怎样上两步应用题的“结构课‘

小学生在学习一步应用题的过程中,经过两步应用题“渗透”课的教学,为两步应用题的学习打下了坚实的基础。教学实践还告诉我们,小学二年级学生在学习两步应用题时,对题中的条件与条件、条件与问题的关系,往往搞不清楚,其原因是不能够正确分析两步应用题的结构。为此,我从教学实际出发,专门上了两步应用题的“结构课”。     

两步计算加减应用题的结构训练与对比训练

两步计算加减征用题是学生初步接触的两步应用题,加强两步计算应用题的结构训练和对比训练,能够帮助学生掌握解题思路和解题方法。一、结构训结两步计算应用题的特点是：题目中只有一个直接已知条件,另一个条件没有直接给出,应该先算出这个直接条件（即中间问题）。能否正确地找到中间问题,是顺利解答两步计算应用题的关键。熟悉两步计算应用题的结构特征是熟练地找寻中间问题的基础。对此,可通过应用题的扩缩变换,帮助学生了解两步计算应用题的结构特征。l、缩编训练。把两步计算应用题压缩成一步计算应用题。如：红星商店有食盐160…     

掌握结构特征 找准中间问题——“含有两个条件的两步计算应用题”教学构想

含有两个条件的两步计算应用题,是在学生学习了含有三个条件的两步计算应用题的基础上教学的。这类两步计算的应用题,由于其中一个已知条件要在解题过程中使用两次,学生过去解答应用题时     

《两步计算的加减应用题》的思维训练

《两步计算的加减应用题》是学习两步应用题的开始,在教学中,如果我们对学生加强两步应用题的结构、思路训练,对提高学生的思维能力是颇为有益的。一、结构训练两步计算的加减应用题的特点是题目中只告诉了一个直接条件,另一个是间按条件,在解答时,     

“两个条件的两步应用题”的教学

两个已知条件的两步应用题.即其中的一个已知条件在解题的过程中要用两次,这是第五册两步应用题教学的一个难点。也是两个条件的两步应用题教学的难点。如何突破这个难点呢?我在教学中采取了以下几点做法。一、领会教材编排意图,明确要求在教学中,我认真钻研了大纲、教参、教材,明确了教材的编排意图。本节教材是把两步应用题分为     

两步应用题教学整体构想浅谈

在整体结构思想的指导下,我尝试进行两步计算应用题的教学,打破了以往分类型进行教学的模式,让学生从两步应用题的结构着眼,分析数量关系入手,由浅入深地认识——理解——掌握分析解答各类两步应用题的有关知识和方法。 一、用整体观念认识两步应用题的结构 两步应用题的结构大致可分为两类型: 第一种:即题目中出现三个已知条件,第一步利用其中的两个条件解决中间问题,第二步才能解答题目要求的问题。第二种:即题目只出现两个条件,先用这两个条件将间接条件转化成直接条件,而后再用其中一个与问题对应的条件解答题目     

浅谈两步计算应用题的教学

从解答简单应用题到解答两步计算的应用题有一个质的飞跃 ,两步应用题同简单应用题比较 ,不仅条件的数量增加了 ,而且已知条件及已知条件同问题之间的数量关系复杂了。特别是已知条件与问题不像简单应用题那样明显对应着 ,学生要根据题里的已知条件 ,找出中间问题 ,才能解答。这对于小学生来说是比较困难的 ,怎样使学生顺利地掌握两步计算应用题的解答方法 ,下面谈一下具体作法和浅见。一、加强基础训练解答两步计算的应用题 ,可以让学生循着一步应用题的思路 ,通过议论进一步分析数量关系 ,找出中间问题 ,由于这种分析不是全新的 ,只是在分…     

试析应用题的几种解题方法

在多年的小学数学的教学实践中,我深深地感到只有帮助学生掌握分析解答两步应用题的方法,才能提高解答应用题的能力,下面谈谈九义教材三年级两步应用题的几种解题方法。一、运用图解法有些两步应用题可启发学生先画线段图,然后借助线段图在图上分析寻找到间接条件,帮助学生理解     

“两步计算的加减应用题”教学建议

一、教学重点和难点本单元的教学重点,一是根据题中的“隐藏量”揭示“中间问题”,把间接条件转化成直接条件,掌握解题思路,这是解答两步计算应用题的关健;二是连减的两步应用题,用两种方法解答;三是使学生初步认识到两步以上的应用题,有的可以有几种不同的解法,以达到培养学生灵活解题,发展思维能力的目的.\     

两步计算应用题教学

两步计算应用题是通向复合应用题的大门。可以说掌握好两步计算应用题的解题思路,是为解答多步应用题架设由未知通向已知的桥梁。分析法与综合法是分析应用题的基本方法,我从教两步计算应用题开始,就让学生逐步掌握这两种思维方法。一、提前渗透,作好铺垫教材在进行两步计算应用题教学前,就安排了给应用题补条件,提问题和解答有两个连续问题的     

N-(4-羟基苯基)马来酰亚胺合成条件的探讨

以马来酸酐和对氨基酚为原料,采用两步法合成N-(4-羟基苯基)马来酰亚胺,并采用正交实验方法研究了原料配比、反应时间、催化剂用量等对产率的影响,确定了优化合成条件。     

含有双参数的非局部反应扩散方程的奇摄动问题

1 Introduction A kind of problems for ordinary differentialequations with two small parameters has been studiedin [1 -4] and a class of singularly perturbed reaction-diffusion equations has been studied in [5 -6] . Untilnow, few papers discussed the partial differentialequation with two small parameters .Now we considera class of non-local reaction-diffusion equations involv-ing two parameters as follows : u t-(εL1u μL2u) =f(x,u,Tu) , 0 相似文献   

氰化物测定中糠醛干扰的消除研究

针对糠醛对废水中氰化物测定产生干扰的现象。从糠醛对氰化物测定的干扰机理出发，探讨消除糠醛干扰的方法，试验和比较了银盐沉淀，石油醚萃取。石油醚二次萃取等干扰消除方法，表明以石油醚二次萃取方法的消除效果最好。可以使糠醛允许量达到250倍，应用于实际水样分析取得满意的结果。     

非扩张映象的具误差的两步粘性迭代逼近

引入非扩张映象的具误差的两步粘性迭代序列,得出了Banach空间中非扩张映象的具误差的两步粘性迭代序列的收敛性及强收敛于其不动点的条件.从而将文[1-2]的一步粘性迭代推广到具误差项的两步迭代.结果改进和推广了最新的一些结果.     

Data mining approach to professional education market segmentation: a case study

In this research, a combination of both quantitative and qualitative approaches is used to identify different market segments in the education industry. To solve the research problem, an exploratory approach to data mining is used and, using a series of interviews with experts, the factors affecting segmentation are identified. Then, using the clustering method (in the form of specific two-step and K-means algorithms), customers are clustered and features of each cluster are identified. This research is based on data provided by a large Iranian research and education company. After examining the clusters identified in both methods, it is determined that the clusters provided by the two-step algorithm are more in line with the organizational and market reality of the business. Finally, the marketing mix model is used to formulate strategic approaches and actions.     

N-异辛基吩噻嗪的高效合成与表征

以廉价的吩噻嗪为母体,分别采用一次反应、二次连续反应和二次连续反应加氢化钠三种不同的方法有效地合成了脂溶性异辛基吩噻嗪,并运用傅立叶变换红外光谱、质谱、元素分析、核磁共振谱等手段进行了表征;研究表明采用第三种方法合成产率最高;这为高效合成脂溶性有机中间体进行了有益的探索。     

RLS channel estimation with adaptive forgetting factor in space-time coded MIMO-OFDM systems

INTRODUCTION The very dramatic increase in demand for high-rate data transmission stimulated greater re- search efforts in developing wideband wireless communication systems which could support high- rate transmission over wireless channels. But we have to face the challenges from the multi-path effects because multi-path propagation of wire wave is usu- ally seen as a harmful factor which leads to one of the most troublesome radio channel problems. However, the multi-path effects can beco…     

鲁棒区间算法在能源规划中的应用

采用鲁棒区间算法解决目标函数和约束条件中的不确定性问题,开发一个鲁棒区间能源系统规划模型,通过求解得到模型全局最优解,以获得最小的能源成本及最优的能源分配方案．案例研究结果显示。通过此优化模型进行的综合环境约束的规划,能使城市能源消费整体结构得到优化,能源利用效率明显提高,可实现城市的能源经济环境的协调发展．     

Covariate Balance in Bayesian Propensity Score Approaches for Observational Studies

Abstract

Bayesian alternatives to frequentist propensity score approaches have recently been proposed. However, few studies have investigated their covariate balancing properties. This article compares a recently developed two-step Bayesian propensity score approach to the frequentist approach with respect to covariate balance. The effects of different priors on covariate balance are evaluated and the differences between frequentist and Bayesian covariate balance are discussed. Results of the case study reveal that both the Bayesian and frequentist propensity score approaches achieve good covariate balance. The frequentist propensity score approach performs slightly better on covariate balance for stratification and weighting methods, whereas the two-step Bayesian approach offers slightly better covariate balance in the optimal full matching method. Results of a comprehensive simulation study reveal that accuracy and precision of prior information on propensity score model parameters do not greatly influence balance performance. Results of the simulation study also show that overall, the optimal full matching method provides the best covariate balance and treatment effect estimates compared to the stratification and weighting methods. A unique feature of covariate balance within Bayesian propensity score analysis is that we can obtain a distribution of balance indices in addition to the point estimates so that the variation in balance indices can be naturally captured to assist in covariate balance checking.     

圆柱周围湍流场的数值模拟

In practical problems, the variation of the free surface around a circular pier is severe. For the Fluent CFD, the multiphase flow models cannot be used together with the LES model to calculate the free surface. Present paper provides a two-step method which joints the 2D compressible ideal-gas equations and the LES model to calculate the 3D flow field with free surface around the pier. The effects of the free surface on the flow structures are studied in detail.