This study was conducted to verify the structural stability of the chassis frame of the Small electric low-floor bus. The chassis frame model was analyzed under its own weight and external loads to determine deformation and stress distribution. A finite element method (FEM)-based structural analysis was performed to verify the strength and durability of the chassis frame assembly components. The analysis results identified the maximum stress values and their locations throughout the system. Furthermore, considering the differences in materials used in each component, the maximum stress values for each component were individually calculated. Comparing the maximum stress values with the yield strength of each material confirmed the structural stability of the designed Small electric low-floor bus chassis frame.

Recently, changes in the electric vehicle transition policy have necessitated improved user acceptance by securing the competitiveness of electric vehicles over internal combustion engine vehicles. In particular, the importance of reliable condition diagnosis technology to prevent safety accidents such as battery pack fires has been receiving significant attention. However, lithium-ion battery packs, primarily used in domestic electric vehicles, require the development of battery pack health diagnosis technology that considers real-world driving characteristics, such as high energy density and irregular and incomplete charge/discharge patterns. This study utilized OBD-II data from 100 real-world electric vehicles to extract health indicators for assessing battery pack aging over time using IC curves. Using IC curves during charging, the most stable environment during real-world driving, key factors associated with battery pack aging were identified. The IC curves confirmed that aging increased with mileage from 30,000 km to 260,000 km, demonstrating the potential for developing integrated aging maps for the same vehicle model. Furthermore, this study is considered a practical tool for immediate condition assessment of electric vehicles without the need for additional equipment.

This study analyzes the usage behavior and travel characteristics of shared micro-electric vehicle (micro-EV) mobility services using large-scale empirical data collected over three years (2023-2025) from three pilot regions in Korea: Daejeon, Mokpo, and Jeju Island. By integrating the location-based driving records, user information, trip surveys, and weather data, 66,843 valid trips were extracted, including 49,264 trips matched with user attributes. Usage behavior was first examined through statistical analyses of user demographics and surveybased information on trip purposes, multimodal connections, and user satisfaction. The results indicate that micro-EV services support diverse usage behaviors, ranging from commuting and campus travel to leisure, with distinct regional differences in user composition and service roles. A travel pattern analysis further revealed clear temporal and environmental characteristics, including pronounced seasonal peaks between July and October, higher weekday utilization associated with commuting demand, high concentration of trips during daytime hours, and a nonlinear response to weather conditions, in which usage increased under moderate temperatures but declined during extreme heat, cold, or precipitation. A distance-based analysis showed that micro-EV trips were generally short-distance in nature, while substantial regional variations existed. Daejeon was dominated by ultra-short campus-oriented trips, Mokpo exhibited a broader distribution of short urban trips linked to daily activities and tourism, and Jeju Island demonstrated a higher share of mid-distance trips reflecting industrial park commuting and inter-destination travel. A spatial origin-destination (OD) analysis further highlighted region-specific network structures, with Daejeon forming a compact hub-based network, Mokpo displaying a dispersed pattern centered on major transit facilities, and Jeju Island exhibiting a multipurpose network shaped by commuting and tourism mobility. These findings provide empirical evidence that shared micro-EV services function as flexible region-dependent mobility solutions, underscoring the need for differentiated operational strategies, station-based service planning, and integration with local transport systems to support sustainable urban mobility.

This study was conducted to examine the structural stability of a lightweight structure for a sliding-type battery rack system located under an electric bus. To address the shortcomings of the existing sliding battery rack systems, the battery rack system was designed by applying lightweight materials and utilizing a bolt-mounting connection type. Finite Element Method(FEM)-based structural analysis was performed, considering both the system’s self-weight and the weight of the installed batteries. The analysis identified the maximum stress value and its location within the entire system. Furthermore, considering the different materials used in various components, the maximum stress values for each component were individually derived. By comparing the maximum stress with the yield strength of each material, it was confirmed that the designed lightweight battery rack system had secured structural stability.

전기추진 선박의 보급이 확대됨에 따라 추진축계의 정렬 불량, 비틀림 등 기계적 이상상태를 조기에 진단하기 위한 예지보전 (PHM) 기술의 필요성이 커지고 있다. 그러나 실제 운항 선박에서는 안전성과 운항 제약으로 인해 다양한 이상 상태를 의도적으로 재현하 기 어렵고, 이에 따른 학습·검증용 진동 데이터 확보에도 한계가 있다. 본 연구에서는 이러한 문제를 해결하기 위해 50kW급 전기추진 육 상 시험 시스템(Land‑Based Test System, LBTS)을 기반으로 전기추진 선박 추진축계의 비틀림 정렬 불량을 모사할 수 있는 실험 장치를 설계·구현하였다. LBTS는 SRPM(Synchronous Reluctance assisted Permanent Magnet)형 모터/발전기, AFE(Active Front End) 및 DC/DC 컨버터, 리 튬인산철 에너지저장장치(ESS)로 구성되며, PTO 모터를 슬라이딩 베이스에 장착하여 축 중심을 ±20mm 범위에서 조정할 수 있도록 제작 하였다(ESS 및 DC/DC 컨버터는 향후 추가적인 운전 조건 모사를 위해 탑재되었으며, 본 실험에서는 미사용). 이를 통해 정상 상태(0mm) 와 두 단계의 비틀림 상태(2mm, 4mm)를 설정한 후, 2,000rpm에서 3축 가속도계와 OROS사의 진동 분석기를 이용해 다채널 가속도 데이터 를 계측하고 FFT 분석을 수행하였다. 실험 결과, 비틀림이 증가할수록 진폭 및 주파수 성분의 변화 패턴이 관찰되었다. 본 연구에서 구축 한 0/2/4 mm 라벨링 진동 데이터셋과 LBTS 실험 환경은 향후 향후 1D/2D CNN 기반 PHM 알고리즘의 학습·검증에 활용될 수 있으며, 상태 분류 성능(Accuracy, Macro-F1)을 기준으로 오분류율 목표를 설정하여 정량 평가를 수행할 예정이다.

기후변화 대응을 위한 국가 온실가스 감축목표 달성을 위해 해운부문의 역할이 중요함에도 불구하고, 국내 해운부문 외부사업 참여는 특정 방법론에 편중되어 있다. 본 연구에서는 친환경선박 전환 기조에 따라 개발된 전기·하이브리드 추진 내항여객선 도입 방법 론을 분석하고, 적용 범위와 조건 개선 방안을 도출하였다. 기존 화석연료 추진 여객선을 동일 제원의 전기추진 선박으로 대체할 경우 연 간 약 210톤의 온실가스 감축효과가 발생하는 것으로 확인되었다. 또한, 현행 방법론이 내항여객선에 한정된 구조를 전체 연안선박으로 확대할 경우 감축 잠재량이 기존 대비 약 5배 이상 증가할 수 있음을 제시하였다. 이를 위해 신규 도입 선박의 경우 단계적으로 내항여객 선 외 다른 선박으로 적용 범위를 확대하도록 운항 데이터 기반 배출계수 개발이 필요함을 제시하고, 국제항해 선박도 국내항해 실적에 한하여 외부사업 참여가 가능하도록 개선 방안을 제시하였다. 이를 바탕으로 해운부문 외부사업 참여를 활성화하고 온실가스 감축 실적 을 제도적으로 반영함으로써, 국가 온실가스 감축목표 달성에 기여할 수 있을 것으로 기대된다.

Electric arc furnace (EAF) steelmaking is increasingly adopting sustainable carbon sources to improve slag foaming and reduce energy consumption. Among them, spent tire-derived carbon represents a viable alternative to coal, offering high volatile and carbon contents. However, its elevated sulfur level and modified slag chemistry can markedly affect foaming stability and desulfurization. This study elucidates the interactive effects of spent tire substitution (0-30 wt%) and slag basicity (CaO/SiO2 = 1.5-2.4) on foaming dynamics, bubble evolution, and sulfur behavior at 1,600 °C. Real-time imaging and quantitative analyses demonstrated that moderate substitution (10-20 wt%) enhanced initial foaming due to volatile-induced gas release, whereas excessive addition (30 wt%) caused unstable coalescence and premature collapse from sulfur-driven surface tension reduction. Lower basicity limited early foaming but improved long-term stability via increased viscosity, while higher basicity promoted rapid collapse and reduced sulfur retention. The optimal condition (CaO/SiO2 = 2.0) maintained stable foaming for over 40 min, achieving superior sulfur capture (about 24 %) and minimal refractory attack. Overall, these findings reveal the mechanistic coupling between carbon source, basicity, and interfacial properties, offering practical guidance for sustainable slag design and efficient sulfur control in EAF operations employing waste-derived carbonaceous materials.

Magneto-mechano-electric (MME) energy harvesters have emerged as a promising solution for maintenance-free power generation in rapidly expanding Internet of Things (IoT) environments, where replacing or wiring batteries is impractical. MME devices convert weak alternating magnetic fields, ubiquitous around power infrastructures, into useful electrical energy through sequential magnetic, mechanical, and electrical transduction processes. This review summarizes recent advances across triboelectric-, piezoelectric-, and hybrid MME architectures. Triboelectric MME generators employing nano-engineered polymer surfaces, flash-induced surface modification, and nanoscale pattern replication demonstrate low-cost fabrication routes while achieving significantly enhanced voltage and current outputs. Piezoelectric MME systems based on Mn-doped PMN-PZT single crystals highlight strategies for improving mechanical quality factors and resonance-driven power generation. Further, hybrid MME designs that integrate piezoelectric and electromagnetic induction mechanisms enable high-power outputs exceeding tens of milliwatts, sufficient to operate multifunctional IoT platforms and charge practical energy-storage devices. Collectively, these studies illustrate a transition of MME harvesting technologies from laboratory concepts to application-ready self-powered systems. Future opportunities lie in broadband resonance design, modular harvester integration, advanced power management, and multi-source hybridization for robust long-term operation in real environments.

Electric double-layer capacitors (EDLCs) have attracted significant interest as a promising energy storage solution because of their high-power density, exceptional charge/discharge cycle stability, and extended lifespan. Porous carbon is a key component of EDLCs given its outstanding chemical stability, high electrical conductivity, large specific surface area, and cost effectiveness. We fabricated porous carbon from oak wood as a raw material using an environment-friendly steam activation process (physical activation). Pretreatment (stabilization) was conducted using a mild acid (phosphoric acid) to achieve a high specific surface area and maintain structural stability. Oak wood-derived porous carbon (Oak-PC) produced with varying activation times following phosphate stabilization achieved high specific surface area (1050–1990 m2/ g), pore volume (0.44–0.95 cm3/ g), and carbonization yield (36%). Oak-PC retained ~ 90% of its performance at a high current density (10 A/g), demonstrating superior EDLC performance compared to that of commercial porous carbon. These results were attributed to the significant enhancement of the electrical properties of Oak-PCs, achieved by removing char through phosphate stabilization and strengthening bond stability. This study provides foundational data for developing sustainable energy storage technologies and enhancing the efficiency of next-generation energy storage systems by utilizing environmentfriendly biomass materials such as oak wood.

This study presents the results of compression, drop impact, and vibration durability analyses conducted to evaluate the mechanical reliability of Battery Pack Cases (BPCs) in electric vehicle (EV) systems. BPCs are essential structural components that must endure compressive loads, impact forces, and vibrational fatigue. Finite Element Analysis (FEA) was applied to a representative BPC model to assess deformation, impact resistance, and vibration endurance. The results indicate that the BPC maintained integrity within yield strength limits under compressive loading and effectively absorbed energy under drop impact. Furthermore, Power Spectral Density (PSD) analysis identified stress concentration regions, providing insights for structural optimization. Overall, the findings support the development of lightweight and reliable BPC designs for advanced EV applications.

전기추진 선박의 추진축계 이상상태는 심각한 선박 운항 장애를 초래할 수 있으므로, 추진 시스템의 상태를 정확히 진단하고 사전에 예방 유지보수를 수행하는 Prognostics and Health Management(PHM) 기술의 필요성이 증가하고 있다. 본 연구에서는 전기추진 선박 의 추진축 이상상태를 조기에 감지하고 진단하기 위하여 진동 데이터를 기반으로 한 머신러닝 기반 PHM 시스템의 개발과 성능 평가를 수행하였다. Land-Based Testing System(LBTS) 시스템에서 수집된 정상 상태와 축 정렬 이상 상태(0.5 mm, 1.0 mm, 1.5 mm)의 진동 데이터를 활용하여 데이터 전처리 및 특성 추출을 수행하였다. 연구에서는 Fully Connected Neural Network(FCNN) 및 Convolutional Neural Network(CNN)을 적용하여 이상 상태를 진단하는 모델을 개발하고 비교 분석하였다. FCNN 기반 모델은 단순한 구조로 빠른 학습이 가능 하여 실시간 모니터링에 적합한 반면, CNN 모델은 미세한 상태 변화를 효과적으로 탐지하는 데 탁월한 성능을 보였다. 성능 평가 결과 FCNN 모델은 평균 95% 이상의 정확도를 나타냈으며, CNN 모델은 이보다 더욱 향상된 성능을 제공하였다. 본 연구를 통해 개발된 진동 기반 PHM 시스템은 전기추진 선박 추진축 이상상태를 효과적으로 조기에 진단할 수 있는 능력을 입증하였다. 이러한 연구 성과는 전기 추진 선박의 안전하고 효율적인 운항을 위한 신뢰성 높은 유지보수 전략 수립에 중요한 기여를 할 것으로 기대된다. 향후 연구로는 데이 터 품질 개선 및 추가적인 딥러닝 모델 적용을 통한 성능 향상을 목표로 한다.

The development of high specific surface area and mesoporous activated carbons is required to improve the electrochemical performance of EDLC. In this study, kenaf-derived activated carbons (PK-AC) were prepared for high-power-density EDLC via phosphoric acid stabilization and steam activation. The pyrolysis behavior of kenaf with respect to the phosphoric acid stabilization conditions were examined via TGA and DTG. The textural properties of PK-AC were studied with N2/ 77 K adsorption–desorption isotherms. In addition, the crystalline structure of PK-AC was observed via X-ray diffraction. The specific surface area and mesopore volume ratio of PK-AC were determined to be 1570–2400 m2/ g and 7.7–44.5%, respectively. In addition, PK-AC was observed to have a high specific surface area and mesopore volume ratio than commercial coconut-derived activated carbon (YP-50F). The specific capacitance of PK-AC was increased from 77.0–99.5 F/g (at 0.1 A/g) to 49.3–88.9 F/g (at 10.0 A/g) with activation time increased. In particular, K-P-15-H-9–10 observed an approximately 35% improvement in specific capacitance at a higher current density of 10.0 A/g compared to YP-50F. As a result, the phosphoric acid stabilization method was confirmed to be an efficient process for the preparation of high specific surface area and mesoporous biomass-derived activated carbons, and the kenaf-derived activated carbons prepared by this process have great potential for application as electrode active materials in high-power EDLC.

The most basic control algorithm of the electric power steering system in the Korean refrigerating cart CoCo was first commercialized as a prototype in 2022 after the Motor Driven Power Steering (Electric Power Steering) was verified and applied to automobiles. In order to overcome the heavy load of small machines such as refrigerating carts weighing 750Kgf, the driver's great power is required, which can cause muscle skeletal disorders, causing many female drivers to complain of pain, and recently applied electric steering technology because it was urgent. In this study, we study a control algorithm that complements the stability of the existing control algorithm applied to the electric power steering device for electric carts and analyze and verify the steering performance of refrigerated carts through analysis using MATLAB/SIMULINK.