摩尔概念的历史变迁及其科学价值*

“摩尔”概念的变化历史贯穿人类近代化学以来发展的所有历史,是学科史中科学思维变化的关键性事件,其变化背后的科学实践、思维、决策深刻影响着化学学科的发展。厘清摩尔概念变迁的历史,有助于厘清其背后的哲学与历史对科学认识和科学教学的价值。研究发现,有关摩尔概念的发展史主要分为萌芽期、发展期和成熟期等3个阶段,其历史是科学思维与科学实践结合的典型例证,蕴含丰富的科学决策与论证思想,也是学生概念发现与意义学习的重要材料。     

上海市工业废水排放量的多元非线性回归预测

根据2000年至2009年上海市的人均生产总值和工业重复用水量并结合工业废水排放量的资料,构建了一种基于时间序列的多元非线性回归预测模型,并进行了评估和分析.模型具有较高的拟合精度,能客观反映工业废水的排放量,可以为决策者提供参考,提高相关部门的管理水平.     

回归模型方法与河流流量的估算与分析

通过对渭河20多条支流建立的回归模型及分析,获得了回归方程系数b与河流流域产流能力的关系;回归方程的常数项a与基流估算的关系;以及流域临界降水量与流域水土流失程度的估算.     

定形相变墙板改善轻质墙体夏季隔热性能研究

本文提出了将定形相变蓄能墙板安装在轻质保温墙体内侧,取代传统重质材料,改善围护结构夏季隔热性能的方法.以北京地区为例,比较了定形相变蓄能墙板与重质混凝土在改善轻质围护结构隔热性能方面的差异,并从相变温度和相变墙板厚度两个方面对定形相变蓄能墙板的使用效果进行了优化.研究表明定形相变蓄能墙板能有效改善轻质保温墙体的隔热性能,而对建筑自身承重增加很小.     

The threshold method for estimating total rainfall

The threshold method estimates the total rainfall F _G in a region G using the area B _G of the subregion where rainfall intensity exceeds a certain threshold value c. We model the rainfall in a region by a marked spatial point process and derive a correlation formula between F _G and B _G. This correlation depends not only on the rainfall distribution but also on the variation of number of raining sites, showing the importance of taking account of the spatial character of rainfall. In the extreme case where the variation of number of raining sites is dominant, the threshold method may work regardless of rainfall distributions and even regardless of threshold values. We use the lattice gas model from statistical physics to model raining sites and show a huge variation in the number of raining sites is theoretically possible if a phase transition occurs, that is, physically different states coexist. Also, we show by radar observation datasets that there are huge variations of raining sites actually.     

Molecular iodine: a powerful catalyst for the easy and efficient synthesis of quinoxalines

Various biologically important quinoxaline derivatives were efficiently synthesized in excellent yields using inexpensive, nontoxic, and readily available bench top chemical, iodine in catalytic amount (10 mol %). Besides this, a systematic study was carried out to evaluate parameters such as solvent and catalyst loading. Several aromatic as well as aliphatic 1,2-diketones and aromatic 1,2-diamines, such as substituted phenylene diamines, tetra amines were further subjected to condensation using catalytic amounts of iodine to afford the products in excellent yield.     

Statistical linguistic characterization of variability in observed and synthetic daily precipitation series

This paper deals with an application of Zipf law in climatology. This analysis allows the extraction of information not available by standard methods. In particular, rainfall temporal aggregation patterns associated with different climates are characterized by means of exponents derived from the resulting scaling laws. The analogy with linguistic analysis is obtained using a particular coding of precipitation as a discrete variable with four states (corresponding to four standard precipitation thresholds); each weekly symbolic sequence of observed precipitation is considered as a “word”, and each local station defines a “language” characterized by the observed words in a period representative of the climatology. To characterize these precipitation languages, we obtained characteristic exponents derived from the Zipf law for a set of representative stations of the main Köppen's climates and subclimates. We found different scaling behaviors for different subclimates, given by a single exponent in the range 0.6$0.6$ (humid tropical climates) to 1.4$1.4$ (polar climates); some humid middle-latitude subclimates exhibit a crossover with two different characteristic exponents corresponding to high and low frequency aggregation patterns (no explanation for this behavior is provided).     

A numerical solution of infiltration

A fully implicit finite difference scheme is used to evaluate one-dimensional infiltration. The method makes it possible to solve a general infiltration problem; nonhomogeneous soil profile and saturated-unsaturated seepage can be treated. To solve special problems of hydrology and soil physics, several types of boundary conditions are formulated and numerically expressed. The type of boundary conditions may vary in time depending on the values of the unknown function. High accuracy of solution is emphasized. Several applications of this method are presented.     

大错位量散斑干涉法测量残余应力

本文提出大错位量激光散斑干涉法结合钻孔法测量残余应力,对单向拉伸残余应力进行了测量,试验结果与理论解非常吻合,并且实现了对真实构件表面残余应力的测量.     

Feasibility study of artificial rainfall system using ion seeding with high voltage source

A non-linear computational modelling of ions from the ground station for electrifying the atmosphere to make feasibility study of artificial rainfall system is proposed and analyzed. The model considers generation of intermediate ions and ionized airflow velocity. The governing electro hydrodynamic (EHD) equations of the model shows that the space charge density, electric field intensity and velocity of the ionized airflow are function of high input voltage applied to generate the ions. The number of ions generated and their velocity is proportional to the applied ion generator voltage.These artificial ions will be introduced in the atmosphere which will act in a similar manner as cosmic rays. These ions will ionize the aerosols and catalyze nucleation processes and thus electrify the atmosphere which will form cloud droplets to get artificial rain. The mathematical model to study the feasibility of artificial rainfall is also validated under favourable conditions.