To see the other types of publications on this topic, follow the link: Diffuse light.
Dissertations / Theses on the topic 'Diffuse light'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Diffuse light.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
LaMarr, John Henry. "Diffuse light correction for field reflectance measurements." Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/279899.
Full textAbstract:
The Remote Sensing Group of the Optical Sciences Center at the University of Arizona performs absolute radiometric calibration of Earth-viewing sensors using vicarious methods. The reflectance and irradiance-based methods require the nadir-view reflectance of a calibration site at sensor overpass. Errors in these reflectance data contribute directly to errors in the retrieved at sensor radiance, and therefore errors in the calibration. This research addresses two areas of improvement for the reflectance retrieval. The discreet laboratory data of the reference panel is spectrally interpolated using the measured hemispherical reflectance rather than a polynomial fit. This interpolation better fits an absorption feature of the reference material near 2200 nm. The desired reflectance is due to the directly-transmitted solar irradiance, but field measurements also include irradiance due to diffuse light. Non-lambertian properties of the reference and surface cause the ratio of the reflected total radiances to differ from the ratio of the reflected solar radiances. This difference can be corrected using additional field measurements, shaded surface/shaded-reference, output from a radiative transfer code, RTC-only, or a combination of both, shaded-reference. For the shaded-reference and RTC-only methods the shape of the bi-directional reflectance factor of the surface must be known to better than 10% to maintain a 2% accuracy for the retrievals, while the shaded-surface/shaded-reference method does not use the surface BRF. All three methods were applied to measurements of calibrated reflectance tarpaulins, and to measurements made at White Sands Missile Range. These data demonstrate that the shaded-surface/shaded-reference and RTC-only methods improve the surface reflectance retrieval, while the shaded-reference method is too sensitive to variations between the actual and modeled diffuse sky irradiance to be useful. This research represents significant improvements in the calculation of surface reflectance for vicarious calibration. The hemispherical reflectance interpolation will reduce uncertainties in the short wave infrared by 1%, and the diffuse corrections will reduce the errors in blue by 2% in some cases.
2
Aquotte, Fabio de Almeida. "Real-time diffuse indirect illumination with virtual light meshes." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/164054.
Full textAbstract:
A iluminação indireta é capaz de elevar consideravelmente a qualidade visual de cenas renderizadas, mas é também uma operação custosa. Por este motivo, há muito esforço de pesquisa voltado para a renderização de iluminação indireta em tempo real. Apesar de atualmente existirem técnicas poderosas para a iluminação indireta em tempo real, elas fornecem ao artista apenas um controle grosseiro do equilíbrio entre qualidade e desempenho. Nós propomos uma Malha de Luzes Virtuais para calcular a iluminação indireta difusa numa cena, inspirados pelo uso de outras malhas auxiliares, como Malhas de Navegação e Malhas de Colisão. Uma Malha de Luzes Virtuais (MLV) é uma malha simplificada de luzes poligonais usadas para aproximar a luz refletida pela geometria real. Juntamente com a MLV, nós projetamos uma estrutura de dados de aceleração para atingir um desempenho eficiente com iluminação indireta usando uma MLV complexa. O uso da MLV apresenta algumas características vantajosas: maior controle artístico dos atributos da iluminação indireta; a possibilidade de integração com técnicas existentes como animação esquelética e geração procedural; e integração simples com ferramentas e processos de produção de arte existentes. Nossos resultados experimentais mostram que a iluminação indireta controlada por artistas é uma alternativa viável a métodos existentes.Indirect illumination on a rendered scene can add a great deal to its visual quality, but it is also a costly operation. Therefore, a lot of research targets how to render indirect illumination in real-time. While powerful techniques for real-time indirect illumination currently exist, they provide only coarse-grained artistic control over the trade-off between quality and speed. We propose a Virtual Light Mesh to compute the scene’s diffuse indirect illumination, inspired by the use of other current auxiliary meshes such as Navigation Meshes and Collision Meshes. A Virtual Light Mesh (VLM) is a simplified mesh of polygonal lights used to approximate the light bounced by the real geometry. Together with the VLM, we design an acceleration data structure for efficient indirect illumination performance with a complex VLM. The use of VLM presents some positive properties: greater artistic control of the indirect illumination characteristics; the possibility of integration with existing techniques such as skeletal animation and procedural generation; and simple integration into existing asset production tools and pipelines. Our experimental results show that artist controlled indirect illumination is a viable alternative to existing methods.
3
Everitt, David Lewis. "Imaging of tissue-like media with diffuse light : analysis and optimization of a diffuse photon tomography /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2002. http://uclibs.org/PID/11984.
Full text
4
Gómez, Rivas Jaime. "Light in strongly scattering semiconductors diffuse transport and Anderson localization /." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2002. http://dare.uva.nl/document/63879.
Full text
5
Sridhar, Susmita. "Elliptically polarized light for depth resolved diffuse reflectance imaging in biological tissues." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/404053.
Full textAbstract:
Polarization gating imaging is a popular and widely used imaging technique in biomedical
optics to sense tissues, deeper volumes, and also selectively probe sub-superficial volumes.
Due to the "polarization memory" effect of polarized light, elliptical polarization-gating
allows access to tissue layers between those of accessible by linear or circular polarizations.
As opposed to the conventional linearly polarized illumination, we focus on polarization
gating methods that combine the use of elliptically polarized light to select polarization maintaining photons and eliminate the background while providing superior contrast and
depth information. With gating, it has also become possible to access user-defined depths
(dependent on optical properties) in biological tissues with the use of images at different
ellipticities. Furthermore, this investigation allowed the application of polarization gating
in spectroscopy to selectively quantify the concentration of tissue chromophores at userdesired depths. Polarization gating methods have been validated and demonstrated with in vivo experiments on abnormalities of human skin (nevus, burn scar) and also on the exposed cortex of an anaesthetized rat. Finally, as a first step towards the use of coherent illumination, adding the concept of polarimetry to laser-speckle imaging was demonstrated.
Preliminary tests on phantoms (solid and liquid) suggested evidence of the influence of
polarization ellipticity on the formation and behaviour of speckles, which could pave the
way for more insight in the study of blood flow in tissues.L’imagerie de filtrage en polarisation est une technique populaire largement utilisée en optique pour le biomédical pour le sondage des tissus superficiels, pour le sondage de volumes plus profonds, mais aussi pour l’examen sélectif de volumes sub-surfaciques. Du fait de l’effet de ’mémoire de polarisation’ de la lumière polarisée, l’imagerie de filtrage en polarisation elliptique est sensible à des épaisseurs de tissus différentes, depuis la surface, accessible avec la polarisation linéaire, jusqu’à une épaisseur critique accessible par la polarisation circulaire. Nous nous concentrons sur des méthodes utilisant des combinaisons de polarisations elliptiques afin de sélectionner la portion de lumi ère ayant maintenu son état de polarisation et éliminer le fond pour un meilleur contraste avec, de plus, une information sur la profondeur. Avec ce type de filtrage, il est possible d’accéder à des profondeurs de tissus biologiques bien définies (selon ses propriétés optiques) selon l’ellipticité de polarisation. De plus, ces travaux ont permis d’étendre la méthode à la spectroscopie pour quantifier sélectivement la concentration en chromophores à une profondeur spécifique. Les méthodes développées ont été validées in vivo à l’aide d’expériences réalisées sur des anomalies de la peau (grain de beauté, cicatrice de brûlure) et aussi sur le cortex exposé d’un rat anesthésié. Enfin, une étude préliminaire a été réalisée pour examiner la possibilité d’étendre la méthode à l’imagerie de tavelures (speckle). Des tests Préliminaires réalisés sur fantômes (solides et liquides) montrent l’influence de l’ellipticité de polarisation sur la formation et le comportement du speckle, ce qui offre la possibilité d’accéder à des informations sur le flux sanguin à des profondeurs spécifiques dans les tissus.
"Polarization gating imaging" es una técnica de imagen muy popular y ampliamente empleada en óptica biomédica con el fin de caracterizar tejidos y sondear volúmenes subsuperficiales de manera selectiva incluso a regiones profundas. Debido al efecto conocido como memoria de polarización de la luz polarizada, la técnica de "polarization gating" elíptica permite el acceso a capas de tejido que, de otro modo, no son accesibles mediante polarización lineal y circular. En contra de la iluminación linealmente polarizada convencional, nuestro estudio se centra en los métodos de "polarization gating" en combinación con luz elípticamente polarizada. Esto permite discriminar aquellos fotones que mantienen una polarización concreta, eliminando así el fondo al mismo tiempo que proporciona un mayor contraste y profundidad de campo, incrementando notablemente la información extraída. Gracias a esta técnica es posible el acceso a distintas profundidades en tejidos biológicos definidas por el usuario (dependiendo de las propiedades ópticas) mediante el empleo de imágenes a distinta elipticidad. Es más, este estudio ha permitido la aplicación del método "polarization gating" a la espectroscopia con el fin de cuantificar la concentración de ciertos cromóforos presentes en tejidos biológicos de manera selectiva y a distintas profundidades deseadas. Los métodos de "polarization gating" han sido validados, establecidos y demostrados en experimentos in-vivo sobre anomalías en tejidos epiteliales humanos (nervios, cicatrices por quemadura) y también en el córtex expuesto de una rata anestesiada. Finalmente, como primer paso en el uso de iluminación coherente, se ha añadido y demostrado el concepto de polarimetría a la técnica de speckle imaging por láser. Los test preliminares en "phantoms" (tanto en sólido como en líquido) arrojan indicios sobre una influencia de la polarización elíptica en la formación y comportamiento de la distribución de las motas (speckle), lo cual podría abrir nuevas puertas y dar un nuevo enfoque sobre la comprensión de la circulación de la sangre en los tejidos.
6
Niemeyer, Andreas [Verfasser], and M. [Akademischer Betreuer] Wegener. "On Cloaking for Diffuse Light and its Limits / Andreas Niemeyer ; Betreuer: M. Wegener." Karlsruhe : KIT-Bibliothek, 2021. http://d-nb.info/1229514708/34.
Full text
7
Zraket, David Camus. "Testing the value of the one-dimensional transport equation with a diffuse light approximation in predicting light flux in tissue." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14649.
Full textAbstract:
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1987.Title as it appears in M.I.T. Graduate List, Sept. 1987: Testing the predictive value of the one-dimensional transport equation with a diffuse light approximation in predicting light flux in tissue.
Bibliography: leaf 37.
by David Camus Zraket.
M.S.
8
Badieirostami, Majid. "Design and implementation of ultra-high resolution, large bandwidth, and compact diffuse light spectrometers." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26644.
Full textAbstract:
Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.Committee Chair: Adibi, Ali; Committee Member: Bhatti, Pamela; Committee Member: Callen, William; Committee Member: Gaylord, Thomas; Committee Member: Zhou, Hao-Min. Part of the SMARTech Electronic Thesis and Dissertation Collection.
9
Brodersen, Craig. "The Absorption and Utilization of Direct, Diffuse and Low Angle Light by Plant Leaves." ScholarWorks @ UVM, 2008. http://scholarworks.uvm.edu/graddis/31.
Full textAbstract:
The light environment of plants is extremely complex and questions relating to how direct, diffuse, or low-angle light affect plants at the leaf-level have remained largely unanswered. Global-change scenarios suggest a trend of increasing diffuse light due to expected increases in cloud cover and atmospheric water vapor concentrations. Here we present three different examples where changes in the directional quality of light affect leaf-level processes. First, some understory plants have well-developed lens-shaped epidermal cells, which have been shown to focus collimated light, but their optical function under diffuse light has been largely speculative. To assess the role of epidermal cell shape in capturing direct vs. diffuse light, we measured leaf reflectance and transmittance with an integrating sphere system using leaves with flat and lens-shaped epidermal cells. Regardless of epidermal cell shape, direct light was absorbed more than diffuse light in all species studied by approximately 2–3%. These data suggest that lensshaped epidermal cells do not aid the capture of diffuse light, and palisade and mesophyll cell anatomy and leaf thickness appear to have more influence in the capture and absorption of light than does epidermal cell shape. Second, community-level productivity has been shown to increase under diffuse light conditions and has been attributed to more uniform distribution of light within the forest canopy. Leaf-level responses to the directional quality of light, however, are unknown. Here we show that leaf-level photosynthesis in sun leaves of both C3 and C4 plants can be 10–15% higher under direct light compared to equivalent absorbed irradiances of diffuse light, while shade-adapted leaves showed no preference for direct or diffuse light at any irradiance. Sun leaves with multiple palisade layers may be adapted to better utilize direct than diffuse light, while shade leaf structure does not appear to discriminate light based on its directionality. Thus, it appears that leaf-level and canopy-level photosynthetic processes react differently to the directionality of light, and previously observed increases in canopy-level photosynthesis occur even though leaf-level photosynthesis decreases under diffuse light. Third, we tested how changes in the directional quality of light affect the penetration of light at the leaf-level. Using chlorophyll fluorescence imaging we were able to determine that low-angle and diffuse light do not penetrate as deeply into leaves as direct light. Upon entering the leaf, diffuse light appears to scatter and remain in the upper tissue layers, while direct light penetrates through more leaf tissue. Absorption of diffuse light is reduced compared to direct light, with the greatest differences in absorption occurring near the interface of the palisade and spongy mesophyll tissue. Changes in the directional quality of light can therefore alter the absorption of light at the leaf-level, and a shift in the absorption profile could potentially decrease light utilization, potentially contributing to the leaf-level photosynthetic differences observed. Overall, it is now clear that plants are much more sensitive to the directional quality of light than we once believed. Also, the directional quality of light has different effects when scaling from the leaf to the landscape, and models of both leaf-level and community-level photosynthesis should be revised to account for these new findings.
10
Ritchey, Adam M. "The Abundance of Boron in Diffuse Interstellar Clouds." Connect to full text in OhioLINK ETD Center, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1250896589.
Full textAbstract:
Dissertation (Ph.D.)--University of Toledo, 2009.Typescript. "Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Physics." Bibliography: leaves 113-121.
11
Marco, Pérez L. (Leandro). "Hardware improvements for detecting modulated near-infrared light in diffuse optical measurements of the human brain." Master's thesis, University of Oulu, 2015. http://jultika.oulu.fi/Record/nbnfioulu-201501211031.
Full textAbstract:
Abstract. Functional near-infrared spectroscopy (fNIRS) is a non-invasive in vivo brain imaging method. fNIRS systems can be used to detect diseases that alter the hemodynamics of the brain, but they are also applicable to the study of hemodynamics in healthy brains to investigate, for example, how brain hemodynamics change in response to external stimuli. The work carried out in this thesis involved improving parts of the light detection hardware that forms the core of a frequency-domain/spatially-resolved fNIRS system.
Different narrow band-pass filter configurations were analyzed to determine the best option for a system of that type. Among the various alternatives, multifeedback filters and resonator filters were simulated and compared. Finally, two different resonator filter sets were physically implemented using printed circuit technology.
The second part of the thesis describes the manufacture of six low-noise, high-sensitivity NIR light detectors designed to extend the light detection capabilities of the system. All these detectors were implemented on printed circuit boards.
After implementation, the circuits were tested separately and in combination with other parts of the system, achieving good results in both cases. The most significant result was the detection of blood flow pulsations from the finger and forehead of a subject using the designed light detectors in combination with the designed filters and a lock-in amplifier. This result shows that the circuits are fully functional and can be used to expand the capabilities of the fNIRS device.Laitteistoparannuksia moduloidun lähi-infrapunavalon detektoimiseksi ihmisaivojen diffuusi optisessa mittausmenetelmässä. Tiivistelmä. Toiminnallisella lähi-infrapunaspektroskopialla tarkoitetaan usein ei-invasiivista aivojen optista kuvantamista. Menetelmää voidaan hyödyntää aivoperäisten sairauksien tutkimisessa, mutta myös terveiden aivojen toimintojen tutkimisessa, esimerkiksi tutkimalla kuinka ulkoinen ärsyke aiheuttaa aktivaation aivoissa, näkyen menetelmällä mitattavissa olevina aivojen happitasojen muutoksina. Tämän diplomityön aiheena oli olemassa olevan laitteiston vastaanotintekniikan kehittäminen, jota käytetään lähi-infrapunavalon FD-modulointiin perustuvassa tekniikassa.
Useanlaisia kapeakaistaisia suodatinkonfiguraatioita analysoitiin parhaan suodatintyypin valitsemiseksi. Eri vaihtoehdoista valittiin ns. multifeedback- ja resonaattorisuodattimet, joita simuloitiin ja verrattiin keskenään. Lopuksi suunniteltiin kaksi resonaattorisuodatinsarjaa toteuttaen PCB-piirilevyllä. Diplomityön toisena osana suunniteltiin kuusi pienikohinaista ja herkkää lähi-infrapunavalovastaanotinta käytettäväksi olemassa olevassa laitteistossa. Kaikki vastaanottimet rakennettiin PCB-piirilevylle.
Suunnitellut piirilevyt testattiin erikseen ja yhdistettynä laitekokonaisuuteen, saaden siinä hyviä tuloksia sekä suodattimilla että vastaanottimilla. Testeissä veren virtauksen pulsaatioita pystyttiin mittaamaan sormesta ja aivoista otsalohkon alueelta hyödyntäen olemassa olevaa ns. lock-in tekniikkaa. Testitulokset osoittivat, että suunnitellut piirilevyt toimivat hyvin ja paransivat mittalaitteen vastaanottimen suoritustasoa.
12
Edjlali, Ehsan. "Fluorescence diffuse optical tomographic iterative image reconstruction for small animal molecular imaging with continuous-wave near infrared light." Thèse, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/10673.
Full textAbstract:
L’approximation par harmoniques sphériques (SPN) simplifiées de l’équation de transfert
radiatif a été proposée comme un modèle fiable de propagation de la lumière dans les tissus
biologiques. Cependant, peu de solutions analytiques ont été trouvées pour ce modèle. De
telles solutions analytiques sont d’une grande valeur pour valider les solutions numériques
des équations SPN, auxquelles il faut recourir dans le cas de tissus avec des géométries
courbes complexes. Dans la première partie de cette thèse, des solutions analytiques pour
deux géométries courbes sont présentées pour la première fois, à savoir pour la sphère et
pour le cylindre. Pour les deux solutions, les conditions aux frontières générales tenant
compte du saut d’indice de réfraction à l’interface du tissus et de son milieu environnant,
telles qu’applicables à l’optique biomédicale, sont utilisées. Ces solutions sont validées à
l’aide de simulations Monte Carlo basées sur un maillage de discrétisation du milieu. Ainsi,
ces solutions permettent de valider rapidement un code numérique, par exemple utilisant
les différences finies ou les éléments finis, sans nécessiter de longues simulations Monte
Carlo. Dans la deuxième partie de cette thèse, la reconstruction itérative pour l’imagerie
par tomographie optique diffuse par fluorescence est proposée sur la base d’une fonction
objective et de son terme de régularisation de type Lq-Lp. Pour résoudre le problème inverse
d’imagerie, la discrétisation du modèle de propagation de la lumière est effectuée
en utilisant la méthode des différences finies. La reconstruction est effectuée sur un modèle
de souris numérique en utilisant un maillage multi-échelle. Le problème inverse est
résolu itérativement en utilisant une méthode d’optimisation. Pour cela, le gradient de la
fonction de coût par rapport à la carte de concentration de l’agent fluorescent est nécessaire.
Ce gradient est calculé à l’aide d’une méthode adjointe. Des mesures quantitatives
utilisées en l’imagerie médicale sont utilisées pour évaluer la performance de l’approche
de reconstruction dans différentes conditions. L’approche Lq-Lp montre des performances
quantifiées élevées par rapport aux algorithmes traditionnels basés sur des fonction coût
de type somme de carrés de différences.Abstract : The simplified spherical harmonics (SPN) approximation to the radiative transfer equation has been proposed as a reliable model of light propagation in biological tissues. However, few analytical solutions have been found for this model. Such analytical solutions are of great value to validate numerical solutions of the SPN equations, which must be resorted to when dealing with media with complex curved geometries. In the first part of this thesis, analytical solutions for two curved geometries are presented for the first time, namely for the sphere and for the cylinder. For both solutions, the general refractiveindex mismatch boundary conditions, as applicable in biomedical optics, are resorted to. These solutions are validated using mesh-based Monte Carlo simulations. So validated, these solutions allow in turn to rapidly validate numerical code, based for example on finite differences or on finite elements, without requiring lengthy Monte Carlo simulations. provide reliable tool for validating numerical simulations. In the second part, iterative reconstruction for fluorescence diffuse optical tomography imaging is proposed based on an Lq-Lp framework for formulating an objective function and its regularization term. To solve the imaging inverse problem, the discretization of the light propagation model is performed using the finite difference method. The framework is used along with a multigrid mesh on a digital mouse model. The inverse problem is solved iteratively using an optimization method. For this, the gradient of the cost function with respect to the fluorescent agent’s concentration map is necessary. This is calculated using an adjoint method. Quantitative metrics resorted to in medical imaging are used to evaluate the performance of the framework under different conditions. The results obtained support this new approach based on an Lq-Lp formulation of cost functions in order to solve the inverse fluorescence problem with high quantified performance.
13
Hartke, Johanna [Verfasser], and Ortwin [Akademischer Betreuer] Gerhard. "Substructures, accretion events, and surrounding diffuse intra-group light in bright early-type galaxies / Johanna Hartke ; Betreuer: Ortwin Gerhard." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2018. http://d-nb.info/1170582826/34.
Full text
14
Vogt, William C. "Development of Mechanical Optical Clearing Devices for Improved Light Delivery in Optical Diagnostics." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/51842.
Full textAbstract:
Biomedical optics is a rapidly expanding field of research focusing on the development of methods to detect, diagnose, and treat disease using light. While there are a myriad of optical systems that have been developed for biological tissue imaging, optical diagnostics, and optical therapeutics, all of these methods suffer severely limited penetration depths due to attenuation of light by tissue constituent chromophores, including cells, water, blood, and protein structures. Tissue optical clearing is a recent area of study within biomedical optics and photonics, where chemical agents have been used to alter tissue optical properties, reducing optical absorption and scattering and enabling light delivery to and collection from deeper tissue regions. However, there are concerns as to the safety and efficacy of these chemical clearing agents in vivo, especially in the skin, where the projective barrier function of the stratum corneum must be removed.
Mechanical optical clearing is a recently developed technology which utilizes mechanical loading to reversibly modify light transport through soft tissues, and much of the work published on this technique has focused on applications in skin tissue. This clearing technique enables deeper light delivery into soft tissues but does not require use of exogenous chemicals, nor does it compromise the skin barrier function. While this clearing effect is thought to be resultant from interstitial water and blood transport, the underlying mechanism has not been concretely identified nor characterized.
The hypothesis of this body of work was that interstitial transport of tissue chromophores (e.g. water and blood) causes intrinsic optical property changes, reduces tissue optical absorption and scattering, and improves light delivery in diagnostic applications. To test this hypothesis, we first developed a mathematical framework to simulate mechanical optical clearing, using both mechanical finite element models and optical Monte Carlo simulations. By directly simulating interstitial water transport in response to loading, data from mechanical simulations was combined with optical Monte Carlo simulations, which enabled prediction of light transmission measurements made during mechanical indentation experiments. We also investigated changes in optical properties during mechanical indentation using diffuse reflectance spectroscopy. These studies used controlled flat indentation by a fiberoptic probe to dynamically measure intrinsic optical properties as they changed over time. Finally, we apply mechanical optical clearing principles to functional near-infrared spectroscopy for neuroimaging. By building a prototypical mechanical optical clearing device for measuring cerebral hemodynamics, we demonstrated that mechanical optical clearing devices modify measured cerebral hemodynamic signals in human subjects, improving signal quality.Ph. D.
15
Moody, Hannah Leigh. "Detection of condom lubricants and starches in the presence of biologicals by diffuse reflectance infrared fourier transform spectroscopy and polarized light microscopy." Thesis, Boston University, 2013. https://hdl.handle.net/2144/21221.
Full textAbstract:
Thesis (M.S.F.S.) PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.Condoms have been used in sexual assaults as a means of preventing the transmission of biological fluids. Current sexual assault evidence collection kit processing protocols do not regularly take advantage of the information that can be gathered by examining residues left by condoms during intercourse. A biphasic liquid-liquid extraction technique was developed to separate polar and non-polar condom residues, which had been collected on cotton tipped swabs. This research involved the examination of twenty condom brands by Diffuse Reflectance Infrared Fourier Transform Spectroscopy. Five brands were selected to examine the consistency of this technique when the lubricants were exposed to body and storage temperature conditions for various times and in the presence of oral, vaginal, and blood samples. Additionally, starches collected from the condoms under each of the above conditions were examined. Although all lubricants were identifiable using this IR technique, the nonoxynol-9 (spermicide) containing samples produced spectra which were not identical to those produced by nonoxynol-9 standards. Although there was a decrease in the percent transmittance within IR spectra as the time between the collection and the extraction of the swabs increased, the condom residues of interest remained identifiable at all time points examined. The use of vaginal and oral swabs in the collection caused a negligible amount of background interference, which could be eliminated through spectral subtraction of the swab.
2031-01-01
16
Yan, Hao, Shao-Qiang Wang, Rocha Humberto R. da, Alexandru Rap, Damien Bonal, Nathalie Butt, Natalia Restrepo Coupe, and Herman H. Shugart. "Simulation of the Unexpected Photosynthetic Seasonality in Amazonian Evergreen Forests by Using an Improved Diffuse Fraction-Based Light Use Efficiency Model." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/626446.
Full textAbstract:
Understanding the mechanism of photosynthetic seasonality in Amazonian evergreen forests is critical for its formulation in global climate and carbon cycle models. However, the control of the unexpected photosynthetic seasonality is highly uncertain. Here we use eddy-covariance data across a network of Amazonian research sites and a novel evapotranspiration (E) and two-leaf-photosynthesis-coupled model to investigate links between photosynthetic seasonality and climate factors on monthly scales. It reproduces the GPP seasonality (R-2=0.45-0.69) with a root-mean-square error (RMSE) of 0.67-1.25gCm(-2)d(-1) and a Bias of -0.03-1.04gCm(-2)d(-1) for four evergreen forest sites. We find that the proportion of diffuse and direct sunlight governs the photosynthetic seasonality via their interaction with sunlit and shaded leaves, supported by a proof that canopy light use efficiency (LUE) has a strong linear relationship with the fraction of diffuse sunlight for Amazonian evergreen forests. In the transition from dry season to rainy season, incident total radiation (Q) decreased while LUE and diffuse fraction increased, which produced the large seasonal increase (similar to 34%) in GPP of evergreen forests. We conclude that diffuse radiation is an important environmental driver of the photosynthetic seasonality in tropical Amazon forests yet depending on light utilization by sunlit and shaded leaves. Besides, the GPP model simulates the precipitation-dominated GPP seasonality (R-2=0.40-0.69) at pasture and savanna sites. These findings present an improved physiological method to relate light components with GPP in tropical Amazon. Plain Language Summary Understanding the mechanism of photosynthetic seasonality in Amazonian evergreen forests is critical for its formulation in global climate and carbon cycle models. However, the control of the unexpected photosynthetic seasonality is highly uncertain. Here we use eddy-covariance data across a network of Amazonian research sites and a novel evapotranspiration (E) and two-leaf-photosynthesis-coupled model to investigate links between photosynthetic seasonality and climate factors on monthly scales. It reproduces the GPP seasonality (R2= 0.45-0.69) for four evergreen forest sites. We find that the proportion of diffuse and direct sunlight governs the photosynthetic seasonality via their interaction with sunlit and shaded leaves, supported by a proof that canopy light-use efficiency (LUE) has a strong linear relationship with the fraction of diffuse sunlight for Amazonian evergreen forests. We conclude that diffuse radiation is an important environmental driver of the photosynthetic seasonality in tropical Amazon forests yet depending on light utilization by sunlit and shaded leaves. Besides, the GPP model simulates the precipitation-dominated GPP seasonality (R2= 0.40 similar to 0.69) at pasture and savanna sites. These findings present an improved physiological method to relate light components with GPP in Amazon.
17
Baughman, Brian. "Re-examining the diffuse gamma-ray excess from the inner galaxy : looking back at EGRET data in light of a modern Monte Carlo simulation /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2007. http://uclibs.org/PID/11984.
Full text
18
Kalyagina, Nina. "Diffuse Reflectance Endoscopic Imaging for Bladder Early-Stage Cancer and Pre-Cancer Diagnosis : Instrumentation, Modelling and Experimental Validation." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0099/document.
Full textAbstract:
L'objectif de cette thèse est d'évaluer les performances d'une méthode d'imagerie optique non-invasive pour la détection de précancers et cancers précoces de la vessie, à l'aide d'une analyse de lumière laser rétro-diffusée. L'analyse de la distribution spatiale de la lumière à la surface de fantômes multi-couches imitant l'épithelium de vessie avec différentes propriétés d'absorption et de diffusion nous a permis de montrer les modifications de ces propriétés optiques entraînent des changements de la taille de la surface du spot de lumière rétro-diffusée, mesurables par une caméra vidéo. La méthode développée est également sensible à l'accumulation d'un photosensibilisateur et est applicable aussi bien pour des études en réflectance diffuse qu'en fluorescence induite. Les paramètres optiques des fantômes synthétiques tri-couches imitant différents états des épithéliums de vessie ont été calculés à partir de la théorie des ondes électromagnétiques appliquée aux diffuseurs sphériques sans et avec une couche. Ces paramètres ont servi comme entrées aux simulations de Monte Carlo qui ont permis d'obtenir les matrices des distributions d'intensité de réflectance diffuse. Notre étude démontre que les mesures en imagerie de réflectance diffuse non-polarisée permettent de fournir des informations utiles au diagnostic tissulaireThe present thesis aimed to evaluate the performance of non-invasive optical method for bladder pre- and early- cancer detection by means of diffuse-reflected laser light analysis. The analysis of light distribution at the surface of multi-layered bladder phantoms with different scattering and absorption properties showed that the changes in the optical properties lead to increase or decrease of the diffuse-reflected light spot area, detectable by a video camera. It was also determined, that the presented method is capable of detection of the photosensitizer accumulation, and can be applied for both (diffuse-reflected laser and fluorescence) studies simultaneously. The calculations for spherical and ?coated?-spherical tissue scatterers, based on the electromagnetic wave theory, allowed for obtaining optical parameters of three-layered biological phantoms and of bladder tissues at different states. These parameters served as inputs for Monte Carlo simulations, which provided us with matrices of diffuse-reflected light distributions. The study showed that the measurements of non-polarized back-scattered laser light can provide useful information on the tissue state
19
Effenberger, Adam. "Pozorování amplitudových a fázových předmětů přes rozptylující prostředí pomocí holografického mikroskopu s kontrolovatelnou koherencí." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-232190.
Full textAbstract:
This diploma thesis deals with phase and amplitude objects observation through scattering media by means of a coherence-controlled holographic microscope (CCHM). A brief history of development and construction of the microscope, its advantages compared to the classical light microscopy and hologram processing are described. Quantitative phase imaging through scattering media by means of ballistic as well as diffuse light is verificated in the experimental part. A comparison of an image obtained through a scattering layer by means of CCHM and a classical microscopy in the light field is demonstrated.
20
Fortunato, Thereza Cury. "Imagens de refletância difusa para detecção de inclusões absorvedoras em meio espalhador." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-21102016-102314/.
Full textAbstract:
Dentre as diversas aplicações da luz em nosso dia-a-dia, as ligadas à área biomédica merecem destaque e são frequentemente objetos de pesquisa tanto para o desenvolvimento quanto para o aprimoramento de técnicas para o diagnóstico e terapias. Os tecidos biológicos são, em sua maioria, estruturas complexas, não-homogêneas e opticamente muito espalhadoras. Apesar das centenas de estudos existentes acerca da propagação da luz em tecidos biológicos, sua complexidade exige que novos estudos sejam conduzidos a fim de aprimorar o conhecimento já existente, que ainda apresenta muitas lacunas. A presença de heterogeneidades nos tecidos (vasos sanguíneos, hematomas, cistos, tumores e outras alterações macroscópicas) mudam a propagação da luz e dificultam a previsibilidade do seu comportamento por modelos matemáticos. O presente trabalho teve por objetivo estabelecer um método empírico que utiliza imagens de refletância difusa obtidas através de uma instrumentação simples, baseada em uma fonte de luz contínua no visível (laser de diodo em 660 nm) e uma câmera CMOS monocromática, para verificar a possibilidade de localização de inclusões absorvedoras embebidas em phantoms altamente espalhadores. Foi avaliada a capacidade de detectar inclusões de dois diferentes tipos de materiais em diversas geometrias e tamanhos, posicionadas em diferentes profundidades. O ângulo de incidência do feixe laser também foi variado, bem como a distância entre a fonte e o objeto, a fim de avaliar quais as melhores condições experimentais. Os resultados obtidos mostraram que os objetos puderam ser detectados, e suas formas puderam ser satisfatoriamente recuperadas através de um algoritmo desenvolvido para o processamento das imagens. Em algumas situações, mesmo para a maior profundidade utilizada, que foi de 20 mm, a inclusão pôde ser detectada nas imagens de refletância difusa processadas. Apesar da capacidade de detecção das formas geométricas representar um avanço com relação às possibilidades de identificação de estruturas em meios túrbidos, a determinação da profundidade ainda é um desafio a ser superado.Among the various applications of light in our daily life, those connected with biomedicine should be highlighted and are frequently subject of researches aiming for the development and for the enhancement of techniques for diagnosis and therapy. Biological tissues are mostly complex, non-homogeneous and optically highly scattering structures. Despite the hundreds of existent studies on the propagation of light in biological tissues, its complexity requires new studies to be conducted in order to improve the existing knowledge, which still has many gaps. The presence of heterogeneities in tissue (blood vessels, bruises, cysts, tumors and other macroscopic alteration) changes the light propagation and impedes the predictability of its behavior by mathematical models. This work aimed to establish an empirical method using diffuse reflectance images acquired with simple instrumentation, based on a source of continuous light in the visible (diode laser at 660 nm) and a monochromatic CMOS camera, to check the possibility of the location of absorbing inclusions embedded in highly scattering phantoms. The ability to detect inclusions of two different kinds of materials in different sizes and geometries, positioned at different depths were evaluated. The laser beam angle of incidence was also varied, as well as the distance between the source and the object, in order to evaluate the best experimental conditions. The results showed that the objects could be detected, and their shapes might be satisfactorily recovered by an algorithm developed for image processing. In some situations, even at the greatest depth used, which was 20 mm, the inclusion could be detected in diffuse reflectance processed images. Although the detection capability of geometric shapes represents an improvement over the structures of identification possibilities in turbid media, the determination of depth is still a challenge to be overcome.
21
Kulyk, Olena. "Light-tissue interactions for developing portable and wearable optoelectronic devices for sensing of tissue condition, diagnostics and treatment in photodynamic therapy (PDT)." Thesis, University of St Andrews, 2016. http://hdl.handle.net/10023/13199.
Full textAbstract:
This thesis presents the development and in-vivo applications of wearable and portable devices for the investigation of light interaction with tissue involved in Photodynamic therapy (PDT) and during contraction of muscles. A hand-held device and a clinical method were developed for time course in-vivo imaging of the fluorescence of the photosensitizer Protoporphyrin IX (PpIX) in healthy and diseased skin with the aim to guide improvement of PDT protocols. The device was used in a small clinical study on 11 healthy volunteers and 13 patients diagnosed with non-melanoma skin cancer (NMSC). Two types of PpIX precursors were administered: Ameluz gel and Metvix® cream. The fluorescence was imaged with a 10 minute time step over three hours which was the recommended metabolism time before commencing PDT treatment at Ninewells Hospital, Dundee. The fluorescence time course was calculated by integrating the areas with the highest intensity. The fluorescence continued to grow in all subjects during the three hours. The time course varied between individuals. There was no statistical significance between either healthy volunteers or patients in Ameluz vs Metvix® groups; nor was there statistical difference between the three lesions groups (Actinic keratosis (AK) Ameluz vs AK Metvix® vs Basal cell carcinoma (BCC) Metvix®). The p-value was larger than 0.05 in a two sample t-test with unequal variances for all the groups. However, there was strong body site dependence between the head & neck compared to the lower leg & feet, or the trunk & hands body site groups (p-value < 0.01). One of the possible explanations for this was temperature and vasculature variation in skin at different body sites: the temperature is higher and the vasculature structure is denser at the head and the neck compared to the lower leg or the trunk. The temperature was not measured during the study. So in order to support this hypothesis, typical skin temperatures at the lesion sites were taken from the IR thermal images of healthy skin available in literature. PpIX fluorescence had a positive correlation to temperature. If this hypothesis is true, it will be highly important to PDT treatment. Increasing the temperature could speed up the metabolism and reduce the waiting time before starting the treatment; ambient temperature should be taken into account for daylight PDT; cooling air as pain management should be administered with caution. Potential improvements for wearable PDT light sources were investigated by modelling light transport in skin for the current LED-based Ambulight PDT device, a commercial OLED for future devices and a directional OLED developed in the group. The optical models were implemented in commercial optical software (with intrinsic Monte Carlo ray tracing and Henyey-Greenstein scattering approximation) which was validated on diffuse reflectance and transmittance measurements using in-house made tissue phantoms. The modelling was applied to investigate the benefits from diffusive and forward scattering properties of skin on light transmission in treatment light sources. 1 mm thick skin can only compensate approximately 10% of non-uniform irradiance. It means that uniform illumination is crucial for the treatment light sources. Forward scattering in skin showed a 10% improved light transmission from a collimated emission compared to a wide angle Lambertian emission. However, depth-dependent transmission measurements of directional vs Lambertian emission from organic light emitting films (a nano-imprinted grating was fabricated to provide directional emission in one of the films), collimated vs diffused HeNe laser light through fresh porcine skin did not show the expected improvement. This could be explained by skin roughness which was previously found to change the optical properties and may also affect light coupling. The modelling was applied to guide an optical design of another wearable device – a muscle contraction sensor. Muscle is fibrous and because of that scatters light differently in different directions. The sensor detects the change in backscattered light in parallel and perpendicular directions with respect to muscle fibres. The sensor was implemented on a wearable bandage on fully flexible substrate with flexible OLED and organic photodiodes. The major advantages of organic optoelectronic sensing compared to conventional electromyography (EMG) sensors are the ability to distinguish two types of contractions (isotonic and isometric), insensitivity to electromagnetic interference and the absence of an immune response due to non-invasive electrode-free sensing. Optical modelling was performed to understand the operation of the sensor. A 3D anisotropic optical model of scattering in muscle was created by geometrical manipulations with the standard Henyey-Greenstein scattering volumes. The penetration depth from the Super Yellow OLED was found to be 20-25 mm; the optimal separation between the source and the detector was found to be 20 mm. This distance provided a still detectable signal along with the best discrimination between the two backscatterings. When a 2 mm thick layer of skin and a 2 mm thick layer of adipose tissue were added to the model, the signal was hugely diffused. The discrimination between the two backscatterings decreased by three orders of magnitude, the penetration depth in muscle was reduced, and the intensity of the signal dropped down but was still detectable. With 5 mm thick adipose tissue and 2 mm thick skin the signal was too diffused and interacted with very shallow layers of muscle which approached the limits of the optical sensing of muscle activity.
22
Lošťák, Martin. "Koherencí řízená holografická mikroskopie v opticky rozptylujících prostředích." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-234254.
Full textAbstract:
This thesis deals with imaging through diffuse media in coherence-controlled holographic microscope (CCHM) developed in IPE FME BUT. The mutual coherence function as well as the signal dependence on the lateral mutual shift between both arms of the CCHM are calculated. Both functions are related to each other. The latter dependence is measured experimentally. A principle of imaging with CCHM through diffuse media with both ballistic and diffuse light is explained by a simple geometrical model. This model is then verified experimentally by imaging a sample through diffuse medium. The point spread function (PSF) of CCHM for imaging through diffuse media is then calculated. Results of PSF calculation are proved experimentally.
23
Andreani, Anna. "Conception d’un dispositif de mesure de BSDF pour l’éco-conception de bâtiments." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSET003.
Full textAbstract:
Dans un contexte de raréfaction des énergies primaires, il est nécessaire d’œuvrer pour la réduction des consommations énergétiques liées à l’éclairage dans les bâtiments tout en garantissant que les occupants bénéficient d'un bon confort visuel. La simulation physico-réaliste à l’aide de logiciels de simulation de la lumière constitue un outil d’évaluation de diverses variantes d’un bâtiment. Elle peut être mobilisée au sein d’approches d’optimisation multi-critères dans l’optique du déploiement de systèmes d’aide à la décision ayant vocation à identifier les meilleurs compromis possibles entre consommation énergétique et confort des usagers. Dans la mesure où les propriétés optiques des matériaux constitutifs des bâtiments (opaques, transparents, colorés, isotropes, anisotropes et présentant des textures ou des micro-reliefs) constituent une donnée d’entrée des logiciels de simulation de la lumière, leur caractérisation est un préalable essentiel à la mise en œuvre de cette démarche d'éco-conception des bâtiments. Les propriétés optiques des matériaux sont décrites par le formalisme mathématique de la BSDF (Bidirectional Scattering Distribution Function) et peuvent être intégrées dans la plupart des logiciels de simulation de la lumière sous la forme de modèles analytiques ou sous la forme de mesures tabulées. Les modèles analytiques largement utilisés permettent de caractériser des matériaux optiquement simples mais s’étendent difficilement aux matériaux plus complexes. De plus, aucun dispositif ne permet, à ce jour, de caractériser finement, via des mesures tabulées, toute la diversité des matériaux constitutifs du bâtiment en un temps opérationnel. Aussi, ce travail de thèse a pour objectif de concevoir un dispositif de mesure rapide et précis des caractéristiques optiques de matériaux pour la simulation physico-réaliste de bâtiments. Un premier dispositif de mesure a été conçu et a montré la faisabilité de l’exploitation d’un instrument muni de multicapteurs comme détecteur. Il a permis d’identifier les écueils à éviter ainsi que les obstacles à contourner pour la conception d'un second dispositif de mesure plus opérationnel, aux capacités accrues. S’appuyant sur un instrument muni de multicapteurs et sur un système de positionnement pilotable informatiquement, il permet la mesure des propriétés optiques des matériaux constitutifs du bâtiment dans un contexte opérationnel. Les phases d'acquisition et de traitement des données brutes sont supervisées informatiquement. La durée des mesures se situe entre 5 minutes 40 secondes et 3 heures 2 minutes et 30 secondes. Leur répétabilité moyenne est de 97.88%In a context of increasing scarcity of primary energy, it is necessary to work to reduce energy consumption related to lighting in buildings while ensuring that occupants enjoy good visual comfort. Physical-realistic simulation using light simulation software is a tool for evaluating various variants of a building. It can be used in multi-criteria optimization approaches with a view to deploying decision-support systems designed to identify the best possible trade-offs between energy consumption and user comfort. Insofar as the optical properties of building materials (opaque, transparent, coloured, isotropic, anisotropic and with textures or micro-reliefs) are an input to light simulation software, their characterization is an essential prerequisite for the implementation of this eco-design approach for buildings. The optical properties of materials are described by the mathematical formalism of the BSDF (Bidirectional Scattering Distribution Function) and can be integrated into most light simulation software in the form of analytical models or tabulated measurements. Widely used analytical models can be used to characterize optically simple materials but are difficult to extend to more complex materials. Moreover, no device currently exists that can finely characterise the full range of materials in a building in an operational time frame using tabulated measurements. Therefore, the aim of this thesis work is to design a device for the fast and accurate measurement of the optical characteristics of materials for the physico-realistic simulation of buildings. A first measuring device has been designed and has shown the feasibility of operating an instrument equipped with multi-sensors as a detector. It identified the pitfalls to be avoided as well as the obstacles to be circumvented for the design of a second, more operational measuring device with increased capabilities. Based on an instrument equipped with multi-sensors and a computer-controlled positioning system, it allows the measurement of the optical properties of the building's constituent materials in an operational context. The raw data acquisition and processing phases are supervised by computer. The duration of the measurements ranges from 5 minutes 40 seconds to 3 hours 2 minutes and 30 seconds. Their average repeatability is 97.88%
24
Palla, Martin. "Simulátory solárního záření pro testování solárních článků." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-220120.
Full textAbstract:
The first part deals with an introduction to the basic fundamentals and presentation of theory from the assignment. The fundamentals are presented and described in detail. This part is followed by chapter describing possibilities of using solar energy. The paper presents possibilities of using both direct and diffuse solar radiation. The last chapter of the theoretical part is devoted to the basic description of the IEC 60904 and IEC 60904-9 standards. The practical part presents selected solar simulators and their measurement. Classification class according to IEC 60904-9 is determined from this measurement. The last part of the work is devoted to the construction of a solar simulator composed of LEDs. The simulator is then measured and its class is determined by emitted spectrum.
25
Dresel, Eva. "Development and Characterization of a Light Diffuser for a Concentrating PV Collector." Thesis, Högskolan i Gävle, Avdelningen för bygg- energi- och miljöteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-9873.
Full textAbstract:
Hybrid solar systems as well as concentrating solar collectors are promising solar technologies. To run them efficiently in northern countries is a task Solarus AB is working on.The objective of this MSc project is to investigate and experimentally evaluate the option of implementing a light diffusing sheet in acompound parabolic concentrator (CPC) solar collector, called the “Scania Model”. This component should improve the non-uniform illumination of the photovoltaic cells in concentrating solar collectors.Therefore, scientific publications on this kind of solar collectors were read up on, e.g.Adsten, M. Brogren, M., Roos, A., Karlsson, B. Nilsson, J. and Leutz, R.After researching and procuring possible diffuser materials, experimental tests were carried out and the different materials were reviewed. Implemented in a solar simulator the IV curves of the collector with the different diffusers were generated. Furthermore, the influence of the materials on light was reviewed using daylight, laser light and an artificial light source. In the following, the light intensity distribution on the absorber of the Scania Model was defined and evaluated.The results of this project show that the main problem regarding diffuser material is to provide sufficient diffusion without much transmission losses.
26
Schultz, Ross Dane. "On the characterisation of diffused light and optical elements in high concentrator photovoltaic modules." Thesis, Nelson Mandela Metropolitan University, 2015. http://hdl.handle.net/10948/5170.
Full textAbstract:
High Concentrated Photovoltaics (H-CPV) promise a more efficient, higher power output than traditional photovoltaic modules. This is achieved by concentrating sunlight onto a small triple junction (CTJ) InGaP/InGaAs/Ge cell (ranging from 3.14 mm2 to 1 cm2) by using precision optical systems. These systems utilise non-imaging optics to concentrate and distribute the incident solar flux uniformly onto the CTJ device receiver to achieve maximum performance and power output from an H-CPV module. However, the performance of the device can be reduced due to the partial or complete absorption of a range of wavelengths present in the solar spectrum by the optical materials that are used for concentration. An investigation to determine the current density topographies of each subcell in a CTJ cell by multiple raster scans of an optical fibre receiver of a spectrometer in the plane of the aperture of the secondary’s optical element was conducted. Results showed that the physical properties of the optical elements’ material absorbed different amounts of the spectral content with respect to the subcell photosensitive wavelength regions. The facet properties of the primary optical Fresnel lens showed that the more rounded the Fresnel facets were, the lower the concentration of sunlight incident onto the CTJ cell. The increase in facet numbers showed an increase in scattering of the incident sunlight and chromatic aberrations. Chromatic aberration created by the refractive optics showed a variation in the amount of concentration on each individual subcell as well as the difference in intensity profiles across for the different subcells. Based on these results and the development of new multi-junction devices by industry, the performance of a four and six-junction device with the optical materials was investigated by simulations. The simulations showed that the careful integration of an additional subcell in a multi-junction device could rectify current mismatch between the subcells in the device. Based on the simulations, the best performing multi-junction cell was identified as the four-junction device that showed a cell and module efficiency under operation of 42.5 % and 35.5 %, respectively. Additionally, based on the performance results observed from the H-CPV module, the development of an HCPV module that would attempt to harness the incident tracked diffuse sunlight available to a concentrator photovoltaic (CPV) module for additional energy yield was undertaken. The part of the study comprised of measurements of the solar source, design of a prototype Hybrid High Concentrator Photovoltaic (HH-CPV) module. Results showed that power generation from the H-CPV system was highly dependent on the DNI levels and fluctuates greatly with variation in the DNI. The irradiance levels within the diffuse regions of the H-CPV module showed that the baseplate and vertical sides had an average irradiance range of 140-450 and 50-225 W.m-2, respectively. Irradiance topographic raster scans revealed that the baseplate and vertical sides had a relatively uniform intensity distribution and was identified as favourable sites for diffuse cell population. Simulations of various PV technologies showed the most suitable technology for the placement within the cavity of the HH-CPV module. The developed HH-CPV module was finalized with the utilization of CIS modules to harness the diffuse irradiance. During a 3 month power monitoring of the HH-CPV system, it was determined that the major power generation for the HH-CPV module come from the CPV component, while the CIS modules showed a minor power contribution. The total energy yield for the monitoring period was 45.99, 3.89 and 1.76 kW.h for the CPV, four-vertical sides and baseplate components, respectively. The increase in energy yield of the HH-CPV module when compared to the standard H-CPV module was determined to be 12.35 % for the monitoring period. The incorporation of the CIS modules into the H-CPV module to create the HH-CPV module did increase the energy yield of the module during high DNI conditions and did offset the almost zero power generation during low DNI conditions.
27
Varatharajah, Paramanathan. "Propagation of light beams at the interface separating nonlinear diffusive dielectrics." Diss., The University of Arizona, 1991. http://hdl.handle.net/10150/185543.
Full textAbstract:
Diffusion effects on the stationary TE nonlinear surface waves and guided waves and the beam propagation characteristics at the interface separating two or more nonlinear diffusive Kerr-like media are studied extensively. The shape of the nonlinear surface and guided waves are computed for differing diffusion mechanisms and diffusion lengths. Stability of these waves is determined using the beam propagation method. The power and the shape of the nonlinear surface or guided waves are seen to be sensitive to the scaled diffusion length. However, many features including the stability criteria from the diffusionless case remain in the presence of the diffusion. An equivalent particle theory, describing the propagation of a self-focused light channel at the interface of two nonlinear dielectric media, is extended to include diffusion of the nonlinear excitation within each medium. The theory replaces the computationally intensive beam propagation problem by a much simpler Newtonian dynamical problem of studying the motion of an equivalent particle in an effective potential. This simpler Newtonian dynamical problem provides quantitative information on the asymptotes of the reflected, transmitted or trapped channels as well as the stability of the latter as a function of increasing diffusion length. The main results are that increased diffusion makes light transmission more difficult and tends to wash out the local equilibria of the equivalent potential representing unstable or stable TE nonlinear surface waves. The dynamics of two beams interacting at an interface separating two nonlinear dielectrics is studied. Using the two-soliton solution of the nonlinear Schrodinger equation (NLS) and performing a perturbation analysis, ordinary differential equations (ODE) approximation for the two beam interaction dynamics are derived. The numerical results of the ODE model are verified by comparison with numerical solutions of the governing full partial differential equation (PDE). This ODE model is reduced to a simple form to carry out a useful analysis for a special case where a single beam propagating as a trapped surface wave acts as a power controllable switch to direct a second beam incident at a finite angle to the interface. In this case the shape of the effective potential for the second beam is obtained and predicts the behavior of such a beam using the equivalent particle theory.
28
Das, Arnab. "Development of high-efficiency boron diffused silicon solar cells." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44718.
Full textAbstract:
The objective of the proposed research is to develop low-cost, screen-printed 20% efficient silicon solar cells. In the first part of this thesis, a ~19% efficient, screen-printed cell was fabricated using the commercially-dominant aluminum back surface field (Al-BSF) cell structure. Device modeling was then used to determine that increasing the efficiency to 20% required improvements in both back surface passivation and rear reflectance. In the second part of this thesis, a passivated, transparent boron BSF (B-BSF) structure was proposed as a high-throughput method for realizing these improvements. The first step in fabricating the proposed B-BSF cell involved the successful development of a water-based, spin-on solution of boric acid as a low-cost, non-toxic and non-pyrophoric alternative to common boron diffusion sources such as boron tribromide. A review of the literature shows that a common problem with boron diffusion is severe bulk lifetime degradation, with Fe contamination being commonly speculated as the cause. An experimental study was therefore devised in which the impact of boron diffusion and subsequent cell process steps on the bulk lifetime and bulk iron contamination was tracked. From this study, a model for boron diffusion-induced Fe contamination was developed along with methods for gettering Fe from the substrate. A key achievement of this thesis was the discovery of a novel, negatively charged, aluminum-doped spin-on glass (SOG) which can, in a short thermal step, simultaneously getter Fe and provide stable, high-quality passivation of planar, boron-diffused Si surfaces. Since past attempts at achieving low-cost, high-efficiency, boron-diffused cells have suffered from bulk lifetime degradation and difficulties with passivating a boron-diffused Si surface, the Al-doped SOG provides a solution to both challenges. Since a high rear reflectance is important for achieving high-efficiencies, an experimental study of various reflectors was undertaken and a silver colloid material was found which exhibits both high electrical conductivity and Lambertian reflectance >95%. The work on boric acid diffusion, iron gettering, surface passivation and rear reflectors was successfully integrated into a 20.2% efficient, screen-printed, B-BSF cell fabricated on 300 µm thick, p-type float-zone (FZ) Si wafers. Both device theory and modeling was used to show that, due to its well-passivated surfaces, this cell would suffer a large loss in efficiency due to light-induced degradation (LID) if it were fabricated on commercial p-type Czochralski (Cz) Si substrates. Since n-type Si substrates do not suffer from LID, the p-type process was slightly tweaked and applied to n-type FZ wafers, resulting in 20.3% efficient cells on 190 µm thick wafers. Computer modeling shows that both the p-type and n-type cells can maintain efficiencies of 20% for wafers as thin as 100 µm.
29
Sharp, Richard Paul. "Computational approaches for diffusive light transport finite-elements, grid adaption, and error estimation /." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1154705561.
Full text
30
Khodnevych, Vitalii. "Etudes de lumière diffusée pour le système de métrologie optique LISA." Thesis, Université Côte d'Azur, 2020. https://tel.archives-ouvertes.fr/tel-03177562.
Full textAbstract:
Le Laser Interferometer Space Antenna (LISA) est un observatoire spatial d’ondes gravitationnelles, qui est actuellement en phase A. La détection d’ondes gravitationnelles est effectuée par des mesures interférométriques hétérodynes très précises. Si de la lumière, non prise en compte dans la conception (lumière parasite), se couple aux faisceaux destinés aux mesures interférométriques, alors ces dernières seront faussées. La lumière diffusée se distingue des autres types de lumière parasite (comme la diffraction aux ouvertures, la réflexion ou la transmission parasites) dans le sens où elle résulte d'un profil de rugosité inconnu ou d'une distribution de contamination de poussières: aucune évaluation exacte n'est possible. Cette thèse est consacrée à l'étude de l’impact de la lumière diffusée sur les mesures interférométriques. Lorsqu’une une surface rugueuse est éclairée par un faisceau de lumière monochromatique et cohérente, elle diffuse alors la lumière et cette lumière diffusée prend alors une structure granuleuse, appelée tavelures (speckle en anglais). Cette thèse est consacrée à l'étude de la diffusion de lumière cohérente et à la perturbation des signaux en sortie d'un interféromètre perturbé par de la lumière diffusée. Pour ces études de diffusion de la lumière cohérente, j'ai utilisé deux approches: la modélisation numérique et les mesures expérimentales.J'ai développé un modèle numérique de la diffusion cohérente due à la microrugosité. Il est en accord avec le modèle Harvey-Schack de la fonction de distribution de réflectance bidirectionnelle (BRDF). En outre, il décrit correctement les caractéristiques observées de la diffusion cohérente: amplitude, distribution d'intensité et dimension spatiale d’un grain de speckle.Un autre modèle numérique, que j'ai développé, est utilisé pour décrire la rétrodiffusion cohérente dans les fibres optiques. Le résultat du modèle coïncide avec celui du modèle conventionnel incohérent. De plus, il décrit correctement les caractéristiques de la diffusion cohérente observées sur une expérience réalisée à l'Institut Albert Einstein à Hanovre: distribution d'intensité et dépendance avec la température. Deux montages interférométriques fibrés (à 1.55 µm et 1.06 µm) ont été mis en oeuvre pour des études expérimentales de la diffusion cohérente. Ces études sont motivées par la nécessité d'une description précise des effets de diffusion cohérente dans les montage interférométriques fibrés tels que LISA. Les deux configurations ont montré une réponse de type speckle à l'orientation de la surface de l'échantillon. Un algorithme de traitement du signal a été spécialement développé pour mesurer les faibles valeurs de rétrodiffusion des surfaces optiques. Le plancher de mesure de la configuration 1.06 µm atteint 10-13 en puissance relative, et 10-5 1/sr en BRDF, ce qui correspond à l'état de l'art des diffusomètres.Les mêmes dispositifs expérimentaux ont été utilisés pour étudier la diffusion cohérente due à la contamination. Les résultats des mesures ont été comparés avec la théorie de diffusion de Mie.Par ailleurs, j'ai utilisé des méthodes conventionnelles pour étudier la lumière diffusée due à l'impact des micrométéorites. L'impact sur une surface optique par une micrométéoroïde donne naissance à un type spécifique de lumière parasite propre aux instruments optiques spatiaux. La lumière est diffusée pour deux raisons: le cratère d'impact et la contamination par les ejecta. Je propose une méthode d'estimation de la lumière parasite et l'applique au cas du télescope LISA. J'ai ainsi estimé une limite supérieure à la rétrodiffusion pour des durées de mission nominales (4 ans) et étendues (10 ans).Ce travail apporte un ensemble d'études expérimentales et de modélisations qui améliorent la connaissance des propriétés de la diffusion cohérente de la lumière et de ses conséquences et ses conséquences dans les instruments interférométriques de haute précisionThe Laser Interferometer Space Antenna (LISA) is a space-based gravitational wave observatory now in Phase A. The measurements of the gravitational waves are performed by precise heterodyne interferometric measurements. If any light, which was not intended into the design (stray light), couples to the interfering beams, the measurements will be perturbed. Scattered light differs from other types of stray light (such as diffraction at apertures, stray reflection or transmission) in that it results from an unknown roughness profile or dust contamination distribution: no exact evaluation is possible. The thesis is dedicated to the studies of the consequences of the scattered light on interferometric measurements. When a rough surface is illuminated by a coherent, monochromatic beam of light, a scattering process takes place, and the scattered light shows a grainy structure called speckle. A similar pattern is also observed in the case of scattering from particulate contamination, or due to the irregularities in the structure of optical fibers. This thesis is devoted to the study of the scattering of coherent light, and the perturbation of the readout of an interferometer due to the presence of scattered light. For these studies of coherent light scattering, I use two approaches: numerical modeling and experimental measurements. I have developed a numerical model of coherent scattering due to microroughness. It is in agreement with the Harvey-Schack model of the Bidirectional Reflectance Distribution Function (BRDF). From the other side, it correctly describes the observed features of coherent scattering: amplitude and intensity distribution, the spatial dimension of the single speckle grain. Another numerical model, which I have developed, is used to describe coherent backscattering in optical fibers. The result of the model coincides with the conventional, incoherent model. In addition to this, it correctly describes the features of coherent scattering observed on an experiment made at the Albert Einstein Institut in Hannover: intensity distribution and temperature change rate.Two fibered, homodyne interferometric setups (at 1.55 µm and 1.06 µm) were built for experimental studies of the coherent scattering. These studies' necessity is driven by the need for an accurate description of coherent scattering effects in interferometric setups, such as LISA. Both setups have demonstrated the presence of a speckle type response. A signal processing algorithm was specially developed to measure low backscattering values from the optical surfaces. The measurement floor of the 1.06 µm setup reaches 10-13 in relative power, and 10-5 1/sr in BRDF, which matches modern, state-of-the-art BRDF meters.The same experimental setups were used to study coherent scattering due to contamination. The results of the measurements were compared with the Mie scattering theory. Besides this, I have used conventional methods to study scattered light due to micrometeoroid damage. The impact on an optical surface by a micrometeoroid gives rise to a specific type of stray light inherent only in space optical instruments. This causes a double source of light scattering: the impact crater, and the ejected contamination. I propose a method of stray light estimation and apply it to the case of the LISA telescope. I have estimated upper limits for the backscattering fraction for nominal (4 years) and extended (10 years) mission durations.This work brings an ensemble of experimental and modeling studies that improve the knowledge of the properties of coherently scattered light, and its consequences in high precision interferometric instruments
31
Sharp, Richard Paul Jr. "Computational approaches for diffusive light transport: finite-elements, grid adaption, and error estimation." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1154705561.
Full text
32
Lai, Puxiang. "PHOTOREFRACTIVE CRYSTAL-BASED ACOUSTO-OPTIC IMAGING IN THE NEAR-INFRARED AND ITS APPLICATIONS." Thesis, Boston University, 2010. https://hdl.handle.net/2144/1378.
Full textAbstract:
Acousto-optic (AO) sensing and imaging (AOI) is a dual-wave modality that
combines ultrasound with diffusive light to measure and/or image the optical properties of optically diffusive media, including biological tissues such as breast and brain. The light passing through a focused ultrasound beam undergoes a phase modulation at the ultrasound frequency that is detected using an adaptive interferometer scheme employing a GaAs photorefractive crystal (PRC). The PRC-based AO system operating at 1064 nm is described, along with the underlying theory, validating experiments, characterization, and optimization of this sensing and imaging apparatus. The spatial resolution of AO sensing, which is determined by spatial dimensions of the ultrasound beam or pulse, can be sub-millimeter for megahertz-frequency sound waves.A modified approach for quantifying the optical properties of diffuse media with AO sensing employs the ratio of AO signals generated at two different ultrasound focal pressures. The resulting “pressure contrast signal” (PCS), once calibrated for a particular set of pressure pulses, yields a direct measure of the spatially averaged optical transport attenuation coefficient within the interaction volume between light and sound. This is a significant improvement over current AO sensing methods since it produces a quantitative measure of the optical properties of optically diffuse media without a priori knowledge of the background illumination. It can also be used to generate images based on spatial variations in both optical scattering and absorption.
Finally, the AO sensing system is modified to monitor the irreversible optical changes associated with the tissue heating from high intensity focused ultrasound (HIFU) therapy, providing a powerful method for noninvasively sensing the onset and growth of thermal lesions in soft tissues. A single HIFU transducer is used to simultaneously generate tissue damage and pump the AO interaction. Experimental results performed in excised chicken breast demonstrate that AO sensing can identify the onset and growth of lesion formation in real time and, when used as feedback to guide exposure parameters, results in more predictable lesion formation.Bernard M. Gordon Center for Subsurface and Imaging Systems (CenSSIS) via the NSF ERC award number EEC-9986821.
33
Mujat, Claudia. "MULTIPLE SCATTERING OF LIGHT IN INHOMOGENEOUS MEDIA AND APPLICATIONS." Doctoral diss., University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4455.
Full textAbstract:
Light scattering-based techniques are being developed for non-invasive diagnostics of inhomogeneous media in various fields, such as medicine, biology, and material characterization. However, as most media of interest are highly scattering and have a complex structure, it is difficult to obtain a full analytical solution of the scattering problem without introducing approximations and assumptions about the properties of the system under consideration. Moreover, most of the previous studies deal with idealized scattering situations, rarely encountered in practice. This dissertation provides new analytical, numerical, and experimental solutions to describe subtle effects introduced by the properties of the light sources, and by the boundaries, absorption and morphology of the investigated media. A novel Monte Carlo simulation was developed to describe the statistics of partially coherent beams after propagation through inhomogeneous media. The Monte Carlo approach also enabled us to study the influence of the refractive index contrast on the diffusive processes, to discern between different effects of absorption in multiple scattering, and to support experimental results on inhomogeneous media with complex morphology. A detailed description of chromatic effects in scattering was used to develop new models that explain the spectral dependence of the detected signal in applications such as imaging and diffuse reflectance measurements. The quantitative and non-invasive characterization of inhomogeneous media with complex structures, such as porous membranes, diffusive coatings, and incipient lesions in natural teeth was then demonstrated.Ph.D.
Optics and Photonics
Optics and Photonics;
Optics
34
Dhital, Bishnu Kumar. "Diffused light storage of seed potatoes in the hills of Nepal in relation to seed tuber physiology, production, environment and socio-economics." Thesis, University of Newcastle Upon Tyne, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310169.
Full text
35
Utermann, Sonia Verfasser], Wolfgang [Akademischer Betreuer] Schröter, Stephan [Akademischer Betreuer] [Herminghaus, and Annette [Akademischer Betreuer] Zippelius. "Friction and diffusive light transport in a granular medium / Sonia Utermann. Gutachter: Stephan Herminghaus ; Annette Zippelius. Betreuer: Wolfgang Schröter." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2012. http://d-nb.info/1043606823/34.
Full text
36
Liukaityte, Simona. "Nouvelle métrologie large bande à grande dynamique pour la mesure des flux transmis, réfléchis et diffusés par des filtres optiques à hautes performances." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4351.
Full textAbstract:
De nombreux efforts fournis sur l’avancement de la technologie de dépôt afin de répondre au besoin des utilisateurs des filtres interférentiels ont donné la naissance à la nouvelle génération des composants optiques. Les progrès techniques permettent de fabriquer les filtres avec la structure particulièrement complexe et atteindre les performances spectrales remarquables, mais aussi soulèvent de nouveaux problèmes au niveau de la diffusion. Les indicatrices de diffusion de ces filtres présentent les variations extrêmement rapides en fonction de l’angle de reprise et de la longueur d’onde, ce qui amoindrit sérieusement les performances des composants. Il est donc d’essentiel d’être capable de caractériser la diffusion lumineuse angulairement et spectralement résolue. L’objectif de cette thèse a alors été de développer l’outil expérimental, déduit pour la métrologie fine de la réponse spectrale et de la diffusion lumineuse. Le travail réalisé a donné naissance au banc SALSA (pour Spectral and Angular Light Scattering characterization Apparatus), un nouveau diffusomètre spectralement et angulairement résolu. Grâce au banc SALSA nous pouvons effectuer les mesures de diffusion sur large gamme spectrale [400 nm -1000 nm] avec la dynamique de 8 décades et la précision meilleure que 1%. Par ailleurs, le banc peut être utilisé pour la mesure de la transmission avec la dynamique de 12 décades, ce qui est performance unique sur l’échèle mondialeDue to market demand and technical progresses, a new generation of optical components requires much more sophisticated structures with a great number of layers. These complex structures enable to achieve severe optical performances but, at the same time, enhance light scattering processes. For these reasons, it is essential to develop a metrological tool which provides an accurate quantification of the spectral and angular behavior of scattering losses, with sufficient angular and spectral resolution. In order to face this issue, new investigations were performed during this PhD thesis and led to the development of the new scatterometer SALSA (Spectral and Angular Light Scattering characterization Apparatus). The use of both a broad-band source and a tunable filter allows to accurately select the illumination wavelength and the spectral bandwidth on the whole spectral range of CCD detectivity. Set-up SALSA allows us to perform the measurements of scattering losses on a wide spectral range (400-1000 nm), with high dynamics (>8 decades), high accuracy and low detectivity (a few 10-8 sr-1). Moreover, with set-up SALSA we are able to measure the transmission of interferential filters on the same spectral range, with high accuracy (1%) and a high dynamic (>10 decades, which is a unique performance)
37
Machová, Petra. "Denní osvětlení prostor světlovody." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240303.
Full textAbstract:
This thesis deals with the illuminance space through light guide. It describes it's basic principles, technical features and ways of differentiation between the technologies. The thesis also includes latest methods for evaluation of illumination of space supported by various computer simulations.
38
Kolman, Pavel. "Koherencí řízený holografický mikroskop." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-233906.
Full textAbstract:
ransmitted-light coherence-controlled holographic microscope (CCHM) based on an off-axis achromatic and space-invariant interferometer with a diffractive beamsplitter has been designed, constructed and tested. It is capable to image objects illuminated by light sources of arbitrary degree of temporal and spatial coherence. Off-axis image-plane hologram is recorded and the image complex amplitude (intensity and phase) is reconstructed numerically using fast Fourier transform algorithms. Phase image represents the optical path difference between the object and the reference arms caused by presence of an object. Therefore, it is a quantitative phase contrast image. Intensity image is confocal-like. Optical sectioning effect induced by an extended, spatial incoherent light source is equivalent to a conventional confocal image. CCHM is therefore capable to image objects under a diffusive layer or immersed in a turbid media. Spatial and temporal incoherence of illumination makes the optical sectioning effect stronger compared to a confocal imaging process. Object wave reconstruction from the only one recorded interference pattern ensures high resistance to vibrations and medium or ambience fluctuations. The frame rate is not limited by any component of the optical setup. Only the detector and computer speeds limit the frame rate. CCHM therefore allows observation of rapidly varying phenomena. CCHM makes the ex-post numerical refocusing possible within the coherence volume. Coherence degree of the light source in CCHM can be adapted to the object and to the required image properties. More coherent illumination provides wider range of numerical refocusing. On the other hand, a lower degree of coherence makes the optical sectioning stronger, i.e. the optical sections are thiner, it reduces coherence-noise and it makes it possible to separate the ballistic light. In addition to the ballistic light separation, CCHM enables us to separate the diffused light. Multi-colour-light
39
Castro, Robson Costa de. "Comparação da difusão de fósforo em solos brasileiros para diferentes fertilizantes granulados usando fluorescência de raios X por reflexão total por radiação síncroton (SR-TXRF)." Universidade do Estado do Rio de Janeiro, 2015. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=9481.
Full textAbstract:
O fósforo (P) é um nutriente essencial para o crescimento das plantas. Milhões de toneladas de P são aplicados aos solos anualmente. No entanto, apenas uma pequena fração do
P aplicado com fertilizantes é aproveitada nas lavouras no ano de aplicação, bem como a eficácia do fertilizante fosfatado diminui com o tempo. Para melhorar a nossa compreensão
dos mecanismos, a esta resposta do P no campo, este trabalho visa estudar a migração desse elemento em solos tropicais brasileiros (Latossolo vermelho e Latossolo amarelo) tratados
com três tipos de fertilizantes: fosfato monoamônico (MAP), o polímero revestido de fosfato monoamônio (MAPP) e fosfato organomineral (OMP) em um experimento de placa de Petri.
Fluorescência de Raios X por Reflexão Total (TXRF) foi usada para determinar o fluxo difusivo P a distâncias radiais diferentes (entre 0 e 7,5 mm, entre 7,5 e 13,5 mm, 13,5 e 25,5
mm e entre 25,5 e 43 mm) a partir do grânulo de fertilizante. As análises usando TXRF foram realizadas no Laboratório Nacional de Luz Síncrotron (LNLS), em Campinas, São Paulo, na linha de Fluorescência de Raios X (Beamline D09B). Depois de um período de cinco semanas, a concentração total de P, Ca e Al foram obtidas e comparadas analisando o tipo de solo/textura, o pH e o respectivo extrator de P, que nesse estudo foram usados o Mehlich 1 e água régia. De forma geral, concluiu-se que 80,0 % de fósforo proveniente dos fertilizantes usados nessa proposta ficaram concentrados em distâncias menores que 10 mm do ponto de aplicação dos fertilizantes, independentemente do tipo de solo, do pH e da respectiva textura. Em relação à utilização da técnica TXRF, o sistema foi eficiente, dentre outras características, na discriminação dos picos de fósforo dos picos de enxofre, principalmente nas amostras de solo usadas a partir da extração com Mehlich 1. Destaca-se isso, pois os raios X
característicos desses elementos são muitos próximos.Phosphorus is an essential nutrient for plant growth. Million of tones of P are applied to the soils annually. However, only a small fraction of the P applied with fertilizers is taken up by crops in the year of application, and the effectiveness of any residual P fertilizer declines with time. To improve our understanding of the mechanisms underlying this response to P in the field, this work aims to study the migration of this element in Brazilian tropical soils (red and yellow Oxisol) treated with three types of fertilizers: monoammonium phosphate (MAP), polymer coated monoammonium phosphate (MAPp) and Organomineral phosphate (OMP) in a Petri dish experiment. Total Reflection X-Ray Fluorescence (TXRF) was used to determine the P diffusive flux at different distances (0 - 7.5, 7.5 13.5, 13.5 25.5 and 25.5 43 mm) from granular fertilizer. TXRF analyses were performed at the X-Ray Fluorescence Beamline D09B at Brazilian National Synchrotron Light Laboratory (LNLS), in Campinas, São Paulo. After a period of five weeks, the total concentration of P, Ca and Al were obtained and compared by analyzing the type/soil texture, pH, and the respective extractor P, this study used the Mehlich 1 and aqua regia . In general, it was found that 80.0 % of phosphorus from the fertilizer used in this proposal were concentrated in distances smaller than 10 mm from the point of application of fertilizers , regardless of the soil type , pH, and its texture. Regarding the use of TXRF technique , the system was efficient , among other features , the breakdown of phosphorus peaks of the sulfur peaks , especially in the soil samples used from the extraction with Mehlich 1. It is noteworthy that, as the rays X characteristic of these elements are very close.
40
Fujdiak, Radek. "Analýza a optimalizace datové komunikace pro telemetrické systémy v energetice." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-358408.
Full textAbstract:
Telemetry system, Optimisation, Sensoric networks, Smart Grid, Internet of Things, Sensors, Information security, Cryptography, Cryptography algorithms, Cryptosystem, Confidentiality, Integrity, Authentication, Data freshness, Non-Repudiation.
41
周卓平. "Imaging inhomogeneous penetrable media:electromagnetic inverse scattering and diffuse light imaging techniques." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/04259713504241466819.
Full text
42
Chen, Bo-Ruei, and 陳柏瑞. "The External Light Trapping Using Luminescent Down Shifting Polymer and Diffuse Trench Reflectors." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/28098072395354251628.
Full textAbstract:
碩士國立交通大學
電子研究所
105
External light trapping has been proposed as a choice to replace internal light trapping. To date, the mechanisms of light trapping can be classified into two parts, external and internal. Although the design of internal light trapping can enhance the cell efficiency and JSC, it may affect the electrical diode characteristic of solar cells and structure. On the other hand, the advantage of external light trapping is that the electrical and optical characteristics can be designed separately. Additionally, the degree of enhancement by external light trapping can be much higher than what is achievable by internal ones. In this paper, we present a simple approach for enhancing the efficiency and JSC of amorphous silicon solar cell by diffuse trench reflectors with luminescent down shifting polymer. A >110 % enhancement of the JSC can be observed with proper designs and configurations. The proposed external light trap can be applied to nearly all thin-film solar cell technologies since the external optical components do not affect the electrical diode characteristic of the solar cells. The efficient external light trap is attributed to the high reflectance of the disuse mirror and its wide-angle diffractions, optical confinement due to the trench reflector, and the additional short-wavelength spectral enhancement by the luminescent down shifting mechanism.
43
Chiu, Ching-Wen, and 邱靖雯. "Enhanced light diffuse reflectance of silicon substrate using a micro/nano-scale hybrid structure." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/21207249773704406012.
Full textAbstract:
碩士國立臺灣科技大學
電子工程系
105
There are two parts in the study. One study is about the micro/nano- scale composite structure effected to 6-inch silicon wafer. We used silicon pyramid structure then we sputtering silver film. For the Dewetting phenomenon, it can change the silver morphology to ball-like shape. Due to the tension of silver film and the coefficient of heat expansion difference between substructure and film. By changing annealing temperature, we get different size mask of ball-like silver. Metal assisted electroless chemical etching (MAEE) was used to fabricate hole structures which had advantage for anti-reflection. The benefit of this method is that it can fabricate large area, simple to product, low cost. It is an effective way to reduce reflection and increasing the ability of capturing photons. For the diameter of 100 nm and 100 nm depth hole, the diffuse reflection rate of whole wavelength(250-1100nm) decreasing to 3.3 % however, the carrier lifetime not obviously decreased. The second part of study is about the Indium nanoparticle characteristic of LSPR (Localized Surface Plasmon Resonance). When light interacting to metal, the electric field and magnetic field were periodically changed with time and space. It influence the distribution of electron in metal. The effect cause to the changed of charge density, energy level transition and polarization. The electric field was produces by these effects interact coupling to the electric field induce non by itself showed different optical and electronic phenomenon as scattering, absorption, refraction and dispersion. In this study it help to absorption of ultraviolent wavelength. When the hole diameter of 200 nm and 100 nm depth, deposition 2.5 min indium film then undergo thermal annealing, the diffuse reflection rate decreacing to 1.9 % and total reflection rate decreasing to 2.2% in ultraviolent wavelength(250-400 nm). Theses phenomenon improve the external quantum efficiency and improve the minority carriers lifetime by localized surface electric field. Moreover it can increasing the solar cell device power conversion efficiency.
44
Istfan, Raeef Eric. "Frequency-domain diffuse optical spectroscopy for cardiovascular and respiratory applications." Thesis, 2021. https://hdl.handle.net/2144/42606.
Full textAbstract:
Frequency Domain Diffuse Optical Spectroscopy (FD-DOS) is an emerging optical technique that uses near infrared light to probe the hemodynamics of biological tissue. Compared to more common Continuous Wave (CW) methods, FD-DOS uses light that is temporally modulated on the order of MHz to quantify the absorption and scattering of tissue. FD-DOS can also be used to obtain absolute concentration of tissue chromophores such as oxy- and deoxy-hemoglobin, which allow for quantitative measurements of tissue hemodynamics. This dissertation focuses on the evolution of our lab’s custom digital FD-DOS as a platform for taking optical measurement of biological tissue for respiratory and cardiovascular applications. Several important instrumentation improvements will be reviewed that have enhanced the performance of the system while making it more portable and clinic ready. Two translational applications will be described in detail: 1) the use of high-speed FD-DOS for the non-invasive extraction of venous oxygen saturation (SvO2) and 2) the use of FD-DOS to monitor the hemodynamics of the sternocleidomastoid (SCM) muscle towards the non-invasive monitoring of patients on mechanical ventilation. The custom FD-DOS system parameters were adjusted for each application, with a focus on high speed to extract the cardiac signal for the SvO2 project, and a focus on high SNR to measure the highly absorbing SCM. Measurements on healthy volunteers and rabbits were used to assess the feasibility of using FD-DOS for these applications. Finally, preliminary work was conducted to characterize a miniature FD-DOS source and detector with the goal of moving towards a wearable version of FD-DOS.2022-05-15T00:00:00Z
45
Machado, Miguel Pais. "Visible light communications for drivers assistance systems." Master's thesis, 2018. http://hdl.handle.net/10773/28363.
Full textAbstract:
Motivated by the topic of promoting traffic safety applications and information systems, this work aims to bring a study on VLC outdoor application scenarios. The developed topic is part of intelligent transportation systems (ITS) that aim at the delivery of traffic safety and information amongst other safety functions. VLC technology in traffic communication applications gains interest due to some advantages it presents. The use of LEDs in traffic signaling infrastructures and vehicle headlights started to be a growing standard. With the combination of illuminating proprieties and communication in the same device, VLC becomes a very attractive technology for the implementation of outdoor communication systems for traffic information and control. Outdoor VLC channels present variable ambient conditions, with the presence of different optical sources. One major problem in this communication channel is the presence of shot-noise, generated by optical background radiance from different light sources. This dissertation presents two different communication scenarios for traffic information systems, the first being directed at the infrastructure to car (I2C) link and the second one for car to car (C2C) communication. In order to simulate the communication link performance with variable ambient channel conditions, several models for optical propagation, emitter, receiver and noise sources were implemented in MATLAB. Models for different optical sources were also implemented, with field measurements on the illuminance incident on a photo detector and their impact on the noise generated. In the simulation’s performance of the VLC link, several baseband modulation schemes were considered, aiming at the assessment of link performance, based on the traditional digital modulation performance metrics.Motivado em promover o tópico de segurança rodoviária e sistemas de informação, este trabalho providência um estudo dedicado a sistemas de comunicação por luz visível (VLC) para aplicação em cenários de exterior. O tópico desenvolvido faz parte de sistemas de transporte inteligentes (ITS) cujo propósito é a disseminação de sistemas de segurança no tráfego e transferência de informação, para aplicações de segurança. A tecnologia VLC aplicada a sistemas de comunicação de tráfego rodoviário suscita elevado interesse devido a vantagens que esta apresenta. O uso de LED’s em semáforos e faróis de carros começa a ser bastante comum. Com a combinação de diferentes valências, como iluminação e transferência de dados no mesmo dispositivo, a tecnologia VLC torna-se muito atrativa para a implementação em sistema de comunicação exterior dedicados a sistemas de informação e controlo de tráfego. O canal de comunicação VLC exterior apresenta condições variáveis, devido ao fato de existirem condições ambientais diferentes. Um grave problema neste tipo de canal de comunicação é a presença de ruido Shot, que é normalmente gerado devido á radiância causada por diferentes fontes de luz de fundo. Nesta dissertação estão presentes dois tipos de cenários para sistemas de informação de tráfego, em que o primeiro dedica-se á comunicação semáforo-carro (I2C) e o segundo cenário para a comunicação entre carros (C2C). Para simular o desempenho do canal de comunicação com diferentes condições ambientais, foram implementados em MATLAB modelos para a propagação ótica, descrição do emissor, recetor e fontes de ruido. Também foram incluídos modelos para diferentes fontes óticas de radiação, com medições de campo da iluminância incidente num foto recetor e modulado o impacto na geração de ruido. Nas simulações de desempenho da comunicação por luz visível, foram considerados diferentes esquemas de modulação da informação com o intuito de avaliar o desempenho da ligação, a qual foi feita recorrendo a métricas clássicas de desempenho de modulações digitais.
Mestrado em Engenharia Eletrónica e Telecomunicações
46
Hernandez, Luis Manuel Ortiz. "Deconvolution of light scattering and diffuse reflectance signatures for delineation of mucosal cancer cells using wavelet analysis." Thesis, 2005. http://hdl.handle.net/10125/20548.
Full text
47
Varma, Hari M. "Mathematical And Numerical Studies On The Inverse Problems Associated With Propagation Of Field Correlation Through A Scattering Object." Thesis, 2010. http://etd.iisc.ernet.in/handle/2005/1215.
Full textAbstract:
This thesis discusses the inverse problem associated with the propagation of field autocorrelation of light through a highly scattering object like tissue. In the first part of the thesis we consider the mathematical issues involved in inverting boundary measurements made from diffuse propagation of light through highly scattering objects for their optical and mechanical properties. We present the convergence analysis of the Gauss-Newton algorithm for the recovery of object properties applicable for both diffuse correlation tomography (DCT) and diffuse optical tomography (DOT). En route to this, we establish the existence of solution and Frechet differentiability of the forward propagation equation. The two cases of the delta source and the Gaussian source illuminations are considered separately and the smoothness of solution of the forward equation in these cases is established. Considering DCT as an example, we establish the feasibility of recovering the particle diffusion coefficient (DB ) through minimizing the data-model mismatch of the field autocorrelation at the boundary using the Gauss-Newton algorithm. Some numerical examples validating the theoretical results are also presented. In the second part of the thesis, we reconstruct optical absorption coefficient, µa, and particle diffusion coefficient, DB , from simulated measurements which are integrals of a quantity computed from the measured intensity and intensity autocorrelation g2(τ ) at the boundary. We also recovered the mean square displacement (MSD) distribution of particles in an inhomogeneous object from the sampled g2(τ ) measured on the boundary. From the MSD, we compute the storage and loss moduli distributions in the object. We have devised computationally easy methods to construct the sensitivity matrices which are used in the iterative reconstruction algorithms for recovering these parameters from these measurements. The results of reconstruction of inhomogeneities in µa, DB , MSD and the visco-elastic parameters, which are presented, show forth reasonably good positional and quantitative accuracy. Finally we introduce a self regularized pseudo-dynamic scheme to solve the above inverse problem, which has certain advantages over the usual minimization method employing a variant of the Newton algorithm. The computational difficulties involved in the inversion of ill-conditioned matrices arising in the nonlinear inverse DCT problem are avoided by introducing artificial dynamics and considering the solution to be the steady-state response (if it exists) of the artificially evolving dynamical system, represented by ordinary differential equations (ODE) in pseudo-time. We show that the asymptotic solution obtained through the pseudo-time marching converges to the optimal solution which minimizes a mean-square error functional, provided the Hessian of the forward equation is positive definite in the neighborhood of this optimal solution. The superior noise tolerance and regularization-insensitive nature of pseudo-dynamic strategy are proven through numerical simulations in the context of DCT.
48
Chia-YinChuang and 莊家胤. "Light Extraction Improvement of Flip-Chip Light-Emitting-Diode Using Diffused Nanorod Reflector." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/91842310183103991564.
Full textAbstract:
碩士國立成功大學
微電子工程研究所碩博士班
100
From previous references, the metal reflector and the ZnO nanorod array were useful method to enhance light output power of light-emitting-diodes (LEDs). In this work, the diffused ZnO nanorod reflectors were designed to improve the light extraction of conventional flip-chip light-emitting-diodes (FCLEDs). By depositing the high reflective Al metal on the ZnO nanorod arrays, the diffused ZnO nanorod reflectors were fabricated. As the result of the roughened high reflective Al metal and the light scattering in the low refractive ZnO nanorod array, the light output power and the light distribution of the conventional FCLEDs were improved by using the diffused ZnO nanorod reflectors. Compared with the conventional FCLEDs, the increase percentage of 56.6% of the light output power was enhanced for the FCLEDs with diffused 500-nm-long ZnO nanorod reflector.
49
Lin, Chih-Lung, and 林志龍. "Synthesis of Light Diffusers and Its Optical Properties." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/41274803713321923330.
Full textAbstract:
碩士國立成功大學
化學工程學系碩博士班
93
Uniformly polymer microspheres are prepared by using dispersion polymerization, and then, the microspheres are applied to the light diffuser films of the LCD backlight so to achieve the scattering function of light; hence it is also called the light diffuser. Three types of light diffusers which have narrow particle size distribution, including solid-centred PS diffuser with 1.10 μm, 3.13 μm and 5.21 μm, solid-centred PMMA with 3.84 μm, and porous PS diffuser with 1.10 μm, are successfully synthesized via well controlled reaction condition. Then, the light diffuser films are prepared via coating the mixture which contained various kinds of diffuser and acrylate resins. In addition, the optical properties, including diffusion ratio and total transmittance, corresponding to the diffuser size, amount of diffuser, refractive index and the total surface areas, is examined in this study. The results show that more the diffusers are added, larger the total surface areas are increased, thus, the higher of the light diffusion is. In addition, the light diffusion will increase with the increasing of the differences of refractive index between the matrix and diffuser. However, the total transmittance ratio will oppositely decrease with the light diffusion.
50
Utermann, Sonia. "Friction and diffusive light transport in a granular medium." Doctoral thesis, 2012. http://hdl.handle.net/11858/00-1735-0000-0006-B54C-1.
Full text