• Journal of the Korean Geosynthetics Society
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• v.11 no.3
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• pp.1-9
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• 2012

If the railways consisting of soil subgrade is applied to repetitive loading, elastic deformation and plastic deformation will occur at the same time. So the repeat traffic loading condition should be considered to predict the long-term deformation on railway roadbed. In this study, laboratory data from the repeated load triaxial tests and cylinder model test were used to predict accumulated settlement on railway foundation and results were analyed based on the nonliear models and stress state considered. It has proposed predict model using power function model on plastic settlement of roadbed materials.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.415-415
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• 2019

본 연구에서는 낙동강 본류에서 10년(2008~2017) 동안 관측된 자료의 월별 평균 자료를 이용하여, DO, BOD, COD의 시공간 변동 및 그 영향인자들과의 상관관계를 분석하였다. 관측소별 수질은 상류에서 하류로 갈수록 나빠졌으며, BOD와 COD는 ST5에서 가장 높았다. 10개 관측소별 수질성분의 상관성을 분석한 결과, DO와 수온의 상관계수는 -0.90 이상이고, BOD와 Chl-a의 상관계수는 0.48~0.85, COD와 TOC의 상관계수는 ST5와 ST10 관측소를 제외하고 0.65 이상이었다. 모든 관측소 자료를 이용한 회귀분석 결과, 수온과 DO는 감소하는 선형함수로서 결정계수는 0.90, chl-a와 BOD는 증가하는 파워함수로서 결정계수는 0.83, TOC와 COD는 증가하는 로그함수로서 결정계수는 0.58 정도이었다. 10개 관측소별 TOC 분해율을 산정한 결과, BOD에 의한 분해율의 평균은 15.5~36.3%, COD에 의한 분해율의 평균은 57.4~89.6%의 범위로 나타났다.

• Journal of the Korean Society for Marine Environment & Energy
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• v.20 no.2
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• pp.91-99
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• 2017

The parametric study was performed for performance enhancement of wave energy converter(WEC) using a submerged pendulum plate. The wave exciting moment and hydrodynamic moment were obtained by means of eigenfunction expansion method based on the linear potential theory, and then the roll response of a pendulum plate and time averaged extracted power were investigated. The optimal PTO damping coefficient was suggested to give optimal extracted power. The peak value of optimal extracted power occurs at the resonant frequency. The resonant peak and it's width increase, as the height and thickness of a pendulum plate increase. The mooring line installed at the end of the pendulum plate is effective for extracting wave energy because it can not only induce the resonance with the waves of the installation site but also increase the restoring moment in case of PTO-on. The WEC using a rolling pendulum plate suitable for the shallow water acts as breakwater as well as energy extraction device.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7A
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• pp.702-708
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• 2006

본 논문에는 초광대역 통신시스템을 위한 주파수 영역의 통계학적 채널 모델을 서술하고 있다. 채널 모렐링은 3개의 사무실 환경, 46개의 송, 수신 위치에서 얻어진 23,000개의 채널응답함수로 부터 얻어졌다. 측정실험을 통해 얻어진 데이터를 바탕으로 주파수 변화에 따른 경로감쇄지수 변화에 대해 서술한 후 전파환경과 가시경로의 존재여부에 따른 수신신호의 확률분포모델을 연구하였다. 마지막으로는 수신된 주파수 톤에 해당하는 수신파워의 표준편차와 같은 통계적 특성들을 고찰하였는데, 가시경로가 존재하는 경우에는 송, 수신기 사이의 거리가 멀어지면서 표준편차 값이 커지고 그에 따라 수신 주파수 톤의 파워가 평균 수신파워에서 일정한 범위 안에 들어올 확률이 떨어지는 것을 알 수 있었다.

• The Journal of the Acoustical Society of Korea
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• v.35 no.2
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• pp.102-109
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• 2016

This paper proposes a noise suppression method through SNR (Singal-to Noise Ratio) estimation in the two microphone array environment of close spacing. The conventional method uses a noise suppression method for a gain function obtained through the SNR estimation based on coherence function from full band. However, this method cause performance decreased by the noise damage that affects all the feature vector component. So, we propose a noise suppression method that allocates a frequency domain signal into N constant multi frequency band and each frequency band gets a gain function through SNR estimation based on coherence function. Performance evaluation of the proposed method is shown by comparison with PESQ (Perceptual Evaluation of Speech Quality) value which is an objective quality evaluation method provided by the ITU-T (International Telecommunications Union Telecommunication).

• The Journal of the Acoustical Society of Korea
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• v.27 no.6
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• pp.271-278
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• 2008

The electro-mechanical characteristics were theoretically analyzed for the wideband ultrasonic transducer made of non-uniform thickness piezoelectric vibrator. This paper proposes a combination of exponential functions which describes the thickness variation along the length of the vibrator to derive the input admittance and power transfer function of the transducer. The bandwidth and the power transfer function of the transducer were investigated while the lateral shape of the vibrator changes. The results showed there is an optimum shape for the wideband characteristics of the transducer, and the bandwidth has increased up to over 100% as the ratio of minimum value of thickness to maximum value decreases. However, the power transfer function had a downward trend as the ratio of thickness decreases. Also we confirmed that even though the value of transfer function increases as the length of the piezoelectric vibrator increases, the shape providing wideband characteristics is very limited. It means that precision processing is required to manufacturing a wideband ultrasonic transducer with high efficiency.

• Journal of Advanced Marine Engineering and Technology
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• v.19 no.3
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• pp.70-76
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• 1995

생산스케쥴링의 기준이 되는 정보는 각 부품의 생산시간이나 생산비용인데, 이들은 고정된 값으로 취급되는 경우가 많다. 그러나, 실제적으로는 가공조건에 의하여 그 값들이 변화한다. 가공조거는 절삭깊이(depth of cut), 이송속도(feed rate), 및 절삭속도(cutting speed)로 구성되어 있다. 본 연구에서는 주어진 조건에 있어서 가공의 최적절삭조건을 최적이론의 하나인 페널티 함수이론(SUMT)을 이용하여 결정하는 할고리즘을 개발하였다. 알고리즘에서 목표함수(objective functions)로는 표면거칠기, 파워 소비, 등을 고려했다. 개발된 알고리즘 프로그램의 유용성을 증명하기 위해 선반가공의 예를 실행하여 그 결과를 예시하였다.

• 전기의세계
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• v.44 no.10
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• pp.40-46
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• 1995

소음을 줄이고자 하는 위치 혹은 공간의 선정문제, 또한 제어용 음파가 원래 제어하고자 하는 음파와 함께 섞인 상태에서 관찰하게 됨으로서 발생하는 문제, 제어용 음원의 위치 선정에 관련된 사항 등 가관측성 및 가제어성으로 대별될 수 있는 부분과 제어대상 물리량, 즉 제어대상 가격함수 선정의 물리적 적합성 등이 있을 수 있다. 전술한 가관측성 및 가제어성 관련 사항은 참고문허[3]에 비교적 상세히 기술되어 있으므로 본 고에서는 제어대상 가격함수의 선정과 관련된 음향학적 사실들을 중점적으로 다루도록 한다.

• Korean Journal of Optics and Photonics
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• v.8 no.6
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• pp.492-499
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• 1997

We proposed and studied an all-optical switching device made of a bent nonlinear waveguide and an all-optical logic gate made of a bent nonlinear Y-junction. The proposed devices as switch and a logic function are based on the evolution of nonlinear guided wave along a bent nonlinear waveguide. Since the characteristics of beam propagation depens on the nonlinearity, input power and bent angle of waveguide, the characteristics of output power transmission is calculated by variation the such parameters. Furthermore, by calculating the output power through the nonlinear media with different positions of detector in nonlinear media, we could find the ideal digital switching performance at specific position of detector and implement several all-optical logic functions (AND, OR, XOR) by power contrast between waveguide end and nonlinear media.

• Journal of radiological science and technology
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• v.32 no.1
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• pp.17-24
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• 2009

Noise evaluation for an image has been performed by root mean square (RMS) granularity, autocorrelation function (ACF), and Wiener spectrum. RMS granularity stands for standard deviation of photon data and ACF is acquired by integration of 1 D function of distance variation. Fourier transform of ACF results in noise power spectrum which is called Wiener spectrum in image quality evaluation. Wiener spectrum represents noise itself. In addition, along with MTF, it is an important factor to produce detective quantum efficiency (DQE). The proposed evaluation method using Wiener spectrum is expected to contribute to educate the concept of Wiener spectrum in educational organizations, choose the appropriate imaging detectors for clinical applications, and maintain image quality in digital imaging systems.