Modern Physics Letters B

The effect of channel uniaxial strain on thermal conductivity of graphene nano-ribbon field effect transistor (GNRFET) is analyzed by self-consistent Hückel method. The supposed strains are tensile and its values are 2% to 24% of lattice constant. All of the assumed strains are applied to the channel length direction. Energy band gap, density of states (DOS), phonon transmission, thermal conductivity, and I–V characteristics of the GNRFET have been calculated. The results show that by increasing the strain, the energy band gap of the channel is increased and the drain current is decreased. Also by increasing the band gap, phonon transmission is decreased. Maximum phonon transmission occurs in 8% strain. By considering all of these parameters, the results show that there is a maximum thermal conductivity versus temperature in 8% uniaxial strain that is more than the bare one and its value is decreased intensively in 16% and 24% strain. This is due to maximum phonon transmission that is observed in 8% strain and increasing the DOS around the energy band gap in this value. Also, it is observed that in the energy range of more than 0.75 eV, by increasing the strain, thermal conductivity is increased.

In this paper, NiO/Al/NiO transparent conductive films were prepared by magnetron sputtering at the room temperature. Effects of the NiO and Al layers thicknesses on the optical and electrical properties of the NiO/Al/NiO laminated films were analyzed. When the light wavelength falls in range 300–900 nm, with the increase of the NiO and Al layers thicknesses, the transmittance of the laminated film first increases significantly and then decreases slightly, finally tends to be stable. The laminated film obtained the best optical and electrical properties when the NiO layer is 40 nm and the Al layer is 12 nm. The maximum transmittance is 83%, the average transmittance is 77.3%, the film resistivity is $4.0572\times 10^{-3}\mathrm{\Omega }\cdot \mathrm{\text{cm}}$ and the carrier concentration is $3.206\times {10}^{21}{\mathrm{\text{cm}}}^{-3}$. At the same time, the transmittance of laminated film is simulated by FDTD software. But the simulation curve is different from the experimental data. Analysis results show that, with the NiO dielectric is added on both sides of the metal Al film, the light reflection characteristic of laminated film has been completely different from that of the single Al metal film because of the change of interface characteristics between Al film and NiO film, and the actual luminous transmittance greatly increases.

In this paper, we study a Kundu–Eckhaus equation with variable coefficients, which describes the ultra-short optical pulses in an inhomogeneous optical fiber. We construct the Lax pair under certain variable-coefficient constraints. With the gauge transformation, one/N-fold binary Darboux transformations and limit forms of the one-fold binary Darboux transformation are obtained. Based on such transformations, one/N-dark (N = 2,3, $\dots$) soliton solutions under those constraints are derived. Linear, periodic and parabolic dark solitons are presented, and numerical simulations are used to investigate the influence of the group velocity dispersion on the structures of the one-dark solitons. Based on the two-dark soliton solutions under certain variable-coefficient constraints, we also discuss the influence of the group velocity dispersion on the structures of the two-dark solitons. Head-on and overtaking collisions between the two linear, parabolic and cubic-type dark solitons are presented.

In this work, nature of the residual stress developed in the convex corners created in underlying Si at the fixed end of SiO₂ microantilevers (MCs) fabricated by wet chemical etching method was investigated using micro-Raman spectroscopy with visible excitation. It revealed the presence of tensile stress near the sharp edge of the convex corner and is attributed to the localized stress generated in the neighborhood of the discontinuities, acting as stress concentration region. Residual stress estimated by micro-Raman technique across the convex corner was also validated by FEM simulations. Micro-Raman also revealed the presence of tensile stress on the etched Si surface, which is explained on the basis of stress induced by native oxide shells covering the etched features.

In the real world, building the high quality cloud computing framework is the challenge for the researcher in the present scenario where on demand service is required. The services which are performing the non-functional activities are referred to as Quality-of Service (QoS). The experience of real-world usage services are generally required to obtain the QoS. Many organizations offer various cloud services, such as Amazon, HP and IBM, to the customers. No technique is available to measure the real-world usage and estimate the ranking of the cloud services. From the customer side, it is a very tough job to choose the right cloud service provider (SP), which fulfills all the requirements of the customers. To avoid the confusion to select the right CSP, this paper proposes QoS ranking prediction methods such as Cloud Rank1, Cloud Rank2 and Cloud Rank3. Various experiments are done on the real-world QoS data by using EC2 services of Amazon and providing healthy results and solutions.

Coarse-graining of complex networks is one of the important algorithms to study large-scale networks, which is committed to reducing the size of networks while preserving some topological information or dynamic properties of the original networks. Spectral coarse-graining (SCG) is one of the typical coarse-graining algorithms, which can keep the synchronization ability of the original network well. However, the calculation of SCG is large, which limits its real-world applications. And it is difficult to accurately control the scale of the coarse-grained network. In this paper, a new SCG algorithm based on K-means clustering (KCSCG) is proposed, which cannot only reduce the amount of calculation, but also accurately control the size of coarse-grained network. At the same time, KCSCG algorithm has better effect in keeping the network synchronization ability than SCG algorithm. A large number of numerical simulations and Kuramoto-model example on several typical networks verify the feasibility and effectiveness of the proposed algorithm.

This paper presents a study on the issue of current-driven distributed feedback (DFB) semiconductor lasers (LD) experiencing nonlinear laser frequency variation in the course of linear frequency modulation. A theoretical model of the linear frequency modulation process of DFB semiconductor lasers is established. On this basis, the relationship between injection current and laser frequency is analyzed and a correction method has been put forward, to improve the linearity of the laser frequency variation. It was eventually verified that the proposed correction method can greatly improve the linearity of the linear frequency modulation (LFM) output laser signal.

First-principles calculations have been performed to investigate the doping defects in CuI with group-IIB elements such as Zn, Cd and Hg. The calculated transition energies for substitutional Zn, Cd and Hg are 1.32, 1.28 and 0.60 eV, respectively. These group-IIB elements at the substitutional sites complex with a copper vacancy $(V_{\mathrm{\text{Cu}}})$ have the lower formation energies as compared to dopants located at the substitutional sites or interstitial sites, respectively. Among all the complex defects considered, $[{\mathrm{\text{Hg}}}_{\mathrm{\text{Cu}}}+V_{\mathrm{\text{Cu}}}]$ has the lowest formation energy and it induces the acceptor level $𝜀(0/-)=0.18$ eV above the valence-band maximum (VBM), which is close to the acceptor level $𝜀(0/-)=0.1$ eV of $V_{\mathrm{\text{Cu}}}$, suggesting that Hg may be a good dopant for CuI to improve its p-type conductivity.

Modifying optical properties of crystal is very fundamental need for designing various photonic devices, hence in the current investigation, the L-proline (LP) has been firstly doped in cadmium thiourea acetate (CTA) crystal with the aim to optimize the UV–Visible, second harmonic generation (SHG) efficiency, luminescence and third-order nonlinear optical (TONLO) properties of CTA crystal. The pure and doped CTA crystals have been grown by slow solvent evaporation technique at $35^{\circ }$C. The structural parameters of grown crystals have been determined using the single crystal X-ray diffraction technique. The incorporation of LP in CTA crystal matrix has been confirmed by Fourier transforms infrared analysis. The UV–Visible studies have been employed within the wavelength range of 200–900 nm to explore the enhancing impact of LP on CTA crystal. The LP doped CTA crystals were subjected to Kurtz–Perry test and Z-scan analysis to identify the nonlinear nature of studied crystals. The SHG efficiency of LP-CTA crystal shows significant increase owing to enhanced charge transfer over the organic ligand of LP. The laser-induced TONLO properties of LP-doped CTA crystal have been determined at 632.8 nm. The nature of nonlinear refraction and absorption has been explored by close and open aperture Z-scan configuration. The magnitude of nonlinear refraction $(n_2)$, absorption coefficient $(\beta )$, cubic susceptibility $({\chi }^3)$ and figure of merit has been determined using the transmittance data. The color-centered luminescence studies have been carried out which established the prominent redshift in peak maxima of emission wavelength of CTA crystal due to doping of LP. Comparative analysis of pure and doped crystal confirmed the dominance of LP doping.

In this paper, solderability, microstructure and hardness of SAC0705-xNi solder joints on Cu and graphene-coated Cu (G-Cu) substrates were studied. As Ni content increases in the solder, the solderability improves gradually on both the Cu and G-Cu substrates. The solderability of SAC0705-xNi is better on G-Cu substrate than that on Cu substrate. The increasing Ni content in the solder has a positive effect on the microstructure refinement of both the kinds of substrates. Such effect is more significant on G-Cu substrate than that on Cu substrate. With the increase of Ni content, the thickness of the interfacial intermetallic compound (IMC) shows an increasing trend first and then decreasing trend on the two kinds of substrates. Since the graphene layer works as a diffusion barrier, the IMC on G-Cu is thinner than that on Cu substrate. The addition of Ni leads to the strengthening of the microstructure and thus increases the hardness of the solder bulks.

Long-wave–short-wave resonance interaction (LSRI) equations have been studied in the plasmas, gravity waves, nonlinear electron-plasma and ion-acoustic waves. By virtue of the bilinear method, two soliton solutions of the variable-coefficient LSRI equations are attained. Interaction of the solitons are studied when the coefficients are taken as the generalized Gauss functions. New types of the soliton interaction are exhibited. Position and width of the disturbances can be controlled.

In this work, nonlinear Schrödinger’s equation along with group velocity dispersion and spatio-temporal dispersion is considered in $(n+1)$ dimensions with Kerr and quadratic-cubic law nonlinearities which expose the propagation of light pulses in fiber optics. Dark, singular and periodic singular optical solitons in $(n+1)$ dimensions are retrieved and generalized through versatile modified simple equation method. The constraint conditions that righteously guarantee the perseverance of these soliton solutions are obtained as an outgrowth. The results presented in this paper are new and generalized which are already available in the literature.

Nonlinear Schrödinger equation (NLSE) with higher-order nonlinearity and dispersion terms in parabolic law medium is investigated in detail. By transforming the NLSE into integral form and using the complete discrimination system for polynomial method, all electric envelop solutions are obtained. In particular, the consistent conditions of parameters are given. These results show the complete and rich envelop traveling wave patterns of the NLSE in parabolic law medium.

Magnesium alloy welding suffers from problems such as burn through and loss of alloying elements during conventional welding process due to high heat input. Variable polarity gas metal arc welding (VP-GMAW) features low heat input. Therefore, it is an attractive method for welding of magnesium alloy. However, the principles governing the correlations among welding current parameters, metal transfer modes, and bead formation are not well understood. Identifying optimal welding current parameters by trial and error is unrealistic. Therefore, peak current, base current, and negative current were selected as independent variables. Their impact mechanism on metal transfer and bead formation were investigated by experiments with high-speed photographs. Then, weld quality evaluation was conducted by a fuzzy comprehensive evaluation. A mathematical method was proposed to calculate optimal current parameters for VP-GMAW of magnesium alloy. In addition, a significant sequence of current parameters is obtained. The results indicate that almost defect-free weld joint is produced by the optimal welding current parameters. The significance sequence of current parameters on weld quality is negative current, peak current, and base current.