Hygrothermal effect of bamboo by dynamic mechanical analysis

Dynamic properties of bamboo, Phyllostachys pubescens, with moisture content (MC) ranging from −130 to 130°C, were studied by dynamic mechanical analysis (DMA). The results showed that the hygrothermal effect on dynamic mechanical properties was negative. The storage modulus decreases with increasing temperature and MC, and glass transition temperature decreases with increasing MC. The glass transition temperature and tan delta of bamboo were 30.5°C, 0.02 and 10.61°C, 0.04, when MC was 10% and 34%, respectively. __________ Translated from Journal of Nanjing Forestry University (Natural Sciences Edition), 2006, 30(1): 65–68 [译自: 南京林业大学学报(自然科学版), 2006, 30(1): 65–68]     

华山松木蠹象自然种群生命表初报

通过林间定期周年跟踪观察研究,编制出了华山松木蠢象自然种群生命表,并对影响华山松木蠢象自然种群的关键阶段进行了分析,计算出华山松木蠢象自然种群趋势指数,初步对华山松木蠹象种群变化趋势进行了预测.     

FRW阻燃胶合板的DMA分析

目前世界范围内木材资源短缺的情况日益加剧,发展人造板工业已成为世界各国解决木材资源严重不足的重要途径.其中,胶合板作为室内装饰的主要材料,其产量和需求量都在急剧增长.我国胶合板产量从1980年的33.00万m3增长到2004年的2 098.62万m3,呈现大幅度增长的趋势(张文标等,2000).但由于普通胶合板具有易燃性,在许多领域的应用上受到限制.因为一旦发生火灾,不仅造成重大的经济损失,而且往往会发生人员伤亡.1950-2003年全国共发生火灾4 177 730起,直接经济损失2 434.525 1亿元,因火灾死亡174 855人,受伤329 352人.     

毛乌素沙地臭柏年轮生长动态的研究

以毛乌素沙地天然臭柏为材料 ,用实体解剖镜和光学显微镜研究观察臭柏的年轮形态特征 ,应用树干解析法研究毛乌素沙地沙丘顶部臭柏和滩地臭柏的径向生长和伸长生长动态。结果表明 :沙丘顶部臭柏偏心生长明显 ,长径与短径比为 14 0 .36 % ,伪年轮发生频率为 12 .0 7% ;滩地臭柏偏心生长不明显 ,长径与短径比为 10 5 .2 2 % ,伪年轮发生频率为 1.80 % ;根据年轮数推断 ,沙丘顶部臭柏群落的年龄至少有 12 3a以上 ,滩地臭柏年龄有 5 0a以上 ;沙丘顶部臭柏径生长缓慢 ,生长过程中没有明显的峰值 ,年平均生长量为 0 .94mm ,累积生长曲线的S型特征不明显 ;滩地臭柏的径生长高峰出现在 35年 ,年平均生长量为 1.5 1mm ,是沙丘顶部臭柏的 1.6倍 ,累积生长曲线的S型特征也不明显 ;沙丘顶部臭柏的匍匐茎长度与年龄之间表现出指数函数关系 ,而滩地臭柏的匍匐茎长度与年龄之间存在着显著的线性相关关系     

河南省森林碳储量及动态变化研究

利用河南省1949—2003年间8次森林资源清查资料,建立不同优势树种生物量与蓄积量之间的回归方程,对河南省54a来森林的碳储量进行了推算。结果表明:河南省54a间森林的总碳储量虽然存在一定的波动现象,但总体呈上升的趋势。全省森林的总碳储量由1949年的2 863.91万t C增加到2003年的4 673.43万t C,共增加1 809.52万t C,年均增加33.51万t C。阔叶林占全省各时期森林总碳储量的80%以上,栎类和杨树两个树种占主导地位。河南森林幼、中龄林占的比重较大。全省森林平均碳密度为22.86~23.64t C/hm2,远低于全国、世界的平均水平。     

The method for designing the profile of forest roads supported by genetic algorithm

This study examines a method for designing an optimum profile of a forest road in a short matter of time. In this method, a genetic algorithm (GA) searches for points where the gradient changes and dynamic programing (DP) designs the longitudinal slope. This method can be applied to the ground heights of an actual forest road. The evaluation function of the DP assesses the total expenditure. The inverse of this function is the fitness function. Crossover and mutation are operators of an evolution simulation of a GA. They are each repeated 20 times and 420 profiles are designed and assessed, all within about 10 min. A comparison of the profile designed by the GA with that of an actual forest road shows only one section where the formation level differed substantially. Overall, both profiles seem to show a high degree of correspondence. From this result, we believe that the profile designed by the GA is best, or the one of the best. A conventional method takes about 65 h to calculate all changing points of gradients. However, by using the GA, the calculation time was reduced to about 1/389 that of the coventional method, showing that the method which uses the GA through the profile design is very useful.     

Characterization of wood-based multi-material systems under dynamic impact stress

ABSTRACT

Due to its naturally grown properties, wood has played a rather subordinate role as a material for technical applications up to now. In this paper, multi-material systems based on veneers of beech (Fagus sylvatica) with different reinforcing variants were investigated. In addition to the influence of different adhesive systems (urea formaldehyde and polyurethane), the effect of reinforcing by aramid fiber fabric and stainless steel foil in different climates was examined. At the center of the investigations were dynamically sudden loads, in the form of impact bending and dart drop tests (penetration and impact mode). It has been shown that the use of the reinforcing materials leads to a significant improvement in material properties. The penetration energy of the composites reinforced with the aramid fiber fabric could be increased by 43%. The maximum force in the dart drop test (impact mode) could be increased by 29% with the stainless steel foil, the damping decreased by 48%. The aramid fiber reinforcement achieved an increase in impact resistance by 27% in impact bending test, the steel reinforced achieved an increase of 39%. A clear dependency on both, the climate and the adhesive within the composite, could be demonstrated.     

Study on dynamics of stem form of Korean pine trees in natural forest stand

INTRODUCTIONThcstcmfonl1ofnaturalKorcanpincforcst.ot\ingtothcsupprcsscdandshadcd,isvcry'difTcrcntt`iththatofplantation.Itis\'cry't'aluabIctostud}'thcstcmfonnforn1orcac-knot`lcdgcabouttl1ctrccd)-nan1icsofnaturalKorcanpinc.n1crcl1asbccnconsidcrabIcrescarchontl1cstc111for111cquationsasatoolforforcstmanagcmcnt,butitalmostbasnorclationshipt`-iththcbiologicalgrowthproccss.soitisx'ery'dimcuIttouscthccquationtoanalxrsisthcd\'amicsofstclllform.Hcrcthcdct'clopmcntofstcmformt"ascxPCctcdfornotonI\…     

落叶松人工林间伐技术优化研究*

本文以林分生长模型为基础，将林分的经营指数作为状态变量，将主伐时林分平均直径作为目标，将达到这一目标时林分总收获蓄积量作为指标函数，建立了离散确定性动态规划模型，编制了计算机模拟系统。利用此系统即可对落叶松不同培育目标下的最佳间伐时间、间伐强度和主伐年龄等进行决策。结果表明，优化决策方法在保留株数、间伐次数和总收获蓄积量上都优于一般决策方法，它既可对落叶松林分进行生长预测，也可为制定经营单位的经营     

中低强度间伐对杆材阶段马尾松林生物量的影响

对杆材阶段不同密度的马尾松林在低强度间伐后生物量的动态变化进行了分析对比，结果表明间伐后平均木的单株生物量和各器官生物量随密度增加而减少；随林分年龄的增加，单株生物量与树干、皮、根的生物量因积累而增大，但枝、叶的生物量先增加后减少，在林分年龄为20a时达到最大值，随后又接近间伐前的数值；林分生物量随年龄增加而增加，其中密度为3000株