• 한국광학회:학술대회논문집
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• 한국광학회 2006년도 동계학술발표회 논문집
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• pp.373-374
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• 2006

This paper physically demonstrates that our proposed method improves the Signal-to-Noise Ratio (SNR) of significantly increase the number of acceptable optical signals in PON(Passive Optical Network) systems. This method reduced Optical Beat Interference(OBI) by using CDMA.

• Wind and Structures
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• 제29권1호
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• pp.1-13
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• 2019

A numerical investigation on forces and flow around three square cylinders in side-by-side arrangement is conducted at a Reynolds number Re = 150 with the cylinder center-to-center spacing ratio L/W = 1.1 ~ 9.0, where W is the cylinder side width. The flowat this Re is assumed to be two-dimensional, incompressible, and Newtonian. The flow simulation is conducted by using ANSYS-Fluent. The flow around the three side-by-side cylinders entails some novel flow physics, involving the interaction between the gap and free-stream side flows as well as that between the two gap flows. An increase in L/W from 1.1 to 9.0 leads to five distinct flow regimes, viz., base-bleed flow (L/W < 1.4), flip-flopping flow (1.4 < L/W < 2.1), symmetrically biased beat flow (2.1 < L/W < 2.6), non-biased beat flow (2.6 < L/W < 7.25) and weak interaction flow (7.25 < L/W < 9.0). The gap flow behaviors, time-averaged and fluctuating fluid forces, time-averaged pressure, recirculation bubble, formation length, and wake width in each flow regime are discussed in detail.

• 대한의용생체공학회:의공학회지
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• 제20권3호
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• pp.299-305
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• 1999

본 연구에서는 잡음이 포함된 심전도 신호로부터 진단 파라미터 추출을 위한 대표 비트 설정에 관한 알고리즘들을 비교 분석하였다. 사용된 알고리즘들은 중앙 집중치를 계산하기 위하여 사용되는 방법들로써 산술평균, 중앙값 , 최빈값 ; 절사 평균을 이용하였다. 첨가된 잡음들은 심전도 신호에서 자주 발생되는 근전도 잡음, 60Hz 전원잡음, 급작성 기저선 변동 , 호흡에 의한 기저선 변동을 제한시켰고 각각의 잡음들이 첨가되었을 때의 신호대 잡음비를 계산하였다. 연구 결과, 신호 평균화 방법은 근전도 잡음이 포함되었을 때 신호 대 잡음비가 가장 높았으며, 중앙값 , 최빈값 , 절사 평균을 이용하는 방법들은 급작성 기저선 변동과 같이 입력 신호에 극단값이 존재할 때 높은 신호 대 잡음비를 가지고 있다. 특히 호흡에 의한 기저선 변동 잡음이 포함된 경우에는 절사 평균을 이용하여 설정된 대표 비트의 ST 레벨 변화가 0 V 로써 가장 효율적이었다.

• 한국전자파학회논문지
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• 제11권2호
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• pp.302-312
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• 2000

8-VSB(Vestigial Side- Band) 변조 기술을 이용하여 ATSC(Advanced Television Systems Committee) 규격을 만족하늑 디지털 TV 듀너를 개발하였다. 이중(double) 주파수 변환 방식 및 능동 트래킹 여파기를 이용하여 이미지 응답 및 IF(Intermediate Frequency) Beat성분들의 억압, 인접 채널과 다채널 수신 시 상호 간섭배제 성능올 만족한 수 있도록 하였다. 제작된 디지털 TV 튜너는 디지털 성능 평가에 필수적인 넓은 동작 범위, 통과 대역에서의 평탄도 및 낮은 위상 잡음 성능을 만족할 뿐만 아니라 아날로그 및 디지털 TV 수선기에 동시에 이용될 수 있다.

• 한국감성과학회:학술대회논문집
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• 한국감성과학회 1999년도 추계학술대회 논문집
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• pp.211-215
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• 1999

It is well known that a long-term exposure to a loud noise environment affects performance, since it distracts attention, and also is able to evoke stress accompanied by negative emotional states. The purpose of this study was to analyze dynamics of subjective and physiological variables during long-lasting (30 min) exposure to intensive white noise (85 dB[A]). Physiological signals on 23 college students were recorded by BIOPAC, Grass Neurodata systems and AcqKnowledge 3.5 software. Autonomic variables, namely skin conductance level (SCL), non-specific SCR number (N-SCR), inter-beat intervals in ECG (RR intervals), heart rate variability index (HF/LF ratio of HRV), respiration rate (RESP), and skin temperature (SKT) were analyzed on 5 min epoch basis. Psychological assessment (subjective rating of stress level) was also repeated on every 5 min basis. Regression and correlation analyses were employed to trace the time course of the dynamics of the subjective and autonomic physiological variables and their relationship. Results showed that intense noise evokes subjective stress with associated autonomic nervous system responses. However, it was shown that physiological variables endure specific changes in the process of exposure to loud white noise. Discussed are probable psychophysiological mechanisms mediating reactivity to long-term auditory stimulation of high intensity.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2009년도 추계학술대회
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• pp.758-761
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• 2009

FM-CW 레이다 시스템에서는 이동 목표물 및 기상 현상 등의 원격탐지를 위하여 각 거리에 따른 변이 주파수 및 추가적인 도플러 스펙트럼의 추정이 필요하다. 이러한 주파수 대역에 따른 신호의 크기는 목표물의 탐지 여부 및 추적을 위한 매우 중요한 파라메터이다. 그러나 레이다 운용환경에서는 매우 큰 크기를 갖는 클러터등의 성분이 효과적으로 제거되지 않는다면 시스템의 성능이 현저히 저하될 수 있다. 즉 레이다 시스템에서의 위상잡음으로 인하여 신호 및 클러터 등이 스펙트럼 영역에서 분산되어 나타나는 경우 클러터 제거뿐만 아니라 추정 주파수에도 심각한 악영향을 미치게 된다. 본 논문에서는 이러한 위상잡음이 목표물 정보 추출을 위한 주파수 추정에 미치는 영향을 분석하였다.

• 한국소음진동공학회논문집
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• 제25권12호
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• pp.874-880
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• 2015

This paper presents the vibration analysis of a deploying beam with spin when the beam has a time-dependent spinning speed. In the previous studies for the deploying beams with spin, the spinning speed was time-independent. However, it is more reasonable to consider the time-dependent spinning speed. The present study introduces the time-dependent spinning speed in the modeling. The Euler-Bernoulli beam theory and von Karman nonlinear strain theory are used together to derive the equations of motion. After the equations of motion are transformed into the weak forms, the weak forms are discretized. The natural frequency and dynamic response are obtained. The effect of the time-dependent spinning speed on the dynamic response is studied.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.836-841
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• 2002

The nonlinear vibration of moving viscoelastic belts excited by the eccentricity of pulleys is investigated through experimental and analytical methods. Laboratory measurements demonstrate the nonlinearities in the responses of the belt, particularly in the resonance region and with the variation of tension. The measurements of the belt motion were made using a noncontact laser sensor Jump and hysteresis phenomenon are observed experimentally and are studied with a model which considers the nonlinear relation of belt stretch. An ordinary differential equation is derived as a working form of the belt equation of motion. Numerical results show good agreements with the experimental observations, which demonstrates the nonlinearity of viscoelastic moving belts

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.779-783
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• 2012

The gas compressor is one of the important machine in the petrochemical industry. It is likely to have high vibration problems due to having large reaction source and structural characteristic. In this paper we analyze the cause of high vibration in the reciprocating compressor and present a solution to this problems. By performing this case study, we confirm the effectiveness of vibration reduction through excitation source changes.

• Journal of the Optical Society of Korea
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• 제17권6호
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• pp.471-480
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• 2013

The beating of two or more lasers that have the same or a finite difference in the central frequencies, is the main source of noise in spectral amplitude coding optical code division multiple access (SAC OCDMA) systems. In this paper we adopt a spatial multiplexing (SM) scheme for SAC OCDMA systems to mitigate this beat noise. The results show that for different code weights and different data rates SM SAC can support a larger number of users than the conventional SAC for all different laser source configurations. However, SM SAC requires a more complex system than the conventional SAC, and almost twice as much optical component.