Significant change in water contact angle of electrospray‐synthesized SiO2 films depending on their surface morphology

Amorphous SiO₂ films were deposited by means of an electrospray technique. The relation between the water contact angle (WCA) of the deposited SiO₂ films and the surface morphology is investigated. The feeding rate of the electrospray process greatly affects the morphology of the synthesized SiO₂ films. There is also a significant change in the WCA on the surface of the films: the rougher the surface, the greater the WCA. A model based on the Cassie–Baxter formulation is used to explain the change observed in the WCA on the SiO₂ films. Copyright © 2012 John Wiley & Sons, Ltd.     

Meissner Anisotropy in Deuterated (TMTSF)2Clo4

Both the Meissner-signal (flux expulsion on cooling through T_c) and the shielding signal (obtained by turning on a field in the superconducting state) have been observed in deuterated single crystals for fields oriented both along and normal to the chain axis. A possible isotope effect on T_c is discussed. We find complete diamagnetism in normal fields and incomplete (～ 40 %) diamagnetism in parallel fields. A dramatic drop of the Meissner-effect in parallel fields well below H_c1 is observed and not yet well explained.     

Numerical methods for light propagation in large LC cells: a new approach

Accurate numerical methods for the propagation of light in large 3D samples with strong lateral variation of the director field require prohibitive amounts of time. We consider and compare a standard spectral method and the Finite Difference in Frequency Domain method, showing that the CPU time can be reduced by one or two orders of magnitude using a perturbation approach or a recently developed Reduced Order Method. The equations obtained are applied to liquid crystal cells with in-plane switching, illuminated by a large incoherent source. The developed formalism, based on numerically exact equations, is particularly suitable for treating magnetic or optically active media and for extending to such media the well known approximations based on the 4 × 4 (Berreman) or 2 × 2 (Jones) matrices.     

蒸发器支撑板板孔精密测量系统

建立了蒸发器支撑板板孔精密测量系统,并提出了基于边缘约束条件的轮廓参量测量方法.首先采用图像处理技术将待测目标转化为二维离散坐标点,计算其最小外接矩形并对轮廓进行预定位;然后将轮廓分割成相互重合的"扩展邻域轮廓",建立以曲率角为原则的边缘约束算法对各轮廓段精确定界,实现对轮廓参量的精密测量.实验和误差分析表明,该系统测量准确度优于0.02mm,对具有复杂轮廓的零件参量测量有参考价值.     

Conductivity anomalies in Y–Ba–Cu–O at 40K and 100K under high quasihydrostatic pressures

Electrical resistance measurements at low temperatures and high quasihydrostatic pressures on superconducting and non-superconducting varieties of Y_0.8Ba_1.2Cu₂O₅ (obtained by annealing in oxygen and air respectively) show striking anomalies in the vicinity of 100K and 40K. Arguments are presented to show that these anomalies as also the occurrence of T 's in the oxide superconductors either in the vicinity of 100K or of 40K are connected with their layered structure containing planes of Cu-O otahedral complexes.     

INFLUENCE OF THERMAL TREATMENTS ON THE POLYMORPHISM IN STEREOIRREGULAR ISOTACTIC POLYPROPYLENE: EFFECT OF STEREO-DEFECT DISTRIBUTION

The influence of cooling rate from the melt on the polymorphism and crystallinity is investigated as a function of isotacticity and stereo-defect distribution in polypropylenes. Detailed analysis of wide angle x-ray diffraction patterns shows that crystallinity in the materials used is nearly independent of the experimental cooling rates (0.5–40°C/min). At high cooling rates, the materials exist mainly in the α-phase, whereas the amount of the γ-phase increases at the lower cooling rates. With an increasing amount of stereo-defects, this cooling-rate dependence of the polymorphism is enhanced. The effect of different stereo-defect distributions, as observed in metallocene-(random) and Ziegler–Natta (blocklike) derived isotactic polypropylenes, was investigated. The formation of the γ-phase is more prevalent in materials with a random defect distribution compared to the materials in which the stereo-defects have a blocklike distribution. The crystallinity decreases more rapidly as a function of the tacticity in the random defect-distributed materials.     

Dihedral angle study in Hesperidin using NMR Spectroscopy

Hesperidin is flavonoid molecule found in citrus fruits (Citrus reticulata), especially difficult to extract, classify and characterize. Present work is to study the unresolved relative configuration of Hesperidin through the dihedral angle, coupling constant and different NMR techniques. The Karplus equation and its modifications have been originated from the valence bond theory and associated with dihedral angle and coupling constant. The result data set of calculated dihedral angle can probe significant method to assign the virtual configuration of natural products and also resolved stereochemistry of Hesperidin at C‐2 position in. Copyright © 2016 John Wiley & Sons, Ltd.     

Solid‐state drawing of β‐nucleated polypropylene: Effect of additives on drawability and mechanical properties

Isotactic polypropylene (i‐PP) can crystallize in different crystal modifications. In this article, the effect of sepiolite (one‐dimensional) and carbon black (three‐dimensional) fillers on the solid‐state drawability of i‐PP is discussed. The cross‐hatched structure of thermodynamically most stable α‐crystal phase in i‐PP does not allow for perfect chain alignment during solid‐state drawing. The β‐phase i‐PP, obtained by addition of specific nucleating agents, crystallizes in a non‐cross‐hatched spherulitic structure and allows more easy drawing. Depending on the filler type, β–α transformation takes place at different draw ratios, as was observed by in situ wide‐angle X‐ray diffraction measurements. It was observed that β‐nucleated i‐PP has a lower yield stress and can be drawn further than i‐PP crystallized in the α‐crystal phase. If added in the right amount, both carbon black and sepiolite have a reinforcing effect on PP tapes. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1071–1082     

MATLAB在光学界面发生反射时的分析与应用

基于MATLAB的计算功能及可视化功能计算并分析了光学中的菲涅耳公式,更加直观的揭示了光波在两介质界面发生反射时的变化规律。使学生更加深入、直观地掌握光波在界面发生变化的条件、实质及布儒斯特角与全反射临界角的物理意义,同时也学会了分析研究方法,且提高了学习的主动性和创造性。