Spelling suggestions: "subject:"a'method"" "subject:"20method""
331 |
quantum Monte Carlo studies on highly correlated system. / 強關聯系統的量子蒙地卡羅方法研究 / The quantum Monte Carlo studies on highly correlated system. / Qiang guan lian xi tong de liang zi Mengdi Kaluo fang fa yan jiuJanuary 2012 (has links)
本論文主要包括三種量子蒙地卡羅(QMC)方法的介紹及將其應用到不同的強關聯系統的結果。當中所涉及的強關聯系統主要是兩個不同的量子液體系統--自旋液體及玻色液體。 / 第二章將詳細介紹三個QMC方法,包括針對非零溫巨正則系統的行列式蒙地卡羅方法(DQMC),針對零溫正則系絶並解決部分負值問題的限制線軌蒙地卡羅方法(CPMC),及主要應用在非零溫雜質系統上的Hirsch-Fye蒙地卡羅方法(HFQMC)。 / 自發現高溫起導體以後,其奇異特性如具有非費米液體特性的贗能隙(Pseudogap)引起科學界爭論,由此提出很多不同的理論嘗試解釋。RVB是其中一個具代表性的理論,當中把高溫超導體理解成輕度摻雜的莫特絶緣體(Mott insulator)及引入自旋-電荷分離(charge-spin separation)把系統兩個自由度分開處理,具費米特性的自旋子(spinon)及具玻色特性的空穴子(holon)因而產生。這兩種準粒子的特性在解釋高溫超導的奇異性中最為關鍵。 / 第三章將應用DQMC及CPMC研究擁有各向及各自旋相異費米面的吸引勢赫伯德模型。模型的起源在於有理論[1]提出玻色子的基態有可能因阻挫作用而不發生愛因斯坦-玻色凝聚,這種非凝聚的基態稱為d-波玻色液體。在本研究所採用的模型中,將由庫柏電子對取代原先的正則玻色子。模型在準一准雙排梯子晶格的特性最近已被密度矩阵重整化群(DMRG)方法詳細研究[2],而本研究將率先使用QMC方法研究模型在準一維雙排、四排梯子及二維正方晶格的特性。QMC有部分證據顯示電子對液體確實在二維存在,在本論文中會作出交代。 / 第四章將應用CPMC研究阻挫作用(frustration)下的排斥勢赫伯德模型,而其具體晶格情況為在正方格子上加上單向斜線躍遷項,稱為t-t'-TH模型。有證據提出在此模型中有可能存自旋液體的基態,並可有效解釋最近在實驗中所觀察到的有機超導體超低溫自旋無序的特性[3]。t-t'-TH模型的導帶半滿情況被曾各種方法詳細研究,本項研究將採用不同 的導帶填充情況及阻挫作用強度,用其比較以觀察阻挫作用對模型基態自旋作用的影響。研究發現阻挫作用將對不同的長程自旋序作出不同程度的影響。 / 第五章則會說明HFQMC的可能應用,在雜質系統如安德遜模型中,HFQMC是研究其非零溫特性的有效方法。此外,這章亦會交代未來在這方面可能進行的研究,而最後一章則會總結全文。 / In this thesis, three quantum Monte Carlo(QMC) algorithms would be reviewed, including determinant Quantum Monte Carlo (DQMC), constraint path Quantum Monte Carlo(CPMC) and Hirsch-Fye Quantum Monte Carlo (HFQMC). These QMC methods would be used to study strongly correlated system. In chapter 3 and 4, DQMC and CPMC methods would be used to study two kinds of quantum liquid, Bose liquid and spin liquid. In chapter 5, the possible application of HFQMC would be discussed. / After the discovery of high T{U+ABB1} cuprate, intensive effort has been paid to construct its theoretical explanation. One of the most puzzling features in cuprate is the pseudogap(strange-metal) phase with non-Fermi liquid behaviour. To search for an non-Fermi liquid to represent this phase, resonating valence bond(RVB) theory proposed a picture of lightly doped spin liquid. Fermionic spinon and bosonic holon arise from the spin-charge separation, and the behaviors of these quasi-particle are important for explanation for high T{U+ABB1} superconductivity. / In chapter 3, we study possible Bose liquid. Motrunich and Fisher [1] proposed a possible uncondensed bosonic phase d-wave Bose liquid(DBL) which will not undergo BEC at ground state. A prior studies[2] has shown that Cooper pairs can be used to replace bosons and N-leg ladder lattice could be used to approach behaviour of 2D lattice. Inspired by them, determinant quantum Monte Carlo(DQMC) and constraint path Monte Carlo(CPMC) techniques are used to study the fermionic attractive Hubbard Model with spin-independent anisotropic Fermi surface. The probable (Local) Cooper Pair Bose metal is detected in 2-leg, 4-leg ladder and 2D lattice. / In chapter 4, we study possible spin liquid. The Hubbard model on an anisotropic triangular lattice called t - t¹ - TH model has been proposed to possess a non-magnetic insulating(spin liquid) state, induced by geometrical frustration. The effect of filling and degree of frustration on magnetic property is investigated by CPMC in the studies. / Chapter 5 is devoted to introducing the usages and possible research projects related to HFQMC. HFQMC is a quantum Monte Carlo method based on path integral formalism, and it is an efficient way to study impurity model at low temperature. A physical background of impurity model is also reviewed. In the last chapter, we would summarize this thesis by comparing the QMC methods used and discussing the result obtained. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Tang, Ho Kin = 強關聯系統的量子蒙地卡羅方法研究 / 鄧皓鍵. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 83-88). / Abstracts also in Chinese. / Tang, Ho Kin = Qiang guan lian xi tong de liang zi Mengdi Kaluo fang fa yan jiu / Deng Haojian. / Chapter 1 --- Introduction to Strongly Correlated System: High T{U+ABB1} superconductivity and Quantum Liquid --- p.1 / Chapter 1.1 --- Types of strongly correlated electron systems --- p.1 / Chapter 1.2 --- High T{U+ABB1} superconductivity --- p.3 / Chapter 1.2.1 --- Phase diagram --- p.4 / Chapter 1.2.2 --- Mott insulator and Anti-ferromagnetic(AFM) order --- p.6 / Chapter 1.2.3 --- Spin-glass --- p.7 / Chapter 1.2.4 --- Pseudogap --- p.7 / Chapter 1.2.5 --- Superconducting --- p.7 / Chapter 1.2.6 --- The complexity and related theory --- p.7 / Chapter 1.3 --- Importance of quantum liquids in high T{U+ABB1} superconductivity --- p.10 / Chapter 1.3.1 --- Spin liquid --- p.10 / Chapter 1.3.2 --- Bose Liquid --- p.11 / Chapter 2 --- Methods --- p.12 / Chapter 2.1 --- Introduction to Quantum Monte Carlo --- p.12 / Chapter 2.2 --- Determinant Quantum Monte Carlo(DQMC) --- p.13 / Chapter 2.2.1 --- Purpose of DQMC --- p.13 / Chapter 2.2.2 --- Overall information of DQMC --- p.14 / Chapter 2.2.3 --- Green function in DQMC --- p.20 / Chapter 2.2.4 --- Observable measurement --- p.21 / Chapter 2.2.5 --- Numerical Implementation --- p.24 / Chapter 2.2.6 --- Limitation --- p.26 / Chapter 2.3 --- Constraint Path Quantum Monte Carlo(CPMC) --- p.26 / Chapter 2.3.1 --- Purpose of CPMC --- p.26 / Chapter 2.3.2 --- Algorithm discussion --- p.28 / Chapter 2.3.3 --- Implementation Issues --- p.32 / Chapter 2.4 --- Hirsch-Fye Quantum Monte Carlo(HFQMC) --- p.35 / Chapter 2.4.1 --- Algorithm outline --- p.35 / Chapter 2.4.2 --- Program Structure --- p.38 / Chapter 3 --- A Possible Realization of Bose Liquid: Attractive Hubbard Model with Spin-dependent Anisotropic Hopping --- p.41 / Chapter 3.1 --- Idea of Bose metal --- p.41 / Chapter 3.2 --- Model Hamiltonian --- p.44 / Chapter 3.3 --- Phases and its detection --- p.45 / Chapter 3.3.1 --- Measurement --- p.45 / Chapter 3.3.2 --- Phases --- p.46 / Chapter 3.4 --- Multi-leg ladder Lattice --- p.47 / Chapter 3.4.1 --- Band structure --- p.47 / Chapter 3.4.2 --- Two-leg ladder: Cooper-pair Bose Metal Phase --- p.51 / Chapter 3.4.3 --- Four-leg ladder: Cooper-pair Bose Metal Phase --- p.55 / Chapter 3.5 --- 2D Lattice --- p.56 / Chapter 3.5.1 --- Band structure --- p.56 / Chapter 3.5.2 --- 2D Lattice: Local Cooper-pair Bose Metal(LCPBM) Phase --- p.60 / Chapter 3.6 --- Summary --- p.61 / Chapter 4 --- A Possible Realization of Spin Liquid: Square Lattice Hubbard Model with Geometrical Frustration --- p.65 / Chapter 4.1 --- Frustration and Spin Liquid --- p.65 / Chapter 4.1.1 --- Physical systems --- p.66 / Chapter 4.1.2 --- Recent developments of t-t’-TH model --- p.67 / Chapter 4.2 --- Model Hamiltonian --- p.67 / Chapter 4.3 --- Band structure --- p.68 / Chapter 4.4 --- Frustration Effect on Magnetism --- p.70 / Chapter 4.5 --- Summary --- p.73 / Chapter 5 --- Possible Application of HFQMC --- p.75 / Chapter 5.1 --- Anderson Model --- p.75 / Chapter 5.1.1 --- Physical Issues --- p.75 / Chapter 5.1.2 --- Model proposal and mean field result --- p.76 / Chapter 5.1.3 --- Properties of model with quantum degree of freedom --- p.77 / Chapter 5.2 --- The application cases --- p.78 / Chapter 6 --- Summary --- p.80 / Chapter 6.1 --- Three QMC methods --- p.80 / Chapter 6.2 --- Two practical models --- p.80 / Bibliography --- p.83
|
332 |
Financial modeling and forecasting using Monte Carlo covariance simulation.January 1974 (has links)
Summary in Chinese. / Thesis (M.B.A.)--Chinese University of Hong Kong. / Bibliography: leaves 65-67.
|
333 |
Finite element methods for Maxwell's equations.January 1999 (has links)
Chan Kit Hung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 90-93). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Model Elliptic Boundary-Value Problems --- p.2 / Chapter 1.2 --- Applications of the Model Boundary-Value Problem --- p.4 / Chapter 1.2.1 --- Curl-Curl Formulation --- p.4 / Chapter 1.2.2 --- Vector Potential Formulation --- p.6 / Chapter 1.2.3 --- Darwin Model and Quasistatic Model --- p.7 / Chapter 1.3 --- Spurious Solutions --- p.8 / Chapter 2 --- Finite Element Formulation --- p.11 / Chapter 2.1 --- Preliminaries --- p.11 / Chapter 2.2 --- Weak Formulation --- p.14 / Chapter 2.2.1 --- Galerkin Method --- p.17 / Chapter 2.2.2 --- The Rayleigh-Ritz Method --- p.19 / Chapter 2.3 --- H1(Ω) Conforming Finite Element Method --- p.23 / Chapter 2.3.1 --- The Dirichlet Problem --- p.24 / Chapter 2.3.2 --- The Neumann Problem --- p.27 / Chapter 3 --- Numerical Implementations --- p.29 / Chapter 3.1 --- Introduction --- p.29 / Chapter 3.2 --- Implementation of Boundary Conditions --- p.32 / Chapter 3.3 --- Numerical Integration Formula --- p.39 / Chapter 3.4 --- Discrete L2-norms --- p.40 / Chapter 3.5 --- Solution of Linear System of Equations --- p.42 / Chapter 3.6 --- Automatic Mesh Generation --- p.43 / Chapter 3.6.1 --- The Cubic Domain Ω --- p.44 / Chapter 3.6.2 --- The Spherical Shell Domain Ωs --- p.44 / Chapter 4 --- Numerical Experiments --- p.50 / Chapter 4.1 --- Numerical Experiments for Dirichlet Problem --- p.50 / Chapter 4.1.1 --- Original Formulation --- p.50 / Chapter 4.1.2 --- Experiments --- p.52 / Chapter 4.1.3 --- Penalty Factor Effect --- p.56 / Chapter 4.2 --- Numerical Experiment for Neumann Problem --- p.61 / Chapter 4.2.1 --- Original Formulation --- p.61 / Chapter 4.2.2 --- Experiments --- p.62 / Chapter 4.2.3 --- Penalty Factor Effect --- p.66 / Chapter 4.2.4 --- Comparison with the Dirichlet Problem --- p.70 / Chapter 4.3 --- Numerical Experiment of Dirichlet Problem with Boundary Condition E = E --- p.71 / Chapter 4.3.1 --- Original Formulation --- p.71 / Chapter 4.3.2 --- Experiments --- p.73 / Chapter 4.3.3 --- Penalty Factor Effect --- p.76 / Chapter 4.4 --- Numerical Experiment on Spherical Shell Domain --- p.81 / Chapter 4.4.1 --- The Spherical Shell Domain --- p.81 / Chapter 4.4.2 --- Dirichlet Problem --- p.82 / Chapter 4.5 --- Some Numerical Phenomena --- p.86 / Chapter 4.5.1 --- GMRES Convergence Accelerator --- p.86 / Chapter 4.5.2 --- Sparsity Improvement --- p.88 / Bibliography --- p.90 / List of Tables --- p.94
|
334 |
Particle filter using acceptance-rejection method with emphasis on the target tracking problem.January 2006 (has links)
Tsang Yuk Fung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 59-62). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Sequential Monte Carlo --- p.5 / Chapter 2.1 --- Recursive Bayesian estimation --- p.7 / Chapter 2.2 --- Bayesian sequential importance sampling --- p.8 / Chapter 2.3 --- Sclcction of iiiipoitance function --- p.10 / Chapter 2.4 --- Particle filter --- p.12 / Chapter 3 --- Target tracking and data association --- p.15 / Chapter 3.1 --- Target tracking and its applications --- p.16 / Chapter 3.2 --- Data association and JPDA method --- p.16 / Chapter 4 --- Particle filter using the acceptance-rejection method --- p.21 / Chapter 4.1 --- Particle Filter using the acceptance-rejection method --- p.22 / Chapter 4.2 --- Modified accoptance-rcjoction algorithm --- p.24 / Chapter 4.3 --- Examples --- p.26 / Chapter 4.3.1 --- Example 1: One dimensional non-linear case --- p.26 / Chapter 4.3.2 --- Example 2: Bearings-only tracking example --- p.27 / Chapter 4.3.3 --- Example 3: Single-target tracking --- p.31 / Chapter 4.3.4 --- Example 4: Multi-target tracking --- p.33 / Chapter 4.4 --- A new importance weight for bearings-only tracking problem --- p.34 / Chapter 5 --- Conclusion --- p.41
|
335 |
A Method Of Moments Approach for the Design Of RF Coils for MRIObi, Aghogho A 12 May 2008 (has links)
Magnetic Resonance Imaging (MRI) is a widely used soft-tissue imaging modality that has evolved over the past several years into a powerful and versatile medical diagnostic tool capable of providing in-vivo diagnostic images of human and animal anatomies. Current research efforts in MRI system design are driven by the need to obtain detailed high resolution images with improved image signal-to-noise ratio (SNR) at a given magnetic field strength. Invariably, this requirement demands the development of high performance MRI radio frequency (RF) coils. However, the complexities and stringent requirements of modern clinical MRI systems necessitate the development of new modeling methodologies for the design of high performance RF coils. This dissertation addresses this need by developing a distinct Method of Moments (MoM) modeling approach suitable for the simulation of RF coils loaded with biological tissues. The unique implementation utilizes two distinct basis functions in order to collectively describe the surface current density on the RF coil, and the sum of the volume current density and the displacement current density in the associated biological tissue. By selecting basis functions with similar properties to the actual physical quantities they describe, we avoided spurious solutions normally associated with MoM based implementations. The validity of our modeling method was confirmed by comparisons with analytical solutions as well as physical measurements, yielding good agreement. Furthermore, we applied the MoM based modeling method in the design and development of a novel 4-channel receive-only RF coil for breast imaging in a clinical 1.5T system. The new coil design was inspired by the multi-channel array concept, where multiple conducting strips were arranged in an anatomically conforming profile with the intention of improving sensitivity and SNR. In addition, the coil structure featured an open breast coil concept in order to facilitate MRI-guided biopsy and patient comfort. A comparison of simulation results and actual physical measurements from the prototype RF coil demonstrated good agreement with one another. Also, imaging tests were conducted on a pair of MRI phantoms as well as on a human patient after obtaining proper authorization. The tests revealed good magnetic field homogeneity and a high SNR in the region of interest. In addition, performance comparisons between the prototype 4-channel RF coil and existing high end clinical 4-channel RF breast coils indicated an achievement of superior SNR in conjunction with very good magnetic field homogeneity. Currently, the prototype 4-channel RF coil has outperformed all existing high end clinical 4-channel RF coils used in comparison studies.
|
336 |
Weighted Markov chain Monte Carlo and optimization. / CUHK electronic theses & dissertations collectionJanuary 1997 (has links)
by Liang Fa Ming. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (p. 150-161). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web.
|
337 |
Empirical investigation of the performance of Mplus for analyzing structural equation model with mixed continuous and ordered categorical variables.January 2003 (has links)
Lam Ho-Suen Joffee. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaf 40). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Review of Mplus --- p.3 / Chapter 3 --- Design of the Simulation Study --- p.6 / Chapter 3.1 --- Simulation Design --- p.6 / Chapter 3.2 --- Covariance Structure Analysis and Mplus Restriction --- p.10 / Chapter 3.3 --- Implementation --- p.10 / Chapter 4 --- Method of Evalution --- p.12 / Chapter 4.1 --- Accuracy of Parameter Estimates --- p.12 / Chapter 4.2 --- Distribution of the Goodness-of-fit Statistic --- p.13 / Chapter 4.3 --- Precision of Standard Errors --- p.14 / Chapter 4.4 --- Number of Replications --- p.15 / Chapter 5 --- Results of the Simulation Study --- p.17 / Chapter 5.1 --- Accuracy of the Parameter Estimates --- p.17 / Chapter 5.2 --- Distribution of the Goodness-of-fit Statistic --- p.18 / Chapter 5.3 --- Precision of the Standard Error --- p.19 / Chapter 5.4 --- Results when the Sample Size is Extremely Large --- p.20 / Chapter 5.5 --- Conclusion --- p.21 / Chapter 6 --- Additional Simulation Study --- p.27 / Chapter 6.1 --- Precision of Standard Error when the Model Consists of Only Con- tinuous and Only Ordinal Variables --- p.28 / Chapter 6.2 --- Comparison of the Simulation Results of Mplus and LISREL --- p.29 / Chapter 6.3 --- Conclusion --- p.31 / Chapter 7 --- Conclusion and Discussion --- p.33 / Chapter A --- Mplus Sample Program (Condition C1 S2 N=500) --- p.36 / Chapter B --- PRELIS Sample Program (Condition C1 S1 N=500) --- p.37
|
338 |
A Review of Plant Propagation MethodsAritajat, Somsong 01 May 1966 (has links)
The purpose of this study was to consider how the rooting of cuttings may be affected by such methods and factors as: type of cutting, time of year when cuttings are best taken, differences between individual species, use of chemicals for the treatment of cuttings, rooting media, and the care of cuttings in the propagation beds.
In the past 35 years scientists have done considerable experimenting with the application of organic chemicals on the roots, stems and leaves of various plants. These organic chemicals have come to be known as "plant hormones" or "plant regulators." They have proved to be extremely useful and have affected the plants in rather unusual ways. Growth regulating chemicals are no longer on trial. They now are being used with several kinds of farm crops and ornamental plants.
Hormones or growth regulators are chemical substances, made in one part of an organism and transported to other parts where they produce their effects, and they are effective in very minute amounts. This paper will give the present status of knowledge on the use and effectiveness of growth regulators in plant propagation.
|
339 |
The effect of cooking method upon iron and zinc bioavailability in riceShahnaseri, Mahnaz, University of Western Sydney, Hawkesbury, Faculty of Science, Technology and Environment, School of Food Science January 2001 (has links)
Prevention of iron deficiency rather than treatment is preferred by most nutritionists. The presence of a maximal iron supply is not advised because an excessive or unnecessary iron supplement may have biologically adverse effects, such as impaired immune resistance or negative interaction with other trace elements. All cereals and most vegetables contain phytate (inositol hexaphosphate) which can bind iron and zinc and reduce their biological availability. The amount of iron available for absorption in any given diet depends to a large extent on the composition of the diet, e.g., the presence of vitamin C and haem iron, and the absence of phytate. Rice is one of the most important staples in the Iranian diet and, in fact, rice, for most Iranians, is not a side dish but a main dish to which other foods or ingredients are added. An awareness of the effects of cooking method on nutrient content is important because cooking techniques influence the overall quality of a group's diet. The goal of this study is to determine the bioavailability of iron and zinc in traditional Iranian rice dishes and to assess the effect of traditional methods of cooking rice upon iron and zinc bioavailability. Iranian migrants residing in Sydney were surveyed in order to determine their food habits and traditional cooking methods, for the assessment of their effects upon the bioavailability of iron and zinc in Iranian rice dishes. Rice contains phytate, which is a potent inhibitor of iron absorption. The amount of phytate in rice depends on whether the rice is polished or not. The pre-cooking treatment such as soaking can also influence the phytate content of the rice. Soaking prior to cooking also reduced the amount of ion and zinc. The inhibitory effect of phytate is also overcome by adding different herbs, vegetables and legumes used traditionally in rice dishes cooked by Iranians. Herbs or vegetables such as coriander, parsley and cauliflower, used in Iranian rice dishes, increased the bioavailability iron and zinc. Results obtained from this research show that method of cooking, as well as the food mixture, is very important for the absorption of iron and zinc from the diet / Doctor of Philosophy (PhD)
|
340 |
單調法在非線性微分方程式之研究 / Monotone Methods for Nonlinear Differential Equations張凱君, Chang, Kai-Jiun Unknown Date (has links)
本文旨在討論非線性拋物型積分微分方程式(組)的解之存在性.首先藉由與上解及下解相關的若干假設,我們得到一個比較性的結果.然後我們利用單調法建構出兩個單調收歛到方程式解的序列,從而驗證了方程式解的存在性. / In this paper, the existence of the solutions for nonlinear integro-differential equations and systems is discussed. First, by the assumption of weak upper and weak lower solutions for the given problem, we obtain the comparison result. Next, we provide the method of monotony and construct two sequences which converge monotonically to the solution.
|
Page generated in 0.0719 seconds