International Journal of Modern Physics B

This paper introduces the fractal form of the generalized nonlinear Schrödinger equation, newly named as the Biswas–Milovic model (BM). The BM equation theoretically explains the transmission of solitons for transatlantic and transcontinental distances utilizing optical fibers. The BM equation relating to Kerr law, parabolic law and nonlinearity quadratic law was studied using a variational approach for optical soliton solutions. Essential novel conditions are presented that guarantee the existence of the appropriate solitons. Besides, the physical action of the solution obtained was recorded in terms of 3D and contour plots for distinct parameters for the three different nonlinearities. This study shows the relevance and huge potential of the variational approach to the generalized nonlinear Schrödinger equation.

In this work, we study the nonlinear Josephson dynamics of Fermi superfluids in the crossover from Bardeen–Cooper–Schrieffer (BCS) superfluid to a molecular Bose-Einstein condensate (BEC) in a double-well potential. Under a two-mode approximation, we derive a full two-mode (fTM) model including all interaction energy terms. By solving the fTM model numerically, we study the zero-phase and $\pi$-phase modes of Josephson oscillations in the BCS–BEC crossover. We find that in the strongly interacting regime the cross interaction terms not appearing in the two-mode model cannot be easily ignored. The cross interactions can alter the behaviors of Josephson dynamics substantially, and interestingly the alterations for the zero-phase and $\pi$-phase modes are just opposite.

Through the sub-waveform optimization of the laser field, a potential method to produce the water window single-order harmonic (SOH) has been proposed. First, by properly introducing the chirps of two-color field, the SOHs from 303th order to 616th order can be obtained. Theoretical analyses show that the folding region on the harmonic emission process, caused by the multiple accelerations, is responsible for the enhanced SOH. Moreover, the folding region is dependent on the neighbor two half-cycle profiles. Thus, through further controlling the sub-waveform of the folding region by using the unipolar pulse, the folding region on the harmonic emission process will be extended to the higher photon energy region, including the water window region. Finally, by properly choosing the combinations of chirps and unipolar pulses, the water window SOH from 446th order to 833th order (from 345 eV to 645 eV) can be obtained.

This paper is about the study of space–time fractional Fokas–Lenells equation that describes nonlinear wave propagation in optical fibers. Three prominent schemes are employed for extracting different types of exact soliton solutions. In particular, the ${exp}_a$ function method, the hyperbolic function method and the simplest Riccati equation scheme are investigated for the said model. As a sequel, a series of soliton solutions are obtained and verified through MATHEMATICA. The obtained solutions are significant additions in some specific fields of physics and engineering. Furthermore, the 3D graphical descriptions are left to analyze the pulse propagation for the reader.

In this paper, we investigated a new form of nonlinear Schrödinger equation (NLSE), namely the Biswas–Arshed model (BAM) for the analysis of complete integrability with the help of Painlevé test ($P$-test). By applying this test, we analyze the singularity structure of the solutions of BAM, knowing the fact that the absence of specific sort of singularities like moveable branch points is a patent signal for the complete integrability of the discussed model. Passing the $P$-test is a powerful indicator that the studied model is resolvable by means of inverse scattering transformation (IST).

The application of the subwavelength planar structure to control the propagation direction of surface plasmon polaritons (SPPs) has attracted many interests in recent years. However, the traditional unidirectional transmission devices of SPPs are limited by the low extinction ratio, narrow working band and the incapability of controlling the transmission directions. In this study, a novel SPPs unidirectional transmission device based on metallic aperture arrays of the right triangle (RT) is proposed and demonstrated by numerical simulations (finite-difference time-domain method). The maximum extinction ratio of the unidirectional transmission device can reach upto 33 dB under the irradiation of linearly polarized light, and the device possesses a wide operating band ($\sim 300$ nm) while the extinction ratio is greater than 10 dB. Moreover, the transmission direction of SPPs can be flexibly controlled by tuning the polarization of the incident beam. This broadband, polarization-mediated and high extinction ratio unidirectional transmission device shows great potential in the compact plasmonic devices.

In this work, SiC nanowires (SiC NWs) reinforced SBG (Sn-58Bi-0.05GNSs) composite solder was prepared using powder metallurgy route. The effect of SiC NWs on melting temperature, wetting behavior, shear properties, microstructure of the prepared solder joints and interfacial reaction were studied in detail. Results reveal that incorporating SiC NWs can develop the wetting behavior and shear properties of solder joint but has a little effect on melting temperature. The microstructure of solder is refined markedly with the addition of SiC NWs, which is one of the reasons for the increase in the shear strength of the solder joints. Additionally, the dimension of Cu₆Sn₅ IMC grains diminishes with the doping of SiC NWs, which resulted in the thinning of Cu₆Sn₅ IMC layer. Thence, the addition of SiC NWs may be an effective way to improve the reliability of solder joints.

The effect of hydrostatic pressure on binding energy and polaron effect of the bound polaron in a wurtzite Al${}_y$Ga${}_{1-y}$N/Al${}_x$Ga${}_{1-x}$N parabolic quantum well (QW) is studied using the Lee–Low–Pines intermediate coupling variational method in the paper. The numerical relationship of binding energy and polaron effect of the bound polaron are given as a functions of pressure $p$, composition $x$ and well width $d$. In the theoretical calculations, the anisotropy of the electron effective band mass, the optical phonon frequency, the dielectric constant and other parameters in the system varying with the pressure $p$ and the coordinate $z$ are included. The electron–optical phonon interaction and the impurity center–optical phonon interaction are considered. The results show that hydrostatic pressure has a very obvious effect on binding energy and polaron effect of the bound polaron in the wurtzite Al${}_y$Ga${}_{1-y}$N/Al${}_x$Ga${}_{1-x}$N parabolic QW. For QWs with determined structural parameters, the contributions of the three branch of phonons, i.e., the confined (CF) phonon, half-space (HS) phonon and the interface (IF) phonon, to binding energy of the polaron increase with the increase of the pressure $p$, the CF phonons contribute the most. Under the condition of a certain well width and hydrostatic pressure, with the increase of the composition $x$, the ground state binding energy of the bound polaron in the wurtzite Al${}_y$Ga${}_{1-y}$N/Al${}_x$Ga${}_{1-x}$N parabolic QW increases, and the contribution of the IF phonon and HS phonons to the binding energy decreases, while the contribution of the CF phonons and the total contribution of all phonons increase significantly. In the wurtzite Al${}_y$Ga${}_{1-y}$N/Al${}_{0.3}$Ga${}_{0.7}$N parabolic QW, the ground state binding energy of the bound polaron decreases with the increase of the well width. The decrease rate is greater in the narrow well, and smaller in the wide well. The contribution of different branches of phonons to binding energy varies with the change of the well width. With the increase of the well width, the contribution of CF phonons to binding energy increases, the contribution of HS phonons to binding energy decreases, and the IF phonon contribution and the total phonon contribution first increase to the maximum value and then gradually decrease slightly. The changing trend of binding energy of bound polaron in the wurtzite Al${}_y$Ga${}_{1-y}$N/Al${}_x$Ga${}_{1-x}$N parabolic QW, of the contribution of different branch phonons to binding energy with the pressure $p$, composition $x$ and well width $d$ is similar to that of the GaN/Al${}_x$Ga${}_{1-x}$N square QW, but the change in the parabolic QW is more obvious.

In this article, the authors carry out a pioneering study of monocrystalline TlInS${}_2〈5\%\mathrm{\text{C}}〉$ at higher than room-temperatures using impedance spectroscopy. It is shown that in TlInS${}_2〈5\%\mathrm{\text{C}}〉$ crystals at temperatures higher than 400 K, the nature of conductivity is predominantly ionic. Moreover, characteristics of impedance spectra behavior of TlInS${}_2〈5\%\mathrm{\text{C}}〉$ monocrystal samples were studied using the measurement frequency range of 25–10⁶ Hz. For the measured frequency range, it is shown that curves of active and reactive impedance components undergo a dispersion characterized by decreasing values of $Z^{\prime }$ and $Z^{\prime \prime }$, as the frequency of the electric field and radiation dose increases.

The interface state in two-dimensional (2D) sonic crystals (SCs) was obtained based on trying or cutting approach, which greatly limits its practical applications. In this paper, we theoretically demonstrate that one category of interface states can deterministically exist at the boundary of two square-lattice SCs due to the geometric phase transitions of bulk bands. First, we derive a tight-binding formalism for acoustic waves and introduce it into the 2D case. Furthermore, the extended 2D Zak phase is employed to characterize the topological phase transitions of bulk bands. Moreover, the topological interface states can be deterministically found in the nontrivial bandgap. Finally, two kinds of SCs with the $C_{4v}$ symmetry closely resembling the 2D Su–Schrieffer–Heeger (SSH) model are proposed to realize the deterministic interface states. We find that tuning the strength of intermolecular coupling by contacting or expanding the scatterers can effectively induce the bulk band inversion between the trivial and nontrivial crystals. The presence of acoustic interface states for both cases is further demonstrated. These deterministic interface states in 2D acoustic systems will be a great candidate for future waveguide applications.

In this work, TlIn${}_{1-x}$Ga${}_x$Se₂ single crystals were grown by zone recrystallization methods and their X-ray phase analysis was performed. The lattice parameters were determined and it was found that crystals based on the original TlIn${}_{1-x}$Ga${}_x$Se₂ compound crystallized in the same tetragonal symmetry, the space group $D_{4h}^{18}(I4/\mathrm{\text{mcm}})$. It was revealed that with partial substitution of indium atoms by gallium atoms in the TlIn${}_{1-x}$Ga${}_x$Se₂ lattice, the parameters of unit cells change according to the additivity law. First time it was found that with the simultaneous influence of electromagnetic and sound waves, an electromotive force (e.m.f.) occurs or short circuit current. The studies were carried out in the frequency range of electromagnetic radiation of 50–143 kHz. It was revealed that when the investigated crystals were irradiated with magnetic radiation in the absence of sound waves, there was no e.m.f. on the electrodes as well as memory when exposed only to sound. Based on the existing theoretical information, the nature of the revealed single crystal of the acousto-photovoltaic effect was explained.

In this work, we demonstrate the sensing principle to simultaneously detect the salinity and temperature of seawater using a 1D-defective photonic crystal structure. We designed a one-dimensional defective mode photonic crystal based on the well-known transfer matrix method (TMM) for detecting the seawater salinity and temperature. Our proposed optical sensor is based on the following concept. Since the concentration of the salinity in the seawater changes the refractive index of the seawater, the sensitivity can be calculated by a peak wavelength shift happening in the output transmission spectrum for its variation of different concentration of samples. By adjusting the design parameters of our proposed structure such as the thickness of the defect layer, the temperature and the salinity, we investigated the corresponding optical properties response where the resulted transmittance peak can be turned over the considered range.

Earthquake is a natural disaster that causes enormous losses to human society and its prediction is a major scientific challenge widely concerned by the society. However, the mechanism of earthquake is far from clear, and the mainstream view in the international seismology community is that earthquakes are unpredictable. Based on some new concepts and new knowledge developed in physics, this study scrutinizes the incubation and occurrence of earthquake from a novel perspective, and introduces a new understanding of earthquake principle. It is found that the view of earthquake unpredictability originates from the incorrect understanding of both earthquake principle and the self-organized criticality (SOC). That is to say, earthquake is consistent with the laws of SOC, which means it would be impossible to make a medium- or long-term prediction, yet the short-term prediction should still be possible. The preconditions for successful prediction include understanding correctly of earthquake principle, obtaining sufficient characteristic precursory information, and gathering relevant geological data. Traditional seismology is based on the solid continuum mechanics which holds the view that earthquakes are caused by brittle fracture of crustal rocks through the so-called “elastic rebound” mechanism. This point of view is seriously inconsistent with many field observations, cannot account for many seismic phenomena. It therefore cannot obtain and understand the earthquake precursory information correctly, and naturally reach the false conclusion that earthquake is unpredictable. Based on the simple fact that the crust is composed of rock blocks with fault gouges filling in between them, we treat the crust as a discrete system and understand the earthquake incubation process by means of granular physics. The new understanding gained is that the tectonic force propagates through force chains formed by the rock blocks, and the rock blocks move in the manner of stick-slip. Furthermore, by carefully analyzing how the strength of crustal rocks and the distributions of tectonic force vary with depth, we propose that the physical mechanism of earthquake is plastic sliding of rock and a jamming — unjamming transition of rock motion. Our novel theory on the earthquake principle and the earthquake processes can explain many seismological phenomena that could not be understood in terms of traditional seismology, such as the heat-flow paradox and the cause of deep-focus earthquake, etc. Based on this new understanding of earthquake principle, we put forward suggestions on how to obtain the earthquake precursory information correctly, so as to realize the goal of short-term prediction of earthquake.

The specific values of the conductivity $(\sigma )$ and its variation with temperature $(T)$ of 2-pentanol and 2-methyl-1-pentanol liquids doped with different concentrations of NaI (abbreviated as 2PEN-$x$NaI and 2M1PEN-$x$NaI, respectively) ($x=0\%$, 1% and 5%) are measured by the commercial equipment. The results show that whether NaI is doped or not, $\sigma$ of 2PEN-$x$NaI and 2M1PEN-$x$NaI all have a conductivity peak in the range of 300–350 K different from that of typical glass-formers of small molecules. In addition, $\sigma$ goes up with increasing $x$, and the temperature corresponding to $\sigma$ maximum increases with rising NaI content. Moreover, there is a nonlinear behavior of $\sigma$ with $x$, i.e., with rising $x$, $\sigma /x$ decreases at low-temperatures, but increases at high-temperatures. Moreover, the liquid structure and its variation with $T$ are further analyzed based on the ionic conductivity.

Biological cells sense external concentrations via stochastic receptor signals and respond by regulating the expression of target proteins. Two main signaling mechanisms have been found to encode signal molecular concentrations: continuous modulation (CM), where the receptor signals continuously whenever a ligand is bound, and bursty modulation (BM), where the receptor signals shortly and with fixed size only upon the binding of a ligand. The two mechanisms are often subject to noise which influences the reliability of information transmission. However, how the relationship between noise and information transmission works in the two mechanisms is still unanswered. Here, we analyze a two-component signaling system with multiple receptors which can produce continuous or bursty signals, and decompose the total noise into three terms: intrinsic noise, extrinsic noise and correlated noise. Based on the obtained formulas, we study the information transmission and noise correlations in two signaling mechanisms. We find that (1) the intrinsic noise of BM is always not less than that of CM, whereas the correlation noise of the former is negative and that of the latter is zero; (2) the extrinsic noise of BM can be higher or lower than that of CM, or the former equals the latter, which depends on the mean duration ratio of the receptors at active and inactive states; and (1) the relationship between output noise and mutual information is inversely proportional in the two signaling mechanisms. Our results reveal the correlation between information transmission and noise which can be used to analyze the dynamics of two-component systems.

The research work has demonstrated the effect of hydrothermal ageing ($121^{\circ }$C, 40 h, 1.034 bar) on friction and wear behavior of SrO-doped zirconia toughened alumina (ZTA) composite. Surface topography and wear regime behavior are established in the perspective of ageing time, load, phase transformation and toughening phenomena. The estimated critical load is confirming the expedition of mild to severe wear in the presence of microcrack formation during adhesive and abrasive wear between SrO-doped ZTA (disc) and ZrO₂ (ball) tribo couples, where adhesion between the SrO–ZTA disc and ZrO₂ ball results in transfer of ZrO₂ particles from ball to disc. Roughness parameters ($R_a$, $R_q$) are elucidated to understand the influence of load and ageing conditions, as well as the in vitro bioactivity of sintered specimens is assessed in simulative body fluid (SBF) solution.