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MIXED DISCONTINUOUS GALERKIN METHOD FOR QUASI-NEWTONIAN STOKES FLOWS

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Journal of Computational Mathematics 2024年第3期42卷 885-910页

作者： Yanxia Qian Fei Wang Wenjing Yan School of Mathematics and Statistics Xi'an Jiaotong UniversityXi'an 710049China School of Mathematics and Statistics&State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

In this paper,we introduce and analyze an augmented mixed discontinuous Galerkin(MDG)method for a class of quasi-Newtonian Stokes flows.In the mixed formulation,the unknowns are strain rate,stress and velocity,which are approximated by a discontinuous piecewise polynomial triplet ■for k≥0.Here,the discontinuous piecewise polynomial function spaces for the field of strain rate and the stress field are designed to be symmetric.In addition,the pressure is easily recovered through simple postprocessing.For the benefit of the analysis,we enrich the MDG scheme with the constitutive equation relating the stress and the strain rate,so that the well-posedness of the augmented formulation is obtained by a nonlinear functional analysis.For k≥0,we get the optimal convergence order for the stress in broken ■(div)-norm and velocity in L^(2)-norm.Furthermore,the error estimates of the strain rate and the stress in-norm,and the pressure in L^(2)-norm are optimal under certain conditions.Finally,several numerical examples are given to show the performance of the augmented MDG method and verify the theoretical results.Numerical evidence is provided to show that the orders of convergence are sharp.

关键词： Quasi-Newtonian fows Mixed discontinuous Galerkin method Symmetric strain rate Symmetric stress Optimal convergence orders

Nickel-catalyzed carbonylative four-component 1,4-dicarbofunctionalization of 1,3-enynes

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science China Chemistry 2024年第6期67卷 2029-2038页

作者： Yan Zhao Qi-Chao Shan Hong xin Pin Gao Xu Yang xin-Hua Duan Li-Na Guo Department of Chemistry School of ChemistryXi’an Key Laboratory of Sustainable Energy Material Chemistry and Engineering Research Center of Energy StorageMaterials and DevicesMinistry of EducationXi’an Jiaotong UniversityXi’an710049China School of Electrical Engineering Xi’an Jiaotong UniversityXi’an710049China

An efficient Ni-catalyzed four-component 1,4-carbocarbonylation of 1,3-enynes with activated alkyl halides and arylboronic acids under atmospheric pressure of CO is presented.By tuning the electronic and steric effects of alkyl radicals,both electronrich and electron-deficient 1,3-enynes were compatible with this cascade.This protocol features mild conditions,broad substrate scope,excellent functional group compatibility and facile gram-scale synthesis,providing a practical approach to the quaternary carbon center-containing allenyl ketones.Mechanistic study revealed that the acyl-NiIIspecies plays an important role in both the coupling and the alkyl radical generation processes.

关键词： Ni catalysis four-component 1 4-carbocarbonylation 1 3-enynes

Learning to select the recombination operator for derivative-free optimization

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science China Mathematics 2024年第6期67卷 1457-1480页

作者： Haotian Zhang Jianyong Sun Thomas Back Zongben Xu School of Mathematics and Statistics Xi’an Jiaotong UniversityXi’an710049China Leiden Institute of Advanced Computer science Leiden UniversityLeiden2333 CANetherlands

Extensive studies on selecting recombination operators adaptively,namely,adaptive operator selection(AOS),during the search process of an evolutionary algorithm(EA),have shown that AOS is promising for improving EA's performance.A variety of heuristic mechanisms for AOS have been proposed in recent decades,which usually contain two main components:the feature extraction and the policy setting.The feature extraction refers to as extracting relevant features from the information collected during the search process.The policy setting means to set a strategy(or policy)on how to select an operator from a pool of operators based on the extracted feature.Both components are designed by hand in existing studies,which may not be efficient for adapting optimization problems.In this paper,a generalized framework is proposed for learning the components of AOS for one of the main streams of EAs,namely,differential evolution(DE).In the framework,the feature extraction is parameterized as a deep neural network(DNN),while a Dirichlet distribution is considered to be the policy.A reinforcement learning method,named policy gradient,is used to train the DNN.As case studies,the proposed framework is applied to two DEs including the classic DE and a recently-proposed DE,which result in two new algorithms named PG-DE and PG-MPEDE,respectively.Experiments on the Congress of Evolutionary Computation(CEC)2018 test suite show that the proposed new algorithms perform significantly better than their counterparts.Finally,we prove theoretically that the considered classic methods are the special cases of the proposed framework.

关键词： evolutionary algorithm differential evolution adaptive operator selection reinforcement learning deep learning

Water-soluble organic matter with various polarities in PM_(2.5) over xi'an,China:Abundance,functional groups,and light absorption

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Particuology 2024年第1期84卷 281-289页

作者： Xueting Yang Shasha Huang Dan Li Hongmei Xu Yaling Zeng Liu Yang Diwei Wang Ningning Zhang Junji Cao Zhenxing Shen Department of Environmental science and Engineering Xi'an Jiaotong UniversityXi'an710049China School of Environmental science and Engineering Southern University of Science and TechnologyShenzhen518055China State Key Laboratory of Loess and Quaternary Geology Institute of Earth EnvironmentChinese Academy of SciencesXi'an710049China

Humic-like substances(HULIS)are a major component of brown carbon and consequently play a major role in climate change.In this study,70 PM_(2.5) samples were collected from xi'an in winter 2019 and summer 2020.Neutral HULIS(HULIS-n),acidic HULIS(HULIS-a),and high-polarity water-soluble organic compounds(HP-WSOC)were analyzed to determine their carbon concentrations and measure their ultraviolet-visible absorption and infrared spectra.Of the three components,HULIS-n had the highest carbon content in both winter(3.29±1.45μg m^(-3))and in summer(1.38±1.10μg m^(-3)).The semi-quantitative results for the functional groups revealed that HP-WSOC was rich in carboxylic acids and had high aromaticity in winter,whereas HULIS-n was rich in carboxylic acids in summer.Moreover,HULJS-a was richer in nitrate esters and saturated aliphatic hydrocarbons in summer than in winter.The results for specific ultraviolet absorbance(SUVA)and E_(250)/E_(365) revealed that HULIS had higher molecular weight and aromaticity in winter than in summer.HULIS-n dominated in the total light absorption of HULIS+HP-WSOC in both winter(73.08%)and summer(48.57%).Overall,the results on the carbon content,optical properties,and functional groups of WSOCs with differing polarity can improve un-derstanding of environmental and climatic effects.

关键词： Humic-like substances(HULIS) Aromaticity Fourier-transform infrared(FTIR) spectroscopy Light absorbance

Photocatalytic transformation of selected biomass derivatives to value added chemicals and hydrogen fuel

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Chinese Chemical Letters 2024年第3期35卷 19-26页

作者： xiangjun Liu Shuai Zhang Miao Wang Junqi Wang School of Human Settlements and Civil Engineering Xi'an Jiaotong UniversityXi'an 710049China

Biomass is the most bountiful renewable carbon resource on earth.Photocatalytic transformation is a promising method to utilize biomass to obtain high-value-added chemicals and it has more obvious advantages compared with thermochemical and biological processes due to the milder operational conditions,fewer reagents and equipment.Semiconductor material is one of the most common kinds of heterogeneous biomass photocatalysts,which has the advantages of high selectivity,stable catalytic performance,long activation time,and low cost.In this paper,the significant research progress on the photocatalytic transformation of biomass with semiconductor materials to produce high-value-added chemicals is reviewed,and the three most typical semiconductor photocatalysts(TiO_(2),Cd S,and g-C_(3)N_(4))are detailed.The photocatalytic mechanism and photocatalytic system optimization including structural modification,metal co-catalyst loading,and introduction of heterojunction are presented.Besides,the main problems,the development direction and trend of semiconductor materials in photocatalytic transformations of biomass in the future are prospected,which provide guidance and inspiration for the further development of semiconductor photocatalysts and make contributions to the progress in efficient utilization of biomass.

关键词： Photocatalytic transformation Biomass Semiconductor material H_(2) High value-added chemical

Characteristics of bioaerosols under high-ozone periods,haze episodes,dust storms,and normal days in xi'an,China

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Particuology 2024年第7期90卷 140-148页

作者： Yiming Yang Liu Yang xiaoyan Hu Zhenxing Shen Department of Environmental science and Engineering Xi’an Jiaotong UniversityXi’an710049China Key Lab of Aerosol Chemistry&Physics SKLLQGInstitute of Earth EnvironmentChinese Academy of SciencesXi’an710049China

The characteristics of bioaerosols and their effects on human beings'health have become a major public concern in the recent years.This study compared the characteristics of bioaerosols under different types of pollution(high-ozone[HO]episodes,haze episodes,and dust storms[DSs]),with those of bioaerosols on normal days(NDs)in xi'an,China.The concentrations,diurnal variations,and size distribution of bacteria,fungi,and total airborne microbes(TAMs)were investigated.The results showed that the bacterial and fungal concentrations were the highest during DSs and on NDs,reaching 425.2 and 956.9 colony-forming units/m^(3),respectively.The concentration of TAMs was the highest during HO episodes,reaching 10.7×10^(6)cells/m^(3),which was significantly higher than that during the other events.The maximum concentrations of bacteria and fungi during HO episodes were observed in the morning,while they appeared separately in the morning and evening during haze episodes.Bacteria and TAMs during DSs reached peak concentrations in the morning and evening,which is opposite to the particulate matter(PM)distribution pattern.On NDs,temperature and relative humidity had significant effects on bioaerosols.The size distributions of airborne bacteria exhibited bimodal patterns,whereas unimodal distributions were observed for fungi.Fungi mainly attached in fine particles(<2.1μm)with proportions of 67.4%and 60.5%during haze episodes and DSs,respectively,which means that fungi were easily penetrated into the human respiratory system.The evaluation of influence factors revealed that PM_(2.5) and PM10 had negative effects on fungal concentration during DSs,and ozone concentration and temperature were inversely correlated with fungal concentration during HO episodes.These results provide valuable reference data for elucidating the formation and evolution of bioaerosols under different types of pollution.

关键词： Bacteria Fungi Total airborne microbe Different air pollution types Influence factors

A polarization sensitive interferometer:Delta interferometer

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Chinese Physics B 2024年第3期33卷 369-377页

作者：卫超奇刘建彬董翼飞孙雨农周宇郑淮斌刘严严闫秀生李福利徐卓 Key Laboratory of Multifunctional Materials and Structures Ministry of Education & International Center for Dielectric ResearchSchool of Electronic Science and EngineeringXi'an Jiaotong UniversityXi'an 710049China MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter Department of Applied PhysicsXi'an Jiaotong UniversityXi'an 710049China science and Technology on Electro-Optical Information Security Control Laboratory Tianjin 300308China

A new type of polarization sensitive interferometer is proposed,named the Delta interferometer,inspired by its geometry resembling the Greek letter Delta.The main difference between the Delta interferometer and other existing interferometers,such as Michelson,Mach-Zehnder and Young's double-slit interferometers,is that the two interfering paths are asymmetrical in the Delta interferometer.The visibility of the first-order interference pattern observed in the Delta interferometer is dependent on the polarization of the incidental light.Optical coherence theory is employed to interpret this phenomenon and single-mode continuous-wave laser light is employed to verify the theoretical predictions.The theoretical and experimental results are consistent.The Delta interferometer is a perfect tool to study the reflection of electromagnetic fields in different polarizations and may find applications in polarization-sensitive scenarios.

关键词： phase sensitive interferometer Fresnel formula first-order interference

Comparison-embedded evidence-CNN model for fuzzy assessment of wear severity using multi-dimensional surface images

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Friction 2024年第6期12卷 1098-1118页

作者： Tao SHAO Shuo WANG Qinghua WANG Tonghai WU Zhifu HUANG Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System Xi’an Jiaotong UniversityXi’an 710049China State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China

Wear topography is a significant indicator of tribological behavior for the inspection of machine health conditions.An intelligent in-suit wear assessment method for random topography is here proposed.Three-dimension(3D)topography is employed to address the uncertainties in wear evaluation.Initially,3D topography reconstruction from a worn surface is accomplished with photometric stereo vision(PSV).Then,the wear features are identified by a contrastive learning-based extraction network(WSFE-Net)including the relative and temporal prior knowledge of wear mechanisms.Furthermore,the typical wear degrees including mild,moderate,and severe are evaluated by a wear severity assessment network(WSA-Net)for the probability and its associated uncertainty based on subjective logic.By integrating the evidence information from 2D and 3D-damage surfaces with Dempster–Shafer(D–S)evidence,the uncertainty of severity assessment results is further reduced.The proposed model could constrain the uncertainty below 0.066 in the wear degree evaluation of a continuous wear experiment,which reflects the high credibility of the evaluation result.

关键词： wear severity assessment contrastive learning subjective logic Dempster-Shafer(D-S)evidence theory

Covalently Bonded Ni Sites in Black Phosphorene with Electron Redistribution for Efficient Metal‑Lightweighted Water Electrolysis

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Nano-Micro Letters 2024年第6期16卷 233-245页

作者： Wenfang Zhai Ya Chen Yaoda Liu Yuanyuan Ma Paranthaman Vijayakumar Yuanbin Qin Yongquan Qu Zhengfei Dai State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049People’s Republic of China School of Chemistry and Chemical Engineering Northwestern Polytechnical UniversityXi’an 710072People’s Republic of China SSN Research centre SSN College of EngineeringChennaiTamil Nadu 603110India

The metal-lightweighted electrocatalysts for water splitting are highly desired for sustainable and economic hydrogen energy deployments,but challengeable.In this work,a low-content Ni-functionalized approach triggers the high capability of black phosphorene(BP)with hydrogen and oxygen evolution reaction(HER/OER)bifunctionality.Through a facile in situ electro-exfoliation route,the ionized Ni sites are covalently functionalized in BP nanosheets with electron redistribution and controllable metal contents.It is found that the as-fabricated Ni-BP electrocatalysts can drive the water splitting with much enhanced HER and OER activities.In 1.0 M KOH electrolyte,the optimized 1.5 wt%Nifunctionalized BP nanosheets have readily achieved low overpotentials of 136 mV for HER and 230 mV for OER at 10 mA cm^(−2).Moreover,the covalently bonding between Ni and P has also strengthened the catalytic stability of the Ni-functionalized BP electrocatalyst,stably delivering the overall water splitting for 50 h at 20 mA cm^(−2).Theoretical calculations have revealed that Ni–P covalent binding can regulate the electronic structure and optimize the reaction energy barrier to improve the catalytic activity effectively.This work confirms that Ni-functionalized BP is a suitable candidate for electrocatalytic overall water splitting,and provides effective strategies for constructing metal-lightweighted economic electrocatalysts.

关键词： Black phosphorus Water electrolysis Electrocatalyst Electron redistribution Covalent functionalization