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Transonic Airfoil Drag Reduction Using Suction and Loaded Leading Edge Control

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Journal of Thermal Science 2023年第1期32卷 264-277页

作者： LI Jiahe liu yanming WANG Jiang School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China

To overcome the huge drag on an airfoil in transonic flow,a hybrid flow control method using suction and loaded leading edge(SLLE)is proposed and its active feedback control effect is studied in the different operation *** loaded leading edge structure can redistribute the pressure as a passive flow control technique,while the suction slot is used to control shock wave’s position and flow separation,which can be conducted actively and automatically using feedback control ***,the investigation is conducted in steady flow,and a significant drag reduction performance is *** highest drag reduction rate of 22.5%can be got when attack angle is 5°,and the increasing of lift-drag ratio can be obtained in each attack angle ***,a heuristic approach to feedback flow control is conducted in off-design inflow conditions,where a feedback-based SLLE control method is *** results show the SLLE control can achieve a fair drag reduction performance which is over 10%,which indicates to a flow control method with good applicability in changing flow conditions.

关键词： flow control drag reduction feedback control numerical simulation

Lock threshold deterioration induced by antenna vibration and signal coupling effects in hypersonic vehicle carrier tracking system of Ka band

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Chinese Journal of Aeronautics 2018年第4期31卷 776-781页

作者： Congying ZHU Lei SHI Xiaoping LI yanming liu Wei AI School of Aerospace Science and Technology Xidian University

The envelope of a hypersonic vehicle is affected by severe fluctuating pressure, which causes the airborne antenna to vibrate slightly. This vibration mixes with the transmitted signals and thus introduces additional multiplicative phase noise. Antenna vibration and signal coupling effects as well as their influence on the lock threshold of the hypersonic vehicle carrier tracking system of the Ka band are investigated in this study. A vibration model is initially established to obtain phase noise in consideration of the inherent relationship between vibration displacement and electromagnetic wavelength. An analytical model of the Phase-Locked Loop（PLL）, which is widely used in carrier tracking systems, is established. The coupling effects on carrier tracking performance are investigated and quantitatively analyzed by imposing the multiplicative phase noise on the PLL model. Simulation results show that the phase noise presents a Gaussian distribution and is similar to vibration displacement variation. A large standard deviation in vibration displacement exerts a significant effect on the lock threshold. A critical standard deviation is observed in the PLL of Binary Phase Shift Keying（BPSK） and Quadrature Phase Shift Keying（QPSK） signals. The effect on QPSK signals is more severe than that on BPSK signals. The maximum tolerable standard deviations normalized by the wavelength of the carrier are 0.04 and 0.02 for BPSK and QPSK signals,respectively. With these critical standard deviations, lock thresholds are increased from à12 andà4 d B to 3 and à2 d B, respectively.

关键词： Antenna vibration Carrier tracking performance Lock threshold Phase locked loop Tracking Telemetry and Command(TT&C) signals

Optoelectronic Synapses Based on MXene/Violet Phosphorus van der Waals Heterojunctions for Visual‑Olfactory Crossmodal Perception

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Nano-Micro Letters 2024年第6期16卷 38-52页

作者： Hailong Ma Huajing Fang Xinxing Xie yanming liu He Tian Yang Chai Center for Advancing Materials Performance From the Nanoscale(CAMP‑Nano) State Key Laboratory for Mechanical Behavior of MaterialsXi’an Jiaotong UniversityXi’an 710049People’s Republic of China Institute of Microelectronics and Beijing National Research Center for Information Science and Technology(BNRist) Tsinghua UniversityBeijing 100084People’s Republic of China Department of Applied Physics The Hong Kong Polytechnic UniversityHong KongPeople’s Republic of China

The crossmodal interaction of different senses,which is an important basis for learning and memory in the human brain,is highly desired to be mimicked at the device level for developing neuromorphic crossmodal perception,but related researches are ***,we demonstrate an optoelectronic synapse for vision-olfactory crossmodal perception based on MXene/violet phosphorus(VP)van der Waals *** from the efficient separation and transport of photogenerated carriers facilitated by conductive MXene,the photoelectric responsivity of VP is dramatically enhanced by 7 orders of magnitude,reaching up to 7.7 A W^(−1).Excited by ultraviolet light,multiple synaptic functions,including excitatory postsynaptic currents,pairedpulse facilitation,short/long-term plasticity and“learning-experience”behavior,were demonstrated with a low power ***,the proposed optoelectronic synapse exhibits distinct synaptic behaviors in different gas environments,enabling it to simulate the interaction of visual and olfactory information for crossmodal *** work demonstrates the great potential of VP in optoelectronics and provides a promising platform for applications such as virtual reality and neurorobotics.

关键词： Violet phosphorus MXene Van der Waals heterojunctions Optoelectronic synapses Crossmodal perception

Nonstationary channel model of reentry plasma sheath for spacecraft: Overview, parameter estimation, and perspective

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Chinese Journal of Aeronautics 2024年第10期37卷 26-49页

作者： Lei SHI Zongyuan liu Weimin BAO Bo YAO Yifan WANG Xiaoping LI yanming liu Fangyan LI School of Aerospace Science and Technology Xidian UniversityXi’an 710126China Key Laboratory of Equipment Efficiency in Extreme Environment Ministry of EducationXi’an 710126China China Aerospace Science and Technology Corporation Beijing 100048China

The Tracking,Telemetering,and Command(TT&C)communication of spacecraft faces severe limitations during *** Electromagnetic(EM)propagation channel is influenced by changes in the flight state and fluid *** addition to the high-speed spatial channel,the Plasma Sheath Channel(PSC),which covers the surface of spacecraft,exhibits unique nonstationary and highly dynamic time-varying *** absence of a channel model for the reentry process of spacecraft negatively impacts the quality evaluation and system design of TT&C *** paper summarizes the methods for nonstationary PSC modeling,involving calculation methods for attenuation and phase shift in the channel,as well as a multistate nonstationary channel statistical model based on a hidden Markov ***,the correlation between amplitude variation and phase variation with electron density is *** paper also provides statistical characteristics of the channel and channel parameters at typical frequencies in the S/C/X/Ka *** findings serve as a reference for the design and evaluation of TT&C communication systems for reentry ***,the paper discusses the prospects of various aspects related to the channel characteristics and modeling of spacecraft PSCs in the shortwave and terahertz/laser bands,as well as the potential challenges in cross-domain spacecraft channel sensing and prediction.

关键词： Spacecraft Plasma sheaths Electromagnetic wave transmission Communication channels Channel estimation

Adaptive protograph-based BICM-ID relying on the RJ-MCMC algorithm:a reliable and efficient transmission solution for plasma sheath channels

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Plasma Science and Technology 2022年第4期24卷 96-105页

作者： yanming liu Hailiang WEI Lei SHI Bo YAO Key Laboratory of Information and Structure Efficiency in Extreme Environment Ministry of Education of ChinaXi'an 710071People's Republic of China School of Aerospace Science and Technology Xidian UniversityXi'an 710071People's Republic of China

For reentry communication,owing to the influence of the highly dynamic plasma sheath(PS),the parasitic modulation effect can occur and the received phase shift keying(PSK)signal constellation can be severely rotated,leading to unacceptable demodulation performance *** this work,an adaptive non-coherent bit-interleaved coded modulation with iterative decoding(BICM-ID)system with binary PSK(BPSK)modulation and protograph lowdensity parity-check under the PS channel is *** proposed protograph-based BICMID(P-BICM-ID)system can achieve joint processing of demodulation and decoding,where the soft information is adaptively estimated by reversible-jump Markov chain Monte Carlo(RJMCMC)*** results indicate that compared to existing algorithms,the proposed system can adapt well to the dynamic characteristics of the PS channel and can obtain a 5dB performance improvement at a bit error rate of 10^(-6).

关键词： plasma sheath BICM-ID Markov model joint demodulation and decoding

Enhanced electrochemical oxidation of perfluorooctanoic acid on Ti/SnO_(2)-Sb electrode by surface morphology regulation

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Chinese Chemical Letters 2024年第3期35卷 140-143页

作者： Kaiqiang Hou Genwang Zhu Yujie Feng yanming liu Xie Quan Key Laboratory of Industrial Ecology and Environmental Engineering(Ministry of Education China)School of Environmental Science and TechnologyDalian University of TechnologyDalian 116024China State Key Laboratory of Urban Water Resource and Environment School of EnvironmentHarbin Institute of TechnologyHarbin 150090China

Electrochemical oxidation is an effective method to degrade persistent organic ***,due to the limited catalytic activity of traditional thin film electrodes,the anodic oxidation process is slow and usually requires high energy ***,Ti/SnO_(2)-Sb electrode with regulated surface structure was reported to enhance the performance for electrochemical oxidation of persistent organic *** electrode deposited with SnO_(2)-Sb nanoneedles(Ti/N-SnO_(2)-Sb)showed higher oxidation *** kinetic constant for perfluorooctanoic acid(PFOA)oxidation was 2.0 h^(-1)and the total organic carbon removal rate was 81.7%(4 h)at a relatively low current density of 6 mA/cm^*** with Ti/SnO_(2)-Sb thin film and nanoparticles,Ti/N-SnO_(2)-Sb significantly improved the electrochemical active area and·OH yield,and simultaneously reduced the electron transfer resistance,which enabled it to oxidize PFOA more rapidly even at a lower *** work provides a new strategy for promoting the electrochemical oxidation performance.

关键词： Electrochemical oxidation Nanoneedle SnO_(2)-Sb Perfluoroalkyl compounds Electrochemical degradation Persistent organic pollutants

(DarkAI)Mapping the large-scale density field of dark matter using artificial intelligence

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Science China(Physics,Mechanics & Astronomy) 2024年第1期67卷 143-159页

作者： Zitong Wang Feng Shi Xiaohu Yang Qingyang Li yanming liu Xiaoping Li School of Aerospace Science and Technology Xidian UniversityXi’an 710126China Department of Astronomy School of Physics and Astronomyand Shanghai Key Laboratory for Particle Physics and CosmologyShanghai Jiao Tong UniversityShanghai 200240China Tsung-Dao Lee Institute and Key Laboratory for Particle Physics Astrophysics and CosmologyMinistry of EducationShanghai Jiao Tong UniversityShanghai 200240China Institute for Astronomy University of EdinburghRoyal ObservatoryEdinburgh EH93HJUnited Kingdom

Herein,we present a deep-learning technique for reconstructing the dark-matter density field from the redshift-space distribution of dark-matter *** built a UNet-architecture neural network and trained it using the COmoving Lagrangian Acceleration fast simulation,which is an approximation of the N-body simulation with 5123 particles in a box size of 500 h^(-1)***,we tested the resulting UNet model not only with training-like test samples but also with standard N-body simulations,such as the Jiutian simulation with 61443particles in a box size of 1000 h^(-1)Mpc and the ELUCID simulation,which has a different *** real-space dark-matter density fields in the three simulations can be reconstructed reliably with only a small reduction of the cross-correlation power spectrum at 1%and 10%levels at k=0.1 and 0.3 h Mpc-1,*** reconstruction clearly helps to correct for redshift-space distortions and is unaffected by the different cosmologies between the training(Planck2018)and test samples(WMAP5).Furthermore,we tested the application of the UNet-reconstructed density field to obtain the velocity&tidal field and found that this approach provides better results compared with the traditional approach based on the linear bias model,showing a 12.2%improvement in the correlation slope and a 21.1%reduction in the scatter between the predicted and true ***,our method is highly efficient and has excellent extrapolation reliability beyond the training *** provides an ideal solution for determining the three-dimensional underlying density field from the plentiful galaxy survey data.

关键词： dark matter large-scale structure cosmology

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Denoising of X-ray pulsar observed profile using biorthogonal lifting wavelet transform

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Journal of Systems Engineering and Electronics 2016年第3期27卷 514-523页

作者： Mengfan Xue Xiaoping Li yanming liu Haiyan Fang Haifeng Sun Lirong Shen School of Aerospace Science and Technology Xidian University

In X-ray pulsar-based navigation, strong X-ray background noise leads to a low signal-to-noise ratio（SNR） of the observed profile, which consequently makes it very difficult to obtain an accurate pulse phase that directly determines the navigation precision. This signifies the necessity of denoising of the observed profile. Considering that the ultimate goal of denoising is to enhance the pulse phase estimation, a profile denoising algorithm is proposed by fusing the biorthogonal lifting wavelet transform of the linear phase characteristic with the thresholding technique. The statistical properties of X-ray background noise after epoch folding are studied. Then a wavelet-scale dependent threshold is introduced to overcome correlations between wavelet coefficients. Moreover, a modified hyperbola shrinking function is presented to remove the impulsive oscillations of the observed profile. The results of numerical simulations and real data experiments indicate that the proposed method can effectively improve SNR of the observed profile and pulse phase estimation accuracy, especially in short observation durations. And it also outperforms the Donoho thresholding strategy normally used in combination with the orthogonal discrete wavelet transform.

关键词： X-ray pulsar denoising linear phase wavelet-scale dependent threshold

Wideband radar cross-section reduction using plasma-based checkerboard metasurface

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Plasma Science and Technology 2022年第8期24卷 98-104页

作者： Zhiming ZHAO Xiaoping LI Guoxiang DONG yanming liu School of Aerospace Science and Technology Xidian UniversityXi'an 710126People's Republic of China

For stealth technology,in order to overcome the limitations of thin-layer plasma for electromagnetic waves attenuation and further broaden the radar cross-section(RCS)reduction(RCSR)band of the metasurface,the plasma-based checkerboard metasurface composed of plasma and checkerboard metasurface is investigated to achieve better *** designed a checkerboard metasurface which can achieve abnormal reflection to reduce RCS and whose-10d B RCSR bandwidth is from 8.1 to 14.5 GHz,the RCSR principle of it lies in the backscattering cancellation,which depends on the phase difference of artificial magnetic conductor(AMC)*** designed plasma-based checkerboard metasurface is a thin composite structure,including a checkerboard metasurface,a plasma layer,and an air gap which is between *** wave simulations confirm that the plasma-based checkerboard metasurface’s–10 dB RCS reduction bandwidth and RCS reduction amplitude,are both increased under different polarized waves compared with the only single plasma or the only *** also introduced the reason and mechanism of the interaction between plasma and the checkerboard metasurface to improve the RCSR effect in *** plasma-based checkerboard metasurface does not need the plasma to be too thick for plasma stealth,its application in practical scenarios is easier to implement.

关键词： abnormal reflection plasma-based checkerboard metasurface radar cross section reduction(RCSR) stealth technology