考虑滚动阻抗的线性接触模型离散元宏细观参数敏感性研究*

为克服无黏性土的离散元研究中未考虑颗粒间抗转动作用的缺陷,基于抗转动线性接触模型开展一系列排水固结三轴压缩模拟试验,结合随机森林算法详细探讨抗转动线性接触模型中各细观参数（有效模量、刚度比、摩擦系数、抗转动系数）与试样的宏观参数（初始弹性模量、泊松比、峰值强度）间的关系。结果表明:颗粒有效模量的提高会使试样的初始弹性模量提高而泊松比提高,权重值分别为0.695 14和0.201 57;刚度比的增加会使试样的初始弹性模量降低而泊松比提高,权重值分别为0.751和0.193 64;抗转动系数与摩擦系数提高会显著提高试样的抗剪强度,权重值分别为0.564 72和0.427 5;抗转动系数对试样的剪胀性具有显著影响。     

Exploring relationships between microscopic kinetic parameters of tires under normal driving conditions,road characteristics and accident types

IntroductionFreeway accidents are a leading cause of death in China, which also triggers substantial economic loss and an emotional burden to society. However, the internal mechanism of how microscopic kinetic parameters of vehicles influenced by road characteristics determine the occurrence of different types of accidents has not been explicitly studied. This research aimed to explore the “link role” of tire microscopic kinetic parameters in road characteristic variables and traffic accidents to aid in facilitating the traffic design and management, and thus to prevent traffic accident. Method: A mountain freeway in Zhejiang Province, China was used as the research object and the data used in this paper were obtained through a real-time vehicle experiment. Multiple estimation models, including the standard ordered logit (SOL) model, fixed parameters logit (FPL) model, and random parameters logit (RPL) model were established. Results: The findings show that road characteristics will affect the longitudinal kinetic characteristics of the vehicle and, consequently, map the level of risk of rear-end accidents. Driving compensation effects were also identified in this paper (i.e., the drivers tend to be more cautious in complicated driving circumstances). Another finding relating to the mountain freeway is that different tunnel characteristics (e.g., tunnel entrance and tunnel exit) have different effects on different types of traffic accidents. Practical Applications: The framework proposed in this article can provide new insight for researchers to enlarge the research subjects of both explanatory and outcome variables in accident analysis. Future research could be implemented to consider more driving conditions.     

正压空气呼吸器定期检验及存在问题分析

正压空气呼吸器是抢险救援的重要装备。本文对正压空气呼吸器的基本组成、工作原理进行了阐述，对长庆油田在用正压空气呼吸器使用现状和存在的问题进行了汇总和分析，提出了定期检验的内容、依据和程序．明确了开展定期检验是确保正压空气呼吸器正常使用、减少隐患的重要手段。     

应用BP神经网络进行隧道围岩快速分级

在隧道施工过程中,为准确、及时地进行围岩快速分级,引入BP神经网络方法,通过制定快速分级参数标准,对已经开挖的隧道工作面按照隧道围岩分级规范进行分级,并测量其快速分级参数,将围岩分级的结果与其对应的快速分级参数建立BP神经网络的训练集合,从而得到围岩分级模型。最后测量正在开挖隧道工作面的快速分级参数,并提供给模型进行判别,从而达到快速、精确分级目的。通过某隧道围岩样品实例验证,该模型判断结果与实际施工情况吻合,可用于指导施工阶段的隧道围岩快速分级。     

还原雷击参数的“黑匣子”——雷击在线实时监测记录仪研究

本文所研究的＂黑匣子＂是一种在线监测、记录、还原雷击参数的智能仪表,对特定环境设施（如：避雷针、低压供、配电线路与信息传输线路）入侵的雷击具备在线实时监测、记录并还原雷击参数的雷电流幅值、持续时间、极性（雷击电流走向）与波形的功能。     

Traffic Parameters Estimation to Predict Road Side Pollutant Concentrations using Neural Networks

The analysis aims to evaluate which is the most important among traffic parameters (flows, queues length, occupancy degree, and travel time) to forecast CO and C₆H₆ concentrations. The study area was identified by Notarbartolo Road and bounded by Libertà Street and Sciuti Street in the urban area of Palermo in Southern Italy. In this area, various loop detectors and one pollution-monitoring site were located. Traffic data related to the pollution-monitoring site immediately near the road link were estimated by Simulation of Urban MObility (SUMO) traffic microsimulator software using as input the flows measured by loop detectors on other links of road network. Traffic and weather data were used as input variables to predict pollutant concentrations by using neural networks. Finally, after a sensitivity analysis, it was showed that queues length were the mostly correlated traffic parameters to pollutant concentrations. An erratum to this article can be found at     

极端温度条件典型引信电参数变化规律和失效机理

目的 研究某电子时间引信在?60~140 ℃下电参数的变化规律和失效机理。方法 利用高低温试验机开展步进应力强化试验,增加和细化引信检测参数,在被试引信工作状态下全程记录电参数的变化,开展失效机理分析。结果 得到了引信基准频率、电能损耗率等电参数的温度特性规律和参数变化范围,发现了?60 ℃低温掉电、130 ℃高温短路等故障模式和机理,并提出改进建议。结论 验证了极端温度应力叠加电应力的强化试验方法,获得了引信电性能参数变化规律,发现了极端温度条件下新的失效模式和失效机理。     

丰水期洪湖水质空间变异特征及驱动力分析

通过对丰水期不同程度富营养化的洪湖全湖139个监测点位的高密度采样分析,采用GIS空间插值技术得到洪湖水体中各污染因子、水生植物生物量和水质类别的空间分布特征图.结果表明,丰水期TN、TP、NH+4-N、高锰酸盐指数的质量浓度总体上呈现出自南向北逐步增高的变化趋势:北部河流入湖区围网养殖区开阔水体保护区南部长江入湖区;水质参数的贡献率依次为TNTP高锰酸盐指数NH+4-NDO.受工农业废水、生活污水、饵料投放、水生植物、水体交换等因素的影响,TN在丰水期超过目标水质59%,TP超标35.2%,高锰酸盐指数超标13.7%,NH+4-N超标4.3%,综合水质超标66.2%.在季风等环境因子的影响下水体中的DO达到水质目标.通过水质空间变异性分析,能直观反映人类活动、土地利用类型和环境因子之间相互作用对洪湖水环境产生的巨大影响.为了使洪湖水环境更有利于人们的生产和生活,应大力控制北部区域工农业废水和生活污水的排放,控制养殖面积,逐步恢复洪湖水体自净能力,实现洪湖水环境生态的可持续发展.     

Variation in Parameters of Siberian Larch Trees in Different Forest Types in the Angara River Basin

Taxonometric parameters and morphological characters of cones and seeds were studied in larch trees growing in uneven-aged larch forests of the green-moss and herbaceous types. Significant differences in trunk volume and the number of cones in the crown was revealed. Differences in the parameters of cones and the quality of seeds proved to be insignificant. Correlations between the taxonometric parameters of trees and the morphological characters of cones and seeds were analyzed.     

Changes of Structural and Physicochemical Parameters of Spruce Forest Ecosystem under the Effect of Moose (Alces alces L.)

The role of moose in the dynamics of structural, physical, and chemical parameters of a forest community is considered using an example of a southern taiga wood-sorrel spruce forest. It is shown that the activities of these animals affect the vertical structure of the underbrush and understory layers, the dynamics of phytomass accumulation, and the state of the ground vegetation. Changes in the nitrogen and hydrocarbon flows through the ecosystem under the effects of moose activities are analyzed.