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arXiv 2024年

作者： Wen, Jiquan Chen, Huajin Zheng, Hongxia Xu, Xiaohao Yan, Shaohui Yao, Baoli Lin, Zhifang School of Automation Guangxi University of Science and Technology Guangxi Liuzhou545006 China School of Electronic Engineering Guangxi University of Science and Technology Guangxi Liuzhou545006 China State Key Laboratory of Surface Physics Department of Physics Fudan University Shanghai200433 China Guangxi Key Laboratory of Multidimensional Information Fusion for Intelligent Vehicles Guangxi Liuzhou545006 China State Key Laboratory of Transient Optics and Photonics Xi'an Institute of Optics and Precision Mechanics Chinese Academy of Sciences Xi'An710119 China Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing210093 China

Owing to the ubiquity and easy-to-shape property of optical intensity, the intensity gradient force of light has been most spectacularly exploited in optical manipulation of small particles. Manifesting the intensity gradient as an optical torque to spin particles is of great fascination on both fundamental and practical sides but remains elusive. Here, we uncover the existence of the optical intensity-gradient torque in the interaction of light with chiral particles. Such a new type of torque derives from the interplay between chirality induced multipoles, which switches its direction for particles with opposite chirality. We show that this torque can be directly detected by a simple standing wave field, created with the interference of two counterpropagating plane-like waves. Our work offers a unique route to achieve rotational control of matter by tailoring the field intensity of Maxwell waves. It also establishes a framework that maps a remarkable connection among the optical forces and torques, across chiral to nonchiral. Copyright © 2024, The Authors. All rights reserved.

关键词： Chirality

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Research on Guidance and Control Law Design of Decelerating Transition and Vertical Landing for a STOVL UAV

Research on Guidance and Control Law Design of Decelerating ...

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第六届设计工程与科学国际会议

作者： Zixu Dong Yang Ren Kun Chen Yaohui Chen National Key Laboratory of Transient Physics Nanjing University of Science and Technology China Research and development Academy of Machinery Equipment

In this paper, an integrated design method for guidance and control laws for a short takeoff and vertical landing(STOVL) unmanned aerial vehicle(UAV) during decelerating transition and vertical landing phases under thrust vector control is studied. Based on the principle of time-scale separation, the outer-loop guidance law adopts an implicit dynamic inverse method to provide attainable overload vector control instructions for decelerating transition and vertical landing phases. Meanwhile, the inner-loop control law adopts an improved eigen-structure assignment method, which tracks guidance instructions and maintains a stable attitude. The attitude nozzles are joined to the attitude control with the dropping of dynamic pressure, thereby assisting aerodynamic surfaces to stabilize ***, the feasibility and effect of the control methods for a STOVL UAV during decelerating transition and vertical landing phases are verified by a 6-DOF flight simulation platform. The simulation results demonstrate that the integrated design method is beneficial for a quick evaluation of the overall scheme.

关键词： Research on Guidance and Control Law Design of Decelerating Transition and Vertical Landing for a STOVL UAV

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Study on the influence of rigid wall surface on the bubble characteristics of underwater explosion 2

Study on the influence of rigid wall surface on the bubble c...

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2nd Spring International Conference on Defence technology, ICDT 2020

作者： Meng, L. Huang, R.Y. Qin, J. Wang, J.X. Liu, L.T. National Key Laboratory of Transient Physics Nanjing University of Science and Technology Nanjing210094 China Naval Research Academy Beijing100161 China

In order to investigate the influence of rigid wall surface on the bubble characteristics of underwater explosion, the underwater explosion experiment under the boundary conditions of free surface and rigid wall surface was carried out on 2.5g cylindrical charge TNT in a 2×2×2m tank. The time history curves of shock wave and bubble pulsation were obtained by underwater pressure sensor, and the bubble pulsation process was observed by high-speed photography. The experimental results show that compared with the free surface underwater explosion, the shock wave peak pressure and the bubble pulse peak pressure in rigid wall surface underwater explosion are increased, and a large cavitation area appeared at the junction of rigid wall and water surface. After the bubbles contacted the rigid wall surface, the bubble morphology changed significantly, the first bubble pulsation period and the maximum radius of bubble expansion became larger. After the first bubble pulsation, the bubble partially collapsed and split into two parts, bubbles continued to pulsate in the direction of the rigid wall and the bottom of the water. Finally, combined with the experimental data of rigid wall surface at different explosion depths, the relationship between the first bubble pulsation period, the maximum bubble expansion radius and the explosion depth of 2.5gTNT under rigid wall conditions is given. © 2020 Published under licence by IOP Publishing Ltd.

关键词： Shock waves

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Terabit FSO communication based on a soliton microcomb

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Photonics Research 2022年第12期10卷 2802-2808页

作者： WEN SHAO YANG WANG SHUAIWEI JIA ZHUANG XIE DUORUI GAO WEI WANG DONGQUAN ZHANG PELXUAN LIAO BRENT ELITTLE SAI TCHU WEI ZHAO WENFU ZHANG WEIQIANG WANG XIAOPING XIE State Key Laboratory of Transient Optics and Photonics Xi’an Institute of Optics and Precision Mechanics(XIOPM)Chinese Academy of SciencesXi'an 710119China School of Future Technology University of Chinese Academy of SciencesBeijing 100049China University of Chinese Academy of Sciences Beijing 100049China Department of Physics and Materials Science City University of Hong KongHong KongChina

Free-space optical(FSO)communication technology is a promising approach to establish a secure wireless link,which has the advantages of excellent directionality,large bandwidth,multiple services,low mass and less power requirements,and easy and fast *** the communication capacity is the perennial goal in both scientific and engineer *** this paper,we experimentally demonstrate a Tbit/s parallel FSO communication system using a soliton microcomb as a multiple wavelength laser *** communication terminals are installed in two buildings with a straight-line distance of~1 km.102 comb lines are modulated by10 Gbit/s differential phase-shift keying signals and demodulated using a delay-line *** the transmitted optical power is amplified to 19.8 dBm,42 optical channels have optical signal-to-noise ratios higher than 27 dB and bit error rates less than 1×10^(-9).Our experiment shows the feasibility of a wavelength-division multiplexing FSO communication system which suits the ultra-high-speed wireless transmission application scenarios in future satellite-based communications,disaster recovery,defense,last mile problems in networks and remote sensing,and so on.

关键词： communication FSO interferometer

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Critical diffraction of irregular structure detonations and their predictability from experimentally obtained D-κ data

arXiv

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arXiv 2022年

作者： Zangene, Farzane Xiao, Qiang Radulescu, Matei Department of Mechanical Engineering University of Ottawa OttawaONK1N6N5 Canada the National Key Laboratory of Transient Physics Nanjing University of Science and Technology Nanjing210094 China

The present work reports new experiments of detonation diffraction in a 2D channel configuration in stoichiometric mixtures of ethylene, ethane, and methane with oxygen as oxidizer. The flow field details are obtained using high-speed schlieren near the critical conditions of diffraction. The critical initial pressure for successful diffraction is reported for the ethylene, ethane and methane mixtures. The flow field details revealed that the lateral portion of the wave results in a zone of quenched ignition. The dynamics of the laterally diffracting shock front are found in good agreement with the recent model developed by Radulescu et al. (physics of Fluids 2021). The model provides noticeable improvement over the local models using Whitham’s characteristic rule and Wescott, Bdzil and Stewart’s model for weakly curved reactive shocks. These models provide a link between the critical channel height and the critical wave curvature. The critical channel heights and global curvatures are found in very good agreement with the critical curvatures measured independently by Xiao and Radulescu (Combust. Flame 2020) in quasi-steady experiments in exponential horns for three mixtures tested. Furthermore, critical curvature data obtained by others in the literature was found to provide a good prediction of critical diffraction in 2D. These findings suggest that the critical diffraction of unstable detonations may be well predicted by a model based on the maximum curvature of the detonation front, where the latter is to be measured experimentally and account for the role of the cellular structure in the burning mechanism. This finding provides support to the view that models for unstable detonations at a meso-scale larger than the cell size, i.e., hydrodynamic average models, are meaningful. Copyright © 2022, The Authors. All rights reserved.

关键词： Diffraction

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Numerical analysis of railgun muzzle flow field with multi-component plasma 2

Numerical analysis of railgun muzzle flow field with multi-c...

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2nd Spring International Conference on Defence technology, ICDT 2020

作者： Gao, Y. Ni, Y.J. Li, B.M. National Key Laboratory of Transient Physics Nanjing University of Science and Technology Nanjing Jiangsu210094 China China Academy of Ordnance Beijing100089 China

The railgun is a new concept launching weapon with high supersonic launching capability. Under the acceleration of Lorentz force produced by the discharge of strong pulse power source, the projectile leaves the muzzle in hypersonic speed. Due to the severe friction of armature in bore and the phenomenon of transition ablation, metal vapor is produced in the interior ballistic process and rush out of muzzle along with armature's movement. Because of the open structure at both ends of the railgun, the pressure in the bore is much lower than the standard atmosphere, so there exists the phenomenon of muzzle gas backflow. In this paper, the coupled interface method and the multi-component plasma model are used to simulate the movement of metal vapor in the process of projectile moving out of the bore. The pressure boundary conditions and gas composition in the muzzle region of the simulation results are fitted and introduced into the MHD calculation model. The gas backflow phenomenon under the influence of multi-component gas and arc is further simulated. The results show that the muzzle arc improves the energy level of the muzzle flow field and promotes the gas backflow to a certain extent. © Published under licence by IOP Publishing Ltd.

关键词： Rail guns

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Experimental Study on Plasma Ignited Single-base Propellant using SEM and EDS 2

Experimental Study on Plasma Ignited Single-base Propellant ...

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2nd Spring International Conference on Defence technology, ICDT 2020

作者： Yang, Chunxia Jin, Yong Li, Haiyuan Yang, Yong Ni, Yanjie Li, Zhenxiao Li, Baoming National Key Laboratory of Transient Physics Nanjing University of Science and Technology Nanjing Jiangsu210094 China China Academy of Ordnance Beijing100089 China

To explore the reaction mechanism in the plasma-propellant interaction, plasma ignition and conventional ignition experiments are carried out on a single-base propellant. The samples after ignition are analyzed by scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). Results show that the plasma jet brought a variety of high enthalpy flows into the propellant and deposited them on the surface of the propellant. These high enthalpy particles reacted with the propellant on the surface rapidly and produced voids and cracks different from the surface melting mode in the conventional ignition process. These voids provided microchannels for ignition and heat transmission. The area of ignition and combustion increased accordingly. © Published under licence by IOP Publishing Ltd.

关键词： Scanning electron microscopy

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Study on the solid propellant burning rate enhanced by plasma in the closed bomb 2

Study on the solid propellant burning rate enhanced by plasm...

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2nd Spring International Conference on Defence technology, ICDT 2020

作者： Ni, Yanjie Jin, Yong Wan, Gang Yang, Chunxia Li, Baoming National Key Laboratory of Transient Physics Nanjing University of Science and Technology Nanjing Jiangsu210094 China China Academy of Ordnance Beijing100089 China

A closed bomb experimental system is employed to discuss the ignition and combustion characteristics of the solid propellant with the capillary plasma generator (CPG). 4/7 high-nitrogen solid propellant, 5/7 high-graphite solid propellant and 5/7 low temperature sensitivity coated propellant are ignited in the closed bomb. Compared with the experimental results with the conventional ignition, the ignition delay time with the CPG is reduced and the burning process of the propellant is enhanced. The pressure changing rate is used to analyse the enhanced gas generation rate (EGGR) of the propellant with the plasma. Compared with the pressure changing rate with different igniters, the enhanced gas generation rate during electrical discharge (EGGRDED) is proved. When 4/7 high-nitrogen solid propellant and 5/7 low temperature sensitivity coated propellant are ignited in the closed bomb, the enhanced gas generation rate post electrical discharge (EGGRPED) appears. The EGGRPED is mainly influenced by the composition of the propellant. The influence of the electrical parameters of the CPG and the distance between the CPG and the solid propellant is studied by the closed bomb experiments. The ignition delay time and the burning time of the propellant reduce with the increasing of the electric power or the decreasing of the distance between the CPG and the propellant. Depending on the pressure changing rate in the closed bomb experiments, the EGGRDED increases with the increasing of the electric power or the decreasing of the distance between the CPG and the propellant, while the EGGRPED is not influenced by the electric power or the distance between the CPG and the propellant. © Published under licence by IOP Publishing Ltd.

关键词： Temperature

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Experimental and Numerical Investigations on the Microstructural Features and Mechanical Properties of Explosive Welded Niobium-Steel Interface

SSRN

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SSRN 2022年

作者： Xu, Junfeng Ma, Honghao Yang, Ming Shen, Zhaowu Zhang, Bingyuan Rui, Tianan Zhao, Ruijin CAS Key Laboratory of Mechanical Behavior and Design of Materials Department of Modern Mechanics University of Science and Technology of China Anhui Hefei230027 China State Key Laboratory of Fire Science University of Science and Technology of China Anhui Hefei230026 China National Key Laboratory of Transient Physics Nanjing University of Science and Technology Nanjing210094 China Nanjing Baotai Special Materials Co. Ltd Nanjing211100 China University of Science and Technology of China China

The microstructural characteristics of the explosive welded niobium-steel interface were systematically investigated by various characterizations and a two-step numerical simulation. A coupled Lagrange-Eulerian simulation was firstly developed to compute the impact velocity, this model allows to establish an accurate impact condition. Microstructure observations show that the niobium-steel interface is featured by a wave structure with two vortices located at the wave front and back, and micro defects like voids and cracks were detected inside the vortex. Grains of the niobium and steel matrix near the interface were characterized by elongated and fine equiaxed structures, respectively, while that in vortex area was fine columnar grains. Then, the interfacial thermokinetics was investigated by a smoothed particles hydrodynamics simulation to reveal the formation of the observed defects and diverse grains. The ultimate strength of the composite exceeds 350 MPa with disparate heat-treated temperatures obtained by the tensile tests. Meanwhile, tensile-shear test shows a robust bonding strength of 220 MPa. The strong mechanical properties of the composite guarantee a great prospect of its application in the nuclear industry. © 2022, The Authors. All rights reserved.

关键词： Vortex flow

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Analysis and optimization of the two-dimensional model of the armature rotation on the electromagnetic railgun 2

Analysis and optimization of the two-dimensional model of th...

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2nd Spring International Conference on Defence technology, ICDT 2020

作者： Liu, Xiangrong Ma, Fuqiang Wei, Jiufu Li, Baoming National Key Laboratory of Transient Physics Nanjing University of Science and Technology Nanjing Jiangsu210094 China China Academy of Ordnance Beijing100089 China

In order to generate enough electromagnetic torque on the armature during the electromagnetic launching process, an asymmetrical structure is adopted in this paper. And a two-dimensional armature model is established for analyzing this asymmetrical structure. Based on this model and the translational equation of the armature, the size parameters of the armature are optimized under the premise of the fixed device parameters of the pulse power supplies and the barrel. The effective length of the armature is between 5mm and 20mm, and the radius of the internal contour for the armature is between 0 and 4mm. The results show that when the above two parameters are 20mm and 4mm respectively, the armature can obtain the largest angular velocity. The maximum value is up to 1087.3rad/s. It is meaningful to guide the armature design of the electromagnetic railgun. © Published under licence by IOP Publishing Ltd.

关键词： Rail guns

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