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基于XGBoost-RFECV算法和LSTM神经网络的PEMFC剩余寿命预测

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电子测量与仪器学报 2022年第1期36卷 126-133页

作者：常家康吕宁詹跃东昆明理工大学信息工程与自动化学院昆明650500 昆明理工大学计算中心昆明650500

针对质子交换膜燃料电池(PEMFC)寿命预测方法中PEMFC特征对其寿命的影响程度未知和模型预测精度低的问题,提出一种基于XGBoost-RFECV算法和长短期记忆(LSTM)神经网络的PEMFC剩余寿命预测方法。首先通过等间隔采样和SG卷积平滑法对PEMFC... 详细信息

针对质子交换膜燃料电池(PEMFC)寿命预测方法中PEMFC特征对其寿命的影响程度未知和模型预测精度低的问题,提出一种基于XGBoost-RFECV算法和长短期记忆(LSTM)神经网络的PEMFC剩余寿命预测方法。首先通过等间隔采样和SG卷积平滑法对PEMFC原始数据进行重构和平滑处理,有效提取PEMFC退化趋势。然后利用XGBoost-RFECV算法计算PEMFC不同特征的重要度,并选择平均交叉验证均方误差最小的10个PEMFC特征组成最优特征子集。最后将最优特征子集输入构建的双层LSTM神经网络实现PEMFC的剩余寿命预测。实验结果表明,该方法的平均绝对误差和均方根误差分别为0.0019和0.0025,决定系数R^(2)为0.974,与XGBoost-RNN、XGBoost-LSTM和XGBoost-RFECV-RNN方法相比预测精度更高,能够有效地预测PEMFC剩余寿命。

关键词： XGBoost-RFECV算法 LSTM神经网络 PEMFC 剩余寿命

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同轴旋转可压缩气流中黏性液体射流形态研究

内燃机学报 2024年第1期42卷 53-60页

作者：吕明郭立梅宁智北京交通大学机械与电子控制工程学院北京100044

采用射流线性稳定性分析方法,考虑液体黏性、周围气流的同轴旋转运动以及可压缩性的条件下,建立了描述同轴旋转可压缩气流中黏性液体射流的数学模型,并进行了验证,研究了气流量纲为1旋转强度以及流体物性对液体射流不稳定形态的影响.研... 详细信息

采用射流线性稳定性分析方法,考虑液体黏性、周围气流的同轴旋转运动以及可压缩性的条件下,建立了描述同轴旋转可压缩气流中黏性液体射流的数学模型,并进行了验证,研究了气流量纲为1旋转强度以及流体物性对液体射流不稳定形态的影响.研究表明:周围气流的旋转速度较小时,对射流起促稳作用,继续增大气流量纲为1旋转强度,开始对射流起促分裂作用;且随着气流旋转强度的增大,射流扰动沿周向方向发展,射流柱变的高度不对称.在研究参数范围内,气体可压缩性和气/液密度比均能促进射流的失稳,并会影响射流空间形态,尤其是在周向方向上能够改变射流的占优模式,增强射流的不对称性;液体黏性以及表面张力对射流均具有增强稳定性的作用.

关键词：液体射流气流旋转数学模型射流形态

Deployment analysis of composite thin-walled lenticular tubes with effect of storage time and temperature

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Chinese Journal of Aeronautics 2024年第1期37卷 162-172页

作者： Jinfeng DENG ning AN Qilong JIA Xiaofei MA School of Aeronautics and Astronautics Sichuan UniversityChengdu 610065China State Key Laboratory for Strength and Vibration of Mechanical Structures School of AerospaceXi’an Jiaotong UniversityXi’an 710049China State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of TechnologyDalian 116024China Xi’an Institute of Space Radio Technology Xi’an 710100China

Composite Thin-walled Lenticular Tube(CTLT)is increasingly utilized in small satellites missions as a lightweight,foldable,and rollable structural material that facilitates the construction of large deployable *** CTLT is initially flattened and coiled around a central hub for storage before launch,during which elastic energy is stored as deformation energy,allowing it to be self-deployed on demand for use in *** work presents a comprehensive investigation into the coiling,storage and deployment behaviors of CTLT that wraps around a central hub.A nonlinear explicit dynamic finite element model was developed with both deformable CTLT and rigidbodies mechanisms including the central hub and guide rollers,as well as the complex interactions among *** coiling mechanics characteristics such as stored strain energy and rotational moment were presented and validated against experimental data in the ***,the dynamic deployment behaviors were analyzed in terms of two different deployment methods,namely,controlled deployment and free *** effect of material property change during storage was also discussed through numerical experiments.

关键词： Composite deployable structures Deployment dynamics Finite element method Stress relaxation Thin-walled booms

PPB structure elimination,DRX nucleation mechanisms and grain growth behavior of the3rd-generation PM superalloy for manufacturing aviation components

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Chinese Journal of Aeronautics 2024年第1期37卷 325-344页

作者： Baoyun ZHANG Yongquan ning Zhaotian WANG Qiaomu LIU School of Materials Science and Engineering Northwestern Polytechnical UniversityXi’an 710072China AECC Sichuan Gas Turbine Establishment Chengdu 610500China

Previous Particle Boundary(PPB),as the detrimental structure in Powder Metallurgy(PM)components,should be eliminated by subsequent hot process to improve the mechanical *** objective is to investigate the Dynamic Recrystallization(DRX)nucleation mechanisms and grain growth behavior of the 3rd-generation PM superalloy with PPB *** observation reveals that PPB decorated with(Ti,Ta,Nb)C carbides belongs to the discontinuous chain-like *** elimination of PPB networks can be achieved effectively via hot deformation due to the occurrence of *** different DRX nucleation mechanisms were proposed and discussed in detail according to the special microstructure characteristics of the PM ***,local lattice rotations can be detected in the vicinity of(Ti,Ta,Nb)C carbides during hot deformation and thus PPB structure serves as the preferential nucleation sites for DRX grains via Particle-Stimulated Nucleation(PSN).Then,Discontinuous-DRX(DDRX)characterized by grain boundary bulging dominates the microstructure refinement and Continuous-DRX(CDRX)operated by subgrain rotation can be regarded as an important assistant *** last,the initial Σ3 boundaries would lose their twin characteristics owing to the crystal rotation and then transform into the general High Angle Grain Boundaries(HAGBs).The distorted twins provide additional DRX nucleation sites,viz.,twin-assisted *** attention was focused on the grain growth behavior of the PM superalloy in subsequent annealing *** recrystallization temperature was determined to be about 1110.C and 1140.C can be considered as the critical temperature for grain *** findings would provide theoretical support for microstructure refinement of the 3rd-generation PM superalloy,which is of pivotal significance for improving the mechanical properties of aviation components.

关键词： PM superalloy Previous Particle Boundary(PPB) DRX nucleation Grain growth Microstructure refinement

Fullerenes and derivatives as electrocatalysts: Promises and challenges

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Green Energy & Environment 2024年第1期9卷 7-27页

作者： Kun Guo ning Li Lipiao Bao Xing Lu State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan430074China

Carbon-based metal-free nanomaterials are promising alternatives to precious metals as electrocatalysts of key energy storage and conversion *** paramount signiﬁcance are the establishment of design principles by understanding the catalytic mechanisms and identifying the active *** from sp2-conjugated graphene and carbon nanotube,fullerene possesses unique characteristics that are growingly being discovered and exploited by the electrocatalysis *** instance,the well-deﬁned atomic and molecular structures,the good electron afﬁnity to tune the electronic structures of other substances,the intermolecular self-assembly into superlattices,and the on-demand chemical modiﬁcation have endowed fullerene with incomparable advantages as electrocatalysts that are otherwise not applicable to other carbon *** increasing studies are being reported on this intriguing topic,it is necessary to provide a state-of-the-art overview of the recent *** review takes such an initiative by summarizing the promises and challenges in the electrocatalytic applications of fullerene and its *** content is structured according to the composition and structure of fullerene,including intact fullerene(e.g.,fullerene composite and superlattices)and fullerene derivatives(e.g.,doped,endohedral,and disintegrated fullerene).The synthesis,characterization,catalytic mechanisms,and deﬁciencies of these fullerene-based materials are explicitly *** conclude it by sharing our perspectives on the key aspects that future efforts shall consider.

关键词： Fullerene Fullerene derivative Metal-free catalyst Structural defect Electrocatalyst

Unveiling evapotranspiration patterns and energy balance in a subalpine forest of the Qinghai-Tibet Plateau:observations and analysis from an eddy covariance system

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Journal of Forestry Research 2024年第3期35卷 175-188页

作者： Niu Zhu Jinniu Wang Dongliang Luo Xufeng Wang Cheng Shen ning Wu ning Zhang Binghui Tian Aihong Gai Chengdu Institute of Biology Chinese Academy of SciencesChengdu 610041People's Republic of China College of Resources and Environmental Sciences Gansu Agricultural UniversityLanzhou 730070People's Republic of China Mangkang Ecological Monitoring Station Tibet Ecological Security Barrier Ecological Monitoring NetworkQamdo 854500People's Republic of China Northwest Institute of Eco Environmental Resources Chinese Academy of SciencesLanzhou 730000People's Republic of China

Evapotranspiration is an important parameter used to characterize the water cycle of *** under-stand the properties of the evapotranspiration and energy balance of a subalpine forest in the southeastern Qinghai-Tibet Plateau,an open-path eddy covariance system was set up to monitor the forest from November 2020 to October 2021 in a core area of the Three Parallel Rivers in the Qing-hai-Tibet *** results show that the evapotranspira-tion peaked daily,the maximum occurring between 11:00 and 15:*** factors had significant effects on evapotranspiration,among them,net radiation the greatest(R^(2)=0.487),and relative humidity the least(R^(2)=0.001).The energy flux varied considerably in different seasons and sensible heat flux accounted for the main part of turbulent *** energy balance ratio in the dormant season was less than that in the growing season,and there is an energy imbalance at the site on an annual time scale.

关键词： Evapotranspiration Energy balance Subalpine forest Three Parallel Rivers region Southeast Qinghai-Tibet Plateau

Dynamic analysis and bifurcation control of a delayed fractional-order eco-epidemiological migratory bird model with fear effect

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International Journal of Biomathematics 2024年第3期17卷 1-33页

作者： Caihong Song ning Li College of Sciences Northeastern University 110819 ShenyangLiaoningP.R.China

In this paper,a new delayed fractional-order model including susceptible migratory birds,infected migratory birds and predators is proposed to discuss the spread of diseases among migratory *** of predators is considered in the model,as fear can reduce the reproduction rate and disease transmission rate among ***,some basic mathematical results of the proposed model are ***,time delay is regarded as a bifurcation parameter,and the delay-induced bifurcation conditions for such an uncontrolled system are established.A novel periodic pulse feedback controller is proposed to suppress the bifurcation *** is found that the control scheme can successfully suppress the bifurcation behavior of the system,and the pulse width can be arbitrarily selected on the premise of ensuring the control *** with the traditional time-delay feedback controller,the control scheme proposed in this paper has more advantages in practical application,which not only embodies the advantages of low control cost and easy operation but also caters to the periodic changes of the *** proposed control scheme,in particular,remains effective even after the system has been disrupted by a *** simulation verifies the correctness of the theoretical results.

关键词： Delayed fractional-order migratory birds fear Hopf bifurcation periodic pulse feedback

基于工业计算机断层成像的装药底隙无损检测方法研究

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兵工学报 2015年第1期36卷 157-162页

作者：吕宁徐更光北京理工大学爆炸科学与技术国家重点实验室北京100081

在弹药装药底隙检测中，运用密度对比法结合体积效应，将底隙测量转化为弹底密度变化的测量，建立弹底扫描断层中心部位计算机断层成像（CT）值变化与底隙值之间的数学模型，解决底隙测量理论与实际操作中的难题。预置底隙测量实验结果... 详细信息

在弹药装药底隙检测中，运用密度对比法结合体积效应，将底隙测量转化为弹底密度变化的测量，建立弹底扫描断层中心部位计算机断层成像（CT）值变化与底隙值之间的数学模型，解决底隙测量理论与实际操作中的难题。预置底隙测量实验结果表明：该模型可完成对0．20～0．50mm底隙的测量，最大相对误差小于3．5％，可实现对装药底隙的定性判断与定量检测。

关键词：兵器科学与技术工业计算机断层成像密度对比底隙定量检测

Multi-Robot Cooperative Localization: Time-Varying Unobservable Subspace Analysis and Consistent Algorithm Design

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Journal of Systems Science & Complexity 2024年第5期37卷 1937-1955页

作者： HAO ning HE Fenghua YAO Yu School of Astronautics Harbin Institute of Technology

This paper investigates the problem of cooperative localization(CL) for a multi-robot system(MRS) under dynamic measurement topology, which involves a group of robots collectively estimating their poses with respect to a common reference frame using ego-motion measurements and robot-to-robot relative measurements. The authors provide a theoretical analysis of the time-varying unobservable subspace and propose a consistent cooperative localization algorithm. First, the authors introduce the relative measurement graph(RMG) to represent the relative pose measurements obtained by the MRS at each instant. Then, the authors derive the local observability matrix over a time *** equivalent relationship is established between the local observability matrix and the spectral matrices of the RMG. Moreover, the authors present a method for constructing the unobservable subspace based on the RMG under different topology conditions. Based on this analysis, the authors design a consistent cooperative localization algorithm that satisfies the constraints of the time-varying unobservable subspace. An analytical optimal solution is derived for the constrained optimization *** Carlo numerical simulations are conducted to demonstrate the consistency and accuracy of the proposed method.

关键词： Consistency cooperative localization multi-robot system null space relative measurement graph time-varying unobservable subspace

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