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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
191

Some aspects of curvature in general relativity

Rendall, Alan D. January 1987 (has links)
The purpose of this thesis is to study in depth the relationship between the curvature of space-time and the other geometrical objects which naturally arise in general relativity. Most of the results obtained apply to the generic case. Chapter 1 contains a discussion of certain aspects of fibre bundle theory required in later chapters which may be unfamiliar to many relativists, while chapter 2 contains preliminary material on curvature in relativity and proves a continuity property of the algebraic classification of the Weyl and energy-momentum tensors. Chapter 3 describes the generic behaviour of the Riemann, Weyl and energy-momentum tensors, and chapter 5 goes on to use this description to investigate the relationship of the Riemann tensor to the metric, conformal class and connection of space-time in the generic case. In particular it is proved that the Riemann tensor uniquely and continuously determines the connections. The information obtained in chapter 3 on the algebraic type of curvature in the general case is related in chapter 4 to the topology of the underlying manifold. In chapter 6 a topology is defined on the set of sectional curvatures of all Lorentz metrics on a given manifold. The remainder of the chapter attempts to do for the sectional curvature what was done for the Riemann tensor in chapter 5 but, because sectional curvature is more difficult to handle, the results obtained are necessarily more modest.
192

Exploring time perception and related neural activity in ADHD and non-ADHD young adults.

Viviers, Jean-Pierre 05 September 2014 (has links)
Attention-Deficit Hyperactivity Disorder (ADHD) is one of the most prevalent disorders diagnosed in children. However, less is known about the clinical manifestation of the disorder in adults and the impact thereof on for instance social and occupational functioning. With respect to temporal perception deficits in both child and adult ADHD, contemporary findings have produced mixed results. In line with this, the current investigation aimed to identify whether young adults who possess significant ADHD symptomology have pure time perception deficits and/or differences in self-reported habitual time perception. Stratification of the ADHD and non-ADHD group was achieved using the Adult ADHD Self-report Scale (ASRS V1.1). Between group differences in self-reported temporal orientation was investigated using the Zimbardo Time Perspective Inventory (ZTPI). These outcome scores were compared using an ANOVA. The investigation into pure psychophysical time perception was conducted on a sub sample of that used in the self-report investigation. The ADHD group consisted of 12 participants whereas the non-ADHD group consisted of 10 participants. These two groups conducted temporal estimation and temporal discrimination tasks. Between groups, performances on these tasks were compared using an ANOVA. In addition to this, electroencephalography (EEG) recordings of frontal, frontal midline and parietal activity during resting states and task performance were conducted. This allowed for between group comparisons in absolute and relative power scores at four different frequency bands (delta, theta, alpha and beta) to be made. A non-parametric Mann-Whitney-U test was used in this regard. The same statistical technique was used to compare the theta/beta ratios elicited by the resting state and temporal perception conditions. Results showed that those with significant ADHD symptomology have a characteristically different selfreported habitual time perception. This is illustrated by negative thoughts towards past and present life events, and an absence of future orientated behaviour. In terms of the objective psychophysical measures, the current investigation found no group differences in estimation or discrimination task performance. Despite this absence of difference, the group with significant ADHD symptomology showed significantly different EEG recorded neural activity, during resting states and during task performance. The nature of this activity was in line with a generalised cortical under arousal hypothesis of ADHD. Taken together, these findings indicate that individuals with significant ADHD symptomology do not only consciously perceive time differently to those who do not have significant symptomology, but also show different neuro-physiological processes when performing tasks that require the utilisation of temporal processing mechanisms. In this way, the findings provide insight into possible objective measures that could be utilised in ADHD diagnosis.
193

Essays in time series analysis

Huang, Naijing January 2015 (has links)
Thesis advisor: Zhijie Xiao / I have three chapters in my dissertation. The first chapter is about the estimation and inference for DSGE model; the second chapter is about testing financial contagion among stock markets, and in the last chapter, I propose a new econometrics method to forecast inflation interval. This first chapter studies proper inference and asymptotically accurate structural break tests for parameters in Dynamic Stochastic General Equilibrium (DSGE) models in a maximum likelihood framework. Two empirically relevant issues may invalidate the conventional inference procedures and structural break tests for parameters in DSGE models: (i) weak identification and (ii) moderate parameter instability. DSGE literatures focus on dealing with weak identification issue, but ignore the impact of moderate parameter instability. This paper contributes to the literature via considering the joint impact of two issues in DSGE framework. The main results are: in a weakly identified DSGE model, (i) moderate instability from weakly identified parameters would not affect the validity of standard inference procedures or structural break tests; (ii) however, if strongly identified parameters are featured with moderate time-variation, the asymptotic distributions of test statistics would deviate from standard ones and would no longer be nuisance parameter free, which renders standard inference procedures and structural break tests invalid and provides practitioners misleading inference results; (iii) as long as I concentrate out strongly identified parameters, the instability impact of them would disappear as the sample size goes to infinity, which recovers the power of conventional inference procedure and structural break tests for weakly identified parameters. To illustrate my results, I simulate and estimate a modified version of the Hansen (1985) Real Business Cycle model and find that my theoretical results provide reasonable guidance for finite sample inference of the parameters in the model. I show that confidence intervals that incorporate weak identification and moderate parameter instability reduce the biases of confidence intervals that ignore those effects. While I focus on DSGE models in this paper, all of my theoretical results could be applied to any linear dynamic models or nonlinear GMM models. The second chapter, regarding the asymmetric and leptokurtic behavior of financial data, we propose a new contagion test in the quantile regression framework that is robust to model misspecification. Unlike conventional correlation-based tests, the proposed quantile contagion test allows us to investigate the stock market contagion at various quantiles, not only at the mean. We show that the quantile contagion test can detect a contagion effect that is possibly ignored by correlation-based tests. A wide range of simulation studies show that the proposed test is superior to the correlation-based tests in terms of size and power. We compare our test with correlation-based tests using three real data sets: the 1994 Tequila crisis, the 1997 Asia crisis, and the 2001 Argentina crisis. Empirical results show substantial differences between two types of tests. In the third chapter, I use Quantile Bayesian Approach-- to do the interval forecast for inflation in the semi-parametric framework. This new method introduces Bayesian solution to the quantile framework for two reasons: 1. It enables us to get more efficient quantile estimates when the informative prior is used (He and Yang (2012)); 2. We use Markov Chain Monte Carlo (MCMC) algorithm to generate samples of the posterior distribution for unknown parameters and take the mean or mode as the estimates. This MCMC estimator takes advantage of numerical integration over the standard numerical differentiation based optimization, especially when the likelihood function is complicated and multi-modal. Simulation results find better interval forecasting performance of Quantile Bayesian Approach than commonly used parametric approach. / Thesis (PhD) — Boston College, 2015. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Economics.
194

Time series analysis of some economic and ecological data.

January 1984 (has links)
by Man Ka Sing. / Bibliography: leaves 69-70 / Thesis (M.Ph.)--Chinese University of Hong Kong, 1984
195

Empirical likelihood in long-memory time series models.

January 2006 (has links)
Yau Chun-Yip. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 64-65). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Fractional Integration --- p.1 / Chapter 1.2 --- Fractionally Intergrated Autoregressive Moving-Average Models With Conditional Heteroscedasticity --- p.6 / Chapter 1.3 --- Empirical Likelihood --- p.8 / Chapter 2 --- Whittle Likelihood Estimation in Long-Memory Time Series --- p.13 / Chapter 2.1 --- Exact Gaussian Maximum likelihood Estimation --- p.13 / Chapter 2.2 --- Whittle's approximate MLE --- p.16 / Chapter 3 --- Empirical Likelihood For ARFIMA models --- p.20 / Chapter 4 --- Empirical Likelihood For ARFIMA-GARCH models --- p.40 / Chapter 4.1 --- Empirical likelihood for GARCH models --- p.40 / Chapter 4.2 --- Empirical likelihood for ARFIMA-GARCH models --- p.44 / Chapter 5 --- Simulation --- p.48 / Chapter 5.1 --- Test of independece for periodogram ordinates --- p.49 / Chapter 5.2 --- Confidence Region --- p.53 / Chapter 5.3 --- Coverage error of empirical likelihood confidence intervals --- p.57 / Chapter 6 --- Conclusions and Further Research --- p.62 / Reference --- p.64
196

Identification of a unit root based on aggregate time series: a polyvariogram approach.

January 2007 (has links)
Tam, Chik Fai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 66-67). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Problem of identifying d in ARIMA model --- p.1 / Chapter 1.2 --- Another Approach --- p.4 / Chapter 2 --- Polyvariogram approach --- p.8 / Chapter 2.1 --- Variogram --- p.8 / Chapter 2.2 --- Polyvariogram --- p.11 / Chapter 2.3 --- A testing procedure --- p.13 / Chapter 2.4 --- Testing with integrated white noise series --- p.14 / Chapter 3 --- Aggregate time series in ARIMA --- p.17 / Chapter 3.1 --- The preservation of unity in ARIMA model under aggregation --- p.17 / Chapter 3.1.1 --- "Aggregation model of ARIMA(0,1,0)" --- p.20 / Chapter 3.1.2 --- "Aggregation model of ARIMA(0,1,1)" --- p.23 / Chapter 3.1.3 --- "Aggregation model of ARIMA(1,1,0)" --- p.26 / Chapter 4 --- Aggregation effects on the power of the test --- p.33 / Chapter 4.1 --- "Testing integrated white noise ARIMA(0,1.0) under aggregation" --- p.35 / Chapter 4.1.1 --- Simulation scheme --- p.35 / Chapter 4.1.2 --- Result --- p.39 / Chapter 4.2 --- "Testing ARIMA(0,1,1) under aggregation" --- p.42 / Chapter 4.2.1 --- Simulation scheme --- p.42 / Chapter 4.2.2 --- Result --- p.45 / Chapter 4.3 --- "Testing ARIMA(1, 1,0) under aggregation" --- p.52 / Chapter 4.3.1 --- Simulation scheme --- p.53 / Chapter 4.3.2 --- Result --- p.56 / Chapter 5 --- Conclusions and Discussions --- p.64
197

Design, fabrication and performance evaluation of a tandem time-of-flight mass spectrometer. / CUHK electronic theses & dissertations collection

January 2012 (has links)
基質輔助鐳射解吸電離飛行時間質譜儀是一種重要的儀器被用來對生物樣品做結構分析,通過諸如源後裂解和碰撞誘導裂解兩種方式實現。然而同碰撞誘導裂解比較,源後裂解具有較低的裂解效率。 / 本課題的目的就是提升我們原有的基質輔助鐳射解吸電離飛行時間質譜儀在結構分析方面的能力。對儀器的改造包括(a)將原有的兩級反射器替換為曲線場反射器(b)安裝一個高壓浮地的碰撞室(c)安裝一個同軸的粒子探測器。曲線場反射器和同軸粒子探測器可以實現母離子跟碎片離子的同時監測,碰撞室可以實現母離子的碰撞裂解。在儀器的性能評估實驗中,母離子和所有的源後裂解的碎片離子同時被探測器記錄。在碰撞誘導裂解實驗中,母離子與碰撞氣體分子發生高能碰撞後大多生成了小質量數的碎片離子,實驗中還發現將碰撞室浮地後,碎片離子的質量解析度和信號強度都有了顯著改進。 / 通過比較曲線場反射器和兩級反射器的性能,我們提出了一種雜化反射器設計,這種反射器在第二片和最後一片電極片上都有可調電壓。第二片和最後一片電極片之間的電場遵循曲線場分佈。這種反射器有兩種操作模式:MS 和MS/MS 模式。類比實驗和分析計算的結果顯示在MS 模式裡,通過調整兩個可調電壓u1 和u2,不同質量離子在反射器裡的反轉點可以被設置在一個最優的位置從而得到最優的質量解析度。在MS/MS 模式裡,一個全質量範圍的譜圖和若干個較窄質量範圍的譜圖可以通過改變兩個可調電壓獲得,其中較窄質量範圍的譜圖具有更高的質量解析度用來分析某個質量範圍內的碎片離子的細節資訊。這些結果表明這種雜化反射器兼具曲線場反射器和兩級反射器的優點。 / Matrix-assisted laser desorption/ionization time-of-flight mass spectrometer (MALDI-TOFMS) is an important instrument for structural analysis of biological samples through such as post-source-decay (PSD) or collision-induced dissociation (CID) analysis. However, PSD analysis is a relatively low-efficiency method compared with CID analysis. / This project aims to upgrade the TOF instrument to a high performance TOF/TOF instrument. The modification involves (a) the replacement of the two-stage reflectron with a home-built curved-field reflectron (CFR); (b) the fabrication of a high voltage floated collision cell; and (c) the installation of a coaxial microchannel plate (MCP) detector. The CFR and coaxial detector allow simultaneous reflection of precursor ions and all fragment ions. The collision cell provides an effective means of ion activation (CID). In the performance test, precursor ions with almost all the fragment ions were recorded simultaneously in PSD analysis. In CID experiments, the precursor ions were found to undergo fragmentation due to high energy collision with the target gas and by floating the collision cell to high potential (several kV), the mass resolution and signal intensities of low mass fragment ions were improved substantially. / By comparing the performance of curved-field and two-stage reflectron, a hybrid reflectron was proposed, which has adjustable high voltages U1 and U2 on the second and last electrode element, respectively. The electrostatic potential between the second and last electrode element follows curved-field distribution. There are two operation modes for this reflectron: MS and MS/MS mode. Results from theoretical investigation and experiments showed that in MS mode, optimal energy compensation could be achieved through tuning the values of U1 and U2; in MS/MS mode, a full mass scale spectrum as well as spectra segments with high mass resolution within a narrower mass range could be obtained by setting U1 and U2 with appropriate values. These results indicated that the hybrid reflectron had the advantages both of curved-field reflectron and two-stage reflectron. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Li, Gang. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 131-137). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / TABLE OF CONTENTS / LIST OF FIGURES / LIST OF TABLES / ABBREVIATIONS / Chapter Chapter One --- Background Introduction / Chapter 1.1 --- Matrix-assisted laser desorption/ionization (MALDI) --- p.2 / Chapter 1.1.1 --- Laser desorption --- p.2 / Chapter 1.1.2 --- Matrix-assisted laser desorption/Ionization --- p.3 / Chapter 1.2 --- Time-of-flight mass spectrometry --- p.8 / Chapter 1.2.1 --- Linear time-of-flight mass spectrometer --- p.8 / Chapter 1.2.2 --- Reflectron time-of-flight mass spectrometer --- p.9 / Chapter 1.2.2.1 --- Linear-field reflectron --- p.11 / Chapter 1.2.2.2 --- Nonlinear-field reflectron --- p.14 / Chapter 1.3 --- Structural analysis using time-of-flight mass spectrometer --- p.17 / Chapter 1.3.1 --- Post-source decay (PSD) analysis --- p.17 / Chapter 1.3.2 --- Collision-induced dissociation (CID) analysis --- p.20 / Chapter 1.4 --- Project introduction --- p.26 / Chapter Chapter Two --- Instrumentation / Chapter 2.1 --- Instrumentation --- p.28 / Chapter 2.1.1 --- Laser system --- p.28 / Chapter 2.1.2 --- Flight tube and vacuum system --- p.28 / Chapter 2.1.3 --- Ion source --- p.32 / Chapter 2.1.4 --- Deflector and time ion selector --- p.36 / Chapter 2.1.5 --- Two-stage gridless reflectron --- p.39 / Chapter 2.1.6 --- Detectors, digitizer and computer system --- p.42 / Chapter Chapter Three --- Fabrication of the Modified Tandem Time-of-flight Mass Spectrometer / Chapter 3.1 --- Introduction --- p.48 / Chapter 3.2 --- Implementation of a coaxial MCP detector --- p.51 / Chapter 3.3 --- Design, fabrication and implementation of a curved-field reflectron --- p.57 / Chapter 3.4 --- Design, fabrication and implementation of a floated collision cell --- p.61 / Chapter 3.5 --- Summary --- p.66 / Chapter Chapter Four --- Performance Evaluation of the Modified Instrument / Chapter 4.1 --- MS analysis by using the modified instrument --- p.68 / Chapter 4.2 --- MS/MS analysis by using the modified instrument --- p.73 / Chapter 4.2.1 --- Post-source-decay (PSD) analysis --- p.73 / Chapter 4.2.2 --- Collision-induced-dissociation analysis --- p.75 / Chapter 4.3 --- Mass calibration for the modified instrument --- p.84 / Chapter Chapter Five --- A Design of Hybrid Reflectron / Chapter 5.1 --- Introduction of the hybrid reflectron --- p.90 / Chapter 5.2 --- Characterization of the hybrid reflectron --- p.93 / Chapter 5.2.1 --- Calculations using analytical equations --- p.93 / Chapter 5.2.1.1 --- Analytical calculations for MS operation mode --- p.93 / Chapter 5.2.1.2 --- Analytical calculations for MS/MS operation mode --- p.99 / Chapter 5.2.2 --- Simulation experiments by SIMION --- p.106 / Chapter 5.3 --- Calibration of the instrument using the hybrid reflectron --- p.112 / Chapter 5.4 --- Summary --- p.115 / Chapter Chapter Six --- Fabrication and Performance Evaluation of the Hybrid Reflectron / Chapter 6.1 --- Hardware fabrication of the hybrid reflectron --- p.117 / Chapter 6.2 --- Performance evaluation of the hybrid reflectron --- p.121 / Chapter Chapter Seven --- Concluding Remarks --- p.128 / References --- p.131 / Appendix --- p.138 / Chapter Appendix 1 --- Mathematica program for analytical calculations / Chapter Appendix 2 --- Geometry file used in SIMION simulation experiment / Chapter Appendix 3 --- User program for controlling reflectron high voltage
198

The linear stability of Reissner-Nordström spacetime for small charge

Giorgi, Elena January 2019 (has links)
In this thesis we prove the linear stability to gravitational and electromagnetic perturbations of the Reissner-Nordström family of charged black holes with small charge. Solutions to the linearized Einstein-Maxwell equations around a Reissner-Nordström solution arising from regular initial data remain globally bounded on the black hole exterior and in fact decay to a linearized Kerr-Newman metric. We express the perturbations in geodesic outgoing null foliations, also known as Bondi gauge. To obtain decay of the solution, one must add a residual pure gauge solution which is proved to be itself controlled from initial data. Our results rely on decay statements for the Teukolsky system of spin +/-2 and spin +/-1 satisfied by gauge-invariant null-decomposed curvature components, obtained in earlier works. These decays are then exploited to obtain polynomial decay for all the remaining components of curvature, electromagnetic tensor and Ricci coefficients. In particular, the obtained decay is optimal in the sense that it is the one which is expected to hold in the non-linear problem.
199

Total recall: encapsulating city & memory.

January 2003 (has links)
Chan Yuen Lai. / "Architecture Department, Chinese University of Hong Kong, Master of Architecture Programme 2002-2003, design report." / Includes bibliographical references. / Chapter 00_ --- FOREWORD: I BEGAN CREATING MY TIME CAPSULE BOXES / Chapter 01_ --- INVENTORY OF BOXES / Chapter 02_ --- "THE ARCHIVE GALLERY, AS AN INVENTED PROGRAM" / Chapter 03_ --- HABITATION / MAN AND HIS ENVIRONMENT / TOURISTIC EXPERIENCE / DEAN MACCANNELL / "ADVENTURER, TRAVELLER, TOURIST" / CHRISTIAN NORBERG-SCHULZ / RELPH EDWARD / INSIDENESS AND OUTSIDENESS / "THE ONE, THE THING, THE PLACE" / AUTHENTICITY VS PEUSDO-EVENT / THE HOME / Chapter 04_ --- THE SITE / TOPOLOGY VS GEOGRAPHY / TIME AND MOVEMENT / ANDY WARHOL / DAN GRAHAM / UMBERTO ECO / ENCODING AND DECODING / AS SIGN AND AS MIRROR / TIME CAPSULE / "REGISTRATION, RETENTION, RECALL OF MEMORY" / WALTER BENJAMIN / CITY AND MEMORY / THE METAPHOR / Chapter 05_ --- THE STATEMENT / OUR WORLD. REALITY VS VIRTUAL ITY. LABYRINTH. MIRROR. METAPHOR. CUBE. PLANE. LINE. POINT. MODEL. ARCHITECTURE. THESIS / GRID. LABYRINTH. TIME. BODY. MIRROR / Chapter 06_ --- LABYRINTH AND MIRROR / THESEUS AND MINOTAUR / NARCISSUS / RACHEL WHITEREAD / SARAH SZE / JOSEPH CORNELL / MEMORY BOXES / WORLD AND SELF / ITALO CALVINO / LABYRINTHINE CHARACTER / ZAIRA AND ITS PAST / NETWORK / MEDIATION / MIRROR REFLECTIVITY / THE BIG STONE FEDORA AND THE LITTLE FEDORAS IN THE GLASS GLOBES / IMAGES OF CONTAINMENT / ENCLOSURE / Chapter 07_ --- THE PROGRAM / THE ARCHIVE GALLERY / "START OF THE JOURNEY, COLLECTION OF THE BOX" / "THE THING, THE BOX, THE LETTER" / STORAGE OF THE BOX / "RETRIEVAL OF THE BOX, THE ARTIST'S CONVERSATION" / "FROM THE BOX TO THE INSTALLATION AND SO ON, THE CYCLE" / Chapter 08_ --- MODELS / DRAWINGS / SKETCHES / SNAPSHOTS / ENCAPSULATED / Chapter 09_ --- CREDITS / Chapter 10_ --- DEDICATIONS: THIS THESIS IS SOMEWHERE SOMETIME WITH SOMEONE
200

Mixing characterization in novel high throughput minibioreactors: scale-down modeling from bench scale

Silva, João Fernando de Andrade Cardoso da January 2010 (has links)
Tese de mestrado integrado. Engenharia Química. Faculdade de Engenharia. Universidade do Porto. 2010

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