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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
301

Monolitická železobetonová nádrž / Monolithic reinforced concrete tank

Kollárik, Adrián January 2020 (has links)
The thesis deals with design and assessment of all supporting parts of cast-in-place reinforced concrete tank. The thesis includes a technical report, static analysis, drawing documentations, construction proces and visualization. The drawing documentation consists of shape and reinforcement drawings of supporting parts.
302

Vliv cementářských odprašků na vlastnosti alkalicky aktivované strusky / Effect of cement by-pass dust on properties alkali-activated slag

Janíčková, Vlasta January 2020 (has links)
This masters thesis deals with influence of cement bypass kiln dust on physico-mechanical properties of alkali activated slag and influence of chosen compounds of cement bypass kiln dust on alkali activated slag. Using alkali activated slag is limited by its shrinkage. The setting time with different amount of cement bypass kiln dust and its chosen compounds (CaO, KCl and K2SO4) were measured by isotermal and isoperibolic calorimetry too. The strength and length changes of the mixtures with different amount of cement bypass kiln dust were measured. Samples were analysed by X-Ray diffraction analysis and scanning electron microscopy. It has been found that the increasing addition of dust reduce setting time, flexural and compresive strength and shrinkage. Presence of free CaO was found being one of the reasons for accelerated setting. KCl and K2SO4 have retarding effect but influece of free CaO prevails even for its lower contents. Long-term properties evolution is strongly dependent on curing regime due to potential volume expansion.
303

Dimensional Stability of Geosynthetic Clay Liners in Landfill Applications

Olsen, Gregory R. 01 December 2011 (has links)
An investigation was conducted related to the dimensional stability of geosynthetic clay liners (GCLs) in landfill applications. Multiple occurrences of panel separation of overlap seams in GCLs have been documented; however, explanation for the relative contribution of various mechanisms causing shrinkage has been limited. A systematic test program was conducted to determine the effects of a variety of conditions on GCL dimensional stability. Effects of initial moisture content, permeant type, and overburden pressure were tested by subjecting various GCL products to wet-dry cycles and measuring the dimensional change with each cycle. Different GCL types were each tested under various combinations of initial moisture content (as-received, 50, 75, 100, and 125%), permeant types (tap water, distilled water, and 0.1 M CaCl2), and overburden pressures (0, 6, and 20 kPa). Thermal expansion tests were conducted by heating or cooling GCL test specimens to temperatures of 0, 10, 40, 60, and 80°C at constant moisture content. Subgrade tests were conducted by placing GCL test specimens on compacted clay and sand subgrades in different orientations and hydration conditions in sealed containers and measuring dimensional change over time. Mechanical necking tests were conducted by subjecting GCL specimens to varying levels of tension and measuring the longitudinal and transverse strains at each load increment. Field simulation tests were conducted by placing specimens on a compacted sand subgrade beneath an exposed geomembrane liner outdoors in late summer. Initial moisture content tests resulted in shrinkage strains as high as 20% after 20 wet-dry cycles. GCLs ranged from slightly anisotropic [approximately 1.1:1 ratio of machine (MD) to cross-machine (XMD) shrinkage] to highly anisotropic (approximately 3:1 ratio of MD to XMD shrinkage). Most combinations of GCL type and initial moisture content resulted in GCL MD shrinkage strains greater than a value that would cause panel separation (termed panel separation threshold, PST) at roll ends during the first wet-dry cycle. All test specimens contracted beyond the PST in the MD within 3 wet-dry cycles. GCL specimens without attached geomembranes contracted beyond the PST in the XMD within 5 cycles. Permeant type tests demonstrated that hydration with 0.1 M CaCl2 reduced shrinkage by 50-80% compared to permeation with tap water. Overburden tests demonstrated that applying 6 kPa and 20 kPa reduced specimen shrinkage by at least 60% and 80%, respectively. Thermal expansion tests indicated that temperature changes at constant moisture content had little effect on GCL dimensional stability. Subgrade tests demonstrated that subgrade type and moisture as well as GCL type and orientation had effects on dimensional stability. Tensile necking tests demonstrated that transverse shrinkage occurred due to tensile forces in GCLs, but shrinkage was nearly always less than PST. Field simulation tests demonstrated that wet-dry cycles in the field were less intense and/or less frequent than in the laboratory. Results of this testing provide a basis for GCL overlap specifications necessary to maintain full coverage and future research to confirm a suggested method of preconditioning bentonite to prevent shrinkage.
304

Biologická vyhnívací linka / Sludge Digester Tank

Hurčík, Vít January 2013 (has links)
Master’s thesis deals with the design and assessment of the bearing structure of sewage treatment plant and development of the drawnings. The thesis solves the main part of the structure: base slabs, walls and ceiling slabs. Thesis solves the ultimate limit state and ultimate limit serviceability.
305

Vliv podmínek ošetřování na vlastnosti alkalicky aktivované strusky / Effect of curing conditions on the properties of alkali activated slag

Rypák, Peter January 2015 (has links)
Combination of fine ground granulated slag with proper alkaline activator gives alkali-activated slag – a material with remarkable properties. Theoretical part of the thesis deals with summarizing basic informations about alkali-activated slag, its properties, production and utilization. It also follows research devoted to effects of curing of alkali activated slag and shrinkage-reducing admixtures on its properties. Objective of the experimental part is to determine the influence of curing conditions on the mechanical properties and microstructure of alkali-activated slag. These properties are also monitored in alkali-activated slag with carbon nanotubes and hydroxypropylmethylcellulose as an shrinkage-reducing admixtures.
306

Využití řízeného naplyňování slitin Al-Si při tlakovém lití / Use of controlled gassing of Al-Si alloys during die casting

Jankes, Erik January 2015 (has links)
This master thesis will cover the possibility of using directed gassing of Al-Si alloys in a high pressure die casting foundry. As a control gas, rotary degasser with gaseous 20 % H2 in N2 as a medium was used. Castings were casted via high pressure die casting machine. The aim of this research is to compare internal defect such as porosity or shrinkage of a casts made from degassed and control gassed melt.
307

Latexem modifikované cementové kompozity / Latex Modified Cement Composites

Kunc, Michal January 2013 (has links)
The subject of dissertation is a study of physic-mechanical properties and development of self-leveling polymer-cement composite of the ternary binder system PC-CAC-CS modified with chemical additives and polymeric substances. The dissertation systematically describes a four-step optimalization of the composite considering its key properties. Experimental part has been focused on monitoring the impact of composite components on selected final properties. Basic physico-mechanical, structural properties and its relations (compressive strength, porosity, flow abilities, setting times) have been analyzed for deeper understanding of the effects of individual composite components. Methods which quantify the existence of the newly formed hydration product – ettringite (XRD, SEM with EDS, calorimetry, dilatometry) has been chosen as additional study methods on selected combinations. A working prototype of self-leveling polymer-cement composite was successfully developed based on systematic process and using of testing procedures and measuring methods.
308

Problematika nvrhu a testovn­ beton pro vodonepropustn tunelov ostÄn­ / Issues of design and testing of waterproof concrete fot tunnel lining

Merta, Michael January 2016 (has links)
The diploma thesis deals with the issue of waterproof concrete and testing its properties. The theoretical part is conceived through research on existing knowledge relating to waterproof concrete. Emphasis is placed on the possibility of using a waterproof concrete for structures, such is e.g. tunnel lining. The experimental part is focused on the laboratory testing of waterproof concrete. Particulary examined was the effect of various admixtures as a partial replacement of cement. Monitored was the development of compressive strength and flexural strength, development of temperature during hydration in the early stages of maturation of concrete, water resistance of concrete, concrete surface resistance to water and chemical de-icing agents, as well as development of shrinkage during concrete maturation.
309

Resilience to Urban Shrinkage in Riga

Akmentina, Lita 09 May 2017 (has links)
Riga has suffered a population loss of more than 29% between 1990 and 2014 which has led to increasing number of abandoned and degraded buildings in the city and optimization of the network of educational and cultural institutions. These trends are characteristics of urban shrinkage – a complex process affecting Riga for more than two decades and resulting in a pattern of growing, shrinking, and stable districts. A similar pattern has also been identified in other shrinking cities in Europe, but it has not been researched in more detail. In the given context, this research aims to narrow the knowledge gap on processes occurring in shrinking cities and to provide some understanding of the determinants of these processes on the city and local level through analysis of single embedded case study of Riga. To achieve this aim, resilience is used as an analytical concept. It allows to conceptualize urban shrinkage as a slow-burn (slowly occurring disturbance) and propose three possible responses - adaptation, transformation, and decline. These responses emerge from actions of actors on various spatial scales and lead to different outcomes. It also provides the basis for analyzing the determinants of these responses by conceptualizing them as sources of resilience and suggesting seven different aspects found in literature: leadership, networks, resources, learning, people-place connection, common cause, and system of institutions and governance. Finally, these theoretical assumptions are used to define two main research questions: (1) what are responses to urban shrinkage in Riga? (2) what are sources of resilience to urban shrinkage in Riga? The need for in-depth research of urban processes led to choosing mixed method strategy for both selecting the embedded units of analysis (districts) in Riga and finding answers to the proposed research questions. Based on combined results of secondary data analysis, controlled expert group discussion, and structured site visits, five districts in Riga were selected – Avoti, Maskavas forštate, Bolderāja, Sarkandaugava, and Ķīpsala. Further data collection and analysis included semi-structured interviews with different actors at the city and district level and document analysis. The study finds that there are four different responses to urban shrinkage in Riga: mitigation, adaptation, transformation, and possible decline. Mitigation can be identified on city (also national) level and is closely linked with the strategic actions proposed by the local and national government in response to population decline. Adaptation can be observed on the city and local level. It is the dominant response type in Riga emerging from strategic actions and different activities by various actors in response to all of the identified processes associated with urban shrinkage in Riga. Transformation, however, can be found only on local level – district (in one specific case) or unit level. It emerges from activities of mostly non-government actors that are making use of the opportunities provided by urban shrinkage in Riga. Finally, further decline is a potential response in several Riga districts resulting from strategic actions of local municipality and inability of some of the actors to deal with the existing situation. The analysis of sources of resilience reveals that there are four main determinants of adaptation and transformation – leadership, networks, resources, and learning. Other sources of resilience (people-place connection, common cause, and engaged governance) function as additional drivers or catalysts. All of these sources of resilience can be identified in Riga, but not consistently across all spatial scales and units or actor groups. The main deficiencies are linked with availability of resources (human and financial) among different actor groups, the existing system of governance (involvement of actors in the decision-making process) and leadership (on city level). The study also shows differences related to responses to urban shrinkage and different sources of resilience, especially leadership, learning, and resources. Overall, the findings support the main theoretical assumptions of the study and allow refining the understanding of responses to urban shrinkage and sources of resilience. The results can be used as the basis for developing an approach for assessment of the level of resilience to urban shrinkage or other slow burns in the urban context.
310

Odliv mladých lidí z města Šumperka - analýza příčin a návrh řešení problému / An outflow of young people from the city of Šumperk - cause analysis and solution suggestion

Strachotová, Eliška January 2017 (has links)
The diploma thesis is a case study of the outflow of young people from the town of Šumperk. The aim of this work is to explain the main causes of the problem, to determine the extent to which suburbanization is involved in the process, to evaluate the town's existing policies to solve the problem and to suggest possible solutions. The research is based on the theoretical concepts of the public policy cycle, which helps to determine the stage at which the problem is at the town level, works with the theory of city shrinkage, the theory of suburbanization, and push-pull migration theory. The original research is based on data from sociological research and interviews. Conclusions of the thesis include the finding that the main causes of the outflow of young people are inadequate job opportunities for college students and poor housing offers. Suburbanisation also contributes to the process of shrinking. The town's current policy lacks a strategic concept that would prevent the outflow. In conclusion, the author suggests possible partial solutions to the problem, such as creation of a coworking center or a change in the zone planning strategy.

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