In the auction market, allocation and pricing will affect participants’ behavior, honesty, and the success of the auction. A proper mechanism will help to achieve higher utility. In a combinatorial double auction, buyers bidding for commodity combinations of different sellers solve the problem of resource allocation in the real market more efficiently. In view of the problem of allocation and pricing of resource such as cloud resource allocation and spectrum auction, this paper designs the TCD4GB mechanism based on the scene of combined double auction, which determines winners, allocates goods and calculates payments. The concept of unit difference is introduced to this paper in order to solve winner determination problem in the group-buying mechanism. The matched sellers who have the minimum cost is directly chosen to be the winning sellers in the process of selecting the winning buyers. The mechanism also calculates payment by using the unit difference of overlapping buyers and apportion it to the matching sellers through the idea of second-price in VCG mechanism. This mechanism avoids the higher utility of buyers when they report falsely. Through theoretical and simulation experiments, it is proved that the TCD4GB mechanism satisfies the economic attributes of individual rationality and budget balance.

Market investment is always a popular method to make a profit. With different investment means, there are tens of thousands of portfolios in the market for investors to choose and combine. In order to maximize profit and minimize risk, some evaluation must be done to those portfolios. Many capital asset pricing models are used in calculating the present value and expected value of the portfolios, and one of the most popular is the model called CAPM (this refer in particular to the model from William Sharpe and John Lintner) The Sharpe ratio is also a necessary index in evaluating the value of the portfolios，which indicates the rate of the expected return against an extra unit of risk taken. The analysis on CAPM are mainly theoretical, and the core function of CAPM will be introduced. Through collecting data from The Morning Star website(cn.morningstar.com), three funds are analyzed to explain the characteristic of Sharpe ratio, which will lead to a persuative conclusion. The conclusion shows that these two models are simple and easy to understand, which means they are very popular, but they have made many assumptions that are not according with the real market environment and they made too many simplifications, which may lead to inaccurate results.