Modern Physics Letters B

Pulsed laser-assisted etching is a simple but effective method for fabricating small regular structures directly onto a surface. We have successfully fabricated submicro- or nano-meter sized spikes on a solid surface immersed in liquids with femtosecond laser pulse irradiations. This method is applicable to different metals such as stainless steel, copper, titanium, cobalt, as well as different semiconductors, such as Si and GaAs. The femtosecond laser method is much faster than other methods. We can control the experimental conditions to design and fabricate nanostructures in different materials and on the surfaces with different morphologies. Here, we discuss the nanostructures formation with femtosecond pulse laser irradiations, and introduce our results of the nanostructure for applications in sensing, biology and artificial photosynthesis. The femtosecond laser irradiation technique can efficiently integrate metal, semiconductor and polymer nanostructures in various small devices to leverage the expertise in other research fields and applications.

The entropies of several typical coupled bosonic oscillators are calculated by virtue of the generalized Hellmann–Feynman theorem (GHFT). The relation between GHFT and entropy-variation is construct by using von Neumann entropy, which provides us with a new approach for deriving entropy of some complicated systems.

The phenomena of soliton resonance can occur in (2+1)-dimensional modified Kadomtsev–Petviashvili equation (mKP). In this paper, we study the multisoliton solutions in Hirota's forms for isospectral and non-isospectral mKP. We take two-soliton solutions as examples to investigate soliton resonances occurring in uniform and non-uniform media according to different values of the phase shift parameter.

The electronic paramagnetic resonance g factors g_‖, g_⊥ of Dy³⁺ centers and the hyperfine structure constants A_‖ and A_⊥ of ¹⁶¹Dy³⁺ and ¹⁶³Dy³⁺ isotopes in ZrSiO₄ crystal are theoretically studied from the perturbation formulas of the spin Hamiltonian parameters for a 4f⁹ ion in tetragonal symmetry. In these formulas, the contributions to g factors due to the J-mixing among the ground ⁶H_15/2, the first excited ⁶H_13/2 and second excited ⁶H_11/2 states via crystal-field interaction, the admixtures among the states with the same J value via spin-orbit coupling interaction and the interactions between the lowest Kramers doublet Γγ and other 20 Kramers doublets Γ_X within the states ⁶H_J (J=15/2, 13/2 and 11/2) via crystal-field and orbital angular momentum interactions are considered. The calculated EPR parameters show reasonable agreement with the observed values. The results are discussed.

We propose an all-optical channel switch based on lattice solitons with weak light to control an intense light. Through adjusting the power, position and incident angle of the controlling light, the signal light can be switched to different channels. In the switching process, the signal light loses little energy.

A novel microwave sensor based on waveguide filled with a metamaterial particle, which is composed of meander line and split-ring-resonator (SRR), is presented and modeled using a full wave electromagnetic commercial simulator CST. Simulating results show that evanescent mode are enhanced and transmitted through the structured particle within the frequency band that exhibits negative permittivity and permeability. Evanescent mode is sensitive to permittivity of dielectric material in the detecting zone. Comparing with conventional microwave resonant sensor, the microwave sensor using evanescent mode allows for much higher detection sensitivity.

The thermodynamic properties of MgSiO₃ post-perovskite are predicted at high pressures and temperatures using the Debye model for the first time. This model combines with ab initio calculations within local density approximation using pseudopotentials and a plane wave basis in the framework of density functional theory, and it takes into account the phononic effects within the quasi-harmonic approximation. It is found that the calculated equation of state of MgSiO₃ post-perovskite is in excellent agreement with the latest observed values. Based on the first-principles study and the Debye model, the thermal properties including the Debye temperature, the heat capacity, the thermal expansion, and the entropy are obtained in the whole pressure range from 0 to 150 GPa and temperature range from 0 to 2000 K.

Based on the general model of thermally-driven Brownian motors, an equivalent cycle system is established and the Onsager coefficients and efficiency at the maximum power output of the system are analytically calculated from non-equilibrium thermodynamics. It is found that the Onsager reciprocity relation holds and the Onsager coefficients are affected by the main irreversibilities existing in practical systems. Only when the heat leak and the kinetic energy change of the particle in the system are negligible, can the determinant of the Onsager matrix vanish. It is also found that in the frame of non-equilibrium thermodynamics, the power output and efficiency of an irreversible Brownian motor can be expressed to be the same form as those of an irreversible Carnot heat engine, so the results obtained here are of general significance. Moreover, these results are used to analyze the performance characteristics of a class of thermally-driven Brownian motors so that some important conclusions in literature may be directly derived from the present paper.

In this paper, some criteria are derived for global robust asymptotic stability of a class of interval neural networks with multiple constant or time-varying delays via the Lyapunov–Krasovskii stability theory for functional differential equations and the linear matrix inequality (LMI) approach. The main results are applied to the uncertain systems with single delay, and several new criteria to determine the asymptotical convergence of these systems are obtained. Numerical examples are also given to show the effectiveness of our results.

A passive quench circuit is used to study the punch-through characters of avalanche photodiodes under the Geiger mode. The photocurrent–voltage curve indicated clearly the punch-through voltage while the dark current–voltage curve is insensitive to the punch-through. The experiments demonstrate different distributions of the carries. The dark carriers counts increase much faster than the photo-carriers counts due to the different collection efficiency. A proper selection of the bias can increase the signal-to-noise ratio (SNR) of the single photon detector.

Using the complete discrimination system for polynomial method, we study the (2+1)-dimensional Davey–Stewartson equation and obtain the classifications of all its envelope traveling wave solutions. This is very convenient in practice to give the corresponding solutions for the concrete parameters.

Nanocrystalline MgCuZnFe₂O₄ and BaTiO₃ powders were synthesized using the microwave hydrothermal (M-H) method at 160°C for 45 min for the preparation of xBaTiO₃+(1-x)MgCuZnFe₂O₄. The nanopowders were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The particle size of the powders was found to be ~30 and ~40 nm for MgCuZnFe₂O₄ and BaTiO₃, respectively. The nanopowders were mixed at different weight percentages and densified at 910°C for 30 min using the microwave sintering method. The sintered composites were characterized using XRD and scanning electron microscopy (SEM). The density of the composites varies 93–96% of theoretical density. The density of the present composites increases as the weight percentage of BaTiO₃ content increases. The frequency variation of dielectric constant (ε), dissipation factor (D), initial permeability (μ_i) and quality factor (Q) were measured from 1 kHz to 1 MHz.