运动性疲劳对纵跳动力学特征的影响

为揭示下肢运动性疲劳对纵跳的动力学特征的影响,22名男性体育教育专业大学生志愿参加了实验。结果表明,随着下肢负荷时间的增加纵跳的垂直方向分力和冲量下降,而左右、前后方向分力和冲量增加,三个方向的力矩随负荷时间的延长而增加。     

A Lakatosian Framework to Analyze Situations of Cognitive Conflict and Controversy in Students' Understanding of Heat Energy and Temperature

The objective of this study is to analyze secondary school students' interactions (conflicts, controversies, and arguments) as they participate in an intact classroom activity designed to facilitate their understanding of heat energy and temperature. The study is based on 32 ninth-grade students in a public school in Londrina, Brazil. Results obtained show that the differentiation between heat energy and temperature constitutes considerable difficulties for the students, and can be considered as part of the hard-core of their understanding (Lakatos, 1970, Criticism and the Growth of Knowledge, Cambridge University Press, Cambridge, UK, pp. 91–196). Student interactions (video taped) were classified into an Alternative Model, Transitional Model, and Scientific Model, depending on the degree to which they reflected a progressive transition in their hard-core. Students generally resisted a change in their conceptual understanding. Some students were able to question the hard-core of their beliefs and construct a Transitory Model. Some students experienced a further progressive transition by constructing a Scientific Model, based on the understanding that Temperature only measures the energy of agitation. Methodology used also provided a glimpse of how a particular student grappled with the conflicts in order to facilitate progressive transition in understanding. It is concluded that given the opportunity to discuss, reflect, consider alternative/conflicting situations, students can construct models that increase progressively in their heuristic/explanatory power.     

Can the Study of Thermochemistry Facilitate Students’ Differentiation between Heat Energy and Temperature?

The objectives of this study are: (a) Evaluate science major freshman students’ ability to differentiate between heat energy and temperature, after having studied the topic of thermochemistry; (b) ascertain the degree to which students resist change from the caloric to the kinetic-molecular theory; (c) study the ability to differentiate between heat energy and temperature and its relationship to solving a problem of thermochemistry. Science major freshman students (n = 76) were tested on a three-item Test of Heat Energy and Temperature (THT) and a Thermochemistry Problem (TP). Both THT and the TP formed part of a semester exam given after the topic of thermochemistry had been studied in class. Results obtained show that even after having studied thermochemistry in an introductory freshman course, students have considerable difficulty in differentiating between heat energy and temperature. Although, all three items of THT required the understanding of kinetic-molecular theory, percentage of correct responses varied considerably: Item 1 (72%), Item 2 (64%), and Item 3 (51%). A correct response on Item 3 meant that different amounts of water in two different vessels at 100 °C, would have the same average kinetic energy, but the heat energy required to attain 100 °C was different—hence the confusion with heat as a substance (caloric theory). It was found that students who had good conceptual understanding on the TP did not perform significantly (χ ² = 0.023) better on the THT. It is concluded that as science teachers we must be aware of the difficulties associated with the differentiation between heat energy and temperature and hence the need for teaching thermochemistry in order to facilitate conceptual understanding.     

表面活性剂增敏催化光度法测定痕量亚硝酸根

基于在稀硫酸介质中溴代十六烷基吡啶 (CPB)对亚硝酸根 (NO-2 )催化溴酸钾氧化碘曙红褪色反应的增敏作用 ,建立了测定NO-2 的表面活性剂增敏催化动力学光度法 .由于加入增敏剂 ,灵敏度显著提同 .lgA0 /A值与NO-2 含量在 0～ 1.0 μg/mL范围内存在线性关系 ,检出限量为0 .0 6 μg/ml.方法用于水样、蔬菜中痕量亚硝酸根的测定 ,结果较好     

磺化麦草碱木质素热分析动力学研究

为研究磺化碱木质素在高温条件下的热稳定性能，实验采用热重－红外分析(TG-IR)和差示扫描量热分析(DSC) 研究了磺化麦草碱木质素在非氧状态下热分解反应的动力学过程。利用多升温速率法Kissingr法和Ozawa法，分别计算了磺化麦草碱木质素热动力学方程中的表观活化能(Ｅ)和频率因子lnA，分别为118.3 kJ•mol-1、121.46 kJ•mol-1；20.40min-1、15.92min-1；利用Kissingr法计算了热动力学方程的反应级数是1.8。     

完全弹性碰撞过程中的功、能转换

在物体的完全弹性碰撞过程中，系统内部的功能转换是非常复杂的，一般力学教材对碰撞过程都没有作详细分析。本通过实际举例，对弹性碰撞的全过程作了较详细的分析。     

物体的非完全弹性碰撞解析

以动量和动能的计算为前提，通过对非完全弹性碰撞的末速度的求解、恢复系数的测定和动能损失的讨论使得我们对非完全弹性对心正硅有一个既深刘又全面的了解。     

Optimization of a Reduced Chemical Kinetic Model for HCCI Engine Simulations by Micro-Genetic Algorithm

A reduced chemical kinetic model （44 species and 72 reactions） for the homogeneous charge compression ignition （HCCI） combustion of n-heptane was optimized to improve its autoignition predictions under different engine operating conditions. The seven kinetic parameters of the optimized model were determined by using the combination of a micro-genetic algorithm optimization methodology and the SENKIN program of CHEMKIN chemical kinetics software package. The optimization was performed within the range of equivalence ratios 0.2-1.2, initial temperature 310- 375 K and initial pressure 0, 1-0.3 MPa, The engine simulations show that the optimized model agrees better with the detailed chemical kinetic model （544 species and 2 446 reactions） than the original model does.     

Ce（Ⅳ）离子氧化环己酮的反应动力学及机理

在25～40℃范围内用分光光度法研究酸性介质中Ce（Ⅳ）离子氧化环己酮（Re）的动力学机理．结果表明：反应对Ce（Ⅳ）为一级反应,对还原剂环己酮为一级反应;表观速率常数随[H^＋]的增加而增加,随[HSO4^-]的增加而减小;无盐效应;反应中有自由基的存在．据此,提出了Ce（Ⅳ）氧化环己酮的反应机理,能很好地解释全部实验现象,结合反应机理找到了本反应体系的动力学活性物种Ce（SO4）^2＋,并求得30℃时,速控步骤的速率常Kn=3.12mol^-1Lmin^-1.     

半无界区域上热传导方程第三和动力学边界条件的开拓法求解

关于半无界区域上带有第一,第二边界条件的热传导方程,前人已经用开拓法求解出它们的解的一般表达式。但第三边界问题,目前还没有现成的解的表达式;而动力学边界条件,国内外的书籍都甚少涉及。基于此,本论文尝试用开拓法求解第三边界和动力学边界问题的解的表达式。