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Evolution of hypersurfaces by the mean curvature minus an external force field

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Science China Mathematics 2007年第2期50卷 231-239页

作者： yan-nan liu huai-yu jian Department of Mathematical Sciences Tsinghua UniversityBeijing 100084China

In this paper, we study the evolution of hypersurface moving by the mean curvature minus an external force field. It is shown that the flow will blow up in a finite time if the mean curvature of the initial surface is larger than some constant depending on the boundness of derivatives of the external force field. For a linear force, we prove that the convexity of the hypersurface is preserved during the evolution and the flow has a unique smooth solution in any finite time and expands to infinity as the time tends to infinity if the initial curvature is smaller than the slope of the force.

关键词： parabolic equation mean curvature flow maximum principle (for tensor) 35K45 53A05

Effects of logjams on river hydrodynamics under inundation conditions

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Journal of Hydrodynamics 2024年第4期36卷 757-771页

作者： huai-jian Bao Ping Wang Wei-jie Wang yu-yan liu Tian-jiao Feng School of Soil and Water Conservation Beijing Forestry UniversityBeijing100091China State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin China Institute of Water Resources and Hydropower ResearchBeijing100048China

Large wood in rivers can lead to accumulations in the river channel, affecting local flow structures, aquatic habitats, and the river’s topography. This plays a crucial role in the ecological restoration of the river. This paper presents flow field measurements downstream of six types of logjams at different flow velocities using acoustic Doppler velocimetry (ADV) for artificially designed engineered logjams. The results indicate that the presence of logjams reduces the flow velocity and increases the turbulent kinetic energy in the wake region, and as the distance downstream increases, the flow velocity and turbulence intensity in the wake region gradually return to the upstream level. The minimum values of normalized flow velocity under different conditions are located in the region of the bottommost logs. The differences in normalized flow velocity at various flow rates are not significant. Jets are less likely to be generated in logjams with larger and more concentrated projection areas, but the strength of the jet is influenced by the physical structure of the logjam (projection area, gap ratio). The flow distribution behind the logjam is primarily influenced by the proportion of the projected area in different regions. Changes in the vertical physical structure of the logjam have minimal effect on the lateral flow distribution. Flow velocity in the gap area (b0) at the bottom of different logjams is influenced by their physical structure. The larger the overall blockage area of the logjams, the larger the flow velocity in the bottom gap area will be. The flow velocity in the bottom gap area of a densely placed logjam is mainly influenced by the gap ratio. The velocity of flow in the gap area can impact the initiation and deposition of sediment near the logjam. However, the internal structure complexity of the logjam does not significantly affect river energy dissipation and flow attenuation. This study broadens the applicability of certain theoretical models a

关键词： Open channel flow engineered logjams nonuniform logs flow structure river ecological restoration

Copolymerization of(10-oxo-10-hydro-9-oxa-10λ~5-phospha-phenanthrene-10-yl)-methyl acrylate with styrene

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Chinese Chemical Letters 2009年第7期20卷 881-884页

作者： Li yan jian Ping liu nan Zhen yu Bin Zheng Department of Polymer Material Dalian University of Technology Dalian 116012 China College of Chemistry and Materials Engineering Wenzhou University Wenzhou 325027 China

A phosphorus-containing monomer （lO-oxo-10-hydro-9-oxa-10λ^5-phosphaphenanthrene-10-yl）-methyl acrylate （MD was copolymerized with styrene to give a potential flame retardant copolymer of high thermal stability. The structures of monomer and copolymer were characterized by FT-IR and ^1H NMR measurements. The reactivity ratios for free-radical of the monomer （M1） and styrene （Mz） were studied. The calculated results are as follows： r1 = 0.225, r2 = 0.503; Q1 = 0.413, e1 = 0.476; azeotropic point = 0.37. TGA and DTG curves indicated that Ml is a potential flame retarding monomer for styrenic polymers. C 2009 yu Bin Zheng. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

关键词： Flame retardant Copolymerization Phosphorus-containing monomer Styrene

Partitioning of heavy metals in the surface sediments of Quanzhou Bay wetland and its availability to Suaeda australis

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Journal of Environmental Sciences 2006年第2期18卷 334-340页

作者： LI yu-hong yan Chong-ling yuAN jian-jun liu Jing-chun CHEN huai-yu HU Jun School of Life Sciences Xiamen University Xiamen 361005 China State Key Laboratory of Marine Environmental Science Xiamen University Xiamen 361005 China iology Department of Quanzhou Normal College Quanzhou 362000 China

In order to investigate distributions of heavy metal pollution in Quanzhou Bay wetland, the total concentration and chemical partitioning of a number of heavy metals （Cu, Zn, Cd, Pb, Cr, Hg） in sediments of three sampling sites of Quanzhou Bay wetland and their availability to Suaeda australis were analyzed. The Geoaccumulation Index （Igeo） values reveal that the sediments of three sampling sites may all be considered as moderately contaminated for Pb and Zn, and all sediments might be strongly contaminated with cadmium. The partitioning analyses revealed the measured heavy metals in three sites are bound to the exchangeable fraction at lower concentrations. The measured metals in a considerable amount are bound to the reducible and oxidizable fractions, and a high proportion of the measured heavy metals were distributed in the residual fraction in the sediment samples. The concentrations of Cd in each chemical phase extracted from the sediments are above natural global background levels and should be further investigated because of its toxicity. Suaeda australis has different accumulation abilities for the measured heavy metals. For the root and stem, the bioaccumulation ability assessed by bioaccumulation factor （BAF） for the measured heavy metals follows the decreasing order as： Cu〉Cr〉 Zn〉Cd, Pb, Hg. In the leaf, stronger bioaccumulation ability for Hg is exhibited. The heavy metal concentrations in Suaeda australis roots have positive correlations with their available fractions, while the exchangeable fraction of Cu and Cd might have be more important to both mature plant roots and seedling roots uptake than other fractions; as for Cr, the oxidizable fraction might make a greater contribution to the plant root uptake; as for Zn, the reducible fraction might make so contribution ; and for Pb, the oxidizable fraction might make a significant contribution to the mature plant root uptake, however, the exchangeable fraction might have a significant contribution to th

关键词： bioavailability geoaccumulation factor partitioning heavy metals Suaeda australis sediment Quanzhou Bay wetland

Precipitates and corrosion resistance of an Al-Zn-Mg-Cu-Zr plate with different percentage reduction per passes

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Rare Metals 2018年第5期37卷 381-387页

作者： yu-Hao liu Liang-Ming yan Xiao-Hu Hou Dong-nan Huang jian-Bo Zhang jian Shen School of Materials Science and Engineering Inner Mongolia University of Technology Institute of Engineering and Research Jiangxi University of Science and Technology State Key Laboratory of Nonferrous Metals and Processes General Research Institute for Nonferrous

7055 aluminum alloy plates with the same size were rolled by two processes： small percentage reduction per pass （PRPP） and large percentage reduction per pass, respectively. Meanwhile, the effect of PRPP on the precipitates and corrosion resistance of 7055 aluminum alloy plate was investigated. The mechanisms were analyzed and discussed by optical microscopy （OM）, transmission electron microscopy （TEM）, high-resolution transmission electron microscopy （HRTEM） and electron back-scattered diffraction （EBSD） technique. Large PRPP can improve the corrosion resistance. For the plate rolled by small PRPP, the main precipitate is guinier-preston （GP） zone and continuous grain boundary precipitates （GBPs）, while, for the plate rolled by large PRPP, the main precipitates are the GP zone and η precipitate, and the GBPs are discontinuous.

关键词： 7055 aluminum alloy Microstructure Rolling Corrosion resistance

Direct chemical vapor deposition growth of graphene on Ni particles using solid carbon sources

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Rare Metals 2021年第8期40卷 2275-2280页

作者： Feng Zheng Ying liu Cai-Li Zhang jian Wang nan Dong Pei-De Han yan-Xia Wu yu-Cheng Wu College of Materials Science and Engineering Taiyuan University of TechnologyTaiyuan030024China Institute of New Carbon Materials Taiyuan University of TechnologyTaiyuan030024China

Graphene has attained a considerable amount of popularity as an attractive ultra-thin reinforcement for nickel(Ni)matrix composites in recent ***,its excellent reinforcement efficiency is suffered from the agglomeration of graphene nanosheets in manufacturing process and the poor bonding strength of graphene with Ni *** overcome these two problems,one of the efficient strategies is to in-situ grow graphene reinforcements on Ni particles for powder *** work aims to synthesize uniform graphene@Ni composite particles by using polymethyl methacrylate(PMMA)as the solid sources for chemical vapor deposition(CVD)*** results demonstrate that few-layer or multilayer graphene with different morphologies can be grown on the particles by controlling the PMMA content and annealed temperature,*** optimum condition for the formation of high-quality few-layer graphene is 1.0 mg·ml^(-1) PMMA and 900℃.A competition mechanism rises from the growth kinetic,and the spatial confinement effect has led to the formation of graphene with different microstructures and morphologies.

关键词： Graphene Ni particles Solid carbon sources Growth mechanism

Number concentration and size distributions of submicron particles in Jinan urban area:Characteristics in summer and winter

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Journal of Environmental Sciences 2007年第12期19卷 1466-1473页

作者： GAO jian WANG Jin CHENG Shu-hui XUE Li-kun yan huai-zhong HOU Lu-jian jianG yu-quan WANG Wen-xing Environment Research Institute Shandong University Jinan 250100 China Environment Monitoring Station of Jinan Shandong Province Jinan 250014 China Shandong Technical College of Labor and Vocation Shandong Province Jinan 250022 China

The aerosol number concentration and size distribution were measured with the newly developed Wide-range Particle Spectrometer in summer and winter of 2006 at the urban site of Jinan City. Here reported the characteristics of fine particles of the different observation seasons. Relative high number concentrations for the particles in the diameter range of 10-500 nm were observed in both seasons. It was found that the dominant number distributed in particle diameter smaller than 100 nm and the percentage over the number concentration of all air particles is much higher than what has been measured in other urban sites over the world. The number mean diameter in summer was much smaller than in winter, strongly suggesting the different origin of ultrafine particles in different seasons. That is, particles in ultrafine mode mainly came from nucleation and new particle formation in summer while from traffic emission in winter. The diurnal variation also supported this point. Number concentration in the diameter range of 10-200 um got their peak values at noontime, well correlated with the mixing ratio of SO2 and the intensity of solar radiation in summer. While in winter, those in the same diameter range showed the main peaks during the traffic hours happened in the morning and evening.

关键词： number concentration size distribution seasonal variation diurnal variation

The Role of the AMPK Pathway in ZEA-induced Cellcycle Arrest in Rat Sertoli Cells

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Biomedical and Environmental Sciences 2019年第12期32卷 944-948页

作者： CHEN yu Lian CHEN Yong Fang FENG nan nan liu Zong Ping BIAN jian Chun College of Veterinary Medicine Yangzhou UniversityYangzhou 225009JiangsuChina jiangsu Co-innovation Center for Preve ntion and Control of Imports nt An imal In fectious Diseases and Zoonoses Yan gzhou 225009Jia ngsuChina

Zearalenone(ZEA),a non-steroidal estrogen-like mycotoxin biosynthesized by several Fusarium species through the polyketide pathway,is also known as the F-2 toxin[1].ZEA is one kind of common mycotoxins frequently found in feed ingredients and compound feed that can specifically and competitively bind to estrogen receptors resulting in sexual hormone disorder which can negatively affectthe expressi on of sec on dary sexual characteristics[2].

关键词： competitive cycle steroidal

A Single Central Pattern Generator for the Control of a Locomotor Rolling Wave in Mollusc Aplysia

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Research 2023年第3期2023卷 711-726页

作者： Hui-Ying Wang Ke yu Zhe yang Guo Zhang Shi-Qi Guo Tao Wang Dan-Dan liu Ruo-nan Jia yu-Tong Zheng yan-nan Su Yi Lou Klaudiusz RWeiss Hai-Bo Zhou Feng liu Elizabeth C.Cropper Quan yu jian Jing State Key Laboratory of Pharmaceutical Biotechnology Institute for Brain SciencesChinese Academy of Medical Sciences Research Unit of Extracellular RNAJiangsu Engineering Research Center for MicroRNA Biology and BiotechnologyAdvanced Institute for Life SciencesChemistry and Biomedicine Innovation CenterSchool of Life SciencesNanjing UniversityNanjingJiangsu 210023China National Laboratory of Solid State Microstructures Department of PhysicsInstitute for Brain Sciencesand Collaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjingJiangsu 210093China Department of Neuroscience and Friedman Brain Institute Icahn School of Medicine at Mount SinaiNew YorkNY 10029USA School of Electronic Science and Engineering Nanjing UniversityNanjingJiangsu 210023China Peng Cheng Laboratory Shenzhen 518000China

Locomotion in mollusc Aplysia is implemented by a pedal rolling wave,a type of axial ***-studied examples of axial locomotion(pedal waves in Drosophila larvae and body waves in leech,lamprey,and fish)are generated in a segmented nervous system via activation of multiple coupled central pattern generators(CPGs).Pedal waves in molluscs,however,are generated by a single pedal ganglion,and it is unknown whether there are single or multiple CPGs that generate rhythmic activity and phase shifts between different body *** locomotion in intact Aplysia,bursting activity in the parapedal commissural nerve(PPCN)was found to occur during tail contraction.A cluster of 20 to 30 P1 root neurons(P1Ns)on the ventral surface of the pedal ganglion,active during the pedal wave,were *** cluster analysis revealed that there are 2 phases to the motor program:phase I(centered around 168°)and phase II(centered around 357°).PPCN activity occurs during phase *** majority of P1Ns are *** P1Ns tend to be electrically *** classes of pedal interneurons(PIs)were *** 1(PI1 and PI2)is active during phase *** axons make a loop within the pedal ganglion and contribute to locomotor pattern *** are electrically coupled to P1Ns that fire during phase *** 2(PI3)is active during phase II and innervates the contralateral pedal ***3 may contribute to bilateral ***,our findings support the idea that Aplysia pedal waves are generated by a single CPG.

关键词： phase cluster pattern