Modern Physics Letters B

In this paper, we successfully fabricate compact and uniform cadmium telluride (CdTe) films on flexible nickel foils using simple electrodeposition technique and sintering in a nitrogen atmosphere. The effect of the concentration of sodium tartrate on the structures and properties of the deposited CdTe thin films are studied. Various test techniques are used to characterize the results. The results of XRD analysis show that the highest crystallinity film is obtained when the added sodium tartrate concentration is 0.05 M. With the increase of sodium tartrate concentration, the composition of the film gradually changes from Te-rich to Cd-rich, and the thickness of the film becomes thin gradually. We also find that the CdTe thin film prepared under 0.05 M sodium tartrate shows the best optical and optoelectronic properties. Thus, a moderate amount of sodium tartrate is added into an acidic solution as surfactant for CdTe thin film fabrication. Moreover, sodium tartrate is easily volatilized from the film during the annealing process because of its small molecular weight, which can prevent the carbon precipitation.

Complex networks have attracted a great deal of attention from scientific communities, and have been proven as a useful tool to characterize the topologies and dynamics of real and human-made complex systems. Laplacian spectrum of the considered networks plays an essential role in their network properties, which have a wide range of applications in chemistry and others. Firstly, we define one vertex–vertex graph. Then, we deduce the recursive relationship of its eigenvalues at two successive generations of the normalized Laplacian matrix, and we obtain the Laplacian spectrum for vertex–vertex graph. Finally, we show the applications of the Laplacian spectrum, i.e. first-order network coherence, second-order network coherence, Kirchhoff index, spanning tree, and Laplacian-energy-like.

Low frequency noise in the indium–zinc oxide thin-film transistors (IZO TFTs) at low drain voltage is investigated in this paper. First, the contact resistance is extracted from transfer characteristics. By analyzing the noise behavior under different bias conditions, the measured noises in IZO TFTs have been separated into contributions from the channel and contacts. Determined by the channel and the contact, the normalized noise varied with two slopes ($m=-1.09$ and 2) with the increment of effective gate voltage. Moreover, the values of flat-band voltage noise spectral density and Coulomb scattering parameter have been extracted. By considering contact resistance, the normalized noise has also been modeled by the use of carrier number with the correlated mobility fluctuation $(\mathrm{\Delta }N-\mathrm{\Delta }\mu )$ model.

The harmonic emissions from hydrogen molecular ion at different initial vibrational states have been simulated by numerically solving the time-dependent Schrödinger equation. The results show that the nuclear motion exhibits different effects on the spectral structure for different vibrational states. For lower vibrational state, the odd harmonics experience obvious harmonic shifting; however, for higher vibrational state, the even harmonics are emitted from the symmetric system due to the asymmetric electronic distribution in the coupling region of two lowest electronic states.

In this paper, we propose a micro-ring resonator model based on gallium nitride (GaN) and graphene, which exhibits tunable properties of nonlinearity. It provides a great bandwidth covering from visible to telecommunication band. Especially, based on the characteristic of GaN, it has unique advantages in shorter wavelength, which is used for demonstrating the ultrafast signal processing including wavelength conversion, temporal amplification and pulse compression. Moreover, the tunable signal processing is achieved via the method of applying additional bias voltage to graphene without changing the geometric dimension of the device. These results have significant potential applications of nonlinear optics and optical communications.

Deep neural network (DNN) has recently been successfully adopted as a regression model in speech enhancement. Nonetheless, training machines to adapt different noise is a challenging task. Because every noise has its own characteristics which can be combined with speech utterance to give huge variation on which the model has to operate on. Thus, a joint framework combining noise classification (NC) and speech enhancement using DNN was proposed. We first determined the noise type of contaminated speech by the voice activity detection (VAD)-DNN and the NC-DNN. Then based on the noise classification results, the corresponding SE-DNN model was applied to enhance the contaminated speech. In addition, in order to make method simpler, the structure of different DNNs was similar and the features were the same. Experimental results show that the proposed method effectively improved the performance of speech enhancement in complex noise environments. Besides, the accuracy of classification had a great influence on speech enhancement.

This paper retrieves different types of soliton solutions for coupled nonlinear Schrödinger equation (NLSE). We use extended F-expansion method to find bright, dark and other trigonometric solutions with Kerr law and anti-cubic law. We also find Gausson soliton for coupled NLSE under log law nonlinearity.

We consider the (3+1)-dimensional generalized shallow water wave (GSWW) equation. By virtue of the binary Bell polynomials theory, we obtain the bilinear form of the equation. Then its lump wave solutions, a kind of rational solution localized in all directions of the space, are derived by employing its bilinear form at the special situation for $z=x$. Furthermore, it is worth noting that the lump wave solutions can interact with single-stripe soliton waves and double-stripe solution waves to generate lumpoff waves and a kind of predictable rouge waves, respectively. Especially, it is interesting that we can predict when and where the peculiar rouge waves will occur. Moreover, in order to understand the dynamics and propagation of the lump waves and the interaction solution, some graphic analyses are exhibited by selecting special parameters. The results of this work can be used to understand the propagation behavior of these solutions of the GSWW equation, which is of great significance for ocean engineering.

In this paper, we study the interaction solutions of the first BKP equation by using the Hirota direct method and taking long-wave limit. In order to obtain the interaction solutions, the multi-soliton solutions are firstly derived using the Hirota direct method, then the interaction solutions are successfully constructed by properly choosing appropriate parameters and taking long-wave limit on the soliton solutions. These parameters have great influences on the propagation directions, shapes as well as energy. Moreover, the dynamic properties of these obtained solutions are illustrated vividly by some graphs. The results in this work could be used to solve nonlinear problems in nonlinear optics and engineering field.

We investigate the generalized discrete Hirota equation, which is an integrable discrete version of Hirota equation. The generalized $(2,N-2)$-fold Darboux transformation (i.e. generalized $(n,N-n)$-fold Darboux transformation when $n=2$ with two spectral parameters) is presented to derive the novel localized wave interaction solutions. Moreover, some inelastic interaction evolution phenomena of rogue wave and breather are studied graphically. Numerical simulations are used to explore the dynamical behaviors of certain localized wave interaction solutions, which show that their evolutions are stable against a small noise. The results obtained in this paper can be used to find the interaction properties of localized nonlinear waves in nonlinear optics and relevant fields.

Compositions with x = 0.15, 0.20, 0.25, 0.30 and 0.35 were synthesized in the system ${\mathrm{\text{Ba}}}_{1-x}{\mathrm{\text{Sr}}}_x{\mathrm{\text{TiO}}}_3$ using conventional solid state reaction method and characterized by X-Ray Diffraction (XRD), Raman spectroscopy and Scanning Electron Microscopy (SEM). Tetragonal phase was confirmed in all the samples using Rietveld refinement of the XRD patterns and observation of their Raman spectra. Dielectric and impedance measurements were carried out in the temperature range 300–723 K in the frequency range 1 Hz to 1 MHz. The samples exhibit diffuse phase transition (DPT). Equivalent circuit model involving combination of Constant Phase angle Elements (CPE) and resistances (R) was developed which represents the data well. Expressions for the values of resistances (R) were established in terms of composition and temperature empirically. P-E loops indicated normal ferroelectric behavior for all the samples. Dielectric constant was also measured in the frequency range 8–12 GHz in the X band of microwaves.

Aqueous silk fibroin (SF) sol is a colloidal solution. With the colloidal hydration layer and electrostatic repulsion, the SF sol can hardly make the efficient collision/assembly among micelles and perform like a following sol for a long time. In this paper, hydrophilic silk-based sequences (HSF) derived from SF molecules were obtained by immersing the dried SF condensates with water and extracting the dissolving fraction. The HSF was obtained by immersing the SF condensate dried at the temperature of $20$–$25^{\circ }\mathrm{\text{C}}$ and relative humid of 55–60% in water and collected the lixivium. The dissolving ratio was about 30%. The HSF sol (0.5%, w/v) self-assembled into the mesoscopic 3D nanofibrous network within 8 h. The obtained HSF nanofibers were 10–100 $\mu \mathrm{\text{m}}$ in length and 50–100 nm in diameter. The HSF nanofiber possesses similar hierarchical structure consisting of nanofibrils bundles to the native silk fiber. There were significant aggregation structure transitions from random coil to $\beta$-sheet and amorphous chains to Silk II crystal aggregation during the formation of HSF nanofibers. The HSF nanofiber holds the potential to give further insight into the reconstruction of native silk in vitro and the fabrication of tough silk-based biomaterials.

The discovery of high-temperature superconductivity in compressed ${\mathrm{\text{H}}}_3\mathrm{\text{S}}$ by Drozdov and co-workers [A. Drozdov et al., Nature 525 (2015) 73] heralded a new era in superconductivity. To date, the record transition temperature of $T_c=260\mathrm{\text{K}}$ stands with another hydrogen-rich compound, ${\mathrm{\text{LaH}}}_{10}$ [M. Somayazulu et al., Phys. Rev. Lett. 122 (2019) 027001] which becomes superconducting at pressure of $P=190\mathrm{\text{GPa}}$. Despite very intensive first-principle theoretical studies of hydrogen-rich compounds compressed to megabar level pressure, there is a very limited experimental dataset available for such materials. In this paper, we analyze the upper critical field, $B_{c2}(T)$, data of highly compressed ${\mathrm{\text{H}}}_3\mathrm{\text{S}}$ reported by Mozaffari and co-workers [S. Mozaffari et al., LA-UR-18-30460. https://doi.org/10.2172/1481108] by utilizing four different models of $B_{c2}(T)$. As the result, we find that the ratio of superconducting energy gap, $\mathrm{\Delta }(0)$, to the Fermi energy, ${𝜀}_F$, in all considered scenarios is $0.03<\mathrm{\Delta }(0)/{𝜀}_F<0.07$, with respective ratio of $T_c$ to the Fermi temperature, $T_F$, $0.012<T_c/T_F<0.039$. These characterize ${\mathrm{\text{H}}}_3\mathrm{\text{S}}$ as unconventional superconductor and places it on the same trend line in $T_c$ versus $T_F$ plot, where all unconventional superconductors are located.

This study focuses on acquiring new complex hyperbolic and trigonometric function solutions to the generalized conformable fractional Gardner equation by using two distinct integration schemes, namely: the modified Kudryashov method and the hyperbolic function method with the help of symbolic computation package. We generate new closed-form solitary wave solutions to the governing model. Implemented schemes are pragmatically effective for solving various types of nonlinear partial differential equations with integer or fractional order arising in various fields of applied sciences.