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Refined asymptotics for minimal graphs in the hyperbolic space

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Science China Mathematics 2019年第2期62卷 381-390页

作者： weiming Shen Yue wang Beijing International Center for Mathematical Research Peking University School of Mathematical Sciences Peking University

We study the boundary behaviors of solutions f to the Dirichlet problem for minimal graphs in the hyperbolic space with singular asymptotic boundaries and characterize the boundary behaviors of f at the points strictly located in the tangent cones at the singular points on the boundary. For n =2, we also obtain a refined estimate of f.

关键词： asymptotic behaviors minimal graphs singular domains

Simulating and validating the effects of slope frost heaving on canal bed saturated soil using coupled heat-moisture-deformation model

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International Journal of Agricultural and Biological Engineering 2017年第2期10卷 184-193页

作者： wang Enliang Fu Qiang liu Xingchao Li Tianxiao Li jinling School of Water Conservancy and Civil Engineering Northeast Agricultural UniversityHarbin 150030China Heilongjiang Provincial Collaborative Innovation Center of Grain Production Capacity Improvement Northeast Agricultural UniversityHarbin 150030China Key Laboratory of High Efficient Utilization of Agricultural Water Resource of Ministry of Agriculture Northeast Agricultural UniversityHarbin 150030China

The lining canals in seasonal frozen soil areas can be severely damaged by frost *** freezing and thawing contributes to the continual change of the temperature field and moisture field beneath lining canal,which will seriously affect the safe operation of the *** order to study the frost heaving damage mechanism of lining canal and to solve the associated engineering problems,the permafrost body was regarded as an elastomer,and a three-field,coupled,partial differential equation describing the temperature,moisture and deformation fields for a saturated two-dimensional canal bed was derived and established based on the Harlan *** coupling equations were discretized using the finite element method in space and the finite difference method in *** parameters were simplified appropriately based on compliance with the actual conditions and were simulated using finite element *** results of a sample simulation showed that the simulated results and test results were basically consistent with variation laws,which proved the correctness of the numerical simulation theory and solution methods and the reliability of the *** model can simulate the water,heat and deformation issues in the side slope of saturated canal bed soil in a seasonally frozen area and forecast freezing damage in the canals.

关键词： seasonally frozen area canal soil of the side slope coupling of water heat and deformation model

Direct growth of globally aligned graphene nanoribbons on reconstructed sapphire substrate using PECVD

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Nano Research 2023年第1期16卷 62-69页

作者： Mingzhi Zou weiming liu Yue Yu Shanshan wang Bo Xu liu Qian Tianze Tong Jin Zhang College of Chemistry and Molecular Engineering Beijing Science and Engineering Center for NanocarbonsBeijing National Laboratory for Molecular SciencesPeking UniversityBeijing 100871China Science and Technology on Advanced Ceramic Fibers and Composites Laboratory College of Aerospace Science and EngineeringNational University of Defense TechnologyChangsha 410000China

Graphene nanoribbons(GNRs)are regarded as an ideal candidate for beyond-silicon ***,synthesis of aligned GNR arrays on insulating substrates with high efficiency is *** this work,we develop a facile strategy,involving KOH pre-treatment and high-temperature annealing,to construct parallel steps on the two-fold symmetry a-plane sapphire *** GNRs as narrow as 15.1 nm with global alignment across a region of 20 mm^(2)are then grown on the step edgeenriched substrate through plasma enhanced chemical vapor deposition(PECVD)*** align well along the atomic steps on sapphire([■]direction)with their widths and densities swiftly adjustable by step morphology modification on substrate surface.A step-edge confined growth mechanism is proposed,attributing the constraint on the nanoribbon broadening to a relatively low growth temperature in PECVD,which restrains the activation energy to suppress GNRs across step edges on sapphire and prevents detrimental nanoribbon *** results provide a new perspective for scalable synthesizing well aligned nanoribbons of other two-dimensional materials.

关键词： graphene nanoribbon(GNR) global alignment sapphire insulating substrates plasma enhanced chemical vapor deposition(PECVD)

New approach to calculating tree height at the regional scale

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Forest Ecosystems 2021年第2期8卷 311-329页

作者： Congrong Li jinling Song Jindi wang State Key Laboratory of Remote Sensing Science Jointly Sponsored by Beijing Normal University and Aerospace Information Research Institute of Chinese Academy of SciencesFaculty of Geographical ScienceBeijing Normal UniversityBeijing 100875China Key Laboratory of Digital Earth Science Aerospace Information Research Institute Chinese Academy of SciencesNo.9 Dengzhuang South RoadBeijing 100094China

Background:Determining the spatial distribution of tree heights at the regional area scale is significant when performing forest above-ground biomass estimates in forest resource management *** geometric-optical mutual shadowing(GOMS)model can be used to invert the forest canopy structural parameters at the regional ***,this method can obtain only the ratios among the horizontal canopy diameter(CD),tree height,clear height,and vertical *** this paper,we used a semi-variance model to calculate the CD using high spatial resolution images and expanded this method to the regional *** then combined the CD results with the forest canopy structural parameter inversion results from the GOMS model to calculate tree heights at the regional ***:The semi-variance model can be used to calculate the CD at the regional scale that closely matches(mainly with in a range from-1 to 1 m)the CD derived from the canopy height model(CHM)*** difference between tree heights calculated by the GOMS model and the tree heights derived from the CHM data was small,with a root mean square error(RMSE)of 1.96 for a 500-m area with high fractional vegetation cover(FVC)(i.e.,forest area coverage index values greater than 0.8).Both the inaccuracy of the tree height derived from the CHM data and the unmatched spatial resolution of different datasets will influence the accuracy of the inverted tree *** the error caused by the unmatched spatial resolution is small in dense ***:The semi-variance model can be used to calculate the CD at the regional scale,together with the canopy structure parameters inverted by the GOMS model,the mean tree height at the regional scale can be *** study provides a new approach for calculating tree height and provides further directions for the application of the GOMS model.

关键词： Geometric-optical mutual shadowing(GOMS)model Semi-variance model Canopy diameter Tree height Regional scale

Thermodynamic Performance Analysis of E/F/H-Class Gas Turbine Combined Cycle with Exhaust Gas Recirculation and Inlet/Variable Guide Vane Adjustment under Part-Load Conditions

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Journal of Thermal Science 2024年第1期33卷 348-367页

作者： LI Keying CHI jinling wang Bo ZHANG Shijie Key Lab of Advanced Energy and Power Institute of Engineering ThermophysicsChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China School of Mechanical Electronic&Information Engineering China University of Mining&Technology-BeijingBeijing 100083China

Exhaust gas recirculation control(EGRC),an inlet air heating technology,can be utilized in combination with inlet/variable guide vane control(IGV/VGVC) and fuel flow control(FFC) to regulate the load,thereby effectively improving the part-load(i.e.,off-design) performance of the gas turbine combined cycle(GTCC).In this study,the E-,F-,and H-Class EGR-GTCC design and off-design system models were established and validated to perform a comparative analysis of the part-load performance under the EGR-IGV-FFC and conventional IGV-FFC strategies in the E/F/H-Class *** show that EGR-IGV-FFC has considerable potential for the part-load performance enhancement and can show a higher combined cycle efficiency than IGV-FFC in the E-,F-,and H-Class ***,the part-load performance improvement in the corresponding GTCC was weakened for the higher class of the gas turbine because of the narrower load range of EGR action and the deterioration of the gas turbine ***,EGR-IGV-FFC was inferior to IGV-FFC in improving the performance at loads below 50% for the H-Class *** results obtained in this paper could help guide the application of EGR-IGV-FFC to enhance the part-load performance of various classes of GTCC systems.

关键词： E/F/H-Class gas turbine combined cycle performance improvement part-load conditions exhaust gas recirculation inlet/variable guide vane

Research on mode localization of reticulated shell structures

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Earthquake Engineering and Engineering Vibration 2011年第1期10卷 75-84页

作者： Yan weiming wang Zhuo He Haoxiang Beijing Laboratory of Earthquake Engineering and Structural Retrofit Beijing University of Technology Beijing 100124 China The Open University of China Beijing 100031 China

Reticulated shell structures （RSSs） are characterized as cyclically periodic structures. Mistuning of RSSs will induce structural mode localization. Mode localization has the following two features： some modal vectors of the structure change remarkably when the values of its physical parameters （mass or stiffness） have a slight change; and the vibration of some modes is mainly restricted in some local areas of the structure. In this paper, two quantitative assessment indexes are introduced that correspond to these two features. The first feature is studied through a numerical example of a RSS, and its induced causes are analyzed by using the perturbation theory. The analysis showed that internally, mode localization is closely related to structural frequencies and externally, slight changes of the physical parameters of the structure cause instability to the RSS. A scaled model experiment to examine mode localization was carried out on a Kiewit single-layer spherical RSS, and both features of mode localization are studied. Eight tests that measured the changes of the physical parameters were carried out in the experiment. Since many modes make their contribution in structural dynamic response, six strong vibration modes were tested at random in the experimental analysis. The change and localization of the six modes are analyzed for each test. The results show that slight changes to the physical parameters are likely to induce remarkable changes and localization of some modal vectors in the RSSs.

关键词： reticulated shell structure mistuning mode localization perturbation theory seismic performance analysis damage identification

Theoretical analysis of a new segmented anchoring style in weakly cemented soft surrounding rock

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International Journal of Mining Science and Technology 2016年第3期26卷 401-407页

作者： Zhao Zenghui wang weiming wang Lihua Shandong Provincial Key Laboratory of Civil Engineering Disaster Prevention and Mitigation Shandong University of Science & Technology State Key Laboratory of Mining Disaster Prevention and Control Co-founded by Shandong Province and the Ministry of Science & Technology College of Mining and Safety Engineering Shandong University of Science & Technology College of Civil Engineering and Architecture Shandong University of Science & Technology

According to the tensile failure of rock bolt in weakly cemented soft rock, this paper presents a new segmented anchoring style in order to weaken the cumulative effect of anchoring force associated with the large deformation. Firstly, a segmented mechanical model was established in which free and anchoring section of rock bolt were respectively arranged in different deformation zones. Then, stress and displacement in elastic non-anchoring zone, elastic anchoring zone, elastic sticking zone, softening sticking zone and broken zone were derived respectively based on neural theory and tri-linear strain softening constitutive model of soft rock. Results show that the anchoring effect can be characterized by a supporting parameter b. With its increase, the peak value of tangential stress gradually moves to the roadway wall, and the radial stress significantly increases, which means the decrease of equivalent plastic zone and improvement of confining effect provided by anchorage body. When b increases to 0.72, the equivalent plastic zone disappears, and stresses tend to be the elastic solutions. In addition, the anchoring effect on the displacement of surrounding rock can be quantified by a normalization factor δ.

关键词： Weakly cemented soft rock Segmented anchorage Strain softening Analytical model

Erosion Behavior of NiCoCrFeNb_(0.45) Eutectic High-Entropy Alloy in Liquid-Solid Two-Phase Flow

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Acta Metallurgica Sinica(English Letters) 2022年第8期35卷 1266-1274页

作者： Kai wang Zhenjiang wang jinling Lu Zhijun wang Wei wang Xingqi Luo State Key Laboratory of Eco-Hydraulics in Northwest Arid Region Xi'an University of TechnologyXi'an 710048China State Key Laboratory of Solidification Procesing Northwestern Polytechnical UniversityXi'an 710072China

The metal components exposed to the high-velocity liquid-solid flow can be rapidly eroded by the accelerated *** an excellent combination of strength and toughness,the NiCoCrFeNb_(0.45)eutectic high-entropy alloy(EHEA)has emerged as a promising material to resist erosion *** this study,the erosion behavior of NiCoCrFeNb_(0.45)EHEA in high-velocity multiphase flow is investigated through the coupling analysis of material properties,multiphase flow,and particle–surface impact *** inherent mathematical relationship is discovered between the erosion rates and the impact velocity,impact angle,and test *** results show that the NiCoCrFeNb_(0.45)EHEA has superior erosion resistance than the commonly used machinery *** principal material removal mechanism is the formation and brittle fracture of the platelets,accompanied by micro-cutting and ploughing at some oblique *** higher work-hardenability of NiCoCrFeNb_(0.45)EHEA could mitigate the erosion damage as time proceeds,and this effect becomes more apparent as the impact angle ***,the evolution of erosion damage with time varies significantly depending on the impact *** on the test data and computational fluid dynamics(CFD)modeling of the near-wall flow field,a power exponential function relationship between erosion depth and the corresponding impact velocity at various locations on the material surface is established.

关键词： Eutectic high-entropy alloy Erosion evolution Multiphase flow Computational fluid dynamics(CFD)modeling

A review of measurement methods for peracetic acid (PAA)

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Frontiers of Environmental Science & Engineering 2020年第5期14卷 127-136页

作者： Chen Cheng Haodong Li jinling wang Hualin wang Xuejing Yang National Engineering Laboratory for Industrial Wastewater Treatment East China University of Science and Technology(ECUST)Shanghai 200237China State Key Laboratory of Chemical Engineering ECUSTShanghai 200237China

Peroxyacetic acid has been widely used in food,medical,and synthetic chemical fields for the past several ***,peroxyacetic acid has gradually become an effective alternative disinfectant in wastewater disinfection and has strong redox capacity for removing micro-pollutants from drinking ***,commercial peroxyacetic acid solutions are primarily multi-component mixtures of peroxyacetic acid,acetic acid,hydrogen peroxide,and *** the process of water treatment,peroxyacetic acid and hydrogen peroxide(H2O2)often coexist,which limits further investigation on the properties ofperoxyacetic ***,analytical methods need to achieve a certain level of selectivity,particularly when peroxyacetic acid and hydrogen peroxide *** review summarizes the measurement and detection methods of peroxyacetic acid,comparing the principle,adaptability,and relative merits of these methods.

关键词： Peroxyacetic acid Measurement methods Titration Colorimetric Chromatography NMR