• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.617-635
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• 2020

The purpose of this study is to discuss how to improve the maneuverability of lifting and diving for underwater vehicle's vertical motion. Therefore, to solve these problems, applied the 3-D numerical simulation, Taguchi's Design of Experiment (DOE), and intelligent parameter design methods, etc. We planned four steps as follows: firstly, we applied the 2-D flow simulation with NACA series, and then through the Taguchi's dynamic method to analyze the sensitivity (β). Secondly, take the data of pitching torque and total resistance from the Taguchi orthogonal array (L9), the ignal-to-noise ratio (SNR), and analysis each factorial contribution by ANOVA. Thirdly, used Radial Basis Function Network (RBFN) method to train the non-linear meta-modeling and found out the best factorial combination by Particle Swarm Optimization (PSO) and Weighted Percentage Reduction of Quality Loss (WPRQL). Finally, the application of the above methods gives the global optimum for multi-quality characteristics and the robust design configuration, including L/D is 9.4:1, the foreplane on the hull (Bow-2), and position of the sail is 0.25 Ls from the bow. The result shows that the total quality is improved by 86.03% in comparison with the original design.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.275-280
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• 2001

Recycling of coal combustion by-product(Ash) are becoming more improtant in the utilization business as a result of the increased use of NOx reduction technologies at coal-fired power plants. current disposal methods of these by-products create not only a loss of profit for the power industry, but also environmental concerns that breed negative public opinion. Since inherent characteristics make these by-product suitable for building materials, several types of artificial aggregates and construction bricks are manufactured and tested to verify the engineering properties.

• ETRI Journal
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• v.33 no.1
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• pp.136-139
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• 2011

A modular upgrade design for packet transport switch nodes is presented where packet loss is dramatically reduced by intra-module and inter-module buffer sharing. This modular design offers significant cost and power reduction in a high-data-rate system where buffers are highly costly and power-greedy.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.4
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• pp.370-376
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• 2000

In this paper, a communication system that is not using the communication line but power line is presented. It will be very useful for an information-oriented society with tele-metering and home automation. Conventional system has a difficulty in transmitting information due to decreasing communication voltage and increasing carrier current. Proposed idea is a special type switching amplifier system which has a low inner resistance. It can provide reactive power and does not have low impedance between the transceivers. This new system is proposed to overcome the loss of conductor load in a PLC system.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.6
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• pp.476-483
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• 2017

In this paper, a voltage-based model predictive control (MPC) scheme for a modular multilevel converter is used to reduce switching loss. The proposed method calculates an offset voltage that clamps the switching operation of submodules in which the current greatly flows at every sampling period by using the reference phase voltage and the reference phase current. To use the offset voltage, the proposed method converts the current-based MPC to the voltage-based MPC. The proposed voltage-based MPC then generates a new reference pole voltage that clamps the switching of submodules by applying the calculated offset voltage to the phase voltage. Therefore, the proposed method can reduce the switching loss by stopping the switching operation of submodules in which the current greatly flows. The switching loss reduction effect of the proposed method is verified by comparing its loss data with those of the conventional MPC method.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.2
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• pp.53-58
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• 2006

This paper proposes a small low-cost power quality compensator to be installed at the electricity supply inlet of residential customer. The compensator is composed of a single-phase active power filter with a simple controller using analog electronics, which can correct the power factor and damp out the harmonics. The operation and performance of proposed compensator was verified through simulations with PSCAD/EMTDC and experimental works with hardware prototype. The proposed compensator can offer reduction of power loss and improvement of power quality to the residential customer.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.804-811
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• 2015

The presence of responsive loads in the promising active distribution networks (ADNs) would definitely affect the power system problems such as distributed generations (DGs) studies. Hence, an optimal procedure is proposed herein which takes into account the simultaneous placement of DGs and smart meters (SMs) in ADNs. SMs are taken into consideration for the sake of successful implementing of demand response programs (DRPs) such as direct load control (DLC) with end-side consumers. Seeking to power loss minimization, the optimization procedure is tackled with genetic algorithm (GA) and tested thoroughly on 69-bus distribution test system. Different scenarios including variations in the number of DG units, adaptive power factor (APF) mode for DGs to support reactive power, and individual or simultaneous placing of DGs and SMs have been established and interrogated in depth. The obtained results certify the considerable effect of DRPs and APF mode in determining the optimal size and site of DGs to be connected in ADN resulting to the lowest value of power losses as well.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.1056-1058
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• 1998

Voltage dips caused by transmission system faults are usually of a short duration. High speed relaying and breaker operation will typically limit the disturbance to 0.1 seconds. Most motor controllers obtain their control power directly from the bus by means of a control transformer. Under this condition, a voltage dip can cause the contactor to drop out. disconnecting the motor from the line. The rapid re-energizing of the controller is in effect a fast reclosure which may result in motor damage. The time delay re-energizing of controller will result in a greater loss of speed and possibly loss of stability. Other means of controller can be used to prevent the motor from being disconnected from line during the fault. This can be accomplished by DC power controller or mechanically latched controller. This paper demonstrates that DC power controller or mechanically latched type controller to prevent the motor from being disconnected from line during the fault is, the most effective in minimizing speed reduction, transient motor current, transient motor torque and transient shaft torque by EMTP calculation.

• Nuclear Engineering and Technology
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• v.28 no.3
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• pp.265-273
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• 1996

Among those tests performed during the Yonggwang Nuclear Power Plant Units 3 and 4 (YGN 3&4) Power Ascension Test period, the Loss of a Main Feedwater Pump test at l00% power is one of the major test which characterize the capability of YGN 3&4. In this event, one of the two normally operating main feedwater pumps is tripped resulting in a 50% reduction in the feedwater flow. Unless the NSSS and Turbine/Generator control systems actuate properly, the reactor will be tripped on low SG water level or high pressurizer pressure. The test performed at Unit 3 was successful by meeting all acceptance criteria, and the plant was stabilized at a reduced power level without reactor trip. The measured test data for the major plant parameters are compared with the predictions made by the KISPAC computer code, an updated best-estimate plant performance analysis code, to verify and validate its applicability. The comparison results showed good agreement in the magnitude as well as the trends of the major plant parameters. Therefore, the KISPAC code can be utilized for the best-estimate nuclear power plant design and simulation tool after a further verification using other plant test data.

• Current Photovoltaic Research
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• v.11 no.1
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• pp.34-37
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• 2023

Solar energy had become the main energy industry of renewable energy along with hydroelectric power generation. One of the technologies that contributed to the popularization of photovoltaic power and the decrease in the unit price of photovoltaic modules was the large-area solar cell. However, as the area increased, the light receiving area increased and the current value increased accordingly. Since power loss occurs when the current value was large, the number of busbar was increased to increase the current collection rate, and a technology to lower the current value through half-cutting was developed. The bus bar of the solar cell served as a passage through which the generated current was transmitted. This was because when the number of busbar decreases, the moving distance of electrons increased, so the amount of power generation decreases and when it increases, shadows occured. An important aspect of the electrode design was the optimal balance of these busbars and number of fingers. Therefore, in this study, the characteristics of the solar cell according to the number of front bus bars of the large-area solar cell were simulated using Griddler 2,5 pro. After selecting the number of busbar with the best characteristics, the difference was compared by varying the number of fingers and a better direction for the number of cutting was presented.