Submitted by Mario BC (mario@bc.ufrpe.br) on 2018-07-23T14:50:16Z No. of bitstreams: 1 Nathalia Barbosa da Silva.pdf: 2192959 bytes, checksum: b37dabac91b4ee92a2aed0b0c84c84ab (MD5) / Made available in DSpace on 2018-07-23T14:50:16Z (GMT). No. of bitstreams: 1 Nathalia Barbosa da Silva.pdf: 2192959 bytes, checksum: b37dabac91b4ee92a2aed0b0c84c84ab (MD5) Previous issue date: 2017-02-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The grape cv. Sweet Sapphire® is a new hybrid variety which has as its main characteristics the black color, seedless and a larger shape than the common grape, is described as elongated tubular with a dimpled end. This new variety, cultivated in the city of Petrolina-PE, was submitted to the connective drying to obtain raisins, and this study had as objective to evaluate the potential of grape cv. Sweet Sapphire® for the production of raisins, to define the influence of drying temperature and chemical immersion pretreatment (K2CO3 and extra virgin olive oil solutions) on the final quality of the raisins, as well as determining the effects of the convective drying on the physicochemical characteristics, the content of phenolic compounds, antioxidant properties and sensorial evaluation of the obtained product. In order to define the optimal drying conditions, factorial design 24-1 was applied, having as independent variables the concentration of K2CO3 (2 to 6%), concentration of extra virgin olive oil (0.5 to 2.5%), time immersion (0.5 to 5 min) and drying temperature (45 to 60). The drying temperature was the variable that influenced significantly the moisture, water activity, soluble solids and weight of the samples, while the immersion time influenced the phenolic content. In this way, the optimal drying condition for obtaining raisins cv. Sweet Sapphire® was a temperature of 55°C, immersion time of 2.5 minutes, concentration of K2CO3 of 2% and of extra virgin olive oil of 0.5%, showing significant efficiency in reducing the total drying time. The grapes in nature and raisins were submitted to chemical composition and physico-chemical analyzes and the difference between the evaluated parameters was significant, with concentration in the content of compounds due to loss of moisture. The raisin presented low firmness; high content of phenolic compounds and total anthocyanins and, consequently, exhibited antioxidant potential, since it demonstrated efficiency in the capture of the radicals DPPH● and ABTS+• and ferric reduction (FRAP). The obtained raisins presented satisfactory sensorial quality (percentage of acceptability greater than 70%) and suitable intention of purchase by the consumers, being able to be considered a food with functional characteristics, with potential for the diversification of the commercial production, making it possible to obtain of a new competitive product on the commerce. / A uva cv. Sweet Sapphire® é uma nova variedade de uva híbrida que possui como características principais a cor negra, sem sementes e um formato maior que a uva comum, descrito como tubular alongada com uma extremidade convinde. Esta nova variedade, cultivada no município de Petrolina-PE, foi submetida à secagem conectiva para obtenção de uva-passa, e este estudo teve como objetivo avaliar o potencial da uva cv. Sweet Sapphire® para a produção de uva-passa, verificando a influência da temperatura de secagem e do pré-tratamento químico de imersão (soluções de K2CO3 e azeite de oliva extra virgem) na qualidade final das uvas-passas, bem como determinar os efeitos da secagem convectiva sobre as características físico-químicas, o teor de compostos fenólicos, propriedade antioxidante e qualidade sensorial do produto obtido. Para definir as melhores condições de secagem foi aplicado o planejamento fatorial 24-1 tendo como variáveis independentes: a concentração de K2CO3 (2 a 6% p/v), concentração de azeite de oliva extra virgem (0,5 a 2,5% v/v), tempo de imersão (0,5 a 5 min) e temperatura de secagem (45 a 60ºC). A temperatura de secagem foi a variável que influenciou significativamente na umidade, atividade de água, sólidos solúveis e peso das amostras, enquanto que o tempo de imersão influenciou no teor de fenólicos. Desta forma, a melhor condição de secagem para obtenção da uva-passa cv. Sweet Sapphire® foi temperatura de 55°C, tempo de imersão de 2,5 minutos, concentração de K2CO3 de 2% e de azeite de oliva extra virgem de 0,5%, mostrando eficiência significativa na redução do tempo total de secagem. As uvas in natura e as uvas-passas foram submetidas às análises de composição química e físico-química e a diferença entre os parâmetros avaliados foi significativa, ocorrendo concentração no conteúdo de compostos devido a perda de umidade. A uva-passa apresentou baixa firmeza; elevado teor de compostos fenólicos e antocianinas totais e consequentemente, exibiu potencial antioxidante, uma vez que demonstrou eficiência na captura dos radicais DPPH● e do ABTS+• e na redução de ferro (FRAP). A uva-passa obtida apresentou qualidade sensorial satisfatória (percentual de aceitabilidade maior que 70%) e boa intenção de compra por parte dos consumidores, podendo ser considerada um alimento com características funcionais, com potencial para a diversificação da produção comercial, tornando possível a obtenção de um novo produto competitivo no mercado.

Current design models, approaches and theories are highly fragmented, have seldom been compared with one another, and rarely attempted to be consolidated. Novelty is a measure of creativity of engineering products and positively influences product success. Using physical laws and effects for designing can improve the chances of creativity but they cannot be used directly owing to their inadequate current representations. It is important to address activities, outcomes, requirements and solutions in designing. Conceptual design is an early phase in engineering design and needs to be supported better. A systematic approach for designing often increases effectiveness and efficiency. Thus, the broad objective of this thesis is to develop and validate a comprehensive understanding of how designing occurs during the conceptual phase of engineering design, and to support variety and novelty of designs during this phase. The approach followed is: (a) formulate and validate an understanding of novelty and its relationships to the designing constructs, in current designing, and(b)develop and validate a support, founded on the current designing, to improve novelty. The understanding and the support are addressed, respectively, through an integrated model and a systematic framework for designing; the model and the framework comprise activities, outcomes(including laws and effects), requirements and solutions. An integrated model of designing, GEMS of SAPPhIRE as req-sol is developed by combining activities(Generate, Evaluate, Modify, Select– GEMS), outcomes (State change, Action, Parts, Phenomenon, Input, oRgans, Effect–SAPPhIRE), requirements (req) and solutions (sol), identified from a comprehensive survey of existing design models and approaches. Validation of SAPPhIRE model with existing systems indicates that the model can be used to describe analysis and synthesis, both of which together constitute designing. Validation of the integrated model using existing videos of design sessions, to check if all its constructs are naturally used in designing, reveals that:(a) all the constructs are naturally used;(b) not all the outcomes are explored with equal intensity;(c) while high numbers of action and parts are observed, only low numbers of phenomenon, effects and organs are found. Empirical study using another set of design sessions to study the relationships between novelty and the outcomes reveals that novelty of a concept space depends on the variety of the concept space, which in turn depends on the variety of the idea space explored. Novelty and variety of a concept space also depend on the number of outcomes explored at each abstraction level. Thus, phenomena and effects are also vital for variety and novelty. Based on the above, GEMS of SAPPhIRE as req-sol framework for designing is proposed. The framework is divided into: Requirements Exploration Stage(RES) and Solutions Exploration Stage(SES). In RES and SES, requirements and solutions respectively at all the abstraction levels including SAPPhIRE are generated, evaluated, modified and selected. The framework supports task clarification, conceptual and early embodiment phases of designing, and provides process knowledge. Comparison of the framework against existing design models, theories and approaches reveals that:(a) not all existing models, theories and approaches address activities, outcomes, requirements and solutions together;(b) those that address all these constructs together do not make a distinction between requirements and solutions; and(c) no model or approach explicitly addresses novelty. The usability of the framework and Idea-inspire is assessed by applying them in an industrial project for designing novel concepts of lunar vehicle mobility system. The use of this combined support enables identification of critical requirements, development of a large variety of ideas and concepts. One of these concepts is physically and virtually modelled, and tested, and is found to satisfy all the requirements. A catalogue of physical laws and effects is developed using SAPPhIRE model to provide assistance to designers, especially for phenomena, effects and organs. Observations found during this development are reported. A comparative validation of the framework and the catalogue for their support to design for variety and novelty is done using comparative observational studies. Results from the observational studies reveal that the variety and the novelty of concept space improve with the use of the framework, or with the frame work and the catalogue, as compared to variety and novelty with no support.

No abstract available. / Thesis (PhD)--University of Pretoria, 2010. / Physics / unrestricted

Experimental evidence is presented that supports the theory that beats between transverse modes are responsible for the fast modulation carried on occasions by laser relaxation oscillations. / Thesis / Master of Engineering (ME)

No description available.

No description available.

This dissertation focuses on developing new technologies for ultra-low-cost sapphire fiber-optic high-temperature sensors. The research is divided into three major parts, the souceless sensor, the simple Fabry-Perot (F-P) interrogator, and the sensor system. Chapter 1 briefly reviews the background of thermal radiation, fiber optic F-P sensors, and F-P signal demodulation. The research goal is highlighted. In Chapter 2, a temperature sensing system is introduced. The environmental thermal radiation was used as the broadband light source. A sapphire wafer F-P temperature sensor head was fabricated, with an alumina cap designed to generate a stable thermal radiation field. The radiation-induced optical interference pattern was observed. We demodulated the temperature sensor by white-light-interferometry (WLI). Temperature resolution better than 1°C was achieved. Chapter 3 discusses a novel approach to demodulate an optical F-P cavity at low-cost. A simple interrogator is demonstrated, which is based on the scanning-white-light-interferometry (S-WLI). The interrogator includes a piece of fused silica wafer, and a linear CCD array, to transform the F-P demodulation from the optical frequency domain to the spatial domain. By using the light divergence of an optical fiber, we projected a tunable reference F-P cavity onto an intensity distribution along a CCD array. A model for S-WLI demodulation was established. Performance of the new S-WLI interrogator was investigated. We got a good resolution similar to the well-known traditional WLI. At last, we were able to combine the above two technologies to a sapphire-wafer-based temperature sensor. The simple silica wafer F-P interrogator was optimized by focusing light to the image sensor. This approach improves the signal to noise ratio, hence allows the new integrator to work with the relatively weak thermal radiation field. We, therefore, proved in the experiment, the feasibility of the low-cost sourceless optical Fabry-Perot temperature sensor with a simple demodulation system. / PHD

As specialized materials are developed for various applications, it becomes desirable to test them under adverse conditions, such as at elevated temperatures and in harsh environments. It is increasingly important that sensors be developed to meet the growing needs of research and industry. The ability of sapphire to withstand elevated temperatures and many chemically harsh environments has long been recognized. However, currently available sapphire fiber possesses poor optical quality and is not available with a cladding. It has found use in a variety of temperature sensors, but the investigation of sapphire-based strain and displacement sensors has been limited. The primary development of a white-light Michelson interferometer that utilizes a sapphire fiber sensing head is presented in this thesis. Development includes efforts to combat the poor optical quality of the sapphire fiber, minimize polarization mode fading, and preferentially excite the fundamental mode of the sapphire fiber. This thesis demonstrates the feasibility of fabricating a Michelson white-light interferometer capable of measuring displacements in environments ranging from room temperature to 800 degrees Celsius. The sensor developed in this work is capable of measuring displacements exceeding 6.4 millimeters at room temperature, and exceeding 1 millimeter at 800 degrees Celsius. This thesis also presents the application of this sensor to the alignment of a sapphire-fiber based Fabry-Perot sensor. This technique allows the Fabry-Perot sensor to be aligned so that usable fringes are always obtained. Alignment of the sapphire-fiber based Fabry-Perot sensors has been considered prohibitively difficult. / Master of Science

In this thesis, we report the development of two types of optical sensors, one for high temperature pressure measurements and the other for real-time particle detection. With a high melting temperature (over 2000°C), low optical loss, and excellent corrosion resistance, sapphire (α-Al₂O₃) is ideal for high temperature sensing applications. Fabry-Perot (FP) cavity with optical interrogation of pressure response. The prototype is based on an extrinsic FP interferometer design and is constructed by combining reactive ion etching (RIE) with direct wafer bonding. Long-term testing proves that the adhesive-free wafer bond is sufficient to create a sealed Fabry-Perot cavity as a pressure transducer. Pressure measurement over a range of 6 to 200 psi has been demonstrated at room temperature using white-light interferometry. For the other sensor, the goal is to detect the presence of micro- and nanoparticles in real time. The sensor is based on a silica fiber taper, and we aim to detect particle presence by measuring optical scattering and absorption induced by particles attached to the taper surface. To establish the relationship between particle density and optical transmission loss, we first consider a model where Au nanospheres are self-assembled on taper surface through electrostatic interaction. An analytical model is established to describe the adsorption of gold nanospheres onto cylindrical and spherical silica surfaces from quiescent aqueous particle suspensions. The curved surfaces of the fiber taper and microspheres are coated with nm-thick layer of a polycation, enabling irreversible adsorption of the negatively charged spheres. Our results fit well with theory, which predicts that the rates of particle adsorption will depend strongly on the surface geometry. In particular, adsorption is significantly faster on curved than on planar surfaces at times long enough that the particle diffusion length is large compared to the surface curvature. This is of particular importance for plasmonic sensors and other devices where particles are deposited from a suspension onto surfaces which may have non-trivial geometries. We have established a theoretical model that can describe optical loss generated by particles on taper surface. This theory is validated by measuring, in real time, optical loss during the self-assembly of gold nanoparticles. We find that the measured optical loss can be quantitatively explained by the presence of multiple guided modes within the fiber taper region. Based on this work, we incorporate a fiber taper into a cascade impactor and show that welding aerosols attached to the fiber taper surface can induce measurable transmission loss during the welding process. / Ph. D.

The popularity of III-nitride materials has taken up the semiconductor industry to newer applications because of their remarkable properties. In addition to having a direct and wide band gap of 3.4 eV, a very fascinating property of GaN is the band gap tuning from 0.7 to 6.2 eV by alloying with Al or In. The most common orientation to grow optoelectronic devices out of these materials are the polar c-plane which are strongly affected by the intrinsic spontaneous and piezoelectric polarization fields. Devices grown in no polar orientation such as (1 0 –1 0) m-plane or (1 1 –2 0) a-plane have no polarization in the growth direction and are receiving a lot of focus due to enhanced behaviour. The first part of this thesis deals with the development of non-polar epimGaN films of usable quality, on an m-plane sapphire by plasma assisted molecular beam epitaxy. Growth conditions such as growth temperature and Ga/N flux ratio were tuned to obtain a reasonably good crystalline quality film. MSM photodetectors were fabricated from (1 0 -1 0) m-GaN, (1 1 -2 0) a-GaN and semipolar (1 1 -2 2) GaN films and were compared with the polar (0 0 0 2) c-GaN epilayer. Later part of the thesis investigated (1 0 -1 0) InN/ (1 0 -1 0) GaN heterostructures. Further, we could successfully grow single composition nonpolar a-plane InxGa1-xN epilayers on (1 1 -2 0) GaN / (1 -1 0 2) sapphire substrate. This thesis focuses on the growth and characterisation of nonpolar GaN, InxGa1-xN and InN by plasma assisted molecular beam epitaxy and on their photodetection potential. Chapter 1 explains the motivation of this thesis work with an introduction to the III-nitride material and the choice of the substrate made. Polarization effect in the polar, nonpolar and semipolar oriented growth is discussed. Fabrication of semiconductor photodetectors and its principle is explained in details. Chapter 2 discusses the various experimental tools used for the growth and characterisation of the film. Molecular beam epitaxy technique is elaborately explained along with details of the calibration for the BEP of various effusion cells along with growth temperature at the substrate. Chapter 3 discusses the consequence of nitridation on bare m-sapphire substrate. Impact of nitridation step prior to the growth of GaN film over (1 0 -1 0) m-sapphire substrate was also studied. The films grown on the nitridated surface resulted in a nonpolar (1 0 -1 0) orientation while without nitridation caused a semipolar (1 1 -2 2) orientation. Room temperature photoluminescence study showed that nonpolar GaN films have higher value of compressive strain as compared to semipolar GaN films, which was further confirmed by room temperature Raman spectroscopy. The room temperature UV photodetection of both films was investigated by measuring the I-V characteristics under UV light illumination. UV photodetectors fabricated on nonpolar GaN showed better characteristics, including higher external quantum efficiency, compared to photodetectors fabricated on semipolar GaN. Chapter 4 focuses on the optimization and characterisation of nonpolar (1 0 -1 0) m-GaN on m-sapphire by molecular beam epitaxy. A brief introduction to the challenges in growing a pure single phase nonpolar (1 0 -1 0) GaN on (1 0 -1 0) sapphire without any other semipolar GaN growth is followed by our results achieving the same. Effect of the growth temperature and Ga/N ratio on the structural and optical properties of m-GaN epilayers was studied and the best condition was obtained for the growth temperature of 7600C and nitrogen flow of 1 sccm. Strain in the film was quantitatively measured using Raman spectroscopy and qualitatively analyzed by RSM. Au/ nonpolar GaN schottky diode was fabricated and temperature dependent I-V characteristics showed rectifying nature. Chapter 5 demonstrates the growth of (1 0 -1 0) m-InN / (1 0 -1 0) m-GaN / (1 0 -1 0) m-sapphire substrate. Nonpolar InN layer was grown at growth temperature ranging from 3900C to 440C to obtain a good quality film at 4000C. An in-plane relationship was established for the hetrostructures using phi-scan and a perfect alignment was found for the epilayers. RSM images on the asymmetric plane revealed highly strained layers. InN band gap was found to be around 0.8 eV from absorption spectra. The valance band offset value is calculated to be 0.93 eV for nonpolar m-plane InN/GaN heterojunctions. The heterojunctions form in the type-I straddling configuration with a conduction band offsets of 1.82 eV. Chapter 6 focuses on the optimization of nonpolar (1 1 -2 0) a-GaN on (1 -1 0 2) r-sapphire by molecular beam epitaxy. Effect of the growth temperature and Ga/N ratio on the structural and optical properties of a-GaN epilayers was studied and the best condition was obtained for the growth temperature of 7600C and nitrogen flow of 1 sccm. An in-plane orientation relationship is found to be [0 0 0 1] GaN || [-1 1 0 1] sapphire and [-1 1 0 0] GaN || [1 1 -2 0] sapphire for nonpolar GaN on r-sapphire substrate. Strain in the film was quantitatively measured using Raman spectroscopy and qualitatively analyzed by RSM. UV photo response of a-GaN film was measured after fabricating an MSM structure over the film with Au. EQE of the photodetectors fabricated in the (0 0 0 2) polar and (1 1 -2 0) nonpolar growth directions were compared in terms of responsively, nonpolar a-GaN showed the best sensitivity at the cost of comparatively slow response time. Chapter 7 demonstrates the growth of non-polar (1 1 -2 0) a-plane InGaN epilayers on a-plane (1 1 -2 0) GaN/ (1 -1 0 2) r-plane sapphire substrate using PAMBE. The high resolution X-ray diffraction (HRXRD) studies confirmed the orientation of the films and the compositions to be In0.19Ga0.81N, In0.21Ga0.79N and In0.23Ga0.77N. The compositions of the films were controlled by the growth parameters such as growth temperature and indium flux. Effect of variation of Indium composition on the strain of the epilayers was analyzed from the asymmetric RSM images. Further, we report the growth of self-assembled non-polar high indium clusters of In0.55Ga0.45N over non-polar (1 1 -2 0) a-plane In0.17Ga0.83N epilayer grown on a-plane (1 1 -2 0) GaN / (1 -1 0 2) r-plane sapphire substrate. The structure hence grown when investigated for photo-detecting properties, showed sensitivity to both infrared and ultraviolet radiations due to the different composition of InGaN region. Chapter 8 concludes with the summary of present investigations and the scope for future work.