浅谈数形结合的方法

数形结合思想是一种重要的数学思想,它的实质就是根据数与形之间的对应关系,通过数与形的相互转化来解决问题.用数形结合思想解题能简化推理和运算,具有直观、快捷的优点.在历年高考试题的解答中都体现了数形结合思想的广泛应用.     

可拓数据挖掘在高校教学质量评价中的应用

高校在教学和管理工作中积累了大量的数据,但这些数据没有得到有效利用.将可拓数据挖掘技术引入教学领域,从教学评价数据中提取出隐藏在数据之中的有用信息,为教学管理者提供决策支持.首先通过可拓分析,寻找质量达到要求、可进行有效挖掘的教学评价数据,然后对这些数据进行两方面的挖掘:影响教学质量的关键因素挖掘、教学质量与教师特征之间的关联规则挖掘.     

Developing shock-capturing difference methods

A new shock-capturing method is proposed which is based on upwind schemes and flux-vector splittings. Firstly, original upwind schemes are projected along characteristic directions. Secondly, the amplitudes of the characteristic decompositions are carefully controlled by limiters to prevent non-physical oscillations. Lastly, the schemes are converted into conservative forms, and the oscillation-free shock-capturing schemes are acquired. Two explicit upwind schemes (2nd-order and 3rd-order) and three compact upwind schemes (3rd-order, 5th-order and 7th-order) are modified by the method for hyperbolic systems and the modified schemes are checked on several one-dimensional and two-dimensional test cases. Some numerical solutions of the schemes are compared with those of a WENO scheme and a MP scheme as well as a compact-WENO scheme. The results show that the method with high order accuracy and high resolutions can capture shock waves smoothly.     

双波长双指示物催化光度法测定痕量铜

1引言 催化动力学光度法测定痕量铜已有报道。但目前的研究大多在寻找合适的指示剂，用单指示物在单一波长下进行测定，要提高灵敏度往往较为困难。本实验在弱碱性介质中，以KC1为活化剂，利用Cu（Ⅱ）催化H2O2氧化胭脂红和溴甲酚紫双指示物，分别在两指示物的最大吸收波长处测量催化反应和非催化反应体系的吸光度，利用两波长处吸光度差值的加和性与Cu（Ⅱ）浓度呈线性关系，建立了双波长、双指示物动力学光度法测定铜的新方法，用于水样中痕量铜的测定。