Volatile Organic Compounds in the Area of Madrid: A Chemometrical Approach

Multivariate techniques have been applied to the set of dataobtained after one year sampling of volatile organic compounds(VOCs), including volatile aldehydes in the area of Madrid inorder to evaluate the possible correspondence among groups ofanalysed compounds, as far as modelling of different emissionsources in relation to location and season. The measurements were carried out at four sites in Madrid, characteristic for urban and suburban areas. Additionally, as reference, a rural area 100 km far from the city was considered. Results of correlation analysis, factor and cluster analysis are presented.Higher correlations were found between variables related withtraffic emissions. Factor analysis results showed two mainsignificant variables related to anthropogenic and biogenicemissions respectively. In relation to cluster analysis, samples were grouped according to sampling site and seasonal variations.     

基于CiteSpace的温室气体监测发展动态可视化分析

采用文献计量方法，利用CiteSpace软件对Web of Science核心合集中2004—2020年以"Greenhouse Gases Monitoring"为主题词检索到的2 514篇文献进行可视化分析，从时间分布、国际合作、研究机构合作、研究领域、共被引分析和关键词分析等方面，揭示该领域的发展动态、研究实力分布、热点前沿等。结果表明：2004—2020年温室气体监测研究领域的发文数量总体呈现上升趋势，在全球应对气候变化的重大事件时间节点发文数量增幅较大；该领域发文量较多的国家和机构皆以发达国家为主，发展中国家中中国居首位，国家、机构合作关系紧密；温室气体监测研究涉及的学科领域较广，环境科学与生态学、环境科学、工程为排名前3位的学科领域，2010年后研究逐步拓展到建筑学、影像学、计算机科学、经济学等领域；该领域的研究知识基础主要聚焦温室气体浓度监测、来源去向、影响因素及变化趋势分析，温室气体监测技术方法研究及应用，以及森林、农业土壤碳汇研究等方面；通过不同时段关键词分析发现CO₂、CH₄和N₂O一直是温室气体监测研究的重点对象，关注视角逐渐转向多因素、多领域、多技术、多方法、多策略研究。基于分析结果和中国实际，提出今后一段时期中国温室气体监测领域的研究重点和工作方向。     

黄河三角洲不同类型湿地土壤盐分的剖面分异特征

为探究高强度人为干扰是否改变滨海湿地土壤盐分的剖面特征,采集黄河三角洲典型自然湿地和人为干扰湿地不同植物群落下的土壤剖面样品,进行实验室测定。运用单因素方差分析、非参数检验、聚类分析等方法,对土壤剖面含盐量及理化性状进行统计分析。结果显示：由陆向海湿地土壤从轻度盐渍化向盐土过渡,盐分剖面特征受人为活动影响显著,同时人为影响因植被类型而异。总体而言,人为干扰湿地土壤盐渍化程度高于自然湿地。土壤盐分剖面类型可划分为表聚型、震荡型和均匀型三种,空间上由海向陆土壤盐分剖面类型由表聚型、震荡型向均匀型转变。人为干扰湿地中的柽柳（Tamarix chinensis）群落和裸地土壤盐分表聚特征明显,属于表聚型剖面,表聚系数为63%,均匀型剖面占比最高,达到2/3。当地人为筑坝修路等建设活动,通过直接阻断或改变地形等方式削弱了湿地潮汐的水文连通过程,进而改变土壤含水率、容重等生境要素,可能成为影响盐分剖面特征的重要因素。通过闸阀调控、生态补水工程等水文连通恢复措施,改善湿地土壤盐碱化问题,有助于推动黄河三角洲滨海湿地的可持续发展与管理。     

城市安全生产画像构建与应用探讨

为使城市安全生产监管部门及时掌控安全生产状态,实现监管资源的合理调配与工作部署,本文针对城市安全生产领域监管系统多、数据量庞大、数据分析不深入等问题,利用城市安全生产画像的表现形式,对城市安全生产画像构建的各个环节进行针对性探讨;以某地安全监管部门为例,整合该地下属8个区域的执法检查和处罚数据,构建辅助当地安全生产监管力量部署的多维画像,并通过脸谱聚类图这种可视化形式来表征此地区监管力量的局部与总体特征。结果表明:城市安全生产画像,是一种有效的大数据分析手段,有助于监管部门迅速掌握城市整体及局部安全状况,预判安全趋势,合理部署监管资源,降低事故风险概率,显著提高城市安全生产管理水平。     

Socio-demographic and experience factors affecting drivers’ runoff risk along horizontal curves of two-lane rural highway

Introduction: An improper driving strategy is one of the causative factors for a high probability of runoff and overturning crashes along the horizontal curves of two-lane highways. The socio-demographic and driving experience factors of a driver do influence driving strategy. Hence, this paper explored the effect of these factors on the driver’s runoff risk along the horizontal curves. Method: The driving performance data of 48 drivers along 52 horizontal curves was recorded in a fixed-base driving simulator. The driving performance index was estimated from the weighted lateral acceleration profile of each driver along a horizontal curve. It was clustered and compared with the actual runoff events observed during the experiment. It yielded high, moderate, and low-risk clusters. Using cross-tabulation, each risk cluster was compared with the socio-demographic and experience factors. Further, generalized mixed logistic regression models were developed to predict the high-risk and high to moderate risk events. Results: The age and experience of drivers are the influencing factors for runoff crash. The high-risk event percentage for mid-age drivers decreases with an increase in driving experience. For younger drivers, it increases initially but decreases afterwards. The generalized mixed logistic regression models identified young drivers with mid and high experience and mid-age drivers with low-experience as the high-risk groups. Conclusions: The proposed index parameter is effective in identifying the risk associated with horizontal curves. Driver training program focusing on the horizontal curve negotiation skills and graduated driver licensing could help the high-risk groups. Practical applications: The proposed index parameter can evaluate driving behavior at the horizontal curves. Driving behavior of high-risk groups could be considered in highway geometric design. Motor-vehicle agencies, advanced driver assistance systems manufacturers, and insurance agencies can use proposed index parameter to identify the high-risk drivers for their perusal.     

Influence of built-in obstacles on unconfined vapor cloud explosion

The obstacle structure in the vapor cloud has a significant influence on the gas explosion. Obstacles could not only lead to the acceleration of flame, but also they may occupy some space, thus affecting the amount of combustible gas. In this paper, a new two-step method was proposed to respectively study the effects of the obstacles amount and volume blockage ratio (VBR) on the gas explosion by using Computation Fluid Dynamic software AutoReaGas, and the obstacles in the vapor cloud were set to “Solid” instead of “Subgrid”. Based on the results and analysis, it is found that the peak overpressure and the maximum combustion rate rise with the increase of the number of obstacles for a single VBR, which indicated that the vapor cloud explosion of more obstacles was more dangerous for a single VBR. However, under a single number of obstacles, the peak overpressure and the maximum combustion rate increase firstly and then decrease as VBR increases and reach the highest at the VBR of 0.74, which indicated that the intensity of vapor cloud explosion reach a peak at a certain VBR in the middle instead of the largest. In addition, the existence and structure of obstacles have little effect on the size of explosion fireball when the size and concentration of combustible gas cloud are the same.     

A study of the blast wave shape from elongated VCEs

Elongated congestion patterns are common at chemical processing and petroleum refining facilities due to the arrangement of processing units. The accidental vapor cloud explosion (VCE) which occurred at the Buncefield, UK facility involved an elongated congested volume formed by the trees and undergrowth along the site boundary. Although elongated congested volumes are common, there have been few evaluations reported for the blast loads produced by elongated VCEs. Standard VCE blast load prediction techniques do not directly consider the impact of this congested volume geometry versus a more compact geometry.This paper discusses an evaluation performed to characterize the blast loads from elongated VCEs and to identify some significant differences in the resulting blast wave shape versus those predicted by well-known VCE blast load methodologies (e.g., BST and TNO MEM). The standard blast curves are based on an assumption that the portion of the flammable gas cloud participating in the VCE is hemispherical and located at grade level. The results of this evaluation showed that the blast wave shape for an elongated VCE in the near-field along the long-axis direction is similar to that for an acoustic wave generated in hemispherical VCEs with a low flame speed. Like an acoustic wave, an elongated VCE blast wave has a very quick transition from the positive phase peak pressure to the negative phase peak pressure, relative to the positive phase duration. The magnitude of the applied negative pressure on a building face depends strongly on the transition time between the positive and negative phase peak pressures, and this applied negative phase can be important to structural response under certain conditions. The main purpose of this evaluation was to extend previous work in order to investigate how an elongated VCE geometry impacts the resultant blast wave shape in the near-field. The influence of the normalized flame travel distance and the flame speed on the blast wave shape was examined. Deflagration and deflagration-to-detonation transition regimes were also identified for unconfined elongated VCEs as a function of the normalized flame travel distance and flame speed attained at a specified flame travel distance.     

The Role of Cloud Processing in the Relationship Between Wet Deposited Sulphur and Sulphur Dioxide Emissions

It is well established that wet deposition of sulphate in the UKhas fallen by a much smaller fraction than have emissions of sulphur dioxide. Dry deposition of sulphur has decreased in proportion to the decline in emissions. A number of suggestionshave been made which offer possible explanations for this non-linearity between emissions and wet deposition. In this paper amodel of the processing of sulphur dioxide by aqueous phase cloudchemistry in a cloudy boundary layer is presented. This work doesnot simulate all the details of the mechanisms by which sulphate is incorporated into precipitation. It does, however, explorethe non-linearity of this oxidation process. It is shown that theoxidation of sulphur dioxide, in these conditions, over the UK isdominated by oxidation by ozone. The rate of sulphate productionis then controlled by the availability of the one basic trace gasin the atmosphere ammonia. Using realistic concentrations of thereacting species this is found to simulate well the observed non-linearity. The model predicts that sulphate and sulphur dioxideconcentrations will be uncorrelated in the cloudy boundary layerbut that ammonium and sulphate will be well correlated. Fieldobservations at a cloudy site in Northern England are consistentwith these predictions.     

内蒙古草原光合有效辐射的计算方法

2002年夏季,对内蒙古草原太阳分光辐射以及气象因素进行了同步观测。依据一定的物理基础,在对实测资料进行分析的基础上,计算得到了内蒙古草原地区光合有效辐射某一时段累计值的经验公式。实际天气条件下,计算结果与观测值比较接近,该经验公式的适用性亦比较好。根据不同条件,可以选择不同的因子来计算光合有效辐射。当选择全部因子时,计算值与观测值的最大相对偏差为8 13%,平均相对偏差为2 45%。研究表明,大气中所有物质对光合有效辐射的吸收作用小于它们的散射作用。