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段祝庚 《中南林业科技大学学报(自然科学版)》2003,23(2):114-116
对全站仪对边测量原理及精度进行了分析,讨论了对边测量的最佳图形和最差图形时测站点的位置及相应精度,以及最佳图形和最差图形时提高对边测量精度的方法. 相似文献
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介绍了GPS在沙漠地区资源调查、工程造林中地块测量的精度,选择已知地物作为测量对象,对测量误差及其精度进行分析计算,结果表明:GPS测量在沙漠地区资源调查、工程造林中林地测量精度不能完全满足林业中的应用要求,同时对GPS在实际应用中应注意的问题提出建议。 相似文献
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对RTK-DGPS及其工作原理、作业流程进行了简要介绍,并以某大型围堰工程的测量工作为例,对RTK的测量定位结果和全站仪的测量结果的精度进行了比较和分析,认为RTK技术不仅不易受到周围环境的影响,并且测量精度和效率也均优于全站仪。 相似文献
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王唤良 《中南林业科技大学学报(自然科学版)》1998,(2)
分析了高等级公路平面控制网导线边投影长度变形与测区平均高程及投影带宽度的关系．根据长度变形是否满足国家标准GB50026－93要求（≤2．5cm／1km）而确定坐标系统．给出了不同坐标系统之间的换算关系．文中算例表明：用简单算法能达到公路工程测量的精度要求． 相似文献
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对间歇失重式胶粘剂流量测量方案的测量精度进行了理论分析。认为测量胶罐的最大毛重太大，与被测的胶粘剂瞬时流量不相适应，因而难以达到较高的测量精度。改进的途径应是大幅度降低测量胶罐的最大毛重，并应改变测量方案。 相似文献
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基于磁弹性原理设计并搭建了扭矩测量实验台,其主要技术指标为:量程0～100N.m、线性度和重复性两个误差指标均为0.1%。扭矩测量结果表明,在磁头与轴不同间隙条件下,扭矩与磁感应强度之间始终存在线性正比例关系,依据这种关系并利用磁力计先测量出磁感应强度值,然后再计算出相应的扭矩值,以实现扭矩的间接测量。 相似文献
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林业数字式测高测距仪的研制 总被引：2，自引：0，他引：2
鄢前飞 《中南林业科技大学学报(自然科学版)》2007,27(5):66-70
林业数字式测高测距仪是以测量新方法树基标尺法和前后标尺法为理论基础,以倾角传感器、单片机、显示屏等电子器件所组成的集中电路并结合机械设计与加工为技术特征的仪器装置.仪器具有结构轻巧、操作简便、高精度与高效率等特点,主要解决了森林计测中测点灵活选择与数字化测高测距问题.对其构造、原理、特点等进行了阐述,以期将科技成果迅速转化为现实生产力. 相似文献
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An improved technique, cheaper and less time-consuming, to measure standing wood volume by using an electronic theodolite was tested, by which greater information from the forest could be acquired accurately and non-destructively. This was achieved by recording the diameter at breast height and ground-level diameter of a tree as well as the included angle between the electronic theodolite and the left and right tangents of the stem at any point. The standing wood volume then was computed precisely by section. In addition, the factors that influence the precision of the method (observable distance and number of segments) were also analysed. In the study, 175 Larix gmelinii (Rupr.) Kuzen. trees and 190 Populus tomentosa Carrière trees chosen randomly for sampling were measured with the electronic theodolite, and then were cut down for measurement of the average cross-section volume. Based on the data acquired from 100 sample trees, a standard volume table was compiled, and then the data for the remaining random 10 sample trees in each group were selected for a comparison test. The results indicated that the optimal distance for indirect observation should be as high as the sample tree, and the optimal visual distinguished section was about 2?m. The correlation coefficient between the value measured non-destructively and the value of the felled trees of L. gmelinii was 0.97, with an average relative error of 1.62%. With regard to P. tomentosa, the correlation coefficient between the two values obtained by the two methods was 0.905 with an average relative error of 8.40%. It was concluded that the standard volume model based on the non-destructive measurement technique meets the requirements for precision in forest surveys. The precision of the standard volume model for L. gmelinii (a coniferous tree) was superior to that of the model for P. tomentosa (a broad-leaved tree). The electronic theodolite method provides an alternative technique for measuring trees without destructive sampling and is widely applicable for forest surveys. 相似文献
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选择四川高山竹类分布区的23个县市39个引种点,与平武王朗、卧龙、宝兴引种试验区的4个主要气象因子,采用相似分析和聚类分析法进行研究。结果表明,所计算的147个相似距中,距离在0.1～0.3Ⅰ级相似距有33个点,0.3～0.5Ⅱ级相似距有81个点,0.5～1.0Ⅲ级不相似有33个点。Ⅰ～Ⅱ级相似距所代表的点之间可以直接引种或间接引种驯化。相似距与实际引种效果检验表明,相似距的可靠程度为71.43％。通过相似距进一步聚类分析发现,39个引种点形成6个气候类区,在同一类区间可以相互引种。由于各区引种点的海拔高度不同,反映出一般气候水平分布和垂直地带性特征。本文还提出了四川省最佳引种方案,为开展全省性引种提供依据。 相似文献
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S. C. Chafe 《Wood Science and Technology》1985,19(4):329-345
Summary The relationships among collapse, volumetric shrinkage, moisture content and basic density and their distribution within the stem were examined for trees of E. regnans. It was found that collapse and volumetric shrinkage each were significantly related to moisture content (positively), basic density (negatively), and (positively) to the derived values P (per cent of theoretical saturation) and Q (per cent of cell cavity volume containing water). Notwithstanding the inverse association evident between moisture content and density in the living tree, moisture content was shown to be independently related to each of collapse and volumetric shrinkage.Within the stem, collapse and volumetric shrinkage were negatively correlated with height in the tree although the significance of this relationship was qualified by the adjustment for other variables. Samples containing sapwood displayed collapse values significantly lower than heartwood samples. This was reflected in the presence of a positive relationship between collapse and distance from the periphery when all material was considered, but a negative relationship when sapwood-containing samples were omitted. Basic density was positively correlated with height in the tree and negatively correlated with distance from the periphery. Moisture content, P and Q were negatively correlated with both height in the tree and distance from the periphery although the latter relationship for moisture content was dependent on adjustment for density.The highly significant relationship between volumetric shrinkage and collapse suggested that the former could confidently be used in assessing collapse severity. Moisture content was determined to be an independent indirect indicator of collapse whereas basic density, P, Q and green density could all be of indicatory value, especially the last in view of its ease of measurement. 相似文献
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林木无性系育种若干遗传参数估算的研究进展 总被引：6，自引：1，他引：6
遗传参数估算是林木育种程序中最主要的环节之一。林木无性系育种具有方法简单、投产迅速和增益较高，但其遗传参数的估算方法却不尽完善。目前，几乎所有的无性系育种研究都采用有性育种的估算方法来估算遗传参数，这难免不影响估算的精度或使结论产生偏差。本文深入分析了无性繁殖材料的特点，推出了估算无性系材料遗传参数估算的精确算式。同时，对当前广为关注的无性系混种数目问题进行了理论探讨和定量描述。 相似文献
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以火攻火战术是在森林火灾扑救中一种比较有效的间接灭火方法,但以往单独应用以火攻火战术存在着点烧不准确、不能进行长距离点烧等不足。近年来,我们在扑火实战中,把卫星定位系统的使用与以火攻火战术的运用结合起来,较好地解决了单独应用以火攻火战术中存在的问题。本文就火灾扑救中如何应用卫星定位系统来实施以火攻火以及应注意的问题进行了讨论,对今后部队、地方更好的完成森林火灾的扑救工作有一定的指导意义。 相似文献
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两种测定天然次生林叶面积指数方法的比较 总被引：6，自引：3，他引：3
采用叶面积指数直接测定方法（称重法）与间接测定方法（冠层分析仪测定法）,对帽儿山天然次生林区叶面积指数进行测定,运用相关性分析和对比分析对测定结果进行研究。研究结果表明,直接测定法结果为实测叶面积指数,间接测定方法结果小于前者,精度比前者低25％-40％,但两组结果相关关系显著,间接测定值能较好地反映林木的叶面积指数大小变化。天然次生林中林层结构对冠层分析仪测定有很大的影响,是造成两种方法差异的主要原因。 相似文献
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以西塘古镇为例,构建了不同时间尺度下旅游者重游意愿的结构方程模型,探讨了地方依恋和满意度对短期、中期和长期重游意愿的影响机制。研究表明,地方依恋对短期重游意愿有直接和间接正向影响,对中期和长期重游意愿只有间接正向影响;满意度对短期和中期重游意愿均有直接正向影响,并通过中间变量对长期重游意愿产生间接正向影响;地方依恋因子中"相比其他景区,对西塘更满意"和满意度因子中"总的来说,对这次旅游感到满意"对重游意愿的影响最大。因此,西塘古镇可从培育地方依恋和提升满意感知2个方面着手,提高旅游者在各个时期的重游意愿。 相似文献