CELL computer code

The Car-Parrinello simulations were performed using the MOTECC-90 computer code [13]. All considered systems consist of 64 atoms in a cubic unit cell with a length of 23.4 a.u. and periodic boundary conditions. The plane-wave cut-off was chosen to be 6 Ryd. The atomic cores were described by the pseudopotentials of Bachelet et al. [14]. 

We can express the use of all the different units in evolution in the language of thermodynamics. While the genome is defined by a DNA sequence so that each base has a singular intensive property as in a computer code of symbols, by way of contrast, the protein content of a cell is an extensive property being concentration dependent and therefore varies under circumstances such as temperature and pressure although... 

The computational code used in solving the hydrodynamic equation is developed based on the CFDLIB, a finite-volume hydro-code using a common data structure and a common numerical method (Kashiwa et al., 1994). An explicit time-marching, cell-centered Implicit Continuous-fluid Eulerian (ICE) numerical technique is employed to solve the governing equations (Amsden and Harlow, 1968). The computation cycle is split to two distinct phases a Lagrangian phase and a remapping phase, in which the Arbitrary Lagrangian Eulerian (ALE) technique is applied to support the arbitrary mesh motion with fluid flow. 

Presented band structure calculations have been done by computer code SOLID 2000 [4,5], The lattice parameters of MgB2 (hexagonal structure, space group P6mmm), with the fraction coordinates of the unit cell atoms Mg = (0,0,0) B1 = (1/3,2/3,1/2) B2 = (2/3,1/3,1/2), have been optimized in a good agreement with the experiment, a/ Equilibrium - undistorted geometry... 

For this example, we do not give the MATLAB code for the differential equations. The code can be fairly complex and, thus, its development is prone to error. The problem is even more critical in the spreadsheet application where several cells need to be rewritten for a new mechanism. We will address this problem later when we discuss the possibility of automatic generation of computer code based on traditional chemical equations. 

This assumption is unrealistic using even the most powerful single processor PC available in late 2002. A more rational estimate is between 10 and 10 unit cells per second for a well optimized computer code. 

The unit cell reduction using Delaunay-Ito method can be easily automated as is done in the ITO indexing computer code, which is discussed in section 5.11. The Delaunay-Ito reduced unit cell, however, may not be the one with the shortest possible vectors, although the latter is conventionally defined as a standard reduced unit cell. 

This algorithm realizes a zone search indexing method combined with the Delaunay-Ito technique (see section 5.10.1) for the reduction of the most probable unit cell. The most commonly used versions of computer codes are ITO 13 and IT015. The program arrives at a solution by using the following algorithm ... 

You are now ready to enter the equations for the internal and boundary nodes. Some spreadsheets may start solving the equations as you enter them leading to all sorts of error messages. To avoid this outcome, define a constant in, say, cell A3 (first column, third row) to be zero, and multiply each equation by A3 as you enter it. Then, when you have completed entering all the equations, you need to solve the problem, change A3 from 0 to 1, and begin iteration. A formula is entered in a cell, but the formulas themselves are not displayed in the cell on the screen. What is displayed is the value given by the formula. For example, to show the product in cell DIO of the feed located in cell F24 and the concentration located in F25, you would enter into cell DIO the formula F24 F25. It is recommended that you set up the overall material balances about specific process units in addition to the equations entered on the main part of the spreadsheet. If you take this step, you can quickly check for errors in the setup of the balances. Also, as you enter equations and data, check interim calculations just as you would check out a computer code as it was written. 

Figure 3.3 is an example of the change in composition of fuel in a PWR during irradiation, calculated by the computer code CELL [B2]. In this example fuel charged to the reactor contained 3.2 w/o in total uranium. The extent of irradiation, plotted along the x axis, is... 

Watt [W2] has used the computer codes CELL and CORE to evaluate the reactivity-limited bumup of a 1060-MWe PWR operated with modified scatter refueling as a function of the... 

Weight percents from this table are plotted against burnup as the points in Fig. 3.29. These points are to be compared with the lines, taken from Fig. 3.3, representing weight percents calculated by the more accurate point-depletion computer code CELL [B2]. Agreement is excellent for U and fair for Pu, but poor for the higher plutonium isotopes at hi bumup. This is because the effective absorption cross section of Pu decreases as its... 

Figure 3.29 Change of nuclide concentrations in PWR with bumup. iP) Equations of this chapter ( ) Pu, equations of this chapter ( ) Pu, equations of this chapter (—) computer code CELL.

The reactivity equals zero at a burnup of 20,833 MWd/MT. This is in excellent agreement with the reactivity-limited burnup of 21,085 MWd/MT for batch irradiation of 3.2 w/o fuel in this reactor obtained by Watt [W2] using the computer codes CELL [B2] and CORE [Kl]. 

B2. Beaudreau, J. J. Development and Evaluation of the Computer Code CELL, thesis submitted to the Department of Nuclear Engineering, Massachusetts Institute of Technology, Cambridge, Mass., in partial fulfillment of requirements for the M.S. degree, 1967. 

The first stage of any lattice simulation is to equilibrate the structure, i.e. bring it to a state of mechanical equilibrum. The simplest procedure is to equilibrate under conditions of constant volume, i.e. with invariant cell dimensions. Extensions to the procedure were introduced by Parker (1982, 1983) who introduced the use of constant pressure minimization in the computer code METAPOCS, in which lattice energy minimization was performed with respect... 

The two-phase motion problem is very stiff, with a wide separation of timescales and a transport matrix which becomes singular as the solution relaxes to its quasi-steady state. The asymptotic analysis presented eliminates the stiffness that is the bane of numerical simulations, affording computational speed-up of 3-4 orders of magnitude over the full system. Building this model into a unit cell simulation code promises huge reductions in computational cost and admits the possibility of performing either full stack-based calculations or doing extensive inverse calculations and parameter estimation. 

Hot Cell Facility Department Computer Code Calculations... 

Structure Thus no symmetry relations, beyond the helix operation, are assumed. They are to be inferred from the resulting stable inking arrangements. However, this plan results in discovering the primitive unit cell. Very (Aen it is a convenience to impose some symmetry operations so that a symmetry-centered cell results directly. It is quite feasible to write a computer code that allows these operations to be imposed or not, according to the problem studied. 

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