International Journal of Modern Physics B

In this paper, we address the impact of the electric field on superconductors which are insulators in the normal state, semiconductors at low carrier concentration and ultracold gas of fermions in the strongly interacting regime. The electric field penetrates these systems and effects on the Cooper pairs. We show that if there are Cooper pairs above the superconductor critical temperature, the electric field forces the Cooper pairs to Bose condensate and the onset of the superconductivity, thereby increasing the critical temperature. To study this phenomenon, we numerically solve the Maxwell equations for $s$-wave superconductors obtained from the time-dependent Ginzburg–Landau theory. Our investigation designs an experimental way for verification of the pairing of Fermions preceding superconductivity and superfluidity.

We reported a simple, high yield and large-scale preparation method for silver nanoparticles. Silver nanoparticles with 8–13 nm in diameter were successfully synthesized by silver nitrate as raw material, sodium borohydride as reducing agent, dispersan-5040 (polycarboxylate sodium salt) as surface modifier in aqueous solution. The effects of sodium borohydride and dispersan-5040 on the morphologies of silver nanoparticles were investigated. Further, the conductive inks were prepared with as-synthesized silver nanoparticles as conductive fillers in the presence of deionized (DI) water and additives. The effects of conductive fillers and additives on the pH, conductivity, surface tension and viscosity of the inks were investigated. The conductive patterns were fabricated by inkjet printer and their performances were studied. The sheet resistances of the printed pattern with seven-layer was 1.2 $\mathrm{\Omega }/\square$ when the printed pattern was heat-treated at 120${}^{\circ }$C for 60 min. We succeeded in printing a simple conductive circuit on photographic paper, which can light three 0.06 W LED beads. The successful fabrication of the functional circuit proves the feasibility of the ink and provides some ideas for future paper-based circuits.

The first-excited-state (ES) binding energy of hydrogenic impurity bound polaron in an anisotropic quantum dot (QD) is obtained by constructing a variational wavefunction under the action of a uniform external electric field. As for a comparison, the ground-state (GS) binding energy of the system is also included. We apply numerical calculations to KBr QD with stronger electron–phonon (E–P) interaction in which the new variational wavefunction is adopted. We analyzed specifically the effects of electric field and the effects of both the position of the impurity and confinement lengths in the xy-plane and the $z$ direction on the ground and the first-ES binding energies (BEs). The results show that the selected trial wavefunction in the ES is appropriate and effective for the current research system.

The signed network depicts individual cooperative or hostile attitude in a system. It is very important to study the characteristics of complex networks and predict individual attitudes by analyzing the attitudes of individuals and their neighbors, which can divide individuals into different modules or communities. To detect the modules in signed networks, first, a modularity function for signed networks is utilized on the basis of the existing modularity function. Then, a new module detection algorithm for signed networks has also been put forward, which has high efficiency. Finally, the algorithm has been applied on both artificial and real networks. The results show that the number of modules given by our proposed algorithm is consistent with that of the number of actual modules.

Titanium nitride (TiN) thin films have excellent physical and chemical properties, and are widely used as cutting tools, drills and die protective coatings. However, their limited hardness and corrosion resistance caused by the rough, loose, columnar structure will affect its application in extreme environments. TiN films with refined grains and nanostructure might solve this problem. In this paper, Co and Cr atoms were doped into TiN film to tailor its structure. The effects of Co and Cr content on the Ti(CoCr)N film structure, mechanical properties and corrosion resistance were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), microhardness tester and electrochemical corrosion tester. The results show that Co and Cr doping can disturb the columnar growth of TiN films, and lead to refinement of TiN grains. Compared to TiN films without Co and Cr doping, the hardness of Ti(CoCr)N with 2.7 at.% Co and 1.9 at.% Cr increases by about 37% to 31.3 GPa. And Ti(CoCr)N films with 2.7 at.% Co and 1.9 at.% Cr have the best corrosion resistance.

In this work, Mn${}^{2+}/$Eu${}^{3+}$ co-doped Zn₂GeO₄ (Zn₂GeO₄:Mn${}^{2+},{\mathrm{\text{Eu}}}^{3+})$ was prepared by high-temperature solid phase method. Compared with common fluorescent materials Zn₂GeO₄:Mn${}^{2+}$, Zn₂GeO₄:Mn${}^{2+},{\mathrm{\text{Eu}}}^{3+}$ could not only emit strong green fluorescence of 535 nm, but also maintain excellent persistent luminescence performance. Through Density Functional Theory calculation, we obtained the fine band structure of Zn₂GeO₄:Mn${}^{2+},{\mathrm{\text{Eu}}}^{3+}$. The results of the band structure were consistent with the experimental spectral data. On this basis, we proposed a new luminescence mechanism model of Zn₂GeO₄:Mn${}^{2+},{\mathrm{\text{Eu}}}^{3+}$ to explain the phenomena observed in experiment reasonably, though which was not completely consistent with previous works. When Zn₂GeO₄:Mn${}^{2+},{\mathrm{\text{Eu}}}^{3+}$ was excited, electron–hole separation occurred in the valence band (VB), and the electron transitioned to the conduction band (CB) directly. Through CB, the electron was trapped by trap levels (⁷F${}_0{\sim }^7$F₅ of Eu${}^{3+})$ and maintained metastable for a long time. Under the action of thermal stimulation, electron returned to CB from the trap level slowly. The electron was captured again by the ⁴T₂(D) level of Mn${}^{2+}$. Then the electron transitioned down toward VB and recombined with the previous hole and emitted a photon with 535 nm (afterglow). The samples were being irradiated, trap levels accommodated the excited electrons to saturation. More electrons excited into the CB could not be captured by the trap levels any more. They were captured directly by the ⁴T₂(D) and transitioned directly to VB, then emitted green fluorescence.

The paper presents and discusses the results of performed calculations for YAlO₃ (111) surfaces using a hybrid B3LYP description of exchange and correlation. Calculation results for SrTiO₃, BaTiO₃ and BaZrO₃ (111) as well as YAlO₃, SrTiO₃, BaTiO₃ and BaZrO₃ (001) surfaces are listed for comparison purposes in order to point out systematic trends common for these four ABO₃ perovskite (001) and (111) surfaces. According to performed ab initio calculations, the displacement of (001) and (111) surface metal atoms of YAlO₃, SrTiO₃, BaTiO₃ and BaZrO₃ perovskite, upper three surface layers for both AO and BO₂ (001) as well as AO₃ and B (111) surface terminations, in most cases, are considerably larger than that of oxygen atoms. The YAlO₃, SrTiO₃, BaTiO₃ and BaZrO₃ (001) surface energies for both calculated terminations, in most cases, are almost equal. In contrast, the (111) surface energies for both AO₃ and B-terminations are quite different. Calculated (111) surface energies always are much larger than the (001) surface energies. As follows from performed ab initio calculations for YAlO₃, SrTiO₃, BaTiO₃ and BaZrO₃ perovskites, the AO- and BO₂-terminated (001) as well as AO₃- and B-terminated (111) surface bandgaps are almost always reduced with respect to their bulk bandgap values.

The potential of mean forces (PMFs) has been determined for an isobutane dimer in various solvent environments such as water, methanol and acetonitrile at a temperature of 298 K and pressure of 1 bar using GROMACS software. All the molecular dynamics (MD) simulations are carried out using a TIP3P water model under a CHARMM36 forcefield. Following Umbrella Sampling technique, PMFs are calculated and analyzed using Weighted Histogram Analysis Method (WHAM) and coordination number of first solvation shell is extracted for all solvents using radial distribution function. The shape of PMFs contains contact minima, solvent-separated minima and desolvation maxima. The values of contact minima are not affected much by solvent environment and found to be at 0.5377, 0.5480 and 0.5495 nm for water, methanol and acetonitrile respectively. The corresponding energy depths are found −0.9134, −0.7080 and −0.5295 kcalmol${}^{-1}$. The variation observed at solvent-separated minima is noticeable and found at 0.9012, 0.9721 and 0.9151 nm for water, methanol and acetonitrile, respectively. The coordination number of the first solvation shell by taking an isobutane molecule as a reference from their center of mass is found to be 28.1, 16.9 and 14.8 for water, methanol and acetonitrile, respectively. There is a soft hydrophobic interaction between isobutane dimer and solvents like methanol and acetonitrile relative to water, might be due to the presence of competitive methyl group of methanol and acetonitrile in the solvent medium.

A series of Cu–34Mn–6Ni–$x$Sn (wt.%) braze fillers that were used for brazing stainless steel (SS) were prepared. The microstructures, melting temperatures, wettability and mechanical properties of the braze fillers were investigated. An Sn-rich phase was formed in braze fillers with an Sn content above 6 wt.% (including) because of the segregation performance of Sn. The melting temperatures of braze fillers decreased markedly with an increase in Sn content. The addition of 6 wt.% Sn resulted in the highest wettability of braze fillers on the SS. With an increase in Sn content, the tensile strength and hardness increased, whereas the plasticity and toughness of the braze fillers decreased owing to the solid solution and segregation of Sn.

With the rapid development of the Internet, social media networks have become the primary platform for people to express their views. In addition, network public opinion has a considerable influence on society. Thus, considering the significant impact of online public opinion on society, it is necessary to study and analyze the propagation process for public opinion. In this study, we propose the Media and Interpersonal Relationship-SEIR (MI-SEIR) model based on the SEIR model. Our proposed model considers the impact of media transmission and interpersonal relationships on opinion propagation. Our MI-SEIR model divides the propagation nodes into three categories: support, neutral and opposition. There is a discussion mechanism between these nodes that represents the node’s viewpoint value evolution rule based on the node firmness, influence of nodes, quality of media coverage and parameters of infection. The state transition of nodes is decided based on the change of opinion value. Our simulation experimental results show that this model is more representative of the real propagation of online public opinion and is thus of practical significance for research and opinion analysis applications.

A comprehensive and systematic study of superconducting state parameters (SSPs) of Bi-based binary alloys of the form ${\mathrm{\text{Bi}}}_{1-C}{M}_C$ has been carried out in the framework of pseudopotential theory at different concentrations ($C$) of impurity atom-$M$ in host atom Bi which varies from 0 to 1. Impurity atom $M$ has been replaced by In, Tl, Sb and Pb to form four alloy systems. The density-based local form of the pseudopotential proposed by Fiolhais et al. has been used in this study to compute SSPs such as electron–phonon coupling strength ($\lambda$), Coulomb pseudopotential (${\mu }^{\ast }$), transition temperature ($T_C$), effective interaction strength ($N_{0}V)$ and isotopic effect parameter ($\alpha$) of Bi-based binary alloy systems. Computed results of SSPs of alloys under study are in good agreement with available experimental and other theoretical results. In order to investigate the effect of pressure on SSPs of alloys under study, a theoretical calculation of SSPs as a function of compressed volume is reported. The volume dependence of Debye temperature has been accounted by using Debye–Gruneisen model which involves the Gruneisen parameter. Thus, to describe the effect of pressure on SSPs accurately, the value of Gruneisen parameter should be as accurate as possible. But reported results of Gruneisen parameter in the literature are highly scattered. Due to this reason, we have used two sets of Gruneisen parameter obtained by different methods to understand its role in the computation of SSPs as a function of compressed volume. Further, critical volumes for all alloys at different concentration have been predicted at which electron–phonon coupling strength and Coulomb pseudopotential are equal ($\lambda ={\mu }^{\ast }$). At critical volume, superconductivity quenches where transition temperature, $T_C$, and effective interaction strength, $N_{0}V$, become zero. It is observed that critical volumes predicted by all approaches used in this study are in excellent agreement with each other.

The safety and robustness of the network have attracted the attention of people from all walks of life, and the damage of several key nodes will lead to extremely serious consequences. In this paper, we proposed the clustering H-index mixing (CHM) centrality based on the H-index of the node itself and the relative distance of its neighbors. Starting from the node itself and combining with the topology around the node, the importance of the node and its spreading capability were determined. In order to evaluate the performance of the proposed method, we use Susceptible–Infected–Recovered (SIR) model, monotonicity and resolution as the evaluation standard of experiment. Experimental results in artificial networks and real-world networks show that CHM centrality has excellent performance in identifying node importance and its spreading capability.

The traffic bottleneck effects are investigated on a ring road with up- and down-slopes to the semi-discrete model under the Lagrange coordinate. The kinetic wave theory is applied to discuss all types of stationary solutions for a small relaxation time. Moreover, the analytical formulas of the queuing lengths before bottlenecks and the critical densities of the saturated flux are derived. The stability of the stationary solution on every road section under different mass increments is discussed. The relation between the slope gradient and saturated flux platform is also obtained. The numerical simulation reproduces many complex nonlinear phenomena, such as the steady-state flow, oscillatory congested traffic and saturated flux platform. This study helps to explain the empirical features on inhomogeneous roads in the real-world traffic.

In this work, the transfer matrix method (TMM) is used to calculate the transmission of superconductor-dielectric 1D photonic crystal with central defect of semiconductor material (GaAs) at high superconductor critical temperature ($T_c)$. It is noticed that there is a red shift to high wavelength region by increasing the thickness of constituent materials. Also we study the effect of changing the incident angle, the doping density of GaAs and the applied pressure. The results show that the sense and change of photonic bandgap and transmittance peaks based on the thickness, incident angle, doping density of GaAs and hydrostatic pressure. In the case of change the thickness and hydrostatic pressure, the PBG and peak of transmittance shifted to higher wavelengths (red shift), while in the case of changing the incident angle and doping density, the PBG and peak of transmittance shifted to shorter wavelengths (blue shift).