Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Previous studies on wood instability have identified some wood basic properties which influence the timber distortion and shape changes while the wood is losing or gaining moisture. These properties include wood anisotropic shrinkage, equilibrium moisture content (EMC) in both desorption and adsorption, fibre saturation point (FSP) and water diffusion coefficient. This study investigated the stability related wood properties and their variations within the stems of the New Zealand grown radiata pine trees. The basic density, EMC and shrinkage for the earlywood and the latewood were also experimentally determined. In taking into account these properties and their variations, an analytical model was developed to simulate the wood distortion. The equilibrium moisture content was determined at 30°C and humidity range from 27% to 90%. It was found that the EMC difference between the earlywood and the latewood was negligible. The experimental results also show that the EMC decreases from pith towards the bark over the disc cross section and the trend is most obvious at high humidities (70-90%). Along the tree height, the EMC decreases from ground towards the top of the stem. The tangential shrinkage results were highly variable but, in general, the latewood has higher values than the earlywood. The opposite trend was found for the longitudinal shrinkage, higher values for the earlywood than the latewood. In the tree height direction, the tangential shrinkage was found to decrease with the tree height. This follows the same trend as the microfibril angle which in general also decreases with the tree height. The fibre saturation point (FSP) was determined from the tangential shrinkage values at different equilibrium moisture contents. These were taken as the intersection point of the tangential shrinkage line with the moisture content axis. The experimental results have revealed a trend that the FSP decreases from the pith towards the bark and also decreases with the tree height. Similar behaviour was found for the tangential and longitudinal swelling during the adsorption. The moisture transport within radiata pine was investigated based on the diffusion theory under transient and isothermal condition of 30°C. The moisture dependant diffusion coefficient was derived from the experimental data using the inverse analysis method. The surface emission coefficient was determined by taking into account the variable surface moisture content, wood density and the ambient conditions. In the experiments, 138 samples in total (46 samples for each XIV of the longitudinal, tangential and radial directions) were used and their diffusion coefficients were determined for both the adsorption and the desorption with moisture content ranging from 6% to 22%. The derived diffusion coefficients are comparable with the reported data in the literature. Further investigation of the wood type influence on the diffusion coefficient revealed that compression wood has the lowest diffusion coefficients in the three directions (longitudinal, tangential and radial) both in the desorption and in the adsorption. In addition, the moisture content has the least influence on the diffusion coefficient in the compression wood. Investigation on the effects of the wood density has shown that in general, the diffusion coefficient decreases with increasing wood density although the correlations are only significant for the longitudinal direction in desorption. An analytical model for the simulation of the wood twist was developed which is based on the geometry and geometrical changes of the grains aligning non parallel to the pith. A board consists of numerous such grains which change the length and shape with moisture content change. The model predictions confirm that the grain angle, the tangential and longitudinal shrinkage and the conical angle all affect the development of the board twist. However, the discrepancies between the model prediction and the experimental data are significant, partly due to the experimental uncertainties and partly due to the model errors. In this study, sound velocity in the longitudinal direction was measured for the test samples used in the shrinkage experiments. The results revealed that the correlations between the sound velocity and the volumetric shrinkage at oven dry are significant. Based on this finding, the relationship between the tangential shrinkage and the radial shrinkage, the tangential shrinkage can be predicted from the sound velocity measurements. As the tangential shrinkage has significant influence on the wood distortion, this method can be used to segregate logs which may be prone to wood distortion.

In the military arena there is an increase in demand for Low Observable (LO) flight vehicles. This drive for low observability imposes limits on Leading Edge (LE) sweep angles and prohibits the use of a tailplane/fin resulting in unconventional configurations; a typical example of which are Unmanned Combat Aerial Vehicles (UCAVs). This class of aircraft poses stability and control problems due to the early onset of flow separation. The focus of this project is on the on the use of Tangential Leading Edge Blowing (TLEB) as a means of separation suppression on such vehicles. This project is unique in that the TLEB slot is positioned on the wing lower surface facing the oncoming freestream. Also, the model in this project is representative of the outboard panel of a UCAV wing, a geometry on which TLEB has not been explored in the past. A swept wing model (LE sweep = 47 degrees, AR = 3) was designed. The model has a TLEB nozzle with a slot on the lower surface at approx. 1% yawed chord that spans 0.58 m (approx. 70% LE length). Baseline wing characteristics were obtained with the full slot exposed. The wing showed a variation in pitch between CL = 0 and 0.6 which from oil flow visualisation is believed to be due to laminar separation. At CL = 0.6 there is a positive pitch break which flow visualisation suggests is due to the occurrence of a LE vortex. Sensitivity studies for slot configuration, Re number and transition fixing were carried out. The blowing rates 0.0025, 0.005, 0.025, 0.05 were tested for two slot lengths; one full span (0.58 m) and another third span positioned at the midpoint of the full slot. All blowing rates show some suppression of the LE vortex and therefore reduction in severity of the pitch break at CL = 0.6. High blowing rates produce a negative shift in CM, which CFD suggests is due to a large amount of suction produced on the lower wing surface adjacent to the slot exit. This means the available trim power is less than for the lower blowing rates. Wool tuft results for high blowing rates from the middle slot show an increase in streamwise flow at the TE suggesting TLEB is capable of improving the effectiveness of TE devices. The effectiveness of TLEB at low blowing rates has been shown to be high compared to that found in literature. A 1st order analysis of the impact of TLEB on a full scale system shows realistic options.

Made available in DSpace on 2014-06-11T19:35:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2003-08Bitstream added on 2014-06-13T21:07:15Z : No. of bitstreams: 1 romao_lpc_dr_araiq.pdf: 435919 bytes, checksum: 41d1a98abe8648f0ce971267eb617cda (MD5) / Um procedimento de ultrafiltração com fluxo tangencial e membrana polietersulfônica de porosidade 1 kDa foi utilizado na determinação da capacidade de complexação (CC) e constantes de estabilidade condicional (K) do íon cobre(II) para amostras de matéria orgânica natural, substâncias húmicas aquáticas e substâncias húmicas de solo de diferentes regiões do Brasil. As substâncias húmicas de solos apresentaram maiores valores de CC em relação à matéria orgânica natural e substâncias húmicas aquáticas. Os valores das capacidades de complexação das amostras de matéria orgânica aquática (1,25±0,07, 1,18±0,05 e 1,81±0,30) e das amostras de substâncias húmicas aquáticas (1,23±0,11, 1,12±0,05 e 1,44±0,04) foram similares, indicando que o procedimento de extração utilizando resina acrílica XAD-8 não modificou significativamente as características complexantes originais das amostras. Os valores das capacidades de complexação da matéria orgânica natural (MON) determinados por ultrafiltração para Cu(II) variaram de 0,17 a 1,99 mmol Cu(II)g-1 COT e os valores das constantes de estabilidade condicional variaram de 2,30 a 4,35 (log K1) e 1,36 a 2,60 (log K2) A validação da metodologia de ultrafiltração em fluxo tangencial foi feita comparando as médias das capacidades de complexação para cobre(II) determinadas por UF, e àquelas obtidas por eletrodo íon seletivo utilizando o teste de student t. Os resultados mostraram que não existem diferenças entre os valores das capacidades de complexação determinados por ambos os procedimentos. Resultados de experimentos de troca entre íons Cu(II) adicionados e espécies metálicas (Ni, Al e Fe) originalmente complexadas por substâncias húmicas, permitiram estabelecer a seguinte ordem decrescente de estabilidade relativa do complexo SH-metal: Fe<Al<<Ni. / An tangential-flow ultrafiltration (TF-UF) procedure a polyethersulfone membrane filter (cut-off 1 kDa) was used to determine the copper(II) complexation capacity (CC) and conditional stability constants (K) of the copper(II) ion from samples of aquatic organic matter, aquatic humic substances and soil humic substances (all from different regions of Brazil). The humic soil substances presented larger values of CC compared to the aquatic organic matter and aquatic humic substances. The complexation capacities from samples of aquatic organic matter (1,25±0,07, 1,18±0,05 and 1,81±0,30) and aquatic humic substances (1,23±0,11, 1,12±0,05 and 1,44±0,04) samples were similar, indicating that the extraction procedure using XAD-8 acrylic resin didn't, significantly, modify the original complexation characteristics of the samples. The values of complexation capacities of aquatic organic matter (AOM) by Cu(II) using ultrafiltration varied from 0,17 to 1,99 mmol Cu(II)g-1 TOC and the values of the conditional stability constants varied from 2,30 to 4,35 (log K1) and 1,36 to 2,60 (log K2). The validation of the tangential-flow ultrafiltration (TF-UF) methodology was done comparing the averages of complexation capacities determined by TF-UF and those obtained by selective ion electrode using the student test t. The results showed that there aren’t any differences between the values of complexation capacities for copper(II) determined by both the methods. Results of exchange experiments among Cu(II) ions added and metallic species (Ni, Al and Fe) originally complexed for humic substances allowed the establishment of the following decreasing order of relative stability of the compound HS-metal: Fe <Al << Ni.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This dissertation sought to understand the mechanisms of mass transfer along the inner surface of cylindrical microfiltration membranes, which are associated with phenomena of diffusion and convection of one or more chemical species in a suspension. The chemical species present in the suspension are separated based on differences between the sizes of particles in relation to the average diameter of pore membrane. The driving force used in the separation process is the transmembrane pressure at which the membrane is submitted. Mathematical models capable of representing the concentration profile of solute along the membrane were used and solved using the lines method with finite differences in order to describe, in general, the behavior of chemicals, especially enzymes, along with cylindrical membranes (hollow fibers or capillary membranes or tubular membranes). Tangential filtration process was studied in the transient and permanent flow. The data obtained with the solutions of the model were compared with experimental data obtained from literature for the á and â amylases enzymes from corn malt (Zea mays) and found that the numerical method of finite differences used to solve the numerical model produced consistent results with experimental data and they are representative of the phenomenon. / Nesta dissertação buscou-se entender os mecanismos de transferência de massa junto à superfície interna de membranas cilíndricas de microfiltração, onde estão associados fenômenos de difusão e convecção de uma ou mais espécies químicas presentes em uma suspensão. As espécies químicas presentes na suspensão são separadas com base nas diferenças entre os tamanhos das partículas em relação ao diâmetro médio de poros da membrana. A força motriz utilizada no processo de separação é a pressão transmembranar a que a membrana é submetida. Modelos matemáticos capazes de representar o perfil de concentração do soluto ao longo da membrana foram utilizados e resolvidos utilizando o método das linhas associado com o método das linhas associado ao método das diferenças finitas com o objetivo de descrever, de uma forma geral, o comportamento de substâncias químicas, especialmente de enzimas, ao longo de membranas cilíndricas (hollow fibers ou membranas capilares ou membranas tubulares). O processo de filtração tangencial foi estudado operando em regime transiente e estacionário. Os dados obtidos com as soluções do modelo foram comparados com os dados experimentais obtidos da literatura para as enzimas á e â amilase a partir do malte de milho (Zea mays) e verificou-se que o método numérico das diferenças finitas, utilizado para resolver o modelo numérico, produziu resultados compatíveis com os dados experimentais e são representativos do fenômeno estudado. bioproduto.

Orientador: Leandro Palermo Junior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-09T18:20:53Z (GMT). No. of bitstreams: 1 Goncalves_PauloCesar_M.pdf: 702369 bytes, checksum: ed3744e613bcdec2cfeeb3545685db46 (MD5) Previous issue date: 2006 / Resumo: O método dos elementos de contorno foi usado no estudo de problemas de estados planos. O objetivo deste trabalho é a introdução do operador diferencial tangente no núcleo das equações integrais de forças de superfície, como uma alternativa para a aplicação do método dos elementos de contorno. A singularidade forte do tipo 2 1 r , presente no núcleo da equação integral de contorno, foi reduzida a uma singularidade de ordem r 1 com o uso do operador diferencial tangente. A formulação trabalhou com elementos de contorno contínuos e descontínuos. Na determinação de deslocamentos e tensões para pontos próximos do contorno, trabalhou-se apenas com núcleos com uma singularidade de ordem r 1. A técnica da regularização indireta, quando se evitam expressões analíticas, foi aplicada na equação integral de deslocamentos. Quando o ponto de colocação foi levado ao contorno, a singularidade, presente nas equações integrais de contorno, foi tratada pelo valor principal de Cauchy para elementos lineares na obtenção de tensões internas e no contorno. A formulação do método dos elementos de contorno dual usou a equação integral de forças de superfície, com a aplicação do operador diferencial tangente, no tratamento de problemas com trinca em análises da mecânica da fratura elástico-linear. Os fatores de intensidade de tensão são obtidos através do método da extrapolação de deslocamentos / Abstract: The Boundary Element Method was used to study plane state problem. The aim of this study is an application of the tangential differential operator in the kernels of boundary integrals equations for tractions, as an alternative for the applications of Boundary Element Method. Strong singularity of order 2 1 r , present in the kernels of boundary integrals equations was reduced to a weakly singularity of order r 1 when the tangential differential operator was used. The formulation worked with continuous and discontinuous boundary elements. On determination of displacements and stresses for boundary near points, the equation worked only with kernels contained singularity of order r 1. The indirect regularization technique, with avoided analytic expressions, was applied on the boundary integral equations for displacements. When the collocation points was led to boundary, the singularity, present on the boundary integrals equations, was treated by the Cauchy principal value sense for linear boundary elements. The formulation of the dual boundary elements methods used a boundary integral equation for traction, with the application of the tangential differential operator, to treat plane problems with cracks of the linear elastic fracture mechanics. The stress intensity factors are obtained with the displacement extrapolation method / Mestrado / Estruturas / Mestre em Engenharia Civil

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The goal of this thesis is on improving the understanding of mechanical and tribological mechanisms in microelectronic wire bonding. In particular, it focusses on the development and application of quantitative models of ultrasonic (US) friction and interfacial wear in wire bonding. Another objective of the thesis is to develop a low-stress Cu ball bonding process that minimizes damage to the microchip. These are accomplished through experimental measurements of in situ US tangential force by piezoresistive microsensors integrated next to the bonding zone using standard complementary metal oxide semiconductor (CMOS) technology. The processes investigated are thermosonic (TS) Au ball bonding on Al pads (Au-Al process), TS Cu ball bonding on Al pads (Cu-Al process), and US Al wedge-wedge bonding on Al pads (Al-Al process). TS ball bonding processes are optimized with one Au and two Cu wire types, obtaining average shear strength (SS) of more than 120 MPa. Ball bonds made with Cu wire show at least 15% higher SS than those made with Au wire. However, 30% higher US force induced to the bonding pad is measured for the Cu process using the microsensor, which increases the risk of underpad damage. The US force can be reduced by: (i) using a Cu wire type that produces softer deformed ball results in a measured US force reduction of 5%; and (ii) reducing the US level to 0.9 times the conventionally optimized level, the US force can be reduced by 9%. It is shown that using a softer Cu deformed ball and a reduced US level reduces the extra stress observed with Cu wire compared to Au wire by 42%. To study the combined effect of bond force (BF) and US in Cu ball bonding, the US parameter is optimized for eight levels of BF. For ball bonds made with conventionally optimized BF and US settings, the SS is ≈ 140 MPa. The amount of Al pad splash extruding out of bonded ball interface (for conventionally optimized BF and US settings) is between 10–12 µm. It can be reduced to 3–7 µm if accepting a SS reduction to 50–70 MPa. For excessive US settings, elliptical shaped Cu bonded balls are observed, with the major axis perpendicular to the US direction. By using a lower value of BF combined with a reduced US level, the US force can be reduced by 30% while achieving an average SS of at least 120 MPa. These process settings also aid in reducing the amount of splash by 4.3 µm. The US force measurement is like a signature of the bond as it allows for detailed insight into the tribological mechanisms during the bonding process. The relative amount of the third harmonic of US force in the Cu-Al process is found to be five times smaller than in the Au-Al process. In contrast, in the Al-Al process, a large second harmonic content is observed, describing a non-symmetric deviation of the force signal waveform from the sinusoidal shape. This deviation might be due to the reduced geometrical symmetry of the wedge tool. The analysis of harmonics of the US force indicates that although slightly different from each other, stick-slip friction is an important mechanism in all these wire bonding variants. A friction power theory is used to derive the US friction power during Au-Al, Cu-Al, and Al-Al processes. Auxiliary measurements include the current delivered to the US transducer, the vibration amplitude of the bonding tool tip in free-air, and the US tangential force acting on the bonding pad. For bonds made with typical process parameters, several characteristic values used in the friction power model such as the ultrasonic compliance of the bonding system and the profile of the relative interfacial sliding amplitude are determined. The maximum interfacial friction power during Al-Al process is at least 11.5 mW (3.9 W/mm²), which is only about 4.8% of the total electrical power delivered to the US transducer. The total sliding friction energy delivered to the Al-Al wedge bond is 60.4 mJ (20.4 J/mm²). For the Au-Al and Cu-Al processes, the US friction power is derived with an improved, more accurate method to derive the US compliance. The method uses a multi-step bonding process. In the first two steps, the US current is set to levels that are low enough to prevent sliding. Sliding and bonding take place during the third step, when the current is ramped up to the optimum value. The US compliance values are derived from the first two steps. The average maximum interfacial friction power is 10.3 mW (10.8 W/mm²) and 16.9 mW (18.7 W/mm²) for the Au-Al and Cu-Al processes, respectively. The total sliding friction energy delivered to the bond is 48.5 mJ (50.3 J/mm²) and 49.4 mJ (54.8 J/mm²) for the Au-Al and Cu-Al processes, respectively. Finally, the sliding wear theory is used to derive the amount of interfacial wear during Au-Al and Cu-Al processes. The method uses the US force and the derived interfacial sliding amplitude as the main inputs. The estimated total average depth of interfacial wear in Au-Al and Cu-Al processes is 416 nm and 895 nm, respectively. However, the error of estimation of wear in both the Au-Al and the Cu-Al processes is ≈ 50%, making this method less accurate than the friction power and energy results. Given the error in the determination of compliance in the Al-Al process, the error in the estimation of wear in the Al-Al process might have been even larger; hence the wear results pertaining to the Al-Al process are not discussed in this study.

The goal of this thesis is on improving the understanding of mechanical and tribological mechanisms in microelectronic wire bonding. In particular, it focusses on the development and application of quantitative models of ultrasonic (US) friction and interfacial wear in wire bonding. Another objective of the thesis is to develop a low-stress Cu ball bonding process that minimizes damage to the microchip. These are accomplished through experimental measurements of in situ US tangential force by piezoresistive microsensors integrated next to the bonding zone using standard complementary metal oxide semiconductor (CMOS) technology. The processes investigated are thermosonic (TS) Au ball bonding on Al pads (Au-Al process), TS Cu ball bonding on Al pads (Cu-Al process), and US Al wedge-wedge bonding on Al pads (Al-Al process). TS ball bonding processes are optimized with one Au and two Cu wire types, obtaining average shear strength (SS) of more than 120 MPa. Ball bonds made with Cu wire show at least 15% higher SS than those made with Au wire. However, 30% higher US force induced to the bonding pad is measured for the Cu process using the microsensor, which increases the risk of underpad damage. The US force can be reduced by: (i) using a Cu wire type that produces softer deformed ball results in a measured US force reduction of 5%; and (ii) reducing the US level to 0.9 times the conventionally optimized level, the US force can be reduced by 9%. It is shown that using a softer Cu deformed ball and a reduced US level reduces the extra stress observed with Cu wire compared to Au wire by 42%. To study the combined effect of bond force (BF) and US in Cu ball bonding, the US parameter is optimized for eight levels of BF. For ball bonds made with conventionally optimized BF and US settings, the SS is ≈ 140 MPa. The amount of Al pad splash extruding out of bonded ball interface (for conventionally optimized BF and US settings) is between 10–12 µm. It can be reduced to 3–7 µm if accepting a SS reduction to 50–70 MPa. For excessive US settings, elliptical shaped Cu bonded balls are observed, with the major axis perpendicular to the US direction. By using a lower value of BF combined with a reduced US level, the US force can be reduced by 30% while achieving an average SS of at least 120 MPa. These process settings also aid in reducing the amount of splash by 4.3 µm. The US force measurement is like a signature of the bond as it allows for detailed insight into the tribological mechanisms during the bonding process. The relative amount of the third harmonic of US force in the Cu-Al process is found to be five times smaller than in the Au-Al process. In contrast, in the Al-Al process, a large second harmonic content is observed, describing a non-symmetric deviation of the force signal waveform from the sinusoidal shape. This deviation might be due to the reduced geometrical symmetry of the wedge tool. The analysis of harmonics of the US force indicates that although slightly different from each other, stick-slip friction is an important mechanism in all these wire bonding variants. A friction power theory is used to derive the US friction power during Au-Al, Cu-Al, and Al-Al processes. Auxiliary measurements include the current delivered to the US transducer, the vibration amplitude of the bonding tool tip in free-air, and the US tangential force acting on the bonding pad. For bonds made with typical process parameters, several characteristic values used in the friction power model such as the ultrasonic compliance of the bonding system and the profile of the relative interfacial sliding amplitude are determined. The maximum interfacial friction power during Al-Al process is at least 11.5 mW (3.9 W/mm²), which is only about 4.8% of the total electrical power delivered to the US transducer. The total sliding friction energy delivered to the Al-Al wedge bond is 60.4 mJ (20.4 J/mm²). For the Au-Al and Cu-Al processes, the US friction power is derived with an improved, more accurate method to derive the US compliance. The method uses a multi-step bonding process. In the first two steps, the US current is set to levels that are low enough to prevent sliding. Sliding and bonding take place during the third step, when the current is ramped up to the optimum value. The US compliance values are derived from the first two steps. The average maximum interfacial friction power is 10.3 mW (10.8 W/mm²) and 16.9 mW (18.7 W/mm²) for the Au-Al and Cu-Al processes, respectively. The total sliding friction energy delivered to the bond is 48.5 mJ (50.3 J/mm²) and 49.4 mJ (54.8 J/mm²) for the Au-Al and Cu-Al processes, respectively. Finally, the sliding wear theory is used to derive the amount of interfacial wear during Au-Al and Cu-Al processes. The method uses the US force and the derived interfacial sliding amplitude as the main inputs. The estimated total average depth of interfacial wear in Au-Al and Cu-Al processes is 416 nm and 895 nm, respectively. However, the error of estimation of wear in both the Au-Al and the Cu-Al processes is ≈ 50%, making this method less accurate than the friction power and energy results. Given the error in the determination of compliance in the Al-Al process, the error in the estimation of wear in the Al-Al process might have been even larger; hence the wear results pertaining to the Al-Al process are not discussed in this study.