Modern Physics Letters B

The theoretical model and numerical simulations are established by the rate equation of thulium ion. Using the coherent population oscillation effect, we realize the controllable light velocity in the thulium doped fiber. We show that coherent population oscillations effect produces a very narrow spectral hole and anti-holes in the spectrum. The hole caused the amplitude modulation beam experience a large change of the group of refractive index, and makes us to achieve fast light propagation. Therefore, the pump intensity can be used as a control parameter to increase the fractional advance. In addition, we can confirm that the larger input intensity can lead to large time advancement, and saturation phenomenon of fast light exists in low frequency.

In this letter, a (2+1)-dimensional variable-coefficient Bogoyavlensky-Konopelchenko equation is investigated, which describes the interaction of a Riemann wave propagating along the y-axis and a long wave propagating along the x-axis in a fluid. Under two different constraints of the time-dependent coefficients in this equation, two different bilinear forms are derived by virtue of the binary Bell polynomials. Multiple solitary waves are constructed via the Hirota method, whose propagation properties and interaction characteristics are investigated graphically as well. Propagation and interaction of the solitons are illustrated graphically: (i) time-dependent coefficients affect the shape of the solitons; (ii) interaction of the solitons is elastic, i.e., amplitude, velocity and shape of each soliton remain invariant after each interaction except for a phase shift.

Based on the Hirota bilinear form, two classes of lump-type solutions of the (4+1)-dimensional nonlinear Fokas equation, rationally localized in almost all directions in the space are obtained through a direct symbolic computation with Maple. The resulting lump-type solutions contain free parameters. To guarantee the analyticity and rational localization of the solutions, the involved parameters need to satisfy certain constraints. A few particular lump-type solutions with special choices of the involved parameters are given.

The grid structure is widely used in architectural and mechanical field for its high strength and saving material. This paper will present a study on an acoustic metamaterial beam (AMB) based on the normal square grid structure with local resonators owning both flexible band gaps and high static stiffness, which have high application potential in vibration control. Firstly, the AMB with variable cross-section frame is analytically modeled by the beam–spring–mass model that is provided by using the extended Hamilton’s principle and Bloch’s theorem. The above model is used for computing the dispersion relation of the designed AMB in terms of the design parameters, and the influences of relevant parameters on band gaps are discussed. Then a two-dimensional finite element model of the AMB is built and analyzed in COMSOL Multiphysics, both the dispersion properties of unit cell and the wave attenuation in a finite AMB have fine agreement with the derived model. The effects of design parameters of the two-dimensional model in band gaps are further examined, and the obtained results can well verify the analytical model. Finally, the wave attenuation performances in three-dimensional AMBs with equal and unequal thickness are presented and discussed.

Large-scale silicon oxide nanowires (SiO${}_x$ NWs) with a diameter about 250 nm on silicon wafers were synthesized by thermal evaporation of silicon monoxide (SiO) powder. In order to investigate the role of distance on the physical properties of SiO${}_x$ NWs, Si substrates were positioned at 5 cm and 10 cm apart from the boat position set at 1150${}^{\circ }$C. The local temperatues of the samples were 1100${}^{\circ }$C and 1050${}^{\circ }$C, respectively. The SEM images and EDS spectra showed interweaved networks of SiO${}_x$ NWs with x = 0.62 and 0.65 in these layers. The XRD patterns showed S1 has a polycrystalline structure (cristobalite), while S2 has amorphous nature. The PL spectra showed an intense blue peak at 468 nm in S1, and a violet peak at 427 nm in S2 that could be related to the differences in the crystallite structures and oxygen vacancies in these samples.

Liquid ³He injected in a carbon nanotube is of high interests due to different behavior of the liquid helium in the quasi-one-dimensional systems. In this work, a variational approach has been performed to calculate some thermodynamic properties of this quantum system. In order to do so, a single-walled carbon nanotube containing liquid ³He is considered, applying the Lennard-Jones and Stan–Cole potentials for ³He–³He and ³He–C interactions, respectively. Finally the total energy, equation of state and incompressibility of the system have been calculated. Our calculations show the high values for the incompressibility at high densities, especially for high radii.

In this paper, the geometric and electronic structure of MoS₂ monolayer (ML) adsorbed on SiO₂ (0001) surface were studied by using density functional theory calculations. The calculated interfacial binding energy shows that the MoS₂/SiO₂ hybrid system is stable. MoS₂ ML is bound to the SiO₂ surface with a big interlayer spacing and no covalent bonds form at the interface. The study of the density of states and the charge transfer indicates that the interaction between MoS₂ ML and the SiO₂ substrate is very weak. As a result, the electronic properties of MoS₂ ML are almost not affected by the SiO₂ substrate. This work will be beneficial to the design of MoS₂ ML-based devices where a substrate is needed.

We present the design and numerical simulations of an ultrabroadband visible metamaterial absorber (MMA) with polarization-insensitive and wide-angle based on three-dimensional (3D) metallic nanostructure. Distinct from previous designs, the proposed visible MMA only consisted of structured 3D metallic film constructed with an assembly of four vertical split-rings (FVSR) structure. For the optimized design of our MMA, the absorbance of over 90% with a relative bandwidth of 94.8% can be obtained. Further simulation results indicate that our design is polarization-insensitive and also operated well in a wide range of incident angles for both TE and TM modes. In addition, the designed visible MMA design can tolerate some geometric parameters errors in fabrication. Thus, the proposed visible MMA can be potential application in the photodetectors, thermal imaging, photoelectrochemical, and solar energy harvesting devices.

A series of Dy:LiNbO₃ crystals with x mol.% Mg${}^{2+}$ ions (x =0, 4, 5 and 6 mol.%) were grown by the Czochralski method. The effective segregation coefficient of Mg${}^{2+}$ and Dy${}^{3+}$ ions was studied by the inductively coupled plasma-atomic emission spectrometry (ICP-AES). UV-VIS-NIR absorption spectra and Judd–Ofelt theory were used to investigate their spectroscopic properties. J–O intensity parameters (${\mathrm{\Omega }}_2=7.53\times 10^{-20}{\mathrm{\text{cm}}}^2$, ${\mathrm{\Omega }}_4=6.98\times 10^{-20}{\mathrm{\text{cm}}}^2$, and ${\mathrm{\Omega }}_6=3.09\times 10^{-20}{\mathrm{\text{cm}}}^2$) and larger spectroscopic quality factor (X = 2.26) for Mg:(6 mol.%)Dy:LiNbO₃ crystals were obtained.

In this paper, an integrated microfluidic analysis microsystems with bacterial capture enrichment and in-situ impedance detection was purposed based on microfluidic chips dielectrophoresis technique and electrochemical impedance detection principle. The microsystems include microfluidic chip, main control module, and drive and control module, and signal detection and processing modulet and result display unit. The main control module produce the work sequence of impedance detection system parts and achieve data communication functions, the drive and control circuit generate AC signal which amplitude and frequency adjustable, and it was applied on the foodborne pathogens impedance analysis microsystems to realize the capture enrichment and impedance detection. The signal detection and processing circuit translate the current signal into impendence of bacteria, and transfer to computer, the last detection result is displayed on the computer. The experiment sample was prepared by adding Escherichia coli standard sample into chicken sample solution, and the samples were tested on the dielectrophoresis chip capture enrichment and in-situ impedance detection microsystems with micro-array electrode microfluidic chips. The experiments show that the Escherichia coli detection limit of microsystems is $5\times 10^4$ CFU/mL and the detection time is within 6 min in the optimization of voltage detection 10 V and detection frequency 500 KHz operating conditions. The integrated microfluidic analysis microsystems laid the solid foundation for rapid real-time in-situ detection of bacteria.