Modelação da furação de laminados por elementos finitos

Furação de estruturas em compósitos de matriz poliméricaO recurso ao Método de Elementos Finitos (MEF) para a simulação e estudo da maquinagem tem vindo a merecer um interesse crescente. Neste trabalho comparam-se os resultados experimentais obtidos usando diferentes brocas helicoidais com uma simulação numérica da furação usando elementos sólidos tridimensionais do software ABAQUS® Explicit. Os resultados obtidos mostram a aplicabilidade do modelo, nomeadamente no que respeita à variação do principal parâmetro de corte no processo de furação – o avanço – e da geometria da ferramenta. O desenvolvimento das forças axiais durante a furação está directamente relacionado com a selecção dos parâmetros de corte e geometria de ferramenta e contribui para a existência de danos na placa. Assim, a minimização destas forças permite reduzir o risco de delaminação. Os resultados relativos à força para o início da delaminação são comparados com modelos analíticos já conhecidos. Os resultados numéricos apresentam uma concordância apreciável com os obtidos experimentalmente

Adsorption of yellow lanasol 4g reactive dye in a simulated textile effluent on gallinaceous feathers

Adsorption is one of the most efficient physicochemical processes known to remove colour in textile industry effluents. Activated charcoal is conventionally the most used material for this purpose and although its efficiency is very high also is its price. The aim of this study was to know the variables that influence the adsorption process of wool reactive dye Yellow Lanasol 4G in a simulated textile effluent, on an inexpensive and abundant material, gallinaceous feathers, so as to optimize the operating conditions. Factorial experimentation within a certain domain was used to determine the influence level of several parameters, such as, temperature, initial pH of the solution, "size" and adsorbent's concentration and their interactions. A statistical analysis of the results showed that within the selected domain all the parameters have influence at a significance level of 1% excepting initial pH that only has influence at a significance level of 5%. Some of the possible interactions between these parameters also have significant influence on the adsorption process specially first order ones, including significance levels of 5 and 1%. In industrial practice it will be possible to take advantage of the prominent effect of a temperature increase on adsorption capacity as effluents of wool dyeing baths are already at an elevated temperature. Besides that as the influence of "granulometry" becomes rather smaller for higher temperatures there will be no need to grind the adsorbent. This means then that optimization of operating conditions in industrial wastewaters treatment using the studied adsorption technique will not imply additional costs except those concerning pH adjustment. This emphasizes the importance of gallinaceous feathers as an alternative to activated carbon.(undefined

Naked-eye visualization of geometric frustration effects in macroscopic spin ices

We study planar rectangular-like arrays composed by macroscopic dipoles (magnetic bars with size around a few centimeters) separated by lattice spacing a and b along each direction. Physical behavior of such macroscopic artificial spin ice (MASI) systems are shown to agree much better with theoretical prediction than their micro- or nano-scaled counterparts, making MASI "almost ideal prototypes" for readily naked-eye visualization of geometrical frustration effects

The relevance of the two calcium sites inthe structure of the catalytic subunit (NrfA)

The Journal of Biological Chemistry Vol. 278, No. 19, Issue of May 9, pp. 17455–17465, 2003The gene encoding cytochrome c nitrite reductase(NrfA) from Desulfovibrio desulfuricans ATCC 27774 was sequenced and the crystal structure of the enzyme was determined to 2.3-Å resolution. In comparison with homologous structures, it presents structural differences mainly located at the regions surrounding the putative substrate inlet and product outlet, and includes a well defined second calcium site with octahedral geometry, coordinated to propionates of hemes 3 and 4, and caged by a loop non-existent in the previous structures. The highly negative electrostatic potential in the environment around hemes 3 and 4 suggests that the main role of this calcium ion may not be electrostatic but structural, namely in the stabilization of the conformation of the additional loop that cages it and influences the solvent accessibility of heme 4. The NrfA active site is similar to that of peroxidases with a nearby calcium site at the heme distal side nearly in the same location as occurs in the class II and class III peroxidases. This fact suggests that the calcium ion at the distal side of the active site in the NrfA enzymes may have a similar physiological role to that reported for the peroxidases

Perinatal hypoxic-ischemic encephalopathy: acute period and outcome

Ninety four neonates with hypoxic ischemic encephalopathy HIE attended at the University of Ribeirão Preto since 1982 were studied in terms of the neurological alterations during the acute phase and outcome over a mean period of 47 months. From 43 newborns with HIE I, 40 recovered within 96 hours and 3 died. Among 40 infants with HIE II, 37.5% recovered within the first week, and the others continued abnormal beyond the 7th day. All 11 infants with HIE III died before the second month of life. The HIE I group had no motor sequelae. Among the HIE II group, 34.5% showed cerebral palsy and 17.7% neuromotor retardation. 80.0% of those with sequelae persisted abnormal beyond 7th day of life, during the acute phase of the HIE. Epilepsy occurred in 17.5% of cases with HIE grade II, only among those with neuromotor sequelae. The 1Q test did not show statistically significant difference between the HIE I, II without motor sequelae and the control groups. The authors reaffirm the value of the findings in the acute phase of HIE on the outcome of these patients.Noventa e quatro recém-nascidos com encefalopatia hipóxico-isquêmica (EHI), atendidos no Hospital das Clínicas de Ribeirão Preto desde 1982, foram avaliados evolutivamente na fase aguda e por período médio de 47 meses. De 43 casos com EHI 1,40 se recuperaram em 96 horas e 3 faleceram. Dos 40 com EHI II, 37,5% se recuperaram até o sétimo dia e demais permaneceram com alterações. Os 11 casos com grau III faleceram até o segundo mês de vida. As crianças com EHI grau I não apresentaram seqüelas motoras. Do grupo com EHI grau II 34,5% apresentaram paralisia cerebral e 17,7% atraso neuromotor. 80% dos casos com sequela apresentaram exame neurológico anormal além do sétimo dia, na fase aguda da EHI. Epilepsia ocorreu em 17,5% dos casos com EHI grau II e somente no grupo com seqüelas motoras. Teste de QI não evidenciou diferença significativa entre os grupos com grau I, II sem seqüelas motoras e o grupo controle. Com esses dados os autores reafirmaram a importância prognostica da evolução da EHI na fase aguda.77177

A straightforward method to obtain the cohesive laws of bonded joints under mode I loading

A simple procedure to measure the cohesive laws of bonded joints under mode I loading using the double cantilever beam test is proposed. The method only requires recording the applied load–displacement data and measuring the crack opening displacement at its tip in the course of the experimental test. The strain energy release rate is obtained by a procedure involving the Timoshenko beam theory, the specimen’s compliance and the crack equivalent concept. Following the proposed approach the influence of the fracture process zone is taken into account which is fundamental for an accurate estimation of the failure process details. The cohesive law is obtained by differentiation of the strain energy release rate as a function of the crack opening displacement. The model was validated numerically considering three representative cohesive laws. Numerical simulations using finite element analysis including cohesive zone modeling were performed. The good agreement between the inputted and resulting laws for all the cases considered validates the model. An experimental confirmation was also performed by comparing the numerical and experimental load–displacement curves. The numerical load–displacement curves were obtained by adjusting typical cohesive laws to the ones measured experimentally following the proposed approach and using finite element analysis including cohesive zone modeling. Once again, good agreement was obtained in the comparisons thus demonstrating the good performance of the proposed methodology

Cancro infantil e comportamento parental

Procurou construir-se uma teoria sobre o comportamento de pais de crianças com cancro. Os participantes são oito mães e um pai de crianças com cancro diagnosticado entre os oito meses e os dez anos de idade. Foram feitas entrevistas semiestruturadas, codificadas e analisadas segundo o método Grounded Theory. Quatro das entrevistas tinham sido realizadas anteriormente por Gonçalves (2000). A partir do momento do diagnóstico, a maior preocupação dos pais é o medo da morte da criança e a incerteza inerente, que se traduz num choque, é inexplicável, permanente, invasiva, e que os pais procuram ocultar. Perante este receio, os pais desenvolvem uma estratégia fundamental – a centralização na criança. A criança doente torna-se o centro da dinâmica familiar, exigindo novos recursos e competências ao papel parental: apoio conjugal ou de terceiros, estratégias de minimização do sofrimento, a focalização das atenções no filho doente, procurar viver um dia de cada vez e do modo mais aproximado da normalidade possível. ------ ABSTRACT ------ The purpose of this study is to construct a theory about the behaviour of parents of children with cancer. The participants are eight mothers and one father of children with cancer diagnosed between eight months to ten years old. We coded and analysed eight semi-structured interviews according to the Grounded Theory method. We included in this analysis four interviews previously made by Gonçalves (2000). Since the moment of diagnosis, parents’ main concern is the fear of the child’s death and the inherent uncertainty, which is shocking, unexplainable, permanent, invasive and which parents try to hide. Confronted by this fear, parents develop a main strategy – centralisation on the ill child. Child becomes the centre of the family’s dynamic, which requires new resources and competencies of the parental functions: conjugal or others’ support, strategies of reducing pain, focusing on the ill child, trying to live one day at a time and as near to normality as possible

Modelação por elementos finitos do processo de furação em laminados de carbono/epóxido

Neste trabalho apresentam-se os resultados obtidos em simulações numéricas dafuração de laminados de carbono/epóxido usando elementos sólidos tridimensionais dosoftware ABAQUS® Explicit. O início e propagação do dano são simulados recorrendo ainstruções específicas do programa, bem como a remoção dos elementos ao longo doprocesso. Os resultados obtidos numericamente são comparados com resultadosexperimentais obtidos previamente pelos autores. Verifica-se uma boa concordância entre osresultados numéricos e os experimentais, confirmando a validade do modelo proposto