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仪器误差的精确测定和消除对于提高子午环的观测精度有着至关重要的意义。本文简单介绍了低纬子午环的观测原理和仪器结构，系统地探讨了它的各种仪器误差的来源、测定和处理方法。为了进一步完善采用组合固定角距法测定对径改正的方法，在第三章，研究了提高对径改正测量精度的方法，重新推导了对径改正的计算公式，并就某些具体的条件，对其进行了模拟验证，得到了较为满意的结果 相似文献
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This study compares the accuracies of diameter at breast height (DBH) estimations by three initial (minimum bounding box, centroid, and maximum distance) and two refining (Monte Carlo and optimal circle) circle-fitting methods The circle-fitting algorithms were evaluated in multi-scan mode and a simulated single-scan mode on 157 European beech trees (Fagus sylvatica L.). DBH measured by a calliper was used as reference data. Most of the studied circle-fitting algorithms significantly underestimated the mean DBH in both scanning modes. Only the Monte Carlo method in the single-scan mode significantly overestimated the mean DBH. The centroid method proved to be the least suitable and showed significantly different results from the other circle-fitting methods in both scanning modes. In multi-scan mode, the accuracy of the minimum bounding box method was not significantly different from the accuracies of the refining methods The accuracy of the maximum distance method was significantly different from the accuracies of the refining methods in both scanning modes. The accuracy of the Monte Carlo method was significantly different from the accuracy of the optimal circle method in only single-scan mode. The optimal circle method proved to be the most accurate circle-fitting method for DBH estimation from point clouds in both scanning modes. 相似文献
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我国定向钻进技术的研究已进入世界先进国家行列。列举了我国在定向钻进器具方面的科研成果及典型的定向钻进应用实例,着重介绍了目前国际上与定向钻进有关的先进技术,并就我国拓宽定向钻进应用新领域及相应需要研究的新技术提出了参考性建议。 相似文献
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简要分析大直径嵌岩灌注桩的承载机理，根据国家现行规范，结合地方实践经验。对岩溶地区大直径人工挖孔桩设计与施工中的若干难点技术作初步探讨。 相似文献
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CMS协议在Diameter中的应用及其安全性研究 总被引：1，自引：0，他引：1
对Diameter做了简要的介绍，分析Diameter协议中存在的安全隐患，例举了CMS协议在Diameter中的应用，对应用作了安全性分析，并在分析基础上对该协议作了一定的改进。 相似文献
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LUMBRES Roscinto Ian Canicosa LEE Young Jin CHOI Hyung Soon KIM Sung Yong JANG Mi Na ABINO Azyleah Caizares SEO Yeon Ok KIM Chan Soo PARK Jung Hwan 《山地科学学报》2014,11(2):442-448
This study was conducted to fit the diameter-height data of Quercusglaucain Jeju Island, South Korea to the four commonly used stem taper equations andto evaluate the performance of the four stem taper models using four statistical criteria： Fit index （FI）, root mean square error （RMSE）, bias （）,and absolute mean difference （AMD）. Results showed that the Kozak02stem taper equation provided the best FI（0.9847）, RMSE（1.5745）,（-0.0030 cm） and AMD （1.0990 cm） whileMax and Burkhart model had the poorest performance among the four stem taper models based on the four evaluation statistics （FI ： 0.9793,RMSE ： 1.8272, ： 0.3040 cm and AMD ： 1.3060 cm）. These stem taper equations can serve as a useful tool for forest managers in estimating the diameter outside bark at any given height, merchantable stem volumes and total stem volumesof the standing trees of Quercusglaucain theGotjawal forests located in Mount Halla, Jeju Island, South Korea. 相似文献
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An analytical method has been proposed to predict the ultimate uplift capacity of single vertical piles embedded in sand considering
arching effect. The present analysis takes into consideration of various pile and soil parameters such as length (L), diameter (d) of the pile, angle of internal friction of soil (ϕ), soil pile friction angle (δ) and unit weight of soil (γ). A modified value of coefficient of lateral earth pressure in uplift has been developed considering the arching effect of
soil. A comparative assessment of the uplift capacity of piles predicted by using proposed theory and the existing available
theories is made with the existing field and model test results. It has been observed that the present model considering the
arching effect predicts the results closer. 相似文献
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评述了各种度盘对径改正的方法；用玫瑰系列法对DCMT进行N=180的抽样实验测试，估计DCMT度盘常规读数对径误差为±0．25"。通过对度盘所有对径测试（N=5400）的精度统计特性的分析，得出49°30'、46°40'、43°12'是最优化的玫瑰系列测试组合；此外还论证了当对精度的统计特性的随机性要求不很严格时，在DCMT上实施小玫瑰角系列是可行的，其最优化组合是0°10'、46°40'、50°24'角系列。 相似文献