Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>In this paper, finite-time synchronization of fractional-order multi-weighted complex networks (FMCNs) with uncertain parameters and external disturbances is studied. Firstly, based on fractional calculus characteristics and Lyapunov stability theory, quantized controllers are designed to guarantee that FMCNs can achieve synchronization in a limited time with and without coupling delay respectively. Then, appropriate parameter update laws are obtained to identify uncertain parameters in FMCNs. Finally, numerical simulation examples are given to validate the correctness of the theoretical results.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Finding crucial vertices is a key problem for improving the reliability and ensuring the effective operation of networks, solved by approaches based on multiple attribute decision that suffer from ignoring the correlation among each attribute or the heterogeneity between attribute and structure. To overcome these problems, a novel vertex centrality approach, called VCJG, is proposed based on joint nonnegative matrix factorization and graph embedding. The potential attributes with linearly independent and the structure information are captured automatically in light of nonnegative matrix factorization for factorizing the weighted adjacent matrix and the structure matrix, which is generated by graph embedding. And the smoothness strategy is applied to eliminate the heterogeneity between attributes and structure by joint nonnegative matrix factorization. Then VCJG integrates the above steps to formulate an overall objective function, and obtain the ultimately potential attributes fused the structure information of network through optimizing the objective function. Finally, the attributes are combined with neighborhood rules to evaluate vertex’s importance. Through comparative analyses with experiments on nine real-world networks, we demonstrate that the proposed approach outperforms nine state-of-the-art algorithms for identification of vital vertices with respect to correlation, monotonicity and accuracy of Top-10 vertices ranking.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The spinel-type LiMn<jats:sub>2</jats:sub>O<jats:sub>4</jats:sub> is a promising candidate as cathode material for rechargeable Li-ion batteries due to its good thermal stability and safety. Experimentally, it is observed that structural phase transitions occur to this compound slightly below room temperature from cubic (<jats:italic>Fd</jats:italic>bar{3}<jats:italic>m</jats:italic>) to tetragonal (<jats:italic>I4</jats:italic> <jats:sub> <jats:italic>1</jats:italic> </jats:sub>/<jats:italic>amd</jats:italic>) phase. To understand the phase transition mechanism, we compared the Gibbs free energies between cubic and tetragonal phases by including the configurational entropy. Our results showed that the configurational entropy contributes substantially to the stability of the cubic phase at room temperature, due to the disordered Mn<jats:sup>3+</jats:sup>/Mn<jats:sup>4+</jats:sup> distribution as well as the orientation of the Jahn-Teller elongation of the Mn<jats:sup>3+</jats:sup>O<jats:sub>6</jats:sub> octahedra in the spinel phase. Meanwhile, the phase transition temperature was predicted to be 267.8 K, which is comparable to the experimental observation. These results are a good complement to the experimental study, and are beneficial to improve the electrochemical performance of LiMn<jats:sub>2</jats:sub>O<jats:sub>4</jats:sub> cathode.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Measure synchronization in hybrid quantum-classical systems is investigated in this paper. The dynamics of classical subsystem is described by the Hamiltonian equations, while the dynamics of quantum subsystem is governed by Schr<jats:italic>ö</jats:italic>dinger equation. By increasing the coupling strength in between the quantum and classical subsystems, we reveal the existence of measure synchronization in coupled quantum-classical dynamics under energy conservation for the hybrid systems.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Topological superfluid state is different from the normal superfluid one due to the excitation energy gap on the boundary. How to obtain the topological superfluid state by using spin-orbit coupling to control the s-waves paired mass-imbalanced Fermi gas is a recent novel topic. In this paper, we study the topological superfluid phase diagram of two-dimensional mass-imbalanced Fermi gas with Rashba spin-orbit coupling at zero temperature. We find that due to the competition between mass imbalance, pairing interaction and spin-orbit coupling, there is a double-well structure in the thermodynamic potential, which affects the properties of the ground state of the system. We comprehensively give the phase diagrams of the system on the plane of spin-orbit coupling and chemical potential, and the phase diagrams on the plane of the reduced mass ratio and two-body binding energy. This study not only points out the stable region of topological superfluid state of mass-imbalanced Fermi gas, but also provides a detailed theoretical basis for better observation of topological superfluid state in experiments.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Given the enhanced channel capacity of wave chirality, acoustic communications based on the orbital angular momentum (OAM) of acoustic-vortex (AV) beams are of significant interest for underwater data transmissions. However, the stringent beam alignment is required for the coaxial arrangement of transceiver arrays to ensure the accuracy and reliability of OAM decoding. To avoid the required multiple measurements of the traditional orthogonality-based algorithm, the beam alignment algorithm based on the OAM spectrum decomposition is proposed for AV communications using simplified ring-arrays. Numerical studies of the single-OAM and OAM-multiplexed AV beams show that the error of the OAM spectrum increases with the translation distance and the deflection angle of transceiver arrays. To achieve an ideal arrangement, two methods of the single-array translation alignment and the dual-array deflection alignment are developed based on the least standard deviation of the OAM spectrum (SD-OAM). By decreasing the SD-OAM towards zero using transceiver arrays of 16 transmitters and 16 receivers, accurate beam alignments are accomplished by multiple adjustments in three dimensions. The proposed method is also demonstrated by experimental measurements of the OAM dispersion and the SD-OAM for misaligned beams. The results demonstrate the feasibility of the rapid beam alignment based on the OAM spectrum decomposition using simplified transceiver ring-arrays, and suggest more application potentials for acoustic communications.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This paper proposes an image encryption algorithm based on spatiotemporal chaos and middle order traversal in binary tree. Firstly, the other programming software is used to perform the middle order traversal, and the plaintext image is sorted according to the middle order traversal sequence on the permutation; Secondly, the chaotic sequence is generated by using the coupled map lattice to set the chaotic interference value. Finally, the XOR operation between the adjacent pixel values of the replacement image is completed to generate the ciphertext matrix. The simulation results and experimental results show that the proposed algorithm can resist typical attacks and has good robustness.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A crack-free HVPE-AlN thick film with 4.5 μm thickness was grown on a 2-inch hole-type nano-patterned sapphire substrates (NPSSs). The coalescence, stress evolution, and dislocation annihilation mechanisms in the AlN layer have been investigated. The large voids located on the pattern region was caused by the undesirable parasitic crystallites grown on the sidewalls of the nano-pattern in early growth stage. The coalescence of the c-plane AlN was hindered by these three-fold crystallites and the special triangle void appeared. The cross-sectional Raman line scan was used to characterize the change of stress with film thickness, which corresponds to the characteristics of different growth stages of AlN. Threading dislocations (TDs) mainly originate from the boundary between misaligned crystallites and the c-plane AlN and the coalescence of two adjacent c-plane AlN crystals, rather than the interface between sapphire and AlN.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>X-ray analyzer-based imaging (ABI) is a powerful phase-sensitive technique that can provide a wide dynamic range of density and extract useful physical properties of the sample. It derives contrast from X-ray absorption, refraction, and scattering properties of the investigated sample. However, X-ray ABI setups can be susceptible to external vibrations, and mechanical imprecisions of system components, e.g. the precision of motor, which are unavoidable in practical experiments. Those factors will provoke deviations of analyzer angular positions and hence errors in the acquired image data. Consequently, those errors will introduce artefacts in the retrieved refraction and scattering images. These artefacts are disadvantageous for further image interpretation and tomographic reconstruction. For this purpose, this work aims to analyze image artefacts resulting from deviations of analyzer angular positions. Analytical expressions of the refraction and scattering image artefacts were derived theoretically and validated by synchrotron radiation experiments. The results showed that for the refraction image, the artefact was independent of the sample’s absorption and scattering signals. By contrast, artefact of the scattering image was dependent on both the sample’s refraction and scattering signals, but not on absorption signal. Furthermore, the effect of deviations of analyzer angular positions on the accuracy of the retrieved images was investigated, which can be of use for optimization of data acquisition. This work offers the possibility to develop advanced multi-contrast image retrieval algorithms that suppress artefacts in the retrieved refraction and scattering images in X-ray analyzer-based imaging.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We have presented a high resolution spectroscopy of Rb in magnetic field by far-detuning electromagnetically induced transparency (EIT). The EIT spectrum in the $\Xi$-type configuration is usually companied by a double resonance optical pumping (DROP) due to the strong optical coupling between the two upper states, leading to the spectral lines seriously deformed and widely broadened for complex relaxation processes in DROP. Here we demonstrate a high resolution spectroscopy by far-detuning EIT for $^{87}\rm{Rb}$ $\rm{5S_{1/2}\rightarrow5P_{3/2}\rightarrow5D_{5/2}}$ in magnetic fields. The method of far-detuning eliminates the relaxation in DROP to the most extent and decreases the spectral linewidth from more than 20 MHz down to its natural linewidth limit (6 MHz). The deformation of the spectral lines also disappears and the observed spectra are well in accordance with the theoretical calculation. Our work shows that far-detuning EIT is a reliable high resolution spectroscopic method when the relaxation in DROP can't be neglected, especially for the case of transition to low excited states.</jats:p>