排序方式: 共有11条查询结果,搜索用时 15 毫秒
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1基本情况王屋灌区位于龙口市中部丘陵区和中北部平原区,是龙口市的主要产粮区。设计灌溉面积2.15万hm2,灌区由以王屋水库为骨干的7座地表水库、1座地下水库联合调度供水,有东、西两条干渠,总长80.2km,支渠23条,总长62.5km。渠道为20世纪60年代初修建,多数渠段为土渠,未进行防渗处理,仅部分填方渠段及渗漏较严重的地段利用浆砌石进行衬砌。灌区工程运行多年来,对于促进龙口市经济发展起到了积极作用。由于经过数十年运用,工程严重退化老化,渠道渗漏水严重,水的利用率低,灌溉水利用系数仅能达到0.53,这种状况难以担负国民经济持续发展所赋予… 相似文献
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自动喷水灭火系统可靠性探讨 总被引:1,自引:0,他引:1
自动喷水灭火系统的迅速普及,使其运行可靠性变得越来越重要.对自动喷水灭火系统灭火失败的原因进行分析,总结出设计、施工及管理维护是决定自动灭火系统安全运行的三大关键因素.对比美国NFPA、FM认证的一些细节要求,总结了在提高自动喷水灭火系统的可靠性、降低系统运行失败可能性上的不足,为以后的设计、施工及运行维护提供借鉴. 相似文献
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A metal rod is used in the high temperature testing for ultrasonic propagation and heat output,but the trailing echoes generated by ultrasonic penetration through the metal rod seriously affect the recognition and extraction of characteristic signals.According to the phenomenon,the Finite Element Method(FEM)is used to analyze ultrasonic penetration through a metal rod,the reason of the trailing echoes and the regularity of ultrasonic signals.The motion equation of ultrasonic propagation in a metal rod is established and calculated,then the simulation signals and instantaneous cartographies of the process are obtained.Based on the results of the analysis,it can be concluded that the intervals of the trailing echoes are determined by the rod’s diameter and wave velocity.In practical applications,the FEM is used to analyze ultrasonic propagation in the designed buffer rod at first.Based on the characteristics of the simulation signals,the material and dimension are adjusted and selected,aiming to identify the characteristic echo and trailing echoes in time domain and extract characteristic echo from the ultrasonic signals available. 相似文献
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