La « shadow corrosion » est un phénomène observé sur les gaines en alliages de zirconium des assemblages de combustibles dans les réacteurs nucléaires. Il consiste en l'augmentation de la corrosion sur les zones de la gaine qui sont à proximité d'autres parties de l'assemblage en Inconel. Afin d'améliorer la compréhension de ses mécanismes, des modèles numériques sont développés suivant deux axes d'études. Un premier modèle de couplage galvanique a pour but de dégager les facteurs de premier ordre. Les résultats des simulations montrent que l'intensité du courant anodique, et sa dépendance en potentiel, contrôlent le caractère local (effet d'ombre) de ce phénomène. D'autre part, cet effet nécessitant un courant cathodique assez élevé révèle l'importance du pouvoir oxydant de l'électrolyte. Un deuxième modèle d'oxydation du zirconium est développé en intégrant le transport multi particules dans l'oxyde. Ce modèle, couplé aux effets d'interfaces (métal/oxyde et oxyde/électrolyte), permet de démontrer le rôle crucial de la polarisation et de l'hydrogène provenant de la dissociation de l'eau sur les cinétiques d'oxydation. A partir de ces modèles, un scénario explicatif de la shadow corrosion est élaboré suggérant l'importance de la radiolyse de l'eau. / La « shadow corrosion » est un phénomène observé sur les gaines en alliages de zirconium des assemblages de combustibles dans les réacteurs nucléaires. Il consiste en l'augmentation de la corrosion sur les zones de la gaine qui sont à proximité d'autres parties de l'assemblage en Inconel. Afin d'améliorer la compréhension de ses mécanismes, des modèles numériques sont développés suivant deux axes d'études. Un premier modèle de couplage galvanique a pour but de dégager les facteurs de premier ordre. Les résultats des simulations montrent que l'intensité du courant anodique, et sa dépendance en potentiel, contrôlent le caractère local (effet d'ombre) de ce phénomène. D'autre part, cet effet nécessitant un courant cathodique assez élevé révèle l'importance du pouvoir oxydant de l'électrolyte. Un deuxième modèle d'oxydation du zirconium est développé en intégrant le transport multi particules dans l'oxyde. Ce modèle, couplé aux effets d'interfaces (métal/oxyde et oxyde/électrolyte), permet de démontrer le rôle crucial de la polarisation et de l'hydrogène provenant de la dissociation de l'eau sur les cinétiques d'oxydation. A partir de ces modèles, un scénario explicatif de la shadow corrosion est élaboré suggérant l'importance de la radiolyse de l'eau.

Skuggor är centrala för hur människan uppfattar världen. Inom datorspel och andra interaktiva 3D-applikationer är det viktigt att underlätta förståelsen av scenen och det finns även ofta en stark vilja att skapa realistiska miljöer. Detta samt att skuggsättning är en komplicerad och prestandakrävande operation gör det till ett viktigt område inom realtidsgrafik. Vi undersöker i denna avhandling relationen mellan prestandan (renderingstiden) för de två populära metoderna för skuggsättning inom realtidsgrafik, shadow mapping och shadow volumes. Undersökningen avgränsas till två utvalda varianter av de ursprungliga algoritmerna. I och med lanseringen av den nya versionen av Direct3D, version 10, öppnas möjligheten för optimeringar av algoritmerna genom användandet av framförallt geometry shaders. På grund av detta implementerar vi algoritmerna både med och utan den nya funktionalitet som introduceras i Direct3D 10 för att besvara om det är möjligt att förbättra prestandan för algoritmerna i Direct3D 10. Resultatet visar tydligt shadow mapping-algoritmens överlägsenhet för annat än scener med mycket få polygoner. Variabler så som ljusets infallsvinkel och objekts storlek har liten inverkan på det slutgiltiga resultatet för när vilken algoritm har bättre prestanda. Resultatet visar även tydligt att användandet av geometry shaders ger en mycket kraftig försämring av prestandan för båda algoritmerna. / Inom interaktiv 3D-grafik som exempelvis datorspel är det viktigt att skapa realistiska miljöer. Att rita ut en realistisk 3D-värld såpass snabbt att användaren inte kan se enskilda bildrutor kräver mycket kraft av datorn. Det är därför viktigt att datorprogrammet använder snabba och effektiva algoritmer. Skuggor är viktigt för att skapa realistiska 3D-miljöer. Detta arbete jämför snabbheten och effektiviteten mellan två olika metoder för att bestämma vad i 3D-världen som ligger i skugga.

This master's project focuses on basic techniques of creating shadows in 3D computer graphics. Two basic techniques are compared. Those are shadow maps and shadow volumes. Another technique combining previouse two is proposed.

This work discusses shadowing methods, analyses them and describes implementation in DirectX 11 API. Theoretical part describes historical evolution of shadow usage in 3D applications and also analyzes shadowing algorithms. This work compares 2 variants of shadow mapping algorithm for omnidirectional lights, based on cube mapping and paraboloid projection, on demo application using quality, performance and implementation aspects.

Nowadays, 3D rendering has been widely applied in video games. Every year companies strive to come up with new solutions and implementations that potentially will increase the complexity of an algorithm, combined with trying to improve the realism of the graphics. An algorithm called Cascaded Shadow Maps will be compared and experimented upon with a regular Shadow Maps algorithm. To further provide information regarding the subject at hand. Objectives. The aim of this experiment is to implement Shadow Maps and Cascaded Shadow Maps in Unity and compare said algorithms to each other. Furthermore, come to a conclusion of which algorithms perform better. Data that will be researched is the Frame rate, Memory consumption, RAM, and Total memory used with the help of Unity's built-in tools. Methods. Shadow Maps and Cascaded Shadow Maps were implemented in Unity Engine by the following literature. Additionally, with help of built-in tools from unity, the Unity Profiler Module. It was possible to take measures to compare each technique of said data. The data were collected five times and then calculated into an average number. Resulting in a collection of data structured and displayed with graphs. Lastly, analyses were performed based on collected data. Results. The data measured and compared showed that Shadow Maps were superior to Cascaded Shadow Maps regarding frame rate, memory consumption, and total memory used. However, Cascaded Shadow Maps could be considered as a algorithm with better complexity to quality ratio than Shadow Maps.  Conclusions. It is Concluded that the Cascaded Shadow Maps utilizes more resources, having less frame rate, higher memory consumption and total memory used. However, Cascaded Shadow Maps were proven in some cases to have better complexity to quality ratio. Additionally, Cascaded Shadow Maps solves the problem Shadow Maps creates, Aliasing. Leads to well-rounded and improved shadows for realism with Cascaded Shadow Maps and in some cases at a small cost.

This paper concerns aliasing removal methods during the shadow displaying. Method of shadow mapping, its principles, procedure and mainly its drawbacks in the form of aliasing development are described. For the removal of this undesirable phenomenon, several aliasing suppressing methods are described - Percentage Closer Filter, Variance Shadow Map, Convulotion Shadow Map, Exponential Shadow Map a Bilateral Filter. I conclude my work with a proposal and implementation of a demonstrative application, which demonstrates the implemented results adequately. Also, the comparison of individual methods on the basis of their quality and computational demands is included.

In this work, two approaches for computing the near-field distribution around wind turbines are proposed, including: (1) Huygens Principle and (2) the parabolic equation technique. In order to simplify the problem, the cylinder model is utilized to represent the wind turbines and transform the problem into a two-dimensional case. To make Huygens Principle computationally tractable, several approximations are made based on the problem geometry especially modelling the cylinder as a plate. The expression of the electromagnetic field radiated by the equivalent magnetic current can be analytically solved by the error function. To verify the results, FEKO is utilized to simulate the scattering of infinitely long cylinders using periodic boundary condition (PBC). In order to solve the problem of multiple cylinders, a modified method is derived. For more accurate results, the parabolic equation (PE) technique is utilized to solve this problem, which is usually utilized to solve wave propagation problems. In this case, wide-angle approximation is used to solve the parabolic equation, which can obtain accurate results in a region of up to 45 degrees. Although these two approaches are not full-wave simulation, the calculation time is significantly reduced and the error is acceptable. To further verify the computed results by the parabolic equation technique, two commercial transceivers from Time Domain Corporation are used to measure the field distribution behind a finite-length metal pole. The frequency-domain results are obtained from the measured time-domain results using the fast Fourier transform. It is shown that the computed results by the parabolic equation technique agree well with the measurement results. / text

This thesis consists of three parts. The first part is an introduction and referencessome recent work on 2D electromagnetic scattering problems at high frequencies. It alsopresents the basic integral equation types for impenetrable objects. A brief discussionof the standard elements of the method of moments is followed by summaries of thepapers.Paper I presents an accurate implementation of the method of moments for a perfectlyconducting cylinder. A scaling for the rapid variation of the solution improves accuracy.At high frequencies, the method of moments leads to a large dense system of equations.Sparsity in this system is obtained by modifying the integration path in the integralequation. The modified path reduces the accuracy in the deep shadow.In paper II, a hybrid method is used to handle the standing waves that are prominentin the shadow for the TE case. The shadow region is treated separately, in a hybridscheme based on a priori knowledge about the solution. An accurate method to combinesolutions in this hybrid scheme is presented.

A simple, quick, and inexpensive technique to improve visualization of aspen (Populus tremuloides) tree rings under the microscope, the ‘shadow technique’, is described. The technique assumes appropriate preparation of increment cores or cross-sections and works well on the lighter portions of the sample with fungus- and bacteria-free wood. The shadow technique was used successfully to elucidate tree-ring boundaries in small diameter (<5 cm DBH) aspen from northern Utah that commonly had >100 annual rings. Crossdating verified whether the elusive rings were missing or false rings. Aspen tree-ring measurement will be greatly enhanced with the shadow technique and preliminary investigation suggests it could be used on other species such as curlleaf mountain mahogany (Cercocarpus ledifolius).

Este ensaio objetiva refletir sobre minha série fotográfica Chiaroscuro, na qual trabalho constrastes entre luz e sombra e as consequentes representações de vazio e memória. Para tanto, elejo os teóricos da antropologia da imagem Jacques Rancière, Georges Didi-Huberman, Victor Stoichita e Hans Belting como meus interlocutores. Uma vez que um dos propósitos deste trabalho abrange observar possíveis inter-relações entre a série e alguns artistas contemporâneos, estabeleço reflexões acerca da produção fotográfica de Candida Höfer, Abelardo Morell e Hiroshi Sugimoto. O percurso em Chiaroscuro, bem como o estudo de elementos de composição da imagem, como o referente, o duplo, a luz e o tempo, auxiliaram-me a uma melhor compreensão do papel da fotografia em minha produção artística. Além disso, a representação da memória a partir do vazio, presente nas imagens da série, atesta a importância de se pensar a linguagem fotográfica em paralelo à pintura, à cultura, à mitologia e a outras linguagens que configuram a arte contemporânea. / This essay aims to reflect on my photographic series Chiaroscuro, in which I deal with contrasts between light and shadow and the consequent representation of emptiness and memory. For this purpose I elect the scholars from anthropology of the image Jacques Rancière, Georges Didi-Huberman, Victor Stoichita and Hans Belting as my interlocutors. As one of the purposes of this work covers to observe possible interrelations between my series and some contemporary artists, I establish reflections about the photography of Candida Höfer, Abelardo Morell and Hiroshi Sugimoto. The course in Chiaroscuro, and the study of elements of image composition, such as the referent, the double, the light and time, helped me to improve my understanding of photography role in my artistic production. In addition, the representation of memory out of emptiness, in this series of images shows the importance of thinking about the photographic language in parallel to painting, culture, mythology and other languages that shape contemporary art.