SOLUTE TRANSPORT IN THREE‐DIMENSIONAL SATURATED POROUS MEDIA HAVING SELF‐SIMILAR HYDRAULIC CONDUCTIVITY DISTRIBUTION1

ABSTRACT: Customarily, it has been assumed that hydraulic conductivity is a stationary, homogeneous stochastic process with a finite variance for stochastic analysis of solute transport in the subsurface. That the distribution of hydraulic conductivity may have a fractal behavior with long range correlations was suggested from field data analyses. This motivates us to further investigate how the fractal behavior of permeability distribution impacts solute transport in porous media. This study provides longitudinal and transverse macrodispersivity coefficients and the variance of the solute concentration. Longitudinal and transverse macrodispersivity coefficients are found to depend strongly on the fractal dimension (D) of logarithmic hydraulic conductivity (logK). The longitudinal and transverse macrodispersivity coefficients are the highest when D = 1, and the values decrease monotonically to zero at D = 2. Both coefficients correspond to the characteristic length scale of the logK distribution, thus are scale dependent parameters. The ratio of the transverse to the longitudinal macrodispersivity coefficient is on the order of 10^‐1 to 10^‐4. Concentration variance also decreases with the fractal dimension of logK. There is no spatial spreading of solute for D = 2, and the concentration variance reaches zero for this case.     

一起煤气管道泄漏事故的剖析

通过对某公司通向居民生活区新建埋设煤气主管道发生泄漏事故的剖析，全面分析了引起泄漏事故的因素。找出了事故的原因。对预防煤气管道泄漏，确保煤气管道的安全畅通具有重要意义。对钢铁企业、市政建设等所涉及的各种埋地管道、电缆的安全运行具有参考价值。     

城市污水一级强化处理工艺——高负荷生物吸附再生法的应用研究

根据理论分析提出生物吸附-沉淀-再生的城市污水处理工艺,即高负荷生物吸附再生法.该工艺对污染物去除的作用主要包括污泥的絮凝作用、吸附作用和生物代谢作用,而以前两者的作用为主.对城市污水的生产性试验研究结果表明,该工艺能够较大程度地提高SS、COD、SCOD和BOD等污染物的去除率,具有明显的处理效果,对于西北干旱缺水地区实现污水资源化是切实可行的方法.     

冻融对污水河道沉积物特性及脱水性能的影响

为了降低污水河道治理过程中污染沉积物的含水率以减少其对环境的二次污染,对污水河道沉积物在自然条件下和人为条件下进行冻融实验研究,通过冻融前后沉积物比阻抗、含水率、颗粒分布及渗出液中污染物含量等实验说明冻融对污染沉积物脱水性能及其特性有影响.研究表明,冻融过程使沉积物的比表面积变小,体均粒径变大,泥水明显分离,含水率从冻前83%～85%降到融后的50%～60%;大量间隙水、毛细结合水和表面粘附水游离出来,提高了沉积物的脱水性能;比阻值由(1.2～4.1)×10⁹s²/g降为(3.8～5.2)×10⁷s²/g;同时渗出液的SS含量由1 000～1 200mg/kg降到340～380 mg/kg、氨氮含量由150～170 mg/kg降到100～120 mg/kg、BOD含量由300～310 mg/kg降到50～60 mg/kg,但渗出液中油类物质含量由1～2mg/kg提高到11～12 mg/kg,即如果沉积物不是被油类物质污染,冻融可使渗出液污染程度小于冻前沉积物的渗出液.     

长江流域鄂西四河流大型底栖动物群落结构特征及水质生物学评价

鄂西水系是国家级水源保护区,也是湖北省重要的生态旅游区。为了解鄂西水生态健康状况,于2014年10月~2017年1月不同时段在宜昌国家可持续发展实验示范区卷桥河（J）、清江利川段（Q）、宜昌市水源地黄柏河（H）和丹江口入库河流天河郧西段（T）开展了底栖动物群落特征研究。研究表明：4个河段共采集到大型底栖动物5门8纲18目61科。基于底栖动物指示种耐污性及其丰度占比分析,表明J、Q和T三河流污染程度沿水流方向呈加重趋势,而H水体健康状况整体较好。运用FBI和SIGNAL底栖生物评价指数,显示四条河流健康程度沿水流方向均呈下降趋势,但H变化趋势平缓,结果表明H水体上下游均处于较健康状态,其他3条河流上游或源头水体健康状况良好,下游受到较重污染。对主要环境因子（TP、NH₃-N、COD_Mn和TN）做主成分分析表明,轴1的解释率达到65.1%,表明轴1可以有效表征主要环境压力梯度。FBI和SIGNAL指数与轴1线性拟合度均较高,表明二者在鄂西河流水生态健康评估中可作为快速生物评价指数。     

The journey to leave: Understanding the roles of perceived ease of movement,proactive personality,and person–organization fit in overqualified employees' job searching process

Despite intensive research on perceived overqualification, empirical evidence on overqualified employees' job search behavior remains relatively insufficient. Notably, no studies have explored the possible link between perceived overqualification and internal job searching behaviors. In the present study, we consider whether—and more importantly when—employees with high perception of overqualification search for internal and external job opportunities. Applying the ability–motivation–opportunity (AMO) framework, we propose and test a model that specifies how motivation and opportunity to move or stay activate differential effects in overqualifiers' job searching process. Results from two studies surveying employees in Taiwan (Study 1: N = 268; Study 2: N = 210) show that overqualifiers displayed greater intentions to leave the current job and, in turn, engaged in more external job search behaviors; this relation was strongest for those whose perceived ease of movement and proactive personality increased or person–organization (PO) fit decreased. Furthermore, overqualifiers displayed greater intentions to leave the current job and also increased their internal job search behaviors; this relation was strongest for those whose perceived ease of movement and PO fit increased. A series of supplemental analyses also lends support to our theorizing.     

危险废物回转式流化冷渣多段焚烧系统焚烧特性研究

危险废物的处理和处置是摆在我国各级市政府面前的紧迫任务。然而我国已经运行的危险废物焚烧装置普遍存在回转窑挂壁结渣、热灼减率偏高和污染排放超标等问题,作者通过将回转窑和流化床特点相结合的方法提出了一种新型危险废物回转式流化冷渣多段焚烧处置装置。该装置采用回转窑(一燃室)、二燃室和流化床结合的热解-流化焚烧工艺,特别是采用控制窑头温度避免了回转窑挂壁结渣;采用流化冷渣装置延长未燃烬渣的焚烧时间,解决了热灼减率偏高问题;水冷式烟气急冷装置可以将烟气温度从1 100℃降到200℃,防止了二恶英的尾部低温再生成。该系统运行稳定可靠,可以处理医疗垃圾和大多数的固态和液态危险废物,实现了烟气污染物尤其是二恶英排放达到国家标准的目标。同时对该系统运行时窑头温度分布、二燃室炉膛出口氧量变化、回转窑和炉膛升温特性、燃烧室外壁温度分布等几方面运行数据都进行了详细的介绍,为危险废物焚烧炉的运行提供了宝贵的经验数据。     

活性炭纤维载体生物膜法处理洗车废水研究

为了实现洗车废水的循环使用,进行了以聚丙烯腈基活性炭纤维(PAN-ACF)为生物膜载体处理洗车废水的实验研究。以LAS、COD和NH3-N等指标考察了活性炭纤维生物膜反应器对洗车废水的处理效果。结果表明:在常温下、pH=6.5~7,当进水流量在30 mL/min时,反应器达到最佳运行参数,活性炭纤维载体生物膜法对LAS、COD和NH3-N等的去除率分别达到了97%、80%和60%。出水水质完全达到《生活杂用水水质标准》(CJ/T48-99)中洗车用水主要水质指标的规定。此外,实验表明PAN-ACF作为生物膜载体具有很好的生物亲和性和再生性。     

Pyrolysis characteristics of organic components of municipal solid waste at high heating rates

The pyrolysis characteristics of six representative organic components of municipal solid waste (MSW) and their mixtures were studied in a specially designed thermogravimetric analysis apparatus with a maximum recorded heating rate of 864.8 degrees Cmin(-1). The pyrolysis behavior of individual components was described by the Avrami-Erofeev equation. The influence of final temperature on individual components was studied, and it was concluded that final temperature was a factor in reaction speed and intensity, but that it played only a limited role in determining the reaction mechanism. The interactions between different components were evaluated, and it was concluded that the interaction between homogeneous materials was minimal, whereas the interaction between polyethylene and biomass was significant.     

Thermal behavior characteristics of Adhesive residue

Solid wastes from organic Adhesive production are identified as toxicant hazardous wastes in China’s National Catalogue of Hazardous Wastes. The aim of this study is analyzing the thermal behavior of Adhesive residue. Its pyrolysis and combustion characteristics were investigated using thermogravimetric analysis (TGA). Experiments were carried out in the temperature range of 50–950 °C in both nitrogen and air. The results indicate that combustion under these experimental conditions largely occurs between 210 and 410 °C, whereas pyrolysis proceeds between 260 and 430 °C. Almost all weight lost takes place before 430 °C during both pyrolysis and combustion of the residue. Fourier transform infrared spectroscopy (FTIR) was used to characterize the emission characteristics during pyrolysis. When the sample is heated in an inert atmosphere, the evolution of volatiles starts around 260 °C, and reaches a peak rate at 394 °C. Most organic products evolve in a narrow temperature range during pyrolysis. The evolving gaseous products were identified as Butyraldehyde, Ether, Acetonitrile and CO₂, accompanied with some CO.