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Effect of surface nanocrystallization on the corrosion behavior of Zircaloy-4

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science china(Technological sciences) 2009年第8期52卷 2227-2231页

作者： ZHU YuTao1,2 & ZHANG XiYan1,2,3 1 College of materials science and Engineering, Chongqing university, Chongqing 400045, china 2.national Engineering Research center for Magnesium Alloys, Chongqing university, Chongqing 400044, china 3 School of Physical science and Engineering technology, Guangxi university, Nanning 530004, china College of materials science and Engineering Chongqing University national Engineering Research center for Magnesium Alloys Chongqing University 3School of Physical science and Engineering technology Guangxi University

The contrastive corrosion experiments between surface nanocrystallined Zircaloy-4 and coarse-grained Zircaloy-4 under the condition of 673 K/10.3 MPa in pure water are carried out, and the microstructure of oxide films has been studied. The results indicate that the growth rate of oxide films formed on the nanocrystalline Zircaloy-4 is lower than that of oxide films formed on the coarse-grained Zircaloy-4. Simultaneously, the oxide/metal interface of the former is more regular and glossy than that of the latter. For nanocrystalline Zircaloy-4, the low oxygen diffusion rate through the oxide/metal interface can hinder the reaction of oxygen ion with metal ion. Furthermore, more tetragonal ZrO2 are observed in the oxide films, which can delay the martensite phase transition from tetragonal to monoclinic phase in oxide films.

关键词： nanocrystalline Zircaloy oxide film microstructure

A virtual reference satellite differential method for relative correction of satellite ephemeris errors

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science china(Physics,Mechanics & Astronomy) 2010年第12期53卷 2300-2306页

作者： CAI ChengLin 1,3 , LI XiaoHui 2,3 & WU HaiTao 2,3 1 Gulin university of Electronic technology, 541004, china 2.national Time service center, Chinese Academy of sciences, Lintong 710600, china 3 Key Laboratory of Precision Navigation and Timing technology, national Time service center, Chinese Academy of sciences, Lintong 710600, china Gulin university of Electronic technology Gulin China Chinese Academy of sciences Key Laboratory of Precision Navigation and Timing Technology National Time Service Center Lintong China (GRID:grid.9227.e) (ISNI:***) Chinese Academy of sciences National Time Service Center Lintong China (GRID:grid.9227.e) (ISNI:***) Chinese Academy of sciences Key Laboratory of Precision Navigation and Timing Technology National Time Service Center Lintong China (GRID:grid.9227.e) (ISNI:***)

In order to solve the problems that the novel wide area differential method on the satellite clock and ephemeris relative correction (CERC) in the non-geostationary orbit satellite constellation, a virtual reference satellite (VRS) differential principle using relative correction of satellite ephemeris errors is proposed. It is referred to be as the VRS differential principle, and the elaboration is focused on the construction of pseudo-range errors of VRS. Through qualitative analysis, it can be found that the impact of the satellite’s clock and ephemeris errors on positioning can basically be removed and the users’ positioning errors are near zero. Through simulation analysis of the differential performance, it is verified that the differential method is universal in all kinds of satellite navigation systems with geostationary orbit (GEO) constellation, Medium orbit (MEO) constellation or hybrid orbit constellation, and it has insensitivity to abnormal aspects of a satellite ephemeris and clock. Moreover, the real time positioning accuracy of differential users can be maintained within several decimeters after the pseudo-range measurement noise is effectively weakened or eliminated.

关键词： wide area differential method virtual reference satellite (VRS) satellite ephemeris errors satellite clock errors constellation

Information content security on the Internet:the control model and its evaluation

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science china(Information sciences) 2010年第1期53卷 30-49页

作者： FANG BinXing1, GUO YunChuan2,3 & ZHOU Yuan4 1School of Computer, beijing university of Posts and Telecommunications, beijing 100029, china 2Institute of Computing technology, Chinese Academy of sciences, beijing 100190, china 3Graduate university of Chinese Academy of sciences, beijing 100049, china 4national Computer Network Emergency Response Technical Team/Coordination center of china, beijing 100029, china School of Computer Beijing University of Posts and Telecommunications Institute of Computing technology Chinese Academy of Sciences Graduate university of Chinese Academy of sciences national Computer Network Emergency Response Technical Team/Coordin

Flooding of harmful information on the Internet seriously endangers the physiological and mental health of teenagers. Due to the user-friendliness of the Internet as well as the difficulty in the authentication for the access of specific categories of information, curbing the transmission of harmful information, i.e., assuring the information content security (ICS), has become a reasonable yet challenging alternative. At present, there is an urgent need to develop a systematic model that can effectively carry out the curbing. In fact, curbing the transmission of harmful information by way of filtering can be modeled by access control. In the paper, based on the three core-elements of communication, namely, "Who communicates with whom", "How do they communicate" and "What is the content of communication", we propose a control model, called ICCON. Unlike the existing access control, the reference monitor (RM) of our model is placed in the transmission channel, and moreover, an evaluation frame is proposed, through which the effectiveness of the RM in controlling information transmission on the Internet can be quantitatively evaluated.

关键词： content security access control quantitative evaluation

Re-Os(ICP-MS)dating of the massive sulfide ores from the Jinchuan Ni-Cu-PGE deposit

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science china Earth sciences 2005年第10期48卷 1672-1677页

作者： YANG Gang1,2, DU Andao1, LU Jiren3, QU Wenjun1 & CHEN Jiangfeng2 1. national Research center of Geoanalysis, beijing 100037, china 2. Laboratory for Earth Material Cycling, School of Earth and Space sciences, university of science and technology of china, Hefei 230026, china 3. Institute of Mineral Resource, Chinese Academy of Geological sciences, beijing 100037, china national Research center of Geoanalysis university of science and technology of china Chinese Academy of Geological sciences

Massive sulfide ore from the Jinchuan Ni-Cu-PGE deposit was dated by Re-Os technique using Carius Tube digestion, Os distillation, Re extraction by acetone and ICP-MS measurement. An isochron giving an age of 833 ± 35 Ma, initial 187Os/188Os ratio of 0.279 ± 0.018 (MSWD = 1.7) and γOs = 130 ± 15 is obtained. The Re-Os age obtained agrees, within analytical uncertainties, with previous SHRIMP zircon U-Pb age of 827 ± 8 Ma (n=5, MSWD = 4.3). The result suggests that the deposit was formed at Neoproterozoic and that the formation of the Jinchuan Ni-Cu-PGE sulfide deposit may be closely related to the plume activity, which were attributed to the breakup of the Rodinia supercontinent. The high γOs of the massive ores sug-gests that crustal material was involved in the formation of the Jinchuan deposit, however, the quantity of the added crustal material is less than 10%.

关键词： Jinchuan Ni-Cu-PGE deposit, Re-Os dating, ICP-MS.

Fluorescence dynamics of interactions between polyamide PyPyPyβDp and DNA

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science china Chemistry 2006年第1期49卷 75-80页

作者： ZHANG Huijuan1,2, WANG Jin3, WU Yishi1, YUAN Gu3, AI Xicheng1, WANG Li4 & ZHANG Jianping1 1. State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of sciences, beijing 100080, china 2. School of Life science and technology, beijing Institute of technology, beijing 100081, china 3. College of Chemistry and Molecular Engineering, Peking university, beijing 100080, china 4. center for Condensed Matter Physics, Institute of Physics, Chinese Academy of sciences, beijing 100080, china Correspondence should be addressed to Ai Xicheng and Zhang Jianping State Key Laboratory for Structural Chemistry of Unstable and Stable Species Institute of Chemistry Chinese Academy of Sciences Beijing China School of Life science and technology Beijing Institute of Technology Beijing China College of Chemistry and Molecular Engineering Peking University Beijing China center for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing China

The photophysical properties of the polyamide PyPyPyβDp (PPP) were investigated by means of steady-state absorption and fluorescence spectroscopies, as well as time-resolved fluo-rescence spectroscopy. It was found that the excited-state properties of PPP are very sensitive to solvents. In TKMC buffer PPP exhibited weak fluorescence with a decay time constant of 16 ps, while with the decrease of the solvent polarity PPP showed the blue-shifted peak position, increased inten-sity and lengthened life-time for its fluorescence behavior. In the presence of calf thymus DNA, it was observed that the fluorescence intensity was enhanced and the fluorescence lifetime increased from 16 to 32 ps for PPP, which verified that PPP bound into the minor groove of DNA duplex.

关键词： polyamide (PPP), calf thymus DNA (ctDNA), time-resolved fluorescence spectroscopy, recognition dynamics.

P2P traffic optimization

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science china(Information sciences) 2012年第7期55卷 1475-1492页

作者： ZHANG GuoQiang 1,2 ,TANG MingDong 3 ,CHENG SuQi 2,4 ,ZHANG GuoQing 2 ,SONG HaiBin 5 ,CAO JiGuang 6 & YANG Jing 7 1 School of Computer science and technology,Nanjing Normal university,Nanjing 210046,china 2 Institute of Computing technology,Chinese Academy of sciences,beijing 100190,china 3 School of Computer science and Engineering,Hunan university of science and technology,Xiangtan 411201,china 4 Graduate university of Chinese Academy of sciences,beijing 100190,china 5 Nanjing R&D center,Huawei Technologies,Nanjing 210012,china 6 china Academy of Telecommunication Research of MIIT,beijing 100191,china 7 china Mobile Research Institute,beijing 100053,china School of Computer science and technology Nanjing Normal University Nanjing China Institute of Computing technology Chinese Academy of Sciences Beijing China School of Computer science and Engineering Hunan University of Science and Technology Xiangtan China Graduate university of Chinese Academy of sciences Beijing China Nanjing R&D center Huawei Technologies Nanjing China china Academy of Telecommunication Research of MIIT Beijing China china Mobile Research Institute Beijing China

Peer-to-peer (P2P) based content distribution systems have emerged as the main form for content distribution on the Internet,which can greatly reduce the distribution cost of content providers and improve the overall system ***,the mismatch between the overlay and underlay networks causes large volume of redundant traffic,which intensifies the tension between P2P content providers and ***,how to efficiently use network resources to reduce the traffic burden on the ISPs is crucial for the sustainable development of P2P *** paper surveys the state-of-art P2P traffic optimization technologies from three perspectives:P2P cache,locality-awareness and data *** details,comparison between these technologies and their applicabilities are presented,followed by a discussion of the issues that remain to be addressed and the direction of future content distribution research.

关键词： P2P traffic localization P2P traffic optimization P2P cache locality-awareness network coding content-centric network

A three-dimensional variational ocean data assimilation system:Scheme and preliminary results

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science china Earth sciences 2006年第11期49卷 1212-1222页

作者： ZHU Jiang1,2, ZHOU Guangqing1, YAN Changxiang1, FU Weiwei1 & YOU Xiaobao1,3 1. International center for Climate and Environment sciences, Institute of Atmospheric Physics, Chinese Academy of sciences, beijing 100029, china 2. Jiangsu Key Laboratory of Meteorological Disaster, Nanjing university of Information science and technology, Nanjing 210044, china 3. beijing Institute of Applied Meteorology, beijing 100029, china International center for Climate and Environment sciences Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China Jiangsu Key Laboratory of Meteorological Disaster Nanjing University of Information Science and Technology Nanjing China beijing Institute of Applied Meteorology Beijing China

A new 3DVAR-based Ocean Variational Analysis System (OVALS) is developed. OVALS is capable of assimilating in situ sea water temperature and salinity observations and satellite altimetry data. As a component of OVALS, a new variational scheme is proposed to assimilate the sea surface height data. This scheme considers both the vertical correlation of background errors and the nonlinear temperature-salinity relationship which is derived from the generalization of the linear balance constraints to the nonlinear in the 3DVAR. By this scheme, the model temperature and salinity fields are directly adjusted from the altimetry data. Additionally, OVALS can assimilate the temperature and salinity profiles from the ARGO floats which have been implemented in recent years and some temperature and salinity data such as from expendable bathythermograph, moored ocean buoys, etc. A 21-year assimilation experiment is carried out by using OVALS and the Tropical Pacific circulation model. The results show that the assimilation system may effectively improve the estimations of temperature and salinity by assimilating all kinds of observations. Moreover, the root mean square errors of temperature and salinity in the upper depth less than 420 m reach 0.63℃ and 0.34 psu.

关键词： data assimilation, 3DVAR, sea surface height, ARGO floats.

Microstructure and formation mechanism of twins of laths of austenite with high nitrogen

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science china(Technological sciences) 2007年第6期50卷 755-764页

作者： WU CuiLan1,2 & LUO ChengPing2 1 center for High Resolution Electron Microscopy, College of materials science and Engineering, Hunan university, Changsha 410082, china 2 College of Mechanical Engineering, South china university of technology, Guangzhou 510641, china center for High Resolution Electron Microscopy College of Materials Science and Engineering Hunan University College of Mechanical Engineering South China University of Technology

The microstructure of composite diffusion layer of the nitrided and chromized 0.2% carbon steel is investigated using TEM and EDS. It is found that laths of austenite with high nitrogen (γ N) precipitate from α-ferrite matrix in the deeper zone of the diffusion layer. These γ N laths are all twins, with their {111} twinning planes parallel to the lath axis, thus forming a characteristic "back-to-back" morphology. There are two types of γN lath. The first is a genuinely {111} twin, and γ N and α keep the accurate K-S relationship, and each γ N and α form a sharp and smooth γ N/α inter- face of {335}γN//{341}α, namely habit plane {335}fcc. The second is a pseudo-twin, with micro-twins {111} or faults formed within the two twin components. Localized lattice deformation (relaxation) seems to have occurred at the interfaces of the second type of γ N due to the formation of micro-twins or faults within the twin components. These micro-twins or faults make the orientation relationship (OR) between each of the γN and the α-matrix deviate from the accurate K-S OR, and the OR between two γ N twin components deviate from the genuine {111} twin relation- ship. In addition, the γ N/α interface of the second type of γ N is not as sharp or smooth as that of the first one.

关键词： austenite containing nitrogen, twins, steel 20, nitriding, composite chromizing

Experimental investigation of high temperature thermal contact resistance with interface material

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Theoretical & Applied Mechanics Letters 2011年第5期1卷 41-44页

作者： Xiaoping Zheng1,Donghuan Liu,2,3 Dong Wei,4 and Xinchun Shang 2,3 1) Applied Mechanics Laboratory,Department of Engineering Mechanics,Tsinghua university,beijing 100084,china 2) Department of Applied Mechanics,university of science & technology beijing,beijing 100083,china 3) national center for materials service safety,university of science & technology beijing,beijing 100083,china 4) china Aerodynamics Research and Development center,Mianyang 621000,china Tsinghua Univ Dept Engn Mech Appl Mech Lab Beijing 100084 Peoples R China Univ Sci & Technol beijing Dept Appl Mech Beijing 100083 Peoples R China Univ Sci & Technol beijing Natl Ctr Mat Serv Safety Beijing 100083 Peoples R China china Aerodynam Res & Dev Ctr Mianyang 621000 Peoples R China

Thermal contact resistance plays a very important role in heat transfer efficiency and thermomechanical coupling response between two materials,and a common method to reduce the thermal contact resistance is to fill a soft interface material between these two materials.A testing system of high temperature thermal contact resistance based on INSTRON 8874 is established in the present paper,which can achieve 600 C at the *** on this system,the thermal contact resistance between superalloy GH600 material and three-dimensional braid C/C composite material is experimentally investigated,under different interface pressures,interface roughnesses and temperatures,*** the same time,the mechanism of reducing the thermal contact resistance with carbon fiber sheet as interface material is experimentally *** show that the present testing system is feasible in the experimental research of high temperature thermal contact resistance.

关键词： thermal contact resistance interface material experimental research high temperature alloy C/C composite material