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针对橡塑渗灌管变异系数高、在线源式灌溉过程中水头损失大等问题,本文以橡塑渗灌管为柱状出流面,再结合迷宫流道技术设计了一种点源式灌溉的地埋式橡塑渗灌滴头。通过水力性能测试、短周期抗堵塞试验以及土壤入渗试验对滴头性能进行了分析。结果表明,滴头流量变异系数为4.17%,压力-流量关系式为q=0.6435h0.4161,符合国家生产标准,并具备一定的压力补偿性能;在3种泥沙浓度(W1=0.5 g·L-1,W2=0.1 g·L-1,W3=1.5 g·L-1)、100 kPa工作压力下,滴头有效灌溉次数分别为15、11、5次,达到灌水器抗堵塞性能平均标准;将滴头深埋30 cm进行土壤入渗试验,在100 kPa工作压力下,未出现深层渗漏现象,湿润锋在580 min后到达土壤表面,可有效减少灌溉水蒸发,节约水资源。该地埋式橡塑渗灌滴头水力性能优秀,抗堵塞性能良好,湿润体体积大,土壤含水率分布均匀,可广泛适用于果园灌溉以及科研试验等。 相似文献
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Kranenburg LC van Ree HE Calis AN de Pater M Buter GJ van Maanen C Sloet van Oldruitenborgh-Oosterbaarn MM 《Tijdschrift voor diergeneeskunde》2011,136(4):237-243
Equine proliferative enteropathy caused by Lawsonia intracellularis is an emerging disease of weanling foals and affects their growth and development. The prevalence of Lawsonia intracellularis in The Netherlands is not known. The aim of the study was to investigate the seroprevalence of Lawsonia intracellularis in horses in The Netherlands. Blood samples were taken from healthy foals before and after weaning and from healthy yearlings and mature horses on farms throughout The Netherlands. These samples were analysed for the presence of Lawsonia intracellularis-specific antibodies with a blocking ELISA. White blood cell count, packed cell volume, and total protein concentration were also measured in all foals. Information regarding housing, pasture access, and contact with pig manure on the premises was obtained for all animals. The prevalence of Lawsonia intracellularis antibodies in foals increased significantly from 15% before weaning to 23% after weaning (p = 0.019); it was 89% in yearlings and 99% in horses older than 2 years. There was no significant difference in seroprevalence between the pasture-kept and stable-confined adult horses (97% and 100%, respectively), and there was no significant influence of contact with pig manure. None of the sampled animals showed clinical disease. In conclusion, the results suggest that Lawsonia intracellularis is widespread in The Netherlands and that seropositivity is not necessarily associated with clinical problems. The high seroprevalence in adult horses suggests long-term persistence of antibodies against Lawsonia intracellularis or constant exposure to the bacterium. 相似文献
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