This paper presents an algorithm for detecting one of the most commonly used types of digital image forgeries - splicing. The algorithm is based on the use of the VGG-16 convolutional neural network. ...The proposed network architecture takes image patches as input and obtains classification results for a patch: original or forgery. On the training stage we select patches from original image regions and on the borders of embedded splicing. The obtained results demonstrate high classification accuracy (97.8% accuracy for fine-tuned model and 96.4% accuracy for the zero-stage trained) for a set of images containing artificial distortions in comparison with existing solutions. Experimental research was conducted using CASIA dataset.
The problem of natural convective boundary-layer flow of a nanofluid past a vertical plate is revisited. The model, which includes the effects of Brownian motion and thermophoresis, is revised so ...that the nanofluid particle fraction on the boundary is passively rather than actively controlled. In this respect the model is more realistic physically than that employed by previous authors.
•The problem of natural convective boundary-layer flow of a nanofluid past a vertical plate is revisited.•The model is revised so that the nanofluid particle fraction on the boundary is passively rather than actively controlled.•The model is more realistic physically than that employed by previous authors.
The purpose of this paper is to study the onset of bioconvection in a horizontal layer filled with a nanofluid that also contains gyrotactic microorganisms. The idea is to use microorganisms to ...induce or enhance convection in a nanofluid. A linear instability analysis is used to solve this problem. A Galerkin method is utilized to obtain an analytical solution for the critical Rayleigh number for the non-oscillatory situation. As in the case of a regular nanofluid (without the microorganisms), the presence of nanoparticles can either reduce or increase the value of the critical Rayleigh number, depending on whether the basic nanoparticle distribution is top-heavy or bottom-heavy. In contrast, the effect of gyrotactic microorganisms is always destabilizing.
The classical Cheng–Minkowycz problem considers natural convection past a vertical plate in a fluid-saturated porous medium. In our previous work we extended the Cheng–Minkowycz problem to the case ...when a porous medium is saturated by a nanofluid. We utilized Buongiorno’s nanofluid model that includes the effects of Brownian motion and thermophoresis. The major limitation of our previous model was active control of nanoparticle volume fraction at the boundary. Here we revisited our previous model and extended it to the case when the nanofluid particle fraction on the boundary is passively rather than actively controlled. This makes the model physically more realistic than our previous model as well as models employed by other authors simulating nanofluid flow in porous media.
The Cheng–Minkowycz problem of natural convection past a vertical plate, in a porous medium saturated by a nanofluid, is studied analytically. The model used for the nanofluid incorporates the ...effects of Brownian motion and thermophoresis. For the porous medium the Darcy model is employed. A similarity solution is presented. This solution depends on a Lewis number Le, a buoyancy-ratio number Nr, a Brownian motion number Nb, and a thermophoresis number Nt. The dependency of the Nusslelt number on these four parameters is investigated.
The natural convective boundary-layer flow of a nanofluid past a vertical plate is studied analytically. The model used for the nanofluid incorporates the effects of Brownian motion and ...thermophoresis. A similarity solution is presented. This solution depends on a Lewis number Le, a buoyancy-ratio number Nr, a Brownian motion number Nb, and a thermophoresis number Nt. For various values of Pr and Le, the variation of the reduced Nusselt number with Nr, Nb and Nt is expressed by correlation formulas. It was found that the reduced Nusselt number is a decreasing function of each of Nr, Nb and Nt.
The Gaver–Stehfest algorithm for numerical inversion of Laplace transform was developed in the late 1960s. Due to its simplicity and good performance it is becoming increasingly more popular in such ...diverse areas as geophysics, operations research and economics, financial and actuarial mathematics, computational physics, and chemistry. Despite the large number of applications and numerical studies, this method has never been rigorously investigated. In particular, it is not known whether the Gaver–Stehfest approximations converge or what the rate of convergence is. In this paper we answer the first of these two questions: We prove that the Gaver–Stehfest approximations converge for functions of bounded variation and functions satisfying an analogue of Dini criterion.
In complex multilayer structures made from PCM, metal inclusions of small sizes (from 0.1 ÷ 0.2 to 15 mm) randomly distributed throughout the material (at depths up to 100 mm), are unacceptable for ...normal operation, as they can penetrate into the material structure of a finished product. This paper is aimed at developing a device that provides a small error in determining the coordinates of small-sized metal inclusions in PCM when they are detected in real conditions of production and operation. Some devices capable of detecting the content of small particles in fluids or capable of detecting metal objects in various environments are known. The disadvantages of these devices are that they can only detect magnetically active particles, or large objects-more than 3-6 mm, while the location accuracy is recorded with a big error, insufficient for the detection process of small metal inclusions in PCM-from 30 mm and higher. This determines the urgency of developing a device for detecting small metal inclusions in finished products from PCM and in the technological cycle of their production. In this paper, the basic principles of the developed device are described, a block diagram of the device is presented, including the configuration of the eddy current transducer and the main processing units of the signals coming from the transducer. As confirmation of the operation of the developed device, photos of experimental studies and their results are presented in the form of the obtained dependences of the value of metal inclusions on the depth of their occurrence, from which it can be seen that the error in determining the depth of small-sized metal inclusions by the developed device did not exceed 10% and unchanged for all small-sized metal inclusions.
We have obtained propagators in the position space as an expansion over Landau levels for the charged scalar particle, fermion, and massive vector boson in a constant external magnetic field. The ...summation terms in the resulting expressions consisted of two factors, one being rotationally invariant in the 2-dimensional Euclidean space perpendicular to the direction of the field, and the other being Lorentz-invariant in the 1+1-dimensional space-time. The obtained representations are unique in the sense that they allow for the simultaneous study of the propagator from both space-time and energetic perspectives which are implicitly connected. These results contribute to the development of position-space techniques in QFT and are expected to be of use in the calculations of loop diagrams.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The onset of convection in a horizontal layer of a porous medium saturated by a nanofluid is studied analytically. The model used for the nanofluid incorporates the effects of Brownian motion and ...thermophoresis. The analysis reveals that for a typical nanofluid (with large Lewis number) the prime effect of the nanofluids is via a buoyancy effect coupled with the conservation of nanoparticles, the contribution of nanoparticles to the thermal energy equation being a second-order effect. It is found that the critical thermal Rayleigh number can be reduced or increased by a substantial amount, depending on whether the basic nanoparticle distribution is top-heavy or bottom-heavy, by the presence of the nanoparticles. Oscillatory instability is possible in the case of a bottom-heavy nanoparticle distribution.
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