Requirements in mathematics textbooks: a five-dimensional analysis of textbook exercises and examples

Mathematics textbooks play a very important role in mathematics education and textbook tasks are used by students for practice to a large extent. Since the nature of the tasks may influence the way students think it is important that the textbooks provide a balance of a variety of tasks. The analyses of the requirements in textbook tasks contain the usual dimensions of content, cognitive demands, question type and contextual features. The aim of this study is to embed a new fifth dimension into the framework: mathematical activities. This addresses the question of what a student should do in a particular textbook task: to represent, to compute, to interpret or to use argumentation. The analysis encompassed more than 22,000 tasks from the most commonly used Croatian mathematics textbooks in the 6th, 7th and 8th grade. The results show that the textbooks do not provide a full range of task types. There is an emphasis on computation, while argumentation and interpretation activities, reflective thinking and open answer tasks are underrepresented. The study revealed that incorporating mathematical activities into the multidimensional framework of textbook tasks may help to better understand the opportunities to learn which are afforded students by using mathematics textbooks.     

1996~2017年《Operations Research》期刊发文统计分析

《Operations Research》(OR)是运筹与管理科学领域的顶级期刊,对其刊文进行统计分析,剖析国际运筹学科领域的主流研究机构及合作影响,探究当前研究热点问题及学科发展趋势,对于促进我国运筹学科领域的发展具有十分重要的指引作用.基于对WOS核心数据库中该期刊1996至2017年间全部刊文的统计分析,得出以下结论:近年来我国学者发文量稳步提升,表明我国运筹学科领域研究水平的显著提高,但其影响力仍有待进一步提升;机构合作、国际合作都有助于文章引文量的提升;引证分析显示柔性制造(流程柔性及效率)、巢式Logit模型的应用、网络收益管理等7个研究方向是当前、并继续成为运筹领域的研究热点.     

基于碳交易的闭环供应链碳减排与定价策略研究

在消费者对低碳产品存在偏好的碳交易市场中,研究两级闭环供应链中的减排与定价决策问题.对于制造商负责回收模式下的回收再制造过程,采用指数分布来刻画废旧产品质量水平的不确定性.假设新产品和再制造品存在竞争关系,建立制造商和零售商间的Stackelberg博弈模型,给出制造商确定减排投资和回收参考价格以及零售商决定两种产品的差别定价策略,通过算例分析回收产品的残值和碳交易价格对最优策略和供应链成员利润的影响.研究表明,为了获得利润最大,当碳交易的市场价格升高时,制造商应加大减排投资,且零售商应采取提高产品零售价的策略.     

Effects of knowledge spillover on inter-organizational resource sharing decision in collaborative knowledge creation

Collaborative knowledge creation is important for firms to gain new competitive advantages, but knowledge outgoing spillover harms their existing competitive advantages, which puts them into a dilemma when investing R&D resources. This study formalizes and investigates this dilemma using the Stackelberg leader–follower framework. Through our analyses, we find that, (1) current knowledge creation efforts and prior knowledge are substitutable in collaborative knowledge creation, and through controlling the ratio of current knowledge creation efforts to prior knowledge invested, the leader and the follower can gain benefits from collaboration and restrict knowledge outgoing spillover simultaneously; (2) because the leader invests resources first and faces moral hazards, it has the incentives to participate in collaborative knowledge creation only when its benefits from collaborative knowledge creation fruits and knowledge incoming spillover are bigger than those of the follower, and the more moral hazards it confronts, the more it demands; (3) the leader and the follower invest resources at ratios consistent with the benefits and costs the resources bring to them if they can determine the amount, or the collaboration is unstable.     

带负顾客和非空竭服务随机休假的M~([x])/G/1可修排队系统

研究了带负顾客和非空竭服务随机休假的M~([X])/G/1可修排队系统.负顾客不仅仅移除一个正在接受服务的正顾客,而且还使得服务器损坏而立即进行修理.通过构造一个具有吸收态的马尔可夫链求得了系统稳态存在的充分必要条件.利用补充变量法求得了系统的排队指标和可靠性指标.最后我们还给出了一个数值实例.     

基于效益最优的企业物流外包决策的量化研究

供应链管理要求相关企业进行优化合作,将非核心业务外包,其中最典型的是物流外包.目前大多数文献仅仅从定性角度出发阐述企业物流外包决策的原因,而没有将其定量化研究.尝试由基本的需求函数出发,根据企业利润最大化原则,从成本和收益的角度去量化分析企业物流外包的必然性和建立高效供应链的必要性,找到基于利润和核心竞争力的企业物流外包的动力.     

关于Steiner问题的一个注记——连接五点之最小网络的一种寻优方案

本文讨论如何寻找连接平面上五个给定点的最小网络这一问题．通过发展越民义证明Pollack在1978年所给出的一个关于寻找连接平面上四个给定点的最小网络的重要结论的方法,我们给出了一个采用简单几何作图方法快速求解该问题的方案．     

CIR框架下的投资组合效用微分博弈

建立了Cox-Ingersoll—Ross随机利率下的关于两个投资者的投资组合效用微分博弈模型．市场利率具有CIR动力,博弈双方存在唯一的损益函数,损益函数取决于投资者的投资组合财富．一方选择动态投资组合策略以最大化损益函数,而另一方则最小化损益函数．运用随机控制理论,在一般的效用函数下得到了基于效用的博弈双方的最优策略．特别考虑了常数相对风险厌恶情形,获得了显示的最优投资组合策略和博弈值．最后给出了数值例子和仿真结果以说明本文的结论．     

带多面体控制锥的锥约束凸向量优化问题的有效解集的非空有界性的刻画

本文刻画了控制锥为多面凸锥的锥约束凸向量优化问题有效解集的非空有界性．然后将其中的一个重要条件应用于一类罚函数方法收敛性的研究．