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历次中强地震发生前,孕震区附近的小震活动在时间上和空间上会出现从无序到有序的演化过程,反映了小震活动序列中隐含着许多与未来强震发生有关的重要信息。本文选取了河南及邻区小震活动资料,从系统的观点,利用地震活动信息熵值的变化探讨孕震体前后的某种整体行为。通过资料计算分析,河南及邻区中强地震前信息熵值的变化较为明显,中强地震一般发生在高熵值过后的下降段或恢复段,熵值的时序变化与地震序列具有较好的对应性;不同的地质构造地震活动差异,对熵值曲线的形态细节变化存在着一定影响,但对熵值总体变化趋势影响不大。 相似文献
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The multiple scales of landscape topography produce a wide distribution of groundwater circulation cells that control the
hydro-geological environments surrounding geological repositories for nuclear waste. The largest circulation cells tend to
discharge water into major river reaches, large freshwater systems or the nearby Baltic Sea. We investigated numerically the
release of radionuclides from repositories placed in bedrock with depths between 100 to 2000 meters in a Swedish coastal area
and found that leakage from the deeper positions emerges primarily in the major aquatic systems. In effect, radionuclides
from the deeper repositories are more rapidly transported towards the Sea by the stream system compared to leakage from more
shallow repositories. The release from the shallower repositories is significantly retained in the initial stage of the transport
in the (superficial) landscape because the discharge occurs in or near low-order streams with high retention characteristics.
This retention and residence time for radioactivity in the landscape control radiological doses to biota and can, thus, be
expected to constitute an essential part of an associated risk evaluation. 相似文献
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It is widely accepted that ductility design improves the seismic capacity of structures worldwide. Nevertheless, inelastic deformation allows serious damage to occur in structures. Previous studies have shown that a certain level of postyield stiffness may reduce both the peak displacement and residual deformation of a structure. In recent years, several high-strength elastic materials, such as fiber-reinforced polymer (FRP) and high-strength steel bars, have been developed. Application of these materials can easily provide a structure with a much higher and more stable postyield stiffness. Many materials, members, and structures that incorporate both high-strength elastic materials and conventional materials show significant postyield hardening (PYH) behaviors. The significant postyield stiffness of PYH structures can help effectively reduce both peak and residual deformations, providing a choice when designing resilient structures. However, the findings of previous studies of structures with elastic-perfectly plastic (EPP) behavior or small postyield stiffness may not be accurate for PYH structures. The postyield stiffness of a structure must be considered an important primary structural parameter, in addition to initial stiffness, yielding strength, and ductility. In this paper, extensive time history and statistical analyses are carried out for PYH single–degree-of-freedom (SDOF) systems. The mean values and coefficients of variation of the peak displacement and residual deformation are obtained and discussed. A new R-μp-T-α relationship and damage index for PYH structures are proposed. A theoretical model for the calculation of residual deformation is also established. These models provide a basis for developing the appropriate seismic design and performance evaluation procedures for PYH structures. 相似文献
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定义了地震活动模糊熵概念，计算了唐山地震前地震活动模糊熵随时间，空间的变化，发现唐山Ｍｓ７．８地震发生前，地震活动模糊熵值下降，唐山Ｍｓ７．８地震发生在地震活动模糊熵值较低的地方，这符合大地震前震源区地震活动从无序趋向有序的规律，地震活动模糊熵反模糊因子与震群活动熵统一起来，比震群活动熵更突出地反映地震活动异常。 相似文献
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在较大地震的孕育过程中, 随着弹性应变能的不断积累, 孕震区有可能从原来的无序状态转变为一种在时间、 空间上的有序状态, 与之相联系的各种信息量的有序程度都有可能增加。 本文引入信息熵来描述前兆观测资料的空间扫描特征: 结果表明: 在4次福建地区中等地震前半个月至2个月, 在未来震中附近围成异常区域, 但异常表现各不相同, 异常区和异常量的大小与震级无明显关系, 震后异常区域均消失; 在4次地震中, 有1次地震发生在信息熵空间扫描围出的异常区内, 另外3次地震虽然不发生在异常区域内, 但震中都处于异常区域边缘, 最大距离不超过50 km以内, 这为判定震中位置提供了一定的依据。 相似文献
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The salinity of groundwater increases with depth in the Canadian Shield (up to 1.3 kg/L of density). The existence of brine can be critically important for the safe geologic disposal of radioactive wastes, as dense brine can significantly retard the upward migration of radionuclides released from repositories. Static and flushing conditions of the deep brine are analyzed using a U-tube analogy model. Velocity reduction due to the presence of dense brine is derived under flushing conditions. A set of illustrative numerical simulations in a two-dimensional cross section is presented to demonstrate that dense brine can significantly influence regional groundwater flow patterns in a shield environment. It is implied from the results that (1) the existence of Shield brine can be an indicator of a hydrogeologically stable environment, (2) activities near ground surface may not perturb the stable groundwater environment in the deep brine region, and thus, (3) the deep brine region can be considered as a candidate geologic site for the safe disposal of waste. In addition to brine, other issues associated with long-term waste disposal, such as geological, glacial and seismic events, may need to be considered for the safe storage of spent nuclear fuel in a shield environment. 相似文献
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A molecular dynamics study of uranyl-carbonate complexes adsorbed on basal surfaces of clay minerals
《Acta Geochimica》2015,(2)
We use molecular dynamics simulation to study the mechanisms involved in the adsorption of aqueous uranyl species(UO_2~(2+)) to the basal surfaces of clay minerals,including kaolinite,pyrophyllite and montmorillonite.Uranyl ion can form various complexes with carbonates,namely,[UO_2(H_2O)_5]~(2+),[UO_2(H_2O)3(CO_3)],[UO_2(H_2O)2(CO_3)_2]~(2-),[UO_2(CO_3)_3]~(4-).The simulations show that at aqueous clay interfaces,both uranyl species and surface type control the adsorption pattern.The noncarbonato and monocarbonato uranyl species can form outer-sphere complexes on siloxane surfaces through electrostatic interaction,but the dicarbonato and tricarbonato uranyl complexes rarely adsorb on the siloxane surfaces.Strong outer-sphere adsorptions of the uranylcarbonate complexes on gibbsite surfaces are observed,which are fixed by hydrogen bonds between the ligands(carbonate and/or H_2O) and surface hydroxyls.The sorption behaviors derived in this study provide new insights into understanding the migration and enrichment of uranium and other radionuclides. 相似文献
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地震是一种随机事件 ,它的发生具有极大的不确定性 ,因而可以用熵来进行描述。地震以最无序的方式在各地发生 ,意味着地震熵达到了极大值。古登堡 (Gutenberg)和里克特 (Richter)根据资料和经验得出的地震频度 -震级关系式实际上是在给定的约束条件下 ,当地震熵取极大值时得到的一种负指数分布。文中从最大熵原理得出了同一形式的地震频度 -震级关系 ,使它的来源从理论上得到了解释 相似文献
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Performance assessments of repositories for the underground disposal of nuclear fuel and waste include models of ground water flow and transport in the host rocks. Estimates of hydraulic conductivity, K, based on field measurements may require adjustment (upscaling) for use in numerical models, but the choice of upscaling approach can be complicated by the use of nested modeling, large-scale fracture zones, and a high degree of heterogeneity. Four approaches to upscaling K are examined using a reference case based on exhaustive site data and an application of nested modeling to evaluate performance assessment of a waste repository. The upscaling approaches are evaluated for their effects on the flow balance between nested modeling domains and on simple measures of repository performance. Of the upscaling approaches examined in this study, the greatest consistency of boundary flows was achieved using the observed scale dependence for the rock domains, measured values from the large-scale interference test for the conductor domain, and a semivariogram regularization based on the Moye model for packer test interpretation. Making the assumption that large fracture zones are two-dimensional media results in the greatest changes to the median of travel time and improves the flow balance between the nested models. The uncertainty of upscaling methods apparently has a small impact on median performance measures, but a significant impact on the variances and earliest arrival times. 相似文献
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本文采用极值理论、线性预测和最大熵谱分析三种不同的概率统计预报方法，从不同的角度对滇西南地区地震活动进行研究，得到滇西南５年内将有１次６．５－６．９级地震活动，１９９２年有６．０－６．４级发震可能的中短期预报结果。 相似文献
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Multi-scale entropy analysis of Mississippi River flow 总被引：4，自引：3，他引：1
Zhongwei Li You-Kuan Zhang 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(4):507-512
Multi-scale entropy (MSE) analysis was applied to the long-term (131 years) daily flow rates (Q) of the Mississippi River (MR) to investigate possible change in the complexity of the MR system due to human activities
since 1940s. Unlike traditional entropy-based method that calculates entropy at only one single scale, the MSE analysis provided
entropies over multiple time scales and thus accounts for multi-scale structures embedded in time series. It is found that
the sample entropy (S
E) for Q of the MR and its two components, overland flow (OF) and base flow (BF), generally increase as time scale increases. More
importantly, it is found that there have been entropy decreases in Q, OF, and BF over large time scales. In other words, the MR may have been losing its complexity since 1940s. We explain that
the possible loss in the complexity of the MR system may be due to the major changes in land use and land cover and soil conservation
practices in the MR basin since 1940s. 相似文献
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Input data selection for solar radiation estimation 总被引：1，自引：0，他引：1
Model input data selection is a complicated process, especially for non‐linear dynamic systems. The questions on which inputs should be used and how long the training data should be for model development have been hard to solve in practice. Despite the importance of this subject, there have been insufficient reports in the published literature about inter‐comparison between different model input data selection techniques. In this study, several methods (i.e. the Gamma test, entropy theory, AIC (Akaike's information criterion)/BIC (Bayesian information criterion) have been explored with the aid of non‐linear models of LLR (local linear regression) and ANN (artificial neural networks). The methodology is tested in estimation of solar radiation in the Brue Catchment of England. It has been found that the conventional model selection tools such as AIC/BIC failed to demonstrate their functionality. Although the entropy theory is quite powerful and efficient to compute, it failed to pick up the best input combinations. On the other hand, it is very encouraging to find that the new Gamma test was able to choose the best input selection. However, it is surprising to note that the Gamma test significantly underestimated the required training data while the entropy theory did a better job in this aspect. This is the first study to compare the performance of those techniques for model input selections and still there are many unsolved puzzles. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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熵的原理与地震活动研究 总被引：3，自引：2，他引：3
熵是多种学科的一个重要交叉点。熵的原理广泛适用于物理、化学、生物、医学、气象乃至社会经济等科学领域,并已取得了令人注目的成果。本文以熵的基本含意出发,简要地阐述了熵概念的扩展,包括热温熵、信息熵以及条件熵等。将地震孕育过程作为一个复杂的开放系统,基于耗散结构理论的基本思想,为定量描述地震活动时、空、强分布的有序度,引入地震活动熵作为序参量,并将其应用于大地震前后地震活动演变特征的研究。初步结果表明,随着临近大地震的发生,在一定范围内地震活动熵值减小,即地震活动分布状态从无序趋向有序。可以预期,把熵的原理引入地震研究领域必将加深人们对地震发生物理过程本质的认识。同时也将为探索地震预测提供新的思路和新的途径。 相似文献
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This paper deals with the effects of foundation embedment on the floor response spectra of big base isolated structures such as nuclear power plants. Analyses of a finite element model, representative of a real nuclear power plant, have been carried out. It has been demonstrated that, in agreement with previous work, base rocking excitation, induced by soil–structure interaction, may amplify the non-isolated modes׳ response and thus it must not be overlooked. 相似文献
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Wolfango Plastino Romano Plenteda George Azzari Andreas Becker Paul R. J. Saey Gerhard Wotawa 《Pure and Applied Geophysics》2010,167(4-5):559-573
Understanding radioxenon time series and being able to distinguish anthropogenic from nuclear explosion signals are fundamental issues for the technical verification of the Comprehensive Nuclear-Test-Ban Treaty. Every radioxenon event categorisation methodology must take into account the background at each monitoring site to uncover anomalies that may be related to nuclear explosions. Feedback induced by local meteorological patterns on the equipment and on the sampling procedures has been included in the analysis to improve a possible event categorisation scheme. The occurrence probability of radioxenon outliers has been estimated with a time series approach characterising and avoiding the influence of local meteorological patterns. A power spectrum estimator for radioxenon and meteorological time series was selected; the randomness of the radioxenon residual time series has been tested for white noise by Kolmogorov–Smirnov and Ljung–Box tests. This methodological approach was applied to radioxenon data collected at two monitoring sites located at St. John’s, Canada and Charlottesville, USA, equipped with two different noble gas systems. It shows different feedback with local meteorological patterns and randomness for the radioxenon data recorded at the selected sites of St. John’s and Charlottesville as well as a different occurrence probability of the outliers in the normalized radioxenon original and residual time series. 相似文献
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The geologic architecture in aquifer systems affects the behavior of fluid flow and the dispersion of mass. The spatial distribution and connectivity of higher-permeability facies play an important role. Models that represent this geologic structure have reduced entropy in the spatial distribution of permeability relative to models without structure. The literature shows that the stochastic model with the greatest variance in the distribution of predictions (i.e., the most conservative model) will not simply be the model representing maximum disorder in the permeability field. This principle is further explored using the Shannon entropy as a single metric to quantify and compare model parametric spatial disorder to the temporal distribution of mass residence times in model predictions. The principle is most pronounced when geologic structure manifests as preferential-flow pathways through the system via connected high-permeability sediments. As per percolation theory, at certain volume fractions the full connectivity of the high-permeability sediments will not be represented unless the model is three-dimensional. At these volume fractions, two-dimensional models can profoundly underrepresent the entropy in the real, three-dimensional, aquifer system. Thus to be conservative, stochastic models must be three-dimensional and include geologic structure. 相似文献
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为了对混凝土框架结构的地震破坏机制和抗震性能进行控制,在框架柱中配置高强钢筋,并将纤维增强混凝土(FRC)用于框架结构的预期损伤部位。结构柱中的高强钢筋用来减小结构的残余变形,FRC材料用来增加结构的耗能能力和损伤容限。设计了三个框架,采用动力弹塑性时程分析方法进行分析。研究结果表明,采用高强钢筋提高了结构的整体承载能力,在层间侧移角达到3%之前避免了柱铰的出现(包括底层柱底),并且减小了结构的残余变形;预期损伤部位采用FRC材料能够提高结构的塑性耗能。 相似文献