共查询到20条相似文献,搜索用时 140 毫秒
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一、低洼盐碱地的形成新民县位于辽宁省西部,地处辽河中下游的冲积平原。境内有辽河、柳河、绕阳河、养息牧河、秀水河、蒲河和小浑河等七条较大的河流,纵贯南北,水流汇集,低洼易涝面积达160万亩,素有“九河梢下,十年九涝”之称。特别是柳河、绕阳河发源于内蒙,流经沙漠地区,地形是上陡下坦,造成上冲下淤。每年汛期从上游输送来大量的 相似文献
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HJ-1A/B卫星在干旱应急监测中的应用 总被引:3,自引:2,他引:1
利用我国环境与灾害监测小卫星(HJ-1A/B)的CCD和IRS数据,提出了针对这种新数据源的适用性应用方法,基于成熟应用的植被健康指数,对2010年3月湄公河流域发生的干旱进行应急监测,结果表明湄公河流域大部分区域农田发生干旱,中国无论从旱情发生面积和干旱严重程度上都是最为严重的。着重分析流域上游中国境内的4个水电站的水面和水位的变化信息,探讨对下游干旱的影响,得出上游大坝建设与流域下游干旱并无直接关系的结论。进一步说明了环境与灾害卫星在干旱监测应用中的可行性,将为我国乃至全球决策部门提供辅助支持信息。 相似文献
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在中国辽宁、陕西、上海的部分地区对美国帕尔默旱度模式中水量平衡模型的适用性进行了检验,针对应用中存在的问题对该模型进行了修正,修正后的水量平衡模型的精确性有了较大提高,为在中国推广应用帕尔默旱度模式提供参考。 相似文献
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研究城市供水系统的高效路径均衡算法。供水系统根据供水请求调控供水路径,在早晚城市用水高峰期供水请求突增,待均衡的供水路径任务骤增加大了均衡计算量,传统方法只选用较少的高层节点作为均衡节点,高层节点因超额的工作量不能承担起均衡任务的突增,造成网络数据传输路径均衡的效率较低。为了解决这一难题,提出基于开销能量的供水系统ZigBee网络路径均衡算法。通过建立供水系统各节点能量消耗代价开销模型,在模型中根据开销能量将路径均衡控制的任务分派到网络的各个节点中共同分担完成路径均衡的任务,避免了只利用少数高层节点均衡而带来的均衡效率不高的问题。仿真结果表明,改进方法能够高效完成供水系统路径的均衡控制,取得了满意的结果。 相似文献
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以甘肃景电灌区盐化土壤为对象用水汽平衡吸附法就盐分对土壤的水汽吸附和土壤水能量状态的影响进行了研究 .结果表明盐分显著增加了土壤水汽吸附量 ,水汽饱和度为 98%的情况下 ,含盐量为 1 0 .772 g/kg和 1 2 .887g/kg的两个土壤的水汽吸附量分别达到了 1 9.4 5 %和 2 5 .34 % .水汽饱和度大于65 %左右时水汽吸附有一个明显的转折点 ,.水汽饱和度大于 65 %时水汽吸附量主要受含盐量影响 ,而当饱和度小于 65 %时则主要受物理性粘粒含量的影响 .盐分非常显著地降低了土壤的水势 ,可以用盐化土样的水势与脱盐处理土样的水势估算盐化土样的渗透势 .估算结果表明在低水势段以及在相当大含水量范围内盐化土壤因盐分浓度所产生的渗透势的绝对值远大于基质势的绝对值 相似文献
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《Advances in Engineering Software》2007,38(2):102-111
The physical process of scour around bridge piers is complicated. Despite various models presented to predict the equilibrium scour depth and its time variation from the characteristics of the current and sediment, scope exists to improve the existing models or to provide alternatives to them. In this paper, a neural network technique within a Bayesian framework, is presented for the prediction of equilibrium scour depth around a bridge pier and the time variation of scour depth. The equilibrium scour depth was modeled as a function of five variables; flow depth and mean velocity, critical flow velocity, median grain diameter and pier diameter. The time variation of scour depth was also modeled in terms of equilibrium scour depth, equilibrium scour time, scour time, mean flow velocity and critical flow velocity. The Bayesian network predicted equilibrium and time-dependent scour depth much better when it was trained with the original (dimensional) scour data, rather than using a non-dimensional form of the data. The selection of water, sediment and time variables used in the models was based on conventional scour depth data analysis. The new models estimate equilibrium and time-dependent scour depth more accurately than the existing expressions. A committee model, developed by averaging the predictions of a number of individual neural network models, increased the reliability and accuracy of the predictions. A sensitivity analysis showed that pier diameter has a greater influence on equilibrium scour depth than the other independent parameters. 相似文献
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无机盐-恒沸有机水溶液体系相平衡计算 总被引:2,自引:0,他引:2
针对无机盐-恒沸有机水溶液体系相平衡问题,提出用Gibbs自由能最小法计算。通过Pitzer理论与NRTL方程相结合来描述体系中各组分的活度系数,建立体系Gibbs自由能的计算模型,从而将相平衡计算转化为有约束的最小化问题,并应用遗传算法求解,进而得到体系平衡时的各相组成。以2个体系的相平衡计算为例,结果表明此方法可行有效,可为无机盐作盐析剂分离恒沸有机水溶液体系这一化工过程建立一定的理论基础和计算依据。 相似文献
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Vapor–liquid equilibrium data for the poly(vinylpyrrolidone) (PV P)+NaH2PO4+H2O system have been determined experimentally using the improved isopiestic method at 298.15, 308.15 and 318.15 K. The effect of temperature on the vapor–liquid equilibrium has been studied and compared with that on the liquid–liquid equilibrium of the aqueous PV P+NaH2PO4 two-phase system. It was found that the slope of constant water activity lines and tie-lines increased with increasing the temperature. The results have been discussed on the basis of the effect of temperature on the hydrophobicity of the polymer. Furthermore, the segment-based local composition Wilson model has been used for the correlation of the experimental water activity data. The agreement between the correlation and the experimental data is good. 相似文献
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针对循环冷却水中硅酸盐的析出过程,提出一个热力学模型。模型着重考虑温度、pH值、离子对的离解-缔合平衡、难溶盐的溶解-沉淀平衡、离子强度等对析出硅酸盐影响,求得各难溶硅酸盐的(Ca_2SiO_3、CaSiO_3、Mg_2SiO_4、MgSiO_3、Mg(OH)_2、MgCO_3、Ca(OH)_2、CaCO_3和CaMg(CO_3)_2)热力学成垢势和最大平衡成垢量,进而预测可能的垢组成。理论结果与实测值几乎一致。 相似文献
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基于二价金属离子配合物体系水解平衡的热力学原理,推导了该体系水解平衡的通用数学模型,并用C语言开发了绘制水解平衡图及确定金属离子净化过程最佳pH值的计算机程序。 相似文献
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We consider a water distribution system as an example of resource allocation, and investigate the use of a population game for its control. We use a game-theoretic approach based on two evolutionary dynamics, the Brown–von Neumann–Nash and the Smith dynamics. We show that the closed-loop feedback interconnection of the water distribution system and the game-theoretic-based controller has a Nash equilibrium as an asymptotically stable equilibrium point. The stability analysis is performed based on passivity concepts and the Lyapunov stability theorem. An additional control subsystem is considered for disturbance rejection. We verify the effectiveness of the method by simulations under different scenarios. 相似文献