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1.
In the design of smoke ventilation systems, a crucial input parameter for balcony spill plume calculations is the mass flow
rate of gases at the spill edge. In some cases, depending upon the specific geometry, these calculations can require the entrainment
of air into a flow from a compartment opening to a higher projecting balcony to be determined. Entrainment of air into these
smoke flows are not well understood and the current guidance available to the designers of smoke ventilation systems is crude.
This work presents a simple empirical correlation to predict the entrainment of air into these flows, and hence, the subsequent
mass flow rate of gases at the spill edge. A combination of computational fluid dynamics modelling and physical scale modelling
was used in the analysis. In general, this work has demonstrated that the current guidance on the entrainment of air into
these flows is conservative. 相似文献
2.
化学杀虫剂对德国小蠊的胃毒及接触毒性测定试验 总被引:1,自引:0,他引:1
本文通过十种化学杀虫剂对德国小蠊成虫的胃毒及接触毒性测定试验,观察不同杀虫剂在常用浓度下对蜚蠊的主要毒杀作用方式。结果表明白蚁灵,硅白灵,敌敌畏,敌百虫,残杀威,毒死蜱对试虫的经口毒性及接触毒性均较明显,乙酰甲胺磷与灭蚊灵对试虫有经口毒性大于接触毒性的趋势,硼酸对试虫具经口毒性与接触毒性,而双氧威在短期内对试虫的毒效不明显。 相似文献
3.
文章引入水足迹理论,分析了影响水资源利用的因素,确定了由流域水足迹供需指标、流域水足迹效益效率指标、流域水资源安全指标和流域水资源可持续利用指标等四类指标构成的评价体系框架,并根据此框架提出了七个二级指标,最后通过对每一个指标进行量化最终确定了评价的指标集,并综合各指标及其定量因子较为系统地构建出了水资源利用评价指标体系。 相似文献
4.
本文描述了河槽一般冲刷、桥墩局部冲刷、水面线、能量水头损失等的计算理论,引入成温邛快速路金马河大桥这一工程实例,运用计算理论得出拟建跨河桥梁所引起的阻水总面积、桥住断面过水面积缩窄率、水位壅高值、水位降低值,以及河槽一般冲刷深度、桥墩局部冲刷深度、近岸流速的变化等;并由此分析拟建桥梁对河道泄洪及河势稳定的影响,最后得出拟建桥梁方案是否可行的的结论。 相似文献
5.
Edivaldo L. Thomaz Leandro R. Vestena Carlos E. Ramos Scharrón 《Water and Environment Journal》2014,28(4):547-555
Unpaved roads may induce adverse effects on downstream water resources by increasing suspended sediment concentration (SSC). This study documents the localized impacts on stream SSC of six unpaved road–stream crossings in the rural Guabiroba River Catchment, in southern Brazil. Results demonstrated that SSC values downstream of road–stream crossings was between 3.5 and 10 times higher than upstream SSC at all third‐ and fourth‐order stream locations. However, downstream values were statistically undistinguishable from those collected upstream of road–stream crossings at fifth‐order sampling sites. These findings suggest that localized road effects on stream SSCs are scale‐dependent in that these are important for low‐order headwater streams yet undetectable for their higher order counterparts. Findings point to the importance of low‐order stream crossings in increasing SSC and the need to further explore the role of unpaved roads as agents of water quality degradation in agriculturally active rural settings. 相似文献
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平原河网地区水体黑臭预测评价关键指标研究 总被引:18,自引:0,他引:18
水体黑臭判断标准尤其是关键指标的选取,是水体黑臭预测、评价和修复的依据.在综合考虑水体黑臭的产生机理、现有国内外研究成果以及上海中心城区中、小河道水质现状的基础上,选取造成平原河网地区水体黑臭的关键指标DO、CODMn、BOD5、NH3-N和TP构建水体黑臭预测评价指标体系.在结合单因子评价和综合指数评价两种方法的基础上,提出了预测和评价水体黑臭关键指标的控制要求:DO≥2 mg/L,CODMn≤15 mg/L,BOD5≤20 mg/L,NH3-N≤8 mg/L,TP≤0.8 mg/L. 相似文献
8.
贵州省长岗地下河系由主流和9条支流组成,被隔水边界封闭,结构完整,地下岩溶管道深切而狭窄,有跌水和深槽,地下水深埋,水力坡度大,动态极不稳定,是峰丛山区地下河的典型。地下河系内地表水与地下水统一于一体,水资源十分丰富,地下河出口水头落差大,具有良好的水力发电条件,修建地表水和地下水联合水库,使岩溶水得到充分利用。 相似文献
9.
A. McNEILL 《Water and Environment Journal》1989,3(5):496-504
This study examines the effects of timber preservative spillages on the ecology of the River Lossie whilst the river's quality was recovering following the removal of an unsatisfactory discharge of sewage effluent. The effects of spillages on a minor tributary of the River Lossie are also presented. 相似文献
10.
K. SCHOFIELD BSc PhD J. SEAGER BSc MIBiol CBiol R. P. MERRLMAN BSc MIBiol 《Water and Environment Journal》1990,4(2):176-186
Pollution from farm wastes has been one of the principal causes of deterioration in river quality in recent years. However, little is understood of how, and which, farming activities affect the chemical and biological quality of rivers. To address this problem, a field study has been initiated in the Eastern Cleddau catchment, West Wales, to investigate relationships between land use, farm waste management practices and river quality.
Water quality of small tributaries in this area is poor, and intensive chemical monitoring has shown that discharges from farmyards are a major source of pollution. Rainfall has been shown to exacerbate this effect either through field runoff or wastes washing directly from the farmyards. The status of benthic macroinvertebrate communities in these tributaries is poor and, typically, only a few pollution-tolerant species are present.
Small tributaries from farms appear to affect both the water chemistry and biology of larger watercourses, although this effect may be quite localized.
Future research will look at ways to reduce the impact of farm wastes on river quality. This will provide the basis for producing recommendations and guidelines for catchment management aimed at minimizing pollution of rivers from farming practices. 相似文献
Water quality of small tributaries in this area is poor, and intensive chemical monitoring has shown that discharges from farmyards are a major source of pollution. Rainfall has been shown to exacerbate this effect either through field runoff or wastes washing directly from the farmyards. The status of benthic macroinvertebrate communities in these tributaries is poor and, typically, only a few pollution-tolerant species are present.
Small tributaries from farms appear to affect both the water chemistry and biology of larger watercourses, although this effect may be quite localized.
Future research will look at ways to reduce the impact of farm wastes on river quality. This will provide the basis for producing recommendations and guidelines for catchment management aimed at minimizing pollution of rivers from farming practices. 相似文献
11.
目前国内还没有实施冷热电三联供和江水源热泵复合系统项目,其技术的先进性及经济的合理性备受投资者关注。以重庆市某中央商务区建设复合系统项目为例,对商务区采用以天然气为一次能源进行发电,利用发电余热制冷制热的三联供和江水源热泵复合系统方案的技术先进性、经济可行性进行研究,为该项目的最终兴建提供了决策依据,并可供类似建设项目借鉴。 相似文献
12.
J. H. Loveless PhD AKC DIC CEng MICE R. H. J. Sellin DSc FICE CEng T. B. Bryant MEng P. R. Wormleaton PhD CEng MICE S. Catmur R. Hey PhD MASCE 《Water and Environment Journal》2000,14(6):447-455
A large-scale model hydraulic study of inbank and over-bank river flow, using a regular sinuous river channel with a mobile bed, was carried out in the Flood Channel Facility at HR Wallingford, UK. The selected sediment had a wide range of particle sizes present over the 'fine sand to coarse sand'range. Flow velocity, local and global sediment transport rates, and channel conveyance were all measured. The resulting bed forms were determined and used to explain the secondary circulation in the sinuous channel as well as the size sorting of the sediment. The paper gives an early overview of this major project. 相似文献
13.
在快速城市化的背景下,对温瑞塘河进行了保护规划,针对其存在的问题,从空间的角度,以用地管制为主要手段,确定了保护主体的范围,明确了用地控制和管理权限,从而起到确保流域生态安全的作用,这是对城市内河水网保护途径的一种新尝试。 相似文献
14.
随着我国道路建设的快速推进,对公路桥防洪工程的要求越来越高。本文主要结合防洪评价标准,以西灵山大桥为例,从保证河道行洪安全和工程布置合理性等方面分析论证了桥梁与河道行洪之间的相互影响,提出了合理的桥梁布置和建议。 相似文献
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Influence of eco‐hydrological factors on aquatic plant succession in a regulated river: a case study of the Petchburi River,Thailand
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Monitoring of aquatic plant biomass in the Petchburi River, a regulated river system in Thailand, was carried out together with the examination of eco‐hydrological characters and the sedimentary organic content. The surveys were performed during May, August and November of 2010 and 2011. The results indicated temporal variation in water velocity (0.08–2.51 m/s) and medium to low organic levels (0.58–4.68%) of the benthic substrates. Dominant aquatic plants were Hydrilla verticillata (L.F.) Royle and Potamogeton malaianus Miq. with the highest biomass of 70.84 and 182.72 g/m2, respectively. The biomass was substantially decreased during the flood‐induced discharge period. This study indicates that Potamogeton has more adaptive potential to high water velocities than Hydrilla, while Hydrilla prefers lower water velocities. Discharge velocities of less than 0.5 m/s could provide positive growth rates of such submerged plants. Approaching the discharge control from this ecological point of view can further contribute to river habitat conservation. 相似文献
17.
Impact of chemical amendment of dairy cattle slurry on phosphorus, suspended sediment and metal loss to runoff from a grassland soil 总被引:2,自引:0,他引:2
Emerging remediation technologies such as chemical amendment of dairy cattle slurry have the potential to reduce phosphorus (P) solubility and consequently reduce P losses arising from land application of dairy cattle slurry. The aim of this study was to determine the effectiveness of chemical amendment of slurry to reduce incidental losses of P and suspended sediment (SS) from grassland following application of dairy cattle slurry and to examine the effect of amendments on metal concentrations in runoff water. Intact grassed-soil samples were placed in two laboratory runoff boxes, each 200-cm-long by 22.5-cm-wide by 5-cm-deep, before being amended with dairy cattle slurry (the study control) and slurry amended with either: (i) alum, comprising 8% aluminium oxide (Al2O3) (1.11:1 aluminium (Al):total phosphorus (TP) of slurry) (ii) poly-aluminium chloride hydroxide (PAC) comprising 10% Al2O3 (0.93:1 Al:TP) (iii) analytical grade ferric chloride (FeCl2) (2:1 Fe:TP), (iv) and lime (Ca(OH)2) (10:1 Ca:TP). When compared with the study control, PAC was the most effective amendment, reducing dissolved reactive phosphorus (DRP) by up to 86% while alum was most effective in reducing SS (88%), TP (94%), particulate phosphorus (PP) (95%), total dissolved phosphorus (TDP) (81%), and dissolved unreactive phosphorus (DUP) (86%). Chemical amendment of slurry did not appear to significantly increase losses of Al and Fe compared to the study control, while all amendments increased Ca loss compared to control and grass-only treatment. While chemical amendments were effective, the reductions in incidental P losses observed in this study were similar to those observed in other studies where the time from slurry application to the first rainfall event was increased. Timing of slurry application may therefore be a much more feasible way to reduce incidental P losses. Future work must examine the long-term effects of amendments on P loss to runoff and not only incidental losses. 相似文献
18.
该文从空间入手,以杭州城西水街为例,研究了水与城市有机结合的方法和必要性,阐明其中所蕴含的文化沉积和历史底蕴是值得我们去感悟的。 相似文献