by Chiah Man Fat. / "March 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Studying quasi-one-dimensional (1D) semiconductor nanostructures is an attractive and active research field in nanoscience and nanotechnology. Their controllable growth is the foundation for observing novel properties and fabricating useful nano-devices and is also a challenge. / We believe that our work in perfecting the fabrication of aligned 1D semiconductor nanostructures and control of their morphology, crystal structure and orientation will shed more light on the understanding on 1D physics and advancement in nanotechnology. / We have studied the control of the structure, morphology and alignment of Zn-Cd-Se 1D nanostructures by fine tuning their growth conditions and judiciously choosing substrates in a metalorganic chemical vapor deposition (MOCVD) reactor. We found that the products are zincblende structured nanoneedles at relatively low temperatures and pressures, and wurtzite structured nanowires at high temperatures and pressures. We have fabricated aligned 1D nanostructures of different chemical compositions by exploiting the epitaxial relationship between the lattices of Zn-Cd-Se system and GaAs substrate. From the systematic studies of the orientations of the aligned samples, we demonstrated that they can be controlled by the crystallographic surface of the substrate. We also found that the orientation can be affected by the growth temperature. Three growth models are suggested to explain the aligned growth for zincblende and wurtzite 1D nanostructures and complex shaped three-bladed nanoswords. Observations and angular measurements of the orientations and growth directions by electron microscopy and analyses by pole stereographs offer supporting evidences for the models. Polarized photoluminescence studies of individual CdSe nanowires obtained under controlled growth have been achieved. / Liu, Zhuang = 通過金屬有機物化學氣相沉積法合成晶體結構, 形貌及生長取向性可控的硒鋅鎘族准一維納米結構 / 劉壯. / "July 2007." / Adviser: Sui Kong Hark. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1062. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract in English and Chinese. / School code: 1307. / Liu, Zhuang = Tong guo jin shu you ji wu hua xue qi xiang chen ji fa he cheng jing ti jie gou, xing mao ji sheng chang qu xiang xing ke kong de xi xin ge zu zhun yi wei na mi jie gou / Liu Zhuang.

Submitted by PPG Engenharia e Tecnologia de Materiais (engenharia.pg.materiais@pucrs.br) on 2018-10-24T19:04:42Z No. of bitstreams: 1 dissertacao.loris.pdf: 3349640 bytes, checksum: 322a19b58e9bb00ff35471c3d49f70e1 (MD5) / Approved for entry into archive by Sheila Dias (sheila.dias@pucrs.br) on 2018-10-26T12:32:00Z (GMT) No. of bitstreams: 1 dissertacao.loris.pdf: 3349640 bytes, checksum: 322a19b58e9bb00ff35471c3d49f70e1 (MD5) / Made available in DSpace on 2018-10-26T12:38:44Z (GMT). No. of bitstreams: 1 dissertacao.loris.pdf: 3349640 bytes, checksum: 322a19b58e9bb00ff35471c3d49f70e1 (MD5) Previous issue date: 2018-08-31 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Due to the usual biological, antimicrobial and antioxidant activities, the essential oils have a potential interest in several industries as food, pharmaceutical, cosmetics, perfumery, hygiene and cleaning, in the manufacture of paints and in biological control of the agricultural pests. With the market?s growth, alternatives have been sought for economic and social development, while the nature is preserve in to keep natural resources available for the next generations. Aiming at further discussions on the theme environmental preservation, a theoretical and practical research was introduced through the essential oil extraction process of the aromatic plant Pentacalia desiderabilis (Velloso) Cuatrec., by obtaining and characterizing the product allied to proposals for the generated residues destination. In order, the extraction process was done with a pilot steam distillation unit at three different pressure conditions. After the extractive method, are produced: the essential oil and the liquid (aqueous extract and hydrolyzate) and solids (remaining aromatic plant) residues. Three mathematical models were tested to simulate the extraction process. The antioxidant and antimicrobial activity of oil and aqueous extract was evaluated. The essential oil?s chemical composition and aroma was also studied. The solid residue was assess as a possible biosorbent for the adsorption of methylene blue, caffeine and chromium. According to the experimental data, the diffusive one-dimensional model for rectangular geometry proved to be the most adequate. The results also showed that the extracted essential oil, as well as the evaluated solid and liquid residues, have biotechnological potential to be explored. / Devido ?s frequentes atividades biol?gica, antimicrobiana e antioxidante, os ?leos essenciais despertam interesse em diversas ind?strias, tais como aliment?cia, farmac?utica, cosm?tica, de perfumaria, higiene e limpeza, como tamb?m na fabrica??o de tintas e no controle biol?gico de pragas agr?colas. Com o crescimento do mercado surgem debates sobre alternativas de desenvolvimento econ?mico, social e que, ao mesmo tempo, preservem a natureza de modo a manter os recursos naturais dispon?veis para as pr?ximas gera??es. Com o objetivo de ampliar estudos que apresentem discuss?es sobre o tema preserva??o ambiental, realizou-se uma pesquisa te?rica e pr?tica em rela??o ao processo de extra??o do ?leo essencial da planta arom?tica Pentacalia desiderabilis (Velloso) Cuatrec., atrav?s da obten??o e caracteriza??o do produto aliado a propostas para a destina??o dos res?duos gerados. Para tanto, a extra??o foi realizada com um equipamento em escala piloto de destila??o por arraste a vapor em tr?s diferentes condi??es de press?es. Ap?s o processo extrativo, s?o produzidos: o ?leo essencial e os res?duos l?quidos (extrato aquoso e hidrolato) e s?lidos (planta arom?tica remanescente). Tr?s modelos matem?ticos foram testados para simula??o do processo de extra??o. Avaliou-se a capacidade de atividade antioxidante e antimicrobiana do extrato aquoso e do ?leo, sendo que este ?ltimo tamb?m foi estudado em rela??o a sua composi??o qu?mica e seu aroma. Analisou-se a utiliza??o dos res?duos s?lidos como poss?veis biossorventes mediante ensaios de adsor??o com azul de metileno, cafe?na e cromo. De acordo com os dados experimentais, o modelo difusivo unidimensional para geometria retangular mostrou-se o mais adequado. Os resultados tamb?m apresentaram que o ?leo essencial, assim como os res?duos s?lidos e l?quidos avaliados, possuem potenciais biotecnol?gicos a serem explorados.

Resumo: Este trabalho tem como objetivo a análise da influência de parâmetros adimensionais e grandezas dimensionais no projeto de turbomáquinas operando em diferentes situações de pressão, temperatura e vazão mássica de vapor. O trabalho é divido em duas partes principais, sendo que inicialmente são analisados os parâmetros adimensionais e as grandezas dimensionais que influenciam diretamente o valor do rendimento interno das turbomáquinas térmicas que utilizam o vapor como fluido de trabalho. Na segunda parte do trabalho são abordadas as classes de pressão e rotação específica, e sua influência no comportamento de parâmetros adimensionais. A aplicação dos resultados está diretamente ligada a especificação de turbomáquinas em sistemas de cogeração para aproveitamento de fluxos térmicos provenientes de processos, queima de combustíveis ou gases de escape de uma máquina térmica, para os quais os projetistas necessitam estimar o rendimento de tais componentes por ocasião da análise de viabilidade econômica. / Abstract: This work has as objective the analysis of the influence of dimensionless parameters and dimensional greatness in the project of turbomachinery operating in different pressure situations, temperature and flow steam. This work is shared in two main parts, which are initially analyzed the dimensionless parameters and the dimensional greatness that directly influence the internal efficiency of the thermal turbomachinery that using steam as the working fluid. In the second part of the work are accosted the classes of pressure and specific rotation, and its influence on the behavior of dimensionless parameters. The application of the results is directly linked to the specification of turbomachinery in cogeneration systems for use of heat flows from processes, burning of fuel or the exhaust gases of a thermal machine, for which the designers needs to estimate the efficiency of such components at analysis of economic feasibility. / Orientador: Paulo Magalhães Filho / Coorientador: José Nédilo Carrinho de Castro / Banca: Carlos Daniel Ebinuma / Banca: José Rui Camargo / Mestre

There is a growing need for the clean generation of electricity in the world, and increased efficiency is one way to achieve cleaner generation. Increased efficiency may be achieved through an improved understanding of the heat flux of participating media in combustion environments. Real-time in-situ optical measurements of gas temperature and concentrations in combustion environments is needed. Optical methods do not disturb the flow characteristics and are not subject to the temperature limitation of current methods. Simpler, less-costly optical measurements than current methods would increase the ability to apply them in more circumstances. This work explores the ability to simultaneously measure gas temperature and H2O concentration via integrated spectral intensity ratios in regions where H2O is the dominant participating gas. This work considered combustion flows with and without fuel and soot particles, and is an extension of work previously performed by Ellis et al. [1]. Five different combustion regimes were used to investigate the robustness of the infrared intensity integral method first presented by Ellis et al. [1]. These included Post-Flame Natural Gas (PFNG), Post-Flame Medium Wood (PFMW), Post-Flame Fine Wood (PFFW), In-Flame Natural Gas (IFNG), and In-Flame Fine Wood (IFFW). Optical spectra were collected as a function of path length for each regime. Methods for processing the spectra to obtain gas temperature, gas concentration, broadband temperature, and broadband emissivity were developed. A one-dimensional spectral intensity model that allowed for specular reflection, and investigated differences between measured and modeled spectral intensities was created. It was concluded that excellent agreement (within 2.5%) was achieved between optical and suction pyrometer gas temperatures as long as 1) the optical probe and cold target used were well-aligned 2) the path length was greater than 0.3 m and 3) the intensity from broadband emitters within the path was smaller than the gas intensity. Shorter path lengths between 0.15 – 0.3 m produced reasonable temperatures with 7 % error while path lengths of 0.05 m or less were as much as 15% in error or the signal would not effectively process. Water vapor concentration was less accurate being at best within 20% (relative) of expected values. The accurate determination of concentration requires first an accurate temperature concentration as well low broadband participation. Some optical concentrations were in error as much as 85%. The 1-D model was compared to the measurement and it was found that the model peaks were sharper and shifted 0.167 cm-1 compared to the measured data. The reason for the shift can be attributed to the uncertainty of the reference laser frequency used in the FTIR. No conclusion was found for the cause of the sharper peaks in the model. The integrated area of bands used to find temperature and concentration matched well between the model and measured spectrum being typically within 3%.

Estágio realizado na Petrogal, S.A. e orientado pelo Eng.º Manuel Leão Tavares / Tese de mestrado integrado. Engenharia Química. Faculdade de Engenharia. Universidade do Porto. 2008

Tese de mestrado integrado. Engenharia Mecânica. Faculdade de Engenharia. Universidade do Porto. 2010

The atmosphere is a heterogeneous system which is rich in potential chemistry. The processes taking place within this system as well as at the interface of its constituents are of immense importance in understanding how the atmosphere in turn can impact the well-being of all living on the surface of earth. Thus, the heterogeneous chemistry of atmospheric aerosols has since long been subjected to extensive scientific investigation, in view of broadening our understanding of this imperative system. In this study, the heterogeneous interactions of water vapor and gaseous HNO3 on goethite (a-FeOOH), a prominent component of mineral dust aerosol is investigated with quartz crystal microbalance (QCM) measurements and attenuated total reflectance - Fourier transform IR (ATR-FTIR) spectroscopy. Laboratory synthesized goethite samples of varying size (microrods of specific surface area 34 m2/g and nanorods of specific surface area 121 m2/g) were used in order to identify the size dependent interaction of goethite with H2O and HNO3. The study revealed that the exposure of goethite to gas phase H2O and HNO3 results in the uptake of these gases via surface adsorption. Additionally, this novel combined approach of QCM and ATR-FTIR spectroscopy allowed for quantification of the amount of uptake while the spectroscopic data provided information on the speciation of adsorbed products. Thus, with the QCM and spectroscopic data in hand, a precise interpretation of the reactivity as well as its size dependence was sought. In a general sense, the reactivity of a substance is believed to increase with decreasing particle size. The results of this investigation show that in the case of H2O, both microrods and nanorods take up water while the total amount of adsorbed water, when normalized to surface area, is similar for both particle sizes. However, for HNO3, the saturation coverage of total and irreversibly bound HNO3 on microrods was observed to be higher than that on nanorods. With supplementary analysis, this anomalous size effect was attributed to structural features such as the involvement of surface hydroxyl groups in determining the reactivity, which would be subjected to change as a function of particle size. Furthermore, an investigation of the behavior of HNO3 reacted goethite in aqueous media and the uptake of H2O and HNO3 at their mutual presence was carried out such as to better understand the effects of atmospheric processing upon dispersal within the hydrosphere. Further analysis is warranted before arriving at a general conclusion on the size-dependent reactivity of goethite. However, we may argue that goethite containing aerosols may indicate the same pattern of reactivity within the atmosphere as that observed here. Thus, the inference of this investigation proves to be significant in broadening our understanding of this atmosphere as well as the entire biosphere as a whole.

Graphene, two dimensional sheet of carbon atoms has recently gained attention as some of its properties are promising for electronics applications e.g. higher mobility that translates to higher operating frequency for devices geared towards radio frequency applications. Excellent optical transmittance combined with its semi metallic behavior makes it an important material for transparent contacts in solar cells. To bring graphene to the production level, synthesis methods are needed for its growth on wafer scale. It has been shown that chemical vapor deposition (CVD) is one of the techniques that can potentially synthesize wafer scale graphene. Recently copper has gained popularity as an important substrate material for graphene growth due to its lower carbon solubility, which allows better control over number of graphene layers. Here we report optimization of graphene growth on copper foils with our home made atmospheric pressure chemical vapor deposition (APCVD) setup. Graphene growth on copper under APCVD was non self-limiting similar to other reports. It was found that apart from growth parameters surface texture plays a very important role in graphene growth. In fact, few layer and bilayer graphene were obtained on the regions where copper surface was not uniform, confirmed by Raman spectroscopy. To improve copper surface texture thin layer of copper film was evaporated by electron beam evaporation before the graphene growth process. After this modification, monolayer graphene was obtained on areas as large as 300 um × 300 um confirmed by Raman area maps. Graphene transfer procedure was also optimized so that graphene on metal surface could be transferred to insulating substrate

Volatile chlorinated solvents such as trichloroethylene (TCE), 1,2 dichloroethane (1,2 DCA), and perchloroethylene (PCE) have been identified in the indoor air of residences located near Hill Air Force Base (AFB), Utah. These vapors can originate from either volatilization of contaminates from shallow contaminated groundwater and transport into residences or from sources within the residence. The focus of the thesis was the development of a testing strategy for determining sources of TCE, 1,2 DCA, and PCE in the indoor air of residences near Hill AFB. Eight residences were selected for this study by Hill AFB based on prior detections of TCE, 1,2 DCA, and PCE in indoor air. Residents were asked to turn off the heating, ventilation, and air conditioning (HVAC) system and keep windows and doors closed for at least 3 hours prior to the sampling visit to reduce mixing of residence air. Indoor air samples were collected on Tenax© sorbent tubes from various locations within the residences to determine the location of the potential source(s). Sampling tubes were analyzed by thermal desorption gas chromatography/mass spectrometry (GC/MS). Results from a tracer experiment using sulfur hexafluoride gas confirmed the effectiveness of sampling approach. In cases where elevated levels of chlorinated solvents were found, the suspected source materials(s) were removed and the room air was re-sampled. If removal of the materials reduced or eliminated indoor air contamination, an emission chamber was used to determine contaminant emission from the materials. Sources were identified in three of the sampled residences. Sampling in two of the residences was discontinued due to scheduling problems. Sources were not located in the remaining residences. The emission of contaminants from items identified as sources in two of the residences was measured using an emission chamber developed for this project. An ornament from residence U8-8452 emitted 36.4 ng/min/cm2 of 1,2 DCA. The emission of 1,2 DCA from a wedding dress located at residence U8-8211 was below the method detection limit of 1.99 pg/min/cm2 but the emission of PCE was 18.9 ng/min/cm2 and decreased by a factor of 7 during repeated measurements.