The checkerboard model of social interaction

The checkerboard model is a computer simulation of social interaction among members of two groups. The checkerboard represents a social field on which two groups of checkers move on the board on the basis of positive, neutral or negative attitudes toward one another assigned to them. The resulting pattern of positions of the pieces represents the social structure. The theoretical basis for the checkerboard model is explained and the rules for operating the model are outlined. This is followed by illustrative runs named Crossroads, Mutual Suspicion, Segregation, Social Climber, Social Worker, Boy‐Girl, Couples and Husband‐Wives, showing intermediate and final positions on the board for each. It is concluded that the checkerboard model is capable of demonstrating the intimate connection between attitudes of group members toward their own group and toward others to a continuous social interactional process and to the resulting social structure.     

基于社会福利最大化的油气资源税费研究

合理的油气资源税费能够引导企业优化开发决策,平衡当代与后代利益关系,实现跨期资源有效配置。从跨期油气资源最优分配的角度,通过最优控制理论构建寡头垄断市场中社会福利最大化和企业利润最大化目标下的油气资源开发决策模型,并以社会福利最大化目标下的资源开发决策为基准,研究从价、从量、储量三种不同形式的油气资源税费对资源开发决策的调节作用,研究发现:(1)征收从价税费,最优的从价税率为26.4%,政府既可以保障社会最优,还可以获得较多的税费收入;(2)征收从量税费,从量税率为1.77元/吨,政府可以保证社会福利最大化,但相比从价税费政府的税费收入较少;(3)征收储量税费,社会福利最大化下的储量税费为-0.13元/吨,也就是政府需向企业进行补贴才可以保证社会最优,会形成一定的财政压力。     

The Effect of Robotics Competitions on High School Students' Attitudes Toward Science

This study was designed to examine the impact of participating in an after‐school robotics competition on high school students' attitudes toward science. Specifically, this study used the Test of Science‐Related Attitude to measure students' social implications of science, normality of scientists, attitude toward scientific inquiry, adoption of scientific attitudes, enjoyment of science lessons, leisure interest in science, and career interest in science. Results indicated that students who participated in a robotic competition had a more positive attitude toward science and science‐related areas in four of the seven categories examined: social implications of science, normality of scientists, attitude toward scientific inquiry, and adoption of scientific attitudes. Implications of results on students' attitudes are discussed.     

Improving fairness in ambulance planning by time sharing

Most literature on the ambulance location problem aims to maximize coverage, i.e., the fraction of people that can be reached within a certain response time threshold. Such a problem often has one optimum, but several near-optimal solutions may exist. These may have a similar overall performance but provide different coverage for different regions. This raises the question: are we making ‘arbitrary’ choices in terms of who gets coverage and who does not? In this paper we propose to share time between several good ambulance configurations in the interest of fairness. We argue that the Bernoulli–Nash social welfare measure should be used to evaluate the fairness of the system. Therefore, we formulate a nonlinear optimization model that determines the fraction of time spent in each configuration to maximize the Bernoulli–Nash social welfare. We solve this model in a case study for an ambulance provider in the Netherlands, using a combination of simulation and optimization. Furthermore, we analyze how the Bernoulli–Nash optimal solution compares to the maximum-coverage solution by formulating and solving a multi-objective optimization model.     

贸易和产业政策对企业产品质量的影响博弈

在纵向产品差异化的双寡头竞争的框架下,对政府的贸易和产业政策做了分析,得到的主要结论为,只要国内企业生产低质量的产品,则贸易自由化会导致国内企业的产出水平下降和所有产品价格的提高;在贸易和产业政策一定的情况下,当国内企业的技术水平比较低时,国内企业生产低质量产品可以使社会福利达到最大化;另外,政府可以通过关税和补贴的干预使企业的产品质量产生跃进,超过国外竞争者.     

DEGREE OF ECONOMIC UNSUSTAINABILITY IN THE MANAGEMENT OF RENEWABLE RESOURCES

A criterion commonly used to determine economic sustainability posits that the discounted welfare should not decrease over time. Resource management problems involving fluctuating stocks may be exacerbated by a lack of sustainable policies unless some violations of this condition are accepted. Moreover, sustainable policies may lead to the minimal welfare levels. To alleviate these problems, a new notion of sustainability is suggested. In this new form of sustainability, violations of nondecreasing welfare are accepted to a certain degree. The policies that maximize the discounted welfare under the constraint for the largest accepted violation for sustainability satisfy a dynamic programming type of fixed‐point condition that can be effectively utilized for finding optimal policies. The new notion of sustainability can also be utilized in defining an index for measuring the degree of overall unsustainability of resource management problems and different harvesting policies.     

Effects of risk aversion and decision preference on equilibriums in supply chain finance incorporating bank credit with credit guarantee

We constructed a Stackelberg game in a supply chain finance (SCF) system including a manufacturer, a capital‐constrained retailer, and a bank that provides loans on the basis of the manufacturer's credit guarantee. To emphasize the financial service providers' risks, we assumed that both the bank and the manufacturer are risk‐averse and formulated trade‐off objective functions for both of them as the convex combination of the expected profit and conditional value‐at‐risk. To explore the effects of the risk preferences and decision preferences on SCF equilibriums, we mathematically analyzed the optimal order quantities, wholesale prices, and interest rates under different risk preference scenarios and performed numerical analyses to quantify the effects. We found that incorporating bank credit with a credit guarantee can effectively balance the retailer's financing risk between the bank and the manufacturer through interest rate charging and wholesale pricing. Moreover, SCF equilibriums with risk aversion are highly affected by the degree of both the lender's and guarantor's risk tolerance in regard to the borrower's default probability and will be more conservative than those in the risk‐neutral cases that only maximize expected profit.     

Estimation of asset demands by heterogeneous agents

We develop optimization models to analyze the demand for financial assets by heterogeneous agents. The models extend Frankel's [J. Portfolio Manage. 11 (4) (1985) 18] earlier approach, and relax the assumption of normality of asset returns. Instead, we assume that investors maximize an expected utility of terminal wealth based on heterogeneous attitudes toward risk. Solving a bi-level optimization program, we endogenously estimate the risk aversion parameters and derive the optimal asset holdings for each agent. The models are tested on United States market data, explaining the market structure better than previously postulated models.     

考虑路网可靠性和空间公平性的次优拥挤收费模型

根据随机路网环境下出行者规避风险的路径选择行为,提出了一种考虑路网可靠性和空间公平性的次优拥挤收费双层规划模型。其中,上层模型以具有空间公平性约束条件下最大化路网的社会福利为目标,下层模型是实施拥挤收费条件下考虑行程时间可靠性的弹性需求用户平衡模型。鉴于双层规划模型的复杂性,设计了基于遗传算法和FrankWolfe算法的组合式算法来求解提出的模型。算例结果表明:考虑行程时间可靠性的次优拥挤收费会产生不同于传统次优拥挤收费的平衡流量分布模式,表明出行者的路径选择行为对拥挤收费结果会产生直接影响;此外,算例结果还说明遗传算法对参数设置具有很强的鲁棒性。     

The impact of an out‐of‐school STEM education program on students’ attitudes toward STEM and STEM careers

There is an increasing awareness of out‐of‐school program value in enhancing student interest and understanding of science, technology, engineering, and mathematics (STEM). This study examined the impact of an out‐of‐school STEM education program on student attitudes toward STEM disciplines and STEM careers. A STEM education program implemented at a public research university was designed to integrate STEM disciplines with hands‐on problem‐based activities. Design features included authentic learning contexts, engineering design processes, and content integration. Data sources included an attitude survey and interviews conducted with forty sixth grade middle school student participants. The analysis revealed significant differences between pre and posttests on student attitudes toward personal and social implications of STEM, science and engineering learning, and their relationship to STEM. Findings showed that the program contributed to students’ developing interest in STEM fields, and helped them make connections between schoolwork and daily lives. Recommendations for future research on out‐of‐school STEM education programs were discussed.     

Cooperation in dividing the cake

This paper defines models of cooperation among players partitioning a completely divisible good (such as a cake or a piece of land). The novelty of our approach lies in the players’ ability to form coalitions before the actual division of the good with the aim to maximize the average utility of the coalition. A social welfare function which takes into account coalitions drives the division. In addition, we derive a cooperative game which measures the performance of each coalition. This game is compared with the game in which players start cooperating only after the good has been portioned and has been allocated among the players. We show that a modified version of the game played before the division outperforms the game played after the division.     

Students' Attitudes Toward Science as Predictors of Gains on Student Content Knowledge: Benefits of an After‐School Program

High‐quality after‐school programs devoted to science have the potential to enhance students' science knowledge and attitudes, which may impact their decisions about pursuing science‐related careers. Because of the unique nature of these informal learning environments, an understanding of the relationships among aspects of students' content knowledge acquisition and attitudes toward science may aid in the development of effective science‐related interventions. We investigated the impact of a semester‐long after‐school intervention utilizing an inquiry‐based infectious diseases curriculum (designed for use after‐school) on 63 urban students' content knowledge and aspects of their attitudes toward science. Content knowledge increased 24.6% from pretest to posttest. Multiple regression analyses indicated suggested that the “self‐directed effort” subscale of the Simpson–Troost Attitude Questionnaire—Revised best predicted increases in students' science content knowledge. The construct “science is fun for me” served as a suppressor effect. These findings suggest that future after‐school programs focusing on aspects of attitudes toward science most closely associated with gains in content knowledge might improve students' enthusiasm and academic preparedness for additional science coursework by improving student attitudes toward their perceptions of their self‐directed effort.     

On some measures and distances for positive random variables

A number of conventional measures of risk as real‐valued functions on the space of positive random variables are considered: the expected shortfall, the mean excess over the threshold, the stop‐loss and some others. Ordering of risks, based on these measures and the distances between corresponding distribution functions, are described. The perturbed measures, describing the effect of changing environment, are discussed. These measures are defined by the accelerated life and proportional hazards models widely used in reliability and survival analysis. The case of a random environment is of a prime interest in the paper. The main result states that if, for instance, the stochastic environment is ‘neutral in expectation’ with respect to the baseline one, the distance between the corresponding distribution functions can be still sufficiently large. Copyright © 2003 John Wiley & Sons, Ltd.     

多方式弹性需求下公交定价双层规划模型

为描述多方式城市交通网络下公交定价与出行选择行为的相互作用与影响,将出行方式选择与路径选择涵盖于同一网络,建立了上层模型分别以企业利润最大化、乘客出行成本最小化和社会福利最大化为目标函数,下层模型为多方式弹性需求随机用户配流模型的公交定价双层规划模型。运用改进遗传算法对模型整体进行求解,下层模型采用综合对角化算法和MSA算法的组合求解算法。最后,设计了一个算例以说明模型应用。结果表明:运用双层规划模型所确定的公交票价较传统静态票价可使政府、企业及出行者三方都获得更高收益,且上层模型以社会福利最大化为目标函数能代表社会群体中多数人利益,优化效果最为理想。     

Efficient frontier cutoff policies in credit portfolios

Historically, account acquisition in scored retail credit and loan portfolios has focused on risk management in the sense of minimizing default losses. We believe that acquisition policies should focus on a broader set of business measures that explicitly recognize tradeoffs between conflicting objectives of losses, volume and profit. Typical business challenges are: ‘How do I maximize portfolio profit while keeping acceptance rate (volume, size) at acceptable levels?’ ‘How do I maximize profit without incurring default losses above a given level?’ ‘How do I minimize the risk of large loss exposures for a given market share?’ In this paper we are not concerned with which combination of objectives are appropriate, but rather focus on the cutoff policies that allow us to capture a number of different portfolio objectives. When there are conflicting objectives we show that optimal policies yield meaningful tradeoffs and efficient frontiers and that optimal shadow prices allow us to develop risk-adjusted tradeoffs between profit and market share. Some of the graphical solutions that we obtain are simple to derive and easy to understand without explicit mathematical formulations but even simple constraints may require formal use of non-linear programming techniques. We concentrate on models and insights that yield decision strategies and cutoff policies rather than the techniques for developing good predictors.     

Content Knowledge,Attitudes, and Self‐Efficacy in the Mathematics New York City Teaching Fellows (NYCTF) Program

The purpose of this study was to understand the mathematical content knowledge new teachers have both before and after taking a mathematics methods course in the NYCTF program. Further, the purpose was to understand the attitudes toward mathematics and concepts of self‐efficacy that Teaching Fellows had over the course of the semester. The sample included 42 new Teaching Fellows who were given a mathematics content test, attitudes toward mathematics questionnaire, and teaching self‐efficacy questionnaire at the beginning and end of the semester. Further, the teachers kept teaching and learning journals. Findings revealed a significant increase in both mathematical content knowledge and positive attitudes toward mathematics. Additionally, Teaching Fellows were found to have positive attitudes and high self‐efficacy at the end of the semester, and relationships were found between attitudes and self‐efficacy. Finally, Teaching Fellows generally found that classroom management was the biggest issue in their teaching, and that problem solving and numeracy were the most important topics addressed in their learning. Future studies should address self‐efficacy differences between preservice and in‐service teachers and the effects of alternative certification teacher knowledge, attitudes toward mathematics, and self‐efficacy on students in the classroom.     

基于消费者效用模型的贵重首饰经销商决策行为研究

以异质性消费者为对象,研究关税税率调整对贵重首饰经销商决策行为的影响。在个人理性与激励相容的约束条件下,构建基于异质性消费者效用模型的需求函数,分析不同市场类型下经销商的最优决策选择。考虑消费者价格敏感度对社会福利的影响,并在此基础上分析了最优关税税率水平。研究发现:(1)贵重首饰经销商决策行为不仅受政府关税税率的影响,还受消费者价格敏感度的影响;(2)在消费者价格敏感度一定的前提下,若想通过关税来调控贵重首饰市场,关税税率应该控制在一定的区间范围;(3)在关税税率一定的条件下,贵重首饰市场的类型主要受消费者价格敏感度的影响。     

Fair allocation using a fast smart market auction

Allocation of network resources may be formulated as an optimization problem seeking to maximize the sum of the utility function of each flow. Individual flows collectively achieve social welfare with a constraint that global fairness must be provided by a congestion control scheme using congestion indication feedback signals. However, in the reality, non-cooperative flows without employing any congestion control scheme do not respond to congestion indication feedback signals. In this paper, we analyze fairness of congestion control with cooperative and non-cooperative flows for communication networks. Furthermore, we propose a fast smart-market auction (FSMA) approach to achieve social welfare in the environment that cooperative and non-cooperative flows coexist. Through detailed simulations, the proposed approach is proven to be effective in providing fairness.     

A marriage matching mechanism menagerie

For each of several measures of social welfare we present a marriage matching mechanism that produces a welfare maximizing matching, and our basic approach generalizes to many other welfare measures.     

Imposing no‐arbitrage conditions in implied volatilities using constrained smoothing splines

We apply constrained smoothing B‐splines to the construction of arbitrage‐free implied volatilities and derived measures. The constrained smoothing B‐splines allows the imposition of the constraints of monotonicity and convexity given by the no‐arbitrage conditions in the pricing function. We illustrate the methodology in the construction of implied volatilities and also in the construction of derived measures such as risk‐neutral densities, showing that it can be used as an effective tool for general treatment of option prices. Copyright © 2011 John Wiley & Sons, Ltd.