在六年級中講述液体內部的压强

六年級物理教学經驗表明,学生学習“液体由于本身的重量而产生的压强”一节是有很大困难的。这一部分原因是由于缺少闡明压强跟深度和液体比重的数量关系的好实驗。而学生沒有了解清楚这部分教材,就不能很好地了     

直流同步随动系統的理論分析

<正> 現代許多生产机械,如大型桥式起重机,大型水庫閘門,重型車床等生产机械,往往要求两根或多根机械軸的旋轉速度完全一样,或保持一定的比例关系,換言之,即要求两根或多根軸同步协調旋轉.关于实現同步协調,可采用机械的办法,也可采用电的办法,在一般情况下,由于要求同步协調旋轉的两根或多根軸的装設位置不同,彼此相距很远(达数十米或更远),如采用机械方法联系,不但制造困难,成本高,而且由于条件限制,不是弹性变形不能滿足刚度上的要求,就是完全不可能,因此需要采用电的办法实現同步协調.     

CP—600型网格高速摄影机的改造

英国J.Lattgham Thompson公司生产的CP—600型网格式高速摄影机在快门控制,测速显示和图像再现判读等方面都存在一些问题,影响了推广使用。我校根据用户建议,对CP—600型机进行了改造。用电磁快门代替仅适于高频段的机械快门,可在全     

手性胺诱导的甲基多巴不对称合成

本文报导在相转移催化下和用1-(3,4-亚甲二氧基苯基)-2-丙酮与氯仿, 手性胺进行不对称合成反应, 以期诱导产生新的手性中心, 产物又经氢解, 水解, 得到光学活性的α-甲基多巴。     

非自治发展方程的收敛的逼近惯性流形族

本文讨论非自治无穷维动力系统的解的长时间行为·在谱间隙条件成立的情况下，对一类非自治发展方程，我们构造了一族收敛的逼近惯性流形·     

Fredholm映射的集值紧摄动的拓扑度

Suppose that X is a paracompact oriented C` -Banach-Fredholm manifold, Ω is an open subset of X, E is a Banach space, f:Ω→E is a proper continuous map, f:Ω→E is an admissible (nonlinear) C′-Fredholm map of index zero,G:Ω→2^E is an upper semicontinuous compact set-valued map with compact convex values, p∈ E\(f-G)(?Ω). In this paper the degree deg(f-G,Ω,p) is defined.     

具无界值上半连续集值映射的拓扑度

设X和Y是Banach空间。用C(X)表示X中一切非空闭凸子产集所成之族。对于X中的点x与非空子集A和B,记,其中ε>0。 X×Y中的范数定义为。     

从一道光学习题得到的启示

从一道光学习题得到的启示山东建材学院逄锡森，范素华大学工科物理试题库中有这样一道光学题目：用波长为λ＝６００ｎｍ（１ｎｍ＝１０－９ｍ）的光垂直照射由两块玻璃平板构成的空气劈尖薄膜，劈尖角θ＝２×１０－４ｒａｄ．改变劈尖角，相邻两明条纹间距缩小△ι＝１...     

3D-QSAR Study on Apicidin Inhibit Histone Deacetylase

For Histone Deacetylase (HDAC) Inhibitor, four 3D-QSAR models for four types of different activities, were constructed.The cross-valldated q^2 value of CoMFA Model 1 is 0.624 and the noncross-validated r2 value is 0.939. The cross-validated q^2 value of Model 2 for training set is 0.652 and the noncross-validated r^2 value is 0.963. The cross-validated q^2 value for Model 3 is 0.713, with noncross-validated r^2 value 0.947. The crossvalidated q2 value for Model 4 is 0.566 with noncross-validated r^2 value 0.959. Their predicted abilities were validated by different test sets which did not include in training set. Then the relationship between substituents and activities was analyzed by using these models and the main influence elements in different positions (positions 8 and 14) were found. The polar donor electron group of position 8 could increase the activity of inhibition of HDAC, because it could form chelation with the catalytic Zn. Suitable bulk and positive groups at position 14 are favorable to anti-HDAC activity. These models could web interpret the relationship between inhibition activity and apicidin structure affording us important information for structurebased drug design.