Advanced Materials Research Vols. 160-162

Abstract: An experimental study of plasma duty-cycled actuation over slender forebodies is performed on a 20° circular-cone-cylinder model using a pair of Single Dielectric Barrier Discharge (SDBD) plasma actuators near the cone apex combined with a duty-cycle technique. The tests are carried out in a low-turbulence 3.0 m ×1.6 m low-speed wind tunnel at an angle of attack of 45°. The Reynolds number based on the cone base diameter is 50, 000. The frequency of the duty cycle is 10 Hz. The mechanisms of the unsteady excitations over various duty cycles of frequency 10 Hz are studied using ten Kulite pressure transducers mounted around a cross section of the cone forebody at angle of attack of 45°.The circumferential pressure distributions over a station on the cone forebody is measured by unsteady pressure tappings, Phase-locked averaged pressures are studied and compared with ensemble-averaged pressures.

Abstract: The main cable is made of PPWS. Its large displacement and nonlinear mechanical properties are shown by their own elastic deformation and its geometry changes affecting the system balance. To get the real main cable-shaped of long-span suspension bridge, based on the finite element method, the element stiffness matrix was derived, which displacement field was same to the element shape. Then through the horizontal and vertical direction equilibrium equations were solved, the relationship between main cable shape and the system parameters was obtained. The calculation method was compiled to MATLAB 7.0 programs, and applied to ascertain the main cable-shaped of one long-span suspension bridge. When the paper calculated result was contrasted with the design value, it could be concluded that: the main cable-shaped of long-span suspension bridge could be accurately obtained by the paper method, and the method was convenient for compiling.

Abstract: In this paper, we report on the microwave absorbing properties of the Ni/SiO2 core/shell soft magnetic material which was synthesized by the tetraethyl orthosilicate (TEOS) hydrolysis method. The SEM patterns were shown that the particles of Ni/SiO2 were more dispersed and homogeneous. Microwave absorbing properties were measured in the range of 0.1–18 GHz. A reflection loss (RL) exceeding −20 dB in the frequency range of 2.6–8.9 GHz was achieved for an absorber thickness of 2.0–5.6 mm, and an optimal RL of −49.5 dB was obtained at 4.4 GHz for the thickness of 3.5 mm. The good microwave absorption properties resulted from a proper impedance match as a consequence of the insulator SiO2 around Ni particles.

Abstract: Fe-Co soft magnetic films with tuneable in-plane uniaxial anisotropy were successfully electrodeposited onto ITO conductive glass. The influence of composition and electrolyte temperature on in-plane magnetic anisotropy field was investigated. Our results show that the in-plane uniaxial anisotropy can be induced by a magnetic field applied in the film plane during electrodeposition. Fe-Co films with various Fe content in the range from 35 at.% to 53 at.% were obtained and the magnetic anisotropy field was very sensitive to the composition. Moreover, the influence of electrolyte temperature on magnetic anisotropy field was investigated and it was found that the in-plane uniaxial anisotropy field can be tuned by varying the electrolyte temperature from 5 to 40 oC.

Abstract: In this work, the Z-type barium ferrite of single phase was prepared by the salt-molten method which was a novel, economical and environmentally friendly method. The results showed that the salt was helpful to get single phase and could effectively modify the shape of the powder. Based on the microwave measurement, reflection losses exceeding −20 dB of Co2Z composite were obtained in the frequency range of 4.1–14.5 GHz for absorber thicknesses of 2.1–3.5 mm and the minimum value of the reflection loss was -42.9 dB at 4.9 GHz for the thickness of 2.9 mm. For those unique properties, Co2Z could be a good candidate for electromagnetic (EM) materials and other practical applications at the high frequency.

Abstract: For the sake of thinner electromagnetic wave absorbers used in quasimicrowave band, planar anisotropy carbonyl-iron (PACI) coated with amorphous SiO2 particles as absorber and paraffin as matrix were prepared. The complex permeability, complex permittivity and microwave absorption properties were investigated in the frequency range of 0.1-18 GHz. Both the real parts of permeability and permittivity are increased with the increasing of PACI/SiO2 particles volume concentrations. The minimum reflection loss shifts to the low frequency region with increase in PACI/SiO2 particles volume concentrations. The decrease of matching frequency could be well explained by the increasing of and . The PACI/SiO2 core-shell material exhibits great potential in application absorbers in quasimicrowave frequency range.

Abstract: Nano-crystalline titania coatings were prepared by microarc oxidation (MAO) on titanium alloy (TC4) substrates in Na2CO3-KF electrolytic solution. The coating thickness was measured by an optical microscopy with a CCD camera. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were employed to characterize the microstructure and phase composition of coatings. The results show that the coatings are porous nano-crystalline structures mainly composed of anatase and rutile (TiO2). With the increase of anode voltage, both the relative contents of rutile and the sizes of micropores increase gradually, whereas the sizes of the nano-crystalline decrease first and then increase. The prepared samples were employed to study the photo degradation characteristics of Rhodamine B. The results show that the photodegradation performance of the samples prepared under 220V is the best.

Abstract: Resistance spot welding (RSW) is an important welding process in modern industrial production, and the quality of welding nugget determines the strength of products to a large extent. Limited by the level of RSW quality monitor, however, RSW has rarely been applied to the fields with high welding quality requirements. Associated with the inversion theory, in this paper, an electromagnetic inverse model of RSW was established, and the analysis of influence factors, such as the layout of the probes, the discrete program and the regularization method, was implemented as well. The result shows that the layout of the probe and the regularization method has great influence on the model. When the probe is located at the y direction of x-axis or the x direction of y-axis and Conjugate Gradient method is selected, a much better outcome can be achieved.

Abstract: Based on the nonlinear flux creep model, the V-I curves are numerically studied considering the influences of surface barrier. The influences of surface barrier to critical current of the high temperature superconductors (HTSC’s) are carried out. The results show that as the strength of surface barrier increases, critical current increases. Besides, with the existence of surface barrier, history effect was found in V-I loop, which indicates that surface barrier is one of the important factors to make history effect.

Abstract: Fe/Al2O3 and Fe3Al/Al2O3 composites were prepared by mechanochemical synthesis. Microwave characteristics were measured in 0.1–18 GHz. A reflection loss (RL) exceeding -10 dB in the frequency range of 1.5-8.5 GHz for an absorber of 6-1.5 mm was achieved for the Fe3Al/Al2O3 composites. Optimal RL of -41 dB was obtained at 2.8 GHz for an absorber thickness of 3.9 mm. The good microwave-absorption properties results from a proper impedance match as a consequence of the insulator Al2O3 around Fe and Fe3Al. Microwave reflection results show that the corresponding frequency and the matching thickness is closely related to the quarter wavelength matching condition and these composites can be attractive candidates for electromagnetic wave absorption materials.