Band 75, Heft 10

The Snyder-de Sitter (SdS) model which is invariant under the action of the de Sitter group, is an example of a noncommutative space-time with three fundamental scales. In this paper, we considered the massless Dirac fermions in graphene layer in a curved Snyder space-time which are subjected to an external magnetic field. We employed representation in the momentum space to derive the energy eigenvalues and the eigenfunctions of the system. Then, we used the deduced energy function obtaining the internal energy, heat capacity, and entropy functions. We investigated the role of the fundamental scales on these thermal quantities of the graphene layer. We found that the effect of the SdS model on the thermodynamic properties is significant.

In this paper, we study the second harmonic generation and its interaction with the fundamental mode in a magnetised dense positron-ion plasma interacting with laser pulses. It has been shown that different harmonics propagate with different phase velocities. The gradual evolution of the fundamental wave into higher harmonics is studied, and the conversion efficiency is calculated. Dependence of conversion efficiency on wavenumber shifts and the applied magnetic field has also been examined.

The primary motive of this study is to examine boundary layer flow of Carreau fluid over a convectively heated disk stretching with nonlinear velocity. The flow is assumed to be two dimensional. Moreover, viscous dissipation possessions are taken into description. The dominating nonlinear differential equations involving partial derivatives are changed into nonlinear differential equations involving ordinary derivatives by applying suitable transformations. Numerical outcomes for velocity and temperature are obtained from MATLAB’s built-in solver bvp4c and presented graphically and in tabular form.

Spontaneous localisation is a falsifiable dynamical mechanism which modifies quantum mechanics and explains the absence of position superpositions in the macroscopic world. However, this is an ad hoc phenomenological proposal. Adler’s theory of trace dynamics, working on a flat Minkowski space-time, derives quantum (field) theory and spontaneous localisation, as a thermodynamic approximation to an underlying noncommutative matrix dynamics. We describe how to incorporate gravity into trace dynamics, by using ideas from Connes’ noncommutative geometry programme. This leads us to a new quantum theory of gravity, from which we can predict spontaneous localisation and give an estimate of the Bekenstein-Hawking entropy of a Schwarzschild black hole.

A variational principle enabling one to compute individual Floquet states of a periodically time-dependent quantum system is formulated, and successfully tested against the benchmark system provided by the analytically solvable model of a linearly driven harmonic oscillator. The principle is particularly well suited for tracing individual Floquet states through parameter space, and may allow one to obtain Floquet states even for very high-dimensional systems which cannot be treated by the known standard numerical methods.

This article presents the design and analysis of 4-hexyl-4′-biphenylcarbonitrile (6CB) nematic liquid crystal (NLC)–based rectangular patch antenna for S-band and C-band communication applications. Two glass substrates with permittivity of 6.4, loss tangent of 0.01 and thickness of 1 mm each with 21 × 25 mm 2 and 19 × 19 mm 2 dimension has been used, and 0.005 mm air gap has been placed to fill 6CB NLC. A rectangular patch of 10 × 11 mm 2 size has been considered over the top substrate to achieve the application specific bands. The designed antenna model-1 with air gap is resonating at 5 GHz (4.01–7.85 GHz) with minimum S 11 of −24.2 dB. The proposed antenna model-2 is filled with 6CB NLC in the air gap between glass substrates is resonating at 3.3 GHz (2.61–4.45 GHz) with minimum S 11 of −29.75 dB. Antennas of both air gaps filled, and liquid crystal material filled models are fabricated and tested through combinational analyser for validation. The correlation between transmitted and received signals of the antenna models are analysed with time domain analysis by taking the identical antennas in face to face and side by side condition. The simulated results from HFSS electromagnetic tool and fabricated antennas results in chamber are exhibiting good agreement with each other.

The structure, elastic, electronic and optical properties of two-dimensional (2D) MI 2 (M = Pb, Ge, Cd) under strain are systematically studied by the first-principles method. It is proved that the monolayer structure of 2D-MI 2 is stable by phonon spectra. Moreover, the large ideal strain strength (40%), the large range of strain and the elastic constants of far smaller than other 2D materials indicate that the single-layer PbI 2 and GeI 2 possess excellent ductility and flexibility. By applying appropriate strain to the structure of 2D-MI 2 , the band gaps of single-layer MI 2 can be effectively controlled (PbI 2 : 1.04 ∼ 3.03 eV, GeI 2 : 0.43 ∼ 2.99 eV and CdI 2 : 0.54 ∼ 3.36 eV). It is found that the wavelength range of light absorbed by these three metal iodides is 82–621 nm, so 2D-MI 2 has great absorption intensity for ultraviolet light in a large wavelength range, and the strain of structure can effectively regulate the optical parameters.

Thin films of chemical bath deposited tin antimony sulphide (Sn 2 Sb 2 S 5 ) were tuned by varying the deposition time between 1 and 3 h, and postdeposition heat treatments. The films were grown on soda lime glass (SLG) and on molybdenum glass (Mo-SLG) substrates, respectively. The film thickness increased with deposition time up to 2 h and decreased thereafter. Structural analysis from X-ray diffractometry showed that the films were single phase. This was corroborated by X-ray photoelectron spectroscopy (XPS) analysis. Energy-dispersive spectroscopy results give antimony/sulphur (Sb/S) ratio and antimony/tin (Sb/Sn) ratio that increased with deposition time in the SLG substrates only. Optical constants extracted from optical spectroscopy measurements give optical absorption coefficient ( α ) > 10 4  cm −1 , and direct energy bandgap with values in the range 1.30 to 1.48 eV. The Hall effect measurements performed on films grown on the SLG substrates indicated that the films were p-type electrical conductivity with electrical resistivity in the range 10 3 to 10 4  Ωcm. The films grown on the Mo-SLG served as absorber layers to fabricate thin film heterojunction solar cell devices in the substrate configuration with a cadmium sulphide (CdS) window partner. The best device yielded a short-circuit current density of 20 mA/cm 2 , open-circuit voltage of 0.012 V and a solar conversion efficiency of 0.04%.