Effect of hydrodynamic characteristics on reaeration process

The equilibrium-perturb technique was used in the flume reaeration experiment.The interfacial mass transfer coefficients of DO were obtained by implementation of the oxyge-flux theory in the study.The turbulency characteristics of the flow field were investigated by numerical simulation approach.The expression of interfacial mass transfer coefficient related with velocity and turbulence kinetic energy was built.Examination with the experimental datum of different cases showed the validation of the expression.     

中国各省区生态环境质量评价与排序

本文建立了区域生态环境质量综合评价的指标体系,并应用这一指标体系,通过层次分析和综合评价方法对我国各省区的生态环境质量做了定量评价与分析,为生态环境管理和宏观决策提供依据。     

畜禽废弃物处理对规模养殖环境效率的影响

以蛋鸡为例,利用我国5个鸡蛋主产省份蛋鸡规模养殖户的调研数据,从蛋鸡粪便处理的角度采用Super-SBM模型和分位数回归相结合的方法实证分析了蛋鸡规模养殖环境效率及其影响因素.结果表明:蛋鸡规模养殖环境效率低于技术效率,且环境效率存在区域差异;养殖过程中仍然存在投入冗余和期望产出不足、非期望产出过剩的现象;机械化、高频率清粪有利于蛋鸡规模养殖环境效率保持在较高水平,而粪便利用方式对蛋鸡养殖环境效率并没有持续的显著影响;我国所推行的规模化、标准化养殖有利于提升蛋鸡养殖环境效率.     

Chemical formation and source apportionment of PM2.5 at an urban site at the southern foot of the Taihang mountains

The region along the Taihang Mountains in the North China Plain (NCP) is characterized by serious fine particle pollution. To clarify the formation mechanism and controlling factors, an observational study was conducted to investigate the physical and chemical properties of the fine particulate matter in Jiaozuo city, China. Mass concentrations of the water-soluble ions (WSIs) in PM_2.5 and gaseous pollutant precursors were measured on an hourly basis from December 1, 2017, to February 27, 2018. The positive matrix factorization (PMF) method and the FLEXible PARTicle (FLEXPART) model were employed to identify the sources of PM_2.5. The results showed that the average mass concentration of PM_2.5 was 111 μg/m³ during the observation period. Among the major WSIs, sulfate, nitrate, and ammonium (SNA) constituted 62% of the total PM_2.5 mass, and NO₃^? ranked the highest with an average contribution of 24.6%. NH₄⁺ was abundant in most cases in Jiaozuo. According to chemical balance analysis, SO₄^2?, NO₃^?, and Cl^? might be present in the form of (NH₄)₂SO₄, NH₄NO₃, NH₄Cl, and KCl. The liquid-phase oxidation of SO₂ and NO₂ was severe during the haze period. The relative humidity and pH were the key factors influencing SO₄^2- formation. We found that NO₃^? mainly stemmed from homogeneous gas-phase reactions in the daytime and originated from the hydrolysis of N₂O₅ in the nighttime, which was inconsistent with previous studies. The PMF model identified five sources of PM_2.5: secondary origin (37.8%), vehicular emissions (34.7%), biomass burning (11.5%), coal combustion (9.4%), and crustal dust (6.6%).     

福建地震灾害损失计算分析与思考

介绍了福建城乡震灾快速评估系统。根据震害预测模型,利用该系统平台对1992年以来发生的对福建有较大影响的5级以上中强地震进行震灾快速评估。将系统震害计算结果与实际震害调查评估结果进行对比分析,给出了系统评估结果与实际调查结果的数量差异关系,并提出了建立基于遥感影像的震害评估模型的设计思考,从而为震害预测系统设计提供重要的参考意义。     

基于Level Set方法的风暴追踪

利用现代计算机技术和信息处理技术,建立灾害性天气预警系统,是对灾害性天气进行识别和预报的最有效手段之一.研究探索风暴运动过程中多普勒雷达图像的数据处理和算法优化,是预警系统工作中的关键技术.基于计算机技术,应用TITAN算法及改进的Level set方法可以较好地实现对雷达图像中风暴体的追踪,提高灾害性天气预警效率.     

如何防止运动损伤

主要症状是肌肉僵硬、疼痛难忍,一时不易缓解。在一般情况下,冬春交替季节,肌肉抽筋现象要比夏、秋季节多。最易发生抽筋的部位是小腿后部的腓踢肌(即小腿肚子),其次是脚底的屈指肌和屈拇肌。     

叉车门架结构分析和定期检验探讨

叉车产品改变了型式试验样机门架结构的情况普遍存在,是目前特种设备安全监察管理的一项空白。本文提出了首次检验时补充查询具备叉车稳定性和1.33倍额定载荷超载、偏载试验的自行测试与计算能力,生产条件评审时增加制造单位自行测试试验条件审查的建议,以完善叉车法定检验管理。     

沈阳市铁西区水污染物排放总量的核定

系统分析、核定了沈阳市铁西区水污染物排放总量,通过对排污总量的可靠性分析和度量,提出了提高系统信息可靠性的监测与改进建议.认为加强泵站信息的监测与调查有利于对重金属类污染物实施总量控制;而且,在此基础上追加细河黄蜡坨子断面的监测不仅可以清晰识别细河入浑河的排污量,而且可以对有机污染物进行总量控制作出有针对性的、及时的反应.     

循环荷载作用下粗粒料与掺砾粘土接触面单剪试验研究

土石坝内部存在较多的接触面,在静、动力荷载作用下,接触面的力学特性对坝体的稳定性具有显著的影响.基于动态单剪仪,开展了粗粒料与掺砾粘土接触面循环单剪试验.试验结果表明,初始剪应力加载方向对相对位移有较大影响:相对位移总是在沿初始剪应力加载方向一侧较大;在一个剪切循环内,正、反向加载时,若剪应力较小,发生剪缩变形,若剪应...