Kwok, Ho Man = 多體系統中的量子臨界現象與保真度 / 郭灝民. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (p. 106-109). / Abstracts in English and Chinese. / Kwok, Ho Man = Duo ti xi tong zhong de liang zi lin jie xian xiang yu bao zhen du / Guo Haomin. / Chapter 1 --- Overview of Quantum Phase transitions --- p.1 / Chapter 1.1 --- Classification of QPTs --- p.2 / Chapter 1.2 --- Teaching model: The quantum Ising model --- p.4 / Chapter 1.3 --- Critical exponents and universality classes --- p.6 / Chapter 1.4 --- A new tool to the QPT: Fidelity --- p.8 / Chapter 1.5 --- Fidelity susceptibility --- p.12 / Chapter 1.6 --- Motivation of this report --- p.16 / Chapter 2 --- Analysis of the One Dimensional Quantum XY model --- p.17 / Chapter 2.1 --- Introduction to the model Hamiltonian --- p.17 / Chapter 2.2 --- Diagonalizing the Hamiltonian --- p.18 / Chapter 2.2.1 --- Jordan-Wigner transformation --- p.18 / Chapter 2.2.2 --- Bogoliubov transformation --- p.22 / Chapter 2.3 --- Ground state properties --- p.24 / Chapter 2.4 --- Calculating the fidelity susceptibility --- p.25 / Chapter 2.5 --- Fidelity susceptibility in Quantum Ising model --- p.31 / Chapter 2.6 --- Numerical comparison --- p.36 / Chapter 3 --- The Lipkin-Meshkov-Glick model --- p.40 / Chapter 3.1 --- Literature Review --- p.40 / Chapter 3.1.1 --- Scaling Behaviour --- p.41 / Chapter 3.1.2 --- Quantum Phase Transition --- p.42 / Chapter 3.1.3 --- Mathematical formalism --- p.44 / Chapter 3.1.4 --- Conserved quantities --- p.46 / Chapter 3.2 --- Energy spectrum for isotropic case --- p.47 / Chapter 3.3 --- Energy spectrum for anisotropic case --- p.49 / Chapter 3.3.1 --- The Holstein-Primakoff mapping --- p.49 / Chapter 3.3.2 --- Bogoliubov transformation for Boson systems --- p.53 / Chapter 3.4 --- Fidelity susceptibility in the isotropic case --- p.55 / Chapter 3.4.1 --- h> h0 --- p.56 / Chapter 3.4.2 --- h0 > h> h1 --- p.57 / Chapter 3.4.3 --- h1 > h > h2 --- p.57 / Chapter 3.5 --- Fidelity susceptibility in the anisotropic case --- p.60 / Chapter 3.5.1 --- "h > 1, driving by γ - xF(γ)" --- p.60 / Chapter 3.5.2 --- "h > 1, driving by h - xF(h)" --- p.62 / Chapter 3.5.3 --- "h < 1, driving by γ - xF(γ)" --- p.63 / Chapter 3.5.4 --- "h < 1, driving by h - xF(h)" --- p.64 / Chapter 3.6 --- Discussion and numerical analysis --- p.65 / Chapter 3.7 --- A possible resolution to the isotropic case: Partial-state fidelity and its susceptibility --- p.71 / Chapter 3.7.1 --- Review of the formalism --- p.72 / Chapter 3.7.2 --- Continuous level crossing and fidelity in the isotropic model --- p.74 / Chapter 3.7.3 --- Partial-state fidelity susceptibility --- p.77 / Chapter 4 --- Numerical Approach to Fidelity Susceptibility --- p.81 / Chapter 4.1 --- The Scaling Ansatz and Critical exponents --- p.81 / Chapter 4.2 --- Examples --- p.83 / Chapter 4.2.1 --- One Dimensional Quantum Ising model --- p.83 / Chapter 4.2.2 --- LMG model --- p.86 / Chapter 4.2.3 --- Two Dimensional Quantum Ising model --- p.90 / Chapter 4.2.4 --- Two Dimensional XXZ model --- p.93 / Chapter 4.2.5 --- One Dimensional Heisenberg model --- p.96 / Chapter 4.3 --- Discussion --- p.100 / Chapter 5 --- Summary --- p.105 / Bibliography --- p.106

Few and many-body systems usually feature interesting and novel behaviors compared with their counterparts in three dimensions. On one hand, low dimensional physics presents challenges due to strong interactions and divergences in the perturbation theory; On the other hand, there exist powerful theoretical tools such as the renormalization group and the Bethe ansatz. In this thesis, I discuss two examples: three interacting bosons in two dimensions and interacting bosons/fermions in one dimension. In both examples, there are intraspecies repulsion as well as interspecies attraction, producing a rich spectrum of phenomena. In the former example, a universal curve of three-body binding energies versus scattering lengths is obtained efficiently by evolving a matrix renormalization group equation. In the latter example, exact solutions for the BCS-BEC crossover are obtained and the unexpected robust features in their excitation spectra are explained by a comprehensive semiclassical analysis.

<p>Предмет&nbsp; истраживања&nbsp; тезе&nbsp; је&nbsp; из области&nbsp; паралелног&nbsp; програмирања,<br />имплементација&nbsp; CFD&nbsp; (Computational Fluid&nbsp; Dynamics)&nbsp; методе&nbsp; на&nbsp; више<br />хетерогених&nbsp; вишејезгарних&nbsp; уређаја истовремено.&nbsp; У&nbsp; раду&nbsp; је&nbsp; приказано<br />неколико&nbsp; алгоритама&nbsp; чији&nbsp; је&nbsp; циљ убрзање&nbsp; CFD&nbsp; симулације&nbsp; на персоналним&nbsp; рачунарима.&nbsp; Показано је&nbsp; да&nbsp; описано&nbsp; решење&nbsp; постиже задовољавајуће&nbsp; перформансе&nbsp; и&nbsp; на HPC&nbsp; уређајима&nbsp; (Тесла&nbsp; графичким картицама).&nbsp; Направљена&nbsp; је симулација&nbsp; у&nbsp; микросервис архитектури&nbsp; која&nbsp; је&nbsp; портабилна&nbsp; и флексибилна и додатно олакшава рад на персоналним рачунарима.</p> / <p>Predmet&nbsp; istraživanja&nbsp; teze&nbsp; je&nbsp; iz oblasti&nbsp; paralelnog&nbsp; programiranja,<br />implementacija&nbsp; CFD&nbsp; (Computational Fluid&nbsp; Dynamics)&nbsp; metode&nbsp; na&nbsp; više<br />heterogenih&nbsp; višejezgarnih&nbsp; uređaja istovremeno.&nbsp; U&nbsp; radu&nbsp; je&nbsp; prikazano<br />nekoliko&nbsp; algoritama&nbsp; čiji&nbsp; je&nbsp; cilj ubrzanje&nbsp; CFD&nbsp; simulacije&nbsp; na personalnim&nbsp; računarima.&nbsp; Pokazano je&nbsp; da&nbsp; opisano&nbsp; rešenje&nbsp; postiže zadovoljavajuće&nbsp; performanse&nbsp; i&nbsp; na HPC&nbsp; uređajima&nbsp; (Tesla&nbsp; grafičkim karticama).&nbsp; Napravljena&nbsp; je simulacija&nbsp; u&nbsp; mikroservis arhitekturi&nbsp; koja&nbsp; je&nbsp; portabilna&nbsp; i fleksibilna i dodatno olakšava rad na personalnim računarima.</p> / <p>The&nbsp; case&nbsp; study&nbsp; of&nbsp; this&nbsp; dissertation belongs&nbsp; to&nbsp; the&nbsp; field&nbsp; of&nbsp; parallel programming,&nbsp; the&nbsp; implementation&nbsp; of CFD&nbsp; (Computational&nbsp; Fluid&nbsp; Dynamics) method&nbsp; on&nbsp; several&nbsp; heterogeneous multiple&nbsp; core&nbsp; devices&nbsp; simultaneously. The&nbsp; paper&nbsp; presents&nbsp; several&nbsp; algorithms aimed&nbsp; at&nbsp; accelerating&nbsp; CFD&nbsp; simulation on common computers. Also it has been shown&nbsp; that&nbsp; the&nbsp; described&nbsp; solution achieves&nbsp; satisfactory&nbsp; performance&nbsp; on<br />HPC&nbsp; devices&nbsp; (Tesla&nbsp; graphic&nbsp; cards). Simulation is&nbsp; created&nbsp;&nbsp;&nbsp; in&nbsp; micro-service architecture that is portable and flexible and&nbsp; makes&nbsp; it&nbsp; easy&nbsp; to&nbsp; test&nbsp; CFD<br />simulations on common computers.</p>

Dans cette thèse, nous présenterons une architecture de communication multi-utilisateurs à base des réseaux de capteurs sans fil dans un environnement industriel fortement bruité. Deux modes de fonctionnement de cette architecture sont présentés ; un mode Many-To-One reliant plusieurs capteurs émetteurs à un seul récepteur et un mode One-To-Many reliant un émetteur à plusieurs capteurs récepteurs. La couche physique de ce système est basée sur une modulation par transformée par paquets d'ondelettes inverse (IDWPT) à l'émission et une transformée par paquets d'ondelette discrète (DWPT) en réception. Pour tester notre architecture, un modèle de canal industriel est proposé qui tient compte des phénomènes des multi-trajets et des évanouissements en plus du bruit additif. Ce dernier étant modélisé comme un bruit gaussien auquel s'additionne un bruit impulsionnel causant une dégradation significative des signaux. L'architecture est testée pour différentes configurations de communications sans fil et pour différentes formes d'ondelettes afin de proposer un mode de communication optimal. Aussi, une amélioration de la robustesse de notre système est effectuée en ajoutant un codage correcteur d'erreur du canal et un seuillage du bruit impulsionnel à la réception pour minimiser les effets du bruit industriel sur les signaux reçus. En utilisant un code correcteur d'erreur, la détection et reconstitution des signaux se fait sans erreur à partir d'un SNR de 8dB pour un taux de codage 1/4 pour une transmission sur à canal à évanouissement. Pour un récepteur optimal à base du seuillage du bruit, les performances en termes de taux d'erreur binaires sont améliorées de 10dB pour une transmission sur un canal à bruit industriel. Enfin, une comparaison de la robustesse de notre architecture impulsionnelle avec un système à base d'une modulation multi-porteuse classique OFDM est effectuée. Ceci nous amène à proposer un système de communication multi-utilisateurs robuste à base des réseaux de capteurs sans fil pour des communications en milieu industriel difficile. / In this thesis, we will present a multi-user communication architecture based on wireless sensor networks in a noisy industrial environment. Two modes of operation of this architecture are presented ; a Many-To-One mode linking several transmitter sensors to a single receiver and a One-To-Many mode linking a transmitter to several receiver sensors. The physical layer of this system is based on the inverse transform (IDWPT) at transmission and the discrete wavelet packet transform (DWPT) at reception. To test our architecture, an industrial channel model is proposed that takes into account the phenomena of multipath and fading in addition to additive noise. The latter being modelled as Gaussian noise to which is added an impulse noise causing significant signal degradation. The architecture is tested for different wireless communication configurations and wavelet shapes to provide an optimal communication mode. Also, an improvement in the robustness of our system is achieved by adding channel error correction coding and pulse noise thresholding at reception to minimize the effects of industrial noise on the received signals. Using an error-correcting code, the detection and reconstruction of signals is error-free from an SNR of 8dB for a coding rate of 1/4 for transmission on a fading channel. For an optimal receiver based on noise thresholding, the performance in terms of binary error rates is improved by 10dB for transmission over an industrial noise channel. Finally, a comparison of the robustness of our pulse architecture with a system based on a conventional OFDM multi-carrier modulation is carried out. This leads us to propose a robust multi-user communication system based on wireless sensor networks for communications in difficult industrial environments.

No description available.

Current task-centric many-core schedulers share a “naive” view of processor architecture; a view that does not care about its thermal, architectural or power consuming properties. Future processor will be more heterogeneous than what we see today, and following Moore’s law of transistor doubling, we foresee an increase in power consumption and thus temperature. Thermal stress can induce errors in processors, and so a common way to counter this is by slowing the processor down; something task-centric schedulers should strive to avoid. The Thermal-Task-Interleaving scheduling algorithm proposed in this paper takes both the application temperature behavior and architecture into account when making decisions. We show that for a mixed workload, our scheduler outperforms some of the standard, architecture-unaware scheduling solutions existing today. / QC 20120215

No description available.

Thesis--Ph. D., University of Hong Kong, 1983.

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (p. 113-118).

In this dissertation, the applications of many-body physics in neutral bosons and electronic systems in transition metal oxides are discussed. In the first part of the thesis, I will introduce the concepts of Bose condensation, emphasize the significance of the order parameter in superfluids (macroscopic wave function), and its consequence such as the emergence of exotic vortex states under rotation. Dated back to the importance of the vortex dynamics in the properties of high T[subscript c] superconductors, people have introduced a dual vortex description to describe the dynamics of charged bosons in a magnetic field. Similarly, the dual description is adapted to the problems of neutral bosons under rotation. Based on that picture, vortices behave like charges in an effective magnetic field which has been known to demonstrate different quantum phases such as Wigner crystal phase, and fractional quantum Hall liquid phases depending on the relative fraction of the number of bosons and vortices. In this work, we would like to address the validity of the picture by low energy effective theory. We can identify the origin of the vortex masse and the parameter regimes in which the vortex dual description is appropriate. In the second part of the dissertation, density functional theory is used to describe the strongly correlated matters with local density approximation and local Hubbard U interaction(LDA+U). We are particularly interested in the interface states in the heterojunction systems of two different perovskite oxides. What we found is that the interface states can be engineered to appear in certain transitional metal oxide layers by controlling the number of positive and negative charged layers, leading to the formation of quantum wells in two dimension. This type of systems ignite the hope to search for broken symmetry states in the interface which can be tunable with chemical doping or electric field doping. Even room temperature superconducting state may or may not exist in the interface is still an intriguing issue. / text