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351.
ABSTRACT: The SMEMAX transformation, its modified versions and power transformation were applied to 55 long-term records of annual maximum flood flows tested previously for independence, homogeneity and completeness. Even though SMEMAX transformation reduced the coefficient of skewness to near zero for flood data, their distribution was not a true normal distribution. In almost all cases, the coefficient of kurtosis was quite different from 3.0 of the normal distribution. Empirical criteria showed that SMEMAX transformation performed well only for 40 (70 percent) of the 55 stations tested. Its performance level dropped, especially for stations which had both the coefficient of skewness and kurtosis greater than 3.0 and 10.0, respectively. Power transformation was generally better in transforming the flood data to a normal distribution. It performed well for 50 (90 percent) of the 55 stations tested. The coefficient of skewness in case of the data transformed by power transformation was much closer to the zero value than in the case of SMEMAX transformed series. The SMEMAX transformation and its two modified versions yielded identical results when flood frequency analysis was performed. Computationally, all three methods were equally simple and easy to apply for flood frequency analysis. In some cases, the coefficient of kurtosis for the transformed distributions obtained both by SMEMAX and power transformations deviated farther from that for the normal distribution than for the parent distribution. 相似文献
352.
本文分析了作者以前得到的一种扩散系数的某些结果,认为这种扩散系数解释了垂直湍流和风切变的联合作用使水平扩散增大的实验观测结果;建立了与雷诺应力间的函数关系,在简化情况下,与泰勒理论得到的结论类似。在边界层低层,湍流扩散系数与粘性系数是不相等的,有时会有较大差别。 相似文献
353.
Chen Guowei Xi Pengge Xu Deqian Yu Hanqing 《Frontiers of Environmental Science & Engineering in China》2007,1(1):63-66
In order to study the minimization of excess sludge production, the reduction in the excess sludge production in the presence
of an inhibitor and uncoupler was studied in this work. The experimental results show that such an addition could effectively
reduce the production of excess sludge. With the energy uncoupling model established in this work, energy uncoupling coefficient
(E
u) was used to evaluate the reduction in excess sludge production. The energy uncoupling coefficients in the presence of dinitrophenol
(dNP), Zn2+, and Cu2+ was 0.75, 0.46, and 0.18, respectively. The analysis demonstrated that energy spilling occurred in the presence of dNP, and
that dNP was an effective uncoupler for reducing the production of excess activated sludge without affecting the microbial
respiration activity. 相似文献
354.
将UBET用于求解压缩圆环问题 ,可简便快速地取得上限解 ;进而采用该解绘制塑性加工中测量摩擦系数的理论校准曲线。对中性层的位置进行了精确求解 ;分析了绘制理论校准曲线时 ,总压缩量、压缩步长量等参数对其结果的影响 相似文献
355.
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357.
我国低纬度、亚热带地区的降水化学及其雨水酸化趋势分析 总被引:24,自引:1,他引:24
在世界上酸沉降研究尚为空白的低纬度、亚热带地区建立了酸沉降监测网。通过两年的监测,结果表明降水中酸度和离子总浓度季节变化明显,Ca ̄(2+)和NH在降水离子构成中占百分率较高,阳离子总和略大于阴离子总和。两广地区降水酸度是雨水中多种阴、阳离子综合作用的结果,降水中SO浓度高的地区是SO_2排放量高的地区,控制雨水逐年酸化趋势的唯一途径是限制SO_2排放。 相似文献
358.
Calculation method of quantum efficiency to TiO2 nanocrystal photocatalysis reaction 总被引:2,自引:0,他引:2
The quantum yield is an important factor to evaluate the efficiency of photoreactor.This article vires an overall calculation method of the quantum efficiency(Φ) and the apparent quantum efficiency(Φa) to the TiO2/UV photocatalysis system.Furthermore,for the immobility system(IS),the formulation of the faction of light absorbed by the TiO2 thin film is proposed so as to calculate the quantum efficiency by using the measured value and theoretic calculated value of transmissivity(T).For the suspension system(SS),due to the difficulty to obtain the adsorption coefficient(α) of TiO2 particulates,the quantum efficiency is calculated by means of the relative photonic efficiency(ζr)and the standard quantum yield(Φstandard). 相似文献
359.
360.
本文介绍了用FoxPor语言编制的秩相关系数、相关系数和匹配度计算程序,可在环境监测中代替计算器使用,具有效率高、稳定好、操作简便等优点。 相似文献