The overarching goal of this research was to generate a menu of shape memory alloys (SMAs) actuator materials capable of meeting the demands of aerospace applications. Material requirements were recognized to meet the demand for high temperature SMAs with actuating temperatures above 85 °C and provide material options capable of performing over 100K actuation cycles. The first study is a preliminary characterization for the down selection of Ni-rich NiTiHf15 compositions chosen for a more in-depth examination of the nano-precipitation and evolution of the H-phase. To make this selection, the effect of Ni content in Ni-rich NiTiHf high temperature shape memory alloys (HTSMAs) on processability, microstructure, and hardness was analyzed for three compositions (Ni50.1TiHf15, Ni50.3TiHf15, Ni50.5TiHf15). Each composition was characterized under three conditions: homogenized, 25%, and 50% thickness reduction through hot-rolling. The second study emphasized the processing and aging response of an industrially produced, hot-extruded Ni50.3Ti29.7Hf20 (at%) HTSMA. The samples were sectioned into two halves with half remaining as-extruded and the other half hot-rolled to a 25% reduction in thickness. A portion of both conditions underwent conventional aging for 3 hours at various temperatures ranging from 450-750 °C, and the other portion was pre-aged for 12 hours at 300 °C followed by conventional aging treatments. After processing, the samples were characterized by differential scanning calorimetry (DSC), Vickers hardness (HV) testing, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and synchrotron radiation X-ray diffraction (SR-XRD). The relationship between the introduction of texturing, pre-aging, and aging on Ni-rich and high Hf-content compositions was investigated.

Thesis advisor: Chia-Kuang F. Tsung / Thesis advisor: Dunwei Wang / In order to understand the lattice strain effect and its relationship to size, shape, composition, and catalytic performance, novel well-defined nanocrystal archetypes were designed and synthesized by taking advantage of wet chemical, seed-mediated (mild) reduction routes developed by our lab. First, the current synthesis challenges are addressed in creating smaller monometallic shape-controlled metal nanocrystals, and novel cuboctopods via a hybrid nanoparticle stabilizer. A look at the relationship between lattice strain and morphology is then shown in a single-component system, where still new features have been observed for the first time by the traditional technique of powder x-ray diffraction. Synthesis methods for differently strained Pd surfaces are described and catalysis by these surfaces is discussed. Finally, studies of the synthesis, characterization, electrocatalytic activity, and restructuring of novel and more sophisticated strained architectures are presented: core-island-shell nanocrystals, phase-segregated nanoboxes, island nanoframeworks, and core-sandwich-shell nanoparticles. Lattice strain and composition effects were studied in carbon monoxide, small alcohol, and formic acid electrocatalytic oxidations as well as in oxygen reduction, the latter of which, governs the commercial viability of automotive fuel cells, a sustainable energy and zero-emission technology. Here it is demonstrated how a tunable thickness of Ni sandwich layers can be used to improve catalytic performance by increasing lattice strain on the Pt surface. The sandwich archetype offers a new platform for the investigation of lattice strain and could be a promising, industrially relevant, catalyst design concept, to help address the need for a more sustainable energy future. The results help paint a new picture of catalysis by metal nanocrystals; one which brings lattice strain to the forefront of the discussion, as an important parameter for further study and for use in developing higher-performing catalysts. / Thesis (PhD) — Boston College, 2015. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

<div>Process induced dimensional changes in composite parts has been the topic of interest for many researchers. The residual stresses that are induced in composite laminates during curing process while the laminate is in contact with the process tool often lead to dimensional variations such as spring-in of angles and warpage of flat panels. The traditional trial-and-error approach can work for simple geometries, but composite parts with complex shapes require more sophisticated models. When composite laminates are subjected to thermal stresses, such as the heating and cooling processes during curing, they can become distorted as the in-plane and the throughthickness</div><div>coffcients of thermal expansion are different, as well as chemical shrinkage of the resin, usually cause spring-in. Deformed components can cause problems during</div><div>assembly, which significantly increases production costs and affects performance. This thesis focuses on predicting these shape deformations using software simulation of composite manufacturing and curing. Various factors such as resin shrinkage, degrees of cure, difference between through thickness coefficient of thermal expansion of the composite laminate are taken into the consideration. A cure kinetic model is presented which illustrates the matrix behavior during cure. The results obtained using the software then were compared with the experimental values of spring-in from the available literature. The accuracy of ACCS package was validated in this study. Analyzing the effects of various parameters of it was estimated that 3D part simulation is an effective and cost and time saving method to predict final shape of the composite part.</div>

Over the past decade, research into computer vision has proliferated with the goal to incorporate artificial intelligence into a wide range of applications. These applications can be as sophisticated as intelligent assistants in smartphones and self-driving cars or as mundane as text and face recognition. While most of these applications are software based, they represent unique challenges when it comes to industrial implementation. This thesis concentrates on an optical non-destructive testing (NDT) and automatic classification methodology using customized image processing techniques. In contrast to conventional spatial analyses, which are highly susceptible to noise and human perception, our proposed transform domain approach provides a high degree of robustness and flexibility in feature selection and hence a better classification efficiency. Our presented algorithm classifies the Part-Under-Test (PUT) into two bins of either acceptable or faulty using transform domain techniques in conjunction with a classifier. Because the classification is critically dependent on the features extracted from these images, a sophisticated scalable database was created. This thesis applies transform domain techniques such as Discrete Wavelet Transform (DWT) and Rotated Wavelet Transform (RWT) for feature extraction and then classifies the PUT based on those features. Although, this approach achieves promising classification efficiency, it does not meet industrial standards. It was concluded that in order to achieve those standards, the effect of emissivity fluctuations of the PUT should be negated. The research was then extended to apply an image acquisition algorithm in the form of shape from polarization. The approach exploits the partially linearly polarization of reflected light from the PUT surface. It was observed that this method could not only detect if the PUT is faulty or fault free, but also highlight the locations of the flaws.

O Método das Densidades de Força (MDF), proposto primeiramente por Linkwitz (1971) e depois por Scheck (1974), é uma alternativa conveniente para encontrar configurações de redes de cabos e membranas, uma vez que fornece geometrias viáveis com uma única análise linear de equilíbrio. O Método das Densidades de Força Natural (MDFN) é uma extensão do MDF para busca de formas de estruturas de membranas, que preserva a linearidade do método original e supera suas dificuldades em lidar com malhas irregulares. Foi primeiramente sugerido por Pauletti em 2006, baseado no elemento triangular de membrana introduzido por Argyris em 1974. O Método tem sido aplicado com sucesso em vários projetos. O MDFN original requer o uso de malhas compostas exclusivamente por elementos triangulares. Esta dissertação apresenta uma extensão do método para elementos quadrangulares, considerando um elemento composto por quatro subelementos triangulares. Mesmo que a ideia básica seja muito simples, algumas dificuldades surgem do fato de que nesta abordagem, o elemento de quatro nós pode não conter todos os nós em um mesmo plano, especialmente no caso de superfícies anticlásticas, sendo que não existe um campo de tensões bem definido para o interior do elemento. O trabalho compara alguns resultados obtidos com malhas exclusivamente triangulares, como requerido pelo método original, com os resultados obtidos com o elemento quadrangular proposto, discutindo a forma de combinar as tensões dos subelementos triangulares para originar as tensões atuantes no elemento quadrangular. Os modelos obtidos no MDFN são inseridos no programa Ansys, e os resultados são comparados para analisar a viabilidade da solução proposta e dos resultados obtidos por meio desta. / The Force Density Method (FDM), first proposed by Linkwitz(1971) and after by Scheck(1974), is a convenient alternative for finding configurations of cable nets and membranes, since it provides viable geometries in a single linear equilibrium analysis. The Natural Force Density Method (NFDM) is an extension of the FDM to the shape finding of membrane structures, which preserves the linearity of the original method and overcomes the difficulties of the original method to deal with irregular meshes. It was first suggested by Pauletti in 2006, based on a triangular membrane element introduced by Argyris in 1974. The method has been successfully applied to several design cases. The original NFDM required the use of meshes composed exclusively of triangular elements. This text presents an extension of the method to quadrangular elements, considering an equivalent assemblage of flat triangular elements. Even if the basic idea is very simple, some difficulties arise from the fact that in this approach, the quadrangular element can have a non-flat configuration, especially in the anticlastic shape, and there is not a know stress field into the interior of the element. The text compares several results obtained with fully triangulated meshes, as required by the original NFDM, to those obtained with the proposed quadrangular element, discussing the different strategies that have been explored to map stresses from the internal triangular mesh to the four nodes of the element. The models obtained in the NFDM are inserted in software Ansys and the results compared to approve the solution and the results obtained.

Engineers have utilized CAE technique as an analysis tool to refine the engineering design over decades. However, CAE alone is not the key to open the door for the final goal. In order to achieve the practical solution to the real-time engineering problem, we need to integrate CAD, CAE and optimization techniques into a single framework. / In the optimization algorithm part, apart from the general parametric steepest descent (ST) algorithm, we also study the least square (LSQ) based optimization algorithm. As a result, we can solve the problem arisen from the variant dimensional sizes of the different design variables by using the weighted sensitivity information. / In the problem of the structural optimizations, three categories of the approaches can be identified: size, shape and topology optimizations. For size optimization, explicit dimensions are usually chosen as the design variables, for example, the thickness of a beam or the diameter of a cylinder. For shape optimization, the shape related parameters of the geometrical boundary are always considered to be the design variables, like the positions of the control points for a Bezier curve. However, these two methods are lack of the capability to handle the topological changes of the geometry. On the contrary, topology optimization is the generalization of size and shape optimizations, which offers a more flexible and powerful tool to determine the best layout of the materials and the topology to the design problem, and it is becoming increasingly important in the conceptual design phase. In other words, topology optimization gives one the inspiration for the locations where we put holes to reach the best design. / In this thesis, we put forward the algebraic level set (ALS) model with the consideration of the constructive solid geometry (CSG) model so that it is consistent with half-space primitive concept in CSG. Based on general shape derivative, we propose the general shape design sensitivity analysis (SDSA) formulations for general geometric primitives that are represented implicitly, such as line and circle primitives in two-dimensional space and plane primitive in three-dimensional space. We then extend the relevant formulations into corresponding parametrically represented primitives as they are widely used in today's mainstream CAD systems. / The material density method and the boundary-variation method are the popular methods adopted in both academia and industrial community. Even though the former method is dominant in industry, the latter method is more preferable these years owing to its boundary description nature. Undoubtedly, the level set based method is the most promising technique of the boundary-variation type. Scientists successfully developed the optimization algorithms based on the level set method (LSM) in the past few years. With the implicit representation of the LSM, topological changes of the design can be handled easily and the geometrical complexity is then reserved. / The numerical examples for the design optimization problem are successfully implemented with both the implicit geometric representation (2D cases) and the parametric geometric representation (3D cases), which proves the feasibility of the proposed framework. The results show that both shape and topology optimizations of a design could be accomplished in a natural way. / The optimal result given by conventional topology optimization usually involves tedious post-processing to form CAD geometry. Using our parameterizations with basic primitives and the proposed optimization algorithms, we can deliver comparatively complicated shapes with rich topological information. Therefore, the detail design could be conducted directly later. / Zhang, Jiwei. / "December 2010." / Adviser: Yu Michael Wang. / Source: Dissertation Abstracts International, Volume: 73-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 119-129). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

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Data were collected from a 1,000 cow commercial dairy unit during three different time periods to determine the interrelationships between teat shape, teat erosion, mastitis (as measured by the California Mastitis Test and somatic cell counts), and milk production. Results showed no relationship between teat shape or teat end erosion and milk or fat production. The relationship between teat end erosion and mastitis appeared to be masked by the high level of teat erosion. There was an indication that cows with flat and cone shaped teat ends were prone to higher California Mastitis Test scores than cows with pointed, round, or disk shaped teat ends. Pointed teat ends showed the highest amount of erosion and cone and flat teat ends showed the least amount of erosion. There was a high correlation between the California Mastitis Test and somatic cell counts. Teat end erosion and California Mastitis Test scores decreased and milk production increased when a change in milking equipment and milking technique occurred and teat dipping was instigated.

The current study evaluated the ability of 20 younger and 20 older adults to discriminate shapes depicted by Glass patterns. On any given trial, observers identified a particular pattern as either possessing a radial or concentric organization. Detecting a shape defined by a Glass pattern requires the successful detection of the orientations of its constituent local dipoles. In addition, long-range processes are needed to integrate the spatially separated dipoles into perceivable contours that have a particular (e.g., radial or concentric) organization. In the current experiment, the shapes were defined by either 40 or 200 oriented dipoles spread over an area with a diameter of either 6 or 25 degrees visual angle. Three amounts of visual noise were added to the patterns to manipulate task difficulty: 1) no added noise points, 2) low amounts of noise (a 1:1 ratio of randomlyplaced noise points and signal dipoles), and 3) large amounts of noise (a 5:1 ratio of randomly-placed noise points and signal dipoles). The results of the current study indicate that human observers, both younger and older, possess an effective ability to integrate visual information across space (using Glass patterns as stimuli). There is a small age-related deterioration in discrimination performance and this is most likely due to the deficits in orientation discrimination that accompany reductions in inhibitory GABA activity in visual cortex.

NiTiHf alloys have emerged as potential materials for applications requiring high transformation temperatures (> 100 °C) with high strength and work output. Although they have high transformation temperatures, their low damping capacity, brittleness and poor superelastic responses (of Ti-rich NiTiHf) impedes their wider usage in many industrial applications. In this study, the quaternary alloying element of Pd has been added to NiTiHf alloys to improve and tailor their shape memory behavior,. NiTiHfPd alloys were systematically examined regarding the composition and heat treatments effects. Effects of substituting Hf with Ti on the shape memory behavior of NiTHfPd alloys were investigated. There compositions were selected as Ni40.3Ti34Hf20Pd5 Ni40.3Ti39.7Hf15Pd5 and Ni40.3Ti44.7Hf10Pd5 (at.%). Their transformation temperatures, microstructure and shape memory properties were revealed and compared with conventional shape memory alloys. It was revealed that their transformation temperatures increases but transformation strain decreases with the increment of Hf content. Additionally, superelastic responses of Ni45.3Ti29.7Hf20Pd5 andNi45.3Ti39.7Hf10Pd5 alloys were investigated. Transformation temperatures of polycrystalline Ni45.3Ti29.7Hf20Pd5are highly dependent on aging temperatures and they can be altered widely from room temperature to 250 oC. Finally, the damping capacity of the Ni45.3Ti39.7Hf10Pd5 polycrystal and [111]-oriented Ni45.3Ti29.7Hf20Pd5 single crystal were investigated. The damping capacities were found to be 16-25 J.cm-3, and 10-23 J.cm-3 for the Ni45.3Ti39.7Hf10Pd5 and [111]-oriented Ni45.3Ti29.7Hf20Pd5 alloys, respectively.