Дисертації з теми "Ray-based"
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Lindeberg, Johan. "X-ray based tree ring analyses /." Umeå : Dept. of Silviculture, Swedish Univ. of Agricultural Sciences, 2004. http://epsilon.slu.se/s299.pdf.
Повний текст джерелаFernandes, Louis Edward. "Pyroelectric crystal-based X-ray diffractometer." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40901.
Повний текст джерелаIncludes bibliographical references (p. 49-50).
We investigate the use of an Amptek Cool-X X-ray Generator for an instructional tool in the physics of x-rays, as well as a source for x-rays for crystal diffraction experiments. The x-ray source is a solid-state two-phase air-cooled source with a time-varying photon output. Two detectors are used in this experiment, the first being an Amptek X-123 Spectrometer and the second a combination scintillator/Polaroid film setup. We collimate the x-ray beam and determine that the system, although low flux and low resolution, will function as a quick and easy tool for the investigation of x-ray physics.
by Louis Edward Fernandes.
S.B.
Cline, David. "Sampling Methods in Ray-Based Global Illumination." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd2056.pdf.
Повний текст джерелаOllinger, Christoph German Josef. "A waveguide-based lens-less x-ray microscope." Doctoral thesis, [S.l.] : [s.n.], 2006. http://webdoc.sub.gwdg.de/diss/2006/ollinger.
Повний текст джерелаFuhse, Christian. "X-ray waveguides and waveguide-based lensless imaging." Doctoral thesis, [S.l.] : [s.n.], 2006. http://webdoc.sub.gwdg.de/diss/2006/fuhse.
Повний текст джерелаDurany, Vendrell Jaume. "Geometrical room acoustics: ray based simulation for room acoustics." Doctoral thesis, Universitat Pompeu Fabra, 2016. http://hdl.handle.net/10803/395190.
Повний текст джерелаRoom acoustics is the science devoted to study sound propagation in enclosures where the sound conduction medium is bounded on all sides by walls, ceiling and floor. The acoustic information of any room, the so-called impulse response, is expressed in terms of the acoustic field as a function of space and time. The analytical formulation of the sound variables distribution is, in general, extremely hard to obtain and there only exist solutions of very simple and unrealistic scenarios. Therefore the use of computers for solving this type of problems has emerged as a proper alternative to calculate impulse responses. In this Thesis we focus on the use of the ray-based methods to compute impulse responses. More precisely, we present the design and implementation of a sound ray tracing engine that computes the impulse response in any given environment not only for the pressure but also for the velocity vector of the acoustic field. With this extra information we have all the necessary data to model the propagation of sound and we can then naturally spatialize the sound to any speakers layout. This research contributes to the main aspects in the computation of impulse responses using a ray-based approach. The presented ray tracing engine includes a method developed to apply the analytical solution for the Acoustic Bidirectional Reflectance Distribution Function (A-BRDF) in the Vector Based Scattering Model (VBS), which reduces dramatically the computational cost.
Ciydem, Mehmet. "Ray Based Finite Difference Method For Time Domain Electromagnetics." Phd thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606633/index.pdf.
Повний текст джерелаs hyperbolic partial differential equations directly, Geometrical Optics tools (wavefronts, rays) and Taylor series have been utilized. Discontinuities of electromagnetic fields lie on wavefronts and propagate along rays. They are transported in the computational domain by transport equations which are ordinary differential equations. Then time dependent field solutions at a point are constructed by using Taylor series expansion in time whose coefficients are these transported distincontinuties. RBTD utilizes grid structure conforming to wave fronts and rays and treats all electromagnetic problems, regardless of their dimensions, as one dimensional problem along the rays. Hence CFL stability condition is implemented always at one dimensional eqaulity case on the ray. Accuracy of RBTD depends on the accuracy of grid generation and numerical solution of transport equations. Simulations for isotropic medium (homogeneous/inhomogeneous) have been conducted. Basic electromagnetic phenomena such as propagation, reflection and refraction have been implemented. Simulation results prove that RBTD eliminates numerical dispersion inherent to FDTD and is promising to be a novel method for computational electromagnetics.
Hirvasniemi, J. (Jukka). "Novel X-ray-based methods for diagnostics of osteoarthritis." Doctoral thesis, Oulun yliopisto, 2015. http://urn.fi/urn:isbn:9789526210384.
Повний текст джерелаTiivistelmä Nivelrikko on maailman yleisin nivelsairaus. Se aiheuttaa merkittävää kärsimystä potilaille, ja sillä on suuri taloudellinen vaikutus yhteiskuntaan. Nivelrikko aiheuttaa palautumattomia muutoksia nivelrustokudoksen ja rustonalaisen luun koostumukseen ja rakenteeseen. Nivelrikon diagnoosi perustuu kliiniseen tutkimukseen ja röntgenkuvien silmämääräiseen arviointiin. Nykyiset nivelrikon kliiniset kuvantamismenetelmät ovat subjektiivisia eivätkä riittävän tarkkoja nivelrikon varhaisten muutosten osoittamiseen, minkä vuoksi rustokudoksen koostumuksen ja rustonalaisen luun muutosten arviointiin tarvitaan uusia menetelmiä. Tämän väitöskirjantyön tarkoituksena oli tutkia uusien röntgensäteilyyn perustuvien menetelmien soveltuvuutta polvinivelen rustokudoksen proteoglykaanipitoisuuden sekä luun tiheyden ja rakenteen arviointiin. Rustonalaisen luun tiheyttä ja rakennetta arvioitiin digitaalisesta röntgenkuvasta tietokonepohjaisilla menetelmillä ja tuloksia verrattiin mikrotietokonetomografiassa nähtävään luun kolmiulotteiseen rakenteeseen. Röntgenkuvasta laskettavia muuttujia verrattiin myös eriasteisesta nivelrikosta kärsivien henkilöiden välillä. Rustokudoksen proteoglykaanipitoisuutta epäsuorasti mittaavaa tietokonetomografiamenetelmää verrattiin vastaavaan magneettikuvausmenetelmään henkilöillä, jotka olivat menossa polven niveltähystykseen. Röntgenkuvasta laskettu rustonalaisen luun tiheys ja rakenne olivat tilastollisesti selkeästi yhteydessä luun tilavuusmäärään ja mikrorakenteeseen, ja ne erosivat eriasteisesta nivelrikosta kärsivien henkilöiden välillä. Proteoglykaanipitoisuutta arvioivien tietokonetomografia- ja magneettikuvausmenetelmien välillä oli tilastollisesti merkitsevä korrelaatio. Ruston proteoglykaanipitoisuutta arvioivan magneettikuvausmenetelmän ja röntgenkuvasta laskettavan luun rakenteen välillä oli myös tilastollinen yhteys. Loppupäätelmänä voidaan todeta, että luun tiheyttä ja rakennetta on mahdollista arvioida kliinisesti saatavilla olevista röntgenkuvista. Tietokonetomografiamenetelmän käyttöä tulee harkita tutkimuksissa silloin, kun rustokudoksen tilasta halutaan kolmiulotteista tietoa
Ippolito, Alessandro <1977>. "Oblique ionograms automatic scaling and eikonal based ray tracing." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/6888/.
Повний текст джерелаBardi, Niki. "Tissue equivalent X-ray dosimetry based on carbon nanotubes." Thesis, University of Surrey, 2017. http://epubs.surrey.ac.uk/841216/.
Повний текст джерелаLee, Kyoung-Jin. "Efficient ray tracing algorithms based on wavefront construction and model based interpolation method." Texas A&M University, 2005. http://hdl.handle.net/1969.1/3771.
Повний текст джерелаDammertz, Holger [Verfasser]. "Acceleration methods for ray tracing based global illumination / Holger Dammertz." Ulm : Universität Ulm. Fakultät für Ingenieurwissenschaften und Informatik, 2011. http://d-nb.info/1016659350/34.
Повний текст джерелаMen, Shuang. "X-ray photoelectron spectroscopy of ionic liquid-based catalytic systems." Thesis, University of Nottingham, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.557146.
Повний текст джерелаGee, Ian Andrew. "X-ray photoelectron spectroscopy studies of oxide based glass systems." Thesis, University of Warwick, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365230.
Повний текст джерелаVIEIRA, PEDRO SAMPAIO. "A SPINE 3D MODELING SYSTEM BASED ON X-RAY IMAGES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=14919@1.
Повний текст джерелаNos dias atuais, pesquisas envolvendo a computação gráfica e a área médica, têm contribuído muito para a evolução tecnológica de exames e diagnósticos. Uma vertente desses trabalhos está relacionada diretamente à reconstrução 3D de estruturas anatômicas do corpo humano, em específico a coluna vertebral. O sedentarismo e a alta dependência dos computadores vêm aumentando e agravando os problemas posturais das pessoas. Por esse motivo, novas técnicas de reconstrução 3D baseada em exames de tomografia computadorizada (TC), ressonância magnética (RM) e raios-x são desenvolvidas, tornando as avaliações clínicas cada vez mais precisas. Neste trabalho é proposto um sistema de modelagem 3D baseado em radiografias digitais com a finalidade de recriar a coluna vertebral em um ambiente virtual. A recuperação das informações tridimensionais de cada vértebra ajuda a melhorar a avaliação feita atualmente com base apenas em imagens 2D. A técnica utilizada no desenvolvimento do método se baseia na estereoradiografia. E a utilização de radiografias, em relação à TC, reduz consideravelmente o tempo de exposição do paciente à radiação, além de ser mais acessível à população pelo seu menor custo. Os resultados obtidos apresentaram uma boa precisão do sistema. Além do mais, o método proposto atingiu resultados bem próximos aos de pesquisas baseadas em TC e RM, onde os dados de entrada são bem mais legíveis do que as imagens de raiosx.
Research involving computer graphics and laboratory exams has contributed much to the quality of the Medical diagnose. One aspect of these researches is directly related to 3D reconstruction of anatomical structures of the human body, especially the spine. The sedentary lifestyle and the high dependence of computers have increased the postural problems of the population. Therefore, new techniques for 3D reconstruction based on Computed tomography (CT), magnetic resonance imaging (MRI) and x-ray images are required, in order to make the clinical evaluation increasingly accurate. This work proposes a 3D modeling system based on x-ray images that yields a virtual spine model. The recovery of three-dimensional information of each vertebra helps improve the assessment currently made using only 2D images. The technique used here is based on stereo radiographic. The use of x-ray images instead of CT, significantly reduces the exposure time of the patient to radiation, and is more useful to the general population due to its lower cost. The results presented here show good accuracy despite its lower cost. The proposed method has achieved results very close to those based on expensive CT or MRI, where the input image is better than x-ray images.
Souza, Geovane Grossi Araújo de. "X-Ray fluorescence imaging system based on Thick-GEM detectors." Universidade de São Paulo, 2019. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-21032019-233121/.
Повний текст джерелаOs GEMs (Gas Electron Multiplier) e Thick-GEMs (Thick-Gas Electron Multiplier) são estruturas do tipo MPGD (Micropattern Gas Detector) que fazem parte da nova geração de detectores de radiação a gás e permitem altas taxas de contagens, baixo custo quando comparados com os detectores de estado sólido, uma elevada resistência à radiação e ganhos elevados, quando utilizadas estruturas múltiplas para multiplicação. Além disso, o manuseio e manutenção desses detectores é relativamente simples, sendo versáteis em relação à montagem podendo detectar diferentes tipos de radiação. Sendo assim, a utilização desses detectores é uma alternativa eficiente para montar um sistema de imagem com grande área sensível. Este trabalho consiste no estudo e caracterização de um conjunto de detectores gasosos, mais especificamente os Thick-GEMs produzidos pelo grupo de Física de altas energias e Instrumentação do IFUSP, que foram testados para serem empregados em um sistema de imagem de fluorescência de raios-X. Os Thick-GEMs testados apresentaram resultados promissores em termos de ganho, resolução em energia e estabilidade operacional. No entanto, devido à baixa relação sinal-ruído, um sistema de imagem de fluorescência de raios-X foi montado utilizando GEMs. Durante o trabalho as ferramentas de software necessárias para processamento e reconstrução de imagens foram desenvolvidas, assim como um estudo paralelo de simulações computacionais para entender melhor o funcionamento de detectores gasosos. Técnicas como o imageamento por fluorescência de raios-X são de suma importância pois são consideradas não invasivas e não destrutivas. Sua utilização tem uma importância imprescindível nas áreas da medicina e na análise de patrimônios histórico e cultural. Atualmente, a verificação e validação de autenticidade de obras é um requisito obrigatório e alguns museus começam a se interessar cada vez mais em áreas da Física e da instrumentação necessária para caracterizar o seu patrimônio.
Samothrakitis, Stavros. "Neutron & X-ray scattering studies of Fe-based materials." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8459/.
Повний текст джерелаChan, Raymond C. "Model-based estimation of arterial diameter from X-ray angiograms." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/41346.
Повний текст джерелаIncludes bibliographical references (leaves 122-124).
by Raymond C. Chan.
M.S.
Cipiccia, Silvia. "Compact gamma-ray sources based on laser-plasma wakefield accelerator." Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=23936.
Повний текст джерелаSheikh, Muhammad Imran. "Ray-optics based propagation tools for future wireless communication networks." Thesis, University of Birmingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633234.
Повний текст джерелаTseng, Hsin-Wu. "Task-Based Image Quality Assessment in X-Ray Computed Tomography." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/593630.
Повний текст джерелаSantos, Ana. "Advanced X-ray photoelectron spectroscopy of N-based ionic liquids." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/49383/.
Повний текст джерелаSmith, Jonathan Chase. "Examining soil based construction materials through X-ray computed tomography." Thesis, Durham University, 2015. http://etheses.dur.ac.uk/11113/.
Повний текст джерелаAgnarsson, Joakim. "Simulation of a radar in Flames : a ray based radar model." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-201093.
Повний текст джерелаZanazzi, Enrico. "Characterization of X-ray detectors based on organic semiconducting single crystals." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8750/.
Повний текст джерелаPrakoonwit, Simant. "The reconstruction and manipulation of object-based 3D X-ray images." Thesis, Imperial College London, 1996. http://hdl.handle.net/10044/1/7330.
Повний текст джерелаPoulsen, Henrik. "Potential of GPU Based Hybrid Ray Tracing For Real-Time Games." Thesis, Blekinge Tekniska Högskola, Avdelningen för för interaktion och systemdesign, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-3488.
Повний текст джерелаVine, David John. "New quantitative methods in analyser-based phase contrast X-ray imaging." Monash University. Faculty of Science. School of Physics, 2008. http://arrow.monash.edu.au/hdl/1959.1/57830.
Повний текст джерелаYang, Yong Suk Tony. "Time resolved X-ray studies of crystallization in Zr-based glasses." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74548.
Повний текст джерелаWe have used these new techniques of time resolved x-ray diffraction experiments to study the crystallization kinetics of amorphous NiZr$ sb2,$ CoZr$ sb2,$ FeZr$ sb2$ and Ni$ sb{36.5}$Zr$ sb{63.5}.$ The experiments were performed at beamline X20C National Synchrotron Light Source.
We have mostly focussed on the crystallization behaviour at high temperatures and therefore faster kinetics. We have found many new results and unexpected metastable phases in these systems. Most of these phases would not be seen using conventional techniques showing the importance of in situ time resolved structural measurements to study the kinetics of phase transitions.
Nussey, James Peter. "Terrestrial and space-based applications of microchannel plate X-ray optics." Thesis, University of Leicester, 2005. http://hdl.handle.net/2381/8992.
Повний текст джерелаKelly, Kathryn L. "Phase contrast imaging with a laboratory-based microfocus X-ray source." Thesis, Durham University, 2007. http://etheses.dur.ac.uk/2453/.
Повний текст джерелаWilliams, Jamie Oscar David. "From terahertz to X-ray : developing new graphene-based photodetector technologies." Thesis, University of Leicester, 2018. http://hdl.handle.net/2381/42405.
Повний текст джерелаRomell, Jenny. "Comparison of Grating- and Speckle-Based X-Ray Phase-Contrast Imaging." Thesis, KTH, Biomedicinsk fysik och röntgenfysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-189056.
Повний текст джерелаForde, Declan J. "FTIR and X-ray investigation of triphenylene based discotic liquid crystals." Thesis, Sheffield Hallam University, 2000. http://shura.shu.ac.uk/19655/.
Повний текст джерелаSong, Jungki. "Metrology and mechanics for manufacturing space-based x-ray grating spectrometers." Thesis, Massachusetts Institute of Technology, 2021. https://hdl.handle.net/1721.1/130846.
Повний текст джерелаCataloged from the official PDF of thesis.
Includes bibliographical references (pages 223-231).
Small errors in critical dimensions (CDs) or deformation of optical components can lead to severe performance degradation in high-resolution imaging and spectroscopy tools. Consistent innovations towards more precise optical elements and assembly procedures have led to high-resolution optical systems in many fields - including telescope, microscopy, lithography, and display technologies. A space x-ray telescope needs more stringent requirements as it observes distant space objects using a limited number of x-ray photons in a harsh space environment. The optical instruments for x-ray telescopes need to be high-resolution, efficient in collecting x-ray photons, and lightweight. Optical elements in x-ray telescopes have large-apertures (typically around 1-2 m²) which are realized by populating them with > 1000 high-quality optical sub-elements (i.e., mirrors or gratings).
In this thesis, we limit our attention to an xray grating spectrometer, one of the essential elements in x-ray telescopes. It is placed downstream of the focusing optics and prior to the x-ray detector to disperse nonmonochromatic x rays from distant sources for space-based x-ray spectroscopy. A critical-angle transmission (CAT) grating, a lightweight, freestanding, high-aspect ratio x-ray grating with 200-nm period and 4 [mu]m depth, is a building block for grating spectrometers. More than 1000 high-quality CAT gratings need to be manufactured and precisely aligned within tolerance to build future CAT grating spectrometers. This thesis attacks this manufacturing challenge through 1) inventing metrologies for characterizing CDs, 2) developing alignment processes, and 3) performing design and analysis of CAT grating structural supports. First, a metrology to characterize period variation of CAT gratings was developed.
Metrology repeatability of 0.004 nm rms was achieved, successfully characterizing period variations of 0.018 nm rms (1 sigma) over large-area CAT gratings patterned with traditional interference lithography. The demonstrated metrology uncertainty and period variations fulfill the requirements for future x-ray telescope missions. Second, alignment metrology and protocols were developed, demonstrating an ability to align multiple CAT gratings to satisfy alignment requirements ( <6 arcmin or 0.1 deg). The developed alignment protocol is reliable and scalable for flight-level alignment, for which a large volume (>1000) of CAT gratings need to be aligned in a fast and accurate manner. Third, a metrology to characterize grating bar tilt variations was developed using small-angle x-ray scattering and a laser setup. The developed metrology demonstrated repeatability of <0.01 deg (1 [sigma]) and accuracy of ~0.08 deg (4.8 arcmin).
It successfully characterized bar tilt angle variations from CAT gratings and results agree well with synchrotron measurements. It enabled us to close the loop in process optimization for CAT grating fabrication, and contributed towards suppressing bar tilt (or blaze) error within tolerance ( <6 arcmin or 0.1 deg). Fourth, analytical and finite element studies were performed to design CAT grating structural supports that minimize x-ray blockage at a given stiffness. In-plane and out-of-plane stiffness of several 2D-lattice topologies were examined. A triangular lattice shows 23-580% on stiffness improvement ( depending on mode of stiffness) over the current hexagonal lattice design for the same open area fraction. Adopting the new 2D lattice design is expected to increase open area fraction by ~5% without compromising stiffness.
by Jungki Song.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineering
Luz, Pedro Hugo Ferreira Natal da. "Development of neutron and X-ray imaging detectors based on MHSP." Doctoral thesis, Universidade de Aveiro, 2009. http://hdl.handle.net/10773/2682.
Повний текст джерелаA Micro-Hole & Strip Plate (MHSP) é uma microestrutura desenvolvida recentemente em instituições universitárias portuguesas. Neste trabalho, o seu desempenho como detector para imagiologia é explorado, tendo como objectivo a imagiologia não só de neutrões, mas também de raios X. A aplicação do método da divisão resistiva de carga é aplicada a uma MHSP especialmente desenhada para sensibilidade em posição. Várias abordagens em termos da electrónica de aquisição de sinal são testadas, sem perder de vista a relação desempenho-preço. Resoluções espaciais abaixo de 1 mm foram obtidas com a MHSP a operar em xénon e tetrafluorometano, com um sistema de detecção a um preço modesto quando comparado com as alternativas, e apropriado para inúmeras aplicações em imagiologia de neutrões e de raios X.
The Micro-Hole & Strip Plate (MHSP) is a Micropattern Gaseous Detector developed recently in Portuguese institutions. In this work, its performance as a imaging detector is characterised, aiming neutron imaging, but also with results in X-ray imaging. The application of the method of resistive charge division is used in a MHSP specially designed for position sensitivity. Several different electronic approaches for signal collection are tested, always taking into account the performance-price ratio. Position resolutions below 1 mm were achieved with the MHSP operating in xenon and in tetrafluoromethane, in a very cost effective detector setup, suitable for many applications in neutron and X-ray imaging.
Grätz, Matthias. "Characterisation and application of a laser-based hard X-ray source." Lund : Lund Institute of Technology, 1998. http://catalog.hathitrust.org/api/volumes/oclc/68945036.html.
Повний текст джерелаZhou, Tunhe. "Laboratory X-Ray Phase-Contrast Imaging : Methods and Comparisons." Doctoral thesis, KTH, Biomedicinsk fysik och röntgenfysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-192593.
Повний текст джерелаFaskontrastavbildning med röntgenstrålning är en teknik som har utvecklats kraftigt de senaste årtiondena, eftersom den fungerar bättre än traditionella, absorptionsbaserade röntgenundersökningar för objekt med låg absorption. Den har dock höga krav på koherens, vilket gjort att den huvudsakligen används vid stora synkrotron-anläggningar. Tack vare utveckligen av nya avbildningstekniker, laboratoriekällor och röntgenoptik kan numera faskontrast användas även med laboratoriesystem, vilket är lovande då tekniken kan användas vid ett större antal olika tillämpningsområden Denna avhandling syftar till att tillämpa, utveckla och jämföra olika faskontrastmetoder i laboratoriemiljö, med en metallstråleröntgenkälla. De tre faskontrastmetoderna som behandlas i denna avhandling är propogation, gitter och speckelbaserad faskontrast. Den gitterbaserade metoden har implementerats i ett laboratoriesystem med en metallstrålekälla som ger flera gånger högre radians än en vanlig, fast mikrofokuskälla. Den högre radians en möjliggör kortare exponeringstider eller högre signal-brusförhållande. Den gitterbaserade tekniken har jämförts experimentellt och numeriskt med den propageringsbaserade metoden. Den strålningsdos som krävs för observera ett objekt, som funktion av dess diameter, har jämförts för de båda teknikerna, den här gången via simuleringar. Resultaten visar på en lägre strålningsdos för den propagationsbaserade tekniken i detta fall, men även att det finns en potentiell fördel för den gitterbaserade tekniken för något större objekt med monokromatisk röntgenstrålning. Speckelbaserade tekniker, nämare bestämt den som bygger på att spåra speckel och den som bygger på att scanna diffusorn, har för första gången implementerats i laboratoriemiljö. Därmed har visats att de fungerar även för strålning med låg tidskoherens. Tekniken har även använts för tomografi och visar möjliga tillämpningar inom kvantitativ analys av material. För att förenkla framtida optimeringar och jämförelser av tekniken med andra metoder, har brusegenskaperna för den speckelbaserade metoden studerats och visat sig likna den gitterbaserade metoden.
QC 20160921
Carroli, Marco. "Novel materials for direct X-ray detectors based on semiconducting organic polymers." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9345/.
Повний текст джерелаFlórez, Díaz Jorge Eliécer. "Improvements in the ray tracing of implicit surfaces based on interval arithmetic." Doctoral thesis, Universitat de Girona, 2008. http://hdl.handle.net/10803/7885.
Повний текст джерелаImplicit surfaces are useful in many areas related to computer graphics. One of their main advantages over other representations is that they can be easily used as primitives for modeling. However, they are not widely used for this purpose because the models created with implicit surfaces take a long time to be rendered. When a precise visualization of an implicit surface is required, the best option is to use ray tracing. However, thin features can be missed in models that have thin parts. These problems are caused by the truncation performed in the floating-point representation in the computers: come bits ae lost in the mathematical operations during the intersection test. In this work, algorithms to deal with those problems are presented. The research is based on Modal Interval Analysis that includes tools for solving quantified uncertainty. Modal Interval Analysis gives the mathematical foundations used in the development of these algorithms.
Berglund, Magnus. "A compact soft X-ray microscope based on a laser-plasma source." Doctoral thesis, KTH, Physics, 1999. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-2845.
Повний текст джерелаHamann, Borrero Jorge Enrique. "X-ray studies of magnetism and electronic order in Fe-based materials." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-64870.
Повний текст джерелаChabior, Michael. "Contributions to the characterization of grating-based x-ray phase-contrast imaging." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-81705.
Повний текст джерелаPlogmaker, Stefan. "Techniques and Application of Electron Spectroscopy Based on Novel X-ray Sources." Doctoral thesis, Uppsala universitet, Yt- och gränsskiktsvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-168799.
Повний текст джерелаWang, Te-Kang. "A powder X-ray diffraction study of two aluminum-lithium based alloys." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/43736.
Повний текст джерелаThe microstructures of solution treated, quenched and aged A1-2.5 wt. %Li and A1-2.0 wt.%Li-2.76 wt.%Mg-1.03 wt.%Cu alloys were studied by powder X- ray diffraction. The as-quenched alloys showed extensive X-ray line broadening due to particle size effects and the intensity measurements indicated a significant amount ordering in the as-quenched state. These results were interpreted using a 'spinodal ordering' model which suggests that A1-Li-based alloys order during quenching and then spinodally decompose into regions of order and disorder so that the final microstructure comprises small ordered regions (size 40 nm) in a disordered matrix Studies on the aged A1-2.5 wt.%Li alloy indicated that after initial short-time aging, particle growth follows Ostwald ripening kinetics in agreement with previous work. Studies on the aged quaternary alloy indicated that T1 and S phases grow in this system so that precipitates are not a dominant strengthening mechanism in this alloy.
Xu, Feng, Yik-Kiong Hue, and Satya P. Ponnaluri. "Channel Modeling Based on Bidirectional Analytic Ray Tracing and Radiative Transfer (RT²)." International Foundation for Telemetering, 2012. http://hdl.handle.net/10150/581636.
Повний текст джерелаThe extremely large electrical-size and complexity of terrain scene poses great challenge in channel modeling of aeronautic telemetry. It becomes even more difficult if severe multipath and fading present due to scattering and attenuation of ground, terrain objects and precipitation [Rice, 2004]. This is critical in more sophisticated test scenarios involving low flying unmanned air vehicles and helicopters tested over water at high sea states, in hilly terrain, or even over urban environment. Conventional ray tracing and simple Fresnel reflection are not sufficient to characterize such complex channels. Hence, the novel bidirectional analytic ray tracing and radiative transfer (RT²) is proposed for advanced telemetry channel modeling.
Junejo, Faraz. "X-ray based machine vision system for distal locking of intramedullary nails." Thesis, Loughborough University, 2009. https://dspace.lboro.ac.uk/2134/35949.
Повний текст джерелаAlamoudi, Dalal. "Dose enhancement near metal interfaces in synthetic diamond based X-ray dosimeters." Thesis, University of Surrey, 2016. http://epubs.surrey.ac.uk/812968/.
Повний текст джерелаInwood, David Warwick. "X-ray and electrochemical studies of bimetallic Pt-based oxygen reduction electrocatalysts." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/417989/.
Повний текст джерелаEloh, Komlavi Sényo. "FFT-based modelling of X-Ray Diffraction peaks : application to dislocation loops." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0097.
Повний текст джерелаIn this work, we propose and test an original numerical method of simulation of X-ray diffraction peaks by single crystals. This method is based on the use of Fast Fourier Transform (FFT) algorithms for the calculation of mechanical fields resulting from external loading and / or linear defects such as dislocation loops. These defects are modeled by stress-free strain fields (eigenstrains) in a periodic microstructure subjected to thermomechanical loadings. In the first part, we present an improved approach by FFT-type algorithms which allows to accurately obtain the local mechanical fields without numerical oscillation at material's discontinuities. This improvement is due to the use of a discrete and periodic Green operator. This is obtained by solving the Lippmann-Schwinger equation in the Fourier space and using an appropriate spatial discretization. The fourth order modified Green operator allows to calculate the values of the strain and stress fields at all voxels. We also propose a third order periodic green operator to compute the displacement field. The computed displacement field is then corrected by a sub-voxelization method which removes the artifacts appearing in the case of dislocation loops inclined with respect to the reference grid. Numerical examples on reference cases show the effect of the Green operators for the calculation of local mechanical fields without oscillation and the efficiency of the sub-voxellization method. The final displacement field obtained is the input data of the simulation of X-ray diffraction patterns. The method of simulation of X-ray diffraction peaks of FCC (Face-Centered Cubic) single crystals is then presented. The diffracting material is modelled by a representative volume containing dislocation loops in (111) slip planes. We calculate the amplitude then the intensity of the diffracted beam near a node of the reciprocal lattice. This 3D distribution of the diffracted intensity is processed to obtain 1D diagrams that will be analyzed. The simulations demonstrate foremost the elimination of the artifacts on the diffraction diagrams which are due to the oscillations of the uncorrected mechanical fields. The diffraction peaks are analyzed by different statistical methods (Fourier transform of intensity, method of moments, etc.) which allow to evaluate the distribution parameters of dislocations (density, polarization factor, etc.) and compare them with their theoretical values