This study investigated the seasonal water quality characteristics of two key environmental flow sources for the Gwangju Stream: the Yeongsan River water supply and effluent from a sewage treatment plant. Monitoring data collected between 2019 and 2023 were analyzed for both sources, and field surveys from October 2023 to June 2024 examined confluence points where environmental flows entered the Gwangju Stream, measuring both main-stream and inflow waters. The Yeongsan River supply recorded its highest spring organic matter levels (mean BOD: 5.2 mg L-1; maximum: 8.7 mg L-1), while the sewage treatment plant effluent exhibited pronounced seasonal variation in total nitrogen (T-N), ranging from a summer low of 8.2 mg L-1 to a winter high of 13.8 mg L-1. Upstream water quality remained stable; however, downstream BOD increased annually by 8.2%, and total phosphorus (T-P) peaked sharply in summer (0.567 mg L-1). Field survey results indicated that in spring, T-N increased by up to 495%, BOD by 182%, and T-P by 290%; in winter, T-N rose by 239%, BOD by 164%, and COD by 73%. These findings reveal marked seasonal variability in the influence of environmental flow sources, with T-N showing the most substantial increase in spring. The results highlight the need for targeted nutrient management strategies, such as increasing the proportion of the plant’s effluent in spring to stabilize nutrient loads and improving its biological treatment efficiency in winter to reduce T-N concentrations. Season-specific measures of this kind can improve water quality and help sustain the ecological integrity of the Gwangju Stream.

This study analyzed the emission characteristics of major air pollutants from 97 domestic municipal solid waste incineration facilities using tele-monitoring system (TMS) data collected from 2015 to 2023. Focusing on the effects of the enforcement of enhanced national emission standards in 2019, this research examined changes in emission factors (EFs) of dust and nitrogen oxides (NOX) by facility capacity and aging level. The results showed that the average EFs for dust and NOX significantly decreased by up to 30% after enforcement (p<0.01~0.001), indicating the practical effectiveness of the strengthened standard. This trend was observed consistently across all facility sizes and aging levels, including large-scale and older facilities. In contrast, hydrogen chloride (HCl) and carbon monoxide (CO) did not show clear reductions and remained highly variable, suggesting that emission standards alone may not be sufficient for stable control. These findings demonstrate the need for optimized combustion conditions and improved post-treatment systems for pollutants such as HCl and CO. This study provides empirical evidence highlighting the importance of appropriate facility scale and systematic refurbishment cycles for stable emission reduction in municipal waste incinerators.

This study analyzed fall accidents involving boatswain’s chairs over the past ten years to investigate their underlying causes and effective preventive measures. The fall accidents in this study were classified according to construction type, work category, and sequence of work. Next, their direct causes were identified by applying the concept of serious injury factor. A focus group interview was conducted with six experts in boatswain’s chair-type scaffolding to derive preventive measures. The results of the investigation indicate that the majority of accidents occurred in maintenance works among construction types, and painting, caulking, and cleaning tasks among work categories. In terms of work sequence, most fall accents occurred while working with descending due to rope defects (loosening, breakage, or insufficient length) and anchorage failures. Based on these findings, two key preventive measures were proposed: (1) installing lifelines as a fail-safe measure to provide safety redundancy, and (2) implementing inherent safety measures to prevent rope defects and failures such as regular inspections, use of high-performance ropes, and ensuring proper anchorage strength. The findings of this study can be utilized in development of effective safety guidelines and policies for boatswain’s chair operations.

This study investigates the vibration characteristics of an aluminum subframe for small and high-speed vessels through modal and resonance analysis using the finite element method (FEM). Due to the low stiffness and damping of aluminum, concerns arise over structural resonance and fatigue. A 3D model based on actual design drawings was analyzed to extract six natural frequencies and corresponding mode shapes. Significant deformation was observed in the first and second modes (90.65 Hz, 110.60 Hz), which may overlap with operational frequencies. The fifth mode (263.70 Hz) showed high amplitude with Y-axis concentration, indicating lateral resonance vulnerability. Deformation ratios were used to identify dominant vibrational directions. Based on the findings, design strategies such as structural reinforcement, RPM adjustment, and damping device application were proposed to improve vibration safety in the early design stage.

본 연구에서는 벼메뚜기 탈지 추출물을 이용한 친환경 적인 은나노입자(AgNPs)의 생합성 가능성을 확인하고, 합 성된 AgNPs의 물리·화학적 특성과 항균 활성을 평가하였 다. AgNPs의 형성은 용액 색상 변화와 함께, 448 nm 부 근에서 특유의 표면 플라스몬 공명 흡광 피크가 관찰된 UV-Vis 스펙트럼을 통해 확인되었다. DLS 및 zeta potential 분석 결과, 평균 입자 크기는 98.4±0.9 nm, zeta potential은 -22.8±0.5 mV로 안정적인 분산 특성을 나타냈다. TEM 및 HR-XRD 분석을 통해 구형의 결정성 입자가 관찰되었 고, FT-IR 결과에서는 단백질 유래 작용기가 AgNPs의 환 원 및 안정화에 관여한 것으로 나타났다. 항균 활성은 disk diffusion assay를 통해 확인되었으며, 합성된 AgNPs는 S. Typhimurium, E. coli, S. aureus, B. cereus를 포함한 4종 식중독균에 대해 유의미한 항균 효과를 보였다. 이상의 결 과는 벼메뚜기 탈지 추출물이 AgNPs의 생합성 소재로 활 용 가능함을 시사하며, 향후 식품안전 응용에 활용될 수 있는 가능성을 제시한다.