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51.
Surface waves and roughness in self-aerated supercritical flow 总被引:1,自引:1,他引:1
In high-velocity open channel flows, free-surface aeration is commonly observed. The effects of surface waves on the air–water
flow properties are tested herein. The study simulates the air–water flow past a fixed-location phase-detection probe by introducing
random fluctuations of the flow depth. The present model yields results that are close to experimental observations in terms
of void fraction, bubble count rate and bubble/droplet chord size distributions. The results show that the surface waves have
relatively little impact on the void fraction profiles, but that the bubble count rate profiles and the distributions of bubble
and chord sizes are affected by the presence of surface waves. 相似文献
52.
Efficient statistical mapping of avian count data 总被引:3,自引:0,他引:3
J.?Andrew?RoyleEmail author Christopher?K.?Wikle 《Environmental and Ecological Statistics》2005,12(2):225-243
We develop a spatial modeling framework for count data that is efficient to implement in high-dimensional prediction problems. We consider spectral parameterizations for the spatially varying mean of a Poisson model. The spectral parameterization of the spatial process is very computationally efficient, enabling effective estimation and prediction in large problems using Markov chain Monte Carlo techniques. We apply this model to creating avian relative abundance maps from North American Breeding Bird Survey (BBS) data. Variation in the ability of observers to count birds is modeled as spatially independent noise, resulting in over-dispersion relative to the Poisson assumption. This approach represents an improvement over existing approaches used for spatial modeling of BBS data which are either inefficient for continental scale modeling and prediction or fail to accommodate important distributional features of count data thus leading to inaccurate accounting of prediction uncertainty. 相似文献
53.
Srinivasa Jayachandra Urban Ja D’Souza 《Journal of environmental science and health. Part. B》2013,48(4):271-278
The objective of this research is to study the possible reproductive adverse effects of diazinon on rat offspring exposed in utero and during lactation. Twenty-four Sprague–Dawley female rats (10–12 week old) were randomly assigned to four groups, each consisting of six rats. Group 1 served as the control and these rats were given normal saline orally. Rats in groups 2, 3, and 4 were administered diazinon, dissolved in saline at 10, 15, 30 mg/ kg?1 body weight, per oral, once daily, during mating, pregnancy and lactation. The male offsprings were examined at puberty and adulthood for body weight, testis weight, epididymis weight, sperm count, motility and morphology, pituitary-gonadal hormone levels. At 30 mg kg?1 dose, the male offsprings showed a decrease in testicular weight, sperm count, motility, with an increase in abnormal sperm percentage and a decline in pituitary-gonadal hormones, at puberty. Upon attaining adulthood, there was a decrease in testicular weight, sperm count and motility with an increase in abnormal sperm percentage and a decrease in pituitary hormone level. There was evidence of some adverse reproductive effects on the male offspring at the 15 mg/ kg?1 dose. Most of the adverse effects were irreversible and were evident at both puberty and adulthood in the offsprings, although a few parameters reverted to the normal growth pattern. Diazinon is a reproductive toxicant for male offsprings if exposed during prenatal and postnatal phases. 相似文献
54.
利用水力学实验室自主研发的多孔板与文丘里管组合式水力空化装置来杀灭原水中的病原微生物.以水体中大肠杆菌和菌落总数为指示菌,用平板计数法测得不同工况下的大肠杆菌和菌落总数的杀灭率,研究了空化数、孔口排布、孔口数量、运行时间、原水配比浓度、喉部长短对病原微生物杀灭率的影响.试验结果表明:提高孔口流速和喉部流速、延长运行时间、降低空化数、增多孔口数量、改进孔口排布、选取合适配比浓度、延长喉部长度可以提高大肠杆菌和菌落总数的杀灭率.水力空化是一种无消毒副产物、安全、高效的饮用水消毒新技术,具有潜在的应用前景. 相似文献
55.
Chemistry of groundwater in Gulbarga district, Karnataka, India 总被引:1,自引:0,他引:1
Majagi S Vijaykumar K Rajshekhar M Vasanthkumar B 《Environmental monitoring and assessment》2008,136(1-3):347-354
Groundwater quality of Gulbarga District is extensively monitored for two years of study period from October 1999 to September
2001. Twenty-five different sampling stations were selected for the study purpose in the city and five selected villages in
the district. Gulbarga districts lies in the northern plains of Karnataka State, covers an area of 16,244 km2 and lies between 16°-11′ and 17°-19′N latitude and 76°-54′E longitude The study revealed that the water sources in the area
are heavily polluted. The major water quality parameters exceeding the permissible limits during all the seasons are total
hardness, calcium hardness, magnesium hardness, alkalinity and MPN (Bacterial count) and other parameters have shown distinctive
variation in different stations and season. Most of these parameters are correlated with one another. Statistical analysis
of the data is presented. 相似文献
56.
57.
对燃煤超细微粒的排放特性进行研究,利用自行搭建的气溶胶实验平台,使用快速粒径谱仪FMPS对燃煤超细颗粒(5.6~560 nm)数量粒径谱进行了测量,同时利用颗粒物动态演变模型,通过最优化算法,得到颗粒沉积损失率和排放率随粒径的分布,并计算了燃煤颗粒的排放因子.结果表明,在颗粒生成的初始阶段,燃煤颗粒数量粒径谱是多分散的复杂谱,初始粒径谱主要由10 nm、30~40 nm及100~200 nm这3个模态组成,其中,10 nm模态颗粒数浓度较高,100~200 nm模态颗粒粒径谱呈对数正态分布,数量中位径CMD均值为16 nm.随着时间的推移,总数量浓度呈指数规律衰减,CMD先增大后逐渐趋于稳定.排放因子的计算结果显示,在室温条件下,燃煤颗粒的排放因子达到(5.54×1012±2.18×1012)个·g-1. 相似文献
58.