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排序方式: 共有314条查询结果,搜索用时 15 毫秒
161.
Lauren E. Hay Gregory J. McCabe Martyn P. Clark John C. Risley 《Journal of the American Water Resources Association》2009,45(3):580-596
Abstract: The accuracy of streamflow forecasts depends on the uncertainty associated with future weather and the accuracy of the hydrologic model that is used to produce the forecasts. We present a method for streamflow forecasting where hydrologic model parameters are selected based on the climate state. Parameter sets for a hydrologic model are conditioned on an atmospheric pressure index defined using mean November through February (NDJF) 700‐hectoPascal geopotential heights over northwestern North America [Pressure Index from Geopotential heights (PIG)]. The hydrologic model is applied in the Sprague River basin (SRB), a snowmelt‐dominated basin located in the Upper Klamath basin in Oregon. In the SRB, the majority of streamflow occurs during March through May (MAM). Water years (WYs) 1980‐2004 were divided into three groups based on their respective PIG values (high, medium, and low PIG). Low (high) PIG years tend to have higher (lower) than average MAM streamflow. Four parameter sets were calibrated for the SRB, each using a different set of WYs. The initial set used WYs 1995‐2004 and the remaining three used WYs defined as high‐, medium‐, and low‐PIG years. Two sets of March, April, and May streamflow volume forecasts were made using Ensemble Streamflow Prediction (ESP). The first set of ESP simulations used the initial parameter set. Because the PIG is defined using NDJF pressure heights, forecasts starting in March can be made using the PIG parameter set that corresponds with the year being forecasted. The second set of ESP simulations used the parameter set associated with the given PIG year. Comparison of the ESP sets indicates that more accuracy and less variability in volume forecasts may be possible when the ESP is conditioned using the PIG. This is especially true during the high‐PIG years (low‐flow years). 相似文献
162.
夏季局地环流对京津冀区域大气污染影响 总被引:1,自引:0,他引:1
为研究局地环流对京津冀大气污染分布特征的影响,利用京津冀区域大气污染监测网7个站点的大气污染物浓度观测资料,结合WRF数值模式对气象场的模拟结果,对区域夏季局地环流对大气污染浓度水平和空间分布特征进行了研究。结果表明,2010年6月局地环流发生时,京津冀大气中PM10的平均浓度可高达156.4μg/m3,而在强天气系统过境时仅为89.1μg/m3。京津冀受区域局地环流控制时,大气中可吸入颗粒物比强天气系统过境时高75%;海-陆风回流携带的高浓度污染物,导致海滨区域夜间大气中PM10平均浓度从46.2μg/m3上升到64.7μg/m3;山地-平原风导致京津冀大气本底区域河北兴隆臭氧浓度峰值较北京城区滞后3 h。京津冀近年来强天气过程比例逐渐下降,目前仅占月20%,而以山地-平原风和海-陆风叠加的局地环流气象条件占比增加,造成京津冀区域大气污染易聚难散。 相似文献
163.
Gajendra Singh Biplab Bhattacharya G.N. Tiwari 《International Journal of Sustainable Engineering》2016,9(3):170-181
A modified brushed permanent magnet DC (PMDC) motor has been developed and fabricated for a photovoltaic (PV)-operated solar systems. The conventional PMDC motor has been plagued with constraints, the most critical being ingestion of vapours of working fluid inside the rotor and stator, damaging the insulation of windings and forming a thin film of moisture between commutator and brushes. This flaw results into a very low mean time between failures of the motor. In the past, many attempts have been made where-in variety of seals to isolate the working fluid vapours from inner parts of motor have been tried out, but to no avail. Even Brushless DC motors have been designed in the past but their exorbitant cost makes the entire arrangement not viable economically. The modification attempted in this article overcomes the problem of working fluid ingestion inside the motor. It is found that mass flow rate of working fluid obtained at maximum peak sunshine hours is 17.5 l/min at 3030 rpm of motor driven by a PV module of 40 W at 16.20 V. This low-cost modified PMDC motor has been robust with high mean time between failures as no breakdown observed during 18 months of operation. 相似文献
164.
中试螺旋式自循环厌氧反应器处理安乃近制药废水的稳定性能简 总被引:1,自引:0,他引:1
以制药废水实验了50 m3螺旋式厌氧反应器(SPAC反应器)的稳定性。采用Augmented Dickey-Fuller(ADF)单位根检验表明,螺旋式反应器具有良好的启动和运行稳定性。负荷冲击实验显示,SPAC反应器具有较好的耐浓度冲击能力和耐水力冲击能力,所能耐受的最大浓度冲击强度大于60 000 (mg·h)/L(进水浓度提升2倍),所能耐受的最大水力冲击强度为300(m3·h)/d(进水流量提升50%)。SPAC反应器还具备受扰恢复能力。在反应液pH低于5.74,出水浓度、COD去除率和容积COD去除速率(VRR)分别为3 500 mg/L、22.30%和2.52 kg/(m3·d)的工况下,经过30 d恢复,出水浓度、COD去除率和VRR的恢复程度达到80%~90%。 相似文献
165.
Vertical ozone distributions observed using tethered ozonesondes in a coastal industrial city, Kaohsiung, in southern Taiwan 总被引:1,自引:0,他引:1
This work presents the vertical distributions of ozone and meteorological parameters observed with tethered ozonesondes and
meteorological radiosondes in the lower atmosphere during an ozone episode on March 25–27, 2003, in Kaohsiung City in southern
Taiwan. Kaohsiung is a coastal industrial city with inland mountain ranges to the east. Extremely complicated ozone structures
were identified that spanned day and night during the experimental period. During afternoons, the lower atmosphere was divided
into two stratified air layers with substantially different ozone concentrations. On the episode day (March 26), average ozone
concentration in the near-ground layer was 85 ppb and the aloft layer was 140 ppb. A very high ozone peak of 199 ppb measured
aloft likely resulted from an elevated large point source. Several no-ozone air layers, distributed throughout 400–750 m,
were observed to transport onshore during the nigh. As well, elevated ozone layers peaking at 60–90 ppb and 90–160 ppb were
detected below and above the no-ozone air layers, respectively. These complicated ozone structures were likely formed through
titration of plumes from large point sources and the circulations of sea breezes or combined sea-breeze/mountain flows in
the study area. 相似文献
166.
167.
厌氧水解—高负荷生物滤池处理城镇污水的中试研究 总被引:5,自引:0,他引:5
厌氧水解 -高负荷生物滤池是一种利用附着在塑料模块填料上的微生物系统对城镇污水中的污染物质进行降解处理的绿色环保技术。厌氧水解池和高负荷生物滤池采用的塑料模块填料具有高空隙率、高附着面积、高布水性能和抗堵塞的优异性能 ,并无须回流。当厌氧水解池水力停留时间为 4h ,生物滤池水力负荷为 30m3/ (m2 ·d) ,该系统处理城镇污水的CODcr去除率达 75 % - 85 % ,BOD5去除率达 85 % - 95 % ,SS去除率达 85 % -95 % ,处理后出水的上述各项指标均可满足国家二级生物处理排放标准的要求。 相似文献
168.
浅谈循环经济与畜禽粪便资源化 总被引:2,自引:0,他引:2
我国畜禽养殖业发展迅速,但由于相关政策脱节、缺乏合理规划与布局、技术研究落后等原因,畜禽废弃物未经有效处理直接排入环境中,造成毒化水源、污染大气、传播病菌、危害农田等一系列危害.运用循环经济理论指导畜禽粪便环境污染治理,使其实现减量化、资源化、无害化,具有很大的经济效益和环境效益. 相似文献
169.
围绕扬水造流技术的两个关键控藻参数Vmix(水体垂直混合速率)和Emix:Eu(混合深度与真光层深度之比),分别在实验室和现场围隔中开展模拟实验探讨藻类的时空分布.结果表明,实验开始20h后藻类垂直分布趋向动态平衡,Vmix31.08cm/min时2h内藻类未出现浮聚现象,Vmix31.35cm/min则能够长期(320h)遏制表面水华;根据20h平衡分布变异系数对光照和混合组合条件下的控藻效果进行了分类.藻类生消实验显示衰亡速率常数K与Emix:Eu呈正相关(R2=0.85,P<0.05,n=5),表明增大Emix:Eu在一定程度上有利于促进藻类衰亡.现场围隔实验结果表明,Emix:Eu对藻类生长消亡的显著影响,并认为在自然条件下,扬水造流技术要发挥控藻效用,Emix:Eu必须33:1. 相似文献
170.
ICAR-BF组合工艺处理猪粪废水的实验研究 总被引:3,自引:0,他引:3
采用有效容积为18L的内循环厌氧反应器(ICAR)和7.5L的生物滤池(BF)组合工艺处理猪粪废水,首先通过实验确定ICAR的水力停留时间(HRT),并使BF挂膜成功,在此基础上进行了组合工艺处理猪粪废水的研究。结果表明,在温度33±2℃I、CAR水力停留时间为6h、进水COD浓度为7000~8000mg/L时,组合工艺运行稳定;COD和NH3-N去除率分别在95%和93%左右,悬浮固体(SS)去除率在99%以上,是适于养殖场废水处理的一项新工艺。 相似文献