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Effect of Limestone Powder on Microstructure of Concrete

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Journal of Wuhan university of Technology(Materials Science) 2010年第2期25卷 328-331页

作者：刘数华 State Key Laboratory of Water Resource and Hydropower engineering Science Wuhan University

The effect of limestone powder on microstructure of concrete was studied by using mercury intrusion porosimetry （MIP）, backscattering scanning electron（BSE）, scanning electron mi- croscopy （SEM） and X-ray diffraction （XRD） techniques. The experimental results show that the compressive strength of concrete containing 100 kg/m3 limestone powder can meet the strength requirement. Limestone powder has not pozzolanic activity; it is still unhydrated at the age of 2. days. But its filling effect can make the paste matrix and the interfacial transition zone between matrix and aggregate denser, which will improve the performance of concrete.

关键词： concrete limestone powder microstructure filling effect hydration characteristic

Effect of Limestone Powder and Fly Ash on Magnesium Sulfate Resistance of Mortar

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Journal of Wuhan university of Technology(Materials Science) 2010年第4期25卷 700-703页

作者：刘数华 State Key Laboratory of Water Resources and Hydropower engineering Science Wuhan University

The effect of limestone powder and fly ash on magnesium sulfate resistance of mortar was studied by testing on the strength, expansion and hydration products of the specimens stored in MgSO4 solution at certain periods. The experimental results show that the strength of mortar stored in MgSO4 solution increases a little before 2. d, but decreases fast subsequently. The more the contents of limestone powder and fly ash, the less the strength losses. Mortar swells in the MgSO4 solution with the soaking time. And the more the contents of limestone powder and fly ash, the less the expansion rate is. The expansion or strength loss of mortars results from the expansion of gypsum, as well as the loss of Ca（OH）2.and other hydration products of cement. The magnesium sulfate resistance of the mortars containing limestone powder and fly ash is high.

关键词： limestone powder fly ash mortar magnesium sulfate resistance

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空间刚架结构的广义逆力法

力学季刊 2004年第1期25卷 38-45页

作者：刘西拉王开健张春俊上海交通大学土木工程系上海200030 北京清华大学土木工程系北京100084 中元国际工程设计研究院北京100089

在结构计算中,根据算法中所采用的基本未知量的不同,结构分析方法可以分为力法、位移法和混合法。其中位移法由于适宜计算机处理而在结构计算领域得到了广泛的应用,经典力法相比之下应用就远不如位移法普遍,虽然力法本身在力学上有其独... 详细信息

在结构计算中,根据算法中所采用的基本未知量的不同,结构分析方法可以分为力法、位移法和混合法。其中位移法由于适宜计算机处理而在结构计算领域得到了广泛的应用,经典力法相比之下应用就远不如位移法普遍,虽然力法本身在力学上有其独特的优势。广义逆矩阵做为一种较新的数学工具,自二十世纪五十年代诞生以来正日益表现出越来越旺盛的生命力。广义逆力法就是一种基于力法和广义逆矩阵理论的新的迭代算法。这种算法是一种完全适合计算机处理的力法方法。该算法的思路以及对于求解线弹性空间刚架结构问题的具体公式均在文中给出并给出了算例。从算例计算结果可以看到广义逆力法有着较好的计算效率和计算精度。该算法的提出为力法在计算机计算领域的应用开拓了新的发展空间。该算法在材料非线性问题和结构并行计算方面也有着较好的应用前景。

关键词：广义逆矩阵广义逆力法空间刚架结构结构计算结构分析结构力学

掺超细粉煤灰高性能混凝土Ⅲ型轨枕的力学性能试验研究

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铁道学报 2004年第2期26卷 91-96页

作者：罗小勇余志武谢友均彭少军中南大学土木建筑学院云南华能澜沧江水电有限公司云南昆明650011

对掺超细粉煤灰的HPC Ⅲ型轨枕和普通C Ⅲ型轨枕的力学性能,如枕中和枕下截面的抗裂、极限承载力、轨枕端部局压和轨枕的疲劳性能进行了对比试验研究。试验表明,各种龄期HPC Ⅲ型轨枕与C Ⅲ型轨枕枕中和枕下的开裂荷载与极限承载力均比... 详细信息

对掺超细粉煤灰的HPC Ⅲ型轨枕和普通C Ⅲ型轨枕的力学性能,如枕中和枕下截面的抗裂、极限承载力、轨枕端部局压和轨枕的疲劳性能进行了对比试验研究。试验表明,各种龄期HPC Ⅲ型轨枕与C Ⅲ型轨枕枕中和枕下的开裂荷载与极限承载力均比较接近,满足标准的要求。还对轨枕端部进行了非线性有限元分析,分析很好地验证了试验结果,分析与试验结果均表明,轨枕端头局压破坏为主拉劈裂破坏,试验实测的超细粉煤灰HPC Ⅲ型轨枕端部局压的极限承载力远大于锚固板设计最大张拉预应力,有较大的安全储备。HPC Ⅲ型轨枕的疲劳性能与C Ⅲ型轨枕的相近,HPC Ⅲ型轨枕的疲劳残余裂缝宽度略小于C Ⅲ型轨枕。

关键词：超细粉煤灰 Ⅲ型轨枕锚固板局部受力疲劳

Effect of Coarse Aggregate Size on Relationship between Stress and Crack Opening in Normal and High Strength Concretes

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Journal of Materials Science & Technology 2005年第5期21卷 85-94页

作者： Jun ZHANG Qian LIU and Lin WANGDepaxtment of civil engineering,{2., beijing 100084, china department of civil {2. Tsinghua University Beijing 100084 China

Fine and coarse aggregates play an important role in the fracture of concrete. However, quantitative informationavailable on the effect of the coarse aggregate size on the fracture properties of concrete is still limited. In the presentpaper, the effect of coarse aggregate size (single grade of 5~10, 10~16, 16~2. and 2.~2. mm) on stress-crackopening (σ-ω) relation in normal and high strength concretes (compressive strength of 40 and 80 MPa, respectively)was studied. The investigation was based on three-point bending tests implemented by fictitious crack analysis. Theresult shows that coarse aggregate size and cement matrix strength significantly influence the shape of σ-ω *** a given total aggregate content, in normal strength concrete, smaller size of aggregate leads to a high tensilestrength and a sharp stress drop after the peak stress. The smaller the coarse aggregate, the steeper the σ-ω *** contrast, in high strength concrete, the effect of aggregate size on σ-ω relation almost vanishes. A similar σ-ωrelation is obtained for the concrete except for the case of 2.~2. mm coarse aggregate size. The stress drop afterthe peak stress is more significant for high strength concrete than that for normal strength concrete. Meanwhile, thesmaller the coarse aggregate size, the higher the flexural strength. Fracture energy and characteristic length increasewith increasing coarse aggregate size in both normal and high strength concretes.

关键词： Aggregate size Stress-crack opening relation Fracture energy Bending test

Self-Organizing Tunnel Peers

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计算机工程 2002年第S1期28卷 7-12页

作者： CHEN Maoke , LI Xing (department of Electronic engineering,{2., beijing 100084,china ) department of Electronic engineering Tsinghua University Beijing 100084China

Tunneling is an important approach in IPv6 transition techniques. The tunnel broker model provides a way to build virtual IPv6 networks without manual ***, neither it adapts performance variation on the IPv4 infrastructure, norit is a scalable solution for a wide-area IPv6 networking environment. In this paper, a self-organizing tunnel peer (SOTP) model is *** peers are clustered in the SOTP system so that optimization is scalable. Four primitive operations related to --cluster constructionarrest,release,division and deathendow the system with the nature of self-organization. Occurrence and behavior of the operations are decided by criteria on the IPv4 end-to-end performance; hence measurement is an indispensable component of the system. The metabolism of cluster relaxes the requirement to accuracy of measurement and optimization.

关键词： S elf-organizationTunnelingEnd-to-end measurementIPv6

Development of SOM combustion model for Reynolds-averaged and large-eddy simulation of turbulent combustion and its validation by DNS

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Science china(Technological Sciences) 2008年第8期51卷 1073-1086页

作者： ZHOU LiXing department of engineering Mechanics,{2., beijing 100084, china department of engineering Mechanics Tsinghua University

The derivation and closure methods of the second-order moment (SOM) combus- tion model are proposed. The application of this model to Reynolds averaged (RANS) and large-eddy simulation (LES) of turbulent swirling diffusion combustion, jet diffusion combustion, and bluff-body stabilized premixed combustion is sum- marized. It is indicated that the SOM model is much better than the eddy-beak-up (EBU) and presumed PDF models widely used in commercial software and engi- neering. The SOM modeling results are close to those obtained using the most accurate but much more complex PDF equation model. Moreover, it can save much more computation time than the PDF equation model. Finally, the SOM model is validated by the direct numerical simulation (DNS) of turbulent reacting channel flows.

关键词： turbulent combustion second-order moment model Reynolds averaged simulation large-eddy simulation

TEXTURE DETERMINATION OF THIN FILM ZrO_2.BY ELECTRON DIFFRACTION

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Acta Metallurgica Sinica(English Letters) 1993年第12期6卷 472-473页

作者： WANG Yinghua tsinghua university,beijing,{2. department of Materials Science and engineering,tsinghua university,beijing 100084,{2. tsinghua Univ Beijing China

A method for semi-quantitative determination of thin film texture using electron diffrac- tion is *** texture state of a zirconia thin film with a cubic structure has been determined in this way and is presented as an... 详细信息

关键词： texture thin film electron diffraction ZrO_2

A MESSAGE-DRIVING FORMALISM FOR MODELING AND SIMULATION OF MULTI-AGENT SUPPLY CHAIN SYSTEMS

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Journal of Systems Science and Systems engineering 2011年第4期20卷 385-399页

作者： Wenzhe TAN1 Yueting CHAI2.Yi LIU3 1department of Automation, tsinghua university, {2., 100084, china 2.0} of Automation, tsinghua university, {2., 100084, china 3department of Automation, tsinghua university, {2., 100084, china department of Automation Tsinghua University Beijing China

To acquire a competitive advantage in the expanding market, manufacturing enterprises should be able to manage their supply chains as effectively as possible. It is now becoming popular to model supply chains as multi-agent systems and use discrete event simulation to learn more about their behaviors or investigate the implications of alternative configurations. In order to enhance the computational efficiency and keep the simulation credibility, this paper proposes a message-driving formalism for the simulation of multi-agent supply chain systems. Through the message-driving formalism, the problem of shared variables is addressed and the parallel operation of agents is implemented. Simulation experiments with a prototype implementation show that the message-driving formalism is able to provide credible results in significantly less simulation time.

关键词： Supply chain multi-agent system modeling and simulation parallel discrete event simulation message-driving formalism