abstract: Composite materials are finally providing uses hitherto reserved for metals in structural systems applications – airframes and engine containment systems, wraps for repair and rehabilitation, and ballistic/blast mitigation systems. They have high strength-to-weight ratios, are durable and resistant to environmental effects, have high impact strength, and can be manufactured in a variety of shapes. Generalized constitutive models are being developed to accurately model composite systems so they can be used in implicit and explicit finite element analysis. These models require extensive characterization of the composite material as input. The particular constitutive model of interest for this research is a three-dimensional orthotropic elasto-plastic composite material model that requires a total of 12 experimental stress-strain curves, yield stresses, and Young’s Modulus and Poisson’s ratio in the material directions as input. Sometimes it is not possible to carry out reliable experimental tests needed to characterize the composite material. One solution is using virtual testing to fill the gaps in available experimental data. A Virtual Testing Software System (VTSS) has been developed to address the need for a less restrictive method to characterize a three-dimensional orthotropic composite material. The system takes in the material properties of the constituents and completes all 12 of the necessary characterization tests using finite element (FE) models. Verification and validation test cases demonstrate the capabilities of the VTSS. / Dissertation/Thesis / Masters Thesis Engineering 2015

Orientador: Paulo José Rocha de Albuquerque / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-18T12:18:12Z (GMT). No. of bitstreams: 1 Gon_FernandadosSantos_M.pdf: 3553132 bytes, checksum: 8dab8d580ffbd8ac354ff9f5d15529e7 (MD5) Previous issue date: 2011 / Resumo: Este trabalho teve como objetivo obter, estudar e avaliar algumas propriedades geotécnicas do subsolo da região norte de Campinas, de grande importância para a pratica e desenvolvimento da engenharia geotécnica da região e do Estado de São Paulo. Foram coletadas amostras indeformadas e deformadas através da abertura de um poço de inspeção no Campo Experimental para estudos de Mecânica dos Solos e Fundações da UNICAMP (Campus Campinas), localizado na FEC - Faculdade de Engenharia Civil, Arquitetura e Urbanismo. Procurou-se atingir tais objetivos através da realização de ensaios laboratoriais (caracterização, resistência, deformabilidade, permeabilidade e sucção) e de correlações entre os parâmetros obtidos através dos ensaios, visando classificar o subsolo, dando enfoque a sua condição laterítica e não saturada. Ensaios edométricos simples foram realizados com o solo na condição natural e com inundação nas tensões de 100kPa, 200kPa e 400kPa para analise da colapsibilidade. Dos resultados obtidos, verificou-se que o solo se apresenta colapsível para todas as tensões de inundação. A partir dos resultados experimentais, fez-se a correlação de alguns parâmetros utilizando-se o programa de computador Wolfram Mathematica 7.0, verificando-se qual função melhor se ajustava para a correlação desejada / Abstract: This research aimed to study and evaluate some geotechnical properties of the northern region of Campinas soil profile, which have great importance for practice and development of geotechnical engineering in the Sao Paulo State. Disturbed and undisturbed samples from the subsoil were collected through the opening of inspection shafts at the experimental site for studies of Soil Mechanics and Foundations, UNICAMP (Campus Campinas), located on the FEC - Faculty of Civil Engineering, Architecture and Urbanism. In order to achieve these goals, laboratory tests have been performed, such as: characterization, resistance, compressibility, permeability and suction as well as correlation between parameters obtained from the tests to classify subsoil, giving emphasis to its unsaturated and lateritic condition. Oedometer tests were performed with the soil in natural and flooded condition with 100 kPa, 400 kPa and 200 kPa for analysis of collapsibility. From the results, it was verified that the soil is collapsible for all flooding stresses. High values of collapse potential were found and the results allowed to do correlations of some parameters using the computer program Wolfram Mathematica 7.0, verifying which function was the most appropriated to the desired correlation / Mestrado / Geotecnia / Mestre em Engenharia Civil

In this study commercial ultrastable Y zeolite was modified by different synthesis methods as precipitation, impregnation, and thermal hydrolysis, with different titanium and zirconium precursors. The intention was to investigate the effect of these metals in the framework on the zeolite acidity properties and how this influences the performance of the final catalyst on oil processes such as hydrocracking. For precipitation modification, different samples were synthesized varying the time precipitating ranging from one injection up to 9 hours. Samples in impregnation modification were synthesized along with thermal hydrolysis to compare different modification synthesis methods. Zeolite has a strong dealumination effect below pH 2 but low pH is needed to maintain titanium precursor in solution. Thermal hydrolysis shows an improvement in activity compared to precipitation and impregnation better selectivity compared to thermal hydrolysis. Metals preserve aluminum content when exposed to acidic post-treatment and shows improvements in yield of isomers compared to blanks. NH3-TPD showed decrease of weak and strong acid sites with increase of medium acid sites when exposed to acid post-treatment. BAS controls the yield of isomers.

Glucose entry into the brain and its subsequent metabolism to L-lactate, regulated by astrocytes, plays a major role in synaptic plasticity and memory formation. A recent study has shown that L-lactate produced by the brain upon stimulation of glycolysis, and glycogen-derived L-lactate from astrocytes and its transport into neurons, is crucial for memory formation. A recent study revealed the molecular mechanisms that underlie the role of L-lactate in neuronal plasticity and long-term memory formation. L-lactate was shown to induce a cascade of molecular events via modulation of redox-sensitive N-Methyl-D-aspartate (NMDA) receptor activity that was mimicked by nicotinamide adenine dinucleotide hydride (NADH) co-enzyme. This indicated that changes in cellular redox state, following L-lactate transport inside the cells and its subsequent metabolism, production of NADH, and favouring a reduced state are the key effects of L-lactate. Therefore, we are investigating the role of L-lactate in modulating NMDA receptor function via redox modulatory sites. Accordingly, crucial redox-sensitive cysteine residues, Cys320 and Cys87, of the NR2A NMDA receptor subunit are mutated using site-directed mutation, transfected, and expressed in HEK293 cells. This cellular system will then be used to characterise and monitor its activity upon Llactate stimulation, compared to the wild type. This will be achieved by calcium imaging, using fluorescent microscopy. Our data shows that L-lactate potentiated NMDA receptor activity and increased intracellular calcium influx in NR1/NR2A wild type compared to the control condition (WT NR1/NR2A perfused with (1μM) glutamate and (1μM) glycine agonist only), showing faster response initiation and slower decay rate of the calcium signal to the baseline. Additionally, stimulating with L-lactate associated with greater numbers of cells having high fluorescent intensity (peak amplitude) compared to the control. Furthermore, L-lactate rescued the mutated NMDA NR1/NR2A C320A C87A receptor response that showed altered activity upon mutation up to the control level. Future experiments need to be carried out on different redox-sensitive residues of various NMDA receptor subunits to reveal the exact molecular mechanisms of L-lactate.

In this work, digital holography (DH) is extensively utilized to characterize microparticles. Here, “characterization” refers to the determination of a particle’s shape, size, and, in some cases, its surface structure. A variety of microparticles, such as environmental dust, pollen, volcanic ash, clay, and biological samples, are thoroughly analyzed. In this technique, the microscopically fine interference pattern generated by the coherent superposition of an object and a reference wave fields is digitally recorded using an optoelectronic sensor, in the form of a hologram, and the desired particle property is then computationally extracted by performing a numerical reconstruction to form an image of the particle. The objective of this work is to explore, develop, and demonstrate the feasibility of different experimental arrangements to reconstruct the image of various arbitrary-shaped particles. Both forward- and backward-scattering experimental arrangements are constructed and calibrated to quantify the size of several micron-sized particles. The performance and implications of the technique are validated using the National Institute of Standards and Technology (NIST)-traceable borosilicate glass microspheres of various diameters and a Thorlabs resolution plate. After successful validation and calibration of the system, the resolution limit of the experimental setup is estimated, which is ~10 microns. Particles smaller than 10 microns in size could not be imaged well enough to ensure that what appeared like a single particle was not in fact a cluster. The forward- and backward-scattering holograms of different samples are recorded simultaneously and images of the particles are then computationally reconstructed from these recorded holograms. Our results show that the forward- and backward-scattering images yield different information on the particle surface structure and edge roughness, and thus, reveal more information about a particle profile. This suggests that the two image perspectives reveal aspects of the particle structure not available from a more commonly used forward-scattering based image alone. The results of this work could be supportive to insight more on the particles’ morphology and subsequently important for the advancement of contactree particle characterization technique.

Process forces arising during Friction Stir Welding (FSW) have become of interest to investigators interested in obtaining weld quality information from recorded weld data. Successful analysis of process forces require the separation of force signals stemming from material flow mechanisms within the weld from signals influenced by the FSW machine. Three modes of FSW control were characterized for system response: Servo Position (SPC), Electronic Deflection Compensation (EDC), and Constant Load Control (CLC). The gain value of the feedback loops associated with EDC and CLC modes were altered and characterized. SPC mode response to vertical changes in the tool position was also characterized. Machine-specific force signatures associated with the motor transmission assembly and spindle resonance were also identified. Characterization of the influence of machine control modes and other machinespecific frequencies on process force signals will allow future investigators to identify segments of welds during which machine actions influenced recorded force data.

This thesis delivers an in-depth investigation into electrochemical carbon dioxide reduction (CO2R), a process with the potential to convert CO2 gas into value-added chemicals and fuels. However, the efficiency and operational durability of current CO2 reduction processes are limited by catalytic performance. To address this, the thesis focuses on gaining a deep understanding of the transformations that CO2R electrocatalysts undergo under realistic conditions, such as morphological, phase structure, and compositional changes. These insights inform the design of next-generation materials by identifying performance descriptors and degradation patterns. A key aspect of this thesis is the development and application of in-situ liquid phase transmission electron microscopy (LP-TEM), an advanced platform that directly correlates nanoscale changes in catalyst materials under the influence of electrode potentials in CO2R reactive environments. Despite its potential, the use of in-situ LP-TEM presents a range of challenges, which this thesis addresses alongside exploring potential advancements for enhancing its accuracy and applicability. With the evolution of nanofabricated liquid cells, dynamic nanoparticle tracking, and high-resolution imaging in a liquid medium, this technology can more accurately mimic realistic exposure conditions. Cumulatively, this thesis systematically navigates the technical hurdles, advancements, and future prospects of in-situ LP-TEM in the context of electrochemical CO2R. The findings not only advance our understanding of the in-situ LP-TEM technical process but also guide new researchers in the field of in-situ TEM of electrocatalyst materials, aiding in the optimization of catalyst design, and paving the way for more sustainable and economically competitive CO2R technologies. The application of in-situ LP-TEM extends to the examination of two specific catalysts: Palladium (Pd) and a bi-metallic alloy of Copper (Cu) and Silver (Ag). By employing in-situ LP-TEM and selected area diffraction (SAD) measurements, we trace the morphological and phase structure transformations of the Pd catalyst under CO2R conditions. Interestingly, our findings indicate that alterations in reaction energetics, rather than morphological or phase structure changes, chiefly govern catalyst selectivity. This provides invaluable insights for designing more efficient catalysts. Further, we observe the morphological transformation of a metallic copper catalyst structure into a Cu-Ag bimetallic alloy during a galvanic replacement method. We then investigate the stability of both catalyst structures under operational CO2R conditions. Our results reveal that the metallic Cu structure undergoes significant morphological deformation during CO2R, leading to migration, detachment, and recrystallization of the catalyst surface. Contrarily, the Cu-Ag bimetallic alloy demonstrates notable thermodynamic stability under a similar applied potential. / Thesis / Candidate in Philosophy / This PhD thesis focuses on the development and implementation of cutting-edge technologies to address the climate change implications of CO2 emissions - a potent greenhouse gas. CO2 molecules could be electrochemically converted into various chemical feedstock and fuels. This process involves the development of efficient catalyst designs that can reduce CO2 gas at high conversion rates. Acquiring mechanistic insights on the behavior of the developed catalysts under reaction conditions would significantly assist on producing performance descriptors for catalyst design in CO2 conversion approach. Among a range of different advanced techniques, in-situ liquid phase transmission electron microscopy (LP-TEM) technology is selected for this study. This technique is capable of correlating dynamic nanoscale compositional and morphological changes with the electrochemical response of the catalysts. The primary focus of the thesis is on developing and implementing in-situ LP-TEM techniques to achieve electrochemical CO2 conditions while tracking particle morphology and phase structures as functions of electrochemical potential and time. Furthermore, the thesis investigates the performance of different catalyst designs under CO2 reduction (CO2R) operational conditions, which includes palladium (Pd) nanoparticles and copper–silver (Cu–Ag) bimetallic alloys. On a fundamental level, these studies provide a detailed understanding of the phase transformation and structural changes of these catalysts during CO2R that contributes valuable knowledge to the field and can be used to design next-generation CO2R catalysts.

<p> The work in this thesis focuses on the search for a system that would allow for the controlled anionic polymerization of N,N-dimethylacrylamide. The resulting polymer would serve as a macromonomer equipped with a chain end functional group originated from diallylamine.</p> <p> Poly(dimethylacrylamide) macromonomers were produced on a laboratory scale by reacting diallylamine with sec-butyllithium initiator, followed by the monomer addition. The synthesis was terminated, the polymer product precipitated in hexane, and dried in a vacuum oven at 45°C. The reactions were performed at 0°C and -77°C in tetrahydrofuran solvent.</p> <p> The polymerization control was achieved as a means of controlling the molecular weight and stereoregularity of the macromonomer, which in turn dictated solubility of the final product in the reaction solvent. The addition of triethylborane coordinating agent allowed for the polymerization of soluble product. The produced macromonomers characterized with atactic and syndiotactic structure were completely soluble in tetrahydrofuran.</p> <p> The molecular weights of macromonomers were evaluated by a gel permeation chromatography, GPC. The best results were obtained by using dimethylformamide as a mobile phase and poly(methylmethacrylate) standards</p> <p> The macromonomer yield was evaluated by 1H NMR and the stereoregularity by 13C NMR. Although the molecular weight of the macromonomer was under good control, the NMR measurements did not show the best yield control.</p> <p> The study of the triethylborane coordinating power showed that varying concentration of this ligand affected the solubility of the polymer in the reaction solvent. The soluble macromonomer was synthesized when triethylborane was in 1.5 molar excess over the initiator concentration. The 13C NMR measurements indicated that 23% of isotactic and atactic structure was required as a borderline for the solubility.</p> <p> The kinetic measurements performed in a batch reactor proved the livingness of the polymerization system with the propagation rate constant kobs equal to 1.9 · 10^-3 [1/s].</p> / Thesis / Master of Engineering (MEngr)

Environmental issues and regulations are pushing the automotive industry to produce more efficient and environmentally friendly vehicles. To address these issues, reducing the weight of the vehicles by use of aluminum alloys is increasing. AA6022-T43 is a new sheet aluminum alloy designed specifically for automobile enclosure panels. Because this alloy is new, little data exists on its mechanical properties in the open literature. AA6022-T43 is received by the automotive industry in 1-mm thick sheet stock and subsequently stamped into the desired component. The design and manufacturing processes of the component are guided by the materials mechanical behavior. This study characterizes the mechanical and microstructural properties of uniaxially strained AA6022-T43.

The objective of this study is to characterize critical component structure-properties on a Dodge Neon for material response refinement in crashworthiness simulations. Crashworthiness simulations using full-scale finite element (FE) vehicle models are an important part of vehicle design. According to the National Highway Traffic Safety Administration (NHTSA), there were over six million vehicle crashes in the United States during 2004, claming lives of more than 40,000 people. Crashworthiness simulations on a detailed FE model of a 1996 Plymouth/Dodge Neon were conducted on the NHTSA for different impact crash scenarios. The top-ten energy-absorbing components of the vehicle were determined. Material was extracted from the as-built vehicle and microstructural analyses were conducted. Tension tests at different temperatures and strain rates were performed as well as microhardness tests. Different microstructural spatial clustering and mechanical properties were found for diverse vehicle components. A plasticity model based on microstructure was used to predict the material response of the front bumper.