Orientador: Magali Conceição Monteiro da Silva / Banca: Natália Soares Janzantti / Banca: Mércia Fátima Manente Bettini / Resumo: O suco de laranja é um produto de grande importância para a economia nacional, tendo papel relevante na pauta de exportações brasileiras. Em torno de 80% da laranja produzida no Brasil é processada na forma de suco de laranja concentrado e congelado (frozen concentrated orange juice-FCOJ). Durante o processamento do suco, podem ocorrer alterações das características do suco influenciando sua aceitação pelo consumidor. Os objetivos desse trabalho foram reunir informações referentes às características da laranja e à produção, à exportação, ao consumo de FCOJ, às etapas do processamento, às alterações sensoriais e físico-químicas que podem ocorrer durante o processamento, e avaliar a aceitação sensorial e a estabilidade físico-química do suco de laranja proveniente das etapas do processamento do suco concentrado e congelado. Uma equipe de 101 julgadores avaliou a cor, a impressão global, o aroma, o sabor e a textura do suco das etapas de extração, de filtração, de concentração, de resfriamento e de mistura de duas coletas, processados no início e no final da safra de 2009 da laranja da variedade Pêra-Rio. A estabilidade físico-química do suco de laranja proveniente das etapas do processamento do suco concentrado e congelado também foi avaliada no decorrer da safra de 2009, em cinco coletas. Foram realizadas análises do teor de sólidos solúveis, da acidez total titulável, de açúcares redutores, de açúcares totais, de ácido ascórbico, além do ratio e pH nos sucos das etapas de extração, filtração, concentração, resfriamento e mistura. Os sucos das etapas de extração e de filtração foram os mais aceitos pelos julgadores em relação aos atributos impressão global, aroma e sabor, e apresentaram maior intenção de compra entre os termos "provavelmente compraria" e "certamente compraria". O suco da etapa de mistura, apesar... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The orange juice is a great importance product to the Brazilian economy, having a relevant role in Brazilian exports. Around 80% of oranges produced in Brazil are processed in the form of frozen concentrated orange juice (FCOJ). During the juice processing can result changes of the juice characteristics, influencing consumer acceptance. The aim of this work was to gather information regarding of orange characteristics and its production, exports and consumption of FCOJ, the processing steps and changes in sensory and physical-chemical properties that may occur during processing and to evaluate the sensorial acceptance and physical-chemistry stability of the juice coming from different steps of the concentrate juice processing. A group of 101 judges evaluated the color, the overall impression, aroma, flavor and texture of the juice from the steps of extraction, filtration, concentration, cooling and blend of two collections, processed at the beginning and end of the crop of pêra-rio orange variety in 2009. The physical-chemistry stability of the juice coming from the steps of processing of the concentrated juice was also evaluated during the 2009 harvest, in five collections. Were analyzed the soluble solids content (SS), total titratable acidity (TTA), reducing sugars (RS), total sugars (TS), ascorbic acid (AA), besides the ratio and pH in the juices of extraction, filtration, concentration, cooling and blend steps. The juices of the extraction and filtration steps were the most accepted for the attributes of overall impression, aroma and flavor, and showed higher purchase intention between "probably would purchase" and "definitely would purchase". The juice of the blend step, despite being added essences to provide better aroma and flavor, had an average accepting less than that of the juice of cooling and concentration steps, which was not added essences, in both collections... (Complete abstract click electronic access below) / Mestre

Com o desenvolvimento e crescimento na produção equina, passou-se a utilizar o concentrado em substituição à parte da forragem na alimentação, principalmente por grãos de cereais ricos em amido, a fim de suprir as necessidades energéticas do animal. O amido não degradado no intestino delgado pode atingir o ceco e cólon, acarretando em mudanças na microbiota e consequentes distúrbios gastrointestinais. O objetivo desse estudo foi avaliar o efeito da suplementação de levedura Saccharomyces cerevisiae sobre a digestibilidade aparente, identificar as implicações nas respostas glicêmicas, insulinêmicas, valores de pH fecal e avaliar o nível de inclusão de levedura para cavalos alimentados com dietas de alta e baixa relação concentrado:volumoso. Foram utilizados oito animais da raça Mini-horse, machos, castrados, com idade média de 36 meses e peso médio inicial de 113±12 kg, em dois experimentos, sendo no experimento 1 utilizado dieta de baixa proporção concentrado:volumoso (BC), constituída de 30% concentrado comercial peletizado e 70% de feno de gramínea, e no experimento 2 utilizado dieta de alta proporção de concentrado:volumoso (AC), constituída de 70% concentrado comercial peletizado e 30% de feno de gramínea, cuja variação foi a inclusão de Saccharomyces cerevisiae, com níveis de 0g (controle), 10g, 20g, e 30g, de produto com concentração de 5x108 UFC/g. O delineamento experimental utilizado foi em quadrado latino duplo 4x4 com medidas repetidas no tempo e os dados obtidos foram submetidos à análise de variância e regressão polinomial com nível de significância de 5%. Para a dieta BC, não ocorreu diferenças na digestibilidade dos nutrientes e na resposta glicêmica e insulinêmica, contudo foi observado efeito quadrático (P=0,0087) para pH fecal, porém os valores permaneceram dentro do considerado ideal para o equilíbrio da microbióta. Com relação à dieta AC, foi observado efeito quadrático nos coeficientes de digestibilidade aparente da MO, FDN, FDA e PB (P=0,0023, P=0,0334, P=0,0238, P=0.0224), respectivamente, assim como para as concentrações plasmáticas de insulina (P=0,0012), no entanto, os valores encontrados não foram diferentes ao tratamento controle. Sendo assim, não foi possível avaliar o efeito da suplementação de levedura Saccharomyces cerevisiae para cavalos alimentados com dietas de baixa e alta relação concentrado:volumoso. / The development and growth in equine production increased the use of concentrate to replace part of the forage in the diet, mainly cereal grains rich in starch, in order to meet the energy needs of the animal. The starch that is not degraded in the small intestine can reach the cecum and colon, resulting in changes in the microbiota and consequently in gastrointestinal disturbance. The objective of this study was to evaluate the effect of supplementation of the yeast Saccharomyces cerevisiae on an apparent digestibility, identify the implications for glycemic and insulinemic responses and fecal pH values, and evaluate the level of inclusion of yeast into horses fed with high and low ratio concentrate: roughage diets. Eight Mini-horses were used: gelding, male, mainly 36- month old, and initial average weight of 113 ± 12 kg in two experiments. It was used in the experiment 1 a low ration concentrate: roughage diet (LC), consisting of 30% commercial concentrate pellets and 70% grass hay, and in the experiment 2, it was used a high ration concentrate: roughage diet (HC) consisting of 70% commercial concentrate pellets and 30% grass hay, which change was the inclusion of Saccharomyces cerevisiae, with levels of 0 g (control), 10g, 20g, and 30g of product concentration of 5x10 8 CFU/g. The experimental design was a double 4x4 Latin Square with repeated measures over the time and the data were subjected to analysis of variance and polynomial regression with a significance level of 5%. In the LC diet, there were no differences in nutrient digestibility, glycemic and insulin response, however it was observed a quadratic effect (P = 0.0087) for fecal pH, but values remained within the considered ideal for the balance of the microbiota. In the AC diet, a quadratic effect was observed in the apparent digestibility of OM, NDF, ADF and CP (P = 0.0023, P = 0.0334, P = 0.0238, P = 0.0224) respectively, as well as for plasma insulin concentrations (P = 0.0012), however, the values were not different to control. Therefore, it was not possible to evaluate the effect of supplementation of yeast Saccharomyces cerevisiae for horses fed with low and high ratio concentrate: roughage diets.

Plank (tongue and groove) wood decking is a product that is commonly used in post and beam timber construction to transfer gravity loads on roofs and floors. In 2010, The National Building Code of Canada changed the application area of the specified concentrated roof live loads from 750 mm x 750 mm to 200 mm x 200 mm. The change was made to better reflect the area which a construction worker with equipment occupies. Preliminary analysis showed that the change in the application area of concentrated loads may have a significant impact on the design of decking systems. Little research or development has been done on plank decking since the 1950’s and 1960’s. An experimental program was undertaken at the University of Ottawa’s structural laboratory to better understand the behaviour of plank decking under uniformly distributed and concentrated loads. Non-destructive and destructive tests were conducted on plank decking systems to investigate their stiffness and failure mode characteristics under uniformly distributed as well as concentrated loads. The experimental test program was complimented with a detailed finite element model in order to predict the behaviour of a plank decking system, especially the force transfer between decks through the tongue and groove joint. The study showed that the published deflection coefficients for uniformly distributed loads can accurately predict the three types of decking layup patterns specified in the Canadian Design Standard (CSA O86, 2009). For unbalanced uniformly distributed loads on two-span continuous layup, it was found that the deflection coefficient of 0.42 was non-conservative. It was also found that under concentrated loads, the stiffness of the decking system increased significantly as more boards were added. A deflection coefficient of 0.40 is appropriate to calculate the deflection for the three types of decking layup patterns specified in the Canadian Design Standard (CSA O86, 2009) under concentrated load on an area of 200 mm by 200 mm. Significant load sharing was observed for plank decking under concentrated loads. An increase in capacity of about 1.5 to 2.5 times the capacity of the loaded boards was found. Furthermore, it was found that placing sheathing on top of a decking system had a significant effect in the case of concentrated load with an increase of over 50% in stiffness and over 100% in ultimate capacity.

A solar simulator was used to test whether a carbon black additive could increase the solar absorption of a low temperature organic PCM (consisting of a eutectic mixture of palmitic acid and stearic acid). Various PCM and carbon black composites (0.01 % to 6 %) were tested, with the 0.06 % carbon black composites showing the fastest temperature increase, reaching 75 °C much quicker (350 % faster) than the pure PCM. All of the tested PCM composites reached 75 °C in less than half the time it took the pure PCM. It can therefore be seen that carbon black is very effective at increasing the solar absorption of the PCM. The carbon black did not have a negative impact on the melting/solidifying onset temperature or the latent heat of the PCM. This proves that at these low concentrations carbon black can help reduce the shortcomings of the PCM without adversely affecting its energy storage properties. The optimal carbon black concentration changes with the size of the PCM: a shallow PCM layer (2 cm) showed the fastest temperature increase at higher concentrations (between 0.06 % and 0.5 % carbon black), while the deep PCM layer (9 cm) showed the fastest temperature increase at lower concentrations (between 0.01 % and 0.08 % carbon black). The poor optical properties of the PCM were vastly improved by the carbon black, making the composite an effective direct solar absorber. The carbon black, however, does not provide meaningful thermal conductivity enhancements. Therefore additional heat transfer enhancements (like graphite) are needed if this novel PCM composite is to be used in a combined system (direct solar absorber, heat transfer fluid and energy storage system). / Dissertation (MEng)--University of Pretoria, 2016. / Chemical Engineering / MEng / Unrestricted

A novel type of parabolic trough collector was characterised using a very basic theoretical model. This model looked at an ideal case and provided a basic expectation that was compared to actual measurements. The model showed that greater improvements can be achieved if heat losses to the environment are limited or omitted. This can be achieved by using a glass shield to insulate the receiver in a vacuum to limit the effect wind has and therefore limit convective losses. The experimental characterisation of the PTC consisted of taking six different temperature measurements to better understand the energy balances taking place. Four different configurations were tested, using two different types of concentrator and in each case a receiver that was either unpainted or painted with a semi matte black paint. The different types of concentrator were either stainless steel sheet metal or discretised glass mirror strips, similar to a linear Fresnel collector. Experimental runs were conducted on cloudless days for an hour and 15 minutes. This allowed for three runs to be performed on a single day. Using the theoretical model and comparing it to the experimental data, an efficiency was calculated. This efficiency averaged 14 % when the receiver was unpainted and 13 % when the receiver was painted for the metal sheets. The glass mirror strips had average efficiencies of 54 % and 45 % for an unpainted and painted receiver respectively. The model is very basic and can be improved upon if more variables are taken into consideration, such as convective heat losses. It was also recommended that wind measurements are taken in future tests. A property looked at to evaluate the effectiveness of each type of configuration was the average energy supplied to the thermal heating fluid over the course of an experimental run. For this the averaged values over all the experimental runs conducted for stainless steel sheet metal were 258 W and 332 W for an unpainted and painted pipe respectively. When using the glass mirrors an average energy value of 1049 W was supplied when the pipe was unpainted and an average of 1181 W was gained in the runs conducted after the pipe had been painted. Painting the receiver had little to no effect. The surface temperature of the receiver after painting the pipe was not higher and a slight increase in the energy gained by water was observed. This was explained by inaccuracies during testing as scattered light may have caused an interference on some of the measurements. There were also human inaccuracies in testing which should be omitted in future tests by implementing, for one, a functional tracking system. Future tests should be designed in such a way to completely omit irradiance affecting the thermocouple taking the measurement. Glass mirrors fared far better than the stainless steel sheet metal counterpart. It was recommended that they are used as the concentrator of choice. Higher efficiencies were achieved and in some cases almost four times the energy was supplied to the water in the pipe. This was attributed to a much lower concentrator temperature, on average 11 °C lower than the temperature of the metal sheets, as well as a much better ability to concentrate sunlight onto a single focal point. However, the glass mirror strips were proven to be very fragile and as such, require protection from the elements. While the strips were lighter and caused less of a load during windy conditions, they were susceptible to oscillations from gusty wind. This led to a number of strips breaking and needed to be replaced. By discretising the strips into individual pieces, they had the benefit of only needing to replace the strips that were damaged. This is also true for all future runs. It is still recommended that a tarp be used to protect the glass mirrors. Using glass mirror strips as a concentrator combined LFC technology with PTC technology and a novel PTC design was achieved. The design still required the installation area of a PTC. The novel design was compared to Industrial Solar’s industrial LFC module, LF-11, as it shares many similarities to LFC technology. The peak thermal output of the rig was significantly lower at 346 W/m2 compared to the industrial value of 562 W/m2. However, the noteworthy differences in design and optimisation between the two modules meant the results achieved were comparable. It is expected that better and more comparable results can be realised once the inherent flaws in the design, such as tracking the sun, aperture size and adding a vacuum absorber, are addressed. It is recommended that more research and emphasis is put into this field as an alternative energy power plant for South Africa. / Dissertation (MEng)--University of Pretoria, 2017. / Chemical Engineering / MEng / Unrestricted

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No description available.

Commercial aluminum (Al) alloys are often precipitation strengthened to improve strength and wear resistance. However, localized corrosion due to the galvanic coupling between the precipitates and Al matrix often leads to degraded performance when these alloys are exposed to corrosive environment. In this work, Al-based solid solution was synthesized to simultaneously improve the strength and corrosion resistance of Al alloys, which ultimately led to high tribocorrosion resistance. Specifically, the effects of testing condition (e.g. sliding frequency) and alloying effects (e.g. Mn and Mo) on the corrosion and tribocorrosion behavior of Al-based binary and ternary solid solutions were studied. To understand the effects of wear condition on the depassivation-repassivation kinetics during tribocorrosion, in the first study, the tribocorrosion behaviors of Al-20 at.%Mn alloys were investigated in simulated seawater by changing the sliding frequency from 0.05 to 1 Hz in reciprocal motion. The results show that the depassivation rate of passive film increased with increasing sliding frequency. Mechanical wear also increased with increasing sliding frequency, which was mainly related to the increase of coefficient of friction and real contact area. Chemical wear tended to increase with scratching frequency, most likely due to faster repassivation kinetics at lower frequency. The surface layer was analyzed by cross-sectional transmission electron microscopy, indicating the passive film was primarily consisted of aluminum oxide where manganese was selectively dissolved. Despite extensive past research, the fundamental understanding of the alloying effects on the atomistic structure, composition, and chemical state of the passive layer of Al alloys and their formation mechanism is still not well understood. In the second study, the effects of Mn on the aqueous corrosion of Al-Mn alloys were investigated. It was confirmed that Mn alloying could enhance the corrosion resistance of Al without participating in the surface oxidation. Atom probe tomography analysis confirmed the absence of Mn in the anodized and corroded surface of Al-Mn alloys. The selective dissolution of Mn in these alloys was believed to increase the free volume at the metal/oxide interface to facilitate the formation of a denser, thinner oxide layer with closer to stoichiometry composition, leading to its enhanced corrosion resistance than pure Al. Lastly, to better understand the corrosion and tribocorrosion resistance of Al-based lightweight concentrated alloys and the effects of alloying concentrations on the structure and property of the passive layer, the third study investigated the effects of a passive element (Mo) and non-passive element (Mn) on the corrosion and tribocorrosion behavior of Al-Mn-Mo alloys. Specifically, Al80Mn8Mo12 exhibited higher corrosion resistance than Al80Mn20 due to the formation of a more compact and less defective passive film, as explained by the roles Mo played in both the substrate and the passive film. It was found that the pitting potential and corrosion current density of Al-Mn-Mo increased with Mo%. The effect of Mo alloying concentration on the tribocorrosion behavior of Al-Mn-Mo alloys was investigated as well. Adding Mo to Al-Mn alloys led to a lower wear and tribocorroison resistance of Al-Mn-Mo alloys. In addition, decreasing Mn and Mo concentrations resulted in a reduction of the tribocorrosion resistance in the ternary alloy, which was mainly dominated by the mechanical response under the selected testing conditions. / Doctor of Philosophy / Various critical current and future applications in the fields of aerospace, transportation, energy, and biomedical industries require not only a strong and tough metal, but one that is robust and reliable when interacting with some very corrosive environment. Such corrosive environment is testing the limits of most engineering metals and challenging the current understanding of the underlying degradation mechanism. For example, strength and wear resistance in most precipitation-hardened Al (aluminum) alloys is often achieved at the expense of sacrificed corrosion resistance, mainly due to micro-galvanic coupling between the soft matrix and hard precipitates. In addition, the performance of Al alloys deteriorates dramatically when there is combined wear and corrosion, i.e. tribocorrosion attack at the surface, due to the depassivation on the wear track as a result of mechanical removal of the passive film. Recent study shows that alloying Al with appropriate transition metals in supersaturated solid solution simultaneously improves the corrosion and wear resistance of Al. In this thesis, Al-Mn and Al-Mn-Mo solid solutions was synthesized and studied to understand the effects of testing condition (e.g. sliding frequency) and alloy composition (e.g. Mn and Mo concentration) on the corrosion and tribocorrosion behavior. First, the depassivation mechanism during tribocorrosion of Al-Mn alloys was investigated by performing tribocorrosion test using different sliding frequency from 0.05 to 1 Hz in 0.6 M NaCl aqueous solution. Results showed that both chemical and mechanical wear increased with increasing frequency. The mechanical wear increased with scratching frequency due to faster depassivation rate and increased real contact area, while chemical wear increased with frequency due to higher repassivation kinetics. Secondly, the effects of Mn on the aqueous corrosion and passivation of Al-Mn solid solution alloys were investigated by electrochemical experiments and advanced surface characterization. It was found that Mn addition enhanced the corrosion resistance of Al without participating in the surface oxidation. A denser, thinner oxide layer was formed on Al-Mn due to the increased free volume at the metal/oxide interface as a result of Mn dissolution. Lastly, the effects of alloying concentration on the aqueous corrosion and tribocorrosion of Al-Mn-Mo alloys were studied experimentally. The pitting potential and corrosion current density of Al-Mn-Mo were found to increase with Mo%. The passive film thickness depended on the total alloy concentration, while its compactness and defect density on the individual ones. The tribocorrosion resistance of Al-Mn-Mo alloys decreased with increasing Mn and Mo concentrations. In summary, the results from this thesis develop mechanistic understanding of the corrosion and tribocorrosion mechanisms of Al-based solid solution alloys, which sheds light on a new alloy design strategy for making lightweight, strong, and corrosion-resistant metals.

This paper is devoted to the fast solution of interface concentrated finite element equations. The interface concentrated finite element schemes are constructed on the basis of a non-overlapping domain decomposition where a conforming boundary concentrated finite element approximation is used in every subdomain. Similar to data-sparse boundary element domain decomposition methods the total number of unknowns per subdomain behaves like $O((H/h)^{d−1})$, where H, h, and d denote the usual scaling parameter of the subdomains, the average discretization parameter of the subdomain boundaries, and the spatial dimension, respectively. We propose and analyze primal and dual substructuring iterative methods which asymptotically exhibit the same or at least almost the same complexity as the number of unknowns. In particular, the so-called All-Floating Finite Element Tearing and Interconnecting solvers are highly parallel and very robust with respect to large coefficient jumps.

Poster exhibited at GPSC Student Showcase, February 24th, 2016, University of Arizona. / To make photovoltaics (PV) and concentrated solar thermal power (CSP) more practical forms of alternative energy, creative innovations to current solar energy methods must be employed. The PVMirror – a new technology – is our solution to that problem. The PVMirror combines PV and CSP technologies by splitting the spectrum of sunlight using a dichroic mirror film. Light that is not transmitted to the solar cell is to instead be reflected to a focus, by way of a curved mirror. This hybrid of technologies is competitive, as it is both efficient and affordable compared to many other innovations in renewable energy. The PVMirror is designed to be an easy and cost-effective replacement to the reflectors used in existing CSP plants. Ultimately, we hope to demonstrate this PVMirror technology on a large scale and market it. As validated from interviewing with industry professionals, this technology has the potential to impact the world of solar energy because many industrial companies and utility-scale CSP project developers are interested in pairing CSP and PV to increase efficiency. Currently, using an outdoor sun tracker, we are testing an 18 inch by 18 inch prototype with four solar cells.