Pusan National University

This paper examines the electrical characteristics of no-insulation (NI) high-temperature superconducting (HTS) coils impregnated with an electrically conductive epoxy. The NI winding technique refers to a method of winding HTS coils without insulating materials between the winding turns and is regarded as the most promising method to protect the HTS coils from the quench phenomenon. Thus far, many analytical and experimental studies focusing on the electrical characteristics of NI HTS coils have been conducted. From these studies, the quench tolerance levels of NI HTS coils were verified, and the possibility of using NI HTS coils in high-field-magnet applications was confirmed. In addition, studies have recently attempted to apply NI HTS coils to electrical rotating machines. The use of NI HTS coils as field coils in electrical rotating machines is expected to enhance their thermal/electrical stability, but there may also be technical issues related to charging/discharging delays and mechanical reliability. In this paper, we propose a NI HTS coil impregnated with an electrically-conductive epoxy to resolve these issues. In the proposed method, a commercially available epoxy resin is mixed with electrically conductive particles, after which HTS coils are wet-wound using the electrically conductive epoxy. In addition, it was confirmed in charging/discharging tests and in a quench test that HTS coils manufactured by the proposed method show reduced charging/discharging delay times in conjunction with quench-tolerant characteristics. The results here demonstrate the potential of the proposed electrically conductive epoxy impregnated NI HTS coil for electrical rotating machine applications.

The Busan Ion Beam Accelerator (BIBA) is a compact linear accelerator facility utilizing the 28 GHz Superconducting Electron Cyclotron Resonance Ion Source (SC-ECRIS) at the Korea Basic Science Institute (KBSI). The primary objective of the BIBA is to produce fast neutrons tailored for high-resolution radiography technology and application. A recent development of a new ion implantation system employs the multi-charged ion beams, produced by 28 GHz SC-ECRIS. The 28 GHz SC-ECRIS generates a high magnetic field for strong plasma confinement. For the reliable operation of superconducting magnets, it is essential to analyze their electromagnetic characteristics to minimize the forces inducing coil motion and strain during excitation. In this paper, we have employed the inner yoke of the superconducting magnets to enhance the operational stability. The effect of the inner yoke has been analyzed by both a three-dimensional static finite element method simulation and magnetic field measurements in the plasma chamber. The research presents an analysis of the magnetic field and the electromagnetic force of the superconducting magnets under various conditions of the inner yokes. As a result, the magnetic field measurements were found to be in good agreement with the simulated results.

The middle graph [Formula: see text] of a graph [Formula: see text] is the graph obtained by subdividing each edge of [Formula: see text] exactly once and joining all these newly introduced vertices of adjacent edges of [Formula: see text]. It is known that the decision problems for Italian domination number [Formula: see text], [Formula: see text]-rainbow domination number [Formula: see text] and Roman domination number [Formula: see text] are NP-complete. Recently, it was proved that [Formula: see text] for a graph [Formula: see text] of order [Formula: see text]. In this paper, we continue to study several domination and domatic numbers in middle graphs. We also obtain closed formulas for domination, secure domination and total domination numbers in middle graphs of rooted product graphs.

This paper consists of two parts. The first part of the paper is to propose an explicit robust estimation method for the regression coefficients in simple linear regression based on the power-weighted repeated medians technique that has a tuning constant for dealing with the trade-offs between efficiency and robustness. We then investigate the lower and upper bounds of the finite-sample breakdown point of the proposed method. The second part of the paper is to show that based on the linearization of the cumulative distribution function, the proposed method can be applied to obtain robust parameter estimators for the Weibull and Birnbaum-Saunders distributions that are commonly used in both reliability and survival analysis. Numerical studies demonstrate that the proposed method performs well in a manner that is approximately comparable with the ordinary least squares method, whereas it is far superior in the presence of data contamination that occurs frequently in practice.

The process capability index (PCI), C pk , one of the widely-used tools for assessing the capability of a manufacturing process, expresses the deviation of the process mean from the midpoint of the specification limits. The C pk is known to perform well under the general assumption that the experimental data are normally distributed without contamination. Under this assumption, the sample mean and sample standard deviation are used for the estimation of the PCI. However, the sample mean and sample standard deviation are quite sensitive to data contamination and this will result in underperformance of C pk. Therefore, in this paper, we propose alternatives to the conventional method by replacing the sample mean and sample standard deviation with robust location and scale estimators. We also propose a method for constructing a robust PCI C pk confidence interval which lends itself to robust statistical hypothesis testing. The robust hypothesis testing methods based on this confidence interval are shown to be quite efficient when the data are normally distributed yet also outperform the conventional method when data contamination exists.

The growing concerns regarding cancer recurrence, unpredictable bone deficiencies, and postoperative bacterial infections subsequent to the surgical removal of bone tumors have highlighted the need for multifaceted bone scaffolds that afford tumor therapy, bacterial therapy, and effective vascularized bone reconstruction. However, challenging trilemma has emerged in the realm of bone scaffolds regarding the balance between achieving appropriate mechanical strength, ensuring biocompatibility, and optimizing a degradation rate that aligns with bone‐regenerative rate. Considering these challenges, innovative theragenerative platform is developed by utilizing 3D printing‐based nanospikes for the first time. This platform comprises tissue‐specific nanospiked hydroxyapatite decorated with magnesium (nMg) and adhesive DNA (aDNA). The incorporation of nMg within polylactic acid (PLA) matrix confers photothermal capabilities and helps to modulate mechanical and degradation properties and improve the biocompatibility of theragenerative platform. Simultaneously, the immobilized aDNA contributed to the enhancement of vascularized bone healing. These 3D‐printed tissue‐adhesive theragenerative platforms exhibit superior mechanical properties and offer controlled degradability. Moreover, they enable the eradication of bacteria and osteosarcoma through hyperthermia and promote angiogenesis and osteogenesis, both in vitro and in vivo. This groundbreaking approach is poised to pave the way for the fabrication and design of novel implantable biomaterials that integrate therapeutic and regenerative functions.

Single‐walled carbon nanotubes (SWCNTs) have gained significant interest for their potential in biomedicine and nanoelectronics. The functionalization of SWCNTs with single‐stranded DNA (ssDNA) enables the precise control of SWCNT alignment and the development of optical and electronic biosensors. This study addresses the current gaps in the field by employing high‐throughput systematic selection, enriching high‐affinity ssDNA sequences from a vast random library. Specific base compositions and patterns are identified that govern the binding affinity between ssDNA and SWCNTs. Molecular dynamics simulations validate the stability of ssDNA conformations on SWCNTs and reveal the pivotal role of hydrogen bonds in this interaction. Additionally, it is demonstrated that machine learning could accurately distinguish high‐affinity ssDNA sequences, providing an accessible model on a dedicated webpage (http://service.k‐medai.com/ssdna4cnt). These findings open new avenues for high‐affinity ssDNA‐SWCNT constructs for stable and sensitive molecular detection across diverse scientific disciplines.

Given that the skin is the largest tissue in the human body, performing external barrier functions with innate and adaptive immunity and undergoing substantial changes during aging, it is under investigation as a major target of various bioactive molecules. In the present study, we examined the biological activity of the senolytic piperlongumine by analyzing alterations in mRNA expression of notable skin genes using transformed aneuploid immortal epidermal keratinocytes, HaCaT cells. We observed that piperlongumine increased the mRNA expression of genes playing critical roles in skin barrier function. In addition, piperlongumine increased expression enzymes involved in the synthesis of ceramide, a major component of intercellular lipids. Furthermore, we measured the protein levels of various cytokines secreted by epidermal keratinocytes and found changes in the release of GRO-αβγ, CCL5, and MCP1. Additionally, we observed that piperlongumine treatment modulated the expression of keratinocyte-specific aging markers and influenced telomerase activity. Based on these findings, piperlongumine could regulate the physiological activity of epidermal keratinocytes to induce beneficial effects in human skin by regulating important skin-related genes.

Recently, research results on PC-based or alkali-activated slag cement (AASC) using seawater as mixing water have been reported. Unlike seawater, reverse osmosis brine (brine) is waste discharged into the ocean from seawater desalination plants. There is a need to develop new and effective methods of disposing or utilizing brine to reduce marine pollution, protect marine ecosystems, and increase marine plant construction. However, research on cement or concrete using brine as a mixing water is very limited. Brine has almost the same composition as seawater, and the ion concentration is 2–4 times higher. Therefore, it is believed that new methods of using brine can be investigated and developed based on existing research and experimental results on seawater. The effects of brine and aluminum oxide (AO) on activated slag with calcium hydroxide (CH) were investigated for hydration and mechanical properties. 5% and 10% of CH were used, and samples using fresh water (FC) were prepared at the same time for comparison with brine. The slag sample without CH has a low initial (1 and 3d) strength of about 10 MPa for both FC and brine, but increases rapidly from 7d. Incorporation of CH was effective in improving the mechanical performance of FC and brine samples. In addition, the brine sample exhibited higher strength than the FC sample because it formed fewer C3AH6 phases that cause volume instability than the FC sample and affected the hydration promotion of slag particles. And more calcite phases were observed in the brine samples than in the FC samples. Through this study, the possibility of using brine as a building material was confirmed. In addition, the effect of chloride ion adsorption of slag mixed with AO and CH on the physical properties and mechanical performance of the hydration reaction was confirmed.

Isoprene affects new particle formation rates in environments and experiments also containing monoterpenes. For the most part, isoprene reduces particle formation rates, but the reason is debated. It is proposed that due to its fast reaction with OH, isoprene may compete with larger monoterpenes for oxidants. However, by forming a large amount of peroxy-radicals (RO2), isoprene may also interfere with the formation of the nucleating species compared to a purely monoterpene system. We explore the RO2 cross reactions between monoterpene and isoprene oxidation products using the radical Volatility Basis Set (radical-VBS), a simplified reaction mechanism, comparing with observations from the CLOUD experiment at CERN. We find that isoprene interferes with covalently bound C20 dimers formed in the pure monoterpene system and consequently reduces the yields of the lowest volatility (Ultra Low Volatility Organic Carbon, ULVOC) VBS products. This in turn reduces nucleation rates, while having less of an effect on subsequent growth rates.

With the current advancements in artificial intelligence and machine learning, data has become a powerful tool for major improvements in various fields. In the field of aerodynamic design, most algorithms utilize an iterative method to reach their target function or geometry due to their robustness. Deep learning models enable us to exploit the data generated during those iterations to leverage the design algorithm. In this paper, design procedures and guidelines were presented for the use of multilayer feedforward neural network (MFNN) and long-short term memory (LSTM) network to predict the target geometry with early generated data of the design algorithm to reduce its computational cost. The impact of various parameters and hyperparameters on the quality of the target prediction was discussed and early results were presented for various representations of input data using the NACA-0011 airfoil aerodynamic design data. The results indicated that selecting the appropriate network and hyperparameters can yield a reliable estimate of the target geometry using only 20 % to 30 % of the available data.

Background Multiple attempts of thrombectomy have been linked to a higher risk of intracerebral hemorrhage and worsened functional outcomes, potentially influenced by blood pressure (BP) management strategies. Nonetheless, the impact of intensive BP management following successful recanalization through multiple attempts remains uncertain. Aims This study aimed to investigate whether conventional and intensive BP management differentially affect outcomes according to multiple-attempt recanalization (MAR) and first-attempt recanalization (FAR) groups. Methods In this secondary analysis of the OPTIMAL-BP trial, which was a comparison of intensive (systolic BP target <140 mm Hg) and conventional (systolic BP target 140-180 mm Hg) BP managements during the 24 hours after successful recanalization, we included intention-to-treat population of the trial. Patients were divided into the MAR and the FAR groups. We examined a potential interaction between the number of thrombectomy attempts (MAR and FAR groups) and the effect of BP managements on clinical and safety outcomes. The primary outcome was functional independence at 3 months. Safety outcomes were symptomatic intracerebral hemorrhage within 36 hours and mortality within 3 months. Results Of the 305 patients (median 75 years), 102 (33.4%) were in the MAR group and 203 (66.6%) were in the FAR group. The intensive BP management was significantly associated with a lower rate of functional independence in the MAR group (intensive, 32.7% vs. conventional, 54.9%, adjusted OR 0.33, 95% CI 0.12-0.90, p = 0.03). In the FAR group, the proportion of patients with functional independence was not significantly different between the BP managements (intensive, 42.5% vs. conventional, 54.2%, adjusted OR 0.73, 95% CI 0.38-1.40). Incidences of symptomatic intracerebral hemorrhage and mortality rates were not significantly different according to the BP managements in both MAR and FAR groups. Conclusions Among stroke patients who received multiple attempts of thrombectomy, intensive BP management for 24 hours resulted in a reduced chance of functional independence at 3 months and did not reduce symptomatic intracerebral hemorrhage following successful reperfusion.

To reduce uncertainties in future sea level projections, it is necessary to closely monitor the evolution of the Antarctic ice-sheet. Here, we show that seawater oxygen isotopes are an effective tool to monitor ice-sheet freshwater discharge and its contributions to sea level rise. Using the isotope-enabled Community Earth System Model with imposed estimates of future meltwater fluxes, we find that the anthropogenic ice-sheet signal in water isotopes emerges above natural variability decades earlier than salinity-based estimates. The superiority of seawater isotopes over salinity in detecting the ice-sheet melting can be attributed to the higher signal-to-noise ratio of the former and the fact that future sea ice changes only contribute little to seawater isotopes but a lot to salinity. We conclude that in particular in the Ross Sea sector, continuous seawater oxygen isotope measurements could serve as an early warning system for rapid anthropogenic Antarctic ice-sheet mass loss.

The growing demand for high‐performance semiconductors, driven by the advancement of emerging industries such as artificial intelligence (AI), necessitates the development of novel materials for thermal management. In this respect, hexagonal boron nitride (h‐BN) has emerged as a promising candidate due to its unique properties. However, challenges arise from its two‐dimensional layered structure, resulting in thermal transfer anisotropy and poor fluidity when mixed with polymers for thermal management. To address these challenges, researchers have attempted to fabricate h‐BN into spherical shapes. In this study, we propose a two‐step synthesis method of spherical h‐BN (s‐BN) particles via control of the precursor morphology and a subsequent thermal reaction. Therefore, as‐fabricated s‐BN exhibits solid spherical shapes with a uniform size distribution, with a median particle size of 0.955 µm. These s‐BN particles, when integrated into epoxy resin, disperse homogeneously, forming efficient heat transfer networks that achieve a 138% improvement in thermal conductivity compared to h‐BN particles with similar diameters, even at lower viscosities. This can overcome the limitations found in the conventional particle shapes while preserving the advantages of h‐BN. Furthermore, it is anticipated that the s‐BN will be applied in thermal management systems, thereby accelerating advancements in electronic technology. This article is protected by copyright. All rights reserved.

The effect of Nb on austenite grain growth kinetics was investigated in 10Cr-3Co-2W martensitic heat-resistant steel under various tempering conditions (temperature and time). The results demonstrate that Nb effectively refines the austenite grain size; this result is attributed to the combined effect of Nb atom solute drag effect and pinning effect of NbC precipitates. Based on the measured values, an empirical model was developed to predict the grain growth behavior of this alloy system. In addition, the key conditions and parameters for application to the microstructure evolution model of MatCalc software were derived. Results will enable the prediction of grain size at different Nb contents and temperature parameters, and provide useful information for designing heat treatment processes and alloys. Graphic Abstract

Advanced transfer printing technologies have enabled the fabrication of high-performance flexible and stretchable devices, revolutionizing many research fields including soft electronics, optoelectronics, bioelectronics and energy devices. Despite previous innovations, challenges remain, such as safety concerns due to toxic chemicals, the expensive equipment, film damage during the transfer process and difficulty in high-temperature processing. Thus a new transfer printing process is needed for the commercialization of high-performance soft electronic devices. Here we propose a damage-free dry transfer printing strategy based on stress control of the deposited thin films. First, stress-controlled metal bilayer films are deposited using direct current magnetron sputtering. Subsequently, mechanical bending is applied to facilitate the release of the metal bilayer by increasing the overall stress. Experimental and simulation studies elucidate the stress evolution mechanisms during the processes. By using this method, we successfully transfer metal thin films and high-temperature-treated oxide thin films onto flexible or stretchable substrates, enabling the fabrication of two-dimensional flexible electronic devices and three-dimensional multifunctional devices.

Marine dissolved organic matter (DOM) cycles play a pivotal role in sustaining marine ecosystems and regulating the ocean's carbon sequestration from the atmosphere. However, the response of DOM cycles, including dissolved organic carbon (DOC) and dissolved organic phosphorus (DOP), to future climate change remains highly uncertain. Using the Community Earth System Model version 2 large ensemble simulations, we find that the C:P ratios in DOM are projected to increase by up to two‐fold in oligotrophic gyres by 2100. Increased upper ocean stratification reduces surface phosphate availability, thereby elevating phytoplankton C:P ratios and enhancing phytoplankton utilization of DOP, both acting to deprive DOM of P. Moreover, ocean stratification has a direct effect on exporting less DOC to the subsurface while accumulating more DOC at the sea surface. As a result of the strong sensitivity to ocean surface warming, the anthropogenically driven trends in upper ocean DOM concentration and its C:P ratios are estimated to emerge earlier from the simulated natural variability than upper ocean phosphate concentrations and net primary production—two key biogeochemical variables that are frequently monitored. This study suggests that changes in the C:P ratios of DOM could serve as a sensitive fingerprint of anthropogenic ocean warming, potentially exerting broad impacts on marine microbes. Our estimated 4% reduction in the globally integrated DOC export below 100 m is comparable to a 2% reduction in particulate organic carbon (POC) export by 2100, implying that global warming is likely to weaken the biological carbon pump through both DOC and POC.