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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.
81

Enhancing structural integrity of adhesive bonds through pulsed laser surface micro-machining

Diaz, Edwin Hernandez 06 1900 (has links)
Enhancing the effective peel resistance of plastically deforming adhesive joints through laser-based surface micro-machining Edwin Hernandez Diaz Inspired by adhesion examples commonly found in nature, we reached out to examine the effect of different kinds of heterogeneous surface properties that may replicate this behavior and the mechanisms at work. In order to do this, we used pulsed laser ablation on copper substrates (CuZn40) aiming to increase adhesion for bonding. A Yb-fiber laser was used for surface preparation of the substrates, which were probed with a Scanning Electron Microscope (SEM) and X-ray Photoelectron Spectroscopy (XPS). Heterogeneous surface properties were devised through the use of simplified laser micromachined patterns which may induce sequential events of crack arrest propagation, thereby having a leveraging effect on dissipation. The me- chanical performance of copper/epoxy joints with homogeneous and heterogeneous laser micromachined interfaces was then analyzed using the T-peel test. Fractured surfaces were analyzed using SEM to resolve the mechanism of failure and adhesive penetration within induced surface asperities from the treatment. Results confirm positive modifications of the surface morphology and chemistry from laser ablation that enable mechanical interlocking and cohesive failure within the adhesive layer. Remarkable improvements of apparent peel energy, bond toughness, and effective peel force were appreciated with respect to sanded substrates as control samples.
82

Laser Ablation Laser Induced Fluorescence for the Sensitive Detection of Heavy Metals in Water

Godwal, Yogesh Unknown Date
No description available.
83

PATTERN EVALUATION FOR IN-PLANE DISPLACEMENT MEASUREMENT OF THIN FILMS

Thota, Phanikrishna 01 January 2003 (has links)
The term Gossamer is used to describe ultra-lightweight spacecraft structures that solve the aerospace challenge of obtaining maximum performance while reducing the launch costs of the spacecraft. Gossamer structures are extremely compliant, which complicates control design and ground testing in full scale. One approach is to design and construct smaller test articles and verify their computational models experimentally, so that similar computational models can be used to predict the dynamic performance of full-scale structures. Though measurement of both in-plane and out-of-plane displacements is required to characterize the dynamic response of the surface of these structures, this thesis lays the groundwork for dynamic measurement of the in-plane component. The measurement of thin films must be performed using non-contacting sensors because any contacting sensor would change the dynamics of the structure. Moreover, the thin films dealt with in this work are coated with either gold or aluminum for special applications making the film optically smooth and therefore requiring a surface pattern. A Krypton Fluoride excimer laser system was selected to fabricate patterns on thin-film mirror test articles. Parameters required for pattern fabrication were investigated. Effects of the pattern on the thin-film dynamics were studied using finite element analysis. Photogrammetry was used to study the static in-plane displacement of the thin-film mirror. This was performed to determine the feasibility of the photogrammetric approach for future dynamic tests. It was concluded that photogrammetry could be used efficiently to quantify dynamic in-plane displacement with high-resolution cameras and sub-pixel target marking.
84

Characterization of Pb and selected trace elements in amazonitic K-feldspar

Sokolov, Maria, 1969- January 2006 (has links)
Amazonitic K-feldspar is characteristic of evolved granitic pegmatites of NYF (niobium-yttrium-fluorine) type, associated with A-type granite emplacement. In this work, I focus on four notable examples of such an association: (1) West Keivy, Kola Peninsula, Russia, (2) Saint-Ludger-de-Milot, Quebec, (3) Lac Sairs, Quebec, and (4) Morefield, Virginia. A fifth locality, the Broken Hill metamorphosed exhalative-type volcanogenic deposits in Australia, is an unusual type of amazonitic K-feldspar formed in an ore environment. A total of nineteen samples of amazonitic K-feldspar were characterized geochemically and mineralogically on the basis of X-ray diffraction, electron-microprobe and laser-ablation ICP-MS analyses. Lead, as an essential requirement for formation of the blue-green amazonitic color, has received particular attention. In every case, the analytical data show elevated amounts of Pb and rare alkalis, which strongly partition into the K-rich phase of the perthite intergrowth. Unusual micrometric grains, highly enriched in Pb, are found in cracks in the material from West Keivy. Some of the grains represent a new mineral species, a Pb-dominant feldspar. The presence of amazonitic K-feldspar in a granitic pegmatite is more than a curiosity. It can shed light on important petrogenetic issues such as metasomatic rejuvenation of crustal rocks prior to regional melting in a period of extension.
85

Femtosecond laser microprocessing of aluminum films and quartz

Doerr, David W. January 1900 (has links)
Thesis (Ph.D.)--University of Nebraska-Lincoln, 2007. / Title from title screen (site viewed Dec. 4, 2007). PDF text: xii, 80 p. : ill. ; 6 Mb. UMI publication number: AAT 3273191. Includes bibliographical references. Also available in microfilm and microfiche formats.
86

Analysis of metal vapour generation by laser ablation

Farjad, Shervin. January 2007 (has links)
Thesis (M.Eng.)--University of Wollongong, 2007. / Typescript. Includes bibliographical references: leaf 94-98.
87

Environmental analysis of biologically inspired self-cleaning surfaces

Raibeck, Laura January 2008 (has links)
Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Bert Bras; Committee Member: David Rosen; Committee Member: Jeannette Yen
88

Ion-exchange sample probe for laser ablation-ICP-AES /

Yip, Hung-chiu. January 1998 (has links)
Thesis (M. Phil.)--University of Hong Kong, 1998. / Includes bibliographical references (leaf 154).
89

Investigation of solution nebulization and laser ablation sample introduction techniques for inductively coupled plasma-atomic emission spectroscopy (ICP-AES) /

Leung, Pui-king. January 1996 (has links)
Thesis (M. Phil.)--University of Hong Kong, 1996. / Includes bibliographical references (leaf 147).
90

Free electron laser ablation of soft tissue the effects of chromophore and pulse characteristics on ablation mechanics /

Uhlhorn, Stephen R. January 1900 (has links)
Thesis (Ph. D. in Biomedical Engineering)--Vanderbilt University, Aug. 2002. / Title from title screen. Includes bibliographical references.

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