6. Regularized additive schemes

Keyword(s):  
1996 ◽  
Vol 465 ◽  
Author(s):  
E. R. Vance ◽  
K. P. Hart ◽  
R. A. Day ◽  
M. L. Carter ◽  
M. Hambley ◽  
...  

ABSTRACTThree wt% each of Cs and Tc were mixed with the standard Synroc precursor and the ceramic was formed by hot-pressing. Attempts were made to incorporate the Tc as either metal or Tc 4+, using different redox conditions in processing. Volatile losses of Tc during calcination were < 0.1% in all cases. Short-term Tc leach rates when the Tc was present as a metal alloy were in the order of 10−4 g/m /d at 90°C with frequently changed water, and decreased with increasing leaching time. The valence of the Tc was monitored by X-ray absorption spectroscopy at the drying and calcination stages of the production. The general viability of Synroc/glass composites for immobilising the Hanford HLW sludges is further demonstrated by using further refinements of additive schemes for the inactive “All-blend” formulation and initial studies using the U-containing “All-blend” waste formulation.


2008 ◽  
Vol 8 (4) ◽  
pp. 393-405 ◽  
Author(s):  
P.N. VABISHCHEVICH

AbstractAt the present time, the domain decomposition methods are considered as the most promising ones for parallel computer systems. Nowadays success is attained mainly in solving approximately the classical boundary value problems for second-order elliptic equations. As for the time-dependent problems of mathematical physics, there are, in common use, approaches based on ordinary implicit schemes and implemented via iterative methods of the domain decomposition. An alternative technique is based on the non-iterative schemes (region-additive schemes). On the basis of the general theory of additive schemes a wide class of difference schemes (alternative directions, locally one-dimensional, factorized schemes, summarized approximation schemes, vec-tor additive schemes, etc.) as applied to the domain decomposition technique for time-dependent problems with synchronous and asynchronous implementations has been investigated. For nonstationary problems with self-adjoint operators, we have considered three dif-ferent types of decomposition operators corresponding to the Dirichlet and Neumann conditions on the subdomain boundaries. General stability conditions have been obtained for the region-additive schemes. We focused on the accuracy of domain decom-position schemes. In particular, the dependence of the convergence rate on the width of subdomain overlapping has been investigated as the primary property. In the present paper, new classes of domain decomposition schemes for nonstationary problems, based on the subdomain overlaping and minimal data exchange in solving problems in subdomains, have been constructed.


1982 ◽  
Vol 60 (4) ◽  
pp. 480-485 ◽  
Author(s):  
John T. Edward

Additive schemes for calculating the molar volumes and heats of vaporization of liquid alkanes from increments characteristic of the numbers and different types of carbon atoms (primary, secondary, tertiary, quaternary), of the mole fraction Zg of gauche conformations, and (where necessary) of other steric factors have been developed. It is suggested that schemes for correlating physical properties of alkanes with connectivity indices mχt are successful because these indices are also correlated with numbers and types of carbon atoms and with Zg.


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