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Sasaki, Shinji. "A bifurcation phenomenon of Stokes curves around a double turning point, and influence of virtual turning points upon the transition probabilities for three-level systems." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215284.
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Patel, Hamantkumar Vasudev. "The kinetics of liquid-liquid extraction of metals in a rotating diffusion cell : a rotating diffusion cell is used to study the rates of extraction of divalent transition metals by di-(2-ethylhexyl)-phosphoric acid and a sulphur analogue : a chemical-diffusion model describes the rate curves." Thesis, University of Bradford, 1988. http://hdl.handle.net/10454/5025.
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A rotating diffusion cell (RDC) has been used to study the kinetics of extraction of the transition metals cobalt (II), nickel (II), copper (II) and zinc (II) from sulphate solutions into either of two extractants held in n-heptane; di-(2-ethylhexyl) phosphoric acid (D2EHPA) or di-(2- ethylhexyl) dithiophosphoric acid (D2EHDTPA). The metal concentration was 10 mM and the aqueous pH was held at 4.5. The extractant concentration was varied between 0.015 to 0.4 M. In the case of cobalt extraction by D2EHPA, the metal concentration and the pH were varied Different diluents and modifiers were also studied.The rate of extraction by D2EHDTPA was found to be faster than D2EHPA. A comprehensive mathematical model, based upon established two film theory, was developed and used to describe the above experimental results. The model was also used to predict values of the important parameters. ... These values compared well with those found by other authors but using quite different experimental techniques. OS4 In the case of cobalt extraction by D2EHPA, the more polar diluents lowered the initial rate. The overall model predicts such behaviour where the rate is also dependent on the partition coefficients of the extractant. Finally, the theory of the RDC allows the prediction of the diffusion layer thicknesses, this information together with the reaction zone thickness is used to explore the influences of diffusion and chemical reaction on the overall transfer process. The diffusion processes are calculated to be the most important of the two. This is especially so for the D2EHDTPA systems.
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Cabot, Hervé. "Analyse des courbes de lumière et interprétation de l'activité des comètes lointaines : application à la comète P/Schwassmann-Wachmann 1." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10078.
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Les cometes sont les objets connus les moins evolues du systeme solaire. Leur etude permet de mieux comprendre la formation ainsi que l'evolution du systeme solaire. La comete p/schwassmann-wachmann 1 (p/sw1) se situe sur une orbite quasi-circulaire entre 5. 7 et 6. 4 unites astronomiques. A cette distance du soleil, la sublimation de glace d'eau est negligeable et pourtant, cette comete est tres active, presentant parfois des sursauts d'activite de plusieurs magnitudes appeles outbursts. Elle pourrait donc nous renseigner sur les mecanismes d'activite cometaires. Nous avons montre dans ce travail que la probabilite de collision avec un objet interplanetaire etait tres faible et que cette hypothese ne pouvait expliquer les frequents outbursts observes. Une analyse des magnitudes de la comete p/sw1 sur 70 ans a ete realisee. Nous n'avons pas trouve de periodicite dans le signal, mais nous avons mis en evidence une correlation entre le niveau moyen d'activite de la comete et la distance heliocentrique. Toutefois, il existe un retard de l'ordre de quelques annees entre le maximum d'activite et le passage au perihelie. Nous savons que les cometes ont ete formees a de tres basses temperatures et doivent contenir de la glace amorphe a l'origine. Cette glace a pu rester sous cette forme, notamment dans le cas de p/sw1, qui reste toujours loin du soleil. Des gaz tels que le monoxyde de carbone (co) peuvent etre pieges dans la matrice amorphe, et relaches lors de la cristallisation. Nous pensons que ce phenomene peut etre a l'origine des outbursts observes, alors que l'activite permanente serait due a la sublimation du co en profondeur, ce qui expliquerait le retard observe. Nous avons egalement simule de facon independante des processus cometaires (diffusion de gaz, propagation d'une onde de chaleur) et realise un modele simpliste de noyau cometaire. Ces simulations montrent que les hypotheses de notre scenario sont credibles et qu'un phenomene exothermique tel que la transition de phase devrait exister dans les noyaux cometaires pour pouvoir rendre compte des outbursts observes
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Khandaker, Md Shahriar K. "Investigation on the Mechanisms of Elastomechanical Behavior of Resilin." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/64362.
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Resilin is a disordered elastomeric protein and can be found in specialized regions of insect cuticles. Its protein sequence, functions and dynamic mechanical properties vary substantially across the species. Resilin can operate across the frequency range from 5 Hz for locomotion to 13 kHz for sound production. To understand the functions of different exons of resilin, we synthesize recombinant resilin-like hydrogels from different exons, and investigate the water content and dynamic mechanical properties, along with estimating surface energies relevant for adhesion. The recombinant resilin-like hydrogel has 80wt% water and does not show any sign of tack even though it satisfies the Dahlquist criterion. Finally, doubly shifted dynamic moduli master curves are developed by applying the time-temperature concentration superposition principle (TTCSP), and compared to results obtained with natural resilin from locusts, dragonflies and cockroaches. The resulting master curves show that the synthetic resilin undergoes a prominent transition, though the responsible mechanism is unclear. Possible explanations for the significant increase in modulus include the formation of intramolecular hydrogen bonds, altered structural organization, or passing through a glass transition, all of which have been reported in the literature for polymeric materials. Results show that in nature, resilin operates at a much lower frequency than this glass transition frequency at room temperature. Moreover, recombinant resilins from different clones have comparable resilience with natural resilin, though the modulus is around 1.5 decades lower. Results from the clones with and without chitin binding domains (ChBD) indicate that the transition for the clone without ChBD occurs at lower frequencies than for those with the ChBD, perhaps due to the disordered nature of the clone without ChBD.
Atomistic molecular modeling is applied on the repetitive motifs of resilin and different elastomeric proteins to better understand the relationship between elastomeric behavior and amino acid sequences. Results show that the motifs form a favorable bent conformation, likely enabled by glycine's lack of steric hindrance and held in place through intramolecular hydrogen bonds. During Steered Molecular Dynamic (SMD) pulling of these motifs, the hydrogen bonds break and they reform again when the peptides are released to move freely, returning to similar bent conformations. The transition seen in the master curves of recombinant resilins might be due to either these intramolecular hydrogen bonds or to glass transition behavior, though evidence indicates that the transition probably due to the glass transition. What we learned from the synthesized recombinant resilin and simulating the repetitive motifs of resilin may be applicable to the biology and mechanics of other elastomeric biomaterials, and may provide deeper understanding of their unique properties.Ph. D.
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Hashemi, Seyyed Amirreza. "Transition to turbulent flow in finite length curved pipe using nek5000." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1450458762.
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De, Santis Ruggero. "Curve spline generalizzate di interpolazione locale." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9016/.
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Questa tesi presenta un metodo generale per la costruzione di curve spline generalizzate di interpolazione locale. Costruiremo quest'ultime miscelando polinomi interpolanti generalizzati a blending function generalizzate. Verrano inoltre verificate sperimentalmente alcune delle proprietà di queste curve.
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Pleshkan, Viktoriya Y. "Nurse Practitioners' Experiences with Role Transition: Supporting the Learning Curve Through Preceptorship." ScholarWorks, 2018. https://scholarworks.waldenu.edu/dissertations/5586.
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The nurse practitioner (NP) role transition is difficult and ill-supported before and after graduation. Although preceptorships are essential in supporting a NP's role transition, there is a paucity of data on student and novice NPs' experiences with their role transition and how it is supported through preceptorships. The purpose of this hermeneutic phenomenological study was to understand and describe the meaning of NPs' role transition experiences while in a preceptorship before and after graduation. Schlossberg's transition theory and the cognitive apprenticeship models were used to guide the exploration of concepts of role transition and preceptorship. One face-to-face, 3 Skype, and 12 phone interviews were conducted with NPs who were currently practicing in the NP role (>3 months but <5 years) in those states that require collaborative practice agreement. Transcribed interviews were coded using Van Manen's analysis strategies. Findings suggested that NPs' difficult transition to practice was related to their preceptorship support in NP school and in NP work settings. The data showed ill-supported preceptorships when in NP programs. Lack of preceptorships after the graduation was accompanied by employers' expecting novice NPs to function at an expert level, frequently with minimal guidance. Understanding how NPs transition to practice and how their role transition is supported through preceptorships can be used to inform NP educators and organizations that hire NPs of the changes needed to strengthen NPs' role transition. These findings may promote positive social change by guiding stakeholders to improve the NP role transition, which could, in turn, increase NPs' autonomy, retention, and job satisfaction.
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Ghosh, Jewel Kumar. "Aspects of Holographic Renormalization Group Flows on Curved Manifolds." Thesis, Sorbonne Paris Cité, 2019. http://www.theses.fr/2019USPCC071.
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La correspondance CFT (Anti-De Sitter) (AdS) / Théorie des champs conformes (CFT), également connue sous le nom de dualité holographique, constitue un lien remarquable entre la théorie des cordes (qui inclut la gravité) et les théories de jauge. Elle relie une CFT dans un espace-temps d-dimensionnel à une théorie de la gravité dans un espace-temps dimension supérieur, également appelé bloc. Ce dernier a une limite dans laquelle réside la théorie du champ conforme.Dans cette thèse, le sujet d'étude est la description holographique des flux de groupes de renormalisation (RG) des théories (de champ) sur les espaces-temps à symétrie maximale. Le cadre théorique que j'ai utilisé est la théorie d'Einstein-scalaire. L'inclusion du champ scalaire dynamique correspond à la rupture de l'invariance conforme aux limites. Dans ce travail, les limites et les tranches du bloc sont choisies pour être des espaces-temps à symétrie maximale et l'évolution des champs en bloc est étudiée. Il décrit les écoulements RG holographiques sur des variétés courbes. De plus, deux applications sont présentées dans cette thèse. La première application s'inscrit dans le contexte des théorèmes F et la seconde concerne un défaut incurvé dans les flux RG holographiques en masse.Les théorèmes F pour les théories de champs quantiques (QFT) définies dans des espaces-temps tridimensionnels exigent l'existence de fonctions dites F. Ce sont des fonctions décroissantes de façon monotone le long du flux RG. Dans ce travail, de nouvelles fonctions F pour les théories holographiques ont été découvertes. Elles sont construites à partir de l'action sur la parois d'une solution de flux holographique RG sur une sphère à 3-sphères. Ils permettent une interprétation entropique, fournissant ainsi un lien direct entre la formulation entropique du théorème F et sa définition en termes d’énergie libre.La deuxième application des flux RG holographiques explorée dans cette thèse se situe dans le contexte de modèles affichant un mécanisme d'auto-ajustement en tant que résolution proposée du problème de la constante cosmologique (CC). Dans ces modèles, notre univers à 4-dimensions est réalisé comme une brane intégrée dans un volume à 5-dimensions. Ce cadre permet des solutions où la géométrie de la brane est plate malgré la présence d'une énergie de vide non triviale sur son worldvolume. Ceci est appelé réglage automatique. De chaque côté de la brane, les solutions sont des flux RG holographiques. Le nouvel aspect introduit dans cette thèse consiste à utiliser les flux RG holographiques sur des variétés courbes, ce qui permet à son tour d’étudier des solutions à réglage automatique dans lesquelles la brane est également courbeThe Anti-de Sitter (AdS)/Conformal Field Theory (CFT) correspondence, also known as holographic duality, is a remarkable connection between string theory (which includes gravity) and gauge theories. It relates a CFT in a d-dimensional space-time to a gravity theory in higher dimensional space-time which is also referred to as the bulk. The latter has a boundary on which the conformal eld theory may be thought to reside. In this thesis, the subject of study is the holographic description of Renormalization Group (RG) fows of (field) theories on maximally symmetric space-times. The theoretical framework I used is Einstein-scalar theory. Inclusion of the dynamical scalar field corresponds to breaking boundary conformal invariance. In this work, both the boundary and bulk slices are chosen to be maximally symmetric space-times and the evolution of bulk fields is studied. It describes holographic RG flows on curved manifolds. Furthermore, two applications are presented in this thesis. The first application is in the context of F-theorems and the second is regarding a curved defect in the bulk holographic RG flows.F-theorems for Quantum Field Theories (QFT) defined on 3-dimensional space-times demand the existence of so-called F-functions. These are monotonically decreasing functions along the RG flow. In this work, new F-functions for holographic theories have been found which are constructed from the on-shell action of a holographic RG flow solution on a 3-sphere. They allow an entropic interpretation, therefore providing a direct connection between the entropic formulation of the F-theorem and its definition in terms of free energy. The second application of holographic RG flows explored in this thesis is in the context of models displaying a self-tuning mechanism as a proposed resolution of the cosmological constant (CC) problem. In these models, our 4-dimensional universe is realized as a brane embedded in a 5-dimensional bulk. This framework allows solutions where the brane geometry is flat despite of the presence of non-trivial vacuum energy on its worldvolume. This is referred to as self-tuning. On each side of the brane, the solutions are holographic RG flows. The new aspect introduced in this thesis is to use the holographic RG flows on curved manifolds, which in turn allows the study of self-tuning solutions where the brane is also curved
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Davidsson, Simon. "Global energy transitions : Renewable energy technology and non-renewable resources." Licentiate thesis, Uppsala universitet, Naturresurser och hållbar utveckling, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-245307.
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The global energy system is dominated by the use of fossil fuels. This system suffers from several problems, such as different environmental issues, while the long-term energy security is sometimes questioned. As an alternative to this situation, a transition to a global energy system based on renewable energy technologies, to a large extent solar and wind energy, is commonly proposed. Constructing the technology needed for such a transition requires resources and how fast this could happen is somewhat disputed. This thesis explores methods to assess the potential constraints for realizing such a transition by looking at potential technology growth rates and outlooks of production of the required natural resources. The thesis is based on three papers presenting case studies that look at growth rates of wind energy as well as future production outlooks of lithium and phosphate rock. Using different types of growth patterns reaching proposed installed capacities of wind power, annual commissioning requirements are investigated, taking account for the limited life expectancy oftechnology. Potential outlooks of mineral production are explored using resource constrained curve-fitting models on global lithium production. A more disaggregated model looking at individual countries are used on phosphate rock production to investigate new perspectives on production outlooks. It is concluded that the growth rates of individual energy technologies affect the resource requirements and prospective constraints on energy transitions. Resource constrained modelling of resource production can provide spans of potential outlooks for future production of resources required for anenergy transition. A higher disaggregation of the modelling can provide new perspectives of potential constraints on future production. These aspects should be further investigated when proposing alternative future energy systems.
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He, Lijuan. "A global search algorithm for phase transition pathways in computer-aided nano-design." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50248.
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One of the most important design issues for phase change materials is to engineer the phase transition process. The challenge of accurately predicting a phase transition is estimating the true value of transition rate, which is determined by the saddle point with the minimum energy barrier between stable states on the potential energy surface (PES). In this thesis, a new algorithm for searching the minimum energy path (MEP) is presented. The new algorithm is able to locate both the saddle point and local minima simultaneously. Therefore no prior knowledge of the precise positions for the reactant and product on the PES is needed. Unlike existing pathway search methods, the algorithm is able to search multiple transition paths on the PES simultaneously, which gives us a more comprehensive view of the energy landscape than searching individual ones. In this method, a Bézier curve is used to represent each transition path. During the searching process, the reactant and product states are located by minimizing the two end control points of the curve, while the shape of the transition pathway is refined by moving the intermediate control points of the curve in the conjugate directions. A curve subdivision scheme is developed so that multiple transitions paths can be located. The algorithm is demonstrated by examples of LEPS potential, LEPS plus harmonic oscillator potential, and PESs defined by Rastrigin function and Schwefel function.
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Kendall, Michael R. "Effects of centrifugal instabilities on laminar/turbulent transition in curved channels with 40 to 1 aspect ratios." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/26517.
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Dean vortices in curved channels with 40 to 1 aspect ratios were measured and studied over the range of Dean numbers from 50 to 450. At low Dean numbers (50) the flow is fully laminar. At higher Dean numbers, the development of vortex pairs as the primary instability was a function of Dean number and the angle of curvature. Higher Dean numbers required less curvature to produce the vortices. At Dean numbers from 75 to 200, secondary instabilities developed in the form of vortex pair modulations, vortex pair twisting, and in the form of events where vortex pair undulations, vortex pair twisting, and in the form of events where vortex pairs appear and disappear. The secondary instabilities are also a function of Dean number and curvature. Twisting leads to increase in longitudinal fluctuating intensities, particularly in the upwash region from the concave wall, which are especially significant at Dean numbers above 150
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Fuqua, Steven Jay. "Study of the transition to turbulence within a curved rectangular channel with 40 to 1 aspect ratio." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/28577.
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Eliasson, Ann-Charlotte. "Smooth transitions in macroeconomic relationships." Doctoral thesis, Stockholm : Economic Research Institute, Stockholm School of Economics (Ekonomiska forskningsinstitutet vid Handelshögsk.) (EFI), 1999. http://www.hhs.se/efi/summary/516.htm.
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Zúñiga, Munizaga Andrés Jahir. "Entire solutions to the inhomogeneous allen-cahn equation in R^2, with a transition on a noncompact curve." Tesis, Universidad de Chile, 2012. http://www.repositorio.uchile.cl/handle/2250/111186.
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Ingeniero Civil MatemáticoEste trabajo de memoria de título presenta un estudio de la ecuación de perturbación singular de Allen-Cahn con inhomogeneidad: \begin{equation}\ep^2\div\left(a(x)\cdot\nabla_{x}u(x)\right)+a(x)f(u(x))=0,\quad\text{ en }\quad\R^2 \label{AllenCahnEq}\end{equation} donde $\varepsilon>0$ es un parámetro pequeño, $a(x)$ es un potencial uniformemente positivo y suave, que induce una forma de medir distancias para puntos en $\R^2$, y $f$ es la nolinealidad dada por $f(u)=u-u^3$. El estudio aborda la construcción de soluciones enteras de~\eqref{AllenCahnEq}, bajo la condición que $u$ se anule cerca de una curva $\Gamma\subset \R^2$. El enfoque propuesto asume que $\Gamma$ es una curva no acotada, geodésica no-degenerada relativa al funcional de longitud de arco $\int_{\Gamma}a(\vec{x})$, con curvatura $k_{\Gamma}$ suave que decae a una tasa polinomial. Es de interés el estudio de la ecuación de Allen-Cahn con presencia de un término de inhomogeneidad $a(x)\not\equiv 1$, ya que esto conlleva el estudio de curvas geodésicas para una métrica no trivial de $\R^2$. Además, es relevante considerar que el conjunto nodal de $u$ yace cerca de una curva no acotada, pues esto se refleja en el estudio de ecuaciones diferenciales en contextos no compactos. El resultado principal asegura la existencia de una solución de~\eqref{AllenCahnEq}, la cual converge exponencialmente a $\pm 1$ cuando $x$ se aleja de $\Gamma$. Un segundo resultado entrega ejemplos de potenciales $a(x)$ y curvas $\Gamma$, para los cuales es posible construir una solución $u$ con el comportamiento antes descrito. La demostración de este resultado está basada en una técnica conocida como reducción infinito dimensional de Lyapunov-Schmidt, la cual motiva a la elección de un candidato a solución del tipo $u = w + \phi$, donde $w$ en coordenadas adecuadas resuelve $w''+f(w)=0$, y determina el perfil de $u$ a orden principal. Además $\phi$ es una función de corrección, con el fin de convertir a $u$ en solución exacta de~\eqref{AllenCahnEq}, lo que obliga a $\phi$ a resolver una ecuación diferencial no lineal. De ahí en más, el problema consiste en estudiar la existencia y unicidad de la última ecuación en un espacio funcional adecuado. Esto se realizó analizando el operador linealizado asociado a la ecuación de Allen-Cahn, y luego el problema no-lineal que es resuelto mediante un esquema de punto fijo. Para el ultimo análisis, fue necesario ajustar $\Gamma$ en un parámetro de perturbación $h$, lo que equivale a una EDO no lineal en $h$ donde participa la segunda variación del funcional de largo $l_{a,\Gamma}$ asociado a $\int_{\Gamma}a(\vec{x})$. Finalmente, el método utilizado no sólo provee la existencia de una solución $u$ de~\eqref{AllenCahnEq}, sino que además entrega una caracterizacón completa de ésta, tanto en tamaño como en comportamiento cualitativo en coordenadas relacionadas a la curva $\Gamma$.
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Davidsson, Simon. "Natural resources and sustainable energy : Growth rates and resource flows for low-carbon systems." Doctoral thesis, Uppsala universitet, Naturresurser och hållbar utveckling, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-301930.
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Large-scale deployment of low-carbon energy technologies is important for counteracting anthropogenic climate change and achieving universal energy access. This thesis explores potential growth rates of technologies necessary to reach a more sustainable global energy system, the material and energy flows required to commission these technologies, and potential future availability of the required resources. These issues are investigated in five papers. Potential future growth rates of wind energy and solar photovoltaics, and the associated material requirements are explored, taking the expected service life of these technologies into account. Methodology for assessing net energy return and natural resource use for wind energy systems are analyzed. Potential future availability of lithium and phosphate rock are also investigated. Estimates of energy and materials required for technologies such as wind energy and photovoltaics vary, and depend on the assumptions made and methods used. Still, it is clear that commissioning of low-carbon technologies on the scale required to reach and sustain a low-carbon energy system in coming decades requires significant quantities of both bulk materials and scarcer resources. For some technologies, such as thin film solar cells and electric vehicles with lithium-ion batteries, availability of materials could become an issue for potential growth rates. Future phosphate rock production could become highly dependent on few countries, and potential political, social and environmental aspects of this should be investigated in more detail. Material and energy flows should be considered when analyzing growth rates of low-carbon technologies. Their estimated service life can indicate sustainable growth rates of technologies, as well as when materials are available for end-of-life recycling. Resource constrained growth curve models can be used to explore future production of natural resources. A higher disaggregation of these models can enable more detailed analysis of potential constraints. This thesis contributes to the discussion on how to create a more sustainable global energy system, but the methods to assess current and future energy and material flows, and availability of natural resources, should be further developed in the future.
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Tomé, Paôla Tatiana Felippi. "Uma Metodologia para identificação de curvas semelhantes de tráfego rodoviário através de técnicas de agrupamento." reponame:Repositório Institucional da UFSC, 2012. http://repositorio.ufsc.br/xmlui/handle/123456789/94041.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia de Produção, Florianópolis, 2010Made available in DSpace on 2012-10-25T05:50:11Z (GMT). No. of bitstreams: 1 278909.pdf: 67156522 bytes, checksum: 2cb8958feec929bacd50b452f44f1e4d (MD5)
O conhecimento do volume de tráfego das rodovias é uma informação valiosa para o planejamento do sistema rodoviário, porém demanda custos elevados, inviabilizando muitas vezes a implementação de um robusto programa de contagem. Neste sentido, este trabalho apresenta uma metodologia para identificar grupos de trechos de rodovias com curvas de tráfego homogêneas ao longo de determinado período, através de técnicas de agrupamento. Baseada em dados coletados de tráfego, inicialmente é realizada uma análise para determinar o número ideal de grupos através de métodos hierárquicos de agrupamento, de forma que seja possível identificar o menor número de grupos, mas que ainda atenda um nível mínimo de precisão desejado. Após esta etapa, são utilizados métodos não-hierárquicos para a realização do agrupamento em si. Dessa forma, cada um dos grupos apresenta uma curva de tráfego característica que representa todos os trechos pertencentes ao mesmo grupo. Essa idéia é explorada com o intuito de reduzir os custos associados à implementação de programas de contagem, uma vez que para cada um dos grupos pode ser implementado apenas um contador permanente, e através de fatores de expansão, possam ser expandidos os volumes dos trechos pertencentes ao mesmo grupo, mas que não possuem coletas ininterruptas. Além disso, é feita uma revisão bibliográfica relacionada à termos, conceitos e sobre programas de contagens de tráfego realizados em âmbito nacional e internacional.
Knowing the volume of road traffic is valuable information for planning the road system, but demand high costs, often making it impossible to implement a robust counting program. Thus, this paper presents a methodology to identify groups of stretches of highway with curves of homogeneous traffic over a certain period, through clustering techniques. Based on data collected from traffic, is initially performed an analysis to determine the optimal number of groups using hierarchical clustering methods, so that you can identify the smallest number of groups, but still meet a minimum level of accuracy desired. After this step, are used non-hierarchical methods to achieve the group itself. Thus, each group has a traffic characteristic curve that represents all the parts from the same group. This idea is explored in order to reduce the costs associated with implementation of programs to count, since for each group can be implemented only one permanent counter and through expansion factors, can be expanded volumes of the parts belonging the same group, but do not have collections uninterrupted. Moreover, it is a literature review related terms, concepts and programs on traffic counts carried out nationally and internationally.
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Schrader, Lars-Uve. "Receptivity of Boundary-Layer Flows over Flat and Curved Walls." Doctoral thesis, KTH, Stabilitet, Transition, Kontroll, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-25439.
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Direct numerical simulations of the receptivity and instability of boundary layers on flat and curved surfaces are herein reported. Various flow models are considered with the aim to capture aspects of flows over straight and swept wings such as wall curvature, pressure variations, leading-edge effects, streamline curvature and crossflow. The first model problem presented, the flow over a swept flat plate, features a crossflow inside the boundary layer. The layer is unstable to steady and traveling crossflow vortices which are nearly aligned with the free stream. Wall roughness and free-stream vortical modes efficiently excite these crossflow modes, and the associated receptivity mechanisms are linear in an environment of low-amplitude perturbations. Receptivity coefficients for roughness elements with various length scales and for free-stream vortical modes with different wavenumbers and frequencies are reported. Key to the receptivity to free-stream vorticity is the upstream excitation of streamwise streaks evolving into crossflow modes. This mechanism is also active in the presence of free-stream turbulence. The second flow model is that of a Görtler boundary layer. This flow type forms on surfaces with concave curvature, e.g. the lower side of a turbine blade. The dominant instability, driven by a vertically varying centrifugal force, appears as pairs of steady, streamwise counter-rotating vortical rolls and streamwise streaks. The Görtler boundary layer is in particular receptive to free-stream vortical modes with zero and low frequencies. The associated mechanism builds on the excitation of upstream disturbance streaks from which the Görtler modes emerge, similar to the mechanism in swept-plate flows. The receptivity to free-stream vorticity can both be linear and nonlinear. In the presence of free-stream turbulence, nonlinear receptivity is more likely to trigger steady Görtler vortices than linear receptivity unless the frequencies of the free-stream fluctuations are very low. The third set of simulations considers the boundary layer on a flat plate with an elliptic leading edge. This study aims to identify the effect of the leading edge on the boundary-layer receptivity to impinging free-stream vortical modes. Three types of modes with streamwise, vertical and spanwise vorticity are considered. The two former types trigger streamwise disturbance streaks while the latter type excites Tollmien-Schlichting wave packets in the shear layer. Simulations with two leading edges of different bluntness demonstrate that the leading-edge shape hardly influences the receptivity to streamwise vortices, whereas it significantly enhances the receptivity to vertical and spanwise vortices. It is shown that the receptivity mechanism to vertical free-stream vorticity involves vortex stretching and tilting - physical processes which are clearly enhanced by blunt leading edges. The last flow configuration studied models an infinite wing at 45 degrees sweep. This model is the least idealized with respect to applications in aerospace engineering. The set-up mimics the wind-tunnel experiments carried out by Saric and coworkers at the Arizona State University in the 1990s. The numerical method is verified by simulating the excitation of steady crossflow vortices through micron-sized roughness as realized in the experiments. Moreover, the receptivity to free-stream vortical disturbances is investigated and it is shown that the boundary layer is most receptive, if the free-stream modes are closely aligned with the most unstable crossflow modeQC 20101025
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Vassura, Edoardo. "Path integrals on curved space and the worldline formalism." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13448/.
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Lo scopo primario di questa tesi e' l’analisi di una nuova procedura di regolarizzazione di path integral su spazi curvi, presentata inizialmente dal fisico J. Guven e applicata al caso di una teoria di campo scalare , ma mai utilizzata per svolgere ulteriori calcoli espliciti. Questa procedura, se corretta, permetterebbe di utilizzare il formalismo di path integral su spazi piatti anche nel caso in cui la varieta' di background risulti localmente curva. Tale procedura trasforma di fatto un modello sigma non lineare in un modello efficace lineare, permettando pertanto di aggirare le usuali complicazioni dovute alla generalizzazione di path integral. Una prova diretta della correttezza della procedura di Guven sembra mancare in letteratura: per questo motivo in questa tesi verranno eseguiti vari test volti a tale verifica. Alcuni errori sono stati riscontrati nella proposta iniziale, tra i quali un termine di potenziale che risulta essere non corretto. Ad ogni modo siamo stati in grado di identificare un potenziale che permetta di riprodurre correttamente i primi due coefficienti dell’espansione in serie dell’heat kernel. Utilizzando lo stesso metodo abbiamo poi cercato di ottenere il successivo coefficiente dell’espansione (cubico in termini di curvatura): il risultato ottenuto non risulta essere corretto, cosa che segnala il fallimento di tale metodo ad ordini superiori. Visti tali risultati preliminari, siamo stati indotti a considerare una classe speciale di spazi curvi, quella degli spazi massimamente simmetrici, trovando invece che su tali spazi la procedura di Guven riproduce i risultati corretti. Come verifica abbiamo ottenuto la parte diagonale dell’heat kernel, che ́ stata poi utilizzata per riprodurre l’anomalia di traccia di tipo A per campi scalari in dimensioni arbitrarie fino a D = 12. Questi risultati sono in accordo con quelli attesi. Viene pertanto fornita una prova della validita' di tale procedura su questi spazi.
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Ochirkhuyag, Myagmersuren. "Water Management in Mongolia." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-160459.
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The world experiences large-scale ecosystems degradation in an every part of the planet - in rich as well as in and poor parts. Unstable economic conditions together with weak law enforcements make low income countries face more severe forms of natural destruction. This draws the attention on the need to design economic policies that are environmentally sound and while at the same time ensuring the well-being of their inhabitants in economic, social and natural settings. A number of countries in Central and Eastern Europe and Central Asia have experienced a unique historical period of transition from communist regimes to free democratic societies. This has been followed by numerous effects on their financial situations as economic hardships caused by the collapse of economies injected by the assistance from the Soviet and committees of socialist countries mutually aiding each other, opening up of opportunities as private ownership and market liberations. Not all countries succeeded in liberalizing their economic structures and reforming economic and political environments. Simultaneously, the natural environment underwent various effects, both positive and negative, after the Iron Curtain fell and exposed destructing effects of command and control economy. Mongolia has experienced all the hard aspects of the transition and started to climb up on the income ladder from the low income to the lower middle-income list of the World Bank, but also seen many negative price aspects of development. Water resources have been severely degraded in recent years due to anthropogenic impact. However, there are reforms taking place in water sector institutions that have recently attracted wide attention nationwide.This thesis will give detailed picture on current state of water resources in the country and the system that coordinates them. The Environmental Kuznets Curve (EKC) is used as an approach to highlight the relationship between water resource quality and income per capita in Mongolia. This is followed by a detailed discussion on water institutions development and the coordinating mechanisms badly needed among sectors involved. The research suggests that collaborative actions are important if sustainable water management is to be reached. More generally, I recommend further research issues on the generated topic as my thesis is one of the first discussions coupling the EKC and institutional theory aspects together.
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Valle, Orero Jessica. "Dynamics and thermal behaviour of films of oriented DNA fibres investigated using neutron scattering and calorimetry techniques." Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2012. http://tel.archives-ouvertes.fr/tel-00734670.
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The majority of structural studies on DNA have been carried out using fibre diffraction, while studies of its dynamics and thermal behaviour have been mainly performed in solution. When the DNA double helix is heated, it exhibits local separation of the two strands that grow in size with temperature and lead to their complete separation. This work has investigated various aspects of this phenomenon. The experiments reported in this thesis were carried out on films of oriented fibres of DNA prepared with the Wet Spinning Apparatus. Thus, sample preparation and characterisation are essential parts of the research. The structures of two forms of DNA, A and B, have been explored as a function of relative humidity at fixed ionic conditions. A method to eliminate traces of ever-present B-form contamination in A-form samples was established. The high orientation of the DNA molecules within the samples allowed us to investigate dynamical fluctuations and the melting transition of DNA using neutron scattering, which can provide the spatial information crucial to understand a phase transition, probing the static correlation length along the molecule as a function of temperature. The transition has been investigated for A and B-forms in order to understand its dependence on molecular configuration.Furthermore, after the first melting, denatured DNA films show typical glass behaviour. Their thermal relaxation has been explored using calorimetry.Neutron and X-ray inelastic scattering (INS and IXS) were used in the past to measure longitudinal phonons in fibre DNA, and the results shown disagreement. Recent INS measurements supported with phonon simulations have been crucial to understand the different dispersion curves reported to date. Experiments using INS and IXS have been carried out to continue with this investigation. Attempts to observe the transverse fluctuations associated to the thermal denaturing of DNA, never experimentally investigated before, have been made.
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Meier, Roland. "Curie temperature and magnetic phase transition of nanostructured ultrathin Fe/GaAs(001) size dependence and relevance of dipolar coupling." Berlin mbv, 2009. http://d-nb.info/100028090X/04.
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Yang, Ning. "Synchrotron Diffraction Studies of Spontaneous Magnetostriction in Rare Earth Transition Metal Compounds." Washington, D.C. : Oak Ridge, Tenn. : United States. Dept. of Energy. Office of Science ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2004. http://www.osti.gov/servlets/purl/835381-gxv1Km/webviewable/.
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Sieber, Lars. "Zur Beurteilung der Sprödbruchgefährdung gelochter Stahltragwerke aus Flussstahl." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-223593.
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Bei der Beurteilung der Sicherheit bestehender Konstruktionen aus altem Baustahl (i. A. Flussstahl) und der Entscheidung über notwendige Instandsetzungs- und Verstärkungsmaßnahmen ist der Nachweis ausreichender Werkstoffzähigkeit (der Sicherheit gegen ein sprödes Versagen) von wesentlicher Bedeutung. Die in DIN EN 1993-1-10 normativ geregelten Nachweismethoden zur Beurteilung der Sprödbruchgefährdung wurden basierend auf umfangreichen bruchmechanischen Untersuchungen entwickelt. Sie gelten für Schweißkonstruktionen und „Stähle aus neuerer Zeit“ mit in der Regel hohen Zähigkeitswerten. Die Quantifizierung der Zähigkeit in Werkstoffnormen erfolgt durch Kerbschlagbiegeversuche. Die Beziehung zwischen der Übergangstemperatur der Kerbschlagarbeit und der Referenztemperatur der Bruchzähigkeit wird durch die modifizierte Sanz-Korrelation hergestellt, die nur für diese Stähle abgeleitet wurde. Das in der Norm verankerte Verfahren ist für alte Flussstahlkonstruktionen mit Lochschwächung durch Niet- und Schraubenverbindungen nicht geeignet. Einerseits unterscheiden sich Kerbwirkung und Eigenspannungszustand von geschweißten und genieteten Konstruktionen und damit die Zähigkeitsanforderungen wesentlich voneinander. Auf der anderen Seite unterliegen die Zähigkeitseigenschaften von Flussstählen deutlich größeren Streuungen.
In der vorliegenden Arbeit werden experimentelle und rechnerische Untersuchungen zum Sprödbruchverhalten gelochter Konstruktionen aus altem Flussstahl vorgestellt. Wesentlicher Bestandteil sind dabei die umfangreichen Werkstoffanalysen zur Ermittlung der bruchmechanischen Werkstoffzähigkeit im spröd-duktilen Übergangsbereich nach dem Master-Curve-Konzept (ASTM E1921). Die Auswertungen belegen, dass in Abhängigkeit des Herstellungsverfahrens unterschiedliche Werkstoffgüten definiert werden können. Um den Einfluss des Stanzens von Löchern auf das Sprödbruchverhalten alter Flussstähle zu beurteilen, werden Gefügeuntersuchungen und Mikrohärtemessungen durchgeführt.
Ausgehend von einer umfassenden Analyse typischer Konstruktionsformen bestehender Tragwerke des Stahlhochbaus erfolgen bruchmechanische FE-Berechnungen an Anschlüssen von Winkelprofilen zur Bestimmung der Zähigkeitsanforderungen. Die dabei gewonnenen Ergebnisse des Spannungsintensitätsfaktors werden durch Modifikation bekannter Lösungen aus der Fachliteratur für die weitere Anwendung aufbereitet. Darauf aufbauend wird für die untersuchten Konstruktionsdetails im Rahmen einer bruchmechanischen Sicherheitsanalyse ein praxisgerechtes Verfahren zur Beurteilung der Sprödbruchgefährdung genieteter und geschraubter Bauteile abgeleitet. Mit Hilfe statistischer Methoden werden Streuungen der Festigkeits- und Zähigkeitskennwerte der Flussstähle erfasst und nach der Verifizierung durch Bauteilversuche in ein semi-probabilistisches Nachweiskonzept überführt.
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Guimarães, Valdir Alves. "Determinação da temperatura de referência T0 da curva mestre na região de transição dúctil-frágil de aços ARBL /." Guaratinguetá : [s.n.], 2006. http://hdl.handle.net/11449/116078.
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Resumo: Materiais estruturais utilizados no projeto de equipamentos e instalações industriais podem apresentar mudança de seu comportamento à fratura quando se varia a temperatura. Este tipo de comportamento caracteriza-se pela existência de uma curva de transição, onde 3 regiões ficam bem definidas: os patamares inferior e superior e a região de transição. Na região de transição, os resultados experimentais apresentam alto espalhamento e são bastante dependentes da geometria ensaiada. Para solucionar este problema, foi desenvolvido um modelo analítico experimental, que resultou na edição da norma ASTM E1921-97. O trabalho inclui um estudo da influência de diversas rotas de tratamentos térmicos aplicadas em um aço 4130 utilizado pela indústria aeronáutica, um aço de qualidade API utilizado pela indústria petrolífera e um aço da classe A516 atualmente utilizado pela indústria nacional de vasos de pressão, na microestrutura, propriedades mecânicas de tração e tenacidade à fratura. Os resultados mostraram que o aço 4130 A450, apresentou a melhor correlação entre resistência e tenacidade entre as microestruturas pesquisadas. Este comportamento deve estar associado a rota de tratamento térmico aplicada a esta condição. O tratamento de austêmpera possibilita a formação de bainita que, tradicionalmente é conhecida por apresentar elevados valores de tenacidade. O método proposto pela ASTM pode ser considerado viável para as diversas microestruturas pesquisadas ampliando a aplicação da metodologia que recomenda o ensaio apenas para aços ferríticos. No entanto, a metodologia da Curva Mestra em materiais tratados termicamente deve ser conduzida de forma a se estabelecer parâmetros que considerem as modificações microestruturais sofridas pelo material.Abstract: Structural materials used in industrial equipments design can change fracture behavior when the temperature is varied. This type of behavior is characterized by the existence of a transition curve, where 3 areas are well defined: inferior and superior landings and the ductile brittle transition. In ductile brittle transition, experimental results present high scatter and depend highly of specimen geometry. In order to solve this problem, an analytical experimental model was developed, resulting in ASTM E1921-97 standard edition. This work includes the influence of several heat treatments analysis applied in a 4130 steel used by the aeronautical industry, a API X70 steel used by the line pipe industry and a ASTM A516 steel used by pressure vases national industry, where it was analyzed the influence in the microstructure, mechanical properties and fracture toughness. The results showed that the 4130 A450 steel presented the best correlation between resistance and toughness among the researched microstructures. This behavior should be associated with the heat treatment route applied. The isothermal quenching treatment makes possible bainite formation which, traditionally it is known by its high toughness values. The methodology proposed by ASTM is considered viable for the several researched microstructures enlarging the application of the methodology that just recommends the rehearsal for ferritics steels. However, Master Curve methodology in heat treated materials must have some parameters settling down considering the microstructure modifications suffered by the material.
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Purcel, Alexandra-Anca. "Economic Development and Environmental Quality Nexus in Developing and Transition Economies." Thesis, Université Clermont Auvergne (2017-2020), 2020. http://www.theses.fr/2020CLFAD013.
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Cette thèse aborde l'un des sujets les plus discutés et en vogue dans le domaine de l'économie, à savoir le lien entre le développement économique et la qualité environnementale. En particulier, on met l’accent sur les effets du développement économique—tant dans ses dimensions économique, sociale que politique—sur la qualité de l'environnement pour les économies en développement et en transition. Le chapitre I, divisé en trois phases clés, à savoir la revue de la littérature théorique, la partie empirique et la revue de la littérature empirique, contribue à la littérature en donnant diverses informations sur le lien entre la croissance économique et la pollution de l'environnement dans les économies en développement et en transition. Globalement, les résultats révèlent que des études empiriques récentes, parvenant à réduire certaines lacunes suggérées par la théorie, pourraient en effet indiquer un certain consensus sur la relation entre la croissance et la pollution, à savoir la validité de l'hypothèse de la Courbe de Kuznets Environnementale (CKE). Le chapitre II examine le lien pollution-croissance dans les pays d'Europe Centrale et Orientale (PECO), en ajoutant à la littérature empirique l’utilisation de l'hypothèse étendue de l'CKE comme cadre théorique. D'une part, il révèle un lien de croissance non linéaire entre le PIB et le CO2 agrégé, qui est fortement robuste pour différents estimateurs et variables de contrôle. En revanche, l'analyse au niveau des pays révèle que la relation entre le PIB et le CO2 se caractérise par une grande diversité dans les PECO. Ainsi, malgré une tendance globale à la hausse, certains PECO ont réussi à assurer à la fois un PIB plus élevé et une réduction des émissions de CO2. Du point de vue politique, les décideurs de l'UE pourraient accorder plus d'attention à ces pays, c'est-à-dire envisager une intégration plus rigoureuse des hétérogénéités des pays et, en même temps, soutenir la croissance économique sans nuire à l'environnement. Le chapitre III étudie la réponse des émissions de CO2 agrégées et sectorielles résultant des perturbations externes du PIB et de l'urbanisation, en supposant un canal de transmission qui intègre deux des éléments clés utilisés dans la lutte contre la dégradation de l'environnement—les énergies renouvelables et l'efficacité énergétique. Les résultats, robustes à plusieurs spécifications alternatives, indiquent que la production globale, l'urbanisation et l'intensité énergétique augmentent les émissions totales de CO2, tandis que les énergies renouvelables ont l'effet inverse. Par ailleurs, en ce qui concerne la réponse du CO2 aux chocs de production et d'urbanisation, le modèle suggère que ces pays atteindront le seuil maximum qui conduirait à un changement de la tendance des émissions à la baisse. Cependant, les résultats varient en fonction du niveau de revenu et du statut des pays sur la ratification/l'adhésion au Protocole de Kyoto. Ensuite, l'analyse sectorielle montre que les transports, les bâtiments et les secteurs non-combustion sont plus susceptibles de contribuer à l'augmentation des niveaux futurs de CO2. En général, ce chapitre peut fournir des informations précieuses sur les perspectives de durabilité environnementale dans les pays en développement. Le chapitre IV explore les effets de la stabilité politique sur la dégradation de l'environnement, donnant une perspective renouvelée sur ce sujet dans les pays en développement. Il montre qu'une évolution non linéaire en forme de cloche décrit la relation entre les variables au niveau agrégé. De plus, bien que ce résultat reste stable pour plusieurs spécifications alternatives, nous identifions des hétérogénéités significatives dans les caractéristiques distinctes des pays et les mesures alternatives de pollution. En outre, des estimations désagrégées révèlent des schémas contrastés pour la relation entre le CO2 et la stabilité politique. (...)This thesis tackles one of the most debatable and in vogue topics in economics, namely the economic development and environmental quality nexus. Notably, it studies the economic development's effects—in terms of its economic, social, and political dimensions—on the environmental quality for developing and transition economies. Chapter I, which is divided into three key phases, namely theoretical review, empirical exercise, and empirical review, contributes to the literature by giving various insights regarding the link between economic growth and environmental pollution in developing and transition economies. Overall, it reveals that the recent empirical studies, indeed, succeeding to curtail some of the deficiencies suggested by theoretical contributions, might indicate a certain consensus regarding pollution-growth nexus and Environmental Kuznets Curve (EKC) hypothesis validity. Chapter II examines the pollution-growth nexus in Central and Eastern European (CEE) countries, adding to the related empirical literature using the extended EKC hypothesis as a theoretical background. On the one hand, it unveils an increasing nonlinear link between GDP and CO2 at the aggregate level, which is powerfully robust to different estimators and control variables. On the other hand, the country-level analysis reveals that the relationship between GDP and CO2 is characterized by much diversity among CEE countries. Thus, despite an aggregated upward trend, some CEE countries managed to secure both higher GDP and lower CO2 emissions. From a policy perspective, EU policymakers could pay more attention to these countries and amend the current unique environmental policy to account for country-heterogeneities to support economic growth without damaging the environment. Chapter III investigates the aggregated and sector-specific CO2 emissions' responsiveness following exogenous shocks to growth and urbanization, considering a transmission scheme that incorporates two of the widely used instruments in mitigating environmental degradation—renewables and energy efficiency. First, robust to several alternative specifications, the results indicate that output, urbanization, and energy intensity increase the aggregated CO2 emissions, while renewable energy exhibits an opposite effect. Moreover, regarding the CO2 responsiveness in the aftermath of output and urbanization shocks, the pattern may suggest that these countries are likely to attain the threshold that would trigger a decline in CO2 emissions. However, the findings are sensitive to both countries' economic development and Kyoto Protocol ratification/ascension status. Second, the sector-specific analysis unveils that the transportation, buildings, and non-combustion sector exhibits a higher propensity to increase the future CO2 levels. Generally, this chapter may provide useful insights concerning environmental sustainability prospects in developing states. Chapter IV explores the effects of political stability on environmental degradation, giving a renewed perspective on this topic in developing states. It shows that a nonlinear, bell-shaped pattern characterizes the relationship between variables at the aggregate level. Moreover, while this result is robust to a broad set of alternative specifications, significant heterogeneities are found regarding countries' distinct characteristics and alternative pollution measures. Besides, the country-specific estimates unveil contrasting patterns regarding the relationship between CO2 and political stability. Broadly speaking, the findings suggest that both the formal and informal sides of political stability play a vital role in mitigating CO2 pollution in developing countries, and may provide meaningful insights for policymakers. (...)
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Han, Mangui. "Critical Behavior of Thermal Expansion and Magnetostriction in the Vicinity of the First order transition at the Curie Point of Gd5(SixGe1-x)4." Ames, Iowa : Oak Ridge, Tenn. : Ames Laboratory ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2004. http://www.osti.gov/servlets/purl/837267-32IBIb/webviewable/.
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Thesis (Ph.D.); Submitted to Iowa State Univ., Ames, IA (US); 19 Dec 2004.Published through the Information Bridge: DOE Scientific and Technical Information. "IS-T 2309" Mangui Han. US Department of Energy 12/19/2004. Report is also available in paper and microfiche from NTIS.
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Heidarian, Negar. "A Homologous Study of Lifetimes and Oscillator Strengths of Ultraviolet Transitions in Singly Ionized Lead, Tin, and Germanium." University of Toledo / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1500466694480909.
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Callisesi, Giulia. "Simplified worldline path integrals for p-forms and type-A trace anomalies." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/17060/.
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In this work we study a simplified version of the path integral for a particle on a sphere, and more generally on maximally symmetric spaces, in the case of N=2 supersymmetries on the worldline.
This quantum mechanics is generically that of a nonlinear sigma model in one dimension with two supersymmetries (N=2 supersymmetric quantum mechanics), and it is mostly used for describing spin 1 fields and p-forms in first quantisation. Here, we conjecture a simplified path integral defined in terms of a linear sigma model, rather than a nonlinear one. The use of a quadratic kinetic term in the bosonic part of the particle action should
be allowed by the use of Riemann normal coordinates, while a scalar effective potential is expected to reproduce the effects of the curvature. Such simplifications have already been proven to be possible for the cases of N=0 and N=1 supersymmetric quantum mechanics. As a particular application, we employ our construction to give a simplified worldline representation of the one-loop effective action of gauge p-forms on maximally symmetric spaces. We use it to compute the first three Seeley-DeWitt coefficients, denoted by a_(p+1)(d;p), namely a_1(2;0), a_2(4;1) and a_3(6;2), that appear in the calculation of the type-A trace anomalies of conformally invariant p-form gauge potentials in d=2p+2 dimensions. The simplified model describes correctly the first two coefficients, while it seems to fail to reproduce the third one. One possible reason could be that the model is based on a conjecture about the effective potential that has been oversimplified in our analysis. Future work could improve our construction, in order to give a correct description to all orders, or alternatively disprove the possibility of having such a simplification in the full N=2 quantum mechanics.
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Duan, Runrun. "Investigation of xBi(B')O₃-(1 -- x)PbTiO₃ and xBi(B',B")O3-(1 -- x)PbTiO3 perovskite solid solutions with high transition temperatures." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/24688.
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he extent of BiInO₃ substitution in the perovskite system xBiInO(₃)-(1 - x)PbTiO₃ and the corresponding raise in the transition temperature were investigated using thermal analysis, dielectric measurements, x-ray diffraction, and electron microscopy. Maximum tetragonal perovskite distortion (c/a = 1.082) was obtained for x = 0.20, with a corresponding Curie temperature of 582°C. Phase-pure tetragonal perovskite was obtained for x less than or equal to 0.25. Compound formation after calcining mixed oxide powders resulted in agglomerated cube-shaped tetragonal perovskite particles, which could be fired to 94.7% of theoretical density (TD). Niobium-modified BIPT ceramics with PT contents of 80% and 85% were found to possess significantly lower dielectric loss at elevated temperatures, making it possible to polarize the materials. Piezoelectric properties were measured for a 1.5 mol% Nb -0.15BI-0.85PT composition with a transition temperature of 542°C; the longitudinal piezoelectric coefficient and coercive field were found to be 60 pC/N and 125 kV/cm, respectively.
Compositions of xBiLaO₃-(1 − x)PbTiO₃ over the range 0 < x < 0.225 were calcined and sintered. Dielectric constant with temperature and differential scanning calorimetry measurements were in excellent agreement with respect to a Curie-like tetragonal to cubic transformations starting at 495°C for pure PbTiO₃, shifting to lower temperatures with increasing x. For compositions of x > 0.05, a second higher-temperature (∼600°C) endotherm, and matching dielectric anomaly, were consistently observed, for which there were no structural changes indicated by hot-stage x-ray diffraction. This transformation was interpreted to be similar to a Curie transformation in relaxor ferroelectrics in which localized segregation of B-site cations (below the resolution limit of x-ray diffraction) facilitated ferroelectric behavior.
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Schwartz, Frédéric. "Etude des parametres d'elaboration de rubans amorphes par la methode du flot planaire : influence d'elements de substitution sur les proprietes d'un alliage amorphe fe::(79)b::(16)si::(5)." Paris 6, 1986. http://www.theses.fr/1986PA066574.
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Description de la methode de filage depuis l'etat liquide. Influence des parametres de fabrication sur la qualite micrographique des rubans amorphes de composition donnee. Application de cette methode a l'amorphisation de l'alliage ferromagnetique fe::(79)b::(16)si::(5). Effet de la substitution de differents elements sur les temperatures de cristallisation et de curie de l'alliage ferromagnetique
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Ferreño, Blanco Diego. "Integridad estructural de vasijas nucleares en base a la curva patrón obtenida mediante probetas reconstruidas." Doctoral thesis, Universidad de Cantabria, 2008. http://hdl.handle.net/10803/10603.
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En esta tesis se ha caracterizado el acero, virgen e irradiado, de la vasija de una central nuclear española actualmente en servicio, en la región de temperaturas conocida como Zona de Transición Dúctil-Frágil. Para ello, se han ensayado probetas propias de la Mecánica de Fractura, reconstruidas a partir de mitades de probetas de impacto previamente ensayadas. Para describir la tenacidad a fractura en la Zona de Transición se ha empleado el modelo de la Curva Patrón.Finalmente, se ha analizado el impacto del procedimiento de caracterización y del modelo de la Curva Patrón sobre la Integridad Estructural de la vasija, comparando sus predicciones con las que se obtienen de aplicar los procedimientos convencionales que contempla la normativa vigente, representada por el Código ASME. En esta comparación se ha hecho uso del procedimiento FITNET de Integridad Estructural.In this thesis, the steel, virgin and irradiated, from the vessel of a Spanish Nuclear Plant currently operating, has been characterized in the range of temperatures known as Ductile to Brittle Transition Region. For this purpose, Fracture Mechanics specimens, reconstituted from halves of impact specimens previously broken, have been tested. To describe fracture toughness in the Transition Region, the Master Curve method has been used.Eventually, the influence of the characterization procedure together with the Master Curve method on the Structural Integrity of the vessel has been analyzed, comparing their predictions with those coming from applying conventional procedures proposed by the current regulations, represented by the ASME Code. In this comparison, the FITNET Structural Integrity procedure has been used.
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Saïd, Alami Mohammed. "Influence du recuit sur l'effet Hall de couches minces de nickel-argent amorphes et microcristallisées." Rouen, 1986. http://www.theses.fr/1986ROUES014.
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Détermination de la composition pour laquelle l'alliage nickel-argent devient amorphe et ferromagnétique, à partir de l'étude de l'effet Hall et de la structure par microscopie électronique. On montre que la température de Curie reste constante dans la phase désordonnée. Apparition d'une phase superparamagnétique au sein de la matrice initiale par recuits successifs
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Beauclair, François. "Contribution a l'etude de l'effet hall dans les materiaux ferromagnetiques amorphes." Paris 6, 1988. http://www.theses.fr/1988PA066047.
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Etude des variations de l'effet hall dans les rubans amorphes en effectuant des substitutions sur un ruban proche du metglas 260553 en fonction de leurs compositions et de leur temperature. Determination a temperature ambiante des constantes de hall extraordinaires et des resistivites en l'absence d'induction. Extrapolation des valeurs des temperatures de curie et des constantes de hall ordinaires. Mesures des constantes de hall extraordinaires apres recuit. Le mecanisme du saut lateral semble etre preponderant et un rearrangement des atomes aurait lieu durant le recuit
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Václavík, Martin. "Predikce teplotní závislosti lomové houževnatosti." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231943.
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The thesis is focused on the prediction of the fracture toughness temperature dependence through a universal curve of fracture toughness (also known as the master curve). To determine the parameters of the universal curve of fracture toughness, values acquired from the measurement results of fracture toughness and tensile tests of structural steel P91 are used. The theoretical part is based on a summary of the relevant information from the field of fracture mechanics and brittle-ductile fracture behavior of steels that are important for the understanding of fracture-strain response of materials depending on load conditions. The experimental part of the thesis contains the results from practical measurements and analyses, which were used for determining the parameters of a universal curve of fracture toughness as well as for the evaluation of fracture behavior and description of the impact of structural parameters on this behavior in case of steel P91.
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DEY, SONAL. "ELASTICITY OF MAIN CHAIN LIQUID CRYSTAL ELASTOMERS AND ITS RELATIONSHIP TO LIQUID CRYSTAL MICROSTRUCTURE." Kent State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=kent1385403238.
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Bekka, Ahmed. "Etude cristallographique et magnétique de nouveaux ferrites de type [béta]" [A(y)B(n+)((1-y)/n)] (1+x) Zn (x) Fe(11-x) O17 (x [à peu près égal à] 0,9) avec A,B = Li, Na, K, Ag, Ca, Sr, Ba, Pb." Grenoble 1, 1986. http://www.theses.fr/1986GRE10138.
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Preparation sous forme de monocristaux et de polycristaux de na::(4,2) k::(1,8) fe::(30) me::(3) o::(51) (me = zn, mg, cu). Determination de la structure cristalline, et mesures de conductivite ionique, d'aimantation, determination des temperatures de curie et des constantes d'anisotropie magnetocristalline. Substitution partielle des cations na et k par li, na, k, ag, ca, sr, ba, pb. Caracterisation par diffraction rx, microscopie a balayage et a transmission
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Zeghib, Abdelhakim. "Contribution à l'étude de phénomènes de transport dans les couches minces Ni-Ag amorphes et microcristallisées." Rouen, 1987. http://www.theses.fr/1987ROUES014.
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Extension du modèle de Ziman aux alliages Ni-Ag et interprétation qualitative du comportement de la résistivité et du coefficient de température en fonction de la composition atomique d'argent. Etude de la structure de bandes de Ni-Ag à partir de mesures magnétiques. Mise en évidence d'un niveau lié virtuel dans les alliages majoritaires en argent, par la technique des plasmons de surface
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Savioli, Rafael Guimarães. "Estudo experimental do comportamento à fratura frágil em aços estruturais ferríticos e aplicações à determinação da curva mestra." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3135/tde-23062016-074259/.
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Este trabalho apresenta uma investigação experimental sobre o comportamento à fratura frágil de aços estruturais ferríticos, ASTM A285 Gr C e ASTM A515 Gr 65. Os resultados deste trabalho ampliam a base de dados de propriedades mecânicas utilizadas nas análises de integridade de estruturas pressurizadas tais como vasos de pressão e tanques de armazenamento construídos com esta classe de material. O trabalho tem por objetivo também avaliar a aplicabilidade de corpos de prova de dimensões reduzidas, PCVN, na determinação da temperatura de referência, T0, por meio da metodologia da Curva Mestra, a qual define a dependência da tenacidade à fratura do material em função da temperatura. Os ensaios de tenacidade à fratura foram conduzidos utilizando-se corpos de prova solicitados em flexão três pontos com geometria SE(B), PCVN e PCVN com entalhe lateral, extraídos de chapas laminadas. Os resultados dos ensaios foram obtidos em termos de integral J no momento da instabilidade, denotados por Jc. Dados adicionais de resistência à tração e de Impacto Charpy convencional também foram obtidos para caracterizar o comportamento mecânico dos aços utilizados. Os resultados mostraram uma forte influência da geometria dos corpos de prova sobre os valores de Jc, evidenciada pela grande variação nos valores de tenacidade à fratura.This work presents an experimental investigation on the cleavage fracture behavior of structural ferritic steels, ASTM A285 Grade C and ASTM A515 Grade 65. One purpose of this study is to enlarge a previously reported work on mechanical and fracture properties for this class of steel to provide a more definite database for use in structural and defect analyses of pressurized components, including pressure vessels and storage tanks. Another purpose is to address the applicability of Precracked V-notch Charpy specimens to determine the reference temperature, T0, derived from the Master Curve Methodology which defines the dependence of fracture toughness with temperature for the tested material. Fracture toughness testing conducted on single edge bend specimens in three-point loading (SE(B), PCVN Plain Side and PCVN Side Grooved) extracted from laminated plates provides the cleavage fracture resistance data in terms of the J-integral at cleavage instability, Jc. Additional tensile and conventional Charpy tests produce further experimental data which serve to characterize the mechanical behavior of the tested materials. The results reveal a strong effect of specimen geometry on Jc values associated with large scatter in the measured values of cleavage fracture toughness.
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Ahmed, Selver. "FORMATION, DYNAMICS AND CHARACTERIZATION OF SUPPORTED LIPID BILAYERS ON SiO2 NANOPARTICLES." Diss., Temple University Libraries, 2012. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/213126.
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ChemistryPh.D.
This work is devoted to understanding the formation of supported lipid bilayers (SLBs) on curved surfaces as a function of lipid properties such as headgroup charge/charge density and alkyl chain length, and nanoparticle properties such as size and surface characteristics. In particular, the formation of SLBs on curved surfaces was studied by varying the size of the underlying substrate SiO2 nanoparticles with size range from 5-100 nm. Curvature-dependent shift in the phase transition behavior of these supported lipid bilayers was observed for the first time. We found that the phase transition temperature, Tm of the SLBs first decreased with decreasing the size of the underlying support, reached a minimum, and then increased when the size of the particles became comparable with the dimensions of the lipid bilayer thickness; the Tm was above that of the multilamellar vesicles (MLVs) of the same lipids. The increase in Tm indicated a stiffening of the supported bilayer, which was confirmed by Raman spectroscopic data. Moreover, Raman data showed better lipid packing and increased lateral order and trans conformation for the SLBs with increasing the curvature of the underlying support and decrease of the gauche kinks for the terminal methyl groups at the center of the bilayer. These results were consistent with a model in which the high free volume and increased outer headgroup spacing of lipids on highly curved surfaces induced interdigitation in the supported lipids. These results also support the symmetric lipid exchange studies of the SLBs as a function of the curvature, which was found to be slower on surfaces with higher curvature. Further, the effect of surface properties on the formation of SLBs was studied by changing the silanol density on the surface of SiO2 via thermal/chemical treatment and monitoring fusion of zwitterionic lipids onto silica (SiO2) nanoparticles. Our findings showed that the formation of SLBs was faster on the surfaces with lower silanol density and concomitantly less bound water compared to surfaces with higher silanol density and more bound water. Since the two SiO2 nanoparticles were similar in other respects, in particular their size and charge (ionization), as determined by zeta potential measurements, differences in electrostatic interactions between the neutral DMPC and SiO2 could not account for the difference. Therefore the slower rate of SLB formation of DMPC onto SiO2 nanoparticles with higher silanol densities and more bound water was attributed to greater hydration repulsion of the more hydrated nanoparticles. Lastly, we have investigated the effect and modulation of the surface charge of vesicles on the formation of SLBs by using different ratios of zwitterionic and cationic DMPC/DMTAP lipids. Through these studies we discovered a procedure by which assemblies of supported lipid bilayer nanoparticles, composed of DMPC/DMTAP (50/50) lipids on SiO2, can be collected and released from bilayer sacks as a function of the phase transition of these lipids. The lipids in these sacks and SLBs could be exchanged by lipids with lower Tm via lipid transfer.
Temple University--Theses
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Ayed, Othman. "Etude des interactions entre atomes alcalins (li, na, k) et monoxyde de carbone en matrices de gaz rares : analyse en spectroscopie vibrationnelle et calcul quantiques de quelques complexes." Paris 6, 1987. http://www.theses.fr/1987PA066117.
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Dans le cas de li(le plus reactif), identification de li(co)::(n), ou n = 1,2,3,4,(ou 6), avec des frequences de vibration de valence de co plus perturbees que pour les metaux de transition carbonyle,et de li::(m) co, ou m = 2,3, avec frequences nu (co) abaissees. Pour na et k, observation d'especes de haute stoechiometrie (c::(n)o::(n))**(2-) (m**(+))::(2) ou n = 2,3,4, formees apres irradiation uv-visible et correspondant a des transformations chimiques. Essai d'interpretation de ces differences de reactivite par une description quantique des agregats de plus basse stoechiometrie : dans le complexe 1 :1, les deux etats electroniques inferieurs sont l'etat **(2)sigma non liant et l'etat **(2)pi liant; la courbe de potentiel de lico possede un minimum pour li-c equiv. A 2,5 a au-dessous de la courbe de l'etat **(2)pi alors que pour naco, le minimum de la courbe pour l'etat **(2)pi est au-dessous de la courbe de l'etat **(2)sigma ; le calcul met en evidence le caractere ionique de m::(2)c::(2)o::(2) (acetylenediolate) resultant d'une reaction chimique
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Morin-Grognet, Sandrine. "Etude structurale et magnétique de rubans Fe-(Cu)-Si-B-(Nb, Zr, Mo) amorphes et nanocristallins. Effet d'un traitement thermochimique de nitruration." Rouen, 1999. http://www.theses.fr/1999ROUES012.
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Depuis 1988, l'alliage ferromagnétique de composition Fe 7 3, 5Cu 1Nb 3Si 1 3 , 5b 9 (Finemet) est étudié pour ces propriétés magnétiques douces remarquables, combinant les avantages des amorphes à base de fer et ceux des amorphes à base de cobalt. Ces propriétés sont reliées à l'état nanocristallin, constitué de nanograins magnétiques de -Fe(Si) dispersés dans une matrice amorphe magnétique. Pour obtenir cette nanostructure, nous avons utilisé, pour la première fois sur des alliages Fe-(Cu)-Si-B-(Nb, Zr, Mo) bruts de trempe, un traitement thermochimique de nitruration. Ce traitement nécessite un temps de recuit plus élevé par rapport à celui utilisé habituellement pour un traitement thermique conventionnel. Cette étude montre qu'une structure nanocristalline peut être obtenue après TTN (520°C, 6 h), dans les échantillons contenant un élément inhibiteur (Nb, Zr, Mo). La nature de l'élément influence la taille de grains, la teneur en silicium dans -Fe(Si) et la fraction cristallisée. L'étude magnétique a permis de corréler l'obtention de bonnes propriétés magnétiques douces avec la structure nanocristalline. L'étude des échantillons nanocristallisés par TTN (520,6), montre une pénétration partielle de l'azote ; ceci est expliqué par la présence d'une phase amorphe résiduelle qui ralentit la diffusion de l'azote. Dans les zones nitrurées, nous avons détecté la formation de fer pur. La formation de la phase -Fe lors du processus de nitruration est expliquée par la bonne affinité du silicium avec l'azote, conduisant à l'apparition probable de la phase Si 3N 4. Ceci entraîne une augmentation de la température de Curie de la fraction cristalline. La nitruration conduit également à une diminution de la magnétostriction, en accord avec une fraction cristalline plus importante et entraîne une augmentation de H C du fait de la présence de Fe 4N. Nous avons proposé un mécanisme de nitruration dans ces échantillons et montré l'influence de la nitruration sur les propriétés magnétiques douces.
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Even, Raymond. "Les premiers semiconducteurs moleculaires : les derives radicalaires des phtalocyanines." Paris 6, 1987. http://www.theses.fr/1987PA066161.
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Synthese de composes pc::(2)lu, pc::(2)ln(ln = yb,tm,dy,nd) a l'etat de grande purete et etude de leurs proprietes electriques intrinseques, ainsi que de celles de pcli, sur monocristaux et sur couches minces; mise en evidence de la possibilite de dopage de pc::(2)lu avec des composes organiques donneurs et accepteurs et avec pcli. Etude de l'absorption optique et observation de bandes de transfert de charge intramoleculaire, confirmee par ailleurs par rpe. Possibilite d'application de couches minces de pclu a la detection de gaz
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Hliwa, Mohamed. "Traitement simplifie des interactions moleculaires en chimie quantique." Toulouse 3, 1988. http://www.theses.fr/1988TOU30038.
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Calculs ab initio sur le systeme hautement degenere cr h: mise en evidence d'un fort couplage entre etats ioniques et neutres et analyse des fonctions d'onde dans une description diabatique. Proposition d'une methode perturbative pour calcul des energies de dispersion entre un systeme versatil a (decrit dans une grande base) et un systeme quasi passif b (traite a l'approximation en coeur gele et caracterise par sa polarisabilite); calcul scf + ci de (a + b gele), du champ electrique exerce par a sur b, et de ses fluctuations, a l'aide d'un hamiltonien effectif; application a l'etude des courbes de potentiel des premiers etats excites des molecules diatomiques de ar avec na, k ou mg. Emploi de la theorie des pseudopotentiels et des potentiels modeles pour le calcul de potentiels impulsifs d'atomes inertes transferables a des systemes moleculaires; a partir de ces potentiels, calcul d'energies de dispersion applicable a la spectroscopie d'atomes alcalins en matiere de gaz rare
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(9842759), Simon Wagner. "Derailment risk assessment." Thesis, 2004. https://figshare.com/articles/thesis/Derailment_risk_assessment/13416902.
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"There is a large quantity of literature available on longitudinal train dynamics and risk assessment but nothing that combines these two topics. This thesis is focused at assessing derailment risks developed due to longitudinal train dynamics. A key focus of this thesis is to identify strategies that can be field implemented to correctly manage these risks. This thesis quantifies derailment risk and allows a datum for comparison. A derailment risk assessment on longitudinal train dynamics was studied for a 107 vehicle train consist travelling along the Monto and North Coast Lines in Queensland, Australia. The train consisted of 103 wagons and 4 locomotives with locomotives positioned in groups of two in lead and mid train positions. The wagons were empty hopper wagons on a track gauge of 1067mm. The scenarios studied include: the effect of longitudinal impacts on wagon dynamics in transition curves; and the effects of longitudinal steady forces on wagon dynamics on curves. Simulation software packages VAMPIRE and CRE-LTS were used. The effects of longitudinal impacts from in-train forces on wagon dynamics in curves were studied using longitudinal train simulation and detailed wagon dynamics simulation. In-train force impacts were produced using a train control action. The resulting worst-case in-train forces resulting from these simulations were applied to the coupler pin of the wagon dynamics simulation model. The wagon model was used to study the effect of these in-train forces when applied in curves and transitions at an angle to the wagon longitudinal axis. The effects of different levels of coupler impact forces resulting from different levels of coupling slack were also studied. Maximum values for wheel unloading and L/V ratio for various curve radii and coupler slack conditions were identified. The results demonstrated that the derailment criteria for wheel unloading could be exceeded for a coupler slack of 50mm and 75mm on sharper curves, up to 400m radii. A detailed study of the effect of steady in-train forces on wagon dynamics on curves also was completed. Steady in-train forces were applied to a three wagon model using VAMPIRE. Maximum and minimum values of wheel unloading and L/V ratio were identified to demonstrate the level of vehicle stability for each scenario. The results allowed the worse cases of wheel unloading and L/V ratio to be studied in detail. Probability density functions were constructed for the occurrence of longitudinal forces and coupler angles for the Monto and North Coast Lines. Data was simulated for a coupler slack of 25, 50 and 75mm and force characteristics were further classified into the occurrences of impact and non-impact forces. These probability density functions were analysed for each track section to investigate the effects of coupler slack, track topography and gradient on wagon dynamics. The possible wagon instability in each of these scenarios was then assessed to give a measure of the potential consequences of the event. Risk assessment techniques were used to categorise levels of risk based on the consequences and likelihood of each event. It was found that for the train configuration simulated, the Monto Line has a higher derailment risk than the North Coast Line for many of the scenarios studies in this thesis. For a coupler slack of 25mm no derailment risks were identified, 50mm coupler slack derailment risks were only identified on the Monto track and the majority of derailment risks were identified for a 75mm coupler slack." -- abstract
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El, Mabchour Asma. "Obésité abdominale et autres déterminants du risque cardiométabolique dans deux populations urbaines noires apparentées : Port-au-Prince (Haïti) et Cotonou (Bénin)." Thèse, 2016. http://hdl.handle.net/1866/15982.
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L’obésité est un problème de santé publique reconnu. Dans la dernière décennie l’obésité abdominale (OA) a été considérée comme une maladie métabolique qui contribue davantage au risque de diabète et de maladies cardiovasculaires que l’obésité générale définie par l’indice de masse corporelle. Toutefois, dans les populations d’origine africaine, la relation entre l’OA et les autres biomarqueurs de risque cardiométabolique (RCM) demeure obscure à cause du manque d’études chez ces populations et de l’absence de valeurs-seuils spécifiques pour juger d’une OA. Cette étude visait à comparer la prévalence des biomarqueurs de RCM (OA, hypertension artérielle, hyperglycémie, dyslipidémie, résistance à l'insuline et inflammation pré-clinique) chez les Béninois de Cotonou et les Haïtiens de Port-au-Prince (PAP), à étudier l’association de l’OA avec les autres biomarqueurs de RCM, à documenter le rôle du niveau socio-économique (NSE) et du mode de vie dans cette association et à ’identifier les indicateurs anthropométriques de l’OA -tour de taille (TT) et le ratio TT/hauteur (TT/H)- et les seuils qui prédisent le mieux le RCM à Cotonou et à PAP.
Il s’est agi d’une analyse de données transversales chez 452 adultes (52 % hommes) apparemment en bonne santé, âgés de 25 à 60 ans, avec 200 sujets vivant à Cotonou (Bénin) et 252 sujets à PAP (Haïti). Les biomarqueurs de RCM considérés étaient : le syndrome métabolique (SMet) d’après les critères harmonisés de 2009 et ses composantes individuelles - une OA à partir d’un TT ≥ 94cm chez les hommes et ≥ 80cm chez les femmes, une hypertension, une dyslipidémie et une hyperglycémie; la résistance à l’insuline définie chez l’ensemble des sujets de l’étude à partir du 75e centile de l’Homeostasis Model Assessment (HOMA-IR); un ratio d’athérogénicité élevé (Cholestérol sérique total/HDL-Cholestérol); et l’inflammation pré-clinique mesurée à partir d’un niveau de protéine C-réactive ultrasensible (PCRus) entre 3 et 10 mg/l. Le ratio TT/H était aussi considéré pour définir l’OA à partir d’un seuil de 0,5. Les données sur les habitudes alimentaires, la consommation d’alcool, le tabagisme, les caractéristiques sociodémographiques et les conditions socio-économiques incluant le niveau d’éducation et un proxy du revenu (basé sur l’analyse par composante principale des biens et des possessions) ont été recueillies au moyen d’un questionnaire. Sur la base de données de fréquence de consommation d’aliments occidentaux, urbains et traditionnels, des schémas alimentaires des sujets de chaque ville ont été identifiés par analyse typologique. La validité et les valeurs-seuils de TT et du ratio TT/H prédictives du RCM ont été définies à partir des courbes ROC (Receiver Operating Characteristics).
Le SMet était présent chez 21,5 % et 16,1 % des participants, respectivement à Cotonou et à PAP. La prévalence d’OA était élevée à Cotonou (52,5 %) qu’à PAP (36%), avec une prévalence plus élevée chez les femmes que chez les hommes. Le profil lipidique sérique était plus athérogène à PAP avec 89,3 % d’HDL-c bas à PAP contre 79,7 % à Cotonou et un ratio CT/HDL-c élevé de 73,4 % à PAP contre 42 % à Cotonou. Les valeurs-seuils spécifiques de TT et du TT/H étaient respectivement 94 cm et 0,59 chez les femmes et 80 cm et 0,50 chez les hommes. Les analyses multivariées de l’OA avec les biomarqueurs de RCM les plus fortement prévalents dans ces deux populations montraient que l’OA était associée à un risque accru de résistance à l’insuline, d’athérogénicité et de tension artérielle élevée et ceci, indépendamment des facteurs socio-économiques et du mode de vie. Deux schémas alimentaires ont émergé, transitionnel et traditionnel, dans chaque ville, mais ceux-ci ne se révélaient pas associés aux biomarqueurs de RCM bien qu’ils soient en lien avec les variables socio-économiques.
La présente étude confirme la présence de plusieurs biomarqueurs de RCM chez des sujets apparemment sains. En outre, l’OA est un élément clé du RCM dans ces deux populations. Les seuils actuels de TT devraient être reconsidérés éventuellement à la lumière d’études de plus grande envergure, afin de mieux définir l’OA chez les Noirs africains ou d’origine africaine, ce qui permettra une surveillance épidémiologique plus adéquate des biomarqueurs de RCM.Obesity is recognized as a major public health problem. In the last decade abdominal obesity (AO) was considered as a metabolic disorder which further contributes to the risk of diabetes and cardiovascular disease than the general obesity defined by body mass index. However, in African origin population groups, the relationship between AO and other cardiometabolic risk (CMR) biomarkers remained unclear because of the lack of studies in these population groups and the lack of specific cut-off values to define AO. This study aimed to compare the prevalence of CMR biomarkers (OA, hypertension, hyperglycemia, dyslipidemia, insulin resistance and subclinical inflammation) in Beninese from Cotonou and Haitians from Port-au-Prince (PAP), to assess the association between AO and other CMR biomarkers in relation to Cotonou and PAP participants’ socioeconomic and lifestyle parameters and to define anthropometric indicators of AO -waist circumference (WC) and waist-to-height ratio (WHtR)- and specific thresholds that best predict the CMR in both Cotonou and PAP. The cross-sectional study included 452 apparently healthy adults (52 % men), aged 25-60 years, 200 subjects from Cotonou (Benin) and 252 subjects from PAP (Haiti). The CMR biomarkers were: the metabolic syndrome (MetS) according to the harmonized criteria of 2009, its individual components - AO defined by a WC ≥ 94cm in men and ≥ 80 cm in women, hypertension, dyslipidemia and hyperglycemia - Insulin resistance was set at the 75th centile of Homeostasis Model Assessment (HOMA-IR) for the whole sample of subjects. High atherogenicity index (total serum cholesterol/HDL-Cholesterol), subclinical inflammation according to high-sensitivity C-reactive protein (hsCRP) concentration between 3 to 10 mg/L was also assessed. WHtR from a cut-off point of 0.5 was also considered to assess AO. Data on dietary habits, alcohol consumption, tobacco, sociodemographic and socioeconomic status, including education level and a proxy of income (based on principal component analysis of property and possessions) were documented by a questionnaire. Dietary patterns were generated from Western, urban and traditional food frequency in each city by cluster analysis. Receiver Operating Characteristic (ROC) curves were used to assess the performance of specific WC and WHtR cut-offs to predict the CMR. MetS was present in 21.5 % and 16.1 % of participants in Cotonou and PAP respectively. AO was higher in Cotonou (52.5 %) than in PAP (36 %) with higher prevalence in women than in men. The serum lipid profile was more atherogenic in PAP with 89.3 % of low HDL-C in PAP comparing to 79.7 % in Cotonou and high seum TC / HDL-C ratio of 73.4 % in PAP versus 42 % in Cotonou. The specific WC and WHtR cut-off values were respectively 94 cm and 0.59 in women and 80cm and 0.50 in men. Multivariate analysis of AO with the most prevalent CMR biomarkers in these two population groups showed that AO was associated with increased risk of insulin resistance, high atherogenic index and high blood pressure, irrespective of socioeconomic and lifestyle factors. Two dietary patterns were defined: transitional and traditional in each city, but these were not associated with the CMR biomarkers although they were related to socioeconomic variables. This study confirms the presence of several CMR biomarkers in apparently healthy subjects. Additionally, AO was a key element of the CMR in both population groups. However, current WC thresholds should be reconsidered in light of larger studies to better define AO among Black African groups, which will improve the epidemiological surveillance of the CMR biomarkers.
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Siedband, Marc A. "A flow visualization study of laminar/turbulent transition in a curved channel." Thesis, 1987. http://hdl.handle.net/10945/22269.
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沈聰益. "The Application Study of Transitional Curve in Railway Engineering." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/80832271953726939322.
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碩士國立臺北科技大學
土木與防災技術研究所
89
The main target of this study was to investigate railway alignment in relation to the structure of curves finite elements ,and develop the alignment work process and procedures to help the staff of track engineer in alignment(paper location) enhance the ability of inspection. For the purpose of convenient reference for alignment, this study explored the theory, the calculation formula, flowchart, and consecution of each transition which was widely applied on overseas as well as domestic alignment presently, such as the use of highly order continue spiral planar cures and half sine by Taiwan High Speed Railway, the Taiwan’s traditional railway system(narrow track) and the general in continent railway were adapted cubic parabola. On the other hand, there was a program in this study represented in Chinese which included two functions of the main program of curve and the auxiliary program of alignment. Collecting the present domestic major transportation engineering construction of the final alignment design actual data and used as on experiment the fundamental standard values of this study and the results calculated elements of curves from application alignment system. Comparing and Analyzing with each other can double check the final data. Finally the result of data will show up kilometric, coordinate, and azimuth of tangent, chart, comparison and explanation. The comparison of the grade of each curve are helpful for selection and decision making. Hopefully, this study result can facilitate the alignment work and provide a good example for future study. Keywords：alignment , half sine, cubic parabola
48
Aminzadeh-Goharrizi, Behdad. "The transition between sharp and diffusive wetting fronts as a function of imbibing fluid properties." Thesis, 2009. http://hdl.handle.net/2152/ETD-UT-2009-12-683.
Full textAbstract:
The efficiency of one fluid displacing another in a permeable medium depends on the pore-scale dynamics at the main wetting front. Experiments have shown that the frontal dynamics can result in two different flow regimes: a sharp and a diffuse front. In the sharp front regime, the displacing fluid occupies nearly all the pores and throats behind the main wetting front and the saturation changes abruptly. In contrast, in the diffuse front regime, pores are filled gradually at the main wetting front, and the saturation change is gradual in space. The different fronts can greatly alter the relative permeability curves, the trapping mechanisms, and the displacement efficiency.
Directly measuring the sharpness of the front is difficult. Instead, here we correlate the front sharpness to saturation overshoot, which occurs for moderate to high flux vertical displacements of low density fluid by a higher density fluid in 1-D homogeneous permeable media.
We hypothesize the sharpness of wetting front can be explained by competition between two different pore - filling mechanisms (called snap-off and piston-like) with the competition controlled by the velocity of the front and thus the injected flux. We conduct series of infiltration experiments to determine the saturation profile as a function of flux for seven different fluids. We find that for each fluid there is a flux (called overshoot flux) below which saturation overshoot ceases and the front is diffuse. We find that the overshoot flux depends inversely on the invading fluid’s viscosity, and shows little or no dependence on the invading fluid’s surface tension, vapor pressure, and its miscibility with watertext
49
Ming-Hung, Hsieh, and 謝明宏. "Study on the Residual Wall Thickness at Dimensional Transitions and Curved Sections in Water-Assisted Molded Circular Tubes." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/34432534495091679720.
Full textAbstract:
碩士長庚大學
機械工程研究所
93
ABSTRACT This research is majority on the Water-Assisted Injection Molded Circular Tubes and study the different circular tube junction of the residual wall thickness and melt heaped as well as the curve section difference situation. It can compare the Water Assisted and Air Assisted in different circular tubes ratio for their geometry transparency and empty situation. There are totally five sets of changeable mold design for studying. The result found that the major influence the residual wall thickness and melt heaped was the mold geometry design and the melting adhesive temperature distribution. For single parameter of Water Assisted process, the influence of circular tube of residual wall thickness and melt heaped parameter was the time delaying and short injection dimension. Except the influence of process parameter, the geometry of molding design is also a factor to affect the residual wall thickness and melt heaped. If the molding design add a leading angle, it can improve the melt heaped and increase the evenly of residual wall thickness. In additionally, the design of leading angle 45° for finish good is much better than the 30°. Meanwhile, the Water Assisted injection of forming the residual wall thickness, transparency and difference inside the circular tube is much better than the Air Assisted forming. For No Circular Tubes deviation M0 status, the Water Assisted injection forming can keep in low difference rate. Due to the liquid without the compression property, it has a good modification for flowing resistance of melting adhesive and can achieve the evenly and stable effect for the flowing delay.
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Baig-Meininghaus, Tariq. "Influence of Heterogeneities on Waves of Excitation in the Heart." Doctoral thesis, 2017. http://hdl.handle.net/11858/00-1735-0000-002E-E48D-7.
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