Journal of the Korean Physical Society最新文献

In January 2020, our study delved into the US stock market’s dynamics as COVID-19 began to affect the global economy. We scrutinized the Dow Jones Industrial Average (DJI) stocks, focusing on the correlations of their returns. We discerned patterns and anomalies through a structural and dynamic analysis of the correlation network facilitated by a distance function applied to the correlation coefficients. The study emphasized the significance of the minimum spanning tree (MST) in shaping the network’s structure and influencing the expansion of subnetworks. Central nodes with high connectivity in the MST emerged as crucial, particularly when the market exhibited abnormal behavior. These nodes’ daily variations and correlation structures provided insights into the market’s evolving nature. We observed that the MST’s radius was particularly reactive to market abnormalities, serving as a potential crisis indicator. Our analysis connected the alterations in the MST’s central nodes and the overall network structure with shifts in the four fundamental statistical moments of the correlation coefficients and distance weights. These elements proved to be instrumental in detecting and analyzing market irregularities.

In animals, the presence of food stimulates appetite and induces feeding behaviors. This is an important mechanism, instrumental for animals’ competitiveness in fluctuating environment. To learn fundamental principles of feeding regulation, it is useful to study simple model organisms, whose feeding dynamics can be quantitatively measured. Recently, we measured the feeding dynamics of the nematode C. elegans, whose feeding consists of pumping bacteria from the environment into the gut, and demonstrated that it matches its feeding activity with the availability of food by modulating the frequency and duration of persistent fast pumping periods. Here, we develop an effective model that described these dynamics as a random walk on the pumping-rate axis, experiencing food-dependent transition probabilities. This model suggests the existence of two classes of fast pumping: the first is characterized by persistent fast-rate pumping, while the other exhibits only transient fast pumping. We show, however, that it is the dynamics of transient fast pumping that is governed by the presence of food. Furthermore, we use the model to show that serotonin is used by worms both in a food-independent mechanism that promotes acceleration of pumping and address the different roles of two pairs of serotonergic neurons.

This paper presents two novel classification techniques, the customized template matching classifier (CTMC) and the dynamic template matching classifier (DTMC), which aim to significantly enhance the performance of the minimum distance classifier (MDC). CTMC tailors a feature subspace specifically for MDC, leveraging a set of effective templates that capture the distinguishing characteristics of each class. This customized feature space ensures accurate representation and enhanced distinguishability between classes, thereby improving MDC’s classification accuracy. DTMC, on the other hand, builds upon the CTMC approach by introducing a dynamic template optimization process. Inspired by semi-supervised learning techniques, DTMC utilizes unlabeled data to enrich class information and iteratively update the templates in the feature space. This dynamic optimization process allows DTMC to adapt to variations in the data, further enhancing the classification performance of MDC. Our key contributions include: (1) introducing the concept of a customized feature space tailored for MDC, demonstrating its effectiveness in improving classifier performance; (2) presenting CTMC and DTMC as comprehensive classification systems that seamlessly integrate feature extraction and classification, outperforming traditional loosely coupled approaches; and (3) incorporating a reliability mechanism to assess the classification of test samples, enabling the selection of high-reliability samples to update class templates, effectively addressing the issue of limited labeled data and further boosting the overall performance of the classification system.

Ga-doped ZnO (GZO) thin films were deposited on a glass substrate using RF-magnetron sputtering at various operating pressure and its electrical, structural and optical properties have been studied. In previous studies, resistivity was affected by both electron concentration and electron mobility, whereas in this study, resistivity was only controlled by electron mobility. Low operating pressure results in high conductivity due to high electron mobility. The enhanced electron mobility is attributed to the reduction in surface scattering by oxygen adsorption, which is a consequence of the reduction in the number of oxygen ions and the surface area. Under controlling the operating pressure, surface scattering exerts a more significant influence on electron mobility than grain-boundary scattering. The average transmittance (400–800 nm) was over 86% and increased with lower operating pressure. Therefore, the surface scattering plays a major role to achieve better electrical properties of GZO thin films sputtered under operating pressure conditions.

Surface-enhanced Raman scattering (SERS)–fluorescence bimodal composites have attracted great interest for biomedical applications. Herein, we report the characterization of Au-decorated CaTiO₃:Eu³⁺ nanocomposites (CaTiO₃:Eu³⁺@Au NCs) using SERS and fluorescence properties. X-ray diffraction (XRD) of the CaTiO₃:Eu³⁺@Au NCs shows orthorhombic phases, which are in good agreement with the standard CaTiO₃ XRD peaks. The photoluminescence (PL) spectra show a strong visible red emission at 614 nm (⁵D₀ → ⁷F₂) with an excitation wavelength of 380 nm. The PL-emission intensity of the CaTiO₃:Eu³⁺@Au NCs increased more than that of the CaTiO₃:Eu³⁺ powder. The maximum PL-emission intensity of the CaTiO₃:Eu³⁺@Au NCs was obtained at an Au doping concentration of 0.8 mol/L; however, the intensity at higher Au doping concentrations (> 0.8 mol/L) was lower. This behavior is consistent with the SERS results. These results suggest that varying the Au nanoparticle concentration can control the PL-emission intensity and SERS of the CaTiO3:Eu³⁺@Au NCs. Therefore, CaTiO₃:Eu³⁺@Au NCs may be useful for multiplex detection and bioimaging.

In this study, we calculate the dc resistivity of the half-filled disordered Hubbard model near the Mott and Anderson metal–insulator transitions. We employ the standard Kubo formula with typical medium dynamical mean field theory to perform our calculations. Our investigation explores the effects of random potential, on-site Coulomb interaction, and temperature on the dc resistivity within the model. In addition, we highlight and discuss the distinct resistivity behaviors observed near the Mott and Anderson transitions.

Love numbers h, k, and l are convenient parameters to assess the deformation of the Earth or other planet due to external perturbing forces. While the elastic Love numbers are used for tidal deformation, the correct amount of permanent tidal deformation can be assessed using the fluid Love numbers. Accurate values of the elastic Love numbers of Earth have been repeatedly attained for several Earth models, and also the fluid Love numbers h_f and k_f of the Earth were recently reported. In this short note, new evaluation of the Earth’s fluid Love number as well as secular Love number, both originally defined by Munk and MacDonald, is presented using updated values of the Earth’s physical property model and with minute enhancement in the formulation; ({(h}_{s}, {k}_{s}) =(1.9437, 0.9437)) by their 1st approach and ({(h}_{f}, {k}_{f}) =(1.9337, 0.9337)) by their 2nd approach. Through numerical calculations with gradual stepwise reduction in rigidity, the three fluid Love numbers of the Earth were determined as: (h_f, k_f, l_f) = (1.935, 0.935, 1.07) for PREM and (h_f, k_f, l_f) = (1.937, 0.937, 1.07) for ak135-F Earth models. In addition, the fluid Love numbers of other spherical harmonic degrees 0, 3, 4, and 5 were estimated. The permanent tide of the Earth ellipsoid due to the Moon and the Sun has been re-calculated: the vertical displacement of the permanent tide is 0.1924 m at the equator and (- 0.3801) m at the pole, while the horizontal displacement of the permanent tide is found to be 0.317 m at mid-latitude.

Exploring the localized surface plasmon resonance (LSPR) of Cu nanostructures with native oxidation layers is very important for attaining plasmonic applications. A Cu nanodot array (NDA) was fabricated on an indium tin oxide substrate using an anodic aluminum-oxide layer with through-holes as a shadow mask. The surface chemical states and plasmonic properties of the Cu NDA and Cu film prepared for comparison were investigated via X-ray photoelectron spectroscopy (XPS) and ultraviolet‒visible spectroscopy. The XPS-depth profile indicated that the native oxide layer on the 50-nm-thick deposited Cu film was approximately 4.3 nm thick. For the Cu film, an absorption dip was observed at 573 nm, with two shoulder peaks attributed to the surface-oxide layer. The LSPR of the Cu NDA with a dot diameter of 60(± 5) nm was clearly observed at 652 nm despite the presence of a native oxide layer.

In this paper, we present a novel structured THz BWO based on a rectangular waveguide grating with improved output characteristics. The circuit enabled, with a simple change, separation of the two sections without increasing the overall size. A conventional one-stage circuit with 45 grooves and a novel two-stage circuit with 15 and 25 grooves were quantitatively compared using the 3D MAGIC PIC code. The oscillation time could be drastically reduced, and the conversion efficiency could be increased by more than two times. Importantly, this structure enabled an output increase without increasing the circuit size. It can be expected to improve the output of a compact high-power THz source.