• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.4
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• pp.16-21
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• 2011

This paper described an analysis of dynamic mechanism for the industrial two-step folding automatic door using commercial software packages. Two modeling types of operating on the guide rail, the sliding one and the rolling, were adopted to investigate effects of impact force when the door ascends the guide rail. The magnitude of impact force was found very peaklike large over an initial duration of the door's moving up. The amount of damping coefficient for alleviating this shock was controlled to such a moderate degree that the operating conditions can be obtained for the purpose of design. Moreover the behavior of both dynamic stress and deformation were observed for acquirement of structural reliabilities of the combined guide rail and rolling mechanism. This research will be a very useful tool in the near future for the dynamic analysis of the multi-step folding automatic door.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.812-817
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• 2004

Recently drastic improvement of railway technology has been accompanied by the construction of very high-speed tracks. It should be noticed that Continuously Welded Rail(CWR) has played significant role in technical development of railway and that installation of CWR is now being scheduled on existing lines as well as newly-built lines. In general, interaction between CWR and bridge deck takes place on bridge section and additional axial force and displacement is to be developed owing to temperature and braking/acceleration forces. This interaction is known to be mainly governed by span organizations and arrangements of foot bearings. In common practice, movable bearing is stationed and designed on the assumption that it is not able to transfer the horizontal force of upper decks. However, it is well known that horizontal resistance is developed in movable bearings due to friction and that friction coefficient of movable bearing is ranged from 0.03 to 0.20 depending on the material of bearings and magnitude of reactions. Therefore, it is easily reasoned out that friction of movable bearing can influence the mutual behavior of CWR and bridge decks. Suggested in this study is to investigate the validity and efficiency of friction effect of movable bearings in controlling the axial force and displacement of CWR on continuous railway bridges.

• Proceedings of the Korea Information Processing Society Conference
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• 2020.05a
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• pp.368-371
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• 2020

반도체 제조시설의 효율성을 위해 대부분의 현장에서는 물류 자동화 시스템 (AMHS, Automated Material Handling System)을 도입하여 운영하고 있다. OHT(Overhead Hoist Transfer)는 반도체 공정에서 주로 활용되는 Monorail 컨베이어 형태의 자동 반송 시스템의 일종으로 작업물을 들고 제조라인 위에 설치된 레일을 따라 자율적으로 이동하는 방식으로 운영된다. 도체 물류 시스템의 계층적인 구조적 특징과 고가의 재료를 다루고, 외부유출이 어려운 실제 공정 현장, 실험 환경의 시간, 공간적 구축 등의 현실적 특징 때문에 반도체 제조 공정의 자동화 물류시스템에 대한 모델링 및 시뮬레이션을 통한 연구의 필요성이 대두되고 있다. 본 논문에서는 OHT를 효율적으로 제어하기 위해 DEVS(Discrete Event System Specifications) 형식론을 기반으로 OHT 시스템 모델링 및 시뮬레이션 설계 방법을 제안한다. 이를 위해 반도체 제조 시스템의 전반적인 물류 과정에 대해 분석하고, DEVS 형식론에 대해 연구하며, 이를 바탕으로 반도체 물류 시스템을 위한 모델링 및 시뮬레이션을 설계하였으면, 실험을 통해 제안된 모델리 반도체 물류 시스템 시뮬레이션을 수행할 수 있음을 보인다.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.2
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• pp.309-316
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• 2019

In this paper, a low-jitter delay-locked loop that compensates for local clock skew is presented. The proposed DLL consists of a phase splitter, a phase detector(PD), a charge pump, a bias generator, a voltage-controlled delay line(VCDL), and a level converter. The VCDL uses self-biased delay cells using current mode logic(CML) to have insensitive characteristics to temperature and supply noises. The phase splitter generates two reference clocks which are used as the differential inputs of the VCDL. The PD uses the only single clock from the phase splitter because the PD in the proposed circuit uses CMOS logic that consumes less power compared to CML. Therefore, the output of the VCDL is also converted to the rail-to-rail signal by the level converter for the PD as well as the local clock distribution circuit. The proposed circuit has been designed with a $0.13-{\mu}m$ CMOS process. A global CLK with a frequency of 1-GHz is externally applied to the circuit. As a result, after about 19 cycles, the proposed DLL is locked at a point that the control voltage is 597.83mV with the jitter of 1.05ps.

• Journal of The Korean Society For Urban Railway
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• v.6 no.4
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• pp.249-257
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• 2018

The number of deaths for railway traffic accidents is mainly caused by working close to the track, or when unauthorized passage pass through the track. The safety fences are being used to ensure safety for workers close to the track, and to improve the efficiency of the work, without interfering with the passage of trains. However, a safety fence for railway tracks needs to be examined to see if it will interfere with the passage of trains. The purpose of this study is to analyze the safe distance between train and safety fence developed in Korea. In addition, the lateral load condition of wind pressure by trains is estimated and numerical analysis is carried out according to the installation intervals of railway safety fences. It has been confirmed that the proper spacing between the train and the railway safety fence should be at least 200 mm from the vehicle limit, and that the proper spacing of railway safety fence must be calculated in consideration of the wind pressure by trains.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.4
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• pp.148-156
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• 2009

This paper presents a new image rejection algorithm based on the analysis of the distortion of a single-frequency continuous-wave (CW) signal due to the I/Q mismatch. Existing methods estimated the gain mismatch and phase mismatch on RF receivers and compensated them However, this paper shows that the circular trajectory of a single-frequency CW signal is distorted elliptic-type trajectory due to the I/Q mismatch. Utilizing the analysis, we propose a I/Q mismatch compensation method. It has two processing steps. In the first processing step, the generated signal is rotated to align the major axis of the elliptic-type trajectory diagram with the x-axis. In the second processing step, the Q-channel signal in the regenerated signal is scaled to align the regenerated signal with the transmitted single-frequency CW signal. Simulation results show that a receiver using the proposed image rejection algorithm can achieve an image rejection ratio of more than 70dB. And, simulation results show that the bit error rate performances of receivers using the proposed image rejection algorithm are almost the same as those of conventional coherent demodulators, even in fading channels.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.9
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• pp.115-124
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• 2004

This paper proposes a high efficient and low power FIR filter chip for partial-response maximum likelihood (PRML) disk drive read channels; it is a 6-bit, 8-tap digital FIR filter. The proposed filter employs a parallel processing architecture and consists of 4 pipeline stages. It uses the modified Booth algorithm for multiplication and compressor logic for addition. CMOS pass-transistor logic is used for low power consumption and single-rail logic is used to reduce the chip area. The proposed filter is actually implemented and the chip dissipates 120mV at 100MHz, uses a 3.3V power supply and occupies 1.88 ${\times}$ 1.38 $\textrm{mm}^2$. The implemented filter requires approximately 11.7% less power compared with the existing architectures that use the similar technology.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.7
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• pp.648-656
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• 2009

We perform an analysis of the characteristics of the time-reversal pulse in Rayleigh or Ricean fading channel environments. We verify it by using Monte Carlo simulation. In a time-reversal system, each antenna in the time-reversal array receives signals from the transmitter and reverse the received signal in the time axis and then resend it to the original transmitter. We assume that the channel characteristics varies very slowly and the spatial separation between the antennas is not large. Hence the signals received by each antenna are correlated. In this paper, the effect of the correlation on the time-reversed pulse is examined, which includes the spatial properties of the time-reversal pulse such as the focus size, and spatial power distribution.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.11
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• pp.1371-1379
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• 2012

This paper presents a method for estimating the contribution of vibration sources in gasoline direct injection engine parts with a multiple-input system. A partial coherence function was used to identify the cause of the linear dependence indicated by an ordinary coherence function. To apply the partial coherence function to vibration source identification in the powertrain system of a gasoline direct injection engine, a virtual model of a two-input and single-output system is simulated. For the validation of this model, the vibration of the powertrain parts was measured by using triaxial accelerometers attached to the selected vibration sources-a high-pressure pump, fuel rail, injector, and pressure sensor. After calculating the partial coherence between each source based on the virtual model, the vibration contribution of the powertrain system is calculated. This virtual model based on the partial coherence function is implemented to determine the quantitative vibration contribution of each powertrain part.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9A
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• pp.749-754
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• 2005

It is well-known that mobile communication systems are usually limited in their performance and capacity by three major impairments, which are multipath fading, delay spread and co-channel interference (CCI). OFDMA (OFDM-FDMA) system can cope with the multipath fading and delay spread easily due to the beneficial properties of OmM technology. Though OFDMA scheme avoids intra-cell interference using the orthogonality among subcarriers, the scheme contains difficulty of reducing co-channel interference. Therefore, in this paper, adaptive antenna techniques are deployed into OFDMA/TDD system to minimize the co-channel interference induced by adjacent cells and to enhance the uplink performance. For the improvement of downlink performance, we apply TxAA (Transmit Adaptive Array), a kind of transmit diversity technique, utilizing preamble symbols for training antenna may into OFDMA/TDD transmitter side. Simulation results show that the uplink and downlink performance under multipath Rayleigh fading channel improved 9dB and 7dB each compared with the case of single antenna system at target BER $10^{-3}$ .