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61.
Bei‐Kai Yang Chen‐An Wang Wen‐Yan Zhang Jrjeng Ruan 《Journal of Polymer Science.Polymer Physics》2017,55(19):1448-1457
For the ordered phases of hairy‐rod semiconductive poly(2,5‐bis(3‐tetradecylthiophene‐2‐yl)thieno[3,2‐b]thiophene) (PBTTT) sandwiched in between crystalline platelets of hexamethylbenzene, the successive stepwise evolution of layer‐stacking framework upon guest intercalation has been studied in this research. The direct consequence of the guest intercalation into side‐chain layers is evaluated to cause the lateral shift of thiophene backbones along π–π stacking, resulting in stepwise shift of ultraviolet absorption wavelength. The thermal motions of vapor guests within disordering side‐chain layers subsequently cause progressive expansion of host stacking framework. With the increase in side‐chain length, thicker layers of disordering side chains in liquid crystals (LCs) accommodate additional vapor guests and larger amplitudes of thermal motions of guests, hence promoting the level of reversible d‐spacing change. The mixing between mobile vapor guests and aliphatic side chains is clarified as the mechanism of guest intercalation, which rationalizes successive guest intercalation during heating and the contribution of disordering side‐chain layers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1448–1456 相似文献
62.
In this article we discuss the finite element discretization of the two-dimensional, incompressible, and turbulent boundary layers. The formulation of the momentum equation is essentially due to Baker and Soliman [1] with some modifications.The versatility and the accuracy of the method is established by considering several test cases. The predictions are satisfactory and compare favorably with alternative numerical techniques. 相似文献
63.
The evolution of 2-D disturbances in hypersonic boundary layer with Mach number 6,8, and 10 was investigated numerically by
three different numerical schemes. At the entrance, second mode T-S waves with different amplitudes were introduced, and the
relation between the Mach number and the amplitude of the disturbance when shocklets started to appear was investigated. By
comparing the disturbance velocity profiles with those provided by linear stability theory, the effects of shocklets on flow
structures were also investigated. 相似文献
64.
The present study evaluates the growth kinetics of the boride layer Fe2B in AISI 1045 steel, by means of neural networks and the least square techniques. The Fe2B phase was formed at the material surface using the paste boriding process. The surface boron potential was modified considering different boron paste thicknesses, with exposure times of 2, 4 and 6 h, and treatment temperatures of 1193, 1223 and 1273 K. The neural network and the least square models were set by the layer thickness of Fe2B phase, and assuming that the growth of the boride layer follows a parabolic law. The reliability of the techniques used is compared with a set of experiments at a temperature of 1223 K with 5 h of treatment time and boron potentials of 2, 3, 4 and 5 mm. The results of the Fe2B layer thicknesses show a mean error of 5.31% for the neural network and 3.42% for the least square method. 相似文献
65.
A device of multiple nano-TiO2 layers was proposed and fabricated to prevent a dye/nano-TiO2 region from serious photo-degradation. In this device, the top of the dye/TiO2 region was designed to be coated using sol-gel nano-TiO2 thin films to shield UV irradiation from the photo-degradation effect. The sol-gel TiO2 was prepared in a low temperature (75 °C) and verified as nano-sized particles and an anatase crystalline structure. Different devices of the multi-layer samples fabricated using different compositions of nano-TiO2 were produced and exposed for UV irradiation tests. Results show that the presence of the sol-gel TiO2 films coated on top of the dye/TiO2 region can significantly alleviate the dye photo-degradation under UV irradiation. This multi-layer device can effectively improve the photo-stability of the dye/TiO2 region in a UV-exposure environment. 相似文献
66.
Hyperfine Interactions - The giant magnetoresistance (GMR) effect was an epoch-making discovery in the field of magnetic materials research. In this article, studies on magnetic multilayered... 相似文献
67.
68.
基于边界层转捩后阶段的高精度直接数值模拟结果,发现流向条纹结构的低速条纹的演化过程中存在不连续现象,以及随高速条纹的发展会出现称之为"高速斑"的新特性. 通过详细剖析边界层转捩过程中的复杂涡系结构以及上喷下扫流动现象,证实流向高低速条纹新特性与流场涡系结构的演化过程紧密相关.
关键词:
流向条纹
边界层
转捩
直接数值模拟 相似文献
69.
Balek V. Mitsuhashi T. Šubrt J. Bakardjieva S. Málek Z. 《Journal of Thermal Analysis and Calorimetry》2003,72(1):119-127
Emanation thermal analysis (ETA) was used for characterization of thermal behaviour of SiCf/SiC composites on heating in argon and air, respectively. Effect of gas environment (argon, air) and helium ions implantation
on the microstructure development of the SiCf/SiC composite prepared by chemical vapour infiltration (CVI) from Nicalon CG fibres was investigated under in situ conditions
of heating. The annealing of near surface structure irregularities was observed in the range 280-700°C and evaluated by means
of the mathematical model, assuming that the structure irregularities served as diffusion paths for radon. The ETA reflected
the formation of amorphous silica and its subsequent crystallization to crystoballite. Morphology of the SiCf/SiC samples before and after the heat treatments was characterized by means of SEM.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
70.
H. Krzy
anowska A. von Bohlen R. Klockenkmper 《Spectrochimica Acta Part B: Atomic Spectroscopy》2003,58(12):5698-2067
A new method suitable for depth profiling of shallow layers on different materials is presented. It is based on a soft and planar ion sputtering combined with differential weighing, total-reflection X-ray fluorescence (TXRF) spectrometry and Tolansky interferometry. By means of a stepwise repetition of these techniques it is possible to determine both density/depth and concentration/depth profiles. The respective quantities are expressed in terms inherent only to the sample and traceable to the SI-units or subunits gram, nanometer and mole. It is a unique feature of this method that density/depth profiles can directly be obtained from measurements without any calibration or theoretical approximation. The method is applied to a Si wafer implanted with Co ions of 25 keV energy and a nominal dose of 1×1016 cm−2. The depth resolution is shown to be <3 nm while a total depth of some 100 nm can be reached. The concentration/depth profile is compared with RBS measurements, wet-chemical etching plus TXRF and Monte Carlo simulations. In view of the fact that only similar but not exactly the same samples have been examined by these methods, a good correspondence can be noticed. 相似文献