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习惯上林区公路路线设计为多挖少填。这是因为过去施工技术装备较差,对路基填方的压实密度不易达到,加上施工完成使用后养护又未能很好跟上,所以路堤的稳定性差,人们对路堤设计有一定的顾虑。而挖方路基只要在施工过程中不破坏(或拢动)路基范围以外的山体,其稳定性就认为可以得到保证。同时,填方多了,会出现一些防护工程,造价比挖方高,突破限额投资而不得不採用低价方案,所以主张多挖少填。对此笔者持不同看法。1、填方只要认真做好压实和对坡脚作妥善的稳定技术处理工作,再经过一定的雨季,它比深挖的路堑边坡稳定。仔细观察林区公路,由于路基不稳定而阻碍交通者,路堤与路堑相比还是路堑者居多。因在施工时,尤其是不经计算用的药量而过量用药的爆破施工路段,破坏了山体的固有的平衡状态, 相似文献
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土方调配如何将切方区域的土方合理的调往填方区域,而使土方的总立方米公里为最小。这个问题可以应用线性规划的表上作业法求解。表上作业法,方法简单、易推广应用,经济效果显著。 相似文献
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1994年5月,在深圳至汕头一级汽车专用公路东段13标段的施工过程中,由于南方公司土方队决定提前退场,因而出现对其已完成工程量进行确认计量的工作。 深汕一级汽车专用公路,路基顶宽为24.5m,路基边坡为1:2。在k287 100至k289 200路段内,路堤填高平均为3.12m,填方总量为21万m~3,挖方仅1175m~3, 相似文献
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Mechanism of formaldehyde adsorption of (+)-catechin 总被引：1，自引：1，他引：0
Toshiyuki Takano Tomomi Murakami Hiroshi Kamitakahara Fumiaki Nakatsubo 《Journal of Wood Science》2008,54(4):329-331
The reaction of (+)-catechin with formaldehyde vapor was investigated as a model reaction of formaldehyde adsorption of (+)-catechin.
It was found by H nuclear magnetic resonance spectroscopy, matrix-assisted laser desorption/ionization time-of-flight mass
spectrometry, and gel permeation chromatography of the product that the vapor reaction of (+)-catechin with formaldehyde without
a solvent or a catalyst proceeds via methylolation, condensation, and polymerization. This is the same as the reaction in
a solvent in the presence of an acid or a base. The formation of polyoxymethylenes such as paraformaldehyde was not confirmed. 相似文献
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永平县森林生物量的碳储量初步估算 总被引：1，自引：0，他引：1
以云南省永平县的森林资源数据为基础,采用公式:碳储量(C)=林木蓄积湿重×比值×(1-含水率)×含碳率,分别计算林木、林下灌木、林下草本植物、林下凋落物生物量的碳储量,并以2005年为基准年,采用复利公式Cnt=A(1+B)n对永平县2005~2015年森林生物量的碳储量进行了预估. 相似文献
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沙米种子的萌发特性探讨 总被引：1，自引：0，他引：1
在实验室条件下研究了沙米种子的萌发特性,结果表明：沙米种子在全光照和半光照条件下表现出很高的发芽率和出苗率,而在黑暗条件下出苗率很低但发芽率仍然很高;沙米种子在埋深为0．5cm、1cm、2cm条件下表现出很高的发芽率和出苗率,而在埋深为3cm条件下发芽率和出苗率很低;沙米种子的发芽率和出苗率随降雨量的增加而增大,其中在降雨量为5mm条件下沙米种子几乎不能出苗。另外,即使在满足发芽的条件下,沙米种子也不会全部发芽,而是表现出明显的休眠性,以适应流沙特殊的环境条件。 相似文献
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The technology of liquefying processed-waste bamboo with phenol is investigated by single factor trials and an orthogonal
design. We studied the preparation technology and properties of adhesives from this phenol-liquefied bamboo with formaldehyde
(BPF). The results show that temperature has a significant effect on liquefaction. The effect of the mass ratio of phenol
to bamboo comes second and the catalyst dosage within the range of 2%–4% is the least effective. The optimum conditions of
liquefaction are as follows: a mass ratio of phenol to bamboo 3.5, a catalyst dosage of 4%, liquefying temperature 145°C and
liquefying time 60 min. The liquefaction rate of bamboo reached 99.1%. For the preparation of the adhesive, a mass ratio of
liquefied bamboo products to formaldehyde (37%) is 100 to 164.8–199.5, while the ratio 100 to 108.2 is the best. This adhesive
has a lower curing temperature than that of normal PF resin. At a hot-press temperature of 130 or 140°C, this new adhesive
provides excellent bonding strength of plywood. The most favorable temperature for hot-pressing is 140°C.
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Translated from Chemistry and Industry of Forest Products, 2007, 27(6): 65–70 [译自: 林产化学与工业] 相似文献
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We used a two-dimensional finite element method to analyze the load-slip characteristics of nailed wooden joints sheathed with a panel. We used tests of nail bending, nail shank embedment in a wood or a panel, nail-head embedment in a face of a panel, nail withdrawing from a wood, friction between a wood and a panel, and initial axial forces of the nails. The values of the material properties for the analytical models were determined with the above tests. With a conventional one-dimensional analysis it is impossible to evaluate the shearing performance accurately because the axial forces of the nail are not calculated. Therefore, we used two-dimensional geometric nonlinear analysis. The computed load-slip curves closely matched the original experimental results; and when the friction and initial axial forces were considered, the computed curves were more likely to match the original experimental results. Our results suggested that it is better to use geometric nonlinear analysis to analyze the shearing characteristics of nailed joints, and that friction and axial forces are important factors for accurate analysis.Parts of this report were presented at the 7th World Conference on Timber Engineering, Malaysia, August 2002 相似文献
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二乔刺槐愈伤组织超低温保存及适宜降温方法 总被引：1，自引：0，他引：1
二乔刺槐叶片在添加5 mg·L-16-BA的MS培养基上诱导出愈伤组织.将愈伤组织在冻存液(MS+10%DMSO+0.5 mol·L-1蔗糖)中于4℃预冷2 h,置人程序降温仪以1℃·min-1的速率降温至-7℃停留1 h,再以0.1℃·min-1的冷却速率将样品冷却至-20℃,平衡1 h,接下来以0.3℃·min-1的冷却速率将样品冷却至-40℃投入液氮保存,是适宜的降温方法.液氮保存1天后以38℃温水浴解冻.解冻后将愈伤组织用液体培养基(MS+6-BA 5 mg·L-1+30 g·L-1蔗糖)洗涤后转入恢复培养基暗培养,14天后放于光照下培养.光培养3天后冻后愈伤组织上开始长出新生愈伤组织颗粒,成活率最高可达52%,新生愈伤组织可诱导成苗. 相似文献
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福建省县域森林转型社会经济影响因素分析 总被引：1，自引：0，他引：1
【目的】研究森林转型的主要社会经济影响因素,为推动区域社会经济与森林生态协调发展提供参考。【方法】基于福建省32个典型样本县2000—2016年遥感影像,获取森林面积数据,结合社会经济统计数据,利用分位数回归方法研究不同森林资源条件下社会经济和制度等因素对森林转型的影响。【结果】1)林农人均收入水平对森林面积增长具有显著促进作用,在森林资源适中的地区,人均收入提高对森林转型的促进效应较大,而在森林资源较为丰富或相对匮乏的地区,人均收入提高对森林转型的促进效应较小;2)人均粮食产量对森林转型具有显著正向作用,在森林资源相对匮乏的地区,人均粮食产量提高对森林面积增长的促进效应更显著;3)集体林权制度改革对森林转型具有负向影响。【结论】林农收入增长和人均粮食产量提高是促进福建省县域森林转型的重要因素,提高林区人均收入水平、促进土地集约化利用有助于森林面积恢复和增长;集体林权制度改革对森林转型具有负向作用,应进一步完善集体林权制度配套改革,形成促进林农投资林业的长效激励。 相似文献
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本文分析了我国刨花板的生产、销售现状,说明了刨花板是人造板中使用范围最广、市场潜力最大的产品,是实体木材好的代用品。但在产品中存在着甲醛释放量过高的问题,只有解决这个问题,才能使刨花板有好的销售市场,有更大的发展空间。 相似文献
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《Scandinavian Journal of Forest Research》2012,27(6):496-504
The effect of the timing of precommercial thinning on the productivity of work was examined in young Norway spruce [Picea abies (L.) Karst.] stands in southern Finland. The common problem of large variation between sample plots in time studies was avoided by introducing a new approach based on a combination of stand measurements, tree-ring analysis and existing work productivity functions. The results indicated that a 2 year delay in the precommercial thinning of a stand was enough to cause an increase of 10-42% in the consumption of working time at a mean height of 1.5-3.1 m. At a later thinning, at a mean height 4.1-7.2 m, the increase was 8-24%. The development of the stand up to the first commercial thinning was not significantly influenced by a 2 year delay in the late precommercial thinning. 相似文献