职前化学教师化学建模能力测评研究*

化学教师化学建模能力水平的高低直接影响着所培养学生建模能力的强弱。基于Rasch模型从模型表征能力、模型建构能力、模型应用能力3个维度开发四水平测查的《职前化学教师化学建模能力问卷调查》,对83名职前化学教师的化学建模能力进行测评,研究发现:被调查的职前化学教师化学建模能力总体较差,参照《普通高中化学课程标准(2017年版)》对化学建模能力的具体要求,分别仅有88%、42%、54%的职前化学教师的模型表征能力、模型建构能力、模型应用能力达标。因此,建议高等师范院校加强对职前化学教师化学建模能力的培养。     

以实验为情境问题的PBL教学法在元素化学教学中的应用

元素化学是无机化学课程的学习重点和讲授难点。针对元素化学内容繁杂、易学难巩固的特点,本文以铁、铜化合物实验为情境问题,在元素化学的教学中实施PBL教学方法以激发学生的学习兴趣,促进并巩固教学效果。     

分子印迹聚合物负载Fe(III)催化剂的底物识别性能

分别以o-, m-和p-硝基苯甲醇与FeCl₃的配合物为模板分子,丙烯酰胺为功能单体,二甲基丙烯酸乙二醇酯为交联剂,采用本体聚合法制备了三种Fe(III)含量相同的分子印迹聚合物(MIP)o-Fe(III)-MIP,m-Fe(III)-MIP和p-Fe(III)-MIP.并采用扫描电镜、N₂吸附-脱附及红外光谱等方法对催化剂结构进行了表征.在以水为溶剂,过氧化氢(30%)为氧化剂的苯甲醇衍生物氧化反应中,该类催化剂表现出优异的催化活性和独特的底物识别性能.当以p-Fe(III)-MIP为催化剂时,p-硝基苯甲醇的转化率达到80%,而在其他两个催化剂上均低于58%.这表明Fe(III)-MIP催化剂结构中具有与底物分子匹配的印迹空腔与识别位点,对底物分子表现出专一识别性,因而提高了催化剂对底物的选择性.     

基于超收敛和外推方法的一类新的瀑布型多重网格方法

本文运用有限元超收敛理论和外推技巧提出了一类求解椭圆型方程的新的瀑布型多重网格方法(ACMG).数值结果表明新方法具有超收敛性.     

ON THE CROSSING NUMBER OF THE COMPLETE TRIPARTITE GRAPH K_(1,8,n)

The well known Zarankiewicz' conjecture is said that the crossing number of the complete bipartite graph Km,n (m≤n) is Z(m,n). where Z(m,n) = [m/2] [(m-1)/2] [n/2] [(n-1)/2](for and real number x, [x] denotes the maximal integer no more than x). Presently, Zarankiewicz' conjecture is proved true only for the case m≤G. In this article, the authors prove that if Zarankiewicz' conjecture holds for m≤9, then the crossing number of the complete tripartite graph K1,8,n is Z(9, n) 12[n/2].     

Variation of benzyl anions in MgAl-layered double hydroxides: Fire and thermal properties in PMMA

Magnesium aluminum layered double hydroxides (MgAl-LDHs) intercalated with a range of benzyl anions were prepared using the coprecipitation method. The benzyl anions differ in functionality (i.e. carboxylate, sulfonate, and phosphonate) and presence or absence of an amino substituent. Various methods for preparing LDHs (i.e. ion exchange, coprecipitation and rehydration of the calcined LDH methods) have been compared with the MgAl-benzene phosphonate and their effect on fire and thermal properties was studied. After characterization, the MgAl-LDHs were melt-blended with poly(methyl methacrylate) (PMMA) at loadings of 3 and 10% by weight to prepare composites. Characterization of the LDHs and the PMMA composites was performed using FTIR, XRD, TGA, transmission electron microscopy (TEM) and cone calorimetry. FTIR and XRD analyses confirmed the presence of the charge balancing benzyl anions in the galleries of the MgAl-LDHs. Improvements in fire and thermal properties of the PMMA composites were observed. The cone calorimeter revealed that the addition of 10% MgAl-LDHs reduces the peak heat release rate by more than 30%.     

19F-NMR测定甲磺酸帕珠沙星样品中的氟

研究了19F-NMR技术测定甲磺酸帕珠沙星药物样品中氟的检测条件.优化了实验参数,选用三氟乙酸钠作为内标,重水与去离子水混合液作为溶剂的内标绝对法进行定量分析.测定了甲磺酸帕珠沙星药物样品中氟含量.实验表明,氟的加标回收率在99.2%-100.9%之间,标准偏差为0.00446%-0.0652%,相对标准偏差小于1.459%.     

被捕食者带有第三边值的捕食模型的正稳态解的存在性

该文研究了一类被捕食者带有第三边值的捕食模型. 首先获得了它存在正稳态解的充要条件是a>mb+d₁λ₁; 然后研究了它的正稳态解的局部稳定性和唯一性;最后讨论了充分大的扩散参数对它的正稳态解的存在性的影响.     

The general form of Hilbert’s inequality and its converses

Summary The general form of Hilbert’s inequality and its converses are established. The integral analogues of such inequalities are also given. They are significant improvements and generalizations of many known results.