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Brougher, Jeremy Adam. "Development of a microscopic moiré interferometry system." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1193080056/.
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Cuneo, David J. (David Joseph) 1972. "A system-wide evaluation of a traffic control system using microscopic simulation." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/10104.
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Sadat, Nabi S. Hasan. "Microscopic origin of magnetism in the Hematite-Ilmenite system." Diss., lmu, 2010. http://nbn-resolving.de/urn:nbn:de:bvb:19-117570.
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Morgan, Daniel J. (Daniel John) 1977. "A microscopic simulation laboratory for advanced public transportation system evaluation." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/84807.
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Anwar, Zubair. "Enabling microscopic simulators to perform system-level analysis of viscoelastic flows." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/42943.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 249-261).
State-of-the-art methods for simulating viscoelastic flows couple the conservation equations for mass and momentum with a model from kinetic theory that describes the microstructural state of the polymer. Introduction of appropriate numerical discretization and boundary conditions for these equations leads to a hybrid simulation for studying the dynamic behavior of polymeric liquids in complex geometries. This approach represents a rare example of a successful multiscale solution of a physical problem, as it allows investigation of arbitrary models of kinetic theory. The simulations, however, are not amenable to standard numerical techniques for system-level stability, bifurcation, and control analysis as this requires closed form equations. These simulation either use stochastic descriptions for the polymer microstructure that cannot be reduced to closed form, or involve equations for the evolution of a distribution of polymer conformations, which can only be written in closed form by invoking mathematical closure approximations that can have a significant qualitative impact on the predictive ability of these simulations. The focus of this thesis was to develop a novel numerical method that can enable hybrid simulations to perform system-level analysis of polymeric flows. This numerical approach has been applied directly to kinetic theory models and hybrid simulations to obtain stationary states and associated bifurcations and stability information. The method is general in its applicability in that it treats kinetic theory models and hybrid simulations as black boxes that are then used to obtain system-level information without any modification. The methods developed here are illustrated in a variety of problems.
(cont) Steady state results have been obtained for the non-interacting rigid dumbbell model in steady shear, and for the free-draining bead-spring chain model in both steady shear and uniaxial elongation that are in excellent agreement with previous studies and steady state computed from direct integration. The method is also applied to a hybrid simulation for the pressure-driven flow of non-interacting rigid dumbbells in a planar channel with a linear array of equally spaced cylinders. The computed steady state is in agreement with direct integration and qualitatively matches previous computations with closed models. Bifurcation analysis has been performed for the Doi model at equilibrium with the Onsager excluded volume potential. This analysis agrees with previous studies and accurately predicts the isotropic-nematic transition and turning point for the unstable to stable transition on the prolate solution branch. Bifurcation analysis has also been performed for the Doi model in the weak shear flow limit for the Maier-Saupe excluded volume potential. It is found that stable stationary solutions are lost at a limit point beyond which time-periodic tumbling orbits are the only stable solution. This transition occurs via an infinite period global bifurcation, while the limit point approaches a threshold value as the shear rate approaches zero. This result matches a recently published scaling analysis and demonstrates the ability of the method to provide general bifurcation analysis of kinetic theory models. Stability analysis of the fiber-spinning process for polymeric fluids has also been performed by using a hybrid simulation that couples the one-dimensional conservation equations for mass and momentum with a stochastic description for the configuration fields of the Hookean dumbbell model. The steady-state velocity profiles are in good agreement with previous studies with the Oldroyd-B model.
(cont) The analysis predicts onset of the draw resonance instability via a Hopf bifurcation and subsequent stabilization via second Hopf bifurcation in draw ratio parameter space. This result is in good agreement with experimentally observed behavior during polymer fiber-spinning.
by Zubair Anwar.
Ph.D.
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WANG, JIAN. "MICROSCOPIC STUDY OF PHOSPHOROUS REMOVAL PROCESS IN AN ACTIVATED SLUDGE SYSTEM." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1131120207.
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Linke, Sebastian. "Laser scanning system for microscopic and macroscopic investigations of chemical semiconductor-sensors." Thesis, Queen Mary, University of London, 2011. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8836.
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The aim of this thesis was to develop laterally resolved measurement systems for analysing Metal Insulator Semiconductor (MIS)-based potentiometric chemical sensors. Therefore, the Light-Addressable Potentiometric Sensors (LAPS) principle was used to provide chemical images. Two main system variants were under investigation. The first was a high-resolution so called LAPS-Microscope suitable for life science applications such as the investigation of pH changes of living cells. The second was developed for the analysis of the gas response of alloys on large scale semiconductor samples (25x25 mm2). Therefore, the system was called a LAPS-Macroscope. The LAPS-Microscope resolution depends on the optical focus and semiconductor properties. To reduce the semiconductor dependent resolution, 18 different types of samples were prepared varying the boron and carbon doping in thin silicon films. To analyse the LAPS resolution, different techniques were developed. A resolution improvement down to 3 μm compared to bulk silicon was achieved. A sputter target configuration was developed to produce ternary alloys on semiconductor samples with a continuous gradient in metal concentration. Different analysis methods such as EDX and AES were used to characterise the thin alloy films. Using the LAPS-Macroscope, the gas sensitivity of more than 106 different alloy compositions at a single sample can be investigated. As a result, metal concentration differences down to 0.03% can be distinguished. Typically, the sensor response of 625 different alloy compositions to changes in the hydrogen concentration was investigated within 16 min. The ternary alloy system PdxNiyCo1-x-y was analysed with the LAPS-Macroscope showing that nickel in the range up to 24 atom% reduces the hydrogen sensitivity. There was no significant influence of cobalt in the concentration range tested. Further, poisoning experiments with H2S showed improved behaviour of palladium alloys with nickel in the range of ~5-10 atom%. It was shown that an effective high-throughput method for the characterisation of ternary alloys was established, which is called a Continuous Gradient High Throughput Screening Macroscope CG-HTSM.
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Park, Mi-Kyung Huang Tung-Shi. "Development of microscopic imaging system for rapid detection of salmonella in raw chicken." Auburn, Ala, 2009. http://hdl.handle.net/10415/1856.
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Geiger, Dietrich Horst. "Immunoelectron microscopic characterization of glial intermediate filaments in human gliomas." Thesis, Stellenbosch : University of Stellenbosch, 1993. http://hdl.handle.net/10019.1/3386.
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Thesis (MMed (Biomedical Sciences. Anatomy and Histology))--University of Stellenbosch, 1993.Glial fibrillary acidic protein (GFAP) is found in varying amounts in the cytoplasm of most normal and neoplastic cells of astroglial origin. Though not glial specific, immunoelectron microscopy has shown that vimentin and GFAP are coexpressed as monomers of glial intermediate filaments. These structures display irreversible assembly and a slow metabolic turnover. Although currently applied as astroglial markers, these intermediate filament proteins may reflect the functional and developmental differentiation status of the cells in which they are expressed. Some authors have tried to apply these aspects as diagnostic parameters for grades of malignancy and anaplasia whilst other workers have indicated variable concentrations of GFAP in different astroglial cell types and entities. Different processing protocols, including the use of epoxy and acrylic resins, omission of osmium tetroxide and variations in concentration and incubation time of primary fixatives, were evaluated to find a compromise between antigen availability and acceptable ultrastructure. Thin sections were labelled on grid for GFAP (Dako A561) and vimentin (Dako M725) by means of the indirect immunogold method. For semi- quantification of relative antigen concentrations, a novel method was devised to calculate the labelling density, percentage heterogeneity of the particle distribution and the surface area investigated. This allowed expression of labelling results as a three figure unit. Standardized post-embedding immunoelectron microscopy was performed on 11 normal and neoplastic human tissue specimens. The tissue was exposed to conventional immersion fixation in glutaraldehyde and osmium tetroxide prior to modified embedding in LR White resin. The validity of these results was verified by correlation with conventional histopathological, immunohistochemical and clinical data obtained for each specimen. The presence of epoxy resin in thin sections was shown to reduce antigen availability to such an extent that very low to negative labelling was encountered. Acrylic LR White resin allowed more acceptable immunodetection, but at the cost of inferior ultrastructure and greater instability of thin sections in the electron beam. This masked the effects of glutaraldehyde fixation on the density of the tissuefixative matrix which included destruction of the vimentin and some GFAP associated epitopes. Although osmium tetroxide was required for acceptable ultrastructure, it reduced the labelling sensitivity by 20% and was responsible for premature curing of acrylic resin during impregnation of tissue. Despite superior resolution gained by electron microscopy and the advantage of semi-quantification of labeling results, the labelling sensitivity of this technique is lesser than that of light microscopical immunohistochemistry. Immunoelectron microscopy confirmed the association between GFAP and glial intermediate filaments in almost all the glial tumours studied, correlating well with GFAP expression in matching specimens demonstrated at light microscopical level. In the absence of intermediate filaments, no positivity for GFAP or vimentin was found in oligodendroglial components of mixed tumours. GFAP positivity in astrocytomas was demonstrated by between 17 and 126 particles / µm2, whilst lower figures were obtained for the glioblastoma (PD = 8) and some of the mixed gliomas (Pd = 6). Rosenthal fibres showed both peripheral and central positive labelling for GFAP, thus providing more evidence for their hypothetical degenerative, astroglial nature. The meningioma studied, was GFAP negative, but produced low density positivity for vimentin. Coexpression of GFAP and vimentin was demonstrated in an astroblastoma and degenerative infant brain tissue, thus supporting the presence of both these proteins development of glial structures. Although sites of likely glial intermediate filament synthesis were found, the antigen availability for vimentin was too low to allow a reliable assessment of specific vimentin localization and determination of the GFAP : vimentin ratio in individual intermediate filaments and/or astroglial fibres. Variations in particle densities (PD) which demonstrated GFAP in the various astroglial entities studied, were considered to be a result of variable technical and tissue processing factors rather than truly significant differences in expression of GFAP in individual intermediate filaments. This lead to the conclusion that the GFAP concentration / glial intermediate filament area is likely to be constant for mature glial intermediate filaments and therefore cannot be used to distinguish between different astroglial cells or entities. Whether each cell has a different number of glial intermediate filaments, has not been established satisfactorily. Following complementary conventional immunohistochemistry and careful orientation of biopsy material, the procedure can be applied to suitable specimens for the electron microscopical localization of high concentrations of aldehyde resistant, cytoplasmic antigens.
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Schmitt, Miriam. "Microscopic description of magnetic model compounds." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-110282.
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Solid state physics comprises many interesting physical phenomena driven by the complex interplay of the crystal structure, magnetic and orbital degrees of freedom, quantum fluctuations and correlation. The discovery of materials which exhibit exotic phenomena like low dimensional magnetism, superconductivity, thermoelectricity or multiferroic behavior leads to various applications which even directly influence our daily live. For such technical applications and the purposive modification of materials, the understanding of the underlying mechanisms in solids is a precondition. Nowadays DFT based band structure programs become broadly available with the possibility to calculate systems with several hundreds of atoms in reasonable time scales and high accuracy using standard computers due to the rapid technical and conceptional development in the last decades. These improvements allow to study physical properties of solids from their crystal structure and support the search for underlying mechanisms of different phenomena from microscopic grounds.
This thesis focuses on the theoretical description of low dimensional magnets and intermetallic compounds. We combine DFT based electronic structure and model calculations to develop the magnetic properties of the compounds from microscopic grounds. The developed, intuitive pictures were challenged by model simulations with various experiments, probing microscopic and macroscopic properties, such as thermodynamic measurements, high field magnetization, nuclear magnetic resonance or electron spin resonance experiments. This combined approach allows to investigate the close interplay of the crystal structure and the magnetic properties of complex materials in close collaboration with experimentalists. In turn, the systematic variation of intrinsic parameters by substitution or of extrinsic factors, like magnetic field, temperature or pressure is an efficient way to probe the derived models. Especially pressure allows a continuous change of the crystal structure on a rather large energy scale without the chemical complexity of substitution, thus being an ideal tool to consistently alter the electronic structure in a controlled way. Our theoretical results not only provide reliable descriptions of real materials, exhibiting disorder, partial site occupation and/or strong correlations, but also predict fascinating phenomena upon extreme conditions. In parts this theoretical predictions were already confirmed by own experiments on large scale facilities.
Whereas in the first part of this work the main purpose was to develop reliable magnetic models of low dimensional magnets, in the second part we unraveled the underlying mechanism for different phase transitions upon pressure. In more detail, the first part of this thesis is focused on the magnetic ground states of spin 1/2 transition metal compounds which show fascinating phase diagrams with many unusual ground states, including various types of magnetic order, like helical states exhibiting different pitch angles, driven by the intimate interplay of structural details and quantum fluctuations. The exact arrangement and the connection of the magnetically active building blocks within these materials determine the hybridization, orbital occupation, and orbital orientation, this way altering the exchange paths and strengths of magnetic interaction within the system and consequently being crucial for the formation of the respective ground states. The spin 1/2 transition metal compounds, which have been investigated in this work, illustrate the great variety of exciting phenomena fueling the huge interest in this class of materials.
We focused on cuprates with magnetically active CuO4 plaquettes, mainly arranged into edge sharing geometries. The influence of structural peculiarities, as distortion, folding, changed bonding angles, substitution or exchanged ligands has been studied with respect to their relevance for the magnetic ground state. Besides the detailed description of the magnetic ground states of selected compounds, we attempted to unravel the origin for the formation of a particular magnetic ground state by deriving general trends and relations for this class of compounds. The details of the treatment of the correlation and influence of structural peculiarities like distortion or the bond angles are evaluated carefully.
In the second part of this work we presented the results of joint theoretical and experimental studies for intermetallic compounds, all exhibiting an isostructural phase transition upon pressure. Many different driving forces for such phase transitions are known like quantum fluctuations, valence instabilities or magnetic ordering. The combination of extensive computational studies and high pressure XRD, XAS and XMCD experiments using synchrotron radiation reveals completely different underlying mechanism for the onset of the phase transitions in YCo5, SrFe2As2 and EuPd3Bx.
This thesis demonstrates on a series of complex compounds that the combination of ab-initio electronic structure calculations with numerical simulations and with various experimental techniques is an extremely powerful tool for a successful description of the intriguing quantum phenomena in solids. This approach is able to reduce the complex behavior of real materials to simple but appropriate models, this way providing a deep understanding for the underlying mechanisms and an intuitive picture for many phenomena. In addition, the close interaction of theory and experiment stimulates the improvement and refinement of the methods in both areas, pioneering the grounds for more and more precise descriptions. Further pushing the limits of these mighty techniques will not only be a precondition for the success of fundamental research at the frontier between physics and chemistry, but also enables an advanced material design on computational grounds.
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Klages, Rainer. "Microscopic chaos, fractals, and transport in nonequilibrium steady states Mikroskopisches Chaos, Fraktale und Transport in stationären Nichtgleichgewichtszuständen /." [S.l. : s.n.], 2005. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB11675344.
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Grumert, Ellen. "Cooperative Variable Speed Limit Systems : Modeling and Evaluation using Microscopic Traffic Simulation." Licentiate thesis, Linköpings universitet, Kommunikations- och transportsystem, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-106926.
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During the last decades the road traffic has increased tremendously leading to congestion, safety issues and increased environmental impacts. As a result, many countries are continuously trying to find improvements and new solutions to solve these issues. One way of improving the traffic conditions is by the use of so called intelligent transport systems, where information and communication technologies are being used for traffic management and control. One such system commonly used for traffic management purposes are variable speed limit systems. These systems are making use of signs to show speed limits adjusted to the prevailing road or traffic conditions. The rapid development in telecommunication technologies has enabled communication between vehicles, and between vehicles and the infrastructure, so called cooperative systems. This opens up for the possibility to further improve the performance of a standard variable speed limit system by adding cooperative system features. The overall aim of this thesis is to investigate the potential benefits of incorporating infrastructure to vehicle communication and autonomous control to an existing variable speed limit system. We show how such a cooperative variable speed limit system can be modeled and evaluated by the use of microscopic traffic simulation. Results from the evaluation indicate increased flow harmonization in terms of narrowing of the acceleration rate distribution and reduced exhaust emissions. Further, we compare four control algorithms for deciding on speed limits in variable speed limit systems. Differences in the resulting traffic performance between the control algorithms are quantified by the use of microscopic traffic simulation. It is concluded that the dened objective for the algorithms have a decisive influence on the effects of the variable speed limit system. The results from this thesis are useful for further development of variable speed limit systems, both with respect to incorporating cooperative features and by improving the speed setting control algorithms.
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Li, Tao. "General Aviation Demand Forecasting Models and a Microscopic North Atlantic Air Traffic Simulation Model." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/71663.
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This thesis is focused on two topics. The first topic is the General Aviation (GA) demand forecasting models. The contributions to this topic are three fold: 1) we calibrated an econometric model to investigate the impact of fuel price on the utilization rate of GA piston engine aircraft, 2) we adopted a logistic model to identify the relationship between fuel price and an aircraft's probability of staying active, and 3) we developed an econometric model to forecast the airport-level itinerant and local GA operations. Our calibration results are compared with those reported in literature. Demand forecasts are made with these models and compared with those prepared by the Federal Aviation Administration. The second topic is to model the air traffic in the Organized Track System (OTS) over the North Atlantic. We developed a discrete-time event model to simulate the air traffic that uses the OTS. We proposed four new operational procedures to improve the flight operations for the OTS. Two procedures aim to improve the OTS assignments in the OTS entry area, and the other two aim to benefit flights once they are inside the OTS. The four procedures are implemented with the simulation model and their benefits are analyzed. Several implementation issues are discussed and recommendations are given.Ph. D.
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Viscardy, Sébastien. "Viscosity and microscopic chaos: the Helfand-moment approach." Doctoral thesis, Universite Libre de Bruxelles, 2005. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210964.
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Depuis les premiers développements de la physique statistique réalisés au 19ème siècle, nombreux ont été les travaux dédiés à la relation entre les processus macroscopiques em>irréversibles(tels que les phénomènes de transport) et les propriétés de la dynamique réversible des atomes et des molécules. Depuis deux décennies, l'hypothèse du chaos microscopique nous en apporte une plus grande compréhension. Dans cette thèse, nous nous intéressons plus particulièrement aux propriétés de viscosité.
Dans ce travail, nous considérons des systèmes périodiques de particules en interaction. Nous proposons une nouvelle méthode de calcul de la viscosité valable pour tous systèmes périodiques, quel que soit le potentiel d'interaction considéré. Cette méthode est basée sur la formule dérivée par Helfand exprimant la viscosité en fonction de la variance du moment de Helfand croissant linéairement dans le temps.
Dans les années nonante, il a été démontré qu'un système composé de seulement deux particules présente déjà de la viscosité. Les deux disques durs interagissent en collisions élastiques dans un domaine carré ou hexagonal avec des conditions aux bords périodiques. Nous appliquons notre méthode de calcul des propriétés de viscosité dans les deux réseaux. Nous donnons également une explication qualitative des résultats obtenus.
L'étude de la relation entre les propriétés de viscosité et les grandeurs du chaos microscopique représente l'une des principales tâches de cette thèse. Dans ce contexte, le formalisme du taux d'échappement joue un rôle majeur. Ce formalisme établit une relation directe entre cette grandeur et la viscosité. Nous étudions numériquement cette relation et la comparaison avec les résultats obtenus par notre méthode sont excellents.
D'autre part, le formalisme du taux d'échappement suppose l'existence d'un répulseur fractal. Après avoir mis en évidence son existence, nous appliquons le formalisme proposant une formule exprimant la viscosité en termes de l'exposant de Lyapunov du système (mesurant le caractère chaotique de la dynamique)et de la dimension fractale du répulseur. L'étude numérique de cette relation dans le modèle à deux disques durs est réalisée avec succès et sont en excellent accord avec les relations obtenus précédemment.
Enfin, nous nous penchons sur les systèmes composés de N disques durs ou sphères dures. Après une étude de l'équation d'état et des propriétés chaotiques, nous avons exploré les propriétés de viscosité dans ces systèmes. Les données numériques obtenues sont en très bon accord avec les prévisions théoriques d'Enskog. D'autre part, nous avons utilisé notre méthode de calcul de la viscosité dans des systèmes de Lennard-Jones. De plus, nous avons proposé une méthode analogue pour le calcul numérique de la conduction thermique. Nos résultats sont en très bon accord avec ceux obtenus par la méthode de Green-Kubo.
In this thesis, we first devote a section on the history of the concept of irreversibility; of the hydrodynamics, branch of physics in which the viscosity appears; of the kinetic theory of gases establishing relationships between the microscopic dynamics and macroscopic processes like viscosity; and, finally, the interest brought in statistical mechanics of irreversible processes by the theory of chaos, more precisely, the microscopic chaos. We propose a method based on the Helfand moment in order to calculate the viscosity properties in systems of particles with periodic boundary conditions. We apply this method to the simplest system in which viscosity already exists: the two-hard-disk model. The escape-rate formalism, establishing a direct relation between chaotic quantities of the microscopic dynamics (e.g. Lyapunov exponents, fractal dimensions, etc.), is applied in this system. The results are in excellent agreement with those obtained by our Helfand-moment method. We extend the calculation of the viscosity properties to systems with more than two hard balls. Finally, we compute viscosity as well as thermal conductivity thanks to our own method also based on the Helfand moment.
Doctorat en sciences, Spécialisation physique
info:eu-repo/semantics/nonPublished
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ROSATI, ROBERTO. "Microscopic modeling of energy dissipation and decoherence in nanoscale materials and devices." Doctoral thesis, Politecnico di Torino, 2015. http://hdl.handle.net/11583/2599755.
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Primary goal of this thesis work is to develop and implement microscopic modeling strategies able to describe semiconductor-based nanomaterials and nanodevices, overcoming both the intrinsic limits of the semiclassical transport theory and the huge computational costs of non Markovian approaches.
The progressive reduction of modern optoelectronic devices space-scales, triggered by the evolution on semiconductor heterostructures at the nanoscale, together with the decrease of the typical time-scales involved, pushes device miniaturization toward limits where the application of the traditional Boltzmann transport theory becomes questionable, and a comparison with more rigorous quantum transport approaches is imperative. In spite of the quantum-mechanical nature of electron and photon dynamics in the core region of typical solid-state nanodevices, the overall behavior of such quantum systems is often governed by a highly non-trivial interplay between phase coherence and dissipation/dephasing. To this aim, the crucial step is to adopt a quantum mechanical description of the carrier subsystem; this can be performed at different levels, ranging from phenomenological dissipation/decoherence models to quantum-kinetic treatments. However, due to their high computational cost, non-Markovian Green’ s-function as well as density-matrix approaches like quantum Monte Carlo techniques or quantum-kinetics are currently unsuitable for the design and optimization of new-generation nanodevices. On the other end, the Wigner-function technique is a widely used approach which, in principle, is well suited to describe an interplay between coherence and dissipation: in fact it can be regarded both as a phase space formulation of the electronic density matrix and a quantum equivalent of the classical distribution function. The evolution of this quasi-distribution function is governed by the Wigner-equation, which is usually solved by applying local spatial boundary conditions. However, such a scheme has recently shown some intrinsic limits. In this thesis work we analyze both the reasons for these unphysical features –pointing out the needing of different and purely quantum approaches– and the limits in which they should not appear, thus justifying why these problems had not been encountered in numerous quantum-transport simulations based on this procedure.
For these reasons here we present a novel single-particle simulation strategy able to describe the interplay between coherence and dissipation/dephasing. In the presence of one- as well as two-body scattering mechanisms, we apply the mean-field approximation to the many-body Lindblad-type (hence, positive-definite) scattering superoperators provided by a recently proposed Markov approach, and we derive a closed equation of motion for the electronic single-particle density matrix. Although the resulting scattering superoperator turns out to be, at finite or high carrier densities, nonlinear and non-Lindblad, we prove that it is able to guarantee the positivity of the evolution (in striking contrast with conventional Markov approaches) independently of the scattering mechanisms, an essential prerequisite of any reliable kinetic treatment of semiconductor quantum devices; furthermore, it may be extended to the cases of quantum systems with open spatial boundaries (in this regard, it provides a formal derivation of a recently proposed Lindblad-like device-reservoir scattering superoperator). The proposed theoretical scheme is able, one the one hand, to recover the space-dependent Boltzmann equation and, on the other, to point out the regimes where a relevant role may be played by scattering-nonlocality effects, e.g. scattering-induced variations of the spatial charge-density which may not be provided by semiclassical treatments. Supplementing our analytical investigation with a number of simulated experiments in homogeneous as well as inhomogeneous GaN-based systems, we provide a rigorous treatment of scattering nonlocality in semiconductor nanostructures: in particular, we show how the scattering-nonlocality effects (i) are particularly significant in the presence of a carrier localization on the nanometric space scale, (ii) cause a speedup of the diffusion and (iii) in superlattice structures induce, with respect to scattering-free evolutions, a suppression of coherent oscillations between adjacent wells. These genuine quantum effects may be predicted also by other simplified treatments of the dissipation/decoherence like, e.g., the Relaxation Time Approximation: the latter however turns out to be, contrary to the proposed microscopic theoretical scheme, totally nonlocal, e.g. it is unable to recover the local character of the Boltzmann collision term in the semiclassical limit and it leads, especially for the case of quasielastic dissipation processes, to a significant overestimation of the diffusion speedup.
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Kesting, Arne. "Microscopic Modeling of Human and Automated Driving: Towards Traffic-Adaptive Cruise Control." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1204804167720-57734.
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The thesis is composed of two main parts. The first part deals with a microscopic traffic flow theory. Models describing the individual acceleration, deceleration and lane-changing behavior are formulated and the emerging collective traffic dynamics are investigated by means of numerical simulations. The models and simulation tools presented provide the methodical prerequisites for the second part of the thesis in which a novel concept of a traffic-adaptive control strategy for ACC systems is presented. The impact of such systems on the traffic dynamics can solely be investigated and assessed by traffic simulations. The focus is on future adaptive cruise control (ACC) systems and their potential applications in the context of vehicle-based intelligent transportation systems. In order to ensure that ACC systems are implemented in ways that improve rather than degrade traffic conditions, the thesis proposes an extension of ACC systems towards traffic-adaptive cruise control by means of implementing an actively jam-avoiding driving strategy. The newly developed traffic assistance system introduces a driving strategy layer which modifies the driver's individual settings of the ACC driving parameters depending on the local traffic situation. Whilst the conventional operational control layer of an ACC system calculates the response to the input sensor data in terms of accelerations and decelerations on a short time scale, the automated adaptation of the ACC driving parameters happens on a somewhat longer time scale of, typically, minutes. By changing only temporarily the comfortable parameter settings of the ACC system in specific traffic situations, the driving strategy is capable of improving the traffic flow efficiency whilst retaining the comfort for the driver. The traffic-adaptive modifications are specified relative to the driver settings in order to maintain the individual preferences. The proposed system requires an autonomous real-time detection of the five traffic states by each ACC-equipped vehicle. The formulated algorithm is based on the evaluation of the locally available data such as the vehicle's velocity time series and its geo-referenced position (GPS) in conjunction with a digital map. It is assumed that the digital map is complemented by information about stationary bottlenecks as most of the observed traffic flow breakdowns occur at these fixed locations. By means of a heuristic, the algorithm determines which of the five traffic states mentioned above applies best to the actual traffic situation. Optionally, inter-vehicle and infrastructure-to-car communication technologies can be used to further improve the accuracy of determining the respective traffic state by providing non-local information. By means of simulation, we found that the automatic traffic-adaptive driving strategy improves traffic stability and increases the effective road capacity. Depending on the fraction of ACC vehicles, the driving strategy "passing a bottleneck" effects a reduction of the bottleneck strength and therefore delays (or even prevents) the breakdown of traffic flow. Changing to the driving mode "leaving the traffic jam" increases the outflow from congestion resulting in reduced queue lengths in congested traffic and, consequently, a faster recovery to free flow conditions. The current travel time (as most important criterion for road users) and the cumulated travel time (as an indicator of the system performance) are used to evaluate the impact on the quality of service. While traffic congestion in the reference scenario was completely eliminated when simulating a proportion of 25% ACC vehicles, travel times were significantly reduced even with much lower penetration rates. Moreover, the cumulated travel times decreased consistently with the increase in the proportion of ACC vehiclesIn der Arbeit wird ein neues verkehrstelematisches Konzept für ein verkehrseffizientes Fahrverhalten entwickelt und als dezentrale Strategie zur Vermeidung und Auflösung von Verkehrsstaus auf Richtungsfahrbahnen vorgestellt. Die operative Umsetzung erfolgt durch ein ACC-System, das um eine, auf Informationen über die lokale Verkehrssituation basierende, automatisierte Fahrstrategie erweitert wird. Die Herausforderung bei einem Eingriff in das individuelle Fahrverhalten besteht - unter Berücksichtigung von Sicherheits-, Akzeptanz- und rechtlichen Aspekten - im Ausgleich der Gegensätze Fahrkomfort und Verkehrseffizienz. Während sich ein komfortables Fahren durch große Abstände bei geringen Fahrzeugbeschleunigungen auszeichnet, erfordert ein verkehrsoptimierendes Verhalten kleinere Abstände und eine schnellere Anpassung an Geschwindigkeitsänderungen der umgebenden Fahrzeuge. Als allgemeiner Lösungsansatz wird eine verkehrsadaptive Fahrstrategie vorgeschlagen, die ein ACC-System mittels Anpassung der das Fahrverhalten charakterisierenden Parameter umsetzt. Die Wahl der Parameter erfolgt in Abhängigkeit von der lokalen Verkehrssituation, die auf der Basis der im Fahrzeug zur Verfügung stehenden Informationen automatisch detektiert wird. Durch die Unterscheidung verschiedener Verkehrssituationen wird ein temporärer Wechsel in ein verkehrseffizientes Fahrregime (zum Beispiel beim Herausfahren aus einem Stau) ermöglicht. Machbarkeit und Wirkungspotenzial der verkehrsadaptiven Fahrstrategie werden im Rahmen eines mikroskopischen Modellierungsansatzes simuliert und hinsichtlich der kollektiven Verkehrsdynamik, insbesondere der Stauentstehung und Stauauflösung, auf mehrspurigen Richtungsfahrbahnen bewertet. Die durchgeführte Modellbildung, insbesondere die Formulierung eines komplexen Modells des menschlichen Fahrverhaltens, ermöglicht eine detaillierte Analyse der im Verkehr relevanten kollektiven Stabilität und einer von der Stabilität abhängigen stochastischen Streckenkapazität. Ein tieferes Verständnis der Stauentstehung und -ausbildung wird durch das allgemeine Konzept der Engstelle erreicht. Dieses findet auch bei der Entwicklung der Strategie für ein stauvermeidendes Fahrverhalten Anwendung. In der Arbeit wird die stauvermeidende und stauauflösende Wirkung eines individuellen, verkehrsadaptiven Fahrverhaltens bereits für geringe Ausstattungsgrade nachgewiesen. Vor dem Hintergrund einer zu erwartenden Verbreitung von ACC-Systemen ergibt sich damit eine vielversprechende Option für die Steigerung der Verkehrsleistung durch ein teilautomatisiertes Fahren. Der entwickelte Ansatz einer verkehrsadaptiven Fahrstrategie ist unabhängig vom ACC-System. Er erweitert dessen Funktionalität im Hinblick auf zukünftige, informationsbasierte Fahrerassistenzsysteme um eine neue fahrstrategische Dimension. Die lokale Interpretation der Verkehrssituation kann neben einer verkehrsadaptiven ACC-Regelung auch der Entwicklung zukünftiger Fahrerinformationssysteme dienen
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Henclewood, Dwayne Anthony. "Real-time estimation of arterial performance measures using a data-driven microscopic traffic simulation technique." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44792.
Full textAbstract:
Traffic congestion is a one hundred billion dollar problem in the US. The cost of congestion has been trending upward over the last few decades, but has experienced slight decreases in recent years partly due to the impact of congestion reduction strategies. The impact of these strategies is however largely experienced on freeways and not arterials. This discrepancy in impact is partially linked to the lack of real-time, arterial traffic information. Toward this end, this research effort seeks to address the lack of arterial traffic information.
To address this dearth of information, this effort developed a methodology to provide accurate estimates of arterial performance measures to transportation facility managers and travelers in real-time. This methodology employs transmitted point sensor data to drive an online, microscopic traffic simulation model. The feasibility of this methodology was examined through a series of experiments that were built upon the successes of the previous, while addressing the necessary limitations. The results from each experiment were encouraging. They successfully demonstrated the method's likely feasibility, and the accuracy with which field estimates of performance measures may be obtained. In addition, the method's results support the viability of a "real-world" implementation of the method. An advanced calibration process was also developed as a means of improving the method's accuracy. This process will in turn serve to inform future calibration efforts as the need for more robust and accurate traffic simulation models are needed.
The success of this method provides a template for real-time traffic simulation modeling which is capable of adequately addressing the lack of available arterial traffic information. In providing such information, it is hoped that transportation facility managers and travelers will make more informed decisions regarding more efficient management and usage of the nation's transportation network.
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Kesting, Arne. "Microscopic Modeling of Human and Automated Driving: Towards Traffic-Adaptive Cruise Control." Doctoral thesis, Technische Universität Dresden, 2007. https://tud.qucosa.de/id/qucosa%3A24070.
Full textAbstract:
The thesis is composed of two main parts. The first part deals with a microscopic traffic flow theory. Models describing the individual acceleration, deceleration and lane-changing behavior are formulated and the emerging collective traffic dynamics are investigated by means of numerical simulations. The models and simulation tools presented provide the methodical prerequisites for the second part of the thesis in which a novel concept of a traffic-adaptive control strategy for ACC systems is presented. The impact of such systems on the traffic dynamics can solely be investigated and assessed by traffic simulations. The focus is on future adaptive cruise control (ACC) systems and their potential applications in the context of vehicle-based intelligent transportation systems. In order to ensure that ACC systems are implemented in ways that improve rather than degrade traffic conditions, the thesis proposes an extension of ACC systems towards traffic-adaptive cruise control by means of implementing an actively jam-avoiding driving strategy. The newly developed traffic assistance system introduces a driving strategy layer which modifies the driver's individual settings of the ACC driving parameters depending on the local traffic situation. Whilst the conventional operational control layer of an ACC system calculates the response to the input sensor data in terms of accelerations and decelerations on a short time scale, the automated adaptation of the ACC driving parameters happens on a somewhat longer time scale of, typically, minutes. By changing only temporarily the comfortable parameter settings of the ACC system in specific traffic situations, the driving strategy is capable of improving the traffic flow efficiency whilst retaining the comfort for the driver. The traffic-adaptive modifications are specified relative to the driver settings in order to maintain the individual preferences. The proposed system requires an autonomous real-time detection of the five traffic states by each ACC-equipped vehicle. The formulated algorithm is based on the evaluation of the locally available data such as the vehicle's velocity time series and its geo-referenced position (GPS) in conjunction with a digital map. It is assumed that the digital map is complemented by information about stationary bottlenecks as most of the observed traffic flow breakdowns occur at these fixed locations. By means of a heuristic, the algorithm determines which of the five traffic states mentioned above applies best to the actual traffic situation. Optionally, inter-vehicle and infrastructure-to-car communication technologies can be used to further improve the accuracy of determining the respective traffic state by providing non-local information. By means of simulation, we found that the automatic traffic-adaptive driving strategy improves traffic stability and increases the effective road capacity. Depending on the fraction of ACC vehicles, the driving strategy "passing a bottleneck" effects a reduction of the bottleneck strength and therefore delays (or even prevents) the breakdown of traffic flow. Changing to the driving mode "leaving the traffic jam" increases the outflow from congestion resulting in reduced queue lengths in congested traffic and, consequently, a faster recovery to free flow conditions. The current travel time (as most important criterion for road users) and the cumulated travel time (as an indicator of the system performance) are used to evaluate the impact on the quality of service. While traffic congestion in the reference scenario was completely eliminated when simulating a proportion of 25% ACC vehicles, travel times were significantly reduced even with much lower penetration rates. Moreover, the cumulated travel times decreased consistently with the increase in the proportion of ACC vehicles.In der Arbeit wird ein neues verkehrstelematisches Konzept für ein verkehrseffizientes Fahrverhalten entwickelt und als dezentrale Strategie zur Vermeidung und Auflösung von Verkehrsstaus auf Richtungsfahrbahnen vorgestellt. Die operative Umsetzung erfolgt durch ein ACC-System, das um eine, auf Informationen über die lokale Verkehrssituation basierende, automatisierte Fahrstrategie erweitert wird. Die Herausforderung bei einem Eingriff in das individuelle Fahrverhalten besteht - unter Berücksichtigung von Sicherheits-, Akzeptanz- und rechtlichen Aspekten - im Ausgleich der Gegensätze Fahrkomfort und Verkehrseffizienz. Während sich ein komfortables Fahren durch große Abstände bei geringen Fahrzeugbeschleunigungen auszeichnet, erfordert ein verkehrsoptimierendes Verhalten kleinere Abstände und eine schnellere Anpassung an Geschwindigkeitsänderungen der umgebenden Fahrzeuge. Als allgemeiner Lösungsansatz wird eine verkehrsadaptive Fahrstrategie vorgeschlagen, die ein ACC-System mittels Anpassung der das Fahrverhalten charakterisierenden Parameter umsetzt. Die Wahl der Parameter erfolgt in Abhängigkeit von der lokalen Verkehrssituation, die auf der Basis der im Fahrzeug zur Verfügung stehenden Informationen automatisch detektiert wird. Durch die Unterscheidung verschiedener Verkehrssituationen wird ein temporärer Wechsel in ein verkehrseffizientes Fahrregime (zum Beispiel beim Herausfahren aus einem Stau) ermöglicht. Machbarkeit und Wirkungspotenzial der verkehrsadaptiven Fahrstrategie werden im Rahmen eines mikroskopischen Modellierungsansatzes simuliert und hinsichtlich der kollektiven Verkehrsdynamik, insbesondere der Stauentstehung und Stauauflösung, auf mehrspurigen Richtungsfahrbahnen bewertet. Die durchgeführte Modellbildung, insbesondere die Formulierung eines komplexen Modells des menschlichen Fahrverhaltens, ermöglicht eine detaillierte Analyse der im Verkehr relevanten kollektiven Stabilität und einer von der Stabilität abhängigen stochastischen Streckenkapazität. Ein tieferes Verständnis der Stauentstehung und -ausbildung wird durch das allgemeine Konzept der Engstelle erreicht. Dieses findet auch bei der Entwicklung der Strategie für ein stauvermeidendes Fahrverhalten Anwendung. In der Arbeit wird die stauvermeidende und stauauflösende Wirkung eines individuellen, verkehrsadaptiven Fahrverhaltens bereits für geringe Ausstattungsgrade nachgewiesen. Vor dem Hintergrund einer zu erwartenden Verbreitung von ACC-Systemen ergibt sich damit eine vielversprechende Option für die Steigerung der Verkehrsleistung durch ein teilautomatisiertes Fahren. Der entwickelte Ansatz einer verkehrsadaptiven Fahrstrategie ist unabhängig vom ACC-System. Er erweitert dessen Funktionalität im Hinblick auf zukünftige, informationsbasierte Fahrerassistenzsysteme um eine neue fahrstrategische Dimension. Die lokale Interpretation der Verkehrssituation kann neben einer verkehrsadaptiven ACC-Regelung auch der Entwicklung zukünftiger Fahrerinformationssysteme dienen.
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Berciu, Mona Inesa. "A microscopic model for non-fermi-liquid behavior and charge carrier pairing in a purely repulsive two-dimensional electron system." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ49975.pdf.
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Newbury, James. "Limit order books, diffusion approximations and reflected SPDEs : from microscopic to macroscopic models." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:825d9465-842b-424b-99d0-ff4dfa9ebfc5.
Full textAbstract:
Motivated by a zero-intelligence approach, the aim of this thesis is to unify the microscopic (discrete price and volume), mesoscopic (discrete price and continuous volume) and macroscopic (continuous price and volume) frameworks of limit order books, with a view to providing a novel yet analytically tractable description of their behaviour in a high to ultra high-frequency setting. Starting with the canonical microscopic framework, the first part of the thesis examines the limiting behaviour of the order book process when order arrival and cancellation rates are sent to infinity and when volumes are considered to be of infinitesimal size. Mathematically speaking, this amounts to establishing the weak convergence of a discrete-space process to a mesoscopic diffusion limit. This step is initially carried out in a reduced-form context, in other words, by simply looking at the best bid and ask queues, before the procedure is extended to the whole book. This subsequently leads us to the second part of the thesis, which is devoted to the transition between mesoscopic and macroscopic models of limit order books, where the general idea is to send the tick size to zero, or equivalently, to consider infinitely many price levels. The macroscopic limit is then described in terms of reflected SPDEs which typically arise in stochastic interface models. Numerical applications are finally presented, notably via the simulation of the mesocopic and macroscopic limits, which can be used as market simulators for short-term price prediction or optimal execution strategies.
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Tanguy, Quentin. "Design and fabrication of a MEMS scanner for OCT imaging endo-microscopic probe." Thesis, Bourgogne Franche-Comté, 2018. http://indexation.univ-fcomte.fr/nuxeo/site/esupversions/8d6ab7ed-eac5-4e11-997b-f9e9af4e8808.
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Les travaux présentés dans cette thèse reposent d'une part sur le design et la modélisation electro-thermo-mécanique d'un micro scanner optique et d'autre part sur sa fabrication, et sa caractérisation ainsi qu'un début d'intégration à un micro interféromètre de Mirau pour le développement d'une sonde endoscopique conçue pour la détection des cancers gastrointestinaux dans leur phase initiale par une technique d'imagerie appelée Tomography de Cohérence Optique (OCT). Le coeur de la contribution de cette thèse porte sur le développement et la fabrication de micro actionneurs commandés thermiquement pour l'orientation controlée d'un micro miroir conçu à cet effet. Différentes architectures de micro scanners sont proposées afin de répondre au mieux aux problématiques imposées par les exigences en matière de qualité d'imagerie optique et de compatibilité avec les normes dans le cadre de l'utilisation médical emph{in vivo} du dispositif final. Ces travaux s'inscrivent dans le projet DEMO4 financé par le LabEx Action en coopération entre les départements MN2S et AS2M de l'institut de recherche Français Femto-ST ainsi que de l'université de Floride aux États-Unis afin de délivrer un premier démonstrateur de sonde endoscopique OCT.Plusieurs séries de fabrication ont été mises en oeuvre grâce à des techniques de microfabrication de semiconducteurs dévelopés en échange entre l'université de Floride et Femto-ST avant d'être assemblées (à défaut d'intégration monolithique) par procédés robotisés à un micro-interféromètre dévelopé à Femto-ST.Finalement, un montage expérimental pour la caractérisation du micromiroir est également proposé pour permettre l'évaluation des performances atteintes et afin d'amorcer les premiers test d'imagerie optiques du micro systèmeThe work presented in this manuscript consists in the conception of an electro-thermo-mechanical optical micro-scanner. In a first time, a design and a model are proposed and the micro-device was fabricated, characterized and a draft of integration onto a Mirau micro-interferometer was carried out in order to build an endoscopic probe for the detection of early stage gastrointestinal cancers using an imaging technique called Optical Coherence Tomography (OCT). The very contribution of the thesis is the development and the fabrication of micro actuators driven electrothermally to control the angular position a micro mirror plate conceived in this purpose. Different architectures of micro-scanners are proposed to best comply with the specifications determined by both the optical expectations and the medical standards requirements of the final apparatus emph{in vivo}.This work, part of a project called textquote{DEMO4} was financed by the French LabEx Action funding source in cooperation between the departments AS2M and MN2S of the French research institute Femto-ST as well as the university of Florida in the USA to deliver a first demonstrator of endoscopic OCT probe.Several batches of fabrication were realized my means of techniques of ac{CMOS}-based microfabrication in exchange between Femto-ST and the university of Florida before being assembled (for lack of monolithic integration capability) onto a micro-interferometer using automated processes specifically developed in this purpose.Finally, an experimental setup is proposed to characterize in order to evaluate the performances achieved and initiate the first tests of optical imaging using the micro-system
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Njobelo, Gwamaka Lameck. "A Microscopic Simulation Study of Applications of Signal Phasing and Timing Information in a Connected Vehicle Environment." UNF Digital Commons, 2018. https://digitalcommons.unf.edu/etd/786.
Full textAbstract:
The connected vehicle technology presents an innovative way of sharing information between vehicles and the transportation infrastructure through wireless communications. The technology can potentially solve safety, mobility, and environmental challenges that face the transportation sector. Signal phasing and timing information is one category of information that can be broadcasted through connected vehicle technology. This thesis presents an in-depth study of possible ways signal phasing and timing information can be beneficial as far as safety and mobility are concerned. In total, three studies describing this research are outlined.
The first study presented herein focuses on data collection and calibration efforts of the simulation model that was used for the next two studies. The study demonstrated a genetic algorithm procedure for calibrating VISSIM discharge headways based on queue discharge headways measured in the field. Video data was used to first compute intersection discharge headways for individual vehicle queue position and then to develop statistical distributions of discharge headways for each vehicle position. Except for the 4th vehicle position, which was best fitted by the generalized extreme value (GEV) distribution, the Log-logistic distribution was observed to be the best fit distribution for the rest of vehicle positions. Starting with the default values, the VISSIM parameters responsible for determining discharge headways were heuristically adjusted to produce optimal values. The optimal solutions were achieved by minimizing the Root Mean Square Error (RMSE) between the simulated and observed data. Through calibration, for each vehicle position, it was possible to obtain the simulated headways that reflect the means of the observed field headways. However, calibration was unable to replicate the dispersion of the headways observed in the field mainly due to VISSIM limitations. Based on the findings of this study, future work on calibration in VISSIM that would account for the dispersion of mixed traffic flow characteristics is warranted.
The second study addresses the potential of connected vehicles in improving safety at the vicinity of signalized intersections. Although traffic signals are installed to reduce the overall number of collisions at intersections, rear-end collisions are increased due to signalization. One dominant factor associated with rear-end crashes is the indecisiveness of the driver, especially in the dilemma zone. An advisory system to help the driver make the stop-or-pass decision would greatly improve intersection safety. This study proposed and evaluated an Advanced Stop Assist System (ASAS) at signalized intersections by using Infrastructure-to-Vehicle (I2V) and Vehicle-to-Vehicle (V2V) communication. The proposed system utilizes communication data, received from Roadside Unit (RSU), to provide drivers in approaching vehicles with vehicle-specific advisory speed messages to prevent vehicle hard-braking upon a yellow and red signal indication. A simulation test bed was modeled using VISSIM to evaluate the effectiveness of the proposed system. The results demonstrate that at full market penetration (100% saturation of vehicles equipped with on-board communication equipment), the proposed system reduces the number of hard-braking vehicles by nearly 50%. Sensitivity analyses of market penetration rates also show a degradation in safety conditions at penetration rates lower than 40%. The results suggest that at least 60% penetration rate is required for the proposed system to minimize rear-end collisions and improve safety at the signalized intersections.
The last study addresses the fact that achieving smooth urban traffic flow requires reduction of excessive stop-and-go driving on urban arterials. Smooth traffic flow comes with several benefits including reduction of fuel consumption and emissions. Recently, more research efforts have been directed towards reduction of vehicle emissions. One such effort is the use of Green Light Optimal Speed Advisory (GLOSA) systems which use wireless communications to provide individual drivers with information on the approaching traffic signal phase and advisory speeds to arrive at the intersection on a green phase. Previously developed GLOSA algorithms do not address the impact of time to discharge queues formed at the intersection. Thus, this study investigated the influence of formed intersection queues on the performance of GLOSA systems. A simulation test-bed was modeled inside VISSIM to evaluate the algorithm’s effectiveness. Three simulation scenarios were designed; the baseline with no GLOSA in place, scenario 2 with GLOSA activated and queue discharge time not considered, and scenario 3 with GLOSA activated and where queue dissipation time was used to compute advisory speeds. At confidence level the results show a significant reduction in the time spent in queue when GLOSA is activated (scenarios 2 and 3). The change in the average number of stops along the corridor was found not to be significant when the base scenario was compared against scenario 2. However, a comparison between scenarios 2 and 3 demonstrates a significant reduction in the average number of stops along the corridor, and also in the time spent waiting in queues
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Nguyen, Dinh hoang. "Development of an optical system for preclinical molecular imaging of atherothrombosis." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCD062/document.
Full textAbstract:
Dans ce travail de thèse, nous développons des protocoles d'imagerie optique pour l'observation des nanoparticules sur des coupes de tissus afin de relier leur localisation et leur «comportement» à l'environnement biologique, en particulier son éventuel état pathologique. Nous avons synthétisé des agents de contraste bimodaux, sous forme de nanoparticules -NP- visibles en résonance magnétique et en optique, à base d'oxydes de fer et de zinc (Zn(Fe)O) avec une nouvelle méthode de polyol azéotropique dans des solvants glycoliques (DEG et PG). L'élimination de l'eau à l'aide de l'appareil Dean-Stark est une nouvelle stratégie pour la synthèse de NP dans une solution de polyol, avec un rendement élevé et produisant des particules de petite taille. Les NP les plus visibles, selon leur contraste IRM, ont été revêtus de carboxyméthyl pullulane, de polyéthylène glycol, de carboxyméthyl dextrane et de fucoïdane, ce dernier étant un polysaccharide capable de se lier spécifiquement à la paroi vasculaire. Les NPs montrent de bonnes propriétés magnétiques et optiques à température ambiante. Les NP recouvertes ont été injectées dans un modèle de rat d’athérothrombose pour localiser le thrombus par IRM avant sacrifice et collecte des tissus pour étude des coupes histologiques par microscopie optique. La différence entre les images IRM avant et après l'injection de fucoïdane-NPs et de CMD-NPs est claire. Les résultats montrent que les NP recouvertes de fucoïdane sont liées au thrombus. Certains types de microscopies, tels que la microscopie de fluorescence, la microscopie en champ sombre, la microscopie hyperspectrale à champ sombre et la microscopie interférentielle à champ sombre ont été développés pour la détection des NPs en milieu liquide et dans les tissus. En analysant le spectre de chaque pixel et en le comparant au spectre des matériaux de référence, la microscopie hyperspectrale peut détecter la présence de NPs sur des coupes de tissus, les localiser, les identifier et les caractériser. Zn(Fe)O NPs constituerait donc un agent de contraste bimodal potentiel pour l’IRM et l’imagerie optique. Cependant, bien que de nombreux outils optiques avancés aient été développés, nous avons constaté qu'il est toujours difficile d'identifier de manière fiable les NP dans le tissuIn this thesis work, we develop optical imaging protocols for the observation of then anoparticles on tissue slices in order to further link their localization and their “behaviour” to the biological pathological environment. Bimodal zinc and iron oxide-based MRI/optical nanoparticle contrast agents (Zn(Fe)O) have been synthesised with a novel azeotropicpolyol method in glycol solvents (DEG and PG). The most potent NPs, as regard to their MR contrast power, have been coated with carboxymethyl pullulan, polyethylene glycol,carboxymethyl dextran (CMD) and fucoidan, the latter being a polysaccharide able to specifically bind to the vascular wall. The coated NPs were injected into rat to locate atherothrombosis by MRI. Then the histological slices of harvested diseased tissue were imaged with our homemade optical microscope. Water removal using Dean-Stark apparatus is a novel strategy for the synthesis of NPs in polyol solution with high yield and small size.The NPs show the good magnetic and optical properties at room temperature. The coated nanoparticles were injected into an atherothrombotic rat model to locate the thrombus by MRI prior to sacrifice of the animals and tissue collection for histological study by optical microscopy. The difference of MRI images between before and after injection with Fucoidan-NPs and CMD-NPs is clear. The results indicated that fucoidan-NPs are linked to the thrombus. Some type of microscopies, such as fluorescent microscopy, dark field microscopy, hyperspectral dark field microscopy and interference dark field microscopy have been developed for the detection of NPs in liquid medium and in the histological tissue. By analyzing the spectrum of every pixel and comparing to the spectrum of reference materials, hyperspectral microscopy can detect the presence of nanomaterial on exposed tissue slices, locate, identify, and characterize them. Zn(Fe)O NPs would therefore constitute a potential bimodal contrast agent for MRI and optical imaging. Although many advance optical tools have been developed, but we found it is still a challenge to identify reliably the NPs in the tissue
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Madai, Vince István [Verfasser]. "Virtual pre-embedding labeling : a method for correlative fluorescence and electron microscopic imaging and double-labeling in the central nervous system of the rat / Vince István Madai." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2012. http://d-nb.info/1027307558/34.
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Madai, Vince Istvan [Verfasser]. "Virtual pre-embedding labeling : a method for correlative fluorescence and electron microscopic imaging and double-labeling in the central nervous system of the rat / Vince István Madai." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2012. http://d-nb.info/1027307558/34.
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Klages, Rainer. "Microscopic Chaos, Fractals, and Transport in Nonequilibrium Steady States. - (Die Veröffentlichung einer ergänzten und überarbeiteten Version bei "World Scientific Publishing" ist für 2005/06 geplant.)." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2004. http://nbn-resolving.de/urn:nbn:de:swb:14-1107426004665-22819.
Full textAbstract:
A fundamental challenge is to understand nonequilibrium statistical mechanics starting from microscopic chaos in the equations of motion of a many-particle system. In this thesis we summarize recent theoretical advances along these lines. We focus on two different approaches to nonequilibrium transport: One considers Hamiltonian dynamical systems under nonequilibrium boundary conditions, another one suggests a non-Hamiltonian approach to nonequilibrium situations created by external electric fields and by temperature or velocity gradients. A surprising result related to the former approach is that in simple low-dimensional periodic models the deterministic transport coefficients are typically fractal functions of control parameters. These fractal transport coefficients yield the first central theme of this thesis. We exemplify this phenomenon by deterministic diffusion in a simple chaotic map. We then construct an arsenal of analytical and numerical methods for computing further transport coefficients such as electrical conductivities andchemical reaction rates. These methods are applied to hierarchies of chaotic dynamical systems that are successively getting more complex, starting from abstract one-dimensional maps generalizing a simple random walk on the line up to particle billiards that should be directly accessible in experiments. In all cases, the resulting transport coefficients turn out to be either strictly fractal, or at least to be profoundly irregular. The impact of random perturbations on these quantities is also investigated. We furthermore provide some access roads towards a physical understanding of these fractalities. The second central theme is formed by a critical assessment of the non-Hamiltonian approach to nonequilibrium transport. Here we consider situations where the nonequilibrium constraints pump energy into a system, hence there must be some thermal reservoir that prevents the system from heating up. For this purpose a deterministic and time-reversible modeling of thermal reservoirs was proposed in form of Gaussian and Nose-Hoover thermostats. This approach yielded simple relations between fundamental quantities of nonequilibrium statistical mechanics and of dynamical systems theory. Our goal is to critically assesses the universality of these results. As a vehicle of demonstration we employ the driven periodic Lorentz gas, a toy model for the classical dynamics of an electron in a metal under application of an electric field. Applying different types of thermal reservoirs to this system we compare the resulting nonequilibrium steady states with each other. Along the same lines we discuss an interacting many-particle system under shear and heat. Finally, we outline an unexpected relationship between deterministic thermostats and active Brownian particles modeling biophysical cell motility.
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Шеляг, Р. В. "Биофизика зрительной сенсорной системы человека." Thesis, Сумский государственный университет, 2015. http://essuir.sumdu.edu.ua/handle/123456789/43930.
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Зрительная сенсорная система – это система, которая воспринимает излучение видимого спектра, после чего формируется изображение предметов окружающей среды в виде определенных ощущений
(сенсорных чувств).
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Klages, Rainer. "Microscopic Chaos, Fractals, and Transport in Nonequilibrium Steady States. - (Die Veröffentlichung einer ergänzten und überarbeiteten Version bei "World Scientific Publishing" ist für 2005/06 geplant.)." Doctoral thesis, Technische Universität Dresden, 2003. https://tud.qucosa.de/id/qucosa%3A24458.
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A fundamental challenge is to understand nonequilibrium statistical mechanics starting from microscopic chaos in the equations of motion of a many-particle system. In this thesis we summarize recent theoretical advances along these lines. We focus on two different approaches to nonequilibrium transport: One considers Hamiltonian dynamical systems under nonequilibrium boundary conditions, another one suggests a non-Hamiltonian approach to nonequilibrium situations created by external electric fields and by temperature or velocity gradients. A surprising result related to the former approach is that in simple low-dimensional periodic models the deterministic transport coefficients are typically fractal functions of control parameters. These fractal transport coefficients yield the first central theme of this thesis. We exemplify this phenomenon by deterministic diffusion in a simple chaotic map. We then construct an arsenal of analytical and numerical methods for computing further transport coefficients such as electrical conductivities andchemical reaction rates. These methods are applied to hierarchies of chaotic dynamical systems that are successively getting more complex, starting from abstract one-dimensional maps generalizing a simple random walk on the line up to particle billiards that should be directly accessible in experiments. In all cases, the resulting transport coefficients turn out to be either strictly fractal, or at least to be profoundly irregular. The impact of random perturbations on these quantities is also investigated. We furthermore provide some access roads towards a physical understanding of these fractalities. The second central theme is formed by a critical assessment of the non-Hamiltonian approach to nonequilibrium transport. Here we consider situations where the nonequilibrium constraints pump energy into a system, hence there must be some thermal reservoir that prevents the system from heating up. For this purpose a deterministic and time-reversible modeling of thermal reservoirs was proposed in form of Gaussian and Nose-Hoover thermostats. This approach yielded simple relations between fundamental quantities of nonequilibrium statistical mechanics and of dynamical systems theory. Our goal is to critically assesses the universality of these results. As a vehicle of demonstration we employ the driven periodic Lorentz gas, a toy model for the classical dynamics of an electron in a metal under application of an electric field. Applying different types of thermal reservoirs to this system we compare the resulting nonequilibrium steady states with each other. Along the same lines we discuss an interacting many-particle system under shear and heat. Finally, we outline an unexpected relationship between deterministic thermostats and active Brownian particles modeling biophysical cell motility.
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Swinford, Richard William. "An AFM-SIMS Nano Tomography Acquisition System." PDXScholar, 2017. https://pdxscholar.library.pdx.edu/open_access_etds/3485.
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An instrument, adding the capability to measure 3D volumetric chemical composition, has been constructed by me as a member of the Sánchez Nano Laboratory. The laboratory's in situ atomic force microscope (AFM) and secondary ion mass spectrometry systems (SIMS) are functional and integrated as one instrument. The SIMS utilizes a Ga focused ion beam (FIB) combined with a quadrupole mass analyzer. The AFM is comprised of a 6-axis stage, three coarse axes and three fine. The coarse stage is used for placing the AFM tip anywhere inside a (13x13x5 mm3) (xyz) volume. Thus the tip can be moved in and out of the FIB processing region with ease. The planned range for the Z-axis piezo was 60 µm, but was reduced after it was damaged from arc events. The repaired Z-axis piezo is now operated at a smaller nominal range of 18 µm (16.7 µm after pre-loading), still quite respectable for an AFM. The noise floor of the AFM is approximately 0.4 nm Rq. The voxel size for the combined instrument is targeted at 50 nm or larger. Thus 0.4 nm of xyz uncertainty is acceptable. The instrument has been used for analyzing samples using FIB beam currents of 250 pA and 5.75 nA. Coarse tip approaches can take a long time so an abbreviated technique is employed. Because of the relatively long thro of the Z piezo, the tip can be disengaged by deactivating the servo PID. Once disengaged, it can be moved laterally out of the way of the FIB-SIMS using the coarse stage. This instrument has been used to acquire volumetric data on AlTiC using AFM tip diameters of 18.9 nm and 30.6 nm. Acquisition times are very long, requiring multiple days to acquire a 50-image stack. New features to be added include auto stigmation, auto beam shift, more software automation, etc. Longer term upgrades to include a new lower voltage Z-piezo with strain-gauge feedback and a new design to extend the life for the coarse XY nano-positioners. This AFM-SIMS instrument, as constructed, has proven to be a great proof of concept vehicle. In the future it will be used to analyze micro fossils and it will also be used as a part of an intensive teaching curriculum.
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Zanlungo, Francesco <1976>. "Microscopic dynamics of artificial life systems." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/355/1/tesi_zanlungo.pdf.
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Zanlungo, Francesco <1976>. "Microscopic dynamics of artificial life systems." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/355/.
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França, Rodrigo Casasanta. "Avaliação do desgaste das lâminas de corte do sistema Reciproc através da utilização do microscópio eletrônico de varredura MEV." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/23/23145/tde-19122013-195214/.
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Quando se utilizam os instrumentos rotatórios, oscilatórios e os recíprocos, de NiTi (Níquel-Titânio), cortando ou raspando as paredes do conduto radicular, estes também sofrem desgastes em suas lâminas de corte. Tal ocorrência determina atritos cada vez maiores, proporcionais à perda do corte de suas lâminas, diminuindo a eficiência do instrumento, exigindo mais torques e força de penetração, aumentando ainda mais o atrito e o esforço que este sofre para desgastar a dentina, predispondo acidentes. O presente estudo avaliou o desgaste nas lâminas de corte das limas Reciproc, após 3,6 e 9 usos em canais de dentes naturais. Foram utilizados 180 dentes pré-molares inferiores e 40 instrumentos R40. Após o preparo dos canais os instrumentos foram incluídos em corpos de prova e submetidos a cortes transversais a 3 mm e 6 mm, contados a partir da ponta do instrumento. Nas imagens dessas secções transversais obtidas no MEV foi mesurada a distância entre as extremidades das lâminas de corte. O desgaste dos instrumentos foi estabelecido pela diferença entre as medidas das distâncias dos instrumentos sem uso com a média de cada instrumento, nos diferentes grupos experimentais. Observou-se diferença significante, quando comparados os grupos de 6 e 9 usos com o grupo controle. Já o grupo com 3 utilizações não apresentou diferença estatisticamente significante em relação ao grupo controle. As diferenças percentuais de desgaste a 3 mm após 3, 6 e 9 utilizações foram de 5,96%, 8,01% e 18,09%, respectivamente, em relação ao Grupo controle. As diferenças percentuais de desgaste a 6 mm, após 3, 6 e 9 utilizações foram de 2,32%, 9,54% e 21,00%, respectivamente, em relação ao Grupo controle. Conclui-se, assim, que ocorre desgaste significante das lâminas de corte dos instrumentos Reciproc, já a partir do terceiro uso reforçando a recomendação do fabricante em utilizar cada instrumento em molar e, então, descartá-lo. Palavras-chave: Microscopia eletrônica de varredura. Sistema Rotatório.The fracture of nickel-titanium instrument, whose consequences can range from the difficulty of its removal until the absolute inaccessibility to the apical portion of the canal, remains a situation to be avoided in the safest way possible. When using the rotary instruments, and reciprocal oscillatory, NiTi, cutting or scraping the walls of the root canal, they also suffer wear in its cutting blades. Such an occurrence determines friction increasing in proportion to the loss of cutting blades, reducing the efficiency of the instrument, requiring higher torque and penetration force, further increasing friction and effort that suffers when wearing the dentin. Different rotational speeds to the long axis of the active part of the instrument are thus provoked in areas of high friction, favoring fractures, regardless of the type of movement, even if it is rotating or reciprocating. The present study sought to assess whether there is wear on cutting blades System Reciproc, since this system works through reciprocal movement within the root canal. For that, we will instrumentation in selected teeth with the kinematic system recommended by the manufacturer at zero, three, six and nine uses, corresponding to a molar tooth, two molar teeth and three molar teeth after 10 uses in each experimental group (zero , three, six and nine) according to the number of uses. The instruments are inserted into a quadrangular centralized device in the same position, and fixed in resin, which have been cut into their cross initial 3 mm and 6 mm initial these selected samples with the cross section of the system is brought to the SEM, and thus wear measured by measuring the radius of your cutting blades, and thus statistically analyzed. The results showed statistically significant differences after successive instrumentations.
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Sutton, Daniel Colin. "Microscopic Hamiltonian systems and their effective description." Thesis, University of Bath, 2013. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.600217.
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The universal theme connecting the topics of this thesis is how microscopic details can help us understand the macroscopic behaviour of Hamiltonian systems. We will focus on three aspects of Hamiltonian dynamics which we now describe, this is not intended to be a comprehensive description, we provide a comprehensive introduction to each aspect in the corresponding chapters.
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Mohamad, David Kassim. "Spectroscopic and microscopic studies of organic photovoltaic systems." Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.557133.
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Bostanci, Umut. "Development Of Atomic Force Microscopy System And Kelvin Probe Microscopy System For Use In Semiconductor Nanocrystal Characterization." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608812/index.pdf.
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Atomic Force Microscopy (AFM) and Kelvin Probe Microscopy (KPM) are two surface characterization methods suitable for semiconductor nanocrystal applications. In this thesis work, an AFM system with KPM capability was developed and implemented. It was observed that, the effect of electrostatic interaction of the probe cantilever with the sample can be significantly reduced by using higher order resonant modes for Kelvin force detection. Germanium nanocrystals were grown on silicon substrate using different growth conditions. Both characterization methods were applied to the nanocrystal samples. Variation of nanocrystal sizes with varying annealing temperature were observed. Kelvin spectroscopy measurements made on nanocrystal samples using the KPM apparatus displayed charging effects.
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Liu, Xiaoqiu. "Microscopic tissue image processing for pathological evaluation /." free to MU campus, to others for purchase, 2000. http://wwwlib.umi.com/cr/mo/fullcit?p9999304.
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Zribi, Abir. "Apprentissage par noyaux multiples : application à la classification automatique des images biomédicales microscopiques." Thesis, Rouen, INSA, 2016. http://www.theses.fr/2016ISAM0001.
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Cette thèse s'inscrit dans le contexte de diagnostic assisté par ordinateur pour la localisation subcellulaire des protéines dans les images microscopiques. L'objectif est la conception et le développement d'un système de classification automatique permettant d'identifier le compartiment cellulaire dans lequel une protéine d'intérêt exerce son activité biologique. Afin de surmonter les difficultés rencontrées pour discerner les compartiments cellulaires présents dans les images microscopiques, les systèmes décrits dans la littérature proposent d'extraire plusieurs descripteurs associés à une combinaison de classifieurs. Dans cette thèse, nous proposons un schéma de classification différent répondant mieux aux besoins de généricité et de flexibilité pour traiter différentes bases d'images.Dans le but de fournir une caractérisation riche des images microscopiques, nous proposons un nouveau système de représentation permettant d'englober de multiples descripteurs visuels identifiés dans les différentes approches d'extraction de caractéristiques : locale, fréquentielle, globale et par région. Nous formulons ensuite le problème de fusion et de sélection des caractéristiques sous forme d'un problème de sélection de noyaux. Basé sur l'apprentissage de noyaux multiples (MKL), les tâches de sélection et de fusion de caractéristiques sont considérées simultanément. Les expériences effectuées montrent que la plateforme de classification proposée est à la fois plus simple, plus générique et souvent plus performante que les autres approches de la littérature. Dans le but d'approfondir notre étude sur l'apprentissage de noyaux multiples, nous définissons un nouveau formalisme d'apprentissage MKL réalisé en deux étapes. Cette contribution consiste à proposer trois termes régularisant liés à la résolution du problème d'apprentissage des poids associés à une combinaison linéaire de noyaux, problème reformulé en un problème de classification à vaste marge dans l'espace des couples. Le premier terme régularisant proposé assure une sélection parcimonieuse des noyaux. Les deux autres termes ont été conçus afin de tenir compte de la similarité entre les noyaux via une métrique basée sur la corrélation. Les différentes expérimentations réalisées montrent que le formalisme proposé permet d'obtenir des résultats de même ordre que les méthodes de référence, mais offrant l'avantage d'utiliser moins de fonctions noyauxThis thesis arises in the context of computer aided analysis for subcellular protein localization in microscopic images. The aim is the establishment of an automatic classification system allowing to identify the cellular compartment in which a protein of interest exerts its biological activity. In order to overcome the difficulties in attempting to discern the cellular compartments in microscopic images, the existing state-of-art systems use several descriptors to train an ensemble of classifiers. In this thesis, we propose a different classification scheme wich better cope with the requirement of genericity and flexibility to treat various image datasets. Aiming to provide an efficient image characterization of microscopic images, a new feature system combining local, frequency-domain, global, and region-based features is proposed. Then, we formulate the problem of heterogeneous feature fusion as a kernel selection problem. Using multiple kernel learning, the problems of optimal feature sets selection and classifier training are simultaneously resolved. The proposed combination scheme leads to a simple and a generic framework capable of providing a high performance for microscopy image classification. Extensive experiments were carried out using widely-used and best known datasets. When compared with the state-of-the-art systems, our framework is more generic and outperforms other classification systems. To further expand our study on multiple kernel learning, we introduce a new formalism for learning with multiple kernels performed in two steps. This contribution consists in proposing three regularized terms with in the minimization of kernels weights problem, formulated as a classification problem using Separators with Vast Margin on the space of pairs of data. The first term ensures that kernels selection leads to a sparse representation. While the second and the third terms introduce the concept of kernels similarity by using a correlation measure. Experiments on various biomedical image datasets show a promising performance of our method compared to states of art methods
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Vermelho, Paulo Moreira 1967. "Sistemas adesivos universais = resistência de união ao esmalte e dentina, padrão de fratura e análise ultramorfológica = Universal adhesive systems: bond strength to enamel and dentin, failure pattern and ultramorphology analysis." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/287800.
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Orientador: Marcelo GianniniTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: Os objetivos deste estudo foram analisar as características ultramorfológicas da interface de união dente-resina, a resistência de união ao esmalte e dentina pelo método da microtração e os padrões de fratura dos espécimes testados. Dois adesivos "universais ou multi-molde" (Scotchbond Universal, 3M ESPE e All-Bond Universal, Bisco) foram testados nos modos autocondicionantes e com condicionamento prévio e comparados aos métodos tradicionais de união ao esmalte e dentina (grupos controles) utilizando os adesivos Optibond FL (Kerr) e Clearfil SE Bond (Kuraray Noritake). Esmalte e dentina de terceiros molares humanos foram utilizados nos procedimentos adesivos, os quais foram realizados com as instruções dos fabricantes. Após a aplicação dos adesivos, um bloco de compósito foi construído em incrementos. Os dentes foram seccionados longitudinalmente para obtenção de espécimes em formato de "palitos" para o ensaio de resistência de união por microtração (n=8) e as análises em microscopia eletrônica de transmissão (MET) (n=2). Os espécimes foram testados após 24 horas ou um ano de armazenamento em saliva artificial. Para a MET, solução traçadora de nitrato de prata foi utilizada para mostrar espaços nanométricos e evidências de degradação na área de união. As superfícies fraturadas dos espécimes foram observadas em microscopia eletrônica de varredura e os dados de resistência de união analisadas pela ANOVA três-fatores, teste de Tukey e Dunnett (5%). O condicionamento prévio do esmalte aumentou a resistência de união dos adesivos universais, mas essa reduziu após o armazenamento por um ano. Os adesivos universais mostraram menor resistência de união em esmalte que o grupo controle quando utilizados no modo autocondicionante no tempo de 24 horas. Nenhuma diferença significativa foi encontrada na resistência de união em dentina nos dois tempos de avaliação quando comparados aos adesivos universais e os controle. O armazenamento por um ano reduziu a resistência de união em dentina apenas para um adesivo universal usando no modo autocondicionante. A análise fractográfica em esmalte mostrou predomínio de fraturas mistas e coesivas na camada de adesivo. Em dentina, o predomínio foram fraturas mistas, adesivas e coesivas em compósito. A observação da ultramorfologia em MET mostrou a formação de hibridização e zonas de interação entre todos os adesivos em esmalte e dentina nos dois modos de aplicação. Sinais de nanoinfiltração foram identificados na área de união dentina-resina para os adesivos Scotchbond Universal e Clearfil SE Bond após armazenamento por um ano. Os resultados sugerem que armazenamento por um ano pode reduzir a resistência de união quando os adesivos universais foram aplicados em esmalte condicionado, mas em dentina condicionada não houve redução da resistência de união, exceto para o adesivo Scotchbond Universal. No esmalte a resistência de união do grupo controle foi maior que a dos adesivos universais no modo autocondicionante. Após o armazenamento por um ano, a resistência de união dos adesivos universais em esmalte tratado com ácido fosfórico não diferiu do grupo controle. Em dentina, não foi encontrada diferença significativa entre adesivos universais e os grupos controles, independente do modo de condicionamento
Abstract: The aims of this study were to analyze the ultramorphological characteristics of tooth¿resin interfaces, the microtensile bond strength of multimode adhesive systems bonded to enamel and dentin, and the failure pattern of tested specimens. Two multimode adhesives (Scotchbond Universal, 3M ESPE; All-Bond Universal, Bisco) were tested in both self-etch and etch-and-rinse modes and compared to control groups using traditional bonding techniques (Optibond FL, Kerr; Clearfil SE Bond, Kuraray Noritake) in enamel and dentin. Enamel and dentin from third human molars were used for bonding and adhesives used according to the manufacturer¿ instructions. A composite resin block was incrementally applied to bonded surfaces, and teeth were sectioned transversely to the tooth-composite interface to obtain specimens for microtensile bond strength (n=8) and transmission electron microscopy (TEM) analysis (n=2). Specimens were tested after storage for either 24 hours or 1 year in artificial saliva. For TEM, a silver tracer solution was used to reveal nanometer-sized spaces and evidence of degradation within resin¿dentin interfaces. Fractured surfaces of tested specimens were analyzed under scanning electron microscopy. Bond strength data were analyzed by three-way ANOVA and by Tukey¿s and Dunnett¿s tests (?=5%). The acid-etching mode increased the enamel bond strength of multimode adhesives; however, bond strength decreased after storage for 1 year. Multimode adhesives showed lower enamel bond strength than the control group adhesive when used in self-etch mode for 24 hours. No significant differences in dentin bond strength were noted between multimode and control adhesives in either evaluation period. Storage for 1 year only reduced the dentin bond strength for a multimode adhesive used in self-etch mode. Mixed and cohesive-within-adhesive-layer failures were predominant in enamel. In dentin most fractures were mixed, adhesive along the dentin or enamel, and cohesive within the composite layer. TEM analysis identified hybridization and interaction zones in dentin and enamel for all adhesives and application modes. Silver impregnation was detected on dentin¿resin interfaces after storage of specimens for 1 year only with the Scotchbond Universal and Clearfil SE Bond samples. Results suggested that storage for 1 year can reduce bond strength when multimode adhesives are applied on an etched surface, but the dentin bond strength was not affected when using the etch-and-rinse mode (except for the Scotchbond Universal sample). The enamel bond strengths of the control group adhesives were higher than those obtained for multimode adhesives in the self-etch mode. After storage for 1 year, the bond strengths of multimode adhesives in etched enamel did not differ from those of the control group adhesive. In dentin, no significant difference was noted between the multimode and control group adhesives, regardless of etching mode
Doutorado
Dentística
Doutor em Clínica Odontológica
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Robbins, Mark J. "Describing colloidal soft matter systems with microscopic continuum models." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/9383.
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In this thesis we explore two different theories for modelling soft matter systems. We start by discussing density functional theory (DFT) and dynamical density functional theory (DDFT) and consider the thermodynamics underpinning these theories as well as showing how the main results may be derived from the microscopic properties of soft matter. We use this theory to set up a model for the evaporation of the solvent from a thin film of a colloidal suspension. The general background for such systems is discussed and we display some of the striking nanostructures which self-assemble during the evaporation process. We show that our theory successfully reproduces some of these patterns and deduce the various mechanisms and transport processes behind the formation of the different structures. In the second part of this thesis we discuss results for a second model; the phase field crystal (PFC) model. The model equations are discussed, showing how they may be derived from DDFT as well as discussing the general background of PFC models. We present some results for the PFC model in its most commonly used form before going on to introduce a modified PFC model. We show how the changes in the model equations are reflected in the thermodynamics of the model. We then proceed by demonstrating how this modified PFC model may be used to qualitatively describe colloidal systems. A two component generalisation of the modified PFC model is introduced and used to investigate the transition between hexagonal and square ordering in crystalline structures. We conclude by discussing the similarities and connections between the two models presented in the thesis.
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Zheng, Pengjun. "A microscopic simulation model of merging operation at motorway on ramps." Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289589.
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Gonçalves, Valdeci Donizete [UNESP]. "Desenvolvimento de um sistema de análise de imagem para quantificação do tamanho e distribuição de partículas de desgaste." Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/105336.
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Este trabalho descreve o desenvolvimento de um sistema de análise de imagens de partículas de desgaste encontradas em óleos lubrificantes de equipamentos industriais. Para tanto, foi utilizado um sistema de aquisição de imagem para capturar imagens de amostras de óleo retidas em membranas de filtro e, também, desenvolvida uma metodologia analítica que faz a classificação quantitativa e qualitativa das partículas, relacionando-as ao modo de desgaste na qual foram geradas. Para a classificação quantitativa utilizou-se a norma ISO 4406 e para a qualitativa, a análise por meio de Redes Neurais Artificiais. O sistema aplicado consiste em uma câmera digital, um microscópio óptico monocular, um sistema de filtragem de óleo e dois programas computacionais desenvolvidos para realização da análise automatizada das imagens das partículas de desgaste obtidas. Foram utilizados óleos minerais de redutores de máquinas industriais no processo de obtenção de amostras. As partículas de desgaste foram analisadas pelo processo de microscopia óptica para obtenção da imagem da amostra relacionada ao desgaste. Os resultados obtidos mostraram que o sistema de análise desenvolvido realiza a classificação individual das partículas, através de Redes Neurais Artificiais, com uma eficiência de até 96%, além de analisar as múltiplas partículas contidas nas amostras, exibindo um relatório de acompanhamento e evolução do desgaste. Os programas computacionais desenvolvidos para essa análise possuem interface gráfica de fácil utilização. Eles podem ser amplamente utilizados no estudo e avaliação das partículas de desgaste obtidas de amostras de óleos industriais em empresas ou em universidades para fins educacionais. O sistema pode ser utilizado para análise de superfícies de metais obtidos pelo processo de metalografia ou na análise de imagens de microorganismos obtidas...
This paper describes the development of an image analysis system for wear particles found in industrial equipment lubricating oil. Hence, it was utilized an image acquisition system to capture image samples of the oil held in filter membranes. An analytical methodology was also developed to classify the particles quantitatively and qualitatively, relating them to the wear mode where they had been generated. The ISO 4406 standard was applied for quantitative classification and Artificial Neural Networks were used for qualitative classification analysis. The applied system consists of a digital camera, a monocular optical microscope, one oil filtering system and two software programs developed to perform the automated analysis of the acquired wear particles images. Mineral oils of gearbox industrial machines were used in the process of achieving the samples. The wear particles were analyzed by an optical microscopy system, to obtain the sample image related to the wear. The results showed that the analysis system that was developed classifies the individual particles through Artificial Neural Networks with 96% accuracy, in addition to analyzing the multiple particles contained in the samples and generating an evaluation report and wear evolution. The software programs developed for the analysis have a graphical interface easy to use. They can be used in the study and evaluation of the wear particles obtained from industrial oil samples in the companies or in the universities for educational purposes. The system can be applied to analyze the surface of metals acquired by metallographic processes or in the image analysis of microorganisms acquired from blood samples, opening a wide field of application within universities and researches.
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Janson, Oleg. "DFT-based microscopic magnetic modeling for low-dimensional spin systems." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-91976.
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In the vast realm of inorganic materials, the Cu2+-containing cuprates form one of the richest classes. Due to the combined effect of crystal-field, covalency and strong correlations, all undoped cuprates are magnetic insulators with well-localized spins S=1/2, whereas the charge and orbital degrees of freedom are frozen out. The combination of the spin-only nature of their magnetism with the unique structural diversity renders cuprates as excellent model systems. The experimental studies, boosted by the discovery of high-temperature superconductivity in doped La2CuO4, revealed a fascinating variety of magnetic behaviors observed in cuprates. A digest of prominent examples should include the spin-Peierls transition in CuGeO3, the Bose-Einstein condensation of magnons in BaCuSi2O6, and the quantum critical behavior of Li2ZrCuO4. The magnetism of cuprates originates from short-range (typically, well below 1 nm) exchange interactions between pairs of spins Si and Sj, localized on Cu atoms i and j. Especially in low-dimensional compounds, these interactions are strongly anisotropic: even for similar interatomic distances |Rij|, the respective magnetic couplings Jij can vary by several orders of magnitude. On the other hand, there is an empirical evidence for the isotropic nature of this interaction in the spin space: different components of Si are coupled equally strong. Thus, the magnetism of cuprates is mostly described by a Heisenberg model, comprised of Jij(Si*Sj) terms. Although the applicability of this approach to cuprates is settled, the model parameters Jij are specific to a certain material, or more precisely, to a particular arrangement of the constituent atoms, i.e. the crystal structure. Typically, among the infinite number of Jij terms, only several are physically relevant. These leading exchange couplings constitute the (minimal) microscopic magnetic model. Already at the early stages of real material studies, it became gradually evident that the assignment of model parameters is a highly nontrivial task. In general, the problem can be solved experimentally, using elaborate measurements, such as inelastic neutron scattering on large single crystals, yielding the magnetic excitation spectrum. The measured dispersion is fitted using theoretical models, and in this way, the model parameters are refined.
Despite excellent accuracy of this method, the measurements require high-quality samples and can be carried out only at special large-scale facilities. Therefore, less demanding (especially, regarding the sample requirements), yet reliable and accurate procedures are desirable. An alternative way to conjecture a magnetic model is the empirical approach, which typically relies on the Goodenough-Kanamori rules. This approach links the magnetic exchange couplings to the relevant structural parameters, such as bond angles. Despite the unbeatable performance of this approach, it is not universally applicable. Moreover, in certain cases the resulting tentative models are erroneous. The recent developments of computational facilities and techniques, especially for strongly correlated systems, turned density-functional theory (DFT) band structure calculations into an appealing alternative, complementary to the experiment. At present, the state-of-the-art computational methods yield accurate numerical estimates for the leading microscopic exchange couplings Jij (error bars typically do not exceed 10-15%).
Although this computational approach is often regarded as ab initio, the actual procedure is not parameter-free. Moreover, the numerical results are dependent on the parameterization of the exchange and correlation potential, the type of the double-counting correction, the Hubbard repulsion U etc., thus an accurate choice of these crucial parameters is a prerequisite. In this work, the optimal parameters for cuprates are carefully evaluated based on extensive band structure calculations and subsequent model simulations.
Considering the diversity of crystal structures, and consequently, magnetic behaviors, the evaluation of a microscopic model should be carried out in a systematic way. To this end, a multi-step computational approach is developed. The starting point of this procedure is a consideration of the experimental structural data, used as an input for DFT calculations. Next, a minimal DFT-based microscopic magnetic model is evaluated. This part of the study comprises band structure calculations, the analysis of the relevant bands, supercell calculations, and finally, the evaluation of a microscopic magnetic model. The ground state and the magnetic excitation spectrum of the evaluated model are analyzed using various simulation techniques, such as quantum Monte Carlo, exact diagonalization and density-matrix renormalization groups, while the choice of a particular technique is governed by the dimensionality of the model, and the presence or absence of magnetic frustration.
To illustrate the performance of the approach and tune the free parameters, the computational scheme is applied to cuprates featuring rather simple, yet diverse magnetic behaviors: spin chains in CuSe2O5, [NO]Cu(NO3)3, and CaCu2(SeO3)2Cl2; quasi-two-dimensional lattices with dimer-like couplings in alpha-Cu2P2O7 and CdCu2(BO3)2, as well as the 3D magnetic model with pronounced 1D correlations in Cu6Si6O18*6H2O. Finally, the approach is applied to spin liquid candidates --- intricate materials featuring kagome-lattice arrangement of the constituent spins. Based on the DFT calculations, microscopic magnetic models are evaluated for herbertsmithite Cu3(Zn0.85Cu0.15)(OH)6Cl2, kapellasite Cu3Zn(OH)6Cl2 and haydeeite Cu3Mg(OH)6Cl2, as well as for volborthite Cu3[V2O7](OH)2*2H2O. The results of the DFT calculations and model simulations are compared to and challenged with the available experimental data.
The advantages of the developed approach should be briefly discussed. First, it allows to distinguish between different microscopic models that yield similar macroscopic behavior. One of the most remarkable example is volborthite Cu3[V2O7](OH)2*2H2O, initially described as an anisotropic kagome lattice. The DFT calculations reveal that this compound features strongly coupled frustrated spin chains, thus a completely different type of magnetic frustration is realized.
Second, the developed approach is capable of providing accurate estimates for the leading magnetic couplings, and consequently, reliably parameterize the microscopic Hamiltonian. Dioptase Cu6Si6O18*6H2O is an instructive example showing that the microscopic theoretical approach eliminates possible ambiguity and reliably yields the correct parameterization.
Third, DFT calculations yield even better accuracy for the ratios of magnetic exchange couplings. This holds also for small interchain or interplane couplings that can be substantially smaller than the leading exchange. Hence, band structure calculations provide a unique possibility to address the interchain or interplane coupling regime, essential for the magnetic ground state, but hardly perceptible in the experiment due to the different energy scales.
Finally, an important advantage specific to magnetically frustrated systems should be mentioned. Numerous theoretical and numerical studies evidence that low-dimensionality and frustration effects are typically entwined, and their disentanglement in the experiment is at best challenging. In contrast, the computational procedure allows to distinguish between these two effects, as demonstrated by studying the long-range magnetic ordering transition in quasi-1D spin chain systems.
The computational approach presented in the thesis is a powerful tool that can be directly applied to numerous S=1/2 Heisenberg materials. Moreover, with minor modifications, it can be largely extended to other metallates with higher value of spin. Besides the excellent performance of the computational approach, its relevance should be underscored: for all the systems investigated in this work, the DFT-based studies not only reproduced the experimental data, but instead delivered new valuable information on the magnetic properties for each particular compound.
Beyond any doubt, further computational studies will yield new surprising results for known as well as for new, yet unexplored compounds. Such "surprising" outcomes can involve the ferromagnetic nature of the couplings that were previously considered antiferromagnetic, unexpected long-range couplings, or the subtle balance of antiferromagnetic and ferromagnetic contributions that "switches off" the respective magnetic exchange. In this way, dozens of potentially interesting systems can acquire quantitative microscopic magnetic models.
The results of this work evidence that elaborate experimental methods and the DFT-based modeling are of comparable reliability and complement each other. In this way, the advantageous combination of theory and experiment can largely advance the research in the field of low-dimensional quantum magnetism. For practical applications, the excellent predictive power of the computational approach can largely alleviate designing materials with specific properties.
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Varjo, S. (Sami). "A direct microlens array imaging system for microscopy." Doctoral thesis, Oulun yliopisto, 2016. http://urn.fi/urn:isbn:9789526213828.
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Abstract This work presents the development of a new optical imaging system. Previous objections have claimed that it is easier to build a single good quality field lens than a large number of good microlenses and it is therefore better to use a field objective. The possible benefits from a field lens are here traded for a more compact and cost-efficient design that would be suitable for field diagnostics. The new imaging setup described in this work is based on a microlens array capable of capturing light field data and no other refractive optics are used. Hundreds of lenses with a diameter range 100 to 200 µm are used to capture small elementary images containing a small part of the sample. The design uses a single light source aperture enabling signal separation between the elementary images from the neighboring lenses. Prior art uses, for example, physical structures behind lenses for signal separation, making the suggested approach less complex. Further, the possibility for using printed microlens arrays for imaging instead of expensive glass lenses is studied. The captured light field data consisting of elementary images must be rendered for human viewing. A new method is developed where the rendering is based on gathering the resulting pixel values on a plane set freely in object space, enabling single pass rendering with possibilities to apply statistics to the contributing data improving the rendering quality. Commonly used projection or mosaicing based integration approaches do not allow this. The developed system has its resolution limited by the camera sensor pixel size and objects a few micrometers in size can be resolved. The results show that the imaging setup can be used to capture semi-microscopic images without expensive magnifying optics and it is useful in selected applications. For example, it is shown that the eggs of parasites causing Schistosomiasis can be detected automatically in a microscope sample. It is estimated that the system could be mass produced at low cost. The new system has no moving parts making it less susceptible to mechanical failures and it is compact in comparison with conventional microscopes. It could be a part of a point of care solution needed in diagnostic fieldworkTiivistelmä Tässä väitöskirjassa kuvataan ja tarkastellaan uutta mikrolinsseihin perustuvaa mikroskooppista kuvantamismenetelmää. Aiemmin mikrolinssejä on käytetty tavanomaisten mikroskooppien ominaisuuksien laajentamiseen. Tässä työssä perinteiset mikroskooppiobjektit korvataan linssimatolla, kompaktin ja kustannustehokkaan rakenteen saavuttamiseksi. Käyttökohteena laitteelle on kenttädiagnostiikka. Uusi kuvausjärjestelmä perustuu mikrolinssimattoihin, joilla pystytään näytteistämään valokenttää. Muuta taittavaa optiikka ei käytetä. Sadat halkaisijaltaan 100-200 µm olevat linssit kuvaavat kukin pienen osan näytteestä. Linssien välisten signaalien sekoittumisen estämiseen käytetään hyvin kontrolloitua valonlähdettä. Aiemmin esitetyissä ratkaisuissa käytetään esimerkiksi fyysisiä rakenteita yksittäisten linssien takana. Nyt esitetty ratkaisu on yksinkertaisempi. Työssä esitetään uusi menetelmä osakuvista muodostuvan datan rekonstruktioon. Tuloskuvien muodostamiseksi pikselien arvot kerätään rekonstruktiopinnalle, joka on sijoitettu vapaasti esineavaruuteen. Tämä mahdollistaa laskennallisesti tehokkaan tuloskuvan muodostuksen, sekä tilastollisten menetelmien käytön tuloksen laadun parantamiseen. Kehitetyn järjestelmän resoluutiota rajoittaa kameran pikselikoko ja sillä voidaan havaita muutaman mikrometrin kokoisia kohteita. Tulokset osoittavat, että kuvausmenetelmä sopii mikroskooppisten kohteiden kuvaamiseen ilman kalliita suurentavia linssejä. Menetelmän käyttökelpoisuutta havainnollistetaan, muun muassa, automaattisella Schistosoma parasiitin munien tunnistuksella virtsanäytteestä. Uusi kuvausjärjestelmä on mahdollista toteuttaa edullisesti, siinä ei ole liikkuva osia ja se on pieni verrattuna tavanomaiseen mikroskooppiin. Esitetty ratkaisu soveltuu yhdeksi vaihtoehdoksi kenttädiagnostiikan tarpeisiin
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Chang, Michael Ming Yuen. "A computer-controlled system in transmission electron microscopy." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292941.
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Lim, Kwang Yong S. M. Massachusetts Institute of Technology. "Optical system for high-speed Atomic Force Microscope." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61912.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 191-192).
This thesis presents the design and development of an optical cantilever deflection sensor for a high speed Atomic Force Microscope (AFM). This optical sensing system is able to track a small cantilever while the X-Y scanner moves in the X-Y plane at 1KHz over a large range of 50x50 microns. To achieve these requirements, we evaluated a number of design concepts among which the lever method and the fiber collimator method were selected. Experiments were performed to characterize the performance of the integrated AFM and to show that the cantilever tracking while the scanner is in operation was accomplished. A triangular grating was imaged with the lever method optical subassembly integrated with the scanner to demonstrate the effectiveness of the approach.
by Kwang Yong Lim.
S.M.
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Dhanapala, Hembathanthirige Yasas. "Dielectric Constant Measurements Using Atomic Force Microscopy System." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1347907325.
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Mignard-Debise, Lois. "Tools for the paraxial optical design of light field imaging systems." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0009/document.
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L'imagerie plénoptique est souvent présentée comme une révolution par rapport à l'imagerie standard. En effet, elle apporte plus de contrôle à l'utilisateur sur l'image finale puisque les dimensions spatiales et angulaires du champ de lumière offrent la possibilité de changer le point de vue ou de refaire la mise au point après coup ainsi que de calculer la carte de profondeur de la scène. Cependant, cela complique le travail du concepteur optique du système pour deux raisons. La première est qu'il existe une multitude d'appareils de capture plénoptique différents, chacun avec sa propre spécificité. La deuxième est qu'il n'existe pas de modèle qui relie le design de la caméra à ses propriétés optiques d'acquisition et qui puisse guider le concepteur dans sa tâche. Cette thèse répond à ces observations en proposant un modèle optique du premier ordre pour représenter n'importe quel appareil d'acquisition plénoptique. Ce modèle abstrait une caméra plénoptique par un réseau équivalent de caméras virtuelles existant en espace objet et qui effectue un échantillonnage identique de la scène. Ce modèle est utilisé pour étudier et comparer plusieurs caméras plénoptiques ainsi qu'un microscope plénoptique monté en laboratoire, ce qui révèle des lignes directrices pour la conception de systèmes plénoptiques. Les simulations du modèle sont aussi validées par l'expérimentation avec une caméra et le microscope plénoptiqueLight field imaging is often presented as a revolution of standard imaging. Indeed, it does bring more control to the user over the final image as the spatio-angular dimensions of the light field offer the possibility to change the viewpoint and refocus after the shot and compute the scene depth map.However, it complicates the work of the optical designer of the system for two reasons. The first is that there exist a multitude of different light field acquisition devices, each with its own specific design. The second is that there is no model that relates the camera design to its optical properties of acquisition and that would guide the designer in his task. This thesis addresses these observations by proposing a first-order optical model to represent any light field acquisition device. This model abstracts a light field camera as en equivalent array of virtual cameras that exists in object space and that performs the same sampling of the scene. The model is used to study and compare several light field cameras as well as a light field microscope setup which reveals guidelines for the conception of light field optical systems. The simulations of the model are also validated through experimentation with a light field camera and a light field microscope that was constructed in our laboratory
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Münks, Matthias [Verfasser]. "Scanning Tunneling Microscopy and Atomic Force Microscopy Measurements on Correlated Systems / Matthias Münks." Konstanz : Bibliothek der Universität Konstanz, 2017. http://d-nb.info/1142788520/34.
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Cottman, Nicholas James. "Modelling the impacts of intelligent transport systems using microscopic traffic simulation /." [St. Lucia. Qld.], 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17339.pdf.
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Hu, Teh-Min. "Power laws and dynamics in macroscopic & microscopic systems : pharmaceutical perspectives /." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486457871783884.
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