长武塬区苹果园和农田相互转换的深层土壤水环境效应

研究长武塬区苹果园和农田相互转换后0~1 000 cm土壤含水量特征，分析了苹果园土壤干燥化和苹果园转换为农田后土壤水分的恢复效应。结果表明：2、7、17、23、29 a苹果园200~1 000 cm的平均土壤含水量分别为22.8%、21.4%、16.8%、15.4%、14.9%。500~1 000 cm土层中，29 a苹果园平均土壤含水量（14.5%）高于23 a的果园（13.3%）；17~29 a的苹果园均表现为轻度干燥化；基于苹果园和农田转换后土壤水分变化情况估算，苹果园最大种植年限为21 a。苹果园转换为农田1、5、10 a后，农田200~1 000 cm土层土壤含水量分别为：15.3%、15.7%和16.2%，恢复到土壤稳定湿度以上的土层厚度分别为140 cm（1 a）、220 cm（5 a）和400 cm（10 a）。     

基于季节特征的土壤退墒模型建立与率定

利用河南省南阳市2011—2015年12个墒情站的土壤水分监测资料,分析研究了无增墒情况下土壤含水量消退规律,构建出基于不同季节(夏季、春秋季与冬季)的土壤含水量与衰减系数的数学模型,运用规划求解法率定模型参数,并利用2016—2017年资料对模型进行检验。结果表明,不同季节土壤水分衰竭系数模型分别为α=1.023(1-ω~2/4353)~(1/2)(夏季)、α=1.013(1-ω~2/7005)~(1/2)(春秋季)与α=1.008(1-ω~2/9303)~(1/2)(冬季),所建立的数学模型适用于南阳市相应季节壤土与粘壤土小麦、水稻与休闲地土壤旱情预测,但不适用于夏季与春秋季砂土特别是休闲地砂土土壤墒情预测。     

不同保水剂对土壤特性及烤烟生长的影响

为提高秦巴山区黄棕壤烟田的土壤性能,减少季节性干旱对烤烟生长的影响,以不施保水剂为对照,在烟田整地起垄前分别施入聚丙烯酸钾(K-PAM)、聚丙烯酰胺(PAM)和腐殖酸钾(KHm)3种保水剂,测定施用不同保水剂后的土壤容重、土壤水分和烤烟生长状况、常规化学成分及经济性状。结果表明,聚丙烯酸钾和聚丙烯酰胺保水剂均降低0～40cm土层土壤容重,在烤烟旺长期提高0～40cm土层土壤水分。不同保水剂均可提高烤烟常规化学成分含量,其中腐殖酸钾保水剂显著降低烤烟的糖碱比和氮碱比。聚丙烯酸钾保水剂提高烤烟的产量、产值、上等烟比例及净增产值,而聚丙烯酰胺和腐殖酸钾保水剂处理组则降低烤烟的净增产值。因此,建议秦巴山区黄棕壤烟田选用聚丙烯酸钾类保水剂。     

分流叶片对高速井泵压力脉动的影响

针对高速井泵采用分流叶片设计带来的稳定性问题,运用Creo3.0软件建立了叶轮、导叶等关键零件的三维模型;在CFX数值模拟数据与外特性试验数据吻合较好的基础上,将分流叶片的进口直径d₁与叶轮外径D₂的比值定义为一个表达分流叶片综合特性参数的量纲一化系数σ.σ分别取值0.60,0.62,0.65,设计分流叶片长短不同的3个叶轮方案,且对各方案的动静干涉区域进行了详细的压力脉动数值模拟计算及分析.结果表明:压力脉动幅值大小与监测点和交界面的径向距离有关,径向距离越大,压力脉动幅值越小;各监测点压力脉动随分流叶片长度的减小逐渐减弱,当分流叶片长度减小到某一临界值以后,压力脉动基本保持不变;当σ=0.62时,压力脉动幅值较小,脉动周期清晰;除中流线上的监测点以外,各监测点压力脉动主频受叶轮叶频的影响较大,分流叶片对中流线上监测点的压力脉动影响较大.     

浅谈几种概率分布之间的相互关系

本文简述了几种常用的概率分布之间的相互关系     

Impact of postovulatory food deprivation on the ova transport, hormonal profiles and metabolic changes in sows.

The effect of food deprivation on ova transport, hormonal profiles and metabolic changes was studied in 20 crossbred multiparous sows during their second oestrus after weaning. To determine the time of ovulation, transrectal ultrasonographic examination was performed. The sows were divided into 2 groups, one control group (C-group), which was fed according to Swedish standards, and one experimental group (E-group). The E-group sows were deprived of food from the first morning meal after ovulation until slaughter. Blood samples were collected every second hour from about 12 h before expected ovulation in the second oestrus after weaning until slaughter and were analysed for progesterone, prostaglandin F2 alpha-metabolite, insulin, glucose, free fatty acids and triglycerides. All sows were slaughtered approximately 48 h after ovulation and the genital tract was recovered. The isthmic part of the oviduct was divided into 3 equally long segments and flushed separately with phosphate buffered saline (PBS). Uterine horns were also flushed with PBS. A significantly greater number of ova were found in the first and second part of the isthmus in the E-group (p = 0.05) while in the C-group most of the ova were found in the third part of the isthmus or the uterus (p = 0.01). The level of prostaglandin F2 alpha-metabolite was significantly higher in the E-group compared with the C-group. The concentration of progesterone increased in both groups after ovulation but there were no significant differences between the groups. The other blood parameters showed that the food-deprived sows were in a catabolic state. The 48 h period of fasting results, directly or indirectly in an delayed ova transport, which may be due to a delayed relaxation in the smooth circular muscle layer of the isthmus.     

兵团农机产业化的若干思考

农机产业化是社会分工细化、生产专业化深化的必然产物，其实质是传统农业转变为现代产业的过程。日前，兵团农机产业化进程中存在着一些问题。为此，结合兵团实际，提出了推进农机产业化发展的基本思路。     

电超滤浸提土壤养分的研究 Ⅰ.石灰性土壤的电超滤特性

石灰性土壤的电超滤(EUF)特性主要是浸提时因需控制电流而必须大大降低电压。在一定范围内,降压程度与土壤 CaCO_3%有密切关系。控流限额愈低,电压需成比例地下降,但土壤EUF-值减小不多。电流控制在一定值时,离子的解吸总量亦为定值。控流主要控制了各石灰性土壤解吸/溶解份额特大的 Ca+Mg 量近于定值,对于含量小的其他养分离子则并无多大影响,仍可区辨各土壤间的差别。通过冬小麦盆栽试验和有关化学测试法等方面的相关研究,表明采用国际通用的5g 土样和控电流方法测定 EUF-K 和-P 等有效养分,对于石灰性土壤也是可行的,但其EUF-(Ca+Mg)值则毫无植物营养有效性的意义。土壤 EUF 值只是一种指数,并非真正的解吸离子量。石灰性土壤 EUF-K 值因浸提时降压控流而略低,80℃时5min 内解吸的钾不一定是非交换性钾。由于 Ca-P 和 CaCO_3在高温高电压时浸出较多,故石灰性土壤 EUF-P 和-(Ca+Mg)的80℃值/20℃值之比,与酸性土壤或非石灰性土壤相比要大得多。     

有摩擦的高速气体管流

本文以多变热力过程为基础建立了有摩擦管路的计算公式,并对计算方法和有关问题作了分析说明.