6 results on '"Cao, Xiaowei"'
Search Results
2. NiMnO 3 Anchored on Reduced Graphene Oxide Nanosheets: A New High-Performance Microwave Absorbing Material.
- Author
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Zhang, Pin, Yao, Yao, Zhou, Wenke, Liu, Yawen, Cao, Xiaowei, and Zhang, Zhi
- Abstract
With the increasing influence of electromagnetic radiation on precision instruments and organisms, there is an urgent need for research on lightweight and high-strength electromagnetic wave absorbing materials. This study has probed into a new composite absorbing material based on reduced graphene oxide (rGO)-NiMnO
3 , where the like-core-shell NiMnO3 is anchored on the rGO nanosheets to significantly improve the electromagnetic wave dissipation ability of the composite material using the inter-component dipole polarization and interface polarization. At the same time, NiMnO3 can effectively adjust the impedance matching ratio of rGO so that electromagnetic waves can effectively enter the absorbing material. At a thickness of 3.73 mm, the maximum absorption strength of rGO-NiMnO3 reaches −61.4 dB at 6.6 GHz; at a thickness of 2.5 mm, the adequate absorption bandwidth is 10.04–18.00 GHz, achieving a full coverage for the Ku band. As a new option for preparing lightweight and broadband electromagnetic wave absorbing materials, rGO-NiMnO3 is an ideal material for electromagnetic wave protection. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
3. In Situ Experimental Study of the Friction of Sea Ice and Steel on Sea Ice.
- Author
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Wang, Qingkai, Li, Zhijun, Lu, Peng, Cao, Xiaowei, and Leppäranta, Matti
- Subjects
SEA ice ,GRAIN orientation (Materials) ,ATMOSPHERIC temperature - Abstract
The kinetic coefficient of friction
μ k was measured for sea ice, stainless steel, and coated steel sliding on a natural sea ice cover. The effects of normal stress (3.10–8.11 kPa), ice columnar grain orientation (vertical and parallel to the sliding direction), sliding velocity (0.02–2.97 m·s–1 ), and contact material were investigated. Air temperature was higher than −5.0 °C for the test duration. The results showed a decline ofμ k with increasing normal stress withμ k independent of ice grain orientation. Theμ k of different materials varied, partly due to distinct surface roughnesses, but all cases showed a similar increasing trend with increasing velocity because of the viscous resistance of melt-water film. The velocity dependence ofμ k was quantified using the rate- and state- dependent model, andμ k was found to increase logarithmically with increasing velocity. In addition,μ k obtained at higher air temperatures was greater than at lower temperatures. The stick-slip phenomenon was observed at a relatively high velocity compared with previous studies, which was partly due to the low-stiffness device used in the field. Based on the experimental data, the calculation of physical models can be compared. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
4. Mass and Heat Balance of a Lake Ice Cover in the Central Asian Arid Climate Zone.
- Author
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Lu, Peng, Cao, Xiaowei, Li, Guoyu, Huang, Wenfeng, Leppäranta, Matti, Arvola, Lauri, Huotari, Jussi, and Li, Zhijun
- Subjects
ARID regions ,ICE on rivers, lakes, etc. ,TERRESTRIAL radiation ,HEAT ,SOLAR radiation ,SUBGLACIAL lakes ,LAKE management - Abstract
To improve the understanding of the seasonal evolution of the mass and heat budget of ice-covered lakes in the cold and arid climate zone, in-situ observations were collected during two winters (2016–2017 and 2017–2018) in Lake Wuliangsuhai, Inner Mongolia, China. The mean snow thickness was 5.2 and 1.6 cm in these winters, due to low winter precipitation. The mean ice thickness was 50.9 and 36.1 cm, and the ice growth rate was 3.6 and 2.1 mm day
−1 at the lower boundary of ice. Analyses of mass and heat balance data from two winters revealed that the surface heat budget was governed by solar radiation and terrestrial radiation. The net heat flux loss of the ice was 9–22 W m−2 , affected by the snow and ice thickness. Compared to boreal lakes, Lake Wuliangsuhai received more solar radiation and heat flux from the water. The ice temperature had a strong diurnal variation, which was produced by the diurnal cycles of solar radiation, and air and water temperatures. These results expand our knowledge of the evolution of mass and heat balance in temperate lakes of mid-latitude arid areas. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
5. IKULDAS: An Improved kNN-Based UHF RFID Indoor Localization Algorithm for Directional Radiation Scenario.
- Author
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Shi, Weiguang, Du, Jiangxia, Cao, Xiaowei, Yu, Yang, Cao, Yu, Yan, Shuxia, and Ni, Chunya
- Subjects
K-nearest neighbor classification ,UHF detectors ,RADIO frequency identification systems ,UHF antennas ,PROBLEM solving - Abstract
Ultra high frequency radio frequency identification (UHF RFID)-based indoor localization technology has been a competitive candidate for context-awareness services. Previous works mainly utilize a simplified Friis transmission equation for simulating/rectifying received signal strength indicator (RSSI) values, in which the directional radiation of tag antenna and reader antenna was not fully considered, leading to unfavorable performance degradation. Moreover, a k-nearest neighbor (kNN) algorithm is widely used in existing systems, whereas the selection of an appropriate k value remains a critical issue. To solve such problems, this paper presents an improved kNN-based indoor localization algorithm for a directional radiation scenario, IKULDAS. Based on the gain features of dipole antenna and patch antenna, a novel RSSI estimation model is first established. By introducing the inclination angle and rotation angle to characterize the antenna postures, the gains of tag antenna and reader antenna referring to direct path and reflection paths are re-expressed. Then, three strategies are proposed and embedded into typical kNN for improving the localization performance. In IKULDAS, the optimal single fixed rotation angle is introduced for filtering a superior measurement and an NJW-based algorithm is advised for extracting nearest-neighbor reference tags. Furthermore, a dynamic mapping mechanism is proposed to accelerate the tracking process. Simulation results show that IKULDAS achieves a higher positioning accuracy and lower time consumption compared to other typical algorithms. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
6. IKULDAS: An Improved k NN-Based UHF RFID Indoor Localization Algorithm for Directional Radiation Scenario.
- Author
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Shi W, Du J, Cao X, Yu Y, Cao Y, Yan S, and Ni C
- Abstract
Ultra high frequency radio frequency identification (UHF RFID)-based indoor localization technology has been a competitive candidate for context-awareness services. Previous works mainly utilize a simplified Friis transmission equation for simulating/rectifying received signal strength indicator (RSSI) values, in which the directional radiation of tag antenna and reader antenna was not fully considered, leading to unfavorable performance degradation. Moreover, a k -nearest neighbor ( k NN) algorithm is widely used in existing systems, whereas the selection of an appropriate k value remains a critical issue. To solve such problems, this paper presents an improved k NN-based indoor localization algorithm for a directional radiation scenario, IKULDAS. Based on the gain features of dipole antenna and patch antenna, a novel RSSI estimation model is first established. By introducing the inclination angle and rotation angle to characterize the antenna postures, the gains of tag antenna and reader antenna referring to direct path and reflection paths are re-expressed. Then, three strategies are proposed and embedded into typical k NN for improving the localization performance. In IKULDAS, the optimal single fixed rotation angle is introduced for filtering a superior measurement and an NJW-based algorithm is advised for extracting nearest-neighbor reference tags. Furthermore, a dynamic mapping mechanism is proposed to accelerate the tracking process. Simulation results show that IKULDAS achieves a higher positioning accuracy and lower time consumption compared to other typical algorithms.
- Published
- 2019
- Full Text
- View/download PDF
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