Linking continuum mechanics and 3D discrete dislocation simulations

A technique is developed for linking the methods of discrete dislocation dynamics simulation and finite element to treat elasto-plasticity problems. The overall formulation views the plastically deforming crystal as an elastic crystal with continuously changing dislocation microstructure which is tracked by the numerical dynamics simulation. The FEM code needed in this regard is based on linear elasticity only. This formulation presented here is focused on a continuous updating of the outer shape of the crystal, for possible regeneration of the FEM mesh, and adjustment of the surface geometry, in particular the surface normal. The method is expected to be potentially applicable to the nano- indentation experiments, where the zone around the indenter-crystal contact undergoes significant permanent deformation, the rigorous determination of which is very important to the calculation of the indentation print area and in turn, the surface hardness. Furthermore, the technique is expected to account for the plastic history of the surface displacement under the indenter. Other potential applications are mentioned in the text

A robust uniform B-spline collocation method for solving the generalized PHI-four equation

In this paper, we develop a numerical solution based on cubic B-spline collocation method. By applying Von-Neumann stability analysis, the proposed technique is shown to be unconditionally stable. The accuracy of the presented method is demonstrated by a test problem. The numerical results are found to be in good agreement with the exact solution

Hepatoprotective effect of basil (Ocimum basilicum L.) on CCl4-induced liver fibrosis in rats

The hepatoprotective effect of basil (Ocimum basilicum) extract against liver fibrosis-induced by carbon tetrachloride (CCl4) was studied in rats. Rats were allocated into five groups: Group I (control group); Group II [CCl4 group; rats were injected subcutaneously with CCl4 (1 ml/kg b.w.) twice weekly for 4 weeks (phenobarbital, 350 mg/L, was added to the drinking water throughout the experiment)]; Group III received daily oral doses of basil extract of 200 mg/kg b.w. along with CCl4 and phenobarbital for 6 weeks; Groups IV and V rats were treated with phenobarbital and CCl4 for 6 weeks then treated daily with oral dose of 200 mg/kg b.w basil extract, or by 300 mg/kg b.w dimethyl diphenyl bicarboxylate (DDB), respectively for 6 weeks. Basil-treatment significantly reduced the liver content of hydroxyproline and significantly increased the activity of hyaluronidase (HAase). The hepatic activity of superoxide dismutase (SOD) was stimulated while the lipid peroxidation was significantly reduced by the effect of basil extract. Treatment with CCl4 significantly increased the activities of transaminases [aspartate aminotransferase (AST), alanine aminotransferase (ALT)], and alkaline phosphatase (ALP). These activities were significantly decreased by basil extract. The higher levels of serum urea and creatinine in CCl4 group were significantly guarded by the protection of basil.Key words: Carbon tetrachloride, liver fibrosis, antioxidant, Ocimum basilicum, dimethyl diphenyl bicarboxylate

Postirradiation fiber debonding and pull-out in Sic-Sic composites *

Abstract The toughness of ceramic matrix composites is contributed by crack bridging, matrix crack deflection, fiber debonding and pull-out and other minor effects. Crack bridging relies on fibers being intact close to the crack tip, while pull-out toughening relies on the debonding and frictional characteristics of the fiber-matrix interface. The interface friction depends on the interface pressure (i.e., on misfit strains) and interface roughness. In this paper, a calculational model for postirradiation fiber debonding and pull-out toughness in Sic-Sic composites is presented. It is shown that fiber debonding and pull-out toughness in Sic-Sic composites vary significantly with neutron fluence and irradiation tem~rature, which is a direct wnsequen~ of the dependence of the misfit strain on these irradiation variables. I~t~uction Sic-Sic composites have been proposed for structural applications in fusion reactor first walls and blankets. The fracture toughness of these composites can be measured from work-of-fracture experiments, and can be theoreticafly determined by investigating the mechanisms of energy dissipation during composite failure. In addition to matrix toughness and matrix crack deflection, two other contributions are considered important in toughening SIC-SIC materials. First is the crack-tip bridging by intact fibers, which contributes a closure traction and lowers the stress intensity at the crack tip. This contribution is important in case of small cracks. The second contribution is caused by fiber debonding, fiber fracture and pull-out, which occurs at significant crack openings, thus involving * This material is based upon work supported by the US Department of Energy under award number DE-FGO3-91ER.54115. energy dissipation by interface friction. Fiber bridging, debonding and pull-out depend on the composite mismatch stresses, i.e., on misfit strains. Neutron irradiation alters the composite behavior in a complex fashion. In addition to basic property changes under irradiation, irradiation-induced swelling and creep change the mismatch stress state, which has a direct influence on the fracture strength and toughness of Sic-Sic composites. Detailed calculations of the time-evolution of mismatch stresses in Sic-Sic composites under high-temperature neutron irradiation are performed [l]. General inelastic wnstitutive equations for Sic fibers and SiC matrix, which are developed by the present authors 121 are used for that purpose. It is found that misfit strains change significantly during early irradiation, and that long-term changes depend on helium swelling and creep only, regardless of the initial thermal mismatch state. Accordingly, fiber debonding and pull-out behavior are expected to depend on the neutron fluence, In the present work, we calculate the postirradiation pull-out toughness and fiber debonding in Sic-Sic composites as functions of neutron fluence and irradiation temperature. 0022-3115/94/$07.00 0 1994 Elsevier Science B.V. All rights reserved SSDZ 0022-3115(94)00058-

A probabilistic multi-objective approach for FACTS devices allocation with different levels of wind penetration under uncertainties and load correlation

This study presents a probabilistic multi-objective optimization approach to obtain the optimal locations and sizes of static var compensator (SVC) and thyristor-controlled series capacitor (TCSC) in a power transmission network with large level of wind generation. In this study, the uncertainties of the wind power generation and correlated load demand are considered. The uncertainties are modeled in this work using the points estimation method (PEM). The optimization problem is solved using the Multi-objective particle swarm optimization (MOPSO) algorithm to find the best position and rating of the flexible AC transmission system (FACTS) devices. The objective of the problem is to maximize the system loadability while minimizing the power losses and FACTS devices installation cost. Additionally, a technique based on fuzzy decision-making approach is employed to extract one of the Pareto optimal solutions as the best compromise one. The proposed approach is applied on the modified IEEE 30-bus system. The numerical results evince the effectiveness of the proposed approach and shows the economic benefits that can be achieved when considering the FACTS controller

Accuracy of the cutoff value of the third molar maturity index: an Egyptian study

Abstract Background This study aimed to test the sensitivity and specificity of the third molar maturity index (I3M) cutoff value to discriminate between individuals above and below 18 years of age in an Egyptian sample. Material and methods Digital images of 247 orthopantographs (97 boys and 150 girls) were evaluated. The cutoff value of I3M obtained from the results of Cameriere et al. (Int J Legal Med 122:493–497, 2008) was evaluated in both girls and boys. Results Sensitivity (the proportion of individuals being 18 years of age or older) was 95% and 73% in boys and girls, respectively. Meanwhile, specificity (the proportion of individuals younger than 18) was 100% in boys and 97% in girls. The proportion of correctly classified boys was 97% while it was 59% in girls. Conclusion It can be concluded that the third molar maturity index can discriminate between individuals who are 18 years and over and those under 18 with higher accuracy in boys

Statistical characterization of dislocation ensembles

We outline a method to study the spatial and orientation statistics of dynamical dislocation systems by modeling the dislocations as a stochastic fiber process. Statistical measures have been introduced for the density, velocity, and flux of dislocations, and the connection between these measures and the dislocation state and plastic distortion rate in the crystal is explained. A dislocation dynamics simulation model has been used to extract numerical data to study the evolution of these statistical measures numerically in a body-centered cubic crystal under deformation. The orientation distribution of the dislocation density, velocity and dislocation flux, as well as the dislocation correlations have been computed. The importance of the statistical measures introduced here in building continuum models of dislocation systems is highlighted

Novel Li3ClO based glasses with superionic properties for lithium batteries

Three types of next generation batteries are currently being envisaged among the international community: metal-air batteries, multivalent cation batteries and all-solid-state batteries. These battery designs require high-performance, safe and cost effective electrolytes that are compatible with optimized electrode materials. Solid electrolytes have not yet been extensively employed in commercial batteries as they suffer from poor ionic conduction at acceptable temperatures and insufficient stability with respect to lithium-metal. Here we show a novel type of glasses, which evolve from an antiperovskite structure and that show the highest ionic conductivity ever reported for the Li-ion (25 mS cm-1 at 25 °C). These glassy electrolytes for lithium batteries are inexpensive, light, recyclable, non-flammable and non-toxic. Moreover, they present a wide electrochemical window (higher than 8 V) and thermal stability within the application range of temperatures