桉木单板层积材生产工艺的优化

采用响应面法(RSM)和中心组合旋转设计(CCRD),研究了桉树单板层积材(LVL)的生产工艺条件,并对优化工艺所得的预测值进行了实验验证。方差分析结果表明:面粉添加量对桉木LVL的静曲强度(MOR)和弹性模量(MOE)有着显著影响,而热压温度和热压时间的影响不显著。通过回归分析,建立了相应的回归模型。回归模型的预测值与实验值的拟合良好,说明回归方程能用来预测和优化桉木LVL的力学强度性能。最佳工艺条件为:热压温度130℃,热压时间1.5 min/mm,面粉添加量5%(质量分数)。在此工艺条件下压制的桉木LVL垂直加载条件下的静曲强度(MOR⊥)和弹性模量(MOE⊥)分别为89 MPa和16 722 MPa,平行加载条件下的静曲强度(MOR∥)和弹性模量(MOE∥)分别为88 MPa和15 067 MPa,MOR和MOE分别达到了结构用单板层积材国家标准的优等品和140E级别。     

基于时延神经网络的木材干燥温湿度建模研究

利用神经网络建立了木材干燥的温湿度模型,给出了其时延神经网络辨识结构。分别提出温、湿度控制模型(控制信号与温、湿度之间的关系模型)和木材干燥基准模型(温、湿度与木材含水率之间的关系模型),并利用实验干燥窑得到的实际数据进行了仿真研究。仿真结果表明,利用此方法建模是可行的,所建模型是有效的。图10参16。     

基于人工神经网络的树高曲线模型研究

本文利用人工神经网络建模技术,以河南农业大学三区内毛白杨人工林99株的断面积平均直径和树高资料为基础,研建了树高曲线人工神经网络BP模型和幂函数模型。通过两个函数模型的比较表明:人工神经网络建模技术精度高、误差小,具有很强的泛化能力。在用幂函数拟合较差的情况下,人工神经网络也取得很高的精度,其拟合效果具有明显的优势。     

Factors influencing the production of structural plywood in Tasmania,Australia from Eucalyptus nitens rotary peeled veneer

Harvested logs supplied from five fibre-managed Eucalyptus nitens plantation coupes with different growing environments were assessed for quality and stiffness. Billets extracted from the logs were rotary peeled for veneer. When averaged across the five coupes, 30% of veneer recovered could be used directly in structural plywood production and an additional 20–25% could be used after further processing. In visual assessment most veneer was assigned an Australian/New Zealand Standard AS/NZS2269.0:2012 Quality D. Acoustic testing during processing showed veneer peeled from a drier and lower elevation coupe had significantly higher dynamic MOE values than veneer processed from logs harvested from wetter higher elevation coupes. To examine the utility of the E. nitens peeled veneer in the production of structural plywood, it was combined with veneer of a known higher stiffness, rotary peeled from regrowth forest Tasmanian oak species logs. Structural seven-ply panels were manufactured from the veneer prepared in three different ply arrangements. Mechanical testing of the panels in accordance with AS/NZS2269.0:2012 showed that an F17 target stress-grade panel product of 83% E. nitens and 17% Tasmanian oak species could be produced, if E. nitens veneer of higher stiffness were selected from veneer segregated by estimated dynamic Modulus of Elasticity value. Panels with 50% E. nitens and 50% Tasmanian oak veneer could be produced by selecting E. nitens veneer of lower stiffness after segregation. In the majority of panels tested stress-grade rating was limited by perpendicular bending strength. Outcomes from the study indicate that structural plywood can be manufactured using differing proportions of E. nitens veneer, rotary peeled from fibre-managed plantations, provided it can be segregated into stiffness categories and selected to achieve a target stress-grade.     

Prediction of pine mistletoe infection using remote sensing imaging: A comparison of the artificial neural network model and logistic regression model

In this study, the prediction of pine mistletoe distribution in Scots pine ecosystems was explored using remote sensing variables to compare the multilayer perceptron (MLP) artificial neural network (ANN) and logistic regression (LR) model performances. For this purpose, 109 sample plots were distinguished in pure Scots pine forests (natural) in the Eastern Black Sea Region of Turkey. Distinguishing mistletoe-infected stands (69) and uninfected stands (40) was performed with field observations. The variables acquired from Landsat 8 (Level 1) images were used as independent variables for independent-sample t-test, MLP ANN and LR models. Remote sensing variables indicated that mistletoe-infected stands were in drier areas with a lower vegetation-leaf area index. Based on the performance results of both models, the sensitivity (SEN), specificity (SPE), positive predictive value (PPV), negative predictive value (NPV) and accuracy of the MLP ANN model were superior to those of the LR model. The prediction percentages (SEN, SPE, PPV and NPV) of mistletoe-infected stands were better than the prediction percentages of uninfected stands. The prediction accuracies of LR and MLP ANN models were 74.3% and 89.6%, respectively. However, all remote sensing variables were included in the prediction equation of the MLP ANN model, while the thermal infrared 1 (TIRS1) variable was included in the LR model. In the MLP ANN model, the TIRS1 variable also had the highest normalized importance (100%). The area under the curve (AUC) value for identifying the mistletoe-infected stands of Scots pine forests used by the MLP ANN model (0.892 ± 0.034) was higher than in the LR model (0.838 ± 0.039), explaining the more accurate predictions obtained from the MLP ANN model. The MLP ANN model showed much better performance than the LR model. The results of this study are expected to make important contributions to the identification of potential mistletoe-infected areas.     

Potential model of the modulus of elasticity in flexure for plywood

Summary Once the modulus of elasticity (MOE) when calculating the bending properties of plywood is obtained, the result is one of the requirements necessary in order to characterize these panels. For this purpose the A.S.T.M. D-3043 Standard establishes the span between the supports and the geometric characteristics of the samples. This is valid only if the modulus of elasticity is independent of sample geometry. The results obtained in this study demonstrate that the modulus of elasticity changes with these parameters (span and width). This report proposes a mathematical model including the experimental data which allows the representation of the variation in MOE as a function of the ratio: span between the support/width of the samples.     

Buttock temperature in a sedentary posture on plywood flooring of varying thickness over the ONDOL heating system

This study investigated the thermophysiological responses of healthy subjects that sat on the plywood covering of the ONDOL floor heating system. Environmental chambers were constructed for this study, wherein ambient temperature, and wall and ceiling surface temperature were controlled at 24°C, and relative humidity was 50%. The temperature of supply water (t _sw) flowing into the floor coil was altered from 15°C to 40°C at 5°C intervals. The floor covering materials used in this experiment were mortar and three types of plywood with thicknesses of 2.7, 7.5, and 12mm. The floor surface temperatures (t _f) and the skin temperatures of eight subjects were measured while they were sitting on the floor. Buttock temperature, in particular, was monitored. This experiment yielded the following results: (1) t _f was 17.0°–35.2°C on mortar finishing and 19.1°–30.2°C on 12-mm plywood covering; (2) the buttocks skin temperature increased with t _sw higher than 30°C on mortar finishing and for t _sw higher than 30°, 25°, and 20° on 2.7-, 7.5-, and 12-mm plywood finishing, respectively; (3) the differences of buttock temperature when t _sw was varied between 15° and 40°C were 11.4°C on mortar, 7.9°C on 2.7-mm plywood, 6.5°C on 7.5-mm plywood, and 5.0°C on 12-mm plywood; (4) using regression analysis, the neutral point temperature of buttocks was determined to be 32.8°C.Part of this report was presented at the 53rd Annual Meeting of the Japan Wood Research Society, Fukuoka, Japan, March 2003     

人工挂巢招引白眉[姬]鹟控制森林害虫的研究

在内蒙古赛罕乌拉自然保护区人工挂巢招引白眉［姬］翁鸟Ｆｉｃｅｄｕｌａｚａｎｔｈｏｐｙ－ｇｉａ（Ｈａｙ）控制森林虫害的试验中,采用巢区测定法测定取食范围,剖胃分析法和束颈法进行食性分析和食虫量测定,并结合样地内该鸟种群数量调查,综合分析后得出一对白眉［姬］翁鸟控制虫害面积约０．４ｈｍ２,挂巢密度为３．３巢／ｈｍ２,一对成鸟及一窝雏鸟在该区停留期间共食虫８０２５８条,其中落叶松叶蜂占５２％,舞毒蛾３０．５％,采用人工招引白眉［姬］翁鸟等益鸟控制森林虫害效果显著。     

遗传神经网络在板材优化下料中的应用

本文介绍了广泛用于下料优化中的遗传算法和神经网络,并将这两种优化算法的结合用于家具生产板材下料中。实验采用了3650 mm 1850 mm的板材生产100套写字桌吊桶。该板材的利用率达到94.14%,运算时间仅用了35秒。实验结果证明,用遗传算法训练神经网络权值的方法可提高板材利用率并减少神经网络的搜索时间,同时可以提高神经网络的全局搜索能力。表1参5     

Prediction of post-thinning stem volume in slash pine stands by means of state and transition models

New Forests - Predicting growth and production is the key to effective forest management, especially in those stands where silvicultural treatments are more intensive, such as silvopastoral...     

Improvement of fire retardancy of plywood by incorporating boron or phosphate compounds in the glue

A practical approach to enhancing the fire retardancy of wood-based materials by adding fire-retardant chemicals to the glue was developed. Plywoods were manufactured using urea melamine formaldehyde resin mixed with ammonium pentaborate or dihydrogen phosphate. Treated plywoods had better incombustibility than untreated ones. X-ray photoelectron spectroscopy (XPS) analysis clearly demonstrated the distribution of boron and phosphorus, which had migrated from the glue to the wood, contributing to better fire retardant properties. The cross-sectional micrographs from scanning electron microscopy showed that untreated specimens exhibited a foamy structure near the interface in the glue layer and the deformed structure of wood cells. The cell structure and cell wall thickness retained intact in the specimens treated with urea melamine formaldehyde resin mixed with ammonium pentaborate or dihydrogen phosphate. When observing the effect of the thickness of overlay veneers on incombustibility, a shorter glowing time was obtained from the specimens with a thicker surface layer when the fire retardant chemical was added at 2%, but the differences were smaller at the higher chemical retention of 4%. A similar tendency was observed for the char length.Part of this paper was presented at the International Tropical Wood Conference in Kuala Lumpur, Malaysia, June 1997     

Estimation of the internal shear strength distribution of the element for laminated veneer lumber by nonlinear least-squares method

Until now we developed an estimation method for strength distributions of laminated veneer lumber (LVL) element by nonlinear least-squares method (NLM). Estimated strengths by this method were modulus of elasticity (MOE) and modulus of rupture (MOR) in the horizontal use direction and the vertical use direction, tensile strength and compression strength. But to use LVL for structural members, shear strength was also needed. Therefore, we tried to estimate the shear strength distribution of LVL element by NLM same as MOE and MOR in the horizontal use direction and the vertical use direction, the tensile strength of LVL and the compression strength of LVL in the previous reports. We conducted shear strength test for LVL and estimated element shear strength distribution by LVL strength data in the horizontal and vertical use direction. Next, we simulated LVL shear strength distribution using element shear strength distribution and compared with experimental ones in each use direction. They were overlapped in both use direction. Therefore, we could validate NLM for estimating element shear strength distribution.     

Fracture energy approach for the identification of changes in the wood caused by the drying processes

Specific fracture energy measurements were applied to identify changes caused by wood-drying processes of solid wood. Specimen design and geometry as well as parameters and specifications for a fracture energy test were determined experimentally. The specific test set-up was applied on plantation teakwood sample sets of standard as well as alternating convection kiln dryings and one oven drying. The results show that alternating changes of the drying temperature along with the equilibrium moisture content (EMC) in a kiln schedule have a small but significant decreasing effect on the specific fracture energy in the radial/longitudinal as well as the tangential/longitudinal testing direction. Furthermore, oven drying at constant high drying temperature along with low EMC did not result in a significant change of specific fracture energy compared with standard drying, but caused greater scattering values in both transverse crack propagation systems.     

应用遥感、人工神经网络叶面积模型和模拟过程模型估计湿地松人工林碳储量

全球气候变化引起人们对森林碳固定作用的关注。碳存储速率依赖于生态系统流通量(光合作用和生态系统呼吸),量化为净生态系统二氧化碳交换。在没有密集采样点的情况下,我们需要采用估测森林净生态系统交换的方法准确地估计林分水平和更大尺度的碳固定量。本文通过祸合遥感估算的叶面积指数和生长过程拟合模型,估计了佛罗里达州内9 770公顷湿地松人工林一年里净生态系统交换总量。地面图神经网络模型和陆地卫星数据估计的森林叶面积指数平均值是1.06(数值范围0-3.93,包括森林边界)。输入神经网络叶面积指数值,湿地松拟合模型(SPM2)估计的森林净生态交换值在-5.52 Mg·hm-2·a-1到11.06Mg·hm-2·a-1之间,平均值是3.47 Mg·hm-2·a-1。年总的碳储量是33920t,约合3.5 t/hm2。估计的叶面积指数和森林净生态交换均对对施肥高度敏感。图3表1参30。     

沙棘裸地嫩枝扦插育苗技术

为寻求当地生产适用、经济有效的沙棘繁殖途径与方法，在裸地支扦插试验，重点介绍了裸地嫩枝扦插苗床的设置，扦插育苗技术，苗期管理等配套措施。     

柳林污水处理系统净化效率研究

该文模拟污水土地处理系统,在太湖西山岛上某农庄营建了1个柳树特色的污水处理系统,该系统由3级慢渗带(垂直型)和1级表流湿地组成,总长度100 m,平均宽6.5 m。模拟农村实际生活污水中总氮(TN)、总磷(TP)、化学需氧量(COD)和铵态氮(NH+4-N)等富营养盐浓度,人工配制污水累计290 t,在5 d内陆续灌溉到处理系统中,观测结果表明位于系统末端收集池中富营养污染物TN,TP,COD和NH+4-N(铵态氮)去除率分别达到75.4%,99.2%,89.9%和95.4%,其中TP,COD和NH+4-N含量均优于或达到五类水标准。净化效率总体呈现出随着柳林处理级数的增加,污水的净化效率也增加;同一天同一级柳林湿地不同时间段出水中TN,TP,COD和NH3-N的浓度变化不明显。     

Estimating the onset of cambial activity in Scots pine in northern Finland by means of the heat-sum approach

We estimated the date of onset (Date(est)) of cambial activity by the pinning method in Scots pine (Pinus sylvestris L.) trees at Vanttauskoski (Site 1) and Laanila (Site 2) near the latitudinal limit of Scots pine in northern Finland. In each year and at each site, observations were made on a different set of five trees. The estimated dates of onset of cambial activity were compared with the corresponding heat sums, calculated in degree-days according to two models. Within years, Date(est) varied among trees by up to 15 days at Site 1 and up to 13 days at Site 2. Among years, mean Date(est) varied by 15.3 days at Site 1 and 12.0 days at Site 2. The overall mean Date(est) differed between sites by 6 days (June 5 at Site 1 and June 11 at Site 2). Among all trees in all years, the mean number of degree days (d.d.) calculated from mean daily temperature above a threshold of 5 degrees C before Date(est) ranged from 68.7 to 135 d.d. at Site 1 and from 37.4 to 154.7 d.d. at Site 2. Among years, the mean heat sum before Date(est )ranged from 94 to 112.5 d.d. at Site 1 and from 61.4 to 136 d.d. at Site 2. Variation among years in heat sum before Date(est) at Site 2 was highly significant, indicating that one or more factors other than, or in addition to, heat sum determines the onset of cambial activity in Scots pine. Similar results were obtained when heat sum was computed from the area between the sine wave generated by daily maximum and minimum temperature and the threshold temperature.     

Effects of high temperature kiln drying on the practical performances of Japanese cedar wood (Cryptomeria japonica) I: changes in hygroscopicity due to heating

The effect of heating on the hygroscopicity of Japanese cedar wood was investigated as a simple evaluation of thermal degradation in large-dimension timber being kiln-dried at high temperatures (>100°C). Small wood pieces were heated at 120°C in the absence of moisture (dry heating) and steamed at 60°, 90°, and 120°C with saturated water vapor over 2 weeks, and their equilibrium moisture contents (M) at 20°C and 60% relative humidity (RH) were compared with those of unheated samples. No significant change was induced by steaming at 60°C, while heating above 90°C caused loss in weight (WL) and reduction in M of wood. The effects of steaming were greater than those of dry heating at the same heating temperature. After extraction in water, the steamed wood showed additional WL and slight increase in M because of the loss of water-soluble decomposition residue. The M of heated wood decreased with increasing WL, and such a correlation became clearer after the extraction in water. On the basis of experimental correlation, the WL of local parts in large-dimension kiln-dried timber was evaluated from their M values. The results indicated that the thermal degradation of inner parts was greater than that of outer parts.