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Three-dimensional unstructured-mesh eutrophication model and its application to the Xiangxi River,China

Journal of Environmental Sciences 2012年第9期24卷 1569-1578页

作者： Jian li Danxun li Xingkui wang State Key Laboratory of Hydroscience and Engineering Department of Hydraulic Engineering Tsinghua University Beijing 100084 China

The Xiangxi River is one of the main tributaries in the Three Gorges reservoir, with the shortest distance to the Three Gorges Project Dam. Severe and frequent algal bloom events have occurred frequently in the Xiangxi River in recent years. Therefore, the current study develops a three-dimensional unstructured-mesh model to investigate the dynamic process of algal bloom. The developed model comprises three modules, namely, hydrodynamics, nutrient cycles, and phytoplankton ecological dynamics. A number of factors, including hydrodynamic condition, nutrient concentration, temperature, and light illumination, that would affect the evolution of phytoplankton were considered. Moreover, the wave equation was used to solve the free surface fluctuations and vertical Z-coordinates with adjustable layered thicknesses. These values, in turn, are suitable for solving the algal bloom problems that occurred in the fiver style reservoir that has a complex boundary and dramatically changing hydrodynamic conditions. The comparisons between the modeling results and field data of years 2007 and 2008 indicate that the developed model is capable of simulating the algal bloom process in the Xiangxi River with reasonable accuracy. However, hydrodynamic force and external pollution loads affect the concentrations of nutrients, which, along with the underwater light intensity, could consequently affect phytoplankton evolution. Thus, flow velocity cannot be ignored in the analysis of fiver algal bloom. Based on the modeling results, building an impounding reservoir and increasing the releasing discharge at appropriate times are effective ways for controlling algal bloom.

关键词： unstructured-mesh model algal bloom phytoplankton Xiangxi River

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On the energy conservation and critical velocities for the propagation of a "steady-shock" wave in a bar made of cellular material

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Acta Mechanica Sinica 2013年第3期29卷 420-428页

作者： li-li wang li-Ming Yang Yuan-Yuan Ding Mechanics and Material Science Research Center Ningbo University

The propagation of shock waves in a cellular bar is systematically studied in the framework of continuum solids by adopting two idealized material models, viz. the dynamic rigid, perfectly plastic, locking （D-R-PP-L） model and the dynamic rigid, linear hardening plastic, locking （D-R-LHP-L） model, both considering the effects of strain-rate on the material properties. The shock wave speed relevant to these two models is derived. Consider the case of a bar made of one of such material with initial length L 0 and initial velocity v i impinging onto a rigid target. The variations of the stress, strain, particle velocity, specific internal energy across the shock wave and the cease distance of shock wave are all determined analytically. In particular the ＂energy conservation condition＂ and the ＂kinematic existence condition＂ as proposed by Tan et al. （2005） is re-examined, showing that the ＂energy conservation condition＂ and the consequent ＂critical velocity＂, i.e. the shock can only be generated and sustained in R-PP-L bars when the impact velocity is above this critical velocity, is incorrect. Instead, with elastic deformation, strain-hardening and strain-rate sensitivity of the cellular materials being considered, it is appropriate to redefine a first and a second critical impact velocity for the existence and propagation of shock waves in cellular solids. Starting from the basic relations for shock wave propagating in D-R-LHP-L cellular materials, a new method for inversely determining the dynamic stress-strain curve for cellular materials is proposed. By using e.g. a combination of Taylor bar and Hopkinson pressure bar impact experimental technique, the dynamic stress-strain curve of aluminum foam could bedetermined. Finally, it is demonstrated that this new formulation of shock theory in this one-dimensional stress state can be generalized to shocks in a one-dimensional strain state, i.e. for the case of plate impact on cellular materials, by simply making proper

关键词： Cellular solids 1D shock theory D-R-PP-L model D-R-SHP-L model Energy conservation across shock Critical velocities

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High Performance Long Chain Polyamide/Calcium Silicate Whisker Nanocomposites and the Effective Reinforcement Mechanism

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Chinese Journal of Polymer Science 2016年第8期34卷 991-1000页

作者： li-li wang 董侠 Xing-rui wang Gan-yu Zhu Hui-quan li Du-jin wang Beijing National Laboratory for Molecular Sciences CAS Key Laboratory of Engineering PlasticsInstitute of ChemistryChinese Academy of SciencesBeijing 100190China Key Laboratory of Green Process and Engineering and National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China

PA1012/calcium silicate whisker nanocomposites with contents of whisker ranging from 10 wt% to 40 wt%, are prepared by twin screw extruder without any additions of coupling agent. The effect of whisker on the matrix is analyzed by the studies of morphology, the mechanical properties, water absorption and thermal stabilities. SEM micrographs obviously demonstrate, even under the high filler content of 40 wt% and without surface treatment, calcium silicate whisker can be homogeneously dispersed in polyamide, directly leading to the enhanced mechanical properties. The mechanism of higher efficiency of reinforcement is needle-like shape whisker, having access to be intercalated, and mutual affinity caused by hydrogen bonding interaction between carbonyl group in polyamide chain and hydroxyl group in whisker surface. Both aspects attach matrix with excellent stress-transfer properties. In addition, with the assistance of whisker, the nanocomposite favors an improved water absorption as well as thermal stability, which is intimately associated with physical performance.

关键词： PA1012 Calcium silicate whisker No coupling agent Homogeneous dispersion Enhanced properties.

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Numerical investigation of breakup process of molten blast furnace slag through air quenching dry granulation technique

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Journal of Iron and Steel Research International 2021年第1期28卷 10-18页

作者： li-li wang Yu-zhu Zhang Yue Long College of Metallurgy and Energy North China University of Science and TechnologyTangshan 063210HebeiChina

Molten slag is broken up by supersonic air into droplets through the air quenching dry slag granulation *** breakup process of blast furnace slag directly determines the droplet diameter and the waste heat *** order to gain deep insight into the granulation mechanism and visualize the breakup process,three-dimensional unsteady numerical simulation based on the k-x based shear stress transport turbulence model was conducted to simulate the transient breakup process of molten slag(k is the turbulent kinetic energy,and x is the specific dissipation rate).The coupled level-set and volume-of-fluid method was utilized to capture the sharp air–liquid *** results show that a flat film is formed firstly under the effects of air impingement,recirculation zone and pressure ***,the axial wave and the spanwise wave appear simultaneously and the film is broken up into ligaments owing to the generation of vortex and hole structure at the intersection of axial trough and spanwise ***,the ligaments are broken up into droplets owing to Rayleigh–Taylor instability at the air–liquid *** droplets smaller than 3.00 mm account for 80%,with the average diameter of 1.95 mm.

关键词： Breakup process Granulation mechanism Molten slag Air quenching Computational fluid dynamics

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Chemical Constituents of Siegesbeckia orientalis L.

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Journal of Integrative Plant Biology 2006年第8期48卷 991-995页

作者： li-li wang li-Hong Hu Shanghai Research Center for Modernization of Traditional Chinese Medicine Shanghai Institute of Materia Medica Shanghai Institutes for Biological Sciences the Chinese Academy of Sciences Shanghai 201203 China School of Pharmacy East China University of Science and Technology Shanghai 200237 China

The aerial parts of Siegesbeckia have been used as the traditional Chinese medicine in the treatment of rheumatic arthritis, hypertension, malaria, neurasthenia, and snakebite. In order to find new and bioactive compounds, the chemical constituents of the aerial parts of S. orientalis L. were investigated and two new compounds, namely β-D-glucopyranosyl-ent-2-oxo-15,16-dihydroxy-pimar-8（14）-en-19-oic-late （compound 1 ） and [1 （10） E,4Z]-8β-angeloyloxy-9α-methoxy-6α, 15-dihydroxy-14-oxogermacra-1 （10）,4,11 （13）-trien-12-oic acid 12,6-1actone （compound 2）, as well as five known ent-pimarane diterpenes （compounds 3-7） were isolated. The structures of the two new compounds were identified by their physicochemical properties and spectral analysis, particularly oneand two-dimensional nuclear magnetic resonance spectral methods.

关键词： ent-pimarane diterpenoids melampolide Siegesbeckia orientalis.

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On Finite Groups with Some Semi Cover-Avoiding Subgroups

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Acta Mathematica Sinica,English Series 2007年第9期23卷 1689-1696页

作者： Xiu Yun GUO li li wang Department of Mathematics Shanghai University Shanghai 200444 P. R. China

A subgroup H of a finite group G is said to have the semi-cover-avoiding property in G if there is a chief series of G such that H covers or avoids every chief factor of the series. In this paper, some new results are... 详细信息

关键词： semi-cover-avoidance property fitting subgroups supersolvable groups

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Microstructure and embrittlement of the fine-grained heat-affected zone of ASTM4130 steel

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International Journal of Minerals,Metallurgy and Materials 2011年第4期18卷 419-423页

作者： li-ying li Yong wang Tao Han Chao-wen li College of Mechanical and Electronic Engineering China University of Petroleum Dongying 257061 China

The mechanical properties and microstructure features of the fine-grained heat-affected zone（FGHAZ） of ASTM4130 steel was investigated by optical microscope（OM）,scanning electron microscope（SEM）,transmission electron microscope（TEM）,and welding thermal simulation *** is found that serious embrittlement occurs in the FGHAZ with an 81.37% decrease of toughness,compared with that of the base *** analysis reveals that the FGHAZ is mainly composed of acicular,equiaxed ferrite,granular ferrite,martensite,and martensite-austenite（M-A） *** FGHAZ embrittlement is mainly induced by granular ferrite because of carbides located at its boundaries and ***,the existence of martensite and M-A constituent,which distribute in a discontinuous network,is also detrimental to the mechanical properties.

关键词： ASTM4130 steel welding heat-affected zone microstructure embrittlement

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Flame-retardant Coating by Alternate Assembly of Poly(vinylphosphonic acid) and Polyethylenimine for Ramie Fabrics

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Chinese Journal of Polymer Science 2014年第3期32卷 305-314页

作者： li-li wang Tao Zhang Hong-qiang Yan 彭懋 Zheng-ping Fang Yan li wang Hao MOE Key Laboratory of Macromolecular Synthesis and Functionalization Institute of Polymer CompositesZhejiang University Laboratory of Polymer Materials and Engineering Ningbo Institute of TechnologyZhejiang University School of Aerospace Engineering and Applied Mechanics Tongji University Centre of Excellence in Engineered Fibre Composites University of Southern Queensland

A novel intumescent flame retardant coating, consisting of poly（vinylphosphonic acid）（PVPA） as the acid source and branched polyethylenimine （BPEI） as the blowing agent, was constructed on the surface of ramie fabrics by alternate assembly to remarkably improve the flame retardancy of ramie. The PVPA/BPEI coating on the surface of individual fibers of ramie fabric pyrolyzes to form protective char layer upon heating/burning and improves the flame retardancy of ramie. Thermogravimetric analysis reveals that the PVPA/BPEI-coated ramie fabrics left as much as 25.8 wt% residue at 600 ~C, while the control （uncoated） fabric left less than 1.4 wt% residue. Vertical flame test shows that all PVPA/BPEI-coated fabrics have shorter after-flame time, and the residues well preserved the original weave structure and fiber morphology, whereas, the uncoated fabric left only ashes. Microscale combustion calorimetry shows that the PVPA/BPEI coatings greatly reduce the total heat release by as much as 66% and the heat release capacity by 76%, relative to those of the uncoated fabric.

关键词： Alternative assembly Poly(vinylphosphonic acid) Flame retardant Ramie fabric.

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BOUNDING PYRAMIDS AND BOUNDING CONES FOR TRIANGULAR BEZIER SURFACES

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Journal of Computational Mathematics 2000年第6期18卷 609-620页

作者： Jian-song Deng Fa-lai Chen li-li wang Department of Mathematics University of Science and Technology of ChinaHefei 230026China Information Center of Bengbu Bengbu 233000China

This paper describes practical approaches on how to construct bounding pyramids and bounding cones for triangular Bezier surfaces. Examples are provided to illustrate the process of construction and comparison is made between various surface bounding volumes. Furthermore, as a starting point for the construction, we provide a way to compute hodographs of triangular Bezier surfaces and improve the algorithm for computing the bounding cone of a set of vectors. [ABSTRACT FROM AUTHOR]

关键词： triangular Bezier surface patch hodograph bounding pyramid bounding cone

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Changes in sea surface temperature in western South China Sea over the past 450 ka

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Chinese Science Bulletin 2009年第18期54卷 3335-3343页

作者： li li wang Hui li JianRu ZHAO MeiXun wang PinXian State Key Laboratory of Marine Geology Tongji University Shanghai 200092 China

Sea surface temperature over the past 450 ka was obtained by the unsaturation of molecular fossil-long chain alkenone with a resolution of about 1 ka from the western South China Sea. This is the longest temperature profile in the South China Sea at such high resolution. The U3k7′-SST results revealed similar glacial-interglacial cycles as the δ18O profile of planktonic foraminifera, with SST variability of 23―25.5℃ for glacial and 25―28℃ for interglacial periods. The highest SST (28.4℃) was recorded at MIS5.5 and lowest SST (22.6℃) during MIS2. The SST record preceded the planktonic foraminiferal δ18O on five glacial-interglacial transitions. Comparison of temperature records from the Southern and Northern Hemispheres indicated a more Southern Hemisphere-like pattern for the temperature variation in the SCS. Strong precession and semiprecession signals in the spectra of our SST record manifest the tropical phenomena.

关键词：华南西部海表温度中国浮游有孔虫海温变化海上间冰期表面温度

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