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Iyun, Oluwatope Ebenezer. "Plant-wide diagnosis : cause-and-effect analysis using process connectivity and directionality information." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9296.
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Production plants used in modern process industry must produce products that meet stringent environmental, quality and profitability constraints. In such integrated plants, non-linearity and strong process dynamic interactions among process units complicate root-cause diagnosis of plant-wide disturbances because disturbances may propagate to units at some distance away from the primary source of the upset. Similarly, implemented advanced process control strategies, backup and recovery systems, use of recycle streams and heat integration may hamper detection and diagnostic efforts. It is important to track down the root-cause of a plant-wide disturbance because once corrective action is taken at the source, secondary propagated effects can be quickly eliminated with minimum effort and reduced down time with the resultant positive impact on process efficiency, productivity and profitability. In order to diagnose the root-cause of disturbances that manifest plant-wide, it is crucial to incorporate and utilize knowledge about the overall process topology or interrelated physical structure of the plant, such as is contained in Piping and Instrumentation Diagrams (P&IDs). Traditionally, process control engineers have intuitively referred to the physical structure of the plant by visual inspection and manual tracing of fault propagation paths within the process structures, such as the process drawings on printed P&IDs, in order to make logical conclusions based on the results from data-driven analysis. This manual approach, however, is prone to various sources of errors and can quickly become complicated in real processes. The aim of this thesis, therefore, is to establish innovative techniques for the electronic capture and manipulation of process schematic information from large plants such as refineries in order to provide an automated means of diagnosing plant-wide performance problems. This report also describes the design and implementation of a computer application program that integrates: (i) process connectivity and directionality information from intelligent P&IDs (ii) results from data-driven cause-and-effect analysis of process measurements and (iii) process know-how to aid process control engineers and plant operators gain process insight. This work explored process intelligent P&IDs, created with AVEVA® P&ID, a Computer Aided Design (CAD) tool, and exported as an ISO 15926 compliant platform and vendor independent text-based XML description of the plant. The XML output was processed by a software tool developed in Microsoft® .NET environment in this research project to computationally generate connectivity matrix that shows plant items and their connections. The connectivity matrix produced can be exported to Excel® spreadsheet application as a basis for other application and has served as precursor to other research work. The final version of the developed software tool links statistical results of cause-and-effect analysis of process data with the connectivity matrix to simplify and gain insights into the cause and effect analysis using the connectivity information. Process knowhow and understanding is incorporated to generate logical conclusions. The thesis presents a case study in an atmospheric crude heating unit as an illustrative example to drive home key concepts and also describes an industrial case study involving refinery operations. In the industrial case study, in addition to confirming the root-cause candidate, the developed software tool was set the task to determine the physical sequence of fault propagation path within the plant. This was then compared with the hypothesis about disturbance propagation sequence generated by pure data-driven method. The results show a high degree of overlap which helps to validate statistical data-driven technique and easily identify any spurious results from the data-driven multivariable analysis. This significantly increase control engineers confidence in data-driven method being used for root-cause diagnosis. The thesis concludes with a discussion of the approach and presents ideas for further development of the methods.
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Martineau, Eugénie. "Linking single cell directionality to dynamic multicellular transitions in Myxococcus xanthus : a multiscale analysis." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0089.
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La δ-proteobactérie Myxococcus xanthus est étudiée depuis des décennies pour sa capacité à s’auto-organiser en réponse à des stimuli environnementaux. Cette bactérie colonise des niches écologiques favorables grâce à sa capacité à se mouvoir sur des surfaces. Cette motilité lui permet d’avoir un comportement prédateur envers des organismes proies, alors qu’en absence de nutriments, elle met en place un processus développemental permettant la formation de corps fructifères contenant des myxospores résistant aux stress environnementaux. Tous ces comportements multicellulaires requièrent un contrôle dynamique de la polarité de la cellule, établi par trois protéines polaires : MglA, MglB et RomR. Ensemble, elles définissent la direction de la cellule, qui peut être rapidement inversée sous l’action du système chimiotactique Frz (réversion). Dans ce travail de thèse, à travers une approche expérimentale et computationnelle, nous avons mis en évidence que le système de régulation forme un nouveau type d’oscillateur protéique, contrôlé par deux protéines RomR et FrzX, qui agissent ensemble et de manière complémentaire pour déclencher la réversion à l’arrière des cellules. L’architecture unique de ce système permet une réponse très large à différents stimuli, essentielle pour de nombreux comportements multicellulaires. Afin de comprendre l’importance de ces transitions, nous avons mis au point un outil à haute résolution spatiale et temporelle afin de connecter les cellules individuelles aux comportements multicellulaires, et ainsi comprendre le rôle du système Frz dans un modèle multicellulaire de prédation<br>The δ-proteobacteria Myxococcus xanthus has been a model of study for decades for its self-organized behavior as a response of environmental stimuli. It colonizes favorable ecological niches by using surface motility. In particular, this motility allows M.xanthus to predate collectively over prey microorganisms, while under starvation they start a developmental process to form macroscopic fruiting bodies, filled with environmental resistant myxospores. All these multicellular behaviors require a dynamic control of the cell polarity established by the polarity proteins MglA, MglB and RomR. Together, they define the direction of movement of the cell, which can be rapidly inverted by the Frz chemosensory system (reversion). In this thesis work, through combined computational/experimental approaches, we highlight that the regulation system forms a new type of biochemical oscillator, controlled by two proteins RomR and FrzX, which act together through complementary action to trigger the reversion at the lagging pole. The unique architecture of this system allows a wide response to various stimuli, which could be very beneficial for collective cell behaviors. To understand the importance of these transitions, we have developed a new high-resolution single cell assay linking single cMARTINEAU EUGENIE 2018AIXM0089/016ED62 2018/03/21 62 SCES SCHell behaviors to multicellular structures at unprecedented spatial and temporal resolutions. This way, we have investigated the role of the newly identified biochemical oscillator in the multicellular model of predation
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Parsa, Amanullah. "EFFECT OF BUILDING ORIENTATION ON STRUCTURAL RESPONSE OF REINFORCED CONCRETE MOMENT RESISTING FRAME STRUCTURES." OpenSIUC, 2020. https://opensiuc.lib.siu.edu/theses/2698.
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In time history analysis of structures, the geometric mean of two orthogonal horizontal components of ground motion in the as-recorded direction of sensors, have been used as measure of ground motion intensity prior to the 2009 NEHRP provision. The 2009 NEHRP Provisions and accordingly the seismic design provisions of the ASCE/SEI 7-10, modified the definition of ground motion intensity measure from geometric mean to the maximum direction ground motion, corresponding to the direction that results in peak response of the oscillator. Maximum direction response spectra are assumed to envelope the range of maximum possible responses over all nonredundant rotation angles. Two assumptions are made in the use maximum ground motion as the intensity measure: (1) the structure’s strength and stiffness properties are identical in all directions and (2) azimuth of the maximum spectral acceleration coincides with the one of the principal axes of the structure. The implications of these assumptions are examined in this study, using 3D computer models of multi-story structures having symmetric and asymmetric layouts and elastic vibration period of 0.2 second and 1.0 second subjected to a set of 25 ground-motion pairs recorded at a distance of more than 20 km from the fault. The influence of the ground-motion rotation angle on structural response (here lateral displacement and story drift) is examined to form benchmarks for evaluating the use of the maximum direction (MD) ground motions. The results of this study suggest that while MD ground motions do not always result in largest structural response, they tend to produce larger response than the as-recorded ground motions. On the other hand, more research on non-linear seismic time history analysis is recommended, especially for asymmetric layout plan buildings.
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Henebry, Michael Lee. "Biological and Ecological Trait Associations and Analysis of Spatial and Intraspecific Variation in Fish Traits." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/33894.
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Traits provide an informative approach to examine species-environment interactions. Often, species-by-species approaches are inefficient to generate generalizable ecological relationships and do not predict species responses to environmental changes based on specific traits species possess. Multiple lines of inquiry and multi-scale approaches are best for assessing environment-trait responses. This thesis examines important questions not specifically addressed before in traits-based research. Chapter one explores biological and ecological trait associations incorporating ontogenetic diet shifts for New River fishes. Niche shift analysis as a chapter one sub-objective quantitatively support where species-specific diet shifts likely occur. Strong biological-ecological trait associations, some intuitive and others not so intuitive, were found that relate biological structure to ecological function. Improved understanding of trait associations, including what factors influence others, supports inference of ecology of fishes. Chapters two and three examine spatial and intraspecific trait variability. Chapter two specifically examines large-scale life history trait variability along latitudinal gradients for twelve widely distributed fish species, including directionality of trait variation, and hypothesizing how optimal traits change with large-scale environmental factors. Strong positive and negative patterns found include average total length of newly hatched larvae, average total length at maturation, average spawning temperature, average egg diameter, and maximum length. These five traits are correlated with other adaptive attributes (i.e. growth rate, reproductive output, and longevity/population turnover rate). In contrast to latitudinal scale, Chapter three examines trait variability of white sucker (Catostomus commersonii) and fantail darter (Etheostoma flabellare) as a function of small-watershed scale spatial factors and anthropogenic disturbance. Toms Creek and Chestnut Creek white sucker and fantail darter displayed positive response to disturbance, contrary to past studies. Lower resource competition, and / or competitive exclusion of fishes with similar niche requirements are possible mechanisms. All three objectives support understanding of trait association and variability as a useful foundation in ecological applications and for formulating plans for conservation and management of species.<br>Master of Science
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Appel, Jan Kristoffer [Verfasser]. "Particle Flux Directionality and other Aspects of the Martian Radiation Environment: An Analysis of MSL/RAD Observation Data and Simulation Data / Jan Kristoffer Appel." Kiel : Universitätsbibliothek Kiel, 2019. http://d-nb.info/1176518895/34.
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Plišková, Diana. "Analýza směrovosti neuritů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442501.
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Práca je zameraná na navrhnutie vhodnej metódy analýzy smerovosti neuritov. Využité boli snímky neurónov z fluorescenčnej mikroskopie. Pred samotnou segmentáciou bolo potrebné snímky predspracovať, pričom sa postupne využila úprava kontrastu, ostrenie a adaptívna filtrácia pomocou Weinerovského filtru. Jednotlivé návrhy metód segmentácie pozostávali z prostého prahovania, narastaním oblastí a využitím morfologických operácií. Následná analýza smerovosti využívala smer gradientov v obraze. Navrhnutá metóda bola využitá aj ako klasifikátor, ktorý dokázal rozdeliť jednotlivé snímky do skupín podľa smeru rastu.
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Jeong, Sang Min. "Analysis of Vibration of 2-D Periodic Cellular Structures." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7122.
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The vibration of and wave propagation in periodic cellular structures
are analyzed. Cellular structures exhibit a number of desirable
multifunctional properties, which make them attractive in a variety of
engineering applications. These include ultra-light structures, thermal
and acoustic insulators, and impact amelioration systems, among others.
Cellular structures with deterministic architecture can be considered
as example of periodic structures. Periodic structures feature unique
wave propagation characteristics, whereby elastic waves propagate only
in specific frequency bands, known as "pass band", while they are
attenuated in all other frequency bands, known as "stop bands". Such
dynamic properties are here exploited to provide cellular structures
with the capability of behaving as directional, pass-band mechanical
filters, thus complementing their well documented multifunctional
characteristics.
This work presents a methodology for the analysis of the dynamic
behavior of periodic cellular structures, which allows the evaluation
of location and spectral width of propagation and attenuation regions.
The filtering characteristics are tested and demonstrated for
structures of various geometry and topology, including cylindrical
grid-like structures, Kagom and eacute; and tetrhedral truss core lattices.
Experimental investigations is done on a 2-D lattice manufactured out
of aluminum. The complete wave field of the specimen at various
frequencies is measured using a Scanning Laser Doppler Vibrometer
(SLDV). Experimental results show good agreement with the methodology
and computational tools developed in this work. The results demonstrate
how wave propagation characteristics are defined by cell geometry and
configuration. Numerical and experimental results show the potential of
periodic cellular structures as mechanical filters and/or isolators of
vibrations.
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Vecchi, Pierpaolo. "Defect analysis in directionally solidified multicrystalline silicon." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21177/.
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This project studies how the microstructure and metallic impurities affect the electrical properties of mc-Si wafers, to improve the efficiency and the production yield of photovoltaic solar cells.
Dislocations and impurities in silicon are recombination centres that reduce free carrier lifetime and thus efficiency of solar cells. The quality of the material can be improved by finding optimal growth conditions and a threshold value for the contamination that does not compromise the device efficiency.
Two sets of p-type mc-Si wafers located at different heights and lateral positions of two directionally solidified ingots, one contaminated with iron and one with aluminum, were analysed with several characterization techniques.
The two ingots show similar microstructure, but the top of the iron contaminated ingot has a significantly lower lifetime, as it contains more dislocation clusters decorated with segregated iron. Aluminum is less detrimental at this low concentration level and it is more homogeneously distributed along the ingot height.
A Mott-Schottky analysis after evaporation of aluminum contacts confirmed the p-type nature of the samples and estimated the free charge carrier concentration.
Current profiles and local I-V curves measured with Conductive Atomic Force Microscopy show that decorated grain boundaries are a preferential path for electrical conduction compared to the grain regions and iron precipitates affect more heavily the electrical properties of the wafer compared to aluminum precipitates.
The shape of the current profile at the boundary was justified with a theoretical model that assumes a redistribution of charge density due to a Coulombic potential introduced by a spherical and positively charged precipitate, that can be identified with b-FeSi2.
The results from this characterization show that metallic contamination at grain boundaries in Si is responsible for enhanced free carrier recombination and thus efficiency reduction in mc-Si cells.
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Angart, Samuel Gilbert. "Microstructure Analysis Of Directionally Solidified Aluminum Alloy Aboard The International Space Station." Thesis, The University of Arizona, 2015. http://hdl.handle.net/10150/595975.
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This thesis entails a detailed microstructure analysis of directionally solidified (DS) Al-7Si alloys processed in microgravity aboard the International Space Station and similar duplicate ground based experiments at Cleveland State University. In recent years, the European Space Agency (ESA) has conducted experiments on alloy solidification in microgravity. NASA and ESA have collaborated for three DS experiments with Al- 7 wt. % Si alloy, aboard the International Space Station (ISS) denoted as MICAST6, MICAST7 and MICAST12. The first two experiments were processed on the ISS in 2009 and 2010. MICAST12 was processed aboard the ISS in the spring of 2014; the resulting experimental results of MICAST12 are not discussed in this thesis. The primary goal of the thesis was to understand the effect of convection in primary dendrite arm spacings (PDAS) and radial macrosegregation within DS aluminum alloys. The MICAST experiments were processed with various solidification speeds and thermal gradients to produce alloy with differences in microstructure features. PDAS and radial macrosegregation were measured in the solidified ingot that developed during the transition from one solidification speed to another. To represent PDAS in DS alloy in the presence of no convection, the Hunt-Lu model was used to represent diffusion-controlled growth. By sectioning cross-sections throughout the entire length of solidified samples, PDAS was measured and calculated. The ground-based (1-g) experiments done at Cleveland State University CSU were also analyzed for comparison to the ISS experiments (0-g). During steady state in the microgravity environment, there was a reasonable agreement between the measured and calculated PDAS. In ground-based experiments, transverse sections exhibited obvious radial macrosegregation caused by thermosolutal convection resulting in a non-agreement with the Hunt- Lu model. Using a combination of image processing techniques and Electron Microprobe Analysis, the extent of radial macrosegregation was found to be a function of processing conditions and PDAS.
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McAllister, Mark Laing. "Analysis of laboratory and field measurements of directionally spread nonlinear ocean waves." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28762.
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Surface gravity waves exist in the oceans as multi-directional nonlinear phenomena. Understanding how these two properties interact is intrinsically important in itself. Furthermore, an understanding of this relationship may be used to gain insight into other oceanic phenomena. This thesis first describes an experimental investigation into the relationship between directionality and non-linearity (Part I). This relationship was then used as a tool to estimate the directional spreading of field data (Part II). Experiments have been conducted in which directionally spread focused wave groups were created in a wave tank. The relationship between the degree of directional spreading and the second-order bound harmonics of the wave groups was examined, in particular the formation of a `set-up'. These measurements were then compared to predictions from second-order theories, finding good agreement. The two-dimensional structure of the bound waves was explored giving new insight into the underlying physics. Experiments were then carried out for directionally spread crossing wave groups. It is believed that the crossing of two sufficiently separated wave groups may be the cause of an anomalous set-up in the second-order bound waves observed for some extreme and potentially freak waves. This set-up is reproduced experimentally. Again, the results of these test agreed very well when compared to second-order theory. The insight gained from the foregoing experiments was then utilised in the analysis of field data. A method, which requires only a single measurement to estimate the observed degree of directional spreading, was applied to a large dataset of field measurements from the North Alwyn platform in the North Sea. This method was then compared to conventional approaches, which require multiple concurrent measurements. The method that requires only a single measurement was shown to be effective, and presents a promising approach to gaining additional insight about the directional spreading of point observations.
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Rech, Bryan Andrew. "Thermomechanical analysis of a novel directionally reinforced shape-memory polymer for minimally invasive surgical devices." Connect to online resource, 2008. 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:1453562.
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Trento, Mariana Muchatte. "Estudo de densidade e direcionalidade musicais como recurso para o regente coral e sua performance." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/27/27158/tde-21032019-161846/.
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Esse trabalho tem como objeto o estudo das variações de densidade e seu diálogo com direcionalidade nos processos de composição musical estabelecendo indicações para análise interpretativa. Uma vez que problematizamos os conceitos de densidade e direcionalidade, buscamos estabelecer leituras dessas variáveis tanto quanto ao seu comportamento harmônico, rítmico, contrapontístico, timbrístico, transformações de intensidade, seja vertical ou horizontalmente, quanto à trama psicológico-dramática nas relações entre texto e música, assim como no uso do silêncio. O pensamento metodológico está apoiado tanto no Referencial Silva Ramos de Análise de obras corais (2003), que deu origem as nossas reflexões sobre densidade e direcionalidade, quanto em outras referências, igualmente estruturais, que são: Wallace Berry (1976), Arnold Schoenberg (1969, 2012), Barenboim (2007, 2009), Riemann (1896), Menezes (2002, 2006) e Schenker (1996, 2000). Ao tratar diretamente do significado destes parâmetros na estrutura musical, buscamos responder a principal pergunta deste trabalho: como tais variáveis e seus entrelaçamentos podem contribuir para uma análise voltada para construção de possíveis futuras performances. Divide-se em três capítulos, no primeiro constituímos três premissas de densidade: i) densidade vertical, a partir da análise das obras de Berry (1976), ii) densidade horizontal, com base nos fundamentos composicionais de Schoenberg (2012), iii) densidade dramática, fundamentada a partir de Ramos (2003). Realizamos a análise do madrigal Moro Lasso de Carlo Gesualdo para compreender o significado da densidade na estrutura musical e a sua contribuição para uma análise voltada para performance. No segundo capítulo, desenvolvemos as ideias de direcionalidade como um movimento transformador, destacando a direcionalidade melódica e harmônica, caracterizando também na ausência desta, a adirecionalidade. Percebemos na revisão bibliográfica e análise comparativa conceitual, a importância do conflito e do contraste para a caracterização e/ou intensificação da direcionalidade. Por fim, na análise interpretativa da obra Salmo 22 de Claudia Alvarenga, apontamos para as variações de densidade, em toda sua abrangência, como um possível elemento formador dos conflitos, contrastes e estranhamentos influenciadores de direcionalidade.<br>This work has as its object the study of density variations and its dialogue with directionality in the processes of musical composition, establishing indications for interpretative analysis. Once we have problematized the concepts of density and directionality, we seek to establish readings of these variables as well as their harmonic, rhythmic, contrapuntal, timbre, and intensity transformations, either vertically or horizontally, as well as the psychological-dramatic plot in the relationships between text and music, as well as in the use of silence. Methodological thinking is supported both in the Silva Ramos Reference Framework for Choral Works (2003), which gave rise to our reflections on density and directionality, as well as in other, equally structural, references that are: Wallace Berry (1976), Arnold Schoenberg (1969, 2012), Barenboim (2007, 2009), Riemann (1896), Menezes (2002, 2006) and Schenker (1996, 2000). When dealing directly with the meaning of these parameters in the musical structure, we try to answer the main question of this work: how these variables and their interlacings can contribute to an analysis directed to the construction of possible future performances. It is divided into three chapters, in the first one we establish three density assumptions: (i) horizontal density, based on the compositional foundations of Schoenberg (2012), (ii) the density of the vertical density, from the analysis of Berry\'s works (1976), (iii) density based on Ramos (2003). We performed the analysis of the madrigal Moro Lasso by Carlo Gesualdo to understand the meaning of density in the musical structure and its contribution to a performance - oriented analysis. In the second chapter, we develop the ideas of directionality as a transforming movement, highlighting the melodic and harmonic directionality, also characterizing in the absence of this, the adirecionalidade. We noticed in the bibliographic review and conceptual comparative analysis, the importance of conflict and contrast for the characterization and / or intensification of directionality. Finally, in the interpretative analysis of Claudia Alvarenga\'s Psalm 22, we point to the density variations, in all their scope, as a possible element forming the conflicts, contrasts and strangeness that influence directionality.
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Hausgen, Paul E. "A thermal analysis of an alkali metal thermal to electric converter with geometrically designed interior surfaces exhibiting directionally dependent radiative properties." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/16701.
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Mirković, Djordje [Verfasser]. "Solidification of AM and AZ magnesium alloys characterized by heat transfer modeled thermal and calorimetric analysis and microsegregation study of directionally solidified microstructure / submitted by Djordje Mirković." [Clausthal-Zellerfeld] : [Univ.-Bibliothek], 2008. http://d-nb.info/989647579/34.
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Bansal, Rohan. "Analysis and feedback control of the scanning laser epitaxy process applied to nickel-base superalloys." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/51714.
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Scanning Laser Epitaxy (SLE) is a new layer-by-layer additive manufacturing process being developed in the Direct Digital Manufacturing Laboratory at Georgia Tech. SLE allows for the fabrication of three-dimensional objects with specified microstructure through the controlled melting and re-solidification of a metal powder placed atop a base substrate. This dissertation discusses the work done to date on assessing the feasibility of using SLE to both repair single crystal (SX) turbine airfoils and manufacture functionally graded turbine components. Current processes such as selective laser melting (SLM) are not able to create structures with defined microstructure and often have issues with warping of underlying layers due to the high temperature gradients present when scanning a high power laser beam. Additionally, other methods of repair and buildup have typically been plagued by crack formation, equiaxed grains, stray grains, and grain multiplication that can occur when dendrite arms are separated from their main dendrites due to remelting. In this work, it is shown that the SLE process is capable of creating fully dense, crack-free equiaxed, directionally-solidified, and SX structures. The SLE process, though, is found to be currently constrained by the cumbersome method of choosing proper parameters and a relative lack of repeatability. Therefore, it is hypothesized that a real-time feedback control scheme based upon a robust offline model will be necessary both to create specified defect-free microstructures and to improve the repeatability of the process enough to allow for multi-layer growth. The proposed control schemes are based upon temperature data feedback provided at high frame rate by a thermal imaging camera. This data is used in both PID and model reference adaptive control (MRAC) schemes and drives the melt pool temperature during processing towards a reference melt pool temperature that has been found to give a desired microstructure in the robust offline model of the process. The real-time control schemes will enable the ground breaking capabilities of the SLE process to create engine-ready net shape turbine components from raw powder material.
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Tsai, Shang-yu, and 蔡尚祐. "Simulation and analysis of light extraction and directionality for LEDs with micro structures." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/99724718366220512002.
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碩士<br>國立中央大學<br>光電科學研究所<br>97<br>In this thesis, we build the optical model for photon recycling effect of LEDs based on Monte Carlo ray tracing method. According to this model, under different absorption coefficients of the active layer, we analyze the light extraction efficiency with respect to GaN and AlGaInP LEDs. Furthermore, we select two kinds of GaN LED structures such as surface texture of ThinGaN LEDs and patterned substrate of sapphire-based LEDs. Based on these two structures, we analyze the enhancement of the directionality and the light extraction efficiency when the slanted angles of the pyramid array are different.
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Anjos, Pedro Filipe dos Santos. "Development of a fundus camera for analysis of photoreceptor directionality in the healthy retina." Master's thesis, 2015. http://hdl.handle.net/10362/15618.
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The Stiles-Crawford effect (SCE) is the well-known phenomenon in which the brightness of light perceived by the human eye depends upon its entrance point in the pupil. This physiological characteristic is due to the directional sensitivity of the cone photoreceptors in the retina and it displays an approximately Gaussian dependency which is altered in a number of pathologies. Retinal imaging, a widely spread clinical practice, may be used to evaluate the SCE and thus serve as diagnostic tool. Nonetheless, its use for such a purpose is still underdeveloped and far from the clinical reality.
In this project a fundus camera was built and used to assess the cone photoreceptor directionality by reflective imaging of the retina in healthy individuals. The physical and physiological implications of its development are addressed in detail in the text: the optical properties of the human eye, illumination issues, acquiring a retinal image formed by the eye, among others. A full description of the developmental process that led to the final measuring method and results is also given.
The developed setup was successfully used to obtain high quality images of the eye fundus and in particular the parafoveal cone photoreceptors. The SCE was successfully observed and characterized. Even though considerable improvements could be done to the measurement method, the project showed the feasibility of using retinal imaging to evaluate the SCE thus motivating its usage in a clinical environment.
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Lin, Po-Chang, and 林柏滄. "Vertical Directionality Analysis of Low Frequency Ambient Noise in South China Sea Experiment of ASIAEX." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/68004112398579752157.
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碩士<br>國立中山大學<br>海下技術研究所<br>92<br>This study is based upon the vertical line array (VLA) in South China Sea experiment of the Asian Seas International Acoustic Experiment (ASIAEX), dated from May 3, 2001 to May 16, 2001, in which the ambient noise in shallow water was measured. In this paper, we use the beamforming method to calculate the vertical directionality of ambient noise in shallow water, for discussing the noise source distribution, and environmental effects on vertical directionality. The results show that distant shipping noise was observed near the horizontal angles, and surface noise occurred at high grazing angles. It is also discussed that the wind speed effect on the vertical directionality in this paper. Because of the typhoon Cimaron passed the experimental area during the experiment, which make wind speed changed obviously, so it can be found out the wind effect of ambient noise. By analyze the noise fluctuation, it is concluded that the threshold frequency of wind wave affected ambient noise levels were about 400 Hz. And after analyzing the vertical directionality, it is verified that the threshold was lower to 200 Hz. On the other hand, we also note the phenomena of “noise notch” appeared at some duration when calculating the vertical directionality. The environmental effects (sound speed profile) on the notch, and the presentation of noise notch at different frequencies were discussed. In the end part of this paper, we determined the time when the notch occurred by using the power difference of vertical directionality, and we expect that the results would be important for similar researches in the future.
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Lee, Yu-Heng, and 李雨衡. "An Analysis of Translation Process and Directionality in Chinese-English Translation: A Think-Aloud Protocol Study." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/81001097565663675093.
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碩士<br>國立臺灣師範大學<br>翻譯研究所<br>103<br>This study utilizes think-aloud protocol (TAP) to identify the difficulties facing translators and the strategies they adopt while translating into and out of their mother tongue. Eight participants, including five native speakers of Chinese and three of English, all in the third year of translation training, were asked to complete two translation tasks in both directions while using TAP.
Regardless of directions, the result shows that conversion of terms, sentence structures, and collocations are common difficulties. Translation into the mother tongue features comprehension difficulties at word level and reliance on knowledge of the mother tongue during conversion. Translation out of the mother tongue is characterized by conversion difficulties at word level and reliance on external resources in decision-making. There is no clear association between the quality of translation and directionality.
This is perhaps the first TAP study in Taiwan that includes native speakers of English. The result indicates that the translation process varies within the group, which may be explained by the different Chinese proficiency levels and the degree of topic familiarity of the participants.
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Lin, Yang-Cheng, and 林泱鉦. "Design of the Reference Sound Source and Analysis of Its Sound Intensity and Directionality for Calibrating Miniature Anechoic Chambers." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/69243541044541981689.
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碩士<br>元智大學<br>機械工程學系<br>98<br>In the calibration of anechoic or semi-anechoic chambers, it is required to have a reference sound source (RSS) to generate a standard noise for testing whether they can meet the ISO international standards. In general, the dimensions of the standard anechoic chamber are relatively too large for testing the small products such as those 3C products. It is better to have smaller chambers for saving the construction cost and reducing occupied space. In the mean time, it also needs a small RSS for calibrating the chambers.
This study developed a new type of reference sound source by focusing on the two critical factors of its sound intensity and directionality as specified in the ISO standards. Based on the RSS for the large standard chambers, an initial design of a small reference sound source (RSS-0.25) which was about the quarter size of RSS was developed and tested. Analysis with the Fluent software and experiment of wind speeds were conducted and compared with each other for the verification of the analysis model. By checking the wind speeds of the existing RSS and RSS-0.25, a new type of small reference sound source (RSS-0.5) was designed and simulated for its wind speeds. The results showed that when at a distance of 0.5 m, the wind speed analyzed is 1.46 m/s. According to the relationship between wind speed and noise measured on the RSS and RSS-0.25, the wind speed will not affect the accuracy of microphone measurement when it is less than 1.5 m/s. The model of RSS-0.5 with the corresponding analyzed geometric dimensions is then used for manufacturing the new RSS-0.5. The wind speed and noise intensity and directionality are investigated further.
The experimental results of RSS-0.5 showed that the wind speed was 1.44 m / s when measured at a distance of 0.5 m. Also, the maximum sound intensity generated was 71.4 dB though its intensity will vary as the motor speed changed. For the two designs with and without an opening on the cover plate of the fan top, it was found that the former still had directionality problem at the 90∘location and the latter had totally solved this problem no matter in the low or medium-high frequency ranges. Besides, the sound pressure differences are all within 6 dB between 100 Hz ~ 10 kHz following the ISO standards except that of 2.5 kHz which is 6.9 dB. This slight deviation at the solely high frequency is believed not affecting much on the newly developed reference sound source RSS-0.5 for the calibration of a small anechoic chamber.
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Morávek, Martin. "Analýza strukturálních změn nanovlákenných scaffoldů vzhledem k jejich relativnímu prodloužení." Master's thesis, 2016. http://www.nusl.cz/ntk/nusl-344015.
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The goal of this thesis was to find a suitable method for evaluating structural changes of scaffolds as influenced by external mechanical pressure and to verify the validity of hypothesis which assumes a change of directionality of fibers and also thinning of fibers according to the stretching of a scaffold. Assumptions formulated in these three hypothesis were tested on a scaffold with a plasma surface treatment and without any plasma surface treatment. To examine structural changes an electrone microscope was used to observe the surface of scaffolds. Incurred photos were then processed with the help of automatic software picture analysis and observed data were statisticly evaluated. The result of this experiment is a description of used method which can be used in future for larger studies. It was found that by the effect of external mechanical pressure fibers of examinated scaffolds turn in the direction of the pull. It has also been found that the average thickness of fibers didn't change. Results of this work give insight into the evaluation of structural changes of scaffolds when pressured by an external mechanical power and open possibilities for deeper and more exact research in this field. Key words: scaffold, picture analysis, fiber directionality, fiber thickness.
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Yu-ShyangGuo and 郭祐祥. "Experimental Analysis of Static Magnetic Fieldson the Microstructures of Directionally Solidified Lead-Tin Alloys." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/g9qhd5.
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Li-ChiehWu and 吳俐潔. "Experimental Analysis of Control-Parameter Effects on the Solidification Microstructures of Directionally Solidified Lead-Tin Alloys." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/94887257475052376750.
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碩士<br>國立成功大學<br>工程科學系碩博士班<br>101<br>Solidification processes play an important role in the morphology control of microstructures. The morphology of solidification microstructure is difficult to master in a casting process. Accordingly, in the thesis, four experimental models of different heating styles, contact surfaces of copper chill, environment temperatures and casting methods are used to study their effects on the directionally solidified lead-tin alloys. The heating style could affect the grain size. The copper chill supply an axial temperature gradient, which could make columnar grains grow along the opposite directional of the heat flow. The columnar growth could decrease the lateral grain boundaries and elevate the material life span. In addition, the microstructure observation through an optical microscope incorporated with the macrostructures and temperature-measured data is used to investigate the influences of the four experimental models on the constraint of dendrite growth, the equiaxed zone at the bottom of the casting, the competition zone of preferred growth directions for the columnar grains and the grain size. Furthermore, based on the classification of the microstructure morphology, the differences among the castings are analyzed.
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Yu-FanLin and 林宇凡. "Experimental Analysis of Thermal and Solutal Effects on the Microstructure of Directionally Solidified Lead-Tin Alloys." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/3w8q46.
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