混凝土连续箱梁长期受力性能试验研究

目前混凝土连续箱梁普遍存在开裂等病害现象,研究表明混凝土连续箱梁设计理论的不完善是引起结构开裂的重要原因之一.对钢筋混凝土连续箱梁模型均布荷载作用下的长期受力性能进行1006 d的试验观测表明:受拉钢筋的应变增长相对较小,受压钢筋和受压混凝土的应变增长相对较大,且跨中截面的压应变增长较中间支座截面显著,中间支座截面受压翼缘有效分布宽度系数较跨中截面增加更显著.对试验模型持荷1006 d的内力重分布规律进行试验观测,与理论预测结果吻合较好.对现行设计规范进行参数修正后能较好地预测连续箱梁各控制截面的裂缝宽度,跨中长期挠曲变形实测值较理论计算值偏大约11.4%.     

基于二维平面拟合的电网脆弱性分析

电网的脆弱性分析对于指导事故防控和确保系统安全稳定运行具有重要意义。文中同时考虑影响电网脆弱性的运行状态和拓扑参量因素，在一定的电网运行条件下，结合加权改进的小世界模型，提出了基于二维平面拟合的电网脆弱性分析方法。主要研究扰动后潮流转移过程中电网结构改变与运行状态变化之间的相互关系，分析具有不同输送潮流和不同结构特征的线路故障导致的转运潮流改变和电网拓扑变化对于系统脆弱性的影响，并从中找出电网的脆弱线路，这对于指导电网中相关重要元件的监控、维护工作提供了可供参考的依据。算例结果表明所述方法合理、有效，具有在线应用的前景。     

一种基于混沌的真随机源电路

提出了一种基于混沌的随机源电路,通过利用电容上电荷的再分配,实现了一个离散混沌系统.该电路在0 .8μm CMOS工艺下流片成功,核心面积小于4 2 0 0 μm2 ,功耗小于1m W,优于目前已有的几种实现方法.     

A physically based method for triangulated surface flattening

This paper introduces a new method of generating 2D flat patterns from a 3D triangulated surface by opening the bending configuration of each winged triangle pair. The flattening can be divided into four steps. First, a 3D triangulated surface is modeled with a mass-spring system that simulates the surface deformation during the flattening. Second, an unwrapping force field is built to drive the mass-spring system to a developable configuration through the numerical integration. Third, a velocity redistribution procedure is initiated to average velocity variances among the particles. Finally, the mass-spring system is forced to collide with a plane, and the final 2D pattern is generated after all the winged triangle pairs are spread onto the colliding plane. To retain the size and area of the original 3D surface, a strain control mechanism is introduced to keep the springs from over-elongation or over-shrinkage at each time step.     

A Chinese sky trust?: Distributional impacts of carbon charges and revenue recycling in China

The introduction of carbon charges on the use of fossil fuels in China would have a progressive impact on income distribution. This outcome, which contrasts to the regressive distributional impact found in most studies of carbon charges in industrialized countries, is driven primarily by differences between urban and rural expenditure patterns. If carbon revenues were recycled on an equal per capita basis via a ‘sky trust,’ the progressive impact would be further enhanced: low-income (mainly rural) households would receive more in sky-trust dividends than they pay in carbon charges, and high-income (mainly urban) households would pay more than they receive in dividends. Thus a Chinese sky trust would contribute to both lower fossil fuel consumption and greater income equality.     

The effect of wettability heterogeneity on capillary pressure and relative permeability

The effect of wettability on fluid flow properties in porous media has been extensively studied, and is still a subject of highly active investigation. Most of the work has focused on cores of homogeneous wettability. Little attention has been paid to wettability heterogeneity effects at the core or pore scale. In a previous paper, we reported on a series of centrifuge experiments performed to study the effect of wettability heterogeneity on capillary pressure. An experimental technique, named cyclic aging, was developed to create regions of different wetting in the same core sample. In this paper, the work is extended to study the effect of wettability heterogeneity on both capillary pressure and relative permeability curves using centrifuge, continuous injection and steady state techniques.The experimental procedure consists of three steps: (1) the core plug is fully saturated with brine and subsequently a drainage experiment is performed targeting an initial oil saturation S_oi, (2) after aging, oil is displaced by water to residual oil saturation S_or, and (3) oil is injected targeting higher initial oil saturation. In the secondary drainage experiment (step 3), oil first displaces water from the pores exposed to crude oil in primary drainage (step 1) and then enters fresh pores not exposed to crude oil before.In our previous study, it was found that wettability heterogeneity caused a step change in capillary pressure which correlated very well with the saturation at which wettability contrast was expected. However, the height of the step could not be explained by wettability contrast and/or water trapping alone. An experimental artifact caused by the centrifuge technique made the step higher than expected. The experimental artifact was the result of the nonuniform saturation profile developed across the core at the end of the centrifuge experiment. In this study, new techniques were used which resulted in a uniform saturation profile along the core sample during the primary drainage experiment. It was found that in this case the step in the capillary pressure is determined by wettability contrast and water trapping. It was also found that the relative permeability curve changes its characteristics when oil accesses the pores not previously exposed to crude oil.The results of this study show that (1) only the part of the pore space exposed to crude oil undergoes wettability changes on both core scale and pore scale, and (2) ignoring wettability heterogeneity can lead to large errors in the estimated two phase flow functions with important consequences with respect to fluid flow in porous media.     

Stress Redistribution in Ore Block During Breaking

The stress fields are calculated for the pattern of short-delay blasting in ore block with the formation of curved free surfaces. It is established that in all breaking stages, the tension areas favoring the reduction in the energy intensity of failure arise in the massif.     

基于比例冲突再分配理论的目标识别应用研究

目前证据推理理论算法的改进仍然是热门的方向,其应用也越来越广,因此主要介绍了当前证据推理理论的两种最新的改进思想--最新的DSmT理论以及比例冲突再分配(PCR)方法;归纳总结了证据理论的主要应用及其在应用中的关键问题之--基本置信指派的主要构造方法;最后利用人工神经网络训练数据的方法构造基本置信指派,对比例冲突再分配(PCR5)方法在序列图像目标识别中的应用进行了仿真分析,仿真实验结果表明该算法可以有效地提高序列图像目标识别的准确性.     

周转箱管理（CMC）项目在上海通用汽车的实施

研究周转箱管理方式在零部件入厂物流方面的应用,分析实施周转箱管理项目的原因和可能性,提出了总体设计规划思路和具体实施、推广方法,提供了具体的流程、步骤、框图和实例,并就项目的持续优化进行了分析。实现了通过科学地强化对入厂物流的控制和管理,既控制了零部件的物流运行风险,又降低约20％的周转箱投入成本。     

内置钢箱-混凝土连续组合梁受力性能试验

为研究超静定内置钢箱-混凝土组合梁的塑性设计方法,进行了4根两跨内置钢箱-混凝土连续组合梁试验,获得了试验梁裂缝分布与开展、变形发展、破坏特征及塑性内力重分布等方面的试验结果.通过分析,给出了内置钢箱-混凝土连续组合梁等效塑性铰区长度计算公式,提出了以支座控制截面弯矩弹性计算值与组合梁正截面破坏时钢箱所承担弯矩之差为调幅对象、以相对塑性转角为自变量的弯矩调幅设计方法.