• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.97-98
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• 2008

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.127-128
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• 2008

• Journal of Astronomy and Space Sciences
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• v.27 no.2
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• pp.129-134
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• 2010

Rain attenuation can cause a serious problem that an availability of space communication link on Ka band becomes low. To reduce the effect of rain attenuation on the error performance of space communications in Ka band, an adaptive coding and modulation (ACM) scheme is required. In this paper, to achieve a reliable telemetry data transmission, we propose an adaptive coding and modulation level using turbo code recommended by the consultative committee for space data systems (CCSDS) and various modulation methods (QPSK, 8PSK, 4+12 APSK, and 4+12+16 APSK) adopted in the digital video broadcasting-satellite2 (DVB-S2).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.229-232
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• 1997

A free space transmission method using standard gain horn antennas in the frequency range from 9.0 to 10.5GHz is applied to determine the dielectric properties of grain such as rough rice, brown rife and barley. The dielectric constant and loss factor, which depend on the moisture content of the wetted grain are obtained from the measured attenuation and phase shift by vector network analyzer. The effect of density fluctuation, which is an important parameter governing the dielectric properties of grain, on the dielectric constant and loss factor is presented. A new density-independent model in terms of measured attenuation and moisture density is proposed for reducing the effects of density fluctuation on the moisture content measurement.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.346-349
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• 1994

This paper is concerned with a motion control of a manipulator under parametric uncertainties and external disturbances. The parametric uncertainties are regarded as internally generated disturbances in the manipulator. Based on this idea, we formulate a model reference control problem with desired disturbance attenuation. The solution of this control problem not only reduces the worst-case effect on tracking error due to internal and external disturbances (combined disturbances) as much as possible, but also achieve optimal tracking when perturbations are absent. In order to solve the control problem which is formulated in this paper we reduce it to a constrained minmax cost control problem. A differential game theory is used to treat this constrained minmax cost control problem. The differential game theory leads to a sufficient condition for the global solvability of the model reference control problem with desired disturbance attenuation.

• Journal of Magnetics
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• v.20 no.4
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• pp.421-426
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• 2015

This paper presents a practical method for estimation of average temperature in the permanent magnet (PM) of electric machine by using finite element analysis (FEA) and dynamo load experiment. First of all, the temperature effect of PM to the torque has been employed by FEA in order to evaluate the Temperature-Torque characteristic curve. The 1st order polynomial equation which is torque attenuation coefficient is derived by the FEA result of the Temperature-Torque curve. Next, torque saturation test with constant current condition is performed by dynamo load experiment. Then, the temperature trend can be estimated by adding the initial starting temperature using the torque attenuation coefficient and torque saturation curve. Lastly, estimated temperature is validated by infrared thermometer which measures temperature of PM surface. The comparison between the estimated result and experimental result gives a good agreement within a deviation of maximum $8^{\circ}C$.

• Journal of Power System Engineering
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• v.17 no.2
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• pp.121-127
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• 2013

The air spring is used widely because of the easy change of spring constant, and, a superior vibration and shock insulation performance. Among the apparatus using the merits of that, the air spring connected an auxiliary chamber has been developed and used as a component of suspension system for an automobile and a railroad car. The purpose of this study is to suggest a design method reflecting heat transfer effect for an air spring system connected auxiliary chamber. In order to do so, this study investigates change of reaction force along with variations in heat transfer coefficient, and, analyzes an effectiveness of a heat transfer characteristics of an auxiliary chamber for external force attenuation characteristics and impedance characteristics of an air spring connected an auxiliary chamber.

• Journal of the Korean Society for Nondestructive Testing
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• v.3 no.1
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• pp.19-25
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• 1983

Some studies have been made on the effects of the attenuation on the result of ultrasonic examination of austenitic stainless steel weldment and also on the cause of false indications. The differences in the amplitudes and the metal paths of the ultrasonic examinations have been measured experimentally, for two kinds of waves, one passed through only the parent material and the other one through the weldment. The effect of probe angles and frequency on the examination data have been investigated using the shear wave. It has been found that the false indications were caused by back reflection from the weld metal surface due to the characteristics of ultrasonic wave propagation. It has been confirmed that the probe of $2.25\;MHz\;and\;60^{\circ}$ is the best choice in the ultrasonic examination and that the correction of amplitude for attenuations is necessary.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.9
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• pp.1375-1380
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• 1989

Mobility reduction parameters are extracted using a method based on the exploitatiion of Id-Vg and Gm-Vg characteristics of short channel n-MOSFETs in strong inversion region at room temperature. It is found that the reduction of the maximum field effect mobility, \ulcornerFE,max, with the channel length is due to i) the difference between the threshold voltage and the gate voltage which corresponds to the maximum transconductance, and ii) the channel length dependence of the mobility attenuation coefficient, \ulcorner The low field mobility, \ulcorner, is found to be independent of the channel length down to 0.25 \ulcorner ofeffective channel length. Also, the channel length reduction, -I, the mobility attenuation coefficient, \ulcorner the threshold voltage, Vt, and the source-drain resistance, Rsd, are determined from the Id-Vg and -gm-Vg characteristics n-MOSFETs.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.389-394
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• 1994

The lattice filter formed transfer function has the advantage of computer simulation in the analysis of muffler. The transfer function is derived by using z-transformation for perforated elements in through-flow, cross-flow and reverse-flow type. A computer program for the prediction of the performance of automotive mufflers is developed using the transfer functions for uniform tube, open termination, expansion element, perforated elements, etc. The analytical results are verified by comparing with the experimental results for the transmission loss of a muffer. The effect of geometric configuration change of the muffler was invesigated in order to improve the performance of noise attenuation.