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151.
Comparison of cokriging and adaptive neuro-fuzzy inference system models for suspended sediment load forecasting 总被引:1,自引:0,他引:1
Mehdi Vafakhah 《Arabian Journal of Geosciences》2013,6(8):3003-3018
The present research was carried out by using artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS), cokriging (CK) and ordinary kriging (OK) using the rainfall and streamflow data for suspended sediment load forecasting. For this reason, the time series of daily rainfall (mm), streamflow (m3/s), and suspended sediment load (tons/day) data were used from the Kojor forest watershed near the Caspian Sea between 28 October 2007 and 21 September 2010 (776 days). Root mean square error, efficiency coefficient, mean absolute error, and mean relative error statistics are used for evaluating the accuracy of the ANN, ANFIS, CK, and OK models. In the first part of the study, various combinations of current daily rainfall, streamflow and past daily rainfall, streamflow data are used as inputs to the neural network and neuro-fuzzy computing technique so as to estimate current suspended sediment. Also, the accuracy of the ANN and ANFIS models are compared together in suspended sediment load forecasting. Comparison results reveal that the ANFIS model provided better estimation than the ANN model. In the second part of the study, the ANN and ANFIS models are compared with OK and CK. The comparison results reveal that CK was a better estimation than the OK. The ANFIS and ANN models also provided better estimation than the OK and CK models. 相似文献
152.
Mehdi Hosseini Mohammad Reza Saradjian 《Journal of the Indian Society of Remote Sensing》2014,42(4):719-726
High difference between dielectric constant of water (dielectric constant about 80) and dielectric constant of dried soil (dielectric constant about 2–3) makes Synthetic Aperture Radar (SAR) highly capable in soil moisture estimation. However, there are other factors which affect on radar backscattering coefficient. The most important parameters are vegetation cover, surface roughness and sensor parameters (frequency, polarization and incidence angle). In this paper, the importance of considering the effects of these parameters on SAR backscatter coefficients is shown by comparing different soil moisture estimation models. Moreover, an experimental soil moisture estimation model is developed. It is shown that this model can be used to estimate soil moisture under a variety of vegetation cover densities. The new developed model is based on combination of different indices derived from Landsat5-Thematic Mapper and AIRSAR images. The AIRSAR image is used for extraction of backscattering coefficient and incidence angle while TM image is used for calculation of Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), Normalized Difference Water Index (NDWI) and Brightness Temperature. Then a soil moisture estimation model which is named as Hybrid model is developed based on integration of all of these parameters. The accuracies of this model are assessed in the NDVI ranges of 0–0.2, 0.2–0.4 and 0.4–0.7 by using SAR data in C band and L band frequencies and also in different polarizations of HH, HV, VV and TP. The results show that for instance in L band with HV polarization, R-square values of 0.728, 0.628 and 0.527 are obtained between ground measured soil moisture and estimated soil moisture values using the Hybrid model for NDVI ranges of 0–0.2, 0.2–0.4 and 0.4–0.7, respectively. 相似文献
153.
In this paper we study the interacting dark energy model in the framework of Hořava-Lifshitz cosmology. Using an additional
canonical scalar field, we formulate Hořava-Lifshitz cosmology with an effective interacting dark energy sector. We show that
the interacting dark energy model in the framework of Hořava gravity exhibiting phantom behavior. 相似文献
154.
155.
Suitable materials for use as shell of embankment dams are clean coarse-grained soils or natural rockfill. In some sites these materials may not be available at an economic distance from the dam axis. The use of in-situ cohesive soils reinforced with geotextiles as the shell is suggested in this study for such cases. Dynamic behavior of reinforced embankment dam is evaluated through fully coupled nonlinear effective stress dynamic analysis. A practical pore generation model has been employed to incorporate pore pressure build up during cyclic loading. Parametric analyses have been performed to study the effect of reinforcements on the seismic behavior of the reinforced dam. Results showed that reinforcements placed within the embankment reduce horizontal and vertical displacements of the dam as well as crest settlements. Maximum shear strains within the embankment also decreased as a result of reinforcing. Furthermore, it was observed that reinforcements cause amplification in maximum horizontal crest acceleration. 相似文献
156.
Moment tensor inversion of nine events in Iran using INSN data 总被引:1,自引:0,他引:1
Aref Bali Lashak Mehdi Zare Gholamreza Mortezanejad Shahrokh Pour Beyranvand 《Journal of Seismology》2010,14(4):751-760
In this research, moment tensor (MT) inversion procedure in frequency domain is applied to nine events in order to evaluate
the data efficiencies in computing source parameters of earthquakes in Iran. The events are recorded by Iranian National Seismological
Network (INSN) stations, currently comprising 22 broadband stations. For the purpose of this study, first, the inversion procedure
is applied to obtain source parameters. Then, the results obtained here are compared with those of Harvard global centroid
moment tensors (GCMT) in order to estimate their reliabilities. The results show reasonable consistencies with those of Harvard
GCMT within 0.075 uncertainties in logarithmic scalar moment or 0.05 in moment magnitude and 20° in Kagan angle for focal
angles. Furthermore, according to the present research, the calculated source parameters are not significantly sensitive to
the azimuthal gap. 相似文献
157.
Mehdi Eshagh 《Acta Geophysica》2010,58(2):215-243
The traditional expressions for gravity gradients in local north-oriented frame and tensor spherical harmonics have complicated
forms involved with first- and second-order derivatives of spherical harmonics and also singular terms. In this paper we present
alternative expressions for these quantities, which are simpler and contain no singular terms. The presented formulas are
useful for those disciplines of geosciences which are involved with potential theory, tensor spherical harmonics and second-order
derivatives of spherical harmonic series in the local north-oriented frame. A simple numerical test on the solution of the
gradiometric boundary value problems presents the correctness of these new expressions and ability of the solutions to continue
the gravity gradients from satellite level down to sea level using spherical harmonics. 相似文献
158.
Two integral transformations between the stress function, differentiation of which gives the meridian and prime vertical components of the sub-crustal stress due to mantle convection, and the satellite-to-satellite tracking (SST) data are presented in this article. In the first one, the SST data are the disturbing potential differences between twin-satellites and in the second one the line-of-sight (LOS) gravity disturbances. It is shown that the corresponding integral kernels are well-behaving and therefore suitable for inversion and recovery of the stress function from the SST data. Recovery of the stress function and the stress components is also tested in numerical experiments using simulated SST data. Numerical studies over the Himalayas show that inverting the disturbing potential differences leads to a smoother stress function than from inverting LOS gravity disturbances. Application of the presented integral formulae allows for recovery of the stress from the satellite mission GRACE and its planned successor. 相似文献
159.
In this study, a scheme to estimate oceanic and hydrological effects in the GRACE (Gravity Recovery and Climate Experiment) data is presented. The aim is to reveal tectonic signals for the case of the Sumatra earthquake on 26 December 2004. The variations of hydrological and oceanic effects are estimated with the aid of data set of GRACE, altimetry, World Ocean Atlas, and the GLDAS model for a period of January 2003 to December 2006. The time series of computed gravity changes over Sumatra region show some correlations to the deformation resulting from the earthquake occurred in December 2004. The maximum and minimum impacts of hydrological and oceanic effects on gravity changes are about 3 μGal in radial direction and–5 μGal in northward direction. The maximum and minimum amounts of gravitational gradient changes after the correction are 0.2 and–0.25 mE, which indicates the significant influences of hydrological and oceanic sources on the desired signal. 相似文献
160.
Mehdi Najafi-Alamdary Alireza A. Ardalan Seyed-Rohallah Emadi 《Studia Geophysica et Geodaetica》2012,56(1):153-170
An ellipsoidal Neumann type geodetic boundary-value problem (GBVP) for the computation of disturbing potential on the surface
of the Earth based on the surface gravity disturbance as the boundary data is formulated. The solution methodology of the
GBVP can be algorithmically summarized as follows: (i) using global navigation satellite systems (GNSS) coordinates of the
gravity stations, the surface gravity disturbances are generated as the boundary data. (ii) Applying the deflection correction
to the gravity disturbances to arrive at the derivative of the surface disturbing potential along the ellipsoidal normal.
(iii) Removing the low frequencies part of the gravity field using harmonic expansion to degree and order 110. (iv) Using
the short wavelength part of the corrected gravity disturbances derived in the previous section as the boundary data within
the constructed GBVP to derive the short wavelength disturbing potential over the Earth surface. (v) The computed shortwave
length signals of disturbing potentials are converted to disturbing potential values by restoring the removed effects. 相似文献