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Stephen D. Reay Joanne M. Thwaites Roberta L. Farrell Patrick J. Walsh 《Integrated Pest Management Reviews》2001,6(3-4):283-291
The role of the bark beetle Hylastes ater in the re-establishment of Pinus radiata forest in New Zealand is discussed. H. ater was found to be a dominant factor in seedlings mortality in the first year following planting. However, seedling mortality is usually relatively low. In contrast, it was found the large numbers of seedlings were sub-lethally damaged by H. ater feeding attempts, particularly in high risk sites. High risk sites were identified as sites that were harvested during March and April (autumn) when the peak flight activity of H. ater occurred, and subsequently planted with P. radiata seedlings the following winter. H. ater was found to vector sapstain fungi to seedlings during feeding attempts, and a strong relationship between the severity of damage and presence of sapstain fungi was identified. The role of H. ater as a vector of these fungi and the potential implications to the New Zealand forest industry are discussed. 相似文献
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为了提高某超声速飞机的空气动力学效率和机动性能，本文采用低阶的三维板块法和DATCOM半经验公式，在亚声速和超声速条件下，对不同马赫数和迎角情况计算了基本气动外形的飞机空气动力学特性、表面压力分布以及最大升力。此外还开发了一套软件以实现由引进的先进气动操纵面（如鸭翼等）控制的二维推力矢量技术。试验结果表明：气动操纵面结合推力矢量技术能够产生足够的低头力矩，且有能力满足高度机动飞行时的稳定性要求。此外，不论是亚声速还是超声速飞行，气动操纵面均可以提高气动效率5％-6％。 相似文献
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Efficacy of Trichoderma spp. to reduce sunflower head rot caused by Sclerotinia sclerotiorum was evaluated in the field. A mixture of six isolates, including Trichoderma koningii , T. aureoviride and T. longibrachiatum , was tested in five field trials at Balcarce, Argentina. Trichoderma formulation (TF) included Trichoderma conidia and viable hyphal fragments, industrial talc and milled corn kernels. Honeybees ( Apis mellifera ) were used to disperse TF for six weeks from the onset of flowering. Two days after the first TF delivery, sunflower heads were inoculated with S. sclerotiorum ascospores. When 100 g TF was taken by honeybees in a 10-h per day period, head rot incidence was significantly reduced. This approach was successful in reducing disease incidence until physiological maturity of the crop, in environments highly conducive to head-rot development. 相似文献
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并联式TBCC发动机排气系统性能数值模拟 总被引：1，自引：0，他引：1
针对一个并联式涡轮基组合循环(Turbine Based Combined Cycle, TBCC)发动机排气系统的气动方案,对其在整个飞行包线范围内典型工作点上的流场进行了数值模拟研究,获得了飞行包线范围内排气系统相应的推力系数、升力、俯仰力矩随飞行马赫数的变化关系。计算结果显示,在整个飞行包线范围内,排气系统的轴向推力系数随着飞行马赫数先减小后增大,在跨声速飞行时降到最低 Ma=0.9,涡喷不加力时为0.562,加力时0.662),在设计点附近达到最大;升力和俯仰力矩性能在亚声速及跨声速飞行时较差,在超声速飞行时随着飞行马赫数增加逐渐好转。表明排气系统在跨声速飞行范围内工作时应采取措施以改善其性能。 相似文献
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指出在当前社会背景下,农村劳动力流动行为是基于多种力量综合作用的结果,并深入分析了这些作用力。 相似文献
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采用TYG推力轴承的同步电动机在抽水站中的应用 总被引：1，自引：1，他引：1
淮安第一抽水站在加固改造工程中选用了配置新式推力轴承(TYG)的同步电动机。该同步电动机组具有整件发运安装、安装难度小、周期短、免维护等优点。通过长时间运行，机组运行平稳，各项指标优于改造前的老式机组。文章简要地介绍了这种电动机的特点和应用前景。 相似文献