• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 577
  • 413
  • 182
  • 79
  • 36
  • 26
  • 22
  • 22
  • 20
  • 18
  • 18
  • 15
  • 9
  • 9
  • 9
  • Tagged with
  • 1778
  • 453
  • 376
  • 289
  • 281
  • 276
  • 221
  • 214
  • 183
  • 183
  • 182
  • 178
  • 171
  • 170
  • 170
  • 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.
81

Analysis of localized solutions in coupled Gross-Pitavskii equations

Qadir, Muhammad Irfan January 2013 (has links)
Bose-Einstein condensates (BECs) have been one of the most active areas of research since their experimental birth in 1995. The complicated nature of the experiments on BECs suggests to observe them in reduced dimensions. The dependence of the collective excitations of the systems on the spatial degrees of freedom allows the study in lower dimensions. In this thesis, we first study two effectively one-dimensional parallel linearly coupled BECs in the presence of external potentials. The system is modelled by linearly coupled Gross-Pitaevskii (GP) equations. In particular, we discuss the dark solitary waves and the grey-soliton-like solutions representing analogues of superconducting Josephson fluxons which we refer to as the fluxon analogue (FA) solutions. We analyze the existence, stability and time dynamics of FA solutions and coupled dark solitons in the presence of a harmonic trap. We observe that the presence of the harmonic trap destabilizes the FA solutions. However, stabilization is possible by controlling the effective linear coupling between the condensates. We also derive theoretical approximations based on variational formulations to study the dynamics of the solutions semi-analytically. We then study multiple FA solutions and coupled dark solitons in the same settings. We examine the effects of trapping strength on the existence and stability of the localized solutions. We also consider the interactions of multiple FA solutions as well as coupled dark solitons. In addition, we determine the oscillation frequencies of the prototypical structures of two and three FA solutions using a variational approach. Finally, we consider two effectively two-dimensional parallel coupled BECs enclosed in a double well potential. The system is modelled by two GP equations coupled by linear and nonlinear cross-phase-modulations. We study a large set of radially symmetric nonlinear solutions of the system in the focusing and defocusing cases. The relevant three principal branches, i.e. the ground state and the first two excited states, are continued as a function of either linear or nonlinear couplings. We investigate the linear stability and time evolution of these solutions in the absence and presence of a topological charge. We notice that only the chargeless or charged ground states can be stabilized by adjusting the linear or nonlinear coupling between the condensates.
82

Cavity mode entanglement in relativistic quantum information

Friis, Nicolai January 2013 (has links)
A central aim of the field of relativistic quantum information (RQI) is the investigation of quantum information tasks and resources taking into account the relativistic aspects of nature. More precisely, it is of fundamental interest to understand how the storage, manipulation, and transmission of information utilizing quantum systems are influenced by the fact that these processes take place in a relativistic spacetime. In particular, many studies in RQI have been focused on the effects of non-uniform motion on entanglement, the main resource of quantum information protocols. Early investigations in this direction were performed in highly idealized settings that prompted questions as to the practical accessibility of these results. To overcome these limitations it is necessary to consider quantum systems that are in principle accessible to localized observers. In this thesis we present such a model, the rigid relativistic cavity, and its extensions, focusing on the effects of motion on entanglement and applications such as quantum teleportation. We study cavities in (1+1) dimensions undergoing non-uniform motion, consisting of segments of uniform acceleration and inertial motion of arbitrary duration that allow the involved velocities to become relativistic. The transitions between segments of different accelerations can be sharp or smooth and higher dimensions can be incorporated. The primary focus lies in the Bogoliubov transformations of the quantum fields, real scalar fields or Dirac fields, confined to the cavities. The Bogoliubov transformations change the particle content and the occupation of the energy levels of the cavity. We show how these effects generate entanglement between the modes of the quantum fields inside a single cavity for various initial states. The entanglement between several cavities, on the other hand, is degraded by the non-uniform motion, influencing the fidelity of tasks such as teleportation. An extensive analysis of both situations and a setup for a possible simulation of these effects in a table-top experiment are presented.
83

Quantum and semiclassical calculations of electron transport through a stochastic system

Hardwick, David Peter Andrew January 2007 (has links)
In this thesis, I present a semiclassical and quantum mechanical study of a biased superlattice with a tilted magnetic field applied. This system exhibits non-KAM chaotic behaviour which can be controlled by the ratio between the cyclotron and Bloch frequencies. I will use a semiclassical model to show that electron trajectories become unbounded when this ratio takes an integer value. These extended electron trajectories cause peaks in the electron drift-velocity, which lead to current enhancements calculated using a drift-diffusion model. Furthermore, I will explain this current enhancement with reference to the electric field and charge carrier density across the superlattice. These results will then be compared to experimentally measured current-voltage characteristics. A second superlattice is also studied, which has a high probability of interminiband tunnelling. I will outline several theoretical models to account for interminiband tunnelling and will ultimately use an empirical method. The current-voltage results obtained via this method will then be compared to experimental data. Finally, I will use a quantum mechanical model to determine the electron eigenstates for the first superlattice. These quantum mechanical eigenstates will be compared to the semiclassical results to determine the degree of correspondence between the two models. Furthermore, I will use the eigenstates to calculate the energy level structure of the system and investigate how this varies for different applied field strengths. Ultimately, I will suggest a combined band transport plus scattering model to explain experimental current-voltage data obtained for high magnetic fields.
84

The evolution of Japan's constitution and implications for U.S. forces on Okinawa

Stavale, Giuseppe A. 12 1900 (has links)
Approved for public release, distribution is unlimited / Okinawa serves as a strategic base for U.S. forces in maintaining regional security and protecting Japanese and American interests based on the 1960 Treaty of Mutual Cooperation and Security between Japan and the United States and its 1951 predecessor. This thesis assesses the developing factors in Japan's constitutional debate after the terrorist attacks of September 11, 2001. It examines the myriad issues influencing the reinterpretation or potential revision of Article 9 of Japan's constitution and what implications revision would have on Japan-based U.S. forces stationed primarily in Okinawa. This thesis argues that Tokyo's reinterpretation or revision of Article 9 of Japan's constitution would not require a major withdrawal of U.S. forces from Okinawa. Regional threats still validate the half-century old U.S.-Japan Security Alliance and most of its current structure. The major questions the thesis addresses are how and why Japan is reinterpreting or may revise its constitution, what dangers threaten Japanese and American security and interests, and how Okinawa's bases contribute to the security and stability of the region and at what price. Furthermore, this thesis evaluates the validity of perceptions regarding U.S. troops on Okinawa, and it seeks to clarify the situation on Okinawa. This thesis' arguments set the stage for a policy-prescriptive conclusion which is predicated on six individual premises. A major point is the validation of a viable and proven U.S. expeditionary force to remain stationed within Japan. Also, it offers practical recommendations for what is next for U.S. forces on Okinawa, including maintaining the status quo with certain adjustments, overhauling public relations and media interactions, and examining the merits of Kadena Air Base and Ie Island for the relocation of Marine Corps Air Station Futenma. / Captain, United States Marine Corps
85

Afghanistan's constitutions a comparative study and their implications for Afghan democratic development

Sherman, Zoe Bernadette 03 1900 (has links)
Afghan constitutions have had a tendency to marginalize Afghan society. As a result, the continued ethnic fragmentation of Afghanistan has minimized the capacity of constitutions of the past to achieve societal stability. Instead, past Afghan constitutions have explicitly supported regimes rather than address the problems of the fragmentation of Afghanistan into small ethnic, linguistic, familial, and in some cases religious elements. While Afghanistan's current constitution accommodates the multi-ethnic pattern of Afghan society, it provides only a partial solution to the challenges of state building created by multi-ethnic societies. The central purpose of this thesis, therefore, is to determine the sustainability of Afghanistan's current constitution by analyzing the legacy and impact of past constitutions on the current document and its relationship with Afghan society and polity. Each of Afghanistan's constitutions of the past is missing important elements that prevented its impact on even the nearest reach of the rural tribal society. The realities of the 2003 Constitutional Loyal Jirga, the manner in which it represented the population, and the language that it codified in Afghanistan's 2004 constitution will therefore have a lasting impact on Afghanistan's future as well as reveal critical policy implications regarding state building.
86

Jean-Jacques Rousseau : de la théorie à la politique appliquée

Fortier, Vincent January 2002 (has links)
Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.
87

Ústavní záruky nestrannosti soudců a její sociální konotace / Constitutional guarantees of Impartiality of Judges and its Social connotations

Žižko, Igor January 2014 (has links)
Modern society is based on respect for the individual and at the same time it has created the institute of justice under which parties, in the interest of maintaining social cohesion, should resolve their disputes using the system of applying rights. The task of the judiciary is therefore to be an impartial arbiter, which is an absolute criterion for the acceptance of authoritativeness of this body, or more precisely the functionality and signification of this institute within the social contract. Only an unbiased judge can be the only guarantee for the nemo iudex in causa sua principles to be observed. The European Convention imposes on the states - members of the Council of Europe such legal conditions which guarantee every country the right for their affairs to be discussed fairly, in public and in a reasonable time limit by an independent and impartial court established by law which will decide about their civil rights and obligations or of any criminal charges raised against them. The Constitutional Order of the Czech Republic guarantees everybody the right to a fair trial conducted in accordance with the law before an impartial judge. Constitutional guarantees of fair legal proceedings before an impartial judge are supplemented with legal rules of the sub constitutional law. Yet, it is the...
88

Ústavní vývoj Anglie od počátků do 17. století / Constitutional development in England from the beginning until the 17th century

Kollárová, Zuzana January 2013 (has links)
Constitutional Development in England from the beginning until the 17th century This thesis analyses the constitutional development and the evolution of the law and the society on the English territory from the formation of the first Anglo-Saxon kingdoms until the beginning of the 17th century. The aim of this work is to study the constitutional and legal development on the basis of historical events and thus offer an integrated interpretation and explanation of the issue. The thesis consists of eleven chronological chapters, in each of which the most important aspects of the constitutional development of the period are scrutinized. The emphasis is put on the most importan law heritage on the evolution of the law and law institutes, of the central as well as local state authorities and of the position and role of the sovereign/monarch in the given period. Particular attention is paid to the origin and the development of parliamentarism, its relation towards the monarch and their mutual interaction. The first chapter deals with the Anglo-Saxon period and the genesis of the origins of the legal development on the current English territory, with the arrival of Anglo-Saxon tribes and with the formation of the first political statehoods in this territory. The chapter focuses on the analysis of the most important...
89

Non-equilibrium dynamics of Bose-Einstein condensates

Welch, Nathan January 2015 (has links)
In the following work we investigate the dynamics of Bose-Einstein condensates(BECs) under the influence of time-dependent potentials. The response of such a sensitive system to external perturbations is a matter of increasing interest. This is because of the enormous growth in understanding the physics and emerging applications of BECs in many areas of physics such as sensing, microscopy and quantum information.
90

Přechod k demokracii v Peru v 80. letech a následný vývoj země / Transition to democracy in Peru in the 80s and the following development of the country

Zavoralová, Veronika January 2010 (has links)
This thesis analyses the transition to democracy in Peru and monitors the following development of the country after installing democratic regime. Since the democracy is the fundamental notion of this thesis, first of all it is defined and after is evaluated the current state of democracy in the world and more in detail in Latin America. The thesis shows that the transition to democracy in Peru was in many was similar to the others democratic processes in the region but also that it has certain specialities. In the end, the thesis evaluates the current state of democracy in Peru according to perception of the inhabitants of this country.

Page generated in 0.0468 seconds