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Acta Mathematicae Applicatae Sinica 2024年第3期40卷 823-839页

作者： kai-ming YANG Yong-jiang GUO School of Science Beijing University of Posts and TelecommunicationsBeijing 100876China

For a 2-station and 3-class reentrant line under first-buffer first-served(FBFS)service discipline in light traffic,we firstly construct the strong approximations for performance measures including the queue length,workload,busy time and idle time *** on the obtained strong approximations,we use a strong approximation method to find all the law of the iterated logarithms(LILs)for the above four performance measures,which are expressed as some functions of system parameters:means and variances of interarrival and service times,and characterize the fluctuations around their fluid approximations.

关键词： reentrant line queueing network FBFS service discipline strong approximation LIL Brownian motion

Spin-orbit interaction induced Casimir-Lifshitz torque between two-dimensional electron gases

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Science China(Physics,Mechanics & Astronomy) 2024年第8期67卷 134-142页

作者： Jia-Nan Rong Liang Chen kai Chang State Key Laboratory of Superlattices and Microstructures Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China School of Mathematics and Physics North China Electric Power UniversityBeijing 102206China School of Physics Zhejiang UniversityHangzhou 310027China College of Materials Science and Opto-electronic Technology University of Chinese Academy of SciencesBeijing 100049China

We investigate theoretically the Casimir interaction between two parallel two-dimensional electron gases(2DEGs)with Rashba and Dresselhaus spin-orbit interactions(SOIs),based on the quantum field *** derive an analytical expression for the polarization tensor and obtain the solution to the motion equation of the electromagnetic(EM)*** calculate the CasimirLifshitz torque(CLT)between two parallel 2DEGs with Rashba and Dresselhaus SOIs,which can be tuned by changing the relative strength between two *** anisotropic Casimir energy between 2DEGs caused by the interplay between the SOIs of 2DEGs offers a new origin of CLT and a new type of optoelectronic device.

关键词： Casimir torque two-dimensional electron gas spin-orbit interaction

How to Construct a Lower Risk FOF Based on Correlation Network? The Method of Principal Component Risk Parity Asset Allocation

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Journal of Systems Science & Complexity 2024年第3期37卷 1052-1079页

作者： BAI Wei ZHANG Junting LIU Haifei LIU kai School of Management and Engineering Nanjing UniversityNanjing 210093China Postdoctoral Workstation of Bank of Jiangsu Co. LtdNanjing 210006China College of Finance Nanjing Agricultural UniversityNanjing 210095China University of Prince Edward Island 550 University AveCharlottetownPE C1A4P3Canada

In order to build a low-risk Fund of Funds(FOF), from the perspective of correlation, the principal component factor is used to improve the traditional risk parity model. Principal component analysis is used to decompose the underlying assets and generate unrelated principal component factors,and then the authors can construct a principal component risk parity portfolio. The proposed empirical results based on China’s mutual fund market show that the performance of principal component risk parity portfolio(PCRPP) is better than that of equal weight portfolio(EWP) and traditional risk parity portfolio(RPP). That is to say, not only the PCRPP in this paper has much lower risk than EWP and RPP, but also slightly better than EWP and RPP in terms of average return. Moreover, the study of dividing the underlying assets shows that the PCRPP in this paper is not sensitive to the underlying assets. The PCRPP in this paper is better than EWP and RPP for both the better performing funds and the worse performing funds. In addition, the empirical results on dynamic portfolio adjustments show that it is not appropriate to adjust asset allocation too frequently when the expected rate of return is calculated using the arithmetic mean.

关键词： Fund of funds(FOF) mutual funds portfolio risk principal component analysis risk parity portfolio

Effect of boundary conditions on shakedown analysis of heterogeneous materials

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Applied Mathematics and Mechanics(English Edition) 2024年第1期45卷 39-68页

作者： Xiuchen GONG Yinghao NIE Gengdong CHENG kai LI State Key Laboratory of Structural Analysis Optimization and CAE Software for Industrial EquipmentInternational Research Center for Computational MechanicsDepartment of Engineering MechanicsDalian University of TechnologyDalian 116023Liaoning ProvinceChina

The determination of the ultimate load-bearing capacity of structures made of elastoplastic heterogeneous materials under varying loads is of great importance for engineering analysis and design. Therefore, it is necessary to accurately predict the shakedown domains of these materials. The static shakedown theorem, also known as Melan's theorem, is a fundamental method used to predict the shakedown domains of structures and materials. Within this method, a key aspect lies in the construction and application of an appropriate self-equilibrium stress field(SSF). In the structural shakedown analysis, the SSF is typically constructed by governing equations that satisfy no external force(NEF) boundary conditions. However, we discover that directly applying these governing equations is not suitable for the shakedown analysis of heterogeneous materials. Researchers must consider the requirements imposed by the Hill-Mandel condition for boundary conditions and the physical significance of representative volume elements(RVEs). This paper addresses this issue and demonstrates that the sizes of SSFs vary under different boundary conditions, such as uniform displacement boundary conditions(DBCs), uniform traction boundary conditions(TBCs), and periodic boundary conditions(PBCs). As a result, significant discrepancies arise in the predicted shakedown domain sizes of heterogeneous materials. Built on the demonstrated relationship between SSFs under different boundary conditions, this study explores the conservative relationships among different shakedown domains, and provides proof of the relationship between the elastic limit(EL) factors and the shakedown loading factors under the loading domain of two load vertices. By utilizing numerical examples, we highlight the conservatism present in certain results reported in the existing literature. Among the investigated boundary conditions, the obtained shakedown domain is the most conservative under ***, utilizing PBCs to

关键词： heterogeneous material self-equilibrium stress field(SSF) shakedown analysis effect of boundary conditions

Motion Planning for Autonomous Driving with Real Traffic Data Validation

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Chinese Journal of Mechanical Engineering 2024年第1期37卷 74-86页

作者： Wenbo Chu kai Yang Shen Li Xiaolin Tang Western China Science City Innovation Center of Intelligent and Connected Vehicle Chongqing 400044China College of Mechanical and Vehicle Engineering Chongqing UniversityChongqing 400044China School of Civil Engineering Tsinghua UniversityBeijing 100084China

Accurate trajectory prediction of surrounding road users is the fundamental input for motion planning,which enables safe autonomous driving on public *** this paper,a safe motion planning approach is proposed based on the deep learning-based trajectory prediction *** begin with,a trajectory prediction model is established based on the graph neural network(GNN)that is trained utilizing the INTERACTION ***,the validated trajectory prediction model is used to predict the future trajectories of surrounding road users,including pedestrians and *** addition,a GNN prediction model-enabled motion planner is developed based on the model predictive control ***,two driving scenarios are extracted from the INTERACTION dataset to validate and evaluate the effectiveness of the proposed motion planning approach,i.e.,merging and roundabout *** results demonstrate that the proposed method can lower the risk and improve driving safety compared with the baseline method.

关键词： Trajectory prediction Graph neural network Motion planning INTERACTION dataset

Decouple charge transfer reactions in the Li-ion battery

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Journal of Energy Chemistry 2024年第5期92卷 759-798页

作者： Yuxuan Bai Qiu-An Huang kai Wu Jiujun Zhang Institute for Sustainable Energy/College of Sciences Shanghai UniversityShanghai 200444China Ningde Contemporary Innovation Laboratory Contemporary Amperex Technology Co.LimitedNingde 352100FujianChina

In the development of Li-ion batteries(LIBs)with high energy/power density,long cycle-life,fast charging,and high safety,an insight into charge transfer reactions is *** electrochemical impedance spectroscopy(EIS)is regarded as a powerful diagnosis tool,it is not a direct but an indirect *** respect to this,some critical questions need to be answered:(i)why EIS can reflect the kinetics of charge transfer reactions;(ii)what the inherent logical relationship between impedance models under different physical scenes is;(iii)how charge transfer reactions compete with each other at multiple *** work aims at answering these questions via developing a theory framework so as to mitigate the blindness and uncertainty in unveiling charge transfer reactions in *** systematically answer the above questions,this article is organized into a three-in-one(review,tutorial,and research)type and the following contributions are made:(i)a brief review is given for impedance model development of the LIBs over the past half century;(ii)an open source code toolbox is developed based on the unified impedance model;(iii)the competive mechanisms of charge transfer reactions are unveiled based on the developed EIS-Toolbox@*** work not only clarifies theoretical fundamentals,but also provides an easy-to-use open source code for EIS-Toolbox@LIB to optimize fast charge/discharge,mitigate cycle aging,and improve energy/power density.

关键词： Electrochemical impedance spectroscopy Unified impedance model Charge transfer reactions Solid/electrolyte diffusion Porous electrode EIS-Toolbox@LIB

Lanthanide-based microlasers:Synthesis,structures,and biomedical applications

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Nano Research 2024年第1期17卷 97-111页

作者： Qian Zhang Yawei Liu kai Liu Hongjie Zhang Engineering Research Center of Advanced Rare Earth Materials(Ministry of Education) Department of ChemistryTsinghua UniversityBeijing 100084China State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China Xiangfu Laboratory Jiaxing 314102China

The large size of lasers limits their applications in confined spaces,such as in biosensing and in vivo brain tissue *** this regard,micron-sized lasers have been *** exhibit great potential for biological detecting,remote sensing,and depth tracking due to their small sizes,sensitive properties of their spectral fingerprints,and flexible positional modulation in the ***-based luminescent materials that possess long excited-state lifetime,narrow emission bandwidth,and upconversion behaviors are promising as gain mediums for novel *** addition,lanthanide-based microlasers could be generated under natural ambient conditions with pumped or continuous light sources,which significantly promotes the practical applications of *** progress in the design,synthesis,and biomedical applications of lanthanide-based microlasers has been outlined in this *** ions doped and upconverted lanthanide-based microlasers are highlighted,which exhibit advantageous structures,miniaturized dimensions,and high lasing *** applications of lanthanide-based microlasers are further discussed,the upconverted microlasers show great advantages for biological applications owing to their tunable excitation and emission characteristics and excellent environmental ***,perspectives and challenges in the field of lanthanide-based microlasers are presented.

关键词： microlasers lanthanide-based luminescent materials upconversion nanoparticles biological applications

Thermal Decomposition and Oxidative Decomposition Mechanism of HFC-134a by Experimental and DFT Method

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Journal of Thermal Science 2024年第5期33卷 1990-2003页

作者： XU Yunting ZHANG kai DAI Xiaoye SHI Lin Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Energy and Power EngineeringTsinghua UniversityBeijing 100084China

In response to the Kigali Amendment to the Montreal Protocol and global low-carbon emission environmental requirements,the phase-out and decomposition of numerous HFC refrigerants have become urgent,necessitating efficient and mild decomposition *** study investigates the thermal decomposition and oxidative thermal decomposition pathways of the typical hydrofluorocarbon refrigerant HFC-134a,employing a combination of experimental and quantum chemical DFT simulation *** chemical simulations reveal that the initial reaction bond cleavage serves as the rate-determining step during the thermal decomposition process,with the most easily detectable closed-shell products including CF_(2)=CHF,HF,CH_(3)F,CHF_(3),CH_(2)F_(2),and CF_(4).Reactive oxygen species can significantly reduce the Gibbs free energy barrier for HFC-134a *** achieve efficient degradation of HFC-134a,appropriate catalysts should be developed and selected to increase the level of reactive oxygen species in the reaction *** studies further corroborate that HFC-134a may undergo degradation through distinct reaction pathways under varying temperature(240℃to360℃)and pressure(0.1 MPa to 4.5 MPa)conditions,in agreement with simulation predictions.

关键词： HFC-134a pyrolysis oxidative thermal decomposition DFT refrigerant

Nitrogen-doped carbon dots as photocatalysts for organic synthesis:Effect of nitrogen content on catalytic activity

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Nano Research 2024年第6期17卷 4825-4833页

作者： kai-kai Niu Chao-Qun Ma Rui-Zhi Dong Hui Liu Sheng-Sheng Yu Ling-Bao Xing School of Chemistry and Chemical Engineering Shandong University of TechnologyZibo 255000China

Regulating the doping of carbon dots(CDs)and the generation of reactive oxygen species(ROS)is essential to selectively control their application in photocatalytic organic *** study successfully synthesized five newly developed nitrogen-doped carbon dots(CDs 1-5)with varying nitrogen content,which have the ability to generate ROS when exposed to light radiation,specifically superoxide anion radicals(O_(2)•-)and singlet oxygen(^(1)O_(2)).The utilization of the aforementioned nitrogen-doped CDs as photocatalysts enables the realization of their potential in facilitating efficient photocatalytic organic ***,it was observed that the photocatalytic efficiency exhibited a gradual decrease when the nitrogen content in the CDs *** order to provide more evidence for this claim,we employed a set of five CDs in the context of photocatalytic dehalogenation ofα-bromoacetophenone,photocatalytic oxidative coupling reaction of amines to imines,photooxidation reaction of sulfides to sulfoxides,and cross-dehydrogenation coupling(CDC)reaction,in which it was further observed that there was a steady decrease in the yields of photocatalytic organic reactions as the nitrogen content in CDs ***,CDs 1 exhibited the best photocatalytic efficiency,thereby reinforcing the hypothesis that a higher nitrogen content corresponds to a decreased catalytic *** study not only investigates the impact of the nitrogen content on the catalytic performance of CDs,but also offers valuable insights for the future utilization of CDs for photocatalytic organic reactions in water.

关键词： carbon dots nitrogen-doped reactive oxygen species photocatalysis

Random Forest-Based Fatigue Reliability-Based Design Optimization for Aeroengine Structures

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Computer Modeling in Engineering & Sciences 2024年第7期140卷 665-684页

作者： Xue-Qin Li Lu-kai Song School of Energy and Power Engineering Beihang UniversityBeijing100191China Department of Mechanical Engineering The Hong Kong Polytechnic UniversityKowloonHong Kong999077China Research Institute of Aero-Engine Beihang UniversityBeijing100191China

Fatigue reliability-based design optimization of aeroengine structures involves multiple repeated calculations of reliability degree and large-scale calls of implicit high-nonlinearity limit state function,leading to the traditional direct Monte Claro and surrogate methods prone to unacceptable computing efficiency and *** this case,by fusing the random subspace strategy and weight allocation technology into bagging ensemble theory,a random forest(RF)model is presented to enhance the computing efficiency of reliability degree;moreover,by embedding the RF model into multilevel optimization model,an efficient RF-assisted fatigue reliability-based design optimization framework is *** the low-cycle fatigue reliability-based design optimization of aeroengine turbine disc as a case,the effectiveness of the presented framework is *** reliabilitybased design optimization results exhibit that the proposed framework holds high computing accuracy and computing *** current efforts shed a light on the theory/method development of reliability-based design optimization of complex engineering structures.

关键词： Random forest reliability-based design optimization ensemble learning machine learning