Adsorbing behavior of polycarboxylate superplasticizer in the presence of the ester group in side chain

The effect of the ester group in side chain on adsorbing behavior and dispersion of polycarboxylate superplasticizer (PC) was studied by comparing the performance of two types of PC. The fluidity of cement paste was tested to discuss the dispersing ability and dispersing retention ability of PC. The total organic carbon analyzer was used to measure the adsorption amount, and the adsorption layer was obtained by x-ray photoelectron spectroscopy. Fourier-transform infrared spectroscopy, nuclear magnetic resonance, and pH value were used to verify the stability of the ester group, and the electrokinetic properties of cement particle were confirmed using the zeta potential measurement. The results show that the ester group in side chain reduces the initial dispersing ability while it increases the dispersing retention ability. The dispersing retention ability depends on the increase of adsorption amount and adsorption layer in 5–60 minutes, and the greater increase leads to the better dispersing retention ability. The ester group can be decomposed to release carboxyl group to enhance the adsorbing ability of PC under the condition of cement hydration, which is the main reason for the greater increase of adsorption amount and adsorption layer and the improvement in dispersing retention ability. It suggests that grafting the ester group is a good way to enhance the dispersing retention ability.     

Discrepancy of structural stability against temperature between metallic liquids and their glasses

The stability of the disordered structure in liquid or glass states could be characterized by the glass-forming ability (GFA) and thermal stability (TS), respectively. The two quantities are often, but not always, positively correlated. Here we show that the discrepancy between GFA and TS originates from the competition between entropy and enthalpy which fairly much relies on local structural characteristics. This inherent interaction and competition determines hierarchy of phase stability against temperature. As a result, the time susceptibility of GFA and temperature susceptibility of TS were derived from the time-temperature-transformation diagram, which are coincided with the above mentioned entropy-enthalpy competition perspective. Thus, the interrelationship among entropy, enthalpy and local cluster feature provides a potential resolution to design and optimize glass formers, and have implications for better understanding the nature of glass transition.     

《微分方程数值解》课程教学改革与实践

针对一般本科院校的教学实际,研讨《微分方程数值解》课程教学改革的一些体会,主要包括教学定位的确定、课程教学内容的优化、教学方法的改革以及教学手段的更新等问题.     

从“求圆截线平面问题”的研究谈学生能力的培养

对“求圆截线平面问题”作了深入研究,给出了四种解法,得到了与椭球面交线是圆的平面的充分必要条件,交线圆的中心和半径,并结合该问题谈了基础课教学中对学生能力的培养．     

低电感大电流长寿命同轴型电容器

 介绍了一种应用于高功率脉冲源的低电感、高通流能力、长寿命的同轴型电容器。通过理论计算,综合考虑电容器的工作电压、电感、通流能力、与开关的连接方式等,确定了电容器的芯子结构、绝缘子结构及电极结构。通过设计实验线路,测试了电容器的电压、电感、通流能力、寿命等参数。实验结果表明：电容器电容量1.5 μF,工作电压100 kV,工作电流250 kA,峰值电流大于300 kA,电容器电感小于20 nH,储能密度205 J/L,工作寿命大于6 000次。     

Crystallization kinetics, glass transition kinetics, and thermal stability of Se70−xGa30Inx (x=5, 10, 15, and 20) semiconducting glasses

Crystallization and glass transition kinetics of Se_70−xGa₃₀In_x (x=5, 10, 15, and 20) semiconducting chalcogenide glasses were studied under non-isothermal condition using a Differential Scanning Calorimeter (DSC). DSC thermograms of the samples were recorded at four different heating rates 5, 10, 15, and 20 K/min. The variation of the glass transition temperature (T_g) with the heating rate (β) was used to calculate the glass transition activation energy (E_t) using two different models. Meanwhile, the variation of the peak temperature of crystallization (T_p) with β was utilized to deduce the crystallization activation energy (E_c) using Kissinger, Augis-Bennet, and Takhor models. Results reveal that E_t decreases with increasing In content, while both T_g and E_c exhibit the opposite behavior, and the crystal growth occurs in one dimension. The variation of these thermal parameters with the average coordination number <Z> was also discussed, and the results were interpreted in terms of the type of bonding that In makes with Se. Assessment of thermal stability and glass forming ability (GFA) was carried out on the basis of some quantitative criteria and the results indicate that thermal stability is enhanced while the crystallization rate is reduced with the addition of In to Se-Ga glass.     

一种生成迭代数列的新方法

围绕两个典型迭代数列的构造问题,以问题为驱动,提出一种生成迭代数列的新方法,并通过数值实验或理论证明验证迭代数列的收敛性.     

培养学生科学思维和创新能力的研究与实践——谈大学数学研究型教学

通过从一个导数值等式的证明谈起,探讨教师在课堂教学中如何根据教学内容创设能激起学生新异感的问题情景,启发和引导学生发散思考,类比、联想、猜想,探索和发现新问题并给出解答.使学生思维不断攀升,丰富教学内容,激发学生兴趣,培养学生科学思维方法和创新能力.     

基于识别能力的人脸特征向量均衡

在人脸识别中,通常是把人脸图像投影在特征向量组成的空间中,特征向量决定了人脸识别的效果。同一人的人脸图像在好的特征向量上的投影应具有较集中的分布,反之亦然。从微观意义上提出了每个向量的识别能力的概念,通过计算识别能力的大小,选择具有较大的识别能力的特征向量。为了使每个向量在识别中发挥与其识别能力相对应的作用,根据每个向量的识别能力对它们进行均衡化处理,赋予不同权重,提高了识别率。通过在ORL、Yale人脸数据库上进行试验,验证了该方法的有效性。