• KEPCO Journal on Electric Power and Energy
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• v.6 no.4
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• pp.393-397
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• 2020

Shunt reactor, a facility for reactive power compensation, is switched several times a day depending on the load pattern. When the circuitbreaker opens the shunt reactor over-voltage is generated by several factors which degrade the insulating performance of internal parts of the circuit-breaker and cause severe voltage stress on the equipment in the power system. Transient phenomenon occurring during the switching of shunt reactor are available in laboratories that verify the performance of the circuit-breaker by simulating the power system. However, it is difficult to measure the transient phenomenon that occurs during actual operation in actual power system due to many limitations. Therefore, this paper deals with the modeling using EMTP to analyze the reignition and current chopping which causes more severe transient recovery voltage in the small inductive current breaking in actual power systems. In addition, this paper analyzes the main phenomenon that cause circuit-breaker failure in opening shunt reactor using EMTP model.

• Journal of Navigation and Port Research
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• v.45 no.3
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• pp.165-172
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• 2021

Breaking wave is one of the important design factors in the design of coastal and port structures as they are directly related to various physical phenomena occurring on the coast, such as onshore currents, sediment transport, shock wave pressure, and energy dissipation. Due to the inherent complexity of the breaking wave, many empirical formulas have been proposed to predict breaker indices such as wave breaking height and breaking depth using hydraulic models. However, the existing empirical equations for breaker indices mainly were proposed via statistical analysis of experimental data under the assumption of a specific equation. In this study, a new Munk-type empirical equation was proposed to predict the height of breaking waves based on a representative linear supervised machine learning technique with high predictive performance in various research fields related to regression or classification challenges. Although the newly proposed breaker height formula was a simple polynomial equation, its predictive performance was comparable to that of the currently available empirical formula.

• Journal of Korean Society on Water Environment
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• v.35 no.4
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• pp.299-307
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• 2019

The purpose of this study was to investigate the effect of low temperature thermal pre-treatment on biodegradation of waste activated sludge for anaerobic digestion as a countermeasure for increasing sludge generation. The experimental condition was accomplished in 2 %, 4 %, and 6 % TS concentration, and $70^{\circ}C$, $80^{\circ}C$, $90^{\circ}C$ of temperature for a maximum of 120 minutes retention time. Then, it was followed by analysis of physical/chemical properties, BMP test and composition of biogas. The biogas characteristic was evaluated by applying the modified Gomperz model. As a result, solubility of dissolved substrate, such as $SCOD_{Cr}$, soluble carbohydrate, and soluble protein, and biogas production increased as temperature increased. Solubilization efficiency at $90^{\circ}C$ was 18.4 %, 17.03 % and 16.88% in 2 %, 4 %, and 6 % TS concentration respectively. Also, solubilization rates of carbohydrate and protein similarly increased. BMP test results also showed that methane production in excess sludge increased to 0.194, 0.187 and $0.182m^3/kg$ VS. respectively, and lag phase decreased to 0.145, 0.220, 0.351 day due to acceleration of the hydrolysis step. Consequently, low-temperature thermal pre-treatment could increase biodegradability of sludge, positively affecting biogas production and sludge reduction.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.3
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• pp.165-171
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• 2019

The study of the computer architecture has shown that major improvements in price-to-energy performance stems from domain-specific hardware development. This paper analyzes the tensor processing unit (TPU) ASIC which can accelerate the reasoning of the artificial neural network (NN). The core device of the TPU is a MAC matrix multiplier capable of high-speed operation and software-managed on-chip memory. The execution model of the TPU can meet the reaction time requirements of the artificial neural network better than the existing CPU and the GPU execution models, with the small area and the low power consumption even though it has many MAC and large memory. Utilizing the TPU for the tensor flow benchmark framework, it can achieve higher performance and better power efficiency than the CPU or CPU. In this paper, we analyze TPU, simulate the Python modeled OpenTPU, and synthesize the matrix multiplication unit, which is the key hardware.

• Korean Journal of Remote Sensing
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• v.35 no.1
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• pp.39-55
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• 2019

In this study, we have proposed an improved method to detect forest fires by correcting the reflected signals of day images using the middle-wavelength infrared (MWIR) channel. The proposed method is allowed to remove the reflected signals only using the image itself without an existing data source such as a land-cover map or atmospheric data. It includes the processing steps for calculating a solar-reflected signal such as 1) a simple correction model of the atmospheric transmittance for the MWIR channel and 2) calculating the image-based reflectance. We tested the performance of the method using the MODIS product. When compared to the conventional MODIS fire detection algorithm (MOD14 collection 6), the total number of detected fires was improved by approximately 17%. Most of all, the detection of fires improved by approximately 30% in the high reflection areas of the images. Moreover, the false alarm caused by artificial objects was clearly reduced and a confidence level analysis of the undetected fires showed that the proposed method had much better performance. The proposed method would be applicable to most satellite sensors with MWIR and thermal infrared channels. Especially for geostationary satellites such as GOES-R, HIMAWARI-8/9 and GeoKompsat-2A, the short acquisition time would greatly improve the performance of the proposed fire detection algorithm because reflected signals in the geostationary satellite images frequently vary according to solar zenith angle.

• Journal of IKEEE
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• v.23 no.2
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• pp.667-674
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• 2019

The recent incidents of Nuclear Power Plant(NPP) gave rise to a total power outage caused by the loss of the functions of the off-site and the emergency power supply. Currently, emergency power supply of NPP have been taken into account by Li-ion batteries instead of existing lead-acid batteries. In order to judge the applicability of the cylindrical Li-ion battery, it is necessary to analysis the results of various electrical tests. This paper investigates the basic electrical characteristics test of three types of cylindrical batteries in order to select the most suitable battery and estimate state of battery through equivalent circuit model and propose method to solve the problem.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.3
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• pp.61-69
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• 2019

The concept of carsharing involves sharing a small number of reserved cars to be used individually by a larger number of people as required. This study examines the operating parameters of one-way carsharing systems in order to determine the appropriate operating conditions that minimizes the lost sales rate. Five operating parameters are tested in this study: the number of stations, the average number of vehicles per station, the rate of one-way trip, the average number of staffs per station, and the relocation policy. The performance of round-trip carsharing systems is also compared to that of one-way carsharing systems. A simulation model is developed and simulations are performed to determine the appropriate combination of operating parameter and levels. The simulation results show that the average number of vehicles per station is the most critical parameter. Other key findings obtained from this research are as follows. First, applying the appropriate relocation policy to one-way carsharing systems can allow more customers to rent vehicles than the traditional round-trip carsharing systems. Second, the appropriate relocation policy should be selected based on the average number of vehicles per station in order to minimize the lost sales rate. Third, the number of stations does not affect the lost sales rate. This study findings will provide tools to understand impact of the carsharing system parameters on the efficiency of the carsharing operations.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.22 no.5
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• pp.460-469
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• 2019

Purpose: The ${\beta}3-adrenergic$ receptor (ADRB3) is expressed in visceral adipose tissue and has been speculated to contribute to lipolysis, energy metabolism, and regulation of the metabolic rate. In this study, we aimed to investigate the association of polymorphism of the ADRB3 gene with the sex of children with obesity and related pathologies. Methods: ADRB3 gene trp64arg genotyping was conducted in 441 children aged 6-18 years. Among these subjects, 264 were obese (103 boys; 161 girls) and 179 were of normal weight (81 boys; 98 girls). In the obese group, fasting lipids, glucose and insulin levels, and blood pressure were measured. Metabolic syndrome (MS) was defined according to the modified World Health Organization criteria adapted for children. Results: The frequency of trp64arg genotype was similar in obese and normal weight children. In obese children, serum lipid, glucose, and insulin levels; homeostasis model assessment of insulin resistance (HOMA-IR) scores; and MS were not different between arg allele carriers (trp64arg) and noncarriers (trp64trp). In 264 obese children, genetic analysis results revealed that the arg allele carriers were significantly higher in girls than in boys (p=0.001). In the normal weight group, no statistically significant difference was found between genotypes of boys and girls (p=0.771). Conclusion: Trp64arg polymorphism of the ADRB3 gene was not associated with obesity and MS in Turkish children and adolescents. Although no relationships were observed between the genotypes and lipids, glucose/insulin levels, or HOMA-IR, the presence of trp64arg variant was frequent in obese girls, which can lead to weight gain as well as difficulty in losing weight in women.

• The Research Journal of the Costume Culture
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• v.27 no.5
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• pp.415-432
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• 2019

The purpose of the present study was to generate a list of business ethics components according to business area for small and medium-sized fashion companies. Based on the literature review, 21 components of business ethics components were identified within five business areas. Ten CEOs(Chief Executive Officers) each participated in an in-depth interview, sharing ethical and unethical cases from their own businesses. Constant comparative analysis was used to generate important business ethics components from those cases. In results, important business ethics components for each business area are: 1) using human-friendly materials, strengthening sustainable technologies, using vegan materials, concerning safe process, and reducing waste in the material production and sourcing area, 2) enhancing an efficiency in design, developing recycle/reuse designs, avoiding to copy designs, and using messages for public interest in the product design area, 3) concerning fair-trade, reducing harmful substance, saving energy, and using ethical supply channels in the distribution and logistics area, 4) acquiring certifications, promoting consumer protection, avoiding exaggerative/false advertisements, and promoting social contributions in the management and marketing area, and 5) promoting workers' rights, complying with the law, and investing on employee educations in the labor management area. All of the ethical and unethical cases of the ten companies have involved aspects of the 21 components, thereby enhancing understandings on how each issue is being seriously considered and/or handled in the small and medium-sized fashion companies. Study findings may provide a basis for development of a research model for quantitative studies and/or educational programs related to business ethics in the fashion industry.

• Journal of Korea Water Resources Association
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• v.52 no.5
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• pp.373-380
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• 2019

In this study, the optimum pump operation technique is suggested to decrease the damage rate of water distribution system. Pump operation system was developed to achieve the effective pump operation. Pressure sensors which can communicate with pumps are installed at the end of water distribution system. Pump operation system can control the pressure of water pump according to data sent from the pressure sensors. Therefore, water distribution system can reduce the pressure and maintain enough pressure which can supply the demand of water users. For proving effectiveness of new system, reliability model was introduced to compare the results of damage rates between the maintaining high pressure and selective pressure in water pump. Unsteady analysis was conducted with several scenarios. And the results were used to calculate the probability of pipe breakage. From the results, it was found that new pump operation system can reduce the energy usage and probability of pipe breakage by applying to pumps.