New matrix method for analyzing vibration and damping effect of sandwich circular cylindrical shell with viscoelastic core

Based on the linear theories of thin cylindrical shells and viscoelastic materials, a governing equation describing vibration of a sandwich circular cylindrical shell with a viscoelastic core under harmonic excitation is derived. The equation can be written as a matrix differential equation of the first order, and is obtained by considering the energy dissipation due to the shear deformation of the viscoelastic core layer and the interaction between all layers. A new matrix method for solving the governing equation is then presented With an extended homogeneous capacity precision integration approach. Having obtained these, vibration characteristics and damping effect of the sandwich cylindrical shell can be studied. The method differs from a recently published work as the state vector in the governing equation is composed of displacements and internal forces of the sandwich shell rather than displacements and their derivatives. So the present method can be applied to solve dynamic problems of the kind of sandwich shells with various boundary conditions and partially constrained layer damping. Numerical examples show that the proposed approach is effective and reliable compared with the existing methods.     

无压烧结制备Y2MgAl4SiO12∶Ce3+荧光陶瓷及光学性能

Y₃Al₅O₁₂∶Ce³⁺荧光粉是目前白光LED的主要发光材料,但在使用时存在封装树脂因散热不佳而发生老化等问题。本文采用无压烧结制备了Y₂MgAl₄SiO₁₂∶Ce³⁺透明陶瓷荧光体,用于替代荧光粉体和调控发光性能。首先通过化学共沉淀法制备前驱体粉体,经高温煅烧后采用冷等静压成型,最后在马弗炉中1 600℃煅烧制得透明荧光陶瓷。研究了Ce³⁺掺杂浓度和样品厚度对材料性能的影响,其中掺杂量为0.5%的样品在800 nm处具有56%的透过率,在450 K下发光强度仍能保持室温强度的84%。与蓝光芯片组装成器件测试表明,荧光陶瓷在蓝光LEDs/LDs的激发下发出白光,其CIE色度坐标分别为(0.307 6,0.332 9)和(0.308 0,0.331 6),光效分别为62.6 lm/W和146.3 lm/W。研究结果表明,YMAS∶Ce荧光陶瓷可应用于白光LEDs/LDs领域。     

Synthesis of New Ruthenium(II) Bipyridyl Complexes and Studies on Their Photophysical and Photoelectrochemical Properties

IntroductionDye sensitizedsolarcells (DSSC)havebecomethefocusofmanyinvestigationssinceMichaelGr tzelandco workersmadethedyemoleculesadsorbedonaporousnet workoftheinterconnectednanometer sizedcrystallinesofawidebandgapsemiconductor.1 3Animpressivesolar to electricalenergyconversionefficiencyof 10 %hasbeenre portedanditmakespracticalapplicationfeasible .4 Thissystemconsistsofadye coatedsemiconductorelectrodeandacounterelectrodearrangedinasandwichconfigura tionandtheinter electrodespaceisfilled…     

Periodic and Chaotic Breathers in the Nonlinear Schroedinger Equation

The breathers in the cubic nonlinear Schroedinger equation are investigated numerically by using the symplectic method. We show that the solitonlike wave, the periodic, quasiperiodic and chaotic breathers can be observed with the increase of cubic nonlinear perturbation. Finally, we discuss the breathers in the cubic-quintic nonlinear Schroedinger equation with the increase of quintic nonlinear perturbation.     

高强钢波纹夹芯结构的力学性能研究

本文利用ABAQUS仿真软件分析了高强钢波纹夹芯结构在三点弯曲以及面内压缩时的力学响应。将计算结果与实验值和理论值进行了对比,验证了数值模拟的准确性。分析了芯板材料属性（高强钢DP900和普通低碳钢DC01）以及波纹芯板排列方向(横向、纵向)对夹芯结构力学性能的影响。结果表明DP900高强钢波纹芯板夹芯结构抗弯强度是DC01低碳钢夹芯结构的2.39倍,抗压强度是低碳钢夹芯结构的1.40倍,纵向波纹夹芯结构比横向波纹夹芯结构弯曲刚度高11.63倍。     

复数矢径虚拟边界谱方法在二维空穴声辐射和散射问题中的应用

基于复数矢径虚拟边界积分法,通过将虚拟积分曲线上的未知源强密度函数用Fourier级数展开,同时借助快速数值Fourier变换计算程序,提出了一种求解二维任意形状空穴声辐射和散射问题的复数矢径虚拟边界谱方法．该方法具有以下特点：(1)不存在奇异积分处理;(2)采用复数矢径虚拟边界积分方法,不仅保证了解的唯一性,而且由于虚拟源强密度函数采用Fourier级数展开,克服了用单元离散方法不能用于较高频率范围的缺点;(3)采用快速数值Fourier变换技术使计算效率大幅度提高．文中给出的计算结果表明：在求解任意形状二维空穴声辐射和散射问题上较通常采用的FEM、BEM和VBEM更为有效．     

变厚度圆柱壳的轴对称变形

文献[1]用有限板条法求解了变厚度矩形板的稳定与振动问题。本文利用这个基本思想,把它推广到求解在任意支承下带封端和加劲环的变厚度圆柱壳的轴对称变形中去。文中导出了圆柱壳元的传递矩阵和节线的相关矩阵。相关矩阵的迁移同样从两端开始,同时向中间节线延伸。最后,只归结为解一个二元一次代数方程组。这样,计算既简便又迅速。     

变厚度矩形板的稳定与振动

近年来许多作者研究了用有限板条法解矩形板的各种问题,实践证明这是有效的方法。本文提出的离散化方法计算十分简便。 1、节点线的相关矩阵 对于离散化了的板,每一个板单元相当于一个等厚度的板条。板条宽δ_i和板条厚t_i随具体分割而定。设所研究的板搁在弹性地基上,面内沿x方向承受均布压力N(图1)。板激振后的运动可展成单三角级数形式     

Chater梁屈曲传播的动态分析

本文从非线性有限元的一般方法出发,结合应用加权残数技术和ALE边界元法,对Chater梁的屈曲传播进行了完全的动态分析,抛弃了前人一直采用的准静态和动稳态假设;另外,基于势流理论和非线性液面条件,还考虑了结构充液后由于流固耦合作用对屈曲传播所造成的影响,大量算例揭示了结构的菲线性、作用载荷、屈曲传播速度以及液体介质之间的内在关系,从而对屈曲传播有了更深入的认识。     

变水深环境下中厚度浮板耦振问题的一个变分解

本文从Reissner 板的理论出发,提出并论证了变水深环境下中厚度浮板耦振问题的一个局部变分原理,它是建立中厚度浮板各种近似分析方法的一个有力工具,借助这个变分原理,文中还导得了一个计算中厚度浮板固有频率的一个变分式,数值算例表明本文方法具有精度高和省机时的优点。