Earticle

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.

In this study, the heat transfer characteristics of a liquid hydrogen (LH2) tank with multilayer insulation (MLI) were numerically investigated. The temperature distribution inside the LH2 tank and within the MLI, as well as the temperature variation according to positional changes, heat transfer rate, and boil-off rate (BOR), were compared and analyzed. The results showed a distinct stepwise temperature drop in Case 4 with 20 MLI layers and Case 8 with 40 MLI layers, where the insulation thickness was greatest. Under the same number of layers, the temperature gradient became more gradual as the MLI thickness increased. In addition, the temperature variation in the tank head region indicated that increasing the number of MLI radiation layers reduced the radiative heat flux, resulting in a gentler temperature variation and a longer temperature drop range. Furthermore, the analysis of heat transfer and BOR showed that both rates decreased under the condition with the greatest MLI thickness and number of layers, demonstrating the best insulation performance. In particular, under the same 40-layer condition, the BOR value of Case 8 was more than three times lower than that of Case 5, indicating a significant improvement in thermal insulation efficiency.

This paper examines security vulnerabilities in current authentication methods for remote patient monitoring in Wireless Medical Sensor Networks (WMSNs), including offline password guessing and man-in-the-middle attacks. We propose a novel three-factor authentication protocol using fuzzy extractors and lightweight cryptography. Formal analysis via the Real-or-Random (ROR) model and Tamarin Prover confirms its robustness, perfect forward/backward secrecy, mutual authentication, anonymity, and untraceability. Performance comparisons demonstrate reduced overhead and enhanced security, offering a promising framework for IoMT development.

This study investigates the thermodynamic processes of reduction for iron, manganese, silicon, aluminum, magnesium, and calcium within a blast furnace. We analyzed two primary mechanisms, indirect and direct reduction, to determine the conditions under which these elements are converted from their oxides into metallic form. For indirect reduction, driven by gas-solid reactions with carbon monoxide, calculations show that iron is effectively reduced at temperatures above 967 K and a carbon monoxide partial pressure greater than 0.575. However, other elements like manganese, silicon, aluminum, magnesium, and calcium require extremely high temperatures and carbon monoxide partial pressures approaching 1.0. This makes their indirect reduction in a typical blast furnace environment highly improbable. In contrast, direct reduction involves solid carbon (coke) directly reducing the oxides. Our analysis reveals that iron can be reduced at temperatures above 1000 K, which is well within the blast furnace's operating range. Manganese and silicon can also be produced through this direct reduction pathway at the high temperatures found in the furnace's lower zone, above 1691 K and 1952 K, respectively. However, aluminum, magnesium, and calcium require significantly higher temperatures that fall outside the normal operating conditions of the blast furnace. In conclusion, iron is effectively produced by both indirect and direct reduction mechanisms. While manganese and silicon are difficult to reduce indirectly, they are successfully produced through direct reduction in the high-temperature zone. Aluminum, magnesium, and calcium, on the other hand, are not produced in a blast furnace because their reduction temperatures are too high. This explains why only specific elements are reduced and incorporated into the final pig iron product.

In this study, composite pouch films incorporating ionite were fabricated, and their structural properties as well as temperature variations during charge–discharge cycles were evaluated to examine their applicability as heat-suppression pouch films for secondary batteries. The films were prepared using a film coater (Coretech, CT-AF300), with variations in ionite content and particle size. In addition, the effects of plasma treatment on the surface state of PET films were investigated to enhance coating adhesion, with the aim of determining the optimal fabrication conditions. Furthermore, an infrared thermal imaging camera and a custom-built test device were employed to measure the temperature differences with and without the pouch films during charge–discharge processes, thereby assessing the potential of developing next-generation high-performance pouch films.

This study investigates the effect of orifice-pipe misalignment on flow characteristics and pressure hunting in a pilot valve using transient CFD analysis. Four models were created with a circular orifice (1 mm radius, 1 mm length) placed at offsets of 0.25 mm, 0.5 mm, 0.75 mm, and 1 mm from the pipe centerline (pipe diameter: 4 mm). Simulations were performed in ANSYS CFX with a 6.8 m/s inlet velocity and 3.2 bar outlet static pressure. A High Resolution advection scheme and Second-order Backward Euler time integration were used. Results showed that greater eccentricity led to more severe pressure hunting, with the 0.75 mm model showing a maximum of 7.61%. In contrast, the 1 mm model stabilized quickly after initial fluctuations. Velocity and streamline analyses also confirmed that asymmetry promotes swirl and backflow. These findings highlight the importance of orifice alignment in achieving stable valve performance.

This study presents a non-invasive method for current estimation using the voltage drop across automotive MICRO-2 fuses. Unlike conventional techniques that require additional hardware, the proposed approach utilizes the inherent milliohm-level resistance of fuses, enabling current monitoring without circuit modification. Experiments were performed on 7.5[A] A fuses to analyze resistance variations with rating, temperature, and contact position. Based on these results, a current estimation model with temperature and tolerance correction was developed. Validation showed that the optimized resistance model (Ropt) achieved the lowest error (MAE: 0.0197 A, MAPE: 0.84%), demonstrating the feasibility of fuse-based current sensing for real vehicle applications and leakage current diagnostics.

In the present study, to investigate the seismic behavior of a cabinet under earthquakes, three types of mass blocks (top load, center load, and bottom load) were selected as the cabinet's internal structure, and the vibration characteristics according to the load arrangement were studied. The internal structure simulates the device modules installed inside the cabinet. The cabinet's modal characteristics and response spectrum were evaluated under the three types of loads. Six modes, displacement, and acceleration responses for each load were analyzed. The analysis results showed that mode 1 had the lowest frequency, and that the frequency increased by approximately two times as the mode increased. The change in natural frequency according to load placement was confirmed through modal analysis of the cabinet. The cabinet's displacement and acceleration were greatest in the x-axis and lowest in the y-axis. Displacement and acceleration according to the load distribution at the top, center, and bottom were within a certain range, so the vibration characteristics of the internal structure of the cabinet were limitedly affected.

This study analyzes how the damping characteristics of anisotropic magnetorheological elastomers (MREs) change according to magnetic flux density, the volume fraction of carbonyl iron powder (CIP), and pre-stress. MREs are intelligent materials whose mechanical properties change depending on the magnetic field, and while research on stiffness changes has been actively conducted, analysis of damping characteristics is relatively insufficient. Consequently, the damping characteristics of MREs showed nonlinear responses depending on the interaction among magnetic flux density, CIP volume fraction, and pre-stress, confirming that damping performance can be utilized as a controllable material parameter. These results suggest the possibility that, in the design of MRE-based vibration control systems, not only stiffness but also damping characteristics can be actively controlled, and they provide basic data for the future development of high-performance vibration reduction technologies.

In this study, for the design of the impeller and volute casing shape of the water pump for flood prevention, performance was predicted through numerical analysis to secure the theoretical power and hydraulic efficiency of the front well at the discharge well 300m3/h, which is the target design specification, and the flow characteristics of each flow rate were checked and verified. Through the results of this flow analysis, it was possible to secure the basic shape design of the impeller and volute casing of the water pump for flood prevention. In the future, we will perform an interpretation to confirm structural safety according to shape and material.

This study was conducted to evaluate the feasibility of applying a bending process as an alternative to the conventional welding method for rolled homogeneous armor(RHA) steel used in the turret structures of tanks. After analyzing the turret geometry and the mechanical characteristics of RHA steel, the upper and lower die profiles were optimized based on the MIL-DTL-12560 specification. Through forming simulations, the appropriate die opening width and punch stroke were derived. In particular, the final bending conditions were determined by accounting for springback effects. Structural analysis results confirmed that the maximum residual stress and total strain remained within the allowable mechanical limits of RHA steel, and the strain values approached the material’s elongation limit of approximately 15%, ensuring practical forming stability. This study presents a practical guideline for die design and bending conditions applicable to high-strength armor steels, and is expected to serve as a foundational reference for process optimization in the manufacturing of military vehicles and protective structures.

It is important to secure numerical accuracy while ensuring adhesion with high transparency and low yellowing properties to protect against physical impacts outside the drone. In addition, in order to derive high-quality results for preventing damage and discoloration from ultraviolet rays and atmospheric chemicals, a release layer process technology in which a silicone-based release is coated at a certain thickness and then cured at an appropriate temperature and time, and a technology for optimizing adhesion of adhesive thickness and solid content during adhesive coating were confirmed, and the protective film confirmed the results of surface suitability, retention, and stability evaluation over time for drone aircraft and external parts over a long period of time.

Global population growth and industrial development are leading to water shortages, and water supplies from surface and groundwater sources are facing serious challenges. Many countries are projected to experience water shortages by 2025. More than 50% of these countries will face water resource depletion, and Korea is also expected to face water shortages, necessitating the development of water supply measures. This study explores the application of refrigeration technology to address this water shortage. It explores a small-scale seawater desalination system that utilizes the phenomenon of freshwater contained in seawater accumulating on the surface of a brine-cooled drum-type evaporator. This system exploits the phenomenon of freshwater contained in brine freezing on the low-temperature drum surface. Experiments were conducted to determine the amount of freshwater captured by varying the brine temperature entering a brine-cooled drum-type ice maker and the gap between the blades used to cut the frozen ice. When tested using seawater as the base, it was found that when the circulating brine temperature in the drum-type ice maker was -30℃ and the gap between the drum-type ice maker and the cutting blade was 1 mm, the salinity was removed by about 95%, and about 2.28 liters of fresh water could be produced per hour. It was also found that it was easy to install for small-scale seawater desalination and could be used with a low power capacity of about 2.3 kW.

Ear clamps are components used to securely fasten pipes and hoses in various industrial applications. They achieve clamping force by inducing plastic deformation at the ear region during installation, which can lead to accumulated structural damage and affect fatigue life. Moreover, the fatigue life is influenced by the design shape of the ear. Therefore, in this study, tensile and fatigue tests were conducted on two types of ear clamps with different ear geometries. Finite element analysis (FEA) was performed to obtain the stress distribution around the ear region, and these results were correlated with the experimentally obtained fatigue life. Based on this correlation, an S-N curve for simulation-based fatigue life estimation was established. This approach confirms the possibility of predicting the fatigue life of ear clamps with modified geometries using only finite element analysis, without the need for repeated fatigue testing.

The air gap in a generator, defined as the space between the rotor and stator, is a critical factor that significantly influences electromagnetic induction and overall machine performance. The size and uniformity of the air gap affect magnetic flux distribution, electromotive force, losses, vibration, and noise characteristics. Any eccentricity or non-uniformity in the air gap can cause electromagnetic force imbalances, leading to increased mechanical vibrations and noise, which may reduce the machine’s lifespan. Therefore, optimal air gap design is essential for maximizing generation efficiency and ensuring durability. This requires precise control of the air gap dimensions and shape through detailed electromagnetic analysis and experimental validation. This study presents an electromagnetic force analysis conducted to optimize the air gap design of a 30 kW-class high-speed (15,000 rpm) AC generator. Based on both simulation results and experimental validation, the air gap was optimized to improve power generation efficiency and enhance product durability. As a result, a rational design and testing methodology for military AC generators is proposed.

This study evaluated the design, fabrication, and performance of CFRP composite propeller blades for naval applications. The blades were designed with a sandwich structure and a dovetail hub connection to achieve both high strength and reduced weight. During fabrication, the outer skin and Melamine Foam core were bonded using adhesive films and integrated through autoclave molding and post-curing. The finished blades were coated with a low-gloss urethane clear finish, and the leading-edge areas received additional coating to ensure surface protection and operational identification. Static bending tests and finite element analysis were conducted to assess failure behavior under maximum load and local stress concentrations, while natural frequency measurements(Hammer test) confirmed agreement between analytical and experimental results, verifying the reliability of dynamic response predictions. The results demonstrate that the composite blades offer superior weight reduction and vibration damping compared to metal counterparts and can serve as a foundational reference for future naval propeller design and optimization of various rotating and winged structures.

The accelerator pedal of a KLTV was applied in the form of a carryover utilizing the products of a civilian vehicle. There was case in which it was damaged because it did not reflect the military's specificity, Therefore the material and shape of the accelerator pedal were improved to confirm the strength improvement effect of about 86%, It can prevent accidents and contribute to securing mobility by presenting and applying fracture strength standards suitable for the military operation environment.

The 30mm wheel type anti-aircraft gun replaces the aging anti-aircraft gun in the front and is a weapon system for local anti-aircraft defense against enemy aircraft and small unmanned vehicles. In the field, damage to the turret hatch/closed hatch pin occurred between the operation of the wheel type anti-aircraft gun. As a result of the sem analysis of the hatch pin fracture surface, it appears that brittleness fracture occurred and fatigue fracture occurred at the final fracture surface while reaching the fatigue strength by repetitive loads. The hatch angle fixing pin and bracket shapes were changed to disperse the stress concentration. As a result of checking the location of the vulnerable area of the hatch pin and the shear stress value through structural analysis, the safety factor improved from 1.46 to 2.95 after improvement. Through this study, it is expected to be used as a reference material for failure analysis and design plan for the existing system in the future.

The thermodynamic efficiency of the stirling engine has a high theoretical efficiency closest to that of the Carnot cycle, and various heat sources can be used as an external combustion engine. In the early days of the invention, the sealing technology was not good, so it was pushed to the steam engine and was not put to practical use, and in modern times, it was not used due to the development of internal combustion engines. Sterling cryogenic refrigerators using linear compressors have advantages such as low vibration, small size, light weight, low required power, and sufficient durability compared to conventional cryogenic refrigerators, so they are widely used as infrared sensors for night vision goggles (0.5 to 1.9 W at 77 K) and superconducting filters for mobile communication wireless base stations (3 to 6 W at 77 K). By examining the characteristics of the refrigerator using such a stirling refrigerant refrigerator, the difference from the existing refrigeration air conditioning system using refrigerant gas can be seen, and this study showed that the manufacturing method of the motor part and the design of the inlet voltage and current and frequency of the motor greatly affect the performance of small linear stirling refrigerators when manufacturing a compressor of a linear stirling refrigerator.

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.