Effect of intermittent heat treatment on crystallinity in wood cellulose

The effect of intermittent heat treatment on cellulose crystallites in wood was studied to evaluate quantitatively the changes of crystallinity induced by intermittent and continuous heating. The changes in crystallinity were found to be strongly affected by the intermittent heat treatment. The increased crystallinity, the width of the crystals, and the piezoelectric properties were the same for the first intermittent heating as for continuous heating. Further intermittent heating for the same time duration and temperature had no effect on the above properties, probably due to the stopping of the thermal reaction during the interval. Our results suggested that intermittent heat treatment has certain critical cooling temperatures that stop the thermal reaction and are closely related to the duration of the interval. Samples once exposed to a certain duration of heat treatment and then cooled need more time, about twice that of the first duration of intermittent heating compared with continuous heating, to reach maximum crystallinity in wood cellulose.     

湿热蒸汽处理木质材料温度动态监测研究

作为一种替代溴甲烷熏蒸木材的技术,湿热蒸汽处理具有突出的环保性。试验通过智能换热站提供湿热蒸汽,设计了钢材框架悬挂耐高温气囊的试验装置,对原木、樟子松拼板、樟子松锯材和单板层积材进行湿热蒸汽处理,并对木材内部升温进行动态监测。利用温度记录仪收集了各温度监测点4 h内的温度实时数据,以及耐高温气囊内部的环境温度实时数据,对湿热蒸汽环境下木质材料不同位置的升温过程进行比较分析,结果表明:木质材料与湿热蒸汽的接触面积是影响其升温速率的关键因素;较大尺寸的木质材料升温速率更高;人造板材与天然木材升温速率基本相同。     

毛竹材材性变异的研究

通过对毛竹材纤维形态，组织比量、纤维素含量和基本的分析测定，研究了不同年龄、不同胸径、竹秆不同部位栲生性状的变异特点结果表明，竹材纤维长度主要受竹秆部位的影响，与年龄和胸径无显著相关，组织比量与年龄无显著相关，与胸径有一定相关；纤维素含量和基本密度与年龄、胸径、竹秆部位均有关系，从材性变异特点来看，经营培育小径级毛竹对制浆造纸更有利。     

温湿度控制系统对木材干燥的影响及优化设计

通过对常规蒸汽窑干燥木材过程中影响空气温度、湿度控制稳定性因素的分析,以及对当前国内木材干燥行业所使用的温、湿度控制仪器中控制类型及控制方式的分析,认为采用干、湿球温度计方式;以先进的智能湿度测控仪表、一些逻辑元件及电子电路组成适合于木材干燥工艺的木材干燥温、湿度半自动控制是比较经济实用的。分析了全自动控制的优缺点并对其不足之处提出了一些改进建议。     

木材工业和可持续发展──世界木材工业的发展趋势

进入80年代以来,世界经济已开始由工业化社会向生态化社会发展,林业和木材工业的目标也开始由传统的以生产木材和木材制品为主向可持续经营,实现森林的生态、环境、社会和木材等多方面效益发展。木材工业的进一步发展面临木材资源紧缺、环境保护压力增加等重大问题的挑战。遵循可持续发展原则,加强工业人工林的培育和利用,发展环境协调技术和产品,改进林业和木材工业的竟争地位,更好地适应市场的需求,实现林业和木材工业的协调发展,是木材工业通向未来之路。     

中国主要人工林树种幼龄材与成熟材及人工林与天然林木材性质比较研究

本文对中国１０种人工林和４种天然林的幼龄材与成熟材及４个树种的人工林木材与天然林木材的构造特征、化学性质、物理性质、力学性质的３３项材性指标差异进行了比较研究。结果表明,在幼龄材与成熟材之间,在统计上表现出差异显著性的为幼龄材比成熟材生长轮宽,管胞列数多,管胞短,直径小,微纤丝角大,密度小,径向干缩小,差异干缩大,流体扩散性高,抗弯强度、抗弯弹性模量、顺纹抗压强度、径面顺纹抗剪强度、径面抗劈力和冲击韧性低等１５项,即４６％的测试项目差异显著;表明在木材加工和用作结构材时应将幼龄材和成熟材视作两个性质不同的总体来考虑,在培育结构材时应研究如何缩短幼年期或改善幼年期材性。在人工林与天然林木材之间,采取人工林幼龄材性质与天然林幼龄材性质相比,人工林成熟材性质与天然林成熟材性质相比,结果表明,多数性质在统计上差异不显著,只有人工林木材比天然林木材胞壁率小、顺纹抗压强度低、差异干缩大、流体扩散性高等４项,即只有１２％的很少数测试项目差异显著;表明有可能通过人工培育的方法培育出与天然林木材性质相近的木材。     

Crown morphology of Norway spruce from usual tree measurements

Intr0ducti0nNorwayspruce(PiceaabiesKarst)is0l1eoflI1e111ostimportal1tc011iferinFra11ce.lnl99l,tI1etotaIareaofNorwaysprLICewasestimatedt0be723000I11112.ItsvoIUmewasl27Inilli0I1m3.Tl1eanl1uaIvoILl111eiI1crc-mentwas5.74millionm3.ltiswideIyacceptedII1atIargeri11itialspacingssI1ouldbeusednow.l111940's,thedensity0ftl1epIantatiol1rangedfr0m5000to10000stems/hm2.Nowtl1einitiaIdensityvariesbetweenI000to250Ostems/I1m2.TI1eIargestspacit1g111aybe650~800stems/hm2.S0ithasasignifica11cetostLldyt…     

Structural mechanics of wood composite materials I: Ultrasonic evaluation of internal bond strength during an accelerated aging test

This research attempts to observe indirectly the variation of internal bond characteristics for wood composite materials during accelerated aging test treatment using ultrasonic pulse-transmission techniques. Particleboard (PB) and oriented strandboard (OSB) were the representative specimens. The transit time of the ultrasonic wave propagating through the samples along the nominal length and thickness directions was recorded using an apparatus called PUNDIT (C.N.S. Electronic, London). The transit times were measured in the samples under an oven-dried condition after treating them with boiling water at different treating time stages, and the velocity was then calculated based on the transit time. Examination of the internal bond strength conducted on the same samples was done according to JIS A 5908. A study of the relations among springback, internal bond strength, and velocity indicated that a high correlation existed between ultrasonic velocity measured in the length or thickness direction and the internal bond strength for the PB specimen, but no significant correlation was observed between the velocity measured in the length direction and the internal bond strength for the OSB specimen. The results of this research suggested that ultrasound techniques can be applied to predict or evaluate the internal bond state of some wood-composite materials made of relatively small particles, such as PB especially, during accelerated aging test treatment processes.Part of this paper was presented at the 47th annual meeting of the Japan Wood Research Society, Kochi, April 1997     

木材选用咨询专家系统的设计

阐述了木材选用咨询专家系统的建立，着重介绍了面向对象的知识表示方法在系统的规划与设计过程中的实现，以及系统结构、知识库和推理策略的设计与实现，并指出在实际生产中的意义。     

Testing and evaluation of natural durability of wood in above ground conditions in Europe – an overview

Natural durability of wood is determined by the European standard EN 252 for specimens in ground contact and EN 113 for basidiomycetes in the laboratory, but no test exists for above ground conditions. For above ground conditions, the European prestandard ENV 12037 and EN 330 are used to determine the durability of treated wood. The most important factors for fungal establishment on the surface and within wood are the moisture content, the surrounding temperature, and the relative humidity. Strength tests are the most sensitive for decay detection, but neither strength tests nor identification of fungi responsible for the decay are included in the standards of above ground durability in field tests. To detect decay, visual examination, pick or splinter tests, and mass loss determination are used. Identifying fungi with traditional methods, e.g., growth on solid medium, is time consuming and complicated. Molecular methods like polymerase chain reaction and sequencing do not require mycological skill for identification to species level, and furthermore the methods do not depend on the subjective judgement like most traditional methods, but are based on the objective information of the target organism (e.g., nucleotide sequences). The next generation of standard field tests will probably consider the drawbacks of standard tests today and be rapid and include both quality tests like molecular identification and nondestructive quantitative tests, e.g., acoustic tests. Laboratory tests can be improved by using fungi identified from field trials and by combining different fungi in the same test and thus simulate degradation in practice.