Wood defect detection method with PCA feature fusion and compressed sensing

We used principal component analysis (PCA) and compressed sensing to detect wood defects from wood plate images. PCA makes it possible to reduce data redundancy and feature dimensions and compressed se...     

基于专利的压缩木技术发展分析

以中国知识产权局专利数据库-s系统为数据源,利用专利分析的专利图理论(Patent map简称PM)定量分析了压缩木技术的分布年限、主要发明人、国家分布、重要申请人等数据。结果表明:压缩木为提高木制品质量的核心技术;近年来专利申请发展迅速,并处于平稳期;技术专利集中于中国和日本;国内技术专利以职务发明为主。压缩木技术未来应以集成技术开发为主,企业应加强与高校科研院所合作,促进集成创新。     

Mechanism of partial fixation of compressed wood based on a matrix non-softening method

Abstract

Three different mechanisms to explain the partial fixation of the compressive deformation of wood are postulated: non-softening, cross-linking and stress relaxation. This study attempted to fix the compressive deformation of wood by the non-softening mechanism of the cell-wall matrix using acetylation of the cell wall making it more hydrophobic. In this method, partial recovery of compressive deformation by wetting decreased at room temperature as the acetyl content increased. However, almost complete recovery occurred by boiling the compressed wood in water or soaking in acetone. This is due to the ability of boiling water or acetone to soften the cell-wall matrix of acetylated wood enough to enable recovery from compression. It is, therefore, possible to partially fix the compressive deformation of wood, preventing the resoftening of the cell-wall matrix in water.     

Effect of shear deflection on vibrational properties of compressed wood

In this paper, we have investigated vibrational properties of compressed Japanese cedar (Cryptomeria japonica D. Don). The test specimens were compressed in the radial direction at 180°C for 5 h. Compression ratios (the ratio of deformation to the initial thickness) were 33% and 67%, and the vibrational properties were measured by free-free flexural vibration test. The contribution of shear deflection was large when the length-to-depth ratio was small and the Youngs modulus to shear modulus ratio was large. The Youngs to shear modulus ratio increased as the compression ratio increased and was larger under vibration in the radial than in the tangential direction. The loss tangent increased when the contribution of shear deflection to total measured flexural deflection increased.     

Density profile and morphology of viscoelastic thermal compressed wood

The viscoelastic thermal compression (VTC) of low-density hybrid poplar (Populus deltoides × Populus trichocarpa) from fast growing trees was performed in order to produce specimens with three different degrees of densification (63, 98, and 132%). The morphology and density profile of the VTC specimens were studied. Three different methods for the preparation of specimens for microscopy were used in order to find a technique that makes it possible to examine the VTC wood microscopically in the completely deformed state. It was found that the abrasive surface preparation of oil-embedded blocks was the most promising technique. Microscopic observation revealed that the deformations in the VTC wood were mostly the result of the viscous buckling of cell walls without fracture. The volume of the void areas in the specimens decreased with the degree of densification. The results showed that the density profile of the VTC wood varied with the degree of densification as a consequence of different temperature and moisture gradients formed before and during wood compression. The density profile is also visible on the cross-section of the VTC specimens.     

Feature Extraction of defects on wood surface

IntroductionAtpresent,usingthecomputerimageprocessil1gsys-temtofinishthefeatureextractiol1ofw0oddefectsisi11anexpIorat0rystage.ThismetI1odmaydecreasetI1ellmitati0noftl1eexperilnel1talcol1ditions,suChasIights,instrumentsandsomespccialmateriaIs.Itiscol1venic11ttousethiswayandthegoodresuItswilIbeacI1ieved.TherearethreetypicaIwo0dsurfacedefectst0bestudiedintheexperiment,whicI1arekn0t,boreI1oleal1ddecayofLarixandBeIlIlu.Tl1eworkist0separatetl1edefectsfromthewoodsurfaceimagesandprovideagoodba…     

传感器数量对应力波检测原木内部缺陷精度的影响

木材无损检测技术是高效利用木材的方法之一.该文阐述了应力波法检测木材缺陷的原理,分析了传感器数量对图像的拟合度和误差率两个指标的影响.结果表明,当原木直径在20～40cm范围内时,若需对原木缺陷进行精确测量,要求图像拟合度接近90%和误差率在0.1左右时,至少需12个传感器才能满足要求;当不需要对原木缺陷进行精确测量,只需确定缺陷的大致位置时,宜选用10个传感器进行测量;当仅仅需要判断原木是否存在缺陷时,选用6个传感器就能满足要求.图3表4参8.     

Effect of sensor quantity on measurement accuracy of log inner defects by using stress wave

Wood nondestructive testing （NDT） is one of the high efficient methods in utilizing wood. This paper explained the principle of log defect testing by using stress wave, and analyzed the effects of sensor quantity on defect testing results by using stress wave in terms of image fitting degree and error rate. The results showed that for logs with diameter ranging from 20 to 40 cm, at least 12 sensors were needed to meet the requirement which ensure a high testing accuracy of roughly 90% of fitness with 0.1 of error rate. And 10 sensors were recommended to judge the possible locations of defects and 6 sensors were sufficient to decide whether there were defects or not.     

木材干燥产生缺陷的预防措施及补救方法

缺陷对木材的加工及使用影响很大 ,本文对木材干燥产生的缺陷及产生的原因进行了探讨 ,提出干燥引起缺陷的预防措施。     

Nondestructive testing method of wood moisture content based on a planar capacitance sensor model

For our research, a new hybrid experimental-computational method is presented. We applied a least squares fitting     

不同处理方法对杨树木材压缩变形恢复率的研究

采用加热和水蒸气处理方法对人工林杨树木材进行压缩变形恢复率的研究,目的是为了改善人工林软质木材的材性,提高其尺寸稳定性。结果表明:加热和水蒸气处理都是固定人工林木材压缩变形的有效方法;在处理温度相同时,水蒸气处理方法只需要4 min或8 min,而高温加热处理需要10 h或20 h。水蒸气处理方法更加经济。     

不同处理方法对人工林杨木压缩变形恢复率的研究

采用加热和水蒸气处理方法对人工林杨木进行压缩变形恢复率的研究,目的是为了改善人工林软质木材的材性,提高其尺寸稳定性。结果表明:加热和水蒸气处理都是固定人工林木材压缩变形的有效方法。     

基于声发射技术模拟蛀木害虫羽化孔洞缺陷检测

[目的]针对木材蛀干害虫羽化孔洞缺陷检测问题,通过对声发射信号的时频分析,研究木材蛀干害虫羽化孔洞缺陷的AE信号特征.[方法]首先,对无孔洞和3种不同尺寸的钻孔缺陷的木材试件,参照ASTM-E976标准采用铅芯折断方式产生AE源,通过采样频率为500 kHz的2通道木材声发射信号采集系统获取原始AE信号.然后,对原始A...     

SPOT5全色与多光谱遥感影像融合方法研究

以吉林省白河林业局的SPOT5全色与多光谱遥感影像融合为研究对象，利用Erdas Imagine9.1遥感影像处理软件，对8种融合方法的结果进行定量分析。结果表明：在提高空间分辨率能力和保持光谱特征的完整性上，Ehlers融合法、基于HIS变换的小波变换法、HIS变换法融合效果较好。     

木材微纤丝角两种测试方法的对比研究

木材微纤丝角是木材各项性质中最重要的指标之一,它的大小对木材的解剖、物理、力学性能和化学性能有着很大的影响。笔者使用两种方法测定分析了杉木的微纤丝角,为研究者选择合适的实验方法提供依据。分别利用X射线衍射法和偏振光显微镜法得到杉木的木材微纤丝角及其变异规律,并对这两种方法进行分析比较,结果表明：（1）X射线衍射法测定速度快,代表性强,适用于大量试样的变异研究,但对实验仪器要求高。（2）偏振光显微镜法测定速度较慢,但实验仪器成本相对较低,适合实验室试样的少数测定。     

Changes of chemical composition and crystalline of compressed Chinese fir wood in heating fixation

The changes in relative crystalline, chemical composition and internal structure of compressed Chinese fir wood after different heating fixations were found strictly related to fixation conditions. The compressed wood powders were fixed either by heating at different temperatures all resulting in a 10% recovery, or by incubating at 180℃ for different periods with subsequent recovery levels. Both X-ray diffraction and infrared absorption of those samples have been measured. Relative crystalline increases at early stage of heating fixation, and then decreased gradually. Hemicellulose and lignin decomposition were induced by the fixation process, especially at 180℃, and lignin was degraded actively. Furthermore, absorbed water was lost after heating, but cellulose did not change markedly. Although different fixation pathways can result in the same recovery level, the major chemical reactions underlying them vary, which is consistent with the difference of fixation mechanisms.     

Effects of preheating temperatures on the formation of sandwich compression and density distribution in the compressed wood

Sandwich compression of wood that can control the density and position of compressed layer(s) in the compressed wood provides a promising pathway for full valorization of low-density plantation wood. This study aims at investigating the effects of preheating temperatures (60–210 °C) on sandwich compression of wood, with respect to density distribution, position and thickness of the compressed layer(s). Poplar (Populus tomentosa) lumbers with moisture content below 10.0% were first soaked in water for 2 h and stored in a sealed plastic bag for 18 h, the surface-wetted lumbers were preheated on hot plates at 60–210 °C and further compressed from 25 to 20 cm under 6.0 MPa at the same temperature on the radial direction. The compressed lumbers were characterized in terms of density distribution, position and thickness of compressed layer(s). It was found that depending on preheating temperatures, sandwich compressed wood with three structural modes, namely, surface compressed wood, internal compressed wood and central compressed wood can be formed. Density of the compressed layer(s) in wood increased gradually as a result of the elevated preheating temperatures. Higher preheating temperatures gave rise to bigger distance between compressed layer(s) and the surface, and preheating temperature elevation from 90 to 120 °C contributed to a maximal distance increase of 2.71 mm. In addition, higher preheating temperatures resulted in bigger thickness of compressed layer(s) over 60–150 °C and temperature elevation from 120 to 150 °C lead to the layers integration from two into one. Further temperature elevation over 150 °C reduced the thickness of the compressed layer in wood. SEM scanning suggested that cell wall bucking rather than cell wall crack occurred in compressed layer(s) and transition layer(s).     

STUDY ON MEASUREMENT OF WOOD SURFACEROUGHNESS BY COMPUTER VISION

The working processes,machining devices and tools,cutting amount,consumptionof materials,productivity and quality of products are directly affected wood surface roughness.This paper gives an extensive review of methods used previously to measure wood surfaceroughness,and concludes that computer vision is the most suitable.The preliminarystudy shows that computer vinon method has the advantages of a noncontact,three--dimensionalmeasurement,high speed and well correlates with stylus tracing method.The method can be usedin classification and in-time measurement of wood surface roughness after being improved.