Multi-period models of portfolio selection have been developed in the literature with respect to certain assumptions. In this study, for the first time, the portfolio selection problem has been modeled based on mean-semi variance with transaction cost and minimum transaction lots considering functional constraints and fuzzy parameters. Functional constraints such as transaction cost and minimum transaction lots were included. In addition, the returns on assets parameters were considered as trapezoidal fuzzy numbers. An efficient genetic algorithm (GA) was designed, results were analyzed using numerical instances and sensitivity analysis were executed. In the numerical study, the problem was solved based on the presence or absence of each mode of constraints including transaction costs and minimum transaction lots. In addition, with the use of sensitivity analysis, the results of the model were presented with the variations of minimum expected rate of programming periods.

The aim of this research is to determine and to assess the effective factors on customer loyalty, concerning the internet-purchase of products and services of Tehran tourism agencies. For this purpose, the standardized questionnaire was distributed among on-line internet customers of Tehran tourism agencies and finally 384 questionnaires were applied in analyzing the research hypotheses. The data obtained from customers were analyzed using confirmatory factor analysis technique and the structural equations modeling (SEM). The findings of the research with regard to the proposed model and its nine hypotheses from the highest to lowest route coefficients and hypothesis confirmation are respectively: the effect of customer loyalty with the route coefficient of 0.559; the effect of search capability with the route coefficient of 0.481; the effect of satisfaction on customer trust with the route coefficient of 0.388; the effect of transaction cost on customer satisfaction with the route coefficient of 0.321; the effect of search capability on customer trust with the route coefficient of 0.292; the effect of trust on customer loyalty with the route coefficient of 0.184; the effect of the perceived security on customer satisfaction with the route coefficient of 0.159. The above seven hypotheses have been confirmed and the effect perceived security effect on customer trust and the effect of transaction cost on customer trust with the route coefficient of 0.018 were finally rejected.