Modern Physics Letters B

A sliding discharge (SD) plasma actuator designed for the control of a circular cylinder wake is examined experimentally in this paper. This kind of discharge demonstrates a thicker and higher maximum speed wall jet than a Dielectric Barrier Discharge (DBD). The plasma actuator mounted strategically on the rear part of the cylinder model can induce either a downward or upward jet into the flow around the circular cylinder by simply adjusting the electrodes’ electrical circuits. Experiments were performed in a low-speed and low-turbulence wind tunnel at Reynolds numbers between 7000 and 24,000 based on the diameter of the circular cylinder. Wake measurements by particle image velocimetry (PIV) showed that both the mean velocity and the turbulence level in the cylinder wake were modified under the plasma actuation. Reducing or increasing the cylinder drag force estimated from the velocity field could be realized by changing plasma actuation directions. They showed that up to 30% drag reduction and 24% drag increase were obtained with the downstream and upstream actuation respectively at the continuous plasma blowing. The efficiency of flow control was found to be about 1.8% for drag reduction. This study suggests that an appropriate arrangement of an SD actuator can practically suppress flow separation or enhance flow mixing.

In this theoretical study, a path was adapted to investigate the redshifting of the TiO₂ absorption edge by molybdenum (Mo), yttrium (Y) and nitrogen (N) doping. The geometrical model, band gap and photo response were noted in the developed model of anatase TiO₂. The tri-doped model showed very small modification in the structure as compared to a reference TiO₂ model. The 3d states of Mo mix up with the 3d states of Ti, resulting in the reduction of band gap. The Y 2p states were introduced around the middle of the band gap of Y-doped TiO₂. Good reduction was found in the gap of tri-doped TiO₂ model and the created states were occupied. The doping of N via oxygen (O) substitution in tri-doped model resulted in the band gap reduction by introducing states in the band gap due to the mixing of N 2p and O 2p states.

A complex line beam, whose intensity distribution is uniform along a line shape and phase distribution is linearly gradient, can be applied in automatic directional transportation and optical separation of microparticles. Generally, complex amplitude beam shaping methods are used to control both the amplitude and phase of an output beam with a single phase-only element. However, for the complex line beam, although the phase gradient can be controlled well, the intensity of the beam is unevenly distributed, i.e. most of the energy of the beam is distributed in the two ends of the lateral direction. In this paper, we propose an intensity-compensation method based on the complex amplitude beam shaping method, in which the target intensity distribution of the output beam is modulated with a Gaussian profile on purpose. The simulation and experimental results show that the intensity uniformity of the complex line beam has been increased by 80.6% while the phase of the beam has been controlled as linearly gradient.

The energetically favorable crystal structures for stoichiometric ratio as 1:1 (CN) are studied systematically based on the density functional theory combined with the particle-swarm optimization (PSO) method. The predicted favorite phase Pnnm-C₄N₄ (Pnnm, No. 58) is in excellent agreement with the results of experimental and theoretical studies. The predicted Pnnm-C₄N₄ phase exhibits the highest bulk modulus and shear modulus of 351 and 335 GPa, respectively. Those are comparable to that of 376 and 390 GPa for c-BN. The calculated phonon dispersions indicate that the Pnnm-C₄N₄ phase is dynamically stable at ambient conditions, while others require high-pressure condition. The calculated DOS illustrates that the Pnnm-C₄N₄ phase is an insulator with indirect band gap of 3.746 eV. Moreover, the high hardness of 54 GPa is estimated to the most stable Pnnm-C₄N₄ phase, indicating it is a potentially superhard material.

The most prominent dynamic characteristic of metamaterials is that they possess the frequency pass bands and band gaps. In the bandgap, the elastic waves will attenuate significantly, and this property is potentially used to control low-frequency vibrations in civil engineering. To open the low-frequency bandgap of the Timoshenko beam, inerter-based dynamic vibration absorbers (IDVAs) are arranged periodically in the beam. An analytical methodology based on transfer matrix method was developed to predict the flexural wave dispersion characteristics, and was validated by test and numerical experiments. The band gaps can be simultaneously tuned by the parameters of the IDVAs, including spring stiffness, inertance and attached mass. Moreover, the band gaps generated by single IDVAs are independent of each other, and a super-wide bandgap can be achieved by splicing the band gaps for metamaterial beams with graded IDVAs. Explicit formulas with respect to the parameters of IDVAs have been developed to determine the condition of bandgap merging, which can broaden the bandwidth effectively. Finally, a computer-based program was presented to determine the reasonable design parameters.

In this work, we execute the generalized exponential rational function (GERF) method to construct numerous and a large number of exact analytical solitary wave solutions of the nonlinear extended Zakharov–Kuznetsov (EZK) dynamical equation in (3+1)-dimensions. The implemented method is one of the best, most reliable, and efficient techniques in the present time for determining numerous closed-form wave analytic solutions to NPDEs. We have accomplished a variety of solitary wave solutions related to some arbitrary parameters under various family cases. These solutions take the following forms based on the free parameters chosen: exponential functions form, trigonometric functions form, and hyperbolic functions form. The obtained solutions are dissimilar and entirely new from the previous findings available in the literature. The dynamics of obtained solutions, namely, soltion, singular soliton wave, a periodic wave, bell-shape, anti-bell-shape wave, breather wave, and multisoliton wave solutions by the special-choice of parameters, are shown graphically in 3D, 2D, and corresponding density profiles. The results demonstrate that the employed computational strategy is efficient, direct, concise, and can be executed in various complex phenomena with symbolic computations. Furthermore, it is revealed that the generalized exponential rational function technique can be effectively utilized for several other NPDEs in engineering, sciences, and mathematical physics.

In this paper, we give the form of $q$-cmKP hierarchy generated by the gauge transformation operator $T_{n+k}$. We show a necessary and sufficient condition to reduce the generalized $q$-Wronskian solutions from the $q$-mKP hierarchy to generalize $q$-Wronskian solutions of $M$-component $q$-cmKP hierarchy.

This paper presents the stronger moment conditions which are sufficient to show the finiteness of the first collision time between $N$-dimensional Gaussian jump particle and another $N$-dimensional Brownian particle in a fractured medium. To obtain these conditions, we use the triangular arrays of the random sequence vector which gives all probable positions of the first collision at any time. This study is an extension of the analytical study which is detailed in Alzulaibani and El-Hadidy [Int. J. Mod. Phys. B 33(28) (2019) 1950334] using the uniform integrability conditions.