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基于对"弱电解质的电离"教学课例的再研究,从教学活动设计的角度阐述了以化学观念为统领设计教学整体框架,以实验为支撑体现概念的建构过程,通过系列问题引导学生在问题分析解决过程中形成相应的认识思路与方法等内容,对如何实施化学观念教学进行了探讨。 相似文献
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通过建立模型分析了近6年来的北京市高考试题。从试题水平来看,学生需要建立水溶液问题的基本认识角度和分析思路;从能力要求来看,部分试题实现了对关键能力的融合考查。在此基础上进行试题命制和施测,发现学生不能自主调用多个认识角度形成思路,提出了比较不同问题情境中的共同认识角度与建立“水溶液-平衡”二元分析模型的教学改进策略。 相似文献
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弗兰德斯互动分析系统可以量化课堂教学中的语言行为。以初中化学一节常态课为研究课例,基于弗兰德斯互动分析系统,结合教师他评和自评,从教学目标、教学内容、教学过程和教学效果等4方面进行了全面的分析与评价,并根据评价结果,针对教学目标制订、有效提问、科学的课堂语言结构的营造以及实验探究的实施等提出了可行性的有效策略,从而为青年教师通过教学实践来促进个人专业发展提供依据。 相似文献
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以王磊提出的化学学科能力框架为理论依据,对“物质构成的奥秘”主题进行分析,从核心知识经验、认识角度思路、认识对象及问题、能力活动要素等4个维度构建了“物质构成的奥秘”主题的学科能力模型。运用实验法进行教学实践,证实了本研究设计的教学方式更有利于学生学科能力的发展提升。最后提出学科能力导向的“物质构成的奥秘”教学设计模式和教学实施的有效策略:(1)单元整体系统化设计,有层次有梯度的发展学生学科能力;(2)侧重应用实践型任务的解决,外显知识的输出性功能和价值;(3)重视核心知识和认识角度的建立过程;(4)追问、外显学生的认识角度和认识思路。 相似文献
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以"溶解度"的概念教学为例,分析概念建构过程中如何促进学生的认识发展。在概念教学中,应关注学生的前科学认识,挖掘学生的认识角度和思路,发展学生的认识方式,从而形成学生的认识能力。 相似文献
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On-line fermentation gas analysis is of general interest because it permits the determination of metabolic rates in almost any biological process using living organisms. The consumption and production of gases (O2, CO2, CH4, etc.) and volatile compounds may be determined without causing any risk of infection. Elemental balancing permits the determination of other metabolic rates if the stoichiometry is known. This was studied with the production of poly-β-hydroxybutyrate (PHB) by Alcaligenes latus. Estimations were based on the measurement of gas partial pressure and flow-rates, pH and alkali consumption rate. Experiments with a small quadrupole mass spectrometer showed unacceptable error propagation. Therefore, dynamic error propagation for all rates was studied using simulation. It was found that, for example, a 1% relative offset-calibration error for oxygen can result in an error in PHB estimation of > 50%. It is suggested that this culture is used in combination with elemental balancing for thorough tests of the accuracy of on-line gas analysis equipment. An on-line process gas analyser based on a quadrupole mass spectrometer (Balzers PGM 407) gave the following precision values (abs. vol.?%) during cultivation of Bacillus subtilis: nitrogen (m/z 14), 0.024; oxygen (m/z 32), 0.020; argon (m/z 40), 0.0011; and carbon dioxide (m/z 44), 0.0034. These values, combined with automatic recalibration, would be sufficient for reasonable estimation of PHB, biomass and substrates. 相似文献
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A. Saravanakumaar A. Senthilkumar S. S. Saravanakumar M. R. Sanjay Anish Khan 《International Journal of Polymer Analysis and Characterization》2018,23(6):529-536
This study aims to examine the effect of sodium hydroxide (NaOH) treatment on the physico-chemical properties, structure, thermal, tensile and surface topography of Carica papaya fibers (CPFs). The surface of raw CPFs was modified by soaking with 5% NaOH solution for 15, 30, 45, 60, 75 and 90?min. The results of thermo-gravimetric analysis revealed that the optimum treatment time for alkali treatment was 60?min. It was found that the alkali treatment improved the properties of the CPFs. The results of TGA, FT-IR, XRD and AFM suggest that the treated CPF is a suitable alternative as reinforcement in polymer composites. 相似文献
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Giridharan Loganathan Suresh Krishnaraj Jayaprakash Muthumanickam Ravichandran K 《Journal of Chemometrics》2015,29(1):59-68
In order to bring out the nature of the factors influencing lake water composition, multivariate statistical analysis and trend analysis were performed based on the hydrochemical data of the study area, namely, South Chennai. Change in land use pattern and settlements along the banks of the lakes alters the quality and quantity of the surface water. In the present study, the R‐mode factor analysis and cluster analysis were applied to the geochemical parameters of the water to identify the factors affecting the chemical composition of the lake water. Dendograms of both the seasons give three major clusters, reflecting the groups of unpolluted to moderately polluted, polluted, and heavily polluted stations. The movement of stations from one cluster to another clearly brings out the seasonal variation in the chemical composition of the lake water. The complex hydrochemical data of the surface water were interpreted by condensing them into three major factors. Factor score analysis was used successfully to delineate the stations under study and the role of the contributing factors, and the nature of factors responsible for the variation in chemical composition of the water has been clearly brought out. Results of trend analysis using ArcGIS clearly indicate that the trend in water quality is deteriorating at a faster rate in the eastern part of the study area. It is understood that although natural shifts probably can account for some of the variation, it is most likely that human activities play a major role in affecting the water quality on a regional scale. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Edmund R. Malinowski 《Journal of Chemometrics》2011,25(6):323-328
Determining the rank of a chemical matrix is the first step in many multivariate, chemometric studies. Rank is defined as the minimum number of linearly independent factors after deletion of factors that contribute to random, nonlinear, uncorrelated errors. Adding a matrix of rank 1 to a data matrix not only increases the rank by one unit but also perturbs the primary factor axes, having little effect on the secondary axes associated with the random errors in the measurements. The primary rank of a data matrix can be determined by comparing the residual variances obtained from principal component analysis (PCA) of the original data matrix to those obtained from an augmented matrix. The ratio of the residual variances between adjacent factor levels represents a Fisher ratio that can be used to distinguish the primary factors (chemical as well as instrumental factors) from the secondary factors (experimental errors). The results gleaned from model studies as well as those from experimental studies are used to illustrate the efficacy of the proposed methodology. The method is independent of the nature of the error distribution. Limitations and precautions are discussed. An algorithm, written in MATLAB format, is included. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Analysis of time series tries to extract tendencies from measured values dependent on time. For this purpose the cusum technique has proved to be a very sensitive tool for the evaluation of both current and completed time series. Even very weak tendencies can be detected at a high level of noise. Time-series analysis further tries to predict values to come from hitherto performed measurements. As a very flexible model exponential smoothing could be successfully used. Even for processes with a high extent of non-stationarity this model allowed a good prediction owing to the dynamics of the process. Three types of time-series analysis, i.e., evaluation of current measurements, retrospective evaluation and prediction of data (also known as “in vivo”, “post mortem” and “in futurum” time-series analysis) are demonstrated for problems stemming from analytical process control. 相似文献
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文章介绍了新材料的重要性及发展方向,分析化学在新材料研制中起着耳目的作用,另一方面新材料也为分析化学的进展提供了课题与条件。微量分析、微区分析、表面分析是此领域中的重点。在未来的发展中,分析化学在材料的发展中的地位不会改变,并期待着分析灵敏度与空间分辩率的进一步提高。 相似文献
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《Analytical letters》2012,45(6):899-908
Abstract To determine mercury in geological materials, samples are digested with nitric acid and sodium dichromate in a closed teflon vessel. After bringing to a constant weight, the digest is mixed with air and a sodium chloride-hydroxylamine hydrochloride-sulfuric acid solution and then Hg(II) is reduced to Hg with stannous chloride in a continuous flow manifold. The mercury vapor is then separated and measured using cold vapor atomic absorption spectrophotometry (CV-AAS). For a 100 mg sample the limit of detection is 20 parts per billion (ppb) Hg in sample. To obtain a 1% absorption signal, the described method requires 0.21 ppb Hg solution (equal to 16 ppb in sample). Precision is acceptable at less than 1.2% RSD for a 10 ppb Hg aqueous standard. Accuracy is demonstrated by the results of the analysis of standard reference materials. Several elements do interfere but the effect is minimal because either the digestion procedure does not dissolve them (e.g., Au or Pt) or the; are normally of low abundance (e.g., Se or Te). 相似文献
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Quality evaluation of moluodan concentrated pill using high‐performance liquid chromatography fingerprinting coupled with chemometrics 下载免费PDF全文
Lingyan Tao Qing Zhang Yongjiang Wu Xuesong Liu 《Journal of separation science》2016,39(24):4673-4680
In this study, a fast and effective high‐performance liquid chromatography method was developed to obtain a fingerprint chromatogram and quantitative analysis simultaneously of four indexes including gallic acid, chlorogenic acid, albiflorin and paeoniflorin of the traditional Chinese medicine Moluodan Concentrated Pill. The method was performed by using a Waters X‐bridge C18 reversed phase column on an Agilent 1200S high‐performance liquid chromatography system coupled with diode array detection. The mobile phase of the high‐performance liquid chromatography method was composed of 20 mmol/L phosphate solution and acetonitrile with a 1 mL/min eluent velocity, under a detection temperature of 30°C and a UV detection wavelength of 254 nm. After the methodology validation, 16 batches of Moluodan Concentrated Pill were analyzed by this high‐performance liquid chromatography method and both qualitative and quantitative evaluation results were achieved by similarity analysis, principal component analysis and hierarchical cluster analysis. The results of these three chemometrics were in good agreement and all indicated that batch 10 and batch 16 showed significant differences with the other 14 batches. This suggested that the developed high‐performance liquid chromatography method could be applied in the quality evaluation of Moluodan Concentrated Pill. 相似文献