• Journal of the Korean Society of Food Culture
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• v.35 no.5
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• pp.450-458
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• 2020

This study examined the optimal temperature and time conditions to maintain high quality Dongchimi during the fermentation and storage period. Dongchimi was fermented at low (5℃), medium (10 and 15℃), and high (20℃) temperatures until the acidity reached 0.2, 0.3, and 0.4%. respectively. From the consumer's preference test enrolling five consumers, Dongchimi fermented at 15℃ until an acidity of 0.3% (for approximately six days) was evaluated to be the optimal status because of its high score of overall acceptance, taste, and odor of consumers. To determine the optimal storage temperature of fermentation, Dongchimi was stored at three different temperatures (-1, 2, 5℃) for four weeks after fermenting at 15℃ for six days. During the storage period, most of the physicochemical properties (pH, acidity, reducing sugar content, and organic acid) and microbiological properties changed significantly in the 2 and 5℃ groups, resulting in a significant change in descriptive sensory analysis of Dongchimi. These results indicate that fermentation at 15℃ and storage at -1℃ for Dongchimi enables it to maintain the best quality for a long time.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.6_1
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• pp.907-915
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• 2020

Specification selection, Layout, specifications and combinations of Power Drives, and Ship motions were studied for FGPP(Floating Gas-fired Power Plants), which are still needed in areas such as the Caribbean, Latin America, and Southeast Asia where electricity is not sufficiently supplied. From this study, the optimal equipment layout in ships was derived. In addition, the difference between engine and turbine was verified through LCOE(Levelized Cost of Energy) comparison according to the type and combination of Power Drives. Analysis of Hs(Significant Height of wave) and Tp(spectrum Peak Period of wave) for places where this FGPP will be tested or applied enables design according to wave characteristics in Brazil and Indonesia. Normalized Sloshing Pressures of FGPP and LNG Carrier are verified using a sloshing analysis program, which is CFD(Computational Fluid Dynamics) software developed by ABS(American Bureau of Shipping). Power Transmission System is studied with Double bus with one Circuit Breaker Topology. A nd the CFD analysis allowed us to calculate linear roll damping coefficients for more accurate full load conditions and ballast conditions. Through RAO(Response Amplitude Operator) analysis, we secured data that could minimize the movement of ships according to the direction of waves and ship placement by identifying the characteristics of large movements in the beam sea conditions. The FGPP has been granted an AIP(Approval in Principle) from a classification society, the ABS.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.2
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• pp.282-287
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• 2010

This paper gives a description of an experimental study of the ultrasonic welding of metals. In ultrasonic metal welding, high frequency vibrations are combined with pressure to join two materials together quickly and securely, without producing significant amount of heat. Ultrasonic metal welder consists of Transducer, Booster, and horn that are designed very accurately to get the natural frequencies and vibration mode. In this study, The horn was designed and analyzed the natural frequency by the modal analysis and harmonic analysis. And using a fiber optic sensor, we measured the amplitude and analyzed the Fast Fourier Transformed result. Using the horn, Ultrasonic metal welding between Cu sheet and Cu sheet of 0.1mm thickness was accomplished under the optimal conditions of static pressure 0.15MPa, vibration amplitude 30% and welding time of 0.28s. This result can be used for ultrasonic metal welding in manufacturing industry.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.343-346
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• 2002

In recent, complex SVPWM (Space Vector PWM) algorithm can be easily implemented by high performance microprocessor and DSP. Various SVPWM techniques are widely studied due to the advantages of low harmonic distortion and high use ratio of D.C. link voltage. Most of various studies for improving of VS-PWM inverter performance are concentrated about switching pattern and zero pulse pattern split algorithms. However, dc link voltage that is determined at rated load and speed conditions is not proper in the low speed and under rated load. In this paper, analysis of current ripple with digitally implemented SVPWM inverter is introduced according to link voltage. The optimal link voltage in the designed inverter system and load condition is provided in order to suppress output voltage error and current ripple. As remaining the effective voltage vector interval per sampling period sufficiently, additional voltage error and current ripple are suppressed. The proposed algorithm is verified through digital simulation and experimental results.

• Journal of applied mathematics & informatics
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• v.40 no.3_4
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• pp.633-656
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• 2022

Many regions of the world are now facing the second wave of boomed cases of COVID-19. This time, the second wave of this highly infectious disease (COVID-19) is becoming more devastating. To control the existing situation, more mass testing, and tracing of COVID-19 positive individuals are required. Furthermore, practicing to wear a face mask and maintenance of physical distancing are strongly recommended for everyone. Taking all these into consideration, an optimal control problem has been reformulated in terms of nonlinear ordinary differential equations in this paper. The aim of this study is to explore the control strategy of coronavirus-2 disease (COVID-19) and thus, minimize the number of symptomatic, asymptomatic and infected individuals as well as cost of the controls measures. The optimal control model has been analyzed analytically with the help of the necessary conditions of very well-known Pontryagin's maximum principle. Numerical simulations of the optimal control problem are also performed to illustrate the results.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.10
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• pp.1212-1216
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• 2014

This study aims to find out the best anode location for buried pipelines. Numerical simulation program known as CATPRO (Elsyca, Belgium) were used for confirming the best location of anodes and the effects of impressed current cathodic protection system. Applied conditions for numerical simulation were similar to on-site environmental conditions for optimal application of cathodic protection system. Used criterion of cathodic protection was NACE SP 0169, which describes that minimum requirement for cathodic protection is -850mV vs. CSE. Various layouts for anodes' installation were applied, which were distance between anodes, anode installation location, and applied current. The areas where cathodic protection potential was lower than -850mV vs. CSE was limited up to 50m from anode installation locations. It was founded numerical analysis obtain cost-effective and efficient cathodic protection methods before design and application the impressed cathodic protection system to on-site environment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.6
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• pp.1020-1027
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• 2003

A traditional mold design has been conducted by an experience-based trial and error, whereby the mold designer would decide the gate locations and processing conditions based on the caring characteristics and its functional requirements. The paper suggests an optimal gate location and processing conditions in the injection molding using a global search method referred to as micro genetic algorithm( ${\mu}$ GA). ${\mu}$ GA yields the optimal solution with a small size of population without respect to design variables for saving time that is needed to calculate the fitness of many individuals. Due to the reason, the paper uses a commercial analysis package of injection molding(CAPA) to analysis a state of flux. In addition to that, axiomatic approach .is applied in the beginning of design. It is a useful method to draw a well-organized and reasonable idea to handle a problem.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.1
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• pp.29-39
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• 2010

The system performance of the regenerative gas-turbine cycle with the steam injection into the combustor has been studied through the thermodynamic cyclic analysis. The effects of the pressure ratio, the steam injection ratio, the ambient temperature, and the turbine inlet temperature are investigated on the thermal efficiency, the fuel consumption, and the specific power as well as the operating conditions for the maximum thermal efficiency of the system. The results of the present analysis find that the use of steam injection in the regenerative gas-turbine system can greatly enhance the thermal efficiency and the specific power of the system.

• Journal of Power Electronics
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• v.12 no.3
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• pp.468-476
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• 2012

The interior permanent magnet synchronous motor (IPMSM) has been widely used in electric vehicle applications due to its excellent power to weigh ratio. This paper proposes the maximum torque control of an IPMSM drive using an adaptive learning (AL) fuzzy neural network (FNN) and an artificial neural network (ANN). This control method is applicable over the entire speed range while taking into consideration the limits of the inverter's rated current and voltage. This maximum torque control is an executed control through an optimal d-axis current that is calculated according to the operating conditions. This paper proposes a novel technique for the high performance speed control of an IPMSM using AL-FNN and ANN. The AL-FNN is a control algorithm that is a combination of adaptive control and a FNN. This control algorithm has a powerful numerical processing capability and a high adaptability. In addition, this paper proposes the speed control of an IPMSM using an AL-FNN, the estimation of speed using an ANN and a maximum torque control using the optimal d-axis current according to the operating conditions. The proposed control algorithm is applied to an IPMSM drive system. This paper demonstrates the validity of the proposed algorithms through result analysis based on experiments under various operating conditions.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.4
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• pp.751-762
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• 2021

This study aims to examine whether an increased disclosure has a positive impact on firm performance and whether the opposite impact of increased disclosure on firm performance can occur in certain conditions - high proprietary information and competition. The sample for this study consists of Indonesian firms listed on the Indonesia Stock Exchange (IDX). The data were selected based on purposive sampling and panel data spanned eleven years (2006-2016). A panel GLS regression using moderated regression analysis (MRA) was adopted. The results of this study reveal that an increased disclosure has a positive effect on firm performance, but an increased disclosure has a negative impact on firm performance when proprietary information is high, and vice versa. Also, if the disclosure is increased, the negative impact of proprietary information on firm performance will get exacerbated in conditions where the competition level is high. The findings of this study suggest that, since the positive effect of continuously-increased disclosure on firm performance leads to the reversal (negative) impact when certain conditions occur (high proprietary information and competition), the level of disclosure quality is most likely to tap an 'optimal' point. In this regard, however, a broader investigation of all firms across countries still needs to be conducted.