• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.2
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• pp.42-47
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• 2014

The urban railway station is a structure that consumes a large amount of electric energy. Thus, the rationalization of using electric power is acutely demanded, but statistical data and design criteria that consider operating power load characteristics and structures, are very insufficiency. Therefore, this study investigated and analyzed that electricity consumption a year, characteristics, gross floor area of the station, structure, and etc, on the basis of Seoul metro station 1~4 line. Through regression analysis theory, we verified the overall features and the main tendency by analysis of specific parameter value(average, maximum, minimum, etc). The object of this study is the analysis about power density considering structure of the urban railway station, managing electric energy for the rationalization and setting a new standard of maintenance and construction.

• Nuclear Engineering and Technology
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• v.32 no.3
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• pp.227-234
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• 2000

It is known that loose parts in the reactor coolant system (RCS) cause serious damage to the systems. This paper is concerned with estimating the mass of a loose part in the steam generator of a nuclear power plant. We developed the mass estimation algorithm based on the Hertz theory in order to estimate the mass of the loose parts and applied the algorithm to the impact test data of YGN3. The mass estimation values were compared with real values in order to verify the algorithm. The result showed that the average error of the mass estimation value is less than 27%.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2004.10a
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• pp.349-352
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• 2004

In this paper, we propose a newly energy-efficient routing protocol, which is called Maximum Utility Routing(MUR), in mobile ad hoc networks (MANETs) so as to investigate the minimum energy and maximum lifetimes issues together. We present a utility-based framework so as to meet various incompatible constraints simultaneously and fairly. To explore this issue, we use the concepts and mathematics of microeconomics and game theory. Though simulation results, we show that our routing scheme has much better performance especially in terms of network efficiency, network lifetime, and average power consumption.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.3
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• pp.109-117
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• 2002

High accuracy of the load forecasting for power systems improves the security of the power system and generation cost. However, the forecasting problem is difficult to handle due to the nonlinear and the random-like behavior of system loads as well as weather conditions and variation of economical environments. So far. many studies on the problem have been made to improve the prediction accuracy using deterministic, stochastic, knowledge based and artificial neural net(ANN) method. In the conventional load forecasting method, the load forecasting maximum error occurred for the holidays on Saturday and Monday. In order to reduce the load forecasting error of the daily peak load for the holidays on Saturday and Monday, fuzzy concept and linear regression theory have been adopted into the load forecasting problem. The proposed algorithm shows its good accuracy that the average percentage errors are 2.11% in 1996 and 2.84% in 1997.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.11a
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• pp.233-237
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• 2005

It is increased electrical energy consumption with the development of intelligence society in the general hospitals and thus an energy conservation through efficient use of electricity became more important. This paper shows a reasonable design demand factor in office buildings, that was made by the systematic and statistical way considering actual conditions, such as investigated electric equipment capacity, peak power consumption, demand factor, etc., for 32 general hospitals and 9 electrical design offices. In this dissertation, it is necessary to analyse the key features and general trend from the investigated data. It made an analysis of the feature parameters, such as average, standard deviation, median, maximum, minimun and thus it was carried linear and nonlinear regression analysis.

• Nuclear Engineering and Technology
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• v.27 no.3
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• pp.336-343
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• 1995

The Self Tuning Regulator(STR) method which is an approach of adaptive control theory, is ap-plied to design the fully automatic power controller of the nonlinear reactor model. The adaptive control represent a proper approach to design the suboptimal controller for nonlinear, time-varying stochastic systems. The control system is based on a third­order linear model with unknown, time-varying parameters. The updating of the parameter estimates is achieved by the recursive extended least square method with a variable forgetting factor. Based on the estimated parameters, the output (average coolant temperature) is predicted one-step ahead. And then, a weighted one-step ahead controller is designed so that the difference between the output and the desired output is minimized and the variation of the control rod position is small. Also, an integral action is added in order to remove the steady­state error. A nonlinear M plant model was used to simulate the proposed controller of reactor power which covers a wide operating range. From the simulation result, the performances of this controller for ramp input (increase or decrease) are proved to be successful. However, for step input this controller leaves something to be desired.

• Geomechanics and Engineering
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• v.30 no.5
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• pp.401-411
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• 2022

To obtain the dynamic mechanical properties, fracture modes, energy and brittleness characteristics of Furong Baijiao coal rock, the dynamic impact compression tests under 0, 4, 8 and 12 MPa confining pressure were carried out using the split Hopkinson pressure bar. The results show that failure mode of coal rock in uniaxial state is axial splitting failure, while it is mainly compression-shear failure with tensile failure in triaxial state. With strain rate and confining pressure increasing, compressive strength and peak strain increase, average fragmentation increases and fractal dimension decreases. Based on energy dissipation theory, the dissipated energy density of coal rock increases gradually with growing confining pressure, but it has little correlation with strain rate. Considering progressive destruction process of coal rock, damage variable was defined as the ratio of dissipated energy density to total absorbed energy density. The maximum damage rate was obtained by deriving damage variable to reflect its maximum failure severity, then a brittleness index BD was established based on the maximum damage rate. BD value declined gradually as confining pressure and strain rate increase, indicating the decrease of brittleness and destruction degree. When confining pressure rises to 12 MPa, brittleness index and average fragmentation gradually stabilize, which shows confining pressure growing cannot cause continuous damage. Finally, integrating dynamic deformation and destruction process of coal rock and according to its final failure characteristics under different confining pressures, BD value is used to classify the brittleness into four grades.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.145.2-145.2
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• 2016

We report the phase transformation of Co thin films on a sapphire substrate induced by laser irradiation. As grown Co films were initially strained and tetragonally distorted. With low power laser irradiation, the surface was ruptured and irregular holes were formed. As the laser power was increased, the films changed into round shape Co nanocrystals with well-defined 6-fold structure. By measuring the XRD of Co nanostructure as a function of laser energy densities, we found that the change of morphological shapes from films to nanocrystals was accompanied with decrease of the tetragonal distortion as well as strain relaxation. By measuring the size distribution of nanocrystals as a function of film thickness, the average diameter is proportional to 1.7 power of the film thickness which was consistent with the prediction of thin film hydrodynamic (TFT) dwetting theory. Finally, we fabricated the formation of size controlling nanocrystals on the sapphire substrate without strain.

• Journal of KIISE:Computer Systems and Theory
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• v.28 no.10
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• pp.530-540
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• 2001

As mobile applications are required to handle more computing-intensive tasks, many mobile devices are designed using VLIW processors for high performance. In VLIW machines where a single instruction contains multiple operations, the power consumption during instruction fetches varies significantly depending on how the operations are arranged within the instruction. In this paper, we describe a post-pass optimal operation rearrangement method for low-power VLIW instruction fetch, The proposed method modifies operation placement orders within VLIW instructions so that the switching activity between successive instruction fetches is minimized. Our experiment shows that the switching activity can be 34% on average fro benchmark programs.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.12
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• pp.1479-1485
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• 1999

This paper proposes a fuzzy decision making method for power transformer protection to identify an internal fault from other transient states such as inrush, over-excitation and an external fault with current transformer (CT) saturation. In this paper, analyzing over 300 EMTP simulations of disturbances, four input variables are selected and fuzzified. At every sampling interval from half to one cycle after a disturbance, from the EMPT simulations, different fuzzy rule base is composed of twelve if-then fuzzy rules associated with their basic probability assignments for singleton- or compound-support hypotheses. Dempster's rule of combination is used to process the fuzzy rules and get the final decision. A series of test results clearly indicate that the method can identify not only an internal fault but also the other transients. The average of relay operation times is about 12(ms). The proposed method is implemented into a Digital Signal Processor (TMS320C31) and tested.