Deformation analysis of timber-framed panel dome structure I: simulation of a dome model connected by elastic springs     

Ying Gao  Masamitsu Ohta 《Journal of Wood Science》2007,53(2):100-107

This study develops an analytical method that enables the simulation of the deformation of timber-framed plywood panel dome structures, of which strength is largely governed by the rigidity of joints. A hybrid truss structure model was employed to analyze this structure. In this model, we aimed to incorporate the mechanical properties of bolted and nailed joints, which were employed to build the structures, although the present investigation focused on the deformation characteristics of a dome in which the panel elements were connected mutually by elastic springs. The results of the theoretical analysis are compared with those obtained by experiments. The simulated results were found to be in good agreement with the results of the experiments under similar loading conditions.  相似文献   

Stand structure of an uneven-aged fir–beech forest with an irregular diameter structure: modeling the development of the Belevine forest, Croatia     

Juro Čavlović  Mario Božić  Andrej Boncina 《European Journal of Forest Research》2006,125(4):325-333

This study focuses on the problem of irregular diameter structure in a silver fir–beech selection (plenter) forest with a “surplus” of large diameter trees and a lack of natural regeneration and small diameter trees. We sampled 274 plots (900 m² each) in the Belevine research site (266.24 ha) in the mountain region Gorski Kotar (Croatia), where diameter (dbh) distribution, diameter increment, and natural regeneration were analyzed in detail. A low density of natural regeneration, weak annual recruitment of small (10 cm dbh) diameter trees (only five trees per hectare), delayed diameter growth of trees, and a low annual rate of trees reaching the next dbh class were attributed to the current irregular dbh structure. The stand development prediction for the next 50 years is based on a simulation model, which considers the current diameter structure, increment, recruitment, and future cutting regime. Intensive cutting in the first of five 10-year cutting cycles (intensity higher of 25%) is needed to initiate natural regeneration and to accelerate growth of young silver fir trees. In the next 50 years, the irregular diameter structure will be gradually improved.  相似文献   

Genetic differences between autochthonous and breeding populations of common cypress (Cupressus sempervirens L.) in Greece     

Aristotelis C. Papageorgiou  Reiner Finkeldey  Hans H. Hattemer  Sotirios Xenopoulos 《European Journal of Forest Research》2005,124(2):119-124

Individuals were selected for resistance against the imperfect fungus Seiridium cardinale Wag in six common cypress populations (Cupressus sempervirens L.) in Greece. A total of 109 resistant clones and 140 trees from their base populations were surveyed at several allozyme loci. The comparison yielded information on changes in genetic variation due to artificial selection. The genetic structure of the breeding populations was similar to their base populations. Nevertheless, the number of rare alleles among the resistant clones had decreased, showing a similar trend at most loci and for most comparisons. Possible implications for breeding strategies are discussed.  相似文献   

Lignin fragments rich in detached side-chain structures found in water-soluble LCC     

Hikaru Aimi  Yuji Matsumoto  Gyosuke Meshitsuka 《Journal of Wood Science》2005,51(3):252-255

The content of the glyceraldehyde-2-aryl ether-type structure in water-soluble lignin–carbohydrate complex (LCC) fractions, which were obtained from Japanese cedar and birch residual wood meal after milled wood lignin isolation, was determined by ozonation. Quite high amounts of the glyceraldehyde-2-aryl ether-type structure were found in water-soluble LCC fractions of both species; about 3–5 times higher than those of other fractions. This result, as well as the high content of the β-1 structure in these fractions shown in our previous reports, suggest that lignin in these fractions has the characteristics of endwise-type lignin, because the glyceraldehyde-2-aryl ether-type structure and β-1 structure are typical characteristics of this type of lignin fraction. These results are in good agreement with the generally accepted hypothesis that the glyceraldehyde-2-aryl ether-type structure and β-1 structure are generated at the same time by a radical coupling reaction. The results also indicated that these two structures are present in close proximity in the lignin.  相似文献   

基于3S技术的森林城市景观结构分析     

叶伟  吴荣良  赖日文  谢雪莉  汪琴  陈思雨 《中南林业科技大学学报(自然科学版)》2015,(1)

以福建省永安市为研究对象,基于3S技术手段,运用景观分析软件Fragstats4.1,计算不同水平上不同景观要素的特征值,对永安市现有城市景观和城市森林景观在类型水平和景观水平上的景观格局进行研究。结果表明:研究区各景观类型分布较为均匀,不存在明显的优势主体;城市森林整体分布不够均衡,研究区还未形成生态功能较为完善的城市森林结构。研究结果可为地区森林城市建设的可持续发展提供决策支持。  相似文献   

天童林场杉木人工林间伐后林下植物结构特征的研究     

王良衍  陈波  陈方达 《浙江林业科技》2003,23(6):5-8,14

对种植26a的天童林场杉木人工林林下植物的群落结构进行了初步的调查研究。结果表明，杉木人工林林下共有植物59种，主要包括樟科、壳斗科、山茶科等．其中分布最多的树种是红楠、栲树、薄叶润楠、细枝柃、南酸枣、枫香、细叶青冈、赤皮青冈、山杜英等；大多数林下植物的高度在2．0～2．5m，有10．6％的植株高度在3．5～4．0m，大于6m的植株数量约占全部的6．8％。林下常绿树种的胸径多在1．0—3．5cm，落叶树种南酸枣和枫香的平均胸径较大，分别为3．6和6．2cm。  相似文献   

Safety of the tram car for slopes examined by stress analysis of the ground structure     

Masaki Jinkawa  Hirokazu Yamaguchi  Kuniaki Furukawa  Toshiaki Satake  Hiroshi Kobayashi 《Journal of Forest Research》2006,11(2):77-88

For monorail systems, it is very important to ensure the safety of the ground structure. We developed a tram car for slopes that utilizes the mechanism of the monorail and analyzed the stress of the ground structure that had double rails. First, we divided the ground structure into seven components, and formulated a procedure for calculating the stress of the ground structure. As a result, the stress that acts upon the main rail and the main rail connecting part was near the allowable stress, and each calculated value was within the allowable stress. We measured the stress by running the vehicle, and compared the measured values with the calculated values. As a result, some measured values were larger than the calculated values. However, the ratio of measured value to allowable stress was 90% or less. Finally, we calculated the static loading coefficient for each part, results of which were as follows: main and subrail: 1.1; rail connection part and prop foundation part: 1.0; rail installation part: 1.3. In the recalculations, it became clear that the recalculated values exceeded the allowable stresses. These results suggest that we need to review the ground structure materials.  相似文献   

福建永春油杉天然林群落结构及物种多样性研究     

邹秀红  郭志坚  刘建斌  吴丽清  郭连城 《林业科技开发》2005,19(6):27-29

在对福建永春油杉天然林群落系统调查的基础上,对该群落的植物区系成分、结构特征和物种多样性进行了研究.结果表明：该群落共有维管束植物131种,隶属于60科111属 .包括藤本植物在内的高位芽植物占总数的71.75%,区系组成以泛热带成分较高 ,群落结构较为复杂.物种多样性指数（Shannon-Wiener指数）以草本层最高,为2.245 1.  相似文献   

家具设计新理念--智能家具     

王洪亮  于伸 《木材工业》2006,20(1):31-33

概述智能家具的概念、理论结构,总结国外智能家具的种类以及智能家具的设计原则,分析我国智能家具研发、设计等方面存在的问题,提出发展措施,并对我国智能家具的发展进行了展望.  相似文献   

Chemical structures of the condensed tannins in the fruits of Diospyros species     

Fumiaki Nakatsubo  Kenichi Enokita  Koji Murakami  Keizo Yonemori  Akira Sugiura  Naoki Utsunomiya  Suranant Subhadrabandhu 《Journal of Wood Science》2002,48(5):414-418

The structural variety of the condensed tannins (proanthocyanidins) in the fruits of 16Diospyros species are reported. Eleven species contained condensed tannins mostly consisting of a mixture of catechin (CA) and gallocatechin (GCA) repeating units; the other five species did not. The GCA content in the CA-GCA total varied from 0.3% to 84.6%. The number of esterified gallic acid per one flavan repeating unit (degree of galloylation, DG) ranged from 0.01 to 0.89. The GCA content was found to be proportional to the DG values. Thus, 16Diospyros species tested may be classified into five groups by the analytical data of their condensed tannins. It may be interesting to compare their structural characteristics with those of the condensed tannins in other fruits, leaves, woods, and barks from the viewpoint of their biosynthesis and function in the plants.Part of this paper was presented at the 46th Annual Meeting of the Japan Wood Research Society, Tokyo, April 1995  相似文献