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This paper presents an exact analysis of deformation and stress field in a finite cylinder under axisymmetric boundary conditions. The problem is formulated based on the state space formulation for transversely isotropic piezoelectric media. Upon the separation of variables method, we get a set of general solutions spanning over the complete solution space to cover all axisymmetric boundary conditions. Furthermore, a rigorous solution which satisfies the end conditions is determined by using eigenfunction expansion. Numerical results show that the local effect is significant but confined to boundary layer near the fixed end where the displacement and stress are remarkably different from those of other regions.

Purpose For general quasi-static problems of viscoelastic functionally graded materials (VFGMs), the correspondence principle can be applied only for simple structures with a closed form solution of the corresponding elastic problem exists. In this paper, a new symplectic approach, according to the correspondence principle between linearly elastic and viscoelastic solids, is proposed for quasi-static VFGMs. Design/methodology/approach Firstly, by employing the method of separation of variables, all the fundamental eigenvectors of the governing equations are obtained analytically. Then, the satisfactions of boundary conditions prescribed on the ends and laterals are discussed based on the variable substitution and the eigenvector expansion methods. Findings In the numerical examples, some boundary condition problems are given. The results show the local effects due to the displacement constraints. Originality/value The paper provides an innovative technique for quasi-static problems of VFG Ms. Its correctness and the efficiency are well suported by numerical results.

Ocean underwater vertical sensor structure is a kind of modern marine observation platform. But most of the current ocean sensors work independently, and it lacks a suitable method to assemble them in a control system. Having good expansibility and convenient structure, the ocean buoy platform with contactless data transmission technology is possible to organise a long-term, real-time and autonomous working observation network. The contactless data transmission model with a two-stage electromagnetic coupler is investigated. A prototype of communication system using the differential phase shift keying method is constructed. Due to attenuation in seawater, it is difficult to realise the long distance and low bit error rate transmission. To solve this problem, an equivalent two-terminal network model with compensation capacitor is proposed to make this contactless transmission system work at the resonance frequency. In 1000 m deep sea experiment, the sensors equipped with this vertical structure base...

A novel eigenvector expansion method under the symplectic system is introduced for boundary condition problems of thermo-viscoelastic materials. On the basis of the state space formalism and the use of the Laplace integral transform, the general solutions of the governing equations, zero and non-zero-eigenvalue eigenvectors, are obtained analytically. Since the eigenvectors are expressed in concise analytical forms, the adjoint symplectic relation in the Laplace domain is generalized to the time domain. Using this method, various boundary conditions and the particular solution of non-homogeneous governing equations can be conveniently described by combinations of the eigenvectors.

The effects of argon pressure on the microstructure and magnetic properties of the sputtered FeCoSiB amorphous films were investigated. At low deposition pressure the samples show flat and dense surface, while those at higher pressure show columnar growth with rough surface. The formation of the columnar grains results in the perpendicular magnetic anisotropy due to the shape anisotropy. Stripe magnetic domains were observed in the latter samples. Both the magnetic contrast in magnetic force microscope images and the coercivity of FeCoSiB films increase first and then decrease with the increasing of the sputtering pressure. It is suggested that the columnar grains introduce shape anisotropy which plays an important role in tuning the magnetic behaviors of the FeCoSiB films with the sputtering pressure.

BaFe 12 O 19 ferrite thick films were screen-printed and sintered at 1150°C under pressure (hot press sintering). The effects of the hot press sintering on the properties of barium hexaferrite thick films were investigated. The X-ray diffraction pattern shows improvement of the (00l) texture under pressure. The porosity size of the hot press sintering samples decreases obviously and the surface compactness is improved as the pressure is increased. The films are quite anisotropic with magnetic easy axis perpendicular to the film plane. The largest remanence ratio achieved is 0.75 under the highest pressure of 4 MPa.

We present a family of soliton solutions of the quasi-one-dimensional Bose–Einstein condensates with time-dependent scattering length, by developing multiple-scale method combined with truncated Painleve expansion. Then, by numerical calculating the solutions, it is shown that there exhibit two types of dark solitons—black soliton (the zero minimum amplitude at its center) and gray soliton (the minimum density does not drop to zero) in a repulsive condensate. Furthermore, we propose experimental protocols to realize the exchange between black and gray solitons by varying the scattering length via the Feshbach resonance in currently experimental conditions.

The effects of tensile and compressive stress on the magnetic domains of amorphous FeCoSiB films are investigated. It is observed that the unstressed sample consists of irregular domains while the stressed samples show stripe domains. With the increase of the tensile stress, the stripe domain of the stressed films tends to align parallel to the direction of the stress, while with the increase of the compressive stress the stripe domain of the stressed films tends to align perpendicular to the direction of the stress. The magnetic domain and its evolution under the stress are explained by introducing the magnetoelastic anisotropy induced by the stress.

The effect of stress on the magnetic domain and anisotropy of FeCoSiB amorphous films is investigated. It is observed that the unstressed sample consists of irregular domain while the stressed samples show the strip domain. The strip domain of the sample under tensile stress aligns parallel to the direction of the stress while that of the sample under compressive stress aligns perpendicular to it. The variation of the magnetic domain is explained with the magnetoelastic anisotropy induced by the stress, which has been verified by the hysteresis loops, remanences and the anisotropy field. It is also obtained that the stress-induced anisotropy increases with the increase of the stress. The effects of the stress on the magnetic properties of the FeCoSiB films have been discussed.

We report the effects of oxygen content on the transport properties of La 0.7 Ca 0.3 MnO 3-δ thin films grown epitaxially on LaAlO 3 (001) substrates by RF magnetron sputtering. The as-deposited thin films were annealed and treated by oxygen plasma to improve the oxygen content. We observe that the La 0.7 Ca 0.3 MnO 3-δ films annealed at 850°C is highly oriented growth on (001) LAO substrate. However, the XRD patterns of the samples annealed at lower than 850°C show no distinct diffraction peaks. This evidence indicates that the samples annealed at lower than 850°C are still amorphous or nanocrystalline. The La 0.7 Ca 0.3 MnO 3-δ films without oxygen plasma do not suffer insulator to metal transition at the temperature range from 213 to 293 K. But, at the same temperature range, for the 650°C, 750°C, and 850°C annealed samples with oxygen plasma treatment show an insulator to metal transition at 239 K, 239 K, and 257 K, respectively. Moreover, compared to without oxygen plasma treatment, the resistivity of the sample with oxygen plasma treatment is dramatically decreased. These results imply that the insulator to metal transition is strongly determined by the ratio of Mn 4+/ Mn 3+ and the oxygen content of the films. The increases of the ratio of Mn 4+/ Mn 3+ and the oxygen content lead to a higher insulator to metal transition temperature.

Simple and effective model is demanded which enables the design and structural optimization of the microwave MEMS switch efficiently. For this purpose the microwave behaviors of series metal cantilever MEMS switch have been modeled by “simple” circuit in this paper. The microwave characteristics have been calculated and compared with the experiment data based on the developed model. The results show that the microwave characteristics of series metal cantilever MEMS switch can be described very well with this model. Based on this model, the influences of the structural parameters of the switch on the microwave characteristics have been discussed extensively.

FeCoSiB/Cu/FeCoSiB sandwich layers were deposited on flexible substrate to develop flexible stress/strain sensors. The influence of stress on the impedance of the multilayers is reported. The results show that the variation of the impedance increases with the increase in deflection of the free end of the cantilever. A relative change in impedance of 6.4% is obtained in the FeCoSiB(1.5 μm)/Cu(0.25 μm)/FeCoSiB(1.5 μm) sandwich layers at 1 MHz with deflection of 2 mm. The stress impedance effects are sensitive to the frequency of the current and the thickness of both FeCoSiB and Cu layers. The stress impedance effect increases with the increase in the thickness of FeCoSiB or Cu layers. The stress impedance effect increases slightly with the increase in frequency and decreases with the further increase in frequency, which can be understood by the stress and frequency-dependent permeability of magnetic films.

The effect of stress on the magnetic properties of FeCoSiB amorphous films is investigated. It has been observed that the unstressed sample is isotropic in the film plane. The samples under tensile stress show clear easy axis along the stress while the samples under compressive stress show easy axis perpendicular to the stress axis. With increasing of the tensile stress, the coercivity of the films decreases monotonically. The coercivity increases with increase of the compressive stress when the stress is not large and then decreases with further increase of the compressive stress. The variation of the coercivity with stress is understood by taking into account the influences of stress on the rotational and wall displacement magnetization reversal processes.