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Information topology graph has been extensively used in modeling network management, where it is necessary to continually optimize the management of the dynamic network. However, frequent reconfiguration may lead to an increased overhead and a degraded latency. Since the mobility in a vehicular network is restricted by the road, there is an internal relatively stable part embedded in the entire dynamic network. Thus, in this study, this characteristic is first used to reduce reconfiguration, where the maximum stable subgraph is extracted and configuration only needs to be reconsidered for the rest of the network. However, there are three main challenges in the modeling and solving procedure, namely the evaluation of stability of part of the network, the assurance of the coherence in the set of extracted vehicles and the huge computation complexity of the subgraph enumeration. Therefore, in this study, first, the vehicular network is modeled by constructing the time-evolving information topology graph, in which a subgraph similarity is constructed to quantify the stability of part of network. Second, a maximum stable subgraph extraction optimization problem is presented, where the coherence constraint of vehicles is proposed. Finally, a gradual contraction extraction algorithm is proposed to solve the optimization problem with a low complexity. The simulation results reveal that the proposed algorithm can extract a stable subgraph with an approximate maximum size, and has a higher adaptability than the compared ones. Furthermore, it was found that the application of the proposed algorithm in resource allocation can effectively reduce the reconfiguration.

In this paper, the stiffness of carbon nanotube bundle (CNTB) reinforced composite is predicted by means of the Mori-Tanaka method and Eshelby method. The curvature of one CNTB on uniaxial aligned ...

This study develops a TEMH (thermoelectric energy micro harvester) chip utilizing a commercial 0.18 μm CMOS (complementary metal oxide semiconductor) process. The chip contains a TEMH and temperature sensors. The TEMH is established using a series of 54 thermocouples. The use of the temperature sensors monitors the temperature of the thermocouples. One temperature sensor is set near the cold part of the thermocouples, and the other is set near the hot part of the thermocouples. The performance of the TEMH relies on the TD (temperature difference) at the CHP (cold and hot parts) of the thermocouples. The more the TD at the CHP of the thermocouples increases, the higher the output voltage and output power of the TEMH become. To obtain a higher TD, the cold part of the thermocouples is designed as a suspended structure and is combined with cooling sheets to increase heat dissipation. The cooling sheet is constructed of a stack of aluminum layers and is mounted above the cold part of the thermocouple. A finite element method software, ANSYS, is utilized to compute the temperature distribution of the TEMH. The TEMH requires a post-process to obtain the suspended thermocouple structure. The post-process utilizes an RIE (reactive ion etch) to etch the two sacrificial materials, which are silicon dioxide and silicon substrate. The results reveal that the structure of the thermocouples is completely suspended and does not show any injury. The measured results reveal that the output voltage of the TEMH is 32.5 mV when the TD between the CHP of the thermocouples is 4 K. The TEMH has a voltage factor of 8.93 mV/mm2K. When the TD between the CHP of the thermocouples is 4 K, the maximum output power of the TEMH is 4.67 nW. The TEMH has a power factor of 0.31 nW/mm2K2.

In intelligent manufacturing and robotic technology, various sensors must be integrated with equipment. In addition to traditional sensors, stretchable sensors are particularly attractive for applications in robotics and wearable devices. In this study, a piezoresistive stretchable strain sensor based on laser-induced graphene (LIG) was proposed and developed. A three-dimensional, porous LIG structure fabricated from polyimide (PI) film using laser scanning was used as the sensing layer of the strain sensor. Two LIG pattern structures (parallel and vertical) were fabricated and integrated within the LIG strain sensors. Scanning electron microscopy, an X-ray energy dispersive spectrometer, and Raman scattering spectroscopy were used to examine the microstructure of the LIG sensing layer. The performance and strain sensing properties of the parallel and vertical stretchable LIG strain sensors were investigated in tensile tests. The relative resistance changes and the gauge factors of the parallel and vertical LIG strain sensors were quantified. The parallel strain sensor achieved a high gauge factor of 15.79 in the applied strain range of 10% to 20%. It also had high sensitivity, excellent repeatability, good durability, and fast response times during the tensile experiments. The developed LIG strain sensor can be used for the real-time monitoring of human motions such like finger bending, wrist bending, and throat swallowing.

The design, fabrication, and measurement of a microelectromechanical system (MEMS) three-axis magnetic field sensor (MFS) based on the commercial complementary metal oxide semiconductor (CMOS) process are investigated. The MFS is a magnetic transistor type. The performance of the MFS was analyzed employing the semiconductor simulation software, Sentaurus TCAD. In order to decrease the cross-sensitivity of the three-axis MFS, the structure of the MFS is planed to accommodate two independent sensing components, a z-MFS utilized to sense magnetic field (M-F) in the z-direction and a y/x-MFS composed of a y-MFS and a x-MFS to be utilized to sense M-F in the y- and x-directions. The z-MFS incorporates four additional collectors to increase its sensitivity. The commercial 1P6M 0.18 μm CMOS process of the Taiwan Semiconductor Manufacturing Company (TSMC) is utilized to manufacture the MFS. Experiments depict that the MFS has a low cross-sensitivity of less than 3%. The sensitivities of z-, y-, and x-MFS are 237 mV/T, 485 mV/T, and 484 mV/T, respectively.

The hygro-thermo-mechanical behavior of a ultra-high strength steel (UHSS) gasket under radial mechanical loads is investigated. By adopting an appropriate displacement function, the displacement, ...

A micromechanical model for short fiber-reinforced composites (SFRCs) with functionally graded interphases and a systematic prediction scheme to determine the effective properties are presented. The matrix and the fibers are regarded to be linear elastic, isotropic, and homogeneous. Fibers are assumed to be ellipsoids coated perfectly by functionally graded interphases, which is supposed to be formed chemically or physically by the constituents near the interface. First, to analyze the grading interphase effect, layer-wise concept is followed to divide the functionally graded interphases into multi-homogeneous sub-layers. Next, to take the effect of functionally graded interphases into account, a combination of multi-inclusion method and Mori–Tanaka method is applied to predict effective elastic properties of this unidirectional SFRCs with respect to the content and aspect ratio of the inclusions. By employing coordinate transformation, spatially elastic moduli are obtained. Finally, Voigt homogenization scheme is used to obtain the overall, averaged, symmetrical elastic properties of the SFRCs. Numerical examples and analyses demonstrate the applicability of the proposed method and indicate the influences of graded interphase, orientation, and aspect ratio of inclusions as well as properties and contents of the constituents on the overall properties of SFRCs.

Knots in long DNA molecules are prevalent in biological systems and serve as a model system for investigating static and dynamic properties of biopolymers. We explore the dynamics of knots in double-stranded DNA in a new regime of nanometer-scale confinement, large forces, and short time scales, using solid-state nanopores. We show that DNA knots undergo isomorphic translocation through a nanopore, retaining their equilibrium morphology by swiftly compressing in a lateral direction to fit the constriction. We observe no evidence of knot tightening or jamming, even for single-digit nanopores. We explain the observations as the malleability of DNA, characterized by sharp buckling of the DNA in nanopores, driven by the transient disruption of base pairing. Our molecular dynamics simulations support the model. These results are relevant not only for the understanding of DNA packing and manipulation in living cells but also for the polymer physics of DNA and the development of nanopore-based sequencing technologies.

In this paper, thermo-electro–elastic behavior of a hollow cylinder made of carbon nanotubes bundles–reinforced electro-active polymer considering the hierarchical structure of carbon nanotube bund...

In this paper, two formulae that can predict the tensile strength of composites are derived. One of the formulae is suitable for predicting the tensile strength of composites in which there is no f...

This study describes the fabrication of an ammonia gas sensor (AGS) using a complementary metal oxide semiconductor (CMOS)&ndash, microelectromechanical system (MEMS) technique. The structure of the AGS features interdigitated electrodes (IDEs) and a sensing material on a silicon substrate. The IDEs are the stacked aluminum layers that are made using the CMOS process. The sensing material, polypyrrole/reduced graphene oxide (PPy/RGO), is synthesized using the oxidation&ndash, reduction method, and the material is characterized using an electron spectroscope for chemical analysis (ESCA), a scanning electron microscope (SEM), and high-resolution X-ray diffraction (XRD). After the CMOS process, the AGS needs post-processing to etch an oxide layer and to deposit the sensing material. The resistance of the AGS changes when it is exposed to ammonia. A non-inverting amplifier circuit converts the resistance of the AGS into a voltage signal. The AGS operates at room temperature. Experiments show that the AGS response is 4.5% at a concentration of 1 ppm NH3, and it exhibits good repeatability. The lowest concentration that the AGS can detect is 0.1 ppm NH3

This study involves the fabrication and measurement of a flexible thermoelectric generator (FTG) using micromachining and electroplating processes. The area of the FTG is 46 &times, 17 mm2, and it is composed of 39 thermocouples in series. The thermoelectric materials that are used for the FTG are copper and nickel. The fabrication process involves patterning a silver seed layer on the polymethyl methacrylate (PMMA) substrate using a computer numerical control (CNC) micro-milling machine. Thermoelectric materials, copper and nickel, are deposited on the PMMA substrate using an electroplating process. An epoxy polymer is then coated onto the PMMA substrate. Acetone solution is then used to etch the PMMA substrate and to transfer the thermocouples to the flexible epoxy film. The FTG generates an output voltage (OV) as the thermocouples have a temperature difference (&Delta, T) between the cold and hot parts. The experiments show that the OV of the FTG is 4.2 mV at &Delta, T of 5.3 K and the output power is 429 nW at &Delta, T of 5.3 K. The FTG has a voltage factor of 1 &mu, V/mm2K and a power factor of 19.5 pW/mm2K2. The FTG reaches a curvature of 20 m&minus, 1.

The elastic-plastic deformation of materials provides limited displacement for metal gaskets, so as to ensure the sealing performance of flanges. In order to study the sealing performance of a novel metal gasket with a convex structure of a semi-cylindrical shell between two flanges, the compression-springback behavior of semi-cylindrical shell is investigated. By introducing the rebound and anti-coupled system consisting of the compressed body and the resilient body, meanwhile based on von Karman nonlinear theory and Mises yield criterion, the incremental thermo-elastoplastic stress-strain constitutive relation of the semi-cylindrical shell is theoretically derived. Utilizing the finite difference method in space domain and nonlinear term iteration technique, the plastic stage problem including the semi-cylindrical shell and the sheet with flattening single-corrugated structure is solved. The influence factors of material properties, temperature, geometrical parameters of semi-cylindrical shells and cyclic loads are considered. Results show that the compression-springback behavior of nickel-based alloy is better than that of stainless steel in thermal environment, while the compression-springback behavior of stainless steel is closed to that of nickel-based alloy at room temperature. The width of semi-cylindrical shell and depth of base material significantly affect the compression-springback behavior of stainless steel. In addition, the cyclic load can cause the plastic hardening of stainless steel.

Adequate micro-modeling for composites is the basic and key precondition for their property prediction. This study takes fiber-reinforced composites (FRCs) as an example and focuses on the linkages among fiber content, porosity and aggregation in the microstructure of composites, as well as their effect on the overall mechanical properties. A novel two-parameter agglomeration model is developed to take both the tightly packed filler assemblies and the porosity into account, in which the fiber weight fraction is used as an independent variable to express the volumetric composition. Meanwhile, an improved two-scale approach based on Mori–Tanaka (M–T) homogenization theory is utilized to predict the effective properties of FRCs. Three typical FRCs: three-dimensional (3D) randomly distributed FRCs, two-dimensional (2D) randomly distributed ones and unidirectionally (UD) distributed ones, are investigated in detail. The proposed model and method are validated by available experimental data. A parametric study reveals that due to the synergistic influence of fiber content, porosity and local aggregation, a maximum stiffness of FRCs can be achieved by making fibers uniformly dispersed in the matrix and setting the fiber weight fraction to be a certain transition value, which is characterized as a best possible condition with high fiber content and low porosity.

Springback prediction for a metal sheet during the forming process has always been a practical problem. In this paper, based on the mixed plastic hardening rule, which comprehensively describes the Bauschinger effect, transient behavior and permanent softening, a mechanical model considering the variable elastic modulus effect, nonlinear elastic recovery, initial anisotropy yielding criterion and damage evolution is established. Influence of damage on time-dependent springback for a U-shaped HSLA steel plate is investigated. The results obtained from numerical examples show that the hardening exponent, bending radius-thickness ratio, friction coefficient, blank holder force and damage have great influences on the springback of the U-shaped HSLA steel plate. Comparison example is conducted to verify the validity of the present model which can accurately predict the springback behavior of the U-shape HSLA steel plate.

The thermoviscoelastic dynamic response of a simply supported rectangular steel plate under laser processing is studied in this paper. Three-dimensional transient temperature field of the laser processing thermoviscoelastic rectangular steel plate is solved by the method of separation of variables. Meanwhile, based on von Karman nonlinear strain–displacement relationships and classical thin plate theory, a list of nonlinear dynamic equilibrium equations for a rectangular thermoviscoelastic steel plate are deduced. Then the entire problem is solved by utilizing the Newmark method and the iterative method. Finally, numerical results show that laser moving speed, laser power density and thickness-to-length ratio have a great influence on the thermoviscoelastic response of the rectangular DP980 steel plate.

In this paper, thermoviscoelastic behavior of a hollow cylinder made of short fiber-reinforced polymer considering porosity is investigated by an analytical method. Material properties, except the Poisson’s ratio and coefficient of thermal expansion, are assumed to be changed with the volume of constituents and porosity. Utilizing the finite Hankle integral transform and Laplace transform, analytical solutions for thermoviscoelastic behaviors of short fiber-reinforced polymer hollow cylinders under thermal and mechanical loads are obtained. Numerical examples show the influences of thermal load, mechanical load, and material porosity on the thermoviscoelastic behaviors of short fiber-reinforced polymer cylindrical structures.

Cylindrical structures consisted of functionally graded materials (FGMs) are frequently used in various engineering applications in the modern aerospace, marine, nuclear and military industries, automotive industries, etc. This paper reviews most of the researches done in recent years (2005–2015) on FGM cylindrical structures with an emphasis on coupled mechanics, including thermo-elastic coupling, multi-physic fields coupling, structure–foundation coupling and fluid–solid coupling. The main aim of this review article is to collate the research performed in the area of coupled mechanics on FGM cylindrical structures during the last 10 years, thereby giving a broad perspective of the state of art in this field.

Based on the von Karman equation and classical theory of thin plates, a set of nonlinear governing equations for a rectangular high strength low alloy (HSLA) steel plate subjected to low velocity impact is deduced, they are expressed with displacements of the mid-plane for the HSLA steel plate. By using the finite difference method and the Newmark method, the unknown variable functions are discretized in the space and time domains, the whole problem is solved by the iterative method synthetically. Numerical results denote that the thickness to length ratio, boundary conditions and initial impact velocity of the impactor have great influences on the nondimensional deflection and normal stress of the HSLA plate that subjected to low velocity impact, moreover, the initial impact velocity affects a lot on the contact force.

The study investigates the design and fabrication of a micromachined radio frequency (RF) capacitive switch using the complementary metal oxide semiconductor-microelectromechanical system (CMOS-MEMS) technology. The structure of the micromachined switch is composed of a membrane, eight springs, four inductors, and coplanar waveguide (CPW) lines. In order to reduce the actuation voltage of the switch, the springs are designed as low stiffness. The finite element method (FEM) software CoventorWare is used to simulate the actuation voltage and displacement of the switch. The micromachined switch needs a post-CMOS process to release the springs and membrane. A wet etching is employed to etch the sacrificial silicon dioxide layer, and to release the membrane and springs of the switch. Experiments show that the pull-in voltage of the switch is 12 V. The switch has an insertion loss of 0.8 dB at 36 GHz and an isolation of 19 dB at 36 GHz.

The fabrication and characterization of a thermoelectric energy harvester using the complementary metal oxide semiconductor (CMOS)-microelectromechanical system (MEMS) technology were presented. The thermoelectric energy harvester is composed of eight circular energy harvesting cells, and each cell consists of 25 thermocouples in series. The thermocouples are made of p-type and n-type polysilicons. The output power of the energy harvester relies on the number of the thermocouples. In order to enhance the output power, the energy harvester increases the thermocouple number per area. The energy harvester requires a post-CMOS process to etch the sacrificial silicon dioxide layer and the silicon substrate to release the suspended structures of hot part. The experimental results show that the energy harvester has an output voltage per area of 0.178 mV·mm−2·K−1 and a power factor of 1.47 × 10−3 pW·mm−2·K−2.

In this paper, analytical solutions for three-dimensional steady and transient heat conduction problems of a double-layer plate with a local heat source are presented, the double-layer structure includes a coating layer and FGM layer. The Poisson method and layer wise (LW) approach are applied to solve the three-dimensional steady heat conduction problem. Meanwhile, to solve the three-dimensional transient heat conduction problem of the double-layer plate, the method of separation of variables (SOV) and LW approach are together applied. The aim of this research is to understand the influences of selected coating material, local heat source and structural parameters on temperature distribution of the double-layer plate, and to guide engineers designing the double-layer structures in thermal environment.

In this paper, the displacement and stress distribution in a rotating FGM (Functionally graded material) circular disk with a variable angular speed are studied. The modulus of elasticity and mass density of the circular disk are assumed to vary along its radius and relate to the volume fraction of the materials, while the Poisson’s ratio remains to be a constant. The motion equations of the FGM rotating circular disk are simplified into boundary value problems of ordinary differential equation, which are solved by Runge-Kutta method, and the whole problem is solved by utilizing shooting method. Numerical results show that the functionally graded index, angular speeds and geometric shape all have significant effect on the mechanical behaviors of the rotating FGM circular disk. The results of this study may be useful for other investigations of a rotating FGM circular disk.

Micro magnetic field (MMF) sensors developed employing complementary metal oxide semiconductor (CMOS) technology are investigated. The MMF sensors, which are a three-axis sensing type, include a magnetotransistor and four Hall elements. The magnetotransistor is utilized to detect the magnetic field (MF) in the x-axis and y-axis, and four Hall elements are used to sense MF in the z-axis. In addition to emitter, bases and collectors, additional collectors are added to the magnetotransistor. The additional collectors enhance bias current and carrier number, so that the sensor sensitivity is enlarged. The MMF sensor fabrication is easy because it does not require post-CMOS processing. Experiments depict that the MMF sensor sensitivity is 0.69 V/T in the x-axis MF and its sensitivity is 0.55 V/T in the y-axis MF.

In this paper, transient response analysis of a circular sandwich plate with a functionally graded material (FGM) central disk and two piezoelectric layers is presented. Material properties of the FGM central disk for the circular sandwich plate are assumed to vary through the structural thickness according to a power law and the Poisson’s ratio is assumed as the same constant. Based on the first-order shear deformation theory and geometric nonlinear relationship, the nonlinear motion equations of the circular sandwich plate are formulated by using the Hamilton’s variational principle, then combining with the boundary and initial conditions, the whole problem is solved by adopting the finite difference method, Newmark method and iterative method. Numerical results are presented to illustrate that the volume fraction index, geometric parameters, mechanical and electrical loads have a great influence on transient response of the circular sandwich plate.

In this paper, a novel model which considers initial strain related to the material’s yielding stress, the combination of stretch and bending strain and isotropic hardening rule is introduced to predict U-bending springback and time-dependent springback behaviors for a high strength and low alloy (HSLA) steel plate. It is noteworthy that time-dependent springback is associated with plastic strain hardening for the HSLA steel plate. The results obtained from the performed analysis show that the hardening exponent, bending radius and thickness ratio, friction coefficient, and blank holder force have great influences on the springback angle and stress level. Based on this novel model, the prediction of HSLA steel plate’s springback is done in the stage of tool design and hence, the accuracy of drawn part is increased.

Three-dimensional thermodynamic analysis of simply supported high strength and low alloy (HSLA) rectangular steel plates under laser shock processing are carried out in this paper. Three-dimensional transient temperature field of the laser shock processing the rectangular HSLA steel plate is solved by the method of separation of variables. Meanwhile, the displacement and stress fields are derived by using the state-space method. It could be found that some parameters such as laser moving speed and thickness to length ratio do not affect the temperature field only, but also have great influences on the displacement and stress field. The closer the laser from the center of plate is, the greater is the revulsion amplitude of HSLA steel plate’s temperature on laser area. The vibration frequency of HSLA steel plate is proportional to the increasing of laser moving speed. The thickness to length ratio affects HSLA plate’s displacement and stress, but the variation law of in-plane displacement U ∗ is not consistent with other displacement and stress components. It can be observed that applied loading form affects the deflection greatly, both on the order of magnitude and displacement shape.

Based on von Karman nonlinear strain-displacement relationships and classical thin plate theory, a list of nonlinear dynamic equilibrium equations for a viscoelastic composite material thin narrow strip under thermal and mechanic loads are deduced. According to the material constitutive relationship and the relaxation modulus in the form of the Prony series, combing with the Newmark method and the Newton-cotes integration method, a new numerical algorithm for direct solving the whole problem in the time domain is established. By applying this numerical algorithm, the viscoelastic composite material thin narrow strip as the research subject is analyzed systematically, and its rich dynamical behaviors are revealed comprehensively. To verify the accuracy of the present work, a comparison is made with previously published results. Finally, the viscoelastic composite material thin narrow strip under harmonic excitation load and impact load are discussed in detail, and many valuable thermoviscoelastic dynamic characteristics are revealed.

An analytic method for bending analysis of a cylindrical shell composed by a functionally graded material (FGM), placed in a uniform magnetic field, subjected to mechanical and thermal loads is presented. Based on the classical linear shell theory, the equations with the radial deflection and horizontal displacement are derived, and exact solution of the magnetothermoelastic bending problem is obtained. For the FGM cylindrical shell with fixed and simply supported boundary conditions, the effects of mechanical load, thermal load, magnetic intensity, volume exponent, and geometric parameters on the bending deformation of the FGM cylindrical shell are discussed.

Dynamic response analysis of a high strength low alloy (HSLA) steel circular plate subjected to mechanical load in thermal environments is investigated. Based on the von Karman equation and classical theory of thin plate, the nonlinear governing equations for the HSLA steel circular plate are obtained by using the kirchhoff hypothesis. The unknown variable functions are discrete in space and time domains by utilizing the finite difference method and Newmark method, the whole problem is solved by the iterative method. Numerical results indicate that some of the important geometrical and physical parameters are important factors affecting the dynamic response of the HSLA steel circular plate and the design of structures.

In this paper, an underwater structure is modeled as a cylindrical shell with internal bulkheads, and closed by a truncated conical shell, and it consists of metal substrate and sound absorbing coating, whose FGM core is considered. Suppose the inner cavity and outer space of the structure are filled with air and fluid mediums, the mechanical response of the underwater structure is calculated with Galerkin method while the acoustic response is investigated by means of the Helmholtz integral. Some numerical examples are given and the effect of geometrical size and material parameters on mechanical and acoustic response is discussed.

This paper studies the buckling analysis for a ring-stiffened cylindrical shell consisted of functionally graded material (FGM) subjected to hydrostatic pressure and thermal loads. Material properties of the ring-stiffened FGM cylindrical shell are assumed to be temperature-dependent, and vary smoothly through the thickness direction of the structure according to a volume exponent. Based on the Donnell assumptions, buckling loads of the ring-stiffened FGM cylindrical shell are presented by utilizing the Galerkin method. Numerical results reveal that thermal loads, volume exponent and geometric parameters have significant effects on the buckling behavior of the ring-stiffened cylindrical shell.

Based on the von Karman equation and classical thin plate theory, thermomechanical behavior of a high strength low alloy (HSLA) steel circular plate under impact load is investigated. Firstly, when the HSLA steel circular plate is impacted by a rigid impactor, the relation of the contact radius and the instantaneous relative displacement is obtained by using the modified nonlinear Hertzian contact law, and the contact force is solved by using the time increment method. Secondly, the nonlinear governing equations in the form of displacements for the HSLA steel circular plate under the impact load are obtained by using the Hamilton variational principle. Finally, the unknown variable functions are discretized in space and time domains by utilizing the finite difference method and Newmark method, and the whole problem is solved by the iterative method. Numerical results denote that the geometrical parameters, boundary conditions of the HSLA steel circular plate and the initial velocity of impactor have great influences on deformation, the contact force and stresses of the HSLA steel circular plate.

In this article, analysis of vibrations and transient responses of a hollow cylinder made of functionally graded materials (FGMs) under a radially symmetric dynamic load is presented. The material of the FGM hollow cylinder is assumed to be isotropic with constant Poisson's ratio, exponentially-varying elastic modulus, and exponentially-varying density through the radial thickness. By means of the finite difference method and Newmark method, the governing equation of the FGM hollow cylinder under dynamic loads is solved. As numerical examples, the FGM hollow cylinder under impulsive load and that under sinusoidally varying dynamic load are discussed, and then many valuable characteristics are revealed.

Acoustic and vibration control for an underwater structure under mechanical excitation has been investigated by using negative feedback control algorithm. The underwater structure is modeled with cylindrical shells, conical shells, and circular bulkheads, of which the motion equations are built with the variational approach, respectively. Acoustic property is analyzed by the Helmholtz integration formulation with boundary element method. Based on negative feedback control algorithm, a control loop with a coupling use of piezoelectric sensor and actuator is built, and accordingly some numerical examples are carried out on active control of structural vibration and acoustic response. Effects of geometrical and material parameters on acoustic and vibration properties are investigated and discussed.

An analytic study for thermoelastic bending of a functionally graded material (FGM) cylindrical shell subjected to a uniform transverse mechanical load and non-uniform thermal loads is presented. Based on the classical linear shell theory, the equations with the radial deflection and horizontal displacement are derived out. An arbitrary material property of the FGM cylindrical shell is assumed to vary through the thickness of the cylindrical shell, and exact solution of the problem is obtained by using an analytic method. For the FGM cylindrical shell with fixed and simply supported boundary conditions, the effects of mechanical load, thermal load and the power law exponent on the deformation of the FGM cylindrical shell are analyzed and discussed.

Analytical study for electromagnetothermoelastic behavior of a solid cylinder composed of functionally graded piezoelectric material (FGPM), placed in a uniform magnetic field, subjected to electric, thermal, and mechanical loadings is presented. For the case that material properties obey an identical power law, exact solutions for stresses and perturbation of magnetic field vector in the FGPM solid cylinder are determined by using the theory of electromagnetothermoelasticity. Numerical examples and some useful discussions are presented to show the significant influence of material inhomogeneity; adopting a certain value of the inhomogeneity parameter and applying suitable loads can optimize the FGPM solid cylindrical structures.

In this paper, creep buckling and post-buckling of a hybrid laminated viscoelastic functionally graded material (FGM) cylindrical shell under in-plane loading are investigated. Considering the high-order transverse shear deformation and geometric nonlinear theory, the von Karman geometric relation of the hybrid laminated viscoelastic FGM cylindrical shell with initial deflection is established. Based on the Donnell theory, elastic piezoelectric theory and Boltzmann superposition principle, nonlinear creep governing equations of the hybrid laminated viscoelastic FGM cylindrical shell under in-plane loading are derived. By means of the finite difference method and the Newton–Newmark method, the problem for creep buckling and post-buckling of the laminated shell’s structure is solved. Numerical results are presented to show effects of geometric parameters, power law index and loading on creep buckling and post-buckling of the hybrid laminated viscoelastic FGM cylindrical shell.

In this paper, free vibration of a circular plate composed of a transversely isotropic functionally graded piezoelectric material (FGPM) placed in a uniform magnetic field is investigated. Material properties are assumed to depend on the thickness of the circular plate and they are expressed as the same exponential function of h. The problem of free vibration for the transversely isotropic FGPM circular plate with clamped and simply supported boundary conditions is solved by means of the state space method. Numerical examples and some useful discussions are given to demonstrate the significant influence of material inhomogeneity, and adopting a certain value of the graded index can optimize structures of the circular plate. This will be of particular importance in modern engineering design.

This paper presents the fabrication and characterization of energy harvesting thermoelectric micro generators using the commercial complementary metal oxide semiconductor (CMOS) process. The micro generator consists of 33 thermocouples in series. Thermocouple materials are p-type and n-type polysilicon since they have a large Seebeck coefficient difference. The output power of the micro generator depends on the temperature difference in the hot and cold parts of the thermocouples. In order to increase this temperature difference, the hot part of the thermocouples is suspended to reduce heat-sinking. The micro generator needs a post-CMOS process to release the suspended structures of hot part, which the post-process includes an anisotropic dry etching to etch the sacrificial oxide layer and an isotropic dry etching to remove the silicon substrate. Experiments show that the output power of the micro generator is 9.4 mW at a temperature difference of 15 K.

This article presents an analytical study for forced vibration of a cylindrical shell which is composed of a functionally graded piezoelectric material (FGPM). The cylindrical shell is assumed to have two-constituent material distributions through the thickness of the structure, and material properties of the cylindrical shell are assumed to vary according to a power-law distribution in terms of the volume fractions for constituent materials, the exact solution for the forced vibration problem is presented. Numerical results are presented to show the effect of electric excitation, thermal load, mechanical load and volume exponent on the static and force vibration of the FGPM cylindrical shell. The goal of this investigation is to optimize the FGPM cylindrical shell in engineering, also the present solution can be used in the forced vibration analysis of cylindrical smart elements.

This paper is concerned with two-dimensional (r, θ) thermoelastic dynamic responses of a long functionally graded hollow cylinder subjected to asysmmetrical thermal and mechanical loads. The material properties, except the Poisson's ratio, are assumed to be temperature independent and vary exponentially and continuously in the radial direction. By means of finite difference method and Newmark method, the motion governing equations of the long FGM hollow cylinder are solved. Comparisons between this paper's results and the corresponding analytical results validate the proposed solution. In addition, the effects of the volume fraction, temperature boundary conditions on the hollow cylinder's deformations and stresses distributions are examined, and many other valuable thermoelastic dynamic characteristics are revealed.