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Wood elastic constants are needed to describe the elastic behaviors of wood and be taken as an important design parameter
for wood-based composite materials and structural materials. This paper clarified the relationships between compliance coefficients
and engineering elastic constants combined with orthotropic properties of wood, and twelve elastic constants of Betula platyphylla Suk. were measured by electrical strain gauges. Spreading the adhesive quantity cannot be excessive or too little when the
strain flakes were glued. If excessive, the glue layer was too thick which would influence the strain flakes’ performance,
and if too little, glues plastered were not firm, which could not accurately transmit the strain. Wood as an orthotropic material,
its modulus of elasticity and poisson’s ratios are related by two formulas: μ ij/Ei=μji/Ej and μ ij<(Ei/Ej)1/2. The results showed that the elastic constants of Betula platyphylla Suk. measured by electrical strain gauges were accurate and reliable. The results of shear elastic modulus G
TL and G
LR show a high linear regression correlation coefficient (>0.95) between the reciprocal of elastic modulus MOE
−1 and the square of the ratio of depth to length (h/l)2, which indicate that shear modulus values measured were reliable by three point bending experiment. 相似文献
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五种家具常用木材弹性常数及力学性能参数的测定 总被引:1,自引:0,他引:1
采用电测法和三点弯曲法对5种家具常用木材的弹性常数及主要力学性能参数进行了试验测定,并根据木材的正交异性原理对试验结果进行了统计分析。对木材物理力学性能参数测定的试验方法进行研究和探讨,为实木家具结构力学设计提供材料性能参考数据。 相似文献
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通过对大兴安岭林业集团公司森林经营部技术推广站白桦强化种子园中的3年生杂交的白桦幼树高生长及径生长资料进行方差分析,结果表明:白桦不同杂交品系间存在显著差异,初步筛选出XBH23×J欧2和XBH23XJ欧3两个优良家系,2个试验组树高、地径的遗传增益分别为47.2~49.5扣26.2~33.0。 相似文献
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Introduction6Birch(BetulaplatyphyllaSuk.)isaphotophilousandbroad-leaftreespecies,whichisdistributedwidelyinthenortheastofChina,especiallyinclearcuttingorburnedforestareasaftertheoriginalvegetationisdamaged(Zhou1986).Birchisjustapioneertreespeciesthroughsecondary-forestsuccession.Sincebirchpopulationoftengrowsrapidlyinalargearea,itusuallyhasagreatamountofseedstorage.Itstimberisanimportantrawmaterialinbuildingmaterials,suchasplywood,veneer,etc..Itsforesightisbroadlyprospectedonexplorationandap… 相似文献
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白桦天然次生林生长规律研究 总被引:1,自引:0,他引:1
系统地了解和掌握林木生长规律,是科学合理经营森林的重要依据。本研究以河北省塞罕坝白桦(Betula platyphylla Suk.)天然次生林为研究对象,利用多年调查的临时样地资料,借助Excel、SPSS11.0和ForStat统计分析软件,对主要林分因子生长进行模拟,以了解其生长规律。结果表明:抛物线方程拟合其立木株数生长过程效果最好,Logistic方程拟合其蓄积量生长过程效果最好,对数方程拟合其胸径、树高生长过程效果最好,Richards方程拟合其材积生长过程效果最好;胸径年平均生长量为0.30cm,速生期前10a;树高年平均生长量为0.25m,速生期为前5a;材积年平均生长量为0.00251m3,速生期前20a,数量成熟龄为38a。 相似文献
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该文研究了不同基质配方对白桦容器苗根系形态及生物量的影响。结果表明:处理1(沼渣∶椰糠∶蛭石=4∶4∶2)比根长、根系总表面积、根系直径及总根尖数均达到了最大值,分别为660.23cm/g、455.39cm2、0.83mm、5997条,分别比对照提高了33.11%,58.49%、62.75%、72.23%。处理1(沼渣∶椰糠∶蛭石=4∶4∶2)地下部分和地上部分生物量均为最大,分别为3.78g与13.71g,与对照相比,地下部分生物量提高88.06%,地上部分生物量提高73.98%。从研究结果可以看出,处理1(沼渣∶椰糠∶蛭石=4∶4∶2)为最优的白桦育苗基质,可作为白桦容器苗优良配方基质推广使用。 相似文献
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白桦伐根萌芽幼、中龄林生长规律的初步研究 总被引:1,自引:0,他引:1
对内蒙古乌兰察布市卓资县上高台林场的白桦伐根萌芽幼、中龄林实施长期封禁,通过固定标准地对白桦萌芽林多项生长因子进行定期调查测定,开展白桦萌芽林不同龄级年均生长量和根系生长发育、林木分化和自然稀疏强度以及立地条件变化对生长的影响等的分析研究,结果表明:全封育的白桦萌芽林树高年均生长量最大期在6~15年之间;胸径年均生长量... 相似文献
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应用隶属函数法以及基因型分组法对白桦(Betula platyphylla Suk.)子代家系优劣和稳定性进行评价和分析,结果表明,参试家系的生长优劣和稳定系存在这差异,生长最优的家系为203310313316和325,而310为生长高产稳产型家系,为适合辽宁丹东地区生长的优良家系,研究结果可以作为白桦优良家系的评价和选择提供理论支持。 相似文献
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为进一步提高木材的实际应用价值,并为森林资源经营提供理论支持,对兴安白桦木材生长轮密度的径向变异进行研究。采集兴安白桦试样21株,对其生长轮密度的径向变化规律进行时间序列分析,依据最小信息量AIC原则,选择ARIMA(0,1,1)为最优模型;白噪声检验结果表明,残差序列为白噪声序列,模型诊断通过;序列预测值与实测值相对误差在10%之内,模型获得较好的预测效果。 相似文献
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林分直径结构是林分内各种大小直径林木的分配状态,它是最基本也最重要的林分结构。了解林分的直径结构,也就对单木生长以及林分竞争所产生的结果有了清楚的认识;探讨林分直径结构动态变化规律更是有利于揭示林分发展规律的实质[1]。本研究以木兰林管局孟滦林场华北落叶松白桦混交林为研究对象,采用标准地调查法对林内胸径大于3cm的林木进行每木检尺,并使用Forstat2.1统计软件对主要树种直径结构分布规律进行研究,研究发现,各树种处于中间径阶的林木株数最多;小径阶林木较少,林分更新较差;综观拟合效果,正态分布、伽玛分布、对数正态分布、二项分布以及泊松分布更能反映出林分的直径分布规律。 相似文献
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白桦不同部位及种源间白桦酯醇含量的差异分析 总被引:2,自引:0,他引:2
以白桦为研究材料,在白桦酯醇提取方法的选择下,采用高效液相色谱仪(HPLC)分析了白桦不同部位和种源间白桦酯醇含量的变化。结果表明:索氏提取和超声波醇提的白桦酯醇含量较高,分别为240.25和239.57 mg/g,而回流法和氯仿浸提的白桦酯醇含量稍低,为207.88和194.09 mg/g。白桦酯醇在白桦不同部位的含量分布差异显著,依次分别为:外皮>枝皮>内皮>芽>叶>根>花粉;13种8年生白桦种源树皮内白桦酯醇的含量为132.45~257.11 mg/g,且种源间差异呈极显著水平。进一步分析可得,同龄树种的生长状况对白桦酯醇的含量影响不显著;而白桦酯醇的含量不仅受自身种源及遗传背景的影响,同时也受到其所处地理位置和气候因素的影响,即属于基因与环境互作的表现性状。 相似文献
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By the methods of morphological anatomy and investigation in the sample fields, the main studies were carried out such as
morphological anatomy of reproductive organs, birch population’s reproductive ages, reproductive allotment value and seed
behavior. The relationship between birch population and their surroundings was studied. The results showed that birch’s flower
organs and its seeds were suitable well for spreading by wind. The seeds by wind can fly far away in a short time. The quantity
of seed spreading greatly varied with different communities. Birch’s reproduction age can be changed in different ecological
surroundings. The reproductive allotment value of birch was obviously different at different reproductive stages. In the mesic
habitat, birch can grow well. The lowest reproductive age of them was 12, average age 15. In most cases the age of branches
to bearing fruits was more than 18. The order of reproductive allotment values was as follows: a flowering phase > flower
bud phase > fruit phase. 相似文献
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《林业研究》2020,31(5)
DNA methylation is widespread in plants and associated with plant development and defense mechanisms. However, the relationship between DNA methylation and plant secondary metabolism has rarely been reported. Here, when birch suspension cells were treated with 5-azacytidine(5-azaC), which blocks DNA methylation, triterpenoid accumulation was significantly promoted and antioxidant and defense enzymatic activity changed.For studying triterpenoid accumulation, 0.1 m M aza C was optimal. A qRT-PCR assay revealed increased expression of genes encoding key triterpenoid biosynthetic enzymes.Evaluation of methylation polymorphisms at CCGG sites showed that the methylation level was lower in cells treated with 5-azaC. These results demonstrated that 5-aza C treatment led to an increase in the production of triterpenoids in cell cultures through a mechanism that involved in DNA methylation, which resulted in the induction of genes encoding the key enzymes. The study providesevidence of a relationship between DNA methylation and regulation of secondary metabolism. 相似文献
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Betulin, oleanolic acid, and betulinic acid are naturally occurring pentacyclic triterpenoids that have significant medicinal value. Considerable amounts of these triterpenoids are available in the out... 相似文献
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