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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.
1

Three Dimensional Characterization of Vocal Fold Fluid Structure Interactions

Nielson, Joseph R. 05 July 2012 (has links) (PDF)
Voice quality is strongly linked to quality of life; those who suffer from voice disorders are adversely affected in their social, family, and professional relationships. An effort has been made to more fully understand the physics behind how the voice is created, specifically the fluid structure interactions that occur during vocal fold vibration. Many techniques have been developed and implemented to study both the motion of the vocal folds and the airflow that creates the motion. Until recently these techniques have sought to understand a highly three-dimensional phenomenon with 1D or 2D perspectives.This research focuses on the development and implementation of an experimental technique to obtain three-dimensional characterizations of vocal fold motion and fluid flow. Experiments were performed on excised human vocal fold models at the University Hospital Erlangen Medical School in Erlangen, Germany. A novel technique for tracking the motion of the vocal folds using multiple camera viewpoints and limited user interaction was developed. Four high-speed cameras (2000 fps) recorded an excised vocal fold model vibrating at 250 Hz. Based on the images from these four cameras a fully 3D reconstruction of the superior surface of the vocal folds was achieved. The 3D reconstruction of 70 consecutive time steps was assembled to characterize the motion of the vocal folds over eight cycles. The 3D reconstruction accurately modeled the observed behavior of vocal fold vibration with a clearly visible mucosal wave. The average reprojection error for this technique was on par with other contemporary techniques (~20 micrometers). A whole field, time resolved, three-dimensional reconstruction of the vocal fold fluid flow was obtained using synthetic aperture particle image velocimetry. Simultaneous 3D flow fields, subglottal pressure waves, and superior surface motion were presented for 2 consecutive cycles of oscillation. The vocal fold fluid flow and motion measurements correlated with behavior observed in previous three-dimensional studies. A higher resolution view of one full cycle of oscillation was compiled from 16 time resolved data sets via pressure data. The result was a full three-dimensional characterization of the evolution and disintegration of the glottal jet.
2

Fabrication and characterisation of SWCNT-PMMA and charcoal-PMMA composites with superior electrical conductivity and surface hardness properties

Mada, Mykanth Reddy, Materials Science & Engineering, Faculty of Science, UNSW January 2009 (has links)
Fabrication of SWCNT-PMMA and Activated Charcoal- PMMA composites was carried out by the compression moulding technique. Then Mechanical and Electrical properties of the composites were investigated. The morphological studies of composites showed a) good dispersion of fillers and b) good interaction between fillers and matrix. Electrical conductivity of SWCNT-PMMA composites was increased by 9 orders of magnitude (at 0.8 % volume fraction of SWCNT) and that of AC-PMMA composites increased by 16 orders of magnitude (at 17 % volume fraction of AC). The percolation threshold of both composites turned out to be lower compared to the theoretical values. A significant improvement in mechanical properties was obtained ??? particularly in AC-PMMA composites which showed a 400 % improvement in Vickers microhardness ??? raising the polymer matrix abrasion property literally to that of Aluminium alloys (Dobrazanski et al 2006). In conclusion, it is to be noted that Activated Charcoal - PMMA composites have a great potential for cost effective conducting polymer composite production by the use of cheap filler: In addition, the compression moulding technique shows good potential for cost effective fabricating technique for amorphous polymers with high electrical and mechanical properties.

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