116 research outputs found
Investigation of stability, electronic, optical and mechanical properties of honeycomb BeN2 monolayer: A DFT study
No full textIn this work, from the DFT calculations, we investigate the physical properties of the 2D BeN2 monolayer with a honeycomb lattice. The dynamic stability of the BeN2 monolayer is demonstrated by the presence of real modes in its phonon spectrum. The theoretical electronic band structure and density of states reveal the semiconductor nature of the BeN2 sheet. The semi-local PBE results show a bandgap of 1.32 eV, while HSE hybrid functional computation yields a higher bandgap of 3.16 eV. Our results suggest that HSE approximation employing ultrasoft pseudopotentials can accurately predict the most important electronic property of BeN2 structure that is not only in excellent agreement with the most accurate GW predictions but also better than those reported before with the same functional. The wide-bandgap semiconductor properties make BeN2 nanostructure a highly promising 2D material for innovative applications in nanoelectronic devices. The optical analysis obtained from HSE calculations reveals that the BeN2 nanostructure has optical absorption in the violet range of visible light with a low static dielectric constant of 2.55. Further, our results indicate that this material presents low bulk and shear moduli of 61.3 and 12.0 N/m, respectively
First-principles calculations to investigate strain-tunable electronic bandgap of black phosphorus-structured nitrogen with desirable optical and elastic properties
No full textAdsorption of Polylactic-co-Glycolic Acid on Zinc Oxide Systems: A Computational Approach to Describe Surface Phenomena
No full textZinc oxide and polylactic-co-glycolic acid (ZnO-PLGA) nanocomposites are known to exhibit different biomedical applications and antibacterial activity, which could be beneficial for adding to wound dressings after different surgeries. However, possible cytotoxic effects along with various unexpected activities could reduce the use of these prominent systems. This is correlated to the property of ZnO, which exhibits different polymeric forms, in particular, wurtzite, zinc-blende, and rocksalt. In this study, we propose a computational approach based on the density functional theory to investigate the properties of ZnO-PLGA systems in detail. First, three different stable polymorphs of ZnO were considered. Subsequently, the abilities of each system to absorb the PLGA copolymer were thoroughly investigated, taking into account the modulation of electrical, optical, and mechanical properties. Significant differences between ZnO and PLGA systems have been found; in this study, we remark on the potential use of these models and the necessity to describe crucial surface aspects that might be challenging to observe with experimental approaches but which can modulate the performance of nanocomposites
The Impact of Corporate Income Tax Rates on Research and Development Expenditures of Small- to Medium-sized Enterprises
No full textElectronic structure of 1,4-Phenylenediacrylic acid on graphene and bilayer graphite: from experiments to DFT and ab initio molecular dynamics simulations
No full textIn this work, density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations were implemented to expand the knowledge about the interaction of graphene and bilayer graphite surface with 1,4-Phenylenediacrylic acid (C12H10O4). The DFT calculations demonstrated that C12H10O4 molecule has an opening band gap of 0.0062 eV at the top position over the graphene sheet higher than the cross and bridge sites with lower band gaps of 0.0050 eV and 0.0046 eV, respectively. The HOMO-LUMO splitting calculations confirmed more mixture of LUMO states of the C12H10O4 and graphene in the carbon-carbon double bond in vinyl segment and the COOH functional group in the C12H10O4@Graphene (top) adsorption site. Then, the increasing of the molecule units on the graphene substrate resulted in a higher electronic band gap of 0.0068 eV and LUMO energy level of 0.9528 than 0.9383 eV for the monomer ones. The AIMD calculations were used to mimic the self-assembly process of the C12H10O4 molecules on the graphene layer at room temperature, remarking high adsorption capabilities of the latter one. The imaginary and real parts of dielectric constant have been evaluated and for all cases the maximum intensity of the main first peak has been found at 2.43 THz. The results of the static part of dielectric constant showed high Re(ω) for the adsorption of C12H10O4 monomers on the graphene surface, while by increasing the number of C12H10O4 units Re(ω) resulted remarkably reduced. The maximum value predicted is 7817 in C12H10O4@Graphene (cross) along the in-plane xx polarization and 2747 for 4C12H10O4@Graphene along the in-plane yy directions. Finally, the adsorption of C12H10O4 layer on the AB stacking bilayer graphite has been considered to simulate the experimental scanning tunnelling microscopy (STM) image of self-assembled C12H10O4 on highly oriented pyrolytic graphite (HOPG) surface. The zero-band gap has been predicted since the electronic structure of graphene near the K point varies by increasing its thickness
Spectrum sharing of 80 MHZ channels for high altitude platform station with fixed satellite service uplink in the frequency range 5850-7075 MHZ
No full textSpectrum
No full textAbstract � HAPS is a new technology in the wireless communications field. The straightforwardness with which HAPS gets along with service providers will make this system a unique feature of future wireless networks. Most of the HAPS criteria have been well documented by the International Telecommunication Union (ITU) or subscribed to in World Radio Conferences (WRCs) periodicals. This procedure will prolong to function for various frequency ranges in future, most notably in WRC-12. Here, the emphasis is on HAPS spectrum sharing with FSS in the Frequency range 5850-7075 MHz. To clarify, FSS links are planted in the C-Band frequency range for tropical and subtropical regions, with high amounts of rain, which serve to condense the propagation attenuation. Furthermore, FSS uplink frequency ranges between 5925 and 6725 MHz. Therefore, FSS uplink intervenes with HAPS frequency range causing interference. This paper will assess and clarify the prospects of implementing HAPS gateway links in co- and adjacent channels of FSS uplink regarding MD and NFD techniques. 1
Two-dimensional analysis of the influence of windbreaks on airflow over a high-speed train under crosswind using lattice Boltzmann method
No full text This research is concerned with identifying the effects of windbreak geometry on attenuating aerodynamic loads that can be strong enough to disturb the running safety of high-speed trains. The idea is to suggest the proper geometry for the windbreaks that can make them more efficient and increase their overall performance. Generally speaking, the desired windbreak is the one that can minimize the aerodynamic forces on the surface of trains. In order to reach such an aim, the flow of air around an Intercity-Express 3 high-speed train has been estimated through a two-dimensional modeling by using the lattice Boltzmann method. The flow of crosswind that hits the train is considered as turbulent. The geometry of the windbreaks including the height, the slot, and the edge angles has been investigated. It has been concluded that the windbreak performance, among other parameters, is highly dependent on its height and edge angle. This research expedites the trail for finding suitable choices of windbreak geometries that can in turn provide a reliable degree of running safety of the railway fleet. </jats:p
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