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Zhihao Tang,Peiqing Liu,Hao Guo,Jie Yan,Guangchao Li 한국항공우주학회 2015 International Journal of Aeronautical and Space Sc Vol.16 No.4
The numerical simulation of two-dimensional moving blade row interactions is conducted by CFD means to investigate the interactions between the front and rear propeller in a stratospheric airship contra-rotating open propeller configuration caused by different rotational speeds. The rotational speed is a main factor to affect the propeller Reynolds number which impact the aerodynamic performance of blade rows significantly. This effect works until the Reynolds number reaches a high enough value beyond which the coefficients become independent. Additionally, the interference on the blade row has been revealed by the investigation. The front blade row moves in the induced-velocity field generated by the rear blade row and the aerodynamic coefficients are influenced when the rear blade row has fast RPMs. The rear blade row moving behind the front one is affected directly by the wake and eddies generated by the front blade row. The aerodynamic coefficients reduce when the front blade row has slow RPMs while increase when the front blade row moves faster than itself. But overall, the interference on the front blade row due to the rear blade row is slight and the interference on the rear blade row due to the front blade row is much more significant.
Metalens for improving optical coherence tomography
Guo Songming,Feng Weibin,Long Yong,Liu Zhihao,Fu Xiao,Liang Haowen,Li Juntao 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.81 No.1
Optical coherence tomography is one of the most attractive new tomographic techniques, especially in the detection and imaging of biological tissues. For the detection and imaging of human corneas, the current ultra-high-resolution optical coherence tomography technology faces the challenge that the depth of focus is too short to scan the entire human cornea in a single amplitude scan. Here, we propose and design a silicon metalens to replace the objective lens in the sample arm of the optical coherence tomography system. In our simulation, a uniform focused beam with a depth of focus of 886 μm, an axial resolution of 3.1 μm and a lateral resolution of 2.2 μm can be generated by the metalens, which is under the excitation of broadband Gaussian light with wavelength coverage from 800 to 900 nm. This metalens fully satisfies the depth of focus and resolution requirements of the ultra-high-resolution optical coherence tomography system for human corneas, hence expands the application of optical coherence tomography in medical science for the benefit of mankind.
Zhihao Zhu,Zhi Gao,Yu Guo 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.2
The distributed global velocity-free attitude coordination control problem for multiple formation spacecraft without unwinding phenomenon and with disturbance is investigated in this paper. Initially, a fixed-time observer is constructed to estimate the states of the virtual leader in fixed time. For the formation spacecraft with attitude-only measurements, a filter system is developed. To estimate the disturbance, a fixed-time extended state observer is proposed. With the application of the fixed-time observers and the filter system, a distributed global velocity-free attitude coordination controller is designed to grantee that the leader with time-varying trajectory can be tracked coordinately by the formation spacecraft, where the unwinding problem of the spacecraft can be avoided. In addition, a distributed velocity-free attitude coordination controller on the basis of the fixed-time extended state observer is designed to compensate the effect of the lump disturbance. Finally, the effectiveness of the proposed controller is demonstrated by numerical simulation.
Performance of Contra-Rotating Propellers for Stratospheric Airships
Zhihao Tang,Peiqing Liu,Jingwei Sun,Yaxi Chen,Hao Guo,Guangchao Li 한국항공우주학회 2015 International Journal of Aeronautical and Space Sc Vol.16 No.4
Small advance ratio and low Reynolds number of stratospheric propulsion system bring lots of challenges to the design of propellers. Contra-rotating propeller configuration is proposed to improve the propulsion efficiency. In this paper, the feasibility of contra-rotating propeller for stratospheric airship has been assessed and its performance has been investigated by wind tunnel tests. The experimental results indicate, at relatively low Reynolds number, although the advance ratio is fixed, the performance of propellers is different with variation of Reynolds number. Moreover, at the same Reynolds number, the efficiency of contra-rotating propeller achieved appears to be a few percent greater than that for a standard conventional propulsion system. It can be concluded that contra-rotating propellers would be an efficient means to improve the performance of stratospheric airship propulsion system.
Yangyang Guo,Bin Xu,Ying Liu,Wenzhong Yang,Xiaoshuang Yin,Yun Chen,Jinxun Le,Zhihao Chen 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.56 No.-
The ionic liquids, 1-vinyl-3-aminopropylimidazolium hexafluorophosphate ([VAIM][PF6]) and 1-vinyl-3-aminopropylimidazolium tetrafluoroborate ([VAIM][BF4]) acted as the corrosion inhibitors. Weight lossmeasurements showed the corrosion inhibition efficiencies of [VAIM][PF6] and [VAIM][BF4] were 90.53%and 54.01% at 45 C, respectively. The ILs were mix-type inhibitors. Raising the temperature can have adecreased inhibition efficiency of [VAIM][BF4], while [VAIM][PF6] presented an opposite trend. Inaddition, [VAIM][PF6] obeyed Langmuir monolayer adsorption isotherm, while [VAIM][BF4] obeyed EIAwadykinetic-thermodynamic adsorption for blocking active sites. Moreover, Molecular DynamicSimulations showed that [VAIM][PF6] owned a higher adsorption energy, which may be responsible forthe more adsorption groups of [VAIM][PF6].
Tang, Zhihao,Liu, Peiqing,Guo, Hao,Yan, Jie,Li, Guangchao The Korean Society for Aeronautical and Space Scie 2015 International Journal of Aeronautical and Space Sc Vol.16 No.4
The numerical simulation of two-dimensional moving blade row interactions is conducted by CFD means to investigate the interactions between the front and rear propeller in a stratospheric airship contra-rotating open propeller configuration caused by different rotational speeds. The rotational speed is a main factor to affect the propeller Reynolds number which impact the aerodynamic performance of blade rows significantly. This effect works until the Reynolds number reaches a high enough value beyond which the coefficients become independent. Additionally, the interference on the blade row has been revealed by the investigation. The front blade row moves in the induced-velocity field generated by the rear blade row and the aerodynamic coefficients are influenced when the rear blade row has fast RPMs. The rear blade row moving behind the front one is affected directly by the wake and eddies generated by the front blade row. The aerodynamic coefficients reduce when the front blade row has slow RPMs while increase when the front blade row moves faster than itself. But overall, the interference on the front blade row due to the rear blade row is slight and the interference on the rear blade row due to the front blade row is much more significant.
Performance of Contra-Rotating Propellers for Stratospheric Airships
Tang, Zhihao,Liu, Peiqing,Sun, Jingwei,Chen, Yaxi,Guo, Hao,Li, Guangchao The Korean Society for Aeronautical and Space Scie 2015 International Journal of Aeronautical and Space Sc Vol.16 No.4
Small advance ratio and low Reynolds number of stratospheric propulsion system bring lots of challenges to the design of propellers. Contra-rotating propeller configuration is proposed to improve the propulsion efficiency. In this paper, the feasibility of contra-rotating propeller for stratospheric airship has been assessed and its performance has been investigated by wind tunnel tests. The experimental results indicate, at relatively low Reynolds number, although the advance ratio is fixed, the performance of propellers is different with variation of Reynolds number. Moreover, at the same Reynolds number, the efficiency of contra-rotating propeller achieved appears to be a few percent greater than that for a standard conventional propulsion system. It can be concluded that contra-rotating propellers would be an efficient means to improve the performance of stratospheric airship propulsion system.
Ammonia etched petroleum pitch-based porous carbon as efficient catalysts for CO2 electroreduction
Ning Hui,Guo Zhihao,Wang Wenhang,Wang Xiaoshan,Yang Zhongxue,Ma Zhengguang,Tian Yangming,Wu Chenghao,Hao Jian,Wu Mingbo 한국탄소학회 2022 Carbon Letters Vol.32 No.3
Electrochemical reduction of carbon dioxide to valuable chemicals is a promising way of storing renewable energy through electric-to-chemical energy conversion, while its large-scale application is in urgent need of cheap and high-performance catalysts. Herein, we invent a convenient method to synthesize N-doped porous carbon by ammonia etching the pyrolysis carbon of petroleum pitch. We found the ammonia etching treatment not only increase the pyridinic-N content, but also enlarge the specific surface area of the petroleum pitch-based porous carbon. As a cheap and easily available catalyst for carbon dioxide electroreduction, up to 82% of Faradaic efficiency towards carbon monoxide was obtained at − 0.9 V vs the reversible hydrogen electrode in 0.1 M KHCO3. After a long time electrocatalysis of more than 20 h, the Faradaic efficiency of carbon monoxide remains 80%, indicating the porous carbon as made have an ultra-high stability as catalyst for carbon dioxide reduction. Our work provides a new technology to economically prepare efficient electrocatalysts for carbon dioxide reduction.