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。     

弯道路段集重型大型货物运输车辆通过宽度研究*

为研究集重型大型货物运输车辆在弯道路段不同圆曲线半径条件下的通过宽度,基于Ackerman转向原理建立集重型大型货物运输车辆转弯模型,研究道路圆曲线路段车辆通过所需道路宽度与牵引车前轴中心运行半径和液压轴线挂车长度间的关系;得到车辆外廓弯道最外侧点的判别方法,以及牵引车前轴中心运行半径、液压轴线挂车长度对车辆通过所需道路宽度的影响强度、相对优势影响区域及三者间的分段函数关系;得到典型车辆通过不同半径弯道所需道路宽度与牵引车前轴中心运行半径间的关系。结果表明:计算方法及结果可为大型货物运输道路规划设计和集重型大型货物的运输路径优选提供理论依据。     

Vegetation structure, niche width, niche overlap and types of competition in temperate grazingland of Garhwal Himalaya, India

Temperate grazing lands in Garhwal Himalaya are rich in herbaceous vegetation and extensively used for grazing by locally owned livestock. Capillipedium parviflorum is a frequently occurring and dominant grass species under Pine canopy in associate with several herbs. Beside, grazing and extensive fire, interactions among associated species is a determining factor of community structure. In this article the dominant diversity pattern of vegetation in temperate grazing land along two different altitudes and having different slope aspects is described. Interaction between dominant and co-dominant species with their niche appearance and niche overlap measurement was also observed and presented here. South and west facing slopes had maximum species and diversity values while east north facing slopes had higher species dominant. Capillipedium parviflorum and other grasses had maximum niche values and were dominant and co dominant species. Three types of interspecific interaction were observed between species and grasses were observed as succeeding species in all sites of different topographic conditions. Dominant diversity pattern along with resource partitioning and interspecific competition is discussed and presented here.     

不同房间结构下人员疏散的CA模拟研究

采用元胞自动机模型分别对不同房间结构中的人员疏散进行了模拟,重点研究了人员密度和出口条件对疏散时间的影响.结果表明,疏散时间随着人员密度线形增加;根据建筑结构的不同,采用多出口对疏散时间有不同程度的减少.该模拟结果对于出口的设计和人员的安全疏散具有一定的指导意义.     

基于修正的两段法对某电站水库松散堆积体岸坡塌岸预测

水库塌岸是影响水电站库区移民工程的重要地质灾害问题,研究其塌岸模式、预测方法并预测最终塌岸宽度是十分必要的。通过对某水电站库区重点库段塌岸进行调查分析,该水电站库区塌岸模式以冲蚀磨蚀型和坍塌型为主;分析几种常用的塌岸预测方法,确定采用修正后的两段法预测该库区塌岸最终宽度;采用现场工程地质调查法、工程类比法等手段确定了库区塌岸预测参数,并对该水电站库区塌岸进行了预测,预测结果表明库区塌岸总长30.5km,塌岸预测最终宽度为5~50m。该研究可为库区移民工程提供重要依据。     

基于基本顶断裂位置分析剩余煤柱稳定性

为简化支承应力表达式及全面分析煤柱稳定性,基于基本顶断裂位置建立工作面剩余煤柱载荷力学模型,将指数函数型支承应力曲线简化为与其拟合的幂函数抛物线,推导出剩余煤柱载荷及极限宽度B表达式。计算得出312工作面基本顶断裂位置与非开采帮塑性区边缘距离d为8.6～11.5 m,B为8.06～8.85 m。研究结果表明：随着d增加,煤柱载荷及B均逐渐增大;B随煤层黏聚力与内摩擦角的增加而减小,随煤层埋深、应力集中系数、侧压力系数、煤层厚度及工作面采高的增加而增大。研究结果有助于更加全面地分析煤柱稳定性,为工程实践提供一定理论指导。     

采空区处理方法研究进展

采空区处理问题一直是国内外普遍存在的采矿技术难题。简要综述"崩"、"充"、"撑"、"封"等4类基本的采空区处理方法和4种简单联合法。认为联合法是一类最有发展前景的采空区处理方法。专门阐述几种采空区处理的新方法。提出采空区处理方法的发展方向:切合实际、经济简便、技术可行,能定量设计与分析,能消除冲击地压,能控制开采地压,能智能选择,其发展应以围岩应力和变形仿真为核心。