检索结果-南通市图书馆

Speciation of the elements and compositions on the surfaces of dust storm particles:The evidence for the coupling of iron with sulfur in aerosol during the long-range transport

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2005年第8期50卷 738-744页

作者： ZHANG Xingying1,2, ZHUANG Guoshun1,2,3, CHEN Jianmin2 & XUE Huaxin2 1. Center for Atmospheric Environment Study, Department of Chemistry, beijing Normal University, beijing 100875, china 2. Center for Atmospheric Chemistry Study, Department of Environ- mental Science and Engineering, Fudan University, Shanghai 200433, china 3. LAPC/NZC, institute of Atmospheric Physics, NZC/LAPC, Chinese Academy of Sciences, beijing 100029, china Center for Atmospheric Environment Study Department of Chemistry Beijing Normal University Beijing 100875 China Center for Atmospheric Chemistry Study Department of Environmental Science and Engineering Fudan University Shanghai 200433 China LAPC/NZC Institute of Atmospheric Physics NZC/LAPC Chinese Academy of Sciences Beijing 100029 China

The speciation of the elements on the surface of the particles collected during dust storm and non-dust storm in beijing and Inner Mongolia was studied by XPS. The ma- jor species of iron on the surface were oxides, sulfate, silicate, FeOOH and minor part sorbed on SiO2/Al2O3. Sulfate is the dominant species of sulfur on the surface. SiO2 and Al2O3 are the main components of Si and Al on the surface respectively. One of the most important findings was that the Fe(II) (FeS and FeSO4) produced could account for up to 44.3% and 45.6% of the total Fe on the surface in the aerosol sample collected at that night and next day of the “peak” time of the dust storm occurring on March 20, 2002, while Fe2(SO4)3, one of the Fe(III) species on the surface decreased from 67.1% to 49.5% and 48.0% respectively. Both S and Fe en- riched on the surface of aerosol particles. Fe(II) accounted for 1.3%?5.3% of total Fe in bulk aerosol samples during dust storm. These results provided strong evidence to sup- port the hypothesis of the coupling between iron and sulfur in aerosols during the long-range transport, which would have important impact on the global biogeochemical cycle.

关键词：物种形成原理 XPS 大气悬浮物 Fe-S结合粒子集合

Recent progress in fingerprint recognition

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2006年第3期16卷 231-240页

作者： TIAN Jie, CHEN Xinjian, ZHANG Yangyang, YANG Xin, HE Yuliang, LI Liang, XIE Weihua and ZHENG Zhipeng (Center for Biometrics and Security research, Key Laboratory of Complex Systems and Intelligence Science, institute of Automation, Chinese Academy of Sciences, beijing 100080, china Graduate School of the Chinese Academy of Sciences, beijing 100080, china) [a]Center for Biometrics and Security research Key Laboratory of Complex Systems and Intelligence Science Institute of Automation Chinese Academy of Sciences Beijing China [b]Graduate School of the Chinese Academy of Sciences Beijing China

Fingerprint recognition has been increasingly used to realize personal identification in civilian' s daily life, such as ID card, fingerprints hard disk and so on. Great improvement has been achieved in the on-line fingerprint sensing technology and automatic fingerprint recognition algorithms. Various fingerprint recognition techniques, including fingerprint acquisition, classification, enhancement and matching, are highly improved. This paper overviews recent advances in fingerprint recognition and summarizes the algorithm proposed for every step with special focuses on the enhancement of low-quality fingerprints and the matching of the distorted fingerprint images. Both issues are believed to be significant and challenging tasks. In addition, we also discuss the common evaluation for the fingerprint recognition algorithm of the Fingerprint Verification Competition 2004 (FVC2004) and the Fingerprint Vendor technology Evaluation 2003 (FpVTE2003), based on which we could measure the performance of the recognition algorithm objectively and uniformly.

关键词： biometrics fingerprint enhancement matching minutia image registration similarity measures.

Finding Signals for Plant Promoters

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Genomics, Proteomics & Bioinformatics 2003年第1期1卷 68-73页

作者： Weimou Zhenginstitute of Theoretical Physics, Chinese Academy of Sciences, beijing 100080, china beijing Genomicsinstitute, Chinese Academy of Sciences, beijing 101300, china institute of Theoretical Physics Chinese Academy of Sciences Beijing 100080 China beijing Genomics institute Chinese Academy of Sciences Beijing 101300 China

The strongest signal of plant promoter is searched with the model of single motif with two types. It turns out that the dominant type is the TATA-box. The other type may be called TATA-less signal, and may be used in gene finders for promoter recognition. While the TATA signals are very close for the monocot and the dicot, their TATA-less signals are significantly different. A general and flexible multi-motif model is also proposed for promoter analysis based on dynamic programming. By extending the Gibbs sampler to the dynamic programming and introducing temperature, an efficient algorithm is developed for searching signals in plant promoters.

关键词： for on is as et Pro Finding Signals for Plant Promoters been of into

Transition of china's Diplomacy and Foreign Relations

在线全文

学校读者我要写书评

暂无评论

china & World Economy 2009年第3期17卷 93-101页

作者： Yizhou Wang Senior research Fellow,institute of World Economics and Politics,Chinese Academy of Social Sciences,beijing,china. Senior research Fellow Institute of World Economics and Politics Chinese Academy of Social Sciences Beijing China.

The present paper focuses on the transformation of china＇s foreign affairs. The transformation is closely associated with and mutually reinforced by the developmental changes that have taken place in china. china＇s strong economic focus has had a profound effect on its foreign relations and international strategies. With sustained growth over the past three decades （1978-2008）, china has become an important member of the world community. In particular, its influence has been growing in the Asia-Pacific area. china＇s unique developmental model and path are recognized and scrutinized worldwide. The present paper discusses special aspects of foreign aid and also explores the changes in principles of and approaches taken in the application of foreign aid policies. Under dual external and internal pressure, china has to constantly adjust, renew and improve its approach to diplomatic and international relations.

关键词： developing countries foreign aid foreign relations transition

Numerical simulation of Richtmyer-Meshkov instability

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2004年第z1期47卷 234-244页

作者： FU Dexun, MA Yanwen, ZHANG Linbo & TIAN BaolinState Key Laboratory of Nonlinear Mechanics, institute of Mechanics, Chinese Academy of Sciences, beijing 100080, china State Key Laboratory of Scientific and Engineering Computing, institute of Computational Mathematics, Chinese Academy of Sciences, beijing 100080, china 1. State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences 100080 Beijing China2. State Key Laboratory of Scientific and Engineering Computing Institute of Computational Mathematics Chinese Academy of Sciences 100080 Beijing China

The compressible Navier-Stokes equations discretized with a fourth order accurate compact finite difference scheme with group velocity control are used to simulate the Richtmyer-Meshkov (R-M) instability problem produced by cylindrical shock-cylindrical material interface with shock Mach number Ms=1.2 and density ratio 1:20 (interior density/outer density). Effect of shock refraction, reflection, interaction of the reflected shock with the material interface, and effect of initial perturbation modes on R-M instability are investigated numerically. It is noted that the shock refraction is a main physical mechanism of the initial phase changing of the material surface. The multiple interactions of the reflected shock from the origin with the interface and the R-M instability near the material interface are the reason for formation of the spike-bubble structures. Different viscosities lead to different spike-bubble structure characteristics. The vortex pairing phenomenon is found in the initial double mode simulation. The mode interaction is the main factor of small structures production near the interface.

关键词： R-M instability, direct numerical simulation, shock-interface interaction.

A TWO-SCALE SECOND-ORDER MOMENT PARTICLE TURBULENCE MODEL FOR GAS-PARTICLE FLOW

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2006年第6期18卷 659-665页

作者： ZENG Zhuo-xiong ZHOU Li-xing Department of Engineering Mechanics Tsinghua University Beijing 100084 China Department of Mechanical Engineering Nanchang Institute of Aeronautical Technology Nanchang 330034China

A two-scale second-order moment two-phase turbulence model was developed and used to simulate gas-particle flow in a sudden-expansion chamber and a channel. The simulation results were in agreement with the experimental results, and the results were compared with those of the single-scale second-order moment two-phase turbulence model. Several improved features show that the two-scale model is to a certain extent better than the single-scale model, which may be attributed to the fact that particle turbulence is well characterized by the two-scale turbulence model.

关键词： gas-particle flow second-order moment model,two-scale fluctuation

A class of additive-accelerated means regression models for recurrent event data

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2010年第12期53卷 3139-3151页

作者： LIU Li 1, MU XiaoYun 2 & SUN LiuQuan 2 1 School of Mathematics and Statistics, Wuhan University, Wuhan 430072, china 2 institute of Applied Mathematics, Academy of Mathematics and Systems Science, Chinese Academy of Sciences, beijing 100080, china 1. School of Mathematics and Statistics Wuhan University Wuhan 430072 China2. Institute of Applied Mathematics Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100080 China

In this article, we propose a class of additive-accelerated means regression models for analyzing recurrent event data. The class includes the proportional means model, the additive rates model, the accelerated failure time model, the accelerated rates model and the additive-accelerated rate model as special cases. The new model offers great flexibility in formulating the effects of covariates on the mean functions of counting processes while leaving the stochastic structure completely unspecified. For the inference on the model parameters, estimating equation approaches are derived and asymptotic properties of the proposed estimators are established. In addition, a technique is provided for model checking. The finite-sample behavior of the proposed methods is examined through Monte Carlo simulation studies, and an application to a bladder cancer study is illustrated.

关键词： additive-accelerated means model counting process marginal model model checking recurrent events

Quantitative analysis of soil pores under natural vegetation successions on the Loess Plateau

在线全文

学校读者我要写书评

暂无评论

Science china Earth Sciences 2010年第4期53卷 617-625页

作者： ZHAO ShiWei1,ZHAO YongGang1,2 & WU JinShui3 1 State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau,institute of Soil and Water Conservation,Northwest Agriculture & Forestry University,Yangling 712100,china 2 Graduate University of Chinese Academy of Sciences,beijing 100049,china 3 institute of Subtropical Agriculture,Chinese Academy of Sciences,Changsha 410125,china 1. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau Institute of Soil and Water Conservation Northwest Agriculture & Forestry University Yangling 712100 China2. Graduate University of Chinese Academy of Sciences Beijing 100049 China3. Institute of Subtropical Agriculture Chinese Academy of Sciences Changsha 410125 China

Soil pore is a key attribute of the soil structure that affects soil reservoir under natural vegetation recovery on the Loess *** study is to quantitatively analyze soil pore parameters,measured with Computed Tomography(CT) at 15-57 mm depths under five different vegetation succession stages using a concept of substituting "space" for "time" in the Ziwuling Forest Region of the Loess *** results showed that the soil pore parameters,such as pore number,porosity,circularity,and fractal dimension,increased significantly under the natural vegetation successions and varied with the pattern climax community stage>pioneering arbor community stage>scrub community stage>herbaceous community stage>abandoned farmland stage,indicating that natural vegetation recovery could remarkably improve soil pore *** the vegetation succession,this positive effect will be strengthened gradually,which means that the soil pore parameters may appear to be best at the climax community *** organic matter content increased linearly with the soil pore parameters(P<0.001).Increased organic matter accumulation was one of the major reasons for the changes in soil pore characteristics in natural vegetation succession.

关键词： Computed Tomography Loess Plateau natural vegetation succession soil pore soil organic matter

CRACK GROWTH,FRACTURE FEATURE AND RUPTURE LIFE DURING CYCLIC CREEP OF SUPERALLOY GH2132

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 1999年第1期12卷 92-96页

作者： M.F. Geng1), T. Wang1) and X.A. Zhang2) 1) Department of special Metal Materials and Products, Luoyang Ship Material research institute, Luoyang 471039, china2) Mechanical Properties Laboratory, beijing institute of Aeronautical Materials, beijing

The effects of cyclic loading on crack growth, fracture feature and rupture life of superalloy GH2132 have been studied in the present paper. The crack growth tests were carried out at 550 on compact tension specimens under a wide range of load levels and various periods of hold time, and the fracture surfaces were examined on a scanning electron microscope. The results show that, for both static and cyclic creep, Stage-I of crack growth is related with initial test stress, during which the crack extension is about 0.5mm, and that the final effect of cyclic loading on rupture life depends on the counteraction of its two reversed effects on crack growth rate before and after the point n=0.2.

关键词： cyclic creep crack growth fracture feature rupture life initial test stress tensile yield stress