• Journal of the Korea Society for Simulation
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• v.31 no.1
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• pp.29-41
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• 2022

As one of the alternatives to solve the problem of unstable food supply and demand imbalance caused by abnormal climate change, the need for plant factories is increasing. Airflow in plant factory is recognized as one of important factor of plant which influence transpiration and heat transfer. On the other hand, Digital Twin (DT) is getting attention as a means of providing various services that are impossible only with the real system by replicating the real system in the virtual world. This study aimed to develop a digital twin model for airflow prediction that can predict airflow in various situations by applying the concept of digital twin to a plant factory in operation. To this end, first, the mathematical formalism of the digital twin model for airflow analysis in plant factories is presented, and based on this, the information necessary for airflow prediction modeling of a plant factory in operation is specified. Then, the shape of the plant factory is implemented in CAD and the DT model is developed by combining the computational fluid dynamics (CFD) components for airflow behavior analysis. Finally, the DT model for high-accuracy airflow prediction is completed through the validation of the model and the machine learning-based calibration process by comparing the simulation analysis result of the DT model with the actual airflow value collected from the plant factory.

• Journal of Broadcast Engineering
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• v.27 no.2
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• pp.185-197
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• 2022

Recently, deep learning networks with high performance for object recognition are emerging. In the case of object recognition using deep learning, it is important to build a training data set to improve performance. To build a data set, we need to collect and label the images. This process requires a lot of time and manpower. For this reason, open data sets are used. However, there are objects that do not have large open data sets. One of them is data required for license plate detection and recognition. Therefore, in this paper, we propose an artificial license plate generator system that can create large data sets by minimizing images. In addition, the detection rate according to the artificial license plate arrangement structure was analyzed. As a result of the analysis, the best layout structure was FVC_III and B, and the most suitable network was D2Det. Although the artificial data set performance was 2-3% lower than that of the actual data set, the time to build the artificial data was about 11 times faster than the time to build the actual data set, proving that it is a time-efficient data set building system.

• Journal of the Korean Institute of Gas
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• v.26 no.1
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• pp.1-6
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• 2022

This paper is a purpose to study and analyze the engine starting failure examples for LPG car. The first example, the researcher verified the phenomenon that didn't supply the fuel because of filter clogging by fine alien substance in the gas valve line when he inspected the emergency cutting valve. The second example, there was no the influence of gas leakage when the solenoid operated at first. But the damage part of solenoid assemblying face wad downed a durability according to running a valve. Eventually, the researcher checked on the phenomenon of engine stopping by no gas feeding in solenoid because of leaking of gas. The third example, the researcher sought that the wiring sheaths of connector fin between EGR 10A fuse and LPG switch verified the burn-out phenomenon due to the bad contacting as tension damage produced the overheating. Therefore, the manager of a car has to do pre-inspection no producing electric failure and he must maintain his car with optimum condition.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.2
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• pp.1-8
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• 2022

The corrosion of reinforcement is the main reason for the performance degradation of concrete structures. The pre-rusted parts of rebar in concrete structures are vulnerable to the corrosion, especially if the structure is exposed to wet or chlorinated environments. In this study, effects of different curing solution on corrosion behavior of the pre-rusted rebars in the cement composites were investigated. HCl(3%) and CaCl₂(10%) solution were utilized to accelerate the pre-rust of the rebar, and each pre-rust condition rebar including reference (RE) were placed in mortar cylinder. Three kinds of samples then were cured in CaCl₂ (3%) solution and tap water respectively for 120 days. Electrochemical polarization and half-cell potential measurement were used to monitor the influence of curing water on the corrosion behavior of pre-rusted steel bar in cement composite. The surface morphology and composition of corroded steel bar were analyzed by scanning electron microscope and energy dispersive X-ray diffraction. The results show that the corrosion rates of pre-rusted samples in both curing water are higher than that of non-pre-rusted samples. The corrosion rates of RE, CaCl₂ and HCl pre-rusted samples in salt water were 8.14, 4.48, 13.81 times higher than those in tap water respectively, on the 120th day.

• Tunnel and Underground Space
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• v.31 no.6
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• pp.623-646
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• 2021

As the demand for electric power increases with acceleration of electrification at home and abroad, the needs for coal-fired electrical power plant are accordingly increased. However, these coal-fired electrical power plants induce also many environmental problems such as increase of air pollutants, increase of possibility of land contamination by reclamation of coal ash, even though these power plants have a good economical efficiency. In case of a by-product of coal-fired electrical power plants, only 70% of them are recycled and the remaining 30% of by-product are fully buried in surrounding ground. Consequently, this study deals with coal ash backfilling mechanism in abandoned mine openings for the purposes of increasing the coal ash recycling rate as well as securing the mine area stability. In order to analyze the backfill and ground reinforcement by interaction between rock mass and backfills, the copying samples of discontinuous surface with different roughnesses were produced for bond strength tests and direct shear tests. And statistical analysis was also conducted to decide the characteristics of bond and shear behavior with joint roughness and their curing day. Numerical simulations were also analyzed for examining the effect of interface behavior on ground stability.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.2
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• pp.113-119
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• 2022

In order to improve the mechanical reliability of next-generation electronic devices including flexible, wearable devices, a high level of mechanical reliability is required at various flexible joints. Organic adhesive materials such as epoxy for bonding existing polymer substrates inevitably have an increase in the thickness of the joint and involve problems of thermodynamic damage due to repeated deformation and high temperature hardening. Therefore, it is required to develop a low-temperature bonding process to minimize the thickness of the joint and prevent thermal damage for flexible bonding. This study developed flexible laser transmission welding (f-LTW) that allows bonding of flexible substrates with flexibility, robustness, and low thermal damage. Carbon nanotube (CNT) is thin-film coated on a flexible substrate to reduce the thickness of the joint, and a local melt bonding process on the surface of a polymer substrate by heating a CNT dispersion beam laser has been developed. The laser process conditions were constructed to minimize the thermal damage of the substrate and the mechanism of forming a CNT junction with the polymer substrate. In addition, lap shear adhesion test, peel test, and repeated bending experiment were conducted to evaluate the strength and flexibility of the flexible bonding joint.

• Korean Journal of Poultry Science
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• v.49 no.2
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• pp.61-67
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• 2022

The effects of dietary exogenous hydrophilic emulsifiers on the growth, nutrient digestibility, and carcass characteristics of broilers were evaluated. A total of 200 one-day-old broilers (Ross 308) were allotted to one of four treatment groups in a randomized complete block design in five replicates with 10 birds per pen during a 5-week growth experimental period. Birds were fed a corn-soybean meal-based diet with or without the addition of 0.025, 0.050, or 0.075% exogenous hydrophilic emulsifiers. The diets contained 3,025 and 3,075 metabolizable energy/kg for Phases 1 and 2, respectively. For each phase and the overall experimental period, body weight gain (linear, P<0.05) and feed conversion ratio (linear, P<0.05) improved in proportion to the dietary exogenous hydrophilic emulsifier level, while the average daily feed intake was not affected by dietary treatment. Improvement in growth performance by dietary treatments was observed during the last two weeks rather than the first three weeks of the growth phase. In carcass traits, abdominal fat content increased as dietary exogenous hydrophilic emulsifier level increased (linear, P<0.05), whereas dietary emulsifier level did not affect the relative weight of the liver, breast, and leg muscles. In conclusion, addition of dietary exogenous hydrophilic emulsifiers from 0 to 0.075% in broiler diets improved the growth rate and feed efficiency of broilers without any deleterious effects on nutrient digestibility, although a corn-soybean meal-based diet had less energy content (3,025 and 3,075 metabolizable energy/kg) for 0-3 weeks and 3-5 weeks, respectively.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.4
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• pp.610-619
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• 2022

Hydrogen is emerging as an alternative fuel for eco-friendly ships because it reacts with oxygen to produce electrical energy and only water as a by-product. However, unlike regular fossil fuels, hydrogen has a material with a high risk of explosion due to its low ignition point and high flammability range. In order to safely use hydrogen in ships, it is an essential task to study the flow characteristics of hydrogen leakage and diffusion need to be studied. In this study, a numerical analysis was performed on the effect of leakage, ventilation, etc. on ventilation performance when hydrogen leaks in an enclosed space such as inside a ship. ANSYS CFX ver 18.1, a commercial CFD software, was used for numerical analysis. The leakage rate was changed to 1 q, 2 q, and 3 q at 1 q = 1 g/s, the ventilation rate was changed to 1 Q, 2 Q and 3 Q at 1 Q = 0.91 m/s, and the ventilation method was changed to type I, type II, type III to analyze the ventilation performance was analyzed. As the amount of leakage increased from 1 q to 3 q, the HMF in the storage room was about 2.4 to 3.0 times higher. Furthermore, the amount of ventilation to reduce the risk of explosion should be at least 2 Q, and it was established that type III was the most suitable method for the formation of negative pressure inside the hydrogen tank storage room.

• Journal of the Korean Institute of Gas
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• v.26 no.3
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• pp.27-37
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• 2022

With the recent increase in the spread of ESS (Electric Storage System), the damage to human life and property is also rapidly increasing due to continuous fires caused by ESS. In the manufacture of urethane sandwich panels used in ESS, it is necessary to improve the flame retardant performance. In this study, in order to realize the flame retardant properties of flexible polyurethane foam, the effect of the tissue density of the product due to the change of the isocyanate functional group parameter that changes the physical properties of the product on the fire performance was studied. The product was manufactured by changing the density of the urethane structure, and combustion performance tests, gas toxicity tests, and smoke density tests were performed. As a result, it was confirmed that the total amount of heat released had excellent performance when the isocyanate functional group was high, and had no correlation with the maximum heat release rate. When the value of the isocyanate functional group was 2.7 or more, the collapse of the shape could be prevented. In the gas hazard test, the performance was increased when the isocyanate functional group was relatively high, so a flame retardant for the Char system, which had a dense structure and easy to form a carbonized film, was added. confirmed to be. Therefore, as a result of this study, it is thought that it will be possible to lay the foundation for the development of a flame retardant to replace the cheap urethane sandwich panel used in the past.

• Composites Research
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• v.35 no.3
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• pp.127-133
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• 2022

Polypropylene (PP) has been received great attention as a next-generation high-voltage power cable insulation material that can replace cross-linked polyethylene (XLPE). However, the PP cannot be used alone as an insulation material because of its high elastic modulus and vulnerability to impact, and thus is mainly utilized as a form of a copolymer with rubber phases included in the polymerization step. In this paper, a soft PP-based blend was prepared through melt-mixing of impact PP, polyolefin elastomer, and propylene-ethylene random copolymer. The elastic modulus and impact strength of the blend could properly be decreased or increased, respectively, by introducing elastomeric phases. Furthermore, the blends showed a high storage modulus even at a temperature of 100℃ or higher at which the XLPE loses its mechanical properties. In addition, the blend was found to be effective in suppressing the space charge compared to the pristine PP as well as XLPE.