Earticle

Transport workers and logistics drivers operating electric delivery vehicles and freight trucks depend on charging infrastructure that is authenticated through vehicle-to-grid (V2G) protocols. This paper audits a widely cited ECC-based V2G authentication framework and exposes four structural vulnerabilities that directly threaten transport worker fleet operations: an executability gap in online verification steps where verifiers cannot reconstruct stated check values from transmitted messages, ecosystem-wide credential exposure triggered by a single service-provider compromise, timestamp-only freshness that permits replay attacks within clock-drift tolerances, and a session key assembled from static identifiers without a fresh ephemeral secret. A targeted redesign is proposed that retains the original three-party architecture while introducing nonce-bound ECC key agreement, rotating pseudonyms, and station-scoped authorization tickets. Evaluated across 100 to 800 concurrent vehicles, the revised protocol achieves complete replay detection and substantially improved compromise containment with a latency overhead of only 1.8 ms at peak load.

Workers who simultaneously engage in dementia caregiving and paid employment represent a critically vulnerable group facing compounded mental health burdens. This study developed a machine learning-based nomogram to predict depression risk among 25,634 family caregivers of home-dwelling dementia patients in South Korea, using data from the 2019-2020 national community health survey. LightGBM identified six key predictors from 135 variables: subjective stress level, subjective health status, cognitive impairment counseling history, economic activity status, gender, and dementia screening history. A Bayesian nomogram derived from multiple logistic regression achieved an AUC of 0.82, accuracy of 0.85, precision of 0.83, recall of 0.85, and F1-score of 0.83 under 10-fold cross-validation. Economically active female caregivers with a history of cognitive impairment counseling and high subjective stress showed a 96% predicted probability of depression, underscoring the urgent need for targeted mental health screening among workers who balance caregiving and employment responsibilities.

Healthcare workers who simultaneously provide patient care and manage telecare sensor monitoring systems represent a vulnerable workforce balancing caregiving and technical responsibilities. This study examines security vulnerabilities in the LightAuth lightweight authentication framework deployed in smart healthcare sensor networks used by these dual-role workers. Analysis reveals critical weaknesses: insufficient freshness verification enabling replay attacks with 82% baseline detection, flawed key agreement susceptible to man-in-the-middle manipulation, and persistent exposure of static patient/worker identifiers undermining privacy. We propose practical countermeasures including timestamp+nonce validation, mutual signature verification, dynamic pseudonyms, and perfect forward secrecy integration. Experimental evaluation on Raspberry Pi sensor nodes demonstrates that enhanced protocol achieves 100% replay detection while incurring acceptable overhead: authentication latency increases from 38.5ms to 46.8ms (21%), and throughput reduces from 290 to 245 TPS (15%), remaining within practical limits for telecare workloads supporting dual-role healthcare workers.

Swing automatic doors are widely used in various industrial and commercial environments as key facilities for automating the convenience and performance of buildings. However, the performance of the automatic door largely depends on mechanical design factors such as hinge structure, force transmission method, and motor output selection, and when the design is insufficient, durability deterioration, noise, vibration and failure problems occur. In particular, difficulties such as lack of structural analysis, hinge fatigue problem, force transmission inefficiency, and motor selection reference member exist in existing sites. These problems lead to lower product quality and increased maintenance cost. Therefore, the purpose of this study is to present design criteria by systematically analyzing the mechanical structure of the swing automatic door opening and closing device and quantitatively analyzing the relationship between hinge structure, force transmission mechanism, motor output and door.

The automatic door system is an electromagnetic device in which the control unit automatically opens and closes the door by driving the motor when the motion detection unit detects a person who wants to enter. The automatic door system consists of a motion detection unit using an infrared sensor or radar sensor, a control unit using an AVR, a motor unit using a DC motor or AC motor, a wired/wireless/ contactless switch, and a safety sensor module. Through this study, we intend to solve the structure analysis of swing automatic doors, mechanical and fatigue measurement methods, detection and device module miniaturization methods, hinge (arm) structure change methods, and door load relationship analysis compared to motor rated output.

This study presents the design and structural stability evaluation of a precision watering seeder that supplies a metered amount of water to the seed hole immediately after seeding. The proposed system detects the rotational position of the seeding drum using a Hall sensor and neodymium magnets, and an Arduino Mega controls the opening time of a solenoidvalve through a MOSFET module. The main design feature is the 628.32 mm valve position reference, which is three times the 209.44 mm seeding interval of a six-spike drum. This integer-multiple arrangement synchronizes the watering point with the previously formed seed hole. Static structural analysis using ANSYS showed a representative probe stress of 47.934 MPa and a safety factor of 4.28, while ADAMS flexible-body dynamic analysis showed a maximum hot-spot stress of 81.31 MPa and a safety factor of 2.53. Watering tests demonstrated that the proposed system delivered approximately 20 mL under representative operating conditions, confirming the basic functional feasibility of the watering module.

This study aims to design and fabricate an agricultural spraying drone equipped with a two-axis gimbal nozzle and a variable landing-guard system. Conventional agricultural spraying drones[1] generally use fixed nozzles, which cause the spray direction to change according to the attitude variation of the drone body during flight. This may lead to pesticide drift, reduced spraying accuracy, and environmental contamination. To address this problem, a two-axis gimbal nozzle was implemented to maintain the spray direction independently of the drone body motion. In addition, a variable landing-guard system utilizing a four-bar linkage mechanism was developed to integrate the functions of landing gear and propeller guards into a single structure. The proposed system was designed using three-dimensional modeling, and its aerodynamic and dynamic characteristics were evaluated through ANSYS and ADAMS analyses. A prototype was fabricated using 3D-printed parts and assembled with an S500 drone frame. The basic operation of the gimbal nozzle, water pump, and variable landing-guard mechanism was verified through prototype tests.

An experimental analysis of noise reduction in road traffic by applying the Micro Grooving technique to concrete highway pavements is explored. Initiated in 1984 to address the aging and damage issues observed in South Korea's concrete highways, Micro Grooving is known for creating fine grooves on the cement pavement surface to increase friction, prevent hydroplaning, and inhibit ice formation, while reducing vehicle friction noise by 3∼5dB(A). It is determined from noise measurement results that the application of the Micro Grooving method can be expected to reduce roadside noise and enhance the safety of drivers' driving experience.

In order to study the noise propagation characteristics and noise evaluation of military helicopters, this study conducted continuous noise monitoring of 20 noise-sensitive areas within 3 km around a military heliport in South Korea over a period of 5 days, and the results showed that the noise values at the 20 measurement points around the military heliport were lower than the limit of WECPNL 75 stipulated in the standard for civil airports, and it was found that the maximum noise level had the greatest influence on the evaluation indexes. The study found that the maximum noise level has the greatest influence on the evaluation index. At the same time, the analysis of the noise source spectrum shows that the helicopter noise is dominated by low and medium frequencies, and the low-frequency noise is more irritating in a short period of time.

Tire noise is generated from the mutual friction between the tire and the road surface when driving. In this paper, we analyze various factors affecting tire noise generation, reduce environmental noise pollution, and increase ride comfort. The EU carried out the EC 1222/2009 tire labeling system in 2012, which was a severe blow to the tire exporting countries of all countries due to the stringent demand for tire noise. In this paper, 5 tires from 3 countries were selected and selected as test subjects. The purpose of this study is to analyze the noise of road / tire noise according to road condition of each tire.

After the opening of the Umyeonsan Tunnel, we aim to establish a noise and vibration measurement analysis system that continuously observes the impact of noise and vibration caused by vehicle traffic through the Seoul Arts Center on the architectural structures of the Design Museum, Opera House, Music Hall, and Calligraphy Museum. We want to identify elements that could affect performances due to noise and vibration from vehicle traffic. Additionally, we plan to record and store the measurement results of noise and vibration caused by vehicle traffic after the tunnel's opening and use this data as analysis material to reduce noise and vibration in the future.

This study investigates the structural and optical randomness of InP/ZnSe/ZnS Core/Shell quantum dots for hardware security applications. Blue, green, and red emitting QDs were synthesized and mixed with IBXA. The QDs syrup was bar-coated to form a 50 ㎛-thick active layer sandwiched between 50 ㎛ PET films and UV cured. Cross-sectional SEM revealed irregular micro-scale QD clusters formed by uneven fluid dynamics during processing, creating unreplicable structural entropy. The hybrid film exhibited a unique multi-peak PL spectrum with ten independent peaks without mutual interference. The combination of unpredictable microscopic spatial distribution and the ten-wavelength spectral fingerprint offers a vast combination of cryptographic keys. These findings demonstrate that the proposed multicolor QD film possesses high physical randomness and significant potential as a toxic-free, flexible optical Physical Unclonable Function (PUF) medium.

Plastic products manufactured by injection molding process are deformed due to various process variables such as stress generated during cooling in the mold and contraction generated during cooling, which greatly affects the quality of the product. In this study, an injection molding analysis was performed to select an appropriate gate position by analyzing the effects of the injection molding process of portable oral products

Sound insulation means reflecting and absorbing sound from the material to prevent the incident sound from passing through. Methods such as sound pressure level difference, transmittance, and sound transmission loss are used to display sound insulation, and in general, transmission loss for each frequency band is mainly used. In this study, the CAE technique was used to predict the negative transmission loss for the wall made up of various structures. Through this, it was possible to identify the frequency characteristics of the sound source and present the structure of the wall that could effectively reduce the sound in the frequency band of interest.

With the strengthening of greenhouse gas (GHG) regulations by the International Maritime Organization (IMO), Rotor Sails have attracted increasing attention as a wind-assisted propulsion technology for improving fuel efficiency and reducing carbon emissions in ships. This study investigates the aerodynamic performance of cylindrical and conical Rotor Sails for a 17,000 DWT multipurpose maritime demonstration vessel using computational fluid dynamics (CFD). Numerical simulations were performed using ANSYS Fluent with the k-ω SST turbulence model to evaluate the effects of the Spin Ratio (SR), end-plate diameter ratio, rotor geometry, and rotor arrangement on aerodynamic performance. The results indicate that both cylindrical and conical Rotor Sails achieved the highest aerodynamic efficiency at SR = 2, while the parallel (P) arrangement exhibited the lowest performance due to increased aerodynamic interference. These findings provide useful design guidelines for optimizing Rotor Sail geometry and arrangement and are expected to contribute to the practical application of wind-assisted propulsion systems for environmentally friendly ships.

PEMFC is increasingly used as power sources for eco-friendly transportation systems. In this study, the effects of air inlet temperature and relative humidity on PEMFC stack power were analyzed using AMESim. The stack power increased with relative humidity and then decreased under high-humidity conditions. The maximum stack power of approximately 32,340 W was obtained at 80°C and 60% RH. These results can provide fundamental data for determining operating conditions and developing thermal management strategies for fuel cell systems in small special-purpose vehicles.

This study analyzed the heat generation characteristics of a PEMFC stack for a compact firefighting special-purpose vehicle according to the temperature and relative humidity of the supplied air. The heat generation was predicted using AMESim at air inlet temperatures of 50°C and 80°C under various relative humidity conditions. The results showed a nonlinear trend in which heat generation initially decreased and then increased with increasing relative humidity at both temperatures. The minimum heat generation occurred at approximately 70% RH at 50°C and 50–60% RH at 80°C. In particular, heat generation increased noticeably above 60% RH at 80°C, indicating a significant effect of relative humidity under high-temperature and high-humidity conditions. These results can provide fundamental data for designing thermal management systems and determining the operating conditions of automotive PEMFC systems.

This paper presents a Computational Fluid Dynamics (CFD) study optimizing an ion filter distribution chamber for beverage processing. To prevent localized media channeling caused by conventional axial-flow filters, the proposed configurations incorporate multi-directional outlets and internal flow-distribution features. Seven geometric variants were evaluated under steady-state conditions using ANSYS Fluent. The study identifies an optimum configuration that balances a near 50/50 mass flow split with low hydraulic resistance, maximizing ion-exchange resin utilization while avoiding destructive, high-velocity jets.

This study examined the utilization patterns of major types of construction equipment at construction sites in Korea and evaluated the noise characteristics associated with their operation. It also assessed how equipment-generated noise may affect both workers at construction sites and residents in nearby communities. The findings showed that the hydraulic breaker produced the highest noise level, reaching 101.5 dB(A). Such a high noise level indicates that breaker operations may significantly contribute to noise propagation beyond site boundaries and may increase the likelihood of complaints from nearby residents. These results provide quantitative evidence for understanding construction-equipment noise and may serve as useful reference data for establishing effective noise-control measures, improving relevant regulations, and developing construction-site noise management policies.

This study focuses on the structural design of a functional tumbler and its filter system for kidney disease patients who require low-potassium beverages. Existing filter systems often suffer from clogging due to pulp and fibers in drinks. To resolve this, we redesigned the filter holder's discharge holes and developed a double-filter structure using CAD. Additionally, various types of pouring containers and filter attachments were designed and prototyped using 3D printing to optimize the filtration process. Through seven iterations of design and testing, a final prototype was selected, and two patents were filed for the improved tumbler and filter holder structures.Master's student, Dept. of Mechanical Engineering, Gyeongguk National University.

In this study, a finite element analysis based on continuous impacts was performed to examine the straightening of a shaft bent after long-term rotational operation. Two upper locations were set to be impacted to artificially induce the bending, and one lower location for straightening it, with 20 continuous circumferential impacts applied at each location under the same conditions. The eccentricity, approximately 0.02 mm at the mid-span after the bending-inducing analysis, was restored to approximately 0.01 mm or less at the same location after the shaft was rotated by 180° and impacted again.

본 연구에서는 직경 3mm인 세라믹 바의 표면 정밀도를 향상시키기 위한 자기 연마 가공(Magnetic Abrasive Polishing, MAP) 기술을 개발하고자 하였다. 자기장은 세라믹 재료가 회전하고 영구자석이 진동운동을 진행하는 정자장 타입의 초정밀 가공 방법을 채택하였고 회전 운동은 8000 ~ 20000-rpm, 진동운동은 세라믹 재료의 축 방향으로 3-mm, 10-Hz로 운동하는 방식이 채택되었다. 연마 공구(Magnetic tools)은 전해 철분, 인조다이아몬드 페이스트, 공업용 오일(Light oil)로 구성되었다. 자석은 희토류 자석을 사용하였으며 자력의 밀도를 높이기 위하여 자극을 사용하였다. 연구에 사용된 MAF processing은 High spindle을 통하여 고정된 피삭재(Bar)가 회전하고 슬라이드 운동을 통하여 진동하는 자극부를 가진 시스템으로 구성되어 있다. 이때 자극부는 진동운동에 따라 진동하지만, 자극부에서 형성된 자장이 피삭재가 위치한 자장을 벗어나지 않기 때문에 정자장으로 구분된다. 결과에 따르면 8000-rpm에서 초기 5분 표면 거칠기는 0.08μm이었으며 이후 10분에서 0.06μm, 30분에서 최소인 0.04μm를 달성하고 진동한다. 14000-rpm에서는 초기 5분에서 0.07μm를 달성 이후 15분에 0.05μm를 달성한 후 40분에 최적의 표면거칠기인 0.04μm를 달성한다. 20000-rpm에서는 5분에서 0.08μm, 20분에 0.04μm를 달성하고 이후 40분에 최적인 0.03μm를 달성할 수 있는 것을 알 수 있다.

This within-subject preliminary study compared heart rate (HR) responses between initial dual-instruction flights and the first solo flight in student pilots and assessed the feasibility of a wearable-based measurement and analysis workflow in flight-training settings. HR was recorded at 1-min intervals using a wearable band (Xiaomi Band) from engine start to engine shutdown during initial dual-instruction flights (~90 min each) and the first solo flight (~45 min). Mean HR (HR_mean) was the primary outcome and the 95th percentile HR (HR_p95) was a robust secondary metric. Paired t-tests or Wilcoxon signed-rank tests were used with effect sizes. To address duration-related bias, a sensitivity analysis compared the solo flight with an equal-length 45-min segment extracted from the dual-instruction flight. To improve interpretability given the non-specific nature of HR, subjective stress was assessed pre- and post-flight during the first solo flight using 7-point Likert items (6 pre-flight and 7 post-flight items), and Spearman correlations with HR metrics were explored. Differences in HR metrics between dual-instruction and solo flights were observed, with similar patterns in the equal-length sensitivity analysis. Subjective stress changed from pre-flight to post-flight during the first solo flight, and exploratory associations with HR metrics were identified. A wearable HR–based repeated-measures approach is feasible in flight training. Equal-length comparisons and complementary subjective stress measures may strengthen interpretation. Larger studies with covariate control are warranted.

We reviewed prior studies to investigate the impact of cultural value differences between civilian and military pilots on performance. The results showed that power distance does not have a direct effect on the job performance of civilian and military pilots. This suggests that a new approach is required regarding the power distance factor, which has been discussed and supported until now as having a negative impact on flight performance. By confirming that uncertainty avoidance acts as a negative factor on performance for both civilian and military pilots, the study demonstrated the necessity and importance of further research on this topic. Individualism and collectivism were identified as diametrically opposite influencing factors on performance for civilian and military pilots. While individualistic tendencies had a positive effect on performance for civilian pilots, collectivistic tendencies had a positive effect on performance for military pilots. These results served as an opportunity to confirm that cultural factors can influence pilots' job performance differently within the same national culture, even when the same factors are applied across different organizational cultures.

This paper presents the design and implementation of a miniaturized, high-precision 3-axis gimbal system for Unmanned Aerial Vehicles (UAVs) to ensure stable image acquisition under high-frequency vibrations and rapid attitude changes. To overcome the Size, Weight, and Power (SWaP) constraints of small UAVs, a lightweight mechanical structure driven by Brushless DC (BLDC) motors was developed. A quaternion-based kinematic model was applied to prevent gimbal lock and improve computational efficiency. For accurate attitude estimation, an Extended Kalman Filter (EKF) was designed to fuse data from a low-cost MEMS Inertial Measurement Unit (IMU), effectively compensating for gyro drift and high-frequency noise. Furthermore, a cascade Proportional-Integral-Derivative (PID) control strategy, consisting of an inner velocity loop and an outer position loop, was implemented to rapidly reject external disturbances. A physical hardware testbed was constructed to evaluate the proposed system. Experimental results demonstrate that the developed gimbal system significantly attenuates external vibrations and precisely tracks target angles, validating its suitability for real-time monitoring and inspection missions using small UAVs.

This study presents a performance comparison and analysis of attitude estimation systems integrating state-of-the-art high-performance IMUs (ICM-42688, BMI088, ICM-45686) and a 3-axis geomagnetic sensor (RM3100), which are crucial for autonomous driving, robotics, and drone applications. Sensor characteristics were analyzed, and high-speed data acquisition was conducted in a microcontroller-based logging environment. Six-face calibration was performed to correct gyroscope and accelerometer biases, while ellipsoid fitting was applied to compensate for hard- and soft-iron errors in the RM3100. A quaternion-based Extended Kalman Filter (EKF) was designed for sensor fusion, and the static and dynamic attitude estimation errors (RMSE) for each sensor combination were quantitatively evaluated using a motion capture system as ground truth.

This study compared and analyzed the noise characteristics of original mufflers and tuning mufflers on a Daelim VJF125 motorcycle. Experimental results revealed that the tuning muffler produced significantly higher overall noise—by more than 30 dB—compared to the original muffler. Noise levels rose from 61.1 dB to 90.1 dB at 2,000 RPM, and from 65.6 dB to 96.7 dB (peaking at 98.7 dB) at 5,000 RPM. This sharp increase occurred because removing the internal noise-reduction structure allowed exhaust energy to be discharged directly. In particular, noise in the 1–4 kHz high-frequency range, to which human hearing is most sensitive, increased substantially, maximizing auditory discomfort and harshness. In conclusion, muffler modification was confirmed to cause significant noise pollution and discomfort. The study suggests that further research is required to evaluate its actual impact on vehicle performance, such as power output and torque, beyond noise characteristics.

This study evaluated the dynamic response and vibration characteristics of a Rotax 915 iS engine suspension mount for personal air vehicles (PAV) using finite element analysis. A 3D CAD model was developed in CATIA V5, and modal and harmonic response analyses (Modal SSD) were performed in Abaqus. At the primary excitation frequency (4,000 RPM, 66.67 Hz), the support node (Node 164) showed a peak velocity of 0.0437 IPS, satisfying the vibration criterion (≤0.05 IPS), while the critical node (Node 34207) reached 0.1850 IPS with 76.4% attenuation to the support. In the high-frequency range (800–3,600 Hz), responses at 1.62 kHz (0.1063 IPS) and 2.43 kHz (1.1024 IPS) exceeded the criterion despite 90.4% attenuation. These results indicate that the mount satisfies the vibration criterion at the primary operating speed, but additional damping or structural reinforcement is required to reduce high-frequency resonance.

This study evaluates load redistribution and residual safety of a ROTAX 915 iS engine mount after single-point damage. Models developed in CATIA V5 and analyzed using Abaqus showed that removing Pin 3 produced the highest von Mises stress of 447.6 MPa and a safety factor of 0.97. These results indicate that Pin 3 is the most critical mounting point and requires structural reinforcement. The findings provide useful design criteria for developing fail-safe engine mounts that can maintain residual structural integrity after local damage.