Crash risk in metropolitan areas arises from the interaction among driver behavior, enforcement infrastructure, and urban environmental conditions; however, microspatial evidence remains scarce. This study examines the effects of automated speed-enforcement cameras on the crash risk in Seoul at the legal-dong level using the accident risk index, which accounts for both crash frequency and injury severity. The dataset combines crash records, enforcement infrastructure, school-zone information, demographic indicators, and land-use characteristics. Methodologically, a Bayesian negative binomial regression model was employed to address overdispersed crash data, whereas gradient-boosting machine and eXtreme Gradient Boosting models with SHAP interpretations were applied to capture nonlinear effects, heterogeneity, and variable interactions. The results reveal that the crash risk is spatially concentrated, with a small proportion of districts contributing disproportionately to the overall exposure. Regression analysis highlights enforcement and behavioral factors as significant predictors, whereas machine-learning models emphasize the added importance of structural and demographic characteristics, such as road area and floating population. This divergence reflects the sensitivity of the regression to collinearity and linearity assumptions in contrast to the flexibility of tree-based methods in uncovering nonlinear and context-dependent influences. In general, the findings reflect the value of integrating statistical and machine-learning approaches for a more comprehensive understanding of crash risk at the microspatial scale. This study advances the methodological diversity in traffic-safety research and provides practical evidence that cameradeployment strategies should be context sensitive while targeting areas with concentrated risks and distinct structural and demographic profiles.

This study presents the design and FPGA implementation of a low-power, high-throughput digital modem for Medical Implant Communication System (MICS) applications. The proposed system applies a π /4-D8PSSK modulation technique to achieve high data efficiency while maintaining low power consumption. Implemented on a Xilinx Spartan-7 FPGA, the modem achieves a data rate of 16.4 ± 0.3 Mbps, with a power consumption of 0.6 ± 0.02 W/h, demonstrating a 40% improvement in energy efficiency compared to conventional 4FSK systems. The system satisfies IEEE 802.15.6 and ITU-R RS.1346 standards, with verified waveforms through MATLAB–Simulink and Chipscope. This work contributes to localization of medical implant communication technologies and provides a foundation for ASIC-based integration for next-generation biomedical and industrial wireless systems.

Truck platooning technology, which utilizes vehicle-to-vehicle communication to enable two or more autonomous trucks to travel in a platoon, is garnering attention. However, before platooning is implemented, an environment that can stably maintain a constant speed must be established. Therefore, maintaining a constant speed is a key prerequisite for truck platooning. To overcome the limitations of previous studies, which relied on traffic simulations or limited experiments, this study analyzes second-by-second truck DTG driving records obtained from highways near major domestic ports. Based on these data, a sliding-window technique was employed to detect constant-speed driving patterns and estimate the rate of constant-speed driving by section. The analysis revealed a high rate of constant-speed driving at the Noeun JCT–Dongcheongju IC, where the traffic volume was low and the road alignment was gentle. However, a low rate was observed at the Gunpo IC–Donggunpo IC, where ramp entries and exits were frequent. Subsequently, a multivariate fractional polynomial model was employed to analyze factors influencing constant-speed driving. The main factors identified were speed dispersion, average duration of constantspeed driving, and volume of large trucks per lane. This shows that speed stability, continuity of driving patterns, and vehicle composition within a section are more important factors in determining constant-speed driving than the average driving speed or traffic volume. This study is significant because it empirically elucidates the characteristics and factors influencing constant-speed driving using large-scale field data. Furthermore, it is expected to provide fundamental data for selecting suitable sections for truck platooning and establishing logistics efficiency policies.

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.