Flexural Behavior of Typical Chinese Traditional Timber Stitching Beams

In Chinese traditional timber buildings, stitching is very common. When the bearing capacity or the rigidity is inadequate, a timber beam is often strengthened with another beam using the stitching method. The timber stitching beams are mainly of two types—the small-top/big-bottom type and the big-top/small-bottom type. To study the bending behavior of these two types of timber stitching beams, including the failure mode, the flexural capacity, the strain distribution at mid-span section, and the maximum deflection, bending tests are carried out on 14 timber stitching beams with Chinese traditional conformation for seven pine beams and seven fir beams. The results show that the failure modes of the small-top/big-bottom type of stitching beams all show brittle fractures at the bottoms of the bottom beams. The failure modes of the big-top/small-bottom type of stitching beams all show brittle fractures at the bottoms of the top beams. The distribution of section strain along the height of each part of the beam basically obeys plane hypothesis. Based on the theoretical and experimental analysis, the calculation formulas of flexural capacity and maximum deflection of these two types of timber stitching beams made of pine and fir are presented.     

基于丰度反演及光谱变换的书画霉斑虚拟修复

古书画在保存过程中容易滋生霉斑病害，霉斑不仅影响书画的外观，还会对纸质文物造成不可逆转的永久性破坏。为了给霉斑清洗提供直观参考，提出基于丰度反演及光谱变换的书画霉斑提取与虚拟修复方法。选取与霉斑区域光谱曲线存在明显差异的450～600 nm之间244个波段作为特征波段，通过连续最大角凸锥端元提取与灰度分割，提取霉斑区域。再对高光谱影像进行主成分变换，选取包含信息量最大的前三主成分合成影像，利用Criminisi算法对霉斑区域进行修复，再将修复后的影像进行主成分逆变换，完成高光谱影像的虚拟修复。以中国近现代画家倪田的《捕鱼图》为例进行了研究，发现修复后的霉斑区域与画体融入性较好，边界自然平滑，均方根误差值普遍变小。研究结果可为书画霉斑清洗提供直观的修复依据，具有较强的实用性。