排序方式： 共有53条查询结果，搜索用时 15 毫秒
41.
位于中扬子地台东南缘的大沙坪剖面下奥陶统留咀桥组下段重力流沉积非常发育，重力流沉积类型以富基质的Ａ型碎屑流沉积为主。经区域资料横向对比，这种发育是局部性的。对这种局部性的重力流沉积，本文应用自发振动原理进行了阐述，分析了沉积迁移常数Ｋ、沉积物滑移的最大坡度角αｍａｘ、最小坡度角αｍｉｎ、沉积物输入速率η等参数。αｍａｘ、αｍｉｎ控制了一个自发振动系统，△α（αｍａｘ－αｍｉｎ）、Ｋ、η一起控制了重力流形成的振动周期 相似文献
42.
Morphological instabilities in periodic patterns occurring both in precipitation and crystallization processes (Liesegang rings and crystal zoning) are investigated and compared with similar patterns in geological samples (zebra rocks and mud bands in snow sediments). In classical Liesegang systems, undisturbed parallel or concentric precipitation bands are emanated from even or concentric diffusion sources in homogeneous diffusion matrices of gelatine or other gels. In the case of superposing diffusion sources, sources with undulatory curvatures or local diffusion barriers there may occur several types of instabilities within the sequence of regular patterns: (a) gaps within the bands forming radial alleys free of precipitate, (b) transition from broken bands to speckled patterns and (c) apparent branching of bands linked together by so-called anastomoses. Calculations with a competitive particle growth (CPG) model show that lateral instabilities in Liesegang bands (gaps and radial alleys of gaps) are the result of Ostwald ripening effects taking place after precipitation. Apparent branching of bands or formation of anastomoses can be simulated with a prenucleation model according to Ostwald's supersaturation theory. Similar irregularities can be observed in zebra rocks (e.g. banded siderite) whose bandings are commonly explained by sequential sedimentation processes. A very different mechanism is assumed to be responsible for the origin of mud bands in snow sediments. An initially homogeneous distribution of intrinsic mud in snow sediments can be arranged into parallel bands according to a crystal zoning mechanism which is based on repeated thawing and freezing of the snow sediment due to the daily alternation of sun and darkness. 相似文献
43.
自组织临界性与地震预测：对目前地震预测问题争论的评述（之一） 总被引：12，自引：0，他引：12
目前国际上围绕地震预测问题的争论,很大程度上与地震的自组织临界性模型有关。根据地震ＳＯＣ模型,地震预测被认为是不可能的。事实上,这是一个误解这个误解又是关于地震的ＳＯＣ模型的诸多误解中的一个。在地震的ＳＯＣ模型中,地震的能量－频度关系具有重要的地位。 相似文献
44.
海湾扇贝是雌雄同体的贝类 ,其壳色有橙、棕、黄、紫、白等色彩。利用壳色可遗传的特性 ,采用自体受精的交配策略 ,于 2 0 0 2年成功地建立了 4个橙色、3个紫色、4个白色等 3类共 1 1个海湾扇贝自交系 ,并对不同家系的受精卵大小、胚胎孵化率及幼虫、稚贝和养成阶段的生长速率与存活率等生物学参数进行了比较。结果表明 ,在幼虫和稚贝等早期发育阶段 ,3类壳色的不同家系在生长速率和存活率等方面没有表现出差异 ,但是在养成阶段 ,在高温的7、8月 ,白壳色家系的生长速率和存活率均明显高于其它 2种壳色的家系。 相似文献
45.
开挖过程的非线性理论分析 总被引：19，自引：3，他引：16
本文从岩土介质力学非线性和变形破坏过程自组织非线性的角度对开挖过程岩土体非线性行为进行了探讨。以此为依据,分析了岩土从微观破坏、滑移面形成、直至整体变形破坏全过程的自组织发生机理,在此基础上,建立了伴随开挖过程岩土体变形破坏的非线性动力学描述方程。 相似文献
46.
河西走廊西端地下水资源 总被引：6，自引：0，他引：6
利用 1995年度《河西走廊西端水文地质工作空白区 1∶50万区域水文地质调查》成果 ,结合毗邻空白区的以往资料及红外遥感图片解释成果资料 ,采用大气降水入渗法和水均衡法 ,对河西走廊西端地下水资源进行了概算。概算出河西走廊西端地下水资源总量为 12 14 3 83万m3/a ,其中山地 2 4 4 4 94万m3/a ,走廊平原 (盆地 ) 9698 89万m3/a(已扣除重复量 )。 相似文献
47.
The application of stationary parameters in conceptual hydrological models, even under changing boundary conditions, is a common yet unproven practice. This study investigates the impact of non‐stationary model parameters on model performance for different flow indices and time scales. Therefore, a Self‐Organizing Map based optimization approach, which links non‐stationary model parameters with climate indices, is presented and tested on seven meso‐scale catchments in northern Germany. The algorithm automatically groups sub‐periods with similar climate characteristics and allocates them to similar model parameter sets. The climate indices used for the classification of sub‐periods are based on (a) yearly means and (b) a moving average over the previous 61 days. Classification b supports the estimation of continuous non‐stationary parameters. The results show that (i) non‐stationary model parameters can improve the performance of hydrological models with an acceptable growth in parameter uncertainty; (ii) some model parameters are highly correlated to some climate indices; (iii) the model performance improves more for monthly means than yearly means; and (iv) in general low to medium flows improve more than high flows. It was further shown how the gained knowledge can be used to identify insufficiencies in the model structure. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
48.
迎接“数字地球”的挑战——关于内涵、机遇及对策的讨论 总被引：4，自引：0，他引：4
本文在叙述了“数字地球”的产生背景的基础上,着重分析了“数字地球”的科学内涵、“数字地球”给地球科学带来的新契机和我们应有的对策.笔者认为,“数字地球”是国家利益和现代科学技术的综合产物;“数字地球”的科学内涵可分为宏观战略层、技术实现层和应用层三个层面;“数字地球”是一个战略,并不能代替相关的学科和技术领域,现有的科学技术水平也不能完全满足“数字地球”的要求;“数字地球”的兴起给地球科学带来了大好机遇,使地球科学在对地球整体性认识、数字虚拟、对地球复杂巨系统的研究等方面都大大深化;面临“数字地球”的挑战,我们应该采取的策略是积极借鉴数字地球的思想,在继续大力发展现有的相关学科和技术领域的同时,努力进行自主创新,力求通过“中国数字地球”或“数字中国”的建设来占领制高点. 相似文献
49.
V. Naudet M. Lazzari A. Perrone A. Loperte S. Piscitelli V. Lapenna 《Engineering Geology》2008,98(3-4):156-167
Most of Basilicata region in the southern Italian Apennines is characterized by landslides often developing in clayey–marly formations. Many events have been triggered by extreme rainfall or snowmelt. The most important happened (on February–March 2005) at Bosco Piccolo 5 km far from Potenza. This landslide developed subsequently to rapid snowmelt occurred during alternating short periods of high temperatures and intense and continuous snowfalls. This complex landslide affected 4 ha of surface and reached a maximum depth of 20 m inducing damage and collapse of about 80% of the buildings in the village. An integrated multidisciplinary approach has been adopted to study the landslide. A multitemporal aerial photo interpretation and detailed geomorphological surveys have been carried out. Combined Electrical Resistivity Tomography (ERT) and Self-Potential (SP) measurements have been performed and calibrated with boreholes stratigraphy. Such an integrated approach allowed us to partially reconstruct the geometry of the investigated body and to evaluate the effectiveness of drainage system planned for the area. 相似文献
50.
智能岩石力学及其内容 总被引：6，自引：0，他引：6
本文针对岩石力学研究中目前存在的问题和信息时代的要求, 提出了21世纪的智能岩石力学的新思想和研究内容。它是综合现有各种行之有效的方法, 系统研究岩石工程问题, 提高岩石力学解决复杂问题的准确性。 相似文献