制Cl2选用KClO3还是KMnO4?

高中化学(试验修订本·必修)课本第一册第四章的实验中要用到大量 Cl_2,为了方便、省时,实验室一般不采用课本上制 Cl_2的方法,而是直接往固体 KClO_3或KMnO_4上逐滴滴加浓 HCl 制得 Cl_2。无论用 KClO_3还是用 KMnO_4都能制得 Cl_2,而用这2种方法制得的 Cl_2进行性质实验时,效果却不相同。表1 选用 KClO_3或 KMnO_4制 Cl_2的对比分析     

用复数讨论抛体运动

本文用复数讨论了抛体运动在不同情形下的运动方程式,同时展示用复数解决二维运动问题的特点.     

用复数讨论抛体运动

本文用复数讨论了抛体运动在不同情形下的运动方程式，同时展示用复数解决二维运动问题的特点。     

一道值得商榷的化学习题

有这样一道习题:“淀粉-KI 试纸常用来检验Cl_2,但__(能或不能)用来检验氯化物或 KClO_(?)里的氯”。笔者认为值得商榷。使用淀粉-KI 试纸可检验 Cl_2,是因为 Cl_2与     

复数域的格序化问题研究

推广了关于复数域格序化问题的Birkhoff-Pierce定理,证明了复数域作为二维实代数其上的偏序只有离散偏序和平凡偏序。     

氯气的实验室制法及其拓展

一、制备原理根据氧化还原反应原理,实验室里用MnO_2和浓HCI制取CI_2,反应方程式如下:4HCl MnO_2(△==)MnCl_2 2H_2O Cl_2↑拓展:(1)用氧化剂氧化浓盐酸:2NaCl 3H_2SO_4 MnO_2(△==)2NaHSO_4 MnSO_4 2H_2O Cl_2↑16HCl 2KMnO_4==2KCl MnCl_2 8H_2O 5Cl_2↑6HCl KClO_3==KCl 3H_2O 3Cl_2↑     

Cl_2的实验室制法简介及联想拓展

Cl_2是中学化学中常见的气体之一,其实验室制法是同学们学习的重点.下面将Cl_2实验室制法的有关知识及拓展简介如下,供同学们参考,以帮助大家更好地掌握这部分内容.一、反应原理在实验室里,Cl_2可以用浓盐酸与MnO_2起反应来制取,反应的化学     

对一道数型题的探究

试题:NH_3和Cl_2可迅速进行下列反应: 2NH_3 3Cl_2=N_2 6HCl 下图为反应后气体总体积(V升)随原混合气体中Cl_2的体积百分含量(x％)而变化的坐标图。试计算: (1)当反应结束如处于A、n两点时,原混合气体中Cl_2的体积百分含量各是多少? (2)当反应结束如处于A、B两点时,混合气体的总体积是多少?     

还是用Ba(NO_3)_2溶液作试剂好

现行初中化学课本中,对硫酸及可溶性硫酸盐的检验,采用在试液中滴加 B_(?)Cl_2溶液的方法。大家知道,不仅 H_2SO_4溶液及可溶性硫酸盐溶液中滴加 B_(?)Cl_2溶液能产生不溶于盐酸的白色沉淀,AgNO_3溶液中滴加 B_(?)Cl_2溶液同样能生成不     

浅谈氧化性、还原性的强弱判断

<正>一般情况下,氧化性、还原性的强弱规律为:氧化性:氧化剂>氧化产物;还原性:还原剂>还原产物。但是请注意,此规律是有应用条件的,即仅限于自发的氧化还原反应。借此顺便提出,中学化学常见的氧化剂中,不时会见到关于O_2和Cl_2两者氧化性孰强孰弱的争执,有人依狄康法制Cl_2,由"前强后弱"推出O_2的氧化性大于Cl_2,忽视了反应条件及催化剂的作用,而实际上我们都知道,Cl_2与H_2O     

A Comparison of Item Calibration Procedures in the Presence of Test Speededness

In the presence of test speededness, the parameter estimates of item response theory models can be poorly estimated due to conditional dependencies among items, particularly for end‐of‐test items (i.e., speeded items). This article conducted a systematic comparison of five‐item calibration procedures—a two‐parameter logistic (2PL) model, a one‐dimensional mixture model, a two‐step strategy (a combination of the one‐dimensional mixture and the 2PL), a two‐dimensional mixture model, and a hybrid model‐–by examining how sample size, percentage of speeded examinees, percentage of missing responses, and way of scoring missing responses (incorrect vs. omitted) affect the item parameter estimation in speeded tests. For nonspeeded items, all five procedures showed similar results in recovering item parameters. For speeded items, the one‐dimensional mixture model, the two‐step strategy, and the two‐dimensional mixture model provided largely similar results and performed better than the 2PL model and the hybrid model in calibrating slope parameters. However, those three procedures performed similarly to the hybrid model in estimating intercept parameters. As expected, the 2PL model did not appear to be as accurate as the other models in recovering item parameters, especially when there were large numbers of examinees showing speededness and a high percentage of missing responses with incorrect scoring. Real data analysis further described the similarities and differences between the five procedures.     

复杂尺寸链的计算机算法研究

本介绍复杂尺寸链的Method of Traces计算方法，针对这种传统手工计算方法的不足，提出了LU分析计算机算法的原理及实现方法，为CAPP提供了模块．     

二维超分子配位化合物[Cu（mal）（tpm）（H2O）]·2H2O的合成、结构及表征

合成了氢键连接的二维超分子配位化合物[Cu（mal）（tpm）（H2O）]·2H2O（mal=丙二酸,tpm=三吡唑甲烷）,并用元素分析和电子顺磁共振谱进行了表征。X射线单晶衍射表明该化合物的晶体属单斜晶系,Cc空间群,晶胞参数a=1．3624（2）nm,b=0．79318（14）nm,c=1．7526（3）nm,α=90°,β=102．352（3）°,γ=90°,V=1．8501（6）cm^3,Z=4。中心Cu（Ⅱ）离子为五配位,处于扭曲的四方锥配位环境中。晶格水与配位水形成较强的氢键将配合物连接成二维超分子结构。     

有关复数域一些问题的研究

本文阐明了域和同构的概念,并证明了有序实数组、二维向量和二阶矩阵的同构关系,指出特殊的实数组、二维向量和二阶矩阵都可以定义复数域。     

二维双曲Euler公式的推广

本文考察了二维双曲Euler公式的若干性质,在四维双曲复空间的拟时区建立了四维双曲Euler公式。     

有界闭模糊复数集上映射的一些性质

有界闭模糊复数是一类应用最为广泛的模糊数,它具有良好的结构和性质.本文重点研究了有界闭模糊复数集上的映射的一些性质,得到了一些新结论,为后继研究工作奠定了一定的基础.     

Perceptual development and category generalization.

This work is concerned with developmental changes in the structure of classifications. The central claim is that young children's undifferentiated perceptions of complex stimuli are highly structured by wholistic similarity whereas older children's perceptions are structured by component dimensions. It is shown in 2 experiments that young children systematically and spontaneously generalize a category if it is well organized by overall similarity but not if it is organized by a criterial dimension. Older children, on the other hand, spontaneously apprehend and extend a category by its dimensional structure. The third experiment was designed to test the hypothesis that criterial property categories are preferred in classification tasks requiring the explicit discovery of a general rule. It was found that younger children's attention to the dimensional relations within a category increases under rule-discovery instructions, although they still have difficulty ignoring wholistic similarity relations. The trend from similarity to dimensional classification is discussed in the context of Piagetian classification tasks and family-resemblance accounts of natural categories.     

Complex numbers and plane geometry

The representation of complex numbers as points of the Euclidean plane naturally leads to a two-way interaction between geometry and numbers. The geometry of the plane has a very deep influence in the study complex analytic functions. In this article, we illustrate the other way aspect by a few simple-minded application of complex numbers to give elegant solutions of problems in plane geometry, such as Ptolemy’s Theorem, Euler-line and Nine-point Circle Theorem. Anant R Shastri is a Professor at IIT, Bombay. His research inerests are in algebraic topology and algebraic geometry. He is also keen in math education and music. This article is based on a talk given to an audience consisting mainly students of class IX and X, at Nehru Science Centre under the aegis of Bombay Association for Science Education and Bombay Math. Colloq. on 25th Jan. 2003. An earlier version of this article was published in Bona Mathematica, Vol.14 Nos.1–2, 2003.     

The cranial nerve skywalk: A 3D tutorial of cranial nerves in a virtual platform

Visualization of the complex courses of the cranial nerves by students in the health‐related professions is challenging through either diagrams in books or plastic models in the gross laboratory. Furthermore, dissection of the cranial nerves in the gross laboratory is an extremely meticulous task. Teaching and learning the cranial nerve pathways is difficult using two‐dimensional (2D) illustrations alone. Three‐dimensional (3D) models aid the teacher in describing intricate and complex anatomical structures and help students visualize them. The study of the cranial nerves can be supplemented with 3D, which permits the students to fully visualize their distribution within the craniofacial complex. This article describes the construction and usage of a virtual anatomy platform in Second Life?, which contains 3D models of the cranial nerves III, V, VII, and IX. The Cranial Nerve Skywalk features select cranial nerves and the associated autonomic pathways in an immersive online environment. This teaching supplement was introduced to groups of pre‐healthcare professional students in gross anatomy courses at both institutions and student feedback is included. Anat Sci Educ 7: 469–478. © 2014 American Association of Anatomists.     

复指数函数的定义问题

对实数域中指数函数的定义在复数域上的推广及欧拉公式与复指数函数的关系进行了探讨。