• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 90
  • 10
  • 10
  • 10
  • 10
  • 10
  • 8
  • 7
  • 6
  • 6
  • 2
  • 1
  • 1
  • Tagged with
  • 117
  • 63
  • 59
  • 50
  • 43
  • 26
  • 25
  • 24
  • 23
  • 23
  • 17
  • 15
  • 15
  • 13
  • 13
  • 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.
91

La lutte contre la prolifération des armes légères et de petit calibre en droit international / The action against the proliferation of small arms and light weapons in international law

Ancelin, Julien 13 November 2014 (has links)
La prolifération des armes légères et de petit calibre est un phénomène nouvellement saisi par le droit international. En tant que menace pour la paix et la sécurité internationale, elle fait, depuis la fin de la guerre froide, l’objet d’attentions grandissantes. Tout d’abord abordée par des organisations internationales régionales, elle constitue désormais le domaine d’action privilégié de l’Organisation des Nations Unies en matière de désarmement. Néanmoins, la construction d’une lutte contre la prolifération ambitieuse et cohérente est difficile et doit faire face à des oppositions nombreuses justifiées par des intérêts étatiques profondément divergents. Le corpus normatif adopté est donc sujet à d’importantes limites et insuffisances. Par ailleurs, les instruments classiques de l’ordre juridique international apparaissent inaptes à garantir l’effectivité de ces nouvelles règles qui étendent le champ du droit international. La lutte contre la prolifération nécessite, pour être effective, de reposer sur des mécanismes plus approfondis que ceux régissant le droit international de la coopération duquel les règles classiques de désarmement étaient jusqu’alors issues. / The proliferation of small arms and light weapons has only recently been inquired into by international law. As for threatening the global peace and security, it has increasingly been scrutinized since the end of the Cold War. First handled by regional international organizations, it henceforth constitutes, regarding disarmament, the elected field of action for the United Nations. Structuring, nevertheless, an ambitious and coherent action against this proliferation appears quite challenging and has thus to overcome numerous oppositions grounded in profoundly diverging static interests. The current body of norms appears rather limited and inadequate. Furthermore, the classical instruments of the international legal order do not seem suitable to secure the effectiveness of those recent norms that expand the reach of international law. Successfully acting against this proliferation requires to relying on mechanisms that are deeper than the current international law of cooperation, and out of which the classical rules of disarmament have been hitherto extracted.
92

Retinal associations of diabetes and vascular disease

Jeganathan, V. Swetha January 2009 (has links)
Background: Diabetes mellitus and vascular diseases have a significant impact on the eye. / Aim: To determine the prevalence, risk factors, and racial/ethnic differences of major eye conditions, particularly retinal conditions, associated with diabetes and vascular diseases. / Scope: To date, the majority of studies have examined the association of retinal vascular calibre and diabetes in predominantly white Caucasian populations. Further elucidation of ethnic differences in effects of hyperglycaemia on early microvascular disease is relevant, particularly amongst Asians where diabetes is likely to see the largest increase in prevalence over the next decade. We therefore examined these findings from three Asian population-based studies, the Singapore Malay Eye Study (n=3280), Singapore Prospective Cohort Study and Singapore Cardiovascular Cohort Study 2 (n=3748). / Results: The prevalence of diabetic retinopathy in the Singapore Malay Eye Study was 35%, and associated with longer duration of diabetes, poorer glycemic and blood pressure control. More importantly, 9.0% had vision-threatening retinopathy, and retinopathy was found in 6.0% of people without diabetes. Retinal vascular calibre changes were incriminated in diseases such as diabetes and hypertension, independent of traditional cardiovascular risk factors. Wider venular calibre was independently associated with early age-related macular degeneration. We also found a novel association between peripheral artery disease and glaucoma, stronger in persons with diabetes, independent of vascular risk factors, supporting the vascular theory of glaucoma. / Implications: Subtle changes in retina, including retinal vascular calibre may be early markers of widespread microvascular changes in diabetes, resulting from chronic hyperglycaemia and other pathogenic processes. These results will have broad implications for understanding the impact of both microvascular and macrovascular complications of diabetes in the Asia Pacific region and targeting relevant therapeutic interventions.
93

Critical factors for project success in an engineering environment / Francois Vorster

Vorster, Francois January 2008 (has links)
Not every project deserving of success achieves it. Conversely, not every project heading for the scrap heap arrives. The journey to project success is long and hard and does not happen overnight. To understand the journey to project success we need to understand what makes a project successful. A successful project can be classified as a Project of which the costs did not exceed 25% of the agreed capital approved with a less than 25% schedule slip and with all the operational problems being sorted out in less than a year. Project success potential, can be increased by focusing on the critical factors listed in this study, namely: Project Front End Loading (FEL), high calibre project teams, and people skills/soft skills of project management. The success of a project can be increased when the project has high calibre project teams starting the project with very effective Front End Loading (FEL) and keep project team members continuity based on the fact that the project is managed by a project manager understanding people who have the soft skill to lead and influence the project team, rather than managing the team. The research was conducted by means of a literature and empirical study. The literature study documents the critical factors for project success. Knowledge gained from the literature study formed the basis for the empirical study to test critical factors for project success in practice and the recommendations can be read in chapter four. / Thesis (M.B.A.)--North-West University, Vaal Triangle Campus, 2009.
94

Critical factors for project success in an engineering environment / Francois Vorster

Vorster, Francois January 2008 (has links)
Not every project deserving of success achieves it. Conversely, not every project heading for the scrap heap arrives. The journey to project success is long and hard and does not happen overnight. To understand the journey to project success we need to understand what makes a project successful. A successful project can be classified as a Project of which the costs did not exceed 25% of the agreed capital approved with a less than 25% schedule slip and with all the operational problems being sorted out in less than a year. Project success potential, can be increased by focusing on the critical factors listed in this study, namely: Project Front End Loading (FEL), high calibre project teams, and people skills/soft skills of project management. The success of a project can be increased when the project has high calibre project teams starting the project with very effective Front End Loading (FEL) and keep project team members continuity based on the fact that the project is managed by a project manager understanding people who have the soft skill to lead and influence the project team, rather than managing the team. The research was conducted by means of a literature and empirical study. The literature study documents the critical factors for project success. Knowledge gained from the literature study formed the basis for the empirical study to test critical factors for project success in practice and the recommendations can be read in chapter four. / Thesis (M.B.A.)--North-West University, Vaal Triangle Campus, 2009.
95

Teoria da gravitação num espaço-tempo de Weyl não-integrável

Lima, Ruydeiglan Gomes 25 February 2016 (has links)
Submitted by Vasti Diniz (vastijpa@hotmail.com) on 2017-09-12T13:25:21Z No. of bitstreams: 1 arquivototal.pdf: 1212419 bytes, checksum: 6d3ca7625ab07b583f3f68045187a552 (MD5) / Made available in DSpace on 2017-09-12T13:25:21Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1212419 bytes, checksum: 6d3ca7625ab07b583f3f68045187a552 (MD5) Previous issue date: 2016-02-25 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / In 1918 the German Hermann Weyl developed a unified theory of gravitation and electro­magnetism becoming geometrical both interactions, that is, he associated the potential elec­tromagnetic a 1-form a, after considering that the length of a vector is not preserved under parallel transport as well as with the direction, this also meant that the covariant derivatives of the metric tensor ceased to be null becoming Vag" = a, The gravitational and electromagnetic field equations are obtained from the action I = f (R2 ± v Ft" ) —gd4x in a gauge any and "natural gauge"R = A = constant taking into account that they, as well as the action, should be both invariant under coordinate transformations as invariant under the gauge transformations introduced, namely, gliv = of gin, and di, = cp.+ hi, actually, the first person to speak in scale invariance in physics was the Weyl himself in his article. It is also found that the solutions to the emptiness of Einstein's field equations are also solutions of the corresponding Weyl's field equations. Finally it is shown that the Weyl affine geo­desic may not come from a variational principle by analysing the Helmholtz conditions for the inverse problem of the calculus of variations and discusses about Einstein's criticism of the theory, on which it is concluded that the even seized an inadequate definition of proper time to give his opinion on the work of Weyl, thus, a problem to be solved was to find a good definition of proper time, which leaves open a final version of the Weyl theory. / Em 1918 o alem-do Hermann Weyl desenvolveu sua teoria de unificndo entre gravitacao e eletromagnetismo geometrizando ambas as internOes, isto é, ele associou o potencial eletromagnetico a uma 1-forma a, depois de ter considerado que o comprimento de um vetor nao preserva-se sob transporte paralelo assim como acontece com a direcao, isso tambem fez com que a derivada covariante do tensor metrico deixasse de ser nula tornando­se V agii, = glivaa. As equagOes de campo gravitacionais e eletromagneticas sdo obti­das da nao I = f (R2 ±AF,,,,Filv)\/—gd4x em um calibre qualquer e no "calibre natural" R = A = const ante levando em conta que elas, assim como a nao, devem ser tanto invari­antes por transformnOes de coordenadas como invariantes sob as transformnOes de calibre introduzidas, a saber, gliv = of gin, e di, = al, + hi, na verdade, a primeira pessoa a falar em invarifincia de escala na fisica foi o prOprio Weyl em seu artigo. Tambem é verificado que as solucOes para o vazio das equagOes de campo de Einstein tambem sac) solucOes das equnOes de campo de Weyl correspondentes. Por fim mostra-se que as geodesicas afins de Weyl nao podem advir de um princfpio variacional atraves da analise das condicOes de Helmholtz para o problema inverso do calculo de varinOes e discute-se sobre a critica de Einstein a teoria, onde conclui-se que o mesmo se apoderou de uma definicao inadequada de tempo proprio para dar seu parecer sobre o trabalho de Weyl, assim, um problema a ser resolvido seria encontrar uma boa definicao de tempo pr6prio, o que deixa em aberto uma versdo final da teoria de Weyl.
96

A extensão ub−l(1) do modelo padrão

Freitas, Felipe Ferreira de 08 March 2013 (has links)
Submitted by Vasti Diniz (vastijpa@hotmail.com) on 2017-09-18T13:07:50Z No. of bitstreams: 1 arquivototal.pdf: 727578 bytes, checksum: b15ffe582074573c53ae0805d8b1edcb (MD5) / Made available in DSpace on 2017-09-18T13:07:50Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 727578 bytes, checksum: b15ffe582074573c53ae0805d8b1edcb (MD5) Previous issue date: 2013-03-08 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The fact that neutrinos are massive indicates that the Standard Model (MP) should be extended. In this thesis we study the gauge extension called B-L, which is based on the symmetry group SUci (3) SUL (2) Uy (1) UB_L(l). The additional factor UB_L(l) brings up a new boson, called Z ', then the addition of a new scalar is needed to break this new symmetry. We will show that this model provides a natural background for right-handed neutrinos and the see-saw mechanism of mass production. Moreover, we find some phenomenological aspects of this model, as the absence of anomalies and some decay widths of the new boson. Finally, a brief analysis is made of how this new boson can be produced in acleradores particle and its lower bounds of his mass. / 0 fato de os neutrinos serem massivos indica que o Modelo Padrao (MP) deve ser extendido. Nesta dissertagdo, é estudada a extensao de calibre denominada B-L, a qual é baseada no grupo de simetria SUc(3) SUL(2) Uy (1) UB_L(1). 0 fator adicional UB_L(l) faz corn que aparega urn novo bOson, denominado Z'. logo, a adigao de urn novo escalar se faz necessaria para quebrarmos essa nova simetria. Vamos mostrar que esse modelo fornece urn cenario natural para os neutrinos de mao direita, bem como o mecanismo see-saw de produgdo de massa para os mesmos. Alem disso, verificamos alguns aspectos fenomenolOgicos desse modelo, como a ausencia de anomalias e algumas larguras de decaimento desse novo bOson. Por fim, é feita uma breve analise de como esse novo bOson pode ser produzido nos aceleradores de particulas e seu limite inferior de massa.
97

Efeitos térmicos na teoria quântica de campos em (2+1) dimensões / Thermal Effects in Quantum Field Theory in (2 +1) dimensions.

Silvana Perez 03 June 2003 (has links)
Efeitos térmicos em teorias de calibre em (2+1) dimensões são estudados em espaços onde as coordenadas podem ou não comutar. No caso comutativo, a dependência com a temperatura do tensor de polarização é calculada a um laço em teorias envolvendo tanto bósons quanto férmions. Como aplicação, são calculados os processos de blindagem em tais modelos, chegando ao interessante resultado de que cargas magnéticas não sofrem tais efeitos na QED3. Uma prova válida em qualquer ordem de perturbação é desenvolvida, confirmando este comportamento. Em teorias não comutativas, são estudadas as correções a um laço ao coeficiente de Chern-Simons, sendo encontrado que não existe o fenômeno da mistura UV/IR na teoria Chern-Simons-Higgs. O comportamento assintótico de tal coeficiente é analisado no regime de altas temperaturas. Vários outros aspectos envolvendo os efeitos térmicos em teorias de Chern-Simons são explorados. / Thermal effects in (2+1)-dimensional gauge theories are studied in both commutative as well as noncommutative manifolds. In the first situation, the finite temperature polarization tensor is computed a tone loop for fermionic and bosonic couplings. As an application, the screening masses are evaluated and it is found the surprising result that magnetic charges are not screened in QED3. It is demonstrated that this result holds to any order in pertubationtheory. In the noncommutative case, the one loop correction to the Chern-Simons coefficient is studied, and it is found that there is no UV/IR mixing in the Chern-Simons-Higgs model. The asymptotic behavior of such coefficient is analised in the high temperature regime. Several other interesting aspects involving thermal effects of Chern-Simons theories are also discussed.
98

Campos de calibre artificiais em condensados de Bose-Einstein / Artificial gauge fields on Bose-Einstein condensates

Diogo Lima Barreto 11 February 2015 (has links)
Nesta dissertação nós revisamos a teoria básica que descreve a junção Josephson bosônica para uma e duas espécies partindo do modelo de Bose-Hubbard. Em seguida explicamos como é possível gerar campos de calibe artificiais em um sistema de átomos neutros, como é o caso do condensado de Bose-Einstein. Finalmente, utilizando os conhecimentos teóricos desenvolvidos anteriormente nós buscamos os estados estacionários de um sistema de pseudospin 1/2 submetido a um campo de calibre não-Abeliano artificial, que torna a dinâmica da junção muito mais complexa e rica. Nós também exploramos um novo desbalanceamento de população que surge no sistema, devido a presença do campo de calibre, com características similares as do Macroscopic Quantum Self-Trapping. / In this dissertation we review the basic theory that describes the bosonic Josephson junction for one and two species using the Bose-Hubbard model. Afterwards, we explain how it is possible to generate artificial gauge fields for neutral atoms, like a Bose-Einstein condensate. Finally, using this theoretical background we search for stationary states of a pseudospin 1/2 system subject to a non-Abelian artificial gauge field which turns the dynamic of the junction much more complex and rich. We also explore a possible new populational imbalance that appears on the system due to the presence of the gauge field, with similar features as the Macroscopic Quantum Self-Trapping.
99

Análise clássica e quântica de sistemas com simetrias locais e suas aplicações

Rizzuti, Bruno Ferreira 29 February 2012 (has links)
Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-04-26T17:48:21Z No. of bitstreams: 1 brunoferreirarizzuti.pdf: 507162 bytes, checksum: 6ccfc7f9025a41c3c8bc647f63d413ea (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-05-13T12:04:02Z (GMT) No. of bitstreams: 1 brunoferreirarizzuti.pdf: 507162 bytes, checksum: 6ccfc7f9025a41c3c8bc647f63d413ea (MD5) / Made available in DSpace on 2017-05-13T12:04:02Z (GMT). No. of bitstreams: 1 brunoferreirarizzuti.pdf: 507162 bytes, checksum: 6ccfc7f9025a41c3c8bc647f63d413ea (MD5) Previous issue date: 2012-02-29 / Passados mais de 60 anos da sua formulação inicial, o método de Dirac-Bergmann para hamiltonização de sistemas lagrangianos singulares continua sendo uma ferramenta poderosa para análise e investigação de modelos atuais de física teórica. Como motivação, apresentaremos vários exemplos onde o método é utilizado e o descreveremos em detalhes em uma sequência de passos. O objetivo central deste trabalho será então apresentar uma série de aplicações distintas do método de Dirac, incluindo a busca de simetrias locais para teorias singulares, a construção da proposta de relatividade especial dupla de Magueijo-Smolin, a formulação da mecânica clássica com invariância de reparametrizações e sua quantização e por fim, discutiremos um modelo semiclássico mecânico que, quando quantizado, reproduz a equação de Dirac. / After more than 60 years of its initial development, the Dirac-Bergmann method for hamiltonization of constrained systems is still a powerful tool for analysis and investigation of modern theoretical models. As a motivation, we shall present several models where the method is applied, then we will describe it in details, with a sequence of steps. The main objective of this work is to provide distinct applications of the Dirac method, including the search for local symmetries of singular theories, the construction of the Magueijo-Smolin doubly special relativity proposal, the formulation of classical mechanics with reparametrization invariance and its quantization and finally, we discuss a semiclassical mechanical model that produces the Dirac equation through quantization.
100

As ambiguidades de escolha de calibre e de parametrização da métrica em gravitação quântica

Gonçalves, Jeferson Dias 27 February 2018 (has links)
Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2018-04-11T18:45:14Z No. of bitstreams: 1 jefersondiasgoncalves.pdf: 877599 bytes, checksum: 55b47e460c6f0960d499ee03cfdfbd27 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-04-11T19:36:44Z (GMT) No. of bitstreams: 1 jefersondiasgoncalves.pdf: 877599 bytes, checksum: 55b47e460c6f0960d499ee03cfdfbd27 (MD5) / Made available in DSpace on 2018-04-11T19:36:44Z (GMT). No. of bitstreams: 1 jefersondiasgoncalves.pdf: 877599 bytes, checksum: 55b47e460c6f0960d499ee03cfdfbd27 (MD5) Previous issue date: 2018-02-27 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nesta tese expomos primeiramente um breve histórico-motivacional para a construção de uma teoria de gravitação quântica, bem como, rápidas revisões orientadas sobre elementos de teorias quânticas de campos e sobre a técnica de Schwinger-Dewitt. De posse destas ferramentas, discutimos a dependência de calibre e da parametrização para uma teoria quântica de gravitação em um espaço-tempo de dimensão arbitrária D. Com este objetivo, calculamos explicitamente as correções quânticas a 1-loop, da ação efetiva da teoria, considerando a parametrização mais geral possível para a métrica quântica. Essa parametrização contém inicialmente sete parâmetros, sendo que alguns deles serão fixados através da condição de fixação de calibre, o que torna o nosso cálculo um pouco mais simples. Por fim, para esta teoria, confirmamos a validade de um teorema geral, o qual garante a independência das divergências on-shell, a 1-loop, com respeito às ambiguidades nas escolhas de calibre e de parametrização da métrica quântica. / In this thesis we first present a brief historical-motivational for a construction of a theory of quantum gravitation, as well as quick reviews oriented on elements of quantum field theory and Schwinger- Dewitt technique. In possession of these tools, the gauge and parametrization dependence is discussed in quantum gravity in an arbitrary dimension D. Explicit one-loop calculations are performed within the most general parametrization of quantum metric with seven arbitrary parameters. On the other hand, some of the gauge fixing parameters are fixed to make the calculations relatively simple. We confirm the general theorem stating that the on shell local terms in the one-loop effective action are independent of the gauge and parametrization ambiguity.

Page generated in 0.0354 seconds