检索结果-南通市图书馆

A mathematical model for solid liquid and mass transfer coupling and numerical simulation for hydraulic fracture in rock salt

在线全文

学校读者我要写书评

暂无评论

progress in Natural science:Materials International 2005年第8期15卷 742-748页

作者： LIANG Weiguo 1,2* and ZHAO Yangsheng1(1. Mining technology institute, Taiyuan university of technology, Taiyuan 030024, china 2. rock and Soil Mechanics institute, Chinese Academy of sciences, Wuhan 430071, china) Mining technology institute Taiyuan University of Technology Taiyuan 030024 China. rock and Soil Mechanics institute Chinese Academy of Sciences Wuhan 43007! China

The hydraulic fracture in rock salt is a complicated solid fluid and mass transfer coupling process. Through theoretical analysis, a solid fluid and mass transfer coupling mathematical model of hydraulic fracture in rock salt is established in this work, and numerical simulations are carried out with the model. The simulation results indicate that rock salt cracks in the typical way of wing-crack(or tensile crack) during the fracture, and the relation of fracture aperture (w) with expanding distance (x) and fracture time (t) is w=(0.0034+0.0006t)e (0.0007+0.0018t)x. Furthermore, it has been found that both the water pressure in the crack and the expanding velocity of the crack decrease gradually as a result of the influence of salt dissolving during fracturing. These numerical simulations well illustrate the process of hydraulic fracture in rock salt and are significantly meaningful in engineering practice.

关键词： rock salt hydraulic fracture solid liquid and mass transfer coupling mathematical model numerical simulation.

Early Hydration of Composite Cement with Thermal Activated Coal Gangue

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Wuhan university of technology(Materials science) 2010年第1期25卷 162-166页

作者：郭伟 Department of Material Engineering Yancheng Institute of Technology institute of Material science and Engineering Nanjing University of Technology

Composite cement samples were prepared by mixing clinker, gypsum with burnt coal gangues which was calcined at various temperatures. The mechanical strength and Ca（OH）2 content in the cement paste were tested, and the paste composition and microstructure were analyzed by thermogravimetry-differential thermal analysis （TG-DSC）, X-ray diffraction（XrD）, scanning electronic microscopy （SEM） and pore structure analysis. results demonstrate that the thermal activated coal gangue could accelerate the early hydration of cement clinker obviously, which promotes the gangue hydration itself. The early hydrated products of the cement are C-S-H gel, Ca（OH）2 and AFt. The cement with 30% （in mass） the gangue exhibits higher mechanical strength, and among all the cement samples the one with the gangue burnt at 700 ℃ displays the highest hydration rate, mechanical strength, the most gel pores and the lowest total porosity.

关键词： blended cement hydration microstructure hydration product

A Theoretical Study on pyrolysis and Sensitivity of Energetic Compounds(Ⅴ)──Nitro Derivatives of Methylbenzene

在线全文

学校读者我要写书评

暂无评论

Chemical research in Chinese Universities 2000年第1期16卷 21-30页

作者： GU Zhi-ming FAN Jian-fen XIAO He-ming and DONG Hai-shan (Department of Chemistry, nanjing university of science and technology, nanjing 210094, p. r. china Department of Chemistry, Suzhou university, Suzhou 215006, p. r. china institute of Chemical M 南京理工大学江苏南京 210094 苏州大学江苏苏州 215006 中国工程物理研究院化工材料所四川绵阳 610003

UHF-SCF-AM1 MO calculations were performed for two kinds of pyrolysis reactions of seven nitro derivatives of methylbenzene(homolysis reactions by the rupture of bond C-NO_2 into radicals and isomerization reactions in the way of methyl H transferring to the ortho nitro O atom). The molecular geometries of the reactants, the transition states and the products of the fourteen reactions were fully optimized. The activation energies for these two kinds of reactions have been obtained. The results indicate that this category of compounds is more easily pyrolyzed by being initiated via isomerization reactions. A parallel relationship exists between the activation energy of the isomerization reactions and the impact sensitivity of the seven titled compounds.

关键词： Nitro derivatives of toluene pyrolysis reaction UHF-SCF-AM1 MO calculation

The steady-state solution of dendritic growth from the undercooled binary alloy melt with the far field flow

在线全文

学校读者我要写书评

暂无评论

science china(Technological sciences) 2009年第8期52卷 2280-2287页

作者： CHEN MingWen1,2, WANG ZiDong2 & XU JianJun2,3,4 1 School of Applied sciences, university of science and technology Beijing, Beijing 100083, china 2 School of Materials science and Engineering, university of science and technology Beijing, Beijing 100083, china 3 School of Mathematical sciences, Nankai university, Tianjin 300071, china 4 Department of Mathematics and Statistics, McGill university, Montreal H3A 2K6, Canada School of Applied sciences University of Science and Technology Beijing Beijing 100083 China School of Materials science and Engineering University of Science and Technology Beijing Beijing 100083 China School of Mathematical sciences Nankai University Tianjin 300071 China Department of Mathematics and Statistics McGill University Montreal H3A 2K6 Canada

The steady-state dendritic growth from the undercooled binary alloy melt with the far field flow is considered. By neglecting the interface energy, interface kinetics and buoyancy effects in the system, we obtaine the steady-state solution for the case of the large Schmidt number, in terms of the multiple variable expansion method. The changes of the temperature and concentration fields, the morphology of the interface, the normalization parameter and the peclet number of the system induced by uniform external flow are derived. The results show that, compared with the system of dendritic growth from undercooled pure melt, the convective flow in the system of growth from undercooled binary alloy has stronger effects on the morphology of the interface. Nevertheless, the shape of the interface still remains nearly a paraboloid.

关键词： binary alloy melt convection dendritic growth interfaces steady-state solution multiple variable expansion method

Structure and pozzolanic Activity of Calcined Coal Gangue during the process of Mechanical Activation

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan university of technology(Materials science) 2009年第2期24卷 326-329页

作者：郭伟 Department of Material Engineering Yancheng Institute of Technology institute of Material science and Engineering Nanjing University of Technology

On the basis of analyzing coal gangue＇s chemical and mineral compositions, the structure change of coal gangue during the mechanical activation was investigated by XrD, FTIr, NMr, and the mechanical strength of the cement doped coal gangue with various specific surface area was tested. The experimental results indicate that, the lattice structure of metakaolin in coal gangue samples calcined at 700 ℃ disorganizes gradually and becomes disordered, and the lattice structure of α-quartz is distorted slightly. The pozzolanic activity of the coal gangue increases obviously with its structural disorganization.

关键词： coal gangue mechanical activation structure NMr tetrahedron

Evaluation of zeolites synthesized from fly ash as potential adsorbents for wastewater containing heavy metals

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental sciences 2009年第1期21卷 127-136页

作者： WANG Chunfeng,LI Jiansheng,SUN Xia,WANG Lianjun,SUN XiuyunSchool of Chemical Engineering,nanjing university of science and technology,nanjing 210094,china. School of Chemical Engineering Nanjing University of Science and Technology Nanjing 210094 China

The pure-form zeolites （A and X） were synthesized by applying a two-stage method during hydrothermal treatment of fly ash prepared initial Cu and Zn gel. The difference of adsorption capacity of both synthesized zeolits was assessed using Cu and Zn as target heavy metal ions. It was found that adsorption capacity of zeolite A showed much higher value than that of zeolite X. Thus, attention was focused on investigating the removal performance of heavy metal ions in aqueous solution on zeolite A, comparing with zeolite HS （hydroxyl-solidate） prepared from the residual fly ash （after synthesis of pure-form zeolite A from fly ash） and a commercial grade zeolite A. Batch method was used to study the influential parameters of the adsorption process. The equilibrium data were well fitted by the Langmuir model. The removal mechanism of metal ions followed adsorption and ion exchange processes. Attempts were also made to recover heavy metal ions and regenerate adsorbents.

关键词： fly ash zeolite heavy metal adsorption recovery

Formation flying in elliptic orbits with the J_2 perturbation

在线全文

学校读者我要写书评

暂无评论

research in Astronomy and Astrophysics 2012年第11期12卷 1563-1575页

作者： Xi-Yun Hou, Yu-Hui Zhao and Lin Liu School of Astronomy and Space science, nanjing university, nanjing 210093, china institute of Space Environment and Astrodynamics, nanjing university, nanjing 210093, china School of Astronomy and Space science Nanjing University Nanjing 210093 China institute of Space Environment and Astrodynamics Nanjing University Nanjing 210093 China

relative dynamics between the chief satellite and the deputy ones in for- marion flying is crucial to maintaining the formation. A good choice of the forma- tion usually requires a lower control frequency or less control energy. For formation flying missions in highly elliptic orbits, the well-known C-W equation is not accu- rate enough. Instead, Lawden＇s equation is often used. First, the solution to Lawden＇s equation with a very simple form is deduced. Then the J2 perturbation is added. It is found that Lawden＇s solution is not necessarily valid when the J2 perturbation is con- sidered. Completely discarding Lawden＇s solution and borrowing the idea of mean orbit elements, two rules to initialize the formation are proposed. The deviation speed is greatly reduced. Different from previous studies on the J2 perturbation, except for the relatively simple expression for the semi-major axis, the tedious formulae of the long period terms and the short period terms of other orbital elements are not used. In addition, the deviation speed is further reduced by compensation of the nonlinear effects. Finally, a loose control strategy of the formation is proposed. To test the ro- bustness of this strategy, a third body perturbation is added in numerical simulations.

关键词： celestial mechanics

Two Methods for Deriving Members′Weights in Group Decision Making

在线全文

学校读者我要写书评

暂无评论

Journal of Systems science and Systems Engineering 2001年第1期13卷 15-19页

作者： XU Ze\|shui pla university of science and technology nanjing, Jiangsu 210016, china pla university of science and technology nanjing Jiangsu 210016 China

：The Analytic Hierarchy process is a powerful technique for group decision making. Both theWeighted Arithmetic Mean Method (WAMM) and Weighted Geometric Mean Method (WGMM) are themost common group preference aggregation methods in AHp. In order to use the WAMM and WGMM, onehas to find the weights to be assigned to the members of the group. This is often a difficult task, especiallyso if the group is large as in the case of public policy decisions. These situations need an objective method toderive members'weights. But a few studies are available in the literature. Based on judgement matrices anderror analyses, this paper presents two practical and efficient methods for addressing such situations. Somenumerical examples are also given.

关键词： group decision making judgement matrix weight

pollen records of Holocene vegetation and climate changes in the Longzhong Basin of the Chinese Loess plateau

在线全文

学校读者我要写书评

暂无评论

progress in Natural science:Materials International 2007年第12期17卷 1445-1456页

作者： Tang Lingyu1 and An Chengbang2(1. nanjing institute of Geology and paleontology, Chinese Academy of sciences, nanjing 210008, china 2. Key Laboratory of Western china’s Environment Systems, MOE, Lanzhou university, Lanzhou 730000, china) nanjing institute of Geology and paleontology Chinese Academy of Sciences Nanjing 210008 China Key Laboratory of Western china’s Environment Systems MOE Lanzhou University Lanzhou 730000 China

pollen records with an average time resolution of 20-200 years from Holocene loess sections at Dingxi, Qin'an, and other localities of Gansu province reveal a detailed history of vegetation and climate changes in the western Loess plateau. For most time of the Holocene, the landscape was dominated by grasslands or forest steppes. However, during the middle Holocene (7.5-5.8 ka Bp), relatively dense forests developed, and the endemic vegetation flourished, suggesting a much warmer and more humid climate condition than the present. Superimposed upon this general pattern are several dry intervals marked by the episodic expansion of grasslands or forest steppe. Xeric vegetation expanded after 3.8 ka Bp, indicating a trend towards dry conditions.

关键词： pollen records glasslands coniferous forests Holocene Loess plateau.