生产工艺对巨尾桉/聚乙烯膜复合材料质量的影响

采用巨尾桉基材、胶合剂聚乙烯膜制备三层木塑复合材料,分析热压温度、热压时间、热压压力、施胶量这四个因素对复合材料胶合强度的影响。结果表明：在热压温度160℃、热压时间50s/mm、热压压力0.7MPa、施胶量为119g/m2的工艺条件下,巨尾桉/聚乙烯膜复合材料的胶合性能最优,能够达到II类胶合板标准。     

竹地板薄木贴面工艺试验

为了丰富竹地板的外观效果,扩大竹地板的种类,采用正交试验方法,探讨了竹地板表面进行0.6 mm榉木和2.0 mm枫木薄木贴面工艺。结果表明:利用榉木和枫木薄木贴面竹地板切实可行,其较佳工艺参数分别为:榉木热压压力0.8 MPa,热压温度100℃,热压时间240 s,涂胶量为120 g/m2;枫木热压压力1.2 MPa,热压温度120℃,热压时间360 s,涂胶量140 g/m2。     

不同工艺参数对UF工业大麻秆刨花板性能的影响研究

工业大麻秆是一种优质的轻质非木质原料,利用脲醛树脂为胶黏剂可以制备出性能优良的刨花板产品.笔者主要分析不同的工艺参数,包括密度、热压时间、热压温度和施胶量对板材性能的影响.研究结果表明,密度和施胶量对板材性能的影响要比热压温度和热压时间明显,随着板材密度、热压温度和热压时间的增加,板材的力学性能大多先增加后减小;而随着施胶量的增加,板材的力学性能呈增加趋势.在目标密度0.55 g/cm3,施胶量10％,热压温度130℃或170℃条件下,板材的力学性能可达到国标普通刨花板的标准要求;当目标密度等于或高于0.65 g/cm3、施胶量等于或高于12％、热压温度在140～ 160℃、热压时间在20 ～ 45s/mm之间时,除TS外,板材的其他力学性能可达到国标室内装饰和家具用材的标准要求,并可与相同工艺条件下,目标密度为0.75 g/cm3的木质刨花板的各项性能相媲美.可见,工业大麻秆是一种优质的非木质原料,利用该原料在低温条件下制备低密度的刨花板是可行的.     

改性豆基蛋白胶杨木刨花板的制造工艺

探讨利用改性豆基蛋白胶压制杨木刨花板的工艺,分析热压温度、热压时间、施胶量和防水剂加入量对杨木刨花板性能的影响,提出厚12 mm、密度0.70 g/cm3杨木刨花板的最佳工艺条件为:热压温度170℃,热压时间14min,施胶量10%,防水剂加入量1.4%。在此条件压制的板材的性能超过GB/T 4897.4-2003的要求。     

麦秸/聚苯乙烯复合材料工艺参数研究

以麦秸和废旧聚苯乙烯塑料为原料,采用冷混-热压工艺,通过正交试验和单因子试验,研究热压时间、热压温度、复合材料密度、聚苯乙烯比例和施胶量等工艺参数对麦秸/聚苯乙烯复合材料性能的影响.结果表明:热压时间7 min、热压温度190℃、聚苯乙烯比例为35%、施胶量3%、复合材料密度0.6 g·cm-3和0.65 g·cm-3时,压制出的麦秸/聚苯乙烯复合材料各项物理力学性能指标达到刨花板国家标准(GB/T 4897.1-4897.7-2003)要求,确定了试验的最佳工艺参数和工艺条件.     

改性大豆蛋白胶黏剂制造杨木胶合板热压工艺

利用单因素试验方法,研究了热压温度、热压时间、热压压力和施胶量对使用改性大豆蛋白胶黏剂制造的杨木胶合板胶合强度的影响规律.结果表明:在100～ 220℃热压温度范围内,随着热压温度的增加,胶合强度显著增大;在35～60 s/mm热压时间范围内,胶合强度随热压时间的增加呈上升趋势,当时间从60 s/mm升至85 s/mm,胶合强度几乎保持一致;热压压力在1.25 MPa时,胶合强度达到最大值;施胶量在130 ～430g/m2热压时间范围内,胶合强度随施胶量的增加呈上升趋势.由此得出最优工艺参数为:热压温度180℃,热压压力1.25 MPa,热压时间60 s/mm,施胶量为310g/m2.     

植物蛋白胶细木工板加工技术的研究

笔者使用的植物蛋白胶是以富含蛋白质的生物质为主要原料制备的无甲醛释放的胶粘剂。由于其初粘性不如"三醛胶"大,因此不能利用传统细木工板的生产工艺。针对该胶粘剂的特点,通过研究新的施胶工艺,确定木材含水率8%～12%,第1次预压15 min,热压第一阶段最佳工艺参数:施胶量170 g/m2,热压时间8 min,压力17 MPa,温度105℃;第2次预压15 min,热压第二阶段最佳工艺参数:施胶量155 g/m2,热压时间4 min,施胶量155 g/m2,温度100℃,压力15 MPa,板材外观能达到优等品标准,理化性能符合GB/T5849-2006的要求。     

新型复合竹地板热压工艺探讨

对以大径毛竹竹条为面层原料、毛竹梢头或小径竹碾压竹片为芯层和底层原料的新型复合竹地板的热压工艺进行了正交试验和验证试验,结果表明,研制的新型复合竹地板具有较好的物理力学性能,各项指标都达到竹地板标准要求;生产复合竹地板较佳的热压工艺参数为:正压压力2.0 MPa、侧压压力3.0 MPa、热压时间0.6min/mm、热压温度110℃.     

狼尾草刨花板制造工艺研究

采用正交实验设计的方法,研究了施胶量、热压温度、热压时间等工艺因素对狼尾草刨花板的静曲强度、弹性模量、内结合强度、吸水厚度膨胀率等性能的影响.研究结果表明:狼尾草应用在刨花板制造中是可行的;其中狼尾草刨花板制造的最佳工艺参数为施胶量13%、热压时间40 s/mm(板厚)、热压温度180℃.     

竹席/竹碎料新型建筑模板制备工艺研究

将小径竹及竹材加工剩余物加工成一定规格的竹碎料。以竹碎料为芯层,以竹席为表层组成板坯,通过热压制备竹席/竹碎料新型建筑模板。采用正交试验,选取热压时间、热压温度和施胶量作为工艺因素,对竹席/竹碎料复合新型建筑模板制备工艺进行了研究。研究发现,施胶量对产品的各项性能指标的影响最显著,其次是热压时间和热压温度。通过分析得出优化工艺:热压时间70 s.mm-1,热压温度为170℃,施胶量为10%。     

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.     

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.     

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。     

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.     

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.     

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.