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张叔峰 《中国农村水利水电》1984,(1)
无压引水式电站,在具有较长引水渠道的情况下,大都为非自动调节渠道,在前池中或其附近均没有泄水建筑物。当电站突然增加负荷时,前池水位将急遽降低,形成引水渠道中的不恒定流。此后,降低水位的速度基本不变,至某时刻后,前池降至最低水位。在依据其他条件确定了压力前池的平面尺寸之后,前池最 相似文献
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章超英 《中国农村水利水电》1989,(1)
有些农村小电站,由于前池水位失控,往往导致水位上涨,溢出后淹没庄稼,毁坏农田,造成不良后果。为了防止事故的发生,有必要对水电站前池水位加以预警控制。现介绍一种简易水位自动报警装置,原理参看线路图。当水位上涨到 A 点时,电路导通,经过 Z 整流,继电器 J 工作,电笛 DD 发出呜叫声。变压器 B 的输出电压一般小于36伏,继电器 J 可选用24伏直流继电器,调节水中静触点的距离可改变直流电压的大小。 相似文献
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凌松盛 《中国农村水利水电》1986,(2)
引水式电站前池安装水位信号器,能使运行人员在中控室看到前池水位的变化,以便于及时调节发电出力,保持高水位运行,防止溢流弃水。水位信号器成本低,制作安装方便。经过二年多的使用,证明性能稳定可靠。能满足小型水电站控制水位的要求。 相似文献
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林集兴 《农田水利与小水电》1995,(11):6-7
澎水电站为目前福建省最高水头电站,其压力管道管线长,压力水头变化大,是该电站的关键工程,并制约着工程的安全与投资。对该压力管道的管线布置、管径确定、管材选择及壁厚计算等设计问题进行探讨与优化。 相似文献
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针对自压喷灌中地形落差大于管道允许承压能力时需建减压池的情况,从减压池水位控制的要求出发,研制了一套自压喷灌减压池水位自动控制装置,该装置可靠,能满是喷灌的工作要求。 相似文献
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马世祥 《中国农村水利水电》1999,(4):37-38
小型水电站压力前池一般都是单室式的。这种压力前池在一些河流沙含量较大的电站,沉沙效果往往达不到要求,致使汛期大量悬移质泥沙涌入压力水管,磨损水轮机,降低水轮机使用效率,缩短水轮机使用寿命。针对这一问题,推荐一种有前、后两室的压力前池双室式压力前池,这种压力前池可使电站运行工况转好,费用降低。 相似文献
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自压喷灌减压池水位自动控制装置的研究 总被引:2,自引:0,他引:2
针对自压喷灌中地形落差大于管道允许承压能力时需建减压池的情况,从减压池水位控制的要求出发,研制了一套自压喷灌减减池水位自动控制装置,该装置可靠,能满足喷灌的工作要求。 相似文献
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林集兴 《中国农村水利水电》1995,(11)
澎水电站为目前福建省最高水头电站,其压力管道管线长(1255.5m),压力水头变化大(74~511.5m),是该电站的关键工程,并制约着工程的安全与投资。对该压力管道的管线布置、管径确定、管材选择及壁厚计算等设计问题进行探讨与优化。 相似文献
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黄立财 《中国农村水利水电》2006,(9):121-124
惠蓄电站压力钢筋混凝土岔管,结构体形复杂,承受内水压力约7.5MPa,PD值高达6000,是本工程关键部位。在广蓄电站压力岔管的基础上,通过分析研究国内外岔管形式,提出6种体形方案,通过水头损失、投资、电能效益、有限元计算等进行分析比较,寻求满足结构安全要求、经济和体形尽量简单的岔管体形。 相似文献
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《Journal of Agricultural Engineering Research》1998,69(3):249-254
A model to represent the discolouration of dried powder of carrots as a function of temperature was developed. Two types of carrots, Asian and European, containing large amount of lycopene and β-carotene, respectively, were tested. The dried powder was stored under an atmosphere with O2and at three different temperatures, 5,20 and 35°C. The surface colour of the powder was monitored during storage by a Hunter colour ratioa/b. In the proposed model, the rate of oxidation was assumed to be represented by the product of the fraction of concentration of oxidized pigment at arbitrary time and a specific rate of oxidation of pigment. The rate parameters in the proposed model were calculated by fitting the experimental data with smooth curves by trial and error at the end of the induction period but before discolouration took place. The frequency constant and activation energy, expressing the temperature dependence of the rate parameters, were expressed by the Arrhenius relation. The simulation results of a Hunter colour ratioa/bof dried powder at 25°C showed good agreement with the experimental data, suggesting that the proposed model was effective for the prediction of discolouration of dried powder of both types of carrot. The use of the induction period in the manner described may enable the shelf life of dried powder to be predicted. 相似文献
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感官检验棉花的品级,这是农村常见的一种检测手段.它的一个主要特点就是存在不确定性.这是由于检验员的品级检验水平存在一定的差异,其中有很多因素制约着检验的结果.文章对影响感官检验结果的因素进行了系统的分析. 相似文献
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The fractional outflow rate of water from the rumen, measured as the rate of disappearance of the chromium complex of ethylenediamine tetra-acetic acid, was related to a number of dietary factors. A multiple regression equation was derived which expressed fractional outflow rate as a function of the intakes of dry matter, ash, acid-detergent fibre and crude protein.The data analysed consisted of 243 observations for sheep on 59 diets, including forage, concentrate and mixed diets. The ranges covered by the data were: fractional outflow rate 0.7–3.6 day?1; dry matter intake 560–1400g/day; ash 4–30%, acid-detergent fibre 7–41%, crude protein 5–26 % of dry matter; there were no observations for sheep of less than 34 kg liveweight.The equation accounted for 56·3 % of the total variance. Between-sheep variance could not be calculated for the whole of the data but was undoubtedly substantial since, for a sixth of the data, it was known to account for 38 % of the total variance. 相似文献
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从灾害经济学的角度探讨了城镇供水优化调度的必要性和可能性,认为在缺水不可避免的情况下,对供水进行优化调度可以减小缺水带来的损失,产生较好的减灾效益,特别是可以大大减小严重干旱的灾害效应。并根据水资源的特性,提出了缺水损失的计算模式以及优化调度的原则和方法。 相似文献