Korea National University of Education

This study proposes a hybrid forecast-enabled adaptive crowbar coordination strategy to enhance low-voltage ride-through (LVRT) performance of doubly fed induction generator (DFIG) wind turbines. A unified electro-mechanical model in the αβ/dq frames with dual closed-loop control for rotor- and grid-side converters is built in MATLAB/Simulink (R2018b), and LVRT constraints on current safety and DC-link energy are explicitly formulated, yielding an engineering crowbar-resistance range of 0.4-0.8 p.u. On the forecasting side, a CEEMDAN-based decomposition-modeling-reconstruction pipeline is adopted: high- and mid-frequency components are predicted by a dual-stream Informer-LSTM, while low-frequency components are modeled by XGBoost. Using six months of wind-farm data, the hybrid forecaster achieves best or tied-best MSE, RMSE, MAE, and R2 compared with five representative baselines. Forecasted power, ramp rate, and residual-based uncertainty are mapped to overcurrent and DC-link overvoltage risk indices, which adapt crowbar triggering, holding, and release in coordination with converter control. In a 9 MW three-phase deep-sag scenario, the strategy confines DC-link voltage within ±3% of nominal, shortens re-synchronization from ≈0.35 s to ≈0.15 s, reduces rotor-current peaks by ≈5.1%, and raises the reactive-support peak to 1.7 Mvar, thereby improving LVRT safety margins and grid-friendliness without hardware modification.

Selecting elite youth athletes requires evaluating their current performance and future potential. In badminton, performance determinants differ according to event type and sex, making it essential to establish systematic evidence-based selection criteria. This study aimed to prioritize selection indicators for elite women's single badminton players using expert consensus through Analytic Hierarchy Process. Thirteen badminton experts participated in an Analytic Hierarchy Process survey to assess the relative importance of the indicators across three hierarchical levels. At the primary level, Anthropometric factors (0.58) ranked higher than Motor-performance factors (0.42). At the secondary level, Body Composition (0.47) was the highest within Anthropometric factors, whereas Physical strength (0.76) ranked highest in Motor-performance factors. At the tertiary level, Skeletal muscle mass (0.40), Thigh circumference (0.36), and Height (0.42) were prioritized for Anthropometric factors, whereas Agility (0.28) and Visual ability (0.63) were prioritized for Motor-performance factors. These findings provide objective, prioritized criteria for evaluating and selecting elite women's single players, supporting a more transparent and tailored identification process. This approach may serve as a foundation for developing selection systems that reflect event- and sex-specific demands in badminton.

The Oriental stork (Ciconia boyciana Swinhoe, 1873) is an endangered species, with active restoration efforts ongoing in Korea. Despite the ecological importance of host-specific parasites, such as chewing lice (Phthiraptera), information on the chewing lice fauna associated with C. boyciana in Korea remains unclear. Previous records of 2 chewing louse species from the host have been questioned due to potential misidentification. To clarify the chewing lice fauna of the host, we conducted a survey of captive C. boyciana at Yesan Oriental Stork Park, Korea, in October 2022. Morphological identification of collected louse specimens revealed 3 species: Neophilopterus incompletes (Denny, 1842), Ardeicola ciconiae (Linnaeus, 1758) and Colpocephalum zebra Burmeister, 1838. These species are typical ectoparasites of Ciconiiform birds and represent the first verified louse records of chewing lice from C. boyciana in Korea. Unlike with a previous report, Cuclotogaster heterographus (Nitzsch, 1866) and Anaticola anseris (Linnaeus, 1758) were not detected. Our findings provide an updated checklist of chewing louse species for C. boyciana in Korea, contributing to a more accurate understanding of host-parasite associations and supporting future conservation efforts for both the host and its associated parasite fauna.

Abstract String compactification in the framework of the low energy effective supergravity requires the perturbative control in both the large volume and the weak coupling expansions. However, when the complex structure moduli couple to some lattice structure, the Sp$(2(h^{2,1}+1))$ symmetry of the tree level K"ahler potential allows the correction to the K"ahler potential to diverge in the large field limit of the complex structure moduli, resulting in the breakdown of the perturbative control. Here the lattice structure naturally appears in the presence of a tower of states like the Kaluza-Klein or the string modes, an essential ingredient of the distance conjecture. The similar situation can be found from the axio-dilaton contribution to the corrected K"ahler potential, where the SL$(2, \mathbb{Z})$ symmetry as well as the coupling between the axio-dilaton and the lattice structure allow the correction to diverge in the weak coupling limit. In order to keep the perturbative control, the values of the complex structure moduli as well as the dilaton must have the upper bound, which is determined by the volume of the internal manifold and the string coupling constant, hence the Kaluza-Klein and the string mass scales. The form of the bounds are quite similar to that given by the distance conjecture, both prevents the descent of a tower of states.

Abstract This study assesses regional heavy rainfall patterns in Korea in. the summer of 2024. Torrential rainfall and disasters were reported during this time. In total 7 episodes of heavy rainfalls were observed in west Cheongju city. Total rainfall over the summer months was 795.0 mm representing 64.5% of the region’s mean annual rainfall (1232.4 mm). There is summer rainfall occurred over two distinct periods “the Changma season of steady rain” in June-July, and a heavy rain season in August-September associated with “convective cloud bands in a subtropical convergence zone” (SCZ).

An ongoing debate in education has centered on the concept of domain-general reasoning practices and whether such a position can explain how student learning in one discipline can influence their practices in another. For example, student learning in science impacts their learning in mathematics. Based on a model highlighting a significant relationship between reasoning practices used across science and mathematics, this study explored the lasting impact of learning science through the Science Writing Heuristics (SWH) approach on inductive and deductive reasoning in mathematics as well as deductive reasoning in science. Utilizing fourth-grade student data and follow-up data collected over three subsequent years, we applied the generalized DINA (deterministic inputs, noisy “and” gate) and linear regression models for analysis. The findings provide evidence of the immeote utilization of inductive reasoning in mathematics and a delayed advantage of deductive reasoning in both mathematics and science. These results support the implementation of argument-based approaches, like the SWH approach, on student development and utilization of domain-general reasoning. The findings of this study highlight the need for further research on the development of such reasoning resources when students are immersed in epistemically rich learning environments as proposed by national curricula. Additionally, further investigation is needed to determine whether these reasoning skills are applied across different disciplines, regardless of context.

ABSTRACT Freewriting is a writing technique where individuals write continuously for a set time without editing or revising. This study examines its effects on English as a foreign language (EFL) writing fluency, emotions, and learner perceptions among 149 Korean 8th‐grade students. Over ten weeks, students participated in eight five‐minute freewriting sessions as an instructional intervention. Data were collected through pre‐ and post‐intervention recount writing tests, writing anxiety and enjoyment questionnaires, and a learner perception survey. Fluency was measured by words per minute. The results revealed that second language (L2) writing fluency development through freewriting practice followed a non‐linear trajectory, marked by a shallow U‐shaped pattern: a decline in fluency was followed by a gradual upward trend, culminating in the highest level in the final session. The results also indicated improved fluency in recount writing tests, which suggests the gains achieved through freewriting practice transferred to new contexts. In addition, findings indicate that freewriting reduced writing anxiety and enhanced enjoyment. Most students believed freewriting helped improve their writing skills. The most frequently mentioned benefit was increased self‐confidence and written output, while the primary limitation was insufficient freewriting time. Overall, findings highlight freewriting as a valuable fluency‐based approach that supports fluency development and affective growth in secondary EFL contexts.