针叶树材纵向气体渗透的三维流阻网络

气体在木材中的渗透是通过木材内的孔隙通道进行 ,而木材内的孔隙结构非常复杂 ,在纵向、径向、弦向的连接特性均不相同。以往关于针叶树材气体渗透的模型或理论 ,只考虑针叶树材内气体渗透通道在 1个或 2个方向上的连接。本文根据针叶树材管胞流阻和管胞在纵向、径向、弦向的连接特性 ,建立了一个描述针叶树材纵向气体渗透性的三维流阻网络 ,并运用重正化变换求解出流阻网络的流阻 ,计算了针叶树材气体纵向渗透系数。所得马尾松木材气体纵向渗透系数计算值与其测量结果进行比较 ,两者十分吻合 ,表明本文关于针叶树材气体纵向渗透三维流阻网络理论的科学性     

试样加入-离子选择性电极法测定氟

建立了一种离子选择性电极法测定氟的新方法.该方法在体积为100.0 mL、量浓度为1.000×10-4 mol·L-1的标准溶液中加入1.000 mL 较高浓度试样,加入前后测定其电动势,由这两个电动势和溶液体积计算试样的含氟量.10次测定的标准偏差S为0.0 027～0.0 039,相对标准偏差SR为0.017～0.039,3个水平、6次测定的回收率在95.0 %～100.8 %之间.该方法用于分析工业废水和化学试剂简便快速、准确可靠,得到了满意的结果.     

针叶树材径向和弦向气体渗透的三维流阻网络

将针叶树材气体渗透的三维流阻网络理论进行了扩充 ,提出了气体径向和弦向渗透次级流阻网络的二维等效流阻网络及二维等效流阻网络流阻基元的确定和等效流阻的求解方法 ,将三维流阻网络从关于针叶树材气体纵向渗透性研究 ,扩展到针叶树材气体径向和弦向渗透性研究。提出了针叶树材径向和弦向气体渗透三维流阻网络理论 ,计算了马尾松试件径向和弦向渗透系数 ,并与测量值进行比较 ,结果表明两值相符合。将本文的针叶树材径向和弦向气体渗透三维流阻网络理论与此前关于针叶树材纵向气体渗透的三维流阻网络工作相结合 ,可以使用三维流阻网络计算针叶树材纵向、径向、弦向的气体渗透系数 ,其在木材干燥、改性、防腐有应用价值     

一种新型土白蚁巢探测仪

利用土白蚁巢内气体CO2浓度是空气中CO2浓度20～333倍的特性,提出全新的土白蚁巢气体探测技术,即通过蚁道抽取蚁巢内气体,测量其CO2含量,从而达到探测土白蚁巢的目地,据此成功研制了土白蚁探测仪,该探测仪重量<2 kg,探测所需时间<1 min,使用环境温度-10℃～50℃,探测准确率100%.     

基于非稳态法测定木材水分扩散系数

锯材在纤维饱和点以下干燥时,水分的迁移过程主要是以非稳态扩散形式进行的,非稳态扩散指木材内部的水流通量和含水率梯度随时间和空间而变化。为了给木材干燥提供依据,采用非稳态法在一定的试验条件下测定了木材的水分扩散系数,探讨了不同材种、干燥介质温度、初始含水率、纹理方向对扩散系数的影响。结果表明:扩散系数与树种有一定的关系,通过比较,樟子松的扩散系数为7.06×10~(-6)cm~2/s,杨树的扩散系数为9.61×10~(-6)cm~2/s,杨树的扩散系数大于樟子松的扩散系数;在纤维饱和点以下,初始含水率30%时樟子松的木材水分扩散系数为7.54×10~(-6)cm~2/s,25%时为7.06×10~(-6)cm~2/s,20%时为6.61×10-6cm~2/s,15%时为6.37×10~(-6)cm~2/s,初始含水率越高,水分扩散系数越大;在相同条件下,干燥介质的温度为90℃、80℃、70℃、60℃、50℃时,对应的樟子松木材水分扩散系数分别为8.04×10~(-6)cm~2/s、7.32×10-6cm~2/s、6.63×10~(-6)cm~2/s、5.94×10~(-6)cm~2/s、4.91×10~(-6)cm~2/s,扩散系数随着温度的升高而增大;在不同的纹理方向,木材水分扩散系数不同,樟子松纵向、径向、弦向的扩散系数分别为7.06×10~(-6)cm~2/s、3.63×10-6cm~2/s、2.14×10~(-6)cm~2/s,由大到小依次为纵向、径向、弦向。     

基于森林资源连续清查体系的贵州省杉木林分结构及有机碳储量动态变化

基于森林资源连续清查数据,研究了2000~2010年间贵州省杉木林分生物量及有机碳储量的动态变化。结果发现2000、2005和2010年杉木林生物量及有机碳储量分别为24.6334×10~6 t、35.7368×10~6 t和46.9948×10~6t,以及13.0481×10~6 t、18.9401×10~6 t和24.7912×10~6 t。生物量及有机碳储量呈持续增长趋势。杉木林样地数量持续10年保持444个,没有增加也没有减少,表明杉木林得到有效保护。0~10cm、10~22cm和≥22cm径级的样地数量分别增加-19.59%、20.72%和-1.13%,绝对纯林、相对纯林和混交林样地数量分别增加-8.54%、15.38%和7.50%,杉木林分质量逐步提高。     

大气中有机污染物气-液采样技术初探

开发探讨了大气中有机污染物气-液采样技术,并以六种多环芳烃(6-PAHs)为有机污染物的代表物对该技术进行了可行性和模拟采样的研究。结果表明该采样技术以二氯甲烷为吸收溶剂,在常见的温度范围内,气体流速在2000～5000 mL/min内,对气态的6-PAHs(苊、芴、菲、芘、苯并(a)芘、苯并(ghj)苝)的回收率达90%±10%。该技术与传统的利用聚氨酯泡沫或XAD类树脂吸附有机污染物气体相比,具有装置结构简单,材料价格低廉,采集过程和样品的后处理步骤简便等特点。     

沉香10种化学成分的变异及其与生长性状的相关性

文章采用气相色谱-质谱联用技术测定了人工通体结香处理的35个中国沉香样品和51个越南沉香样品的化学成分,并选取了相对含量较高的10种化学成分进行分析.结果表明,10种化学成分的个体间变异都很大,且各种成分相对含量均与沉香树的生长性状呈正相关.此外,越南沉香和中国沉香绝大部分的化学成分相对含量存在显著或极显著差异,中国样品有2种成分含量显著高于越南沉香(P＜0.05),越南样品有6种成分含量极显著高于中国样品(P＜0.01),显著性的差异可能是由于林木的遗传特性和环境差异造成的.     

几种植物生长调节剂对枸杞硬枝插穗温床处理效果的影响

为了提高枸杞硬枝扦插育苗效果,采用温床处理技术对5种植物生长调节剂促进枸杞插穗生根成苗的效果进行比较。结果表明,经过10d、20℃温床处理,用15×10~(-6)萘乙酸、15×10~(-6) ABT1、10×10~(-6)复硝酚钠、20×10~(-6)的胺鲜酯、0.1×10~(-6)芸苔素内酯处理的枸杞插穗的生根量分别为0.28、0.38、0.06、0.15和0条/插穗,以15×10~(-6)的ABT1促进插穗生根的效果最优,与15×10~(-6)的萘乙酸的差异不显著,显著高于其他3个处理。这5个处理的枸杞插穗温室成苗率分别为93.75%、96.87%、44.69%、48.96%和41.88%,以15×10~(-6)的ABT1的成苗率最高,与15×10~(-6)的萘乙酸的差异不显著,显著高于其他3个处理。总体以15×10~(-6)的ABT1和15×10~(-6)的萘乙酸促进枸杞硬枝插穗生根和成苗的效果最佳。     

基于WMS技术的机动车尾气CO和CO_2同时监测

基于对机动车尾气中CO和CO_2同时测量的需求,提出并实现了利用WMS-2f/1f免校准技术实现两种气体的无标测量。结果表明:在选择恰当吸收谱线的基础上,对CO和CO_2的混合气体进行浓度检测,并对测量结果进行Allan方差评价,认为在系统积分时间为2 s时,CO和CO_2的最低检测限分别为0.76×10~(-6)和0.89×10~(-6),所用激光传感器系统的精度满足机动车尾气的测量要求。     

Fluid permeability in poplar tension and normal wood in relation to ray and vessel properties

The impact of ray and vessel features on the radial air permeability and liquid penetration was compared between poplar (Populus nigra) tension and normal wood. Air permeability was measured by the falling-water volume-displacement method. To measure liquid penetration, specimens were saturated with safranin solution by the full-cell process at low pressure, and the pattern of red color penetration was then examined. Results revealed no significant difference in vessel frequency, intervessel and vessel-ray pit diameter between tension and normal wood, whereas porosity and average vessel lumen area in normal wood were significantly greater than those in tension wood. Regarding rays, their length was not different between normal and tension wood, but the latter had more frequent rays per millimeter. Since xylem rays are important flow conduits in lateral movement of fluids, it could be hypothesized that a larger number of rays in tension wood would lead to improved radial permeability. However, neither air permeability nor liquid penetration varied significantly in the studied specimens. Consequently, the results proved that ray frequency has no determining role in radial fluid flow in poplar tension and normal wood and that the share of intervessel and vessel-ray pits in radial permeability is more important.     

3种不同处理方法对木材渗透性影响的研究

本文通过对长白鱼鳞云杉和臭冷杉生材分别进行普通气干处理和酒精置换处理以及对其气干材进行水浸处理,研究了这３种不同处理方法对木材气渗透性的影响及其影响机理。研究结果表明,长白鱼鳞云杉边材、心材和臭冷杉心村的生材经普通气干处理后,其气体渗透性较低,分别约为０．１１４、０．０４５和０．１１１ｄａｒｃｙ;长白鱼鳞云杉边材、心材和臭冷杉心材的生材经酒精置换处理后,其气体渗透性分别约为１１．７１３、０．０７４和０．１４４ｄａｒｃｙ,比普通气干处理对照组试样的平均渗透性分别增加约１０１．５倍、６２％和３０％,ｔ检验表明,前者差异非常显著,但后两者差异不显著;已气干１８个月的长白鱼鳞云杉边材、心材和臭冷杉心材经水浸处理后,其平均气体浸透性较处理前分别增加约８５％、４９％、６５．５％,ｔ检验表明差异均显著。长白鱼鳞云杉生材边材经     

木材可压缩流体渗透中滑流的研究

在气体平均压力倒数为1.4-48atm~(-1)范围内测定了长白鱼鳞云杉和红松木材可压缩流休渗透中滑流效应及影响滑流的因素,论述了木材中流体流动形态和机理。研究表明,两种木材可压缩流体渗透中均产生滑流,但长白鱼鳞云杉中滑流高于红松。前者滑流渗透性与真渗透性百分比、比名义渗透性与真渗透性比、滑流因素分别为69.39％、1.69、0.356atm;后者分别为37.64％、1.376、0.197atm。滑流的大小与木材有效毛细管半径、真渗透性和气体平均压力有高度紧密相关。木材有效毛细管半径愈小,真渗透性愈低,或气体平均压力愈低,则滑流效应愈大。     

木材可压缩流体的流动型态分析

本文针对可压缩流体在木材中渗透时出现的粘性流、滑流与非线性流,根据木材解剖构造特性运用统计物理和流体力学有关理论,分析讨论了粘性流、滑流与非线性流产生的原因和机理,及其与木材中可压缩流体渗透性的关系。粘性流存在于木材中流体通过的所有孔隙,而滑流存在于木材中满足滑流产生条件的那部分孔隙中。在通常的渗透压强条件下Ｒｅ≤１０,木材中流体渗透的流动型态不存在湍流。流体动能损失导致的非线性流的出现,使可压缩流体的流动特性偏离达西定律,当使用Ｋｌｉｎｋｅｎｂｅｒｇ方程和Ａｄｚｕｍｉ方程分析测量数据研究木材可压缩流体渗透性时,要注意非线性流的影响,降低渗透压强能减少或避免非线性流。木材可压缩流体渗透性与可压缩流体的流动型态间有一定关联。     

Experimental determination of the convective heat and mass transfer coefficients for wood drying

The knowledge of the convective heat and mass transfer coefficients is required for the characterization of the boundary conditions of the heat and mass transfer equations of a wood drying model based on water potential. A new experimental method for the determination of the convective mass transfer coefficient is presented. This method is based on the measurement of the moisture content, and indirectly the water potential, at the surface of a wood specimen at different drying times. Drying experiments were performed on red pine (Pinus resinosa Ait.) sapwood from nearly saturated to dry conditions at 56 °C, 52% relative humidity and air velocities of 1.0, 2.5 and 5.0 m s⁻¹. The results show that the convective mass transfer coefficient is constant until the wood surface moisture content reaches about 80% and then decreases more or less gradually as the moisture content decreases further. The convective mass transfer coefficient increases with air velocity. A regression analysis shows that there is no significant improvement in considering the water potential gradient near the wood surface when the difference in water potential between the surface and the surrounding air (ψ_s − ψ_∞) is used to determine the convective mass flux at the surface. Also, ψ_s − ψ_∞ is more appropriate than the water vapour pressure difference (pv_s − pv_∞) as the responsible driving force of the moisture flux leaving the wood surface. The convective heat transfer coefficient was determined during the same experiments. A plateau is observed at high values of moisture content corresponding to the constant drying rate period. Received 27 February 1998     

Unsteady-State gas permeability of wood

Steady-state permeability experiments yield a single value for permeability in each of the three structural directions of wood. A high value indicates that passage through the wood is easy, but it does not necessarily mean that all voids are filled readily with a fluid.This research aimed at developing an experimental method that would give a better insight in this dual nature of wood permeability.Cylindrical wood specimens, 50 cm x 7.5 cm diameter were evacuated and a known quantity of gas was admitted to the system. A comparison of the pressure/time curve with theoretically derived results gave values for the transverse or longitudinal gas permeability.The most important results are: 1. Several species show a definitely dual permeability in the transverse direction; 2. the longitudinal/transverse permeability ratio for large specimens is considerably lower than steady-state results on small specimens indicate.Paper No. 2793 of the Journal Series of the North Carolina Agricultural Experiment Station, Raleigh, N.C.; a condensation of part of Ph. D. thesis from the Department of Wood and Paper Science of North Carolina State University 1967 under the direction of Alfred J. Stamm, Robertson, Professor of Wood and Paper Science.     

γ射线辐射杉木压缩木材的固定和蠕变(英文)

为了探讨木材压缩变定固定的机理 ,该研究对杉木压缩木材进行γ射线辐射处理 ,射线辐射剂量分别为 0 (作为对照试材 ) ,10 3 ,5× 10 3 ,10 4 ,5× 10 4 ,10 5,5× 10 5,10 6,5× 10 6Gy ,然后测定和讨论了γ射线辐射杉木压缩木材的重量损失率、平衡吸湿含水率 (EMC)、吸湿回复率 (RSA)和吸水回复率(RSW )、绝干状态下和吸湿解吸过程中的蠕变。该研究表明 :γ射线的辐射剂量对杉木压缩木材的重量损失率、EMC、RSA、RSW有重要的影响 ,当辐射剂量超过 10 6Gy后 ,试材的重量损失率和EMC显著增大 ,RSA和RSW显著下降 ;另外 ,随着γ射线辐射剂量的增大 ,绝干状态和吸湿解吸过程中杉木压缩木材的瞬时柔量和蠕变柔量均呈增大趋势 .从该研究结果可以推测 ,当γ射线辐射剂量较大时 ,特别当辐射剂量在 5× 10 6Gy左右时 ,杉木压缩木材的细胞壁中发生了降解反应或非结晶化反应 .而且 ,该研究证明了压缩木材细胞壁主成分发生的降解反应能够使木材压缩变定得到一定程度的固定     

Permeability to water of the cell wall material of spruce heartwood

Summary The permeability to water of spruce heartwood has been measured by applying a known osmotic pressure difference across specimens in which the cell walls were water swollen and most of the void space was filled with paraffin wax. To ensure that solute molecules should not penetrate the cell wall aqueous solutions of polyethylene glycol of molecular weight 6,000 and dextran of molecular weight 40,000 were used to generate the osmotic pressures. The mean values of the permeability k×10²¹ defined by the Darcy equation were 67.5 m² for longitudinal flow, 7.12 m² for radial flow and 4.03 m² for tangential flow. Permeability was probably overestimated by about 10% owing to water entering some of the void space not filled by wax. The measured values are 10 to 100 times smaller than those calculated assuming all water in the cell walls is free to flow and this is probably caused by much of the water being bound to cell wall material. This work was made possible by Research Grants from the Leverhulme Trust Fund and the Science Research Council, and we thank both organisations for their support. We wish to thank Hickson's Timber Products Ltd for kindly supplying some of the specimen holders and Professor J. D. Matthews for his encouragement of this work Paper presented at the Seminar on “Flow and Permeability in Wood” of the Royal Microscopical Society, Wood Anatomy Group, held in Princes Risborough, 17, October 1979     

The effects of cell wall swelling on the permeability of grand fir wood

Summary The longitudinal permeability of Abies grandis wood swollen to varying degree by water vapour sorption has been measured using a non-swelling liquid. The results obtained show that cell wall swelling causes a reversible decrease in permeability in both air dried and solvent exchange dried specimens.Direct microscopic measurements have shown that change in lumen diameter cannot explain the observed effect.Mathematical analysis of the data suggests that the permeability decrease may be due to increase in thickness of bordered pit membrane fibrils resulting from sorption of water.