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41.
Alireza Garakaninezhad Morteza Bastami Mohammad Reza Soghrat 《Journal of Seismology》2017,21(6):1505-1516
The evaluation of seismic risk of spatially distributed systems requires the spatial correlation model for ground motion intensity measures. This study investigates the spatial correlation of four earthquakes recorded in northern Iran. The intra-event spatial correlation for both horizontal and vertical components of spectral acceleration at eight periods in the range of 0.0–3.0 s is estimated using geostatistical tools. An exponential form is chosen to fit experimental semivariograms, and the correlation ranges of spectral accelerations as a function of period are derived. The results show similar trend of correlation ranges for both components. It should be mentioned that the ranges for the vertical component, in general, are higher than those observed for the horizontal one. For both components, the correlation ranges as a function of period are divided into three segments. The first and the third one are increasing while the second one is decreasing with increasing period. 相似文献
42.
Emad Zolqadr Seyed Shahaboddin Yasrobi Mohammad Norouz Olyaei 《Geomechanics and Geoengineering》2016,11(1):1-12
This study surveys the performance of temporary soil nail walls with a maximum height of 29.3 m in the Yas project, located in Tehran. Some numerical models, with various modelling approaches, were developed using finite element software and the proper modelling approaches were specified and verified.The modelling results were analysed and compared with the in situ monitored data. The results demonstrate the model’s horizontal deformations are generally greater than the in situ monitored values. To decrease the differences between models and monitored results, the effect of variations of the soil parameters had been surveyed and the limits of needed variations were specified. 相似文献
43.
Mohammad Sh. Odeh 《Experimental Astronomy》2004,18(1-3):39-64
A new criterion for lunar crescent visibility has been established using 737 observations, almost half of them obtained by
the Islamic Crescent Observation Project (ICOP). This criterion is based on two variables, viz. the topocentric arc of vision
and the topocentric crescent width. The new model is able to predict the visibility of the lunar crescent both for naked eye
and optically aided observations. From the database we found a Danjon limit of 6.4 degrees.
Vice-President of “Crescents, Calendars and Mawaqeet Committee” of AUASS. 相似文献
44.
Mohammad Qausar 《Pure and Applied Geophysics》1989,131(4):703-713
The attenuation properties of eight rheological models have been studied theoretically. The expressions forQ have been obtained by using dissipated and stored energies and/or complex modulus for each model. The dependence ofQ on frequency has been demonstrated. The three-element elastic model appears to be the best one to represent the viscoelastic nature of the earth's material for a finite value ofQ. 相似文献
45.
46.
The scaled boundary finite‐element method has been developed for the dynamic analysis of unbounded domains. In this method only the boundary is discretized resulting in a reduction of the spatial dimension by one. Like the finite‐element method no fundamental solution is required. This paper extends the scaled boundary finite‐element method to simulate the transient response of non‐homogeneous unbounded domains with the elasticity modulus and mass density varying as power functions of spatial coordinates. To reduce the number of degrees of freedom and the computational cost, the technique of reduced set of base functions is applied. The scaled boundary finite‐element equation for an unbounded domain is reformulated in generalized coordinates. The resulting acceleration unit‐impulse response matrix is obtained and assembled with the equation of motion of standard finite elements. Numerical examples of non‐homogeneous isotropic and transversely isotropic unbounded domains demonstrate the accuracy of the scaled boundary finite‐element method. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
47.
Ali M. Rajabi Mohammad R. Mahdavifar M. Khamehchiyan V. Del Gaudio 《Natural Hazards》2011,59(2):1189-1203
Earthquake-induced landslides are responsible worldwide for significant socioeconomic losses and historically have a prominent
position in the list of natural hazards affecting the Iran plateau. As a step toward the development of tools for the assessment
and the management of this kind of hazard at regional scale, an empirical estimator of coseismic displacements along potential
sliding surfaces was obtained through a regression analysis for the Zagros region, a mountainous Iranian region subjected
to earthquake-induced landslides. This estimator, based on the Newmark’s model, allows to evaluate the expected permanent
displacement (named “Newmark displacement”) induced by seismic shaking of defined energy on potential sliding surface characterized
by a given critical acceleration. To produce regression models for Newmark
displacement estimators, a data set was constructed for different critical
acceleration values on the basis of 108 accelerometric recordings from 80 Iranian earthquakes with moment magnitudes between 3.6 and 7.
The empirical estimator has a general form, proposed by Jibson (Eng Geol 91:209–218, 2007), relating Newmark
displacement to Arias
intensity (as parameter representing the energy of the seismic forces) and to critical
acceleration (as parameter representing the dynamic shear resistance of the sliding mass). As an example of application, this relation
was employed to provide a basic document for earthquake-induced landslide hazard assessment at regional scale, according to
a method proposed by Del Gaudio et al. (Bull Seismol Soc Am 93:557–569, 2003), applied to the whole Iranian territory, including Zagros region. This method consists in evaluating the shear resistance
required to slopes to limit the occurrence of seismically induced failures, on the basis of the Newmark’s model. The obtained
results show that the exposure to landslide seismic induction is maximum in the Alborz Mountains region, where critical
accelerations up to ~0.1 g are required to limit the probability of seismic triggering of coherent type landslides within 10% in 50 years. 相似文献
48.
A Study on the Surface Wettability of Clastic Rocks with Potential Application for CO2 Storage Sites
Umar Bappah Adamu Gholami Raoof Raza Arshad Downey William Samuel Sarmadivaleh Mohammad Shah Afroz A. Nayak Prasanta 《Natural Resources Research》2020,29(3):2051-2061
Natural Resources Research - There have been many studies carried out in the past decades attempting to develop strategies for a safe injection of CO2 into storage sites without leakage and... 相似文献
49.
Among numerous offshore structures used in oil extraction, jacket platforms are still the most favorable ones in shallow waters. In such structures, log piles are used to pin the substructure of the platform to the seabed. The pile’s geometrical and geotechnical properties are considered as the main parameters in designing these structures. In this study, ANSYS was used as the FE modeling software to study the geometrical and geotechnical properties of the offshore piles and their effects on supporting jacket platforms. For this purpose, the FE analysis has been done to provide the preliminary data for the fuzzy-logic post-process. The resulting data were implemented to create Fuzzy Inference System (FIS) classifications. The resultant data of the sensitivity analysis suggested that the orientation degree is the main factor in the pile’s geometrical behavior because piles which had the optimal operational degree of about 5° are more sustained. Finally, the results showed that the related fuzzified data supported the FE model and provided an insight for extended offshore pile designs. 相似文献
50.
Ocean Dynamics - Hydrodynamics of highly nonlinear cnoidal waves and their subsequent strong plunging breakers are among the least understood and most significant issues in coastal engineering. In... 相似文献