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AFM study on the adsorption and aggregation behavior of dissolved humic substances on mica

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Science china Chemistry 2006年第3期49卷 256-266页

作者： GE Xiaopeng1, ZHOU Yanmei2. Lü Chunhua1 & TANG Hongxiao1 1. State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, beijing 100085, china {2., beijing jiaotong university, beijing 1.0044, china State Key Laboratory of Environmental Aquatic Chemistry Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing China school of civil {2. & architecture Beijing Jiaotong University Beijing China

Humic substances constitute the major organic fractions of soils, sediments and natural waters, and play a dominant role in the binding, mobilization, transport and ultimate fate of organic contaminants in subsurface systems. In this paper, two humic acid samples, Guanting and Tianjin, with different origin and chemical compositions have been investigated with AFM imaging for their adsorption and aggregation behaviors on mica. While the Tianjin humic sample is found to form small spheres with 2.0 to 330 nm in diameter at lower concentrations, irregular loop-chain assemblies of hundreds of nanometer in diameter with the chain width of about 40 nm are dominant for the Guanting humic sample, which may attribute to the more polar aliphatic fractions in the chemical composition in the latter. The heterogeneous and polydisperse nature of humic substances with multiple structural features, such as sponge-like structures, perforated sheets, aggregate of spheres, branches and chain-like assemblies etc., is apparent at higher concentrations for both humic samples, showing morphologically new evidence for the dominant view of the humic dual-mode sorption model. With naphthalene introduced, the assemblies of Guanting humic substances clearly become more compact with significantly narrowed branches and less porous the perforated sheet-like structures. It is indica- tive of that smaller nanometer scale rings present along the perforated assemblies could potentially represent hydrophobic domains, which may facilitate the adsorption and aggregation of naphthalene onto the natural particle surfaces and therefore lead to an important role of dissolved humic sub- stances in the sorption of environmental pollutants.

关键词： atomic force microscopy (AFM) dissolved humic substances morphology aggregation adsorption

On time-step in structural seismic response analysis under ground displacement/acceleration

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Earthquake engineering and engineering Vibration 2009年第3期8卷 341-347页

作者： TianYuji~+ and Yang Qingshan~(++) school of civil {2.,beijing jiaotong university,beijing 1.0044,china +Associate Professor ++Professor school of civil {2. Beijing Jiaotong University Beijing China

There are two models in use today to analyze structural responses when subjected to earthquake ground motions, the Displacement Input Model （DIM） and the Acceleration Input Model （AIM）. The time steps used in direct integration methods for these models are analyzed to examine the suitability of DIM. Numerical results are presented and show that the time-step for DIM is about the same as for AIM, and achieves the same accuracy. This is contrary to previous research that reported that there are several sources of numerical errors associated with the direct application of earthquake displacement loading, and a very small time step is required to define the displacement record and to integrate the dynamic equilibrium equation. It is shown in this paper that DIM is as accurate and suitable as, if not more than, AIM for analyzing the response of a structure to uniformly distributed and spatially varying ground motions.

关键词： integration time step multi-supported structure displacement input model acceleration input model spatially varying ground motions

A geometrical and physical nonlinear finite element model for spatial thin-walled beams with arbitrary section

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Science china(Technological Sciences) 2010年第3期53卷 829-838页

作者： YANG QingShan 1 &WANG XiaoFeng 2.1 school of civil {2.,beijing jiaotong university,beijing 1.0044,china 2.College of civil {2.,Tongji university,Shanghai 2.0092.china school of civil {2. Beijing Jiaotong University Beijing China College of civil engineering Tongji University Shanghai China

Based on the theories of Bernoulli-Euler beams and Vlasov's thin-walled members,a new geometrical and physical nonlinear beam element model is developed by applying an interior node in the element and independent interpolations on bending angles and warp,in which factors such as traverse shear deformation,torsional shear deformation and their coupling,coupling of flexure and torsion,and second shear stress are all ***,geometrical nonlinear strain in total Lagarange(TL) and the corresponding stiffness matrix are *** plastic model is applied to physical nonlinearity to comply with the yield rule of Von Mises and incremental relationship of *** stiffness matrix is derived by numerical integration on the basis of the finite segment *** show that the developed model is feasible in analysis of thin-walled structures with high accuracy.

关键词： Spatial beams thin-walled structures geometrical and physical nonlinearity finite element arbitrary section

A new seismic isolation system and its feasibility study

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Earthquake engineering and engineering Vibration 2010年第1期9卷 75-82页

作者： Jia Gaofeng~+ and Shi Zhifei~(++) school of civil {2.,beijing jiaotong university,beijing 1.0044,china Graduated Student ++ Professor school of civil {2. Beijing Jiaotong University Beijing China

This paper introduces a new seismic isolation system called a periodic foundation （PF）, where inclusions are periodically arranged. The PF is different from traditional base isolation in that it causes a fundamental frequency shift in the structure, thus reducing its response and generating a frequency gap. If the frequency contents of a seismic wave fall into the gap, it can not propagate in the foundation. Thus, it will exert no influence on the structure above. A systematic study of the band of frequency gap for a 2. PF is conducted. The influence of physical and geometrical parameters such as density and elastic modulus as well as filling fraction of the PF and its materials on the band of frequency gap are investigated, and a design with a frequency gap as low as 2.49-3.72.Hz is achieved. This band of frequency gap corresponds well to the design spectra in earthquake engineering. Numerical simulations of a six-story frame structure with different foundations demonstrate that a proposed PF can greatly reduce the seismic response of an isolated structure. This investigation shows that PFs have great potential in future applications of seismic isolation technology.

关键词： seismic isolation periodic foundation band of frequency gap

A note on the derivation of the derivatives of invariants of stretch tensor to the right Cauchy-Green tensor

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Progress in Natural Science:Materials International 2006年第1期16卷 96-99页

作者： TIAN Dongyan, JIN Ming and DUI Guansuo (Institute of engineering Mechanics, school of {2. engineering and architecture, beijing jiaotong university, beijing 1.0044, china) Institute of engineering Mechanics School of Civil Engineering and Architecture Beijing Jiaotong University Beijing 100044 China

A new approach for the derivation of the principal invariants of the stretch tensor with respect to the right Cauchy- Green tensor is presented in this paper. According to the definition of the derivation of tensor function, the three first-order derivatives for the principal invariants of the stretch tensor are obtained through derivation directly to the right Cauchy-Green tensor by incremental method. Then the three second-order derivatives are yielded by the derivation to the right Cauchy-Green strain tensor directly. Furthermore, an explicit expression of the tangent modulus of the general Varga material is given as an example.

关键词： continuum mechanics invariant strain energy tangent modulus.

CRITERION FOR JUDGING SATISFACTION OF CONSISTENCY CONDITIONS IN RATE-DEPENDENT CONSTITUTIVE RELATIONS

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Acta Mechanica Solida Sinica 1999年第4期12卷 356-364页

作者： Wang Zhe (College of civil engineering and {2.,Northern jiaotong university,beijing 1.0044,china) Coll. of Civ. Eng. and architecture Northern Jiaotong University Beijing 100044 China

Based on irreversible thermodynamics, the criterion for judging the satisfaction of consistency conditions in rate-dependent constitutive relationship is deduced by introducing four basic hypotheses. Formulas for solving internal variables are given. It makes the rate-dependent model applicable no matter whether the consistency conditions can be satisfied or not.

关键词： rate-dependent constitutive relations consistency condition irreversible thermodynamics

Optimization of Regulation Valve Location for Heating System

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湖南大学学报（自然科学版） 2009年第S1期36卷 88-90页

作者： LIU Ling-ling,CHEN Hong-bing,LI De-ying(school of Environment and Energy engineering,{2. university of civil engineering and architecture,{2. 1.0044,china) school of Environment and Energy engineering Beijing University of Civil Engineering and Architecture Beijing 100044 China

This paper mainly studied how to determine the best location of the self-operated flow control valve at the heating system *** the location of regulating valve directly affects the pipe network performance,the simulation and analysis of pressure change in heating system was carried out with Computational Fluid Dynamics(CFD)*** study shows the best location of regulating valve varies with the change of the supply and return pipe length when the heating area of each user is small,and when the heating area of each user is large(2.000 000～3 000 000 m2.,the best location is on the supply pipe.

关键词： regulating valve optimization CFD simulation

THEORETICAL STUDIES ON MICROBUCKLING MODE OF ELASTIC MEMORY COMPOSITES

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Acta Mechanica Solida Sinica 2010年第1期23卷 20-28页

作者： Zhengdao Wang Zhengfa Li Zhiyuan Xiong Linyun Wang(Department of Mechanics,school of civil {2.,beijing jiaotong university,beijing 1.0044,china) Department of Mechanics School of Civil Engineering Beijing Jiaotong University Beijing China

Elastic memory composites （EMCs） have great potential applications in future deployable space structures due to their high packaging strain and shape memory characteristics. Microbuckling of compressed fibers is the primary deformation mechanism of such structures to receive a higher packaging strain than that of traditional fiber-reinforced composites. In order to have a better understanding of such deformation mechanism, the microbuckling model of EMC laminates under bending is analyzed firstly. Then the theoretical critical microbuckling parameters are predicted, which are compared with experimental observations and other models.

关键词： elastic memory composite deployable structure microbuckling model

NONEL High Precision MS Delay Detonator

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Journal of university of Science and Technology beijing 2001年第3期8卷 164-166页

作者： Daze Lin, Peng Yang civil and Environmental engineering {2., university of Science and Technology beijing, beijing 100083, china civil and Environmental Eng. school Univ. of Science and Tech. Beijing Beijing 100083 China

The NONEL high precision MS Delay Detonator (FDG-1detonator) is introduced. The main aspects about the FDG-1 detonator include the choice of structure, delay composition, control of the gas chamber, optimum charge and density, suitable explosives per meter in the NONEL tube, base firing charge and the main specifications. The improvement of the characteristics of FDG-1 detonator has been tested systematically. The testing method is reliable and its precision can meet the demand for usage.

关键词： NONEL high precision MS Delay Detonator delay time