弯曲射线追踪中Dijkstra算法的改进与实现   总被引：5，自引：5，他引：0       下载免费PDF全文

王汪根  刘盛东  张平松 《地球物理学进展》2006,21(4):1120-1126

文章针对图论中寻找最短路径的Dijkstra算法内存占用量大,效率低的缺点,对该算法进行了改进,修改后的算法计算效率是原来的四倍,内存使用量和图中节点数呈线性关系.在此基础上,用新算法求出了激发点和接收点的最短走时路径,并由激发接收点的旅行时结合联合迭代法对理论模型和实际场地进行了反演.结果表明：和直射线追踪相比,弯曲射线路径能更好地反演出地质体内部的速度场分布.理论模型和实际探测结果证实改进后的算法是有效的.  相似文献   

A theoretical study of the factors which influence the measurement of fishing netting mesh size     

F. G. O&#x;Neill 《Ocean Engineering》2003,30(16):2053-2063

A theoretical investigation is carried out of the mesh size measurement of an idealized fishing netting mesh. It is assumed that the bending moment of the netting twine is proportional to curvature and that there is no twine extension and no cross-sectional deformation of the twine. The corresponding momentum and force balance equations are analyzed. The measurement method our analysis most approximates is that of the ICES gauge. The effect on mesh measurement of twine bending stiffness, frictional resistance, boundary slope, gauge force and gauge thickness are all examined.  相似文献   

A Generalized Point Conforming Rectangular Plate Element     

Wang Deyu Chen Tieyun Associate Professor 《中国海洋工程》1995,(3)

- A generalized point conforming rectangular element for plate bending is proposed. The present element displacement field can not only satisfy the continuity of normal displacement and its derivative at the element node, but also satisfy the generalized continuity at the middle point of each element boundary, where the generalized conforming condition is to make the non-conforming residual to be minimum. Numerical results show that the proposed element is more accurate than the ordinary 4-node non-conforming rectangular plate element (ACM element).  相似文献   

圆形网箱框架用PE管材的弯曲疲劳试验   总被引：1，自引：0，他引：1  

关长涛  陆光炯  林德芳  杨长厚  徐斌  黄滨 《中国海洋大学学报(自然科学版)》2006,36(2):236-240

网箱框架在风、浪、流单一载荷或其复合载荷的作用下,始终处于动态变化中,在这样的工况条件下,很容易发生疲劳破坏。本文通过对网箱框架工况条件的分析,认为网箱框架在沿直径方向的弯曲疲劳为主要因素,且在弯曲过程中周长保持不变。以圆形框架在直径方向产生20%的压缩变形为极端条件,通过几点假设,将工况条件向试验条件进行转化,提出1种圆形网箱框架用PE管材的弯曲疲劳试验方法。采用此方法对3种改性配方的聚乙烯管材样品进行了弯曲疲劳试验。结果表明,经10万次弯曲试验,3种配方的试样表面均无开裂等破坏现象,各配方的最大应力水平分别下降了14.3%,9.4%和16.9%。  相似文献   

High‐resolution mapping of Manawatu palaeochannels          下载免费PDF全文

Giulia Lo Re  Ian C. Fuller  Giulia Sofia  Paolo Tarolli 《New Zealand geographer》2018,74(2):77-91

New remote sensing techniques, such as airborne laser scanning (LiDAR), have led to a dramatic increase in terrain information, providing new opportunities for landform analysis. A major advance in using LiDAR‐derived high‐resolution topography (HRT) is the capability to provide an accurate and detailed terrain morphology. This study aims to use LiDAR HRT to identify palaeochannels of the Manawatu River (New Zealand) using an automated procedure based on the statistical analysis of landform curvature. The approach can provide rapid assessment and classification of floodplain topography. The proposed analysis is crucial, especially for intensively used floodplains requiring effective flood management and mitigation.  相似文献   

基于有限元分析的卷管法管道安装实时研究     

李英  李婧一  刘志龙 《海洋工程》2019,37(3):35-41

采用卷管法铺设管道时,管道和铺设设备之间的接触作用十分复杂,并且管道在弯曲过程中将会产生塑性变形并可能发生局部屈曲,导致管道失效。基于有限元模型(FEM)实时模拟卷管法安装的整个过程,研究管道与铺设设备之间的接触作用;分析管道对于环境载荷和船体运动的动态响应;获得管道的应力应变值以校核局部屈曲。研究结果表明,管道弯矩大部分来源于管道与安装设备间的接触作用,而环境载荷及船体运动对管道的弯曲应力影响较小。  相似文献   

火灾中集装箱船剩余极限强度研究   总被引：2，自引：1，他引：1  

付丹文  王德禹 《海洋工程》2018,36(1):83-90

采用ISO规定的火灾的标准温度—时间曲线建立船体结构的火灾模型。基于能量守恒原理建立热传导微分方程,计算热传导、对流和辐射对结构温度分布的影响。考虑火灾发生位置的差异性,分析得到着火区域的温度场。根据高温下钢材的力学性能,针对火灾发生位置的不同,利用非线性有限元方法,分析火灾对集装箱船剩余弯曲极限强度(中拱、中垂)的影响。结果表明,集装箱船不同位置发生火灾时,对船体结构极限强度的影响具有显著差异。船舱某一位置发生火灾时,对船体梁中拱和中垂极限强度的影响也分别不同。对集装箱船火灾的瞬态分析结果表明,火灾对船体梁极限强度的衰减作用主要发生在火灾发展过程中的前期,船体梁极限强度的衰减速度随火灾发展的时间逐渐减慢。  相似文献   

Curvature of Flexibility Matrix for Damage Identification in Legs of Jacket Platforms     

陈立  马骏  赵德有  邬君 《中国海洋工程》2008,22(4):547-559

In this paper a new nondestructive damage identification method is introduced. The method based on flexibility matrix can be used to detect and locate structm＇al damage and evaluate the severity of damage in legs of jacket platforms by modal parameters of a structure. With the modal data for only the few lower modes in both the intact and damaged states, the one-dimensional and two-dimensional distributed curvatures can be used to analyze damage location and the severity. Instead of directly comparing the curvatures before and ＇after damage, the method here uses modal parameters only in the damaged structure to detect the damage and it consists of three parts. First, ilexibility matrix is obtained by use of the absolute maximum in each column. Second, because the legs of jacket platforms are the pipe-like structure, the circumferential flexibility curvature matrix is obtained by use of the circular curvature. At last, equivalent curvature ratio is defined and the curve meaning equivalent curvature ratio and the severity of damage relationship for one element is given through the data of damage severity from ten percent to ninety percent by numerical simulation. Many existing damage detection methods need two steps, locate the damage firstly and evaluate the severity of the damage. However, the method present- ed! in this paper can locate and then evaluate the severity of damage at the same time. The numerical analysis results in- dicate that the present method is effective, useful and only need the first and the second mode data of the structure.  相似文献   

煤矿井下套铣打捞技术研究与应用          下载免费PDF全文

杨轶  王建强  洪建俊 《探矿工程》2021,48(2):64-69

基于煤矿开采深度的增加,在复杂地层中进行定向钻孔施工发生卡钻事故的风险也在急剧增加。采用套铣打捞技术进行卡钻事故处理,能够提高事故处理的成功率,并起到保护原钻杆的作用,降低经济损失。文章分析研究了套铣打捞钻具的选择、冲洗液选择、工艺参数以及工艺方法,结合在玉溪矿和临涣矿打捞实例,优化了套铣打捞工艺及相关参数。  相似文献   

曲率积分约束的GPS浮动车地图匹配方法     

曾喆  李清泉  邹海翔  万剑华 《测绘学报》2015,44(10):1167-1176

提出了以轨迹曲线的曲率积分值作为地图匹配特征的匹配方法,利用轨迹曲率积分值约束前后相邻轨迹点的关联匹配,采用不同类型行驶路径以及不同采样间隔,实施了浮动车地图匹配试验,结果表明,以匹配正确率和稳定性评判,本文提出的曲率积分约束的浮动车地图匹配方法优于现有的未采用曲率特征匹配的经典浮动车地图匹配方法。  相似文献