فصلنامه مدل سازی در مهندسی
پیاپی 22 (پاییز 1389)

Conflict Resolution is an important procedure in many intelligent systems such as rule-based systems. This procedure determines the sequence of firing rules when more than one rule can fire. This paper presents an Intelligent Decision Support System wherein when a conflict occurs; it follows distinct reasoning line for each incompatible rule, and informs the decision maker about all possible options. This idea is applied in a system which is implemented for the purpose of assisting a player in a Real-Time Strategic Game. Obtained results indicate that player with help from this intelligent assistant can have better achievements over other players.

After compressing and increasing the pressure of natural gas in compress station, it has high exergy pressure. The pressure of natural gas is decreased in reduction station by regulators, but this issue can waste exergy. Since energy resources are restricted and its price is increasing in one hand, the exergy analysis method of thermodynamic issue is brought out with economical issues on the other hand, therefore the exergy analysis method is considered as significant issue. This article addresses exergy analysis with using the governing thermodynamic equations and considering natural gas deviation from ideal state and the exergy analysis of natural gas in reduction city gate station (the station No. 1 of Semnan is considered as a case study). The amount of exergy waste is calculated and guideline for its reduction is presented. In accordance with carried out calculations, on the average 198.7 MW of exergy is wasted in the Pressure Reduction Station No.1 located in Semnan in the year of 2009, we can prevent to waste the 231.98KW of exergy with regulating the appropriate temperature of heater when it is working and the studied station.

Supply chain consists of multifaceted structure which focuses integration of all processes such as sourcing, manufacturing, and on-time distribution of end products to customers. Growing interest in supply chain systems has leaded the need to adopt proper approach which can manage complexity, and broadness of supply chain. The operations of supply chain are a function of many variables having strong interrelationships. Main objective of supply chain is optimization of performance of whole supply chain subjected to dynamic behavior. In this paper we model a framework to simulate supply chain operations with moderate complexity. This model has four echelons around a central make-to-order manufacturer with systems dynamics approach. The objective of this paper is to model the operation of the supply chain network and obtain a true reflection of its behavior with integrating information system flow. Furthermore, performance measures including inventory, safety stock, backlog, and customer satisfaction level are evaluated in primary condition and under four scenarios of four echelon of supply chain. Results of system’s behavior are obtained through simulation of primary condition and each scenario during one year.

Even though composite columns in buildings and other structures have been used widely more than 50 years and also this procedure is increasing worldwide, likewise very common in practice to either neglect the synergetic contribution of either the steel or the concrete or to treat the synergetic action is a simplistic manner. The efficient utilizing the composite columns requires different theory on behavior between composite and steel or concrete columns in design process. Current code provisions (i.e. AISC,-2010; EC-4,-2004; BS-5400-2005) have filled many gaps in the design of composite elements such as columns. Therefore, in this paper, comparison between strength of concrete filled steel tube column (CFT) that obtained from experimental test specimens with predicted strength column by the existing design codes; AISC-2010, EC-2004 and BS-5400-2005. The results showed EC-4-2004 code with respect to two other codes indicates more close results relative to the experimental results.

Fatigue life and crack growth retardation due to periodic tensile overloads which are superposed on constant amplitude cycles have been investigated. In the numerical analysis the Forman/Mettu equation with the generalized Willenborg model is used. Analyses and experiments are performed on C(T) specimens made of 7075 aluminium. In the experiments and analyses the periodicity of overloads was remained constant and the effect of overload ratio on the fatigue life has been researched. Results of the experiments and analyses reveal that the N/NCA versus OLR curve has a maximum which indicates that there are greater retardation effects in intermediate OLR values. Also the numerical and experimental results show that in occurrence ratio of 1/50 the overload ratio of 1.5 lead to the maximum interaction.

Design of the structural supports has always been practically important in engineering applications. In addition to holding a structure properly, supports can also be utilized to improve the structural performances. In this study, by using finite element method (FEM) and Particle Swarm Optimization (PSO), the optimal support positions of structures is determined to minimize the maximum of bending moment in structure that is subjected to multi loads. PSO is based on the premise that social sharing of information among members of a species offers and evolutionary advantage. As compared to other design optimization methods, PSO is robust, more efficient, requiring fewer number of function evaluations, while leading to better quality of results. Results show that support position optimization can reduce the maximal moment significantly, and deserves more investigation.

Eccentrically braced frames have high stiffness and suitable energy damping against the lateral forces like the earthquake. In this bracing system, the required stiffness and formability of the frame is provided by the link beam, and are dependent on the details and characteristics of the link beam. In recent years, Eccentrically Braced Frames (EBF) has been utilized as a resistant system against the earthquake lateral forces. In this paper, using non-linear static analysis, the behavior factors of MRF, CBF, and EBF frames in some models are investigated. These studies are carried on three-storey, six-storey, and ten-storey models, statically linear and non-linear. The results indicate that the EBF behavior factor is largely affected by the link beam. It is also concluded by the investigating of relative and overall displacements of the mentioned models that these parameters are dependent greatly on the length of the link beam.