智慧放手,培养学生“量感”能力的探究

“量感”是学生在生活、学习过程中主动地、自觉地理解运用“量”的主观想法,是一种“准确运用量”的直觉、对量的敏感性、对“量”的精准性.量感有助于提升对量的理解,提升对量的应用,同时也可以培养学生的估算、估测能力,对于提高学生数学核心素养具有重要意义和价值.培养量感,教师应该“智慧放手”,不断创设活动场景,生活情境,指引孩子认真观察、动手操作、不断探究和内化体验,积累丰富的“量”的素材,建立“量感”能力.     

二元选择面板模型的截面相关检验

鉴于CD统计量对截面相关形式是不稳健的,需对CD统计量进行修正。从而本文提出了渐近服从标准正态分布的MCD统计量,与已有的LM_(BC)统计量和CD统计量比较发现:(1)三个统计量不存在明显的水平扭曲;(2)当截面间相关度有正有负,且规模较为接近时,CD统计量的功效很低,MCD统计量和LM_(BC)统计量对于截面相关方式更稳健,而在同向截面相关模型中CD统计量的功效明显更好;(3)当模型存在分布误设或异方差时,CD统计量、LM_(BC)统计量和MCD统计量的表现都较为稳健。我们将这三个统计量应用到国内上市公司现金分红行为模型中,发现公司间分红行为具有显著的相关性。     

广义Cauchy张量的正定性及互补问题的研究

广义Cauchy张量是由Cauchy张量推广而来,将在Cauchy张量的基础上,围绕广义Cauchy张量的正定性及共正性展开研究,并提出关于广义Cauchy张量互补问题的几个结论.     

基于旋量理论的开链机器人动力学Kane方程研究

首先介绍了旋量的基本理论、指数积及雅可比矩阵．在此基础上定义了基于旋量理论的主动力旋量、惯性力旋量、偏速度旋量、广义主动力及广义惯性力等概念,之后推导出了基于旋量理论的开链机器人动力学Kane方程,再者阐明了偏速度旋量几何计算,最后以示例验证结论的正确性．     

焦点量与鞍点量的关系

对于一般情形,给出焦点量和鞍点量计算与约化的Maple算法,从而统一了焦点量和鞍点量的计算,并给出细焦点与细鞍点的变换,利用变换推导了焦点量和鞍点量的关系.     

焦点量与鞍点量的关系

对于一般情形,给出焦点量和鞍点量计算与约化的Maple算法,从而统一了焦点量和鞍点量的计算,并给出细焦点与细鞍点的变换,利用变换推导了焦点量和鞍点量的关系．     

把握度量本质:让量感培养落地生根

在小学数学课堂中培养“量感”,既能帮助学生更深刻地理解“量”的概念,提升其对量的敏感性与直觉能力,又进一步在提升学生数学思维的基础上,强化其学科核心素养的落实.基于此,本文尝试从“对比参照物体,催生‘量’的感知;强化操作实验,丰富‘量’的体验;勾连生活估测,内化‘量’的感悟;解决实际问题,深化‘量’的应用”四部曲入手,聚焦于如何在小学数学课堂中有效培养学生“量感”,助力核心素养落地.     

高阶张量Pareto-特征值的若干性质

考虑高阶张量特征值互补问题,由于求解张量的最大Pareto-特征值是一个NP难问题,关注于Pareto-特征值的估计,并给出若干关于Z-张量和M-张量的Pareto-特征值的性质.     

模糊量及模糊数的表现特性

模糊集的表现定理是模糊数学的最基本理论.在表现定理的基础上,对各种模糊量:包括凸模糊量、正规模糊量、正规凸模糊量、凸有界模糊量、模糊数、有限模糊数、对称模糊数的表现定理进行了深入的研究,从而建立了不同类型模糊量与普通集合之间的联系.     

基本量方法

在一些数学问题中,虽然涉及到许多量,但其中有几个量是可以独立取值的,而其它量则是这些量的函数。我们选定任一组这样的量做为基本量,那么问题就归结为研究诸基本量之间的关系了。这就是所谓     

培养学生科学思维和创新能力的研究与实践——谈大学数学研究型教学

通过从一个导数值等式的证明谈起,探讨教师在课堂教学中如何根据教学内容创设能激起学生新异感的问题情景,启发和引导学生发散思考,类比、联想、猜想,探索和发现新问题并给出解答.使学生思维不断攀升,丰富教学内容,激发学生兴趣,培养学生科学思维方法和创新能力.     

Mexican high school students' social representations of mathematics,its teaching and learning

This paper reports a qualitative research that identifies Mexican high school students’ social representations of mathematics. For this purpose, the social representations of ‘mathematics’, ‘learning mathematics’ and ‘teaching mathematics’ were identified in a group of 50 students. Focus group interviews were carried out in order to obtain the data. The constant comparative style was the strategy used for the data analysis because it allowed the categories to emerge from the data. The students’ social representations are: (A) Mathematics is…(1) important for daily life, (2) important for careers and for life, (3) important because it is in everything that surrounds us, (4) a way to solve problems of daily life, (5) calculations and operations with numbers, (6) complex and difficult, (7) exact and (6) a subject that develops thinking skills; (B) To learn mathematics is…(1) to possess knowledge to solve problems, (2) to be able to solve everyday problems, (3) to be able to make calculations and operations, and (4) to think logically to be able to solve problems; and (C) To teach mathematics is…(1) to transmit knowledge, (2) to know to share it, (3) to transmit the reasoning ability, and (4) to show how to solve problems.     

On the relation of abstract and concrete in scientists’ graph interpretations: A case study

The notions of abstract and concrete are central to the conceptualization of mathematical knowing and learning. Much of the literature takes a dualist approach, leading to the privileging of the former term at the expense of the latter. In this article, we provide a concrete analysis of a scientist interpreting an unfamiliar graph to show how engagement with some object leads to the working out of existing, concrete practical understanding and the articulation of categorical statements (“generalizations”); because the scientist knew something at the end of his interpretive work that he did not prior to it, the event is understood to constitute an episode of learning. The analysis shows that rather than being a movement from concrete to abstract or from abstract to concrete, development occurs in a movement that appears to be simultaneously from concrete to abstract and from abstract to concrete.     

Self-converse mixed graphs are extremely rare

A mixed graph is cospectral to its converse, with respect to the usual adjacency matrices. Hence, it is easy to see that a mixed graph whose eigenvalues occur uniquely, up to isomorphism, must be isomorphic to its converse. It is therefore natural to ask whether or not this is a common phenomenon. This note contains the theoretical evidence to confirm that the fraction of self-converse mixed graphs tends to zero.     

A multivariate adaptive regression splines cutting plane approach for solving a two-stage stochastic programming fleet assignment model

The fleet assignment model assigns a fleet of aircraft types to the scheduled flight legs in an airline timetable published six to twelve weeks prior to the departure of the aircraft. The objective is to maximize profit. While costs associated with assigning a particular fleet type to a leg are easy to estimate, the revenues are based upon demand, which is realized close to departure. The uncertainty in demand makes it challenging to assign the right type of aircraft to each flight leg based on forecasts taken six to twelve weeks prior to departure. Therefore, in this paper, a two-stage stochastic programming framework has been developed to model the uncertainty in demand, along with the Boeing concept of demand driven dispatch to reallocate aircraft closer to the departure of the aircraft. Traditionally, two-stage stochastic programming problems are solved using the L-shaped method. Due to the slow convergence of the L-shaped method, a novel multivariate adaptive regression splines cutting plane method has been developed. The results obtained from our approach are compared to that of the L-shaped method, and the value of demand-driven dispatch is estimated.     

Evaluation of stock allocation policies in a divergent inventory system with shipment consolidation

In this paper we consider a one-warehouse N-retailer inventory system characterized by access to real-time point-of-sale data, and a time based dispatching and shipment consolidation policy at the warehouse. More precisely, inventory is reviewed continuously, while a consolidated shipment (for example, a truck) to all retailers is dispatched from the warehouse at regular time intervals. The focus is on investigating the cost benefits of using state-dependent myopic allocation policies instead of a simple FCFS (First-Come-First-Serve) rule to allocate shipped goods to the retailers. The analysis aims to shed some light on when, if ever, FCFS is a reasonable policy to use in this type of system? The FCFS allocations of items to retailers are determined by the sequence in which retailer orders (or equivalently customer demands) arrive to the warehouse. Applying the myopic policy enables the warehouse to postpone the allocation decision to the moment of shipment (from the warehouse) or the moments of delivery (to the different retailers), and to base it on the inventory information available at those times. The myopic allocation method we study is often used in the literature on periodic review systems.     

随机数学教学设计与实践——关注理解、掌握与应用

本文通过分析教学案例并总结课程教学交流体会,探讨在大学《概率论与数理统计》课程教学中如何引导学生理解概念、掌握方法并灵活应用以解决相关实际问题;培养学生善学睿思,增强其自主创新实践能力。     

A study of leveraged ETF based on geometric return

Leveraged (inverse) exchange-traded funds (LETFs) seek to deliver multiples (opposite) of the performance of the index or benchmark they track. LETFs typically are designed to achieve their stated performance objectives on a daily basis. Many real-life and hypothetical examples have been given to show that the performance of these ETFs over a period longer than one day can differ from their stated daily performance objectives. Formulae have been found using both continuous method and discrete method. A discrete method was used to find a formula linking the return of a leveraged fund with the corresponding multiple of the return of the unleveraged fund and its realized variance but the method needs to use some assumptions and statistical properties to create the volatility term. A CME report finds a very simple way to include volatility in their formula but fails to link to the return of the corresponding unleveraged product. In this paper, we find a natural way to link a leveraged fund with its corresponding unleveraged product and its realized variance in a discrete manner. Our derivation process is similar to that in the CME report, so we do not need to use assumptions and statistical properties to create the volatility term. Unlike the CME method, we use geometric return as opposed to arithmetic return. So, we are able to connect with the return of the corresponding unleveraged product.     

出租车司机社会贡献评价方法研究

出租车司机的社会贡献对于促进城市经济发展和社会进步具有重要的作用,评价出租车司机的社会贡献是激励出租车司机多做社会贡献的重要手段。为了评价出租车司机的社会贡献,本文提出了一种基于实际出租车运营数据的评价方法。本文设计了运营特性、重点区域、恶劣天气、大事件四个体现司机社会贡献的指标,以此构建了出租车司机社会贡献评价指标体系,进而选用了主观赋权法G1法和客观赋权法拉开档次法相结合的赋权方式对指标赋权,并选择四种评价信息集结方法建立了出租车司机社会贡献评价模型。最后,通过实际的出租车运营数据验证了本方法的可行性。本文为评价出租车司机社会贡献提供了一种研究思路和方法,并对政府政策的制定和企业策略的实施具有一定的启示。     

Strategic commitment to price to stimulate downstream innovation in a supply chain

It is generally in a firm’s interest for its supply chain partners to invest in innovations. To the extent that these innovations either reduce the partners’ variable costs or stimulate demand for the end product, they will tend to lead to higher levels of output for all of the firms in the chain. However, in response to the innovations of its partners, a firm may have an incentive to opportunistically increase its own prices. The possibility of such opportunistic behavior creates a hold-up problem that leads supply chain partners to underinvest in innovation. Clearly, this hold-up problem could be eliminated by a pre-commitment to price. However, by making an advance commitment to price, a firm sacrifices an important means of responding to demand uncertainty. In this paper we examine the trade-off that is faced when a firm’s channel partner has opportunities to invest in either cost reduction or quality improvement, i.e. demand enhancement. Should it commit to a price in order to encourage innovation, or should it remain flexible in order to respond to demand uncertainty. We discuss several simple wholesale pricing mechanisms with respect to this trade-off.