Drivers of future streamflow changes in watersheds across the Northeastern United States

Accurate projections of streamflow, which have implications for flooding, water resources, hydropower, and ecosystems, are critical to climate change adaptation and require an understanding of streamflow sensitivity to climate drivers. The northeastern United States has experienced a dramatic increase in extreme precipitation over the past 25 years; however, the effects of these changes, as well as changes in other drivers of streamflow, remain unclear. Here, we use a random forest model forced with a regional climate model to examine historical and future streamflow dynamics of four watersheds across the Northeast. We find that streamflow in the cold season (November–May) is primarily driven by 3-day rainfall and antecedent wetness (Antecedent Precipitation Index) in three rainfall-dominant watersheds, and 30-day rainfall, antecedent wetness, and 30-day snowmelt in the fourth, more snowmelt-dominated watershed. In the warm season (June–October), streamflow is driven by antecedent wetness and rainfall in all watersheds. By the end of the century (2070–2099), cold season streamflow depends on the importance placed on snow in the machine learning model, with changes ranging from −7% (with snow) to +40% (without snow) in a single watershed. Simulated future warm season streamflow increases in two watersheds (56% and 193%) due to increased precipitation and antecedent soil wetness, but decreases in the other two watersheds (−6% and −27%) due to reduced precipitation.     

长三角区域一体化的环境治理效应评估——基于DID模型的实证研究

随着长三角一体化的范围不断扩大,融入区域一体化的城市不断增加,对区域城市环境协同治理提出了更高要求。本文采用2003—2019年中国225个地级以上城市面板数据,利用双重差分法评估长三角区域一体化对地区环境治理的影响和作用机制。研究发现长三角区域一体化能显著促进整体城市和原位城市的污染排放强度下降,但对新进城市的环境治理影响并不显著。长三角区域一体化对不同规模城市的环境治理效应没有显著差异;对非资源型城市和高行政等级城市的环境改善作用则优于资源型城市和低行政等级城市。进一步机制分析表明,长三角区域一体化带来污染排放强度整体下降,这一结果主要来自经济集聚效应和技术进步效应,来自产业结构升级的环境治理效应并不显著;同时,长三角区域一体化对环境治理具有显著的反向空间溢出效应,即在降低本地污染排放强度的同时,加大了周边城市污染排放强度。     

压缩空气泡沫水平管路压力损失数值模拟研究

为厘清压缩空气泡沫水平管道输运压力衰减规律,考虑压缩空气泡沫实际工程运用,利用STAR-CCM软件研究泡沫液种类、混合比和管径对湿泡沫水平管网输运过程中压力衰减的影响规律,并结合理论分析建立压缩空气泡沫水平输运过程中的压力衰减预测模型。研究结果表明：管路压降与泡沫液黏度呈正相关性,在混合液流量270 L/min,气体流量1 750 L/min条件下,相同管径高黏度抗溶性水成膜泡沫(AFFF/AR)压降约为低黏度A类和水成膜泡沫(AFFF)1.3倍;对于相同类型泡沫,混合比对管路压降影响较小,100 m长90 mm管径不同混合比之间最大压降差值约为7.21 kPa;管径对压降影响较大,相同泡沫条件下,50 mm管径压降是80 mm管径压降的约9.4倍,80 mm管径压降是100 mm管径压降的约2.8倍,当管径大于80 mm时,不同泡沫对压降的影响逐步减小。压力衰减预测模型计算的压降值与模拟值较前人开展研究所得实验值误差在18%以内,研究结果可以为压缩空气泡沫水平管网设计提供一定理论参考。     

基于知识的管道系统泄漏检测方法

提出了3种基于知识的管道系统泄漏检测方法,分别是:通过对负压波波形分段符号化处理,采用上下文无关法表示波形结构模式的模式识别诊断系统;以选取合适维数的功率谱特征向量而建立的神经网络泄漏检测系统;与泄漏机理数学模型结合的泄漏诊断专家系统。     

A water quality monitoring network design methodology for the selection of critical sampling points: Part II

In order to resolve the spatial component of the design of a water quality monitoring network, a methodology has been developed to identify the critical sampling locations within a watershed. This methodology, called Critical Sampling Points (CSP), focuses on the contaminant total phosphorus (TP), and is applicable to small, predominantly agricultural-forested watersheds. The CSP methodology was translated into a model, called Water Quality Monitoring Station Analysis (WQMSA). It incorporates a geographic information system (GIS) for spatial analysis and data manipulation purposes, a hydrologic/water quality simulation model for estimating TP loads, and an artificial intelligence technology for improved input data representation. The model input data include a number of hydrologic, topographic, soils, vegetative, and land use factors. The model also includes an economic and logistics component. The validity of the CSP methodology was tested on a small experimental Pennsylvanian watershed, for which TP data from a number of single storm events were available for various sampling points within the watershed. A comparison of the ratios of observed to predicted TP loads between sampling points revealed that the model's results were promising.     

铁路油罐车充装过程火灾爆炸危险性分析

铁路油罐车在成品油充装过程中,由于油品本身的易燃易爆特性以及静电等危险因素的作用,极易发生火灾爆炸事故. 通过对静电等危险因素产生的过程及原因进行分析,阐述了在充装工艺过程中,防止静电等危险有害因素产生的控制方法,并提出了在铁路油罐车成品油充装过程中,防止火灾爆炸事故发生的技术对策措施.     

铁路安全评价方法的探讨与分析

安全是铁路运输永恒的主题.目前,安全评价已经成为当代安全管理中最有成效的一种方法.从安全评价的角度出发,对影响铁路运输安全的因素进行了分析,得出人的因素是影响铁路运输安全的主要因素.在国内外当前铁路安全评价方法研究的基础上进行了探讨与分析,指出了国内外在研究铁路安全及安全评价上的不同,以及目前研究中还存在的一些问题,对铁路安全评价提出了一些见解.     

基于有上下界风量约束的矿井风量极值流算法研究

为解决既有方法不能准确求出矿井最大通风量与最小配风量,从而导致矿井通风系统产生能源浪费或难以满足矿井通风需求,出现安全隐患与改造难度大、潜力低等问题,提出1种基于有上下界风量约束的矿井风量极值流算法.该算法首先利用最大流算法求解满足节点流量平衡与分支上下界容量限制条件的可行流问题,若存在可行流,在求得可行流基础上,再利...     

Scenario deduction of Natech accident based on dynamic Bayesian network: A case study of landslide accident in a liquor storage tank area in Guizhou Province,China

Industrial technical accidents caused by natural disasters are defined as Natech accidents, such as earthquakes and landslides, which can cause tremendous damage to industrial storage tanks, and lead to accidental leakage and even serious fire and explosion accidents. In this study, a landslide-induced storage tank accident model under earthquake disasters was proposed, and the relationship between landslide mass impact and target impact resistance was taken into account. Also, tank failure and the formation of the pool fire were considered to be the consequences of the Natech accident. Through scenario deduction, the dynamic process of landslide Natech was transformed qualitatively into a disaster chain network diagram composed of a scenario state, a disaster-causing factor and emergency management. The Bayesian network was used to learn and deduce the parameters of the network diagram, and in this process, the prior probability and conditional probability of nodes were obtained primarily by Monte Carlo simulation, and by an improved expert scoring method based on the fuzzy set theory. Through visualization software, the sensitivity analysis of landslide Natech was achieved. Finally, a case study of a liquor storage tank area in Guizhou Province, China was carried out, and the results show that a large amount of hazardous material leakage caused by buckling is key to the formation of pool fire accidents, and several prevention measures for earthquake-induced landslide Natech was proposed according to the sensitivity analysis.     

线路交换开关级联失效的评估

本文主要针对信号线路交换网络设计中的失效问题展开讨论,对输出信号在传输网络中失效性进行了评估,根据失效评估在设备可靠性设计方面做了相应的考虑。