Paramedics are highly likely to be exposed to high levels of stress and emotional exhaustion. Emotional exhaustion arises from excessive workload and sustained tension, negatively impacting not only individual mental health but also job performance. This study aims to investigate the level of emotional exhaustion among paramedics. A survey was conducted among fire officials across various regions in South Korea, analyzing the degree of emotional exhaustion by gender, age, years of service, and position. The analysis revealed statistically significant differences in emotional exhaustion based on age, years of service, and position among fire officials, with paramedics showing higher levels of emotional exhaustion compared to rescue, fire suppression, and internal administrative positions. Notably, younger age groups, shorter years of service, and paramedic positions were associated with higher levels of emotional exhaustion. This study contributes to assessing the level of emotional exhaustion among paramedics and exploring specific measures for mental health recovery, ultimately aiming to improve work efficiency and enhance the quality of emergency medical services. Future research should focus on developing concrete support systems and stress management programs to continuously monitor and improve the mental health of paramedics.

The development of liquid CO₂ storage tanks and liquid CO₂ handling technology are key for liquid CO₂ carriers, and it is necessary to extract core patents of competitors that may lead to patent disputes in the future, establish response strategies, and strengthen the IP portfolio by creating new IPs. As a result of patent analysis for this purpose, patent applications and technology development are being led by the three large domestic shipbuilding companies(Hyundai, Samsung, and Hanwha) and the large Japanese shipbuilding company(MHI), and the handling of liquid CO₂ storage tanks and liquid CO₂ (prevention of dry ice formation) Technology-related patent applications and technology development are actively taking place, so there may be concerns about patent infringement. Currently, It has been confirmed that there are no core patents that are likely to cause patent disputes in the future. However, the technology concept in question lacks patentability as it is a combination of known technologies, so the creation of new IP is necessary to establish exclusive rights. Accordingly, through this project, four new IP creations and patent applications based on competitors' patents were completed. ① Technology to prevent the release of dry ice during unloading using filters, ② Technology to prevent the creation of dry ice in the unloading piping during unloading, ③ BOG reliquefaction technology to respond to CO₂ emission ban regulations, and ④ Technology that can utilize BOG within ships.

In recent years, the redevelopment and reconstruction of buildings has been actively trending as part of urban development projects, and the number of buildings being demolished is also rapidly increasing. However, various valid institutional and technical standards are required to ensure safety related to demolition and dismantling and to reasonably manage field work, but there is a lack of research and data on them. Accordingly, this study seeks to re-establish realistic working conditions applicable to complete dismantling construction through research on various variables in examining the structural safety of total dismantling construction. In particular, the purpose is to secure work safety at the demolition site by dismantling rahmen-type reinforced concrete buildings in urban areas by inserting equipment into the upper floor slab and evaluating structural safety according to the loading height of demolition debris. This study can be used to ensure the safety of field workers and as a useful guide for engineers to plan and carry out demolition work.

This study aims to identify the effects of coffee grounds on plant growth in order to propose new ways to recycle this waste product. As a way to recycle coffee grounds, the effect of placing coffee grounds on the surface of kidney bean plants on plant growth was investigated by determining the root, stem, leaf front growth, and seed germination rates. To maximize the effectiveness of coffee grounds, the effect of heat treated temperature for coffee grounds on plant growth was investigated. Normal kidney bean growth was checked for seed germination and seedling growth. The germination rate was 80 % for the non-treated case without coffee grounds, but 100% for the coffee grounds treated at 100 ℃ and 250 ℃ of heat treatment. Stem, root, and leaf growth were all improved with the use of coffee grounds compared to the non-treated case. This can be attributed to the organic matter present in the coffee grounds and the fact that coffee grounds are hydrophilic, which makes them more hydrating for plants. The coffee grounds were utilized to enhance plant growth, which could be utilized as a new way to recycle coffee grounds.

In this paper, anomaly detection methods for a collaborative robot during the chemical drum assembly process in the semiconductor industry are presented. The manual assembly of chemical drums has been automated using robots to prevent industrial accidents. However, the automation may increase downtime due to anomalies or failures in the robot manipulator tasks. To prevent this issue in advance, the methods to diagnose anomalous behaviors and conditions in the robotic automation workflow and subsequently resume tasks are proposed. To detect and diagnose anomalies in the tasks, the Random Forest classification method was utilized. Using this Random Forest classification, the collaborative robot anomaly detection model achieved an accuracy of 98.91%, successfully detecting all anomalies in the assembly process.

Recently, vision-based displacement(VBD) has been attracting attention as a convenient and economical method. VBD has the advantage of being easy to install and operate, but it also has the disadvantage of being difficult to obtain results that reflect high-frequency characteristics well. On the other hand, indirect displacement measurement through double integration of acceleration may in some cases result in distortion in the low-frequency region, making integration itself impossible. Therefore, neither can be a suitable method alone for measuring the dynamic displacement of bridges under moving loads. In this context, this paper studies how to obtain more accurate dynamic displacement responses of bridges over the entire frequency range by combining two methods, VBD and acceleration integration. The practical applicability was examined through simulation and model experiments. The simulation results show that both basic methods have fundamental limitations in each frequency range, while the combined method can be an good alternative to overcome these limitations. The applicability of the combination method through model experiments also showed relatively good results, but the results were inferior to those in the theoretical case. The reason is that errors in each basic measurement methods are transferred to the combined method. In other words, it is important that the basic measurement method also secures sufficient accuracy at least in each advantageous frequency band. In conclusion, combining the strengths of different methods to create a better alternative is always a good approach, and the method in this paper is meaningful in that it demonstrates one such alternative.

While metaheuristics have profoundly impacted various fields, domestic financial portfolio optimization research, particularly in asset allocation, remains underdeveloped. This study investigates metaheuristic algorithms for investment strategy optimization. Results reveal that metaheuristic-optimized portfolios outperform the Dow Jones Index in Sharpe ratios, highlighting their potential to significantly enhance risk-adjusted returns. A comparative analysis of Ant Colony Optimization (ACO) and Cuckoo Search Algorithm (CSA) shows CSA's slight superiority in risk-adjusted performance. This advantage is attributed to CSA's maintained randomness and Lévy flight model, which effectively balance local and global search, whereas ACO may converge prematurely due to path reinforcement. These findings underscore metaheuristics' capacity to maximize expected returns at given risk levels, offering flexible, robust solutions for investment strategy optimization.

Recently, the demand for energy storage has increased, serial cell configurations are commonly used for high-capacity secondary batteries. Initially, when identical cells are configured in series, the battery cells operate without voltage differences. However, over time, voltage imbalances occur due to differences in the environmental and physical properties of the cells. In addition, the unique characteristics of cells change during charging and discharging, which greatly affects to the degradation of battery efficiency and performance. Various cell balancing techniques have been proposed to achieve high efficiency and performance in battery. This paper proposes a minimum voltage selective balancing topology based on a flyback converter for module balancing of batteries based on active cell balancing techniques. In the proposed topology, the output voltage of each battery is shared through a single transformer, the energy from the converter's primary side is transferred to the battery modules with the minimum voltage. The proposed module balancing circuit can be easily applied to the battery reuse industry. The proposed minimum voltage battery module selective balancing topology was verified through PSIM simulations and experiments.

As a wide range of industries using iron, such as water and sewerage pipes, gas pipelines, heat pipes, electric engines, communication pipes, and oil pipelines, rapidly become active, there is a demand for reliability and low cost of DC power supplies that can prevent corrosion of pipe networks. In particular, high-efficiency corrosion prevention systems due to changes in the perception of carbon emissions and energy saving are essential elements. Therefore, the construction of a switching-type corrosion current controller is being activated. Also, in such systems, DC/DC converters capable of multi-channel current control are demanded for corrosion prevention functions and uniform consumption of sacrificial anodes. This paper proposes a new current supply system for preventing pipeline corrosion using a low-cost SMPS dedicated chip. The proposed method can maintain excellent parallel operation function, protection function, and response speed by configuring a current controller using a hybrid method using analog and digital. The proposed method verified its superiority through simulations and experiments.

The technology for hydrogen production from by-product gases generated in steel mills has recently garnered significant attention, with commercialization gradually progressing. Hydrogen production based on by-product gases presents a critical technological breakthrough, enabling the reduction of carbon emissions in steel production while promoting sustainable energy generation. In this study, a consequence analysis of potential accidents was conducted by analyzing the components of a newly proposed membrane-PSA hybrid process aimed at reducing the cost of hydrogen production from the PSA-only process. The findings indicate that the extent of pipeline damage and weather conditions significantly influence the range of hydrogen leakage, the radiative heat from jet fires, and the overpressure range in vapor cloud explosions. These results provide essential foundational data for evaluating the risks associated with hydrogen leakage accidents and for establishing safety design and preventive measures.

This study developed an anomaly detection algorithm for underground hydrogen pipelines using Distributed Acoustic Sensing (DAS) and Distributed Temperature Sensing (DTS) technologies. The LSTM-AE-based algorithm was tested in a real-world testbed, showing high performance in detecting third-party construction activities and gas leaks. The model achieved 99.86% accuracy, 100% precision, 99.74% recall, and a 99.87% F1 score for DAS data, and 99.95% accuracy, 100% precision, 95.24% recall, and a 97.44% F1 score for DTS data. These results demonstrate the algorithm's effectiveness in real-time monitoring and its potential to enhance the safety of hydrogen pipeline infrastructure. Future research will focus on optimizing the algorithm for broader applications.

This study aims to present a method for reducing human error, time spent on design, and waste of design manpower when designing plant pipe hanger & support using sketches based on piping and steel structure drawings in plant. The method involves organizing the pipe hanger & support design process based on codes and standards and developing a program to facilitate this. The design of whole plant systems, including pipe hangers & supports, is conducted within 3D plant CAD software that applies BIM (Building Information Modeling). All attribute information of the pipe hanger & support is digitized as a digital asset, and the design is executed as an add-in module. This module is then used for BOM(generating Bill of Materials) and installation drawings, which are essential for the fabrication and on-site installation of pipe hangers & supports.

This paper is about an electric water pump used in an electric vehicle cooling system. An electric water pump is operated by a BLDC motor compared to a mechanical one, so it operates only as much as necessary, improving fuel efficiency. The use of an electric water pump reduces exhaust gas and has the advantage of being free to install, so it can be applied to automobiles, ships, and aircraft. In order to optimize the production of a BLDC motor used as an electric water pump, FEM and electromagnetic field analysis were performed. The dimensions and materials of the stator and rotor were selected by applying the values obtained through the analysis. In addition, the output characteristics of the motor were analyzed through parameter analysis and shape change through self-equivalent circuit analysis to reduce the outer diameter and increase the torque. The electromagnetic hazard of the PCB board was verified, and power integrity analysis was performed to reduce resonance and noise.

This study investigated the effect of protease in ginger powder on tenderness of bovine dorsi muscle after freeze-drying at 0%, 1%, 2%, and 4% ratios. It will. Beef loin chunks were pickled in distilled water (control), 1% ginger powder (G1), 2% ginger powder (G2), and 4% ginger powder (G4). As a result, there was a slight significant difference in pH (p<0.01), and there was no significant difference in the redness (a) of the meat between the control group and the sample group. The cooking loss of G4 was the highest (p<0.001), and the shear force value was lower in the sample group compared to the control group (p<0.001).

The calculation of the waste landfill unit price at the S landfill located in I city was analyzed in two cases: Method A by statistical techniques and Method B by reflecting policy variables such as the prohibition of direct landfilling of household waste and the right to emit greenhouse gases. As a result, in the case of method B, the landfill unit price increased by 34.1% to 57.6% depending on the type of waste compared to method A. By landfill unit price composition, landfill work cost, operation and management cost, greenhouse gas emission rights transaction cost, and resident support fund increased by 61.0%, 68.3%, 63.5%, and 34.1% to 57.6%, respectively. Therefore, considering the characteristics of the landfill, which requires more than 30 years of mid- to long-term operation and management even after the end of the landfill, policy variables should be identified periodically for stable landfill operation and management. In addition, periodic activities to calculate the landfill unit cost are considered necessary, such as predicting the amount of landfill waste and deriving additional future cost factors such as greenhouse gas emission rights.

The purpose of this study was to evaluate the effects of various layer thicknesses and build angles on the flexural strength and surface roughness of repaired 3D-printed denture base resin. 3D-printed bar-shaped specimens with a 45° bevel were fabricated according to layer thickness(50 ㎛ and 100 ㎛) and build angle(0-degree, 45-degree, and 90-degree). Denture relining resin was applied to the 2 mm repair area Flexural strength was measured by a three-point bending test using a universal testing machine, and surface roughness(Ra) and surface topography were observed using a digital optical microscope at ×500 magnification. Statistical significance was analyzed using two-way ANOVA, one-way ANOVA, and Games-Howell post hoc(α = .05). Except for the 90-degree group, the group with a layer thickness of 100 ㎛ showed better flexural strength values than the group with a layer thickness of 50 ㎛(p < .05). Additionally, within the same layer thickness, the 45-degree group showed the lowest flexural strength value. The Ra values of the 0-degree and 90-degree groups, where the build angle was 45° to the layer orientation, were higher at 100 ㎛ than at 5 0 ㎛ layer thickness(p < .05), and the Ra value of the 45-degree group, where the build angle was parallel to the layer orientation, was lower than those of other build angles(p < .05). Layer thickness and build angle significantly affected the surface roughness of 3D-printed denture base resin, and the surface roughness was confirmed to be closely related to the bonding strength with denture relining resin.

The fuel supply pipe connected to the hydrogen fueled vehicle hydrogen tank is very complicated. Therefore, the fixed portion of the pipe should be determined according to the external vibration. In particular, in order to avoid the resonance frequency range of the hydrogen fueled vehicle, it is necessary to examine the vibration characteristics of the fuel supply pipe and the stress concentration generation part for each frequency. Therefore, the purpose of this study is to understand the resonance potential for the natural frequency of the fuel supply pipe for hydrogen fueled vehicles and the excitation force(vibration of the motor etc.) applied to the external excitation frequency range(1-40Hz). Vibration characteristics were analyzed using the finite element method(FEM) to secure basic data for future seismic vibration tests of fuel supply pipes and to evaluate the safety of fuel supply pipe system.

The purpose of this study is to examine the moderating effect of job content on the relationship between job satisfaction and turnover intention among firefighters. Given the urgent and hazardous nature of their work, firefighters' job satisfaction and turnover intention are significantly influenced by their unique work environment. A survey conducted nationwide collected data on job satisfaction, job content, and turnover intention. The findings indicate that higher job content reduces the impact of job satisfaction on turnover intention, highlighting the importance of enhancing job quality through diversity and autonomy. This study suggests organizational strategies to improve job satisfaction and reduce turnover, contributing to greater organizational stability and efficiency.

Due to the rapid development of the industry, the use of iron is increasing rapidly in various industrial fields. Among these iron use areas, problems caused by corrosion of iron are seriously occurring in water-related industries. In particular, as the importance of environmental management has emerged, the water industry market desperately needs to replace aging water infra structure due to corrosion. In order to overcome this problem, research on a method capable of corrosion prevention system is being actively conducted. As the method for corrosion prevention system has various voltages and currents applied depending on the surrounding environment, the demand for an appropriate voltage regulator is increasing rapidly. In particular, as the IOT industry develops, the capacity of corrosion prevention system is increasing by expanding the area in which the method machine operates. Therefore, rectifiers for preventing corrosion are being changed from conventional flyback systems suitable for small capacities to inverter-type rectifiers suitable for large capacities. The inverter-type rectifier has various problems by reducing it to the initial rush current when starting. Therefore, this paper proposes a new starting method that can reduce initial inrush current in inverter-type rectifiers. T he proposed method can secure DC phase voltage for stable operation of the inverter by implementing discontinuous boosting operation using the switch of the inverter. In addition, the excellence of the proposed method was verified through simulations and experiments.

Automation systems have gained great attention with the evolution of communications technology. A smart automation is an Internet of Things (IoT) application that employs the Internet to monitor and control appliances using an automation system. Lack of IoT technology adoption, unattractive user interface, restricted wireless transmission range, and expensive costs are the constraints of existing home automation systems. The idea of integrating a large number of devices has a substantial impact on the widespread advancement in the field of autonomous systems. The Internet of Things is being used more and more to create internet-connected gadgets. In addition, a wide range of data and services centered on human connection are accessible through mobile sensing devices powered by the Internet of Things, such as smartphones, tablets, digital cameras, sensors, etc. This study describes the implementation and analysis of a MQTT protocol-based IoT-based home automation system utilizing NodeMCU. This enables customers to use a mobile application over the internet to monitor and manage household appliances from a distance.

In this study, fundamental research was conducted on the development of an adsorption-desorption ventilation system incorporating thermoelectric elements to improve indoor air quality (IAQ) and energy efficiency. The experiment was conducted using a thermoelectric module and silica gel as a commonly used adsorbent to evaluate the cooling and heating effects during the adsorption and desorption process. The main experimental results show that applying 3W power to the thermoelectric module reduces the outlet air temperature and improves the adsorption efficiency, while excessive power (4-5W) reduces the adsorption efficiency due to increased heat load. Additionally, when the flow rate on the adsorption side is increased, the completion time decreases. On the other hand, if the flow rate on the desorption side is increased, the completion time is also shortened. It was confirmed that as the flow rate increases, the movement of heat and moisture generated during the adsorption and desorption process becomes faster, and the reaction progresses more quickly.

Setting RAM target value of a weapon system, which is one of the essential elements when developing a weapon system, should be quantitatively evaluated throughout the development stage. When setting RAM target value of a weapon system, it is very crucial to choose an appropriate methodology along with suitable and available data. In this study, a process for setting RAM target value based on the similar system field data and the conversion factors derived from expert survey is presented. In particular, a method for calculating and applying conversion factors is proposed, which converts similar system operating and maintenance times into those of the weapon system to be developed. A case study of a specific weapon system shows that the proposed RAM target value setting method can be effectively utilized. The proposed RAM target setting method is expected to better reflect the distribution of expert survey responses than the existing method due to the use of skewness for selecting an appropriate statistic and the weighted averages obtained considering expert group's weights of expertise. And therefore it is expected that the proposed method can produce more realistic RAM target value of weapon system.

This paper is a basic test study for the performance verification of equipment and facilities used in extreme environmental conditions, and includes research using a chamber that can artificially create a low-temperature environment. The facility can create a temperature environment from room temperature to -65℃ and is constructed to create special environments such as wind speed, artificial snow removal, and artificial ice removal. By artificially creating a polar environment below -40℃ and verifying it through installation and preliminary performance tests of the equipment, it is possible to identify potential risk factors that may occur at the work site in advance and prepare for safety accidents. The temperature distribution was observed when descending to a low temperature in a limited space in the chamber, and how the flow changes when the wind speed is applied. Based on this study, we plan to analyze the effects of implementing special environments such as artificial snow removal and artificial ice removal in the future.

There are a variety of evaluation methods used to evaluate and provide feedback to students, recognize shortcomings, and establish future plans. The purpose of the academic achievement evaluation is to check whether the student understands the content taught, identify areas that the student is unfamiliar with or misunderstand, and then provide supplementary study to prevent learning deficits. Multiple choice has been the evaluation system in Korea since the early 1970s, influenced by Tyler's goal-centered evaluation model that evaluates achievement of educational goals and Bloom's educational goal classification system. The most important item in education is the evaluation of whether you have properly understood the lesson and how deeply you know it. Therefore, in this study, in order to minimize cases where test takers stochastically answer the correct answer in a multiple-choice evaluation, the change in the standard deviation of grades was analyzed by applying a grading method that assigns negative points to incorrect answers. As a result of the study, it was found that the average score of the incorrect response evaluation was 1 to 4 points lower, and the standard deviation was wide. This showed that the test taker's discrimination ability was high in the wrong answer appraisal type.

The Integrated Condition Assessment System (ICAS) is a system that supports Condition Based Maintenance (CBM) by diagnosing the status of major onboard equipment on a naval ship in real time and allowing maintenance personnel to immediately perform maintenance when an abnormal condition occurs to maintain the operational performance of the on-board equipment. This study introduces the necessity of data preprocessing collected from naval ship, and compare and review baselines generated through statistical and designed machine learning algorithms using the same data preprocessing. Through these, this paper analyzes and proposes the suitability of a baseline algorithm, a machine learning methods that has not been applied to the condition based maintenance of naval ship equipment.

This study analyzed psychological burnout among firefighters in fire suppression units and identified factors that influence it. Fire suppression work involves high levels of stress and repeated exposure to traumatic events, making psychological burnout particularly severe in this field. This burnout negatively impacts job performance and organizational efficiency. This study conducted an online survey of firefighters across South Korea, with 120 respondents, and analyzed the level of psychological burnout based on factors such as age, years of service, and rank. The results showed that the mean score for overall psychological burnout was 2.8 out of 5, indicating a moderate level of burnout among firefighters. Furthermore, personnel in lower ranks (firefighters, senior firefighters, fire sergeants, and fire lieutenants) experienced higher levels of psychological burnout compared to those in higher ranks (fire captains, deputy fire chiefs, etc.). These findings suggest the need for rank-specific burnout management strategies. Overall, the results of this study contribute to alleviating psychological burnout among firefighters, enhancing organizational efficiency, and strengthening public safety.

This study examines the role of job satisfaction in influencing the turnover intention of firefighters. Firefighters operate in urgent and hazardous conditions, and these unique working environments can significantly affect their job satisfaction and turnover intentions. To investigate this issue, a nationwide survey was conducted to examine the job satisfaction and the turnover intentions of firefighters. The data were then analyzed using the independent t-test, one-way ANOVA, and Duncan's post-hoc test, as well as multiple linear regression analysis. These analyses revealed a significant relationship between the two, showing that higher job satisfaction is associated with lower turnover intentions. These findings highlight the importance of enhancing job satisfaction to reduce turnover intentions among firefighters. As such, organizational support and management strategies are necessary to address the unique challenges faced by firefighters and foster a better working environment. Based on these findings, the study also provides policy implications for improving job satisfaction and reducing the turnover rate among firefighters.

The purpose of this study was to develop a scale to measure the psychological phenomena experienced by firefighters at disaster sites. After a literature review and verifying the content validity with firefighters and related experts, a questionnaire was developed, and a survey was conducted on 344 firefighters. Through factor analysis, the "Disaster Psychology Scale" was completed, which is divided into two subscales: "The Effects of Stress and Trauma" and "Automatic Response and Initial Judgment Errors." Both subscales showed excellent model fit, and the internal consistency reliability was also high. Additionally, significant results in content validity and construct validity confirmed that this is a valid scale. The scale developed in this study can be used as a tool for self-assessment of physical and mental health behaviors at disaster sites experienced by firefighters, and it can also serve as a useful tool for evidence-based interventions through the assessment of disaster-related psychological behaviors in firefighters.

This study selected the town area where parking problems occur. Parking lot users were divided into groups and parking consciousness was investigated. The statistical significance of each group was tested. This is a case study to reflect this result in the establishment and implementation of parking policies. The user group was divided into four, and a total of 264 people were surveyed. The user group was set as an independent variable, and current and future satisfaction was set as the dependent variable. Statistical significance was tested by conducting analysis of variance and paired sample t-test. The analysis results are as follows. By user group, the change in satisfaction score for improvement compared to the current was the largest in the group of visitors and shop owners. By item, improvement is required in the order of additional construction of parking spaces, strong crackdown on illegal parking, and free or reduced parking fees.

Recently, as a method of hair loss treatment, a non-surgical method of applying the technology of isolating a patient's specific autologous progenitor cells after biopsy and using it by injecting isolated uncultured targeted exosomes has been suggested. The effect of progenitor cell micrograft is that hair loss is treated by maintaining the micro environment by side population phenomena, niche concept, and extracellular matrix (ECM). In this experiment, a female patient in her 50s was observed for about five months from the micrograft in June until October 2023, and the experimental equipment used in this experiment was the Bio-Q developed by a local specialized technology development project. For the experiment, a biopsy of 2,5 ∅ 3 punches was performed on the back of the patient's head where there was no hair loss, and about 5cc (0.1cc each) of suspension (targeted exosomes) was immediately injected on the same day into 50 sites on her scalp where hair loss occurred, and the hair growth status was investigated afterward. Hair growth occurred at the micrograft sites, but many hairs with weak hair growth that had not yet penetrated the epidermal layer were observed growing in coils at the lower part of the epidermal layer, and the length of the coils was also found to increase at the bottom of the scalp. The number of hairs with hair growth capability increased rapidly after discovering the cause of the coil phenomenon.

The development of high-performance underwater propulsion devices has gained importance with the expansion of recreational and industrial diving applications. This study aims to develop and validate a waterjet-type diver propulsion system capable of achieving a top speed of 3.8 knots and an operational time of over 120 minutes. Utilizing advanced modeling and simulation techniques, the design focuses on minimizing hydrodynamic resistance and optimizing buoyancy. Structural and fluid dynamic analyses were conducted to ensure the device's stability and performance under 20 atm pressure at a depth of 200 meters. The propulsion system employs a sensorless BLDC motor and a 36V lithium-ion battery pack to enhance efficiency and reliability. Field tests confirmed an average speed of 3.88 knots and a continuous operation time of 150 minutes, exceeding the initial targets. This research demonstrates significant advancements in diver propulsion technology, providing valuable insights for future underwater equipment development. The outcomes are poised to enhance the safety, efficiency, and usability of diver propulsion devices, with broader applications in marine research, environmental monitoring, and resource exploration.

In this study, 3 dental implants were implanted in each femur of NZW rabbits, and only the right experimental group was irradiated with 850 nm infrared and 3 MHz ultrasonic waves for 10 minutes every day. After 3 and 6 weeks, a torsional test was performed using a universal testing machine to determine the changes in osseointegration. As a result, in the specimen subjected to 3 weeks, the maximum value of 3.01 MPa was measured in specimen #1, and the minimum value of 1.20 MPa was measured in specimen #1. In the control group, the maximum value of 0.75 MPa was measured in specimen #6, and the minimum value of 0 .10 MPa was measured in specimen #4. The average value of specimens #1 to #3 of the experimental group was 1.76 MPa, and the average value of specimens #4 to #6 of the control group was 0.48 MPa. In the third week, among the torsion test results, for the control group, specimens #4 to #6, the specimen with the lowest initial osseointegration progress was measured at 0.10 MPa, and all of the measurement values at a total of 9 sites, including 3 sites for each specimen, were measured below 1.0 MPa. This is a very key part of this study, indicating that the initial osseointegration was very low. On the other hand, for the experimental group specimens #1 to #3, all of the measurement values at a total of 9 sites were measured above 1.0 MPa, and the maximum value was 3.01 MPa, confirming that 850 nm infrared light irradiation and 3 MHz ultrasound irradiation have an effect on improving osseointegration and bone quality with dental implants.

In this study, the formability was predicted using a finite element method-based forming simulation program to manufacture ring-shaped parts with multiple rectangular grooves through a hot forging process. The hot forging process was designed into four processes. In the first and second processes, the disk-shaped raw material was transformed into the shape of a bowl. In the third process, the inner lower part of the bowl was sheared to form a ring shape. In the fourth process, the outer surface of the upper part of the ring was partially sheared to create multiple rectangular grooves. Since the lower mold for the first and second processes is the same, mold costs can be reduced. In the third process, burrs are expected to occur on the shear surface, so burr removal work is required in the actual process. The fourth process requires more than one forging operation because the rectangular groove cannot be made uniformly in one operation.