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Dynamic tree-based authenticated group key exchange protocol

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Science china(Information sciences) 2010年第8期53卷 1591-1602页

作者： li Hui 1,2., WU ChuanKun 1 & TENG JiKai 1,2.1 State Key Laboratory of Information Security, {3. of Software,{2., beijing 100190, china 2.Graduate University of{2., beijing 100049, china State Key Laboratory of Information Security Institute of Software Chinese Academy of Sciences Beijing China Graduate University of chinese academy of sciences Beijing China

Authenticated group key exchange protocols allow a group of users over a public network to establish a shared secret key for the subsequent cryptographic goals. In this paper, we extend BD-II scheme into a dynamic setting, and propose a tree-based authenticated key exchange protocol which is more suitable for dynamic groups in such as ad hoc networks. Our protocol is proven secure in random-oracle model. Additionally, we analyze the costs of our protocols in both communication and computation terms, and compare its performance with three well-known protocols.

关键词： tree-based group key exchange dynamic provable security

Size-dependent hydroxyl radicals generation induced by SiO_2.ultra-fine particles: The role of surface iron

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Science china Chemistry 2009年第7期52卷 1033-1041页

作者： SHANG Yu1, ZHU Tong1, li Yi1,2.& ZHAO JinCai3.1 College of Environmental sciences and Engineering, Peking University, {2. 100871, china 2.chinese academy of Meteorological sciences, {2. 100871, china 3.institute of Chemistry, chinese academy of sciences, {2. 100871, china College of Environmental sciences and Engineering Peking University Beijing China chinese academy of Meteorological {2. Beijing China institute of Chemistry Chinese Academy of Sciences Beijing China

Oxidative stress and hydroxyl radicals (·OH) play important roles in adverse health effects caused by inhalable ambient air particles (PM10). The ultra-fine fraction of PM10 has been hypothesized as one of the critical contributors to ·OH generation. Both in vivo and in vitro studies have shown that ultra-fine particles (UFPs) or nano-particles generate more ·OH than larger particles with identical mass and composition. Both the surface area and surface-adsorbed redox-active metals have been suggested as factors to determine the oxidative capacity of UFPs. In this study, the ·OH-generating capability of dif-ferent sizes of SiO2.particles was investigated in order to determine which factor influences particle-induced ·OH generation. The amount of ·OH generated in both acellular and cellular systems was quantified using a capillary electrophoresis method following exposure to SiO2.particles with diameters of 14, 100, and 500 nm. The amount of ·OH was strongly dependent on particle size, and a significant enhancement was observed only with 14 nm particles. Further studies indicated a close association between ·OH and iron ion concentration (R2.= 0.812. p2.particles is presented as a possible mechanism of UPFs-induced ·OH generation. The SiO2.acted as an inert substrate, and the surface of ultra-fine SiO2.particles acted as a carrier for iron.

关键词： ultra-fine particles nano-particles ·OH oxidative stress size-effect

Experimental investigation and numerical simulation on the effect of fissure water pressure in vertical sliding surface

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Science china(Technological sciences) 2005年第Z1期48卷 53-64页

作者： ZHANG Lei1,2. li Shihai1, liAN Zhenzhong1,2.& WANG Yuannian1 1. {2. of Mechanics, chinese academy of sciences, beijing 100080, china 2. Graduate School, chinese academy of sciences, beijing 100060, china institute of Mechanics Chinese Academy of Sciences Beijing 100080 China Graduate School Chinese Academy of Sciences Beijing 100060 China

This paper studies the effect of fissure water pressure in different fractures on the critical angle of landslide by laboratory investigation and numerical simulation in order to understand the mechanisms of fissure water pressure on landslide stability. Laboratory observations show that the effect of fissure water pressure on the critical angle of landslide is little when the distance between water-holding fracture and slope toe is three times greater than the depth of fissure water. These experimental results are also simulated by a three-dimensional face-to-face contact discrete element method. This method has included the fissure water pressure and can accurately calculate the critical angle of jointed slope when fissure water pressure in vertical sliding surface exists. Numerical results are in good agreement with experimental observations. It is revealed that the location of water-holding structural surface is important to landslide stability. The ratio of the distance between water-holding fissure and slope toe to the depth of fissure water is a key parameter to justify the effect of fissure water pressure on the critical angle of landslide.

关键词： jointed rock slope, discrete element method, fracture in vertical sliding surface, model experiment,fissure water pressure.

Bio-regeneration of p-complexation desulfurization adsorbents

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Science china Chemistry 2005年第6期48卷 538-544页

作者： li Wangliang1,2. XING Jianmin1, XIONG Xiaochao1,2. SHAN Guobin1,2.& liU Huizhou1 1. Laboratory of Separation Science and Engineering, institute of Process Engineering, chinese academy of sciences, beijing 100080, china 2. Graduate School of the chinese academy of sciences,beijing 10003., china Laboratory of Separation Science and Engineering Institute of Process Engineering Chinese Academy of Sciences Beijing China Graduate School of the chinese academy of sciences Beijing China

The coupling of adsorption desulfurization and biodesulfurization is a new approach to produce clean fuels. Sulfur compounds are firstly adsorbed on adsorbents, and then the ad-sorbents are regenerated by microbial conversion. p-Complexation adsorbent, Cu(I)-Y, was ob-tained by ion exchanging Y-type zeolite with Cu2. and then by auto-reduction in helium at 450℃ for 3.h. Dibenzothiophene (DBT) was used as a model compound. The effects of cell concentra-tion, volume of oil phase, the ratio of aqueous phase to adsorbent on DBT desorption by a bac-terium were studied. The amounts of DBT desorbed and 2.HBP produced can be apparently increased with addition of n-octane. BDS activity can be improved by increasing cell concentra-tion and the ratio of water-to-adsorbent. 89% of DBT desorbed from the adsorbents can be converted to 2.HBP within 6 h and almost 100% within 2. h, when the volume ratio of oil-to-water was 1/5 mL/mL, the cell concentration was 60 g·L?1, and the ratio of adsorbent-to-oil was 0.03.g·mL?1. The amount of 2.HBP produced was strongly dependent on the volume ratio of oil-to- water, cell concentration and amount of adsorbent. Adsorption capacity of the regenerated ad-sorbent is 95% that of the fresh one after being desorbed with Pseudomonas delafieldii R-8, washed with n-octane, dried at 100℃ for 2. h and auto-reduced in He.

关键词： adsorption desulfurization p-complexation adsorbents bio-regeneration Pseudomonas delafieldii desorption.

New evidence for lack of CMB power on large scales

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Science china(Physics,Mechanics & Astronomy) 2010年第3期53卷 567-570页

作者： liU Hao1 & li TiPei1,2.3.1 Key Laboratory of Particle Astrophysics, {2. of high Energy Physics, chinese academy of sciences, beijing 100049, china 2.Department of Physics & Center for Astrophysics, Tsinghua University, beijing 100084, china 3.Department of Engineering Physics & Center for Astrophysics, Tsinghua University, beijing 100084, china Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing China Department of Physics & Center for Astrophysics Tsinghua University Beijing China Department of Engineering Physics & Center for Astrophysics Tsinghua University Beijing China

A digitalized temperature map is recovered from the first light sky survey image published by the Planck team, from which an angular power spectrum of the cosmic microwave background (CMB) is derived. The amplitudes of the low multipoles (low-l) measured from the preliminary Planck power spectrum are significantly lower than those reported by the WMAP team. Possible systematical effects are far from enough to explain the observed low-l differences.

关键词： cosmology cosmic microwave background data analysis

An analysis of the wide area differential method of geostationary orbit satellites

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Science china(Physics,Mechanics & Astronomy) 2009年第2期52卷 310-314页

作者： CAI Chenglin1,2.3., li XiaoHui1 & WU HaiTao1 1 National Time Service Center,{2., lintong 710600, china 2.Hunan institute of Humanities, Science and Technology, Loudi 417000, china 3.Graduate University of{2., beijing 100049, china National Time Service Center Chinese Academy of Sciences Lintong China Hunan institute of Humanities Science and Technology Loudi China Graduate University of chinese academy of sciences Beijing China

This work aims to obtain a wide area differential method for geostationary orbit (GEO) constellation. A comparison between the dilution of precision (DOP) of four-dimensional (4D) calculation including sa- tellite clock errors and ephemeris errors and that of three-dimensional (3.) calculation only including ephemeris errors with the inverse positioning theory of GPS shows the conclusion that all the 3. PDOPs are greatly reduced. Based on this, a basic idea of correcting satellite clock errors and ephem- eris errors apart is put forward, and moreover, a specific method of separation is proposed. Satellite clock errors are separated in a master station with time synchronization, and all the remaining pseu- do-range errors after the satellite clock errors have been deducted are used to work out ephemeris corrections of all GEO satellites. By a comparative analysis of user positioning accuracy before and after differential, the wide area differential method is verified to be quite valid for GEO constellation.

关键词： geostationary orbitsatellite dilution of precision satellite ephemeris errors satellite clock errors wide area differential method

Estimating possible impact of human activity on the warm season temperature in beijing since the industrial era

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chinese Science Bulletin 2010年第16期55卷 1590-1593页

作者： QIN li1,2.& ZHOU Xin1,2.1 {3. of Geology and Geophysics,{2. academy of sciences,beijing 10002.,china 2.Graduate University of chinese academy of sciences,beijing {13.,china institute of Geology and Geophysics Chinese Academy of Sciences Beijing China Graduate University of chinese academy of sciences Beijing China

Global surface temperature shows an increasing trend over the past 100 *** and natural factors have been invoked to explain this warming, but their relative contribution and the spatial variability remain *** on a 2.50-year temperature record from a stalagmite near beijing, we explore the possible impacts of human activity on the warm season temperature in beijing since the industrial era using the method of singular spectrum analysis (SSA).The results suggest that the warm season temperature in beijing under the natural forcing should have an overall decreasing trend for the past 13. years (1870 to 2.00 AD) with an amplitude of 0.45±0.84°C, while the instrumental record and stalagmite data show an increase of 1.08°*** imply that human activity would have caused an increase in the warm season temperature of beijing for about 1.53.0.84°C compared to its natural trends, from 1870 AD to 2.00 *** results also suggest that anthropogenic forcing began to significantly influence the temperature since 1870 AD, and the effect further intensified since 1915 AD.

关键词：人类活动北京温度工业时代季节温暖估计地表气温

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

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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,{2., beijing 100080, china 2. Graduate School of The{2., beijing 100085, china Multiphase Reaction Laboratory Institute of Process Engineering Chinese Academy of Sciences Beijing China Graduate School of The chinese academy of sciences 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.

Sporopollen analysis of Core B10 in the southern Yellow Sea and the reflected characteristics of climate changes

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chinese Science Bulletin 2003年第B6期48卷 42-48页

作者： FU Mingzuo~(1,2.3., li Zhen~1, XU Xiaowei~1 & SHl Xuefa~1 1. Key Laboratory of Marine Sedimentology and Environmental Geology, First institute of Oceanography. State Oceanic Administration, Qingdao 2.6061.{2. 2. institute of Oceanology, chinese academy of sciences, Qingdao 2.6071.{2. 3. Graduate School, chinese academy of sciences, beijing 10003..{2. Key Laboratory of Marine Sedimentology and Environmental Geology First institute of Oceanography State Oceanic Administration Qingdao China institute of Oceanology Chinese Academy of Sciences Qingdao China Graduate School Chinese Academy of Sciences Beijing China

Eight sporopollen zones have been divided based on the results of high-resolution sporopollen analysis of Core B10 in the southern Yellow Sea. Based on the results along with ^14C datings and the subbottom profiling data,climatic and environmental changes since the last stage of late Pleistocene are discussed. The main conclusions are drawn as follows: (1) the vegetation evolved in the process of coniferous forest-grassland containing broad-leaved trees→coniferous and broad-leaved mixed forest→coniferons and broad-leaved mixed forest-grassland prevailed by coniferous trees→coniferous and broad-leaved mixed forest-grassland containing evergreen broad-leaved trees→coniferons and broad-leaved mixed forest-grassland prevailed by broadleaved trees→deciduous broad-leaved forest-meadow containing evergreen broad-leaved trees→coniferous and broadleaved mixed forest-grassland prevailed by broad-leaved trees→coniferous and broad-leaved mixed forest containing evergreen broad-leaved trees; ({3. eight stages of climate changes are identified as the cold and dry stage, the temperate and wet stage, the cold and dry stage, the warm and dry stage, the temperate and wet stage, the hot and dry stage, the temperate and dry stage, then the warm and dry stage in turn; (3. the sedimentary environment developed from land,to littoral zone, to land again, then to shore-neritic zone; and (4) the Yellow Sea Warm Current formed during early-Holocene rather than Atlantic stage.

关键词：中国黄海气候变化碳14年代测定底基压型数据更新世沉积环境大西洋