This thesis deals with practical implementation of photon mapping algorithm. To achieve better results some basic and some more advanced methods of global illumination has been examined. These time demanding algorithms are often practically unusable and their further optimization is necessary. Optimized ray tracer is essential for practical implementation. Computing diffuse interreflection by Monte Carlo sampling is also very time demanding operation. Therefore it is appropriate to use it along with proper interpolation.

Bifacial photovoltaic (PV) modules have greater energy yield than traditional monofacial modules because they convert front and rear incident irradiance to electrical energy. Single-axis tracking systems can further increase energy yield and reduce the levelized cost of energy by rotating the modules throughout the day. However, racking elements in tracking systems introduce both shade and reflections on the rear face, increasing irradiance nonuniformity and fostering further electrical mismatch that reduces module power. The impact of racking, particularly that of the torque tube which spans the middle of the rear collector surface, must be accurately quantified in energy yield predictions to increase stakeholder confidence, and hasten the adoption of tracked bifacial modules. Isolating the torque-tube-reflected irradiance incident on the modules is crucial for this work. This is achieved by implementing arbitrary two-dimensional (2D) irradiance sampling on a module under test in bifacial_radiance, a ray tracing bifacial PV model, and taking the difference in rear irradiance profiles for simulations with a reflective and an absorptive torque tube at each timestamp. We calculate the TT reflection for the central one-in-portrait (1P) and two-in-portrait (2P) modules on horizontal single-axis trackers over hourly timestamps in a typical meteorological year in Livermore, California, USA. We introduce the TT reflection 2D irradiance profiles as additional light sources in DUET to quantify the TT reflection's impact on irradiance, electrical mismatch, and energy yield, as well as an incidence angle modifier's impact on TT reflection. We analyze the TT reflection based on sun zenith and diffuse fraction to group consistent illumination conditions across the year. We identify that TT reflection reduces electrical mismatch by partially offsetting TT shading, and increases annual energy yield by 0.11% and 0.18% in our particular 1P and 2P systems. While the overall impact of TT reflection is greater in the 2P system due to direct beam light incident on the TT, the TT reflection's greatest instantaneous relative contribution to total energy yield is larger for the 1P system, at high diffuse fractions and sun zeniths. For future work, we recommend validating simulation results with and without TT reflection against experimental data. The simulation method used for isolating the TT reflection may also be repurposed to help inform new TT designs that minimize electrical mismatch. Finally, instead of relying on bifacial_radiance to isolate the TT reflection, we recommend incorporating the TT as a Lambertian reflective surface in 3D view factor models with detailed shading for further TT reflection simulations.

An accurate PDF of irradiance for a FSO channel is important when designing a laser radar, active laser imaging, or a communications system to operate over the channel. Parameters such as detector threshold level, probability of detection, mean fade time, number of fades, BER, and SNR are derived from the PDF and determine the design constraints of the receiver, transmitter, and corresponding electronics. Current PDF models of irradiance, such as the Gamma-Gamma, do not fully capture the effect of aperture averaging; a reduction in scintillation as the diameter of the collecting optic is increased. The Gamma-Gamma PDF of irradiance is an attractive solution because the parameters of the distribution are derived strictly from atmospheric turbulence parameters; propagation path length, Cn2, l0, and L0. This dissertation describes a heuristic physics-based modeling technique to develop a new PDF of irradiance based upon the optical field. The goal of the new PDF is three-fold: capture the physics of the turbulent atmosphere, better describe aperture averaging effects, and relate parameters of the new model to measurable atmospheric parameters. The modeling decomposes the propagating electromagnetic field into a sum of independent random-amplitude spatial plane waves using an approximation to the Karhunen-Loeve expansion. The scattering effects of the turbulence along the propagation path define the random-amplitude of each component of the expansion. The resulting PDF of irradiance is a double finite sum containing a Bessel function. The newly developed PDF is a generalization of the Gamma-Gamma PDF, and reduces to such in the limit. An experiment was setup and performed to measure the PDF of irradiance for several receiver aperture sizes under moderate to strong turbulence conditions. The propagation path was instrumented with scintillometers and anemometers to characterize the turbulence conditions. The newly developed PDF model and the GG model were compared to histograms of the experimental data. The new PDF model was typically able to match the data as well or better than the GG model under conditions of moderate aperture averaging. The GG model fit the data better than the new PDF under conditions of significant aperture averaging. Due to a limiting scintillation index value of 3, the new PDF was not compared to the GG for point apertures under strong turbulence; a regime where the GG is known to fit data well.

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Simuler efficacement l'éclairage global est l'un des problèmes ouverts les plus importants en infographie. Calculer avec précision les effets de l'éclairage indirect, causés par des rebonds secondaires de la lumière sur des surfaces d'une scène 3D, est généralement un processus coûteux et souvent résolu en utilisant des algorithmes tels que le path tracing ou photon mapping. Ces techniquesrésolvent numériquement l'équation du rendu en utilisant un lancer de rayons Monte Carlo. Ward et al. ont proposé une technique nommée irradiance caching afin d'accélérer les techniques précédentes lors du calcul de la composante indirecte de l'éclairage global sur les surfaces diffuses. Krivanek a étendu l'approche de Ward et Heckbert pour traiter le cas plus complexe des surfaces spéculaires, en introduisant une approche nommée radiance caching. Jarosz et al. et Schwarzhaupt et al. ont proposé un modèle utilisant le hessien et l'information de visibilité pour raffiner le positionnement des points de la cache dans la scène, raffiner de manière significative la qualité et la performance des approches précédentes. Dans ce mémoire, nous avons étendu les approches introduites dans les travaux précédents au problème du radiance caching pour améliorer le positionnement des éléments de la cache. Nous avons aussi découvert un problème important négligé dans les travaux précédents en raison du choix des scènes de test. Nous avons fait une étude préliminaire sur ce problème et nous avons trouvé deux solutions potentielles qui méritent une recherche plus approfondie. / Efficiently simulating global illumination is one of the most important open problems in computer graphics. Accurately computing the effects of indirect illumination, caused by secondary bounces of light off surfaces in a 3D scene, is generally an expensive process and often solved using algorithms such as path tracing or photon mapping. These approaches numerically solve the rendering equation using stochastic Monte Carlo ray tracing. Ward et al. proposed irradiance caching to accelerate these techniques when computing the indirect illumination component on diffuse surfaces. Krivanek extended the approach of Ward and Heckbert to handle the more complex case of glossy surfaces, introducing an approach referred to as radiance caching. Jarosz et al. and Schwarzhaupt et al. proposed a more accurate visibility-aware Hessian-based model to greatly improve the placement of records in the scene for use in an irradiance caching context, significantly increasing the quality and performance of the baseline approach. In this thesis, we extended similar approaches introduced in these aforementioned work to the problem of radiance caching to improve the placement of records. We also discovered a crucial problem overlooked in the previous work due to the choice of test scenes. We did a preliminary study of this problem, and found several potential solutions worth further investigation.

[pt] A avaliação e a caracterização da cor constituem fatores críticos do processo de controle de qualidade de produtos, que também devem atender exigências dos clientes e consumidores finais. A cor de um objeto depende fortemente das características da iluminação. Nesse contexto, a presente pesquisa analisou e comparou os diferentes métodos especificados em normas internacionais, que qualificam o desempenho dos simuladores de luz do dia utilizados em avaliações visuais (cabines de luz) e instrumentais (espectrofotômetros). Para alcançar tais objetivos, foram verificadas as condições de medição estabelecidas pela CIE (intervalo de medição e largura de banda espectral) e elaborados e validados procedimentos de medição de diferentes fontes luminosas. Com base nestes procedimentos, foram realizadas medições de simuladores de luz do dia para adquirir as suas distribuições espectrais de potência, as quais foram utilizadas para avaliá-los e para comparar os métodos especificados em normas. Como principais resultados da pesquisa destacam-se: (i) a constatação de que, de fato, as recomendações da CIE para medição de fontes luminosas devem ser incorporadas ao processo de medição; (ii) o aumento da confiabilidade metrológica através da validação dos procedimentos espectroradiométricos com base em análises de repetitividade das medições; e (iii) a comparação realizada entre os diferentes métodos de avaliação de simuladores de luz do dia, o que permitiu documentar para os casos estudados a presença ou a falta de correlação entre os mesmos. O trabalho contribuiu também ao introduzir uma sistemática normalizada de rotinas para se expressar a incerteza associada à medição espectroradiométrica. / [en] The evaluation and the characterization of the colour constitute critical factors of the process of quality control of products, that also must take care of requirements imposed by customers and final consumers. The colour of an object depends greatly on the characteristics of the illumination. In this context, this research is aimed at discussing the different international standards that characterize the performance of the daylight simulators used in instrumental (spectrophotometers) and visual (light booths) evaluations and also at analysing the differences between the various methods specified in these standards. To reach these objectives the measurement conditions established by the CIE (interval and spectral band-width) were verified and elaborated and validated procedures for the measurement of different luminous sources. Based on these procedures, measurements of daylight simulators were carried out to acquire their spectral power distributions. The measurement results were then used to analyze the evaluations methods specified in standards. The following main results have been accomplished: (i) the CIE recommendations for the measurement of luminous sources must, in fact, be incorporated into the measurement process; (ii) the increase in the metrological reliability through the validation of the spectroradiometric procedures based on the analyses of the repeatability of the measurements; and (iii) the comparison established among the different evaluation methods of daylight simulators, leading to the distinction between the presence or the lack of correlation present in the different methods investigated. The work also contributed by the introduction of standard routines to express the uncertainty associated with spectroradiometric measurements.

Field and laboratory studies were used to elucidate the factors affecting temporal and spatial variations of species abundance and structure of macroalgal assemblage and environmental variables between fish farming (FFA) and non-fish farming (NFFA) areas in Hsiao-Lu-Chiao island, a coral island in southwestern Taiwan. Four experiments have been approached: 1. field surveys of macroalgal assemblage structure on 5-m and 10-m depth at 3 sampling sites at FFA (FFA1, FFA2 and FFA3) and 1 sampling site at NFFA from September 2004, January 2005 and April 2005; 2.the relationship between abiotic (monthly maximum air temperature, monthly minimum air temperature, monthly mean air temperature, monthly cumulative precipitation, monthly cumulative irradiance, seawater temperature, light extinction coefficient, water motion, and nutrient (NO3-, NO2-, NH4+, SRP, DON, and DOP) and biotic (seaurchin density) factors and spatio-temporal variations in macroalgal structures analyzed by non-parametric multivariate model; 3. Factors affecting macroalgal abundance and structure: (1). Comparison of growth temperature ranges in different species to field temperature fluctuation; (2).Comparison of growth irradiance ranges in different species to field irradiance fluctuation; 4.Herbivore pressure: (1). Spatio-temporal variations of sea urchin abundance and structure of assemblage; (2). Gut contents and food preference of sea urchin experiment; (3). Herbivore exclusion experiment. Macroalgal %cover, biomass, species richness, diversity (H¡¦) and evenness (J¡¦) showed temporal and spatial variations, low values in January 2005 and also low values in the 5 m- and 10 m-depth areas of FFA1 and the 10 m-depth areas of FFA2. The data of k-dominance curve, hierarchical cluster and ANOSIM tests indicate that macroalgal assemblage is different between 4 sampling sites, between 2 depths and between 3 seasons. Ceratodictyon spongiosum is the most important species that separates September and January assemblages from April assemblage and separates the FFA1 and FFA2 assemblages from the FFA3 and NFFA assemblages. BVSTEP analysis shows that nutrients (NO3-, DON, DOP), temperature, monthly cumulative precipitation, and sea urchin density are the factors corresponding to variations of macroalgal assemblages, this correlation is more significant for 5 m-depth assemblage. Fish farming area FFA1and FFA2 assemblage are affect by sea urchin density, temperature and DON. Sea urchin influnces macroalgal abundance and assemblage structure in FFA1 and FFA2. Macroalgal %cover in 5 m-depth area shows a reversal relationship with sea urchin density; however, this relationship is not observed for 10 m-depth area. FFA1 and FFA2 are belong to high grazing pressure sites as indicated by high sea urchin density and exclusion experiment. Sea urchin gut contents and feeding preference test show that sea urchin has strong food selectivity with Hypnea charoides and Gracilaria coronopifolia as the most preferred species. Herbivore exclusion experiment shows that Hypnea charoides and Gracilaria coronopifolia are the species recruited in the cages. Ceratodictyon spongiosum had high biomass in FFA1 and FFA2 in January, which was ¡¥low DOP/high DON¡¦. The coindicence of temporal variations in FFA3 assemblage structure with a change from ¡¦Halimeda opuntia and Boodlea compostia¡¦ ¡÷ ¡¦Amphiroa fragilissima, Corallina phhulifera and Galaxaura oblongata¡¦ ¡÷¡¦Halimeda opuntia and Boodlea compostia¡¦ with low nitrogen/ high phosphorous¡¦ ¡÷¡¦ high nitrogen/ low phosphorous¡¦ ¡÷ ¡¦low nitrogen/ high phosphorous¡¦ suggest a role of ¡¦low nitrogen (NO3-)/high phosphorous (DOP)¡¦ for FFA3 structure modification. NFFA assemblage is controlled by temperature and monthly cumulative precipitation. Monthly cumulative precipitation in September was higher than January and April, in which Boodlea compostia and Gracilaria coronopifolia were dominant algae in September. The temperature growth responses of algae using the continuous-flow outdoor laboratory tank culture system fit their seasonal growth, reflecting the temperature-dependent manner of seasonal variations in abundance. It could be concluded from the present investigation that the structure of benthic macroalgal assemblage in Hsiao-Lu-Chiao island in southwestern Taiwan is affected by predicted natural and pulse disturbances. Temperature fluctuations involve in overall temporal variations in structure. Sea urchin herbivory and nutrient as pulse nutrient modulate the structure in fish farming area while monthly cumulative precipitation is associated with algal structure in non-fish farming area.

Le Soleil est une étoile variable dont l’éclairement présente un large spectre de périodicités (de quelques minutes à plusieurs décennies). L’amplitude de ces variabilités présente une forte dépendance en longueur d’onde. La mesure précise de l’éclairement spectral hors atmosphère et de cette variabilité selon une échelle radiométrique absolue constituent une entrée fondamentale pour les domaines de recherche suivants :<p>- En physique solaire, ces mesures permettent de valider les modèles étudiant la composition de l’atmosphère solaire, les processus physiques internes et leur variabilité.<p>- La photochimie atmosphérique terrestre et les modèles climatiques. La composition, la structure thermique et la dynamique de l’atmosphère terrestre sont dépendantes du flux solaire incident, de sa distribution en longueur d’onde et de sa variabilité. Les mesures sont requises pour une validation des modèles de transfert radiatif et climatiques.<p>La nécessité d’une mesure continue dans le temps et hors atmosphère s’impose car chaque cycle solaire possède ses propres caractéristiques. Ces mesures sont réalisées depuis plus de 30 ans par des spectroradiomètres adaptés à l’environnement spatial. L’instrument SOLSPEC (SOLar SPECtrum) a apporté une contribution majeure à ces mesures.<p>Le travail présenté dans ce manuscrit est associé à la sélection de SOLSPEC pour une mission à bord de la Station Spatiale Internationale (ISS). Les objectifs ont consisté à adapter l’instrument pour une mission à long terme (2008-2016), à étendre la plage spectrale couverte par SOLSPEC et à réduire l’incertitude de mesures. Il est structuré en deux parties :<p>- La remise à niveau de l’instrumentation et son étalonnage radiométrique.<p>- Le traitement des données pour les premières mesures en orbite.<p>L’instrument a été modifié pour satisfaire de nouvelles exigences de dimensions et de masse. De nouveaux sous-systèmes optiques (unité interne d’étalonnage, pointeur solaire) ont été développés pour permettre la détection et la correction de toute dérive angulaire ou de réponse absolue de manière autonome. La plage spectrale de fonctionnement a été étendue entre 166 et 3088 nm. Une caractérisation radiométrique approfondie de SOLSPEC a été effectuée. L’étalonnage absolu a été réalisé à partir de l’étalon primaire en éclairement spectral (rayonnement du corps noir) du PTB (Physikalisch-Technische Bundesanstalt). Une estimation des incertitudes standard utilisant le formalisme mathématique appliqué en métrologie a été développée. Les résultats donnent une incertitude réduite entre 2 % à 4 % pour la plage 166-370 nm, inférieure à 2 % entre 370 et 2350 nm, comprise entre 2 et 5 % pour l’intervalle 2350-2580 nm et de 5 à 10 % entre 2580 et 2920 nm. Une valeur inférieure à 1 % est atteinte entre 500 et 1900 nm. Les mesures consécutives à la mise en orbite de SOLSPEC ont confirmé le maintien des performances radiométriques. Le spectre solaire hors atmosphère a été déterminé et comparé aux résultats antérieurs et actuels des missions respectives SOLSPEC ATLAS et SORCE. Il correspond à l’activité solaire du début de la mission SOLAR (mi-2008).<p><p>The Sun is a variable star. Its irradiance presents a wide range of periodicity varying from minutes to decades. The amplitude of this variability is strongly wavelength dependent. The accurate determination of the solar spectral irradiance above the atmosphere in absolute radiometric scale and the study of its variability are main issues for the following researches:<p>- In solar physics, these measurements are required for the validation of the models studying the composition of the solar atmosphere, the internal physical processes and their variability.<p>- For the photochemistry of the Earth’s atmosphere and the climate modeling. The composition, the thermal structure and the dynamics of the atmosphere are dependant on the incoming solar flux, its spectral distribution and variability. The measurements are required for the validation of radiative transfer and climate models.<p>As each solar cycle presents a different behavior, there was a need for continuous measurements above the atmosphere. Such measurements were performed since more than 30 years by means of space qualified spectroradiometers. The SOLSPEC (SOLar SPECtrum) instrument brought a major contribution in this respect. <p>The present work is devoted to the SOLSPEC instrument that was selected for a new mission on board the International Space Station (ISS). The objectives were to refurbish the instrument and to adapt it for a long term mission (2008-2016), to extend the wavelength coverage and to reduce the uncertainties on the measurements. This work is developed in two parts:<p>- The refurbishment and the radiometric characterization of the instrument.<p>- The data processing of the first results after the launch.<p>The instrument was modified in order to fulfill new requirements of dimensions and mass. Different optical sub-systems (internal lamp unit, passive solar sensor) were developed in order to obtain on board capabilities for the detection and the correction of any trend in the absolute response. The spectral range was extended to 166 - 3088 nm. A full radiometric characterization of SOLSPEC has been carried out and is presented in this work. The absolute calibration was performed using the primary standard of spectral irradiance (black-body radiation) of the PTB (Physikalisch-Technische Bundesanstalt). The evaluation of the standard uncertainties is presented using the mathematical methodology applied in metrology. The results provide an uncertainty limited to 2 % - 4 % between 166 and 370 nm, below 2 % from 370 to 2350 nm, between 2 and 5 % for the spectral range 2350 - 2580 nm and 5 % to 10 % between 2580 and 2900 nm. The uncertainty is below 1 % between 500 and 1900 nm. The stability of the radiometric performances was demonstrated from the analysis of the first measurements after the launch, at the beginning of the mission. The solar spectrum above the atmosphere was determined and compared to results obtained from the previous SOLSPEC ATLAS and ongoing SORCE missions. This spectrum corresponds to the solar activity at mid-2008.<p> / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

Biogeochemical processes of reefs have been studied for over fifty years, however, information is still lacking on several fundamental reef processes. This lack of information has been limited essentially by techniques that cannot repeatedly sample large spatial areas. These limitations can be reduced with the use of an optical model to estimate biogeochemical processes. This project applied Monteith's light-use efficiency model to coral reef communities for determining photosynthetic and calcification efficiency of light. Gross primary production and net calcification were pooled from the peer-reviewed literature to calculate efficiency. Process efficiency was then compared across functional types of reef communities (i.e., coral, algae/seagrasses, mixed, and sand), and by year, location, season, and depth. Photosynthetic efficiency was calculated from 19 studies, showing an average of 0.039 mol O2 mol-1 photons. Photosynthetic efficiency differed significantly for mixed communities between studies, and for algae/seagrass communities among depths. Calcification efficiency averaged at 0.007 mol CaCO3 mol-1 photons. Significant differences were found in calcification efficiency of algae/seagrasses and mixed reef communities among studies and localities. Additionally, calcification efficiency of algae/seagrasses varied significantly in accordance with depth. Future use of the light-use efficiency model will require determining the efficiency of each functional type to estimate gross production and calcification. Additionally, further investigation of the light-use efficiency model will require long-term measurements of APAR, which is the fraction of incident light absorbed, and the incorporation of environmental parameters that reduce efficiency.

The Master’s Thesis prospects the suitability of installing a photovoltaic system and a cogeneration unit in the LIPOELASTIC manufacturing facility and proposes their actual realization. Theoretical part describes said facility, its current energy supply situation and presents the proposed realizations' principle of operation. Practical part contains concrete calculations needed for realizations' proposal and their economic evaluation both independently and jointly.