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901.
902.
LIU Guilin CHEN Baiyu WANG Liping ZHANG Shuaifang ZHANG Kuangyuan LEI Xi 《海洋湖沼学报(英文)》2019,(2):448-460
When exploring the temporal and spatial change law of ocean environment, the most common method used is using smaller-scale observed data to derive the change law for a larger-scale system. For instance, using 30-year observation data to derive 100-year return period design wave height. Therefore, the study of inherent self-similarity in ocean hydrological elements becomes increasingly important to the study of multi-year return period design wave height derivation. In this paper, we introduced multifractal to analyze the statistical characteristics of wave height series data observed from oceanic hydrological station. An improvement is made to address the existing problems of the multifractal detrended fluctuation analysis (MF-DFA) method, where trend function showed a discontinuity between intervals. The improved MFDFA method is based on signal mode decomposition, replacing piecewise polynomial fitting used in the original method. We applied the proposed method to the wave height data collected at Chaolian Island, Shandong, China, from 1963 to 1989 and was able to conclude the wave height sequence presented weak multi-fractality. This result provided strong support to the past research on the derivation of multi-year return period design wave height with observed data. Moreover, the new method proposed in this paper also provides a new perspective to explore the intrinsic characteristic of data. 相似文献
903.
阻尼器是一种效果良好的减震装置,将阻尼器安装于结构中能够适时为结构体系提供阻尼力,从而减小地震作用对结构的破坏。黏滞阻尼器对振动的反应比较敏感,在结构受到较小振动时就可以发挥其减震效果,其阻尼力会随着振动周期和使用状态温度的不同而变化。当地震发生时,安装在结构中的阻尼器会消减地震作用,降低传导到主结构体系的地震能量,减小结构相对位移。本文介绍了黏滞阻尼器的工作原理和安装有黏滞阻尼器的结构体系的阻尼比的计算方法,对减震结构的减震效果的评析方法做出探讨,并以一安装有黏滞阻尼器的台湾某既有钢框架结构为例,分析了(1)该结构在遭受地震作用时的地震反应;(2)该结构体系在不同地震作用水平时的阻尼比,包括主体结构阻尼比和黏滞阻尼器阻尼比;(3)结构安装黏滞阻尼器后的减震效果。实例对本文的减震评析方法和减震效果进行了说明和分析,计算及分析结果表明利用黏滞阻尼器加固既有结构能够取得较好的减震效果,本文所提减震效果评析方法是一种实用有效的评析方法,对类似工程的减震评析具有一定的参考价值。 相似文献
904.
905.
The recent concerns regarding the seismic safety of the existing building stock have highlighted the need for an improvement of current seismic assessment procedures. Alongside with the development of more advanced commercial software tools and computational capacities, nonlinear dynamic analysis is progressively becoming a common and preferable procedure in the seismic assessment of buildings. Besides the complexity associated with the formulation of the mathematical model, major issues arise related with the definition of the seismic action, which can lead to different levels of uncertainty in terms of local and global building response. Aiming to address this issue, a comparative study of different code‐based record selection methods proposed by Eurocode 8, ASCE41‐13 and NZS1170.5:2004 is presented herein. The various methods are employed in the seismic assessment of four steel buildings, designed according to different criteria, and the obtained results are compared and discussed. Special attention is devoted to the influence of the number of real ground motion records selected on the estimation of the mean seismic response and, importantly, to the efficiency that is achieved when an additional selection criteria, based on the control of the spectral mismatch of each individual record with respect to the reference response spectrum, is adopted. The sufficiency of the methods with respect to the pairs of M–R of the selected group of records and the robustness of the scaling procedure are also examined. The paper closes with a study which demonstrates the suitability of a simplified probability‐based approach recently proposed for estimating mean seismic demands. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
906.
本文采集了3种典型的富锰沉积物样品,即岩石漆、树枝晶与土壤铁锰胶膜,并制作了相应的纵切片。运用光学显微镜、原位微区拉曼光谱仪、扫描电镜、EDX能谱仪分别对其形貌学与矿物学特征进行了研究。结果表明岩石漆呈黑色致密层状、葡萄状,主要由水钠锰矿、赤铁矿、针铁矿、粘土矿物等组成,是一种高度混杂的沉积物。宏观上岩石漆与基岩有截然的接触面,发育有微层理结构,在微观上的表现即锰含量的周期性波动。树枝晶呈黑色分枝状,主要由锰钡矿组成,极端富锰而贫硅铝,与基质呈交织结构。土壤铁锰胶膜呈黑色粘稠层状,由水钠锰矿、赤铁矿、针铁矿、钛铁矿、粘土矿物等组成,可细分为外层黑褐色的富锰条带和内层黄棕色的富铁条带。这3种富锰沉积物的形貌学和元素分布特征与各自的成因机制密切相关。 相似文献
907.
The present study includes results of the application of a program consisting of a genetic algorithm routine and a conventional refinement part (“hybrid method”) for the evaluation of Mössbauer spectra published elsewhere. It is shown that the saving of total evaluation time compared with conventional refinement routines is very high due to the rapid finding of adequate starting parameters. Contrary to a recently published work on a similar topic our algorithm provides solutions of the combined interaction Hamiltonian with a minimum of conventional input data. 相似文献
908.
A large and uniform dataset is used to find equations for the prediction of absolute spectral acceleration ordinates in Europe and adjacent areas, in terms of magnitude, source-distance and site geology. The dataset used is shown to be representative of European strong motion in terms of the attenuation of peak ground acceleration. The equations are recommended for use in the range of magnitudes from MS 4⋅0 to 7⋅5 and for source-distances of up to 200 km. 相似文献
909.
与多羟基化合物络合是去除和分离溶液中微量硼的有效手段,但我们对多羟基化合物与硼酸盐的反应缺乏深入认识。本文通过测定硼酸/硼砂与木糖醇、D-果糖、D-山梨醇和D-甘露醇在水溶液中反应的pH、电导率及Raman光谱,综合对比研究了硼酸/硼砂与四种多羟基化合物的络合反应。对于多羟基化合物/硼酸水溶液,随着多羟基化合物浓度的增加,溶液的pH值降低,电导率显著增加。对于多羟基化合物/硼砂水溶液,随着多羟基化合物浓度的增加,溶液的pH值和电导率都是首先明显降低,之后缓慢降低。为使硼酸/硼砂络合完全,多羟基化合物与硼酸的物质量的比要大于2。四种多羟基化合物与硼酸反应后,都出现了新的Raman峰,D-甘露醇与硼酸在溶液中反应后,在1 207 cm~(-1)处出现了较强的Raman峰。在四种多羟基化合物中,D-甘露醇与硼酸/硼砂的反应效果更好。 相似文献
910.
Earthquakes damage engineering structures near, relatively to the rupture's size, to the source. In this region, the fault's dynamics affect ground motion propagation differently from site to site, resulting in systematic spatial variability known as directivity. Although a number of researches recommend that records with directivity‐related velocity pulses should be explicitly taken into account when defining design seismic action on structures, probabilistic seismic hazard analysis (PSHA), in its standard version, seems inadequate for the scope. In the study, it is critically reviewed why, from the structural engineering point of view, hazard assessment should account for near‐source effects (i.e., pulse‐like ground motions), and how this can be carried out adjusting PSHA analytically via introduction of specific terms and empirically calibrated models. Disaggregation analysis and design scenarios for near‐source PSHA are also formulated. The analytical procedures are then applied to develop examples of hazard estimates for sites close to strike–slip or dip–slip faults and to address differences with respect to the ordinary case, that is, when pulse‐like effects are not explicitly accounted for. Significant increase of hazard for selected spectral ordinates is found in all investigated cases; increments depend on the fault‐site configuration. Moreover, to address design scenarios for seismic actions on structures, disaggregation results are also discussed, along with limitations of current design spectra to highlight the pulse‐like effects of structural interest. Finally, an attempt to overcome these, by means of disaggregation‐based scenarios specific for the pulse occurrence case, is presented. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献