课程文献中心 更多>>

关键词： 牛膝   傅里叶红外光谱法   二阶导数光谱  

摘要： 目的建立不同产地牛膝的红外光谱和红外导数光谱并对其差异性进行分析,为牛膝药材的快速鉴别提供依据。方法运用傅里叶红外光谱技术结合二阶导数光谱对不同产地的牛膝药材进行鉴别,采用聚类分析和主成分分析对红外光谱数据进行统计分析。结果牛膝的红外吸收峰主要在3289、2975、2890、1723、1630、1403、1321、1241、1018、927、814、773 cm-1附近,虽然不同产地牛膝所含化学成分具有相似性,但不同产地牛膝红外吸收峰的位置和相对强度存在一定差异;并且在二阶导数红外图谱的1800~800 cm-1波段中有更加明显差别,可以为其鉴别提供更准确的依据。聚类分析显示不同批次间相似度很高,主成分分析结果表明在1723、1630、927、814、651 cm-1等处的吸收峰对区分不同产地牛膝药材的贡献较大,内蒙古自治区赤峰市和河南省焦作市武陟县的牛膝药材综合评分较高。结论红外光谱法与二阶导数光谱相结合不仅可以提供中药材所含化学成分的相关信息,还可以对其不同产地进行区分,实现对牛膝的快速鉴别。

关键词： 分数阶微分方程   分数差分   数值解  

摘要： 文章针对一类非线性分数阶微分方程的数值解进行探讨.利用可微函数的Taylor展式,将方程中的分数阶微分项展成幂级数形式,进而得到微分方程的近似解,数值算例验证了方法求解问题的有效性.

关键词： 高等数学   问题驱动教学方法   有效问题   思考  

摘要： 根据高等数学高度抽象的特点,以问题驱动为导向的高等数学课程的教学方式受到越来越多的关注。本文将以高等数学中多元函数偏导数为引例,充分讨论了适当引入问题是提高学生课堂学习效率的有效方法之一。问题驱动下的教学方式就是要求教师根据课堂内容精心组织一系列问题,引导学生积极思考,深刻理解课堂内容的本质特点与核心思想,同时反过来,学生通过思考,再提出问题。这样一个良性循环的教学模式不仅有利于提高课堂教学效率,而且在一定程度上可以激发和增加学生自主自觉求知的动力。

关键词： 高中数学   导数   试题分析   教学策略  

摘要： 导数在高中数学中占据重要地位,是研究函数变化率等问题的常用工具,探究学生学习导数中的障碍,对促进导数教学具有积极意义。调查发现高中生导数学习中存在导数几何意义理解不完整、取得极值条件不清楚、运算性质记忆不牢、导数应用能力不足等问题。分析主要原因包括数学阅读理解能力差、公式记忆运算求解能力差、缺乏基本解题思路方法等。建议培养学生阅读能力,加强对导数概念阐述,培养学生运算能力,提高学生学习导数的兴趣,提升导数教学效率。

关键词： Stochastic Volterra integro-differential   equations   Nonlinear integral equations   Spectral collocation method   Brownian motion process   Moving least squares  

摘要： In this paper, an attractive idea using moving least squares (MLS) and spectral colloca-tion method is extended to estimate the solution of nonlinear stochastic Volterra integro-differential equations (NSVIDEs) that arise in mathematical modeling of natural systems in financial mathematics, physics, and engineering. An essential advantage of the proposed technique is that it does not require any preprocessing, such as mesh refinement. Another advantage that may be appealing to the readers of this article is that acceptable results can be obtained using a small number of points and basis functions, so the calculations are reduced. Applying the proposed scheme leads to the conversion of the problem into a system of algebraic equations. An error bound is presented to ensure the convergence and reliability of the method. Some illustrative examples are presented to reveal the efficiency and applicability of this technique. (c) 2021 Elsevier Inc. All rights reserved.

关键词： Representation of solutions   Second order   Delayed matrix functions   Multiple delays   Non-permutable matrices   Laplace transform  

摘要： Nonhomogeneous linear systems of second order differential equations with pure delay and multiple delays are considered. Representations of their solutions without a commutativity assumption on the matrix coefficients are obtained by using delayed matrix functions and Laplace transform. Our results improve and extend previous results. (c) 2021 Elsevier Inc. All rights reserved.

关键词： 分数阶发展方程   非局部问题   强连续半群   存在性  

摘要： 运用算子半群理论、Schaefer不动点定理和Banach不动点原理,研究了分数阶微分发展方程非局部问题T_(α)u t=Au t+f t,u t,Gu t,Su t,t∈[0,c],u 0+g u=u 0温和解的存在性和唯一性,并举出实例说明所得结果的适用性.

关键词： 生产周期   更新换代   平衡点   稳定性   数值仿真  

摘要： 多数商品需要生产时间,为了增加市场竞争力,它们更需要更新换代.基于生产周期和更新换代对商品需求量,价格和供给量的内在影响,利用微分动力学的相关理论建立两个商品微分动力学模型.对模型进行定性分析得出一些与实际情况相吻合的结论.当商品仅受生产周期影响时,不同条件下,需求量,价格和供给量会稳定地收敛于正平衡点或围绕正平衡点作周期性波动.在生产周期和更新换代叠加效应影响下,需求量,价格和供给量均有上限并且在某一时刻后,三者均会作周期性波动.最后,用数值仿真验证相关结论的正确性.

摘要： IFN-gamma-inducible protein 16 (IFI16) recognizes viral DNAs from both nucleus-replicating viruses and cytoplasm-replicating viruses. Isoform 2 of IFI16 (IFI16-iso2) with nuclear localization sequence (NLS) has been studied extensively as a well-known DNA sensor. However, the characteristics and functions of other IFI16 isoforms are almost unknown. Here, we find that IFI16-iso1, with exactly the same length as IFI16-iso2, lacks the NLS and locates in the cytoplasm. To distinguish the functions of IFI16-iso1 and IFI16-iso2, we have developed novel nuclear viral DNA mimics that can be recognized by the nuclear DNA sensors, including IFI16-iso2 and hnRNPA2B1. The hexanucleotide motif 5'-AGTGTT-3' DNA form of the nuclear localization sequence (DNLS) effectively drives cytoplasmic viral DNA nuclear translocation. These nuclear viral DNA mimics potently induce IFN-beta and antiviral IFN-stimulated genes in human A549 cells, HEK293T cells, and mouse macrophages. The subcellular location difference of IFI16 isoforms determines their differential functions in recognizing viral DNA and activating type I IFN-dependent antiviral immunity. IFI16-iso1 preferentially colocalizes with cytoplasmic HSV60mer and cytoplasm-replicating vaccinia virus (VACV), whereas IFI16-iso2 mainly colocalizes with nuclear HSV60-DNLS and nucleus-replicating HSV-1. Compared with IFI16-iso2, IFI16-iso1 induces more transcription of IFN-beta and IFN-stimulated genes, as well as stronger antiviral immunity upon HSV60mer transfection or VACV infection. IFI16-iso2, with the ability of nuclear-cytoplasmic shuttling, clears both invaded HSV type 1 and VACV significantly. However, IFI16-iso2 induces more type I IFN-dependent antiviral immunity than IFI16-iso1 upon HSV60-DNLS transfection or HSV type 1 infection. Our study has developed potent agonists for nuclear DNA sensors and also has demonstrated that IFI16 isoforms with cytoplasmic and nuclear locations play differential roles in innate immunity against D

关键词： 随机时滞微分方程   变时滞   截断型θ-EM算法   强收敛率  

摘要： 考虑了一类非线性随机时滞微分方程,漂移项系数和扩散项系数均是超线性增长的,其时滞会随着时间变化而变化.建立了这类方程的截断型θ-EM算法,并得到了数值解的收敛率,最后用一个例子验证了理论结果.