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August 15,2015
Volume 8,Issue 15
Pages -
Subject Area:Explosion Mechanics,Fluid Mechanics,Applied Physics,Condensed Matter Physics,Electromagnetism

Title: Research on shock wave demagnetization of Nd2Fe14B hard ferromagnetic at low shock wave pressure

Authors: LI Chuan, WU Junying, CHEN Lang, LI Shengcai, LU Feng
PP: 1649-1654
Abstract: To study the shock wave demagnetization laws of Nd2Fe14B under low shock wave pressure, the flyer driven by a light gas gun loading Nd2Fe14B experimental device was designed and the shock wave demagnetization experiments were conducted. The induced electromotive force and magnetic flux losses were obtained. The processes of the flyer loading Nd2Fe14B were simulated. The shock wave pressures and their change laws were also obtained. The results show that initial shock wave pressure of Nd2Fe14B would be higher with the increase of the flyer velocity, which results in the higher demagnetization rate of Nd2Fe14B. When the initial shock wave pressure is closed to 7.45 GPa, Nd2Fe14B would be completely demagnetized. The critical pressure of serious demagnetization of Nd2Fe14B should be between 3-7 GPa.
Keywords: explosion mechanics; Nd2Fe14B ferromagnetic; shock wave demagnetization; shock wave; pulsed power source

Title: CFD simulation on the towing kite assisted navigation ship

Authors: ZHAO Binbin, LIU Qiang
PP: 1640-1648
Abstract: Mechanical properties of the towing kite were studied using the open source computational fluid dynamics (CFD) package OpenFOAM and Spalart-Allmaras turbulence model. We presented lift and drag coefficients of towing kites of different shapes, different ratios of width to length and different cambers under different angles of attack. In order to improve the computational efficiency of numerical simulation, we adopted a domain decomposition parallel computing method and a computing strategy combined calculation of potential flow and viscous flow. These calculation methods were also validated. Then, we calculated the assisted navigation power of the towing kite, an estimation formula of energy-saving rate to the whole ship of towing kite under different Beaufort scales and different altitudes based on ship resistance and propulsion efficiency point of view was also presented.
Keywords: fluid mechanics; assisted navigation towing kite; high Reynolds number; Spalart-Allmaras; assisted navigation power; OpenFOAM

Title: Numerical investigation of fluid-structure interation characteristics of flexible hydrofoils

Authors: GAO Yuan, WU Qin, HUANG Biao, WANG Guoyu
PP: 1633-1639
Abstract: Concerned with the numerical investigation of the hydroelastic behavior of a flexible hydrofoil, the characteristics of the hydrodynamic loads and deformations are analyzed using the fluid-structure interaction method. The results also show that there is a good agreement between the numerical and experimental results. The lift coefficient of flexible hydrofoil is higher than that of the rigid one at the same angle of attack, and the absolute value of the maximum negative pressure on the suction side of the foil increases from the fixed end to the free end, which is due to the effect of fluid-structure interaction caused by the deformation. The local angle of attack from the fixed end to the free end increases, which is responsible for the increase of the lift coefficient.
Keywords: fluid mechanics; flexible hydrofoil; fluid-structure interaction; hydrodynamic load

Title: Imitation analysis on brain electromagnetic field using HFSS software

Authors: XU Zhanxian
PP: 1626-1632
Abstract: We apply the HFSS software imitation to analyze brain electromagnetic field, the influence and harm on environment and the human body health of the electromagnetic radiation are also evaluted through combining it and the national, international electromagnetic radiation standards. The strength of the electromagnetic radiation depends on the field, wave type, frequency, effect time, human body, radiation spacing, job site, personnel's age and gender etc. Simulation shows that the brain's largest electric field value Emax2 is 0.157 kV/m. For the human brain, after all, how to withstand the electric field need to be further studied. The stronger electromagnetic field affection will be a result of the brain in imperceptible in causing a person's energy and physical impairment and is prone to cataracts leukemia, brain tumors and brain dysfunction. This study provides theoretical reference for green electromagnetic environmental protection.
Keywords: applied physics; electromagnetic radiation; specific absoption rate; Ansoft HFSS; electromagnetic simulation

Title: Several useful peak-holding circuits in nuclear experiments

Authors: LIN Sibo, GE Yucheng
PP: 1621-1625
Abstract: We introduced operational principal of peak-holding circuit and designed several useful peak-holing circuits for high-speed Gauss pulse with 500 ns pulse width. We use LF398 and OPA615 to sample and hold IC to get two kinds of peak-holding circuits and test their features. With simple structures, these circuits, to some extent, can reach the target of peak-holding.
Keywords: nuclear physics; peak-holding; LF398; OPA615; high-speed pulse

Title: Separation of bulk lifetime and surface recombination velocity in silicon wafer

Authors: SONG Chengyuan, LI Ping, WANG Yuxuan, WANG Yujun, LIU Aimin
PP: 1614-1620
Abstract: The surface recombination velocity and the bulk lifetime of minority carriers are important electronic properties for silicon solar cell materials. In this work, according to the one-dimensional continuity equation of non equilibrium minority carrier concentration in silicon wafer, and through the numerical analysis under quasi-steady state photoconductance (QSSPC) test model, we separate bulk time and surface recombination velocity. Based on the calculation on the P silicon wafer with different resistivities, we find that bulk lifetime depending upon carrier density influences the density distribution vitally rather than taking bulk lifetime as a constant at high injection level.
Keywords: semiconductor physics; silicon solar cells; quasi-steady state photoconductance; bulk lifetime; surface recombination velocity

Title: Investigation on surface passivation mechanism of AlOx thin film thickness by atomic layer deposition

Authors: XIE Hongli, ZHANG Bingye, WANG Yujun, LIU Aimin
PP: 1608-1613
Abstract: Various thicknesses of AlOx thin films were fabricated on P-type textured crystalline silicon (c-Si) wafers by atomic layer deposition (ALD). The thickness of AlOx thin films was altered through changing the deposition cycles. Using field emission scanning electron microscopy (FESEM), the surface morphology structures were characterized. The reflectances of the samples were also tested. Through adjusting the thicknesses of AlOx thin films, the optical and electrical properties were significant improved. The reflectances of various thicknesses of AlOx thin films were decreased from 10.40% to 0.96% with the increasing of thickness, which is demonstrated that the AlOx thin films show an effective antireflection properties. Moreover, the passivation effect of AlOx thin films was identified. The effective minority carrier life time (τeff) exhibits a significant improvement with the variety of film thicknesses from 6.67 μs to 29.28 μs (when Δp=1×1015 cm-3). When the thickness of AlOx thin films is 32 nm, the life time (τeff) arrives at the highest. The capacity-voltage (C-V) was induced to explain the increasing of τeff. It can be found that it shows a large shift of C-V curves in positive direction with the increasing of thickness for all samples, indicating the existence of negative equivalent oxide charge density (Qf). It also find that when the thickness of AlOx thin films is 32 nm, the Qf arrives at highest (Qf=-9.51×1012 cm-2). The high Qf indicates that the AlOx thin films can provide better field-effect passivation effects in P-type semiconductors.
Keywords: semiconductor physics; AlOx; surface passivation; quasi steady state photo conductance; effective lifetime

Title: Effects of supercooling degree on performances of single-domain SmBCO superconductor prepared by new TSIG process

Authors: LI Qiang, YANG Wanmin
PP: 1601-1607
Abstract: In order to reduce the solid solubility x in the (Sm1+xBa2-xCu3Oy) crystals, we provide a new method to fabricate single-domain SmBCO superconductors by top seeded infiltration and growth process (TSIG) with (Sm2O3+1.2BaCuO2) as new solid phase. The effects of the supercooling degree on the crystal growth dynamics, microstructures and properties of the SmBCO bulks are also investigated. The results show that the growth rate of the SmBCO crystal increases gradually with the increase of the supercolling degree at first, but decreases when the supercooling degree is too high; the higher the supercooling degree, the smaller the average size of Sm211 particles captured in the SmBCO bulks; the lower the onset superconducting transition temperature, the wider the transition temperature width, and the higher the critical current density. These results indicate that the physical properties of SmBCO bulks can be greatly improved by this new method because of the greatly reduced Sm3+/Ba2+ substitution during the TSIG process, which provides an important new way for the fabrication of high-quality SmBCO superconductors.
Keywords: condensed matter physics; SmBCO bulk superconductor; top seeded infiltration and growth; supercooling degree; superconducting transition temperature; critical current density

Title: Active target localization method based on inverse parabolic equation

Authors: ZHOU Liang, LIAO Cheng, SHENG Nan, ZHANG Qinghong
PP: 1594-1600
Abstract: Based on the two way parabolic equation model, the inverse parabolic equation method was applied to the two-dimensional target localization problem. However, while the traditional inverse parabolic equation method was difficult to separate the target echo and the background clutter, time reversal adaptive interference cancellation method is used to eliminate the background echo, and then inverse parabolic equation method is applied to determine the spatial field distribution of the whole region. The target location is estimated by the maximum electric field strength position. The combined algorithm eliminate the localization error problem effectively for strong clutter environment. Finally, the longitudinal localization accuracy is verified by the numerical example.
Keywords: electromagnetism; parabolic equation method; time reversal algorithm; inverse parabolic equation; cluster elimination; target localization

Title: Optical super-resoluntion imaging properties of microscale spherical lenses with immersion medium

Authors: CAO Lingling, YAO Ling, YE Yonghong
PP: 1587-1593
Abstract: In this paper, the imaging properties of three kinds of microspheres [barium titanate glass(BTG), polystyrene (PS) and silica (SS)] semi-immersed or full-immersed in four different refractive index immersion medium (deionized water, ethanol, 50% salt solution, microscope immersion oil) are studied. We find that the three kinds of microspheres semi-immersed or full-immersed in the four immersion medium can magnify the stripe patterns of the disc and have super-resolution imaging ability. Moreover, we find that the image magnification and contrast can be decided by the relative refractive index between a microsphere and the immersion medium. A higher relative refractive index can increase image magnification and contrast. The mechanisms are also discussed with numerical simulations based on CST software.
Keywords: optics; microscale spherical lenses; super-resolution imaging; immersion medium

Title: Effect of off-axis parameter and propagation distance on the propagation properties of off-axis vortex beams

Authors: FENG Jiawen, ZHU Zhengtian, ZHAO Qi, CHEN Yuankai, LIU Yisi
PP: 1581-1586
Abstract: The analytical expression for the propagation of off-axis vortex beams with topological charge through a single slit diffraction is derived based on the Fresnel diffraction integral, which is used to study the propagation of central phase singularity of off-axis vortex beams by using Mathematica software to numerical simulation. The simulation results show that after the off-axis vortex beam passing through a single slit diffraction, the spatial distribution of phase singularities depends on propagation distance, the half-width of a single slit and off-axis parameter. Then, we study the anisotropic elliptical vortex beams. The analytical expression for the propagation of off-axis elliptical vortex beams with different topological charges in free space is derived, which is used to study the intensity distribution and propagation of phase singularity of off-axis elliptical vortex beams in detail by using Mathematica software to numerical simulation. The results show that in the case of off-axis, the intensity distributions of beams will change significantly. And the position of phase singularity is always changed. The spatial distribution of phase singularities depends on propagation distance and off-axis parameter. There are some different changes for different topological charges.
Keywords: optics; vortex beams; off-axis; properties of propagation; phase singularity; intensity distribution

Title: Characteristic research on photonic band gaps square-lattice photonic crystals based on 8-shaped scatters

Authors: PAN Saihu, XU Quan
PP: 1573-1580
Abstract: A novel photonic crystal based on 8-shaped scatters with two-dimensional square-lattice is presented. By employing the MPB of Massachusetts Institute of Technology (MTT), the relationship between the structural parameters of the photonic crystals and the properties of photonic band gaps are investigated. The calculation results of 8-shaped scatters with two-dimensional square-lattice demonstrate that big complete band gap exists in transverse magnetic (TM) field mode, which provides application for the design of the filter and the total reflection based on the complete band gap characteristics. On the other hand, small complete band gap exists in transverse electric (TE) field mode with rather complicated energy band characteristics, which provides application for the design of negative refraction and self alignment characteristics based on energy band characteristics. By optimizing the structural parameters, the maximum absolute photonic band gaps of 0.102 8ωa/2πc is obtained and six absolute photonic band gaps are existed when 32.3≤εr≤33.5.
Keywords: optics; photonic crystals; complete band gaps; 8-shaped; scatter

Title: Study on light of laser display system based on phosphor

Authors: YE Xinxin, ZHAO Qi
PP: 1567-1572
Abstract: In this paper, we study the laser optics display of fluorescent powder calculation method of the color coordinate of mixed white light and the coordinates, color temperature and flux white with the change of proportion of fluorescence powder. Blue laser motivated monochromatic color wheel of red green and yellow, we use integrating sphere to collect spectra, get color coordinates of each monochromatic fluorescent. According to the single color coordinate, we use the method of color coordinate on color mixing to simulate the color coordinate about different proportion of fluorescence. The simulation results with the experimental measurement data error is .4%. The results showed that increasing the ratio of gray spaces (blue), the color coordinate of white light will be reduced. Increasing the ratio of yellow fluorescent, the luminous flux will be raised, while the color temperature decreases. We can obtain various of white light source with different color coordinates, color temperatures and luminous flux according to the different color wheel of different proportion of fluorescence.
Keywords: optics; laser display; color wheel of fluorescence; color coordinate; color temperature

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