• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.2
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• pp.185-190
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• 2010

This paper presents the estimation on switching technique via output power source analysis of power conversion unit in electric railway vehicle. The focus of this study suggested an alternative on critical problems by using head electric power(HEP). To achieve this, we have measured output power of HEP, and measurement devices set up at output of transformer connected HEP to analysis quality on output power source of head electric power(HEP) unit in electric railway vehicle. Using results of measurement of it, parameters are assumed for simulation to confirm estimation on switching technique. It is confirmed that switching technique is Selected Harmonic Elimination PWM(SHEPWM) and inverter switching frequency is less than 500[Hz]. Throughout experiment and simulation, it is estimated that switching technique used HEP is advanced SHEPWM and switching frequency is about 300[Hz]. Also leakage inductance in transformer is about $180[{\mu}H]$ less than $365[{\mu}H]$ known.

• Journal of Power Electronics
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• v.19 no.3
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• pp.645-654
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• 2019

In this paper, a new high step up DC/DC converter with a modified super-lift technique is presented. The coupled inductor technique is combined with the super-lift technique to provide a tenfold or more voltage gain with a proper duty cycle and a low turn ratio. Due to a high conversion ratio, the voltage stress on the semiconductor devices is reduced. As a result, low voltage ultra-fast recovery diodes and low on resistance MOSFET can be used, which improves the reverse recovery problems and conduction losses. This converter employs a passive clamp circuit to recycle the energy stored in the leakage inductance. The proposed convertor features a high conversion ratio with a low turn ratio, low voltage stress, low reverse recovery losses, omission of the inrush currents of the switch capacitor loops, high efficiency, small volume and reduced cost. This converter is suitable for renewable energy applications. The operational principle and a steady-state analysis of the proposed converter are presented in details. A 200W, 30V input, 380V output laboratory prototype circuit is implemented to confirm the theoretical analysis.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.31B no.8
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• pp.87-98
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• 1994

Object-oriented analysis-synthesis coding subdivides each image of a sequence into moving objects and compensates the motion of each object. Thus it can reconstruct real motion better than conventional motion-compensated coding techniques at very-low-bit-rates. It uses a mapping parameter technique for estimating motion information of each object. Since a mapping parameter technique uses gradient operators it is sensitive to redundant details and noise. To accurately determine mapping parameters, we propose a new analysis method using integral projections for estimation of gradient values. Also to reconstruct correctly the local motion the proposed algorithm divides an image into segmented objects each of which having uniform motion information while the conventional one assumes a large object having the same motion information. Computer simulation results with several test sequences show that the proposed image analysis method in object-oriented analysis-synthesis coding shows better performance than the conventional one.

• Geomechanics and Engineering
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• v.17 no.3
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• pp.227-236
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• 2019

In practice, the natural slopes are frequently with soils of spatial properties and irregular features. The traditional limit analysis method meets an inherent difficulty to deal with the stability problem for such slopes due to the normal condition in the associated flow rule. To overcome the problem, a novel technique based on the upper bound limit analysis, which is called the discretization technique, is employed for the stability evaluation of complex slopes. In this paper, the discretization mechanism for complex slopes was presented, and the safety factors of several examples were calculated. The good agreement between the discretization-based and previous results shows the accuracy of the proposed mechanism, proving that it can be an alternative and reliable approach for complex slope stability analysis.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.186-188
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• 2005

Because forest fire changes the direction according to the environmental elements, it is difficult to predict the direction of it. Currently, though some researchers have been studied to which predict the forest fire occurrence and the direction of it, using the remote detection technique, it is not enough and efficient. And recently because of the development of the sensor technique, a lot of In-Situ sensors are being developed. These kinds of In-Situ sensor data are used to collect the environmental elements such as temperature, humidity, and the velocity of the wind. Accordingly we need the prediction technique about the environmental elements analysis and the direction of the forest fire, using the In-Situ sensor data. In this paper, as a technique for predicting the direction of the forest fire, we propose the correlation analysis technique about In-Situ sensor data such as temperature, humidity, the velocity of the wind. The proposed technique is based on the clustering method and clusters the In-Situ sensor data. And then it analyzes the correlation of the multivariate correlations among clusters. These kinds of prediction information not only helps to predict the direction of the forest fire, but also finds the solution after predicting the environmental elements of the forest fire. Accordingly, this technique is expected to reduce the damage by the forest fire which occurs frequently these days.

• KIEE International Transactions on Power Engineering
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• v.11A no.4
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• pp.1-8
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• 2001

This paper presents a discrete wavelet transform approach for detecting voltage sags initialized by fault conditions and starting of larger motors. The proposed technique is based on utilizing the summation value of D1(at scale 1) coefficients in multiresolution analysis(MRA) based on the discrete wavelet transform. In this paper, the proposed technique is tested under various cases of voltage sags. It is shown that the voltage sag detection technique based on the wavelet transform is a satisfactory and reliable method for detecting voltage sags in power quality disturbance analysis.

• Applied Microscopy
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• v.45 no.4
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• pp.189-194
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• 2015

Backside Ar ion milling technique for the preparation of cross-sectional transmission electron microscopy (TEM) specimens, and backside-ion milling combined with focused ion beam (FIB) operation for electron holography were introduced in this paper. The backside Ar ion milling technique offers advantages in preparing cross-sectional specimens having thin, smooth and uniform surfaces with low surface damages. The back-side ion milling combined with the FIB technique could be used to observe the two-dimensional p-n junction profiles in semiconductors with the sample quality sufficient for an electron holography study. These techniques have useful applications for accurate TEM analysis of the microstructure of materials or electronic devices such as arrayed hole patterns, three-dimensional integrated circuits, and also relatively thick layers (> $1{\mu}m$).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.397-401
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• 1995

ESPI(Electronic Speckle Pattern Interfermetry) is an optical technique to measure surface deforamtion of engineering components and materials in industrial ares. This optical method is capable of providing full-field results with high spatial resolution, high speed and is the non-contact technique. One of important application aspects using electronic speckle pattern interferometry is to generate contours of a diffuse object in order to provide data for 3-D shape analysis and topography measurement. The contouring method by modified dual-beam speckle pattern interferometry is proposed. We introduce a shift of the illumination beams through optical fiber in order to obtain the contour fringe patterns. The speckle pattern correlation technique is suitable for providing measurement range from millimeters to several centimeters. The complete geometric analysis of the contoretical and experimental results are obtained.

• Proceedings of the KIEE Conference
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• 1992.07a
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• pp.138-140
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• 1992

This paper represents how to reduce the computer time in small signal stability analysis by selecting the dominant oscillation modes with frequency of 0.5 to 1.2 Hz using the clustering technique. Clustering technique links the buses which are expected to be similar with zero-impedance lines and the voltage variations of these buses are regarded to be identical. The computer time was reduced remarkably with this technique and the effect of clustering will be powerful in the analysis of large-scale power systems.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.469-475
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• 1991

In this paper, we suggest the exact perturbation analysis(Exact_PA) technique with respect to the buffer storage in tandem queueing networks, through which the optimal buffer storage design problem is considered. The discrete event dynamic equations for the departure time of a customer are presented together with the basic properties of Full Out(FO) and No Input(NI) with respect to the buffer storage. The new perturbation rules with respect to the buffer storage are suggested, from which the exact perturbed path can be obtained. The optimal buffer storage problem is presented by introducing a performance measure consisting of the throughput and the buffer storage cost. An optimization algorithm maximizing this performance measure is derived by using the Exact_PA technique. The proposed perturbation analysis technique and the optimization algorithm are validated by numerical examples.