Modern engineering analysis requires accurate, reliable and efficient evaluation of outputs of interest. These outputs are functions of "input" parameter that serve to describe a particular configuration of the system, typical input geometry, material properties, or boundary conditions and loads. In many cases, the input-output relationship is a functional of the field variable - which is the solution to an input-parametrized partial differential equations (PDE). The reduced-basis approximation, adopting off-line/on-line computational procedures, allows us to compute accurate and reliable functional outputs of PDEs with rigorous error estimations. The operation count for the on-line stage depends only on a small number N and the parametric complexity of the problem, which make the reduced-basis approximation especially suitable for complex analysis such as optimizations and designs. In this work we focus on the development of finite-element and reduced-basis methodology for the accurate, fast, and reliable prediction of the stress intensity factors or strain-energy release rate of a mode-I linear elastic fracture problem. With the use of off-line/on-line computational strategy, the stress intensity factor for a particular problem can be obtained in miliseconds. The method opens a new promising prospect: not only are the numerical results obtained only in miliseconds with great savings in computational time; the results are also reliable - thanks to the rigorous and sharp a posteriori error bounds. The practical uses of our prediction are presented through several example problems. / Singapore-MIT Alliance (SMA)

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As the introduction of renewable energy sources increase in the power market, the need for effective use of electricity by consumers gains importance. The Swedishpower market is characterized by demand inelasticity. Thus, resulting in a system where supply follows demand. Increased demand response in electricity markets is essential in order to cope with future challenges. Electricity retailers can encourage an increased demand response by offering contracts to their customers such as “Realtime pricing” and “Fixed price with the right to return”. Under these contracts consumers are exposed to the hourly prices of electricity, thus benefitting by shifting the load to hours when the price is low. Electricity retailers benefits theoretically by risk eliminations. The aim of this paper is to quantify the economic consequences of increased demand response, for electricity retailers by offering the two contracts.This is done in two parts; firstly a simulation model of demand response is developed based on spot prices and different levels of price elasticity, secondly the results from the simulations are used in a model for calculations regarding an electricity retailers’ economy. The results show that an electricity retailers’ profit increases with increased demand response, greater response results in greater profits. Using low,medium and high demand response results in a profit increase of 34 %, 38 % and 55 % respectively. / Marknadsbaserade styrmedel i bostadssektorn

The objective of this study is to conduct a marketing mix modeling to measure the effectiveness of past marketing activities on the product sales using a time-varying effect model (TVEM) approach. The longitudinal intensive data for this study has come from a large ice cream manufacturer in USA. Traditionally, static regression models have been used to measure the effectiveness of marketing mix variables to predict sales. And, these models used to find the time independent effect of the covariate on the dependent variable. On the other hand, a dynamic model such as time-varying effect model takes time into consideration. Researchers can model the changes in the relationship between dependent and independent variables over time using time-varying effect model. This is the first study, where a time-varying effect model approach has been used to measure the effectiveness of marketing mix elements in the ice cream industry. In addition, we have compared the predictive validity of both static and dynamic models using this data set.

Transportation costs represent a significant role in the economics of packaged hay and biomass crops. The material’s low bulk density limits transportation efficiency. Density is currently limited by the ability of the baling twine to withstand the expansion forces generated by the baled material shortly after it is ejected from the bale chamber. It was hypothesized that compromising the structure of the plant, particularly the plant nodes could reduce the amount of energy stored in the material as it is compressed and thereby reduce the material’s elastic response to compression. Literature pertinent to the biomass material’s behavior in compression was reviewed. Bulk samples of switchgrass and miscanthus were subject to uniaxial compression, and the required pressure needed to obtain a target density of 256 kg/m3 was compared on a wet and dry density basis. Both switchgrass and miscanthus showed a statistically significant decrease in the required compression pressure, and the interaction between the moisture level and required pressure was also significant. Existing models for the pressure density relationship of compressed bulk material were evaluated for suitability. Individual nodes and internode sections were subject to radial compression and the apparent modulus of elasticity and maximum contact stress were determined.

Made available in DSpace on 2014-06-11T19:23:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-02-26Bitstream added on 2014-06-13T18:50:41Z : No. of bitstreams: 1 silva_lm_me_bauru_prot.pdf: 4671896 bytes, checksum: eb79f47df3c9400614b7c74b221948a0 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Os recentes avanços científicos permitiram um aumento significativo na qualidade de vida e por consequência, na longevidade. Como consequência disso, a população de idosos aumentou consideravelmente e com isso, doenças relacionadas à idade como osteoporose levam o governo a ter que gastar consideráveis quantias em próteses ortopédicas. Há também uma grande demanda devido aos acidentes de trânsito. Os materiais metálicos mais usados na manufatura de próteses são divididos em três grupos: aços inoxidáveis, ligas a base de Co e ligas a base de Ti. Dentre estes três grupos, os biomateriais mais utilizados são aqueles a base de Ti, pois apresentam excelente biocompatibilidade e elevada resistência à corrosão. A liga de Ti mais utilizada para aplicações biológicas é a liga Ti-6Al-4V, porém alguns estudos associam o V a efeitos citotóxicos e reações adversas em tecidos, enquanto o Al tem sido associado com desordens neurológicas. Para sanar este problema, novas ligas de Ti que apresentam em sua composição elementos como Nb, Ta, Zr, Fe e Mo estão sendo pesquisadas e o desenvolvimento de novas ligas de Ti contendo Nb para aplicação ortopédica é um tema de grande importância social e tecnológica, pois o Nb é um elemento não tóxico e não alergênico, possui elevada biocompatibilidade e tem o Brasil como seu maior produtor, daí a importância de desenvolvimento de ciência e tecnologia utilizando tal material. A presença de elementos intersticiais (O, C, N e H) altera de significativamente as propriedades mecânicas da liga, principalmente suas propriedades elásticas, causando endurecimento ou enfraquecimento da liga. As medidas de espectroscopia mecânica são uma ferramenta poderosa para o estudo da interação destes elementos substitucionais e intersticiais com os elementos que compõem a liga. Este trabalho apresenta o efeito... / Recent scientific advances have led to a significant increase in life's quality and consequently, longevity. As a result, the elderly population has increased considerably and thus age-related disease such as osteoporosis lead the government to spend considerable sums of money with orthopedic prostheses. There is also a great demand for orthopedic prostheses due to accidents. The metallic materials commonly used in the manufacture of prostheses are divided into three groups: stainless steel, Co-based alloys and Ti-based alloys. Among these three groups, the most widely used as a biomaterial are the Ti-based alloys, since they have excellent biocompatibility and high corrosion resistance. The most used Ti-based alloy for biological applications is the Ti-6Al-4V alloy, but some studies associate the V to the cytotoxic effects and adverse reactions in tissues, while Al has been associated with neurological disorders. To solve this problem, new Ti-based alloys that have in their composition elements such as Nb, Ta, Zr, Fe and Mo are being researched. The development of new Ti-based alloys containing Nb for orthopedic application is a topic of great social and technological relevance, as this element is a non-toxic, non allergenic, has high biocompatibility and has Brazil as its biggest producer, hence the importance of development of science and technology using this material. The presence of interstitial elements (O, C, N and H) changes significantly the mechanical properties of the alloy, particularly its elastic properties, causing hardening or softening of the alloy. Mechanical spectroscopy measurements represent a powerful tool for studying the interaction of substitutional and interstitial elements with the metal matrix. This work presents the effect of interstitial oxygen in solid solution in some mechanical properties and biocompatibility of two alloys of the Ti-Nb system... (Complete abstract click electronic access below)

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Este trabalho apresenta a formulação e implementação numérica do método dos elementos de contorno (MEC) para elasticidade linear tri-dimensional, com avaliação direta das integrais fracamente e fortemente singulares. A implementação segue a formulação tradicional do MEC direto, e a discretização do contorno das variáveis do problema é realizada com elementos descontínuos, permitindo o uso de malhas desconectadas ao longo das superfícies. O cálculo das integrais singulares é realizado através do uso de expansões assintóticas calculadas em torno de um ponto singular genérico. As expressões analíticas destas expansões são apresentadas no trabalho. Estas expansões serão subtraídas do núcleo original regularizando-o e a parte singular é integrada analiticamente, restando apenas uma integral regular, tornando ambas as integrais possíveis de serem calculadas com quadraturas de Gauss. É concluído que o presente método requer menos pontos de integração para o mesmo nível de erro quando comparado com outras técnicas. Alguns casos de elasticidade são resolvidos para ilustrar a eficiência e precisão do método. / This work presents the formulation and implementation of the boundary element method (BEM) to three dimensional linear elastostatics, with the direct evaluation of the strongly singular integral equations. The implementation follows the traditional direct BEM formulation, and the discretization of the boundary is carried out with discontinuous elements, enabling the use of disconnected meshes along the surfaces. The computation of the singular integral equations is accomplished by using the asymptotic expansions derived around a generic singular point. The analytical expressions for these expansions are presented in this work. The expansions are subtracted from the kernel to regularize it. This subtracted part is then added by computing a regular line integral along the boundary of the element. Both the integrals can be calculated with Gauss-type quadratures. It's observed that the present method needs less integration points for the same level of error when compared with other techniques. Several elasticity benchmarks are solved to demonstrate the eficiency and the accuracy of the present method.

Surface plasmon is the quantized collective oscillation of the free electron gas in a metallic material. By coupling surface plasmons with photons in different nanostructures, researchers have found surface plasmon polaritons (SPP) and localized surface plasmon resonance (LSPR), which are widely adopted in biosensing, single molecule sensing and detection via surface enhanced raman scattering (SERS), photothermal ablation treatments for cancer, optical tagging and detection, strain sensing, metamaterials, and other applications. The overall objective of this dissertation is to investigate both how mechanics impacts the optical properties, and also how optics impacts the mechanical properties of metal nanostructures reversely. Mechanically engineering individual nanostructures(forward coupling) offers the freedom to alter the optical properties with more flexibility and tunability. It is shown that elastic strain can be applied to gold nanowires to reduce the intrinsic losses for subwavelength optical signal processing, leading to an increase of up to 70% in the surface plasmon polariton propagation lengths at resonance frequencies. Apart from strain engineering, defects are another important aspect of mechanically engineering nanoscale materials, whose impacts on the optical properties of metal nanostructures remain unresolved. An atomic electrodynamic model has been derived to demonstrate that those effects are crucial for ultrasmall nanoparticles with characteristic sizes around 2 nm, and can be safely ignored for those larger than about 5 nm due to the important contribution of nanoscale surface effects. Another key focus of this research project (reverse coupling) is to investigate the currently unknown effects that an external optical field has on the mechanical properties of metal nanostructures. Since each atom in the nanostructure acts as a dipole due to induced electron motions, this optical excitation introduces additional dipolar forces that add to the standard mechanical atomic interactions, which could alter the mechanical properties of the nanostructures. Furthermore, it is shown that when linking mechanics with LSPR, because the metal is dispersive, the mechanical behavior or the strength of the nanostructure should be dependent on the frequency of the electromagnetic excitation. To study this phenomenon, a simpler case with an electrostatic field excitation is considered first, and conclusions are reached on how static fields can be used to tune the elasticity of metallic nanostructures with different sizes and axial orientations and surfaces. Then building upon those understandings, studies were carried out in determining the effects of an optical field, specifically at LSPR frequency, on the mechanical properties of metallic nanostructures. It is found that the initial relaxation strain induced by the static field or optical field is the key factor leading to the variations in the stiffness of the metallic nanostructures that are excited by optical fields at the LSPR frequencies.