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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.
241

Konstrukční studie axiálních bezucpávkových čerpadel / Design studies of axial sealing pumps

Dobrovolný, Martin January 2018 (has links)
Review of axial hydraulic machines and elementary procedures of design hydraulic machines are listed in the first part of thesis. Second part is dedicated axial pump with annular motor and measurement its characteristic curve. In the third part of thesis, procedure of design axial pump with tube motor is described, also there are listed CFD results and characteristic curve of axial pump with tube motor is predicted.
242

Fosfátové konverzní povlaky / Phosphate conversion coatings

Ševčíková, Barbora January 2012 (has links)
The main objective of the master’s thesis is to study the influence of phosphate coating structure on the mechanical properties of screw connection. The theoretical part describes the conventional phosphating process and it is followed by an analysis of current knowledge of phosphating technology. Experiments are carried out on screw valves mounted to a high pressure diesel pump by Bosch Diesel s.r.o., made of unalloyed carbon steel. To investigate the effect of the structure on the connection sealing, twelve kinds of phosphate coatings varying in one process parameter were prepared. The monitored parameters determining the phosphate structure are – type of phosphate and activation bath, its temperature and concentration and time of immersion. The sealing connection is examined during simulated assembly process by angle controlled tightening while measuring torque and permanent material deformation. Prepared layers are characterized by determination of weight per unit area and their structure observed by electron microscope.
243

Dielektrické vlastnosti epoxidové pryskyřice plněné nanočásticemi / Dielectric properties of epoxy with nano particle

Ráček, Tomáš January 2010 (has links)
This diploma thesis is focused on the analysis of basic problematics of dielectrics and nanocomposites. It describes the fabrication of experimental samples of nanocomposites from sealing epoxy resin and nanoparticles of titanium dioxide with various weight filling. Further, the thesis deals with measuring and evaluation of dielectric properties of the samples. It examines the influence of weight filling, temperature and frequency of the electric field on volume resistivity, relative permitivity and loss factor.
244

Proudění ve spárách / FLow in cracs

Ocásek, Adam January 2013 (has links)
This Master’s thesis investigates the flow in sealing gaps of impeller within pumps and turbines. Sealing gaps are installed to improve the volumetric efficiency in this type of fluid machinery. Despite present extensive research this subject has not been entirely documented and the thesis’ aim is to improve our knowledge in this matter. At the beginning, the practical experiment is used in order to establish appropriate numerical description of flow in seals and to calibrate software FLUENT. In chapter five, the thesis analyses the influence of seal design on volumetric efficiency of pumps and turbines and defines its optimal construction to improve the efficiency. The thesis then examines the effect of rotor eccentricity on flow properties, flow rate and pressure distribution within the sealing gap. In the last section, through chapters six to eight, the flow results provided by numerical solution in FLUENT and selected analytical equations, or their modified forms, are being discussed. The degree of correspondence between the results is also studied.
245

Rekonstrukce protitlakové parní turbiny / Retrofit Backpressure Steam Turbine

Hlavinka, Miloslav January 2015 (has links)
Tématem diplomové práce je revize parní turbíny Mitsubishi a výpočet utahovacích momentů šroubů dělící roviny. Tato práce je rozdělena do několika částí. Úvodní část práce obsahuje seznámení s rozsahem prováděných servisních prací na parních turbínách. Poté je zde samotná revize parní turbíny Mitsubishi. Tato revize je dělena podle jednotlivých komponent turbíny. Poté je zde stanoven seznam nutných oprav a také seznam doporučených oprav pro příští odstávku. V další části je zde shrnut výpočet utěsnění dělicích rovin a to s nebo bez odlehčení. Dále jsou rozebrány nejčastěji používané typy závitů spojovacího materiálu parních turbín. Hlavní částí práce je samotný výpočet utahovacího momentu. Výstupem této práce je poté program pro výpočet utahovacího momentu v programu Excel.
246

Design of a rotary valve for pressurised steam / Utveckling av rotationsventil för trycksatt ånga

Nyawo, Talent January 2016 (has links)
Denna rapport är gjord på ett examensarbete som var utfört på uppdrag av det svenska företaget Ranotor AB. Syftet var att utveckla en konceptuell lösning för en rotationsventil som skall fungera i en miljö med hög temperatur och högt tryck. Ventilen skall arbeta under höga rotationshastigheter, vilket kräver korta öppettider.Tekniska hjälpmedel såsom SolidWorks, ANSYS och MATLAB användes för att modellera och analysera de konceptuella lösningarna. Slutlösningen valdes från ett flertal olika koncept, varpå detta vidareutvecklades och optimerades. Betydande material och gastätningslösningar identifierades och utvärderades för att hitta den bästa lösningen. Optimering av individuella komponenter och hela anordningen gjordes med avseende på spänning, termisk- och dynamisk analys. De givna specifikationerna uppfylldes och resultaten var tillfredsställande. Resultaten ger en teoretisk bas för vidareutveckling och applicering av en rotationsventil in en miljö med hög temperatur och högt tryck. / This Master thesis is a project commissioned by the Swedish company Ranotor AB. The objective of this thesis is to develop a conceptual solution for a rotary valve mechanism that has to work efficiently in a high-temperature and high-pressure environment. The valve is to operate at high rotational speeds which calls for very short opening time.Modern engineering tools namely Solidworks, Ansys and Matlab, were employed for modelling and analysis of the conceptual solution.The best design solution was selected from three developed concepts, and the selected concept was further developed and optimized. Major material candidates and gas-tight sealing solution were identified and evaluated and the optimal material and seal design was chosen. Optimization of the individual components as well as the whole assembly was performed based on stress, thermal and dynamic analysis. The given design specifications and functions were fulfilled and the results were satisfactory. The obtained results provide a theoretical foundation for the development and application of a rotary valve in high-temperature and high-pressure environment.
247

Visualization, modeling and consequences of residual stresses in glass frit sealing of a UV light source

Hurtigh Grabe, Vilma January 2023 (has links)
PureFize Technologies AB develops and manufactures a broadband ultraviolet (UVC) light technology device that is mercury-free and based on nanotechnology, using the principle of field emission. The light source is made of Ti and glass, which are hermetically bonded, using a low-temperature glass frit, at elevated temperatures. The bonding procedure will induce stresses in the device originating from the mismatch of the coefficient of thermal expansion (CTE) between the materials. Brittle materials, as glass, withstands tensile stresses poorly. Therefore, the stress magnitude and distribution needs to be understood.  This work develops a quality inspection method for the glass bond and internal stresses, as well as stress simulations of the device, to be used in production at the company. The glass bond width and the internal stresses in the device were classified and analyzed by light optical microscopy and by polarised light optical microscopy. The optical analysis was followed by pressure tests of the devices using a chamber that allowed for pressurized air up to 7 bar. In parallell with the experimental work, stress and deformation simulations of the device using the finite element method (FEM) was made. Data collected from the inspections and pressure tests were compiled and analyzed, showing clear connections between the glass bond quality and the device's ability to withstand external pressure. A narrow glass bond could withstand external pressure poorly, whereas a wide glass bond could withstand external pressure well. Correlations could be made both between the glass bond appearance and the stress patterns, as well as between the FEM simulations and the stress patterns in the device. It is clear that the stresses induced in the device after bonding originates from the CTE mismatch of the bonded components when cooling it from the bonding temperature to room temperature. The pressure testing method proved to be an efficient way of verifying the maximum pressure capacity of the devices.  The knowledge from this thesis can be used when further investigating induced stresses from glas frit bonding.
248

A Sociological Approach to Indoor Environment in Dwellings : Risk factors for Sick Building Syndrome (SBS) and Discomfort

Engvall, Karin January 2003 (has links)
<p>The principal aim was to study selected aspects of indoor environment in dwellings and their association with symptoms compatible with the sick building syndrome (SBS). A validated questionnaire was developed specifically for residential indoor investigations, using sociological principles and test procedures. The questionnaire was mailed to 14,243 multi-family dwellings in Stockholm, selected by stratified random sampling. Females, subjects with a history of atopy, those above 65 y, and those in new buildings reported more symptoms. Subjects owning their own dwelling had less symptoms. A multiple regression model was developed, to identify residential buildings with a higher than expected occurrence of SBS. In total, 28.5% reported at least one sign of building dampness in their home (condensation on windows, humidity in the bathroom, mouldy odour, water leakage). All indicators of dampness were related to symptoms, even when adjusting for demographic data, and other building characteristics (OR=2.9-6.0). Associations between symptoms and other building data was evaluated in older houses, built before 1961. Subjects in older buildings with a mechanical ventilation system had fewer symptoms. Heating by electric radiators, and wood heating was associated with an increase of most types of symptoms (OR=1.2-5.0). Multiple sealing measures (OR=1.3), and major reconstruction (OR=1.1-1.9), was associated with an increase of symptoms. The effect of seasonal adapted ventilation (SAV) was studied in a small experimental study. A 20% reduction of ventilation flow from 0.5-0.8 ac/h to 0.4-0.5 ACH during the heating season increased the perception of poor indoor air quality in the dwelling in general, and in the bedroom. In conclusion, low building age, and building dampness in the dwelling are associated with SBS. In older houses, mechanical ventilation is beneficial. The thesis did not support the view that energy saving measures in general is an important risk factor for SBS, but major reconstruction and multiple sealing measures can be risk factor for symptoms. Reducing the outdoor ventilation flow below the current Swedish ventilation standard (0.5 ACH) may increase the perception of impaired air quality. </p>
249

A Sociological Approach to Indoor Environment in Dwellings : Risk factors for Sick Building Syndrome (SBS) and Discomfort

Engvall, Karin January 2003 (has links)
The principal aim was to study selected aspects of indoor environment in dwellings and their association with symptoms compatible with the sick building syndrome (SBS). A validated questionnaire was developed specifically for residential indoor investigations, using sociological principles and test procedures. The questionnaire was mailed to 14,243 multi-family dwellings in Stockholm, selected by stratified random sampling. Females, subjects with a history of atopy, those above 65 y, and those in new buildings reported more symptoms. Subjects owning their own dwelling had less symptoms. A multiple regression model was developed, to identify residential buildings with a higher than expected occurrence of SBS. In total, 28.5% reported at least one sign of building dampness in their home (condensation on windows, humidity in the bathroom, mouldy odour, water leakage). All indicators of dampness were related to symptoms, even when adjusting for demographic data, and other building characteristics (OR=2.9-6.0). Associations between symptoms and other building data was evaluated in older houses, built before 1961. Subjects in older buildings with a mechanical ventilation system had fewer symptoms. Heating by electric radiators, and wood heating was associated with an increase of most types of symptoms (OR=1.2-5.0). Multiple sealing measures (OR=1.3), and major reconstruction (OR=1.1-1.9), was associated with an increase of symptoms. The effect of seasonal adapted ventilation (SAV) was studied in a small experimental study. A 20% reduction of ventilation flow from 0.5-0.8 ac/h to 0.4-0.5 ACH during the heating season increased the perception of poor indoor air quality in the dwelling in general, and in the bedroom. In conclusion, low building age, and building dampness in the dwelling are associated with SBS. In older houses, mechanical ventilation is beneficial. The thesis did not support the view that energy saving measures in general is an important risk factor for SBS, but major reconstruction and multiple sealing measures can be risk factor for symptoms. Reducing the outdoor ventilation flow below the current Swedish ventilation standard (0.5 ACH) may increase the perception of impaired air quality.
250

Salvaging Wasted Waters for Desert-Household Gardening

Fink, D. H., Ehrler, W. L. 15 April 1978 (has links)
From the Proceedings of the 1978 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 14-15, 1978, Flagstaff, Arizona / With the objective of determining if sufficient water would be salvaged by a typical desert, urban-household from normally wasted sources associated with the lot and household to adequately irrigate a garden and orchard, a 2000 sq ft house on a typical one fifth acre lot in three cities having climates similar to Phoenix, Tucson, or Prescott, Arizona was hypothesized and the amount of water available for yard watering calculated, provided that (1) only rainfall was available, (2) rainfall-runoff from covered areas associated with or adjacent to the lot was salvaged (roof, street, alley etc.), (3) gray-water from the household was utilized, (4) a portion of the lot was waterproofed to concentrate the runoff on the untreated portion, and (5) various combinations of the above were utilized to increase the amount of available water. It is demonstrated that these sources could be used singly or in combination to obtain the required amount of water with the actual amount available depending upon the precipitation, runoff and runon areas, runoff efficiency of the contributing area, and the number of people in the household. A number of horticultural plants are suggested that should best fit such an irregular irrigation scheme.

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