<p>The development of ultracold atom physics enables people to study fundamental questions in quantum mechanics within this highly-tunable platform. This dissertation focuses on several topics of the dynamical evolution of quantum systems.</p><p>Chapter 2 and 3 talk about Loschmidt echo, a simple quantity that reveals many hidden properties of a system’s time evolution. Chapter 2 looks for vanishing Loschmidt echo in the complex plane of time and the corresponding dynamical quantum phase transitions (DQPT) in the thermodynamic limit. For a two-site Bose-Hubbard model consisting of weakly interacting particles, DQPTs reside at the time scale inversely proportional to the interaction, where highly entangled pair condensates also show up. Chapter 3 discusses the revival of Loschmidt echo in a discrete time crystal, a Floquet system whose discrete temporal transition symmetry is spontaneously broken. We propose a new design and demonstrate its robustness against the fluctuations in the driving field. It can also be used in precision measurement to go beyond the Heisenberg limit. Experimental schemes are presented.</p><p>Out-of-time-order correlator (OTOC) is a more complicated variant of Loschmidt echo. Experimentally it requires reversing the time evolution. In Chapter 4, by exploiting the SU(1,1) symmetry of a weakly interacting BEC and connecting its quantum dynamics to a hyperbolic space, we obtain a geometric framework that enables experimentalists to manipulate the evolution with great freedom. Backward evolution is then realized effectively to measure OTOC of such SU(1,1) systems.</p><p>Chapter 5 discusses the decoherence of a spin impurity immersed in a spinor BEC. Our calculations show that by looking at the dynamics of the impurity’s reduced density matrix, the phase of the spinor BEC can be detected.</p>

No description available.

[EN] Zeolites are microporous crystalline materials showing channels and cavities of molecular dimensions in its interior. The main advantage of these materials is their high thermal and chemical stability as well as the possibility to change the topology and dimensions of the channels and cavities. The main goal of this thesis is to obtain new microporous materials (zeolites) and to widen the composition range of some existing materials, using high-throughput techniques of synthesis and characterization. Four families of structure directing agents (SDAs) are synthesized to obtain these microporous materials and each family is formed by quaternary tetraalkylammonium cations. The size and the volume of the members of each SDA family are increased to carry out a study on how it affects this increase on the type of zeolite that crystallizes Taking into account the importance of each of the various parameters that influence on the hydrothermal synthesis of zeolites and trying to cover all the possible range of composition, a factorial design of experiments for each obtained and characterized SDA is performed. The materials of interest obtained in these experiments are subjected to an exhaustive characterization, in order to determine its structure and properties. Known materials such as zeolites ITQ-3, ITQ-43 and ITQ-44 have been obtained with the SDAs used. But the most important thing of this thesis has been obtaining two new materials, which we refer to as ITQ-57 and ITQ-60. The structure of the zeolite ITQ-60 is completely determined and we can conclude that it is an intergrown material, formed by two layers and presenting a two-dimensional system of 10 x 12 MR channels. On the other hand, the structure of the zeolite ITQ-57 is in its final stages of definition, but we are able to determine is that it presents a large orthorhombic unit cell. We must also mention the obtaining of an optimized synthesis method of the chiral zeolite SU-32. This zeolite has been synthesized as a racemic mixture with a chiral SDA. Using theoretical calculations it has been found that every one of the enantiomers of the SDA is able to lead to the formation of each one of the enantiomers of chiral zeolite. The last step is to synthesize each enantiomer of the SDA separately, allowing us to obtain the two chiral zeolites. / [ES] Las zeolitas son materiales cristalinos microporosos que presentan canales y cavidades de dimensiones moleculares en su interior. La principal ventaja de estos materiales es su elevada estabilidad térmica y química, así como la posibilidad de poder variar la topología y dimensiones de los canales y cavidades. El principal objetivo de esta tesis doctoral es la obtención de nuevos materiales microporosos (zeolitas) y ampliar el rango de composición de alguno ya existente, empleando técnicas de síntesis y caracterización de alta capacidad. Para la obtención de estos materiales microporosos se sintetizan cuatro familias de agentes directores de estructura (ADEs), formadas por cationes tetraalquilamonio cuaternarios. En cada familia de ADEs se aumentan el tamaño y el volumen del agente para poder realizar un estudio sobre cómo afecta este aumento sobre el tipo de zeolita que cristaliza. Obtenidos y caracterizados los agentes directores de estructura, se lleva a cabo un diseño factorial de experimentos para cada uno de ellos teniendo en cuenta cada una de las variables que influyen sobre la síntesis hidrotermal de zeolitas e intentando cubrir el mayor rango posible de composición. Los materiales de interés obtenidos en estos experimentos se someten a una caracterización exhaustiva, para poder determinar su estructura y propiedades. Con los ADEs con los que se ha trabajado se ha obtenido materiales conocidos entre los que destacan las zeolitas ITQ-3, ITQ-43 e ITQ-44. Pero lo más importante de la realización de esta tesis ha sido la obtención de dos nuevos materiales, a los que se les ha denominado ITQ-57 e ITQ-60. La estructura de la zeolita ITQ-60 está completamente determinada y podemos concluir que es un material intercrecido, formado por dos capas y que presenta un sistema bidimensional de canales formados por anillos de 10 y 12 miembros. Por otro lado, la estructura de la zeolita ITQ-57 se encuentra en sus últimas etapas de determinación, pero ha podido determinarse que presenta una celda unidad ortorrómbica de grandes dimensiones. También es de destacar la obtención de un método optimizado de síntesis de la zeolita quiral SU-32. Esta zeolita se ha sintetizado en forma de mezcla racémica y empleando un ADE quiral. Mediante cálculos teóricos se ha podido comprobar que cada uno de los enantiómeros del ADE es capaz de dirigir hacia la formación de cada uno de los enantiómeros de la zeolita quiral. El último paso consiste en sintetizar por separado los enantiómeros del ADE, lo que nos permitirá obtener las dos zeolitas quirales. / [CA] Les zeolites son materials cristal·lins microporosos que presenten canals i cavitats de dimensiones moleculars al seu interior. El gran avantatge de estos materials és la seua estabilitat térmica i química, així com la possibilitat de poder variar la topología i dimensiones dels canals i cavitats. El principal objectiu de esta tesi doctoral es l'obtenció de nous materials microporosos (zeolites) i ampliar el rang de composició d'algú ja existent, fent ús de tècniques de síntesi i caracterització d'alta capacitat. Per a l'obtenció d'estos materials microporosos se sintetitzen cuatre famílies d'agents directors d'estructura (ADEs), formades per cationes tetraalquilamoni cuaternaris. En cada familia d'ADEs s'augmenta la grandària i el volum de l'agent per a poder realizar un estudi sobre com afecta esta augment sobre el tipus de zeolita que cristal·litza. Obtinguts i caracteritzats els agents directors d'estructura, es du a terme un disseny factorial d'experiments per a cadascun d'ells tenint en compte cadascuna de les variables que influïxen sobre la síntesi hidrotermal de zeolites i intentant cobrir el major rang possible de composició. El materials d'interés obtinguts en estos experiments es sotmeten a una caracteritzación exhaustiva, per a poder determinar la seua estructura i propietats. Amb els ADEs amb els quals s'ha treballat s'han obtingut materials coneguts entre els quals destaquen les zeolites ITQ-3, ITQ-43 i ITQ-44. Però el més important de la realitzación d'esta tesi ha sigut l'obtenció de dos nous materials, al quals se'ls ha denominat ITQ-57 i ITQ-60. L'estructura de la zeolita ITQ-60 està completament determinada i podem concloure que és un material intercrescut, format per dos capes i que presenta un sistema bidimensional de canals format per anells de 10 i 12 membres. D'altra banda, l'estructura de la zeolita ITQ-57 es trova en les seues últimes etapes de determinació, però ha pogut determinar-se que presenta una cel·la unitat ortoròmbica de grans dimensions. També cal destacar l'obtenció d'un método optimitzat de síntesi de la zeolita quiral SU-32. Esta zeolita s'ha sintetitzat en forma de mescla racèmica i emprant un ADE quiral. Per mitjà de càlculs teòrics s'ha pogut comprobar que cadascun dels enantiómers de la zeolita quiral. L'últim pas consisteix a sintetitzar per separat els enantiómers de l'ADE, la qual cosa ens permtetrà obtindre les dos zeolites quirals. / Diaz Canales, EM. (2015). Síntesis de Nuevos Materiales Microporosos Mediante Técnicas High-Throughput [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/59230

La multiplication des besoins des utilisateurs dans le domaine des télécommunications a conduit à une surexploitation du spectre de fréquence. Ceci a engendré la raréfaction des bandes de fréquence conduisant à une nécessité de gestion rationnelle des fréquences. Des contraintes ont été rajoutées aux systèmes d’émission / réception et en particulier sur les filtres pour éviter la saturation des services. Dans cette thèse, les travaux s’orientent surtout vers la conception de résonateurs, de filtres planaires et volumiques (3D) accordables dans le domaine des fréquences millimétriques (>= 30 GHz) en utilisant une nouvelle technique d’accordabilité basée sur des principes microfluidiques. Il s’agit d’une nouvelle approche d’agilité qui consiste à faire circuler de la matière (liquides conducteur, diélectrique ou magnétique) dans un substrat diélectrique par le biais de micro canaux. Le substrat diélectrique utilisé, est une résine SU-8 qui offre une souplesse dans la réalisation des micros canaux et des structures volumiques grâce à son bon facteur de forme (≈ 50%). La circulation de liquides dans le substrat, permet de modifier localement les propriétés électromagnétiques du milieu, ce qui conduit à une modification de la fréquence de résonance du dispositif. / The proliferation of user needs in the field of telecommunications, has led to overexploitation of the frequency spectrum. This led to the scarcity of frequency bands leading to a need for efficient management of frequencies. Constraints were added to the transmitting / receiving systems and in particular on the filters to prevent the saturation of the services. In this thesis, work is mainly oriented towards the design of resonators, planar and volumetric (3D) tunable filters in the field of millimeter wave frequencies (> = 30 GHz) using a new tunable technique which is microfluidic. This is a new approach to agility which consists of circulating the material (conductive, dielectric or magnetic liquids) in a dielectric substrate through micro channels. The dielectric substrate used is a resin SU-8 which provides flexibility in the implementation of microchannels and volumetric structures thanks to its good form factor (≈ 50%). The circulation of fluid in the substrate allows to locally modifying the electromagnetic properties of the medium. This leads to a change in the resonant frequency of the device.

University of Macau / Faculty of Social Sciences. / Department of Government and Public Administration

University of Macau / Faculty of Social Sciences and Humanities / Department of Government and Public Administration

University of Macau / Faculty of Social Sciences and Humanities / Department of Government and Public Administration

No description available.

We studied the structural instabilities of one-dimensional (1D) and quasi-one-dimensional (Q1D) electron-phonon systems at low temperature through two models, SuSchrieffer-Heeger (SSH) and molecular crystal (CM) with and without spin. The phase diagrams are obtained using a Kadanoff-Wilson renormalization group approach (GR). For the 1D half-filled system the study of the frequency dependence of the electronic gap allowed us to connect continuously the two limits, adiabatic and non-adiabatic. The Peierls and Cooper channels interference and the quantum fluctuations reduce the gap. A regime change occurs when the frequency becomes of the order of mean field gap, marking a quantum-classical crossover that is the Kosterlitz-Thouless type. At this level, the effective coupling behaves in power law function on frequency. For the case with spin, a gapped Peierls state is maintained in the non-adiabatic limit, while for the case without spin, the system transits to ungapped disordered state, namely the Luttinger liquid stat (LL). For the SSH model without spin, the GR confirms the existence of a threshold phonon coupling beyond which the gap is restored. The study of the rigidities of the two models without spin allowed us to trace the main features of the LL state predicted by the bosonization method. The study of the Holstein-Hubbard model has allowed us not only to reproduce the phase diagrams already obtained by the Monte Carlo method, but to highlight two additional phases, namely, free fermions phase and the bond charge-density-wave phase. We have extended this study to the quarter-filled Q1D Peierls systems at finite temperature. Within the SSH model, an unconventional superconducting phase with spin singlet symmetry SS-s emerges at low temperature when the deviation to the perfect nesting of the Fermi surface is strong enough. Peierls-SS transition is characterized by the presence of a quantum critical point at low frequency and by a power law behavior of the transition temperature as a function of frequency with an exponent identical to one of 1D system. This exponent which universality has been verified contrasts with the BCS result. Coulomb interactions have been introduced through the study of the extended SSH-Hubbard model. The extension of this work to half-filled SSH and CM cases was also performed.

研究目的 我國農地政策向以農地農有、農地農用，培養自耕農為主導。現行的農地政策，為保 護農業的生產條件，對農地有著嚴格的對人及對地的雙重管制。唯隨經濟環境改變， 近來屢有議者提出「小農經營制度，已不適於經濟原則，應由農企業公司購買農地， 實施企業化的大農經營，以促使農業升級」，則是否農地應該開放自由買賣？企業化 的大農經營是否適合當前台灣農業生產結構？開放農地買賣對農村社會又會造成什麼 影響？是為本文研究的目的。 主要參考文獻 現階段台灣農地問題之探討一劉泰英。經濟自由化與農地保護一陳明健。企業法人承 受農問題之探討一蘇志超。 研究方法 １•搜集次級資料探討當前農業問題與農業生產環境，以研究當前的農業問題之癥結 ，是否以開放農企業購買農地能有助於農業問題的舒解。 ２•以問卷調的方式，探討農家與農企業法人購地或售地意願，並進一步探討開放農 地買賣可能造成的影響。 研究內容 １•對於農業整體面，嘗試以農場經營規模，農業勞力結構轉換，農業機械化推行， 農產運銷、農業技術改良、作物、價格政策、土地管制等項目來分析。 ２•農家與企業家意願則以問卷內容為研究內容。