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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.
261

Characterization of Silver-Polyaniline-Epoxy Conductive Adhesives

Gumfekar, Sarang January 2013 (has links)
Electrical conductive adhesives (ECAs) containing silver filler and polyaniline co-filler were characterized for their electro-mechanical properties. Polyaniline is a conductive polymer and has a moderate conductivity in between those of the silver and epoxy. Incorporation of polyaniline (μm sized) in silver-epoxy facilitated the electrical conduction in ECAs and reduced the percolation threshold- a minimum volume of filler necessary to initiate the conduction. It also prevented the localization of charge carriers due to aggregation of silver filler particles. ‘Bridging effect’ was observed due to addition polyaniline in which the polyaniline enhanced the tunneling of electrons over the silver filler particles. We have investigated the polyaniline co-fillers as a promising alternative way to tune the mechanical and electrical properties of the ECAs and have provided a detailed analysis of the electro-mechanical properties of silver-epoxy (Ag-epoxy) and silver-polyaniline-epoxy (Ag-PANI-epoxy) system in both partially-cured/ viscoelastic and fully-cured states. Analysis of electro-mechanical properties of silver-epoxy and silver-polyaniline-epoxy also provided the insights into electrical contact resistance of ECAs under compressive force. Electro-mechanical properties of ECAs were measured ‘in-situ’ using micro-indentation technique. We also synthesized the electrically conductive and highly crystalline nanotubes of polyaniline by mini-emulsion polymerization of aniline. The motivation behind the synthesis of polyaniline was to propose a potential filler/co-filler for replacement of metallic filler in ECAs. Electrical conductivity of polyaniline nanotubes was tuned by in-situ doping using hydrochloric acid as a dopant. Increase in dopant caused the polyaniline crystallite to grow along (400) plane. Optical, structural, electrical and thermal properties of polyaniline nanotubes are reported with varying amount of dopant. We fabricated the flexible electrically conductive coating of polyaniline tubes with uniform dispersion of polyaniline. Electrical performance of as-synthesized flexible coating is also revealed.
262

Mechanical And Thermal Properties Of Thermotropic Liquid Crystalline Copolyester (tlcp) And Its Mixtures With Poly(ethyleneterephthalate) And Denture Base Poly(methyl Methacrylate)

Ozturk, Hale Bahar 01 August 2004 (has links) (PDF)
In this study, the thermal and mechanical properties of poly(ethylenetheraphthalate) (PET)-thermotropic liquid crystal polyester (TLCP), mixtures and poly(methyl methacrylate) (PMMA)-TLCP mixtures were studied. The curing of PMMA-TLCP mixtures was done by heat, gamma radiation and microwave. The amount of TLCP in mixtures was % 0.5, 2 and 5 TLCP by weight. TLCP was synthesized by melt-acidolysis system, and PET-TLCP mixtures were prepared by using lab scale batch mixer. PMMA samples were prepared according to denture manufacturer&rsquo / s procedure. The characterization of polymer samples and mixtures were carried by FT-IR, NMR, DSC, DMA, tensile, impact, three point bending tests and light microscopy. The mixing of TLCP with PMMA yielded heterogeneous dispersions. This was observed from light micrographs. The mechanical and rheological properties of all polymers were not positively affected by inclusion of TLCP. It is also worthwhile to note that weakening of PET-TLCP mixtures were due to the thermal degradation as the thermal age of the mixtures is much higher.
263

Origin And Significance Of A Quartz-tourmaline Breccia Zone Within The Central Anatolian Crystalline Complex, Turkey

Demirel, Serhat 01 September 2004 (has links) (PDF)
The aim of this study is to investigate the petrography, geochemistry and evolution of quartz-tourmaline-rich rocks occurring in a wide breccia zone within the Late Cretaceous Kerkenez Granitoid (Central Anatolian Crystalline Complex (CACC), Turkey). The approximately 40-m wide main breccia zone has a NE-SW trend and is characterized by intense cataclastic deformation. The breccia zone can be traced several kilometers towards the west and generally occurs as tourmaline-filled faults and 1mm-30cm-thick veins within the granitoid. On the basis of mineralogical and textural features, rocks within this zone are defined as tourmaline veins, tourmaline-breccias and quartz-tourmaline rocks. These rocks are generally composed of quartz, tourmaline and granitic fragments. Petrographical investigations and electron-microprobe analyses indicate that, there are three optically and chemically different tourmaline generations. From oldest to youngest, the tourmalines are classified as blue pleochroic feruvites, blue-green pleochroic schorls and green-light green pleochroic schorls. The chemistry of the tourmalines suggests that these tourmalines crystallized from boron rich fluids derived from an evolving magma. Consequently, the quartz tourmaline-breccia zone is considered to have formed by the injection of overpressured boron rich fluids into faults and fractures present within the Kerkenez Granitoid. Fluid-filled faults and fractures were sealed by quartz-tourmaline crystallization. This led to further fractionation in the magma, new fluid pressure accumulations, reactivation of faults and crystallization of different tourmaline generations. Tourmaline-breccia zones are scarce in the literature and the presence of such rocks within the CACC is first reported in this study.
264

Effect Of Rigid Rod Molecular Structures On The Properties Of Regenerated And Virgin Polyethyleneterephtalate

Duru, C. Zeynep 01 September 2004 (has links) (PDF)
In recent years,the recycling of plastic waste incerased worldwide.The basic impetus for this increase is the public awereness regarding polltuion of the environment.Many different types of recycling processes are being used to reduce the use of raw materials and to reduce energy consumption.PET recycling is one of the most important recycling processes.addition of thermotropic liquid crystalline polymers has also become wide-spread in recent years to increase their mechanical properties and other selected properties.In this study,it is aimed to obtai a continous or discontinous fiber from the termotropic liquid crystalline copolyester and recycled PET blend.In this study X7G was used as a copolyester.In the polymer mixtures small amounts of liquid crystalline plymer phase resulted in significantr improvements in the mechanical properties of the fibers produced in the study.The blending method used gave an alost homogeneous poymer mixture which was unexpected tat needs further study to elaborate.The preliminary DSC,SEM, tensile testing and intrinsic viscosity measurements support this conclusion.The material obtained approached to fiber grade PET in terms of fiber forming properties which therefore can be used as a second grade fiber material.
265

Extended Depth Optical Coherence Tomography for Anterior Segment and Accommodation Imaging in Real-Time.

Ruggeri, Marco 08 December 2011 (has links)
The changes in the human crystalline lens shape and its internal structure during accommodation and with aging are a fundamental component of the dynamic mechanism of accommodation and presbyopia, the loss of near vision with age. A better understanding of the crystalline lens changes during accommodation will help in developing new treatments to correct for presbyopia. The goal of this dissertation is to design and develop an imaging system to study the dynamic changes in lens shape during accommodative response. An imaging system based on spectral domain optical coherence tomography (SD-OCT) was developed with long axial range, high axial and lateral resolution and high speed for in vivo imaging the anterior segment along its entire length at video-rate. A slit-lamp mounted optical delivery scanning device for the extended depth SD-OCT system was developed. The delivery system was combined with a custom made unit that provides accommodation and disaccommodation step stimuli. A method to correct for the distortions of the OCT images was also developed that provides corrected two dimensional biometric data at different accommodative states.
266

Influence of environmental and chemical factors on cellular signaling in lens epithelial cells

Long, Amy Carise, January 2007 (has links)
Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 120-147).
267

Long-term results of phakic refractive lenses for correction of myopia and hyperopia /

Koivula, Annemari, January 2007 (has links)
Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 4 uppsatser.
268

Safety limit estimation for cataract induced by ultraviolet radiation /

Dong, Xiuqin, January 2005 (has links)
Diss. (sammanfattning) Stockholm : Karolinska institutet, 2005. / Härtill 5 uppsatser.
269

Posterior capsule opacification and postoperative endophthalmitis following cataract surgery : predictive and protective factors /

Wejde, Gisela, January 2005 (has links)
Diss. (sammanfattning) Stockholm : Karolinska institutet, 2005. / Härtill 6 uppsatser.
270

The role of kynurenine and UV light in lens protein modification

Parker, Nicole Renee. January 2005 (has links)
Thesis (Ph.D.)--University of Wollongong, 2005. / Typescript. EMBARGOED - This thesis is subject to a 12 month embargo (07/03/06 to 07/03/07) and may only be viewed and copied with the permission of the author. For further information please Contact the Archivist. Includes bibliographical references: leaf 236-266.

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