耐压柱壳参数化设计与灵敏度分析          下载免费PDF全文

刘峰  王贺  苗怡然  屠超华  赵彦凯 《海洋技术学报》2019,38(1)

为提高耐压柱壳设计效率,设计了耐压柱壳参数化分析流程。研究了有限元分析所涉及的材料属性、载荷施加、边界条件设置等内容,确定了采用弧长法分析耐压柱壳稳定性。利用Python语言对于ABAQUS软件进行了二次开发,利用Isight软件实现了ABAQUS的集成,实现了耐压柱壳有限元分析模型的网格自动划分、自动分析计算等。选择样本点进行参数化分析,利用响应面模型对于样本点进行了拟合,得到了具有较高拟合精度、满足工程需要的近似模型,进行了设计变量的灵敏度分析。研究结果表明:参数化分析流程可实现耐压柱壳的自动分析、近似模型及灵敏度分析,可降低耐压柱壳分析难度,均可提高耐压柱壳设计效率。  相似文献   

River centerline extraction using the multiple direction integration algorithm for mixed and pure water pixels     

Quanwen Li  Xiaoxia Zhao  Yuming Wu 《地理信息系统科学与遥感》2019,56(2):256-281

The river centerline is a basic hydrological characteristic. Most prior studies have used remote sensing data to extract the river centerline from the open water region in a pure water pixel region. Extracting this type of river is relatively easy. However, extracting the centerline of a micro-river, which is mainly composed of mixed water pixels, is challenging. This paper presents a novel method, called the Multiple Direction Integration Algorithm (MDIA), to extract the river centerline using an image-enhancing method combined with river morphology. MDIA can be applied to regions mainly composed of pure water pixels, as well as to regions consisting of mixed water pixels in the index image. The method first calculates the normalized difference vegetation index (NDVI) and enhances the river linear structure using a Hessian matrix. Second, a small window is constructed as a circular structural element. In the window region, the local threshold is automatically obtained using water-oriented clustering segmentation and prior river knowledge to judge the pixel type. After completing the river centerline extraction in the current window, the next detecting window is generated to continue judgment. The structural element automatically executes river centerline judgment until the entire river centerline is extracted. The Landsat 8 images of six regions with different geomorphologies were chosen to analyze the method’s performance. The test sites include high mountain region, low mountain region, plains region with farmland and a residential region. The experimental results show that the optimal threshold of the processing results ranged from 0.2 to 0.3. In this range, the user’s accuracy is 0.813 to 0.997, and the producer’s accuracy is 0.981 to 1. The MDIA effectively and correctly extracts the river network in mixed-pixel regions. The presented method provides an effective algorithm for river centerline extraction that can be used to expand and update river datasets and provide reliable river centerline data for relevant hydrology studies.  相似文献   

苏、皖石炭系石灰岩的胶结作用     

王琦  涂仁亮  文丽  吴光华  洪三九  王广运 《中国海洋大学学报(自然科学版)》1993,(4)

分析了苏、皖石炭系石灰岩的胶结作用。查明了胶结物的晶形、碳、氧同位素成分、发光特征及包体均一化温度。指出胶结作用主要发生在大气淡水补给较充分的含水层内,这与本区属海退成岩序列有关。  相似文献   

Meiobenthos in estuary part of ha long bay (gulf of tonkin, south china sea, vietnam)   总被引：1，自引：0，他引：1  

Olga Pavlyuk  Yulia Trebukhova  Nguyen Vu Thanh  Nguyen Dinh Tu 《Ocean Science Journal》2008,43(3):153-160

The distribution of the taxonomical composition and the density of meiobenthos depending on some factors of environment has been studied in bottom sediments of the northern estuary part of Ha Long Bay (Cua Luc estuary). The basic factor of influence on meiobenthic community structure was the granulometric composition of sediment. The greatest taxonomic diversity is noted in the silted sands, lowest — in the silty sediments. The density of meiobenthic community was higher in the silty sediments. Slightly expressed correlation between the density of nematodes and the percentage of silty particles in the sediments is detected (Spearman rank correlation coefficient was 0.49±0.21, p=0.035). The nematodes were dominant at all stations. In total, representatives of 66 species of nematodes belonging to 17 families and 52 genera were identified.  相似文献   

汶川特大地震后安县疫情的地理流行病学分析方法     

闫磊  任玉环  陈诚  姚建义  陈伟  黄晓霞  王世文 《地球信息科学学报》2009,11(3):349-354

在分析汶川特大地震后安县2008年5~7月份的流行病学数据的过程中,作者探索了安县震后疫情地理分布、疾病构成、易感人群及其时序变化等特征的地理流行病学方法,并给出了有关专题地图、过程曲线和统计表格。它们能够形象、直观、准确地反映安县震后的疫情态势地理分布,进而使防控工作有的放矢、对症下药,收到事半功倍的效果。在此基础上,作者分析了地理流行病学方法的固有优势、实施关键、应用模式,以及今后的防治方向。为确保震后疫情流行病学数据在空间性、时效性和完整性上的质量,今后对地理流行病学方法的研究,应该从目前的疫情现状描述层次,尽快地向疫情分析预测、防控决策支持等层次延伸。  相似文献   

Modeling and calculating for the compaction characteristics of waste rock masses     

Defu Zhu  Shihao Tu  Hangsheng Ma  Hongmin Wei  Haocheng Li  Chen Wang 《国际地质力学数值与分析法杂志》2019,43(1):257-271

Bearing and deformation behaviors of waste rock masses (WRM) are more usually considered in stress distribution in caved waste. As WRM is widely located in hidden and dangerous environments, herein, numerical calculation is the preferred research method, but there are no modules specifically designed to simulate WRM, and the distribution of blockiness size, void, and properties of WRM in existing programs is still immature. A construction and subdivision method for modeling WRM is proposed in this paper. That is on the basis of the intact rock mass numerical model established in 3D Voronoi, the blocks in the intact rock mass are removed at random to achieve the purpose of retrieving the WRM structure by means of predetermined porosity. Also, the Weibull distribution is introduced to describe the properties of joints randomly, and a uniaxial compression experiment is used to research the compaction characteristics of WRM. The modeling and parametric methods can more accurately reflect fragmentation characteristics, bulking characteristics, and compaction characteristics of WRM. Compared with the existing theoretical and experimental results, this method has a high degree of consistency with them. This experimental study provides a new and effective method for the safety control of backfilling technics of WRM in coal mines.  相似文献   

Dissipation mechanism of interplanetary alfvenic fluctuation     

Chuan-yi Tu  Li Dong 《Chinese Astronomy and Astrophysics》1985,9(1):60-65

Observations on board Helios 1 and 2 have shown that, in 0.3–0.9 AU, the decay of the Alfvenic fluctuations is greater than is calculated by the WBK solution of the propagation of Alfven waves. The additional decay can be expressed by an exponential factor with a “dissipation length” λ, which varies with the frequency but is approximately constant for frequencies higher than 0.01 Hz. In this paper, we deduce the analytical expression for the dissipation length in both the wave energy cascade model, given in a previous work [7] and the viscous decay model [8]. After inserting the observed values of the solar wind parameters, we find the dissipation length given by the cascade model agrees with the observed length both in size and in its variation with frequency, while the one given by the viscous decay model differs greatly from the observations.  相似文献   

Public Participation in Rural Environmental Governance around the Water Source of Xiqin Water Works in Fujian     

SU Shipeng  LI Xin  HUANG Ansheng  SUN Xiaoxia 《资源与生态学报(英文版)》2018,9(1):66-77

Public participation is an important way to improve the overall effect and social recognition of rural environmental governance in water source areas. Public participation makes environmental governance measures more targeted and effective, contributes to protecting the basic environmental rights of the public, and makes it easier to meet the livelihood needs of rural people. Public participation in rural environmental governance in water source areas is characterized by complex behavior and is dependent on public willingness to participate. Amongst other factors, it is subject to the combined influences of both internal (psychological cognition) and external (environmental regulation) conditions. This paper builds a theoretical framework for understanding public participation behavior in rural environmental governance, and uses it to analyze a case in the rural area surrounding the Xiqin Water Works in Fujian Province. In the case study, the public shows high willingness to participate, but low actual rates of participation. At the same time, the willingness of villagers to pay for the control of pollution from livestock and poultry breeding varies greatly from village to village, and there are also noticeable individual differences in public participation in the use of public collection points for rural household waste. We found that gender, understandings of environmental protection and perception of environmental regulation, play a key role in influencing the willingness of farmers to pay for the control of pollution from livestock and poultry breeding. Individual awareness of environmental protection, environmental protection facility conditions, and environmental service quality had a significant influence on public participation in the use of public collection points for rural household waste.  相似文献   

基于改进U-Net网络的高分遥感影像水体提取     

何红术  黄晓霞  李红旮  倪凌佳  王新歌  陈崇  柳泽 《地球信息科学学报》2020,22(10):2010-2022

传统基于光谱信息的水体提取未能考虑水体形状、纹理、大小、相邻关系等问题,且存在同物异谱、异物同谱现象,导致水体提取精度较低。而传统基于分类提取水体方法设计特征过程较为繁琐,且不能挖掘深度信息特征。因此,本文提出改进的U-Net网络语义分割方法,借鉴经典U-Net网络的解编码结构对网络进行改进：① 将VGG网络用于收缩路径以提取特征;② 在扩张路径中对低维特征信息进行加强,将收缩特征金字塔上一层的特征图与下一层对应扩张路径上的特征图进行融合,以提高提取结果分割精度;③ 在分类后处理中引入条件随机场,以将分割结果精细化。在保持相同训练集、验证集和测试集的情况下,分别用SegNet、经典U-Net网络和改进的U-Net网络做对照试验。试验结果表明,改进的U-Net网络结构在IoU、精准率和Kappa系数指标上均高于SegNet和经典U-Net网络,与SegNet相比,3项指标分别提升了10.5%、12.3%和0.14,与经典U-Net网络结果相比,各个指标分别提升了5.8%、4.4%和0.05。改进的网络水体提取结果较为完整,对小目标水体能够准确提取。改进的U-Net网络能够有效地实现水体提取任务。  相似文献   

树木年轮碳稳定同位素在气象中的应用   总被引：4，自引：0，他引：4  

吕军  屠其璞  钱君龙 《气象》2001,27(1):9-13

对树木年轮碳同位素方法在气象中的应用及其成果作了综合评述，并对该领域目前存在的问题和前景作了一定的展望。  相似文献