Made available in DSpace on 2016-06-02T20:27:38Z (GMT). No. of bitstreams: 1 2986.pdf: 2823547 bytes, checksum: f441262673832018c0efbb46e2a10221 (MD5) Previous issue date: 2010-05-24 / Financiadora de Estudos e Projetos / In this work we study dimensional reductions in some quantum systems; such reductions occur due to confinement of the particle from a tube in space to a curve. Our main goal is to find the effective hamiltonian operator that describes the motion of the particle after confinement. We consider three particular situations. (1) In the first situation, we study an infinitely long tube generated by a curve with non-trivial torsion and curvature. Here the tube cross sections always have the same diameter. (2) We also study tubes in space deformed in a specific way, i.e., the diameter of the cross sections have a unique global maximum. Such tubes also have non-trivial torsion and curvature. (3) Finally, we analyze the question of which self-adjoint extension of the one-dimensional hydrogen atom would be physically relevant. We consider such atom in a three-dimensional tube and take the limit as the tube converges to the x axis, and it is shown that the Dirichlet (at the origin) extension is always obtained after such confinement. / Neste trabalho estudamos reduções de dimensões em alguns sistemas quânticos; tais reduções ocorrem devido ao confinamento do movimento de partículas, inicialmente em tubos no espaço, a curvas. Nosso principal objetivo é encontrar o operador efetivo que descreve o movimento da partícula após o confinamento. (1) Na primeira situação estudamos um tubo infinito gerado por uma curva com torção e curvaturas não-triviais. Aqui as seções transversais possuem sempre o mesmo diâmetro. (2) Estudamos também tubos no espaço deformados de uma forma específica, ou seja, o diâmetro das seções transversais possui um único máximo global. Tais tubos também apresentam curvatura e torção não-triviais. (3) Finalmente analisamos a questão de qual extensão auto-adjunta do átomo de hidrogênio unidimensional seria fisicamente relevante. Consideramos tal átomo num tubo tridimensional e estudamos o limite de quando o tubo converge ao eixo-x, e isso mostrou que a extensão de Dirichlet foi sempre obtida após o confinamento.

This dissertation describes work carried out between June 1987 and October 1991, in the Low Temperature Physics Group at the Cavendish Laboratory, Cambridge. The aim of this work was to use electron tunnelling spectroscopy to measure the density of excitation states of the recently discovered high-temperature superconductors. Tunnelling is the most sensitive method for measuring a superconductor’s energy gap, and historically has provided important evidence for the microscopic mechanism of superconductivity in conventional metals. It was hoped that electron tunnelling would prove equally successful in revealing the mechanism of superconductivity in these new materials. Preliminary experiments showed that a thick, degraded surface layer prevented preparation of high-quality tunnel junctions by conventional evaporation techniques. For this reason, apparatus for the formation and fine control of low-temperature point-contact junctions was constructed, together with new measurement electronics and a computer-controlled data-acquisition system. To test this apparatus, point-contact junctions were formed on conventional superconductors. By increasing pressure of the tip on the sample the junction could be moved from the tunnelling to the metallic regime. Point-contact measurements were then made on a number of ceramic, single-crystal and thin-film high-temperature superconducting materials; some not previously investigated by tunnelling. Although ‘gap-like’ structure was occasionally observed, anomalous features (e.g., voltage-dependent background, broadening, large zero-bias conductance) were always present and usually dominated the tunnelling characteristics. These complicate estimation of the energy gap and preclude measurement of more subtle properties such as gap anisotropy or the effective phonon spectrum, α2F. The origins of these non-ideal features have been much debated in the literature and are reviewed in this dissertation. In the case of thin films deposited by laser ablation the tunnelling characteristics were dominated by single-electron tunnelling effects (Coulomb gap and staircase structure). The results suggest that the surface region consists of numerous, isolated normal metal particles.

Submitted by Israel Vieira Neto (israel.vieiraneto@ufpe.br) on 2015-03-04T17:54:03Z No. of bitstreams: 2 DISSERTAÇÃO Oscar Bezerra Pezo.pdf: 5982903 bytes, checksum: b9759670a74301d6ab644f498ad40ad1 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) / Made available in DSpace on 2015-03-04T17:54:03Z (GMT). No. of bitstreams: 2 DISSERTAÇÃO Oscar Bezerra Pezo.pdf: 5982903 bytes, checksum: b9759670a74301d6ab644f498ad40ad1 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Previous issue date: 2013-07-02 / CAPES / A presente dissertação analisa, em termos do comportamento carga-recalque, um banco de dados organizado por Wilson Cartaxo Soares (2011), de fundações em grupo de estacas e radier estaqueados, executados em solo arenoso de várias camadas da área litorânea de João Pessoa/PB, com 07 provas de carga, estáticas, em estacas do tipo Hollow Auger, construídas em escala real, com 300 mm de diâmetro e 4,5 m de comprimento. Os dados foram retroanalisados com o Método dos Elementos Finitos (MEF 3D), utilizando o programa CESAR-LCPC v4 (Cleo 3D versão 1.07). Na modelagem do comportamento tensão-deformação do solo foi utilizado o modelo constitutivo de Mohr-Coulomb. Os parâmetros geotécnicos iniciais utilizados em cada um desses modelos foram obtidos através de correlações a partir de valores de NSPT obtidos por SOARES (2011). Os resultados dessas simulações numéricas foram comparados com os resultados experimentais, medidos nas provas de carga. Definiu-se os parâmetros geotécnicos do solo a partir da retroanálise por meio da modelagem numérica para serem empregados em futuras simulações no maciço. Análises paramétricas são executadas com o intuito de obter um maior conhecimento do comportamento da fundação em radier estaqueado, usando o modelo elásticoplástico de Mohr-Coulomb. Isso ocorre mediante algumas alterações de sua configuração que inclui a espessura do radier, número, diâmetro, espaçamento e comprimento das estacas embutido no solo. Carga vertical central está sendo considerada para a análise paramétrica. O recalque máximo, recalque diferencial e distorção angular do radier diminuem, com o aumento da espessura do radier, do número, comprimento e diâmetro das estacas.

El objetivo principal de esta tesis es entender el impacto de cambios abruptos en la geometría de la placa subductante (slab) en el proceso de ruptura sísmica de los terremotos de subducción en el norte de Chile, tomando como caso de estudio el terremoto de Tocopilla (Mw 7.7) de 2007, para lo cual se utilizan diversas metodologías. En primer lugar, se realiza una exploración de los efectos de este rasgo morfotectónico, basada en la modelación directa del campo de deformación superficial, utilizando el modelo propuesto por Okada [1985]. De los resultados obtenidos se desprende que los modelos del campo de deformación superficial se ven fuertemente influenciados por un quiebre abrupto en la geometría de la subducción, tanto de forma cualitativa, como cuantitativa. Determinado el dominio de influencia del quiebre abrupto desde los modelos directos, se procede a la inversión del campo de deformación superficial, basada en datos de geodesia espacial (estaciones permanentes de GPS e InSAR), utilizando dos metodologías: Okada [1985] y Bouchon [1981]. La primera de ellas considera el medio como un semi-espacio elástico homogéneo, mientras que la segunda utiliza un modelo de velocidades en un medio elástico estratificado, ambas para la obtención de modelos de deslizamiento. Los resultados indican que el terremoto de Tocopilla rompe la parte más profunda de la zona sismogénica, junto con una segmentación a lo largo de rumbo y en profundidad. En consecuencia, se observa que tanto la Península de Mejillones, como el quiebre abrupto propuesto en la geometría, actúan como una barrera geométrica para la ruptura del terremoto. Se explora la cinemática de la ruptura con modelos directos, para la obtención de velocidades de ruptura, utilizando como base los modelos de deslizamiento estático obtenidos desde estaciones permanentes de GPS. Dichos modelos se encuentran en concordancia con lo expuesto en otros trabajos que utilizan datos de estaciones permanente de GPS y geometrías de plano similares a las propuestas en este trabajo [Minson, 2010; Ruiz, 2012]. Los resultados que se obtienen con un quiebre abrupto en la geometría de la subducción no reflejan buenos ajustes, lo que revela la necesidad de desarrollar modelos de inversión cinemática de la ruptura, para la obtención conjunta de modelos de deslizamiento y velocidades de ruptura [ej., Simons et al., 2011; Minson et al., 2013]. Se realizan cálculos del Cambio en el Esfuerzo de Coulomb Estático, para analizar los efectos de un quiebre en la geometría de la subducción, en relación a la inducción de réplicas producto de los cambios en los esfuerzos generados por el terremoto. Los resultados muestran que las réplicas de mayor magnitud (Mw > 6.0) de tipo thrust, son inducidas en zonas donde los esfuerzos aumentan notoriamente, además de revelar una correlación entre la ubicación del quiebre abrupto, la profundidad de dichas réplicas y los cambios en los esfuerzos. Por otra parte, se analiza una réplica del tiposlab push, y desde los resultados es posible apreciar que se ve generada por un deslizamiento asísmico en la parte más profunda de la zona sismogénica. Los resultados obtenidos en esta tesis, por lo tanto, revelan la importancia de poder constreñir la geometría de la subducción (contacto interplaca) y de forma particular, que los quiebres abruptos en la placa, implicarían efectos a considerar en el estudio del proceso de ruptura sísmica en terremotos de subducción. Se concluye que dicho rasgo, actuaría en forma de barrera para terremotos generados en la parte más profunda de la zona sismogénica, revelando una compleja segmentación en profundidad de la subducción. En consecuencia, se obtiene que la geometría es un elemento de primer orden para la comprensión de los procesos de ruptura de terremotos de subducción y la segmentación de la zona sismogénica. / Magíster en Ciencias, Mención Geofísica

In this paper, a state of charge (SOC) and a state of health (SOH) estimation method for lead-acid batteries are presented. In the algorithm the measurements of battery’s terminal voltage, current and temperature are used in the process of SOC calculation. The thesis was written in cooperation with Micropower AB. The algorithm was designed to fulfill the specific requirements of the electric vehicles application: an error below 5% of SOC, computational simplicity and the possibility of being implemented in a basic programming languages. The current used method at Micropower, Coulomb counting, is compared with a method presented by Chiasson and Vairamohan 2005 based on modified Thevein circuit during charging and discharging of the battery. The Thevenin based method gave better result compared to Coulomb counting but seems not to fulfill Micropowers requirements. A correction method based on periods of no charging or discharging, possible to be used together with Coulomb counting as well as with the Thevenin method was developed. The evaluation method indicates that when using also the correction method the Micropowers requirements are fulfilled. / I detta papper, är ett laddningstillstånd (SOC) och hälsotillstånd (SOH) skattningsmetod för blybatterier presenteras. I algoritmen mätningarna av batteriets polspänning, ström och temperatur används i processen för SOC beräkning. Avhandlingen är skriven i samarbete med Micropower AB. Algoritmen har utformats för att uppfylla de särskilda kraven för elektriska fordon: ett fel under 5% av SOC, computational enkelhet och möjligheten att genomföras i ett grundläggande programmeringsspråk. Den nuvarande metoden vid Micropower, Coulomb räkning, jämförs med en metod som presenteras av Chiasson och Vairamohan 2005 baserad på modifierad Thevein kretsen under laddning och urladdning av batteriet.

The vortex fluctuations have proved to be responsible for the onset of dissipation in thin type-II superconducting Aims. There is also growing evidence that dissipation in high- temperature superconductors exhibits the same kind of two-dimensional (2D) behavior. However, a proper analysis of these materials requires a thorough understanding of the two-dimensional fluctuations. This thesis may be considered to consist of two parts. The first is concerned with two models that have often been used as models for 2D superconductors, the 2D Coulomb gas and the 2D XY model. The second part contains analyses related to high-temperature sup er conductivity. Through analysis of some renormalization equations for the Kosterlitz-Thouless (KT) transition, it is shown that the region governed by the KT critical behavior is very small and only applies at very low values for the flux-flow resistance. It is concluded that this critical behavior not is observable in superconductors, and, furthermore, that the only available method to test for 2D fluctuations at the onset of resistance, is through comparison with the 2D resistance scaling function. The critical temperature for the 2D XY model is determined by means of a finite- size scaling relation for the helicity modulus. The linearly screened potential in the XY model is written in terms of a correlation function. The analogy to the 2D Coulomb gas is found to be exact with a temperature-dependent bare interaction and a new expression for vorticity. It is also demonstrated that the Coulomb gas scaling concept may be applied to XY-type models. An analysis of resistance data for YBCO/PBCO superlattices in terms of the 2D resistance scaling function gives evidence for 2D behavior in the cases with large separation of the superconducting layers. In the superlattices with stronger interlayer coupling, the crossover to three-dimensional behavior is seen as a deviation from the scaling function as Tc is approached from above. The anisotropic three-dimensional (3D) XY model is examined as a model for high- temperature superconductors. It is shown that the density of vortices above Tc are closely equal in the anisotropic 3D model and the 2D model. This is taken as evidence that the 3D to 2D crossover found in the superlattices also is present in the anisotropic 3D XY model. / digitalisering@umu.se

Die onbevredigende konsep van die interne wrywingskoeffisient wat as basis dien vir numeries-bruikbare fraktuurkriteria vir brosmateriale, onder andere die van Coulomb-Mohr, impliseer dat daar meriete in die kriteria bestaan, maar dat daar ook fundamentele aspekte van die fraktuur.meganika vir brosmateriale bestaan wat nog ontsluit moet word. Met hierdie as onderliggende behoefte, word die probleem geidentifiseer deur eers die waarskynlike tekortkominge in die interpretasie van die bestaande teoriee in oenskou te neem. So word byvoorbeeld die rol van die inter.mediere hoofnormaalspanning met behulp van die stereografiese projeksiemetode geillustreer waaruit afgelei kan word dat die probleem, in teenstelling met die opinie van sommige ander navorsers, wel drie-dimensioneel van aard is. Daar word oak aangetoon dat die gemiddelde normaalspanningsvlak meganistiese eienskappe bevat wat daarop dui dat dit die kritieke fraktuurvlak kan wees. Aangesien hierdie vlak egter invariant ten opsigte van die normaalspanningsverwysingsnetwerk is, word die begrip netto-normaalspanning ingevoer wat 'n funksie van die Poissonverhouding is. Deur 'n funksionele verwantskap af te lei vir die helling van die Mohrenvelop wat die Mohrsirkel raak by die punt wat verteenwoordig word deur die gemiddelde netto-hoofnor. maalspanning in terme van die normaalspannings en die Poissionverhouding, word 'n moontlike materiaal-afhanklike verklaring van die interne wrywingskoeffisient verkry. Dit word bevind dat hierdie vergelyking sinvolle waardes van die interne wrywingskoeffisient voorspel, wat impliseer dat daar meriete in die benaderingswyse bestaan wat die formulering van die verwantskap voorafgegaan het. 'n Uitvloeisel van die benaderingswyse is dat dit aanleiding gee tot 'n gewysigde vorm van voorstelling van eksperimentele data. Daar word bevind dat die gewysigde voorstelling baie gevoelig is vir sekere veranderlikes en die rol van invariante toestande word ook deur hierdie voorstelling beklemtoon. 'n Afleiding wat uit hierdie verhandeling gemaak kan word, is dat dit moontlik behoort te wees om 'n fraktuurkriterium in terme van elastisiteitskonstantes te formuleer. / Dissertation (MSc)--University of Pretoria, 1976. / gm2014 / Mechanical and Aeronautical Engineering / Unrestricted

abstract: 4H-SiC has been widely used in many applications. All of these benefit from its extremely high critical electric field and good electron mobility. For example, 4H-SiC possesses a critical field ten times higher than that of Si, which allows high-voltage blocking layers composed of 4H-SiC to be approximately a tenth the thickness of a comparable Si device. This, in turn, reduces the device on-resistance and power losses while maintaining the same high blocking capability. Unfortunately, commercial TCAD tools like Sentaurus and Silvaco Atlas are based on the effective mass approximation, while most 4H-SiC devices are not operated under low electric field, so the parabolic-like band approximation does not hold anymore. Hence, to get more accurate and reliable simulation results, full-band analysis is needed. The first step in the development of a full-band device simulator is the calculation of the band structure. In this work, the empirical pseudopotential method (EPM) is adopted. The next task in the sequence is the calculation of the scattering rates. Acoustic, non-polar optical phonon, polar optical phonon and Coulomb scattering are considered. Coulomb scattering is treated in real space using the particle-particle-particle-mesh (P3M) approach. The third task is coupling the bulk full-band solver with a 3D Poisson equation solver to generate a full-band device simulator. For proof-of-concept of the methodology adopted here, a 3D resistor is simulated first. From the resistor simulations, the low-field electron mobility dependence upon Coulomb scattering in 4H-SiC devices is extracted. The simulated mobility results agree very well with available experimental data. Next, a 3D VDMOS is simulated. The nature of the physical processes occurring in both steady-state and transient conditions are revealed for the two generations of 3D VDMOS devices being considered in the study. Due to its comprehensive nature, the developed tool serves as a basis for future investigation of 4H-SiC power devices. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2020

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22258号 / 理博第4572号 / 新制||理||1656(附属図書館) / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)准教授 伊藤 喜宏, 教授 James Mori, 教授 岩田 知孝 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

A nonlinear Mohr-Coulomb constitutive model with a strain dependent yield surface and non-associated flow was employed to study the plastic soil properties which affect the rate of surface fault rupture propagation in reverse events. These numerical simulations show a trend for soils with higher stiffness to have a higher rate of rupture propagation. Additionally the study shows the effects of strain softening and hardening on the rate of rupture propagation. Soils which strain harden exhibiting ductile behavior typically require more basal offset to rupture to the surface than soils which strain soften exhibiting brittle behavior. These results agree with our previous fault box studies, which showed that soils with higher near surface shear wave velocity were more likely to propagate rupture to the surface for a given reverse event. The numerical modeling allowed for a more comprehensive evaluation of material types and fault angles than the fault box, and provided confidence in these findings.