No description available.

Thesis (Ph.D.(Chemistry))--University of Pretoria, 2009. / Includes abstract in English. Includes bibliographical references. Also available online.

The technique of Raman spectroscopy was used in a study of shards of known (Ming and Meissen) and unknown (archaeological) origin. A tile shard from the Citadel of Algiers was included in this study as further confirmation of the consistency of the methods that are developed. The Citadel from which the tile shard was obtained was built in 1516 and represents a landmark from pre-colonial Algeria. The results were compared with those obtained from studies on intact museum pieces of known (Ming) origin. A consistent method of studying underglaze pigments on glazed ceramic artifacts by directing the laser beam through the predominantly silicate glaze was developed. The glaze depth profiling method developed proved to be very useful in the analysis and gives not only a detailed composition for the glaze/ceramic interfacial pigment, but also the order in which the various interfacial pigment layers were applied at the time of manufacture. The information acquired leads to an understanding of the level of technological development of the manufacturers. The detailed study and characterisation of the pigments that were analysed in this way gives insight into trade relations among ancient societies of the Mediterranean and will also assist archaeologists in establishing cut-off dates for the archaeological sites from which the artifacts were recovered. All the shards, except one from Meissen (Germany), were provided by the National Cultural History Museum of South Africa and the intact Ming dynasty plates were provided by the J.A. van Tilburg Museum of the University of Pretoria. The tile shard sample from the Citadel of Algiers was donated for the study. The results indicate that none of the archaeological shards could possibly be of Ming dynasty origin based on, firstly, the use of amorphous carbon to darken the cobalt blue (CoAl2O4) used as decoration on the shards, and secondly on the use of white (synthetic) anatase to whiten the ceramic surface before the application of the pigment since this synthetic anatase is known to have been manufactured for the first time around 1920. An ancient rediscovered ternary pigment (Pb2SnSbO6.5) previously found on Italian paintings of the 16th century, for example, “Lot and his daughters” by G.B. Langetti and “Entrance of Christ in Jerusalem” by Luca Giordano, was identified on the Citadel tile and successfully characterised. A Pb-O vibrational Raman band at 127 cm-1 for this pigment was assigned for the first time. Additional pigments identified on the tile include Naples yellow (Pb2Sb2O7), lead (II) stannate (Pb2SnO4), cobalt blue (CoAl2O4) and cassiterite (SnO2). The bulk of the tile body is composed mainly of hematite (á-Fe2O3), maghemite (ã-Fe2O3), magnetite (Fe3O4) and quartz (á-SiO2), with traces of calcite (CaCO3) and amorphous carbon. The unique non destructive depth profiling method that was developed in this study can now be applied to the study of underglaze pigments on intact porcelain artifacts in museums and private collections around the world for authentication purposes and for comparison with archaeological shard samples. / Thesis (PhD)--University of Pretoria, 2010. / Chemistry / unrestricted

In this thesis, the fabrication technology of Roman lead glazes were examined using a number of materials science techniques: namely, electron probe microanalysis, X-ray diffraction, and inductively coupled plasma atomic emission spectroscopy. The overall aim of this work was to discern particular technological styles for a wide group of lead glazes by quantifying the chemical and microstructural features of glaze production. Using experimental replication, it was found that two basic methods of glazing could be identified chemically. When applying PbO alone to an earthenware ceramic, the resulting glaze was in equilibrium with the ceramic as indicated by flat compositional profiles obtained along the glaze cross-section. However, when applying PbO·SiO₂ mixtures to earthenware ceramics, gradient profiles indicative of diffusive mass transfer were obtained from the glaze cross-section. On the basis of these chemical criteria, these two methods of glazing were identified in archaeological material. It has been determined that the earliest lead glazes from Anatolia and Italy (approximately 1^st century B.C.) were made using PbO·SiO₂ mixtures applied to calcareous clays with Fe and Cu oxides added as colourants. Later production (post 2^nd century A.D.), seems to have employed PbO alone applied to non-calcareous clays with no intentionally added colourants. The Roman production of lead glazes was compared to both those of Late Antiquity (4^th – 10^th centuries A.D.) which continued to use PbO applied to non-calcareous clays, and to those of Byzantine and Islamic contexts (8^th – 14^th centuries A.D.) which seem to have used PbO·SiO₂ mixtures applied to both calcareous and non-calcareous clays. It is also argued that the technological features of the Byzantine and Islamic glaze production shared more in common with the contemporary Chinese lead glazing tradition (the Sancai wares of the 7^th century A.D.) which also used PbO·SiO₂ mixtures applied to non-calcareous clays, than with the Late Antique glazing tradition.

L’ensemble constitué par les céramiques en terre cuite à glaçure plombifère, auparavant regroupées sous le terme de « céramiques de Bernard Palissy » puis « suites de Palissy » ou « atelier d’Avon », n’a plus aujourd’hui d’attache géographique concrète ni d’histoire attestée. Il est en effet avéré que la légende et le mythe ont, depuis le début du XIXe siècle, toujours largement dominé. En dépit de leur présence importante au sein des collections publiques françaises et étrangères, la fragilité des connaissances actuelles sur ces pièces rend aujourd’hui leur étude approfondie indispensable. De nature fondamentalement transdisciplinaire, ce travail de thèse explore d’une part leur matérialité, avec la création d’un corpus des œuvres conservées en collections publiques (plats rustiques, pièces de vaisselle moulées, statuettes) et la prise en compte des analyses physico-chimiques ; d’autre part, par un travail minutieux de dépouillement d’archives et de recensement du matériel archéologique, il permet de mieux les situer dans une époque et dans un contexte de production parisien. Ces travaux reviennent ainsi sur l’histoire oubliée de ces objets en enquêtant sur leur origine, leur destination initiale et leur parcours depuis les collections du XVIIe siècle jusqu’aux celles des érudits du XIXe siècle qui les léguèrent en tant qu’objets d’art aux grands musées nationaux. / This PhD thesis studies the whole terracotta lead-glazed ceramics produced in France at the end of the XVIth century and the beginning of the XVIIth century usually attributed to Bernard Palissy himself or his unidentified followers under the name Palissy ware ceramics. Legend and myth are widespread since the beginning of the XIXth century. As a consequence the study of these pieces which have proved to be very numerous in the French and foreign public collections has become essential. This transdisciplinary research examines on the one hand their materiality putting together a body of work (rustique figulines, relief-moulded dishes, statuettes) and taking into account physico-chemical analyses. On the other hand, it helps to place these ceramics in their Parisian historical production context by a meticulous study of archives and archaeological material. The research investigates their origin, their initial destination from the XVIIth century to the collections of French scholars or national museums' collections in the XIXth century.

<p>The impact of window area on the energy balance of a building was investigated by simulations in DEROB-LTH. The glazed area was varied in three types of buildings with different types of glazing and for several climates.</p><p>One low energy house was compared to a less insulated house but identical in size and layout. Three different types of glazing were used; uncoated double glazing, double glazing with one low-e coated pane and triple glazing with two low-e coated panes. Climates with variations in solar radiation, mean temperature, altitude and latitude were chosen.</p><p>The results show that if energy efficient window alternatives are chosen the flexibility of choosing the glazed area and orientation is higher. Choosing a larger area facing south resulted in a higher heating demand for uncoated double glazing in the standard house. An increased area also resulted in an increased peak load for heating for all the simulated cases. Choosing the energy efficient glazing type gave a decrease in heating demand for increased south facing glazed area in the standard house. In the low energy house the difference in heating demand between different areas was smaller than for the standard house. </p><p>An office module with two types of switchable glazing and one solar control glazing unit was used in three different climates; Stockholm, Brussels and Rome. Larger window areas increase the cooling demand but if glazing types with lower solar transmittance are used, the difference in cooling demand between different window areas decreases. An extremely large window area, however, increases the peak load both for cooling and for heating and should therefore be avoided. Energy can be saved by using switchable windows instead of solar control or in particular standard glazing.</p>

The impact of window area on the energy balance of a building was investigated by simulations in DEROB-LTH. The glazed area was varied in three types of buildings with different types of glazing and for several climates. One low energy house was compared to a less insulated house but identical in size and layout. Three different types of glazing were used; uncoated double glazing, double glazing with one low-e coated pane and triple glazing with two low-e coated panes. Climates with variations in solar radiation, mean temperature, altitude and latitude were chosen. The results show that if energy efficient window alternatives are chosen the flexibility of choosing the glazed area and orientation is higher. Choosing a larger area facing south resulted in a higher heating demand for uncoated double glazing in the standard house. An increased area also resulted in an increased peak load for heating for all the simulated cases. Choosing the energy efficient glazing type gave a decrease in heating demand for increased south facing glazed area in the standard house. In the low energy house the difference in heating demand between different areas was smaller than for the standard house. An office module with two types of switchable glazing and one solar control glazing unit was used in three different climates; Stockholm, Brussels and Rome. Larger window areas increase the cooling demand but if glazing types with lower solar transmittance are used, the difference in cooling demand between different window areas decreases. An extremely large window area, however, increases the peak load both for cooling and for heating and should therefore be avoided. Energy can be saved by using switchable windows instead of solar control or in particular standard glazing.

No description available.

Lors des procédés de mise en forme à chaud des matériaux métalliques, les surfaces des outillages sont soumises à des sollicitations thermiques, mécaniques et physico-chimiques. Le frottement et l'usure jouent un rôle important dans l'endommagement de ces surfaces. De plus, les couches d'oxyde dues à la haute température influencent les mécanismes d'usure. L'objectif de ce travail est de définir un modèle phénoménologique des mécanismes activés dans un contact haute température durant les premiers instants de frottement à partir du concept du troisième corps. Des essais tribologiques pion-disque de très faible durée ont été effectués avec pour particularité la création de pièges à troisième corps à la surface des pions. Ces pièges nous ont permis d'identifier le troisième corps qui circulait dans le contact, et ont mis en avant les différents débits de premiers et de troisième corps qui se sont activés. A partir d'observations MEB couplées à des analyses EDS, le troisième corps a été identifié, et il apparaît qu'il en existe plusieurs types qui ont cependant tous pour origine commune le pion. Une fois la source du troisième corps connue, les mécanismes de sa formation et de sa circulation ont été déterminés. Enfin, les mécanismes d'accommodation de la différence de vitesse et les débits de particules ont été définis et ont permis d'établir un modèle phénoménologique d'un contact à haute température. / In high temperature forming processes, the tool surfaces are the privileged places for thermal, mechanical, and physico-chemical solicitations. Friction and wear play an important part in tool surface damage. Thus, oxide scales due to the high temperature influence the wear mechanisms. The aim of this work is to define a phenomenological model of the activated mechanisms in a high temperature contact during the first seconds of friction, based on the third body concept. Very short tribological tests, using a pin-on-disc tribometer were carried out. The main characteristic of these tests was the creation of third body traps on the pin surface. The aim of these traps was to identify the third body which was circulating in the contact, and to highlight the activated flows of the first and third bodies. SEM observations and EDS investigations have revealed that different types of third body circulate in the contact, but each type was a part of the pin. Once the source of the third body was identified, its formation and circulation mechanisms were determined. Finally, accommodation mechanisms and particles flows were defined and used to develop a phenomenological model of a high temperature contact.

The aim of my thesis was to propose two variants of the steel construction of the car showroom. The ground dimensions of the structure are 35 x 50 meters. The building reaches a height of 8.8 m above the surrounding terrain. The building consists of two parts. The exhibition part of the car showroom will be partially glazed and also includes office space. The second part is the adjacent car workshop. The variants differ in the construction of the enclosure of the exhibition part of the car showroom. The work includes two static designs of the supporting steel structure of the car showroom. The winning variant of the frame construction a solution of selected details and drawing documentation.