Modelagem do caminhar humano e avaliação de conforto humano de passarelas de pedestres.

Com o passar dos anos a engenharia estrutural passou a lidar com a exigência cada vez maior de estruturas que ocupem menos espaço e sejam consideravelmente mais leves. No caso de passarelas de pedestres, a esbeltez da estrutura aliada a um baixo peso pode acarretar em problemas de vibrações devido à ressonância com o caminhar dos pedestres. Estes problemas podem variar desde uma simples sensação de desconforto até problemas mais graves como o colapso estrutural. Com base nestas premissas, esta dissertação visa investigar dois modelos estruturais, um em concreto armado e outro misto, do tipo aço concreto, onde os modelos serão estudados mediante o emprego do método dos elementos finitos através do programa ANSYS. Os modelos numéricos permitem determinar as frequências naturais da estrutura e consequentemente estudar as respostas dos modelos mediante análises de vibrações forçadas. As respostas dinâmicas da estrutura serão obtidas em termos dos valores dos deslocamentos máximos e das acelerações de pico. Os resultados obtidos foram comparados com os principais guias que regem o conforto humano no caso de caminhar de pessoas em passarelas de pedestres, de forma que houve indicativos de possíveis desconfortos após a análise dos resultados obtidos ao longo da investigação. Finalmente, foi feito um estudo considerando-se movimentos aleatórios dos pedestres sobre as passarelas, objetivando estudar os níveis da resposta dinâmica das estruturas nestas situações.

Estudo do comportamento estrutural e análise de conforto humano de edifícios de concreto armado.

Atualmente, os projetos de edifícios altos necessitam cada vez mais de sistemas estruturais simples, que agilizem sua montagem, reduzindo os custos e promovendo maior flexibilidade de utilização para os espaços construídos. Com essa finalidade, estruturas com poucas vigas vêm sendo muito utilizadas. Entretanto, o sistema estrutural com poucas vigas pode ocasionar dois tipos de problemas, relacionados entre si, a saber: diminuição do sistema de contraventamento da edificação e vibrações excessivas. Portanto, é fundamental, nesses casos, a verificação da estabilidade global da estrutura, utilizando índices de sensibilidade além de outros parâmetros de projeto, como também, o desenvolvimento de um estudo minucioso acerca do conforto humano da edificação. Assim sendo, neste trabalho de pesquisa foram investigados quatro modelos estruturais de edifícios altos de concreto armado, com base no estudo da variação entre o número de pavimentos e a quantidade de vigas existentes em cada modelo, objetivando-se verificar quais os efeitos que tais variações podem vir a gerar sobre a estabilidade global e, bem como, sobre o conforto humano dos sistemas estruturais investigados. A modelagem numérica dos edifícios em estudo foi realizada através do emprego do programa ANSYS e, para tal, foram utilizadas técnicas básicas de discretização, por meio do método dos elementos finitos. As conclusões alcançadas ao longo da investigação versam acerca do estudo da resposta estrutural estática e dinâmica dos edifícios, no que diz respeito as variações dos valores dos parâmetros de instabilidade, dos valores dos deslocamentos e esforços, e, bem como, dos níveis de conforto humano de cada modelo estrutural analisado.

Modelagem do comportamento estrutural estático e dinâmico e avaliação de conforto humano de edifícios de concreto armado.

Nas últimas décadas, a partir do crescimento substancial da população das grandes cidades, a demanda por espaço para habitação tem crescido de maneira importante. Para atender a estas necessidades, edificações cada vez mais altas e mais esbeltas são projetadas e vãos cada vez maiores são utilizados. Novos materiais são criados e aprimorados para que seja extraído o máximo de desempenho com o menor custo. Deste modo, esta dissertação tem como objetivo o estudo do comportamento estrutural e avaliação de conforto humano de edifícios de concreto armado. Para tal, são considerados ao longo do estudo quatro projetos de edificações de concreto armado distintos, com alturas variando na faixa de 30m a 70m (11 a 24 pavimentos), submetidos às ações das cargas usuais de projeto atuantes sobre edifícios residenciais, além das cargas de vento. No que tange ao desenvolvimento dos modelos computacionais são empregadas técnicas usuais de discretização, via método dos elementos finitos, por meio do programa ANSYS. Inicialmente, a resposta estrutural estática (deslocamentos e esforços) e dinâmica (acelerações de pico) dos modelos é obtida e comparada com base nos valores limites propostos por normas e recomendações de projeto. A partir de análises qualitativas e quantitativas desenvolvidas sobre a resposta dos modelos em estudo o desempenho estrutural dos edifícios analisados é avaliado, no que diz respeito ao conforto humano.

Recent advance in the study of ribosomal model.

With the technological developments of cryoelectron microscope, X-ray diffraction and the growing data available on various components of ribosome, some marvelously intricate structural models of the Escherichia coli 70S ribosome have been reconstructed. The picture of the ribosomal model are detailed, including the placement of the mRNA, the arrangement of the A-site and P-site tRNAs and the peptidyltransferase within the interface gap as well as the path of nascent polypeptide chain, which results in a better understanding of the structure and function of ribosome as well as the translational process.

焦虑的因素结构及其在中学生中的验证

Since anxiety exists as a certain kind of relation between the subject and his stimuli, present study proposed the criterion that every one of the anxiety’s structural components had to manifest the properties of the relation, not the subject’s properties, and not the stimuli’s properties, too; and that every component must be a bridge from the subject to the object. Several structural models on anxiety were judged by the criterion, and three suited factors were drawn out, which were controllability, importance and urgency. Then through various methods of interview, questionnaire, laboratorial experiment, events graded, the research examined the relations between the three factors and normal anxiety, and explored the interaction of controllability, importance and urgency when they worked together. The results were as the following: 1. The hypothesis that controllability, importance and urgency were the structural components of normal anxiety sounds reasonable, which was supported in different degrees by the results of several secondary research with various methods. 2. With a totally different method of constructing items from the prevalent integrative anxiety inventory, an effective normal anxiety inventory of middle school students was developed based on this theoretical consideration. Reliability and validity research showed that the coefficient of homogeneity and test-retest reliability were high. The construct validity and criterion validity were good enough. The inventory was a useful scale to measure the normal anxiety for middle school students. 3. It’s through their interaction that controllability and importance effect on the level of anxiety which was produced by the relevant event. 4. Anxiety arises with the increasing of importance or urgency. Though there’s a very close connection between controllability and anxiety, the concrete situation is very complicated. Not only is the level of anxiety affected by the interaction of controllability and importance, but when controllability tends to be extremely high or extremely low, importance may also begin to vary with controllability. What’s more, dispositional optimism and self-efficacy still exert influences that cannot be ignored on the relationship between controllability and anxiety. All the results indicated that it was reasonable to regard and study anxiety as a kind of relation between the subject and his environment, and to some extent it’s even necessary if the intention was to clarify the structure of anxiety. Since all the other emotion also exists as a kind of relation between the subject and his stimuli, the wholeness principle which was first proposed and recommended in this study will be of great value to the related researchers. And the interaction between controllability and importance may suggest a valid coping strategy of anxiety.

The structure of nano sized poorly-crystalline iron oxy-hydroxides

In this thesis the structures of three nano sized poorly-crystalline iron oxy-hydroxides, feroxyhyte, ferrihydrite and schwertmannite, are studied and analyzed with the aim of clarifying some dubious structural features. The widely used Rietveld re�nement and EXAFS analysis are employed in order to address the consistency of the structural models proposed for these materials, one of which, feroxyhyte, is suggested in this thesis. Furthermore, a new computer program exploiting the Reverse Monte Carlo algorithm and the Debye Scattering Equation is presented and used in order to analyze the elusive structures of these iron oxy-hydroxides.

First principles simulation of amorphous silicon bulk, interfaces, and nanowires for photovoltaics

Amorphous silicon has become the material of choice for many technologies, with major applications in large area electronics: displays, image sensing and thin film photovoltaic cells. This technology development has occurred because amorphous silicon is a thin film semiconductor that can be deposited on large, low cost substrates using low temperature. In this thesis, classical molecular dynamics and first principles DFT calculations have been performed to generate structural models of amorphous and hydrogenated amorphous silicon and interfaces of amorphous and crystalline silicon, with the ultimate aim of understanding the photovoltaic properties of core-shell crystalline amorphous Si nanowire structures. We have shown, unexpectedly, from the simulations, that our understanding of hydrogenated bulk a-Si needs to be revisited, with our robust finding that when fully saturated with hydrogen, bulk a-Si exhibits a constant optical energy gap, irrespective of the hydrogen concentration in the sample. Unsaturated a-Si:H, with a lower than optimum hydrogen content, shows a smaller optical gap, that increases with hydrogen content until saturation is reached. The mobility gaps obtained from an analysis of the electronic states show similar behavior. We also obtained that the optical and mobility gaps show a volcano curve as the H content is varied from 7% (undersaturation) to 18% (mild oversaturation). In the case of mild over saturation, the mid-gap states arise exclusively from an increase in the density of strained Si-Si bonds. Analysis of our structures shows the extra H atoms in this case form a bridge between neighboring silicon atoms which increases the corresponding Si-Si distance and promotes bond length disorder in the sample. That has the potential to enhance the Staebler-Wronski effect. Planar interface models of amorphous-crystalline silicon have been generated in Si (100), (110) and (111) surfaces. The interface models are characterized by structure, RDF, electronic density of states and optical absorption spectrum. We find that the least stable (100) surface will result in the formation of the thickest amorphous silicon layer, while the most stable (110) surface forms the smallest amorphous region. We calculated for the first time band offsets of a-Si:H/c-Si heterojunctions from first principles and examined the influence of different surface orientations and amorphous layer thickness on the offsets and implications for device performance. The band offsets depend on the amorphous layer thickness and increase with thickness. By controlling the amorphous layer thickness we can potentially optimise the solar cell parameters. Finally, we have successfully generated different amorphous layer thickness of the a-Si/c-Si and a-Si:H/c-Si 5 nm nanowires from heat and quench. We perform structural analysis of the a-Si-/c-Si nanowires. The RDF, Si-Si bond length distributions, and the coordination number distributions of amorphous regions of the nanowires reproduce similar behaviour compared to bulk amorphous silicon. In the final part of this thesis we examine different surface terminating chemical groups, -H, - OH and –NH2 in (001) GeNW. Our work shows that the diameter of Ge nanowires and the nature of surface terminating groups both play a significant role in both the magnitude and the nature of the nanowire band gaps, allowing tuning of the band gap by up to 1.1 eV. We also show for the first time how the nanowire diameter and surface termination shifts the absorption edge in the Ge nanowires to longer wavelengths. Thus, the combination of nanowire diameter and surface chemistry can be effectively utilised to tune the band gaps and thus light absorption properties of small diameter Ge nanowires.

Pyrrolidinium Ionic Liquid Crystals

N-Alkyl-N-methylpyrrolidinium cations have been used for the design of ionic liquid crystals, including a new type of uranium-containing metallomesogen. Pyrrolidinium salts with bromide, bis(trifluoromethylsulfonyl)-imide, tetrafluoroborate, hexafluorophosphate, thiocyanate, tetrakis(2-thenoyltrifluoroacetonato)europate(III) and tetrabromouranyl] counteranions were prepared. For the bromide salts and tetrabromouranyl compounds, the chain length of the alkyl group CnH2n+1 was varied from eight to twenty carbon atoms (n =8. 10-20). The compounds show rich mesomorphic behaviour: highly ordered smectic phases (the crystal smectic E phase and the uncommon crystal smectic T phase), smectic A phases, and hexagonal. columnar phases were observed, depending on chain length and anion. This work gives better insight into the nature and formation of the crystal smectic T phase, and the Molecular requirements for the appearance of this highly ordered phase. This uncommon tetragonal mesophase is thoroughly discussed on the basis of detailed powder X-ray diffraction experiments and in relation to the existing literature. Structural models are proposed for self-assembly of the molecules within the smectic layers. In addition, the photophysical properties of the compounds containing a metal complex anion were investigated. For the uranium-containing mesogens, luminescence can be induced by dissolving them in an ionic: liquid matrix. The europium-containing compound shows intense red photoluminescence with high colour Purity.

Unfunded pension liabilities and sponsoring firm credit risk: an international analysis of corporate bond spreads

This paper tests empirically whether pension information derived by corporate pension accounting disclosures is priced in corporate bond spreads. The model represents a hybrid of more traditional accounting ratio-based models of credit risk and structural models of bond spreads initiated by Merton (1974). The model is fitted to 5 years of data from 2002 to 2006 featuring companies from the US and Europe. The paper finds that while unfunded pension liabilities are priced in the overall sample, they are not priced as aggressively as traditional leverage. Furthermore, an extended model shows that the pension–credit risk relation is most evident in the US and Germany, where unfunded pension liabilities are priced more aggressively than traditional forms of leverage. No pension–credit risk relation is found in the other countries sampled, notably the UK, Netherlands and France.

Functional analysis of the large periplasmic loop of the Escherichia coli K-12 WaaL O-antigen ligase

WaaL is a membrane enzyme implicated in ligating undecaprenyl-diphosphate (Und-PP)-linked O antigen to lipid A-core oligosaccharide. We determined the periplasmic location of a large (EL5) and small (EL4) adjacent loops in the Escherichia coli K-12 WaaL. Structural models of the EL5 from the K-12, R1 and R4 E. coli ligases were generated by molecular dynamics. Despite the poor amino acid sequence conservation among these proteins, the models afforded similar folds consisting of two pairs of almost perpendicular alpha-helices. One alpha-helix in each pair contributes a histidine and an arginine facing each other, which are highly conserved in WaaL homologues. Mutations in either residue rendered WaaL non-functional, since mutant proteins were unable to restore O antigen surface expression. Replacements of residues located away from the putative catalytic centre and non-conserved residues within the centre itself did not affect ligation. Furthermore, replacing a highly conserved arginine in EL4 with various amino acids inactivates WaaL function, but functionality reappears when the positive charge is restored by a replacement with lysine. These results lead us to propose that the conserved amino acids in the two adjacent periplasmic loops could interact with Und-PP, which is the common component in all WaaL substrates.

Automated Methods for Virtual Maintainability & Aerospace Maintenance Planning

Abstract. Modern business practices in engineering are increasingly turning to post manufacture service provision in an attempt to generate additional revenue streams and ensure commercial sustainability. Maintainability has always been a consideration during the design process but in the past it has been generally considered to be of tertiary importance behind manufacturability and primary product function in terms of design priorities. The need to draw whole life considerations into concurrent engineering (CE) practice has encouraged companies to address issues such as maintenance, earlier in the design process giving equal importance to all aspects of the product lifecycle. The consideration of design for maintainability (DFM) early in the design process has the potential to significantly reduce maintenance costs, and improve overall running efficiencies as well as safety levels. However a lack of simulation tools still hinders the adaptation of CE to include practical elements of design and therefore further research is required to develop methods by which ‘hands on’ activities such as maintenance can be fully assessed and optimised as concepts develop. Virtual Reality (VR) has the potential to address this issue but the application of these traditionally high cost systems can require complex infrastructure and their use has typically focused on aesthetic aspects of mature designs. This paper examines the application of cost effective VR technology to the rapid assessment of aircraft interior inspection during conceptual design. It focuses on the integration of VR hardware with a typical desktop engineering system and examines the challenges with data transfer, graphics quality and the development of practical user functions within the VR environment. Conclusions drawn to date indicate that the system has the potential to improve maintenance planning through the provision of a usable environment for inspection which is available as soon as preliminary structural models are generated as part of the conceptual design process. Challenges still exist in the efficient transfer of data between the CAD and VR environments as well as the quantification of any benefits that result from the proposed approach. The result of this research will help to improve product maintainability, reduce product development cycle times and lower maintenance costs.

Prediction of Transonic LCOs using an Aeroelastic Harmonic Balance Method

This work proposes a novel approach to compute transonic Lim
it Cycle Oscillations using high fidelity analysis. CFD based Harmonic Balance methods have proven to be efficient tools to predict periodic phenomena. This paper’s contribution is to present a new methodology to determine the unknown frequency of oscillations, enabling HB methods to accurately capture Limit Cycle Oscillations (LCOs); this is achieved by defining a frequency updating procedure based on a coupled CFD/CSD Harmonic Balance formulation to find the LCO condition. A pitch/plunge aerofoil and delta wing aerodynamic and respective linear structural models are used to validate the new method against conventional time-domain simulations. Results show consistent agreement between the proposed and time-marching methods for both LCO amplitude and frequency, while producing at least one order of magnitude reduction in computational time.

Prediction of Limit Cycle Oscillations Using an Implicit Aeroelastic-Harmonic Balance Method

This work proposes a extends a novel approach to compute tran sonic Limit Cycle Oscillations using high fidelity analysis. CFD based Harmonic Balance methods have proven to be efficient tools to predict periodic phenomena. This paper’s contribution is to present a methodology to determine the unknown frequency of oscillations using an implicit for- mulation of the HB method to accurately capture Limit Cycle Oscillations (LCOs); this is achieved by defining a frequency updating procedure based on a coupled CFD/CSD Harmonic Balance formulation to find the LCO condition. A pitch/plunge aerofoil and respective linear structural models is used to exercise the new method. Results show consistent agreement between the proposed and time-marching methods for both LCO amplitude and frequency.

Prediction of Transonic Limit-Cycle Oscillations Using an Aeroelastic Harmonic Balance Method

This work proposes a novel approach to compute transonic limit-cycle oscillations using high-fidelity analysis. Computational-Fluid-Dynamics based harmonic balance methods have proven to be efficient tools to predict periodic phenomena. This paper’s contribution is to present a new methodology to determine the unknown frequency of oscillations, enabling harmonic balance methods to accurately capture limit-cycle oscillations; this is achieved by defining a frequency-updating procedure based on a coupled computational-fluid-dynamics/computational-structural-dynamics harmonic balance formulation to find the limit-cycle oscillation condition. A pitch/plunge airfoil and delta wing aerodynamic and respective linear structural models are used to validate the new method against conventional time-domain simulations. Results show consistent agreement between the proposed and time-marching methods for both limit-cycle oscillation amplitude and frequency while producing at least a one-order-of-magnitude reduction in computational time.

Autonomy and Relatedness in Mainland Chinese Adolescents: Social or Personal? Accommodation or Distinctiveness?

Three studies comprised the current research program, in which the major goals were to propose and validate empirically the proposed two-level (universal and culture-specific) model of both autonomy and relatedness, as well as to develop reliable and valid measures for these two constructs. In Study 1, 143 mainland Chinese adolescents were asked open-ended questions about their understanding of autonomy and relatedness in three social contexts (peer, family, school). Chinese youth’s responses captured universal and culturally distinctive forms of autonomy (personal vs. social) and relatedness (accommodation vs. distinctiveness), according to a priori criteria based on the theoretical frameworks. Also, scenarios designed to reflect culture-specific forms of autonomy and relatedness suggested their relevance to Chinese adolescents. With a second sample of 201 mainland Chinese youth, in Study 2, the obtained autonomy and relatedness descriptors were formulated into scale items. Those items were subject to refinement analyses to examine their psychometric properties and centrality to Chinese youth. The findings of Study 1 scenarios were replicated in Study 2. The primary goal of Study 3 was to test empirically the proposed two-level (universal and culture-specific) models of both autonomy and relatedness, using the measures derived from Studies 1 and 2. A third sample of 465 mainland Chinese youth completed a questionnaire booklet consisting of autonomy and relatedness scales and scenarios and achievement motivation orientations measures. A series of confirmatory factor analysis (CFA) autonomy and relatedness measurement models (first-order and second-order), as well as structural models linking culture-specific forms of autonomy and relatedness and achievement motivation orientations, were conducted. The first-order measurement models based on scale and scenario scores consistently confirmed the distinction between personal autonomy and social autonomy, and that of accommodation and distinctiveness. Although the construct validity of the two culture-specific forms of autonomy gained additional support from the structural models, the associations between the two culture-specific forms of relatedness and achievement motivation orientations were relatively weak. In general, the two-level models of autonomy and relatedness were supported in two ways: conceptual analysis of scale items and second-order measurement models. In addition, across the three studies, I explored potential contextual and sex differences in Chinese youth’s endorsement of the diverse forms of autonomy and relatedness. Overall, no substantial contextual variability or sex differences were found. The current research makes an important theoretical contribution to the field of developmental psychology in general, and autonomy and relatedness in particular, by proposing and testing empirically both universal and culture-specific parts of autonomy and relatedness. The current findings have implications for the measurement of autonomy and relatedness across social contexts, as well as for socialization and education practice.