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Multifunctional Nacre‑Like Nanocomposite Papers for Electromagnetic Interference Shielding via Heterocyclic Aramid/MXene Template‑Assisted In‑Situ Polypyrrole Assembly

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Nano-Micro Letters 2025年第3期17卷 37-54页

作者： Jinhua Xiong Xu Zhao Zonglin Liu He chen Qian Yan Huanxin Lian yunxiang chen Qingyu Peng Xiaodong He National Key Laboratory of Science and Technology On Advanced Composites in Special Environments Center for Composite Materials and StructuresHarbin Institute of TechnologyHarbin 150080People’s Republic of China

Robust, ultra-flexible, and multifunctional MXene-basedelectromagnetic interference (EMI) shielding nanocomposite filmsexhibit enormous potential for applications in artificial intelligence,wireless telecommunication, and portable/wearable electronic *** this work, a nacre-inspired multifunctional heterocyclic aramid(HA)/MXene@polypyrrole (PPy) (HMP) nanocomposite paper withlarge-scale, high strength, super toughness, and excellent tolerance tocomplex conditions is fabricated through the strategy of HA/MXenehydrogel template-assisted in-situ assembly of PPy. Benefiting from the"brick-and-mortar" layered structure and the strong hydrogen-bondinginteractions among MXene, HA, and PPy, the paper exhibits remarkable mechanical performances, including high tensile strength (309.7 MPa),outstanding toughness (57.6 MJ m−3), exceptional foldability, and structural stability against ultrasonication. By using the template effect ofHA/MXene to guide the assembly of conductive polymers, the synthesized paper obtains excellent electronic conductivity. More importantly,the highly continuous conductive path enables the nanocomposite paper to achieve a splendid EMI shielding effectiveness (EMI SE) of 54.1 dBat an ultra-thin thickness (25.4 μm) and a high specific EMI SE of 17,204.7 dB cm2g−1. In addition, the papers also have excellent applicationsin electromagnetic protection, electro-/photothermal de-icing, thermal therapy, and fire safety. These findings broaden the ideas for developinghigh-performance and multifunctional MXene-based films with enormous application potential in EMI shielding and thermal management.

关键词： MXene Remarkable mechanical properties Heterocyclic aramid Electromagnetic interference shielding Polypyrrole Multifunctionality

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Residual lifetime prediction model of nonlinear accelerated degradation data with measurement error

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Journal of Systems Engineering and Electronics 2017年第5期28卷 1028-1038页

作者： Zhongyi Cai yunxiang chen Qiang Zhang Huachun Xiang Equipment Management & Safety Engineering College Air Force Engineering University Defense Technology Research Academy China Aerospace Science & Industry Corporation

For the product degradation process with random effect (RE), measurement error (ME) and nonlinearity in step-stress accelerated degradation test (SSADT), the nonlinear Wiener based degradation model with RE and ME is built. An analytical approximation to the probability density function (PDF) of the product's lifetime is derived in a closed form. The process and data of SSADT are analyzed to obtain the relation model of the observed data under each accelerated stress. The likelihood function for the population-based observed data is constructed. The population-based model parameters and its random coefficient prior values are estimated. According to the newly observed data of the target product in SSADT, an analytical approximation to the PDF of its residual lifetime (RL) is derived in accordance with its individual degradation characteristics. The parameter updating method based on Bayesian inference is applied to obtain the posterior value of random coefficient of the RL model. A numerical example by simulation is analyzed to verify the accuracy and advantage of the proposed model.

关键词： accelerated degradation test residual lifetime (RL) prediction measurement error random effect nonlinearity

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A dynamic condition-based maintenance optimization model for mission-oriented system based on inverse Gaussian degradation process

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Journal of Systems Engineering and Electronics 2022年第2期33卷 474-488页

作者： LI Jingfeng chen yunxiang CAI Zhongyi WANG Zezhou Equipment Management and UAV Engineering College Air Force Engineering UniversityXi’an 710051China

An effective maintenance policy optimization model can reduce maintenance cost and system operation risk. For mission-oriented systems, the degradation process changes dynamically and is monotonous and irreversible. Meanwhile, the risk of early failure is high. Therefore, this paper proposes a dynamic condition-based maintenance(CBM) optimization model for mission-oriented system based on inverse Gaussian(IG) degradation process. Firstly, the IG process with random drift coefficient is used to describe the degradation process and the relevant probability distributions are obtained. Secondly, the dynamic preventive maintenance threshold(DPMT) function is used to control the early failure risk of the mission-oriented system, and the influence of imperfect preventive maintenance(PM)on the degradation amount and degradation rate is analysed comprehensively. Thirdly, according to the mission availability requirement, the probability formulas of different types of renewal policies are obtained, and the CBM optimization model is constructed. Finally, a numerical example is presented to verify the proposed model. The comparison with the fixed PM threshold model and the sensitivity analysis show the effectiveness and application value of the optimization model.

关键词： inverse Gaussian(IG)process imperfect preventive maintenance(PM) mission-oriented system dynamic preventive maintenance threshold(DPMT) maintenance optimization

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Storage reliability assessment model based on competition failure of multi-components in missile

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Journal of Systems Engineering and Electronics 2017年第3期28卷 606-616页

作者： yunxiang chen Qiang Zhang Zhongyi Cai Lili Wang Equipment Management and Safety Engineering College Air Force Engineering UniversityXi’an 710051China Defense Technology Research Academy of China Aerospace Science and Industry Corporation Beijing 100854China

The degradation data of multi-components in missile is derived by periodical testing. How to use these data to assess the storage reliability (SR) of the whole missile is a difficult problem in current research. An SR assessment model based on competition failure of multi-components in missile is proposed. By analyzing the missile life profile and its storage failure feature, the key components in missile are obtained and the characteristics voltage is assumed to be its key performance parameter. When the voltage testing data of key components in missile are available, a state space model (SSM) is applied to obtain the whole missile degradation state, which is defined as the missile degradation degree (DD). A Wiener process with the time-scale model (TSM) is applied to build the degradation failure model with individual variability and nonlinearity. The Weibull distribution and proportional risk model are applied to build an outburst failure model with performance degradation effect. Furthermore, a competition failure model with the correlation between degradation failure and outburst failure is proposed. A numerical example with a set of missiles in storage is analyzed to demonstrate the accuracy and superiority of the proposed model.

关键词： competition failure model storage reliability (SR) missile degradation degree (DD) proportional risk model individual variability

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Methods for predicting the remaining useful life of equipment in consideration of the random failure threshold

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Journal of Systems Engineering and Electronics 2020年第2期31卷 415-431页

作者： WANG Zezhou chen yunxiang CAI Zhongyi GAO Yangjun WANG Lili Equipment Management&UAV Engineering College Air Force Engineering UniversityXi’an 710051China

The value range of the failure threshold will generate an uncertain influence on the prediction results for the remaining useful life(RUL) of equipment. Most of the existing studies on the RUL prediction assume that the failure threshold is a fixed value,as they have difficulty in reflecting the random variation of the failure threshold. In connection with the inadequacies of the existing research, an in-depth analysis is carried out to study the effect of the random failure threshold(RFT) on the prediction results for the RUL. First, a nonlinear degradation model with unit-to-unit variability and measurement error is established based on the nonlinear Wiener process. Second, the expectation-maximization(EM) algorithm is used to solve the estimated values of the parameters of the prior degradation model, and the Bayesian method is used to iteratively update the posterior distribution of the random coefficients. Then, the effects of three types of RFT constraint conditions on the prediction results for the RUL are analyzed, and the probability density function(PDF) of the RUL is derived. Finally,the degradation data of aero-turbofan engines are used to verify the correctness and advantages of the method.

关键词： remaining useful life(RUL)prediction random failure threshold(RFT) nonlinear Wiener process measurement error unit-to-unit variability

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Remaining useful lifetime prediction for equipment based on nonlinear implicit degradation modeling

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Journal of Systems Engineering and Electronics 2020年第1期31卷 194-205页

作者： CAI Zhongyi WANG Zezhou chen yunxiang GUO Jiansheng XIANG Huachun Equipment Management and UAV Engineering College Air Force Engineering University

Nonlinearity and implicitness are common degradation features of the stochastic degradation equipment for *** features have an uncertain effect on the remaining useful life(RUL)prediction of the *** current data-driven RUL prediction method has not systematically studied the nonlinear hidden degradation modeling and the RUL distribution *** paper uses the nonlinear Wiener process to build a dual nonlinear implicit degradation *** on the historical measured data of similar equipment,the maximum likelihood estimation algorithm is used to estimate the fixed coefficients and the prior distribution of a random *** the on-site measured data of the target equipment,the posterior distribution of a random coefficient and actual degradation state are step-by-step updated based on Bayesian inference and the extended Kalman filtering *** analytical form of the RUL distribution function is derived based on the first hitting time *** with the two case studies,the proposed method is verified to have certain advantages over the existing methods in the accuracy of prediction.

关键词： remaining useful life(RUL)prediction Wiener process dual nonlinearity measurement error individual difference

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Remaining lifetime prediction for nonlinear degradation device with random effect

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Journal of Systems Engineering and Electronics 2018年第5期29卷 1101-1110页

作者： CAI Zhongyi chen yunxiang GUO Jiansheng ZHANG Qiang XIANG Huachun Equipment Management and Unmanned Aerial Vehicle Engineering College Air Force Engineering University Defense Technology Academy China Aerospace Science and Industry Corporation Limited

For the large number of nonlinear degradation devices existing in a project, the existing methods have not systematically studied the effects of random effect on the remaining lifetime(RL),the accuracy and efficiency of the parameters estimation are not high, and the current degradation state of the target device is not accurately estimated. In this paper, a nonlinear Wiener degradation model with random effect is proposed and the corresponding probability density function(PDF) of the first hitting time(FHT)is deduced. A parameter estimation method based on modified expectation maximum(EM) algorithm is proposed to obtain the estimated value of fixed coefficient and the priori value of random coefficient in the model. The posterior value of the random coefficient and the current degradation state of target device are updated synchronously by the state space model(SSM) and the Kalman filter algorithm. The PDF of RL with random effect is deduced. A simulation example is analyzed to verify that the proposed method has the obvious advantage over the existing methods in parameter estimation error and RL prediction accuracy.

关键词： remaining lifetime(RL) prediction nonlinear degradation model Wiener process random coefficient Kalman filter algorithm

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Evidence combination method in time domain based on reliability and importance

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Journal of Systems Engineering and Electronics 2018年第6期29卷 1308-1316页

作者： LUO chengkun chen yunxiang XIANG Huachun WANG Weijia WANG Zezhou Equipment Management and Safety Engineering College Air Force Engineering University

In order to achieve the information fusion in the time domain based on the evidence theory, an evidence combination method in the time domain based on reliability and importance is proposed according to the idea of evidence discount. Firstly, the distortion of the time-domain evidence is judged based on single exponential smoothing. The real-time reliability of the evidence at the adjacent time is obtained by the real-time reliability assessment method of the evidence based on the credibility decay ***, the relative importance of the evidence at the adjacent time is obtained by comprehensively considering improved conflict degree and uncertainty. Finally, based on the criterion of evidence discount and the Dempster’s rule of combination, the evidence combination is carried out to achieve the sequential combination of time-domain evidence. The numerical simulation and analysis show that this method has fully embodied the dynamic characteristics of time-domain evidence combination, and it has strong processing ability for conflict information and anti-disturbing *** proposed method has good applicability to information fusion in the time domain.

关键词： evidence theory time-domain evidence combination evidence discount reliability importance

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A machine-learning-based electron density (MLED) model in the inner magnetosphere

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Earth and Planetary Physics 2022年第4期6卷 350-358页

作者： QingHua Zhou yunxiang chen FuLiang Xiao Sai Zhang Si Liu Chang Yang YiHua He ZhongLei Gao School of Physics and Electronic Sciences Changsha University of Science and TechnologyChangsha 410114China Hunan Provincial Key Laboratory of Flexible Electronic Materials Genome Engineering Changsha University of Science and TechnologyChangsha 410114China

Plasma density is an important factor in determining wave-particle interactions in the *** develop a machine-learning-based electron density(MLED)model in the inner magnetosphere using electron density data from Van Allen Probes between September 25,2012 and August 30,*** MLED model is a physics-based nonlinear network that employs fundamental physical principles to describe variations of electron *** predicts the plasmapause location under different geomagnetic conditions,and models separately the electron densities of the plasmasphere and of the *** train the model using gradient descent and backpropagation algorithms,which are widely used to deal effectively with nonlinear relationships among physical quantities in space plasma *** model gives explicit expressions with few parameters and describes the associations of electron density with geomagnetic activity,solar cycle,and seasonal *** various geomagnetic conditions,the electron densities calculated by this model agree well with empirical observations and provide a good description of plasmapause *** MLED model,which can be easily incorporated into previously developed radiation belt models,promises to be very helpful in modeling and improving forecasting of radiation belt electron dynamics.

关键词： background electron density inner magnetosphere machine learning Van Allen Probes observation

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TiO_(2)-carbon porous nanostructures for immobilization and conversion of polysulfides

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Chinese Chemical Letters 2023年第1期34卷 527-533页

作者： Keke Gao Rui Xu yunxiang chen Zongtao Zhang Jiashuo Shao Haipeng Ji Liying Zhang Shasha Yi Deliang chen Junhua Hu Yanfeng Gao School of Materials Science and Engineering Zhengzhou UniversityZhengzhou 450001China School of Materials Science and Engineering Shanghai UniversityShanghai 200444China

Lithium-sulfur batteries(LSBs)are among the most promising series of next-generation high density energy storage ***,the problem of“shuttle effect”caused by dissolution and migration of polysulfide intermediates has severely inhibited their practical ***,TiO_(2)-carbon nanocomposites embedded hierarchical porous carbon(T-hPC)interlayers are fabricated via Ti_(3)C_(2)MXene assisted phase separation and annealing *** T-hPC processes micro-to macro-scale multipores along with highly adsorptive and catalytic carbon supported TiO_(2) nanoparticles,which significantly enhances the polysulfides immobilization and improves the redox reaction kinetics when applied as lithium-sulfur battery *** initial discharge specific capacity of 1551.1 m Ah/g and a stable capacity of 893.8 m Ah/g after 200 cycles at 0.5 C are obtained,corresponding to a capacity decay rate of only 0.04%per *** investigations in this paper can provide a simple and effective strategy to enhance the electrochemical properties for lithium-sulfur batteries.

关键词： Hierarchical porous carbon Phase separation MXene Interlayer Lithium-sulfur battery

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