Ground roll attenuation using the S and x-f-k transforms   总被引：2，自引：0，他引：2  

Roohollah Askari †  Hamid R. Siahkoohi 《Geophysical Prospecting》2008,56(1):105-114

Ground roll, which is characterized by low frequency and high amplitude, is an old seismic data processing problem in land‐based seismic acquisition. Common techniques for ground roll attenuation are frequency filtering, f‐k or velocity filtering and a type of f‐k filtering based on the time‐offset windowed Fourier transform. These techniques assume that the seismic signal is stationary. In this study we utilized the S, x‐f‐k and t‐f‐k transforms as alternative methods to the Fourier transform. The S transform is a type of time‐frequency transform that provides frequency‐dependent resolution while maintaining a direct relationship with the Fourier spectrum. Application of a filter based on the S transform to land seismic shot records attenuates ground roll in a time‐frequency domain. The t‐f‐k and x‐f‐k transforms are approaches to localize the apparent velocity panel of a seismic record in time and offset domains, respectively. These transforms provide a convenient way to define offset or time‐varying reject zones on the separate f‐k panel at different offsets or times.  相似文献   

Simple formulas for the dynamic stiffness of pile groups     

Reza Taherzadeh  Didier Clouteau  Régis Cottereau 《地震工程与结构动力学》2009,38(15):1665-1685

Simple formulas are derived for the dynamic stiffness of pile group foundations subjected to horizontal and rocking dynamic loads. The formulations are based on the construction of a general model of impedance matrices as the condensation of matrices of mass, damping, and stiffness, and on the identification of the values of these matrices on an extensive database of numerical experiments computed using coupled finite element–boundary element models. The formulations obtained can be readily used for the design of both floating piles on homogeneous half‐space and end‐bearing piles and are applicable for a wide range of mechanical and geometrical parameters of the soil and piles, in particular for large pile groups. For the seismic design of a building, the use of the simple formulas rather than a full computational model is shown to induce little error on the evaluation of the response spectra and time histories. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Shake table study on an ordinary low‐rise building seismically isolated with SU‐FREIs (stable unbonded‐fiber reinforced elastomeric isolators)     

Hamid Toopchi‐Nezhad  Michael J. Tait  Robert G. Drysdale 《地震工程与结构动力学》2009,38(11):1335-1357

This paper reports on the investigation of novel fiber reinforced elastomeric isolator (FREI) bearings, which do not have thick end plates, and are used in an unbonded application. Owing to the stable lateral load‐displacement response exhibited by the unbonded FREI bearings, the proposed bearings are referred to as stable unbonded (SU)‐FREIs. A shake table test program was conducted on a two‐story test‐structure having well‐defined elastic response characteristics. Compared with the results for the corresponding fixed base (FB) structure, the peak response values, distribution of lateral response throughout the height of the structure, and response time histories of the tested base isolated (BI) structure indicate that significantly improved response can be achieved. This study clearly indicates that SU‐FREI bearings can provide an effective seismic isolation system. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

绿洲耕地变化趋势及其驱动力——塔里木盆地南部策勒绿洲为例   总被引：48，自引：0，他引：48  

瓦哈甫·哈力克  海米提·依米提  塔西甫拉提·特依拜  熊黑钢 《地理学报》2004,59(4):608-614

以多年的野外实地调查资料和统计资料,分析了塔里木盆地南部策勒绿洲50年以来耕地面积变化的总体趋势、空间差异和驱动因子。基于GPS现场定位,应用GIS进行空间分析,通过建立多元回归模型,最终对该绿洲2010年和2020年的耕地数量进行了初步的预测。分析结果表明社会经济发展动态、农业科技进步和水土资源的限制等3大类因素是影响耕地数量的3个主成分,其结果将为进一步研究整个塔里木盆地南部绿洲耕地变化提供借鉴,为合理利用和保护耕地、为干旱区可持续发展提供科学依据。  相似文献   

Imagery in the Presence of Turbulence Using Slit Aperture Telescope With Partial Adaptive Corrections     

Dr Hamid Touma 《Astrophysics and Space Science》2000,273(1-4):233-243

The objective of this communication is to study and totest numerically the concept of partial adaptive correction with arotating Slit Aperture Telescope (SAT). After a brief summary of theprinciple of image reconstruction with the rotating SAT operating withoutthe atmospheric turbulence, we describe the simulations of imagereconstruction when a partial atmospheric correction is performed in onedimension only, along the long axis of the rotating SAT. Thereconstruction algorithm performs the inversion of the Radon transform.The SAT can use a small adaptive optics system with far fewer actuatorsthan conventional two-dimensional devices, but a relatively high degree ofone-dimensional correction is needed to recover a satisfactorytwo-dimensional image. The effect of additive noise on the reconstructedimage is also investigated.  相似文献   

Fourier analysis of the light changes of four Algol-type eclipsing variables     

Hamid M. K. Al-Naimiy  Assem O. Al-Sikab 《Astrophysics and Space Science》1984,103(1):115-124

The aim of the present paper is to present the analysis of the light curves of four totally-eclipsing systems (BM Ori, VW Cyg, TW Dra, and RW Mon), using the automated Fourier techniques in the frequency-domain, developed recently by Kopal and his school at Manchester University.New Physical and geometrical elements for the above systems are derived.  相似文献   

The Iraqi National Astronomical Observatory     

Hamid M. K. Al-Naimiy 《Astrophysics and Space Science》1986,118(1-2):51-56

Iraq is currently experiencing a praid cultural, scientific, and technical renaissance, and astronomy is a natural focus for the country's pride in the past achievements of the civilization which have flourished in Iraq. The current plans of the Space and Astronomy Research Center (SARC) include building a major observatory to work in the optical, IR and radio region of the spectrum.The core of the optical facility will be a 3.5 m optical telescope, together with 1.25 m telescope designed for efficient performance in the IR. These telescopes will be equipped with instruments for photographic, photometric and spectroscopic observations. A 30 m dish is also being built for millimeter/radio observations.SARC has selected an excellent observing site in the northern mountains of Iraq which has good seeing and clear dark skies. The sites selection was made with the collaboration of several leading astronomers and observatories from various countries.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984  相似文献   

A GIS‐based multi‐criteria seismic vulnerability assessment using the integration of granular computing rule extraction and artificial neural networks          下载免费PDF全文

Hossein Sheikhian  Mahmoud Reza Delavar  Alfred Stein 《Transactions in GIS》2017,21(6):1237-1259

This study proposes multi‐criteria group decision‐making to address seismic physical vulnerability assessment. Granular computing rule extraction is combined with a feed forward artificial neural network to form a classifier capable of training a neural network on the basis of the rules provided by granular computing. It provides a transparent structure despite the traditional multi‐layer neural networks. It also allows the classifier to be applied on a set of rules for each incoming pattern. Drawbacks of original granular computing (GrC) are covered, where some input patterns remained unclassified. The study was applied to classify seismic vulnerability of the statistical units of the city of Tehran, Iran. Slope, seismic intensity, height and age of the buildings were effective parameters. Experts ranked 150 randomly selected sample statistical units with respect to their degree of seismic physical vulnerability. Inconsistency of the experts' judgments was investigated using the induced ordered weighted averaging (IOWA) operator. Fifty‐five classification rules were extracted on which a neural network was based. An overall accuracy of 88%, κ = 0.85 and R² = 0.89 was achieved. A comparison with previously implemented methodologies proved the proposed method to be the most accurate solution to the seismic physical vulnerability of Tehran.  相似文献   

Risk assessment of agricultural water requirement based on a multi-model ensemble framework,southwest of Iran     

Zamani  Reza  Akhond-Ali  Ali-Mohammad  Roozbahani  Abbas  Fattahi  Rouhollah 《Theoretical and Applied Climatology》2017,129(3-4):1109-1121

Water shortage and climate change are the most important issues of sustainable agricultural and water resources development. Given the importance of water availability in crop production, the present study focused on risk assessment of climate change impact on agricultural water requirement in southwest of Iran, under two emission scenarios (A2 and B1) for the future period (2025–2054). A multi-model ensemble framework based on mean observed temperature-precipitation (MOTP) method and a combined probabilistic approach Long Ashton Research Station-Weather Generator (LARS-WG) and change factor (CF) have been used for downscaling to manage the uncertainty of outputs of 14 general circulation models (GCMs). The results showed an increasing temperature in all months and irregular changes of precipitation (either increasing or decreasing) in the future period. In addition, the results of the calculated annual net water requirement for all crops affected by climate change indicated an increase between 4 and 10 %. Furthermore, an increasing process is also expected regarding to the required water demand volume. The most and the least expected increase in the water demand volume is about 13 and 5 % for A2 and B1 scenarios, respectively. Considering the results and the limited water resources in the study area, it is crucial to provide water resources planning in order to reduce the negative effects of climate change. Therefore, the adaptation scenarios with the climate change related to crop pattern and water consumption should be taken into account.

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Standard thermodynamic data for Rhodochrosite from equilibrium decomposition curve     

Ali Reza Fazeli  J. A. K. Tareen  B. Basavalingu  G. T. Bhandage 《Journal of Earth System Science》1991,100(1):37-39

Hydrothermal equilibrium decomposition curve for MnCO₃⇌MnO + CO₂ in the total CO₂ pressure range of 100–1700 bars and temperature range of 500–800°C was studied. The standard thermodynamic data obtained are: ΔH⁰ _f= − 894.382 ± 0.74 kj/mol and ΔG⁰ _f = − 822.170 ± 0.74 kj/mol. These values are more negative than the reported calorimetric data.  相似文献