Search

The inversion of parameters characterizing reservoir property based on rock physics model is an important content in seismic exploration, while the strong nonlinearity between basic parameters and seismic attributes makes it challenging in practice or computationally expensive. This study focuses on the issue of wave propagation in porous media saturated with two immiscible fluids and proposes to utilize deep neural network (DNNs)-based surrogate model to conduct forward analysis and parameter inversion. First, three classical rock physics models were employed to generate the dataset for training DNNs. Among them, five basic parameters (the porosity, bulk modulus and shear modulus of rock matrix, the solid density, and the saturation) were sampled within each reasonable range, and then, the corresponding phase velocity and inverse quality factor of seismic wave were calculated based on the three models. Next, DNNs were trained as surrogate models of the three rock physics models for sensitivity analysis. Then, such approach was applied to parameter inversion and different scenarios with different provided information and unknown quantities were designed to investigate the feasibility. The results showed the sensitivity of different models to basic parameters determines the corresponding inversion accuracy. When providing the information on the compressional wave, the porosity can be well inferred in most cases, while the accuracies of inverting saturation based on different models vary. Furthermore, it was found that adding the information of the shear wave can improve the performance of parameter inversions to a high level. From the obtained results, it was concluded that the DNNs-based surrogate models can serve as efficient tools for forward and inverse problems. [ABSTRACT FROM AUTHOR]

A locally rotationally symmetric Bianchi type-I model has been studied with two fluids within the framework of the f (T) theory of gravity. Bianchi type-I is an immediate generalization of the Friedmann–Lemaître–Robertson–Walker (FLRW) metric. We have derived the exact field equations in f (T) gravity by considering the Bianchi type-I metric and applying the action for f (T) theory of gravity. We have utilized the torsion scalar T and the Lagrangian for matter. The field equations are obtained by taking the variation of the action with respect to the vierbein, leading to a set of equations that includes the energy–momentum tensor for two fluid sources: matter and radiation. We fit the H (z) curve using 57 data points and the R 2 -test, achieving an R 2 value of 0.9321, indicating a strong fit with the Observational Hubble Dataset (OHD). Cosmological parameters like energy density, pressure, and state finder diagnostics are also discussed. [ABSTRACT FROM AUTHOR]

Simulating and predicting wave propagation in porous media saturated with two fluids is an important issue in geophysical exploration studies. In this work, wave propagation in porous media with specified structures saturated with two immiscible fluids was studied, and the main objective was to establish a wave equation system with a relatively simple structure. The wave equations derived by Tuncay and Corapcioglu were analyzed first. It was found that the coefficient matrix of the equations tends to be singular due to the inclusion of a small parameter that characterizes the effect of capillary stiffening. Therefore, the previously established model consisting of three governing equations may be unstable under natural conditions. An improved model based on Tuncay and Corapcioglu’s work was proposed to ensure the nonsingularity of the coefficient matrix. By introducing an assumption in which one fluid was completely wrapped by the other, the governing equation of the wrapped fluid was degenerated. In this way, the coefficient matrix of wave equations became nonsingular. The dispersion and attenuation prediction resulting from the new model was compared with that of the original model. Numerical examples show that although the improved model consists of only two governing equations, it can obtain a result similar to that of the original model for the case of a porous medium containing gas and water, which simplifies the complexity of the calculations. However, in a porous medium with oil and water, the predictions of dispersion and attenuation produced by the original model obviously deviate from the normal trend. In contrast, the results of the improved model exhibit the correct trend with a smooth curve. This phenomenon shows the stability of the improved model and it could be used to describe wave propagation dispersions and attenuations of porous media containing two immiscible fluids in practical cases.

In this work the homogeneous and isotropic Universe of Friedmann-Robertson-Walker is studied in the presence of two fluids: stiff matter and radiation described by the Schutz's formalism. We obtain to the classic case the behaviour of the scale factor of the universe. For the quantum case the wave packets are constructed and the wave function of the universe is found. [ABSTRACT FROM AUTHOR]

In the present paper, we have considered the Friedmann-Robertson-Walker universe in the frame work of f( R) gravity. The source of the gravitational fluid is the two co-moving perfect fluids: one fluid represents the matter content of the universe and the other modeling the cosmic microwave background radiation. Interacting and non-interacting cases of the two fluids are investigated. It is found that the universe is closed in the non-interacting Zeldovich fluid model and it is open at the present in the dust fluid model, whereas in interacting models, there is energy transfer from the radiation era to the matter era. Dynamical and kinematical properties of the models are also discussed. [ABSTRACT FROM AUTHOR]

Present paper deals with Axially Bianchi type-I Mesonic cosmological models with two fluid sources in Lyra Geometry. In the model one of the fluids represents the matter content of the universe and another fluid is the CMB radiation. For this purpose we have solved the field equations by considering time varying displacement field and uniform displacement field. We have also investigated the behaviours of some physical parameters. [ABSTRACT FROM AUTHOR]

Fluid flow and heat transfer in a square enclosure diagonally divided by a conductive thin plate has been numerically investigated. The upper diagonal zone of the enclosure filled with a saturated porous medium while the subdiagonal zone of the enclosure filled with air as working fluids. The enclosure was heated partially from below and cold from upper surface isothermally while the two vertical surface are insulated. The governing equations are solved using finite difference methods. Results were obtained for different value of Rayleigh number (103 ≤ Ra ≤ 105) for air and different value of modified Rayleigh number (100 ≤ Ra* ≤ 500) for porous medium as well as different dimensionless length of the heated surface (0.2 , 0.4 , 0.5 and 0.6 ). The results show that the increasing in Rayleigh number in both sides of the enclosure (Ra* & Ra) causes increasing in the Nusselt number. The percentage increasing is approximately is (92% at Ra*=100, 1000≤ Ra≤105 and 71% at Ra*=500, 1000≤ Ra≤105 for S=1 ) and ( 90% at Ra*=100 , Ra=104 and 0.2≤S≤0.6 and 80% at Ra*=500 , Ra=104 for 0.2≤S≤0.6 ). The flow become multi-cellular in porous media side also the increasing in dimensionless length of the heated surface causes increasing in the Nusselt number. [ABSTRACT FROM AUTHOR]

Tilted homogeneous plane symmetric two fluids cosmological models with matter and radiating source are investigated. In the model one of the fluids represents the matter content of the universe and another fluid is the CMB radiation. The tiltedness is also considered .With the help of variation for Hubble's parameter proposed by Bermann a cosmological model with negative constant deceleration parameter is obtained. We have also investigated the behaviours of some physical parameters. [ABSTRACT FROM AUTHOR]

We have presented anisotropic, homogeneous two-fluid cosmological models using Bianchi type-V space-time. Here one fluid represents the matter content of the universe and another fluid is chosen to model the CMB radiation. The radiation and matter content of the universe are in interactive phase. Also we have discussed the behavior of fluid parameters and kinematical parameters. [ABSTRACT FROM AUTHOR]

• A new picture for the coexistence of FM & SC in UGe 2 is established, in terms of the two-fluid model. • The collective spin-flop behavior of itinerant quasiparticles. • A sudden delocalization of part of 5f electrons near 1.2 GPa for the appearance of SC. The microscopic origin of heavy fermions is a central concept in correlated matter where the hybridization between localized spins and conduction electrons gives rise to exotic itinerant quasiparticles with enhanced effective masses. Although the two-fluid model provides a phenomenological description, the coexistence of localized and itinerant characters remains highly debated. Here we report the coexisting two fluids in a prime ferromagnet, UGe 2 , in which an unconventional superconductivity occurs in a limited pressure range. Except for localized moments, itinerant quasiparticles give an additional magnetic moment, resulting in a first-order-like transition with increasing magnetic field at high pressures. Our findings suggest a collective spin-flip behavior of itinerant quasiparticles, instead of the previously reported metamagnetic transition. Moreover, we record the pressure evolution of the two fluids, revealing a sudden delocalization of part of 5f electrons at P X ≈ 1.2 GPa. The valence instability with strong fluctuations sheds new light on the appearance of superconductivity adjoining ferromagnetism. [ABSTRACT FROM AUTHOR]