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991.
We find a sufficient condition for the existence of surface (Rayleigh) waves based on the Rayleigh-Ritz variational method.
When specialized to a homogeneous half-space, the sufficient condition recovers the known criterion for the existence of subsonic
surface waves. A simple existence criterion in terms of material properties is obtained for periodic half-spaces of general
anisotropic materials. Further, we numerically compute the dispersion relation of the surface waves for a half-space of periodic
laminates of two materials and demonstrate the existence of surface wave band gaps. 相似文献
992.
Khadija Mhada Bouazza Braikat Heng Hu Noureddine Damil Michel Potier-Ferry 《International Journal of Solids and Structures》2012,49(21):2978-2989
Various macroscopic models to describe instability pattern formation are discussed in this paper. They are similar to the Ginzburg–Landau envelope equation, but they can remain valid away from the bifurcation and are based on the technique of Fourier series with slowly varying coefficients. We focus on two questions: the need to take phase changes into account and the boundary conditions to be associated with macroscopic models. The analysis is carried out on the basis of numerical simulations for the problem of a compressed beam on a nonlinear foundation that is quite similar to the well known Swift–Hohenberg equation. The first macroscopic model involves a real envelope so that the phase is assumed to be constant. The second model is also macroscopic and it is a sort of Ginzburg–Landau equation with a complex envelope. The third one follows from a multi-scaled approach with a numerical bridging between the full model near the boundary and a macroscopic model in the bulk. 相似文献
993.
Wei Zhao Yi Zhang Xiao Wang Xiaowen Hu Feng Liu Thomas P. Russell Guofu Zhou 《Journal of polymer science. Part A, Polymer chemistry》2018,56(20):1369-1375
Block copolymer (BCP) films with long-range lateral ordering and orientation are crucial for many applications. Here, we report a simple, versatile strategy based on a solution casting procedure, to produce millimeter thick film of BCPs with highly oriented nanostructures. Transmission electron microscope (TEM), small angle X-ray scattering (SAXS), and Hansen solubility parameters were used to study the morphology and interactions of the system. A variety of BCP-solvent pairs were investigated. Factors including set-up geometry, BCP characteristics, solvent evaporation, surface tension, and interactions, such as solvent-BCP, solvent-substrate, and BCP-substrate were examined. A mechanism is proposed to describe the observed long-range lateral ordering and orientation in films up to 1 mm in thickness. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1369–1375 相似文献
994.
We present a high power red-green-blue (RGB) laser light source based on cascaded quasi-phasematched wavelength conversions
in a single stoichiometric lithium tantalate. The superiority of the experimental setup is: the facula of the incident beam
is elliptical to increase interaction volume, and the cavity was an idler resonant configuration for realizing more efficient
red and blue light output. An average power of 2 W of quasi-white-light was obtained by proper combination of the RGB three
colors. The conversion efficiency for the power of the quasi-white-light over pump power reached 36%. This efficiency and
powerful RGB laser light source has potential applications in laser-based projection display et al. 相似文献
995.
Zhuangzhuang Liu Aimin Sha Liqun Hu Yongwei Lu Wenxiu Jiao Zheng Tong Jie Gao 《Chemical Papers》2017,71(4):741-751
Portland cement have to hydrate in cold climates in some particular conditions. Therefore, a better understanding of cement hydration under low temperatures would benefit the cement-based composites application. In this study, Portland cement was, therefore, kinetically and thermodynamically simulated based on a simple kinetics model and minimization of Gibbs free energy. The results of an evaluation indicate that Portland cement hydration impact factors include the water–cement ratio (w/c), temperature, and specific surface area, with the latter being an especially remarkable factor. Therefore, increasing the specific surface area to an appropriate level may be a solution to speed the delayed hydration due to low temperatures. Meanwhile, the w/c ratio is believed to be controlled under cold climates with consideration of durability. The thermodynamic calculation results suggest that low-temperature influences can be divided into three levels: irrevocable effects (<0 °C), recoverable effects (0–10 °C), and insignificant effects (10–20 °C). Portland cement was additionally measured via X-ray diffraction, thermal gravity analysis, and low-temperature nitrogen adsorption test in a laboratory and comparisons were drawn that validate the simulation result. 相似文献
996.
Andrew J. Thompson Dr. Jerome Dabin Javier Iglesias‐Fernández Dr. Albert Ardèvol Dr. Zoran Dinev Assoc. Prof. Spencer J. Williams Dr. Omprakash Bande Dr. Aloysius Siriwardena Carl Moreland Dr. Ting‐Chou Hu David K. Smith Prof. Harry J. Gilbert Prof. Carme Rovira Prof. Gideon J. Davies 《Angewandte Chemie (International ed. in English)》2012,51(44):11171-11171
997.
Zhao-Long Hu Zhesi Shen Chang-Bing Tang Bin-Bin Xie Jian-Feng Lu 《Physics letters. A》2018,382(14):931-937
Locating sources in a large network is of paramount importance to reduce the spreading of disruptive behavior. Based on the backward diffusion-based method and integer programming, we propose an efficient approach to locate sources in complex networks with limited observers. The results on model networks and empirical networks demonstrate that, for a certain fraction of observers, the accuracy of our method for source localization will improve as the increase of network size. Besides, compared with the previous method (the maximum–minimum method), the performance of our method is much better with a small fraction of observers, especially in heterogeneous networks. Furthermore, our method is more robust against noise environments and strategies of choosing observers. 相似文献
998.
999.
Yuhong Chen Qishuai Jiao Liang Wang Yawei Hu Na Sun Yushuang Shen Yuhua Wang 《Comptes Rendus Chimie》2013,16(9):845-849
In order to improve the thermal stability and dynamic performance of LiCo1/3Ni1/3Mn1/3O2 materials, Cl-doped and Br-doped materials were synthesized via the co-precipitation method. The morphology, structure, electrochemical performance and thermal stability were characterized by environment scanning electron microscopy (ESEM), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), charge–discharge cycling and differential scanning calorimetry (DSC). Results show that all materials had a stable layered structure with α-NaFeO2 and that Cl-doping slightly increased the size of grains. Both Cl-doping and Br-doping improved the high rate of discharge capacity, cycle-life performance and thermal stability, but Cl-doping was better than Br-doping in improving the material structure stability, dynamic performance and thermal stability. 相似文献
1000.