极端情况下对我国股市风险的实证研究

准确地度量风险是对风险进行有效管理的前提也是投资者做出合理的投资决策的基础,然而在极端事件频繁发生的情况下,传统的VaR计算方法难以准确地度量股市风险,极值理论却可以很好地解决这一问题。本文特别关注了由2007年美国"次贷" 危机所引发的全球金融危机爆发时我国股市的风险度量问题,考虑到全球股市间极端事件的联动效应,利用基于极值理论的POT模型对上证综指日收益率的尾部数据直接建模拟合分布,进而计算出风险值VaR和CVaR,通过比较危机前后的风险值,发现随着金融危机的到来,我国股市的风险有了一定程度的释放。     

金融资产的动态非线性相关:一个新的模型

基于Kendall’sτ秩相关系数的优越性和定义,本文提出了新的具有明确经济意义的动态条件相关copula模型,将常用的Gaussian、Clayton和Gumbel函数统一根据该演化方程实现动态化,构造出三种Kendall’sτ动态条件相关copula模型,可用于刻画不同的相关模式。这些模型不仅参数少、容易估计,避免了现有动态条件相关copula模型构建方法各异导致的在实证中不利于比较的缺点,而且能够进行多步向前预测,有效地减少了进行样本外预测时的计算量,从而为刻画时变、非线性、非对称性和尾部相关等复杂的动态相关模式提供了新方法。     

制度因素对我国国际储备的惯性影响

本文在缓冲储备理论中引入了习惯形成因素,在BS模型的基础上构造了一个既包括国际收支波动性和机会成本同时又考虑了习惯形成因素的动态调整模型。利用1996-2009年间中国国际储备的月度数据进行了实证分析,结果表明:(1)一国国际储备是国际收支不确定性和机会成本的函数,它们三者之间存在长期均衡关系,也就是说BS理论预期模型在经过适当的修正后对中国外汇储备规模的实证研究是适用的。(2)习惯形成参数越大,以往的制度因素形成的惯性对后期储备积累的影响就越大,国际收支不确定性以及机会成本对储备的影响也越小,并且这个惯性一旦形成,很难立刻改变。(3)正是由于考虑了习惯形成因素,外汇储备规模关于国际收支不确定性的弹性以及机会成本的弹性更接近于BS模型的理论预期值。     

团队成员交换、社会因素策略与新员工社会化

团队工作方式在组织中日益普遍,团队成员成为影响新员工社会化的重要因素。探讨团队成员交换对新员工社会化结果的影响及其作用机制,尤其是社会因素策略这一组织社会化策略在其中的中介作用,选取201个入职时间在一年半以内的销售人员为调查样本,运用结构方程模型路径分析方法对研究模型进行检验。研究结果表明,团队成员交换对新员工社会化结果产生显著影响;新员工感知的社会因素策略在团队成员交换与任务掌握、角色清晰、工作满意度之间起部分中介作用,在团队成员交换与离职倾向之间起完全中介作用。这表明高质量的团队成员交换关系可以促进新员工感知更多来自组织的正向社会支持以及组织内部人的角色模范作用,最终帮助他们成功社会化。     

考虑噪声因子的参数和公差经济性设计策略

基于并行工程思想的参数和公差经济性设计,以成本为优化目标来确定最优的设计参数和公差范围.就并行参数和公差设计通过双响应曲面均值和方差模型实现其稳健性,本文提出了包含噪声因子的响应曲面建模策略,应用这一模型将参数和公差同时优化.该参数和公差经济性设计优化模型以质量损失和制造成本之和为目标函数,以过程方差置信域为约束.实例结果表明,在双响应曲面方法中,对均值设置偏倚量比其刚性约束具有较大的成本优势,在不降低稳健性的前提下引入偏倚可以降低成本.面向噪声因子的设计策略其成本低于基于双响应的有偏倚的设计,说明考虑噪声因子的设计是最有效的.     

Foodborne Exposure to Pesticides and Methylmercury in the United Arab Emirates

As part of a comprehensive environmental health strategic planning project initiated by the government of Abu Dhabi, we assessed potential dietary exposure in the United Arab Emirates (UAE) to methylmercury (in seafood) and pesticides (in fruits and vegetables) above international guideline levels. We present results for the UAE population by age, gender, and body mass index. Our results show very low daily risks of exposure to pesticides in fruits and vegetables at levels exceeding WHO guidelines even under the conservative assumption that no pesticides are removed during washing and food preparation. Thus, exposure to pesticides on fruits and vegetables does not appear to be a major public health concern in the UAE. The chances of exposure to methylmercury in seafood are much higher; our model estimates a mean 1 in 5 daily risk of exceeding the FAO/WHO provisional tolerable weekly intake. However, great caution should be used in interpreting these results, as we analyzed only the risks and not the substantial benefits of fish consumption. In fact, previous studies have demonstrated that exposure to the n‐3 polyunsaturated fatty acids in fish can increase IQ in developing children, and it can substantially decrease the risk in adults of coronary heart disease and stroke. Further research is warranted to compare the risk of Me‐Hg exposure from fish to the nutritional benefits of fish consumption in the UAE and to determine appropriate methods to communicate risk and benefit information to the UAE population.     

Pricing Decisions During Inter‐Generational Product Transition

How should companies price products during an inter‐generational transition? High uncertainty in a new product introduction often leads to extreme cases of demand and supply mismatches. Pricing is an effective tool to either prevent or alleviate these problems. We study the optimal pricing decisions in the context of a product transition in which a new‐generation product replaces an old one. We formulate the dynamic pricing problem and derive the optimal prices for both the old and new products. Our analysis sheds light on the pattern of the optimal prices for the two products during the transition and on how product replacement, along with several other dynamics including substitution, external competition, scarcity, and inventory, affect the optimal prices. We also determine the optimal initial inventory for each product and discuss a heuristic method.     

Inventory Policy with Parametric Demand: Operational Statistics,Linear Correction,and Regression

In this paper, we consider data‐driven approaches to the problem of inventory control. We first consider the approach of operational statistics and review related results which enable us to maximize a priori expected profit uniformly over all parameter values, when the demand distribution is known up to the location and scale parameters. For the case of the unknown shape parameter, we first suggest a heuristic approach based on operational statistics to obtain improved ordering policies and illustrate the same for the case of a Pareto demand distribution. In more general cases where the heuristic is not applicable, we suggest linear correction and support vector regression approaches to better estimate ordering policies, and illustrate these using a Gamma demand distribution. In certain cases, our proposed approaches are found to yield significant improvements.     

Transfer of risk in the newsvendor model with discrete demand

In this paper we consider the transfer of risk in a newsvendor model with discrete demand. We view the newsvendor model as a leader/follower problem where the manufacturer (leader) decides the wholesale price and the retailer (follower) decides the quantity ordered. Taking a Pareto-optimal contract as a starting point, the manufacturer wishes to design a real option contract to enhance profits. A new real option contract is said to be feasible if both parties' expected profit is at least as great as in the original contract. When demand is discrete, there are usually infinite feasible contracts that yield maximum expected profits to the manufacturer. In the paper we show that either all, some or none of these real option contracts offer an improved position for the retailer.