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91.
92.
Jason M. Zink Gregory D. Jennings 《Journal of the American Water Resources Association》2014,50(5):1354-1358
Channel roughness, often described by Manning's n, is used to represent the amount of resistance that flow encounters, and has direct implications on velocity and discharge. Ideally, n is calculated from a long‐term record of channel discharge and hydraulic geometry. In the absence of these data, a combination of photo references and a validated qualitative method is preferable to simply choosing n arbitrarily or from a table. The purpose of this study was to use United States Geological Survey (USGS) streamflow data to calculate roughness coefficients for streams in the mountains of North Carolina. Five USGS gage stations were selected for this study, representing drainage areas between 71.5 and 337 km2. Photo references of the study sites are presented. Measured discharges were combined with hydraulic geometry at a cross‐section to calculate roughness coefficients for flows of interest. At bankfull flow, n ranged between 0.039 and 0.064 for the five study sites. Roughness coefficients were not constant for all flows in a channel, and fluctuated over a large range. At all sites, roughness was highest during low‐flow conditions, then quickly decreased as flow increased, up to the bankfull elevation. 相似文献
93.
基于定量构效关系(QSAR),运用线性(逐步多元回归MLR)和非线性(支持向量机SVM)两种计算方法开发了两种可靠且高效预测聚苯乙烯二乙烯基苯树脂(XAD)和空气之间分配系数(KXAD-A)的模型.构建模型的数据包含醇类(Alcohols),苯类(Benzenes),多氯联苯(PCBs)和多环芳香烃(PAHs)等,共计70种有机污染物.两个模型的决定系数R2adj和外部验证系数Q2ext均在0.930以上,同时所有物质均在定义的应用域内,结果表明两种QSAR模型有较高的拟合度、稳健性和较为优秀的预测能力,且非线性(SVM)模型比线性(MLR)模型的拟合效果更好. 相似文献
94.
污水水质和污泥特性不同,活性污泥1号模型(ASM 1)参数的测定结果也不相同。研究以甲醇和葡萄糖为基质,对分别经过甲醇和葡萄糖驯化的活性污泥,通过呼吸计量法测定高食微比、中食微比和零食微比下的氧利用速率(OUR)随时间变化的曲线。确定了异养菌产率系数(YH)、异养菌最大比增长速率(μ^H)和衰减系数(bH),并根据YH、μ^H和bH的测定结果和对中食微比下OUR曲线的数值拟合确定了异养菌半饱和常数(ks)、最大比水解速率(kh)和慢速可生物降解底物水解的半饱和常数(KX)。研究结果表明,在20℃下,采用甲醇和葡萄糖为基质测得的YH、bH、μ^H、ks、KX和kh分别为0.53、0.48、5.75、0.9、0.03、3.0和0.87、1.03、2.27、4.45、0.01、7.0。YH、bH、μ^H和ks的值与ASM1中城市污水的推荐值0.67、0.62、6.0、20.0不同,反映了不同基质对参数测定结果的影响。对于慢速可生物降解有机物(Xs)含量低的水质来说,KX和kh对生化反应过程影响不大,可采用ASM1模型的推荐值。 相似文献
95.
96.
Porous media has a significant effect on flame and overpressure of methane explosion. In this paper, the pore diameter and thickness of porous media are studied. Nine experimental combinations of different pore diameter and thickness on the propagation of flame and overpressure of methane explosion in a tube are analyzed. The results show that the porous media not only can suppress the explosive flame propagation, but the porous media with large pore diameter can cause deflagration and accelerate the transition of flame from laminar to turbulent. The pore diameter of the porous media mainly determines the quenching of the flame. Simply increasing the thickness of porous media may cause the flame to temporarily stop propagating, but the flame is not completely extinguished for larger pore diameter. However, the deflagration propagation speed of flame is affected by the thickness. The attenuation of overpressure by porous media is mainly reflected in reducing the duration of overpressure and the peak value of overpressure. The smaller the pore diameter, the greater the thickness, and the more remarkable the reduction in overpressure duration and peak value. Suitable pore diameter and thickness of porous media can effectively suppress flame propagation and reduce the maximum value and duration of overpressure. 相似文献
97.
Sorption coefficients (Kp) of several organochlorine insecticides (OCs) in volcanic ash silt from Central Java are presented. Selected experimental and estimated octanol‐water partition coefficient (P) values are used to study log‐log regressions with Kp data collected from the literature (PAHs, chlorophenols, phenylureas, chloro‐s‐triazines, carbamates and organophosphorus insecticides) and those of the OCs determined in the present study. Leaching distances and bioactivities in soil are correlated with the Kp values of the pesticides, and with the organic matter and the water content of the soil. 相似文献
98.
99.
Norman F. Hampton Bennett Y. Ryan 《Journal of the American Water Resources Association》1980,16(3):508-513
ABSTRACT: A comprehensive nationwide recognizance-level assessment of water needs for energy development over the 1985 to 2000 time frame and options for overcoming any actual or potential water supply problems are summarized. Water requirements for energy production and other uses are totaled for each geographic region of the United States and compared with available stream flow to identify regions with potentially inadequate water supplies to meet expanding energy needs. Water quality impacts and water-related institutional factors affecting energy development are also considered. It is concluded that, if proper planning measures are not initiated, water demands for energy production will not be satisfied by the year 2000, particularly in those areas with known fossil energy resources. No unmanageable water quality problems are foreseen, and water-related institutional factors will primarily delay rather than exclud energy development. 相似文献
100.
Thomas T. Shen 《Environmental management》1982,6(4):297-305
Air pollution from hazardous waste landfills and lagoons is largely unknown. Routine monitoring of toxic air contaminants associated with hazardous waste facilities is difficult and very costly. The method presented in this paper would be useful for air quality assessment in the absence of monitoring data. It may be used as a screening process to examine the question of whether or not volatilization is considered to be significant for a given contaminant and also to evaluate permit applications for new hazardous waste facilities concerning waste volatilization problems. 相似文献