There are many log and wood properties of interest to wood processors. There is also high variability in important attributes between and within growing regions and between and within individual stems which influence financial returns to wood processors. This review summarises recent studies of segregation technologies and techniques which have shown that:
regional or stand level attribute models will facilitate a coarse level of segregation but not account well for the between and within stem variation;
many tools and techniques are available for segregating wood based on internal properties but few have been implemented commercially. Some are better suited for application in mills than in forests;
the benefits of segregating stands, stems and logs based on wood properties are not clear due to high variability in wood properties, poor market signals (in terms of price) for wood with superior properties, and poor understanding of the costs across the value chain; and
most of the existing economic models tend to look at the economics of segregation from the perspective of a single participant in the value chain, e.g. a structural mill or a central processing yard. Only a few models look across the value chain and these have limitations often poorly representing some participants in the value chain.
The manufacturing technology and characteristics of I-joist used for light wood structures are introduced in brief.The requirements for quality and performance of I-joist in North America as well as relevant test items,principles,characteristic value calc 相似文献
AbstractThe objective of this study was to examine the potential of acoustic measurement as a rapid and nondestructive method to predict the dimensional stability of young-growth Sitka spruce and western hemlock. Ultrasonic velocity, peak energy, specific gravity, and radial and tangential shrinkages were measured on twenty-four 25-×102-×y 25-mm specimens obtained from a 58-year-old stand in Southeast Alaska. We found that specific gravity and peak energy of ultrasonic signals were not good predictors of transverse shrinkage, as indicated by poor correlations. Ultrasonic velocity, on the other hand, was found to be a significant predictor of transverse shrinkage and therefore has good potential to be used as a field method to evaluate dimensional stability. The single-parameter prediction model explained 86% of transverse shrinkages in western hemlock and 71% of transverse shrinkages in Sitka spruce. Further study is needed to test the capability and feasibility of using acoustic velocity to predict both longitudinal and transverse shrinkages of wood in standing trees. 相似文献