Modeling level-of-safety for bus stops in China

Objective: Safety performance at bus stops is generally evaluated by using historical traffic crash data or traffic conflict data. However, in China, it is quite difficult to obtain such data mainly due to the lack of traffic data management and organizational issues. In light of this, the primary objective of this study is to develop a quantitative approach to evaluate bus stop safety performance.

Methods: The concept of level-of-safety for bus stops is introduced and corresponding models are proposed to quantify safety levels, which consider conflict points, traffic factors, geometric characteristics, traffic signs and markings, pavement conditions, and lighting conditions. Principal component analysis and k-means clustering methods were used to model and quantify safety levels for bus stops.

Results: A case study was conducted to show the applicability of the proposed model with data collected from 46 samples for the 7 most common types of bus stops in China, using 32 of the samples for modeling and 14 samples for illustration. Based on the case study, 6 levels of safety for bus stops were defined. Finally, a linear regression analysis between safety levels and the number of traffic conflicts showed that they had a strong relationship (R² value of 0.908).

Conclusions: The results indicated that the method was well validated and could be practically used for the analysis and evaluation of bus stop safety in China. The proposed model was relatively easy to implement without the requirement of traffic crash data and/or traffic conflict data. In addition, with the proposed method, it was feasible to evaluate countermeasures to improve bus stop safety (e.g., exclusive bus lanes).     

基于可拓云理论的泥炭质土场地沉降风险评价

为更好地研究泥炭质土场地地铁车站基坑周边沉降问题,预测和评估施工时及施工后的沉降风险,在分析了泥炭质土的特点后,选择土层厚度、有机质质量分数、重度、天然含水率、孔隙比、土层埋深和压缩模量7个指标,建立沉降风险评估指标体系,并根据改进层次分析法和改进熵权法求出主观权重与客观权重,最后用理想点法耦合主客观权重求出各评价指标的综合权重;根据沉降等级分类标准,生成每个评价指标的云滴图,计算得到各评价因子的可拓云矩阵,进而将综合权重向量与可拓云矩阵相乘得到综合确定度,根据综合确定度最大原则确定样本沉降风险等级。以昆明某地铁车站施工监测数据为例,用建立的可拓云模型对泥炭质土场地的沉降风险进行评价,最终评价结果与实际监测结果吻合较好,验证了分析方法的合理性及可行性。该评价方法充分考虑了多种因素影响,明确了沉降的风险等级,评价结果为泥炭土场地上建(构)筑物的设计施工及应急处理提供了理论依据。     

基于无线局域网(WLAN)的油田安全监控系统研究

针对油田监控对象具有点多、面广、跨区域的特点,指出对油田进行无线监控的必要性,并对6种常见的无线通信手段的特点进行比较;根据油田安全监控的业务需求,提出基于WLAN技术的油田安全监控系统硬件结构和软件功能设计方案;并结合工程实施案例介绍系统中无线设备的选型、安装和防雷接地等方面的工程问题。该研究成果实现油田的安全监控预警,减少或避免事故发生的可能性,有利于提高油田安全管理的科学性,具有实用推广价值。     

洪水作用下汽车的起动流速研究

针对洪水作用下汽车的起动条件开展了一系列的研究:首先分析部分淹没状态下汽车的受力情况,结合滑动平衡的临界起动条件建立相关方程,导出了洪水中汽车起动流速公式;然后在室内水槽中对三款模型车进行了一系列的起动试验。试验结果表明:对于同一款模型车,平行于水流方向放置时,起动流速与水深的相关性较好;并且水深越大,起动流速越小。接着运用试验资料率定了起动流速公式中的相关参数。最后采用模型相似率及率定后的计算公式估算了原型车辆在不同水深下的起动流速,两种方法所得的结果较为接近,故预测结果较为可靠。     

Nutrient Inputs to the Laurentian Great Lakes by Source and Watershed Estimated Using SPARROW Watershed Models1

Robertson, Dale M. and David A. Saad, 2011. Nutrient Inputs to the Laurentian Great Lakes by Source and Watershed Estimated Using SPARROW Watershed Models. Journal of the American Water Resources Association (JAWRA) 47(5):1011‐1033. DOI: 10.1111/j.1752‐1688.2011.00574.x Abstract: Nutrient input to the Laurentian Great Lakes continues to cause problems with eutrophication. To reduce the extent and severity of these problems, target nutrient loads were established and Total Maximum Daily Loads are being developed for many tributaries. Without detailed loading information it is difficult to determine if the targets are being met and how to prioritize rehabilitation efforts. To help address these issues, SPAtially Referenced Regressions On Watershed attributes (SPARROW) models were developed for estimating loads and sources of phosphorus (P) and nitrogen (N) from the United States (U.S.) portion of the Great Lakes, Upper Mississippi, Ohio, and Red River Basins. Results indicated that recent U.S. loadings to Lakes Michigan and Ontario are similar to those in the 1980s, whereas loadings to Lakes Superior, Huron, and Erie decreased. Highest loads were from tributaries with the largest watersheds, whereas highest yields were from areas with intense agriculture and large point sources of nutrients. Tributaries were ranked based on their relative loads and yields to each lake. Input from agricultural areas was a significant source of nutrients, contributing ～33‐44% of the P and ～33‐58% of the N, except for areas around Superior with little agriculture. Point sources were also significant, contributing ～14‐44% of the P and 13‐34% of the N. Watersheds around Lake Erie contributed nutrients at the highest rate (similar to intensively farmed areas in the Midwest) because they have the largest nutrient inputs and highest delivery ratio.     

点声源环境噪声声场区域二维图形化表征方法研究

针对环境噪声监测中单一点声源声场图形化表征机理,依据点声源衰减规律建立了点声源声场二维平面表征算法,据此以网格化区域范围内非均匀布置少量监测点方法确定声源点,再经克里金插值法反演点声源声场平面分布规律,最后通过ArcGIS软件平台实现噪声图形化展示.以5×5网格化区域为例,其非均匀布点数应不少于3个,最佳布点数为3组共计6个点,其实测值与理论值最大误差为4.3％.仿真试验验证表明,点声源图形表征符合实际声场分布规律.     

降雨、地形对非点源污染产输影响机理综述

随着工业点源的逐步控制,非点源因其来源多样、涉及范围广、控制难度大,已成为影响水环境质量的主要污染源。非点源污染产输机理是开展定量研究、模型模拟及污染治理的基础,也是非点源污染研究领域的重点和难点。降雨是非点源污染产输的直接驱动力,地形是影响非点源污染产输的重要因素,两者对非点源污染的产输均具有重要影响。对国内外在降雨、地形对非点源污染产输影响机理方面的研究进行综述,以期为非点源污染相关研究提供参考和借鉴。     

混合溶剂的闪点变化规律探析

为考察不同类型溶剂对混合液易燃特性的影响,探索混合溶剂闪点的变化规律,分别将不燃溶剂、阻燃型溶剂、高闪点溶剂及低闪点溶剂与乙醇按不同比例混合,采用闭杯闪点测试仪进行混合液的闪点测试。研究结果表明,添加不燃或阻燃溶剂时,混合液闪点整体呈现逐渐升高趋势,不燃或阻燃溶剂易于提高混合溶剂的安全性能,当不燃或阻燃溶剂体积分数超过0.7以上时,混合液闪点提高幅度较大;添加可燃溶剂时,可燃溶剂的结构不同,对混合液的燃烧特性影响也不同,添加高闪点溶剂可能提高混合液闪点,也可能降低混合液闪点;而添加低闪点溶剂,降低混合液闪点,甚至可能比混合液任一组分闪点值都低;因此选用混合溶剂时,不能盲目,需要严格关注其混合后易燃特性参数的变化。     

中国北方某流域不同污染源污染贡献分析研究

研究了中国北方某流域不同污染源的污染贡献,结果表明：COD贡献量点源为719.21 t,农业面源污染为7 488.02 t,农业面源污染是该流域水环境污染的主要来源.农业面源污染物等标污染负荷总量为8 359.44×106 m3/a.不同污染源污染贡献比例：农田化肥占49.24％、畜禽养殖占35.10％、农村生活占14.69％、农作物秸秆仅占0.97％.污染物贡献量比例.TN占56.46％、TP占39.06％、COD仅占4.48％.     

URBAN INFLUENCE ON PHOSPHORUS AND SEDIMENT LOADING OF WEST POINT LAKE,GEORGIA1

ABSTRACT: West Point Lake is a 10,360 ha mainstream impoundment of the Chattahoochee River located 95 kilometers downstream of Atlanta, Georgia. Origins and magnitude of external total phosphorus (TP) and total suspended solids (TSS) loads from the West Point Lake basin were estimated over a one-year period. Partitioning the drainage basin allowed the sources of these loads to be determined. The upper subbasin area, from Franklin, Georgia, to the headwaters of the Chattahoochee River, contributed 96 percent of the discharge and 97 percent of the TP and TSS loads into West Point Lake. The lower subbasin area, from Franklin to West Point Lake dam, only contributed 3 percent of the TP and TSS loads. Ninety-one percent and 87 percent of the TP and TSS loads, respectively, from the upper subbasin originated from the Atlanta area. Point sources discharged 70 percent and 3 percent of the upper subbasin TP and TSS loads, respectively. A large portion (66 percent) of the TP from the upper subbasin was in the bioavailable form.