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纳米科技是21世纪知识创新和技术创新的源泉,纳米木材学是纳米科技与木材科学交叉融合的必然产物.提出了纳米木材学的研究领域和发展方向. 相似文献
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纳米硬度测量的计算机仿真研究进展 总被引：1，自引：0，他引：1
综述了纳米硬度测量的计算机仿真国内外研究进展,介绍了纳米硬度测量过程仿真(有限元方法和分子动力学方法)的研究现状等,指出了纳米硬度测量的未来发展趋势。 相似文献
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纳米复合材料是本世纪最有前景的材料。聚合物纳米复合材料商业化用途虽然处于发展初期,但正在实现经济和技术上的重要突破。在塑料母料中加入纳米粒子可以优化其物理性能、导电及导热性能。目前主要有三种纳米粒子用于合成聚合物纳米复合材料,分别为:纳米黏土、碳纳米 相似文献
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本文就我国纳米科技发展的现状进行了阐述,指出我国在纳米科技发展方面主要存在有六个方面的问题,最重要的是人才不足和研究开发方向重点不突出的问题.最后,笔者提出了我国发展纳米科技的建议. 相似文献
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以商品南方松溶解浆、漂白桉木浆为原料,采用硫酸水解法、纤维素酶预处理法、2,2,6,6-四甲基哌啶氧自由基(TEMPO)氧化法以及机械法分别制备了纳米纤维素,利用透射电镜(TEM)、原子力显微镜(AFM)详细表征了不同方法制备的纳米微晶纤维素(CNC)和纳米纤丝纤维素(CNF)。采用了多种商品粒度仪快速定性表征了纳米纤维素的大小,CNC为棒状纳米晶须结构,直径约为20 nm,长度为10~200 nm;CNF一般为网状结构,尺寸较大且分布较宽,单根CNF直径从几纳米到几百纳米不等。依据离心分离以及布朗运动制备的2种仪器非常适合半定量快速表征非网状结构的纳米微晶纤维素,实验重复性也很好。 相似文献
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纳米,就在人们刚刚熟悉了计算机和网络,对基因还没弄太明白的时候,这个物理学的老名词带来了新的技术,开始席卷全球。纳米技术的应用将远远超过计算机工业,并成为未来信息的核心。利用纳米技 相似文献
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Alaa A. Bashandy Alaa E. El-Habashi Ahmed K. Dewedar 《Wood material science & engineering》2018,13(4):241-253
This research aims to study the feasibility of repair and strengthening of timber cantilever beams used in historic buildings. It is conducted to investigate the feasibility of using different valid materials and techniques to repair and strengthen timber cantilever beams in new and historic timber buildings. The study is performed in terms of structural performance as well as historic and architectural values. An experimental program of several different materials and techniques is executed. The results are driven in terms of initial cracking load, crack propagation for the tested samples at different loading stages, deflection values, and failure load for each repaired or strengthened material and technique. The main variables are timber types (new and historic), repair and strengthening materials (steel plates, Glass Fiber Reinforced Polymer wrap, and Carbon Fiber Reinforced Polymer laminates), repair or strengthening techniques (near surface mounted and externally bonded system), and cantilever length (1000 and 1250?mm). Test results indicated that using steel plates, glass fiber wrap, and carbon fiber laminates increases the value of failure loads and decreases the deflection at both; repaired and strengthened timber cantilever beams compared to control beams. 相似文献
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IntroductionMaskedciVet(Paguma18vata),Mammalia,Viverridae,ismainlydiStributedinShanxi,Sichuan,Tibet,Yunnanprovinces,etc..Itsmeatisdeliciousandhasspecialflavor.Itiseasytoberaisedartificially,withhighproduCtivity.Nutria(MyocasterCOypus),Rodentia,Capromyidae,originatedinArgentina,Chili,etc.insouthAmerica.Itisakindofherbivoresfur-bearer.itsartificialraisinghassuchmeritsasdurablefurandlowcostandhighproduCtivity.MaskedcivetandnutriahavehigheconomicvalueandwideprospeCtofutilization.Atpresen… 相似文献
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胡云楚 《中南林业科技大学学报(自然科学版)》1994,(2)
本文探讨了用苯芴酮萃取分光法测定微量锗的实验条件和步骤．结果表明，用此法测定微量锗灵敏度高、操作简便、准确，是测定微量锗的较好方法．可用于对植物和食品中的微量锗进行检测． 相似文献
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自然保护区合作管理(共管)理论研究综述 总被引：6，自引：0，他引：6
自然保护区合作管理自20世纪80年代末期开始逐步兴起,在资源管理中被广泛使用。文章介绍了共管的含义、共管实施原则、分析框架和评价指标。从公共部门和私有部门的互动模式、集体行动类型的不同、政府和资源使用者的参与管理方式三个方面论述了共管的模式。分析了政府和社区在共管实施过程中的作用,指出共管仍面临着分权不够、合作中的文化障碍、组织类型简单和信息交流不充分、社区参与能力和认识能力不足等挑战。 相似文献
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《Scandinavian Journal of Forest Research》2012,27(7):577-584
ABSTRACTThe connection between chemical composition and anatomy of wood is poorly studied. Abiotic and biotic growth conditions affect the synthesis of structural compounds and the anatomy of wood at the same time as they affect growth. In this study, the wood chemical composition, and connections between wood chemistry and anatomy were studied in downy birch (Betula pubescens Ehrh.) grown on four growth sites possessing mineral and peat soils. Lignin, holocellulose, extractive and ash contents, and effective heating value were analysed and compared with libriform fibre double wall thickness and lumen diameter, vessel size and number, and ray and axial parenchyma numbers. Measured lignin and extractive contents were exceptionally high and holocellulose content low. Correlations between wood anatomy and effective heating value were partly different on different soils. Correlations between holocellulose and anatomy were the opposite of the correlations between other chemical compounds and anatomy. The significant correlations between chemical composition and anatomy were commonly opposite in trees grown on peat than in trees grown on mineral soil. Particularly, vessel characteristics and fibre wall thickness correlated significantly with wood chemistry in trees grown on mineral soil. The connections between wood anatomy and chemistry proved to be soil-dependent. 相似文献
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Temuulen Tsagaan Sankey 《New Forests》2008,35(1):45-55
Spatial patterns, rates, and density of encroaching forests into adjacent grasslands have important implications for long-term
land use management and resource planning. This study examines the effects of Douglas-fir (Pseudotsuga menzeisii) and aspen (Populus tremuloides) regeneration mechanisms on sucker and seedling spatial patterns, distance from adult trees, and density in encroaching forests.
A total of 8,924 aspen suckers and 1,244 Douglas-fir seedlings were counted and mapped in 2,920 quadrats (5 m × 5 m) in 106
plots along a lower forest-grassland ecotone in the Centennial Valley, MT, USA. Sucker and seedling spatial patterns were
analyzed using Morisita’s I index. Average sucker and seedling density per quadrat and distance from adult trees were estimated for each plot and compared
between aspen-dominated plots and Douglas-fir-dominated plots using ANOVA tests. Aspen suckers were established in a clustered
spatial pattern at a significantly higher density and a significantly shorter distance from the adult trees. In contrast,
Douglas-fir seedlings were established in varying spatial patterns at a significantly lower density and a significantly greater
distance from the adult trees. Forest encroachment into the adjacent grassland in the Centennial Valley is occurring in contrasting
patterns and at varying rates and densities due to the difference in aspen and Douglas-fir regeneration mechanisms. 相似文献
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G.W.W. Wamelink H.J.J. Wieggers G.J. Reinds J. Kros J.P. Mol-Dijkstra M. van Oijen W. de Vries 《Forest Ecology and Management》2009
Changes in the Earth's atmosphere are expected to influence the growth, and therefore, carbon accumulation of European forests. We identify three major changes: (1) a rise in carbon dioxide concentration, (2) climate change, resulting in higher temperatures and changes in precipitation and (3) a decrease in nitrogen deposition. We adjusted and applied the hydrological model Watbal, the soil model SMART2 and the vegetation model SUMO2 to asses the effect of expected changes in the period 1990 up to 2070 on the carbon accumulation in trees and soils of 166 European forest plots. The models were parameterized using measured soil and vegetation parameters and site-specific changes in temperature, precipitation and nitrogen deposition. The carbon dioxide concentration was assumed to rise uniformly across Europe. The results were compared to a reference scenario consisting of a constant CO2 concentration and deposition scenario. The temperature and precipitation scenario was a repetition of the period between 1960 and 1990. All scenarios were compared to the reference scenario for biomass growth and carbon sequestration for both the soil and the trees. 相似文献