Modification of multiwalled carbon nanotubes by carboxy groups and determination of the degree of functionalization

Multiwalled carbon nanotubes were modified by carboxy groups. Four independent methods for the determination of the degree of functionalization of the surface were proposed: ¹³C NMR spectroscopy, thermogravimetry, titrimetry, and fluorimetry. The first two methods show the total content of carboxy groups in the sample, and the latter two methods give information about the content of the surface groups only. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 291–295, February, 2008.     

有向全图的幂敛指数和周期

设G是有向图,T(G)表示G的有向全图.本文得到了它们的幂敛指数k(G)和k(T)之间的关系:对任何有向图G,周期p(T(G))=1;当G是本原图时,k(T)≤k(G)+1,文中给出了取得k(G)+1的两类图;当G是无圈图时,k(T)=2k(G)-1,当G是有向圈时,k(T)=2|V(G)|-1,当G是强连通时得到了k(T)的一些估计.     

PERIODIC SOLUTIONS OF PLANAR SYSTEM WITH SIX DELAYS

In this paper we obtain some sufficient conditions for the existence of non-constant periodic solutions of the following planar system with six delaysOur approach is based on the continuation theorem of the coincidence degree.     

正系数多项式倒数逼近的点态和整体估计

利用Ditzian-Totik光滑模对于[0,1]上定义的非角连续函数f(x)，且f(x)≠0，文中证明存在正系数多项式Pn(x)及常数C，使得|f9x)-1/Pn(x)|≤Cωψ^λ（f,n^-1/2(ψ(x) 1/√n)^1-λ)。当λ＝1时，上述结果导出已有的整体估计，而当0≤λ＜1时，得到倒数逼近一个新的点态局部估计。     

A minimal pair joining to a plus cupping Turing degree

A computably enumerable (c.e.) degree a is called nonbounding, if it bounds no minimal pair, and plus cupping, if every nonzero c.e. degree x below a is cuppable. Let NB and PC be the sets of all nonbounding and plus cupping c.e. degrees, respectively. Both NB and PC are well understood, but it has not been possible so far to distinguish between the two classes. In the present paper, we investigate the relationship between the classes NB and PC , and show that there exists a minimal pair which join to a plus cupping degree, so that PC ? NB . This gives a first known difference between NB and PC . (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

理想流体一维绝热稳定流动能量方程推导

对理想流体一维绝热稳定流动作了讨论．对一般理想流体(可压缩或不可压缩)，用两种方法推出了能量方程．在此基础上，讨论了流动可逆性及不同流体性质对流动参数的影响．     

图的度序列不等式

用代数的方法证明了有关图度序列的几个不等式，并且得到了其相应的极图。     

Positive periodic solution for a two-species ratio-dependent predator-prey system with time delay and impulse

A two-species ratio-dependent predator-prey model with time delay and impulse is investigated. By using the continuation theorem of coincidence degree theory, the existence of a positive periodic solution for this system is established.     

氩等离子体物态方程的TF简化模型

对于高温高压下氩等离子体的电离度和物态方程,本文给出了一种基于Thomas-Feimi(TF)统计模型的简化计算新方法:首先将TF模型电离势的数值结果进行函数逼近,给出一个便于数值求解的计算电离度的近似计算方法,并由此计算了局部热动平衡下的氩等离子体在10～1000 eV高温范围内的物态方程.计算结果与国外报道的其他几种理论模型的计算结果均符合很好,与实验值也吻合较好.本文所提出的简单模型也适用于计算混合物物态方程,可以在电磁发射技术领域中的强电离等离子体中有更为广阔的应用前景.