4种常用装饰装修木材表面特性分析

对筒状非洲楝、水曲柳、古夷苏木和杉木4种常用装饰装修木材表面特性进行测定分析,结果表明:在CIE(1976)L*a*b*色空间中,筒状非洲楝和古夷苏木明度L*平均值较低,属于深材色树种;杉木明度L*平均值为70.28,属于较高明度。从整体分布情况来看,4种常用装饰装修木材的a*和b*都分布在0以上,明度分布在40以上,色调标号都分布在YR的区间;古夷苏木和水曲柳木材表面润湿性大于筒状非洲楝和杉木。     

基于碳和木材目标的森林空间经营规划研究

以大兴安岭地区塔河林业局盘古林场为例,以模拟退火算法为优化技术,以经济收益为基础,建立能够兼顾森林木材生产、碳储量和经营措施时空分布的多目标规划模型。规划周期由3个10年的分期组成,目标函数包括最大化木材和碳储量贴现净收益、最小化采伐成本,而约束条件则主要涉及最小收获年龄、收获次数、收获均衡以及空间邻接约束等。同时,还评估了一系列碳价格对规划结果的影响。结果表明:由于规划模型中空间和非空间约束的限制,规划期内获得的各种经济收益、木材产量以及碳储量等均随着碳价格的增加呈显著的非线性变化趋势;与碳价格为0元/t时的规划结果相比,当碳价格为我国当前现行碳交易的平均(25元/t)和最高(50元/t)价格时,规划期末的总经济收益分别增加了2.06%和3.91%,但规划期内木材产量和碳储量却无显著差异;如果仅从经济角度考虑,则能够使规划期末单位面积碳储量增加的最低碳价格为1 000元/t。同时,研究结果还表明碳价格虽然显著影响规划期内不同经营措施的采伐面积比例,但规划结果均满足均衡收获约束。      

黑荆树工业原料林定向培育经济效益评价

应用动态经济效益评价方法对黑荆树短周期工业原料林项目经济效益进行了评价，该项目的净现值（NPV）为16146．95元／hm^2。净现值率（NPVR）0．74，效益成本率（B／C）为1．90，结果表明，从经济效益方面考虑栽培以生产栲胶原料（树皮）和木炭、活性炭原料（树杆）为经营目标的黑荆树短周期工业原料林项目经济效益可观，具有可行性。     

Access cost functions for approximating roundwood supply in northern Sweden

In this article, an engineering approach is used to derive the access cost function for roundwood in northern Sweden. This approach can make use of detailed biological, technological and economic information and can give insights that cannot be gained with statistical methods. The engineering approach gives a reliable estimate of the whole cost function, so it avoids the difficulties of the statistical approaches in discriminating between different functional forms. The computations are based on data from the Swedish Forest Survey. Cost distributions are derived both at the roadside and at the mill and also with and without subsidies to forestry. Some applications to forest policy problems are mentioned. The elasticity of the cost curve near the current price level is the same as previously reported price elasticities.     

基于模态柔度差曲率的云杉锯材梁缺陷检测

在机械和环境荷载作用下,木质构件和结构的局部缺陷如节疤、腐朽和裂缝等会导致使用寿命的缩减.在木结构工程领域,如果能够尽早对结构和构件的最薄弱位置进行检出和评估,可避免因突然破坏而导致的灾难性事故.在本研究中,通过振动测试获取前两阶模态振型,并利用锯材梁损伤前后的模态柔度矩阵差值曲率提出损伤识别指标.为了验证提案损伤指标的有效性,通过人工切除截面质量来模拟不同损伤程度、不同损伤位置和双数个损伤的情景,试验结果表明损伤指标对不同程度、不同位置和双数个损伤均能准确定位,并可对损伤轻重程度进行定性评价.     

关帝山林区天然落叶松林单木生长过程模拟

通过野外试验、室内数据整理、计算机模拟等手段,研究不同立地条件下天然落叶松生长过程变化.结果表明：不同立地条件下天然落叶松胸径生长过程拟合选出的最优方程为Richards方程;落叶松胸径、树高前5 a生长缓慢,5 a后加速生长;落叶松材积在前10a生长缓慢,10 a后加速生长;前30 a落叶松胸径、树高、材积总生长量差别表现不明显,30 a后立地条件越好,生长量越大.     

重组竹热压板坯内部温度变化的研究

利用热电偶测试重组竹压制过程中板坯内部的温度变化,探讨了板坯厚度、板坯含水率、热压温度等因素对重组竹传热的影响。结果表明:①利用检测结果绘制的散点图趋势线有很好的线性关系。②重组竹热压过程中中心层温度的变化曲线可分温度缓慢传递阶段、快速升温阶段和慢速升温阶段。③板坯内含水率越高其传热效果越好。④酚醛树脂在高温下固化形成的隔热层对温度传导不利。     

Damage Detection of Picea asperata Sawn Timber Beams Using Modal Flexibility Curvature

The local damages such as knots,decay, and cracks can be translated into a reduction of service life due to mechanical and environmental loadings.In wood construction,it is very important to evaluate the weakest location and detect damage at the earliest possible stage to avoid the future catastrophic failure.In this study,the modal testing was operated on wood beams to generate the first two mode shapes.A novel statistical algorithm was proposed to extract the damage indicator by computing the modal flexibility curvature before and after damage in timbers.The different damage severities,damage locations,and damage counts were simulated by removing mass from intact beams to verify the algorithm.The results showed that the proposed statistical algorithm was effective and suitable to the designed damage scenarios.It was reliable to detect and locate local damages under different severities,locations,and counts.The peak values of the damage indicators computed from the first two mode shapes were sensitive to different damage severities and locations.They were also reliable to detect the multiple damages.     

Empirical analysis on influencing factors of waste paper recovery rate in China

ABSTRACT

The research calculated the waste paper recovery rate, and analyzed the main factors influencing waste paper recovery rate in China with time series data from 1970 to 2012. The consequent recovery rate and utilization rate of waste paper show that the recovery of paper products has been experiencing a rapid growth in China, but it cannot meet the domestic need. The empirical analysis proves that demand is the main driver to stimulate the increase of waste paper recovery rate in China; the increased average GDP per capita and proportion of waste paper pulp are two other important factors; the increased urbanization rate does not exert significant influence. In the circumstance of insufficient timber supply, the policy of eliminating straw pulp capacities for paper-making indusrty improves the recovery rate of waste paper.     

云南省集体人工商品林采伐管理改革思考

随着集体林权制度改革的不断深入,传统的林木采伐管理制度已越来越不能适应现代林业发展的需要,必须进一步优化限额管理机制,逐步建立与集体林权制度改革相配套、与发展现代林业相适应的林木采伐管理机制。针对现行集体人工商品林在采伐限额管理、采伐指标分配、采伐申请审批等方面存在的一些问题,提出实行森林采伐分类管理,推行伐区资格审查制度和伐区简易设计等对策与建议。