Theoretical Prediction of an Antimony-Silicon Monolayer $$(\hbox {penta-Sb}_{2}\hbox {Si})$$: Band Gap Engineering by Strain Effect

In this paper, using a first principles calculation, a two-dimensional structure of silicon-antimony named penta-Sb\(_{2}\)Si is predicted. The structural, kinetic, and thermal stabilities of the predicted monolayer are confirmed by the cohesive energy calculation, phonon dispersion analysis, and first principles molecular dynamic simulation, respectively. The electronic properties investigation shows that the pentagonal Sb\(_{2}\)Si monolayer is a semiconductor with an indirect band gap of about 1.53 eV (2.1 eV) from GGA-PBE (PBE0 hybrid functional) calculations which can be effectively engineered by employing external biaxial compressive and tensile strain. Furthermore, the optical characteristics calculation indicates that the predicted monolayer has considerable optical absorption and reflectivity in the ultraviolet region. The results suggest that a Sb\(_{2}\)Si monolayer has very good potential applications in new nano-optoelectronic devices.     

Synthesis and physical properties of un- and Zn-doped Ag2S nanoparticles

This study is devoted to the sonochemical synthesis of un- and Zn-doped silver sulfide (Ag₂S) nanostructures and evaluation of the parameters that affect its structural, morphological and optical properties. To unravel any changes in the characteristics of the particles, the XRD and FESEM techniques, in addition to photoluminescence (PL), Raman and UV–Vis–NIR spectroscopies, were applied. According to the analyses, 15?min sonication using 200?W power can provide the highest quality of the Ag₂S crystals. Moreover, it was found out that Zn doping shifts the XRD peaks of Ag₂S to higher angles and declines crystallinity of the samples while it does not change the spherical shape of the Ag₂S particles. The other impact of Zn presence in the crystal lattice of Ag₂S was declared to be increasing the size of the Ag₂S nanostructures. Importantly, based on the PL results, the un- and Zn-doped Ag₂S particles present several emission bands lying in the visible spectrum of light due to their specific optical near band emission (NBE) and crystal defects. As the Tauc plots spectra demonstrated, increasing the Zn concentration decreases the optical band gap energy of the Ag₂S nanostructures. Also, the Raman results unraveled the impact of synthesis conditions on the optical and crystalline properties of the grown structures.     

Second Comment on: ‘‘Characterization of Micro-roughness Parameters in Titanium Nitride Thin Films Grown by DC Magnetron Sputtering’’ [J Fusion Energ DOI 10.1007/s10894-012-9534-4]

At recent comment written by [A. Gelali, A. Shafiekhani, A. Ghorbani, A. Ahmadpourian. J. Fusion Energ. DOI: 10.1007/s10894-012-9542-4] that is a comment on [S. Solaymani, A. Ghaderi, N. B. Nezafat. J. Fusion Energ. DOI: 10.1007/s10894-012-9534-4] some clear and unavoidable errors can be seen. These issues will be discussed by the present brief communication.     

Effect of Si and Ge Surface Doping on the Be<Subscript>2</Subscript>C Monolayer: Case Study on Electrical and Optical Properties

The electronic and optical properties of X (Si, Ge) doped Be₂C monolayer has been investigated using the all-electron full potential linear augmented plane wave (FP-LAPW + lo) method in a scalar relativistic version as embodied in the Wien2k code based on the density functional theory. Using cohesive energy calculation, it has been shown that the Si and Ge doped to Be₂C monolayer have stable structures and the doping processes modified the direct band gaps. The calculated electronic band structure confirm the direct band gap nature since the conduction band minimum and the valence band maximum are located at the center of the Brillouin zone. The total and partial density of states help to gain further information regarding the hybridizations and the orbitals which control the energy band gap. The calculated optical properties help to gain deep insight into the electronic structure. Our calculated results indicate that the X (Si, Ge) doped Be₂C monolayer can be have potential application in optoelectronics devices.     

A numerical approach for MHD Al2O3–TiO2/H2O hybrid nanofluids over a stretching cylinder under the impact of shape factor

In this research, the heat transfer and magnetohydrodynamic stagnation point flow of a (Al₂O₃–TiO₂/H₂O) hybrid nanofluid past a stretching cylinder under the impact of heat generation, nonlinear thermal radiation, and nanoparticles shape factor has been analyzed using the Runge‐Kutta‐Fehlberg fifth order numerically method. The impact of changing diverse parameters, such as nanoparticles shape factor, named hexahedron and lamina, on temperature and velocity profiles and induced magnetic field, has been explored. The main motivation of this article is using hybrid nanoparticles to improve heat transfer. The novel findings of the current research illustrate that the Lorentz force produced by increasing magnetic field parameter () causes a decline in velocity profile; also increasing solar radiation, shape factor and the use of hybrid nanoparticles caused increment in the temperature profile. Furthermore, the lamina nanoparticle shape has more impact on Nusselt number () compared with hexahedron‐shaped nanoparticle.     

Comment on: “secure direct communication based on ping-pong protocol” [Quantum Inf. Process. 8, 347 (2009)]

The crucial issue of quantum communication protocol is its security. In this paper, the security of a secure direct communication based on ping-pong protocol [Chamoli A, Bhandari CM, Quantum Inf Process 8, 347 (2009)] is analyzed. It is shown that in this protocol any dishonest party can obtain all the other one’s secret message with zero risk of being detected by using a special type of attack, i.e., using fake entangled particles (FEP attack). Finally, a simple improvement to resist this attack is proposed.     

Impact of heat,power and hydrogen generation on optimal placement and operation of fuel cell power plants

In this paper, a stochastic model is proposed for planning the location and operation of Fuel Cell Power Plants (FCPPs) as Combined Heat, power, and Hydrogen (CHPH) units. Total cost, emissions of FCPPs and substation, and voltage deviation are the objective functions to be minimized. Location and operation of FCPPs as CHPH are considered in this paper while their investment cost is not taken into account. In the proposed model, indeterminacy refers to electrical and thermal loads forecasting, pressure of oxygen and hydrogen, and the nominal temperature of FCPPs. In this method, scenarios are produced using roulette wheel mechanism and probability distribution function of input random variables. Using this method, the probabilistic problem is considered to be distributed as some scenarios and consequently probabilistic problem is considered as combination of some deterministic problems. Considering the nature of objective functions, the problem of locating and operating FCPPs as CHPH is considered as a mixed integer nonlinear problem. A Self Adaptive Charged System Search (SACSS) algorithm is employed for determining the best Pareto optimal set. Furthermore, a set of non-dominated solutions is saved in repository during simulation procedure. A 69-bus distributed system is used for verifying the beneficiary proposed method.     

Elastic and optical properties of zinc-blende CrSb and its effective mass

The elastic, optical, and effective mass properties of CrSb in zinc-blende（ZB） phase were investigated.The calculations were carried out using the full-potential linearized augmented plane wave plus local orbital according to the density functional theory. The results of elastic calculations by generalized gradient approximation and local density approximation approximations indicate that ZB CrSb is a ductile material and its Debye temperature is rather low. Band structure and density of state calculations introduce the ZB CrSb as a half-metal with spin polarization of100 %. In metal state, 16 th and 17 th bands cut off the Fermi level. Calculations study the effective mass, Fermi velocity,and Fermi surface at 16 th and 17 th bands. In continue,optical quantities such as dielectric function, energy loss function, and optical conductivity were investigated.     

Numerical treatment of magneto Carreau nanofluid over a stretching sheet considering Joule heating impact and nonlinear thermal ray

In this essay, the magnetohydrodynamic flow of a Carreau nanoliquid upon a radiative stretching plate has been reviewed. The impacts of Joule heating and thermal ray are considered. The thermophoresis phenomenon and Brownian motion are applied to model nanoparticles (Buongiorno's model). Governing equations are solved numerically using Runge‐Kutta‐Fehlberg 4.5 after the transformation of partial differential equations into ordinary differential equations. In the obtained outcomes of investigating the impacts of different parameters on the change in velocity, concentration, and temperature profiles for two cases of shear‐thinning liquid and shear thickening liquid are reported as diagrams. Also, in the final segment of this essay, the impacts of diverse parameters on the skin friction coefficient and the local Nusselt number are investigated. The novel findings of current research illustrate that the values of local Nusselt number and surface drag force for shear thickening liquid are higher than shear‐thinning liquid. Also, the temperature profile has direct relationships with thermal radiation and magnetic field.