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991.
C. D. Hoke J. -F. Li Y. -H. Lin L. -C. Chien P. J. Bos S. Hudson 《Liquid crystals》2013,40(3):359-363
Using polarized infrared (IR) spectroscopy we have observed deformation of a polymer network in a liquid crystal host during the reorientation of the liquid crystal by an external electric field. In the system studied, containing 2% BMBB-6 polymerized at zero applied field in the host nematic liquid crystal 6CB, the observed deformation angle was between 20o and 40o 10o. These experimental results provide some of the first conclusive experimental evidence that the polymer network elastically deforms as a direct result of the reorientation of the liquid crystal host. 相似文献
992.
《合成通讯》2013,43(12):1589-1599
Abstract The nitromethyl group of C‐(4,6‐O‐benzylidene‐β‐d‐glucopyranosyl) nitromethane was manipulated by various reduction and oxidation methods and further functionalizations into –CH2NHOH, –CH?NOH, –CN, –CH?O, and –CH2NHCONH2, all with retention of the 4,6‐O‐benzylidene group. Certain reduction methods gave rise to a novel secondary amine via an unusual dimeric aminal. 相似文献
993.
We study theoretically the construction of topological conducting domain walls with a finite width between AB/BA stacking regions via finite element method in bilayer graphene systems with tunable commensurate twisting angles. We find that the smaller is the twisting angle, the more significant the lattice reconstruction would be, so that sharper domain boundaries declare their existence. We subsequently study the quantum transport properties of topological zero-line modes which can exist because of the said domain boundaries via Green’s function method and Landauer−Büttiker formalism, and find that in scattering regions with tri-intersectional conducting channels, topological zero-line modes both exhibit robust behavior exemplified as the saturated total transmissionGtot ≈ 2e2/h and obey a specific pseudospin-conserving current partition law among the branch transport channels. The former property is unaffected by Aharonov−Bohm effect due to a weak perpendicular magnetic field, but the latter is not. Results from our genuine bilayer hexagonal system suggest a twisting angle aroundθ ≈ 0.1° for those properties to be expected, consistent with the existing experimental reports. 相似文献
994.
995.
In this paper, we study the unsteady motion of inhomogeneous incompressible viscous fluids. We present the results corresponding to Stokes' second problem and for the flow between two parallel plates where one is oscillating. 相似文献
996.
In order to understand the effect of the wall permeability on the turbulent vortex structure near porous walls, based on PIV experimental data, a probability density analysis of fluctuating velocities, statistical quadrant and quadrant-hole analyses of the Reynolds shear stress are performed. The investigated flow fields are turbulent channel flows whose bottom walls are made of porous media. The porous media used are three kinds of foamed ceramics which have almost the same porosity (∼0.8) but different permeability. From the discussions on those analyses, a conceptual scenario of the development of the vortex structure near a permeable wall is proposed for a moderate permeability Reynolds number case. It explains the reason why the near-wall long streaky structure tends to vanish near a porous wall with increasing wall permeability. 相似文献
997.
Homotopy analysis solutions for the asymmetric laminar flow in a porous channel with expanding or contracting walls 总被引:6,自引:1,他引:5
Xin-Hui Si · Lian-Cun Zheng · Xin-Xin Zhang · Ying Chao Applied Science School University of Science Technology Beijing Beijing China Department of Mechanical Engineering China Research Institute of Chemical Defense of the P.L.A. Beijing China 《Acta Mechanica Sinica》2011,27(2):208-214
In this paper, the asymmetric laminar flow in a porous channel with expanding or contracting walls is investigated. The governing equations are reduced to ordinary ones by using suitable similar transformations. Homotopy analysis method (HAM) is employed to obtain the expres- sions for velocity fields. Graphs are sketched for values of parameters and associated dynamic characteristics, especially the expansion ratio, are analyzed in detail. 相似文献
998.
G. Wang M. ZengY.C. Ren H. Ozoe Q.W. Wang 《Experimental Thermal and Fluid Science》2011,35(1):105-111
The transient natural convection in an inclined enclosure filled with water is studied experimentally for the time-periodically-varying wall temperature on one side wall and constant average temperature on the opposing side wall. This system has no temperature difference between the opposing two side walls in time-averaged sense. The temperatures of two opposing walls and the heat flux across the enclosure are measured by a heat flux meter. Based on the experimental results, the effects of time-periodically-varying wall temperature and inclined angles of the enclosure on heat transfer characteristics are studied. The experimental results show that, with the upper wall temperature oscillating, the heat flux across the enclosure is also periodically varied with time, and the net heat flux is from the lower wall to the upper wall. Numerical computations are also conducted and numerical results are qualitatively assured by the experimental measurements. 相似文献
999.
1000.
Lixia Wang Lin Jiang Shuang Li Yang Zhang Dongfang Wang Qian Li Changyu Shen 《先进技术聚合物》2020,31(7):1463-1473
The morphology and microstructure as well as their forming mechanism of the parts in microinjection molding process are critical. In this work, the coupling effect of scale factor and injection speed on the morphology of the microparts was systematically investigated. Neat isotactic polypropylene parts with thicknesses of 1 mm, 200 μm, and 100 μm were molded at different injection speeds. Polarized light microscope and wide‐angle X‐ray diffraction were used to inspect the microstructures along the sample thickness. In this way, three kinds of typical morphology were observed in the parts, including typical skin‐core structure for the parts with the thickness of 1 mm, noncore shear layer structure for the parts with the thickness of 200 μm, and special skin‐core structure with large fraction of columnar crystal for the parts with the thickness of 100 μm. Most interestingly, it was intuitively and straightforward found that the wall slip occurs when the injection speed exceeds a certain value. Specifically, opposite morphological change trend can be obtained when the parts were molded at different levels of injection speeds. Based on these experimental observations, the formation mechanism was proposed to interpret the morphological evolution. Our work provides a new insight for better understanding the morphology evolution mechanism for microinjection molding parts. 相似文献