Investigation of iodine concentration in salt,water and soil along the coast of Zhejiang,China

Objective: We aim to describe the environment iodine concentration in salt, water and soil along Zhejiang Province coast in the China foreland. It will be helpful for us to judge whether this area is insufficient in iodine and universal iodized salt is necessary or not. Methods: We collected iodized salt samples, drinking water samples (tap water in the towns, and well water or spring water in the villages), water samples from different sources (ditches, lakes, rivers) and soil samples through random sampling in June, 2005. Salt, water and soil iodine was detected by arsenic-cerium redox method. Statistical analysis was expressed as mean±SEMby Windows SPSS 13.0. Results: (1) The iodine concentration in salt was 27.9±4.33 mg/kg (n=108). (2) Seventy-five water samples were collected. The water iodine value was 0.6～84.8 μg/L (mean of 11.66 μg/L). The watershed along the Qiantang River has significantly higher iodine content than the water in Lin'an in mountain area (P＜0.01). The iodine content and mean iodine content of tap water, well or spring water and natural water sources were 4.30±2.43 μg/L (n=34), 23.59±27.74 μg/L (n=19)and 12.72±10.72 μg/L (n=22) respectively. This indicated that among environmental water sources, the ditch iodine content was the highest with river water iodine being the lowest (P＜0.01). (3) Soil iodine value was 0.11～2.93 mg/kg (mean of 1.32 mg/kg).Though there was no statistical difference of soil iodine in different districts (P=0.131), soil iodine content correlated positively with water iodine content. Conclusion: Iodine concentration in salt accords with national policy of adding iodine in salt. Foreland has more iodine in water than mountain area. The data reflected that water and soil iodine in foreland area was not high, which suggests universal iodized salt should be necessary. Environment iodine has relatively close association with pollution.     

关于积分∫0^＋∞ n↑∑↓k=1 Ak f（akx）／x^2 dx 的计算及应用

利用Froullani积分公式及其推广，给出了一类形如∫0^ ∞ n↑∑↓k=1 Ak f(akx)/x^2 dx的广义积分的计算公式及应用．     

不定积分与定积分的求法

积分学与微分学是数学分析的姊妹篇。两者一起构成数学分析的主体。数学分析中研究多种积分，如不定积分、定积分、重积分、曲线积分、曲面积分、非正常积分、含参变量积分等。其中，不定积分是求导运算的逆运算：定积分是其他各种积分的基础；而定积分的计算大多可归结为求不定积分。因此，不定积分与定积分是整个积分学的基础。本文着重介绍不定积分与定积分的几种求法，以期对广大考生有所帮助。     

浅谈对高等数学多媒体教学的几点认识

随着信息技术的发展,广大高校数学教师越来越重视应用多媒体辅助教学。多媒体技术辅助数学课堂教学有很多优势,它能有效地提高课堂效率,使教学内容更加直观生动,改变了数学教学形式单一,直观性差的缺陷,但是在实践中也存在着许多问题。本文论述了对高等数学多媒体教学的几点认识。     

巧用函数的对称性求某些三角积分

函数的对称性，大大缩小了问题的讨论范围。但对某些三角积分，可构造其对称积分，以简化积分过程。     

《白杨礼赞》指瑕

著名作家茅盾先生所著的《白杨礼赞》一直被誉为脍炙人口的散文佳作,虽历经八次课程改革,仍能在令人眼花缭乱的更迭教材中占据抢眼的位置,可谓大师所著经典穿越时空依然不朽的明证。笔者做学生时,脑袋跟着老师走,师云亦云;刚参加工作,奉教参为圣经,照本宣科;教了几轮后,才发现该文有些细节尚需斟酌甚至是要纠偏。今笔者不揣谫陋,仅以揭示文章主     

“秋千网”破了

每次写了文章,我都会去秋千网发表。这不,刚刚就完成了一篇。亲爱的秋千网,我来了!习惯性地来到论坛,我看到了一个醒目的帖子标题——我的积分莫名其妙地全没了。回帖众说纷纭,最后一条回复说:会不会是‘秋千网'破了个洞?积分全     

Error analysis of non-spherical raindrops on precipitation measurement

Radar cross section (RCS) of non-spherical raindrops is calculated by using the software CST based on finite integral method and compared with RCS of spherical raindrops. The revised factor of non-spherical raindrops is obtained. The radar reflectivity with precipitation change of four distribution models of M-P, Gamma, JD and JT combining the revised factor is gotten using trapezoidal integration. When the influence of non-spherical raindrops is considered, the accuracy of precipitation measurement of four distribution models can be separately improved 8.77%, 8.47%, 10.53% and 8.04% in the case of rain intensity is 100 mm/h.     

基于(G)模糊积分的信息融合方法

采用单一模糊积分进行信息融合的结果有时可能明显失真。例如,(S)模糊积分融合时只考虑了单分类器的识别结果与相应分类器集重要程度中较小的那个量的信息,有时可能会产生错误的分类结果。为了弥补(S)模糊积分等模糊积分的局限性,提出基于(G)模糊积分的信息融合方法,将多个模糊积分的融合结果加权平均作为分类的依据,可以对各单一模糊积分融合效果取长补短,有助于提高多分类器融合系统的识别率和稳健性。     

关于第一型曲线积分Cauchy中值定理“中间点”渐近性的研究

讨论第一型曲线积分Cauchy中值定理"中间点"的渐近性,得到了两个重要定理,这两个定理是定积分Cauchy中值定理相应结果的推广.