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木材导热系数的理论表达式(英文) 总被引:7,自引:0,他引:7
本文从木材的微观结构出发,应用物理力学导出木材弦向和径向导热系数的理论表达式 ,计算20种左右木材导热系数并与相同条件下的实验值比较,平均误差在5%附近,两者吻合 程度令人满意。 相似文献
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利用神经网络所具有的输入-输出之间的高度非线性映射关系,给出一种利用BP神经网络模型预测木材径向导热系数的方法.为了提高网络模型的泛化能力,采用规则化调整的方法.仿真结果表明:利用文中所提出的神经网络模型能够较准确、快速地预测木材径向导热系数的变化,其精度高于推导出的木材径向导热系数的理论公式. 相似文献
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本文从木材的化学组成和微观结构出发,从理论上推导出木材导温系数的理论表达式,应用该表达式计算20种左右木材弦向和径向导温系数,并与实验值对照,得出木材弦向导温系数与理论值的平均误差在7.2%,木材径向导温系数与理论值得误差为6.2%。 相似文献
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利用木材天然多孔的网状结构及富含活性基团羟基和羧基的特性,通过冷热水循环结合冷冻处理的方式,提高了木材的渗透性;利用脉冲式真空浸渍法将氧化石墨烯(GO)与木材充分结合,再使用热压法将木材内部的GO还原,使木材具有三维导电性能。结果表明:当GO质量浓度为3 mg/m L,压缩率为45%,热压温度为220℃,热压时间为45 min时,木材/石墨烯三维导电材料(3D-W/r GO)性能最佳,纵向、径向和弦向体阻率分别为3.0×102,7.0×102和3.9×103Ω·cm。对3D-W/r GO的形貌、结构和性能进行研究,激光共聚焦显微镜和扫描电子显微镜分析结果表明,还原性氧化石墨烯(r GO)在木材管道中均匀分布;X射线光电子能谱和傅里叶红外光谱表明,GO以酯键和氢键的形式与木材紧密结合,且r GO在木材机体中的还原程度较大;X射线衍射光谱分析显示,材料结晶度数值减小;综合热分析表明,材料的热稳定性有所提高。和木材相比,3D-W/r GO的力学性能及尺寸稳定性均有明显提升,是一种极具前景的导电材料。 相似文献
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Brief report on theoretical research upon wood thermal property 总被引:2,自引:0,他引:2
lntroductionThermaIpropertiesofwoodsuchasspecificheat,thermalconductivityandsoonareparameterswhichisrequiredinscientificresearchandheattreatmentofwood.BecausewoodisakindofnaturaIpolymerorganismwhosechemicaleIementandmicrostruc-tureareverycomplicated,it'sverydif=ficulttostudyitsthermaIpropeFtytheoreticalIy,therefOre,foraImostonecentury,itwasbymeansofexperimentthatthescientistsathomeandabroadstudiedthethermalpropertyofwooddirectIy(Dunlap19121KotImann1968,Cheng1985,Gao1985,Zhang1986)Buttheq… 相似文献
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Thermal conductivity and diffusivity of wood 总被引:5,自引:0,他引:5
Summary Transient simultaneous measurements of thermal conductivity and diffusivity of Swedish wood have been performed with the
plane source technique on oven-dry hardwood (birch) samples at room temperature and at 100 °C. The influences of temperature,
density, porosity and anisotropy on thermal conduction were investigated. The measurements were done in longitudinal (parallel
to the grain) and transverse (intermediate between radial and tangential) directions. As the temperature increased from 20
to 100 °C, the thermal conductivity of each sample increased slightly for both longitudinal and transverse directions. The
effect of density and porosity on the thermal conductivity may be related to the presence of other scattering mechanisms such
as voids and cell boundaries. It seems that the dominant mechanism of heat transfer across the cell lumina in these types
of wood is the heat conduction through the voids. An attempt was made to explain the behaviour of the effective thermal conductivity
by adopting a model based on the ratio between heat conduction in parallel and serial layers of gas, liquid, and solid phases.
Received 7 May 1997 相似文献
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To investigate the effect of wall thickening around cell corners on the tangential Young's modulus of coniferous early wood, tapered beam cell models in which the variation of the cell wall thickness in the axial direction was taken into account were constructed for seven species. Their tangential Young's moduli were compared with the experimental results. The calculated Young's moduli of tapered beam cell models were larger than those of the models composed of the cell walls with uniform thickness, although both models showed almost the same density. For some species the calculated Young's moduli of the models in which the cell wall thickness increased curvilinearly in the axial direction were much closer to the experimental values. The reduction of the radial cell wall deflection due to the increase of the stiffness around cell corners was considered to increase the tangential Young's modulus of a wood cell.This report was presented at the 49th annual meeting of the Japan Wood Research Society, Tokyo, April 1999 相似文献
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木材结构特性对氧指数的影响 总被引:2,自引:0,他引:2
采用氧九法对4种树种木材、5种阻燃物质燃烧特性的研究发现,未阻燃木材的氧指数在纵横向上有差异性,纵向高于横向,径弦向差异很小。这主要是木材结构各向异性以及各方向上的导热系数不同所致。木材树种不同氧指数也有差异,原因之一密度不同所致。阻燃处理可使方向上的的差异逆转,即横向高于纵向。同一阻燃物质对不同树种木才的作用效果不同,即树料与阻燃物质之间存在适应性问题。树种铎氧指数有很大影响。 相似文献