Journal of the Korean Physical Society最新文献

We investigate new physics effects on (Brightarrow D^{(*)}tau nu) decays in a general and model-independent way. The (chi ^2) fits for fractions of the branching ratios (R(D^{(*)})) and other polarization parameters are implemented. We parameterize the relevant Wilson coefficients with a new physics scale and its power together with combined fermionic couplings. Constraints from (B_crightarrow tau nu) are imposed such that its branching ratio is less than 30%. For a moderate range of our parameters we find that the new physics scale goes up to (lesssim 27~textrm{TeV}) for ordinary new particle contributions. It turns out that the polarization asymmetry of (tau) for (Brightarrow D) transition can be negative only for a few combinations of the new physics operators. We also discuss related processes (B_crightarrow J/Psi tau nu) and (Lambda _brightarrow Lambda _ctau nu) decays.

This paper focuses on exploring dust-acoustic solitary (DAS) waves in a plasma that includes negative dust fluid, nonthermal–nonextensive Cairns–Tsallis (CT) distributed electrons and Boltzmannian ions using Sagdeev pseudopotential formulism. In this study, we observed that the presence of CT-distributed electrons and thermal ions results in the occurrence of rarefactive solitons. It is found that the plasma parameters such as nonthermal spectral index ((alpha )), nonextensive parameter (q), dust temperature ((sigma )) and Mach number (M) significantly influence the solitary structures for DAS waves. In addition, the analytic results reveal an intricate combination between spectral indices q and α, dust temperature, drift velocity, electron number density and critical Mach number. Our results highlight the influence of CT distribution on the characteristics of space plasma waves, thereby improving our understanding of electrostatic nonlinear structures and the complexity of electrostatic waves in astrophysical plasmas.

The present multicomponent dusty plasma of positive ions, negative dusts, and nonextensive electrons with variable pressure, dust ion-acoustic (DIA) solitary waves are investigated by Korteweg–de Vries (KdV) and modified Korteweg–de Vries (mKdV) equations, derived by the reductive perturbation technique (RPT). In this new investigation, we observed that both amplitude and width of the DIA solitary waves are significantly influenced by the nonextensive parameter (q). Interestingly, an increase in the nonextensive parameter (q) results in a linear rise in both amplitude and width of DIA solitons. Furthermore, the analysis shows that the mKdV solitons exhibit considerably higher amplitudes compared to the KdV solitons. In this theoretical investigation, for some pairs of streaming speed of ions and dusts, only compressive solitons are seen, whereas for some other pairs, rarefactive KdV solitons with distinct characteristics are observed. Also, we investigated the critical roles of ion-to-electron temperature ratio ((alpha )), dust-to-ion density ratio ((sigma )), initial streaming speeds of ions ((u_{i0})) and dust particles ((u_{d0})), and the number of dust charges ((Z_d)), in the formation of DIA solitons.

We investigate the Coulomb dipole excitation (CDE) of neutron-rich carbon isotopes, focusing on (^{15})C and (^{19})C, which consist of a core nucleus and one valence neutron. The Coulomb dipole strength distribution (dB (E1) / dE_{text {x}}) is extracted from experimental Coulomb dissociation cross sections using both general and relativistic calculations of virtual photon numbers. Despite similar beam energies, the dissociation cross section of (^{19})C + Pb is significantly larger than that of (^{15})C + Pb, reflecting their difference in neutron separation energy. We also compute theoretical strength distributions using a simple model involving the spectroscopic factor S and the potential radius (r_{0}), achieving good agreement with the experimental data. The extracted parameters (S, (r_{0})) are reasonable within physical expectations. This study confirms the importance of low neutron separation energy in enhancing Coulomb breakup reaction and provides a useful framework for understanding dipole excitation mechanisms in weakly bound neutron-rich nuclei. In particular, the Coulomb dipole excitation (CDE) potential, which incorporates the Coulomb dipole strength distribution, plays a crucial role in describing the Coulomb breakup of weakly bound neutron-rich nuclei.

Power generation plays a major role in any country’s industrial revolution and growth. Due to substantial worldwide economic and demographic expansion, there is an increased demand for energy globally. However, fossil fuels such as coal, gas, and oil constitute the main cause of climate change, contributing to over 90% of CO₂ emissions and 75% of greenhouse gas emissions. In the global energy shift, hydrogen technologies are regarded as one of the key participants. To achieve net-zero emission targets, several national and international programs suggest using hydrogen to decarbonize the energy, industrial, and transportation sectors. Green H₂ is a viable alternative to the present energy system based on carbon. Using a range of renewable resources, it can be utilized as a carbon-free energy source for homes, transportation, and industrial applications. The carbon footprint of green H₂ is primarily indirect and depends on the carbon content of the electricity used for electrolysis. Green H₂ is categorized as the most viable choice for clean energy generation because it produces only 0.0072 kg of CO₂ every kilogram of hydrogen. The recent developments in various green H₂ production methods have been examined in detail in this article.

This investigation pertains to the influence of non-linear thermal radiation on unsteady stagnation flows of a hybrid nanofluid consisting of single-wall and multi-wall carbon nanotubes dispersed in the engine oil. The analysis is performed using similarity transformations and the Runge–Kutta–Fehlberg method with a shooting technique. A key innovation of this work lies in the combined evaluation of nonlinear thermal radiation and thermal stratification within a hybrid nanofluid framework, which has not been explored in prior literature. The study examines how nanoparticle shape, volume fraction, and thermophysical properties influence velocity and temperature distributions. The results indicate that the velocities and the temperatures of SWCNT-MWCNT/engine oil are greater than those of the mono nanofluid (SWCNT/engine oil). The velocity and temperatures are enhanced with increasing volume fraction of SWCNT. Blade-shaped nanotubes show higher temperatures. Surface drag reduces linearly with unsteadiness parameter and increases with stagnation flow parameter. Nusselt number increases with radiation and shape factor parameters. Increase in Nusselt number with blade-shaped nanotubes is very significant. These findings have practical implications for the design of advanced cooling systems in aerospace, electronics, and energy industries.

Metallic nano-gap structures in the terahertz (THz) frequency range are of increasing interest due to their ability to enhance localized electromagnetic fields, enabling applications in nonlinear optics and sensing. However, lithography-based fabrication processes often leave metallic residues and structural defects around the nano-gap region, which is especially detrimental for very narrow (~ 10 nm) gaps. In this study, we apply a thermal annealing process to mitigate these issues and analyze its effects at various temperatures. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) show that annealing reduces surface roughness and removes residual metals, improving structural consistency. The annealing also increases transmittance and blue-shifts the resonance frequency of the THz nano-gaps, which indicates removal of the occasional metallic bridges blocking the gap. These results demonstrate that thermal annealing is a simple and effective post-treatment method for improving the performance of nano-gap-based THz devices.

Inhibitor-free area selective atomic layer deposition (AS-ALD) of SiO₂ thin films was studied using a dual-chamber system designed to alternate surface cleaning and deposition without air exposure. In the cleaning chamber, NF₃ and NH₃ were reacted in a remote plasma to form an ammonium fluoride-based etchant, which enabled selective etching of SiO₂ over SiN. This step allowed pre-cleaning to remove native oxides and post-cleaning to restore the non-growth SiN surface. However, when only NF₃ and NH₃ were used, excessive residual fluorine remained on the surface. During repeated cleaning and deposition cycles, this fluorine increased the etch rate of the ALD SiO₂, preventing accurate thickness control. To solve this problem, O₂ was added. Oxygen reacted with hydrogen from NH₃ to form H₂O, which reduced surface fluorine and stabilized thickness control through multiple cycles. In the ALD chamber, SiO₂ thin films were deposited at 200 ℃ using diisopropylamino silane (DIPAS) and O₃. Owing to its inherent chemo-selective adsorption characteristic, DIPAS exhibited shorter incubation cycles on SiO₂ than on SiN, enabling preferential nucleation. As a result, the ALD SiO₂ could be deposited more effectively on SiO₂ surfaces, while repeated post-cleaning maintained selectivity on SiN. By continuing this cycle, thickness differences between SiO₂ and SiN regions were steadily accumulated. Selective growth on patterned wafers was confirmed by in situ ellipsometry, residual gas analysis, high-resolution transmission electron microscopy, and atomic force microscopy.

We present a new stellar model which employs the Buchdahl metric potential for the temporal metric potential in the spherical symmetric configuration, following the Mazur–Mottola (MM) gravastar conjecture within the Einsteinian geometric framework. It is thought to be a promising alternative to the Black Holes (BH). Three regions make up the gravastar’s structure: the interior, intermediate shell, and the exterior region. In our model, the interior core region is characterized by a pressure equal to the constant negative matter energy density. This gives rise to a constant repulsive force acting on the shell. This shell is modeled as being composed of an ultra-relativistic plasma fluid. In conformity with Zeldovich’s stiff fluid conjecture, where the pressure is proportional to the energy density of the matter cancels the repulsive force exerted by the interior region. We have described the exterior region’s geometry by the Schwarzschild solution with the spacetime being a vacuum. The specifications lead to a family of exact solutions for the gravastar, free of singularities possessing a physically valid features within the ((3 + 1)) dimensional spacetime paradigm. Moreover, our discussion has covered the junction and the energy conditions in detail, highlighting their role in the production of the thin shell. We conducted a comprehensive stability analysis of our gravastar model through the study of surface redshift and speed of sound. Thus, we have successfully formulated a stable gravastar model that overcomes the singularity problem of BHs, within the context of General Relativity (GR).

This work explores the design and analysis of the analog and radio-frequency (RF) performances of the NC-FinFET structure. A comparative study is conducted with the baseline (BL) FinFET. The investigation involves optimizing the device parameters for the ferroelectric negative capacitance metal ferroelectric–metal–insulator–semiconductor (MFMIS) transistor, including varying the thickness of the ferroelectric material region. Sensitivity analysis is performed to evaluate the response of neutral biomolecules by adjusting the dielectric values. Density variation is examined for its impact on electric, analog, and RF parameters. The study includes electric metrics, such as switching ratio, energy band, surface potential, subthreshold swing, and threshold voltage V_TH, as well as sensitivity performances to identify binding sites for biomolecules.