再谈吸水井工艺设计     

鄂学民  郭泽林 《林业科技情报》2001,33(2):48-48

在目前尚缺乏计算吸水井有效容积理论依据的情况下,作者通过对吸水井类型及其有效容积的分析,推荐了一种先按最小尺寸法确定吸水井容积,再按最小容积法校核的设计方法。对吸水井设计具有一定的指导意义。  相似文献   

Arboreal lichen in uncut and partially cut subalpine fir stands in woodland caribou habitat, northern Idaho and southeastern British Columbia     

Eric M. Rominger  Lydia Allen-Johnson  John L. Oldemeyer 《Forest Ecology and Management》1994,70(1-3):195-202

To better understand the effects of partial cutting on arboreal lichen production within woodland caribou (Rangifer tarandus caribou) habitat, lichen was hand picked from 1228 branches on 307 subalpine fir (Abies lasiocarpa) trees in Idaho (ID), and in British Columbia (BC). Lichen biomass from partially cut stands was compared with biomass on trees from adjacent uncut stands at each site. Arboreal lichen biomass did not differ significantly between uncut and partially cut stands. Total number of branches per tree did not differ significantly between uncut and partially cut stands. Live branches had more lichen than dead branches. Species composition of arboreal lichen changed in partially cut stands compared with adjacent uncut stands. The ratio of live to dead branches was substantially different within the BC partial cut.  相似文献   

在椭圆抛物柱模型中扁方材和板材材积精确解析解推导   总被引：1，自引：0，他引：1  

马岩  张宁 《木材工业》1990,4(2):24-27

本文以椭圆抛物柱模型计算了毛边板,钝棱板,扁方材等体积的精确解析解。为制材CAD与CAM和下锯图优化提供了精度更高的数学模型。  相似文献   

最小二乘估计和最隹线性无偏估计的关系     

陈定庚 《湖南农业大学学报(自然科学版)》1989,16(1)

本文讨论广义线性模型的均值向量的最小二乘估计和最佳线性无偏估计的关系,得到了它们相等的充要条件以及它们的偏差关系和偏差范数估计;并在欧氏范数下,进一步讨论了这种偏差估计。  相似文献   

利用变动系数求林分平方平均直径的株数累积百分数     

周彬  官凤英  陈光清 《北京林业大学学报》2001,23(4):84-86

对于直径遵从正态分布的同龄纯林 ,通常只从经验上判定其平方平均直径在株数累积分布曲线上的位置介于 5 5 %～ 6 4%之间 .该文从林分算术平均直径 ( d) ,林分平方平均直径 (Dg)和直径变动系数 (c)三者之间的数学关系 ,导出f(c) =1+c2 - 1 c是正态分布的分布函数的自变量 ,并从数学上证明了其Dg 的株数累积百分数的范围在 5 4%～ 5 6 8%之间 ,同时介绍了用Excel中Normsdist函数求解Dg 株数累积百分数的方法 ,并用一组数据进行验证 ,计算结果与实际情况吻合 ,可靠性 95 %以上 .  相似文献   

兰州市安宁区培黎广场改造近期规划设计   总被引：1，自引：0，他引：1  

蒋倩  李彬 《甘肃农业大学学报》2001,36(1):79-82

介绍了兰州市培黎广场现状和广场改造指导思想，同时结合设计理念确定广场改造的总体布局、景观特色及种植设计。  相似文献   

二代棉铃虫低龄幼虫的取食行为研究   总被引：1，自引：0，他引：1  

王琛柱  杨奇华  周明牂 《植物保护学报》1991,18(4):335-338

根据被害率、相对取食量和严重被害率三个指标,对被害棉蕾十二个部位的解剖观测,详细揭示了二代棉铃虫低龄幼虫的取食部位和侵害路径。棉铃虫低龄幼虫对花蕾各部位均取食为害,但取食量不等,嗜食性不同。花药、柱头、花丝、花柱、雄蕊柱和花冠管,相对取食量大,且嗜食性好,是低龄幼虫为害的主要部位;苞叶、花萼和花瓣,相对取食量大,但嗜食性差,是抵抗棉铃虫侵入的主要有效部位,可阻止31％的幼虫进入蕾内,其中以花萼作用最大。低龄幼虫有躲避油腺取食行为,但随着幼虫日龄的增加这种选择取食行为逐渐弱化。  相似文献   

沙障工程防治格状沙丘前移的风洞实验研究   总被引：1，自引：0，他引：1  

邸耀全  王锡来  刘贤万 《干旱区研究》1996,(1)

分析研究表明，格状沙丘主梁是在主风作用下形成的横向新月形沙丘链；而副梁是在两个次主风的共同作用下，在横向沙丘链迎风坡上逆向形成的纵向沙丘。风洞实验和野外观测结果证明，延缓格状沙丘前移，可以在其主、副梁上采用高立式加半隐蔽式沙障，构成复合沙障，利用其抬高阻滞作用而达到目的。  相似文献   

用活动温度平方法编制期距表预报二代棉铃虫卵峰日研究     

宋广镇  赵乃福  石他山  徐春明  李泽田  张玉花 《中国植保导刊》2001,21(10):8-11

用活动温度平方法计算期距,制作期距表,进行发生期预测,克服了平均期距法时间覆盖面小的缺陷,应用时简便准确,有利于积温法则的推广和应用.经近年多点应用检验,可提前25～38d准确作出二代棉铃虫卵峰日的预报.  相似文献   

Comparative effects of regulated deficit irrigation (RDI) and partial root-zone drying (PRD) on growth and cell wall peroxidase activity in tomato fruits     

Sladjana Savić  Radmila Stikić  Biljana Vucelić Radović  Biljana Bogičević  Zorica Jovanović  Vesna Hadži-Tašković Šukalović 《Scientia Horticulturae》2008

The effects of regulated deficit irrigation (RDI) and partial root-zone drying (PRD) on tomato fruit growth and cell wall peroxidase activity in tomato exocarp were investigated in growth chamber conditions. The RDI treatment was 50% of water given to fully irrigated (FI) plants and the PRD treatment was 50% of water of FI plants applied to one half of the root system while the other half dried down, with irrigation shifted when soil water content of the dry side decreased 15–20%. RDI significantly reduced fruit diameter, though PRD reduced fresh weight while having no significant effect on fruit diameter. The activity of peroxidase was significantly higher in RDI and PRD treated plants compared to those of FI. Differences between RDI and PRD were expressed on temporal basis. In the fruits of RDI treated plants peroxidase activity began to increase in the phase when fruit growth started to decline with the peak of enzyme activity of 6.1 HRPEU g⁻¹ FW reached in the phase of mature green fruits when fruit growth rate was minimal. Increase of peroxidase activity in PRD fruits coincided with the ripening phase and the peak of enzyme activity (5.3 HRPEU g⁻¹ FW) was measured at the end of fruit ripening. These data potentially identified contrasting and different roles of tomato exocarp cell wall peroxidase in RDI and PRD treated plants. In RDI treated plants peroxidase may have a role in restricting fruit growth rate, although the increase in enzyme activity during ripening of PRD treated fruit pointed out that peroxidase may also control fruit maturation by inducing more rapid process.  相似文献