• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.4
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• pp.219-235
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• 2013

In order to investigate the changes in sea water characteristics and stratification due to operation of Shihwa tidal power plant, three dimensional numerical model is used. In summer, the density of inner part of Shihwa Lake is more affected by salinity than water temperature due to fresh water discharge. Before tidal power plant operation, the sea water characteristics in Shihwa Lake shows relatively high temperature and low salinity. After tidal power plant operation, water temperature decreases slightly and salinity tends to increase in Shihwa Lake. Also, density increases and stratification tends to weaken by mixing with sea water.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.4
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• pp.364-371
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• 2005

Fuel cell systems(FCS) have a financial and environmental advantage by providing electricity at a high efficiency and useful heat. For use in a residence, a polymer electrolyte fuel cell system(PEFCS) with a battery pack and a hot water storage tank has been modelled and simulated. The system is operated without connection to grid line. Its electric conversion efficiency and heat recovery performance are highly dependent on operation strategies and also on the seasonal thermal and electric load pattern. The output of the fuel cell is controlled stepwise as a function of the state of the battery and/or the storage water tank. In this study various operation strategies for cogeneration fuel cell systems are investigated. Average fuel saving rates at different seasons are calculated to find proper load management strategy. The scheme can be used to determine the optimal operating strategies of PEFCS for residential and building applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.10C
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• pp.921-932
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• 2002

In this research, we seek to identify an effective operation management strategy of telecommunication systems. In order to develop operation management strategies, we implement a quantitative techno-economic analysis. We evaluate related issues and factors, and apply the developed method to PSTN switching systems. In the proposed techno-economic modeling, we apply a well-known factor analysis technique-analytic hierarchy process-to evaluate PSTN operation management strategies. Then, we implement a decision analysis methodology to evaluate the cost of proposed strategies. We evaluate the proposed methodology by using available real data of the PSTN system. The primary impact of this research will be realized in helping PSTN operator select the best operation management strategy of PSTN system.

• Journal of Navigation and Port Research
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• v.29 no.8 s.104
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• pp.709-714
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• 2005

The purpose of this research is to verify the strategic fitness and relevance of the hub port strategy by SCM in Northeast Asia and to find a method to be a hub-port with a competitive edge. The fitness of the hub port development strategy is analysed by the structural equation model. The essential results of the research show that minimizing lead time from arrival of ship to inland transport and maximizing logistic services of each stage are important to provide optimal logistic service. And value-added port supply chain strategy is highly co-related with all the parts of port operation system, port transport system, distribution park and port information system. It shows that: various value added logistic service activity is more important than lowing cost; inland multimodal system should be rightly connected; distribution park should be connected to industry park to be a port cluster; and port information system should be developed.

• Journal of Power Electronics
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• v.17 no.3
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• pp.632-640
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• 2017

Input series output independent (ISOI) dc-dc converter systems are suitable for high voltage input and multiple output applications with low voltage rating switches. This paper proposes a novel control strategy consisting of one output voltage regulating (OVR) control loop and n-1 (n is the number of modules in the ISOI system) input voltage sharing (IVS) control loops. An ISOI system with the proposed control strategy can be applied to applications where the output loads of each module are the same. Under these conditions, IVS can be achieved and output voltages copying can be realized in an ISOI system. In this control strategy there is only one controller for each module and the design process of the control loops is simple. Since no central controller is needed in the system, modularity of the system is improved. The operation principle of the new control strategy is introduced and the control effect is simulated. Then the output power and voltage characteristics of an ISOI system under this new control strategy are analyzed. The stability of the proposed control strategy is explored base on a Hurwitz criterion, and the design guide line of the control strategy is given. A two module ISOI system prototype is fabricated and tested in the laboratory. Experimental results verify the effectiveness of the proposed control strategy.

• Journal of the Korean Operations Research and Management Science Society
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• v.32 no.1
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• pp.147-160
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• 2007

In this paper, the optimal decision making strategy for resource management is viewed in terms of a combined strategy of planting and producing time. A model which can be used to determine the optimal management strategy is developed, and focuses on how to design the operation of a Markov chain so as to optimize its performance. This study estimated a dynamic stochastic model to compare alternative production style and used the net present value of returns to evaluate the scenarios. The managers in this study may be able to increase economic returns by delaying produce in order to market larder, more valuable commodities.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.366-373
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• 1998

In this paper, a new control strategy to reduce switching losses in three-phase voltage-source PWM converters is proposed according to Modified-Period-Average-Model (MPAN). The basic concept of this strategy is aimed at calculating the phase control voltages for controlling the source currents to be sinusoidal and in phase with the source voltages, and reducing the number of switching in each period. The phase control voltages of Period-Average-Model(PAM) is obtained according to analyzing the operation of PWM converter. In order to reduce the sensitivity to system parameters in PAM, MPAM is deduced. Then a square wave whose frequency is three times of utility frequency is added to the phase control voltages derived from MPAM. The control strategy reduces the switching losses since there exists about one-third blanking time for every phase in one period. The theoretical derivation and the control strategy are experimentally verified on a 2.5 kW three-phase voltage source converter.

• International Journal of Precision Engineering and Manufacturing
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• v.6 no.2
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• pp.61-71
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• 2005

The study reported deals with investigating the feasibility of control strategy for a serial rigid link manipulator that applies impulsive torques at the joints. The strategy is illustrated for a planar three rigid link manipulator. An impulse-based concept which uses successive torque impulses on rigid link as the controller for motion correction was introduced. This control strategy was tested over the entire trajectory to demonstrate that the tracking error could be reduced effectively. The best condition for minimizing the tracking error with the least impulse input at each joint is investigated by considering one design and one operating parameter. The first was the damping in the system, and the second was the sampling time during operation. The results show that this approach can provide useful guidance for the design and control of robot manipulators that require minimum impulse feedback for accurate tracking.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.30B no.7
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• pp.59-69
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• 1993

In this paper, a new matching strategy for 3-D object recognition, based on the Surface Normal Images (SNIs), is proposed. The matching strategy using the similarity decision function [9,10] lost the efficiency and the reliability of matching, because all features of models within model base must be compared with the scene object features, and the weights of the attributes of features is given by heuristic manner. However, the proposed matching strategy can solve these problems by using a new approach. In the approach, by searching the model base, a model object whose features are fully matched with the features of sceme object is selected. In this paper, the model base is constructed for the total 26 objects, and systhetic and real range images are used in the test of the system operation. Experimental result is performed to show the possibility that this strategy can be effectively used for the SNI based recognition.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.74-76
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• 2019

This paper proposes an open-switch fault tolerant strategy based on the model predictive control for a full bidirectional switches indirect matrix converter (FBS-IMC). Compared to the conventional Indirect Matrix Converter (IMC), the FBS-IMC can provide healthy current path when open-switch fault is occurred. To keep the continuous operation, the fault tolerant strategy is developed by means of reversing the DC-link voltage polarity regardless of the faulty switch location in the rectifier or inverter stage. Therefore, the proposed control strategy can maintain the same input and output performances during the faulty condition as the normal condition. The simulation results are given to verify the effectiveness of the proposed strategy.