• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.774-780
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• 2021

The auxiliary power unit (APU) of a rotorcraft starts the engine during operation/flying. The APU is composed of a gas turbine engine type. The starting principle of the component is that the electric start motor generates the power required for starting by rotating the shaft. In this study, quality improvement was performed by applying an over-running clutch (ORC) between the APU and the starter motor to secure the operability of the starter motor of the APU mounted on the rotorcraft. The starter motor has the main role of starting the APU, but during operation, it is rotated without load by the rotational force of the APU gear shaft, resulting in friction at the brush. This phenomenon causes abrasion of the brush of the starter motor. Consequently, when the APU operation time increases, the brush life decreases, and the operability of the APU is affected. In this study, an ORC that separates the interlocking between the start motor brush abrasion and the APU operation time was applied to improve the operability/durability of the APU starter motor. The effect was verified through a test, and the technical feasibility of the design change was analyzed.

• Journal of Korea Entertainment Industry Association
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• v.14 no.3
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• pp.173-180
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• 2020

According to KISA, many people play smartphone games. stress relieving, time is the reason to beat. Attempts to combine mobile games and education in the Korean game market are continuing. Studies have shown that using commercial games for education can be effective. Also, researches for activation educational games are increasing. Creating educational games requires a lot of time and money. Due to the nature of mobile games, the service is often terminated without updating. If you are able to acquire a naturally educational part while playing mobile games, you will see the effect of one pair of fun and education, both at once. We analyzed the education factors of the game with 'Real Farm' which is a simulation farm game. We focused on analyzing information acquisition and utilization part through indirect experience which is characteristic of simulation and examined educational factors based on design elements of educational game. This can signal the positive aspects of the game and the educational content of existing games. If you use smartphones as a pedagogy, you can expect a positive perception of games and an increase in the average life expectancy of mobile games.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.5
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• pp.86-94
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• 2022

Replacement of FRP rod as steel reinforcement has been attracted significantly to prevent the degradation of the concrete structure due to corrosion. So, the technology development to extend the structure's service life by improving FRP properties has been proceeded worldwide. Accordingly, it is necessary to develop Korea's CFRP rod and CFRP grid, including the manufacturing techniques to improve the properties of high-strength and high-stiffness. Moreover, the research should be conducted to evaluate the structural behavior of the beams using the CFRP rod or grid. This study investigates the flexural and shear behavior of reinforced concrete beam using demonstrated CFRP rod as reinforcement according to the reinforcement ratio and shear span to depth ratio. From the results, when the reinforcement ratio is out of a specific range, it is seemed that the effect on performance improvement of the beam using CFRP rod is cancelled or not significant. Meanwhile, when the CFRP rod was used as reinforcement, the possibility of shear failure occurred, even steel stirrups were installed in the beam with CFRP rod as tensile reinforcement according to the Korean Design Standard. Therefore, when the CFRP rod is used as tensile reinforcement in a beam, it should be prepared that a specific limitation of reinforcement ratio and an investigation against shear failure. Also, the ductility of the beam using the CFRP rod is determined by the deformation energy evaluation method. So, the ductility should be investigated by applying the deformation energy evaluation method that reflects the structural behavior of the beam.

• Journal of the Korean Institute of Gas
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• v.26 no.5
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• pp.1-9
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• 2022

Selection of a suitable artificial lift is important in terms of efficient operation and economics for oil production. In general, process of well design includes the selection of artificial lift, but the oil recovery could be enhanced by use of hybrid system combined with two types of artificial lift method according to reservoir condition for oil production. Electric submersible pump (ESP), as a presentative artificial lift method, is a manner for supplying the pressure in the lower part of oil well by using of a multi-stage centrifugal pump with an electric energy. However, there is a disadvantage that has a limit to the application period because of mechanical defection on ESP. Accordingly, it is possible to reduce the shutdown time of production well by applying the ESP/Gas lift hybrid system, which is to switch to a gas lift when an ESP is defective. This study describes the effect of ESP/gas lift hybrid system compared with ESP method for a onshore horizontal well locating in the of Permian basin, USA. As a result of study, ESP/gas lift hybrid system could make more effective productivity than ESP method. Also, we quantitatively predicted how much economic benefit would be obtained when the hybrid system was applied in the production well.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.93-101
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• 2022

RC Slab bridges in Korea account for more than 70% of the total bridges for more than 20 years of service. As the number of aging structures increases, the importance of safety diagnosis and maintenance of structures increases. For highway bridges, cracks are a main cause of deck deterioration, which is very closely related to the decrease in bridge durability and service life. In addition, the damage rate of expansion joints and bearings accounts for approximately 73% higher than that of major members. Therefore, this study defined damage scenarios combined with devices damages and deck deterioration. The stress distribution and maximum stress on the deck were then evaluated using design vehicle load and daily temperature gradient for single and combined damage scenarios. Furthermore, this study performed damage-spread analysis and predicted condition ratings according to a deck deterioration model generated from the inspection and diagnosis history data of cracks. The heterogeneous damages combined with the member damages of expansion joints and bearings increased the rate of crack area and damage spread, which accelerated the time to reach the condition rating of C. Therefore, damage to bridge members requires proper and prompt repair and replacement, and otherwise it can cause the damage to bridge deck and the spread of the damage.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.28 no.1
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• pp.31-38
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• 2022

Due to the increasing consumer demands for the safety, shelf life, and quality of food, the application and development of active packaging in the food and packaging industry have been improved. According to the standards and specifications of the Republic of Korea for utensils, containers, and packages, the function of active packaging is to remove or alleviate factors that degrade food quality. Although extensive reviews regarding the development and commercialization of active packaging have been conducted, the legal regulations and safety assessments concerning active packaging have rarely been examined. This review provides information regarding the definition, structure, components, operational mechanisms, and applications for active packaging that actively removes oxygen, moisture, carbon dioxide, and ethylene. Furthermore, the legal regulations and research results related to the development of test methods for safety assessments of active packaging are investigated.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6A
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• pp.799-808
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• 2008

The analysis of vehicular loads reflecting the domestic traffic circumstances is necessary for the development of adequate design live load models in the analysis and design of cable-supported bridges or the development of fatigue load models to predict the remaining lifespan of the bridges. This study intends to develop an ANN(artificial neural network)-based Bridge WIM system and Influence line-based Bridge WIM system for obtaining information concerning the loads conditions of vehicles crossing bridge structures by exploiting the signals measured by strain gauges installed at the bottom surface of the bridge superstructure. This study relies on experimental data corresponding to the travelling of hundreds of random vehicles rather than on theoretical data generated through numerical simulations to secure data sets for the training and test of the ANN. In addition, data acquired from 3 types of vehicles weighed statically at measurement station and then crossing the bridge repeatedly are also exploited to examine the accuracy of the trained ANN. The results obtained through the proposed ANN-based analysis method, the influence line analysis method considering the local behavior of the bridge are compared for an example cable-stayed bridge. In view of the results related to the cable-stayed bridge, the cross beam ANN analysis method appears to provide more remarkable load analysis results than the cross beam influence line method.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.4
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• pp.395-406
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• 2023

The first technological advance to improve the output and efficiency of the latest steam turbines operating in co-generation plants in Korea can be said to be progress in the field of materials that can use high-temperature, high-pressures steam. As a result of design efforts to improve the internal efficiency of steam turbines along with the development of materials, only a few manufacturers of steam turbine have produced high efficiency steam turbines. The internal efficiency of a steam turbine on the steam path operating for a long period of time is gradually lost owing to the limit of mechanical life, and efficiency and output decrease. Therefore, this study aims to develop a model that can analyze the steam flow path performance of HP (High Pressure) and IP (Intermediate Pressure) steam turbine for a co-generation plant using a commercial program and propose a performance calculation method. Owing to the complex performance calculation method of steam turbines, major variables are presented to serve as practically useful references for steam turbine practitioners. In addition, the thermal dynamic analysis(such as heat balance diagram calculation) and the the thermal dynamic calculation required for steam turbine performance calculation and the suitability of the steam turbine performance calculation results were compared with the performance test results.

• Explosives and Blasting
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• v.41 no.4
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• pp.9-16
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• 2023

To compare the global warming impact of the TBM and NATM method, which are representative tunnel excavation methods, a life cycle assessment was performed for each method. Life cycle assessment should compare the sum of carbon emissions by considering the pre-manufacturing stage, product manufacturing stage, usage stage, and disposal stage. However, access to TBM (Tunnel Boring Machine) manufacturing and disposal data is limited, so I had no choice but to focus on the analysis for the usage stage. In general, carbon emissions during the pre-product manufacturing stage and product manufacturing stage often exceed 90% of carbon emissions throughout the entire process. Therefore, since it is difficult to achieve the analysis goal only by comparing the usage stage, the analysis scope was expanded, and carbon emissions for the process were calculated for the NATM method with access to manufacturing data. As a result of comparing the relative impact on global warming, the carbon emissions of the TBM method were found to be higher than those of the NATM method even though TBM method was only considered for the usage stage. So there it is, the NATM method can be seen as environmentally friendly in the future when considering the impact of climate change (global warming), which has recently attracted attention among environmental impact fields.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.6
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• pp.689-693
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• 2023

Domestic bridges with a service life of more than 30 years are expected to account for approximately 54% of all bridges within the next 10 years. As bridges rapidly deteriorate, it is necessary to establish an appropriate maintenance plan. Recent domestic and international research have focused on the integration of BIM to digitize bridge maintenance information and then enhance accessibility and usability of the information. Accordingly, this study developed a BIM-FEM interoperability algorithm for bridge decks to convert maintenance information into data and efficiently manage the history of maintenance. After creating an initial crack BIM based on an exterior damage map, bridge specification and damage information were linked to a numerical analysis that performs damage analysis considering damage scenarios and design loads. The spread of cracks obtained from the analysis results were updated into the BIM. Based on the damage spread information on the BIM, an automated technology was also developed to assess both the current and future condition ratings of the bridge deck. This approach can enable an efficient maintenance of the deck using the history data from bridge inspection and diagnosis as well as future information on cracks and defects. The expected early detection and prevention would ultimately improve the lifespan and safety of bridges.