<p>The world’s dependence on oil cannot continue indefinitely. As reserves dwindle and demand continues to increase, prices will soar to new highs and fundamentally change the way society deals with energy generation and consumption. Use of oil and other carbon-based fuels also have detrimental effects on human health, as pollution that arises from the combustion of these fuels necessitates treating respiratory problems in millions of people annually. Moreover, evidence that climate change is anthropogenic has become undeniable and has been proven to be direct related to dependence on carbon-based fuels.</p> <p>Renewable energy offers clean and dependable alternatives for electricity, heating and transport. In particular, solar energy looks to be the most promising owing to its sheer abundance and ubiquity. The main obstacle hindering the adoption of solar cell technology en masse is cost. One of the ways to reduce cost is to fabricate thinner solar cells, but this compromises efficiency due to lower optical absorption that results, especially in silicon. In order to become a serious competitor in the energy market, highly absorptive solar cells must be developed at reduced material costs, which is the essence of light-trapping.</p> <p>In this study, two of the most common ways to trap light by reducing reflection were investigated: the application of anti-reflection coatings and surface texturing in silicon. Analytic models were created to optimize optical design in both single-junction and multi-junction solar cells. The single-junction silicon models accounted for non-normal incidence, which allowed angle-averaged calculations to be made for planar and textured surfaces. Single-junction GaAs models included a GaInP window layer whose optical effects were considered in anti-reflection coating optimization. The multi-junction GaAs-on-silicon (GaAs/Si) and AlGaAs-on-silicon (AlGaAs/Si) models that were created clearly demonstrated the need to adjust individual subcell thicknesses in order to optimize optical design.</p> / Master of Applied Science (MASc)

Les microalgues autotrophes sont une source prometteuse de biomasse pour des applications aussi variées que l'extraction de molécules, l'alimentation animale et humaine, la production énergétique ou la décontamination environnementale. La production de masse est donc en forte augmentation dans le monde. Cependant, les techniques actuelles pour caractériser l'état physiologique des cellules algales au cours de la croissance sont coûteuses en main d'œuvre et en temps, souvent basées sur du matériel de mesure générique répondant mal au cahier des charges. Elles sont inadaptées à la mesure en ligne.De nouveaux outils doivent donc être développés pour optimiser le pilotage des procédés de culture, en effectuant des mesures rapides de l'état physico-chimique des cellules. La spectroscopie visible (VIS) et proche infrarouge (NIR) se présente comme une solution pratique. De plus des travaux antérieurs ont démontrés que les propriétés spectrales d'absorption et de diffusion des cellules d'algues dans le domaine VIS-NIR sont très corrélées à leur caractéristiques chimiques (pigments) et physiques (tailles, densité des cellules). Les densités de cellules considérées en cultures denses sont très élevées (10^6-10^9 cellules/mL), rendant inévitables les phénomènes de multidiffusion. Cependant ces derniers ont été identifiés comme gênants pour l'extraction de données à partir des spectres mesurés, car ils rendent l'hypothèse de validité de la loi de Beer Lambert fausse. Dans cette thèse nous nous intéressons à l'extraction de données sur la physiologie des cellules algales à partir de mesures spectrales effectuées sur des échantillons denses, non-dilués, directement issus du milieu de culture. Notre approche se décline en plusieurs axes, correspondants aux différentes échelles de description du problème. D'abord, l'échelle de l'échantillon algal global est considérée. Nous en définissons les propriétés spectrales apparentes, et analysons le problème pratique de leur mesure. Nous avons utilisé un montage à double sphères d'intégration et développé un protocole de mesure complet, que nous décrivons. Ensuite, les propriétés spectrales linéaires intrinsèques au milieu algal sont abordées, et nous cherchons à les reliées aux propriétés apparentes de l'échantillon. Pour cela nous utilisons le formalisme de l'équation de transfert radiatif (ETR) donnant une modélisation rigoureuse des phénomènes de multidiffusion à l'œuvre dans les milieux turbides. En pratique, résoudre l'ETR ne peut se faire que par une approximation ou la simulation. Dans nos travaux nous examinons la méthode Adding-Doubling et son inverse, utilisées avec succès par d'autres équipes sur des échantillons turbides de tissus biologiques. En troisième lieu, l'échelle de description de la cellule d'algue individuelle est abordée. AlgaSim, un programme de simulation basé sur la théorie de Mie étendue, a été développé au cours de cette thèse pour modéliser les spectres d'absorption et de diffusion d'une cellule algale décrite par ses paramètres physiologiques, tels que la taille et le poids sec, les proportions des différents matériaux cellulaires, la quantité et la composition des pigments. Ainsi, les liens entre propriétés physiques et chimiques de la cellule et ses propriétés spectrales sont étudiés. Enfin, une méthode complète est proposée pour articuler toutes les échelles de description précédemment examinées. Les liens entre propriétés intrinsèques du milieu algal et les propriétés optiques individuelles des cellules sont cherchés. Les paradigmes développés aux différentes échelles sont ensuite mis bout à bout pour relier la description physiologique des cellules d'algue aux propriétés spectrales apparentes mesurées sur un échantillon donné. La méthode est testée sur des échantillons algaux réels. Les premiers résultats sont prometteurs, démontrant le potentiel opérationnel de la spectroscopie VIS-NIR pour le suivi de procédés de culture dense de microalgues. / Autotrophic microalgae are seen as a promising source of biomass for various applications such as chemicals extraction, animal and human food, energy production and environment cleaning. Consequently, the global mass production of microalgae has largely increased over the last decade. However, the current techniques used for the characterization of the algal cells all along the growth process require time-consuming sample preparation, a large amount of costly, standard instrumentation and cannot usually be performed in situ.New tools are needed to optimize the monitoring of the cultivation process by providing a faster measurement of the microalgal cells physical and chemical states. For this purpose, utilizing visible (VIS) and near infrared (NIR) spectroscopy is looked as a promising solution. Moreover, previous studies demonstrated that the spectral absorption and scattering properties of microalgal suspensions in the VIS-NIR domain depend heavily on the chemical characteristics (pigments) and physical characteristics of the cells (size, density of the cells). In a context of cultivation process, cell density in the culture medium is very high (10^6-10^9 cell/mL) which makes the multi-scattering phenomena significant. However, recent studies have showed that the data extraction from spectroscopic measurements performed on turbid samples is highly complicated by the influence of the scattering phenomena on the spectra, making the classical processing methods based on the assumption of Beer law irrelevant. This thesis addresses the issue of retrieving information about the physiological state of microalgal cells from spectral measurements performed on non-diluted, dense bulk culture media. For this purpose, our approach includes successive guidelines, corresponding to different scales of description. First, the scale of the bulk algal aliquot is considered: the apparent spectral properties are defined, and the practical issue of measuring them with an adapted setup is investigated. In particular, a double-integrating sphere setup, as well as a complete measurement protocol are implemented. Second, the intrinsic linear spectral properties of the dense algal medium are defined, and the links between the intrinsic and apparent spectral properties are investigated. The formalism of the radiative transport equation (RTE) is used for this purpose, as it rigorously models the physical phenomena due to multiple scattering. Solving the RTE must be implemented in practice with an approximation or simulation method. In this work, we investigate in particular the Adding-Doubling method and its inverse, which have been proved to be adapted to the case of highly turbid organic tissues and materials. Third, the scale of an individual algal cell is considered. In this thesis we have developed a simulation program called AlgaSim based of the extended Mie theory, which makes it possible to simulate the spectral absorption and scattering properties of an algal cell described by its physiological characteristics, such as its mean size and dry weight, proportions of different cell materials and pigment quantity and composition. The links between the chemical and physical properties of an algal cell and its spectral properties are thus investigated.Finally, a complete method is proposed to link all the scales of description. In particular, the links between the intrinsic spectral properties of an algal medium and the individual properties of the constitutive cells are considered. By organizing all the paradigms previously investigated, it is possible to implement a complete model linking the physiological description of the constitutive algal cells to the apparent spectral properties measured on a dense culture sample. The method and its inverse are tested on real algal samples. They show promising primary results, proving the operational potential of VIS-NIR spectroscopy for the monitoring of dense algal cultures.

Submitted by THANAN WALESZA PEQUENO RODRIGUES null (twalesza@gmail.com) on 2017-04-18T13:46:33Z No. of bitstreams: 1 Tese_Final2017.pdf: 5871584 bytes, checksum: 622c90a26db9966bfc3a2c9aaf97e829 (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-04-18T19:10:58Z (GMT) No. of bitstreams: 1 rodrigues_twp_dr_prud.pdf: 5871584 bytes, checksum: 622c90a26db9966bfc3a2c9aaf97e829 (MD5) / Made available in DSpace on 2017-04-18T19:10:58Z (GMT). No. of bitstreams: 1 rodrigues_twp_dr_prud.pdf: 5871584 bytes, checksum: 622c90a26db9966bfc3a2c9aaf97e829 (MD5) Previous issue date: 2017-03-09 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O presente trabalho teve como objetivo realizar um levantamento detalhado das características bio-ópticas nos reservatórios de Barra Bonita (BB) e Nova Avanhandava (Nav) com o intuito de avaliar o desempenho de uma única abordagem voltada para a estimativa das propriedades ópticas inerentes (POIs), assim como, a concentração de totais sólidos suspensos (TSS). A investigação foi realizada utilizando dados coletados no campo entre 2014 e 2016, incluindo, as POIs, componentes opticamente significativos (COSs) e reflectância de sensoriamento remoto (R_rs). Os dados apresentados dos COSs confirmaram que BB é um ambiente mais túrbido que Nav por apresentar maior produção fitoplanctônica em função do recebimento de altas cargas de nutrientes provenientes da bacia de drenagem. Por outro lado, Nav é um ambiente mais transparente e com maior influência de material inorgânico, o que favorece o surgimento de macrófitas submersas. A concentração de clorofila-a (Chl-a) em BB alcançou máximo de 797.8 µg l-1 em outubro/2014, enquanto Nav apresentou máximo de 38.6 µg l-1 em maio/2016. A variabilidade nos COS esteve altamente vinculada a frequência de chuvas, sendo que no ano de 2014, ocorreu um evento extremo de seca alterando as características biogeoquímicas dos ambientes. BB reagiu de forma mais abrupta que Nav por apresentar um sistema de operação do tipo acumulação e por estar mais próxima das regiões potencialmente poluidoras, diferente de Nav que apresenta um sistema fio-d’água em que não há acumulação e sim fluxo constante da água. Além disso, no âmbito óptico, a absorção em Nav apresentou maior influência do particulado não-algal (NAP) enquanto que em BB, a absorção foi dominada por fitoplâncton. Com base nesses resultados pode-se concluir que os dois ambientes apresentam não só diferenças na qualidade da água, mas também nas propriedades ópticas, o que leva a afirmação de que um modelo único baseado nos dois ambientes pode não ter um bom resultado quando se pretende utilizar uma abordagem empírica. Um algoritmo quase-analítico (QAA) parametrizado para as condições de Nav (QAAOMR) apresentou resultados significativos com erros (erro médio percentual absoluto – MAPE) inferiores a 17% para o coeficiente de absorção total (a_t), 19% para o coeficiente de absorção orgânico detrital (a_CDM) e 47% para o coeficiente de absorção do fitoplâncton (a_ϕ). O respectivo modelo foi utilizado para verificar seu desempenho em um ambiente eutrofizado como BB e a versão parametrizada por Watanabe et al. (2016) e denominada QAABBHR foi aplicada aos dados de Nav. Como resultado, observamos que as duas versões foram adequadas para estimar a_t com erros inferiores a 40%, no entanto, existe ainda a necessidade de melhorar as etapas para estimativa de a_CDM e a_ϕ. No caso de se aplicar um modelo empírico de única abordagem para estimar concentração de TSS para ambos os reservatórios, observamos que essa abordagem não apresentou resultados satisfatórios, portanto, modelos específicos baseados na banda do vermelho do MODIS foram utilizados para mapear TSS em cada um dos reservatórios. Pode-se concluir então, que o conhecimento acerca das propriedades ópticas da água se mostrou determinante para a modelagem bio-óptica, principalmente no que diz respeito aos ambientes altamente contrastantes como BB e Nav. / The objective of the present work was to perform a detailed survey of the bio-optical characteristics of the reservoirs of Barra Bonita (BB) and Nova Avanhandava (Nav) in order to evaluate the performance of a single approach aimed at estimating the inherent optical properties (IOPs), as well as the concentration of total suspended solids (TSS). The research was carried out using data collected in the field between 2014 and 2016, including the IOPs, optically significant components (OSCs) and remote sensing reflectance (R_rs). The data presented from the OSCs confirmed that BB is more turbid than Nav because it presents higher phytoplankton production due to the input of high nutrient loads from the drainage basin. On the other hand, Nav is more transparent with greater influence of inorganic matter, which favors the appearance of submerged macrophytes. The concentration of chlorophyll-a (Chl-a) in BB reached a maximum of 797.8 μg l-1 in October/2014, while Nav presented a maximum of 38.6 μg l-1 in May/2016. The variability in the COS was highly related to the frequency of rainfall, in the year 2014, an extreme drought event occurred, altering the biogeochemical characteristics. BB reacted more abruptly than Nav because it presented an accumulation type operation system and because it is closer to the potentially polluting region. Nav presents a water system in which there is no accumulation but constant flow of water. In addition, in the optical context, the absorption in Nav presented greater influence of the non-algal particulate (NAP) while in BB, the absorption was dominated by phytoplankton. Based on these results, it can be concluded that the two environments present not only differences in water quality but also in optical properties, which leads to the assertion that a single model based on the two environments may not have a good result when it is intended to use empirical approach. A quasi-analytical algorithm (QAA) parameterized for Nav conditions (QAAOMR) presented significant results with errors (mean absolute percentage error - MAPE) lower than 17% for the total absorption coefficient (a_t), 19% for the carbon detrital matter absorption coefficient (a_CDM) and 47% for the absorption coefficient of phytoplankton (a_ϕ). The respective model was used to verify its performance in a eutrophic environment such as BB and the version parameterized by Watanabe et al. (2016) and named QAABBHR was applied to the Nav data. Thus, we note that the two versions were suitable for estimating a_t with errors (MAPE) less than 40%, however, improvements must be carried out for estimating a_CDM and a_ϕ. In the case of applying a single empirical model to estimate TSS concentration for both reservoirs, we observed that it did not present satisfactory results, so specific models based on the MODIS red band were used to map TSS in each of the reservoirs. It can be concluded, therefore, that knowledge about the optical properties of water has proved to be determinant for the bio-optical modeling, especially with respect to highly contrasting environments such as BB and Nav. / CNPq: 200152/2015-7

Due to the invasive nature of quantification techniques, baseline pigment data for coral-dwelling zooxanthellae are not known. In an attempt to develop a model for non-invasive estimation of zooxanthellae pigment concentrations from corals, field samples were taken from Porites rus and P. lutea in Apra Harbor, Guam. In-situ reflectance spectra (R400-R800) from 22 coral colonies were collected. “Coral truthing” was accomplished by extracting corresponding tissue core samples. Subsequent analysis to quantify the concentrations of 6 zooxanthellae pigments (µg cm-2) was performed using HPLC. Trials of multiple linear regressions were attempted (EJ Hochberg) and found inappropriate, despite previous success. The multivariate calibration technique partial least squares regression (PLS-R) is an excellent tool in the case of co-linear variables. Thus, PLS-R was attempted for chlorophyll c2 and peridinin after demonstration of co-linearity. This may be an appropriate approach for development of bio-optical models to estimate zooxanthellae pigment concentrations. Further, the dinoflagellate diagnostic pigment peridinin may be of great value for reef-scale remote sensing of changes in coral status in the future.

No description available.

Parmi les technologies de solaire thermodynamique, la technologie du linéaire de Fresnel semble la plus adaptée aux régions d’Afrique Sub saharienne. Cela en raison de la simplicité de la technologie. C’est dans cette optique qu’un collecteur de type linéaire de Fresnel d’une superficie de 7,5 m² de miroirs a été construit au laboratoire énergies renouvelables et efficacité énergétique (LabEREE). La construction du collecteur s’est faite en utilisant en priorité les matériaux disponibles localement afinde rendre la technologie plus accessible aux populations locales et de réduire les coûts de fabrication. Des tests sont effectués sur le collecteur afin de déterminer ses rendements optiques, thermiques et globaux. Dans un premier temps, une revue bibliographie des différents collecteurs de type linéaire de Fresnel nous a permis d’identifier les variantes, de cette technologie, les plus adaptées au contexte dela région . Un modèle thermique et un modèle optique ont été mis en place comme outils de dimensionnement et d’optimisation du collecteur. Les résultats expérimentaux obtenus ont été utilisés pour valider les différents modèles mis en place. Le rendement global du collecteur obtenu expérimentalement est de 21% et il a un facteur de concentration local de 6. / Among the different technologies of concentrated solar power plant, the linear Fresnel, thanks to its simplicity, appears the most adapted to rural area of Sub Sahara region. A linear Fresnel collector of 7.5 m² has been built in “laboratoire énergies renouvelables et efficacité énergétique (LabEREE)”. The collector have been designed using material available locally by local man power. This reduces the total cost of the technology and makes it affordable for local population. The collector has been characterized in order to find optical, thermal and global efficiencies. In first time, a review on different linear Fresnel collector allows finding the technology that is most adapted to the Sub-Saharan region. An optical and thermal model of the collector has been done as a tool for designing and optimisation. The experimental results enable to validate the different models done. The collector has an effective concentration factor of 6 and a global efficiency of 21%.

No description available.

In our work an optical bus-coupler is proposed, which enables easy bidirectional connection between two waveguides without interrupting the bus using a core-to-core coupling principle. With bended waveguides the coupling ratio can be tuned by adjusting the overlap area of the two cores. In order to ensure large overlap areas at short coupling lengths, the waveguides have rectangular cross sections. To examine the feasibility of this coupling concept a simulation was performed, which is presented in this paper. Due to multimode waveguides, used in short range data communication, a non-sequential ray tracing simulation is reasonable. Simulations revealed that the bending of the waveguide causes a redistribution of the energy within the core. Small radii push the main energy to the outer region of the core increasing the coupling efficiency. On the other hand, at excessive lowered bend radii additional losses occur (due to a coupling into the cladding), which is why an optimum has to be found. Based on the simulation results it is possible to derive requirements and design rules for the coupling element.

The lateral eyes of the horseshoe crab, Limulus polyphemus, are the largest compound eyes within recent Arthropoda. The cornea of these eyes contains hundreds of inward projecting elongated cuticular cones and concentrate light onto proximal photoreceptor cells. Although this visual system has been extensively studied before, the precise mechanism allowing vision has remained controversial. Correlating high-resolution quantitative refractive index (RI) mapping and structural analysis, it is demonstrated how gradients of RI in the cornea stem from structural and compositional gradients in the cornea. In particular, these RI variations result from the chitin-protein fibers architecture, heterogeneity in protein composition, and bromine doping, as well as spatial variation in water content resulting from matrix cross-linking on the one hand and cuticle porosity on the other hand. Combining the realistic cornea structure and measured RI gradients with full-wave optical modeling and ray tracing, it is revealed that the light collection mechanism switches from refraction-based graded index (GRIN) optics at normal light incidence to combined GRIN and total internal reflection mechanism at high incident angles. The optical properties of the cornea are governed by different mechanisms at different hierarchical levels, demonstrating the remarkable versatility of arthropod cuticle.