基于CT数的煤岩单轴压缩破坏的分叉与混沌分析     

尹光志  黄滚  代高飞  孙国文 《岩土力学》2006,27(9):1465-1470

利用CT机对煤岩在单向压缩应力状态下的破裂演化过程进行了实时扫描,采用现代非线性科学的分叉和混沌理论对煤岩在单向压缩状态下破坏的演化过程进行了研究,对各级应力状态下煤岩的各扫描断面的CT数进行了统计分析,并在此基础上建立了CT数变化的数学模型,其结果表明：当表征煤岩微裂纹存活比和闭合效应的特征量取一定值时,其CT数的变化可用Logistic方程来描述,具有分叉与混沌特征  相似文献   

地球自转日长变化(LOD)和大气角动量(AAM)所对应的动力系统   总被引：3，自引：0，他引：3  

刘式达  刘式适  陈炯 《天文学报》2000,41(1):62-67

利用一个多分维的分形地应的一维映射可以用子波变换反演出来,对地自转日长（ＬＯＤ）资料和大气角动量（ＡＡＭ）资料进行子波变换说明,在２０年尺度上、周年尺度和２－３２年尺度上,ＬＯＤ和ＡＡＭ的突变时间基本一致,所反演出的不同层次上分岔时间的分段映射动力系统也极其相似。  相似文献   

基于分叉理论的岩体局部化现象研究     

强跃  赵明阶  林军志  何建 《岩土力学》2013,34(7):2099-2103

为了研究岩体局部化现象,基于轴向压杆稳定实例,运用数理和力学知识,根据Drucker-Prager（简称D-P）准则,推导了基于分叉理论的通用表达式。在此基础上,结合有限差分理论得出FLAC3D计算中岩体内发生分叉的判定条件,之后在自带的FISH编译语言的辅助下,在FLAC3D中建立数值分析模型,采用D-P本构关系,研究了岩体局部化现象及其发展过程。研究结果表明：在FLAC3D中以20 000步为间隔所得的不平衡力比率模型系统逐渐趋于稳定,不平衡力比率逐渐降低,局部化现象的规模逐渐扩大至稳定,清晰度逐渐增加,证实了分叉理论能够有效地分析研究岩体局部化现象。给出的岩体局部分叉判定条件和数值验证,较为科学合理地阐述了常用分叉判定条件的由来,为解释岩体局部化现象的机制和过程提供了理论支撑,从而对岩体局部化现象研究起到了一定的推进作用。  相似文献   

Interannual variability of transport and bifurcation of the North Equatorial Current in the tropical North Pacific Ocean   总被引：1，自引：0，他引：1  

翟方国  胡敦欣 《中国海洋湖沼学报》2012,30(1):177-185

The relationship of the interannual variability of the transport and bifurcation latitude of the North Equatorial Current (NEC) to the El Ni o-Southern Oscillation (ENSO) is investigated. This is done through composite analysis of sea surface height (SSH) observed by satellite altimeter during October 1992-July 2009, and correspondingly derived sea surface geostrophic currents. During El Nio/La Ni a years, the SSH in the tropical North Pacific Ocean falls/rises, with maximum changes in the region 0-15°N, 130°E-160°E. The decrease/increase in SSH induces a cyclonic/anticyclonic anomaly in the western tropical gyre. The cyclonic/anticyclonic anomaly in the gyre results in an increase/decrease of NEC transport, and a northward/southward shift of the NEC bifurcation latitude near the Philippine coast. The variations are mainly in response to anomalous wind forcing in the west-central tropical North Pacific Ocean, related to ENSO events.  相似文献   

Chute channel dynamics in large,sand‐bed meandering rivers     

Michael Grenfell  Rolf Aalto  Andrew Nicholas 《地球表面变化过程与地形》2012,37(3):315-331

Meander bends of many large, sand‐bed meandering rivers are partitioned by chute channels that convey permanent flow, and co‐exist with the mainstem for decades. As a first step toward understanding the dynamics and morphodynamic implications of these ‘bifurcate meander bends’, this study applied binary logistic regression analysis to determine whether it is possible to predict chute initiation based on attributes of meander bend character and dynamics. Regression models developed for the Strickland River, Papua New Guinea, the lower Paraguay River, Paraguay/Argentina, and the Beni River, Bolivia, revealed that the probability of chute initiation at a meander bend is a function of the bend extension rate (the rate at which a bend elongates in a direction perpendicular to the valley axis trend). Image analyses of all rivers and field observations from the Strickland suggest that the majority of chute channels form during scroll–slough development. Rapid extension is shown to favour chute initiation by breaking the continuity of point bar deposition and vegetation encroachment at the inner bank, resulting in widely‐spaced scrolls with intervening sloughs that are positively aligned with primary over‐bar flow. The rivers plot in order of increasing chute activity on an empirical meandering‐braided pattern continuum defined by potential specific stream power (ω_pv) and bedload calibre (D₅₀). Increasing stream power is considered to result in higher bend extension rates, with implications for chute initiation. In addition, chute stability is shown to depend on river sediment load relative to flow discharge (Qs/Q), such that while the Beni may plot in the region of highly braided rivers by virtue of a high potential specific stream power, the formation of stable chute channels is suppressed by the high sediment load. This tendency is consistent with previous experimental studies, and results in a planform that is transitional between single‐thread meandering and braided. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

The stability of dipolar gyres on a beta-plane     

Steven Herbette  Antoine Hochet  Thierry Huck  Alain Colin de Verdière  Jérémy Collin  Frank Shillington 《地球物理与天体物理流体动力学》2014,108(5):479-502

  相似文献   

Three-dimensional bifurcations of periodic solutions around the triangular equilibrium points of the restricted three-body problem     

E. Perdios  C. G. Zagouras  O. Ragos 《Celestial Mechanics and Dynamical Astronomy》1991,51(4):349-362

Vertically critical, planar periodic solutions around the triangular equilibrium points of the Restricted Three-Body Problem are found to exist for values of the mass parameter in the interval [0.03, 0.5]. Four series of such solutions are computed. The families of three-dimensional periodic solutions that branch off these critical orbits are computed for µ = 0.3 and are continued till their end. All orbits of these families are unstable.  相似文献   

一类三次超越多项式零点的分布及其在时滞生物系统的应用     

阮士贵  魏俊杰  肖冬梅 《南京气象学院学报》2017,9(4):381-390

本文讨论了一类三次超越多项式零点的分布,给出了零点分布在左半复平面、穿过虚轴和进入右半复平面的充分条件.作为应用,考虑了带时滞的三种群食物链模型、带时滞的睾酮分泌模型、带时滞的HIV体内感染动力学模型、带时滞的葡萄糖-胰岛素模型、带时滞的肿瘤-免疫系统作用模型的稳定性和分支问题.  相似文献   

西风带阻塞高压形成及崩溃动力机制的Euler-Lagrange理论解释          下载免费PDF全文

刘春  张春辉  刘自牧  叶秣麟 《气象科学》2023,43(3):384-392

本文主要采用Euler-Lagrange理论,讨论正压剪切流的切变参数对阻塞高压形成的影响。研究表明:存在一个临界参数,当切变参数的绝对值超过这个临界参数,正压剪切流将分歧出阻塞流型,这意味着阻塞高压的形成;反之,当切变参数的绝对值小于这个临界参数,阻塞流型将恢复到剪切流,这意味着阻塞高压的崩溃。该研究一定程度回答了阻塞流型"怎么形成"和"怎么崩溃"这一基本而关键的问题。  相似文献