engineering) Naval Postgraduate School, March 2001.Dissertation supervisor(s): Ha, Tri T. "March 2001." Includes bibliographical references (p. 199-205). Also available in print.
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Tang, Hui. "Forward and Inverse Modeling of Tsunami Sediment Transport." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/77439.
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Tsunami is one of the most dangerous natural hazards in the coastal zone worldwide. Large tsunamis are relatively infrequent. Deposits are the only concrete evidence in the geological record with which we can determine both tsunami frequency and magnitude. Numerical modeling of sediment transport during a tsunami is important interdisciplinary research to estimate the frequency and magnitude of past events and quantitative prediction of future events. The goal of this dissertation is to develop robust, accurate, and computationally efficient models for sediment transport during a tsunami. There are two different modeling approaches (forward and inverse) to investigate sediment transport. A forward model consists of tsunami source, hydrodynamics, and sediment transport model. In this dissertation, we present one state-of-the-art forward model for Sediment TRansport In Coastal Hazard Events (STRICHE), which couples with GeoClaw and is referred to as GeoClaw-STRICHE. In an inverse model, deposit characteristics, such as grain-size distribution and thickness, are inputs to the model, and flow characteristics are outputs. We also depict one trial-and-error inverse model (TSUFLIND) and one data assimilation inverse model (TSUFLIND-EnKF) in this dissertation. All three models were validated and verified against several theoretical, experimental, and field cases.Ph. D.
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Caudillo, Mata Luz Angélica. "Multiscale and upscaling methods for geophysical electromagnetic forward modeling." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/63343.
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Accurate and efficient simulation of electromagnetic responses in realistic geophysical settings is crucial to the exploration, imaging, and characterization of buried natural resources, such as mineral and hydrocarbon deposits. However, in practice, these simulations are computationally expensive. The geophysical settings consider highly heterogeneous media and features at multiple spatial scales that require a very large mesh to be accurately represented. This results in a system of equations to be solved that often exceeds the limits of average computers. Thus, the key is to reduce the problem size but retain the accuracy of the electromagnetic responses.
Upscaling and multiscale techniques have been successfully applied to the problem of simulating fluid flow through heterogeneous porous media, where they are able to drastically reduce the size of the resulting fine-mesh system by casting it into a coarse-mesh system that is much cheaper to solve, while achieving a level of accuracy similar to that obtained with conventional discretization schemes. Recognizing the success that such techniques have had in fluid flow applications, this dissertation extends their use for application to electromagnetic modeling.
In this dissertation, two new parallel simulation methods for the quasi-static Maxwell’s equations in the frequency domain are proposed: an upscaling framework for the electrical conductivity, and a multiscale finite volume with oversampling method. Both methods are combined with an adaptive mesh refinement technique (OcTree) to boost their computational performance. The performance of these methods is demonstrated by using field-inspired and synthetic examples that include a large electrical conductivity contrast.
This investigation shows that both proposed methods are feasible to tackle geophysical electromagnetic problems, where being able to reduce the size of the problem can be particularly advantageous when extended domains are considered or when the mesh must capture the spatial distribution of the media heterogeneity outside the region where the electromagnetic responses are measured. Furthermore, both methods are new contributions to the literature in the field of computational methods in geophysical electromagnetics. Finally, both methods increase the current predictive and analytic capabilities by making the simulation of electromagnetic responses in larger and more complex geophysical settings more feasible than currently is possible.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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Kumar, Sharam Manjo. "Optimization of Laser Induced Forward Transfer by Finite Element Modeling." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-121209.
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This thesis explains a comprehensive study on the thermal modeling aspects of Laser Induced Forward Transfer (LIFT), a laser direct write technique. The LIFT process utilizes a focused laser beam to transfer a donor material coated on a laser wavelength transparent substrate to a receiver substrate kept in close proximity. COMSOL Multiphysics is used to implement a two-dimensional time dependent surface and volumetric heat generation model. The thermal model covers the laser induced heating in a pure copper donor material for nanosecond and picosecond pulsed Nd:YAG (Neodymium doped Yttrium Aluminium Garnett) lasers operating at 355 nm wavelength. The model is used to understand the molten regime of the donor material during LIFT process with a stationary laser beam of Gaussian profile in temporal and spatial domain. The input parameters used in the model include both temperature-dependent as well as temperature-independent thermophysical material properties such as heat capacity and thermal conductivity. In addition, theoretical investigations are done to study the optical properties of the material such as absorption coefficient and reflectivity. Simulations are done by changing pulse length, energy per pulse, donor layer thickness and wavelength. Investigation of the heat loss in the donor substrate is also carried out. The influence of wavelengths for 355 nm, 532 nm and 1064 nm at a fixed laser fluence and thickness is also studied. The simulation result shows strengths and weaknesses of both nanosecond and picosecond systems. A picosecond pulse is much dependent on thickness of the material (a few 100 nanometers) whereas a nanosecond pulse is capable of melting a thicker layer (a few micrometers). Choosing a particular laser pulse depends entirely on the type of applications and requirements. It is observed that the peak surface temperature increases linearly with increasing fluence and falls exponentially with increasing donor layer thickness. Also, it is seen that the longer wavelengths require more energy to reach melting temperature at same fluence and thickness due to increased value of reflectivity and less energetic photons. The simulated results give a good approximation to the experimental results of copper LIFT. The model can be used for other materials also by using the relevant material properties.
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Soares, Nuno Filipe de Almeida. "Modeling of lifetime probability of default and forward-looking adjustment." Master's thesis, Instituto Superior de Economia e Gestão, 2017. http://hdl.handle.net/10400.5/14963.
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Mestrado em Mathematical FinanceA 1 de Janeiro de 2018, a nova norma contabilística para instrumentos financeiros, IFRS 9 Financial Instruments, tornar-se-á obrigatória. Convergendo as necessidades da crise de 2007 para mudanças técnicas, o seu objetivo é alinhar a contabilidade com a gestão de risco. Uma das principais adaptações é o novo modelo de imparidade, que passa de "perdas incorridas" na IAS 39 para "perdas esperadas" na IFRS 9. Para fazer essa transição, é necessário incorporar informação forward-looking nas estimações. Neste caso, a incorporação necessitava de ser feita para as Probabilidades de Default, uma das variáveis usadas para calcular "perdas esperadas". Portanto, nosso objetivo era desenvolver e validar um modelo, alavancando o trabalho anterior, que integrasse projeções macroeconómicas nas estimativas das Probabilidades de Default. Para isso duas abordagens foram comparadas, sendo uma mais técnica, e, a outra mais simples e mais prática. Após a comparação, o modelo final foi definido ao ajustar a melhor abordagem.
On January 1st, 2018, the new financial instruments standard, IFRS 9 Financial Instruments, will turn mandatory. Converging 2007's crisis' needs for technical changes, its objective is to align accounting with risk management. One of the main adaptations is the new impairment model, which passes from "incurred losses" in IAS 39 to "expected losses" in IFRS 9. To make this transition forward-looking information must be incorporated in the estimations. In this case, the incorporation needed to be made for the Probabilities of Default, one of the variables used to calculate "expected losses". Therefore, our objective was to develop and validate a model, while leveraging previous work, to integrate macroeconomic projections in the estimations of the Probabilities of Default. To do so, two approaches were compared, with one being more technical while the other simpler and more practical. After the comparison, the final model was defined by adjusting the best approach.
info:eu-repo/semantics/publishedVersion
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Maerten, Frantz. "Geomechanics to solve geological structure issues : forward, inverse and restoration modeling." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20031.
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Différentes applications de l'élasticité linéaire en géologie structurale sont présentées dans cette thèse à travers le développement de trois types de codes numériques. Le premier utilise la modélisation directe pour étudier les déplacements et champs de contraintes autour de zones faillées complexes. On montre que l'ajout de contraintes inégalitaires, telles que la friction de Coulomb, permet d'expliquer l'angle d'initiation des dominos dans les relais extensifs. L'ajout de matériaux hétérogènes et d'optimisations, telles la parallélisation sur processeurs multi-coeurs ainsi que la réduction de complexité des modèles, permettent l'étude de modèles beaucoup plus complexes. Le second type de code numérique utilise la modélisation inverse, aussi appelée estimation de paramètres. L'inversion linéaire de déplacements sur les failles ainsi que la détermination de paléo-contraintes utilisant une approche géomécanique sont développées. Le dernier type de code numérique concerne la restoration de structures complexes plissées et faillées. Il est notamment montré qu'une telle méthode permet de vérifier l'équilibre de coupes géologiques, ainsi que de retrouver la chronologie des failles. Finalement, nous montrons que ce même code permet de lisser des horizons 3D faillés, plissés et bruités en utilisant la géomécaniqueDifferent applications of linear elasticity in structural geology are presented in this thesis through the development of three types of numerical computer codes. The first one uses forward modeling to study displacement and perturbed stress fields around complexly faulted regions. We show that incorporating inequality constraints, such as static Coulomb friction, enables one to explain the angle of initiation of jogs in extensional relays. Adding heterogeneous material properties and optimizations, such as parallelization on multicore architectures and complexity reduction, admits more complex models. The second type deals with inverse modeling, also called parameter estimation. Linear slip inversion on faults with complex geometry, as well as paleo-stress inversion using a geomechanical approach, are developed. The last type of numerical computer code is dedicated to restoration of complexly folded and faulted structures. It is shown that this technique enables one to check balanced cross-sections, and also to retrieve fault chronology. Finally, we show that this code allows one to smooth noisy 3D interpreted faulted and folded horizons using geomechanics
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Cochrane, Douglas F. Lawson Catherine L. "Modeling Department of Defense controlled atmosphere transshipments for forward deployed forces /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1998. http://handle.dtic.mil/100.2/ADA343617.
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Thesis (M.S. in Management) Naval Postgraduate School, March 1998.Thesis advisor(s): Jim Kerber, Jane Feitler. "March 1998." Includes bibliographical references (p. 151-154). Also available online.
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Cochrane, Douglas F., and Catherine L. Lawson. "Modeling Department of Defense controlled atmosphere transshipments for forward deployed forces." Thesis, Monterey, California. Naval Postgraduate School, 1998. http://hdl.handle.net/10945/8690.
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Approved for public release; distribution is unlimitedThe objective of this thesis is to explore the cost savings, product quality improvement, and process efficiencies that can be realized by the integrated design and application of an innovative logistics system for the purchase and transshipment of fresh fruits and vegetables (FFV) to forward deployed units. The expanding global marketplace, strategic partnerships with private industry, aggressive utilization of commercial-off-the-shelf (COTS) technology, and an aggregate understanding of the logistics pipeline process will enable the Department of Defense (DoD) logistician to provide the customer with a wider variety of fresher, higher quality product, while exploiting monetary savings through competitive pricing, lower transportation costs, and reduced product handling losses and damage. The aggressive application of this process can result in the wholesale shift of the current operational paradigm with regards to the support of forward deployed forces, from the sea. Combat Logistic Forces will have increased flexibility for scheduling and ultimately expand their operational capability, remaining at sea for longer periods of time, carrying more product, and better serving the warfighter. A summary of findings is provided with recommendations for further research into specific applications of technologies, training, and existing processes
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Shen, Yongxing. "Modeling electrostatic force microscopy and related techniques : forward and inverse problems /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Thomas, Scott J. 1961. "Forward modeling and data acquisition for high-accuracy electromagnetic subsurface imaging." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/558108.
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Qin, Jizeng. "Three-dimensional DC resistivity forward modeling and inversion by finite-element method." Diss., The University of Arizona, 1995. http://hdl.handle.net/10150/187064.
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DC resistivity inversion is a method for determining underground geoelectrical structures from discrete measurements of electric potential made on the surface or within a borehole. In this dissertation, a fully three-dimensional (3-0) resistivity inversion algorithm has been developed. Based on a finite-element forward solution of Laplace's equation, the program estimates several thousand unknowns in a rectangular grid by the linearized least-squares method. In the first Chapter, the main 3-D forward modeling techniques were investigated. These techniques include boundary condition implementation, secondary field solution and matrix inversion. Among the various kinds of mixed boundary conditions, the terminal-impedance method is particularly well suited for 3-D resistivity modeling. Its implementation is simple, but eliminates the mesh-edge influence effectively. The advantage of calculating the secondary fields instead of the total fields is that a coarse mesh may be used to achieve the same accuracy, which turns out to be particularly beneficial for 3-D modeling. Compared with other relaxation methods to solve the linear system iteratively, the incomplete Cholesky conjugate gradient (lCCG) algorithm is superior in convergence rate. However, to guarantee a stable solution, this method also requires more regular elements. To make the program capable of overcoming non-uniqueness and handling large numbers of parameters, the sensitivity matrix construction and three constraining conditions are discussed in Chapter two. In 3-D DC resistivity inversion, computing the sensitivity matrix is an enormous task even when using reciprocity. This is because the total number of forward calculations used to construct the sensitivity matrix for one iteration of the inversion is on the order of the number of observed data. By applying the conjugate-gradient method to solve the least-squares system, our program only needs to calculate the product of the sensitivity matrix, or its transpose, with an arbitrary vector, which requires only two forward runs for each source point. The different constraining conditions were tested by several synthetic models. Although each method can give a unique solution, we found that in our case, the smoothest solution method will reduce the data error better than the other two methods, the damped method and the stochastic method. A number of simple but geophysically significant structures are also modeled to test the program. These include a single isolated block anomaly, three connected blocks representing a dipping fault and a multi-layer model. Data were simulated by both integral-equation and finite-element approximations. The main features of most resistivity models were identifiable in the inversion result. As an example of a 3-D inversion program application, a field data set was processed in Chapter three. The effects of some important parameters used in the program were discussed. The results were compared with a 2-D solution and the known geological structures around that area.
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Apte, Advait. "Computational modeling of biochemical systems using cellular automata." VCU Scholars Compass, 2009. http://scholarscompass.vcu.edu/etd/2046.
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Biological systems exhibit complex behaviors through coordinated responses of individual biological components. With the advent of genome-scale techniques, one focus has been to develop methods to model interactions between components to accurately describe intact system function. Mathematical modeling techniques such as constraint-based modeling, agent-based modeling, cellular automata (CA) modeling and differential equation modeling are employed as computational tools to study biological phenomenon. We have shown that cellular automata simulations can be used as a computational tool for 12 predicting the dynamics of biological systems with stochastic behavior. The basic premise for the research was the observations made during a study of biologically important feed-forward motifs where CA simulations were compared with differential equation simulations. It was shown for classes of structural motifs with feed-forward architecture that network topology affects the overall rate of a process in a quantitatively predictable manner. The study which comprised of CA simulations compared with differential equation modeling show reasonable agreement in the predictability of system dynamics, which provided enough support to model biological systems at cellular level to observe dynamic system evolution. The great promise shown by CA simulations to model biochemical systems was then employed to elucidate evolutionary clues as to why biological networks show preference for certain types of motifs and preserve them with higher frequency during evolution. It was followed by modeling apoptotic networks to shed light on the efficacy of inhibitors and to model cellulose hydrolysis to evaluate efficiency of different enzyme systems used by cellulytic bacteria.
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Peter, Daniel B. "Finite-frequency effects in global seismology : forward modeling and implications on tomographic imaging /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17807.
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Zhu, Lei. "Modeling of a-Si:H TFT I-V Characteristics in the Forward Subthreshold Operation." Thesis, University of Waterloo, 2005. http://hdl.handle.net/10012/868.
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The hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) are widely used as switching elements in LCD displays and large area matrix addressed senor arrays. In recent years, a-Si:H TFTs have been used as analog active components in OLED displays. However, a-Si:H TFTs exhibit a bias induced metastability. This problem causes both threshold voltage and subthreshold slope to shift with time when a gate bias is applied. These instabilities jeopardize the long-term performance of a-Si:H TFT circuits. Nevertheless a-Si:H TFTs show an exponential transfer characteristic in the subthreshold region. Moreover, the typical power consumptions for TFTs in the subthreshold region are in the order of nano-watts, thus making them suitable for low power design. For these reasons, a-Si:H TFT I-V characteristics in the forward subthreshold operation are investigated. First, we have derived the static and dynamic models of a-Si:H TFT in the forward subthreshold region. Second, we have verified our theoretical models with experimental results. Third, we have proven that a-Si:H TFT experiences no subthreshold slope degradation or threshold voltage shift in the forward subthreshold operation. Finally, we have studied a-Si:H TFT current mirror circuit applications. Measurements regarding the fidelity of current matching in the forward subthreshold region have been performed, and results are shown.
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Cowan, Devin Christopher. "Forward modeling and inversion of viscous remanent magnetization responses in the time domain." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/58958.
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In this thesis, I develop forward modeling and inversion methods for better characterizing viscous remanent magnetization (VRM) responses in the time-domain. Despite advances since the 1980s, aspects of modeling the VRM response and its impact on time-domain electromagnetic sensors remain elusive. Using Néel relaxation models, I parameterize the off-time viscous remanent magnetization in terms of an amalgamated magnetic property, which I show can be directly obtained using dual-frequency susceptibility measurements. For a half-space model, I derive empirical expressions for characterizing the relationship between the survey geometry and the cartesian components of the VRM response. Final expressions are verified with a 1D forward modeling code and used to determine the cross-over time at which the transient response within a large circular loop becomes dominated by the VRM signal. In order to predict the VRM responses from 3D geological structures, I develop a linear forward modeling code. This is accomplished by discretizing the Earth into a set of cells and implementing the parameterization of the off-time viscous remanent magnetization. Convergence of the forward model as a function of cell size is tested and the code is validated against a 1D code. Lastly, I develop an inversion approach for recovering the distribution of magnetically viscous materials from a set of field observations. A multitude of survey geometries are used to verify that our inversion is robust. A workflow is then presented for removing the VRM response from a set of survey data.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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Siu, Ho Chit. "A discrete forward-modeling method for characterizing occultation lightcurves of tenuous planetary atmospheres." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98677.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 108-110).
We present a discrete numerical approach for forward-modeling lightcurves from stellar occultations by planetary atmospheres. Our discrete approach provides a way to arbitrarily set atmospheric properties at any radius from the occulting body, giving it flexibility for applying models of vertical variation in atmospheric conditions. The method is used to examine trends in lightcurve characteristics resulting from changes in the atmosphere of the occulting body. We find that for Pluto-like atmospheres, temperature and pressure variations affect the characteristics of the lightcurve much more than the gas composition. We also find that the half-light radius is more sensitive to atmospheric changes than either the minimum normalized flux or the slope at half-light. Temperature is found to be the most easily-constrained atmospheric parameter, as the gradients for changes in lightcurve characteristics are much more aligned with the temperature axis of the atmospheric parameter space than any other axis. Trends in lightcurve characteristics were examined in and around the parameter space occupied by the atmospheric conditions predicted for Pluto based on the 2011 and 2013 occultation events. Our error analysis method produced uncertainty values consistent with the reported uncertainties for half-light radius. This kind of lightcurve characterization is potentially useful for constraining the level of precision required in measuring given lightcurve characteristics in order to provide certain uncertainty bounds on the atmospheric conditions of the occulting body.
by Ho Chit Siu.
S.M.
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Matrangola, Sara Louise. "An experimental and simulation based approach toward understanding the effects of obesity on balance recovery from a postural perturbation." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/39388.
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Obesity is associated with an increased risk of falls and subsequent injury. Most falls result from some type of postural perturbation. As such, it is important to understand how obesity influences balance recovery from a postural perturbation. There is limited information on the effects of obesity on balance recovery, and the limited available information is ambiguous. Therefore, the purpose of the research within this dissertation was to investigate the effects of obesity on balance recovery after a postural perturbation in young adults to better understand how obesity contributes to fall risk.
Four separate studies make up this dissertation. The purpose of the first study was to investigate the effects of obesity on balance recovery ability using an ankle strategy in young adults. Normal-weight and obese participants recovered balance using an ankle strategy after three types of postural perturbations: an initial angular displacement, an initial angular velocity from the natural stance, and an initial angular velocity from a prescribed position. Obese participants were unable to recover balance using an ankle strategy as well as normal-weight participants when perturbations involved an initial angular velocity. However, no differences between obese and normal-weight participants were found when perturbations only involved an initial angular displacement. The effect of obesity on balance recovery in young adults was dependent on the perturbation characteristics, and may be explained by a possible beneficial effect of increased inertia on balance recovery after perturbations with little or no initial angular velocity.
The purpose of the second study was to examine the effects of obesity on balance recovery by stepping in young adults. The ankle strategy has the benefit of simplifying the mechanics of balance recovery, but limits generalizability to more realistic fall scenarios where stepping to extend the base of support and recover balance is desired. Similar to the first study, participants attempted to recover balance following two types of postural perturbations: an initial angular displacement from an upright stance (by releasing participants from a static forward lean), and an initial angular velocity while in an upright stance (using a translating platform). In contrast to the first study, the ability to recover balance with a single-step did not differ between young normal-weight and obese adults. These results suggest that the reported increase in fall risk in obese adults is not a result of impaired balance recovery ability (at least among young adults that were tested here).
The third study examined the effects of obesity on body kinematics immediately following a trip-like perturbation in young adults. Obesity was found to increase body angular velocity the perturbation, and that increases in body angular velocity were associated with an increased probability of a failed recovery. These results suggest that when a young obese and young normal-weight individual trip while walking at similar speeds, the young obese individual may be at a greater risk of falling following a trip because the young obese individual will experience a greater body angular velocity. This detrimental effect of obesity on the difficulty of recovering from a trip-like perturbation in young adults is most likely due to how mass is distributed throughout the body and not the amount of mass itself.
The final study examined the relationship between relative strength and functional capability in young adults, and how obesity influences this relationship. To compare relative strength used during a functional task (i.e. balance recovery from a forward fall), the obese and normal-weight individual should complete the task with identical kinematics. Forward dynamic simulations were used to address this research question, instead of human subjects testing, to achieve identical kinematics. Differences in peak relative torques were found between the normal-weight and obese model, with the largest differences seen at the hip. These findings suggest that young obese individuals use greater relative strength at some joints than young normal-weight individuals to perform the time-critical task of balance recovery, and that these differences in relative strength demands may limit functional capability in young individuals who are obese.Ph. D.
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Kulkarni, Sarika Carmichael Gregory R. "Assessment of source-receptor relationships of aerosols an integrated forward and backward modeling approach /." [Iowa City, Iowa] : University of Iowa, 2009. http://ir.uiowa.edu/etd/392.
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Kulkarni, Sarika. "Assessment of source-receptor relationships of aerosols: an integrated forward and backward modeling approach." Diss., University of Iowa, 2009. https://ir.uiowa.edu/etd/392.
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This dissertation presents a scientific framework that facilitates enhanced understanding of aerosol source - receptor (S/R) relationships and their impact on the local, regional and global air quality by employing a complementary suite of modeling methods. The receptor - oriented Positive Matrix Factorization (PMF) technique is combined with Potential Source Contribution Function (PSCF), a trajectory ensemble model, to characterize sources influencing the aerosols measured at Gosan, Korea during spring 2001. It is found that the episodic dust events originating from desert regions in East Asia (EA) that mix with pollution along the transit path, have a significant and pervasive impact on the air quality of Gosan. The intercontinental and hemispheric transport of aerosols is analyzed by a series of emission perturbation simulations with the Sulfur Transport and dEposition Model (STEM), a regional scale Chemical Transport Model (CTM), evaluated with observations from the 2008 NASA ARCTAS field campaign. This modeling study shows that pollution transport from regions outside North America (NA) contributed ∼ 30 and 20% to NA sulfate and BC surface concentration. This study also identifies aerosols transported from Europe, NA and EA regions as significant contributors to springtime Arctic sulfate and BC. Trajectory ensemble models are combined with source region tagged tracer model output to identify the source regions and possible instances of quasi-lagrangian sampled air masses during the 2006 NASA INTEX-B field campaign. The impact of specific emission sectors from Asia during the INTEX-B period is studied with the STEM model, identifying residential sector as potential target for emission reduction to combat global warming. The output from the STEM model constrained with satellite derived aerosol optical depth and ground based measurements of single scattering albedo via an optimal interpolation assimilation scheme is combined with the PMF technique to characterize the seasonality and regional distribution of aerosols in Asia. This innovative analysis framework that combines the output from source - oriented chemical transport models with receptor models is shown to reduce the uncertainty in aerosol distributions, which in turn leads to better estimates of source - receptor relationships and impact assessments of aerosol radiative forcing and health effects due to air pollution.
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Tolwinski-Ward, Susan E. "Inference on Tree-Ring Width and Paleoclimate Using a Proxy Model of Intermediate Complexity." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/241975.
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Forward and inverse modeling studies of the relationship between tree ring width and bivariate climate are performed using a model called VS-Lite. The monthly time-step model incorporates two simple but realistic nonlinearities in its description of the transformation of climate variability into ring width index. These features ground VS-Lite in scientific principles and make it more complex than empirically-derived statistical models commonly used to simulate tree ring width. At the same time, VS-Lite is vastly simpler and more efficient than pre-existing numerical models that simulate detailed biological aspects of tree growth. A forward modeling validation study shows that VS-Lite simulates a set of observed chronologies across the continental United States with comparable or better skill than simulations derived from a standard, linear regression based approach. This extra skill derives from VS-Lite's basis in mechanistic principles, which makes it more robust than the statistical methodology to climatic nonstationarity. A Bayesian parameterization approach is also developed that incorporates scientific information into the choice of locally optimal VS-Lite parameters. The parameters derived using the scheme are found to be interpretable in terms of the climate controls on growth, and so provide a means to guide applications of the model across varying climatologies. The first reconstructions of paleoclimate that assimilate scientific understanding of the ring width formation process are performed using VS-Lite to link the proxy data to potential climate histories. Bayesian statistical methods invert VS-Lite conditional on a given dendrochronolgy to produce probabilistic estimates of local bivariate climate. Using VS-Lite in this manner produces skillful estimates, but does not present advantages compared another set of probabilistic reconstructions that invert a simpler, linear, empirical forward model. This result suggests that future data-assimilation based reconstructions will need to integrate as many data sources as possible, both across space and proxy types, in order to benefit from information provided by mechanistic models of proxy formation.
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Ilves, Kalle. "Modeling and Design of Modular Multilevel Converters for Grid Applications." Doctoral thesis, KTH, Elektrisk energiomvandling, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-153762.
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This thesis aims to bring clarity to the dimensioning aspects and limiting factors of the modular multilevel converter (MMC). Special consideration is given to the dc capacitors in the submodules as they are a driving factor for the size and weight of the converter. It is found that if the capacitor voltages are allowed to increase by 10% the stored energy must be 21 kJ/MW in order to compensate the capacitor voltage ripple. The maximum possible output power can, however, be increased by injecting a second-order harmonic in the circulating current. A great advantage of cascaded converters is the possibility to achieve excellent harmonic performance at low switching frequencies. Therefore, this thesis also considers the relation between switching harmonics, capacitor voltage ripple, and arm quantities. It is shown that despite subharmonics in the capacitor voltages, it is still possible to achieve periodic arm quantities. The balancing of the capacitor voltages is also considered in further detail. It is found that it is possible to balance the capacitor voltages even at fundamental switching frequency although this will lead to a comparably large capacitor voltage ripple. Therefore, in order to limit the peak-to-peak voltage ripple, it is shown that a predictive algorithm can be used in which the resulting switching frequency is approximately 2–3 times the fundamental frequency. This thesis also presents two new submodule concepts. The first submodule simply improves the trade-off between the switching frequency and capacitor voltage balancing. The second submodule includes the possibility to insert negative voltages which allows higher modulation indices compared to half-bridge submodules. A brief comparison of cascaded converters for ac-ac applications is also presented. It is concluded that the MMC appears to be well suited for ac-ac applications where input and output frequencies are close or equal, such as in interconnection of ac grids. In low-frequency applications such as low-speed drives, however, the difficulties with handling the energy variations in the converter arms are much more severe in the MMC compared to the other considered topologies.QC 20141010
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Lee, Kyoung-Jin. "Efficient ray tracing algorithms based on wavefront construction and model based interpolation method." Texas A&M University, 2005. http://hdl.handle.net/1969.1/3771.
Full textAbstract:
Understanding and modeling seismic wave propagation is important in regional and
exploration seismology. Ray tracing is a powerful and popular method for this purpose.
Wavefront construction (WFC) method handles wavefronts instead of individual
rays, thereby controlling proper ray density on the wavefront. By adaptively controlling
rays over a wavefront, it efficiently models wave propagation. Algorithms for a
quasi-P wave wavefront construction method and a new coordinate system used to
generate wavefront construction mesh are proposed and tested for numerical properties
and modeling capabilities. Traveltimes, amplitudes, and other parameters, which
can be used for seismic imaging such as migrations and synthetic seismograms, are
computed from the wavefront construction method. Modeling with wavefront construction
code is applied to anisotropic media as well as isotropic media. Synthetic
seismograms are computed using the wavefront construction method as a new way
of generating synthetics. To incorporate layered velocity models, the model based
interpolation (MBI) ray tracing method, which is designed to take advantage of the
wavefront construction method as well as conventional ray tracing methods, is proposed
and experimental codes are developed for it. Many wavefront construction
codes are limited to smoothed velocity models for handling complicated problems
in layered velocity models and the conventional ray tracing methods suffer from the
inability to control ray density during wave propagation. By interpolating the wavefront
near model boundaries, it is possible to handle the layered velocity model as well
as overcome ray density control problems in conventional methods. The test results
revealed this new method can be an effective modeling tool for accurate and effective
computing.
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Mondal, Debabrata. "Size Effects in Small Scale Forward Extrusion and Metal Forming." ScholarWorks@UNO, 2019. https://scholarworks.uno.edu/td/2675.
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Size effects play a significant role in metal processing when the specimen dimensions are reduced. In this study, influence of size effects were investigated on two problem specific processes. First, numerical simulations of a small-scale forward extrusion with varying grain size were performed for both 2D and 3D cases. Here, grains were assigned to non-homogeneous properties in a random fashion. The computational geometry was obtained from Voronoi tessellation in MATLAB, and python-scripting in ABAQUS. Then the effects of size and property non-homogeneity were investigated. Second, a numerical model was simulated to predict final form shapes, punch load requirement, and thickness distribution of hemispherical bowl-shaped forming. The die, punch and cover plate were fabricated using stereolithographic apparatus (SLA). Numerically obtained punch load requirement, thickness distribution, von-Mises contours, and equivalent plastic strain contours were compared for different thickness specimens. Finally, the models were validated by experimental results.
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Szwillus, Wolfgang [Verfasser]. "Lithospheric structure from forward and inverse modeling of satellite gravity and magnetic data / Wolfgang Szwillus." Kiel : Universitätsbibliothek Kiel, 2019. http://d-nb.info/1190644797/34.
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Bondaryk, Joseph E. (Joseph Edward). "Array processing and forward modeling methods for the analysis of stiffened, fluid-loaded cylindrical shells." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/35397.
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Taslim, Cenny. "Multi-Stage Experimental Planning and Analysis for Forward-Inverse Regression Applied to Genetic Network Modeling." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1213286112.
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Chandramouli, Soumya. "A Broadband Passive Delay Line Structure in 0.18 Micron CMOS For A Gigabit Feed Forward Equalizer." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4764.
Full textAbstract:
This project focusses on the design of a high speed passive delay line for use in a Feed Forward Equalizer (FFE). The FFE is used to equalize a 20 Gbp/s throughput PAM-4 signal after transmission through a 20-inch FR4 backplane channel. Inductor electromagnetic simulations are used to design an inductor for use in the passive delay line and a lumped element inductor model is presented. Measurement results show performance of the delay line at 10 GSym/s.
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Goodfriend, Nathan Thomas. "Advancements and understanding of Blister-Based Laser-Induced Forward-Transfer." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/29607.
Full textAbstract:
Blister-Based Laser-Induced Forward-Transfer (BB LIFT) is a new method of particle transfer, capable of projecting complex and fragile particles into the gas phase. The technique uses a laser pulse to deform a metal or polymer film on a transparent substrate. The deformation of the film creates a blister which can mechanically desorb particles adhered to the surface. This thesis covers the study of the underlying mechanisms of blister formation in relation to laser pulse duration and film properties, whilst also advancing upon the technique by developing new methods for particle transfer of 0-dimensional point particles, 1-dimensional nanotubes, and 2-dimensional crystals. Study of the blister formation was carried out on uncoated 200-400 nm Titanium films, using 120 fs and 7 ns laser pulses. The blisters were studied by Atomic Force Microscopy and optical analysis. Furthermore a theoretical model for the blister formation using ns laser pulses was developed using a linear heat transfer model, showing a good agreement between experiment and theory. From this model mechanisms for blister formation under both of these pulse durations were developed. It was concluded that ns laser pulses heat the thin film causing it to undergo thermal expansion where the temperature and thermal expansion properties of the film define the blister. Femtosecond pulses form blisters due to confined ablation of the film at the interface of the transparent substrate and the film. The expanding gas forces the metal to stretch, where the deformation is dictated by the Young’s modulus of the material with the major factor being the thickness of the titanium film. The velocity distribution of the desorbed material was studied by means of mass spectroscopy. An ionising laser pulse was focused a known distance from the donor film. The ejected particles crossed the laser beam, and with a controlled delay of the time between the blister pulse and ionisation pulse the velocities could be determined for fullerenes (C60) and gold coated silicon nanoparticles (Auroshells). Utilising C60 as the desorbed material we could identify that for ns BB-LIFT the C60 was emitted at a velocity mostly dependent upon the heat expansion coefficient for the titanium film, resulting in a velocity approximating 100 ms-1 with a secondary emission of fullerenes due to evaporation from the hot surface. However, for fs BB-LIFT this evaporated emission was not present and the velocities could be adjusted from 7-70 ms-1 by varying the Ti film thickness from 360 nm to 210 nm respectively. These results are consistent with the mechanisms proposed earlier. The spread of the desorbed particle beam was also studied for nanosecond and femtosecond laser-induced blisters utilising auroshells and C60. This was accomplished by placing a receiver platform at a known distance in front of the donor film in order to collect the desorbed particles. The radial spread was then analysed indicating a flat deposit approximately the size of the initial blister with a 5 degree spread from that point. This indicates that the desorbed beam is highly directional. From this it could be ascertained that the blisters do not form from a single point position on the film but expand uniformly with the area of laser irradiation defining the growth point of the blister. A problem with many molecular beam techniques is that large fragile molecules or nanoparticles cannot be introduced to the gas phase without causing damage to the particles. Studies into the desorption of Auroshells (150 nm diameter), C60 (1 nm), PCBM (a fragile exohedral fullerene), carbon nanotubes (1x1000 nm), and 2D films (1x10000x10000 nm) showed that these materials were successfully transferred from the donor film to a receiver plate without causing damage to the particles. This was determined via Raman, NMR, AFM, and SEM measurements. Lastly a technique that allowed the growth of carbon nanotubes directly on the donor film utilising a a multi-layered substrate was developed, enabling the removal and deposition of the nanotubes, without exposing them to any chemical treatment.
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Mohammadi, Soroor. "Processing and Modeling of Gravity, Magnetic and Electromagnetic Data in the Falkenberg Area, Sweden." Thesis, Uppsala universitet, Geofysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-232714.
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Falkenberg area is located in southwest Sweden formed in the Sveconorwegian orogen and contains an extremely complex geological structure. Multiple geophysical datasets have been acquired and together with available petrophysical information, models corresponding to the subsurface geological structures were generated. The collected data comprise ground magnetic, AMT (Audio Magnetotelluric) and RMT (Radio Magnetotelluric) data. The available airborne magnetic and ground gravity data acquired by the Geological Survey of Sweden (SGU) as well as the reflection seismic section from a study made by Uppsala University further aids in obtaining substantially improved interpretation of the geometry of the structures along the AMT profile. The principal objective of this profile was to delineate and map the possible deformation zone crossed by the profile. The AMT study was expected to complement existing geophysical data and improve existing interpretations. The Ullared deformation zone contains decompressed eclogite facies rocks. The presented results were obtained by comparison of different geophysical methods along the profile. The susceptibility model and resistivity model show that eclogites have higher resistivity and susceptibility than the surrounding structures. However use of the Occam type of inversion on the AMT data, makes the resistivity model smoother than the susceptibility model and as a results it is difficult to estimate the dip of the structures. The AMT profile and the seismic section show the same dip direction (NE) for the eclogite bearing structures although due to the smoothing in the AMT model the dips seen in the seismic section cannot be recovered in the resistivity model.
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Nguyen, Nhat-Minh [Verfasser], and Eiichiro [Akademischer Betreuer] Komatsu. "Bayesian forward modeling of galaxy clustering : cosmology and astrophysics inference / Nhat-Minh Nguyen ; Betreuer: Eiichiro Komatsu." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2020. http://d-nb.info/1213246334/34.
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King, Joshua David. "Using a 3D finite element forward modeling code to analyze resistive structures with controlled-source electromagnetics in a marine environment." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/1371.
Full textAbstract:
Controlled-Source Electromagnetics (CSEM) is a method that has been used since the 1980s in the marine environment for determining electrical properties of the subsurface. Receivers on the seafloor collect total electric and magnetic fields which are produced as a result of interaction of the transmitter generated primary fields with the seawater and subsurface. Badea et al. (2001) coded an existing algorithm for solving Maxwells equations. This finite element 3D forward modeling algorithm is used to simulate CSEM experiments. The objective of the present study is to model the changes in electromagnetic response for a resistive disk and a more geometrically complex structure, which are rough approximations of hydrocarbon reservoirs. The parameters that are varied in studying these subsurface structures are the disk radius, disk depth, the transmitter frequency, the transmitter location, and the structure orientation.The results showed that a disk of finite radius behaves similar to an infinite disk at short range and grades into double half-space behavior at longer ranges. The frequency of the transmitter must be tuned to the disk depth as certain frequencies will penetrate too shallow or too deep to probe the disk. Moving the transmitter away from the receivers causes a decrease in signal strength, but exhibits a greater capacity to distinguish between the double half-space and infinite disk scenarios. The disk was then replaced by a more complex structure. To determine if the 3D nature of the structure may be located a study was undertaken to probe the structure from different perspectives using different transmitter locations and azimuths. It is determined that the 3D nature of the structure could not be observed until the structures thickness is sufficiently large.The goal of the study is to better understand the effect of subsurface parameters on the total fields and show the usefulness of the 3D forward modeling code. Understanding the relationships between these parameters and the resulting signals is important in terms of setting up a real experiment. Marine CSEM studies are costly and using a valuable tool such as an accurate finite element 3D forward modeling algorithm may save time and money.
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Afacan, Kamil. "Modeling And Control Of A Stabilization System." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605576/index.pdf.
Full textAbstract:
Elevation axis model of a barrel stabilization system is constructed. The
nonlinearities which are considered in the model are orifice flow
characteristics, coulomb friction, hard-stop limits, kinematics of the system
and unbalance on the barrel. A Simulink®model for the servo valve, actuation system and barrel is constructed. Servo valve identification is made via the actual test data. Compressibility of the hydraulic fluid is taken into consideration while modeling the actuation system. Friction model is simulated for different cases. Controller of the system is constructed by two PIDs, one for each of the velocity and the position loops. Velocity feed forward can reduce the time to make a quick move by the system. The disturbance is evaluated from a given road profile and disturbance feed forward is applied to the system.
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Acevedo, Valencia John Walter [Verfasser]. "Towards Paleoclimate Reanalysis via Ensemble Kalman Filtering, Proxy Forward Modeling and Fuzzy Logic / John Walter Acevedo Valencia." Berlin : Freie Universität Berlin, 2015. http://d-nb.info/1074404823/34.
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Camacho, Valle Alfredo. "Credit risk modeling in a semi-Markov process environment." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/credit-risk-modeling-in-a-semimarkov-process-environment(ad56ed0b-047f-44df-be68-6accef7544ff).html.
Full textAbstract:
In recent times, credit risk analysis has grown to become one of the most important problems dealt with in the mathematical finance literature. Fundamentally, the problem deals with estimating the probability that an obligor defaults on their debt in a certain time. To obtain such a probability, several methods have been developed which are regulated by the Basel Accord. This establishes a legal framework for dealing with credit and market risks, and empowers banks to perform their own methodologies according to their interests under certain criteria. Credit risk analysis is founded on the rating system, which is an assessment of the capability of an obligor to make its payments in full and on time, in order to estimate risks and make the investor decisions easier.Credit risk models can be classified into several different categories. In structural form models (SFM), that are founded on the Black & Scholes theory for option pricing and the Merton model, it is assumed that default occurs if a firm's market value is lower than a threshold, most often its liabilities. The problem is that this is clearly is an unrealistic assumption. The factors models (FM) attempt to predict the random default time by assuming a hazard rate based on latent exogenous and endogenous variables. Reduced form models (RFM) mainly focus on the accuracy of the probability of default (PD), to such an extent that it is given more importance than an intuitive economical interpretation. Portfolio reduced form models (PRFM) belong to the RFM family, and were developed to overcome the SFM's difficulties.Most of these models are based on the assumption of having an underlying Markovian process, either in discrete or continuous time. For a discrete process, the main information is containted in a transition matrix, from which we obtain migration probabilities. However, according to previous analysis, it has been found that this approach contains embedding problems. The continuous time Markov process (CTMP) has its main information contained in a matrix Q of constant instantaneous transition rates between states. Both approaches assume that the future depends only on the present, though previous empirical analysis has proved that the probability of changing rating depends on the time a firm maintains the same rating. In order to face this difficulty we approach the PD with the continuous time semi-Markov process (CTSMP), which relaxes the exponential waiting time distribution assumption of the Markovian analogue.In this work we have relaxed the constant transition rate assumption and assumed that it depends on the residence time, thus we have derived CTSMP forward integral and differential equations respectively and the corresponding equations for the particular cases of exponential, gamma and power law waiting time distributions, we have also obtained a numerical solution of the migration probability by the Monte Carlo Method and compared the results with the Markovian models in discrete and continuous time respectively, and the discrete time semi-Markov process. We have focused on firms from U.S.A. and Canada classified as financial sector according to Global Industry Classification Standard and we have concluded that the gamma and Weibull distribution are the best adjustment models.
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Onofre, Jose Alberto de Mesquita. "Analysis and modeling of the acoustic tomography signal transmission from Davidson Seamount to Sur Ridge : the forward problem." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA376359.
Full textAbstract:
Thesis (M.S. in Physical Oceanography) Naval Postgraduate School, September 1999."September 1999". Thesis advisor(s): Ching-Sang Chiu, Curtis A. Collins. Includes bibliographical references (p. 39-40). Also Available online.
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Veile, Ines [Verfasser], and T. [Akademischer Betreuer] Bohlen. "Fast 3D forward modeling of single scattered elastic wave fields for borehole configurations / Ines Veile. Betreuer: T. Bohlen." Karlsruhe : KIT-Bibliothek, 2013. http://d-nb.info/1047383497/34.
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van, Manen Dirk-Jan. "Time-reversal and interferometry, with applications to forward modeling of wave propagation and a chapter on receiver functions." Thesis, University of Edinburgh, 2006. http://hdl.handle.net/1842/2563.
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In exploration seismics and non-destructive evaluation, acoustic, elastic and electro-magnetic waves sensitive to inhomogeneities in the medium under investigation are used to probe its interior. Waves multiply scattered by the inhomogeneities carry significant information but, due to their non-linear relation with the inhomogeneities, are notoriously dificult to image or invert for subsurface structure. Recently, however, this paradigm may have been broken as it was shown that high-order multiply scattered acoustic waves can be time-reversed and focused onto their original source location through arbitrary, unknown, inhomogeneous media using a so-called time-reversal mirror: in a first step, the multiply scattered waves are recorded on an array of transducers partially surrounding the medium, in the second step the recorded wavefields are time-reversed and reemitted into the medium (i.e., the time-reversal mirror acts as a linear boundary condition on the medium injecting the time-reversed, multiply scattered wave- field). The multiply scattered waves retrace their paths through the medium and focus on the original source location. In another development the full waveform Green's function between two (passive) receivers has been observed to emerge from crosscorrelation of multiply scattered coda waves. This process is called interferometry. The principal aim of this thesis is to explore the relation between time-reversal and interferometry and to apply the resulting insights to forward modelling of wave propagation in the broader context of inversion. A secondary aim is to see if the seismological receiver function method can be applied to a reflection setting in ways that are both dynamically and kinematically correct. These aims are achieved through: (1) Derivation of an integral representation for the time-reversed wavefield in arbitrary points of an inhomogeneous medium [first, for the acoustic case, based on the Kirchhoff-Helmholtz integral, then for the elastic case based on the Betti-Rayleigh reciprocity theorem]. Evaluation of these integral representations for points other than the original source point will be shown to give rise to the Green's function between the two points. Physically intuitive explanations will be given as to why this is the case. (2) Application of ordinary reciprocity to the integral representation for the time-reversed wavefield to get an expression in terms of sources on the surrounding surface only. This gives rise to an efficient and flexible forward modeling algorithm. By illuminating the medium from the surrounding surface and storing full waveforms in as many points in the interior as possible, full waveform Green's functions between arbitrary points in the volume can be computed by cross correlation and summation only. (3) Derivation of an exact, interferometric von Neumann type boundary condition for arbitrary interior perturbed scattering problems. The exact bound- ary condition correctly accounts for all orders of multiple scattering, both inside the scattering perturbation(s) and between the perturbations and the background model and thus includes all so-called higher-order, long-range interactions. (4) A comprehensive study of the receiver function method in a reflection setting, both kinematically and dynamically. All presented results are verified and illustrated by numerical (finite-difference) modelling. Overall, the results in this thesis demonstrate that, while the original instabilities associated with direct inversion remain, multiply scattered waves can be used in an industrial context { both in real-life experiments and in forward modelling { in ways that are stable. The presented advances in forward modelling are argued to have a significant impact on inversion as well, albeit indirectly.
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Almeida, de Carvalho Ancilla Maria. "Evolution of the Early Cretaceous, South-Atlantic pre-salt lacustrine systems : Insights from Stratigraphic Forward and Geochemical Modeling." Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS590.
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Les roches carbonatées lacustres de la formation de la Barra Velha (BVF), dans le bassin de Santos, présentent des compositions et textures distinctes, avec des hétérogénéités sédimentaires auxquelles se surimposent celles diagenétiques, conduisant à la formation de réservoirs complexes. Pour mieux comprendre et prédire les hétérogénéités latérales/verticales des réservoirs carbonatés du bassin de Santos, nous avons adopté une approche multidisciplinaire, intégrant des analyses sédimentologiques et diagenétiques, des modèles stratigraphiques et de la modélisation géochimique. À partir des données multi-échelles, nous avons (1) caractérisé la distribution spatiale et stratigraphique des différents faciès et phases diagenétiques et leurs principaux facteurs de contrôle, (2) évalué le modèle conceptuel proposé et fourni les conditions initiales pour le modèle d'interaction fluide-roche en utilisant la modélisation stratigraphique (SFM), (3) étudié les conditions physico-chimiques idéales et les schémas de circulation des fluides dans le bassin régissant les altérations diagenétiques observées dans la zone d'étude. L'analyse des données réalisée dans cette étude met en évidence la distribution spatiale et temporelle des différents types d'argiles magnésiennes, les principaux produits diagenétiques et leur association avec les différents faciès. La distribution stratigraphique des argiles magnésiennes indique une influence de la chimie de l'eau du lac. Par ailleurs, le schéma d'altération des argiles magnésiennes et ses caractéristiques diagenétiques suggèrent un contrôle important du cadre structural. Les tendances spatiales et stratigraphiques des caractéristiques sédimentologiques et diagenétiques indiquent, qu’au premier ordre, l’évolution hydrochimique de l'eau du lac contrôle les principaux aspects de dépôt et de diagénèse, étant modulée par des facteurs locaux qui ont renforcé l'empreinte diagenétique. Les données indiquent que trois caractéristiques principales marquent les variations hydrochimiques de l'eau du lac : une phase initiale associée à un apport important de sédiments détritiques, une phase intermédiaire marquée par des conditions d'évaporation plus élevées et une phase finale caractérisée par des fluctuations des conditions d'évaporation avec une contribution détritique plus faible. Dans la deuxième partie de l'étude, nous proposons un modèle numérique stratigraphique basé sur le modèle géologique conceptuel et l'évaluation des contraintes à grande échelle, telles que la subsidence et les variations du niveau du lac. Le modèle aborde également l'évolution des zones hydrologiques. Grâce à ce modèle, nous proposons une grille latérale et verticale de faciès, utilisée pour définir les conditions initiales de la modélisation en transport réactif. Dans la troisième phase de l'étude, une série de calculs géochimiques permet d’estimer le potentiel diagenétique de différentes sources de solutés et les principaux contrôles paléo-environnementaux sur les modifications diagenétiques. Enfin, nous examinons les principaux scénarios diagenétiques à partir de la modélisation de transport réactif, en nous concentrant sur les processus de dolomitisation, de silicification et de dissolution et sur l’impact de la circulation régionale ou locale des fluides sur les altérations diagenétiques. Les hétérogénéités sédimentaires, liées aux caractéristiques intrinsèques des environnements de dépôt, jouent un rôle crucial dans l'évolution des processus diagenétiques. Les résultats démontrent également l’existence de chemins préférentiels de circulation des fluides et d'altérations diagenétiques associés à l’alternance de strates riches en argiles magnésiennes et de faciès présentant une perméabilité plus élevée. L'approche multidisciplinaire fournit une vue spatiale des interactions entre les propriétés des roches et les schémas possibles de circulation des fluides dans le bassinThe lacustrine carbonate rocks of the Barra Velha Formation (BVF), Santos Basin, present distinct composition and texture, with superimposed sedimentary and diagenetic heterogeneities, forming complex reservoirs. To better understand and predict lateral and vertical heterogeneities of the carbonate reservoirs of Santos Basin, we conduct a multidisciplinary approach, integrating sedimentological-diagenetic analyses, stratigraphic forward (process-based) modeling, and geochemical modeling. From a multiscale dataset of a field localized in the Outer High of the Santos Basin, we (1) characterized the spatial and stratigraphic distribution of the different facies and diagenetic phases and their main controlling factors, (2) evaluated the conceptual model proposed and provide the initial conditions for fluid-rock interaction model, using stratigraphic forward modeling (SFM) (3) investigated the ideal physicochemical conditions and basin fluid circulation patterns ruling the diagenetic alterations observed in the study area. The data analysis performed in this study highlights the spatial and temporal distribution of different types of Mg-clay, the main diagenetic products, and their association with different facies. The stratigraphic variations in Mg-clay distribution indicate an influence of the lake water chemistry. Furthermore, the Mg-clay alteration pattern and its diagenetic features suggest a strong control of the structural setting. The spatial and stratigraphic distribution of sedimentological and diagenetic heterogeneities indicate that the lake water’s first-order hydrochemical evolution drove the major depositional and diagenetic aspects, modulated by local factors, which enhanced the diagenetic imprint. Three main characteristics mark the lake water hydrochemical variation: an initial stage associated with a higher input of detrital content, an intermediary phase marked by higher evaporative conditions, and a final stage characterized by fluctuations of the evaporative conditions with a lower detrital contribution. In the second part of the study, we propose a stratigraphic forward model based on the depositional conceptual model and the evaluation of large-scale constraints, like subsidence and lake-level variations. The model also addresses the lake-level variations relying on the hydrologic water balance between precipitation and evaporation rate and provides insights into the evolution of hydrological zones. Through the process-based model, we propose a lateral and vertical grid of facies used to parametrize the reactive transport modeling. In the third part of the study, a series of geochemical calculations were used to estimate the diagenetic potential of different solute sources and the main paleoenvironmental controls on diagenetic modifications. The calculations show that the pH fluctuation is the main factor impacting the Mg-clay preservation, followed by the diagenetic fluids' Mg/Ca and Mg/Si ratios, and emphasize the role of pCO2 in the diagenetic alteration. In addition, the models point out the ability of different Mg-clay types to generate distinctive amounts of diagenetic products. Finally, we explore diagenetic scenarios on the BVF sag phase through reactive transport modeling, focusing on the dolomitization, silicification, and dissolution processes and addressing the impact of regional versus local fluid circulation on diagenetic alteration. The initial facies heterogeneities, intrinsically related to the depositional characteristics, have a crucial role in the evolution of the diagenetic process. The results also highlight the preferential pathways of fluid circulation and diagenetic alteration associated with Mg-clay-rich layers and facies with higher permeability alternation. The multidisciplinary approach provides a spatial view of the interplay between rock properties and possible fluid circulation patterns in the basin
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Li, Xiaojin. "Anammox-based Technologies for Sustainable Mainstream Wastewater Treatment: Process Development, Microbial Ecology and Mathematical Modeling." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/93328.
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The nitritation-anammox process is an efficient and cost-effective approach for biological nitrogen removal, but its application in treating mainstream wastewater remains a great challenge. The key objectives of this dissertation are to develop nitritation-anammox process to treat wastewater with low-nitrogen strength, understand the fundamental microbiology, and optimize its operation through experimental studies and mathematic modeling. Chapter 2 showed that the nitritation-anammox process has been successfully developed in an upflow membrane-aerated biofilm reactor, where pure oxygen was delivered via gas-permeable membrane module. Chapter 3 demonstrated that hybrid anaerobic reactor (HAR) could be an effective pretreatment method to provide a relatively low COD/N ratio for nitritation-anammox reactor. In Chapter 4, a novel mathematical model has been proposed to evaluate the minimum DO requirement for the nitritation-anammox reactor to achieve the maximum TN removal under various COD/N scenarios (controlled by HRTHAR). Chapters 5 and 6 designed an OsAMX system by linking nitritation-anammox to forward osmosis to remove the reverse-fluxed ammonium while using ammonium bicarbonate as a draw solute. The microbial community structures and dynamics, spatial distributions in these bioreactors were characterized by high-throughput sequencing and fluorescent in situ hybridization techniques. The studies in this dissertation have demonstrated that nitritation-anammox process is a promising alternative for sustainable mainstream treatment with the appropriate pretreatment approach and operation optimization.PHD
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BRIGHENTI, ALBERTO. "Moving forward the thermal-hydraulic modeling of superconducting magnets for ITER: from the Insert Coils to the full magnets." Doctoral thesis, Politecnico di Torino, 2019. http://hdl.handle.net/11583/2734577.
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Lambrecht, Lasse [Verfasser], Wolfgang [Akademischer Betreuer] Friederich, and Klaus [Akademischer Betreuer] Hackl. "Forward and inverse modeling of seismic waves for reconnaissance in mechanized tunneling / Lasse Lambrecht. Gutachter: Wolfgang Friederich ; Klaus Hackl." Bochum : Ruhr-Universität Bochum, 2015. http://d-nb.info/1079843175/34.
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Seidel, Marc [Verfasser], Bülent [Gutachter] Tezkan, and Andreas [Gutachter] Hördt. "A 3D Time Domain CSEM Forward Modeling Code using custEM and FEniCS / Marc Seidel ; Gutachter: Bülent Tezkan, Andreas Hördt." Köln : Universitäts- und Stadtbibliothek Köln, 2019. http://d-nb.info/1203798865/34.
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Khanal, Subodha. "Upper crustal shortening and forward modeling of the Himalayan fold-thrust belt along the Budhi-Gandaki river, central Nepal." Thesis, [Tuscaloosa, Ala. : University of Alabama Libraries], 2009. http://purl.lib.ua.edu/2151.
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Hartasánchez, Frenk Diego Andrés 1982. "Modeling and simulation of interlocus gene conversion." Doctoral thesis, Universitat Pompeu Fabra, 2016. http://hdl.handle.net/10803/525842.
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Les regions duplicades del genoma, com ara les duplicacions de segments (SDs), són una característica comuna dels genomes eucariotes i han estat associades a canvis fenotípics. Donada la seva rellevància evolutiva, tenir un model neutre per descriure la seva evolució és essencial. En aquesta tesi, descric el desenvolupament de SeDuS, un simulador computacional endavant en el temps de l'evolució neutra de SDs. Les duplicacions estan sotmeses a un procés de recombinació, anomenat conversió gènica interlocus (IGC), que afecta els patrons de variació i de desequilibri de lligament dins i entre duplicacions. Aquí descric els efectes de sobreposar regions susceptibles de recombinació homòloga amb regions susceptibles d'IGC i d'incorporar dependència d'IGC en la similitud de seqüències. Addicionalment, ja que les SDs són objectius potencial de la selecció natural, informo sobre possibles alteracions a proves estadístiques quan aquestes s'apliquen a regions duplicades sotmeses a IGC. Finalment, exploro la possibilitat de combinar resultats de diferents proves estadístiques aplicades al llarg de tot el genoma per detectar la presència de duplicacions col·lapsades.Duplicated regions of the genome, such as Segmental Duplications (SDs), are a pervasive feature of eukaryotic genomes and have been linked to phenotypic changes. Given their evolutionary relevance, having a neutral model to describe their evolution is essential. In this thesis, I report the development of SeDuS, a forward-in-time computer simulator of SD neutral evolution. Duplications are known to undergo a recombination process, termed interlocus gene conversion (IGC), which is known to affect the patterns of variation and linkage disequilibrium within and between duplicates. Here I describe the effects of overlapping crossover and IGC susceptible regions and of incorporating sequence similarity dependence of IGC. Furthermore, since SDs are potential targets of natural selection, I report potential confounding effects of IGC on test statistics when these are applied to duplications. Finally, I explore the possibility of combining results of different test statistics applied genome-wide to detect the presence of collapsed duplications.
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Sommacal, Silvano, and silvano sommacal@anu edu au. "Computational petrology: Subsolidus equilibria in the upper mantle." The Australian National University. Research School of Earth Sciences, 2004. http://thesis.anu.edu.au./public/adt-ANU20050415.151025.
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Processes that take place in the Earths mantle are not accessible to direct observation. Natural samples of mantle material that have been transported to the surface as xenoliths provide useful information on phase relations and compositions of phases at the pressure and temperature conditions of each rock fragment. In the past, considerable effort has been devoted by petrologists to investigate upper mantle processes experimentally. Results of high temperatures, high pressure experiments have provided insight into lower crust-upper mantle phase relations as a function of temperature, pressure and composition. However, the attainment of equilibrium in these experiments, especially in complex systems, may be very difficult to test rigorously. Furthermore, experimental results may also require extrapolation to different pressures, temperatures or bulk compositions. More recently, thermodynamic modeling has proved to be a very powerful approach to this problem, allowing the deciphering the physicochemical conditions at which mantle processes occur. On the other hand, a comprehensive thermodynamic model to investigate lower crust-upper mantle phase assemblages in complex systems does not exist. ¶
In this study, a new thermodynamic model to describe phase equilibria between silicate and/or oxide crystalline phases has been derived. For every solution phase the molar Gibbs free energy is given by the sum of contributions from the energy of the end-members, ideal mixing on sites, and excess site mixing terms. It is here argued that the end-member term of the Gibbs free energy for complex solid solution phases (e.g. pyroxene, spinel) has not previously been treated in the most appropriate manner. As an example, the correct expression of this term for a pyroxene solution in a general (Na-Ca-Mg-Fe2+-Al-Cr-Fe3+-Si-Ti) system is presented and the principle underlying its formulation for any complex solution phase is elucidated.¶
Based on the thermodynamic model an algorithm to compute lower crust-upper mantle phase equilibria for subsolidus mineral assemblages as a function of composition, temperature and pressure has been developed. Included in the algorithm is a new way to represent the total Gibbs free energy for any multi-phase complex system. At any given temperature and pressure a closed multi-phase system is at its equilibrium condition when the chemical composition of the phases present in the system and the number of moles of each are such that the Gibbs free energy of the system reaches its minimum value. From a mathematical point of view, the determination of equilibrium phase assemblages can, in short, be defined as a constrained minimization problem. To solve the Gibbs free energy minimization problem a Feasible Iterate Sequential Quadratic Programming method (FSQP) is employed. The systems Gibbs free energy is minimized under several different linear and non-linear constraints. The algorithm, coded as a highly flexible FORTRAN computer program (named Gib), has been set up, at the moment, to perform equilibrium calculations in NaO-CaO-MgO-FeO-Al2O3-Cr2O3-Fe2O3- SiO2-TiO2 systems. However, the program is designed in a way that any other oxide component could be easily added.¶
To accurately forward model phase equilibria compositions using Gib, a precise estimation of the thermodynamic data for mineral end-members and of the solution parameters that will be adopted in the computation is needed. As a result, the value of these parameters had to be derived/refined for every solution phase in the investigated systems. A computer program (called GibInv) has been set up, and its implementation is here described in detail, that allows the simultaneous refinement of any of the end-member and mixing parameters. Derivation of internally consistent thermodynamic data is obtained by making use of the Bayesian technique. The program, after being successfully tested in a synthetic case, is initially applied to pyroxene assemblages in the system CaO-MgO-FeO-Al2O3-SiO2 (i.e. CMFAS) and in its constituent subsystems. Preliminary results are presented.¶
The new thermodynamic model is then applied to assemblages of Ca-Mg-Fe olivines and to assemblages of coexisting pyroxenes (orthopyroxene, low Ca- and high Ca clinopyroxene; two or three depending on T-P-bulk composition conditions), in CMFAS system and subsystems. Olivine and pyroxene solid solution and end-member parameters are refined, in part using GibInv and in part on a trial and error basis, and, when necessary, new parameters are derived. Olivine/pyroxene phase relations within such systems and their subsystems are calculated over a wide range of temperatures and pressures and compare very favorably with experimental constraints.
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Ilves, Kalle. "Modeling and Design of Modular MultilevelConverters for Grid Applications." Licentiate thesis, KTH, Elektrisk energiomvandling, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-105779.
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Grid-connected high-power converters are found in high-voltage direct current transmission (HVDC), static compensators (STATCOMs), and supplies for electric railways. Such power converters should have a high reliability, high efficiency, good harmonic performance, low cost, and a small footprint. Cascaded converters are promising solutions for high-voltage high-power converters since they allow the combination of excellent harmonic performance and low switching frequencies. A high reliability can also be achieved by including redundant submodules in the chain of cascaded converters. One of the emerging cascaded converter topologies is the modular multilevel converter (M2C). This thesis aims to bring clarity to the dimensioning aspects and limiting factors of M2Cs. The dc-capacitor in each submodule is a driving factor for the size and weight of the converter. It is found that the voltage variations across the submodule capacitors will distort the voltage waveforms and also induce alternating components in the current that is circulating between the phase-legs. It is, however, shown that it is possible to control the alternating voltage by feed-forward control. It is also shown that if the circulating current is controlled, the injection of a second-order harmonic component can extend the operating region of the converter. The reason for this is that when the converter is operating close to the boundary of overmodulation the phase and amplitude of the second-order harmonic is chosen such that the capacitors are charged prior to the time when a high voltage should be inserted by the submodules. The controller that is used must be able to balance the sbmodule capacitor voltages. Typically, an increased switching frequency will enhance the performance of the balancing control scheme. In this thesis it is shown that the capacitor voltages can be balanced with programmed modulation, even if fundamental switching frequency is used. This will, however, increase the voltage ripple across the aforementioned capacitors. In order to quantify the requirements on the dc-capacitors a general analysis is provided in this thesis which is based on the assumption that the capacitor voltages are well balanced. It is found that for active power transfer, with a 50 Hz sinusoidal voltage reference, the capacitors must be rated for a combined energy storage of 21 kJ/MW if the capacitor voltages are allowed to increase by 10% above their nominal values.QC 20121127
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Wang, Siqi. "NONINVASIVE ASSESSMENT AND MODELING OF DIABETIC CARDIOVASCULAR AUTONOMIC NEUROPATHY." UKnowledge, 2012. http://uknowledge.uky.edu/cbme_etds/5.
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Noninvasive assessment of diabetic cardiovascular autonomic neuropathy (AN): Cardiac and vascular dysfunctions resulting from AN are complications of diabetes, often undiagnosed. Our objectives were to: 1) determine sympathetic and parasympathetic components of compromised blood pressure regulation in patients with polyneuropathy, and 2) rank noninvasive indexes for their sensitivity in diagnosing AN. Continuous 12-lead electrocardiography (ECG), blood pressure (BP), respiration, regional blood flow and bio-impedance were recorded from 12 able-bodied subjects (AB), 7 diabetics without (D0), 7 with possible (D1) and 8 with definite polyneuropathy (D2), during 10 minutes supine control, 30 minutes 70-degree head-up tilt and 5 minutes supine recovery. During the first 3 minutes of tilt, systolic BP decreased in D2 while increased in AB. Parasympathetic control of heart rate, baroreflex sensitivity, and baroreflex effectiveness and sympathetic control of heart rate and vasomotion were reduced in D2, compared with AB. Baroreflex effectiveness index was identified as the most sensitive index to discriminate diabetic AN.
Four-dimensional multiscale modeling of ECG indexes of diabetic autonomic neuropathy: QT interval prolongation which predicts long-term mortality in diabetics with AN, is well known. The mechanism of QT interval prolongation is still unknown, but correlation of regional sympathetic denervation of the heart (revealed by cardiac imaging) with QT interval in 12-lead ECG has been proposed. The goal of this study is to 1) reproduce QT interval prolongation seen in diabetics, and 2) develop a computer model to link QT interval prolongation to regional cardiac sympathetic denervation at the cellular level. From the 12-lead ECG acquired in the study above, heart rate-corrected QT interval (QTc) was computed and a reduced ionic whole heart mathematical model was constructed. Twelve-lead ECG was produced as a forward solution from an equivalent cardiac source. Different patterns of regional denervation in cardiac images of diabetic patients guided the simulation of pathological changes. Minimum QTc interval of lateral leads tended to be longer in D2 than in AB. Prolonging action potential duration in the basal septal region in the model produced ECG and QT interval similar to that of D2 subjects, suggesting sympathetic denervation in this region in patients with definite neuropathy.
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Patel, Chirag S. "Wireless channel modeling, simulation, and estimation." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-03282006-200818/.
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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2006.Andrew, Alfred, Committee Member ; Durgin, Gregory, Committee Member ; Li, Geoffrey, Committee Member ; Ingram, Mary Ann, Committee Member ; Stuber, Gordon, Committee Chair.
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Garcia, Andrew Michael. "Feed-Forward Air-Fuel Ratio Control during Transient Operation of an Alternative Fueled Engine." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366034780.
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