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Laser ablation mechanism of ZrC-SiC-MoSi_(2) ternary ceramic modified C/C

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Journal of Materials Science & Technology 2023年第18期149卷 214-224页

作者： Li Geng Su Cheng Guanghai Liu Qiangang fu Hejun Li Shaanxi Carbon/Carbon Composites Engineering Technology Research Center Northwestern Polytechnical UniversityXi’an 710072China National Engineering Research Center of Ceramic Matrix Composite Manufacture Technology Xi’an 710000China

C/C composites were prepared by chemical vapor infiltration(CVI),and then were subjected to Si,Zr,and MoSi_(2) reactive melt infiltration(RMI)to obtain C/C-SiC,C/C-SiC-ZrC,and C/C-SiC-ZrC-MoSi_(2) *** ablation behavior of these three composites was evaluated by high-energy CO 2 laser *** surface temperature distribution of composite materials was simulated by finite element *** results show that the ablation resistance mechanisms of the three materials are entirely *** C/C-SiC-ZrC-MoSi_(2) com posite showed the best ablation performance among *** is at-tributed to the lower oxygen permeability and richer heat dissipation mechanism of the C/C-SiC-ZrC-MoSi_(2) composite within the total temperature threshold.

关键词： C/C composite Laser ablation UHTCs modification Thermodynamic analysis Finite element simulation

Meta label associated loss for fine-grained visual recognition

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Science China(Information Sciences) 2024年第6期67卷 230-247页

作者： Yanchao LI fu XIAO Hao LI Qun LI Shui YU School of Computer Science Nanjing University of Posts and Telecommunications School of Network Engineering Zhoukou Normal University School of Computer Science University of Technology Sydney

Recently, intensive attempts have been made to design robust models for fine-grained visual recognition, most notably are the impressive gains for training with noisy labels by incorporating a reweighting strategy into a meta-learning framework. However, it is limited to up or downweighting the contribution of an instance for label reweighting approaches in the learning process. To solve this issue, a novel noise-tolerant method with auxiliary web data is proposed. Specifically, first, the associations made from embeddings of well-labeled data with those of web data and back at the same class are measured. Next, its association probability is employed as a weighting fusion strategy into angular margin-based loss, which makes the trained model robust to noisy datasets. To reduce the influence of the gap between the well-labeled and noisy web data, a bridge schema is proposed via the corresponding loss that encourages the learned embeddings to be coherent. Lastly, the formulation is encapsulated into the meta-learning framework, which can reduce the overfitting of models and learn the network parameters to be noise-tolerant. Extensive experiments are performed on benchmark datasets, and the results clearly show the superiority of the proposed method over existing state-of-the-art approaches.

关键词： label associated loss weighting noisy samples fine-grained visual recognition noise-tolerant learning meta-learning

Structural design for electrocatalytic water splitting to realize industrial-scale deployment: Strategies, advances, and perspectives

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Journal of Energy Chemistry 2022年第7期31卷 129-153,I0004页

作者： Xianwei fu Ruijuan Shi Shilong Jiao Mengmeng Li Qiuye Li Engineering Research Center for Nanomaterials National&Local Joint Engineering Research Center for Applied Technology of Hybrid NanomaterialsHenan UniversityKaifeng 475004HenanChina Key Lab for Special functional Materials of Ministry of Education Collaborative Innovation Center of Nano Functional Materials and ApplicationsHenan UniversityHenan UniversityKaifeng 475004HenanChina

The green hydrogen generation powered by renewable electricity promises the potential decarbonization of the hard-to-abate sector and is essential for the fulfillment of the Paris Agreement that attempts to limit the global average temperature rise in the range of 1.5–2.0 ℃ above the pre-industrial level by the end of this century. Tremendous efforts have been devoted to the optimization of the electrocatalytic performance of the catalysts under industrial-relevant current densities via rational structure design,which induces a preferential electron distribution that favors the adsorption/desorption behavior of the key intermediates, thus accelerating the reaction kinetics. In this review, a brief introduction of the current energy status will be first presented to necessitate the importance of green *** by the basic concepts and fundamental understanding of the reaction mechanisms, we present efficient strategies for the enhancement of the electrocatalytic performance of the catalysts to meet the rigorous requirement under industrial conditions and the in-depth understanding behind the reinforcement will be briefly discussed next. Then the recent advances regarding the rational design of electrocatalysts operating at an industrial scale will be summarized. Finally, the challenges and perspectives in this thriving field will be proposed from our point of view.

关键词： Overall water splitting Industrial-scale current density Structural design Hydrogen evolution reaction Oxygen evolution reaction

岩石中三维双裂隙组扩展和贯通过程的试验研究和弹脆性模拟

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岩土力学 2013年第9期34卷 2489-2495页

作者：付金伟朱维申谢富东薛伟强张敦福李勇山东大学岩土与结构工程研究中心济南250061

最新研制了一种完全透明、较低温度下拉压比可达1/6.6的树脂,其与岩石特性的相似性较前人的研究有大幅度提高。制作了一组含三维内置平行双裂隙组的试件,详细描述并分析了单轴加载下试件的裂隙扩展与贯通过程,研究其产生的条件和机制。... 详细信息

最新研制了一种完全透明、较低温度下拉压比可达1/6.6的树脂,其与岩石特性的相似性较前人的研究有大幅度提高。制作了一组含三维内置平行双裂隙组的试件,详细描述并分析了单轴加载下试件的裂隙扩展与贯通过程,研究其产生的条件和机制。试验结果表明:试件的破坏大致经历4个阶段,三维裂隙组的断裂比二维情况复杂得多,产生了多种不同形态的裂纹。在FLAC3D软件框架内建立了一种新的弹脆性本构关系,并采用超细单元和合理形态的网格建模。将数值模拟结果与相关试验进行对比,相符程度良好,表明新数值模拟方法的有效性。当双轴加载时,模拟结果也与前人类似试验结果有很好一致性。

关键词：三维双裂隙扩展试验次生裂纹和贯通模式数值模拟弹脆性本构

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脉冲喷雾冷却传热特性参数影响实验研究

工程热物理学报 2020年第9期41卷 2220-2224页

作者：辛慧陈斌周致富西安交通大学动力工程多相流国家重点实验室西安710049

高能量激光辅以脉冲式制冷剂喷雾的新型溶脂技术既可以有效溶解皮下脂肪,又可以保护表皮和真皮免受冻伤,是一种很有前景的临床治疗新技术。需要深入研究脉冲式制冷剂喷雾冷却参数对传热特性的影响,以对临床治疗的参数选择做出指导。本... 详细信息

高能量激光辅以脉冲式制冷剂喷雾的新型溶脂技术既可以有效溶解皮下脂肪,又可以保护表皮和真皮免受冻伤,是一种很有前景的临床治疗新技术。需要深入研究脉冲式制冷剂喷雾冷却参数对传热特性的影响,以对临床治疗的参数选择做出指导。本文实验研究了喷雾压力、喷雾距离、喷嘴内径和长度对R134a脉冲式喷雾冷却环氧树脂基体传热特性的影响,发现长脉冲下(30ms),喷雾压力越大,传热效果越好。短脉冲下(10ms),喷雾压力对基体传热影响较小。长、短脉冲下的最佳喷雾距离分别为6cm和4cm。随着喷嘴内径增加,最佳喷雾距离增大,所能达到的仿体内最低温度升高,冷却效果变差。喷嘴长度越长,基体内传热效果越好。

关键词：激光溶脂脉冲喷雾冷却 R134a 表面传热特性脉冲时间喷雾压力喷雾距离

Light weight design and integrated method for manufacturing hydraulic wheel-legged robots

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第9期25卷 701-715页

作者： Xu LI Haoyang YU Huaizhi ZONG Haibo FENG Yili fu State Key Laboratory of Robotics and System Harbin Institute of TechnologyHarbin 150001China State Key Laboratory of Fluid Power and Mechatronic Systems Zhejiang UniversityHangzhou 310058China

Design and manufacturing play pivotal roles in hydraulic-driven robotic ***,previous studies have emphasized mainly results and performance,often overlooking the specifics of the design and manufacturing *** paper introduces a novel approach known as light weight design and integrated manufacturing(LD&IM)for hydraulic wheel-legged *** LD&IM method leverages topology optimization and generative design techniques to achieve a substantial 45%weight reduction,enhancing the robot’s dynamic motion *** innovative design method not only streamlines the design process but also upholds the crucial attributes of light weight construction and high strength essential for hydraulic wheel-legged ***,the integrated manufacturing method,incorporating selective laser melting(SLM)and high-precision subtractive manufacturing(SM)processes,expedites the fabrication of high-quality *** the LD&IM approach,a hydraulic-driven single wheel-legged robot,denoted as WLR-IV,has been successfully *** robot boasts low mass and inertia,high strength,and a simplified component *** assess its dynamic jumping capabilities,the control loop integrates a linear quadratic regulator(LQR)and zero dynamic-based controller,while trajectory planning uses the spring-loaded inverted pendulum(SLIP)*** jumping results confirm the WLR-IV single-legged robot’s exceptional dynamic performance,validating both the effectiveness of the LD&IM method and the rationale behind the control strategy.

关键词： Wheel-legged robot Hydraulic driven Topology optimization Wheel-legged robot Hydraulic driven Topology optimization Additive manufacturing(AM) Jump control

Echo State Network Based on Improved Knowledge Distillation for Edge Intelligence

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Chinese Journal of Electronics 2024年第1期33卷 101-111页

作者： Jian ZHOU Yuwen JIANG Lijie XU Lu ZHAO fu XIAO College of Computer Nanjing University of Posts and Telecommunications Jiangsu High Technology Research Key Laboratory for Wireless Sensor Networks

Echo state network(ESN) as a novel artificial neural network has drawn much attention from time series prediction in edge intelligence. ESN is slightly insufficient in long-term memory, thereby impacting the prediction performance. It suffers from a higher computational overhead when deploying on edge devices. We firstly introduce the knowledge distillation into the reservoir structure optimization, and then propose the echo state network based on improved knowledge distillation(ESN-IKD) for edge intelligence to improve the prediction performance and reduce the computational overhead. The model of ESN-IKD is constructed with the classic ESN as a student network, the long and short-term memory network as a teacher network, and the ESN with double loop reservoir structure as an assistant network. The student network learns the long-term memory capability of the teacher network with the help of the assistant network. The training algorithm of ESN-IKD is proposed to correct the learning direction through the assistant network and eliminate the redundant knowledge through the iterative pruning. It can solve the problems of error learning and redundant learning in the traditional knowledge distillation process. Extensive experimental simulation shows that ESN-IKD has a good time series prediction performance in both long-term and short-term memory, and achieves a lower computational overhead.

关键词： Knowledge engineering Training Performance evaluation Computational modeling Time series analysis Artificial neural networks Reservoirs

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Modeling and flapping vibration suppression of a novel tailless flapping wing micro air vehicle

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Chinese Journal of Aeronautics 2022年第3期35卷 309-328页

作者： Siqi WANG Bifeng SONG Ang CHEN Qiang fu Jin CUI School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China Yangtze River Delta Research Institute of Northwestern Polytechnical University Taicang 215400China Research&Development Institute of Northwestern Polytechnical University in Shenzhen Shenzhen 518057China School of Aeronautic Science and Engineering Beihang UniversityBeijing 100083China

This paper establishes and analyzes a high-fidelity nonlinear time-periodic dynamic model and the corresponding state observer for flapping vibration suppression of a novel tailless Flapping Wing Micro Air Vehicle(FWMAV),named ***,a complete modeling of NPU-Tinybird is determined,including the aerodynamic model based on the quasi-steady method,the kinematic and dynamic model about the mechanism of flapping and attitude control,combined with the single rigid body dynamic *** on this,a linearized longitudinal pitch dynamic cycle-averaged model is obtained and analyzed through the methods of neural network fitting and system identification,preparing for the design of flapping vibration suppression *** vibration is an inherent property of the tailless FWMAV,which arises from the influence of time-periodic aerodynamic forces and *** can be captured by attitude and position sensors on the plane,which impairs the flight performance and efficiency of flight controller and *** deal with this problem,a novel state observer for flapping vibration suppression is designed.A robust optimal controller based on the linear quadratic theory is also designed to stabilize the closed-loop *** results are given to verify the performance of the observer,including the closed loop responses combined with robust optimal controller,the comparison of different parameters of observer and the comparison with several classic methods,such as Kalman filter,H-infinity filter and low-pass filter,which prove that the novel observer owns a fairly good suppression effect on flapping vibration and benefits for the improvement of flight performance and control efficiency.

关键词： Flapping vibration Flapping wing Linear quadratic theory Robust control State observer

Au^(δ-)-O_(v)-Ti^(3+):Active site of MO_(x)-Au/TiO_(2) catalysts for the aerobic oxidation of 5-hydroxymethylfurfural

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Green Energy & Environment 2023年第3期8卷 785-797页

作者： weiyao Yang Mengchen fu Chenyu Yang Yiwen Zhang Chun Shen Beijing Key Laboratory of Bioprocess College of Life Science and TechnologyBeijing University of Chemical TechnologyNo.15 of North Three-Ring East RoadChaoyang DistrictBeijing100029China The State Key Laboratory of Chemical Engineering Department of Chemical EngineeringTsinghua UniversityBeijing100084China

Despite wide applications of noble metal-based catalysts in 5-hydroxymethylfurfural(HMF)oxidation,promoting the catalytic performance at low loading amounts still remains a significant ***,a series of metal oxide modified MO_(x)-Au/TiO_(2)(M=Fe,Co,Ni)catalysts with low Au loading amount of 0.5 wt%were *** of transition metal oxides promotes electron transfer and generation of the Au^(δ-)-O_(v)-Ti^(3+)interface.A combination study reveals that the dual-active site(Au^(δ-)-O_(v)-Ti^(3+))governs the catalytic performance of the ratedetermining step,namely hydroxyl group ***^(δ-) site facilitates chemisorption and activation of O_(2) *** the same time,O_(v)-Ti^(3+) site acts as the role of“killing two birds with one stone”:enhancing adsorption of both reactants,accelerating the activation and dissociation of H_(2)O,and facilitating activation of the adsorbed O_(2).Besides,superoxide radicals instead of base is the active oxygen species during the rate-determining *** this basis,a FDCA yield of 71.2% was achieved under base-free conditions,complying with the“green chemistry”*** work provides a new strategy for the transition metal oxides modification of Au-based catalysts,which would be constructive for the rational design of other heterogeneous catalysts.

关键词： 5-Hydroxymethylfurfural Base-free oxidation Interfacial catalysis Active oxygen species