The world’s first large scale offshore wind farm, Horns Rev 1, is approaching the decommissioning phase the profitability of future investments therefore has to be investigated further. Investment decision-making requires the consideration of several perspectives based on a life cycle view of the asset’s condition and profitability. In order to contribute to the economical perspective of Asset Life Cycle Management, a business case model has been developed in two parts, one that represents the whole wind farm and one for a single wind turbine. Through the two models, the user can examine the profitability of a wind farm from a system perspective as well as on a more detailed level. The purposes of these models are to assist in the budget planning of Horns Rev 1 and provide support for investment decisionmaking.

Understanding the contribution of marketing to the shareholder value of a company has been a major challenge for marketing research. The purpose of this dissertation was creating and validating an attitudinal measure of customer equity in hospitality businesses, thus providing a link between return on marketing and the shareholder value of a company. The theoretical background of the customer equity construct was examined, and then systematic scale development processes were initiated. The results produced two concise scales: (1) 17 items that represent the six dimensions of customer equity in the restaurant industry and (2) 19 items that represent the six dimensions of customer equity in the hotel industry. Six dimensions of customer equity achieved strong convergent validity, discriminant validity, and internal consistency, indicating unidimensionality of the constructs. To further validate the newly developed scale, criterion validity was checked in correlation with six criterion measures using data collected from 590 hospitality industry consumers. The results demonstrate that customer equity closely reflects the shareholder value of a company. Also, it was found that value equity, brand equity, relationship equity, and service quality are significantly and positively correlated with overall customer equity of a company. In conclusion, customer equity represents the long-term value of a company, and reflects shareholder value of the company, thus providing a link with return on marketing investments. Theoretical and managerial implications are discussed. / Ph. D.

Many wireless sensor-based applications use LEACH as a preferred routing protocol owing to its unique features such as optimal sleeping time, minimum packet collisions, dynamic channel selection, and least power consumption. The traditional LEACH protocol wastes the transmission opportunities as it processes data only in an event occurring, leading to wastage of resources. To resolve this issue, this paper proposes a more robust Energy Enhanced Threshold Routing Protocol (ETH-LEACH) for WSNs. The working of ETH-LEACH is conceptualized in two parts. In the first part, TDMA is implemented to estimate the opportunistic paths to remove network overhead. Furthermore, in the second part, a threshold value is calculated for choosing the forwarder nodes. The proposed technique minimizes the energy usage of the sensor nodes and consequently enhances the network's lifetime by extending the duration of node death. The ETH-LEACH protocol is contrasted with the different variants of LEACH to verify its effectiveness. The experimental results show that the proposed ETH-LEACH protocol outperforms the traditional routing protocols. In this paper, the ETH-LEACH protocol performs nearly 54.6% efficient than LEACH, 47.6% efficient than Q-LEACH, 41.3% efficient than NR-LEACH, 33.6% efficient than LEACH-GA, and 29.7% efficient than LEACH-POS in reducing the usage of energy in the overall simulation.

No description available.

Les cellules à hétérojonctions de silicium (HET-Si) sont basées sur un substrat de silicium cristallin (c-Si) dopé n (p), une couche très fine de passivation (en général du silicium amorphe (a-Si:H) non dopé), et une couche d’une dizaine de nanomètres de silicium amorphe dopé p (n). Ces cellules atteignent aujourd’hui des rendements de l’ordre de 26% (record de 26,6% par l’entreprise Kaneka en 2017). Un des axes importants de recherche sur les cellules HET-Si porte sur l’étude de l’interface c-Si/a-Si:H qui est un élément clé dans le rendement des cellules. Ce rendement dépend en particulier de la présence d’états recombinants à l’interface c-Si/a-Si:H. Nous nous sommes donc tout particulièrement intéressés aux défauts d’interface en développant un calcul basé sur le modèle du réservoir de défauts (Defect-Pool Model ou DPM) dans le silicium amorphe et en corrélant nos résultats de modélisation avec des résultats expérimentaux de mesure de durée de vie. Afin de déterminer les caractéristiques de l’interface c-Si/a-Si:H, nous avons procédé comme suit : (1) Calcul de la densité d’états (DOS) volumique dans les couches de a-Si:H (dopé et non dopé), en nous appuyant sur le DPM. Dans ce modèle, la DOS varie en fonction notamment de la position du niveau de Fermi par rapport au bord de bande. La courbure des bandes de la jonction a-Si:H/c-Si implique ainsi une variation spatiale de la DOS dans le a-Si:H. (2) Calcul de la DOS surfacique à l'interface par projection des états volumiques présents à l’interface dans le a-Si:H. (3) Calcul des taux de recombinaison puis de la durée de vie effective sur des structures symétriques a-Si:H/c-Si/a-Si:H et comparaison avec des résultats expérimentaux. Nous avons ainsi pu étudier l’impact des paramètres matériaux du a-Si:H sur la durée de vie effective des porteurs minoritaires. L’évolution de la durée de vie avec les paramètres du a-Si:H est parfois contre-intuitive car deux phénomènes de passivation liés à la position du niveau de Fermi à l’interface s’opposent : passivation par la diminution de la densité d’états à l’interface et passivation par effet de champ. Le seul calcul de la DOS à l’interface ne suffit pas toujours à expliquer les variations de durées de vie, un calcul complet sous lumière est nécessaire. Nous avons montré que l’impact de certains paramètres du DPM peut-être grand sur la DOS mais faible sur la durée de vie effective à cause de cette compensation entre les phénomènes de passivation. Nous avons également étudié des structures correspondant aux faces avant : (p)a-Si:H/(i)a-Si:H/(n)c-Si(PIn) et arrière : (n)a-Si:H/(i)a-Si:H/(n)c-Si(NIn) des cellules HET-Si. Nos simulations permettent de montrer que les interfaces NIn sont moins critiques en terme de recombinaisons que les interfaces de type PIn. Nous montrons que la recombinaison aux interfaces PIn est dominée par la capture des électrons par les liaisons brisées de silicium chargées positivement. Nous montrons également que l’énergie d’Urbach est un paramètre qui joue de manière importante dans le calcul de la durée de vie effective et que l’utilisation de valeurs fixes de cette énergie d’Urbach dans la couche de passivation ne permet pas de reproduire les tendances expérimentales dans les structures avec des interfaces PIn. Nous proposons un modèle de variation de l’énergie d’Urbach avec l’épaisseur de la couche de passivation, qui permet de reproduire les tendances expérimentales pour les faibles épaisseurs de la couche de passivation mais qui demande à être complété pour de plus grandes épaisseurs. / Silicon heterojunction (Si- HET) solar cells are based on an n-doped (p-doped) crystalline silicon (c-Si) substrate, a very thin (a few nanometers) passivation layer of undoped hydrogenated amorphous silicon (a-Si:H) and a layer of p-doped (n-doped) a-Si:H, approximately 10 nanometer- thick. These cells currently lead the performance of silicon solar cells with conversion efficiencies in the order of 26% (with a record of 26.6% being achieved by the Kaneka company in 2017). One of the major focal points of research in Si- HET cells is the study of the c-Si/a-Si:H interface, which is a key factor in the cells' efficiency. In particular, this efficiency is strongly dependent on the recombination states at the interface between c-Si and a-Si:H. We therefore focused on developing a model of recombination through interface defects, which were evaluated based on the Defect-Pool Model (DPM) in a-Si:H. We calculated the effective lifetime vs excess carrier density curves and their dependence on the undoped a-Si:H passivation layer thickness and compared them to experimental results.In order to determine the characteristics of the c-Si/a-Si:H interface, we proceeded as follows: (1) Calculation of the volumic density of states (DOS) in a-Si:H layers (doped and undoped) using the DPM. In this model, the DOS varies as a function of the position of the Fermi level in relation to the band edge. The band bending at the a-Si:H/c-Si interface thus implies a spatial variation of the DOS in a-Si:H. (2) Calculation of the surface DOS at the interface by projection from the volumic states present in a-Si:H at the interface. (3) Calculation of the recombination rates and of the effective lifetime curves for symmetrical a-Si:H/c-Si/a-Si:H structures and comparison with experimental results. Thus we were able to study the impact of material parameters of a-Si:H on the effective lifetime curves. The change in lifetime as a function of a-Si:H parameters is sometimes counter-intuitive because two passivation mechanisms, namely passivation by field-effect or by the reduction of the DOS at the a-Si:H/c-Si interface, have opposed behavior in relation to the position of the Fermi level at the interface. A simple calculation of the DOS at the interface is not, therefore, sufficient to explain variations in lifetime, and a complete calculation of effective lifetime under illumination is required and has been performed. We demonstrate that the impact of certain DPM parameters may have a significant effect on the DOS but only a minor effect on the effective lifetime due to the compensation by the field-effect passivation. Moreover we have studied both types of silicon heterojunctions, (p)a-Si:H/(i)a-Si:H/(n)c-Si(PIn), and (n)a-Si:H/(i)a-Si:H/(n)c-Si(NIn) that are used as front emitter and back surface field junctions, respectively, in double-side contacted silicon Si-HET solar cells. Our simulations allowed us to emphasize that NIn interfaces are less critical in terms of recombination than PIn interfaces. We demonstrate that recombination at PIn interfaces is dominated by the capture of electrons by positively charged silicon dangling bonds. We further show that the Urbach energy is the major a-Si:H parameter that determines the effective lifetime in Si-HET solar cells and that the use of fixed values for this Urbach energy in the passivation layer whatever the layer thickness does not permit the experimental trends of PIn interfaces to be reproduced. Instead, we propose a model featuring that the Urbach energy decreases with the thickness of the passivation layer, which does allow experimental trends to be reproduced for very thin passivation layers (< 10 nm), but which requires further elaboration for larger thicknesses, for instance with a combined bandgap variation.

No description available.

Le variateur de vitesse est l’un des convertisseurs de puissance le plus utilisé en industrie ; il alimente les pompes, les ventilateurs, les convoyeurs, les ascenseurs …etc. Dans ces systèmes de conversion, les modules de puissance intégrants des composants IGBT représentent la partie cœur de conversion de l’énergie électrique AC/AC. En fonctionnement, ils sont sujets à des conditions fonctionnelles et environnementales sévères (cycles de température, humidité, vibrations …etc.). En raison de la puissance dissipée au niveau de leurs composants (IGBTs et diodes), le module subit des déformations d’origine thermomécanique, qui s’accumulent au fil du temps en limitant sa durée de vie et en impactant sur sa fiabilité. Dès lors, les industriels se trouvent non seulement face au développement des composants robustes et fiables, mais surtout être capable à élaborer des outils permettant la programmation des phases de maintenance. Dans cette thématique s’inscrivent les travaux de cette thèse. Durant laquelle nous essayons de répondre à ce besoin, en proposant une méthodologie de prédiction de durée de vie restante d’un module de puissance intégré au sein d’un variateur de vitesse de 15kW. En effet, nous développons un modèle de durée de vie restante nécessitant une modélisation électrothermique du système, un algorithme de comptage de cycles de température appelé le Rainflow et une loi de durée de vie obtenue à partir des tests de vieillissement. Le paramètre de durée de vie est ensuite calculé en appliquant la règle de Miner. Enfin nous proposons des stratégies de prise en compte de l’effet de dégradation pour ce modèle. / The motor drive is one of the most used power converters in industry; it drives pumps, fans, conveyers, elevators …etc. In this conversion systems, power modules integrating IGBT devices represent the core part in the AC/AC electrical energy conversion. During operation, they are subjected to severe functional and environmental conditions (temperature cycles, humidity, vibrations …etc.). Due to the dissipated power at the level of their devices (IGBTs and diodes), the module undergoes deformations of a thermomechanical origin, which accumulate over time limiting its lifetime and impacting on its reliability. Therefore, manufacturers are not faced only with the development of robust and reliable components, but above all they need to be able to develop tools for maintenance phases scheduling. In this scope, the thesis work is focused. During it, we try to bring a solution to this need, so we propose a remaining lifetime prediction methodology for an integrated power module inside a 15kW motor drive.Therefore, we develop a remaining lifetime model that requires an electrothermal modeling of the system, a temperature cycles counting algorithm called by the Rainflow and a lifetime law obtained from the aging tests. The lifetime parameter is then calculated by applying the Miner’s rule. Finally, we propose strategies to take into account the degradation effect on this model.

The process of spontaneous emission can be dramatically modified by optical micro- and nanostructures. We studied the modification of fluorescence dynamics using a polymer spacer layer fabricated through layer-by-layer (LbL) self-assembly. The advantages of this method are numerous: The self-assembled spacers can possess exceptional smooth surface morphology; The thickness of the spacer can be controlled with nanometer accuracy; And depending on fabrication conditions, the spacer layer is stimuli responsive and its thickness can be dynamically tuned. This thesis contains three interlinked components. First, we vary LbL spacer layer thickness and explore the change in fluorescence lifetime induced by the modified photonic density of states (PDOS), i.e., Purcell effects. Our experimental results agree well with theoretical predictions based on a classical dipole model, which also yields consistent values for the fluorophores' intrinsic fluorescence lifetime and quantum yield near a dielectric as well as a plasmonic interface. Based on this observation, we further demonstrate that self-assembled fluorophores can be used to probe the modified PDOS near optical micro- and nano-structures. These results naturally lead to the second component of our research. In particularly, based on the PDOS-induced changes in fluorescent lifetime, we develop a non-contact method that can measure morphological changes with nanoscale resolution. Our method relies on quantitatively linking fluorophore position with PDOS, and is validated through direct comparison with ellipsometry and atomic force microscopy (AFM) measurements. To demonstrate the potential application of this method, we investigated the swelling/deswelling of LbL films induced by pH changes. Our results indicate significant difference between a LbL film composed of a single polymer monolayer and a LbL film with 3 monolayers. Such stimuli-responsive polymers can be used to construct active and tunable plasmonic nano-devices. As a proof-of-principle demonstration, we experimentally confirm that it is possible to utilize the swelling/deswelling behavior of stimuli-responsive films to dynamically control the separation between Au nanoparticles and Texas Red (TR) dyes. This result is based on the strong correlation of TR fluorescence lifetime and nanoparticles-TR separation. Finally, we investigate the impact of different lithography processes on the fluorescence properties of self-assembled fluorophores. We consider three methods: direct fluorophore patterning through ultraviolet (UV) ablation, focused ion beam (FIB) milling of self-assembled fluorophores, and self-assembly of fluorescent materials over plasmonic nano-patterns. / Ph. D.

Dissertation thesis is focused on evaluation of influence of exposure in 5% salt fog on fatigue behavior of AZ31 and AZ61 magnesium alloy fabricated by squeeze casting method. Microstructure and mechanical properties of experimental materials have been evaluated. The AZ61 alloy was solution heat treated after prior optimization of the heat treatment process based on microstructural characteristics and mechanical properties. Depths of corrosion damage, corrosion rate and mechanism of corrosion of all three experimental alloys have been evaluated. Influence of prior corrosion exposure for 480 and 1000 hours on fatigue behavior of experimental materials was evaluated. Obtained data were compared with data obtained using smooth test specimens. Fractographic analysis was carried out on both smooth and precorroded specimens. Furthermore, influence of aluminium on corrosion and fatigue behavior of tested alloys was defined.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19312号 / 工博第4109号 / 新制||工||1633(附属図書館) / 32314 / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 木本 恒暢, 教授 引原 隆士, 准教授 船戸 充 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM