Diffusion and propagation in triangular Lorentz lattice gas cellular automata

The diffusion process of point particles moving on regular triangular and random lattices, randomly occupied with stationary scatterers (a Lorentz lattice gas cellular automaton), is studied, for strictly deterministic scattering rules, as a function of the concentration of the scatterers. In addition to the normal and various kinds of retarded diffusion found before on the regular square lattice, straight-line propagation through the scatterers is observed.     

Ensuring population diversity in genetic algorithms: A technical note with application to the cell formation problem

The entropy-based measure has been used in previous works to compute the population diversity in solving the cell formation problem with the genetic algorithm. Population diversity is crucial to the genetic algorithm’s ability to continue fruitful exploration as it may be used in choosing an initial population, in defining a stopping criterion, in evaluating the population convergence, and in making the search more efficient throughout the selection of crossover operators or the adjustment of various control parameters (e.g., crossover or mutation rate, population size). We show in this note that, when a non-ordinal chromosome representation corresponding to the allocation of machines to cells is used, the current way of measuring the population diversity is inaccurate. Consequently, it leads to wrong conclusions when, at various iterations, carrying out fruitful exploration or an efficient search of the solution space is guided by the perceived population diversity degree. An alternative approach based on computing the distance and the similarity between chromosomes is discussed.     

Further mathematical properties of Cayley digraphs applied to hexagonal and honeycomb meshes

In this paper, we extend known relationships between Cayley digraphs and their subgraphs and coset graphs with respect to subgroups to obtain a number of general results on homomorphism between them. Intuitively, our results correspond to synthesizing alternative, more economical, interconnection networks by reducing the number of dimensions and/or link density of existing networks via mapping and pruning. We discuss applications of these results to well-known and useful interconnection networks such as hexagonal and honeycomb meshes, including the derivation of provably correct shortest-path routing algorithms for such networks.     

Multi-objectives for incremental cell formation problem

Over the past three decades considerable amount of research work has been reported in the literature of Group Technology (GT). Most of the research work is concerned with formation of machine cells and part families. This is because cell formation is considered to be the most complex and the most important aspect of Cellular Manufacturing System (CMS). Due to NP completeness of cell formation problem, many heuristics have been developed. These heuristics are developed for both single as well as multiple objectives for the comprehensive cell formation. Here all part types and machine types are considered at a time for cell conversion and that all cells are designed at a single point in time. But planning and implementation of most cell conversions in industry are incremental ones, and not comprehensive. This issue has not been addressed in GT literature adequately. In this paper we consider multiple objectives for incremental cell formation and develop, a lexicographic based simulated annealing algorithm. The performance of the algorithm is tested over several data sets by taking different initial feasible solutions generated using different heuristics.     

On the use of the asymptotic forms of the boolean matrix for designing cellular manufacturing systems - An improved approach

The use of asymptotic forms of the boolean matrix for grouping machines and parts is of recent origin. It has distinct strengths such as the ability to identify bottlenecks. This paper analyses the existing approach and discovers its limitations. Persisting with the idea of exploiting the properties of the boolean matrix, this paper proposes an improved and robust method to identify bottlenecks, the maximum number of natural groups as well as a general method for the design of cellular manufacturing systems.     

具有外部输入和偏差的细胞神经网络的完全稳定性

本文证明了对于由两个细胞组成的细胞神经网络，外部输入和偏差不影响网络的稳定平衡点的存在性和完全稳定性．     

Global invariants and equilibrium states in lattice gases

It is now well known that, in addition to the physical conserved quantities, lattice gases also have other unphysical ones related to the discretization of their phase space. From an abstract point of view a lattice gas can be considered like a full discrete Markov processL and these spurious conserved quantities yield the existence of a nonspatially homogeneous equilibrium state forL ^k. We show that a particular set of these conserved quantities is of special interest: Its elements will be called regular. These regular invariants are simply built from the local ones and their projection on each node is always a locally conserved quantity. Moreover, for most models they are one-to-one related to the Gibbs states ofL ^k which remain factorized. It turns out that all the classical known spurious invariants are regular and one can exhibit simple conditions to build models with only regular invariants. For the latter it is then justified to determine the transport coefficients of the locally conserved densities with the Green-Kubo procedure.     

Fractal dimension at the phase transition of inhomogeneous cellular automata

For random binary mixtures of cellular automata in the square lattice, calculations are made of the fractal dimensions associated with the damage spreading and the propagation time of damage at the transition to chaos. Two rules are mixed and universalities of these quantities are sought with respect to change of the rules.     

Measurement and correlation of volumetric heat transfer coefficients of cellular ceramics

The volumetric heat transfer coefficients (h_v) between cellular ceramics and a stream of air were measured using the single-blow transient experimental technique in conjunction with an inverse analysis. Test specimen made of mullite, YZA, SiC, cordierite and cordierite with LS-2 coating was studied. The number of pores per centimeter (PPC) ranged from 4 to 26 and the specimen thickness ranged from 6 to 12 mm. Based on the experimental data, the volumetric heat transfer coefficients were generalized by developing Nusselt number vs. Reynolds number correlations of the form Nu_v=C Re^m for the materials studied. The effects of pore length-scale and specimen thickness on the volumetric heat transfer coefficients are presented and discussed.