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Stress Control in GaN Grown on 6H-SiC by Metalorganic Chemical Vapor Deposition

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Chinese Physics Letters 2011年第4期28卷 223-226页

作者：陈耀江洋徐培强马紫光王晓丽王禄贾海强陈弘 Beijing National Laboratory of Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190

The strain in GaN epitaxial layers grown on 611-SiC substrates with an AIN buffer by metalorganic chemical vapor deposition is *** is found that the insertion of a graded AlGaN layer between the GaN layer and the AIN buffer can change the signs of strain.A compressive strain in an overgrown thick(2μm)GaN layer is ***-resolution x-ray diffraction,Raman spectroscopy and photoluminescence measurements are used to determine the strain state in the GaN *** mechanism of stress control by inserting graded AlGaN in subsequent GaN layers is discussed briefly.

关键词： GaN AlGaN graded

Household Consumption in China Being Upgraded

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China's Foreign Trade 2019年第4期 38-39页

作者： Liu Xinwei 不详

As the 80s-,90s-,and the post-2000s generations become major consumers,the Internet platform has witnessed the success of more companies,and at the same time,has embraced the arrival of Consumption 4.0 in *** the past,consumers’purchases were determined by a demand economy due to limited ***,with the advancing of economic reforms,consumers were no longer restricted by choices and started to pursue goods of a higher *** we’ve finally come to a stage where diverse needs are satisfied through consumption by means of customization.

关键词： companies Consumption graded

Vibration analysis of FG annular sector in moderately thick plates with two piezoelectric layers

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Applied Mathematics and Mechanics(English Edition) 2019年第6期40卷 783-804页

作者： S.AZARIPOUR M.BAGHANI School of Mechanical Engineering College of Engineering University of Tehran

Free vibration of functionally graded (FG) annular sector plates embedded with two piezoelectric layers is studied with a generalized differential quadrature (GDQ) method. Based on the first-order shear deformation (FSD) plate theory and Hamilton’s principle with parameters satisfying Maxwell’s electrostatics equation in the piezoelectric layers, governing equations of motion are developed. Both open and closed circuit (shortly connected) boundary conditions on the piezoelectric surfaces, which are respective conditions for sensors and actuators, are accounted for. It is observed that the open circuit condition gives higher natural frequencies than a shortly connected condition. For the simulation of the potential electric function in piezoelectric layers, a sinusoidal function in the transverse direction is considered. It is assumed that properties of the FG material (FGM) change continuously through the thickness according to a power distribution law. The fast rate convergence and accuracy of the GDQ method with a small number of grid points are demonstrated through some numerical examples. With various combinations of free, clamped, and simply supported boundary conditions, the effects of the thicknesses of piezoelectric layers and host plate, power law index of FGMs, and plate geometrical parameters (e.g., angle and radii of annular sector) on the in-plane and out-of-plane nat-ural frequencies for different FG and piezoelectric materials are also studied. Results can be used to predict the behaviors of FG and piezoelectric materials in mechanical systems.

关键词： free vibration annular sector piezoelectric functionally graded material (FGM) first-order shear deformation (FSD)

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关于分形理论的哲学思考

哲学动态 1993年第6期 35-,30页

作者：李后强

关于分形理论的哲学思考李后强分形理论被誉为现代非线性科学的前沿领域，也是哲学家们感兴趣的课题之一。由于世界的本质是非线性的，而分形是非线性特征的几何表现，因此，分形性应是大自然的一种基本属性。所谓分形是指一个分形是由... 详细信息

关于分形理论的哲学思考李后强分形理论被誉为现代非线性科学的前沿领域，也是哲学家们感兴趣的课题之一。由于世界的本质是非线性的，而分形是非线性特征的几何表现，因此，分形性应是大自然的一种基本属性。所谓分形是指一个分形是由与整体以某种方式相似的各个部分所组成的客体。分形理论与耗散结构理论、混饨理论是相互补充和紧密联系的，都是在非线性科学研究中所取得的重要成果。分形理论从几何学角度研究不可积系统几何图形的自相似性，可能成为定量描述耗散结构和混饨吸引子这样一些复杂现象的有力工具。部分与整体的关系这对古老的哲学范畴，是分形理论研究对象。把复杂事物分解为要素来研究是一条方法论原则，哲学史上，人们很早就认识区ｕ，整体由部分组成，可通过认识部分来映象整体。系统中每一个元素都反映和含有整个系统的性质和信息，即元素映现系统，这可能是分形论的哲学基础之一。从分析事物的视角方面来看，分形论和系统论分别体现了从两个极端出发的思路。它们之间的互补恰恰完整地构成了辩证的思维方法。分形论的提出，或许有以下几个方面的意义：（１）它打破了整体与部分之间的隔膜，找到了部分过渡到整体的媒介和桥梁即整体与部分之间的相似。

关键词： bottleneck TSP matrices graded up its columns assignment cycles NP-hard P-problem efficient algorithm.

China’s Consumption Structure Steadily Upgraded

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China Today 2020年第9期69卷 54-55页

作者： WANG TIANTIAN Chinese Economic Information Network of the State Information Center

Aa the international community was plagued by raging uncertainty and weak external demand,consumption served as the engine propelling China's economic growth in the past year,stabilizing China's economic growth expect... 详细信息

关键词： Consumption graded stabilizing

Rotating sandwich cylindrical shells with an FGM core and two FGPM layers: free vibration analysis

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Applied Mathematics and Mechanics(English Edition) 2019年第4期40卷 563-578页

作者： R.KARROUBI M.IRANI-RAHAGHI Department of Solid Mechanics Faculty of Mechanical Engineering University of Kashan

The free vibration analysis of a rotating cylindrical shell with an analytical method is investigated. The shell is considered as a sandwich structure, where the middle layer is a functionally graded material(FGM) shell, and it is surrounded by two piezoelectric layers. Considering piezoelectric materials to be functionally graded(FG),the material properties vary along the thickness direction as one innovation of this *** the first-order shear deformation theory(FSDT), the equations of motion of this electromechanical system are derived as the partial differential equations(PDEs) using Hamilton's principle. Then, the Galerkin procedure is used to discretize the governing equations, and the present results are compared with the previously published results for both isotropic and FGM shells to verify the analytical method. Finally, the effects of FGM and functionally graded piezoelectric material(FGPM) properties as well as the thickness ratio and the axial and circumferential wave numbers on the natural frequencies are studied. Moreover, the Campbell diagram is plotted and discussed through the governing equations. The present results show that increasing the non-homogeneous index of the FGM decreases the natural frequencies on the contrary of the effect of non-homogeneous index of the FGPM.

关键词： vibration sandwich structure rotating shell functionally graded material(FGM) functionally graded piezoelectric material(FGPM)

Preparation and Gas Sensing Performance of Hierarchical Porous ZnO-based Materials with Sunflower Rods as a Biological Template

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Chemical Research in Chinese Universities 2019年第5期35卷 755-761页

作者： WANG Bowei ZENG Qingrui CHEN Shu YUE Tongtong HAN Bing FENG Wei YANG Defeng Second Hospital of Jilin University Changchun 130021P.R.China Key Laboratory of Groundwater Resource and Environment Ministry of EducationCollege of Environment and ResourcesJilin UniversityChangchun 130021P.R.China

A graded porous structure SnO2/ZnO composite was prepared with sunflower rods as a biological template. The prepared samples were subjected to phase analysis by scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffractiometry(XRD) and X-ray photoelectron spectroscopy(XPS).ZnO sample was a pure phase of hexagonal wurtzite, and the template had been completely removed. The surface of the sample presented a honeycomb-like structure of a sunflower rod template, which was formed by interconnecting the porous channels, and had a smaller average size and exhibited n-n heterojunction at tlie n-type ZnO interface. Compared with that of pure ZnO, the response of the hierarchical porous structure SnO2/ZnO composite to 100 mg/L w-butanol reached a maximiuTi of 40.61 at 240℃, about 2.7 times higher than that of pure ZnO. Its response time and recovery time are 6 and 3 s, respectively, which are also better than those of pure ZnO. SnO2/ZnO composite exhibits good gas selectivity, which is related to the improvement of the structure and the forming of n-n heterojunctions of the material.

关键词： Sunflower stem SnO2/ZnO graded porous structure Gas sensitivity n-Butanol

Dynamic Fracture Analysis of Functionally Gradient Materials with Two Cracks By Peridynamic Modeling

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Computer Modeling in Engineering & Sciences 2019年第11期121卷 445-464页

作者： Zhanqi Cheng Dongdong Jin Chengfang Yuan Le Li School of Civil Engineering Zhengzhou UniversityZhengzhou450001China

In the research,the dynamic fracture failure problem of functionally graded materials(FGMs)containing two pre-cracks was analyzed using a bond-based Peridynamic(PD)method numerical *** two convergence of decreasing the area of PD horizon(δ-convergence)and uniform mesh refinement(m-convergence)were *** effects of both crack position and distance between two cracks on crack propagation pattern in FGMs plate under tensile loads are ***,the effects of different gradient patterns on the dynamic propagation of cracks in FGMs are also *** simulate results suggest that the cracks positions and the distance between them can significantly influence the dynamic propagation of crack in *** mode also has a certain effect on crack propagation,but the effect of specific gradient variation patterns on dynamic propagation of crack is finite.

关键词： Peridynamic functionally graded materials crack propagation dynamic loads

Cohesion variation during instability evolution of disaster medium in mud inrush of mountain tunnel

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Journal of Mountain Science 2019年第11期16卷 2519-2531页

作者： YANG Teng ZHANG Qing-song ZHANG Xiao LI Xiang-hui ZHANG Jia-qi SUN Yu-xue LI Zhuang Geotechnical & Structural Engineering Research Center Shandong University

Mud inrush in mountain tunnel is an independent geological hazard type different from water inrush,landslide and debris *** intrinsic factor of mud inrush is the instability failure of disaster *** essence is that when the cohesion decreases gradually with the increase of void ratio to the point where the movement of soil particles cannot be restricted,soil particles and groundwater form slurry and gush ***,accurate calculation of cohesion with variable void ratios is crucial for analyzing the reliability of disaster *** this study,the disaster medium was regarded as graded soil and a structural model was established wherein soil particles were simplified as cubes and the inter-particle pores were represented by the clearance between *** the basis of the structure model of disaster medium,a function between the soil particle distance and void ratio was *** is equivalent to the resultant force between soil particles per unit area;thus,a cohesion function was derived in which the void ratio is the main *** function considers the influence of gradation characteristics on cohesion variation and is generally applicable to various types of disaster medium.A series of direct shear tests were carried out to determine the cohesion variation for different types of disaster medium with variable void *** comparing the variation of cohesion obtained through direct shear tests with those deduced by the proposed cohesion function,we verified the validity and general applicability of the cohesion *** is of great significance because the cohesion function can accurately predict the variation of cohesion by using the void ratio,and effectively evaluate the possibility of mud inrush according to the initial mechanical properties of disaster medium.

关键词： Cohesion Disaster medium graded soil Structure model Void ratio Shear test