Stress intensity factors calculation in anti-plane fracture problem by orthogonal integral extraction method based on femol

For an anti-plane problem, the differential operator is self-adjoint and the corresponding eigenfunctions belong to the Hilbert space. The orthogonal property between eigenfunctions (or between the derivatives of eigenfunctions) of anti-plane problem is exploited. We developed for the first time two sets of radius-independent orthogonal integrals for extraction of stress intensity factors (SIFs), so any order SIF can be extracted based on a certain known solution of displacement (an analytic result or a numerical result). Many numerical examples based on the finite element method of lines (FEMOL) show that the present method is very powerful and efficient.

Molecular dynamics studies of brittle fracture of SiO2

By applying for molecular dynamics (MD) simulation and Griffith fracture criterion, the brittle behavior of crack extension of mode I type is investigated. The critical stress intensity factor (SIF)K-Ic(MD) of crack extension is calculated, and the evolution of atoms near crack tip is observed. It is found that K-Ic(MD) is in good agreement with the Griffith ftacture criterion K-Ic(Griffith).

纤维增强复合材料裂纹动态起始行为的研究

本论文主要研究线弹性纤维增强复合材料在冲击载荷作用下裂纹的动态起裂行为。全文共分六章。第一章对裂纹动态起始问题的研究方法和纤维增强复合材料中裂纹动态起始问题的国内外研究现状进行了综述，确定了本论文的主要研究内容和研究方法。第二章用有限元方法研究有限尺度含裂纹纤维增强复合材料板在阶跃冲击载荷作用下的动力响应，分析了裂尖附近的应力分布、应力波在板中的传播和应力强度因子时间历程。第三章根据第二章的计算结果用线弹性简单梁理论和拉格朗日运动方程研究了各向同性材料和纤维增强复合材料中裂纹在阶跃冲击载荷作用下的动力响应和起裂行为，得到了应力强度因子初始上升阶段的数学表达式和裂纹起裂的临界载荷面。第四章提出了用于单向和层合纤维增强复合材料裂纹静态和动态起始预测的拟应力强度因子比准则。该准则将裂纹的起裂和起裂方向的预测合二为一，只需测定材料的四个基本动态断裂韧性，就可据此准则对任意角度单向板中裂纹的起裂和起裂方向进行预测，用于层合板时，还可以对铺层裂纹的起裂顺序进行预测。第五章用SHTB（分离式Hopkinson拉杆）技术对纤维增强复合材料裂纹动态起始问题进行了实验研究。测量了碳纤维增强环氧树脂复合材料板裂纹起裂的I型动态断裂韧性，并首次验证了拟应力强度因子比准则在裂纹动态起裂预测中的合理性。第六章对全文进行了总结，归纳了本论文的主要结论，并展望了今后的研究工作。

Microscopia multimodal prática: registro automático de imagens de microscopia ótica e de microscopia eletrônica de varredura

A discriminação de fases que são praticamente indistinguíveis ao microscópio ótico de luz refletida ou ao microscópio eletrônico de varredura (MEV) é um dos problemas clássicos da microscopia de minérios. Com o objetivo de resolver este problema vem sendo recentemente empregada a técnica de microscopia colocalizada, que consiste na junção de duas modalidades de microscopia, microscopia ótica e microscopia eletrônica de varredura. O objetivo da técnica é fornecer uma imagem de microscopia multimodal, tornando possível a identificação, em amostras de minerais, de fases que não seriam distinguíveis com o uso de uma única modalidade, superando assim as limitações individuais dos dois sistemas. O método de registro até então disponível na literatura para a fusão das imagens de microscopia ótica e de microscopia eletrônica de varredura é um procedimento trabalhoso e extremamente dependente da interação do operador, uma vez que envolve a calibração do sistema com uma malha padrão a cada rotina de aquisição de imagens. Por esse motivo a técnica existente não é prática. Este trabalho propõe uma metodologia para automatizar o processo de registro de imagens de microscopia ótica e de microscopia eletrônica de varredura de maneira a aperfeiçoar e simplificar o uso da técnica de microscopia colocalizada. O método proposto pode ser subdividido em dois procedimentos: obtenção da transformação e registro das imagens com uso desta transformação. A obtenção da transformação envolve, primeiramente, o pré-processamento dos pares de forma a executar um registro grosseiro entre as imagens de cada par. Em seguida, são obtidos pontos homólogos, nas imagens óticas e de MEV. Para tal, foram utilizados dois métodos, o primeiro desenvolvido com base no algoritmo SIFT e o segundo definido a partir da varredura pelo máximo valor do coeficiente de correlação. Na etapa seguinte é calculada a transformação. Foram empregadas duas abordagens distintas: a média ponderada local (LWM) e os mínimos quadrados ponderados com polinômios ortogonais (MQPPO). O LWM recebe como entradas os chamados pseudo-homólogos, pontos que são forçadamente distribuídos de forma regular na imagem de referência, e que revelam, na imagem a ser registrada, os deslocamentos locais relativos entre as imagens. Tais pseudo-homólogos podem ser obtidos tanto pelo SIFT como pelo método do coeficiente de correlação. Por outro lado, o MQPPO recebe um conjunto de pontos com a distribuição natural. A análise dos registro de imagens obtidos empregou como métrica o valor da correlação entre as imagens obtidas. Observou-se que com o uso das variantes propostas SIFT-LWM e SIFT-Correlação foram obtidos resultados ligeiramente superiores aos do método com a malha padrão e LWM. Assim, a proposta, além de reduzir drasticamente a intervenção do operador, ainda possibilitou resultados mais precisos. Por outro lado, o método baseado na transformação fornecida pelos mínimos quadrados ponderados com polinômios ortogonais mostrou resultados inferiores aos produzidos pelo método que faz uso da malha padrão.

Investigation of fluorine three-dimensional redistribution during solid-phase-epitaxial-regrowth of amorphous Si

The fluorine redistribution during partial solid-phase-epitaxial-regrowth at 650°C of a preamorphized Si substrate implanted by F was investigated by atom probe tomography (APT), transmission electron microscopy, and secondary ions mass spectrometry. Three-dimensional spatial distribution of F obtained by APT provides a direct observation of F-rich clusters with a diameter of less than 1.5 nm. Density variation compatible with cavities and F-rich molecular ions in correspondence of clusters are in accordance with cavities filled by SiF 4 molecules. Their presence only in crystalline Si while they are not revealed by statistical analysis in amorphous suggests that they form at the amorphous/crystal interface. © 2012 American Institute of Physics.

Fracture mechanics analysis of cracks in solder joint intermetallic compounds

The trend towards miniaturization of electronic products leads to the need for very small sized solder joints. Therefore, there is a higher reliability risk that too large a fraction of solder joints will transform into Intermetallic Compounds (IMCs) at the solder interface. In this paper, fracture mechanics study of the IMC layer for SnPb and Pb-free solder joints was carried out using finite element numerical computer modelling method. It is assumed that only one crack is present in the IMC layer. Linear Elastic Fracture Mechanics (LEFM) approach is used for parametric study of the Stress Intensity Factors (SIF, KI and KII), at the predefined crack in the IMC layer of solder butt joint tensile sample. Contrary to intuition, it is revealed that a thicker IMC layer in fact increases the reliability of solder joint for a cracked IMC. Value of KI and KII are found to decrease with the location of the crack further away from the solder interfaces while other parameters are constant. Solder thickness and strain rate were also found to have a significant influence on the SIF values. It has been found that soft solder matrix generates non-uniform plastic deformation across the solder-IMC interface near the crack tip that is responsible to obtain higher KI and KII.

Clinical and technical factors associated with skin intrinsic fluorescence in subjects with type 1 diabetes from the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Study

The Diabetes Control and Complications Trial (DCCT)/Epidemiology of Diabetes Interventions and Complications(EDIC) studies have established multiyear mean hemoglobin A1c (HbA1c) as predictive of microvascular complications in persons with type 1 diabetes. However, multiyear mean HbA1c is not always available in the clinical setting. Skin advanced glycation end products (AGEs) are thought to partially reflect effects of hyperglycemia over time, and measurement of skin AGEs might be a surrogate for multiyear mean HbA1c. As certain AGEs fluoresce and skin fluorescence has been demonstrated to correlate with the concentration of skin AGEs, noninvasive measurement by skin intrinsic fluorescence(SIF) facilitates the exploration of the association of mean HbA1c and other clinical/technical factors with SIF using the detailed phenotypic database available in DCCT/EDIC.

The Association of Skin-Intrinsic Fluorescence With Type 1 Diabetes Complications in the DCCT/EDIC Study

OBJECTIVESTo determine whether skin-intrinsic fluorescence (SIF) is associated with long-term complications of type 1 diabetes (T1D) and, if so, whether it is independent of chronic glycemic exposure and previous intensive therapy.RESEARCH DESIGN AND METHODSWe studied 1,185 (92%) of 1,289 active Diabetes Control and Complications Trial (DCCT)/Epidemiology of Diabetes Interventions and Complications (EDIC) participants from 2010 to 2011. SIF was determined using a fluorescence spectrometer and related cross-sectionally to recently determined measures of retinopathy (stereo fundus photography), cardiac autonomic neuropathy (CAN; R-R interval), confirmed clinical neuropathy, nephropathy (albumin excretion rate [AER]), and coronary artery calcification (CAC).RESULTSOverall, moderately strong associations were seen with all complications, before adjustment for mean HbA1c over time, which rendered these associations nonsignificant with the exception of sustained AER >30 mg/24 h and CAC, which were largely unaffected by adjustment. However, when examined within the former DCCT treatment group, associations were generally weaker in the intensive group and nonsignificant after adjustment, while in the conventional group, associations remained significant for CAN, sustained AER >30 mg/24 h, and CAC even after mean HbA1c adjustment.CONCLUSIONSSIF is associated with T1D complications in DCCT\EDIC. Much of this association appears to be related to historical glycemic exposure, particularly in the previously intensively treated participants, in whom adjustment for HbA1c eliminates statistical significance.

Verification of a novel material model to predict damage in composite structures

An intralaminar damage model (IDM), based on continuum damage mechanics, was developed for the simulation of composite structures subjected to damaging loads. This model can capture the complex intralaminar damage mechanisms, accounting for mode interactions, and delaminations. Its development is driven by a requirement for reliable crush simulations to design composite structures with a high specific energy absorption. This IDM was implemented as a user subroutine within the commercial finite element package, Abaqus/Explicit[1]. In this paper, the validation of the IDM is presented using two test cases. Firstly, the IDM is benchmarked against published data for a blunt notched specimen under uniaxial tensile loading, comparing the failure strength as well as showing the damage. Secondly, the crush response of a set of tulip-triggered composite cylinders was obtained experimentally. The crush loading and the associated energy of the specimen is compared with the FE model prediction. These test cases show that the developed IDM is able to capture the structural response with satisfactory accuracy

Vlasov-kinetic computer simulations of electrostatic waves in dusty plasmas: an overview of recent results

A series of numerical simulations based on a recurrence-free Vlasov kinetic model using kinetic phase point trajectories are presented. Electron-ion plasmas and three-component (electron-ion-dust) dusty or complex plasmas are considered, via independent simulations. Considering all plasma components modeled through a kinetic approach, the linear and nonlinear behavior of ion-acoustic excitations is investigated. Maxwellian and kappa-type (superthermal) distribution functions are assumed, as initial conditions, in separate simulations for the sake of comparison. The focus is on the parametric dependence of ion-acoustic waves on the electron-to-ion temperature ratio and on the dust concentration. © 2014 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.

Os diferentes níveis de regulação legal dos conflitos de interesses no âmbito da gestão de fundos de investimento mobiliário

In the context of the activity developed by securities investment funds (hereinafter referred to “SIF”) the holders of investment units have a very tiny power to intervene. Aware of the risks that a decoupling between ownership and control may pose, the legislator has foreseen a number of impositions and limitations to the activity of the managing entities, namely to prevent or prohibit the performance of acts in situations of potential conflicts of interests. Accordingly, the purpose of the dissertation on – “Os diferentes níveis de regulação legal dos conflitos de interesses no âmbito da gestão de FIM” – is exactly to determine the field of application of the several levels of legal regulation of the conflicts of interests that arise within the scope of the management of SIF, both at the level of the new legal requirements governing collective investment undertakings, and at the level of the legal requirements governing the conflicts of interests foreseen in the Portuguese Securities Code, in order to clarify the articulation of these different levels of conflicts of interests regulations.

Évaluation du besoin et de la pertinence de l'implantation d'un service d'injection supervisée en Montérégie

This research project aimed to conduct a strategic analysis of the implementation of a supervised injecting facility (SIF) in Montérégie. Using a mixed design, we first completed a portrait of the injection drug user (IDU) population. We then explored the perceptions of IDU and stakeholders with regard to the relevance of implementing a SIF in the region. Although some similarities were found with the IDU populations of Montreal and the province of Quebec, this population in Montérégie is characterized by a lower frequency of injections in public, less homeless people and lower rates of HIV and HCV infections. Despite these differences, the IDU population in Montérégie was found to have important physical and psychosocial needs. Although the relevance of a SIF in Montérégie is undeniable, improvements regarding the accessibility, continuity and appreciation of the actual services dedicated to IDU remain a priority.

El MERCOSUR como vehículo estratégico de posicionamiento político regional. Caso de estudio: la política exterior de Brasil en el gobierno de Lula

La razón principal del protagonismo regional brasilero se deriva de su continuidad en la construcción de estrategias en política exterior. Fue precisamente esta continuidad, sustentada en una identidad nacional y una visión autónoma de inserción internacional, características propias de su herencia diplomática, lo que le permitió identificarse y ser identificado como un líder regional a través de uno de los mecanismos de integración más grandes en América Latina. Como resultado de la política exterior de Lula y su redireccionamiento hacia la región, Brasil logró impulsar y construir una región suramericana sustentada en un MERCOSUR. Un espacio de cooperación regido por unos intereses y valores compartidos en materia política, económica y cultural que le permitiera por un lado diversificar y expandir su economía y por el otro, un posicionamiento político reflejado en el UNASUR. Con base en lo anterior esta investigación busca responder a la pregunta ¿de qué manera el proyecto de integración MERCOSUR incidió en el posicionamiento político de Brasil en la región durante el gobierno de Lula? Para ello este trabajo se divide en tres partes. La primera explica la construcción de su política exterior hacia la región. La segunda parte busca analizar el rol que ha tenido Brasil en la evolución de MERCOSUR, toda vez que es por medio de este, que Brasil pudo afianzar un protagonismo regional y global. Por último, se explica el posicionamiento político regional brasilero teniendo en cuenta al MERCOSUR como un vehículo estratégico utilizado por Brasil para posicionarse políticamente en la región.

Análisis de perdurabilidad de las empresas que se acogieron a la ley 550 de 1999

A finales del Siglo XX, Colombia se encontraba en un escenario bastante complicado en relación con la situación del país en años anteriores. Todo esto, debido a que el país se vio afligido por una serie de situaciones adversas: el desempleo, la violencia y catástrofes naturales, fueron una de las muchas cosas que generaron un grave periodo de recesión en el país. Frente a estos desafortunados acontecimientos, y en búsqueda de propiciar y fortalecer la economía del país, el Gobierno decide en su momento, intervenir en la economía local, principalmente en el Sector Privado, con el fin de normalizar la actividad productiva del país en todos los sectores económico. Para esto, el Gobierno en conjunto con la Superintendencia de Sociedades y teniendo en cuenta la devaluación de la moneda, las altas tasas de interés que existían en ese entonces, y, la disminución de la demanda, deciden desarrollar mecanismos de conciliación tanto para los deudores como para los acreedores con el fin de reactivar la economía y mejorar la situación financiera y contable del sector productivo y de servicios, con el fin de superar la crisis en la que se encontraban sumergidos en ese entonces. La ley 550, constituida en el año 1999 y también conocida como la Ley de Insolvencia Económica, otorgo herramientas para la reestructuración de empresas que decidieron acogerse a dicha ley, a un total de 1.323 empresas que se encontraban en proceso de liquidación. Para poder acceder a este proceso de reestructuración, además de cumplir con ciertos requisitos que se mencionaran posteriormente, las empresas que podían acceder a esta ley, debían encontrarse en mora en el pago de 2 o más obligaciones por un periodo mayor a noventa días, o, se debían encontrar envueltas en por lo menos 2 demandas ejecutivas por mora en el pago de cualquier deuda adquirida en nombre de dichas empresas.