Pre- and post-defoliation radial growth rates were used to examine the effects of silvicultural thinning and two consecutive years of gypsy moth (Lymantria dispar L.) defoliation on Quercus spp. wood volume production...Pre- and post-defoliation radial growth rates were used to examine the effects of silvicultural thinning and two consecutive years of gypsy moth (Lymantria dispar L.) defoliation on Quercus spp. wood volume production. In the first phase of the study, tree rings from 65 dissected stems, were used to develop polynomial models to estimate annual cumulative volume (m3) increment for the entire merchantable stem, as a function of dbh (tree diameter at 1.37 m above the ground). In Phase II of the study, 81 additional trees were sampled using only increment cores. Cumulative diameter increments from the cores were used in the polynomial models to compare tree volume growth changes during and after defoliation among the thinning treatments. Even though there was no significant difference in estimated volume lost during defoliation among treatments, post-defoliation growth was enhanced by thinning. Total volume reduction from defoliation ranged from 28,049 (±17,462) cm3 to 25,993 (±16,251) cm3 per tree. The stand receiving the thinning treatment with the lowest residual stocking produced significantly more volume (P = 0.002) after defoliation than the other treatments.展开更多
In this present study, we analyzed the effects of Prandtl and Jacob numbers and dimensionless thermal conductivity on the velocity profiles in media (porous and liquid). The transfers in the porous medium and the liqu...In this present study, we analyzed the effects of Prandtl and Jacob numbers and dimensionless thermal conductivity on the velocity profiles in media (porous and liquid). The transfers in the porous medium and the liquid film are described respectively by the improved Wooding model and the classical boundary layer equations. The mesh of the digital domain is considered uniform in the transverse and longitudinal directions. The advection and diffusion terms are discretized with a back-centered and centered scheme respectively. The coupled systems of algebraic equations thus obtained are solved numerically using an iterative line-by-line relaxation method of the Gauss-Seidel type. The results show that the parameters relating to the thermal problem (the dimensionless thermal conductivity, the Prandtl (Pr) and Jacob (Ja) numbers) have no influence on the dimensionless speed, although the thermal and hydrodynamic problems are coupled. Via the heat balance equation. The results obtained show that the parameters relating to the thermal problem have no influence on the dimensionless speed, although the thermal and hydrodynamic problems are coupled via the heat balance equation. So, at first approximation with the chosen constants, we can solve the hydrodynamic problem independently of the thermal problem.展开更多
文摘Pre- and post-defoliation radial growth rates were used to examine the effects of silvicultural thinning and two consecutive years of gypsy moth (Lymantria dispar L.) defoliation on Quercus spp. wood volume production. In the first phase of the study, tree rings from 65 dissected stems, were used to develop polynomial models to estimate annual cumulative volume (m3) increment for the entire merchantable stem, as a function of dbh (tree diameter at 1.37 m above the ground). In Phase II of the study, 81 additional trees were sampled using only increment cores. Cumulative diameter increments from the cores were used in the polynomial models to compare tree volume growth changes during and after defoliation among the thinning treatments. Even though there was no significant difference in estimated volume lost during defoliation among treatments, post-defoliation growth was enhanced by thinning. Total volume reduction from defoliation ranged from 28,049 (±17,462) cm3 to 25,993 (±16,251) cm3 per tree. The stand receiving the thinning treatment with the lowest residual stocking produced significantly more volume (P = 0.002) after defoliation than the other treatments.
文摘In this present study, we analyzed the effects of Prandtl and Jacob numbers and dimensionless thermal conductivity on the velocity profiles in media (porous and liquid). The transfers in the porous medium and the liquid film are described respectively by the improved Wooding model and the classical boundary layer equations. The mesh of the digital domain is considered uniform in the transverse and longitudinal directions. The advection and diffusion terms are discretized with a back-centered and centered scheme respectively. The coupled systems of algebraic equations thus obtained are solved numerically using an iterative line-by-line relaxation method of the Gauss-Seidel type. The results show that the parameters relating to the thermal problem (the dimensionless thermal conductivity, the Prandtl (Pr) and Jacob (Ja) numbers) have no influence on the dimensionless speed, although the thermal and hydrodynamic problems are coupled. Via the heat balance equation. The results obtained show that the parameters relating to the thermal problem have no influence on the dimensionless speed, although the thermal and hydrodynamic problems are coupled via the heat balance equation. So, at first approximation with the chosen constants, we can solve the hydrodynamic problem independently of the thermal problem.
