131 research outputs found
Cristais líquidos discóticos como semicondutores orgânicos para aplicações eletrônicas
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Física, Florianópolis, 2014Nota: Prêmio UFSC de tese 2015Os cristais líquidos (CLs) têm sido reconhecidos recentemente como promissores semicondutores para aplicações na área de eletrônica orgânica. O presente trabalho apresenta a proposta de caracterizar e investigar a potencialidade de novos materiais orgânicos com propriedades líquido-cristalinas para aplicações em dispositivos eletrônicos. Moléculas discóticas constituídas de um centro rígido aromático e cadeias laterais flexíveis vêm sendo amplamente estudada se aplicadas em dispositivos orgânicos tais como os diodos emissores de luz (OLEDs), os transistores de efeito de campo (OFETs) e os fotovoltaicos. Os CLs aliam a organização molecular dos sistemas cristalinos, necessária ao trânsito das cargas, à fluidez de um líquido, facilitando o processamento do material. Eles podem ser processados tanto a partir de solução quanto por evaporação térmica. A principal vantagem na utilização destes materiais é a possibilidade de modificar e controlar a orientação molecular através de estímulos externos, como por exemplo, pela ação de temperatura, aplicação de campos elétrico ou magnético e através de tratamentos de superfície. Com isso pode-se otimizar as suas propriedades ópticas e elétricas. Os CLs discóticos estudados neste trabalho são derivados do centro aromático perileno. Os materiais com o centro perileno vêm sendo empregados como semicondutores tipo-n e têm apresentado elevada mobilidade de carga quando aplicados em dispositivos. Neste trabalho as propriedades mesomórficas, fotofísicas, eletroquímicas e elétricas dos compostos foram investigadas. O comportamento termotrópico dos compostos foi analisado por microscopia óptica de luz polarizada(MOLP), calorimetria diferencial de varredura (DSC) e difração de raio x (DRX). As propriedades fotofísicas foram investigadas através de espectroscopia UV-Vis e espectroscopia de fluorescência. A caracterização morfológica dos filmes finos produzidos pela técnica despin-coating e evaporação térmica foi realizada usando um microscópio de força atômica (AFM). Os níveis de energia LUMO dos compostos foram estimados através da técnica de voltametria cíclica. As propriedades fotofísicas em função da temperatura mostraram uma significativa supressão da fotoluminescência na mesofase colunar causada pela forte agregação molecular do empacotamento p-stacking. As propriedades elétricas foram investigadas através da deposição dos filmes em uma típica estrutura de diodo, ITO/PEDOT:PSS/CL/Ca/Al. A mobilidade de carga foi estudada através da aplicação de um modelo teórico às curvas experimentais de densidade de corrente em função da voltagem aplicada (J/V) e comparada com a mobilidade eletrônica obtida através das técnicas de tempo de voo (TOF) e Foto-CELIV. O alinhamento homeotrópico induzido por tratamento térmico para o composto com o centro perileno diimida resultou em propriedades elétricas aprimoradas, onde foi observado um ganho de quatro ordens de grandeza para a densidade de corrente e cinco ordens de grandeza para a mobilidade. O filme fino produzido pelo processo de evaporação térmica deste composto também apresentou propriedades elétricas notáveis na estrutura de diodo, sendo superior ao desempenho do filme produzido por spin-coating antes do alinhamento. A mobilidade para o filme evaporado foi medida através da estrutura de um transistor e mostrou boa concordância com a mobilidade obtida a partir do modelo aplicado às curvas J/V. A mobilidade para o filme evaporado foi superior a mobilidade encontrada para o filme spin-coating antes do alinhamento, mas inferior a mobilidade exibida pelo filme spin-coating alinhado homeotropicamente na estrutura de diodo. Os dispositivos produzidos a partir da combinação dos dois CLs, em heterojunções de bicamada e de volume, apresentaram um melhor desempenho do que os dispositivos fabricados para os compostos individualmente.Abstract: Liquid crystals (LCs) have been recently recognized as promising semiconductors for applications in the field of organic electronics. This work presents a proposal to characterize and investigate the potential application of new organic materials with liquid-crystalline properties inelectronic devices. Discotic molecules comprising a rigid aromatic core and flexible side chains have been widely studied and applied to organic devices such as light emitting diodes (OLEDs), field effect transistors (OFETs) and photovoltaics. LCs combine the molecular organization of the crystalline systems necessary to the transit of the charge and the fluidity of a liquid, facilitating processing of the material. They can be processed either from solution or by thermal evaporation. The main advantage of using these materials is the possibility of modifying and controlling the molecular orientation by external stimuli, for example, by the action of temperature, applying electric or magnetic fields and through surface treatments. Being possible to optimize their optical and electrical properties.The discotic LCs studied in this work are derivatives of the perylene aromatic core. Materials with perylene core have been used as n-type semiconductors and have shown high mobility of charge when applied to devices. In this work the mesomorphic, photophysical, electrochemical and electrical properties of the compounds were investigated. The thermotropic behavior of the compounds was analyzed by optical polarized light microscopy (MOLP), differential scanning calorimetry (DSC) and x-ray diffraction (XRD). The photophysical properties were investigated by UV-Vis and fluorescence spectroscopy. Morphological characterization of the thin films produced by the technique of spin-coating and thermal evaporation was performed using an atomic force microscope (AFM). The LUMO energy levels of the compounds were estimated using the technique of cyclic voltammetry. The photophysical properties as a function of temperature showed a significant suppression of photoluminescence in the columnar mesophase due to the molecular aggregates caused by the strong p-stacking interactions. The electrical properties were investigated by depositing the films in a typical diode structure, ITO/PEDOT:PSS/CL/Ca/Al. The charge mobility was investigated by applying a theoretical model to experimental curves of the current density as a function of applied voltage (J/V) and compared with the electron mobility obtained by the techniques of time of flight (TOF) and Photo-CELIV. The homeotropic alignment induced by annealing for the compound perylene diimide resulted in improved electrical properties, where a gain of four orders of magnitude for the current density and five orders of magnitude in the mobility was observed. The thin film produced by thermal evaporation process of this compound also showed remarkable electrical properties in a diode structure. It was superior to the performance of the film produced by spin-coating before alignment. Mobility for the evaporated film was measured in a transistor structure and showed good agreement with the mobility obtained from the model applied to curves J/V. The mobility for the evaporated film was higher than the mobility for the spin-coating before alignment, but it was lower than the mobility exhibited by the spin-coating film after annealing in a diode structure. The devices produced from the combination of the two LCs in bilayer and bulk heterojunctions showed better performance than devices manufactured for the compounds individually
Detecting strawberries using different Convolutional Neural Networks
No full textThis paper tries to combat the food waste of strawberries during the harvesting steps.An automatic pipeline must be established to combat this food waste.One of the steps needed in this pipeline is detecting strawberries in images.Therefore, this paper aims to find out which Convolutional Neural Network (CNN) can be best used to detect strawberries. Faster r-cnn, Mask r-cnn and RetinaNet are compared against each other using different setting.Mask r-cnn achieved the highest average bounding box and segmentation mAP with 51.63 and 73.20 respectively.CSE3000 Research ProjectComputer Science and Engineerin
Regulating online harms : an examination of recent developments in the UK and the US through a free speech lens
No full textThe author would like to thank the anonymous reviewers and Dr Hedvig Schmidt for their invaluable feedback on previous drafts of this article.Peer reviewe
Biomechanical properties of canine corticocancellous bone frozen in normal saline solution.
No full textEleven pairs of canine metacarpal bones, 10 pairs of metatarsal bones, and 7 pairs of ribs were harvested cleanly and prepared for banking at -20 C for 1 year. One bone of each pair was randomly assigned to 1 type of storage: plastic pack vs immersion in a normal solution of sodium chloride. The contralateral bone was assigned to the opposite treatment. Six pairs of metacarpal bones and 5 pairs of metatarsal bones were tested in torsion to failure. No significant difference was found within pairs. All ribs, 5 pairs of metacarpal bones, and 5 pairs of metatarsal bones were loaded in 4-point bending to failure. The energy absorbed at failure and the ultimate displacement of ribs and metacarpal and metatarsal bones were increased by 25 to 30% and 18 to 24%, respectively, when the bones were frozen in isotonic saline solution. Corticocancellous grafts frozen in normal saline solution are biomechanically less fragile and brittle than grafts stored in plastic without saline solution.journal article1995 Junimporte
The design of a zero-effluent discharge system for Westcoast Energy inc.’s Fort Nelson Gas Plant
No full textThis project was initiated by Westcoast Energy Inc. (Westcoast) to examine the feasibility of
transforming their Fort Nelson Gas Plant (FNGP) into a zero-effluent discharge (ZED) facility.
Water flow and water chemistry data were collected at the plant. The resulting data set was used to
identify water leaks in the existing distribution network, as well as to identify methods of
optimizing water use at this facility. Designs for implementing a Z ED protocol at the FNGP were
then developed and subsequently evaluated with a computer simulator.
A total of 18 Z E D models were constructed using reverse osmosis (RO) membranes,
nanofilters and other Z ED technology. The final disposal mechanism in 10 of the 18 scenarios was
a brine concentrator - spray dryer (BCS) assembly, which reduced all remaining wastewater into a
solid waste. In the other 8 Z ED designs, final concentrates were disposed of in a deep well. The
best deep well configuration was a 1-stage RO filter; the necessary equipment, excluding the deep
well, would cost an estimated 1.61 and $1.79 million US dollars,
respectively. A step by step approach by which the FNGP can be transformed into a Z ED facility
is detailed in Chapter 8.0 of this report.
While it is possible to implement a Z ED program at the FNGP, there are consequences to this
course of action which need to be considered. The most important is final waste management.
Regardless of whether a deep well or a BCS unit is used, either system will have to be built and
operated in such a way that the final waste products produced by the Z ED treatment train do not
migrate off-site, as this action would violate the Z ED principle. Once a Z E D program is initiated,
wastewater and/or waste solids produced at the FNGP will no longer disappear with the FNR;
they will remain on-site indefinitely.Applied Science, Faculty ofCivil Engineering, Department ofGraduat
Acquisition of weather and ground data for Skylab
No full textThere are no author-identified significant results in this report
The Quaker City: George Lippard's critique of capitalism through sensational advocacy for the disenfranchised
No full textThesis (M.A.)-- Wichita State University, College of Liberal Arts and Sciences, Dept. of EnglishNineteenth-century author and journalist George Lippard advocated for the
underprivileged by devoting himself to his self-founded labor union, "The Brotherhood of the
Union," as well as by incorporating fresh and fiery commentary on the political issues of the day
into his fiction. Novels like Empire City and New York addressed corruption in local politics,
exploitative practices in the emerging finance industry, and the horrors of slavery. Yet, Lippard's
most popular work, The Quaker City, or the Monks of Monk Hall (1845), most clearly provides a
gritty and sensationalized depiction of the political and social corruption rampant in Philadelphia
in the mid-1800s.
In the following thesis, I explore how George Lippard's novel engages with the
antebellum period's unique intersection of spectacle, disability, and labor in order to argue that,
through the character of Devil Bug, Lippard exemplifies how a marginalized body might make
his own way as an independent businessman amidst the capitalist society that attempts to exploit
or negate bodies like his own. In my first section, I turn to the sensationalist popular culture that
prevailed in Lippard's time (freak shows, dime museums, city penny papers, etc.) and his own
engagement with this culture that turned the human body into spectacular entertainment. In my
second section, I further argue how the rise of Northern factory systems reinforced the notion of
the body as an object to be capitalized upon, and how I see Lippard rejecting this corruption of
the body. My final section examines Devil Bug's success operating within this capitalist system,
despite his non-normative physicality. However, I also uncover the drawbacks of Devil Bug's
participation in the capitalist system: although Devil Bug attempts to counteract his isolated
"abnormal" physical state by developing relationships, his all-consuming "goold"-focused
mindset problematically drives him to define these relationships as economic transactions
The analysis of amphorae from Carthaginian settlement assemblages
No full textThis paper discusses the development of amphora studies in Carthage within the frame of
general Phoenician-Punic amphora studies. Building upon an approach applied by Babette
Bechtold and the present author, the amphora material within a stratigraphical sequence in the
Hamburg excavations, below the Decumanus Maximus in Carthage, is analysed. It is suggested
that the rise of local amphorae started already within the first quarter of the seventh century
BCE, earlier than previously thought. Also, the importance of contextual analysis of amphora
finds, and the inclusion of amphora wall sherds in such analyses, is advocated
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