Spillover effect can lead to the free-riding behavior when joint investment takes place in the supply chain. This study examined the investment strategies of two competitive retailers who considered whether to invest a shared contract manufacturer (CM) or not. The supply chain members' operational decisions in four scenarios were analyzed through a Cournot competition model, and the paths of the retailers' investment strategies were examined. The CM's capacity portfolio optimization was NP-hard in nature, and was modelled by an investment portfolio problem. Results show that both retailers jointly invest the CM only when the difference of production costs is not high, and the intentions of joint investment will decrease when the coefficient of spillover and the degree of substitutability between products increase. The CM always benefits as long as one retailer invests, and allocates more investment on the capacity with highest revenue when he emphasizes more on the profit. For optimizing the CM's capacity portfolio problem, an artificial fish swam algorithm with uniform mutation (AFSA_UM) is developed and it shows better convergent performance and higher robustness than the basic AFSA.

Abstract-A method of optimal test frequency selection for analog circuit fault diagnosis is proposed. The method simulates the circuit faulty states only in the bands with highest fault sensitivity and that reduces part of simulation cost. Test frequency selection is considered as a multi-objective optimization problem, discrete particle swarm algorithm is used as a new approach to get optimal test frequency sets. An example shows that the proposed method is effective in frequency selection and works more efficiently compared with genetic algorithm.