• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 43
  • 21
  • 12
  • 9
  • 7
  • 6
  • 5
  • 4
  • 3
  • 2
  • 2
  • 2
  • 1
  • Tagged with
  • 131
  • 48
  • 15
  • 14
  • 14
  • 14
  • 14
  • 12
  • 11
  • 11
  • 11
  • 11
  • 10
  • 9
  • 8
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Heuristic methods for solving two discrete optimization problems

Cabezas García, José Xavier January 2018 (has links)
In this thesis we study two discrete optimization problems: Traffic Light Synchronization and Location with Customers Orderings. A widely used approach to solve the synchronization of traffic lights on transport networks is the maximization of the time during which cars start at one end of a street and can go to the other without stopping for a red light (bandwidth maximization). The mixed integer linear model found in the literature, named MAXBAND, can be solved by optimization solvers only for small instances. In this manuscript we review in detail all the constraints of the original linear model, including those that describe all the cyclic routes in the graph, and we generalize some bounds for integer variables which so far had been presented only for problems that do not consider cycles. Furthermore, we summarized the first systematic algorithm to solve a simpler version of the problem on a single street. We also propose a solution algorithm that uses Tabu Search and Variable Neighbourhood Search and we carry out a computational study. In addition we propose a linear formulation for the shortest path problem with traffic lights constraints (SPTL). On the other hand, the simple plant location problem with order (SPLPO) is a variant of the simple plant location problem (SPLP) where the customers have preferences on the facilities which will serve them. In particular, customers define their preferences by ranking each of the potential facilities. Even though the SPLP has been widely studied in the literature, the SPLPO has been studied much less and the size of the instances that can be solved is very limited. In this manuscript, we propose a heuristic that uses a Lagrangean relaxation output as a starting point of a semi-Lagrangean relaxation algorithm to find good feasible solutions (often the optimal solution). We also carry out a computational study to illustrate the good performance of our method. Last, we introduce the partial and stochastic versions of SPLPO and apply the Lagrangean algorithm proposed for the deterministic case to then show examples and results.
62

Influência dos métodos de fotoativação e fontes de luz nas propriedades de diferentes resinas compostas /

Costa, Simone Xavier Silva. January 2010 (has links)
Resumo: O objetivo deste trabalho, dividido em três estudos, foi avaliar: (1) a influência da utilização de diferentes fontes de luz e métodos de fotoativação sobre o grau de conversão e a contração de polimerização de uma resina composta nanoparticulada; (2) a influência da utilização dos diferentes métodos de fotoativacao, disponibilizados por aparelhos LED de 2a geração, sobre a contração volumétrica das resinas compostas microhíbrida e nanopartículada e (3) as propriedades térmicas e o grau de conversão das resinas compostas microhíbrida e nanopartículada, submetidas aos diferentes métodos de fotoativação disponibilizados por aparelhos LED de 2a geracao. No primeiro estudo, o grau de conversão (GC) foi avaliado pelo metodo da espectroscopia infravermelha transformada de Fourier (FT-IR) e as forças de contração (C) mensuradas em máquina de ensaios universal (EMIC). Os dados obtidos para o GC e C foram analísados estatísticamente pelo teste da análise de variancia (ANOVA), sendo que para as forças de contração, a correção de Welch e o teste Tamhane também foram empregados. No segundo estudo, a contração volumétrica foi avaliada por um mecanismo de vídeo e imagem (AcuvolR/Bisco) e os dados obtidos foram análisados estatísticamente pelos testes ANOVA e Tukey. No terceiro estudo, o método da calorimetria exploratória diferencial foi empregado para avaliar a temperatura de transição vitrea (Tg) e de degradação dos materiais e o GC por FTIR. Os dados relativos ao GC foram análisados estatísticamente pelos testes ANOVA e Tukey. Os resultados demonstraram diferenças na contração de polimerização de acordo com o método de fotoativação empregado. No primeiro e segundo estudos, mesmo empregando diferentes metodologias, o método de fotoativação contínuo apresentou os maiores valores de contração. Por outro lado,o GC não... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The aim of this work, divided into three studies, was evaluate: (1) the influence of different light sources and photo-activation methods on degree of conversion and polymerization shrinkage of a nanocomposite resin; (2) the influence of different photo-activation methods, available by the 2nd generation LED light-curing units, on the volumetric shrinkage of microhybrid and nanocomposite resins and (3) thermal properties and degree of conversion of microhybrid and nanocomposite resins submitted to different photo-activation methods available by 2nd generation LED light-curing units. In the first study, degree of conversion (DC) was evaluated by Fourier transform infrared spectroscopy (FT-IR) and shrinkage forces (S) were measured in a universal testing machine (EMIC). The data obtained for DC and S were analyzed by Analysis of Variance test (ANOVA) and for S Welch's correction and Tamhane's tests were also employed. In the second study, volumetric shrinkage was evaluated by video-imaging device (AcuvolR/Bisco) and data were analyzed by ANOVA and Tukey's test. In the third study, differential scanning calorimetry was used in order to observe glass transition temperature (Tg) and degradation peak of the materials and DC was evaluated for FT-IR. The DC data were analyzed by ANOVA and Tukey's test. The results showed differences in the polymerization shrinkage according to photo-activation method employed. In the first and second studies, the continuous photo-activation methods presented the highest values for shrinkage even though different methodologies were used to assess. Moreover, DC was not influenced by the photo-activation method but was influenced by light sources. The lowest DC values were observed for halogen light-curing unit. In the second study beyond the influence of the photo-activation... (Complete abstract click electronic access below) / Orientador: Marcelo Ferrarezi de Andrade / Coorientador: Alessandra Nara de Souza Rastelli / Banca: Silmara Aparecida Milori Corona / Banca: Denise Pedrini / Banca: Osmir Batista de Oliveira Junior / Banca: José Roberto Cury Saad / Doutor
63

Analýza a inovace systémů osvětlení vozidel / Analysis and Innovation systems of Vehicle Lighting

Straka, Ondřej Unknown Date (has links)
Subject semestral thesis is diagnosis primary objective luminosity plus elaboration background research primary objective plus modern waies lighting. Work includes indicative allocation light fitting, systems plus possibilities increasing safeness on roads by using modern systems facilitating movement and behind handicap. Are here also circumscribed systems facilitating visibility in night o'clock plus manners realization of all these systems.
64

Simulace dopravy za využití dopravních řadičů / Traffic Simulation Using Traffic Controllers

Dressler, David January 2019 (has links)
The aim of this master's thesis is to design an extension of the existing simulation system for designing traffic intersections. The required extension will allow the use of the Siemens sX traffic controllers. The introduction to the topic of traffic engineering, traffic controllers configuration and the dynamic traffic control is discussed first. The next part is dedicated to describing the implementation of the existing simulation system. The following chapter describes the use of the sX traffic controllers and also describes the design of the required extension of the existing simulation system, for a purpose of enabling the use of sX traffic controllers. This is followed by a chapter describing the implementation of this extension. The last chapter is devoted to testing the whole system in terms of functionality and performance. Finally, other possibilities for the future development are outlined.
65

Interiérový set svítidel / Interior Lamps Set

Kaminský, Václav Unknown Date (has links)
The interior light with the changable color temperature, which can react to various daytime and also react to requirements of the customer. This feature is possible by LED technology. The shape of the light comes from undersea inspiration. The light wants to remain to the man his natural environment. And also respect his lighting needs. The light would be made from the segments which are possible to adapt in any interior by size. And also with more segments we can get more light intensity.
66

Optimální nasazení generátorů hypotéz pro detekci semaforů ve snímcích / Optimal Deployment of Multiple Hypotheses Generators for Detecting Traffic Lights in Camera Images

Bajus, Tomáš January 2017 (has links)
Táto práca sa zaoberá detekciou semafórov na snímkoch z kamery. Cieľom je nájsť vhodné nastavenie a kombináciu dostupných detektorov. V prvej časti práce je vysvetlený princíp funkcie použitých detektorov. Nasleduje zhodnotenie vlastností jednotlivých detektorov pred ich optimalizáciou. V ďalšej časti práce je popísaný proces testovania a evaluácie detektorov a predstavený nový systém pre zefektívnenie hľadania optimálneho nastavenia detektorov. V rámci optimizácie je popísaný effekt jednotlivých parametrov na chovanie systému a sú navrhnuté rozpätia vhodných hodnôt pre každý parameter. Taktiež je predstavené nové zapojenie detektorov sú nájdené optimálne pracovné body systému. Posledná časť sa zaoberá použitím vhodných metód na filtorvanie a zhlukovanie hypotéz. Nakoniec je prezentovaná celková funkčnosť systému pred a po optimizácii a výsledky sú zhodnotené.
67

Beam profile characterization of light-emitting-diode curing units and its effect on polymerization of a resin-matrix composite

AlZain, Afnan Omar January 2017 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / The general aim of this study was to investigate the influence of the localized irradiance beam profiles from multiple light-emitting-diode (LED) light-curing units (LCUs) on the polymerization pattern within a resin-matrix composite (RMC). Irradiance beam profiles were generated from one quartz-tungsten-halogen and various single and multiple emission peak LED LCUs using a camera-based beam profiler system combined with LCU power measurements obtained using an integrating sphere/spectrometer assembly. The influence of distance on irradiance, radiant exposure (RE) and degree of conversion (DC) on the top and bottom surfaces of a RMC increment, using various LCUs, at two clinically relevant distances was investigated. Molar absorptivity of the photoinitiators present in the nano-hybrid RMC (Tetric EvoCeram bleaching shade-XL) assessed was using UV-spectrophotometry. The correlation among irradiance, RE and DC was explored. A mapping approach was used to investigate DC, microhardness and cross-link density (CLD) within 5×5×2 mm specimens at various depths; top, 0.5, 0.7, 0.9, 1.1, 1.3,1.5 mm and bottom. The localized irradiance correlation with its corresponding DC, microhardness and CLD was explored, and localized DC correlation with microhardness was assessed. The DC was measured using micro-Raman spectroscopy, and CLD was assessed by an ethanol-softening method (%KHN reduction) using an automated microhardness tester. Molar absorptivity of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide was 20-fold higher than camphorquinone. Non-uniform LCU beam profiles caused localized polymerization discrepancies that were significant at specific depths and points within the specimens with respect to DC, microhardness and CLD, which did not follow a specific pattern regardless of the LCU or curing distance assessed. A moderate correlation was displayed among irradiance, RE and DC. The localized irradiance from the LCUs was weakly correlated with the corresponding DC, microhardness and CLD on the top surface of a RMC at both curing distances. The localized microhardness was moderately correlated with DC. In conclusion, polymerization within the RMC investigated was non-uniform and did not reflect the LCU irradiance pattern at the area assessed. Also, a mapping approach within the specimens provided a detailed polymerization pattern assessment occurring within a RMC increment. Therefore, the LCUs explored may potentially increase the risk of RMC fracture.
68

Improving First-Person Shooter Player  Performance With External Lighting

Dahlström, Erik January 2017 (has links)
This thesis project focuses on the creation and usage of external light effects to accommodate the needs of competitive gamers. Prior to the creation of these light effects, the function of audio in films and games was analyzed by examining the works of Michel Chion, who is the leading scholar in studying audio-vision: the relationship between the screen and sound. Subsequently, the possible application of these theories onto the lighting domain was discussed, showing the similarities and usefulness of these two different modalities. The goal of the thesis project was to improve the gamers’ perceived and objective performance in first-person shooter games. A counterbalanced within-group study was conducted; each participant played the game Doom 3 for 25 minutes with and without light effects. Four functional and informative light effects were created to accommodate the in-game content in an attempt to improve their performance. The players were given identical instructions on how to play the game. Four Philips Hue Go lights were placed in a rectangular shape around the participant with the TV in front. An additional Philips Hue LED strip was placed behind the TV. After each session, a standardized Game Experience Questionnaire (GEQ) was used to collect data on the players’ perceived performance. In-game logs were collected to determine how the players fared in combat. A linear checkpoint system was created to judge how far the participants progressed. The GEQ data showed that the light effects improved the players perceived performance. However, the results from the in-game logs and player progression are inconclusive and not statistically significant. The identified potential reasons were the low sample size (n=14), too little practice time, potential differences in player skill and physical light positioning. / Detta examensarbete fokuserar på skapandet och användandet av externa ljuseffekter  för att ackommodera tävlingsinriktade gamers behov. Inför skapandet av dessa  ljuseffekter genomfördes en utforskning av ljudets funktion i film och spel genom att  analysera Michel Chions verk inom audio-vision (eng); det vill säga förhållandet mellan  bild och ljud. Fortsättningsvis diskuterades huruvida dessa teorier kunde appliceras på  domänen ljus, genom att visa på användbarheten samt de likheter som dessa två olika  modaliteter har.    Målet för examensarbetet var att förbättra gamers upplevda och objektiva prestation i  förstapersonsskjutare (eng: First Person Shooter / FPS). En motviktad användarstudie  (within-group) genomfördes. Fyra funktionella och informativa ljuseffekter skapades för  att ackommodera spelets innehåll i ett försök att förbättra spelarnas prestation. Varje  deltagare spelade FPS-spelet ​Doom 3​ i 25 minuter med och utan ljuseffekter. Spelarna fick  identiska instruktioner om spelets grunder. Fyra Philips Hue Go-lampor var utplacerade  rektangulärt runt spelaren med TVn längst fram i mitten. En ytterligare Philips Hue LED  strip var placerad bakom TVn.    Efter varje session användes ett standardiserat Game Experience Questionnaire (GEQ) för  att insamla data av spelarnas upplevda prestation. Data loggades även inifrån spelet för  att uppmäta hur spelarna presterade i strid. Ett linjärt kontrollstationssystem upprättades  för att avgöra hur långt in i spelet deltagarna nådde.    Datan från GEQ-enkäterna visade att ljuseffekterna förbättrade spelarnas upplevda  prestation. Datan från spelloggarna och kontrollstationssystemet gav ett ofullständigt  resultat och var statistiskt insignifikant. De identifierade potentiella anledningarna var det  låga antalet deltagare (n=14), för lite övningstid, skillnader i spelarfärdighet och fysisk  ljuspositionering.
69

Autonomous Satellite Operations for CubeSat Satellites

Anderson, Jason Lionel 01 March 2010 (has links) (PDF)
In the world of educational satellites, student teams manually conduct operations daily, sending commands and collecting downlinked data. Educational satellites typically travel in a Low Earth Orbit allowing line of sight communication for approximately thirty minutes each day. This is manageable for student teams as the required manpower is minimal. The international Global Educational Network for Satellite Operations (GENSO), however, promises satellite contact upwards of sixteen hours per day by connecting earth stations all over the world through the Internet. This dramatic increase in satellite communication time is unreasonable for student teams to conduct manual operations and alternatives must be explored. This thesis first introduces a framework for developing different Artificial Intelligences to conduct autonomous satellite operations for CubeSat satellites. Three different implementations are then compared using Cal Poly's CP6 CubeSat and the University of Tokyo's XI-IV CubeSat to determine which method is most effective.
70

Homogénéisation d’équations de Hamilton-Jacobi et applications au trafic routier / Homogenization of Hamilton-Jacobi equations and applications to traffic flow modelling

Firozaly, Jérémy 15 December 2017 (has links)
Cette thèse contient deux contributions à l’homogénéisation en espace-temps des équations de Hamilton-Jacobi du premier ordre. Ces équations sont en lien avec la modélisation du trafic routier. Enfin, sont présentés des résultats d’homogénéisation en milieu presque périodique. Le premier chapitre est consacré à l’homogénéisation d’un système infini d’équations différentielles couplées avec temps de retard. Ce système provient ici d’un modèle microscopique de trafic routier simple. Les conducteurs se suivent sur une route rectiligne infinie et l’on tient compte de leur temps de réaction. On suppose que la vitesse de chaque conducteur est une fonction de l’interdistance avec le conducteur qui le précède: on parle d’un modèle du type “follow-the-leader”. Grâce à un principe de comparaison strict, on montre la convergence vers un modèle macroscopique pour des temps de réaction inférieurs à une valeur critique. Dans un second temps, on exhibe un contre-exemple à l’homogénéisation pour un temps de réaction supérieur à cette valeur critique, pour des conditions initiales particulières. Pour cela, on perturbe la solution stationnaire dans laquelle les véhicules sont tous équidistants aux instants initiaux. Le second chapitre porte sur l’homogénéisation d’une équation de Hamilton-Jacobi dont l’Hamiltonien est discontinu en espace. Le modèle de trafic associé est une route rectiligne comportant une infinité de feux tricolores. Ces feux sont supposés identiques, équidistants et le déphasage entre deux feux successifs est supposé constant. On étudie l’influence à grande échelle de ce déphasage sur le trafic. On distingue la portion de route libre, qui sera représentée par un modèle macroscopique, et les feux, qui seront modélisés par des limiteurs de flux périodiques en temps. Le cadre théorique est celui par C. Imbert et R. Monneau (2017) pour les équations de Hamilton-Jacobi sur réseaux. L’étude se décompose en l’homogénéisation théorique, où l’Hamiltonien effectif dépend du déphasage, puis l’obtention de propriétés qualitatives de cet Hamiltonien à l’aide d’observations via des simulations numériques. Le troisième chapitre présente des résultats d’homogénéisation en milieu presque périodique. On étudie tout d’abord un problème d’évolution avec un Hamiltonien stationnaire, presque périodique en espace. À l’aide d’arguments presque périodiques, on effectue dans un second temps une nouvelle preuve du résultat d’homogénéisation du second chapitre. L’Hamiltonien est alors périodique en temps et presque périodique en espace. Sont également présentes des questions encore ouvertes, notamment dans le cas où l’Hamiltonien est presque périodique en temps-espace, et dans le cas d’un modèle de trafic où les feux sont assez proches, avec donc un modèle microscopique entre les feux / This thesis report deals with the homogenization in space and time of some first order Hamilton-Jacobi equations. It contains two contributions. The corresponding equations are derived from traffic flow modelling. We finally present some results of almost periodic homogenization. In the first chapter, we consider a one dimensional pursuit law with delay which is derived from traffic flow modelling. It takes the form of an infinite system of first order coupled delayed equations. Each equation describes the motion of a driver who interacts with the preceding one: such a model is referred to as a ``follow-the-leader" model. We take into account the reaction time of drivers. We derive a macroscopic model, namely a Hamilton-Jacobi equation, by a homogenization process for reaction times that are below an explicit threshold. The key idea is to show, that below this threshold, a strict comparison principle holds for the infinite system. Above this threshold, we show that collisions can occur. In a second time, for well-chosen dynamics and higher reaction times, we show that there exist some microscopic pursuit laws that do not lead to the previous macroscopic model. Such a law is here derived as a perturbation of the stationnary solution, for which all the vehicles are equally spaced at initial times. The second chapter is dedicated to the homogenization of a Hamilton-Jacobi equation for traffic lights. We consider an infinite road where lights are equally spaced and with a constant phase shift between two lights. This model takes the form of a first order Hamilton-Jacobi equation with an Hamiltonian that is discontinuous in the space variable and the notion of viscosity solution is the one introduced by C. Imbert and R. Monneau (2017). Each light is modelled as a time-periodic flux limiter and the traffic flow between two lights corresponds to the classical LWR model. The global Hamiltonian will be time-periodic but not periodic in space for a general phase shift. We first show that the rescaled solution converges toward the solution of the expected macroscopic model where the effective Hamiltonian depends on the phase shift. In a second time, numerical simulations are used to analyse the effect of the phase shift on the effective Hamiltonian and to reveal some properties of the effective Hamiltonian from the numerical observations. In the third chapter, we are interested in some homogenization problems of Hamilton-Jacobi equations within the almost periodic setting which generalizes the usual periodic one. The first problem is the evolutionary version of the work cite {ishii2000almost}, with the same stationary Hamiltonian. The second problem has already been solved in the second chapter but we use here almost periodic arguments for the time periodic and space almost periodic Hamiltonian. We only study the ergodicity of the associated cell problems. We finally discuss open problems, the first one concerning a space and time almost periodic Hamiltonian and the second one being a microscopic model for traffic flow modelling where the Hamiltonian is almost periodic in space

Page generated in 0.0425 seconds