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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.
11

Slotted Ground Structures and Their Applications to Various Microwave Components

Jung, Dong 16 January 2010 (has links)
This thesis discusses microstrip circuits and components with a slotted area on the ground plane. In recent years, various slot geometries have been placed on the ground plane with the purpose of reducing harmonics, producing frequency pass/stop-bands, and enhancing coupling effects. Among several ground slot geometries, a dumbbell shaped slot (DSS) is attractive because of its simple structure and easy analysis. The DSS and its applications to RF/microwave filters are studied and discussed. A lumped equivalent circuit model of the dumbbell shaped ground slot is introduced by utilizing resonator and filter theories. The accuracy of the equivalent circuit model is demonstrated through the comparison of circuit simulations and measurements. A lowpass filter (LPF) using slotted ground structure (SGS) with dumbbell shape is designed and measured to validate its theories. By using SGS techniques presented in this thesis, some other RF/microwave components such as a periodic structure, ultra-wideband bandpass filter (UWB-BPF), and rectenna with SGS-LPF are designed and tested.
12

A 64-channel personal computer based image reconstruction system and applications in single echo acquisition magnetic resonance elastography and ultra-fast magnetic resonance imaging.

Yallapragada, Naresh 15 May 2009 (has links)
Emerging technologies in parallel magnetic resonance imaging (MRI) with massive receiver arrays have paved the way for ultra-fast imaging at increasingly high frame rates. With the increase in the number of receiver channels used to implement parallel imaging techniques, there is a corresponding increase in the amount of data that needs to be processed, slowing down the process of image reconstruction. To develop a complete reconstruction system which is easy to assemble in a single computer for a real-time rendition of images is a relevant challenge demanding dedicated resources for high speed digital data transfer and computation. We have enhanced a 64 channel parallel receiver system designed for single echo acquisition (SEA) MRI into a real-time imaging system by interfacing it with two commercially available digital signal processor (DSP) boards which are capable of transferring large amounts of digital data via a dedicated bus from two high performance digitizer boards. The resulting system has been used to demodulate raw image data in real-time data and store them at rates of 200 frames per second (fps) and subsequently display the processed data at rates of 26 fps. A further interest in realtime reconstruction techniques is to reduce the data handling issues. Novel ways to minimize the digitized data are presented using reduced sampling rate techniques. The proposed techniques reduce the amount of data generated by a factor of 5 without compromising the SNR and with no additional hardware. Finally, the usability of this tool is demonstrated by investigating fast imaging applications. Of particular interest among them are MR elastography applications. An exploratory study of SEA MRE was done to study the temperature dependency of shear stiffness in an agarose gel and the results correlate well with existing literature. With the ability to make MRE images in a single echo, the SEA MRE technique has an advantage over the conventional MRE techniques.
13

Spectroscopie ultra-brève de particules d'aérosols et microcavités

Courvoisier, François Wolf, Jean-Pierre. January 2005 (has links) (PDF)
Reproductin de : Thèse de doctorat : Physique : Lyon 1 : 2005. / Titre provenant de l'écran titre. Bibliogr. en fin de chapitres.
14

Influence of ultra-endurance exercise on immunoglobulin isotypes and subclasses

McKune, AJ, Smith, LL, Semple, SJ, Wadee, AA 30 January 2005 (has links)
Background: Strenuous exercise is associated with tissue damage. This activates the innate immune system and local inflammation. Interaction between innate and adaptive immunity is essential for maintaining health, suggesting that the adaptive immune system may also be altered by exercise. Objectives: To determine exercise induced changes in the adaptive immune system by measuring the immunoglobulin isotype and subclass response to an ultra-marathon. Methods: Venepuncture was performed on 11 experienced volunteers (six men, five women; mean (SD) age 43 (9.8) years) 24 hours before the projected finishing time and immediately after and 3, 24, and 72 hours after an ultra-marathon (90 km). Serum was stored at 280˚C. IgM, IgD, IgA, IgG, IgG1, 2, 3, and 4, and total IgE were measured. Results: The following immunoglobulins were significantly (p(0.05) altered after the race: IgD, immediately (251%) and 24 hours (241%) after; IgM 24 hours after (223%); total IgG immediately after (+12%). There were no reports of symptoms of upper respiratory tract infections after the ultra-marathon. Conclusions: In experienced ultra-endurance runners, alterations in immunoglobulin concentrations after a race suggest an enhanced immune response, including isotype switching, interactions with the innate immune system, and a secondary antibody response. These alterations may have a role in the maintenance of subject health after an ultra-marathon.
15

Atmospheric ultraviolet absorption spectroscopy / by J.L. Lean

Lean, Judith L. January 1980 (has links)
Typescript (photocopy) / xii, 285 leaves [16] leaves of plates (some col.) : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics, 1982
16

Atmospheric ultraviolet absorption spectroscopy /

Lean, Judith L. January 1980 (has links) (PDF)
Thesis (Ph.D.) -- University of Adelaide, Dept. of Physics, 1982. / Typescript (photocopy).
17

Champs laser intenses ultracourts : application à la mesure et création d'impulsions attosecondes et à l'imagerie de paquets d'ondes moléculaires par explosion coulombienne

Constant, Éric. January 1997 (has links)
Thèses (Ph.D.)--Université de Sherbrooke (Canada), 1997. / Titre de l'écran-titre (visionné le 20 juin 2006). Publié aussi en version papier.
18

Pulsed ultra-wideband : transmission, detection, and performance /

Zhao, Shiwei. January 1900 (has links)
Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 112-117). Also available on the World Wide Web.
19

A channelized digital receiver design for UWB sytems in a multipath indoor environment /

Chang, Yuhao. January 1900 (has links)
Thesis (M.S.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 58-59). Also available on the World Wide Web.
20

Étude sur la génération de supercontinuum dans l'infrarouge /

Fortin, Vincent, January 2009 (has links) (PDF)
Thèse (M.Sc.)--Université Laval, 2009. / Bibliogr.: f. [103]-107. Publié aussi en version électronique dans la Collection Mémoires et thèses électroniques.

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