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Alavi, Saman. "Density corrections to transport coefficients from time correlation functions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0019/NQ46308.pdf.
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Jou, Wen Chi. "The theoretical studies of time-correlation functions with the first principle molecular dynamics simulations on surfaces /." Tamsui : Tamkang University, Department of Chemistry, 2007. http://etds.lib.tku.edu.tw/etdservice/view_metadata?etdun=U0002-0207200714531200.
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Freire, Márcio de Melo. "Funções de Green em Mecânica Estatística." reponame:Repositório Institucional da UFC, 2014. http://www.repositorio.ufc.br/handle/riufc/9059.
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FREIRE, Márcio de Melo. Funções de Green em Mecânica Estatística. 2014. 56 f. Dissertação (Mestrado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2014.Submitted by Edvander Pires (edvanderpires@gmail.com) on 2014-09-12T19:48:53Z No. of bitstreams: 1 2014_dis_mmfreire.pdf: 935092 bytes, checksum: 28a3a9a1ed16462d01e40ff411a01564 (MD5)
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Neste trabalho estabeleceremos as definições das funções de Green em mecânica estatística e suas propriedades básicas. Estas funções dependem duplamente do tempo e da temperatura. Isto pode ser observado por meio de suas definições, onde aparecem os valores médios dos produtos de operadores. Neste caso a média é feita sobre o ensemble grão-canônico. Os operadores envolvidos nestas funções satisfazem a equação de movimento de Heisenberg, o que nos permite descrever as equações de evolução para as funções de Green. Por meio da representação espectral das funções de correlação temporal, que é feita através da introdução de uma transformada de Fourier para mudar o sistema do espaço dos tempos para o espaço das frequências, podemos obter as representações espectrais para as funções de Green retardada, avançada e causal. Por último, faremos o uso da função de Green retardada para descrever a condutividade elétrica de um sistema de elétrons submetido a um campo elétrico externo dependente de tempo, em outras palavras, descreveremos o tensor de condutividade elétrica em termos da função de Green retardada e, por último, calcularemos a condutividade elétrica de um sistema de elétrons e fônons.
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Brookes, Sarah. "Fluids in Nanopores." Thesis, Griffith University, 2016. http://hdl.handle.net/10072/365467.
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Molecular modelling plays an important and complementary role to experimental studies. In this thesis we use molecular dynamic simulations and time correlation functions to examine the isomerization of n-butane and to perform a proof-of-concept demonstration, applying the dissipation theorem to calculating transport properties.
Equilibrium molecular dynamics are used to determine the solvent shift and rate constants in the isomerization process of n-butane. Furthermore the effects of confining n-butane to a nanopore are examined and compared to in two different wall-models. The structure and dynamics of a fluid can be affected when confined to pores of nanometre widths. An understanding of the effects of confinement on the equilibrium composition of reacting mixtures, diffusion and adsorption rates, can lead to improvements in industrial processes such as in the food and pharmaceutical industry. A known effect of confinement is wetting of the walls due to interactions between the wall and the fluid. Examination of the local molecular fluid density across the pore has shown that the degree of wetting is a function of pore width, mean fluid density and wall surface density.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Natural Sciences
Science, Environment, Engineering and Technology
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DeVane, Russell H. "Molecular dynamics and time correlation function theories." [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001309.
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De, Silva Weeraddana Manjula Kumara. "Correlation Imaging for Real-time Cardiac MRI." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1471346206.
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Kasprzyk, Christina Ridley. "Practical applications of molecular dynamics techniques and time correlation function theories." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001644.
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Ryderfors, Linus. "Two-Photon Excited Fluorescence Depolarisation : Experimental and Theoretical Development." Doctoral thesis, Uppsala University, Department of Photochemistry and Molecular Science, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9285.
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We have studied fundamental aspects of time-resolved two-photon excited fluorescence depolarisation. The thesis presents experimental as well as theoretical progress. We show that a multi-photon induced instrumental response function obtained from a suspension of gold nanoparticles is appropriate for the analysis of two-photon excited fluorescence decays obtained using time-correlated single photon counting detection. Theoretical expressions have been derived for the fluorescence anisotropy decay obtained upon two-photon excitation of various molecular systems in liquid solutions: a) an anisotropic rigid rotor that undergoes rotational diffusion in the presence of ultrafast unresolved restricted reorientations, e.g. librations. b) a molecular group covalently attached to a stationary macromolecule, and undergoing local reorientation in a uniaxial ordering potential. A new approach to the analysis of two-photon excited fluorescence depolarisation experiments was developed, which combines data obtained by using linearly and circularly polarised excitation light, in a global manner. In the analysis, knowledge about unresolved reorientations was obtained from one-photon excitation studies of the corresponding systems. By means of this procedure it has been possible to obtain quantitative information about the molecular two-photon absorption tensor for perylene and two of its derivatives. Thereby the symmetry of the final excited and intermediate vibronic states could be assigned. The analysis reveals that the two-photon transition studied with the 800 nm laser exhibits mixed character. An important finding from the experiments was that the two-photon absorption tensor appears to be solvent dependent. Furthermore, the thesis presents the first theoretical treatment of two-photon excited donor-donor energy migration in the presence of molecular reorientation and which applies the extended Förster theory. Explicit expressions for molecules that belong to the point groups D2h, D2 and C2v are given. Preliminary experiments are finally also reported on a two-photon excited donor-donor energy migration system consisting of a bisanthryl-bisteroid.
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Martins, Marcio Marques. "Influência de parâmetros moleculares em funções de correlação temporal na dinâmica de solvatação mecânica." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2004. http://hdl.handle.net/10183/6896.
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No presente trabalho descrevemos nossos resultados relativos à investigação da dinâmica de solvatação mecânica por meio de simulações por dinâmica molecular, respeitando o regime da resposta linear, em sistemas-modelo de argônio líquido com um soluto monoatômico ou diatômico dissolvido. Estudamos sistematicamente a influência dos parâmetros moleculares dos solutos (tamanho, polarizabilidade) e da densidade frente a vários modelos de solvatação. Funções de Correlação Temporal da Energia de Solvatação foram calculadas com relação à correlações de n-corpos (n = 2; 3) distinguindo interações repulsivas e atrativas para ambos os sistemas líquidos. Também obtivemos segundas derivadas temporais dessas funções referindo-se à parcelas translacionais, rotacionais e roto-translacionais na solução do diatômico. Encontramos que funções de correlação temporal coletivas podem ser razoavelmente bem aproximadas por correlações binárias a densidades baixas e, a densidades altas, correlações ternárias tornam-se mais importantes produzindo um descorrelacionamento mais rápido das funções coletivas devido a efeitos de cancelamento parciais. As funções de correlação para interações repulsivas e atrativas exibem comportamentos dinâmicos independentes do modelo de solvatação devido a fatores de escalonamento linear que afetam apenas as amplitudes das dessas funções de correlação temporal. Em geral, os sistemas com grau de liberdade rotacional apresentam tempos de correlação mais curtos para a dinâmica coletiva e tempos de correlação mais longos para as funções binárias e ternárias. Finalmente, esse estudo mostra que os sistemas contendo o diatômico relaxam-se predominantemente por mecanismos translacionais binários em modelos de solvatação envolvendo alterações apenas na polarizabilidade do soluto, e por mecanismos rotacionais atrativos binários em modelos envolvendo alterações no comprimento de ligação.In the present work, we describe our results concerning our molecular dynamics investigation of the mechanical solvation dynamics within the linear response regime in model systems composed by liquid argon with a monoatomic or diatomic solute. The effect of molecular parameters (size, polarizability) and density has been elucidated for various solvation models. Time Correlation Functions for the solvation energy were calculated and separated into n-body (n = 2; 3) contributions distinguishing repulsive and attractive interactions in both liquid systems. In addition, we computed second time derivatives of these functions in order to describe translational, rotational, and roto-translational portions in the solutions containing the diatomics. We found that collective time correlation functions are well described by binary correlations at low liquid densities and, at high densities, ternary correlations become more important producing faster decaying collective time correlation functions due to partial cancellation effects. The repulsive and attractive time correlation functions exhibit a dynamic behavior that is independent on the solvation model due to linear scaling factors that only affect the absolute amplitudes of these functions. In general, the systems involving a rotational degree of freedom furnish smaller correlation times for the collective solvation dynamics, but stronger correlated two-body and three-body terms. Finally, this study shows that the solvation dynamics for the solution containing the diatomics relaxes predominatly by binary translational mechanisms when solvation models involving changes only in the polarizability parameter are considered. Binary attractive rotational mechanism become important in models with changes in the bond length.
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Rouhvand, Bahar. "Vesicle-Protein Diffusion and Interaction Study Using Time Resolved Fluorescence Correlation Spectroscopy." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1503261462042903.
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Balasubramaniyan, Rajarajeswari. "Gene expression data analysis using novel methods predicting time delayed correlations and evolutionarily conserved functional modules /." [S.l.] : [s.n.], 2005. http://archiv.ub.uni-marburg.de/diss/z2005/0134/.
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Fransson, Jonas. "Non-Orthogonality and Electron Correlations in Nanotransport : Spin- and Time-Dependent Currents." Doctoral thesis, Uppsala University, Department of Physics, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-2687.
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The concept of the transfer Hamiltonian formalism has been reconsidered and generalized to include the non-orthogonality between the electron states in an interacting region, e.g. quantum dot (QD), and the states in the conduction bands in the attached contacts. The electron correlations in the QD are described by means of a diagram technique for Hubbard operator Green functions for non-equilibrium states.
It is shown that the non-orthogonality between the electrons states in the contacts and the QD is reflected in the anti-commutation relations for the field operators of the subsystems. The derived forumla for the current contains corrections from the overlap of the same order as the widely used conventional tunneling coefficients.
It is also shown that kinematic interactions between the QD states and the electrons in the contacts, renormalizes the QD energies in a spin-dependent fashion. The structure of the renormalization provides an opportunity to include a spin splitting of the QD levels by polarizing the conduction bands in the contacts and/or imposing different hybridizations between the states in the contacts and the QD for the two spin channels. This leads to a substantial amplification of the spin polarization in the current, suggesting applications in magnetic sensors and spin-filters.
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Eklund, Anders. "Computational Medical Image Analysis : With a Focus on Real-Time fMRI and Non-Parametric Statistics." Doctoral thesis, Linköpings universitet, Medicinsk informatik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-76120.
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Functional magnetic resonance imaging (fMRI) is a prime example of multi-disciplinary research. Without the beautiful physics of MRI, there wouldnot be any images to look at in the first place. To obtain images of goodquality, it is necessary to fully understand the concepts of the frequencydomain. The analysis of fMRI data requires understanding of signal pro-cessing, statistics and knowledge about the anatomy and function of thehuman brain. The resulting brain activity maps are used by physicians,neurologists, psychologists and behaviourists, in order to plan surgery andto increase their understanding of how the brain works. This thesis presents methods for real-time fMRI and non-parametric fMRIanalysis. Real-time fMRI places high demands on the signal processing,as all the calculations have to be made in real-time in complex situations.Real-time fMRI can, for example, be used for interactive brain mapping.Another possibility is to change the stimulus that is given to the subject, inreal-time, such that the brain and the computer can work together to solvea given task, yielding a brain computer interface (BCI). Non-parametricfMRI analysis, for example, concerns the problem of calculating signifi-cance thresholds and p-values for test statistics without a parametric nulldistribution. Two BCIs are presented in this thesis. In the first BCI, the subject wasable to balance a virtual inverted pendulum by thinking of activating theleft or right hand or resting. In the second BCI, the subject in the MRscanner was able to communicate with a person outside the MR scanner,through a virtual keyboard. A graphics processing unit (GPU) implementation of a random permuta-tion test for single subject fMRI analysis is also presented. The randompermutation test is used to calculate significance thresholds and p-values forfMRI analysis by canonical correlation analysis (CCA), and to investigatethe correctness of standard parametric approaches. The random permuta-tion test was verified by using 10 000 noise datasets and 1484 resting statefMRI datasets. The random permutation test is also used for a non-localCCA approach to fMRI analysis.
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Mancini, Lorenzo. "Adiabatic and local approximations for the kohn-sham potential in the hubbard model." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/5935/.
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We obtain the exact time-dependent Kohn-Sham potentials Vks for 1D Hubbard chains, driven by a d.c. external field, using the time-dependent electron density and current density obtained from exact many-body time-evolution. The exact Vxc is compared to the adiabatically-exact Vad-xc and the “instantaneous ground state” Vigs-xc. The effectiveness of these two approximations is analyzed. Approximations for the exchange-correlation potential Vxc and its gradient, based on the local density and on the local current density, are also considered and both physical quantities are observed to be far outside the reach of any possible local approximation. Insight into the respective roles of ground-state and excited-state correlation in the time-dependent system, as reflected in the potentials, is provided by the pair correlation function.
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Hofmanová, Aneta. "Posouzení vybraných ukazatelů společnosti pomocí statistických metod." Master's thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2018. http://www.nusl.cz/ntk/nusl-377969.
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Master's thesis deals with the assessment of selected financial indicators of the company through a financial analysis and statistical methods, on the basis of which then evaluates the current situation of the company. The thesis is divided into three parts. The theoretical part contains the issues necessary for the analytical part. The analytical part is focused on the analysis of selected indicators and the subsequent application of statistical methods to predict their future development and to detect dependencies between the indexes. The last part formulates possible solutions to problems caused by financial indicators that do not reach the required values.
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Huston, Steven Paul. "Structural health monitoring of a high speed naval vessel using ambient vibrations." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33848.
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Traditional naval vessels with steel structures have the benefit of large safety factors and
a distinct material endurance limit. However, as performance requirements and budget
constraints rise, the demand for lighter weight vessels increases. Reducing the mass of
vessels is commonly achieved by the use of aluminum or composite structures, which
requires closer attention to be paid to crack initiation and propagation. It is rarely
feasible to require a lengthy inspection process that removes the vessel from service for
an extended amount of time. Structural health monitoring (SHM), involving continuous
measurement of the structural response to an energy source, has been proposed as a step
towards condition-based maintenance. Furthermore, using a passive monitoring system
with an array of sensors has several advantages: monitoring can take place in real-time
using only ambient noise vibrations and neither deployment of an active source nor visual
access to the inspected areas are required.
Passive SHM on a naval vessel is not without challenge. The structures of ships are
typically geometrically complex, causing scattering, multiple reflections, and mode
conversion of the propagating waves in the vessel. And rather than a distinct and
predictable input produced by controlled active sources, the vibration sources are hull
impacts, smaller waves, and even onboard machinery and activity. This research
summarizes findings from data collected onboard a Navy vessel and presents
recommendations data processing techniques. The intent is to present a robust method of
passive structural health monitoring for such a vessel using only ambient vibrations
recordings.
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Bukhari, Syed Kalim Hyder. "Heterogeneity, marginal cost and New Keynesian Phillips Curve." Thesis, University of Leicester, 2015. http://hdl.handle.net/2381/35930.
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The purpose of the thesis is to introduce novel measure of real marginal cost in the New Keynesian Phillips Curve (NKPC) and compares its performance with conventional mea- sures such as output gap and labour share of income. Real marginal cost is derived from a flexible function whereas labour share is based on restrictive assumption of Cobb-Douglas technology. Dynamic correlations and results of NKPC indicate that real marginal cost is better than ad hoc measure of output gap and labour share. Given the heterogeneity in price setting behaviour across sectors, cost functions and NKPC are estimated for the agriculture, manufacturing and other sectors of Pakistan's economy. Real marginal cost is derived from static and dynamic cost functions. In the presence of adjustment costs, dynamic cost functions that are consistent and integrated with their static systems are required. Such dynamic translog cost functions are estimated after testing the theoretical properties and existence of long term relationships in the static functions. Cost attributes, marginal cost, total factor productivity, technological progress, demand and substitution elasticities are derived from static and dynamic functions. Three specifications of forward looking and hybrid form of the Phillips curves are estimated with real marginal cost, output gap and labour share. Results indicate that hybrid specifications perform better than the forward looking models in terms of goodness of fit and statistical significance. Further, comparison of Phillips curves estimated with real marginal cost, output gap and labour share indicate that real marginal cost performs better in explaining inflation dynamics in Pakistan. The results indicate that forward looking behaviour dominates and high level of nominal rigidities persists in Pakistan. Finally, hybrid form of the NKPC is estimated for a panel of sixteen Asian economies. With the consideration of heterogeneity and aggregation bias, the mean group, random coefficient and weighted average coefficients are derived from individual estimates. The unobserved time variant common factors cause cross correlation in the errors that may lead towards inconsistent estimates. Therefore, cross section averages of the explanatory and the dependent variables are augmented in hybrid specification to capture the effect of latent variables. Findings suggest that the discount factor is almost 0.94, the nominal rigidities are 33% and the weights of expected and past inflation are 66% and 33% respectively. Nominal rigidities of the Asian economies are lower than the estimates for US and Euro areas. The weights of expected and past inflation of the Asian economies are consistent with the US but lower than the estimates from the Euro areas.
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Nayyar, Iffat. "Prediction of Optical Properties of Pi-Conjugated Organic Materials for Technological Innovations." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5993.
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Organic ?-conjugated solids are promising candidates for new optoelectronic materials. The large body of evidence points at their advantageous properties such as high charge-carrier mobility, large nonlinear polarizability, mechanical flexibility, simple and low cost fabrication and superior luminescence. They can be used as nonlinear optical (NLO) materials with large two-photon absorption (2PA) and as electronic components capable of generating nonlinear neutral (excitonic) and charged (polaronic) excitations. In this work, we investigate the appropriate theoretical methods used for the (a) prediction of 2PA properties for rational design of organic materials with improved NLO properties, and (b) understanding of the essential electronic excitations controlling the energy-transfer and charge-transport properties in organic optoelectronics. Accurate prediction of these electro-optical properties is helpful for structure-activity relationships useful for technological innovations.
In Chapter 1 we emphasize on the potential use of the organic materials for these two applications. The 2PA process is advantageous over one-photon absorption for deep-tissue fluorescence microscopy, photodynamic therapy, microfabrication and optical data storage owing to the three-dimensional spatial selectivity and improved penetration depth in the absorbing or scattering media. The design of the NLO materials with large 2PA cross-sections may reduce the optical damage due to the use of the high intensity laser beams for excitation. The organic molecules also possess self-localized excited states which can decay radiatively or nonradiatively to form excitonic states. This suggests the use of these materials in the electroluminescent devices such as light-emitting diodes and photovoltaic cells through the processes of exciton formation or dissociation, respectively. It is therefore necessary to understand ultrafast relaxation processes required in understanding the interplay between the efficient radiative transfer between the excited states and exciton dissociation into polarons for improving the efficiency of these devices. In Chapter 2, we provide the detailed description of the various theoretical methods applied for the prediction as well as the interpretation of the optical properties of a special class of substituted PPV [poly (p-phenylene vinylene)] oligomers.
In Chapter 3, we report the accuracy of different second and third order time dependent density functional theory (TD-DFT) formalisms in prediction of the 2PA spectra compared to the experimental measurements for donor-acceptor PPV derivatives. We recommend a posteriori Tamm-Dancoff approximation method for both qualitative and quantitative analysis of 2PA properties. Whereas, Agren's quadratic response methods lack the double excitations and are not suitable for the qualitative analysis of the state-specific contributions distorting the overall quality of the 2PA predictions. We trace the reasons to the artifactual excited states above the ionization threshold. We also study the effect of the basis set, geometrical constraints and the orbital exchange fraction on the 2PA excitation energies and cross-sections. Higher exchange (BMK and M05-2X) and range-separated (CAM-B3LYP) hybrid functionals are found to yield inaccurate predictions both quantitatively and qualitatively. The failure of the exchange-correlation (XC) functionals with correct asymptotic is traced to the inaccurate transition dipoles between the valence states, where functionals with low HF exchange succeed.
In Chapter 4, we test the performance of different semiempirical wavefunction theory methods for the prediction of 2PA properties compared to the DFT results for the same set of molecules. The spectroscopic parameterized (ZINDO/S) method is relatively better than the general purpose parameterized (PM6) method but the accuracy is trailing behind the DFT methods. The poor performances of PM6 and ZINDO/S methods are attributed to the incorrect description of excited-to-excited state transition and 2PA energies, respectively. The different semiempirical parameterizations can at best be used for quantitative analysis of the 2PA properties. The ZINDO/S method combined with different orders of multi-reference configuration interactions provide an improved description of 2PA properties. However, the results are observed to be highly dependent on the specific choice for the active space, order of excitation and reference configurations.
In Chapter 5, we present a linear response TD-DFT study to benchmark the ability of existing functional models to describe the extent of self-trapped neutral and charged excitations in PPV and its derivative MEH-PPV considered in their trans-isomeric forms. The electronic excitations in question include the lowest singlet (S1) and triplet (T1†) excitons, positive (P+) and negative (P-) polarons and the lowest triplet (T1) states. Use of the long-range-corrected DFT functional, such as LC-wPBE, is found to be crucial in order to predict the physically correct spatial localization of all the electronic excitations in agreement with experiment. The inclusion of polarizable dielectric environment play an important role for the charged states. The particle-hole symmetry is preserved for both the polymers in trans geometries. These studies indicate two distinct origins leading to self-localization of electronic excitations. Firstly, distortion of molecular geometry may create a spatially localized potential energy well where the state wavefunction self-traps. Secondly, even in the absence of geometric and vibrational dynamics, the excitation may become spatially confined due to energy stabilization caused by polarization effects from surrounding dielectric medium.
In Chapter 6, we aim to separate these two fundamental sources of spatial localization. We observe the electronic localization of P+ and P- is determined by the polarization effects of the surrounding media and the character of the DFT functional. In contrast, the self-trapping of the electronic wavefunctions of S1 and T1(T1†) mostly follows their lattice distortions. Geometry relaxation plays an important role in the localization of the S1 and T1† excitons owing to the non-variational construction of the excited state wavefunction. While, mean-field calculated P+, P- and T1 states are always spatially localized even in ground state S0 geometry. Polaron P+ and P- formation is signified by the presence of the localized states for the hole or the electron deep inside the HOMO-LUMO gap of the oligomer as a result of the orbital stabilization at the LC-wPBE level. The broadening of the HOMO-LUMO band gap for the T1 exciton compared to the charged states is associated with the inverted bond length alternation observed at this level. The molecular orbital energetics are investigated to identify the relationships between state localization and the corresponding orbital structure.
In Chapter 7, we investigate the effect of various conformational defects of trans and cis nature on the energetics and localization of the charged P+ and P- excitations in PPV and MEH-PPV. We observe that the extent of self-trapping for P+ and P- polarons is highly sensitive on molecular and structural conformations, and distribution of atomic charges within the polymers. The particle-hole symmetry is broken with the introduction of trans defects and inclusion of the polarizable environment in consistent with experiment. The differences in the behavior of PPV and MEH-PPV is rationalized based on their orbital energetics and atomic charge distributions. We show these isomeric defects influence the behavior and drift mobilities of the charge carriers in substituted PPVs.Ph.D.
Doctorate
Physics
Sciences
Physics
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Fischer, Michael. "Non-adiabatic quantum molecular dynamics: - Benchmark systems in strong laser fields - Approximate electron-nuclear correlations." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-148848.
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The non-adiabatic quantum molecular dynamics (NA-QMD) method couples self-consistently classical nuclear motion with time-dependent density functional theory (TDDFT) in basis expansion for the electron dynamics. It has become a versatile approach to study the dynamics of atoms, molecules and clusters in a wide range of scenarios. This work presents applications of the NA-QMD method to important benchmark systems and its systematic extension to include quantum effects in the nuclear motion.
Regarding the first objective, a complete study of the strong-field ionization and dissociation dynamics of nature’s simplest molecule H2+ is performed. By including all electronic and nuclear degrees of freedom and all reaction channels, molecular rotation is shown to play an important role in the ionization process. In addition, strong orientation effects in the energy deposition process of the Buckminster fullerene C60 in short intense laser pulses are surprisingly found in full dimensional calculations. Their consequences on the subsequent nuclear relaxation dynamics shed new light on available experimental data and future experiments are proposed to confirm the detailed predictions.
Regarding the second objective, the NA-QMD formalism is basically extended to take electron-nuclear correlations into account. This extension is achieved by means of a trajectory surface hopping scheme in the adiabatic Kohn-Sham framework. First studied examples from collision physics and photochemistry illustrate the relevance and importance of quantum effects in the nuclear dynamics.
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Martinho, Carla Alexandra Lopes. "Modelos vectoriais ARMA : estudo e potencialidades." Master's thesis, Instituto Superior de Economia e Gestão, 1997. http://hdl.handle.net/10400.5/21745.
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Mestrado em Matemática Aplicada à Economia e GestãoNeste trabalho vai-se proceder ao estudo e à aplicação prática sobre sucessões cronológicas reais dos modelos vectoriais ARMA. Estes modelos generalizam os modelos univariados ARMA e os modelos multivariados de função transferência, tendo vantagem sobre estes últimos porque permitem a análise conjunta de sucessões cronológicas que apresentam efeito de feedback. E de esperar que a modelação conjunta de sucessões potencie a capacidade de as descrever, obtendo-se ganhos significativos em termos previsionais. Deste modo, procerder-se-á ao estudo, com base na análise de dois exemplos concretos, do comportamento dos modelos vectoriais ARMA, conffontando-os com os resultados obtidos pelos modelos univariados e pelos modelos de função transferência.
The aim of this work is to present the methodology of the vectorial ARMA models applied to real time series. These models are generalisations of the univariate ARMA models and of the multivariate transfer function models. The advantage of the vectorial ARMA modelling is to allow the joint analysis of the time series which exhibit feedback effects. It is our intention to show that this joint modelization increases the capacity of describing and forecasting. The application was made with the use of two real examples comparing the results ffom the vectorial ARMA, the univariate and the transfer function modelling.
info:eu-repo/semantics/publishedVersion
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Freire, MÃrcio de Melo. "FunÃÃes de Green em mecÃnica estatÃstica." Universidade Federal do CearÃ, 2014. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=12311.
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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoNeste trabalho estabeleceremos as definiÃÃes das funÃÃes de Green em mecÃnica estatÃstica e suas propriedades bÃsicas. Estas funÃÃes dependem duplamente do tempo e da temperatura. Isto pode ser observado por meio de suas definiÃÃes, onde aparecem os valores mÃdios dos produtos de operadores. Neste caso a mÃdia à feita sobre o ensemble grÃo-canÃnico. Os operadores envolvidos nestas funÃÃes satisfazem a equaÃÃo de movimento de Heisenberg, o que nos permite descrever as equaÃÃes de evoluÃÃo para as funÃÃes de Green. Por meio da representaÃÃo espectral das funÃÃes de correlaÃÃo temporal, que à feita atravÃs da introduÃÃo de uma transformada de Fourier para mudar o sistema do espaÃo dos tempos para o espaÃo das frequÃncias, podemos obter as representaÃÃes espectrais para as funÃÃes de Green retardada, avanÃada e causal. Por Ãltimo, faremos o uso da funÃÃo de Green retardada para descrever a condutividade elÃtrica de um sistema de elÃtrons submetido a um campo elÃtrico externo dependente de tempo, em outras palavras, descreveremos o tensor de condutividade elÃtrica em termos da funÃÃo de Green retardada e, por Ãltimo, calcularemos a condutividade elÃtrica de um sistema de elÃtrons e fÃnons.
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Shalaginova, Daria. "Posouzení vybraných ukazatelů společnosti pomocí statistických metod." Master's thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2020. http://www.nusl.cz/ntk/nusl-414494.
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Master’s thesis is aimed at assessing the selected financial indicators of the company using statistical methods. Based on the results, the current situation of the company is evaluated. The thesis consists of three parts. The first part contains the necessary theoretical bases for processing the analytical part. The second part is devoted to the analysis of selected indicators, which are then applied statistical methods to the prediction of the future development of these indicators and findings, here between these indicators there is a dependence. At the end of this part, there is an evaluation of the analyzed indicators. The third part presents appropriate proposals for solutions to existing problems caused by indicators that deviate from the recommended values.
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Turisová, Alena. "Posouzení vybraných ukazatelů pomocí analýzy časových řad." Master's thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2017. http://www.nusl.cz/ntk/nusl-317063.
Full textAbstract:
Master's thesis deals with the assessment of selected financial indicators of the production company X in order to evaluate its performance and financial situation. Based on the results of the analyzes for the period 2008 to 2015 and the application of statistical methods of time series analysis and regression analysis, prognosis of future development of monitored indicators are obtained. Subsequently, the prognosis are used for the final formulating of proposals to improve future business efficiency of the company.
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Hourany, Karl. "Contribution à l'exploitation du bruit ambiant pour le contrôle santé intégré passif des barres et des tubes." Thesis, Valenciennes, 2015. http://www.theses.fr/2015VALE0039/document.
Full textAbstract:
Les travaux présentés dans ce manuscrit sont basés sur des études précédentes réalisées à l’Institut d’Électronique de Microélectronique et de Nanotechnologie (IEMN) de l’Université de Valenciennes et du Hainaut Cambrésis (UVHC). Ils concernent le développement d’un système de surveillance embarqué destiné au contrôle des matériaux et des structures utilisés dans différents domaines de transport (fluidique, tubulaire, aéronautique, ferroviaire…). Il s’agit du principe de Contrôle Santé Intégré CSI (ou SHM en anglais pour Structural Health Monitoring). L’idée est d’intégrer des capteurs sur les surfaces des structures à contrôler pour aboutir à un système de contrôle non destructif de ces dernières durant la totalité de leurs fonctionnements. Tout d’abord, les travaux réalisés à l’IEMN dans ce domaine sont illustrés, quelques définitions comme celles des ondes ultrasonores, du Contrôle Non Destructif et du Contrôle Santé Intégré sont rappelées, avant d’aborder l’explication du passage d’un contrôle actif à un contrôle passif. Dans un deuxième temps, un algorithme de comparaison d’images basé sur les minimums locaux présents dans ces images a été proposé et testé sur des images simples de seize pixels, et a permis de tester le degré de ressemblance entre elles. L’explication de l’algorithme développé est divisée en deux grandes parties. Dans la première nous expliquons comment extraire les minimums locaux d’une image. La deuxième partie expose la procédure pour déterminer le taux de ressemblance entre les images. La simulation de la propagation d’un signal dans une plaque réverbérante et l’obtention des images temps-fréquence correspondantes à des corrélations filtrées (autocorrélation) ont été décrites. L’algorithme proposé a été validé sur ces images, permettant ainsi la localisation d’une position inconnue de la sourceThe works presented in this manuscript are based on previous studies conducted at the Institute of Electronics Microelectronics and Nanotechnology of the University of Valenciennes and Hainaut Cambrésis. They concern the development of an embedded monitoring system for the control of materials and structures used in different transport domains (pipeline, aerospace, railway ...). This is the Structural Health-Monitoring principle. The idea is to integrate sensors into the surfaces of the controlled structures in order to achieve a non-destructive control system for the control of the latter during their entire lifetime. First the work done at the laboratory in this domain, are illustrated, some definitions such as ultrasonic waves, the Non Destructive Testing and the Structural Health Monitoring are recalled, to switch later to the explanation of the passage from an active control to a passive control. In a second step, an images comparison algorithm based on the local minima present in these images has been proposed and tested on simple images of sixteen pixels and was used to test the degree of resemblance between them. The explanation of the developed algorithm is divided into two parts. In the first one, we explain how to extract the local minima of an image. The second part describes the procedure for determining the rate of resemblance between the images. The simulation of the propagation of a signal in a reverberant plate and the obtaining of the frequency time images corresponding to filtered correlation (autocorrelation) has been described. The algorithm was validated on those images allowing the localization of an unknown source position
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Ricci, Lorenzo. "Essays on tail risk in macroeconomics and finance: measurement and forecasting." Doctoral thesis, Universite Libre de Bruxelles, 2017. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/242122.
Full textAbstract:
This thesis is composed of three chapters that propose some novel approaches on tail risk for financial market and forecasting in finance and macroeconomics. The first part of this dissertation focuses on financial market correlations and introduces a simple measure of tail correlation, TailCoR, while the second contribution addresses the issue of identification of non- normal structural shocks in Vector Autoregression which is common on finance. The third part belongs to the vast literature on predictions of economic growth; the problem is tackled using a Bayesian Dynamic Factor model to predict Norwegian GDP.Chapter I: TailCoRThe first chapter introduces a simple measure of tail correlation, TailCoR, which disentangles linear and non linear correlation. The aim is to capture all features of financial market co- movement when extreme events (i.e. financial crises) occur. Indeed, tail correlations may arise because asset prices are either linearly correlated (i.e. the Pearson correlations are different from zero) or non-linearly correlated, meaning that asset prices are dependent at the tail of the distribution.Since it is based on quantiles, TailCoR has three main advantages: i) it is not based on asymptotic arguments, ii) it is very general as it applies with no specific distributional assumption, and iii) it is simple to use. We show that TailCoR also disentangles easily between linear and non-linear correlations. The measure has been successfully tested on simulated data. Several extensions, useful for practitioners, are presented like downside and upside tail correlations.In our empirical analysis, we apply this measure to eight major US banks for the period 2003-2012. For comparison purposes, we compute the upper and lower exceedance correlations and the parametric and non-parametric tail dependence coefficients. On the overall sample, results show that both the linear and non-linear contributions are relevant. The results suggest that co-movement increases during the financial crisis because of both the linear and non- linear correlations. Furthermore, the increase of TailCoR at the end of 2012 is mostly driven by the non-linearity, reflecting the risks of tail events and their spillovers associated with the European sovereign debt crisis. Chapter II: On the identification of non-normal shocks in structural VARThe second chapter deals with the structural interpretation of the VAR using the statistical properties of the innovation terms. In general, financial markets are characterized by non- normal shocks. Under non-Gaussianity, we introduce a methodology based on the reduction of tail dependency to identify the non-normal structural shocks.Borrowing from statistics, the methodology can be summarized in two main steps: i) decor- relate the estimated residuals and ii) the uncorrelated residuals are rotated in order to get a vector of independent shocks using a tail dependency matrix. We do not label the shocks a priori, but post-estimate on the basis of economic judgement.Furthermore, we show how our approach allows to identify all the shocks using a Monte Carlo study. In some cases, the method can turn out to be more significant when the amount of tail events are relevant. Therefore, the frequency of the series and the degree of non-normality are relevant to achieve accurate identification.Finally, we apply our method to two different VAR, all estimated on US data: i) a monthly trivariate model which studies the effects of oil market shocks, and finally ii) a VAR that focuses on the interaction between monetary policy and the stock market. In the first case, we validate the results obtained in the economic literature. In the second case, we cannot confirm the validity of an identification scheme based on combination of short and long run restrictions which is used in part of the empirical literature.Chapter III :Nowcasting NorwayThe third chapter consists in predictions of Norwegian Mainland GDP. Policy institutions have to decide to set their policies without knowledge of the current economic conditions. We estimate a Bayesian dynamic factor model (BDFM) on a panel of macroeconomic variables (all followed by market operators) from 1990 until 2011.First, the BDFM is an extension to the Bayesian framework of the dynamic factor model (DFM). The difference is that, compared with a DFM, there is more dynamics in the BDFM introduced in order to accommodate the dynamic heterogeneity of different variables. How- ever, in order to introduce more dynamics, the BDFM requires to estimate a large number of parameters, which can easily lead to volatile predictions due to estimation uncertainty. This is why the model is estimated with Bayesian methods, which, by shrinking the factor model toward a simple naive prior model, are able to limit estimation uncertainty.The second aspect is the use of a small dataset. A common feature of the literature on DFM is the use of large datasets. However, there is a literature that has shown how, for the purpose of forecasting, DFMs can be estimated on a small number of appropriately selected variables.Finally, through a pseudo real-time exercise, we show that the BDFM performs well both in terms of point forecast, and in terms of density forecasts. Results indicate that our model outperforms standard univariate benchmark models, that it performs as well as the Bloomberg Survey, and that it outperforms the predictions published by the Norges Bank in its monetary policy report.Doctorat en Sciences économiques et de gestion
info:eu-repo/semantics/nonPublished
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Allam, Lévi. "Etude de la diffusion unidimensionnelle dans les chaines finies : application au tmmc-cd." Toulouse 3, 1987. http://www.theses.fr/1987TOU30063.
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Etude rpe de (ch::(3))::(4) nmn::(1-x) cd::(x) cl::(5) entre 20 et 300 k, pour x = 0,02; 0,08 et 0,2; mesure des temps de relaxation spin-reseau. Mise en evidence de variations importantes en fonction de la composition. Interpretation des resultats au moyen du formalisme de la fonction memoire et d'un modele de la fonction de correlation de spins des chaines finies
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Dejean, de La Batie Rémi. "Etude des mouvements moléculaires dans les polymères en masse par résonance magnétique nucléaire du 13c et simulation de Monte-Carlo." Paris 6, 1986. http://www.theses.fr/1986PA066284.
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Etude des mouvements locaux dans le polyvinylmethylether, le polybutadiene-1,4cis et le polyisoprene-1,4cis, le polyisobutène, les polyéthers en masse; polyoxypropylène et réseaux de polyoxyéthylène, influence de la microstructure sur les mouvements moléculaires locaux. Etude de la transition vitreuse dans les polymères en masse par simulation de Monte-Carlo dynamique; simulation de systemes de polymères places dans le réseau tétraédrique et simulation de systemes de sphères libres et de systemes de polymères en milieu continu.
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Hunter, Brandon. "Channel Probing for an Indoor Wireless Communications Channel." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/64.
Full textAbstract:
The statistics of the amplitude, time and angle of arrival of multipaths in an indoor environment are all necessary components of multipath models used to simulate the performance of spatial diversity in receive antenna configurations. The model presented by Saleh and Valenzuela, was added to by Spencer et. al., and included all three of these parameters for a 7 GHz channel. A system was built to measure these multipath parameters at 2.4 GHz for multiple locations in an indoor environment. Another system was built to measure the angle of transmission for a 6 GHz channel. The addition of this parameter allows spatial diversity at the transmitter along with the receiver to be simulated. The process of going from raw measurement data to discrete arrivals and then to clustered arrivals is analyzed. Many possible errors associated with discrete arrival processing are discussed along with possible solutions. Four clustering methods are compared and their relative strengths and weaknesses are pointed out. The effects that errors in the clustering process have on parameter estimation and model performance are also simulated.
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Smith, Kyle Kurt Gabriel. "Approximate quantum dynamics methods for time correlation functions." Thesis, 2014. http://hdl.handle.net/2152/24986.
Full textAbstract:
The dynamic structure factor of liquid para-hydrogen and ortho-deuterium in corresponding thermodynamic states, (T = 20.0 K, n = 21.24 nm⁻³) and (T = 23.0 K, n = 24.61 nm⁻³) respectively, has been computed by both the Feynman-Kleinert linearized path-integral (FK-LPI) and Ring-Polymer Molecular Dynamics (RPMD) methods and compared with Inelastic X-ray Scattering spectra. The combined use of computational and experimental methods enables a reduction in experimental uncertainties for the determination of the true sample spectrum. Furthermore, the refined experimental spectrum of para-hydrogen and ortho-deuterium is consistently reproduced by both FK-LPI and RPMD at momentum transfers lower than 12.8nm⁻¹. At larger momentum transfers the F K - LP I results agree with experiment much better for ortho-deuterium than for para-hydrogen. More specifically we found that for k ~ 20.0 nm⁻¹ para-hydrogen provides a test case for improved approximations to quantum dynamics. We meet this demand for an improved approximate quantum dynamics method by developing two classes of quasi-classical dynamics that are shown to conserve the initial quantum ensemble when used in conjunction with the Feynman-Kleinert approximation of the density operator. As shown, both classes of dynamics are able to recover the exact classical and high temperature limits of the quantum time correlation function, while a subset is able to recover the exact harmonic limit. A comparison of the approximate quantum time correlation functions obtained from both classes of dynamics are made with the exact results for the challenging model problems of the quartic and double-well potentials. It is found that this new Feynman-Kleinert Quasi-Classical Wigner (FK-QCW) method provides a great improvement over the Feynman-Kleinert implementation of the classical Wigner approximation, also known as FK-LPI, in which purely classical dynamics are used. Furthermore, it is shown that the first class of dynamics reduces to Centroid Molecular Dynamics (CMD) when used within the framework of the classical Wigner approximation for the Kubo transformed time correlation function. Finally, we apply the Feynman-Kleinert Quasi-Classical Wigner (FK- QCW) method to the same liquid para-hydrogen and ortho-deuterium system, previously studied using FK-LPI and RPMD. When applied to this challenging system, it is shown that this new FK-QCW method consistently reproduces the experimental dynamic structure factor for all momentum transfers considered. This shows that FK-QCW provides a great improvement over FK-LPI for not only model problems, but also realistic systems. Furthermore, for small momentum transfers, where RPMD is applicable, it is shown that FK-QCW provides nearly the same results as RPMD, thus suggesting that FK-QCW provides a potentially more appealing algorithm than RPMD since one is not limited to correlation functions involving linear operators. This then suggests that the FK-QCW method is a top contender in the realm of approximate quantum dynamics methods which allow for the practical evaluation of time correlation functions.text
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(10712730), Zizhuang Wu. "Non-Fully Symmetric Space-Time Matern-Cauchy Correlation Functions." Thesis, 2021.
Find full textAbstract:
In spatio-temporal data analysis, the problem of non-separable space-time covariance functions is important and hard to deal with. Most of the famous constructions of these covariance functions are fully symmetric, which is inappropriate in many spatiotemporal processes. The Non-Fully Symmetric Space-Time (NFSST) Matern model by Zhang, T. and Zhang, H. (2015) provides a way to construct a non-fully symmetric non-separable space-time correlation function from marginal spatial and temporal Matern correlation functions.
In this work we use the relationship between the spatial Matern and temporal Cauchy correlation functions and their spectral densities, and provide a modification to their Bochner’s representation by including a space-time interaction term. Thus we can construct a non-fully symmetric space-time Matern-Cauchy model, from any given marginal spatial Matern and marginal temporal Cauchy correlation functions. We are able to perform computation and parameter estimate on this family, using the Taylor expansion of the correlation functions. This model has attractive properties: it has much faster estimation compared with NFSST Matern model when the spatio-temporal data is large; it enables the existence of temporal long-range dependence (LRD), adding substantially to the flexibility of marginal correlation function in the time domain. Several spatio-temporal meteorological data sets are studied using our model, including one case with temporal LRD.
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Kegerreis, Jeb Stuart. "Quantum mechanical calculations of time correlation functions for neat fluids /." 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3362936.
Full textAbstract:
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009.Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3526. Adviser: Nancy Makri. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.
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Tsai, Yu-An, and 蔡宇安. "Non-Markovain Two-Time correlation functions: Exact Result v.s Perturbation Approach." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/22443886533994020497.
Full textAbstract:
碩士國立臺灣大學
物理研究所
99
A two-level system which decays spontaneously into field vacuum is studied through the Jaynes-Cummings model in the rotating wave approximation (RWA).When at most one excitation is considered, this model is exactly solvable. Here we evaluate the non-Markovian two-time correlation functions (CF''s) of system operators for this model in two ways: one by directly solving the system-environment evolution,and the other by using the perturbative time-convolutionless non-Markovian master equation approach. We derive valid to fourth order in system-bath coupling strength a non-Markovain evolution equation for the two-time CF''s of system operators. We use the derived evolution equation to calculate a two-time CF for the two-level model and compare it with the exact result obtained by direct evaluation. Another numerical series acceleration method is applied to the calculation of the perturbation decay, and this method is found to improve the accuracy of the evolution equation. The result obtained by the derived perturbative two-time evolution equation is much better than those by the perturbative Markovian Quantum regression theorem(QRT), the non-Markovian QRT and exact QRT as it agrees more closely with the exact result even when the model is in the regime where the bath correlation time is comparable to the system relaxation time.This demonstrates the validity and usefulness of our derived non-Markovain two-time evolution equation. The exact spontaneous emission spectrum is also calcukated, and it has very different behaviours in the strong coupling an the weak coupling regions.
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Wang, Yu-Jen, and 王佑仁. "Quantum Correction on Bath Time-Correlation Functions: Applications on Excitation Energy Transfer Dynamics." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/x3k6pc.
Full textAbstract:
碩士國立臺灣大學
化學研究所
106
Quantum correction is necessary when calculating dissipative quantum dynamics based on results from classical molecular dynamics simulation in which quantum effects are ignored. Quantum correction has been used in many fields to make use of classical trajectories in quantum simulations, such as calculation of infrared spectra. However, in the context of excitation energy transfer in molecular system, the need of applications of quantum corrections is less discussed. In this study, we examine four quantum correction methods, including the Harmonic method and the Standard method proposed by other groups previously, and the Fitting method and the Prony method proposed by us. We aim to elucidate the performance of the correction by the four correc- tion methods in order to properly apply them to simulating excitation energy transfer dynamics. We focus on a model that describes a two-level system linearly coupled to a harmonic bath to explore the applicability of quantum correction methods in various parameter conditions. Our results reveal the necessity of applying quantum correction when studying excitation energy transfer dynamics based on results of classical molecular dynamics simula- tion. Our calculations also conclude that the Harmonic method performs the best among the four approaches and that the Prony method has serious draw- backs. The Fitting method provides similar results as the Standard method, and both methods perform well at a higher temperature or in the condition where relaxation is driven by coherent evolution.
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Chou, Wen-Chi, and 周文祺. "The theoretical studies of time-correlation functions with the first principle molecular dynamics simulations on surfaces." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/98002793656230998703.
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博士淡江大學
化學學系博士班
95
We successfully developed a series of IR spectrum simulation and corresponding spectrum analysis methods for studying the vibrational dynamics and the reaction dynamics of both molecular and surface systems. The time-correlation function theories were thoroughly studied to build 1) the Fourier trnsformed dipole-moment AutoCorrelation Function(dpACF) for IR spectrum simulation, 2) the Partial Dipole-moment AutoCorrelatoin Function(PaDAF) and the Structural Coordinate AutoCorrelation Function(SCAF) schemes for spectrum analysis, and 3) the Fourier transformed anisotropic dpACF for the IR spectrum simulations on surface systems. By utilizing Density Functional Theory in connection with accurate LCAO basis sets and norm-conserving pseudopotentials, efficient Born-Oppenheimer molecular dynamics(BOMD) simulations would thereby be performed to study the reaction dynamics of adsorbed molecules on surfaes at microscopic level. First of all, our IR spectrum simulation methods were validated by calculating the IR spectra of a series of organic molecules. Based on the success of IR spectrum simulations on gas-phase molecules, furthermore, we employed this IR spectrum simulation and analysis scheme to Si(100) clean surface, monohydride saturated Si(100) surface, i.e. H-Si(100)-2x1 surface, adsorbed styrenes on Si(100) surfaces, and adsorbed one dimensional(1-D) styrene molecular wire on Si(100) surface. Spectrum simulation results for these surface systems are also qualitatively consistent with experimental measurements. In addition, we also successfully studied the reaction dynamics, Partial Density of States(PDOS) evolutions, and the vibrational dynamics within several picoseconds for two kinds of surface reactions of adsorbed styrene on Si(100) surface, say, (1) the [2+2] cycloaddition of styrene on Si(100), and (2) the self-directed growth of 1-D styrene molecular wire on Si(100) via the H-abstraction reaction. On the other hand, we also calculated the transition state structures and their corresponding PDOS variations, however, our results show that the one dimensionality of styrene molecular wire is due to two possible lower energy barrier pathways of H-abstraction along dimer row direction. Finally, we also studied the effects on both IR spectrum of H-Si(100) and the charge dynamics of styrene-Si(100)-H under external electric field. The results show that the H-Si vibrational frequency could be red-shifted or blue-shifted under the presence of external electric field along surface normal, depending on the direction of the electric field. Charge redistribution dynamics of styrene-Si(100)-H accompanying the structure relaxation within 250 femtoseconds were also observed after turning on the external electric field.
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Kuo, Hua-Cheng, and 郭華丞. "The Time Correlation Function in Single Electron Tunneling." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/14938511834529623079.
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廖婉婷. "Correlation between functional MRI signal and reaction time." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/89359377332770651949.
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碩士國立清華大學
原子科學系
90
Functional magnetic resonance imaging (fMRI) detects hemodynamic responses with high spatial and temporal resolution. Capabilities of correlating psychophysical parameters with fMRI allow a better understanding of the neuronal processes. The objective of this study is to examine how fMRI BOLD response parameters vary with behavioral outcome measures (e.g. reaction time). We utilized a lexical decision task with two character-frequency levels and pseudocharaters. In the left inferior frontal lobe, the activation volumes were smaller to high-frequency characters than to low-frequency characters and pseudocharacters (587±261 vs. 3280±822 mm3, 587±261 vs. 2025±548 mm3 ), which is correlated well with the reaction times (417±9 vs. 631±22 ms, 417±9 vs. 658±15 ms ). The linear correlation between the measured reaction times and FWHM (full width half maximum) of the fMRI responses was also observed in the left inferior frontal lobe (p＜0.001). There was no significant correlation between reaction time and onset time of the hemodynamic response. These findings imply left inferior frontal lobe is active during the entire reaction time when executing the lexical decision task. Conversely, the FWHM of fMRI responses in the left primary motor cortex (M1) related to pressing a button for responding at the end of task is not correlated to reaction time. Our results are also coherent with respect to a functional model of lexical decision task. Thus, the different patterns of neuronal activity during the cognitive process could be detected and distinguished through the fMRI hemodynamic responses. In this study, we have demonstrated that the time-resolved fMRI technique has the capacity to exploit the cognitive events by tracing in the temporal responses of fMRI, even if the reaction time is at the time scale of hundred milliseconds.
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Sebatjane, Phuti. "Understanding patterns of aggregation in count data." Diss., 2016. http://hdl.handle.net/10500/22067.
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The term aggregation refers to overdispersion and both are used interchangeably in this thesis. In addressing the problem of prevalence of infectious parasite species faced by most rural livestock farmers, we model the distribution of faecal egg counts of 15 parasite species (13 internal parasites and 2 ticks) common in sheep and goats. Aggregation and excess zeroes is addressed through the use of generalised linear models. The abundance of each species was modelled using six different distributions: the Poisson, negative binomial (NB), zero-inflated Poisson (ZIP), zero-inflated negative binomial (ZINB), zero-altered Poisson (ZAP) and zero-altered negative binomial (ZANB) and their fit was later compared. Excess zero models (ZIP, ZINB, ZAP and ZANB) were found to be a better fit compared to standard count models (Poisson and negative binomial) in all 15 cases. We further investigated how distributional assumption a↵ects aggregation and zero inflation. Aggregation and zero inflation (measured by the dispersion parameter k and the zero inflation probability) were found to vary greatly with distributional assumption; this in turn changed the fixed-effects structure. Serial autocorrelation between adjacent observations was later taken into account by fitting observation driven time series models to the data. Simultaneously taking into account autocorrelation, overdispersion and zero inflation
proved to be successful as zero inflated autoregressive models performed better than zero inflated models in most cases. Apart from contribution to the knowledge of science, predictability of parasite burden will help farmers with effective disease management interventions. Researchers confronted with the task of analysing count data with excess zeroes can use the findings of this illustrative study as a guideline irrespective of their research discipline. Statistical methods from model selection, quantifying of zero inflation through to accounting for serial autocorrelation are described and illustrated.Statistics
M.Sc. (Statistics)
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Hsu, Chih-Chi, and 許植棋. "Orientational time correlation function of liquid water : fourth cumulant." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/7deptd.
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碩士國立交通大學
物理研究所
102
In this thesis, with the SPC/E model of liquid water, I extent the calculations for the orientational correlation function (OCF) up to the fourth cumulant expansion. By the instantaneous normal mode (INM) theory or the power spectra of the angular velocity autocorrelation function (AVAF), we predict the behavior of the OCFs in the short and long time regimes and estimate the time scales for different regimes by using the asymptotic functions of the cumulant expansion. Besides, by Voronoi polyhedra (VP) analysis for liquids generated with classical MD simulations, we study the local-structure effects on the OCFs of this water model. In the short-time regime, the OCFs is a Gaussian decay, no matter what kind of rotational spectrum is used for calculation. In the long-time regime, the behavior of the OCFs predicted by the second cumulant expansion is a single exponential decay calculated with the AVAF spectrum and a logarithmic divergence calculated with the stable-INM spectrum. Up to the fourth cumulant expansion, the long-rime behavior of the OCFs calculated with the stable-INM spectrum agrees well with the results of MD simulation.
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CHEN, YUEH-FU, and 陳岳甫. "Examining the Correlation Between Accommodative Function and Time Duration of Smartphone Usage." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/k39dh7.
Full textAbstract:
碩士中臺科技大學
生物科技暨醫學工程研究所
106
Introduction In recent years, the smartphone has become increasingly popular over traditional desktop PC or laptop due to its convenience of use and portability. However, as with traditional video display screens, which can cause a variety of visual symptoms when used in prolonged period of time, the greater frequency of mobile device usage in today’s digital savvy world also prompted an array of visual symptoms and much more. Digital eye strain related to electronic displays affect visual functions that include accommodation and vergence. However, investigation into the accommodative effect of smartphone use with time has not been thoroughly studied before. In this work, we set out to perform a better controlled experiment to examine the correlation between duration of smartphone use and accommodative functions. Method A total of 31 normal subjects were enrolled in this prospective study to test for accommodative amplitude, response, and facility using a specially designed chin apparatus to minimize inaccuracies in the measurements. Accommodative functions were tested with minus lens to blur, monocular estimation method (MEM), and monocular flipper test after 10, 20, and 30 minutes of smartphone use on separate occasions. Subjective data were collected in form of visual discomfort survey before and after each testing period. Results and Discussion The monocular accommodative amplitude was significantly decreased while visual discomfort increased after smartphone use for 10, 20 and 30 minutes. The accommodative lag after smartphone work was also significantly greater after 20 and 30 minutes of smartphone use. Accommodative facility did not changed significantly after smartphone use for each time period tested. Visual discomfort was not found to be correlated to a decrease in accommodative functions, but may be related to dry eye or binocular vision function. Conclusion After 10 minutes of smartphone use, accommodative function and visual comfort were affected, which means that the 20/20/20 rule may not be a suitable health tip to alleviate the health burden caused by smartphone usage. Therefore, a new health recommendation should be tailored to the smartphone, which exerts more stress and requires greater demands on the visual system than the traditional digital monitors or displays.
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Pai, Yu-Fan, and 白馭帆. "The time series analysis of human heart rate — the application of partial auto-correlation function and intervention models." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/21403947985615865228.
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碩士東海大學
統計學系
97
This research applied the time series analysis to the data of human heartbeat. The main purpose of this research was to investigate the auto-correlation of heartbeat under steady conditions and the level of increase in heartbeat under external stimuli. The heartbeat data of patients with autonomic neuropathy and normal people were used. Partial autocorrelation function and intervention model were used to estimate the autocorrelation of heartbeat and the level of increase in heartbeat under stimuli, and the results served to distinguish between patients with autonomic neuropathy and normal people. According to the analysis, the values of the second order partial autocorrelation function of normal people were mostly significantly negative and those of patients were not. The heartbeat time series data of normal people were best described by mixed autoregressive moving average processes while those of patients were modeled as autoregressive processes. The magnitude of increase in heartbeat in normal people when external stimuli were applied was significantly larger than that of patients. The above results may provide an alternative way for determining whether subjects suffer from autonomic neuropathy.
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Kudela, Maria Aleksandra. "Statistical methods for high-dimensional data with complex correlation structure applied to the brain dynamic functional connectivity studyDY." Diss., 2017. http://hdl.handle.net/1805/12835.
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Indiana University-Purdue University Indianapolis (IUPUI)A popular non-invasive brain activity measurement method is based on the functional magnetic resonance imaging (fMRI). Such data are frequently used to study functional connectivity (FC) defined as statistical association among two or more anatomically distinct fMRI signals (Friston, 1994). FC has emerged in recent years as a valuable tool for providing a deeper understanding of neurodegenerative diseases and neuropsychiatric disorders, such as Alzheimer's disease and autism. Information about complex association structure in high-dimensional fMRI data is often discarded by a calculating an average across complex spatiotemporal processes without providing an uncertainty measure around it. First, we propose a non-parametric approach to estimate the uncertainty of dynamic FC (dFC) estimates. Our method is based on three components: an extension of a boot strapping method for multivariate time series, recently introduced by Jentsch and Politis (2015); sliding window correlation estimation; and kernel smoothing. Second, we propose a two-step approach to analyze and summarize dFC estimates from a task-based fMRI study of social-to-heavy alcohol drinkers during stimulation with avors. In the first step, we apply our method from the first paper to estimate dFC for each region subject combination. In the second step, we use semiparametric additive mixed models to account for complex correlation structure and model dFC on a population level following the study's experimental design. Third, we propose to utilize the estimated dFC to study the system's modularity defined as the mutually exclusive division of brain regions into blocks with intra-connectivity greater than the one obtained by chance. As a result, we obtain brain partition suggesting the existence of common functionally-based brain organization. The main contribution of our work stems from the combination of the methods from the fields of statistics, machine learning and network theory to provide statistical tools for studying brain connectivity from a holistic, multi-disciplinary perspective.
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Fleig, Timo [Verfasser]. "Wave function based relativistic multi-reference electron correlation methods : development and application to atomic and molecular properties / Timo Fleig." 2007. http://d-nb.info/984672672/34.
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Balasubramaniyan, Rajarajeswari [Verfasser]. "Gene expression data analysis using novel methods : predicting time delayed correlations and evolutionarily conserved functional modules / vorgelegt von Rajarajeswari Balasubramaniyan." 2005. http://d-nb.info/976420724/34.
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Fischer, Michael. "Non-adiabatic quantum molecular dynamics: - Benchmark systems in strong laser fields - Approximate electron-nuclear correlations: Non-adiabatic quantum molecular dynamics: - Benchmark systems in strong laser fields - Approximate electron-nuclear correlations." Doctoral thesis, 2013. https://tud.qucosa.de/id/qucosa%3A28198.
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The non-adiabatic quantum molecular dynamics (NA-QMD) method couples self-consistently classical nuclear motion with time-dependent density functional theory (TDDFT) in basis expansion for the electron dynamics. It has become a versatile approach to study the dynamics of atoms, molecules and clusters in a wide range of scenarios. This work presents applications of the NA-QMD method to important benchmark systems and its systematic extension to include quantum effects in the nuclear motion.
Regarding the first objective, a complete study of the strong-field ionization and dissociation dynamics of nature’s simplest molecule H2+ is performed. By including all electronic and nuclear degrees of freedom and all reaction channels, molecular rotation is shown to play an important role in the ionization process. In addition, strong orientation effects in the energy deposition process of the Buckminster fullerene C60 in short intense laser pulses are surprisingly found in full dimensional calculations. Their consequences on the subsequent nuclear relaxation dynamics shed new light on available experimental data and future experiments are proposed to confirm the detailed predictions.
Regarding the second objective, the NA-QMD formalism is basically extended to take electron-nuclear correlations into account. This extension is achieved by means of a trajectory surface hopping scheme in the adiabatic Kohn-Sham framework. First studied examples from collision physics and photochemistry illustrate the relevance and importance of quantum effects in the nuclear dynamics.
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Koubek, Antonín. "Bodové procesy v čase a prostoru." Master's thesis, 2013. http://www.nusl.cz/ntk/nusl-320988.
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In this work we present an introduction to the theory of point processes in space and time with focus on space--time shot--noise Cox process. Further from theoretical point of view we study its simulation, space--time separability, kernel estimate of intensity function and non--parametric estimation of some summary statistics using edge corrections. For two ambit models and one space--time separable model we do numerical calculations using the presented theory and software Wolfram Mathematica 9.0. For these three models we do simulations, we select the best bandwidth for kernel estimate of the intensity function and we also calculate some theoretical summary statistics including the pair correlation function. Powered by TCPDF (www.tcpdf.org)
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Ghosh, Siddharth. "Nanoscale Photonics." Doctoral thesis, 2016. http://hdl.handle.net/11858/00-1735-0000-0023-3ED4-2.
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