The main aim of this paper deals with the problem of sequencing n jobs over m machines in a flow shop without constraints. The scheduling is based on the maximum completion time. A heuristic based on a branch and bound technique is proposed to solve the problem. Though, the idea of our algorithm is in some way similar to Bertolissi's one, the fact that we minimize the makespan instead of the sum of the total flow times, makes them different. In order to show the effectiveness of our heuristic, we compared it to that proposed by Nawaz et al. The numerical evaluation of the two approaches shows that our heuristic is good in term of quality of the solutions, computing times and simplicity of implementation.
In a previous work (Chettibi et al., 2004a) we proposed an efficient method to plan optimal motions for serial manipulators and we asserted that this technique could be extended to handle more complex robotic systems. In this paper, we will show the effectiveness of this method in solving the Optimal Free Motion Planning Problem (OFMPP) for Closed-Chain Robots (CCR) and coordination of multiple robotic mechanisms. These are typical examples of holonomic mechanical systems known to be complex but of a large utility. But the fact that these systems are usually redundantly actuated, induces additional complexity in computing their dynamics and generating optimal motions.
Separation processes using selective adsorption on zeolite are widely applied in chemical industries. The X zeolite is especially used for the separation of xylenes isomers. The objective of this work-based on NaX adsorbent known by its selectivity exclusively geometric to xylene isomers-is a contribution to the comprehension of the separation mechanisms and of the steric effect parameters. Adsorption of o-xylene, m-xylene, p-xylene, and trimethylbenzene was studied in thermobalance at 100, 250, and 420 degreesC and at a constant pressure of 700 Pa. The results show that the adsorption and diffusion process are strongly influenced by the molecules' sizes. Using the Fick law plot, disruption phenomena owing to the steric effect were observed when the supercages of NaX adsorbent were filled.
