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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.
71

Experimental and Modeling Study of the Thermal Management of Li-ion Battery Packs

Wang, Haoting 13 October 2017 (has links)
This work reports the experimental and numerical study of the thermal management of Li-ion battery packs under the context of electric vehicle (EV) or hybrid EV (HEV) applications. Li-ion batteries have been extensively demonstrated as an important power source for EVs or HEVs. However, thermal management is a critical challenge for their widespread deployment, due to their highly dynamic operation and the wide range of environments under which they operate. To address these challenges, this work developed several experimental platforms to study adaptive thermal management strategies. Parallel to the experimental effort, multi-disciplinary models integrating heat transfer, fluid mechanics, and electro-thermal dynamics have been developed and validated, including detailed CFD models and lumped parameter models. The major contributions are twofold. First, this work developed actively controlled strategies and experimentally demonstrated their effectiveness on a practical sized battery pack and dynamic thermal loads. The results show that these strategies effectively reduced both the parasitic energy consumption and the temperature non-uniformity while maintaining the maximum temperature rise in the pack. Second, this work established a new two dimensional lumped parameter thermal model to overcome the limitations of existing thermal models and extend their applicable range. This new model provides accurate surface and core temperatures simulations comparable to detailed CFD models with a fraction of the computational cost. / Ph. D.
72

Analyse expérimentale et modélisation d’éléments de batterie et de leurs assemblages : application aux véhicules électriques et hybrides / Experimental analysis and modelling of battery cells and their packs : application to electric and hybrid vehicles

Li, An 04 February 2013 (has links)
Dans le cadre du développement des véhicules électriques et hybrides, la connaissance et la gestion de l'énergie du pack de batteries est une problématique majeure. Pour cela, les constructeurs automobiles ont besoin de modèles numériques pour représenter le comportement dynamique des batteries. L'objectif de cette thèse est de développer, d'une part une méthodologie de caractérisation du comportement dynamique des cellules de batterie et de leurs assemblages et d'autre part des modèles numériques associés qui soient simples, rapides, robustes, présentant le meilleur compromis précision/simplicité. La première partie du travail de la thèse a consisté à développer une nouvelle méthode de caractérisation expérimentale avec un modèle de circuit électrique équivalent, qui permet de s'appliquer facilement à différentes batteries et de calibrer la complexité du modèle (nombre de circuits utilisés) en fonction de la durée des mesures de la phase de repos après une sollicitation. Le modèle généré est capable de suivre les évolutions rapides et lentes de la tension de la batterie, ce qui peut améliorer l'estimation de la tension dans les applications BMS (Battery Management System). Des essais de validations sur différentes batteries ont montré que les modèles générés permettent une prédiction précise du comportement dynamique de la batterie. Ensuite, le manuscrit aborde les assemblages des cellules en série avec la méthode de caractérisation élaborée. Elle commence par une définition énergétique de l'assemblage. Puis, la modélisation de l'assemblage avec la méthode de caractérisation est discutée. Les essais de validation ont été menés sur différents assemblages et ont montré que le comportement dynamique de l'assemblage peut aussi être bien représenté avec les modèles identifiés / As part of the development of electric and hybrid vehicles, energy management in the battery pack is a major issue. Car manufacturers need a numerical model to represent the dynamic behavior of batteries. The objective of this work is to develop, on the one hand, a characterization method of the dynamic behavior of battery cells and their assemblies, and on the other hand the combined numerical models which are simple, fast, robust and with the best accuracy/simplicity compromise. The first part of the work is dedicated to develop a new experimental characterization method with an equivalent circuit model, which can be applied easily to different battery cells and allows calibrating the complexity of the model (number of the RC circuits) according to the measurement duration of the resting phase after a solicitation. Therefore, the generated model is able to follow the rapid and slow voltage change of the battery cell, which improves voltage and state of charge estimation for the BMS (Battery Management System) applications. The validation tests on different battery cells show that the generated model allows accurate prediction of the battery cell’s dynamic behavior. The second part of the work studies the cell assemblies with cells connected in series. It begins with an energy definition of the cell assembly. Then modelling of the assembly with the developed characterization method is discussed. The validation tests were carried out on different assemblies and show that the dynamic behavior of the assembly can be also well represented with the identified models
73

Thermal and thermal-mechanical simulation for the prediction of fatigue processes in packages for power semiconductor devices / Thermisch und thermisch-mechanische Simulation für die Vorhersage von Ermüdungsprozessen in Gehäusen für Halbleiter-Leistungsbauelemente

Poller, Tilo 12 February 2015 (has links) (PDF)
The knowledge about the reliability of power electronics is necessary for the design of converters. Especially for offshore applications it is essential to know, which fatigue processes happen and how the lifetime can be estimated. Numerical simulation is an important tool for the development of power electronic systems. This thesis analyse the thermal and thermal-mechanical behaviour of packages for power semiconductor devices with the help of simulations. One topic is the evaluation of different thermal models. The main focus is on the description of the thermal cross-coupling between the devices and the influence to the lifetime estimation. The power module is a well established package for power semiconductor devices. It will be explained how the heating period of power cycles influences the failure mode of this package type. Additionally, it will evaluated how SiC devices and DAB substrates influence the power cycling capability. The press-pack is in focus for high power applications as the package short-circuits during an electrical failure without external auxiliary systems. However, the knowledge about the power cycling behaviour is currently limited. With the help of simulations this behaviour will be analysed and possible weak points will be also derived. In the end of the work it will be discussed, how the lifetime can be estimated with help of FEM simulations. / Für die Entwicklung von Umrichtern ist die Kenntnis über die Zuverlässigkeit der Leistungselektronik ein wichtiges Kernthema. Insbesondere für Offshore-Anwendungen ist das Wissen über die stattfindenden Ermüdungsprozesse und die Abschätzung der zu erwartenden Lebensdauer der Bauteile essentiell. Hierfür hat sich die Simulation als ein wichtiges Werkzeug für die Entwicklung und Lebensdauerbewertung von leistungselektronischen Anlagen etabliert. In der folgenden Arbeit wird das thermische und das thermisch-mechanische Verhalten der Leistungselektronik mittels Simulationen untersucht. Hierzu wird ein Vergleich zwischen verschiedenen thermischen Modellen für Leistungsbauelemente durchgeführt. Schwerpunkt ist die Beschreibung der thermischen Kopplung zwischen den Chips und deren Einfluss auf die Lebensdauerabschätzung. Ein weiterer Schwerpunkt ist das Leistungsmodul, welches sich als ein Standardgehäuse etabliert hat. Dazu wird erklärt, wie die Variation der Einschaltzeit im aktiven Lastwechseltest den Fehlermodus dieses Gehäusetyps beeinflusst. Weiterhin wird untersucht, wie SiC als Leistungshalbleiter und DAB als Substrat die Zuverlässigkeit beein- flusst. Der Press-Pack ist für Hochleistungsapplikationen von hohem Interesse, da dieses Gehäuse im elektrischen Fehlerfall ohne äußere Unterstützung kurzschliesst. Jedoch ist das Wissen über diese Gehäusetechnologie unter aktiven Lastwechselbedingungen sehr limitiert. Mit Hilfe von Simulationen wird dieses Verhalten untersucht und mögliche Schwachpunkte abgeleitet. Am Ende der Arbeit werden Möglichkeiten untersucht, wie Mithilfe von FEM Simulationen die Lebensdauer von Leistungsmodulen evaluiert werden kann.
74

Strategiimplementering hos ett "leading the pack"-företag : Avgörande framgångsfaktorer vid implementering av miljöstrategier / A “leading the pack” company's implementation strategy : Crucial success factors when implementing an environmental strategy

Kamryd, Louise, Johannesson, Tessa January 2021 (has links)
Uppsatsen ämnar undersöka ett företags implementering av miljöstrategier. Det undersökta företaget är OKQ8. Miljö och hållbarhet är aktuella ämnen inom organisationen och dagens samhälle. Syftet är definiera hur ett “leading the pack”-företag med hjälp av avgörande framgångsfaktorer kan förenkla implementeringen av miljöstrategier. Baserat på fynden i den första forskningsfrågan har fyra avgörande framgångsfaktorer identifierats vid implementering av miljöstrategier. De fyra funna framgångsfaktorerna är (I) tydligt arbetssätt, (II) hög legitimitet, (III) tydlig kommunikation och (IIII) balanserat styrkort. De fyra avgörande framgångsfaktorerna kombinerat ökar chansen till en lyckad strategiimplementering. / Background: The thesis intends to investigate the implementation of a company's  environmental strategies. OKQ8 is the investigated company. The environment and sustainability are important fields within the organization and in today's society.   Purpose: The purpose is to define how a “leading the pack”-company can, with  help from crucial success factors, simplify the implementation of the environmental strategies. Method:The study is a qualitative study. The thesis has a deductive research  approach with some inductive elements. It is a single case study, and the empirical data was gathered through semi-structured interviews.    Conclusion:  Based on the findings from the first research question four crucial  success factors have been identified when a company's environmental strategy is  being  implemented. The success factors are (I)  distinct working methods, (II) high legitimacy, (III) clear communication and (IIII) having a balanced scorecard. The combination of the four crucial success factors increases the chance of a successful implementation of the strategy.
75

Thermal and thermal-mechanical simulation for the prediction of fatigue processes in packages for power semiconductor devices

Poller, Tilo 03 September 2014 (has links)
The knowledge about the reliability of power electronics is necessary for the design of converters. Especially for offshore applications it is essential to know, which fatigue processes happen and how the lifetime can be estimated. Numerical simulation is an important tool for the development of power electronic systems. This thesis analyse the thermal and thermal-mechanical behaviour of packages for power semiconductor devices with the help of simulations. One topic is the evaluation of different thermal models. The main focus is on the description of the thermal cross-coupling between the devices and the influence to the lifetime estimation. The power module is a well established package for power semiconductor devices. It will be explained how the heating period of power cycles influences the failure mode of this package type. Additionally, it will evaluated how SiC devices and DAB substrates influence the power cycling capability. The press-pack is in focus for high power applications as the package short-circuits during an electrical failure without external auxiliary systems. However, the knowledge about the power cycling behaviour is currently limited. With the help of simulations this behaviour will be analysed and possible weak points will be also derived. In the end of the work it will be discussed, how the lifetime can be estimated with help of FEM simulations. / Für die Entwicklung von Umrichtern ist die Kenntnis über die Zuverlässigkeit der Leistungselektronik ein wichtiges Kernthema. Insbesondere für Offshore-Anwendungen ist das Wissen über die stattfindenden Ermüdungsprozesse und die Abschätzung der zu erwartenden Lebensdauer der Bauteile essentiell. Hierfür hat sich die Simulation als ein wichtiges Werkzeug für die Entwicklung und Lebensdauerbewertung von leistungselektronischen Anlagen etabliert. In der folgenden Arbeit wird das thermische und das thermisch-mechanische Verhalten der Leistungselektronik mittels Simulationen untersucht. Hierzu wird ein Vergleich zwischen verschiedenen thermischen Modellen für Leistungsbauelemente durchgeführt. Schwerpunkt ist die Beschreibung der thermischen Kopplung zwischen den Chips und deren Einfluss auf die Lebensdauerabschätzung. Ein weiterer Schwerpunkt ist das Leistungsmodul, welches sich als ein Standardgehäuse etabliert hat. Dazu wird erklärt, wie die Variation der Einschaltzeit im aktiven Lastwechseltest den Fehlermodus dieses Gehäusetyps beeinflusst. Weiterhin wird untersucht, wie SiC als Leistungshalbleiter und DAB als Substrat die Zuverlässigkeit beein- flusst. Der Press-Pack ist für Hochleistungsapplikationen von hohem Interesse, da dieses Gehäuse im elektrischen Fehlerfall ohne äußere Unterstützung kurzschliesst. Jedoch ist das Wissen über diese Gehäusetechnologie unter aktiven Lastwechselbedingungen sehr limitiert. Mit Hilfe von Simulationen wird dieses Verhalten untersucht und mögliche Schwachpunkte abgeleitet. Am Ende der Arbeit werden Möglichkeiten untersucht, wie Mithilfe von FEM Simulationen die Lebensdauer von Leistungsmodulen evaluiert werden kann.
76

Marketing klubu FK ERA-PACK Chrudim vůči fanouškům / Marketing of the club FK ERA-PACK Chrudim to fans

Houdková, Romana January 2013 (has links)
Title of thesis: Marketing of the club FK ERA-PACK Chrudim to fans Aims of the thesis: The main aim of the thesis is to suggest a new concept of the communication, which is supposed to improve communication process between fans. Methods: personal questioning, written questioning, marketing analysis, SWOT analysis Results: By using selected methods it was found, that the current marketing communication of the club is sufficient. On the base of this fact there was established the concept of communication and suggestions for improving of the current communication in the club. Key words: fans, FK ERA-PACK Chrudim, marketing communication, marketing research, situation analysis
77

The effect of a cooling cuff and moist ice pack on radial artery blood flow and lumen diameter

Gernetzky, Joshua January 2014 (has links)
Submitted in partial compliance with the requirements for the Master’s Degree in Technology: Chiropractic, Durban University of Technology, Durban, South Africa, 2015. / Background: When a soft tissue injury occurs the blood vessels and surrounding tissue are damaged leading to haemorrhaging and inflammation. Cryotherapy (cold therapy) is generally acknowledged as the preferable treatment by manual therapists during this immediate post-traumatic period of an injury. Cryotherapy has been shown to result in vasoconstriction decreasing the rate of blood flow which has a favourable effect on inflammation and pain. The commercially available cooling cuff is a relatively new cryotherapy modality offering a mechanism of cooling that does not require freezing and is easy to use. The polymer granules within the cooling cuff are activated by emersion in water therefore freezing is not required making the cooling cuff readily available compared to more traditional forms of cryotherapy. Aim: The aim of this study was to determine the effect of a moist ice pack and a commercially available cooling cuff radial artery blood flow (cm.s-1) and radial artery lumen diameter (mm) after 15 minutes of application. Method: This study was a pre-test post-test design utilising 43 asymptomatic participants that were randomly allocated to one of two groups. Each group either received a standard moist ice pack or a commercially available cooling cuff, placed on the ventral surface of the participants forearm, over the radial artery, for a duration of 15 minutes. Measurements were taken with a Doppler ultrasound to determine radial artery blood flow and lumen diameter, prior to the intervention and 15 minutes after the cryotherapy application. Data analysis was performed using IBM SPSS VERSION 20 (IBM Corp. Released 2010.IBM SPSS Statistics for Windows, Version 19.0. Armonk, New York: IBM Corp.). Statistical significance was set at a p< 0.05 level. Intra-group and inter-group comparisons were measured using repeated measures ANOVA testing. Results: Both the moist ice pack and commercially available cooling cuff resulted in a significant decrease in radial artery blood flow (p< 0.001) after 15 minutes of application with no significant changes being observed in radial artery diameter Conclusions: The commercially available cooling cuff resulted in a similar effect on radial artery blood flow and lumen diameter as moist ice, indicating that the commercially available cooling cuff may be utilised in the acute phase of an injury to alter blood flow. / M
78

Prise en compte des modes de vieillissement dans la modélisation des performances de batteries lithium-ion pour l’évaluation de leur durée de vie en usage automobile / Aging modes taking into account in the modeling of lithium-ion batteries performance for lifetime assessment in automotive usage

Baghdadi, Issam 06 July 2017 (has links)
L’électrification des moyens de transport est de plus en plus importante. Sa mise en œuvre nécessite des systèmes de stockage de l’énergie plus performants, moins coûteux, et plus sûrs. Actuellement, les batteries lithium-ion équipent la majorité de ces véhicules innovants. Toutefois, ces systèmes sont complexes, onéreux, et leur performance se dégrade au cours du temps. Leur durabilité constitue donc un enjeu majeur.Son estimation est complexe car elle ne dépend pas que des kilomètres parcourues mais des conditions d’usage. Actuellement, les outils de prédiction de durée de vie des batteries sont simplificateurs ou pas compatible avec l’usage automobile.L’objet de ces travaux consiste à développer un outil de simulation capable de reproduire le comportement électrique, thermique, et de vieillissement d’un pack batteries au cours de sa vie. Cet outil doit permettre l’optimisation de la conception et l’usage des packs afin d’augmenter leur durabilités. Des campagnes d’essais ont permis de calibrer et de valider des modèles électrothermiques au niveau de la cellule puis à l’échelle de l’assemblage. De même, la mise en place et l’analyse de tests de vieillissement accélérés ont permis de développer une loi de vieillissement et de mettre en avant un optimum d’usage.Le comportement du pack a été par la suite testé dans différentes conditions d’usage par l’intermédiaire d’un simulateur de scénario. Des stratégies de conception et de recharges ont été donc proposées et vérifiées par simulation. / Lithium batteries are key solutions as power storage systems for several applications including portable devices, aviation, space, and electrified vehicles. Their success is principally due to their high power and energy density. Therefore, several researchers are attempting to develop more powerful, cheaper, longer-lived and more secure batteries. One drawback of lithium batteries is their durability: lithium batteries’ energy and power capability decrease over time. The degradation rate is sensitive to operating conditions. A crucial step towards the large-scale introduction of electrified vehicles in the market is to reduce the cost of their energy storage devices.The aim of this study is to develop a simulation tool at the pack level able to reproduce its electro-thermal-aging behavior overtime. Thanks to an accelerated aging tests and experimental approach the models are calibrated and coupled with a usage scenario simulator at the vehicle level. The behavior of the pack is thus studied under different conditions and simulations were compared and discussed. Strategies of usage and charging were then proposed and validated by simulation.
79

Influência da boretação com pó na resistência ao desgaste, corrosão e oxidação dos aços AISI 1060 e AISI H13 / Influence of pack boriding on the wear, corrosion and oxidation resistance of AISI 1060 and AISI H13 steels

Heck, Stênio Cristaldo 22 July 2010 (has links)
Neste trabalho estudou-se o efeito do tratamento de boretação na resistência ao desgaste, corrosão e oxidação dos aços AISI 1060 e AISI H13. As amostras dos aços foram boretadas com pó a 900 e 1000°C por 2 e 4 horas. Foram realizados ensaios de microdesgaste em máquina do tipo esfera fixa, sem uso de abrasivos, nas amostras boretadas e não boretadas. A resistência à corrosão, das amostras boretadas e não boretadas, em HCl 0.1M foi avaliada por ensaios de polarização potenciodinâmica. Ensaios de oxidação do tipo quase-isotérmica foram realizados nas amostras, utilizando temperatura de 550°C ao ar. Para todas as condições de tratamento empregadas foram formadas camadas de boretos com elevadas durezas sobre os substratos. As propriedades das camadas como dureza, espessura, morfologia da interface camada/substrato e as fases presentes, foram influenciadas pelas composições dos aços. No caso do aço AISI H13, que possui maior quantidade de elementos de liga, as camadas formadas foram mais duras, menos espessas, com interface lisa, e para todas as condições de tratamento foram formadas os compostos de boro Fe2B, FeB e CrB. Já no aço AISI 1060 as interfaces camada/substrato foram do tipo dentada e para a temperatura de boretação de 900°C apenas a fase Fe2B foi formada, aparecendo o FeB a partir da temperatura de boretação de 1000°C. A resistência ao desgaste, corrosão e oxidação dos aços boretados aumentou significativamente, sendo que em relação ao desgaste, os melhores resultados foram obtidos com as amostras boretadas a 1000°C. Quanto à oxidação, os dois aços boretados a 900°C por 2h apresentaram os melhores desempenhos, e quanto à corrosão, os parâmetros do tratamento de boretação não influenciaram significativamente os desempenhos. / In this work the effect of pack boriding on wear, corrosion and oxidation resistance of AISI 1060 and AISI H13 steels were studied. Samples of the steels were pack borided at 900 and 1000°C for periods of 2 and 4h. Fixed-ball microwear tests were performed on borided and non-borided samples, without use of abrasives. The samples corrosion resistances, in HCl 0.1M, were evaluated by potentiodynamic polarization tests. Quasiisothermal oxidation tests were performed at 550°C on air. High hard layers were formed on steels for all treatment conditions employed. The layers properties, such as hardness, thickness, layer/substrate interface morphology and phases formed, were influenced by steels compositions. For AISI H13 steel, which has a larger amount of lloying elements, the formed layers were arder, thinner, with smooth interface and for all treatments conditions the compounds Fe2B, FeB and CrB were formed. For borided AISI 1060 steel, the layer/substrate interfaces showed a saw-tooth morphology and for boriding temperature of 900°C only the Fe2B phase were formed, appearing FeB for boriding temperature of 1000°C. The wear, corrosion and oxidation resistances of borided steels significantly increased and in relation to wear, the best results were btained with the samples borided at 1000°C. In oxidation case, both steels borided at 900°C for 2h showed the best performances, and with respect to corrosion, boriding treatments parameters did not significantly affect the performances.
80

Pack Rust Identification and Mitigation Strategies for Steel Bridges

Chintan Hitesh Patel (5930783) 03 January 2019 (has links)
<div>Pack rust or crevice corrosion is a type of localized corrosion. When a metal is in contact with a metal, or even non-metal, the metal starts to corrode, and rust starts to pack in between the surfaces. When signicant development of pack rust occurs, it can cause overstressing of bolts and rivets causing them to fail, and it can bend connecting plates and member elements thus reducing their buckling capacity. Thus it is important to mitigate the formation and growth of pack rust in bridges. This study was conducted to determine if pack rust occurs frequently and thereby may pose a problem in the state of Indiana. The study is divided into three primary tasks.The rst part of the study involves understanding the parameters involved in the initiation process of crevice corrosion and post-initiation crevice corrosion process. The second part of the study involves reviewing existing mitigation strategies and repair procedures used by state DOTs. The third part of the study involves identifying steel bridges with pack rust in Indiana. Analyses were performed on the data collected from Indiana bridges that have pack rust. This involved nding the components and members of bridges which are most aected by pack rust and nding parameters which in uence the formation of pack rust. Pack rust in the steel bridges were identied using the INDOT inspection reports available through BIAS system. The study revealed that good maintenance practices helped in reducing pack rust formation. The study identied locations on steel bridges which have a high probability towards pack rust formation. A mitigating strategy possessing qualities which can show promising results is identied.</div>

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