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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.

Point source compensation ??? a backpropagation method for underwater acoustic imaging

Yee, Clifford Wing Wei, Physics, Faculty of Science, UNSW January 2003 (has links)
The backpropagation method of image reconstruction has been known for some time with the advantage of fast processing due to the use of Fast Fourier Transform. But its applicability to underwater imaging has been limited. At present the shift-and-add method is the more widely used method in underwater imaging. This is due to the fact that backpropagation has been derived for plane wave insonification, with the scattered waves detected in transmission-mode, or synthetic aperture set-up. One of the methods being used for underwater imaging is to use a point source for the insonification of the target and the scattered waves detected in reflection-mode by a receiver array. An advantage of this scanning method is only one transmission of the source is required to capture an image, instead of multiple transmissions. Therefore motion artifacts are kept to minimum. To be able to exploit the processing speed of the backpropagation method, it must be adapted for point source insonification. The coverage of this configuration in the literature has been scant, methods for spherical sources have been proposed for transmission mode and arbitrary surfaces in geophysical applications. These methods are complex and difficult to use. A novel point source compensation method is proposed in this thesis so that the backpropagation image formation method can be used for the point source insonification set-up. The method of investigation undertaken to derive this new backpropagation method was through theoretical analysis, numerical simulation and experimental verification. The effect of various compensation factors on the image quality was studied in simulation. In the experimental verification, practical issues relating to the application of the new method was addressed. The final proof of concept of our method was undertaken with our experimental verification. The quality of images formed with the point source compensation methods has also been compared with that with the shiftand- add method. Experimental and simulation results show that the point source compensated backpropagation algorithm can produce images of comparable quality with those formed with shift-and-add method for the set-up of wideband point-source insonification with detection in reflection-mode, with the advantage of faster image formation.

Plant planet; recording / recoding invisible energy via the lens of the land

Heymans, Suzanne Elizabeth, Art, College of Fine Arts, UNSW January 2009 (has links)
This research investigates the ???earth / human equation???, in which the land is identified as the indispensable nutrient for human existence. Observation of the ongoing processes of exploitation of the land and the images that result from this, leads to a questioning of some of the Western ideas and concepts that provided the legal and ethical framework for colonisation. A perceived connection between material form and energy as the fundamental paradigm for my studio practice informs my enquiry into theories about energy and its representation. I have chosen to methodologically allegorise and illustrate human dependence upon and connection to the earth by a series of references located in science and spirituality. Concepts of energy, codification and pattern are seen in the terms of ???exchangeable currency???, where organic models function as a ???template??? informing a philosophical framework, illustrative of the complexities of the relationship between earth and people. Within this hybrid structure, part hard science and part intuitive interpretation, some of the patterns formed in the exchange of energy between the earth and its peoples are interpreted in terms of a cultural stance and siting of the land in relation to the self.

Effects of color CRT misconvergence, target size, and nontarget density on visual search performance /

Herb, Isabel Moghissi, January 1990 (has links)
Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 73-77). Also available via the Internet.

Point source compensation : a backpropagation method for underwater acoustic imaging /

Yee, Clifford Wing Wei. January 2003 (has links)
Thesis (Ph. D.)--University of New South Wales, 2003. / Also available online.

Investigations of three-dimensional optical transfer functions /

Raj, Kannan, January 1990 (has links)
Thesis (M.S)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 100-104). Also available via the Internet.

Parameterized computational imaging : optimized, data driven, and time-varying multiphysics modeling for image extension /

Evans, Daniel J. January 1900 (has links)
Thesis (Ph. D., Computer Science)--University of Idaho, August 2009. / Major professor: Mark L. Manwaring. Includes bibliographical references (leaves 172-179). Also available online (PDF file) by subscription or by purchasing the individual file.

Face recognition using infrared imaging /

Pereira, Diogo Camara. January 2002 (has links) (PDF)
Thesis (Electrical Engineer and M.S. in Electrical Engineering)--Naval Postgraduate School, December 2002. / Thesis advisor(s): Monique P. Fargues, Gamani Karunasiri, Roberto Cristi. Includes bibliographical references (p. 93-95). Also available online.

A three dimensional model for generating the texture in B-scan ultrasound images

Goodsitt, Mitchell M. January 1982 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 226-230).

Modulation transfer function measurements, image quality metrics, and subjective image quality for soft-copy color images /

Jorna, Gerard C., January 1993 (has links)
Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 167-176). Also available via the Internet.

Measurement of dose in diagnostic radiology and the effect of dose reduction on image quality

Egbe, Nneoyi Onen. January 2008 (has links)
Thesis (Ph.D.)--Aberdeen University, 2008. / Title from web page (viewed on June 3, 2009). Includes bibliographical references.

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