排序方式： 共有17条查询结果，搜索用时 31 毫秒
1.
Kefayati Sadegh Baghbanan Alireza Torkan Masoud Hashemolhosseini Hamid Dehnavi Roohollah Narimani 《地震工程与工程振动(英文版)》2020,19(4):937-951
Uncertainty in input fracture geometric parameters during analysis of the stability of jointed rock slopes is inevitable and therefore the stochastic discrete fracture network (DFN) — distinct element method (DEM) is an efficient modeling tool. In this research, potentially unstable conditions are detected in the right abutment of the Karun 4 dam and downstream of the dam body as a case study. Two extreme states with small and relatively large block sizes are selected and a series of numerical DEM models are generated using a number of validated DFN models. Stability of the rock slope is assessed in both static and dynamic loading states. Based on the design basis earthquake (DBE) and maximum credible earthquake (MCE) expected in the dam site, histories of seismic waves are applied to analyze the stability of the slope in dynamic earthquake conditions. The results indicate that a MCE is likely to trigger sliding of rock blocks on the rock slope major joint. Furthermore, the dynamic analysis also shows a local block failure by the DBE, which can consequently lead to slope instability over the long term. According to the seismic behavior of the two models, larger blocks are prone to greater instability and are less safe against earthquakes.
相似文献2.
The aim of this study is to develop a two-dimensional hydrodynamic tidal model for the Persian Gulf (PG2017) using 2D-MIKE21 software. The advantages of present study is accounting for the spatial variation of bed friction coefficient besides a precise bathymetry together with a 23-year of combined records of satellite altimetry data. We found that the bed friction coefficient has a significant effect on sea level changes in the region under our modeling consideration. Since the tidal behavior in the northern part of the Qeshm Island is significantly different from the other parts of the Persian Gulf, to present a more accurate hydrodynamic tidal model, the Gulf is divided into two regions where the bed friction coefficient is modeled separately for each region. The root mean square value of the differences between the amplitude of dominant constituents; M2, S2, K1, and O1 derived from the PG2017 model and that of 98 altimetry and coastal tide gauge stations are respectively equal to 1.6, 1.9, 2.8, and 1.3?cm. Moreover, comparing the PG2017 model efficiency with the FES2014, OSU12, EOT11a, DTU10, and Admiralty models shows that the PG2017 model has an improvement of 22.1%, 47.2%, 43.2%, 44.2%, and 57.6% in terms of relative error, respectively. 相似文献
3.
A geodetic boundary value problem (GBVP) approach has been formulated which can be used for solving the problem of height
datum unification. The developed technique is applied to a test area in Southwest Finland with approximate size of 1.5° ×
3° and the bias of the corresponding local height datum (local geoid) with respect to the geoid is computed. For this purpose
the bias-free potential difference and gravity difference observations of the test area are used and the offset (bias) of
the height datum, i.e., Finnish Height Datum 2000 (N2000) fixed to Normaal Amsterdams Peil (NAP) as origin point, with respect
to the geoid is computed. The results of this computation show that potential of the origin point of N2000, i.e., NAP, is
(62636857.68 ± 0.5) (m2/s2) and as such is (0.191 ± 0.003) (m) under the geoid defined by W
0 = 62636855.8 (m2/s2). As the validity test of our methodology, the test area is divided into two parts and the corresponding potential difference
and gravity difference observations are introduced into our GBVP separately and the bias of height datums of the two parts
are computed with respect to the geoid. Obtaining approximately the same bias values for the height datums of the two parts
being part of one height datum with one origin point proves the validity of our approach. Besides, the latter test shows the
capability of our methodology for patch-wise application. 相似文献
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One of the main problems on the numerical solution of integral equations is the resolution of input data. Among the integral equations used in geodesy we have the “onestep inversion” based on the first derivative of the Poisson integral, which transforms gravity values on the Earth’s surface to the gravity potential on the reference ellipsoid. In this study, it is shown that the required spatial resolution of the input gravity data on the Earth’s surface for correct one-step inversion depends on the height of the computational region, the fact that if overlooked can cause totally wrong results. Consequently the following two major questions are posed: (i) How could one know whether the spatial resolution of the input gravity data for correct one-step inversion is sufficient? (ii) What should be done if the spatial resolution is not sufficient? By studying the behaviour of the integral kernel, an algorithm is presented which enables an appropriate answer to the former question. In order to address the latter question, a method is proposed to modify the integral kernel which overcomes the adverse effect of insufficient spatial resolution of the input gravity data. Our answers, which possess the novelty of the study, are numerically verified by means of real and simulated gravity data. The numerical results approve the efficiency of the proposed method in solving the problem of insufficient spatial resolution of the input gravity data for correct one-step inversion. 相似文献
6.
An alternative “direct method” to “mean dynamic topography” (MDT) computations using satellite altimetry-derived “mean sea
surface” (MSS) and “global geopotential model” (GGM), without direct application of the geoid, is devised. The developed approach,
which is based on derivation of an equipotential surface of the gravity field of the Earth that fits to global MSS in least
squares sense, is formulated via a constrained optimization problem. The validity of our method is numerically tested by computing
a global MDT model based on DNSC08 MSS model and EGM2008 GGM as input data. 相似文献
7.
Ground roll attenuation using the S and x-f-k transforms 总被引：2，自引：0，他引：2
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
8.
Manoj Khandelwal Amir Mahdiyar Danial Jahed Armaghani T. N. Singh Ahmad Fahimifar Roohollah Shirani Faradonbeh 《Environmental Earth Sciences》2017,76(11):399
Coal, as an initial source of energy, requires a detailed investigation in terms of ultimate analysis, proximate analysis, and its biological constituents (macerals). The rank and calorific value of each type of coal are managed by the mentioned properties. In contrast to ultimate and proximate analyses, determining the macerals in coal requires sophisticated microscopic instrumentation and expertise. This study emphasizes the estimation of the concentration of macerals of Indian coals based on a hybrid imperialism competitive algorithm (ICA)–artificial neural network (ANN). Here, ICA is utilized to adjust the weight and bias of ANNs for enhancing their performance capacity. For comparison purposes, a pre-developed ANN model is also proposed. Checking the performance prediction of the developed models is performed through several performance indices, i.e., coefficient of determination (R 2), root mean square error and variance account for. The obtained results revealed higher accuracy of the proposed hybrid ICA-ANN model in estimating macerals contents of Indian coals compared to the pre-developed ANN technique. Results of the developed ANN model based on R 2 values of training datasets were obtained as 0.961, 0.955, and 0.961 for predicting vitrinite, liptinite, and inertinite, respectively, whereas these values were achieved as 0.948, 0.947, and 0.957, respectively, for testing datasets. Similarly, R 2 values of 0.988, 0.983, and 0.991 for training datasets and 0.989, 0.982, and 0.985 for testing datasets were obtained from developed ICA-ANN model. 相似文献
9.
Mosayebzadeh Mahdi Ardalan Alireza A. Karimi Roohollah 《Studia Geophysica et Geodaetica》2019,63(2):169-190
Studia Geophysica et Geodaetica - Global geopotential models are widely used in the remove-compute-restore technique for local gravity field modeling. In this paper, a method for regional... 相似文献
10.
Roohollah Sadeghi Ali Mohebbi Mehdi Baniasadi 《International Journal of Mineral Processing》2011,98(1-2):55-65
In this study, a computational fluid dynamics (CFD) modeling accompanied by experimental field measurements has been applied to study the behavior of aqueous–organic dispersion on the performance of the launder of the settler of the copper solvent extraction plant at the Sarcheshmeh copper complex, Iran. Fluid flow field has been calculated by solving the continuity and Navier Stokes equations along with the standard k-ε turbulence model. The simulation results have been compared with the field measurements data to check the accuracy of the CFD work. The effects of picket fence on the launder performance and pressure drop over the picket fences in the launder have been investigated. The model predicts that by setting the picket fences, flow pattern becomes uniform, and turbulent eddies disappear. The results also show that by installing two picket fences without dam in the launder, the phase separation is improved and the performance of the launder is optimized. 相似文献