Volume 76, Issue 6

How to obtain the high signal intensity harmonic spectra with the single harmonic radiation path contribution becomes an important issue in the investigations of the high-order harmonic generation and attosecond science. In this paper, through the nonhomogeneous multicolor laser beams optimization, the best time-spatial laser waveforms, including the positive and negative time-spatial waveforms, to produce the harmonic spectra can be found. As a result, the harmonic plateaus with the single harmonic radiation path contribution and with the enhancement of several orders of magnitudes can be obtained, which can support the generation of the isolated pulses with the durations of 29 as. The physical mechanism behind the improvement of the harmonic spectra is given by the time-spatial profile analyses of the laser pulses and the harmonic spectra.

This paper focusses on developing two species, where only prey species suffers by a contagious disease. We consider the logistic growth rate of the prey population. The interaction between susceptible prey and infected prey with predator is presumed to be ruled by Holling type II and I functional response, respectively. A healthy prey is infected when it comes in direct contact with infected prey, and we also assume that predator-dependent disease spreads within the system. This research reveals that the transmission of this predator-dependent disease can have critical repercussions for the shaping of prey–predator interactions. The solution of the model is examined in relation to survival, uniqueness and boundedness. The positivity, feasibility and the stability conditions of the fixed points of the system are analysed by applying the linearization method and the Jacobian matrix method.

Due to the advantageous property of reduction of load friction, low wear and good damping characteristics, journal bearings are widely used in industry. They are equipping various rotating machineries like small electrical motors to large generators, internal combustion engines, centrifugal pumps, turbine shaft of most jet engines, crankshaft of an automobile engines, etc. In this paper, static and dynamic performances of ferrofluid (FF) lubricated long journal bearing are studied using rotational and translational approach of the journal. Here, FF is controlled by the transverse uniform magnetic field. The modified Reynolds equation is derived by considering FF flow behaviour given by Shliomis and continuity equation in the film region. The dimensionless expressions for load-carrying capacity, frictional force and coefficient of friction are studied for static case, while the dimensionless expressions for stiffness coefficients and damping coefficients are studied for dynamic case. It is observed that comparing with conventional lubricant the bearing performance is significantly modified in the present analysis.

In this paper, we have studied two different mechanisms of nonreciprocal and asymmetric transmission in the one-dimensional asymmetric optical system composed of parity-time (PT) and magneto-optical materials with different defect layers. It is shown that there are three pairs of nonreciprocal dispersive curves with the perfect transmission in the three different band gaps, when the defect layer is filled with normal material. When the defect layer is filled with magneto-optical material, the transmittivity of two nonreciprocal frequencies can be modulated by the magnitude and direction of the defect layer’s external magnetic field and appears to be asymmetric nonreciprocal transmission. One-way frequency corresponding to one direction has extraordinary transmission, and the other one-way frequency corresponding to the opposite direction is suppressed. When the defect layer is filled with loss or gain material, the transmittivity of two nonreciprocal frequencies can be amplificated or attenuated simultaneously, respectively. The nonreciprocal propagation is originated from the resonant modes in the system due to the defect layer, and the nonreciprocal and asymmetric transmission is determined by the broken PT system due to magneto-optical and gain/loss material in the defect layer. Such controllable and asymmetric nonreciprocal propagation in the composite system may have broad potential applications in nonreciprocal communication and integration devices.

The non-relativistic full potential linearized augmented plane wave (FP LAPW) method was applied to investigate the structural, electronic, optical and thermodynamic properties of (ZB)-AlP, AlBi, InP and InBi compounds and their ternary Al x In 1− x P, Al x In 1− x Bi, AlP x Bi 1− x and InP x Bi 1− x and the ordered Al x In 1− x P y Bi 1− y quaternary alloys. For the exchange-correlation potential, the LDA, GGA and WC-GGA have been used to calculate structural parameters. The TB-mBJ approximation was used to compute the band structures. Our results for binary compound agree well with available data found in literature. The lattice constants and the bulk modulus versus compositions x and y deviate from the linearity. All quaternary alloys are semiconductors with direct band gap with the exception for Al 0.25 In 0.75 P 0.25 Bi 0.75 and Al 0.25 In 0.75 P 0.50 Bi 0.50 , which exhibit a half metallic character (the band gap tends to zero). Furthermore, the optical properties such as the dielectric constants, refractive index, absorption, reflectivity and the energy loss have been calculated and analysed in the energy range varying from 0 to 14 eV. At the end, we have investigated some thermodynamic properties, where the lattice constants, the Debye temperature θ D , the heat capacity C V and the entropy S were carried out, plotted and discussed.

Employing plant extracts to obtain nanomaterials is an ecofriendly and highly appreciated synthetic approach. In this work a simple, green chemistry method, based on sol–gel, was used for ZnO nanoparticles synthesis by using two Sudanese medicinal plant extracts: Adanosia digitata (ZnO-A) and Balanites aegyptiaca (ZnO-B) under ultrasonic energy. The X-ray diffraction (XRD) revealed the formation of wurtzite hexagonal ZnO nanostructures, while the scanning electron microscopy (SEM) analysis displayed their diverse morphologies. The X-ray photoelectron spectroscopy (XPS) data showed the impact of extract via the variation in of the O1s and Zn2p 3/2 and Zn2p 1/2 orbitals binding energy of Zn–O. The UV-visible investigation indicated a variation of bandgap energy ( E g ), where the ZnO nanoparticles displayed the lowest E g . The synthesized nanomaterials have exhibited high photocatalytic efficiency towards the methylene blue (MB) dye. The findings revealed the possibility of obtaining nanoparticles with tailored properties by using plants extracts.

The elastic and ultrasonic properties have been evaluated at room temperature between the pressure 0.6 and 10.4 GPa for hexagonal closed packed (hcp) hafnium (Hf) metal. The Lennard-Jones potential model has been used to compute the second and third order elastic constants for Hf. The elastic constants have been utilized to calculate the mechanical constants such as Young’s modulus, bulk modulus, shear modulus, Poisson’s ratio, and Zener anisotropy factor for finding the stability and durability of hcp hafnium metal within the chosen pressure range. The second order elastic constants were also used to compute the ultrasonic velocities along unique axis at different angles for the given pressure range. Further thermophysical properties such as specific heat per unit volume and energy density have been estimated at different pressures. Additionally, ultrasonic Grüneisen parameters and acoustic coupling constants have been found out at room temperature. Finally, the ultrasonic attenuation due to phonon–phonon interaction and thermoelastic mechanisms has been investigated for the chosen hafnium metal. The obtained results have been discussed in correlation with available findings for similar types of hcp metals.

To estimate the structural, electronic, elastic and dynamic properties of ZrInAu and ZrSnPt compounds, the density functional theory within the general gradient approximation was used. The computed lattice parameters, bulk modulus and the derivation of bulk modulus with respect to pressure were displayed and compared with the theoretical result. The indirect band gap for ZrInAu was found to be 0.48 eV, and for ZrSnPt the indirect band gap was found as 1.01 eV. Elastic stiffness constants, bulk, shear and Young’s module, Poisson’s coefficients and Zener anisotropy factor are calculated. Elastic properties showed that the ZrSnPt compound is more durable than the ZrInAu compound. Phonon distribution curves and density of states were investigated using a density functional perturbation theory. Both ZrInAu and ZrSnPt compounds were demonstrated to be dynamically stable. The results of this study were obtained for the first time in the literature. These results will make an important contribution to the literature.