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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.
21

Computer model to predict electron beam-physical vapour deposition (EB-PVD) and thermal barrier coating (TBC) deposition on substrates with complex geometry

Pereira, Vitor Emanuel M. Loureiro S. January 2000 (has links)
For many decades gas turbine engineers have investigated methods to improve engine efficiency further. These methods include advances in the composition and processing of materials, intricate cooling techniques, and the use of protective coatings. Thermal barrier coatings (TBCs) are the most promising development in superalloy coatings research in recent years with the potential to reduce metal surface temperature, or increase turbine entry temperature, by 70-200°C. In order for TBCs to be exploited to their full potential, they need to be applied to the most demanding of stationary and rotating components, such as first stage blades and vanes. Comprehensive reviews of coating processes indicate that this can only be achieved on rotating components by depositing a strain-tolerant layer applied by the electron beam-physical vapour deposition (EB-PVD) coating process. A computer program has been developed in Visual c++ based on the Knudsen cosine law and aimed at calculating the coating thickness distribution around any component, but typically turbine blades. This should permit the controlled deposition to tailor the TBC performance and durability. Various evaporation characteristics have been accommodated by developing a generalised point source evaporation model that involves real and virtual sources. Substrates with complex geometry can be modelled by generating an STL file from a CAD package with the geometric information of the component, which may include shadow-masks. Visualisation of the coated thickness distributions around components was achieved using OpenGL library functions within the computer model. This study then proceeded to verify the computer model by first measuring the coating thickness for experimental trial runs and then comparing the calculated coating thickness to that measured using a laboratory coater. Predicted thickness distributions are in good agreement even for the simplified evaporation model, but can be improved further by increasing the complexity of the source model.
22

Basics of Evaporation and Evapotranspiration

Brown, Paul 12 1900 (has links)
4 pp. / The objective of this and subsequent bulletins in the Turf Irrigation Management Series is to simplify the subject of ET and thereby increase the effective utilization of ET in irrigation management. This bulletin provides some basic background on the related subjects of evaporation and evapotranspiration.
23

Energy balance considerations in the design of floating covers for evaporation suppression.

Cooley, Keith Roy,1935- January 1969 (has links)
This study consists of a theoretical analysis of the energy balance equation for a partially covered body of water, and experimental analyses of the energy balances of partially covered insulated evaporation tanks. The theoretical analysis indicates that surface reflectance for solar radiation and infrared emittance are the most important cover properties. White colored materials were found to satisfy the requirement that both these parameters be as large as possible. Experiments were conducted using covers of foamed wax, lightweight concrete, white butyl rubber, and styrofoam. A variety of shapes and sizes were tested. Cover radiative properties were again noted to be most important, and thin covers proved to be slightly more efficient than thick insulated covers of the same size. Evaporation reduction was found to be proportional to the percent of surface area covered, the constant of proportionality depending upon the color and type of material used. For the white, impermeable materials tested, the constant of proportionality was near unity. It was also noted that reduction in evaporation and reduction in net radiation, as compared to an open tank, were highly correlated. Evaluation of two Dalton-type expressions, the Bowen ratio method and the combination method, for predicting evaporation from an open water surface, showed the combination method to be better under conditions of this experiment. Based on this finding, a modified combination method was derived. This modified equation proved valid for predicting evaporation from a partially covered body of water. The use of insulated evaporation tanks also provided an easy and accurate method of predicting net radiation over other surfaces, and long-wave atmospheric radiation.
24

Upward transport of water and salt from shallow saline watertables

Konukcu, Fatih January 1997 (has links)
No description available.
25

Estimating evaporation prior to reservoir construction

Ghermazien, Tesfai January 2011 (has links)
Digitized by Kansas Correctional Industries
26

Upgrading and commissioning of a high vacuum deposition system for the evaporation of silicon thin-film solar cells

Wolf, Michael, Photovoltaics & Renewable Energy Engineering, Faculty of Engineering, UNSW January 2009 (has links)
Using electron beam evaporation for the production of polycrystalline silicon (pc-Si) thin-film solar cells is an attractive alternative to PECVD deposition. Due to its faster deposition rate, using evaporation technology could significantly reduce module production costs. Other advantages are lower running costs, and the fact that no toxic gases are involved. However, currently no on-shelf equipment is available, and research in this field often relies on in-house designed systems. These can have various problems with reliability, deposition uniformity, and due to their custom design require frequent maintenance. In this work, a newly purchased electron beam evaporation system was upgraded and redesigned to be capable of depositing amorphous Si diodes for the fabrication of pc-Si thin-film solar cells. The main goal of the upgrade was to provide a safe and reliable tool which allows for the deposition of high purity semiconductor material. Reliable and safe operation was accomplished by designing the entire electrical supply circuit and incorporating various safety interlocks. Source cross-contamination issues were addressed by installing a specially designed shroud (source housing). To provide uniform substrate temperatures up to 600??C, a heater was specially designed, fabricated, installed and tested. Accurate design of all mechanical system components was realised by using 3D product design software (ProEngineer). The new evaporator was commissioned, which included testing and calibration of all the system components required for depositing on substrate sizes of up to 10x10cm2. Over this area a Si film thickness uniformity of +/-2%, performed with a maximum deposition rate of 7nm/s was achieved. Initial experiments using solid phase crystallisation and rapid thermal annealing revealed a sheet resistance uniformity of +/-4% for the Phosphorus and +/-7% for the Boron dopant effusion cell. Experimentation via Raman spectrometry and X-ray diffraction has revealed good crystalline properties, of the crystallised Si films, which is comparable to those of existing evaporation systems. Although the system was upgraded to achieve deposition pressures below 3x10-7 mbar, experiments have shown that this quality of vacuum may not be necessary for the fabrication of low impurity films. The system is now ready for further research in the field of thin-film photovoltaics, and the first functioning devices have been fabricated.
27

An investigation of evaporation from the ocean off the Oregon coast, and from Yaquina Bay, Oregon

DeRycke, Richard J. 11 August 1966 (has links)
A weather station was established on the dock of the Oregon State University Marine Science Center, Yaquina Bay, Oregon. A total of 197 weather observations was made from 30 June 1966 to 23 September 1966, with emphasis on the determination of the rate of evaporation from an evaporation pan and from atmometers. Sources of observational error were investigated and corrections applied as necessary. The daily variation in evaporation was determined. The correlation between wind, vapor pressure, and evaporation was found. Atmometers were used to estimate the evaporation from the surface of Yaquina Bay, and the possibility of using atmometers at sea was investigated. / Graduation date: 1967
28

A theoretical and experimental investigation of multi-phase interactions in pure and multicomponent droplet evaporation

Bonuccelli, Courtney Leigh Herring, January 2006 (has links) (PDF)
Thesis (M.S.)--Washington State University, December 2006. / Includes bibliographical references (p. 176-181).
29

Singularities, universality, and scaling in evaporative deposition patterns /

Popov, Yuri Olegovich. January 2003 (has links)
Thesis (Ph. D.)--University of Chicago, Department of Physics, December 2003. / CD-ROM contains PDF files of the entire dissertation. Includes bibliographical references. Also available on the Internet.
30

Exploration of the effects of pressure and temperature on the evaporation rate of selected liquids

Jafarnejad, Aydin. January 2009 (has links)
Thesis (M. Sc.)--University of Alberta, 2009. / Title from pdf file main screen (viewed on Dec. 8, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science, Department of Mechanical Engineering, University of Alberta." Includes bibliographical references.

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