Mesoscale modeling and simulation of microstructure evolution during dynamic recrystallization of a Ni-based superalloy

Microstructural evolution and plastic flow characteristics of a Ni-based superalloy were investigated using a simulative model that couples the basic metallurgical principle of dynamic recrystallization (DRX) with the twodimensional (2D) cellular automaton (CA). Variation of dislocation density with local strain of deformation is considered for accurate determination of the microstructural evolution during DRX. The grain topography, the grain size and the recrystallized fraction can be well predicted by using the developed CA model, which enables to the establishment of the relationship between the flow stress, dislocation density, recrystallized fraction volume, recrystallized grain size and the thermomechanical parameters

The great jerboa (Allactaga major) in the North Azov Region (Ukraine): distribution and abundance

The analysis of the species historical spread in Ukraine was conducted. The dependence of preservation of its localities on the availability of more or less large areas of virgin steppe unsuitable for arable farming was showed. The original data for the past 20 years on the great jerboa’s distribution within the Northern Pryazovia were reported, as well as the conditions of existence of its stable populations in the Azov Upland area. The reasons of further reduction in number and fragmentation of its range are the destruction of virgin steppe because of plowing and afforestation, alongside with increasing the projective vegetation cover due to reduce of grazing. To protect jerboa and other rare steppe species we proposed moratorium on plowing and other kinds of destruction of the virgin steppe and creation of a new environmental legislation on conservation, restoration and sustainable use of the steppe, the National Heritage of Ukraine

Application of boundary integral equation method to numerical solution of elliptic boundary-value problems in R3

In this paper we propose numerical methods for solving interior and exterior boundary-value problems for the Helmholtz and Laplace equations in complex three-dimensional domains. The method is based on their reduction to boundary integral equations in R2. Using the potentials of the simple and double layers, we obtain boundary integral equations of the Fredholm type with respect to unknown density for Dirichlet and Neumann boundary value problems. As a result of applying integral equations along the boundary of the domain, the dimension of problems is reduced by one. In order to approximate solutions of the obtained weakly singular Fredholm integral equations we suggest general numerical method based on spline approximation of solutions and on the use of adaptive cubatures that take into account the singularities of the kernels. When constructing cubature formulas, essentially non-uniform graded meshes are constructed with grading exponent that depends on the smoothness of the input data. The effectiveness of the method is illustrated with some numerical experiments.</jats:p