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,...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 study.Applying 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.展开更多
An increasing number of graded readers thus come out for pedagogical purposes. However, the reliability of text-grading for graded readers remains questionable. Whether they show linguistic difference across levels ne...An increasing number of graded readers thus come out for pedagogical purposes. However, the reliability of text-grading for graded readers remains questionable. Whether they show linguistic difference across levels needs further research given a shifted emphasis on multidimensional features. The study used Co-Metrix to give an assessment on graded readers’text-grading both under unidimensional and multidimensional indices, providing a testimony to publishers’original design and to the feasibility against the new trend. It indicated that across-grade difference only partly corresponded with publishers’text-grading rationale that focused on surface features. But it made no sense in linguistics at a deeper level since no overall difference was found. Therefore, the reassessment and design of graded readers were suggested to take account of multidimensional features for across-grade difference.展开更多
A novel three-dimensional hole gas(3 DHG) enhancement-mode(E-mode) heterostructure fielde?ect transistor(HFET) is proposed and investigated. It features back-to-back graded AlGaN(BGA) barrier layers consisting of a po...A novel three-dimensional hole gas(3 DHG) enhancement-mode(E-mode) heterostructure fielde?ect transistor(HFET) is proposed and investigated. It features back-to-back graded AlGaN(BGA) barrier layers consisting of a positive-graded AlGaN layer and a negative-graded AlGaN layer, which form polarization gradient and subsequently induce the three-dimensional electron gas(3 DEG) and 3 DHG in the positiveand negative-graded AlGaN layers, respectively. The source and drain are located at the same side of the metal-insulator-semiconductor(MIS) trench gate, and the source is in contact with the HfO2 gate insulator.First, the on-state current is significantly improved owing to the high-density 3 DEG in the positive-graded AlGaN. Next, the vertical conductive channel between the source and 3 DEG is blocked by the 3 DHG, thereby realizing the E-mode. The threshold voltage(Vth) can be modulated by a partial doping conductive channel.Subsequently, a high breakdown voltage(BV) is obtained, because the polarization junction formed by the polarization charges assists in depleting the drift region in the o?-state. Next, the BGA-HFET is smaller than the conventional HFET(Con-HFET) owing to the special location of the source. The BV of the proposed HFET sharply increases to 919 V from 39 V of the Con-HFET with the same gate-drain spacing, and the saturation drain current is increased by 103.5%.展开更多
In this paper, we show that there are only seven graded Lie algebras of dimension 5 generated in degree 1 up to isomorphism. By parameterizing the relations of the universal enveloping algebras of three of those grade...In this paper, we show that there are only seven graded Lie algebras of dimension 5 generated in degree 1 up to isomorphism. By parameterizing the relations of the universal enveloping algebras of three of those graded Lie algebras, we construct some new Artin-Schelter regular algebras of global dimension 5. We prove that those algebras are all strongly noetherian, Auslander regular and Cohen-Macaulay, and describe their Nakayama automorphisms.展开更多
The building industry is one of the main contributors to worldwide resource consumption and anthropogenic climate change.Therefore,sustainable solutions in construction are particularly urgent.Inspired by the success ...The building industry is one of the main contributors to worldwide resource consumption and anthropogenic climate change.Therefore,sustainable solutions in construction are particularly urgent.Inspired by the success principles of living nature,biologists and engineers present here an interdisciplinary work:The sustainability assessment of a bio-inspired material technology called graded concrete,which was developed at ILEK.Gradient structural materials can be found in plants on different hierarchical levels,providing a multitude of creative solutions for technology.Graded concrete applies this biological concept of structural optimization to the interior structure of concrete components to minimize material and resource expenditure.To evaluate the sustainability of this innovation,a newly developed quantitative Bio-inspired Sustainability Assessment(BiSA)method is applied.It focuses on the relationship of environmental,social and economic functions and the corresponding burdens quantified basing on life cycle assessment.The BiSA of graded concrete slabs shows significant improvements over conventional concrete for the applied use case.While an overall reduction of environmental burdens by 13%is expected,economic burdens can be reduced by up to 40%and social burdens by 35.7%.The assessment of the graded concrete technology identifies its potential with regard to sustainable construction.The presented work provides a blueprint for the interdisciplinary,integrative work on sustainable,bio-inspired innovations.It shows that the synergies of bio-inspiration and BiSA within technical product development can be fruitful.展开更多
This study presents an analytical solution of thermal and mechanical displacements, strains, and stresses for a thick-walled rotating spherical pressure vessel made of functionally graded materials (FGMs). The pressur...This study presents an analytical solution of thermal and mechanical displacements, strains, and stresses for a thick-walled rotating spherical pressure vessel made of functionally graded materials (FGMs). The pressure vessel is subject to axisymmetric mechanical and thermal loadings within a uniform magnetic field. The material properties of the FGM are considered as the power-law distribution along the thickness. Navier’s equation, which is a second-order ordinary differential equation, is derived from the mechanical equilibrium equation with the consideration of the thermal stresses and the Lorentz force resulting from the magnetic field. The distributions of the displacement, strains, and stresses are determined by the exact solution to Navier’s equation. Numerical results clarify the influence of the thermal loading, magnetic field, non-homogeneity constant, internal pressure, and angular velocity on the magneto-thermo-elastic response of the functionally graded spherical vessel. It is observed that these parameters have remarkable effects on the distributions of radial displacement, radial and circumferential strains, and radial and circumferential stresses.展开更多
The frequency of the Love-type surface waves in a bedded structure con- sisting of a porous piezoelectric (PP) medium and a functionally graded material (FGM) substrate is approximated. The FGM layer is assumed to hav...The frequency of the Love-type surface waves in a bedded structure con- sisting of a porous piezoelectric (PP) medium and a functionally graded material (FGM) substrate is approximated. The FGM layer is assumed to have a constant initial stress. The Wentzel-Kramers-Brillouin (WKB) approximation technique is used for the wave solution in the FGM layer, and the method of separation of variables is applied for the solution in the porous piezoelectric medium. The dependence of the wave frequency on the wave number is obtained for both electrically open and short cases. The effects of the gradient coefficient of the FGM layer, the initial stresses (tensile stress and compressive stress), and the width of the FGM layer are marked distinctly and shown graphically. The findings may contribute towards the design and optimization of acoustic wave devices.展开更多
In this paper,the problem of a functionally graded piezoelectric material strip(FGPM strip)containing an infinite row of parallel cracks perpendicular to the interface between the FGPM strip and a homogeneous layer is...In this paper,the problem of a functionally graded piezoelectric material strip(FGPM strip)containing an infinite row of parallel cracks perpendicular to the interface between the FGPM strip and a homogeneous layer is analyzed under transient thermal loading condition.The crack faces are supposed to be completely insulated.Material properties are assumed to be exponentially dependent on the distance from the interface.Using the Fourier transforms,the electro-thermoelastic problem is reduced to a singular integral equation,which is solved numerically.The stress intensity factors are computed and presented as a function of the normalized time,the nonhomogeneous and geometric parameters.展开更多
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 China.In the...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 China.In the past,consumers’purchases were determined by a demand economy due to limited resources.Later,with the advancing of economic reforms,consumers were no longer restricted by choices and started to pursue goods of a higher quality.Now we’ve finally come to a stage where diverse needs are satisfied through consumption by means of customization.展开更多
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 (F...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.展开更多
Large deformation of a cantilever axially functionally graded (AFG) beam subject to a tip load is analytically studied using the homotopy analysis method (HAM). It is assumed that its Young’s modulus varies along the...Large deformation of a cantilever axially functionally graded (AFG) beam subject to a tip load is analytically studied using the homotopy analysis method (HAM). It is assumed that its Young’s modulus varies along the longitudinal direction according to a power law. Taking the solution of the corresponding homogeneous beam as the initial guess and obtaining a convergence region by adjusting an auxiliary parameter, the analytical expressions for large deformation of the AFG beam are provided. Results obtained by the HAM are compared with those obtained by the finite element method and those in the previous works to verify its validity. Good agreement is observed. A detailed parametric study is carried out. The results show that the axial material variation can greatly change the deformed configuration, which provides an approach to control and manage the deformation of beams. By tailoring the axial material distribution, a desired deformed configuration can be obtained for a specific load. The analytical solution presented herein can be a helpful tool for this procedure.展开更多
In this paper, we introduce and study differential graded(DG for short) polynomial algebras. In brief, a DG polynomial algebra A is a connected cochain DG algebra such that its underlying graded algebra A# is a polyno...In this paper, we introduce and study differential graded(DG for short) polynomial algebras. In brief, a DG polynomial algebra A is a connected cochain DG algebra such that its underlying graded algebra A# is a polynomial algebra K[x1, x2,..., xn] with |xi|= 1 for any i ∈{1, 2,..., n}. We describe all possible differential structures on DG polynomial algebras, compute their DG automorphism groups, study their isomorphism problems, and show that they are all homologically smooth and Gorenstein DG algebras. Furthermore, it is proved that the DG polynomial algebra A is a Calabi-Yau DG algebra when its differential δA≠ 0 and the trivial DG polynomial algebra(A, 0) is Calabi-Yau if and only if n is an odd integer.展开更多
Abstract Recently, pH-sensitive hydrogels have been utilized in the diverse applications including sensors, switches, and actuators. In order to have continuous stress and defor- mation fields, a new semi-analytical a...Abstract Recently, pH-sensitive hydrogels have been utilized in the diverse applications including sensors, switches, and actuators. In order to have continuous stress and defor- mation fields, a new semi-analytical approach is developed to predict the swelling induced finite bending for a functionally graded (FG) layer composed of a pH-sensitive hydrogel, in which the cross-link density is continuously distributed along the thickness direction under the plane strain condition. Without considering the intermediary virtual reference, the initial state is mapped into the deformed configuration in a circular shape by utilizing a total deformation gradient tensor stemming from the inhomogeneous swelling of an FG layer in response to the variation of the pH value of the solvent. To enlighten the capabil- ity of the presented analytical method, the finite element method (FEM) is used to verify the accuracy of the analytical results in some case studies. The perfect agreement con- firms the accuracy of the presented method. Due to the applicability of FG pH-sensitive hydrogels, some design factors such as the semi-angle, the bending curvature, the aspect ratio, and the distributions of deformation and stress fields are studied. Furthermore, the tangential free-stress axes are illustrated in deformed configuration.展开更多
Blocking rockfalls directly by reinforced concrete(RC)flat sheds with thick sand cushions is an outdated method.Such conventional sheds typically accumulate rock heavily,and become progressively damaged and are diffic...Blocking rockfalls directly by reinforced concrete(RC)flat sheds with thick sand cushions is an outdated method.Such conventional sheds typically accumulate rock heavily,and become progressively damaged and are difficult to repair,and are very costly.To address these problems,we propose a new structure called a Graded Dissipating Inclined Steel Rock(GDISR)shed that utilizes the graded energy dissipation method.Here,we study the dynamic response of the GDISR shed with model test and numerical simulation,and give its optimization design combining with a practical engineering case.Our results show that the optimized modular E-block and corrugated steel tube can deform to sufficiently absorb the energy of different impact intensities.This efficiently and economically provides GDISR sheds with two security lines.Compared with conventional RC sheds,GDISR sheds with optimal incline have a more efficient anti-impact function,are faster and easier to repair,and are much simpler and cheaper to build.展开更多
In this paper, correspondence relations between the solutions of the static bending of functionally graded material (FGM) Reddy-Bickford beams (RBBs) and those of the corresponding homogenous Euler-Bernoulli beams are...In this paper, correspondence relations between the solutions of the static bending of functionally graded material (FGM) Reddy-Bickford beams (RBBs) and those of the corresponding homogenous Euler-Bernoulli beams are presented. The effective material properties of the FGM beams are assumed to vary continuously in the thickness direction. Governing equations for the titled problem are formulated via the principle of virtual displacements based on the third-order shear deformation beam theory, in which the higher-order shear force and bending moment are included. General solutions of the displacements and the stress resultants of the FGM RBBs are derived analytically in terms of the deflection of the reference homogenous Euler- Bernoulli beam with the same geometry, loadings and end conditions, which realize a classical and homogenized expression of the bending response of the shear deformable non-homogeneous FGM beams. Particular solutions for the FGM RBBs under specified end constraints and load conditions are given to validate the theory and methodology. The key merit of this work is to be capable of obtaining the high-accuracy solutions of thick FGM beams in terms of the classical beam theory solutions without dealing with the solution of the complicated coupling differential equations with boundary conditions of the problem.展开更多
Within the framework of three-dimensional elasticity theory,this paper investigates the thermal response of functionally graded annular plates in which the material can be transversely isotropic and vary along the thi...Within the framework of three-dimensional elasticity theory,this paper investigates the thermal response of functionally graded annular plates in which the material can be transversely isotropic and vary along the thickness direction in an arbitrary manner.The generalized Mian and Spencer method is utilized to obtain the analytical solutions of annular plates under a through-thickness steady temperature field.The present analytical solutions are validated through comparisons against those available in open literature.A parametric study is conducted to examine the effects of gradient distribution,different temperature fields,different diameter ratio and boundary conditions on the deformation and stress fields of the plate.The results show that these factors can have obvious effects on the thermo-elastic behavior of functionally gradient materials(FGM)annular plates.展开更多
The perturbation method is applied to investigate the frictionally excited thermoelastic dynamic instability (TEDI) of a functionally graded material (FGM) coating in half-plane sliding against a homogeneous half-plan...The perturbation method is applied to investigate the frictionally excited thermoelastic dynamic instability (TEDI) of a functionally graded material (FGM) coating in half-plane sliding against a homogeneous half-plane. We assume that the thermoelastic properties of the FGM vary exponentially with thickness. We also examine the effects of the gradient index, sliding speed, and friction coefficient on the TEDI for various material combinations. The transverse normal stress for two different coating structures is calculated. Furthermore, the frictional sliding stability of two different coating structures is analyzed. The obtained results show that use of FGM coatings can improve the TEDI of this sliding system and reduce the possibility of interfacial failure by controlling the interfacial tensile stress.展开更多
We extend the differential quadrature element method (DQEM) to the buckling analysis of uniformly in-plane loaded functionally graded (FG) plates fully or partially resting on the Pasternak model of elastic support. M...We extend the differential quadrature element method (DQEM) to the buckling analysis of uniformly in-plane loaded functionally graded (FG) plates fully or partially resting on the Pasternak model of elastic support. Material properties of the FG plate are graded in the thickness direction and assumed to obey a power law distribution of the volume fraction of the constituents. To set up the global eigenvalue equation, the plate is divided into sub-domains or elements and the generalized differential quadrature procedure is applied to discretize the governing, boundary and compatibility equations. By assembling discrete equations at all nodal points, the weighting coefficient and force matrices are derived. To validate the accuracy of this method, the results are compared with those of the exact solution and the finite element method. At the end, the effects of different variables and local elastic support arrangements on the buckling load factor are investigated.展开更多
The bending and vibration behavior of a curved FG nanobeam using the nonlocal Timoshenko beam theory is analyzed in this paper. It is assumed that the material properties vary through the radius direction. The governi...The bending and vibration behavior of a curved FG nanobeam using the nonlocal Timoshenko beam theory is analyzed in this paper. It is assumed that the material properties vary through the radius direction. The governing equations were obtained using Hamilton principle based on the nonlocal Timoshenko model of curved beam. An analytical approach for a simply supported boundary condition is conducted to analyze the vibration and bending of curved FG nanobeam. In the both mentioned analysis, the effect of significant parameter such as opening angle, the power law index of FGM, nonlocal parameter, aspect ratio and mode number are studied. The accuracy of the solution is examined by comparing the results obtained with the analytical and numerical results published in the literatures.展开更多
The evolution of the traditional metal oxide semiconductor field effect transistor (MOSFET)from planar single gate devices into 3D multiple gates has led to higher package density and high current drive. However,due t...The evolution of the traditional metal oxide semiconductor field effect transistor (MOSFET)from planar single gate devices into 3D multiple gates has led to higher package density and high current drive. However,due to continuous scaling and as a consequent close proximity between source and drain in the nano-regime,these multigate devices have been found to suffer from performance degrading short channel effects (SCEs). In this paper,a three dimensional analytical model of a trigate MOSFET incorporating non-conventional structural techniques like silicon-on-insulator,gate and channel engineering in addition to gate oxide stack is presented. The electrostatic integrity and device capability of suppressing SCEs is investigated by deriving the potential distribution profile using the three dimensional Poisson's equation along with suitable boundary conditions.The other device parameters like threshold voltage and subthreshold swing are produced from the surface potential model. The validity of the proposed structure is established by the close agreement among the results obtained from the analytical model and simulation results.展开更多
文摘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 study.Applying 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.
文摘An increasing number of graded readers thus come out for pedagogical purposes. However, the reliability of text-grading for graded readers remains questionable. Whether they show linguistic difference across levels needs further research given a shifted emphasis on multidimensional features. The study used Co-Metrix to give an assessment on graded readers’text-grading both under unidimensional and multidimensional indices, providing a testimony to publishers’original design and to the feasibility against the new trend. It indicated that across-grade difference only partly corresponded with publishers’text-grading rationale that focused on surface features. But it made no sense in linguistics at a deeper level since no overall difference was found. Therefore, the reassessment and design of graded readers were suggested to take account of multidimensional features for across-grade difference.
基金supported in part by National Natural Science Foundation of China(Grant Nos.51677021,61234006)National Defense Science and Technology Project Foundation of China(Grant No.1100395)Fundamental Research Funds for the Central Universities(Grant No.ZYGX2014Z006).
文摘A novel three-dimensional hole gas(3 DHG) enhancement-mode(E-mode) heterostructure fielde?ect transistor(HFET) is proposed and investigated. It features back-to-back graded AlGaN(BGA) barrier layers consisting of a positive-graded AlGaN layer and a negative-graded AlGaN layer, which form polarization gradient and subsequently induce the three-dimensional electron gas(3 DEG) and 3 DHG in the positiveand negative-graded AlGaN layers, respectively. The source and drain are located at the same side of the metal-insulator-semiconductor(MIS) trench gate, and the source is in contact with the HfO2 gate insulator.First, the on-state current is significantly improved owing to the high-density 3 DEG in the positive-graded AlGaN. Next, the vertical conductive channel between the source and 3 DEG is blocked by the 3 DHG, thereby realizing the E-mode. The threshold voltage(Vth) can be modulated by a partial doping conductive channel.Subsequently, a high breakdown voltage(BV) is obtained, because the polarization junction formed by the polarization charges assists in depleting the drift region in the o?-state. Next, the BGA-HFET is smaller than the conventional HFET(Con-HFET) owing to the special location of the source. The BV of the proposed HFET sharply increases to 919 V from 39 V of the Con-HFET with the same gate-drain spacing, and the saturation drain current is increased by 103.5%.
基金NSFC (No. 11701515)ZJNSF (No. LY18A010028)Science Foundation of Zhejiang Sci-Tech University (ZSTU)(No. 16062066-Y).
文摘In this paper, we show that there are only seven graded Lie algebras of dimension 5 generated in degree 1 up to isomorphism. By parameterizing the relations of the universal enveloping algebras of three of those graded Lie algebras, we construct some new Artin-Schelter regular algebras of global dimension 5. We prove that those algebras are all strongly noetherian, Auslander regular and Cohen-Macaulay, and describe their Nakayama automorphisms.
基金This work was mainly done under the support of the CRC-Transregio 141“Biological Design and Integrative Structures-Analysis,Simulation and Implementation in Architecture’Vproject C01 funded by the German Research Foundation DFG Significant contributions were made under the support of the project“Leichtbau im Bauwesen”funded by the ministry of economy Ba-den-Wiiittemberg based on the results of the research projects“Effiziente automatisierte Herstellung multi-funktionaler Bauteile mit mineralisierten Hohlkorpem”in the scope of the priority program 1542“Leicht Bauen mit Beton”funded by the German Research Foundation DFG and“Multifunktional gradierte Bauteile fur das nachhaltige Bauen mit Beton”supported by the Ba-den-Wurttemberg Foundation.
文摘The building industry is one of the main contributors to worldwide resource consumption and anthropogenic climate change.Therefore,sustainable solutions in construction are particularly urgent.Inspired by the success principles of living nature,biologists and engineers present here an interdisciplinary work:The sustainability assessment of a bio-inspired material technology called graded concrete,which was developed at ILEK.Gradient structural materials can be found in plants on different hierarchical levels,providing a multitude of creative solutions for technology.Graded concrete applies this biological concept of structural optimization to the interior structure of concrete components to minimize material and resource expenditure.To evaluate the sustainability of this innovation,a newly developed quantitative Bio-inspired Sustainability Assessment(BiSA)method is applied.It focuses on the relationship of environmental,social and economic functions and the corresponding burdens quantified basing on life cycle assessment.The BiSA of graded concrete slabs shows significant improvements over conventional concrete for the applied use case.While an overall reduction of environmental burdens by 13%is expected,economic burdens can be reduced by up to 40%and social burdens by 35.7%.The assessment of the graded concrete technology identifies its potential with regard to sustainable construction.The presented work provides a blueprint for the interdisciplinary,integrative work on sustainable,bio-inspired innovations.It shows that the synergies of bio-inspiration and BiSA within technical product development can be fruitful.
文摘This study presents an analytical solution of thermal and mechanical displacements, strains, and stresses for a thick-walled rotating spherical pressure vessel made of functionally graded materials (FGMs). The pressure vessel is subject to axisymmetric mechanical and thermal loadings within a uniform magnetic field. The material properties of the FGM are considered as the power-law distribution along the thickness. Navier’s equation, which is a second-order ordinary differential equation, is derived from the mechanical equilibrium equation with the consideration of the thermal stresses and the Lorentz force resulting from the magnetic field. The distributions of the displacement, strains, and stresses are determined by the exact solution to Navier’s equation. Numerical results clarify the influence of the thermal loading, magnetic field, non-homogeneity constant, internal pressure, and angular velocity on the magneto-thermo-elastic response of the functionally graded spherical vessel. It is observed that these parameters have remarkable effects on the distributions of radial displacement, radial and circumferential strains, and radial and circumferential stresses.
文摘The frequency of the Love-type surface waves in a bedded structure con- sisting of a porous piezoelectric (PP) medium and a functionally graded material (FGM) substrate is approximated. The FGM layer is assumed to have a constant initial stress. The Wentzel-Kramers-Brillouin (WKB) approximation technique is used for the wave solution in the FGM layer, and the method of separation of variables is applied for the solution in the porous piezoelectric medium. The dependence of the wave frequency on the wave number is obtained for both electrically open and short cases. The effects of the gradient coefficient of the FGM layer, the initial stresses (tensile stress and compressive stress), and the width of the FGM layer are marked distinctly and shown graphically. The findings may contribute towards the design and optimization of acoustic wave devices.
文摘In this paper,the problem of a functionally graded piezoelectric material strip(FGPM strip)containing an infinite row of parallel cracks perpendicular to the interface between the FGPM strip and a homogeneous layer is analyzed under transient thermal loading condition.The crack faces are supposed to be completely insulated.Material properties are assumed to be exponentially dependent on the distance from the interface.Using the Fourier transforms,the electro-thermoelastic problem is reduced to a singular integral equation,which is solved numerically.The stress intensity factors are computed and presented as a function of the normalized time,the nonhomogeneous and geometric parameters.
文摘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 China.In the past,consumers’purchases were determined by a demand economy due to limited resources.Later,with the advancing of economic reforms,consumers were no longer restricted by choices and started to pursue goods of a higher quality.Now we’ve finally come to a stage where diverse needs are satisfied through consumption by means of customization.
文摘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.
基金the China Postdoctoral Science Foundation(No.2018M630167).
文摘Large deformation of a cantilever axially functionally graded (AFG) beam subject to a tip load is analytically studied using the homotopy analysis method (HAM). It is assumed that its Young’s modulus varies along the longitudinal direction according to a power law. Taking the solution of the corresponding homogeneous beam as the initial guess and obtaining a convergence region by adjusting an auxiliary parameter, the analytical expressions for large deformation of the AFG beam are provided. Results obtained by the HAM are compared with those obtained by the finite element method and those in the previous works to verify its validity. Good agreement is observed. A detailed parametric study is carried out. The results show that the axial material variation can greatly change the deformed configuration, which provides an approach to control and manage the deformation of beams. By tailoring the axial material distribution, a desired deformed configuration can be obtained for a specific load. The analytical solution presented herein can be a helpful tool for this procedure.
基金National Natural Science Foundation of China (Grant No. 11001056)the China Postdoctoral Science Foundation (Grant Nos. 20090450066 and 201003244)+1 种基金the Key Disciplines of Shanghai Municipality (Grant No. S30104)the Innovation Program of Shanghai Municipal Education Commission (Grant No. 12YZ031).
文摘In this paper, we introduce and study differential graded(DG for short) polynomial algebras. In brief, a DG polynomial algebra A is a connected cochain DG algebra such that its underlying graded algebra A# is a polynomial algebra K[x1, x2,..., xn] with |xi|= 1 for any i ∈{1, 2,..., n}. We describe all possible differential structures on DG polynomial algebras, compute their DG automorphism groups, study their isomorphism problems, and show that they are all homologically smooth and Gorenstein DG algebras. Furthermore, it is proved that the DG polynomial algebra A is a Calabi-Yau DG algebra when its differential δA≠ 0 and the trivial DG polynomial algebra(A, 0) is Calabi-Yau if and only if n is an odd integer.
文摘Abstract Recently, pH-sensitive hydrogels have been utilized in the diverse applications including sensors, switches, and actuators. In order to have continuous stress and defor- mation fields, a new semi-analytical approach is developed to predict the swelling induced finite bending for a functionally graded (FG) layer composed of a pH-sensitive hydrogel, in which the cross-link density is continuously distributed along the thickness direction under the plane strain condition. Without considering the intermediary virtual reference, the initial state is mapped into the deformed configuration in a circular shape by utilizing a total deformation gradient tensor stemming from the inhomogeneous swelling of an FG layer in response to the variation of the pH value of the solvent. To enlighten the capabil- ity of the presented analytical method, the finite element method (FEM) is used to verify the accuracy of the analytical results in some case studies. The perfect agreement con- firms the accuracy of the presented method. Due to the applicability of FG pH-sensitive hydrogels, some design factors such as the semi-angle, the bending curvature, the aspect ratio, and the distributions of deformation and stress fields are studied. Furthermore, the tangential free-stress axes are illustrated in deformed configuration.
基金the National Key Basic Research Program of China(2016YFB0201003)the National Natural Science Foundation of China(41672356)the 135 Strategic Program of the Institute of Mountain Hazards and Environment,CAS(SDS-135-1704).
文摘Blocking rockfalls directly by reinforced concrete(RC)flat sheds with thick sand cushions is an outdated method.Such conventional sheds typically accumulate rock heavily,and become progressively damaged and are difficult to repair,and are very costly.To address these problems,we propose a new structure called a Graded Dissipating Inclined Steel Rock(GDISR)shed that utilizes the graded energy dissipation method.Here,we study the dynamic response of the GDISR shed with model test and numerical simulation,and give its optimization design combining with a practical engineering case.Our results show that the optimized modular E-block and corrugated steel tube can deform to sufficiently absorb the energy of different impact intensities.This efficiently and economically provides GDISR sheds with two security lines.Compared with conventional RC sheds,GDISR sheds with optimal incline have a more efficient anti-impact function,are faster and easier to repair,and are much simpler and cheaper to build.
基金supported by the National Natural Science Foundation of China with Grant Numbers 11272278 and 11672260.The authors gratefully acknowledge the financial supports.
文摘In this paper, correspondence relations between the solutions of the static bending of functionally graded material (FGM) Reddy-Bickford beams (RBBs) and those of the corresponding homogenous Euler-Bernoulli beams are presented. The effective material properties of the FGM beams are assumed to vary continuously in the thickness direction. Governing equations for the titled problem are formulated via the principle of virtual displacements based on the third-order shear deformation beam theory, in which the higher-order shear force and bending moment are included. General solutions of the displacements and the stress resultants of the FGM RBBs are derived analytically in terms of the deflection of the reference homogenous Euler- Bernoulli beam with the same geometry, loadings and end conditions, which realize a classical and homogenized expression of the bending response of the shear deformable non-homogeneous FGM beams. Particular solutions for the FGM RBBs under specified end constraints and load conditions are given to validate the theory and methodology. The key merit of this work is to be capable of obtaining the high-accuracy solutions of thick FGM beams in terms of the classical beam theory solutions without dealing with the solution of the complicated coupling differential equations with boundary conditions of the problem.
基金The work was supported by the National Natural Science Foundation of China(Grant 11872336)the Natural Science Foundation of Zhejiang Province,China(Grant LY18A020009).
文摘Within the framework of three-dimensional elasticity theory,this paper investigates the thermal response of functionally graded annular plates in which the material can be transversely isotropic and vary along the thickness direction in an arbitrary manner.The generalized Mian and Spencer method is utilized to obtain the analytical solutions of annular plates under a through-thickness steady temperature field.The present analytical solutions are validated through comparisons against those available in open literature.A parametric study is conducted to examine the effects of gradient distribution,different temperature fields,different diameter ratio and boundary conditions on the deformation and stress fields of the plate.The results show that these factors can have obvious effects on the thermo-elastic behavior of functionally gradient materials(FGM)annular plates.
基金National NaturalScience Foundation of China (Grants 11502089 and 11725207).
文摘The perturbation method is applied to investigate the frictionally excited thermoelastic dynamic instability (TEDI) of a functionally graded material (FGM) coating in half-plane sliding against a homogeneous half-plane. We assume that the thermoelastic properties of the FGM vary exponentially with thickness. We also examine the effects of the gradient index, sliding speed, and friction coefficient on the TEDI for various material combinations. The transverse normal stress for two different coating structures is calculated. Furthermore, the frictional sliding stability of two different coating structures is analyzed. The obtained results show that use of FGM coatings can improve the TEDI of this sliding system and reduce the possibility of interfacial failure by controlling the interfacial tensile stress.
文摘We extend the differential quadrature element method (DQEM) to the buckling analysis of uniformly in-plane loaded functionally graded (FG) plates fully or partially resting on the Pasternak model of elastic support. Material properties of the FG plate are graded in the thickness direction and assumed to obey a power law distribution of the volume fraction of the constituents. To set up the global eigenvalue equation, the plate is divided into sub-domains or elements and the generalized differential quadrature procedure is applied to discretize the governing, boundary and compatibility equations. By assembling discrete equations at all nodal points, the weighting coefficient and force matrices are derived. To validate the accuracy of this method, the results are compared with those of the exact solution and the finite element method. At the end, the effects of different variables and local elastic support arrangements on the buckling load factor are investigated.
文摘The bending and vibration behavior of a curved FG nanobeam using the nonlocal Timoshenko beam theory is analyzed in this paper. It is assumed that the material properties vary through the radius direction. The governing equations were obtained using Hamilton principle based on the nonlocal Timoshenko model of curved beam. An analytical approach for a simply supported boundary condition is conducted to analyze the vibration and bending of curved FG nanobeam. In the both mentioned analysis, the effect of significant parameter such as opening angle, the power law index of FGM, nonlocal parameter, aspect ratio and mode number are studied. The accuracy of the solution is examined by comparing the results obtained with the analytical and numerical results published in the literatures.
基金the Ministry of Electronics and Information Technology (MEITy),Govt.of India under its Visvesvaraya PhD Scheme (PhD-MLA/4(55)/2015-16).
文摘The evolution of the traditional metal oxide semiconductor field effect transistor (MOSFET)from planar single gate devices into 3D multiple gates has led to higher package density and high current drive. However,due to continuous scaling and as a consequent close proximity between source and drain in the nano-regime,these multigate devices have been found to suffer from performance degrading short channel effects (SCEs). In this paper,a three dimensional analytical model of a trigate MOSFET incorporating non-conventional structural techniques like silicon-on-insulator,gate and channel engineering in addition to gate oxide stack is presented. The electrostatic integrity and device capability of suppressing SCEs is investigated by deriving the potential distribution profile using the three dimensional Poisson's equation along with suitable boundary conditions.The other device parameters like threshold voltage and subthreshold swing are produced from the surface potential model. The validity of the proposed structure is established by the close agreement among the results obtained from the analytical model and simulation results.