共查询到20条相似文献,搜索用时 265 毫秒
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木棉(Gossampinus malabarica)又名攀枝花、红棉、英雄树、烽火树,属木棉科木棉属落叶高大乔木.木棉广泛分布在我国四川、云南、贵州、广西、广东,生长在江河沿岸、山地阳坡及村边道路旁,喜光、耐高温,对土壤要求不苛刻.在四川攀枝花地区木棉树于1月-2月份开花,先花后叶,花色艳丽,有红色、金黄、淡黄色等颜色,树形高大伟岸,是优良的园林绿化树种.木棉树现是攀枝花市市花和广州市市树,在园林绿化中常作行道树、庭荫树、景园树、盆景树等.木棉经嫁接后2 a-3 a开花,嫁接苗可作盆景矮化栽培,观赏价值高.本文介绍了木棉的嫁接育苗技术. 相似文献
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One compound approach combining factor-analytic model with AMMI and GGE biplot to improve multi-environment trials analysis 总被引:1,自引:0,他引:1
To improve multi-environmental trial(MET)analysis,a compound method—which combines factor analytic(FA)model with additive main effect and multiplicative interaction(AMMI)and genotype main effect plus genotype-by-environment interaction(GGE)biplot—was conducted in this study.The diameter at breast height of 36 open-pollinated(OP)families of Pinus taeda at six sites in South China was used as a raw dataset.The best linear unbiased prediction(BLUP)data of all individual trees in each site was obtained by fitting the spatial effects with the FA method from raw data.The raw data and BLUP data were analyzed and compared by using the AMMI and GGE biplot.BLUP results showed that the six sites were heterogeneous and spatial variation could be effectively fitted by spatial analysis with the FA method.AMMI analysis identified that two datasets had highly significant effects on the site,family,and their interactions,while BLUP data had a smaller residual error,but higher variation explaining ability and more credible stability than raw data.GGE biplot results revealed that raw data and BLUP data had different results in mega-environment delineation,test-environment evaluation,and genotype evaluation.In addition,BLUP data results were more reasonable due to the stronger analytical ability of the first two principal components.Our study suggests that the compound method combing the FA method with the AMMI and GGE biplot could improve the analysis result of MET data in Pinus teada as it was more reliable than direct AMMI and GGE biplot analysis on raw data. 相似文献
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Natural spruce-fir mixed stand is one of the main forest types in the world,and also has huge ecological,economic and social benefits.According to the structural characteristics and succession laws of natural spruce-fir forest,it is urgent and significant to develop scientific management measures for natural spruce-fir mixed stand in line with local conditions.The article outlined the characteristics of the distribution and structure, regeneration and succession laws of natural spruce-fir forest,and analyzed the current situation and existing problems of natural spruce-fir forest management.The following recommendations were eventually made:1) In no cutting area,all logging activities should be banned.In a restricted cutting area,the cutting intensity should be generally controlled within 15%of the stock volume before cutting.On the commodity forest management area, the appropriate cutting intensity should be determined according to the volume per hectare,determine and classification management should be implemented in accordance with the characteristics of forest,to ensure the scientific selective cutting.2) Closure for afforestation,planting and repair planting should be adopted on vegetation-intensive land,sparse shrubs covered land and harvesting slash,in order to accelerate natural regeneration.3) The in situ conservation should be conducted in nature reserves and scientific experiment stations of rare and endangered species,such as Abies chensiensis,Picea neoveitchii,Abies vuanbaoshanensis,to reduce human destruction.4) It is supposed to collect seeds in time,establish nursery,actively establish forest, expand artificial population and promote natural regeneration. 相似文献
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《技术与市场》2007,(1):23
当前现代化的航天、航空、汽车、机械、电子、民用建筑、化工等行业迫切要求具备很高的力学性能及耐热、耐磨、耐化学性能的材料.因此高分子材料发展的一个重要方向就是通过对现有聚合物进行物理和化学改性,使其进一步高性能化、结构化、工程化.北京化工大学研制的聚氯乙烯合金是通过挤出机的力学、化学作用及接枝、复合技术使聚氯乙烯塑料工程化,成为物理性能可与ABS相比拟的新材料.聚氯乙烯合金具有高流动性、高韧性,完全可以代替ABS注塑计算机、电视机、冰箱、照相机、仪表等外壳.聚氯乙烯合金还具有良好的耐寒性,可制作各种规格的异型材,包括门窗、上水管道等.产品市场前景好,具有很强的竞争力,有很好的经济效益和社会效益. 相似文献
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浙江省重点公益林松类生物量模型研究 总被引:2,自引:0,他引:2
根据浙江省森林群落和树种分布特点,在浙江省200万hm^2重点公益林范围内,按气候区、林分类型、林龄组成、立地条件、林分组成等设置松类树种(包括马尾松、黄山松、湿地松、华南松和火炬松)典型样地122个,实测标准木255株。通过相关分析表明,树干干重、木材干重、皮干重、枝干重、冠干重、根干重与胸径和树高的相关系数较大,其冠干重、枝干重、叶干重则与胸径和树高以及枝下高有较大的相关系数,从变量得到的简洁性和准确性考虑,经不同模型的拟合和检验,确定了松类生物量各器官的独立模型,总量、木材、树皮、树根、树干的模型结构为W=c1D^c2H^c3,树叶、树枝、树冠的模型结构为W=c1D^c2L^c3;拟合了浙江省重点公益林松类生物量各器官及总量的独立模型和相容性模型,经检验,各模型均具有较好的拟合精度和预估水平,样本总体预估精度指旨标(P%)在多数分量中以相容性模型最高,而且相对误差绝对值指标(E2%)最小,总量、木材,树干、树皮的预估精度超过了独立模型,其他分量仍保持了独立模型的水平;而且相对误差绝对值均略高于或等于独立模型。 相似文献
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According to the unification principle of system structure and system function of the Water Resource Conservation Forests,seven factors were selected from stand spatial structure,trees structure and healthy of woods,the multifunction management optimization model target was confirmed by using nonlinearity multi-objective programming approach, and the target function-stand spatial structure homogeneity index was defined to establish spatial optimization models with restraining conditions set up in diversity of stand structure and spatial structure.The spatial structure of available typical stand in the wet land area in southern Donting Lake was optimized by means of selective cutting and reinforcement planting.The results showed that the spatial structure was improved obviously and trees diversity and stand health were not weakened.It’s suggested that the established optimization model can effectively guide multifunction management,stand structure optimization and the steadiness of ecological ecosystem and it is convenient and operable in practice,and it’s very important to protect and recover ecosystem of Water Resource Conservation Forests. 相似文献
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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
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
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本文着重地论述了汽车在大修中发现发动机汽缸中活塞拉缸问题并就此分析了产生的原因。 提出了解决拉缸问题的8项措施。 相似文献
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介绍了JXT 60型系列大米窝眼滚筒精选机的结构特点、工作原理、技术性能,详细阐述了窝眼孔的形状和有关参数,并介绍了该系列精选机的堵孔清理机构、纵向倾角调节机构和通风机构等独创设计,这些机构可大大提高精选机的整体性能和成品大米的品质,还可节约投资;分析了米粒在精选机内的运动情况,并对主要参数进行了分析和计算.结果表明:该设备适应性强,可灵活使用,与平转筛相比,其具有巨大的优势,相对其他型号的精选机,其在技术上有很大的改进. 相似文献
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汤家荣 《林业机械与木工设备》2011,39(7)
就某企业所使用工程机械的液压油缸泄漏严重及同步精度低等问题,分析了油缸端盖的密封结构,找出了产生泄漏的原因。对油缸端盖密封结构改进后解决了出现的问题,使设备能够正常工作。 相似文献
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手提二冲程汽油机镀双金属气缸的研究 总被引:1,自引:0,他引:1
手提二冲程汽油机在我国的产量较大。在受气缸工作特点、结构、材料和表面强化技术的限制,它的使用寿命一直低于800h。本文作者从摩擦学的角度出发,对气缸寿命不长的原因进行了全面的分析,并在此基础上研究出新型的镀双金属气缸。试验数据表明,在当前国内制造厂现有的技术条件下,可以将气缸的寿命提高到1000h。 相似文献
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主要研究一种胶合板铺装板坯液压自动裁剪机,进行了液压缸基本参数计算,并合理选择液压缸标准件;设计"人"字结构的裁剪刀,实现减少载荷又使载荷平衡的目的,整机操作平稳,裁剪断面质量好;采用圆形导柱结构的导向装置,具有导向精度高的特点。应用结果表明,当裁剪的板材为最大厚度21 mm,2 440 mm(长)×1 220 mm(宽)规格产品时,传统裁剪方法需设置2 520 mm×1 270 mm,应用本设计只需设置2 480 mm×1 250 mm尺寸就能满足下道工序要求,与此相比,每张板可节约40 mm×20 mm×21 mm木材。设备具有可操作性强,裁剪精度高,减少原材料浪费,生产安全等特点,满足胶合板生产企业的需求,可推广应用。 相似文献
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通过对传统往复活塞式发动机和转子发动机气缸密封结构的分析,针对现存的问题提出对转子发动机气缸径向密封的改进。在原径向密封片的基础上,在其前段与缸体接触的密封面开出圆柱形通孔,在通孔中装入滚针,将径向密封片装入滚针后,把原来的滑动摩擦改变为滚动摩擦,从而改善径向密封片的摩擦特性,增强密封性能。 相似文献
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在分析模压压机柱塞油缸结构的基础上,就柱塞油缸缸体的分段浇注、焊接成型等加工工艺进行了探讨。 相似文献