Applying multifractality and the self‐organized criticality theory to describe the temporal rainfall regimes in Andalusia (southern Spain)     

A. P. García‐Marín  F. J. Jiménez‐Hornero  J. L. Ayuso 《水文研究》2008,22(2):295-308

A multifractal analysis of hourly and daily rainfall data recorded at four locations of Andalusia (southern Spain) was carried out in order to study the temporal structure of rainfall and to find differences between both time resolutions. The results show that an algebraic tail is required to fit the probability distribution of the extreme rain events for all the cases. The presence of a multifractal phase transition associated with a critical moment in the empirical moments scaling exponent function was also detected. Both facts indicate that the rainfall process is a case of self‐organized criticality (SOC) dynamics, although the results differ for each place according to the time resolution and the nature of the rainfall, either convective or frontal. This SOC behaviour is related to a statistically steady state that implies the presence of clusterization in the time‐occurrence sequence of rain events. Such fluctuations have been shown by performing the analysis of the Fano and Allan factors and the count‐based periodogram. The values for the “synoptic maximum”, the typical lifetime of planetary scale atmospheric structures, have been obtained for each place and some important periodicities have been detected when dealing with extremes. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

多值图像的自适应空间索引结构研究     

谈国新  林宗坚  卢健 《武汉大学学报(信息科学版)》1995,(4)

提出一种适于多值图像层次表示的自适应空间索引结构，讨论了该索引结构的构造及检索算法。文中所列试验及分析表明，新提出的数据结构提高了多值图像的空间存贮与检索效率。  相似文献   

Cavernous weathering,dynamical instability and self‐organization     

Alice V. Turkington  Jonathan D. Phillips 《地球表面变化过程与地形》2004,29(6):665-675

Cavernous weathering may be conceptualized as a self‐reinforcing process, characterized by positive feedback within the weathering system. A morphometric study of caverns in the Valley of Fire State Park, Nevada, USA, demonstrates the applicability of a dynamically unstable, or conditionally unstable, model of cavernous weathering systems. Outcrop surfaces displaying caverns tend to show increasing fragmentation of the surface in the early stages of cavernous weathering, succeeded by convergent evolution of the surface in which caverns tend to grow and coalesce. A paradoxical relationship exists between the weathering system output at the scale of individual forms and the outcrop scale: caverns tend toward minimum interior surface area by developing a spheroidal form, yet the outcrop surface tends toward maximum exposed surface area by increasing the degree of fragmentation of the surface. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Analysis of a kinematic self‐centring seismic isolator     

Julio Pinochet  Juan C. de la Llera  C. Lüders 《地震工程与结构动力学》2006,35(12):1533-1561

This investigation deals with the analytical formulation and experimental validation of a prestressed reinforced concrete seismic isolator with kinematic constraints at both ends. The kinematic isolator was proposed initially as a low‐cost solution for seismic protection of low‐income people housing usually placed at the periphery of big cities where regular to bad soil conditions are common. So, the isolator is also a pile foundation with a central prestressed cable and two rolling steel surfaces at the top and bottom ends. By varying the shapes of the end rolling surfaces, different force–deformation constitutive relationships for the isolator may be obtained. Energy dissipation is introduced by yielding of passive reinforcement at the rolling interphase. Apart from stating the large‐deformation formulation of the element, several relevant aspects of the behaviour of these devices are studied herein, such as the increase in the tension of the central prestressed cable, responsible for the self‐centring action of the isolator, the floor uplift that results from the geometry of the isolator, and the vertical stability of the system. Experimental and theoretical results obtained for a group of 9 testing specimens show an excellent agreement in the force–deformation constitutive relationship. Although not the intent of this article, the device proposed may be extended directly as a coupling beam element for shear wall systems. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

线状要素图形综合的渐进方法研究   总被引：1，自引：1，他引：0  

郭庆胜 《武汉大学学报(信息科学版)》1998,(1)

提出了“渐进式”线状要素的２种图形综合方法：基于三角形的纯几何渐进方法和基于图形基本单元“弯曲”的渐进方法。该方法明显优于Ｄｏｕｇｌａｓ综合方法,可以控制线的自交,使地图比例尺从离散式变成连续式,适用于地理信息系统。在兼顾特征点的情况下,其效果更佳。  相似文献   

西南极菲尔德斯半岛岩浆作用非平衡过程的自组织现象          下载免费PDF全文

李兆鼐  李汉声  尚如相 《极地研究》1996,8(1):12-23

对西南极菲尔德斯半岛早第三纪火山岩岩石学、地球化学特征及岩浆作用过程的具体分析表明，其岩浆演化过程是岩浆系统与周围环境（介质）进行能量和物质交换的热能耗散过程，具有动态平衡和阶段性的特点。岩浆结晶的多级复合结构和高位岩浆房中的分带构造，是岩浆作用非平衡过程的自组织现象。这种自组织现象也称作耗散结构  相似文献   

综合物探方法在中坊水库坝体隐患勘查中的应用   总被引：1，自引：0，他引：1  

龚育龄  汤洪志  王良书  刘庆成  莫撼  郭令智 《水文地质工程地质》2002,29(1):49-51

在江、河、湖堤防及水库坝体隐患的勘查中，物探方法以其轻便、快捷的特点被广泛使用。中坊水库是江西省广昌县境内的一个中型水库，近年来坝体漏水现象较严重。为了查明隐患，本文采用探地雷达、高密度电阻率法、自然电位法和激发极化法等综合物探方法。对坝体进行勘查，基本查清了水库漏水地段及漏水通道位置，取得了良好的勘查效果。  相似文献   

乡村游客真实性体验模型研究     

陈才  赵志峰 《地理科学》2021,41(7):1237-1245

关于乡村旅游体验的研究,多以“乡村性”为主题,鲜有基于“真实性”视角的深入探讨。文章基于真实性视角,采用混合研究方法,构建乡村游客真实性体验模型,并进行验证。首先,通过质化研究,构建出“真境”“真情”“真智” “真我”4个维度的概念模型;其次,采用量化研究,验证了“真境”“真情”“真智”“真我”4个维度的合理性,4个维度存在中等程度的关联性,进一步验证表明,4个维度可以收敛在二阶变量“真实性体验”上。乡村游客真实性体验模型既拓展了真实性理论的应用范围,又进一步发展了真实性理论的内涵,为指导乡村旅游实践提供了理论基础。同时,真实性也是乡村游客深层动机的核心元素之一,即可作为乡村性的一个维度,也可独立应用于乡村旅游研究之中。  相似文献   

Shake table test and numerical study of self‐centering steel frame with SMA braces          下载免费PDF全文

Canxing Qiu  Songye Zhu 《地震工程与结构动力学》2017,46(1):117-137

Given their excellent self‐centering and energy‐dissipating capabilities, superelastic shape memory alloys (SMAs) become an emerging structural material in the field of earthquake engineering. This paper presents experimental and numerical studies on a scaled self‐centering steel frame with novel SMA braces (SMAB), which utilize superelastic Ni–Ti wires. The braces were fabricated and cyclically characterized before their installation in a two‐story one‐bay steel frame. The equivalent viscous damping ratio and ‘post‐yield’ stiffness ratio of the tested braces are around 5% and 0.15, respectively. In particular, the frame was seismically designed with nearly all pin connections, including the pinned column bases. To assess the seismic performance of the SMA braced frame (SMABF), a series of shake table tests were conducted, in which the SMABF was subjected to ground motions with incremental seismic intensity levels. No repair or replacement of structural members was performed during the entire series of tests. Experimental results showed that the SMAB could withstand several strong earthquakes with very limited capacity degradation. Thanks to the self‐centering capacity and pin‐connection design, the steel frame was subjected to limited damage and zero residual deformation even if the peak interstory drift ratio exceeded 2%. Good agreement was found between the experimental results and numerical simulations. The current study validates the prospect of using SMAB as a standalone seismic‐resisting component in critical building structures when high seismic performance or earthquake resilience is desirable under moderate and strong earthquakes. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

双层自行式施工平台结构强度评估     

赵鹏飞  夏利娟  杨秀礼  王磊 《海洋工程》2017,35(4):29-35

以一种适合港口施工作业的新型自行式施工平台为研究对象,介绍了该型平台特点与工作流程。根据其工作行走状态及载荷特点,使用有限元方法分析多工况下平台的结构屈服强度,并根据规范进行平台和桩腿结构屈曲评估。该平台由上下两层平台组合而成,针对此平台上下层接触的特点,探讨了不同类型MPC,ABAQUS接触分析的结构强度计算结果。研究对自行式海洋平台设计具有借鉴意义,并对平台结构强度计算研究提供了一定参考。  相似文献