Cell formation and layout design are two important steps for the implementation of the production systems. The existing models majorly have focused on the cell formation issue and the layout design of machines, but have paid little attention to the placement of cells in dynamic environment. In addition, in most of the available papers, binary variables have been used for cell formation, and other information such as volume of production, operation sequences and production costs have played unimportant roles in the structure of the existing models. In this paper, a nonlinear program-ming model under potentially dynamic conditions is proposed which minimizes the cost associated with the difference between the estimated demands from its expected value. The other purpose of the proposed model includes minimization of the total costs of inter/intra cellular movements of elements (forward and backward movements), the existence of exceptional elements, intercellular displacement of machines and cellular reconfiguration and operational costs and constant cost of machineries. The problem is solved via GAMS and a Genetic Algorithm (GA) is employed to solve the large sized problems and the results are analyzed.

With the rapid increase of energy demand, it is becoming increasingly important to obtain accurate energy demand forecasts. To incorporate long time causal relationships, autoregressive with exoge-nous regression components models have received increasing attention from many researchers in this field. These are linear models applied through hybrid methodology of time series and econo-metrics, however, some recent studies find evidences that nonlinear models outperform over linear ones in long term peak demand forecasting. This paper proposed a nonlinear Auto Regressive Integrated Moving Average with Exogenous Inputs (N-ARIMAX) model to forecast sectoral peak demand using a case study of Iran. The results indicate that significant improvements in forecasting accuracy are obtained with the proposed models compared to the existing models.