Earticle

This research identifies security vulnerabilities in IoT-based healthcare authentication, specifically replay attacks, session key predictability, and biometric data leakage. We propose enhancements like adaptive timestamp verification and hybrid entropy sources for stronger session keys. Quantum-resistant cryptography and advanced biometric data protection are also recommended.

A compact vibratory bowl feeder system is proposed to transport lightweight annular film components. Vibration analysis was conducted to calculate its natural frequencies, and the motion characteristics of the bowl and transported parts were analyzed under resonance excitation at varying supply voltage levels. The natural frequencies of the proposed system were found to be 157Hz, 249Hz, and 505Hz. At these resonance frequencies, significant rotational vibrations occurred, while vertical vibrations were relatively small. Especially at 505Hz, bending of the leaf spring caused large rotational motion of the bowl. The part feeding speed increased linearly with the applied voltage, reaching 4mm/sec at 100V and 18mm/sec at 200V. At 157Hz and 249Hz excitation frequencies, large rotational and vertical vibrations were observed, respectively. Under rotational vibration, the parts moved forward via jumping motion when the bowl's velocity amplitude was relatively large, or via slipping when smaller. Minor backward slipping was also observed. Under vertical vibration, parts exhibited forward jumping motion without back-and-forth slipping.

In this study, quantum dots with Au/CdSe complex cores composed of Au as a metal base were synthesized, syrup was prepared, and coated on natural simulated LED unit modules, and the optical properties of traffic signs using them were investigated, and the following conclusions were obtained. The nanoparticles synthesized at 260°C and 280°C grew into irregular shapes with PL wavelengths of 624-627㎛, half-widths of 35㎛, PL-QY ratios of 55-61%, and grain diameters of 5-7㎛. The quantum dot syrup was applied to the LED unit module to produce a traffic sign composed of 4CL unit modules, and the luminance of 179 ㏅/㎡, insulation resistance of 10,000㏁, and insulation withstand of 500V were achieved, meeting the performance and specifications of the standard guidelines for luminescent traffic safety signs. The surface temperature of the unit module laminated with 4CL resin is 24~25℃, which shows a stable heat distribution, confirming that it can be applied as a sign using unit modules.

This study focuses on electro-galvanizing of iron materials. Zinc plating provides superior corrosion resistance at a low cost due to zinc's lower potential (Zn: -0.76V) compared to iron (Fe: -0.44V), enabling it to act as a sacrificial layer. The paper also highlights the need for post-plating chromate or coating treatments to prevent the surface corrosion of zinc itself. The primary objective of this research is to analyze how different electro-galvanizing bath solutions influence key plating characteristics, such as uniformity of deposition and hydrogen embrittlement. The study examines various bath types, including acidic and alkaline solutions. Acidic baths, like zinc sulfate solutions, are shown to be suitable for high-current plating, ideal for high-speed processes like wire rod plating. Alkaline baths, such as cyanide solutions, produce a dense and glossy deposit, commonly used for decorative and anti-corrosion applications. Through a quantitative analysis of each solution's current efficiency and uniformity of deposition, this paper provides valuable insights for selecting the optimal plating bath in industrial applications.

Marine mines are placed in major ports with high cargo volumes and military ports where naval vessels are anchored, and can pose a significant obstacle to naval operations. Thus, minesweeping is a very important operation to open up sea route for warships and merchant ships to enter and exit easily. This paper describes the design and testing of underwater speaker for sweeping acoustic mines. In order predict the performance of the underwater speaker, an acoustic analysis was performed with a unit force of 1N applied to the diaphragm. Then, the driving force and displacement were calculated to satisfy the target performance. Since acoustic testing using microphones can generate undesirable noise sources under anechoic conditions, the results of accelerometer measurements were converted to source levels to predict the results. During the land tests, a laser displacement sensor was simultaneously used to verify the validity of the accelerometer measurement results. Finally, marine testing confirmed that the full-frequency sound pressure levels of the underwater speaker satisfied the target performance.

In this study, when Butyl ether, a type of diether-based oxygenated fuel, is mixed in each volume ratio in a naturally aspirated direct injection diesel engine, the exhaust gas emission characteristics of the oxygenated component in the fuel affect each operating area of the engine I wanted to investigate the effect on. For comparative measurement of engine performance and exhaust emissions, commercial diesel and butyl ether mixed fuels were classified into 4 types according to the mixing ratio and tested. As the content of butyl ether in fuel increases, soot emission reduction increases, and when the maximum mixing amount of butyl ether (diesel 80vol-% + BE 20vol%) is applied, compared to the case of using only diesel as fuel, at 2500 rpm and no load, 39%, and about 32% of smoke reduction effect at full load was confirmed.

This study investigates the flow resistance and heat transfer characteristics of a fin-and-tube heat exchanger, applied to a water-cooled thermal management system designed for a cabinet-mounted high-performance computer operating aboard naval vessels. The analysis was conducted through both experimental and numerical approaches, focusing on the evaluation of heat transfer performance (j factor) and flow resistance (f factor) under varying air flow rates, while maintaining a fixed fin geometry and arrangement. Particular emphasis was placed on assessing the variation of the j factor along the total length of the heat exchanger to understand the impact of exchanger length on thermal performance. In the numerical analysis, instead of modeling the entire heat exchanger, a representative repeated unit composed of a single fin and twelve connected tubes was simulated. The outlet temperature from each tube segment was sequentially used as the inlet condition for the subsequent segment. This methodology significantly enhances computational efficiency while providing reliable predictions of progressive thermal characteristics along the flow path.

The human body has many degrees of freedom (1-3 degrees of freedom) per joint, enabling smooth and stable walking. However, unlike humans, robots require many more joints, and their design necessitates the control of numerous motors. However, controlling more motors leads to lower walking stability. Therefore, this paper studies a real-time control method for stable walking of a bipedal robot. To enable stable walking of a bipedal robot with 12 degrees of freedom, we study a method for generating and supplementing walking patterns between each joint using numerical analysis of the multi-joint robot's kinematics and learning-based AI. This research is to apply the adaptive control of neuron networks for the real-time attitude control of Multi-articulated robot. Multi-articulated robot is expressed with a complicated mathematical model on account of the mechanic, electric non-linearity which each articulation of mechanism has, and includes an unstable factor in time of attitude control. If such a complex expression is included in control operation, it leads to the disadvantage that operation time is lengthened. Thus, if the rapid change of the load or the disturbance is given, it is difficult to fulfill the control of desired performance. In this research we used the response property curve of the robot instead of the activation function of neural network algorithms, so the adaptive control system of neural networks constructed without the information of modeling can perform a real-time control. The proposed adaptive control algorithm generated control signs corresponding to the non-linearity of Multi-articulated robot, which could generate desired motion in real time.

This study investigates the thermal behavior of H7 halogen headlamps through Computational Fluid Dynamics(CFD) analysis and experimental validation. Headlamp geometries were reconstructed via reverse engineering, and simulations incorporated conduction, convection, and radiation effects using the Discrete Ordinate (DO) model. Experiments were conducted using thermocouples and infrared thermography to validate the numerical predictions. The results showed good agreement, with average discrepancies of 3–5% confirming the reliability of the simulation framework. These results demonstrate that current thermo-fluid simulation can accurately capture complex thermal transport phenomena in headlamp assemblies. The proposed methodology is extendable to LED headlamps, providing a practical tool for aftermarket product design, replacement part evaluation, and optimization of next-generation automotive lighting systems.

This study investigates the effect of different objective functions on the topology optimization of a loudspeaker basket for structural resonance avoidance. Three objective functions were considered: maximization of the first natural frequency, minimization of static strain energy, and minimization of dynamic strain energy. The results show that, for all objective functions, the first natural frequency increased significantly compared to the initial design, while both static and dynamic strain energies were reduced, indicating effective suppression of structural resonance. Although the performance differences among the objective functions were not substantial, minimization of static and dynamic strain energy exhibited higher computational efficiency compared to natural frequency maximization. In particular, minimization of static strain energy demonstrated advantages in computational efficiency and ease of implementation, suggesting it as a practical alternative for resonance-avoidance design of loudspeaker baskets. This study highlights the importance of objective function selection by quantitatively comparing optimization outcomes under different formulations.

Pipe organs are an important element of acoustic performance and usage of concert hall, considered as one of indicators of classical music hall. However, only limited numbers are installed or planned for local concert halls. Therefore, in order to investigate the influence of the pipe organ to the concert hall and compare with variable acoustic equipment, acoustic parameters were measured and evaluated in conditions without the pipe organ and after installation. Moreover, acoustic parameters according to acoustic variable equipment were measured and evaluated to figure out an impact on acoustic performance. The result indicates that differences of parameters according to the presence of the pipe organ were, 0.66 sec in reverberation time (RT), 0.1 in bass ratio (BR), 0.66 sec in early decay time(EDT), 2.18dB in clarity (C80), 0.12dB in strength(G), and 0.16 in lateral energy fraction(LFC). Differences of acoustic parameters due to acoustic variable equipment were 0.86 sec in reverberation time(RT), 0.09 in bass ratio(BR), 0.78 sec in early decay time(EDT), 0.64dB in clarity(C80) and 2.34dB in strength(G).

To reduce the transient pressure oscillations (hunting) in pilot valves used in control systems of nuclear power plants, this study investigates the effect of orifice angle design using computational fluid dynamics (CFD). A conical orifice geometry with a base radius of 1.25 mm and a length of 1 mm was modeled with varying angles (10°, 20°, and 30°). The models were analyzed using transient flow simulation in ANSYS CFX, applying a k-ω turbulence model to accurately capture near-wall flow characteristics. The results showed that larger orifice angles led to reduced pressure hunting, improving system stability. Additionally, velocity and pressure distributions demonstrated smoother flow and smaller fluctuations at higher orifice angles. The findings indicate that optimizing orifice angle is an effective strategy to suppress pressure hunting in pilot valve systems.

Active electronically scanned array (AESA) multi-function radars (MFRs) comprise numerous transmit/receive modules (TRMs) whose maximum temperature and temperature uniformity must be tightly controlled. This study proposes a new liquid-cooling-plate flow-channel design for an X-band AESA MFR: a two-layer straight channel incorporating multiple fins irregularly spaced along the flow channel. The proposed design (Type-4) is compared with three baseline channel designs. At the same coolant flow rate, Type-4 reduces the TRM maximum temperature by 28.2 K and the maximum inter-module temperature difference by 19.7 K relative to Type-1. However, the pressure drop increases by 726% because of the added internal surfaces and fins which are flow obstructions. A comprehensive thermo-hydraulic comparison, including pumping power criteria, is conducted over multiple flow-rate conditions. Overall performance was highest for Type-4, followed by Type-2, Type-3, and Type-1. When designs achieve similar maximum temperature and temperature difference with various coolant flowrate condition, Type-2 requires 83.6% less pumping power than Type-1, and Type-4 requires 33.8% less pumping power than Type-2.

This study investigates the enhancement of crew survivability in armored vehicles, particularly against anti-tank mine threats. Human injury criteria were evaluated according to the STANAG 4569 AEP-55, Volume 2 standard to assess the vehicle’s protective performance. Analyses focused on mitigating tibia compression force, identified as a critical challenge in meeting the survivability requirements. Through parametric simulations, the influence of foam compressive strength and thickness on tibia compression force was investigated. Results demonstrate that increasing both foam compressive strength and thickness effectively delays the dissipation of impact energy, leading to a significant reduction in tibia compression force. These findings provide valuable insights for optimizing the design of armored vehicle structures to enhance crew survivability against mine blasts.

This study examines the deformation and stress characteristics of an aerospace turbine wheel under centrifugal, thermal and pressure loads. Design modification is focused on the neck of the disk, which is a structurally critical area. Increasing the neck thickness significantly reduces radial deformation from centrifugal force, while thermal and pressure-induced deformations remain nearly unchanged. Stress at the blade root is minimally affected by geometric changes, but the disk neck stresses decrease notably when the radius is between 3.25 and 4.00 mm. Beyond 4.00 mm, stress rises again due to a shift in the peak stress location to the rear side. Yielding is first observed at a 3.5 mm radius, where deformation is also reduced to 0.29 mm. This geometry thus offers the best balance between strength and deformation. The findings provide a method to determine optimal neck design for prescribed design conditions.

The automotive industry is rapidly shifting from hardware-focused design to Software Defined Vehicles (SDVs), where functions are flexibly updated through software. Embedded systems are central to this transition, ensuring real-time data processing and control across sensors, actuators, and controllers. Yet, most autonomous driving education and competitions have been designed for senior students, creating high entry barriers for early undergraduates. This study proposes an embedded practice-based education model for lower-year students, implemented through an autonomous driving competition. Arduino was adopted as an accessible embedded platform, enabling rapid prototyping and intuitive learning of sensor–controller–actuator integration. The curriculum was structured to advance from interrupt-based programming to Real-Time Operating System (RTOS)-based task scheduling, providing stepwise exposure to core SDV concepts. The model was validated through a mission-oriented competition that included line following, obstacle avoidance, and stop-line detection tasks. Dual assessment—combining technical performance indicators with rubric-based educational outcomes—demonstrated both algorithmic feasibility and pedagogical effectiveness. This work highlights that early undergraduates can gain meaningful SDV-oriented embedded control experience through lightweight competitions. The proposed framework offers an effective pathway for cultivating the next-generation mobility workforce, bridging the gap between theoretical education and practical implementation in the SDV era.

This study analyzes the automotive behavior and its impact on driving safety when the Micro controller Unit (Micom), a core component of the automotive Engine Control Unit (ECU), is exposed to high temperatures. The automotive behavior was observed with and without the ECU housing cover under thermal exposure, and the temperature of the Micom was determined using heat transfer principles. The results showed that with the housing cover in place, a thermal equilibrium was maintained at approximately 160[°C], and the Micom's temperature was about 73[°C], which is within its guaranteed operating limits and did not affect the automotive behavior. When the housing cover was removed, the engine stoped to operate at approximately 220[°C], and it is presumed that the Micom's internal circuitry was damaged. These findings can provide useful quantitative data for future reliability assessments of ECUs and for investigations into sudden unintended acceleration phenomena.

This study presents the design and application of an integrated control logic architecture for a 300BPD ES-SAGD(Expanding Solvent Steam-Assisted Gravity Drainage) demonstration plant, aimed at ensuring operational stability and efficiency. With the global expansion of unconventional oil resource development, ES-SAGD is recognized as a technology advantageous for reducing viscosity and improving energy efficiency compared to conventional SAGD. In this research, the plant process was analyzed to identify key control variables and potential risk factors, and a control logic structure integrating supervisory and unit-level control was designed. The stability and reliability of the control logic were validated through Hardware-in-the-Loop Simulation(HILS) and field implementation. The findings are expected to contribute to safer operation, reduced commissioning periods, and enhanced automation in future oil sands demonstration and commercial plants.

This study investigates nozzle diameter and fuel type effects on combustion characteristics and NOx emissions in radiant tube heating systems through numerical simulation. Four fuels were analyzed: LPG, natural gas, coke oven gas, and hydrogen under varying nozzle conditions using computational fluid dynamics with energy conservation, species transport, and thermal NOx formation models. Results show that nozzle diameter optimization significantly enhances internal recirculation, improving fuel-air mixing and reducing NOx formation. Hydrogen exhibits higher flame temperatures, potentially increasing thermal NOx generation, but optimal nozzle design controls this effect through enhanced mixing patterns. The optimized configuration achieved substantial NOx reduction while maintaining combustion stability across all tested fuels.

In this paper, the structural optimization and experimental validation of lightweight, high stiffness rollers for roll-to-roll(R2R) processing of lithium metal electrodes are presented. Precise dimensional control of electrode thickness below 50㎛ is essential for next-generation high energy density batteries, yet elastic recovery during rolling hinders the achievement of target specifications. To address this challenge, finite element(FE) analysis was employed to determine the optimal rolling gap and roller geometry, and the results were verified through R2R experiments. Simulations indicated that a rolling gap of 153㎛ yielded a final sheet thickness of about 49.6㎛, meeting the design requirement. Experimental results confirmed the validity of the numerical model, with thickness measurements deviating less than ±10% from FE analysis predictions. These findings demonstrate that the proposed roller design not only ensures thickness precision but also improves system efficiency, offering practical guidelines for scalable lithium metal electrode manufacturing.

This study utilized ray tracing and back-ray tracing to optimally design road lighting for optimal visibility for drivers and pedestrians at night. While conventional road lighting focuses on ensuring sufficient brightness, recent developments require diverse characteristics beyond brightness to ensure optimal visibility for drivers and pedestrians, including reduced glare and uniform ground luminance. Existing road lighting was inadequate for drivers and pedestrians due to serious issues such as glare and uneven illumination. To address these issues, moving beyond capacitance-centric design methods and understanding the path light takes to reach the road surface is crucial. Optical simulation, which assumes a sufficient number of rays, is essential for achieving this goal. To achieve these goals, this study explored the application of ray tracing to the design of road lighting reflectors. Design goals such as uniformity of road area per single light, shading angle, and continuous luminance uniformity over long distances were established. Ray tracing was used to design the ideal road lighting conditions. Back-ray tracing was then used to design the road lighting reflectors. By reducing light loss, power consumption was reduced by almost half while achieving the same brightness on the road, and the shading angle was 75 degrees and the brightness uniformity of the road area was 0.6, achieving the ideal design criteria.

In this study, we performed optical simulations for two light sources: internal and external electrode light sources. Based on the optical simulation results, we created a practical design to verify the design validity and extract optimal design factors for each light source. The three key geometric variables in the design of a direct-lit flat panel light source are the distance between the two lamps, the distance between the lamps and the reflector, and the number of lamps. These variables significantly impact the optical design and determine various characteristics of the flat panel light source system. In this study, we used a 26 mm distance between the two lamps, a 4.5 mm distance between the lamps and the reflector, and a total of 20 lamps to derive optimal values ​​for these variables. Under these conditions, we created a practical design and evaluated its performance, achieving an excellent flat panel light source with a central luminance of 6,423 nits and a luminance uniformity of less than 5%. This study demonstrates that optical simulation techniques are an effective method for designing a surface-emitting light source system for medical LCDs, demonstrating the feasibility of achieving high performance while maintaining a low cost.

Explosive Ordnance Disposal (EOD) robots are essential for safeguarding operators and reducing risks in high-threat environments. This study reviews international cases and current technologies to identify limitations and propose improvement strategies. Mission success depends on four core domains: mobility, power, manipulator precision, and communication. Current tracked and wheeled platforms lack self-righting, leading to research on flippers, wheel–leg hybrids, and quadrupedal locomotion. Battery reliance remains critical; short-term solutions include intelligent Battery Management Systems (BMS) and battery-exchange robots, while long-term progress requires high-density energy sources. Manipulator performance is hindered by inertia and backlash, but precision actuators, soft grippers, and sensor fusion with AI can enhance dexterity. Communication faces losses and jamming, requiring multilayered resilience with Software-Defined Radio (SDR), cognitive radio, relay nodes, and hybrid links. By mapping improvements to Technology Readiness Levels (TRL), this study suggests a phased roadmap where mature technologies address immediate needs, while AI-driven autonomy and secure networks define long-term advances.

This paper is to study SOFC(Solid Oxide Fuel Cell) technology which is becoming increasingly more important in recent power development market. I will propose the most suitable fuel cell type through efficiency analysis by type of fuel cell in operation. In this paper, I analyzed the characteristics of SOFC development, theoretical study of the system technology and the level of progress in SOFC technology for each generation. In conclusion, through analysis of the operation data of the installed and operating fuel cell power generation system, it was found that SOFC is 45% more efficient than PAFC and 25% more efficient than MCFC.

To improve vibration reduction in the railway vehicle, the semi-active suspension system using MR damper was developed and the vibration performance of the passive suspension system and a semi-active MR suspension system was compared. For the experiment, the MR damper and suspension system were designed and manufactured. Tensile and compression tests were performed on the MR damper while varying the input current. The damping force of the MR damper was measured and analyzed using the Bingham model. The railway vehicle was modeled with 9 degrees of freedom, and the sky hook control algorithm was simulated using the MR damper, using the Bingham model. This verified the effectiveness of the sky hook controller. Furthermore, to compare the vibration performance of the railway vehicle, the driving test was conducted with the MR damper and the passive damper. The lateral acceleration vibration reduction performance of the suspension system with MR dampers and passive dampers was verified, and it was confirmed that the vibration reduction performance of the vehicle with the semi-active suspension system using MR damper was approximately 50% better than that of the vehicle with the passive damper.

Aerial work platforms are employed to enable efficient operations at elevated positions and confined spaces such as utility poles at various construction and civil engineering sites. As these platforms are mostly operated at positions higher than 10 m, it is essential to verify the structural stability for both the vehicle and the boom. This study investigates structural and mechanical characteristics of an aerial work platform boom under varying wind speeds through numerical analysis. The results indicate that increasing air flow leads to non-uniform pressure distributions around the boom surfaces with external load up to 172.9 Pa at joint part of high structural evaluation. Especially stress concentration was found at the joint between the 3rd and 4th booms, These findings demonstrate that aerodynamic loads induced by increasing wind speed contribute to boom deformation and stress distributions, and they provide a fundamental reference for stability verification with design optimization of the aerial work platforms.

This study proposes a novel methodology for quantitatively evaluating the contribution of input signals in the time domain using Mutual Information (MI). Traditional contribution analysis methods based on Pearson correlation coefficients are limited by their assumption of linearity, making them inadequate for systems with time-varying characteristics or nonlinear transfer paths. To address this, we construct simulation data comprising transient, non-stationary input signals and nonlinear transfer functions, and compute time-local mutual information by adopting the windowing approach commonly used in Short-Time Fourier Transform (STFT). The results demonstrate that the proposed MI-based method outperforms conventional linear techniques in capturing the contributions of inputs under nonlinear and time-varying conditions. Notably, the MI approach provides accurate quantitative assessment even when the system's transfer path responds nonlinearly to input amplitude. This study shows that MI-based contribution analysis is a powerful and effective tool for evaluating input influence in nonlinear, non-stationary, and multi-input systems, and lays a foundation for future applications to experimental data and integration with alternative MI estimation methods.

As high-speed trains operate on both high-speed and conventional lines, wheel-rail interface characteristics have become increasingly important for effective wheel-rail wear management and operational safety. This study compared and analyzed interface characteristics for various combinations of wheels used in high-speed vehicles with various rail configurations, including UIC, KS50, and KS60, to determine the optimal combination. The results were calculated and analyzed for rolling radius differences, equivalent conicity, and wheel-rail contact area characteristics in response to lateral axle displacement. Changes in equivalent conicity and wheel-rail contact area as wear progressed were also analyzed.

Effective stress management in pilots is crucial for flight safety. This study assesses the stress levels of student pilots enrolled in a private pilot course during their initial flights by measuring heart rate variability (HRV) using a wrist watch type heart rate monitoring device. HRV data were collected from 31 student pilots across their first ten flight sessions. Statistical analysis using repeated measures ANOVA revealed that the highest stress levels occurred during the first flight and gradually decreased over subsequent flights. These findings highlight the need for flight instructors to provide supportive guidance during initial flights to help students adapt to flight conditions with minimized stress. Furthermore, the private pilot course curriculum may require revision to incorporate stress management and flight aptitude evaluation. This research contributes important insights into monitoring physiological stress responses in trainee pilots and informs strategies to enhance pilot training effectiveness and safety.

The launcher of a hard-kill type APS (Active Protection System) requires rapid and precise driving to target approaching threats after detection. High angular acceleration is required for rapid driving, which requires high energy consumption. However, the sufficient energy storage of the APS is limited due to weight and space constraints. If energy is insufficient during driving, the charged voltage of the capacitor bank may drop below the minimum operating voltage of the drive motor, which may result in problems such as torque insufficiency or saturation of the controller's integrator. Therefore, it is necessary to determine the maximum angular acceleration possible within the available energy and generate a corresponding driving profile. This paper proposes a method for calculating allowable energy and deriving allowable maximum angular acceleration for driving profile, and validates the proposed method through experiments. We established and implemented a method for deriving maximum angular acceleration through experimental methods to account for unknown frictional forces and mechanical errors in the launcher. By applying the proposed method, we confirmed that the system can operate at high speeds stably by reflecting appropriate angular acceleration even during continuous operation. Therefore, it is expected that the application of the proposed method will improve the operating stability of the APS launcher and enable continuous operation at maximum speed within limited energy.