Sensitivity analysis of cohesive zone model parameters to simulate hydrogen embrittlement effect

For many steels and alloys used in engineering field, the presence of atomic hydrogen in working environment can produce a deleterious effect. In fact, when this small element penetrates into the material lattice induces a drastically decrease of the mechanical properties. This process is known as hydrogen embrittlement. This complex phenomenon involves chemical and physical factors that are strictly dependent on the microstructure of the material. Some examples are hydrogen diffusivity, solubility of hydrogen into the material and concentration related not only to the interstitial lattice sites (NILS) but also to the traps sites that is the most difficult part to quantify. The present work starts from the development of 2D finite elements cohesive zone model reproducing a toughness test of a high-strength low carbon steel, AISI 4130 operating in hydrogen-contaminated environment. With three consequent steps of simulations, the model implements diffusion and crack propagation analyses using cohesive elements. The embrittlement effect of hydrogen is considered by decreasing the cohesive law (TSL), which expresses the constitutive response of the material to the fracture behavior, based on the total hydrogen concentration. It includes NILS and traps sites. Aim of the work is a sensitivity analysis of the parameters included into the model. In particular, the influence of the hydrogen diffusion coefficient as well as the initial concentration set to calculate the total hydrogen concentration at the crack tip are taken into account. Both a comparison of the values used in the model with literature data and a critical discussion of the results obtained by the sensitivity analysis will be presented

Talking about persons--thinking about patients: An ethnographic study in critical care.

BACKGROUND: Nursing involves caring for the 'whole person' and it is considered inappropriate for nurses to think or talk about patients in objectifying or dehumanising ways. Objectifying discourses can dominate within the arena of critical care, and critical care nurses can experience moral distress as they struggle to think about patients as persons. No previous study has examined the role played by 'impersonal' talk in the delivery of nursing care. This paper reports a study which examined the relationship between nursing practice and the way(s) in which critical care nurses think and talk about patients. OBJECTIVES: The study objectives were to (1) identify and characterise the ways in which critical care nurses think and talk about patients; and (2) describe patterns of nursing practice associated with these different ways of thinking. STUDY DESIGN: An ethnographic study was undertaken within one critical care unit in the United Kingdom. Data were collected over 8 months through 92h of participant observation and 13 interviews. Seven critical care nurses participated in the study. Data analysis adopted the perspective of linguistic ethnography. FINDINGS: Analysis of these data led to the identification of seven Discourses, each of which was characterised by a particular way of talking about patients, a particular way of thinking about patients, and a particular pattern of practice. Four of these seven Discourses were of particular significance because participants characterised it as 'impersonal' to think and talk about patients as 'routine work', as a 'body', as '(un)stable' or as a 'medical case'. Although participants frequently offered apologies or excuses for doing so, these 'impersonal' ways of thinking and talking were associated with practice that was essential to delivering safe effective care. CONCLUSIONS: Critical care practice requires nurses to think and talk about patients in many different ways, yet nurses are socialised to an ideal that they should always think and talk about patients as whole persons. This means that nurses can struggle to articulate and reflect upon aspects of their practice which require them to think and talk about patients in impersonal ways. This may be an important source of distress to critical care nurses and emotional exhaustion and burnout can arise from such dissonance between ideals and the reality of practice. Nursing leaders, scholars and policy makers need to recognise and legitimise the fact that nurses must think about patients in many ways, some of which may be considered impersonal

Quarkonium baryons in the topological soliton model

Abstract We show that the bound state version of the topological soliton model for the baryons, which is consistent with both chiral symmetry in the light quark sector and heavy quark spin symmetry in the heavy flavour sector, implies that the c c and b b pseudoscalar mesons form bound states with nucleons, the binding energy increasing with the heavy meson (quark) mass. The result qualitatively agrees with the earlier QCD-based results that heavy quarkonia should bind to nuclei, although the prediction that the binding energy grows with the heavy quark mass disagrees with the (approximate) QCD-based results

Stereopsis in sports: Visual skills and visuomotor integration models in professional and non-professional athletes

Visual skills in sport are considered relevant variables of athletic performance. However, data on the specific contribution of stereopsis—as the ability to perceive depth—in sport performance are still scarce and scattered in the literature. The aim of this review is therefore to take stock of the effects of stereopsis on the athletic performance, also looking at the training tools to improve visual abilities and potential differences in the visuomotor integration processes of professional and non-professional athletes. Dynamic stereopsis is mainly involved in catching or interceptive actions of ball sports, whereas strategic sports use different visual skills (peripheral and spatial vision) due to the sport-specific requirements. As expected, professional athletes show better visual skills as compared to non-professionals. However, both non-professional and professional athletes should train their visual skills by using sensory stations and light boards systems. Non-professional athletes use the visual inputs as the main method for programming motor gestures. In contrast, professional athletes integrate visual information with sport expertise, thus, they encode the match (or the athletic performance) through a more complex visuomotor integration system. Although studies on visual skills and stereopsis in sports still appear to be in their early stages, they show a large potential for both scientific knowledge and technical development

Object-based image analysis for historic maps classification

Heritage maps represent fundamental information for the study of the evolution of a region, especially in terms of landscape and ecologic features. Historical maps present two kinds of hurdle before they can be used in a modern GIS: they must be geometrically corrected to correspond to the datum in use and they must be classified to exploit the information they contain. This study deals the latter problem: the Historical Cadaster Map, created between 1851 and 1861, for the Trentino region in the North of Italy is available as a collection of maps in the ETRS89/UTM 32N datum. The map is a high resolution scan (230 DPI, 24 bit) of the original map and has been used in several ecological studies, since it provides detailed information not only about land property but also about land use. In the past the cadaster map has been manually digitized and for each area a set of attributes has been recorded. Since this approach is time consuming and prone to errors, automatic and semi-automatic procedures have been tested. Traditional image classification techniques, such as maximum likelihood classification, supervised or un-supervised, pixelwise and contextual, do not provide satisfactory results for many reasons: map colors are very variable within the same area, symbols and characters are used to identify cadaster parcels and locations, lines, drawn by hand on the original map, have variable thickness and colors. The availability of FOSS tools for the Object-based Image Analysis (OBIA) has made possible the application of this technique to the cadaster map. This paper describes the use of GRASS GIS and R for the implementation of the OBIA approach for the supervised classification of the historic cadaster map. It describes the determination of the optimal segments, the choice of their attributes and relevant statistics, and their classification. The result has been evaluated with respect to a manually digitized map using Cohens Kappa and the analysis of the confusion matrix. The result of the OBIA classification has also been compared to the classification of the same map using maximum likelihood classification, un-supervised and supervised, both pixelwise and contextual. The OBIA approach has provided very satisfactory results with the ability to automatically remove the background and symbols and characters, creating a ready to be used classified map. This study highlights the effectiveness of the OBIA processing chain available in the FOSS4G ecosystem, and in particular the added value of the interoperability between GRASS GIS and R

Tratamento de água oleosa por eletrofloculação

A técnica de eletrofloculação foi utilizada empregando-se eletrodos de alumínio para separar o óleo da água oleosa sintética contendo uma concentração média de 200 ppm de óleo cru. Para avaliar a sua viabilidade, foram determinados os percentuais de remoção de demanda química de oxigênio (DQO) e óleos e graxas totais (TOG), a concentração de sólidos totais, voláteis e fixos, a condutividade elétrica, o pH, a acidez e a alcalinidade total das amostras do efluente oleoso ao longo do tratamento. Estimou-se, também, o custo energético e operacional para o desenvolvimento da técnica. Neste trabalho construiu-se um reator eletrolítico, de bancada, com capacidade de 4 litros. Em seu interior, eletrodos de alumínio em arranjo paralelo foram conectados a uma placa alternadora de polaridade e a uma fonte de corrente contínua. Testes preliminares foram realizados para definir a melhor relação área do eletrodo por volume de efluente quanto à remoção de DQO. A partir destes testes, fixou-se o maior eletrodo (13,0 X 6,5 X 0,2 cm) por ter apresentado a melhor condição (cerca de 90%). Nos resultados foram verificados: aumento do pH; a condutividade elétrica e a concentração de sólidos apresentaram valores próximos durante o tratamento; a média percentual de remoção de TOG foi de 96%, enquanto que a de DQO foi de 81%. No fim da eletrólise, o efluente resultante ficou qualitativamente transparente. A análise estatística para condutividade elétrica e concentração de sólidos totais mostrou que estas dependem significativamente da concentração de eletrólito no meio (NaCl). Para a DQO e o TOG, somente a distância entre os eletrodos foi o fator significativo. Já a variação de pH inicial não apresentou significância em relação as variáveis analisadas. Quanto ao custo energético, a técnica de eletrofloculação apresentou, em média R$0,32/m3, um consumo do eletrodo de 0,60 g.e um custo operacional R$ 3,41/m3. Frente aos resultados, constatou-se que é possível utilizar a técnica de eletrofloculação no tratamento de água oleosa devido aos valores técnico-econômico satisfatórios, comparados com a literatura