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Coupled fluid-thermal investigation on non-ablative thermal protection system with spiked body and opposing jet combined configuration

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Chinese Journal of Aeronautics 2019年第6期32卷 1390-1402页

作者： Jie HUANG Weixing YAO Xianyang SHAN State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China Key Laboratory of Fundamental Science for National Defense-Advanced Design Technology of Flight Vehicle Nanjing University of Aeronautics and AstronauticsNanjing 210016China System Design Institute Hubei Aerospace Technology AcademyWuhan 430040China

In this paper, a Non-Ablative Thermal Protection System(NATPS) with the spiked body and the opposing jet combined configuration is proposed to reduce the aerodynamic heating of the hypersonic vehicle, and the coupled fluid-thermal numerical analysis is performed to study the thermal control performance of the NATPS. The results show that the spiked body pushes the bow shock away from the protected structure and thus reduces the shock intensity and the wall heat flux. In addition, the low temperature gas of the opposing jet separates the high temperature gas behind the shock from the nose cone of the spiked body, ensuring the non-ablative property of the spiked body. Therefore, the NATPS reduces the aerodynamic heating by the reconfiguration of the flow field, and the thermal control efficiency of the system is better than the Thermal Protection System(TPS) with the single spiked body and the single opposing jet. The influencing factors of the NATPS are analyzed. Both increasing the length of the spiked body and reducing the total temperature of the opposing jet can improve the thermal control performance of the NATPS and the nonablative property of the spiked body. However, increasing the heat conductivity coefficient of the spiked body can enhance benefit the non-ablative property of the spiked body, but has little influence on the thermal control performance of the NATPS.

关键词： Coupled method Non-ablative Opposing jet Spiked body Thermal protection system

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A structure feature algorithm for multi-modal forearm registration

arXiv

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arXiv 2021年

作者： Li, Jiaxin Ding, Yan Zhang, Weizhong Zhao, Yifan Guo, Lingxi Yang, Zhe Key Laboratory of Dynamics and Control of Flight Vehicle Ministry of Education School of Aerospace Engineering Beijing Institute of Technology Beijing100081 China School of Aerospace Transport and Manufacturing Cranfield University Wharley End Bedford United Kingdom Science and Technology on Space Physics Laboratory Beijing100076 China

Purpose: Augmented reality technology based on image registration is becoming increasingly popular for the convenience of pre-surgery preparation and medical education. This paper focuses on the registration of forearm images and digital anatomical models. Due to the difference in texture features of forearm multi-modal images, this paper proposes a forearm feature representation curve (FFRC) based on structure features to extract feature points of forearm images. In addition, we create an FFRC-compliant multi-modal image registration framework (FAM) for the forearm. Methods: FFRC counts the number of feature pixels in each column of the forearm binary image and uses the Kalman filter to eliminate data deviation. FAM screens matching spots using the FFRC feature of forearm pictures before applying affine transformation. FAM-TPS, which adds Thin Plate Spline to FAM, performs deformable registration by using the matched points as the interpolation function’s control points. FAM and FAM-TPS are evaluated on a dataset containing the axial rotation of the forearm. We employ Dice coefficient (DC), Jaccard coefficient (JC), Hausdorff distance (HD), Average surface distance metric (ASD), Average symmetric surface distance (ASSD) indicators to evaluate the registration accuracy of the framework and use Fréchet Inception Distance (FID) and Euler distance (ED) to evaluate the accuracy of the feature point matching. Results:Other classic feature-based registration methods were compared to FAM and FAM-TPS. In the registration experiment, our framework (FAM) achieved the DC of 0.987, JC of 0.974, HD of 387.21, ASD of 1.22, ASSD of 4.02, by adding thin-plate spline interpolation, our framework (FAM-TPS) achieved the DC of 0.991, JC of 0.982, HD of 395.69, ASD of 0.958, ASSD of 3.11. Furthermore, tests of resilience showed that our framework can register forearm images with varying rotation angles. Conclusions: The multi-modal forearm feature points can be retrieved properly using

关键词： Textures

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Simulated Impacts of the Wetter Arid Area of Northwestern China on Energy Budget and Atmospheric Circulation Over Tibetan Plateau and Central Part of North China Plain in Summer

SSRN

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SSRN 2022年

作者： Ma, Di Meng, Xianhong Lv, Shihua Li, Yaohui Yu, Haipeng Shu, Lele Zhao, Lin Li, Zhaoguo College of Atmospheric Sciences Lanzhou University Gansu Province Lanzhou730000 China Key Laboratory for Land Surface Process and Climate Change in Cold and Arid regions Northwest Institute of Eco-Environment and Resources Chinese Academy of Science Gansu Province Lanzhou730000 China School of Atmospheric Sciences Plateau Atmosphere and Environment Key Laboratory of Sichuan Province Chengdu University of Information Technology Sichuan Province Chengdu610225 China Civil aviation flight University of China Sichuan Province Guanghan618307 China

This paper examines the local and non-local climatic effects of wetter arid areas of Northwestern China (ANWC) in summer using a fully coupled climate model. In response to soil moisture increase, the local air temperature significantly decreases, and precipitation increases in summer. Also, the wetter ANWC can result in a warmer and rainless climate over the Central part of North China Plain (CNCP). A cooler climate leads to an abnormal descending motion occurring over ANWC. Meanwhile, an anomalous high pressure and an abnormal anticyclonic circulation in 500hpa over the west of ANWC. A Rossby wave is stimulated and propagates downstream. Correspondingly, a huge anomalous cyclone circulation occurs over the northeastern part of China and Mongolia. This huge anomalous cyclone circulation can block the East Asian summer Monsoon northward and decrease the water vapor transport into Central China Plain. So, the weakened East Asian summer Monsoon leads to rainless over CNCP. Moreover, the influence of increasing soil moisture on the Tibet Plateau (TP) precipitation is negligible due to the high altitude. In addition, the impacts of different wetting magnitudes of ANWC are also discussed. As soil moisture increases over ANWC is stronger, the magnitudes of the atmospheric field become significantly larger. This study highlights the wetter ANWC effect on local climate and provides more information about the mechanism of wetter ANWC remote effect on non-local climate. © 2022, The Authors. All rights reserved.

关键词： Soil moisture

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The Influence of Anisotropic Microstructures on the Ice Adhesion Performance of Rubber Surfaces

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Coatings 2025年第5期15卷 612-612页

作者： Fangyuan Zhang Xiaosen Wang Shilin Zhang Xiaoqing Cao Qiang He Lu Li College of Mechanical and Electrical Engineering Gansu Agricultural University Lanzhou 730070 China School of Mechatronics Engineering Henan University of Science and Technology Luoyang 471003 China Sichuan Key Technology Engineering Research Center for All-Electric Navigable Aircraft Guanghan 618307 China Civil Aircraft Fire Science and Safety Engineering Key Laboratory of Sichuan Province Guanghan 618307 China College of Civil Aviation Safety Engineering Civil Aviation Flight University of China Guanghan 618307 China

Anti-icing and de-icing technologies are crucial in modern aviation, with optimising ice adhesion performance on material surfaces being a key challenge. This study proposes a straightforward method for fabricating hydrophobic silicone rubber surfaces using a mesh to construct microstructures. The influence of microstructure size and anisotropy on surface wettability and ice adhesion performance is systematically investigated. The experimental results demonstrate that introducing microstructures significantly enhances the hydrophobicity of silicone rubber surfaces, achieving a maximum static contact angle of 149.3 ± 1.3°. For microstructures with identical shapes, dimensional variations affect surface roughness and functional performance. Although the structure with the most significant dimension (600#-SR) exhibits the highest surface roughness, smaller structures (e.g., 1400#-SR) demonstrate superior hydrophobicity and lower ice adhesion strength, likely due to enhanced air entrapment and reduced effective solid–liquid and solid–ice contact areas. Furthermore, due to anisotropic microstructures, a marked directional difference in ice adhesion strength is observed: the lowest strength in the X direction is 38.6 kPa, compared to 63.3 kPa in the Y direction. Fine-tuning the size and configuration of microstructures effectively minimises the ice adhesion strength and enables targeted optimisation of surface properties. This research offers theoretical support for developing innovative, energy-efficient materials with superior anti-icing properties and provides new insights for crafting solutions tailored to various anti-icing needs.

关键词： silicone rubber microstructures anisotropy wettability ice adhesion performance

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Fault-Tolerant control for Flexible Air-Breathing Hypersonic Vehicle Based on Tube Robust Model Predictive control

Fault-Tolerant Control for Flexible Air-Breathing Hypersonic...

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Data Driven control and Learning Systems (DDCLS)

作者： Xiaohe Yang Weijie Lv Chaofang Hu Yongtai Hu School of Electrical and Information Engineering Tianjin University Tianjin China Aviation Key Laboratory of Science and Technology on Aircraft Control Facri China

ISBN: (数字)9781728159225

ISBN: (纸本)9781728159232

This paper adopts Tube robust model predictive control (RMPC) approach to achieve the trajectory tracking control for flexible air-breathing hypersonic vehicle (FAHV) with lose efficiency fault of actuator. First of all, Jacobian linearization and tensor-product transformation are used to build the polytopic linear parameter varying (LPV) model for FAHV. Then, the FAHV faulty model is obtained by transforming lose efficiency fault of actuator into the additional disturbance term. Thirdly, fault-tolerant control is realized by composite control law. The error system is obtained by the difference between the actual and the nominal system. By designing the minimum robust positive invariant set (mRPI), the error system state is limited to the mRPI set. The additional disturbance term in mRPI set is suppressed by the auxiliary robust feedback control law. The nominal control law provides a reasonable trajectory for the actual system. And it is calculated by the convex optimization problem, which is constrained by linear matrix inequality (LMI). The fault-tolerant controller guarantees that the actual trajectory is located in the mRPI set all the time and centered on the nominal trajectory. Finally, the designed Tube RMPC controller is validated by simulation.

关键词： Fault tolerant systems Fault tolerance Electron tubes Actuators Trajectory Feedback control Tensors

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Probabilistic Tolerance Method for Omitting Small Fatigue Loads

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Transactions of Nanjing University of Aeronautics and Astronautics 2020年第5期37卷 676-681页

作者： LIN Hanyu YAO Weixing XU Lipu HUANG Jie State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016P.R.China Key Laboratory of Fundamental Science for National Defense-Advanced Design Technology of Flight Vehicle Nanjing University of Aeronautics and AstronauticsNanjing 210016P.R.China

The simplification of fatigue load spectrum,which can effectively reduce experimental cost,is of great importance for structural fatigue *** introducing random variables,the probabilistic tolerance method of removing small amplitude cycles proposed in this paper takes into account the randomness of both load and fatigue *** probability of the damage occurrence caused by the removed small loads is calculated to ensure that it cannot exceed the given probabilistic ***,the omission level is obtained and the truncated spectrum is *** unnotched aluminum sheet specimens are used to perform the fatigue test on the original fatigue spectrum and truncated fatigue spectrum of a *** test results show that there is no statistical difference between the test life of the truncated spectrum and that of the original spectrum,which demonstrates the validity of the small-load-omitting method that considers randomness.

关键词： load spectrum truncation P-S-N curve exceedance frequency curve of load probabilistic tolerance value

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A global to local double embedding method for multi-person pose estimation

arXiv

引用

arXiv 2021年

作者： Xu, Yiming Li, Jiaxin Peng, Yiheng Ding, Yan Wei, Hualiang Yingcai Honors College University of Electronic Science and Technology of China Chengdu China Key Laboratory of Dynamics and Control of Flight Vehicle Ministry of Education School of Aerospace Engineering Beijing Institute of Technology Beijing100081 China School of Computer Science and Technology Donghua University Shanghai China Department of Automatic Control and Systems Engineering University of Shefield ShefieldS1 3JD United Kingdom

Multi-person pose estimation is a fundamental and challenging problem to many computer vision tasks. Most existing methods can be broadly categorized into two classes: top-down and bottom-up methods. Both of the two types of methods involve two stages, namely, person detection and joints detection. Conventionally, the two stages are implemented separately without considering their interactions between them, and this may inevitably cause some issue intrinsically. In this paper, we present a novel method to simplify the pipeline by implementing person detection and joints detection simultaneously. We propose a Double Embedding (DE) method to complete the multi-person pose estimation task in a global-to-local way. DE consists of Global Embedding (GE) and Local Embedding (LE). GE encodes different person instances and processes information covering the whole image and LE encodes the local limbs information. GE functions for the person detection in top-down strategy while LE connects the rest joints sequentially which functions for joint grouping and information processing in A bottom-up strategy. Based on LE, we design the Mutual Refine Machine (MRM) to reduce the prediction difficulty in complex scenarios. MRM can effectively realize the information communicating between keypoints and further improve the accuracy. We achieve the competitive results on benchmarks MSCOCO, MPII and CrowdPose, demonstrating the effectiveness and generalization ability of our method. Copyright © 2021, The Authors. All rights reserved.

关键词： Embeddings

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Smooth Q-learning: Accelerate convergence of q-learning using similarity

arXiv

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arXiv 2021年

作者： Liao, Wei Wei, Xiaohui Lai, Jizhou Key laboratory of Fundamental Science for National Defense-Advanced Design Technology of Flight Vehicle Nanjing University of Aeronautics and Astronautics NanjingJiangsu China State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics NanjingJiangsu China College of Automation Engineering Nanjing University of Aeronautics and Astronautics NanjingJiangsu China

An improvement of Q-learning is proposed in this paper. It is different from classic Q-learning in that the similarity between different states and actions is considered in the proposed method. During the training, a new updating mechanism is used, in which the Q value of the similar state-action pairs are updated synchronously. The proposed method can be used in combination with both tabular Q-learning function and deep Q-learning. And the results of numerical examples illustrate that compared to the classic Q-learning, the proposed method has a significantly better performance. Copyright © 2021, The Authors. All rights reserved.

关键词： Reinforcement learning

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A Novel Unified Framework for Solving Reachability, Viability and Invariance Problems

arXiv

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arXiv 2021年

作者： Liao, Wei Liang, Taotao Wei, Xiaohui Lai, Jizhou Key Laboratory of Fundamental Science for National Defense-Advanced Design Technology of Flight Vehicle Nanjing University of Aeronautics and Astronautics Jiangsu Nanjing China State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics Jiangsu Nanjing China Navigation Research Center Nanjing University of Aeronautics and Astronautics Jiangsu Nanjing China

The level set method is a widely used tool for solving reachability and invariance problems. However, some shortcomings, such as the difficulties of handling dissipation function and constructing terminal conditions for solving the Hamilton-Jacobi partial differential equation, limit the application of the level set method in some problems with non-affine nonlinear systems and irregular target sets. This paper proposes a method that can effectively avoid the above tricky issues and thus has better generality. In the proposed method, the reachable or invariant sets with different time horizons are characterized by some non-zero sublevel sets of a value function. This value function is not obtained by solving a viscosity solution of the partial differential equation but by recursion and interpolation approximation. At the end of this paper, some examples are taken to illustrate the accuracy and generality of the proposed method. Copyright © 2021, The Authors. All rights reserved.

关键词： Level measurement

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A PCNN model for infrared pedestrian segmentation in complex environments

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Infrared Physics and technology 2025年 149卷

作者： Cao, Honggui Ye, Bo Zou, Yangkun Zhu, Zhizhen Wan, Zijie Yin, Shsoda Faculty of Information Engineering and Automation Kunming University of Science and Technology Kunming650500 China Yunnan Key Laboratory of Intelligent Control and Application Kunming650500 China Faculty of Civil Aviation and Aeronautics Kunming University of Science and Technology Kunming650500 China The First Military Representative Office of the Chongqing Military Representative Bureau of the Army Equipment Department Kunming650500 China

Pulse Coupled Neural Network (PCNN) is widely used in infrared pedestrian image segmentation. Due to the complex background, heat source interference, uneven brightness distribution of human targets and easy aliasing with the background in infrared pedestrian images, the segmentation of human targets is incomplete and the segmentation effect is poor. An improved PCNN algorithm for segmenting infrared pedestrian targets in complex environments and a new idea of preferentially segmenting background regions are proposed. The infrared pedestrian image is represented as a graph structure, and the superpixels in the infrared image are represented as nodes of the graph. The score of each node becoming the background region is evaluated by analyzing the structure of the graph, and the score is mapped to the original image as the connection strength of the model. Correspondingly, the dynamic threshold is set as the clustering center of the image background, and the background region of the image is prioritized for classification and output. Infrared pedestrian images with complex environment can be effectively segmented by the model, especially for infrared images with more heat source interference in the background. © 2025 The Authors

关键词： Image segmentation

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