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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.
131

Estimating Surface-Atmosphere Exchange at Regional Scales

Isaac, Peter Robert, peter.isaac@flinders.edu.au January 2006 (has links)
This thesis examines a method for estimating the daytime fluxes of heat, water vapour and carbon dioxide at regional scales by using simple models to combine spatially resolved surface properties with bulk meteorological quantities measured at a central location. The central themes of this thesis are that the spatial and temporal variability of regional scale fluxes are contained in the surface properties and meteorology respectively and that the surface properties can be interpolated across a heterogeneous landscape using remotely sensed data. The regional scale fluxes estimated using this technique are compared to the values from three other methods and this allows some conclusions to be made regarding the relative strengths and weaknesses of each method. The surface property approach yields robust estimates of the fluxes that will be useful in researching exchange processes at regional scales, providing input parameters for, and validation of, the biosphere components of General Circulation Models and testing inventory estimates of CO2 budgets. The surface properties are derived using data from 33 aircraft flights and eight ground-based sites along a 96 km transect established during the 1995 Observations At Several Interacting Scales experiment held near Wagga Wagga, New South Wales, Australia. Surface properties examined are the evaporative fraction (ratio of evapotranspiration to available energy), the Bowen ratio (ratio of sensible heat flux to evapotranspiration), the maximum stomatal conductance (maximum stomatal opening under optimal conditions) and the water-use efficiency (ratio of CO2 flux to evapotranspiration). Maximum stomatal conductance is calculated using a simple model of the stomatal response to light and water vapour deficit assuming soil evaporation occurs at the equilibrium rate. The diurnal trend and day-to-day variability in the surface properties is found to be significantly less than the spatial variability. All of the surface properties examined show some sensitivity to the synoptic conditions. The relationships between the surface properties and the Normalised Difference Vegetation Index (NDVI) are examined using a 130 km by 50 km sub-scene from a Landsat 5 Thematic Mapper (TM) image obtained five days before the start of the experiment period. The ground-based and aircraft observations are used to calculate the source-area influencing each measurement and this is combined with the Landsat 5 TM data to produce an average, source-area weighted NDVI for each ground-based site and each aircraft location. The source-area model is important because it provides the link between the observations and the remotely sensed data by identifying the surface patch that influences the measurements. Linear relationships are found between the source-area weighted NDVI and the surface properties. The observed relationships are used to interpolate the surface properties over the region covered by the satellite image and spatial variations in water loss and CO2 uptake by the surface vegetation are identified that are not resolved by the ground-based network. Analysis of the ground-based data showed that the spatial variability of the bulk meteorological quantities used in the surface property approach was much less than the diurnal trend in these data. With the small temporal variation in the surface properties noted before, this confirms the utility of assigning the spatial and temporal variability of the fluxes to the surface properties and the meteorology respectively. The combination of surface properties derived from the aircraft data and meteorology measured at a single location at the centre of the transect shows good skill in predicting the observed fluxes. Furthermore, the discrepancies between the predictions and the observations are explained by the different source-areas of the aircraft and ground-based data and much of the bias is removed when the surface properties are scaled from the NDVI of the aircraft source-area to the NDVI of the ground-based sites. Regional scale fluxes of heat and water vapour calculated using the surface property approach agree with averages of the ground-based data and this indicates that the ground-based network was representative of the OASIS region. Estimates of regional scale CO2 fluxes are not available from the ground-based network due to the lack of measurements at the driest ground-based site but the surface property approach yields plausible values. The results demonstrate the utility of extrapolating surface properties across heterogeneous landscapes using remotely sensed data.
132

The effect of submerged arc welding parameters on the properties of pressure vessel and wind turbine tower steels

Yang, Yongxu 21 October 2008
Submerged arc welding (SAW) is commonly used for fabricating large diameter linepipes, pressure vessels and wind turbine towers due to its high deposition rate, high quality welds, ease of automation and low operator skill requirement. In order to achieve high melting efficiency required for high productivity, best weld quality and good mechanical properties in manufacturing industries, the welding process parameters need to be optimized. In this study, the effect of SAW current and speed on the physical and mechanical properties of ASME SA516 Gr. 70 (pressure vessel steel) and ASTM A709 Gr. 50 (wind turbine tower steel) were investigated. Three welding currents (700 A, 800 A and 850 A) and four travel speeds (5.9, 9.3, 12.3 and 15.3 mm/s) were used to weld sample plates measuring 915 mm x 122 mm x 17 mm. The weld quality and properties were evaluated using weld geometry measurements, visual inspection, ultrasonic inspection, hardness measurements, optical microscopy, tensile testing, Charpy impact testing and scanning electron microscopy. It was found that the physical and mechanical properties of the weldments were affected by SAW parameters. Severe undercuts were found at high travel speed and welding current. Low heat input caused lack of penetration defects to form in the weldments. The welding process melting efficiency (WPME) achieved was up to 80%. The hardness of the coarse grain heat affected zone (CGHAZ) and the weld metal increased with travel speed. The toughness of both materials increased with increasing travel speed and welding current. The yield and tensile strengths of the weldments of SA516 Gr.70 and A709 Gr.50 steels were within the same range as those of their respective parent metals because all test specimens broke in the parent metals. Also, the parent metals of both steels had the highest fracture strain and percent elongation. The percentage elongation increased with travel speed but decreased with welding current.
133

The effect of submerged arc welding parameters on the properties of pressure vessel and wind turbine tower steels

Yang, Yongxu 21 October 2008 (has links)
Submerged arc welding (SAW) is commonly used for fabricating large diameter linepipes, pressure vessels and wind turbine towers due to its high deposition rate, high quality welds, ease of automation and low operator skill requirement. In order to achieve high melting efficiency required for high productivity, best weld quality and good mechanical properties in manufacturing industries, the welding process parameters need to be optimized. In this study, the effect of SAW current and speed on the physical and mechanical properties of ASME SA516 Gr. 70 (pressure vessel steel) and ASTM A709 Gr. 50 (wind turbine tower steel) were investigated. Three welding currents (700 A, 800 A and 850 A) and four travel speeds (5.9, 9.3, 12.3 and 15.3 mm/s) were used to weld sample plates measuring 915 mm x 122 mm x 17 mm. The weld quality and properties were evaluated using weld geometry measurements, visual inspection, ultrasonic inspection, hardness measurements, optical microscopy, tensile testing, Charpy impact testing and scanning electron microscopy. It was found that the physical and mechanical properties of the weldments were affected by SAW parameters. Severe undercuts were found at high travel speed and welding current. Low heat input caused lack of penetration defects to form in the weldments. The welding process melting efficiency (WPME) achieved was up to 80%. The hardness of the coarse grain heat affected zone (CGHAZ) and the weld metal increased with travel speed. The toughness of both materials increased with increasing travel speed and welding current. The yield and tensile strengths of the weldments of SA516 Gr.70 and A709 Gr.50 steels were within the same range as those of their respective parent metals because all test specimens broke in the parent metals. Also, the parent metals of both steels had the highest fracture strain and percent elongation. The percentage elongation increased with travel speed but decreased with welding current.
134

Fabrication and Application of Microstructured Optical Fiber

Lin, Hsin-Hung 27 July 2010 (has links)
In this study, we will discuss the fabrication detail about the capillary optical fiber and microstructured optical fiber (MOF) from the preform manufacture to the drawing process and apply our capillary optical fiber in a temperature sensor device. First, we discuss the influence of the drawing parameters contribution for the fiber, and we will introduce how to design a preform and discuss how to keep our fibre geometry in drawing process by controlling the drawing parameters. For better fiber products, we need to make some important improvements such as fixing the preform geometry and designing the preform pressure or vacuum input path before the fiber drawing process. In the fiber drawing we want to control the fiber inner diameter and make the interval between three capillary tube disappear. We will solve these problems by different preform making methods or drawing tower hardware design and drawing parameter control. Now we can successfully make single ring hole MOFs by the capillary tube sealed method. But the hole structure is not as good as expectation. We will try to design a pressure and vacuum input device to replace the capillary tube sealed method. And help us to make better and more different MOF structures. We also used our capillary optical fiber to be a temperature sensor. We will describe the principle and the sensing sensitivity of our sensing device in this study. Our temperature sensing device shows a linear relationship between the temperature and operation wavelength, and the sensing sensitivity is 0.038nm/¢XC
135

Insulation Coordination In The Turkish E.h.v. Transmission System

Deniz, Ibrahim 01 January 2011 (has links) (PDF)
This thesis reviews the line insulation coordination practices of Turkish Electricity Transmission Company with special focus on E.H.V. transmission line towers&rsquo / top geometry and ground clearances. In respect of this, the national regulation, &ldquo / Elektrik Kuvvetli Akim Tesisleri Y&ouml / netmeligi&rdquo / , is critically evaluated.The national regulation lags behind the modern world practice and the provisions of the regulation lead to uneconomical designs. The possible benefits of the modern practices are shown by application examples.
136

A Tale of Two Towers: The Impact of Problem Difficulty on Task Equivalence Among Preschool Children

Sheehan, John Christopher 24 November 2015 (has links)
The Towers of Hanoi (ToH) and London (ToL), historically held as isomorphic measures of problem solving, have had their equivalence questioned in recent years. Adult studies that equalized administration and task structure have found increased correlation between Towers, but insufficient evidence exists regarding whether the same results would be found in young children. This study examined 29 typically developing preschoolers. Both Towers, along with four measures of executive function, were administered in two sessions. The Towers were strongly correlated, but the strength of this relationship was impacted by discontinuation type (i.e., quit vs. standardized), and analyses revealed differences in sustained attention and Tower correlations for those who quit. Complex Tower items showed stronger correlations, and Tower performance and visuospatial WM were also highly correlated. Overall, these results suggest that the Towers, when equated in administrative and structural features, are interchangeable measures of problem solving in preschoolers. / Graduate / 0621 / 0620 / 0622 / jsheehan@uvic.ca
137

Kauno ir Klaipėdos apskričių gelžbetoninių vandentiekio bokštų techninės būklės tyrimai / Kauno and Klaipėdos county concrete water towers technical condition tests

Kankalis, Aurimas 15 June 2010 (has links)
Vandentiekio bokštų (toliau – VB) konstrukcijos veikiamos apkrovų ir neigiamo aplinkos poveikio nudėvimos, susiformuoja pažaidos. Pavojingiausios pažaidos, mažinančios konstrukcijų laikančiąją galią. Netekus laikomosios galios kyla grėsmė statinio patikimumui ir ilgaamžiškumui, galima statinio griūtis. Darbo tikslas – įvertinti gelžbetoninių vandentiekio bokštų būklę pagal pastebėtus defektus ir pažaidas. Atlikus natūrinius ir laboratorinius tyrimus buvo nustatytas vandentiekio bokštų: gniuždomojo betono stipris naudojant E. Šmidto plaktuką; betono gniuždomasis stipris, tankis ir įgėris, ištyrus bandinius laboratorijoje. Ekspedicijų metu fiksuotos vandentiekio bokštų pagrindinės pažaidos ir defektai. Dažniausiai pasitaikančios vandentiekio bokštų pažaidos: paviršiniai plyšiai betone iki 0,2–0,3 mm pločio; paviršinio sluoksnio trupėjimas (irimas). Visiems tirtiems VB reikia atlikti remonto darbus. Pagrindiniai žodžiai: pažaidos, vandentiekio bokštas. / Water – supply towers constructions exposed of a load and a negative environmental influence are wear out, and deteriorations are formed. The most dangerous deteriorations are those reduce constructions bearing capasity. Loss of the bearing capasity reduces the reliability and durability of the structure, and the structure may collapse. The aim of the work – to estimate defects and deterioration in reinforced concrete water – supply towers. The field investigations and laboratorial studies were carried out water – supply towers features: compressive strength of concrete by using E. Christian Schmidt (Schmidt E.) hammer; compressive strength, density and volume of concrete, examinating specimens in the laboratory. The main deteriorations and defects of water – supply towers were fixed at time of expeditions. Key words: deteriorations, water – supply tower.
138

Vertical Axis Wind Turbines : Tower Dynamics and Noise

Möllerström, Erik January 2015 (has links)
Vertical axis wind turbines (VAWTs) have with time been outrivaled by the today common and economically feasible horizontal axis wind turbines (HAWTs). However, VAWTs have several advantages such as the possibility to put the drive train at ground level, lower noise emissions and better scaling behavior which still make them interesting for research. The work within this thesis is made in collaboration between the Department of Construction and Energy Engineering at Halmstad University and the Division for Electricity at Uppsala University. A 200 kW VAWT owned by the latter and situated close to Falkenberg in the southwest of Sweden has been the main subject of the research even if most learnings has been generalized to fit a typical vertical turbine. This particular turbine has a wooden tower which is semi-guy-wired, i.e. the tower is both firmly attached to the ground and supported by guy-wires. This thesis has two main topics both regarding VAWTs: eigenfrequency of the tower and the noise generated from the turbine. The eigenfrequency of a semi-guy-wired tower is studied and an analytical expression describing this is produced and verified by experiments and simulations. The eigenfrequency of the wire itself and how it is affected by wind load are also studied.  The noise characteristics of VAWTs have been investigated, both theoretically and by noise measurement campaigns. Both noise emission and frequency distribution of VAWTs has been studied. The work has resulted in analytical expressions for tower and wire eigenfrequency of a semi-guy-wired tower as well as recommendations for designing future towers for VAWTs. The noise emission of VAWTs has been studied and proven low compared to HAWTs. The noise frequency distribution of the 200 kW VAWT differs significantly from that of a similar size HAWTs with for example lower levels for frequencies below 3000 Hz.
139

&quot / the Citadel Of Ankara&quot / :aspects Of Visual Documentation And Analysis Regarding Material Use

Suluner, Hasan Sinan 01 November 2005 (has links) (PDF)
This thesis examines the history, written sources and physical aspects of the citadel at Ankara with respect to building materials, masonry styles, design and topography. The distribution of different types of building materials in selected areas are analyzed and documented by using modern methods.
140

Hayden Covington, the Jehovah's Witnesses and their plan to expand First Amendment freedoms /

Henderson, Jennifer Jacobs. January 2002 (has links)
Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 182-196).

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