• 한국압력기기공학회 논문집
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• 제7권4호
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• pp.26-30
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• 2011

In order to ship low & Intermediate level radioactive waste drums, which have been temporarily stored on site, to a disposal facility, their physical and chemical properties should be evaluated and proven to meet the acceptance guideline prior to their shipment. Ultrasonic velocity method, which has been used to estimate the strength of concrete, can be suggested to evaluate the compressive strength of solidified radioactive waste, which is one of the evaluated properties. The strength is estimated from acoustic velocity. However, a guided wave traveling along a drum is generated when applying ultrasonic method to the drum, and this makes it difficult to analyze the signal due to overlap between transmitted wave through the contents in drum and the guided wave. This paper reported feasibility of ultrasonic method to evaluate of the compressive strength of the solidified LLW. It is observed that the guide wave is greater than transmitted wave, and ultrasonic velocity could be estimated from transmitted wave signal arriving prior to the guided wave

• 대한의용생체공학회:의공학회지
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• 제28권6호
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• pp.798-802
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• 2007

The synthetic focusing in the ultrasonic imaging systems has been formed in the way that one element transmits a circular wave and receives an echo signal. The amplitude of the signal transmitted from one element is too small to propagate a long distance so that the SNR(Signal to Noise Ratio) is very low in an image obtained by the synthetic focusing. To solve this problem, a defocusing method which uses several elements has been proposed. In this method, the SNR is improved due to using several elements to transmit the circular wave. But if the number of transmitting elements increases, the phase distortion is severe in the defocusing method. In this paper, we propose a new method that can generate a circular wave using a lot of elements without phase distortion. At first, we generate limited plane waves with different propagation angles and then superpose them to make a circular wave. We show that the circular wave can be used to improve SNR in the real-time 3D ultrasonic imaging as well as the synthetic focusing through computer simulation and experiments.

• 한국해안해양공학회지
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• 제15권1호
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• pp.11-20
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• 2003

본 논문에서는 규칙파 모델을 이용하여 유공케이슨 방파제로부터의 불규칙파의 반사를 계산하는 몇 가지 방법들을 검토한다. 첫 번째 방법은 불규칙파를 파고 및 주기가 각각 불규칙파의 제곱평균제곱근 파고 및 유의주기와 같은 규칙파로 근사하는 것이다. 두 번째는 불규칙파 스펙트럼의 각 주파수 성분에 대하여 규칙파 모델을 반복적으로 사용하는 것이다. 파의 주기는 성분파의 주파수에 따라 결정되며, 모든 주파수에 대해서 제곱평균제곱근 파고를 사용한다. 세 번째 방법은 두 번째 방법과 같으나, 각 성분파의 에너지에 해당하는 파고를 사용한다. 이전 연구자들의 실험 결과와 비교해 본 결과, 두 번째 방법이 가장 타당하며, 주파수 평균 반사율과 반사파 스펙트럼 모두 실험치와 양호한 일치를 보였다.

• 한국지반공학회논문집
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• 제28권8호
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• pp.55-63
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• 2012

깊이에 따른 지반의 전단파 속도(또는 전단탄성계수) 분포는 일반적인 지반 해석 설계 또는 지진해석과 같은 다양한 지반공학분야에서 사용되는 중요한 물성치이다. 이러한 지반의 전단파속도 주상도는 탄성파 탐사를 통해 결정할 수 있으며, 이를 위한 다양한 탄성파 탐사 방법이 연구개발 되어 있다. 표면파 탐사법은 모든 실험이 지표면에서 이루어지는 탄성파 탐사법들 중의 하나로서 현장 실험, 파장(또는 주파수)에 따른 표면 계측파의 위상속도 곡선인 분산곡선의 결정, 역산을 통한 대상 지반의 전단파 속도 주상도의 결정으로 동일하게 구성되어 있다. 본 논문에서는 표면파 실험을 위한 자동화된 역산 방법을 개발하였으며, 제안된 방법을 가장 최근에 개발된 표면파 탐사법들 중 하나인 HWAW(Harmonic Wavelet Analysis of Waves) 방법에 적용하였다. 제안된 방법에서는 새로운 오차함수를 제안하고 이를 이용한 유전자 알고리즘을 역산에 사용하였다. 제안된 방법의 타당성을 검토하고자 수치모의 실험과 현장 실험을 수행하였으며, 이를 통해 제안된 방법의 현장 적용성 및 타당성을 확인할 수 있었다.

• Journal of the Korean Statistical Society
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• 제31권4호
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• pp.469-482
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• 2002

This paper suggests a new method of compensating for wave nonresponse in panel survey, which combines weighting adjustment and imputation. By deleting less frequent nonresponse patterns, we can get simplicity. A new mean estimator under the new combining method is provided and a limited simulation study employing a real data is conducted.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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• pp.504-509
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• 1998

A new method is proposed for the isolation of resonances from scattered waves for acoustic wave resonance scattering problems. The resonance scattering function consisting purely of resonance information is defined. Acoustic wave scattering from a variety of submerged bodies is numerically analyzed. The classical resonance scattering theory (RST) and the new method compute identical magnitude of the resonance from each scattered partial wave, however, the phases are significantly different. The exact .pi.-radians phase shifts through the resonance and anti-resonance show that the proposed method properly extracts the vibrational resonance information of the scatterer. Due to the difference in the phase of each, partial wave, the new method and RST generate different total resonance spectra.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2000년도 춘계학술대회 논문집
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• pp.140-145
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• 2000

The spectral method which is composed of an eigenfunction expansion of free modes in the wave number domain is used to produce two dimensional unsteady inviscid wave simulation such as progressive waves in a numerical pneumatic wave tank. A spatial and time dependent free surface elevation and the potential are calculated by integrating ODE derived from fully nonlinear kinematic and dynamic free surface boundary condition at each time step. The nonlinear characteristics in the waves by this method were notable as increasing wave steepness. This method is very useful and powerful in terms of saving computational time caused by rapid convergence exponentially with increasing number of nodes, even preserving accurate numerical results. Moreover, it will given us many possibilities to apply to naval and ocean engineering fields.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 심포지엄 논문집 정보 및 제어부문
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• pp.48-50
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• 2006

In this paper, we propose a method to minimize the baseline wandering that make hard to detect R wave in ECG. This method uses a different signal between ECG and ascending slope tracing waves to minimize the baseline wandering. When the slope of ECG signal maintains the value or falls, the ascending slope tracing wave fellows ECG signal directly, and this wave holds that value of ECG signal when the slope begins to rises in a certain time(=hold time). After this hold time, this wave traces ECG signal again. To evaluate this minimizing method for baseline wandering, the experiments are carried out with 5 ECG data in the database of MIT/BIH. R waves in the proposed different signal are detected by using descending slope trace waves and compared with the annotation file. The results show that the proposed method Is sure to minimize the baseline wandering in ECG.

• Journal of applied mathematics & informatics
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• 제28권3_4호
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• pp.611-624
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• 2010

A Numerical scheme based on collocation method using quartic B-spline functions is designed for the numerical solution of one-dimensional modified equal width wave (MEW) wave equation. Using Von-Neumann approach the scheme is shown to be unconditionally stable. Performance of the method is validated through test problems including single wave, interaction of two waves and use of Maxwellian initial condition. Using error norms $L_2$ and $L_{\infty}$ and conservative properties of mass, momentum and energy, accuracy and efficiency of the suggested method is established through comparison with the existing numerical techniques.

• 대한화학회지
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• 제5권1호
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• pp.84-87
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• 1961

A polarographic method for rapid determination of Uranium in the presence of foreign ions was proposed. The method is based on the measurement of polarogram in the sulfuric acid as supporting electrolyte. In this medium Uranyl ions give well defined reduction waves, and half-wave potentials are -0.19V vs. S.C.E. as first wave, and uncertain volt. vs. S.C.E. as second wave in $2.4 N-H_2SO_4.$ The first wave has a linear relationship between the concentration of Uranyl ion and wave height. The author also studied a method for rapid determination of Uranium in Korean monazite sand without eliminating the foreign ions. The Korean monazite sands were analyzed by this method and satisfactory result were obtained.