This master's thesis deals with the influence of the exothermic riser sleeves on the solidification time of aluminum alloys. The thesis is divided into five parts. The first chapter describes solidification of cast alloys. The second chapter deals with the designing of risers. The third chapter is focused on the types of risers. The fourth chapter describes ways of intensification of risers and chemical composition of exothermic and insulating mixtures for production of riser sleeves. The main fifth chapter focuses on experimental measurements of temperatures and solidification time of aluminum alloy in castings, risers and exothermic and insulating riser sleeves.

This master’s thesis deals with preparation of foam glass and explores the possibilies of utilization of this material as an inorganic thermal insulating filler of fired hollow bricks. Foam glass was prepared via powder sintering method from waste packaging glass, using limestone and graphite as foaming agents. After inital analysis of raw materials, the effect of mixture composition and different processing parameters on bulk density, pore size and morphology of foam glass was investigated. Last but not least, different ways of manufacturing thermal insulating bricks, by preparation of foam glass directly in the cavities of fired hollow bricks, were tested.

Modern analog systems processing signals with very small amplitude are prone to distortion, which is caused by leakage between signal traces. Causation of this is contamination of insulating gap, which insulates these traces. Goal of this thesis is to design and manufacturing of test structure, which allows classification of influence of contamination on substrate on leakage, and another goal is classification of technologiacal processes in light of contamination of substrate with electroactive inpurities. Based on results of this experiments are defined rules leading to optimizing of properties of manufactured structures. Attention is applied to ceramic substrates with conductive traces which are created with thick film technology.

Glass and the glass elements found thein way into almou all area sof human aktivity thanks to technological advances of the last 20 years. The are of construction i sof course no exeption, quite the contrary. These days it is difficult to imagine building without the glass element, whether it is a part of the interior or exterior. Yet the theory on this issue is at a very low level in the Czech Republic. The content of my work is static and dynamic analysis of structures of glass, when it is applied in practice, it will save money.

Master thesis deals with electrical insulating fluids in electrical engineering. It includes the distribution of liquids by ISO standard, distribution of oils and the current state of research into alternative electrical insulating liquids and description of selected dielectric properties. Furthermore, measurements were taken of selected electrical properties of the samples, and later their evaluation.

Doctoral thesis is focused on the study, research and development of heat insulating moulded refractory materials. The replacement of shaped instead of unshaped refractories is recently and strongly industrially demanded and belongs to ongoing research topics. With the increasing demand of energy savings, the excellent insulation properties are essential. The insulating properties of castables are the result of targeted porosity formation. The porosity is coming from the controlled air intrusion into material resulted to foamed structure. The foaming process was achieved by mixing of separately prepared aqueous foam into raw castable slurry or by in situ foaming of intensively mixed castable slurry with the surfactant additive. Nevertheless, the study of foam behaviour and the influence of additives on binder hydration and setting processes (i.e. calciumaluminate cement) was substantial for successful preparation of the experimental samples. The two types of the experimental samples were prepared. The first one was based on mixing of kaolin slurry with pre-prepared aqueous foam, whereas the de-aglomeration ability of kaolin specie was utilized to water-particle film formation. In situ foaming of multicomponent system is the second one. The both processes brought some negative attributes, so the optimal properties of prepared castables were achieved by their combination.

Les projets de mise en place dans les prochaines décennies de « super réseaux intelligents », qui prévoient la construction de centrales de production à des milliers de kms des centres de consommation, nécessite le développement à large échelle du transport de très fortes puissances par câbles à courant continu. Les principaux verrous à ce développement se situent au niveau du câble et des appareillages adéquats, qui doivent être conçus sur des critères spécifiques et comporter des matériaux isolants ayant des propriétés particulières. Outre la variation de la résistivité qui dépend fortement du champ électrique et de la température, il est établi que des charges sont injectées dans la matière isolante, donnant lieu à une charge d'espace modifiant la répartition du champ électrique. Dans le cas d'un renforcement du champ électrique, la présence de charges d'espace peut conduire à une accélération du vieillissement électrique et, par suite, à un phénomène auto-accélérant pour la rupture diélectrique. Le comportement de ces matériaux sous fortes contraintes continues et en particulier leur vieillissement reste aujourd'hui mal connu.Ce travail de thèse concerne ainsi l'étude du comportement diélectrique de résines époxydes chargées d'alumine utilisées comme supports isolants dans les disjoncteurs à isolation gazeuse en vue d'évaluer leur aptitude à être utilisées dans des appareillages de coupure haute tension continue. Les différentes propriétés diélectriques de ce matériau à l'état initial (facteur de pertes, résistivité volumique, seuils et coefficients de non linéarité, résistivité surfacique, rigidité diélectrique, évolution des charges d'espace) sont déterminées et étudiées sous contrainte électrique continue et à différentes températures.Afin de mieux évaluer l'effet à long terme de la charge d'espace sur le matériau et d'en tirer des informations approfondies pour la conception des futurs composants pour la haute tension à courant continu, une étude de vieillissement accéléré sous contraintes électriques (champs continus) et thermiques (différentes températures) est réalisée. En plus de la charge d'espace, les autres paramètres analysés (permittivité, pertes diélectriques) constituent également des marqueurs potentiels du vieillissement du matériau. L'analyse de l'évolution de ces marqueurs constitue une phase nécessaire dans la compréhension du comportement du matériau pour une utilisation en haute tension à courant continu. / The development of high voltage dc equipment requires design according to specific criteria and including materials with appropriate properties. Indeed, while in ac the dielectric behaviour is mainly determined by permittivity, which varies little for the used materials with field and temperature at power frequency, the dc behavior is determined by highly non-linear volume and surface conductivity-related phenomena. Thus, it is well known that, in dc conditions, electric charge is injected and trapped in the bulk and on the surface, affecting the distribution of the electric field. Space charge accumulation is able to increase significantly the values of the field, thus accelerating ageing and increasing the risk of breakdown. The electrode nature, the field and temperature dependence of the electrical conductivity of the insulating material are key factors involved in the high dc field phenomena.Epoxy resins form an important category of polymeric insulating materials used in a wide range of electric power installations and equipment. In particular, they have been used especially as insulating supports for ac Gas Insulated Switchgear (GIS), because of their electrical and mechanical properties. However, the behaviour of these materials under high dc stress is less known and needs thorough investigation in view of dc applications.The purpose of this thesis is to investigate dielectric behavior of epoxy resins in order to assess their suitability for use in high DC voltage switchgear and define actions and criteria support for the design of such devices.We start by presenting the most important chemical thermal and dielectric properties of polymers as well as the various properties of the epoxy resin.Dielectric properties of the material at initial state with continuous temperature and electrical stress (loss factor, volume resistivity, thresholds and nonlinearity coefficients, surface resistivity, breakdown, evolution of space charge) are determined and investigated under dc fields at different temperatures.

Materials exposed to the space plasma environment acquire electric charge, which can have harmful effects if it leads to arcing or electrostatic breakdown of important spacecraft components. In fact, spacecraft charging is the leading environmentally induced cause of spacecraft anomalies. This study focuses on measuring electron yield, a property of materials that describes how many electrons are ejected from a material under energetic electron bombardment, which can vary depending on the energy of incident electrons. Intrinsic electron yield is defined as the average number of electrons emitted per incident electron from an electrically neutral material. The specific aim of this work is to improve yield measurements for insulator materials, which can be difficult to test using conventional methods due to charge accumulation in insulators.Most studies of electron yield use a steady current electron beam in a vacuum chamber to irradiate materials to be tested. By comparing the amount of current deposited in the material to the total incident current, the emitted current can be calculated. This works well for conductors; however, insulators charge up quickly, which either repel incident electrons or reattract emitted electrons producing erroneous yield measurements. This study improves on methods that use a pulsed electron beam to measure yield with small amounts of charge per pulse, as well as neutralization methods to dissipate stored charge between pulse measurements.The improvements to instrumentation and data analysis techniques are quantified to demonstrate their validity. These improvements will allow for continued studies on extreme insulator materials. Future studies will provide new understanding of interactions between electron radiation and materials, which will allow for better modeling of spacecraft charging and the development of materials that meet desired electron emission specifications.

The principle of sustainability in the built environment has become much more significant in the past decade, resulting in a push to develop building systems that are more energy efficient, durable, and use fewer natural resources. For residential and light commercial buildings, insulated concrete forms (ICF) have enjoyed increasing popularity for their ability to meet these new demands. ICFs are a stay-in-place concrete formwork system for building structural walls that are also highly insulated, among other benefits. Screen-grid ICFs (SGICF) are a small subset of ICFs that tend to use less concrete than standard ICFs and are sometimes made of recycled materials. These traits make SGICFs attractive, but there is a lack of understanding of their structural characteristics due to their irregular internal concrete structure. Because of this, structures using SGICFs are limited to heights no higher than two stories. Further study should show whether SGICFs structures can safely built to greater heights. This investigation studied two types of SGICFs at a component level in order to gain understanding of their lateral force and drift ratio capacities under cyclic loading. Several variables, including steel reinforcement details, the type of concrete, and the presence of the forms, were altered to measure their impact on the performance of the systems. Test results suggested that the ICF formwork increased lateral strength by up to 100% and lateral deformation capacity by up 60% when compared to identical specimens tested with the formwork removed. Results also showed that confinement of the cement, either by mesh hoops, spiral wire, or fiber-reinforced concrete improved the drift ratio at failure up to 500% when compared to specimens with no confinement material. Computer models were created to gauge their ability to replicate the behavior of the experimental test results. The models typically overestimated the lateral load resistance of the samples by 50-100%, and even more in some cases, depending on the reinforcement. The models were not reliable in determining the drift ratio at which the sample was considered to have failed. In some cases the model failed at 50% lower lateral deformations than the test specimen, while in others the model did not fail at all. Future studies should explore refinements of the models to increase their accuracy and usefulness, as well as accounting for the contributions do to the form material. Future studies should also include using spiral wires, mesh hoops, or fiber reinforced concrete in full-scale walls to verify their efficacy in improving overall wall performance.

The Space Shuttle Columbia accident and the recent excitement surrounding Discovery's return to space brought excessive media attention to the foam products used on the External Tank (ET). In both cases, videos showed chunks of foam or ablative material falling away from the ET during lift off. This led to several years of investigation and research into the exact cause of the accident and potential solutions to avoid the problem in the future. Several design changes were made prior to the return to flight this year, but the ET still shed foam during lift off. Since the Columbia accident, the loss of foam on ETs has been a significant area of interest for NASA, United Space Alliance, and Lockheed Martin. The Columbia Accident Investigation Board did not evaluate alternative materials but certainly highlighted the need for change. The majority of the research previously concentrated on improving the design and/or the application process of the current materials. Within recent years, some research and testing has been done to determine if a glass microsphere composite foam would be an acceptable alternative, but this work was overcome by the need for immediate change to return the shuttle to flight in time to deliver supplies to the International Space Station. Through a better understanding of the foam products currently used on the ET, other products can be evaluated for future space shuttle flights and potential applications on new space vehicles. The material properties and the required functionality of alternative materials can be compared to the current materials to determine if suitable replacement products exist. This research also lends itself to the development of future space flight and unmanned launch vehicles. In this paper, the feasibility of alternative material for the space shuttle's external tank will be investigated. Research on what products are used on the ET and a set of functional requirements driving the selection of those materials will be presented. The material properties of the current ET foam products will be collected and an evaluation of how those materials' properties meet the functional requirements will be accomplished. Then significant research on polymeric foams and ablative materials will be completed to learn how these various products can be applied in this industry. With this research and analysis, the knowledge gained will be used to select and evaluate the effectiveness of an alternate product and to determine feasibility of a product change with the current ET and the importance of maintaining the shuttle launch schedule. This research will also be used to evaluate the potential application of the alternative product on future platforms. There are several possible outcomes to this research. This research could result in a recommended change to the ET foam material or a perfectly acceptable alternative material that could result in a cost or schedule impact if implemented. It is also possible that there exists no suitable alternative material given the existing functional requirements. In any case, the alternative material could have future applications on new space vehicles. A set of results from the research and analysis will be provided along with a recommendation on a future material for use on space vehicles.