This study investigates how long-term changes in mesoscale wind systems have influenced near-surface PM10 concentrations in central Korea, focusing on Chungcheongbuk-do (Chungbuk Province) during spring from 2000 to 2024. Observational data reveal a nationwide decline in near-surface wind speeds, particularly during spring in the 2010s. Empirical Orthogonal Function (EOF) analysis of 850 hPa wind speed anomalies indicates that this weakening trend is linked to synoptic-scale atmospheric variability over the East Asia-North Pacific region. As transboundary contributions of PM10, particularly from eastern China, have declined in recent years, the role of mesoscale wind patterns in shaping local PM10 concentrations in central Korea has become increasingly significant. To assess the influence of weakened mesoscale winds, two contrasting years were analyzed: 2011, marked by anomalously strong winds, and 2023, characterized by anomalously weak winds. Eulerian PM10 flux convergence (PMFC) analysis revealed a shift from divergence-driven dispersion in 2011 to weak PM10 convergence and accumulation in 2023. Despite these stagnant conditions in 2023, PM10 concentrations continued to decline in both Chungbuk and across Korea, underscoring the dominant effect of anthropogenic emission reductions. These findings suggest that although weakened wind conditions can limit pollutant dispersion, sustained emission control measures remain effective in improving air quality.

This study evaluates how road profile and speed affect tire loads of a hydrogen tube trailer using MSC Adams/Car multibody dynamics simulation. A tractor and trailer loaded with 64 high-pressure cylinders were modeled, and four representative road profiles flat, pothole, short-wave, and long-wave were applied at 30, 60, and 80 km/h. Vertical tire load time histories were extracted for five wheel positions. Flat roads yielded stable loads matching static distribution. Potholes produced short, high-amplitude impacts (up to 120 kN at 30 km/h) with reduced peaks at higher speeds. Short-wave profiles caused severe asymmetric roll loads (67 kN at 80 km/h), while long-wave inputs generated smoother, moderate increases over longer durations. Load amplification diminished toward trailer axles due to suspension energy dissipation. The results inform structural design of tube trailers and development of speed-control or active load-mitigation strategies for autonomous hydrogen transport vehicles.

Aircraft Noise is a sound that humans do not want. In this study, based on the Rotax 914 engine used in Korea, the Propeller blade angle was changed by 1 degree for the 3-leaf “K company” Propeller and the 3-leaf “G” wooden Propeller, and the engine RPM was changed to examine the Noise and thrust changes. The purpose of this study is to check whether Noise and thrust loss are the least at the engine's maximum RPM, and to propose an aircraft operation plan in the noisy aerodrome area based on the values. This research further seeks to identify optimal propeller configurations that balance acoustic performance and thrust efficiency. The results are expected to aid in formulating guidelines for quieter flight operations near populated areas.

Most engines for small vessels operating in coastal waters, such as fishing boats, are equipped with a reduction gear to reduce the engine's rotational speed. Small vessels are equipped with engines of fixed output and reduction gears of single reduction ratio only. This paper is a study on the development of a two-stage reducer capable of controlling the reduction ratio according to the light and full load conditions of a ship. Because the torque and rotational speed delivered to the propeller can be flexibly adjusted, the engine load can be maintained appropriately. In addition, because the engine room space is limited, the development of a two-stage reducer with an integrated power take off (PTO) was pursued to minimize the volume. Through this development, we were able to confirm a reduction in fuel consumption rate because we did not have to consume a lot of fuel to maintain maximum output. Reducing fuel consumption can result in reduced harmful exhaust emissions. Additionally, it can be expected that the frequency of failures that may occur due to overload can be reduced.

This study investigated the legibility distance characteristics of variable speed limit signs and variable message signs under foggy conditions according to different luminance levels. In South Korea, the current installation standards for these signs are based on normal weather conditions, and empirical analyses of their visibility under adverse weather conditions remain limited. To address this issue, a controlled large-scale experiment was conducted at the Yeoncheon SOC Test Center, where artificial fog was generated in a tunnel environment. Seventeen elderly participants (average age: 70 years) participated in the experiment. They walked toward a sign to identify the distance at which it became legible. The experiment varied the fog visibility levels (50–80 m, 30–50 m, and 10–30 m) and display luminance (six levels). The results showed that as the fog density increased (that is, visibility decreased), the average legibility distance decreased. Conversely, higher luminance levels consistently improved legibility distance under foggy conditions. Under normal weather conditions, changes in luminance had a minimal impact on legibility. Compared with the minimum legibility distances calculated based on the design speed, many cases under foggy conditions failed to meet these thresholds, particularly at lower luminance levels. These findings indicate that the current luminance standards may not adequately ensure sign legibility under adverse weather conditions, underscoring the need for updated luminance guidelines that reflect environmental conditions. The results of this study provided quantitative data to support policy revisions and technical advancements aimed at improving road safety.

일반적으로 수중함은 대부분의 운항 조건이 수중조건이기 때문에, 수중에서 운항 성능이 최적화될 수 있도록 설계된다. 하지만 수중함은 작전에 따라 다양한 운항 조건이 요구되고, 입/출항 시 수상 조건을 무조건 만나기 때문에 수상 조건에서의 운항성능도 중요한 설계 인자로 다뤄져야 한다. 상선 및 부유체의 내항 성능 해석을 위해 대부분의 조선업계에서는 포텐셜 코드를 이용하여 수치해석을 수 행하고 있으며, 실제 프로젝트에 널리 적용하고 있다. 하지만 수중함의 내항 성능 해석을 위해 포텐셜 코드를 적용할 경우 수중조건에서 는 수치해석이 가능하나, 수상 조건에서는 수치해석의 정확도가 현저히 떨어지는 것으로 알려져 있다. 본 연구에서는 Computational Fluid Dynamics(CFD)를 이용하여 수중함의 수상 조건에서의 내항 성능 해석 정확도를 개선하고자 했으며, 실제 수중함의 작전 상황을 고려하여 함속 변화에 따른 내항 성능 특성을 분석하였다. CFD 계산 결과를 통해 수중함의 전진 속도에 따라 파랑의 조우 주파수가 바뀌고 공진 영역이 변화함을 확인할 수 있었고, 이는 수중함의 수상 조건 운항 시 함속의 변화에 따른 내항성능 특성을 잘 이해하는 것이 중요함을 보여준다.

국제경영 환경에서 지속 가능한 발전 목표가 널리 수용됨에 따라, 기업의 ESG(환경/Environment, 사회/Social, 거버넌스/Governance) 성과는 글로벌 시장에서 다국적기업의 성공을 결정하는 핵심 지표 중 하나로 자리 잡고 있다. 본 연구는 제도이론에 근거하여 신흥시장 다국적기업의 ESG 성과가 국제화 속도에 어떻게 영향을 미치는가 를 탐구하였다. 이와 더불어 본 연구는 ESG 성과와 국제화 속도 간 관계에 대해 최고경영자의 해외 경험과 기업 의 소유구조, 즉 국유기업 여부가 어떠한 조절 효과를 미치는지에 대해서 검증하였다. 2010년부터 2022년까지 중국 A주 시장에 상장된 1,648개 기업의 8,329개 표본을 분석한 결과, 신흥시장 다국적기업의 ESG 성과는 국 제화 속도에 긍정적인 영향을 미치는 것으로 나타났다. 조절 효과의 분석 결과, 다국적기업 최고경영자의 해외 경 험은 이러한 관계를 약화시키는 것으로 나타났는데, 이는 높은 해외 경험을 가진 최고경영자의 경우, 국제화 속도 를 결정하는 데 있어 ESG 성과에 대한 의존도를 줄이는 한편, 보다 신중한 국제화 전략을 취하기 때문으로 해석 할 수 있다. 또한 신흥시장 다국적기업이 국유기업일 경우에, 민간기업에 비해 ESG 성과와 국제화 속도 간의 긍정 적인 관계가 약화되는 것으로 나타났는데, 이는 국유기업이 ESG 성과를 통해 빠른 국제화 속도를 추진할 때 정당 성 확보의 어려움에 직면할 수 있음을 시사한다. 본 연구의 결과는 다국적기업의 ESG 전략 및 성과가 글로벌 시장 에서 정당성을 강화하고 국제화 전략의 중요한 요인이 될 수 있음을 강조하는 동시에, 그 효과가 최고경영자의 특 성과 기업의 소유구조에 따라 달라질 수 있음을 보여준다. 이러한 결과는 신흥시장 다국적기업이 ESG 전략을 효 과적으로 활용하기 위해서는 경영진의 리더십과 소유구조를 함께 고려한 종합적인 접근이 필요함을 시사한다.

Speed management in Korea currently emphasizes the setting of speed limits and controlling vehicle speeds to align with these standards. However, monitoring safe and stable speeds tailored to specific road sections is essential for enhancing pedestrian safety in urban areas. In this study, a crash frequency model was developed to define the speed stability range and identify the critical threshold at which the crash frequency changes rapidly. This threshold serves as a reference point for assessing the speed stability levels. Individual vehicle trajectory data collected from 20 road segments in Daejeon-si were used to calculate the speed-related safety evaluation indicators that served as input variables for the safety model. The speed stability range calculation incorporates speed-related indicators and road facility data from Daejeon-si, allowing the model to consider the surrounding infrastructure. The findings revealed that intersections and crosswalks are positively correlated with cumulative crash occurrences. Crash frequency predictions showed higher crash likelihoods at average driving speeds below 30 km/h, indicating that congested conditions at intersections or at peak times necessitate increased safety management. Measures for maintaining safe and appropriate vehicle speeds within identified safe ranges are critical. The speed stability range calculation methodology provides a foundation for establishing traffic safety management strategies that focus on speed control in urban areas. These results can guide the development of targeted safety interventions that prioritize pedestrian protection and optimize safe driving speeds across various road segments.