# Physica Scripta

Online ISSN: 1402-4896
Print ISSN: 0031-8949
Discipline: Physics, Multidisciplinary
Aims and scope

Physica Scripta is an international journal dedicated to presenting novel and accessible research findings across the breadth of theoretical and experimental physics.

Recent publications
• Jamal suleiman
We report a new study of the X-ray absorption spectrum of Neon near the K-edge and near the KL-edge. The study is performed by calculating the transition probabilities and oscillator strengths for excitations from the ground state to singly and doubly excited states, the calculations were performed using multi-configurational Dirac-Fock (MCDF) method. Breit interaction between electrons and finite nuclear size effects were taken into account during the calculations, the transition probabilities were convoluted into Lorentzian line shape profiles. The results of the calculations were then compared to previous measurements of the X-ray absorption spectrum of Neon, good agreement was observed and many features in the spectrum were explained.

• Peng Zhang
• Zhiyao Ma
• Dengmei Li
Scanning electron microscope (SEM) is widely used in imaging rather than for thermometry. In this work, the temperature-dependent line-scan profiles for two systems (one gold (Au) nanorod (Au-NR) and one silicon (Si) nanorod (Si-NR) on Si substrate, respectively) were investigated by a simulation approach. Various electron signals (secondary electron (SE) and backscattering electron (BSE)) were recorded with different values of temperature at various primary electron (PE) energies. It is found that the SE line-scan profile varies with the temperature and the size of the NR. However, the BSE line-scan profile is almost unchanged with temperature for the Au/Si system, but remarkably varied for the Si/Si system. The deposited energies contributed by full electrons, PEs and cascaded electrons as functions of depth and radial direction at different temperatures for these two systems were also investigated. It was concluded that the influences of the temperature of a solid on the scattering processes of PEs and cascaded electrons are different. Possible mechanisms were systematically analyzed based on the theory of electron-solid interaction. Finally, the temperature effect on the size measurement based on a line-scan profile was also investigated through the regression to baseline method. It was found that the broaden value slightly increases with temperature. This work poses a potential possibility of measuring the temperature of nanostructures by acquiring the temperature-dependent line-scan profile by a standard SEM.

• Kamal A. Aly
Different 〖(GeZn)〗_(100-x) 〖Se〗_x (9≤x≤25 at.%) chalcogenide films have been thermally evaporated onto cleaned glass substrates. The film transmission (T) and reflection (R) spectra have been measured over the wavelength spectral range (0.3-2.5 m). The composition dependence of the optical band gap (Eg) has been illustrated and interpreted in the light of the Mott and Davies Model (MDM). The linear correlation between the changes in the optical band gap (Eg) and in the band tail parameter (∆√B) confirmed the disorder's decrease, which explains the observed increase in Eg values with increasing Se concentrations. The dispersion and Sellmeier parameters have been determined and well discussed. A clear blueshift was observed throughout the observed decrease in values of o and no and the observed shift of the absorption edge to the short wavelengths. The GZS films are transparent in the visible, near- and far-infrared, which makes these glasses suitable for VIS and infrared applications.

• Vien Vo
• H. N. Long
We suggest a low-scale model based on $A_4\times Z_4 \times Z_2$ symmetry and a global lepton number $U(1)_L$ symmetry capable of generating the current neutrino data. The neutrino mass smallness is reproduced by the linear seesaw mechanism. The model can explain the current observed pattern of lepton mixing in which the reactor and atmospheric angles get the best-fit values, and the solar angle and Dirac phase lie within $3\,\si$ limits. The obtained values of the sum of neutrino mass and the effective neutrino mass are below the present experimental limits.

• Ismail Burak Ates
• Sengul Kuru
• Javier Negro
In this paper, a simple method is proposed to get analytical solutions (or with the help of a finite numerical calculations) of the Dirac-Weyl equation for low energy electrons in graphene in the presence of certain electric and magnetic fields. In order to decouple the Dirac-Weyl equation we have assumed a displacement symmetry of the system along a direction and some conditions on the magnetic and electric fields. The resulting equations have the natural form to apply the technique of supersymmetric quantum mechanics. The example of an electric well with square profile is worked out in detail to illustrate some of the most interesting features of this procedure.

• Mohamed Elattar
• Olaf Brox
• Pietro Della Casa
• [...]
• Paul Crump
We present high-power GaAs-based broad-area diode lasers with a novel variant of the enhanced self-aligned lateral structure “eSAS”, having a strongly reduced lasing threshold and improved peak conversion efficiency and beam quality in comparison to their standard gain-guided counterparts. To realize this new variant (eSAS-V2), a two-step epitaxial growth process involving in-situ etching is used to integrate current-blocking layers, optimized for tunnel current suppression, within the p-Al 0.8 GaAs cladding layer of an extreme-triple-asymmetric epitaxial structure with a thin p-side waveguide. The blocking layers are thus in close proximity to the active zone, resulting in strong suppression of current spreading and lateral carrier accumulation. eSAS-V2 devices with 4 mm resonator length and varying stripe widths are characterized and compared to previous eSAS variant (eSAS-V1) as well as gain-guided reference devices, all having the same dimensions and epitaxial structure. Measurement results show that the new eSAS-V2 variant eliminates an estimated 89% of lateral current spreading, resulting in a strong threshold current reduction of 29% at 90 µm stripe width, while slope and series resistance are broadly unchanged. The novel eSAS-V2 devices also maintain high conversion efficiency up to high continuous-wave optical power, with an exemplary 90 µm device having 51.5% at 20 W. Near-field width is significantly narrowed in both eSAS variants, but eSAS-V2 exhibits a wider far-field angle, consistent with the presence of index guiding. Nonetheless, eSAS-V2 achieves higher beam quality and lateral brightness than gain-guided reference devices, but the index guiding in this realization prevents it from surpassing eSAS-V1. Overall, the different performance benefits of the eSAS approach are clearly demonstrated.

• Jie Guan
• Kang Li
• Nan Lu
• Cuiping Yang
Defect engineering and heterostructure construction are important approaches to modulate the properties of two-dimensional semiconductors. We introduced four phosphorene allotropes as the defective structures to construct the corresponding line defects and lateral heterostructures in black phosphorene. In all the constructed phosphorene systems, the P atoms at the boundaries will keep local threefold covalent bonding, forming clean one-dimensional interfaces and exhibiting a high stability. Electronic structure calculations show that all the constructed structures are semiconducting in absent of deep defect states and the band gap values can be regulated by introducing diﬀerent defective structures. Distinct distributions of the electronic frontier states are found in the diﬀerent line defect systems and both type-I and II band alignments can be formed in the semiconducting lateral heterostructures.

The work is devoted to the study of the current flow through a glass cylindrical discharge tube with a metal section. A hydrodynamic model of a one-component conductive liquid is considered. The parameters of the conductive liquid are set in accordance with the parameters of the discharge in neon at a pressure of 1 Torr and a current of 10 mA. It is shown that the presence of a metal section leads to a branching of the discharge current into a component flowing through the gas volume and a component flowing along the approximately equipotential metal surface. Two-dimensional distributions of the electric potential, electric field, and current density are obtained depending on the size of the metal section and the radius of the discharge tube. Based on the calculated electric field, the spatial distribution of excitation sources describing the emission of spectral lines and ionization is calculated. The occurrence of a space charge near the glass-metal interface is analysed.

In this manuscript, we construct a spherical thin shell wormhole in the background of the minimally coupled $f(R,~T)$ model. In this gravitational theory, $f$ is an arbitrary functional form that depends on the Ricci scalar $(R)$ as well as the trace of stress-energy tensor $(T)$. To continue our systematic analysis, we use a cut and paste approach to link two surfaces, i.e., interior and exterior. We find energy-momentum density along with surface pressure for $f(R,~T)$ gravitational $f(R,~T)= R+\alpha R^2+\lambda T$ model, by using the Lanczos equation. We utilize the polytropic equation of state to check the dynamical behavior of the wormhole. A standard potential approach is applied to check the stability of constructed wormhole with throat radius $a_0$. Graphical analysis shows that the stability regions of wormholes rely on the specific values mass $M$ to charge $Q$ ratio.

A three-dimensional broadband absorber structure was proposed based on the crossed-oval shape of graphene(COSG) on a wafer layout. This structure consisted of silicon/gold/silica wafer and a superstrate layer of graphene patterns in the form of crossed-ovals placed on top of the wafer. The effect of geometrical parameters on the absorption was studied. Results show that this structure can absorb over 99 % of the incoming light over a broad range of THz frequencies. The absorption peaks were fine-tuned by changing the geometrical and physical parameters. This property is vital and desirable in optical detectors, chemical sensors, and other optical devices.

The effect of anisotropic grain boundaries on the surface microstructure changes and deuterium retention behavior in tungsten under deuterium plasma irradiation were studied. The samples named as NDW and RDW were cut from RD × TD plane and TD × ND plane of a rolled W plate (ND: normal direction, RD: rolling direction, TD: transverse direction), respectively. The results suggest that both surface morphology and deuterium retention in the RDW samples are suppressed compared to that of NDW samples for 1 h and 25 h deuterium irradiation. For 1 h exposure, the total deuterium retention in the NDW samples is about 1.6 times as much as that of RDW. However, as the exposure time increased to 25 h, the total deuterium retention in the NDW sample is two times the height of RDW sample. The experimental results show that the special grain structure of RDW can alleviate the surface morphology changes and decrease the deuterium retention in tungsten, which is interpreted by the lateral stress model of blistering.

Compression and encryption are the two main steps generally used to ensure fast and secure transmission of digital images over public communication channels. Among the existing crypto compression approaches, those based on compressive sensing and chaotic systems possess good potential. Unfortunately, the present literature presents some limits including speed issue, security issue and reconstruction problem. These problems are mainly due to the poor performances of the measurement matrix exploited. Note that in some cases these measurement matrices are obtained from chaotic sequences with very poor dynamics. To solve this problem, we proposed in this paper, a novel image encryption scheme based on 2D compressive sensing, elliptic curves and a new septic jerk oscillator with multistability. The proposed scheme adopts the compression before encryption topology to reduce the processing time and is divided into two main parts. The first part concerns image compression using compressive sensing. The input image data is divided into 4 blocks. Then, each block is compressed using 2D compressing sensing based on the measurements matrices generated using chaotic sequences coming from the novel septic jerk system. Next, the compressed blocks are combined to form the compressed image. In the second part, to strengthen the security, elliptic curve theory is used to construct a simple and secure S-box for digital image substitution. This S-box is combined with the septic chaotic solutions to change the pixel’s positions and values of the compressed image. The analysis of simulation test indicates that the proposed cipher has good compression effect, good reconstruction capability even for low compression ratio, is fast and highly secure compared to some recent schemes. As such the proposed work can be exploited to compress and secure data in Wireless Body Area Network (WBAN) applications.

In the visible range at blue 455 nm, 482 nm, and red 670 nm under upconversion pumping at a wavelength of 1064 nm, spectroscopic characteristics, and transition rates in Tm3+ doped 0.53 ZrF4, 0.2 BaF2, 0.04 LaF3, and 0.03 AlF3 and 0.2 NaF (ZBLAN) glass matrix are described. The Judd-Ofelt theory is applied to calculate the contributions from electric and magnetic dipoles to the optical intensity parameters (Ωt), which are found to be as follows: Ω2 =1.4703± 0.0675, Ω4=0.7477± 0.0536, Ω6=0.6202± 0.0212. For transitions originating from the 1D2, 1G4, 2F2, 3F3, and 3F4 levels, branching ratios (β), radiative lifetimes (rad in ms units), and transition probabilities (in s-1) have been calculated. Additionally, we evaluated the optical gain at 455 nm, 467 nm and 670 nm, as well as the absorption/emission cross sections for the three visible transitions. According to the obtained results, the transition at 455 nm (1D23F4) had the largest emission cross section values compared to transitions at 482 nm (1G43H6) and 670 nm (3F23H6). Furthermore, the transition probability.is theoretically calculated for the ultraviolet (UV) range 172–283.8 nm. A good agreement is found between the calculations and the measurements for the visible range.

In this study, a tunable and optically transparent water-based wideband metamaterial absorber (MMA) is proposed and verified. By adjusting the thickness of the water layer, the conversion of the absorber absorption band from 7.4-22.4 GHz to 23.1-35.5 GHz can be achieved, which demonstrates the flexibility of MMA. Indium tin oxide (ITO) as the resonant and reflective layers of the material structure. Optically transparent polymethyl methacrylate (PMMA) is used as a medium container to encapsulate the water. Furthermore, the suggested MMA is polarization insensitive and has broad incident angle stability. Experiments verify the excellent properties of the proposed MMA. As a result, the suggested MMA has various applications in military and medical equipment optical windows.

The ITER Edge Thomson scattering (ETS) system provides electron temperature and density profile measurements in the ITER tokamak for plasma control. In collection optics, the front-end metallic first and second mirrors are expected to experience contamination with beryllium and tungsten degrading performance. Plasma cleaning based on a low-pressure radiofrequency discharge is expected to sputter contaminants. In the ETS, a water-cooled first mirror is combined with a powered electrode. Water cooling was realized as a notch filter for the driving frequency, and the electrode was grounded for a DC- voltage. A new breadboard reproducing the ETS mirror geometry was developed for experimental modelling. The notch filter uses equivalent cables. To understand the cleaning effect, ion energies and fluxes were measured in 40-50 MHz discharges in argon and helium at 1-10 Pa with and without the notch filter. Without a notch filter with minimum power losses, 2-4·1018 ions·m-2s-1 ion fluxes with energies of 100-140 eV were produced. With the notch filter, the peak ion energies were 30-50 eV. The power in the plasma was lower than 50 W with ion fluxes of – 1.5-1.9 1018 ions·m-2s-1. 53-m-long cable feeds equivalent to those of a real system were studied at 13-50 MHz and produced significant power loss: more than 95% at 40-50 MHz. A pre-matching element is essential to reduce power losses. A lower radiofrequency may be less sensitive to pre-matching and may be considered for mirrors without water cooling. A 40 MHz discharge is proposed for cleaning due to better stability, higher ion energies and possibly better uniformity. Powers in plasma in the range of hundreds of Watts may be needed to achieve ion fluxes suitable for cleaning. This requires more powerful components and shall be addressed in later experiments. The results are important for plasma cleaning in ETS and in other diagnostics where water-cooled first mirrors are used.

In this work, we analyze the incidence of gravitational decoupling through the extended minimal geometric deformation (e–MGD) approach in the framework of f(R, T ) gravity theory, applying it on a spherically symmetric and static charged isotropic matter distribution. Speciﬁcally, the well– known Krori–Barua toy model is translated to an anisotropic domain by deforming the complete space–time. To do so, the so–called θ–sector has been solved by using the mimic constraint for the radial pressure and a general equation of state relating the components of the θµνsource. A thoroughly study on the main salient features of the output such as density, radial pressure, transverse pressure and anisotropy factor is performed to check the feasibility of the model, in order to determine whether this structure can represent real celestial bodies such as neutron stars. Furthermore, the consequences of e–MGD on some relevant astrophysical parameters, that is, the total mass M, gravitational redshift z and time dilation dτ around the object are explored. It is found that the maximum mass provided by this toy model is M = 2.506M⊙, corresponding to the massive neutron stars.

Investigation of the effects of oxygen absorption on the two types of single walled silicon carbide nanotubes (SWSiCNTs) with different chiral angles were done. Our calculations were performed using density functional theory with quantum ESPRESSO and YAMBO codes. Changes in electrical and optical properties were analyzed after introducing two molecules of oxygen as absorbing gas to both armchair and zigzag nanotubes. Results demonstrated a new future by SWSiCNT in which oxygen absorption significantly closes the band gap which transformed the materials from semiconducting to metallic. This future revealed its potential for application as automobile gas switches for air conditioners. Results from optical calculations revealed that zigzag SiCNT is not optically potential above 20 eV, generally, the (6, 6) SWSiCNT demonstrate higher transmission with and without oxygen absorption in the ultraviolet region. The first absorption peaks appeared within the range of 1 eV to 3.4 eV for all systems, there is higher absorption by the oxygen absorbed (6, 6) SWSiCNT than the oxygen absorbed (6, 0) SWZSiCNT. This demonstrates that armchair form of SWSiCNT absorbs gases more than the zigzag form. The absorption peaks can be seen to fall above 3.5 eV and then rise again up to 10 eV, this behavior justifies the nanotubes potential in automobile day light sensors.

Strong nonlocality with genuine entanglement was first shown by Wang \emph{et al.} using sets of GHZ-like states in tripartite quantum systems [Phys. Rev. A \textbf{104}, 012424 (2021)]. However, it is an open problem whether there exists strong nonlocality with genuine entanglement in four or more partite systems. In this paper, we unify two different concepts of strong nonlocality introduced by Halder \emph{et al.} [Phys. Rev. Lett. \textbf{122}, 040403 (2019)] and by Zhang \emph{et al.} [Phys. Rev. A \textbf{99}, 062108 (2019)]. That is, we use a concept of $k$-strong nonlocality instead of these two different types of strong nonlocality. A set of orthogonal quantum states is $k$-strong nonlocal if it is locally irreducible in every $k$-partition. In fact, the strong nonlocality that is usually said is 2-strong nonlocality. The smaller the $k$ is, the stronger the nonlocality will be. A set of states is $k_{+}$-strong nonlocal if the strong nonlocality of this set is stronger than $k$-strong nonlocality but weaker than $(k-1)$-strong nonlocality. Based on these concepts, firstly, we show 2-strong nonlocality with genuine entanglement by some sets of GHZ-like states with weight $d$ in tripartite systems. These sets are not necessarily complete bases. Secondly, we present 2-strong nonlocality with genuine entanglement for systems with four or more parties. These results solve the open problem raised by Wang \emph{et al.} Finally, we construct a set of GHZ-like states with $n_+$-strong nonlocality in $n$-partite quantum systems.

We study the effect of hydrostatic pressure on resonant frequency (ν1) and its associated lifetime (τ1), and energy (E1) for electrons tunneling through GaAs-AlGaAs two-barrier nanostructure (TBNS). The effective mass mismatch for well and barrier materials is considered using the effective mass theory. Pressure and the Al content, which mainly affect the barrier height and consequently the TBNS’s, are found to have a significant impact on resonant lifetime, resonant frequency, and resonant energy. The current study shows that the resonance lifetime, resonant frequency, and energy are strongly influenced by the barrier thickness and well width. When comparing the results of this study to the data from the experiment, good agreements are found. The GaAs-AlGaAs TBNS's electronic devices are controlled mainly by the hydrostatic pressure.

We propose a new method for constructing a polarizable classical force field using data obtained from QM and QM/MM calculations to account for the charge redistribution at the water/metal interface. The induced charge effects are described by adding dipoles to the system topology following the Rod Model (Iori, F.; et al. J. Comput. Chem.2009, 30, 1465). Furthermore, the force field uses the TIP3P water model, and its functional form is compatible with popular force fields such as AMBER, CHARMM, GROMOS, OPLS-AA, CVFF and IFF. The proposed model was evaluated and validated for water/Pd(111) systems. We tuned the model parameters to reproduce a few critical water/Pd(111) geometries and energies obtained from DFT calculations using both PBE and a non-local van der Waals xc-functional. Our model can reproduce the hexagonal ice layer for the Pd(111)/water systems typically present in low-temperature experiments, in agreement with the experimental information available from the literature. Additionally, the model can also reproduce the experimental metal-water interfacial tension at room temperature.

The GL(1|1) WZWmodel in the free ﬁeld realization that uses the bc system is revisited. By bosonizing the bc system we describe the Neveu–Schwarz and Ramond sector modules VenNS = Ll∈ℤ Venl and VenR = Ll∈ℤ+ 12 Venl in terms of the subspaces of a given fermion number l. We show that there are two sectors of mutually local operators, each consists of all Neveu–Schwarz operators and of Ramond operators with either integer or half-integer spins. Conformal blocks and structure constants are found for operators that correspond the highest weight vectors of the spaces Venl . The crossing and braiding matrices are considered and the hexagon and pentagon equations are shown to be satisﬁed for typical modules. The degenerate case of conformal blocks with atypical (logarithmic) modules as intermediate states is considered. The known conformal block decomposition of correlation functions in the degenerate case is shown to be related to the degeneration splitting in the crossing and braiding relations. The scalar product in atypical modules is discussed. The decomposition of unity in the full correlation functions in the degenerate case in terms of this scalar product is explained.

We investigate the properties of surface magnetoplasmon polaritons (SMPPs) in a graphene-plasmonic structure which is constructed as a graphene film sandwiched with two semi-infinite dielectrics under a perpendicular configuration. By solving Maxwell equations and quantum magneto-hydrodynamic equations with considering the quantum statistical and quantum diffraction effects, we deduce the dispersion relation of graphene SMPPs (GSMPPs) in detail. We show how the graphene electron density, the external magnetic field, and the dielectric constant, affect the features of the dispersion of GSMPPs in both classical and quantum cases. We find that the quantum effects (QEs) significantly alter the properties of GSMPPs, which are entirely different from those in a classical model. We find that the propagation speed of classical GSMPPs has small increases while the propagation speed of quantum GSMPPs has fast and sharp increases along with the increases in graphene electron density. We further find that the propagation speed decreases gradually by increasing the applied magnetic field in both classical and quantum GSMPPs. Moreover, we also find that the propagation speed of classical GSMPPs has fast decreases tending to zero at large wavenumber while the propagation speed of quantum GSMPPs has slow decreases tending to infinity with increasing the dielectric constant. Our findings elucidate that QEs play a crucial role in the properties of GSMPPs and their response to different parameters.

In this paper, we examine the dynamics of quantum correlations in two noninteractive two-level atoms coupled to two separate identical thermal reservoirs. The two atoms are originally produced in a Gisin state, which is a blend of a maximally entangled two-qubit state and a separable mixed state. Quantum entanglement is measured by logarithmic negativity, while the nonclassical correlations are characterised by trace distance discord and local quantum uncertainty. Using the mean photon number of reservoirs and spontaneous emission rates of atoms as inputs, we explore how these quantum resources behave. Consequently, we demonstrate that the dynamics of quantum entanglement and quantum correlations depend upon the parameters driving the system. Importantly, we further demonstrate that certain parameters may be tweaked to preserve the quantum resources in the system. The results give a full grasp of the quantum features of such a two-level atomic system, showing capabilities to construct quantum technology.

Recent experimental study of electron transport in ZnO/ZnMgO and BeZnMgO/ZnO heterostructures containing two-dimensional electron gas (2DEG) channels of two polarities is reported where electrons are accelerated and become hot by a pulsed electric ﬁeld. The measurements with electrical pulses ranging from 2 ns to 10 ns in duration ensure the control of self-heating eﬀect. Electron transport in the ZnO 2DEG channels located in ZnO layers at the ZnMgO or BeZnMgO barrier or in ZnO 3DEG channels is treated mainly in terms of drift velocity. The highest values of 1.3×10^7 cm/s at 360 kV/cm, 2.0×10^7 cm/s at 270 kV/cm, and 2.5×10^7 cm/s and 320 kV/cm, respectively, are attained and explained by emphasizing the eﬀect of hot phonons.

In this paper, a switchable terahertz metasurface based on VO 2 multilayer structure is raised, which utilizes the temperature phase-transition properties of VO 2 to achieve the functions of switchable polarization conversion and reflection phase modulation for arbitrarily polarized waves at different temperatures. The simulation results show that at high-temperature and low-temperature, the metasurface develop a resonant system to achieve polarization conversion for circularly polarized (CP) and linearly polarized (LP) waves, respectively. For the conversion of the CP wave at high-temperature, the polarization conversion rate exceeds 90% in the terahertz frequency range of 1.01~2.00 THz; at low-temperature, the polarization conversion of the LP wave reaches a near-perfect polarization conversion rate at frequencies f =0.65, 1.07, and 1.50 THz. Arbitrary phase regulation can be achieved by rotating the VO 2 strips and altering the geometry of the C-shaped split resonator ring (CSRR) to form a periodic array with a constant gradient phase. In order to verify that the device has the function of wavefront phase modulation, we use the device to simulate the abnormal reflection based on the generalized Snell's law.Additionally, we generated a bifocal focused beam within a cross-channel in LP incidence mode using the propagation phase principle.

Thermoelectric (TE) materials are increasingly attracting the attention of researchers as new energy materials that are capable of converting thermal energy into electrical energy. In this work, combining first-principles calculations and the Boltzmann transport equation, the TE related properties of XTe (X = Ge, Sn and Pb) monolayers have been thoroughly studied. The calculated results show that XTe monolayers are indirect band gap semiconductors, and they possess small effective masses which lead to large carrier mobilities and high electrical conductivities. Except for p-type PbTe, the other XTe monolayers share extremely high PF, thanks to the high Seebeck coefficients and large electrical conductivity. Furthermore, owing to the low phonon group velocity and strong anharmonicity, the lattice thermal conductivities of SnTe and PbTe are quite low. At 500 K, the optimum figure of merit (ZT) values are calculated to be 1.26, 2.61 and 5.91 for GeTe, SnTe and PbTe respectively. The obtained ZT values of the XTe monolayers are larger than these of their bulk counterparts. These results qualify XTe monolayers as promising candidates for building outstanding TE devices.

With the revolution in power generation and the development of electrification, portable electronic gadgets have recently posed escalating needs for suitable energy storage applications. The lithium-ion battery (LIB) is an electrochemical energy storage device that can achieve high energy density while retaining high power density. Here, we build a high energy density LIB module with a ~12.10% increase in energy density over the previous cell. For environmental and safety reasons, several design elements such as electrode thickness, porosity, current density, and particle size were iterated to improve specific capacity and energy density without changing the ambient temperature increment. We have used a simple heat generation system; the temperature raised by ~18.96% from the room environment was close to 29.74 °C. The specific capacity was also improved by ~14.56% as compared to commercial LIB. Besides, we used the gassing and plating methods to reduce the integrated Li-ion loss for both the cathode and anode. All of the remarkable findings in this work will aid in the optimization and design of next-generation LIB cells.

In the liquid-solid phase transition analysis, it was observed that two phenomena namely crystallization and glass transition take place, whenever we cool a liquid or melt a solid. In the present endeavor, we have tried to analyze the comparative study of crystallization kinetics using comprehensive iso-conversional methods in both heating/cooling modes of quaternary Se76Te20Sn2Ge2 glassy material synthesized by a very simple and famous melt quenching technique. Differential Scanning Calorimetry (DSC) was employed for this analysis. The effect of heating, as well as cooling rates on the crystallization kinetics, was investigated. Various kinetic parameters like activation energy using the iso-conversional approach, the reaction rate constant, Avrami index, Meyer-Neldel energy, etc. have been calculated for both heating and cooling modes.

The magnesium-based metallic alloys have been exhibited to be the improved hydrogen storage materials. In the present investigation, a Nanostructured Mg67Ni33 and Niobium substituted intermetallic compound was prepared by a high-energy ball milling technique for hydrogen storage application. Niobium substitution on the pure crystalline intermetallic compound changed the structure of the crystalline to semi-amorphous as well as changed the interplanar spacing after 30 hours of milling. Furthermore, the effect of Nb substitution on the inter-planar shift and its corresponding implications on lattice strain, crystallite size, and unit cell volume of the Mg2Ni compound were also discussed. Transmission electron microscope studies confirm the particle size was reduced to less than 100 nm for 30 hours of milling. However, SEM images confirm the agglomeration of these nanoparticles and form spherical particles of size around 3-5 µm. XRD and EDS authenticate the presence of oxides. Kissinger’s analysis confirmed that Mg2Ni powder exhibited lower activation energy of 64.101 kJ/mol than niobium-substituted alloy powders. The hydrogen charge and discharge potential of these compounds are discussed in detail.

The effect on the ion energy distribution function (IEDF) of plasma produced during a high-power impulse magnetron sputtering (HiPIMS) discharge as the pulse conditions are varied is reported. Pressure was varied from 0.67 -2.00 Pa (5-15 mTorr), positive kick pulses up to 200 V tested with a constant 4 μs delay between negative and positive cycles. The results demonstrate that the resulting plasma during the positive kick pulse is the result of expansion through the largely neutral gas species between the end of the magnetic trap of the target and the workpiece. The plasma potential rises on similar time scale with the evolution of a narrow peak in the IEDF close to the applied bias. The peak of the distribution function remains narrow close to the applied bias irrespective of pulse length, and with only slight pressure dependence. One exception discovered is that the IEDF contains a broad high energy tail early in the kick pulse due to acceleration of ions present beyond the trap from the main pulse separate from the ionization front that follows.

The structural, morphology, optical, magnetic and dielectric properties of the (ZnO)1–x(CoFe2O4)x, (x= 1, 3 and 5 wt.%) nanocomposites synthetized by sonomechanical method were investigated using XRD, FE-SEM, HR-TEM, UV-visible, VSM and BDS. XRD analysis shows that, ZnO and CoFe2O4 acquired hexagonal and cubic phases, respectively. The optical band gap was reduced from 3.22 eV for pure ZnO to 3.15 eV after adding 5wt % of CoFe2O4. Addition of 1wt% CoFe2O4 to ZnO matrix showed a noticeable ferromagnetic behavior that was predominant in the prepared nanocomposites and confirmed by the convex Arrott–Belov–Kouvel curves. The dielectric constant, , at higher frequencies of the investigated nanocomposites is relatively high (8-10) accompanied by low values of dielectric loss,  ranging between 0.001 and 0.003 and hence very low values of the dissipation factor D (= /) making them applicable in the field of microwave shielding. On the other hand, the dc-conductivity, dc at 25 C shows a remarkable increase by Addition of 1wt% CoFe2O4 to ZnO matrix and decreases gradually with further increase of the ferrite. This indicates the effect of mobility and/or the number density of charge carriers on the conductivity. The investigation at higher temperature, 150 C, shows a gradual decrease in the conductivity with increasing CoFe2O4 content.

The Lebowitz solution of the Percus-Yevick hard-sphere mixture is invoked with the square-well potential function to determine Ashcroft-Langreth type three partial correlation functions in binary Cu-In liquid alloys. These computed partial correlation functions have been employed to generate Bhatia-Thornton fluctuations in the considered melts. Using these structural parameters we investigate the temperature and composition-dependent diffusion coefficients of considered melts. The computed values of concentration-concentration fluctuations, in the long-wavelength limit and the Warren-Cowley short-range order parameter, show the formation of chemical compounds between unlike atoms in the In-rich region of Cu-In melts. We find a very good agreement between theoretically formulated and computed data of with the corresponding experimental values. Computed results of and suggest that hetero coordination is favorable over homo coordination in the investigated melts. The validity of the Stokes-Einstein relation was observed over a wide range of temperature and composition in the investigated melts. Further, a new correlation between two body pair excess entropy and the Stoke-Einstein relation has been formulated for square-well binary liquid alloys. Surface tension and compressibility as a function of In composition have been computed through microscopic structural functions of the alloys. Computed , , surface tension and ratio of mutual to intrinsic diffusion (Dm/Did) are found comparable to available simulated data. The computed values of shear viscosity are in good agreement with the experimental data. Calculated results suggest that the combination of hard sphere potential with square-well tail under mean spherical model approximation is one of the good method for determining the structures and transport coefficients of compound forming binary liquid alloys.

In this work, two structures of wire grid reflecting polarizers have been proposed and optimized at the target wavelength of 121.6 nm (H Lyman-α), which aims to realize compact and efficient polarizers for measuring the magnetic field vector of the solar corona. Both structures are based on a high reflective patterned Al/MgF2 bi-layer on top of an absorbent substrate, and a layer of MgF2 is sandwiched in the Al gaps to prevent it from being oxidized. Two promising solutions were selected, exhibiting a polarization degree of more than 99.99% and a TE-reflectance over 0.3. Their sensitivity to nanowire parameters has been carried out to evaluate manufacturing feasibility. The angular and spectral performance demonstrated that such polarizers have the large potential to significantly contribute to the future far-ultraviolet (FUV) instruments.

The modified Sawada-Kotera equation is investigated by prolongation technique and Painleve singularity analysis. As a result, the Lax pair and conservation laws of the modified Sawada-Kotera equation are formulated. It is proved that this equation pasts the Painleve test in sense of having enough arbitrary functions at its resonant points. The auto-Backlund transformation and exact solutions of the modified Sawada-Kotera equation are obtained explicitly.

Dunkl derivative enriches solutions by discussing parity due to its reflection operator. Very recently, one of the authors of this manuscript presented one of the most general forms of Dunkl derivative that depends on three Wigner parameters to have a better tuning. In this manuscript, we employ the latter generalized Dunkl derivative in a relativistic equation to examine two-dimensional harmonic and anharmonic oscillators solutions. We obtain the solutions by Nikiforov-Uvarov and quasi-exact solvability (QES) methods, respectively. We show that degenerate states can occur according to the Wigner parameter values.

A method for constructing general null Lagrangians and their higher harmonics is presented for dynamical systems with one degree of freedom. It is shown that these Lagrangians can be used to obtain non-standard Lagrangians, which give equations of motion for the law of inertia and some dissipative dynamical systems. The necessary condition for deriving equations of motion by using null Lagrangians is presented, and it is demonstrated that this condition plays the same role for null Lagrangians as the Euler-Lagrange equation plays for standard and non-standard Lagrangians. The obtained results and their applications establish a novel role of null Lagrangians in classical dynamics.

In this work, we propose a two dimensional (2D) axisymmetric fluid model for an atmospheric pressure plasma jet (APP jet) driven by a 8kV voltage pulse with a repetition frequency of 50 kHz in order to improve the understanding of the physical phenomena that take place in a cold plasma jet at atmospheric pressure assuming an argon pathway in the air to get closer to reality. The model is built through the coupling between plasma discharge and flow physics using COMSOL@ Multi-physics software. Our simulation results showed that the high value of the electric field in the head of the plasma jet channel attracts free electrons and ensures its propagation around 1cm of length and an electron density of 1020 m- 3. We have also shown that the electrons in the neutral zone of the plasma (channel) have a lower temperature related to electrons in electrostatic sheaths (channel boundaries); although, their temperature remains remarkably higher than the one of neutrals and ions. The total electric current calculated by the proposed model takes a maximum value of 7.71 mA. This value increases with the increase in the diameter of the tube reactor which changes the reactor equivalent capacity making it larger.

In this paper, we theoretically discuss the effect of thermal expansion on the entropy change and the barocaloric properties of non-magnetic materials. For this purpose, we use a microscopic model Hamiltonian that takes into account the lattice vibrations beyond the harmonic approximation. The model was applied to calculate the entropy change and the barocaloric quantities ∆Siso and ∆Tad in the compounds K2TaF7 and AgI.

In this article, we study a fractional-order mathematical model representing tritrophic interaction amongst plants, herbivores, and carnivores with Caputo derivative. The existence and uniqueness of the system are investigated by fixed point theory, while the stability is studied by Hyers-Ulam and generalized Hyers-Ulam stability analysis. The Adams-Bashforth-Moulton scheme is used for numerical calculations. From numerical simulations, it is observed that when the fractional order decreases the system converges to a stable state. It is observed that for a small value of fractional order, the system approaches a stable state rapidly as compared to the integer order. The chaotic behavior of the system is studied using the Lyapunov spectrum. It is noted that two positive exponents of the proposed model show that the system is hyper-chaotic. It is also observed that a small value of attraction constant disrupts the system due to volatile organic compounds.

In this work, we formulate a new generalized nonlinear KdV-type equation of fifth-order using the recursion operator. This equation generalizes the Sawada-Kotera equation and the Lax equation that study the vibrations in mechanical engineering, nonlinear waves in shallow water, and other sciences. To determine the integrability, we use Painlevé analysis and construct solutions for multiple solitons by employing the Hirota bilinear technique to the established equation. It produces a bilinear form for the driven equation and utilizes the Lagrange interpolation to create a dependent variable transformation. We construct the solutions for multiple solitons and show the graphics for these built solutions. The mathematical software program Mathematica employs symbolic computation to obtain the multiple solitons and various dynamical behaviors of the newly generated solutions. The Sawada-Kotera equation and Lax equation have various applications in mechanical engineering, plasma physics, nonlinear water waves, soliton theory, mathematical physics, and other nonlinear fields.

The unique high-temperature properties of refractory high entropy alloys (HEAs) are mainly depended on their phase formation. Therefore, a new approach to predict the phase formation has to be proposed, in order to accelerate the development of refractory HEAs. Here, we use machine learning to build classifiers to predict the phase formation in refractory HEAs. Our dataset containing 271 data only consists of as-cast refractory HEAs data. We simplify the input parameters to element content, and refine the phase formation outputs into five classes. Decision tree has been employed to build our phase classifier, due to its great advantages in solving classification problem. Both training and test accuracy of phase formation prediction achieve 90% using our classifier. The five single phase prediction accuracies are above 97%. Our phase classifier performs effectively in multi-phases classification and prediction of refractory HEAs, and establishes a direct relation between compositions and refractory phase formation.

Residual stress in polycrystalline-Ge thin film realized on glass substrate using Auinduced layer exchange crystallization process is evaluated using X-ray diffraction based technique. The measured stress is found to be tensile in nature, from which we delineate and discuss the extrinsic thermal and intrinsic growth stresses. An in-plane biaxial tensile strain ~ 0.15 % was estimated to be endured by the polycrystalline-Ge thin film. The narrowing effect that such strain and the crystallization or growth-related defects have on the optical energy band gap of the polycrystalline-Ge thin film is elucidated.

At present, most of the encryption algorithms based on chaotic systems use dissipative chaotic systems. However, the dissipative chaotic systems have attractors and are easy to reconstruct, which leads to potential security risks in the process of data transmission. Therefore, a novel ﬁve-dimensional conservative hyperchaotic system is proposed in this paper, and the integer order system is transformed into a fractional-order system based on the Adomian decomposition method(ADM). The dynamic characteristics of the system are discussed by using classical analysis methods such as Lyapunov exponent spectrum(LEs), bifurcation diagram, phase diagram, and timing diagram. By changing the system parameters and the diﬀerential order q, we found a wealth of dynamic phenomena, such as quasiperiodic ﬂow, chaotic ﬂow, and hyperchaotic ﬂow. When the initial value is used as a variable, it is found that the system has initial oﬀset boosting behavior, multiple stability, and special transient behavior. In addition, we use the spectral entropy algorithm to analyze the complexity of the system. Finally, hardware experiments are also carried out using digital signal processor (DSP) to verify the correctness of the numerical simulation, and also to prove the physical realizability of the system, to create conditions for its subsequent engineering applications.

The mode of incorporation of lithium (Li) (as substitution or interstitial position) in zinc oxide (ZnO) has its own importance as far as the potential applications of Li-doped ZnO nanoparticles (NPs) are concerned. Fabrication of p-type ZnO based semiconductors as well as defect engineering based applications demand substitution of Zn2+ by Li+. However, doping of ZnO by Li with interstitial positions can play an important role in controlling the different properties of it. In the present study, we report the successful doping of Li in ZnO NPs up to a Li concentration of 10 mol% employing a simple wet chemical precipitation method in water. Up to a Li concentration of 8 mol%, doping by substitution of Li to the Zn sites have been observed. However, for 10 mol% of Li concentration, doping by incorporation of interstitial sites in addition to the substitution have been confirmed through the complementary characterization techniques. The effects of interstitial Li in ZnO on structural, optical, and antimicrobial properties have been studied in details systematically. For all the cases (structural, optical, and antimicrobial), the properties of Li-doped ZnO NPs have been changed reversibly in the ZnO NPs after incorporation of interstitial sites by Li as compared to the substitution of Li. For example, the microstrain, band gap, and antimicrobial activity have been found to increase with increase in Li concentration up to 8 mol%. However, the microstrain, band gap, and antimicrobial activity are found the decrease for 10 mol% of Li as compared to 8 mol% of Li. This study indicated that the different properties of Li-doped ZnO NPs can be controlled suitably as per the requirements for the practical applications of ZnO based materials.

Half-metallic (HM) ferromagnets (HM-FMs) with large HM gap and high Curie temperature (TC) have a great importance in the field of spintronics. In this study, the geometric features, electronic structure and magnetism of two new double perovskites (DPs) represented by Rb2XMoO6 (X=Cr, Sc) were explored in bulk phase and (001) surface using quantum mechanical total energy calculations based on density functional theory (DFT). The results showed that Rb2CrMoO6 (RCMO) and Rb2ScMoO6 (RSMO) has an optimized lattice constant of 7.96Å and 8.26 Å, respectively, in the cubic phase (Fm-3m, #225). The cohesive energy Ecoh, formation energy Efor and elastic constants (mechanical) calculations proved that materials are stable. The magnetic properties explored in terms of ground state magnetic coupling, total magnetic moment (M) and atomic magnetic moment (m), exchange energy (J), and Curie temperature. It was found that both materials have ferromagnetic coupling in the ground state, with M of integer value of 8.0 µB (4.0 µB), J value of 47 meV(72 meV) and TC of 365 K (557 K) in Rb2CrMoO6 (Rb2ScMoO6). The electronic properties computed with electronic band structure and density of states demonstrated both DPs to be half-metal with HM gap of 1.61 eV (2.1 eV) in Rb2Cr-based (Rb2Sc-based) system. Finally the electronic and magnetic properties of (001) surfaces were investigated and compared with that of bulk phase. Interestingly, bulk HM property was retained in RSMO, but disappeared in RCMO due the emergence of defect states at Fermi level (EF). The reported results suggest that Rb-based DPs carry some fascinating properties for spin-based devices.

In previous work, we presented a model that integrates cancer cell differentiation and immunotherapy, analysing a particular therapy against cancer stem cells by cytotoxic cell vaccines. As every biological system is exposed to random fluctuations, is important to incorporate stochasticity in the models to adequate their behaviour to experimental observations. Thus, we propose a necessary upgrade to the former model incorporating fluctuations in it. On the one hand, we added multiplicative noise throughout the proposed system, and on the other, we specifically analysed the influence of demographic and multiplicative noise on the parameters of reproduction and death in cancer cells. In both cases, we studied the dynamics for different values of the parameters involved. It was observed that the final number of cancer cells decreases for different combinations of these parameters and noise intensity.

In this paper, a Software Defined Radio (SDR) implementation of Cooperative Spectrum Sensing (CSS) is investigated. More precisely, various local spectrum sensing algorithms have been implemented and validated on USRP B210 using the Qt framework. The realized test bed is based on a client-server architecture. In the client interface, different spectrum sensing techniques have been implemented and analyzed. The fusion center interface implements all hard decision combination schemes, namely OR, AND, and the MAJORITY rule. Finally, several realistic scenarios have been considered to validate our SDR implementation. Moreover, these implementations allowed us to assess the efficiency of different hard-decision combination schemes for cooperative detection in the context of cognitive radio. Besides, the performance improvement is analytically evaluated and corroborated by the experimental results. These results regarding real scenarios confirm that Goodness of Fit-based (GoF) sensing methods outperform conventional methods. Furthermore, theoretical and simulation results from CSS have been validated experimentally that OR-rule gives clearly better results than other hard decisions combinations schemes.

Mixed convective study has been popular in recent years because of its large applications, including the cooling of electronic devices, furnaces, lubrication technologies, high-performance building insulation, multi-shield structures used in nuclear reactors, food processing, glass manufacturing, solar power collectors, drying technologies, chemical processing equipment, and others involve mixed convection in a lid-driven cavity flow problems. Graphics process unit (GPU) based multiple-relaxation-time(MRT) lattice Boltzmann method (LBM) has been employed for investigating the numerical simulation of magnetohydrodynamic(MHD) mixed convection with a non-uniformly heated plate at the mid of an enclosure. The physical model consists of a two-dimensional square enclosure with the top wall moving at a constant speed. Thermally adiabatic conditions are imposed on the top and bottom walls, while the two vertical walls are cold. In the center of the enclosure, a plate has been placed that is non-uniformly heated. A magnetic field is applied with different angles of inclination. Numerical simulations were performed for various influential parameters such as Richardson number ($Ri$), Hartmann number ($Ha$), power-law index ($n$), ferroparticles volume fraction ($\phi$), magnetic field angle ($\gamma$) to study the flow phenomena in terms of the velocity and temperature distributions as well as streamlines and isotherms, respectively. The present study also investigates entropy generation due to the convective heat transfer flow for industrial purposes. The results reveal that as the Richardson number rises, the average Nusselt number rises, and as the Hartmann number rises, the average Nusselt number reduces. Furthermore, it is found that the average Nusselt number is inversely proportional to the power-law index. Total entropy generation increases with the increase of the power-law index and Richardson number. Entropy due to fluid friction, heat transfer, and total entropy shows a maximum at $\gamma=90^\circ$.

Composite materials are the largely used engineering materials in aerospace and automobile industries due to their high specific strength and high specific stiffness. The properties of the composites are very much important to design and develop the machine parts. They vary with fiber content, fiber properties, matrix properties, and type of manufacturing process. Number of experiments are required to obtain the properties and the best combination of fibers and matrices. However, several analytical methods are available to find the properties of the composite to avoid the number of experiments. In the present study, the properties of CFRP, GFRP, Amino-functional multi-walled carbon nanotubes (CNT) added CFRP, CNT added GFRP composites have been calculated by using the properties of fiber, interphase between fiber and matrix, matrix, and CNT. The properties of CNT added epoxy are obtained using Halpin-Tsai equation in first stage, and in the second stage, the properties of interphase are calculated using the properties of CNT added epoxy and fiber properties. The third stage, the properties of CFRP and GFRP are calculated using three phase constitutive model by considering the properties of fiber, interphase, and CNT added matrix. The properties are calculated at fiber diameters: 8 μm and 14 μm while varying the fiber volume fraction (%): 0 to 70%, interphase thickness: 50 nm to 500 nm, weight fraction of CNT (%) added in epoxy: 0 to 5%. The addition of CNT has improved the elastic properties of CFRP and GFRP. The elastic properties of the composites are improved significantly with increase in the interphase thickness.

Journal metrics
28%
Acceptance rate
10 days
Submission to first decision
3.081 (2021)
Journal Impact Factor™
1.202 (2021)
Immediacy Index
0.456 (2021)
SJR
Top-cited authors
• Rani Durgawati Vishwavidyalya, Jabalpur
• University of Antwerp