THE APPLICATION OF SPLINE FUNCTION IN THE GEOMETRIC REPRODUCTION OF LOG SHAPE

FORWARDInwood-processingproduction,theeffectivewaytoraiselogutilizationandobtainthebesteconomicalbenefitistohaveaoptimumandreasonablesawcut-tingscheme.Thedeterminationoftheoptimumsawcuttingschemeshou1dbemadein1ightoflognaturalconditions,suchasitsgeometricsize,theoutlinesofthecrosssectionsatitsoppositeends,itsgeometricshape,andalsobasedonsawingwoodspecificationsacquiredandontheprincip1eofoptimumloguti1izationandthebesteconomicalbenefit.Inrecentyears,theresearchpapersconcerningthemethodsofgeom…     

谈贮木场技术改造中的几个问题

贮木场技术改造要从我国目前林业企业的现状出发,充分考虑资金少,设备不足、技术装备落后、原木产品苯重等特点。论述了当前我国林业贮木场技术改造中存在问题,改造方向艰及搞好贮木场改造规划和设计,设备挖潜和更替等问题,并且对卸车,造林、选材、归楞和装车等工序提出了切实可行的改造措施。     

一种恒线速无卡旋切机闭环变速进给控制方法

为了补偿恒线速无卡旋切机变速进给系统存在的干扰,提高单板旋切质量,结合其时变运动学模型,设计了一种基于前馈和比例反馈的闭环控制方法,同时为了增强控制器的适应性,方便控制参数调整,采用遗传算法对比例系数进行在线优化,仿真结果表明这种控制方法是有效的．     

Log decomposition rates in Tasmanian Eucalyptus obliqua determined using an indirect chronosequence approach

Coarse woody debris (CWD) is a fundamental component of forest ecosystems, but one whose management presents challenges for land managers because its inputs and outputs are linked to, but not often in equilibrium with, disturbance events, including wildfire and logging. Understanding its rate of decomposition is one key element in being able to model its dynamics under different disturbance and management scenarios. We employed an indirect chronosequence approach to determine a decomposition rate for CWD of Eucalyptus obliqua, one of the dominant trees of Tasmania's commercially important lowland wet eucalypt forests. In sequence, we developed an understanding of the relationships of (1) decay-class and wood density; (2) decay-class and years-since-disturbance; and (3) wood density and years-since-disturbance, from which we derived decomposition functions, including single negative exponential functions. We found no clear relationship between decomposition rate and either log diameter or the nature of the disturbance event (logging or wildfire). We showed that models developed without a consideration of the effects of log fragmentation imply unrealistically slow decomposition rates. Our derived first-order decomposition rate constant (k) is 0.0085. This suggests that E. obliqua CWD in Tasmania's southern forests decomposes very slowly in comparison with CWD decomposition rates reported from most other parts of the world. We intend to apply our findings to the task of modelling CWD dynamics for informing forest management.     

The effect of taper on the MOE of log stringers

Load sharing between the stringers in gravel-decked log bridges is an important design factor when small- diameter stringers are used with thin gravel decks. In order to estimate the load sharing between the stringers, it is necessary to consider the deflection of the stringers; therefore, accurate estimates of the apparent modulus of elasticity (MOE) for full-size log stringers are required. In this paper, load and displacement data from the full- size bending tests are used to demonstrate that taper near midspan has the greatest effect on the MOE used in common log bridge design methods, where the logs are assumed to have constant cross sections. This paper proposes a method to estimate a MOE that can be used in a constant cross-section model given the geometry of the particular log of interest, and the MOE from full-size bending tests calculated when considering actual log geometry.     

Simulated grading of logs with an x‐ray log scanner‐grading accuracy compared with manual grading

Today sawmills have started to use automatic methods for log grading. The methods used are either optical or gamma‐ray scanners. However, the signals from these scanners are too coarse for accurate log grading and for good control of the sawing process at the single log level. The objective of the present study was to determine the grading accuracy of a log‐scanner with two industrial X‐ray sources. The grading accuracy was compared with the accuracy of manual grading. The results showed that the manual grading of logs and boards is difficult. The accuracy of manual grading was low and the automatic grading systems were more reliable than manual ones. Possibilities for improving the automatic grading systems are discussed.     

贮木场机械系统的优化模型

本文应用线性规划理论研究了贮木场机械系统的优化问题，建立了相应的数学模型，并结合实例对模型进行了解算验证。