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New research progress on the ultrastructure of tectonically deformed coals

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Progress in Natural science:Materials International 2009年第11期19卷 1455-1466页

作者： Yiwen Ju,Xiaoshi Li Laboratory of Computational Geodynamics,College of Earth science,graduate university of chinese academy of sciences,beijing 100049,china Laboratory of Computational Geodynamics College of Earth Science Graduate University of Chinese Academy of Sciences Beijing 100049 China

The structure of tectonically deformed coals shows some characteristics and regulations on the ultra-scale when influenced by different factors such as temperature,pressure and directional *** of the macromolecular structure may induce changes in the nano-scale pore structure,which are very important for gas adsorption and *** geological impact of different mechanisms of deformation on different types of ultrastructure of tectonically deformed coals is not only of significance as a topic for scientific research, but also in studying environments of metamorphism-deformation at differing metamorphic *** research is also very important in studying the accumulation and occurrence conditions of coalbed methane gas,mechanisms of coal and gas outbursts,predictions of coalbed methane resources and dangers of coal and gas *** paper analyzes current research,within china and other countries, in the ultrastructure of tectonically deformed *** research includes(1) structural models of tectonically deformed coals;(2) the relationship between ultrastructure and stress;(3) the structure of tectonically deformed coals and its strain *** results are also based on our own experiments including vitirnite reflectance(Ro,max),X-ray diffraction(XRD) and nuclear magnetic resonance (NMR(CP/MAS + TOSS)).We discuss the important effects of the structure of tectonically deformed coals and their physical properties,and then point out some problems concerning the research progress of tectonically deformed coals.

关键词： Tectonically deformed coals Ultrastructure Pore structure Tectonic stress Strain environment

Existence of unbiased estimate of regression parameters in simple linear EV models

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science china Mathematics 2005年第7期48卷 915-928页

作者： LIU Jixue & CHEN Xiru Department of Statistics and Finance, university of science and Technology of china, Hefei 230026, china Department of Mathematics, graduate School of chinese academy of sciences, beijing 100049, china Department of Statistics and Finance University of Science and Technology of China Hefei 230026 China Department of Mathematics Graduate School Chinese Academy of Sciences Beijing 100049 China

It is well known that for one-dimensional normal EV regression model X = x+ u,Y =α+βx+e, where x, u, e are mutually independent normal variables and Eu=Ee=0, the regression parameters a and β are not identifiable without some restriction imposed on the parameters. This paper discusses the problem of existence of unbiased estimate for a and β under some restrictions commonly used in practice. It is proved that the unbiased estimate does not exist under many such restrictions. We also point out one important case in which the unbiased estimates of a and β exist, and the form of the MVUE of a and β are also given.

关键词： EV regression model unbiased estimate identiflability.

A NUMERICAL STUDY ON A SIMPLIFIED TAIL MODEL FOR TURNING FISH IN C-START

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Journal of Hydrodynamics 2006年第2期18卷 135-142页

作者： YANG Yan TONG Bing-gang The Laboratory for Biomechanics of Animal Locomotion Graduate University of Chinese Academy of SciencesBeijing 100049 China Department of Mechanics and Mechanical Engineering University of Science and Technology of China Hefei230026 China

Most freshwater fish are good at turning manoeuvres. A simulated fish tail model was numerically investigated and discussed in detail. This study deals with unsteady forces and moment exerted on the fish tail-fin in an initial sideways stroke and a subsequent return stroke motion, and visualizes the flow fields and vortex structures, in order to explore the flow control mechanism of the typical turning motion of fish. Further discussion on fluid dynamic consequences corresponding to two different bending forms of fish tail-fins in its C-start is given. The two-dimensional unsteady incompressible Navier-Stokes equations are solved with a developed pseudo-compressibility method to simulate the flow around the fish tail-fin. The computed results and the comparison with experiments indicate that （1） fish performs a turning motion of its body using the impulsive moment produced by the to-and-fro stroke, and each stage of the process exhibits its specific hydrodynamic characteristic, （2） fishes adopt two forms of tail-tip bend （single bend and double bend） to accomplish a C-start turning manoeuvre, in dependence of their physical situations and natural environments, （3） fish can control its turning motion by modulating some key kinematic parameters.

关键词： fish swimming turning manoeuvre C-start,tail fin locomotion 2D Navier-Stokes equations CFD physical mechanism optimal control

A 12-bit multichannel ADC for pixel detectors in particle physics and nuclear imaging

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science china(Technological sciences) 2010年第5期53卷 1208-1214页

作者： WEI Wei1,2,3,WANG Zheng1,3 & ZHAO JingWei1,3 1 Institute of High Energy Physics,chinese academy of sciences,beijing 100049,china 2 graduate university of chinese academy of sciences,beijing 100049,china 3 Key Lab of Nuclear Detection Technology and Nuclear Electronics of chinese academy of sciences,beijing 100049,china Institute of High Energy Physics Chinese Academy of Sciences graduate university of chinese academy of sciences Key Lab of Nuclear Detection Technology and Nuclear Electronics of chinese academy of sciences

Modern pixel detectors in nuclear and particle physics experiments and also in nuclear imaging,starve for highly integrated application specified integrated circuit(ASIC),whereas in china the study of ASIC still stays far away from practical *** lack of ASIC strictly limits the research and development of domestic high energy physics field.A 12-bit multichannel ADC designed for high density readout is introduced as a major candidate for solution.A precise model is discussed and the simulation fully agrees with the model,which indicates a key principle of *** is performed according to the given rule,and novel layout techniques are carried *** results in all aspects are also obtained,showing an excellent real performance,which satisfies the practical requirement.

关键词： application specified integrated circuit high density readout Wilkinson ADC multi-channel ADC

Joint source channel VL coding/decoding for deep space communication networks based on a space trellis

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science china(Information sciences) 2011年第9期54卷 1883-1894页

作者： WU WeiRen 1,TU Juan 2,TU GuoFang 1,GAO ShaoShuai 1 & ZHANG Can 1,3 1 School of Information science and Engineering,graduate university of chinese academy of sciences,beijing 100049,china 2 beijing Institute of Electronic System Engineering,china Aerospace science & Industry Corp.,beijing 100854,china 3 State Key Laboratory of Information Security,graduate university of chinese academy of science,beijing 100049,china School of Information science and Engineering Graduate University of Chinese Academy of Sciences beijing Institute of Electronic System Engineering China Aerospace Science & Industry Corp

This paper presents joint source channel variable length (VL) coding/decoding based on a space *** constructing a joint decoding plane trellis,better decoding performance can be achieved than by using the bit-level decoding ***,the plane trellis is complicated,which results in high decoding complexity for decoding VL turbo *** solve this problem,we construct a space trellis and design a low-complexity joint decoding algorithm with a variable length symbol-a posteriori probability (VLS-APP) algorithm in resource constrained deep space communication *** results show that the proposed approach reduces the decoding complexity by 10% compared with the plane trellis,and the gain of Eb/N0 is about 0.2 dB at SER=***,it provides substantial error protection for variable-length encoded image data.

关键词： joint coding/decoding VL turbo codes space trellis VLS-APP

The influence of moderate ENSO on summer rainfall in eastern china and its comparison with strong ENSO

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chinese science Bulletin 2008年第5期53卷 791-800页

作者： XUE Feng1 & LIU ChangZheng1,2 1 Institute of Atmospheric Physics, chinese academy of sciences, beijing 100029, china 2 graduate university of chinese academy of sciences, beijing 100049, china chinese Acad Sci Inst Atmospher Phys Beijing 100029 Peoples R China.

The 6 major ENSO events since 1979 are classified into the strong and moderate ENSO based on in-tensity. The composite analysis is performed to reveal the influence of ENSO on East Asian summer monsoon (EASM) and summer rainfall in eastern china. It is shown that the influence is changed with the seasonal cycle in summer, with a weaker influence in June and a stronger influence in August, in-dicating a long lagged effect of ENSO on EASM. Besides, the circulation and rainfall anomalies caused by the strong ENSO are also stronger with an earlier starting time, while the influence of the moderate ENSO is evident in August. The composite summer rainfall in eastern china for the moderate ENSO exhibits a northern rainfall pattern, which is totally different from the classical ENSO-type rainfall pat-tern. Based on the composite analysis, two moderate ENSO years with a similar intensity (i.e., 1995 and 2003) are compared. The result shows that, the response of EASM to the moderate ENSO during June and July is, to a certain degree, modulated by the circulation systems in mid-high latitudes of Eurasia and in the Southern Hemisphere, thereby inducing a different rainfall distribution in eastern china. In comparison with the strong ENSO in 1983, it is further revealed that, the strong ENSO plays a dominant role in summer rainfall anomalies in eastern china as well as in controlling the influence of the other factors on EASM. The strong ENSO is therefore different with the moderate ENSO.

关键词：中国东部海洋气象学厄尔尼诺现象东亚季风降雨

Terrestrial transect study on driving mechanism of vegetation changes

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science china Earth sciences 2008年第7期51卷 984-991页

作者： ZHANG YuJin1,2 & ZHOU GuangSheng1 1 State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, chinese academy of sciences, beijing 100093, china 2 graduate university of chinese academy of sciences, beijing 100049, china State Key Laboratory of Vegetation and Environmental Change Institute of Botany Chinese Academy of Sciences Beijing China graduate university of chinese academy of sciences Beijing China

In terms of chinese climate-vegetation model based on the classification of plant functional types, to- gether with climatic data from 1951 to 1980 and two future climatic scenarios (SRES-A2 and SRES-B2) in china from the highest and the lowest emission scenarios of greenhouse gases, the distribution patterns of vegetation types and their changes along the Northeast china Transect (NECT) and the North-South Transect of Eastern china (NSTEC) were simulated in order to understand the driving mechanisms of vegetation changes under climatic change. The results indicated that the vegetation distribution patterns would change significantly under future climate, and the major factors driving the vegetation changes were water and heat. However, the responses of various vegetation types to the changes in water and heat factors were obviously different. The vegetation changes were more sensi- tive to heat factors than to water factors. Thus, in the future climate warming will significantly affect vegetation distribution patterns.

关键词： driving mechanism vegetation terrestrial transect climatic change plant functional types

Effects of the grain size distribution on the temperature-dependent magnetic susceptibility of magnetite nanoparticles

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science china Earth sciences 2010年第7期53卷 1071-1078页

作者： ZHAO XiangYu1,2 & LIU QingSong1 1 Paleomagnetism and Geochronology Laboratory (SKL-LE), Institute of Geology and Geophysics, chinese academy of sciences, beijing 100029, china 2 graduate university of chinese academy of sciences, beijing 100049, china Paleomagnetism and Geochronology Laboratory (SKL-LE) Institute of Geology and Geophysics Chinese Academy of Sciences Beijing China graduate university of chinese academy of sciences Beijing China

Magnetite is an important magnetic remanence carrier in natural samples and therefore is of great interest in paleo-, rock-, and environmental magnetism. The magnetic properties of magnetite depend on many factors, e.g., concentration and grain size distribution (GSD). In this study, we theoretically investigated the temperature-dependent susceptibility (TDS) of magnetite nanoparticles with a lognormal GSD. Results show that the TDS is affected highly by the GSD mainly in three aspects. Firstly, the unblocking process becomes smoother with the increase of distribution width, characterizing as a wider Hopkinson peak on the TDS curve. Secondly, the blocking temperature increases with the increase of the median diameter or/and the distribution width. Thirdly, the maximum susceptibility decreases with the increase of distribution width, and has a logarithmic function relation with the standard deviation of the distribution. As a case study, this model was further applied to the thermal products of the chinese loess/paleosol samples to determine the granulometry of newly-formed magnetite upon heating based on TDS curves. The results demonstrate the fidelity and feasibility of this method to determine the GSD of nano-sized magnetic particles.

关键词： Néel theory temperature dependence of susceptibility grain size distribution

Sea level variations in the South china Sea inferred from satellite gravity,altimetry,and oceanographic data

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science china Earth sciences 2012年第10期55卷 1696-1701页

作者： FENG Wei 1,2,ZHONG Min 1,3 & XU HouZe 1,3 1 State Key Laboratory of Geodesy and Earth’s Dynamics,Institute of Geodesy and Geophysics,chinese academy of sciences,Wuhan 430077,china 2 graduate university of chinese academy of sciences,beijing 100049,china 3 Institute of Geophysics,Huazhong university of science and Technology,Wuhan 430074,china State Key Laboratory of Geodesy and Earth’s Dynamics Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan China graduate university of chinese academy of sciences Beijing China Institute of Geophysics Huazhong University of Science and Technology Wuhan China

Sea level variations(SLVs) can be divided into two major components:the steric SLV and the mass-induced *** two components of SLV in the South china Sea(SCS) are studied by using satellite altimetry,GRACE(Gravity Recovery and Climate Experiment) satellite gravity,and oceanographic data on annual and inter-annual *** the annual timescale,the geographic distribution of mass-induced SLV's amplitude jointly estimated from altimetry and the ECCO(Estimation of the Circulation and Climate of the Ocean) model agrees very well with that from *** observes obvious seasonal mass-induced SLV in the SCS with annual amplitude of 2.7±0.4 cm,which is consistent with the annual amplitude of 2.7±0.3 cm estimated from the steric-corrected *** the inter-annual timescales,the mean SLV in the SCS shows a large oscillation,which is mainly caused by the steric *** trend of mean SLV inferred from altimetry in the SCS is 5.5±0.7 mm/yr for the period of 1993-2009,which is significantly higher than the global sea level rise rate of 3.3±0.4 mm/yr in the same *** is no obvious trend signal in the mass-induced SLV detected from GRACE that indicates the water exchange between the SCS and its adjacent seas and land is in balance within the study period.

关键词： altimetry GRACE ECCO the South china Sea sea level variation