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软X—射线法测定木材生长轮密度的研究 总被引：5，自引：2，他引：3
本文开发了一种用于木材生长轮材质变异分析的软X-射线测量法,对14种木材进行了测定和分析,获得了满意的测量结果。 相似文献
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材性改良研究：Ⅰ.X射线木材密度测定 总被引：6，自引：2，他引：6
利用Ｘ射线衍射（Ｄ－ｍａｘ３Ｂ型）改装成直接扫描式Ｘ射线木材密度计，可快速、高效测定木材密度组成，即木材平均密度，平均早材密度，平均晚材密度，最大木材密度，最小木材密度，木材密度梯度和木材密度的变异幅度，为材性改良提供了新手段，本文用Ｘ射线木材密度计测定１７个树种木材密度。 相似文献
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Yoshiharu Nishiyama 《Journal of Wood Science》2009,55(4):241-249
The current structural models of the cellulose microfibril as well as its mechanical and thermal properties are reviewed.
The cellulose microfibril can be considered as a single thin and long crystalline entity with highly anisotropic physical
properties. The contribution and limit of different methods employed such as electron microscopy, infrared spectroscopy, X-ray
scattering and diffraction, solid state nuclear magnetic resonance spectroscopy, and molecular modeling are also discussed. 相似文献
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Crystallinity is an important property of woody materials; it responds to tree growth traits, structure, and chemical composition,
and has a significant effect on Young’s modulus, dimensional stability, density, and hardness, etc. The ability of near-infrared
(NIR) spectroscopy coupled with multivariate analysis to rapidly predict the crystallinity of slash pine (Pinus elliotii) plantation wood was investigated. The results showed that the NIR data could be correlated with the X-ray diffraction (XRD)-determined
crystallinity of slash pine wood by use of partial least squares (PLS) regression, producing excellent coefficients of determination,
r
2, and root mean square error of calibration, RMSEC. The use of either reduced spectral ranges or the selection of certain
wavelengths consistent with known chemical absorptions did not have any detrimental effect on the quality of PLS models allowing
the use of inexpensive, small, and portable spectrometers. These studies show that NIR spectroscopy can be used to rapidly
predict the crystallinity of slash pine wood. 相似文献
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土壤有机碳（SOC）矿化一般通过培养松散土样来测定,但是松散土样与原状土的结构存在很大差异,二者之间SOC矿化的关系尚不明确;通过填装土柱可以获得接近田间状态的土壤样品,但填装的紧实程度会改变土壤孔隙结构,因此可能影响SOC矿化。本研究首先以施用不同量有机肥的红壤为研究对象,设置松散土样和填装土柱两个处理,采用室内培养法比较二者之间SOC矿化的差异;然后选择其中一种土壤填装土柱,设置四个紧实程度处理,分别为1.1（BD1.1）、1.3（BD1.3）、1.5（BD1.5）和1.7 g?cm-3（BD1.7）,利用X射线显微CT（Computed Tomography, CT）成像技术分析土壤孔隙结构,分析紧实程度对土壤孔隙结构及SOC矿化的影响。结果表明,松散土样与填装土柱的SOC矿化量有显著差异,培养结束时（第57天）,松散土样的有机碳累积矿化量约是填装土柱的4倍。紧实程度增加较大程度地降低了土壤的总孔隙度和大孔隙度,降低比例分别为12.9% ~ 17.4%和18.7% ~ 88.5%;并且使充气孔隙度从63.6%下降到了8.2%,而充水孔隙度从36.4%增加到了91.8%。填装土柱的SOC矿化量随紧实程度增加呈先增加后降低的趋势,培养结束时（第28天）,BD1.5的SOC矿化量最高。回归分析的结果表明,SOC矿化量与总孔隙度、大孔隙度（>16 μm）、充水孔隙度（Water-filled pore space, WFPS）或充气孔隙度（Air-filled pore space, AFPS）之间存在显著的非线性关系。当总孔隙度或大孔隙度低于46%或3.7%时,SOC矿化量随孔隙度增加而增加;反之,SOC矿化量随孔隙度增加而降低。SOC矿化量与WFPS或APFS之间的关系呈现出类似的规律,当WFPS为66%或AFPS为34%时,SOC矿化量最高。以上结果说明,通过培养松散土样测定SOC矿化将会高估田间SOC的矿化潜力;紧实程度的变化会改变土壤的孔隙结构进而影响填装土柱的SOC矿化;SOC矿化量与孔隙度之间存在显著的非线性关系。 相似文献
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Fire scars in dated sequences of tree-rings are regularly used for the reconstruction of histories of forest fire frequency and investigations of various exogenous factors (climate in particular) which may control such events. The potential of the tree-ring archive in this regard is such that in circumstances where no scarring occurs following a particular fire, or where sampling is limited to increment cores which may miss the zone of scarring, alternate means of detecting tree-ring evidence for fire impact must be sought. One possible alternative may be detection of changes in tree-ring chemistry associated with growth years following forest fires. If it was possible to characterize such a change in chemistry an independent proxy for forest fires in tree-ring series might be established. The behavior of various elements within the xylem is however extremely complex so for a dendrochemical approach to fire history to be established, new techniques are required to enhance existing knowledge of elemental behavior in trees affected by fire. In this study, elemental intensities were mapped across scarred and un-scarred vectors of Pseudotsuga macrocarpa (Vasey) Mayr (bigcone Douglas-fir) tree-rings from a site in the Los Padres National Forest, Southern California, using Scanning X-Ray Fluorescence Microscopy (SXFM). The aims were: to assess the potential of this technique for understanding elemental change in relation to fire scars and undamaged contemporary growth; to provide new information on specific elemental behavior in this species; and to contribute to wider research for dendrochemically establishing fire histories. The results highlight the potential of SXFM for mapping elemental changes associated with compartmentalization, callus and woundwood as well as providing some evidence for depletion of certain elements in contemporary un-scarred rings. They also provide a first step towards future work to use cores for dendrochemical construction of fire histories. 相似文献
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