This paper presents a multi-objective Particle Swarm Optimization (PSO) algorithm for worker assignment and mixed-model assembly line balancing problem when task times depend on the worker’s skill level. The objectives of this model are minimization of the number of stations (equivalent to the maximization of the weighted line efficiency), minimization of the weighted smoothness index and minim...

Natural gas is often associated with nitrogen and heavy compounds. The Heavy components in the natural gas not only can feed downstream units, owing to the low temperature process may be formed solid as well. Therefore, heavy components separation can be a necessity and produce useful products. Virtually, all natural gases are containing nitrogen ​​that would lower the heating value of natural ...

Investigating multi cyclic gas (N2 and CO2) huff and puff have been conducted by long sandpack simulations with four different crude oils from Jiangsu oilfield. According to the production differential pressure and the production regularity during huff and puff, the production process was divided into three sections; the first one is free gas production section; the second section is low viscou...

Mixed-model assembly lines are increasingly accepted in many industrial environments to meet the growing trend of greater product variability, diversification of customer demands, and shorter life cycles. In this research, a new mathematical model is presented considering balancing a mixed-model U-line and human-related issues, simultaneously. The objective function consists of two separate com...

A mixed hypergraph is a triple H = (X, C,D), where X is the vertex set and each of C, D is a family of subsets of X, the C-edges and D-edges, respectively. A proper k-coloring of H is a mapping c : X → [k] such that each C-edge has two vertices with a common color and each D-edge has two vertices with distinct colors. A mixed hypergraph H is called circular if there exists a host cycle on the v...

the basic type of assembly line balancing (alb) problem is the allocation of work elements to a set of production work stations considering cycle time, precedence constraints, and assembly diagram to achieve predefined performance criteria such as line efficiency and smoothness index. in this paper, a mixed integer programming model for solving multiple product alb problems with processing time...

Considering the large amount of work that goes into the design of LNG processes, there is surprisingly little attention to their subsequent operation. This partly comes from the assumption that optimal design and optimal operation are the same, but this is not generally true. In this paper we study the optimal operation of a relatively simple LNG process, namely the PRICO process.

We consider the application of a variable V-cycle multigrid algorithm for the hybridized mixed method for second order elliptic boundary value problems. Our algorithm differs from previous works on multigrid for the mixed method in that it is targeted at efficiently solving the matrix system for the Lagrange multiplier of the method. Since the mixed method is best implemented by first solving f...

In this paper, we discuss the design optimization of a relatively simple LNG process; the PRICO process. A simple economic objective function is stated and used on eight different cases with varying constraints. Important constraints are discussed and the results are compared with the commercial PRICO process and with other publications.