排序方式: 共有14条查询结果,搜索用时 0 毫秒
1.
在我多年的教学生涯中,有一个比较突出的现象:有一部分数学基础不错的学生,平时练式子题时都说数学很容易,一到学应用题就"犯傻",对应用题产生胆怯心理,以至于在考试中不知所措,失分较多,成绩也从原来的八九十分直掉至六七十分,甚至不及格. 相似文献
3.
Characteristics and generation of elastic turbulence in a three-dimensional parallel plate channel using direct numerical simulation 下载免费PDF全文
Direct numerical simulations(DNSs) of purely elastic turbulence in rectilinear shear flows in a three-dimensional(3D) parallel plate channel were carried out,by which numerical databases were established.Based on the numerical databases,the present paper analyzed the structural and statistical characteristics of the elastic turbulence including flow patterns,the wall effect on the turbulent kinetic energy spectrum,and the local relationship between the flow motion and the microstructures' behavior.Moreover,to address the underlying physical mechanism of elastic turbulence,its generation was presented in terms of the global energy budget.The results showed that the flow structures in elastic turbulence were 3D with spatial scales on the order of the geometrical characteristic length,and vortex tubes were more likely to be embedded in the regions where the polymers were strongly stretched.In addition,the patterns of microstructures' elongation behave like a filament.From the results of the turbulent kinetic energy budget,it was found that the continuous energy releasing from the polymers into the main flow was the main source of the generation and maintenance of the elastic turbulent status. 相似文献
4.
常规的对数求导法求函数的导数时往往不能直接求出函数在所有可导点处的导数,这大大限制了对数求导法的应用.本文对此进行了研究,给出了相应的改进方法. 相似文献
6.
本文从几何直观角度导出了单叶双曲面单参数形式的直母线族方程,揭示了参数的几何意义,证明单叶双曲面有且仅有两族直母线,且这两族直母线可以由单叶双曲面上的椭圆确定. 相似文献
7.
9.
铝酸钠溶液的电导率与结构的关系 总被引:2,自引:0,他引:2
通过测定不同浓度Na2O和苛性比(αk)的铝酸钠溶液的电导率,计算了不同Na2O浓度下铝酸根阴离子的迁移数,结合铝酸钠溶液的红外光谱表征,研究了铝酸钠溶液的电导率与结构的关系.研究结果表明,低浓度铝酸钠溶液[c(Na2O)175g/L]中,铝酸根阴离子的迁移数约为0.6,其离子结构主要为Al(OH)4-;中等浓度溶液[c(Na2O)=175~330g/L]中,铝酸根阴离子的迁移数约为0.2,其离子结构主要为Al(OH)4-和[Al2(OH)8(H2O)2]2-;而高浓度溶液[c(Na2O)330g/L]中,铝酸根阴离子的离子迁移数接近于0,对应的离子结构主要是Al2O(OH)62-,[Al2(OH)8(H2O)2]2-和少量Al(OH)4-.说明铝酸根离子的导电能力与结构密切相关. 相似文献
10.