布尔矩阵维数的缺断区间(英)

本文证明了n维布尔矩阵维数的一个新的缺断区间为这一结果扩充了一些已知的结论．     

一种含SiO2氧化物玻璃的晶化温度-压力依赖关系

 本文应用DTA及X射线衍射法在常压及高压下对一种含SiO₂的锂离子导体玻璃0.3Li₂O-0.67SiO₂-0.03V₂O₅加热时的晶化行为进行了研究。该氧化物玻璃的晶化过程分两个阶段。在常压下，第一晶化过程发生在560 ℃附近，析出相为Li₂O·2SiO₂。对应的晶化温度T_x1随压力的升高发生了急剧的变化。从常压到0.3 GPa，T_x1从560 ℃升高到620 ℃；继续升压时T_x1突然下降，并在0.4 GPa处跌到528 ℃，呈现一个陡峭的峰值。0.4 GPa以上，T_x1随压力的变化则呈常规行为，比较平稳地，大致线性地升高，一直到最高测定压力2 GPa。 本文最后对这些行为的可能原因进行了讨论。     

Effect of POSS on crystalline transitions and physical properties of polyamide 12

Polyamide 12/Trisilanolphenyl‐POSS (PA 12/POSS) composites were prepared via melt‐compounding. The effect of polyhedral oligomeric silsesquioxane (POSS) on crystalline structure and crystalline transition of PA 12 was investigated by wide‐angle X‐ray diffraction (WAXD) and real time fourier transform infrared spectroscopy (FTIR). WAXD results indicated that PA 12 crystallized into γ‐form as slowly cooling from melt and the presence of POSS did not influence the crystalline structure of PA 12. Both PA 12 and PA 12/POSS composites underwent Brill transitions when they were heated from room temperature to melt point. Real time FTIR patterns showed that an absorption band at 697 cm^?1 ascribed to Amide V (α) mode was emerged along with the disappearance of Amide VI (γ) band at 628 cm^?1 with the increase of the temperature for PA 12 and PA 12/POSS composites, which suggested that the γ‐form crystalline has transformed into α form. The Brill bands were identified and the transformed mechanism was discussed based on the real FTIR results. The addition of POSS enhanced the tensile strength and thermal stability of PA 12. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 121–129, 2009     

Comparative study of the empirical interatomic potentials and density-functional simulations of divacancy and hexavacancy in silicon

The comparison between three classical potentials and density functional theory (DFT) is performed mainly for divacancy and hexavacancy in Si crystal. According to their performances on the formation energies and structural properties (distortion magnitude, relaxation volume and symmetry), the limitations and validities of classical potentials are discussed. It is found that the outward relaxation directions of EDIP and Tersoff (T3) are contrary to the DFT and Stillinger-Weber (SW) directions (inward), which restrict their application in the structural property calculations. Except for the divacancy symmetries, the results of SW are in agreement with the DFT results. Thus, it can be concluded that SW should be the best potential to describe V₂ and V₆.     

漫谈热胀冷缩的``功''与``过''

 热胀冷缩现象在我们周围随处可见，只有更好地掌握它的规律，才能避免或减小它的危害， 利用它为人类造福.     

Determination of inorganic anions in ethyl acetate by ion chromatography with an electromembrane extraction method

In this work, the determination of inorganic anions in slightly water-soluble organic solvents (ethyl acetate) was realized by ion chromatography (IC) with a novel-efficient electromembrane extraction method. From an 8 mL ethyl acetate sample, three inorganic anions migrated through the pores of a polypropylene hollow fiber membrane, and into deionized water inside the lumen of the hollow fiber by the application of 600 V. The transport was forced by an electrical potential difference sustained over the liquid membrane, resulting in electrokinetic migration of inorganic anions from the donor compartment to the acceptor solution. After the electromembrane extraction, the acceptor solution was analyzed by IC with a sodium carbonate-sodium bicarbonate eluent. The applied voltage, stirring speed, and extraction time for controlling the extraction efficiency were optimized. Within 10 min of operation at 600 V, chloride, bromide, and sulfate were extracted with recoveries in the range 76-110%, which corresponded to a linear range of 0.01-1 mg/L. The procedure was applied to the analysis of inorganic anions in a real ethyl acetate sample and expands onto other slightly water-soluble organic solvents.     

Morphology, structure and Raman scattering of carbon nanotubes produced by using mesoporous materials

Carbon nanotubes were prepared by chemical vapor deposition (CVD) of hydrocarbon gas on various substrates. The effect of substrates on the growth, morphology and structure of carbon nanotubes were investigated. Aligned carbon nanotubes with high density and purity were achieved by CVD on mesoporous silica substrate. The Raman scattering of aligned carbon nanotubes was carried out, and the dependence of the phonon properties on the microstructure of the nanotubes has been discussed.