• Korean Journal of Agricultural Science
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• v.29 no.2
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• pp.109-121
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• 2002

In the near future information technology will make more extensive applications to agricultural marketing system through e-commerce system. This paper is to investigate the current trends of e-commerce in agricultural marketing and suggest strategies for increasing agricultural product sales at the farm level as follows ; 1) price and quality control for attracting customers 2) increasing brand power for marketing promotion, and 3) devising more convenient website for internet users.

• Smart Media Journal
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• v.3 no.1
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• pp.22-27
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• 2014

Recently, domestic energy environment is facing new challenges owing to the depletion of fossil fuel such as oil. Renewable energy resources including solar and wind energy are attracting more interests than ever before. However, solar power system is costly in comparison with the conventional power generation systems and also the energy density is low. Furthermore, large area is required in order to install solar power system. Generally, performance of solar power system is affected by weather conditions and alignment of sun and the solar cell modules. In this study, a new type of sun tracking system for solar power system is proposed. To verify the feasibility of the proposed system, actual implementation of prototype system and experiments are carried out.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.4_2
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• pp.639-648
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• 2023

In modern society, UAM (Urban Air Mobility) transportation system is being developed as an alternative to urban traffic congestion and environmental problems, and electric vertical take-off and landing (eVTOL) is a combination of vertical take-off and landing function and electric power. It is attracting attention as an innovative next-generation transportation method as an eco-friendly alternative that reduces noise and air pollution by providing efficient mobility within the city. Since eVTOL development requires designing and implementing airframes suitable for various mission purposes, the power system needs to be developed as a platform concept before airframe development. In this study, we empirically proposed a test bench concept equipped with a stable power supply and an efficient control system, essential in developing a power platform with a combined function in the form of a fuselage and module type specialized for various mission purposes. The proposed drivetrain platform test bench consists of a system verifying the stable take-off and landing software and a power platform adjusting the motor's thrust. It will serve as a verification system that can be developed.

• Journal of the Korean Society of Systems Engineering
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• v.14 no.1
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• pp.1-12
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• 2018

In the energy-guzzling industries such as steel making and cement, power plants utilizing waste heat have been attracting attention to increase energy efficiency. However, the existing economic analysis system doesn't consider the special working fluids and the cost models of the main equipment used in the waste heat recovery power plant. So it is difficult to estimate the plant economics accurately. Therefore, It is required to develop a economic analysis module that can more accurately evaluate for the power plant. In this study, the systems engineering approach was used to design and develop the module that systematically reflects the characteristics of the power plant and various requirements. Specifically, first, the special working fluids and main equipment applied to the power plant were investigated. Next, the cost models for each equipment were developed. Finally, the economic analysis module based on this was developed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.12
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• pp.210-216
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• 2009

Distributed Generation (DG) is predicted to play a important role in electric power system in the near future. insertion of DG system into existing distribution network has great impact on real-time system operation and planning. It is widely accepted that micro turbine generation (MTG) systems are currently attracting lot of attention to meet customers need in the distributed power generation market. In order to investigate the performance of MT generation systems, their efficient modeling is required. This paper presents the modeling and simulation of a MT generation system suitable for stand-alone operation. The system comprises of a permanent magnet synchronous generator driven by a MT. A brief description of the overall system is given, and mathematical models for the MT and permanent magnet synchronous generator are presented. Also, the use of power electronics in conditioning the power output of the generating system is demonstrated. Simulation studies with MATLAB/Simulink have been carried out in stand-alone operation mode of a DG system.

• Transactions of The Korea Fluid Power Systems Society
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• v.1 no.3
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• pp.1-6
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• 2004

In the last few years, a considerable number of studies have been made on On-Off solenoid for fluid control. But, only few attempts have so far been made at solenoid actuator for high-voltage circuit breaker. In case of the high-pressure and high-flow system like high-voltage circuit breaker, a big size of On/Off solenoid is necessary which size is proportional to control pressure and flow rate. So, it is non-effective in the view point of system optimization. In this paper, On/Off solenoid actuator with the farce amplifier connected to the solenoid rod was proposed to get a high mechanical force and a fast response time. The magnetic force and the mechanical stress distributions were analysed using finite element analysis. The performances of suggested solenoid actuator were evaluated through the experimental results and compared with the analysis results.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.316-319
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• 1998

RPWM(Random Pulse Width Modulation) is a switching technique to spread the voltage and current harmonics on the wide frequency area. Using randomly changed switching frequency of the inverter, the power spectrum of the electromagnetic acoustic noise cab be spread to the wide-band area. The wide-band noise is much more comfortable and less annoying than the narrow-band one. So RPWM have been attracting an interest as an excellent method for the reduction of acoustic noise on the inverter drive system. In this paper a new RPPWM (Random Position PWM) is proposed and implemented. Each of three pulses is located randomly in each switching interval. Along with the randomization of PWM pulses, the space vector modulation is executed in the C167 microcontroller also. The experimental results show that the voltage and current harmonics were spread to wide band area and that the audible switching noise was reduced by proposed RPPWM method.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.230-231
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• 2018

Recently, the danger for radioactive materials has become a hot topic. Beginning with the Chernobyl nuclear accident in 1996, in 2011, the Fukushima nuclear power plant in Japan suffered major damage such as large-scale casualties and radioactive dangerous area selection. Concerns about leakage of radioactive materials due to recent earthquakes have been deepening in Korea, such as Wolsong Nuclear Power Plant in Gyeongju, and there is a growing interest in the safety of radioactive materials through the media and the media. However, the route to exposure to radioactive materials is not limited to these large-scale nuclear accidents. Typical examples of this are radioactive substances exposed in daily life. In the case of radon gas, the danger is being revealed through current events programs and news, and natural radiation exposure is attracting attention.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.4
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• pp.339-347
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• 2022

This study proposes the mitigation method for overcurrent and oscillation motor current in an active short-circuit operation. This operation is attracting attention as the safe state of electric vehicle traction inverters. However, the active short-circuit operation generates oscillation and overcurrent of motor currents during a transient state. The proposed method uses two different safe states in PMSM, such as active short circuit and freewheeling. The active short circuit is used for safe state in a steady state. To reduce the overshoot and oscillation, a freewheeling state is injected between active short-circuit operation by comparing the motor phase current with an analytically calculated steady-state motor current. Freewheeling state is only used in a transient state. The performance is demonstrated through simulations and experimental results. The peak current of the motor was reduced from 52 A to 40 A, and oscillation time was reduced.

• Journal of the Korean Society of Industry Convergence
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• v.27 no.3
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• pp.547-553
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• 2024

Hydrogen is considered a key energy source to achieve carbon neutrality through the global goal of 'Net Zero'. Due to limitations in domestic green hydrogen production, Korean companies are interested in importing green hydrogen produced overseas. Because Australia and the Middle East possess high-quality renewable energy resources, they are attracting attention as suitable regions for producing green hydrogen using renewable energy. The cost of constructing and operating a green ammonia plant varies depending on the region. In this study, an economic feasibility comparison of green ammonia plant construction in Australia and the Middle East is conducted. Through this, it is expected to contribute to the economic analysis and feasibility analysis of the project to import hydrogen in the form of green ammonia into Korea.