Journal of the Korean Physical Society最新文献

We report the growth and phase transition of VO₂ single crystals. Millimeter-sized VO₂ single crystals were obtained by a self-flux method, in which the molten phase of V₂O₅ at 1000 °C was slowly cooled to room temperature at a rate of 5 °C/h. Rietveld analysis of X-ray powder diffraction shows a low-temperature monoclinic structure with the V–V dimer spacings of 2.57 Å and 3.20 Å and a high-temperature rutile structure with the V–V spacing of 2.85 Å. Raman scattering measurement suggests that the VO₂ single crystal is highly stoichiometric with negligible oxygen deficiency. Electrical resistivity, magnetic susceptibility, specific heat, and heat flow measurements show drastic changes during heating (~ 338 K) and cooling (~ 334 K) with a narrow temperature range (~ 1 K). The low-temperature insulating phase with negligible magnetic susceptibility changes to a high-temperature metallic phase with Pauli paramagnetic susceptibility. The enthalpy change during the phase transition was estimated to be ~ 87 J/g by specific heat and differential calorimetry measurements. This work provides useful quantitative information for the phase transition of VO₂ single crystals.

In quantum mechanics, the reference frames of the observers are often not explicitly mentioned and quantization for a physical system is usually performed in inertial reference systems. Quantization in noninertial reference systems is an important topic and should be studied systematically. In the framework of nonrelativistic quantum mechanics, the quantum mechanical equations in noninertial reference frames could be derived from those in inertial reference frames using unitary transformation operators. Here, we use canonical quantization scheme to derive quantum mechanics wave equations and Hamiltonian operator in general noninertial coordinate systems in nonrelativistic and relativistic spacetime directly from the classical Hamiltonian formulation based on the basic physical principles. As a special case, the Schrödinger equation in rotating coordinate system of nonrelativistic spacetime, and the KG equation and the first-order wave equation in rotating coordinate systems of Minkowski spacetime were derived from the classical Hamiltonian using canonical quantization scheme. In curved spacetime, the matrix-valued vector field γ^a in the first-order wave equation determines the spacetime metric g_ab and spacetime geometry and has great gauge freedom. In the gauge defined by the gauge constraint γ^b∇_bγ^a = 0, the Dirac equation in curved spacetime is reduced to our first-order wave equation. A Hamiltonian operator in general spacetime is derived from the first-order wave equation, which is Hermitian only in a special class of spacetimes.

This work aims to investigate the magnetohydrodynamic boundary layer flow of Casson fluid due to a moving permeable plate with Soret and Dufour impacts. The mathematical modeling of the current flow problem is obtained by utilizing the mass balance, momentum balance, energy balance, and concentration equations. The flow equations are governed by highly non-linear PDEs, which are converted into ODEs with the help of suitable similarity transformations in order to get simplified versions of the governing equations. The authors have solved these equations with appropriate boundary conditions by employing the BVP4C method in the inbuilt software MATLAB. In this work, we have explored the effect of various prominent parameters such as the Casson fluid parameter, Hartmann number, Soret number, Dufour number, Prandtl number, Forchheimer number, chemical reaction parameter and porosity parameter on the flow quantities such as velocity, temperature, and concentration with the help of graphical plots and tables. After the analysis of results, it is found that as the Casson fluid parameter and Hartmann number increase, the velocity of the Casson fluid decreases, but the concentration and temperature during the Casson fluid flow get enhanced. It is also found from the present work that the fluid temperature and Nusselt number can be controlled by the Dufour number, whereas the concentration and Sherwood number of the fluid can be controlled by the Soret number. Furthermore, it is observed that the temperature and concentration of the Casson fluid decrease steeply for higher values of the Prandtl number. The results of the present work bridge the gap in the body of available literature and may be very useful in lubrication systems with permeable surfaces, flow through porous tissues or membranes, as in dialysis or drug delivery systems, and chemical, pharmaceutical, and food industries, where filtration through permeable plates is needed.

Cu₃Sb_1−xGe_xSe_4−yS_y (0.04 ≤ x ≤ 0.12 and 0.10 ≤ y ≤ 0.25) permingeatite compounds were synthesized via dual doping of Ge and S at the Sb and Se sites, respectively. The structural, charge transport, and thermoelectric properties of these materials were systematically investigated. All samples exhibited high relative densities, ranging from 95.8% to 97.3%, and predominantly consisted of the tetragonal permingeatite phase. However, minor secondary phases, such as Se or Cu₈GeS₆, were detected depending on the S content. The introduction of Ge and S dopants caused a contraction in the lattice parameters of permingeatite. The electrical conductivity exhibited characteristics of a degenerate semiconductor, either remaining stable or slightly decreasing with increasing temperature. An increase in Ge content enhanced electrical conductivity, whereas an increase in S content reduced it. The Seebeck coefficient exhibited p-type behavior with positive values and decreased with increasing Ge content and decreasing S content. Dual doping with Ge and S significantly improved the power factor, with Cu₃Sb_0.96Ge_0.04Se_3.90S_0.10 achieving 0.63 mWm⁻¹ K⁻² at 623 K. In addition, the power factor showed a positive dependence on temperature, indicating the absence of intrinsic transition within the investigated temperature range. The thermal conductivity exhibited an inverse relationship with temperature, influenced by both the doping concentration and the temperature-dependent electronic and lattice components. Consequently, the thermoelectric performance was significantly enhanced by the dual doping strategy, achieving a maximum ZT of 0.37 at 623 K for both Cu₃Sb_0.96Ge_0.04Se_3.90S_0.10 and Cu₃Sb_0.92Ge_0.08Se_3.90S_0.10.

Urban traffic systems are characterized by dynamic interactions between congestion and free-flow states, influenced by human activity and road topology. This study employs percolation theory to analyze traffic dynamics in Seoul, focusing on the transition point (q_textrm{c}) and Fisher exponent (tau). The transition point (q_textrm{c}) quantifies the robustness of the free-flow clusters, while the exponent (tau) captures the spatial fragmentation of the traffic networks. Our analysis reveals temporal variations in these metrics, with lower (q_textrm{c}) and lower (tau) values generally during rush hours representing low-dimensional behavior, within the broader context of the positive correlation between (q_textrm{c}) and (tau). Weight–weight correlations are found to significantly impact cluster formation, driving the early onset of dominant traffic states. Comparisons with uncorrelated models highlight the role of real-world correlations. This approach provides a comprehensive framework for evaluating traffic resilience and informs strategies to optimize urban transportation systems.

The detection of heavy-metal ions is necessary owing to their wide and increasing utilization. Fluorometric detection has been suggested for the detection of heavy-metal ions because of its low cost, high detection speed, and high accuracy. This study investigates heavy-metal detection using carbon dots (CDs) derived from o-phenylenediamine. The CDs were synthesized via hydrothermal synthesis and had an average particle size of 2 nm and a hexagonal lattice structure. The existence of chemical bonds between C, N, O, and H was confirmed by analyzing the XPS and FTIR spectra of the CDs. The CDs exhibited excitation-independent emission characteristics and yellow luminescence at 566 nm under ultraviolet-blue light excitation owing to the carbon–nitrogen bonds in the CDs. When Cr³⁺ was dissolved in the CD solution, the rate of decrease in the luminescence intensity was higher than that of the other experimental samples. The limit of detection was calculated to be 0.161 μM by determining the relationship between the Cr³⁺ concentration and luminescence intensity at 566 nm. Analysis of the luminescence-decay curve and luminescence intensity showed that the decline in yellow luminescence originated from photoinduced electron transfer between the Cr³⁺ ions and CDs. These results indicate that CDs can be utilized as fluorometric sensors for Cr³⁺ detection in wastewater.

The reversed magnetic shear configuration with internal transport barriers (ITBs), high specific pressure, and high bootstrap current is an important means to achieve high parameter operation in tokamaks. In this paper, based on the METIS integrated simulation platform, combined with the parameters of the HL-3 device, the joint injection of ion cyclotron wave (ICW) and electron cyclotron wave (ECW) to achieve the reversed magnetic shear configuration is investigated. By analyzing the effects of the ICW injection time, the ECW injection time, and the direction of the electron cyclotron current drive (ECCD) on the confinement, the reversed magnetic shear scenario of the high parameter is obtained, with the bootstrap current up to 45%, and the β_N up to 3.2. The results show that the injection of ICW at the start-up stage can increase the plasma temperature and the magnetic diffusion time, which is conducive to maintaining the reversed magnetic shear configuration; when the off-axis ECW are injected timely in the magnetic diffusion stage, a strong drive current can be generated, so that the internal transport barrier, the high bootstrap current, and the reversed magnetic shear promote each other, maintain the reversed magnetic shear, and achieve the high confinement operation; when the ICW injection is delayed, the on-axis counter-ECCD can also form a good reversed magnetic shear. The results provide a reference for future reversed magnetic shear experiments in HL-3 to improve the discharge performance.

Efficient bandgap engineering is of great significance for developing high-performance optoelectronic devices. Few-layered GaS photodetectors have shown promising photoresponsivity only with the spectral window in the ultraviolet (UV) region. It is necessary to explore alloying GaS and GaSe to improve the performance of devices. Here, the field-effect transistors (FETs) based on ultrathin layer GaS_0.3Se_0.7 are designed and fabricated. The results show that few-layered GaS_0.3Se_0.7 FETs exhibit typical p-type semiconductor properties. Our study shows the photoresponse of few-layered GaS_0.3Se_0.7 FETs (on SiO₂/Si) at 405 nm in visible light region is 231 mA/W with an ON/OFF ratio of 140, at a power density of 16.5 mW/cm², an external quantum efficiency of 71%, and a detection rate of 4.08 × 10¹¹ Jones. The results provide a method to improve the electrical properties of optoelectronic devices based on a 2D material alloy.

In the current study, micro composites based on copper manganese oxides were created using citric acid as a fuel through the auto combustion method. This study investigates the impact of Ce-doping on the optical, structural, and electrical properties of CuMn₂O₄. We demonstrate that Ce-doping can be a practical way to circumvent this limitation. Our study attempts to provide an explanation for the reduction in grain size and Ce content in the CuMn₂O₄ host material. The attenuated total reflectance spectra place the Ce in octahedral and tetrahedral locations. The plasmonic pure and Ce-doping CuMn₂O₄’s capacity to capture visible light and swiftly transfer photogenerated electrons is responsible for this enhanced performance. The results also demonstrated that as the Ce concentration of the dopant increases, so does the percentage of 4CP (4-ChloroPhenol) degradation. The half-filled La electronic structure may be acting as a trapping center for the charge carriers, which is expected to result in increased photocatalytic activity. This study creates new avenues for assessing how the development of nanomaterials will affect energy and environmental applications.