• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 8848
  • 4814
  • 3953
  • 1259
  • 936
  • 896
  • 388
  • 332
  • 236
  • 153
  • 103
  • 99
  • 95
  • 81
  • 71
  • Tagged with
  • 25575
  • 5976
  • 4097
  • 3815
  • 3208
  • 2899
  • 2021
  • 1937
  • 1841
  • 1805
  • 1681
  • 1658
  • 1658
  • 1504
  • 1445
  • 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.
91

Reservoir Simulation Used to Plan Diatomite Developement in Mountainous Region

Powell, Richard 2012 August 1900 (has links)
In Santa Barbara County, Santa Maria Pacific (an exploration and production company) is expanding their cyclic steam project in a diatomite reservoir. The hilly or mountainous topography and cut and fill restrictions have interfered with the company's ideal development plan. The steep hillsides prevent well pad development for about 22 vertical well locations in the 110 well expansion plan. Conventional production performs poorly in the area because the combination of relatively low permeability (1-10 md) and high viscosity (~220 cp) at the reservoir temperature. Cyclic steam injection has been widely used in diatomite reservoirs to take advantage of the diatomite rocks unique properties and lower the viscosity of the oil. Some companies used deviated wells for cyclic steam injection, but Santa Maria Pacific prefers the use only vertical wells for the expansion. Currently, the inability to create well pads above 22 vertical well target locations will result in an estimated $60,000,000 of lost revenue over a five year period. The target locations could be developed with unstimulated deviated or horizontal wells, but expected well rates and expenses have not been estimated. In this work, I use a thermal reservoir simulator to estimate production based on five potential development cases. The first case represents no development other than the cyclic wells. This case is used to calibrate the model based on the pilot program performance and serves as a reference point for the other cases. Two of the cases simulate a deviated well with and without artificial lift next to a cyclic well, and the final two cases simulate a horizontal well segment with and without artificial lift next to a cyclic well. The deviated well with artificial lift results in the highest NPV and profit after five years. The well experienced pressure support from the neighboring cyclic well and performed better with the cyclic well than without it. Adding 22 deviated wells with artificial lift will increase the project's net profit by an estimated $7,326,000 and NPV by $2,838,000 after five years.
92

Sequential design strategies for mean response surface metamodeling via stochastic kriging with adaptive exploration and exploitation

Chen, Xi, Zhou, Qiang 10 1900 (has links)
Stochastic kriging (SK) methodology has been known as an effective metamodeling tool for approximating a mean response surface implied by a stochastic simulation. In this paper we provide some theoretical results on the predictive performance of SK, in light of which novel integrated mean squared error-based sequential design strategies are proposed to apply SIC for mean response surface metamodeling with a fixed simulation budget. Through numerical examples of different features, we show that SIC with the proposed strategies applied holds great promise for achieving high predictive accuracy by striking a good balance between exploration and exploitation. Published by Elsevier B.V.
93

SASS: South African Simulation Survey a review of simulation-based education

Swart, Robert Nicholas 24 January 2020 (has links)
Background: Simulation-based education (SBE) has been shown to be an effective and reproducible learning tool. SBE is used widely internationally. The current state of SBE in South Africa is unknown. To the best of our knowledge this is the first survey that describes the use and attitudes towards SBE within South Africa. Methods: An online survey tool was distributed by email to: i) the South African Society of Anaesthesiologists (SASA) members; and ii) known simulation education providers in South Africa. The respondents were grouped into anaesthesia and non-anaesthesia participants. Descriptive statistics were used to analyse the data. Ethics approval was obtained: HREC REF 157/2017. Results: The majority of the respondents provide SBE and integrate it into formal teaching programmes. There is a will amongst respondents to grow SBE in South Africa, with it being recognised as a valuable educational tool. The user groups mainly targeted by SBE, were undergraduate students, medical interns, registrars and nurses. Learning objectives targeted include practical skills, medical knowledge, critical thinking and integrated management. Amongst anaesthesia respondents: the tool most commonly used to assess the quality of learner performance during SBE, for summative assessment, was ‘expert opinion’ (33%); the most frequent methods of evaluating SBE quality were participant feedback (42%) and peer evaluation (22%); the impact of SBE was most frequently assessed by informal discussion (42%) and learner feedback (39%). In anaesthesia SBE largely takes place within dedicated simulation facilities on site (47%). Most respondents report access to a range of SBE equipment. The main reported barriers to SBE were: finance, lack of trained educators, lack of equipment and lack of protected time. A limited number of respondents report engaging in SBE research. There is a willingness in both anaesthesia and non-anaesthesia groups (96% and 89% respectively) to collaborate with other centres. Conclusion: To the best of our knowledge this publication provides us with the first cross sectional survey of SBE in anaesthesia and a selection of non-anaesthetic respondents within South Africa. The majority of respondents indicate that SBE is a valuable education tool. A number of barriers have been identified that limit the growth of SBE within South Africa. It is hoped that with a commitment to ongoing SBE research and evaluation, SBE can be grown in South Africa.
94

Linkflow, a linked saturated-unsaturated water flow computer model for drainage and subirrigation

Havard, Peter January 1993 (has links)
No description available.
95

A production scheduling simulator

Nanda, Haripada January 2011 (has links)
Digitized by Kansas State University Libraries
96

A MONTE CARLO SIMULATION OF NEAR INFRARED RADIATION TRANSFER IN CLOUDS

Wu, Yi, 1960- January 1986 (has links)
No description available.
97

A real-time simulation-based optimisation environment for industrial scheduling

Frantze´n, Marcus January 2013 (has links)
In order to cope with the challenges in industry today, such as changes in product diversity and production volume, manufacturing companies are forced to react more flexibly and swiftly. Furthermore, in order for them to survive in an ever-changing market, they also need to be highly competitive by achieving near optimal efficiency in their operations. Production scheduling is vital to the success of manufacturing systems in industry today, because the near optimal allocation of resources is essential in remaining highly competitive. The overall aim of this study is the advancement of research in manufacturing scheduling through the exploration of more effective approaches to address complex, real-world manufacturing flow shop problems. The methodology used in the thesis is in essence a combination of systems engineering, algorithmic design and empirical experiments using real-world scenarios and data. Particularly, it proposes a new, web services-based, industrial scheduling system framework, called OPTIMISE Scheduling System (OSS), for solving real-world complex scheduling problems. OSS, as implemented on top of a generic web services-based simulation-based optimisation (SBO) platform called OPTIMISE, can support near optimal and real-time production scheduling in a distributed and parallel computing environment. Discrete-event simulation (DES) is used to represent and flexibly cope with complex scheduling problems without making unrealistic assumptions which are the major limitations of existing scheduling methods proposed in the literature. At the same time, the research has gone beyond existing studies of simulation-based scheduling applications, because the OSS has been implemented in a real-world industrial environment at an automotive manufacturer, so that qualitative evaluations and quantitative comparisons of scheduling methods and algorithms can be made with the same framework. Furthermore, in order to be able to adapt to and handle many different types of real-world scheduling problems, a new hybrid meta-heuristic scheduling algorithm that combines priority dispatching rules and genetic encoding is proposed. This combination is demonstrated to be able to handle a wider range of problems or a current scheduling problem that may change over time, due to the flexibility requirements in the real-world. The novel hybrid genetic representation has been demonstrated effective through the evaluation in the real-world scheduling problem using real-world data.
98

Real-Time Simulation for System Integration

Allen, Michael P. 10 1900 (has links)
International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Functional integration and validation of complex systems in an operational environment, prior to delivery or installation, can be expensive. Real-time simulation, in a lab environment, can replace hardware subsystems to provide the interfaces necessary to validate and or integrate the test article. The test article can be hardware, software or firmware. Multitasking simulations can provide modeling of subsystems and environmental sensor data for complex system integration. The simulation presented provides the capability to integrate 1553 remote terminals and provide validation of 1553 bus controller software.
99

Contribution to the analog simulation of particular dynamic phenomena in rock mass

Glasspoole, Errol Edward January 2001 (has links)
Dissertation submitted in partial compliance with the requirements for Masters Degree in Technology: Electrical Engineering (Light Current), Technikon Natal, 2001. / M
100

Fabrication assistée par ordinateur pour le procédé EBM / Computer aided manufacturing for electron beam melting manufacturing

Béraud, Nicolas 05 October 2016 (has links)
Le procédé de fabrication par fusion de poudre à l'aide d'un faisceau d'électrons est appelé procédé Electron Beam Melting (EBM). Il permet la fabrication de pièces métalliques à partir de poudres. Grâce au niveau de qualité (géométrique et mécanique) des pièces produites, le procédé peut être utilisé afin de produire des pièces fonctionnelles et non plus uniquement des prototypes. Ce procédé, ainsi que les autres procédés additifs métalliques, permettent d'envisager le passage de l'impression 3D à la fabrication additive métallique.L'utilisation de la fabrication additive dans un contexte industriel impose le respect de critères en termes de qualité, coût et délai des pièces produites. L'ensemble des étapes numériques de mise en production d'une pièce constitue la chaîne numérique. Cette dernière a un impact fort sur l'ensemble de ces trois critères. Ainsi, cette thèse apporte une réponse à la question suivante :Comment la fabrication assistée par ordinateur peut-elle améliorer le triptyque qualité, coût, délai du procédé de fabrication EBM?Le problème est abordé par la question sous-jacente suivante :Quelles caractéristiques doit posséder un environnement de fabrication assistée par ordinateur adapté au procédé EBM ?Pour répondre à cette question, la chaîne numérique actuelle est analysée . Les principales limites identifiées sont :- l'utilisation de fichiers au format STL- l’impossibilité d’optimiser le procédé à différentes échelles- l’impossibilité de simuler le procédé EBMAfin de résoudre l'ensemble des problèmes énoncés, un environnement de FAO est proposé. Celui-ci permet de centraliser l'ensemble des opérations de mise en production au sein d'un environnement unique. Il autorise le travail avec l'ensemble des formats de fichiers reconnus comme les formats natifs des logiciels de CAO ou le format STEP. Des développements informatiques permettent de concrétiser l’environnement proposé.L'implémentation de l'environnement de FAO a mis en évidence le rôle fondamental de la simulation au sein de celui-ci. Il a donc fallu répondre à la question :Comment obtenir une simulation du procédé EBM permettant sa mise au point hors ligne en temps raisonnable ?Bien que la simulation du procédé EBM est largement traitée dans la littérature scientifique, les études proposées reposent sur la méthode des éléments finis et le temps de calcul nécessaire n'est pas compatible avec une utilisation au sein d'un environnement de FAO. Un type de simulation alternatif a donc été créé : une simulation par abaques. Elle est constituée d’une simulation par la méthode des éléments finis qui permet d'obtenir des cartes de températures pour des cas de chauffes et de refroidissements standards. Ces cartes de températures sont ensuite transformées en abaques. La simulation par abaques est vue comme la succession d'une multitude de cas standards. Ainsi l'algorithme de simulation par abaques cherche l'abaque le plus proche de la situation simulée, afin d’estimer les températures au pas de temps suivant.Cette méthode de simulation a permis une réduction des temps de calcul tout en gardant une précision suffisante pour pouvoir être utilisée pour optimiser les paramètres de fabrication.Grâce à une telle simulation, un outil d'optimisation des stratégies de fusion a pu être créé. Il permet d’améliorer la qualité des pièces produites en calculant des stratégies de fusion respectant certains critères thermiques.Les apports majeurs de ces travaux de thèses sont :- l'établissement d'un cahier des charges pour une chaîne numérique performante en EBM- le développement d'un environnement de FAO adapté au procédé EBM- la mise au point d'une simulation rapide du procédé EBM basée sur des abaques- la création d'un outil d'optimisation des stratégies de fusion / The Electron Beam Melting (EBM) process allows to build metallic parts from powder. Thanks to the geometric and mechanical quality of the parts produced, the EBM process can be used to manufacture functional parts and not only prototypes. This process, with other additive metallic processes, make it possible to consider a transition from 3D printing to metallic additive manufacturing.The use of additive manufacturing in an industrial environment requires compliance with quality, cost and time criteria for the parts produced. The production of manufactured parts involves a series of numerical stages which is called the numerical chain. The numerical chain has a significant impact on the three criteria mentioned above. Thus, this thesis provides an answer to the following question:How Computer Aided Manufacturing can improve the quality, cost and time of the EBM manufacturing process?This problem is addressed through the following underlying question:What are the required characteristics for a Computer Aided Manufacturing system adapted to the EBM process?In order to answer this question, the current numerical chain is analyzed. Three main limitations are found:- the use of STL files format- the process cannot be optimized at different scales- the process cannot be simulatedTo solve these issues, a CAM environment is proposed. It allows the centralization of all numerical operations in a single environment. All supported formats can be used within this environment, such as native CAD file formats or STEP format. Software developments are done to prove the feasibility of such an environment.The CAM environment implementation reveals the crucial role of simulation in this system. It is therefore necessary to answer this second question:How to obtain an EBM process simulation allowing the development of parameters, virtually?Although EBM simulation is a recurrent subject in scientific literature, existing studies are based on the finite elements method but the calculation time needed is too important to be used in an CAM environment. Thus, an alternative type of simulation is created in this thesis: a simulation based on abacus. It is composed of a finite elements model, that allows heat maps generation for standards cases of heating and cooling. These heat maps are then transformed in abacus. The simulation algorithm based on abacus search the nearest abacus from the simulated situation in order to estimate the temperatures at the next time step.This simulation method was used to reduce the calculation time while keeping a sufficient precision to optimize process parameters.With the simulation based on abacus, a tool for the optimization of melting strategies is developed. This tool allows quality improvement for the produced parts through the calculation of melting strategies according to thermic criteria.To summarize, the main contributions of this work are:- the definition of requirements specifications of a powerful numerical chain for the EBM process- the development of a CAM environment adapted to the EBM process- the proposal of a fast simulation for the EBM process, based on abacus- the development of a tool for the optimization of melting strategies

Page generated in 0.0972 seconds