Field grid

Field Grid for Testing Winter Feeding by Rabbits or Cottontails... 

Data Sheet 7.1 Results of field grid for food choices by cottontails (or rabbits)... 

Interaction energy values at each grid point are the CoMFA descriptors and are collected into a QSAR matrix where rows represent the molecules and columns the grid points for each considered field. Grid points without variance, i.e. within the volume shared by all molecules, or with small variance, i.e. far away from the van der Waals surface of molecules, are discarded. Moreover, other parameters such as logP... 

The number and shape of the grid blocks in the model depend upon the objectives of the simulation. A 100 grid block model may be sufficient to confirm rate dependent processes described in the previous section, but a full field simulation to be used to optimise well locations and perforation intervals for a large field may contain up to 100,000 grid blocks. The larger the model, the more time consuming to build, and slower to run on the computer. 

Peskin U, Miller W H and Ediund A 1995 Quantum time evolution in time-dependent fields and time-independent reactive-scattering calculations via an efficient Fourier grid preconditioner J. Chem. Phys. 103 10 030... 

Chu S I 1991 Complex quasivibrational energy formalism for intense-field multiphoton and above-threshold dissociation—complex-scaling Fourier-grid Hamiltonian method J. Chem. Phys. 94 7901... 

Besides the aforementioned descriptors, grid-based methods are frequently used in the field of QSAR quantitative structure-activity relationships) [50]. A molecule is placed in a box and for an orthogonal grid of points the interaction energy values between this molecule and another small molecule, such as water, are calculated. The grid map thus obtained characterizes the molecular shape, charge distribution, and hydrophobicity. 

Hybrid grids are used for very complex geometries where combination of structured mesh segments joined by zones of unstructured mesh can provide the best approach for discretization of the problem domain. The flexibility gained by combining structured and unstructured mesh segments also provides a facility to improve accuracy of the numerical solutions for field problems of a complicated nature. Figure 6.3 shows an example of this type of computational mesh. 

It should be emphasized at this point that the basic requirements of compatibility and consistency of finite elements used in the discretization of the domain in a field problem cannot be arbitrarily violated. Therefore, application of the previously described classes of computational grids requires systematic data transfomiation procedures across interfaces involving discontinuity or overlapping. For example, by the use of specially designed mortar elements necessary communication between incompatible sections of a finite element grid can be established (Maday et ah, 1989). 

Once the molecules are aligned, a molecular field is computed on a grid of points in space around the molecule. This field must provide a description of how each molecule will tend to bind in the active site. Field descriptors typically consist of a sum of one or more spatial properties, such as steric factors, van der Waals parameters, or the electrostatic potential. The choice of grid points will also affect the quality of the final results. 

The excellent corrosion-resistant lead dioxide, Pb02, film formed on anodes and lead—acid battery positive grids in sulfuric acid has enabled lead insoluble anodes and lead—acid batteries to maintain the dominant positions in their respective fields. 

Turbulent flame speed, unlike laminar flame speed, is dependent on the flow field and on both the mean and turbulence characteristics of the flow, which can in turn depend on the experimental configuration. Nonstationary spherical turbulent flames, generated through a grid, have flame speeds of the order of or less than the laminar flame speed. This turbulent flame speed tends to increase proportionally to the intensity of the turbulence. 

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