共查询到19条相似文献，搜索用时 262 毫秒
1.
西江林业局尾巨桉人工林一元材种出材率表编制 总被引：1，自引：0，他引：1
在广东省西江林业局尾巨桉无性系人工林中选择并设置70个标准地,分别进行林分因子调查,同时选择163株样木以2.0 m或2.6 m段材长分径阶进行样木伐倒造材,以实际经济材造材出材率为基础拟合并选择较优的单株木一元材积比方程,然后根据材积比方程进行理论造材并编制尾巨桉单株木一元经济材出材率表;接着利用单株木一元经济材出材率表对所调查的标准地进行理论造材,以林分理论造材出材率为基础拟合并选择较优的林分一元材积比方程,最后根据材积比方程研制尾巨桉林分一元经济材出材率表。所编制的数表均符合国家精度检验标准,可为本地区桉树生产经营提供参考。 相似文献
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张羽 《内蒙古林业调查设计》2008,31(3):48-51
在永安市巨桉(Eucalyptus Garndis)林分选择并设置10个标准地,分别进行林分因子调查,以4m段材长分径阶进行样木伐倒造材,应用区分求积式进行材积计算,以实际造材各材种出材率为基础拟合一元材积比方程,根据相关系选择较优的一元材积比方程进行理论造材并编制巨桉林分一元材种出材率表,并进行精度检验,表明精度可达90%以上,可为桉树生产提供一定的参考。 相似文献
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在苍梧县共青林场等集体林场的伐区,随机量测样木548株,年龄为20～21年,直径分布6～26cm,树高6～16m,按2m区分段,量测各段中央处的带皮直径、去皮直径,并现场造材,记录不同材种的出材率。并选择模型7为最适宜削度方程,方程11为最适宜材积方程,确定了不同材种不同材长的出材率,编制了苍梧县杉木出材率表。 相似文献
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贮木场生产和经营管理的好坏,是影响林业企业经济效益的重要环节。因此,有必要对原条造材及原木售价的承包与计算问题提出如下意见,供林业企业工作参考。我们认为,林业局或林场确定贮木场第二年的造材出材率(指平均出材率)和原木平均售价,从而确定其总产值并承包给贮木场,可根据贮木场前一年的原条造材出材率、原木平均售价和第二年的伐区资源状况来确定。林业 相似文献
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应用古田县近年来伐区调查实际造材数据,以林分平均胸径和平均高为自变量,分别以林分总出材率和规格材出材率为因变量,选择理查德方程建立马尾松人工林分一元和二元材种出材率模型。经拟合结果分析,以林分平均胸径D和平均高H的组合D2H作为自变量,其拟合效果和预估精度要高于只用一个平均胸径或平均高的单因子林分材种出材率模型。并编制了林分一元和二元材种出材率表。 相似文献
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采用现场模拟造材方法,建立了各树种(组)单株材种出材率模型,提出了编制单株各树种(组)单株树木材种出材率的基本原理和方法,通过数理统计原理编制吉林省各树种(组)材种出材率。 相似文献
10.
苍梧县杉木削度方程与材积比方程研究 总被引：1，自引：0，他引：1
李宏 《云南林业调查规划设计》1998,23(1):8-14
在苍梧县并青林场等集体林场的伐区，随机量测样木５４８株，年龄为２０～２１年，直径分布６～２６ｃｍ，树高６～１６ｍ按２ｍ区分段，量测各段中央处的带皮直径，去皮直径，并现场造材，记录不同材种的出材率，并选择模型７为最适宜削度方程，方程１１为最适宜材积方程，确定了不同材种不同材长的出材率，编制了苍梧县杉木出材率表。 相似文献
11.
A mill study of 62 trees, in which boards were reassembled into their original logs, permitted the construction of wood quality maps. In this instance stiffness profiles were obtained from butt to upper-top logs, based on machine stress grading of all boards and then averaging values from the 62 trees. Traditionally the butt log has been perceived to be the most valuable log in a tree, because it is bigger and gives a higher recovery of lumber. However, it is shown to contain a wide cone of very low stiffness wood that is confined to the first 2.4–2.7 m above ground level. Above this point stiffness gradients become cylindrical with no noticeable decrease in stiffness up the tree stem. Stiffness in all logs increased radially from pith to cambium with the greatest change being associated with the wood nearest the pith. The low stiffness at the base of the tree suggests that an alternative log bucking strategy should be considered, namely cutting a short 2.4–2.7 m butt log for plywood/LVL or for bolter sawing and only cutting standard length logs above this point.The least stiff logs (lowest 20%) yielded lumber that had an average stiffness that was over 1 GPa less than the average for the population. A case can be made for separating these logs and processing them differently. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(3):368-377
A computer program of a forward reaching algorithm of dynamic programming is presented for optimal log bucking. The application is implemented using an object-oriented programming approach. Sensitivity analyses were applied for evaluating the effects in terms of economic value and usable volume, and of altering the price system for saw wood. The data used consisted of 451 Norway spruce (Picea abies (L.) Karst.) stems collected from 13 forest sites located in three regions in Norway. Grade I and Grade II saw wood and pulpwood were used. The mean timber value increased approximately 1% when the new price system was introduced. The value obtained by introducing the new prices varied between the sites (0.1%-1.6%) as well as between regions (0.3%-1.6%). The analyses based on taper equations over-estimated the total value for all the alternatives. Finally, decreasing the width of stem sections and increasing the number of log length alternatives increased the total value of the sample trees but increased the computation time. 相似文献
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Malinen Jukka; Kilpelainen Harri; Piira Teppo; Redsven Visa; Wall Tapio; Nuutinen Tuula 《Forestry》2007,80(3):309-321
The aim of the study was to compare model-based approaches inthe prediction of timber assortment recovery with bucking simulationbased on detailed stem data. A correction function for the totallength of saw log fragments and two optional saw log reductionmodels, that is, the MELA96 version and MELA05 version, wereapplied. In the bucking simulation, the volumes by timber assortmentswere calculated using a bucking-to-value simulator. The predictionof saw log recoveries varied between the bucking simulationand different versions of saw log reduction models. The levelof the reduction from the MELA96 version was at the same levelas from the bucking simulation where defects were taken intoaccount, but the saw log reduction had a very low variance dueto a small amount of independent variables. The saw log reductionof the MELA05 version included more variation although the levelof the reductions was higher and the variation did not meetwith the bucking simulation. As a conclusion, the model-basedapproaches seem applicable at least for the prediction of sawlog recovery in the large area forest inventories where thevariance of the standwise timber assortment recoveries neednot be predicted. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(3):258-263
Abstract The objective of this study was to test harvester group-guiding methods by comparing how the total log output distribution of independent harvesters differs from the total log output distribution of group-guided harvesters. In this simulation study four harvesters worked in their own stands in the same region for an identical target, given by a sawmill. Group-guiding was done by utilizing other harvesters’ bucking outcomes to fulfil the target log distribution better. Harvesters were combined to form a group in an adapting phase where a new price list was formed. For group-guiding, four different price list adapting methods were developed. There were five different simulations: four with adaptation and one reference simulation without adaptation. Apportionment degree and log/pulpwood proportions were calculated to compare the difference between the methods and reference simulation. With group-guiding, by adapting the price list harvesters reached the target distribution better than working independently. The best group-guiding method fulfilled the target distribution almost 9% better than independently working harvesters. However, the pulpwood proportion increased as a result of using the group-guided method. 相似文献
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原条造材优化设计的遗传算法 总被引：2，自引：0，他引：2
本文首次应用遗传算法对原条造材进行优化设计。每个可能造出原木段为变量x_i,以造出各种规格材累计价值为目标函数值,当满足各种约束条件时目标函数值最大的造材方案为优化方案,算法设计运行结果表明该方法优化造材效果极为理想。 相似文献
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M. Perstorper P. J. Pellicane I. R. Kliger G. Johansson 《Wood Science and Technology》1995,29(3):157-170
Summary The overall aim of this study and series of papers is to address the key variables for timber quality and to optimize the utilization of Norway spruce timber with respect to construction purposes. It is the end-user's degree of overall satisfaction that determines the quality of a product. Therefore, the performance of structural timber cannot solely be defined by mechanical properties. Geometric performance (warp) must be improved if timber is to continue as an important building material.An experimental study of the spatial variation in warp and bending properties of fast-grown Norway spruce is introduced. In this paper, the growth characteristics are presented as a function of stand and location in the tree. The knot area ratio (KAR) was considerably higher in the core (0.31) compared with timber closer to bark (0.21). The top log studs had higher KAR (0.38) than the corresponding butt log studs (0.31). The average grain angle was 3.5% ( 2°) and appeared not to vary radially. The presence of compression wood was much more common in the top log timber (75%) than in the butt log (44%). However, no consistent radial variation in compression wood was found.The authors gratefully acknowledge the support from EEC Forest programme, Contract No. MA2B-0024 and from Södra Timber AG from NUTEK project No. 9100554 相似文献
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Farshad Keivan Behjou 《林业研究》2013,24(3):585-589
Waste wood was studied in an economic enterprise by logging, function, tree species and log size in four Caspian hardwood sites. Damaged logs were recorded with additional information obtained for the location, dimensions and type of damage. The data were analyzed statistically to determine significant differences of damage during logging process. The results indicated that animal harvesting systems cause more volume (40.5% of log volume) and value loss (89.5 $·m?3) to logs than mechanized harvesting systems (13.9% and 6.0 $·m?3), also bucking resulted in significantly more volume (9.9% of log volume) and value loss (5.5 $·m?3) when compared to skidding (0.2% of log volume and 0.2 $·m?3), decking (0.4% of log volume and 0.2 $·m?3) and loading (0.2% of log’s volume and 0.3 $·m?3) operations. Study showed that the processes of skidding, decking and loading of logs have very little impact on damage levels. Volume and value losses of damaged logs are not sensitive to tree species and log size. The information from the field study is important in creating new guidelines or training to help minimize hardwood log damage during the timber harvesting process. 相似文献
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本文研究了国内外原条量材设计的理论和实践。同时,提出建立原条量材设计赋权有向图的模型。用最长路径法求解最优造材方案。并重点阐述了采用Visual Basic编写原条量材设计的Windows环境下的优化软件。 相似文献
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《Scandinavian Journal of Forest Research》2012,27(4):357-362
The impact of log position in European Larch (Larix decidua Mill.) tree on the physical, mechanical, and surface properties of the particleboard was investigated. The logs were divided into five segments from the butt to the top of tree, which were 0–3 m, 3–6 m, 6–9 m, 9–12 m, and 12–15 m, respectively. The fiber length and wall thickness of the wood decreased with the increase in the tree height while the lumen diameter decreased. Similarly, the amount of cellulose and lignin decreased with the increase in tree height while the amount of hemicelluloses increased. The highest solubility values (hot and cold water, NaOH, and alcohol-benzene) and pH of the wood were found in the butt log, followed by the middle log, and top log, respectively. The physical (thickness swelling, water absorption) and mechanical properties (modulus of rupture, modulus of elasticity, and internal bond), and surface quality (surface roughness and contact angle) of the particleboards were negatively affected by increasing tree height. The best properties were obtained for the particleboards produced from the particles of the butt log (0–3 m). 相似文献