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RISS 인기검색어
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- 저자 : Zhengxin Liu (검색결과 4 건)
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Gamma radiation shielding properties of WO3/Bi2O3/waterborne polyurethane composites
Wu Zhengxin,Li Yong,Yan Qiang,Liu Guoqing,Liu Yong,Wang Guowei,He Liang 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.81 No.3
In this study, the gamma-ray shielding performance and the mechanical properties of waterborne polyurethane (WPU) composites embedded with tungsten trioxide (WO3) and bismuth trioxide (Bi2O3) were investigated. The results indicated that the shielding properties of the composites against gamma rays increased with WO3/Bi2O3 loading and that nanocomposites were better able to attenuate gamma rays than microcomposites. The mass ratio of WO3 and Bi2O3 in the composite played an important role in attenuating low-energy gamma rays. With the increment of Bi2O3 loading, the composite’s ability to attenuate 59.5 keV and 121.8 keV gamma rays improved, whereas higher WO3 contents enhanced the ability to attenuate 81 keV gamma ray. In terms of mechanical properties, with WO3/Bi2O3 loading increased, the tensile strength of composites frst increased and then decreased, and the elongation at break steadily decreased. Gamma irradiation also improved the mechanical properties of the WPU composites, as indicated by the increase in tensile strength as the irradiation dose increased from 50 to 200 kGy.
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Huibin Sun,Zhengxin Wu,Yugang Ma,Jinbin Lu,Guoqing Liu,Haige Zhao,Yin Wang,Yanqi Hu 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.75 No.9
The radiation environment in space poses signicant challenges to human health, and it is a ma- jor concern in long duration, manned space missions. Outside Earth's protective magnetosphere, astronauts are exposed to higher levels of galactic cosmic rays (GCRs), whose physical character- istics are distinct from those of terrestrial sources of radiation, such as X-rays and gamma-rays. GCRs include high-energy heavy ions, many of which have ranges that exceed the depth of shielding and can be launched in realistic scenarios. Protecting the astronauts from these particles has been a key issue in manned space missions. Therefore, a need exists for reliable simulations of these harmful effects for risk assessment and shielding optimization in manned space missions. The aim of this work was to investigate shielding materials that can be used in deep space and planetary exploration. In this work, we used the Geant4 radiation transport code, originally developed by the International Geant4 Collaboration, and we compared the radiation shielding effectivenesses of polyethylene, aluminum, water, and carbon ber targets hit by 1GeV/nucleon 56Fe (considered as a representative of high-energy GCR). In addition, the total absorbed doses at the water phantom behind these targets were calculated using the Geant4 simulation code. The calculated results were analyzed, compared, and discussed. The results show that polyethylene is the best space radiation shielding material for a given areal density, followed by water, carbon ber, and then aluminum.
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Sun Yanzhou,Xiaogang Wu,Zhengxin Liu,Yu Boyang 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.2
The hybrid energy source system (HESS) with batteries and super-capacitor can eff ectively prolong the cycle life of batteries in electric vehicles (EVs). In order to further highlight the advantages of HESS in improving EVs effi ciency, The DC/DC converter in HESS should have the advantages of high effi ciency and fast response speed. Therefore, a soft-switching nonisolated buck-boost bidirectional DC/DC converter is applied to the HESS system of EVs in this paper. The converter has the advantages of being a simple circuit, a reduced number of components and can realize ZVS of all switches without an auxiliary circuit. In addition, a non-inductive current circulation control method is adopted in order to further improve the effi ciency of the converter. The controller of the converter is designed based on small signal modeling, and an experimental prototype has been developed. The experimental results show that, compared to the inductive current circulation method, the non-inductive current circulation control method can eff ectively reduce the loss of the inductor, and the maximum effi ciency of the converter is 92.8% in step-down mode and 93.2% in step-up mode.
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Switched‑capacitor‑based high‑gain DC–DC converter for fuel cell vehicle powertrain
Xiaogang Wu,Jiulong Wang,Yun Zhang,Zhengxin Liu 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.4
A novel DC–DC converter with switched capacitor is proposed to satisfy the requirements of fuel cell vehicles for DC–DC converter in terms of step-up ratio, efficiency, and voltage stress. The proposed converter has the advantages of high step-up ratio, low voltage stress of each device, the common ground, high efficiency, and small size. It is compared with other converters in the above aspects. The dynamic model of the proposed converter can be obtained on the basis of the small-signal modeling method and the state space average method. Experimental results show that the proposed converter has a high step-up ratio under a nonextreme duty cycle state, and the highest efficiency is 94.25%. Compared with the dual-switch boost converter, the proposed converter has certain advantages in terms of step-up ratio, component voltage stress, and efficiency. Consequently, it is more suitable for the powertrain of fuel cell vehicles.
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