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Basin flood control system risk evaluation based on variable sets

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Science China(Technological Sciences) 2017年第1期60卷 153-165页

作者： peng yong CHU JingGang XUE ZhiChun Department of Water Resources China Institute of Water Resources and Hydropower Research Beijing 100038 China

Flood control system risk evaluation is an effective measure for flood risk management and *** order to make better flood risk decisions and thereby improve social and economic benefits,the flood control risk evaluation index system should be built to quantify and normalize flood risk effectively and *** the current evaluation index has the binary miscibility characteristic of fuzziness and clarity,this paper establishes a new flood control system risk evaluation method based on the theory of variable sets(VS).Through a comparison of flood control risk evaluation with variable fuzzy sets(VFS) in the same basin flood control system risk evaluation,it is revealed that the new method,i.e.,flood control risk evaluation with variable fuzzy/clear mixture sets(variable sets),will be reasonable in all ***,in one case study,i.e.,the flood control system risk evaluation of Fengman Reservoir Basin,which is located in the southeast central of Jilin Province in China,the risk evaluation levels for each county in the basin as well as the whole flood risk distribution map of the basin could be provided with the new *** provides useful information for basin flood control planning and design.

关键词： variable sets (VS) flood control system risk evaluation evaluation indices flood control risk distribution map

Optimal control approach to stability criteria on Hill's equations

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Applied Mathematics(A Journal of Chinese Universities) 2018年第3期33卷 253-273页

作者： ZU jian LI yong School of Mathematics and Statistics & Center for Mathematics and Interdisciplinary Sciences North-east Normal University Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education Jilin University College of Mathematics Jilin University

This paper gives a tutorial on how to prove Lyapunov type criteria by optimal control methods. Firstly, we consider stability criteria on Hill’s equations with nonnegative potential. By optimal control methods developed in 1990s, we obtain several stability criteria including Lyapunov’s criterion, Neǐgauz and Lidskiǐ’s criterion. Secondly, we present stability criteria on Hill’s equations with sign-changing potential in which Brog’s criterion and Krein’s criterion are included.

关键词： stability criteria optimal control method Hill's equation Lyapunov inequality

Microstructure and high-temperature tensile property of TiAl alloy produced by selective electron beam melting

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Rare Metals 2021年第12期40卷 3635-3644页

作者： Hang-Yu Yue Hui peng yong-Jun Su Xiao-peng Wang Yu-yong Chen School of Materials Science and Engineering Jiangsu University of Science and TechnologyZhenjiang 212003China Key Laboratory of High-Temperature Structural Materials and Coatings Technology Ministry of Industry and Information TechnologyBeihang UniversityBeijing 100191China School of Materials Science and Engineering Beihang UniversityBeijing 100191China Department of Mechanics College of EngineeringLishui UniversityLishui 323000China State Key Laboratory of Advanced Welding and Joining Harbin Institute of TechnologyHarbin 150001China

The microstructure and high-temperature tensile property of a Ti-47Al-2Cr-2 Nb alloy fabricated via selective electron beam melting(SEBM) with hatch spacings of 85,100,and 115 μm were systematically *** the hatch spacing increased from 85 to 115 μm,the microstructure comprising the horizontal cross section changed from coarse lamellar(y/B2) colonies to an inhomogeneous structure and the grain morphology transformed from elongated grains to inhomogeneous and equiaxed grains along the building direction of the vertical cross *** boundary population of the SEBMproduced TiAl alloy samples was dominated by high-angle grain boundaries(≥ 15°),and the volume fraction of these boundaries decreased with hatch spacing ***,the as-built TiAl alloy sample produced under a spacing of 100 μm exhibited the highest room-and elevated-temperature tensile strengths,with the ultimate tensile strength at room temperature(642 MPa) increasing to 674 MPa at 700 ℃.Furthermore,the mechanism of anomalous strengthening at 700 ℃ was discussed in detail.

关键词： Selective electron beam melting TiAl alloy Hatch spacing Microstructure Tensile property

The Maximum Lagrangian of 5-uniform Hypergraphs without Containing Two Edges Intersecting at a Vertex

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Acta Mathematica Sinica,English Series 2022年第5期38卷 877-889页

作者： Biao WU Yue jian peng MOE-LCSM School of Mathematics and StatisticsHu’nan Normal UniversityChangsha 410081P.R.China School of Mathematics Hu’nan UniversityChangsha 410082P.R.China

Obtaining Turán densities of hypergraph through determining Lagrangian densities have been studied *** showed that the Lagrangian density of an r-uniform hypergraph equals the Turán density of the extension of this ***,Lagrangian density and Turán density are the same for a large class of hypergraphs such as hypergraphs covering *** Pr,sbe the r-uniform hypergraph with two edges intersecting at s *** determined the Lagrangian densities of Pr,sfor r=3 and s=1 or 2,or r=4 and s=2 or *** and Keevash determined for r=3 and s=0,and Bene Watts,Norin and Yepremyan determined for r≥4 and s=*** cases r=5 and s=4 or r=6 and s=5 were determined by Norin and *** showed for r=5,6 or 7,and s=3,4 or 5 *** cases r=4 and s=1 or r=5 and s=2 were determined by jiang,peng and Wu,and Hu,peng and Wu *** r=5,the only remaining case is s=*** this paper,we determine for this case.

关键词： Hypergraph Lagrangian Turán number

Jetting of a near-wall cavitation bubble induced by another tandem bubble

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Journal of Hydrodynamics 2024年第3期36卷 444-456页

作者： Hui Han Jing-zhu Wang jian-lin Huang peng-bo Bai yong-gang Chen Yi-wei Wang Key Laboratory for Mechanics in Fluid Solid Coupling Systems Institute of MechanicsChinese Academy of SciencesBeijing100190China School of Engineering Science University of Chinese Academy of SciencesBeijing100049China Guangdong Aerospace Research Academy Guangzhou511458China School of Future Technology University of Chinese Academy of SciencesBeijing100049China jianghuai Advance Technology Center Hefei230088China

Double bubbles near a rigid wall surface collapse to produce a significant jet impact,with potential applications in surface cleaning and ultrasonic ***,the dynamic behaviors of near-wall bubbles remain *** this study,we investigate the jetting of a near-wall bubble induced by another tandem *** define two dimensionless standoff distances,γ_(1),γ_(2),to represent the distances from the center of the near-wall bubble to the rigid wall and the center of controlling bubble to the center of the near-wall bubble,*** observations reveal three distinct jetting regimes for the near-wall bubble:transferred jetting,double jetting,and directed *** further investigate the jetting mechanism,numerical simulations are conducted using the compressibleInterFoam solver in the open-source framework of OpenFOAM.A detailed analysis shows that the transferred jet flow is caused by the pinch-off resulting from the axial contraction velocity at the lower end of the near-wall bubble being greater than the vertical contraction velocity,leading to a maximum jet velocity of 682.58 m/*** the case of double jetting,intense stretching between the controlling bubble and the wall leads to a pinch-off and a double jetting with a maximum velocity of 1096.29 m/*** directed jet flow is caused by the downward movement of the high-pressure region generated by the premature collapse of the controlling bubble,with the maximum jet velocity reaching 444.62 m/s.

关键词： Jetting of near-wall bubble controlling bubble impact velocity

Experimental Study on New Multi-Column Tension-Leg-Type Floating Wind Turbine

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China Ocean Engineering 2018年第2期32卷 123-131页

作者： ZHAO yong-sheng SHE Xiao-he HE Yan-ping YANG jian-min peng Tao KOU Yu-feng State Key Laboratory of Ocean Engineering Shanghai Jiao Tong UniversityShanghai 200030China Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration(CISSE) Shanghai Jiao Tong UniversityShanghai 200030China Shanghai University of Engineering Science School of ManagementShanghai 201620China

Deep-water regions often have winds favorable for offshore wind turbines, and floating turbines currently show the greatest potential to exploit such winds. This work established proper scaling laws for model tests, which were then implemented in the construction of a model wind turbine with optimally designed blades. The aerodynamic,hydrodynamic, and elastic characteristics of the proposed new multi-column tension-leg-type floating wind turbine(Wind Star TLP system) were explored in the wave tank testing of a 1:50 scale model at the State Key Laboratory of Ocean Engineering at Shanghai Jiao Tong University. Tests were conducted under conditions of still water, white noise waves, irregular waves, and combined wind, wave, and current loads. The results established the natural periods of the motion, damping, motion response amplitude operators, and tendon tensions of the Wind Star TLP system under different environmental conditions, and thus could serve as a reference for further research.

关键词： floating wind turbine model test WindS tar TLP dynamic response

Numerical investigation of the interactions between a laser-generated bubble and a particle near a solid wall

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Journal of Hydrodynamics 2021年第2期33卷 311-322页

作者： jian-yong Yin yong-xue Zhang jian-jun Zhu Liang Lü Shi-da Li College of Mechanical and Transportation Engineering China University of Petroleum-BeijingBeijing 102249China Beijing Key Laboratory of Process Fluid Filtration and Separation China University of Petroleum-BeijingBeijing 102249China School of International Education Hainan Medical UniversityHaikou 571199China Department of Thermal Engineering Chengde Petroleum CollegeChengde 067000China

The interactions between the bubbles and the particles near structures are important issues for the applications of the cavitation in the fluid *** study the hidden microscopic mechanisms,a numerical method for simulating the laser-generated bubble between the solid wall and a particle is developed in this paper with considerations of the viscosities and the compressibility of the gas and the liquid phases,as well as the surface tension between *** gas-liquid interface is tracked by the coupling level set and the volume of fluid(CLSVOF)*** numerical results clearly reveal that the particle can influence the cavitation bubble *** potential damage of the nearby structures is numerically quantified in terms of the wall pressure,which helps better understand the synergetic effects of the particle on the *** effects of three dimensionless parameters on the wall pressure are also investigated,especially,on the peak pressure,namely,γ1(defined as L_(1)/R_(max),where L_(1)is the distance from the center of the initial bubble to the solid wall and R_(max)is the maximum bubble radius),γ_(2)(defined as L_(2)/R_(max),where L_(2)is the distance from the lower surface of the spherical particle to the initial bubble center)andθ(defined as Rp/R_(max),where Rp is the spherical particle radius).Further numerical results show that these parameters play a dominant role in determining the peak *** y_(1)1.00,the peak pressure is caused by the shock *** the increase ofθor decrease ofγ_(2),the peak pressure ***γ_(2)>2.00,the effect of the particle on the bubble behavior can be neglected.

关键词： Cavitation bubble spherical particle coupling level set and the volume of fluid(CLSVOF) solid wall OpenFOAM

*** and synthesis of mesoporous sulfonic acid catalysts

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Science Bulletin 2018年第4期63卷 252-266页

作者： peng Wang Yupei Zhao jian Liu jiangsu key laboratory of advanced catalytic materials and technology school of petrochemical engineeringchangzhou universityChangzhou 213164China advanced catalysis and green manufacturing collaborative innovation center changzhou universityChangzhou 213164China state key laboratory of catalysis ich emdalian institute of chemical physicschinese academy of sciencesDalian 116023China department of chemical and process engineering university of surreyGuildfordSurrey GU2 7XHUK

Mesoporous sulfonic acid catalysts(MSAC) are widely used in acid-catalyzed reactions, including biomass conversions with plenty of polar solvents and precursors. The catalytic efficiency of MSAC is greatly affected by the microenvironment around the sulfonic acid sites. In this review, the progress on modification of microenvironment of MSAC is reviewed over the past decade. Hydrophobic modification allows MSAC prevent the adhesion of water molecules onto sulfonic acid sites, to abate the risk of reduced acid strength and catalytic efficiency. In comparison, hydrophilic properties can bring positive effect on acidcatalyzed reactions with the aid of hydrophilic interaction between polar functional groups on MSAC and hydrophilic groups of specific substrates. Amphiphilic MSAC with tunable wettability for specific substrates and solvents tend to improve the efficiency in certain reactions with mixed solvents or reactants of different polarity, especially for biphasic systems of immiscible liquids. Furthermore, much attention has been attracted on modification of surface to simulate the microenvironment of homogeneous solvents and enzyme biocatalysts in recent research. New trends of this field are also highlighted.

关键词： Mesoporous materialsSulfonic acid catalystsNanoreactorsMicroenvironmentBiomass conversion

A generalized L_2-discrepancy for cubature and uncertainty quantification of nonlinear structures

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Science China(Technological Sciences) 2016年第6期59卷 941-952页

作者： CHEN jian Bing SONG peng Yan State Key Laboratory of Disaster Reduction in Civil Engineering & School of Civil Engineering Tongji University College of Civil Engineering and Architecture Hebei University

The numerical method for multi-dimensional integrals is of great importance, particularly in the uncertainty quantification of engineering structures. The key is to generate representative points as few as possible but of acceptable accuracy. A generalized L2（GL2）-discrepancy is studied by taking unequal weights for the point set. The extended Koksma-Hlawka inequality is discussed. Thereby, a worst-case error estimate is provided by such defined GL2-discrepancy, whose dosed-form expression is available. The characteristic values of GL2-discrepancy are investigated. An optimal strategy for the selection of the representative point sets with a prescribed cardinal number is proposed by minimizing the GL2-discrepancy. The three typical examples of the multi-dimensional integrals are investigated. The stochastic dynamic response analysis of a nonlinear structure is then studied by incorporating the proposed method into the probability density evolution method. It is shown that the proposed method is advantageous in achieving tradeoffs between the efficiency and accuracy of the exemplified problems. Problems to be further studied are discussed.

关键词： Koksma-Hlawka inequality cubature L2-discrepancy nonlinear structure stochastic dynamics