基于视频分析的人群密集场所客流监控预警研究

为实现人群密集场所客流安全隐患早发现，辅助管理人员早决策，人群聚集风险区早疏散，提升对灾难的预见性和主动性。在国内外人群异常聚集监测预警现状分析基础上，对比分析得出监控视频分析技术是解决人群密集场所精准预警难题较为理想的解决方案；构建以视频智能分析的人群计数、密度估计、行人追踪、活动烈度识别为核心技术的人群密集场所风险预警技术框架；将该技术框架应用到某大型商圈的商业街区，获得监控区域内的人群总数、密度分布、行人轨迹和异常活动等特征。结果表明:提出的基于视频分析的人群密集场所风险预警技术框架可为城市大型商圈、交通枢纽、大型活动场所等城市公共场所的安全管理提供参考和借鉴。     

Inverse modeling of Asian Rn flux using surface air Rn concentration

When used with an atmospheric transport model, the ²²²Rn flux distribution estimated in our previous study using soil transport theory caused underestimation of atmospheric ²²²Rn concentrations as compared with measurements in East Asia. In this study, we applied a Bayesian synthesis inverse method to produce revised estimates of the annual ²²²Rn flux density in Asia by using atmospheric ²²²Rn concentrations measured at seven sites in East Asia. The Bayesian synthesis inverse method requires a prior estimate of the flux distribution and its uncertainties. The atmospheric transport model MM5/HIRAT and our previous estimate of the ²²²Rn flux distribution as the prior value were used to generate new flux estimates for the eastern half of the Eurasian continent dividing into 10 regions.The ²²²Rn flux densities estimated using the Bayesian inversion technique were generally higher than the prior flux densities. The area-weighted average ²²²Rn flux density for Asia was estimated to be 33.0 mBq m⁻² s⁻¹, which is substantially higher than the prior value (16.7 mBq m⁻² s⁻¹). The estimated ²²²Rn flux densities decrease with increasing latitude as follows: Southeast Asia (36.7 mBq m⁻² s⁻¹); East Asia (28.6 mBq m⁻² s⁻¹) including China, Korean Peninsula and Japan; and Siberia (14.1 mBq m⁻² s⁻¹). Increase of the newly estimated fluxes in Southeast Asia, China, Japan, and the southern part of Eastern Siberia from the prior ones contributed most significantly to improved agreement of the model-calculated concentrations with the atmospheric measurements. The sensitivity analysis of prior flux errors and effects of locally exhaled ²²²Rn showed that the estimated fluxes in Northern and Central China, Korea, Japan, and the southern part of Eastern Siberia were robust, but that in Central Asia had a large uncertainty.     

Determination of specific gravity of municipal solid waste

This investigation was conducted to evaluate experimental determination of specific gravity (G_s) of municipal solid waste (MSW). Water pycnometry, typically used for testing soils was adapted for testing MSW using a large flask with 2000 mL capacity and specimens with 100–350 g masses. Tests were conducted on manufactured waste samples prepared using US waste constituent components; fresh wastes obtained prior and subsequent to compaction at an MSW landfill; and wastes obtained from various depths at the same landfill. Factors that influence specific gravity were investigated including waste particle size, compaction, and combined decomposition and stress history. The measured average specific gravities were 1.377 and 1.530 for as-prepared/uncompacted and compacted manufactured wastes, respectively; 1.072 and 1.258 for uncompacted and compacted fresh wastes, respectively; and 2.201 for old wastes. The average organic content and degree of decomposition were 77.2% and 0%, respectively for fresh wastes and 22.8% and 88.3%, respectively for old wastes. The G_s increased with decreasing particle size, compaction, and increasing waste age. For fresh wastes, reductions in particle size and compaction caused occluded intraparticle pores to be exposed and waste particles to be deformed resulting in increases in specific gravity. For old wastes, the high G_s resulted from loss of biodegradable components that have low G_s as well as potential access to previously occluded pores and deformation of particles due to both degradation processes and applied mechanical stresses. The G_s was correlated to the degree of decomposition with a linear relationship. Unlike soils, the G_s for MSW was not unique, but varied in a landfill environment due both to physical/mechanical processes and biochemical processes. Specific gravity testing is recommended to be conducted not only using representative waste composition, but also using representative compaction, stress, and degradation states.     

陕北黄土丘陵区不同土地利用方式下土壤碳剖面分布特征

黄土高原土层深厚,土壤剖面碳存储受土地利用方式影响明显.为探讨不同土地利用方式对深层土壤碳分布的影响,研究了人工经济林地(陕北米脂)、退耕还林地(神木)和防风固沙林地(榆林榆阳区)0~20.0 m土壤有机碳(SOC)和无机碳(SIC)的分布特征和差异.结果表明,在不同土地利用方式下SOC含量:矮化枣树(2.00 g·kg~(-1))未矮化枣树(1.54 g·kg~(-1))柠条林(0.97 g·kg~(-1))退化人工草地(0.81 g·kg~(-1))樟子松林(0.70 g·kg~(-1))荒草地(0.45 g·kg~(-1)),且各剖面之间SOC含量存在显著性差异(P0.05).在不同土地利用方式下SIC含量:矮化枣树(11.66 g·kg~(-1))≥未矮化枣树(11.59g·kg~(-1))柠条林(9.62 g·kg~(-1))退化人工草地(8.07 g·kg~(-1))樟子松林(4.32 g·kg~(-1))荒草地(0.47 g·kg~(-1));人工经济林和退耕还林(草)样地内所有土壤剖面之间SIC含量无显著性差异;人工经济林、退耕还林(草)剖面和防风固沙林地剖面SIC含量存在显著性差异(P0.05).矮化枣树、未矮化枣树、柠条林、退化人工草地、樟子松林和荒草地土壤剖面无机碳密度分别是有机碳密度的6.19、7.71、10.80、10.78、5.91和1.03倍.综上可见,不同土地利用方式之间土壤碳储量存在明显差异,无机碳的含量远高于有机碳.     

长江口海域底栖生态环境质量评价——AMBI和M-AMBI法

AMBI(AZTI’s Marine Biotic Index)和M-AMBI(Multivariate-AMBI)指数可以有效地评价河口和近岸海域软底质海洋大型底栖动物群落对人为和自然扰动的响应.本研究根据2009年4月在长江口采集的大型底栖动物资料,首次在长江口海域同时运用栖息密度和生物量计算AMBI(BAMBI)和M-AMBI(M-BAMBI),对其进行底栖生态质量评价.结果表明,长江口底栖生态环境皆受到不同程度的干扰,其中受干扰最严重的区域集中在杭州湾、舟山及长江口门区附近海域,与该海域的陆源排污、富营养化以及大量的海岸工程建设等有密切的关系.单因素方差分析表明,运用栖息密度和生物量计算出的两个指数值,评价结果无明显的差异.与AMBI相比,M-AMBI与本研究生物群落结构参数以及环境因子的匹配度更高,能够更有效地评价长江口底栖生态环境质量.Pearson相关分析和一元线性回归分析表明,M-AMBI与底层水体的富营养化指数之间存在线性显著负相关关系,而与表层水体的呈非线性显著负相关;AMBI与富营养化指数之间却无显著相关关系,说明M-AMBI更适合指示长江口水域的富营养化压力.     

新乡市地表水体HCHs和DDTs的分布特征及生态风险评价

为了解新乡市地表水中HCHs和DDTs的分布特征及生态风险,采集新乡市18个地表水样并测定其中HCHs和DDTs的含量,采用概率密度函数重叠面积法和安全阈值法评价了HCHs和DDTs的生态风险.结果表明,新乡市地表水中HCHs和DDTs的质量浓度范围分别为1.28~49.2 ng·L-1和0.42~12.3 ng·L-1,与世界各地的地表水中HCHs和DDTs残留质量浓度相比属于中等污染水平.异构体比值表明HCHs污染的主要来源是林丹的使用,而DDTs的残留来源于工业品DDTs的使用.生态风险评价基于DDD、γ-HCHs和p,p'-DDT的暴露浓度以及相应的毒性数据,概率密度函数重叠面积法和安全阈值法均表明了这3种有机氯农药中DDD的风险最大,其次是γ-HCHs,p,p'-DDT的生态风险最小;安全阈值法进一步表明DDD、γ-HCHs和p,p'-DDT超过影响10%水生生物的概率分别为10.2%、5.94%和0.01%.     

川东北低山丘陵区细颗粒物主要相关因素和季节变化分析——以南充主城区为例

基于中国空气质量在线监测分析平台和全球天气精准预报网的大气质量和气象数据,以四川盆地东北低山丘陵区典型城市南充市主城区为例,检验了细颗粒物(PM_(2.5))浓度的概率密度分布,发现其接近对数正态分布,由相关分析确定了PM_(2.5)浓度的主要相关因素为CO、NO_2(相关系数r分别为0.76、0.55,P0.01),再通过对2014年1月—2016年6月的日数据的逐步回归筛选出最优的回归指标和模拟方程(决定系数R_(adj)~2为0.68,P0.05),2016年7月—2017年6月的数据验证表明模拟效果较好(拟合优度为0.64,相对误差15.48%);最后根据时序插值、浓度和IAQI(PM_(2.5))的时段均值发现PM_(2.5)浓度在年际上有降低趋势;在季节上由高到低依次为冬季、春季、秋季、夏季;PM_(2.5)浓度在1月和6月分别呈现出年内的峰值和谷值,5、10月出现了阶段性峰值,尤其是5月;IAQI(PM_(2.5))的季节变化与浓度变化规律相似;且PM_(2.5)与PM_(10)比值的均值为0.67,表明现阶段南充市主城区大气污染物中细颗粒物占有较大比重。     

亚热带流域氮磷排放与养殖业环境承载力实例研究

畜禽养殖业粪便排放已经成为我国农村地区主要的农业面源污染源之一,也是制约养殖业良性发展的主要瓶颈.本文以湖南省长沙县典型亚热带流域为研究单元,基于流域水环境定位观测、耕地氮(N)磷(P)消纳能力以及养殖业调查和土壤分析资料,初步分析了亚热带丘陵区的面源污染现状及畜禽养殖业的环境承载力.结果表明,研究区金井河流域134.4 km2范围内N、P年负荷分别为N 2.72 t·km-2和P0.11t·km-2,其中养殖粪便对水体总氮(TN)、总磷(TP)负荷的贡献率分别约为42.2％和62.0％.区内平均畜禽养殖密度为3.46 AU·hm-2(相当于流域内年出栏生猪24.39万头),显著高于现有化肥用量条件下流域的实际承载力1.13 AU·hm-2(相当于流域内年出栏生猪6.35万头),因此养殖密度过高是导致研究区水体NP负荷较高的主要原因.区内N、P盈余量分别为N 35.8 kg·hm-2、P 18.61 kg·hm-2.研究区基本不施用化肥条件下畜禽养殖业的最大环境承载力为7.26 AU·hm-2,在有机肥占合理施肥量30％条件下,当地畜禽养殖业的环境承载力为2.74AU·hm-2(相当于流域内年出栏生猪19.50万头).降低养殖密度、调整养殖业空间布局以及提高养殖废弃物的资源化利用率是防治当前面源污染的有效途径.     

北京市道路灰尘中污染物含量沿城乡梯度、道路密度梯度的变化特征

采用网格布点法调查了北京市六环范围内220个样点道路地表灰尘样品中的污染物含量.探讨了样点缓冲区内单位面积道路节点数、道路密度和道路灰尘中污染物含量沿城乡梯度的变化特征及各指标间的相关性.结果表明,各指标在研究区内的变幅较大.沿城乡梯度,道路和污染物主要呈现3种变化趋势:①单位面积道路节点数,道路密度,Cu、Cr和Pb沿城乡梯度降低,且开始时降低较快;②Mn和Cd沿城乡梯度变化的程度较低,均值基本维持恒定;③自中心向外围,Ni和有机碳(TOC)、总氮(TN)先随距离波动降低,随后在郊区均值缓慢增高.道路灰尘中污染物含量趋势转折点位置均大致在距城市中心点15～20 km左右.相关分析表明道路指标和道路灰尘中的Cd含量不具相关性,总硫(TS)、Mn、pH的相关性较弱,与其他各元素的相关性排序为Cu>TN>TOC>Pb>Ni>Cr,较道路密度而言,单位面积节点数和各元素间的相关性更高,该指标可指示道路灰尘中Cu、TN、TOC、Pb、Ni、Cr元素污染.     

Investigation on the changes effected by tool profile on mechanical and tribological properties of friction stir processed AZ31B magnesium alloy

The present study investigates the effect of tool shoulder profile on the mechanical and tribological properties of friction stir processed AZ31B magnesium alloy. The tool rotational speed and feed rate are the chosen process parameters. The experiments were conducted with 3 level 2 factors full factorial design. The recorded responses were tensile strength, wear losses and corrosion rate. The results were analyzed with the help microstructures of the processed samples. The study reveals that, for concave shoulder tool, the strain hardening effect was playing a major role in determining the properties of the processed materials and for the step shoulder tool, the grain size plays a major role in determining the properties of the processed materials.