This paper presents a theoretical study of the electromagnetic wave propagation in a three-layer slab waveguide with a metamaterial core and graphene interfaces on each end. The dispersion relation, field distribution, and power-flux expressions are then analytically formulated to obtain the impact of the magnetic permeability of the central layer and graphene Fermi energy on the guided modes. It is found that by changing core permeability, the basic TE$_0$ mode can be suppressed or allowed, and other higher-order modes can propagate consistently. The analysis of power flux shows how there is forward and backward energy flow, where negative values of the flux show that there is backwards-wave flow in the structure. Moreover, mode confinement and alteration in power distribution within the layers occur with an increase in Fermi energy. It is seen that graphene-metamaterial waveguides have a bright future in terms of reconfigurable photonic platforms, with potential uses in optical communication, slow-light devices, and plasmonic control technologies.
Multilayer optoelectronic devices play a crucial role due to their ability to combine the novel properties of dissimilar materials for superior performance leading to enhanced or novel functionalities. This study focuses on designing, fabricating and characterizing a novel nano multilayer structure of zinc oxide/cerium oxide/ITO in a simple chemical method. X-ray diffraction (XRD) and scanning electron Microscopy (SEM), UV-visible, and photoluminescence were investigated. Optical properties revealed two wide band gaps of 3.15eV for prepared multilayer structures. The multilayer devices exhibit a broad photoluminescent peak at 340eV. Results show significant improvements in charge carrier, optical absorption and quantum efficiency. Addition of the cerium layer enhances conductivity and photocurrent of nano structures by facilitating electron-hole pair separation under photo excitation. These findings highlight the importance of the prepared multilayer nano structure in various optoelectronic technologies such as photodetectors, sensors and light emitting diodes.
Copper oxide nanoparticles (CuO NPs) possess versatile properties that make them valuable in various applications, including electronics, catalysis, sensing, and biomedical fields. However, conventional synthesis routes often require high energy input, hazardous chemicals, and generate environmentally problematic byproducts. In this work, CuO NPs were synthesized through an eco-friendly green method using Mitragyna speciosa (Korth.) Havil leaf extract, whose phytochemicals function as natural reducing and stabilizing agents. The nanoparticles were characterized using UV-visible spectroscopy, FESEM-EDS, and XRD. The optical spectrum exhibited an absorption maximum at similar to 480 nm, and the corrected Tauc analysis yielded an indirect band gap of 1.57 eV. XRD analysis confirmed the formation of monoclinic CuO with crystallite sizes of 82-98 nm (Scherrer and Williamson-Hall methods), consistent with FESEM particle sizes of 50-80 nm. Antibacterial tests revealed activity against both Escherichia coli and Staphylococcus aureus, with minimum inhibitory concentrations (MICs) of 3.98 & times; 104 & micro;g/mL and 1.00 & times; 105 & micro;g/mL, respectively. These results demonstrate that M. speciosa-mediated synthesis offers a viable, cost-effective, and sustainable approach for producing functional CuO nanoparticles, thereby supporting their potential in future environmental and biomedical applications.
The effect of sol-gel preparation on the microstructural and thermal behavior of nanosized mesoporous hydroxyapatite powder was investigated in this study. The powder was synthesized using the sol-gel technique, with preparation carried out at various temperatures: room temperature 100°C and 400°C. FTIR analysis revealed the presence of hydroxyl groups (3423.91 cm−1 to 3600 cm−1), corresponding to the stretching vibration of hydroxyl (OH) and phosphate ions (1102.31 cm−1 to 1644.17 cm−1), indicating the stretching vibration of P - O, and these indicating the functional groups of PO43- , confirmed as the formation of hydroxyapatite. The thermal properties were studied using DSC-TG and provide valuable information on phase transitions such as melting, crystallization, thermal enthalpy, and specific heat capacity. XRD analysis confirmed all materials as nanosized mesoporous hydroxyapatite powder with face-centered cubic unit cells in the hexagonal lattice system. The lattice constants were obtained, a = b = 0.942 nm and c = 0.588 nm; these results were determined by careful analysis using the appropriate interplanar spacing formula. Finally, the surface topology and elemental composition were examined using SEM-EDX, including the atomic ratio of elements in the nanosized mesoporous hydroxyapatite powder. The Ca/P ratios were found to be approximately 1.63 and 1.73 for samples treated at temperatures of 100°C and 400°C, respectively. In the future, nanosized mesoporous hydroxyapatite powder, synthesized by the sol-gel method, could be prepared as a raw material for waste adsorbents.
The standard Tsallis and R´enyi extropies of parameter q are extended to the time-scale domain, and closed-form expressions of these extropies for fractal signals of parameter α are obtained. Wavelet extropy planes are computed for a range of the fractality parameter α and signal length N which allows an unveiling of the properties and potential applications of wavelet q-extropies on fractals. Results indicate that wavelet q-extropies allow accurate description of the complexities of fractals since they are maximum for completely random samples, decreasing for correlated fractals and increasing for uncorrelated fractals. Unlike Shannon and R´enyi, Tsallis extropies display a constant region, symmetric on α, which allows classification of fractals based on a simple heuristic of wavelet extropy values. Finally, the application of wavelet Tsallis extropies allows the differentiation of electroencephalogram (EEG) times series from volunteers with eyes closed and eyes open.
In this work, we explore a wheel-shaped hollow-core photonic crystal fiber (HC-PCF)-based optical alcohol sensor that operates in the terahertz (THz) region. We employ the finite element method (FEM) along with COMSOL Multiphysics software to simulate the structure and perform a numerical analysis of the model. In this configuration, alcohol analytes are integrated into the fiber's core. The results from the FEM simulation indicate that the proposed optical HC-PCF sensor achieves high sensitivity levels of 97.61% for ethanol, 98.80% for butanol, and 98.53% for propanol, all at a frequency of 2.1 THz. The measured low confinement losses at 2.1 THz are 8.0696 x 10-8 dB/m, 7.1966 x 10-11 dB/m and 3.6334 x 10-10 dB/m. Furthermore, the effective areas are 7.5911 x 10-8 m2, 7.8258 x 10-8 m2, and 8.0847 x 10-8 m2 for three types of alcohol. Additionally, we discuss the concepts of effective material loss, effective mode index, and total power fraction. Existing technologies can facilitate the fabrication of this proposed sensor. Moreover, we anticipate that the application of our fabricated sensor will extend to biomedicine, biosensing experiments, industrial applications, material research, healthcare, alcohol detection in drinks and liquids, and other THz communication technologies based on waveguides.
We study, through discrete element simulations, the discharge of granular materials through a circular orifice on the base of a cylindrical silo forced by a surcharge. At the beginning of the discharge, for a high granular column, the flow rate $Q_{\rm ini}$ scales as in the Beverloo equation for free discharge. However, we find that the flow rate $Q_{\rm end}$ attained at the end of the forced discharge scales as $\sqrt{\rho_{\rm b} P}D_{\rm o}^3/D_{\rm s}$, with $\rho_{\rm b}$ the bulk density, $P$ the pressure applied by the overweight, $D_{\rm o}$ the orifice diameter and $D_{\rm s}$ the silo diameter. We use the work--energy theorem to formulate an equation for the flow rate $Q_{\rm end}$ that predicts the scalings only in part. We discuss the new challenges offered by the phenomenology of strongly forced granular flows.
An interacting ghost dark energy with experimental constraint in a non-flat universe with accelerating expansion is studied in this report. Based on the linear relationship between dark energy and the Hubbard function, it is found that the non-gravitational interaction between dark energy and cold dark matter near a = 0 leads to the transfer of energy from cold dark matter to dark energy. The cosmological evolution of the interacting ghost dark energy density, its equation of state and the deceleration parameters in a non-flat universe are obtained analytically. Based on the astronomical observations on the present value of the energy density of state ωD0, we impose restrictions on the interaction factor. It is found that there is a simple reverse linear relationship between ωD0 with the interaction factor, and all the deceleration parameters q0 ⊂ [−0.91, −0.38] are negative, which aligns with the astronomic observation on the accelerated expansion of the universe.
We study the properties of discrete-time random walks on networks formed by randomly interconnected cliques, namely, random networks of cliques. Our purpose is to derive the parameters that define the network structure -- specifically, the distribution of clique size and the abundance of inter-clique links -- from the observation of selected statistical features along the random walk. To this end, we apply a Bayesian approach based on recording the times spent by the walker inside successively visited cliques. The procedure is illustrated with some numerical examples of diverse complexity, where the relevant structural parameters are successfully recovered.
We disclose a critical phenomenon induced by structural properties of the contact pattern in a stylized model of rumor propagation over a population of agents. The contact pattern is given by a random network of cliques, formed by fully interconnected groups of nodes of identical size with randomly distributed connections between groups. As demonstrated numerically using finite-size scaling analysis, the process exhibits a critical transition between a regime where the rumor remains confined to a negligible part of the population and a regime where it attains a finite portion of the system. We determine the critical point and the critical exponent of the transition for different clique sizes. The phenomenon is analogous to that observed for the same kind of process in Watts-Strogatz small-world networks, and is likely due to the combination of large clustering and short mean geodesic distances that also characterizes random networks of cliques.
In this study, the structural, electronic and optical characteristics of Platinum (Pt)-doped cubic BaTiO 3 perovskite were inspected via density functional theory (DFT) calculations. Generalized gradient approximation (GGA) and Pedraw–Wang 91 (PW91) functional, as applied in CASTEP code, provide an atomic level understanding of the influence of substituting 0.125 Pt dopant at Ba and Ti positions. Results indicate that the optimized lattice parameters and band gap are in good agreement with the experimental and theoretical data. Furthermore, the total and projected density of states (TPDOSs) analysis demonstrates that Pt–dopant integration has an impact on diminishing the band gap and shifting the absorption spectra towards the visible light region. Thus, it is suggested that substituting Ti and Ba atoms with Pt would enhance the optoelectronic characteristics of the host system, due to existing Pt–5d electronic states. Moreover, the negative formation energy values indicate the thermodynamic stability of the modeled configurations. These detailed results provide valuable insights into the physical properties of Pt–BaTiO 3 and its behavior across a range of photon wavelengths. To our knowledge, this contribution evaluates for the first time the influence of introducing platinum (Pt) into a BaTiO 3 perovskite system. The overall findings demonstrate a valuable appraisal of support for experimental synthesis of Pt–BaTiO 3 to serve in various optoelectronic devices.
Ferromagnetism is typically discussed in terms of the exchange interaction and magnetic anisotropies. Yet real samples are inevitably affected by the magnetostatic dipole-dipole interaction. Because of this interaction, a theorem [R.B. Griffiths, Free Energy of interacting magnetic dipoles, Phys. Rev. 176, 655 (1968)] forbids a spontaneous magnetization in, nota bene, three-dimensional bodies. Here we discuss perpendicularly and in-plane magnetized ferromagnetic bodies in the shape of a slab of finite thickness. In perpendicularly magnetized slabs, magnetic domains are energetically favored when the lateral size is sufficiently large, i.e., there is no spontaneous magnetization. For in-plane magnetization, instead, spontaneous magnetization is possible below a critical thickness which, in very thin films, could be as small as few monolayers. At this critical thickness, we predict a genuine phase transition to a multi-domain state. These results have implications for two-dimensional ferromagnetism.
The study of precipitation is one of the most intriguing areas in atmospheric sciences, with significant implications for our daily lives and climate change projections. This paper explores the estimation of rainfall trends in South American regions using convolutional neural networks (CNNs). The study focuses on the application of Cloud-Net, a CNN-based model with a format similar to an autoencoder, to obtain qualitative estimates of precipitation patterns. The employed loss functions, Categorical Cross Entropy and Categorical Focal Loss, address the challenges of classifying minority categories in unbalanced data. Regional analysis was conducted, identifying days with high rainfall intensity and the predominant intensities in 25 regions. The CNN model’s performance was compared with the XGBoost algorithm, showing excellent results for extreme rainfall categories and challenging intermediate categories. Furthermore, a comparison was made with Quantitative Precipitation Estimation (QPE) data and ground measurements from rain gauges. While the CNN model provided a valuable qualitative estimate of precipitation trends, achieving precise quantitative estimation would require an extensive data set of in-situ measurements. Overall, this research demonstrates the potential of CNNs for estimating rainfall trends and understanding precipitation patterns in South American regions. The findings offer valuable insights for further applications in meteorology and environmental studies.
In statistical mechanics, measuring the number of available states and their probabilities, and thus the system’s entropy, enables the prediction of the macroscopic properties of a physical system at equilibrium. This predictive capacity hinges on the knowledge of the a priori probabilities of observing the states of the system, given by the Boltzmann distribution. Unfortunately, the successes of equilibrium statistical mechanics are hard to replicate out of equilibrium, where the a priori probabilities of observing states are, in general, not known, precluding the naı̈ve application of common tools. In the last decade, exciting developments have occurred that enable direct numerical estimation of the entropy and density of states of athermal and non-equilibrium systems, thanks to significant methodological advances in the computation of the volume of high-dimensional basins of attraction. Here, we provide a detailed account of these methods, underscoring the challenges present in such estimations, recent progress on the matter, and promising directions for future work.
In this study, we applied the Interacting Boson Model (IBM-I) to compute the electric reduced transition probabilities B(E2)\(\downarrow\) of even-even neutron rich \(^{186}\text{W}\) and \(^{186}\text{Os}\) isobars. The ratio \(R_{4/2} = E(4_{1}^{+}) / E(2_{1}^{+})\) has also been calculated for those isobars and the SU(3) symmetry for those isobars has been reported. \(E(4_{1}^{+})\) and \(E(2_{1}^{+})\) indicate the energy level of \(4_{1}^{+}\) and \(2_{1}^{+}\), respectively. We have described the strength of B(E2) in W.u. for \(^{186}\text{W}\) and \(^{186}\text{Os}\) isobars of some of the low-lying quadrupole collective states in contrast to obtainable measured data. The electric reduced transition probabilities B(E2)\(\downarrow\) from yrast state gamma transition from \(12_1^{+} \rightarrow 10_1^{+}\), \(10_1^{+} \rightarrow 8_1^{+}\), \(8_1^{+} \rightarrow 6_1^{+}\), \(6_1^{+} \rightarrow 4_1^{+}\), \(4_1^{+} \rightarrow 2_1^{+}\) and \(2_1^{+} \rightarrow 0_1^{+}\) and other bands states and B(E2) ratio of \(^{186}\text{W}\) and \(^{186}\text{Os}\) isobars have been compared with obtainable measured data and other previous studies. Also calculated were the systematic strength of B(E2), intrinsic quadrupole moments, and deformation parameters of even-even \(^{186}\text{W}\) and \(^{186}\text{Os}\) isobars. The data from these calculations are in good matching with the obtainable measured data. The IBM-I model for the strength of B(E2) has been systematically deduced in SU(3) limit for a few yrasts states transitions in \(^{186}\text{W}\) and \(^{186}\text{Os}\) isobars.
On December 14, 2020, southern South America experienced a total solar eclipse close to the solar noon. The path of totality, about 90 km wide, extended over the continental region from the Chilean west coast to the Argentine east coast, passing through the provinces of Neuquén, Río Negro and the extreme south of Buenos Aires. In order to study the effects on the atmosphere produced by the total eclipse, the Servicio Meteorológico Nacional Argentino (SMN) and Instituto de Investigaciones Científicas y Técnicas para la Defensa (CITEDEF) carried out a surface radiometric monitoring campaign in Valcheta (40.69°S; 66.15°W), Río Negro, Argentina. In this work, we explore the global surface solar irradiance on a horizontal plane (GHI) with the main objective of quantifying the changes in this parameter for cloudy and clear sky atmospheric conditions, combining ground-based measurements and modeling. A solar limb-darkening function was successfully implemented in the calculation of the irradiance at the top of the atmosphere (TOA) during the eclipse. We estimated a significant GHI attenuation of 41 % between the first (C1) and last (C4) contacts of eclipse compared to similar atmospheric conditions without the total eclipse, which represent a daily reduction of 12 %. In terms of irradiation, a reduction of 3360.1 KJ/m2 was calculated.
Density functional theory (DFT) was used to study the electronic and vibrational properties of the chemical bond between the [6,6]-phenyl-C61-Butyric acid methyl ester (PCBM) and (CuO)n clusters. After chemical adsorption, the HOMO orbitals of PCBM primarily shifted towards (CuO)n, leading to a noticeable reduction in the band gap. Similarly, the bond established is responsible for the spatial redistribution of boundary orbitals, mainly towards the clusters. In addition, the orbital analysis revealed that the primary contributions to the chemical bond originated from the Cu atoms. The PCBM Raman intensity shows a meaningful enhancement consequence of the chemical bond established with the clusters. In addition, new normal modes of PCBM are observed in the Raman activity spectrum after the chemical adsorption.
We numerically study hysteresis in the ferromagnetic random field 3-state clock model in two and three dimensional periodic lattices at zero temperature and in the zero frequency limit of the driving field. The on-site quenched disorders are continuous and are drawn from a uniform distribution. We numerically analyzed the effects of disorder on the dynamics of the model and hence on the shape of the hysteresis loops. We also study the model in the presence of dilution and an absorbing state.
In statistical mechanics, measuring the number of available states and their probabilities, and thus the system's entropy, enables the prediction of the macroscopic properties of a physical system at equilibrium. This predictive capacity hinges on the knowledge of the a priori probabilities of observing the states of the system, given by the Boltzmann distribution. Unfortunately, the successes of equilibrium statistical mechanics are hard to replicate out of equilibrium, where the a priori probabilities of observing states are in general not known, precluding the naïve application of usual tools. In the last decade, exciting developments have occurred that enable the direct numerical estimation of the entropy and density of states of athermal and non-equilibrium systems, thanks to significant methodological advances in the computation of the volume of high-dimensional basins of attraction. Here, we provide a detailed account of these methods, underscoring the challenges that lie in such estimations, recent progress on the matter, and promising directions for future work.
Cerium oxide $\text{CeO}_2$, or ceria, has gained increasing interest owing to its excellent catalytic applications. Under the framework of density functional theory (DFT), this contribution demonstrates the effect that introducing the element nickel (Ni) into the ceria lattice has on its electronic, structural, and optical characteristics. Electronic density of states (DOSs) analysis shows that Ni integration leads to a shrinkage of Ce 4$f$ states and improvement of Ni 3$d$ states in the bottom of the conduction band. Furthermore, the calculated optical absorption spectra of an Ni-doped $\text{CeO}_2$ system shifts towards longer visible light and infrared regions. Results indicate that Ni-doping a $\text{CeO}_2$ system would result in a decrease of the band gap. Finally, Mulliken's charge transfer of the $\text{Ce}_{1-x}\text{Ni}_x\text{O}_2$ system exhibits an ionic bond between Ce or Ni and O, and covalent bonds between Ce and Ni atoms. The analysis of absorption spectra demonstrates that Ni-doped $\text{CeO}_2$ is a material with potential use in photocatalytic, photovoltaic, and solar panels.
