Volatility timing in mutual funds: evidence from daily returns

I use daily mutual fund returns to shed new light on the questionof whether or not mutual fund managers are successful markettimers. Previous studies find that funds are unable to timethe market return. I study the funds' ability to time marketvolatility. I show that volatility timing is an important factorin the returns of mutual funds and has led to higher risk-adjustedreturns. The returns of surviving funds are especially sensitiveto market volatility; those of nonsurvivors are not.     

基于模糊聚类的最大树算法和重心法的区域航空中转站选址研究

首先,利用模糊聚类的最大树算法对城市进行分类,将快递企业的服务区域分成若干个子区域.其次,以运输成本最小为目标,利用重心法确定航空中转站所在的城市.最后,为提高该方法的适用性,进一步设计基于模糊聚类最大树算法的区域划分程序和基于重心法的中转站选址程序.