Search

We fabricated SrRuO3/PbZr0.52Ti0.48O3 heterostructures with an in-plane tensile-strained SrRuO3 layer and investigated the effect of an applied electric field on the anomalous Hall effect. The four-fold symmetry of anisotropic magnetoresistance and the nonmonotonic variation of anomalous Hall resistivity were observed. By applying positive and negative electric fields, the intersecting hump-like features are suppressed and enhanced, respectively. The sign and magnitude of the anomalous Hall conductivity can be effectively controlled with an electric field at a high magnetic field. The electric-field-modulated anomalous Hall effect is associated with the magnetization rotation in SrRuO3. The experimental results are helpful to realize magnetization rotation modulation in spintronic devices based on SrRuO3 heterostructures.

Exact solutions of the fractional Kraenkel–Manna–Merle system in saturated ferromagnetic materials have been studied. Using the fractional complex transforms, the fractional Kraenkel–Manna–Merle system is reduced to ordinary differential equations, (1 + 1)-dimensional partial differential equations and (2 + 1)-dimensional partial differential equations. Based on the obtained ordinary differential equations and taking advantage of the available solutions of Jacobi elliptic equation and Riccati equation, soliton solutions, combined soliton solutions, combined Jacobi elliptic function solutions, triangular periodic solutions and rational function solutions, for the KMM system are obtained. For the obtained (1 + 1)-dimensional partial differential equations, we get the classification of Lie symmetries. Starting from a Lie symmetry, we get a symmetry reduction equation. Solving the symmetry reduction equation by the power series method, power series solutions for the KMM system are obtained. For the obtained (2 + 1)-dimensional partial differential equations, we derive their bilinear form and two-soliton solution. The bilinear form can also be used to study the lump solutions, rogue wave solutions and breathing wave solutions.

Traditional image encryption technology usually encrypts a normal image into a noise matrix, which can protect the image in a certain extent, but noise appearance is easy to arouse the suspicion of attackers. To avoid this problem, a method of encrypting image into carrier image with visual meaning is proposed. Inspired by the existing visually secure encryption technique, we proposed an improved method based on the integer wavelet transform (IWT) and prediction scheme. The secret image is hidden in the high frequency coefficients of IWT to achieve good invisibility, and prediction error are used to replace the pixels of the carrier image to improve the final image quality. Experimental results and analysis show that the quality of the encrypted image is 3.5 dB better than that of the previous ones.

Finite‐difference modeling with a cross‐rhombus stencil with high‐order accuracy in both spatial and temporal derivatives is a potential method for efficient seismic simulation. The finite‐difference coefficients determined by Taylor‐series expansion usually preserve the dispersion property in a limited wavenumber range and fixed angles of propagation. To construct the dispersion‐relationship‐preserving scheme for satisfying high‐wavenumber components and multiple angles, we expand the dispersion relation of the cross‐rhombus stencil to an over‐determined system and apply a regularization method to obtain the stable least‐squares solution of the finite‐difference coefficients. The new dispersion‐relationship‐preserving based scheme not only satisfies several designated wavenumbers but also has high‐order accuracy in temporal discretization. The numerical analysis demonstrates that the new scheme possesses a better dispersion characteristic and more relaxed stability conditions compared with the Taylor‐series expansion based methods. Seismic wave simulations for the homogeneous model and the Sigsbee model demonstrate that the new scheme yields small dispersion error and improves the accuracy of the forward modelling.

Conventional Kirchhoff prestack time migration based on the hyperbolic moveout can cause ambiguity in laterally inhomogeneous media, because the root mean square velocity corresponds to a one‐dimensional model under the horizontal layer assumption; it does not include the lateral variations. The shot/receiver configuration with different offsets and azimuths should adopt different migration velocities as they contribute to a single image point. Therefore, we propose to use an offset‐vector to describe the lateral variations through an offset‐dependent velocity corresponding to the difference in offset from surface points to the image point. The offset‐vector is decomposed into orthogonal directions along the in‐line and cross‐line directions so that the single velocity can be expressed as a series of actual velocities. We use a simple Snell's law‐based ray tracing to calculate the travel time recorded at the image point and convert the travel time to an equivalent velocity corresponding to a pseudo‐straight ray. The double‐square‐root equation using such an equivalent velocity in the offset‐vector domain is non‐hyperbolic and asymmetrical, which improves the accuracy of the migration. Numerical examples using the Marmousi model and a wide azimuth field data show that the proposed method can achieve reasonable accuracy and significantly enhances the imaging of complex structures.

The aim of this letter is to apply the Lie group analysis method to the Fisher's equation with time fractional order. We considered the symmetry analysis, explicit solutions to the time fractional Fisher's(TFF) equations with Riemann-Liouville (R-L) derivative. The time fractional Fisher's is reduced to respective nonlinear ordinary differential equation(ODE) of fractional order. We solve the reduced fractional ODE using an explicit power series method.

Through symbolic computation with Maple, the $ (2+1)- $dimensional B-type Kadomtsev-Petviashvili(BKP) equation is considered. The generalized bilinear form not the Hirota bilinear method is the starting point in the computation process in this paper. The resulting lump solutions contain six free parameters, four of which satisfy two determinant conditions to guarantee the analyticity and rational localization of the solutions, while the others are arbitrary. Finally, the dynamic properties of these solutions are shown in figures by choosing the values of the parameters.

Data mining technology has yielded fruitful results in the area of crime discovery and intelligent decision making. Credit card is one of the most popular payment methods, providing great convenience and efficiency. However, due to the vulnerabilities of credit card transactions, criminals are able to commit fraud to infringe on the interests of the state and citizens. How to discover potential fraudsters while guaranteeing high efficiency becomes an extremely valuable problem to solve. In this work, we talk about the advantages and disadvantages of different models to detect credit card fraud. We first introduce the data preprocessing measures for handling imbalanced fraud detection dataset. Then we compare related models to implement fraudster recognition. We also propose a feature selection approach based on combined feature weights. Some future research interests are also envisioned.

Applying the combination of the qualitative theory of differential equation and bifurcation theory of planar dynamical systems to a combined form of KdV-like equation, the bifurcations of phase portraits to the corresponding traveling system of this equation are presented. The exact representations of smooth and non-smooth traveling wave solutions are obtained under different regions of parametric space. Moreover, numerical simulations are provided for some solutions of the equation.

Fault recognition is an important section in seismic interpretation and there are many methods for this technology, but no one can recognize fault exactly enough. For this problem, we proposed a new fault recognition method based on ant colony optimization which can locate fault precisely and extract fault from the seismic section. Firstly, seismic horizons are extracted by the connected component labeling algorithm; secondly, the fault location are decided according to the horizontal endpoints of each horizon; thirdly, the whole seismic section is divided into several rectangular blocks and the top and bottom endpoints of each rectangular block are considered as the nest and food respectively for the ant colony optimization algorithm. Besides that, the positive section is taken as an actual three dimensional terrain by using the seismic amplitude as a height. After that, the optimal route from nest to food calculated by the ant colony in each block is judged as a fault. Finally, extensive comparative tests were performed on the real seismic data. Availability and advancement of the proposed method were validated by the experimental results.

Intentional electromagnetic interference (IEMI) is a serious threat to the stable operation of computer and other intelligent terminal equipment. For testing research on IEMI, it is very important to build a stable and reliable test system model for accurate analysis of test data. In the time-domain test of IEMI, the z-domain discrete system transfer function is usually used to describe the response characteristics of the test system. However, with the change of sampling frequency, the parameters of the z-domain model should change accordingly, which leads to inconvenience in modeling the test system. In this paper, a δ-domain transfer function model of the test system is constructed by the transformation from z-domain. And the δ-domain model has better stability at high sampling rate and can be approximately equivalent to the system transfer function in the continuous-time domain.

In this paper, ZnS/CdS core/shell nanotubes were successfully synthesized by combining hydrothermal treatment and ion exchange conversion, and the significant influence of CdS content in the shell on photo absorption and photocatalytic activity was also investigated. The core/shell nanotubes structure of CdS deposition on both sides of ZnS nanotube was confirmed by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The room temperature PL spectra of ZnS/CdS core/shell nanotubes indicated that CdS on the shell can reduce the recombination of photon-generated electron and hole. The photocatalytic activity tests prove that ZnS/CdS nanotubes have much higher photocatalytic hydrogen production activity than ZnS nanotube and CdS nanotube. Under the irradiation of visible light, the highest photocatalytic hydrogen production rate of 110 μmol h−1 g−1 is observed over the ZnS/CdS core/shell nanotubes with CdS/ZnS molar ratio of 1:4, which is about 11.02 and 5.56 times more active than ZnS nanotube and CdS nanotube, respectively. The improved performance of ZnS/CdS samples can be due to the strong photo response in the visible light region and the efficient separation of electron–hole pairs.

To address the low-resolution imaging problem in relation to traditional Range Doppler (RD) algorithm, this paper intends to propose a new algorithm based on Fractional Fourier Transform (FrFT), which proves highly advantageous in the acquisition of high-resolution Synthetic Aperture Radar (SAR) images. The expression of the optimal order of SAR range signals using FrFT is deduced in detail, and the corresponding expression of the azimuth signal is also given. Theoretical analysis shows that, the optimal order in range (azimuth) direction, which turns out to be very unique, depends on the known imaging parameters of SAR, therefore the engineering practicability of FrFT-RD algorithm can be greatly improved without the need of order iteration. The FrFT-RD algorithm is established after an analysis of the optimal time-frequency transform. Experimental results demonstrate that, compared with traditional RD algorithm, the main-lobe width of the peak-point target of FrFT-RD algorithm is narrow in both range and azimuth directions. While the peak amplitude of the first side-lobe is reduced significantly, those of other side-lobes also drop in various degrees. In this way, the imaging resolution of range and azimuth can be increased considerably.

Structural complexities are concerns frequently encountered as peculiar features in most hydrocarbon provinces which various attempts has been made to resolve using conventional spatial images of the subsurface as continuous seismic reflections. These structural patterns are either tectonic or sedimentonic in origin and confers anisotropy and heterogeneity in subsurface formations thereby increasing the uncertainty associated with exploring hydrocarbon locked in their pores. Diffraction imaging has been used in various instances to delineate subtle discontinuities that synthesize diffraction waves in hydrocarbon formations, in tandem with reflection seismic and other invasive geophysical logs and core, in comparatively understanding fracture orientations and establishing relationships with the temporal data that are often regarded as most reliable. These data points have been used to infer structural relationship between the naturally fractured clastic formations in an oil and gas field with success. Rock elastic properties and signal anisotropy derived from core and logs resulted in structural attributes that correlated well with seismic diffraction volume inferred properties, giving credence to the relationships established and usefulness of the diffraction volume for characterizing and emphasizing small scale features hitherto classed as sub-seismic.

By symbolic computation and searching for the solutions of the positive quadratic functions of the related bilinear equations, two kinds of lump solutions of the (3[Formula: see text]+[Formula: see text]1)-dimensional weakly coupled Hirota bilinear equation are derived, and the practicability of this method is verified. Then we add an exponential function to the original positive quadratic function, and obtain a new solution of the Hirota bilinear equation. The interaction between the lump solutions and lump-kink solutions is included in the new solution. On this basis, we give the possibility of adding multiple exponential functions. Finally, we give the coupled reduced Hirota bilinear equation lump-kink solitons by combining the above two methods. In order to ensure the analyticity and reasonable localization of the block, two sets of necessary and sufficient conditions are given for the parameters involved in the solution. The local characteristics and energy distribution of bulk solution are analyzed and explained.

Reservoir characterization is indispensable in the development of the Cretaceous structural fractured Bashijiqike tight sandstone reservoir formation, which is the main production zone and known to exhibit high structural variability imparting on production at different scales. We performed an improved workflow based on diffraction extraction and analysis to characterize the fractures especially in locations proximal to the wellbore. Diffraction attributes significantly provide more details in the area, which are proven by three well FMI images and dipmeter logs. The results show that structural fractures in the study area are dominated by the upright shearing stress forming fractures with medium to high angles. The tending direction is also delineated to be similar despite the significant well offset, which is an indication of the underlying tectonic framework responsible for the overall architecture of this section of the basin. We opine due to our success that the proposed approach may be helpful to describe the distribution and direction of fractures in naturally fractured reservoirs tied by the well logs.

Reservoir characterization deals with the description of the reservoir in detail for rock and fluid properties within a zone of interest. The scope of this study is to model lateral continuity of lithofacies and characterize reservoir rock properties using geostatistical approach on multiple data sets obtained from a structural depression in the bight of Bohai basin, China. Analytical methods used include basic log analysis with normalization. Alternating deflections observed on spontaneous potential (SP) log and resistivity log served as the basis for delineating reservoir sand units and later tied to seismic data. Computation of variogram was done on the generated petrophysical logs prior to adopting suitable simulation algorithms for the data types. Sequential indicator simulation (SIS) was used for facies modeling while sequential gaussian simulation (SGS) was adopted for the continuous logs. The geomodel built with faults and stratigraphical attitude gave unique result for the depositional environment studied. Heterogeneity was observed within the zone both in the faulted and unfaulted area. Reservoir rock properties observed follows the interfingering pattern of rock units and is either truncated by structural discontinuities or naturally pinches out. Petrophysical property models successfully accounted for lithofacies distribution. Porosity volume computed against SP volume resulted in Net to gross volume while Impedance volume results gave credibility to the earlier defined locations of lithofacies (sand and shale) characterized by porosity and permeability. Use of multiple variables in modeling lithofacies and characterizing reservoir units for rock properties has been revisited with success using hydrocarbon exploration data. An integrated approach to subsurface lithological units and hydrocarbon potential assessment has been given priority using stochastic means of laterally populating rock column with properties. This method finds application in production assessment and predicting rock properties with scale disparity during hydrocarbon exploration.

Simultaneous estimation of velocity gradients and anisotropic parameters from seismic reflection data is one of the main challenges in transversely isotropic media with a vertical symmetry axis migration velocity analysis. In migration velocity analysis, we usually construct the objective function using the l2 norm along with a linear conjugate gradient scheme to solve the inversion problem. Nevertheless, for seismic data this inversion scheme is not stable and may not converge in finite time. In order to ensure the uniform convergence of parameter inversion and improve the efficiency of migration velocity analysis, this paper develops a double parameterized regularization model and gives the corresponding algorithms. The model is based on the combination of the l 2 norm and the non-smooth l 1 norm. For solving such an inversion problem, the quasi-Newton method is utilized to make the iterative process stable, which can ensure the positive definiteness of the Hessian matrix. Numerical simulation indicates that this method allows fast convergence to the true model and simultaneously generates inversion results with a higher accuracy. Therefore, our proposed method is very promising for practical migration velocity analysis in anisotropic media.

In this paper, by applying the direct symmetry method, we obtain the symmetry reductions, group invariant solutions and some new exact solutions of the Bogoyavlenskii equation, which include hyperbolic function solutions, trigonometric function solutions and power series solutions. We also give the conservation laws of the Bogoyavlenskii equation.

The aim of this paper is to apply the Lie group analysis method to the weakly coupled Kaup–Kupershmidt (KK) equation with time fractional order. We considered the symmetry analysis, explicit solutions to the weakly coupled time fractional KK (TF-KK) equation with Riemann–Liouville (RL) derivative. The weakly coupled TF-KK equation is reduced to a nonlinear ordinary differential equation (ODE) of fractional order. We solve the reduced fractional ODE using the sub-equation method.

Ian McEwan, together with Martin Amis is now the best-known and controversial contemporary British novelist. McEwan seems to be interested in the relationship between reality and imagina-tion, history and fabrication in the process of writing, which is generally considered as one of the themes related to postmodern metafiction writing. He also adopts the postmodern intertextuality in his writing practice. Those postmodern concerns and strategies confirm his position as a post-modernist.

The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising candidate for cancer therapeutics that exhibits the ability to preferentially induce apoptosis in malignant cells. RGD peptides bind to the integrins, ανβ3 and ανβ5, which are selectively expressed in tumor neovasculature and at the surface of certain tumor cells. To enhance the antitumor effect, an RGD-TRAIL protein, in which TRAIL was fused with the RGD motif-containing cell adhesive sequence, GRGDNP (gly-arg-gly-asp-asn-pro), was constructed and evaluated for bioactivity. The soluble TRAIL and RGD-TRAIL proteins were expressed in Escherichia coli BL21 (DE3) and purified using a non-denaturing method. The antitumor effect of the purified RGD-TRAIL on cell proliferation was evaluated in vitro using MTT and wound healing assays and cell apoptosis was assessed by Hoechst 33342 staining and PARP expression analysis. The results revealed that RGD-TRAIL inhibited the proliferation of multiple tumor cell lines (A549, NCI-H1299 and HCC827). Western blot analysis demonstrated that the treatment of tumor cells with RGD-TRAIL activated the apoptotic pathway by the cleavage of PARP, in the same way as wild-type TRAIL (wtTRAIL). These results demonstrate that RGD-TRAIL possesses more potent antitumor effects than wtTRAIL and, therefore, merits further investigation in preclinical and clinical studies.