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从体积置换法测量木材气体渗透系数的基本原理出发,针对水柱上升和水柱下降两种体积置换法的测量装置,分析了体积置换法测量过程中气体渗透压强的变化,以及非稳态条件对体积置换法测量结果的影响.并详细推导了测量中的有关计算式和对非稳态测量补偿的修正因子.此外,运用动力学分析方法,论证了气体渗透压强在测量中的线性变化.其中关于测量的计算及其修正的关键设定的合理性,进一步从理论上阐明了体积置换法测量木材气体渗透系数的精确性. 相似文献
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在包装、家具框架中L型构件是一种比较常见的结构形式.本文通过分析跨距对木塑L型构件结构强度和连接结构强度的影响,得出以下结论:跨距对木塑L型构件结构强度的影响非常显著,跨距越短,结构强度越大;跨距对连接结构强度影响也很大,跨距在190mm左右时,连接性能最好. 相似文献
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Thirty types of three-ply parallel- and cross-laminated woods were prepared from five species, and their static bending strength performance were investigated. The modulus of elasticity (MOE), proportional limit stress, and modulus of rupture (MOR) perpendicular to the grain were increased by cross-laminating, and the extent of the increase increased with decreasing density of the species. The measured values of MOE parallel and perpendi-cular to the grain of parallel-laminated woods and perpendicular to the grain of face laminae of cross-laminated woods were approximately equal to those calculated from true MOEs of individual laminae. However, the MOE parallel to the grain of face laminae of cross-laminated woods was much lower than the calculated MOE owing to the effect of the deflection caused by shear force on the MOE. The percentage of deflection caused by shear force versus total deflection (Y
s) showed high values, from 16.1% (buna) to 40.5% (sugi), and it decreased linearly with increasing shear modulus in the cross section of the core. In addition, there was an extremely high positive correlation between the MOR and the measured MOE parallel to the grain of face laminae of cross-laminated woods. The MOR was also highly dependent on the shear modulus in cross section of the core.Part of this paper was presented at the 50th Annual Meeting of the Japan Wood Research Society, Kyoto, April 2000 相似文献
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新型智能伐根清理机器人切削力的计算 总被引:1,自引:0,他引:1
本文是国家“863”项目——新型智能伐根清理机器人设计计算的一部分。切削力的大小是计算切削功率、设计切削加上设备和刀具的主要依据。本文根据伐根清理机器人设计的要求。以刀具旋切时的最不利情况——横锯切削为计算切削力的依据。适当选取修正系数计算出伐根机切削力及切削功率。乘以安全系数。以此作为机器人驱动元件——液压马达功率选择的依据。 相似文献
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In a detailed study of the relation between the deflection caused by shear force and the constitution of a laminated material
beam, we derived an equation for calculating the shear modulus of a laminated material beam from the shear moduli of individual
laminae. The validity of the derived equation was investigated using crosslaminated wood beams made with five species. The
calculated shear moduli parallel to the grain of face laminae ranged from 48.3 MPa to 351 MPa, while those perpendicular to
the grain of face laminae ranged from 58.0 MPa to 350 MPa. The calculated shear moduli increased markedly with increasing
shear modulus in a cross section of perpendicular-direction lamina of a cross-laminated wood beam. The calculated apparent
modulus of elasticity (MOE) of cross-laminated wood beams agreed fairly well with the measured apparent MOE values. This fact
indicated that the apparent MOE of cross-laminated wood beam was able to be calculated from the true MOE values and shear
moduli of individual laminae. The percentage of deflection caused by shear force obtained from the calculated apparent MOE
(Y
sc) was close to that obtained from the measured apparent MOE (Y
s) and there was a high correlation between both values. From the above results, it was concluded that the derived equation
had high validity in calculation of shear modulus of a cross-laminated wood beam. 相似文献
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The effects of pasture fertilization frequency and two vertical positions in the stem on elasticity and strength parameters
during static bending (modulus of elasticity, stress at proportional limit, modulus of rupture) of Pinus radiata wood growing in a silvopastoral system were evaluated. Twenty-seven trees were selected randomly from three silvopastoral
trials established at Tanumé Experimental Center (34°9′–34°15′ S; 72°53′–72°59′ W). The results indicated that pasture fertilization
frequency had no significant effect on the physical and mechanical parameters evaluated. However, the vertical position in
the stem did have a significant effect on stress at the proportional limit and on the modulus of rupture due to different
average values for the annual ring width and nominal density found in the specimens obtained from logs at two different heights
of the stem.
Received: February 20, 2002 / Accepted: June 5, 2002
Acknowledgments The authors thank the following institutions and people for their support: CONAF, VI Region; Dr. Rolando Rodríguez, CONAF
VIII Region; Cesar Cabrera, Forestry Engineer, CONAF VI Region; Osvaldo Herrera, Director of Experimental Center “Tanumé”;
Dr. Manuel Sánchez, Faculty of Forestry Sciences, University of Concepción; Dr. Glenn Hofmann, Faculty of Physics and Mathematics,
University of Concepción; Alex Opazo, M.Sc.(C), Faculty of Forestry Sciences, University of Concepción; Staff of Experimental
Center “Tanumé”.
Correspondence to:M.H.R. Vidal 相似文献