• 디지털콘텐츠학회 논문지
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• 제12권2호
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• pp.151-156
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• 2011

CT검사 후 재구성 영상 처리 기법인 Ray-sum 기법과 Shaded Surface Display(이하 SSD)기법을 분석 및 영상평가를 하여 위암 환자의 입체적인 정보 제공의 유용성 여부를 확인하고자 하였다. 위암환자 20명을 대상으로 64-MDCT를 이용하여 raw data(원시데이터)를 획득한 후 영상 재구성 처리를 하였다. 분석 결과 Ray-sum과 SSD재구성 영상모두 해부학적 구조를 정확히 묘사하는 것으로 평가 받았고, 영상의 정확도 평가에서 Ray-sum, SSD재구성 영상 대부분에서 병변의 위치가 위장 내시경과 일치하였으며 6cm이상에서 오차가 더 있음을 알 수 있었다. 또한 병변에 대한 영상판독결과와 내시경 및 병리학적 소견의 일치도가 높음을 알 수 있었다.

• Journal of Magnetics
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• 제13권3호
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• pp.85-87
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• 2008

I report a simple method to correct the saturation effect in absorption spectra measured in total electron yield (TEY) mode. It does not require additional measurements of the X-ray penetration depth. In order to check the reliability of the method, X-ray magnetic circular dichroism (XMCD) spectra for polycrystalline Fe were measured at two different incident angles, and then processed with the method. The two resultant XMCD spectra were identical, and their sum rule analysis produced the ratios of orbital magnetic moment to spin magnetic moment, which were very close to the well-known value.

• 천문학회보
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• 제38권2호
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• pp.96.2-96.2
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• 2013

The solar images are taken by the CCD detectors of the Sun monitoring satellites. The solar images are constructed after removing the traces of cosmic rays on the raw CCD data files. Thus, while applying the method of removing the cosmic rays traces, we can estimate the cosmic rays flux by counting the number of traces. The cosmic ray flux in the steady state might be the sum of the solar and galactic cosmic rays. However, the abrupt change in the flux could be assumed to be originated from the Sun. Therefore, we can identify the solar origins of the sudden solar cosmic ray flux changes from the phenomena shown in the processed solar images taken by SOHO/EIT. As the results, the estimated cosmic ray flux in the steady state is the anti-correlated with sunspot numbers, which shows the minima in cosmic ray flux at the solar cycle maxima defined by the sunspot numbers. The profiles of estimated solar cosmic ray associated with the ground level enhancements have the significant increase in the cosmic ray flux with good correlation. Thus, the solar images are valuable data useful in estimating the solar cosmic ray long term and transient flux variations.

• 한국광학회지
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• 제11권6호
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• pp.390-394
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• 2000

사람의 홍채 인식을 통항 보안 통제를 하기 위한 광학계를 설계하였다. 이 렌즈는 종색수차와 Petzval sum을 최소로 하는 triplet형이다. 초점거리를 50mm 유효경을 10mm로 하였고 물체로부터 상까지의 거리는 200mm-300mm로 고려하였다. 눈을 고려한 전체 광학계의 성능은 ray-fan과 spot diagram 그리고 회절광학적인 MTF를 계산하여 평가하였다. 홍채의 크기를 고려하여 물체 높이 0mm, 4mm 그리고 6mm 에 대하여, 파장은 Fraunhofer C, d 및 F-line에 대하여 모두 계산한 결과 spot 크기는 0.05mm 직경을 벗어나지 않았고 MTF 값도 물체 높이 6mm에 대한 486mm 파장의 sagittal MTF를 제외하고는 20 lines/mm의 공간주파수에서 0.5이상이 되었다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.42.2-42.2
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• 2011

Noise generated from wind turbines has been predicted by numerical methods. Sound pressure level(SPL) on the turbines is predicted after aerodynamic analysis is carried out by Wind Turbine Flow, Aeroacoustics and Structure analysis (WINFAS) code. The level of each panel of acoustic sphere is determined by the sum of tonal, turbulence ingestion and airfoil self noise. With the noise source database, the acoustic sphere, SPL on the ground is calculated using the model based on acoustic ray theory. The model has been designed to consider the effects on the condition of terrain and atmosphere. The variations of SPL on the ground occur not only because of the different source level but also because of the nonuniform distributions of the sound speed along the height. Hence, the profile of an effective sound speed which is the sum of the contribution of sound speed to a temperature gradient and a wind speed variation is used by the theory based on atmospheric stability. With the integrated numerical method, the prediction of sound propagation on the wind farm is carried out with the states of the atmospheric stability.

• Nuclear Engineering and Technology
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• 제51권3호
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• pp.818-824
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• 2019

In the present work, we determined the gamma-ray attenuation characteristics of eight different polymers(Polyamide (Nylon 6) (PA-6), polyacrylonitrile (PAN), polyvinylidenechloride (PVDC), polyaniline (PANI), polyethyleneterephthalate (PET), polyphenylenesulfide (PPS), polypyrrole (PPy) and polytetrafluoroethylene (PTFE)) using transmission geometry utilizing the high resolution HPGe detector and different radioactive sources in the energy range 81-1333 keV. The experimental linear attenuation coefficient values are compared with theoretical data (WinXCOM data). The linear attenuation coefficient of all polymers reduced quickly with the increase in energy, at the beginning, while decrease more slowly in the region from 267 keV to 835 keV. The effective atomic number of PVDC and PTFE are comparatively higher than the $Z_{eff}$ of the remaining polymers, while PA-6 possesses the lowest effective atomic number. The half value layer results showed that PTFE ($C_2F_4$, highest density) is more effective to attenuate the gamma photons. Also, the theoretical results of macroscopic effective removal cross section for fast neutrons ($\sum_{R}$) were computed to investigate the neutron attenuation characteristics. It is found that the $\sum_{R}$ values of the eight investigated polymers are close and ranged from $0.07058cm^{-1}$ for PVDC to $0.11510cm^{-1}$ for PA-6.

• 한국자기학회지
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• 제5권5호
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• pp.575-578
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• 1995

X-ray magnetic-circular-dichroism (MCD) spectra, orbital ($$) and spin magnetic moments ($$) for Co(110) monolayers a free standing mode or sandwiched between Pd(Pd/1Co/Pd)and Cu layers (Cu/1Co/Cu) are calculated using the thin film full potential linearized augmented plane wave energy band method. In contrast to the double peak structure predicted for the Co(0001) surface, only a minor side peak is found in the MCD spectra for Cu/Co/Cu, while MCD spectra for the other systems show a single peak structure. The MCD sum rules originally derived from a single ion model are found in the band approach to be valid for the systems investigated. However, for the spin sum rule, the magnetic dipole term ($$) is not negligible and needs to be included.

• 전자공학회논문지
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• 제52권11호
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• pp.105-114
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• 2015

본 논문은 흉부 엑스레이 영상에서 배경 제거 및 관심 영역을 분할하는 기법을 제안한다. 일반적으로 화질 개선 기법을 적용할 때 영상의 밝기 정보나 주파수 정보를 이용하여 영상 선명도와 대비를 개선하는 방법을 사용한다. 이러한 기법을 엑스레이 영상 전체에 적용하는 경우 배경과 같은 영상의 불필요한 정보 때문에 좋은 성능을 얻기 어렵다. 그래서 본 논문은 사용자가 원하는 영역에만 화질 개선 기법을 적용할 수 있도록 배경 제거 및 관심 영역 (ROI)을 분할하는 방법을 제안한다. 배경 제거를 위해 먼저 원본 영상의 히스토그램 분포를 분석하고 문턱치 처리로 몸체와 배경을 일차적으로 분리한다. 다음으로 유도 필터 (guided filter)를 이용하여 몸체 경계 혹은 배경 경계를 보정한다. 관심 영역 분할을 위해서는 먼저 폐의 위치 정보를 이용하여 폐의 주 밝기 값을 찾는다. 이를 이용하여 문턱치 처리를 한 후 번호 매김과 상기 배경 정보를 이용하여 분류 이외의 것을 제거한다. 마지막으로 폐만 검출된 이진영상을 통해 경계 상자 영역을 생성한다. 모의실험을 통해 제안하는 기법의 우수성을 검증하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 추계종합학술대회 논문집
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• pp.809-812
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• 1999

This paper presents the radio propagation effects in the shadow region due to the presence of obstacle, like building and tree, along the path at the B-WLL band. Using the Uniform Theory of Diffraction(UTD), the total field was obtained as the sum of contributions with diffraction ray from the each obstacle's edge, the direct ray, and the reflected rays from ground. The normalized signal level(in ㏈) is calculated with the parameters of the base station elevation and the distance between obstacle and receiver. This results are used to provide the suitable radio cell planning and coverage prediction in the area of shadow region.

• 대한방사선기술학회지:방사선기술과학
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• 제41권2호
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• pp.129-134
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• 2018

The present study made a phantom for gamma ray of 140 keV radiated from $^{99m}Tc$, examined shielding effect of lead by thickness of the shielding material, and measured surface dose and depth dose by body depth. The OSL Nano Dot dosimeter was inserted at 0, 3, 15, 40, 90, and 180 mm depths of the phantom, and when there was no shield, 0.2 mm lead shield, 0.5 mm lead shield, The depth dose was measured. Experimental results show that the total cumulative dose of dosimeters with depth is highest at 366.24 uSv without shield and lowest at 94.12 uSv with 0.5 mm lead shield. The shielding effect of 0.2 mm lead shielding was about 30.18% and the shielding effect of 0.5 mm lead shielding was 74.30%, when the total sum of the accumulated doses of radiation dosimeter was 100%. The phantom depth and depth dose measurements showed the highest values at 0 mm depth for all three experiments and the dose decreases as the depth increases. This study proved that the thicker a shielding material, the highest its shielding effect is against gamma ray of 140 keV. However, it was known that shielding material can't completely shield a body from gamma ray; it reached deep part of a human body. Aside from the International Commission on Radiation Units and Measurements (ICRU) recommending depth dose by 10 mm in thickness, a plan is necessary for employees working in department of nuclear medicine where they deal with gamma ray, which is highly penetrable, to measure depth dose by body depth, which can help them manage exposed dose properly.