The European Physical Journal Plus最新文献

Our aim is to obtain and compare global transonic solutions and self-similar solutions for a hot magnetized accretion flow around a non-rotating black hole. To this purpose, we have considered a magnetized, steady, axisymmetric, viscous, advective accretion flow around a non-rotating black hole. Additionally, we have taken into account thermal conduction and bremsstrahlung cooling in the disc. We have found that thermal conduction has no effect on the radial velocity, temperature, and density of the disc in the self-similar solution. However, the impact of the thermal conduction parameter is slightly more significant in the global solutions; but the effect remains very small due to the narrow range of allowed values. Additionally, both solutions show a decrease in the angular momentum with thermal conduction. Furthermore, we have calculated the maximum disc luminosity for both solutions and have shown that the disc luminosity increases more in self-similar solutions compared to global solutions. Finally, we have determined the luminosity of the Sgr A (^{star }) disc based on our numerical model, and the global accretion solution may be more preferable for studying the black hole’s energetic sources.

The objectives of this article are two fold—first analyze the vibration behavior of Euler nanobeam under hygro-magnetic-thermal environment resting on a Winkler–Pasternak foundation as a forward process, based on two semi analytical techniques: Differential Quadrature Method (DQM) and Differential Transform Method (DTM), second introduced DTM-based inverse problem to obtain the system parameters by using the obtained frequency parameters by forward problem. The governing differential equation is obtained by Hamilton’s principle and the nonlocal strain gradient theory is implemented to capture the nanoscale effects. A complete mathematical process for DQM and DTM has been discussed and vibration frequencies are obtained by using both methods under three different classical boundary conditions: Simply Supported–Simply Supported (SS), Clamped–Simply Supported (CS), and Clamped–Clamped (CC) in the forward problem. In the inverse case, those obtained frequencies are used to find the unknown parameters by inverse DTM. A convergence study for both forward and inverse methods is discussed in terms of frequency and other characteristic parameters under these three boundary conditions. Also the effects of nonlocal parameters, length scale parameters, Winkler–Pasternak foundation, Hygro-Magnetic and Thermal parameters on the vibration have been discussed by tables and graphical results. The main novelty of this work is that DTM-based inverse problem is introduced, which can be extended in experimental works in future research.

The study of memristor simulation of neuronal synapses has been more extensive and in-depth. However, the study of simulation of neuronal connectivity structure in the cerebral cortex has not yet attracted people's attention. In this paper, a novel bistable locally active discrete memristor is proposed as a neuronal autosynapse and synapse to simulate the connection structure of neurons in the cerebral cortex. Dynamical methods such as equilibrium point stability, Lyapunov exponential spectrum and bifurcation diagrams are utilized for analytical studies. Numerical simulations reveal that the proposed multisynaptic coupled Rulkov neural network has multiple brain-like firing patterns. Multiple attractor phase diagrams with periodic-periodic, periodic-chaotic, and chaotic-chaotic coexistence as well as high complexity are found. Digital signal processing-based hardware implementation platform was also developed, on which the attractor phase diagrams realized by the simulation platform were experimentally captured. New ideas are provided for the future construction of cerebral cortical neuron models.

The technology based on quantum theory has super parallel transmission capability and is considered as one of the effective means to solve the difficulties of future wireless communication systems. In this paper, the improved quantum singular value (IQSV)-based channel estimation scheme for millimeter wave (mmWave) massive multiple input multiple output (MIMO) systems is designed by using the quantum computing technology. Firstly, the precoding matrix and the received matrix are extended to the Hermitian form, and the eigenvalues and eigenvectors of the extended precoding matrix are calculated. Secondly, the extended precoding matrix and the extended received matrix are transformed into the quantum states by the quantum coding technology. Therefore, the quantum states of the left and right singular values of the precoding matrix are further given. Then, the quantum state channel information is obtained by the quantum singular value estimation, the quantum controlled rotation operation and the inverse quantum state comparison operation, in which the appropriate quantum circuit and quantum controlled rotation circuit are designed. Finally, this paper proposes the modified quantum state data extraction algorithm, which can effectively extract the amplitude information, the phase information and the symbol information from the output quantum state data. By analyzing the distribution of the quantum parameter in mmWave massive MIMO systems, the convergence and usability of the proposed IQSV-based algorithm is demonstrated. In addition, we provide the complexity of the proposed IQSV-based algorithm. Experimental simulation shows that the proposed IQSV-based algorithm is superior to traditional channel estimation algorithms in estimation accuracy and significantly less than traditional channel estimation algorithms in running time, whether on the classical computer or the IBM quantum cloud platform. Moreover, this paper also studies the influence of quantum noise on the estimation performance of the proposed IQSV-based algorithm. Experimental analysis shows that IBM quantum cloud platform is more conducive to the development and research of channel estimation algorithms based on quantum theory.

A theoretical scheme is proposed to generate a strongly entangled photon pair by a (Lambda )-configured three-level atom interacting with a two-mode quantized cavity field through two strong classical fields resonating with the corresponding atomic transitions. The initial state of the two-mode cavity field is considered to be the tensor product of an arbitrary Fock state of the first mode and the vacuum and one-photon states of the second mode, while that of the three-level atom is prepared in its upper excited state. Then, the time-evolution operator in the interaction picture is used to derive two classes of continuous variable entangled displaced number squeezed states (EDNSSs) in terms of the even and odd states of the second mode, respectively. The quadrature squeezing of the EDNSSs for the first mode in the initial vacuum state is considered concerning the coherent and squeezed fields. The sub-Poissonian statistics and the photon anti-bunching effect corresponding to both the coherent and squeezed fields are investigated in terms of the excited states of the first mode, as well as the coherent and squeezed fields with the same amplitudes. Furthermore, the cross-correlation between the two bosonic modes and their two-qubit entanglement are studied; and for example, it is shown that the destructive interference (anti-correlation) corresponds to an increase in entanglement. We highlight the role of the excited states of the first mode in controlling the nonclassical properties of the even and odd EDNSSs, compared to those of the entangled coherent-squeezed states (ECSSs).

In this work, zinc oxide nanoparticles have been synthesized by facile co-precipitation method and characterized by various analysis techniques to study characteristic properties that are essential for photocatalytic studies. ZnO achieved average particle size of about 37 nm as confirmed by SEM and XRD JPCDS card. The UV–Visible analysis confirmed the bandgap of 3.33 eV of ZnO whereas BET analysis showed a specific surface area, pore diameter and pore volume of 8.20 m²g⁻¹, 19.45 nm and 0.0821 cm³g⁻¹, respectively. The synthesized nanoparticles were then used for degradation of MB dye and Glucophage pharmaceutical. By the findings of UV–Visible spectroscopy for the pollutants, it was observed that ZnO degraded MB and Glucophage up to 92.3% and 89.3%, respectively. After six cycles, it was reduced to 83.9% and 83.99% for MB and Glucophage. By COMSOL simulation, the absorbance and rate constants of incident light for Glucophage in the presence of pure ZnO were studied for the confirmation and validation of experimental findings.

Graphical abstract

Graphical abstract about synthesis, characterizations and applications of pure ZnO NPs.

An understanding of the conduction mechanism can be supported by the structural information expected to be revealed by studying the dielectric behavior and alternating current (AC) conduction of amorphous materials such as chalcogenide glasses. This script presents our recently synthesized multi-component glasses of the quaternary Se_78-xTe₂₀Sn₂In_x (0 ≤ x ≤ 6) system, representing our innovative work. We have specifically looked into the dielectric characteristics of these electronic materials. We have examined how the dielectric constant ((varepsilon^{prime})), dielectric loss ((varepsilon^{primeprime})), and AC conductivity depend on temperature and frequency in the audible frequency range (0.1–500 kHz). A thorough investigation revealed that the Guintini model is followed by dielectric loss ((varepsilon^{primeprime})). AC conduction follows correlated barrier hopping (CBH), with bi-polaron hopping being the leading conduction mechanism. We have also determined the density of localized states by using the CBH model. The CBH model states that electron hopping occurs over the coulombic barrier height W and the distance R between adjacent sites. The Coulomb wells overlap and lower the effective barrier height from W_M to a value of W. We found a new correlation for explaining the barrier hopping. The regression coefficient (R²) for this correlation is 100%. Subsequent investigation reveals that variations in electronegativity explain the sequence of rising charged defect densities and reduce with atomization heat.

This work explores a dinuclear metal complex model as a working substance of a universal Stirling-like cycle under two additional squeezed thermal baths. We demonstrate that the engine can operate in any of the four modes allowed by the Clausius inequality by adjusting the ratio between the working parameters and the squeezing factors. The recent advancements in generating squeezed states of light and mechanical oscillators have enabled the creation of squeezed thermal reservoirs. The performance of the heat engine and refrigerator modes is analyzed by efficiency and the coefficient of performance ((mathcal {C}mathcal {O}mathcal {P})) in terms of the ratio between the working parameters and squeezing factors. The study also shows that the performance of the engine can be improved by changing the squeezing factors of the thermal baths beyond the Carnot bound, while upholding the second law of thermodynamics. This suggests that customized interactions with squeezed thermal reservoirs could improve quantum heat engine performance, enhancing energy management in quantum technologies and nanoscale systems.

The study of stability properties of equilibrium points is a key task to know the behaviour of a dynamical system, in space. This paper deals about a perturbed solar sail problem under the frame of planar elliptic restricted three-body problem in the context of artificial equilibrium points (AEPs), pulsating zero velocity curves (ZVCs) and Floquet stability analysis. First, the proposed problem is formulated under the influence of oblateness of both the primaries, sail lightness number and presence of a disc with density profile and all the AEPs are determined. It is found that due to these perturbations, positions of all the AEPs either shift towards the origin or move away from it. Further, pulsating ZVCs are estimated by establishing an invariant relation and it is seen that impacts of the assumed perturbing factors are very less on the prohibited zones for the motion solar sail. Finally, Floquet stability analysis is performed for all the AEPs with the help of characteristic exponents and transition curves. It is observed that changes in the values of perturbing parameters cause changes in the stability regions as well as position of the bifurcation point on the (mu)-axis of the transition curve. These results can be utilised to study the more generalised solar sail problem in the presence of other kinds of perturbations.

This study examines how environmental pollution influences the dynamics of Lassa fever transmission through a mathematical modelling framework. A novel SEQIR-SEI-C model was developed to incorporate human and rodent populations and environmental contamination as key transmission factors. The model was analysed to understand the influence of key parameters of the model, such as quarantine rates, rodent demographics, and contamination clearance, on the dynamics of disease spread. The study highlights the importance of controlling environmental contamination and quarantining infected individuals to mitigate Lassa fever outbreaks. Numerical simulations reveal that reducing transmission rates from contaminated surfaces and enhancing environmental clearance can significantly lower infection rates. The findings underscore the importance of hygiene practices, rodent population control, and effective quarantine strategies in reducing the endemicity of the disease. This research provides a comprehensive framework for policymakers to design targeted interventions to manage Lassa fever outbreaks.