Growth of the Single Crystal of Solid Solution by "Melting Zone of Different Compositions" Technique

1.IntroductionItiswellknownthatsinglecrystalsofsolidsolu-tionhavewideapplicationsinmanyfieldst1~3].How-ever,asshowninFig.1,greatdifficultiesarisewhenasinglecrystalofsuchaphaseispreparedbecauseofitshighdistribution..effici.ntl4'5].IfthemastermaterialwithacompositionCisprepared,thecompositionofpreparedsinglecrystalinthebeginningwillbeC*.Thenthecontentofas-componentBincreaseswiththegrowingprocessandinducesseriousaxial(alongthegrowingdirec-tion)segregation.Becausetheliquidustemperatureofcomposit…     

National Standard of "General Requeston Biological Safety" Was Officially Issued

May 28 2004, sponsored by Standardization Administration of P.R.China(SAC)and Certi-fication and Accreditation Administration of P.R.Chi-na (CNCA), China National Accreditation Board For Laboratories (CNAL) organized the press conference on National Standard of “General Request on Biolog-ical Safety”in Beijing. The National Standard of “General Request on Bi-ological Safety”(GB 19489-2004) was proposed by the Science and Technology Ministry of P.R.China and CNCA, and w…     

Shanghai Takes the Leading in Setting up the Post of "Standardization Engineer"

With the entry to the WTO and the development of economy and society of China, the work of standardization has been drawing high attention from the government and the enterprise. Shanghai, as the significant hub of economy, science and technology, finance, and trade of China and the Asian-Pacific region, is in urgent need of setting up a specialized personnel on standardization, which requires its staff have their     

Application of "parallel" moiré deflectometry and the single beam Z-scan technique in the measurement of the nonlinear refractive index

In this paper, the application of "parallel" moiré deflectometry in measuring the nonlinear refractive index of materials is reported. In "parallel" moiré deflectometry the grating vectors are parallel, and the resulting moiré fringes are also parallel to the grating lines. Compared to "rotational" moiré deflectometry and the Z-scan technique, which cannot easily determine the moiré fringe's angle of rotation and is sensitive to power fluctuations, respectively, "parallel" moiré deflectometry is more reliable, which allows one to measure the radius of curvature of the light beam by measuring the moiré fringe spacing. The nonlinear refractive index of the sample, including the sense of the change, is obtained from the moiré fringe spacing curve. The method is applied for measuring the nonlinear refractive index of ferrofluids.     

The effect of rippling on the mechanical properties of grapheneOA

Graphene is the stiffest material known so far but, due to its one-atom thickness, it is also very bendable.Consequently, free-standing graphene exhibit ripples that has major effects on its elastic properties. Here we will summarize three experiments where the influence of rippling is essential to address the results. Firstly, we observed that atomic vacancies lessen the negative thermal expansion coefficient(TEC) of free-standing graphene.We also observed an increase of the Young?s modulus wit...     

An overview of recent progress in the development of flexible electrochromic devicesOA

Electrochromic materials are capable of reversibly switching their colors or optical properties through redox reactions under applied voltages, which have shown great potential applications including smart windows, non-emissive displays, optical filters, among others. Although the current rigid electrochromic devices have shown emerging interest and developed rapidly, many applications(e.g., wearable/deformable optoelectronics) are blocked due to their inflexible features. Herein, the adaption o...     

Dynamic properties of a flexible metal-organic framework exhibiting a unique"picture frame"-like crystal morphology

The precise control of the crystal morphology of metal-organic frameworks(MOFs)enables optimization of its adsorptive properties,as well as enables better integration within functional devices.However,the influence of such modifications on the dynamic properties of flexible MOFs is poorly understood Here,we report the synthesis of a series of Cu₂(bdc)₂(bpy)(bdc^2-=1,4-benzenedicarboxylate;bpy=4,4,-bipyridine)crystals having an unusual picture frame-like morphology that results from a restriction in the quantity of bpy pillars added to the reaction mixture during the intercalation of the Cu₂(bdc)₂(MeOH)₂layers.The width of the frames is found to correlate with the quantity of bpy,and importantly,causes the dynamic properties of the resulting Cu₂(bdc)₂(bpy)material to vary between rigid,elastic,and shape memory modes.In all,the results demonstrate the potential for the properties of MOFs to be optimized via subtle manipulations in the crystal morphology rather than changes in the overall material composition.     

Coordinated Control of Fine-Particle and Ozone Pollution by the Substantial Reduction of Nitrogen OxidesOA

<正>1. Introduction In recent years, the air quality in China has improved significantly. In many cities, however, the concentration of fine particulate matter (PM2.5) remains higher than the secondary-level national ambient air quality standard (NAAQS level-2, 35μg·m^-3,GB3095–2012 [1]) and much higher than the first-level NAAQS(15μg·m^-3, GB3095–2012 [1]) and the World Health Organization(WHO) air quality guidelines (5μg·m^-3).     

Calculation of Structural Characteristics Evolution during Superplastic Forming of Shells by

The applications of commercial computer program set "SPLEN-O" based on finite elements method (FEM) for the simulation of superplastic forming (SPF) technology of shells are described. The changes in characteristics of ultrafine-grained (UFG) structure during deformation are taken into account in function of viscosity and solving algorithm. Some examples are shown to illustrate the possibilities of FEM simulation for prediction of numerical grain-size data on different SPF stages of shells.     

Finite Element Modelling and the Experimental Verification of Superplastic Forming

FEM analysis has proved to be a powerful investigative tool capable of encompassing all the aspects that characterise an SPF process. However, despite the high potential of FEM programs they do not allow one to directly and suitably obtain the thickness of a sheet product for high deformation values, as commonly occurs in SPF processes. Many papers have been published on finite element analysis of S.P.F. process but the question of calculus accuracy in thicknesses of a sheet product has not been directly investigated. This problem has been already considered by the authors in a previous study which proposed an algorithm to determine thicknesses for a specific application. The software set up starts out with the results of the FEM modelling, keeps track of the deformation undergone by each element of the mesh and calculates to a good approximation the thicknesses at the end of the forming. Although the original version of the algorithm could only be used for the application studied an updated version is introduced in this study that can be used for any case. In other words, the software generates the thickness profile at the end of the analysis independently of technological set up, item shape and type of simulation (3D and 2D). The proposed algorithm was tested with reference to the superplastic forming of an item of simple geometry beginning with a thin circular plate blocked at the edges and put under constant hydrostatic pressure on one side. The test material, made superplastic by means of a series of repeated laminations, was characterised using an alternative method to the traditional tension test. The results of the experiments are in good accordance with the numerical predictions both in terms of thickness distribution and forming times.     

A coupled FEM-MFS method for the vibro-acoustic simulation of laminated poro-elastic shells

A new simulation method for the vibro-acoustic simulation of poro-elastic shells is presented. The proposed methods can be used to investigate arbitrary curved layered panels, as well as their interaction with the surrounding air. We employ a high-order finite element method (FEM) for the discretization of the shell structure. We assume that the shell geometry is given parametrically or implicitly. For both cases the exact geometry is used in the simulation. In order to discretize the fluid surrounding the structure, a variational variant of the method of fundamental solutions (MFS) is developed. Thus, the meshing of the fluid domain can be avoided and in the case of unbounded domains the Sommerfeld radiation condition is fulfilled. In order to simulate coupled fluid-structure interaction problems, the FEM and the MFS are combined to a coupled method. The implementation of the uncoupled FEM for the shell and the uncoupled MFS is verified against numerical examples based on the method of manufactured solutions. For the verification of the coupled method an example with a known exact solution is considered. In order to show the potential of the method sound transmission from cavities to exterior half-spaces is simulated.     

摩托车发动机壳体辐射噪声控制研究

利用FEM/BEM(Finite Element Method/Boundary Element Method)方法分析摩托车发动机壳体的振动特性,对其表面的辐射噪声进行分析研究,对改进前的摩托车发动机壳体进行模态分析、频率响应分析及噪声辐射仿真分析,并用试验进行验证,仿真数据与试验数据基本吻合,表明理论模型的正确性.根据仿真的结果,对壳体结构进行改进(改变壳体的刚度和形状),并对改进后的壳体进行仿真,计算结果表明,壳体的辐射噪声值降低.最后将改进后的壳体进行试验验证,其辐射的噪声值也降低,说明这两种改进方案的正确性.     

Free vibrations of shells of revolution filled with a fluid

This paper describes the method of determining the normal modes of vibrations and natural frequencies of elastic shells of revolution with an arbitrary meridian, partially filled with a fluid. The modes of vibration of the shells with fluids are determined as a linear combination of the natural modes of vibration in vacuum. The solution of the problem of hydroelastic vibrations has been obtained using the methods of the boundary element (BEM) and the finite element (FEM). Numerical investigations of vibrations of hemi-spherical shells conveying fluid have been conducted and analyzed. Illustrative examples are provided to demonstrate the accuracy and efficiency of the developed numerical procedure.     

不锈钢球壳无模液压胀形过程的有限元模拟

用弹塑情限元对不锈钢球壳液胀形过程进行了数值模拟，给出了胀形过程中壳体外形和焊变化规律，分析了应力应变及残余应力分布规律，并与试验结果进行了比较。     

Experimental and numerical study of stress–strain state of pressurised cylindrical shells with external defects

Work presents the experimental technique with using of strain gauges for determining of strain distribution near longitudinal external defects of semielliptical shape in pressurised cylindrical shells and an appropriate procedure of numerical calculation based on a finite element method (FEM) for assessment of strain state near such defects. Numerical assessment of elastic stress distribution at bottom of external semielliptical notch in pressurised cylindrical shell is in a good agreement with the data received on the base of different analytical models. Here, the FEM results and data based on Glinka-Newport model are the most close for maximal stress. A comparison an experimental and calculation results showed on their acceptable coincidence and this fact gives the ground for using the numerical calculations instead labour-intensive and expensive experimental tests.     

基于变环肋间距的碳纤维/环氧树脂复合材料格栅加筋截顶圆锥壳体稳定性

研究均布外压作用下具有非均匀特征的碳纤维/环氧树脂复合材料格栅加筋（AGS）圆锥壳体构型优化。首先,充分考虑复合材料格栅圆锥壳体中格栅非均匀分布造成结构小端材料利用不充分问题,提出变环肋铺设间距的优化分布方式,使格栅在截顶圆锥壳体结构上小端疏大端密。之后,基于考虑格栅非均匀分布及变环肋间距铺设特征的等效刚度模型,并采用最小势能原理得到环肋铺设优化后的AGS圆锥壳体临界载荷值解析式。针对典型锥壳的有限元验证表明解析算法的误差在1%左右,证实了本文提出的分析方法的可靠性和有效性。最后,通过对环肋间距优化圆锥壳体的参数分析,发现优化环肋分布方式可以使AGS锥壳结构的外压稳定性大幅上升。本文研究内容为碳纤维/环氧树脂复合材料AGS圆锥壳体的优化设计提供了一种具有较高承载力的构型,并为此类结构的计算提供了解析算法。     

Shape optimization of shell structures based on NURBS description using automatic differentiation

The consolidation of the link among four fields in computational mathematics and mechanics is the main objective of this work. Surfaces based on NURBS (non‐uniform rational B‐spline), mathematical optimization, the finite element method (FEM) in structural analysis, and automatic differentiation (AD) are applied in shape optimization of shells. This problem is performed taking into account the fact that material and mechanical characteristics influence both, the structural shape and the thickness variation, in order to obtain the best performance with respect to a specific criterium. Some techniques were implemented to modify the shell geometry conserving the same parameterization without a new finite element mesh generation. The shape modification is carried out using an optimization code based on the data obtained by a finite element analysis and gradients evaluation. In this work the optimization procedure is performed using an SQP (Sequential Quadratic Programming) algorithm, where the variables are the control points in homogeneous coordinates, the knot vectors, and the thickness. The functional value is determined by the FEM and gradients are evaluated using AD. Some examples are analyzed and discussed. As a consequence of the shape optimization, shells with high structural performance and aesthetically beautiful shapes can be obtained. Copyright © 2011 John Wiley & Sons, Ltd.