Enhanced multi-layer fatigue-analysis approach for unbonded flexible risers

This paper proposes an enhanced approach for evaluating the fatigue life of each metallic layer of unbonded flexible risers. Owing to the complex structure of unbonded flexible risers and the nonlinearity of the system, particularly in the critical touchdown zone, the traditional method is insufficient for accurately evaluating the fatigue life of these risers. The main challenge lies in the transposition from global to local analyses, which is a key stage for the fatigue analysis of flexible pipes owing to their complex structure. The new enhanced approach derives a multi-layer stress-decomposition method to meet this challenge. In this study, a numerical model validated experimentally is used to demonstrate the accuracy of the stress-decomposition method. And a numerical case is studied to validate the proposed approach. The results demonstrate that the multi-layer stress-decomposition method is accurate, and the fatigue lives of the metallic layers predicted by the enhanced multi-layer analysis approach are rational. The proposed fatigue-analysis approach provides a practical and reasonable method for predicting fatigue life in the design of unbonded flexible risers.     

Axial vibration analysis of the mud recovery line on deepwater riserless mud recovery drilling system

The series connection of multistage pumping module is the common concept of deepwater riserless mud recovery drilling system. In this system, the influence of the mass of pumping module on the vibration of mud recovery line cannot be ignored, and the lumped mass method has been utilized to discretize the mud recovery line. Based on the analysis of different boundary conditions, the paper establishes the axial forced vibration model of the mud recovery line considering the seawater damping, and the vibration model analysis provides the universal solution to the vibration model. An example of the two-stage pumping system has been used to analyze the dynamic response of mud recovery line under different excited frequencies. This paper has the important directive significance for the application of riserless mud recovery drilling technology in deepwater surface drilling.     

登陆热带气旋Bilis（0604）暴雨增幅与风场结构变化

利用日本气象厅区域谱模式（RSM）20 km再分析资料及改进的调和—余弦算法,对2006年4号台风Bilis登陆后暴雨增幅前后风场的结构变化特征进行了比较分析。Bilis台风登陆西行过程中,于14日18:00（协调世界 时,下同）开始,至15日12:00出现明显的暴雨增幅现象。在暴雨增幅前后时段,暴雨区的全风场及无辐散风分布变化强度小于无旋风。具体表现为:暴雨增幅前,Bilis低层西南部的无旋风速加强,辐合中心与Bilis中心逐步靠近,垂直上升运动加强;在暴雨增幅期间,Bilis西南部的低层和高层的无旋风速都一致持续加强。这种无旋风场上的变化与暴雨强度变化有很好的相关性,即:无旋风在Bilis西南部的增强及辐合增强与该区域暴雨的增强相对应,暴雨增幅的时段与高低层无旋风的风速加大和辐合增强是一致的。对暴雨增幅起主导作用的是无旋风的变化及其引起的散度变化。无旋风速及辐合增强时,暴雨增强并维持;无旋风及辐合减弱后,暴雨强度逐渐减弱。无辐散风强度变化与暴雨强度变化相反,而全风速在暴雨增幅前主要由无旋风决定,暴雨减弱阶段主要由无辐散风决定,对无旋风及无辐散风的分析能更加明显的揭示出暴雨增幅时期风场的具体变化。相对于全风场分析,无辐散风和无旋风能提供更多的风场结构变化与暴雨增幅的关系,这对于预报和分析登陆台风的风雨分布有一定的促进作用。     

Spatial differentiation of tourism impact based on the perception of residents in mountainous valley resorts

Valley economy is a type of economy that comprehensively utilizes the natural economic and social resources of the region based on environmental protection. This economy utilizes the basic role of the market in disposing resources and achieving regional development and social progress. In this paper we studied the town of Yanqi, a valley resort that has developed tourism-based valley economy for several years in the mountainous area of Beijing. This research identifies the spatial differentiation of tourism-related economic, socio-cultural, and environmental impact and level of support for tourism according to the perception and attitude of residents of Yanqi. The research area was divided into three zones （i.e., core, transition, and peripheral） according to the standard proposed by Jaakson. The residents in all three zones showed a positive attitude toward the tourism industry, and the residents in the core zone had a stronger perception toward the impact of tourism. However, several items indicated the converse. Correlation analysis and analysis of variance were used to explore the correlative factors associated with the attitudes of residents toward the tourism industry. Results indicated major differences among the three zones. Multiple factors, including natural conditions, policies, scenic spots, dependence on the tourism industry, and external investment in the three zones resulted in the spatial differentiationof the perception and attitude of residents toward the impact of tourism.     

一户多宅腾空1000余亩土地百姓乐享拆出的甜头——桐庐县开展一户多宅清理整治纪实

<正>今年以来桐庐县以省"三改一拆"行动为契机,以创建全省"无违建县"活动为载体,坚持"源头治理、政府主导、拆用结合、为民惠民"的原则,全面动员全县党员干部和人民群众积极参与,扎实有序地推动"一户多宅"清理活动开展。目前,全县共拆除农村非法"一户多宅"6973户,拆除一户多宅建筑面积114万平方米,占地面积695944平方米,折合土地1000余亩,且已初步规划,300亩可利用土地用于农民建房,350亩用于复耕,350亩用于村道、公园、绿化等公共服务设施建设,百姓乐享拆除的甜头。     

山东长岛——中国唯一的海岛国家地质公园

在我国山东半岛和辽宁半岛间有一个由32个岛屿组成的地方,那就是山东长岛县,在这里随处可遇的海蚀崖、洞、柱、石、象形礁、象形石、彩石岸、球石等惟妙惟肖,令人叹为观止,被地质专家称为东方奇观。它也是我国目前唯一的海岛国家地质公园。在春暖花开的季节,与朋友一起,乘风破浪,与长岛来了个亲密接触。     

基于资源三号卫星影像的极地1∶50000无地面控制成图技术研究

利用国产自主研发的立体测图卫星资源三号卫星遥感影像,采用无地面控制区域网平差方法,试生产极地地区1∶50 000 3D(DLG,DEM,DOM)地理信息产品.通过试生产提出极地1∶50 000比例尺数据成图技术流程图,并对其数据处理过程中的关键技术进行研究和分析,提出相关的技术要求.     

地理国情普查的对象和内容

正普查对象:我国陆地国土范围内的地表自然和人文地理要素。普査内容:一是自然地理要素的基本情况,包括地形地貌、植被覆盖、水域、荒漠与裸露地等的类别、位置、范围、面积等,掌握其空间分布状况;二是入文地理要素的基本情况,包括与人类活动密切相关的交通网络、居民     

星敏感器/GNSS定姿系统的联合非线性预测滤波算法

提出一种联合式非线性预测滤波算法,解决该系统在姿态动力学模型误差非高斯分布条件下的多敏感器信息融合问题。从算法结构和估计准则两个方面证明非线性预测滤波(NPF)与Kalman滤波的等效性,分析联合式NPF的算法流程,讨论模型误差方差矩阵的计算方法,给出加权系数矩阵的设计准则;介绍星敏感器和全球卫星导航系统(GNSS)的定姿原理,推导星敏感器/GNSS组合姿态确定系统的联合式NPF滤波模型,分析系统的算法实现流程;进行数值仿真试验,结果表明联合式NPF算法融合NPF与联邦滤波的优良品质,可有效解决姿态动力学模型误差非高斯分布条件下无陀螺姿态确定系统的多敏感器信息融合问题。     

ALOS卫星PRISM影像严格几何模型的构建与验证

根据ALOS卫星全色遥感立体测绘仪（PRISM）传感器的成像原理,利用卫星影像的辅助数据文件构建无需地面点的严格几何模型。试验发现,直接利用星上提供的轨道姿态数据和严格几何模型进行无控制定位精度较差,经分析发现ALOS卫星辅助数据文件中提供的CCD侧视角可能存在固定的系统误差,经校正后能使定位精度得到显著提高,达到ALOS卫星标称的几何定位精度。不同景影像定位精度的差异可能的原因是CCD侧视角的细微变化。