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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.
421

Vysoké Mýto - napojení na R35 při postupné výstavbě / Vysoké Mýto - connection to motorway R35, phase of construction

Novák, Martin January 2014 (has links)
The thesis deals with the stages of development of Vysoke Myto road network with an emphasis to design an optional diversion of the traffic from the town itself even before the planned R35 is finished. The designed solution, including road connections to the present and future network, is to be functional, utilizable and economically desireable in all the stages of development.
422

Stabilita a řiditelnost experimentálního letounu VUT 001 Marabu / Stability and Manoeuvrability of Experimental Aircraft VUT 001 Marabu

Marešová, Eva January 2009 (has links)
This diploma thesis deals with a stability and manoeuvrability of experimental aircraft VUT 001 MARABU. It contains calculation of aerodynamic stability derivations and other data necessary for evaluation of static and dynamic stability. Assessment of convenient autopilot.
423

Konstrukce zařízení na měření směrové tuhosti pneumatik / Design of experimental device for measurement of tire cornering stiffness

Krůza, Libor January 2011 (has links)
This thesis describes the design of devices that will measure the directional characteristics of the tires. The first step is to analyze the directional characteristics and methods of measurement. The following equipment design, which should be designed to function while it was cheapest. The device is designed as a trailer towing vehicle. It also includes analysis of individual plant components important to measure those variables.
424

Studie mimoúrovňové křižovatky R46 / The study interchanges R46

Dostál, Jan January 2016 (has links)
The master´s thesis focuses on design interchange on R46 highway. The purpose of this thesis is to design optimal solution of transport capacity and safety. The another part of the thesis is solution of connecting on roads II/433 and III/37766. This solution is part of bypass plan, by city plan of Prostějov.
425

Konstrukce zařízení pro měření charakteristik pneumatiky / Design of Device for Tyre Parameters Measurement

Pacut, Patrik January 2016 (has links)
The aim of this thesis is a method selection and design of measuring device for experimental identification of directional tire characteristics for passenger cars. The first part analyse directional characteristic and method of measurement. The next part focuses on the design of the measuring trailer and selecting measuring equipment with description.
426

Asymetrie kostěné pánve ve vztahu k reprodukci člověka / Pelvic asymmetry in relation to the human reproduction

Kodytková, Aneta January 2019 (has links)
This diploma thesis deals primarily with the existence of the asymmetry of the bony pelvis and the sexual dimorphism of the asymmetry of the pelvic canal, which is caused by different reproductive functions of each of the sexes. Furthermore, the correlation or linear dependence of the external pelvic and pelvic canal dimensions was investigated. The study uses 3D pelvic models created in Avizo 7.1 from CT images of the recent French population. The material consists of 74 probands, of which 36 are males and 38 are females. The models were digitalized using Viewbox 4 software, in which 29 landmarks were applied to each pelvic model. These correspond to 24 dimensions divided into three groups: the size of the non-canal pelvis, the dimensions of the pelvic canal and the dimensions for calculating the correlation between the non-canal pelvis and the pelvic canal. The degree of asymmetry was evaluated using the formulas for the calculation of directorial (DA) and absolute (AA) asymmetry. Student's paired t-test was used for statistical analysis of asymmetry to determine asymmetry in previous studies. Gender differences were determined by the Mann-Whitney U test. At the same time, an analysis using the mixed model ANOVA was also performed, which in addition incorporates an intraobservation measurement...
427

Comparison of spool radial grooves influence between water and oil hydraulics

Majdic, Franc January 2016 (has links)
In this paper numerical flow calculations with respect to the annular gaps with added radial grooves normaly used on the spools of directional control valves were carried out. The impact of various annular gap geometries and radial grooves during variable pressure conditions, and while using different hydraulic fluids, on the flows through annular gaps were investigated for different flow regimes. Samples with different geometries and numbers of radial groves on the spool of the directional control valve were also made for the purpose of carrying out flow measurements. The two different hydraulic fluids that were used in the numerical simulations and for the flow measurements were a hydraulic mineral oil and tap water. The results of the numerical calculations for the different models of the radial grooves with axially symmetric geometries show their impact on the internal leakage with respect to three different regimes of flow. The results of the numerical calculations based on the use of a hydraulic oil show a trend that was established by the experimental investigation.
428

Beeinflussung der Gefügestruktur bei der gerichteten Erstarrung von multikristallinem Silicium und deren Auswirkungen auf die elektrischen Eigenschaften

Kupka, Iven 07 July 2017 (has links)
Solar cells convert sunlight into electrical energy using the photo effect. With a mar-ket share of 60%, multicrystalline silicon (mc-Si) is the most frequently used absorber material. Standard mc-Si ingots are directionally solidified in a fused silica (SiO2) crucible, which exhibits a silicon nitride (Si3N4) inner coating. After the entire raw material has been melted, the nucleation takes place on the Si3N4 inner coating at the bottom of the crucible. This results in an inhomogeneous initial grain structure and an increased fraction of dislocation clusters in the upper part of the ingot, which decrease the quality of standard mc-Si. Therefore, the global goal is the development of a cost-effective technology that reduces the formation of clusters and enhances the quality of mc-Si ingots. One way of achieving that goal is to produce the so-called \"high performance multi crystalline silicon\" (HPM-Si). During the directional solidification silicon raw material remains unmelted at the bottom of the SiO2 crucible, whereby crystallization does start on the silicon feedstock a few millimeters above the crucible bottom. Compared to standard mc-Si, a finer grained structure with many small grains is formed, which are separated by so-called random grain boundaries. Since the movement of dislocations across this grain boundary type has rarely been observed, the risk of formation of dislocation clusters, which have a negative impact on the efficiency of solar cells, is greatly reduced for HPM-Si. However, the disadvantage of the HPM-Si compared to the mc-Si is the yield loss resulting from the unmelted raw material at the crucible bottom. Hence, the aim of the present work is to produce mc-Si with a fine-grained structure in combination with a high fraction of random grain boundaries without the disad-vantage of yield loss. In order to investigate the grain structure in dependence of the nucleation conditions G1 ingots having a mass of 14.5 kg and dimensions of 220x220x130 mm³ were directional solidified in a furnace. The analysis of the grain structure with respect to the grain size, grain orientation and the random grain boundary length fraction and the comparison with the HPM-Si reference crystal took place on horizontal wafers with a thickness of 3mm. One possibility to influence the grain structure of mc-Si could be the variation of the cooling conditions before the start of crystallization at the crucible bottom. In a first series of experiments, a gas-flowed cooling plate, positioned below the crucible, was used. An increased gas flow increases the axial heat flow downwards and the cooling rate below the crucible bottom in the same direction. The detected cooling rate, measured by a thermocouple in the silicon melt 5 mm above the crucible bottom, varied in a range between 0.06-1.5 K/min. An increased cooling rate increases the supercooling, with a maximum of 2K. The analysis of the grain structure shows that a reduction in the cooling rate in combination with the lowest supercooling minimizes the average grain size and increases the fraction of random grain boundaries. However, an HPM-Si like grain structure (grain size and fraction of random grain boundaries comparable to HPM-Si) could not completely produced. Furthermore, due to the extended process time, the wafer yield is reduced, whereby the reduction of the cooling rate is not a preferable method for the industrial process. In a second experimental series, which took place under constant cooling rates, the influence of an additional nucleation layer on the initial grain structure was investigated. For this purpose, the additional nucleation layer was applied on the already existing Si3N4 inner coating on the crucible bottom. In order to adjust a HPM-Si like grain structure, the contact angle of the silicon melt on the additional nucleation layer should be lower than on the Si3N4 inner coating. The theoretical basis for this hypothesis is the relationship between the contact angle and the nucleation energy, which states that a reduced contact angle lowers the nucleation energy and can ultimately lead to more nuclei. Furthermore, in order to avoid melting, the additional nucleation layer must have a higher melting point than silicon. Suitable materials for the application as a foreign seed sample are SiC, SiO2 and Al2O3, which are used in the form of particles with different sizes. The production of the additional nucleation layer was carried out by a spraying as well as by an embedding procedure. These layers exhibit different thermal conductivity as well as surface roughness. Embedded nucleation layers generate higher roughness values than sprayed nucleation layers. The analysis of the grain structure identified the surface roughness as the main influencing factor on the initial grain size. While an increased surface roughness (Rq>100μm) results in a fine-grained structure (average grain size: <2mm²) comparable to HPM-Si, the average grain size increases (>2 mm²) with a reduced surface roughness (Rq<100μm). However, the analysis of the grain boundary relationship shows that the fraction of random grain boundaries does not correlate with the average grain size. Only a ma-terial dependency was detected. All SiO2 nucleation layers generate an increased fraction of random grain boundaries, comparable to the HPM-Si material. In contrast, the fraction of random grain boundaries was reduced for all SiC nucleation layers. This result is probably established with the different thermal conductivities of the used materials. The increased thermal conductivity of the sample with the SiC nucleation layers increases the cooling rate, promoting dendritic growth. In contrast the lower thermal conductivity of the SiO2 nucleation layers reduces the cooling rate and dendritic growth is suppressed. Since dendrites exhibit a Σ3 grain boundary relationship in the center, the fraction of this grain boundary type increases for SiC nucleation layers and the fraction of random grain boundaries decreases. In this thesis, various possibilities for influencing the grain structure have been pre-sented. A SiO2 nucleation layer with a roughness value Rq> 200μm represents an industrially relevant solution for the production of mc-Si with comparable properties to the HPM-Si without the disadvantages of yield loss. Hence, it was possible to in-crease the yield with comparable material quality, whereby the production costs could be reduced. Some first crucible manufacturers have already transferred the use of the SiO2 nucleation layers on top of the already existing Si3N4 inner coating at the crucible bottom to production.
429

Modellierung und Untersuchung der Schmelzströmung für die gerichtete Erstarrung in der industriellen Photovoltaik

Bönisch, Paul 08 July 2019 (has links)
Diese Arbeit stellt einen Beitrag zur Modellierung der gerichteten Erstarrung von Silizium für die Photovoltaik dar. Es wurde basierend auf einem industriellen Prozesses ein Modellaufbau der Schmelze mit zwei Induktoren nach der Ähnlichkeitstheorie abgeleitet. Dieser ermöglicht, durch die Verwendung von niedrig schmelzenden Metallen, eine umfassende Messung der Strömungsgeschwindigkeiten mit Ultraschall-Velocimetrie. Basierend auf den experimen- tellen Daten wurde ein numerisches Modell zur Berechnung der Schmelzströmung unter Magnetfeldeinfluss validiert. Es wurden detaillierte Untersuchungen zu Strömungsstrukturen und beeinflussende Parameter durchgeführt, eine Methode zur Klassifizierung entwickelt und die Rotationskennzahl Ro eingeführt, mit welcher man in Abhängigkeit vom Magnetfeld und der Schmelzgeometrie die horizontale Rotation der Schmelzströmung in einem breiten Gültigkeitsbereich vorhersagen kann. Das validierte numerische Modell wurde zur Prozessoptimierung auf die Schmelzströmung des industriellen Prozesses angewendet.
430

The “bi-directional” influence between technology and society: how M-PESA is shaping and being shaped by society in Kenya

Gebregziabher, Sosina Abraha 17 February 2012 (has links)
M-PESA (a mobile banking service in Kenya) was introduced to offer a person-to-person money transfer service. Its extensive adoption and appropriation for purposes other than person-to-person transfers has influenced the technology providers (Safaricom) to widen their services beyond their original intentions. M-PESA provides a wide range of financial services including services for people who were previously unbanked. Users of M-PESA can now pay different utilities, those without credit cards can purchase products online, others can repay loans to microfinance institutions, pay insurance premiums, withdraw money from ATMs, use it as Point of Sale Payment and open savings accounts. This research examines the existence of “bi-directional” influences between technology and society by taking M-PESA business users as a case. It specifically investigates how M-PESA as a technology has influenced the business environment in Kenya and how the design of M-PESA has in turn been influenced by its adoption. The research adopts the Adaptive Structuration Theory as the theoretical framework and interpretive case study research as a methodological approach. Interviews with different stakeholders in the industry were used to collect data. Data was analyzed using Diachronic Analysis. The results of the research show that there is a “bi-directional” influence between technology and people as they affect each other over time. Mobile technologies shape the way businesses operate, allowing them to provide new services and improve existing ones. At the same time, usage and adoption trends affect the design of mobile technologies. Over time, technology is adapted to accommodate the new needs of businesses and other needs in the wider community. This research shows that the impact of technology depends not only on its functionality but also on its use and appropriation in society. / Dissertation (MCom)--University of Pretoria, 2011. / Informatics / unrestricted

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