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1.
This paper forms a continuation of the work on treatment of timber products with gaseous borate esters. Turner and Murphy (1995) in an earlier paper indicated that gas flow rate into the wood substrate was the principle factor limiting the rate of boric acid retention and the depth of penetration into wood products. The current paper considers the impact of this factor on treatment efficacy and considers experimental work designed to evaluate qualitatively, the impact of proposed modifications to the process. Significant improvements in treatment performance were observed. 相似文献
2.
In seventy years, timber use, at first governed by craft practices,has been transformed to a technology determined by scientificprinciples, made possible by the research on wood undertakenduring the period. The pattern of this research, those undertakingit, the factors determining it and its funding in the UnitedKingdom are considered. Today, forest products research is ata low ebb, compared with that in earlier decades, but it issuggested that with a rapidly expanding UK resource, a continuingnational dependence on timber and timber products and the environmental benefits from growing and using wood, the need for aneffective forest products research capability remains as importantas ever. 相似文献
3.
Ingolf Profft Martina Mund Georg-Ernst Weber Eberhard Weller Ernst-Detlef Schulze 《European Journal of Forest Research》2009,128(4):399-413
Wood products are considered to contribute to the mitigation of carbon dioxide emissions. A critical gap in the life cycle
of wood products is to transfer the raw timber from the forest to the processing wood industry and, thus, the primary wood
products. Therefore, often rough estimates are used for this step to obtain total forestry carbon balances. The objectives
of this study were (1) to examine the fate of timber harvested in Thuringian state forests (central Germany), representing
a large, intensively managed forested region, and (2) to quantify carbon stocks and the lifetime of primary wood products
made from this timber. The analyses were based on the amount and assortments of actually sold timber, and production parameters
of the companies that bought and processed this timber. In addition, for coniferous stands of a selected Thuringian forest
district, we calculated potential effects of management, as expressed by different thinning regimes on wood products and their
lifetimes. Total annual timber sale of soft- and hardwoods from Thuringian state forests (195,000 ha) increased from about
136,893 t C (~0.7 t C ha−1 year−1) in 1996 to 280,194 t C (~1.4 t C ha−1 year−1) in 2005. About 47% of annual total timber harvest went into short-lived wood products with a mean residence time (MRT) < 25
years. Thirty-one per cent of the total harvest went into wood products with an MRT of 25–43 years, and only 22% was used
as construction wood and glued wood, products with the longest MRT (50 years). The average MRT of carbon in harvested wood
products was 20 years. Thinning from above throughout the rotation of spruce forests would lead to an average MRT in harvested
wood products of about 23 years, thinning from below of about 18 years. A comparison of our calculations with estimates that
resulted from the products module of the CO2FIX model (Nabuurs et al. 2001) demonstrates the influence of regional differences in forest management and wood processing industry on the lifetime of
harvested wood products. To our knowledge, the present study provides for the first time real carbon inputs of a defined forest
management unit to the wood product sector by linking data on raw timber production, timber sales and wood processing. With
this new approach and using this data, it should be possible to substantially improve the net-carbon balance of the entire
forestry sector. 相似文献
4.
小径原木是当今世界上主要的木材资源之一,各国均在积极开发利用。文内着重介绍了林业发达国家在研究小径原木的材性特征和主要产品加工工艺特点等方面所取得的成果和经验。 相似文献
5.
介绍了上海本材工业改革开放20年的现状、木制品需求和原料结构,分析了实施天然林资源保护工程对它的影响,提出了有关今后发展的一些设想。 相似文献
6.
lntroductionChina'sterritoryisvast,buttheforestedareaisless.About29%areaofChinaisdesertandbaremOuntains(Zhangetal.1997).ThefourthnationaIforestsurvey,whichwasconductedbytheMinistryofForestryin1989~1993,indicatesthat133.7millionhm2or13.92%oftheIandareaofChinaareforest.Thestockoflivingtreesis11.785bilIionm',ofwhich1o.1biIIionisinforest.Thenetgrowthofstandingvolumeiso.4biIIionm3peryear,whiIethecutisO.3billionm',ofwhichatleastonethirdisfarfueIwood.Sotheforestresourcesarenotrich,forestcoveri… 相似文献
7.
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。 相似文献
8.
Air-coupled ultrasound as an accurate and reproducible method for bonding assessment of glued timber
Sergio J. Sanabria Christian Mueller Juerg Neuenschwander Peter Niemz Urs Sennhauser 《Wood Science and Technology》2011,45(4):645-659
Glued timber products are widely used in construction; therefore, it is necessary to develop non-destructive bonding quality
assessment methods for long-term structural health monitoring. Air-coupled ultrasound (ACU) inspection is a novel technique,
with phenomenal improvements in reproducibility compared to traditional contact ultrasonics, unlimited scanning possibilities,
and a high potential for delamination detection in wood products. As part of an ongoing project, glued timber samples of 10 mm
thickness with artificial glue line defects were inspected. A normal through-transmission set-up with 120 kHz transducers
allowed for successful and accurate imaging of the geometry of glued and non-glued areas in all inspected objects. The influence
of wood heterogeneity and the reproducibility of ACU amplitude measurements were analysed in detail, identifying the main
sources of variation. Future work is planned for the inspection of more complex glued timber objects. 相似文献
9.
Christian Brischke Rolf Bayerbach Andreas Otto Rapp 《Wood material science & engineering》2006,1(3):91-107
The need for a reliable database and a corresponding methodology to predict service life of wood and wood-based products emanates from the European Construction Products Directive, as well as from a strong interest by the building industry. A literature review on decay-influencing factors and on previous approaches to implement methods and tools for service life estimations was the basis for a concept for service life prediction of wooden components. The effect of various indirect decay factors was found to be reducible to a few direct decay factors, with material resistance, as well as wood moisture content, wood temperature and their dynamics among the key factors for fungal decay. Approaches that consider only indirect factors, e.g. climate indices, suffer from poor correlation with service life or decay rates. Therefore, the overall consideration of all possible influences, reduced on the key direct decay factors in first instance, is recommended. To fill a theoretical model with a reliable database, various data sources need to be considered, in decreasing order of priority: in-service performance, field test data, laboratory test data, survey analysis and expert opinion. 相似文献
10.
We examined the contribution of rubberwood to the timber export markets of Malaysia and Thailand. In Malaysia, rubberwood
has grown from 26% of total exported wood products in 1998 to 35% in 2007. A high proportion of furniture products (80%) is
rubberwood, whereas the contribution of rubberwood to other wooden products is less than 20%. Only 10% of sawn timber and
logs is rubberwood. In Thailand, rubberwood contributes to around 60% of total exported wood products, arising from a high
share of not only furniture products (70%) but also other wood products (around 50%) and sawn timber and logs, which have
increased in share from 40% in 1998 to 79% in 2007. We conclude that the high proportion of rubberwood products in the wood
export markets of these two countries is a result of: (1) scarcity of raw wood materials because of strict controls on the
logging of natural forests; and (2) governmental support to rubberwood production, including financial support to rubber planters
and technical assistance to downstream timber processors. 相似文献
11.
《Wood material science & engineering》2013,8(1):24-33
Abstract Siberian larch (Larix sibirica Ledeb.) timber is suitable for many uses in the mechanical wood industry. Drying it without any decrease in value, however, is difficult and slow. The purpose of this research was to compare the drying quality of Siberian larch timber dried with three different conventional schedules taking into account the density and annual growth of wood. Five drying tests were performed. The final moisture content (MC), MC gradient, cracks, deformations (bow, crook, twist and cup) and case hardening were measured from the dried timber. The basic density particularly affected the MC, as shown in the differences regarding dried wood, with the denser wood having higher final MC and MC gradient. It was also found that large annual growth increased some deformations. Most of the measured factors were best after drying at the highest temperatures used; however, a slightly different trend was observed for bow, twist and cup. MC factors and twisting were the most problematic properties in drying according to this study. Sorting Siberian larch timber, particularly according to density, would improve the MC properties of dried timber by ensuring sufficient drying time, as economically as possible, for each timber piece. 相似文献
12.
《Wood material science & engineering》2013,8(3-4):91-107
Abstract The need for a reliable database and a corresponding methodology to predict service life of wood and wood-based products emanates from the European Construction Products Directive, as well as from a strong interest by the building industry. A literature review on decay-influencing factors and on previous approaches to implement methods and tools for service life estimations was the basis for a concept for service life prediction of wooden components. The effect of various indirect decay factors was found to be reducible to a few direct decay factors, with material resistance, as well as wood moisture content, wood temperature and their dynamics among the key factors for fungal decay. Approaches that consider only indirect factors, e.g. climate indices, suffer from poor correlation with service life or decay rates. Therefore, the overall consideration of all possible influences, reduced on the key direct decay factors in first instance, is recommended. To fill a theoretical model with a reliable database, various data sources need to be considered, in decreasing order of priority: in-service performance, field test data, laboratory test data, survey analysis and expert opinion. 相似文献
13.
胶合性能是胶合木制品的重要性能之一。在正交胶合木(CLT)中木材特征、胶黏剂性能以及木材与胶黏剂之间界面性能共同决定了正交胶合木的胶合性能。木材作为一种天然各向异性材料,其纹理方向不同,造成组坯方式对于胶合性能影响巨大。在胶合性能测试中,取样尺寸、取样形状对于胶合性能的测试结果都有一定的影响。胶合界面性能表征方面的研究正逐渐兴起,但是针对CLT胶合界面性能表征的相关研究报道并不多。有关CLT胶合的研究多集中在胶黏剂和胶合工艺方面,而针对不同锯材单元的特性对胶合性能尤其是耐久性影响的研究尚少有报道。文中基于现有研究对CLT胶合界面性能影响因素进行总结,梳理对比CLT胶合性能测试方法以及胶合界面性能表征技术,并对今后研究方向提出意见和建议。 相似文献
14.
Liquid water absorption in dried Norway spruce timber measured with CT scanning and viewed as a percolation process 总被引:2,自引:0,他引:2
Liquid flow in dried wood is complicated to study, since wood is a nonhomogeneous, hygroscopic-porous, anisotropic material. However, liquid flow is important to understand, since it has an influence on the durability of wood and on such processes like impregnation, drying, surface treatment, etc. In this study, simulations of liquid water absorption in wood as a fibre network, percolation, were compared with experimental water absorption in the longitudinal direction in spruce timber. With CT scanning, water distribution during liquid flow can be shown visually and measured by image processing. Liquid water absorption in end grain of spruce was measured with CT scanning after 1, 3, 7 and 14?days of liquid water absorption and shown as moisture content (MC) profiles in heartwood and sapwood. It was found that the amount of water absorbed could be expressed as a linear function of the square root of time. The slopes of the lines differed between sapwood and heartwood and also varied depending on the growth condition of the trees. The simulations according to the percolation method show generally good agreement with the measured results for sapwood. 相似文献
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探讨了利用速生杨木单板层积材及科技木生产实木门的可行性,介绍了杨木单板实木门的制造工艺。速生杨木单板层积材压缩率、硬度、抗弯强度、尺寸稳定性等指标均远高于普通板材,是一种很好的结构用材,可用其替代高档硬质实木使用,以提升杨木产品的科技含量和附加值。 相似文献
19.
Over the last three decades the exportation rate of raw sawlogs from Illinois to neighboring states for processing has nearly doubled. While the exportation of sawlogs has adverse impacts on the Illinois wood products manufacturing sector and local forest landowners, little research has been conducted to understand how the spatial arrangement of timber mills affects sawlog exportation. This research models, in a spatial environment, timber mill procurement influence within southern Illinois and the surrounding region in an attempt to understand how the location of mills is a partial explanation of the increase in sawlog exportation. Assuming equal market power, timber mills within the study area were found to be arranged in a manner that results in low competition for sawlogs within Illinois and high competition in neighboring states. Spatial models incorporating differential market power based on mill size characteristics suggest that Illinois experiences little procurement pressure from high production mills operating within the State but is under procurement pressure from high production timber mills operating in neighboring states. 相似文献
20.
High temperature and chemical effects on wood stability 总被引:9,自引:0,他引:9
W. E. Hillis 《Wood Science and Technology》1984,18(4):281-293
Summary The increasing supplies of fast-grown woods grown on short roations contain significantly higher proportions of juvenile wood with properties different from those of mature wood. Improved processes will be required to produce dried wood that is satisfactorily stable with few distortional or dimensional changes. The basic wood features affecting different forms of instability are considered. Variations in the amounts of cellulose, hemicelluloses and lignins in wood, the changes in them and the degradation products formed under different conditions are discussed. Changes in the nature of hemicelluloses appear to play an important role in conveying stability. The different volumes of heartwood in green timber have an effect on moisture levels and other properties. As industry is increasing kiln temperatures for high-temperature drying, the effect of time-temperature-moisture relationships on stability and degradation are discussed. The effect of ammonia and other chemicals on stability is considered. 相似文献