In 21 century finned surfaces are used in almost all condensers to enhance their heat transfer capabilities. A lot of different models are presented in the literature: on horizontal and vertical finned tubes, inside finned tubes. The validation method of the theoretical models is based on comparison between measurement of average heat transfer coefficient and one calculated by the model. But in this case it is impossible to validate all approaches made in the theory.<p>\ / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

La technique de frittage flash (communément appelée Spark Plasma Sintering, SPS) suscite un engouement au niveau mondial. Ce procédé permet la densification de poudres à des vitesses généralement 10 à 100 fois plus élevées que celles des techniques de frittage traditionnelles. Il permet la synthèse de matériaux massifs innovants et originaux, à microstructures contrôlées, de formes complexes et de grandes dimensions. Cependant, la maîtrise du changement d’échelle et de l’homogénéité microstructurale des pièces obtenues par ce procédé nécessite une parfaite connaissance technique des équipements de frittage flash pour limiter notamment les gradients thermiques. La modélisation est une aide précieuse pour aboutir à l’amélioration de cette maîtrise. Une autre potentialité de cette technologie, l’assemblage de métaux, sans apport de matière, permet de répondre à des sollicitations industrielles pour lesquelles cette technique offre une solution alternative intéressante aux procédés d’assemblage actuels. Des aspects technologiques restent, toutefois, à maîtriser pour aller vers la réalisation d’assemblages de bonne qualité. / The flash sintering technique (commonly known as spark plasma sintering, SPS) generates a craze worldwide. This process allows a powder densification from speeds generally 10 to 100 times higher than those of the traditional sintering techniques. In addition, this allows the synthesis of innovative and original dense materials, with a controlled microstructure, complex shapes and, sometimes large sizes. However, the control of scaling and microstructure homogeneity of parts obtained by such a process requires a perfect knowledge of technical equipment including flash sintering to reduce thermal gradients. Modeling is a valuable aid to achieve the improvement of its control. Another potentiality of this technology, the welding of metal without matter, throught industrial demands offers an attractive alternative method to classical welding methods. Technological aspects remain, however, to master to go towards achieving good multi-materials.

This paper reports a simple self-assembly strategy towards bowl-shaped carbon-containing hollow particles, as well as an unprecedented potential application for block copolymer vesicles in energy storage. Kippah vesicles (fully collapsed vesicles), formed by solution self-assembly of an amphiphilic polystyrene-block-poly(ethylene oxide) block copolymer, were employed as the template to guide the formation of bowl-shaped nitrogen-doped carbon hollow particles (BNCHPs). As electrode materials of supercapacitors, BNCHPs exhibit superior electrochemical performance. In particular, compared with their spherical counterpart, BNCHPs largely increase their volumetric packing density, leading to much higher volumetric capacitance or volume reduction of electrodes, which is desired for practical supercapacitor devices.

The project is aimed to design an antenna array for an aircraft positioning system at an airport. The system operates at frequencies 1030 MHz and 1090 MHz. The antenna is also used by the DME/TACAN system operating in frequency range from 1025 MHz to 1150 MHz. The required impedance bandwidth of the antenna array is 125 MHz, i.ee from 1025 MHz to 1150 MHz. The theoretical part of the thesis analyses properties of different patch antennas and discusses the possibility of extending the impedance bandwidth. The practical part is focused on the development of the numerical model of the broadband stacked patch antennas. In addition, properties of the 3-element and 4-element antenna array are compared. At the end, results of the thesis are summarized.

This is a case study that focuses on the oral proficiency in English manifested by the 4-year-old sonof the author. He speaks Swedish as his L1 like his both parents but has been exposed to Englishsince he was one year old from using a tablet. The child’s spoken production was recorded andtranscribed with a focus on the plural-forms and the genitive. An important field that this case studyis motivated by is how child language development may be connected to the concept of innatism,that language is based on innate principles (Lightbown &amp; Spada, 2013:20) as it has been found that anumber of languages are acquired according to predictable patterns and processes (Moskowitz,1994:621-627) such as a the u-shaped learning process and over-generalization which has beenfound when investigating both L1 and L2 acquisition (Abrahamsson, 2013:663). The aim of thisstudy is to find possible similarities within the learning process: whether L2 acquisition follows thesame developmental patterns as in L1 acquisition by analyzing the recordings mainly targeting theplural and the genitive morphemes produced by a 4-year-old L2 speaker of English. Findings in thisresearch revealed that the child demonstrated a similar developmental pattern in the form of theu-shaped learning process (Abrahamsson, 2013:663).

This diploma thesis examines the properties of concrete with reinforcement, designed for the production of a concrete egg-shaped tubes . The stress is put on using various types of fiber reinforcements. Theoretical part is divided into 4 subsections. The topic of the first subsection is a concrete in general. Second subsection deals with various technology of production of concrete pipes. The third subsection is focused on description and summary of basic properties of concrete and reinforced concrete tubes. The last subsection deals with standardized procedures for testing concrete. Experimental part of this thesis is divided into two subsection. First subsection deals with design of a reference sample. Six different samples of a concrete were designed and their rheological properties were tested. Second subsection deals with the additi-on of various types of fiber reinforcement to the reference sample. Eight different admixtures of a concrete were added to the reference sample. Properties of these admixtures were tested in fresh and hardened state.

This thesis presents a design technology of forming a shaped lid focused on cutting, bending, drawing, as well as trimming and making the required holes. There is described several basic variants of sheet metal forming based on the literature. Production of holes of specified cover, for an annual production of 100 pieces of shaped lid, is solved by unconventional technologies. From subsequent economic evaluation of selected technologies is chosen an appropriate technology to minimize production costs.

This PhD work involves the utilization of the femtosecond laser technique to fabricate the novel S-shaped Josephson Junctions on the high - T_C superconducting YBCO thin films. Initially, it was envisaged as the title states to fabricate nano sized Josephson Junctions using this femtosecond laser technique. However in this PhD work, micron sized (1 – 2 µm) and near nano sized (500 – 800 nm) Josephson Junctions where achieved. / University of South Africa / Electrical and Mining Engineering

This Master thesis deals with symbolic objects appearing in the Bronze Age Aegean art in the 3rd and especially the 2nd millennium BCE. Recurrent types of scenes and motifs speak for the fact that there must have existed a complex iconographic system of Minoan and Mycenaean art. An analytical method aiming at single elements of composite scenes may bring us closer to better understanding of this system and to its more objective interpretation. The study, therefore, focuses on the iconography of each individual symbol and also discusses its possible parallels in art of the neighbouring Bronze Age cultures. Nonetheless, the Aegean iconographic system was not strictly codified throughout the entire Bronze Age and some of the themes evolved or were specific only for certain eras. For that reason, the studied material is treated in a diachronic approach so as to stress the iconographic evolution of the symbols' use. The aim is to provide a profound analysis of the rules applied to the symbols in Minoan and Mycenaean art, to investigate their possible origins, and finally to examine their mutual interconnections.

L’étude du problème de la diffusion d’une onde électromagnétique par une suspension de particules non sphériques est une difficulté récurrente dans de nombreux domaines de la recherche et de l’ingénierie. Cela implique d’utiliser des dispositifs expérimentaux hautement spécialisés ou de résoudre les équations de Maxwell, ce qui représente un véritable défi lorsque les particules sont de géométries complexes et avec des distributions statistiques de taille, d’orientation et de forme. L’objectif de la présente thèse est d’explorer l’utilisation de la méthode de Monte Carlo pour résoudre des formulations intégrales du champ électromagnétique diffusé déduites des équations de Maxwell. En particulier, nous résolvons celles de l’approximation de Schiff, de l’approximation de Born ainsi que celle du développement en série de Born. Notre approche est basée sur un travail de reformulation intégrale permettant de concevoir des algorithmes incluant les avancées les plus récentes de la méthode. Cette approche originale, utilisant les outils de la synthèse d’image pour gérer n’importe quelle géométrie, permet de traiter des statistiques de particules ainsi que d’évaluer les sensibilités à des paramètres d’intérêts, sans augmentation significative du temps de calcul. Les outils développés répondent d’ores et déjà aux besoins d’optimisation des photobioréacteurs qui mettent en œuvre des particules à faible contraste d’indice (micro-algues). À l’issue de ce travail, des pistes de recherches ont émergé pour explorer le verrou bien identifié des grandes particules et des forts contrastes d’indice à partir du principe de zéro-variance. / The resolution of the problem of an electromagnetic wave scattered by non-spherical particles suspensions is a significant difficulty encountered in many fields of research and engineering. This implies to use highly specialized experiments or to solve Maxwell’s equations, which is a real challenge when weconsider particles with complex shapes and with statistical distributions of size, orientation and shape.The aim of this thesis is to investigate the use of the Monte Carlo method in order to solve the integral formulations of electromagnetic scattering deduced from Maxwell’s equations. In particular, we solvethose of Schiff’s approximation, Born’s approximation as well as the Born series expansion. Our approachis based on integral reformulation in order to design algorithms including the most recent advances of the method. This original approach, using computer graphics algorithms in order to manage arbitraryshape, permits treating any distributions of parameters as well as evaluating sensitivities to parameters ofinterest, without additionnal CPU time. The developed tools already meet the needs for the optimisation of photobioreactors which bring into play soft particles (micro-algae). From this work, some researchideas have emerged to explore the well-identified issue of large particles and large refractive indices from zero-variance principle.