公路改扩建导致新老路基差异沉降的因素分析

基于有限差分原理建立了三维有限元数值计算模型,对公路改扩建中导致新老路基差异沉降的因素进行探讨。结果表明,公路拓宽部分的沉降明显高于老路的沉降,且在新老路结合部位沉降发展最显著。路面的竖向沉降随公路拓宽宽度增加而增加,随新路基弹性模量增加而减小,随新地基土压缩模量增加而减小。其中拓宽宽度和新地基土压缩模量对路基表面沉降影响较大,新路基土弹性模量对路基表面沉降影响较小。这表明新地基土受到的压应力和新地基土压缩模量是影响路面差异沉降的主要因素。工程上可以着重从降低对新地基土的压应力和提高新地基的压缩模量两个角度来降低路面的差异沉降。     

适宜太湖蓝藻水华形成的风场辐散特征及其形成机制

对太湖周边17个气象观测站的7年常规观测资料聚类分析发现,在适宜蓝藻水华形成的高温、微风气象条件下,太湖湖面风场往往出现辐散特征,在此辐散风场的驱动下,蓝藻水华迁移过程必然与均匀风场驱动下有所不同;数值模拟结果显示,这种辐散风场是由于非绝热加热不均匀造成的局地次级环流叠加在弱的背景风场之上引起的;其强弱程度是受湖陆温差和背景风速共同决定的,并据此给出了湖面风场辐散强度指数.     

The development of a movement-density relationship for people going on four in evacuation

Occupant movement in evacuation models has been simulated and predicted based on a number of variables, including crowd density. This study investigates the relationship between crowd density and occupant crawling movement, as a physical response to environmental conditions in fire. It is an attempt to generate the fundamental speed-density relationship that has been developed for walking movement. This is conducted by examining the impact of population size and exit access width on crowd walking and crawling speeds on a flat surface. The findings of the study suggest that exit access width has a significant impact, whereas occupant configuration (population size) plays less of a factor. The results further demonstrate that there is a significant difference in the crawling speed given the exit access width available, due to the secondary effect of crowd density. The relationship between crowd crawling speed and density is best represented by a quadratic regression model. The study concludes with the need to continuously develop new predictive movement methods, or enhance existing ones in order to cope with the level of detail required to ensure occupant safety and model complexity.     

安全疏散中人群拥挤踩踏现象的理论和模拟分析

为研究出口宽度对人群拥挤踩踏事故发生的影响程度,以某礼堂为例,建立基于排队论的安全疏散模型,理论分析并数值模拟了出口宽度为2m和4m对人员疏散的影响。研究表明,在发生火灾进行人员安全疏散过程中,当平均服务率大于等于平均到达率时,人群疏散有序,疏散效率较高;然而当平均服务率小于平均到达率时,使得人流不畅,出口过于拥堵。并且理论计算和数值模拟获得的选取适当出口宽度结果一致。对于大型场馆的出口设计具有一定的参考价值。     

在校大学生肩宽及疏散速度的测量研究

为了确定疏散软件中符合中国人的疏散基本参数,采用现场测量的方法对在校男大学生的肩宽及各种情况下的疏散速度进行统计,并对测量结果进行分析。结果表明,在校男大学生平均肩宽为46．5 cm,正常状态下水平行走速度为1．37m／s,上楼速度为0．66m／s,下楼速度为1．36m／s,上坡速度为1．34m／s,下坡速度为1．59 m／s;在无障碍的情况下,紧急状态的疏散速度要比正常状态下的速度快得多,测量得到肩宽和疏散速度的数据,为疏散软件的改进及进一步研究人员疏散问题提供科学依据。     

缠绕垫片匹配凹凸面法兰接头密封泄漏的讨论

以一台U型管式a型换热器在进行壳程水压试验时管板与壳体法兰凹面间缠绕垫片被压出泄漏为事例,针对选择低公称压力等级的缠绕垫片用在高设计压力的凹凸面法兰接头密封的影响因素,从垫片最小宽度、法兰凹凸密封面尺寸偏差、垫片与法兰装配以及缠绕垫片特性等方面进行了分析,提出了在设计计算法兰时应考虑垫片最小宽度的合理确定并修订完善相关标准的建议。     

焊后局部热处理的加热范围

对ASME及国内压力容器相关标准的新旧版本关于焊后局部热处理加热范围的规定进行了对比分析,指出某些标准对同类条款表达不准确,容易引起设计、制造和监检等各方争议。个别国内标准在新版中对加热宽度的规定欠妥。     

A hybrid machine learning model for predicting crater width formed by explosions of natural gas pipelines

Despite the existence of industry models for estimating the crater width formed by the explosion of natural gas pipelines, their applicability is still limited since the complex formation mechanisms. In this work, a novel hybrid model was developed to predict crater width formed by explosions of natural gas pipelines, using artificial neural networks (ANN) as the fundamental predictor. Based on the historical accident records, the proposed hybrid model was trained by the pipeline parameter, the operating condition, the installation parameter, and the crater width. A novel nature-inspired optimization algorithm, i.e., the Lévy-Weighted Quantum particle swarm optimization (LWQPSO) algorithm, was proposed to optimize the ANN model's parameters. Three machine learning models were developed for comparative reasons to predict the crater width. The use of precision and error analysis indicators assesses prediction performance. The results show that the proposed hybrid model (LWQPSO-ANN) has high prediction accuracy and stability, which outperforms QPSO-ANN-based benchmark hybrid models and the model without an optimizer (Support Vector Machine, SVM). The parameter sensitivities of the proposed algorithm, including the maximum number of iterations, population size and contraction-expansion coefficient, were determined. The proposed hybrid model is expected to support the quantitative risk assessment (QRA), Right-of-Way (ROW) definition and the inherently safer design of the underground parallel pipelines.     

装置进气口宽度对不同尺寸油盘火旋风燃烧特性影响的研究

为探究进气口宽度对火旋风燃烧特性的影响,利用自然驱动的四面边墙夹缝式装置对不同进气口宽度使用１５０,２００,２５０ mm 3种直径进行实验研究。由燃料质量随时间变化曲线得出准稳态阶段火旋风的质量燃烧速率;利用摄像机记录火焰的连续图像并获得火焰高度。结果表明:针对实验室小型火旋风（150~250 mm）,在进气口宽度为35 mm左右时,火旋风的燃烧速率最大,即火旋风的燃烧强度存在1个最佳的进气口宽度;当火焰高度达到最高时,环量也存在1个临界值。     

多层建筑楼梯疏散宽度组合仿真研究

为探究事故发生时楼梯宽度对多层建筑疏散效率的影响,结合多层建筑楼梯疏散特点,建立多层建筑楼梯疏散模型。基于多层建筑疏散过程,以社会力模型为基础,分析多层建筑行人疏散方式,构建楼梯疏散汇流模型;计算各楼层行人汇流时间以及楼梯汇流疏散效率;以某多层教学楼为仿真案例,构建不同楼梯宽度组合疏散场景,仿真多层建筑物疏散过程,获取各楼层汇流时间及楼梯疏散效率。结果表明:楼层平台汇流持续时间与楼层所在位置正相关,楼层所在位置越高,汇流持续时间越长;低楼层楼梯宽度增加有利于优化中间楼层行人汇流作用,提高多层建筑疏散效率,而高楼层楼梯宽度增加则会加剧中间楼层行人汇流对疏散的不利影响,降低多层建筑疏散效率。