竹青板作为风电叶片复合材料增强相的性能评价   总被引：1，自引：0，他引：1  

黄晓东  江泽慧  陈玲 《林业科技开发》2009,23(1)

针对目前玻璃钢叶片存在的问题,采用分级竹青板作为风电叶片复合材料的增强相,并利用INSTRON 5582 Grading能力学试验机进行检测.结果表明:由一二级竹青板制成的分级竹青层积材复合材料,其物理力学性能均达到或超过目前国外风电叶片在用的常规木材/环氧层积材的特性,完全能够替代目前大量使用的玻璃钢叶片材料.  相似文献   

林分断面积生长率公式探讨     

林寿明  叶金盛 《广东林业科技》2002,18(4):40-44

根据林分生长理论，结合原始调查数据，对林业生产中的3种断面积生长率理论公式Meyer式、Pressler式和张角式的特性作了进一步研究，并对3种方法作了具体验证。研究结果表明：3种断面积生长率计算方法有一定差异，当后期与前期平均断面积比值大于1.30时，Meyer方法计算断面积生长率高于其余两种方法，张角法则和Pressler法则十分接近，但张角法更有理论依据。  相似文献   

A review of stand basal area growth models     

Sun Hong-gang Zhang Jian-guo Duan Ai-guo He Cai-yun 《中国林学(英文版)》2007,9(1):85-94

Growth and yield modeling has a long history in forestry. The methods of measuring the growth of stand basal area have evolved from those developed in the U.S.A. and Germany during the last century. Stand basal area modeling has progressed rapidly since the first widely used model was published by the U.S. Forest Service. Over the years, a variety of models have been developed for predicting the growth and yield of uneven/even-aged stands using stand-level approaches. The modeling methodology has not only moved from an empirical approach to a more ecological process-based approach but also accommodated a variety of techniques such as: 1) simultaneous equation methods, 2) difference models, 3) artificial neural network techniques, 4) linear/nonlinear regres-sion models, and 5) matrix models. Empirical models using statistical methods were developed to reproduce accurately and precisely field observations. In contrast, process models have a shorter history, developed originally as research and education tools with the aim of increasing the understanding of cause and effect relationships. Empirical and process models can be married into hybrid mod-els in which the shortcomings of both component approaches can, to some extent, be overcome. Algebraic difference forms of stand basal area models which consist of stand age, stand density and site quality can fully describe stand growth dynamics. This paper reviews the current literature regarding stand basal area models, discusses the basic types of models and their merits and outlines recent progress in modeling growth and dynamics of stand basal area. Future trends involving algebraic difference forms, good fitting variables and model types into stand basal area modeling strategies are discussed.  相似文献   

代代花的繁殖与栽培     

徐双飞 《安徽林业》2005,(6):36

代代花,又称玳玳花,是芸香科柑橘属常绿小乔木,盆栽可供四季欣赏.春天,叶腋开朵朵白花,清香浓郁,用以窨制的茶叶,称代代花茶;现代制作代代干花,可泡茶饮用养颜,香气久贮不散;花蕾用于饰花、佩花;果实剖开晒干可入药,即"苏积壳",有消积化食、理气宽中、化痰止泻的功效;代代花和叶都可提取香精,是用途很广的经济花卉.  相似文献   

雷州尾叶桉树冠指标与抚育间伐关系的探讨     

蔡惜芜  梁景生  郑剑平  梁峰 《桉树科技》2007,24(1):35-40

通过对雷州尾叶桉树冠有效受光面积、树冠比率、树冠投影面积进行调查研究,分别用树冠有效受光面积、树冠比率、投影面积与胸径建立一元幂函数回归方程进行研究与分析,结果表明树冠有效受光面积公式对指导培育中径材较好;树冠比率与树冠投影面积公式的回归效果基本一致,对指导培育小径材较为理想,并利用上述回归公式编制单株营养面积、公顷立木株数和公顷基面积表为尾叶桉人工林的抚育间伐设计与施工提供理论依据。  相似文献   

林分平均胸径100倍圆法测定每公顷断面积的理论初探(之二)--误差分析与修正系数     

鄢前飞 《林业调查规划》2006,31(1):11-16

通过对100Dg圆公式含义的分析,对影响林分断面积精度的2个主要因子:样地株数密度与林分平均胸径估测值进行了误差分析与探讨,提出了样地株数密度估计林分株数密度采用典型选样,林分平均胸径估测值采用目测法等相应解决办法。其中,当目测值有偏差时采用修正系数可使100Dg圆的可靠性进行了理论上的探讨。  相似文献   

杉木积成材竹片贴面工艺探讨   总被引：1，自引：0，他引：1  

杜春贵 《林业机械与木工设备》2003,31(12):35-36,39

对杉木积成材进行了竹片贴面的初步试验，结果表明：杉木积成材进行竹片贴面切实可行；竹片贴面后的杉木积成材密腹略高于基材；竹片与基材之间的胶合强度大于基材内部的胶合强度；贴面板的MOR和MOE高于基材：24h吸水厚度膨胀率佟明显低于基材。  相似文献   

棉花铃积的气象要素初探     

胡从发  李云清  杨尚福 《中国棉花》1994,(6)

本文利用相关和通径分析法，首次探讨了铃积与气象因子的关系．得出温度是影响铃积的最重要气象因子，在干旱生境下，气象因素对铃积的直接影响排序为温度＞蒸发＞日照＞湿度＞降雨；存在２１℃以上的温度、较少的棉田蒸发、充足的日照是大铃的必备条件。同时，探讨了各项温度子指标与铃积的关系。  相似文献   

广西大青山杉木人工林断面积生长的长期密度与立地效应     

郭光智  李晓燕  姜丽  段爱国  张建国 《东北林业大学学报》2021,49(6):34-39,57

以广西大青山36年生杉木密度试验林为研究对象,分析A(1667株·hm-2)、B(3333株·hm-2)、C(5000株·hm-2)、D(6667株·hm-2)、E(10000株·hm-2)5种初植密度和10、14、16、18等4个立地指数级杉木人工林断面积生长的动态变化,探索南亚热带不同密度、立地条件下杉木林断面积生长的长期规律.结果表明:林分断面积随林龄增长而增加,且11～16年生期间增长快速,除A密度林分,其余密度林分断面积达到峰值后均呈下降趋势.立地指数级相同时,密度越大,林分断面积及其连年生长量、年平均生长量达到峰值越早且峰值越大.不同密度的林分断面积随林龄增长,差距逐步缩小并趋于一致.林分断面积的生长受密度、立地的叠加影响,且较低密度林分受立地的影响更大.幼龄林阶段,林分断面积及其连年生长量、年平均生长量,与林龄、密度、立地指数呈正相关;成熟期,中等密度C的林分断面积最大.  相似文献   

Optimizing any-aged management of mixed boreal forest under residual basal area constraints     

Timo Pukkala  Erkki Lähde  Olavi Laiho 《林业研究》2014,25(3):627-636

The current trend of forest management in many countries is reduced use of clear-felling and planting, and increased use of continuous cover management. In Finland, the new forest act of 2014 made all types of cuttings equally allowable on the condition that if the post-cutting residual stand basal area is too low, the stand must be regenerated within certain time frame. Forest landowner can freely choose between evenand uneven-aged management. This study developed a method for optimizing the timing and type of cuttings without the need to categorize the management system as either even-aged or uneven-aged. A management system that does not set any requirements on the sequence of post-cutting diameter distributions is called any-aged management. Planting or sowing was used when stand basal area fell below the required minimum basal area and the amount of advance regeneration was less than required in the regulations. When the cuttings of 200 stands managed earlier with even-aged silviculture were optimized with the developed system, final felling followed by artificial regeneration was selected for almost 50% of stands. Reduction of the minimum basal area limit greatly decreased the use of artificial regeneration but improved profitability, suggesting that the truly optimal management would be to use natural regeneration in financially mature stands. The optimal type of thinning was high thinning in 97–99 % of cases. It was calculated that the minimum basal area requirement reduced the mean net present value of the stands by 12–16 % when discount rate was 3–5 %.  相似文献