• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 25
  • 10
  • 3
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 58
  • 17
  • 17
  • 15
  • 13
  • 12
  • 10
  • 7
  • 7
  • 6
  • 6
  • 6
  • 5
  • 5
  • 5
  • 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.
21

Technological aspects of corrosion control of metals / Enjeux technologique de la protection contre la corrosion

Taylor, Matthew 06 November 2012 (has links)
La prévention contre la corrosion est un facteur déterminant pour la durabilité des matériaux. Historiquement, le développement des applications des matériaux avancés n'est pas envisageable sans une approche scientifique poussée des mécanismes fondamentaux qui conduisent à la dégradation en service. L'histoire humaine a été ponctuée par les progrès technologiques, qui ont tous été permis par les progrès de la science des matériaux, de l'âge du fer à l'âge de silicium. Par exemple, c'est la fusion du minerai qui a fait basculer l'humanité de l'âge de pierre aux premiers alliages (bronze) et la fondation ultérieure d'une société basée sur les métaux. Ces métaux retournent à l'état naturel en suivant des lois thermodynamiques et cinétiques. l'objet de la thèse vise à comprendre le comportement de certains matériaux dits passivables pour tenter de proposer des lois de comportement à partir du modèle du défaut ponctuel. Cette approche s'appuie sur des caractérisations électrochimique et physico-chimique des matériaux métalliques considérés. / Corrosion control is an important facet of durable and responsible engineering. Historically, the development of advanced materials applications stymied without sufficient scientific understanding of the fundamental mechanisms that dominate degradation in the system of application. Human history has been punctuated by advances in technology, all of which were enabled by advances in materials science, from the iron age to the silicon age. For instance, it was the invention of smelting ores that brought humanity out of the stone age, leading to the first alloys (bronze) and the subsequent foundation of a metals based society. During the infancy of the planet earth, around four billion years ago, the first photosynthesizers began converting carbon dioxide into oxygen. However, oxygen gas was not released into the atmosphere in great quantities because it was immediately bound up with dissolved metals in the ocean; mostly iron, forming a large fraction of the iron ores we rely upon. Producing such metals from oxides formed during the previous four billion years involves flying in the face of the thermodynamic desire to return to the oxide state.
22

Simulation-driven design : Motives, Means, and Opportunities

Sellgren, Ulf January 1999 (has links)
Efficiency and innovative problem solving are contradictory requirements for productdevelopment (PD), and both requirements must be satisfied in companies that strive to remainor to become competitive. Efficiency is strongly related to ”doing things right”, whereasinnovative problem solving and creativity is focused on ”doing the right things”.Engineering design, which is a sub-process within PD, can be viewed as problem solving or adecision-making process. New technologies in computer science and new software tools openthe way to new approaches for the solution of mechanical problems. Product datamanagement (PDM) technology and tools can enable concurrent engineering (CE) bymanaging the formal product data, the relations between the individual data objects, and theirrelation to the PD process. Many engineering activities deal with the relation betweenbehavior and shape. Modern CAD systems are highly productive tools for conceptembodiment and detailing. The finite element (FE) method is a general tool used to study thephysical behavior of objects with arbitrary shapes. Since a modern CAD technology enablesdesign modification and change, it can support the innovative dimension of engineering aswell as the verification of physical properties and behavior. Concepts and detailed solutionshave traditionally been evaluated and verified with physical testing. Numerical modeling andsimulation is in many cases a far more time efficient method than testing to verify theproperties of an artifact. Numerical modeling can also support the innovative dimension ofproblem solving by enabling parameter studies and observations of real and syntheticbehavior. Simulation-driven design is defined as a design process where decisions related tothe behavior and performance of the artifact are significantly supported by computer-basedproduct modeling and simulation.A framework for product modeling, that is based on a modern CAD system with fullyintegrated FE modeling and simulation functionality provides the engineer with tools capableof supporting a number of engineering steps in all life-cycle phases of a product. Such aconceptual framework, that is based on a moderately coupled approach to integratecommercial PDM, CAD, and FE software, is presented. An object model and a supportingmodular modeling methodology are also presented. Two industrial cases are used to illustratethe possibilities and some of the opportunities given by simulation-driven design with thepresented methodology and framework. / QC 20100810
23

Geometrical theory, modeling and applications of channel polarization

Kwon, Seok Chul 12 January 2015 (has links)
Long-term evolution (LTE) standard has been successfully stabilized, and launched in several areas. However, the required channel capacity is expected to increase significantly as the explosively increasing number of smart-phone users implies. Hence, this is already the time for leading researchers to concentrate on a new multiple access scheme in wireless communications to satisfy the channel capacity that those smart users will want in the not-too-distant future. The diversity and multiplexing in a new domain - polarization domain - can be a strong candidate for the solution to that problem in future wireless communication systems. This research contributes largely to the comprehensive understanding of polarized wireless channels and a new multiple access scheme in the polarization domain - polarization division multiple access (PDMA). The thesis consists of three streams: 1) a novel geometrical theory and models for fixed-to-mobile (F2M) and mobile-to-mobile (M2M) polarized wireless channels; 2) a new wireless body area network (BAN) polarized channel modeling; and 3) a novel PDMA scheme. The proposed geometrical theory and models reveal the origin and mechanism of channel depolarization with excellent agreement with empirical data in terms of cross-polarization discrimination (XPD), which is the principal measure of channel depolarization. Further, a novel PDMA scheme utilizing polarization-filtering detection and collaborative transmitter-receiver-polarization (Tx-Rx-polarization) adjustment, is designed considering cellular orthogonal frequency division multiplexing (OFDM) systems. The novel PDMA scheme has large potential to be utilized with the conventional time, frequency, and code division multiple access (TDMA, FDMA, and CDMA); and spatial multiplexing for next-generation wireless communication systems.
24

A new approach for medical device product documentation

Hamnede, Elisabet January 2017 (has links)
Hardware and software developers rely on different tools for document management, product data management (PDM) and software configuration management (SCM). As more and more products include components of both types there is a growing demand for one collaborative system. This becomes even more critical in the medical sector, where a device is under regulatory demands for document management to even be allowed in to the market. Combined systems become more complex and are generally based on PDM-principles rather than SCM. Current development of SCM tends instead towards simpler systems focused on pure version control (VCS) that are easy to use and economically available to small- and medium sized enterprises (SME), which is not the case with generic PDM-systems or combined systems. This study explored the possibility to extend the usage of such a VCS and include hardware documentation as well as software. The aim was to further our understanding of the SME perspective on product documentation for the medical device field. The method was a case study, collaboration with a SME development company. The scope was to explore possible usage of a chosen VCS (GitLab) and to compare it with a generic PDM-system and with existing manual system. The results showed that for several of the hardware document types there are special made Git-solutions to find within the open source community. However, none of the ones tested in the study was deemed good enough with respect to functionality and reliability. Instead the case study used direct storage of the files in their binary format and focused on testing different VCS functions and on how to organize in order to best gain the advantages of using the system. The conclusions showed that hardware documents can be stored in the same iterative manner as software but with limited Git functionality. Compared with a PDM system GitLab can offer the same level of revision control and communication around the specifications but lacks classification of parts and detailed product structures. GitLab offers better iteration history than both a PDMsystem and the existing manual system does. But not being able to use full Git functionality the organization needs a collaboration strategy to handle the decentralized storage. If the collaboration strategy matches the organization development practices, GitLab is a useful alternative for medical device documentation.
25

Data Classification in Product Data Management

Morshedzadeh, Iman January 2013 (has links)
This report is about the product data classification methodology that is useable for the Volvo Cars Engine (VCE) factory's production data, and can be implemented in the Teamcenter software. There are many data generated during the life cycle of each product, and companies try to manage these data with some product data management software. Data classification is a part of data management for most effective and efficient use of data. With surveys that were done in this project, items affecting the data classification have been found. Data, attributes, classification method, Volvo Cars Engine factory and Teamcenter as the product data management software, are items that are affected data classification. In this report, all of these items will be explained separately. With the knowledge obtained about the above items, in the Volvo Cars Engine factory, the suitable hierarchical classification method is described. After defining the classification method, this method has been implemented in the software at the last part of the report to show that this method is executable.
26

IT-Unterstützung zur energiesensitiven Produktentwicklung

Reichel, Thomas, Rünger, Gudula, Steger, Daniel, Xu, Haibin 15 July 2010 (has links) (PDF)
Die Entwicklung kostengünstiger, energiesparender und resourcenschonender Produkte gewinnt zunehmend an Bedeutung. Dabei bildet die Bewertung von Kosten und Energie über den gesamten Lebenszyklus des Produkts, von der Entwicklung und Fertigung über den Betrieb bis hin zum Recycling, auf Basis virtueller Prototypen eine wesentliche Grundlage. Da Entwurfsentscheidungen in frühen Phasen der Entwicklung, in denen noch kein realer Prototyp existiert, einen hohen Einfluss auf spätere Kosten haben können, besteht die Notwendigkeit empirische, entscheidungsrelevante Daten aus IT-Systemen der Produktentwicklung (z.B. Produktdatenmanagementsysteme) und des Betriebs (z.B. Enterprise-Resource-Planning-Systeme) zu extrahieren und dem Konstrukteur geeignete Methoden zur Aggregation der Daten bereitzustellen. Insbesondere bei der Optimierung hinsichtlich der Energieeffzienz von Produkten muss auf Daten des gesamten Lebenszyklus zurückgegriffen werden, um schon in der Entwicklungsphase Abschätzungen über den Energieverbrauch im Produktleben treffen zu können. Eine Optimierung der Energieeffizienz kann dabei sowohl durch die Steigerung der Produktivität bei gleichbleibendem Energieverbrauch als auch durch die Verringerung des Energieverbrauchs bei gleichbleibender Produktivität erfolgen. In diesem Bericht soll der Produktentwicklungsprozess aus IT-Sicht betrachtet werden, indem zunächst aktuelle Methodiken der Produktentwicklung mit ihrer IT-Unterstützung und der beteiligten IT-Systeme untersucht werden. Es werden Anforderungen an ein IT-System formuliert, die Energieeffizienzbewertungen und -optimierungen in allen Phasen der Produktentwicklung unter Nutzung der beteiligten IT-Systeme ermöglichen. Ein solches IT-System zur energiesensitiven Produktentwicklung (energiesensitives Produktentwicklungssystem) soll den Konstrukteur bei der Entwicklung energieeffizenter Produkte unterstützen. Dafür müssen die Funktionalitäten bestehender PDM-Systeme um Methoden zur Analyse, Synthese und Bewertung der Energieeffizienz des Produkts erweitert werden. Es wird abschließend vorgeschlagen, wie die Methoden zur Bewertung energierelevanter Daten durch Workflows umgesetzt werden können.
27

The Storage of Parametric Data in Product Lifecycle Management Systems

Lund, Jonathan Gary 23 March 2006 (has links) (PDF)
Product development companies are continually seeking methods to increase efficiency while maintaining quality. Distributed development is also more important than ever before as industries globalize. These forces have driven firms to adopt formal data management practices that allow groups and individuals to work from singular, centralized data source that are secure, reliable, and support collaboration. This thesis proposes a methodology to leverage globalized infrastructures for the efficient storage of product variations. The methodology is proved through a working prototype using the market leader in Product Lifecycle Management (PLM) systems, Teamcenter Engineering. First, paradigms are set forth for the storage of various types of engineering documents in PLM systems in parametric formats. Then the use of these paradigms is exemplified by various programs retrieving and storing document variations in the form of PLM metadata. Finally, the results show that this methodology produces drastic increases in system performance as well as the enabling of PLM-compatible automation and optimization. The impacts of these findings have significant implications for industry and has generated interest from several global engineering firms and academic journals.
28

Quantitative Image Quality Evaluation of Fast Magnetic Resonance Imaging

Huo, Donglai January 2007 (has links)
No description available.
29

Big Vector: An External Memory Algorithm and Data Structure

Upadhyay, Abhyudaya 16 October 2015 (has links)
No description available.
30

JEM-EUSO prototypes for the detection of ultra-high-energy cosmic rays (UHECRs) : from the electronics of the photo-detection module (PDM) to the operation and data analysis of two pathnders / Prototypes de JEM-EUSO pour la détection des rayons cosmiques d’ultra-haute énergie (UHECRs) : de l’électronique du module de photo-détection (PDM) à l’exploitation et l’analyse des données de deux pathfinders

Jung, Aera 30 May 2017 (has links)
L’expérience JEM-EUSO (traduction de Observatoire spatial de l’univers extrême à bord du module de l'expérience japonaise) est conçu pour observer les UHECR en détectant la lumière fluorescente UV émise par la gerbe qui se développe lorsque les UHECR interagissent avec l'atmosphère terrestre. Les gerbes atmosphériques sont constituées de dizaines de milliards de particules secondaires ou plus traversant l'atmosphère quasiment à la vitesse de la lumière, excitant les molécules d'azote qui émettent ensuite de la lumière dans la gamme UV. Alors que cette « technique de fluorescence » est habituellement utilisée au sol, en opérant ainsi à partir de l'espace, JEM-EUSO, pour la première fois, fournira des statistiques élevées sur ces événements. Avec un large champ de vue de ± 30 °, JEM-EUSO pourra observer depuis l’espace un volume d'atmosphère beaucoup plus grand que ce qui est possible du sol, en collectant un nombre sans précédent d'événements UHECR aux plus hautes énergies.Pour les quatre prototypes d’expériences construites par la collaboration, nous avons développé un ensemble commun d'électronique, en particulier le système central d'acquisition de données capable de fonctionner au sol, sur des ballons à haute altitude et dans l'espace.Ces expériences utilisent toutes un détecteur composé d'un module de détection de photo (PDM) identique aux 137 qui seront présents sur la surface focale JEM-EUSO. La lumière UV générée par les gerbes atmosphériques à haute énergie passe le filtre UV et frappe les tubes à photomultiplicateurs multi-anodes (MAPMT). Les photons UV sont alors transformés en électrons, qui sont multipliés par les MAPMT et le courant qu’ils créent est amplifié par des cartes ASIC de circuit intégré (EC-ASIC), qui effectuent également le comptage des photons et l'estimation de charge. Une carte FPGA nommé PDM board s'interface avec ces cartes ASIC, fournissant des paramètres d'alimentation et de configuration à ces cartes ASIC, collecte alors les données et exécute le déclenchement d’acquisition de niveau 1.Dans le cadre de ces travaux, je me suis occupée de la conception, du développement, de l'intégration et du test la carte FPGA PDM board pour les missions EUSO-TA et EUSO-Balloon ainsi que des tests d'algorithme de déclenchement autonomes d’acquisitions et j'ai également analysé les données de vol d’EUSO-Balloon et de la campagne sol EUSO-TA d’octobre 2015.Dans cette thèse, je donnerai un bref aperçu des rayons cosmiques à haute énergie, y compris de leur technique de détection et des principales expériences pour les détecter (chapitre 1), je décrirai JEM-EUSO et ses pathfinders (chapitre 2), je présenterai les détails de la conception et de la fabrication du PDM (chapitre 3) et de la carte FPGA PDM board (chapitre 4), ainsi que des tests d'intégration d’EUSO-TA et d’EUSO-Balloon (chapitre 5). Je ferai un rapport sur la campagne EUSO-Balloon de 2014 (chapitre 6) et sur ses résultats (chapitre 7), y compris une analyse spécifique développée pour rechercher des variations globales de l'émissivité UV au sol et j’appliquerai une analyse similaire aux données collectées sur le site de Telescope Array (Chapitre 8). Enfin, je présenterai la mise en œuvre et le test du déclencheur de premier niveau (L1) dans la carte de contrôle FPGA (chapitre 9). Un bref résumé de la thèse sera donné au chapitre 10. / The JEM-EUSO (Extreme Universe Space Observatory on-board the Japanese Experiment Module) international space mission is designed to observe UHECRs by detecting the UV fluorescence light emitted by the so-called Extensive Air Shower (EAS) which develop when UHECRs interact with the Earth’s atmosphere. The showers consist of tens of billions or more secondary particles crossing the atmosphere at nearly the speed of light, which excite nitrogen molecules which then emit light in the UV range. While this so-called “fluorescence technique'” is routinely used from the ground, by operating from space, JEM-EUSO will, for the first time, provide high-statistics on these events. Operating from space, with a large Field-of-View of ±30 °, allows JEM-EUSO to observe a much larger volume of atmosphere, than possible from the ground, collecting an unprecedented number of UHECR events at the highest energies.For the four pathfinder experiments built within the collaboration, we have been developing a common set of electronics, in particular the central data acquisition system, capable of operating from the ground, high altitude balloons, and space.These pathfinder experiments all use a detector consisting of one Photo-detection Modules (PDMs) identical to the 137 that will be present on the JEM-EUSO focal surface. UV light generated by high-energy particle air showers passes the UV filter and impacts the Multi-anode Photomultiplier Tubes (MAPMT). Here UV photons are converted into electrons, which are multiplied by the MAPMTs and fed into Elementary Cell Application-Specific Integrated Circuit (EC-ASIC) boards, which perform the photon counting and charge estimation. The PDM control board interfaces with these ASIC boards, providing power and configuration parameters, collecting data and performing the level 1 trigger. I was in charge of designing, developing, integrating, and testing the PDM control board for the EUSO-TA and EUSO-Balloon missions as well as the autonomous trigger algorithm testing and I also performed some analysis of the EUSO-Balloon flight data and data from the EUSO-TA October 2015 run.In this thesis, I will give a short overview of high-energy cosmic rays, including their detection technique and the leading experiments (Chapter 1), describe JEM-EUSO and its pathfinders including a description of each instrument (Chapter 2), present the details of the design and the fabrication of the PDM (Chapter 3) and PDM control board (Chapter 4), as well as the EUSO-TA and EUSO-Balloon integration tests (Chapter 5). I will report on the EUSO-Balloon campaign (Chapter 6) and results (Chapter 7), including a specific analysis developed to search for global variations of the ground UV emissivity, and apply a similar analysis to data collected at the site of Telescope Array (Chapter 8). Finally, I will present the implementation and testing of the first-level trigger (L1) within the FPGA of the PDM control board (Chapter 9). A short summary of the thesis will be given in Chapter 10.

Page generated in 0.0291 seconds