Earticle

Recently, Car weight reduction has become an important development goal to improve fuel efficiency. Car seat frame is a key part of the weight reduction. Existing steel seat frames have the advantages of high rigidity and durability, but have the disadvantage of heavy weight. Recently, Almag material, which are alloy of aluminum and magnesium, is attracting attention because of excellence in strength and weight reduction. At first, the core stiffness members of the seat frame are selected to optimize the weight of the seat frame. And then strength analysis and natural frequency analysis are performed for the existing steel seat frame and Almag seat frame. Based on these analysis results, optimal thickness of the Almag seat frame are determined by an automation program using a genetic algorithm.

This study integrates TabTransformer and CTGAN for predicting job satisfaction among South Korean college graduates. TabTransformer handles complex tabular data relationships with self-attention, while CTGAN generates high-quality synthetic samples. The combined approach achieves an accuracy of 0.85, precision of 0.83, recall of 0.82, F1-score of 0.82, and an AUC of 0.88. Cross-validation confirms the model's robustness and generalizability with a mean accuracy of 0.85 and a standard deviation of 0.008. The integration of TabTransformer and CTGAN enhances predictive accuracy and model generalizability, providing valuable insights for employment policy and research.

Detection and sizing of defects are very important for structure life management base on fracture mechanics. The non-destructive inspection techniques based on the induced current field measurement are newly developed. This paper describes the results obtained by these techniques for artificial surface defects. In the case of the RICFM technique, the potential drop distribution around a surface defects was measured as a smaller potential drop than that in a place without a defect. This potential drop showed a minimum value at the defect location, and the absolute value of this minimum value increases depending on the depth of the defect. In the case of the FEF technique, the potential difference distribution for surface defects was measured as a maximum at the location of the defect. This maximum value showed a difference depending on the depth of the defect.

In this study, power generation characteristics based on water flow dynamics in a pipe system with a mobile firefighting robot were analyzed using 3D CAD modeling and computational fluid dynamics(CFD) simulations. The water flow field which is significantly affected by applied pressure, generates mechanical torque at the turbine blades, enabling power generation. The inlet pressure of the flow field was set to approximately 6 to 12 bar, and the flow characteristics such as velocity, pressure, and mass flow rate, along with power generation characteristics, were analyzed under various turbine rotational velocities. It was observed that higher inlet pressures resulted in increased torque and mechanical power output at the turbine blades. This research is expected to serve as a fundamental design and data reference to improve the performance of firefighting robots at fire sites.

In this paper, we address the issue of temperature uniformity in high-power antenna systems by proposing and analyzing various design strategies. Specifically, when there is significant spatial freedom in the internal coolant pathways of the cooling plate, a counterflow approach is implemented to achieve temperature uniformity. Conversely, in scenarios where spatial constraints exist, a differential fin area design is proposed to effectively manage heat distribution. Additionally, in cases where the design of coolant pathways is restricted and fin design is not feasible, we suggest minimizing temperature variations by adjusting the thermal conductivity of the carriers located beneath the heat-generating components. This comprehensive approach aims to enhance the thermal management of high-power antenna systems, ensuring improved system stability and performance.

This paper defines structural and dynamic analysis of a crane used for electric passenger vehicle fire scenarios. The crane model used in the study has a working radius of 9 meters, and under extreme conditions measured with real-world usage in mind, the load at the boom tip is 24.5kN. The boom is assumed to be made of ATOS80, and the pads are assumed to be made of Monomer Casting Nylon. Structural analysis was conducted based on the crane's materials and configuration, and dynamic analysis was performed by dividing the grab method into gripper and hinge types. In the structural analysis, the maximum stress increased as the telescopic boom faced upwards. In the dynamic analysis, the gripper type facing downward showed more stable stress. For the model with an added badge, the structural analysis showed an increase in maximum stress, but the value was negligible, and the maximum stress of the telescopic boom decreased in the dynamic analysis. Based on the analysis results, the suitable materials for the crane are ATOS80 for the lower articulated boom and the telescopic boom, and DOMEX1300 for the upper articulated boom. The gripper type grab method is more stable than the hinge type.

The hydrogen embrittlement could lead to big damages in bolt/nut, fittings, especially, high pressure valve and high leak-proof valve and so on. Thus, special alloy, for instance, such as Monel and Inconel, is recently used to suppress the problems of hydrogen embrittlement in semiconductor facilities, FCEV(fuel cell electric vehicle) and hydrogen gas stations. The purpose of this study is to investigate the characteristics according to ratio change between drawing and extrusion of Monel material within elastic limit through numerical analysis. As the results, the possibility of plastic deformation in case of drawing was greater than that of extrusion. Consequently, the safety factor related to plastic deformation shows the results depending on the ratio change of force between drawing and extrusion.

In this study, flow analysis was performed using ANSYS CFX to evaluate the performance of the 30kg hydrogen fuel cell hexa-copter drone in hovering flight. In the case of a hydrogen fuel cell hexa-copter drone, a total of four cooling fans are mounted on the drone's body in two pairs on the left and right to cool the fuel cell module. In order to evaluate the effect of the air flow from the cooling fan on the aerodynamic properties of the hydrogen fuel cell drone as the mounted cooling fan operates, the change in thrust for the case where the cooling fan operates and does not operate was compared and analyzed. Looking at the analysis results, it was found that the presence or absence of the drone's cooling fan had little effect on the drone's thrust through the thrust results for the six wings.

The performance of various types of silencers used to reduce the micropressure waves radiated from ventilation holes and inclined shafts, which are being studied as measures to reduce micropressure waves in railway tunnels, was evaluated to find an effective silencer. In order to find the optimal silencer, the magnitude and frequency characteristics of the pressure waves emitted from the inclined shaft were analyzed to find an excellent silencer. The evaluation showed that the model with a porous cylinder and a small diameter outer tube was the simplest but performed the best.

In this study, the calorimeter was used to experimentally investigate the cooling characteristics of the variable A/C system according to changes in loading time and outdoor dry bulb temperature. The cooling capacity, COP and compressor discharge temperature were measured while changing the loading time of the compressor. To develop the correlation for compressor discharge temperature, loading time, indoor and outdoor dry bulb temperatures, evaporation and condensation temperatures were considered as operating variables. As the loading time increased, the cooling capacity and COP increased. The cooling capacity increased linearly with the loading time. The COP increased more at low loading times than at high loading times. The change in condensing temperature according to the loading time had a small temperature fluctuation range, and the evaporation temperature decreased linearly. The compressor discharge temperature increased linearly with the loading time and outdoor temperature, and the maximum deviation between the experimental value and the correlation was within about 2℃.

This paper studied a new shape unit model based on Gibson and Ashby's theory. As a result of theoretical research, the relative density equation is correlated with relative elasticity, and through this study, the theoretical relationship between the relative elasticity equation was defined. The relative elasticity equation was defined based on the model for which the analysis was performed. According to the analysis results, the diameter of the model was set to 3 mm, and the maximum stress values ​​were confirmed by reflecting the same boundary conditions. The maximum stress for each model is 5668.9MPa for Type 1, 5136.7MPa for Type 2, 5642MPa for Type 3, and 6032.9MPa for Type 4 when the truss diameter is 3mm. The relative elasticity equation was defined based on this condition. In the future, compression analysis will have to be performed in the same way, reflecting the diameter of the truss at 5 mm and 7 mm, to find and define the coefficients of the relative elasticity equation, and verification through experiments will have to be carried out based on the theoretical equation. In addition, in order to be applied in each field, proof through prototype production and installation must be carried out.

Recently, the number of elderly driver accidents has been steadily increasing. EDR(Event Data Recorder) helps a lot in understanding traffic accidents. In particular, as anxiety about SUA(Sudden Unintended Acceleration) increases, EDR data is playing an important role in accident analysis. In this study, EDR data of an accident vehicle suspected of SUA was analyzed to identify traffic accident circumstances and detailed accidents. Experimental results were derived and analyzed by simulating the situation of SUA while driving a car. As a result, it was found that normal braking is performed when the brake pedal is operated even in dangerous situations such as mechanical defects and driver malfunctions. Rather than finding the cause of an accident after a traffic accident, countermeasures are needed to prevent mechanical defects and driving malfunctions before a traffic accident.

Analyzing and diagnosing the causes of abnormal conditions through control logic processes at the plant site is critically important. When a process is halted, the steps for cause analysis and corrective action vary depending on the operator's experience and the specific characteristics of the process. Since it's often not feasible to keep the process stopped for an extended period, issues are sometimes resolved by forcibly restarting the PLC(Programmable Logic Controller). However, this can lead to the recurrence of the same error, which may negatively impact process operations. In particular, oil sands development is an uncharted area with anticipated environmental challenges. In this regard, an integrated system between control systems in the oil sands production plant was established to implement control logic, develop the HMI(Human-Machine Interface), and verify the user interface. This allowed for a better understanding of the equipment's operability.

Robots equipped with artificial intelligence technology include learning functions. Purely inductive learning methods formulate general hypotheses by finding empirical regularities over the trainning examples. Purely analytical methods use prior knowledge to derive general hypotheses deductively. Therefore, when the physical environment of a robot is complex, there is a problem of increased computational time required for information processing. In particular, when a large number of robots transmit information, more computational time is required for information processing. The distance-based topological method proposed in this paper first constructs the topology based on the distances between robots, and then generates information weights according to the stages of the topology. The technique proposed in this paper has been experimentally confirmed to have excellent performance in environments with a large number of robots and complex physical conditions.

This study investigates using Conditional Tabular Generative Adversarial Networks (CT-GAN) to generate synthetic data for turnover prediction in large employment datasets. The effectiveness of CT-GAN is compared with Adaptive Synthetic Sampling (ADASYN), Synthetic Minority Over-sampling Technique (SMOTE), and Random Oversampling (ROS) using Logistic Regression (LR), Linear Discriminant Analysis (LDA), Random Forest (RF), and Extreme Learning Machines (ELM), evaluated with AUC and F1-scores. Results show that GAN-based techniques, especially CT-GAN, outperform traditional methods in addressing data imbalance, highlighting the need for advanced oversampling methods to improve classification accuracy in imbalanced datasets.

This study investigates the thermal expansion characteristics of hydroxyl-terminated polybutadiene(HTPB) based solid propellants, focusing on batch-to-batch variability and accelerated aging effects. Coefficient of thermal expansion(CTE) measurements were conducted using thermomechanical analyzer(TMA) on samples from different manufacturing batches and specimens aged at various temperatures for different durations. Results indicate variations in CTE values between batches, highlighting the significance of manufacturing process control. Accelerated aging experiments reveal minimal systematic changes in CTE, suggesting stability of thermal expansion properties under short-term thermal stress. The overall distribution of CTE values shows concentration within a specific range, indicating consistency in thermal expansion characteristics. These findings provide insights into the thermal behavior of HTPB-based solid propellants, contributing to improved missile design and lifecycle prediction models.

In this paper, we developed a thermoelectric storage container that maintains whole blood temperature and studied its characteristics. Using a temperature sensor, we compared the internal temperature with the set temperature in real time and maintained the temperature between 1 and 6°C. In addition, we installed insulation inside the container and used a lithium-ion battery to power the system to ensure a stable whole blood temperature even during long-distance transportation. Instead of a blood pack, a 350-g water bottle was used and the experiment was conducted at an ambient temperature of 25°C. After cooling for 10 minutes, the internal temperature of the container reached 6°C and the battery operated for 60 minutes. In the future, if we improve the thickness and thermal conductivity of the insulation installed in the thermoelectric storage container and utilize phase change materials as a supplement, we will be able to transport more diverse blood products and special reagents stably.

This study is about the evaluation for shock-proof performance of the system, elastically support the low accumulator of the naval artillery against underwater explosion, using DDAM. For the evaluation, the shock analysis procedure using DDAM, supported by MSC/NASTRAN, was briefly described. In addition, in order to perform the shock analysis, the elastic support system was modeled as a finite element. The shock analysis of the elastic support system was performed by selecting the analysis frequency range so that reliable results can be obtained. Finally, the shock-proof performance of the system was evaluated by comparing the shock analysis results with the properties of the elastic support system.

Noise is defined as ‘unwanted sound’ or ‘undesired sound’. Recently, the aviation industry has been rapidly developing through convergence with cutting-edge technologies such as UAM. Accordingly, it is expected that new aviation industry models will continue to be created in Korea. In addition, it is expected that aircraft noise will be raised as a new social problem. The characteristic of aircraft noise is that it has a wide transmission range. Therefore, the area affected by aircraft noise is extensive, and the damage area varies depending on the flight path and flight environment. Additionally, it tends to occur continuously in certain areas. This study is an extension of the previous studies 󰡔Study on noise measurement and analysis of C172 aircraft at Muan Airport󰡕 and 󰡔Study on noise measurement and analysis of SR20󰡕, and investigated the noise characteristics of various piston engine trainer aircraft operated in Korea. We want to measure and analyze noise.

Floating solar power generation is rapidly emerging as an alternative technology to land-based solar power generation around the world, and there are many advantages to developing and operation floating solar power, but it is a buoyant body that floats solar power modules and structures such as typhoons, tsunami, and wave heights. Research and development is actively underway, and in particular, as damage to buoyancy bodies, which is a vulnerability of floating solar power generation facilities, has been highlighted as a cause of eco-friendly(EVA) buoyancy bodies to improve buoyancy excellence was also achieved in various aspects such as resilience, environmental friendliness, maintenance, and durability.

One of the efficient method for DPF(Diesel Particulate Filter) regeneration of diesel engines is using post fuel injection, which is injected into the combustion chamber during the expansion stroke. This method generates a heat for DPF regeneration by oxidation of HC with Pt coated on DOC(Diesel Oxidation Catalyst). This study investigates heat generation of DOC using post fuel injection.

To efficiently develop an automatic assembly system that can enhance the quality and assembly productivity of the shaft assembly in EV relays, a DMU model was utilized. After modeling each component of the assembly system using the CAD software CATIA, a DMU model of the assembly cells and the entire assembly system was created using the assembly model. Additionally, the DMU Kinematics Workbench was employed to verify and validate the design of the automatic assembly system for the shaft assembly, a key component of the EV relay, before actual construction. This approach helped reduce time and costs by minimizing trial and error.

An electric initiator is a component that is located in the thermal battery or propulsion unit to transfer energy first. Initiator tests include X-ray test, non-destructive leak testing, circuit/insulation resistance test, and CBT (Closed Bomb Test). Among them, CBT is a key element in evaluating the performance of initiator, and the reliability of the test results is important for judgment of the required performance. This study conducted inter-laboratory comparative tests to secure the reliability and repeatability & reproducibility of the initiator CBT. A comparative test was conducted with a mass production acceptance test agency to verify whether the reliability was secured.

Liquid hydrogen, a promising energy carrier, necessitates robust storage and transportation systems due to its extremely low boiling point. Consequently, the development of reliable cryogenic adhesives and standardized testing protocols is crucial. This study focused on optimizing the design of a gripper used in single lap shear tests for evaluating cryogenic adhesives, specifically targeting the challenges posed by low-temperature conditions that induce slippage at the gripper interface. The optimal design was performed using a total of five variables, including the position and size of the gripper. By employing the genetic algorithm coupled with finite element analysis, we exhaustively searched through over 1000 models to identify the optimal gripper geometry. We successfully minimized stress concentration at the gripper region while maintaining a uniform stress distribution on the non-bonded surface. Furthermore, the study explored the impact of symmetric versus asymmetric gripper configurations on test results. The findings revealed that symmetric grippers generally yielded more consistent and reliable data. This study's results enable the accurate and stable execution of lap shear tests under the temperature conditions of liquefied hydrogen.

The lane designation and the bus-only lane system for traffic speed and road safety are difficult to crack down on, and for this purpose, crackdown methods using image recognition technologies are being studied. Existing studies require continuous learning or additional equipment, and it is difficult to classify combined vehicles such as vans and pickup trucks. Therefore, in this study, YOLO and EasyOCR were mixed to classify combined vehicles through vehicle type symbols. For combined vehicles, higher accuracy was shown than classification using YOLO. Due to the nature of Hangul, the accuracy was slightly lowered because the OCR was not accurately recognized, but if it is used with the existing YOLO classification, high accuracy of crackdown will be possible.

The recent surge in energy consumption has sharply increased the use of fossil fuels, leading to a steep rise in the concentration of greenhouse gases in the atmosphere. Interest in hydrogen is growing to mitigate the issue of global warming. Currently, hydrogen energy is transported in the form of high-pressure gaseous hydrogen, which has the disadvantages of low safety and energy efficiency. To develop commercial hydrogen vehicles, liquid hydrogen should be utilized. Liquid hydrogen storage tanks have supports between the inner and outer cylinders to bear the weight of the cylinders and the liquid hydrogen. However, research on the design to improve the structural safety of these supports is still insufficient. In this study, through a thermal-structural coupled analysis of liquid hydrogen storage tanks, the model with three supports, which had the lowest maximum effective stress in the outer tank, inner tank, and supports as proposed in the author's previous research, was used to create analysis models based on the diameter of the supports. A structurally safe design for the supports was proposed.

Multidisciplinary Design Optimization(MDO) method that considers principles in various fields affecting big scale structure and system design at the same time is used. Because most variables are connected many engineering phenomena under the classic optimized design method(all-in-one design approach), it is hard to judge the meaning of final design solution obtained, and there are cases where all variables converge before reaching the optimal design value in large-scale design problems with many variables. Collaborative Optimization (CO) method, the most advanced MDO approach, is used to efficiently solve these optimum problems, to efficiently analyze design problems involving numerous design variables and constraints and in which various engineering phenomena occur. However, the application of the MDO problem to CO introduces a number of numerical problems by destroying the numerical properties of the original optimal design problem. Therefore, this study researches one solution by listing the problems of CO after organizing various approaches of MDO.

Wireless sensor systems are primarily used for monitoring natural environments or industrial automation. The physical environment where these systems are installed is often unstable, making it difficult to replenish sensor energy immediately. Complex and harsh conditions can impact the network's structure, affecting monitoring performance. Wireless sensor systems consist of hundreds of sensors that collect data from hazardous environments and transmit information to a central system. However, due to the system's physical structure, information delays or losses may occur. This paper proposes a distance-based tree structure to address these issues in wireless sensor systems, and experimental results confirm its superior performance.

This study aimed to develop a systematic process for identifying components that need to be changed to reduce the Head Injury Criterion (HIC) during pedestrian headform tests. Through simulation and analysis, it was confirmed that the hood, hinge, hinge plate, cowl, fender, and fender bracket significantly influence HIC15. The study identified the specific impact of each component on HIC15, allowing for targeted improvements. The proposed process demonstrated superior performance compared to single-component optimization, yielding more significant reductions in HIC15. Multiple vehicle models were tested, confirming the process's effectiveness in consistently lowering HIC15 values.

In this study, the calorimeter was used to experimentally investigate the heating characteristics of the variable A/C system according to changes in loading time and outdoor dry bulb temperature. The heating capacity, COP and compressor discharge temperature were measured while changing the loading time of the compressor. To develop the correlation for compressor discharge temperature, loading time, indoor dry bulb temperature and outdoor dry bulb temperatures were considered as operating variables. As the outdoor temperature and loading time increased, the heating capacity and COP increased. However, the change in COP showed different trends depending on the outdoor temperature. The evaporation temperature according to the loading time is a good estimate of the outdoor temperature. However, as the temperature difference between indoor and outdoor rooms decreases and the loading time increases, the condensation pressure increases significantly, so the condensation temperature increases. The maximum deviation between the correlation and the experimental value for compressor discharge temperature was within approximately 2℃.