• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.705-708
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• 1988

Ultrasound Doppler Diagnostic System utilizes the Doppler effect for measurement of blood velocity. The sign of the Doppler frequency shift represents blood flow direction. Pulsed Doppler System uses Phase detector and zerocrossing method to produce simultaneous independent audio and velocity signals for forward and reverse blood flow direction in the time domain, had been fabricated. But time-domain analyzing such as audio evaluation and zerocrossing detection for instantaneous and mean frequency measurement doesn't, provide both an accurate and quantitative result. Therefore, it is necessary to adopt frequency domain technique to improve system performance. In this paper, we describe a unit which is composed of Pulsed Doppler System and real-time spectrum analyzer (installed TMS 32010 DSP Chip). This unit shows time-dependent spectrum variation and mean velocity of blood Signal.

• Bulletin of the Korean Chemical Society
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• 제28권8호
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• pp.1371-1374
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• 2007

The velocity auto-correlation (VAC) function of liquid argon in the Green-Kubo formula decays quickly within 5 ps to give a well-defined diffusion coefficient because the velocity is the property of each individual particle, whereas the stress (SAC) and heat-flux auto-correlation (HFAC) functions for shear viscosity and thermal conductivity have non-decaying, long-time tails because the stress and heat-flux appear as system properties. This problem can be overcome through N (number of particles)-fold improvement in the statistical accuracy, by considering the stress and the heat-flux of the system as properties of each particle and by deriving new Green-Kubo formulas for shear viscosity and thermal conductivity. The results obtained for the transport coefficients of liquid argon obtained are discussed.

• Bulletin of the Korean Chemical Society
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• 제34권10호
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• pp.2931-2936
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• 2013

This paper presents results for the calculation of transport properties of noble gases (He, Ne, Ar, Kr, and Xe) at 273.15 K and 1.00 atm using equilibrium molecular dynamics (EMD) simulations through a Lennard-Jones (LJ) intermolecular potential. We have utilized the revised Green-Kubo formulas for the stress (SAC) and the heat-flux auto-correlation (HFAC) functions to estimate the viscosities (${\eta}$) and thermal conductivities (${\lambda}$) of noble gases. The original Green-Kubo formula was employed for diffusion coefficients (D). The results for transport properties (D, ${\eta}$, and ${\lambda}$) of noble gases at 273.15 and 1.00 atm obtained from our EMD simulations are in a good agreement with the rigorous results of the kinetic theory and the experimental data. The radial distribution functions, mean square displacements, and velocity auto-correlation functions of noble gases are remarkably different from those of liquid argon at 94.4 K and 1.374 $g/cm^3$.

• 한국압력기기공학회 논문집
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• 제13권1호
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• pp.40-47
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• 2017

In this paper, we investigate the feasibility of a strategy of failure detection and identification. The point of proposed strategy includes a pattern extraction approach for failure identification using Auto-Associative Kernel Regression (AAKR). We consider a simulation data concerning 605 signals of a Generic Pressurized Water Reactor(GPWR). In the application, the reconstructions are provided by a set of AAKR models, whose input signals have been selected by Correlation Analysis(CA) for the identification of the groups. The failure pattern is extracted by analyzing the residuals of observations and reconstructions. We present the possibility of extraction of patterns for six failure.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.960-963
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• 2003

Sound intensity method is well known as a visualization technique of sound field and sound propagation in noise control. Sound intensity is a vector quantity that describes the magnitude and the direction of net flow of acoustic energy at a given position. The current measuring method is expensive and difficult to identify the noise source exactly. In this paper, we have studied the noise source identification and the characteristics of noise source of rotary compressor for air conditioner using complex sound intensity method. The new method for instantaneous sound intensity is also proposed and it is useful for transient state and steady state. The criteria of these state, select auto correlation coefficient. The advantage, simplicity and economic attribution of this method are verified by analyzing the characteristics of noise source with instantaneous sound intensity compared to mean sound intensity.

• Structural Engineering and Mechanics
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• 제4권6호
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• pp.703-715
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• 1996

In stochastic analysis, the randomness of the structural parameters is taken into consideration and the response variability is obtained in addition to the conventional (mean) response. In the present paper the structural response variability of plate structure is calculated using the weighted integral method and is compared with the results obtained by different methods. The stochastic field is assumed to be normally distributed and to have the homogeneity. The decomposition of strain-displacement matrix enabled us to extend the formulation to the stochastic analysis with the quadratic elements in the weighted integral method. A new auto-correlation function is derived considering the uncertainty of plate thickness. The results obtained in the numerical examples by two different methods, i.e., weighted integral method and Monte Carlo simulation, are in a close agreement. In the case of the variable plate thickness, the obtained results are in good agreement with those of Lawrence and Monte Carlo simulation.

• 반도체디스플레이기술학회지
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• 제13권1호
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• pp.51-55
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• 2014

In this paper, an hybrid automatic focusing method has been proposed for speedy and reliable measurement and inspection in industry. It can improve reliability of focusing position by using not a focusing measure but the hybrid one that is incorporated with sobel operator and auto-correlation. Also, it can not only reduce control time of focusing position using adaptive step size, but also improve accuracy of focusing position by gaussian interpolation. Its performance is verified by experiments. It is expected that it can apply to optical system for measurement and inspection in industry fields.

• Structural Monitoring and Maintenance
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• 제9권2호
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• pp.157-177
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• 2022

In this paper, an innovative finite element updating method is presented based on the variation wavelet transform coefficients of Auto/cross-correlations function (WTCF). The Quasi-linear sensitivity of the wavelet coefficients of the WTCF concerning the structural parameters is evaluated based on incomplete measured structural responses. The proposed algorithm is used to estimate the structural parameters of truss and plate models. By the solution of the sensitivity equation through the least-squares method, the finite element model of the structure is updated for estimation of the location and severity of structural damages simultaneously. Several damage scenarios have been considered for the studied structure. The parameter estimation results prove the high accuracy of the method considering measurement and mass modeling errors.

• 한국음향학회지
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• 제37권5호
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• pp.271-275
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• 2018

두 개 센서에 도래하는 신호 간의 시간 지연을 추정 방법에는 여러 가지가 존재한다. 그중에서 두 센서에 입력되는 서로 다른 신호간의 상호 상관과 신호 백색화로부터 상대적인 지연을 추정하는 GCC-PHAT(Generalized Cross Correlation-Phase Transform) 방법은 안정적인 성능을 내는 전통적으로 유명한 방법이다. 본 논문에서는 GCC-PHAT의 연산 과정 중에서 주기성을 이용하여 잡음을 제거할 수 있는 부분을 파악하였다. 그리고 파악된 부분에 자기상관을 적용하였다. 제안한 방법을 기존의 방법과 비교하여, 백색 가우시안 신호원인 경우 신호 대 잡음비 0 dB 이상에서 평균 자승 추정 오차 5 dB ~ 15 dB까지의 향상이 있음을 보이고, 유색 신호원에서도 신호 대 잡음비 2 dB 이상에서 평균 자승 추정 오차가 성능 개선되어 15 dB까지의 성능 개선 효과가 있음을 보인다.

• 한국해안·해양공학회논문집
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• 제25권3호
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• pp.165-171
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• 2013

조차가 큰 해역에서 조위편차 역시 크게 나타나고 있음은 조위편차 내에 조석성분이 남아있음을 의미한다. 상관관계함수를 통한 분석을 시행한 결과에서도 서해안 해역에서 조석주기 부근의 자기상관계수가 크게 나타나고 있어 이러한 사실을 뒷받침하고 있다. 조위편차의 단주기성분에 해당하는 이러한 조석관련성분을 분석하기 위하여 웨이블릿분석을 시행하였다. 분석 결과에 의하면 조차가 클수록 조석주기성분이 크게 나타나고 있으며 단주기 성분에서 계절별 변화가 심하지 않다는 점과 목포의 경우 천해조성분인 6시간 주기성분이 유독 크게 나타나고 있다는 점에서 단주기 성분과 조석관련성분의 관련성을 연관지을 수 있다. 이와 함께 24시간 이내 단주기 성분의 조위편차는 조석예측오차 및 조석-해일 비선형성 등에 주로 기인하고 있는 것으로 파악되었다. 이러한 조석변조해일성분은 조석자체에 기인하므로 기상조 성분인 해일고와는 구분되어야 한다.