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设C为Hilbert空间H的非空子集,G为一个交换半群.文中定义了G上渐近殆非扩张曲线“(·):G→C,证明了渐近殆非扩张曲线的强遍历收敛定理.应用于半群,得到了在失去凸性的情况下,渐近非扩张型半群的殆轨道的强遍历收敛定理.推广和改进了以前所有的结果。 相似文献
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本文利用两个非齐次马尔科夫链的转移矩阵列的比较,讨论了两个链启遍历性的关系,得到一个非齐次马尔科夫链是强遍历的一些充分条件.本文还分析了非齐次马尔科夫链的一致强、弱遍历性的关系,得到一个非齐次马尔科夫链是一致强遍历的一些充分条件. 相似文献
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罗绍凯 《数学物理学报(A辑)》1994,(2)
本文给出了高阶非型约束加在广义虚位移上的限制条件,建立了变质量高阶非型非线性非完整系统的Routh方程、方程、Nielsen方程和Appell方程;给出了高阶非型约束系统“d”与“δ”之间的交换关系,建立了其积分变分原理;并得到了变质量高阶非型约束系统的广义Noether守恒律. 相似文献
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罗绍凯 《数学物理学报(A辑)》1994,14(2):168-177
本文给出了高了阶非ЧeTaeB约束加在广义虚位移上的限制条件,建立了变质量高阶非ЧeTaeB型非线性非完整系统的Routh方程,ЧaПЛЫГИН方程、Nielsen方程,给出了高阶非ЧeTaeB型约束系统“d”与“δ”之间的产换关系,建立了其积分变分原理,并得到了变质量高阶非ЧeTaeB型约束系统的广义Noether守恒律。 相似文献
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本文首先给出了最小方差集的运算模型,在此基础上指出了非负解的重要意义,并给出了非负解的枚举算法,最后给出了一个实例 相似文献
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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. 相似文献
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我国老库区面临着严重的贫困和生态环境双重问题,而其贫困为典型的环境制约型贫困,贫困与生态环境问题交织在一起,互为因果.对于典型环境制约型贫困的老库区,只有打破贫困与生态环境之间的恶性循环,建立社会、经济和生态环境之间的良性循环才是老库区反贫困的根本途径.本研究以四川省大洪河水库邻水县库区为例,在对老库区反贫困与生态环境可持续性进行分析的基础上,采用不确定多目标规划方法,构建了四川省大洪河水库邻水县库区的生态型反贫困规划模型.通过系统分析和建立规划模型,既定性又定量地进行了四川省大洪河水库邻水县库区反贫困和生态环境可持续性研究,就整个邻水县库区而言,需进行移民8711人,新修梯田3188.24hm2,扩建经济林果园地1413.09hm2,新建人工草地85.47hm2,才有可能达到反贫困和提高生态环境可持续性的目标. 相似文献
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快递业竞争激烈,构建高效合理的航空货运网络是快递企业提高竞争力的重要手段。“枢纽—辐射”式航空货运网络是整合航空快递资源、提高航空快递资源利用效率、提高快递企业竞争力的有效模式。本文以降低航空快递网络成本、加快航空快递处理时间为目标,从航空快递网络枢纽的选取、指派关系的确定、枢纽个数的选择三个方面研究了航空快递网络模型建立问题,选用遗传算法求解不同枢纽个数下航空快递网络的运输成本,并据此进行枢纽的选取,运用重力模型法进行指派关系的确定,在此基础上运用超效率DEA模型确定枢纽个数。接着,以包含17个节点的顺丰航空快递网络的规划为例,对本文所提出的模型和算法进行了验证,验证结果证实了模型的合理性。本文的研究为快递企业构建航空货运网络提供了科学实用的方法,该方法的使用可以降低航空货运成本,提高效率,从而提高快递企业的竞争力。 相似文献
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Gustavo Martínez-Sierra Marisa Miranda-Tirado 《International Journal of Mathematical Education in Science & Technology》2013,44(5):700-720
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. 相似文献
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Benito Chen-Charpentier Mark Jackson 《Mathematical Methods in the Applied Sciences》2020,43(14):8147-8157
Plants are a food source for man and many species. But, plants are subject to diseases, many of which are caused by viruses. Usually, virus propagation is done by a vector. Insect vectors typically have a seasonal behavior, and processes have delays. To combat the vectors, chemical insecticides are commonly used as a control. Unfortunately, these chemicals not only are expensive but also have toxic effects on humans, animals, and the environment. An alternative is to introduce a predator species to prey on the insects and limit the spread of the virus. A combination of insecticide and predators can be used to control the vector population. The question is whether there is an optimal combination. We introduce a mathematical model of ordinary differential equations describing the interaction between plants, vectors, and predators. To determine the optimal amount of predators to introduce and insecticide to use, an objective function giving the total cost to the farmer of the disease is given. We find the controls that minimize the objective function subject to the population variables satisfying the differential equation model and initial conditions together with constraints. There are two main different approaches that can be used to solve the optimal control problem: indirect and direct methods. We use direct methods to solve the problem with and without seasonality and delays. From the practical side, the model can be used to help farmers determine the right balance of insecticide and predators to minimize the total cost. 相似文献
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Yeping Li 《Journal of Differential Equations》2011,250(3):1285-1309
In this paper, we consider a one-dimensional bipolar nonisentropic hydrodynamical model from semiconductor devices. This system takes the nonisentropic Euler-Poisson form with electric field and frictional damping added to the momentum equations. First, we prove global existence of smooth solutions to the Cauchy problem. Next, we also discuss the asymptotic behavior of the smooth solutions. We find that in large time, the densities of electron and hole tend to the same nonlinear diffusive wave, the momentums tend to the Darcy's law, and the temperatures tend to the ambient device temperature. Finally, we can obtain the algebraic decay rate of the densities to the same nonlinear diffusive wave, the momentums to the Darcy's law and the temperatures to the ambient device temperature, and the exponential decay of their difference and the electric field to zero. We can show our results by precise energy methods. 相似文献
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Juan Carlos Ponce Campuzano Kelly E. Matthews Peter Adams 《International Journal of Mathematical Education in Science & Technology》2018,49(4):517-529
In this paper, we report on an experimental activity for discussing the concepts of speed, instantaneous speed and acceleration, generally introduced in first year university courses of calculus or physics. Rather than developing the ideas of calculus and using them to explain these basic concepts for the study of motion, we led 82 first year university students through Galileo's experiments designed to investigate the motion of falling bodies, and his geometrical explanation of his results, via simple dynamic geometric applets designed with GeoGebra. Our goal was to enhance the students’ development of mathematical thinking. Through a scholarship of teaching and learning study design, we captured data from students before, during and after the activity. Findings suggest that the historical development presented to the students helped to show the growth and evolution of the ideas and made visible authentic ways of thinking mathematically. Importantly, the activity prompted students to question and rethink what they knew about speed and acceleration, and also to appreciate the novel concepts of instantaneous speed and acceleration at which Galileo arrived. 相似文献
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对区间型符号数据进行特征选择,可以降低数据的维数,提取数据的关键特征。针对区间型符号数据的特征选择问题,本文提出了一种新的特征选择方法。首先,该方法使用区间数Hausdorff距离和区间数欧氏距离度量区间数的相似性,通过建立使得样本点与样本类中心相似性最大的优化模型来估计区间型符号数据的特征权重。其次,基于特征权重构建相应的分类器来评价所估计特征权重的优劣。最后,为了验证本文方法的有效性,分别在人工生成数据集和真实数据集上进行了数值实验,数值实验结果表明,本文方法可以有效地去除无关特征,识别出与类标号有关的特征。 相似文献
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Complex calculators in the classroom: theoretical and practical reflections on teaching pre-calculus
Jean-Baptiste Lagrange 《International Journal of Computers for Mathematical Learning》1999,4(1):51-81
University and older school students following scientific courses now use complex calculators with graphical, numerical and symbolic capabilities. In this context, the design of lessons for 11th grade pre-calculus students was a stimulating challenge.In the design of lessons, emphasising the role of mediation of calculators and the development of schemes of use in an 'instrumental genesis' was productive. Techniques, often discarded in teaching with technology, were viewed as a means to connect task to theories. Teaching techniques of use of a complex calculator in relation with 'traditional' techniques was considered to help students to develop instrumental and paper/pencil schemes, rich in mathematical meanings and to give sense to symbolic calculations as well as graphical and numerical approaches.The paper looks at tasks and techniques to help students to develop an appropriate instrumental genesis for algebra and functions, and to prepare for calculus. It then focuses on the potential of the calculator for connecting enactive representations and theoretical calculus. Finally, it looks at strategies to help students to experiment with symbolic concepts in calculus.This revised version was published online in September 2005 with corrections to the Cover Date. 相似文献