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Kokkinou, Eleni. "Image processing methods in digital autoradiography." Thesis, University of Surrey, 2002. http://epubs.surrey.ac.uk/844272/.
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Autoradiography is a common method in biomedical research for detecting and measuring biodistributions of labelled biomolecules within a specimen. The conventional method is based on using film or film-emulsions for the image acquisition. Although film autoradiography is still in widespread use, there are several disadvantages such as long exposure times, lack of sensitivity, non-linear response of the film and limited dynamic range that encouraged the development of digital autoradiographic systems. Most of the current digital imaging systems have demonstrated excellent performance as far as the above parameters are concerned but still cannot match the image resolution performance exhibited by film or film-emulsion. This thesis is focused on developing image processing methods for improving the quality of digital autoradiography images corrupted with noise and blur obtained by a hybrid CCD autoradiography system at room temperature. Initially, a novel fixed pattern noise method was developed which takes into account the non-ergodic nature of the dark current noise and its dependence on ambient temperature. Empirical formulae were also deduced as a further improvement of the above method for adapting the parameters of the noise distribution for ambient temperature shifts. Image restoration approaches were developed using simulated annealing as a global optimisation technique appropriate for removing the noise and blur from high particle flux samples. The performance of the proposed methods for low flux distributed sources (microscales and mouse brain sections) labelled with high energy beta emmiters has also been demonstrated at different temperatures and integration times and compared with images acquired by the conventional film-based method. Key words: Digital autoradiography, image restoration, simulated annealing, fixed pattern noise removal.
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Klingshim, Christopher J. "Infrared photoconductive PbTe film processing and oxygen sensitization." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98614.
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Thesis: S.B. in Materials Science and Engineering, Massachusetts Institute of Technology, Department of Physics, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 33-34).
Infrared (IR) thermal detectors and photodetectors have significant applications including thermal imaging, infrared spectroscopy and chemical and biological sensing. In this work we focus on photodetectors, which typically use narrow gap semiconductor materials requiring cryogenic cooling to provide measurable signals above thermally generated noise. Our study investigates one class of photodetectors, namely photoconductive semiconductor films. When embedded within resonant cavities, these films are additionally capable of precise detection at narrow, selectable bands and enable the development of monolithically-integrated detectors that are physically small, highly responsive and able to record data autonomously. Lead chalcogenides such as PbTe are ideal photoconductive material candidates because (i) low-cost thermal deposition produces polycrystalline films that exhibit good mid-IR responsivity without being subject to lattice-matching constraints, and (ii) they do not require cryogenic cooling. We show that the responsivity of polycrystalline PbTe is enhanced by oxidation annealing. This investigation sought to determine a viable set of processing conditions for thermally depositing oxygen-sensitized PbTe photoconductors on Si substrates. Depositions were performed under high vacuum on the order of 1 0-6 Torr. Physical shadow-mask and photolithographic techniques were used to pattern the films in order to produce photoconductive samples with varied film and electrical contact geometries. The introduction of non-functional "dummy layers" within 100-300 pm of the usable samples prevented undesired film peeling during the lift-off process. PbTe films displayed an FCC rocksalt structure and slight preference for (200) texture when thermally deposited on a Si substrate. A 250-nm thick sample exhibited large photoconductivity, with responsivity higher than 100 V/W between 2-3 [mu]m wavelengths, a factor of 4 higher than literature values for similar films. Sn metal formed highly ohmic contacts with the PbTe layer, permitting Hall experiments that showed the film to be p-type with a carrier concentration of 1.49 x 1017 cm-3 and Hall mobility of 21 cm 2 V-1 s-. The carrier concentration was thermally activated with activation energy of 0.137 eV. These values are comparable to past experiments in which the film was sensitized by exposure to oxygen at ambient conditions. Further research is needed to establish the exact origin of the enhanced photoconductivity observed.
by Christopher J. Klingshim.
S.B. in Materials Science and Engineering
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Dattani, Rajeev. "Polymer/fullerene solution processing : impact on thin film morphology." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/23958.
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Polymer:fullerene blends are commonly used in organic solar cells (OSCs) and solution based processing is currently the most widely used fabrication method (Vandewal et al., Macromolecules, 2013, Thompson et al. Angewandte Chemie, 2008) [1, 2]. However, the solution behaviour, polymer chain conformation and thermodynamic interactions within these systems, which critically impact thin film morphology, is not well understood. In this work, a model ternary system is systematically investigated polystyrene (PS), C60 and toluene. PS was chosen as it is a flexible polymer and has been extensively studied in solution, thin films and melt, and C60 is an exceptionally well defined molecule. A range of PS molecular weights is investigated, from 18 to 1000 kg/mol, dilute to semidilute polymer solution regimes and the fullerene solutions (below and above its miscibility limit in toluene). No change in the polymer chain dimensions (Rg, Rh or ξ) is found. C60 is shown to aggregate in solution below the miscibility limit in toluene and is shown to be dependent on PS Mw, PS concentration and time. The results are consistent with polymer/colloid theory in the protein-limit. (Dattani et al. Macromolecules, 2014) [3] Thin films with thicknesses ranging from 60 to 130 nm are fabricated from solutions in a homogenous and precipitated regime and the consequences for film formation and morphology under thermal annealing is investigated and quantified. C60 clusters are grown in solution via light exposure and are the result of light-induced oxidation. C60 epoxides are present in the solution and an aggregation mechanism is proposed. C60 epoxidation and aggregation is found to be dependent on C60 concentration, laser power, solvent, temperature and time. The knowledge gained from the model PS/C60/toluene system is applied to systems containing the much-studied poly-3-hexylthiophene (P3HT)/phenyl-C61-butyric acid methyl ester (PCBM) pair, with qualitatively similar results observed. The change in film morphology, accessible by a simple change in processing conditions, offers a unique method for tuning device efficiencies with respect to the size of the fullerene domains.
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Yakoubian, Jeffrey Scott. "Adaptive histogram equalization for mammographic image processing." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/16387.
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Kim, Jang-Yong. "Processing and On-Wafer Test of Ferroelectric Film Microwave Varactors." Doctoral thesis, Stockholm : Information and Communication Technology (ICT), Kungl. Tekniska högskolan (KTH), 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4226.
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McGrath, Johanne. "The processing of heteroepitaxial thin-film diamond for electronic applications." Thesis, Heriot-Watt University, 1998. http://hdl.handle.net/10399/623.
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Bull, Martyn D. "Developments in acoustic direction sensing, signal processing and PVDF film." Thesis, Heriot-Watt University, 1987. http://hdl.handle.net/10399/996.
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Hamed, Mahmoud S. "Film and video restoration using nonlinear digital image processing techniques." Thesis, University of Strathclyde, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400321.
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Wells, Jonathan James. "Thick film processing of YBaâ†2Cuâ†3Oâ†7â†-â†x." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394377.
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Do, Quoc Bao. "Adaptive Post-processing Methods for Film and Video Quality Enhancement." Paris 13, 2011. http://www.theses.fr/2011PA132030.
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L'introduction des nouvelles technologies numériques de traitement et de codage de contenus visuels dans l'industrie du film a permis de réaliser de grandes avancées dans le monde du cinéma. En effet, l'automatisation de certaines tâches lourdes et la maîtrise des outils numériques ont ainsi permis de réaliser des gains de productivité de qualité considérables et des conditions de travail de plus en plus flexibles et maîtrisables. Dans ce travail de thèse, nous poursuivons cet effort de développement de solutions de traitement automatique pour améliorer la qualité des films numériques haute définition. La qualité d'image est un facteur important dans l'industrie du film qu'il convient de maîtriser. Nous nous intéressons ainsi à quelques artéfacts et limitations des outils et processus de production qui affectent la qualité de l'image. Il s'agit des artéfacts de codage tels que les effets de blocs et l'effet de Gibbs (ringing), le bruit de grain et le cas d'une distorsion couleur appelée "écho d'étalonnage". Pour chaque distorsion ou artéfact, un traitement adaptatif, respectant la fidélité d'image et la cohérence visuelle, est proposé et évalué au moyen de mesures objectives. Les résultats obtenus sont très prometteurs et démontrent l'efficacité des méthodes proposées. Des perspectives réalistes sont envisages pour améliorer et étendre les solutions développées à d'autres types contenus multimédiaThe introduction of new digital processing and coding techniques of visual contents in the film industry has allowed filmmakers to achieve great technological and commercial advancements. Indeed, the automation of certain complex tasks has enabled to achieve productivity gains and has made advances in terms of reliability and technical accuracy. The picture quality is one of the most important factors in the #lm industry. The main objective of the thesis work is then to propose new methods for improving the quality of high de#nition video in the context of digital cinema. Here we focus on some known annoying artifacts and distortions. A new and less studied artifact occurring during the color processing of the film is also analyzed. All the proposed solutions are developed in a highly constrained environment dictated by the cinema post-production framework. The performances of the developed methods are evaluated using some objective measures and criteria. The obtained results show that the proposed methods can provide efficient solutions for improving HD film quality. Some perspectives for extending these solutions to other visual contents are considered
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Madugu, Mohammad Lamido. "Processing of semiconductors and thin film solar cells using electroplating." Thesis, Sheffield Hallam University, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.706121.
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The global need for a clean, sustainable and affordable source of energy has triggered extensive research especially in renewable energy sources. In this sector, photovoltaic has been identified as a cheapest, clean and reliable source of energy. It would be of interest to obtain photovoltaic material in thin film form by using simple and inexpensive semiconductor growth technique such as electroplating. Using this growth technique, four semiconductor materials were electroplated on glass/fluorine-doped tin oxide (FTO) substrate from aqueous electrolytes. These semiconductors are indium selenide (InxSey), zinc sulphide (ZnS), cadmium sulphide (CdS) and cadmium telluride (CdTe). lnxSey and ZnS were incorporated as buffer layers while CdS and CdTe layers were utilised as window and absorber layers respectively. All materials were grown using two-electrode (2E) system except for CdTe which was grown using 3E and 2E systems for comparison. To fully optimise the growth conditions, the as-deposited and annealed layers from all the materials were characterised for their structural, morphological, optical, electrical and defects structures using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), optical absorption (UV- Vis spectroscopy), photoelectrochemical (PEC) cell measurements, current-voltage (I-V), capacitance-voltage (C-V), DC electrical measurements, ultraviolet photoelectron spectroscopy (UPS) and photoluminescence (PL) techniques. Results show that InxSey and ZnS layers were amorphous in nature and exhibit both n-type and p-type in electrical conduction. CdS layers are n-type in electrical conduction and show hexagonal and cubic phases in both the as-deposited and after annealing process. CdTe layers show cubic phase structure with both n-type and p- type in electrical conduction. CdTe-based solar cell structures with a n-n heterojunction plus large Schottky barrier, as well as multi-layer graded bandgap solar cells were fabricated. This means that the solar cells investigated in this thesis were not the conventional p-n junction type solar cells. The conventional cadmium chloride (CdCl2 or CC) treatment was applied to the structures to produce high performance devices; however, by modifying the treatment to include cadmium chloride and cadmium fluoride (CdCl2+CdF2 or CF) device performance could be improved further. The fabricated devices were characterised using I-V and C-V measurement techniques. The highest cell efficiency achieved in this research was ~10%, with an open circuit voltage of 640 mV, short-circuit current density of 38.1 mAcm-2, fill factor of 0.41 and doping concentration of 2.07xl016 cm'3. These parameters were obtained for the glass/FTO/n-InxSey/n- CdS/n-CdTe/Au solar cell structure.
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Jiang, Meng. "Processing and properties of nanostructured thin film energy storage devices." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:e651c635-6d92-4217-8442-43b2619c9c82.
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A spray deposition manufacturing route has been developed for the fabrication of carbon nano-structured and micro-structured energy storage devices in a thin film format, with controlled film thickness, homogeneous film surface morphology and high electrochemical performance for both supercapacitors and lithium ion battery anodes. Three types of low cost commercially available carbon materials (graphite, activated carbon and carbon black) have been investigated, and electrodes characterised in terms of surface morphology, surface chemistry, microstructure and electrochemical properties. By using ball milling, CO2 activation and adding suitable carbon conductive additives, nano-graphite-based film electrodes (one meter long and ~ 3 µm thickness) have been fabricated, with excellent ion transport and low electrical resistance (< 1.8 Ω). Specific capacitance of 110 F/g at a scan rate of 100 mV/s in 1 M H2SO4 was achieved. The high rate performance of activated carbon-based electrodes ( ~2 µm thickness) has been enhanced by reducing the contact resistance of electrode/current collector interface and building a well-interconnected and hierachical meso/macro-porous structure. A specific capacitance of over 120 F/g at a scan rate of 600 mV/s or 20 A/g current density in 1 M H2SO4 was achieved. The performance of carbon black-based electrodes (~4 µm thickness) in different electrolytes has been studied in both two- and three-electrode cells. High specific capacitances of 260 F/g at 1 A/g was achieved in 6 M KOH, together with energy and power densities of 21 kW/kg and 18 Wh/kg in 1 M Na2SO4. Finally, graphite-based electrodes for rechargeable lithium-ion batteries have also been fabricated with controlled film thickness from ~ 900 nm to ~ 40 µm and 98% capacity retention of 371 mA/g after 20 cycles. Spray deposition has been demonstrated to have the potential for scalability in the manufacture of carbon-based thin film electrodes with competitive properties.
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Ding, Ziqian. "Large area vacuum fabrication of organic thin-film transistors." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:e7decca4-14e3-47e7-85ca-0bb14755f282.
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A process has been developed to make the dielectric layer for organic thin-film transistors (OTFTs) in a roll-to-roll vacuum web coater environment. This dielectric layer combined with an organic semiconductor layer and metal layer deposited in vacuum allows a solvent-free process to make organic/inorganic multilayer structures for thin-film electronic devices on a flexible substrate at, potentially, high speed. The polymeric gate dielectric layers were fabricated by flash evaporation of acrylic monomers onto a polymer film with pre-patterned metal gates followed by radiation curing by electron beam, ultra-violent light (UV) or plasma. With a non-polar dielectric surface, charge carrier mobility (μ) of 1 cm2-V-1s-1; on/off curren ratio of 108, sub-threshold swing (SS) of 0.3 V/decade and saturated output curve were routinely achieved in dinaphtho-[2,3-b:2'3'-f]thieno[3,2-b]thiophene (DNTT) transistors with dielectric layer of tripropylene glycol diacrylate (TPGDA) of ~400 nm. Apart from the TPGDA, monomer formulas including 1,6-Hexanediol diacrylate (HDDA) as well as several commercial acrylic resins have been used to make the dielectric layer. The highest areal capacitance of 41nF-cm-2 was achieved with a pin-hole free film of less than 100 nm made of an acrylate mixture resin. A non-polar dielectric surface treatment layer has been developed based on flash evaporation of lauryl acrylate and HDDA mixture. The transistors with the buffer layer showed constant performance and a mobility fivefold greater than those of untreated samples. The effect of humidity, oxygen, and light during switching cycles of both pentacene and DNTT transistors were studied. Water and oxygen/illumination had a distinct effect on both pentacene and DNTT transistors. Oxygen leads to acceptor-like charge traps under illumination, which shifted the turn-on voltage (Vto) to more positive values. In contrast, water in transistors gave rise to donor-like charge traps, which shifted the Vto and the threshold voltage (VT) more negatively. The DNTT devices showed good stability in dry air without encapsulation, while pentacene transistors degraded with either repeating measurement or long term storage. A DNTT transistor with a PS-coated TPGDA dielectric layer showed stable drain current (Id) of ~105A under bias stress of the gate voltage (em>Vg) of -20V and the drain voltage (em>Vd) of -20V for at least 144 hours. The Vto shift after the stress was less than 5 V and was recoverable when the device was kept in dry air for a few days. Possible reasons for the Vto shift have been discussed.
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Hou, Wei-Jen. "Hydrazine-based solution-processing of copper chalcopyrite for thin-film photovoltaics." Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1998530831&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Boutaud, Gabriel. "Growth optimisation and laser processing of thin film phosphors for electroluminescent displays." Thesis, Nottingham Trent University, 2010. http://irep.ntu.ac.uk/id/eprint/345/.
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This thesis presents results of a study of ZnS:Mn thin film phosphors used in Thin Film ELectroluminescent (TFEL) and Laterally Emitting TFEL (LETFEL) devices, examining techniques for phosphor growth optimisation and post deposition processing in order to strengthen development of novel TFEL devices. To achieve this, thin films of phosphor were deposited using RF magnetron sputtering to investigate the use of co-sputtering in order to optimise dopant concentration. 800 nm films of ZnS:Mn were simultaneously co-sputtered from ZnS and ZnS:Mn (1 wt.%) solid targets. The thin films were deposited at different manganese concentrations by varying the relative RF power applied to each target. The films were deposited directly onto 100 mm diameter (100) n-type silicon substrates, or onto a layer of 300 nm of Y2O3 to fabricate electroluminescent test devices. Luminescence from the phosphor films was characterised via photoluminescent excitation using a 337 nm pulsed N2 laser, with the photoluminescence (PL) optimum obtained at 0.38 ZnS:Mn power ratio. Electroluminescence (EL) from TFEL devices were excited by applying a sinusoidal waveform voltage at a frequency of 1 kHz with maximum luminance obtained at 0.36 ZnS:Mn power ratio.
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Dawson, Noel Mayur. "The Processing and Polarization Reversal Dynamics of Thin Film Poly(vinylidene) Fluoride." Thesis, The University of New Mexico, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10641207.
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Many ferroelectric devices benefit from the ability to deposit thin ferroelectric layers. Poly(vinylidene) fluoride (PVDF) is the prototypical ferroelectric polymer, but processing of thin film ferroelectric PVDF remains a challenge due to the formation of large voids in the film during traditional thin film processing. The research described in this dissertation starts by investigating the origin of these voids. The cause of these voids is found to be caused by vapor induced phase separation (VIPS). Guided by the thermodynamics of VIPS, a process is then designed to produce void-free ferroelectric PVDF thin films on polar and non-polar substrates. The films are shown to have a high remnant polarization (~6.5 C m–2). The later part of this dissertation is focused on understanding the temperature and structural phase dependent kinetics of polarization switching in PVDF films. A polarization switching model is developed with considerations of Avrami nucleation and growth, local electric fields, temperature and structural phase. The kinetics of polarization switching are shown to follow a universal behavior when correctly accounting for temperature and structural phase.
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Koh, Jung-Hyuk. "Processing and Properties of Ferroelectric Ag(Ta,Nb)O3 Thin Films." Doctoral thesis, KTH, Microelectronics and Information Technology, IMIT, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3387.
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High tunability and low loss tangent of ferroelectric thinfilms offer unique opportunity for the development of variousmicrowave devices. Silver tantalate niobate, which showsexcellent microwave properties, was selected for this study.Ag(Ta,Nb)O3(ATN) showed week dielectric dispersion in a widefrequency range from 1 kHz up to 100 GHz, negligible losses upto 30 GHz, and ease to tailor paraelectric state in a widetemperature range by Ta:Nb ratio.
This thesis is mainly based on the synthesis andcharacterization of niobate ferroelectric ATN thin films. Thinfilms for various measurements were prepared by pulsed laserdeposition and rf-magnetron sputtering techniques.
X-ray diffraction (XRD) pattern show that ATN/Pt80Ir20films have been found to be (001) preferentiallyoriented, while the epitaxial quality of ATN/LaAlO3heterostructures have been ascertained. Dielectricproperties were analyzed by measuring the relationship betweendielectric permittivity and frequency as well as dielectricpermittivity and temperature. Reliable tracing of theferroelectric hysteresis polarization versus electric loopsindicate the ferroelectric state in ATN films at temperaturebelow 125 K and yields the remanant polarization of 0.4µC/cm2@ 77 K.
The fundamental current-voltage behavior in Ag(Ta,Nb)O3ferroelectric films was measured usingMe/Ag(Ta,Nb)O3/Pt80Ir20, Me = Pd, Au, Cr, and Al, vertical capacitivecell structures with different top electrodes. Various kinds ofconduction mechanisms such as Schottky emission, Poole-Frenkel,Fowler-Nordheim, and ionic conduction were classified.
Finally, by fabricating interdigital capacitors on the oxidesubstrates, the characteristics and performances of Ag(Ta,Nb)O3varactors were examined. Au/Cr/ATN/LaAlO3interdigital capacitors exhibited loss tangent aslow as 0.0033 @ 1 MHz, weak frequency dispersion of 5.8 % in 1kHz to 1 MHz range, tunability as high as 16.4 %,K-factor (tunability/tanδ) higher than 48.
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Gouws, Eugene. "Audio Signal Processing in Ironman A development of film music analysis from a perspective of music technology." Diss., University of Pretoria, 2017. http://hdl.handle.net/2263/63617.
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The advances in music technology and cinematography in recent years has granted a higher level of importance to the film music. There exists a gap in the academic study of film music as it relates to music technology, as no appropriate methodology exists that can accurately measure the contribution that music technology makes towards the music as it exists in film.
This study aims to contribute towards existing methodologies for analysing film music, but from the perspective of music technology, and more specifically how audio processing in the domains of dynamic, spectral, spatial and temporal processing contribute towards the music in the film. This is achieved by building on the proposed methodologies of the study of film music as proposed by Kassabian (2009) and Altman (2000).
This new method can be utilized to create a reference list of contributions that audio processing can make towards the soundtrack of a film by isolating the particular contribution that every moment of music is contributing to the film, and then finding how audio processing adds to this.Mini Dissertation (MMus)--University of Pretoria, 2017.
Music
MMus
Unrestricted
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Yu, Ta-Hua. "Processing and structure-property behavior of microporous polyethylene: from resin to final film." Diss., Virginia Tech, 1996. http://hdl.handle.net/10919/39206.
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Lin, Shin-Jie. "Development of Edible Packaging for Selected Food Processing Applications." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1349125959.
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Mani, Rajesh. "Processing and characterization of polymer-ceramic composite thin film dielectrics for embedded decoupling applications." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/20840.
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Ferreri, Ann Arita. "Novel processing routes for YBa2 Cu3 O7-x thin film via ultrasonic spray pyrolysis." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414978.
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Vijay, Dilip P. "Reliability and processing of ferroelectric thin film capacitors with emphasis on fatigue and etching." Diss., This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-06062008-162341/.
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Li, Tian. "The behaviour of double oxide film defects in the processing of liquid Mg alloys." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7537/.
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The global demand for Mg alloys continually grew in the last 20 years, motivating a wide interest in the improvement of the mechanical properties of Mg-alloy castings. In addition, the existence of double oxide film defects, which were widely recognised as a major factor in the quality and reproducibility of the properties of light-alloy castings, has been demonstrated in Mg-alloy castings. Thus it became important to understand behaviour of double oxide film defects formed in Mg-alloys. In the work reported here, three different Mg alloys (commercial pure Mg, AZ91 alloy, and Mg-Y alloys) and two cover gases (SF6/air and SF6/CO2), were used, in order to involve different doubled oxide films which may have different behaviours. Direct and cross-sectional observations of the double oxide film defects formed the Mg-alloy castings protected by different cover gases were obtained via a Scanning Electron Microscopy (SEM), and the focus ion beam milling (FIB) technique. In addition, oxide films growing on the corresponding Mg-alloy melt surfaces were also investigated. Based on the observed film structures in conjunction with a thermochemical calculation, evolution processes of the different double oxide film defects were suggested. The quality of Mg-alloy castings was evaluated by the Weibull modulus, which is popularly used to discriminate “good” and “bad” castings. A shortcoming of the traditional Weibull estimation method (i.e. linear least square method) was demonstrated, and a new estimation method was therefore come up with. The Weibull modulus result revealed that air can confer an improvement in the quality of AZ91 castings, compared with CO2.
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Stadler, Bethanie J. Hills (Bethany Joyce Hills). "Relationships between optical properties and processing in Al2O3-Y2O3 thin film waveguides and amplifers." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/28082.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1994.Includes bibliographical references (leaves 148-151).
by Bethanie J. Hills Stadler.
Ph.D.
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Mohammed, Mohammed K. "Processing and Properties of Multifunctional Two Dimensional Nanocomposites Based on Graphene Nano-Flakes." Wright State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=wright1600087340883598.
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Damian, Melissa Feres. "Avaliação do tempo de secagem e da qualidade da imagem de radiografias submetidas a banho em alcool etilico em diferentes concentraçãoes." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/289007.
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Orientador: Francisco Haiter NetoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: Com este estudo, teve-se a proposta de avaliar a ação do álcool etílico, nas concentrações de 46ºGL, 70ºGL e 92ºGL, como agente acelerador da secagem de radiografias dentárias, a fim de abreviar o tempo de processamento. Adicionalmente, foi verificado se esse produto poderia causar alterações na dens idade, nas propriedades sensitométricas e na qualidade destas radiografias após um curto período de arquivamento. Para tanto, foram utilizados os filmes radiográficos intra-orais de sensibilidade D (Dspeed), E (E-speed) e E/F (Insight) da Kodak, divididos em grupos de acordo com o uso e a concentração da substância alcoólica. Todos os filmes foram processados manualmente pelo método temperatura/tempo em câmara escura portátil para simular condições clínicas. As radiografias foram submetidas às analises densitométrica e clínica subjetiva, além da construção de curvas características para a obtenção do contraste e da sensibilidade, nos períodos correspondentes a um e seis meses após a realização do experimento, simulando condições de arquivo. Pôde-se observar que o uso do álcool etílico acelerou a secagem das radiografias independentemente do tipo de filme, sendo que o menor tempo foi obtido com a utilização da substância alcoólica de maior concentração. Contudo, os valores de densidade, contraste e sensibilidade foram alterados quando foi utilizado o álcool 70ºGL e o álcool 92ºGL, sendo que este último também foi capaz de alterar a qualidade visual das imagens. Tais alterações puderam ser visualizadas nos dois períodos de avaliação de estudo. Assim, concluiu -se que mesmo que o álcool etílico acelere a secagem das radiografias, sua utilização causou alterações capazes de prejudicar a qualidade da imagem, inclusive após um curto período de arquivamento
Abstract: This study evaluated the action of ethyl alcohol at concentrations of 46ºGL, 70ºGL and 92ºGL as an accelerator of drying of dental radiographs, with a view to reduce the time required for processing. Also, it was observed whether this product might cause alterations in the density, sensitometric properties and quality of these radiographs after a 6- month storage period. For that purpose, intraoral radiographic films D-speed, E-speed and E/F (Insight) of Kodak were employed, which were divided into groups according to the utilization and concentration of the alcoholic substance. All films were developed manually by the time-temperature method in a portable dark room, to simulate the clinical conditions. The radiographs were submitted to densitometric and clinical analyses, besides construction of characteristic curves for achievement of contrast and sensitivity, at periods corresponding to one and six months after accomplishment of the study, simulating conditions of storage. It was observed that the utilization of ethyl alcohol accelerated the drying of radiographs, regardless of the type of film; the shortest time was achieved with utilization of the alcoholic substance of highest concentration. However, the density, contrast and speed of radiographs were altered when concentrations of 70ºGL and 92ºGL were used; being that the latter also altered the visual quality of images. Such alterations could be observed at the two evaluations and study periods. Thus, it was concluded that, even though the ethyl alcohol may accelerate the drying of radiographs, its utilization caused alterations able to impair the quality of image, even after a short period of storage
Doutorado
Radiologia Odontologica
Doutor em Radiologia Odontológica
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Karakuscu, Aylin. "Characterization Of Maghemite Thin Films Prepared By Sol-gel Processing." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607795/index.pdf.
Full textAbstract:
In this study, maghemite (γ
-Fe2O3) thin films were prepared by chemical solution deposition on glass and quartz substrates. The solution was prepared by using 0.3 M iron (III) nitrate [Fe(NO3)3 - 9H2O] as precursor and dissolved in a mixture of 2-methoxyethanol and acetylacetone in a molar ratio of 20:2, by stirring the solution at RT for 2 hours. Substrates were prepared by either piranha etching method or ultrasonic cleaning method. The solution was spin coated on glass and quartz substrates at 1400 and 4000 rpm for 1 minute. The resultant film thickness was found as 65 and 80 nm by SEM. Viscosity of the main solution was found to be approximately as 0.0035 Pa.s by viscosity measurement. TGA/DTA analyses showed that, to produce maghemite thin film, heat treatment should be done between 330 °
C and 440 °
C. Homogeneous and crack free maghemite thin films were observed by Energy Dispersive Spectrometry (EDS) and Scanning Electron Microscope (SEM) methods. TEM studies verified maghemite thin film formation by using electron diffraction and SAED (selected area electron diffraction) method. Thin film characteristics were evaluated by changing the experimental parameters which are annealing temperature, annealing time and thickness of the films using XRD (x-ray diffraction) method. Optical band gap of maghemite thin films were found as approximately 2.64 eV by UV-VIS Spectrophotometer. Magnetic properties of maghemite thin films were also examined by VSM (vibrating sample magnetometer).
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Vernacotola, Mark J. "Characterization of digital film scanner systems for use with digital scene algorithms /." Online version of thesis, 1995. http://hdl.handle.net/1850/11967.
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Eken, Ali Erdem. "Characterization Of Magnetite Thin Films Produced By Sol-gel Processing." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609298/index.pdf.
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Magnetite (Fe3O4) thin films were prepared by a sol-gel process in which, a solution of iron (III) nitrate dissolved in ethylene glycol was applied on glass substrates by spin coating. Xerogel films were obtained by drying the coated films at 110 °C. The films were sintered between 300 °
C and 450 °
C in order to observe the phases existing in the films at different temperatures. Coating solution showed Newtonian behaviour and viscosity was found as 0.0215 Pa.s. DTA analysis showed that, sintering temperature should be selected between 291 °
C and 350 °
C in order to produce magnetite thin films. Prepared magnetite thin films were characterized by XRD, SEM, AFM, TEM, VSM and UV-Vis spectrometer. In-plane grazing angle diffraction studies showed that magnetite phase was present upon sintering the films at 300 °
C. From the SEM studies, it was shown that films with defect free surfaces were obtained and by cross section studies, thickness of the films was found as ~10-200 nm. AFM images showed that no cracks or any other defects on the film surface were present. TEM results proved the existence of single phase magnetite in the produced films. UV-Vis spectrum results showed that transmittance of the films increases with decreasing sintering temperature and increasing spinning rate. Up to 96% transmittance was observed between the wavelengths of 900-1100 nm. Magnetic properties of magnetite thin films were also examined by VSM (Vibrating Sample Magnetometer) and ferromagnetic behaviour was shown using VSM data.
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Sheen, Jade, and jade sheen@deakin edu au. "Women's cognitive and emotional processing during sexual arousal: The effects of erotic film and absorption." Deakin University. School of Psychology, 2004. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20061208.084141.
Full textAbstract:
Sexual arousal is a complex and dynamic element of womens sexuality. Accounts
vary, however most multidimensional models highlight the cognitive, affective and
physiological components of the female sexual arousal response. While literature examining the peripheral physiological changes that occur during female sexual
arousal abounds, there has been a dearth of literature pertaining to the cognitive and
affective components. Thus, while many authors have included cognitive and
emotions as independent components of the female sexual arousal response, there
has been little empirical research to validate this approach. The aim of the current
thesis was to examine the cognitive and affective components of female sexual
arousal in more depth, investigating the nature of the relationship between these components under various experimental conditions. In order to do so, two integrated studies were conducted, each highlighting the effects of either external or internal variables on womens subjective sexual arousal, absorption, positive affect and negative affect.
Study One was designed to evaluate womens emotional and cognitive processing of two elements of erotic film foreplay and erotic context. 60 women were asked to report their subjective sexual arousal, absorption, positive affect and negative affect in response to one of four erotic film excerpts. The erotic excerpts varied in accordance with the degree of foreplay (low vs. high) depicted and the context in which the sexual activities took place (novel vs. habitual context). Women in the study responded more favourably to the high foreplay erotic film excerpt, subsequently reporting higher degrees of subjective sexual arousal, absorption and positive affect. Women also responded favourably to the erotic excerpt filmed in a novel context, reporting greater subjective sexual arousal as a result. The environment in which the sexual encounters were filmed failed to have an effect however, on womens absorption or their positive or negative affect. The results of Study One suggest that stimulus specific variables, such as the degree of foreplay depicted, have a significant influence on female cognitive and emotional processing of erotic film. The results also suggest that a relationship exists between absorption, subjective sexual arousal and positive affect, albeit a correlational one. Specifically, there was evidence of parallel processing during sexual arousal, as participant reported sexual arousal, absorption and positive affect all increased and decreased in unison. Based on the results it was suggested that future research attempt to experimentally manipulate one of these variables, to examine its direct effect on the remaining variable.
Thus, Study Two aimed to examine the effects of absorption on womens cognitive and emotional processing of erotica. Study Two manipulated absorption at two levels (high vs. low), examining the impact of these states on participants subsequent absorption, subjective sexual arousal and positive and negative affect. 62 women were asked to read one of two sets of test session instructions. The first, participant-oriented instruction set, instructed participants to immerse themselves in the erotic film excerpt, as if they were active participants in the sexual exchange. The second, spectator-oriented instruction set, directed participants to observe and evaluate the erotic film. These instructions were designed to elicit high and low degrees of absorption, respectively. The utility of this approach when manipulating female absorption, was demonstrated by self reported ratings of absorption, given at the conclusion of the film presentation. Participants were also asked to report their subjective sexual arousal and positive and negative affect at the conclusion of the erotic film presentation. The findings of this study suggest that the adoption of a participant-oriented (high absorption) perspective elicits more favourable responses from participants than a spectator-oriented (low absorption) perspective, with participants in the former experimental group reporting greater degrees of subjective sexual arousal and positive affect. Negative affect was equivalent across experimental conditions, with the participants reporting that they experienced little to no aversive feelings during either of the experimental conditions. The results suggest that the degree to which a women immerses and absorbs herself in a sexual stimulus has a significant impact in her subsequent cognitive and affective processing of that stimulus. More specifically, it appears that women respond more favourably when they are highly absorbed and immersed in a stimulus, reporting greater subjective sexual arousal and positive affect.
Overall, the results of Studies One and Two highlight the dynamic and complex nature of female sexual arousal. It appears that women have definite cognitive and affective responses to sexual stimuli. The magnitude of these responses may be mediated by a number of factors however, including the intrinsic qualities of the stimulus and the degree to which the woman attends to the stimulus. Both these variables act to either enhance or inhibit the sexual arousal response. There results have important implications for current sexuality literature. While womens cognitions and emotions in response to erotic film were generally highly correlated, in some instances they differed, warranting their inclusion as separate elements in models of female sexual arousal. Furthermore, it might be suggested that the inclusion of an additional variable absorption into current models of female sexual arousal would prove beneficial, aiding researchers to better understand and predict the arousal process. As such, recommendations are made for a revised model of female sexual arousal. In terms of future directions, the results of the present thesis have implications for the treatment of sexual dysfunctions, suggesting that clinicians need to understand the internal and external variables that might contribute to the aetiology and maintenance of their presenting problems.
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Terry, Mason L. Photovoltaic & Renewable Energy Engineering UNSW. "Post???deposition processing of polycrystalline silicon thin???film solar cells on low???temperature glass superstrates." Awarded by:University of New South Wales. Photovoltaic and Renewable Energy Engineering, 2007. http://handle.unsw.edu.au/1959.4/30498.
Full textAbstract:
In polycrystalline silicon (pc-Si) thin-film solar cells, defect passivation is critical to device performance. Isoelectronic or covalently bonded impurities, hydrogenic, extended defects and defects with localized levels in the bandgap (deep level defects) are typically introduced during the fabrication of, and/or are inherent to, pc-Si thin-film solar cells. These defects dramatically affect minority carrier lifetimes. Removing and/or passivating these defects is required to maximize minority carrier lifetimes and is typically done through thermal annealing and passivation techniques. For pc-Si thin-film solar cells on low temperature glass superstrates, rapid thermal annealing (RTA) and hydrogen plasma passivation (hydrogenation) are powerful techniques to achieve effective removal and passivation of these defects. In this thesis, three silicon thin-film solar cells structures on low-temperature glass are subjected to variations in RTA high-temperature plateaus, RTA plateau times, and hydrogen plasma passivation parameters. These solar cells are referred to as ALICIA, EVA and PLASMA. By varying the RTA plateau temperature and time at plateau, the trade-off between extensive dopant diffusion and maximum defect removal is optimized. To reduce the density of point defects and to electrically activate the majority of dopants, an RTA process is shown to be essential. For all three of the thin-film solar cell structures investigated in this thesis, a shorter, higher-temperature RTA process provides the best open-circuit voltage (Voc). Extensive RTA plateau times cause excessive dopant smearing, increasing n = 2 recombination and shunt resistance losses. Hydrogenation is shown to be an essential step to achieve maximum device performance by `healing' the defects inherent to pc-Si thin-film solar cells. If the hydrogen concentration is about 1-2 times the density of oxygen in the cells as measured by secondary ion mass spectroscopy (SIMS), the cells seem to respond best to hydrogenation, with good resultant Voc and short-circuit for all cells investigated in this thesis. The effect of hydrogen passivation on the Voc is spectacular, typically increasing it by a factor of 2 to 3.5. Hydrogen de-bonding from repeated thermal treatments at increasing temperature provides a deeper understanding of what defects exist and the nature of the defects that limit the cell voltage. The variation in RTA and hydrogenation process parameters produces significant empirical insight into the effectiveness of RTA processes for point defect removal, dopant activation, point defect and grain boundary passivation, and impurity passivation. SIMS measurements are used to determine the impurities present in the cells' bulk and the amount of hydrogen available to passivate defects. From the results presented it appears that pc-Si thin-film solar cells on low-temperature glass are a promising, and potentially lower-cost, alternative to Si wafer based cells.
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Harrison, Paul Martin. "Industrial thin film processing applications of high peak power, high average power Nd:YAG laser systems." Thesis, Heriot-Watt University, 2012. http://hdl.handle.net/10399/2613.
Full textAbstract:
Three high speed thin film patterning applications have been investigated using a high average power, high peak power laser system. Throughout this work the spatial intensity profile of the laser output was tailored to produce more efficient results. The first application involved the development of rapid laser patterning of an indium tin oxide layer on a glass substrate in order to generate transparent electrodes for a flat panel display. This work showed that the stitch line that occurs in-between adjacent laser pulses was formed by redeposition of material via the plume generated by the second, slightly overlapping pulse which is deposited within the region of overlap, an area which has an increased surface temperature at that time. The second application, laser edge deletion for thin film solar photo-voltaic panels, was an investigation of whether dual wavelength processing was able to avoid introducing micro-cracks into the soda-lime glass substrate. The third application was an examination of high speed removal of an aluminium coating from a stainless steel substrate which demonstrated that the layer could be adequately removed but required a series of highly overlapped pulses.
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Zeng, Lirong Ph D. Massachusetts Institute of Technology. "High efficiency thin film silicon solar cells with novel light trapping : principle, design and processing." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44392.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.Includes bibliographical references.
One major efficiency limiting factor in thin film solar cells is weak absorption of long wavelength photons due to the limited optical path length imposed by the thin film thickness. This is especially severe in Si because of its indirect bandgap. This thesis invents a novel light trapping scheme, the textured photonic crystal (TPC) backside reflector, which can enhance path length by at least several hundred times the film thickness for sufficient absorption. Physical principles and design optimization of TPC are discussed in detail. Thin film Si solar cells integrated with the new back reflector are successfully fabricated and significant efficiency enhancement is demonstrated.The new back reflector combines a one-dimensional photonic crystal as a distributed Bragg reflector (DBR) and reflection grating. The DBR achieves near unity reflectivity in a wide omnidirectional bandgap completely covering the wavelengths needing light trapping, and the grating can diffract light into large oblique angles and form total internal reflection against the front surface of the cell. The unique combination of DBR and grating tightly confines light inside the cell, effectively changing the path length from the thickness of the cell to its width.The back reflector parameters and the antireflection coating are systematically optimized for thin film Si solar cells through simulation and experiments. A 2 [mu]m thick cell can achieve 54% efficiency enhancement using the optimized design.For proof of concept, the TPC back reflector is integrated with thick crystalline Si solar cells (675 [mu]m thick), which demonstrate external quantum efficiency enhancement up to 135 times in the wavelength range of 1000-1200 nm.
(cont.) To prove the theory on the intended application, top-contacted thin film Si solar cells integrated with the TPC back reflector are successfully fabricated using Si-on-insulator material through an active layer transfer technique. All cells exhibit strong absorption enhancement, similar to that predicted by simulation. The 5 [mu]m thick cells gained 19% short circuit current density improvement, despite machine problems during fabrication. The textured photonic crystal back reflector design can be applied directly to single and poly-crystalline Si solar cells, and its principle is broadly applicable to other materials systems.
by Lirong Zeng.
Ph.D.
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Bouscher, Robert F. "Advancements in Powder Coating Processing and in Real-time Film Formation Analysis of Thermoset Coatings." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1627566578541715.
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Myslinski, Paul Joseph. "Analysis of Cyanate Ester Resins and Graphite Fabric for Use in Resin Film Infusion Processing." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/35804.
Full textAbstract:
The objective of this investigation was to characterize two cyanate ester resins and a eight harness satin (8HS) graphite fabric for use in resin film infusion (RFI) processing. Two cyanate ester resin systems were characterized to determine their cure-kinetics, and viscosities during cure. A 8HS graphite fabric was tested in compaction and through the thickness permeability. A one-dimensional, through the thickness, flow and cure computer simulation was run.
The resin cure-kinetics models predicted the curing behavior of the resins as functions of time, temperature, and degree of cure. The proposed viscosity models determined the resin viscosity as a function of temperature and degree of cure. The 8HS graphite fabric was tested in compaction and through the thickness permeability to determine the effect of compaction pressure on fiber volume fraction and in turn on through the thickness permeability. The one-dimensional RFI flow and cure simulation combined the cure-kinetics and viscosity models of the resins with the characteristics of the graphite fabric and determined resin infiltration and cure times.
The proposed cure-kinetics and viscosity models were more than adequate in modeling the cure and flow behavior of the cyanate ester resin systems. Power law curve fits accurately represented the compaction and through the thickness permeability of the 8HS graphite fabric. Finally, the one-dimensional RFI flow and cure simulation showed that resin viscosity was the major influence on the infiltration times.
Master of Science
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Mu, Shenglong. "A Real-time Study on Mechano-optical Properties of Chitosan during Film Formation and Processing." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1462885413.
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McGrady, Christopher Dwain. "Linking Rheological and Processing Behavior to Molecular Structure in Sparsely-Branched Polyethylenes Using Constitutive Relationships." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/37924.
Full textAbstract:
This dissertation works towards the larger objective of identifying and assessing the key features of molecular structure that lead to desired polymer processing performance with an ultimate goal of being able to tailor-make specific macromolecules that yield the desired processing response. A series of eight well-characterized, high-density polyethylene (HDPE) resins, with varying degrees of sparse long chain branching (LCB) content, is used to study the effect of both LCB content and distribution on the rheological and commercial processing response using the Pom-pom constitutive relationship. A flow instability known as ductile failure in extensional flow required the development a novel technique known as encapsulation in order to carry out shear-free rheological characterization.
Ductile failure prevents the rheological measurement of transient stress growth at higher strains for certain strain-hardening materials. This reduces the accuracy of nonlinear parameters for constitutive equations fit from transient stress growth data, as well as their effectiveness in modeling extensionally driven processes such as film casting. An experimental technique to overcome ductile failure called encapsulation in which the material that undergoes ductile failure is surrounded by a resin that readily deforms homogeneously at higher strains is introduced. A simple parallel model is shown to calculate the viscosity of the core material.
The effect of sparse long chain branching, LCB, on the film-casting process is analyzed at various drawdown ratios. A full rheological characterization in both shear and shear-free flows is also presented. At low drawdown ratios, the low-density polyethylenes, LDPE, exhibited the least degree of necking at distances less than the HDPE frostline. The sparsely-branched HDPE resins films had similar final film-widths that were larger than those of the linear HDPE. As the drawdown ratio was increased, film width profiles separated based on branching level. Small amounts of LCB were found to reduce the amount of necking at intermediate drawdown ratios. At higher drawdown ratios, the sparsely-branched HDPE resins of lower LCB had content film-widths that mimicked that of the linear HDPE, while the sparsely-branched HDPE resins of higher LCB content retained a larger film width. Molecular structural analysis via the Pom-pom constitutive model suggested that branching that was distributed across a larger range of backbone lengths serve to improve resistance to necking. As the drawdown ratio increased, the length of the backbones dominating the response decreased, so that the linear chains were controlling the necking behavior of the sparsely-branched resins of lower LCB content while remaining in branched regime for higher LCB content HDPEs. Other processing variables such as shear viscosity magnitude, extrudate swell, and non-isothermal processing conditions were eliminated as contributing factors to the differences in the film width profile.
The effect of sparse long chain branching, LCB, on the shear step-strain relaxation modulus is analyzed using a series of eight well-characterized, high-density polyethylene (HDPE) resins. The motivation for this work is in assessing the ability of step-strain flows to provide specific information about a material's branching architecture. Fundamental to this goal is proving the validity of relaxation moduli data at times shorter than the onset of time-strain separability. Strains of 1% to 1250% are imposed on materials with LCB content ranging from zero to 3.33 LCB per 10,000 carbon atoms. All materials are observed to obey time-strain separation beyond some characteristic time, Ï k. The presence of LCB is observed to increase the value of Ï k relative to the linear resin. Furthermore, the amount of LCB content is seen to correlate positively with increasing Ï k. The behavior of the relaxation modulus at times shorter than Ï k is investigated by an analysis of the enhancement seen in the linear relaxation modulus, G0(t), as a function of strain and LCB content. This enhancement is seen to 1) increase with increasing strain in all resins, 2) be significantly larger in the sparsely-branched HDPE resins relative to the linear HDPE resin, and 3) increase in magnitude with increasing LCB content. The shape and smoothness of the damping function is investigated to rule out the presence of wall-slip and material rupture during testing. The finite rise time to impose the desired strain is carefully monitored and compared to the Rouse relaxation time of the linear HDPE resins studied. Sparse LCB is found to increase the magnitude of the relaxation modulus at short times relative to the linear resin. It is shown that these differences are due to variations in the material architecture, specifically LCB content, and not because of mechanical anomalies.Ph. D.
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Drobitch, Justine L. "Fabrication and Simulation of Nanomagnetic Devices for Information Processing." VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/6102.
Full textAbstract:
Nanomagnetic devices are highly energy efficient and non-volatile. Because of these two attributes, they are potential replacements to many currently used information processing technologies, and they have already been implemented in many different applications. This dissertation covers a study of nanomagnetic devices and their applications in various technologies for information processing – from simulating and analyzing the mechanisms behind the operation of the devices, to experimental investigations encompassing magnetic film growth for device components to nanomagnetic device fabrication and measurement of their performance.
Theoretical sections of this dissertation include simulation-based modeling of perpendicular magnetic anisotropy magnetic tunnel junctions (p-MTJ) and low energy barrier nanomagnets (LBM) – both important devices for magnetic device-based information processing. First, we propose and analyze a precessionally switched p-MTJ based memory cell where data is written without any on-chip magnetic field that dissipates energy as low as 7.1 fJ. Next, probabilistic (p-) bits implemented with low energy barrier nanomagnets (LBMs) are also analyzed through simulations, and plots show that the probability curves are not affected much by reasonable variations in either thickness or lateral dimensions of the magnetic layers.
Experimental sections of this dissertation comprise device fabrication aspects from the basics of material deposition to the application-based demonstration of an extreme sub-wavelength electromagnetic antenna. Magnetic tunnel junctions for memory cells and low barrier nanomagnets for probabilistic computing, in particular, require ultrathin ferromagnetic layers of uniform thickness, and non-uniform growth or variations in layer thickness can cause failures or other problems. Considerable attention was focused on developing methodologies for uniform thin film growth.
Lastly, micro- and nano-fabrication methods are used to build an extreme sub-wavelength electromagnetic antenna implemented with an array of magnetostrictive nanomagnets elastically coupled to a piezoelectric substrate. The 50 pW signal measured from the approximately 250,000-nanomagnet antenna sample was 10 dB above the noise floor.
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Bapanapalli, Srilatha. "Cds/cdte thin film solar cells with zinc stannate buffer layer." [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001004.
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KARAGULEFF, CHRIS. "DEGENERATE FOUR WAVE MIXING IN THIN FILM OPTICAL WAVEGUIDES (NONLINEAR OPTICS, INTEGRATED, PHASE CONJUGATION, SIGNAL PROCESSING)." Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/187908.
Full textAbstract:
The incentive for conducting Degenerate Four Wave Mixing (DFWM) within guided wave devices is two-fold: (1) By coupling the optical beams into guided wave devices, the optical power densities can be increased orders of magnitude due to the tight confinement of the beams. Such an increase in power density means a concomitant increase in conversion efficiency of the signal beam. (2) The potential signal processing applications of DFWM (logic gates, switching, correlation/convolution), particularly for ultra-fast serial processing, would be better exploited, and adjoined to existing integrated circuit technology, by such an integrated optic/guided wave approach. In this dissertation we describe experiments and present data confirming the presence of DFWM within a planar glass thin film with carbon disulphide as the nonlinear cover medium. Optical pulses from a Q-switched, frequency doubled Nd:YAG laser are coupled into the glass film. The nonlinear polarization required to produce the desired conjugate signal is generated within the CS₂ by the evanescent tails of the guided input beams as they probe the nonlinear cover medium. The signals measured agree well with theory, but because they were so small in magnitude, signal-to noise ratios were small due to stray background radiation scattering from beamsplitters and other associated optics. Additionally, recent studies (Jain & Lind, 1983) indicate nonlinear responses in semiconductor (CdS/Se) doped glasses, commercially available as color glass filters, that are orders of magnitude higher than corresponding nonlinearities within CS₂, in addition to possessing subnanosecond response times. We have performed experiments upon such glasses in an effort to fabricate nonlinear optical waveguides within them via ion-exchange techniques. We have successfully fabricated single mode planar guides, but they are currently too lossy to allow demonstration of any guided wave nonlinearities. Also, we describe experiments in which we have measured (bulk) DFWM grating lifetimes with greater precision than previously reported. Results indicate a fast (20 to 50 pico-seconds, depending on the particular glass) electronic response, superimposed upon, but clearly distinguishable from, a slower (10's of nanoseconds) thermal response.
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O'Neill, Laura. "Nanostructured thin film pseudocapacitive electrodes for enhanced electrochemical energy storage." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:8cfa1203-4162-4b85-9df4-ade8023c6489.
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This thesis presents work relating to the fabrication of novel thin film electrodes for energy storage applications, with a focus on low cost, nanostructured transition metal oxides, and electrode manufacture by atomised spray deposition. Iron oxide (FeOx) nanowires were synthesised hydrothermally and combined with multi-walled carbon nanotubes (MWNT) in sprayed electrodes, which provided the necessary conductivity enhancement for effective energy storage. The spray processing technique allowed for facile control over the relative fraction of MWNTs in the sprayed electrodes. Optimised electrodes were investigated in a range of aqueous electrolytes, and the best energy storage behaviour occurred in Na2SO3 with a maximum capacitance from cyclic voltammetry of 312 Fg-1 at a scan rate of 2 mVs-1. The FeOx/MWNT electrodes were investigated for their suitability as lithium-ion battery anodes and showed reasonable energy storage behaviour. Nickel oxide (NiO) electrodes were manufactured by hydrothermal synthesis and annealing followed atomised spray deposition. The performance of the NiO electrodes was enhanced though combination with aqueous graphene suspensions, produced in-house by ultrasonic exfoliation of graphite. The processing route used to combine the nanomaterials was considered and a co-synthesis route resulted in the best performing electrodes. Different substrates were investigated, as the most commonly used Ni-foam substrate reacted with the basic electrolytes necessary for electrochemical activity of NiO. NiO/graphene electrodes showed charge/discharge capacitances of up to 571 Fg-1 at a current density of 10 Ag-1, which was maintained at over 300 F/g at a very high current density of 100 Ag-1. Asymmetric supercapacitor devices were constructed using various combinations of FeOx, NiO, and commercial carbon black electrodes to extend the operating potential window beyond the ~1.23 V limit of symmetric aqueous-electrolyte devices. Power densities of over 20 kWkg-1 were achieved for an FeOx/MWNT-carbon device, which was comparable with current commercial carbon-only supercapacitors.
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Johnson, Matthew B. "Investigations of the Processing-Structure-Property Relationships of Selected Semicrystalline Polymers." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/29009.
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An investigation was carried out on a three stage method (extrusion/annealing/uniaxial-stretching) (MEAUS) utilized to produce semicrystalline polymeric microporous membranes. The two semicrystalline polymers studied were selected based on a set-of-prerequisites proposed for the formation of highly porous membranes via the method in question. The prerequisites included "fast" crystallization kinetics, presence of an ac relaxation, ability to form a planar stacked lamellar morphology with a "good" crystalline orientation upon melt-extrusion, and rapid heat transfer of the film during extrusion. The first polymer was isotactic poly(4-methyl-1-pentene) (PMP), and the second was polyoxymethylene (POM). Three PMP resins were studied, which differed in weight average molecular weight. Three POM resins were also investigated where two of resins were characterized by relatively narrow molecular weight distributions (MWD) ca 2 while the third POM resin possessed a MWD ca 5.9. The melt-extruded film morphologies and orientation values were a consequence of the melt-relaxation times as a result of the resin characteristics and/or the melt-extrusion conditions.
Following the extrusion stage, the effect of annealing (second stage) on film properties was investigated. The annealing variables investigated included the temperature, time, and level of extension applied during annealing. The annealed films were then subjected to the uniaxially stretching stage (third stage) consisting of a cold and hot step, respectively, where deformation was along the extrusion direction. The variables of interest included the cold and hot stretch temperature and extension level. It was found that starting precursor morphology and orientation, annealing conditions, and stretching variables impact the final film microporous morphology and permeability. Additionally, the proposed prerequisites were verified in both the PMP and POM film series.
In addition to the MEAUS study, a comprehensive investigation was conducted of the optical properties of blown and cast films made from conventional Ziegler-Natta catalyzed linear low density polyethylene (LLDPE) as well as metallocene-catalyzed LLDPE resins. From this work, it was determined that in PE blown and cast films made using conventional processing conditions, the optical haze properties are adversely affected due to enhanced surface roughness caused by the formation of spherulitic-like superstructures in polymer melts that possess fast relaxing and low melt elasticity rheological characteristics. This optical property study was also published in J. Appl. Polym. Sci., 77(13), 2845, (2000).Ph. D.
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Jayathilake, D. Subhashi Y. "Microwave-assisted synthesis and processing of transparent conducting oxides and thin film fabrication by aerosol-assisted deposition." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/32450.
Full textAbstract:
Transparent conducting oxides (TCOs) have become an integral part of modern life through their essential role in touchscreen technology. The growing demand for cheap and superior transparent conducting layers, primarily driven by the smart phone market, has led to renewed efforts to develop novel TCOs. Currently, the most widely used material for transparent conducting applications is Sn-doped indium oxide (ITO), which has outstanding optical and electrical properties. This material is expensive though, due to the extensive use of In, and efforts to develop new low-cost transparent conducting oxides (TCO) have become increasingly important. Similarly attempts to reduce the cost of the fabrication and post-sintering steps used in making doped metal oxide thin films through innovative technologies have gained a lot of attention. With these points in mind, this research project has focused on the development of a novel low-cost aerosol assisted physical deposition method for TCO thin film fabrication and the development of new highly conducting materials to replace the expensive ITO for TCO applications. In this study, a new and simple aerosol assisted vapour deposition technique (i.e AACT) is developed to fabricate TCO films using TCO nanoparticle suspensions. Firstly, to test the validity of the method, ITO thin films are fabricated on float glass substrates from a nanoparticle suspension. The influence of the deposition parameters on the structural and opto-electronic properties of the thin films are investigated to understand the intricacies of the process. In order to investigate the fabrication of replacement materials for ITO, a range of doped zinc oxide powders are synthesised and processed using microwave radiation. Nominally, Al doped ZnO (AZO), Ga doped ZnO (GZO), Si doped ZnO (SZO), Cu doped ZnO (CZO) and Mn doped ZnO (MZO) singly doped ZnO powders are all investigated to determine the best metal dopants for transparent conducting ZnO. AZO and GZO pellets are found to present the best electrical conductivity for the singly doped microwave fabricated powders with values of 4.4 x 10-3 and 4.3 x 10-3 Ω.cm achieved reproducibly. In an effort to further improve the properties of ZnO, co-doping experiments, utilising the two best dopants from the previous work (i.e. Al and Ga) is investigated. ZnO structures that are co-doped with Al and Ga (AGZO) are found to exhibit significantly enhanced electrical properties than the singly doped powders. Typically, electrical conductivity value of 5.6 x 10-4 Ω.cm is obtained for AGZO pellets, which is an order of magnitude better than the previously fabricated materials. Finally, the best AZO, GZO and AGZO materials are utilised to fabricate thin films using the previously verified AACT technique. Further investigations into the opto-electrical properties of the resulting thin films is presented prior to the utilisation of the best films in a practical application. Transparent heaters are fabricated using the best AGZO thin films, which are capable of reaching a mean temperature of 132.3 °C after applying a voltage of 18 V for 10 min. This work highlights the potential for using highly conducting AGZO, particularly fabricated by the microwave synthesis route, as a potential alternative for ITO in a wide variety of applications. The research also highlights the advantages of using microwaves in the thermal processing of TCO materials which significantly reduces the energy impact of the production process.
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Grabowski, Henry Casmir. "Updating and Automating the Virginia Tech Single-Plate Interferometer." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/35247.
Full textAbstract:
The single-plate interferometer is a powerful flow visualization and aerodynamic measurement tool. It can provide full-field data for the density distribution in a non-intrusive manner, and it can be used for highly unsteady flows. While the device itself represents a large decrease in complexity over other forms of interferometry, the data reduction procedure has traditionally been laborious and difficult. To remove these difficulties and to improve the accuracy of the Virginia Tech interferometer setup, the software has been revamped into a black box design removing the need to handle the code directly. Furthermore, the software has been made to be platform independent by implementing the algorithms using the Java programming language. New hardware has also been added which further simplifies the setup procedure.
The improved setup and the new software is used to study the flow around a film cooled turbine blade in the Virginia Tech cascade wind tunnel. The study of this flowfield is used as a validation for the new algorithms and to illustrate the ease of use of the system. Through this analysis, the density distribution for the entire flowfield is acquired. Furthermore the use of Plexiglas as window material was tried. This proved to work, however the manufacturing processing of these windows proved relatively difficult. Studying the film layer close to the surface proved difficult because of inherent limitations with the single-plate interferometer.
Master of Science
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Ullah, Syed Shihab. "Solution Processing Electronics Using Si6 H12 Inks: Poly-Si TFTs and Co-Si MOS Capacitors." Thesis, North Dakota State University, 2011. https://hdl.handle.net/10365/28902.
Full textAbstract:
The development of new materials and processes for electronic devices has been driven by the integrated circuit (IC) industry since the dawn of the computer era. After several decades of '"Moore's Law"-type innovation, future miniaturization may be slowed down by materials and processing limitations. By way of comparison, the nascent field of flexible electronics is not driven by the smallest possible circuit dimension, but instead by cost and form-factor where features typical of 1970s CMOS (i.e., channel length - IO ?m) will enable flexible electronic technologies such as RFID, e-paper, photovoltaics and health monitoring devices. In this thesis. cyclohexasilane is proposed and used as a key reagent in solution processing of poly-Si and Co-Si thin films with the former used as the active layer in thin film transistors (TFTs) and the latter as the gate metal in metal-oxide-semiconductor (MOS) capacitors. A work function of 4.356 eV was determined for the Co-Si thin films via capacitance-voltage (C-Y) characterization which differs slightly from that extracted from ultraviolet photoemission spectroscopy (UPS) data (i.e., 4.8 eV). Simulation showed the difference between the C-V and UPS-derived data may be attributed to the existence of 8.3 x 10 (exponent 10) cm-2 interface charge density in the oxide-semiconductor junction. Poly-Si TFTs prepared using Si6 H12-based inks maintained the following electrical attributes: field effect mobility of 0.1 cm2V-1s-1; threshold voltage of 66 V; and, an on/off ratio of 1630. A BSIM3 version 3 NFET model was modified through global parametric extraction procedure to match the transfer characteristics of the fabricated poly-Si TFT. It is anticipated that this model can be utilized for future design simulation for solution-processed poly-Si circuits.
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Kesim, Mehmet Tumerkan. "Sol-gel Processing Of Organically Modified Ito Thin Films And Characterization Of Their Optoelectronic And Microstructural Properties." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614507/index.pdf.
Full textAbstract:
Indium tin oxide (ITO) thin films were formed on glass substrates by sol-gel method. Coating sols were prepared using indium chloride tetrahydrate (InCl3&bull4H2O) and tin-chloride pentahydrate (SnCl4&bull
5H2O) stabilized in organic solvents (acetylacetone and ethanol). First attempt was to synthesize ITO thin films using standard/unmodified coating sols. The effect of calcination treatment in air (300 &ndash
600 °
C) and number of coating layer(s) (1, 4, 7 or 10) on optoelectronic properties (electrical conductivity and optical transparency), crystal structure and microstructure of ITO thin films were investigated. In addition, single-layer ITO thin films with optoelectronic properties comparable to multi-layered films were prepared by employing organically modified coating sols. Oxalic acid dihydrate (OAD) &ndash
a drying/microstructure control agent&ndash
addition to standard sol formulation was achieved. The rationale was to improve the optoelectronic properties of ITO films through enhancement in microstructure and chemical characteristics upon OAD addition. The effects of OAD content in the sol formulation and post-coating calcination treatment on electrical/optical properties of ITO films have been reported. Finally, the effects of post coating drying temperature (100 &ndash
200 °
C) and time (10 &ndash
60 min) on optoelectronic and microstructural properties of OAD-modified ITO thin films were discussed. Thin films have been characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD),x-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-Vis) spectroscopy, fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM) and four-point probe measurement techniques. It was shown that film formation efficiency, surface coverage and homogeneity were all enhanced with OAD addition. OAD modification also leads to a significant improvement in electrical conductivity without affecting the film thickness (45±
3 nm). Highly transparent (98 % transmittance in visible region) ITO thin films with a sheet resistance as low as 3.8±
0.4 k&Omega
/sqr have been obtained by employing coating sols with optimized OAD amount (0.75 M). The optimum post-coating drying temperature (100 °
C) and drying time (10 min) was also determined for 0.75 M OAD-modified ITO thin films.
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Rottmayer, Michael A. "Processing and Properties of Nanocomposite Thin Films for Microfabricated Solid Oxide Fuel Cells." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479823129215478.
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Roxner, Evelina, and Baumeister Ronja Olsmats. "Processing of Sub-micrometer Features for Rear Contact Passivation Layer of Ultrathin Film Solar Cells Using Optical Lithography." Thesis, International Iberian Nanotechnology Laboratory, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-388779.
Full textAbstract:
Thin film copper, indium, gallium, selenide (CIGS) solar cells are promising in the field of photovoltaic technology. To reduce material and fabrication cost, as well as increasing electrical properties of the cell, research is ongoing towards ultra-thin film solar cells (absorption layer thickness less than 500 nm). Ultra-thin CIGS solar cells has shown a decrease in interface recombination and improved optical properties when adding a rear contact passivation layer of aluminium oxide. In this work, the process of creating sub-micrometer features of a passivation layer using conventional optical lithography is investigated. To specify, the objective was to optimize the development conditions in the optical lithography process when fabricating equidistant line contacts in aluminium oxide with 800 nm feature size. It was found that line contacts with smaller feature sizes require longer development time, than line contacts with larger feature sizes. The experiments conducted showed that the pre-set development and exposure conditions used by the NOA group are not optimized for 800 nm or smaller line contacts. Further, for the optical lithography process, silicon substrates are not comparable with substrates of soda lime glass coated with molybdenum. Slight underdevelopment of a sample, showed line contacts smaller than the resolution of the laser used in the exposure – suggesting an alternative method of processing small line contacts with optical lithography.
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Chau, The-Tu. "Microwave ECR plasma processing of thin film semiconductors." 1988. http://hdl.handle.net/1993/16668.
Full text