高等院校概率论数理统计课程分级教学的实践与思考

系统介绍了我校概率论数理统计课程分级教学的改革实践与经验,深入分析了目前存在的主要问题,并初步探讨了构建合理的分级教学模式、全面提高教学质量的关键因素及解决途径.     

一类Radial基插值的保凸基

本文为 Radial 插值找到了一组保凸基.     

基于学科素养论证分析2020年高考全国卷Ⅰ物理压轴题

2020年高考物理试题依托高考评价体系,结合物理学科特点,考试内容以学科素养考查为导向,即以物理观念、科学思维、科学探究、科学态度与责任的物理学科素养为导向,注重对核心物理概念和规律的考查,引导学生夯实学习发展的基础,促进中学重视培养学生的基础知识、基本技能以及提升学生的基本素养.基于物理学科素养,论证分析2020年高考全国理综卷Ⅰ物理压轴计算题,助力培养学生科学思维.     

A stability study of Navier-Stokes equations (III)

In this paper, the necessary conditions of the existence of C² solutions in some initial problems of Navier-Stokes equations are given, and examples of instability of initial value (at t=0) problems are also given. The initial value problem of Navier-Stokes equation is one of the most fundamental problem for this equation various authors studies this problem and contributed a number of results. J. Lerav, a French professor, proved the existence of Navier-Stokes equation under certain defined initial and boundary value conditions. In this paper, with certain rigorously defined key concepts, based upon the basic theory of J. Hadamard partial differential equations¹, gives a fundamental theory of instability of Navier-Stokes equations. Finally, many examples are given, proofs referring to Ref. [4].     

框架结构主动控制最优时滞研究

在结构振动主动控制中,时滞的大小对结构控制能量和响应均产生影响。在允许时滞的范围内,把结构控制能量和响应作为目标函数,数值仿真发现目标函数随着时滞的变化呈现曲线状态,这说明存在最优时滞。在目标函数处理方面,考虑到控制能量和响应数量级不一致,本文采用了无量纲化处理。同时,考虑到地震波的随机性,本文还推导了含控制力的改进的随机Newmark方法。最后给出了一个计算实例。实例表明本文所提出的方法是有效的。     

钢框架中组合楼盖的面内变形

为了研究影响钢-混凝土组合框架中组合楼盖隔板性能的因素,以楼板厚度、框架侧移刚度以及结构平面刚度布置为参数对钢框架中的组合楼盖进行了弹性有限元分析．分析结果表明,除长宽比外,组合楼盖的隔板性能还与其面内刚度以及支撑体系的特性有关．根据分析结果提出了组合楼盖隔板性能的评价方法, 并与试验结果进行了验证．该方法可以为工程实践中评价组合楼盖的隔板性能作参考．     

强碱性树脂IRA-400对富马酸吸附性能的研究

通过静态吸附试验,研究了强碱性树脂IRA-400对富马酸的吸附性能。结果表明,该树脂与弱碱性树脂IRA-94相比,受pH值影响较小,在pH=3.5时,该树脂对富马酸具有较好的吸附性能,其静态饱和吸附容量为1.466mmol/g湿树脂;该树脂对富马酸的吸附等温线符合Freundlich等温方程,在298.15K,308.15K和318.15K下的相关系数R2均大于0.99,方程的特征参数n1,属"优惠吸附";吸附过程ΔG0,ΔS0,ΔH0,表明此反应过程是放热的,自发进行的,降低温度有利于吸附反应的发生;吸附动力学研究表明,IRA-400树脂对富马酸的吸附过程主要受液膜扩散控制。     

Phenylcarbamoylated β‐CD: π‐Acidic and π‐basic chiral selectors for HPLC

Two types of chiral stationary phases for HPLC based on π‐acidic or π‐basic perphenylcarbamoylated β‐CDs were synthesized. The relative structural features of the two effective chiral selectors are discussed and compared in both normal‐phase and RP modes. In addition, the nature and concentration of alcoholic modifiers were varied for optimal separation in normal phase and the structural variation of the analytes was also examined. The results showed that hydrogen bonding, steric effect and π‐acidic–π‐basic interaction contributed greatly to enantioseparation. Upon comparison, some of the differences in the separation behavior of the two types of chiral stationary phases might be due to the π‐acidic or π‐basic phenylcarbamate groups.     

A comparison of positive and negative ion collision‐induced dissociation for model heptapeptides with one basic residue

The effects of the identity and position of basic residues on peptide dissociation were explored in the positive and negative modes. Low‐energy collision‐induced dissociation (CID) was performed on singly protonated and deprotonated heptapeptides of the type: XAAAAAA, AAAXAAA, AAAAAXA and AAAAAAX, where X is arginine (R), lysine (K) or histidine (H) residues and A is alanine. For [M + H]⁺, the CID spectra are dominated by cleavages adjacent to the basic residues and the majority of the product ions contain the basic residues. The order of a basic residue's influence on fragmentation of [M + H]⁺ is arginine > histidine ≈ lysine, which is also the order of decreasing gas‐phase basicity for these amino acids. These results are consistent with the side chains of basic residues being positive ion charge sites and with the more basic arginine residues having a higher retention (i.e. sequestering) of the positive charge. In contrast, for [M ? H]^? the identity and position of basic residues has almost no effect on backbone fragmentation. This is consistent with basic residues not being negative mode charge sites. For these peptides, more complete series of backbone fragments, which are important in the sequencing of unknowns, can be found in the negative mode. Spectra at both polarities contain C‐terminal y‐ions, but y_n″⁺ has two more hydrogens than the corresponding y_n^?. Another major difference is the production of the N‐terminal backbone series b_n⁺ in the positive mode and c_n^? in the negative mode. Thus, comparison of positive and negative ion spectra with an emphasis on searching for pairs of ions that differ by 2 Da (y_n″⁺ vs y_n^?) and by 15 Da (b_n⁺ vs c_n^?) may be a useful method for determining whether a product ion is generated from the C‐terminal or the N‐terminal end of a peptide. In addition, a characteristic elimination of NH?C?NH from arginine residues is observed for deprotonated peptides. Copyright © 2010 John Wiley & Sons, Ltd.     

碱性季铵盐“一锅法”催化合成四氢苯并[b]吡喃的水相反应研究

报道了以2-二甲氨乙基苄基二甲基氯化铵为催化剂,在水相介质中"一锅法"催化芳醛、丙二腈和5,5-二甲基-1,3-环己二酮合成2-氨基-3-氰基-4-芳基-7,7-二甲基-5-氧代-4H-5,6,7,8-四氢苯并[b]吡喃的方法.该法具有产率高、反应时间短、操作简便、对环境友好、催化剂可重复使用等优点.