O pau de balsa é uma espécie arbórea que apresenta importância econômica principalmente pelos diversos usos da madeira, e ecológica por sua participação na sucessão florestal. Até o presente momento o principal meio de multiplicação desta espécie tem sido por sementes. A obtenção de mudas clonais é a principal dificuldade para o cultivo em larga escala dessa espécie. Portanto, o uso da técnica de propagação vegetativa para a silvicultura clonal, como por exemplo, o processo de estaquia, torna-se uma ferramenta útil para superar as possíveis dificuldades que as mudas produzidas a partir de sementes trazem para a silvicultura. Este trabalho teve como objetivo avaliar o efeito do diâmetro da estaca, o tratamento com promotor de enraizamento (AIB), diferentes tipos de substrato e o uso da câmara úmida, avaliando-se o enraizamento, a formação de calos e sobrevivência de estacas de Ochroma pyramidale. Para tanto, quatro experimentos foram instalados, o primeiro foi realizado para avaliar a interação entre o diâmetro das estacas a serem divididas entre o fino, médio e espesso, relacionado ao uso de AIB nas concentrações de 0 e 5.000 mg.L-1. No segundo experimento avaliou-se a interação entre a aplicação de AIB nas concentrações de 0, 1000, 2000 e 4000 mg.L-1 e a região de origem das estacas no ramo, em basal, mediana e apical. No terceiro experimento foram avaliados os tipos de substrato (Areia, Carolina II, Fibra de coco e Vermiculita) em interação com as estacas das duas diferentes origens do ramo (mediana e apical). Por fim, no quarto experimento avaliou-se o uso de ambiente protegido por câmara úmida e a aplicação de diferentes concentrações de AIB (0, 2000, 4000 e 6000 mg.L-1). Concluiu-se que a sobrevivência das estacas é maior entre estacas de diâmetros médio e espesso (1 a 2 cm de diâmetro) e entre estacas provenientes da parte basal do ramo. Quanto ao uso de AIB, os maiores índices de sobrevivência são apresentados quando se aplica 1000 mg.L-1 de AIB, e também sem o uso de ambiente protegido por câmara úmida. A formação de calos é maior entre as estacas de diâmetros médio e espesso (1 a 2 cm de diâmetro) e entre as estacas da parte basal do ramo. Em relação à formação de calos e utilização de AIB, as maiores taxas ocorreram na ausência, 1000 e 4000 mg.L-1 de AIB. O enraizamento das estacas O. pyramidale ocorreu quando 6000 mg.L-1 de AIB foi aplicado. / The balsa wood is a tree species that has economic importance mainly by the many uses of wood, and ecological for its participation in the forest succession. Until the present time, the main way of multiplication of this species have been by seeds. Obtaining clone stakes is the main difficulty for large-scale cultivation of this species. Therefore, the use of the vegetative propagation technique for the clonal silviculture, as for example by cuttings process, becomes useful tools for overcome the possible difficulties that seedlings produced from seeds bring to forestry. This work aimed to evaluate the effect of the diameter of the cutting, the treatment with rooting promoter (IBA), different types of substrate and the use of the chamber moist, by evaluating the rooting, the callus formation and the survival of cuttings of O. pyramidale. For this purpose, four experiments were set up, the first one was carried out to evaluate the interaction between the diameter of the cuttings to be divided between thin, medium and thick, related to the use of AIB in the concentrations of 0 and 5,000 mg.L-1. In the second experiment was evaluated the interaction between the application of IBA at the concentrations of 0, 1000, 2000 and 4000 mg.L-1 and the source region of the cuttings in the branch, in basal, median and apical. In the third experiment was evaluated the types of substrate (Sand, Carolina II, Fiber of coconut, and Vermiculite) in interaction with cutting of the two different origins of the branch (median and apical). Finally, in the fourth experiment we evaluated the use of protected environment by the chamber moist and the application of different IBA concentrations (0, 2000, 4000 and 6000 mg.L-1). It was concluded that the survival of the cutting is higher among the cutting of diameters of medium and thick (1 to 2 cm in diameter) and between the cutting originating from the basal branch. As to the use of IBA, the highest rates of survival are shown when applied to 1000 mg.L-1 of IBA, and without the use of environment-protected chamber moist. The callus formation is greater between medium and thick diameters cuttings (1 to 2 cm in diameter) and between cuttings from the branch basal part. Regarding to callus formation and IBA utilization, the highest rates occurred in the absence, 1000 and 4000 mg.L-1 of IBA. The O. pyramidale cuttings rooting occurred when 6000 mg.L-1 of IBA was applied.

O objetivo deste estudo foi avaliar ex vivo a influência do alargamento cervical na determinação do instrumento apical inicial (IAI), no comprimento de trabalho (CT), dos canais radiculares de primeiros molares superiores, e determinar a forma do canal a 1 mm do ápice. Cinqüenta dentes foram divididos aleatoriamente em 5 grupos (n=10) de acordo com o preparo dos terços cervical e médio do canal: GI- sem alargamento; GII- brocas Gates- Glidden (#2, #3) (GG); GIII- AET (S1, SC, S2 e S3); GIV- GT Rotary File (20/06, 20/08, 20/10 e 20/10) (GT); GV- LA Axxess (20.06, 35.06) (LA). Os canais foram explorados com lima tipo K inserindo-se passivamente a lima 08 no CT, e limas de diâmetros sucessivamente maiores até obter a sensação de travamento. Foram feitas secções transversais no CT, analisadas em MEV e a área do IAI e a área do canal radicular foram medidas para verificar a porcentagem que o IAI ocupou no interior do canal em cada amostra. A forma do canal radicular foi classificada em circular, oval e achatada. A análise de variância indicou diferença estatisticamente significante entre a área ocupada pelo IAI entre os grupos experimentais (p<0,0001). Os resultados mostraram que, para o canal mésio-vestibular, os valores decrescentes em porcentagem que o IAI ocupou no interior do canal foram: LA Axxess (66,70 ± 7,10) > GT (44,16 ± 9,35) = AET (44,10 ± 8,88) > GG (33,17 ± 6,68) = sem alargamento (23,85 ± 6,86); para o canal disto-vestibular: LA Axxess (75,12 ± 8,56) > GT (58,68 ± 7,70) = AET (54,66 ± 7,12) > GG (39,76 ± 7,52) > sem preparo (26,90 ± 6,10); e para o canal palatino: LA Axxess (66,55 ± 11,40) > AET (51,98 ± 10,67) = GT (49,50 ± 10,05) > GG (35,70 ± 7,62) > sem preparo (21,43 ± 2,79). A forma do canal foi predominantemente achatada para o canal mésio-vestibular, circular para o canal distovestibular e oval para o canal palatino. Pode-se concluir que o preparo dos terços cervical e médio do canal radicular permite melhor determinação do IAI, e que o preparo cervical com brocas LA Axxess apresentou a melhor adaptação do IAI no CT. / The aim of this study was to investigate ex vivo the influence of cervical preflaring on determination the initial apical file (IAI), in the working length (WL), of the root canals of the maxillary first molars and to determine the shape of the canal at 1 mm from the apex. Fifty teeth were randomly divided into 5 groups (n=10) in accordance with the preflaring of the cervical and middle thirds of the canal: GI - without preflaring; GII - Gates-Glidden burs (#2, #3) (GG); GIII - AET (S1, SC, S2 and S3); GIV - GT Rotary File (20/06, 20/08, 20/10 and 20/10) (GT); GV - LA Axxess burs (20.06, 35.06) (LA). The canals were sized with the type K-file, passively inserting the file 08 in the WL and files with successively greater diameters until a binding sensation was felt. Cross sections were made in the WL, analyzed by SEM and the IAI area and the area of the root canal were measured to verify the percentage that the IAI occupied inside the canal in each sample. The shape of the root canal was classified as circular, oval and flattened. The analysis of variance indicated a statistically significant difference between the area occupied by the IAI and the experimental groups (p<0.0001). The results showed that for the mesiobuccal canal, the decreasing values by percentage that the IAI occupied inside the canal were: LA Axxess (66.70 ± 7.10) > GT (44.16 ± 9.35) = AET (44.10 ± 8.88) > GG (33.17 ± 6.68) = without preflaring (23.85 ± 6.86); for the distobuccal canal: LA Axxess (75.12 ± 8.56) > GT (58.68 ± 7.70) = AET (54.66 ± 7.12) > GG (39.76 ± 7.52) > without preflaring (26.90 ± 6.10); and for the palatal canal: LA Axxess (66.55 ± 11.40) > AET (51.98 ± 10.67) = GT (49.50 ± 10.05) > GG (35.70 ± 7.62) > without preflaring (21.43 ± 2.79). The shape of the canal was predominantly flattened for the mesiobuccal canal, circular for the distobuccal canal and oval for the palatal canal. It may be concluded that the preflaring of the cervical and middle thirds of the root canal allows better determination of the IAI and that the cervical preflaring with LA Axxess burs presented better adaptation of the IAI in the WL.

Nos projetos hidráulicos de irrigação são contabilizadas as perdas de carga totais, que seriam as perdas contínuas ou principais e as localizadas, objetivando maximizar a uniformidade de distribuição de água, caracterizando um conjunto motobomba adequado ao sistema de irrigação e com isso, minimizando os custos anuais e de implantação do projeto. Com o uso da informática, problemas de cálculos complexos são resolvidos com muita facilidade; desta forma pode-se aplicar modelos mais complexo para calculo da perda de carga nos sistemas de irrigação, resultando em valores mais próximos da realidade, com maiores riquezas de detalhes. A perda de carga representa a dissipação de energia da água em forma de calor, ao longo da tubulação, decorrente da resistência ao escoamento oferecida pela viscosidade do fluido e pela inércia das partículas. É variável de acordo com o tamanho das rugosidades da parede do tubo, diâmetro da tubulação e com a velocidade da água. A indústria de plásticos e seus derivados, com o auxilio da engenharia, tem aprimorado a qualidade dos materiais destinados à fabricação dos tubos, principalmente de polietileno. A utilização de tubos fabricados de matérias plásticos, de menor custo, destinados à irrigação tem aumentado nos últimos anos. A flexibilidade desses tubos traz como consequência o aumento do diâmetro interno com o aumento da pressão, fato este já observado em pesquisa e que não são levados em consideração pelos equacionamentos matemáticos utilizados para determinação da perda de carga. O presente trabalho propõe um modelo onde leva em consideração o módulo de elasticidade (E) do tubo para determinar a alteração do diâmetro em tubos elásticos provocada pela pressão, afetando assim a determinação da perda de carga contínua. Conhecer detalhadamente a causa da perda de energia, com intuito de cada vez mais otimizar a energia gasta por área irrigada no cenário brasileiro, passa a ser de fundamental importância. O Modelo Elástico proposto associado à Equação Universal, apresentou índice de desempenho médio de 0,9 sendo considerado com uma estimativa muito boa da realidade. / Total head losses are accounted in the irrigation hydraulic projects, that would be the continuous losses and the local head losses, aiming to maximize the uniformity of water distribution, characterizing an adequate pump set to the irrigation system e thus, minimizing the project implantation and annual costs. With informatics support, complex calculation problems are solved with ease, therefore it is possible to apply more complex models for head loss calculation in the irrigation system, resulting in values closer to the reality, with greater details. The head loss represents the water energy dissipation as heat, along the piping, due to the resistance to the flow offered by the fluid viscosity and by the particles inertia. It is variable according to the size of the rugosities of the pipe wall, piping diameter and the water velocity. plastic industry and its derivates, with engineering support, have improved the quality of the materials for the pipe manufacturing, mainly polyethylene. The usage of plastic material pipes for irrigation, of lowest cost, has risen in the latest years. The flexibility of these pipes leads to the internal diameter increase with pressure increase, fact already observed in research and that are not taken into account by mathematics equating used to determine the head loss. This paper proposes a model where it takes into account the elastic module (E) of the pipe to determine the diameter alteration in elastic pipes due to the pressure, affecting the determination of continuous head loss. Elastic Module proposed associated to Universal Equation, showed average performance rate of 0,9% being considered a extremely good estimative of reality.

GaN nanopore arrays with pore diameters of approximately 75 nm were fabricated by inductively coupled plasma etching (ICP) using anodic aluminum oxide (AAO) films as etch masks. Nanoporous AAO films were formed on the GaN surface by evaporating an Al film onto a GaN epilayer and subsequently anodizing the aluminum. To minimize plasma-induced damage, the template was exposed to CF4-based plasma conditions. Scanning electron microscopy (SEM) analysis shows that the diameter and the periodicity of the nanopores in the GaN were directly transferred from the original anodic alumina template. The pore diameter in the AAO film can be easily controlled by tuning the anodization conditions. Atomic force microscopy (AFM), photoluminescence (PL) and micro-Raman techniques were employed to assess the quality of the etched GaN nanopore surface. Such a cost-effective method to produce nano-patterned GaN template would be useful for growth and fabrication of III-Nitrides based nanostructures and photonic band gap materials. / Singapore-MIT Alliance (SMA)

A major difficulty in the fabrication of nanostructure based electronics is the lack of effective processes capable of precisely arranging nanostructures into predefined positions. Top-down approaches introduce increased complexity and a high cost for practical industrial use, while bottom-up approaches are probabilistic in nature and do not provide precise control of nanostructure properties (i.e., number, diameter), which influence device performance. Alternatively, nanomanipulation promises specificity, precision and programmed motion and its automation may facilitate the large-scale fabrication of nanostructure based devices. This study focuses on the development of an automated contact detection algorithm which positions an end-effector in contact with a target surface without the need for additional equipment, devices or sensors. We demonstrate this algorithm as an enabling feature for automated nano-FET biosensor construction with precise control over nanowire parameters thereby reducing device-to-device variability and also potentially allowing us to optimize individual device performance.

A major difficulty in the fabrication of nanostructure based electronics is the lack of effective processes capable of precisely arranging nanostructures into predefined positions. Top-down approaches introduce increased complexity and a high cost for practical industrial use, while bottom-up approaches are probabilistic in nature and do not provide precise control of nanostructure properties (i.e., number, diameter), which influence device performance. Alternatively, nanomanipulation promises specificity, precision and programmed motion and its automation may facilitate the large-scale fabrication of nanostructure based devices. This study focuses on the development of an automated contact detection algorithm which positions an end-effector in contact with a target surface without the need for additional equipment, devices or sensors. We demonstrate this algorithm as an enabling feature for automated nano-FET biosensor construction with precise control over nanowire parameters thereby reducing device-to-device variability and also potentially allowing us to optimize individual device performance.

Inhalt der Diplomarbeit sind Untersuchungen zur Authentifizierung und Verschlüsselung von drahtlosen Netzwerkverbindungen.

All heat pump cycles have one common feature that connects them to one another; this feature is the presence of a heat exchanger. There are even some heat–driven cycles that are completely composed of heat exchangers, every heat exchanger fulfilling a different, though critical role. The need therefore exists to optimize heat exchangers, more specifically Compact Heat Exchangers (CHE). This study deals with the optimization of such a CHE by determining an optimal hydraulic diameter of the micro–channels in a CHE, for minimal hydraulic losses. Two Computational Fluid Dynamics (CFD) models were developed for a single micro–channel that is present in a CHE. The first model had a semi–circular cross–section, the second a triangular cross–section. The results were verified by comparing it with existing experimental data. Following the verification of the results, the micro–channel was optimized by implementing an optimum diameter for the lowest pressure drop over the micro–channel. This was done for both the semi–circular and triangular micro–channel cross–sections. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2011.

Isothermal flow development, gap instability, and gap vortex street generation in eccentric annular channels have been studied experimentally. A representative paradigm of a flow in a highly eccentric annular channel was examined for a channel having an inner-to-outer diameter ratio d/D = 0.50 and an eccentricity e = 0.8 for a Reynolds number Re = 7300. Observation of the flow development has identified three distinct regions: the entrance region, the fluctuation-growth region and the rapid-mixing region. Weak quasi-periodic velocity fluctuations were first detected in the downstream part of the entrance region, and grew into very strong ones, reaching peak-to-peak amplitudes in the narrow gap that were nearly 60% of the bulk velocity. The dependence on inlet conditions, d/D, e and Re on the development and structure of flows was also investigated. Experimental conditions covered the ranges: 0 ≤ Re ≤ 19000, 0 ≤ e ≤ 0.9 and d/D = 0.25, 0.50 and 0.75. For Re < 7000, the Strouhal number, the normalized mid-gap axial flow velocity and the axial and cross-flow fluctuation intensities at mid-gap were found to increase with increasing Re and to depend strongly on inlet conditions. At higher Re, however, these parameters reached asymptotic values that were only mildly sensitive to inlet conditions. A map was constructed for the various stages of periodic motions vs. e and Re and it was found that, for e < 0.5 or Re < 1100, the flow was unconditionally stable as far as gap instability is concerned. For e ≤ 0.5, transition to turbulence occurred at Re ≈ 6000, whereas, for 0.6 ≤ e ≤ 0.9, the critical Reynolds number for the formation of periodic motions was found to increase with eccentricity from 1100 for e = 0.6 to 3800 for e = 0.9. The use of an empirically derived "mixing layer Strouhal number" permitted a universal description of gap vortex street periodicity in eccentric annular channels. This study has contributed to our understanding of the physical mechanisms that lead to gap instability and the development of a gap vortex street and the dependence of these flow phenomena on the channel geometry and the dynamic conditions of the flow.

All heat pump cycles have one common feature that connects them to one another; this feature is the presence of a heat exchanger. There are even some heat–driven cycles that are completely composed of heat exchangers, every heat exchanger fulfilling a different, though critical role. The need therefore exists to optimize heat exchangers, more specifically Compact Heat Exchangers (CHE). This study deals with the optimization of such a CHE by determining an optimal hydraulic diameter of the micro–channels in a CHE, for minimal hydraulic losses. Two Computational Fluid Dynamics (CFD) models were developed for a single micro–channel that is present in a CHE. The first model had a semi–circular cross–section, the second a triangular cross–section. The results were verified by comparing it with existing experimental data. Following the verification of the results, the micro–channel was optimized by implementing an optimum diameter for the lowest pressure drop over the micro–channel. This was done for both the semi–circular and triangular micro–channel cross–sections. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2011.