共查询到20条相似文献，搜索用时 453 毫秒
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制备、表征了酸功能化离子液体1-(3-磺酸)丙基-3-甲基咪唑磷酸二氢盐((HSO3-pmim)H2PO4),并用于催化合成乙酸松油酯的反应研究,考察了反应时间、反应温度、原料配比、催化剂用量等因素对反应的影响.在松油醇5.1 g、n(松油醇):n(乙酸酐)1:1.5、离子液体1.5 g、反应温度40 ℃、反应时间8 h的工艺条件下,松油醇转化率为100 %,乙酸松油酯的选择性为87.2%;并对离子液体(HSO3-pmim)H2PO4的重复使用性能进行了考察,离子液体在不经处理直接重复使用6次后,松油醇的转化率为99.4%,乙酸松油酯的选择性为88.6%,具有较好的重复使用性能. 相似文献
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研究了纳米固体超强酸SO4^2-／ZrO2催化松油醇乙酰化反应。通过正交试验得出反应的最佳工艺条件：反应温度50℃，反应时间5h，催化剂用量3％，乙酐和松油醇摩尔比(酐醇比)为1．3：1。在此条件下进行稳定性实验，产物中总酯的含量为92．79％，主要副产物柠檬烯和异松油烯的含量为5．27％，松油醇的转化率100％；催化剂的活性和选择性都优于普通固体超强酸，而且可重复使用5次。 相似文献
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制备、表征了酸功能化离子液体1-（3-磺酸）丙基-3-甲基咪唑磷酸二氢盐（（HSO，-pmim）H2PO4），并用于催化合成乙酸松油酯的反应研究，考察了反应时间、反应温度、原料配比、催化荆用量等因素对反应的影响。在松油醇5．1g、n（松油醇）：n（乙酸酐）1：1．5、离子液体1．5g、反应温度40℃、反应时间8h的工艺条件下，松油醇转化率为100％，乙酸松油酯的选择性为87．2％；并对离子液体（HSO3-pmim）H2PO4的重复使用性能进行了考察，离子液体在不经处理直接重复使用6次后，松油醇的转化率为99．4％，乙酸松油酯的选择性为88．6％，具有较好的重复使用性能。 相似文献
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用几种稀土元素对单一型固体超强酸SO2-4/TiO2进行改性.结果表明,用Ce4 改性效果较好,且当Ce4 质量分数为7.5 %、经500 ℃焙烧3 h后催化剂SO2-4/TiO2-Ce4 的催化活性最佳,并用TEM、XRD和IR对其结构进行了表征.该改性催化剂属于纳米级材料,粒径为32 nm,粒度均匀.并以该固体超强酸SO2-4/TiO2-Ce4 为催化剂,松油醇和乙酸酐为原料合成乙酸松油酯.利用正交试验得到适宜的合成条件为:反应温度70 ℃、催化剂用量3 %、松油醇与乙酸酐物质的量之比为1∶1.5、反应时间6 h.在此条件下,松油醇转化率达99 %,产物中乙酸松油酯含量达90 %.与普通型固体超强酸进行比较,SO2-4/TiO2-Ce4 具有更高的催化活性和选择性. 相似文献
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用几种稀土元素对单一型固体超强酸SO24-/TiO2进行改性。结果表明,用Ce4 改性效果较好,且当Ce4 质量分数为7.5%、经500℃焙烧3h后催化剂SO24-/TiO2-Ce4 的催化活性最佳,并用TEM、XRD和IR对其结构进行了表征。该改性催化剂属于纳米级材料,粒径为32nm,粒度均匀。并以该固体超强酸SO24-/TiO2-Ce4 为催化剂,松油醇和乙酸酐为原料合成乙酸松油酯。利用正交试验得到适宜的合成条件为:反应温度70℃、催化剂用量3%、松油醇与乙酸酐物质的量之比为1∶1.5、反应时间6h。在此条件下,松油醇转化率达99%,产物中乙酸松油酯含量达90%。与普通型固体超强酸进行比较,SO24-/TiO2-Ce4 具有更高的催化活性和选择性。 相似文献
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磷酸/离子液体复合体系催化合成乙酸松油酯的研究 总被引：7，自引：2，他引：5
将3种磷酸与离子液体组成的复合体系用于催化合成乙酸松油酯的反应,其中,H3PO4/[C4m im]BF4和H3PO4/[C8m im]BF4均显示出很高的催化活性;以H3PO4/[C4m im]BF4为代表,详细考察了反应的影响因素;得出最佳工艺条件:n(松油醇)∶n(乙酸酐)为1∶1.5,松油醇0.03 mol,磷酸0.03 g,反应温度40℃,反应时间10 h,离子液体[C4m im]BF45 g,此条件下所得粗产物中未反应松油醇质量分数仅为0.9%,松油醇的质量分数86.5%,松油烯11.0%。H3PO4/[C4m im]BF4复合体系重复使用7次后,适当补加H3PO4可使催化活性与新催化体系相当。 相似文献
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《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
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《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
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《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
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《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
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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
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《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
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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
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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
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《Scandinavian Journal of Forest Research》2012,27(2):166-178
This study investigated the forest history, structural characteristics, the presence of fungal species suggested to indicate ecological continuity in old-growth forest, and the species composition of saproxylic beetles in 30 old forest ''woodland key habitats'' (WKHs), and compared them with production forest in the same age-class in south-eastern Norway. No statistically significant differences in forest characteristics, community of saproxylic beetles or number of red-listed beetles were found between the WKHs and the production forest, probably owing to a combination of profound long-term logging and a lack of will to delineate sufficiently large WKHs in the one area with significantly less forestry impact. The study indicates the advantage of including forest history information in WKH selection where such data exist, and the importance of restoring habitats in heavily exploited forest landscapes. 相似文献