共查询到20条相似文献,搜索用时 78 毫秒
1.
在对已有试题难度量化工具进行改进的基础上,建构了化学加试题难度评估工具。对2015年至2019年国家新高考实验区浙江省的8次化学选考加试题的难度进行了量化评价。结果表明,8次化学加试题整卷难度变化较大,但同一学年、有相同学生可能参与的2次化学选考的整体难度相近;加试题能力特征和难度差异明显,“有机化学基础”加试题(第32题)难度相对稳定,而第30题(化学反应原理)与第31题(实验化学)加试题难度却表现出一定的波动性。在对8次化学加试题的难度及相关因素进行分析的基础之上,也对如何提高加试题的编制质量,提出了可行性建议。 相似文献
2.
形成性测验作为教学过程中一种重要的和基本的测验方式,其试题的质量直接影响测验的功能能否发挥。本课题通过抽样调查和数据分析的方法,分析了江西省九年级化学试题具有信度高、难度适中、区分度不强及内容效度低的特点,并提出了改进建议。 相似文献
3.
试题分“必考”和“选考”,是新课程高考化学试卷结构有别于传统高考的一个特征,是课程选择性的必然体现。力求不同选考模块试题的等值,是保证受试者选择均等、得分公平的前提。以2008年实验区高考化学试卷为样例,从试题长度、难度和效度3个维度的等值性,探讨了新课程高考化学选考模块试题命制问题,为落实课程选择性和体现高考公平提供了研究视角。 相似文献
4.
以内地新疆高中班预科学生完成初三化学课程中3种固体粉末的鉴别实验为例,了解实验操作考查的评分者间信度的具体情况和影响因素。在本研究中,2位评分者的评分有较大的差异和较低的一致性,评分者间信度较低。试题的复杂性、监考学生的人数、评分标准的设计、评分者对评分标准的理解这4方面影响着评分者间信度。建议实验操作考查组织者控制监考学生的人数,加强评分者的培训工作,真正发挥实验操作考查的评价功能。 相似文献
5.
6.
在对2010年新课程高考理科综合能力测试全国卷中4个不同化学课程模块选考题难度预测和实测结果分析基础上,提出了“合理搭配选考模块”和“综合平衡试题难度”等解决选考题难度等值问题的路径。 相似文献
7.
8.
采用三段式诊断测试的方法,以浙江省某二级重点中学的高三化学选考生为研究对象,从“化学平衡状态的判定”“平衡常数与转化率”“平衡移动的影响因素”等3个维度,探查选考生在化学平衡概念理解上的表现。结果显示,选考生化学平衡概念理解的整体水平良好,但对平衡状态的速率判据理解不够全面,相异构想严重;转化率的计算能力和自信表现稍有不足;对催化剂、压强等平衡移动的影响因素存在认知缺陷,特别是压强因素,还未真正掌握压强影响平衡移动的本质机理。 相似文献
9.
为了提高组卷质量,基于极课大数据建立初中化学校本题库,根据双向细目表,利用该系统的出卷功能进行组卷。采用SPSS软件对试卷难度、区分度、信度和效度进行综合分析和评价,可知基于极课所出试卷各项评价指标较优秀,符合考试要求,试卷质量高。 相似文献
10.
选择部分高考理综化学试卷选择题进行案例分析,认为试题情境背景材料的选择与改造应作为试题命制技术的一项重要内容。基于具体试题的分析与讨论,提出试题情境的背景材料选择及控制应依据考生现有的知识基础、应考量考生已有的知识经验、应满足考生认知的"最近发展区"。试题情境"新""特"背景材料的认知要求如果没有得到合理控制,对试题的测量效度和试题分数的信度都会产生较大影响。 相似文献
11.
Several models have been proposed to describe the carbon number product distribution and mechanism in Fischer-Tropsch synthesis (FTS). However, these models have not fully explained the product distribution and mechanism owing to the wide range and complexity of hydrocarbons in FTS. This study was conducted based on the Yao and Anderson-Schulz-Flory (ASF) carbon number product distribution models for light (C1–C6) hydrocarbon products of a Fe/Al2O3 catalyst. The product distribution based on the molar ratio of olefin to paraffin (O/P) and the neighboring olefins was also studied in order to better understand the mechanism in FTS and C2 olefin deviation during FTS.Two sets of experiments (A and B) with different reaction conditions were conducted in microtubular fixed-bed reactors on the Fe/Al2O3 catalyst for 2249 h and 360 h, respectively. We found that the α values from the Yao and ASF carbon number product distribution models are relatively similar. The α values from the Yao carbon number product distribution plots are relatively constant, irrespective of the reaction conditions.Interestingly, it was also found that the secondary reactions of the C2 olefin by re-adsorption to produce paraffins and long-chain olefins are dependent on the CO conversion and the reaction temperature during the FTS. Also, the product distribution of the neighboring olefins during the reduction condition gave a similar trend to what was observed for other reaction conditions. This result confirmed what was observed in the Yao and ASF carbon number product distribution of the olefins. 相似文献
12.
Rejean Landry Alexander Penlidis Thomas A. Duever 《Journal of polymer science. Part A, Polymer chemistry》2000,38(13):2319-2332
We investigate the effect of the presence of reactive impurities during copolymerization on mathematical model discrimination and determine if impurities adversely affect the model discrimination process, depending on the criteria and response(s) used. Nonlinear mechanistic process models are employed in a multiresponse statistical discrimination scenario. The investigation also considers, via several case studies, the extremely interesting question of whether impurity effects could lead to incorrect choices about the copolymerization mechanism itself (terminal versus penultimate model). The answers to the above questions are that reactive impurities do affect the model discrimination process and, what is more, they may mislead researchers as to the choice of the copolymerization mechanism. The latter unexpected result is further illustrated with experimental data from the literature. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2319–2332, 2000 相似文献
13.
14.
Bharati Bhattacharyya Chitrani Medhi B. R. De S. P. Bhattacharyya 《Journal of Chemical Sciences》1989,101(3):235-242
An MCSCF model including the effects of solvent polarization is developed. The model is applied within the limitations of
INDO approximations to look into the dominant effects of solvent polarization on the electronic structure in the excited states
of a model system (e.g.nπ
* states of H2CO). Important features of macroscopic solvation-induced reorganization of electron density and some consequence thereof are
noted. 相似文献
15.
Russian Journal of Electrochemistry - A method for determination of parameters of a three-wire model and Lichtenecker model on the basis of experimental data of conductivity measurement for... 相似文献
16.
The solubilities of genistin in pure solvents including tetrahydrofuran, acetone, ethyl acetate, acetonitrile, isopropanol, n-butyl alcohol, methanol, cyclohexane, n-hexane, chloroform and ethanol were determined by the high performance liquid chromatography (HPLC) analysis method at T = (283.2, 293.2, 303.2, 313.2 and 323.2) K. The fusion enthalpy of genistin was estimated by the group contribution method. The solubility data of genistin were correlated by the simplified thermodynamic model, the modified Apelblat model, λh model and NRTL (Non-Random Two-Liquid) model. The calculated values by all models were in good agreement with the experimental values and however, the NRTL model could give better correlation results than other three models. 相似文献
17.
高分子黏弹性的经典唯象模型 总被引:2,自引:0,他引:2
高分子流体的黏弹性质是高分子科学和工程中一个非常重要的研究领域.与简单黏性液体和弹性固体不同,外场作用下缠结高分子流体呈现出复杂的黏弹性行为,例如应力不仅仅与应变幅度或应变速率有关,还与整个形变历史相关.近半个世纪以来,人们建立了很多描述这些复杂黏弹性质的模型和理论,其中一类是基于连续性介质力学原理的唯象模型,例如:Maxwell模型、Voigt-Kelvin模型和在时空上所有参数为常量的连续性模型;另一类是瞬态网络模型,该模型把缠结点考虑成瞬态交联点,高分子链看成珠簧链;还有一类是微观分子理论,其中最著名的是"管子模型".本文首先介绍缠结高分子流体的线性黏弹性响应和Boltzmann叠加原理的基本概念,然后,重点综述描述高分子黏弹性质仍非常有实际应用价值的3个经典唯象模型,包括Maxwell模型、Voigt-Kelvin模型和瞬态网络模型,特别是这些理论的详细推导和存在的主要问题.关于高分子黏弹性的微观理论将在其它综述中单独介绍. 相似文献
18.
Simplistic modeling approach to heterogeneous dilute-acid hydrolysis of cellulose microcrystallites 总被引:9,自引:0,他引:9
Pär O. Pettersson Robert W. Torget Robert Eklund Qian Xiang Y. Y. Lee Guido Zacchi 《Applied biochemistry and biotechnology》2003,106(1-3):451-455
The classic kinetic model for cellulose hydrolysis is often referred to as pseudo-homogeneous, a term revealing the insight that the process is actually heterogeneous. During the past 10–15 yr, the shortcomings of this
model have been demonstrated in various studies and the interest in the heterogeneous aspects has increased. The present work
presents a simplistic model in which the intrinsic, heterogeneous hydrolysis and transport rates are coupled by the assumption
of a constant glucosidic surface concentration. The mechanisms affecting these two rates are largely unknown, but the model
serves as a guideline for further exploration of the process. 相似文献
19.
Abstract The log-log relationship between the bioconcentration tendency of organic chemicals in fish and the n?octanol/water partition coefficients breaks down for very hydrophobic compounds. The use of parabolic and bilinear models allows this problem to be overcome. The QSAR equation log BCF = 0.910 log P - 1.975 log (6.8 10?7 P + 1) - 0.786 (n = 154; r = 0.950; s = 0.347; F = 463.51) was found to be a good predictor of bioconcentration in fish. 相似文献
20.
Maxim P. Evstigneev Anatoly S. Buchelnikov Viktor V. Kostjukov Irina S. Pashkova Vladyslav P. Evstigneev 《Supramolecular chemistry》2013,25(4):199-203
Numerous applications dealing with molecular aggregation at the interface of biology, physics and chemistry use either the dimer or the indefinite equilibrium constant models even though there is the well-known property of indistinguishability of the models with respect to fitting experimental data by various experimental techniques. The problem of indistinguishability is uncovered in the present work and the way in which the existing paradigm of how these models should be applied to analysis of molecular self-association is suggested. 相似文献