A geometrical model was derived to describe knots in logs and on the surface of lumber beams sawn from those logs. Each knot is defined by 7 parameters related to the shape and position in the stem. A computer simulation program was written to study knot shapes on a variety of observation planes.An initial investigation on the shape of knots in Scots pine logs and lumber beams suggests that the model is sufficiently accurate to describe knottiness in this species. Potential applications of this model include automated lumber grading, computerized log reconstitution and yield optimization studies.
In an attempt to develop a better understanding of the effect of knottiness on the yield of logs for sawn timber products, the present study examines the position and geometrical characteristics of 429 knots found in seven Norway spruce (Picea abies (L.) Karst) middle logs from southern Finland. The raw data used in this study were in the form of coordinates of points located on the knot surface recorded in a cylindrical (R, L, T) reference frame. The data were smoothed using a non linear three-dimensional model. A curvature analysis of the knot pith was used to differentiate the curved and straight portions of the knots. This analysis made possible calculation of knot angles, symmetry, ovality and volume. The major finding of this study is the uneven distribution of knots around the log circumference. Nearly 50% of the total knot volume was concentrated in one-third of the log facing the south-east. Knots were also more prominent in higher portions of the logs studied. These observations support the argument that the uneven distribution of knots offers potential for improving the grade yield of timber sawn from trees harvested in high-latitude countries.
This study is aimed at developing equations describing the shape of any particular knot in the trunk of a tree. The present model differs from previous models in that it is not limited by the assumption of a straight conical knot. The knot is represented by an assemblage of elliptical cone sections with the axis defined by a Hermite-type cubic equation or a straight line, and ends in a half ellipsoid symbolizing the enclosure of an intergrown knot. Simulations of knot shapes are presented to demonstrate the versatility of the model. The model seems flexible enough to adjust to common knot shapes presented in the literature. This model is intended to be incorporated into tree felling, bucking, and sawing simulation softwares.
An investigation was carried out to find out the nutritional parameters viz. consumption, assimilation and tissue growth etc. of muga silkworm Antheraea assama Westwood (Lepidoptera: Saturniidae) by rearing it indoor on som twigs. During 32 days of its larval life, the total consumption of an individual was 33·925g of which 21·295 g were assimilated by the insect. About 80-1 % of the total consumption took place in the fifth instar alone. The weight of one full grown larva was computed at \3-9304 g. The assimilation and tissue growth were found positively correlated with the consumption as well as with the age of the larva. The approximate digestibility was negatively correlated to the amount of food consumed. Efficiency of conversion of ingested and digested food increased in the first 4 instars and declined in the fifth instar.
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