Size dependent free vibration analysis of functionally graded piezoelectric micro/nano shell based on modified couple stress theory with considering thickness stretching effect

Higher-order shear and normal deformation theory is used in this paper to account thickness stretching effect for free vibration analysis of the cylindrical micro/nano shell subjected to an applied voltage and uniform temperature rising.Size dependency is included in governing equations based on the modified couple stress theory.Hamilton’s principle is used to derive governing equations of the cylindrical micro/nano shell.Solution procedure is developed using Navier technique for simply-supported boundary conditions.The numerical results are presented to investigate the effect of significant parameters such as some dimensionless geometric parameters,material properties,applied voltages and temperature rising on the free vibration responses.

Dynamics of Sutterby fluid flow due to a spinning stretching disk with non-Fourier/Fick heat and mass flux models

The magnetohydrodynamic Sutterby fluid flow instigated by a spinning stretchable disk is modeled in this study.The Stefan blowing and heat and mass flux aspects are incorporated in the thermal phenomenon.The conventional models for heat and mass flux,i.e.,Fourier and Fick models,are modified using the Cattaneo-Christov(CC)model for the more accurate modeling of the process.The boundary layer equations that govern this problem are solved using the apt similarity variables.The subsequent system of equations is tackled by the Runge-Kutta-Fehlberg(RKF)scheme.The graphical visualizations of the results are discussed with the physical significance.The rates of mass and heat transmission are evaluated for the augmentation in the pertinent parameters.The Stefan blowing leads to more species diffusion which in turn increases the concentration field of the fluid.The external magnetism is observed to decrease the velocity field.Also,more thermal relaxation leads to a lower thermal field which is due to the increased time required to transfer the heat among fluid particles.The heat transport is enhanced by the stretching of the rotating disk.

The Continuum Stored Energy for Constitutive Modeling Finite Deformations of Polymeric Materials

With symmetries measured by the Lie group and curvatures revealed by differential geometry, the continuum stored energy function possesses a translational deformation component, a rotational deformation component, and an ellipsoidal volumetric deformation component. The function, originally developed for elastomeric polymers, has been extended to model brittle and ductile polymers. The function fits uniaxial tension testing data for brittle, ductile, and elastomeric polymers, and elucidates deformation mechanisms. A clear distinction in damage modes between brittle and ductile deformations has been captured. The von Mises equivalent stress has been evaluated by the function and the newly discovered break-even stretch. Common practices of constitutive modeling, relevant features of existing models and testing methods, and a new perspective on the finite elasticity-plasticity theory have also been offered.

Modified couple stress and thickness-stretching included formulation of a sandwich micro shell subjected to electro-magnetic load resting on elastic foundation

This paper studies electromagnetoelastic static investigation of a sandwich doubly curved microshell subjected to multi-field loading based on a new thickness stretching included refined higher order shear/normal deformable model.Modified-couple-stress-theory(MCST)is used for accounting small-scaledependency.The numerical results are derived using an analytical method.The effect of small scale parameter in micro scale,initial electric and magnetic potentials and foundation parameters is studied on the electromagnetoelastic bending results.It is confirmed an enhancing in stiffness of small scale shell with an increase in micro length scale parameter.

Renormalized Coordinate Stretching: A Generalization of Shoot and Fit with Application to Stellar Structure

The standard shooting and fitting algorithm for non-linear two-point boundary value problems derives from conventional coordinate perturbation theory. We generalize the algorithm using the renormalized perturbation theory of strained coordinates. This allows for the introduction of an arbitrary function, which may be chosen to improve numerical convergence. An application to a problem in stellar structure exemplifies the algorithm and shows that, when used in conjunction with the standard procedure, it has superior convergence compared to the standard one alone.

Group Theory Analysis of Free Convective BoundaryLayer Behavior at a Stretching Surface

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考虑轴向大拉伸下弹性模量对聚酯系泊动态响应的影响

Owing to the particularity of a polyester fiber material,the polyester mooring undergoes large axial tensile deformation over long-term use.Large axial tensile deformation significantly impacts the dynamic response of the mooring system.In addition,the degrees of large axial tension caused by different elastic moduli are also different,and the force on the mooring line is also different.Therefore,it is of great significance to study the influence of elastic modulus on the dynamic results of the mooring systems under large axial tension.Conventional numerical software fails to consider the axial tension deformation of the mooring.Based on the theory of slender rods,this paper derives the formula for large axial tension using the method of overall coordinates and overall slope coordinates and provides the calculation programs.Considering a polyester mooring system as an example,the calculation program and numerical software are used to calculate and compare the static and dynamic analyses to verify the reliability of the calculation program.To make the force change of the mooring obvious,the elastic moduli of three different orders of magnitude are compared and analyzed,and the dynamic response results after large axial tension are compared.This study concludes that the change in the elastic modulus of the polyester mooring changes the result of the vertex tension by generating an axial tension.The smaller the elastic modulus,the larger the forced oscillation motion amplitude of the top point of the mooring line,the more obvious the axial tension phenomenon,and the smaller the force on the top of the polyester mooring.

伏日探析

“夏至三庚便是伏”,伏日又称三伏天,三伏中的“三”示生,“伏”为降伏、制伏之义,庚为金,对应秋之收敛之气。三伏天为一年中自然界阳气最旺盛之期,地面阳热之气较多,暑热燥烈,主升、主动,此时借助庚日敛降之气,将阳气收敛,降伏于土中。人应天,此时人体阳气最为旺盛,宜顺应天地,借天之阳补人体之阳气,选择夏至后第三个具有肃降、降伏之气的庚金之日将自然界的阳热、燥热之气降伏,可蕴藏阳热之气,孕育生升之气,使人体阳气更充沛。

基于黄元御“一气周流”理论探讨妊娠恶阻论治

黄元御将《黄帝内经》气机运动延伸归纳为“一气周流,土枢四象”理论,肝木、心火、肺金、肾水为人体四象,水火为升降两极,木金为左右翼佐,调节阴阳升降。妊娠恶阻发病为妊胎壅阻产妇体内气机,中失斡旋,一气则郁,气郁则滞塞,滞塞而不降,升降反作,故病上逆。病机有水火不济,枢机失常;金弱水衰,痰饮上泛;木亢无制,冲气上逆。治病求本,治宜修复轮、轴关系。若患者恶心呕吐、头昏头晕等症不甚严重,无其他不适,治宜理气开郁,斡旋中气,方选豆蔻苓砂汤加减。火水不交属心火不足而戊土虚寒者,治疗需补心火,方用香砂六君子汤加丁香、良姜;若属肾水亏虚而戊土失养者,治疗需注意滋肾水,方用六味地黄丸加石斛、党参、白术、半夏、化橘红等。湿邪所致者,用药需同时考虑理气和化饮两方面,理气先理肺、肾,方中需加入炒牛蒡子、紫菀以利肺气,甘草、桔梗以开肺气;化饮为治标,温土暖水为治阳虚痰饮法则,可加入药对茯苓、干姜。木气郁滞日久者,治疗应润木达郁,兼调中土,方选桂枝汤加减。

基于PCA的可变框架模型Retinex图像增强算法

针对恶劣天气下拍摄图像的退化现象,提出了一种基于主成分分析(principal component analysis,PCA)的可变框架模型Retinex图像增强算法。PCA变换提供通道间良好的正交性,可避免由于亮度调整带来的色度失真。该算法通过PCA变换得到图像亮度分量、色度分量,对得到的亮度分量使用改进的可变框架模型Retinex进行处理,适当调整色度分量,最后对处理得到的RGB图像进行去相关拉伸。实验结果表明,该方法能有效改善恶劣天气造成的图像退化现象,提高图像的清晰度。

Thermo-bioconvection transport of nanofluid over an inclined stretching cylinder with Cattaneo–Christov double-diffusion

In this paper,Newtonian nanofluid flow is observed under the effects of the magnetic field,activation energy and motile microorganisms over an inclined stretchable cylinder.The magnificent aspects of nanoliquid are demonstrated by enduring the Brownian motion and thermophoresis diffusion features.Nonlinear higher order partial differential equations are transformed into first-order ordinary differential equations with suitable similarity variables.The attained sets of governing equations are then cracked by bvp4 c procedure in MATLAB mathematical software.The numerical and graphical outcomes of controlling parameters such as Prandtl number,mixed convection,activation energy,thermophoresis,Brownian parameter,Biot number,Lewis number,Peclet number and motile concentration parameter against the velocity,temperature,volumetric concentration and motile concentration of nanoparticles of the fluid are discussed.The velocity is enhanced with the growth valuation in mixed convection and decay by rising variation of buoyancy ratio parameter,magnetic parameter and bio-convective Rayleigh parameter.The evolution in motile microorganisms is due to the increasing values of microorganisms Biot number.The presented data can be helpful in enhancement of manufacturing processes,biomolecules,extrusion systems applications and energy production improvement.

“一气周流”论治心衰探析

清代名医黄元御的“一气周流”理论深刻阐述了人体气机等升降出入以及与脏腑之间的关系。本文结合“一气周流”理论,认为心衰的病机为心肺壅滞,气机不畅;命门火衰,枢轴不利;土败湿盛,四象无序。心衰之病症状多变,虚实交杂,治病须求本,当恢复气机的升降,同时应注意顾护中气,使中气流而不滞,四维转而不息,方得其功。文章旨在探求心衰的病机,为心衰的治疗提供新思路。

Higher-order vibration of thick composite and sandwich plates based on an alternative higher-order model

The transverse stretching vibration of thick sandwich plates,which is attributed to largely different stiffness at the adjacent layers,is a challenging issue,and efficient approach for such issue is less reported in the published literature.Thus,natural frequencies corresponding to stretching vibration modes are generally neglected in engineering design,which might impact structural safety as frequencies of the exciting force are close to transverse stretching vibration frequencies.This paper proposes an alternative higher-order model for dynamic analysis corresponding to the higher-order vibration modes.The proposed model is classified in the displacement-based equivalent single-layer theory,as the number of displacement parameters in the proposed model is independent of the layer number.The continuity of displacements and transverse shear stresses can be fulfilled at the interfaces between the adjacent layers of structures.To demonstrate the capability of the proposed model,typical examples are analyzed by utilizing the proposed model,the threedimensional finite element method and the chosen higher-order models.By comparing with the exact three-dimensional elasticity solutions,it is found that the proposed model can yield more accurate natural frequencies corresponding to the higher-order displacement modes than the selected models.Moreover,the factors influencing reasonable prediction of the higher-order frequencies are investigated in detail,which can provide a reference for the accurate prediction of the higher-order frequencies.

“一气周流”理论临床应用

“一气周流”理论认为,中土为气机升降枢纽和全身气化基础,中土之气通过气机的升降浮沉带动四象之气的转运,循环往复,贯通全身,形成“一气周流”的循环状态。疾病的形成有3种原因,第一,左路肝木之阳升散太过,或右路阴金潜降不及,发为阳盛之热病,或阴虚之热病;第二,左路之肝木升发不及,或右路肺金潜降太过,发为阴盛则寒病,或阳虚则寒病;第三,中土发病,致使升降枢纽不利,治疗应以“扶阳崇阳、培土利枢、统经四象”为原则。甲状腺相关性眼病病机为“脾失健运、肝木郁滞、肺金不利、肾水寒瘀”,用四君子汤合二陈汤加减健运中气,行水化气,逼邪外出。心力衰竭病机为水寒土湿,治当以顾护中气为主,用人参、干姜燥土暖水,甘草、茯苓培土利水。历节病病机为肾水寒不能温肝木,肝生血不足而致血虚,再加外感之邪侵袭,当治以温化寒湿为主,方用桂枝芍药知母汤加减。口疮病机为气机郁滞不通,涩滞于中焦,治当顾护脾胃,宣畅中焦,方用平胃散加生姜、大枣等。健运中土,推动左右旋转,则气能周流,御气祛邪,阴平阳秘。

基于“一气周流”理论探讨肝胃百合汤治疗消化性溃疡

消化性溃疡(peptic ulcer, PU)主要病机为肝胃不和,中气失职,气机左升右降失常,周流失序,不通则痛,气病日久入血,胃络受损,溃疡乃生。且病程中易出现气郁日久则化火伤阴、久痛入络则气滞血瘀互结等病理变化。因此,治疗核心在于恢复中气之职,调节气机升降,使气机通畅,通则不痛。肝胃百合汤为夏度衡教授经验方,由柴胡、乌药、川楝子、黄芩、百合、丹参、郁金组成,可升木达郁,右降肺胃,调畅气机,恢复中气正常升降,使肝气条达,中气复职,四维轮转,升降有序,从而改善PU症状,使疾病向愈。

Investigations of Viscous Dissipation in Stagnation Point Flow Past a Stretchable Riga Wall: Modern Analysis of Heat Transport

This article scrutinizes the features of viscous dissipation in the stagnation point ?ow past through a linearly stretched Riga wall by implementing Cattaneo-Christov heat ?ux model. Viscous dissipation is carried out in Cattaneo-Christov diffusion analysis for the ?rst time in this letter. As a result of Cattaneo-Christov model, some extra terms of viscous dissipation are appeared in the energy equation. These extra terms of viscous dissipation are missing in the literature. On the utilization of suitable transformations, the equations governing the problem are reduced under the boundary layer approximation into the non-linear and dimensionless ordinary differential equations. Convergent approach is utilized to solve the dimensionless governing equations. The solution thus acquired is used to highlight the effects of emerging parameters on velocity distribution and ?uid's temperature through the graphs. Features of the drag force(or skin friction co-e?cient) are graphically interpreted. It is noticed that the presence of modi?ed Hartman number helps to reduce the ?uid's temperature but enhances the velocity pro?le. Further an enlargement in the value of thermal time relaxation parameter helps to decrease the temperature distribution.

空间薄膜反射镜的研究发展现状

空间薄膜反射镜由于具有面密度低,易于折叠展开且成本低等优点很好地满足了空间反射镜的超轻量、超大口径的要求,因此在空间科学研究领域倍受关注。介绍了空间薄膜反射镜的发展,包括薄膜反射镜的理论基础,充气式薄膜反射镜和静电拉伸薄膜反射镜及其他类型的反射镜的代表成果。而后对空间薄膜反射镜的技术难点进行了分析;重点讨论了薄膜反射镜用聚酰亚胺薄膜的生产情况以及薄膜反射镜的面形控制、面形检测和反射镜支撑结构的设计。最后总结了反射镜近期的研制情况、存在的问题和应用发展趋势。认为空间薄膜反射镜作为国内外空间科学的热点,在未来的几十年内将在航天领域的太空望远镜、空间侦察相机、人造太阳、微波天线等方面得到广泛应用。

飞机蒙皮拉伸成形工艺参数优化

拉伸成形是飞机板金的基本成形方法。结合蒙皮拉伸成形常见的缺陷及影响因素,简述了最优化理论结合数值模拟优化工艺参数的必要性。以双曲度蒙皮为例,分析了产生回弹的机理和影响因素。采用正交试验设计建立响应曲面,序列二次规划和混合整数优化相结合的优化算法,以厚度减薄率为约束条件,对成形工艺参数预拉伸率进行优化,并对优化结果进行试验验证。结果表明优化拉形工艺参数后零件变形均匀程度提高,回弹减小了21．87%。

半刚性与柔性基层沥青路面重载适应性对比分析

以路面力学APBI程序为计算工具,对重载车辆荷载作用下的半刚性基层沥青路面和柔性基层沥青路面进行力学响应对比分析,研究路表弯沉、路面结构各层次(包括路表、面层、基层、底基层)的力学特性。结果表明,半刚性路面与柔性路面的重载适应性存在明显差异。通过对半刚性基层与柔性基层结构的合理优化组合,实现两种路面结构的优势互补。

多尺度Retinex算法在简牍图像增强中的应用

简牍图像增强是简牍文字修复和文字信息提取最为关键的一个步骤。以长沙简牍博物馆收藏的简牍文物为实物模型,以该馆提供的简牍数字图像为研究对象,提出了基于多尺度Retinex(MSR)算法的简牍图像增强方法,论述了本算法的原理及实现方法。采用MSR算法来消除光照对简牍图像的退化影响,以达到增强图像暗区细节信息的目的;同时针对MSR输出图像偏暗,提出了直方图拉伸算法。试验结果表明:本算法能够提高简牍图像对比度的同时,能显著地增强图像暗区的细节信息并且使简牍图像具有较好、较高的色彩保真度。本方法克服了目前常规的图像增强方法的不足,能够满足简牍考古人员的要求。