电动树干药液注射机钻头行程控制系统设计

针对目前树木遭受病虫危害的现象,设计一种由单片机控制的电动树干药液注射机钻头行程控制系统,防治病虫危害,矫治缺素症。该系统实现了注射机钻头由直流电机和步进电动机带动,径向进给到树木内部的适当位置,在单片机的控制下退出适当的距离以实现药液的注射,最后实现电动树干注射机钻头的有效退出,最终达到为大树治病的效果。     

柴油机伞喷嘴喷油过程和喷雾特性的研究

主要介绍了用长管法和闪光摄影研究伴喷嘴喷油过程和喷雾特性,并简介了测试装置的结构和工作原理。将伞喷嘴与四气门单缸１３５型柴油机的燃油系统配合,在喷油泵试验台上进行了试验。试验结果表明,在燃油系统其他部分不变的情况下,伞喷嘴的喷油规律图呈近似在角形,最高喷油率和平均喷油率远高于多孔喷嘴;伞形喷雾径向贯穿距离远小于多孔喷雾,喷雾锥角在喷雾早期急剧减小。伞喷嘴喷油特性的研究对相应燃烧系统工作过程的组织和燃烧过程、性能的分析具有指导作用。     

杨树天牛防治新途径研究初报

笔者探讨了杨树天牛的危害特点和防治难点,分析了树干注药防治技术的研究现状。在此基础上开展了自流式树干注药防治试验,结果表明,不同药剂不同用药量的防治效果不同,同一试药量随树木胸径的增大防治效果降低,树木胸径在10cm以下的最佳药剂比为1：3;胸径大于10cm时,胸径每增大2cm,则药量约增加40％．     

柴油发电机组的启动与故障分析

柴油发电机组的启动是一个复杂的过程,在此过程中有各种形式能量的相互转换,这些转换直接关系到柴油机能否正常启动.了解柴油机组的启动原理和启动条件,对我们分析和处理柴油发电机组的启动故障具有重要意义.     

进气掺水降低柴油机排放的实验研究

在485QB柴油发动机上进行进气加湿降排的实验研究,实验采用超声雾化的方法产生微小的水颗粒,通过进气加入不同水量的排放实验,研究进气加湿对柴油机排放的影响。实验分析表明:对柴油发动机进气工质加湿可以有效地降低NOX的排放,一定程度上降低发动机的油耗,同时可以提高发动机的性能。     

Non-industrial Private Forest Owners' Risk Preferences

A set of hypotheses was formulated on the basis of available knowledge about non-industrial private forest (NIPF) owners' risk preferences. The empirical material used for testing the hypotheses was gathered in telephone interviews with 130 randomly selected NIPF owners. The results confirm that direct economic risks such as price and cost changes are seen by this group as much more important than indirect economic risks such as biological damage. The forest owners regarded forest holdings as a safer investment than stocks or bank savings. The results on risk attitudes were ambiguous. However, when larger amounts of money were at stake, the forest owners could be considered risk averters and a decrease in absolute and relative risk aversion could be confirmed.     

Survival and Early Development of Lodgepole Pine

The effect of site fertility, spacing and mode of regeneration on the survival and stand development of lodgepole pine, Scots pine and Norway spruce was studied in a series of experiments comprising 22 study areas in Finland. After 13-14 yrs, lodgepole pine had a mean survival of 68% in planted and 61% in seeded plots, while Norway spruce had the highest (92%) and Scots pine the second highest survival (82%). The survival of planted lodgepole pine was better the wider the spacing. Best survival was achieved on subdry and dry sites, both with planting and with direct seeding. Dominant height was not affected by spacing, but both basal area and volume at the age of 13-14 yrs were significantly higher the denser the spacing. The average difference in the value of the estimated site index H ⁵⁰ was slightly under 3 m for the superiority of lodgepole compared with Scots pine. Seeding resulted in site indices almost as high as those of lodgepole planting.     

打孔注菌防治光肩星天牛试验研究

用杨、柳、榆树的树皮和木质部浸出液为营养对球孢白僵菌进行生长试验,结果证明球孢白僵菌在3种树木的树皮和木质部的浸出液中都可生长;相同条件下,在树皮中比木质部中产量高,杨树树皮是木质部的3.37倍,柳树是4.73倍,榆树是3.86倍。林间试验证明打孔注菌可以防治光肩星天牛幼虫,含菌量4亿/mL～8亿/mL,每株注150 ...     

基于燃烧室外预热的柴油发动机性能分析

能源匮乏和环境污染已成为当今世界各国所面临的两大难题,柴油机凭借高热效率和高可靠性得到越来越广泛的应用。利用自制的电控恒温燃油预热装置,对柴油发动机进行燃油室外预热,分别进行柴油机的负荷特性实验、速度特性实验和排气烟度实验。实验结果表明,能够改善柴油机工作性能的最佳预热温度范围为60—90℃。     

不同热压方法对无胶竹碎料板力学性能影响

分别采用普通热压和喷蒸热压两种热压方法制备了无胶竹碎料板,对它们的物理力学性能进行了对比研究与分析.结果表明,与普通热压法相比,喷蒸热压法制备的无胶竹碎料板的静曲强度、弹性模量与内结合强度明显提高,吸水厚度膨胀率显著减小,这可能是因为两种热压法热压过程中竹碎料发生的化学变化不同所致.