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1.
文章对高硬度水质测定实验中变色不敏锐、终点拖长问题进行了研究并提出改进方法．实验结果表明：加盐酸并煮沸能有效改善高硬度且含大量HCO3水样变色不敏锐的问题,提高了测定的准确度． 相似文献
2.
本文根据酸碱指示剂变色的原理,通过对变色范围相近的指示剂按一定比例混配和与指示剂颜色互补的惰性染料作为指示剂变色的背衬两方面着手,对甲基橙指示剂进行改进。结果使变色范围更窄,变色点更加鲜明.减小了观测误差,大大提高了滴定的准确度。1 实验目的由于甲基橙指示剂在变色点附近其色调变化不够敏锐,终点不易判断且个性差异很大,导致终点 相似文献
3.
综合表述了紫甘蓝色素的变色原理图。以紫甘蓝汁作为酸碱指示剂设计实验,在球型冷凝管中制成色彩炫丽的pH色柱,促进学生形成指示剂变色范围的概念,在稀释溶液和测定常见酸碱指示剂变色范围的实验中培养实验者的动手能力,在设计判断盐酸滴定碳酸钠终点现象的实验中激发参与者的创新意识。 相似文献
4.
龙威 《中学生数理化(高中版)》2012,(8)
酸碱中和滴定的关键:一要准确测定出参加中和反应的酸、碱溶液的体积,二要准确判断中和反应是否恰好完全反应.
酸碱指示剂可在中和反应终点时出现颜色变化,因此终点判断须选择合适指示剂.
酸碱恰好完全中和的时刻叫滴定终点,为准确判断滴定终点,须选用变色明显,变色范围的pH与恰好中和时的pH吻合的酸碱指示剂.
指示剂的变色范围越窄越好,pH稍有变化,指示剂就能改变颜色.石蕊溶液由于变色范围较宽,且在滴定终点时颜色的变化不易观察,所以在中和滴定中不采用. 相似文献
5.
用电位滴定法测定油脂的皂化价,克服了反滴定法测定色泽较深油脂时,在滴定终点指示剂变色点不明显的缺点,测定结果准确可靠,优于国家标准。 相似文献
6.
冉启武 《四川职业技术学院学报》1998,(2)
采用“氨性缓冲溶液与Mg~(2+)—EDTA盐溶液混合法”测定水的总硬度,比用“MgCl_2溶液与EDTA溶液混合法”测定水的总硬度效果好,具有既不影响EDTA标准溶液的浓度,又能提高终点变色敏锐性的特点。 相似文献
7.
利用植物靛蓝与甲基橙组成的混合指示剂测定水的碱度,并与其它种类指示剂测定水碱度的效果进行对比实验研究.结果表明:甲基橙-靛蓝混合指示剂性质稳定,滴定终点变色敏锐,易于操作,可有效地提高测定结果的准确度,是测定水碱度较为理想的指示剂. 相似文献
8.
制定以二甲酚橙（XO）为指示剂的测定复方炉甘石洗剂中ZnO含量的实验室方法,并与以铬黑T为指示剂的药典方法进行比较.其结果显示以XO为指示剂的实验方法与以铬黑T为指示剂的两种方法测定结果相比相差不大,且以XO为指示剂的实验方法具有简单,快捷,准确,滴定终点变色明显,易于观察等优点,更适合于滴定分析实验教学中复方炉甘石洗剂中ZnO含量的测定. 相似文献
9.
本文研究在ＰＨ５．５的六次甲基四胺缓冲体系中，以５－Ｂｒ－ＰＡＤＡＰ作为指示剂，用ＥＤＴＡ滴定铅精矿中铅含量。试验结果表明，终点变色敏锐，测定结果变异系数为０．２７％（ｎ＝５）。 相似文献
10.
本文研究在ＰＨ５．５的六次甲基四胺缓冲体系中，以５－Ｂｒ－ＰＡＤＡＰ作为指示剂，用ＥＤＴＡ滴定铅精矿中铅含量。试验结果表明，终点变色敏锐，测定结果变异系数为０．２７％（ｎ＝５）。 相似文献
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12.
Urban schools and immigrant families: Teacher perspectives 总被引：2，自引：0，他引：2
Thomas D. Gougeon 《The Urban Review》1993,25(4):251-287
Teachers of two urban senior high schools talk about barriers and bridges in communicating with English as Second Language (ESL) minority students and their parents. The paper focuses on student, parent, and school characteristics with respect to intercultural communication. The typical ESL student is characterized to be alienated, displaced, and in denial of other cultures. Typical parents are distrustful of Western ways, resistant to adopting new values, patriarchal, yet dependent on their children. The school system is characterized as ethnocentric and uncommitted to providing equal services to all students including ESL students. The paper then focuses on student, parent, and school needs to enhance intercultural communication effectiveness. ESL students need to feel connected at many levels of society and to develop social communication skiils, self-empowerment, and greater sensitivity to other cultural minorities. Parents need a greater connection with the school system, a greater understanding of the tensions between their culture and the mainstream culture, greater collaboration skills, and less dependency upon their children as interpreters. Members of schools systems need to develop policies that reflect a greater awareness of intercultural problems and a greater commitment to equal educational opportunities.This study is partially supported by the Alberta Advisory Committee for Educational Studies (AACES). A version of this paper was originally presented at the Annual Meeting of the American Educational Research Association in San Francisco, April 1992. 相似文献
13.
Simulation of game analysis based on an agent-based artificial stock market re-examined 总被引：1，自引：0，他引：1
LIU Cheng WU Yi-li YAN Gang-feng 《浙江大学学报(A卷英文版)》2006,7(4):564-569
INTRODUCTION The Santa Fe Institute Artificial Stock Market (SFI-ASM) is a stochastic discrete event agent based model that simulates a market in which a number of agents choose between investing in a risk-free bond with a fixed interest rate, and a stock with an autore- gressive stochastic dividend. In contrast to mathe- matical models of stock markets based on unrealistic assumptions of agents’ knowledge and processing power, the model had been shown to demonstrate features observe… 相似文献
14.
基于对高职院校学生的随机抽样调查数据,通过描述性统计分析和结构方程模型进行研究。结果显示:在线学习投入对在线学习倦怠和在线学习满意有较大正向影响,在线学习倦怠对在线学习满意有较小的负向影响;学习动机和学习专注对在线学习满意有较大正向影响,学习精力对在线学习满意有很大的正向影响;情绪低落和行为不当对在线学习满意有很大的负向影响,低成就感对在线学习满意有较大正向影响。基于研究结果,从课程系统性改革、强化技能训练、参与技能大赛方面提出建议。 相似文献
15.
Knowledge is lacking regarding the extent to which national norms and policies designed to protect minors influence individual attitudes toward child maltreatment. Relying on the tenets of cultural sociology, we examine whether the orientation of a nation influences individual attitudes toward child maltreatment. Specifically, nations with greater economic and political stability tolerate more self-expressive values, focusing on individual autonomy and enhancing quality of life. Conversely, nations with a survivalist orientation, often characterized by greater economic uncertainty, are less supportive of behaviors that may result in further instability. The current study builds on extant research by investigating the effects of national norms and policies and individual-level attitudes and characteristics on individual attitudes toward child maltreatment (N = 66,391) in 53 developing and developed nations. We analyze data from the World Values Survey using Hierarchical Generalized Linear Modeling. Overall, countries with a greater survivalist orientation appear less tolerant of child maltreatment. Moreover, greater support for violence in general at both the national- and individual-level are associated with more supportive attitudes toward child maltreatment. Policy implications and legislative reform are discussed. 相似文献
16.
This article discusses the characteristics of rural versus nonrural principals in the High Plains states. It is based on data from the Schools and Staffing Survey, examining the differences in preparation and experience and the extent to which characteristics of the rural principalship (perceptions of autonomy, workload, etc.) predicted retention. In this study, significant differences were found between rural and nonrural principals on demographic variables. Rural principals reported greater influence over their curriculum, but less influence over the use of the school budget. Overall, rural principals had slightly lower perceptions of autonomy than did nonrural principals, and greater autonomy predicted greater rural principal retention. 相似文献
17.
B.R. Singh 《Educational studies》1996,22(1):41-56
While some researchers place greater emphasis on heredity causes of individual differences in cognitive functioning, others place greater emphasis on cultural and environmental factors (broadly defined). Still others place greater stress on the dynamic interrelationship between the genetic components and the environmental components in accounting for individual cognitive functioning. The paper examines these views and concludes that intelligence is far more complex than hereditarians would admit and that although we may go along with the view that heredity could set the limit to cognitive development, it is not possible to tell what this limit is, if we define intelligence as a multifaCEDSd, multicausal phenomenon, which is partially malleable and capable of expression in many diverse ways. 相似文献
18.
Robert A. Rescorla 《Learning & behavior》1997,25(2):200-209
In five experiments, rats were given Pavlovian pairings of auditory and visual stimuli with delivery of food pellets. Experiment 1 found greater responding to an AB compound after training with the individual A and B stimuli, compared with responding both to the A and B elements and to a separately trained CD compound. Experiment 2 found this enhanced responding to depend on the associative strengths of A and B. In Experiment 3, responding was greater to a CD compound than to the other compounds after an AB-, AD+, BC+ training procedure. In Experiment 4, responding to an AB compound was greater than that to the elements after A was reinforced on a 100% schedule and B on a 50% schedule. In Experiment 5, responding to an AC compound was greater than that to either A or C after an AB+, CD+, A-training procedure. A configural theory, such as that proposed by Pearce (1987), anticipates summation in none of these procedures, unless the conditioned context is assumed to have a salience greater than zero. In order to predict summation in Experiments 3, 4, and 5, a context salience greater than that of the elements must be assumed. However, such an assumption also anticipates that extinction of a 100% stimulus should eliminate responding to a 50% stimulus. The results of Experiment 3 contradicted that prediction. These results conform better to the expectations of elemental models of conditioning. 相似文献
19.
李广斌 《青海师范大学学报(哲学社会科学版)》2001,(1):1-5
受客观条件的制约及其它诸多因素的影响，青海省产业结构偏离度较大，比较劳动生产率偏低，第二、三产业的劳动力需求弹性较大。要提高劳动力资源配置效率，有赖于符合省情的进一步市场化改革。 相似文献
20.
凌毓静 《佳木斯教育学院学报》2012,(7):392-393
通过对实质重于形式原则的概念及重要性探究、实质重于形式原则在会计核算中的应用分析,力图找出该原则更为有效的应用方法和途径,为会计信息使用者提供更可靠有效的决策信息。 相似文献