SYNTHESIS OF SnO2 NANOCRYSTALS BY SOLID STATE REACTION FOLLOWED BY CALCINATION

Nanocrystalline SnO2 was synthesized by direct mixing and grinding of SnCI4-5H2O and NaOH at room temperature, followed by calcination at different temperatures for different times in air. Product samples were characterized by X-ray diffraction and transmission electron microscope, revealing that the amorphous precursor SnO2 was transformed to crystals at 200℃ for 3h, and that the average particle size increased upon raising the calcining temperature or prolonging the calcining time. The mechanism of the phase transformation of the products is discussed.     

规整膜系层厚允许误差的研究

提出了一种通过计算机模拟薄膜的淀积过程来计算规整膜系层厚允许误差的方法,所计算的层厚允许误差不仅取决于膜系的设计结构,还与薄膜的淀积工艺、镀膜设备的监控精度有关.实验结果表明:采用这种方法所计算出的层厚允许误差对于薄膜的实际镀制具有指导意义.     

广义Weyl型李代数Wgl_n(F)上的2-上同调群

设F是一特征为零的域,W是F上的广义Weyl代数,gl_n(F)为F上的一般线性李代教,则结合代数Wgl_n(F)上具有一个诱导的李代数结构,本文讨论了李代数Wgl_n(F)的2-上同调群的结构.     

ICP-AES法对茶叶捕集水溶液中镉(Ⅱ)、铅(Ⅱ)行为的研究

用ICPAES法研究了绿茶和红茶对水溶液中镉(Ⅱ)、铅(Ⅱ)的捕集行为,考察了时间、pH、温度等因素的影响。结果表明,绿茶对水中镉(Ⅱ)、铅(Ⅱ)的捕集30min基本达到平衡,而红茶的捕集平衡时间约为60min。当pH<4时捕集率随pH值减小而显著降低,当pH>4时捕集率变化趋缓;当pH<6时茶样对铅(Ⅱ)的捕集率大于镉(Ⅱ),而当pH>6之后则正相反,这与不同酸度的溶液中茶叶的带电状态及镉(Ⅱ)、铅(Ⅱ)的形态分布有关。升高温度有利于绿茶对镉(Ⅱ)、铅(Ⅱ)的捕集,而红茶变化不大;捕集后的镉(Ⅱ)、铅(Ⅱ)在25℃下用水洗脱困难,其中绿茶与铅(Ⅱ)的相互作用较强。     

Aptameric SERS sensor for Hg~(2+) analysis using silver nanoparticles

Aptamer–silver nanoparticles (AgNPs) based surface-enhanced Raman scattering (SERS) sensor has been developed for Hg²⁺ detection by employing the structure-switching aptamer in the presence of spermine. This simple method shows excellent sensitivity and selectivity owing to the sensitive SERS detection technique and high specificity of aptamer for binding Hg²⁺.     

一类平均算子Markov链的极限定理

该文给出了一类平均算子Ｍａｒｋｏｖ链,并证明了对此类算子Ｍａｒｋｏｖ链,其大数定理,中心极限定理及重对数定律成立。     

A Two-grid Method with Expanded Mixed Element for Nonlinear Reaction-diffusion Equations

Expanded mixed finite element approximation of nonlinear reaction-diffusion equations is discussed. The equations considered here are used to model the hydrologic and bio-geochemical phenomena. To linearize the mixed-method equations, we use a two-grid method involving a small nonlinear system on a coarse gird of size H and a linear system on a fine grid of size h. Error estimates are derived which demonstrate that the error is O(△t + h k+1 + H 2k+2 d/2 ) (k ≥ 1), where k is the degree of the approximating ...     

Multiple enhancements of rate oscillations by non-Gaussian noise in NO reduction with CO on Pt(100)

The effect of the non-Gaussian colored noise(NGN) on the dynamics of nonlinear systems has attracted increasing attention.This work numerically studied the effect of a particular kind of the NGN,mainly in terms of its departure from Gaussian noise,on the rate oscillations(RO) in the catalytic reduction of NO with CO on Pt(100) surfaces.It was found that power spectrum density changes non-monotonically and the signal-to-noise ratio shows several peaks with increasing departure,demonstrating the presence ofde...     

ASYMPTOTIC BEHAVIOR FOR NONOSCILLATORY SOLUTIONS OF REACTION-DIFFUSION DIFFERENTIAL EQUATIONS WITH SEVERAL DELAYS IN THE NEUTRAL TERM

In this paper, we first consider differential equations with several delays inthe neutral term of the formstudy various cases of coefficients in the neutral term and obtain the asymptoticbehavior for nonoscillatory solution of (1~*) under some hypotheses. Moreover,we consider reaction-diffusion differential equations with several delays in theneutral term of the formfor (t, x)∈ R~+ ×Ω. We also study various cases of coefficients in the neutralterm and obtain the asymptotic behavior for nonoscillatory solution of (2~*)under some hypotheses.     

EXTENDABILITY OF SOLUTIONS FOR THE LINEAR SYSTEM OF ELLIPTIC TYPE EQUATIONS

The solutions of linear system of elliptic type equations with first order isdiscussed by using the method of several complex analysis and, a series of newextended results of the solutions for the system of elliptic type are obtained.