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1
Camahort, Gurrea Emilio. "4D light-field modeling and rendering /." Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3023550.
Повний текст джерела
2
Saunders, Michael G. "Electrodynamical Modeling for Light Transport Simulation." Digital Commons @ East Tennessee State University, 2017. https://dc.etsu.edu/honors/373.
Повний текст джерелаАнотація:
Modernity in the computer graphics community is characterized by a burgeoning interest in physically based rendering techniques. That is to say that mathematical reasoning from first principles is widely preferred to ad hoc, approximate reasoning in blind pursuit of photorealism. Thereby, the purpose of our research is to investigate the efficacy of explicit electrodynamical modeling by means of the generalized Jones vector given by Azzam [1] and the generalized Jones matrix given by Ortega-Quijano & Arce-Diego [2] in the context of stochastic light transport simulation for computer graphics. To augment the status quo path tracing framework with such a modeling technique would permit a plethora of complex optical effects—including dispersion, birefringence, dichroism, and thin film interference, and the physical optical elements associated with these effects—to become naturally supported, fully integrated features in physically based rendering software.
3
Evans, Oliver Graham Evans. "Modeling the Light Field in Macroalgae Aquaculture." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1542810712432336.
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4
Philbrick, Robert H. "Modeling of light absorption in solid state imagers /." Online version of thesis, 1990. http://hdl.handle.net/1850/10557.
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5
Ramos, Cristiano Pereira. "Catalytic essays and modeling of light olefin oligomerization." Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/11474.
Повний текст джерелаАнотація:
Mestrado em Engenharia QuímicaNos últimos anos tem-se observado um aumento da procura de diesel, comparativamente com a gasolina. A produção de gasolina aumentou à custa do aparecimento das unidades de FCC. Deparando com este facto, a produção de diesel tem de acompanhar a sua crescente procura, e essa reposta encontra-se precisamente nestas unidades de FCC. Aquando a formação de gasolina nestas unidades, um dos subprodutos gerados em maior quantidade é a corrente de olefinas leves. As olefinas, na presença de um catalisador, e sujeitas a alta pressão e temperatura formam produtos de elevado valor comercial na gama do diesel. Nesta dissertação foi estudada, precisamente, a oligomerização de olefinas leves através de ensaios catalíticos. O processo consiste na combinação no mesmo reator, de um catalisador zeolítico a 200 com uma alimentação de buteno, acompanhado de um caudal de inerte para diluição do reagente. A oligomerização do 1-buteno permite obter produtos na gama diesel C10 a C20. A instalação experimental foi montada no início da dissertação. Antes da sua utilização, sucessivas correcções a nível de fugas, durante vários ciclos de aquecimento, tiveram de ser efectuadas de modo a deixá-la operacional. Foi utilizada para activação do catalisador, calibração do GC e para a realização da oligomerização de 1-buteno. Foi utilizado o catalisador zeolítico H-ZSM-5 comercial (Zeolyst CBV 3024E com uma razão Si/Al=15). Este catalisador devido à sua microporosidade e estrutura permite a ocorrência de selectividade de forma, que favorece a formação de produtos lineares. A instalação foi testada e foram efectuadas experiências a alta pressão (30 bar), tendo sido possível obter produtos na gama do diesel. Estes produtos foram identificados por cromatografia gasosa com um detector FID acoplado. Um modelo de equilíbrio e cinética foi estudado e programado de modo a prever o comportamento da reacção através da variação do tempo adimensional de reacção, pressão, temperatura e da alimentação.
In past years it has been observed an increase demand of diesel compared to gasoline. The production of gasoline has increased significantly after the installation of FCC units. During gasoline production, light olefins are obtained as side product. These light olefins, in the presence of a catalyst and submitted to high temperature and pressure, form high commercial products in diesel range. In this work, 1-butene oligomerization via zeolite catalysis was studied. The process can be conducted in a reactor with an acid catalyst at 200 with 1-butene diluted in nitrogen (feed) to form products in diesel range (C10-C20). The experimental set-up was assembled at the beginning of the thesis. Before use, successive leak tests, consisting of heating-cooling cycles, have been performed to leave the equipment operational. The installation is able to carry out the catalyst activation and 1-butene oligomerization. With respect to the catalyst, commercial H-ZSM-5 (Zeolyst CBV 3024E, Si/Al=15) has been used. This catalyst due its microporosity and its structure provides shape selectivity, which favours the formation of more linear products. The installation was tested and several runs were performed at high pressure (30 bar), which allowed to obtain diesel range products. Their identification was accomplished by gas chromatography with FID detector. The modeling of literature data was studied in order to predict the reaction behaviour for distinct sets of reaction time, pressure, temperature and feed concentration.
6
Camak, Burak. "Modeling On Rayleigh Scattering In Optical Waveguides." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1251675/index.pdf.
Повний текст джерелаАнотація:
In the last few years, interest in polymer optical fibers (POF) has increased because of
their low cost, easy handling and good flexibility even at large diameters. Moreover,
optical cables do not have the problem of electromagnetic interference, which gives, for
instance, the problem of cross-talk in copper telephone cables. In the usage of current
communication and computer systems the yield has gained a big importance and it has
seen from studies that light scattering loss is the only loss, which cannot be eliminated
entirely. Besides, this loss causes its attenuation loss intrinsically and determines the
lower limit of loss in the POF.
In this work, the importance and the dependencies of light scattering were studied, and
calculations were done in order to find more appropriate polymer for using as core
material of POFs. For this aim, a computer program that calculates the light scattering
loss of several amorphous polymers and plots the graph of isotropic scattering loss versus isothermal compressibility and total attenuation loss versus wavelength was
written.
7
Scholz, Ingo. "Reconstruction and modeling of static and dynamic light fields /." Berlin : Logos-Verl, 2008. http://d-nb.info/990755940/04.
Повний текст джерела
8
Biasi, Stefano. "Light propagation in confined photonic structures: modeling and experiments". Doctoral thesis, Università degli studi di Trento, 2020. http://hdl.handle.net/11572/258037.
Повний текст джерелаАнотація:
This thesis explored fundamental concepts of linear optics focusing on the modal interaction within waveguide/microresonator systems. In addition, it investigated a nonlinear process of stimulated degenerate four-wave mixing in a channel waveguide exploiting the analogy between photons and cold boson atoms. The backscattering phenomenon due to the surface wall roughness of a microresonator is addressed by adding to the usual conservative (Hermitian) coupling coefficient, a dissipative (non-Hermitian) term. This allows explaining the experimental measurements of a multimodal microresonator, which exhibits an asymmetrical resonance splitting characterized by a difference in the peak depths of the transmission spectra. It is shown theoretically, numerically and experimentally that the stochastic nature of the roughness along with the inter-modal dissipative coupling could give rise to a different exchange of energy between the co-propagating and the counter-propagating mode. The unbalanced exchange of energy between the two modes with opposite angular momenta can generate a different reflection by swapping the injection of the light between the input and the output ports. This effect lies at the heart of the realization of an unidirectional reflection device and it finds an explanation in the physics of the exceptional points. The realization of an optical setup based on a Mach-Zehnder interferometer, which exploits some particular techniques of data acquisition, allows obtaining a full knowledge of the complex electric field of a propagating mode. In this way, the spectrum of a wedge microresonator vertically coupled to a bus waveguide is explained using analysis methods based on parametric phasors and inverse complex representations. In addition, the energy exchange between the co-propagating and counter-propagating modes is studied from a temporal point of view by extrapolating a simple model based on the Green function. In particular, it is discussed the analytical temporal response of a microring resonator excited through a bus waveguide by an optical rectangular pulse. Here, it is shown theoretically and experimentally, how the temporal response leads to the characterization of the coupling regime simply from the knowledge of the electric field intensity.
In this thesis, the isomorphism between the Schroedinger’s equation and the Helmholtz wave equation is analyzed in the nonlinear case. Considering a bulk nonlinear medium of the Kerr type, the complex amplitude of the optical field is a slowly varying function of space and time, which satisfies a nonlinear Schroedinger equation. The well-known nonlinear optical phenomenon of stimulated degenerate four wave mixing is reformulated in the language of the Bogoliubov theory. This parallelism between photons and cold atoms allows showing that the phase of the signal assumes a peculiar sound-like dispersion under proper assumptions.
9
Biasi, Stefano. "Light propagation in confined photonic structures: modeling and experiments". Doctoral thesis, Università degli studi di Trento, 2020. http://hdl.handle.net/11572/258037.
Повний текст джерелаАнотація:
This thesis explored fundamental concepts of linear optics focusing on the modal interaction within waveguide/microresonator systems. In addition, it investigated a nonlinear process of stimulated degenerate four-wave mixing in a channel waveguide exploiting the analogy between photons and cold boson atoms. The backscattering phenomenon due to the surface wall roughness of a microresonator is addressed by adding to the usual conservative (Hermitian) coupling coefficient, a dissipative (non-Hermitian) term. This allows explaining the experimental measurements of a multimodal microresonator, which exhibits an asymmetrical resonance splitting characterized by a difference in the peak depths of the transmission spectra. It is shown theoretically, numerically and experimentally that the stochastic nature of the roughness along with the inter-modal dissipative coupling could give rise to a different exchange of energy between the co-propagating and the counter-propagating mode. The unbalanced exchange of energy between the two modes with opposite angular momenta can generate a different reflection by swapping the injection of the light between the input and the output ports. This effect lies at the heart of the realization of an unidirectional reflection device and it finds an explanation in the physics of the exceptional points. The realization of an optical setup based on a Mach-Zehnder interferometer, which exploits some particular techniques of data acquisition, allows obtaining a full knowledge of the complex electric field of a propagating mode. In this way, the spectrum of a wedge microresonator vertically coupled to a bus waveguide is explained using analysis methods based on parametric phasors and inverse complex representations. In addition, the energy exchange between the co-propagating and counter-propagating modes is studied from a temporal point of view by extrapolating a simple model based on the Green function. In particular, it is discussed the analytical temporal response of a microring resonator excited through a bus waveguide by an optical rectangular pulse. Here, it is shown theoretically and experimentally, how the temporal response leads to the characterization of the coupling regime simply from the knowledge of the electric field intensity.
In this thesis, the isomorphism between the Schroedinger’s equation and the Helmholtz wave equation is analyzed in the nonlinear case. Considering a bulk nonlinear medium of the Kerr type, the complex amplitude of the optical field is a slowly varying function of space and time, which satisfies a nonlinear Schroedinger equation. The well-known nonlinear optical phenomenon of stimulated degenerate four wave mixing is reformulated in the language of the Bogoliubov theory. This parallelism between photons and cold atoms allows showing that the phase of the signal assumes a peculiar sound-like dispersion under proper assumptions.
10
Friedrich, Franziska [Verfasser], Reinhold [Akademischer Betreuer] Walser, and Wolfgang [Akademischer Betreuer] Elsäßer. "Hybrid coherent light - Modeling light-emitting quantum dot superluminescent diodes / Franziska Friedrich ; Reinhold Walser, Wolfgang Elsäßer." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2019. http://d-nb.info/117991516X/34.
Повний текст джерела
11
Castaneda-Lopez, Luis Carlos. "Kinetic modeling of the hydrotreatment of light cycle oil/diesel." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1061.
Повний текст джерела
12
Mulder, Marisa J. "Numerical modeling of seismic performance of light-frame wood buildings." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/61306.
Повний текст джерелаАнотація:
Light-frame wood structures are the most prevalent construction type in North America, representing over 90% of the residential building stock. Many of these buildings were built prior to the adoption of seismic engineering design practices and thus may be vulnerable in a seismic event. The primary objective of the research is to examine the use of numerical models to predict the seismic behaviour of light-frame wood structures. Models for (i) a full-scale two-storey house, (ii) a full-scale classroom, and (iii) a two-storey school block were created in light-frame wood non-linear analysis packages. The first two models were validated with full-scale shake table tests. The effect of sheathing type, nailing schedule, openings and ground motion characteristics on the seismic behavior of light-frame wood buildings were investigated. A three-dimensional model of a two-storey light-frame timber house with different sheathing configurations was calibrated using non-linear dynamic analysis to the full-scale experimental shake table results. The model of the test structures was able too predict the time-history response of the drift with reasonable accuracy. The contributions of the strength and stiffness from the openings and non-structural sheathing were included in the model. A detailed numerical model (each nail, framing member, hold-down and panel are modeled), as well as a global numerical model was used to predict the seismic behaviour of an additional dynamic shake table testing was also conducted on a full-scale classroom. The effect of openings, sheathing and ground motion duration was further investigated. Finally, the seismic performance of existing structures and the performance of several retrofit options was investigated with the validate modeling techniques using non-linear dynamic analysis of a typical school block built between 1950 – 1960 in Vancouver. The retrofit options met the target performance objectives.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
13
Korbman, Michael. "Modeling light-field-controlled electron motion in atoms and solids." Diss., Ludwig-Maximilians-Universität München, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-159586.
Повний текст джерелаАнотація:
Recent advancements in laser technology are quickly moving the frontiers of research: quantum
dynamics can now be investigated in more detail, on new timescales, with an unprecedented
level of control. These new possibilities offer a new ground for the theoretical study of fundamental processes; at the same time, a proper understanding of phenomena involved is necessary
to explain measurements, and to indicate directions for further experiments. This Thesis deals with the theoretical investigation of particular cases of light-matter interaction, in atoms and in dielectrics. Regimes considered here have just become a subject of intensive investigation: they are acquiring more and more relevance as technological advancements make them experimentally accessible.
In the first part of the Thesis I consider a process as fundamental as the single-photon
ionization of atoms: my modeling will include an ultrashort pulse (full width half maximum
~ 100 as = 10^-16 s) exciting an electron to the continuum, and a strong few-cycle near-infrared
laser field. This configuration is suitable to reproduce recent streaking experiments on atoms. I
developed a numerical tool to simulate these dynamics in three dimensions: the process is quite
elaborate and requires an adequate description of multi-electron atoms. With proper approximations
I was able to calculate photoelectron spectra using just a few dipole matrix elements,
which were obtained with the aid of our external collaborators, from refined atomic structure
calculations. The results of our relatively simple tool are in very good agreement with more
sophisticated numerical calculations. In addition to that, I discuss my contribution to the theoretical support of a fundamental experiment [I]: both simulations and measurements indicate a
delay between two different channel of photoemission in neon. A careful investigation of the limit of validity of approximations employed reveals that the Coulomb-Volkov approximation is
not suitable to describe fine details of the interaction with the laser pulse. I also report on our
analysis of experimental data from angle-resolved attosecond streaking.
The second part of the Thesis is devoted to the investigation of inter-band excitations in
dielectrics; driving this process with a high degree of control is on the edge of current technology.
The ultrafast creation of charge carriers in an insulator is intriguing: dielectric properties of
the medium change drastically, revealing features of the peculiar electron dynamics in such a
situation. I have simulated this process solving the time dependent Schroedinger equation for
a single electron in a one-dimensional lattice and analyzed how the charge Q displaced during
the interaction with the pulse depends on laser parameters. These calculations reproduce to a
good extent the behavior observed in the experiment. Both the theory and the experiment
point out a strong dependence of Q on laser parameters: this promises a high degree of control, and at the same time suggests the possibility of a solid-state device to characterize an optical pulse. I also study in detail the modification occurring in the electric response of the sample to the electric field. The purpose of this analysis is to identify some features directly related to dynamics of newly created charge carriers.
During my investigation of electron dynamics during an excitation process, I have often
faced the difficulty to identify quantities which might resemble eigenstates of the time-dependent
Hamiltonian. Similar field-dressed states would describe the distortion due to the field, of eigenstates of the field-free Hamiltonian. A proper definition of field-dressed states would allow a correct interpretation of the wavefunction in terms of instantaneous excited population, which is otherwise impossible to define.Neueste Fortschritte im Bereich der Lasertechnologie erweitern schnell die Grenzen der Forschung. Quantendynamiken koennen genauer den je untersucht werden, aus kuerzeren Zeitskalen und mit einer hoeheren Kontrollebene. Diese Entwicklung bietet neue Moeglichkeiten, fundamentale Prozesse theoretisch zu untersuchen; darueber hinaus ist ein Verstaendnis der zu Grunde liegenden physikalischen Vorgaenge erforderlich, um Messresultate zu erklaeren und moegliche Richtungen fuer kuenftige Experimente aufzuzeigen. Diese Doktorarbeit befasst sich mit der theoretischen Analyse bestimmter Licht-Materie-Wechselwirkungen in Atomen und Dielektrika. Die im Rahmen dieser Thesis untersuchten Bereiche sind aktuell Thema intensiver Forschung. Dank weiterer technologischer Entwicklungen, die Experimente in diesen Bereichen ausfuehrbar machen, gewinnen sie immer weiter an Relevanz.Neueste Fortschritte im Bereich der Lasertechnologie erweitern schnell die Grenzen der Forschung. Quantendynamiken koennen genauer den je untersucht werden, aus kuerzeren Zeitskalen und mit einer hoeheren Kontrollebene. Diese Entwicklung bietet neue Moeglichkeiten, fundamentale Prozesse theoretisch zu untersuchen; darueber hinaus ist ein Verstaendnis der zu Grunde liegenden physikalischen Vorgaenge erforderlich, um Messresultate zu erklaeren und moegliche Richtungen fuer kuenftige Experimente aufzuzeigen. Diese Doktorarbeit befasst sich mit der theoretischen Analyse bestimmter Licht-Materie-Wechselwirkungen in Atomen und Dielektrika. Die im Rahmen dieser Thesis untersuchten Bereiche sind aktuell Thema intensiver Forschung. Dank weiterer technologischer Entwicklungen, die Experimente in diesen Bereichen ausfuehrbar machen, gewinnen sie immer weiter an Relevanz. Im ersten Teil der Arbeit beschreibe ich den fundamentalen Prozess der atomaren Ionisation durch ein einzelnes Photon. Mein Model enthaelt einen ultrakurzen Lichtpuls mit einer Halbwertsbreite von ~ 100 as = 10^-16 s, der ein Elektron in das Kontinuum anregt, sowie einen starkes Laserfeld im nahen infraroten Spektralbereich mit wenigen Zyklen. Diese Konfiguration erlaubt die Nachbildung von neuesten Streaking Experimenten an Atomen. Ich habe ein numerisches Werkzeug entwickelt, um diese Dynamiken in drei Dimensionen zu simulieren. Der Prozess ist sehr komplex und bedarf einer hinreichenden Beschreibung von Atomen mit mehreren Elektronen. Unter Beruecksichtigung geeigneter Naeherungen war es mir moeglich, Photoelektronenspektren mit Hilfe nur weniger Dipolmatrixelemente zu berechnen, welche in Zusammenarbeit mit unseren externen Kollaborationspartner durch verfeinerte Atomstruktur-Berechnungen bestimmt wurden. Die Ergebnisse unseres verhaeltnismaeßig einfachen Vorgehens stimmen in einem hohen Grad mit fortgeschritteneren numerischen Methoden ueberein. Darueber hinaus diskutiere ich meinen Beitrag zur theoretischen Unterstuetzung eines grundlegenden Experiments. Sowohl Simulationen als auch Messungen weisen auf eine Verzoegerung zwischen zwei Photoemissionskanaelen in Neon hin. Eine sorgfaeltige Pruefung der Gueltigkeit der verwendeten Naeherungen verraet, dass die Coulomb-Volkov Naeherung nicht geeignet ist, um feine Einzelheiten in der Wechselwirkung mit dem Laserpuls zu beschreiben. Außerdem berichte ich ueber unsere Analyse der Messdaten der winkelaufgeloesten Attosekunden Streaking Experimente. Der zweite Teil der Thesis widmet sich der Untersuchung von Interband-Anregungen in Dielektrika. Die kontrollierte Lenkung dieser Ue bergaenge wurde erst mit aktuellster Technologie ermeoglicht. Die ultraschnelle Erzeugung von Ladungstraegern in einem Isolator ist bemerkenswert. Die dielektrischen Eigenschaften aendern sich dramatisch, was Rueckschluesse auf die Elektronendynamik waehrend dieser Anregung zulaesst. Ich habe diesen Prozess durch Loesung der zeitabhaengigen Schroedingergleichung fuer ein einzelnes Elektron in einem eindimensionalen Gitter simuliert und untersucht, wie sich die waehrend des Lichtpulses verlagerte Ladung mit den Laserparametern aendert. Diese Berechnungen reproduzieren in hohem Maße das im Experiment beobachtete Verhalten. Sowohl Theorie als auch Experiment weisen auf eine starke Abhaengigkeit der Ladung von den Laserparametern hin. Dies verspricht ein hohes Maß an Kontrolle und deutet auf eine moegliche Anwendung eines Festkoerperbauelements fuer die Charakterisierung eines optischen Pulses hin. Außerdem untersuche ich detailliert die Modifikationen der elektrischen Antwort des Samples auf ein externes elektrisches Feld. Das Ziel dieser Analyse ist die Identifikation einiger Eigenschaften die direkt mit der Dynamik der erzeugten Ladungstraeger zusammenhaengen. Waehrend der Untersuchung der Elektronendynamiken in einem Anregungsprozeß, stieß ich oft auf die Problematik, Groeßen zu ermitteln, die Eigenzustaenden des zeitabhaengigen Hamilton- Operators aehneln koennten. Aehnliche “Field-dressed States” wuerden die Verzerrung der Eigenzusteande des feldfreien Hamiltonoperators aufgrund des Felds beschreiben. Eine geeignete Definition der Field-dressed States wuerde eine korrekte Interpretation der Wellenfunktion in Abhaengigkeit der instantanen angeregten Besetzung ermoeglichen, welche sich auf anderem Wege nicht bestimmen laesst.
14
Hedberg, Vilhelm. "Evaluation of Hair Modeling, Simulation and Rendering Algorithms for a VFX Hair Modeling System." Thesis, Linköpings universitet, Medie- och Informationsteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-65592.
Повний текст джерелаАнотація:
Creating realistic virtual hair consists of several major areas: creating the geometry, moving the hair strands realistically and rendering the hair. In this thesis, a background survey covering each one of these areas is given. A node-based, procedural hair system is presented, which utilizes the capabilities of modern GPUs. The hair system is implemented as a plugin for Autodesk Maya, and a user interface is developed to allow the user to control the various parameters. A number of nodes are developed to create effects such as clumping, noise and frizz. The proposed system can easily handle a variety of hairstyles, and pre-renders the result in real-time using a local shading model.
15
Li, Shilong. "Probing and modeling of optical resonances in rolled-up structures." Doctoral thesis, Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-159996.
Повний текст джерелаАнотація:
Optical microcavities (OMs) are receiving increasing attention owing to their potential applications ranging from cavity quantum electrodynamics, optical detection to photonic devices. Recently, rolled-up structures have been demonstrated as OMs which have gained considerable attention owing to their excellent customizability. To fully exploit this customizability, asymmetric and topological rolled-up OMs are proposed and investigated in addition to conventional rolled-up OMs in this thesis. By doing so, novel phenomena and applications are demonstrated in OMs.
The fabrication of conventional rolled-up OMs is presented in details. Then, dynamic mode tuning by a near-field probe is performed on a conventional rolled-up OM. Next, mode splitting in rolled-up OMs is investigated. The effect of single nanoparticles on mode splitting in a rolled-up OM is studied. Because of a non-synchronized oscillating shift for different azimuthal split modes induced by a single nanoparticle at different positions, the position of the nanoparticle can be determined on the rolled-up OM. Moreover, asymmetric rolled-up OMs are fabricated for the purpose of introducing coupling between spin and orbital angular momenta (SOC) of light into OMs. Elliptically polarized modes are observed due to the SOC of light. Modes with an elliptical polarization can also be modeled as coupling between the linearly polarized TE and TM mode in asymmetric rolled-up OMs. Furthermore, by adding a helical geometry to rolled-up structures, Berry phase of light is introduced into OMs. A -π Berry phase is generated for light in topological rolled-up OMs so that modes have a half-integer number of wavelengths.
In order to obtain a deeper understanding for existing rolled-up OMs and to develop the new type of rolled-up OMs, complete theoretical models are also presented in this thesis.
16
Nikolaou, Andreas. "Multi-scale modeling of light-limited growth in microalgae production systems." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/39967.
Повний текст джерелаАнотація:
Microalgae are often seen as important candidates for biofuel production. Claimed advantages over conventional oil crops include their fast growth rate and high lipid content as well as an independence from arable land and fresh water. Commercial viability of microalgae-derived biofuel is currently hindered by the high nutrient requirement, the trade-off between growth and lipid accumulation, sub-optimal growth conditions in large-scale culturing systems and difficulties related to the lipid extraction process. This thesis is concerned with the effect that the light conditions have on microalgae growth. The main contributions are related to the development of multi-scale mathematical models that span several orders of magnitude in both time and space and are suitable for predictions of photosynthetic production of microalgae in laboratory as well as industrial scale systems. Advanced mathematical techniques have been used along with state-of-the-art experimental methods in order to accurately represent microalgae cultures. The first three chapters focus on the development and identification of laboratory-scale models, while the last chapter develops a multi-physics modeling framework, where laboratory-scale predictions are extrapolated to industrial scale. More specifically, Chapter 3 presents a model that couples nutrient- and light-limitation, simultaneously accounting for photoacclimation and photoinhibition. This model is able to predict photosynthesis-irradiance (PI) response curves by accounting for different photoacclimation strategies. A self-developed Monte Carlo method has been used to estimate the exact confidence regions of the model parameters. The results show that even though a statistically meaningful coupling between photoacclimation and photoinhibition can be established, the exclusive use of PI curves is insufficient for the estimation of the parameters that describe the fast time-scale photosynthetic processes. Moreover, it is concluded that a quasi steady-state assumption in PI curve modeling may lead to confusing interpretation of the experimental observations. Chapter 4 attempts to resolve the aforementioned issues with the development of a model of chlorophyll fluorescence that couples photosynthetic production, photoinhibition and photoregulation to predict the light-limited photosynthetic operation of microalgae. This model achieves a significant improvement in the utilization of experimental information that is suitable for model identification and enables the quantitative characterization of the state of the reaction centers of photosystem II (PSII) from fluorescence fluxes, giving thereby a detailed description of the photoinhibition dynamics. Moreover, a theoretical connection between fluorescence and PI experimentation is established. In Chapter 5, model-based design of experiments, along with a more advanced description of photoregulation, practically demonstrate the capabilities of the fluorescence model in simultaneously predicting fluorescence fluxes and photosynthesis rate measurements. Additionally, the followed approach leads to the accurate estimation of the parameters representing the fast time-scale photosynthetic processes. Overall, the fluorescence model successfully combines fluorescence, photosynthesis rate and antenna size measurements, enabling thereby the accurate estimation of a large number of parameters. The prediction accuracy of the photosynthesis rate especially, suggests that fluorescence can be used to screen the photosynthetic performance of different microalgae strains as well as predict the photosynthetic productivity of culturing systems. In Chapter 6 the fluorescence model is extended to account for photoacclimation and is integrated with physics models that characterize hydrodynamics and light attenuation in large-scale cultivation systems. More specifically, the hydrodynamic conditions of a raceway pond are characterized in terms of individual cell trajectories using computational fluid dynamics (CFD). Large-scale productivity predictions are then obtained by averaging over all the trajectories. Analysis of the outcomes shows that both mixing and light attenuation affect the photosynthetic productivity in raceway ponds, while photoacclimation and photoinhibition have a significant impact too. The thesis concludes with Chapter 7 where significant contributions and future directions of research are discussed. The focus is on microalgae growth modeling extensions, possible applications of the developed fluorescence models in industrial aquaculture and model-based optimization of light-limited culturing systems.
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Smith, Arlynn W. "Light confinement and hydrodynamic modeling of semiconductor structures by volumetric methods." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/13407.
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Nightingale, James J. N. "AutoLens : automated modeling of a strong lens's light, mass and source." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/38507/.
Повний текст джерелаАнотація:
The intricate analysis of a strong gravitational lens is a complex and computationally demanding problem, requiring the lensed source galaxy's extended light profile to be reconstructed simultaneously with non-linear modeling of the lens galaxy's mass and light. When successful, this analysis gives unrivaled insight into dark matter, cosmology and the most distant Universe. However, such studies remain resigned to small samples, simply due to how long this involved analysis takes. To address this, this thesis presents AutoLens, the first automated framework for comprehensive modeling of a strong gravitational lens's light, mass and source. Reconstruction of the lensed source galaxy uses an adaptive pixel-grid, which is derived in a completely stochastic manner such that a unique pixelization is used for every source reconstruction. This removes biases inherent to pixelized methods associated with the discrete nature of the source-plane. Light profile fitting of the lens galaxy is fully integrated into AutoLens, making it the first method to successfully unify modeling of the lens's light, mass and source into one coherent framework. This allows the method to advocate decomposed mass modeling, which treats separately the lens galaxy's light and dark matter. AutoLens is therefore capable of addressing a diverse range of unique science cases, most notably its ability to determine the central density of a lens galaxy's dark matter halo. These features are incorporated into a fully-automated pipeline, such that the analysis requires no input from the user after an initial setup. This pipeline is tested using a suite of simulated strong lens images which span a variety of source morphologies, lens profiles and lensing geometries. Following the completion of AutoLens's development, the method is ready to analyze the hundreds of archival images of strong gravitational lenses that have been amassed over the past decade, and which are still yet to receive a comprehensive lens analysis. With of order one hundred thousand lenses set to be discovered in the next decade, AutoLens's automated philosophy will be paramount to making analysis of the incoming strong lens samples feasible.
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Psaila-Dombrowski, Maureen J. (Maureen Justine). "Modeling of crack and crevice chemistry in light water reactor environments." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/13997.
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Xu, Jiangtao. "Modeling the physical, optical and biological properties of Chesapeake Bay." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/2185.
Повний текст джерелаАнотація:
Thesis (Ph. D.) -- University of Maryland, College Park, 2005.Thesis research directed by: Marine-Estuarine-Environmental Sciences. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Hollister, Michael A. "Modeling light valve replacements in a training unit : the spare demand process." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1996. http://handle.dtic.mil/100.2/ADA309016.
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De, La Rosa Janie, Pete Roming, and Chris Fryer. "Rapidly Interpreting UV-optical Light Curve Properties Using a “Simple” Modeling Approach." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/627104.
Повний текст джерелаАнотація:
Core-collapse supernovae (CCSNe) have very distinct observational properties that depend on the composition of the progenitor star, the dynamics of the explosion mechanism, and the surrounding stellar wind environment. In recent years, due to the uncertainty behind the type of massive star that evolves into different types of core-collapse events, there has been an increase in core-collapse supernova surveys aiding the advancement of numerical supernova simulations that explore the properties of the star before the explosion. Observationally, the unpredictable nature of these events makes it difficult to identify the type of star from which the CCSNe subtype evolves, but the issue from a theoretical standpoint relies on a gap in our current understanding of the explosion mechanism. The general light curve properties of CCSNe (rise, peak, and decay) by subtype are diverse, but appear to be homogeneous within each subtype, with the exception of Type IIn.. Simplified SN models can be processed quickly in order to explore the properties of the progenitor star along with the explosion mechanism and circumstellar medium. Here, we present a suite of SN light curve models presented using a 1-temperature, homologous outflow light curve code. The SN explosion is modeled from shock breakout through the ultimate uncovering of the nickel core. We are able to rapidly explore the diversity of the SN light curves by studying the effects of various explosion and progenitor star parameters, including ejecta mass, explosion energy, shock temperature, and stellar radii using this "simple" calculation technique. Furthermore, we compare UV and optical modeled light curves to Swift UVOT IIn observations to identify the general initial conditions that enable the difference between SN 2009ip and SN 2011ht light curve properties. Our results indicate that the peak light curve is dominated by the shock temperature and explosion energy, whereas the shape depends on the mass of the ejecta and the explosion energy. Based on this modeling approach, the comparison SN light curves are a product of processes occurring after shock breakout, but before Ni-56 decay. Therefore, the energy from nickel decay does not play a major role in the light curves of these explosions. In general, the diversity between SN 2009ip and SN 2011ht can be explained by the differences in the outer ejecta mass and the explosion energy.
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De, Caluwe Joelle. "Modeling the plant circadian clock: a study of light, photoperiodism, and growth." Doctoral thesis, Universite Libre de Bruxelles, 2017. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/251373.
Повний текст джерелаАнотація:
Le travail présenté dans cette thèse consiste en la création et l'étude des propriétés d'un nouveau modèle computationnel de l'horloge circadienne végétale et de certains processus physiologiques qui en dépendent.L'horloge circadienne est un rythme endogène d'une période d'environ 24 heures que possèdent la plupart des êtres vivants. Il est généré au niveau moléculaire par des boucles de rétroaction transcriptionnelles, traductionnelles et/ou post-traductionnelles. L'horloge permet aux organismes de s'a- dapter à leur environnement. L'horloge des plantes se distingue par un nombre important de composants (gènes et protéines) dont la majorité sont régulés par la lumière.Dans un premier temps, un nouveau modèle computationnel qui combine une structure complexe et hautement interconnectée avec un nombre réduit d'équations et de paramètres est construit. Ce modèle reproduit correctement les profils d'expression des gènes de l'horloge du type sauvage ainsi que les altérations provoquées par une perte de fonction de chacun de ces gènes. Plusieurs extensions modélisant des processus physiologiques dépendant de l'horloge, à savoir la croissance de l'hypocotyle et la régulation de la floraison, sont également testées.Ensuite, la réponse particulièrement complexe de l'horloge végétale à la lumière est explorée en détail afin de déterminer l'utilité de multiples récepteurs lumineux. Pour ce faire, l'entraînement de l'oscillateur par des cycles jour-nuit de durée différente de 24 heures est mesuré et les différents comportements observés (entraînement périodique, quasipériodicité, chaos) sont caractérisés. Les simulations suggèrent que les multiples senseurs lumineux permettent d'allier une grande flexibilité et une résistance aux effets des fluctuations rapides de luminosité, améliorant ainsi l'adaptation des plantes à l'environnement.Enfin, plusieurs hypothèses permettant de rendre compte des différences observées entre l'horloge des racines et celle des feuilles sont explorées, et différents mécanismes de synchronisation entre ces deux oscillateurs sont testés.The circadian clock is an endogenous timekeeper with a period of around 24 hours, found in most living beings, which helps organisms adapt to their environment by anticipating daily and seasonal variations. It originates at the molecular level, from transcriptional-translational feedback loops between a small number of genes.In this thesis, a computational model of the plant circadian oscillator is built based on current knowledge of the underlying genetic network. This network is highly complex and interconnected, but the new model needs only a small number of equations and parameters to accurately predict the expression profiles of the main clock genes in various light conditions, as well as the defects associated with a loss of function in those genes. Clock-regulated processes such as hypocotyl growth and flowering are also reproduced with good accuracy. One of the particularities of the plant clock is a large number of light-sensitive components. A study of the role of those multiple light sensors on the entrainment properties of the clock is presented. It uses the newly built model to subject the clock to a very large range of conditions and generate theoretical light-insensitive mutants. The combination of an intricate oscillator and a multiplicity of light sensors makes the plant clock highly flexible, able to adapt to a wide range of conditions but resistant to the disrupting effects of random fluctuations.Preliminary steps towards a more realistic depiction of the plant clock as multiple interacting oscillators are taken. These include modeling a heterogeneous population by changing parameter values, modifying the model to account for known differences between the clocks of the roots and shoots, and testing possible synchronizing mechanisms between those two organs.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Doudak, Ghasan. "Field determination and modeling of load paths in wood light-frame structures." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100352.
Повний текст джерелаАнотація:
Low-rise buildings, constructed using wood, are vulnerable to extreme wind storms and earthquakes. While several experimental measurements of the environmental loads (mostly wind) on the building envelope have been made at full scale, none of these studies directly linked these external loads with the internal forces and displacements of the structure, as achieved in this research.The thesis presents the experimental and analytical work on two light-frame wooden structures, where one already existed (Forintek shed in Quebec City) and the other (UNB house) was built specifically for the research project on the University of New Brunswick campus in Fredericton. The research goal was to devise and demonstrate methods of identifying load paths in light-frame wood buildings subject to environmental loads. The objectives were also to improve the knowledge on the magnitude of the forces generated by environmental loads on typical low-rise buildings; to measure forces and deformations in test buildings and correlate them with the applied loads; and finally to develop accurate numerical whole-building structural models.
These goals were achieved by carrying out experiments at the element level (studs, sheathings), subsystem level (shear walls) and on the whole-building level (finished and "realistic" light-frame timber buildings). The responses of these buildings to controlled static tests as well as natural environmental loads were observed and compared with a wind tunnel study and with detailed finite element models with good agreement.
Shear walls were tested in isolation and as a part of the whole structure. The tests indicated that neither the strength nor the stiffness decreased by the same magnitude as the wall effective length is reduced. Therefore, the simple concept of effective length, being used presently, is invalid.
For the Forintek shed, the structural monitoring was based on measurements of deformations within a representative segment of the wall and roof surfaces and a matching grid of wall and roof wind pressure taps supplemented with a wind tunnel study at Concordia University. In general, it was shown that the building surroundings had a great effect on the pressure distribution of the surface on the structure and that these effects are cannot always be determined intuitively. Both mean and peak pressure coefficient were measured and they compared well with corresponding values obtained in the wind tunnel tests. In general, the peak pressure coefficients from the full-scale tests were higher than those obtained from the wind-tunnel tests.
The results from controlled static loads on the UNB house indicated that the load was distributed to all walls, and significant load sharing was observed. Mostly, this reflected not only the rigidity of the roof, but also the rigidity of transverse walls. The stiffness of the roof was sufficient to distribute load to walls farthest away from the load application point. Also, the expected vertical paths for load were not observed. It was also found that the internal forces are concentrated near the corners of the building. Under vertical loading on the roof, the load at the roof-to-wall interface was concentrated in a small region of the building plan around the application point. This was not the case at the superstructure-to-foundation interface. The test results also showed that the load was transferred to the transverse walls, even though there were only nominal connection between the wall and the roof trusses.
The results from the analytical modeling showed good agreement with the full-scale test results for shear walls as well as for the whole building. The 3-D model was able to simulate the sharing of racking forces between shear walls, based on experiments reported in the literature. It was also able to reproduce static test results and predict the force measurements obtained from load cells underneath the house structure. In general, the errors in the numerical prediction were small. The model was able to predict the interaction between the roof system and the walls and the interactions amongst walls.
The research relied on the collaboration of several researchers in industry and academia, and was funded by a CRD grant of the Natural Sciences and Engineering Research Council of Canada.
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Ahn, Kyoungho. "Modeling Light Duty Vehicle Emissions Based on Instantaneous Speed and Acceleration Levels." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/28246.
Повний текст джерелаАнотація:
This dissertation develops a framework for modeling vehicle emissions microscopically. In addition, the framework is utilized to develop the VT-Micro model using a number of data sources. Key input variables to the VT-Micro model include instantaneous vehicle speed and acceleration levels. Estimating accurate mobile source emissions is becoming more and more critical as a result of increasing environmental problems in large metropolitan urban areas. Current emission inventory models, such as MOBILE and EMPAC, are designed for developing large scale inventories, but are unable to estimate emissions from specific corridors and intersections. Alternatively, microscopic emission models are capable of assessing the impact of transportation scenarios and performing project-level analyses.
The VT-Micro model was developed using data collected at the Oak Ridge National Laboratory (ORNL) that included fuel consumption and emission rate measurements (CO, HC, and NOx) for five light-duty vehicles (LDVs) and three light-duty trucks (LDTs) as a function of the vehicle's instantaneous speed and acceleration levels. The hybrid regression models predict hot stabilized vehicle fuel consumption and emission rates for LDVs and LDTs. The model is found to be highly accurate compared to the ORNL data with coefficients of determination ranging from 0.92 to 0.99. The study compares fuel consumption and emission results from MOBILE5a, VT-Micro, and CMEM models. The dissertation presents that the proposed VT-Micro model appears to be good enough in terms of absolute light-duty hot stabilized normal vehicle tailpipe emissions. Specifically, the emission estimates were found to be within the 95 percent confidence limits of field data and within the same level of magnitude as the MOBILE5a model estimates. Furthermore, the proposed VT-Micro model was found to reflect differences in drive cycles in a fashion that was consistent with field observations. Specifically, the model accurately captures the increase in emissions for aggressive acceleration drive cycles in comparison with other drive cycles.
The dissertation also presents a framework for developing microscopic emission models. The framework develops emission models by aggregating data using vehicle and operational variables. Specifically, statistical techniques for aggregating vehicles into homogenous categories are utilized as part of the framework. In addition, the framework accounts for temporal lags between vehicle operational variables and vehicle emissions. Finally, the framework is utilized to develop the VT-Micro model version 2.0 utilizing second-by-second chassis dynamometer emission data for a total of 60 light duty vehicles and trucks.
Also, the dissertation introduces a procedure for estimating second-by-second high emitter emissions. This research initially investigates high emitter emission cut-points to verify clear definitions of high emitter vehicles (HEVs) and derives multiplicative factors for newly developed EPA driving cycles. Same model structure with the VT-Micro model is utilized to estimate instantaneous emissions for a total of 36 light duty vehicles and trucks.
Finally, the dissertation develops a microscopic framework for estimating instantaneous vehicle start emissions for LDVs and LDTs. The framework assumes a linear decay in instantaneous start emissions over a 200-second time horizon. The initial vehicle start emission rate is computed based on MOBILE6's soak time function assuming a 200-second decay time interval. The validity of the model was demonstrated using independent trips that involved cold start and hot start impacts with vehicle emissions estimated to within 10 percent of the field data.
The ultimate expansion of this model is its implementation within a microscopic traffic simulation environment in order to evaluate the environmental impacts of alternative ITS and non-ITS strategies. Also, the model can be applied to estimate vehicle emissions using instantaneous GPS speed measurements. Currently, the VT-Micro model has been implemented in the INTEGRATION software for the environmental assessment of operational-level transportation projects.Ph. D.
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Haber, Ludwig Christian. "An investigation into the origin, measurement and application of chemiluminescent light emissions from premixed flames." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/31472.
Повний текст джерелаАнотація:
The chemiluminescent species CH* and OH* are studied in premixed methane combustion to investigate the possible application of their light emissions in gas turbine combustion monitoring systems. The interpretation of integrated and local chemiluminescence measurements are shown to give important qualitative insights into the burning process. The formation path of OH* chemiluminescence is clarified and an accurate chemical kinetic model predicting OH* chemiluminescence emission is developed using GRIMECH 3.0 as a starting point for methane oxidation. CH* chemiluminescence is also modeled but difficulties in obtaining quenching data make the modeling efforts somewhat less successful than that for OH* chemiluminescence. Two combustion models are developed. The first is a semi-empirical model for a Bunsen type flame. The second is a 1-D model for a ceramic honeycomb flat-flame burner using the full chemical kinetics description of the conversion from fuel to products along with a detailed energy equation, accounting for the radiation energy exchange between hot gases and the honeycomb burner ceramic. The results of the modeling calculations show that OH* is superior to CH* chemiluminescence in terms of indicating heat-release rate. The formation of the ratio between CH* and OH* chemiluminescence is shown to be an accurate indicator of equivalence ratio.Master of Science
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Zhu, Qunzhi. "Modeling and Measurements of the Bidirectional Reflectance of Microrough Silicon Surfaces." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5062.
Повний текст джерелаАнотація:
Bidirectional reflectance is a fundamental radiative property of rough surfaces. Knowledge of the bidirectional reflectance is crucial to the emissivity modeling and heat transfer analysis. This thesis concentrates on the modeling and measurements of the bidirectional reflectance for microrough silicon surfaces and on the validity of a hybrid method in the modeling of the bidirectional reflectance for thin-film coated rough surfaces.
The surface topography and the bidirectional reflectance distribution function (BRDF) of the rough side of several silicon wafers have been extensively characterized using an atomic force microscope and a laser scatterometer, respectively. The slope distribution calculated from the surface topographic data deviates from the Gaussian distribution. Both nearly isotropic and strongly anisotropic features are observed in the two-dimensional (2-D) slope distributions and in the measured BRDF for more than one sample. The 2-D slope distribution is used in a geometric-optics based model to predict the BRDF, which agrees reasonably well with the measured values. The side peaks in the slope distribution and the subsidiary peaks in the BRDF for two anisotropic samples are attributed to the formation of {311} planes during chemical etching. The correlation between the 2-D slope distribution and the BRDF has been developed.
A boundary integral method is applied to simulate the bidirectional reflectance of thin-film coatings on rough substrates. The roughness of the substrate is one dimensional for simplification. The result is compared to that from a hybrid method which uses the geometric optics approximation to model the roughness effect and the thin-film optics to consider the interference due to the coating. The effects of the film thickness and the substrate roughness on the validity of the hybrid method have been investigated. The validity regime of the hybrid method is established for silicon dioxide films on silicon substrates in the visible wavelength range.
The proposed method to characterize the microfacet orientation and to predict the BRDF may be applied to other anisotropic or non-Gaussian rough surfaces. The measured BRDF may be used to model the apparent emissivity of silicon wafers to improve the temperature measurement accuracy in semiconductor manufacturing processes. The developed validity regime for the hybrid method can be beneficial to future research related to the modeling for thin-film coated rough surfaces.
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Butaney, Vikas Hari. "Measurements, analysis and modeling of the performance of direct detection receivers with an optical preamplifier." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-11102009-020152/.
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Blasiak, Thomas C. "Modeling holographic grating imaging systems using the angular spectrum propagation method /." Link to online version, 2006. https://ritdml.rit.edu/dspace/handle/1850/2294.
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Li, Zhixia. "Dynamic Dilemma Zone Modeling and Its Protection." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1304021604.
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Hossein, Zavieh Amin. "Optimization and Modeling of electrode structure and composition for novel PEM water electrolyser MEAs." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16329.
Повний текст джерелаАнотація:
Lack of commercial electrocatalysts and membrane electrode assemblies (MEA) which are efficient, durable and reasonably priced for proton exchange membrane water electrolysis was the inspiration of the current project.A reliable, reproducible and optimized membrane electrode assembly preparation protocol for water electrolysis was developed, with emphasis on the oxygen evolution electrode. The MEAs comprised of a Nafion® 115 membrane with commercially available 20 wt% Pt on carbon and in-house synthesized 20 wt% Ir on antimony tin-oxide, manually sprayed onto the membrane using an airbrush, and functioning as the hydrogen and oxygen evolution catalysts, respectively. A current density of 2.1 A/cm2 was obtained at a cell voltage of 1.85 V and 80 °C.In-situ electrochemical characterization such as steady state polarization and cyclic voltametry was performed on the MEAs to be able to predict performance in stationary applications. Effect of loading on cell performance at different cell voltages was studied and 0.8 mgIr/cm2 loaded MEA showed the highest current at 1.85V. Furthermore, cross section and morphology of the catalyst was studied using SEM and TEM. The catalyst layer thickness found to be from 2 to 5 µm for 0.4 to 1.0 mgIr/cm2 loadings.A theoretical one-dimensional model was proposed for current and reaction rate distribution through the catalyst layer. Since the conductivity of the catalyst measured to be higher than Nafion, model shoed at high loadings and potentials (or catalyst layer thicknesses) reaction tends to happen mostly near the membrane while at low loadings and potentials reaction rate is uniform though the layer. In addition, model was compared to experimental data and shown it is reliable for low potentials but it needs some correction for high potential due decrease in specific active area per volume by reducing thickness of the layer and not taking other factors than Tafel polarization into consideration.Introducing accelerated degradation protocol, durability of the catalyst was studied and corrected by subtracting ohmic losses due oxidation and etc. The loss for accelerated degradation found to be 0.3 mV/h. Then structure of the MEA cross-section was investigated using TEM after degradation test so major cause of the loss in performance found to be migration of Iridium nano particles into the membrane
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Smith, Benjamin R. "Inhibitory learning in Hermissenda crassicornis photoreceptors light responses, conductance changes, and computer modeling /." [Bloomington, Ind.] : Indiana University, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3278465.
Повний текст джерелаАнотація:
Thesis (Ph.D.)--Indiana University, Dept. of Neuroscience, 2007.Source: Dissertation Abstracts International, Volume: 68-10, Section: B, page: 6516. Adviser: Joseph Farley. Title from dissertation home page (viewed May 21, 2008).
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Zweigle, Gregary C. "Modeling the spectroscopy of a light collecting molecule coupled to a nanocrystalline semiconductor." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Thesis/Spring2009/g_zweigle_041509.pdf.
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Al, Wahabi Saeed M. H. "Conversion of methanol to light olefins on SAPO-34: kinetic modeling and reactor design." Texas A&M University, 2003. http://hdl.handle.net/1969.1/1579.
Повний текст джерелаАнотація:
In this work, the reaction scheme of the MTO process was written in terms of elementary steps and generated by means of a computer algorithm characterizing the various species by vectors and Boolean relation matrices. The number of rate parameters is very large. To reduce this number the rate parameters related to the steps on the acid sites of the catalyst were modeled in terms of transition state theory and statistical thermodynamics. Use was made of the single event concept to account for the effect of structure of reactant and activated complex on the frequency factor of the rate coefficient of an elementary step. The Evans-Polanyi relation was also utilized to account for the effect of the structure on the change in enthalpy. The structure was determined by means of quantum chemical software.
The number of rate parameters of the complete reaction scheme to be determined from experimental data is thus reduced from 726 to 30. Their values were obtained from the experimental data of Abraha by means of a genetic algorithm involving the Levenberg-Marquardt algorithm and combined with sequential quadratic programming.
The retained model yields an excellent fit of the experimental data. All the parameters satisfy the statistical tests as well as the rules of carbenium ion chemistry. The kinetic model also reproduces the experimental data of Marchi and Froment, also obtained on SAPO-34. Another set of their data was used to introduce the deactivation of the catalyst into the kinetic equations.
This detailed kinetic model was used to investigate the influence of the operating conditions on the product distribution in a multi-bed adiabatic reactor with plug flow. It was further inserted into riser and fluidized bed reactor models to study the conceptual design of an MTO reactor, accounting for the strong exothermicity of the process. Multi-bed adiabatic and fluidized bed technologies show good potential for the industrial process for the conversion of methanol into olefins.
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Berger, Kai [Verfasser], and Marcus [Akademischer Betreuer] Magnor. "Measuring, Modeling, And Verification of Light-Matter Interaction Phenomena / Kai Berger ; Betreuer: Marcus Magnor." Braunschweig : Technische Universität Braunschweig, 2012. http://d-nb.info/1175823171/34.
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Kosiarek, Molly (Molly R. ). "Modeling Pluto's light curve in the near infrared : implications for observation post new horizons." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104599.
Повний текст джерелаАнотація:
Thesis: S.M., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 81-91).
The effects of volatile transport on Pluto's surface on ground-based observations of Pluto's light curve were studied. Due to Pluto's eccentricity of 0.249, obliquity of 123 degrees, and atmosphere, the transfer of volatiles may cause global surface change over the course of Pluto's orbit. Magellan visible and near infrared data were gathered one month before the New Horizons flyby in order to compare ground-based observing with spacecraft data. Furthermore, a model was created in order to predict how volatile transport will affect ground-based observations in the future. The near-infrared data show large scale surface composition as a function of longitude and confirm New Horizons' compositional results. The model determines that the composition of the underlying layer on Pluto's north pole can be determined by monitoring the J - Ks ratio, if the nitrogen ice currently located on the north pole is sublimated due to volatile transport. Therefore, ground based observing can monitor volatile transport and global surface changes can be monitored after the New Horizon's flyby.
by Molly Kosiarek.
S.M.
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Funatomi, Takuya. "Three dimensional shape modeling of human body in various postures by light stripe triangulation." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/59294.
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Ehrenhofer, Adrian, Alice Mieting, Sascha Pfeil, Johannes Mersch, Chokri Cherif, Gerald Gerlach, and Thomas Wallmersperger. "An automatically rainproofing bike helmet through light-sensitive hydrogel meshes: Design, modeling and experiments." SPIE, 2020. https://tud.qucosa.de/id/qucosa%3A74218.
Повний текст джерелаАнотація:
For everyday cycling, one needs to carry rainproof clothing just for the case of unexpected downpours. In the present research, we present a concept for a helmet which is automatically rainproof when the rain starts. When the sun comes out, the helmet is breathable again even before it completely dries up. This functionality is provided by active hydrogel meshes. Hydrogel meshes offer great advantages due to their ability to change the aperture size with swelling and deswelling. In our current work, we present the design and modeling steps for hydrogel-layered active meshes which use (i) swelling and deswelling in hydrated state and (ii) swelling starting from the dry state. The main goal is to close the air openings of a bicycle helmet when rain starts as an automatic rainproofing. This can be achieved through the swelling of the hydrogel pNiPAAM-co-chlorophyllin in the meshes, which leads to closing when hydrated. At the same time, the light-sensitive behavior leads to opening of the apertures under direct sun exposure, i.e. when the sun appears again after the rain. We present the steps of modeling and design using the Normalized Extended Temperature-Expansion-Model (NETEM) to perform simulations in Abaqus. The model is capable of describing both the swelling of the hydrogel under light stimulus and the volume change due to hydration. It is based on the analogy between free swelling and thermal expansion and defined for nonlinear displacements. We also discuss the fabrication process of hydrogel-layered fibers and challenges in their application and simulation. As a proof of concept for hydrogel-layered meshes, we show preliminary experimental results of a poly(acrylamide)/poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAAm/PAMPS) hydrogel with semi-interpenetrated network (SIPN) structure and its swelling capacities on a mesh. Starting from the active hydrogel meshes as presented in the current work, the next step can be smart textiles that harness the power of hydrogels: the adaptation to combinations of stimuli - like humidity, temperature and brightness - that define environments.
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Choi, Tayoung Gabriel. "Modeling, Sizing and Control of Plug-in Light Duty Fuel Cell Hybrid Electric Vehicle." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1230712944.
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Lin, Tsui-Hsun. "Birefringence, Anisotropic Shrinkage and Luminance in Injection Molded Light-Guide Plate: Modeling and Experiment." Akron, OH : University of Akron, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1232005891.
Повний текст джерелаАнотація:
Dissertation (Ph. D.)--University of Akron, Dept. of Polymer Engineering, 2009."May, 2009." Title from electronic dissertation title page (viewed 11/27/2009) Advisor, Avraam I. Isayev; Committee members, James L. White, Thein Kyu, Kevin Kreider, Shi-Qing Wang; Department Chair, Sadhan C. Jana; Dean of the College, Stephen Cheng; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
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Habtemichael, Yishak Tekleab. "Packaging designs for ultraviolet light emitting diodes." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45764.
Повний текст джерелаАнотація:
Aluminum Gallium Nitride (AlGaN) / Gallium Nitride (GaN) based deep ultraviolet (DUV) light emitting didoes (LEDs) with emission wavelengths between 200-280 nm enable key emerging technologies such as water/air purification and sterilization, covert communications and portable bio-agent detection/identification systems for homeland security, and surface and medical device sterilization. These devices produce a large amount of undesired heat due to low quantum efficiencies in converting electrical input to optical output. These low efficiencies are attributed to difficulties in the growth&doping of AlₓGa₁₋ₓN materials and UV absorbing substrates leading to excessive joule heating, which leads to device degradation and a spectral shift in the emission wavelength. With this regard, effective thermal management in these devices depends on the removal of this heat and reduction of the junction temperature. This is achieved by decreasing the package thermal resistance from junction-to-air with cost-effective solutions. The use of heat sinks, thermal interface materials, and high conductivity heat spreaders is instrumental in the reduction of the overall junction-to-air thermal resistance.
This thesis work focuses on thermal modeling of flip-chip packaged deep UV LEDs to gain a better understanding of the heat propagation through these devices as well as the package parameters that have the biggest contributions to reducing the overall thermal resistance. A parametric study focusing on components of a lead frame package is presented to ascertain the thermal impacts of various package layers including contact metallizations, thermal spreading sub-mounts, and thermal interface materials. In addition the use of alternative thermal interface materials such as phase change materials and liquid metals is investigated experimentally.
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Chen, Guang. "Modeling of the optical properties of nonspherical particles in the atmosphere." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1418.
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Atiker, Selen. "Investigation Of Light Attenuation In Lake Eymir." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614047/index.pdf.
Повний текст джерелаАнотація:
ABSTRACT
INVESTIGATION OF LIGHT ATTENUATION IN LAKE EYMIR
Selen ATIKER
M.Sc, Department of Environmental Engineering
Supervisor: Assoc. Prof. Dr. Aysegül Aksoy Co-Supervisor: Assoc. Prof. Dr. Selim Sanin January 2012, 164 pages. Light penetration and attenuation has significant impact on the water quality of lakes. Algal activity, which is important for the levels of several water quality parameters, is dependent on light penetration besides availability of nutrients. In this study, change in light penetration and attenuation in Lake Eymir was studied. The relationships of extinction coefficient (ke), and water quality parameters were investigated. The effect of ke on Chl-a over nutrients were investigated. The water quality parameters measured were
total suspended solid (TSS), phosphate, ammonium, nitrate, photosynthetically active radiation (PAR), chlorophyll-a (Chl-a), Secchi disk depth and lake Depth. The measurements were conducted at five different stations in Lake Eymir. Secchi disk, PAR and lake depth measurements were done on site, while TSS, Chl-a and phosphate analyses were done in laboratory, using standard methods. Nitrate and ammonium analyses were conducted through laboratory kits. Linear and non-linear regression models of ke and Chl-a were developed to understand their relationships with the the measured parameters, using XLSTAT software. Analyses of the data at sampling stations revealed that Station 2 and 3 were the most representative stations in general. The model results indicated that ke is as important as nutrients for Chl-a abundance. Secchi disk and Chl-a are the most correlated parameters with ke. Moreover Secchi disk depth is nonlinearly correlated with ke, while linearly correlation is present between Chl-a and ke. &emsp
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Ma, Cheng. "Modeling and Signal Processing of Low-Finesse Fabry-Perot Interferometric Fiber Optic Sensors." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/77225.
Повний текст джерелаАнотація:
This dissertation addresses several theoretical issues in low-finesse fiber optic Fabry-Perot Interferometric (FPI) sensors. The work is divided into two levels: modeling of the sensors, and signal processing based on White-Light-Interferometry (WLI).
In the first chapter, the technical background of the low-finesse FPI sensor is briefly reviewed and the problems to be solved are highlighted.
A model for low finesse Extrinsic FPI (EFPI) is developed in Chapter 2. The theory is experimentally proven using both single-mode and multimode fiber based EFPIs. The fringe visibility and the additional phase in the spectrum are found to be strongly influenced by the optical path difference (OPD), the output spatial power distribution and the working wavelength; however they are not directly related to the light coherence.
In Chapter 3, the Single-Multi-Single-mode Intrinsic FPI (SMS-IFPI) is theoretically and experimentally studied. Reflectivity, cavity refocusing, and the additional phase in the sensor spectrum are modeled. The multiplexing capacity of the sensor is dramatically increased by promoting light refocusing. Similar to EFPIs, wave-front distortion generates an additional phase in the interference spectrogram. The resultant non-constant phase plays an important role in causing abrupt jumps in the demodulated OPD.
WLI-based signal processing of the low-finesse FP sensor is studied in Chapter 4. The lower bounds of the OPD estimation are calculated, the bounds are applied to evaluate OPD demodulation algorithms. Two types of algorithms (TYPE I & II) are studied and compared. The TYPE I estimations suffice if the requirement for resolution is relatively low. TYPE II estimation has dramatically reduced error, however, at the expense of potential demodulation jumps. If the additional phase is reliably dependent on OPD, it can be calibrated to minimize the occurrence of such jumps.
In Chapter 5, the work is summarized and suggestions for future studies are given.Ph. D.
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Elmaklizi, Ahmed [Verfasser]. "Modeling the propagation, scanning and optimization of focused light beams in scattering media / Ahmed Elmaklizi." Ulm : Universität Ulm. Fakultät für Ingenieurwissenschaften und Informatik, 2015. http://d-nb.info/1080562923/34.
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Ferguson, Matthew Lee. "A biophysical study of clathrin utilizing light scattering, neutron scattering and structure based computer modeling." College Park, Md. : University of Maryland, 2007. http://hdl.handle.net/1903/6787.
Повний текст джерелаАнотація:
Thesis (Ph. D.) -- University of Maryland, College Park, 2007.Thesis research directed by: Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Korbman, Michael [Verfasser], and Ferencz [Akademischer Betreuer] Krausz. "Modeling light-field-controlled electron motion in atoms and solids / Michael Korbman. Betreuer: Ferencz Krausz." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2012. http://d-nb.info/1041584105/34.
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Pathak, Rakesh. "Development of Finite Element Modeling Mesh Generation and Analysis Software for Light Wood Frame Houses." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/40816.
Повний текст джерелаАнотація:
This thesis presents the development of an automatic mesh generator, named WoodFrameMesh, using object oriented C++. The program developed is capable of generating complete finite element models of wooden houses incorporating frames, linear links, springs, nodal loads and restraints at the desired locations. The finite element mesh generated by the program may be triangular or quadrilateral. The triangular mesh can be generated over any arbitrary domain with multiple openings and line constraints. The program implements the advancing front method for triangulation as discussed by Lee and Hobbs. The difference is made by implementing the algorithm using object oriented concepts and the extensive use of the powerful C++ Standard Template Library (STL). Quadrilateral mesh generation is limited to simple quadrilateral domains with no openings or constraint lines. A simple structured technique is implemented to generate the quadrilateral mesh. The amount of time spent in manual generation of the complete finite element model of wooden houses has been considerably reduced by automating the modeling process. Overall, the use of object oriented design has facilitated the code development and has provided a platform for further additions. The program relies on the use of STL as it provides dynamic data structures, algorithms for storage, searching, sorting, etc. Efficiency of the program is improved by the use of the in-built features in STL instead of developing new code.
Analysis of the finite element models generated by the automatic mesh generator is performed using SAP 2000 and WoodFrameSolver. WoodFrameSolver is a finite element analysis engine for WoodFrameMesh, which was developed at Virginia Tech by a group of graduate students (including the author) and professors as a separate project. A chapter discussing the WoodFrameSolver architecture, its extensibility features and its verification is also presented in this thesis. The solver performance and accuracy are similar to those of SAP 2000, which was chosen as the benchmark for testing the analysis results.Master of Science
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BANDI, DILIP KUMAR. "Small Signal Impedance and Optical Modulation Bandwidth Characterization and Modeling of Organic Light Emitting Devices." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1204912125.
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Fu, Xin. "Characterizing, modeling and mitigating microarchitecture vulnerability and variability in light of small-scale processing technology." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0024945.
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