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521.
522.
不同容重的泥石流淤积厚度计算方法研究 总被引:5,自引:0,他引:5
余斌 《防灾减灾工程学报》2010,30(2):207-211
泥石流的淤积厚度是泥石流灾害评估和防治的最重要的参数之一,但迄今还没有较好的方法计算不同容重的泥石流淤积厚度。本文通过研究泥石流屈服应力的特点,提出了用地区参数和泥石流体积浓度来计算泥石流屈服应力,进而计算泥石流淤积厚度的方法。采用本文方法计算已发生泥石流地区不同容重泥石流的淤积厚度,可以很好地应用于泥石流灾害评估和防治。 相似文献
523.
Bayesian estimation of European sulphur emissions using monitoring data and an acid deposition model
A statistical method for estimating national emissions of acidifying air pollutants in Europe is presented. The method uses an acid deposition model to match official emissions data from European countries and measured depositions from a monitoring network. An application to 1990 sulphate data demonstrates the method and suggests some tendencies in the reported emissions. The proposed framework may prove useful for verifying national compliance with emissions standards, and the method should be applicable also to other substances than sulphur dioxide. The problem of designing an optimal monitoring network may also be assessed within the proposed statistical framework. 相似文献
524.
The objective of this present study is to examine the effect of nanobubbles on the physical properties improvement in the chosen water sample. So far, the research outcomes stated that the physical properties could be enhanced by addition of nanoparticles, but very few studies were performed with nanobubbles. The unique properties of nanobubbles (70–120 nanometers) explain their use in a wide range of engineering fields. Simple method for producing nanobubbles in a variety of aqueous solutions along with examples of their use is outlined in this work. Global environmental issues, including the deterioration and depletion of water supply are driving today's need for water treatment technology. As a solution, the use of micro- and nano-bubble (MNB) technologies in wastewater treatment has evolved. This page discuss the fundamentals of water treatment research, including their stability of bubbles, manufacturing processes, and chemical and physical features. 相似文献
525.
干旱区三工河流域土壤有机碳储量及空间分布特征 总被引:5,自引:1,他引:4
精确估算干旱区流域生态系统土壤有机碳库是进行干旱区土壤碳循环研究的重要前提。论文利用改进的土壤类型法--基于网格的土壤类型法,以干旱区典型的三工河流域为例,精确估算流域土壤碳储量,分析土壤碳密度的空间分布特征,为干旱区土壤碳循环研究提供数据支撑。研究结果显示,三工河流域0~20cm土壤有机碳储量为14.35Tg,平均土壤有机碳密度为6.70kgC/m2,其中山地灰褐土土壤有机碳密度最大,这主要是受中山带较低的气温和丰富的森林凋落物的影响;流域土壤有机碳密度表现出了明显的垂直地带性和水平地带性特征,即碳密度从山地区、丘陵区、绿洲区到荒漠区呈逐渐减小的趋势,且随海拔高度的降低碳密度逐渐减小。 相似文献
526.
Brian J. Olsen Russell Greenberg Robert C. Fleischer Jeffrey R. Walters 《Behavioral ecology and sociobiology》2008,63(2):285-294
Over the past two decades, the combination of molecular and field methods has revealed considerable variation in the level
of extrapair fertilizations among socially monogamous birds. Models predicting extrapair young range in scale from a single
population to multiple Orders, and there is no single, unifying theory for these reproductive tactics. We investigated proximate
explanations of extrapair fertilizations in two subspecies of the swamp sparrow, Melospiza georgiana georgiana and Melospiza georgiana nigrescens, across a range of social and environmental conditions. The presence of extrapair young was best predicted by the size of
two male plumage badges (one correlated with parental care and one with territorial aggression) relative to the badge size
of their immediate neighbors, the interaction of these two measures, mean territory size, and the maximum size of the aggression
badge among neighbors. The size of the male’s parental care badge (relative to neighbors) was negatively correlated with the
probability of lost paternity. The relative size of the aggression badge was positively correlated with the presence of extrapair
young when the parental care badge was small and negatively correlated when the badge was large. Controlling for these crown
measures, males with larger territories were less likely to suffer losses in paternity. There was no effect of breeding density,
breeding synchrony, their interaction, subspecies, or weather during the fertile period on the presence of extrapair young.
These results suggest that female preference for males that provide more parental care (or preference for genes that convey
this trait) plays a dominant role in extrapair interactions among swamp sparrows. Models based on female assessments of relative
mate quality offer a promising explanation of patterns in extrapair fertilizations among bird species. 相似文献
527.
混合堆肥过程中容重的层次效应及动态变化 总被引:4,自引:1,他引:3
城市污泥、猪粪混合堆肥表明:升温期和高温期堆体容重分别为0.82g·cm-3和0.66g·cm-3,堆体内的氧气仍能满足微生物生长所需;降温期容重为0.58g·cm-3,通气较充分;腐熟期容重为0.54g·cm-3,通风充分.升温期和高温期仓门附近堆料的容重具有层次效应,降温期大部分堆料的容重具有层次效应,腐熟期堆体容重的层次效应减弱.升温期堆体中轴线附近、高温期仓内壁附近、降温期整个堆体、腐熟期仓门和中轴线附近,堆体深度对容重具有显著影响.升温期和腐熟期,仓门对容重产生显著影响.各堆肥期堆体的容重随深度的增加而呈增大的趋势,容重与堆肥时间满足二级动力学方程. 相似文献
528.
Yajun Wang Xiaoming Zhang Qi Feng Jiexin Zou Chang Zhou Lin Zeng 《International Journal of Green Energy》2020,17(2):157-170
ABSTRACTCarbon corrosion caused by H2/O2 interface during the shut-down process is one of the factors that exacerbate the overall degradation of proton exchange membrane fuel cells (PEMFC) in automotive applications. Numerous studies have shown that system strategies are beneficial for reducing the duration of H2/O2 interface and alleviating performance degradation. In this paper, three different shut-down strategies are investigated and compared based on the internal behaviors acquired by in-situ measurements. For the three shut-down strategies, reverse current and high potential are mainly observed in a lower constant current and constant power strategy. Comparatively speaking, the internal uniformity of the cell under constant current and power load is better than that with constant voltage strategy when the shut-down time is about the same. The results suggest that adopting a higher constant power load followed by a larger voltage load during the shut-down process can effectively shorten the shut-down time and relieve carbon corrosion. These results add significant new insights into the shut-down process and will be of practical importance in directing design of combined shut-down strategy that can withstand carbon corrosion. 相似文献
529.
530.
Introduction: Numerous studies have demonstrated the close relationship between alcohol availability and alcohol-related crashes. However, there is still a lack of spatial empirical analysis regarding this relationship, particularly in large cities of developing countries. Differences in alcohol outlets and drinking patterns in these cities may lead to quite different patterns of crash outcomes. Method: 3356 alcohol-related crashes were collected from the blood-alcohol test report of a forensic institution in Tianjin, China. Density of alcohol outlets such as retail locations, entertainment venues, restaurants, hotels, and companies were extracted based on 2114 Traffic Analysis Zones (TAZ) together with the residential and demographic characteristics. After applying the exploratory spatial data analysis, this research developed and compared the traditional Ordinary Least Square model (OLS), Spatial Lag Model (SLM), Spatial Error Model (SEM) and Spatial Durbin Model (SDM) to explore spatial effects of all the variables. Results: The results of incremental spatial autocorrelation show that the most significant distance threshold of alcohol-related roadway traffic crashes is 3 km. The SDM is found to be the optimal spatial model to characterize the relationship between alcohol outlets and crashes. The number of alcohol-involved traffic crashes is positively related to population density and retail density, but negatively related to the company density, hotel density, and residential density within the same TAZ. Meanwhile, dense population and hotels have reverse spillover effects in adjacent zones. Conclusions: The significant spatial direct effect and spillover effect of alcohol outlet densities on drunk driving crashes should not be neglected. These findings could help improve transportation planning, traffic law enforcement and traffic management for large cities in developing countries. 相似文献