Modern Physics Letters B

The study of complex oxides and oxide heterostructures has dominated the field of experimental and theoretical condensed matter research for the better part of the last few decades. Powerful experimental techniques such as molecular beam epitaxy and pulsed laser deposition have made fabrication of oxide heterostructures with atomically sharp interfaces possible, whereas more and more sophisticated handling of exchange and correlations within first principles methods including density functional theory (DFT) supplemented with Hubbard U corrections and hybrid functionals, and beyond DFT techniques such as dynamical mean field theory (DMFT) have made understanding of such correlated oxides and oxide interfaces easier. The emergence of the high-mobility two-dimensional electron gas with fascinating properties such as giant photoconductance, large negative magnetoresistance, superconductivity, ferromagnetism, and the mysterious coexistence of the latter two have indeed caught the attention of condensed matter community at large. Similarly, strain tuning of oxides have generated considerable interest particularly after the recent discovery of piezoelectric methods of strain generation. Theoretical understanding and prediction of the possible exotic phases emerging in such complex oxides both under strain and in heterostructures will eventually lead to better design of device applications in this new emerging field of oxide electronics, along with possible discovery of exotic physics in condensed matter systems, which may be of wider significance! In this review, we briefly look at theoretical studies of novel phenomena in oxides under strain and oxide heterostructure, and try to understand the role of exchange and particularly correlation in giving rise to such exotic electronic states. This review though primarily focuses on the theoretical aspects on understanding the different mechanism of the phenomena of emergence of exotic phases, does provide a unique overview of the experimental literature as well, accompanied by the theoretical understanding such that relevant device applications can be envisaged.

Under investigation in this paper is a (2+1)-dimensional nonlinear Schrödinger equation, which is a generalization of the standard nonlinear Schrödinger equation. By means of the modified Darboux transformation, the hierarchies of rational solutions and breather solutions are generated from the plane wave solution. Furthermore, the main characteristics of the nonlinear waves including the Akhmediev breathers, Kuznetsov–Ma solitons, and their combined structures are graphically discussed. Our results would be of much importance in enriching and explaining rogue wave phenomena in nonlinear wave fields.

Sound-event recognition often utilizes time-frequency analysis to produce an image-like spectrogram that provides a rich visual representation of original signal in time and frequency. Convolutional Neural Networks (CNN) with the ability of learning discriminative spectrogram patterns are suitable for sound-event recognition. However, there is relatively little effort that CNN makes full use of the important temporal information. In this paper, we propose MCRNN, a Convolutional Recurrent Neural Networks (CRNN) architecture for sound-event recognition, the letter “M” in the name “MCRNN” of our model denotes the multi-sized convolution filters. Richer features are extracted by using several different convolution filter sizes at the last convolution layer. In addition, cochleagram images are used as the input layer of the network, instead of the traditional spectrogram image of a sound signal. Experiments on the RWCP dataset shows that the recognition rate of the proposed method achieved 98.4% in clean conditions, and it robustly outperforms the existing methods, the recognition rate increased by 0.9%, 1.9% and 10.3% in 20 dB, 10 dB and 0 dB signal-to-noise ratios (SNR), respectively.

In this experiment, samarium ion was doping into nickel–copper–cobalt ferrite system by sol–gel self-propagation. The prepared chemical formula is ${\mathrm{\text{Ni}}}_{0.2}{\mathrm{\text{Cu}}}_{0.2}{\mathrm{\text{Co}}}_{0.6}$-${\mathrm{\text{Fe}}}_{2-x}{\mathrm{\text{Sm}}}_x{\mathrm{\text{O}}}_4$ ($x=0.0$, 0.025, 0.05, 0.075 and 0.1). The X-ray diffraction (XRD) analysis of the samples confirms the formation of a cubic spinel structure. The average crystallite sizes are about 66–88 nm for all the prepared samples. Fourier transform infrared spectroscopy (FTIR) measurements showed all the prepared samples had Fe–O absorption peaks. This finding further confirms that the prepared sample has a spinel structure. The morphological changes of the samples were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). According to the characterization results, the surface morphology shows spherical grains. Energy-dispersive X-ray spectroscopy (EDX) test results showed that the as-prepared pure samples contained Ni, Cu, Co, Fe elements, whereas other samples contained Sm elements and the contents were different. This indicates that the prepared samples are purer and the doping amount has been increased. The magnetic parameters of samples were measured by vibration sample magnetometer (VSM) at room temperature. The analysis of magnetic parameters shows that the saturation magnetization $(M_s)$ and remanent magnetization $(M_r)$ of the sample decrease with the increase of the doping amount of samarium ions. From the magnetic parameters, it can be concluded that ${\mathrm{\text{Sm}}}^{3+}$-doped Ni–Cu–Co ferrites have low magnetic properties.

In this paper, with the aid of symbolic computation system Maple, and based on the simplified Hirota method and ansatz technique, we discussed the (3+1)-dimensional generalized Kadomtsev–Petviashvili equation with $p=3$ to obtain lump solutions, lump–kink solutions and three classes of interaction solutions. Comparing our new results with other researchers’ results shows that using this method gives the more opportunity to solve the nonlinear partial differential equations that appear in mathematics, physics, biological engineering and other fields. We also presented profiles of new lump solution, lump–kink solutions and interaction solutions as illustrative examples.

Quantum Hall effect is used to realize resistance standard which is in terms of the Planck constant $h$ and elementary charge $e$ in metrology. The quantum Hall resistance devices are fabricated based on two-dimensional electron gas formed in $\mathrm{\text{GaAs}}/{\mathrm{\text{Al}}}_x{\mathrm{\text{Ga}}}_{1-x}$ as heterostructures. Low-resistance Ohmic contact to the 2DEG is crucial in fabricating quantum Hall devices to obtain reproducible and accurate results. Annealed Au/Ge/Ni multilayer is widely used for Ohmic contacts to GaAs. In this paper, electrical and magnetic properties of optimized Ohmic contacts of quantum Hall devices are studied. For the electrical property evaluation, contact resistances are measured by three-terminal method in the quantum Hall $i=2$ plateau regime. Most of the contacts were Ohmic with values less than 2.4 $\mathrm{\Omega }$ and a good yield of better than 99% is obtained. In the magnetic property study, the annealed Au/Ge/Ni multilayer shows much smaller magnetization than the as-deposited one. TEM-EDS study shows the pure Ni layer diffused into the GaAs and AlGaAs layer and converts into the compounds closed to Ni₂GeAs and NiAs phase. Density functional theory is used to calculate the atomic moments of pure face-centered cubic Ni, hexagonal Ni₂GeAs and NiAs. The calculation results explained the magnetization drop of annealed samples well.

This study presents a partially averaged Navier–Stokes model, MSST PANS, based on a modified SST $k-\omega$ turbulence model to predict turbulent flows with large streamline curvature. The model was validated for turbulent flow in a $90^{\circ }$ curved rectangular duct (Re = 224,000) to assess the MSST PANS capabilities. The predictions are compared against flow simulations for the same curved rectangular duct using four turbulence models including the standard $k-𝜀$ model, SST $k-\omega$ model, $k-𝜀$ PANS model and SST $k-\omega$ PANS model. Comparisons among those numerical results and available experimental data show that the MSST PANS model more accurately predicts the velocity components in all three directions, especially in the wall-bounded region than the other models. The study also shows the advantages of the MSST PANS model for predicting the Reynolds stresses, vorticity, and smaller scale turbulent structures in the wall-bounded region not only qualitatively but quantitatively. Furthermore, the MSST PANS model requires fewer computations than the SST PANS model, indicating that this turbulence model, which takes large streamlines curvature effects into consideration, is an effective alternative for capturing the small-scale turbulence flow structures. This turbulence model is expected to be very useful for engineering applications, especially for flows in turbomachinery.

The multiconsensus problem of first-order multiagent systems with directed topologies is studied. A novel consensus problem is introduced in multiagent systems — multiconsensus. The states of multiple agents in each subnetwork asymptotically converge to an individual consistent value in the presence of information exchanges among subnetworks. Linear multiconsensus protocols are proposed to solve the multiconsensus problem, and the matrix corresponding to the protocol is designed. Necessary and sufficient conditions are derived based on matrix theory, under which the stationary multiconsensus and dynamic multiconsensus can be reached. Simulations are provided to demonstrate the effectiveness of the theoretical results.

We study the phase separation in three-component spin-orbit-angular-momentum coupled Bose–Einstein condensate with spin-1 in three dimensions. Different types of phase-separation are acquired upon an increase of the coupling strength, magnetic gradient strength, spin-dependent interaction strength and particle number above a critical value. Increasing the value of coupling strength and other related parameters shows distinct behaviors which are produced by repulsion for large strengths of spin-orbit angular-momentum (SOAM) coupling. The present investigation is carried out through a numerical Crank–Nicolson method of the underlying mean-field Gross–Pitaevskii equation.

Cache sharing technique is critical in multi-core and multi-threading systems. It potentially delays the execution of real-time applications and makes the prediction of the worst-case execution time (WCET) of real-time applications more challenging. Prioritized cache has been demonstrated as a promising approach to address this challenge. Instead of the conventional prioritized cache schemes realized at the architecture level by using cache controllers, this work presents two prioritized least recently used (LRU) cache replacement circuits that directly accomplish the prioritization inside the cache circuits, hence significantly reduces the cache access latency. The performance, hardware and power overheads due to the proposed prioritized LRU circuits are investigated based on a 65 nm CMOS technology. It shows that the proposed circuits have very low overhead compared to conventional cache circuits. The presented techniques will lead to more effective prioritized shared cache implementations and benefit the development of high-performance real-time systems.

In this paper, the investigation is made on a (3+1)-dimensional generalized Calogero–Bogoyavlenskii–Schiff equation. We obtain the lump, mixed lump-stripe, mixed rogue wave-stripe and breather wave solutions via the Hirota method and symbolic computation. Accordingly, we observe that the shape and amplitude of the lump keep unchanged, while the mixed lump-stripe solutions present that (1) the lump/stripe and one-stripe waves fuse into a one-stripe wave; (2) the one-stripe wave splits into a lump/stripe and a one-stripe wave. We graphically show the interaction between a rogue wave and a pair of stripe waves, and observe that the amplitude of the rogue wave reaches the maximum value at a certain position. Besides, the breather wave propagates steadily in a certain direction.

In this paper, an ultra-long distance transmission fiber link based on bidirectional Raman amplifier is studied by theoretical simulation and experimental verification. The power evolution of pump and WDM signals in optical fiber in 355 km transmission link is simulated theoretically. The performance of the ultra-long distance system based on co-pump/counter-pump/bidirectional-pump Raman amplifier (CORA/CTRA/BiRA) are simulated. And the power budget is also predicted by simulation. The performance of 10*100 Gb/s signal transmission in 355 km fiber link based on bidirectional Raman amplifier are tested experimentally. The theoretical and experimental results are in good agreement.

The crystal structure and magnetic properties of $\mathrm{\text{Mg}}{({\mathrm{\text{Ga}}}_{0.95}{\mathrm{\text{Fe}}}_{0.05})}_2{\mathrm{\text{O}}}_4$ grown by optical floating zone method have been studied. The chemical composition and element ratio in the crystal were analyzed by energy dispersive X-ray spectroscopy (EDS). The results of X-ray diffraction and Raman spectra of the crystal reveal that it has a spinel structure with high crystallinity and purity. The magnetic domain period observed by using magnetic force microscopy (MFM) shows that the crystal has a stable multi-domain structure. According to the superconducting quantum interference device (SQUID) results, the magnetization increases nonlinearly with increasing magnetic field strength and approaches magnetic saturation, proving it is a paramagnetic medium. The magnetization decreases rapidly below Curie temperature and approaches stability with increasing temperature.

This paper studies new solitary waves for the Klein–Gordon–Zakharov equations. The obtained results are diverse and some specific ones emerge as dark, bright and bell-shape. The two integration schemes lead to obtaining waves which propagate without deformation as illustrated in graphical representations. Our obtained results are more specific compared to those obtained by Refs. 8 and 31 [C. H. Zhao and Z. M. Sheng, Acta Phys. Sin. 53 (2004) 29; S. Yakada, B. Depelair, G. Betchewe and S. Y. Doka, Optik 197 (2019) 163108].