检索结果-南通市图书馆

Cooling effect of ripped-stone embankments on Qing-Tibet railway under climatic warming

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science Bulletin 2003年第6期48卷 598-604页

作者： LAI Yuanming1, ZHANG Luxin1 , ZHANG Shujuan1 & MI Long2.1. State Key Lab. of Frozen Soil Engineering, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China 2. department of Civil Engineering, Northern Jiaotong University, beijing 100044, China State Key Lab. of Frozen Soil Engineering Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou China department of Civil Engineering Northern Jiaotong University Beijing China

The heat convection in ballast mass and ripped-stone mass in railway embankments is the problem of heat convection in porous media. In order to calculate the temperature distribution of Qing-Tibet railway embankment, from the governing equations used to study forced convec-tion for incompressible fluids porous media, the finite ele-ment formulae for heat convection in porous media are de-rived by using Galerkin抯 method. The temperature fields of the traditional ballast embankment and the ripped-stone mass embankment, constructed on July 15, have been ana-lyzed and compared under the case that the air temperature in Qinghai-Tibetan Plateau will be warmed up by 2.0℃ in the future 50 years. The calculated results indicate that, the permafrost 5 m below the traditional ballast embankment will be thawed in the regions in which the air yearly-average temperature is larger than -3.5℃ or the yearly-average temperature at the native surface is larger than -1℃. The embankment will cause large thawing settlement. The rail-way embankment will be damaged by permafrost degrada-tion. The ripped-stone mass embankment can not only resist the effect of climatic warm up on it but also provide cool energy for the permafrost under it. It can assure permafrost stability and not subjected to thawing. Therefore, it is highly recommended that the ripped-stone mass embankment be taken as the Qing-Tibet railway embankment structure in high-temperature permafrost regions so that permafrost embankment can be protected as possible as we could.

关键词： cooling effect ripped-stone embankment climatic warming.

The eastward subtropical countercurrent on isopycnal surface in the western North Pacific

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China Earth Sciences 2005年第7期48卷 1065-1073页

作者： LI Rongfeng1, YOU Xiaobao1 & Peter C. Chu2.1. LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, beijing 10002., China 2. department of Oceanography, Naval Postgraduate School, Monterey, CA 93943-512., USA LASG Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China department of Oceanography Naval Postgraduate School Monterey CA 93943-5122 United States

The monthly circulations on isopycnal surface in the western North Pacific are calculated based on the Navy’s Generalized Digital Environmental Model climatological tem- perature and salinity data on a 1/2. × 1/2. grid using a P-vector method. The eastward Sub- tropical Countercurrent (STCC) in the central subtropical gyre has been studied with emphasis on its spatial distribution, vertical structure, volume transport and its nearby eddy phenomenon. The results reproduce the observed feature of STCC, and reveal some new phenomena on isopycnal surface, such as: (1) At σθ = 2..6, there is strong seasonal variability in the distribution, origin and flow status of STCC. There is no STCC in January, February and March. (2. From May to October, a branch of the Kuroshio Countercurrent to the south of Japan merges into STCC, which increases the velocity of STCC and widens its width. (3) The velocity vector field shows that STCC and nearby eddies coexist. (4) The eastward volume transport of STCC across 137.5°E is the strongest in summer with the maximum of 6.9 Sv ( 1 Sv ≡ 106 m3 s?1) in August, and weaker in spring and autumn with 1.7 Sv in April and 1.6 Sv in November. Most of the transports of STCC occur between isopycnal surfaces 2..0σθ and 2..0σθ. (5) The distributions of the zonal flow along 137.5°E show that the flow core of STCC is between 2..3σθ and 2..7σθ .

关键词： P-vector method on isopycnal surface eastward subtropical countercurrent eddy phenomenon.

Mechanisms of Cenozoic deformation in the Bohai Basin, Northeast China: Physical modelling and discussions

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2006年第3期49卷 258-271页

作者： ZHOU Jianxun1 & ZHOU Jiansheng2.1. Key Laboratory for Hydrocarbon Accumulation of Chinese Ministry of Education and department of Earth Science, China University of Petroleum, beijing 102.49, China 2. Dagang Petroleum Sub-corporation of PetroChina Company Limited, Tianjin 3002.0, China 1. Key Laboratory for Hydrocarbon Accumulation of Chinese Ministry of Education and department of Earth Science China University of Petroleum Beijing 102249 China 2. Dagang Petroleum Sub-corporation of PetroChina Company Limited Tianjin 300280 China

The Bohai Basin is a Cenozoic petroliferous extensional basin in China and has apparent geometrical and kinematic similarities with the other Meso-Cenozoic extensional basins located along the eastern margin of Eurasian Plate. However, the deformation mechanisms of the basin are still in dispute. Physcial modelling referring to the Huanghua Depression, located in the central part of the Bohai Basin was conducted employing four sets of planar sandbox experimental models with different extension directions. Only experimental results of the model with N-S extension show good structural similarity with the depression. The results also indicate that complex variations of fault strike in a rift basin are not necessarily the results of complex kinematic mechanisms or polyphase deformation. Based on comparison of experimental results with the actual structures and the good structural simi- larity between Huanghua Depression and the whole Bohai Basin, it is concluded that the Bohai Basin was formed by the N-S extension. The strike slip deformation along the NNE-trending border faults of the basin resulted from the N-S extension and played the role of lateral transformation for the N-S extension. In addition, according to the apparent geometrical and kinematic similarities among the Bohai Basin and other Meso-Cenozoic extensional basins located along the eastern margin of the Eurasian Plate, it is proposed that: (1) this “N-S extension” model provides a better kinematic inter- pretation for the formation of Bohai Basin and the other adjacent basins located along the eastern margin of the Eurasian Plate; and (2. the N-S extension was probably the effect of the “slab window” formed by the subduction of the nearly E-W trending oceanic ridge between the Kula and Pacific Plates. The “slab window” effect can also provide reasonable explanations for the phenomena that initial rifting ages of basins become progressively younger westwards along the eastern margin of the Eurasian Plate

关键词： Bohai Basin, physical modelling, Cenozoic, extensional tectonics.

Effect of concentration on surfactant micelle shapes——A molecular dynamics study

在线全文

学校读者我要写书评

暂无评论

Science China chemistry 2005年第5期48卷 470-475页

作者： GAO Jian1,2. GE Wei1 & LI Jinghai1 1. Multiphase Reaction Laboratory, Institute of Process Engineering, Chinese Academy of Sciences, beijing 100080, China 2. Graduate School of The Chinese Academy of Sciences, beijing 100085, China 1. Multiphase Reaction Laboratory Institute of Process Engineering Chinese Academy of Sciences 100080 Beijing China 2. Graduate School of The Chinese Academy of Sciences 100085 Beijing China

Many aspects of the behavior of surfactants have not been well understood due to the coupling of many different mechanisms. Computer simulation is, therefore, attractive in the sense that it can explore the effect of different mechanisms separately. In this paper, the shapes, structures and sizes of sodium dodecylbenzenesulfonate (SDBS) micelles under different con-centrations in an oil/water mixture were studied via molecular dynamics (MD) simulations using a simplified atomistic model which basically maintains the hydrophile and lipophile properties of the surfactant molecules. Above the critical micellar concentration (cmc), surfactant molecules ag-gregate spontaneously to form a wide variety of assemblies, from spherical to rodlike, wormlike and bilayer micelles. Changes in their ratios of the principle moments of inertia (g1/g3, g2.g3) in-dicated the transition of micelle shapes at different concentrations. The aggregation number of micelle is found to have a power-law dependence on surfactant concentration.

关键词： surfactant, MD simulation, sodium dodecylbenzenesulfonate, micelle shape.

Separation of Red (Y_2._3: Eu^(3+)), Blue (Sr,Ca,Ba)_(10)(PO_4)_6Cl_2. Eu^(2.) and Green (LaPO_4:Tb^(3+),Ce^(3+)) Rare Earth Phosphors by Liquid/Liquid Extraction

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3期24卷 418-423页

作者：梅光军 School of Resource and Environmental Engineering Wuhan University of Technology

A novel process for separation of red （Y2.3： Eu^3＋）, blue （Sr, Ca, Ba）10（PO4）6Cl2. Eu^2. and green （LaPO4： Tb^3＋, Ce^3＋） fine tricolor phosphor powders was established. First, the green phosphor was extracted and separated from three phosphor mixtures in heptane/DMF（N, N-Dimethylformamide） system using stearylamine or laurylamine （DDA） as the cationic surfactant. Then, after being treated with 99.5% ethanol, the blue and red phosphors could be separated in Heptane/DMF system in presence of 1-octanesulfonic acid sodium salt as the anionic surfactant. Satisfactory separation results have been achieved through two steps extractions with their artificial mixtures. The grades and recovery of separated products reached respectively as follows： red product was 95.3% and 90.9%, blue product was 90.0% and 95.2., and green product was 92.2. and 91.8%.

关键词： rare earth phosphor liquid-liquid extraction separation

Lie symmetries of mechanical systems with unilateral holonomic constraints

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2000年第15期45卷 1354-1358页

作者： ZHANG Yi & MEI Fengxiang1. department of Basic Courses, Suzhou Institute of Urban Construction & Environmental Protection, Suzhou 2.5011, China 2. department of Applied Mechanics, {2. Institute of Technology, {2. 10008I, China department of Basic Courses Suzhou Institute of Urban Construction & Environmental Protection Suzhou China department of Applied Mechanics Beijing Institute of Technology Beijing China

In the recent twenty years, the study on the Lie symmetries and conserved quantities of constrained mechanical systems has been making great progress[1-5]. Up to now, however, all the studies are limited to the mechanical systems with ideal bilateral constraints. This note further studies the Lie symmetries of mechanical systems with unilateral holonomic constraints, and two problems of Lie symmetries for the systems are put forward and solved, i.e. finding the conserved quantity from a Lie symmetric transformation of the system and finding the corresponding Liesymmetry from an integral of the systemi ? 梛 ? Jsymmetry from an integral of the system.

关键词： analytical mechanics unilateral constraint holonomic system Lie symmetry conserved quantity.

Experimental study on bed-load sediment transport under irregular wave and current combined flow

在线全文

学校读者我要写书评

暂无评论

Acta Oceanologica Sinica 2001年第2期20卷 271-280页

作者： Wu Yongsheng,Qin Chongren (1. department of Hydraulic Engineering, Tsinghua University, beijing 100084, China 2. School of Civil Engineering, Tianjin University, Tianjin 300072. China) department of Hydraulic Engineering Tsinghua University Beijing 100084 China

Using an irregularly oscillating tray and flume, a series of experiments are completed to evaluate bed-load sediment transport rate under irregular wave -current coexistent field. Testing conditions include three interaction angles 0', 45', 90' and two kinds of median sizes (0.38 and 1.10 mm). The results of transport rate show that the net sediment transport rate can be expressed approximately as the function of the maximum bottom shear stress of waves, mean shear stress of current and the grain size.

关键词： Irregular wave-current bed-load transport rate

Synthesis and Properties of the Polymeric Surfactant Based on Maleamic Acid and Styrene

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) 2011年第1期26卷 79-82页

作者：杨永清 department of Applied chemistry School of Science Northwestern Polytechnical University

An alternative polymeric surfactant P（M3/St） was synthesized by solution polymerization of maleamic acid as hydrophilic monomer and styrene as hydrophobic monomer. Some factors that affect the yield and properties of the polymeric surfactant were investigated systemically. The surface tension of the polymeric surfactant reaches 37-38 mN/m. It is proved that the polymeric surfactant shows very good surface activity and emulsifying ability. The TG analysis shows that the temperature of the thermal degradation can reach 314.4 ℃. It will be used as a new type of polymeric surfactant.

关键词： maleamic acid polymeric surfactant surface activity emulsifying ability thermal resistance

The proof of FFD(L)≤11/9OPT(L) +7/9

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 1997年第15期42卷 1262-1265页

作者： LI Rongheng, YUE Minyi1. department of Mathematics, Hunan Normal University, Changsha 410081, China 2. Institute of Applied Mathematics, Chinese Academy of Sciences, beijing 100080, China department of Mathematics Hunan Normal University Changsha 410081 China Institute of Applied Mathematics Chinese Academy of Sciences Beijing 100080 China

THE one-dimensional bin-packing problem is defined as follows: for a given list L={p1, p2.…, Pn}, where 0i≤1 denotes the item and its size as well, we are to pack all the items in-to bins, each of which has a capaci... 详细信息

THE one-dimensional bin-packing problem is defined as follows: for a given list L={p1, p2./sub>,…, Pn}, where 0i≤1 denotes the item and its size as well, we are to pack all the items in-to bins, each of which has a capacity 1, and the goal is to minimize the number of bins *** first-fit-decreasing （FFD） algorithm is a famous approximate algorithm for the bin-pack-ing problem. The FFD algorithm first sorts all the list into non-increasing order and then pro-cesses the pieces in that order by placing each item into the first bin into which it fits.

关键词： bin-packing minimal counter-example weigtht-function FFD-algorithm.