Korea Naval Academy

Subway systems are highly vulnerable to disasters because of their confined underground structures and limited evacuation routes, making accurate evacuation analysis essential for reducing casualties. Most existing studies overlook panic behavior, leading to unrealistic assessments of evacuation efficiency. This study develops a modeling framework that integrates panic behavior into agent-based subway evacuation simulations. The framework incorporates three behavioral factors: reaction delays to emergency cues, hesitation at decision points, and irrational route choices. Simulation experiments were conducted under different occupancy conditions, and results from panic-integrated and non-panic scenarios were compared. Findings show that the inclusion of panic significantly prolongs evacuation time, with delays of up to 30% in full-scale scenarios due to congestion and route errors. These outcomes demonstrate that panic behavior exerts a decisive influence on evacuation dynamics and should not be neglected in simulation studies. Incorporating panic into evacuation modeling provides a more realistic basis for designing safer subway systems and developing effective emergency response strategies.

During the Coronavirus Disease 2019 (COVID-19) that began in March 2020, nurses encountered unprecedented challenges, leading to significant physical and psychological distress. This study investigated the factors contributing to posttraumatic growth (PTG) among nurses following the pandemic, focusing on personal, social, and organizational predictors. This cross-sectional correlational study used survey data from 307 nurses who provided direct care to COVID-19 patients. Participants completed an online survey that included items on demographic information, trauma experiences, social support from personal and work relationships, occupational factors (e.g., resource availability, job conditions, job satisfaction), and PTG. Multiple regression analyses were conducted to identify the significant predictors of PTG. Coworker support was the strongest predictor of PTG, followed by job conditions, job satisfaction, and personal interactions. Resource availability, specifically that of mechanical ventilators, also significantly predicted PTG. However, supervisor support and PPE availability of personal protective equipment did not significantly influence PTG. This study contributes to the literature on PTG at work by examining the effects of occupational enablers and proposing practical interventions for healthcare organizations. Our findings suggest that occupational health practices should focus on enhancing peer support, improving working conditions, ensuring adequate resources, and providing comprehensive mental health support. These measures can help promote nurses' PTG and ensure their well-being following a traumatic event.

The COVID-19 pandemic highlighted the need for a scientific framework that enables quantitative assessment and control of airborne infection risks in indoor environments. This study identifies limitations in the traditional Wells–Riley model—specifically its assumptions of perfect mixing and steady-state conditions—and addresses these shortcomings by adopting the REHVA (Federation of European Heating, Ventilation and Air Conditioning Associations) infection risk assessment model. We propose a five-tier risk classification system (Monitor, Caution, Alert, High Risk, Critical) based on two key metrics: the probability of infection (Pₙ) and the event reproduction number (R_event). Unlike the classical model, our approach integrates airborne virus removal mechanisms—such as natural decay, gravitational settling, and filtration—with occupant dynamics to reflect realistic contagion scenarios. Simulations were conducted across 10 representative indoor settings—such as classrooms, hospital waiting rooms, public transit, and restaurants—considering ventilation rates and activity-specific viral emission patterns. The results quantify how environmental variables (ventilation, occupancy, time) impact each setting’s infection risk level. Our findings indicate that static mitigation measures such as mask-wearing or physical distancing are insufficient without dynamic, model-based risk evaluation. We emphasize the importance of incorporating real-time crowd density, occupancy duration, and movement trajectories into risk scoring. To support this, we propose integrating computer vision (CCTV-based crowd detection) and entry/exit counting sensors within a live airborne risk assessment framework. This integrated system would enable proactive, science-driven epidemic control strategies, supporting real-time adaptive interventions in indoor spaces. The proposed platform could serve as a practical tool for early warning and management during future airborne disease outbreaks.

Kang, Y.D. and Koo, B., 2023. A study on the validation for the control methodology on outer structures in a laminar boundary layer. In: Lee, J.L.; Lee, H.; Min, B.I.; Chang, J.-I.; Cho, G.T.; Yoon, J.-S., and Lee, J. (eds.), Multidisciplinary Approaches to Coastal and Marine Management. Journal of Coastal Research, Special Issue No. 116, pp. 528-532. Charlotte (North Carolina), ISSN 0749-0208. In this paper, the effectiveness of flow control in the outer layer of the boundary layer destroying the hairpin vortices was visualized in a water channel. Here, hairpin vortices were generated beneath the test plate in a laminar boundary layer by a solenoid pinch valve controlled by a signal generator. The result of flow visualization demonstrated that a jet located outside of a boundary layer can destroy the neck of hairpin vortex, thereby disconnecting the link between the head and legs of the hairpin vortex. Detached from the head, the legs of the hairpin cannot be stretched in the streamwise direction anymore, leading to a reduction in the circulation of streamwise vortices and associated velocity fluctuations in the near-wall region. The data from hot-film were also reconstructed to confirm this procedure of real flow field. Both results showed that the legs of the control case were weakened compared to the uncontrolled case up to 15% in u-component velocity.

BackgroundThe aim of this study was to investigate the changes in isokinetic muscular performance among female adolescent elite handball athletes with the supplementation of Black Maca (BM).MethodsEight elite handball athletes were recruited for the present study. The intake capsules contained 2,500 mg of 100% concentrated BM extract and a placebo each, for 4 weeks. Isokinetic muscular performance and physical fitness were measured three times at 4-week intervals after the intake of BM and placebo, including baseline.ResultsThe one-way Analysis of Variance (ANOVA) analysis showed a significant improvement in 20 m-shuttle run (P < 0.001), 30°/s flexor (P < 0.01), and 120°/s flexor (P < 0.01) in isokinetic muscle function of the trunk, and 180°/s right extensor (P < 0.05), 180°/s left extensor (P < 0.05), and 180°/s left flexor (P < 0.01) in isokinetic muscle function of the knee, after BM supplementation. Post-hoc analysis indicated that the BM group had significantly higher results compared to the baseline and placebo groups in terms of 20 m-shuttle run, 30°/s flexor and 120°/s flexor of the trunk, 180°/s right extensor, 180°/s left extensor, and 180°/s left flexor of the knee.ConclusionBM supplementation can have a positive effect on improving the performance of elite handball players who engage in high-intensity movements by enhancing their isokinetic muscle function and endurance.