Earticle

The International Maritime Organization (IMO) is promoting the transition to eco-friendly fuels such as hydrogen and ammonia, with the goal of achieving net-zero greenhouse gas emissions in the shipping sector by 2050. Hydrogen does not emit greenhouse gases, but it must be stored at an extremely low temperature of -253°C when stored as a liquid. 316L stainless steel is mainly used as a tank material to store liquid hydrogen. FCAW (Flux Cored Arc Welding) is known for its excellent weldability with 316L stainless steel, and it is particularly suited for welding thick metals efficiently, making it an ideal choice for storage tank welding. Finite Element Method (FEM) analysis can simulate the thermal and mechanical deformations occurring during welding with high precision, allowing for accurate prediction of deformation patterns and the derivation of optimal welding conditions. This ensures the stability and quality of the structure while reducing costs. In this study, FCAW butt welding was performed on 316L stainless steel, followed by cross-sectional observation and deformation measurement of the weld area. Based on the cross-sectional observation, a 3D FE model was designed, and heat transfer analysis was conducted. Subsequently, thermo-mechanical analysis was carried out to predict welding deformation.

In this study, a layout was designed to adjust the location of the LPG fuel tank by combining a Z-Spring and an Airbag in an LPG 1-ton truck air suspension assembly, and a structural analysis based on the finite element method was performed considering the load conditions of extreme situations based on the weight taken into account. The study was performed under a total load condition of 2.1 tons per axle with a safety factor of 2, and it was confirmed that the maximum stress value occurring in each part is within the yield strength value of the material. Through these results, it was confirmed that the designed LPG 1-ton truck air suspension assembly is a system with secured structural stability.

The heat transfer characteristics of double-pipe spiral heat exchanger using aluminum oxide nano-fluid were investigated by three different sizes of curvature size, experimentally. Five concentration of nano-fluid as working fluid were made and tested to analyze the heat transfer characteristics. As results, the heat transfer performance was improved at 0.25% of nano-fluid due to high thermal conductivity, however, as the concentration of nanofluid increased (~2.0%), the heat transfer performance deteriorated due to the increase in thermal resistance caused by the sedimentation of particles in the flow path. In addition, the nano-fluid has a higher pressure drop than water due to its high density and viscosity. The optimal range for heat transfer enhancement of nano-fluid was found to be less than 4.0 LPM in flow rate and 0.25% of nano-fluid concentration in this study.

Gait analysis can objectively assess abnormal walking, and some walking parameters can help recognize the disease. Existing commercial systems are either too expensive and require attachments to the body or have limitations in detecting abnormal gait. A vision system has been proposed to address this. However it had limitations where the accuracy was inferior in some parameters such as gait phase, step length and width, etc. Therefore we developed a Tactile sensor-based treadmill to detect gait phase, step length, and width. A pilot test was performed and analyzed through an infrared marker-based motion capture system to compare the accuracy of the proposed system. The measured spatiotemporal gait parameters were analyzed through mean and standard deviation and compared to the baseline system. As a result of the experiments, it was confirmed that higher step width performance was achieved compared to previous studies. Future studies will validate the system with many participants and conduct clinical studies on gait recognition through abnormal gait analysis.

In order to design a seismic safety of a cabinet affected by an earthquake, vibration analysis was performed using a model cabinet. In order to analyze the vibration characteristics of the cabinet under earthquake conditions, 3D finite element analysis was performed using ANSYS Workbench and SolidWorks. The modal analysis of the cabinet showed nine natural modes and natural frequencies, and showed the deformation and vibration of the cabinet panel for each mode. The frequencies of the 1st and 2nd modes, which are low modes, were 10% of the natural frequency value of the 9th mode, so it was easy to predict the possibility of resonance occurrence. The response spectrum due to the earthquake showed that the displacement, acceleration, and stress distribution of the cabinet had different behaviors in the x, y, and z directions, and especially showed very large values ​​in the z direction. Although the vibration characteristics of the structure were evaluated using the modal characteristics and response spectrum for the cabinet, research on the application of a tuned mass damper is necessary for the dynamic characteristics process of the cabinet due to an earthquake and resonance reduction.

In this study, contribution evaluation method applying Independent Component Analysis (ICA) was proposed. The necessity of applying ICA to the contribution evaluation was investigated through numerical simulation. The simulation modeled a scenario where the vibration/noise sources were physically overlapped in a small space, and their frequency characteristics were similar. For comparison between the conventional contribution evaluation method and the proposed method, the contribution evaluation was performed using the ordinary and partial contribution evaluation methods. Through this analysis, it was confirmed that the proposed method can identify contributions by restoring the signal when the frequency characteristics of the vibration/noise sources were similar, and their positions overlapped. These results confirm that the contribution evaluation method based on independent component analysis is effective in appropriately analyzing vibration/noise sources when their frequency characteristics are similar, and their positions overlap.

The launcher of a hard-kill type APS (Active Protection System) requires rapid and precise driving to aim at incoming threats after detection. High angular acceleration is necessary for rapid driving, which demands high energy consumption. However, the capacity of the capacitor bank and power supply unit is limited due to weight and space constraints. If energy becomes insufficient during continuous operation, the voltage of the capacitor bank can drop below the minimum operating voltage of the drive motor, leading to problems such as torque deficiency. Therefore, it is necessary to determine an allowable angular acceleration that satisfies precision within the available energy and generate a driving profile accordingly. This paper proposes a method for deriving an allowable angular acceleration by analyzing the allowable energy and validates it through simulation. We examined the allowable energy by verifying the charged voltage of the capacitor bank, formulated equations for energy at the point of maximum consumption, and derived an equation for allowable angular acceleration through numerical analysis. By applying the proposed algorithm in simulations, we confirmed that the voltage of the capacitor bank did not drop below the minimum operating voltage of the driving motor during three consecutive operations. Therefore, it is expected that the stability of the APS launcher can be improved by applying the proposed algorithm, and continuous operation with limited performance is anticipated to be possible.

This study collected video footage of accident-risk scenarios on actual roads using automobiles and motorcycles. A total of 191,500 km was driven with three vehicles and one motorcycle, capturing 6,550 near-miss accident videos. The footage was analyzed and categorized based on the 27 parameters of the iGLAD(Initiative for the Global Harmonization of Accident Data) accident categories. Parameters difficult to classify under iGLAD were localized to fit domestic conditions, and further analysis identified areas needing optimization. The categorized data was organized into a web-based database platform, providing statistical analysis and search functions for scenario development. Future use of this data will support the creation of safety evaluation scenarios for autonomous vehicles, enhancing traffic accident investigation and analysis systems. Expanding the database to include data from secondary roads and parking areas is expected to increase its applicability and value.

In this study, fire extinguisher system to which form fire extinguisher agents were adopted was applied to the combat vehicle crew room to apply fire extinguishing performance and acid gas safety that meet the national defense standards. As a result of evaluation and verification, the following conclusions were drawn. For standard fire sizes in the combat vehicle crew's standard model, we ignited using a mixture of Novec 1230 and Halon 1301 form extinguisher agent and released form extinguisher agent after 30 seconds to determine the fire extinguishing time. The amount of acid gas generated met the criteria in all cases. When the fire size was increased to 0.12m2 and a 2.0mm nozzle was used, all of the extinguishing time, the amount of acid gas generated, and the concentration of Novec 1230 met the criteria. Despite the more difficult conditions to extinguish the fire by making the fire larger, it was possible to confirm the extinguishing performance of the Novec 1230 form extinguisher agent and its safety against acid gas.

Microreactors, a type of Small Modular Reactor (SMR) under 20 MWt, are being developed globally for use in remote areas, utilizing fourth-generation nuclear technology for enhanced safety. However, there are no established standards for their commercialization. This study reviews road transport regulations for microreactors and proposes necessary design loads and evaluation criteria for their transport. Transport concepts were identified through a review of overseas developments, with requirements derived for both accident and normal conditions. The study also presents an approach for evaluating transport stability based on land-based nuclear plant regulations, considering load conditions from drops and puncture impacts, as well as random vibrations during road transport. This work aims to support the design of mobile reactor transport systems and contribute to new regulatory and licensing procedures for advanced reactors.

This study was conducted using mold heat. By developing the cleaning process technology, the production test was improved by twice, and the heat washing time reduction test and defect rate were also reduced. We designed an automatic production system for automatic heat torches and devised an automated continuous process system to improve the mold process. The production capacity test doubled the production rate of the product per 1 hour from the target of 500 to 1,040 per hour, and the heat cleaning time reduction test measured the time from the beginning of heat injection to the product sample during the production process and the end time, which shortened the development target of 5 seconds (sec) to 2.78 seconds (sec), and the defect rate was reduced to 4.25% as a result of the defect rate test. The system development of this project has doubled the production volume

In this study, we explored the design of improved road lighting for drivers and pedestrians using ray-tracing and reverse ray-tracing methods. Conventional road lighting often poses issues such as glare and unevenly illuminated areas, which can compromise safety and efficiency. These problems stem from traditional design approaches focused solely on achieving high luminance and electrical power. However, our research shows that higher brightness or power consumption does not necessarily equate to better road lighting. By applying ray-tracing techniques, we aimed to design a reflector that enhances visibility while being easier on the eyes of both drivers and pedestrians. Our optimized reflector design demonstrated significant improvements in both central and average illuminance levels, all while reducing energy consumption. This study suggests that careful reflector design is crucial for creating safer and more energy-efficient road lighting solutions.

The results of the measurements using an optical surface roughness meter are shown according to the angle changes of 0, 0.5, 1, 1.5, 2, and 3°. Through the experiment, it can be seen that the measurement value is 3.140 at 0°, 3.148 at 0.5°, 3.140 at 1°, 3.151 at 1.5°, 5.078 at 2°, and 4.790 at 3° setting. In addition, the test statistic (P) value is 0.000, which is smaller than the significance level of 0.005, so it was confirmed through the experiment that a measurement error occurs according to the angle change when measuring the surface roughness.

The research led to the development of a specialized knife for cutting waste ropes and nets from marine waste. The composition of the manufactured knife was analyzed with XRF equipment, and the main components were iron and chromium, with small amounts of molybdenum, vanadium, and nickel. Vickers hardness measurements showed similar hardness values at the surface and center, and a metallographic microscope examination of the knife surface texture revealed a fine-grained martensite structure. The low heating value of the waste rope and waste net was measured, and the low heating value was higher than 3,500 kcal/kg, which is the quality certification standard for solid refuse fuel.

In this study, a pulse jet engine that operates without a shutter valve was developed using a reflector. The pulse jet engine has the disadvantage of being noisy and low in efficiency compared to other engines, but has the advantage of a simple structure and no significant limitations on the fuel used, so research is being conducted to apply this engine to industrial fields such as biomass fuel conversion and boiler systems. Various research is being conducted as it becomes the basis of a pulse detonation engine. In this study, a pulse jet engine is designed, manufactured and tested successfully. The developed pulse jet engine can be used as a power source for various transportation methods such as vehicles and hovercraft through improvement.

Lightweighting is crucial in various industries, especially for bicycles where weight and stiffness are key. Traditional materials like steel, aluminum, and carbon each have pros and cons. This study compares hybrid tubes made of aluminum and carbon composites with conventional aluminum tubes. Using structural analysis and experimental testing, the hybrid tubes showed a weight reduction of up to 17.25% and maintained acceptable deformation levels. Finite element analysis confirmed these findings, demonstrating the hybrid tubes' potential as superior bicycle frame materials. Future research should focus on long-term durability and fatigue characteristics.