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Chen, Xiaoming. "Two-dimensional constrained anisotropic inversion of magnetotelluric data". Phd thesis, Universität Potsdam, 2012. http://opus.kobv.de/ubp/volltexte/2012/6316/.
Pełny tekst źródłaTektonische und geologische Prozesse verursachen häufig eine strukturelle Anisotropie des Untergrundes, welche von verschiedenen geophysikalischen Methoden beobachtet werden kann. Zur Erstellung und Interpretation geeigneter, realistischer Modelle der Erde sind Inversionsalgorithmen notwendig, die einen anisotropen Untergrund einbeziehen können. Für die vorliegende Arbeit habe ich einen magnetotellurischen (MT) Datensatz vom Cape Fold Gürtel in Südafrika untersucht. Diese Daten weisen auf eine ausgeprägte Anisotropie der Kruste hin, da z.B. die MT Phasen außerhalb des erwarteten Quadranten liegen und nicht durch standardisierte isotrope Inversionsalgorithmen angepasst und ausgewertet werden können. Um dieses Problem zu beheben, habe ich eine zweidimensionale Inversionsmethode entwickelt, welche eine anisotrope elektrische Leitfähigkeitsverteilungen in den Modellen zulässt. Die MT Inversion ist im allgemeinen ein nichtlineares, schlecht gestelltes Minimierungsproblem mit einer hohen Anzahl an Freiheitsgraden. Im isotropen Fall wird jeder Gitterzelle eines Modells ein elektrischer Leitfähigkeitswert zugewiesen um den Erduntergrund nachzubilden. Ein Modell mit beispielsweise 100 x 50 Zellen besitzt 5000 unbekannte Modellparameter. Im Gegensatz dazu haben wir im anisotropen Fall die sechsfache Anzahl, da hier aus dem einfachen Zahlenwert der elektrischen Leitfähigkeit ein symmetrischer, reellwertiger Tensor wird, wobei die Anzahl der Daten gleich bleibt. Für die erfolgreiche Inversion von anisotropen Leitfähigkeiten und um die Nicht-Eindeutigkeit der Lösung des inversen Problems zu überwinden, ist eine geeignete Einschränkung der möglichen Modelle absolut notwendig. Dies wird umso wichtiger, da die Sensitivität von MT Daten nicht für alle Anisotropieparameter gleich ist. In der vorliegenden Arbeit habe ich einen Algorithmus entwickelt, welcher die Lösung des anisotropen Inversionsproblems unter Minimierung einer globalen Straffunktion berechnet. Diese besteht aus drei Teilen: der Datenanpassung, den Zusatzbedingungen an die Glätte des Modells und die Anisotropie. Im Gegensatz dazu werden beim isotropen Fall nur die ersten zwei Parameter minimiert. Der neu definierte Anisotropieterm wird mit Hilfe der Summe der quadratischen Abweichung der Hauptleitfähigkeitswerte des Modells gemessen. Die grundlegende Idee dieser Zusatzbedingung ist einfach. Falls ein isotropes Modell die Daten ausreichend gut anpassen kann, wird keine elektrische Anisotropie zusätzlich in das Modell eingefügt. Um eine erfolgreiche Inversion zu garantieren müssen geeignete Regularisierungsparameter für die verschiedenen Nebenbedingungen an das Modell gewählt werden. Tests mit synthetischen Modellen zeigen, dass bei festgesetzten Regularisierungsparametern die Inversion meistens entweder in einem glatten Modell mit hohem RMS Fehler oder einem groben Modell mit kleinem RMS Fehler endet. Die Anwendung einer Relaxationsbedingung auf die Regularisierung nach jedem Iterationsschritt resultiert in glatteren Inversionsmodellen und einer höheren Konvergenz und scheint ein ausgereifter Weg zur Wahl der Parameter zu sein. Die vorgestellte Inversionsmethode ist im allgemeinen in der Lage die Hauptleitfähigkeiten in der horizontalen Ebene zu finden. Wenn keine der Hauptrichtungen der Anisotropiestruktur mit der vorgegebenen Streichrichtung übereinstimmt, können nur die dazugehörigen effektiven Leitfähigkeiten, welche die Projektion der Hauptleitfähigkeiten auf die Koordinatenachsen des Modells darstellen, aufgelöst werden. Allerdings gehen die Informationen über die Rotationswinkel verloren. Am Ende meiner Arbeit werden die MT Daten des Cape Fold Gürtels in Südafrika analysiert. Die MT Daten zeigen in einem Abschnitt des Messprofils (> 10 km) Phasen über 90 Grad. Dieser Teil der Daten kann nicht mit herkömmlichen isotropen Modellierungsverfahren angepasst und daher mit diesen auch nicht vollständig ausgewertet werden. Die vorgestellte Inversionsmethode konnte die außergewöhnlich hohen Phasenwerte nicht wie gewünscht im Inversionsergebnis erreichen, was mit dem erwähnten Informationsverlust der Rotationswinkel begründet werden kann. MT Phasen außerhalb des ersten Quadranten können für gewöhnlich bei Anomalien mit geneigter Streichrichtung der Anisotropie gemessen werden. Um diese auch in den Inversionsergebnissen zu erreichen ist eine Weiterentwicklung des Algorithmus notwendig. Vorwärtsmodellierungen des MT Datensatzes haben allerdings gezeigt, dass eine hohe Leitfähigkeitsheterogenität an der Oberfläche in Kombination mit einer Zone elektrischer Anisotropie in der mittleren Kruste notwendig sind um die Daten anzupassen. Aufgrund geologischer und tektonischer Informationen kann diese Zone in der mittleren Kruste als tiefer Aquifer interpretiert werden, der im Zusammenhang mit den zerrütteten Gesteinen der Table Mountain Group des Cape Fold Gürtels steht.
Adams, Amy Lynn. "Permeability anisotropy and resistivity anisotropy of mechanically compressed mudrocks". Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90036.
Pełny tekst źródłaCataloged from PDF version of thesis.
Includes bibliographical references (pages 313-322).
Permeability anisotropy (the ratio of the horizontal to vertical permeability) is an important parameter used in sedimentary basin models and geotechnical design to model fluid flow, locate hydrocarbon reserves and estimate stress and pressure evolution. The magnitude of the permeability anisotropy for a given mudrock is difficult to measure; further, whether the permeability anisotropy is a constant value or evolves with the basin state is of active debate. This thesis experimentally investigates the development of permeability anisotropy in mechanically compressed mudrocks. A novel measurement method is developed using resedimented cubic specimens. The permeability anisotropy of Resedimented Boston Blue Clay (RBBC) is systematically measured to determine both the magnitude and evolution of the permeability anisotropy. The permeability anisotropy predicted using measurements of the mudrock fabric is compared with the measured permeability anisotropy to understand the relationship between fabric evolution and permeability anisotropy. Finally, resistivity anisotropy is compared with permeability anisotropy to reveal useful field correlations. The results of the RBBC study are contrasted with additional measurements made using mudrocks covering a range of plasticity, clay fraction and mineralogical composition. The permeability anisotropy and the conductivity anisotropy (inverse of the resistivity anisotropy) of uniform RBBC increase from 1.2 to 1.9 as the porosity decreases from 0.49 to 0.36. The permeability decreases by over one order of magnitude and the formation factor triples over this porosity range. Platy particles rotate from ~ 42 to 28 degrees to the horizontal, driving permeability anisotropy development. Further decreasing the porosity of RBBC below porosity 0.36 decreases both the permeability anisotropy and the conductivity anisotropy. Finally, the conductivity anisotropy is shown to equal to the permeability anisotropy within +/-20%. This general behaviour is characteristic of all mudrocks studied. Though small (<2), the permeability anisotropy of uniform mudrocks can significantly increase the permeability anisotropy of larger systems, as shown through layered system models. These models also reveal that the large scale conductivity anisotropy is not equal to the permeability anisotropy, though the relationship identified for uniform mudrocks may still be useful for sites with high measurement resolution.
by Amy Lynn Adams.
Ph. D. in Geotechnical and Geoenvironmental Engineering
Rostamabad, Houshang Mansouri. "Distinguishing stress-induced anisotropy from fracture-induced anisotropy, and the implications of stress-induced anisotropy for time-lapse seismic". Thesis, Heriot-Watt University, 2006. http://hdl.handle.net/10399/108.
Pełny tekst źródłaOuahioune, Nedjma. "MOKE set-upto measure magnetic anisotropy : MOKE set-upto measure magnetic anisotropy". Thesis, Uppsala universitet, Materialfysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-414388.
Pełny tekst źródłaWack, Michael Richard. "Anisotropy of magnetic remanence". Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-145717.
Pełny tekst źródłaRobson, Martin. "The Cosmic Anisotropy Telescope". Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319559.
Pełny tekst źródłaWheatley, Richard James. "The anisotropy of repulsion". Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359829.
Pełny tekst źródłaEisenbach, Markus. "Magnetic anisotropy in nanostructures". Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364862.
Pełny tekst źródłaWalsh, James Paul Slater. "Anisotropy in molecular magnetism". Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/anisotropy-in-molecular-magnetism(11474b91-0d3d-4b0a-97cd-214d1713674e).html.
Pełny tekst źródłaThorsteinsson, Throstur. "Anisotropy of ice Ih : development of fabric and effects of anisotropy on deformation /". Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/6844.
Pełny tekst źródłaChen, Christopher H. K. "Anisotropy of solar wind turbulence". Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/6375.
Pełny tekst źródłaChakravarty, Subhashish. "Bayesian surface smoothing under anisotropy". Diss., University of Iowa, 2007. http://ir.uiowa.edu/etd/169.
Pełny tekst źródłaFard, Samad Moemen Bellah. "Modelling anisotropy in electrotechnical steels". Thesis, Cardiff University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263551.
Pełny tekst źródłaNordquist, Taylor James. "Permeability anisotropy of resedimented mudrocks". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/99578.
Pełny tekst źródłaCataloged from PDF version of thesis.
Includes bibliographical references (pages 257-260).
Permeability anisotropy (ratio of horizontal to vertical permeability) is an important but uncertain parameter used in characterizing underground formations. While it is a fairly unknown parameter, it is integral for the petroleum industry, where a greater permeability anisotropy understanding can greatly aid in basin modelling, pore pressure prediction, and borehole stability. This research experimentally characterizes the permeability anisotropy of several mudrocks, which are clay-rich sedimentary formations, using re-sedimentation, a process of homogenization of naturally-occurring soils and recreation of the sedimentation environment in a controlled laboratory setting. The permeability anisotropy of resedimented Boston Blue Clay (RBBC), an illitic lean clay (CL), increases from 1.5 to 3 when mechanically compressed from 0.1 to 40 MPa, corresponding to porosities ranging from 0.55 to 0.26. Resedimented Gulf of Mexico - Eugene Island mudrock (RGoM-EI), a smectitic fat clay (CH), exhibits permeability anisotropy increasing from 1 to 5 when compressed to the same stresses, corresponding to porosities ranging from 0.6 to 0.25. Not only does smectitic RGoM-EI mudrock transition to greater anisotropy with compression, but the rate of increase accelerates with compression. These measurements are made using a commercially-available Trautwein® constant rate of strain (CRS) consolidometer with vertical drainage combined with a novel radially-outward draining CRS device. The combination of the vertically and radially draining CRS devices produces permeability anisotropy data quickly, with very little scatter. For RGoM-EI, the effects of horizontal shearing to 29.5% shear strain at 0.14 MPa on permeability anisotropy are negligible. Permeability anisotropy of the homogeneous resedimented mudrocks tested, using a cubic specimen constant head permeameter within a triaxial cell, is directly correlated to their electrical conductivity anisotropy. The permeability anisotropy values measured using this technology, however, are lower than those measured using CRS testing.
by Taylor James Nordquist.
S.M.
Lam, Yukyam 1982. "Dark energy and CMB anisotropy". Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32743.
Pełny tekst źródłaIncludes bibliographical references (p. 59-60).
According to the WMAP and earlier COBE observations, the Cosmic Microwave Background (CMB) anisotropy power on large angular scales appears to be significantly lower than predicted by the standard model of cosmology. We propose a scalar field model of the dark energy as a mechanism for suppressing low l multipoles through late-Universe evolution of metric fluctuations and the integrated Sachs-Wolfe (ISW) effect. We find that for a constant dark energy equation of state, theoretical predictions actually give a larger (instead of a desired smaller) value of the quadrupole and other low l multipoles.
by Yukyan Lam.
S.B.
Sugita, Hikaru. "Anisotropy of Osteoporotic Cancellous Bone". Kyoto University, 2000. http://hdl.handle.net/2433/157004.
Pełny tekst źródłaKyoto University (京都大学)
0048
新制・論文博士
博士(医学)
乙第10371号
論医博第1709号
新制||医||742(附属図書館)
UT51-2000-F437
(主査)教授 開 祐司, 教授 堤 定美, 教授 岡 正典
学位規則第4条第2項該当
Wang, Nian. "Intrinsic versus extrinsic seismic anisotropy". Paris, Institut de physique du globe, 2014. http://www.theses.fr/2014GLOB0101.
Pełny tekst źródłaLi, Liang-shi. "Anisotropy in CdSe quantum rods". Berkeley, Calif. : Oak Ridge, Tenn. : Lawrence Berkeley National Laboratory ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2003. http://www.osti.gov/servlets/purl/827094-DOIqqD/native/.
Pełny tekst źródłaPublished through the Information Bridge: DOE Scientific and Technical Information. "LBNL--55023" Li, Liang-shi. USDOE Director. Office of Science. Office of Basic Energy Sciences (US) 09/01/2003. Report is also available in paper and microfiche from NTIS.
Azevedo, Carlos Alberto Cabral de. "Formulação alternativa para análise de domínios não-homogêneos e inclusões anisotrópicas via MEC". Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-18102007-110753/.
Pełny tekst źródłaThis work deals with elastic 2D problems characterized by the presence of zones with different materials and anisotropic inclusions using the boundary element method. The anisotropy can be assumed either over the whole domain or defined only over some particular inclusions, which is the most usual case. Fundamental solutions for anisotropic domains, although well-known, lead to more complex formulations and may introduce difficulties when the analysis requires more complex material models as for instance plastic behavior, finite deformations, etc. The alternative formulation proposed in this work can be applied to anisotropic bodies using the classical fundamental solutions for 2D elastic isotropic domains plus correction given by an initial stress field. The domain region with anisotropic properties or only with different isotropic elastic parameters has to be discretized into cells to allow the required corrections, while the complementary part of the body requires only boundary discretization. The initial stress tensor to be applied to the anisiotropic region is defined as the isotropic material elastic stress tensor correction by introducing a local penalty matrix. This matrix is obtained by the difference between the elastic parameters between the reference values and the anisotropic material. This technique is particularly appropriate for anisotropic inclusion analysis, in which the domain discretization is required only over a small region, therefore increasing very little the number of degrees of freedom of the final algebraic system. The numerical results obtained by using the proposed formulation have demonstrated to be very accurate in comparison with either analytical solutions or the other numerical values.
El-Khatib, Fatima. "Synthèse, caractérisation et études magnétiques de complexes de Co(II) et de Ni(II) avec des ligands de type cryptands". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS018/document.
Pełny tekst źródłaFor molecular magnetic materials to be used in applications, they must retain their magnetization at reasonable temperatures, which can be achieved with high-energy barriers for magnetization reversal and slow relaxation of the magnetization. In the field of Single-Molecule Magnets (SMMs), over the last decade, the main focus has shifted from large spin complexes to highly anisotropic systems which have displayed high energy barriers.1 Here, we used a cryptand ligand that forces a trigonal bipyramidal arrangement to obtain a large (in absolute value) negative zero field splitting parameter D.2 In order to use these molecules as models for entangled quantum bits (qbits), the cryptand ligand was chosen to have two coordination sites allowing the design of chemically stable binuclear complexes with tunable antiferromagnetic coupling. We prepared pentacoordinate complexes of Co(II) and Ni(II) with different bridging ligands (Cl-, Br-, NO3-, N3-, Im-, etc.). Magnetic measurements indicated an Ising type anisotropy and weak antiferromagnetic coupling as expected from the nature of the bridging ligands (N3- and Im-) and the trigonal bipyramidal geometry around the metal ions
Ferraro, Filippo Jacopo. "Magnetic anisotropies and exchange bias in ultrathin cobalt layers for the tunnel anisotropic magnetoresistance". Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAY086/document.
Pełny tekst źródłaIn the context of studying magnetic and spintronics phenomena occurring at the nanoscale, we investigated several aspects of Pt/Co/AlOx asymmetric structures. One of the objectives of this thesis was the control of the oxidation and the tailoring of the magnetic properties of these multilayers. We combined structural (X-Ray Reflectivity), transport (Anomalous Hall Effect) and magnetic measurements (VSM-SQUID), to study the interplay of magnetic and interfacial effects. One objective was to analyze the role that few monolayers (MLs) of CoO (which can form when overoxidizing the Al layer), could have on the properties of the stack. We used a wedge deposition techniques to control the oxidation on a subnanometer scale. We established that few MLs of CoO largely affect the total anisotropy of the stack. To further investigate the impact of the CoO, we engineered ultrathin Co(0.6nm)/CoO(0.6nm) bilayers. We performed field cooled measurements on this system and we found a large exchange bias anisotropy. These results indicate that the CoO keeps a large anisotropy even in the ML regime, help to rule out some of the models proposed to explain the exchange bias effect and imply that the usually neglected CoO presence must be considered in the energy balance of the system. We build perpendicular Tunneling Anisotropic MagnetoResistance (TAMR) devices based on the Pt/Co/AlOx structure. The TAMR is a relatively new spintronics effect in which the rotation of the magnetization in a single magnetic electrode (combined with the Spin-Orbit Coupling) can cause a change of the tunnel probability, which manifests as a magnetoresistance effect. We demonstrated that a careful control of the interface oxidation is crucial for the TAMR effect. The large induced magnetic anisotropy allowed us to achieve enhanced TAMR values compared to similar Pt/Co/AlOx structures
Ballot, Noémie. "Matériaux nanométriques à base de métaux 3d (Fe, Co, Ni) : Nouvelles voies de synthèse et caractérisations". Thesis, Paris 13, 2014. http://www.theses.fr/2014PA132065/document.
Pełny tekst źródłaThe growing interest in nanomaterials based on 3d transition metals such as cobalt, iron and nickel finds its origin in the intrinsic properties of these elements (high magnetization of iron and high magnetocristalline constant of cobalt) combined with particular property due to nanometric size and anisotropy of these alloys. Among the numerous synthetic routes, the polyol method which belongs to the chimie douce routes allows the elaboration of several finely divided inorganic materials (oxides, hydroxides, metals) by means of reduction or forced hydrolysis reactions conducted in polyol medium. The main first contribution of this work was to take advantage of these finely divided oxides and hydroxides elaborated in polyol medium to obtain metals and alloys, through a controlled reduction in solid form under hydrogen flow. Ferromagnetic particles of CoFe2, CoFe, NiFe, Ni3Fe and Fe with a blocking temperature above 300 K were obtained. The second main contribution of this work relates elaboration of anisotropic objects. Further, a new approach is proposed: forced hydrolysis in polyol medium assisted by applying a magnetic field. This type of synthesis leads to akaganeite β7&eOOH nanowires and spinel oxides nanoparticles. A relative mild reduction (300 °C) of akaganeite nanowires allows to obtain spinels phase with same morphology and magnetic properties in agreement with the chemical composition and the particles nanoscale (superparamagnetic behavior with blocking temperaturenear 300 K, high Ms and Hc dependent on the nature of the M element in the spinel MFe2O4, high in the case of cobalt and low for nickel and iron)
Robertson, C. J. "Factors controlling etch anisotropy in plasmas". Thesis, University of Surrey, 1990. http://epubs.surrey.ac.uk/843224/.
Pełny tekst źródłaSmith, Andrew Geoffrey Kent. "Cosmic ray anisotropy at high energies". Title page, contents and overview only, 1996. http://hdl.handle.net/2440/18616.
Pełny tekst źródłaThesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 1996
Bali, R. "Exchange anisotropy in magnetic thin films". Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596311.
Pełny tekst źródłaIrving, J. C. E. "Seismological studies of inner core anisotropy". Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604955.
Pełny tekst źródłaDyer, S. J. R. "Elastic anisotropy in fibre reinforced composites". Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373548.
Pełny tekst źródłaChen, Yu. "Towards anisotropy in ordered conducting polymers". Thesis, University of Aberdeen, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312356.
Pełny tekst źródłaSeah, Tian Ho. "Anisotropy of resedimented Boston Blue Clay". Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/14048.
Pełny tekst źródłaSegovia-Martinez, Manuel. "Texture anisotropy analysis of brain scans". Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/844053/.
Pełny tekst źródłaPandit, Yadav. "AZIMUTHAL ANISOTROPY IN HEAVY ION COLLISIONS". Kent State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=kent1353871180.
Pełny tekst źródłaChilton, Nicholas Frederick. "Magnetic anisotropy of transition metal complexes". Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/magnetic-anisotropy-of-transition-metal-complexes(64b34057-8a7a-44db-a89a-22a233fdefb5).html.
Pełny tekst źródłaRafique, Sadia. "Magnetic Anisotropy of Fe1-xGax Alloys". College Park, Md. : University of Maryland, 2003. http://hdl.handle.net/1903/133.
Pełny tekst źródłaThesis research directed by: Dept. of Materials Science and Nuclear Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
Maranville, Brian Benjamin. "Structure and anisotropy in codeposited CoPt₃ /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC IP addresses, 2003. http://wwwlib.umi.com/cr/ucsd/fullcit?p3112846.
Pełny tekst źródłaMaddock, Jamie Stewart. "Seismic anisotropy in siliciclastic reservoir rocks". Thesis, University of Leeds, 2006. http://etheses.whiterose.ac.uk/299/.
Pełny tekst źródłaBicalho, Elton da Silva [UNESP]. "Estrutura de variabilidade espacial e temporal da emissão de CO2 e atributos do solo caracterizada por dimensão fractal em área de cana-de-açúcar". Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/96815.
Pełny tekst źródłaConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
A emissão de CO2 do solo (FCO2) é influenciada por processos físicos, químicos e biológicos que afetam a produção de CO2 no interior do solo e o seu transporte para a atmosfera, variando no tempo e no espaço em função das condições ambientais e do manejo agrícola da área. O objetivo deste estudo foi investigar a correlação existente entre os padrões de estrutura de variabilidade espacial e temporal de FCO2 e atributos do solo, em área de cana-de-açúcar sob sistema de manejo cana crua, por meio de dimensão fractal (DF), derivada a partir de variogramas isotrópicos e anisotrópicos em diferentes escalas espaciais. A área experimental constituiu-se de uma malha regular de 60 × 60 m contendo 141 pontos espaçados em distâncias mínimas que variaram de 0,5 a 10 m. A emissão de CO2, temperatura e umidade do solo foram avaliadas durante 7 dias, sendo determinados os atributos físico e químicos do solo em amostragem na profundidade de 0,0 a 0,1 m. A média de FCO2 variou de 1,26 a 1,77 μmol m-2 s-1 ao longo dos dias, com dependência temporal na média e longa escalas, em alcances superiores a 20 m. Apesar do comportamento isotrópico observado para FCO2, seus valores de DF, calculados para diferentes direções, evidenciaram maior variabilidade temporal na direção paralela à linha de plantio, indicando influência das práticas de manejo adotadas na área. A variabilidade espacial de FCO2 foi mais bem evidenciada na média (20 a 30 m) e longa (40 a 60 m) escalas, com sua estrutura de variabilidade, caracterizada pelo fractograma, correlacionando-se significativamente com a maioria dos atributos do solo e apresentando comportamento similar à observada para a temperatura do solo e volume total de poros. Além disso, os fractogramas permitiram observar o comportamento da dependência espacial e temporal de FCO2 e...
Soil CO2 emission (FCO2) is influenced by physical, chemical and biological factors that affect the production of CO2 in the soil and its transport to the atmosphere, varying in time and space as a function of environmental conditions and agricultural management. The aim of this study was to investigate the correlation between spatial and temporal variability patterns of FCO2 and soil properties in sugarcane area under green management by using fractal dimension (DF), derived from isotropic and anisotropic variogram at different spatial scales. The experimental area consisted of a regular grid of 60 × 60 m containing 141 points spaced at minimum distances ranging from 0.5 to 10 m. Soil CO2 emission, soil temperature and soil moisture were evaluated over a period of 7 days, and soil physical and chemical properties were determined by sampling at a depth of 0.0 to 0.1 m. The average of FCO2 ranged from 1.26 to 1.77 mol m-2 s-1 throughout the days, with temporal dependence in the medium and large scales, at ranges of more than 20 m. Despite the isotropic behavior observed for FCO2, their DF values, calculated for different directions, showed greater temporal variability in the direction parallel to the row, indicating the influence of area management. Spatial variability of FCO2 was better evidenced in the medium (20 to 30 m) and long (40 to 60 m) scales, with its variability structure, characterized by fractogram, significantly correlated with most soil properties and similar behaving to that observed for the soil temperature and total pore volume. In addition, fractograms allowed to observe the behavior of the spatial and temporal dependence... (Complete abstract click electronic access below)
Rubert, José Benaque. "Grandes deformações e anisotropia por tensores de mapeamento aplicados a problemas de materiais compostos e na conformação de metais". Universidade de São Paulo, 1997. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-21032018-092739/.
Pełny tekst źródłaThe aim of this work is to valuate the performance of the theory of interacting substances in the continuum (role of mixtures) applied to composites including anisotropic substances which are modeled by an isotropic equivalent formulation. In the theoretical field, with respect to the anisotropy consideration by an equivalent isotropic formulation on the deformed configuration, convenient mapping tensors for stresses and strains in the fictitious space are deduced and applied to large deformation problems. The proposed models of anisotropy and composites were implemented in an explicit code for dynamic analysis with large deformations. The code is applied to the solution of sheet metal forming processes and multiphase composites including an analysis of a brittle matrix composite reinforced by short fibers by a simple elastoplastic damage model. The numerical results of the chosen examples are in good agreement with those suggested in some references or with some reported experiments.
Alves, Jozismar Rodrigues. "Difusão rotacional em membrana e anisotropia de fluorescência". Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-27032013-121603/.
Pełny tekst źródłaStructural properties of model membranes, such as lipid vesicles, may be investigated through the addition of fluorescent probes. After incorporation into the biomolecular system, the fluorescent molecules are excited with linearly polarized light and the fluorescence emission is depolarized due to translational as well as rotational diffusion during the life-time of the excited state. The monitoring of emitted light emitted informs on fluorescence decay times, and the decay of the components of the emitted light yield rotational correlation times which inform on the fluidity of the medium. The fluorescent molecule DPH, of uniaxial symmetry, is rather hydrophobic and has collinear transition and emission moments. It has been used frequently as a probe for the monitoring of the fluidity of the lipid bilayer along the phase transition of the chains. The interpretation of experimental data requires models for localization of fluorescent molecules as well as for possible restrictions on their movement. In this study, we develop calculations for three models for uniaxial diffusion of fluorescent molecules, such as DPH, suggested in several articles in the literature. The first model consists of a free randomly rotating dipole in a homogeneous solution, and serves as the basis for the study of the diffusion of models in anisotropic media. In the second model, we consider random rotations of emitting dipoles distributed within cones with their axes perpendicular to the vesicle spherical geometry: this could mimic the movement of the probe axis parallel to an average lipid chain. In the third model, the dipole rotates in the plane of the bilayer spherical geometry, within a movement that might occur between the monolayers forming the bilayer. For each of the models proposed, two methods are used by us in order to analyse the rotational diffusion: (1) solution of the corresponding rotational diffusion equation for a single molecule, taking into account the boundary conditions imposed by the models, for the probability of the fluorescent molecule to be found with a given configuration at time t. considering the distribution of molecules in the geometry proposed, we obtain the analytical expression for the fluorescence anisotropy, except for the cone geometry, for which the solution is obtained numerically; (11) numerical simulations of a rotational random walk restricted in geometries corresponding method very useful in case of low-symmetry geometries or geometries of composition. In this study, we have reproduced existing calculations, in some cases, extended calculations developed previously by other authors, in others, or, still, developed new calculations. As an application of our methodology for analysis of diffusional rotations, we have conducted an exploratory study of the experimental data for DPH in lipid bilayers, in the light of the results for the two models proposed for anisotropic media.
Simas, Emanuelle Reis. "Fotoquímica de polímeros conjugados contendo centros de transferência de carga e migração de energia". Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/75/75131/tde-24032011-093724/.
Pełny tekst źródłaThis work reports the study of energy transfer and migration processes in fully conjugated and segmented polyfluorene derivatives. The excited-state dynamics of the derivatives, PF-BNI, PFOPPV and PFPPV was studied in diluted solution of different solvents by means of ultrafast time-resolved spectroscopy. Poly(9,9\'-dioctylfluorene) end-capped with N-(2-benzothiazole)-1,8-naphthalimide, named PF-BNI, was prepared via Yamamoto-coupling reaction. This derivative is a highly fluorescence material with emission modulated by solvent polarity. Time-resolved fluorescence measurements showed the singlet exciton migration through the polymer backbone and the formation of an intrachain charge transfer excited-state (ICCT). PFOPPV and PFPPV are both fluorene copolymers containing fluorene-vinylene-phenylene moieties in the backbone. Whereas the PFPPV backbone is fully conjugated, the chromophore segment in PFOPPV backbone is confined between aliphatic (-(CH2)8-) flexible segments. The excited-state dynamics of both copolymers is characterized by the presence of conjugated moieties containing cis and trans isomers. The segmented structure of PFOPPV allows the resonant energy transfer between the chromophores, which is provided by dipole-dipole interactions. The energy transfer process leads to the depolarization of PFOPPV fluorescence emission. For PFPPV the energy migration occurs in less than 20 ps and the fluorescence decay is ascribed to the emission of chromophore segments containing cis and trans, already in a photostationary condition.
Martins, Alessandro. "Desenvolvimento do processo de produção e estudo estrutural e magnético de filmes finos ordenados de FePt". Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-24022014-153235/.
Pełny tekst źródłaFePt alloy films, with a chemically ordered face-centered-tetragonal FCT (type LI IND.0) structure and [001] texture, present perpendicular magnetic anisotropy, high coactivity and large polar magneto-optical Kerr effect. However, completely ordered films are usually obtained either by sputtering process at high substrate temperatures (T IND.s MAIOR IGUAL A 600°C) or by postanneling treatment at temperatures higher than 500°C. For technological purposes the preparation temperatures has to be as low as possible. In this work we have searched the more adequate conditions to preparation of FePt films with ordered FCT(001) phase at reduced temperatures. We have investigated the influence of deposition methods, substrate temperature, thickness of film, and type of substrate on the degree of the chemical ordering and preferred texture of FePt films and, consequently, on their magnetic properties. The Fe IND.xPt IND.1-x alloy thin films (with x SEMELHANTE A 50 at%) were prepared by DC Magnetron Sputtering, via two different deposition methods: a conventional code position method and an alternate monatomic layer (DAM) deposition method. The films were grown on SiO IND.2/Si (100), Si (100) and MgO (100) substrates, with and without a Pt buffer layer (thickness ranging from 50 to 76 nm), at T IND.s varying from room temperature to 600°C. The Pt buffer layer was used for obtaining better conditions to the induction of an epitaxial grown of FePt films with the ordered FCT(001) phase. The results of structural and magnetic characterization performed by X-ray diffraction (XRD) and vibrating sample magnetometry (VSM) show that the MgO substrates are adequate to induce an epitaxial growth of FePt films with a FCT structure and [001] texture. However, with the use of an optimized Pt FCC(100) buffer layer pre-deposited on MgO, the best conditions to an epitaxial induced growth were obtained, by both deposition methods. The results show also that the quality of the epitaxial induced growth depends on the thickness of the film. In relation to the deposition method in comparison to the code position method for preparation of FePt FCT(001) films, at reduced temperatures (T IND.s MENOR IGUAL A 400°C). With the use of the DAM method it was possible to obtain the ordered FCT(001) phase in the FePt film grown directly on MgO, at T IND.s = 400°C. For FePt film grown on Pt/MgO, the formation of the FCT(001) phase was verified at T IND.s = 200°C, and high degree of chemical order (S=0,88) was obtained at T IND.s = 400°C. X-ray Absorption Spectroscopy (XAS) studies also were done.
Stiller, Markus, Jose Barzola-Quiquia, Pablo Esquinazi, Daniel Spemann, Jan Meijer, Michael Lorenz i Marius Grundmann. "Strong out-of-plane magnetic anisotropy in ion irradiated anatase TiO2 thin films". Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-216180.
Pełny tekst źródłaMerabtine, Skander. "Etude expérimentale de la multifissuration et de la décohésion de films minces et nanostructures magnétiques sur substrats flexibles : effet sur l'anisotropie magnétique". Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCD058/document.
Pełny tekst źródłaFlexible and stretchable magnetic systems are of increasing interest for the development of electromagnetic devices conformable to non-planar surfaces. In this context, the objective of this thesis is to identify the relationships between irreversible mechanical phenomena (cracking and delamination) at large strains and magnetic properties of thin films of nanometric thicknesses (CoFeB and NiFe alloys) deposited on polymer substrate (Kapton®) by magnetron sputtering. In a first time, tensile tests coupled in situ with atomic force microscopy or electrical resistance measurements were used to study thin film multifissuration and subsequent localized debonding (buckles). These measurements made it possible to highlight areas of macroscopic strains for which each mechanism was predominant. In addition, the adhesion energy could be discussed and estimated from the monitoring of the buckles under applied strain. In a second step, ferromagnetic resonance measurements carried out ex situ made it possible to link the previously identified areas of strains to the evolutions of the magnetic anisotropy of thin films. In addition, a correlation between strain heterogeneities and Gilbert damping coefficient was found. Finally, the magnetomechanical properties of NiFe nanowires arrays have made it possible to highlight the advantage of nanopatterning for these deformable magnetic systems
Geslain, Alan. "Anisotropie naturelle et induite des matériaux poreux : étude expérimentale et modélisation". Phd thesis, Université du Maine, 2011. http://tel.archives-ouvertes.fr/tel-00718301.
Pełny tekst źródłaPlunkett, Brian W. "Plastic anisotropy of hexagonal closed packed metals". [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0012500.
Pełny tekst źródłaModén, Carl S. "Transverse anisotropy in softwoods : Modelling and experiments". Licentiate thesis, KTH, Aeronautical and Vehicle Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3988.
Pełny tekst źródłaTransverse anisotropy is an important phenomenon of practical and scientific interest. Although the presence of ray tissue explains the high radial modulus in many hardwoods, experimental data in the literature shows that this is not the case for pine. It is possible that anisotropy in softwoods may be explained by the cellular structure and associated deformation mechanisms.
An experimental approach was developed by which local radial modulus in spruce was determined at sub-annual ring scale. Digital speckle photography (DSP) was used, and the density distribution was carefully characterized using x-ray densitometry and the SilviScan apparatus. A unique set of data was generated for radial modulus versus a wide range of densities. This was possible since earlywood density shows large density variations in spruce. Qualitative comparison was made between data and predictions from stretching and bending honeycomb models. The hypothesis for presence of cell wall stretching was supported by data.
A model for wood was therefore developed where both cell wall bending and stretching are included. The purpose was a model for predictions of softwood moduli over a wide range of densities. The relative importance of the deformation mechanisms was investigated in a parametric study. A two-phase model was developed and radial and tangential moduli were predicted. Comparison with experimental data showed good agreement considering the nature of the model (density is the only input parameter). Agreement is much better than for a regular honeycomb model. According to the model, cell wall bending dominates at both low and high densities during tangential loading. In radial loading, cell wall stretching dominates at higher densities.
Zhang, Hongbin. "Relativistic Density Functional Treatment of Magnetic Anisotropy". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-25132.
Pełny tekst źródłaSpin-Bahn-Kopplung reduziert die Symmetrie ferromagnetischer Festkörper. Das bedeutet, dass die physikalischen Eigenschaften ferromagnetischer Stoffe anisotrop bezüglich der Magnetisierungsrichtung sind. In dieser Dissertation werden mittels numerischer voll-relativistischer Dichtefunktional-Rechnungen zwei Arten physikalischer Eigenschaften untersucht: magnetische Oberflächen-Anisotropieenergie (MAE) und anisotrope Thermokraft durch Lifshitz-Übergänge. Nach einer kurzen Einführung in die relativistische Dichtefunktional-Theorie in Kapitel 2 wird in Kapitel 3 die MAE ferromagnetischer dünner Filme untersucht. In diesen Systemen ist es für ein Verständnis experimenteller Ergebnisse wichtig, verschiedene Beiträge zu separieren: Volumenanteil der magnetokristallinen Anisotropie (MCA), Formanistropie und Oberflächen bzw. Grenzflächenanisotropie. Durch Anpassen berechneter Daten für dicke Schichten an ein phänomenologisches Modell konnten verlässliche Oberflächen Anisotropien erhalten werden. In dieser Weise wurde die MAE von Co- Schichten mit unterschiedlichen Geometrien untersucht, wobei der Einfluss von Orbitalpolarisations-Korrekturen (OPC) im Vordergrund stand. Es wurde gefunden, dass die Oberflächenanisotropie hauptsächlich von der Geometrie bestimmt wird. Während OPC bessere Ergebnisse für die Orbitalmomente liefert, wird die MAE überschätzt. Im zweiten Teil von Kapitel 3 wird der Einfluss elektrischer Felder auf die MAE von dünnen ferromagnetischen Filmen mit L10-Struktur untersucht. Unter Verwendung eines einfachen Modells zur Simulation des elektrischen Feldes liefern die Rechnungen gute Übereinstimmung mit vorliegenden experimentellen Ergebnissen. Es wird vorhergesagt, dass für CoPt ein noch größerer Effekt existiert. Weiterhin wurde gefunden, dass die magnetoelektrische Kopplung von der Größe der Abschirmladung bestimmt wird. Dies ist eine wichtige Einsicht, um die Magnetisierungsrichtung durch ein elektrisches Feld kontrollieren zu können. In Kapitel 4 werden Lifshitz-Übergänge untersucht, die ein gekantetes Magnetfeld hervorruft. Es wurden mehrere Lifshitz-Übergänge in geordnetem FePt gefunden, welche kleine Anomalien in der Zustandsdichte hervorrufen. Mit Hilfe eines Zweiband-Modells wird gezeigt, dass an solchen Übergängen das singuläre Verhalten kinetischer Eigenschaften durch Interband- Streuung verursacht wird und dass die Singularität proportional zur Ableitung der singulären Zustandsdichte ist. In FePt wird durch chemische Unordnung diese Singularität zu einer Anomalie verschmiert. Der Einfluss einer Verbreiterung der Energieniveaus der kritischen Bänder in FePt wurde mittels CPA untersucht. Es wurde gefunden, dass in experimentell verfügbaren dünnen FePt-Filmen Lifshitz-Übergänge bis zu 3% Erhöhung der Thermokraft erzeugen, wenn die Magnetisierung von der leichten in die harte Richtung gedreht wird
Durrell, John H. "Critical current anisotropy in high temperature superconductors". Thesis, University of Cambridge, 2001. https://www.repository.cam.ac.uk/handle/1810/34606.
Pełny tekst źródłaKontogeorgos, Andreas. "Optomechanical anisotropy in nanoengineered polymer photonic crystals". Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/245235.
Pełny tekst źródłaModén, Carl. "Transverse anisotropy in softwoods : modelling and experiments /". Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3988.
Pełny tekst źródłaHorstemeyer, Mark F. "Physically-motivated modeling of deformation-induced anisotropy". Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/17262.
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