Some General Results on Equilibrium Prices in Large Random Exchange Economies

In this paper we are concerned with a model of a Walrasian exchange economy in which the preferences and endowments of the agents are random. Stochastic interaction among the agents is formally described in terms of dependency neighborhoods. The main result concerns a characterization of the distribution of market-clearing equilibrium prices in a large economy. The paper establishes conditions for asymptotic normality of appropriately normalized equilibrium prices.     

基于CVaR和公平偏好下双渠道供应链回购契约

基于风险度量准则CVaR,构建了零售商具有公平偏好心理行为下基于努力成本分担的回购契约的双渠道决策模型,分析了分散式和集中式双渠道供应链系统中的决策行为.在此基础上,经过理论求解与算例分析,深入分析了公平偏好、成员的风险规避特性和回购契约的交互影响.研究发现:零售商与制造商越厌恶、规避风险,订货数量就越低,他们的利润和供应链的利润都将降低;零售商的订货数量伴随公平偏好系数和批发价的增大而减少.但即使考虑渠道成员的风险规避性和公平偏好特性,只须回购契约的参数取得当的值,就可以协调双渠道供应链.     

Problem types used in math lessons: the relationship between student achievement and teacher preferences

The purpose of this study was to determine the relationship between the problems teachers preferred in mathematics lessons and student achievement in different types of problems. In accordance with this purpose, nine mathematics teachers were interviewed, and corresponding problems were prepared and administered to 225 eighth-grade students. The findings indicate that problem types are dependent on teacher preferences. It was found that curriculum-dependent and routine problems were dominant for teacher preferences. Students are more successful at with missing data, problems that are visual and do not require the use of different strategies. They have lower success at long problems, those that contain irrelevant data, problems that require the use of different strategies and difficult problem types. It was found that problem types at which students were successful and which teachers preferred were related. These results relay information about problems used in the learning environment and effect of problem-solving experiences on students' success.     

Longevity-linked assets and pre-retirement consumption/portfolio decisions

We solve the consumption/investment problem of an agent facing a stochastic mortality intensity. The investment set includes a longevity-linked asset, as a derivative on the force of mortality. In a complete and frictionless market, we derive a closed form solution when the agent has Hyperbolic Absolute Risk Aversion preferences and a fixed financial horizon. Our calibrated numerical analysis on US data shows that individuals optimally invest a large fraction of their wealth in longevity-linked assets in the pre-retirement phase, because of their need to hedge against stochastic fluctuations in their remaining life-time at retirement.     

气相色谱高分辨质谱测定婴儿胎发中含氯持久性有机污染物

婴儿的胎发是评价婴儿在母体环境中污染物累积暴露水平的良好介质。含氯持久性有机污染物是人体中残留浓度最高的持久性有机污染物。本研究依次采用HCl酸化、正己烷/二氯甲烷混合溶液萃取、硅胶和氧化铝混合填充小柱净化,以及气相色谱高分辨质谱法检测了北京20个婴儿胎发中的16种典型含氯持久性有机污染物。结果表明,16种目标物的检出限可达到1.0~2.5μg/kg,替代物五氯硝基苯回收率大于67.6%,加标样品中目标物回收率范围为62.5%~92.3%。20个胎发样品中六氯苯、β-六六六和p,p’-滴滴伊检出率均为100%,γ-六六六、2,4,4’-三氯联苯和2,2’,5,5’-四氯联苯的检出率分别为85%,50%和40%。4种污染物总量的浓度分布范围分别为5.48~8.40μg/kg(六氯苯)、3.86~27.1μg/kg(六六六)、1.16~18.3μg/kg(滴滴涕)和2.20~22.1μg/kg(多氯联苯),平均浓度分别为6.91,6.10,5.53和3.44μg/kg。此方法和分析结果可用于胎儿体内16种含氯持续性有机污染物蓄积水平和母体内累计暴露水平的评价。     

认股权证的修正精算定价研究

基于修正Bladt和Rydberg在无市场假设下关于期权定价的保险精算方法的基础上,从评估实际损失和相应概率分布角度,利用公平保费原则建立认股权证的定价模型,并给出定价公式.且当投资者对原生资产期望回报率为无风险利率时,该定价为风险中性价格.     

Including Preference and Social Distance Dynamics in Multi-Factor Theories of Segregation

All agree that many factors contribute to ethnic segregation, but controversy continues regarding the relevance of particular factors. In my paper I acknowledge the importance of discrimination, but I direct attention to the role of ethnic preferences and social distance dynamics. I do so because many dismiss the relevance of these factors for contemporary segregation without engaging formal theories and analytic models which suggest that dynamics associated with in-group attraction and out-group avoidance may take on increasing importance as past forms of discrimination slowly fade. Agent-based modeling shows promise for exploring the issue of whether prejudice against out-groups and affinity toward in-groups can build and sustain segregation in the absence of discrimination. Research drawing on this approach is at an early stage of development but is significant for highlighting two things. One is that the implications of preferences for segregation are strongly conditioned by the ethnic demography of the city. Another, closely tied to the first, is that different views about the implications of preferences for segregation often hinge on inconsistencies in how notions of integration and segregation are applied in discussions of individual location choices, the ethnic mix of single neighborhoods, and the ethnic distributions for all neighborhoods in a city. Critiques of agent-based models of Schelling-style preference effects will carry more force when they outline models indicating how location decisions guided by preferences documented in surveys can produce or sustain integration.     

The stability of learners’ choices for real-life situations to be used in mathematics

One of the efforts to improve and enhance the performance and achievement in mathematics of learners is the incorporation of life-related contexts in mathematics teaching and assessments. These contexts are normally, with good reasons, decided upon by curriculum makers, textbook authors, teachers and constructors of examinations and tests. However, little or no consideration is given to whether students prefer and find these real-life situations interesting. There is also a dearth of studies dealing explicitly with the real-life situations learners prefer to deal with in mathematics. This issue was investigated and data on students’ choices for contextual issues to be used in mathematics were collected at two time periods. The results indicate that learners’ preferences for contextual situations to be used in mathematics remained fairly stable. It is concluded that real-life issues that learners highly prefer are not normally included in the school mathematics curriculum and that there is a need for a multidisciplinary approach to develop mathematical activities which take into account the expressed preferences of learners.     

考虑偏好异质特征的锦标竞赛激励结构与效果分析

引入心理偏好的锦标竞赛是目前的研究热点,但是忽略了偏好的异质特征。对此,采用行为博弈论方法,研究基于异质偏好分组的分类竞赛和混同竞赛,比较二者的激励结构和激励效果。结果表明:在激励结构方面,无论是奖励强度还是保障强度,自利偏好者之间的分类竞赛总是最大,并且除非偏好异质度较大公平偏好者之间的分类竞赛总是最小而混同竞赛总是居中;在激励效果方面,自利偏好者虽然参与分类竞赛只能够得到最低期望效用即保留效用但是参与混同竞赛可以得到更多期望效用,而公平偏好者参与分类竞赛和混同竞赛都只能够得到最低期望效用即保留效用,委托人的期望利润在分类竞赛下比混同竞赛要多。因此,考虑参赛者的偏好异质特征,甄别偏好类型,制定恰当的激励结构,对提高锦标竞赛的激励效果是必要的。