• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.1 no.2
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• pp.70-73
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• 1987

This paper itltroduces a simple stair-case PWM using the pseudo-sinusoidal method. In a configuration of controller, the value of sine as a fundamental factor divided into stair-case level and the three-phase PWM inverter is composed by digital compound for each value of stair-case level. The three-phase output pulse at a fixed carrier frequency and a variable reference frequency is obtained under the effect of reduced harmonics. In this experiment, using the power FET as the switching device, 0.5 H.P. induction motor operation is performed when the switching frequency is 20KHz.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.285-291
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• 2003

An experimental method to measure Q-parameter in-situ is described. The basic idea comes from the fact that the side necking near a crack tip indicates the loss of stress triaxiality, which can be scaled by Q. From the out-of-plane displacement and the in-plane strain near the surface of side necking, stress field averaged through the thickness is calculated and then Q is determined from the difference between the stress field and the HRR field corresponding to the identical J-integral. To prove the validity, three-dimensional finite element analysis has been performed for a CT configuration with side-groove. Q-value which was calculated directly from the near-tip stress field is compared with that determined by simulating the experimental procedure according to the proposed method, that is, the Q-value determined from the lateral displacement and the inplane strain. Also, the effect of location where the displacement and strain are measured is explored.

• Structural Engineering and Mechanics
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• v.9 no.2
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• pp.169-180
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• 2000

An optimization procedure has been prescribed for the minimum weight design of symmetrical parabolic arches subjected to arbitrary loading. The cross section is assumed to be a symmetrical box section with variable depth and flange areas. The webs are unstiffened and have constant thickness. The proposed sequential, iterative search technique determines the optimum geometrical configuration of the parabolic arch which includes the optimum depth profile and the optimum lengths and areas of the required flange plates corresponding to the prescribed number of curtailments. The study shows that the optimum value of rise to span ratio (h/L) of a parabolic arch is maximum at 0.41 for uniformly distributed loading over the entire span. For any other loading, the optimum value of h/L is less than 0.41.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.1150-1155
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• 1990

This paper proposes an optimal redundancy resolution of a kinematically redundant manipulator while considering homotopy classes. The necessary condition derived by minimizing an integral cost criterion results in a second-order differential equation. Also boundary conditions as well as the necessary condition are required to uniquely specify the solution. In the case of a cyclic task, we reformulate the periodic boundary value problem as a two point boundary value problem to find an initial joint velocity as many dimensions as the degrees of redundancy for given initial configuration. Initial conditions which provide desirable solutions are obtained by using the basis of the null projection operator. Finally, we show that the method can be used as a topological lifting method of nonhomotopic extremal solutions and also show the optimal solution with considering the manipulator dynamics.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.4
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• pp.136-142
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• 1996

Automatic monitoring of cutting process is one of the most important technology in machining. AE sensing technology has been applied to monitoring process and proved to be effective in detecting tool abnor- malities such as tool wear and fracture. In this experimental study. AE signals were detected from the tool holder for continuous and interrupted cutting, which obtained from changing workpice material configuration, under control of constant cutting speed from CNC lathe. From statistical and frequency analysis, the AE signals were analyzed to obtaining the characteristics of continuous and interrupted cutting conditions and tool failure. The Kurtosis values decreased but RMS voltages increased as the cutting speed increased, in both continuous and interrupted cutting. RMS voltage is suddenly increased but Kurtosis value is suddenly decreased when tool failure condition. Power spectrum density of AE signals when tool failure reaches extreme value around 0.065 cycles/ .mu. m.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.7
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• pp.832-838
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• 1999

Recently, there are growing concerns about power frequency electric and magnetic fields coming out from the high voltage transmission lines, because of the wide spread perception of their probable harmful effect on human body. In connection with this trend, this paper describes the electric and magnetic fields measurement result around 154 kV and 345 kV transmission lines, a comparison of measured EMF to calculated one and the correlations between transmission lines currents and measured magnetic fields. Daily maximum and minimum magnetic field quantities under the selected 154 kV and 345 kV transmission lines had been measured for 1 year of 1997 and the average value of magnetic field exposure under the lines were calculated and presented based on the measured data.

• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3265-3268
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• 2013

The multi-hydrogen bonded systems with the solvated electrons are investigated at the B3LYP/6-311++$G^{**}$ basis set level. The symmetrical linear geometrical characteristic is common for the dimer systems, while for the tetramer system, the tetrahedron configuration is generated. The NBO charge analyses demonstrate that the multi-hydrogen-multi-electron (mH-ne) coupling exist in these anion systems, as is supported by the electrostatic potential and the molecular orbital analyses. The positive chemical shift value of the central hydrogen ($H_c$) and the negative chemical shift value of the terminal hydrogen ($H_t$) indicate that the $H_c$ is electronegative while the $H_t$ is electropositive, respectively. Strong coupling between two central hydrogen atoms is demonstrated by the large spin-spin coupling constants. The solvated electron donates significant contributions for the stability of these systems.

• Proceedings of the IEEK Conference
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• 2001.06e
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• pp.189-192
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• 2001

A new configuration of acoustic echo canceler with stepsize predictor and comparator is proposed in this paper. Conventional acoustic echo cancelers using ES(Exponential Step)algorithm has fast convergence speed, but very weak in interference of environment. The proposed stepsize predictor and comparator improve conventional acoustic echo canceler's defects. The Stepsize predictor generates a stepsize value using residual power of error signal. The stepsize comparator selects the stepsize value that is better performance in a acoustic echo canceler using a stepsize decision factor. The Simulation results show superiority of the proposed acoustic echo canceler in environment interference.

• International Journal of High-Rise Buildings
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• v.3 no.2
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• pp.147-154
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• 2014

The purposes of this study were to analyze criteria for measurement chamber design dedicated curtain wall, and how to measure of performance configuration and status of the chamber that is currently being used. Main dealing criteria is AAMA 1503-09. Measurement of data is made in curtain wall Mock-up experiment station with thermal imaging camera. Measurement data using thermal imaging cameras at Mock-up curtain was made at the test site. The results of this study were as follows; There is no U-value test method for actual size of curtain wall. The thermal test outdoor chamber showed heat loss in the connection part of indoor and outdoor chamber. And the indoor chamber showed unstable temperature distribution by height.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.303-304
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• 2014

This paper describes Four Switch Three-Phase Z-Source rectifier with reduced value capacitors. This configuration has some advantages in term of small size of the circuit. The rectifier has buck-boost function by shoot-through state. Also, the rectifier has the advantage of decreasing inrush current in start-up and transient states. In order to reduce harmonics PWM modulation technique with a variable index has been suggested. Four Switch Three-Phase Z-Source rectifier with reduced value capacitors can output stable DC. Principles and dynamics of the system are discussed in detail.