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arXiv 2021年

作者： Peng, Jiang-Zhou Liu, Xianglei Aubry, Nadine Chen, Zhihua Wu, Wei-Tao Key Laboratory of Transient Physics Nanjing University of Science and Technology Nanjing210094 China School of Energy and Power Engineering Nanjing University of Aeronautics and Astronautics Nanjing210016 China Department of Mechanical Engineering Tufts University MedfordMA02155 United States School of Mechanical Engineering Nanjing University of Science and Technology Nanjing210094 China

Heat convection is one of the main mechanisms of heat transfer and it involves both heat conduction and heat transportation by fluid flow;as a result, it usually requires numerical simulation for solving heat convection problems. Although the derivation of governing equations is not difficult, the solution process can be quite complicated and usually requires numerical discretization and iteration of differential equations. In this paper, based on neural networks, we develop a data-driven model for extremely fast prediction of steady-state heat convection of a hot object with arbitrary complex geometry in a two-dimensional space. According to the governing equations, the steady-state heat convection is dominated by convection and thermal diffusion terms, thus the distribution of the physical fields would exhibit stronger correlations between adjacent points. Therefore, the proposed neural network model uses Convolutional Neural Network (CNN) layers as the encoder and Deconvolutional Neural Network (DCNN) layers as the decoder. Compared with fully connected (FC) network model, the CNN based model is good for capturing and reconstructing the spatial relationships of low-rank feature spaces, such as edge intersections, parallelism and symmetry. Furthermore, we applied the signed distance function (SDF) as the network input for representing the problem geometry, which contains more information compared to a binary image. For displaying the strong learning and generalization ability of the proposed network model, the training dataset only contains hot objects with simple geometries: triangles, quadrilaterals, pentagons, hexagons and dodecagons;while the validating cases use arbitrary and complex geometries. According to the study, the trained network model can accurately predict the velocity and temperature field of the problems with complex geometries which has never been seen by the network model during the model training;and the prediction speed is four orders faster

关键词： Heat convection

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Application of flash X-ray radiography system in muzzle image diagnosis of railgun 31

Application of flash X-ray radiography system in muzzle imag...

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31st International Symposium on Ballistics, BALLISTICS 2019

作者： Tian, Hui Gu, Jinliang Jin, Yong Xia, Yan Wan, Gang Li, Baoming National Key Laboratory of Transient Physics Nanjing University of Science and Technology Nanjing Jiangsu210094 China China Academy of Ordnance Beijing100089 China

ISBN: (纸本)9781605956107

Because the X-ray can penetrate the flame and smoke in the railgun's muzzle to detect thearmature situation, an X-ray digital imaging system is assembled for railgun muzzlediagnostics, which consists of Scandiflash 300kV flash X-ray system, PROSCAN 35 X-raycomputer radiography (CR) imaging system and image processing software. The flash Xray system provides short and intense pulses of X-ray. The image plates are placed behindthe armature, perpendicular to the X-ray beam axis. The X-ray digital imaging system cantake 4 time sequence images of 1.4m within the muzzle of projectile. Observing theseimages, the experimental information about the trajectory, attitude and appearance of thearmature can be obtained. And some important ballistic parameters, such as muzzle velocityand the ablation condition of armature also can be obtained via analyzing these images. Theparameters can provide reliable experimental parameters for the mechanism ofelectromagnetic launch and designing the railgun launcher. © 2019 by International Ballistics Society All rights reserved.

关键词： Smoke

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Numerical study of size effect in concrete penetration with LDPM

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Defence technology（防务技术） 2018年第5期14卷 560-569页

作者： Jun Feng Wei-wei Sun Bao-ming Li National Key Laboratory of Transient Physics Nanjing University of Science and Technology Department of Civil Engineering Nanjing University of Science and Technology

Projectile size effect is of great importance since the scaling researches are extensively applied to concrete penetration investigations. This paper numerically deals with the projectile size effect on penetration resistance via the recently developed Lattice Discrete Particles Model(LDPM) which is featured with mesoscale constitutive laws governing the interaction between adjacent particles to account for cohesive fracture, strain hardening in compression and compaction due to pore collapse. Simulations of two different penetration tests are carried to shed some light on the size effect issue. The penetration numerical model is validated by matching the projectile deceleration curve of and predicting the depth of penetration(DOP). By constant velocity penetration simulations, the target resistance is found to be dependent on the projectile size. By best fitting numerical results of constant velocity penetration, a size effect law for target resistance is proposed and validated against literature data. Moreover, the size effect is numerically obtained in the projectile with longer extended nose part meanwhile the shorter extended nose is found to improve the DOP since the projectile nose is sharpened.

关键词： Penetration of concrete Size effect Lattice discrete particle model Target resistance Abnormal nose projectile

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Multiform damages on the rail of an electromagnetic rail launcher 31

Multiform damages on the rail of an electromagnetic rail lau...

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31st International Symposium on Ballistics, BALLISTICS 2019

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

ISBN: (纸本)9781605956107

Electromagnetic launching technology is a new concept launching technology, whichattracts much attention recently. Electromagnetic rail launcher is one of the many modes ofelectromagnetic launching technology. During the launch of the electromagnetic raillauncher, multiform damages have been observed on the rail in several electromagnetic raillauncher such as groove, gouge and erosion. An easily detachable electromagnetic launcherwas designed to research the damages on the rail and some improvements were designed toreduce the damages on rails, such as high hardness and high conductivity material andcoating technology. Results show that it can control the damages on the rails throughselecting the appropriate rail materials and coating parameters. And these technicalmeasures can also enhance the launch efficiency. © 2019 by International Ballistics Society All rights reserved.

关键词： Launching

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A hybrid active contour model using local region-based K-medoids for infrared image segmentation

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Expert Systems with Applications 2025年 290卷

作者： Ge, Pengqiang Wan, Minjie Xu, Yunkai Kong, Xiaofang Kang, Yixuan Weng, Guirong Gu, Guohua Chen, Qian School of Electronic and Optical Engineering Nanjing University of Science and Technology Nanjing210094 China Jiangsu Key Laboratory of Visual Sensing & Intelligent Perception Nanjing University of Science and Technology Nanjing210094 China Advanced Interdisciplinary Research Center for Optics Nanjing University of Science and Technology Nanjing210094 China National Key Laboratory of Transient Physics Nanjing University of Science and Technology Nanjing210094 China Laboratory of Intelligent Perception Xi'an Institute of Applied Optics Xi'an710065 China School of Mechanical and Electric Engineering Soochow University No. 8 Jixue Road Jiangsu Suzhou215137 China

The active contour models (ACMs) are useful tools for the task of image segmentation. However, many existing ACMs, relying only on local data-driven term based on intensity feature, often struggle with infrared (IR) image segmentation due to intensity non-uniformity, which causes edge leakage or local minima trapping possibly. Besides, the extensive convolutions are used for feature extraction during iteration, which significantly adds up computational demand. To resolve these issues, we propose a hybrid active contour model based on local region-based K-medoids (LRKM) for IR image segmentation. First, the multi-feature bias fields are pre-estimated using the LRKM module to derive the local term before iteration, which avoids possible edge leakage and reduces the amount of convolutions. Likewise, the global means of multi-features are considered to construct the global term, which eliminates possible local minima. Next, these two terms are fused via an adaptive weight function into the hybrid term, whose energy range is regularized to enhance iteration stability. After that, the mean filtering ensures the smoothness of level set function (LSF), while its range is regularized to maintain its signed distance function (SDF) at both ends during iteration. Finally, the zero-level set represents the target profile once level set evolution (LSE) converges. Compared with recently developed ACMs and deep learning-based models qualitatively and quantitatively, our LRKM model obtains competitive results in both segmentation efficiency (average CPU runtime (s) and memory (MB)) and segmentation precision (average IoU, average DSC and mIoU) while segmenting IR images with intensity non-uniformity as well as natural and medical MRI images. Experimental results also confirm that this model demonstrates strong robustness to initial contours and noise. © 2025 Elsevier Ltd

关键词： Image segmentation

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Study of the Attitude Algorithm of MEMS IMU Based on Improved Coning Compensation for High Speed Rotating rigid body

Study of the Attitude Algorithm of MEMS IMU Based on Improve...

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IEEE International Conference on Unmanned Systems (ICUS)

作者： Xueyuan Guan Ning Liu Shang Yin Zhenhua Bo Xunqiong Ma Yushun Liu School of National Key Laboratory of Transient Physics Nanjing Nanjing University of Science & Technology Nanjing China Beijing Key Laboratory of High Dynamic Navigation Technology Beijing Information Science& Technological University Beijing China

ISBN: (数字)9781728180250

ISBN: (纸本)9781728180267

The classical algorithms for strap down attitude are dependent upon the first-order rotation vector equation is difficult to fit the high dynamic environment, which is angular rate is higher than 60 rad/s. This paper presents the analysis result of the error composition of coning algorithm on the basis of the classical three-sample coning algorithm. This confirms the high impact of the truncation for the accuracy of attitude calculation in the high dynamic environment. It also indicates that the impact cannot be reduced by increasing samples in a single cycle. For the purpose of reducing the influence of truncation error on attitude calculation, it proposes an attitude algorithm based on an improved coning compensation structure. The proposed algorithm can effectively compensate the truncation error by error compensation model. Simulation based test results prove that the improved performance of new algorithm performance is obviously because of the classical three-sample coning algorithm. The proposed coning algorithm architecture can also be applied to a generalized coning algorithm to arbitrary samples of the gyro.

关键词： Error analysis Discrete wavelet transforms

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Spontaneous emergence of microresonator laser cavity-solitons

Spontaneous emergence of microresonator laser cavity-soliton...

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Integrated Photonics Research, Silicon and Nanophotonics, IPR 2021 - Part of OSA Advanced Photonics Congress 2021

作者： Rowley, Maxwell Hanzard, Pierre Henry Cutrona, Antonio Chu, Sai T. Little, Brent E. Morandotti, Roberto Moss, David J. Gongora, Juan Sebastian Totero Peccianti, Marco Pasquazi, Alessia Lab. Dept. of Physics and Astronomy University of Sussex BN1 9QH United Kingdom Department of Physics City University of Hong Kong Tat Chee Avenue Hong Kong Hong Kong State Key Laboratory of Transient Optics and Photonics Xi’an Institute of Optics and Precision Mechanics CAS Xi’an China INRS-EMT 1650 Boulevard Lionel-Boulet Varennes QuébecJ3X 1S2 Canada Institute of Fundamental and Frontier Sciences University of Electronic Science and Technology Chengdu China Optical Sciences Centre Swinburne University of Technology HawthornVIC3122 Australia

A cartographical study is conducted within the parameter space of a microresonator-filtered fiber laser. We identify a region in which solitons are spontaneously formed and maintained, and we investigate the effects w... 详细信息

ISBN: (纸本)9781557528209

关键词： Microresonators

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Mixing characteristic of both subsonic and supersonic unsteady circular jets

Mixing characteristic of both subsonic and supersonic unstea...

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19th International Conference of Fluid Power and Mechatronic Control Engineering 2018

作者： Zhang, Huanhao Chen, Zhihua Sun, Xun Huang, Zhengui Key Laboratory of Transient Physics Nanjing University of Science and Technology Nanjing210094 China Shanghai Institute of Spaceflight Control Technology Shanghai201109 China

With the use of large eddy simulation (LES), the initial structure and mixing characteristics of both the subsonic and supersonic circular jets are studied, respectively. The stretched-vortex model combined with the high-order hybrid scheme is employed to solve the LES equations. The typical structures of the initial jet at different conditions have been presented and discussed. The formation and evolution process of the vortex ring has been displayed in detail, and the unique characteristics of a compressible vortex ring generated by the unsteady jet have been identified. Furthermore, the engulfment and mixture of ambient gas with the jet gases have been discussed, the different mixing processes of both subsonic and supersonic jets, especially the shock wave effect in a supersonic jet on mixing process, have been illustrated. © 2019 Institution of Engineering and technology. All rights reserved.

关键词： Large eddy simulation

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On-chip generation and telecom-compatible processing of complex photonic systems in time and frequency

On-chip generation and telecom-compatible processing of comp...

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Frontiers in Optics, FiO 2022

作者： Sciara, Stefania Yu, Hao Chemnitz, Mario Fischer, Bennet Roztocki, Piotr Crockett, Benjamin Reimer, Christian Caspani, Lucia Kues, Michael Munro, William J. Chu, Sai T. Little, Brent E. Moss, David J. Wang, Zhiming Azaña, Jose Morandotti, Roberto Institut National de la Recherche Scientifique Centre Énergie Matériaux Télécommunications 1650 Boulevard Lionel-Boulet VarennesQCJ3X 1S2 Canada Institute of Fundamental and Frontier Sciences University of Electronic Science and Technology of China Sichuan Chengdu610054 China Technology Innovation Centre University of Strathclyde 99 George St GlasgowG11RD United Kingdom Hannover Centre for Optical Technologies Leibniz University Nienburger Str. 17 Hannover30167 Germany NTT Basic Research Laboratories Morinosato Wakamiya Kanagawa Atsugi-shi Japan Department of Physics City University of Hong Kong Tat Chee Avenue Kowloon Hong Kong State Key Laboratory of Transient Optics and Photonics Xi'an Institute of Optics and Precision Mechanics Chinese Academy of Science Xinxi Ave Shaanxi Xi'an710119 China Optical Sciences Centre Swinburne University of Technology HawthornVIC3122 Australia

We exploit standard silicon-based chips and fiber telecommunications components to generate and process complex entangled photon states in the discrete time and frequency domains (two-level time-entangled photons, d-l...

ISBN: (纸本)9781557528209

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Fuzzy pid control of electromechanical actuator system

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Journal of physics: Conference Series 2021年第1期1721卷

作者： Cuicui Li Wenjun Yi Hongqiao Yin Jun Guan National Key Laboratory of Transient Physics Nanjing University of Science and Technology Nanjing 210094 China

In order to meet the needs of modern high-performance aircraft, the fuzzy PID control strategy was used to design the electromechanical actuator control system. This control strategy combines the advantages of fuzzy control and PID control, and has better adaptability to time-varying complex systems. The electromechanical actuator control system adopted the three-loop structure, and current loop, speed loop and position loop were built on the platform of MATLAB / Simulink. Considering that the discrete universe fuzzy PID control algorithm has good real-time performance with small online computation, the fuzzy PID controller in discrete universe was designed in the position loop and the system was simulated. The simulation results show that the dynamic and steady performance of discrete universe fuzzy PID control is better than that of traditional PID control, and it is more suitable for electromechanical actuator system.

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