排序方式： 共有37条查询结果，搜索用时 281 毫秒
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为使井灌用户能更加科学地选用井泵，降低抽水费用，提高泵站装置效率，阐述了井泵选型的步骤及井泵工作点校核的方法，探讨了井泵在选型时应考虑的因素，给出了求取机井最优涌水量和井泵扬程的简易方法。 相似文献
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对青岛近海度假区、港口区、养殖区、工业区4类排污口邻近海域异养细菌的组成与分布进行了调查研究,采用海洋异养细菌平板涂布培养法分离细菌,基于16S rDNA的扩增性DNA限制性酶切片段分析(ARDRA)进行聚类筛选并测序鉴定。结果显示,青岛排污口邻近海域可异养培养的菌株分布于变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)、放线菌门(Actinobacteria)和拟杆菌门(Bacteroidetes)4个细菌类群,变形菌门细菌数量占总测序数量的68%,其中γ-变形菌纲的数量在变形菌门中占88%;不同海域中细菌组成与分布有所不同,放线菌门和拟杆菌门的细菌种类较少且各海域分布有所不同,但γ-变形菌纲的弧菌属细菌(Vibrio sp.)在4类海域中均被发现,占总检测量的18.54%,其中溶藻胶弧菌(Vibrio alginolyticus)占弧菌总量的25%。不同海域也检测到V.parahaemolyticus、V.harveyi、V.campbellii、V.parahaemolyticus等水产养殖业的潜在致病菌。根据16S rDNA系统进化关系和细菌门类聚类分析得到的结论推断,工业区与养殖区海域的细菌组成和分布相似度较高,推断各海域的细菌组成与排污口类型有一定相关性。 相似文献
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Russell S. Crosbie Brett Wilson Justin D. Hughes Christopher McCulloch Warren McG. King 《Agricultural Water Management》2008,95(3):211-223
Planting trees has been proposed as part of the solution to dryland salinity in Australia. The best location in the landscape and the spatial arrangement of trees however, is difficult to determine. This paper presents a case study of a field experiment that compared the water use of tree belts with that of pastures in recharge and discharge areas of a first order catchment in the Central West of NSW, Australia.The recharge tree belt and both pasture sites used very similar amounts of water but the discharge tree belt used double the water of the other three land uses by accessing groundwater. The discharge tree belt operated in an energy-limited environment, transpiring at a rate equivalent to atmospheric demand whereas the other three land uses were all water-limited. From a land management point of view, the establishment of more trees on the discharge site would have the biggest impact on reducing saline discharge and the least impact on the agricultural operations. 相似文献
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通过对ＺＳ１５Ｓ１５型轴针式喷油嘴流量特性的试验研究结果表明，该型号喷油嘴技术状态正常时，不同针阀升程其流量在较大范围内变化。经过使用一定时期后，这种变化更加明显，导致喷油规律的改变，影响到发动机实际工作性能指标。 相似文献
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Laboratory experiment on drip emitter clogging with fresh water and treated sewage effluent 总被引：4，自引：0，他引：4
A laboratory experiment was carried out to study the emitter performance of three commonly used emitter types with the application of freshwater and treated sewage effluent (TSE). The three emitter types are the inline-labyrinth types of emitters with a turbulent flow (E1) and a laminar flow (E2) and the online pressure-compensation type of emitters (E3). The qualities of freshwater and TSE were measured, and the emitter performance was evaluated, using the relative emitter discharge, the reduction of emitter discharge (qreduction), the coefficient of variation of emitter discharge (CV), the emission uniformity (EU), Christiansen uniformity coefficient (CU), and the percentage of emitter clogging (Pclog). Results showed that all indices were affected by water quality, emitter type and time of operation. The values of qreduction, CV and Pclog for the TSE treatments were greater than those for the freshwater treatments. The values of EU and CU for the TSE treatment were lower than those for the freshwater treatments. The qreduction, CV and Pclog increased and the EU and CU decreased as operational time increasing for the TSE treatment. For both freshwater and TSE treatments, the emitter clogging was more severe, the CV was greater, and the EU and CU were smaller for emitter type E2 than those for emitter types E1 and E3. Thus a more severe clogging was found for emitter type E2 due to its smaller flow-path dimension and higher manufacturing coefficient of variation in addition to the high pH values and relatively high total dissolved solids (TDS) values of the used water. Analyses of water quality and the precipitation components inside and at the outlet of emitters revealed that chemical precipitation was the main reason for emitter clogging due to high pH and ions’ concentration, especially in the TSE. Flushing emitters and drip pipes did not efficiently alleviate emitter clogging caused by chemical precipitation. In a conclusion, emitter type E3 showed a better anti-clogging function than emitter types E1 and E2 and was recommended for irrigation with TSE in the Beijing area of China. 相似文献
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Macrobrachium nipponense is one of the economic shrimp species of traditional freshwater aquaculture in our province. In order to explore the pollution discharge situation in the aquaculture process, five representative main macrobrachium nipponense breeding test sites in Jiangsu Province were selected to quantitatively calculate the pollution production coefficient and pollution discharge coefficient of macrobrachium nipponense by measuring the four detection indexes of total nitrogen, permanganate index, ammonia nitrogen and total phosphorus in water quality combined with fishery statistical data. The results showed that the production and discharge coefficient of macrobrachium nipponense culture was relatively low and had little impact on the environment. 相似文献
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日光温室热压风压耦合自然通风流量的模拟 总被引：2，自引：0，他引：2
通风是温室环境调节的重要手段,通风流量计算涉及流量系数与风压体型系数,因此有必要定量分析不同通风模式下的通风流量及对应的系数,为通风调节提供理论依据。本文分析了热压风压耦合作用对通风流量的影响机理,构建了通风流量与热压风压作用关系的数理模型;采用CO2气体示踪法测试日光温室模型(按1:5的比例缩小)在不同通风口宽度条件下的通风流量,将试验测得的通风流量、空气温度、风速和通风口宽度等参数代入模型,对模拟值与实测值进行多元线性拟合,得出拟合度最高的流量系数与风压体型系数。结果表明：当温室模型通风口宽度为3、5和7cm（相当于实际温室通风口宽度为15、25、35cm）时,热压风压耦合作用的通风流量可按G=0.81S•（H•?T/T)0.5 +0.078S•u、G=0.63S•（H•?T/T)0.5 +0.067S•u 和G=0.46S•（H•?T/T)0.5 +0.058S•u分别计算,式中S、H、?T、T、u分别为通风口面积、宽度、室内外温差、室外温度和风速;相应的流量系数分别为0.78、0.60和0.44,风压体型系数分别为0.04、0.05和0.07;在总通风流量中,当室外风速高于1.5m·s-1时,风压通风流量所占总通风流量的比例均高于50%,风压通风占主导作用;当室外风速大于2.5m·s-1时,风压形成的通风流量所占比例均大于70%,说明此条件下可忽略温度即热压的影响。 相似文献
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Ferhat Gökbulak Yusuf Serengil Süleyman Özhan Necdet Özyuvacı A. Nihat Balcı 《European Journal of Forest Research》2008,127(3):203-212
The objectives of this study were to quantify the amount of the stream discharge, nutrient fluxes, suspended sediment loss,
and to define the relationship between streamflow and these parameters in a forest-covered watershed. The study was carried
out in an experimental watershed, which has been monitored since 1979 in the Belgrad forest in Istanbul. Significant linear
regressions were obtained between streamflow and discharge of selected water quality parameters. Mean monthly losses were
10.01 kg/ha for HCO3
−, 5.92 kg/ha for CI−, 0.07 kg/ha for total N, 1.29 kg/ha for Mg2+, 3.59 kg/ha for Ca2+, 2.59 kg/ha for Na+, 1.82 kg/ha for K+, 0.0113 kg/ha for P-PO4
3−, and 35.82 kg/ha for suspended sediments. Among the monitored water quality parameters, HCO3
−, CI−, and Ca2+ had greater losses than the rest of the chemical parameters studied in the watershed. Net gains (influx exceeded outflux)
calculated for total N, Mg2+, K+, and P-PO4
3− in the annual basis can be considered as an addition to the ecosystem’s organic nutrient pool. In contrast, net losses occurred
for HCO3
−, CI−, Ca2+, and Na+. 相似文献