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Lingfeng Wang,Guoli Lei,Chong Yan,Hongliang Ge 한국자기학회 2019 Journal of Magnetics Vol.24 No.4
With the development of switching power supplies, miniaturization and high efficiency become hot research issues, and decreasing high-frequency losses is an effective method to achieve it. In this article, the effect of different calcination temperature on the power losses of MnZn ferrites at high frequency (500 kHz) over a broad temperature range is reported. The MnZn ferrites samples were prepared by ceramic process and the effect of calcination temperature was analyzed. The raw materials were calcined at 775 ℃, 800 ℃, 825 ℃, 850 ℃, 875℃, 900 ℃, 925 ℃ and 950 ℃, and the regular fluctuations of particle size (as-calcined), density (as-sintered) and magnetic properties are presented in this work. It is shown that the samples calcined at 850 ℃ exhibit optimal microstructure and magnetic properties. The newly developed MnZn ferrites are characterized by sintered density of 4.61 g/cm³, initial permeability of 1223 (10 kHz/0.1 mT/25 ℃), saturation magnetic flux density of 488 mT (10 kHz/1200 A/m/25 ℃) and power losses of 68 mW/cm³ (500 kHz/50 mT/100 ℃).
Park, Jungjae,Chen, Lingfeng,Wang, Quandou,Griesmann, Ulf Optical Society of America 2012 Optics express Vol.20 No.18
<P>We describe a method to simultaneously measure thickness variation and refractive index homogeneity of 300 mm diameter silicon wafers using a wavelength-shifting Fizeau interferometer operating at 1550 nm. Only three measurements are required, corresponding to three different cavity configurations. A customized phase shifting algorithm is used to suppress several high order harmonics and minimize intensity sampling errors. The new method was tested with both silicon and fused silica wafers and measurement results proved to be highly repeatable. The reliability of the method was further verified by comparing the measured thickness variation of a 150 mm diameter wafer to a measurement of the wafer flatness after bonding the wafer to an optical flat.</P>
An investigation on the dynamics of domain switching of Bi0.5Na0.5TiO3-based ferroelectric ceramics
Zhipeng Gao,Hang Zhang,Yi Liu,Lingfeng Wu,Jia Yang,Tao Zhang,Haiyan Wang,Xuefeng Chen,Genshui Wang,Hongliang He 한국물리학회 2017 Current Applied Physics Vol.17 No.4
The dynamics of domain switching of Bi0.5Na0.5TiO3-based ferroelectric ceramic was investigated. With the electric field increasing, the domain switch experienced three sections of no domain switch region, creep region and flow region. In the creep region, the domain switch is dominated by the thermally activated domain wall movement. In flow region, the domain wall experience the viscous flow motion. For the BNT-BA-Zn ceramic, the activation energy of creep domain switch is much higher than it in flow region. With temperature increasing, the sensitivity of domain wall motion to the frequency is decreasing. This result demonstrated the domain switch of different ferroelectric materials could be quantitatively analyzed and compared based on the simple polarization - current - electric field data.
Dingkun Yuan,Kang Zhang,Lijian Wang,Lingfeng Jin,Xutao Guo,Guangxue Zhang 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.103 No.-
Biomass is carbon-neutral and has the carbon-negative potential if combined with carbon capture andstorage (CCS). This study investigated the thermochemical conversion to high-purity hydrogen of a typicallignite (BYH) and seaweed biomass (BS) with carbon capture in a designed fixed-bed reactor at moderateconditions (1 atm, 873 K). High-purity hydrogen of 486.91–801.5 ml/g-blends with suppressed CO2formation was produced in the alkaline gasification. The alkali can decompose the coal/biomass molecularstructures, in-situ capture CO2 and control the gases to high-purity H2 (80.1%–93.2%). The synergisticeffect of coal and biomass changes the gas evolution behaviors and impacts the chemical structures of thechar. The abundant SiO2 and Al2O3 in the coal can inhibit the catalytic activities of earth alkali metals inthe biomass, but not much. These results are significant to the future development of low-carbon renewableenergy techniques.
Effect of Ignition Position and Sample Thickness on Flame Spread in Flexible Polyurethane Foam
Qi Yuan,Chang Li,Paul Amyotte,Lingfeng Wang,Chunmiao Yuan,Gang Li,Weidong Yan 한국고분자학회 2022 폴리머 Vol.46 No.4
Fire behavior of flexible polyurethane foam (FPUF) at different sample thicknesses and ignition positioningwas investigated. Effects on flame height, mass loss rate and other parameters were tested, and the flame propagationmechanism was analyzed. A method for predicting equivalent combustion diameter (D) values of the dynamic changeof liquid pool at different positions is proposed. Combined with data of sample mass loss rate, flame height can be predicted. Based on a transition state model, a method for predicting the fire risk of FPUF in late stage combustion by calculating the generation time of polyols is proposed. With edge ignition, FPUF burning produces an inclined surfaceduring the combustion process which enhances the length of the preheating zone by means of heat conduction and heatradiation. Flame spread rate (FSV) in FPUF with edge ignition was greater than with center point ignition.
( Yuepeng Song ),( Miaomiao Chen ),( Baoyan Xu ),( Dongsheng Gao ),( Jing Guo ),( Lingfeng Xu ),( Zheng Wang ),( Hyoung Seop Kim ) 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.11
Herein, we report the results of our investigation on the effect of friction and anvil design on the heterogeneous plastic-deformation characteristics of copper during the compressive stage of high-pressure torsion (HPT), using the finite element method. The results indicate that the friction and anvil geometry play important roles in the homogeneity of the deformation. These variables affect the heterogeneous level of strain in the HPT compressed disks, as well as the flash in the disk edge region. The heterogeneous plastic deformation of the disks becomes more severe with the increasing depth of the cavity, as anvil angle and friction coefficient increase. However, the homogeneity increases with increases in the wall angle. The length of flash and the area of the dead metal zone increase with the depth of the cavity, while they decrease at a wall angle of 180°. (Received March 17, 2016; Accepted May 25, 2016)
Analytical Solution of Loosening Pressure Model for Shallow Tunnel Based on Pile-beam-arch Method
Tao Li,Zhongyu Zhang,Muchi Luo,Bo Liu,Yanlong Wang,Lingfeng Li 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.8
Loosening of earth pressure by tunnels is an important parameter for the structural design of subway stations, this study analyzes the difference between the loosening pressures of each span of a shallow multi-span tunnel station using the pile-beam-arch (PBA) method. By conducting a similarity model test of the PBA method, we simulate the complete excavation process. We study the sliding failure mode of the overlying soil of the shallow-buried station and the law of change of the loosening pressure of each span. A simplified calculation model for the loosening pressure of shallow buried multi-span tunnels by the cavity pile method was developed, and the applicability of the formulae and sensitivity analysis of the parameters were carried out. The results reveal that the loosening pressure of the mid-span is transferred to the stress of the side-span during tunnel excavation. This finding contradicts Terzaghi’s and Bierbaumer’s methods, which do not consider the influence of tunnel structure on the loosening pressure of the overlying soil. The side span relaxation pressure is only related to the soil capacity and the depth of burial of the tunnel This research can provide an important theoretical reference for the design of the overburden load and lateral confining pressure of the PBA structure design.