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Study on the resolution of multi-aircraft flight conflicts based on an IDQN

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Chinese Journal of Aeronautics 2022年第2期35卷 195-213页

作者： dong SUI Weiping xu Kai zhang College of Civil Aviation Nanjing University of Aeronautics and AstronauticsNanjing 211106China

With the rapid growth of flight flow,the workload of controllers is increasing daily,and handling flight conflicts is the main workload.Therefore,it is necessary to provide more efficient conflict resolution decision-making support for controllers.Due to the limitations of existing methods,they have not been widely used.In this paper,a Deep Reinforcement Learning(DRL)algorithm is proposed to resolve multi-aircraft flight conflict with high solving efficiency.First,the characteristics of multi-aircraft flight conflict problem are analyzed and the problem is modeled based on Markov decision process.Thus,the Independent Deep Q Network(IDQN)algorithm is used to solve the model.Simultaneously,a’downward-compatible’framework that supports dynamic expansion of the number of conflicting aircraft is designed.The model ultimately shows convergence through adequate training.Finally,the test conflict scenarios and indicators were used to verify the validity.In 700 scenarios,85.71%of conflicts were successfully resolved,and 71.51%of aircraft can reach destinations within 150 s around original arrival times.By contrast,conflict resolution algorithm based on DRL has great advantages in solution speed.The method proposed offers the possibility of decision-making support for controllers and reduce workload of controllers in future high-density airspace environment.

关键词： Air traffic control Conflict resolution Multi-agent system Multi-aircraft flight conflict Reinforcement learning

CSS J075415.6+191052 and NW Leo: Two Contact Binaries at Different Evolutionary Stages

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Research in Astronomy and Astrophysics 2022年第2期22卷 118-127页

作者： Xu-dong Zhang Sheng-Bang Qian Er-Gang Zhao Qi-Jun Zhi Ai-Jun dong Bin zhang School of Physics and Electronic Science Guizhou Normal University550025 GuiyangChina Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processing Guizhou Normal UniversityGuiyang 550025 GuiyangChina Yunnan Observatories Chinese Academy of Sciences(CAS)650216 KunmingChina University of Chinese Academy of Sciences(UCAS) 100049 BeijingChina

Multi-color light curves of CSS J075415.6+191052 and NW Leo are presented and the photometric solutions suggest that CSS J075415.6+191052 is an A-subtype contact binary with low mass ratio(q = 0.178) while NW Leo has a high mass ratio(q = 0.707). For CSS J075415.6+191052, the RI light curves show weakening around the left shoulder of the secondary minimum, which indicates that there may be a dark spot on the secondary component. However, the light curves of BV bands are totally symmetric. It is unreasonable if the dark spot is caused by magnetic activity or mass transfer between the two components. Therefore, weakening of the light curves in this contact binary is caused by something else. A possible explanation is mass transferring from the primary component to the common convective envelope through the inner Lagrangian point, and this part of the mass, for some reason, weakens the RI bands of light from the secondary component. O-C analysis of NW Leo reveals a cyclic period change with a modulation period of 4.7 yr, which may be caused by the light travel time effect of a third body. The positions of CSS J075415.6+191052 and NW Leo in the P–J′_(orb)diagram indicate that CSS J075415.6+191052 mainly abides by the angular momentum loss theory while NW Leo is dominated by the thermal relaxation oscillation theory.

关键词： (stars:)binaries:eclipsing stars:evolution stars:individual(CSS J075415.6+191052 NW Leo)

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单元素相变开关

Science Bulletin 2022年第9期67卷 888-890,M0003页

作者： xu-dong Wang Wei zhang En Ma Center for Alloy Innovation and Design(CAID) State Key Laboratory for Mechanical Behavior of MaterialsXi’an Jiaotong UniversityXi’an 710049China

In the 1960s,Stanford Ovshinsky pioneered electrically controlled ovonic threshold switching(OTS)and ovonic memory switching(OMS),using amorphous chalcogenide materials[1].As sketched in Fig.1a,under small externally applied voltage bias the“amorphous OFF”state allows only a low electric current,thanks to the highly resistive nature of the glassy material.When the voltage bias exceeds a threshold value Vth,the current suddenly increases by several orders of magnitude,as the glassy structure enters its“amorphous ON”regime.Upon the removal of the voltage,the electrical resistance returns to the initial high value.

关键词： resistance amorphous glassy

Numerical Study on the Vertical Water Exit of A Cylinder with Cavity

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China Ocean Engineering 2022年第5期36卷 734-742页

作者： zhang Xing-yu LYU xu-jian FAN xu-dong School of Energy and Power Engineering Nanjing University of Science and TechnologyNanjing 210094China

When a high-speed body with cavity passes through water-air free surface and exits water,its mechanical environment and dynamic characteristics change significantly due to the great difference in density and viscosity between water and air.With focusing on this problem,the Computational Fluid Dynamics(CFD)method is applied to perform numerical calculation on the process of this vapor-liquid-gas flow during the water exit of a high-speed cylinder,with the Volume of Fraction(VOF)multiphase flow interface-capturing techniques and the overset grid technology.After the verification and validation of the CFD model through mesh convergence study and a water-entry experiment,cavity evolution and flow characteristics including pressure and velocity distribution during the water exit are analyzed.The effects of different initial velocities on the pressure distribution and drag characteristics of the cylinder are investigated.Calculated results show that the cavity collapse during water exit causes strong pressure fluctuation on the cylinder;when the cylinder exits water enveloped in a supercavity,the pressure distribution on its wall surface and surrounding water region is relatively uniform,and the drag changes gently,and thus the cylinder has good motion stability.

关键词： water exit cavity CFD

Analysis on phase selection and microstructure evolution in directionally solidified Zn-Al-Mg-Ce alloy

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China Foundry 2023年第4期20卷 347-355页

作者： Ji-peng Li De-gao Qiao Shi-wen dong Peng Peng Xian-tao Yan Xu-dong Zhang Gansu Jiu Steel Group Hongxing Iron and Steel Co. Ltd.Jiayuguan 735199GansuChina School of Materials and Energy Lanzhou UniversityLanzhou 730000China School of Physics and Electronic Information Engineering Qinghai Normal UniversityXining 810016QinghaiChina

In the process of hot-dip Zn-Al-Mg alloy coating,the plating solution dissipates heat in the direction perpendicular to the steel plate,which is considered to be a process of directional solidification.To understand the relationship between microstructure and cooling rate of Zn-Al-Mg alloys,both the phase constitution and microstructure characteristic length scales of Zn-9.5Al-3Mg-0.01Ce(wt.%)alloy were investigated by the directional solidification experiments at different growth velocities(V=40,80,160,250μm·s^(-1)).The experimental results show that the microstructure of directionally solidified Zn-9.5Al-3Mg-0.01Ce alloy is composed of primary Al dendrites and(Zn-Al-Mg2Zn11)ternary eutectics at the growth velocities ranging from 40 to 250μm·s^(-1).The primary Al dendrites are aligned regularly along the growth direction,accompanied with obvious secondary dendrites.The relationship between the microstructure length scale and the thermal parameters of solidification is obtained:λ1=374.66V-0.383,andλ2=167.5V-0.563(λ1is the primary dendrite arm spacing,andλ2 is the secondary dendrit arm spacing).In addition,through the interface response function(IRF)and the nucleation and constitutional undercooling(NCU),the phase selection of Zn-9.5Al-3Mg-0.01Ce is obtained:(Zn+Al+Mg2Zn11)ternary eutectics in the Zn-9.5Al-3Mg-0.01Ce alloy will be replaced by ternary eutectics(Zn+Al+MgZn2)when the growth rate is lower than 7.53μm·s^(-1).

关键词： Zn-Al-Mg alloy directional solidification microstructure length scale phase selection

Effect of Ta on solidification characteristics and mechanical properties of DZ411 Ni-based superalloy

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中国铸造:英文版 2023年第5期20卷 376-386页

作者： Peng Peng Zi-jie Liu Yuan-li xu Xu-dong Zhang Zhi-kun Ma Jia-tai Wang School of Materials and Energy Lanzhou UniversityLanzhou 730000China School of Materials Science and Engineering Northwestern Polytechnical UniversityXi'an 710072China School of Physics and Electronic Information Qinghai Normal UniversityXining 810008QinghaiChina

The effects of Ta content(2.72wt.%,3.10wt.%and 4.00wt.%)on the solidification characteristics and mechanical properties of directionally solidified DZ411 Ni-based superalloys were investigated.It is found that the content of Mo decreases with the increase of Ta in liquid phase after directional solidification,indicating the addition of Ta can reduce the element segregation in alloys.The primary and secondary dendrite arm spacings(PDAS and SDAS)of the DZ411 alloy increase with the addition of Ta,which are consistent with the models by Hunt and Wagner.The increase of PDAS and SDAS can provide enough space for the growth of tertiary dendrite arms,which hinders the growth of unfavorably oriented primary dendrites.As a result,the addition of Ta facilitates the growth of favorably oriented dendrites.More MC carbides andγ-γ'eutectics are formed in the interdendritic regions,which is attributed to the segregation of Ta in the liquid phase.Furthermore,the degree of supersaturation of W,Mo inγmatrix increases with the increase of Ta,thus,the addition of Ta promotes the formation of TCP phase.The addition of Ta also increases the microhardness in both the primary dendrite and interdendritic regions of the alloy,and the microhardness of the primary dendrite is closer to that in interdendritic regions with the increase of Ta.

关键词： DZ411 superalloy directional solidification Ta dendrite arm spacing microhardness

Flexible single-electrode triboelectric nanogenerator with MWCNT/PDMS composite film for environmental energy harvesting and human motion monitoring

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Rare Metals 2022年第9期41卷 3117-3128页

作者： Hao zhang dong-Zhi zhang dong-Yue Wang Zhen-Yuan xu Yan Yang Bao zhang College of Control Science and Engineering China University of Petroleum(East China)Qingdao266580China

With the rapid development of wearable electronic devices,modern portable energy sources pay more attention to lightweight,low cost,high flexibility and high efficiency.This paper proposed a flexible single-electrode triboelectric nanogenerator(S-TENG)composed of multi-walled carbon nanotube(MWCNT)/polydimethylsiloxane(PDMS)film.The S-TENG has the advantages of high flexibility,high hydrophobicity,light weight,low cost,and high output efficiency.The peak-to-peak open circuit voltage can reach 435 V and the maximum short-circuit current density is 13μA·cm^(−2) under continuous pressing.When the external load is 40 MΩ,the maximum output power density is 3.7 mW·cm^(−2).The S-TENG can not only harvest the mechanical energy generated by biological movement,but also can be used as a sensor to effectively detect human movement and handwriting traces.In addition,a 4×4 sensor array and a wireless transmission system were constructed to realize multi-point distributed detection and wireless transmission of portable smart terminals.The S-TENG can harvest energy from falling water droplets,uninterrupted water flow,wind and percussion sounds,which demonstrates its broad application prospects in the field of flexible wearables.

关键词： Flexible Wearable Single-electrode Triboelectric nanogenerator(TENG) Environmental energy

Bi-level Multi-objective Joint Planning of Distribution Networks Considering Uncertainties

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Journal of Modern Power Systems and Clean Energy 2022年第6期10卷 1599-1613页

作者： Shouxiang Wang Yichao dong Qianyu Zhao xu zhang Key Laboratory of Smart Grid of Ministry of Education Tianjin UniversityTianjin300072China State Grid Tianjin Electric Power Company Economic and Technological Research Institute Tianjin 300171China State Grid Tianjin Electric Power Company Tianjin300010China

With the increasing penetration of photovoltaics in distribution networks,the adaptability of distribution network under uncertainties needs to be considered in the planning of distribution systems.In this paper,the interval arithmetic and affine arithmetic are applied to deal with uncertainties,and an affine arithmetic based bi-level multi-objective joint planning model is built,which can obtain the planning schemes with low constraint-violation risk,high reliability and strong adaptability.On this basis,a bi-level multi-objective solution methodology using affine arithmetic based non-dominated sorting genetic algorithm II is proposed,and the planning schemes that simultaneously meet economy and adaptability goals under uncertainties can be obtained.To further eliminate bad solutions and improve the solution qualities,an affine arithmetic based dominance relation weakening criterion and a deviation distance based modification method are proposed.A 24-bus test system and a 10 kV distribution system of China are used for case studies.Different uncertainty levels are compared,and a sensitivity analysis of key parameters is conducted to explore their impacts on the final planning schemes.The simulation results verify the advantages of the proposed affine arithmetic based planning method.

关键词： Affine arithmetic adaptability multi-objective joint planning Pareto optimal front uncertainty

Twisted Integration of Complex Oxide Magnetoelectric Heterostructures via Water‑Etching and Transfer Process

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Nano-Micro Letters 2024年第1期16卷 360-369页

作者： Guannan Yang Guohua dong Butong zhang xu xu Yanan Zhao Zhongqiang Hu Ming Liu State Key Laboratory for Manufacturing Systems Engineering Electronic Materials Research LaboratoryKey Laboratory of the Ministry of EducationEngineering Research Center of Spin Quantum Sensor ChipsUniversities of Shaanxi ProvinceSchool of Electronic Science and EngineeringXi’an Jiaotong UniversityXi’an 710049People’s Republic of China

Manipulating strain mode and degree that can be applied to epitaxial complex oxide thin films have been a cornerstone of strain engineering.In recent years,lift-off and transfer technology of the epitaxial oxide thin films have been developed that enabled the integration of heterostructures without the limitation of material types and crystal orientations.Moreover,twisted integration would provide a more interesting strategy in artificial magnetoelectric heterostructures.A specific twist angle between the ferroelectric and ferromagnetic oxide layers corresponds to the distinct strain regulation modes in the magnetoelectric coupling process,which could provide some insight in to the physical phenomena.In this work,the La_(0.67)Sr_(0.33)MnO_(3)(001)/0.7Pb(Mg_(1/3)Nb_(2/3))O_(3)-0.3PbTiO_(3)(011)(LSMO/PMN-PT)heterostructures with 45.and 0.twist angles were assembled via water-etching and transfer process.The transferred LSMO films exhibit a fourfold magnetic anisotropy with easy axis along LSMO.A coexistence of uniaxial and fourfold magnetic anisotropy with LSMO[110]easy axis is observed for the 45°Sample by applying a 7.2 kV cm^(−1)electrical field,significantly different from a uniaxial anisotropy with LSMO[100]easy axis for the 0°Sample.The fitting of the ferromagnetic resonance field reveals that the strain coupling generated by the 45°twist angle causes different lattice distortion of LSMO,thereby enhancing both the fourfold and uniaxial anisotropy.This work confirms the twisting degrees of freedom for magnetoelectric coupling and opens opportunities for fabricating artificial magnetoelectric heterostructures.

关键词： Magnetoelectric heterostructures Twist angle Epitaxial lift-off Magnetic anisotropy Ferromagnetic resonance