Mechano-sorptive effects in wooden material

Summary The effects on wood of simultaneous mechanical and moisture loading are studied. In order to clarify the mechano-sorptive behaviour of wood, a review of different phenomena presented in the literature is included. Based on this review a constitutive model is proposed for the case of uniaxial stress in the longitudinal direction. The validity of the model is checked independently against test results. The calculations show that the model is capable of describing the response of wood with reasonable accuracy. Simulations indicate that the response of small test specimens is more difficult to describe than that of larger beams. Some differences in behaviour are found to depend on loading mode and nature of moisture cycling. Very large and fast moisture cycles seem to give larger mechano-sorption than smaller variations. The results of the simulations show that there is a significant influence of strain on the shrinkage and swelling response.     

A mathematical model linking tree sap flow dynamics to daily stem diameter fluctuations and radial stem growth

To date, models for simulating sap flow dynamics in individual trees with a direct link to stem diameter variation include only the diameter fluctuation driven by a change in stem water storage. This paper reports results obtained with a comprehensive flow and storage model using whole-tree leaf transpiration as the only input variable. The model includes radial stem growth based on Lockhart's equation for irreversible cell expansion. It was demonstrated that including growth is essential to obtaining good simulation results. To model sap flow dynamics, capacitance of storage tissues was assumed either constant (i.e., electrical analogue approach) or variable and dependent on the water content of the respective storage tissue (i.e., hydraulic system approach). These approaches resulted in different shapes for the desorption curve used to calculate the capacitance of storage tissues. Comparison of these methods allowed detection of specific differences in model simulation of sap flow at the stem base (F(stem)) and stem diameter variation (D). Sensitivity analysis was performed to select a limited subset of identifiable parameters driving most of the variability in model predictions of F(stem) and D Both the electrical analogue and the hydraulic system approach for the flow and storage model were successfully calibrated and validated for the case of a young beech tree (Fagus sylvatica L.). Use of an objective model selection criterion revealed that the flow and storage model based on the electrical analogue approach yielded better predictions.     

The amount of wooden material in a closed room and its effect on the reverberation time

Optimal sound-absorbing materials are vital for desirable room acoustics. The effect of wood used for interior wall decoration on the acoustical environment is explored in a controlled room by changing the amount of wall wooden materials. The effect on the interior reverberation time (RT) is reported in this work. The experiment was conducted in a relatively small concrete brick house (approximate dimensions 4.6 × 3.2 × 4.2 m). Results showed that room shape and the arrangement of wooden wall decoration materials were important factors affecting the RT at different receiving positions. As the amount of wall decorating wood materials increased, the interior RT in the house decreased linearly; however, the RT at low frequencies diverged. After the analysis of covariance, all frequency variables were adjusted to the same level and a general regressive formula was developed as RT = C − 0.005 DR. Where RT is the reverberation time (s), DR is the amount of interior wood materials used (%), and the C values were constants that ranged from 0.888 to 1.606 and varied according to the different octave bands. Furthermore, it was found that the increasing influential effect with the DR showed diminishing marginal utility. This means that the influence of DR on RT was not linear, and, therefore, the marginal utility should be considered in order to use wooden panels economically. Part of this report was presented at 53rd Annual Meeting of the Japan Wood Research Society, Fukuoka, March 2003     

Modelling mould growth on coated modified and unmodified wood substrates exposed outdoors

Mould growth on coated wood is today a genuine challenge for house owners. Environmentally sound wooden facades with long service lives and acceptable appearance are desired. The objective in this study was to investigate the accumulated mould growth on 13 different wood substrates with 3 surface coating systems by identifying the factors that contribute to the variation and to predict future performance. A generalized linear mixed model was fit to the data with the analysis showing that coating and exposure time both had highly significant influences on mould growth. Further, wood substrate was significant, but comparatively less than coating and exposure time. A smaller coefficient for mould coverage in the beginning of the exposure period gave the panels with one of the coating systems, BAP, a delay in mould growth, and the extrapolated values for years 6–12 indicate a longer aesthetic service life than panels with the two other coating systems. Coated heartwood as wood type was less susceptible to mould growth than coated mixed wood and coated sapwood. Acetylated pine as wood substrate and aspen as wood species had lower resistance to mould growth than the other wood substrates and wood species, respectively.     

A mathematical model for generating land-use allocation alternatives for agroforestry systems

Agroforestry has been considered a viable land-use system particularly in the tropical regions. In developing or designing agroforestry systems, various concerns have to be addressed namely: (1) economic; (2) biological and physical; and (3) silvicultural and ecological considerations. This paper addresses these concerns from an interdisciplinary perspective. A land-use allocation model which ensures the simultaneous consideration of these concerns is proposed.     

A mathematical model for neutral sulfite pulping of various broadleaved wood species

Summary A mathematical model for neutral sulfite pulping process was derived. This model represented by a linear logarithmic relationship of the main pulping characteristics (yield and lignin content) to time and temperature parameters, both determined by the H-factor, is expressed by a logarithmic straight line equation. The relationship of yield to lignin content in the high yield pulps after neutral sulfite pulping is also expressed by a logarithmic straight line equation. A suitable way to calculate the main characteristics of neutral sulfite pulping is the power form of the logarithmic straight line equation for the dependence of the ratio yield/lignin vs. lignin content, yield/H-factor vs. H-factor, lignin/H-factor vs. H-factor and their mathematical equivalents (i.e. reciprocal ratio and/or product). A set of power equations characterizing the relationships yield vs. lignin content as well as yield and lignin content vs. H-factor for woodpulps prepared by neutral sulfite pulping of various broadleaved wood species are given.     

浅论强化木地板的性能

随着世界人口的增长,人类文明高速发展。但人类在不断创新自己的同时,也无形中不断地在破坏大自然的资源。许多国家的资源消耗速度特别惊人,例如泰国,1961年森林覆盖率还是53％,到目前为止该国的森林覆盖率已减至25.6％,这种现象不     

可视化木家具生产车间全程监控系统的构建

在分析我国木家具制造车间的监控和管理现状的基础上,提出了基于可视化木家具生产车间监控系统的基本架构——多点信息采集系统、数据处理和调度系统、企业监控管理中心系统和现场信息反馈系统及相关的辅助设施,探讨了基本架构的功能特点,并从基本流程、信息采集、信息处理与调度、信息反馈等方面详细介绍了基于可视化木家具生产车间全程监控系统的监控过程与方法.在此基础上,总结了可视化监控系统在家具生产过程中的应用特点.该系统可为木家具生产机加工车间提供一个具有快速反应、有弹性、精细化特点的制造环境.     

基于logistic模型的灰毛大青播种苗生长规律

采用非线性回归拟合方式对生长曲线进行logistic模型拟合,定量地模拟灰毛大青苗期生长规律。结果表明:logistic方程对灰毛大青1年生苗苗高和地径生长曲线的拟合相关性极显著,并采用数学模型来确定灰毛大青苗木生长的速生期,将生长期划分为4个时期。为育苗经验缺乏的树种育苗及幼苗管理提供了科学依据。     

Hygromechanical behaviour of wooden composites

Summary The objective of this research is to study the moisture deformation of densified in technological pressing wooden composite materials. By generalizing Cosserat's couple-stress theory a structural model for determination of mid-surface strains and curvatures of composite board taking into account asymmetric structure and nonuniform distribution of moisture as well as nonlinear swelling functions of the wooden stuff and dependence of strain characteristics on moisture content is developed. On the basis of a laminate analogy the optimum flake or veneer alignment in board has been estimated for the real composite production process. According to analysis performed, the optimum alignment for hygromechanical properties may not coincide with that for mechanical properties, and for every type of loading, material with a definite structure should be used.     

A new methodology to select hardwood species for wooden products

Abstract

In general, only a few wooden species are used or even considered for any given wooden product, even though hundreds of alternative wood species are available. In many cases, the reason for this is tradition rather than availability, technical or aesthetic considerations and it can result in endangered species being used to an unnecessarily high degree. The purpose of this study was to develop a structured, quantifiable, and easy-to-use methodology to identify suitable hardwood species for a specific product. The methodology combines processes based on quality function deployment and multivariate data analysis in a three-step workflow, and takes different criteria into consideration. To verify the methodology, it was applied to an example product: an electric guitar. It was shown that the methodology was easy to use and provided useful and quantifiable results. Expansion of the underlying wood species data-set will be necessary to improve the performance in the future.     

Effect of moisture and mechanical loading on wooden materials

Summary In a previous paper (Mårtensson 1988 a), results of tests performed on hardboard in tension under cyclic humidity were presented and comparison with a suggested constitutive model was made. This paper presents the result of further work that has been carried out concerning modelling of the behaviour of tempered hardboard subjected to moisture loading combined with mechanical loading. Tests were made both in compression and bending. The tests in compression were of two types, conventional creep tests during moisture cycling and quasi-relaxation tests during moisture cycling. The model was quantified on the basis of the previous tension tests and the compression tests, in both cases creep tests, and was then checked independently against the other types of test.Interaction between moisture change and mechanical loading was found to be significant during the first moisture cycle but much smaller during subsequent cycles. Experimental and numerical analysis of composite structural elements was also performed, showing that internal stresses of significant magnitude are developed as a result of variations in moisture. Such stresses can be predicted with reasonable accuracy using the proposed model. This can be of great value in design and development of wood products and wooden structural elements.     

黔南州食用菌发展现状及木质菌材的保护与利用

通过问卷与实地走访的调查方式,开展黔南地区食用菌发展情况与木质菌材利用现状的调查.对食用菌的食用价值、药用价值、保健功能以及市场发展等进行分析,对木质菌材加工利用、流通管理、采伐监管、资源保护、资源培育等进行调查,针对性地提出木质菌材保护管理利用对策.     

A mathematical model of kraft pulping related to the alkali concentration in the cooking liquor

Summary A new mathematical model for checking and controlling the kraft pulping process has been derived. The model is based on the modified relationship between the lignin content and the alkali concentration of a cooking liquor expressed as the ratio of lignin/active alkali vs. concentration of the active alkali in a cooking liquor. The derived model characterizes the variation of the lignin content of the partially delignified wood or pulp with the concentration of the residual alkali in a cooking liquor during an entire pulping cycle, i.e. during the initial, transition, bulk and residual phases of the kraft delignification. The relationship between the lignin content of the partially delignified wood ships or pulp and the concentration of the residual alkali in a cooking liquor is expressed by the logarithmic straight line equation or its power form. The slope and intercept constants of the derived equation for the individual phase of delignification have different values. Received 5 June 1996     

木本植物多倍体育种研究进展

该文论述了木本植物多倍体的特征、形成途径,展望了多倍体未来发展的方向。     

一个考虑水分影响的森林生长机理模型

文章介绍了林分生长模型GOTILWA+。该模型基于单株林木生长过程,采用光合作用模型等模型的机理模拟树木的生理过程,从而计算林分生长。该模型具有较为广泛的适用范围,是一个较为方便的可科模拟预测气候变化条件下林分生长和森林碳循环的科学工具。     

木地板厂的粉尘控制研究

针对国内外对环境保护日益重视的特点，从木地板厂产生的木粉尘的特性及危害，收集和再利用3个方面简述了对木地板厂粉尘的控制。     

人参叶片愈伤组织诱导数学模型分析

取人参叶片作为外植体诱导愈伤组织,利用二元二次通用旋转组合设计数学模型筛选植物激素浓度组合,结果表明:2,4-D与KT对人参叶片外植体诱导愈伤组织方程为:Y=0.653 30+0.229 63X1+0.140 85X2-0.130 83X12-0.197 48X22+0.100 00X1X2;叶片诱导愈伤组织最佳培养基为MS附加7 mg·L-12,4-D和0.9 mg·L-1KT,诱导率最高可达80%以上。