A review on assembly sequence planning and assembly line balancing optimisation using soft computing approaches

Assembly optimisation activities occur across development and production stages of manufacturing goods. Assembly Sequence Planning (ASP) and Assembly Line Balancing (ALB) problems are among the assembly optimisation. Both of these activities are classified as NP-hard. Several soft computing approaches using different techniques have been developed to solve ASP and ALB. Although these approaches do not guarantee the optimum solution, they have been successfully applied in many ASP and ALB optimisation works. This paper reported the survey on research in ASP and ALB that use soft computing approaches for the past 10years. To be more specific, only Simple Assembly Line Balancing Problem (SALBP) is considered for ALB. The survey shows that three soft computing algorithms that frequently used to solve ASP and ALB are Genetic Algorithm, Ant Colony Optimisation and Particle Swarm Optimisation. Meanwhile, the research in ASP and ALB is also progressing to the next level by integration of assembly optimisation activities across product development stages

Self-domestication in Homo sapiens: Insights from comparative genomics

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Paraffin oil as a "methane vector" for rapid and high cell density cultivation of Methylosinus trichosporium OB3b

Slow growth and relatively low cell densities of methanotrophs have limited their uses in industrial applications. In this study, a novel method for rapid cultivation of Methylosinus trichosporium OB3b was studied by adding a water-immiscible organic solvent in the medium. Paraffin oil was the most effective at enhancing cell growth and final cell density. This is at least partially due to the increase of methane gas transfer between gas and medium phases since methane solubility is higher in paraffin than in water/nitrate minimal salt medium. During cultivation with paraffin oil at 5% (v/v) in the medium, M. trichosporium OB3b cells also showed higher concentrations of the intermediary metabolites, such as formic acid and pyruvic acid, and consumed more methane compared with the control. Paraffin as methane vector to improve methanotroph growth was further studied in a 5-L fermentor at three concentrations (i.e., 2.5%, 5%, and 10%). Cell density reached about 14 g dry weight per liter with 5% paraffin, around seven times higher than that of the control (without paraffin). Cells cultivated with paraffin tended to accumulate around the interface between oil droplets and the water phase and could exist in oil phase in the case of 10% (v/v) paraffin. These results indicated that paraffin could enhance methanotroph growth, which is potentially useful in cultivation of methanotrophs in large scale in industry