Influence of porosity distribution on nonlinear free vibration and transient responses of porous functionally graded skew plates

This article deals with the investigation of the effects of porosity distributions on nonlinear free vibration and transient analysis of porous functionally graded skew(PFGS)plates.The effective material properties of the PFGS plates are obtained from the modified power-law equations in which gradation varies through the thickness of the PFGS plate.A nonlinear finite element(FE)formulation for the overall PFGS plate is derived by adopting first-order shear deformation theory(FSDT)in conjunction with von Karman’s nonlinear strain displacement relations.The governing equations of the PFGS plate are derived using the principle of virtual work.The direct iterative method and Newmark’s integration technique are espoused to solve nonlinear mathematical relations.The influences of the porosity distributions and porosity parameter indices on the nonlinear frequency responses of the PFGS plate for different skew angles are studied in various parameters.The effects of volume fraction grading index and skew angle on the plate’s nonlinear dynamic responses for various porosity distributions are illustrated in detail.

Influence of active constrained layer damping on the coupled vibration response of functionally graded magneto-electro-elastic plates with skewed edges

This article makes the first attempt in assessing the influence of active constrained layer damping(ACLD)treatment towards precise control of frequency responses of functionally graded skew-magneto-electroelastic(FGSMEE)plates by employing finite element methods.The materials are functionally graded across the thickness of the plate in terms of modest power-law distributions.The principal equations of motion of FGSMEE are derived via Hamilton’s principle and solved using condensation technique.The effect of ACLD patches are modelled by following the complex modulus approach(CMA).Additionally,distinctive emphasis is laid to evaluate the influence of geometrical skewness on the attenuation capabilities of the plate.The accuracy of the current analysis is corroborated with comparison of previous researches of similar kind.Additionally,a complete parametric study is directed to understand the combined impacts of various factors like coupling fields,patch location,fiber orientation of piezoelectric patch in association with skew angle and power-law index.

Accurate Free Vibration of Functionally Graded Skew Plates

The present study aims to analyze free vibration of thin skew plates made of functionally graded material(FGM)by using the weak form quadrature element method.The material properties vary continuously through the thickness according to a power-law form.A novel FGM skew plate element is formulated according to the neutral surface based plate theory and with the help of the differential quadrature rule.For verifications,Numerical results are compared with available data in literature.Results reveal that the non-dimensional frequency parameters of the FGM skew plates are independent of the power-law exponent and always proportional to those of homogeneous isotropic ones when the coupling and rotary inertias are neglected.In addition,employing the physical neutral surface based plate theory is equivalent to using the middle plane based plate theory with the reduced flexural modulus matrix.

NAVIER SOLUTION FOR THE ELASTIC EQUILIBRIUM PROBLEMS OF ANISOTROPIC SKEW THIN PLATE WITE VARIABLE THICKNESS IN NONLINEAR THEORIES

This paper discusses the elastic equilibrium problems of anisotropic skew thin plate of variable thickness simply supported on all four sides in nonlinear theories, and uses the Navier method to seek an approach to the problem, and to illustrate the solution with the examples. In conclusion, the mention is made of the scope of application and the convergency of the solution.

全框支厚板转换斜交高层结构抗震性能研究

设计制作1∶15全框支厚板转换高层结构的微粒混凝土振动台试验模型,进行7度小震、中震、大震以及8度大震作用下单向、双向、三向共计44组工况的振动台试验,研究动力特性、动力放大系数、层间位移角等性能指标,揭示结构塑性损伤发展机制,进一步采用数值模型研究上部塔楼斜交角度对结构抗震性能的影响。结果表明,全框支厚板转换高层结构具有优良的抗震性能,模型结构经历8度大震后,全框支层未见明显裂缝,处于轻微损坏与完好之间,塔楼剪力墙底部和连梁端部裂缝发生明显,薄弱部位集中在3~10层;模型结构动力放大系数沿高度呈“S”形分布模式,在塔楼顶部放大明显,而全框支层的动力放大系数在不同烈度地震作用下始终处于1~2之间;塔楼斜交角度对此类结构体系动力特性和动力响应的影响很小,全框支层均能对上部不同斜交角度的塔楼起到充分的约束作用,上部塔楼承担绝大部分地震输入能量,全框支层的动力放大系数和动力响应均远低于上部塔楼,全框支厚板转换斜交高层结构体系能够实现“强全框支层弱塔楼”设计理念。

基于Skew-t-GJRGARCH(1,1)模型的5G板块风险度量研究

本文对5G板块进行风险度量研究,结果表明:对数收益率序列存在有偏、尖峰厚尾、非正态的特征,同时具有ARCH效应;通过拟合不同分布下的GJRGARCH(1,1)模型,发现5G板块不存在杠杆效应;采用GJRGARCH(1,1)模型在不同分布下进行VaR计算,由Kupiec检验得到基于skew-t分布的GJRGARCH(1,1)模型可以更好地度量5G板块的金融风险,其可信度和稳健性强。

Free Vibration Analysis of Functionally Graded Plates with Multiple Circular and Non-circular Cutouts

Cutouts are inevitable in structures due to practical consideration.In order to investigate the free vibration of functionally graded plates with multiple circular and non-circular cutouts,finite element method is used.The volume fraction of the material constituents is assumed to follow a simple power law distribution.The parameters considered in this paper are as follows：cutout size,cutout location,number of cutouts and different boundary conditions.It should be mentioned that free vibration for FG plates（such as rectangular？skew？trapezoidal？circular plates） with multiple cutouts has not been studied yet and hence the results out coming from this paper may be used as bench marks for future works.

Axisymmetric free vibrations of infinite micropolar thermoelastic plate

The propagation of axisymmetric free vibrations in an infinite homogeneous isotropic micropolar thermoelastic plate without energy dissipation subjected to stress free and rigidly fixed boundary conditions is investigated. The secular equations for homogeneous isotropic micropolar thermoelastic plate without energy dissipation in closed form for symmetric and skew symmetric wave modes of propagation are derived. The different regions of secular equations are obtained. At short wavelength limits, the secular equations for symmetric and skew symmetric modes of wave propagation in a stress free insulated and isothermal plate reduce to Rayleigh surface wave frequency equation. The results for thermoelastic, micropolar elastic and elastic materials are obtained as particular cases from the derived secular equations. The amplitudes of displacement components, microrotation and temperature distribution are also computed during the symmetric and skew symmetric motion of the plate. The dispersion curves for symmetric and skew symmetric modes and amplitudes of displacement components, microrotation and temperature distribution in case of fundamental symmetric and skew symmetric modes are presented graphically. The analytical and numerical results are found to be in close agreement.

Prediction of Skewed Bridge Behaviors with Arbitrary Boundary Conditions—— Theoretical Approach and Its Design Application

In this paper, we report on an analytical solution for beam-type skewed highway bridges subjected to truck loading. To confirm the analysis derivation and the solution obtained, the moment and shear responses to the design truck load are acquired using the analytical method for a number of typical US highway bridges and compared with those from numerical finite element method （FEM） analysis. In addition, the lateral distribution factors for moment and shear used in routine design are investigated based on comparison of the analytical approach and FEM. The analytical solution is shown in good agreement with the FEM result. Furthermore, the relevant provisions in the American Association of State Highway Transportation Officials＇ （AASHTO＇s） LRFD Bridge Design Specifications are also discussed here for comparison, particularly with respect to design application. It is observed that the design code specified load distribution factor may not predict well, especially for shear and/or severe skew.

基于群速度校准的超声导波技术及在复合材料缺陷检测中的应用

由于在复合材料板中传播的超声导波具有偏斜效应,使得理论群速度与试验测得的群速度不一致,因此需要对群速度幅值和传播方向进行校准。数值计算复合材料板中超声导波频散方程得到S0模态各个方向的理论相速度频散曲线。运用群速度校准法则对S0模态群速度幅度和传播方向进行修正。校准后的理论群速度与试验测得的群速度较为吻合。试验中采用频率200 kHz的S0模态对碳纤维复合材料板中的模拟缺陷进行检测。结果显示采用校准后群速度和试验测得的群速度可准确定位缺陷,且具有很好的一致性。因此,采用群速度校准法则可有效提高各向异性复合材料结构中超声导波的缺陷定位和识别能力。

沟槽面湍流边界层减阻特性研究

在光滑平板中分别嵌入一段不同尺寸的沟槽板 ,通过分析沟槽板前后流场速度分布、紊动特性等的变化 ,得出 :沟槽板上粘性底层厚度比沟槽板上、下游光滑平板处增大 ,沟槽板上流速分布对数公式中的 C值也比上、下游光滑平板的 C值大 ,说明沟槽板上局部摩擦阻力较小 。

使色谱峰产生拖尾的一个因素──柱出口效应

使用塔板理论证明存在一种使正常色谱峰产生拖尾的因素──柱出口效应。证明符合线性分 配的样品组分虽然在色谱柱内存在３种不同浓度的分布形态，但在流出色谱柱后却都因柱出口效应的 影响而转变成拖尾峰。在不加任何近似处理的情况下，使用塔板理论直接对不同塔板数、容量因子的色 谱峰不对称性进行了计算；计算结果同样支持了柱出口效应的存在。

塔板理论对柱内和柱外浓度分布曲线的描述

使用VisualBasic和QBasic程序 ,分别在Excel和DOS上 ,在不做任何化简的情况下 ,对塔板理论描述的柱内和柱外组分浓度分布进行了研究。发现符合线性分配的样品组分在色谱柱内存在 3种不同的浓度分布形态 ,在色谱柱外则都是拖尾峰形态。分析了不同分配比对柱内和柱外浓度分布曲线最高点和次高点的影响。

基于投影的车牌倾斜检测方法

图像倾斜检测是车牌识别中的关键环节之一。典型的倾斜检测算法是进行 Hough 变换后寻找长直线的倾斜角度。在实际应用中,车牌图像中未必有明显的较长直线,或者长直线对正确检测形成干扰。本文介绍一种基于投影的车牌图像倾斜检测方法,通过对车牌图像做各种角度投影,寻找投影图像峰宽最窄的角度,即是图像的倾斜角度。测试结果表明了这种方法的有效性。

一种对实摄图象的变形矫正算法

提出了一种对实摄图象的变形矫正算法．它通过对目标区域在水平和垂直方向计算差分，并对投影所得结果计算方差，找出使方差达到最大的直线，并按这两条直线来对原图进行矫正．结果显示，用此方法不仅对于矫正实摄车辆牌照字符的变形有较好的效果，而且对其他字符以及一些图形图象也有一定的矫正效果．

斜交板弯曲理论的斜交坐标法

斜交板是工程中的一种常用结构,建立其弯曲微分方程是获得解析解的难点和关键.本文在正交坐标系的薄板弯曲理论的基础上,利用坐标转换,建立了斜交坐标系中各向同性、正交异性和斜交异性的斜板弯曲微分方程,并简要介绍该方法推广应用于平行四边形斜板有限元法的思路.较文献[1-3]的方法而言,利用本文提出的斜交坐标转换法可大大简化弯曲微分方程推导过程,且可方便地推广应用到斜交箱梁等其它结构中.

基于历史车牌识别数据的套牌车并行检测方法

针对现有套牌车检测方法中所具有的成本高及检测效率低等缺点,提出一种基于历史车牌识别数据(ANPR)集的套牌车并行检测方法 TP-Finder,实现了基于整数划分的数据分块策略,能有效求解大规模数据并行处理时的数据倾斜问题,显著提升套牌车辆的发现性能。此外,实现了基于TP-Finder方法的套牌车辆查询系统,可准确呈现所有疑似套牌车辆的历史行车轨迹。最后,在某市真实交通数据集上对TP-Finder方法的性能进行了实验验证。实验结果表明,与缺省的MapReduce分块策略相比较,TP-Finder的分块策略能够带来最大20%的性能提升。

关于斜交异性斜板的弯曲理论

作为对作者以前发表的外交各向异性极弯曲理论[1～3]的改进，文中对这种材料异性极的弯曲，从新的应变关系和物理方程出发，演引出新的弹性平衡微分方程，并提示其实用近似求解方法．

斜交薄壁连续钢箱梁桥设计与受力特性研究

以江苏省丹阳路齐梁路某(30+2×35)m跨线斜交钢箱梁为工程背景,通过比对斜交钢箱梁横隔板布置方式以及支座处隔板布置方式,提出斜交连续梁横向隔板的正交布置方式,得出中间墩支承处采用斜向双隔板布置更有利于结构受力与制造的结论。对箱梁的线型控制、截面总体布置、隔板、纵肋型式、纵肋布置方式和板厚等其他细节进行详细设计。分别建立单梁、空间梁格和板单元有限元模型对桥梁进行受力分析。对3种数值模拟方法计算得出的支座反力、挠度和应力等结果进行分析对比。研究结果表明:单梁法计算结果偏于不安全且无法进行横向计算,梁格法和板单元法均能够对模型进行横向计算,但梁格法计算偏安全,而板单元计算更加细致精确。同时,在同种工况下,斜交钢箱梁钝角区应力值大于锐角区应力值。采用板单元对轮压荷载进行局部分析,表明轮压荷载作用下应力、变形较小。验证了箱梁设计方案的安全合理。

基于灭点的倾斜畸变车牌图像快速校正方法研究

由于相机与汽车牌照之间的方位关系导致了拍摄图像发生倾斜畸变,极大影响了车牌识别率。针对这一问题,利用畸变图像所蕴涵的灭点信息,提出了一种快速校正方法:首先对图像进行预处理,提取车牌的四条边框来产生灭点;然后根据灭点信息快速标定相机内参数并计算空间平面重建矩阵;最后进行空间坐标变换和灰度插值完成畸变图像的校正。实验表明,该方法对于倾斜畸变车牌有良好的校正效果,并有效提高了识别率。