Effective Surface and Boundary Condition for Heterogeneous Salt Media with Insoluble Material

Effective Surface and Boundary Condition for Heterogeneous Salt Media with Insoluble Materia

Mapping Applications to an FPFA Tile

This paper introduces a transformational design method which can be used to map code written in a high level source language, like C, to a coarse grain reconfigurable architecture. The source code is first translated into a control data flow graph (CDFG), which is minimized using a set of behaviour preserving transformations, such as dependency analysis, common subexpression elimination, etc. After applying graph clustering, scheduling and allocation transformations on this minimized graph, it can be mapped onto the target architecture

Dispersion in Porous Media with Heterogeneous Nonlinear Reactions

The upscaling of mass transport in porous media with a heterogeneous reaction at the fluid–solid interface, typical of dissolution problems, is carried out with the method of volume averaging, starting from a pore-scale transport problem involving thermodynamic equilibrium or nonlinear reactive boundary conditions. A general expression to describe the macro-scalemass transport is obtained involving several effective parameterswhich are given by specific closure problems. For representative unit cell with a simple stratified geometry, the effective parameters are obtained analytically and numerically, while for those with complicated geometries, the effective parameters are only obtained numerically by solving the corresponding closure problems. The impact on the effective parameters of the fluid properties, in terms of pore-scale Péclet number Pe, and the process chemical properties, in terms of pore-scale Damköhler number Da and reaction order (n), is studied for periodic stratified and 3D unit cells. It is found that the tortuosity effects play an important role on the longitudinal dispersion coefficient in the 3D case, while it is negligible for the stratified geometry. When Da is very small, the effective reaction rate coefficient is nearly identical to the pore-scale one, while when Da is very large, the reactive condition turns out to be equivalent to pore-scale thermodynamic equilibrium, and the macro-scale mass exchange term is consequently given in a different form from the reactive case. An example of the application of the macro-scale model is presented with the emphasis on the potential impact of additional, non-traditional effective parameters appearing in the theoretical development on the improvement of the accuracy of the macro-scale model

Agriculture and Dairy Production Systems in China: An Overview and Case Studies

The Chinese dairy industry is growing rapidly. Since 1980, the rate of increase in dairy cattle in China's dairy industry (+210,000 cows per year) is 1.7 times higher than the rate of decline of dairy cattle in the US dairy industry (-124,000 cows per year). If the current trends do not change, there will be as many dairy cows in China as in the US-approximately 7.45 million cows in 2012. This two-part Discussion Paper presents the context in which the Chinese dairy industry is developing (Part I) and a study of the Dairy Farm systems and case studies of five farms in the Province of Yunnan, the city of Beijing and the province of Heilongjiang (Part II).Chinese Dairy Industry, Dairy Cows in China, Development of the Chinese Dairy Industry, Chinese Dairy Farm Case Studies, Consumer/Household Economics, Farm Management, International Development, International Relations/Trade, Productivity Analysis,

A Large-Scale Model for Dissolution in Heterogeneous Porous Media

Dissolution of pore-scale soluble substances occurs in applications from environmental hydrogeology to CO2 storage. Development of Darcy-scale models has been widely discussed. This paper proposes an upscaling algorithm to develop large-scale models taking into account Darcy-scale heterogeneities. The theory is based on a comparison between the characteristic length-scale of the Darcy-scale heterogeneities and the length-scale of the dissolution front controlled by a Darcy-scale Damkhler number. The obtained large-scale model is shown to confront favorably to Darcy-scale direct numerical simulations

Effective surface and boundary conditions for heterogeneous surfaces with mixed boundary conditions.

To deal with multi-scale problems involving transport from a heterogeneous and rough surface characterized by a mixed boundary condition, an effective surface theory is developed, which replaces the original surface by a homogeneous and smooth surface with specific boundary conditions. A typical example corresponds to a laminar flow over a soluble salt medium which contains insoluble material. To develop the concept of effective surface, a multi-domain decomposition approach is applied. In this framework, velocity and concentration at micro-scale are estimated with an asymptotic expansion of deviation terms with respect to macro-scale velocity and concentration fields. Closure problems for the deviations are obtained and used to define the effective surface position and the related boundary conditions. The evolution of some effective properties and the impact of surface geometry, Péclet, Schmidt and Damköhler numbers are investigated. Finally, comparisons are made between the numerical results obtained with the effective models and those from direct numerical simulations with the original rough surface, for two kinds of configurations

The `bare' strange stars might not be bare

It is proposed that the `bare' strange matter stars might not be bare, and radio pulsars might be in fact `bare' strange stars. As strange matter stars being intensely magnetized rotate, the induced unipolar electric fields would be large enough to construct magnetospheres. This situation is very similar to that discussed by many authors for rotating neutron stars. Also, the strange stars with accretion crusts in binaries could act as X-ray pulsars or X-ray bursters. There are some advantages if radio pulsars are `bare' strange stars.Comment: 11 pages, 1 Postscript figures, LaTeX, Chin. Phys. Lett. 1998, Vol.15, Nov.12, p.93

Fast computation of the Gauss hypergeometric function with all its parameters complex with application to the Poschl-Teller-Ginocchio potential wave functions

The fast computation of the Gauss hypergeometric function 2F1 with all its parameters complex is a difficult task. Although the 2F1 function verifies numerous analytical properties involving power series expansions whose implementation is apparently immediate, their use is thwarted by instabilities induced by cancellations between very large terms. Furthermore, small areas of the complex plane are inaccessible using only 2F1 power series formulas, thus rendering 2F1 evaluations impossible on a purely analytical basis. In order to solve these problems, a generalization of R.C. Forrey's transformation theory has been developed. The latter has been successful in treating the 2F1 function with real parameters. As in real case transformation theory, the large canceling terms occurring in 2F1 analytical formulas are rigorously dealt with, but by way of a new method, directly applicable to the complex plane. Taylor series expansions are employed to enter complex areas outside the domain of validity of power series analytical formulas. The proposed algorithm, however, becomes unstable in general when |a|,|b|,|c| are moderate or large. As a physical application, the calculation of the wave functions of the analytical Poschl-Teller-Ginocchio potential involving 2F1 evaluations is considered.Comment: 29 pages; accepted in Computer Physics Communication

Upscaling and large-scale modeling of the dissolution of gypsum cavities

The dissolution of geological formations containing gypsum can rapidly create various karstic features, and may potentially generate great risks such as subsidence and collapse [1]. To understand the gypsum dissolution mechanism is very important to develop safety measures. It is not feasible to take into account all the pore-scale details at a large-scale by direct numerical modeling, and some sort of macro-scale models are essential. Such a macro-scale porous medium model can also serve as a diffuse interface model to describe the dissolution at a fluid/solid interface, as done in [2]. The objective of this study is to develop a macro-scale model, starting from the pore-scale transport problem with boundary condition corresponding to non-linear reaction or thermodynamic equilibrium, making use of the method of volume averaging [3], and then implement it for a large-scale cavity dissolution modeling

Upscaling and large-scale modeling of the dissolution of gypsum cavities

The dissolution of geological formations containing gypsum can rapidly create various karstic features, and may potentially generate great risks such as subsidence and collapse. To understand the gypsum dissolution mechanism is very important to develop safety measures. In practical applications, it is not feasible to take into account all the pore-scale details at a large-scale by direct numerical modeling, therefore some sort of macro-scale modeling is necessary. In this study, we will develop a general expression of the macro-scale model for gypsum dissolution, starting from the pore-scale transport problem with boundary condition of thermodynamic equilibrium or non-linear reaction, making use of the method of volume averaging. Then, this macro-scale porous medium model will be used as a diffuse interface model (DIM) to solve for large-scale cavity dissolution examples, typical of situations leading to sinkhole formations, with the mass exchange term for Ca2+ given in the form of a first order reaction. A work-flow is proposed to choose properly the parameters in the model to reflect accurately the interface recession. Additional tests are performed to check which type of momentum balance equation should be used. It is shown that a proper choice for the mass exchange coefficient leads to satisfactory results with the macro-scale model, and that Darcy-Darcy and Darcy-Navier- Stokes formulations give almost the same cavity formation for the studied cases