基于系统动力学的地铁火灾调度安全模型研究

全自动驾驶已经成为城市轨道交通建设发展的必然趋势,车辆火灾场景是影响列车全自动运行安全最大的场景之一,因此制定合理的火灾调度安全控制方案具有极其重要的意义。以地铁全自动驾驶中车辆火灾场景为研究对象,将系统动力学理论方法用于构建调度安全影响因子模型。与传统的地铁安全模型不同,该模型以全自动驾驶场景为标准形成影响因子库。通过德菲尔法相关思想的专家评分法确定各子系统权重比,利用Vensim-PLE软件对模型进行仿真试验,对各影响因子进行动态预测,对比不同的安全投入方案及调度人员配置比方案,优选出最有效的火灾调度安全控制方案。     

CHANGES TO INFILTRATION AND INTERRILL EROSION FROM LONG-TERM PRESCRIBED BURNING IN LOUISIANA1

ABSTRACT: Effects of long-term prescribed burning on infiltration and interrill erosion were assessed on two longleaf pine-bluestem sites in Louisiana. Treatments represented biennially-applied winter, spring, or summer burning on an upland sandy loam site for 20 years; and annual winter or spring, and biennial winter or spring burns on a bottomland silt loam site for 10 years, with unburned controls. Immediate effects of burning were a reduction in surface cover, exposing soil to raindrop impact. Burning the sandy loam site increased interrill erosion after winter and spring treatments, but produced no immediate changes in infiltration capacity or time to runoff irrespective of treatment season. Rapid recovery of under-story vegetation mitigated soil exposure. Biennial burning did not increase interrill erosion, or reduce infiltration capacity and time to runoff on the sandy loam site after 20 years. A complete herbaceous understory covered the silt loam site two years after treatment. Interrill erosion was not significantly increased, or infiltration capacity and time to runoff decreased on burning treatments than unburned controls on the silt loam site. Litter biomass was important in predicting interrill erosion. No surface cover condition could be linked to variability in infiltration capacity. This study provides evidence for the resiliency of a longleaf pine-bluestem association to prescribed burning.     

Relationships between emission sources and air mass characteristics in East Asia during the TRACE-P period

Long-range transport of pollutants influenced by anthropogenic and natural emission sources in East Asia is investigated by using backward trajectory analysis along the NASA TRACE-P flight tracks and a numerical simulation with the three-dimensional chemical transport model (STEM-2k1). Observation-based regional distributions of trace gases are reconstructed using the observations obtained by measurements on board the DC-8 and P3-B aircrafts. Systematic features of the spatial distribution for each species are identified. It is found that the observed concentrations of CO and some NMHCs, and the ratios between these species, are highly associated with the source distribution features and their regional characteristics. Reconstructed fields of the observed and modeled ethane/CO and ethane/propane are found to reproduce well the estimated emission ratios in East Asia. We also investigated the time rate of change of the concentration of species and their ratio along the trajectory. From this analysis the propane/ethane and propane/acetylene ratios are shown to preserve their emission ratios during regional transport. However systematic differences in the propane vs. acetylene/CO relationships are found between the model and observation values. This analysis suggests that further efforts are needed to improve the estimates of biomass burning emissions in SE Asia. The results presented in this paper also suggest ways to further extend the capabilities to derive observation-based inventories.     

抛煤机反转链条炉促燃降污节能系统研制

通过对传统抛煤机反转链条炉的工作机理及特性分析 ,提出了水蒸气促燃降污节能理论 ,建立了相应的物理、化学模型 ,并据此设计了面向对象的促燃降污节能系统应用于实践     

Carbonaceous aerosol emissions from India

Budget estimate for carbonaceous aerosols including black carbon (BC) and organic carbon, emitted from the combustion of various fuels, is very important for regional climate studies. Emission factors for carbonaceous aerosols from bio-fuels and soft coke were determined in a controlled combustion study. The emission factors thus obtained along with those available for other fossil fuels consumed in different sectors have been applied to assess the budget for carbonaceous aerosols from India. Preliminary calculations give a range of 1.6–1.8 Tg of carbonaceous aerosols that include 0.4–1.4 Tg of BC. A major (80%) portion of carbonaceous aerosols emitted from India is found to originate from the use of biomass for energy as 70–80% of energy requirement in rural India is met by combustion of traditional bio-fuels.     

Atmospheric pollution of agriculture-oriented cities in Northeast China: A case in Suihua

Agriculture-oriented cities in Northeastern China have experienced frequent atmospheric pollution events. Deeper understandings of the pollution characteristics, haze causes and effects of management on local air quality are crucial for conducting integrated management approaches for the sustainable development of agriculture-oriented cities. Taking a typical agriculture-dominant city (i.e., Suihua) in Northeast China, we analyzed in detail the characteristics and causes of atmospheric pollution and evaluated the straw-burning prohibition using multisource data. The results showed a clear temporal pattern of air quality index (AQI) on an annual scale (i.e., 2015-April 2019), with two typical pollution periods occurring in late autumn and early spring. The large areas of concentrated straw burning at local and regional scales accounted for the first period (i.e., October and November), while dust emissions and farming disturbances comprised the second period. The interannual variation in pollution periods among these years was large, showing similar trends from 2015 to 2017 and the postponed late-autumn pollution period in 2018. Our evaluation has shown that the prohibition effect of straw burning significantly improved air quality in 2018, with a reduction of 59% ± 88% in the PM_2.5 concentrations in October and November compared to 2015–2017. However, From October to April of the following year, the improvement effect was not significant due to postponement of straw burning to February or March. Our analysis also highlighted the roles of meteorological conditions, Therefore, combined with the promotion of straw utilization, scientifically prescribed burning considering the burning amount and location, meteorological conditions and regional transportation should be implemented.     

太原秋季大气PM2.5中糖类物质的组成及来源解析

糖类物质是一类重要的生物标志物,可用于大气颗粒物的来源识别.采用高效阴离子交换色谱-脉冲安培检测法(HPAEC-PAD)于2018年秋季对山西太原PM_(2.5)中的糖类物质进行定量分析.结果表明,此次检测共检出8种糖类物质,包括4种糖醇(肌醇、赤藓糖醇、阿拉伯糖醇、甘露糖醇)、3种脱水糖(左旋葡聚糖、甘露聚糖、半乳聚糖)和1种单糖(葡萄糖).3种脱水糖总浓度明显大于其他糖类,且与PM_(2.5)之间呈显著相关性(r=0.74、0.59、0.99),表明生物质燃烧对太原地区PM_(2.5)有明显贡献.应用正定矩阵因子分解模型(PMF5.0)进行源解析发现,太原秋季(9月)PM_(2.5)中的糖类物质主要来源于生物质燃烧、花粉和植物碎屑、真菌孢子和土壤灰尘4类.同时应用特征分子比值并结合太原地区农业生产情况识别出太原市的生物质燃烧源主要为硬木和作物残渣的混合贡献.     

南京北郊秋季PM2.5碳质组分污染特征及来源分析

本研究于2015年10~11月在南京北郊分昼夜采集PM_(2.5)样品,采用热光透射法(TOT)和离子色谱法对样品中的有机碳(OC)/元素碳(EC)和左旋葡聚糖(levoglucosan)的质量浓度特征进行分析.观测期间OC和EC的平均浓度分别为(11.3±4.9)μg·m-3和(1.1±0.9)μg·m-3,总碳TC占PM_(2.5)的质量分数为22.9%,OC/EC的平均值为7.4,SOC占OC的质量分数为51.9%.PM_(2.5)、OC、EC和SOC质量浓度都体现出夜晚白天的特征,白天OC和EC的相关性好于夜晚(相关性系数分别为0.86和0.7).通过分析PM_(2.5)、左旋葡聚糖和SOC质量浓度以及后向轨迹和火点数据可知南京北郊在13~16号受到来自河北等地生物质燃烧远距离输送的影响.采样期间K+和左旋葡聚糖与OC、EC和SOC的相关性显著(相关性系数分别为0.78、0.79和0.65),经受体示踪物方法估算采样期间生物质燃烧对OC的贡献为21.9%.     

不同燃烧状态下农作物秸秆PM2.5排放因子及主要成分分析

运用自主设计的生物质燃烧系统,对水稻、小麦、大豆、玉米、花生和油菜6种农作物秸秆采用不同燃烧状态(阴燃和明燃)进行实验室模拟燃烧,分析PM_(2.5)的排放因子及其碳质组分和水溶性离子之间的差异.研究结果表明,不同燃烧状态对秸秆PM_(2.5)的排放因子、碳质组分和水溶性离子的排放均具有显著影响.不同农作物秸秆PM_(2.5)排放因子范围在阴燃和明燃时分别是11.45~23.84 g·kg~(-1)和4.51~12.15 g·kg~(-1).有机碳(OC)、元素碳(EC)的排放因子范围阴燃时分别是5.03~11.04 g·kg~(-1)和0.94~2.70 g·kg~(-1),明燃时分别是1.55~6.02 g·kg~(-1)·kg~(-1)和1.04~2.11 g·kg~(-1),阴明燃具有显著差异且阴燃高于明燃.此外,OC/EC、OC/PM_(2.5)和EC/PM_(2.5)在不同燃烧状态均具有显著差别,可作为区分阴明燃的指标.PM_(2.5)中水溶性离子的主要组分阴燃时为K+(1.011 g·kg~(-1))、Cl~-(0.712 g·kg~(-1))、F~-(0.182 g·kg~(-1)g)和SO_4~(2-)(0.166 g·kg~(-1)),明燃时为K+(0.457 g·kg~(-1))、Cl~-(0.271 g·kg~(-1))、SO_4~(2-)(0.086 g·kg~(-1))和F~-(0.048 g·kg~(-1)),且阴燃条件更有利于离子的排放.此外,水溶性离子的相关性也因燃烧状态的不同而有较大的差异.