Korea Atomic Energy Research Institute

Plastic electronics with deformable semiconducting polymer layers have emerged as a promising future technology. The design of semiconducting layers with tunable mechanical properties is crucial to improving the performance and reliability of plastic electronics, particularly for flexible and stretchable devices. Here, a method is demonstrated for systematically controlling the persistence length, allowing improvement of the mechanical properties of a single conjugated polymer system without the need for complex chemical modifications to the rigid backbone. The effects of plasticizing molecular additives (PMAs) on the rigidity of conjugated chains are thoroughly investigated through persistence length analysis. Solution‐based small‐angle neutron scattering reveals how different PMAs influence the persistence length of the benchmark rigid conjugated polymer PDPP2T‐TT‐OD. The mechanical, thermal, morphological, and electrical properties of PMA‐blended films are evaluated under deformation. The results show that the mechanical modulus is primarily influenced by modification of the persistence length and the formation of uniformly entangled networks with smaller crystalline grains. The analysis suggests that the uniform distribution of PMAs in PDPP2T‐TT‐OD films, combined with physically crosslinked chains, significantly enhances thin film deformability. Notably, charge mobility remains stable even after stretching to 100% strain. These findings provide valuable insights into the design principles of PMA‐blended conjugated polymer systems, offering a pathway for tailoring mechanical properties in future plastic electronics.

Background Diabetes mellitus, a metabolic disorder, leads to complications via oxidative stress and AGEs formation. Antioxidants are promising therapeutic agents for reducing these complications. Eremochloa ophiuroides (Munro) Hack. (centipedegrass), known for its diverse bioactivities, remains understudied for its anti-glycative properties. Objective This study aimed to isolate and characterize bioactive compounds from the aerial part of centipedegrass and evaluate their inhibitory effects on AGEs formation and oxidative stress to identify potential therapeutic candidates for diabetic complications. Methods The aerial parts of centipedegrass were extracted with 70% ethanol, followed by bioactivity-guided fractionation using Diaion HP-20 column chromatography. The most active fraction (CGE03) was analyzed for total flavonoid content and further purified using Toyopearl HW-40, Sephadex LH-20, and YMC gel ODS columns. The structures of the isolated compounds were elucidated using NMR and UV spectroscopy in combination with mass spectrometry. Anti-glycation activity was assessed via fluorescence-based AGEs inhibition assays, and hydroxyl radical scavenging activity was evaluated using a deoxyribose degradation assay. Results Bioactivity-guided fractionation of centipedegrass extract led to the isolation of nine C-glycosylated flavones (1‒9). Structural elucidation using 1D and 2D NMR spectroscopy revealed a rotational isomer of maysin (1), allowing for a more refined understanding of its structure. Among the isolated compounds, maysin exhibited the most potent anti-glycation (IC50 = 5.0 ± 0.1 μM) and hydroxyl radical scavenging activities (IC50 = 1.5 ± 0.2 μM), significantly outperforming the positive controls. The glycosylation pattern, particularly the rare ketosugar moiety at the C-6 position, was found to play a crucial role in bioactivity. Conclusion This study presents a detailed structural analysis of the rotational isomer of maysin, revealing its potent therapeutic potential for managing oxidative stress-related diabetic complications and offering novel insights into C-glycosylated flavonoids from Eremochloa ophiuroides (Munro) Hack.

This study presents the stochastic multibody dynamics formulation to investigate the long time evaluation of dynamic systems under uncertainty. The generalized polynomial chaos method has been developed to investigate uncertainty in the fields of structural dynamics and fluid dynamics. However, in multibody dynamics fields, uncertainty analysis is challenging due to the high degree of nonlinearity of multibody systems and the typical problem of polynomial chaos, which degrades accuracy in the time domain. To address these challenges, a sequential orthogonalization technique with whitening transformation is employed to resolve the ill-condition issue of the Gram-Schmidt process. A correlation based selection of model solutions is also considered to improve computational efficiency at each updating step as well as numerical stability. These methodologies improve polynomial basis reconstruction and manage statistical dependencies, thereby mitigating the rapid accuracy decay over time and ensuring high precision for extended duration. Numerical experiments demonstrate that the proposed method significantly out-performs conventional polynomial chaos methods.

Molten salt reactors operate under high-temperature molten salt environments, rendering the use of materials used in traditional pressurized water reactors unsuitable. Therefore, nickel cladding, characterized by excellent corrosion resistance, has been applied to molten salt reactor systems. In this study, the microstructural characteristics and mechanical properties of nickel cladding fabricated using gas tungsten arc welding (GTAW) and powder laser cladding (PLC) were examined. The GTAW process yielded a cladding with excellent mechanical performance and no internal defects. However, extensive intergranular corrosion was observed after a 100-h immersion test, attributable to the presence of high-energy grain boundaries. Conversely, the PLC specimen exhibited cracks and porosity. However, the presence of low-energy grain boundaries contributed to uniform corrosion behavior and enhanced corrosion resistance. These findings underscore the complementary advantages and limitations of both techniques, highlighting the necessity for further optimization to ensure reliable performance in high-temperature reactor environments.

Artificial intelligence (AI) for controlling mechanical systems has traditionally been used as a mathematical tool, but with the emergence of large language models (LLMs), it is evolving into agents that interact with their environment and make decisions. Based on linguistic reasoning and knowledge acquired through extensive pre-training, LLMs present a new paradigm for machine control by combining machine learning and digital twins. Notably, the approach of fine-tuning pre-trained models for specific fields and improving performance with various techniques at the inference stage has greatly expanded the capabilities of traditional AI. As demonstrated in nuclear reactor autonomy and robotic control among other cases, LLMs can serve as intelligent agents capable of interpreting abstract human instructions and translating them into executable actions within complex mechanical systems. These technological innovations are expected to go beyond mere automation, fostering a new industrial landscape where seamless collaboration between humans and machines becomes the norm. With the increasing adoption of LLM-based control systems in aerospace, shipbuilding, offshore, and heavy industries, the intelligentization of the entire industrial sector is set to occur at an accelerated rate. This paper explores how LLM-based agents, integrated with digital twins, enable autonomous and intelligent control of complex mechanical systems, focusing on nuclear reactor operations as a prime example.

Compacted bentonite buffers are crucial components in engineered barrier systems (EBS) for high-level radioactive waste (HLW) disposal. However, their physical properties significantly attenuate radio frequency (RF) signals, complicating wireless sensor implementation. This paper experimentally investigates the RF attenuation characteristics of various compacted bentonite buffers using software-defined radios (SDRs). Both powder and granule-type bentonite blocks were fabricated and evaluated under different compaction pressures and water contents. For measurements, the SDR transmits frequency-offset single-tone signals with pulse shaping, while changing the transmit power and carrier frequency. Experimental results indicate that granule-type bentonite exhibits greater RF signal attenuation than powder-type bentonite due to its higher dry density. Furthermore, even under identical dry density conditions, granule samples are more sensitive to water content variations than powder samples. Additionally, engineering-scale tests show that each additional 25 cm of buffer thickness increases signal attenuation by about 12 dB at a dry density 1.6 g/cm3. These findings provide valuable insights for designing wireless monitoring sensors in HLW disposal systems, highlighting the impact of bentonite type, density, moisture content, and thickness on RF signal propagation.

Measuring the in situ erosion rate of tungsten using an optical emission spectroscopic diagnostic technique, so called the S/XB method, has recently gained attention in current fusion research. This method calculates the erosion rate by multiplying the S/XB value, which represents ionization per photon emission, with the intensity of the specific spectral line. The S/XB value was given by the ionization rates (S) and the excitation rates (X) from the ground and the metastable levels and the branching ratio (B) for the specific radiative transition of neutral tungsten (W I), assuming a corona equilibrium among the ground, metastable, and upper resonance levels. The conventional S/XB method assumes a Boltzmann distribution for metastable level densities and introduces the free parameter of the tungsten atomic characteristic temperature ( TW). Herein, we propose an improved S/XB method to measure the erosion rates of tungsten in a divertor to eliminate the ambiguity caused by TW. Our approach directly calculates the densities of ground and metastable levels using a set of photon emission equations that relate their densities to multiple spectral line intensities within the framework of coronal equilibrium. Subsequently, the sputtered flux is obtained from the matrix operator form of S/XB and the multiple spectral line intensities given by the measurement. Our proposed method was experimentally tested using the plasma beam irradiation facility by comparing the gross tungsten erosion rates calculated using our method with those obtained from conventional approaches and those determined through the sputtering yield by the Ar⁺ ion beam flux. From the experiment, we obtained the sputtered tungsten flux of 4.0 × 10²⁰ m⁻² s⁻¹ ( ±2.1 × 10²⁰) using our method at a discharge current of 150 A from the plasma source and an ion incident energy of 100 eV, while the previous method yielded a range from 1.4 × 10²⁰ m⁻² s⁻¹–1.9 × 10²¹ m⁻² s⁻¹ by varying TW and spectral lines. Using the sputtering yield method, a sputtered flux of 4.1 × 10²⁰ m⁻² s⁻¹ ( ±1.1 × 10¹⁹) was measured as a reference value. The results demonstrate that our S/XB method significantly reduces ambiguity in the selection of spectral lines and the TW parameter, and closely agrees with the reference values, offering a more accurate and consistent approach for measuring tungsten erosion in fusion reactors.

An X-band linear accelerator (LINAC) system for radiation therapy has beendeveloped. This system is designed to utilize a dual-head gantry radiotherapysystem by Sungkyunkwan university. The electron acceleration cavity is plannedto generate 6 MV photon beam with 70 mA peak current using peak power of1.7 MW RF power. Our study details the development and dosimetric evaluationof an X-band linear accelerator for radiation therapy, equipped with a dualheadgantry for improved treatment precision. Dosimetric analysis was performedusing a solid water phantom and an ionization chamber to measure the PercentageDepth Dose (PDD), with the results affirming the simulation data from theEGSnrc Monte Carlo code. Adjustments were proposed to address beam spotbias caused by the ion pump’s placement. The experimental outcomes demonstratedthe system’s potential for precise cancer treatment, corroborating theeffectiveness of the X-band LINAC technology.

Background Sorghum grains are rich in phenolic compounds, which are noted for their anticancer, antioxidant, and anti-inflammatory properties, as well as volatile compounds (VOCs) that contribute to aroma and fermentation processes. There is a known close relationship between sorghum coat color and phenolic compound content (PCC), particularly flavonoids which are pigments that confer red and purple colors in flowers and seeds. Results Our results showed that black seeds had the highest total tannin content (TTC) and ketone content, which were measured at 457.7 mg CE g-1 and 96 g 100 g-1, respectively, which were 4.87 and 1.35 − fold higher than those of white seeds. L* showed a negative correlation between TTC (r = -0.770, P < 0.01) and ketone (r = -0.814, P < 0.01), while TFC and a* showed a strong positive correlation (r = 0.829, P < 0.001). RNA sequencing analysis identified 1,422 up-regulated and 1,586 down-regulated differentially expressed genes. Weighted gene co-expression analysis highlighted two color-related gene modules: the magenta 2 module associated with TTC, TPC, VOCs and L* value, and the blue module associated with TFC, and a* values. Hub genes identified within these modules included ABCB28 in the magenta 2 module, and PTCD1 and ANK in the blue module. Conclusions We confirmed the relationship between PCC, VOCs, and seed coat color, with darker seed coat colors showing higher tannin, ketone contents and redder colors indicating higher flavonoid content. Network analysis helped pinpoint key genes involved in these traits. This study will provide essential data for improving the food and industrial use of sorghum.

Improving wear resistance in Haynes 25 alloy is crucial for the development of flexible nuclear power reactors. Herein, laser-directed energy deposition (L-DED)-assisted substrate preheating is reported as an efficient strategy to alleviate cracks and pores in the alloy. The substrate-preheated alloy (300PH) exhibited no microcracks and a 45.2% reduction in pore fraction compared to the non-preheated alloy (NonPH). Moreover, 300PH exhibited a 7% lower Vickers microhardness than that of NonPH, whereas its nanohardness decreased by 3.6 and 2.9% in the dendritic and interdendritic regions, respectively. Dislocation strengthening was the dominant contributor to the theoretical yield strength and microhardness. Furthermore, preheating influenced the dislocation contribution substantially by reducing the residual stress leading to reductions in geometrically necessary dislocations and total dislocation density, thereby reducing microhardness. Therefore, preheating the substrate mitigated pores and cracks, effectively improved the structural integrity of L-DED Haynes 25 alloy, without significantly compromising the hardness.

To address gamma spectrometry on complex-shaped materials when the conventional method based on certified reference materials is impractical, we propose a new 3D-scan-based source modeling method for reflecting geometry of complex-shaped materials. Various complex-shaped materials were selected, scanned with tailored methods depending on the scanned objects, and the scanned 3D data were integrated into the source term models for Monte Carlo simulation. The developed method has been confirmed that all complex-shaped materials thus created can be cast into the Monte Carlo simulation toolkit Geant4 as source terms. It produced mesh deviations of all samples within 1 mm, validating its utility for practical applications. The developed method was experimentally validated using CRM, proving the accuracy of the method. The proposed method enables a comprehensive efficiency calibration for radioactivity analysis of complex-shaped materials without the need for destructive preprocessing.

We report new constraints on axionlike particles (ALPs) using data from the NEON experiment, which features 16.7 kg of NaI(Tl) target located 23.7 m from a 2.8 GW thermal power nuclear reactor. Analyzing a total exposure of 3063 kg · day , with 1596 kg · day during reactor-on and 1467 kg · day during reactor-off periods, we compared energy spectra to search for ALP-induced signals. No significant signal was observed, enabling us to set exclusion limits at the 95% confidence level. These limits probe previously unexplored regions of the ALP parameter space, particularly for axion masses ( m a ) near 1 MeV / c 2 . For ALP-photon coupling ( g a γ ), limits reach as low as 6.24 × 10 − 6 GeV − 1 at m a = 3.0 MeV / c 2 , while for ALP-electron coupling ( g a e ), limits reach 4.95 × 10 − 8 at m a = 1.02 MeV / c 2 . This Letter demonstrates the potential for future reactor experiments to probe unexplored ALP parameter space. Published by the American Physical Society 2025

GaN epilayers grown on c-plane sapphire substrates were irradiated with different doses of γ-rays ranging from 300 to 3000 krad. From the photoluminescence (PL) measurement, the yellow PL (YL) intensity decreased with increasing the γ-ray irradiation dose. From the deep level transient spectroscopy (DLTS), three defect states of E1, E2, and E5 levels with activation energies of 0.17 ± 0.02, 0.52 ± 0.01, and 0.97 ± 0.02 eV below the conduction band edge were found in the samples. The E1, E2, and E5 levels originated from the defects of nitrogen vacancy (VN), nitrogen antisite (NGa), and interstitial nitrogen (Ni), respectively. With increasing γ-ray doses, the Nt value of NGa was increased, while the Nt values of VN, Ni, VGa–Ni complex decreased. Therefore, it was suggested that the yellow PL band originated from the VGa–Ni complex.

A quantitative structure–activity relationship (QSAR) model for predicting the stability constant of uranium coordination complexes to accelerate the discovery of novel uranium adsorbents was developed and evaluated. Effective uranium adsorbents are crucial for mitigating environmental and health risks associated with uranium wastewater, an unavoidable byproduct of nuclear fuel production and power generation, as well as for sequestering uranium from seawater. QSAR modeling addresses the limitations of quantum mechanics calculations and offers a time- and cost-efficient computational approach for exploring vast chemical spaces. The QSAR model was built using a dataset of 108 uranium complexes, incorporating features such as physicochemical properties, coordination numbers of ligands, molecular charge, and the number of water molecules. Catboost regressor achieved an R² of 0.75 on the external test set after hyperparameter optimization. Applicability domain analysis was conducted to evaluate model predictive performance. The QSAR model predicts stability constants from the molecular composition alone and is a valuable tool for the efficient design of safer and more sustainable uranium adsorption materials, potentially improving uranium collection processes.

Since the performance of MPD thrusters is highly dependent on the applied magnetic field, we experimentally investigated the effects of magnetic field geometry. Thrust, specific impulse, and ion energy distribution were measured under various operating conditions. The results indicate that the magnetic field configuration of permanent magnets with a magnetic null point may limit effective ion acceleration, leading to reduced thrust while the permanent magnet produces a stronger applied magnetic field ( B A : 0.175 T) than the electromagnet ( B A : 0.016–0.065 T). For the electromagnet configuration, thrust increased more significantly with discharge current at a lower flow rate (500 sccm) and a higher electromagnetic coil current (40 A). When the discharge current was increased to 300 A under the aforementioned conditions, the maximum thrust of 436 mN and the specific impulse of 2935 s were obtained. From these observations, the current-voltage (I–V) characteristics, which are strongly influenced by the magnetic field, appear to be closely linked to the thruster performance, as evidenced by the measured thrust and ion energy distributions. The findings highlight the dominant influence of the magnetic field geometry on the thruster performance, along with the contributions of the discharge current and the argon flow rate.

Vertical farming offers the advantage of providing a stable environment for plant cultivation, shielding them from adverse conditions such as climate change. For fruit‐harvesting plants like tomato, vertical farming necessitates the optimization of plant growth and architecture. The gibberellin 3‐oxidase (GA3ox) genes encode gibberellin 3‐oxidases responsible for activating GA within the pathway and modulating stem length. Among the five SlGA3ox genes, we targeted the coding regions of three SlGA3ox genes (named SlGA3ox3, SlGA3ox4 and SlGA3ox5) using multiplex CRISPR genome editing. The slga3ox4 single mutants exhibited a slight reduction in primary shoot length, leading to a smaller stature. In contrast, the slga3ox3 and slga3ox5 single mutants showed subtle phenotypic changes. Notably, the slga3ox3 slga3ox4 double mutants developed a more compact shoot architecture with minor physiological differences, potentially making them suitable for vertical farming applications. We observed a correlation between total yield and plant size across all genotypes through multiple yield trials. Observations from vertical farm cultivation revealed that slga3ox3 slga3ox4 plants possess a markedly compact plant size, offering potential benefits for space‐efficient cultivation. Our research suggests that targeted manipulation of hormone biosynthetic genes can effectively tailor plant architecture for vertical farming.

The threat of herpes zoster (HZ) is increasing, particularly in the elderly and immunocompromised individuals. Although two platform vaccines are currently available for HZ prevention, the low effectiveness of the live attenuated varicella-zoster virus vaccine (Zostavax®), and the high reactogenicity and limited supply of the AS01 adjuvant gE subunit vaccine (Shingrix®) indicate that, the development of more effective and safe vaccines is required. Compared to conventional vaccines, mRNA vaccines offer the advantages of faster production and generally do not require adjuvants. However, no authorized mRNA vaccine is currently available for HZ. Therefore, we aimed to prepare a gE mRNA vaccine and evaluate the immunogenicity compared with the two commercial vaccines in mice. The gE mRNA vaccine elicited a robust humoral immune response, as measured by an enzyme-linked immunosorbent assay and the fluorescent antibody to membrane antigen test. The mRNA vaccine binding antibody level was comparable to that of Shingrix® and significantly higher than that of Zostavax®. In contrast, in cellular immune responses, which were evaluated by ELISpot assays and intracellular cytokine staining assay, the VZV gE mRNA vaccine induced significantly higher responses than Zostavax® and Shingrix®. In addition, the antibody-dependent cellular phagocytosis activity of the gE mRNA vaccine was comparable to that of the commercial vaccines. However, the highest antibody-dependent cellular cytotoxicity response was achieved by Shingrix®, followed by gE mRNA and then Zostavax®. Our results demonstrate that the mRNA HZ vaccine candidate elicited robust immunogenicity, especially in cellular immunity, and shows a promising potential for HZ prevention.

This study aims to quantitatively evaluate the photoneutrons produced by each accessory of the accelerator head using Monte Carlo simulation. First, the elements simulated in MCNP6 are tungsten, with a density of 19.25 g/cm3, and copper, with 8.96 g/cm3. Second, the accessories include a primary collimator, jaw, flattening filter, and single/composite targets, vary depending on the photon beam energy. The neutron energy spectrum was obtained using the F2 tally function on the sphere’s surface with a field size of 10 × 10 cm2. Additionally, the contribution of neutron generation from each accessory in the head part was analyzed. As a result, neutron generation was observed in the 15–20 MeV energy range, reflecting the threshold energy for the photonuclear interaction of each element. At lower photon beams (8 and 10 MeV), the target consists only of copper. More than 75% of all generated neutrons are caused by the primary collimator. It was found that photoneutron generation is significantly influenced by the composition of the material used and that neutron production increased rapidly near the beam interaction point. Hence, it is concluded that using copper elements could efficiently reduce radiation exposure, minimizing patient dose and contributing to the reduction and management of photoneutron production for improved safety in radiotherapy applications.