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Biomimetic twisted plywood structural materials

national science Review 2018年第5期5卷 703-714页

作者： Si-Ming Chen Huai-Ling Gao Yin-Bo Zhu Hong-Bin Yao Li-Bo Mao Qi-Yun Song Jun Xia Zhao Pan Zhen He Heng-An Wu Shu-Hong Yu Division of Nanomaterials & Chemistry Hefei National Research Center for Physical Sciences at the MicroscaleCAS Center for Excellence in NanoscienceHefei Science Center of CASCollaborative Innovation Center of Suzhou Nano Science and TechnologyDepartment of ChemistryUniversity of Science and Technology of China CAS Key Laboratory of Mechanical Behavior and Design of Materials Department of Modern MechanicsCAS Center for Excellence in Complex System MechanicsUniversity of Science and Technology of ChinaHefei 230027China3 Anhui Key Laboratory of Condensed Matter Physics at Extreme ConditionsHigh Magnetic Field LaboratoryChinese Academy of Sciences CAS Key Laboratory of Mechanical Behavior and Design of Materials Department of Modern MechanicsCAS Center for Excellence in Complex System MechanicsUniversity of Science and Technology of China Anhui Key Laboratory of Condensed Matter Physics at Extreme Conditions High Magnetic Field LaboratoryChinese Academy of Sciences

Biomimetic designs based on micro/nanoscale manipulation and scalable fabrication are expected to develop new-style strong, tough structural materials. Although the mimicking of nacre-like‘brick-and-mortar' structure is well studied, many highly ordered natural architectures comprising 1D micro/nanoscale building blocks still elude imitation owing to the scarcity of efficient manipulation techniques for micro/nanostructural control in practical bulk counterparts. Herein, inspired by natural twisted plywood structures with fascinating damage tolerance, biomimetic bulk materials that closely resemble natural hierarchical structures and toughening mechanisms are successfully fabricated through a programmed and scalable bottom-up assembly strategy. By accurately engineering the arrangement of 1D mineral micro/nanofibers in biopolymer matrix on the multiscale, the resultant composites display optimal mechanical performance, superior to many natural, biomimetic and engineering materials. The design strategy allows for precise micro/nanostructural control at the macroscopic 3D level and can be easily extended to other materials systems, opening up an avenue for many more micro/nanofiber-based biomimetic designs.

关键词： biomimetic designs micro/nanoscale building blocks twisted plywood structures damage tolerance biomimetic bulk materials toughening mechanisms

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NUMERICAL INVESTIGATION ON DIRECT CONTACT CONDENSATION CHARACTERISTICS OF STEAM INJECTION INTO COLD-WATER PIPE UNDER HEAVING CONDITION 30

NUMERICAL INVESTIGATION ON DIRECT CONTACT CONDENSATION CHARA...

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30th International Conference on Nuclear Engineering, ICONE 2023

作者： Wang, Zhiwei He, Yanping Duan, Zhongdi Huang, Chao Liu, Shiwen State Key Laboratory of Ocean Engineering Shanghai Jiao Tong University Shanghai200240 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu China

ISBN: (纸本)9784888982566

Direct contact condensation (DCC) is widely appeared in the nuclear power plants and will lead to serious temperature and pressure fluctuations. For ocean nuclear power plants, the DCC is inevitably affected by the sea conditions, such as rolling, heaving motion. In this study, the integration of volume of fluid model (VOF) and condensation model is adopted to simulate the DCC characteristics under heave conditions. The interfacial heat and mass transfer are calculated by user-defined functions (UDF). The additional inertial force method is used to describe the heave motion. First, the DCC numerical model under heave motion is validated by the experimental data, which coincides well with the experiment results. Then, the characteristics of DCC under different heave parameters are numerically studied. The results show that the average condensation rate increases with an increase in heave amplitude, decreases with an increase in heave period. This is mainly because the heave motion will cause the liquid phase to impact the upper pipe wall, and increasing the contact area of vapor and subcooled water. The pressure oscillations induced by DCC are more complicated under heaving conditions. With heave period continuing to change, the formation mechanisms of the pressure peak are different. When the heave period is relatively small, the pressure peak is mainly induced by the acceleration of water phase under high frequency heaving motion. With an increase in the heave period, the heaving motion accelerated the formation of isolated steam bubble, and caused the condensation induced water hammer (CIWH) events, which in turn induced the pressure peak. In addition, the pressure peak is proportional to the heave amplitude. In summary, the direct contact condensation characteristics are more sensitive to the heave period under heaving conditions. These qualitative conclusions may serve as a reference for direct contact condensation simulations under heaving conditions. © 2023 by

关键词： Nuclear power plants

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Experimental study of thermal and hydraulic characteristics of pressurizertype heating container during blowdown process

Experimental study of thermal and hydraulic characteristics ...

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2020 International Conference on Nuclear Engineering, ICONE 2020, collocated with the ASME 2020 Power Conference

作者： Ke, Bingzheng Gao, Puzhen Wang, Bo Chen, Bowen Li, Ru Tian, Ruifeng Cheng, Kun Lu, Chuan Fundamental Science on Nuclear Safety and Simulation Technology Laboratory Harbin Engineering University Harbin China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu China

ISBN: (纸本)9780791883785

Blowdown process is an important process in LOCA. Studying the internal thermal hydraulic characteristics of the pressurizer during LOCA blowdown process can help to accurately analyze the process of the whole LOCA, which is of great significance to reduce the hazard of accidents and improve the safety of nuclear power plants. An experiment system of blowdown process under low pressure conditions is built, and it uses a pressure gauge and a differential pressure level gauge to measure the pressure and liquid level in the pressurizer-type heating container, and uses a thermocouple to measure the temperature in the pressurizer-type heating container at different heights and distances from the centerline. The changes of pressure, liquid level and temperature characteristics during the blowdown process were obtained. The research results show that the higher the heating power, the greater the slope of pressure change in the heating container, and the pressure changes from negative to positive growth;The greater the heating power is, the faster the liquid level decreases, and the liquid level decreases sharply after the blowdown inflection point. The greater the heating power is, the greater the rate of temperature change, from negative growth to positive growth. The temperature change rate after the blowdown inflection point is reduced. As the height increases, the temperature inside the container first increases and then decreases;the further away from the container's centerline, the higher the measured temperature. © 2020 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Containers

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Experimental investigation on temperature characteristics of direct contact condensation in a natural circulation system

Experimental investigation on temperature characteristics of...

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2020 International Conference on Nuclear Engineering, ICONE 2020, collocated with the ASME 2020 Power Conference

作者： Sun, Jianchuang Ding, Ming Mi, Zhengpeng Zhang, Zhuohua Fundamental Science on Nuclear Safety and Simulation Technology Laboratory Harbin Engineering University Harbin China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu China

ISBN: (纸本)9780791883785

Direct contact condensation (DCC) is a common physical phenomenon appearing in the nuclear power plants and other industrial applications. The current research on DCC focuses on steam-water counterflow or jet flow under forced flow conditions. For some natural-circulation passive safety systems in floating nuclear power plants, the heated section is connected with the heat sink by the horizontal pipes. The heat sink is usually the ocean. In such natural circulation systems (NCSs), the steam produced in the heated section will inevitably contact the subcooled water in the ocean and result in DCC event. In this paper, the fundamental characteristics of two-phase flow were described in detail. In addition, the influences of the subcooled water temperature on the flow rate, outlet temperature, steam bubble behaviors, and pressure surge were emphatically discussed. The experimental results revealed that the subcooled water in the water tank could reversely flow into the pipe, which was able to cause condensation induced water hammer (CIWH) event and flow oscillation. Further research showed that the subcooled water was evidently prevented from reversely flowing into the pipe with the increase in the subcooled water temperature. The position where the DCC event occurs transferred from the pipe to the water tank, and the pressure peak obviously reduced, even disappear when the subcooled water temperature is larger than 61 oC. © 2020 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Water temperature

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Uncertainty Quantification of Spray Nozzle Fatigue Analysis Under Transient Load 1

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作者： Liu, Zhenyu Li, Lijuan Zhang, Liping Li, Hui Shao, Xuejiao Jiang, Lu Zhang, Ying Science and Technology On Reactor System Design Technology Laboratory Nuclear Power Institute of China No. 328 Changshun Avenue Chengdu Sichuan610200 China

ISBN: (数字)9783030683030

ISBN: (纸本)9783030683023;9783030683054

In this paper, the randomness concept of input parameters is introduced into the design of nuclear equipment, and the uncertainty analysis of input parameters is carried out for fatigue analysis. Taking the pressurizer spray nozzle as the research object, considering the random fluctuation of temperature and pressure of the transient load, the reliability and distribution of the fatigue usage are obtained by performing fatigue analysis according to the fatigue analysis method of nuclear power equipment with Monte Carlo sampling method. Taking section No.3 as an example, the thermal analysis and stress analysis models are established. Through the parameter sensitivity analysis, the relative sensitivity of the fatigue usage to each input parameter is obtained. From the results, it is clear which parameters have a significant impact on the results. The results can further optimize the structural design of the nuclear power equipment and improve its fatigue resistance, which has great application value to the life extension of nuclear power equipment. © 2021, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Uncertainty analysis

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Study on analysis method of loca dynamic response for steam generator heat transfer tube 29

Study on analysis method of loca dynamic response for steam ...

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2022 29th International Conference on Nuclear Engineering, ICONE 2022

作者： Lu, Xifeng Xiong, Furui Wang, Xinjun Ai, Honglei Li, Bingjin Shao, Xuejiao Yang, Kang Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu China Nuclear Power Institute of China Chengdu China

ISBN: (纸本)9780791886359

The equivalent effect relationship formula of LOCA hydraulic load in the bend section of the heat transfer tube of the steam generator is deduced. The hydraulic load factors affecting the stress of the heat transfer tube are derived. The spectrum analysis of the corresponding LOCA hydraulic load is carried out, and the spectral curve of the hydraulic load and the spectral characteristics of the hydraulic load are obtained. Modal analysis of steam generator heat transfer tubes is done. The modal analysis of the steam generator heat transfer tubes is performed. The spectral characteristics of the hydraulic load and the natural frequency information of different heat transfer tubes are compared. According to the comparison results, eight heat transfer tubes with the first-order natural frequency and the frequency corresponding to the peak value of the hydraulic load in the frequency domain curve were selected as the analysis objects, and the LOCA dynamic response analysis is carried out. The time-domain analysis of the LOCA hydraulic load of the steam generator heat transfer tube was performed, and the relationship between the hydraulic load and the bending radius of the heat transfer tube was obtained. The transient load of the steam generator heat transfer tube with different bending radii is calculated. By establishing the finite element models of the first, 31, 43, 57, 72, 83, 87, and 112 rows of heat transfer tubes, the time history analysis of the heat transfer tubes under the LOCA load is performed, and The stress distribution of the heat transfer tube under the LOCA load is obtained. The stress of the heat transfer tube calculated by this method is the maximum LOCA response. This method can screen out sensitive heat transfer tubes, avoiding the process of analyzing each heat transfer tube. This method can effectively improve the efficiency of LOCA analysis of heat transfer tubes and is a practical method. © 2022 American Society of Mechanical Engineers (ASME).

关键词： Frequency domain analysis

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Feature Distillation GAN: An Adversarial Example Defense Method Based on Feature Reconstruction 2nd

Feature Distillation GAN: An Adversarial Example Defense Met...

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2nd International Conference on Network Simulation and Evaluation, NSE 2023

作者： Liu, Ruiqi Li, Hu Wang, Dongxia Zhao, Chongyang Li, Boyu National Key Laboratory of Science and Technology On Information System Security Beijing China

ISBN: (纸本)9789819745180

Purifying and reconstructing adversarial examples into benign ones by generative models is a class of defense methods to eliminate adversarial perturbations. These methods do not make assumptions on adversarial attacks or model architectures, and thus can defend classifiers against unseen threats. In this work, we propose a new GAN-based adversarial purification method Feature Distillation GAN (FDGAN). We consider how to eliminate the feature differences between adversarial examples and benign examples which are difficult for humans to perceive. We extract and analyze the differences between the adversarial examples and the benign examples from multiple dimensionals. On the basis of comparing the differences among various features, we propose a new feature-level perspective on adversarial purification, design a new adversarial example purification method for image inputs, and implement our method based on GAN. Experimental results show that FDGAN is effective against unknown adversarial attacks and outperforms all the purification methods we used for comparison. Evaluating FDGAN against strong adaptive attacks, the robust accuracy of FDGAN under AutoAttack (L∞ = 8/255) exceeds the SOTA adversarial training methods on the Robustbench. Furthermore, FDGAN has lower training cost and can be combined with a variety of model-based defense strategies to further improve the defense effectiveness. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.

关键词： Distillation

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An anomaly detection method based on multi-models to detect web attacks

An anomaly detection method based on multi-models to detect ...

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作者： Zhang, Ming Lu, Shuaibing Xu, Boyi National Key Laboratory of Science and Technology on Information System Security Beijing China

ISBN: (纸本)9781538636749

As Web attacks are constantly emerging and have caused enormous loss, the effective methods to protect the Web security are becoming increasingly required. We propose an anomaly detection method based on multi-models to detect Web attacks. The method is designed by inspecting the HTTP request messages to identify attacks. Three machine learning models, namely the probability distribution model, the hidden Markov model, and the one-class SVM model are employed to inspect different fields of the HTTP request messages to detect anomalies. The three models work together and the overall detection result is anomalous if at least one model reports an anomaly. The detection mechanism of each model and the corresponding feature extraction algorithm are presented. The experimental results show that the multi-model based detection method has apparent advantage on detecting Web attacks. It craftily makes each individual model to inspect the HTTP request fields that they excel at, thus achieving a high detection rate while keeping a low false alarm rate. © 2017 IEEE.

关键词： Anomaly detection Hidden Markov model One-class SVM model Probability distribution model Web attacks

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Peridynamic Simulation for Thermal and Mechanical Behavior of Manufactured Structures with MIG Welding 1

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作者： Li, Hui Zhang, Liping Liu, Zhenyu Li, Lijuan Zhang, Yixiong Shao, Xuejiao Science and Technology On Reactor System Design Technology Laboratory Nuclear Power Institute of China No. 328 Changshun Avenue Chengdu Sichuan610200 China

ISBN: (数字)9783030683030

ISBN: (纸本)9783030683023;9783030683054

A new numerical simulation method is developed for the evaluation of thermal and mechanical analyses of manufactured structures with Metal Inert Gas (MIG) welding on the basis of the peridynamics. The peridynamic formulations of the weak coupled thermo-mechanical problems are derived based on a heat transfer model and a microplastic model. To simulate the MIG welding process, a birth–death material point method in the peridynamic framework is proposed to model the addition of weld metal to the workpiece. To simplify the calculation process and improve the computational efficiency due to no need of updating the neighbourhoods of material points, an additional scalar field is introduced in the equations to describe the birth and death states of the material points. In addition, the present method is applied to simulate a classical model of two plates being joined together by the MIG welding. The results indicate that the residual tensile deformations are formed in the welded area while the residual compressive deformations are formed far from the wild line after the release of the clamps on account of the plastic deformation. These results also demonstrate the validity of the present method for the simulation of the MIG welding by comparing with the reference solution. © 2021, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Computational efficiency

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Experimental Study of Turbulent Bubbly Flow in 180-Degree Elbow by PIV-PS Technique

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International Journal of Advanced Nuclear reactor design and technology 2022年第3期4卷 109-120页

作者： Chen, Wuguang Li, Songwei Mu, Xiaocheng Yang, Fan Yan, Zhigang Sun, Jiajin Huang, Guangyuan Cai, Kangbei Hu, Yuanbiao Yin, Junlian Wang, Dezhong School of Nuclear Science and Engineering Shanghai Jiao Tong University Shanghai200240 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610041 China CGN Inspection Technology Co. Ltd. Jiangsu Suzhou215100 China

The curvature effect and bubbles are the key factors that affect the gas-liquid two-phase flow and turbulent characteristics in the 180-degree elbow. Limited by the difficulty of experimental measurement and numerical investigation, little is known about the two-phase flow evolution and turbulent modulation in 180-degree elbow. In this paper, a gas-liquid two-phase measurement technique, simultaneous Particle Image Velocimetry and Pulsed Shadowgraphy (PIV-PS) has been developed by combining two cameras through a spectroscope and optical filters and was applied to explore the two-phase characteristics in 180-degree elbow. In addition, an image post-processing method, based on bubble area detection and remaining particles estimation, was proposed. The characteristics of velocity and turbulent fields in the 180-degree elbow are experimentally studied in different conditions, and the evolution of the flow field in the elbow was also explored in detail. The results show that the horizontal velocity on the centerline of the elbow increases linearly with the liquid flow rates. However, with the introduction of bubbles, the linear feature is eliminated. The turbulent fields show that the introduction of bubbles suppresses turbulence at the low void fraction condition, and enhances at the high void fraction in bubble accumulation areas. © 2022 Xi'an Jiaotong University

关键词： Turbulence

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