The rise of the Environmentalism in every sector of the Industry has lead the aircraft and engine manufacturing companies to develop new generations of more environmentally friendly engines. The companies, encouraged to this purpose, are in a constant research for new manufacturing and production techniques, in order to improve their products, from the environmental point of view, by gaining efficiency in the manufacturing techniques and reduce the fuel consumption and emissions in-flight. Having in mind this scenario, the sponsor of this Project is interested in understanding how changing the materials of the blades, titanium alloys currently, for other lighter materials, such as composites, is going to have an effect in the overall gas turbine efficiency. In the particular case of this Project, it will be studied the influence of the Stiffness and coating Thickness of those non-metallic materials suitable to be employed as coatings on gas turbine fan blades, from the icing point of view. The work procedure will be based on a study of Linear Elastic Fracture Mechanics of bi-material junctions and will extrapolate the general problem to the ice-coatings case, by getting experimental data from tests carried out in an Icing Tunnel. It will be observed that the coating Stiffness has an influence on the Adhesion Level of ice to less stiff materials, if compared with the Adhesion Level of ice to metals. Besides, it will be described how a 0.5 millimetres thin polymeric coating placed over a metallic substrate is enough to reduce the Adhesion Level of ice, hiding any effect that the underneath materials might have on the Adhesion Level.

Methylation is involved in the regulation of varied biological processes, from cancer to embryonic development. In B-DNA, methylation can alter the frequency with which a dinucleotide step samples one of two substates: BI and BII. Changing the BI-BII equilibrium can in turn affect the ability of proteins to bind to DNA, which may ultimately alter the transcription of genes. Using MD simulations, we evaluate the effects of cytosine methylation on the BI-BII equilibrium and the RMS atomic fluctuations of the backbone of two sequences: (GC)5 and the Dickerson dodecamer (DD). Methylation in (GC)5 stabilizes the BII state in CpG steps and stabilizes the BI state in GpC steps, but the BII state is always less favored than the BI state. The activation energy between the BI/BII states in (GC)5 increases in GpC steps and decreases in CpG steps upon methylation, indicating that backbone dynamics are affected by methylation in a step-dependent manner. The DD simulations suggest that methylation stabilizes the BII state in both CpG and GpC steps, although more sampling is needed to determine the significance of these results. Methylation has little effect on the atomic fluctuations of the backbone in (GC)5 or DD simulations. Thus, in these sequences, methylation does not uniformly stabilize one state, nor does methylation stabilize the state that is favored in the native sequence.

L'opto-pyrotechnie (amorçage de la détonation par système optique) est l'une des innovations les plus prometteuses en termes de fiabilité, de sécurité et de performances pour les futurs lanceurs spatiaux. Le but de la thèse est d'étudier et de modéliser le premier des deux étages d'un Détonateur Opto-Pyrotechnique, constitué d'un explosif confiné dans une chambre de combustion fermée où se déroulent les premières phases d'une Transition Déflagration-Détonation. L'amorçage par laser de l'explosif puis la combustion en chambre isochore sont traités par le code EFAE, lequel est couplé au logiciel LS-DYNA qui simule la déformation et la rupture du disque de fermeture de la chambre, puis la propulsion du projectile résultant vers le second étage. En parallèle, diverses techniques expérimentales (adsorption de gaz, vélocimétrie hétérodyne, microscopie) ont mis en valeur plusieurs procédés physiques, ce qui a permis de tester le couplage entre EFAE et LS-DYNA, puis de déterminer et de hiérarchiser les paramètres affectant les critères industriels.

Active magnetic bearings (AMBs) have become a key technology in industrial applications with a continued drive for cost reduction and an increase in reliability. AMBs require position feedback to suspend the rotor. Conventional contactless position sensors are used to measure the rotor's position. The major disadvantages of conventional position sensors are their cost and that the sensors are viewed as a weak point in an AMB system. A self-sensing sensor is a type of sensor which is cost effective, reduces sensor wire-length and increases reliability, thus ideal for the industry. This type of sensor relies on the current and voltage signals of the AMB's to obtain the rotor position. Due to the rapid and advanced development of digital electronics, it has become more powerful and cheaper, thus self-sensing in mass production will be cost effective. Different self-sensing approaches were developed in the past and can be divided into two main categories: state estimation and amplitude modulation approaches. In this research the focus will be on the amplitude modulation approach. Amplitude modulation makes use of two signals, namely the modulation signal and the carrier signal. In a self-sensing AMB system the carrier can be a high frequency component injected into the system or the switching ripple of the switch mode power amplifier can be used. The modulation signal is the change in rotor position which results in changing inductances. The actuator material introduces nonlinear effects on the estimated position. Due to these nonlinear effects, it is rather difficult to obtain the rotor position. The first industrial application of a self-sensing turbomolecular pump system was implemented in 2005 by S2M. The aim of this thesis is to evaluate existing self-sensing schemes, devise improvements and investigate possible new schemes. Four different demodulation methods and two new self-sensing schemes are evaluated. An AMB transient simulation model which includes saturation, hysteresis, eddy currents and cross-coupling is used to evaluate the schemes in simulation. The self-sensing schemes are implemented in hardware and evaluated on a 7 A rms 500 N AMB. A comparative study was done on the different self-sensing schemes. From the comparative study it was determined that the gain- and phase effects have a direct effect on the sensitivity of the system. It was also proved that self-sensing can be implemented on a coupled AMB with a sensitivity of 10.3 dB. / Thesis (Ph.D. (Electrical and Electronic Engineering))--North-West University, Potchefstroom Campus, 2009.

Active magnetic bearings (AMBs) have become a key technology in industrial applications with a continued drive for cost reduction and an increase in reliability. AMBs require position feedback to suspend the rotor. Conventional contactless position sensors are used to measure the rotor's position. The major disadvantages of conventional position sensors are their cost and that the sensors are viewed as a weak point in an AMB system. A self-sensing sensor is a type of sensor which is cost effective, reduces sensor wire-length and increases reliability, thus ideal for the industry. This type of sensor relies on the current and voltage signals of the AMB's to obtain the rotor position. Due to the rapid and advanced development of digital electronics, it has become more powerful and cheaper, thus self-sensing in mass production will be cost effective. Different self-sensing approaches were developed in the past and can be divided into two main categories: state estimation and amplitude modulation approaches. In this research the focus will be on the amplitude modulation approach. Amplitude modulation makes use of two signals, namely the modulation signal and the carrier signal. In a self-sensing AMB system the carrier can be a high frequency component injected into the system or the switching ripple of the switch mode power amplifier can be used. The modulation signal is the change in rotor position which results in changing inductances. The actuator material introduces nonlinear effects on the estimated position. Due to these nonlinear effects, it is rather difficult to obtain the rotor position. The first industrial application of a self-sensing turbomolecular pump system was implemented in 2005 by S2M. The aim of this thesis is to evaluate existing self-sensing schemes, devise improvements and investigate possible new schemes. Four different demodulation methods and two new self-sensing schemes are evaluated. An AMB transient simulation model which includes saturation, hysteresis, eddy currents and cross-coupling is used to evaluate the schemes in simulation. The self-sensing schemes are implemented in hardware and evaluated on a 7 A rms 500 N AMB. A comparative study was done on the different self-sensing schemes. From the comparative study it was determined that the gain- and phase effects have a direct effect on the sensitivity of the system. It was also proved that self-sensing can be implemented on a coupled AMB with a sensitivity of 10.3 dB. / Thesis (Ph.D. (Electrical and Electronic Engineering))--North-West University, Potchefstroom Campus, 2009.

Le volume et la complexité des données générées par les systèmes d'information croissent de façon singulière dans les entrepôts de données. Le domaine de l'informatique décisionnelle (aussi appelé BI) a pour objectif d'apporter des méthodes et des outils pour assister les utilisateurs dans leur tâche de recherche d'information. En effet, les sources de données ne sont en général pas centralisées, et il est souvent nécessaire d'interagir avec diverses applications. Accéder à l'information est alors une tâche ardue, alors que les employés d'une entreprise cherchent généralement à réduire leur charge de travail. Pour faire face à ce constat, le domaine "Enterprise Search" s'est développé récemment, et prend en compte les différentes sources de données appartenant aussi bien au réseau privé d'entreprise qu'au domaine public (telles que les pages Internet). Pourtant, les utilisateurs de moteurs de recherche actuels souffrent toujours de du volume trop important d'information à disposition. Nous pensons que de tels systèmes pourraient tirer parti des méthodes du traitement naturel des langues associées à celles des systèmes de questions/réponses. En effet, les interfaces en langue naturelle permettent aux utilisateurs de rechercher de l'information en utilisant leurs propres termes, et d'obtenir des réponses concises et non une liste de documents dans laquelle l'éventuelle bonne réponse doit être identifiée. De cette façon, les utilisateurs n'ont pas besoin d'employer une terminologie figée, ni de formuler des requêtes selon une syntaxe très précise, et peuvent de plus accéder plus rapidement à l'information désirée. Un challenge lors de la construction d'un tel système consiste à interagir avec les différentes applications, et donc avec les langages utilisés par ces applications d'une part, et d'être en mesure de s'adapter facilement à de nouveaux domaines d'application d'autre part. Notre rapport détaille un système de questions/réponses configurable pour des cas d'utilisation d'entreprise, et le décrit dans son intégralité. Dans les systèmes traditionnels de l'informatique décisionnelle, les préférences utilisateurs ne sont généralement pas prises en compte, ni d'ailleurs leurs situations ou leur contexte. Les systèmes état-de-l'art du domaine tels que Soda ou Safe ne génèrent pas de résultats calculés à partir de l'analyse de la situation des utilisateurs. Ce rapport introduit une approche plus personnalisée, qui convient mieux aux utilisateurs finaux. Notre expérimentation principale se traduit par une interface de type search qui affiche les résultats dans un dashboard sous la forme de graphes, de tables de faits ou encore de miniatures de pages Internet. En fonction des requêtes initiales des utilisateurs, des recommandations de requêtes sont aussi affichées en sus, et ce dans le but de réduire le temps de réponse global du système. En ce sens, ces recommandations sont comparables à des prédictions. Notre travail se traduit par les contributions suivantes : tout d'abord, une architecture implémentée via des algorithmes parallélisés et qui prend en compte la diversité des sources de données, à savoir des données structurées ou non structurées dans le cadre d'un framework de questions-réponses qui peut être facilement configuré dans des environnements différents. De plus, une approche de traduction basée sur la résolution de contrainte, qui remplace le traditionnel langage-pivot par un modèle conceptuel et qui conduit à des requêtes multidimensionnelles mieux personnalisées. En outre, en ensemble de patrons linguistiques utilisés pour traduire des questions BI en des requêtes pour bases de données, qui peuvent être facilement adaptés dans le cas de configurations différentes. Enfin, nous avons implémenté une application pour iPhone/iPad et une interface de type "HTML" qui démontre la faisabilité des différentes approches développées grâce à un ensemble de mesures d'évaluations pour l'élément principal (le composant de traduction) et un scénario d'évaluation pour le framework dans sa globalité. Dans ce but, nous introduisons un ensemble de requêtes pouvant servir à évaluer d'autres système de recherche d'information dans le domaine, et nous montrons que notre système se comporte de façon similaire au système de référence WolframAlpha, en fonction des paramètres d'évaluation.

Fabrication of nanoscale Josephson junctions and Superconducting Quantum Interference Devices (SQUID) is very promising but challenging topic in the superconducting electronics and device technology. In order to achieve best sensitivity of SQUIDs and to reproduce them easily with a straightforward method, new fabrication techniques for realization of nanoSQUIDs needs to be investigated. This study concentrates on investigation of new fabrication methodology for manufacturing nanoSQUIDs with High Temperature Bi-Crystal Grain Boundary Josephson Junctions fabricated onto SrTiO3 bi-crystal substrates using YBa2Cu3O7-δ (YBCO) thin-films. In this process nanoscale patterning of YBCO was realized by using electron beam patterning and physical dry etching of YBCO thin films on STO substrates. YBCO thin films were deposited using RF magnetron sputtering technique in the mixture of Ar and O2 gases and followed by annealing at high temperatures in O2 atmosphere. Structural characterization of YBCO thin films was done by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDX). Superconducting properties of thin films was characterized by AC magnetic susceptibility measurements. Nanoscale structures on YBCO thin films were fabricated by one E-Beam Lithography (EBL) step followed by Reactive Ion Etching (RIE) and physical dry etching. First SiO2 thin film were deposited on YBCO by RF magnetron sputtering and it was patterned by EBL using Polystyrene (PS) as resist material and RIE. Then SiO2 was used as an etch mask for physical dry etching of YBCO and nanoscale structures on YBCO were formed.

Unternehmen agieren heute in einer hochdynamischen Umwelt, wodurch die Anforderungen an Business Intelligence-Systeme (BI-Systeme) sich stetig verändern. Durch zügiges Reagieren darauf können sich Unternehmen Wettbewerbsvorteile verschaffen. Die dazu notwendige Wandlungsfähigkeit von BI-Systemen setzt voraus, dass bereits die BI-Architektur auf Flexibilität ausgelegt ist. Die Anwendung des Paradigmas der modellgetriebenen Softwareentwicklung auf die Domäne des Data Warehouse Engineerings (DWE) kommt diesem Bedarf nach. Zudem muss neben der Agilität von BI-Systemen auch der Faktor der Korrektheitsprüfung nach vorgenommenen Änderungen betrachtet werden. Es soll untersucht werden, inwieweit sich die im modellgetriebenen DWE anfallenden Metadaten zur Unterstützung und Automatisierung von Softwaretests zur Korrektheitsprüfung nutzen lassen. Die so erzielte Verringerung des Überprüfungsaufwandes führt zu einer verbesserten Wandlungsfähigkeit von BI-Architekturen und kommt somit dem Bedarf von effizienten agilen BI-Lösungen nach.

諸多的研究顯示，和塊材相比，低維度的材料其物理性質會有所不同，為了探究熱電材料在低維度下對其熱電性質所造成的效應，我們合成了BixSb2-xTe3-y奈米線並量測其熱電性質。本實驗藉由熱處理薄膜製備奈米線的方法合成單晶BixSb2-x Te3-y奈米線。我們先利用脈衝雷射沉積系統將BixSb2-x Te3鍍在矽基板上形成薄膜，再將薄膜以350 ℃至490 ℃熱處理5到21天，奈米線即為了平衡因薄膜與矽基板彼此熱膨脹係數不同所造成的應力而自薄膜上長出，其直徑為幾十奈米至幾百奈米不等，長度則為幾微米至幾十微米。為了瞭解奈米線之構成與量測其熱電性質，我們結合微影製程及操縱技術，將單根奈米線架空於附有電極、加熱元件及溫度感測元件之量測平台上，由於奈米線已被架空，我們便能透過選區繞射分析奈米線其結晶性，並使用能量散射分析儀得知奈米線之成分，利用四點量測可得知奈米線的電阻率ρ，以加熱元件在奈米線兩端產生溫差，並量測因西貝克效應 (Seebeck effect) 所造成之電壓差即能得到西貝克係數 S (Seebeck coefficient)，三倍頻技術要求所量測的樣品必須要架空於基板上，運用三倍頻技術 (3ω method) 可量測奈米線之熱導率κ及比熱。結合微影製程、操縱技術以及量測系統，我們成功得到單根奈米線的三個熱電係數ρ、S以及κ，並了解低維度對熱電性質所造成的影響。 / Compare with the bulk materials, many researches had revealed that physical properties were different in low dimensional materials. To study the low-dimensional effects on thermoelectric properties of thermoelectric materials, BixSb2-xTe3-y nanowires were synthesized and studied for their thermoelectric properties. Single-crystallized BixSb2-xTe3-y nanowires were synthesized by on-film formation of nanowires. First, BixSb2-xTe3 thin films were deposited on SiO2/Si substrates by using the pulsed laser deposition system. BixSb2-xTe3-y nanowires grew from the films by annealing the films at 350~490 ℃ for 5~21 days through the stress release of the thermal expansion mismatch between the film and the substrate. A series of BixSb2-xTe3-y nanowires were prepared with the diameter from few tens of nanometers to few hundreds of nanometers and the length from few micrometers to few tens of micrometers. In order to analyze the components and measure the thermoelectric properties of the nanowires, the technique of combining microfabrication and manipulation for suspending a single BixSb2-xTe3-y nanowire on a measurement platform with electrodes, heater and thermometers was developed. As long as the wire is suspended, the crystallization of the nanowire is able to be analyzed by the selected area electron diffraction (SAED). The composition of the nanowire can be analyzed by the STEM-EDX. Resistivity ρ is measured by the four-point probe method. In order to get the Seebeck coefficient S, temperature difference were generated by the heater and thermoelectric voltage generated by Seebeck effect were measured. The 3ω method which demands that the wire should be suspended was applied to measure the thermal conductivity κ and specific heat c. By using the developed technique and the measurement system, three thermoelectric parameter ρ, S, κ of a single nanowire were successfully measured and the low-dimensional effect on thermoelectric properties were examined.

Heart disease is the developed world's biggest killer, and the shortage of donor hearts has accelerated the development of mechanical alternatives. Scientists, engineers and clinicians have attempted to replicate the human heart with a mechanical device for over 50 years. Although a number of pulsating devices have been developed, and in some cases worked briefly, they have invariably failed to match the success of heart transplantation. In an attempt to produce a suitable alternative, current research is focused on devices that do not replace the heart; but rather work along side it to assist its function. Many of these devices help the failing left ventricle; however some patients require the additional implantation of a second device to assist a failing right ventricle. This increases implantation time and associated risk, and because of the size of the current devices, reduces the access of smaller patients to this vital technology. The overall thesis objective focuses on the progressive design, development and preliminary evaluation of two novel centrifugal type ventricular assist devices, a bi-left ventricular device (Bi-LVAD) and a single bi-ventricular assist device (Bi-VAD). The devices have the respective capability to assist either the left ventricle, or both ventricles of a failing heart. The current concept for each VAD employs both magnetic and hydrodynamic suspension techniques to float a rotating double impeller, a technique that aims to reduce blood damage and component wear, two of the major problems encountered with current generation devices. Each VAD design was developed by conducting experimentation and drawing conclusions from a variety of engineering research fields, such as flow visualization, rotary pump design and testing, fluid dynamics, hemodynamics and heart failure, and magnetic motor bearing design. In order to evaluate pump prototype designs, it was necessary to design and develop a novel pulsatile systemic and pulmonary mock circulation loop capable of reproducing the hemodynamics of heart failure in the systemic and pulmonary circuits. The investigation then specifically examined the static hydraulic forces on the impeller of a centrifugal blood pump during operation in this mock circulation loop. The recorded magnitude and direction of radial and axial thrust then influenced the selection of magnetic and hydrodynamic bearing configurations to minimise impeller touchdown in the intended hemodynamic environment. This research required the development of correctly designed impeller (semi-open/closed) and volute (single, double, circular) components for each ventricular assist application and a unique test facility to isolate impeller hydraulic forces in addition to the mock circulation loop. The proposed Bi-LVAD incorporates symmetrical blade designs on each side of the double sided impeller. The device assists the function of the left ventricle only with symmetrical axial pressure distribution and elimination of stagnant regions beneath the impeller. These features improve axial touchdown capacity and reduce thrombus formation respectively. The proposed Bi-VAD incorporates different blade designs on each side of the double impeller to augment the function of both the left and right cardiac chambers. The design has the additional potential to act as a total artificial heart (TAH). To date there is no Bi-VAD/TAH system available that incorporates an LVAD and RVAD in one rotary pump. Successful development of each innovative VAD will provide an alternative to heart transplantation, potentially saving lives of many terminal heart patients each year. No longer would heart transplant candidates need to wait for the untimely death of a donor to provide a suitable heart. Instead, this new generation device would be available immediately, and be almost universally compatible with all patients. It has the potential to dramatically increase a patient’s expected lifetime, and to deliver them a higher quality of life.