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UNCONDITIONALLY OPTIMAL ERROR ANALYSIS OF THE SECOND-ORDER BDF FINITE ELEMENT METHOD FOR THE KURAMOTO-TSUZUKI EQUATION

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Journal of Computational Mathematics 2023年第2期41卷 211-223页

作者： YUAN li Xuewei Cui College of Mathematics and Physics Wenzhou UniversityWenzhou 325035China

This paper aims to study a second-order semi-implicit BDF finite element scheme for the Kuramoto-Tsuzuki equations in two dimensional and three dimensional spaces.The proposed scheme is stable and the nonlinear term is linearized by the extrapolation technique.Moreover,we prove that the error estimate in L^(2)-norm is unconditionally optimal which means that there has not any restriction on the time step and the mesh size.Finally,numerical results are displayed to illustrate our theoretical analysis.

关键词： Kuramoto-Tsuzuki equations BDF scheme Finite element method Optimal error analysi

Industrial process fault detection based on locally linear embedded latent mapping

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Science China(Information Sciences) 2022年第4期65卷 272-274页

作者： YUAN li Chengcheng FENG College of Information Engineering Shenyang University of Chemical Technology

Dear editor,Industrial processes have become bigger and more complex with the rapid development of computer, network, and automation technology. However, these advances have increased the potential for faults. Minor faults in the chemical process stream may result in wasting resources or poor product quality; the most serious faults may lead to lifethreatening incidents, such as explosions and fires.

关键词： latent mapping manifold learning local linear embedding TE process fault detection

Detonation driving rules for cylindrical casings under asymmetrical multipoint initiations

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Defence Technology（防务技术） 2023年第5期23卷 35-49页

作者： YUAN li Xiaogang li Yuquan Wen Tao Suo Institute of Extreme Mechanics and School of Aeronautics Northwestern Polytechnical UniversityXi'an710072China State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China

The detonation wave-aiming warhead can effectively enhance the lethality efficiency. In the past, rules for casing rupture and velocity distribution under asymmetrical initiations were not adequately investigated. In this study, X-ray photography and numerical modelling are used to examine the casing expansions under centre point, asymmetrical one-point, and asymmetrical two-point(with central angles of 45° and 90°) initiations. The results indicate that early casing ruptures are caused by local high pressures, induced by the initiation, detonation wave interaction, and Mach wave onset. The fragment shapes are controlled by the impact angle of the detonation wave. The fragment velocity distributions differ under different initiation types, and the end rarefaction waves can affect the velocity distribution.This study can serve as a reference for the design and optimization of high-efficiency warheads.

关键词： Multipoint initiation Fragment shape Velocity distribution X-ray photography

Flow characteristic of polymer solutions in porous media:Influence of the molecular weight and concentration

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Petroleum 2023年第2期9卷 214-222页

作者： Yingjie Dai Jia li li li Yifei liu YUAN li Xiangyu Wang Xuguang Song Caili Dai Bin yuan Key Laboratory of Unconventional Oil&Gas Development(China University of Petroleum East China)Ministry of EducationQingdao 266580China Shandong Key Laboratory of Oilfield Chemistry(China University of Petroleum East China)Qingdao 266580China Nanchong Vocational and Technical College Nanchong 637131China Oil&Gas Technology Research Institute of Changqing Oilfield Company Xi'an 710000China Sinopec Research Institute of Petroleum Engineering Fracturing&Acidizing and Natural Gas Production Research InstituteDongying 257000China Department of Chemical and Materials Engineering University of AlbertaEdmontonAB T6G 1H9Canada

The polymer solution flow in porous media is a central research topic related to hydraulic fracturing measures,formation damage and fracture propagation.Influenced by molecular weights and concentrations,various flow patterns of polymer in pores are presented,resulting in different filtration loss.In this work,the effectiveness of various polymer solutions for filtration loss was assessed by utilizing the core flooding experiment firstly.The result shows that lesser filtration loss normally is inextricably linked to solutions with high molecular weight and concentration.Subsequently,the flow behaviors of polymer solutions investigated by designed micro pore-throat structure and micro-particle image velocimetry(m-PIV)further confirmed the above result.It was found that the central convergent flow pattern benefiting from higher viscous force loss and less filtration loss was observed at high flow rates(0.5 mL/h),and higher molecular weight and concentration were more prone to convergent flow patterns.The viscosity force loss increases by about 4 times varying the molecular weight of polymer from 5×10^(6)to 18×10^(6)g/mol or the concentration from 0.05 to 0.3%.It interprets higher molecular weight and concentration in core studies and field observations with decreased filtration loss of HPAM.This work provides a theoretical foundation for the application of fracturing fluids as well as fresh perspectives on how to access the filtration loss of fracturing fluids.

关键词： Polymer solution Porous media Flow pattern m-PIV

Ferromagnetic half levitation of LK-99-like synthetic samples

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中国科学:物理学、力学、天文学英文版 2023年第10期66卷 114-120页

作者： Kaizhen Guo YUAN li Shuang Jia International Center for Quantum Materials School of PhysicsPeking UniversityBeijing 100871China Collaborative Innovation Center for Quantum Matter Beijing 100871China Interdisciplinary Institute of light-Element Quantum Materials Research Center for Light-Element Advanced MaterialsPeking University Beijing100871China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of SciencesBeijing 100190China

We successfully synthesized polycrystalline LK-99-like ceramic samples with a solid-state-sintering method.Powder X-ray diffraction shows that the main contents are Pb_(10-x)Cu_(x)(PO_(4))_(6)O and Cu_(2)S,consistent with recent reports (arXiv:2307.12037;arXiv:2308.01192).In some small flaky fragments,we successfully observed“half levitation”atop a Nd_(2)Fe_(14)B magnet.Using magnetization measurements on such small pieces,as well as on a large piece which does not exhibit the half levitation,we show that the samples ubiquitously contain weak yet definitive soft ferromagnetic components.We argue that,together with the pronounced shape anisotropy of the small fragments,the soft ferromagnetism is sufficient to explain the observed half levitation in strong vertical magnetic fields.Our measurements do not indicate the presence of the Meissner effect,nor zero resistance,in our samples,leading us to believe that our samples do not exhibit superconductivity.The precise chemical composition and the physics behind the ferromagnetic component remain outstanding questions to be addressed in future research.

关键词： superconducting materials ferromagnetism magnetization curve

Co-Frequency Interference Analysis and Avoidance Between NGSO Constellations: Challenges, Techniques, and Trends

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China Communications 2023年第7期20卷 1-14页

作者： yuanzhi He YUAN li Hao Yin Institute ofSystemsEngineering AMSPLABeijing100141China

In recent years,as giant satellite constellations grow rapidly worldwide,the co-existence between constellations has been widely concerned.In this paper,we overview the co-frequency interference(CFI)among the giant non-geostationary orbit(NGSO)constellations.Specifically,we first summarize the CFI scenario and evaluation index among different NGSO constellations.Based on statistics about NGSO constellation plans,we analyse the challenges in mitigation and analysis of CFI.Next,the CFI calculation methods and research progress are systematically sorted out from the aspects of interference risk analysis framework,numerical calculation and link construction.Then,the feasibility of interference mitigation technologies based on space,frequency domain isolation,power control,and interference alignment mitigation in the NGSO mega-constellation CFI scenario are further sorted out.Finally,we present promising directions for future research in CFI analysis and CFI avoidance.

关键词： co-frequency existence analysis method overview interference avoidance

Local component based principal component analysis model for multimode process monitoring

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Chinese Journal of Chemical Engineering 2021年第6期34卷 116-124页

作者： YUAN li Dongsheng Yang Department of Information Engineering Shenyang University of Chemical TechnologyShenyang 110142China

For plant-wide processes with multiple operating conditions,the multimode feature imposes some challenges to conventional monitoring techniques.Hence,to solve this problem,this paper provides a novel local component based principal component analysis(LCPCA)approach for monitoring the status of a multimode process.In LCPCA,the process prior knowledge of mode division is not required and it purely based on the process data.Firstly,LCPCA divides the processes data into multiple local components using finite Gaussian mixture model mixture(FGMM).Then,calculating the posterior probability is applied to determine each sample belonging to which local component.After that,the local component information(such as mean and standard deviation)is used to standardize each sample of local component.Finally,the standardized samples of each local component are combined to train PCA monitoring model.Based on the PCA monitoring model,two monitoring statistics T^(2) and SPE are used for monitoring multimode processes.Through a numerical example and the Tennessee Eastman(TE)process,the monitoring result demonstrates that LCPCA outperformed conventional PCA and LNS-PCA in the fault detection rate.

关键词： Principal component analysis Finite Gaussian mixture model Process monitoring Tennessee Eastman(TE)process

Facet-dependent activation of oxalic acid over hematite nanocrystals under the irradiation of visible light for efficient degradation of pollutants

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Journal of Environmental Sciences 2024年第8期142卷 204-214页

作者： Zhixiong Yang YUAN li Xiaotian Wang Jiaming li Jiquan Wang Gaoke Zhang Hubei Key Laboratory of Mineral Resources Processing and Environment State Key Laboratory of Silicate Materials for ArchitecturesWuhan University of TechnologyWuhan 430070China Hubei Engineering Consulting Co. Ltd.Wuhan 430071China

Naturally occurring hematite has been widely studied in the Fenton-like system for water pollutant remediation due to its abundance and non-toxicity.However,its inadequate catalytic activity results in difficulty in effectively degrading pollutants in the catalytic degradation system that it constitutes.Thus,we constructed a photochemical system composed of hematite with{001}facet of high activity facet and low-cost and non-toxic oxalic acid(OA)for the removal of various types of pollutants.The removal rate for the degradation of metronidazole,tetracycline hydrochloride,Rhodamine B,and hexavalent chromium by hematite nanoplate with the exposed{001}facet activating OA under visible light irradiation was 4.75,2.25,2.33,and 2.74 times than that by the exposed{110}facet,respectively.Density functional theory(DFT)calculation proved that the OA molecule was more easily adsorbed on the{001}facet of hematite than that on the{110}facet,which would favor the formation of the more Fe(Ⅲ)-OA complex and reactive species.In addition,the reactive site of metronidazole for the attraction of radicals was identified on the basis of the DFT calculation on the molecular occupied orbitals,and the possible degradation pathway for metronidazole included carbon chain fracture,hydroxyethyl-cleavage,denitrogenation,and hydroxylation.Thus,this finding may offer a valuable direction in designing an efficient iron-based catalyst based on facet engineering for the improved activity of Fenton-like systems such as OA activation.

关键词： Hematite Facet exposure Oxalic acid activation Fenton-like system Pollutant removal

Estimating the Size of an Open Population with Massive Datasets Based on a Generalized Varying-Coefficient Model

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Journal of Systems Science & Complexity 2022年第3期35卷 1116-1136页

作者： li Haoqi li yuan School of Economics and Statistics Guangzhou UniversityGuangzhou 510006China School of Mathematics and Statistics Yangtze Normal UniversityChongqing 408100China

A generalized varying-coefficient model is proposed to estimate a population size at a specific time from multiple lists of an open population.The research datasets have millions of records with a very long time span(38 years),bringing challenges to calculations.The authors develop a regularization iterative algorithm to overcome this difficulty.The asymptotic distribution of the proposed estimators is derived.Simulation studies show that the procedure works well.The method is applied to estimate the number of drug abusers in Hong Kong,China over the period 1977–2014.

关键词： Drug abusers generalized varying-coefficient multiple-list open population