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  • 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.
171

Uma interface eletrônica e computacional para medições a três coordenadas / A electronic and computational interface for coordinate measurement

Alessandro Marques 08 December 2003 (has links)
As Máquinas de Medir a Três Coordenadas (MM3Cs) desde sua criação evoluíram sensivelmente, entretanto poucas foram as modificações estruturais observadas. Hoje, para fabricantes de máquinas destacarem-se no mercado, são necessários grandes investimentos na busca de novos materiais estruturais e no desenvolvimento de programas computacionais cada vez mais versáteis. O sistema eletrônico e os programas computacionais utilizados durante as medições são inacessíveis e rígidos. Estes aplicativos normalmente não podem ser analisados nem modificados pelo usuário. São exemplos clássicos desta rigidez as características préestabelecidas pelo programa, ou métodos de ajustes utilizados na definição das grandezas. Este trabalho tem por objetivo exibir a interface eletrônica e computacional que quebra essa rigidez e permite a aquisição dos sinais das escalas da MM3C, possibilitando o desenvolvimento de novos aplicativos computacionais. O sistema foi aplicado em uma MM3C do tipo Ponte Móvel. Foi desenvolvido um programa computacional, MaqMed 2000, que utiliza os valores dos pontos coordenadas capturados no volume de trabalho da MM3C, e faz a compensação das coordenadas dos pontos utilizados, através das equações do Modelo Reduzido de Sintetização de Erros (MRSE). A avaliação da compatibilidade do dispositivo construído foi feita através do MaqMed 2000 em situações práticas. Foram tomados pontos no perfil de artefatos-padrão e os pontos ajustados através de duas rotinas, uma com e outra sem compensação dos erros. Os artefatos foram medidos em várias posições no volume da MM3C e averiguada a proximidade entre os resultados compensados e os não compensados, ao valor calibrado do artefato. O sistema desenvolvido permitiu compensar os erros em até 98% para compensação bidimensional e 87% para tridimensional. / Since the advent Coordinate Measuring Machines (CMMs) have improved substantially. However, only a small number of structural modifications were observed. Nowadays, considerable capital expenditure is needed to keep CMM builders competitive. Most important research fields concern structural material and production of more flexible and versatile software. The electronic system and the software used during measurement with CMM are rigid and inaccessible and no user modification is permitted. Typical examples are the predetermined software features and curve fitting methods used on the magnitudes definition process. This research aims to exhibit an interface that copes with the system stiffness and enables signal acquisition from the scales of the CMM, allowing the development of new types softwares. The proposed system was implemented on a moving bridge type CMM. A program that uses the values of the coordinate points obtained from the CMM work volume was created. The software MaqMed 2000 performs the compensation of the coordinates of the used points by means of synthesized errors equations. Evaluation of the performance of the built device was carried out using MaqMed 2000 in practical situations. Data sets were collected along the profile of artefacts and fitted by means of two routines, one with error compensation and the other not compensated. Artefacts were measured in several locations in the whole volume of the CMM. The proximity between the compensated and noncompensated results with respect to the calibrated artefact value was examined. The developed system allowed for error compensation of 98% for bi-dimensional compensation and 87% for tri-dimensional compensation.
172

Sur une approche isogéométrique pour problèmes multi-champs couplés en grandes transformations / An isogeometric analysis approach for coupled multi-field problems at large strain

Zhang, Lei 05 December 2016 (has links)
La méthode isogéométrique (IGA) récemment proposée en tant que méthode numérique générique offre de réelles perspectives dans l’unification des modèles géométriques et computationnel. La méthode isogéométrique est intiment liée à la méthode des éléments finis (FEM) étant donné que la méthode est basée sur le même cadre variationnel. Cette méthode a montré dans de nombreuses circonstances de très bonne qualités numériques notamment avec des maillages grossiers (précision numérique, capacité à supporter de grandes déformations…). Notre objectif final dans ce travail est de fournir un environnement de base, numérique et logiciel, pour la simulation de problèmes à champs et physiques multiples pour des pièces élastomériques de type industriel. Dans ce contexte, les points numériques à développer pour l’IGA sont le traitement de l’incompressibilité et le caractère multi-champs du problème thermique dans la formulation de Galerkin. Ainsi dans ce travail nous proposons en premier, un paradigme objet de l’IGA intégré au sein d’une architecture orientée objet en Java, initialement con?ue pour résoudre des problèmes multi-champs couplés en transformations finies. L’approche proposée s’appuie pleinement sur le contexte variationnel existant dans le code dans le cadre des éléments finis pour réduire les développements pour MEF et IGA (une formulation développée en IGA tourne en MEF et vice versa). Dans un second temps, nous avons étudié le problème de l’incompressibilité pour notamment réduire le verrouillage numérique existant toujours sur l’IGA standard. Par un souci de simplicité, nous adoptons des formulations mixtes à 2 champs (déplacement/pression). Afin d’essayer de satisfaire la condition inf-sup en relachant la contrainte sur le déplacement, nous avons développé deux idées de la littérature (naturelle en NURBS) qui consiste à soit dupliquer une fois les n?uds intérieurs du patch des déplacements ou subdiviser les éléments du patch des déplacements. Nous avons étendu ce type d’éléments aux transformations finies. Enfin, et de manière originale, nous avons adopté la même stratégie pour les problèmes à 2-champs pour la thermomécanique. Différentes simulations à petites et grandes déformations confirment le potentiel de l’approche. Enfin, nous évaluons l’ensemble sur un modèle quasi-incompressible thermo-visco-élastique de type Zener sur des éprouvettes classiques dans un contexte physique complexe. / Recently proposed as a general purpose numerical method, the Isogeometric Analysis (IGA) offers great perspective to bridge the gap between CAD and CAE. The IGA is closely related to the finite element method (FEM) as the method is based on the same variational framework. Moreover, this method has shown in many circumstances to be have a better accuracy than the FEM (large mesh distortions…). Our final aim in this work is to simulate complex multiphysics problems for elastomers industrial parts. As matter of fact, the two main numerical issues in this context is the incompressibility/quasi-incompressibility of the material and the thermochemical coupling in Galerkin formulations. First, we propose, a programming paradigm of the IGA in an existing Java object-oriented hierarchy initially designed for solving multi-fields coupled problems at finite strains. We develop an approach that fully take benefit of the original architecture to reduce developments for both FEM and IGA (one problem developed in FEM can be run in IGA and vice versa). Second, we investigate volumetric locking issues persisting for low order NURBS element observed with standard displacement formulation as finite elements. To cure the problem, we adopt two-fields mixed formulation (displacement/pressure) for the sake of simplicity and target at assessing different discretizations in stability (inf-sup condition). The basic idea is to first to increase the internal knot’s multiplicity or to subdivide the patch for displacements. These ideas that are directly inspired from patches properties, have been found in the literature for the Stokes problem and extended to large strain in solid mechanics. The comparison between the two-fields mixed formulation and a strain projection method is lead at small and large strains. At last, we originally adopt a similar strategy for thermomechanical problem at small and large strains. In the context two-fields formulation, displacement/temperature, the LBB stability condition must be fulfilled to guaranty stability. Thus, we investigate the choices of patches for two-fields formulation displacement/temperature fields for IGA applied to thermoelasticity. Several numerical results for thermomechanical problems at small and finite strains, linear and nonlinear have been presented. At last, an incompressible viscous thermo-hyperelastic model is evaluated in the IGA framework with the proposed approach.
173

Model-based Air and Fuel Path Control of a VCR Engine / Modellbaserad luft- och bränslereglering av en VCR-motor

Lindell, Tobias January 2009 (has links)
The objective of the work was to develop a basic control system for an advancedexperimental engine from scratch. The engine this work revolves around is a Saabvariable compression engine.A new control system is developed based on the naked engine, stripped of theoriginal control system. Experiments form the basis that the control system isbuilt upon. Controllers for throttles, intake manifold pressure for pressures lessthan ambient pressure and exhaust gas oxygen ratio are developed and validated.They were found to be satisfactory. The lambda controller is tested with severalparameter sets, and the best set is picked to be implemented in the engine. Modelsnecessary for the development and validation of the controllers are developed.These models include models for the volumetric efficiency, the pressure dynamicsof the intake manifold, the fuel injectors and wall wetting.
174

Improving rendering times of Autodesk Maya Fluids using the GPU

Andersson, Jonas, Karlsson, David January 2008 (has links)
Fluid simulation is today a hot topic in computer graphics. New highly optimized algorithms have allowed complex systems to be simulated in high speed. This master thesis describes how the graphics processing unit, found in most computer workstations, can be used to optimize the rendering of volumetric fluids. The main aim of the work has been to develop a software that is capable of rendering fluids in high quality and with high performance using OpenGL. The software was developed at Filmgate, a digital effects company in Göteborg, and much time was spent making the interface and the workflow easy to use for people familiar with Autodesk Maya. The project resulted in a standalone rendering application, together with a set of plugins to exchange data between Maya and our renderer. Most of the goals have been reached when it comes to rendering features. The performance bottleneck turned out to be reading data from disc and this is an area suitable for future development of the software.
175

3D seismic attributes analysis and inversions for prospect evaluation and characterization of Cherokee sandstone reservoir in the Wierman field, Ness County, Kansas

Boumaaza, Bouharket January 1900 (has links)
Master of Science / Department of Geology / Abdelmoneam Raef / Matthew W. Totten / This work focuses on the use of advanced seismically driven technologies to estimate the distribution of key reservoir properties which mainly includes porosity and hydrocarbon reservoir pay. These reservoir properties were estimated by using a multitude of seismic attributes derived from post-stack high resolution inversions, spectral imaging and volumetric curvature. A pay model of the reservoir in the Wierman field in Ness County, Kansas is proposed. The proposed geological model is validated based on comparison with findings of one blind well. The model will be useful in determining future drilling prospects, which should improve the drilling success over previous efforts, which resulted in only few of the 14 wells in the area being productive. The rock properties that were modeled were porosity and Gamma ray. Water saturation and permeability were considered, but the data needed were not available. Sequential geological modeling approach uses multiple seismic attributes as a building block to estimate in a sequential manner dependent petrophysical properties such as gamma ray, and porosity. The sequential modelling first determines the reservoir property that has the ability to be the primary property controlling most of the other subsequent reservoir properties. In this study, the gamma ray was chosen as the primary reservoir property. Hence, the first geologic model built using neural networks was a volume of gamma ray constrained by all the available seismic attributes. The geological modeling included post-stack seismic data and the five wells with available well logs. The post-stack seismic data was enhanced by spectral whitening to gain as much resolution as possible. Volumetric curvature was then calculated to determine where major faults were located. Several inversions for acoustic impedance were then applied to the post-stack seismic data to gain as much information as possible about the acoustic impedance. Spectral attributes were also extracted from the post-stack seismic data. After the most appropriate gamma ray and porosity models were chosen, pay zone maps were constructed, which were based on the overlap of a certain range of gamma ray values with a certain range of porosity values. These pay zone maps coupled with the porosity and gamma ray models explain the performance of previously drilled wells.
176

An on-line acid-base titration applet in the generic tutorial system for the sciences project

Gummo, Thomas Lee 01 January 2002 (has links)
The purpose of this Master's Project was to develop an Acid-Base Titration Simulator. It was also to be a part of the California State University - San Bernardino's GTSS, Generic Tutorial System for the Sciences, project. The main benefit is that students will be able to conduct titration experiments over the Internet without being in the laboratory and without costly equipment or dangerous chemicals. Instructors at the high school and college level can demonstrate the key principles of titration.
177

Investigation of 4D dose in volumetric modulated arc therapy-based stereotactic body radiation therapy: does fractional dose or number of arcs matter? / 強度変調回転放射線治療を用いた体幹部定位放射線治療における4次元線量の研究:1回線量及び回転軌道数の影響

Shintani, Takashi 25 May 2020 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第22642号 / 医博第4625号 / 新制||医||1044(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 武田 俊一, 教授 増永 慎一郎, 教授 鈴木 実 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM
178

Nasazení pokročilých kompenzací na stroji MCV 754 QUICK / Deployment of advanced compensation to the machine MCV 754 QUICK

Andrýsek, Jakub January 2017 (has links)
This work is focused on the software compensation of the geometric and volumetric errors. In the thesis there are descripted the measuring instruments suitable for measuring geometric and volumetric errors of the machine tool. In addition, there are described control systems and selected software compensations currently used in the machine tools. In the experimental part of the thesis there is briefly described the machining machine where the experiment was performed. Detailed procedures for using the used measuring instruments are also described. The aim of this thesis is to determine the influence of the size of the compensated volume on the geometric and volumetric precision of the machine tool.
179

Generování a zobrazování rozsáhlých voxelových scén / Generating and Rendering of Large Voxel-Based Scenes

Čejchan, Daniel January 2019 (has links)
This thesis focuses on creating an application for procedural generation and visualisation of a volumetric terrain using the OpenGL library. The terrain is considered to be mostly static, however with a possibility of modification of individual voxels. The project seeks a compromise between rendering performance and the aesthetics. The design is led in a way so that it could be further used as a foundation for a game. An emphasis is put on accelerating used methods on the GPU.
180

Volumetrická přesnost obráběcích strojů / Volumetric accuracy of machine tools

Máčala, Daniel January 2019 (has links)
The diploma thesis deals with the influence of the volumetric accuracy of the machine tool on the size of the assessed work space. The impact assessment was carried out on the basis of tests of a three-axis vertical CNC machining center. The thesis is divided into two parts, theoretical and practical. The theoretical part is focused on geometric / volumetric accuracy of machine tools, measuring technique for measuring geometric errors and Design of Experiment. In the practical part, there is an analysis of the Design of Experiment according to Shainin, description of the work with the measuring instruments and the measurement of the geometric / volumetric accuracy of the machine including statistical evaluation. The output of the thesis is the description of the influence of volumetric deviation on the size of the measured work space by means of statistical methods.

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