刨切薄竹贴面刨花板加工工艺研究

以刨切薄竹为原料,通过正交试验,对刨切薄竹用于贴面刨花板的生产工艺进行研究.结果表明:当涂胶量135 g·m-2,热压压力为0.8 MPa,热压温度90℃,热压时间4.0 min时,刨切薄竹贴面刨花板的效果较佳,可用于指导生产实践.     

胶合板微薄木贴面生产工艺

本文简述了微薄木贴面应用于胶合板表面装饰的生产工艺。从木方准备,刨切薄木,直到薄木胶拼都有一定的工艺要求。厚度仅有0.25～0.3mm 的微薄木贴面在我国目前生产和使用的较少,其关键在于工艺和设备都尚不成熟,本文所述工艺亦不尽完善。虽如此作者仍将这一生产经验介绍给国内同行,抛砖引玉,博取多采,使其更趋完善。     

竹材刨切工艺的初步研究

毛竹经横截、去节、冲条、刨削等工序，加工成长条；再经干燥、涂胶、组坯、热压等工序，制成竹方；然后经高温水煮软化处理，在刨切机上进行横向热刨切，刨切成竹单板，用于高档贴面装饰，减少贵重木材的消耗。     

微薄木贴面装饰纤维板制造工艺初探

微薄木贴面装饰纤维板制造工艺初探娄四维（中南林学院湖南株洲４１２００６）微薄木贴面装饰人造板，是近年来流行的高档装饰材料，广泛应用于家具制造和室内装饰。应用最多的是用三合板作基材生产的微薄木贴面装饰胶合板（以下筒称装饰胶合板）。可是，胶合板价格较高，...     

刨切竹单板的软化工艺研究

为了克服刨切竹单板在家具曲面构件贴面或封边时出现横向开裂、破损等情况,采用氢氧化钠(Na OH)、碳酸氢钠(Na HCO_3)和尿素(CH_4N_2O)分别对刨切竹单板进行了软化处理。结果表明:刨切竹单板的软化工艺参数对其软化效果有较大影响,大小顺序为软化温度软化剂质量分数软化时间;随着软化温度的升高、软化时间的延长和软化剂质量分数的增大,刨切竹单板的横向柔韧性能逐渐增大;Na OH软化刨切竹单板的适宜工艺参数为:软化温度65℃、软化时间60 min、软化剂质量分数2%,Na HCO_3和CH_4N_2O则为:软化温度65℃、软化时间90 min、软化剂质量分数2%;其中,Na OH对刨切竹单板的软化效果最好。     

刨切薄竹贴面中密度纤维板工艺研究

对刨切薄竹贴面中密度纤维板(MDF)的工艺进行了研究,结果表明:在MDF的上下表面直接粘贴刨切薄竹的工艺可行,并根据试验结果确定了较优的贴面工艺参数.测试结果还显示,刨切薄竹背衬无纺布后再与MDF胶合,其表面胶合强度比刨切薄竹直接贴面MDF时低.     

覆膜厚帘竹胶合板模板的研制

研究了以3 mm以上厚度的竹篾片编织竹帘生产厚帘竹胶合板模板的工艺条件,讨论了热压时间、热压压力、热压温度及浸胶的胶液浓度对覆膜厚帘竹胶合板模板物理力学性能的影响,总结确定出最佳的可供生产应用的热压工艺条件.结果表明,在热压压力1.4 MPa、热压时间60 s/mm板厚、热压温度135 ℃、浸胶胶液浓度26%的条件下生产出的产品各项力学性能指标均达到或超出竹胶合板模板国家标准.     

泡桐制造单板和胶合板的研究

本报告为黄、淮、海地区三种泡桐制造单板和胶合板的研究。通过对单板旋切质量的测定,以及对胶合板胶合工艺、刨切薄木湿贴工艺的研究,得出结论如下: 1.泡桐材质轻软,缺陷较少,易于旋切和刨切,而且整幅单板出板率和一、二等面板率较高。2.采用泡桐和杨木混合组坯,井按特定的热压曲线进行胶合,既消除了纯泡桐结构胶合板卸压时易产生“鼓泡”,又改善了胶合板的胶合强度,提高了生产的经济效益。3.泡桐刨切薄木使用改性乳胶进行中温湿粘,胶层耐水性达到日本同类产品标;隹的要求。本研究为进一步发展泡桐单板和胶合板的生产提供了初步经验。     

枫香木材性质及其加工性能研究

采集浙江各地不同树龄枫香木材,系统研究木材解剖性质,主要物理力学性质,刨切、旋切等加工利用适应性等,结果表明:树龄20～25年是枫香木材物理力学性质的一个转折点,其主要物理性质和力学强度指标居国产阔叶树材中等水平;旋切单板胶合强度超过国家标准规定的技术要求,通过工艺改进后枫香材完全适合生产胶合板;刨切贴面板的刨切效果和贴面后的性能都较好,综合指标相对较高.     

彩色刨切薄竹生产关键技术

彩色薄竹是将水溶性染色剂在一定条件下,对刨切薄竹进行染色处理,使之具有所需均匀颜色的产品。染色是改善竹材视觉效果和提高竹材附加值的重要手段。本文根据国内外技术成果和作者的生产经验,对彩色刨切薄竹生产关键技术进行了总结,重点介绍了薄竹刨切主要生产工艺、薄竹染色关键处理技术和彩色薄竹复合加工工艺等,对彩色薄竹生产成本进行了分析。彩色薄竹是一种优良的装饰材料,可用于家具或人造板贴面,制造成各种装饰材料。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

Modelling of adequate pretwist for obtaining straight timber

Abstract

Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

Growth of Phlebiopsis gigantea in wood of seven conifer species

Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。