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Deterioration Mechanisms of Sulfate Attack on Concrete under Alternate Action

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Journal of Wuhan university of Technology(Materials Science) 2010年第2期25卷 355-359页

作者：高润东 state key Laboratory of hydroscience and {3. Tsinghua University

By micro- and macro-observations, the deterioration mechanisms of concrete under alternate action between repeated sub-high temperature/cooling by water and sodium sulfate solution attack （TW-SA） were studied; meanwhile, the single sodium sulfate solution attack （SA） was also done as comparison. Micro-observations included the analysis of attack products by thermal analysis method and the determination of sulfate-ion content from surface to interior by chemical titrating method （modified barium sulfate gravimetric method）. Macro-observations mainly included the mechanical behaviors such as compressive strength, splitting strength. The experimental results indicate, in both cases, the main attack product is ettringite, only in the first layer of case SA some gypsum is checked; in case SA, the sulfate ions mainly concentrate in the surface layer, so the attack is relatively mild; but in case TW-SA, the repeated sub-high temperature/cooling by water promotes the sulfate ions diffusing inwards, which leads to obvious strength degradation.

关键词： concrete sulfate repeated sub-high temperature/cooling by water attack product sulfate-ion content strength

Quantum threshold group signature

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Science china(Physics,Mechanics & Astronomy) 2008年第10期51卷 1505-1514页

作者： YANG YuGuang1,2,3.& WEN QiaoYan4 1 College of Computer Science and Technology, beijing university of Technology, beijing 100124, {3. 2.state key Laboratory of Integrated Services Network, Xidian university, Xi’an 710071, {3. 3.state key Laboratory of Information Security (Graduate university of Chinese Academy of Sciences), beijing 100049, {3. 4 state key Laboratory of Networking and Switching Technology, beijing university of Posts and Tele-communications, beijing 100876, {3. College of Computer Science and Technology Beijing University of Technology Beijing 100124 China state key Laboratory of Integrated Services Network Xidian University Xi’an 710071 China state key Laboratory of Information Security Graduate University of Chinese Academy of Sciences Beijing 100049 China state key Laboratory of Networking and Switching Technology Beijing University of Posts and Telecommunications Beijing 100876 China

In most situations, the signer is generally a single person. However, when the message is written on behalf of an organization, a valid message may require the approval or consent of several persons. Threshold signature is a solution to this problem. Generally speaking, as an authority which can be trusted by all members does not exist, a threshold signature scheme without a trusted party appears more attractive. Following some ideas of the classical Shamir’s threshold signature scheme, a quantum threshold group signature one is proposed. In the proposed scheme, only t or more of n persons in the group can generate the group signature and any t-1 or fewer ones cannot do that. In the verification phase, any t or more of n signature receivers can verify the message and any t-1 or fewer receivers cannot verify the validity of the signature.

关键词： threshold quantum signature trusted party quantum cryptography

Threshold quantum secret sharing between multi-party and multi-party

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Science china(Physics,Mechanics & Astronomy) 2008年第9期51卷 1308-1315页

作者： YANG YuGuang1,2,3.& WEN QiaoYan4 1 College of Computer Science and Technology,beijing university of Technology,beijing 100124,{3. 2.state key Laboratory of Integrated Services Network,Xidian university,Xi’an 710071,{3. 3.state key Laboratory of Information Security (Graduate university of Chinese Academy of Sciences),beijing 100049,{3. 4 state key Laboratory of Networking and Switching Technology,beijing university of Posts and Tele-communications,beijing 100876,{3. College of Computer Science and Technology Beijing University of Technology Beijing 100124 China state key Laboratory of Integrated Services Network Xidian University Xi’an 710071 China state key Laboratory of Information Security (Graduate university of Chinese Academy of Sciences) Beijing 100049 China state key Laboratory of Networking and Switching Technology Beijing University of Posts and Telecommunications Beijing 100876 China

A threshold quantum secret sharing (TQSS) scheme between multi-party and multi-party was proposed using a sequence of single photons,which is useful and efficient when the parties of communication are not all present. We described the process of this TQSS scheme and discussed its security. It was shown that entan-glement is not necessary for quantum secret sharing. Moreover,the theoretic effi-ciency was improved to approach 100% as almost all the instances can be used for generating the private key,and each photon can carry one bit of information. This protocol is feasible with the present-day technique.

关键词： threshold quantum secret sharing quantum cryptography single photon multi-party and multi-party

A COUPLED 1-D AND 2-D CHANNEL NETWORK MATHEMATICAL MODEL USED FOR FLOW CALCULATIONS IN THE MIDDLE REACHES OF THE YANGTZE RIVER

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Journal of Hydrodynamics 2011年第4期23卷 521-526页

作者： HAN Dong FANG Hong-wei BAIJing HE Guo-jian Department of Hydraulic engineering and state key Laboratory of {3. and engineering Tsinghua University Beijing 100084 China

A coupled one-dimensional （1-D） and two-dimensional （2-D） channel network mathematical model is proposed for flow calculations at nodes in a channel network system in this article. For the 1-D model, the finite difference method is used to discretize the Saint-Venant equations in all channels of a looped network. The Alternating Direction Implicit （ADI） method is adopted for the 2-D model at the nodes. In the coupled model, the 1-D model provides a good approximation with small computational effort, while the 2-D model is applied for complex topography to achieve a high accuracy. An Artificial Neural Network （ANN.） method is used for the data exchange and the connectivity between the 1-D and 2-D models. The coupled model is applied to the Jingjiang-Dongting Lake region, to simulate the tremendous looped channel network system, and the results are compared with field data. The good agreement shows that the coupled hydraulic model is more effective than the conventional 1-D model.

关键词： Coupled 1-D and 2-D model looped channel network system Alternating Driection Implicit (ADI) Jingjiang-Dongting Lake region

Threshold proxy quantum signature scheme with threshold shared verification

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Science china(Physics,Mechanics & Astronomy) 2008年第8期51卷 1079-1088页

作者： YANG YuGuang1,3.4 & WEN QiaoYan2 1 College of Computer Science and Technology,beijing university of Technology,beijing 100124,{3. 2.state key Laboratory of Networking and Switching Technology,beijing university of Posts and Tele-communications,beijing 100876,{3. 3.state key Laboratory of Integrated Services Network,Xidian university,Xi’an 710071,{3. 4 state key Laboratory of Information Security(Graduate university of Chinese Academy of Sciences) ,beijing 100049,{3. 1. College of Computer Science and Technology Beijing University of Technology Beijing 100124 China 3. state key Laboratory of Integrated Services Network Xidian University Xi’an 710071 China 4. state key Laboratory of Information Security (Graduate university of Chinese Academy of Sciences) Beijing 100049 China 2. state key Laboratory of Networking and Switching Technology Beijing University of Posts and Telecommunications Beijing 100876 China

A threshold proxy quantum signature scheme with threshold shared verification is proposed. An original signer could authorize a group as its proxy signers. Then only t or more of n persons in the proxy group can generate the proxy signature on behalf of the original signer and any t-1 or fewer ones cannot do that. When the proxy signature needs to be verified,any t or more of n persons belonging to the verification group can verify the message and any t-1 or fewer ones cannot verify the validity of the proxy signature.

关键词： quantum signature threshold proxy quantum group signature threshold shared verification

Effect of Heat Treatment on High Temperature Stress Rupture Strength of Brazing Seam for Nickel-base Superalloy

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Journal of university of Science and Technology beijing 2001年第2期8卷 123-125页

作者： Junying Zhang, Zhongtai Zhang, Jisheng Sun, Xiaofang Liu, Wei Tian (state key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and engineering, {3., beijing 100084, china) (beijing Institute of Aeronautical Tsing Hua Univ Dept Mat Sci & Engn State Key Lab New Ceram & Fine Proc Beijing 100084 Peoples R China Inst Aeronaut Mat Beijing 100095 Peoples R China Univ Sci & Technol beijing Mat Sci & Engn Sch Beijing 100083 Peoples R China

In order to enhance the high-temperature stress rupture strength of brazing seam by heat treatment, it was diffusion treated, then solution heat treated, and finally aging treated. The microstructure of brazing seam especially morphology of gamma ' phase and boride was observed and the strength of brazing seam was measured in this process. The results show that heat treatment can enhance high-temperature stress rupture strength by improving the microstructure of brazing seam. The strength of brazing seam after solution heat treatment decreases in comparison with that only after diffusion treatment while aging treatment after solution heat treatment increases the strength of brazing seam.

关键词： wide-gap brazing high temperature stress rupture strength microstructure nickel-base superalloy

On the dynamics in a transitional boundary layer

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Communications in Nonlinear Science and Numerical Simulation 2001年第3期6卷 111-171页

作者： C. B. LEE and R. LEE Department of Mechanics and engineering Science/state key Laboratory for Studies of Turbulence and Complex Systems, Peking {3., beijing 100871, china Department of engineering Mechanics, tsinghua university, beijing 100084, Chi Department of Mechanics and engineering Science / state key Laboratory for Studies of Turbulence and Complex Systems Peking University Beijing 100871 China Department of engineering Mechanics Tsinghua University Beijing 100084 China

A model is presented to describe the dynamic physical processes that occur in a transitional boundary layer flow. The CS-solitons, the closed vortex, the secondary closed vortex and the chain of ring-like vortices are postulated to be the basic flow structures of the transitional boundary layer as well as the turbulent boundary layer. It is argued that the central features of transitional and developed turbulent boundary layer flows can be explained in terms of how the series vortices interact with each other, and with the CS-solitons. The physical process that leads to the regeneration of the new closed vortex along the border of the CS-soliton, as well as the processes of evolution of the vortices to high frequency vortices, is described. The model is supported by the important developments in a number of "kernel" experiments, which illustrate both transitional and developed turbulent boundary layer. An important aspect of the model is that it has been formulated to be consistent with accepted rational mechanics concepts that are known to provide a proper physical description of other flows.

关键词： boundary layer transition dynamic processes onset of turbulence

Propagation characteristics of converted refracted wave and its application in static correction of converted wave

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Science china Earth Sciences 2008年第S2期51卷 226-232页

作者： LIU Yang1,2 & WEI XiuCheng3.1 state key Laboratory of Petroleum Resource and Prospecting,china {3. of Petroleum,beijing 102249,china 2 CNPC Geophysical Exploration key Laboratory,china {3. of Petroleum,beijing 102249,china 3.Exploration and Production Research Institute,SINOPEC,beijing 100083.china china Univ Petr State Key Lab Petr Resource & Prospecting Beijing 102249 Peoples R China china Univ Petr CNPC Geophys Explorat Key Lab Beijing 102249 Peoples R China SINOPEC Explorat & Prod Res Inst Beijing 100083 Peoples R China

Three-component seismic exploration through P-wave source and three-component geophone is an effective technique used in complicated reservoir exploration. In three-component seismic exploration data processing,one of the difficulties is static correction of converted wave. This paper analyzes propagation characteristics of non-converted and converted refracted waves,and discovers a favor-able condition for the formation of converted refracted wave,i.e. the velocity of overlaying medium S wave is much lower than that of underlying medium S wave. In addition,the paper proposes the static correction method of converted wave based on PPS converted refracted wave,and processes the real three-component seismic data with better results of static correction of converted wave.

关键词： PPS converted refracted wave converted wave static correction

Numerical exploration of new features on three-dimensional transition of a cylinder wake

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Science china Mathematics 2004年第z1期47卷 69-80页

作者： LING Guocan, XIONG Jun & ZHU Keqinstate key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, beijing 100080, {3. Department of engineering Mechanics, tsinghua university, beijing 100084, {3. Chinese Acad Sci Inst Mech State Key Lab Nonlinear Mech Beijing 100080 Peoples R China Tsing Hua Univ Dept Engn Mech Beijing 100084 Peoples R China

The three-dimensional transition of the wake flow behind a circular cylinder is studied in detail by direct numerical simulations using 3. incompressible N-S equations for Reynolds number ranging from 200 to 3.0. New features and vortex dynamics of the 3. transition of the wake are found and investigated. At Re = 200, the flow pattern is characterized by mode A instability. However, the spanwise characteristic length of the cylinder determines the transition features. Particularly for the specific spanwise characteristic length linear stable mode may dominate the wake in place of mode A and determine the spanwise phase difference of the primary vortices shedding. At Re = 250 and 3.0 it is found that the streamwise vortices evolve into a new type of mode "dual vortex pair mode" downstream. The streamwise vortex structures switch among mode A, mode B and dual vortex pair mode from near wake to downstream wake. At Re = 250, an independent low frequency fm in addition to the vortex shedding frequency fs is identified. Frequency coupling between fm and fs occurs. These result in the irregularity of the temporal signals and become a key feature in the transition of the wake. Based on the formation analysis of the streamwise vorticity in the vicinity of cylinder, it is suggested that mode A is caused by the emergence of the spanwise velocity due to three dimensionality of the incoming flow past the cylinder. Energy distribution on various wave numbers and the frequency variation in the wake are also described.

关键词： cylinder, wake, 3. transition, Fourier-spectral-spectral-element method, direct numerical simulation (DNS).