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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
191

Espalhamento de Férmions sob Influencia da Violação de Lorentz no Setor Fotônico / Scattering of Fermions under Influence of Violation Lorentz Sector Photonic

Santos, Frederico Elias Passos dos 15 December 2010 (has links)
Submitted by Rosivalda Pereira (mrs.pereira@ufma.br) on 2017-06-07T18:34:00Z No. of bitstreams: 1 FredericoSantos.pdf: 963672 bytes, checksum: 82f7ae1b28b9c136b94c6c04439b8c32 (MD5) / Made available in DSpace on 2017-06-07T18:34:00Z (GMT). No. of bitstreams: 1 FredericoSantos.pdf: 963672 bytes, checksum: 82f7ae1b28b9c136b94c6c04439b8c32 (MD5) Previous issue date: 2010-12-15 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa e ao Desenvolvimento Científico e Tecnológico do Maranhão (FAPEMA) / The standard model extension is a theoretical framework which includes the possibility of Lorentz symmetry violation in the Standard Model of elementary interactions. In electrodynamics, this possibility is represented by the term, Kμν∝βFμνF∝β , that violates Lorentz symmetry without jeopardizing CPT symmetry, and the term ε∝μβνV∝Aμ∂βAν, which violates Lorentz and CPT symmetries. These additional terms are inserted in the Maxwell Lagrangena and alter the field equations, as well. In this work we study the influence of Lorentz violation in the photonic sector on fermion scattering processes, regarding individually the CPT-odd and CPT-even coefficients. At first, we present a review through some topics of great interest, as the Dirac equation, Dirac propagator, scattering matrix, Feynman rules, Casimir trick, and the evaluation of the differential cross sections. Next, we implemented the developed techniques to carry out the corrections (to the cross sections) induced by the Lorentz-violating terms. Our results reveal as each Lorentz-violating component changes the cross section. In the CPT-even case, we observed that the contribution of the term tr to the process e− + μ− → e− + μ− is of difficult detection once it can be disguised between the radioactive corrections. The contributions coming from the vector i imply an angular dependence in the differential cross section of the process e− + μ− → e− + μ−, and do not contribute for the process e− + e+ → μ− + μ+. The CPT-even coefficients, (Ke−)ij , lead to significant contributions in both cases. We highlight its influence in the pair electron-positron annihilation process, where they act as the only components that imply sensitive contributions. The contribution stemming from the CPT-odd sector, represented by the Carroll-Field-Jackiw term, is of less relevance, since the contribute are second order ones. Although we have initially developed a perturbative procedure for evaluating the cross section correction, it was also possible to evaluate the exact propagators of the CPT-odd and CPT-even sectors in a tensor closed form. Such tensor expressions may be used to rederive the cross section corrections. / O Modelo Padrão Estendido (MPE)é um arcabouço teórico que considera a possibilidade de violação de simetria de Lorentz no Modelo Padrão das interações elementares. Na eletrodinâmica, esta possibilidade é representada pelo termo Kμν∝βFμνF∝β , que viola a simetria de Lorentz sem violar a simetria CPT, e o termo ε∝μβνV∝Aμ∂βAν, que viola a simetria de Lorentz, juntamente com a simetria CPT. Estes termos extras são incluídos na lagrangena de Maxwell e, consequentemente, também alteram a equação de movimento dos campos. Neste trabalho consideramos a influência da violação de Lorentz no setor fotônico em processos de espalhamento de férmions, e− + μ− ! e− + μ− e e− + e+ ! μ− + μ+, considerando individualmente o setor CPT-ímpar e CPT-par em suas componentes não-birrefringentes. No primeiro momento, apresentamos uma revisão de tópicos de interesse, passando pela equação de Dirac, propagador de Dirac, matriz de espalhamento, regras de Feynman, truque de Casimir, finalizando com o cálculo das seções de choque diferenciais para processos elementares. Em seguida, implementamos as técnicas desenvolvidas para calcular o incremento à seção de choque, oriundo da violação de simetria de Lorentz no setor fotônico. Em nossos resultados, obtivemos como cada componente de violação de Lorentz altera a seção de choque. No caso CPT-par, observamos que a contribuição do termo Kir ao processo e− + e+ → μ− + μ+ é de difícil verificação, pois se confunde com as contribuições radioativas. Já as contribuições advindas do vetor Ki, inserem uma dependência angular na seção de choque diferencial do processo e− + μ− → e− + μ−, mas não contribui no processo e− + e+ → μ− + μ+. Os coeficientes paridade-par, (Ke−)ij , implicam em contribuições relevantes em ambos os processos, e destacamos sua influência no processo de aniquilação elétron-pósitron, onde atuam como únicas componentes que contribuem de forma notável. A contribuição do setor CPT-ímpar (termo de Carroll-Field-Jackiw) é comparativamente de menor relevância, já que as contribuições à seção de choque aparecem apenas em segunda ordem. Embora tenhamos inicialmente desenvolvido um procedimento perturbativo para calcular as contribuições dos parâmetros de quebra de Lorentz à seção de choque, também foi possível obter os propagadores de Feynman exatos tanto para o setor CPT-ímpar quanto para o setor CPT-par. Tais expressões podem ser usadas para recalcular as seções de choque.
192

Carbon K-Shell X-Ray and Auger-Electron Cross Sections and Fluorescence Yields for Selected Molecular Gases by 0.6 To 2 .0 MeV Proton Impact

Bhalla, Raj P. (Raj Pal), 1948 08 1900 (has links)
Absolute K-shell x-ray cross sections and Auger-electron cross sections are measured for carbon for 0.6 to 2.0 MeV proton incident on CH₄, n-C₄H₁₀ (n-Butane), i-C₄H₁₀ (isobutane), C₆H₆ (Benzene), C₂H₂ (Acetylene), CO and CO₂. Carbon K-shell fluorescence yields are calculated from the measurements of x-ray and Auger-electron cross sections. X-ray cross sections are measured using a variable geometry end window proportional counter. An alternate method is described for the measurement of the transmission of the proportional counter window. Auger electrons are detected by using a constant transmission energy Π/4 parallel pi ate electrostatic analyzer. Absolute carbon K-shell x-ray cross sections for CH₄ are compared to the known results of Khan et al. (1965). Auger-electron cross sections for proton impact on CH₄ are compared to the known experimental values of RΦdbro et al. (1979), and to the theoretical predictions of the first Born and ECPSSR. The data is in good agreement with both the first Born and ECPSSR, and within our experimental uncertainties with the measurements of RΦdbro et al. The x-ray cross sections, Auger-electron cross sections and fluorescence yields are plotted as a function of the Pauling charge, and show significant variations. These changes in the x-ray cross sections are compared to a model based on the number of electrons present in the 2s and 2p sub shells of these carbon based molecules. The changes in the Auger-electron cross sections are compared to the calculations of Matthews and Hopkins. The variation in the fluorescence yield is explained on the basis of the multiconfiguration Dirac-Fock model.
193

Medidas de seções de choque de reações nucleares utilizando prótons com energias menores que 30 MeV / Measurements Cross Sections Nuclear Reactions Protons Energies 30 MeV

Gutiérrez, Francis Bringas 04 April 2003 (has links)
Alvos naturais de Mg, Al, Si, Cr, Ti, Ni e Zr foram irradiados com prótons e as seções de choque para várias reações nucleares foram determinadas a energias inferiores a 30 MeV. As irradiações foram efetuadas nos ciclotrons CV-28 e CYCLONE 30 do IPEN, que possuem energia nominal de 24 e 30 MeV, respectivamente. O feixe de prótons foi monitorado por meio de lâminas de Cu ou a partir da formação de nuclídeos na própria amostra com seção de choque conhecida para as energias utilizadas. Especial interesse foi dedicado às reações raras di tipo (p, 2alfa) e (p, ANTPOT.3 H) das quais existem, em geral, poucos dados publicados, principalmente para energias próximas do limiar. A determinação da seção de choque foi realizada a partir da medida da atividade residual dos produtos pelo método de espectroscopia gama simples. Um detector HPG com resolução menor que 2 keV foi utilizado. Devido ao valor reduzido da seção de choque das reações de interesse no intervalo de energia considerado, uma análise estatística cuidadosa dos dado foi necessária. Em áreas reduzidas dos picos detectados precisaram da quantificação, em alguns casos, da contribuição de nuclídeos formados na própria amostra por outras reações, a partir de impurezas ou provenientes do fundo radioativo. Entre os produtos obtidos encontram-se os nuclídeos ANTPOT.22 Na, ANTPOT.26 Al, ANTPOT.44 Ti, e ANTPOT.54 Mn. A detecção de ANTPOT.26 Al nas amostras de Al e Si, permitiu estimar os limites do método proposto para o estudo de reações raras de interesse astrofísico. No total, são apresentados neste trabalho 72 valores de seção de choque. Desse total, 21 dados são apresentados pela primeira vez ou foram obtidos pela primeira vez pelo método proposto ou às energias estudadas. Os resultados mais importantes referem-se às reações ANTPOT.29 Si(p, 2alfa)ANTPOT.22 Na,ANTPOT.53 Cr(p, 2alfa)ANTPOT.46 Sc, ANTPOT.46 Ti(p, ANTPOT.3 H)ANTPOT.44 Ti, )ANTPOT.58 Ni(p, ANTPOT.3 H)ANTPOT.56 Ni e ANTPOT.90 Zr(p, ANTPOT.3 H)ANTPOT.88 Zr. Os resultados foram comparados com valores publicados na literatura e com o resultado do cálculo realizado a partir de modelos teóricos conhecidos, permitindo a obtenção de conclusões relativas ao método experimental, assim como aos mecanismos da reação envolvidos. / Natural targets of Mg, Al, Si, Cr, Ti, Ni and Zr were irradiated with protons and the cross section for several reactions were determined for incident energies up to 30 MeV. The irradiations were performed at the CV-28 and CYCLONE 30 cyclotrons from the IPEN, which have nominal energies of 24 and 30 MeV, respectively. The protons beams were monitored by copper foils or by the nuclide formation in the irradiated targets with known cross sections for the used energy. Special interest was dedicated to rare reactions of the (p, 2alfa) and (p, ANTPOT.3 H) kind, from which we have a few published data, mainly for energies near the threshold. The cross section determination was accomplished by the residual actives measurement of the reaction products by the simple gamma spectroscopy method using an HPGe detector with resolution better than 2 keV. Due to the low value of the cross section for the considered reaction, a careful statistical analysis of the obtained data was needed. The small areas of the detected peaks required the quantification of the contributions of nuclides produced by others reactions, from contaminants or from the radioactive background. Among others, the ANTPOT.22 Na, ANTPOT.26 Al, ANTPOT.44 Ti and ANTPOT.54 Mn products have been detected. The detection of ANTPOT.26 Al in the Al and Si targets allow the estimation of the limits of the proposed method for the study of astrophysical interest reaction. In total, 72 cross section values are being presented. Out of this amount, 21 are being presented for the first time or have been obtained for the first time by the method or for the studied energies. The most important results refer to the ANTPOT.29 Si(p, 2gamma)²²Na, ANTPOT.53 Cr(p, 2gamma)ANTPOT.46 Sc, ANTPOT.46 Ti(p, ANTPOT.3 H)ANTPOT.44 Ti, ANTPOT.58 Ni(p, ANTPOT.3 H)ANTPOT.56 Ni and ANTPOT.90 Zr(p, ANTPOT.3 H)ANTPOT.88 Zr reactions. The results have been compared to published vales and calculations using known theoretical models, allowing the achievement of conclusions related to the experimental method, as well as the reaction mechanism involved.
194

Evaluation des capacités d'écoulement et de stockage d'un aquifère karstique dynamique par caractérisation géologique et modélisation pluie-débit : sources de Dardennes, Toulon, France / Flow and storage capacities assessement of a dynamic karst aquifer by geological characterization and rainfall-discharge modeling : sources of Dardennes, Toulon, France

Baudement, Cécile 19 April 2018 (has links)
Cette thèse a pour but de contribuer à l’étude des aquifères karstiques en (1) identifiant les facteurs influençants le stockage et l’écoulement de l’eau souterraine et en (2) localisant et estimant de manière quantitative les ressources en eau au sein d’une série carbonatée. Cette étude a été réalisée sur l’aquifère de Dardennes, près de Toulon, en France. L’eau de l’aquifère est utilisée pour l’alimentation en eau potable et alimente le fleuve Las, susceptible de provoquer de fortes crues. Le bassin versant de l’aquifère est estimé à 70 km². Des mesures de porosité et de géochimie isotopique sur les roches carbonatées sont mises en relation dans le but de localiser et d’expliquer les vides créés au sein de la série sédimentaire. Des coupes équilibrées et des analyses structurales ont été réalisées pour évaluer la géométrie de l’aquifère. L’acquisition de données en continu (CTD) et de données hydrochimiques permet d’étudier le dynamisme et le fonctionnement de l'aquifère. Une approche de modélisation pluie-débit avec la plateforme de modélisation KarstMod, basée sur les chroniques de précipitations et de débits sur trois années a été utilisée afin d’estimer la part de l’écoulement disponible pour l’eau potable et celle générant des crues éclair. Une déconvolution du débit des sources a été effectuée à l’échelle annuelle et à l’échelle des crues. Les résultats du modèle ont été comparés avec la gestion actuelle de l’aquifère, montrant une exploitation actuelle équilibrée, et ouvrant des perspectives pour la mise en place d’une gestion active, combinant une exploitation plus importante de l’eau, un écrêtage des crues et un respect de l’écologie du cours d’eau en aval. / The aim of this PhD is to contribute to the karst aquifers understanding by (1) identifying the factors influencing the groundwater storage and flow and by (2) locating and quantitatively estimating water resources within the carbonate sedimentary series. This study was conducted on the Dardennes aquifer near Toulon, France. The aquifer water is used for the supply of drinking water and feeds the Las River, which can cause important floods. The recharge area of the aquifer is estimated at 70 km². Measurements of porosity and isotopic geochemistry on carbonate rocks are related in order to locate and explain the voids created within the sedimentary series. Balanced cross-sections and structural analyses were performed to evaluate the geometry of the aquifer at depth. Continuous data acquisition (specific conductivity, temperature and water depth-pressure) and hydrochemical data (major ions, stables isotopes of water and carbon-13) allow to study the aquifer dynamism and functioning. A daily rainfall-discharge modeling approach was used with the KarstMod platform to estimate the flow part available for drinking water and the part that generates karst flash-floods. A hydrograph separation of springs discharge was carried out at annual and floods scales. Model results have been compared with the current groundwater management, showing a balanced current exploitation. In new perspective, it would be interesting to establish active management, combining a greater groundwater exploitation, floods mitigation and stream ecology respect.
195

Electronic State Excitations in the Water Molecule by Collisions with Low Energy Electrons

Thorn, Penny Anne, penny.thorn@flinders.edu.au January 2008 (has links)
The present study was largely concerned with measuring accurate absolute values for the electronic state excitation cross sections in H2O, in the incident electron energy range 15eV to 50eV. It is hoped that these data will eventually help to improve the current state of electron - molecule scattering theory, as well as being useful in various fields of modelling. As an illustration of this latter point, the cross sections determined here were used to calculate quantities of importance in atmospheric modelling, namely, electron energy transfer rates and rates for the excitation of water molecules by auroral secondary electrons.
196

Enhancements to synthetic aperture radar chirp waveforms and non-coherent SAR change detection following large scale disasters

Bayindir, Cihan 26 March 2013 (has links)
Synthetic aperture radar (SAR) is one of the most versatile tools ever invented for imaging. Due to its better Rayleigh resolution, SAR imaging provides the highest quality radar imagery. These images are used for many applications including but not limited to terrestrial mapping, disaster reconnaissance, medical imaging and military applications. Imaging techniques or geometries which can improve the resolution of the reconstructed imagery is always desired in the SAR imaging. In this dissertation both the linear and nonlinear frequency modulated chirp signals are discussed. The most widely used frequency modulated chirp signal, linear frequency modulated chirp signal, and some of its properties such as spectrum, point spread function and matched filter are summarized. A new nonlinear frequency modulated chirp signal which can be used to improve the image resolution is introduced. In order to validate the offered chirp signal, spotlight SAR imaging geometry together with 2D polar and Stolt format reconstruction algorithms are considered. The synthetic examples are generated using both chirps both with polar and Stolt format processing. Additionally a new change detection method which depends on the idea of generating two different final change maps of the initial and final images in a sequence is offered. The specific algorithms utilized for testing this method are the widely used correlation coefficient change statistic and the intensity ratio change statistic algorithms. This method together with the algorithms mentioned is first applied to synthetic data generated by Stolt format processing. It is shown that the method works on synthetic data. The method together with the algorithms mentioned is also applied to two case studies dfreal disasters, one is 2010 Gulf of Mexico oil spill and the second is 2008 China Sichuan earthquake. It is shown that two final change map method can reduce the false identifications of the changes. Also it is shown that intensity ratio change statistics is a better tool for identifying the changes due to oil contamination. The data used in this study is acquired by Japanese Aerospace Agency's Advanced Land Observing Satellite (ALOS) through Alaska SAR Facility (ASF), at the University of Alaska, Fairbanks.
197

Entwicklung einer Version des Reaktordynamikcodes DYN3D für Hochtemperaturreaktoren

Rohde, Ulrich, Apanasevich, Pavel, Baier, Silvio, Duerigen, Susan, Fridman, Emil, Grahn, Alexander, Kliem, Sören, Merk, Bruno 12 December 2012 (has links) (PDF)
Basierend auf dem Reaktordynamikcode DYN3D für LWR, wurde die Codeversion DYN3D-HTR für das Blockkonzept eines graphit-moderierten, helium-gekühlten Hochtemperaturreaktors entwickelt. Diese Entwicklung umfasst die: • methodische Weiterentwicklung der 3D stationären Neutronenflussberechnung für hexagonale Geometrie (HTR-Brennelement-Blöcke), • Generierung von Wirkungsquerschnittsdaten unter Berücksichtigung der doppelten Heterogenität, • Modellierung der Wärmeleitung und des Wärmetransports in der Graphitmatrix. Die nodale SP3-Neutronentransport-Methode in DYN3D wurde auf hexagonale Brennelementgeometrie erweitert. Es wird eine Unterteilung der Hexagone in Dreiecke vorgenommen, so dass die Verfeinerung hexagonaler Strukturen untersucht werden kann. Die Verifikation erfolgte durch Vergleiche mit Monte-Carlo-Referenzlösungen. Für die Behandlung der doppelten Heterogenität der Brennelementstruktur bei Homogenisierung der Wirkungsquerschnitte wurden neue Methoden entwickelt. Zum einen wurde ein zweistufiges Homogenisierungsverfahren basierend auf der Methode der sog. Reactivity Equivalent Transformation (RPT) weiterentwickelt. Zum anderen ermöglichte die Verfügbarkeit des neuen Monte-Carlo-Codes SERPENT die Anwendung eines einstufigen Verfahrens, wobei die 3D heterogenen Strukturen in einem Rechenschritt konsistent erfasst werden können. Weiterhin wur-de in DYN3D ein 3D Wärmeleitungsmodell implementiert, das den radialen und axialen Wärmetransport in der Graphitmatrix beschreiben kann. DYN3D-HTR wurde schließlich anhand der Testfälle für Reaktivitätstransienten erprobt. Die Verifikation erfolgte durch Vergleich zwischen 3D und 1D Berechnung der Wärmeleitung. Schließlich wurde DYN3D mit dem CFD-Code ANSYS-CFX gekoppelt, um auch dreidimensionale Strömungen in Reaktorkernen berechnen zu können. Der Kern wird als poröser Körper modelliert. Die Kopplung wurde an anhand von 2 Testbeispielen, dem Auswurf eines Steuerstabes und einer lokalen Strömungsblockade in einem Brennelement, erprobt.
198

Entwicklung des Neutronentransportcodes TransRay und Untersuchungen zur zwei- und dreidimensionalen Berechnung effektiver Gruppenwirkungsquerschnitte

Beckert, C. 31 March 2010 (has links) (PDF)
Standardmäßig erfolgt die Datenaufbereitung der Neutronenwirkungsquerschnitte für Reaktorkernrechnungen mit 2D-Zellcodes. Ziel dieser Arbeit war es, einen 3D-Zellcode zu entwickeln, mit diesem Code 3D-Effekte zu untersuchen und die Notwendigkeit einer 3D-Datenaufbereitung der Neutronenwirkungsquerschnitte zu bewerten. Zur Berechnung des Neutronentransports wurde die Methode der Erststoßwahrscheinlichkeiten, die mit der Ray-Tracing-Methode berechnet werden, gewählt. Die mathematischen Algorithmen wurden in den 2D/3D-Zellcode TransRay umgesetzt. Für den Geometrieteil des Programms wurde das Geometriemodul eines Monte-Carlo-Codes genutzt. Das Ray-Tracing in 3D wurde auf Grund der hohen Rechenzeiten parallelisiert. Das Programm TransRay wurde an 2D-Testaufgaben verifiziert. Für einen Druckwasser-Referenzreaktor wurden folgende 3D-Probleme untersucht: Ein teilweise eingetauchter Regelstab und Void (Vakuum oder Dampf) um einen Brennstab als Modell einer Dampfblase. Alle Probleme wurden zum Vergleich auch mit den Programmen HELIOS (2D) und MCNP (3D) nachgerechnet. Die Abhängigkeit des Multiplikationsfaktors und der gemittelten Zweigruppenquerschnitte von der Eintauchtiefe des Regelstabes bzw. von der Höhe der Dampfblase wurden untersucht. Die 3D berechneten Zweigruppenquerschnitte wurden mit drei üblichen Näherungen verglichen: Lineare Interpolation, Interpolation mit Flusswichtung und Homogenisierung. Am 3D-Problem des Regelstabes zeigte sich, dass die Interpolation mit Flusswichtung eine gute Näherung ist. Demnach ist hier eine 3D-Datenaufbereitung nicht notwendig. Beim Testfall des einzelnen Brennstabs, der von Void umgeben ist, erwiesen sich die drei Näherungen für die Zweigruppenquerschnitte als unzureichend. Demnach ist eine 3D-Datenaufbereitung notwendig. Die einzelne Brennstabzelle mit Void kann als der Grenzfall eines Reaktors angesehen werden, in dem sich eine Phasengrenzfläche herausgebildet hat.
199

Entwicklung eines 3D Neutronentransportcodes auf der Basis der Ray-Tracing-Methode und Untersuchungen zur Aufbereitung effektiver Gruppenquerschnitte für heterogene LWR-Zellen

Rohde, Ulrich [Projektleiter], Beckert, Carsten 31 March 2010 (has links) (PDF)
Standardmäßig erfolgt die Datenaufbereitung der Neutronenwirkungsquerschnitte für Reaktorkernrechnungen mit 2D-Zellcodes. Ziel dieser Arbeit war es, einen 3D-Zellcode zu entwickeln, mit diesem Code 3D-Effekte zu untersuchen und die Notwendigkeit einer 3D-Datenaufbereitung der Neutronenwirkungsquerschnitte zu bewerten. Zur Berechnung des Neutronentransports wurde die Methode der Erststoßwahrscheinlichkeiten, die mit der Ray-Tracing-Methode berechnet werden, gewählt. Die mathematischen Algorithmen wurden in den 2D/3D-Zellcode TransRay umgesetzt. Für den Geometrieteil des Programms wurde das Geometriemodul eines Monte-Carlo-Codes genutzt. Das Ray-Tracing wurde auf Grund der hohen Rechenzeiten parallelisiert. Das Programm TransRay wurde an 2D-Testaufgaben verifiziert. Für einen Druckwasser-Referenzreaktor wurden folgende 3D-Probleme untersucht: Ein teilweise eingetauchter Regelstab und Void (bzw. Moderator mit geringerer Dichte) um einen Brennstab als Modell einer Dampfblase. Alle Probleme wurden zum Vergleich auch mit den Programmen HELIOS (2D) und MCNP (3D) nachgerechnet. Die Abhängigkeit des Multiplikationsfaktors und der gemittelten Zweigruppenquerschnitte von der Eintauchtiefe des Regelstabes bzw. von der Höhe der Dampfblase wurden untersucht. Die 3D berechneten Zweigruppenquerschnitte wurden mit drei üblichen Näherungen verglichen: linearer Interpolation, Interpolation mit Flusswichtung und Homogenisierung. Am 3D-Problem des Regelstabes zeigte sich, dass die Interpolation mit Flusswichtung eine gute Näherung ist. Demnach ist hier eine 3D-Datenaufbereitung nicht notwendig. Beim Testfall des einzelnen Brennstabs, der von Void (bzw. Moderator geringerer Dichte) umgeben ist, erwiesen sich die drei Näherungen für die Zweigruppenquerschnitte als unzureichend. Demnach ist eine 3D-Datenaufbereitung notwendig. Die einzelne Brennstabzelle mit Void kann als der Grenzfall eines Reaktors angesehen werden, in dem sich eine Phasengrenzfläche herausgebildet hat.
200

Μελέτη μικρομετακινήσεων σε κατολισθαίνοντα πρανή στην περιοχή της Πιτίτσας με επίγειες και φωτογραμμετρικές μεθόδους αποτύπωσης / Smal scale displacements within landslides in the region of Pititsa using earth surveying and photogrammetry

Παπαθάνου, Μαριάννα 14 May 2007 (has links)
H παρούσα Διπλωματική Εργασία Μεταπτυχιακής Ειδίκευσης με θέμα «Μελέτη Μικρομετακινήσεων σε Κατολισθαίνοντα Πρανή στην περιοχή της Πιτίτσας, με Επίγειες και Φωτογραμμετρικές Μεθόδους Αποτύπωσης» ανατέθηκε από τον Επίκουρο Καθηγητή κ. Ιωάννη Κουκουβέλα στα πλαίσια του Προγράμματος Μεταπτυχιακών Σπουδών «Γεωεπιστήμες και Περιβάλλον», στην Κατεύθυνση «Γεωλογία Χρήσεων Γης», του τμήματος Γεωλογίας του Πανεπιστημίου Πατρών και εκπονήθηκε από τη μεταπτυχιακή φοιτήτρια Μαριάννα Παπαθάνου. Η εργασία αυτή πραγματοποιήθηκε ως μια μελέτη με σκοπό την ποιοτική και ποσοτική προσέγγισή της εξέλιξης του φαινομένου των κατολισθήσεων στην περιοχή της Πιτίτσας σε βάθος χρόνου περίπου 20 ετών. Ως περιοχή μελέτης έχει επιλέγει η ευρύτερη περιοχή της Πιτίτσας για τους εξής λόγους : Στην περιοχή έχουν συμβεί μια σειρά κατολισθήσεων οι θέσεις των οποίων έχουν πολλές φορές επαναδραστηριοποιηθεί μετά την κατασκευή του δρόμου. Η δομή των πετρωμάτων (ρήγματα, λιθολογική σύσταση), και η κατασκευή του δρόμου είναι πρακτικά οι μόνοι παράγοντες που επιδρούν στις κατολισθήσεις της περιοχής, ενώ οι βροχοπτώσεις είναι σχεδόν σταθερές και η ανθρώπινη παρέμβαση, εκτός από την κατασκευή του δρόμου, είναι περιορισμένη. Στις κατολισθήσεις που αναλύθηκαν διακρίνονται όσο το δυνατό περισσότερα ιστολογικά στοιχεία των κατολισθήσεων της περιοχής. Η περιοχή παρουσιάζει εμφανή στοιχεία ολισθήσεων όπως διαρρήξεις στην άσφαλτο ή δευτερεύουσες ουλές, οι οποίες δείχνουν στοιχεία ενεργότητας. Προκειμένου να εξαχθούν ασφαλή ποοτικά και ποσοτικά συμπεράσματα για την εξέλιξη των κατολισθήσεων ακολουθήθηκε η εξής μεθοδολογία : Η συλλογή όσο το δυνατό περισσότερων γεωμετρικών και γεωγραφικών στοιχείων διαφορετικών χρονολογιών για την περιοχή. Τα στοιχεία αφορούν αποτυπώσεις αλλά και αεροφωτογραφίες της περιοχής. Η επεξεργασία των στοιχείων με σκοπό την σύνταξη τοπογραφικών χαρτών και τη χάραξη τομών σ’αυτούς, ώστε να είναι εφικτή η σύγκριση των διαφορετικών χρονολογιών. Η σύγκριση των τοπογραφικών χαρτών και τομών διαφορετικών χρονολογιών με σκοπό την εξαγωγή αποτελεσμάτων και τη στατιστική επεξεργασία. Για τη μελέτη των κατολισθητικών φαινομένων χρησιμοποιήθηκαν επίγειες τοπογραφικές αλλά και φωτογραμμετρικές μέθοδοι αποτύπωσης . Αρχικά χρησιμοποιήθηκε ένας τοπογραφικός χάρτης της Διεύθυνσης Έργων της Νομαρχιακής Αυτοδιοίκησης Αχαΐας που εκπονήθηκε στα πλαίσια της Μελέτης Βελτίωσης του δρόμου Σαλμενίκο – Πιτίτσα το 2000 και επιλέχθηκαν συγκεκριμένες κατολισθήσεις που αναγνωρίσθηκαν στον χάρτη αυτόν. Στη συνέχεια στα πλαίσια της παρούσας εργασίας αποτυπώθηκαν εκ νέου οι παραπάνω κατολισθήσεις τα έτη 2004 και 2005. Από τη σύγκριση των χαρτών των τριών χρονολογιών προέκυψαν όχι μόνο ποιοτικά αλλά και ποσοτικά συμπεράσματα για τις κατολισθήσεις. Δηλαδή αναγνωρίσθηκαν οι κινήσεις υλικού αλλά επιπλέον χαράχθηκαν διατομές με βάση τις οποίες υπολογίσθηκαν οι όγκοι του υλικού που κατολίσθησε. Τέλος με βάση τους υπολογισμούς του όγκου του υλικού που κατολίσθησε, υπολογίστηκε ένας μέσος ετήσιος ρυθμός διάβρωσης. Επίσης στα πλαίσια της παρούσας εργασίας παρελήφθη από τη Γεωγρφική Υπηρεσία Στρατού μια σειρά αεροφωτογραφιών της ευρύτερης περιοχής του 1986. Από την επεξεργασία των αεροφωτογραφιών ανά στερεοσκοπικά ζεύγη κατασκευάστηκαν ψηφιακά μοντέλα εδάφους και ορθοφωτοχάρτες των κατολισθήσεων που είχαν επιλεγεί παραπάνω, για τη χρονολογία 1986. Στη συνέχεια, με σκοπό τη σύγκριση των χρονολογιών 1986 και 2000, χαράχθηκαν τομές στους ορθοφωτοχάρτες του 1986. Από τη σύγκριση των χαρτών και των τομών ανάμεσα στις χρονολογίες 1986 και 2000 προέκυψαν επίσης σημαντικά ποιοτικά και ποσοτικά συμπεράσματα για τις κατολισθήσεις. Η παρούσα εργασία αναφέρεται στη μελέτη της εξέλιξης των κατολισθητικών φαινομένων, στην περιοχή της Πιτίτσας, σε βάθος χρόνου σχεδον 20 ετών. Με βάση την παρούσα μελέτη τέλος προέκυψαν συμπεράσματα για τις κατολισθήσεις που αποτυπώθηκαν που αφορούν στα ποιοτικά και ποσοτικά χαρακτηριστικά τους, στη μορφή και στην κίνησή τους, στην ενεργότητα και στο ρυθμό εξέλιξής τους και στις ανθρωπογενείς παρεμβάσεις που δέχτηκαν στο διάστημα αυτό των 20 περίπου ετών. / The present Master Diploma Thesis entitled “Small scale Displacementσ within Landslides in the region of Pititsa using Earth Surveying and Photogrammetry” was assigned by Professor Ioannis Koukouvelas within the framework of the Graduate Studies Program “Geosciences and Environment”, of “Geology of Land Use”, of the University of Patras, Geology department, and was elaborated by the post-graduate student Marianna Papathanou. This project was implemented as a study aiming to approach, qualitative and quantitative, the landslide phenomena in the region of Pititsa over the last 20 years. The region of Pititsa was selected as a case study for the following reasons: The region is characterized by a series of small scale landslides, most of them experiencing reactivation which is damaging the asphalt covered road from Pititsa to Salmeniko villages. The structure of rocks (faults, lithologic composition etc.) and the construction of the road are practically the only factors affecting the landslides, since the precipitation is almost stable within the study area and the man-made modification, apart from the road construction, is limited. A wide range of morphological features within the landslides of the region was detected. The region offers evident elements of slide, for example asphalt fissures or secondary seams, presenting evidence of continuous activity. Qualitative and quantitative conclusions of the landslides was based on the following methodology: The collection of as many as possible geographic and geometric elements of the region, of different chronologies. These elements include different periods of surveying and airphotographs. The process of elements, aiming to set out contour plans. In order to define mass-balance cross-sections were composed to compare the evolution over the different chronologies. The qualitative and quantitative comparison of the contour plans, topographic maps and cross-sections of different chronologies aiming conclusions and statistical elaboration. For the study of landslide phenomena we used earth Surveying methods (repeated on 2004 and 2005 campaing) and Photogrammetry. Initially we used a topographic map provided from the Department of Public Works of the Prefectural Government of Achaia elaborated within the framework of the Improvement Study for the road Salmeniko - Pititsa in 2000, selecting specific locations of landslides identified on this map. The comparison of the sequential maps of the three chronologies resulted in qualitative and quantitative conclusions regarding landslides. Which means that the movements of material were recognized, but moreover cross-sections were composed whereby the volumes of the landslided material was calculated. Also an average rate of landslide-erosion per year was calculated. Furthermore, within the framework of the present project, a set of airphotographs of the wider region of 1986 was received from the Military Geographical Service. From the process on stereopairs of these airphotographs, digital models (DTM) of land and orthophotomaps were created, regarding the chosen landslides for the year 1986. In order to compare the two chronologies 1986 and 2000, cross-sections were composed from the orthophotomaps of 1986. Important qualitative and quantitative conclusions were resulted from the comparison of the maps and the cross-sections between the two chronologies 1986 and 2000. From the repeated surveying and the photogrammetry it concluded that the present project refers to the evolution of the landslides of the Pititsa region, for a period of 20 years. These data suggest continuous erosion increasing from 1986 and onwards at a rate of between 0.34 m/yr to 0.0186m/yr for the last 5 yers. Based on the present project important conclusions, for the mapped landslides, were extracted regarding their qualitative and quantitative characteristics, their shapes and movements, their development for this period of 20 years and also evidence that they are continuously creeping.

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