Дисертації з теми "Three-dimensional inversion"
Щоб переглянути інші типи публікацій з цієї теми, перейдіть за посиланням: Three-dimensional inversion.
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-47 дисертацій для дослідження на тему "Three-dimensional inversion".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте дисертації для різних дисциплін та оформлюйте правильно вашу бібліографію.
1
Debens, Henry Alexander. "Three-dimensional anisotropic full-waveform inversion." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/32407.
Повний текст джерелаАнотація:
Full-waveform inversion (FWI) is a powerful nonlinear tool for quantitative estimation of high-resolution high-fidelity models of subsurface seismic parameters, typically P-wave velocity. A solution is obtained via a series of iterative local linearised updates to a start model, requiring this model to lie within the basin of attraction of the solution space's global minimum. The consideration of seismic anisotropy during FWI is vital, as it holds influence over both the kinematics and dynamics of seismic waveforms. If not appropriately taken into account, then inadequacies in the anisotropy model are likely to manifest as significant error in the recovered velocity model. Conventionally, anisotropic FWI either employs an a priori anisotropy model, held fixed during FWI, or uses a local inversion scheme to recover anisotropy as part of FWI; both of these methods can be problematic. Constructing an anisotropy model prior to FWI often involves intensive (and hence expensive) iterative procedures. On the other hand, introducing multiple parameters to FWI itself increases the complexity of what is already an underdetermined problem. As an alternative I propose here a novel approach referred to as combined FWI. This uses a global inversion for long-wavelength acoustic anisotropy, involving no start model, while simultaneously updating P-wave velocity using mono-parameter local FWI. Combined FWI is then followed by multi-parameter local FWI to recover the detailed final model. To validate the combined FWI scheme, I evaluate its performance with several 2D synthetic datasets, and apply it to a full 3D field dataset. The synthetic results establish the combined FWI, as part of a two-stage workflow, as more accurate than an equivalent conventional workflow. The solution obtained from the field data reconciles well with in situ borehole measurements. Although combined FWI includes a global inversion, I demonstrate that it is nonetheless affordable and commercially practical for 3D field data.
2
Ben, Hadj Ali Hafedh. "Three dimensional visco-acoustic frequency domain full waveform inversion." Nice, 2009. http://www.theses.fr/2009NICE4111.
Повний текст джерелаАнотація:
En exploration sismique, il est primordial d’extraire des données enregistrées les paramètres physiques étudiés du sous-sol afin de localiser correctement les réservoirs potentiels. Dans ce cas, l’imagerie sismique est l’une des plus importantes étapes dans cette quête. Le processus d’imagerie a reposé pendant longtemps sur une décomposition par échelles : la première étape consiste à construire un modèle de vitesse des bas nombres d’ondes qui explique correctement la cinématique du signal enregistré et la seconde à prendre en compte l’amplitude par migration afin de détecter les contrastes de réflectivité. Dans les années 80, une méthode d’imagerie quantitative, nommée inversion des formes d’ondes, a été proposée pour rassembler les deux étapes du processus d’imagerie au sein d’une approche intégrée. L’objectif de l’inversion des formes d’ondes est de construire simultanément tout le spectre des nombres d’ondes en exploitant l’ensemble des arrivées enregistrées par des dispositifs d’acquisition fournissant un large éclairage angulaire du milieu. La méthode est formulée sous la forme d’un problème d’optimisation pour lequel les différences entre les données enregistrées aux récepteurs et les données modélisées sont minimisées au sens des moindres carrés. Dans ce contexte scientifique, l’objectif de cette thèse est de développer et d’évaluer une méthode d’inversion des formes d’ondes en domaine fréquentiel pour la reconstruction de modèles du sous-sol 3-D dans le cadre de l’approximation visco-acoustique ou le milieu est paramétré par la vitesse de propagation des ondes de compression, la densité et l’atténuationIn seismic exploration, it is crucial to extract from the recorded data the physical of the subsurface in order to correctly locate the potential reservoirs. In this context, seismic imaging is an important step in this quest. The imaging process has been for a long time based on a two-scale strategy : the first step consists in building a smooth velocity model, which correctly explains the kinematics, and the second step in taking into account the dynamics through a migration process to detect reflectivity contrasts. In the eighties, a quantitative imaging method, called waveform inversion, has been proposed to bring together the two stages in an integrated approach. The objective of waveform inversion is to build the whole spectrum of wavenumbers by exploiting all the recorded arrivals acquired by wide aperture acquisitions. The method is formulated as a least squares optimization problem which aims to minimize the differences between the recorded and the modelled data. During the last few years, the waveform inversion method has been a main research topic in the academic and industrial communities. Many issues related to the starting anisotropy and elasticity, and the transition from 2-D to 3-D have been investigated. In this context, the objective of this thesis is to investigate and to develop a waveform inversion approach in the frequency domain and within the visco-acoustic approximation for the reconstruction of a 3-D subsurface model where the model is parametrized by the P-waves velocity, density and attenuation
3
Commer, Michael. "Three-dimensional inversion of transient electromagnetic data a comparative study /." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969850174.
Повний текст джерела
4
Shi, Weiqun 1965. "Advanced modeling and inversion techniques for three-dimensional geoelectrical surveys." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9878.
Повний текст джерела
5
Vieira, da Silva Nuno Miguel. "Three-dimensional modelling and inversion of controlled source electromagnetic data." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/9120.
Повний текст джерелаАнотація:
The marine Controlled Source Electromagnetic (CSEM) method is an important and almost self-contained discipline in the toolkit of methods used by geophysicists for probing the earth. It has increasingly attracted attention from industry during the past decade due to its potential in detecting valuable natural resources such as oil and gas. A method for three-dimensional CSEM modelling in the frequency domain is presented. The electric field is decomposed in primary and secondary components, as this leads to a more stable solution near the source position. The primary field is computed using a resistivity model for which a closed form of solution exists, for example a homogeneous or layered resistivity model. The secondary electric field is computed by discretizing a second order partial differential equation for the electric field, also referred in the literature as the vector Helmholtz equation, using the edge finite element method. A range of methods for the solution of the linear system derived from the edge finite element discretization are investigated. The magnetic field is computed subsequently, from the solution for the electric field, using a local finite difference approximation of Faraday’s law and an interpolation method. Tests, that compare the solution obtained using the presented method with the solution computed using alternative codes for 1D and 3D synthetic models, show that the implemented approach is suitable for CSEM forward modelling and is an alternative to existing codes. An algorithm for 3D inversion of CSEM data in the frequency domain was developed and implemented. The inverse problem is solved using the L-BFGS method and is regularized with a smoothing constraint. The inversion algorithm uses the presented forward modelling scheme for the computation of the field responses and the adjoint field for the computation of the gradient of the misfit function. The presented algorithm was tested for a synthetic example, showing that it is capable of reconstructing a resistivity model which fits the synthetic data and is close to the original resistivity model in the least-squares sense. Inversion of CSEM data is known to lead to images with low spatial resolution. It is well known that integration with complementary data sets mitigates this problem. It is presented an algorithm for the integration of an acoustic velocity model, which is known a priori, in the inversion scheme. The algorithm was tested in a synthetic example and the results demonstrate that the presented methodology is promising for the improvement of resistivity models obtained from CSEM data.
6
Heath, Philip John. ""Algorithms for the three-dimensional inversion of potential field tensor data" /." Title page, contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09SB/09sbh438.pdf.
Повний текст джерела
7
Feng, Le. "An in-depth examination of two-dimensional Laplace inversion and application to three-dimensional holography." University of Dayton / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1406814392.
Повний текст джерела
8
Grayver, Alexander [Verfasser]. "Three-dimensional controlled-source electromagnetic inversion using modern computational concepts / Alexander Grayver." Berlin : Freie Universität Berlin, 2013. http://d-nb.info/1036872815/34.
Повний текст джерела
9
Grayver, Alexander V. [Verfasser]. "Three-dimensional controlled-source electromagnetic inversion using modern computational concepts / Alexander Grayver." Berlin : Freie Universität Berlin, 2013. http://nbn-resolving.de/urn:nbn:de:kobv:188-fudissthesis000000094631-2.
Повний текст джерела
10
Qin, Jizeng. "Three-dimensional DC resistivity forward modeling and inversion by finite-element method." Diss., The University of Arizona, 1995. http://hdl.handle.net/10150/187064.
Повний текст джерелаАнотація:
DC resistivity inversion is a method for determining underground geoelectrical structures from discrete measurements of electric potential made on the surface or within a borehole. In this dissertation, a fully three-dimensional (3-0) resistivity inversion algorithm has been developed. Based on a finite-element forward solution of Laplace's equation, the program estimates several thousand unknowns in a rectangular grid by the linearized least-squares method. In the first Chapter, the main 3-D forward modeling techniques were investigated. These techniques include boundary condition implementation, secondary field solution and matrix inversion. Among the various kinds of mixed boundary conditions, the terminal-impedance method is particularly well suited for 3-D resistivity modeling. Its implementation is simple, but eliminates the mesh-edge influence effectively. The advantage of calculating the secondary fields instead of the total fields is that a coarse mesh may be used to achieve the same accuracy, which turns out to be particularly beneficial for 3-D modeling. Compared with other relaxation methods to solve the linear system iteratively, the incomplete Cholesky conjugate gradient (lCCG) algorithm is superior in convergence rate. However, to guarantee a stable solution, this method also requires more regular elements. To make the program capable of overcoming non-uniqueness and handling large numbers of parameters, the sensitivity matrix construction and three constraining conditions are discussed in Chapter two. In 3-D DC resistivity inversion, computing the sensitivity matrix is an enormous task even when using reciprocity. This is because the total number of forward calculations used to construct the sensitivity matrix for one iteration of the inversion is on the order of the number of observed data. By applying the conjugate-gradient method to solve the least-squares system, our program only needs to calculate the product of the sensitivity matrix, or its transpose, with an arbitrary vector, which requires only two forward runs for each source point. The different constraining conditions were tested by several synthetic models. Although each method can give a unique solution, we found that in our case, the smoothest solution method will reduce the data error better than the other two methods, the damped method and the stochastic method. A number of simple but geophysically significant structures are also modeled to test the program. These include a single isolated block anomaly, three connected blocks representing a dipping fault and a multi-layer model. Data were simulated by both integral-equation and finite-element approximations. The main features of most resistivity models were identifiable in the inversion result. As an example of a 3-D inversion program application, a field data set was processed in Chapter three. The effects of some important parameters used in the program were discussed. The results were compared with a 2-D solution and the known geological structures around that area.
11
Wilhelms, Wenke. "Development of a three-dimensional all-at-once inversion approach for the magnetotelluric method." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2016. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-207548.
Повний текст джерелаАнотація:
A three-dimensional inversion was implemented for magnetotellurics, which is a passive electromagnetic method in geophysics. It exploits natural electromagnetic fields of the Earth, which function as sources. Their interaction with the conductive parts of the subsurface are registered when components of the electric and the magnetic field are measured and evaluated.
The all-at-once approach is an inversion scheme that is relatively new to geophysics. In this approach, the objective function – the basis of each inversion – is called the Lagrangian. It consists of three parts: (i) the data residual norm, (ii) the regularisation part, and (iii) the forward problem. The latter is the significant difference to conventional inversion approaches that are built up of a forward calculation part and an inversion part. In the case of all-at-once, the forward problem is incorporated in the objective function and is therefore already taken into account in each inversion iteration. Thus, an explicit forward calculation is obsolete. As an objective function, the Lagrangian shall reach a minimum and therefore its first and second derivatives are evaluated. Hence, the gradient of the Lagrangian and its Hessian are constituent parts of the KKT system – the Newton-type system that is set up in the all-at-once inversion. Conventional inversion approaches avoid the Hessian because it is a large, dense, not positive definite matrix that is challenging to handle. However, it provides additional information to the inversion, which raises hope for a high quality inversion result.
As a first step, the inversion was programmed for the more straightforward one-dimensional magnetotelluric case. This was particularly suitable to become familiar with sQMR – a Krylov subspace method which is essential for the three-dimensional case to be able to work with the Hessian and the resulting KKT system. After the implementation and validation of the one-dimensional forward operator, the Lagrangian and its derivatives were set up to complete the inversion, which successfully solved the KKT system. Accordingly, the three-dimensional forward operator also needed to be implemented and validated, which was done using published data from the 3D-2 COMMEMI model. To realise the inversion, the Lagrangian was assembled and its first and second derivatives were validated with a test that exploits the Taylor expansion. Then, the inversion was initially programmed for the Gauss-Newton approximation where second order information is neglected. Since the system matrix of the Gauss-Newton approximation is positive definite, the solution of this system of equations could be carried out by the conventional solver pcg. Based on that, the complete KKT system (Newton\\\'s method) was set up and preconditioned sQMR solved this system of equations.
12
Hobro, James William Douglas. "Three-dimensional tomographic inversion of combined reflection and refraction seismic travel-time data." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621515.
Повний текст джерела
13
Weißflog, Julia. "Three-dimensional individual and joint inversion of direct current resistivity and electromagnetic data." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2017. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-220995.
Повний текст джерелаАнотація:
The objective of our studies is the combination of electromagnetic and direct current (DC) resistivity methods in a joint inversion approach to improve the reconstruction of a given conductivity distribution. We utilize the distinct sensitivity patterns of different methods to enhance the overall resolution power and ensure a more reliable imaging result. In order to simplify the work with more than one electromagnetic method and establish a flexible and state-of-the-art software basis, we developed new DC resistivity and electromagnetic forward modeling and inversion codes based on finite elements of second order on unstructured grids. The forward operators are verified using analytical solutions and convergence studies before we apply a regularized Gauss-Newton scheme and successfully invert synthetic data sets. Finally, we link both codes with each other in a joint inversion. In contrast to most widely used joint inversion strategies, where different data sets are combined in a single least-squares problem resulting in a large system of equations, we introduce a sequential approach that cycles through the different methods iteratively. This way, we avoid several difficulties such as the determination of the full set of regularization parameters or a weighting of the distinct data sets. The sequential approach makes use of a smoothness regularization operator which penalizes the deviation of the model parameters from a given reference model. In our sequential strategy, we use the result of the preceding individual inversion scheme as reference model for the following one. We successfully apply this approach to synthetic data sets and show that the combination of at least two methods yields a significantly improved parameter model compared to the individual inversion resultsZiel der vorliegenden Arbeit ist die gemeinsame Inversion (\"joint inversion\") elektromagnetischer und geoelektrischer Daten zur Verbesserung des rekonstruierten Leitfähigkeitsmodells. Dabei nutzen wir die verschiedenartigen Sensitivitäten der Methoden aus, um die Auflösung zu erhöhen und ein zuverlässigeres Ergebnis zu erhalten. Um die Arbeit mit mehr als einer Methode zu vereinfachen und eine flexible Softwarebasis auf dem neuesten Stand der Forschung zu etablieren, wurden zwei Codes zur Modellierung und Inversion geoelektrischer als auch elektromagnetischer Daten neu entwickelt, die mit finiten Elementen zweiter Ordnung auf unstrukturierten Gittern arbeiten. Die Vorwärtsoperatoren werden mithilfe analytischer Lösungen und Konvergenzstudien verifiziert, bevor wir ein regularisiertes Gauß-Newton-Verfahren zur Inversion synthetischer Datensätze anwenden. Im Gegensatz zur meistgenutzten \"joint inversion\"-Strategie, bei der verschiedene Daten in einem einzigen Minimierungsproblem kombiniert werden, was in einem großen Gleichungssystem resultiert, stellen wir schließlich einen sequentiellen Ansatz vor, der zyklisch durch die einzelnen Methoden iteriert. So vermeiden wir u.a. eine komplizierte Wichtung der verschiedenen Daten und die Bestimmung aller Regularisierungsparameter in einem Schritt. Der sequentielle Ansatz wird über die Anwendung einer Glättungsregularisierung umgesetzt, bei der die Abweichung der Modellparameter zu einem gegebenen Referenzmodell bestraft wird. Wir nutzen das Ergebnis der vorangegangenen Einzelinversion als Referenzmodell für die folgende Inversion. Der Ansatz wird erfolgreich auf synthetische Datensätze angewendet und wir zeigen, dass die Kombination von mehreren Methoden eine erhebliche Verbesserung des Inversionsergebnisses im Vergleich zu den Einzelinversionen liefert
14
Pirttijärvi, M. (Markku). "Numerical modeling and inversion of geophysical electromagnetic measurements using a thin plate model." Doctoral thesis, University of Oulu, 2003. http://urn.fi/urn:isbn:951427119X.
Повний текст джерелаАнотація:
Abstract
The thesis deals with numerical methods designed for the modeling and inversion of geophysical electromagnetic (EM) measurements using a conductive thin plate model. The main objectives are to study the EM induction problem in general and to develop practical interpretation tools for mineral prospecting in particular.
The starting point is a linearized inversion method based on the singular value decomposition and a new adaptive damping method. The inversion method is introduced to the interpretation of time-domain EM (TEM) measurements using a thin plate in free-space. The central part of the thesis is a new approximate modeling method, which is based on an integral equation approach and a special lattice model. At first the modeling method is applied to the interpretation of frequency-domain EM (FEM) data using a thin plate in conductive two-layered earth. After this time-domain responses are modeled applying a Fourier-sine transform of broadband FEM computations.
The results demonstrate that the approximate computational method can model the geophysical frequency and time-domain EM responses of a thin conductor in conductive host medium with sufficient accuracy, and that the inversion method can provide reliable estimates for the model parameters. The fast forward computation enables interactive interpretation of FEM data and feasible forward modeling of TEM responses. The misfit function mapping and analysis of the singular value decomposition have provided additional information about the sensitivity, resolution, and the correlation behavior of the thin plate parameters.
15
Mackie, Randall Lee. "Three-dimensional magnetotelluric modeling and inversion with applications to the California Basin and Range Province." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13753.
Повний текст джерела
16
Cherevatova, M. (Maria). "Electrical conductivity structure of the lithosphere in western Fennoscandia from three-dimensional magnetotelluric data." Doctoral thesis, Oulun yliopisto, 2014. http://urn.fi/urn:isbn:9789526207100.
Повний текст джерелаАнотація:
Abstract The lithospheric conductivity in the westernmost Fennoscandia has been studied using magnetotelluric (MT) data. The western margin of Fennoscandia was significantly affected in Paleozoic by the Caledonian orogeny and later by the rifting of Laurentia and the opening of the Atlantic Ocean c. 80 Ma ago. Magnetotelluric studies have been carried out in two target areas in southern Norway and in western Fennoscandia. The first study resulted in 2-D geoelectric models of two profiles stretching from Oslo to the Norwegian coast. The interpretation suggests that the basement is in general very resistive with a few conductive upper crustal layers, representing the alum shales, and middle crustal conductors possibly imaging the remnants of the closed ocean basins. A more extensive MT study was performed within the project "Magnetotellurics in the Scandes". Measurements were carried in summers of 2011 to 2013, resulting in an array of 279 MT sites. The data allowed us to derive 2-D geoelectric models for the crust and upper mantle as well as 3-D models for the crust. The inversions revealed a resistive upper crust and a conductive lower crust, two upper crustal conductors in the Skellefteå and Kittilä districts, highly conducting alum shales in the Caledonides and a conductive upper crust beneath the Lofoten peninsula. The thickness of the lithosphere is around 200 km in the north and 300 km in the south-west. The Palaeoproterozoic lithosphere is the thickest, not the Archaean, on contrary to a generally accepted hypothesis. A better image of the lithosphere will help to evaluate the proposed mechanisms of the exhumation of the Scandinavian Mountains. The theoretical part of this study is the development of a new multi-resolution approach to 3-D electromagnetic (EM) modelling. Three-dimensional modelling of MT data requires enormous computational resources because of the huge number of data and model parameters. The development of the multi-resolution forward solver is based on the fact that a finer grid resolution is often required near the surface. On the other hand, the EM fields propagate in a diffusive manner and can be sufficiently well described on a grid that becomes coarser with depth. Tests showed that the total run time can be reduced by five times and the memory requirements by three times compared with the standard staggered grid forward solverTiivistelmä Olemme tutkineet litosfäärin sähkönjohtavuutta Fennoskandian länsiosassa magnetotelluurisen (MT) menetelmän avulla. Fennoskandian länsireuna muokkautui merkittävästi paleotsooisena aikana Kaledonidien vuorijonopoimutuksessa sekä myöhemmin mesotsooisena aikana Laurentia-mantereen repeytyessä ja Atlantin valtameren syntyessä noin 80 miljoonaa vuotta sitten. MT-tutkimukset tehtiin Etelä-Norjassa ja Fennoskandian luoteisosassa. Ensimmäisessä tutkimuksessa kallioperän sähkönjohtavuutta kuvattiin kaksiulotteisilla (2-D) johtavuusmalleilla, jotka ulottuvat Oslosta Norjan rannikolle. Mallien tulkinta viittaa siihen, että maan kuori on pääosin hyvin eristävä lukuun ottamatta muutamaa kuoren ylä- ja keskiosassa olevaa johdekerrosta. Yläkuoren johteet edustavat alunaliuskeita ja keskikuoren johteet todennäköisesti suljetuissa merialtaissa syntyneitä hiilipitoisia sedimenttikerrostumia. Laajempi MT-tutkimus tehtiin ”Magnetotellurics in the Scandes” -hankkeessa. Mittauksia tehtiin 279 mittauspisteessä kesinä 2011–2013. Saadun aineiston avulla voitiin laatia 2-D inversiomallit kuoresta ja ylävaipasta sekä 3-D inversiomalli kuoresta. Tulosten mukaan täällä kuoren yläosa on eristävä kun taas kuoren alaosa on sähköä hyvin johtava. Edellisen lisäksi malleissa näkyy yläkuoren johtavat muodostumat Skellefteån ja Kittilän alueilla, korkean johtavuuden alunaliuskeet Kaledonidien alueella sekä johde Lofoottien alla. Litosfäärin paksuus on noin 200 km mittausverkon pohjoisosassa ja noin 300 km lounaassa. Tämän mukaan litosfääri on paksuin varhaisproterotsooisen litosfäärin alueella, ei arkeeisen litosfäärin alueella vastoin yleistä hypoteesia. Tutkimuksen teoreettisessa osassa kehitettiin sähkömagneettiseen mallinnukseen uusi monitasoiseen diskretisointiin perustuva menetelmä. MT-aineiston 3-D käänteisongelman ratkaisu ja siihen liittyvä suora mallintaminen vaativat suuren laskennallisen kapasiteetin, koska havaintojen ja mallin kuvaamiseen tarvittavien parametrien määrä on erittäin suuri. Moniresoluutio-algoritmi perustuu siihen, että mallin hienojakoisempaa diskretisointia tarvitaan yleensä lähellä maan pintaa kun taas syvemmälle edettäessä, sähkömagneettisen aallon diffuusin etenemisen vuoksi, malli voi olla karkeampi. Tietokonesimulaatioiden mukaan suoritusaika on viidennes ja muistitarve kolmannes verrattuna tavanomaiseen suoran laskennan ”staggered grid” -diskretisointiin
17
Pritchard, Geoffrey Michael. "Electromagnetic induction in a heterogeneous sphere : a three dimensional inversion for the electrical conductivity of the mantle." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620942.
Повний текст джерела
18
KAWAI, HISASHI, KIMINORI BOKURA, SHINJI NAGANAWA, and MASAHIRO YAMAZAKI. "VISUALIZATION OF BRAIN WHITE MATTER TRACTS USING HEAVILY T2-WEIGHTED THREE-DIMENSIONAL FLUID-ATTENUATED INVERSION-RECOVERY MAGNETIC RESONANCE IMAGING." Nagoya University School of Medicine, 2014. http://hdl.handle.net/2237/20547.
Повний текст джерела
19
Iwaki, Asako. "Study on Seismic Wave Propagation Characteristics in a Sedimentary Basin and Waveform Inversion for Three-dimensional Basin Boundary Shape." 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/142385.
Повний текст джерела
20
Rhoades, Joshua L. "Characterizing the Distribution of Hydraulic Properties in the Glacial Lake Agassiz Peatlands Using a Three-Dimensional Numerical Model and Regularized Inversion." Fogler Library, University of Maine, 2009. http://www.library.umaine.edu/theses/pdf/RhoadesJL2009.pdf.
Повний текст джерела
21
Zhang, Ting. "Electromagnetic wave imaging of targets buried in a cluttered medium using an hybrid Inversion-DORT method." Phd thesis, Ecole centrale de Marseille, 2014. http://tel.archives-ouvertes.fr/tel-01037906.
Повний текст джерелаАнотація:
The objective of this thesis work is to detect and to characterize three-dimensional targets in a disordered medium, using electromagnetic excitations. This research domain is of great interest in many applications, such as subsoil probing, medical imaging, non-destructive testing and geophysical exploration, etc. In order to extract the target information from the heterogeneities of the medium, we propose to use one of the time reversal technique, namely the DORT method (French acronym for Décomposition de l'Opérateur de Retournement Temporel). This method permits us to generate different waves that focus selectively on each target in high noisy environment. Moreover, this method is also combined with a non-linear inversion algorithm, which permits not only to localize but also to characterize the targets. The reconstruction resolution appears to be better than the ones obtained with the DORT or the inversion procedure alone, especially in the illumination direction. It is also shown that using full-polarized data is indispensable for achieving better performances rather than in scalar configuration. Moreover, in the half-space configuration, it is mandatory to use the frequency-diversity data to get an accurate reconstruction. These theoretical developments are also confronted to experimental data measured in the optical domain. A full-polarization Tomographic Diffractive Microscopy (TDM) is implemented and a resolution about one-fourth of the wavelength is thus obtained. Furthermore, the DORT method is applied in TDM to realize selective focalization and characterization. In the presence of multiple targets, selective characterization of each scatterer is achieved.This thesis work also deals with the characterization problem using transient data. Different inversion algorithms are validated using synthetic and experimental hyper-frequency data.
22
Christodoulou, Apostolos A. "Etude sismotectonique et inversion tridimensionnelle en Grèce du Nord." Grenoble 1, 1986. http://www.theses.fr/1986GRE10086.
Повний текст джерелаАнотація:
Première Partie: Etude sismotectonique d'un graben complexe, exemple: le graben Mygdonien (Grèce du Nord). Durant les printemps de 1984 et 1985 nous avons installé un réseau sismologique de 29 stations portables dans la région du graben Mydgonien près de Thessaloniki. La sismicité et les mécanismes au foyer ont montré une structure complexe. Des phénomènes compressifs ont été observés au centre du graben. Nous proposons un modèle pour la formation et l'évolution du graben. Au départ la déformation a lieu le long des failles pré-existantes de direction NW-SE ou NNE-SSW avec des mouvements normaux ou décrochants. Dans une deuxième étape il y a formation d'une nouvelle famille de failles normales, dirigées E-W. Cette famille a une direction perpendiculaire à l'axe T moyen, trouvé par les mécanismes au foyer et vient se superposer aux failles initiales. Elle devient rapidement la famille principale et les failles initiales jouent un rôle d'ajusteur de déformation dans cet ensemble. En outre les anciennes failles fonctionnent comme des barrières à l'évo lution des failles dirigées E-W. Deuxième partie: Etudes tridimensionnelle de la croûte et du manteau supérieur à partir de l'inversion des ondes P des téléséismes. A partir des résidus relatifs de temps de parcours des ondes P des téléséismes, enregistrés par le réseau permanent du laboratoire de Géophysique de Thessaloniki, nous avons tenté une inversion tridimensionnelle selon la méthode de Aki, Christofferson et Husebye. Nous avons obtenu des modèles de vitesse en 3D pour les ondes P sous la Grèce du nord, jusqu'à une profondeur de 250 km. Nous avons essayé d'expliquer les variations latérales des vitesses observées, à l'aide de l'isostasie, du flux de chaleur et de la sismicité
23
Weißflog, Julia [Verfasser], Klaus [Akademischer Betreuer] Spitzer, Klaus [Gutachter] Spitzer, Oliver G. [Gutachter] Ernst, and Yuguo [Gutachter] Li. "Three-dimensional individual and joint inversion of direct current resistivity and electromagnetic data / Julia Weißflog ; Gutachter: Klaus Spitzer, Oliver G. Ernst, Yuguo Li ; Betreuer: Klaus Spitzer." Freiberg : Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2017. http://d-nb.info/1221068652/34.
Повний текст джерела
24
Wilhelms, Wenke [Verfasser], Klaus [Akademischer Betreuer] Spitzer, Klaus [Gutachter] Spitzer, Michael [Gutachter] Eiermann, and Dmitry [Gutachter] Avdeev. "Development of a three-dimensional all-at-once inversion approach for the magnetotelluric method / Wenke Wilhelms ; Gutachter: Klaus Spitzer, Michael Eiermann, Dmitry Avdeev ; Betreuer: Klaus Spitzer." Freiberg : Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2016. http://d-nb.info/1220912778/34.
Повний текст джерела
25
Hering, Philip [Verfasser], Andreas [Akademischer Betreuer] Junge, Colin [Akademischer Betreuer] Brown, Andreas [Gutachter] Junge, and Colin [Gutachter] Brown. "Advances in magnetotelluric data processing, interpretation and inversion, illustrated by a three-dimensional resistivity model of the Ceboruco volcano / Philip Hering ; Gutachter: Andreas Junge, Colin Brown ; Andreas Junge, Colin Brown." Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2019. http://d-nb.info/1226180604/34.
Повний текст джерела
26
Ismail, Nazli. "Controlled Source Radiomagnetotelluric (CSRMT) Applications in Environmental and Resource Exploration." Doctoral thesis, Uppsala universitet, Geofysik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-102750.
Повний текст джерелаАнотація:
An integrated use of radio magnetotelluric (RMT) and controlled source tensor magnetotelluric (CSTMT) measurements, the so-called CSRMT method, has been employed in environmental and resource exploration studies. A number of case histories, including a groundwater investigation in glacial deposits, a study of fracture zones for geotechnical purposes and a mining exploration study of a copper deposit, are presented in this thesis in order to illustrate the usefulness and capability of the CSRMT method. The resolutions of the estimated models using various types of data are studied. Magnetotelluric transfer functions are used to analyze the dimensionality, the near surface resistivity distortions and the near field effects in the case of CSTMT data analysis. The near field effects in CSTMT data have also been identified by performing 2½D forward modelling. Data analysis, dimensionality tests and forward modelling show that at the lowest frequencies used the CSTMT transfer functions are generally distorted by source effects, except when the source-receiver distances are sufficient large compared with the penetration depth. Regarding CSTMT transfer functions, apparent resistivities are generally less distorted than phases. TM mode transfer functions are more affected by the sources than TE mode, while tipper vectors generally contain source signatures at all frequencies. Based on the analysis of dimensionality and source effects 2D inverse modelling of CSTMT and RMT data, as well as their combination, have been performed under the plane wave assumption. The RMT method proved to be a powerful tool for imaging the upper 50 m near-surface, but their penetration depth reduces as a conductive layer structures cover the targets at depth. The penetration depth can be increased by including the CSTMT data in the modelling if the measurements are in the far field range. The resolution of the deeper parts of the models may be improved by performing a joint inversion of TE and TM modes, if the strike direction is well-defined. Alternatively, inversion of determinant data can be performed, since the determinant data are less affected by 3D structures and source effects. However the resolution of the determinant models is somewhat degraded compared to the models inverted from combined TE and TM modes.
27
Carcolé, Carrubé Eduard. "Three-dimensional spatial distribution of scatterers in the crust by inversion analysis of s-wave coda envelopes. A case study of Gauribidanur seismic array site (Southern india) and Galeras volcano (South-western Colombia)." Doctoral thesis, Universitat Ramon Llull, 2006. http://hdl.handle.net/10803/9321.
Повний текст джерелаАнотація:
In this thesis, coda waves recorded by local seismographic networks will be analyzed to estimate the three-dimensional spatial distribution of scatterers (SDS). This will be done by using the single scattering approximation. This approach leads to a huge system of equations that can not be solved by traditional methods. For the first time, we will use the Simultaneous Iterative Reconstructive Technique (SIRT) to solve this kind of system in seismological applications. SIRT is slow but provides a means to carry out the inversion with greater accuracy. There is also a very fast non-iterative method that allows to carry out the inversion 102 times faster, with a higher resolution and reasonable accuracy: the Filtered Back-Projection (FBP). If one wishes to use this technique it is necessary to adapt it to the geometry of our problem. This will be done for the first time in this thesis. The theory necessary to carry out the adaptation will be developed and a simple expression will be derived to carry out the inversion.FBP and SIRT are then used to determine the SDS in southern India. Results are almost independent of the inversion method used and they are frequency dependent. They show a remarkably uniform distribution of the scattering strength in the crust around GBA. However, a shallow (0-24 km) strong scattering structure, which is only visible at low frequencies, seems to coincide with de Closepet granitic batholith which is the boundary between the eastern and western parts of the Dharwar craton.
Also, the SDS is estimated for the Galeras volcano, Colombia. Results reveal a highly non-uniform SDS. Strong scatterers show frequency dependence, which is interpreted in terms if the scale of the heterogeneities producing scattering. Two zones of strong scattering are detected: the shallower one is located at a depth from 4 km to 8 km under the summit whereas the deeper one is imaged at a depth of ~37 km from the Earth's surface. Both zones may be correlated with the magmatic plumbing system beneath Galeras volcano. The second strong scattering zone may be probably related to the deeper magma reservoir that feeds the system.
28
Kubo, Hisahiko. "Study on rupture processes of large interplate earthquakes estimated by fully Bayesian source inversions using multi period-band strong-motion data －The 2011 Tohoku-oki and the 2011 Ibaraki-oki earthquakes－." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199110.
Повний текст джерела
29
Guilbaud, Claude. "Étude des inversions thermiques : application aux écoulements atmospghériques dans des vallées encaissées." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10068.
Повний текст джерелаАнотація:
Le code Submeso est développé dans le but de comprendre et d'analyser les phénomènes d'inversion thermique dans les vallées encaissées. Les grandes échelles de l'écoulement (LES) sont obtenues par la résolution des équations tridimensionnelles du mouvement écrites sous leur forme compressible et non-hydrostatique en coordonnées dites gal-chen. Un modèle sous-maillé basé sur une équation de transport de l'énergie cinétique turbulente permet de transférer la production d'énergie turbulente générée au sol vers les couches supérieures de l'atmosphère. Les échanges entre le sol et l'atmosphère sont décrits par un modèle de sol (sm2-isba), couplé à un modèle de paroi performant. Le modèle de sol est validé sur deux campagnes de mesures sur site efeda et hapex - mobilhy. La prise en compte de l'interaction sol-atmosphère a été validée par deux études de la couche limite planétaire: une couche limite atmosphérique pleinement convective et l'évolution d'une couche limite planétaire correspondant à l'expérience de Wangara. Une étude complète de la structure des écoulements atmosphériques dans des vallées encaissées est réalisée. Dans un premier temps, on étudie l'évolution temporelle d'un scalaire passif émis dans un relief complexe 3D avec des échanges sol-atmosphère simplifiés. Puis, les phénomènes d'inversions thermiques sont étudiés dans une vallée stylisée, pour deux saisons. Le modèle réaliste des échanges sol-atmosphère a permis de simuler le cycle diurne complet. On met en évidence une variabilité saisonnière du comportement de l'inversion. L'été, les phénomènes ont une durée de vie et des périodes de transition plus longue qu'en hiver. Contrairement au cas hivernal, la structure spatiale de la couche convective estivale est symétrique par rapport à l'axe médian de la vallée.
30
Bazin, Sara. "Three-dimensional crustal structure of East Pacific rise discontinuities from tomographic inversions /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2000. http://wwwlib.umi.com/cr/ucsd/fullcit?p3035403.
Повний текст джерела
31
Toomey, Douglas R. "The tectonics and three-dimensional structure of spreading centers--microearthquake studies and tomographic inversions." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/58497.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1987.Supervised by Mike Purdy, Sean C. Solomon.
Includes bibliographical references.
Two-thirds of the Earth's surface has been formed along a global system of spreading centers that are presently manifested in several different structural forms, including the classic rift valley of the Mid-Atlantic Ridge, the more morphologically subdued East Pacific Rise, and the pronounced en echelon structure of the Reykjanes Peninsula within southwestern Iceland. In this thesis, each of these different spreading centers is investigated with microearthquake studies or tomographic inversion of travel times. Results of these studies are used to constrain the spatial variability of physical properties and processes beneath the axis of spreading and, together with other observations, the temporal characteristics of crustal accretion and rifting. In Chapter 2 the theoretical basis of seismic body-wave travel-time tomography and techniques for the simultaneous inversion for hypocentral parameters and velocity structure are reviewed. A functional analysis approach assures that the theoretical results are independent of model parameterization. An important aspect of this review is the demonstration that travel time anomalies due to path and source effects are nearly independent. The discussion of the simultaneous inverse technique examines theoretically the dependence of tomographic images on the parameterization of the velocity model. In particular, the effects of parameterization on model resolution are examined, and it is shown that an optimum set of parameters averages velocity over localized volumes. Chapter 2 ends with the presentation of the results of tomographic inversions of synthetic data generated for a model of the axial magma chamber postulated to exist beneath the East Pacific Rise. These inversions demonstrate the power of the tomographic method for imaging three-dimensional structure on a scale appropriate to heterogeneity along a spreading ridge axis. Chapter 3 is the first of two chapters that present the results of a microearthquake experiment carried out within the median valley of the Mid-Atlantic Ridge near 230 N during a three week period in early 1982. In this chapter, the experiment site, the seismic network, the relocation of instruments by acoustic ranging, the hypocenter location method, and the treatment of arrival time data are described. Moreover, hypocentral parameters of the 26 largest microearthquakes are reported; 18 of these events have epicenters and focal depths which are resolvable to within ±1 km formal error at the 95% confidence level. Microearthquakes occur beneath the inner floor of the median valley and have focal depths generally between 5 and 8 km beneath the seafloor. Composite fault plane solutions for two spatially related groups of microearthquakes beneath the inner floor indicate normal faulting along fault planes that dip at angles of 300 or more.
Douglas Ray Toomey.
Ph.D.
32
Migliari, Wellington. "From the effectiveness of the right to housing to the right to the city: a three-dimensional rationality for Brazil and Spain." Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/664047.
Повний текст джерелаАнотація:
The conflict between property system and the right to housing has evolved into a more complex inquiry since the beginning of the present research. Our initial analysis on the effectiveness of the social function in ownership discovered in tribunal decisions how restricted was the understanding of property concept. The liberal perception of non-interference in the economy of real estate market reduced the legal debate about the internal limits of property to a financial binary relation, for instance, individuals affected by mortgages and credit institutions, tenants and non-residential landlords, families living in vulnerable socioeconomic conditions and investors. However, the housing problem causes yet a certain legal inquietude since the number of non-occupied properties and the cost of rents are still increasing in Brazil and Spain. Examining the data available for both countries, we found a macroeconomic variable in urban development and housing access intimately linked to stock exchange markets. In addition, the absolute notion of property right is an obstacle inherited from the civil law tradition that impedes the openness of the ownership system to its social dimension. The aim of our thesis is the effective defence of the right to housing as a legal instrument associated with the social function of property and as a connecting factor to other rights in urban context. Our hypothesis requires a three- dimensional rationality for adequate judgments beyond the task of tribunals. A set of reasons of how both societies can limit the transnational real estate speculation, overcome the civil law tradition in an inert tension with democratic sovereignties and use the social function like a legal category so that the effectiveness of the right to housing serves as a turning point for the right to city.El conflicto entre el sistema de propiedad y el derecho a la vivienda se ha convertido en una investigación más compleja desde el comienzo del presente trabajo. Nuestro análisis inicial sobre la efectividad de la función social de la propiedad identificó en decisiones de tribunales un ejercicio de comprensión muy estricto del concepto de propiedad. La percepción liberal de la no injerencia en la economía del mercado inmobiliario redujo el debate legal sobre los límites internos de la propiedad a una relación binaria financiera, por ejemplo, individuos afectados por hipotecas e instituciones de crédito, inquilinos y propietarios no residenciales, familias que viven en condiciones de vulnerabilidad socioeconómica e inversores. Sin embargo, la vivienda causa todavía cierta inquietud jurídica, ya que el número de propiedades no ocupadas y el costo de los alquileres siguen aumentando en Brasil y España. Examinando los datos disponibles para ambos países, encontramos una variable macroeconómica en el desarrollo urbano y el acceso a la vivienda íntimamente vinculados a los mercados bursátiles. Además, la noción absoluta de derecho de propiedad sigue siendo un obstáculo heredado de la civil law que impide la apertura del sistema de propiedad en su dimensión social. El objetivo de nuestra tesis es contribuir a la defensa efectiva del derecho a la vivienda como instrumento jurídico asociado a la función social de la propiedad y como factor de conexión con otros derechos en el contexto urbano. Nuestra hipótesis requiere una racionalidad tridimensional para juicios adecuados más allá de la tarea de los tribunales. Un conjunto de razones de cómo las dos sociedades pueden limitar la especulación inmobiliaria transnacional, superar la tradición del civil law en tensión inerte con las soberanías democráticas y utilizar la función social como categoría jurídica para que la efectividad del derecho a la vivienda sirva de punto de inflexión para el derecho a la ciudad.
O conflito entre o sistema de propriedade e o direito à moradia tornou-se uma indagação mais complexa desde o início da presente pesquisa. Nossa análise inicial sobre a eficácia da função social da propriedade identificou em decisões judiciais um exercício de compreensão muito estreita sobre o conceito de propriedade. A percepção liberal da não interferência na economia do mercado imobiliário reduziu o debate jurídico sobre os limites internos da propriedade para vínculos financeiros binários, por exemplo, pessoas afetadas por inadimplência de suas hipotecas versus instituições de crédito, inquilinos contra propriedades de pessoas jurídicas, famílias em condições de vulnerabilidade socioeconômica contra investidores. No entanto, a habitação ainda causa alguma inquietude legal, já que o número de imóveis desocupados e o custo de aluguéis continuam a aumentar no Brasil e na Espanha. Com base em análise de dados disponíveis para ambas realidades, encontramos uma variável macroeconômica no desenvolvimento urbano e o acesso a moradias intimamente ligados aos mercados de ações. Além disso, a noção absoluta sobre o direito de propriedade continua a ser um obstáculo herdado da tradição do direito civil que impede a abertura do sistema de propriedade a dimensões sociais. O objetivo da nossa tese é contribuir para a defesa efetiva do direito à moradia como instrumento jurídico associado à função social da propriedade e como fator de conexão para outros direitos em contexto urbano. Nossa hipótese requer uma racionalidade tridimensional para julgamentos adequados além da tarefa dos tribunais. Um conjunto de razões sobre como as duas sociedades podem limitar a especulação imobiliária transnacional, superar a tradição do direito civil em tensão inerte com soberanias democráticas e usar a função social como uma categoria legal para que a efetividade do direito à habitação sirva enquanto ponto de inflexão para o direito à cidade.
33
Lima, Frederico Romagnoli Silveira. "Modelagem tridimensional de problemas inversos em condução de calor: aplicação em problemas de usinagem." Universidade Federal de Uberlândia, 2001. https://repositorio.ufu.br/handle/123456789/14793.
Повний текст джерелаАнотація:
Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorThis work proposes a methodology to obtain the transient cutting tool temperature. The physical phenomenon is treated by a three-dimensional analysis. The inverse heat conduction technique is proposed to estimate the generated heat flux on the rake face of the tool. This technique is based on conjugate gradient method with adjoint equation. The machining process is instrumented with thermocouples at the bottom face of the tool, opposite to its main rake face. The signals are automatically received and processed using a data acquisition system and a PC-Pentium. The direct solution is numerically solved using finite volumes method with the heat flux estimated. The experimental data are processed using a computational algorithm developed specifically for inverse heat flux estimation in machining processes. Experimental temperatures are obtained during several cutting tests using cemented carbide and ceramic tools. The influence of the cutting parameters on the temperature distribution is verified. An error analysis of the results is also presented.
O objetivo deste trabalho é propor uma metodologia para a obtenção da distribuição da temperatura na superfície de corte da ferramenta em um processo de usinagem por torneamento. Nesse sentido, o problema térmico de usinagem é caracterizado de maneira bem realista através de uma abordagem tridimensional. Para a obtenção dos campos térmicos na região de corte propõe-se o uso de técnicas de problemas inversos em condução de calor. Assim, a solução do problema térmico é obtida em duas etapas: solução inversa e solução direta. A solução inversa baseia-se no método do gradiente conjugado e da equação adjunta para a estimar o fluxo de calor gerado na região de corte que flui para a ferramenta. Nesse caso, são usados termopares soldados na face oposta da ferramenta que fornecem a informação necessária para que a solução inversa consiga estimar o fluxo de calor. Com a obtenção do fluxo de calor que flui para a ferramenta utiliza-se a solução direta do problema térmico para o cálculo da temperatura na região de corte. A implementação computacional da solução inversa e da solução direta é apresentada sob a forma de um programa de computador intitulado GRAD3D 1.0. Nesse programa, além da solução proposta para o problema térmico de usinagem é possível simular numericamente problemas térmicos correlatos. Testes experimentais unidimensionais e tridimensionais com condições controladas são apresentados para a validação do algoritmo computacional. Nos testes experimentais de usinagem, a aplicabilidade da técnica proposta é avaliada para o processo de usinagem por torneamento de uma barra de ferro fundido cinzento usando-se ferramentas de metal duro (WC) e de cerâmica (Si3N4). Apresenta-se ainda uma análise dos erros que podem estar presentes nos resultados obtidos.
Doutor em Engenharia Mecânica
34
Lizar, Jéssica Caroline. "Comparação dosimétrica 3D de tratamentos de câncer de mama com técnica conformacional 3D usando filtros e com IMRT direto e inverso na presença do movimento respiratório." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/59/59135/tde-30082017-152201/.
Повний текст джерелаАнотація:
A radioterapia externa pós-operatória em mulheres diagnosticadas com câncer de mama em estágio inicial é tido como um procedimento padrão, no entanto durante o planejamento para irradiação do volume alvo as possíveis incertezas dosimétricas introduzidas dado o movimento respiratório intrínseco da paciente são desconsideradas. Este estudo avalia não apenas a influência da respiração na distribuição tridimensional da dose, mas como essa distribuição se modifica dado a técnica radioterápica empregada para o tratamento. Três técnicas de planejamento foram analisadas: a radioterapia conformacional tridimensional (3D-RT) com filtros, a radioterapia com intensidade modulada (IMRT) usando planejamento direto e o IMRT inverso. A fim de simular o movimento de contração e expansão da caixa torácica, utilizou-se uma plataforma com amplitudes de oscilação pré-determinadas, sendo a frequência de oscilação provida por uma fonte de tensão variável. Para simular a mama usou-se objetos simuladores semiesféricos preenchidos com gel dosimétrico (MAGIC-f). Os planejamentos para cada técnica foram realizados sobre a mesma tomografia computadorizada (CT) do objeto simulador preenchido com água no modo estático. Foram produzidos três lotes de dosímetro gel para o projeto, cada lote foi irradiado com uma técnica radioterápica diferente, sendo que cada lote inclui cinco objetos simuladores e um conjunto de nove tubos de calibração preenchidos com gel MAGIC-f. O primeiro dos objetos simuladores é utilizado como referência, o segundo é irradiado no modo estático, os demais são irradiados em diferentes amplitudes, respectivamente: 0,34 cm, 0,88 cm e 1,22 cm. A informação volumétrica de dose foi obtida utilizando imagens por ressonância magnética nuclear (IRMN), para cada lote foram adquiridos IRMN com sequência multi spin echo e os mapas de relaxometria, que são associados à dose, foram extraídos em um software desenvolvido e aprimorado pelo nosso grupo de pesquisa. A comparação quantitativa dos mapas de relaxometria dos objetos simuladores em movimento em relação ao modo estático foi realizado pelo índice gamma tridimensional (3% / 3mm / 15% Threshold). Para o 3D-RT a porcentagem de pontos aprovados do objeto estático em relação ao oscilante na amplitude de 0,34 cm foi de 96,44%, para amplitude de 0,88 cm foi de 93,23% e para amplitude de 1,22 cm foi de 91,65%. Para o IMRT direto a porcentagem de pontos aprovados do objeto estático em relação ao oscilante na amplitude de 0,34 cm foi de 98,42%, para amplitude de 0,88 cm foi de 95,66% e para amplitude de 1,22 cm foi de 94,31%. Para o IMRT inverso a porcentagem de pontos aprovados do objeto estático em relação ao oscilante na amplitude de 0,34 cm foi de 94,49%, para amplitude de 0,88 cm foi de 93,51% e para amplitude de 1,22 cm foi de 86,62%. A partir dos resultados, infere-se que a movimentação respiratória de baixa amplitude, para tratamentos de câncer de mama, não é um fator preocupante para a rotina clínica, porém o aumento da amplitude da oscilação aumenta a inomogeneidade de dose e pode afetar os parâmetros dosimétricos da cobertura do volume alvo em relação ao planejamento do tratamento. Observou-se em conjunto que a distribuição de dose se modifica claramente com a técnica em uso e no caso do IMRT inverso para amplitude de oscilação de 1,22 cm a aprovação no índice gamma foi menor que 90%External postoperative radiotherapy in women diagnosed with early stage breast cancer is considered as a standard procedure, however during planning for target volume irradiation as possible dosimetric uncertainties reabsorption of the patient\'s intrinsic respiratory movement are disregarded. This study evaluates not only the influence of respiration on the three-dimensional distribution of the dose but how this distribution is modified due to the radiotherapy technique used for treatment. Three planning techniques were analyzed: three-dimensional conformational radiotherapy (3D-RT) with filters, intensity-modulated radiotherapy (IMRT) using direct planning and inverse IMRT. In order to simulate the movement of contraction and expansion of the chest wall, a platform with predetermined oscillation amplitudes was used, the oscillation frequency was provided by a variable voltage source. To simulate the breast, semi-spherical simulator objects filled with dosimetric gel (MAGIC-f) were used. The plannnings for each technique were performed on the computerized tomography (CT) of the simulator object filled with water in static mode. Three batches of gel dosimeters were prepared for the project, each batch was irradiated with a different radiothermic technique and comprised five simulator objects and a set of nine calibration tubes filled with MAGIC-f gel. The first simulator objects is used as reference, the second is irradiated in the static mode, the others are irradiated using different amplitudes, respectively: 0,34 cm, 0,88 cm and 1,22 cm. Volumetric dose information was obtained using Nuclear Magnetic Resonance Imaging, each batch was scanned with a multi spin echo sequence and the dose-related relaxometry maps were extracted in a software developed and improved by our Group of research. The quantitative comparison of the relaxometry maps of the moving simulator objects with respect to the static mode was performed by the three-dimensional gamma index (3% / 3mm / 15% threshold). For the 3D-RT, the percentage of approved points of the static object with respect to the oscillator in the amplitude of 0.34 cm was 96.44%, for amplitude of 0.88 cm was 93.23% and for amplitude of 1.22 cm was 91.65%. For the direct IMRT the percentage of approved points of the static object in relation to the oscillator in the amplitude of 0.34 cm was 98.42%, for amplitude of 0.88 cm was 95.66% and for amplitude of 1.22 cm was 94.31%. For the inverse IMRT, the percentage of approved points of the static object in relation to the oscillator in the amplitude of 0.34 cm was 94.49%, for amplitude of 0.88 cm was 93.51% and for amplitude of 1.22 cm was 86.62%. From the results, it is inferred that a low-amplitude respiratory movement, for breast cancer treatments, is not a worrying factor for clinical routine, however, increasing the amplitude of the oscillation increases the inomogeneity of the dose and this affects the dosimetry parameters of the target volume coverage. It was observed that the dose distribution changes with the technique in use and in the case of the inverse IMRT for amplitude of oscillation of 1.22 cm, less than 90% of points were approved in the gamma index evaluation
35
Carvalho, Solidônio Rodrigues de. "Determinação do campo de temperatura em ferramentas de corte durante um processo de usinagem por torneamento." Universidade Federal de Uberlândia, 2005. https://repositorio.ufu.br/handle/123456789/14729.
Повний текст джерелаАнотація:
Fundação de Amparo a Pesquisa do Estado de Minas GeraisDuring machining, high temperatures are generated in the region of the tool cutting edge, and these temperatures have a controlling influence on the wear rate of the cutting tool and on the friction between the chip and the tool. However, direct measurement of temperature using contact type sensors at the tool-work interface is difficult to implement due to the rotating movement of the workpiece and the presence of the chip. Therefore, the use of inverse heat conduction techniques represents a good alternative since these techniques takes into account temperatures measured from accessible positions. This work proposes a new experimental methodology to determine the thermal fields and the heat generated in the chiptool interface during machining process using inverse problems techniques. This work develops a numerical 3-D transient thermal model that takes into account both the tool and toolholder assembly. The thermal model represents the direct problem and is solved using finite volume techniques on a non uniform mesh. The related inverse problem is solved by using the golden section technique. The experimental data and inverse technique are processed using a computational algorithm developed specifically for inverse heat flux estimation in manufacturing processes called INV3D. An error analysis of the results and the experimental procedures to determine the cut area and the tool holder temperature are also presented. Besides the machining problem, INV3D is also able to solve different thermal problems. As an example of its generality, this work also presents an application of this software in the thermal fields study during a welding process.
Durante a usinagem de metais, altas temperaturas são geradas na interface de cavacoferramenta. Essas temperaturas, por sua vez, têm forte influência no controle da taxa de remoção de material e no atrito entre o cavaco e a ferramenta de corte. Observa-se, entretanto que a medição direta de temperaturas nessa região é de difícil execução devido ao movimento da peça e a presença do cavaco. Assim, o uso de técnicas inversas em condução de calor se apresenta como uma boa alternativa para a obtenção dessas temperaturas uma vez que essas técnicas permitem o uso de dados experimentais obtidos em regiões acessíveis. Este trabalho propõe uma nova metodologia experimental para a determinação dos campos térmicos e do fluxo térmico gerado em ferramentas de corte durante um processo de torneamento. Uma das inovações apresentadas é o desenvolvimento de um modelo térmico tridimensional transiente que considera além da ferramenta de corte, o conjunto ferramenta, calço e porta-ferramenta. O problema direto é então resolvido numericamente usando-se diferenças finitas a partir de uma malha de discretização não uniforme. O problema inverso, por sua vez, é resolvido por meio da técnica de otimização da seção áurea. Para a solução dos problemas envolvidos, desenvolveu-se um código computacional específico, denominado INV3D. O programa INV3D contém ainda uma série de funções que auxiliam na aquisição dos dados experimentais, na geração da malha tridimensional e na análise em ambiente gráfico. O trabalho apresenta também os procedimentos experimentais usados na medição das temperaturas na ferramenta, calço e porta-ferramenta e na identificação da área de interface de corte. Os resultados obtidos são validados por meio de experimentos controlados em laboratório e de análises qualitativas. Além do problema de usinagem investigado, como exemplo da generalidade do Inv3D na solução de problemas térmicos, apresenta-se também uma aplicação deste software no estudo de campos térmicos decorrentes de um processo de soldagem TIG em alumínio.
Doutor em Engenharia Mecânica
36
Li, Yaoguo. "Inversion of three-dimensional direct current resistivity data." Thesis, 1992. http://hdl.handle.net/2429/3142.
Повний текст джерелаАнотація:
A direct current (d.c.) resistivity experiment investigates subsurface geo-electrical structures
by measuring the electric field set up by introducing current into the earth. Information about
geo-electrical structures is extracted by inverting the observed data to generate an image of the
conductivity or to construct a conductivity model. The goal of this thesis is to develop efficient
inversion techniques for the interpretation of three-dimensional (3d) d.c. resistivity data. The
study assumes data consisting of pole-pole potentials measured over a regular grid on the surface
for many current locations. The Born approximation is employed to linearize the inverse problem.
The source of the electric field measured in the d.c. resistivity is the accumulated electric
charges. Different aspects of the charge accumulation are reviewed, enlarged with new insights
and presented in a unified notation. This provides the basis for understanding the fundamentals
of d.c. resistivity experiments. Two algorithms are developed to image simple 2d conductivities.
The first constructs a structural image by combining the charge density images obtained by
inverting multiple sets of common current potentials. The second constructs a conductivity
image directly. Processing and displaying the apparent conductivity, and constructing equivalent
sources from secondary potentials are studied as the means of imaging. Assuming a multiplicative
perturbation to a uniform half-space, the potential anomaly of pole-pole arrays is expressed as a
depth integral of the logarithmic perturbation convolved with a kernel function in the horizontal
directions. Applying the Fourier transform decomposes the data equation for a 3d problem into a
set of id equations. A rapid approximate 3d inversion is developed based upon this decomposition
by solving a sequence of id inversions in the wavenumber domain. The approximate 3d inversion
is used to construct iterative inversion algorithms using the AIM (Approximate Inverse Mapping)
formalism. The approximate inversion and an exact forward mapping are used to update the
model successively so that the final result reproduces the observed data. The AIM inversion is
applied to analyse a set of field data.
37
Bender, Christopher Matthew. "Three-dimensional geoacoustic perturbative inverse technique for the shallow ocean water column." 2012. http://hdl.handle.net/2152/19707.
Повний текст джерелаАнотація:
This work focuses on developing an inversion scheme to estimate water-column sound-speed fields in three dimensions. The inversion scheme is based on a linearized perturbative technique which utilizes estimates of modal travel times. The technique is appropriate in the littoral ocean where measurements are made across range and cross-range distances greater than 10 km to ensure sufficient modal dispersion. Previous applications of then inversion technique has been limited to one or two dimensions and/or focused primarily on the seabed.
Compared to past applications, the accuracy and uncertainty of the solution is improved by employing approximate equality constraints within the context of \textit{a priori} estimates of model and data covariances. The effectiveness of the constrained technique is explored through a one-dimensional example. The robustness of the technique is illustrated by introducing different types of errors into the inversion and considering the accuracy. A further examination of the technique is given by exploring a three-dimensional example. Several case studies are presented to investigate the effects of different levels of environmental variability and spatial sampling.text
38
Weißflog, Julia. "Three-dimensional individual and joint inversion of direct current resistivity and electromagnetic data." Doctoral thesis, 2016. https://tubaf.qucosa.de/id/qucosa%3A23113.
Повний текст джерелаАнотація:
The objective of our studies is the combination of electromagnetic and direct current (DC) resistivity methods in a joint inversion approach to improve the reconstruction of a given conductivity distribution. We utilize the distinct sensitivity patterns of different methods to enhance the overall resolution power and ensure a more reliable imaging result.
In order to simplify the work with more than one electromagnetic method and establish a flexible and state-of-the-art software basis, we developed new DC resistivity and electromagnetic forward modeling and inversion codes based on finite elements of second order on unstructured grids. The forward operators are verified using analytical solutions and convergence studies before we apply a regularized Gauss-Newton scheme and successfully invert synthetic data sets. Finally, we link both codes with each other in a joint inversion.
In contrast to most widely used joint inversion strategies, where different data sets are combined in a single least-squares problem resulting in a large system of equations, we introduce a sequential approach that cycles through the different methods iteratively. This way, we avoid several difficulties such as the determination of the full set of regularization parameters or a weighting of the distinct data sets. The sequential approach makes use of a smoothness regularization operator which penalizes the deviation of the model parameters from a given reference model. In our sequential strategy, we use the result of the preceding individual inversion scheme as reference model for the following one. We successfully apply this approach to synthetic data sets and show that the combination of at least two methods yields a significantly improved parameter model compared to the individual inversion results.Ziel der vorliegenden Arbeit ist die gemeinsame Inversion (\"joint inversion\") elektromagnetischer und geoelektrischer Daten zur Verbesserung des rekonstruierten Leitfähigkeitsmodells. Dabei nutzen wir die verschiedenartigen Sensitivitäten der Methoden aus, um die Auflösung zu erhöhen und ein zuverlässigeres Ergebnis zu erhalten. Um die Arbeit mit mehr als einer Methode zu vereinfachen und eine flexible Softwarebasis auf dem neuesten Stand der Forschung zu etablieren, wurden zwei Codes zur Modellierung und Inversion geoelektrischer als auch elektromagnetischer Daten neu entwickelt, die mit finiten Elementen zweiter Ordnung auf unstrukturierten Gittern arbeiten. Die Vorwärtsoperatoren werden mithilfe analytischer Lösungen und Konvergenzstudien verifiziert, bevor wir ein regularisiertes Gauß-Newton-Verfahren zur Inversion synthetischer Datensätze anwenden. Im Gegensatz zur meistgenutzten \"joint inversion\"-Strategie, bei der verschiedene Daten in einem einzigen Minimierungsproblem kombiniert werden, was in einem großen Gleichungssystem resultiert, stellen wir schließlich einen sequentiellen Ansatz vor, der zyklisch durch die einzelnen Methoden iteriert. So vermeiden wir u.a. eine komplizierte Wichtung der verschiedenen Daten und die Bestimmung aller Regularisierungsparameter in einem Schritt. Der sequentielle Ansatz wird über die Anwendung einer Glättungsregularisierung umgesetzt, bei der die Abweichung der Modellparameter zu einem gegebenen Referenzmodell bestraft wird. Wir nutzen das Ergebnis der vorangegangenen Einzelinversion als Referenzmodell für die folgende Inversion. Der Ansatz wird erfolgreich auf synthetische Datensätze angewendet und wir zeigen, dass die Kombination von mehreren Methoden eine erhebliche Verbesserung des Inversionsergebnisses im Vergleich zu den Einzelinversionen liefert.
39
Commer, Michael [Verfasser]. "Three-dimensional inversion of transient electromagnetic data : a comparative study / vorgelegt von Michael Commer." 2003. http://d-nb.info/969850174/34.
Повний текст джерела
40
Fathi, Arash. "Full-waveform inversion in three-dimensional PML-truncated elastic media : theory, computations, and field experiments." Thesis, 2015. http://hdl.handle.net/2152/30515.
Повний текст джерелаАнотація:
We are concerned with the high-fidelity subsurface imaging of the soil, which commonly arises in geotechnical site characterization and geophysical explorations. Specifically, we attempt to image the spatial distribution of the Lame parameters in semi-infinite, three-dimensional, arbitrarily heterogeneous formations, using surficial measurements of the soil's response to probing elastic waves. We use the complete waveforms of the medium's response to drive the inverse problem. Specifically, we use a partial-differential-equation (PDE)-constrained optimization approach, directly in the time-domain, to minimize the misfit between the observed response of the medium at select measurement locations, and a computed response corresponding to a trial distribution of the Lame parameters. We discuss strategies that lend algorithmic robustness to the proposed inversion schemes. To limit the computational domain to the size of interest, we employ perfectly-matched-layers (PMLs). The PML is a buffer zone that surrounds the domain of interest, and enforces the decay of outgoing waves. In order to resolve the forward problem, we present a hybrid finite element approach, where a displacement-stress formulation for the PML is coupled to a standard displacement-only formulation for the interior domain, thus leading to a computationally cost-efficient scheme. We discuss several time-integration schemes, including an explicit Runge-Kutta scheme, which is well-suited for large-scale problems on parallel computers. We report numerical results demonstrating stability and efficacy of the forward wave solver, and also provide examples attesting to the successful reconstruction of the two Lame parameters for both smooth and sharp profiles, using synthetic records. We also report the details of two field experiments, whose records we subsequently used to drive the developed inversion algorithms in order to characterize the sites where the field experiments took place. We contrast the full-waveform-based inverted site profile against a profile obtained using the Spectral-Analysis-of-Surface-Waves (SASW) method, in an attempt to compare our methodology against a widely used concurrent inversion approach. We also compare the inverted profiles, at select locations, with the results of independently performed, invasive, Cone Penetrometer Tests (CPTs). Overall, whether exercised by synthetic or by physical data, the full-waveform inversion method we discuss herein appears quite promising for the robust subsurface imaging of near-surface deposits in support of geotechnical site characterization investigations.
41
Chen, Wan-Li, and 陳宛勵. "On Three-Dimensional Stress Altered Hole Inversion-Layer Mobility in (001) and (110) p-MOSFETs." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/56506337595782478085.
Повний текст джерелаАнотація:
碩士國立交通大學
電子研究所
101
Hole inversion-layer mobility under three-dimensional stresses in (001)/<110> and (110)/<110> of p-MOSFETs is investigated by using a self-consistent six-band k‧p solver. The three significant scattering mechanisms are included: optical phonon scattering, acoustic phonon scattering, and surface roughness scattering with the screening effect taken into account. This leads to a clearer physical insight into 3-D-stress-induced hole mobility change in terms of three parts: (1) effect of strained k‧p deformation potentials a, b, and d; (2) phonon-limited and/or surface-roughness-limited mobility change; and (3) scattering-time-limited and conductivity-effective-mass-limited mobility change. Finally, the conclusions indicate that (1) for the effect of the hole mobility change, a is weak, b is moderate, and d is strong, particularly for the uniaxial compressive stress in the <110> direction. The experimentally-calibrated values are: a = 2.46eV, b = -1.6 ~ -2.1eV, and d = -3.1eV; (2) the phonon-limited mobility change is more stress-sensitive than the surface-roughness-limited one; and (3) the mobility change ratio can be related to the reversely proportional conductivity effective mass and density-of-states effective mass in the absence of the surface roughness mobility change.
42
Hole, John A. "Structure of the Queen Charlotte Basin and underlying crust from modelling and inversion of three-dimensional seismic refraction data." Thesis, 1993. http://hdl.handle.net/2429/2180.
Повний текст джерелаАнотація:
A combined seismic reflection and refraction survey was carried out in 1988 to investigate the structure and tectonic evolution of the Queen Charlotte (QC) Basin and underlying crust off the northern coast of British Columbia. While the marine multichannel reflection data were being collected, refracted and wide-angle reflected energy from the large airgun array were recorded at surrounding land sites in both inline (2d) and broadside (3d) geometries. The broadside refraction data recorded on the QC Islands provide good 3d coverage beneath western Hecate Strait. In this study, these data are interpreted to determine the 3d structure of the basin and underlying crust.
Modelling procedures are developed to interpret densely sampled 3d seismic travel time data. An inversion algorithm to determine the depth of a refracting interface and atomographic inversion algorithm to determine velocity structure are described. Travel times for 3d models are computed using a rapid finite difference algorithm that is extended to allow large velocity contrasts, the determination of rays, variable sampling of the model, and the computation of reflection times. The inversion in both algorithms is parameterized in a simple manner that eliminates the need to store or solve large systems of linear equations. Iterative nonlinear procedures allow arbitrarily large 3d anomalous velocities and interface structures to be determined. The advantages in computational speed of the procedures allow dense spatial sampling of the models, providing spatially well-resolved 3d images. Variations of the first arrival travel times from the broadside refraction data are inverted to determine the 3d basement depth structure of the QC Basin. The thickness of the basin varies rapidly between ,,,200 m and km in a complex sequence of 3d fault-bounded subbasins. The orientation of, and topography across, several major faults and the overall complexity of the subbasins support a distributed strike-slip extension evolutionary model for the basin. The first arrival travel times are then inverted to determine the 3d velocity structure of the upper (<12 km depth) crust beneath western Hecate Strait. The average 1 d velocity structure and the significant lateral variations are interpreted in terms of regional geology. Wide angle reflection travel times from the Moho constrain the thickness of the crust to be 29 km beneath the eastern coast of the QC Islands. The Moho is deeper under the QC Islands than under Hecate Strait or QC Sound, suggesting that crustal thinning during Tertiary extension was greatest beneath the surface expression of the QC Basin. In an alternate or additional explanation, compression at the plate margin during the last 4 Mamay have been taken up by thickening or under plating of the continental crust adjacent to the margin beneath the QC Islands.
43
Bai, Chao-Ying. "Three dimensional seismic kinematic inversion with application to reconstruction of the velocity structure of Rabaul volcano / by Chao-ying Bai." 2004. http://hdl.handle.net/2440/22132.
Повний текст джерелаАнотація:
"July 2004"Bibliography: leaves 215-230.
viii, 230 leaves : ill., maps ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Thesis (Ph.D.)--University of Adelaide, School of Chemistry and Physics, Discipline of Physics, 2004
44
Bai, Chao-ying. "Three dimensional seismic kinematic inversion with application to reconstruction of the velocity structure of Rabaul volcano / by Chao-ying Bai." Thesis, 2004. http://hdl.handle.net/2440/22132.
Повний текст джерела
45
Soeffky, P. "Delineating the deep crustal fluid link between the Paralana Enhanced Geothermal System and the Beverley Uranium Mine using magnetotellurics." Thesis, 2012. http://hdl.handle.net/2440/95486.
Повний текст джерелаАнотація:
This item is only available electronically.The global demand for clean energy alternatives is constantly increasing, creating significant interest for more sustainable energy resources such as uranium and geothermal. Australia is host to over 25% of the world's known uranium resources as well as having significant geothermal potential. The Mount Painter Domain, in the Northern Flinders Ranges in South Australia, is in a region of anomalously high heat flow generated by radiogenic decay of uranium and thorium rich granites. Two distinct uranium deposits have formed from dissolved uranium carried from the ranges by fluids, being deposited where reduction in sediment pH precipitates uranium. In May 2012 a magnetotelluric profile was collected, extending from the Northern Flinders Ranges to the Lake Frome embayment to help constrain existing resistivity models. Precipitation of uranium at the Beverley Mine site is anomalous as no surface water flow is present, suggesting the presence of subsurface processes. This pathway is linked to a 50m conductive body at the brittle-ductile boundary of the mid-crust, directly under the Paralana geothermal prospect. 3D modelling of the Paralana geothermal prospect suggests deep conductive features connecting with features at the surface.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Earth and Environmental Sciences, 2012
46
Lee, Chien-Chih, and 李建志. "A New In-House Fast Sophisticated Quantum Simulator for Silicon Hole Band Structure and Inversion-Layer Mobility under Three-Dimensional GPa-Level Stresses." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/10883282420260933054.
Повний текст джерелаАнотація:
博士國立交通大學
電子研究所
101
The continuously scaled electronic devices encounter not only the extra quantum confinement (no matter from the field confinement or from the space confinement) but also the complicated mechanical stresses (no matter the intentional or unintentional stressors along the arbitrary directions). Both of these two phenomena cause the crucial impacts on the valence-band structure which can greatly alter the hole electrical properties. In other words, these lead to the extra complexities and the heavy computation burden in the theoretical work. Since the evaluation of the hole electrical properties such as hole mobility fully rely on the valence subband structures, with no surprise the precise and fine quality of valence subband structures are urgently required to achieve the satisfactory calculations. With the six-band k•p Schrödinger-Poisson self-consistent method this dissertation will focus on the hole electrical properties in p-type inversion layer of the electronic devices via the self-developed simulator, p-NEP (abbreviation of p-type Nano Electronics Physics). The main purpose of the dissertation is to investigate the hole electrical properties in silicon inversion layer beneath on the significant quantum confinement and the complicated mechanical stresses. Based on this main topic, the organization of this dissertation is described below. First, an introduction to the valence band structures in p-type inversion layer is described. Then, the dissertation is focused on the numerical techniques and physical models of p-NEP. However, according to the algorithm of p-NEP, the CPU time is extraordinarily long. To overcome the issue, we present a novel computational accelerator to intrinsically boost a self-consistent six-band k•p Schrödinger-Poisson simulation. This accelerator comprises a triangular potential based six-band k•p simulator, a hole effective mass approximation (EMA) technique, and an electron analogue version of the self-consistent Schrödinger and Poisson’s equations solver. The outcome of the accelerator furnishes the initial solution of the confining electrostatic potential and is likely to be close to the realistic one, valid for different temperatures, substrate doping concentrations, inversion hole densities, and surface orientations. The results on (001) and (110) substrates are supported by those published in the literature. The overall CPU time is reduced down to around 8% of that without the accelerator. The application of the proposed accelerator to more general situations is projected as well. Secondly, according to three distinct sets of the bulk oriented Luttinger parameters γ1, γ2, and γ3, the validity of the bulk oriented Luttinger parameters in the six-band k•p Schrödinger-Poisson self-consistent method is confirmed. With the the bulk oriented Luttinger parameters, the realistic hole subband structures in (110) p-MOSFETs can be well reproduced in comparison with the recent Shubnikov-de Haas (SdH) oscillation experiment by Takahashi, et al. Thirdly, the hole mobility change for GPa-level uniaxial stresses along each of three crystallographic directions are distinguished into four contributing componds: (i) phonon-limited, (ii) surface-roughness-limited, (iii) scattering-time-limited, and (iv) conductive-mass-limited mobility changes. It is also dedicated to three key strain-related material parameters, namely the Bir-Pikus deformation potentials a□, b, and d, which are widespread in magnitude. To improve such large discrepancies, we conduct sophisticated calculations on <110>/(001) and <110>/(110) hole inversion-layer mobility. We find that, to affect the calculated hole mobility enhancement, a□ is weak, b is moderate, and d is strong, particularly for the uniaxial compressive stress along the <110> direction. This provides guidelines for an experimental determination of the primary factor, d, and the secondary factor, b, with the commonly used values for a□. The user interface (UI) and simulation process of p-NEP are further demonstrated. The resulting subbnad structures, threshold voltage, capacitance, and gate direct tunneling current are all addressed. Finally, we summarize the conclusions of our works.
47
Hsieh, Ming-Che, and 謝銘哲. "Efficient waveform inversions for finite-source models of moderate and large earthquakes in three-dimensional structures." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/06919330181140364420.
Повний текст джерелаАнотація:
博士國立中央大學
地球科學學系
103
For hazard mitigation and risk assessment, an efficient and well-designed algorithm to determine earthquake rupture properties in a short time is on demand. It is also important to account for effects of surface and subsurface structures to wave propagation and predict ground motion more accurately. In this thesis, we have developed an efficient three-step process which is used in solving for a finite-source model: A point-source focal mechanism is determined in the first step. Then, the two nodal planes in the point-source solution are used as trial candidates to solve for an average finite-rupture model and identify the actual fault plane. In the final step, a full slip distribution inversion is carried out based on the identified fault plane. We have adopted the source determination scheme to earthquakes near Nantou in central Taiwan for tectonic interpretations. We solved for the rupture properties of a series of moderate events (MW≈6), which show similar focal mechanisms but with different focal depths. Our determination on the rupture planes of these earthquakes suggest that the most of the shallow-focus ruptures occur on the low-angle plane, but on the high-angle plane for most of the deeper events, consistent with the background seismicity and support the existence of tectonically co-located active conjugate faulting system in central Taiwan. We also demonstrated the slip distribution inversion of a moderate earthquake in eastern Taiwan by our three-step procedure. Both broadband and strong motion stations are included in the inversion. Our results show that three-dimensional velocity model could provide better waveform fittings than one-dimensional model, and slip distribution is much more concentrated. Applications to moderate events (MW≈6) in southeastern and eastern Taiwan show that our source inversion technique is effective for semi-automatic, near real-time determinations of finite-source parameters for seismic hazard mitigation purposes.