• 한국전산유체공학회지
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• 제10권2호
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• pp.7-14
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• 2005

In this study, the shallow water equations on the sphere is simulated by the proposed method which has high spatial resolution and is based on the CIP(Cubic Interpolated Pseudoparticle) method. The governing equations are approximated on the longitude-latitudinal coordinate system. To avoid the problems resulting from the convergence of the meridians toward high-latitude and singularities on the poles, the semi-Lagrangian and finite volume method are employed. in addition, the CIP method is employed to solve the advection equations and is extended to apply on the equations in the polar coordinate system. The mathematical formulation and numerical results are also described. To verify of the efficiency, accuracy and capability of proposed algorithm, the standard test cases proposed bv Williamson et. al are simulated and the results are compared with other results. As a result, it is found that the present scheme gives a good properties in preserving shapes of solution and settles the pole problems in solving the shallow water equations on the sphere.

• 산업융합연구
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• 제21권7호
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• pp.83-92
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• 2023

유전체 전위장벽방전방식에 의한 플라즈마 젯의 블렛 형상은 인가되는 유량과 전기장의 크기에 따라 달라지고 이러한 변화는 DBD 플라즈마 젯의 밀도차이에 의한 스펙트럼 분포의 차이로 나타난다. 발생된 플라즈마 젯의 스펙트럼의 분석을 통한 활성종의 발생과 강도의 차이는 장치를 활용하는데 있어서 중요한 요소이다. 본 논문에서는 Ar가스를 이용한 대기압 볼륨 DBD방식의 플라즈마 젯 발생장치를 제안된 설계방법에 따라 구성하였다. 플라즈마 젯의 발생을 위한 유량의 의존도를 규명하기 위한 Ar가스의 유동해석을 시뮬레이션을 통해 확인하였고 프로토타입 시스템에서는 MFC를 통한 유량제어를 통해 최적의 플라즈마 젯 불렛형상을 발생시키고 발생된 플라즈마 젯의 특성을 분석하기 위해 스펙트로미터를 이용한 플라즈마 젯의 특성을 분석하였다. 제안된 시스템의 설계방법을 통한 장치에서 최적의 플라즈마 젯 형상 확립방법과 EOS 상에서 활성종에 대한 결과를 확인하였다.

• 지구물리와물리탐사
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• 제16권3호
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• pp.180-189
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• 2013

물리탐사는 금속광상에서 광화대를 탐사하는데 효율적인 방법으로 국내 외에서 전략광물자원을 개발하기 위하여 널리 이용되고 있다. 물리탐사 결과로부터 광화대를 정확하게 해석하기 위하여 암석의 물리적 특성을 이해하는 것이 매우 중요하다. 따라서 이 연구는 국내 대표적 스카른 광상인 가곡광산의 광석 및 모암을 대상으로 실내에서 다양한 물성을 측정하였으며, 그 결과로부터 가곡 스카른 광상을 구성하는 지층의 물리적 특성을 파악하고자 하였다. 암석시료는 시추코어 및 노두에서 채취하였으며, 시료의 물성은 실내 암석물성 측정시스템을 이용하여 밀도, 대자율, 전기비저항, 광대역 유도분극을 측정하였다. 그 결과 광석은 모암에 비하여 낮은 전기비저항과 높은 대자율 및 밀도를 보였으며, 광대역 유도분극에서 큰 위상과 특정한 임계주파수가 나타났다. 광석의 광대역 유도분극 측정 자료를 Cole-Cole 역산을 통하여 얻은 충전성과 시간상수로부터 황화광물의 함량과 입자의 크기를 추정할 수 있어 스카른 광상 탐사에서 유용할 것으로 기대된다.

• 대한기계학회논문집
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• 제18권6호
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• pp.1535-1541
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• 1994

The void content of carbon fiber reinforced composite laminates was determined by the ultrasonic nondestructive technique. The ultrasonic immersion, through-transmission method developed stresses the utilization of spectral analysis and frequency dependence of the attenuation due to porosity. The measured attenuation shows approximately linear behavior over the frequency range investigated. The linear relationship between the void content and the attenuation slop (d $\alpha$/df) is found to hold, but the constant of proportionality is quite different for samples with different pore morphology. The void volume fraction determined by the attenuation slope agreed very well with that obtained by the acid digestion analysis.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.476-477
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• 2009

The smallest green laser containing a built-in temperature controlling unit has been demonstrated. The device volume was just 0.5 cubic centimeters, which is nearly the same size as existing red and blue diode lasers, has an electrical-to-optical conversion efficiency of 10% and 150 mW power output. Furthermore as an alternative approach for compact green laser development, a quasi-phase matching method with wide spectral bandwidth for the reduction of speckle noise will be presented.

• 대한원격탐사학회지
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• 제23권1호
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• pp.7-14
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• 2007

Atmospheric correction is one of critical procedures to extract quantitative information related to biophysical variables from hyperspectral imagery. Most atmospheric correction algorithms developed for hyperspectral data have been based upon atmospheric radiative transfer (RT) codes, such as MODTRAN. Because of the difficulty in acquisition of atmospheric data at the time of image capture, the complexity of RT model, and large volume of hyperspectral data, atmospheric correction can be very difficult and time-consuming processing. In this study, we attempted to develop an efficient method for the atmospheric correction of EO-1 Hyperion data. This method uses the pre-calculated look-up-table (LUT) for fast and simple processing. The pre-calculated LUT was generated by successive running of MODTRAN model with several input parameters related to solar and sensor geometry, radiometric specification of sensor, and atmospheric condition. Atmospheric water vapour contents image was generated directly from a few absorption bands of Hyperion data themselves and used one of input parameters. This new atmospheric correction method was tested on the Hyperion data acquired on June 3, 2001 over Seoul area. Reflectance spectra of several known targets corresponded with the typical pattern of spectral reflectance on the atmospherically corrected Hyperion image, although further improvement to reduce sensor noise is necessary.

• Nuclear Engineering and Technology
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• 제55권9호
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• pp.3401-3408
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• 2023

In this study, we used the Monte Carlo N-Particle program to simulate the gamma-ray spectra obtained from plastic scintillators holes filled with bismuth nanoparticles. We confirmed that the incorporation of bismuth nanoparticles into a plastic scintillator enhances its performance for gamma-ray spectroscopy using the subtraction method. The subtracted energy spectra obtained from the bismuth-nanoparticle-incorporated and the original plastic scintillator exhibit a distinct energy peak that does not appear in the corresponding original spectra. We varied the diameter and depth of the bismuth-filled holes to determine the optimal hole design for gamma-ray spectroscopy using the subtraction method. We evaluated the energy resolutions of the energy peaks in the gamma-ray spectra to estimate the effects of the bismuth nanoparticles and determine their optimum volume in the plastic scintillator. In addition, we calculated the peak-to-total ratio of the energy spectrum to evaluate the energy measuring limit of the bismuth nanoparticle-containing plastic scintillator using the subtraction method.

• 대한원격탐사학회지
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• 제29권5호
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• pp.509-516
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• 2013

초분광 영상에 내재된 비선형 현상을 다루기 위해서는 과거에 주로 사용되었던 선형 피처 추출 방법은 적합하지 않았다. 따라서 최근 Manifold learning이라 불리우는 비선형 피처 추출 방법이 초분광 원격탐사 분야를 비롯 여러 분야에서 관심이 증가되고 있다. Manifold learning 방법 중 널리 이용되는 Isomap은 분류와 분광 혼합 분석 등의 분야에서 좋은 결과를 보여주지만, 지나치게 복잡하고 높은 계산량은, 특히 원격탐사 자료와 같이 자료의 크기가 큰 경우 문제가 된다. 따라서 자료의 일부분을 이용하는 랜드마크 기법이 해결책으로 제안 되었다. 본 연구에서는 좀 더 통제가 가능한 랜드마크 추출을 위해 자료를 구성하는 최대 부피를 지닌 Simplex를 이용하여 랜드마크를 선택하는 방법을 제안한다. 초분광 영상을 이용하여 랜드마크의 개수, 선택 방법에 따른 분류 정확도와 편차, 그리고 처리 시간을 비교하였고, 그 결과 제안된 랜드마크 선택 기법은 분류 정확도, 처리시간 모두에서 효율적인 결과를 보여주었다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.222-228
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• 2004

The effects of rotation on the unsteady laminar flow past a circular cylinder is numerically investigated in the present study. We obtained the numerical solutions for unsteady two-dimensional governing equation for the flow using two different numerical schemes. One is an accurate spectral method and another is finite volume method. Above all, the flow around a stationary circular cylinder is investigated to understand the basic phenomenon of flow separation, bluff body wake. Also, the validation of our own codes, expecially based on FVM, is carried out by the comparison of results obtained from our simulations using two different schemes and previous numerical and experimental studies. By the effect of rotation, the mean lift increases and drag deceases, which well represent the previous study.

• 천문학회지
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• 제37권5호
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• pp.349-353
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• 2004

Magnetic fields are an important ingredient of galaxy clusters and are indirectly observed on cluster scales as radio haloes and radio relics. One promising method to shed light on the properties of cluster wide magnetic fields is the analysis of Faraday rotation maps of extended extragalactic radio sources. We developed a Fourier analysis for such Faraday rotation maps in order to determine the magnetic power spectra of cluster fields. In an advanced step, here we apply a Bayesian maximum likelihood method to the RM map of the north lobe of Hydra A on the basis of our Fourier analysis and derive the power spectrum of the cluster magnetic field. For Hydra A, we measure a spectral index of -5/3 over at least one order of magnitude implying Kolmogorov type turbulence. We find a dominant scale of about 3 kpc on which the magnetic power is concentrated, since the magnetic autocorrelation length is ${\lambda}_B = 3 {\pm} 0.5\;kpc$. Furthermore, we investigate the influences of the assumption about the sampling volume (described by a window function) on the magnetic power spectrum. The central magnetic field strength was determined to be ${\~}7{\pm}2{\mu}G$ for the most likely geometries.