地铁区间隧道火灾与防范

介绍了地铁区间隧道火灾发生的原因及危害性,对地铁区间隧道火灾中烟气流动和火焰传播特性进行理论分析,对区间隧道火灾的防范及消防管理进行初步探讨.     

长江交通体系亟待重新构造——尽快建设沿江铁路与综合运输体系

<正> 1998年夏季,长江干流因洪水封航、断航达40多天之久,沿江地带不仅正常交通被打乱,甚至连防汛物资运输都深受影响。长江流域交通体系如此脆弱和落后的严峻现实,把我国交通、经济界长期讨论的一个重要问题,即沿江的铁路及其综合运输体系建设问题再次提上议程。     

以京沪港渝为枢纽重构全国综合交通网

一、京沪港渝四大增长极 经济学的增长极理论认为，经济发展在时间和空间上都不是均衡分布的，在集聚着经济主导产业、富有创新能力的大城市，通常具有最大增长势能和潜力，成为区域经济增长极。区域增长极凭借自身的经济实力、创新能力和沟通腹地的经济网络，对腹地产生强大的集聚和辐射效应，引导和带动区域发展。     

Numerical method on load sharing problem of thick laminate joints

Accurately and efficiently predicting the load sharing of multi~bolt thick laminate joints is necessary to quicken the optimization of the large-scale structures over various design variables, and a two-dimensional （2D） finite element method （FEM） is introduced to meet such a demand. The deformation contributions of the joint zone are analyzed and calculated separately, including the shearing deformation of the fasteners shank, the bending deformation of the fasteners shank, and the bearing deformation of the fasteners and joint plates. These deformations are all transferred and incorporated into the components of the fastener＇s flexibility. In the 2D finite element model, the flexibilities of the beam elements and bush elements are used to simulate different components of the fastener＇s flexibility. The parameters of the beam elements which include the bending moment of inertia and intersection area, and the parameters of the bush elements which include the stiffness in different directions, are all obtained through equalizing the fasteners flexibilities. In addition, the secondary bending effect introduced by the single-lap joints is also taken into account to verify the flexibilities of the fasteners in practical application. The proposed FEM is testified to be more accurate than the traditional 2D FEMs and more efficient than the three-dimensional （3D） FEM in solving load sharing problem of multi-bolt single-lap thick laminate joints. With the increase of joint plates＇ thickness, the advantages of the proposed method tend to be more obvious. The proposed 2D FEM is an effective tool for designing bolted joints in large-scale composite structures.     

构建长株潭数字城市群的理论分析与实施建议

通过阐述长株潭数字城市群的建设背景、概念,运用博弈理论,建立了政府与项目公司之间的博弈模型,讨论特许权期、项目公司建设成本、补偿费用等因素之间的关系,提出了构建长株潭数字城市群的基本框架和实施建议,提供建设长株潭数字城市群的发展思路。     

泥水盾构泥水分离系统除渣效率对泥浆的影响

环流系统是泥水盾构的重要环节,通过环流系统的筛分机能及时分离泥水和渣土颗粒。筛分机的筛分效果对泥浆性质影响很大,关系到泥浆的造浆成本。某大型泥水盾构穿越粉细砂地层时,每掘进一环,泥浆密度会从1.12 g/cm3降为1.06 g/cm3,现场需要添加大量膨润土来提高泥浆的密度。针对粉细砂地层分析,根据环流系统中土颗粒的质量守恒进行计算,研究了环流系统的筛分效果对循环后的泥浆密度指标的影响,并与现场实际测量进行比较,得知地层中粒径小于75 μm的土颗粒对提高泥浆密度有利,应该充分利用。提出应当控制好筛分机的筛分效率,使地层中的细颗粒保留下来,为造浆服务,提高泥浆的密度。     

Excel在适线法中的应用

推求设计洪水时中常采用图解适线法,但计算绘图工作量大,计算结果也因人而异,为此,本文基于Microsoft Excel的内置函数、图表处理及脚本编程,编写了简单的Excel表,实现了参数优选的程序化和规范化。