三角网模型在场地平整中的应用

本论文是利用三角网模型对场地平整的应用研究,主要是利用三角网的已知数据及三棱柱法对整个场地进行填挖方的计算。同时还对场地平整结果作了优化,当计算出的结果如不能满足需要时,那么就在此基础上进行重新计算,直到达到要求为止。     

最小二乘法在贮木场场地平整工程中的应用

在贮木场工程设计中，对场地平整和填挖方量的计算把最小二乘法的原理应用于方格网法，能使填挖实现基本平衡，工程量得到合理控制，节省平整场地的工程投资。     

基于GIS的场地平整技术研究

场地平整是工程建设中先行的步骤,通过GIS软件的三维分析模块、地统计分析模块能精确有效地分析目标平整场地所需挖填的土方量及其分布位置。文章总结了在场地平整施工设计方法的基础上,探讨GIS技术中的数字地形分析在常规工程测量作业中的优势,研究以成都植物园作为平整设计的假设,基于ArcGIS软件平台对高程点测量数据构建TIN,并对TIN进行修正以反映真实地形特征,通过TIN转化得来的DEM格网与设计最优高程拟合曲面进行栅格数据运算得出挖填土方量。     

绿化工程施工过程中的几个重要环节

本文叙述了场地平整、种植放线和苗木种植这三道工序在绿化工程施工过程中的重要性,及其在实际施工中要注意的一些问题,供绿化工程施工人员参考。     

关于拟建贮木场经济楞深计算方法的探讨

贮木场楞深的大小合理与否,是影响贮木场基建投资和经营管理的重要参数之一。以前此项研究,都是在贮木场场地已经平整,大铁专用线装车线已经建好的基础上进行的。为满足生产实践的要求,本文在贮木场筹建之初,就按照基建费与运营费之和最小的原理,探讨了经济楞深的计算方法,为修建楞场、装车线及建成后的经营管理提供了数据。     

开口薄壁箱平转施工拱桥重心的计算方法及应用

考虑平转桥必须计算半跨转动体系转体合龙前的重心位置这一实际情况,从平转桥的设计原理出发分析得出结构重心的计算方法——"弹性支撑法"。以贵州花江的开口薄壁箱平转施工拱桥为实例,运用该方法对转动体系的重心进行了建模计算与参数分析,并根据计算结果对该桥转动体系进行了配重调整重心,最后通过现场实测转动体系的重心基本调整到位,验证了此方法的可行性与应用价值,为同类型桥的顺利转体提供了参考。     

浅谈利用PhotoShop精确计算图形面积

指出了利用PhotoShop计算图形面积的优势,分析了其操作步骤,并对误差计算进行了探讨,为森林资源调查中的图形面积计算工作提供参考。     

草方格铺设机器人平衡系统中重心位置设计与计算

对草方格铺设机器人平衡系统中的重心位置进行了计算，提出了与草方格铺设机器人类似结构的机器重心位置计算的思路。     

浅谈草坪的场地准备工作

新建草坪不论采用哪种繁殖方式，在种植前，场地必须经过一系列的准备工作。这些工作主要包括场地的清理、地形整理、土壤改良、排灌系统的设置、场地平整、耕作和压实等。做好这些准备工作，可以使新建的草坪地形合乎要求，排水良好，为今后草坪植物生长、养护打下良好的基础。１　场地清理为便于草坪养护管理，草坪场地的清理是非常必要的。场地清理包括石块、废物、树根和杂草的清理及灭菌、杀毒等。石块、废物、树根的清理，可以通过人工翻土捡净，再对土壤进行消毒杀菌处理，以防止菌类和白蚁的发生或腐料后洼地的形成等。场地杂草清除…     

横观各向同性场地的速度特征及场地分类

从弹性波理论出发,研究了各向异性介质中地震波的速度特征、波型和测试方法等影响因素,探讨了目前规范中场地分类存在的若干问题以及场地卓越周期的计算问题.考虑卓越周期对地震动特性以及结构抗震设计的影响,提出了利用场地卓越周期及考虑各向异性主轴进行场地分类和各向异性场地卓越周期确定的新方法.     

紫叶小檗硬枝扦插技术的研究

为扩大紫叶小檗繁殖途径 ,探讨新的繁殖方法 ,对紫叶小檗硬枝扦插育苗中采穗母树的年龄、插穗的剪取部位、插穗粗度、ABT1生根粉处理浓度、扦插基质与插穗生根成活的关系进行了研究。结果表明 ,2a生母树上的插穗生根率、根量、根长和新梢长度极显著高于多年生母树上的插穗 ,树龄越大 ,表现越差 ;粗插穗的生根率显著高于细插穗 ;枝条不同部位的插穗生根率差异不显著 ;ABT1生根粉处理浓度以 15 0mg kg效果最佳 ;以蛭石为基质的插穗的生根率明显高于河沙为基质的插穗。     

The relationship between shelterwood cuts and crown thinnings and the abundance and distribution of birds in a southern New England forest

Forest regeneration methods such as shelterwood treatments have been shown to substantially increase the diversity of bird species, specifically of species that prefer early seral forests, now rare in the eastern United States. Stand improvement techniques such as thinnings have also been found to increase avian diversity under some conditions. A sustainably managed forest, however, must simultaneously apply regenerative harvesting with stand improvements, and the effect of such treatment combinations on bird community composition is not clear. We compared bird distribution and abundance on shelterwood cuts, crown thinnings, and unmanaged stands at the Yale Myers Forest, a large privately owned and actively managed forest in southern New England. Bird abundance and species diversity was highest in shelterwood cuts and lowest in unmanaged forest, with thinnings being intermediary. Different suites of species inhabited the three treatments, with 18 of 49 common species differing significantly in their abundances between treatments. Characteristics of the vegetation that were directly influenced by silvicultural intervention, including canopy openness, seedling regeneration and vertical structural diversity, appeared to be the dominant drivers of bird abundance. The abundances of some species or groups of species were correlated with the number of trees retained in the implementation of the forestry practices. In conjunction with the conservation of a variety of mature forest habitats, regenerative cuts and stand improvement techniques can be used together to sustain a diverse assemblage of bird species.     

单株平衡法的建立

单株平衡法的建立孙长忠，黄宝龙（西北林学院林学系杨陵７１２１００）（南京林业大学南京２１００３７）关键词黄土高原，蒸腾量，蒸发量，单株平衡法，单株平衡方程，蒸发偏量在黄土高原地区，水分因素对植物生长及生存具有强烈的限制作用。研究植物生长与环境水分条件...     

Deviations of kerf by handsaws III: the bend of saw blade by unsymmetrical set

To clarify the inducing mechanism of kerf deviation caused by unsymmetrical set of the handsaw, we hypothesized that the moment on the bottom edge of the saw blade, which is generated by the unsymmetrical set on handsaw teeth, bends the saw blade and this deformation should be one factor of the kerf deviation. To verify this hypothesis, the bend of a saw blade was examined by experiment and by calculation. In the experiments, a model tooth was attached to an actual handsaw. In the calculations, a saw model with a rectangular prism as the model tooth was analyzed by the finite element method. Loads were applied on the model tooth or the rectangular prism. From both the experiments and the calculations, the following results were obtained: (1) the deformation of the handsaw was caused by the unsymmetrical set in the length direction and the height direction of the saw blade; (2) the deformation and the inclination of the blade was larger at the front part of the saw than at the butt part; and (3) comparing the saw handle fixing conditions, the kerf deviation in the sawing line was supposed to be larger in the free handle condition and that kerf deviation in the depth direction was larger in the fixed handle condition. Based on the above results, it is apparent that one of the kerf deviation mechanisms originated from unsymmetrical set on the saw teeth. Part of this report was presented at the 54th Annual Meeting of the Japan Wood Research Society, Sapporo, Japan, August 2004.     

原条重心位置的测定与变化规律的研究

用缆索起重机测量了红松、云杉、冷杉、椴木、杨木、桦木、栬木和榆木等树种原条的重心位置。以数理统计理论和微机分析确定了原条重心距的变化规律与变动区间。     

我国南方湿地松木材物理力学性质变异初探

我国南方五省区湿地松木材的密度、晚材率和各项力学强度,随纬度的增加,呈递减状态。纬度与气干容重之间的直线回归方程为:G=1.28—0.027L,相关系数r=0.984.产生此现象的主要原因是,木材的管胞宽度和厚度随着纬度的增加逐渐变窄、变薄。产地的年平均气温和年降水量对湿地松树木的年轮宽度和晚材带宽度影响较大;年轮和晚材带的平均宽度随产地自北向南依次增加,随着山地海拔的升高而减小。     

用电子显微镜研究干法无胶硬质纤维板的结构

用扫描电子显微镜对未浸水和浸水后的干法无胶硬质纤维板进行观察，以获得有关无胶纤维板内在结构的变化，这可以更好地了解无胶纤维板的强度和耐水性能，在制造纤维板过程中，通过热磨使木材纤维在胞间层分离，并在热压时受压力作用再次结合，纤维重新结合的状况决定了纤维板的物理力学性能，经电镜观察的无胶纤维板，纤维间相互交织且结合紧密，即使是浸水后，纤维间的结合仍未出现松散现象，这表明不施加胶粘剂制造的干法硬质纤维板可以具有优越的强度和耐水性能。     

Effect of growth rate on wood specific gravity and selected mechanical properties in individual species from distinct wood categories

Summary This study examined the relationships of wood specific gravity and selected mechanical properties (MOR, MOE and Cmax) with growth rate in 16 timber species from four distinct wood categories: 1) first softwood category (FSC); 2) second softwood category (SSC); 3) diffuse-porous wood category (DPC); and 4) ring-porous wood category (RPC). And genetic, silvicultural and environmental influence on the relationships was briefly discussed. Statistical results show that the relationships of specific gravity and the mechanical properties with growth rate vary remarkably with both the wood property and the wood category. In general, the mechanical properties in the FSC species decrease remarkably with increasing growth rate, while they appear to be less influenced in the SSC species. Compared with the softwoods studied, the physico-mechanical properties in the hardwoods studied are remarkably less influenced. In the DPC species, growth rate generally has very a little influence on both specific gravity and the mechanical properties. In the RPC species, the physico-mechanical properties appear not to decrease with increasing growth rate, and in some species they even tend to increase. Among the three mechanical properties studied, MOE is remarkably less influenced by growth rate than MOR and Cmax. Compared with specific gravity, however, the mechanical properties are generally more influenced by growth rate. Therefore, the impact of growth rate on wood mechanical properties in a species can not be estimated exactly through the relationship of wood specific gravity with growth rate. Path analysis reveals that growth rate has a large effect on the mechanical properties which can be accounted for by the affected specific gravity. In addition to this indirect effect through specific gravity, growth rate still has an additional effect on the mechanical properties which can not be explained by specific gravity. In the SFC species, such effect is significant, and this, to a lesser extent, applies to the DPC species. However, this effect is not remarkable in the SSC species and may be negligible in the RPC species.     

Fuelwood characteristics of tree species in homegardens of Kerala, India

Indiscriminate use of natural resources in the past has lead to fuelwood shortages in many parts of the tropical world. To surmount this domestic energy crisis, not only degraded sites must be planted with trees having high fuel value potential, but also agroforestry promoted on arable lands. To enable choice of species for such energy plantations/agroforests in the humid tropics of peninsular India, we assessed the heat of combustion and physical properties that determine combustion of phytofuels, such as ash content, specific gravity and moisture content. Bark and wood samples of 45 multipurpose tree species in the homegardens of Kerala, India and three fuel materials of local importance (coconut [Cocos nucifera] endocarp, dried coconut spathe and dehiscent rubber [Hevea braziliensis] pericarp) were evaluated. Variations abound in the calorific values and physical properties of species and tissue-types. In general, heat of combustion and specific gravity followed the sequence: heartwood > sapwood > bark, while mean ash percentage followed a reverse order (bark > sapwood > heartwood). Ash content had a negative correlation with heat of combustion, but specific gravity exerted a positive influence. Furthermore, ash content and wood specific gravity were inversely related. Although green moisture content increased in the order: bark < heartwood < sapwood, it failed to show any predictable relationship with heat of combustion.This revised version was published online in November 2005 with corrections to the Cover Date.