Modern Physics Letters B

We investigate a stochastic model for single species population growth with strong and weak Allee effects subjected to coupling between non-Gaussian and Gaussian colored noise as well as nonzero cross-correlation in between. Stationary probability distribution of population model is obtained depending on the Fokker–Planck equation. The mean first-passage time is also calculated in order to quantify the time of transition between survival state and extinction state with Allee effect in population. The intensity of non-Gaussian colored noise can induce phase transition, and population may be vulnerable to extinction due to the increase in the intensity of non-Gaussian colored noise. Whether Allee effect is strong or weak, the increase in Allee threshold will not contribute to the survival and stability of the population. Further, the phenomenon of resonant activation is firstly discovered in the study of population dynamics with Allee effect. These behaviors can be interpreted on the basis of a biological model of population evolution.

The contact plays an important role in the study of ultracold atoms. We determine the contact from the high-frequency asymptotic behavior of radio-frequency spectrum for a homogeneous Fermi gas at unitarity in the normal phase. The contact is obtained within the framework of the non-self-consistent T-matrix approximation with particle–hole fluctuation.

In this work, modification in structural and electrical properties of zirconium nitride (ZrN) thin films induced by silicon-ion irradiation is studied. ZrN thin films are grown on glass substrate over Zirconium (Zr) layer using cathodic arc evaporation method. The samples of the film are irradiated with silicon ions of energy 2.08 MeV at different fluences ranging from $5\times 10^{13}$ ions/cm${}^{-2}$ to $5\times 10^{15}$ ions/cm${}^{-2}$. The structural and electrical properties of the prepared films are investigated using X-ray diffraction (XRD), Raman spectroscopy and four-point probe method. XRD analysis shows significant shift in the peak corresponding to (111) crystallographic plane of ZrN at low fluence ($5\times 10^{13}$ ions/cm${}^{-2}$) while modest peak shift at high fluence rate ($5\times 10^{15}$ ions/cm${}^{-2}$) is observed. Under the electrical properties point of view, it is observed that the decrease in resistivity is small at high ion fluence as compared to that at low ion fluence. At highest fluence of $5\times 10^{15}$ ions/cm${}^{-2}$, resistivity of the irradiated sample approaches the resistivity of the un-irradiated sample indicating very small changes in structure at very high dose irradiance.

In this research, we study the exact solutions of the Rosenau–Hyman equation, the coupled KdV system and the Burgers–Huxley equation using modified transformed rational function method. In this paper, the simplest equation is the Bernoulli equation. We are not only obtain the exact solutions of the aforementioned equations and system but also give some geometric descriptions of obtained solutions. All can be illustrated vividly by the given graphs.

Wireless sensor networks (WSNs) are ubiquitous nowadays and have applications in variety of domains such as machine surveillance, precision agriculture, intelligent buildings, healthcare etc. Detection of anomalous activities in such domains has always been a subject undergoing intense study. As the sensor networks are generating tons of data every second, it becomes a challenging task to detect anomalous events accurately from this large amount of data. Most of the existing techniques for anomaly detection are not scalable to big data. Also, sometimes accuracy might get compromised while dealing with such a large amount of data. To address these issues in this paper, a unified framework for anomaly detection in big sensor data has been proposed. The proposed framework is based on data compression and Hadoop MapReduce-based parallel fuzzy clustering. The clusters are further refined for better classification accuracy. The modules of the proposed framework are compared with various existing state-of-art algorithms. For experimental analysis, real sensor data of ICU patients has been taken from the physionet library. It is revealed from the comparative analysis that the proposed framework is more time efficient and shows better classification accuracy.

The effects of oxygen partial pressure on the microstructure, electrical and photo-sensitive properties of the Sn-doped In₂O₃ (ITO) films deposited by different Ar–O₂ flow rates (10:0.4, 10:1, 10:1.8 and 10:3) were investigated systematically by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), Hall effect, UV-Vis and optical measurements. The XRD and SEM measurements show that the ITO film deposited at oxygen flow rate of 0.4 sccm prefers to (400) orientation and has a rough sawtooth-shaped surface. However, the ITO films deposited at oxygen flow rates of 1 sccm, 1.8 sccm and 3 sccm prefer to (222) orientation and exhibit a flat smooth surface. The conductivity, mobility and photosensitive property of ITO films are also sensitive to oxygen flow rate. The ITO film deposited at oxygen flow rate of 0.4 sccm has a high carrier concentration (up to $1.29\times 10^{21}$ cm${}^{-3}$) and mobility (16.7 cm²/vs), low resistivity $(2.883\times 10^{-4}\mathrm{\Omega }\cdot \mathrm{\text{cm}})$, and a long response time but good sensitivity to ultraviolet light. It can be concluded that the surface morphology plays a dominant role in sensitivity to ultraviolet light. The good sensitivity of ultraviolet light is gained from the ITO film with sawtooth-shaped surface.

Graphdiyne–ZnO composite is constructed to investigate field-emission. We hope the tip effect of graphdiyne can be strengthened by doping ZnO. We find that the effective movement of the Fermi level and the dwindling of band gap have contributed to the modification of the electronic structures of this composite significantly with increase in the electric field. The high binding energy indicates that the composite model is very stable. In addition, the ionization energies and work functions decrease linearly with the increasing electric field, which represents an improvement of field-emission properties. It implies that graphdiyne–ZnO composite may become a promising material for field-emission.

Analytic wave solutions including homoclinic wave, kink wave and soliton solutions for the 2D coupled complex Ginzburg–Landau equations are obtained using the auxiliary function method, Hirota method and the ansatz function technique under certain constraint conditions of coefficients in equations, respectively. The result shows that there exists a kink-wave solution which tends to one and the same periodic wave solution as time tends to infinite.

This paper is concerned with the asymptotic anti-synchronization problem of the memristor-based bidirectional associative memory neural networks (MBAMNNs) and its application in network secure communication. First, we propose a new model of MBAMNNs with probabilistic delays. By establishing a Bernoulli distributed stochastic variable, the information of transmittal time-varying delays is studied. Second, in order to provide a more robust and secure system, we develop a new anti-synchronization model based on the MBAMNNs. The adaptive laws are carefully designed to confirm the process of encryption and decryption in networks secure communication system. Finally, several numerical examples are presented to demonstrate the effectiveness and applicability of our proposed mechanism.

We report on the effect of 500 keV He${}^{+}$ ion implantation with a fluence of $3\times 10^{16}$ ions/cm² on Rb${}^{+}$-K${}^{+}$ ion exchanged KTiOPO₄ optical waveguide. The refractive index distribution after ion implantation, ion exchange, and ion implantation and subsequent ion exchange were reconstructed by reflectivity calculation method, inverse Wentzel–Kramers–Brillouin, and intensity calculation method, respectively. The near field intensity distribution of the waveguides was simulated by Beam Propagation Method. The phase analysis of the samples was measured by X-ray diffraction technique. The damage layer formed in the depth of maximum nuclear energy deposition by ion implantation acts as a barrier to block the ions diffusion into the sample. Results exhibit that ion implantation and subsequent ion exchange are effective means for optical waveguide formation.

We have proposed an approach for rapid generation of perfect vortex beam without side lobes through a digital micromirror device (DMD). Employing this method, the amplitude and phase of far field can be controlled indirectly by changing the rotation state of each unit on the DMD. The perfect vortex beams of equal rings diameter independent of their topological charges are generated commendably and the side lobes are avoided. Moreover, we have demonstrated rapid switching among the generated orbital angular momentum modes at the speed of 10 kHz, which is much faster than that of the usual method realized by spatial light modulators (SLMs). The proposed method is very beneficial for the optical communication and trapping or manipulating the small particle based on orbital angular momentum modes.

We investigate the stochastic resonance of periodic volatility in two financial markets with stock crashes for Dow Jones component stocks and Hang Seng index, based on the modified Heston model with an effective potential to describe the stock crashes. We introduce a cosine term to Heston model and develop a modified Heston model with periodic stochastic volatility for capturing the periodicity of the volatility process or volatility clustering which was observed in historical financial data sets. The proposed model was tested against Dow Jones industrial and Hang Seng index data. The experimental results demonstrate that the proposed model fits the historical data well when compared with the original Heston model. The signal power amplification (SPA) is calculated and studied to investigate the stochastic resonance of the proposed dynamic system. Experimental results suggest that: (i) optimal values of volatility parameters can be identified which maximize the effects of systematic and non-systematic randomness to the market periodicity; (ii) different values of correlation strength between noise sources will cause critical phenomenon and induce single or multiple resonances.

In this paper, the influence of van der Waals force on the wave propagation in viscoelastic double-walled carbon nanotubes (DWCNTs) is investigated. The governing equations of wave motion are derived based on the nonlocal strain gradient theory and double-walled Timoshenko beam model. The effects of viscosity, van der Waals force, as well as size effects on the wave propagation in DWCNTs are clarified. The results show that effects of van der Waals force on waves in inner and outer layers of DWCNTs are different. Flexural wave (FW) in outer layer and shear wave (SW) in inner layer are sensitive to van der Waals force, and display new phenomena. This new finding may provide some useful guidance in the acoustic design of nanostructures with DWCNTs as basic elements.

Traffic capacity of a network is very vital to a variety of complex networks, such as communication networks and road networks, in which the bandwidth of every link is limited or finite. In this work, inspired by the deployment process of nodes and links in real networks, we assume the bandwidth of every link is composed of a constant part and a degree-related one that can be updated iteratively with the network hardware update. We propose a link bandwidth-based routing mechanism to enhance the network traffic capacity. Extensive simulations in both scale-free networks and random networks are done to confirm the effectiveness of our proposed method. Comparing results with the shortest path routing and a weighted routing, our method achieves better network traffic capacity among all used routing strategies without obvious extra cost including the network diameter, average path length and average packet traveling time. Our work studies network routing from a very new perspective and might have potential applications in real network systems such as the communication networks.