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This paper presents a methodology to solve the manufacturing cell creation and the production scheduling problems for designing virtual cellular manufacturing systems (VCMSs). The objective is to minimize the total materials and components travelling distance incurred. The methodology consists of (i) a mathematical model that describes the characteristics of a VCMS and includes constraints such as delivery due dates of products, maximum capacities of resources, critical tools limitation, and (ii) an ant colony optimization (ACO) algorithm for manufacturing cell formation and production scheduling. Since the proposed ACO algorithm does not indicate a feasible schedule explicitly, two simple heuristics are developed to assign workstations to the operations of the jobs, and to construct the final schedule.To demonstrate the effectiveness of the proposed methodology, both the ACO algorithm and the genetic algorithm are applied to design manufacturing cells for a company in China producing internal combustion engine components. Comparison of the results obtained with the results supplied by the company on the existing manufacturing system show that both the ACO algorithm and the genetic algorithm together with the virtual cellular manufacturing concept perform better than the current manufacturing practice in terms of average workstation utilization, product completion time and system throughput. Also, the results of a set of randomly generated numerical experiments show that the proposed ACO algorithm generates excellent final solutions in a much shorter computation time when compared with the genetic algorithm. Therefore, the mathematical model and the ACO algorithm proposed in this paper form a simple, but effective and efficient methodology to solve the manufacturing cell creation and production scheduling problems for designing VCMSs.

Seven new iridabenzenes were prepared by the addition of (Z)-1,2-diphenyl-3-(2-lithioethenyl)-1-cyclopropene to the Vaska-type complexes [IrCl(CO)(PR3)2], containing differing phosphine ligands. The iridabenzenes could be isolated from the reaction mixture either by direct means or after heating of the crude solution. In the case of the reactions using PMe3 and PEt3, a σ-vinyl/η²-cyclopropene Ir(I) complex, best described as an iridabenzvalene, could be isolated and fully characterized. The metallabenzvalene intermediate could be cleanly converted to the corresponding iridabenzene by heating in solution. The PEt3-substituted iridabenzene and iridabenzvalene were characterized by X-ray crystallography. Plausible mechanisms for the formation of both iridacycles from the lithiated vinylcyclopropene as well as the isomerization of the benzvalene into the benzene are postulated.

Isolation of the avian embryo from its normal food material is an essential step in a fundamental study of embryonic nutrition. With present methods, however, it has not been possible to grow embryos in culture for much longer than one day. In 1932 Waddington described methods of growing explanted embryos on serum clots. Several years later Spratt (1947, 1952) devised simplified media for embryos cultured on agar with which he studied various aspects of morphogenesis and carbohydrate needs of the young embryo. New (1955) has recently reported another technique for growing explanted embryos which allows development to proceed to about 60 hours, 40 hours of which are in vitro. A number of workers have injected various nutrients, antimetabolites, drugs, poisons, and hormones, directly into the yolk sac or other areas of the egg (e.g. Landauer, 1954).