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Effektivare övervakning i distributionsnät / More efficient monitoring in distribution gridsFransson, Benjamin January 2016 (has links)
SCADA is the primary system for control and monitoring of distribution grids. As the expectations on how the grid must operate changes with the increased use of renewable energy sources, it also requires new methods of monitoring. Phasor Measurement Units (PMU) measures the phase angle and amplitude synchronously with GPS. A collaboration between U.C Berkeley and Power Standard Lab researches the possibilities of implementing synchrophasors in distribution grids. These devices are called micro-PMU and will provide similar services available for transmission grids, though adapted for lower voltage levels. Synchrophasors are useful in the development of a smarter distribution network, which consequently makes them interesting for the Swedish electricity market. Martin Gahr, a student at Berkeley / ETH, has developed a method to determine the topology of a distribution grid using micro-PMU's. The method compares calculated values from SCADA with values from micro-PMU's. The smallest difference between the two readings clarifies the topology. In this thesis the method is used to study an existing distribution grid in central parts of a medium-sized Swedish city. The method gives a satisfactory result when it is implemented on the mashed parts of the distribution grid. There are also indications that micro-PMU's must not be placed at every node to provide a reliable result. Although the method seems to be working on mashed parts of a Swedish distribution grid, it is not particulary interesting to implement the method in reality.
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An experimental and numerical investigation of vaporizer tubes associated with micro gas turbinesOlivier, Andre Jacobus 03 1900 (has links)
Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: This study is an introductory investigation into vaporizer technology as implemented in micro
gas turbines. Experimental investigations are aimed at the development of expectations
concerning the internal flow structure though vaporizers by generating application specific
flow maps. Consolidation of these maps with other experimental data suggests that annular
flow leads to increased evaporation rates. In addition, it was discovered that flow structure is
affected by the injection angle and air and fuel flow rates. An investigation into the numerical
modelling of vaporizers is based on two phase flow theory using a flow structure approach.
The numerical behaviour is observed for parametric variations to establish the impact of
assumptions. A final numerical model is formulated with empirically determined coefficients
with fair correlation to experimental data. The results of this study yield recommendations
towards the implementation and analysis of vaporizers with applied use in micro gas turbines. / AFRIKAANSE OPSOMMING: Hierdie studie is 'n inleidende ondersoek na verdamper tegnologie soos toegepas in mikro
gasturbines. Eksperimentele ondersoeke is gerig op die ontwikkeling van kennis rakende die
interne vloeistrukture deur verdampers met die bou van toepassingspesifieke vloeikaarte.
Konsolidering van hierdie kaarte met verdere eksperimentele data dui daarop dat annulêre
vloei lei tot verhoogde verdampingstempo’s. Daar is ook bevestig dat die vloei struktuur deur
die inspuitingshoek en vloeitempo’s affekteer word. 'n Ondersoek na die numeriese
modellering van verdampers is gebasseer op twee-fase vloei met 'n vloeistruktuur benadering.
Die numeriese gedrag is waargeneem vir parametriese variasies om sodoende die impak van
aannames te bevestig. Die numeriese model is voltooi met empiriese bepaalde koëffisiënte en
lei tot goeie korrelasie met eksperimentele data. Resultate van hierdie studie lei tot
aanbevelings rakende die implementering en ontleding van verdampers met spesifieke
toepassing op mikro gas turbines.
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Etude des mécanismes de défaillance du contact électrique dans un micro-interrupteur en technologie MEMSMaxime, Vincent 07 May 2010 (has links) (PDF)
Le but de cette thèse est l'amélioration, en termes de performances et de fiabilité, du contact électrique d'un micro-interrupteur en technologie MEMS. Ces travaux s'inscrivent dans le cadre d'une collaboration entre la Direction de l'Innovation de Schneider Electric et le Département d'Intégration Hétérogène sur Silicium du CEA-Leti. De cette collaboration a résulté un micro-interrupteur MEMS dont la fiabilité est supérieure à l'état de l'art mondial. Sa durée de vie est cependant limitée par la dégradation de son contact électrique. La première partie de cette thèse a ainsi porté sur l'étude des mécanismes à l'origine des défaillances de ce contact. Les essais d'endurance électrique avec courant coupé (« hot switching ») réalisés directement sur les prototypes de micro-interrupteurs, couplés à des analyses physico-chimiques et électriques ont permis d'identifier cinq mécanismes de défaillance principaux, différant en fonction du matériau de contact utilisé et du calibre de test. La seconde partie de la thèse présente le développement d'un banc permettant d'évaluer l'endurance de nouveaux matériaux de contact en remplacement de l'or et du ruthénium utilisés dans le micro-interrupteur. Ce banc d'endurance a été intégralement développé, réalisé et testé durant la thèse. Il reproduit le fonctionnement d'un micro-contact électrique et permet de réaliser plusieurs millions de cycles de fermeture/ouverture en faisant varier de nombreuses conditions de test telles que l'atmosphère environnante. La troisième partie de ce travail porte sur l'étude des mécanismes d'établissement et d'interruption du courant lorsque l'espace inter-contacts est réduit à quelques dizaines de nanomètres. L'utilisation non conventionnelle d'un microscope à force atomique à pointe conductrice en mode approche-retrait a permis de simuler à vitesse réduite l'actionnement d'un micro-contact. Cette étude a mis en évidence un phénomène d'émission électronique Fowler-Nordheim lors des derniers instants précédant la fermeture du contact. Les conséquences de cette émission électronique sont une dégradation des matériaux de contact, aboutissant à un transfert du matériau de contact de l'anode vers la cathode. L'ensemble de ces travaux est alors utilisé dans le chapitre de conclusion pour définir les règles de conception d'un micro-contact fiable.
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International Growth Strategies for Start-Up and Micro CompaniesNoller, Sarah, Han, Xu January 2009 (has links)
<p> </p><p>sonami AG is a company that is located in the Principality of Liechtenstein. It was founded in 2007. Since then it didn’t gain many customers and it is questionable how long the?company will be able to survive with having that few customers. In order to get rid of the current situation and to achieve a sustainable expansion strategy in the long run sonami asked us for help. The question thus is; how would an international expansion strategy look like.</p><p>In order to answer this question a case study approach was used. Four successful micro companies were interviewed and asked about their international strategy and their recommendations for expanding abroad.</p><p>In addition internationalization literature has been reviewed. Furthermore the concept of strategy, strategic planning and strategic management has been discussed.In the end a framework for sonami was developed. Different approaches, mixed with different recommendations and insights of the case studies were used to develop it.</p><p>The result is that sonami has major problems internally, which should be solved before entering any international path. Our developed framework names several pre‐requisites that need to be fulfilled before moving on to the next step. We have tried to generate a deliberate strategy for sonami. We also recommended sonami to take advantage of opportunities given. This would however mean that sonami would then follow an emergent strategy.??</p><p> </p>
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Effect of negative air ions on primary root cariesBurke, Francis Martin Mary January 1999 (has links)
No description available.
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Evaluation of a manganese oxidising bacterium isolated from an upland water sourceMurdoch, Fiona January 2000 (has links)
No description available.
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Utilization of a MAGIChip for mtDNA typingLlewellyn, Barbara Ellen January 2003 (has links)
No description available.
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Studies on three-way DNA junctions related to the development of a novel method for the detection of genetic polymorphismsAssenberg, Rene January 2001 (has links)
No description available.
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Aspects of the microbiology of Feta cheese brineBintsis, Thomas January 2001 (has links)
No description available.
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The vascular supply of the lower transverse rectus abdominus (TRAM) flapEl-Mrakby, Hamdy Hamid January 2002 (has links)
No description available.
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