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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.
31

FRICTIONAL PROPERTIES OF NOVEL BRACKET SYSTEMS: AN IN-VITRO STUDY

Haverkos, Stephen M 01 January 2019 (has links)
Orthodontic brackets undergo resistance during sliding that includes classical friction, binding, and notching. Current bracket systems are hampered by these challenging forces. As a result, the clinician usually needs to apply additional forces to overcome the resistance which increases the risk of root resorption and discomfort for the patient. This study evaluated frictional properties of a novel bracket that had polytetrafluoroethylene (Teflon™) coated rollers in its design. Five types of brackets (n = 10, each), including a passive self-ligating bracket, a traditional ligated bracket, a three-dimensionally printed direct metal laser sintering (DMLS) bracket with and without Teflon™ rollers, and computer numeric controlled (CNC) machine milled bracket with Teflon™ rollers were tested. The peak resistance values were assessed at 0°, 4°, and 8° of tip on a 0.019 x 0.025” arch wire. At 8° of tip, the DMLS and the CNC milled bracket systems, both with Teflon™ rollers, exhibited less friction as compared to the other brackets tested (p
32

Fabrication of Polymer Based Optical Devices for Communication and Sensing

Pochiraju, Sandhya 01 January 2006 (has links)
Polymer waveguides present a potentially low cost alternative to electronics in communication systems. Polymers offer relatively straightforward and economical fabrication when compared to conventional materials. In this study, a fabrication process for Bragg gratings in polymer waveguides was developed. Waveguides were designed using finite-element analysis, patterned via e-beam lithography, and a detailed fabrication method was developed. Surface-Plasmon Resonance (SPR) is a widely accepted method for biological and chemical sensing. Measurement of bulk refractive index changes and specific surface binding is a crucial part in any biosensing. Design and fabrication of a novel self-referencing SPR sensor is described and its functionality is tested.
33

DIRECT ELECTRON-BEAM PATTERNING OF TEFLON-AF AND ITS APPLICATION TO OPTICAL WAVEGUIDING

Karre, Vijayasree 01 January 2009 (has links)
Thin films of Teflon AF have been directly patterned by electron-beam lithography without the need for post exposure chemical development. The relationship between pattern depth and exposure dose was found to be linear over a wide range of doses. Pattern depth was also observed to be dependent on initial film thickness. Teflon AF can be directly patterned at doses similar to typical e-beam resists. High resolution features as small as ~200 nm have been resolved. FTIR measurements revealed that CF3 and fluorinated dioxole groups play a significant role in the patterning mechanism. Teflon AF films also exhibited an increase in refractive index upon exposure to the electron-beam. This property has been exploited in waveguiding applications. Waveguides in Teflon AF were patterned using direct electron beam lithography technique. Waveguides were clearly visible to the naked eye. Characterization in the visible region showed evidences of light guiding through the waveguides. However light could not cross the entire chip. Characterization in the infrared region revealed the slab mode even though individual waveguides were not detected.
34

Inibicao das reacoes de polimerizacao e de desproporcionamento, exotermicas e explosivas, do monomero tetrafluoroetileno

MOURA, ESPERIDIANA A.B. de 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:43:42Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:53Z (GMT). No. of bitstreams: 1 06502.pdf: 9031757 bytes, checksum: 4eb0a51540742e535950d2d55abcd40e (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
35

Inibicao das reacoes de polimerizacao e de desproporcionamento, exotermicas e explosivas, do monomero tetrafluoroetileno

MOURA, ESPERIDIANA A.B. de 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:43:42Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:53Z (GMT). No. of bitstreams: 1 06502.pdf: 9031757 bytes, checksum: 4eb0a51540742e535950d2d55abcd40e (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
36

Membraneless Water Purification via diffusiophoresis

Lyu, Shicheng 16 May 2020 (has links)
Clean water is hard to obtain in certain areas, such as remote locations and during emergency response. Our study developed a membraneless water purification system using diffusiophoresis and tested the influence of various factors (gas pressure, liquid flow rate, etc.) on the turbidity of filtered water. The main component in the separation system is a tube-in-tube-in-tube separator. The inner tube and the middle tube are made of a semipermeable material (Teflon AF-2400), which allows gas (CO2) to permeate through it, but retains liquid (water). In this strategy, the CO2 permeates through the inner tube (the end is sealed) then dissolves into the dirty water/particle suspension passing through the middle tube. It then diffuses radially to the outer tube, where a vacuum collects the CO2, forming a concentration gradient of ions through the water, which induces the migration of charged particles to concentrate at the inner wall of the middle tube. The vacuum phase in the outer tube can increase the concentration gradient of ions in the water and recycle the CO2. Finally, purified water can be collected from the center of the middle tube by a needle in the effluent. The purification system is able to take initial turbid water (243 NTU) to below the WHO drinking water standard (
37

Measurement of Time Projection Chamber Optical Properties and Xenon Circulation System Development for The LZ Experiment

Whitis, Thomas James 01 February 2019 (has links)
No description available.
38

Fixed boundary extrusion orientation crystallization of Teflon 100 – Effect of the die geometry on the resultant extrudate

Pandya, Bharat P. January 1982 (has links)
No description available.
39

Fep as a material for solar energy application

Sehanobish, Kalyan January 1982 (has links)
No description available.
40

Etablierung eines 3D-Tissue-Engineering-Modells zur Bindegewebsherstellung / Establishment of a 3D-Tissue-Engineering-Model to Fabricate Connective Tissue

Karatas, Hevin 21 September 2015 (has links)
No description available.

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