• 대한전자공학회논문지TC
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• 제44권2호
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• pp.15-21
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• 2007

본 논문에서는 Impulse-radio-based Ultra Wideband (IR-UWB)를 이용한 에너지 검출 기반의 비동기 수신기에서 저사양의 ADC와 간단한 디지털 회로 만으로 이루어진 심벌 동기 획득(acquisition) 및 심벌 동기 추적(tracking) 방식을 제안한다. 기존의 심벌 동기 방식이 정확한 심벌 동기 '시점을 찾는 것에 초점을 맞추었다면, 제안하는 방식은 심벌 동기 '구간'을 찾아 그 구간 내에서 데이터를 판단함으로써 하드웨어 복잡성을 낮추었고, 전력 소모를 줄였다. 이를 위해 심벌 동기 구간에 해당하는 BDW (Bit Decision Window)를 정의하고 SNR(Signal to Noise Ratio), 하드웨어 자원 및 BDW의 크기와 BER (Bit Error Rate)와의 관계를 분석하였다. 주어진 SNR과 하드웨어 자원으로 BER을 최소화하기 위한 BDW의 크기를 구한다. 제안한 알고리즘은 실제 임펄스 채널 특성을 고려하여 모의실험을 통하여 검증하였다.

• Journal of Biosystems Engineering
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• 제33권5호
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• pp.317-325
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• 2008

The electrocardiogram (ECG) measurement system consists of I/O interface to input the ECG signals from two electrodes, FPGA (Field programmable gate arrays) module to process the signal conditioning, and real time module to control the system. The algorithms based on wavelet transform were developed to remove the noise of the ECG signals and to determine the QRS-waves. Triangular wave tests were conducted to determine the optimal factors of the wavelet filter by analyzing the SNRs (signal to noise ratios) and RMSEs (root mean square errors). The hybrid rule, soft method, and symlets of order 5 were selected as thresholding rule, thresholding method, and mother wavelet, respectively. The developed wavelet filter showed good performance to remove the noise of the triangular waves with 10.98 dB of SNR and 0.140 mV of RMSE. The ECG signals from a total of 6 subjects were measured at different measuring postures such as lying, sitting, and standing. The durations of QRS-waves, the amplitudes of R-waves, the intervals of RR-waves were analyzed by using the finite impulse response (FIR) filter and the developed wavelet filter. The wavelet filter showed good performance to determine the features of QRS-waves, but the FIR filter had some problems to detect the peaks of Q and S waves. The measuring postures affected accuracy and precision of the ECG signals. The noises of the ECG signals were increased due to the movement of the subject during measurement. The results showed that the wavelet filter was a useful tool to remove the noise of the ECG signals and to determine the features of the QRS-waves.

• 한국정보통신학회논문지
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• 제5권5호
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• pp.892-901
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• 2001

유성 버스트 통신로는 재래식 무선 경로에 비해 많은 장점이 있는데도 그 도통율이 수%이 하로 적기 때문에 일반 상용 통신망에는 아직 넓게 이용되지 못하고 있다 이러한 수분의 일초이하의 짧은 시간에 발생하는 버스트를 통해서 가능한 한 많은 데이터 량을 전송하려면 특별히 개발된 정교한 통신 프로토콜이 필요하다. 이 논문은 통제국이 주기적인 탐색신호를 송출함으로서 버스트를 효과적으로 탐지하고 신속 히 포착하며 이 버스트가 존속하는 짧은 시간에 이 버스트를 통해서 가능한 한 많은 량의 데이터를 전송할 수 있도록 하는 통신 프로토콜을 소개한다. 각 단계의 처리 시간을 해석하여 버스트의 여러 가지 길이에 따라 메시지를 최소한의 지연으로 전송할 수 있는 최적합한 데이터 패킷의 길이를 도출한다. 이 해석결과 에 따라 버스트의 평균 지속시간을 분석하여 최적합한 패킷길이를 도출하는 루틴을 개발하고, 이것을 사용함으로서 주워진 시간에 가능한 한 많은 메시지를 전송할 수 있도록 하는 유성 버스트 통신로를 위한 프로토콜을 제안한다.

• 한국ITS학회 논문지
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• 제16권6호
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• pp.42-52
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• 2017

본 연구는 대전광역시 중구에 위치한 대고오거리와 성모오거리를 대상으로 회전교차로 도입 시 나타나는 효과에 대하여 미시적 교통시뮬레이션 프로그램인 VISSIM을 이용하여 분석하였다. 분석결과 기존 교차로의 구간 별 평균 통행속도는 31.51km/h로 분석되었으며, 평균 지체시간은 32.5초로 분석되었다. 대고오거리만 회전교차로로 전환시 평균 통행속도 35.04km/h, 평균 지체시간 24.5초로 분석되었고, 성모오거리만 회전교차로로 전환될시 구간별 평균 통행속도는 34.79km/h, 지점별 평균 지체시간은 28.0초로 분석되었다. 마지막으로 대상지 2개 지점을 쌍구형 회전교차로로 전환 될 시의 구간 별 평균 통행속도는 38.62km/h, 지점별 평균 지체시간은 20.4초로 분석되었다. 이와 같이 두 개 교차로를 각각 회전교차로로 전환하는 시나리오에서 지체시간이 감소하는 것으로 나타났고, 두 개 지점을 모두 회전교차로로 연결하는 쌍구형 회전교차로 전환시 지체시간이 가장 적게 나타나 기존 교차로에 비해 효율적이라고 판단되었다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.1511-1516
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• 2011

The maintenance of the turnout is composed of signal field and track field on business, the electrical and mechanical field on system. adjustment and maintenance carry forward through coordination with these fields. In the case of turnout equipment used in a first phase of Seoul-Busan high-speed train, it is treated by classifying as mechanical adjustments and electrical adjustments. Mechanical adjustment is conducted with focus on fine adjustment to meet maintenance standards limits(1mm or less) about interval of basic rail and tongue rail about each part of track transition equipment. This refers to mechanical adjustments performed mainly with physical changes and movement characteristics between basic rail and tongue rail by considering the overall environment surrounding track side of section installed track transition equipment. However, these series of maintenance are conducted in state that high-speed train is not in the process from 1 am to 4 am at night, but common workers for maintenance are not familiar with the operation and checking about various situation, and the workers are even insufficient. Maintenance training using mixed reality is conducted in the place of business, we tried to overcome several problems of safety and time reduction through this training.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1999년도 학술발표대회 논문집 제18권 2호
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• pp.131-134
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• 1999

This paper considers the acoustical characteristics of the mechanical valve employed in the Korean type Artificial Heart. $Bj\"{o}rk-Shiley$ tilting disc valve was chosen for the study and acoustic measurements were performed for the artificial heart operated in a mock circulation system as well as implanted to an animal as a Bi Ventricular Assist Device (BVAD). In the mock system, three different conditions of the valve were examined which were normal, damaged (torn off), pseudothrombus attached. Microphone measurements for the BVAD were carried out at a regular time interval for 5 days after the implantation operation. Of the recorded acoustic emissions from the artificial heart, click sounds mainly originated from the valves were further analyzed using Multiple Signal Classification (MUSIC) for estimating their spectral properties. It was shown that the spectral peaks below 4 kHz and the optimal order number for MUSIC, equivalent to the number of the spectral component, might be the key parameters which were highly correlated to the physiological states of the valve like the mechanical damage of the valve or the formation of thrombus on the valves.

• 대한전자공학회논문지
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• 제20권2호
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• pp.35-40
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• 1983

본 논문에서는 PCM/FM시스템에 대한 비트(bit)오차 확률식을 구하여 이를 수치적으로 계산하여 검토를 행했다. 변조전 필터를 거친 NRZ-L 이진 펄스예을 변조 신호로 하여 반송파를 주파수 변조하였고, 리미터와 변별기를 검출기로 이용하였다. RF 스펙트럼의 제한과 비트 오차 확률의 감소면에서 볼 때, 주파수 편이화 h를 3WT가 되도록 설계하는 것이 적당함을 알 수 있었다. 여기서 W는 변조전 필터의 대역폭이고 T는 한 비트당 시간 간폭이다.

• 말소리와 음성과학
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• 제2권3호
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• pp.141-148
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• 2010

In this paper, voice activity detection (VAD) for dual-channel noisy speech recognition is proposed in which spatial cues are employed. In the proposed method, a probability model for speech presence/absence is constructed using spatial cues obtained from dual-channel input signal, and a speech activity interval is detected through this probability model. In particular, spatial cues are composed of interaural time differences and interaural level differences of dual-channel speech signals, and the probability model for speech presence/absence is based on a Gaussian kernel density. In order to evaluate the performance of the proposed VAD method, speech recognition is performed for speech segments that only include speech intervals detected by the proposed VAD method. The performance of the proposed method is compared with those of several methods such as an SNR-based method, a direction of arrival (DOA) based method, and a phase vector based method. It is shown from the speech recognition experiments that the proposed method outperforms conventional methods by providing relative word error rates reductions of 11.68%, 41.92%, and 10.15% compared with SNR-based, DOA-based, and phase vector based method, respectively.

• 대한산업공학회지
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• 제31권1호
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• pp.87-98
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• 2005

This research investigates economic-statistical characteristics of variable sampling size and interval (VSSI)$\bar{X}$charts under two assignable causes. A Markov chain approach is employed in order to calculate average run length (ARL) and average time to signal (ATS). Six transient states are derived by carefully defining the state. A steady state cost rate function is constructed based on Lorenzen and Vance(1986) model. The cost rate function is optimized with respect to six design parameters for designing the VSSI $\bar{X}$ charts. Computational experiments show that the VSSI $\bar{X}$ chart is superior to the Shewhart $\bar{X}$ chart in the economic-statistical sense, even under two assignable causes. A comparative study shows that the cost rate may increase up to almost 30% by overlooking the second cause. Critical input parameters are also derived from a sensitivity study and a few guideline graphs are provided for determining the design parameters.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.327-330
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• 2006

With the increasing requirements for the survey and development of the ocean, the demands on the of AUV(Autonomous Underwater Vehicle) technologies have been increased. Reconstruction and replay of the AUV motion on the basis of the data stored during the execution of mission, can help the development of control strategies for AUVs such as mission planning and control algorithms. While an AUV cruises for her mission, her attitude and position data are is recorded. The data can be used for visualization of the motion in off-line. However, because most of the position data gathered from acoustic sensors have long time-interval and include intermittent faulty signal, the replayed motion by the graphic simulator can not demonstrate the motion as a smooth movie. In this paper, interpolation methods are surveyed to reconstruct the AUV position data. Then, an efficient 3D visualization method for AUV motion using the interpolation method is proposed. Simulation results arc also included to verify the proposed method.