火电湿法烟气脱硫流程优化的实现方案研究

在给定脱硫流程模拟优化参数的情况下,尝试了基于DCS系统和基于OA局域网的两种优化控制改进方案,后一种方案解决了优化控制系统的安全性、稳定性、扩展性、易管理等问题。同时采用该控制系统的3号脱硫系统的控制效果最佳,且脱硫效率循环浆液泵功率比随着操作方式相近度的提高而呈递增趋势。     

白洋淀喹诺酮类抗生素污染特征及其与环境因子相关性研究

利用超高效液相色谱串联质谱法(HPLC-MS)对白洋淀水体和沉积物中喹诺酮类(Quinolones,QNs)抗生素进行检测,并研究其生态风险空间分异特征,探究其与环境因子的相关性.结果表明:①白洋淀氧氟沙星(Ofloxacin,OFL)和氟甲喹(Flumequine,FLU)的检出率最高(100%),其次为马波沙星(Marbofloxacin,MAR)和氟罗沙星(Fleroxacin,FLE)(≥60%),其余QNs的检出率较低(≤35%);②白洋淀水体和沉积物中QNs抗生素浓度范围分别为153.39～1550.07 ng·L~(-1)和10.22～381.85 ng·g~(-1),水体中QNs在S1处浓度最高,S4处最低,沉积物中QNs在S2处浓度最高;③相关性分析结果表明,水体透明度(Secchi depth,SD)、总氮(Total nitrogen,TN)、总磷(Total phosphorus,TP)、硝氮(Nitrate nitrogen,NO~-_3-N)、沉积物氨氮(Ammonia nitrogen,NH_3-Ns)和沉积物总氮(TNs)与QNs相关性显著,其中,SD、TP和NH_3-Ns与部分QNs(MAR、恩诺沙星(Enrofloxacin,ENR)和FLE)显著相关(p0.01),表明生活污水和养殖废水对QNs的贡献较大;④生态风险评价结果表明,白洋淀QNs总体处于中低风险水平,其中,ENR处于中高风险水平,其余QNs处于低风险水平;就空间分布而言,除S1和S9为高风险区外,其余各点为中低风险区.     

丹江口水库水质要素变化特征及其相互关系

采用丹江口水库 1987～ 1996年间的水环境常规监测资料 ,应用因子分析方法探讨了丹江口水库不同区域水环境要素变化特征及其相互关系 ,分析表明 :丹江口水库目前水质良好 ,大多数情况下能满足地面水一类水质标准要求 :库区不同断面水体水质要素及污染因子间的相互关系可以用 6个主导因子表达。同一主导因子不同断面标识因子的差异反映了库区不同区域水质分布差异及产生这种差异的环境过程 ;影响库区水质的主要因素是上游随降水产生的面源污染、库周点源排放、水体自净以及气候因素 ,不同断面水质影响因素及其程度存在差异。     

A stochastic-advective transport model for NAPL dissolution and degradation in non-uniform flows in porous media

Remediation schemes for contaminated sites are often evaluated to assess their potential for source zone reduction of mass, or treatment of the contaminant between the source and a control plane (CP) to achieve regulatory limits. In this study, we utilize a stochastic stream tube model to explain the behavior of breakthrough curves (BTCs) across a CP. At the local scale, mass dissolution at the source is combined with an advection model with first-order decay for the dissolved plume. Field-scale averaging is then employed to account for spatial variation in mass within the source zone, and variation in the velocity field. Under the assumption of instantaneous mass transfer from the source to the moving liquid, semi-analytical expressions for the BTC and temporal moments are developed, followed by derivation of expressions for effective velocity, dispersion, and degradation coefficients using the method of moments. It is found that degradation strongly influences the behavior of moments and the effective parameters. While increased heterogeneity in the velocity field results in increased dispersion, degradation causes the center of mass of the plume to shift to earlier times, and reduces the dispersion of the BTC by lowering the concentrations in the tail. Modified definitions of effective parameters are presented for degrading solutes to account for the normalization constant (zeroth moment) that keeps changing with time or distance to the CP. It is shown that anomalous dispersion can result for high degradation rates combined with wide variation in velocity fluctuations. Implications of model results on estimating cleanup times and fulfillment of regulatory limits are discussed. Relating mass removal at the source to flux reductions past a control plane is confounded by many factors. Increased heterogeneity in velocity fields causes mass fluxes past a control plane to persist, however, aggressive remediation between the source and CP can reduce these fluxes.     

Contribution of anthropogenic pollutants to the increase of tropospheric ozone levels in the Oporto Metropolitan Area, Portugal since the 19th century

The main purpose of this study was to evaluate the contribution of anthropogenic pollutants to the increase of tropospheric ozone levels in the Oporto Metropolitan Area (Portugal) since the 19th century. The study was based on pre-industrial and recent data series, the results being analyzed according to the atmospheric chemistry. The treatment of ozone and meteorological data was performed by classical statistics and by time-series analysis. It was concluded that in the 19th century the ozone present in the troposphere was not of photochemical origin, being possible to consider the respective concentrations as reference values. For recent data a cycle of 8h for ozone concentrations could be related to traffic. Compared to the 19th century, the current concentrations were 147% higher (252% higher in May) due to the increased photochemical production associated with the increased anthropogenic emissions.     

膨胀聚苯乙烯热分解动力学分析和寿命预测

针对既有聚苯乙烯泡沫类外墙外保温系统的防火问题,在空气和氮气气氛下对非阻燃和阻燃型膨胀聚苯乙烯泡沫进行了热重分析。样品由10℃/min、20℃/min、40℃/min和50℃/min四个升温速率从室温加热至800℃。热分解动力学参数由Flynn-Wall-Ozawa(FWO)等转化率方法和多参数非线性回归方法(multivariate non-linear re-gression method)计算,结果表明六溴环十二烷(HBCD)阻燃剂可一定程度上提高EPS的热稳定性。EPS在空气和氮气气氛下热解可认为是单步反应。非阻燃聚苯乙烯泡沫在空气和氮气气氛下的热解过程可由自催化n阶反应机理描述。阻燃EPS在空气气氛下的热解机理为自催化n阶反应,在氮气气氛下则为n阶反应机理。基于动力学参数和反应机理,对聚苯乙烯泡沫在不同温度下的寿命进行了预测。     

Investigating the effect of geometric dimensions of median traffic barriers on crashes: Crash analysis of interstate roads in Wyoming using actual crash datasets

IntroductionDespite the numerous safety studies done on traffic barriers’ performance assessment, the effect of variables such as traffic barrier’s height has not been identified considering a comprehensive actual crash data analysis. This study seeks to identify the impact of geometric variables (i.e., height, post-spacing, sideslope ratio, and lateral offset) on median traffic barriers’ performance in crashes on interstate roads.MethodGeometric dimensions of over 110 miles median traffic barriers on interstate Wyoming roads were inventoried in a field survey between 2016 and 2018. Then, the traffic barrier data collected was combined with historical crash records, traffic volume data, road geometric characteristics, and weather condition data to provide a comprehensive dataset for the analysis. Finally, an ordered logit model with random-parameters was developed for the severity of traffic barrier crashes. Based on the results, traffic barrier’s height was found to impact crash severity.ResultsCrashes involving cable barriers with a height between 30″ and 42″ were less severe than other traffic barrier types, while concrete barriers with a height shorter than 32″ were more likely involved with severe injury crashes. As another important finding, the post-spacing of 6.1–6.3 ft. was identified as the least severe range in W-beam barriers.Practical applicationsThe results show that using flare barriers should reduce the number of crashes compared to parallel barriers.     

通风机站风流间相互影响阻力特性研究*

为研究双风机并联机站进口、出口风流相互影响的机站局部阻力特性，构建机站通风局部阻力计算的数学模型，同时运用相似原理建立双风机并联通风机站实验模型，并佐以数值模拟对比验证，分析计算不同风机间距的无量纲数A、不同扩散器结构参数条件下的综合影响系数Kc。结果表明:A与Kc具有二次函数关系，且存在较优的A，使得Kc值最小；Kc值随着L/Df增加而线性减小。研究结果有利于Kc的选取，为高效率通风机站结构设计提供技术及数据支撑。     

对叉车额定起重量的分析和探讨

本文对叉车的额定起重量和实际起重量之间的联系与区别进行了分析,指出了额定起重量只是供叉车设计使用的参数,建议不要将额定起重量标识在叉车铭牌上,叉车用户应按照载荷曲线图来确定操作时的实际起重量.     

Study on explosion risk of aluminum powder under different dispersions

This paper mainly studied the influence of particle size distribution on the explosion risk of aluminum powder under the span of large particle size distribution. The measurement was carried out with the 20 L explosion ball and the Hartmann tube. The statistical analysis was used to analyze the relevance between the parameters of explosion risk and the particle size parameters. Test results showed that with the increase of particle size, the sensitivity parameter increases and the intensity parameter deceleration decreases. The effect of particle size change on MEC and MIE of small particle size aluminum powder is relatively small but greater impact on Pm and (dP/dt)m. The small particle size components greatly increasing the sensitivity of the explosion and accelerating the rate of the explosion reaction; while the large particle size component contributes to the maximum explosion pressure. D_3,2 particle size dust determines the risk of aluminum powder explosion.