Modern Physics Letters B

Based on the stress responses of individuals, the susceptible-infected-susceptible epidemic model was improved on the small-world networks and BA scale-free networks and the simulations were implemented and analyzed. Results indicate that the behaviors of individual’s stress responses could induce the epidemic spreading resistance and adaptation at the network level. This phenomenon showed that networks were learning how to adapt to the disease and the evolution process could improve their immunization to future infectious diseases and would effectively prevent the spreading of infectious diseases.

The performance of one-way and two-way continuous variable quantum key distribution (CVQKD) protocols can be increased by adding some noise on the reconciliation side. In this paper, we propose to add noise at the reconciliation end to improve the performance of CVQKD with untrusted source. We derive the key rate of this case and analyze the impact of the additive noise. The simulation results show that the optimal additive noise can improve the performance of the system in terms of maximum transmission distance and tolerable excess noise.

Thermophysical properties, such as density, specific heat, viscosity and thermal conductivity, vary sharply near critical point. To evaluate these properties of hydrocarbons accurately is crucial to the further research of fuel system. Comparison was made by the calculating program based on four widely used equations of state (EoS), and results indicated that calculations based on the Peng–Robinson (PR) equation of state achieve better prediction accuracy among the four equations of state. Due to the small computational amount and high accuracy, the evaluation method proposed in this paper can be implemented into practical application for the design of fuel system.

Attractive potential applications of cubic boron nitride (c-BN) derive from the properties of semiconductors, widely used in optoelectronic and microelectronic devices. In this paper, the effects of element doping on the electronic structures and optical properties in cubic boron nitride are investigated. The Al- and Ga-doped systems have the lower bonding energies of −11.544 eV and −5.302 eV, respectively, indicating better stability. Difference charge density maps demonstrate that the electron loss increases after P doping and decreases after Al, Ga and As dopings, indicating that the covalent character of polar covalent bonds decreases by doping in the range of P, Al, Ga and As, which is in accordance with the calculated atom population values. The Al- and Ga-doped systems show lower dielectric loss, absorption and reflectivity in the lower energy region, displaying the “transparent-type” characteristic and their potential applications in electron devices.

The indicative values of reduced Pease–Braginskii (P–B) currents are estimated for a nitrogen and oxygen plasma focus. The values of depletion times indicate that in N₂ and O₂ with estimated 3–4% of pinch energy radiating away over the duration of the pinch, we may expect some cooling effects leading to small reductions in radius ratio. In other gases with higher atomic number, the pinch duration is much more than the depletion time, so radiative contraction may be anticipated. The Lee model was employed to study the soft X-ray from PF1000 operated with nitrogen and oxygen. We found nitrogen soft X-ray yield in the water window region of 3.13 kJ, with the corresponding efficiency of 0.9% of the stored energy $(E_0)$, while for the oxygen it was found to be $Y_{\mathrm{\text{sxr}}}$ = 4.9 kJ, with the efficiency of 1.4% $E_0$. The very modest enhancement of compression (radius ratios around 0.1) in the pinches of these two gases gives rise to rather modest pinch energy densities (PEDs) under 10⁹ Jm${}^{-3}$. This is in contrast to Kr or Xe where it had been shown that the radiative collapse leads to radius ratios of 0.007 and 0.003, respectively, with PEDs going to large values considerably exceeding 10${}^{12}$ Jm${}^{-3}$.

In this paper, a U-shaped meander-line slow-wave structure (SWS) with stub-loading is proposed for applications in Ka-band traveling-wave tube (TWT). This new slow-wave structure, loaded with a stub at the center of the U-turn section, has higher interaction impedance and lower phase velocity compared with conventional U-shaped meander-line SWSs, indicating that the devices based on this structure may have a lower operating voltage and higher output power. The dispersion characteristic, interaction impedance, transmission characteristics, and beam-wave interaction are simulated by utilizing simulation tool. The simulation result predicts that the millimeter-wave traveling-wave tube design based on this slow-wave structure is capable of delivering over 200 W with a gain of 33 dB and interaction efficiency 14.5% at the center frequency 34 GHz. This design, more compact and powerful in comparison with those based on more conventional vacuum electronic mechanisms, is demonstrated as a prospective option for integrated millimeter-wave power modules (MMPMs) empowering a broad spectrum of fields, from target detection, to imaging and telecommunications, among others.

In this paper, a semi-discrete coupled nonlinear Schrödinger equation is investigated via the Darboux transformation (DT) method. Based on the Lax pair, the N-fold DT and conservation laws are constructed. Some new discrete soliton solutions under the vanishing and nonvanishing backgrounds are also derived. The dynamic features of those solutions are displayed through figures. The modulation instability (MI) is analyzed and the dispersion relation is derived.

In this paper, we investigate the dynamics of a generalized Davydov model derived from an infinite chain of alpha helical protein molecules which contain three hydrogen bonding spines running almost parallel to the helical axis. Through the introduction of the auxiliary function, the bilinear form, one-, two- and three-soliton solutions for the generalized Davydov model are obtained firstly. Propagation and interactions of solitons have been investigated analytically and graphically. The amplitude of the soliton is only related to the complex parameter $\mu$ and real parameter $𝜃$ with a range of $[0,2\pi ]$. The velocity of the soliton is only related to the complex parameter $\mu$, real parameter $𝜃$, lattice parameter $𝜀$, and physical parameters ${\beta }_1$, ${\beta }_3$ and ${\beta }_4$. Overtaking and head-on interactions of two and three solitons are presented. The common in the interactions of three solitons is the directions of the solitons change after the interactions. The soliton derived in this paper is expected to have potential applications in the alpha helical proteins.

In this paper, the relaxation of the electrical resistance of a YBa${}_2$Cu${}_3$O${}_{\mathrm{\text{7}}-x}$ single crystal that is kept for a long time at room temperature in air atmosphere is investigated. It is shown that with increasing time of keeping, relaxation of the electrical resistivity at room temperature is observed, controlled by a single channel and the classical oxygen ion diffusion mechanisms. The faster transport of oxygen ions in the initial stage of the implantation process can take place along one-dimensional nonstoichiometric vacancies in a single-file diffusion mode. The final stage of oxygen transport in this compound is described by an ordinary classical diffusion mechanism.

Lead halo borate glass systems containing manganese ions have been investigated to study the role of halide ions on the physical, optical and EPR studies. The amorphous phase of the prepared glass samples $x$PbX₂–(30$-x$)PbO–69.5B₂O₃–0.5MnO₂ with X = F, Cl and Br and $5\le x\le 25$ mol% was confirmed from their X-ray diffraction spectra. Ionic radii of the halides played an important role in the physical properties. From the optical absorption spectra, optical band gap and Urbach energy values were evaluated. The EPR spectra have shown a six-line hyperfine (HF) structure centered at $g\approx 2.0$ and attributed to Mn${}^{2+}$ centers in octahedral symmetry. The other signals at $g\approx 3.3$ and 4.3 were attributed to the rhombic surroundings of Mn${}^{2+}$ ions. The negative shift in $g$-value revealed highly ionic environment around the Mn${}^{2+}$ ion in the glass hosts. The HF splitting constant (A), number of spins (N) and susceptibility $(\chi )$ values of the prepared glasses were also reported.