• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.77-80
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• 1999

This paper deals with a design of a symbol timing recovery circuit of QAM using the interpolation in AWGN channel. To reduce timing jitter and the amount of processing data, we employ MGA (Modified Gardner Algorithm) as a symbol timing error detector which is called NDA(Nondecision Directed Algorithm). We show the characteristics (S-curve and the variance) of timing error detector with the roll-off factor of a shaping filter, which are compared with GA. Also, we compare the BER curve of interpolation method with that of ideal case. The performance of the STR is shown to be close to that of ideal case. This result shows that this method can be useful to implement symbol timing recovery circuit for multi-level modulation.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.613-616
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• 2003

This paper describes the design and implementation of wideband 360$^{\circ}$ phase shifter by using I/Q vector method. One of four quadrants was selected by a switching operation and the desired phase value was obtained by varying attenuation level of attenuator located in I/Q path. The minimum phase RMS error of 3.6$^{\circ}$ and the maximum phase RMS error of 25.2$^{\circ}$ were measured over 6~180Hz frequency range. Those characteristics are good enough for the requirement of ECM radar equipment. The phase values can be adjusted by control module.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.646-649
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• 2007

Although the up-to-date(high) technique is developing and automating in many fields, the center of the all fields is closely connected with the human resource. Also, the railway driver is required to have both high technique and high level of mental work. Therefore, this research will grasp the types of the railway driver groups through railway driver's task stress analyze(JCQ and Job Content Questionnaire), and then analyze the human errors which the types can occur. Finally, this research will propose the way to reduce the human errors.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.736-741
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• 2004

In high-capacity disk drives with ever-growing track density, the allowable level of position error signal (PES) is becoming smaller and smaller. In order to achieve the high TPI disk drive, it is necessary to improve the writing accuracy during the STW(servo track writing) process through the reduction of TMR sources. Among the main contributors of the NRRO(Non-Repeatable Run-out) PES, the disk vibration and the HSA(head-stack assembly) vibration is considered to be one of the most significant factors. Also the most contributors of RRO(Repeatable Run- out) come from the contributors of NRRO which is written-in at the time of STW(servo track writing) process. In this paper, the experimental test result shows that the effect of NRRO on servo written-in RRO effectively can be reduced through a STW process under low dense medium condition such as semi-vacuum.

• IEIE Transactions on Smart Processing and Computing
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• v.3 no.2
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• pp.83-87
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• 2014

This paper introduces a refined opportunistic interference alignment (OIA) technique that uses minimum mean square error (MMSE) detection at the receivers in multiple-input multiple-output multi-cell uplink networks. In the OIA scheme under consideration, each user performs the optimal transmit beamforming and power control to minimize the level of interference generated to the other-cell base stations, as in the conventional energy-efficient OIA. The result showed that owing to the enhanced receiver structure, the OIA scheme shows much higher sum-rates than those of the conventional OIA with zero-forcing detection for all signal-to-noise ratio regions.

• 한국정보통신설비학회:학술대회논문집
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• 2006.08a
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• pp.53-56
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• 2006

WiBro service provider have made an effort to provide the subscriber's location and have deployed LBS system using cell-ID method. Cell-ID method has a location error problem if repeater is used on the other cell places at the same time. We introduce and analysis LMU(Location Measurement Unit) on the repeater fer location detection of subscriber which is serviced via the repeater. In this paper we propose the method using LMU on the repeater to avoid these location errors and to provide more exact location to the subscriber. we can conclude that the location error can be more exact at the building which uses repeater. It represents in which level the subscriber is serviced at the building.

• Fibers and Polymers
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• v.6 no.4
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• pp.348-354
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• 2005

These days consumers' various demands are accelerating research on apparel manufacturing system including automatic measurement, pattern generation, and clothing simulation. Accordingly, methods of reconstructing human body from point-clouds measured using a three dimensional scanning device are required for apparel CAD system to support these functions. In particular, we present in this study a human body reconstruction method focused on two issues, which are the decision of the number of control point for each sectional curve with error bound and the local knot removal for reducing the unusual concentration of control points. The approximation of sectional curves with error bounds as an approximation criterion leads all sectional curves to their own particular shapes apart from the number of control points. In addition, the application of the local knot removal to construction of human body sectional curves reduces the unusual concentration of control points effectively. The results may be used to produce an apparel CAD system as an automatic pattern generation system and a clothing simulation system through the low level control of NUBS or NURBS.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.262-267
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• 2001

In this study, the Reliability of degraded steam turbine blade was evaluated using the limited fatigue data. The statistical estimation of limited fatigue data implies that some unknown uncertainties which may be involved in fatigue reliability analysis. Therefore, an appropriate distribution in the fatigue strength was determined by the characteristic distribution - linear correlation coefficient, fatigue physics, error parameter. 3-parameter Weibull distribution is the most appropriate distribution to assume for infinite region. The load applied on the blade is mainly tensile. The maximum Von-Mises stress is 219.4 MPa at the steady state service condition. The failure probability($F_p$) derived from the strength-stress interference model using Monte carlo simulation under variable service condition is 0.25% at the 99.99% confidence level.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1772-1774
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• 2002

Because the overhead transmission lines are exposed to the outdoor weather, the faults of the transmission lines are due to natural conditions, and among these faults, the outage rate by lightning is about 50%. The lightning causes the damage of power system equipments, the shut down of electricity and the electro-magnetic interference. To study the basic research of the lightning parameters for power system operation, LPATS-III (Lightning Positioning and Tracking System) has been introduced since 1995 in Korea. This paper describes the inspection result about location information error and the statistical distribution of lightning current.

• Journal of Biomedical Engineering Research
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• v.5 no.2
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• pp.133-142
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• 1984

The EMG signal can be considered as a signal source that expresses the intention of man because it is a electrical signal generated when the man contracts muscles. For proportional control of prostheses, the control signal proportional to the mousle contraction level must be estimated. Typically a foul-wave rectifier and low-pass filter are used to estimate the proportional control signal from the EMG signal. In this paper, it is proposed to use a logarithmic transformation and a linear minimum mean square error estimator. A logarithmic transformation maps the myoelectric signal into an additive control signal-plus-noise domain and the Kalman filter is used to estimate the control signal as a linear minimum mean square error estimator. The performance of this estimator is verified by the computer simulation and the estimator is applied to the EMG obtained from the biceps brachii muscle of normal subjects.