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Dissertations / Theses on the topic 'Affine dependence in the parameter'
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1
Geffen, Nathan. "Pattern recognition and the nondeterminable affine parameter problem." Master's thesis, University of Cape Town, 1998. http://hdl.handle.net/11427/9563.
Full textAbstract:
Bibliography: leaves 112-121.This thesis reports on the process of implementing pattern recognition systems using classification models such as artificial neural networks (ANNs) and algorithms whose theoretical foundations come from statistics. The issues involved in implementing several classification models and pre-processing operators - that are applied to patterns before classification takes place - are discussed and a methodology that is commonly used in developing pattern recognition systems is described. In addition, a number of pattern recognition systems for two image recognition problems that occur in the field of image matching have been developed. These image recognition problems and the issues involved in solving them are described in detail. Numerous experiments were carried out to test the accuracy and speed of the systems developed to solve these problems. These experiments and their results are also discussed.
2
Moreau, Antoine. "Calcul des propriétés homogénéisées de transfert dans les matériaux poreux par des méthodes de réduction de modèle : Application aux matériaux cimentaires." Thesis, La Rochelle, 2022. http://www.theses.fr/2022LAROS024.
Full textAbstract:
Cette thèse propose de coupler deux outils préexistant pour la modélisation mathématique en mécanique : l’homogénéisation périodique et la réduction de modèle, afin de modéliser la corrosion des structures de béton armé exposées à la pollution atmosphérique et au sel marin. Cette dégradation est en effet difficile à simuler numériquement, eu égard la forte hétérogénéité des matériaux concernés, et la variabilité de leur microstructure. L’homogénéisation périodique fournit un modèle multi-échelle permettant de s’affranchir de la première de ces deux difficultés. Néanmoins, elle repose sur l’existence d’un volume élémentaire représentatif (VER) de la microstructure du matériau poreux modélisé. Afin de prendre en compte la variabilité de cette dernière, on est amenés à résoudre en temps réduit les équations issues du modèle multi-échelle pour un grand nombre VER. Ceci motive l’utilisation de la méthode POD de réduction de modèle. Cette thèse propose de recourir à des transformations géométriques pour transporter ces équations sur la phase fluide d’un VER de référence. La méthode POD ne peut, en effet, pas être utilisée directement sur un domaine spatial variable (ici le réseau de pores du matériau). Dans un deuxième temps, on adapte ce nouvel outil à l’équation de Poisson-Boltzmann, fortement non linéaire, qui régit la diffusion ionique à l’échelle de la longueur de Debye. Enfin, on combine ces nouvelles méthodes à des techniques existant en réduction de modèle (MPS, interpolation ITSGM), pour tenir compte du couplage micro-macroscopique entre les équations issues de l’homogénéisation périodiqueIn this thesis, we manage to combine two existing tools in mechanics: periodic homogenization, and reduced-order modelling, to modelize corrosion of reinforced concrete structures. Indeed, chloride and carbonate diffusion take place their pores and eventually oxydate their steel skeleton. The simulation of this degradation is difficult to afford because of both the material heterogenenity, and its microstructure variability. Periodic homogenization provides a multiscale model which takes care of the first of these issues. Nevertheless, it assumes the existence of a representative elementary volume (REV) of the material at the microscopical scale. I order to afford the microstructure variability, we must solve the equations which arise from periodic homogenization in a reduced time. This motivates the use of model order reduction, and especially the POD. In this work we design geometrical transformations that transport the original homogenization equations on the fluid domain of a unique REV. Indeed, the POD method can’t be directly performed on a variable geometrical space like the material pore network. Secondly, we adapt model order reduction to the Poisson-Boltzmann equation, which is strongly nonlinear, and which rules ionic electro diffusion at the Debye length scale. Finally, we combine these new methods to other existing tools in model order reduction (ITSGM interpolatin, MPS method), in order to couple the micro- and macroscopic components of periodic homogenization
3
Kremer, Jonas [Verfasser]. "Ergodicity and parameter estimation for some affine models / Jonas Kremer." Wuppertal : Universitätsbibliothek Wuppertal, 2018. http://d-nb.info/1166336786/34.
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4
Pang, Erwin. "Parameter estimation and efficient implementation of affine transforms for digital images." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ28850.pdf.
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5
Bharadwaj, Shashank. "Investigation of oxide thickness dependence of Fowler-Nordheim parameter B." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000251.
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6
Garcia, Alberto J. "Parameter Dependence of Pair Correlations in Clean Superconducting-Magnetic Proximity Systems." Thesis, California State University, Long Beach, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10841350.
Full textAbstract:
Cooper pairs are known to tunnel through a barrier between superconductors in a Josephson junction. The spin states of the pairs can be a mixture of singlet and triplet states when the barrier is an inhomogeneous magnetic material. The purpose of this thesis is to better understand the behavior of pair correlations in the ballistic regime for different magnetic configurations and varying physical parameters. We use a tight-binding Hamiltonian to describe the system and consider singlet-pair conventional superconductors. Using the Bogoliubov-Valatin transformation, we derive the Bogoliubov-de Gennes equations and numerically solve the associated eigenvalue problem. Pair correlations in the magnetic Josephson junction are obtained from the Green's function formalism for a superconductor. This formalism is applied to Josephson junctions composed of discrete and continuous magnetic materials. The differences between representing pair correlations in the time and frequency domain are discussed, as well as the advantages of describing the Gor'kov functions on a log scale rather than the commonly used linear scale, and in a rotating basis as opposed to a static basis. Furthermore, the effects of parameters such as ferromagnetic width, magnetization strength, and band filling will be investigated. Lastly, we compare results in the clean limit with known results in the diffusive regime.
7
El, Hor Hamid. "Temperature dependence of lattice dynamics in quasicrystals." Doctoral thesis, Universitätsbibliothek Chemnitz, 2004. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200400105.
Full textAbstract:
The work presented in this thesis was motivated by the large amount of experimental investigations of the phonons in quasicrystals. The generalized vibrational density of states (GVDOS) was measured for many quasicrystalline phases and in some cases at different temperatures [suck et al (1997), Dugain et al (1997)]. The progress achieved in the structure determination of approximants to some quasicrystals was a legitimate motivation for numerical investigations of lattice dynamics in these structures. Two different types of interatomic interactions were used: the spring model and the ab-initio pair potentials. The investigations explained the shape of some experimentally measured GVDOS (d-AlNiCo, o-Al13Co4 and i-ZnMgY) via the calculation of the partial vibrational densities of states. Both calculated and measured GVDOS of the d-AlNiCo phase showed an intensity excess at low energies relatively to the ideal Debye behaviour. This excess was found to be a consequence of the existence of special modes at theses energies which are called ``quasi-localized modes''. These modes seem to be characteristic of the lattice dynamics in the complex Al-TM structures. To calculate the frequency shift due to the shift of the GVDOS through low energies observed experimentally at high temperatures, a new method based on a Monte-Carlo simulation was developed. It was shown that the quasi-localized modes introduce large frequency shifts at low energies. Finally, the vibrational entropy was also investigated, and it was found that it contributes to the stabilization of the complex structures over the relatively simple structures at high temperaturesDie Arbeit, die in dieser Dissertation präsentiert wird, wurde durch eine Vielzahl von experimentellen Beobachtungen von Phononen in Quasikristallen motiviert. Die verallgemeinerte vibrationelle Zustandsdichte (GVDOS, generalized vibrational density of states) wurde für viele quasikristalline Phasen gemessen und für einige auch bei verschiedener Temperatur [Suck et al. (1997), Dugain et al. (1997)]. Der Fortschritt, der in der Bestimmung von Näherungen für einige Quasikristalle erreicht wurde war eine legitime Motivation für numerische Untersuchungen der Gitterdynamik auf diesen Strukturen. Es wurden zwei unterschiedliche interatomare Wechselwirkungen verwendet: Das Federmodell und die ab-initio Paar Potentiale. Die Untersuchungen erklärten die Form einiger experimenteller GVDOS-Messungen (d-AlNiCo, o-Al13Co4 und i-ZnMgY) mittels der Berechnung der partiellen vibrationellen Zustandsdichte. Beide, berechnete und gemessene, GVDOS der d-AlNiCo Phase zeigten einen Intensitätsanstieg bei kleinen Energien relativ zum idealen Debye Verhalten. Dieser Anstieg stellte sich als Konsequenz der Existenz von besonderen Moden bei diesen Energien heraus, die quasi-lokalisierte Moden genannt werden. Diese Moden scheinen charakteristisch für die Gitterdynamik in den komplexen Al-TM Strukturen zu sein. Um die experimentell beobachtete Frequenzverschiebung aufgrund der Verschiebung der GVDOS durch niedrige Energien zu berechnen, wurde eine neue, auf Monte-Carlo Simulation beruhende, Methode entwickelt. Es wurde gezeigt, daß die quasi-lokalisierten Moden große Frequenzverschiebungen bei kleinen Energien hervorrufen. Letzt-lich wurde auch die vibrationelle Entropie untersucht und es stellte sich heraus, daß sie bei hohen Temperaturen dazu beiträgt die komplexen Strukturen gegenüber den relativ einfachen zu stabilisieren
8
Miyazaki, Syuji, Masaomi Yoshida, and Hirokazu Fujisaka. "Parameter dependence of ballistic velocity in deterministic diffusion in the form of devil's staircase." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194664.
Full textAbstract:
By using simple extended mapping models showing chaotic diffusion, nonperturbative non-Gaussian characteristics of diffusive motion are examined in the framework of the large deviation statistical theory. Furthermore by rigorously solving the large deviation statistical quantities, it is found that the same type of anomalous, complex control parameter dependence as that for the diffusion coefficient reported by Klages and Dorfman is also observed in the large deviation statistical quantities such as the weighted average, the generalized diffusion coefficient and the generalized power spectrum densities.
9
Miyazaki, Syuji, Masaomi Yoshida, and Hirokazu Fujisaka. "Parameter dependence of ballistic velocity in deterministic diffusion in the form of devil’s staircase." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-195516.
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10
Miyazaki, Syuji, Masaomi Yoshida, and Hirokazu Fujisaka. "Parameter dependence of ballistic velocity in deterministic diffusion in the form of devil's staircase." Diffusion fundamentals 3 (2005) 9, S. 1-34, 2005. https://ul.qucosa.de/id/qucosa%3A14300.
Full textAbstract:
By using simple extended mapping models showing chaotic diffusion, nonperturbative non-Gaussian characteristics of diffusive motion are examined in the framework of the large deviation statistical theory. Furthermore by rigorously solving the large deviation statistical quantities, it is found that the same type of anomalous, complex control parameter dependence as that for the diffusion coefficient reported by Klages and Dorfman is also observed in the large deviation statistical quantities such as the weighted average, the generalized diffusion coefficient and the generalized power spectrum densities.
11
Miyazaki, Syuji, Masaomi Yoshida, and Hirokazu Fujisaka. "Parameter dependence of ballistic velocity in deterministic diffusion in the form of devil’s staircase." Diffusion fundamentals 2 (2005) 31, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14362.
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12
Edwards, Samuel Zachary. "Forecasting Highly-Aggregate Internet Time Series Using Wavelet Techniques." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/33223.
Full textAbstract:
The U.S. Coast Guard maintains a network structure to connect its nation-wide assets. This paper analyzes and models four highly aggregate traces of the traffic to/from the Coast Guard Data Network ship-shore nodes, so that the models may be used to predict future system demand. These internet traces (polled at 5â 40â intervals) are shown to adhere to a Gaussian distribution upon detrending, which imposes limits to the exponential distribution of higher time-resolution traces. Wavelet estimation of the Hurst-parameter is shown to outperform estimation by another common method (Sample-Variances). The First Differences method of detrending proved problematic to this analysis and is shown to decorrelate AR(1) processes where 0.65< phi1 <1.35 and correlate AR(1) processes with phi1 <-0.25. The Hannan-Rissanen method for estimating (phi,theta) is employed to analyze this series and a one-step ahead forecast is generated.Master of Science
13
Al-Ramadhani, Sohaib Talal Hasan. "A dynamical systems analysis of movement coordination models." Thesis, University of Exeter, 2018. http://hdl.handle.net/10871/34020.
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In this thesis, we present a dynamical systems analysis of models of movement coordination, namely the Haken-Kelso-Bunz (HKB) model and the Jirsa-Kelso excitator (JKE). The dynamical properties of the models that can describe various phenomena in discrete and rhythmic movements have been explored in the models' parameter space. The dynamics of amplitude-phase approximation of the single HKB oscillator has been investigated. Furthermore, an approximated version of the scaled JKE system has been proposed and analysed. The canard phenomena in the JKE system has been analysed. A combination of slow-fast analysis, projection onto the Poincare sphere and blow-up method has been suggested to explain the dynamical mechanisms organising the canard cycles in JKE system, which have been shown to have different properties comparing to the classical canards known for the equivalent FitzHugh-Nagumo (FHN) model. Different approaches to de fining the maximal canard periodic solution have been presented and compared. The model of two HKB oscillators coupled by a neurologically motivated function, involving the effect of time-delay and weighted self- and mutual-feedback, has been analysed. The periodic regimes of the model have been shown to capture well the frequency-induced drop of oscillation amplitude and loss of anti-phase stability that have been experimentally observed in many rhythmic movements and by which the development of the HKB model has been inspired. The model has also been demonstrated to support a dynamic regime of stationary bistability with the absence of periodic regimes that can be used to describe discrete movement behaviours.
14
Sirtkaya, Salim. "Moving Object Detction In 2d And 3d Scenes." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/12605310/index.pdf.
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This thesis describes the theoretical bases, development and testing of an integrated moving object detection framework in 2D and 3D scenes. The detection problem is analyzed in stationary and non-stationary camera sequences and different algorithms are developed for each case. Two methods are proposed in stationary camera sequences: background extraction followed by differencing and thresholding, and motion detection using optical flow field calculated by &ldquoKanade-Lucas Feature Tracker&rdquo
. For non-stationary camera sequences, different algorithms are developed based on the scene structure and camera motion characteristics. In planar scenes where the scene is flat or distant from the camera and/or when camera makes rotations only, a method is proposed that uses 2D parametric registration based on affine parameters of the dominant plane for independently moving object detection. A modified version of the 2D parametric registration approach is used when the scene is not planar but consists of a few number of planes at different depths, and camera makes translational motion. Optical flow field segmentation and sequential registration are the key points for this case. For 3D scenes, where the depth variation within the scene is high, a parallax rigidity based approach is developed for moving object detection. All these algorithms are integrated to form a unified independently moving object detector that works in stationary and non-stationary camera sequences and with different scene and camera motion structures. Optical flow field estimation and segmentation is used for this purpose.
15
Inkaya, Alper. "Option Pricing With Fractional Brownian Motion." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613736/index.pdf.
Full textAbstract:
Traditional financial modeling is based on semimartingale processes with stationary and independent
increments. However, empirical investigations on financial data does not always
support these assumptions. This contradiction showed that there is a need for new stochastic
models. Fractional Brownian motion (fBm) was proposed as one of these models by Benoit
Mandelbrot. FBm is the only continuous Gaussian process with dependent increments. Correlation
between increments of a fBm changes according to its self-similarity parameter H. This
property of fBm helps to capture the correlation dynamics of the data and consequently obtain
better forecast results. But for values of H different than 1/2, fBm is not a semimartingale and
classical Ito formula does not exist in that case. This gives rise to need for using the white noise
theory to construct integrals with respect to fBm and obtain fractional Ito formulas. In this
thesis, the representation of fBm and its fundamental properties are examined. Construction of
Wick-Ito-Skorohod (WIS) and fractional WIS integrals are investigated. An Ito type formula
and Girsanov type theorems are stated. The financial applications of fBm are mentioned and
the Black&Scholes price of a European call option on an asset which is assumed to follow a geometric fBm is derived. The statistical aspects of fBm are investigated. Estimators for the self-similarity parameter H and simulation methods of fBm are summarized. Using the R/S methodology of Hurst, the estimations of the parameter H are obtained and these values are used to evaluate the fractional Black&
Scholes prices of a European call option with different maturities. Afterwards, these values are compared to Black&
Scholes price of the same option to demonstrate the effect of long-range dependence on the option prices. Also, estimations of H at different time scales are obtained to investigate the multiscaling in financial data. An outlook of the future work is given.
16
Rutkowski, Mitchell M. "Growth Parameter Dependence and Correlation of Native Point Defects and Dielectric Properties in BaxSr1-xTiO3 Grown by Molecular Beam Epitaxy." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366299175.
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17
Cohen, Albert. "Analyse et transformation de programmes: du modèle polyédrique aux langages formels." Phd thesis, Université de Versailles-Saint Quentin en Yvelines, 1999. http://tel.archives-ouvertes.fr/tel-00550829.
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Les microprocesseurs et les architectures parallèles d'aujourd'hui lancent de nouveaux défis aux techniques de compilation. En présence de parallélisme, les optimisations deviennent trop spécifiques et complexes pour être laissées au soin du programmeur. Les techniques de parallélisation automatique dépassent le cadre traditionnel des applications numériques et abordent de nouveaux modèles de programmes, tels que les nids de boucles non affines, les appels récursifs et les structures de données dynamiques. Des analyses précises sont au c{\oe}ur de la détection du parallélisme, elles rassemblent des informations à la compilation sur les propriétés des programmes à l'exécution. Ces informations valident des transformations utiles pour l'extraction du parallélisme et la génération de code parallèle. Cette thèse aborde principalement des analyses et des transformations avec une vision par instances, c'est-à-dire considérant les propriétés individuelles de chaque instance d'une instruction à l'exécution. Une nouvelle formalisation à l'aide de langages formels nous permet tout d'abord d'étudier une analyse de dépendances et de définitions visibles par instances pour programmes récursifs. L'application de cette analyse à l'expansion et la parallélisation de programmes récursifs dévoile des résultats encourageants. Les nids de boucles quelconques font l'objet de la deuxième partie de ce travail. Une nouvelle étude des techniques de parallélisation fondées sur l'expansion nous permet de proposer des solutions à des problèmes d'optimisation cruciaux.
18
Low, Choy Samantha Jane. "Hierarchical models for 2D presence/absence data having ambiguous zeroes: With a biogeographical case study on dingo behaviour." Thesis, Queensland University of Technology, 2001. https://eprints.qut.edu.au/37098/12/Samantha%20Low%20Choy%20Thesis.pdf.
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This dissertation is primarily an applied statistical modelling investigation, motivated by a case study comprising real data and real questions. Theoretical questions on modelling and computation of normalization constants arose from pursuit of these data analytic questions.
The essence of the thesis can be described as follows.
Consider binary data observed on a two-dimensional lattice. A common problem with such data is the ambiguity of zeroes recorded. These may represent zero response given some threshold (presence) or that the threshold has not been triggered (absence). Suppose that the researcher wishes to estimate the effects of covariates on the binary responses, whilst taking into account underlying spatial variation, which is itself of some interest. This situation arises in many contexts and the dingo, cypress and toad case studies described in the motivation chapter are examples of this.
Two main approaches to modelling and inference are investigated in this thesis.
The first is frequentist and based on generalized linear models, with spatial variation modelled by using a block structure or by smoothing the residuals spatially. The EM algorithm can be used to obtain point estimates, coupled with bootstrapping or asymptotic MLE estimates for standard errors.
The second approach is Bayesian and based on a three- or four-tier hierarchical model, comprising a logistic regression with covariates for the data layer, a binary Markov Random field (MRF) for the underlying spatial process, and suitable priors for parameters in these main models. The three-parameter autologistic model is a particular MRF of interest. Markov chain Monte Carlo (MCMC) methods comprising hybrid Metropolis/Gibbs samplers is suitable for computation in this situation. Model performance can be gauged by MCMC diagnostics.
Model choice can be assessed by incorporating another tier in the modelling hierarchy. This requires evaluation of a normalization constant, a notoriously difficult problem. Difficulty with estimating the normalization constant for the MRF can be overcome by using a path integral approach, although this is a highly computationally intensive method.
Different methods of estimating ratios of normalization constants (N Cs) are investigated, including importance sampling Monte Carlo (ISMC), dependent Monte Carlo based on MCMC simulations (MCMC), and reverse logistic regression (RLR). I develop an idea present though not fully developed in the literature, and propose the Integrated mean canonical statistic (IMCS) method for estimating log NC ratios for binary MRFs. The IMCS method falls within the framework of the newly identified path sampling methods of Gelman & Meng (1998) and outperforms ISMC, MCMC and RLR. It also does not rely on simplifying assumptions, such as ignoring spatio-temporal dependence in the process. A thorough investigation is made of the application of IMCS to the three-parameter Autologistic model. This work introduces background computations required for the full implementation of the four-tier model in Chapter 7.
Two different extensions of the three-tier model to a four-tier version are investigated. The first extension incorporates temporal dependence in the underlying spatio-temporal process. The second extensions allows the successes and failures in the data layer to depend on time. The MCMC computational method is extended to incorporate the extra layer. A major contribution of the thesis is the development of a fully Bayesian approach to inference for these hierarchical models for the first time.
Note: The author of this thesis has agreed to make it open access but invites people downloading the thesis to send her an email via the 'Contact Author' function.
19
Pretorius, Carel Diederik. "Investigating viral parameter dependence on cell and viral life cycle assumptions." Thesis, 2007. http://hdl.handle.net/10539/2183.
Full textAbstract:
Student Number: 9811822T -
MSc Dissertation -
School of Computational and Applied Mathematics -
Faculty of ScienceThis dissertation reviews population dynamic type models of viral infection and introduces some new models to describe strain competition and the infected cell lifecycle. Laboratory data from a recent clinical trial, tracking drug resistant virus in patients given a short course of monotherapy is comprehensively analysed, paying particular attention to reproducibility. A Bayesian framework is introduced, which facilitates the inference of model parameters from the clinical data. It appears that the rapid emergence of resistance is a challenge to popular unstructured models of viral infection, and this challenge is partly addressed. In particular, it appears that minimal ordinary differential equations, with their implicit exponential lifetime (constant hazard) distributions in all compartments, lack the short transient timescales observed clinically. Directions for future work, both in terms of obtaining more informative data, and developing more systematic approaches to model building, are identified.
20
LeBel, Stefan. "Path following control of wheeled mobile robots combining piecewise-affine, linear parameter-varying, and backstepping theories." Thesis, 2007. http://spectrum.library.concordia.ca/975532/1/MR34753.pdf.
Full textAbstract:
This thesis presents a novel controller synthesis method for path following of a wheeled mobile robot (WMR). The proposed control method consists of a three-step procedure mixing piecewise-affine (PWA) and linear parameter-varying (LPV) techniques with backstepping. In the first step, two curvature limits and a curvature rate of change limit are defined for the desired path and the nonlinear WMR parameterized path kinematics are approximated by an uncertain piecewise-affine parameter-varying (PWAPV) system, while assuming that the WMR forward velocity is constant. A numerical method is proposed for determining PWA bounds on the uncertainty terms such that the original nonlinear parameter-dependent system is contained in the uncertain PWAPV system. Then, a PWAPV steering control law is designed using a parameter-dependent quadratic Lyapunov function. In the second step, a backstepping-type approach is used to include the vehicle dynamics and design the wheel control torques that guarantee convergence of the WMR forward and rotational velocities to the desired values. Finally, in the third step, the actuator dynamics are included and the input voltages are designed using backstepping. There are four primary advantages to the path following controller synthesis method proposed in this thesis. First, the PWAPV controller synthesis method can be formulated as a convex optimization program subject to a parameterized set of Linear Matrix Inequalities (LMIs), which will be approximated by a finite set of LMIs using LPV theory and then solved efficiently using available software. Second, it includes both a general, non-singular path parameterization and the actuator dynamics. Third, the PWAPV control law can also stabilize the type of nonlinear parameter-dependent system considered here. And fourth, it is a first step toward including hard nonlinearities in the actuator dynamics, which are important PWA characteristics. The effectiveness of the proposed path following control method is demonstrated through numerical simulations.
21
El, Hor Hamid. "Temperature dependence of lattice dynamics in quasicrystals." Doctoral thesis, 2003. https://monarch.qucosa.de/id/qucosa%3A18100.
Full textAbstract:
The work presented in this thesis was motivated by the large amount of
experimental investigations of the phonons in quasicrystals. The
generalized vibrational density of states (GVDOS) was measured for
many quasicrystalline phases and in some cases at different
temperatures [suck et al (1997), Dugain et al (1997)].
The progress achieved in the structure determination of approximants
to some quasicrystals was a legitimate motivation for numerical
investigations of lattice dynamics in these structures.
Two different types of interatomic interactions were used: the spring
model and the ab-initio pair potentials.
The investigations explained the shape of some experimentally measured
GVDOS (d-AlNiCo, o-Al13Co4 and i-ZnMgY)
via the calculation of the partial vibrational densities of states.
Both calculated and measured GVDOS of the d-AlNiCo phase showed an
intensity excess at low energies relatively to the ideal Debye
behaviour.
This excess was found to be a consequence of the existence of special
modes at theses energies which are called ``quasi-localized
modes''. These modes seem to be characteristic of the lattice dynamics
in the complex Al-TM structures.
To calculate the frequency shift due to the shift of the GVDOS through
low energies observed experimentally at high temperatures, a new
method based on a Monte-Carlo simulation was developed. It was shown
that the quasi-localized modes introduce large frequency shifts at
low energies.
Finally, the vibrational entropy was also investigated, and it was
found that it contributes to the stabilization of the complex
structures over the relatively simple structures at high temperatures.Die Arbeit, die in dieser Dissertation präsentiert wird, wurde durch eine Vielzahl von experimentellen Beobachtungen von Phononen in Quasikristallen motiviert. Die verallgemeinerte vibrationelle Zustandsdichte (GVDOS, generalized vibrational density of states) wurde für viele quasikristalline Phasen gemessen und für einige auch bei verschiedener Temperatur [Suck et al. (1997), Dugain et al. (1997)]. Der Fortschritt, der in der Bestimmung von Näherungen für einige Quasikristalle erreicht wurde war eine legitime Motivation für numerische Untersuchungen der Gitterdynamik auf diesen Strukturen. Es wurden zwei unterschiedliche interatomare Wechselwirkungen verwendet: Das Federmodell und die ab-initio Paar Potentiale. Die Untersuchungen erklärten die Form einiger experimenteller GVDOS-Messungen (d-AlNiCo, o-Al13Co4 und i-ZnMgY) mittels der Berechnung der partiellen vibrationellen Zustandsdichte. Beide, berechnete und gemessene, GVDOS der d-AlNiCo Phase zeigten einen Intensitätsanstieg bei kleinen Energien relativ zum idealen Debye Verhalten. Dieser Anstieg stellte sich als Konsequenz der Existenz von besonderen Moden bei diesen Energien heraus, die quasi-lokalisierte Moden genannt werden. Diese Moden scheinen charakteristisch für die Gitterdynamik in den komplexen Al-TM Strukturen zu sein. Um die experimentell beobachtete Frequenzverschiebung aufgrund der Verschiebung der GVDOS durch niedrige Energien zu berechnen, wurde eine neue, auf Monte-Carlo Simulation beruhende, Methode entwickelt. Es wurde gezeigt, daß die quasi-lokalisierten Moden große Frequenzverschiebungen bei kleinen Energien hervorrufen. Letzt-lich wurde auch die vibrationelle Entropie untersucht und es stellte sich heraus, daß sie bei hohen Temperaturen dazu beiträgt die komplexen Strukturen gegenüber den relativ einfachen zu stabilisieren.
22
Acar, Elif Fidan. "Nonparametric Estimation and Inference for the Copula Parameter in Conditional Copulas." Thesis, 2010. http://hdl.handle.net/1807/25916.
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The primary aim of this thesis is the elucidation of covariate effects on the dependence structure of random variables in bivariate or multivariate models. We develop a unified approach via a conditional copula model in which the copula is parametric and its parameter varies as the covariate. We propose a nonparametric procedure based on local likelihood to estimate the functional relationship between the copula parameter and the covariate, derive the asymptotic properties of the proposed estimator and outline the construction of pointwise confidence intervals. We also contribute a novel conditional copula selection method based on cross-validated prediction errors and a generalized likelihood ratio-type test to determine if the copula parameter varies significantly. We derive the asymptotic null distribution of the formal test. Using subsets of the Matched Multiple Birth and Framingham Heart Study datasets, we demonstrate the performance of these procedures via analyses of gestational age-specific twin birth weights and the impact of change in body mass index on the dependence between two consequent pulse pressures taken from the same subject.
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余昱穎. "Bias Dependence and Geometry Effect of SiGe HBTs Equivalent circuit Elements using Direct Parameter-Extraction Method." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/77801493815957913719.
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Chang, Li-Hsin, and 張立欣. "The Study of Temperature Dependence of Characteristics of AlGaAs/GaAs Heterojunction Bipolar Transistor and Thermal Parameter Extraction." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/22171552929069507220.
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碩士國立成功大學
電機工程學系
89
Recent advances in communication, radar and computational systems demand very high performance electronic circuit. Heterojunction bipolar transistors (HBTs) have potential of providing a more efficient solution to many key system requirements through intrinsic device advantages than competing technologies. HBTs have also shown great potential both for microwave power and low-voltage applications. Many applications will require HBTs transistor to operate above ambient temperature due to high power density and poor thermal conductivity of GaAs substrate. In this thesis, the temperature dependence of current gain is investigated for GaAs-base HBT. The thermionic- emission current plays an important role for the hole current, which results in a negative temperature coefficient for current gain. The dependence of the collector-emitter offset voltage (Voffset) on the base current, substrate temperature. We found that Voffset decreases at moderate base current, and begins to increase at very high IB. Moreover, Voffset increases linearly with the temperature. Under high self-heating operating conditions, a technique is presented that can directly extract the mean device junction and thermal impedance. The method uses three trivial dc measurements of the device where the junction temperature is known to be the same. Result show that the thermal impedance varied with both ambient temperature and power dissipation at high junction temperature.
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Li, Jian-Yi, and 李建億. "The effect of revising the temperature dependence of dispersion term and volume parameter on phase equilibrium predictions from PR+COSMOSAC." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/53984218258039210348.
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碩士國立中央大學
化學工程與材料工程學系
105
The knowledge of thermodynamic properties and phase behavior for pure substances and mixtures over a wide range of temperature and pressure is of importance not only for engineers to design, develop and optimize the equipment and processes in chemical and related industries but for the safety of our daily life and environmental protection. Recently, Hsieh and Lin proposed a method PR+COSMOSAC(2010) which utilizes quantum mechanical and COSMO solvation calculations to obtain the parameters in PR EOS. This method has been applied to predict several types of phase equilibrium, such as VLE, SVE or supercritical fluid systems. The first part of this work is to revise the dispersion energy term (〖∆▁G_i〗^(*dsp)) of PR+COSMOSAC(2010) because the linearity between 〖∆▁G_i〗^(*dsp) and natural logarithm of temperature is better than that between 〖∆▁G_i〗^(*dsp) and temperature. Then, three different sets of dispersion parameters are obtained by the regression of three different regions of vapor pressure data to study which one can provide the lowest deviation of vapor pressure prediction. The second part is to investigate the effect of the modified volume parameter on vapor pressure prediction because a polynominal relationship is found between bPR and Vi,COSMO. Finally, the PR+COSMOSAC(2017) is proposed on the basis of the results in the first two parts. Moreover, we compare the prediction deviation of vapor pressures for 1125 pure substances (ALD-P = 0.199), sublimation pressures for 1140 pure substances (ALD-P = 0.679), critical properties (AARD-Pc = 8.1%, AARD-Tc = 4.8% and AARD-Vc = 18.05% for 351, 435 and 283 pure substances, respectively) and VLE for 1118 binary systems (AARD-P = 22.4% and AAD-y1 = 9.2%) from PR+COSMOSAC(2017) with those from PR+COSMOSAC(2010) and PR+COSMOSAC(2015). The results show that the prediction accuracy of PR+COSMOSAC(2017) is superior to the versions of 2010 and 2015 except for the critical temperature, critical volume and the vapor phase composition of binary VLE systems.
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Kueng, Tz-Liang, and 龔自良. "Parameter Estimation and Future Value Prediction of Growth Curve Model with Power Transformation, Random Effects and General AR(g) Dependence." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/79457760304771058796.
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碩士國立交通大學
統計所
89
In this paper, we devote ourselves to a generalized growth curve model with power transformation, random effects and AR($g$) dependence via Bayesian and Maximum-Likelihood (ML) approaches. Inferences on the parameters as well as the future value are discussed. Some numerical results with real and simulated data are also given.\ {\bf Key words}: Approximation, Bayesian, Longitudinal data, Maximum likelihood, Markov Chain Monte Carlo, Real data, Simulated data.
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Dong, Fang. "Copula theory and its applications in computer networks." Thesis, 2017. https://dspace.library.uvic.ca//handle/1828/8319.
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Traffic modeling in computer networks has been researched for decades. A good model should reflect the features of real-world network traffic. With a good model, synthetic traffic data can be generated for experimental studies; network performance can be analysed mathematically; service provisioning and scheduling can be designed aligning with traffic changes. An important part of traffic modeling is to capture the dependence, either the dependence among different traffic flows or the temporal dependence within the same traffic flow. Nevertheless, the power of dependence models, especially those that capture the functional dependence, has not been fully explored in the domain of computer networks. This thesis studies copula theory, a theory to describe dependence between random variables, and applies it for better performance evaluation and network resource provisioning. We apply copula to model both contemporaneous dependence between traffic flows and temporal dependence within the same flow. The dependence models are powerful and capture the functional dependence beyond the linear scope. With numerical examples, real-world experiments and simulations, we show that copula modeling can benefit many applications in computer networks, including, for example, tightening performance bounds in statistical network calculus, capturing full dependence structure in Markov Modulated Poisson Process (MMPP), MMPP parameter estimation, and predictive resource provisioning for cloud-based composite services.Graduate
0984
fdong@uvic.ca
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Nývltová, Veronika. "Prostorová ekonometrie." Master's thesis, 2015. http://www.nusl.cz/ntk/nusl-350905.
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This thesis is devoted to the models that are suitable for modelling spatial data. For this purpose, random fields with finite index set are used. Based on the neighbourhood relationship a spatial weight matrix is introduced which describes spatial dependencies. A recognition and testing of spatial dependence is mentioned and it is applied for macroeconomic indicators in the Czech Republic. Spatial models originated from generalization of usual time series models are subsequently combined with linear regression models. The parameter estimators are derived for selected models by three different methods. These methods are ordinary least squares, maximum likelihood and method of moments. Theoretical asymptotic results are supplemented by a simulation study that examines the performance of estimators for finite sample size. Finally, a short illustration on real data is demonstrated. Powered by TCPDF (www.tcpdf.org)
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Štěrba, Jan. "Porovnání výsledků zátěžových testů na kajakářském ergometru s dosahovaným výkonem v rychlostní kanoistice." Master's thesis, 2013. http://www.nusl.cz/ntk/nusl-328571.
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- 6 - Abstract Title: Comparison of performance tests results determined during kayak spiroergometry with achieved kayak paddling performance. Objectives: The aim of the study was to determine relationships between functional parameters values found during kayak spiroergometry and sport performance at 1000 meters distance, and how are these relationships going to change based on training period. Methods: To determine statistical dependence between sport performance at 1000 meters distance and choosen factors of sport performance, the correlation research was used - as a variable-dependent value the final result of sport performance at 1000 meters distance was used, as a variable-independent amounts functional parameters values found during kayak spiroergometry were used. To discover the statistical dependence methods of Pearson's correlation coefficient and regression analysis were used. Results: General level of kayak-athletes from testing file indicated by functional parameters values and demonstrated by kayak spiroergometry performance depends on kayak- athlete's level of sport performance at 1000 meters distance in prepared-training period only, when importance for general condition is emphasized. We did not discover the same phenomenon based on pre-racing period testing results. Sport performance at...
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Ραφτοπούλου, Χριστίνα. "Εκτίμηση των παραμέτρων στο μοντέλο της διπαραμετρικής εκθετικής κατανομής, υπό περιορισμό." Thesis, 2013. http://hdl.handle.net/10889/7800.
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Η παρούσα μεταπτυχιακή διατριβή εντάσσεται ερευνητικά στην περιοχή της Στατιστικής Θεωρίας Αποφάσεων και ειδικότερα στην εκτίμηση των παραμέτρων στο μοντέλο της διπαραμετρικής εκθετικής κατανομής με παράμετρο θέσης μ και παράμετρο κλίμακος σ. Θεωρούμε το πρόβλημα εκτίμησης των παραμέτρων κλίμακας μ και θέσης σ, όταν μ≤c, όπου c είναι μία γνωστή σταθερά. Αποδεικνύουμε ότι σε σχέση με το κριτήριο του Μέσου Τετραγωνικού Σφάλματος (ΜΤΣ), οι βέλτιστοι αναλλοίωτοι εκτιμητές των μ και σ, είναι μη αποδεκτοί όταν μ≤c, και προτείνουμε βελτιωμένους. Επίσης συγκρίνουμε του εκτιμητές αυτούς σε σχέση με το κριτήριο του Pitman. Επιπλέον, προτείνουμε εκτιμητές που είναι καλύτεροι από τους βέλτιστους αναλλοίωτους εκτιμητές, όταν μ≤c, ως προς την συνάρτηση ζημίας LINEX. Τέλος, η θεωρία που αναπτύσσεται εφαρμόζεται σε δύο ανεξάρτητα δείγματα προερχόμενα από εκθετική κατανομή.The present master thesis deals with the estimation of the location parameter μ and the scale parameter σ of the two-parameter exponential distribution. We consider the problem of estimation of locasion parameter μ and the scale parameter σ, when it is known apriori that μ≤c, where c is a known constant. We establish that with respect to the mean square error (mse) criterion the best affine estimators of μ and σ in the absence of information μ≤c are inadmissible and we propose estimators which are better than these estimators. Also, we compare these estimators with respect to the Pitman Nearness criterion. We propose estimators which are better than the standard estimators in the unrestricted case with respect to the suitable choise of LINEX loss. Finally, the theory developed is applied to the problem of estimating the location and scale parameters of two exponential distributions when the location parameters are ordered.
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Dittmar, Jörg. "Modellierung dynamischer Prozesse mit radialen Basisfunktionen." Doctoral thesis, 2010. http://hdl.handle.net/11858/00-1735-0000-0006-B4DD-9.
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