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151.
本章分析了船舶冬季航行存在的风险,介绍了船舶冬季航行应采取的措施和操船方法以及人员防寒防冻措施,供同行们借鉴。 相似文献
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153.
Computer-aided hip surgery planning and implant design applications require accurate segmentation of femoral head and proximal acetabulum. An accurate outer surface extraction of femoral head using marching cubes algorithm remains challenging due to deformed shapes and extremely narrow inter-bone regions. In this paper, we present an automatic and fast approach for segmentation of femoral head and proximal acetabulum which leads to accurate and compact representation of femoral head using marching cubes algorithm. At first, valley-emphasized images are constructed from original images so that valleys stand out in high relief. Otsu’s multiple thresholding technique is applied to seperate the images into bone and non-bone classes. Region growing method and threedimensional (3D) morphological operations are performed to fill holes in the bone. In the reclassification process, the bone regions are further segmented, and the boundaries of the bone regions are further refined based on Bayes decision rule. Finally, marching cubes algorithm is applied to reconstruct a 3D model and extract the outer surface of femoral head and proximal acetabulum. Experimental results show that this method is an accurate segmentation technique for femoral head and proximal acetabulum and it can be applied as a tool in medical practice. 相似文献
154.
应用高精度定位解算软件PANDA对框架网进行解算,并与Bernese解进行比较,探讨不同软件模型下框架网的点位坐标解算方法及其精度;通过算例表明PANDA软件的定位解算结果与Bernese的解有较好的一致性,表明PANDA软件有较高的可靠性和稳定性。 相似文献
155.
[Objective ] To meet the requirements of remotely controlling ship in curved, narrow and crowded inland waterways, this paper proposes an approach that consists of CNN-based algorithms and knowledge based models under ship-shore cooperation conditions. [Method]On the basis of analyzing the characteristics of ship-shore cooperation, the proposed approach realizes autonomous perception of the environment with visual simulation at the core and navigation decision-making control based on deep reinforcement learning, and finally constructs an artificial intelligence system composed of image deep learning processing, navigation situation cognition, route steady-state control and other functions. Remote control and short-time autonomous navigation of operating ships are realized under inland waterway conditions, and remote control of container ships and ferries is carried out. [Results]The proposed approach is capable of replacing manual work by remote orders or independent decision-making, as well as realizing independent obstacle avoidance, with a consistent deviation of less than 20 meters. [Conclusions]The developed prototype system carries out the remote control operation demonstration of the above ship types in such waterways as the Changhu Canal Shenzhou line and the Yangtze River, proving that a complete set of algorithms with a CNN and reinforcement learning at the core can independently extract key navigation information, construct obstacle avoidance and control awareness, and lay the foundation for inland river intelligent navigation systems. © 2022 Journal of Clinical Hepatology. All rights reserved. 相似文献
156.
对北京市南水北调南干渠盾构机穿越排气阀井施工方法进行了深度分析,通过优化招标图设计方案,采用在施工完成后的排气阀井内回填碎石+土层的方法,较全面地进行了方案设计,安全、快速完成施工任务。 相似文献
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158.
Optimal sensor placement on freeway corridor is of great interest to transportation authorities. However, current traffic sensors are easily subject to various failures. Therefore, it is necessary to incorporate sensor failure into the optimal sensor placement model. In this article, a two-stage stochastic model is proposed for the purpose of travel time estimation on freeway corridor. To balance the effectiveness and reliability, a stochastic conditional value at risk (CVaR) model is also proposed. Since both models are too complicated, a customized genetic algorithm is developed. Numerical experiments show that considering sensor failure makes a significant performance improvement in the sensor placement pattern. Sensitivity analysis is also applied to investigate the impact of a number of allowable sensors and different traffic sensor failure probability. 相似文献
159.
为了预测圆形隧道施工引起地表以下不同埋深地层沉降特征,首先,通过理论推导不同地层最大沉降位移与沉降槽宽度系数的函数关系;然后,建立包括试验台架、地层模型、圆形隧道开挖模型以及测量地层变形装置的平面应变模型试验系统。通过理论解析和模型试验可知:1)地表以下地层的最大沉降位移与沉降槽宽度系数成反比;2)不同深度地层的沉降位移随着地层埋深的增加而增大,且地表以下地层沉降槽曲线仍然符合正态分布;3)通过对模型试验数据进行回归分析,得到黏土地表以下不同深度地层沉降槽宽度系数的计算公式,从而为预测圆形隧道施工地表以下不同深度地层竖向位移提供了一种可靠的计算方法。 相似文献
160.
小直径盾构施工中管片纵向应力监测研究 总被引:1,自引:0,他引:1
为了探索小直径盾构法隧道在施工过程中管片纵向应力的变化规律,对北京槐房再生水厂污水隧道管片纵向应力进行了现场监测:将第976环、第1 054环管片分别设为第1和第2监测断面,2监测断面各预埋5个纵向应力计,各监测断面从本监测断面管片安装后即开始监测,当盾构掘进至第1 129环时停止监测。研究表明:1)在管片离开盾尾50环后,其纵向应力波动值小于管片拼装期间应力值的5%。2)在盾构掘进期间,管片距离盾构越远,其纵向压应力值越小。3)在管片拼装期间,管片距离盾构越远,其纵向压应力经历了先增大后减小的过程。4)管片距离盾构108环后,该管片纵向压应力趋近于0.2~0.3 MPa。5)随着盾构推进,管片纵向应力经历了4个阶段的变化过程,即周期性剧烈波动阶段—动态稳定阶段—逐渐衰减阶段—趋于稳定阶段。 相似文献