In this paper, we describe the control of safely grasping various objects using a three-finger gripper. An experimental device was constructed for the characteristic experiment of a three-finger gripper, a control system for closed-loop control was constructed, and experiments were conducted to obtain proportional gain and differential gain experimentally. As a result of the experiment, the proportional gain of the three-finger gripper was Kp=0.25, and the differential gain was Kd=5.0. As a result of the special experiment, the rising time was within 0.31 seconds, the steady-state error was within ±0.02 N, and the overshoot was within 0.03 N. By applying this to control the gripping force, it was possible to safely grip various objects. Therefore, we believe that applying the control method of this study to a three-finger gripper will enable it to grasp various objects safely.
This study investigated the influence of alloying elements on the elastic modulus variation of titanium alloys and conducted theoretical density calculations, yielding the following conclusions. In Ti-M (M=Zr, Ag, Au, and Cu) alloys, the Md value ranges from 2.89325 to 11.1530, and the Bo value ranges from 2.30180 to 3.22978. Ti-Zr alloys are most suitable as optimal dental implant materials in terms of electronic structural stability and strength. Ti–Au and Ti–Ag primarily contribute to biocompatibility, corrosion resistance, and antibacterial performance, while offering less benefit for mechanical strengthening. Ti-Cu, while having low structural stability, exhibits excellent antibacterial functionality and is therefore worthy of consideration as a supplementary alloying element. The physical properties of ‑titanium–based Ti–M binary alloys have been examined, and future research will focus on extending the study to ternary and quaternary titanium alloy systems.
The global maritime industry is undergoing rapid transformation driven by the dual demands of greenhouse gas reduction and digitalization. This study developed a Digital Twin (DT) model of a 9.77-ton small fishing vessel and conducted simulations under realistic operating conditions to analyze its propulsion performance and fuel efficiency. The vessel’s main components—governor, engine, reduction gear, propeller, and marine environment—were mathematically modeled and integrated using MATLAB Simulink. To achieve higher fidelity in representing energy consumption, a fuel consumption model reflecting specific engine characteristics was incorporated. Simulation results confirmed that propeller thrust and marine environmental loads increased proportionally with engine speed, while the application of the proposed fuel consumption model led to reduced fuel injection rates near the engine’s optimal efficiency range. The proposed DT model serves as a robust simulation platform for the pre-verification of eco-friendly equipment, alternative fuel adoption, and operational efficiency improvements. It is expected to provide a valuable foundation for future demonstration studies of green technologies in small- and medium-sized fishing vessels.
This study examines security management issues of small aviation facilities with F-class landing strips in Korea. Under the Airport Facility Act Enforcement Regulation, F-class runways (1,080-1,280 m) mainly serve light aircraft and flight training operations, but many are used continuously outside the national aviation security framework. A comparative review of ICAO, FAA, and EASA regulations shows that foreign systems apply responsibility-based self-regulation, assigning minimum security obligations to operators. However, Korea lacks such mechanisms for small but regularly operated facilities. To address this gap, this study proposes establishing a new Small Aerodrome category and incorporating a Security Management Plan into the National Aviation Security Programme (NASP). These measures will enhance proportional, operator-centered security oversight and strengthen integration within the national aviation security system.
In this study, extinction limit and emission characteristics of COG(Coke Oven Gas), was numerically investigated using counterflow nonpremixed flames to verify usage as a combustion fuel. Also, ammonia (NH3) added COG was studied to reduce carbon emission. OPPDIF code with GRI 3.0 detailed kinetic mechanism was used to predict the extinction limit, EINOx and NO production rates. As results, the extinction limit of COG was greatly expanded compared to CH4, and it was confirmed that the maximum flame temperature at the extinction point was also greatly reduced due to H2, which accounts for 55% of COG. When NH3 was added, the extinction limits gradually decreased, and the maximum flame temperature at the extinction point increased, which is due to the low combustion reactivity of NH3. Meanwhile, it can be confirmed that NOx emissions increased rapidly as NH3 was added.
In this study, a hybrid cooling system combining thermoelectric modules and a vapor compression cycle was applied to a cold storage unit, and the effect of enhancing energy efficiency through the application of mist spraying technology to the heat exchanger coils was analyzed. The hybrid cooling system was designed to operate the vapor compression cycle during the initial temperature reduction phase (from ambient to 5°C), and to maintain the set temperature using thermoelectric modules thereafter. Separate heat exchangers were installed for the thermoelectric and vapor compression components, and mist spraying was applied individually to each heat exchanger coil. Experimental results showed that mist spraying reduced power consumption by approximately 20% during vapor compression operation, and by about 1~2% during thermoelectric operation. This study empirically demonstrates the potential of mist spraying technology as an energy-saving enhancement for hybrid cooling systems, and the findings can serve as a foundation for the development and commercialization of integrated heat exchangers in the future.
This study proposes a surrogate model framework that integrates finite element analysis and deep learning to rapidly estimate equivalent material properties of patterned sheets. Conventional homogenization methods can only be applied after the pattern geometry has been finalized, requiring additional modeling and simulation. In contrast, the proposed approach establishes a surrogate model in advance, enabling the immediate estimation of equivalent material properties once the pattern geometry is defined. A dataset of 5,000 cases was generated using simulations, and Bayesian hyperparameter optimization was applied to improve model performance. The surrogate model achieved R² values above 0.99 for all target properties, confirming high internal consistency. Experimental validation with patterned STS304 specimens yielded meaningful results, with all errors remaining within 15%, which demonstrates the reliability of the proposed surrogate model despite minor deviations caused by fabrication imperfections and limited training data. Despite these limitations, the proposed system enables instant estimation of equivalent properties from pattern geometries, offering significant reduction in computational cost and design time. This approach enhances design reliability and provides a practical tool for the application of patterned materials in industrial engineering.
This paper presents the design and experimental validation of an intelligent tire alignment and lifting control system for an under-vehicle autonomous parking robot. The proposed system enables the robot to autonomously enter beneath a vehicle, recognize tire positions using a LiDAR-based sensing module, and perform precise lifting through a fork-type mechanism. A YOLOv8 instance segmentation algorithm is employed to detect tire regions from LiDAR point cloud data and estimate their geometric centers. The detected tire positions are then matched with a vehicle database to determine the correct alignment for lifting. Experiments were conducted on three different vehicle types under various surface conditions. The results show that the proposed system achieved a tire recognition accuracy exceeding 95%, a lifting success rate of 100%, and an average lifting operation time of 12.3 seconds. These results demonstrate the reliability and practicality of the proposed method for real-world autonomous parking applications.
This study compares the shear behavior of anisotropic magnetorheological elastomers (MREs) using natural rubber (NR) and silicone rubber (Si) as matrices. The effects of magnetic flux density and compressive pre-stress on the shear modulus were experimentally investigated. Results showed that silicone-based MREs exhibited a 10–20% higher magnetorheological effect than NR-based ones due to stronger particle–matrix bonding and stable chain alignment under magnetic fields. In contrast, NR-based MREs showed greater stiffness variation under compressive stress, attributed to strain-hardening and volumetric constraint effects. These findings indicate that matrix selection significantly governs the magneto-mechanical response: silicone MREs are suitable for precision control and sensing, while NR MREs perform better in high-stress damping systems. This study provides fundamental insight for tailoring MREs according to design requirements.
In shipyards, various types of outdoor cranes are utilized to construct large vessels using the block assembly method. The total number of outdoor cranes in domestic shipyards is estimated to be close to 1,000 units. To prevent potential accidents caused by strong winds or other external forces when cranes are in an idle state, safety locking devices must be installed on the lower rail of each crane to prevent unintended movement. Currently, most shipyards employ hydraulic safety locking devices. However, these systems have several drawbacks, including oil leakage, difficulties in power supply maintenance, and the inability to visually confirm the exact locking condition between the device and the rail. To address these issues, this study proposes a new type of motor-driven safety locking device. The design was validated through structural safety evaluation based on finite element analysis(FEA), followed by prototype fabrication and operational testing. The test results confirmed that the developed system met key performance criteria such as operation time, clamping force, and safety factor. The application of the proposed safety device is expected to enhance the operational safety of crane systems and reduce the workload of operators, thereby contributing to a safer working environment in shipyards.
In the manufacturing industry of metallic bellows, accurate cost estimation and quotation generation are crucial because the design dimensions and material specifications vary with each OEM order. This study aims to develop a Microsoft Excel-based software that automatically calculates production costs and generates quotations for single-type and double-type circular bellows based on the EJMA (Expansion Joint Manufacturers Association) 10th Edition design standards. The proposed program integrates the essential cost components — raw materials, forming processes, welding, assembly, inspection, and overhead — into a modular calculation system. Using VBA (Visual Basic for Applications), the system allows users to input design parameters (such as pitch, convolution height, mean diameter, and thickness), after which it automatically computes material consumption, manufacturing time, and total cost, providing an itemized quotation sheet. This automation not only reduces manual calculation errors but also significantly shortens the lead time for quotation preparation. The research demonstrates that the developed system achieves cost estimation accuracy within ±3% of actual production costs and can be easily adapted to different bellows configurations, thereby enhancing productivity and competitiveness in OEM manufacturing environments.
This study compares the optical and radiative cooling performance of single-layer films embedded with TiO2 or Al2O3 nanoparticles dispersed in a polymer matrix and backed with an aluminum reflector. Optical constants of both materials were obtained from literature, and wavelength-dependent scattering efficiencies were calculated using Mie theory. A Monte Carlo ray-tracing simulation was performed to evaluate the spectral reflectance, absorptance, and emissivity of each film across the solar and thermal-infrared regions. The TiO2-based film exhibited strong visible-light scattering but suffered significant ultraviolet (UV) absorption, resulting in an average solar reflectance of ~0.90. In contrast, the Al2O3-based film showed negligible UV absorption and maintained high reflectance (> 0.95) throughout the 0.3-2.5 μm solar band, leading to a higher net cooling power of approximately 105 W/m² compared to 85 W/m² for TiO2. These results demonstrate that UV reflectance is a key determinant of effective radiative cooling and indicate that Al2O3-based coatings offer strong potential for passive cooling applications in buildings and agricultural environments.
This study investigates the effects of asymmetric circular orifice patterns on pressure fluctuations in a pilot valve through computational fluid dynamics (CFD) analysis. Models with 2 to 5 circular orifices were developed, maintaining equal angular spacing around the pipe axis. The analysis was conducted using ANSYS CFX, and results such as outlet pressure, pressure hunting, velocity distribution, and turbulence kinetic energy were examined. The study found that increasing the number of orifices leads to a slight increase in outlet pressure, a decrease in the magnitude of pressure hunting, and a reduction in turbulence kinetic energy. Volume rendering and streamline visualization revealed that flow became more stable and linear as the number of orifices increased. These results suggest that increasing orifice count can contribute to mitigating pressure hunting and stabilizing flow characteristics in pilot valves.
With the rapid expansion of renewable energy deployment, power systems are increasingly exposed to issues such as higher output variability. Photovoltaic generation, as the most widely installed variable renewable energy source both domestically and internationally, exhibits significant fluctuations due to weather conditions. These characteristics lead to operational challenges including increased curtailment, higher reserve requirements, and even risks of large-scale outages. This study aimed to improve the accuracy of photovoltaic power generation forecasting by developing a data quality control procedure for meteorological data collected at a PV plant. The quality-controlled data were used as inputs to SVM and XGBoost, resulting in improved forecasting accuracy, with MAPE decreasing from 7–10% to 6.32% and 6.08%, respectively. The results demonstrate that meteorological data quality control significantly enhances PV forecasting performance and can contribute to distributed energy resource operation and curtailment mitigation strategies.
The molecular dynamic simulation method is usually used to analyse microscopic fluid fields. To use this method in engineering problems with real scales of molecules needs more time and greater computer power than we have now. To overcome these limitations, the expansion method using dimensionless and similarity of physical quantities of molecules is studied and introduced for the engineering scale fluid dynamics.
In this study, We aim to provide design data for a low-temperature refrigeration system to select operating conditions for predicting maximum performance of an eco-friendly binary refrigeration system based on changing operating conditions The operating variables considered in this paper are evaporating temperature, condensing temperature, superheating degree, subcooling degree, and compression efficiency. The main results are summarized as follows: In the low temperature range of -50℃ to -30℃, the COP of the system increased as the evaporating temperature and subcooling degree of the binary refrigeration system for R744-R717 increased, but the COP decreased as the condensing temperature and superheating degree increased. It was confirmed that factors such as superheating, subcooling, condensing temperature, evaporating temperature, cascade temperature difference, and compression efficiency affect the performance coefficient of the binary refrigeration cycle for R744 and R717, and it was found that each of these factors has a cascade evaporating temperature that maximizes the performance of the binary refrigeration cycle.
This study was conducted to examine the structural stability of a lightweight structure for a sliding-type battery rack system located under an electric bus. To address the shortcomings of the existing sliding battery rack systems, the battery rack system was designed by applying lightweight materials and utilizing a bolt-mounting connection type. Finite Element Method(FEM)-based structural analysis was performed, considering both the system’s self-weight and the weight of the installed batteries. The analysis identified the maximum stress value and its location within the entire system. Furthermore, considering the different materials used in various components, the maximum stress values for each component were individually derived. By comparing the maximum stress with the yield strength of each material, it was confirmed that the designed lightweight battery rack system had secured structural stability.
With the rapid expansion of the electric vehicle (EV) market, the importance of high-efficiency thermal management systems is increasingly being emphasized. The Octo-valve, a key component in Tesla's integrated thermal management system, plays a pivotal role in controlling the flow of refrigerant and coolant to optimize the efficiency of the heat pump system. This study aims to analyze the detailed internal flow characteristics of a single Octo-valve unit and to explore methods for its performance enhancement. For this purpose, an actual Octo-valve was disassembled, and its internal flow paths were modeled in three dimensions using a high-precision 3D scanner. Based on this model, a numerical analysis was conducted using Computational Fluid Dynamics (CFD) to simulate the thermo-fluid phenomena within the valve. Changes in temperature, pressure distribution, and flow velocity were analyzed under various operating conditions and variables, and the resulting pressure drop was quantified. Furthermore, the influence of these internal flow characteristics on the overall system's Coefficient of Performance (COP) and heat transfer efficiency was evaluated. The findings of this research provide a fundamental understanding of the complex fluid dynamics inside the Octo-valve and offer essential baseline data for the design of next-generation, high-efficiency Octo-valves.
To improve the seismic performance of a cabinet, a TMD was designed and its dynamic behavior was experimentally investigated as a basic study on vibration reduction. For TMD vibration test, a testing machine base, sliding base and jig were constructed. TMD and base were excited at the same frequency, and their natural frequencies showed a phase difference of approximately 90 degrees. The specifications of the experimental TMD were 20 kg mass, 10% damping ratio, and 7 L of oil. Seismic tests were conducted to investigate the dynamic behavior of the cabinet under earthquakes and the vibration characteristics of the cabinet with and without TMD. Vibration tests were conducted with the cabinet door fully closed, and the acceleration at the top of the cabinet was measured. The maximum acceleration was reduced by approximately 36% when TMD was installed compared to when it was not installed. The experimental results clearly demonstrated the effectiveness of TMD in reducing cabinet vibration.
As modern weapon systems become increasingly complex, the need for integrated management of component standardization and airworthiness certification has grown significantly. This study proposes a system-based approach to establish an integrated management framework that addresses inefficiencies, certification delays, and supply chain risks inherent in current military aircraft development processes. The research reviews the functional scope of component standardization and compares airworthiness certification systems across domestic and international defense sectors. It identifies limitations caused by the fragmented management of parts and certification processes, and proposes a digital platform that interconnects parts databases, configuration control, quality assurance, and certification modules. The framework incorporates AI and digital twin technologies to monitor and manage reliability across the entire life cycle of a weapon system. This study lays the foundation for enhancing the operational efficiency of national defense technologies, and contributes to strengthening the autonomy and global competitiveness of the Korean defense industry.