共查询到20条相似文献，搜索用时 62 毫秒
1.
该研究以杂种毛白杨无性系（ＰｏｐｕｌｕｓｔｏｍｅｎｔｏｓａＢＬ）４年生幼龄格为原料，应用喷蒸坟和传统热压两种方法来生产杨木刨花板．刨花板内施胶量为１０％的脲醛树脂胶（ＵＦ），目标厚度分别取１０，１５，２０，２５ｍｍ，热压温度固定在１８０℃．喷蒸热压时所用饱和蒸汽的压力为０３～０５ＭＰａ，每种厚度下喷时间一定，取两个压时间；传统热压时每种厚度下各取４个热压时间．然后测定刨花板试件的力学强度和物理性能．在这部分里，主要讨论了责任中热压法生产的刨花板的静曲强度和内结合强度．结论为：相对于传统热压法，喷蒸热压可以明显缩短杨木刨花板生产所需的热压时间，而且使刨花板具有优异的内结合强度；但是，它对饱花板的静曲强度并没有显著影响 相似文献
2.
该研究采用传统热压和喷蒸热压两种方法来生产杨木刨花板．刨花板内施加１０％的脲醛树脂胶（ＵＦ），目标厚度分别取１０，１５，２０，和２５ｍｍ，热压温度均为１８０℃．喷蒸热压时饱和蒸汽的压力为０．３～０．５ＭＰａ，每种厚度下喷汽时间一定，取两个热压时间；传统热压时每种厚度下各取４个热压时间．然后测定试件的吸水厚度膨胀率、吸水率、密度、含水率及力学性能．本文重点讨论了喷蒸热压对杨木刨花板尺寸稳定性的影响．结论认为：喷蒸热压相对于传统热压，在保证刨花板的强度、缩短热压时间的条件下，明显改善了杨木刨花板的尺寸稳定性． 相似文献
3.
水泥刨花板快速固化工艺的研究 总被引：7，自引：1，他引：7
以毛白杨、兴安落叶松和普通硅酸盐水泥为主要原料，采用二氧化碳气体喷射法研究水泥刨花板的快速固化工艺，探讨了水灰比、二氧化碳气体压力，养护条件等对水泥反应特征和水泥刨花板性能的影响。结果表明，最佳制板工艺参数为：ＣＯ２气体压力０．７ＭＰａ，通气时间３ｍｉｎ，木灰比０．２（毛白杨）或０．５（落叶松），水灰比０．３５（毛白杨）或０．４（落叶松）；水灰比不但影响成板的可能性，而且对反应特征和水泥刨花板的力 相似文献
4.
异氰酸酯胶芦苇刨花板生产工艺研究 总被引：11，自引：0，他引：11
芦苇的ＳｉＯ２含量高，使用脲醛胶（ＵＦ）难以获得良好的胶合结果，本研究采用二苯基甲烷二异氰酸酯（ＭＤＩ）胶粘剂压制芦苇刨花板，试验结果表明，当ＭＤＩ施胶量为４％和５％，刨花板的密度为０．７０ｇ／ｃｍ＾３时，其物理力学性能指标分别达到我国Ａ类刨花板优等品种和二等品的标准要求，如果ＭＤＩ单价由现在２０．００元／ｋｇ下降到１７．３０元／ｋｇ，ＭＤＩ芦苇创花板和ＵＦ芦苇刨花板的生产成本相同。 相似文献
5.
《林业机械与木工设备》1997,(12)
专利简介油棕丝生产中密度纤维板、碎料板其工艺流程为：油棕果（壳）→拉丝→烘干→切断→浸泡→蒸煮→成型→预压→热压→锯边。技术效果为：ＭＯＲ（ＭＰａ）４０．０８；ＩＢ（ＭＰａ）０．５２；ＴＳ（％）９．３７５；Ｐ（ｇ／ｍｍ↑［３］）０．７６；Ｈ（％）７．... 相似文献
6.
不同增强材料对刨花板性能影响的初步研究 总被引：1，自引：0，他引：1
为了扩大刨花板的应用范围，适应建筑、汽车等行业对高强度板材的需要，本文对以尼龙网、玻璃纤维布、玻璃纤维网、玻璃纤维束以及碳纤维为增强材料的刨花板的强度性能进行了初步探讨，研究结果表明：玻璃纤维是一种比较理想的刨花板增强材料，网孔较密的玻璃纤维布虽能提高刨花板的强度和刚性（ＭＯＲ和ＭＯＥ），但刨花板的内结合强度和刚性（ＭＯＲ和ＭＯＥ），但刨花板的内结合强度（ＩＢ）和吸水厚度膨胀率（ＴＳ）很难达到德国 相似文献
7.
异氰酸酯胶在刨花板中的应用 总被引：3，自引：1，他引：3
异氰酸酯胶作为刨花板胶粘剂，具有刨花含水率适应范围广（０～２５％），施胶量低、无游离甲醛释放、适合制造轻质刨花板等优点。施胶量为５％、密度为０．４５ｇ／ｃｍ３和０．６１ｇ／ｃｍ￣３的二苯基甲烷二异氰酸酯（ＭＤＩ）小黑杨刨花板的物理力学性能分别达到Ａ类刨花板二等品和优等品的指标要求。密度为０．６５ｇ／ｃｍ￣３时，只要ＭＤＩ施胶量达到３％，刨花板的物理力学性能指标能达到Ａ类刨花板的国家标准要求。试验还表明：ＭＤＩ具有较好的耐水性，但耐湿热性和长期耐水性不如酚醛胶。生产１ｍ￣３刨花板ＭＤＩ与ＰＦ和ＵＦ胶粘剂成本比为２．０５：１．７８：１．００。 相似文献
8.
异氰酸酯胶无毒低密度杉木刨花板的制造 总被引：1，自引：0，他引：1
本研究探讨了用异氰酸酯胶粘剂制造低密度杉木刨花板的工艺条件,讨论了施胶量、热压温度、热压时间、热压压力和刨花含水率对板材性能的影响。结果表明,当板材密度为０．４３～０．４８ｇ／ｃｍ＾２时,施胶量只需５％,刨花含水率适应范围广,所制成的刨花板无毒,耐水性好。 相似文献
9.
玻璃纤维束增强刨花板的研究 总被引：1，自引：0，他引：1
采用玻璃纤维束增强刨花板的试验结果表明,随着玻璃纤维束施加量的增加,刨花板的强度和刚度（ＭＯＲ和ＭＯＥ）有显著的提高,但施加量达到一定程度后,升高趋势逐渐平缓;随着玻璃纤维束间距的减小,刨花板的强度和刚度（ＭＯＲ和ＭＯＥ）呈直线上升,而内结合强度（ＩＢ）变化规律不明显,当间距小到一定程度后,ＩＢ很难达到德国室外用刨花板标准ＤＩＮ ６８７６３ Ｖ１００的要求;随着琉璃纤维束在刨花板厚度方向上的位置由 相似文献
10.
杨木单板连续式热压干燥的研究 总被引：3，自引：0，他引：3
本文以生长在苏北地区的美洲黑杨单板（名义厚度１．７ｍｍ）为试材,在连续式热压干燥机上进行了生产型试验研究,采用高温导热油为载热体,热板温度１９２℃,热板压力０．０９ＭＰａ（前段）至０．１８ＭＰａ（后段）。研究结果表明：采用高温连续式热压干燥的方式辅以适当的“呼吸”周期,可在２ｍｉｎ内将生材单板（初含水率１４９％）干至８％以下的终含水率。干单板基本平整、光滑,终含水率均匀,无撕裂。单板厚度干缩率平均５．３％,横纹干缩率４．９％。胶合强度平均０．８１２ＭＰａ略高于网带对流干燥的０．７７９ＭＰａ,结果说明此法干燥人工林场木单板是可行的。 相似文献
11.
《Scandinavian Journal of Forest Research》2012,27(5):427-435
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. 相似文献
12.
《Scandinavian Journal of Forest Research》2012,27(3):206-217
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. 相似文献
13.
《Scandinavian Journal of Forest Research》2012,27(1):53-61
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. 相似文献
14.
《Scandinavian Journal of Forest Research》2012,27(1):15-27
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. 相似文献
15.
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。 相似文献
16.
《Scandinavian Journal of Forest Research》2012,27(2):131-138
The effects of soil scarification (mounding), slash removal and clear-cut age on the natural regeneration in clear-cuts was evaluated using data from four sites in southern Sweden. The treatments were carried out during a good seed and establishment year for birch ( Betula pubescens Ehrh. and B. pendula Roth). Scarification had the strongest positive effect on the density of naturally regenerated seedlings, especially in birch, but also in pine ( Pinus sylvestris L.) and spruce [ Picea abies (L.) Karst]. Slash removal had a positive effect on birch density. No statistically significant effect of clear-cut age was found. In addition, no statistically significant interactions between clear-cut age and scarification or slash removal were found. The ingrowth of field vegetation was the fastest in areas that were not scarified, less rapid in areas scarified on old clear-cuts, and the slowest after scarification in fresh clear-cuts. In conclusion, it may be possible to control the density of birch during a good establishment year for birch. If birch is desired, the best combination of treatments is to remove the slash and scarify; otherwise, these treatments should be avoided. 相似文献
17.
18.
《Scandinavian Journal of Forest Research》2012,27(5):472-479
Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken. 相似文献
19.
Srisuda Thippayarugs Banyong Toomsan Patma Vityakon Viriya Limpinuntana Aran Patanothai Georg Cadisch 《Agroforestry Systems》2008,72(2):137-148
In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic
or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts
(stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea
(Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content
as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest
N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized
to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea,
largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for
N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant
components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N
released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures
were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality
components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in
the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols.
Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest
age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its
components are mixed. 相似文献
20.
A. Rigueiro-Rodríguez M. R. Mosquera-Losada E. Gatica-Trabanini 《Agroforestry Systems》2000,48(3):245-256
The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste
disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization,
(2) milk sewage sludge at 40 kg N ha−1 target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two
pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha−1. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha−1) + Trifolium repens L. group Ladino (4 kg ha−1) + Trifolium pratense L. var. Marino (1 kg ha−1); (2) Lolium perenne L. var. Tove (25 kg ha−1) + Trifolium repens L. group Ladino (4 kg ha−1) + Trifolium pratense L. var. Marino (1 kg ha−1). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea
(Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m2, with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect
on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage
sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but
affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral
systems.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献