• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 55
  • 16
  • 10
  • 9
  • 6
  • 3
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 126
  • 21
  • 13
  • 13
  • 12
  • 12
  • 11
  • 10
  • 8
  • 8
  • 8
  • 8
  • 8
  • 8
  • 7
  • 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.
91

Hangár / Hangar

Matějková, Pavla January 2019 (has links)
Diploma thesis contains a design of steel load-bearing structure of a hangar placed in Brno-Medlánky. The ground dimensions are 40.0×44.0 m, the height of the building is 10.0 m. Two preliminary variants of the design solution were processed; main difference is the shape of the truss girder. Both variants were assessed for a combination of seventeen load cases. The comparison of the variants led to the selection of the final variant, which was assessed in detail. The girder truss in this variant is an arched truss, the height of the truss is 1.5 m, the individual elements are made of square hollow sections. A detailed static calculation was performed including the calculation of joints, drawing documentation and technical report. The main construction material is S235JR steel.
92

Skleník / Glasshouse

Sejbalová, Kateřina January 2019 (has links)
This master thesis deals with design of a load-bearing steel structure, i tis located in ZOO Zlín areal. The building serves as a glasshouse. It is a single-storey building with circle plan, 39,04 m diameter and 15,63 m height. Space construction follows spherical cap of a sphere with diameter 40 m. Variant A building is design as a fuller dome. Variant B building consists of hexagons, which are getting smaller with height, at the upper part is the hexagonal geometry cancelled and geometry made from triangles follows. This thesis contains design of a pedestrian bridge, which carries all technical loads. The thesis contains static report of the beams a design of main joints.
93

Three-Dimensional Tomographic Features of Dome-Shaped Macula by Swept-Source Optical Coherence Tomography / スウェプトソース光干渉断層計によるドーム型黄斑の3次元構造解析

ABDALLAH, A. ELLABBAN 23 March 2015 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第18855号 / 医博第3966号 / 新制||医||1007(附属図書館) / 31806 / 京都大学大学院医学研究科医学専攻 / (主査)教授 河野 憲二, 教授 黒田 知宏, 教授 富樫 かおり / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM
94

Magma Mixing and Dome Formation: Dacite of East Pass Creek, Colorado

Streffon, Jenna C. 09 August 2019 (has links)
No description available.
95

USING PATTERNED SURFACE WETTABILITY TO ENHANCE AIR-SIDE HEAT TRANSFER THROUGH FROZEN WATER DROPLET VORTEX GENERATORS

Koopman, Andrew Ernest 10 January 2020 (has links)
No description available.
96

Ray Tracing Algorithm for Dielectric Domes / Algoritm för strålföljning i dielektriska kupoler

Pubill, Maria January 2023 (has links)
Almost hemispherical scanning capabilities are required for modern wireless communication systems to produce broad coverage without performance degradation. Phased array antennas are commonly used as a fully-electronic beam-steering solution for its rapidity in beam switching. However, the effective aperture for high scanning angles is reduced, causing a reduction of the gain with the cosine of the elevation angle. Quasi-optical systems are used to achieve high directivity for wide scanning in combination with phased arrays. An interesting solution is the dielectric dome antenna, where rotationally symmetric dielectric lenses are used to enhance the scanning performance of an antenna with limited scanning capabilities. Using a full-wave simulator to evaluate lenses combined with arrays is very time-consuming, making the lens design inefficient and laborious. In this work is presented a Ray-Tracing tool used to simulate in a fast and efficient way the far-field of two-dimensional dielectric lenses. While a full-wave simulation of a three-dimensional lens could take approximately 3 hours, the Ray-Tracing evaluation takes less than 3 minutes, making possible the full optimization and design of these lenses. A numerical calculation of the ray path is used to evaluate the phase of the electric field at the lens aperture, while the amplitude is evaluated using ray-tube power theory. The far-field radiation pattern of the lens antenna is calculated using the Kirchhoff-Fresnel diffraction formula. In this work, it is also presented a full study of the reflection and absorption losses, which is something that was not previously done in the state of the art. Matching layers are designed and evaluated to reduce the reflection losses at each interface. To demonstrate the effectiveness of this approach, we compare the radiation patterns produced by a two-dimensional dielectric dome antenna with those computed using COMSOL, showing a significant reduction in time and computational resources. / För moderna trådlösa kommunikationssystem krävs nästan halvklotformiga skanningsmöjligheter för att åstadkomma bred täckning utan försämrad prestanda. Fasstyrda antenner används vanligen som en helt elektronisk lösning för strålstyrning på grund av dess snabbhet vid byte av strålar. Den effektiva aperturen för höga skanningsvinklar minskar dock, vilket leder till att förstärkningen minskar med cosinus av elevationsvinkeln. Kvasiooptiska system används för att uppnå hög riktningsförmåga för bred avsökning i kombination med fasade matriser. En intressant lösning är den dielektriska kupolantennen, där rotationssymmetriska dielektriska linser används för att förbättra skanningsegenskaperna hos en antenn med begränsad skanningskapacitet. Att använda en fullvågssimulator för att utvärdera linser i kombination med matriser är mycket tidskrävande, vilket gör linsdesignen ineffektiv och arbetskrävande. I detta arbete presenteras ett Ray-Tracing-verktyg som används för att på ett snabbt och effektivt sätt simulera fjärrfältet för tvådimensionella dielektriska linser. Medan en fullvågssimulering av en tredimensionell lins kan ta ungefär 3 timmar tar strålföljningssimuleringen mindre än 3 minuter, vilket gör det möjligt att optimera och konstruera dessa linser fullt ut. En numerisk beräkning av strålbanan används för att utvärdera fasen hos det elektriska fältet vid linsaperturen, medan amplituden utvärderas med hjälp av strålrörsteori. Linsantennens strålningsmönster i fjärrfältet beräknas med hjälp av Kirchhoff-Fresnel-diffraktionsformeln. I detta arbete presenteras också en fullständig studie av reflektions- och absorptionsförlusterna, vilket är något som inte tidigare har gjorts inom detta forskningsområde. Anpassningsskikt utformas och utvärderas för att minska reflektionsförlusterna vid varje gränssnitt. För att visa hur effektivt detta tillvägagångssätt är, jämför vi strålningsdiagrammen som produceras av en dielektrisk kupolantenn med dem som beräknats med COMSOL, vilket visar på en betydande minskning av beräkningsresurserna.
97

An Approach to Mapping of Shallow Petroleum Reservoirs Using Integrated Conventional 3D and Shallow P- and SH-Wave Seismic Reflection Methods at Teapot Dome Field in Casper, Wyoming

Okojie-Ayoro, Anita Onohuome 17 November 2007 (has links) (PDF)
Using the famous Teapot Dome oil field in Casper, Wyoming, USA as a test case, we demonstrate how high-resolution compressional (P) and horizontally polarized shear (SH) wave seismic reflection surveys can overcome the limitations of conventional 3D seismic data in resolving small-scale structures in the very shallow subsurface (< 100-200 m (~328-656 ft)). We accomplish this by using small CMP intervals (5 ft and 2.5 ft, respectively) and a higher frequency source. The integration of the two high-resolution seismic methods enhances the detection and mapping of fine-scale deformation and stratigraphic features at shallow depth that cannot be imaged by conventional seismic methods. Further, when these two high-resolution seismic methods are integrated with 3D data, correlated drill hole logs, and outcrop mapping and trenching, a clearer picture of both very shallow reservoirs and the relationship between deep and shallow faults can be observed. For example, we show that the Shannon reservoir, which is the shallowest petroleum reservoir at Teapot Dome (depth to the top of this interval ranging from 76-198 m (250-650 ft)) can only be imaged properly with high-resolution seismic methods. Further, northeast-striking faults are identified in shallow sections within Teapot Dome. The strike of these faults is approximately orthogonal to the hinge of Teapot Dome. These faults are interpreted as fold accommodation faults. Vertical displacements across these faults range from 10 to 40 m (~33 to 131 ft), which could potentially partition the Shannon reservoir. The integration of 3D and high-resolution P-wave seismic interpretation helped us determine that some of the northeast-striking faults relate to deeper faults. This indicates that some deeper faults that are orthogonal to the fold hinge cut through the shallow Shannon reservoir. Such an observation would be important for understanding the effect on fluid communication between the deep and shallow reservoirs via these faults. Furthermore, the high-resolution seismic data provide a means to better constrain the location of faults mapped from drill hole logs. Relocation of theses faults may require re-evaluation of well locations as some attic oil may have not been drained in some Shannon blocks by present well locations. Therefore our study demonstrates how conventional 3D seismic data require additional seismic acquisition at smaller scales in order to image deformation in shallow reservoirs. Such imaging becomes critical in cases of shallow reservoirs where it is important to define potential problems associated with compartmentalization of primary production, hazard mitigation, enhanced oil recovery, or carbon sequestration.
98

Petrology and Geochemistry of Some Archean Volcanics, Dome Township, Central Red Lake Area, Ontario

Cunningham, Susan M. 04 1900 (has links)
<p> A petrological and geochemical study has been carried out on some Archean mafic and felsic volcans of Dome Township, Central Red Lake area, Ontario. Included are a discussion on petrographic descriptions along with chemical investigations of the rocks and a discussion concerning the general problem of petrogenesis. Analytical methods used are explained, and di scussions of the results are included. </p> / Thesis / Bachelor of Arts (BA)
99

High frequency model for transient analysis of transformer windings using multiconductor transmission line theory

Fattal, Feras 30 March 2017 (has links)
Transients encountered by transformers in power stations during normal operation can have complex oscillatory overvoltages containing a large spectrum of frequency components. These transients can coincide with the natural frequencies of the transformers windings, leading to voltages that can be greater or more severe than the current factory proof tests. This may lead to insulation breakdown and catastrophic failures. Existing lumped parameter RLCG transformer models have been proven to be less accurate for very fast transient overvoltages (VFTO) with frequencies over 1 MHz. A white box model for transient analysis of transformer windings has been developed using Multiconductor Transmission Line (MTL) Theory. This model enables the simulation of natural frequencies of the transformer windings up to frequencies of several MHz, and can be used to compute voltages between turns by representing each turn as a separate transmission line. Both continuous and interleaved disk windings have been modelled and a comparison and validation of the results is presented. / May 2017
100

Measurement of Lead Isotopes in Snow and Ice from Law Dome and other sites in Antarctica to characterize the Lead and seek evidence of its origin

Vallelonga, Paul Travis January 2002 (has links)
Human activities such as mining and smelting of lead (Pb) ores and combustion of alkyllead additives in gasoline have resulted in extensive global Pb pollution. Since the late 1960's studies of polar ice and snow have been undertaken to evaluate the extent of anthropogenic Pb emissions in recent times as well as to investigate changes in anthropogenic Pb emissions in the more distant past. The polar ice sheets have been used to investigate Pb pollution as they offer a long-term record of human activity located far from pollution sources and sample aerosol emissions on a hemispheric scale. Lead isotopes have been previously used to identify sources of Pb in polar snow and ice, while new evaluations of Pb isotopic compositions in aerosols and Pb ore bodies allow more thorough evaluations of anthropogenic Pb emissions. Lead isotopic compositions and Pb and Barium (Ba) concentrations have been measured in snow and ice core samples from Law Dome, East Antarctica, to produce a detailed pollution history between 1530 AD and 1989 AD. Such a record has been produced to evaluate changes in anthropogenic Pb emission levels and sources over the past 500 years, to determine when industrial (anthropogenic) activities first began to influence Antarctica and also to investigate natural Pb fluxes to Antarctica. Additional samples were also collected from Law Dome snow and ice cores to respectively investigate seasonal variations in Pb and Ba deposition, and the influence of the 1815 AD volcanic eruption of Tambora, Indonesia. All samples were measured by thermal ionisation mass spectrometry, for which techniques were developed to reliably analyse Pb isotopic compositions in Antarctic samples containing sub-picogram per gram concentrations of Pb. / Particular attention was given to the quantity of Pb added to the samples during the decontamination and sample storage stages of the sample preparation process. These stages, including the use of a stainless steel chisel for the decontamination, contributed ~5.2 pg to the total sample analysed, amounting to a concentration increase of ~13 fg g-1. In comparison, the mass spectrometer ion source contributed typically 89 +/- 19 fg to the blank, however its influence depended upon the amount of Pb available for analysis and so had the greatest impact when small volumes of samples with a very low concentration were analysed. As a consequence of these careful investigations of the Pb blank contributions to the samples, the corrections made to the Pb isotopic ratios and concentrations measured are smaller than previously reported evaluations of Pb in Antarctica by thermal ionisation mass spectrometry. The data indicate that East Antarctica was relatively pristine until -1884 AD, after which the first influence of anthropogenic Pb in Law Dome is observed. "Natural", pre-industrial, background concentrations of Pb and Ba were - 0.4 pg/g and - 1.3 pg/g, respectively, with Pb isotopic compositions within the range 206Pb/207Pb = 1.20 - 1.25 and 208Pb/207Pb = 2.46 - 2.50 and an average rock and soil dust Pb contribution of 8-12%. A major pollution event was observed at Law Dome between 1884 and 1908 AD, elevating the Pb concentration fourfold and changing 206Pb/207Pb ratios in the ice to ~1.12. Based on Pb isotopic systematics and Pb emissions statistics, this was attributed to Pb mined at Broken Hill and smelted at Broken Hill and Port Pirie, Australia. / Anthropogenic Pb inputs to Law Dome were most significant from ~1900 to 1910 and from ~1960 to 1980. During the 20th century, Ba concentrations were consistently higher than "natural" levels. This was attributed to increased dust production, suggesting the influence of climate change and/or changes in land coverage with vegetation. Law Dome ice dated from 1814 AD to 1819 AD was analysed for Pb isotopes and Pb, Ba and Bismuth (Bi) concentrations to investigate the influence of the 1815 AD volcanic eruption of Tambora, Indonesia. The presence of volcanic debris in the core samples was observed from late-1816 AD to 1818 AD as an increase in sulphate concentrations and electrical conductivity of the ice. Barium concentrations were approximately three times higher than background levels from mid-1816 to mid1818, consistent with increased atmospheric loading of rock and soil dust, while enhanced Pb/Ba and Bi/Ba ratios, associated with deposition of volcanic debris, were observed at mid-1814 and from early-1817 to mid-1818. From the results, it appeared likely that Pb emitted from Tambora was removed from the atmosphere within the 1.6 year period required to transport aerosols to Antarctica. Increased Pb and Bi concentrations observed in Law Dome ice ~1818 AD were attributed to either increased heavy metal emissions from Mount Erebus, or increased fluxes of heavy metals to the Antarctic ice sheet resulting from climate and meteorological modifications following the Tambora eruption. / A non-continuous series of Law Dome snow core samples dating from 1980 to 9185 AD were analysed to investigate seasonal variations in the deposition of Pb and Ba. It was found that Pb and Ba at Law Dome do exhibit seasonal variations in deposition, with higher concentrations of Pb and Ba usually observed during Summer and lower concentrations of Pb and Ba usually observed during the Autumn and Spring seasons. At Law Dome, broad patterns of seasonal Pb and Ba deposition are evident however these appear to be punctuated by short-term deposition events or may even be composed of a continuum of short-term deposition events. This variability suggests that complex meteorological systems are responsible for the transport of Pb and Ba to Law Dome, and probably Antarctica in general.

Page generated in 0.0311 seconds