高中生化学预习现状的调查研究

新课程强调学生自主学习,恰当地指导学生进行预习则是激发学生主动学习,培养思维能力和自学能力的重要途径。对北京市2所示范高中的254名学生进行问卷调查,结果表明：大部分学生认为预习很有必要,但很少有预习的习惯;在元素化合物知识方面,大部分学生预习主要限于记录难点,而不会利用“类别-通性-特性”的化学思维;在概念原理方面,约50%的学生能运用常规思维方式来预习,但在预习过程中独立思考较少;在实验方面,大部分学生能关注实验涉及的常规问题,但缺乏设计意识。基于此,提出了相应的教学建议。     

Multi-resolution image analysis using the quaternion wavelet transform

This paper presents the theory and practicalities of the quaternion wavelet transform. The contribution of this work is to generalize the real and complex wavelet transforms and to derive for the first time a quaternionic wavelet pyramid for multi-resolution analysis using the quaternion phase concept. The three quaternion phase components of the detail wavelet filters together with a confidence mask are used for the computation of a denser image velocity field which is updated through various levels of a multi-resolution pyramid. Our local model computes the motion by the linear evaluation of the disparity equations involving the three phases of the quaternion detail high-pass filters. A confidence measure singles out those regions where horizontal and vertical displacement can reliably be estimated simultaneously. The paper is useful for researchers and practitioners interested in the theory and applications of the quaternion wavelet transform.     

概念格的粗糙近似比较研究

形式背景产生了概念格,每个节点由外延和内涵组成.对形式背景论域中的任何一个子集,可用外延来近似,在这方面已有了4种方法.对这些方法进行了比较研究,利用粗糙集理论证明了用这些方法所求出的概念的上近似外延是相同的,并利用粗糙集理论研究了概念格属性约简后,原来方法对结果的一致性.     

A theorem on parastatistics and its application

Proceeding from the assumption that nature chooses a riskless strategy, we consequently obtain a distribution over parastatistics. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 150, No. 3, pp. 511–512, March, 2007.     

略论分子量测定在大分子概念形成中的作用

本文介绍了高分子概念的起源,对大分子的早期认识,分子量测定方法的发展和大分子概念的确立过程,讨论了分子量测定方法在大分子概念形成中的作用。     

HSAB-driven regioselectivity difference in the Lewis-acid catalyzed reactions of 2-C-substituted glycals with sulfur and oxygen nucleophiles: direct versus allylic substitution

A remarkable regioselectivity difference in the Lewis-acid catalyzed reactions of 2-C-acteoxymethyl glycals with thiophenols and phenols has been observed. The reaction with thiophenols led to preferential formation of a new class of compounds viz. 2-C-arylthiomethyl glycals via direct attack at the C-2 side chain primary carbon bearing the leaving group. In contrast, phenols were reported to afford predominantly 2-C-methylene-O-aryl glycosides via allylic attack at the anomeric carbon. The observed results correlate well with the HSAB principle proposed earlier for similar type of reactions with simple glycals. In addition, formation of an unusual bis-thioarylated product in presence of an excess of thiophenol is also reported.     

The performance of undergraduate students in the limit concept

In this work, we investigated first-year university students’ skills in using the limit concept. They were expected to understand the relationship between the limit-value of a function at a point and the values of the function at nearby points. To this end, first-year students of a Turkish university were given two tests. The results showed that the students were able to compute the limit values by applying standard procedures but were unable to use the limit concept in solving related problems.     

Diastereomeric isomerization of Fischer's base analogs of LTAM molecules in organic solvents: mechanistic investigation

Three possible mechanistic routes for the diastereomeric isomerization of the leuco-triarymethane (LTAM) molecules have been proposed, depending on the formal breaking of the carbon-carbon double bond via either heterolytic, homolytic or molecula splitting/reassembling.     

解释驱动探究促进学生化学概念理解的研究

采用准实验研究设计,选择高一年级2个班的学生作为实验对象,对实验组学生进行教学干预,让他们采用解释驱动探究学习电解质和氧化还原反应概念,控制组学生按照学校正常教学安排进行。结果显示实验组学生的概念理解高于控制组,并且对氧化还原反应概念的理解呈现显著性差异。解释驱动探究有效促进了学生对科学概念的理解和迁移,并消除了相异构想。     

On problematic aspects in learning trigonometry

In this paper, research on some problematic aspects high school students have in learning trigonometry is presented. It is based on making sense of mathematics through perception, operation and reason in the case of trigonometry. We analyzed students' understanding of trigonometric concepts in the frame of triangle and circle trigonometry contexts, as well as the transition between these two contexts. In the conclusion, we present some new problematic aspects we noticed.

The research was carried out with two groups of high school students, one of them at the beginning of their trigonometry learning (17 years old) and the other at the end of their high school education (19 years old). The students were given a questionnaire similar to that of Chin and Tall, and we analyzed the students' response. In our research, we noticed that students have difficulties with properties of periodicity and the fact that trigonometric functions are not one-to-one. In addition, there is poor understanding of radian measure and a lack of its connection to the unit circle.