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1
Rowland-Jones, R. L. "A multi-variant investigation of CdTe/CdS photovoltaic material." Thesis, Bangor University, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.518693.
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Pan, Jie. "MATERIAL PROPERTY STUDY ON DYE SENSITIZED SOLAR CELLS AND CU(GA,IN)SE2 SOLAR CELLS." Miami University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=miami1240594917.
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Pan, Jie. "Material property study on dye sensitized solar cells and cu(ga,in)se2 solar cells." Oxford, Ohio : Miami University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=miami1240594917.
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Ka, Oumar. "Composes 2-6 serigraphies : preparation et caracterisation de cds et cdte." Paris 6, 1988. http://www.theses.fr/1988PA066319.
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Etude des proprietes fondamentales (structures cristallographiques, proprietes transport, luminescence, etc. ) des couches cdte et cds deposees par serigraphie (depot de la pate contenant le semiconducteur desire, sechage puis frittage haute temperature). Application a la fabrication de photopiles solaires en raison de son faible cout
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Ehrhart, Gilles. "Élaboration et caractérisation de films vitreux nanostructurés par voie sol-gel. Mise en évidence du transfert d'énergie entre les nanoparticules semi-conductrices de CdS ou de ZnS et les ions Eu3+." Phd thesis, Université des Sciences et Technologie de Lille - Lille I, 2006. http://tel.archives-ouvertes.fr/tel-00264740.
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Ce travail concerne l'élaboration et la caractérisation de guides d'onde planaires non dopés et dopés par des nanoparticules semi-conductrices et/ou des ions de terre rare. Ce type de dispositif trouve son intérêt dans l'étude de nouveaux systèmes dans le cadre des technologies avancées pour les télécommunications optiques. Il est bien connu que les systèmes optiques nécessite l'emploi d'amplificateurs afin de compenser les pertes optiques dans les circuits. Ces amplificateurs pourraient avoir un meilleur rendement et une plus grande souplesse grâce au transfert d'énergie entre nanoparticules semi-conductrices et ions de terre rare. En effet, les nanoparticules de semi-conducteur présentent d'une part des sections efficaces d'absorption plus importantes, de plusieurs ordres de grandeur que celles des ions de terre rare, et d'autre part des bandes d'absorption plus larges permettant l'accordabilité du pompage et l'augmentation du rendement optique. Afin d'étudier le phénomène de transfert d'énergie entre les nanoparticules de semiconducteur et les ions de terre rare, nous avons préparé des guides d'onde à base de ZrO<sub>2</sub>, non dopés et dopés, par le procédé sol-gel. Leurs propriétés optogéométriques ont été déterminées en utilisant la spectroscopie m-lines et en mesurant leurs coefficients d'atténuation. La spectroscopie Raman en configuration guidée a été utilisée pour caractériser la structure de ces guides et pour étudier les mécanismes accompagnant leur densification. Cette étude a été complétée par le biais de différentes techniques expérimentales telle que la spectroscopie d'émission utilisant l'ion Eu<sup>3+</sup> comme sonde structurale. La mise en évidence de l'influence du dopage par les ions Eu<sup>3+</sup> se traduit par un ralentissement du processus de densification du réseau de zircone. Un autre dopage a ensuite été opéré à l'aide de nanoparticules de CdS et de ZnS. Les précurseurs des métaux et du soufre ont été introduits directement dans le sol de ZrO<sub>2</sub> amenant à la précipitation in situ des particules lors du recuit. Leur taille et leurs propriétés d'émission ont été étudiées par les spectroscopies d'absorption UV-visible, d'émission et d'excitation. Enfin, le transfert d'énergie a été caractérisé lors du co-dopage de ZrO<sub>2</sub> par ZnS:Eu<sup>3+</sup>. La spectroscopie d'émission de l'ion Eu<sup>3+</sup> par excitation dans l'UV nous a montré une exaltation de rémission d'un facteur 42 à 10 K. La spectroscopie d'excitation de l'ion Eu<sup>3+</sup> a confirmé l'existence du transfert d'énergie par l'émergence d'une bande liée à l'absorption des particules.
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Gros-Jean, Mickaël. "Fabrication et caractérisation de structures nanocomposites silicium poreux/CdS." Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10186.
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Ce travail est consacre a la fabrication et a la caracterisation de structures nanocomposites silicium poreux/cds. Une etude approfondie de la chimie des solutions contenant des ions cd + + et l'utilisation d'un precurseur de soufre tres reactif, la thioacetamide, ont permis de mettre au point un procede de depot de cds adapte au silicium poreux (faible ph et temperature ambiante). Ce procede de depot, appele depot sequentiel, utilise deux bains separes : un premier bain pour l'adsorption d'hydroxyde de cadmium et un deuxieme bain pour la transformation de cet hydroxyde de cadmium en cds. L'utilisation de techniques de caracterisation comme la spectrometrie auger, la spectrometrie rutherford, la spectrometrie d'electrons ou la diffraction des rayons x confirme qu'il se forme du cds dans les pores du silicium ce qui conduit par ailleurs a la compression de la structure poreuse. La spectrometrie d'electrons et la spectroscopie infrarouge revelent que le materiau poreux est oxyde par les bains de depot, ce qui est probablement a l'origine de la perte de ses proprietes de luminescence. La methylation prealable du squelette poreux avant depot de cds permet d'eviter cette oxydation. Les couches nanocomposites ainsi obtenues conservent leur propriete de photoluminescence et permettent d'obtenir des structures electroluminescentes pour des polarisations electriques d'environ 2 volts, avec cependant un rendement qui reste faible.
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Nygårds, Emma. "Optimering av CdS-buffertlager för alkalibehandlade CIGS-solceller." Thesis, Uppsala universitet, Fasta tillståndets elektronik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-324427.
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An increase in conversion efficiency of CIGS thin film solar cells has been reached at Ångström Solar Center (ÅSC) due to an introduction of a post-deposition-treatment (PDT) with potassium fluoride (KF) on the CIGS absorber layer. The PDT will however affect the growth of the cadmium sulfide (CdS) buffer layer normally deposited on the CIGS layer. The purpose of this study has therefore been to increase the conversion efficiency of the CIGS solar cells by optimizing the process parameters when growing CdS with a chemical bath deposition process (CBD) on CIGS with KF-PDT. The purpose has also been to understand how CdS grows on CIGS with KF-PDT. CdS has been deposited with CBD on both CIGS with KF-PDT and on soda lime glass samples by varying process parameters such as time, bath temperature and concentrations. The solar cells were characterized using current-voltage measurements as well as external quantum efficiency measurements. Further methods of analysis were profilometry, x-ray fluorescence spectroscopy and scanning electron microscopy. It was found that the solar cells with the best performance were obtained at a bath temperature of 70 °C, process time of 3 min after preheating the cadmium acetate and ammonia solutions for 6 min and using the concentrations of the baseline process for CBD of CdS at ÅSC. The best cell of this sample resulted in a conversion efficiency of 19.1 % without antireflective coating.
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Khallaf, Hani. "Chemical Bath Deposition of Group II-VI Semiconductor Thin Films for Solar Cells Applications." Doctoral diss., University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2101.
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Chemical bath deposition (CBD) is the analog in liquid phase of the well-known chemical vapor deposition technique in the vapor phase. In CBD, deposition of thin films takes place from aqueous solutions at low temperatures by a chemical reaction between dissolved precursors, with the help of a complexing agent. Among all techniques used to grow Group II-VI semiconductors, CBD has the advantage of being a simple, low temperature, and inexpensive large-area deposition technique. So far, its contribution in thin film solar cells industry has been mainly limited to growing n-type CdS and/or ZnS window layers for CdTe-based and CIGS-based solar cells. In this work we first optimize the CBD process of CdS using nitrilotriacetic acid and hydrazine as complexing agents as an alternative to ammonia. We then study the effect of the cadmium precursor on the optical/electrical properties, as well as crystal structure, morphology, and composition of CBD-CdS films. A better understanding of the CBD process of CdS as a whole has been achieved and high quality CBD-CdS films have been obtained. Next, we investigate in-situ doping of CBD-CdS with group III elements, such as B, Al, In, and Ga. The objective is to show that CBD is capable of not only growing CdS but also of doping it to reduce its resistivity and, as a result, facilitate its use in solar cells as well as other optoelectronic device fabrication. A four orders of magnitude drop of film resistivity has been achieved without a significant change in film bandgap, structure, or morphology. Finally, we test the possibility of using CBD to grow transparent conducting oxide (TCO) films, such as Al-doped ZnO films and cadmium stannate films. First, we study CBD of ZnO and later in-situ doping of ZnO using Al. High quality ZnO thin films have been grown using CBD with the help of four different complexing agents. Post heat treatment in argon ambient helped reduce resistivity of CBD-ZnO undoped films to ~ 10-1 Ω-cm. In-situ doping of such films using Al shows promising results. Such films could be an alternative to indium tin oxide (ITO) layers that are commonly used as TCO layers for solar cells. Another approach is to use CBD to grow CdO and SnO2 thin films, with the goal of obtaining Cd2SnO4 by later annealing of these two layers. Cadmium stannate is another TCO candidate that could replace ITO in the near future. We have succeeded in growing CBD-CdO thin films using three different complexing agents. Undoped CBD-CdO films with a resistivity as low as 1.01 x10-2 [omega]-cm and a carrier density as high as 2.59 x 1020 cm-3 have been obtained. SnO2 films have been successfully grown using CBD. Fabrication of Cadmium stannate thin films using CBD is investigated. In summary, our objective to expand the use of CBD beyond just growing CdS and ZnS, and to test the possibility of using it for in-situ doping of group II-VI semiconductors as well as TCO layers fabrication proved to be successful. We believe that this may have a significant impact on solar cells as well as other optoelectronic devices fabrication industry, due to the simplicity and the cost-effectiveness of CBD.<br>Ph.D.<br>Department of Physics<br>Sciences<br>Physics PhD
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Jia, Tiantian. "Photocatalytic hydrogen production over layered materials." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:6426c02b-f2b1-4326-a767-2384c303faf3.
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The technology of semiconductor-based photocatalytic water splitting to produce hydrogen using solar energy has been considered as one of the most important approaches to solve the world energy crisis. Therefore, the development of the effective semiconductor photocatalysts has undergone considerable research. However, the traditional photocatalysts suffer from the negative effects from rapid charge recombination, which reduces the excited charges by emitting light or generating phonons. Efficient charge separation and fast charge transport, avoiding any bulk/surface recombination, are fundamentally important for photocatalytic hydrogen generation through water splitting. Here, we have introduced assembled layered materials as photocatalyst systems with their unique physicochemical properties to realize the effective charge separation and high photocatalytic activity. Using graphene as a two-dimensional supporting matrix, we have succeeded in selective anchoring of semiconductor and metal nanoparticles as separate catalytically active sites on the graphene surface. The ability of graphene to capture, transfer and store electrons and its potential to serve as a conductive support are demonstrated. The TiO<sub>2</sub> semiconductor/metals nanocrystals-graphene ensemble makes it possible to carry out selective catalytic processes at the separate sites and provides the potentials for applications in water splitting reactions. After demonstrating the positive role of graphene in such photocatalytic system, we then fabricate a simple but highly cooperative ensemble with CdS and MoS<sub>2</sub> nanocrystals dispersed on graphene sheets. It is demonstrated that CdS nanocrystals can also capture visible light energy and facilitate excited electron transfer to MoS<sub>2</sub> (as metal substituent) for catalytic hydrogen production via the 2-D graphene which plays a key role as an efficient electron mediator. Hexagonal multilayer MoS<sub>2</sub> with a layered structure in this system serves to provide active sites for hydrogen evolution by its exposed Mo edges. Hence, multilayer MoS<sub>2</sub> is an ideal cocatalyst of semiconductors for hydrogen generation. This crystalline-layered structure also shows semiconducting properties, however, its characteristic indirect band gap displays a poor light capture and emission ability with excited electrons and holes with different momentum. In contrast, single layer MoS<sub>2</sub> shows a direct band gap behavior. Our studies have clearly shown that single layer MoS<sub>2</sub> prepared with lithium intercalation indeed displays encouraging results in hydrogen evolution due to the direct band gap and quantum confinement effects. In addition, the exfoliated single layer MoS<sub>2</sub> exhibits extraordinary enhanced activity and stability in combination with the Eosin Y sensitized system when compared to those of multilayer MoS<sub>2</sub> and bulk MoS<sub>2</sub> counterparts, which is attributed to the improvement of the density of surface active sites with stronger adsorption for the Eosin Y molecules on the single layer MoS<sub>2</sub>. In addition, this multifunctional catalyst on graphene sheet can also create adsorption sites on a defective basal surface of single layer MoS<sub>2</sub> through adsorption of Eosin Y where electron transfer from photoexcited Eosin Y molecule to graphene via the 2-D MoS<sub>2</sub> mainly takes place. Thus, the photo-generated electrons are then effectively transported to the exposed active sites of MoS<sub>2</sub> for the proton reduction to hydrogen molecule. It is believed the above novel assembled molecular layered systems may be applicable for a wide range of catalytic,photocatalytic and electrocatalytic reactions.
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Colbert, Mark. "APPEARANCE-DRIVEN MATERIAL DESIGN." Doctoral diss., University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2608.
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In the computer graphics production environment, artists often must tweak specific lighting and material parameters to match a mind's eye vision of the appearance of a 3D scene. However, the interaction between a material and a lighting environment is often too complex to cognitively predict without visualization. Therefore, artists operate in a design cycle, where they tweak the parameters, wait for a visualization, and repeat, seeking to obtain a desired look. We propose the use of appearance-driven material design. Here, artists directly design the appearance of reflected light for a specific view, surface point, and time. In this thesis, we discuss several methods for appearance-driven design with homogeneous materials, spatially-varying materials, and appearance-matching materials, where each uses a unique modeling and optimization paradigm. Moreover, we present a novel treatment of the illumination integral using sampling theory that can utilize the computational power of the graphics processing unit (GPU) to provide real-time visualization of the appearance of various materials illuminated by complex environment lighting. As a system, the modeling, optimization and rendering steps all operate on arbitrary geometry and in detailed lighting environments, while still providing instant feedback to the designer. Thus, our approach allows materials to play an active role in the process of set design and story-telling, a capability that was, until now, difficult to achieve due to the unavailability of interactive tools appropriate for artists.<br>Ph.D.<br>School of Electrical Engineering and Computer Science<br>Engineering and Computer Science<br>Computer Science PhD
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Khan, Erum. "IMAGE-BASED MATERIAL EDITING." Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3242.
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Photo editing software allows digital images to be blurred, warped or re-colored at the touch of a button. However, it is not currently possible to change the material appearance of an object except by painstakingly painting over the appropriate pixels. Here we present a set of methods for automatically replacing one material with another, completely different material, starting with only a single high dynamic range image, and an alpha matte specifying the object. Our approach exploits the fact that human vision is surprisingly tolerant of certain (sometimes enormous) physical inaccuracies. Thus, it may be possible to produce a visually compelling illusion of material transformations, without fully reconstructing the lighting or geometry. We employ a range of algorithms depending on the target material. First, an approximate depth map is derived from the image intensities using bilateral filters. The resulting surface normals are then used to map data onto the surface of the object to specify its material appearance. To create transparent or translucent materials, the mapped data are derived from the object's background. To create textured materials, the mapped data are a texture map. The surface normals can also be used to apply arbitrary bidirectional reflectance distribution functions to the surface, allowing us to simulate a wide range of materials. To facilitate the process of material editing, we generate the HDR image with a novel algorithm, that is robust against noise in individual exposures. This ensures that any noise, which would possibly have affected the shape recovery of the objects adversely, will be removed. We also present an algorithm to automatically generate alpha mattes. This algorithm requires as input two images--one where the object is in focus, and one where the background is in focus--and then automatically produces an approximate matte, indicating which pixels belong to the object. The result is then improved by a second algorithm to generate an accurate alpha matte, which can be given as input to our material editing techniques.<br>Ph.D.<br>School of Electrical Engineering and Computer Science<br>Engineering and Computer Science<br>Computer Science
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Wong, Chau Ping. "Synthesis and characterizations of CdS nanoribbons and their optical properties." access abstract and table of contents access full-text, 2006. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21449120a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2006.<br>"Master of Science in Materials Engineering & Nanotechnology dissertation." Title from title screen (viewed on Nov. 21, 2006) Includes bibliographical references.
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Potter, Mark David George. "Luminescence spectroscopy of CdTe/CdS based photovoltaic devices and associated materials." Thesis, Durham University, 2000. http://etheses.dur.ac.uk/4607/.
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This thesis contains primarily a study of CdTe/CdS heterojunction solar cells^ chiefly using photoluminescence spectroscopy. These solar cells show a good potential for commercial power generation in the near Aiture and are of interest to several major companies. A vital but little understood step in the manufacturing process is: annealing the cells in the presence of chlorine prior to back contact application. Studies are performed on a selection of thin film CdTe/CdS cells subjected to CdCl(_2) anneals of different duration. A chemical bevel etch was used to study the spectra at different depths into the sample and laser intensity arid sarhple temperature variations to identify the mechanisms behind the observed photoluminescence peaks. Evidence was found for the CdCl(_2) anneal promoting sulphur diffusion and subsequent grain boundary passivation in the CdTe, leading to increased minority carrier lifetimes and device efficiencies Attempts to obtain electroluminescence from the CdTe/CdS solar cells were madei By using current pulses electroluminescence was obtained in the 780-850nm range with discernible spectral features. Photoluminescence (PL) studies were also performed on a single crystal of CdTe grown to an unprecedented size of approx. 5 cm diameter at Durham university by a multi-tube seeded vapour method of crystal growth. Much higher resolution spectra were: obtained for this than for the solar cells. Several peaks were identified arid the mechanisms responsible were theorised. By taking slices of the crystal boule the PL spectra at different points-throughout the bulk of the crystal were determined. A series of high quality ion-implanted CdTe crystals were also studied! by intensity and temperature dependent PL in order to obtain a better understanding of the effects of known concentrations of known impurities on the PL spectra of CdTe. Specific PL features associated with certain dopants were observed.
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Echendu, Obi Kingsley. "Thin film solar cells using all-electrodeposited ZnS, CdS and CdTe materials." Thesis, Sheffield Hallam University, 2014. http://shura.shu.ac.uk/19597/.
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The urgent global need for affordable alternative and clean energy supply has triggered extensive research on the development of thin-film solar cells since the past few decades. This has necessitated the search for low-cost, scalable and manufacturable thin-film semiconductor deposition techniques which in turn has led to the research on electrodeposition technique as a possible candidate for the deposition of semiconductor materials and the fabrication of thin-film solar cells using these materials. Electronic quality ZnS, CdS, and CdTe thin layers have been successfully electrodeposited from aqueous solutions on glass/fluorine-doped tin oxide (FTO) substrates, using simplified two-electrode system instead of the conventional three-electrode system. This process was also carried out in a normal physical chemistry laboratory instead of the conventional cleanroom that is very expensive to maintain. The electrodeposited materials were characterised for their structural, optical, electrical, morphological and compositional properties using x-ray diffraction, optical absorption, photoelectrochemical cell, current-voltage, scanning electron microscopy and energy dispersive x-ray techniques respectively. The results show that amorphous n-type and p-type ZnS layers were deposited by varying the concentrations of Zn[2+] and S[2-] in the deposition electrolyte. The CdS layers show hexagonal structure with n-type electrical conduction while CdTe layers show cubic structure with n-type electrical conduction, in the cathodic deposition potential range explored. Using CdTe as the main absorber material, fully fabricated solar cell structures of the n-n hetero-junction + large Schottky barrier type were fabricated instead of the conventional p-n junction type structure. Conventional post-deposition CdCl[2] treatment of CdTe rather carried out with a mixture of CdCl[2] and CdF[2], resulted in pronounced improvement of all the device parameters. Characterisation of the fully fabricated solar cells was done using current-voltage and capacitance-voltage techniques. Promising device parameters were obtained for the best devices, with barrier heights greater than (1.00 - 1.13) eV, short-circuit current densities of (20 - 48) mAcm[-2], open-circuit voltages of (500 - 670) mV, fill factors of (0.33 - 0.47) and overall conversion efficiencies of (5.0 - 12.0)%. Remarkably, the two highest efficiency figures of 10.4% and 12.0% came up for solar cells involving ZnS as buffer layer and window layer with the structures, glass/FTO/n-ZnS/n-CdS/n-CdTe/Au and glass/FTO/n-ZnS/n-CdTe/Au, respectively. At present, the reproducibility and consistency of these devices is poor, but these results demonstrate that these devices structures have the potential to achieve efficiency values over 20% when fully optimised.
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Khan, Simeen. "Colloidal PbS and PbS/CdS Core/Shell Nanosheets." Bowling Green State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1447955111.
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Yan, Yueran. "CdTe, CdTe/CdS Core/Shell, and CdTe/CdS/ZnS Core/Shell/Shell Quantum Dots Study." Ohio University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1327614907.
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Ramme, Mark. "Ultrafast Laser Material Processing For Photonic Applications." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5846.
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Femtosecond Laser Direct Writing (FLDW) is a viable technique for producing photonic devices in bulk materials. This novel manufacturing technique is versatile due to its full 3D fabrication capability. Typically, the only requirement for this process is that the base material must be transparent to the laser wavelength. The modification process itself is based on non-linear energy absorption of laser light within the focal volume of the incident beam. This thesis addresses the feasibility of this technique for introducing photonic structures into novel dielectric materials. Additionally, this work provides a deeper understanding of the light-matter interaction mechanism occurring at high pulse repetition rates. A novel structure on the sample surface in the form of nano-fibers was observed when the bulk material was irradiated with high repetition rate pulse trains. To utilize the advantages of the FLDW technique even further, a transfer of the technology from dielectric to semiconductor materials is investigated. However, this demands detailed insight of the absorption and modification processes themselves. Experiments and the results suggested that non-linear absorption, specifically avalanche ionization, is the limiting factor inhibiting the application of FLDW to bulk semiconductors with today's laser sources.<br>Ph.D.<br>Doctorate<br>Electrical Engineering and Computer Science<br>Engineering and Computer Science<br>Electrical Engineering
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Chen, Sen-Yong. "Phonon Modulation by Polarized Lasers for Material Modification." Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5159.
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Magnetic resonance imaging (MRI) has become one of the premier non-invasive diagnostic tools, with around 60 million MRI scans applied each year. However, there is a risk of thermal injury due to radiofrequency (RF) induction heating of the tissue and implanted metallic device for the patients with the implanted metallic devices. Especially, MRI of the patients with implanted elongated devices such as pacemakers and deep brain stimulation systems is considered contraindicated. Many efforts, such as determining preferred MRI parameters, modifying magnetic field distribution, designing new structure and exploring new materials, have been made to reduce the induction heating. Improving the MRI-compatibility of implanted metallic devices by modifying the properties of the existing materials would be valuable. To evaluate the temperature rise due to RF induction heating on a metallic implant during MRI procedure, an electromagnetic model and thermal model are studied. The models consider the shape of RF magnetic pulses, interaction of RF pulses with metal plate, thermal conduction inside the metal and the convection at the interface between the metal and the surroundings. Transient temperature variation and effects of heat transfer coefficient, reflectivity and MRI settings on the temperature change are studied. Laser diffusion is applied to some titanium sheets for a preliminary study. An electromagnetic and thermal model is developed to choose the proper diffusant. Pt is the diffusant in this study. An electromagnetic model is also developed based on the principles of inverse problems to calculate the electromagnetic properties of the metals from the measured magnetic transmittance. This model is used to determine the reflectivity, dielectric constant and conductivity of treated and as-received Ti sheets. The treated Ti sheets show higher conductivity than the as-received Ti sheets, resulting higher reflectivity. A beam shaping lens system which is designed based on vector diffraction theory is used in laser diffusion. Designing beam shaping lens based on the vector diffraction theory offers improved irradiance profile and new applications such as polarized beam shaping because the polarization nature of laser beams is considered. Laser Pt diffusion are applied on the titanium and tantalum substrates using different laser beam polarizations. The concentration of Pt and oxygen in those substrates are measured using Energy Dispersive X-Ray Spectroscopy (EDS). The magnetic transmittance and conductivity of those substrates are measured as well. The effects of laser beam polarizations on Pt diffusion and the magnetic transmittance and conductivity of those substrates are studied. Treated Ti sheets show lower magnetic transmittance due to the increased conductivity from diffused Pt atoms. On the other hand, treated Ta sheets show higher magnetic transmittance due to reduced conductivity from oxidation. Linearly polarized light can enhance the Pt diffusion because of the excitation of local vibration mode of atoms. Laser Pt diffusion and thermo-treatment were applied on the Ta and MP35N wires. The Pt concentration in laser platinized Ta and MP35N wires was determined using EDS. The ultimate tensile strength, fatigue lives and lead tip heating in real MRI environment of those wires were measured. The lead tip hating of the platinized Ta wires is 42 % less than the as-received Ta wire. The diffused Pt increases the conductivity of Ta wires, resulting in more reflection of magnetic field. In the case of the platinized MP35N wire, the reduction in lead tip heating was only 1 °C due to low concentration of Pt. The weaker ultimate tensile strength and shorter fatigue lives of laser-treated Ta and MP35N wires may attribute to the oxidation and heating treatment.<br>Ph.D.<br>Doctorate<br>Optics and Photonics<br>Optics and Photonics<br>Optics
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GIACOPETTI, LAURA. "Degradation of Cd-yellow pigment: an ab initio study of defects and adsorption of oxygen and water on CdS." Doctoral thesis, Università degli Studi di Cagliari, 2016. http://hdl.handle.net/11584/266674.
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The cadmium yellow paints used in impressionist and modernist paintings in early
1900s are undergoing several deterioration processes, including whitening and discoloration.
Relevant e↵ects produced at the surface of modern paintings include the
growth of discolored crusts, formed mainly by white globular hydrated cadmium sulfate
CdSO4*nH2O and cadmium carbonate (CdCO3 ). In view of the fact that the
pigment, cadmium sulfide, was historically synthesized by means of dry and wet processes
and that CdCO3 and CdSO4 are reagents for this procedure, their identification
alone does not constitute conclusive proof of photo-oxidation. The origins of such
chemical and physical alterations are still under debate.
Structural defects in CdS, among other possible causes like photo-oxidation processes,
may play a role in the degradation process. Their presence in the pigment surface
alters the electronic structure of cadmium sulfide by forming acceptor levels in the gap
of the semiconductor. Such levels make the surface more reactive in the interaction
with external agents (oxygen, water ...).
To this end, we present a theoretical study of points defects, namely Cd- and S- vacancies,
in the structural wurtzite structure (bulk) and [10¯10] CdS surface. In order to
understand, at atomic level, the oxidation and hydration mechanisms of these whitish
globules, we present the early stages of the interaction between the hexagonal clean
and defective [10¯10] surface of CdS and O2 and H2O molecules to simulate the combined
e↵ects of exposure to air and humidity.
The geometrical and electronic structures as well as the vacancy formation and adsorption
energies are determined with the use of a first principles method. All the
calculations are performed within the framework of the Density Functional Theory
(DFT) in the Generalized Gradient Approximation (GGA-PBE) with the use of ultrasoft
pseudopotentials. Despite the standard DFT-GGA ensures a correct order of
electronic states, the G0W0 calculations are strongly required to attribute an accurate position of the trap level.
Considering the possibility to investigate in a broader spectral range, such theoretical
method would be helpful in the interpretation of experimental evidences on fluorescence
emissions produced from by yellow altered. This thesis highlights the key role
that first-principles methods can play in the application of materials science to art
conservation.
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Paudel, Naba Raj. "Stability Issues in Sputtered CdS/CdTe Solar Cells." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1321639226.
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Borchardt, Lars. "Carbide and Carbide-Derived Carbon Materials with Hierarchical Pore Architecture." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-107865.
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This thesis addressed the development of new porous carbides and carbide-derived carbons; in particular materials based on silicon-, boron-, tungsten-, and titanium carbide. Therefore, different hard- and soft-templating approaches were applied and the materials were additionally functionalized with catalytic active components and shaped into nm- and mm-sized spherical particles.
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Neves, Wellington de Queiroz. "CARACTERIZAÃÃO ÃTICA E ESTRUTURAL DE FILMES DE CdS DEPOSITADOS POR BANHO QUÃMICO." Universidade Federal do CearÃ, 2013. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=9740.
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Neste trabalho estudamos as propriedades Ãticas de filmes de sulfeto de cÃdmio (CdS) crescidos sobre um substrato de vidro. Os filmes foram obtidos por meio da tÃcnica de deposiÃÃo por banho quÃmico (Chemical Bath Deposition, CBD). Os filmes de CdS sÃo preparados numa soluÃÃo aquosa, sob agitaÃÃo, a uma temperatura de 80 oC durante 60 minutos sobre substrato de vidro. Alguns dos filmes foram obtidos com duplo depÃsito em dois banhos sucessivos iguais. Como fonte de Ãons de cÃdmio à usado sulfato de cÃdmio (CdSO4,) como fonte de Ãons de enxofre à usado a tioureia, como tampÃo à usado cloreto de amÃnia, e como agente complexante o Ethylenediamine tetra acetic acid (Edta) em vÃrias concentraÃÃes. ApÃs o crescimento, os filmes foram submetidos a um tratamento tÃrmico no ar nas temperaturas de 300 ou 400 oC por uma hora. Foram realizadas medidas experimentais usando a tÃcnicas de difraÃÃo de raios-X, fototransmissÃo Ãtica UV-VIS e espectroscopia Raman. Os filmes de CdS obtidos possuem estrutura cÃbica e sÃo de coloraÃÃo amarelada, homogÃneos e muito aderentes ao substrato de vidro. SÃo analisados os efeitos da concentraÃÃo de Edta, tratamento tÃrmico no ar, tempo de deposiÃÃo e temperatura de crescimento dos filmes de CdS. Nossos resultados mostram que, sob as condiÃÃes estudadas, os filmes de CdS nÃo possuem fase hexagonal em sua estrutura. O gap dos filmes de CdS està em torno de 2,45 eV, com pequenas variaÃÃes (2,40 â 2,51 eV) devido Ãs condiÃÃes experimentais de crescimento ou tratamento tÃrmico apÃs o crescimento. Observamos o modo LO, de simetria A1, em torno de 300 cm-1 e atà trÃs sobremodos desse fÃnon. Em alguns casos, os espectros Raman aparecem sobre uma larga fotoemissÃo, dependendo das condiÃÃes experimentais.
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Högblad, Jon. "Auger Electron Spectroscopy of Controlled Delaminating Materials on Aluminium Surfaces." Thesis, Karlstad University, Division for Engineering Sciences, Physics and Mathematics, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-1634.
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<p>This master thesis in physics mainly treats Auger spectroscopy of interfaces that has been adhesively bond together with so called controlled delaminating materials (CDM). CDM is a new technology which involves adhesives with the distinctive property that they by the appliance of electricity can be released from a substrate. The reason for using Auger spectroscopy was that it gives a surface sensitive view of the chemical composition of the samples examined and this was believed to give hints of the mechanisms behind loss of adhesion. The samples were so called laminates which is an aluminium foil, CDM adhesive, aluminium foil structure. As expected Auger spectroscopy produced some promising results, especially regarding the breakdown of a certain anion contained into the examined CDM adhesive. This awoke new questions regarding how this anion was decomposed and the idea that it could be due to hydrolysis took form. The by far most important result within this work is that the anion breaks down. This could lead to the formation of hydrofluoric acid if this breakdown in fact is due to hydrolysis and the hydrofluoric acid could then react with the aluminium causing loss of adhesion. This could be the good starting point of a continuing work on CDM.</p>
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Parenti, Cristina. "VARIATION OF THE LOCAL MATERIAL PROPERTIES OF AORTA." Master's thesis, Temple University Libraries, 2010. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/70843.
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Mechanical Engineering<br>M.S.E.<br>Understanding the aortic wall deformation and failure during traumatic aortic rupture (TAR), which is a leading cause of fatality in motor vehicle accidents is of great concern. The specific objective of the present study is to develop a material model that can describe the multi layer nature of the aortic wall.
Fundamentally, the aortic wall is composed mainly of three layers, tunica intima, media and adventitia, and they are known to have different structures. Understanding the material properties of these layers is essential in order to study the local mechanisms of deformation, force transmission, and failure.
The hypothesis of this study is that the tissue's instantaneous shear modulus grows along the radial direction while moving from the intima toward the adventitia. The higher compliance of the tissue near the intima, which is partly due to the concentration of the smooth muscle cells and partly due to the arrangement of collagen and elastin fibers, can explain the nature of aorta failure which is primarily generated from the inside towards the outer layers.
A combination of micro- and nano-indentation tests were used to measure the local material properties of porcine aorta at the length scales of 160 µm and 40 µm respectively. The material properties of aorta were investigated in the lateral (left) region in several longitudinal locations of the descending aorta and the observed viscoelastic behavior was summarized in the form of instantaneous shear moduli and reduced relaxation functions.
The instantaneous shear modulus was found to generally increase along the radial direction to about 0.6 normalized radial distance and then became almost constant but with higher variability. The reduced relaxation functions were generally independent of the location and test method. Comparing the mechanical results with the histological results obtained through Van-Guisen staining showed that the material properties are partly related to the distribution of smooth muscle cells.
The results of this study can be used to explain the mechanisms of failure in aorta and contribute to improve the computational modeling of aorta's deformation which is valuable in a variety of applications including automotive accidents, endovascular grafts, and angioplasty.<br>Temple University--Theses
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Romanov, Vasily Vladimirovich. "MATERIAL PROPERTIES OF AORTA FROM BIAXIAL OSCILLATORY TESTS." Master's thesis, Temple University Libraries, 2010. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/117228.
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Mechanical Engineering<br>M.S.E.<br>This project addresses characterization of the material properties of aortic tissue. Understanding of these properties is important for a variety of studies including tissue engineering, effects of aging and diseases, stents engineering, and traumatic aorta rupture. The goal of the presented research was to characterize the stress-strain relationship of aorta in dynamic oscillatory biaxial loading. A setup was developed that supplied pressure loading from the physiological to sub-failure levels (between 7 and 76 kPa) to porcine aorta at frequencies ranging from 0.50Hz to 5.00Hz. Samples tested were constrained at both ends while the deformation and the pressure were recorded. Volumetric strain versus pressure was used to characterize the structural behavior of the material which showed frequency dependency and hysteresis indicating viscoelastic response. An offset method was developed to account for drifting behavior exhibited by some of the samples. The structural behavior of aorta was modeled using a quasi-linear viscoelastic (QLV) creep theory. The QLV model included a logarithmic steady state elastic function v = 0.663 +/- 0.040 + 0.241 +/- 0.011 ln(P) for pressure in kPa, and a Prony series creep function ( J0 = 0.472 +/- 0.021, J2 = 0.109 +/- 0.060, J3 = 0.419 +/- 0.056). Modeling results were then used to determine the relationships between the circumferential and longitudinal stresses and strains of the material. The results exhibited that the stress in the transverse direction was about 1.5 times larger than in the axial direction. However, in the axial direction material was stiffer and the deformation was 30% less. The relaxation function of the material was determined by linearizing the non-linear component of the QLV model and applying to it the linear viscoelastic theory. Furthermore, literature comparison revealed that aorta's creep function, as well as its elastic modulus, is within the range of what has been reported in the literature. In conclusion, an experimental model was developed that can be used to predict the behavior of porcine aorta under physiological and sub-failure conditions at quasi-static and dynamic loading.<br>Temple University--Theses
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Smith, Kevin. "Fracture Toughness of a Hyperelastic Material During Surgical Cutting." Honors in the Major Thesis, University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1564.
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Despite being one of the most important organs of vertebrates, the material properties of skin are also one of the most poorly understood. In the field of designing medical devices and surgical tools there are significant advantages to having a model that describes the interaction of forces between a blade tip and skin during surgical cutting. In general, skin can best be described as a composite layer consisting of a viscoelastic dermis with interwoven collagen and elastin fibers beneath a superficial epidermis. The purpose of this research is to study the fracture toughness of porcine skin during practical cutting applications, the behavior of skin under quasistatic loads, and viscoelastic behavior of skin during stress relaxation. To fully describe the mechanics of skin in this model tensile test are conducted to determine the material properties of skin. The fracture toughness of the material is calculated by measuring the energy release rate of the material during required during cutting with Number 11 scalpel blade with a tip radius of 12 [micro]m . These results are then compared to a finite element analysis with a debonding interface and a Mooney-Rivlin hyperelastic material model with viscoelastic relaxation in an effort to predict the loads required by tools during surgical applications. The main outcome of this research is the development of a testing protocol and material model of skin that can be used in finite element simulations of uniaxial loads and surgical cutting.<br>B.S.M.E.<br>Bachelors<br>Engineering and Computer Science<br>Mechanical and Aerospace Engineering
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Azhar, Bilal. "Experimental validation of the predicted emergent magnetism in diamagnetic cadmium sulfide (Cds) doped with boron." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/132613.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, May, 2020<br>Cataloged from the official PDF version of thesis.<br>Includes bibliographical references (pages 41-42).<br>The large and persistent photoconductivity displayed by some semiconductors provides a way to control magnetism with light, through illumination-control of free carrier concentration and thereby magnetic interaction in dilute magnetic semiconductors. CdS is a wide band-gap semiconductor that displays large and persistent photoconductivity and is predicted to become magnetic when doped with certain dopants such as Boron[1]. In this work, we experimentally test the prediction of magnetic CdS:B, and lay groundwork for testing the hypothesis that magnetism can be controlled by photoconductivity. We make CdS:B nanoparticles by co-precipitation[2]. We use X-ray diffraction and plasma optical emission spectroscopy to quantify boron doping. We use magnetometry to confirm the presence of magnetic B.<br>by Bilal Azhar.<br>S.B.<br>S.B. Massachusetts Institute of Technology, Department of Materials Science and Engineering
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Wu, Jingjin. "Development of low cost CdS/CdTe thin film solar cells by using novel materials." Thesis, University of Liverpool, 2016. http://livrepository.liverpool.ac.uk/3001883/.
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Dench, Erin. "Maternal decision making in obstetrical interventions." Honors in the Major Thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1393.
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This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.<br>Bachelors<br>Nursing<br>Nursing
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Gao, Jie, Zhibo Pang, Qiang Chen, and Li-Rong Zheng. "Interactive Packaging Solutions Based on RFIDTechnology and Controlled Delamination Material." KTH, Elektroniksystem, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-50193.
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Interactive packaging is an emerging research area in recent years. It brings people convenient and smart lives, reduces consumption of traditional packaging materials and direct or indirect labor costs as well. Being integrated in interactive packaging, Radio Frequency Identification (RFID) technology becomes one of the most proactive development enablers. In this paper, an interactive and intelligent packaging solution integrating passive RFID system and Controlled Delamination Material (CDM) is given at first. Package opening action is electrically controlled by the RFID system. CDM is primarily used in aerospace applications in the past and the conductor/adhesive joint can be easily opened by applying a little electric power on to the material. Some related works will be shown about the electrochemical characteristics of CDM in order to facilitate the system design. A demonstration system was developed and the test results have proved feasibility of the solution and shown the potential of low cost for mass production. Based on this solution, an interactive medication package for pervasive healthcare is further developed, using EPCglobal Gen2 RFID technology. It will make the medication being accessible for patient only at the prescribed dose and time, and medication taking information will be delivered as well. Such medication package will not only give unprecedented high patient compliance, but also improve the communication between patients and healthcare staffs.<br>QC 20111202
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Hemmasizadeh, Ali. "Characterization of Heterogeneous Material Properties of Aorta Using Nanoindentation." Diss., Temple University Libraries, 2013. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/240046.
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Mechanical Engineering<br>Ph.D.<br>Arterial mechanical properties have received increasing attention in the past few decades due to their vast effect on predicting cardiovascular diseases and injuries. The heterogeneity of thoracic aortic tissue was characterized in terms of viscoelastic material properties and correlations were obtained between these properties and tissue morphology. Additionally, the effect of material preservation on the material properties was determined. Changes in the mechanical properties of porcine thoracic aorta wall in the radial direction were characterized using a quasi-linear viscoelastic modeling of nanoindentaiton tests. Two layers of equal thickness were mechanically distinguishable in descending aorta based on the radial variations in the instantaneous Young's modulus E and reduced relaxation function G(t). Overall, comparison of E and Ginf of the outer half (70.27±2.47 kPa and 0.35±0.01) versus the inner half (60.32±1.65 kPa and 0.33±0.01) revealed that the outer half was stiffer and showed less relaxation. The results were used to explain local mechanisms of deformation, force transmission, tear propagation and failure in arteries. A multimodal and multidisciplinary approach was adopted to characterize the transmural morphological properties of aorta. The utilized methods included histology and multi-photon microscopy for describing the wall micro-architecture in the circumferential-radial plane, and Fourier-Transform infrared imaging spectroscopy for determining structural protein, and total protein content. The distributions of these quantified properties across the wall thickness of the porcine descending thoracic aorta were characterized and their relationship with the mechanical properties was determined. It was revealed that there is an increasing trend in mechanical stiffness, Elastic lamella Density (ELD), Structural Protein (SPR), Total Protein (TPR), and Elastin and Collagen Circumferential Percentage (ECP and CCP) from inner layers toward the outer ones. Finally two larger regions with equal thickness (inner and outer halves) were determined based on cluster analysis results of ELD which were in agreement with the cluster analysis of instantaneous Young's modulus. Changes to the local viscoelastic properties of fresh porcine thoracic aorta wall due to three common storage temperatures (+4 oC, -20 oC and -80 oC) within 24 hours, 48 hours, 1 week and 3 weeks were characterized. The changes to both elastic and relaxation behaviors were investigated considering the multilayer, heterogeneous nature of the aortic wall. For +4 oC storage samples, the average instantaneous Young's modulus (E) decreased while their permanent average relaxation amplitude (Ginf) increased and after 48 hours these changes became significant (10%, 13% for E, Ginf respectively). Generally, in freezer storage, E increased and Ginf showed no significant change. In prolonged preservation (> 1 week), the results of +20 oC storage showed significant increase in E (20% after 3 weeks) while this increase for -80 oC was not significant, making it a better choice for tissue cold storage applications. Results from this dissertation present a substantial step toward the anatomical characterization of the aortic wall building blocks and establishing a foundation for understanding the role of microstructural components on the functionality of blood vessels. A better understanding of these relationships would provide novel therapeutic targets and strategies for the prevention of human vascular disease.<br>Temple University--Theses
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Sreeramakavacham, Bindu. "FILM GROWTH OF NOVEL FREQUENCY AGILE COMPLEX-OXIDE PIEZOELECTRIC MATERIAL." Master's thesis, University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3104.
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Piezoelectric materials are well known for their applications in surface (SAW) and bulk acoustic wave (BAW) devices such as oscillators, resonators and sensors. Quartz has been the main material used in such applications. Ternary calcium gallium germanate (CGG) structure-type materials, so-called langasites, recently emerged as very promising because of their piezoelectric properties superior to quartz. This thesis discusses the growth of langasite-type La3Ga5.5Ta0.5O14 (LGT) films by liquid phase epitaxy (LPE) technique and their chemical and structural characterization. In addition, the different techniques suitable for the growth of LGT are discussed and compared. To adjust the materials properties for given applications, doping by selected ions can be used. However, the dopants must be homogeneously distributed. In the current study, Al, Ti, Cr and Ca were investigated as dopants. In an earlier study, Al and Ti had been chosen because of their ability to substitute the octahedral site of LGT, normally occupied by Ga (CN=VI) with a segregation coefficient near unity in Czochralski growth. Doping with Ca and Cr has never been reported before, and therefore, the segregation behavior was unknown. In this study, Al, Ti and co-doping with Cr and Ca has been investigated for both X and Y-oriented films. The dopant distribution in the films was quantitatively evaluated by Secondary Ion Mass Spectroscopy (SIMS), using ion-implanted LGT substrates as standards. The drop of dopant concentration, in the SIMS profile, allows for the identification of the film-substrate interface and to accurately measure the thickness of the films. The film thickness is found to be typically of the order 0.5 to 2µm, depending on growth conditions. The solvent was found a reliable choice, as solvent ions were not incorporated in the films above the detection limits of the characterization techniques. A lead oxide solvent system is used as a solvent for the growth of LGT LPE films with different orientations. Extensive structural characterization was performed. The crystallinity of substrates and films grown with different orientations was compared by X-ray diffraction (XRD). The films show a very high structural perfection, with typically FWHM values of 0.035 for the (004) reflection of the XRD rocking curve. The films were also characterized by TEM. The optical transmittance of the films was characterized by Varian optical spectrophotometer, and the value obtained of approximately 80% is comparable with the transmittance value of the Czochralski grown polished substrate.<br>M.S.M.S.E.<br>Department of Mechanical, Materials and Aerospace Engineering<br>Engineering and Computer Science<br>Materials Science & Engr MSMSE
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Inghels, Eric. "Comportement mecanique de composites a fibres et matrices ceramiques : definition d'une methode d'analyse dans le cas de deux composites tisses a matrice de carbure de silicium." Paris, ENMP, 1987. http://www.theses.fr/1987ENMP0036.
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Dans le cas de composites ceramiques a fibres continues, l'existence de plusieurs mecanismes de degradation peut rendre le comportement non-lineaire, la caracterisation necessitant alors une approche specifique a chaque type de materiau. On developpe une telle approche dans le cas de deux composites tisses c/sic et sic/sic. On realise et on interprete des essais mecaniques a partir d'eprouvettes de traction, de flexion et d'eprouvettes entaillees. On propose une approche theorique du comportement mecanique pour illustrer les resultats experimentaux
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Song, Qiong. "FAST RESPONSE DUAL FREQUENCY LIQUID CRYSTAL MATERIALS." Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3112.
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Dual frequency liquid crystal (DFLC) exhibits a positive dielectric anisotropy at low frequencies and negative dielectric anisotropy at high frequencies. The frequency where dielectric anisotropy is zero is called crossover frequency. DFLC can achieve fast rise time and fast decay time with the assistance of applied voltage. However, one drawback of DFLC is that it has dielectric heating effect when driven at a high frequency. Thus, the first part of this dissertation is to develop low crossover frequency DFLC materials. The dielectric relaxation and physical properties of some single- and double-ester compounds were investigated. Experimental results indicate that the double-ester compound exhibits a ~ 3 X lower dielectric relaxation frequencies and larger dielectric anisotropy than the single ester, but its viscosity is also higher. More generally, ten groups of dual frequency liquid crystals were compared in terms of dielectric relaxation frequency and dielectric anisotropy. The dielectric relaxation theory was discussed at last. To realize fast response time, high birefringence and low viscosity LC are required. From these two aspects, firstly four new high birefringence laterally difluoro phenyl tolane liquid crystals with a negative dielectric anisotropy were studied. These materials are used to enhance the birefringence of DFLC. They have a fairly small heat fusion enthalpy (~3000 cal/mol) which improves their solubility in a host. We dope 10 wt% of each compound into a commercial negative mixture N1 and measured their birefringence, viscoelastic constant and figure of merit. Birefringence varies very little among homologues while viscoelastic constant increases as alkyl chain length increases. Secondly, we studied the effects of six diluters for lowering the viscosity while stabilizing the vertical alignment (VA) of the laterally difluoro terphenyl host mixture at elevated temperatures. The pros and cons of each diluter are analyzed. These lateral difluoro terphenyls exhibit a high birefringence, fairly low viscosity, and modest dielectric anisotropy, but their molecular alignment in a VA cell is gradually deteriorated at elevated temperatures as their concentration increases. As a result, the device contrast ratio is decreased noticeably due to the light leakage through the crossed polarizers. Finally, liquid crystal doped with metallic nanoparticles, such as Pd, Ag, or Ag-Pd, which are protected with ligand molecules, such as nematic liquid crystal were studied. The metal nanoparticles doped LC exhibit a frequency modulation (FM) electro-optical (EO) response in the millisecond to submillisecond range together with the ordinary root-mean-square voltage response.<br>Ph.D.<br>Optics and Photonics<br>Optics and Photonics<br>Optics PhD
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Ren, Xinhua. "High Temperature Materials Characterization and Sensor Application." Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5456.
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This dissertation presents new solutions for turbine engines in need of wireless temperature sensors at temperatures up to 1300oC. Two important goals have been achieved in this dissertation. First, a novel method for precisely characterizing the dielectric properties of high temperature ceramic materials at high temperatures is presented for microwave frequencies. This technique is based on a high-quality (Q)-factor dielectrically-loaded cavity resonator, which allows for accurate characterization of both dielectric constant and loss tangent of the material. The dielectric properties of Silicon Carbonitride (SiCN) and Silicoboron Carbonitride (SiBCN) ceramics, developed at UCF Advanced Materials Processing and Analysis Center (AMPC) are characterized from 25 to 1300oC. It is observed that the dielectric constant and loss tangent of SiCN and SiBCN materials increase monotonously with temperature. This temperature dependency provides the valuable basis for development of wireless passive temperature sensors for high-temperature applications. Second, wireless temperature sensors are designed based on the aforementioned high-temperature ceramic materials. The dielectric constant of high-temperature ceramics increases monotonically with temperature and as a result changes the resonant frequency of the resonator. Therefore, the temperature can be extracted by measuring the change of the resonant frequency of the resonator. In order for the resonator to operate wirelessly, antennas need to be included in the design. Three different types of sensors, corresponding to different antenna configurations, are designed and the prototypes are fabricated and tested. All of the sensors successfully perform at temperatures over 1000oC. These wireless passive sensor designs will significantly benefit turbine engines in need of sensors operating at harsh environments.<br>Ph.D.<br>Doctorate<br>Electrical Engineering and Computer Science<br>Engineering and Computer Science<br>Electrical Engineering
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Dey, Cynthia L. "Nursing interventions for promoting maternal-fetal attachment." Honors in the Major Thesis, University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1252.
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This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.<br>Bachelors<br>Nursing<br>Nursing
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Rastgar, Agah Mobin. "Material Characterization of Aortic Tissue for Traumatic Injury and Buckling." Diss., Temple University Libraries, 2015. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/324268.
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Mechanical Engineering<br>Ph.D.<br>While traumatic aortic injury (TAI) and rupture (TAR) continue to be a major cause of morbidity and mortality in motor vehicle accidents, its underlying mechanisms are still not well understood. Different mechanisms such as increase in intraluminal pressure, relative movement of aorta with respect to mediastinal structures, direct impact to bony structures have been proposed as contributing factors to TAI/TAR. At the tissue level, TAI is assumed to be the result of a complex state of supra-physiological, high rate, and multi-axial loading. A major step to gain insight into the mechanisms of TAI is a characterization of the aortic tissue mechanical and failure properties under loading conditions that resemble traumatic events. While the mechanical behavior of arteries in physiological conditions have been investigated by many researchers, this dissertation was motivated by the scarcity of reported data on supra-physiological and high rate loading conditions of aorta. Material properties of the porcine aortic tissue were characterized and a Fung-type constitutive model was developed based on ex-vivo inflation-extension of aortic segments with intraluminal pressures covering a range from physiological to supra-physiological (70 kPa). The convexity of the material constitutive model was preserved to ensure numerical stability. The increase in ë_è from physiological pressure (13 kPa) to 70 kPa was 13% at the outer wall and 22% at the inner wall while in this pressure range, the longitudinal stretch ratio ë_z increased 20%. A significant nonlinearity in the material behavior was observed as in the same pressure range, the circumferential and longitudinal Cauchy stresses at the inner wall were increased 16 and 18 times respectively. The effect of strain-rate on the mechanical behavior and failure properties of the tissue was characterized using uniaxial extension experiments in circumferential and longitudinal directions at nominal strain rates of 0.3, 3, 30 and 400 s-1. Two distinct states of failure initiation (FI) and ultimate tensile strength (UTS) were identified at both directions. Explicit direct relationships were derived between FI and UTS stresses and strain rate. On the other hand, FI and UTS strains were rate independent and therefore strain was proposed as the main mechanism of failure. On average, engineering strain at FI was 0.85±0.03 for circumferential direction and 0.58±0.02 for longitudinal direction. The engineering strain at UTS was not different between the two directions and reached 0.89±0.03 on average. Tissue pre-failure linear moduli showed an average of 60% increase over the range of strain rates. Using the developed material model, mechanical stability of aorta was studied by varying the loading parameters for two boundary conditions, namely pinned-pinned boundary condition (PPBC) and clamped-clamped boundary condition (CCBC). The critical pressure for CCBC was three times higher than PPBC. It was shown that the relatively free segment of aorta at the isthmus region may become unstable before reaching the peak intraluminal pressures that occur during a trauma. The mechanical instability mechanism was proposed as a contributing factor to TAI, where elevations in tissue stresses and strains due to buckling may increase the risk of injury.<br>Temple University--Theses
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Lee, Young Shin. "MATERNAL DETERMINANTS OF OOCYTE AND EMBRYO QUALITY." Diss., Temple University Libraries, 2011. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/111983.
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Molecular Biology and Genetics<br>Ph.D.<br>Oocyte quality plays a critical role in establishment of pregnancies, embryo development, implantation and the health of offspring. The oocyte provides maternal factors necessary for the initial development of its embryo during the period of transcriptional silence. Despite the consistent increase in number of couples seeking assisted reproductive treatments, oocyte quality still remains as an obstacle in successful fertility treatments and the mechanisms governing the quality of oocyte are poorly understood. Among various factors that may potentially affect the quality of oocyte, the acquisition of oocyte developmental competence seems to mainly occur during the final stage of oocyte maturation. The correct temporal regulation of series of molecular events and the proper exchange of signals with surrounding follicular environment during this critical period will ensure the developmental competence of oocyte and its subsequent embryo. In order to identify molecular factors affecting oocyte quality, I have compared oocytes and cumulus cells of different qualities at a molecular level. I present in this thesis the pathways and molecules that may determine the developmental competence of oocyte as well as candidate molecular markers of oocyte and embryo quality. A cDNA microarray analysis was performed, comparing the transcriptomes of rhesus monkey MII oocytes of different qualities, high quality VVM oocytes and poor quality IVM oocytes. A small set of 59 Oocyte quality plays a critical role in establishment of pregnancies, embryo development, implantation and the health of offspring. The oocyte provides maternal factors necessary for the initial development of its embryo during the period of transcriptional silence. Despite the consistent increase in number of couples seeking assisted reproductive treatments, oocyte quality still remains as an obstacle in successful fertility treatments and the mechanisms governing the quality of oocyte are poorly understood. Among various factors that may potentially affect the quality of oocyte, the acquisition of oocyte developmental competence seems to mainly occur during the final stage of oocyte maturation. The correct temporal regulation of series of molecular events and the proper exchange of signals with surrounding follicular environment during this critical period will ensure the developmental competence of oocyte and its subsequent embryo. In order to identify molecular factors affecting oo was identified as differentially expressed between the two types of oocytes. These mRNAs are involved in steroid metabolism, cell-cell interactions, cellular homeostasis, cell adhesion, mRNA stability and translation. In addition, the overexpression of several imprinted genes in IVM oocytes were detected, indicating a possible loss of correct epigenetic programming during IVM. These results indicate that normal oocyte-somatic cell interactions may be disrupted during IVM and the interruptions of these interactions during the final phase of oocyte maturation may be the prime cause of reduced developmental competence of IVM oocytes.
To elucidate oocyte quality factors linked to the cumulus cell phenotype, the transcriptomes of two types of rhesus monkey cumulus cells, IVM and VVM, were compared using a cDNA microarray analysis. In contrast to a relatively small difference between IVM and VVM oocytes, a large number of genes were differentially expressed between IVM and VVM rhesus cumulus cells. Moreover, a much larger number of differential mRNA expressions were observed comparing the transitions from pre-maturation cumulus cells to the IVM and VVM cumulus cells. The results from these array comparisons indicated that the cumulus cells may fail to achieve successfully normal gene regulation during IVM and thus make a remarkable amount of changes in gene expression to compensate for the loss. Numerous genes involved in lipid metabolism are incorrectly regulated during IVM, and the synthesis of sex hormones appears not suppressed during IVM. In addition, a panel of 24 cumulus cell markers of oocyte quality was identified.
Genetic effects on oocyte quality were explored by comparing transcriptomes of oocytes obtained from two different inbred mouse strains, B6 and D2, and F1 hybrid. A clustering analysis and statistical tests showed that the transcriptome of F1 oocytes is more similar to the B6 transcriptome than to the D2 at both GV and MII stages. Also, comparison analyses of GV stage oocyte transcriptomes with MII oocyte transcriptomes from three different mouse strains indicated that the number of overdominance genes at the MII stage is bigger than the number of overdominance genes at the GV stage. In order to investigate how the genes gain the overdominance during the GV to MII transition, overdominance genes were categorized according to their mRNA expression patterns at GV and MII stages. The results showed that more than 80% of overdominance genes belong to one of the four major transition groups. The further evaluation of changes in array intensities from GV to MII stage transition revealed that F1 oocytes and inbred strain oocytes differentially regulate the mRNA abundance during oocyte maturation and that the differential regulation of mRNA abundance by the F1 genotype is responsible for the increase of the number of overdominance genes during maturation from GV stage to MII stage. A mRNA sequence analysis indicated that the gain of overdominant low in F1 mRNA expression pattern during maturation may be regulated by 3'UTR motif elements. The number of dominance genes also increase during GV to MII transition. At both GV and MII stages, there are more genes with B6 dominant mRNA expression pattern than those with D2 dominance pattern. Lipid metabolism, small molecule biochemistry and cell death are biofunctions overrepresented in both dominance and overdominance genes. In addition, `blebbing' was identified as a biofunction significantly downregulated in the F1 and B6 MII eggs, indicating that the cellular function may be involved in oocyte maturation.<br>Temple University--Theses
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Palma, Joseph John. "X-ray Diffraction Studies of Amorphous Materials." Diss., Temple University Libraries, 2013. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/231213.
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Physics<br>Ph.D.<br>This thesis presents a study on two types of X-ray diffraction methodologies applied to the characterization of amorphous materials. The purpose of this study was to assess the feasibility of measuring the diffractive spectrum of amorphous materials by Energy-Dispersive X-ray Diffraction (EDXRD) utilizing Cadmium Zinc Telluride detectors. The total scattering intensity (coherent plus incoherent scatter) spectra precisely measured by high-energy Wide-Angle X-ray Scattering (WAXS) were compared to the EDXRD spectra to determine the level of agreement between the two techniques. The EDXRD spectra were constructed by applying a spectra fusing technique which combined the EDXRD spectra collected at different scattering angles rendering a continuous total scattering spectrum. The spectra fusing technique extended the momentum transfer range of the observed scattered spectrum beyond the limitations of the X-ray source and CZT detection efficiencies. Agreement between the WAXS and fused EDXRD spectra was achieved. In addition, this thesis presents the atomic pair correlation functions and coordination numbers of the first coordination shell for four hydrogen peroxide solutions of varying mass concentrations using Empirical Potential Structural Refinement (EPSR). The results are compared to the state-of-the art ad initio quantum mechanical charge field molecular dynamics (QMCF MD) model of the hydrogen peroxide in solution to support the model's predictions on why hydrogen peroxide is stable in water. The EPSR results using the coherent scattering intensity calculated from the WAXS data set predicts a hydration shell of 6.4 molecules of water surrounding hydrogen peroxide. The results also indicate that hydrogen peroxide is more likely to behave as a proton donor than acceptor. These findings are in agreement with QMCF MD model of aqueous hydrogen peroxide.<br>Temple University--Theses
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Hong, Yan. "Encapsulated nanostructured phase change materials for thermal management." Doctoral diss., University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4929.
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A major challenge of developing faster and smaller microelectronic devices is that high flux of heat needs to be removed efficiently to prevent overheating of devices. The conventional way of heat removal using liquid reaches a limit due to low thermal conductivity and limited heat capacity of fluids. Adding solid nanoparticles into fluids has been proposed as a way to enhance thermal conductivity of fluids, but recent results show inconclusive anomalous enhancements in thermal conductivity. A possible way to improve heat transfer is to increase the heat capacity of liquid by adding phase change nanoparticles with large latent heat of fusion into the liquid. Such nanoparticles absorb heat during solid to liquid phase change. However, the colloidal suspension of bare phase change nanoparticles has limited use due to aggregation of molten nanoparticles, irreversible sticking on fluid channels, and dielectric property loss. This dissertation describes a new method to enhance the heat transfer property of a liquid by adding encapsulated phase change nanoparticles (nano-PCMs), which will absorb thermal energy during solid-liquid phase change and release heat during freeze. Specifically, silica encapsulated indium nanoparticles, and polymer encapsulated paraffin (wax) nanoparticles have been prepared using colloidal method, and dispersed into poly-alpha]-olefin (PAO) and water for high temperature and low temperature applications, respectively. The shell, with a higher melting point than the core, can prevent leakage or agglomeration of molten cores, and preserve the dielectric properties of the base fluids. Compared to single phase fluids, heat transfer of nanoparticle-containing fluids have been significantly enhanced due to enhanced heat capacities. The structural integrity of encapsulation allows repeated uses of nanoparticles for many cycles.; By forming porous semi crystalline silica shells obtained from water glass, supercooling has been greatly reduced due to low energy barrier of heterogeneous nucleation. Encapsulated phase change nanoparticles have also been added into exothermic reaction systems such as catalytic and polymerization reactions to effectively quench local hot spots, prevent thermal runaway, and change product distribution. Specifically, silica-encapsulated indium nanoparticles, and silica encapsulated paraffin (wax) nanoparticles have been used to absorb heat released in catalytic reaction, and to mitigate the gel effect during polymerization, respectively. The reaction rates do not raise significantly owing to thermal buffering using phase change nanoparticles at initial stage of thermal runaway. The effect of thermal buffering depends on latent heats of fusion of nanoparticles, and heat releasing kinetics of catalytic reactions and polymerizations. Micro/nanoparticles of phase change materials will open a new dimension for thermal management of exothermic reactions.<br>ID: 029809237; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (Ph.D.)--University of Central Florida, 2011.; Includes bibliographical references (p. 164-191).<br>Ph.D.<br>Doctorate<br>Mechanical Materials and Aerospace Engineering<br>Engineering and Computer Science
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Weidman, Matthew. "Laser Filamentation Interaction with Materials for Spectroscopic Applications." Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5563.
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Laser filamentation is a non-diffracting propagation regime consisting of an intense core that is surrounded by an energy reservoir. For laser ablation based spectroscopy techniques such as Laser Induced Breakdown Spectroscopy (LIBS), laser filamentation enables the remote delivery of high power density laser radiation at long distances. This work has shown a quasi-constant filament-induced mass ablation along a 35 m propagation distance. The mass ablated was sufficient for the application of laser filamentation as a sampling tool for plasma based spectroscopy techniques. Within the scope of this study, single-shot ablation was compared with multi-shot ablation. The dependence of ablated mass on the number of pulses was observed to have a quasi-linear dependence on the number of pulses, advantageous for applications such as spectroscopy. Sample metrology showed that both physical and optical material properties have significant effects on the filament-induced ablation behavior. A relatively slow filament-induced plasma expansion was observed, as compared with a focused beams. This suggests that less energy was transferred to the plasma during filament-induced ablation. The effects of the filament core and the energy reservoir on the filament-induced ablation and plasma formation were investigated. Goniometric measurements of the filament-induced plasma, along with radiometric calculations, provided the number of emitted photons from a specific atomic transition and sample material. This work has advanced the understanding of the effects of single filaments on the ablation of solid materials and the understanding of filament-induced plasma dynamics. It has laid the foundation for further quantitative studies of multiple filamentation. The implications of this work extend beyond spectroscopy and included any application of filamentation that involves the interaction with a solid material.<br>Ph.D.<br>Doctorate<br>Optics and Photonics<br>Optics and Photonics<br>Optics
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Aboelsoud, Walid. "Study of Transport Phenomena in Carbon-Based Materials." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5593.
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In air-cooled heat exchangers, air-side thermal resistance is usually the largest compared to conduction and liquid-side thermal resistances. Thus, reducing the air-side thermal resistance with fin-like structures can greatly improve overall cooling performance. The performance of these structures is usually characterized by the rate of heat which can be transferred and the pumping power required. One promising solution is to use a high-thermal-conductivity material with a large surface per unit volume such as carbon foam. This study presents a method of utilizing V-shape corrugated carbon foam. The air-side heat transfer coefficient and the pressure drop across the foam have been investigated using different V-shape foam geometrical configurations obtained by varying its length and height. Based on design considerations and availability, the foam length has been chosen to be 25.4, 38.1 and 52.1 mm while its height is 4.4, 6.8 and 11.7 mm, resulting in nine different test pieces of foam with different heights and lengths.
A total number of 81 experiments were carried out and results show that of the nine V-shape configurations, the foam with the shortest length and tallest height gives the best performance. Experimental results are also compared with the results of prior work using different carbon foam geometries. It is shown that V-shape corrugated carbon foam provides higher heat transfer coefficient and better overall performance.
Numerical method is performed next. The effect of the foam length and height on thermal and hydraulic performance is demonstrated and discussed. There is excellent agreement between numerical and experimental results. An analysis is also made to better understand the transport phenomena that occur within the porous matrix. For laminar flow of air, one of the findings is the high heat transfer effectiveness of the foam which means a foam thickness of 1 mm or less is sufficient for heat transfer enhancement for air speed of up to 4 m/s.
To demonstrate the feasibility of using carbon foam, an analytical case study of carbon foam heat exchanger was performed and compared to traditional heat exchanger with the same heat load. Results show that a volume saving of up to 55% can be obtained by using carbon foam instead of traditional aluminum fins.
Another attractive carbon-based material is the highly oriented pyrolytic graphite (HOPG) which has an in-plane thermal conductivity of about 1700 W/m.K and an out-of-plane k of about 8 W/m.K at room temperature. HOPG is a graphite material with a high degree of preferred crystallographic orientation. HOPG can be very useful in thermal applications when axial conduction is critical and needed to be minimized as in recuperators used in cryocoolers and compact power generation. Also, an analysis of HOPG for micro-channel applications shows that the high in-plane thermal conductivity of HOPG, which is far greater than that of copper and aluminum, allows a taller height for the micro-channel. This translates to an increase in the heat flux removal rate by two to three times.<br>Ph.D.<br>Doctorate<br>Mechanical and Aerospace Engineering<br>Engineering and Computer Science<br>Mechanical Engineering
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Nieves, Melissa. "Is Experiential Avoidance a Factor in Maternal Overprotection?" Master's thesis, University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5830.
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The current study examined experiential avoidance (EA) as an explanation for parental overprotectiveness, a behavior often found among parents of anxious children. EA parenting theory posits that parents engage in overprotective behaviors in order to reduce their own anxiety. In order to test the theory, mothers' electrodermal activity (EDA) and blindly-coded overprotective behaviors were examined when a child with SAD was engaged in a reading performance task. In line with EA theory, it was hypothesized that EDA levels would increase before an overprotective behavior (OB) occurred and decrease afterwards as a result of decrease in anxiety. The sample consisted of mothers with a child diagnosed with SAD (n=5) and mothers with a child with no diagnoses (n=5). Each mother-child dyad participated in an ABAB design protocol consisting of a baseline period, two 10-minute reading tasks, and a recovery period between the two tasks. Although mothers of both groups displayed OBs, mothers of children with SAD displayed OBs more often. In addition, mothers of children with SAD displayed more promotion of avoidance while mothers of normal control children displayed higher frequencies of control over the reading task. The EDA activity that surrounded the first occurrence of any coded OB was examined. Contrary to the hypothesis, all mothers (regardless of child's anxiety status) displayed similar trends in their EDA data, with levels increasing but then decreasing shortly before an OB behavior occurred, rather than afterwards. However, one mother with an elevated social anxiety score revealed an EDA pattern similar to what was hypothesized. Possible explanations for these alternate findings are discussed and include a multidisciplinary conceptualization. The study's findings hold theoretical and practical implications, particularly for parent training in the treatment of childhood anxiety disorders. Limitations such as small sample size and directions for future research are discussed.<br>M.S.<br>Masters<br>Psychology<br>Sciences<br>Psychology Clinical
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Bowers, Toni L. "Maternal and perinatal outcomes in alternative birthing methods." Honors in the Major Thesis, University of Central Florida, 2001. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/265.
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This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.<br>Bachelors<br>Health and Public Affairs<br>Nursing
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Frascati, Joseph William. "Effects of Position, Orientation, and Infiltrating Material on Three Dimensional Printing Models." Master's thesis, University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2962.
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This research defined and evaluated mechanical properties of prototypes created using a plaster based three-dimensional printing (3DP) system commercialized by Z Corporation. 3DP is one of the fastest growing forms of rapid prototyping. Till date, there is little or no information available on material properties of infiltrants used in 3DP. This research work evaluated and documented some of the useful information for 3DP users by determining the effect of build position, build orientation and infiltration materials on the strength of prototypes. The study was performed in three different phases to limit the processing variables and to arrive at definite conclusions on relationship between materials properties and process variables. All specimens were built on the Z Corporation Spectrum Z510. In Phase 1, effects of build location on specimen strength was studied. Phase 2 evaluated the influence of build orientation on specimen strength. System Three Clear Coat epoxy was used during both Phase 1 and 2 for infiltration. The same infiltrant was in both of these phases to limit variables. Using results of Phase 1 & 2, the effects of infiltrant material on tensile strength of prototypes was calculated in Phase 3. Seven different infiltrating materials were tested during Phase 3. These materials included 2 cyanoacrylates and 5 epoxies. The tensile strength, flexural strength, and density and porosity of the specimens were determined and correlated. In each phase six specimens were built for each test performed. Two consistent methods of infiltration were utilized to infiltrate cyanoacrylates and epoxies into the as-processed specimens. It was found that the orientation of the specimen has more of an impact on strength than position within the build platform. The layering build process of rapid prototyping creates a variance in strength depending on the build orientation. Specimens infiltrated with epoxy achieved much higher strength than the specimens infiltrated with cyanoacrylate. Cyanoacrylates may be a good choice in making color concept models; however they are not good candidate materials where strength requirement is important. The epoxies with lower viscosities demonstrated higher part strength among the materials tested.<br>M.S.<br>Department of Mechanical, Materials and Aerospace Engineering<br>Engineering and Computer Science<br>Mechanical Engineering MSME
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Kuravi, Sarada. "Numerical Study of Encapsulated Phase Change Material (EPCM) Slurry Flow in Microchannels." Doctoral diss., University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4093.
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Heat transfer and flow characteristics of phase change material slurry flow in microchannels with constant heat flux at the base were investigated. The phase change process was included in the energy equation using the effective specific heat method. A parametric study was conducted numerically by varying the base fluid type, particle concentration, particle size, channel dimensions, inlet temperature, base heat flux and melting range of PCM. The particle distribution inside the microchannels was simulated using the diffusive flux model and its effect on the overall thermal performance of microchannels was investigated. Experimental investigation was conducted in microchannels of 101 [micro]m width and 533 [micro]m height with water as base fluid and n-Octadecane as PCM to validate the key conclusions of the numerical model. Since the flow is not fully developed in case of microchannels (specifically manifold microchannels, which are the key focus of the present study), thermal performance is not as obtained in conventional channels where the length of the channel is large (compared to length of microchannels). It was found that the thermal conductivity of the base fluid plays an important role in determining the thermal performance of slurry. The effect of particle distribution can be neglected in the numerical model under some cases. The performance of slurry depends on the heat flux, purity of PCM, inlet temperature of the fluid, and base fluid thermal conductivity. Hence, there is an application dependent optimum condition of these parameters that is required to obtain the maximum thermal performance of PCM slurry flows in microchannels.<br>Ph.D.<br>Department of Mechanical, Materials and Aerospace Engineering;<br>Engineering and Computer Science<br>Mechanical Engineering PhD
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Sen, Shiladitya. "Metatheatricality on the Renaissance Stage, the Audience and the Material Space." Diss., Temple University Libraries, 2012. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/165652.
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English<br>Ph.D.<br>My dissertation examines how early modern metatheater enabled the Renaissance stage and its original audience to develop a complex and symbiotic relationship. Metatheater--by which I mean a particular mode of theatre, in which actors, playwrights, dramatic characters and/or (in particular) audiences express or share a perception of drama as a fictional and theatrical construct--pervaded Renaissance drama, not by simple happenstance but arising almost inevitably from the complex context within which it functioned. The early modern stage was a particularly conflicted forum, which monarchs and playwrights, town fathers and actors, censors and audiences, impresarios and anti-theatricalists, all strove to influence and control. The use of the metatheatrical mode allowed playwrights and players to better navigate this difficult, sometimes dangerous, space. In particular, the development of Renaissance metatheater derived from (and, simultaneously, affected) the unique nature of its original spectators, who practiced a much more actively engaged participation in the theater than is often recognized. Performers and playwrights regularly used metatheatricality to adapt to the needs and desires of their audience, and to elicit the intellectual and emotional responses they desired. My study utilizes a historically contextualized approach that emphasizes the material conditions under which Renaissance drama arose and functioned. It begins by examining the influence of the surrounding milieu on the Renaissance stage and its spectators, especially its facilitation of the development and use of metatheater. Then, via close readings of four plays--Kyd's The Spanish Tragedy, Shakespeare's Henry V and Antony and Cleopatra, and Beaumont's The Knight of the Burning Pestle--the dissertation indicates how varied and versatile early modern metatheater was, and how it responded to and influenced the nature of its audiences. My study demonstrates the centrality of metatheater to early modern theatrical practice, delineates its pervasive influence on the stage-audience relationship in Renaissance theaters, and underlines the influence of material conditions on the creation and dissemination of Elizabethan and Jacobean drama.<br>Temple University--Theses
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Barragan, Oscar R. "The puzzling nature of material objects: A study of co-location." Diss., Temple University Libraries, 2015. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/332590.
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Philosophy<br>Ph.D.<br>My goal in this dissertation is to analyze the question, why is co-location a problem for the metaphysics of material objects? I believe that the existing literature on the topic identifies three possible answers to this question: Either, (i) co-location is a problem because it violates the no-coincidence principle, or because (ii) co-location violates the claim that the best available explanation for the relationship between objects that share the same empirically discriminable properties is the relationship of numerical identity, or finally because (iii) co-location violates the thesis of microphysical determination. I argue that (i), (ii), and (iii) are not sufficient reasons to think that co-location is metaphysically problematic, and that a denial of these assumptions does not warrant a rejection of co-location. I maintain that, instead, if co-location is a problem, it is so in virtue of violating a more basic assumption. Co-location is a problem for the view that the individuation and persistence conditions of any given material object is completely and solely determined by the physical or material properties of such an object. I advance reasons to believe that the latter view is fundamental in the sense that (i), (ii), and (iii), are consequences of it, and that co-location is in conflict with (i), (ii) and (iii), because it questions the basic physicalist view that provides the conditions for (i), (ii), and (iii). The fact that (i), (ii) and (iii) depend on the belief that physical properties exhaust the individuation and persistence of material objects, explains why they are not good reasons against co-location: They cannot establish that co-location is a problem for an account of material objects because they depend on the belief that co-location denies. Therefore, (i), (ii), and (iii) provide no more than three different ways of begging the question against co-location. I argue that, in order to show that co-location is a problem, we must show that physicalism with respect to material objects is the correct, or at least the most plausible, metaphysics of material objects, and this is something that neither (i), (ii), or (iii) can show. This statement of the relationship between co-location and anti-colocation reasons is also a contribution to the discussion of co-location.<br>Temple University--Theses
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Esteves, Ana Catarina de Carvalho. "Nanocompósitos de matriz polimérica do tipo SIO2/ polímero e Cds/ Polímero." Master's thesis, Universidade de Aveiro, 2002. http://hdl.handle.net/10773/21907.
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Mestrado em Ciência e Engenharia de Materiais<br>O principal objectivo desta dissertação foi estudar novas perspectivas na
preparação de nanocompósitos de matriz polimérica, através da síntese e
caracterização de nanomateriais do tipo SiO2/ polímero e CdS/ polímero.
O primeiro capítulo consiste numa revisão bibliográfica, com destaque para os
principais tópicos discutidos ao longo da tese. São efectuadas algumas
considerações sobre a utilização de nanopartículas inorgânicas como cargas,
e sobre os aspectos mais relevantes da aplicação de polímeros como
matrizes. São ainda descritas, algumas estratégias utilizadas para
compatibilizar estes componentes. A revisão é concluída com uma breve
descrição das metodologias aplicadas na preparação de nanocompósitos de
matriz polimérica.
No segundo capítulo apresenta-se a síntese e caracterização das cargas
inorgânicas. Seguindo métodos descritos na literatura, foram preparadas
nanopartículas de SiO2, esféricas e sob a forma de fibras ocas, nanocristais de
CdS e compósitos inorgânicos do tipo SiO2@CdS. Estes últimos, foram
sujeitos a um tratamento superficial orgânico com TOPO e ainda com SiO2.
Para os materiais tratados com TOPO verificou-se uma melhoria das suas
propriedades ópticas, nomeadamente ao nível da fotoluminescência à
temperatura ambiente.
No terceiro e quarto capítulos, são apresentados os nanocompósitos do tipo
SiO2/ polímero, que foram sintetizados por polimerização in situ de matrizes
semicristalinas (poliamidas e poliuretanos), e amorfas (poli(estireno)). A sua
caracterização foi efectuada por espectroscopia de IV, SEM, TEM, TGA e
DSC.
Os nanocompósitos de matriz semicristalina foram preparados por
polimerização por etapas. No caso das poliamidas, foi investigada a influência
das cargas de SiO2 com diferentes morfologias e tratamentos de superfície, no
processos de fusão e cristalização da matriz. Os materiais de matriz amorfa
foram preparados por polimerização radicalar em emulsão e dispersão. Neste
caso o estudo incidiu sobre a morfologia das partículas dos nanocompósitos,
nas possíveis condições experimentais que a determinam e na influência
destas sobre as propriedades térmicas do nanocompósito.
Por fim descreve-se no quinto capítulo a síntese e caracterização dos
nanocompósitos do tipo CdS/ polímero. Estes materiais foram preparados por
polimerização radicalar em solução, na presença de nanocristais de CdS, e
compósitos inorgânicos do tipo SiO2@CdS. A inserção das cargas na matriz
promoveu as suas propriedades de fotoluminescência à temperatura ambiente.
Foram ainda avaliadas as propriedades térmicas de algumas amostras
representativas.
Neste trabalho foram preparados uma série de novos nanocompósitos de
matriz polimérica, que fazem antever futuras aplicações tecnológicas. Foram
ainda estabelecidos novos caminhos para a compreensão dos mecanismos de
formação de materiais híbridos, e das interacções que ocorrem ao nível das
interfaces de natureza orgânica/ inorgânica.<br>The aim of this thesis was to study new methods for the preparation of polymer
based nanocomposites, through the synthesis and characterisation of
SiO2/polymer and CdS/ polymer nanomaterials.
The first chapter consists in an introduction to the aim topics that are discussed
in the thesis as well as a literature review. Some considerations are made
regarding the use of inorganic nanoparticles as fillers, and to the methods used
to modify the inorganic materials surface in order to make them more
compatible with the organic nature of polymeric matrices. In this introduction
some relevant aspects of the use of polymers as matrices are reported, and a
brief review of the polymerisation methods to be used in the nanocomposites
preparation is given.
The second chapter is devoted to the preparation and characterisation of the
fillers. Following methods previously described on the literature, SiO2
nanoparticles with spherical and hollow fibres morphologies, CdS
nanocristalites and SiO2@CdS inorganic composites were prepared. The last
were organically treated with TOPO and also with SiO2. It was concluded that
the TOPO capping results in improved room temperature photoluminescence
properties.
In the third and fourth chapters, the synthesis and characterisation of SiO2/
polymer nanocomposites is discussed. Using several in situ polymerisation
techniques semi-crystalline (polyurethanes and polyamides) and amorphous
(poly(styrene)) matrices were prepared. The materials were characterised by
FTIR spectroscopy, TEM and SEM, TGA and DSC analysis. The semicrystalline
polymeric matrix nanocomposites were prepared by steppolymerisation.
In the case of the polyamide based nanocomposites the
influence of the SIO2 nanoparticles on the melting and crystallization behaviour
of the matrices is discussed. As regards the amorphous matrix nanocomposites
these were prepared by radical emulsion and dispersion polymerisation. The
morphology of the nanocomposite particles is discussed in light of changes in
experimental conditions, and its possible influence on thermal properties.
Finally, the chapter five is concerned with CdS/ polymer nanocomposites
prepared by in situ polymerisation in the presence of CdS nanocrystals, and
SiO2@CdS inorganic composites. TOPO capping results in higher affinity of the
fillers to the matrix, and its insertion on the matrices promotes their optical
properties, namely room temperature photoluminescence. The thermal
properties of some representative samples were also studied.
In this work a wide range of novel polymer based nanocomposites were
prepared. This study showed that nanomaterials have unique properties that
can anticipate potential technologic applications. Furthermore, new routes have
been opened to the understanding of the mechanisms of nanocomposites
formation, as well as the nature of interactions between organic/ inorganic
interfaces.
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Sloan, Jesse. "THE GENDERED ALTAR: WICCAN CONCEPTS OF GENDER AND RITUAL OBJECTS." Master's thesis, University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3743.
Full textAbstract:
Many ethnographic accounts within the annals of anthropological literature describe the religious beliefs and magical rituals of peoples throughout the world. Fewer scholars have focused on the relatively young Neo-Pagan religious movement. "Neo-Pagan," explains Helen Berger in Voices from the Pagan Census (2003), "is an umbrella term covering sects of a new religious movement, the largest and most important form of which is…Wicca" (Berger et al. 2003: 1). This thesis examines the relationship between practice and ideology by analyzing the material culture of Wiccan altars as used by Wiccans in Central Florida, USA. Particular attention is paid to beliefs concerning concepts of gender associated with ritual objects, and concepts of gender and sexuality as understood by practitioners. Many Wiccans see divinity as manifested in two complementary beings: the Goddess and the God. The fertility that these divine beings achieve through sexual union is the subject of an elaborate ritual called the Great Rite. A pair of Wiccans, often a masculine High Priest and a feminine High Priestess, conduct this ritual by manipulating specific objects, which are believed to be strongly gendered. I argue that Wiccan rituals reflect, construct, and reinforce the Wiccan precept of a gender-balanced cosmos through the interaction of these primary ritual actors and the gendered objects they manipulate. As a practicing Wiccan, my theoretical approach is aligned with that of the native scholar. The native scholar faces challenges distancing her or himself from research, but gains opportunities from insider knowledge. Wiccan ideology stands in contrast to heteronormative conventions of gender and sexuality. However, gay, lesbian, bisexual, and transgender Wiccans may need to actively negotiate for representation in this movement, where fertility is stressed. Wiccans continuously reinvent established practices in an attempt to create a more satisfying religious community.<br>M.A.<br>Department of Anthropology<br>Sciences<br>Anthropology MA