在这篇短文中，给出了关于社会福利函数F的防止策略性操纵的概念，并且证明了如果备选对象至少有三个，则下面结论是相互等价的：（1）F满足Pareto与IIA性质；（2）F满足Pareto与RID性质；（3）F是独裁的；（4）F是满的、正向响应的；（5）F是防止策略操纵的且F是满的。

本文引入在险收益（Eamings-at-Risk，EaR）的风险概念，并考虑连续时间Markowitz均值一方差型证券投资组合选择问题，其中度量风险的方差被替代为终端财富的在险收益。在Black-Scholes设置下，我们给出了均值一在险收益意义下的最优常数再调整（best constant-rebalanced）证券组合投资策略以及有效边界的显式表达式。这一结果可方便地应用于动态投资决策与管理的实践中。我们还给出概念与结论的一些经济学解释。

从经典的CRRA效用模型到近期关于LA和DA效用的研究，金融理论在新古典范式的基础上辅助了对行为和心理的分析。本文认为尤其值得指出的是，行为和心理研究带给金融学的新视角不仅从概念上对资产分配决策问题进行了革新，而且还逐渐将人们的行为特征模型化、数学化，这就大大推进了投资者在面临复杂的不确定性时的投资决策问题的研究。本文希望通过对CRRA、LA、DA三种效用模型的比较分析，对“不确定性”下的投资决策问题的研究提供有益的思路。

In this paper we consider a financial market model with frictions which include transaction costs, bid-ask spread and taxes. By using optimization, linear and nonlinear programming and convex programming techniques, several necessary and sufficient conditions are derived for the weak no-arbitrage. Some results on state prices are also provided. The results of this paper can provide at least some theoretical insight to the problem.

We study the optimal portfolio selection problem with transaction costs. In general, the ecient frontier can be determined by solving a parametric non-quadratic programming problem. In a general setting, the transaction cost is a V-shaped function of dierence between the existing and the new portfolio. We show how to transform this problem into a quadratic programming model. Hence a linear programming algorithm is applicable by establishing a linear approximation on the utility function of return and variance.