• Journal of the Korean Society of Radiology
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• v.15 no.5
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• pp.731-739
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• 2021

This work compared the bright calibration of digital radiation with signal-to-noise ratio and basic spatial resolution according to multi frame to enable effective inspection of welding parts of structures at industrial sites. A total of 130 images were obtained by using a ⁷⁵Se radiation source for flat weld test pieces and segmenting bright calibration and multi frame prior to shooting. The study confirms that the signal-to-noise ratio improves as the number of bright calibrations and the number of multi frame increases. The basic spatial resolution satisfied the baseline for both radiographic images. It was confirmed that the number of signal-to-noise ratio was similar by comparing images taken after installing lead shielding for scattering radiation. Although signal-to-noise ratio increases as multi frame increases, it is believed that good quality digital radiographs can be obtained if appropriate radiographic techniques are devised because exposure time of radiation affects workers' exposure and work efficiency.

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2811-2814
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• 2003

본 논문에서는 Sub-nano 수준의 위치정밀도와 분해능을 갖는 Piezo actuator 의 제어기 설계를 목적으로 하였다. 이산 시간 상태 공간에서의 Piezo actuator를 이용한 1 축 스테이지 드라이브 시스템 SISO 제어기를 설계하였다. Piezo actuator 의 소재 자체의 특성으로는 Hysteresis 가 있으며, 이는 정상상태에서 Piezo actuator 의 위치 오차를 발생하는 주요 원인이 된다. 제어기의 설계는 극점 배치 방법을 기본으로 하여 Hysteresis 에 대한 보상을 목적으로 적분제어방식과 외란 추정기를 각각 적용하였다. 모의실험을 통하여 제어기의 설계 및 시뮬레이션 하였으며, Hysteresis 에 대한 보상이 이루어짐을 보았고, 실험을 통하여 이를 증명하였다.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06e
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• pp.243-246
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• 1998

집속음장의 고조파성분을 이용한 초음파영상의 특성을 해석하기 위해 집속된 가우스 음원에 직선 edge를 초점면 및 초점면의 전, 후방에 삽입하여 edge의 후방에서 생성되는 음장을 조사하였다. 계산에서는 그린함수의 간단화를 위해 Fresnel근사를 이용하였고, 실험에서는 성형전극을 형성시킨 1.9MHz 요면진동자에 의한 가우스분포의 음장을 갖는 초음파빔에 수직하게 edge를 삽입시켰다. 음장의 이론해석 및 실험결과, 초점면의 제2고조파의 빔형상을 제외하고는 계산치와 실험치가 잘 일치하고 있으며, 제2고조파의 공간 분해능이 기본파에 비해 높음을 알았다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.05a
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• pp.271-274
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• 2016

CT quality assurance imaging evaluation and enforcement as quantitative assessment by phantom image evaluation, assessment items include There are also contrasting the water attenuation coefficient, uniformity, noise, resolution, spatial resolution, 10mm slice thickness evaluation, contrast resolution, space for the resolution, the slice thickness evaluation, it is possible to estimate the error due to the evaluation by the subjective judgment of the tester, using a subjective error image processing program to be computed to minimize the objective evaluation. Basic recording conditions of the CT image quality control assessment is the same as special medical equipment quality control checks, the images were evaluated quantitatively using IMAGE J. For a CT attenuation coefficient, the uniformity, noise evaluation, were evaluated as CT quality control image the standard deviation of the measured value of the digital processing of image smaller and less noise uniform images than the, contrast and resolution assessment is the size of the diameter of a circle having a large the 1 inch, 0.75 inch, 0.5 inch quality if the diameter of the circle, was evaluated in the small circle in the near circle ellipse. Spatial resolution is evaluated by using a self-extracting features of an image processing program, all of the groups of members comprising the acceptance criteria to automatically extract, was evaluated to be very useful for the quantitative assessment. When CT image quality control assessment on the basis of the results such as the above, if using an image processing program to minimize the subjective judgment of the error evaluator and is determined more efficient than would be made quantitative evaluation.

• The Journal of the Korea Contents Association
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• v.16 no.8
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• pp.592-600
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• 2016

AAPM CT performance for special medical equipment quality control checks using a standard phantom for evaluation, using the evaluator's subjective assessment as to minimize errors due computerized assessment program to evaluate their usefulness. Phantom for evaluation AAPM CT Performance Phantom: was used, the default shooting conditions are the same as quality control checks. And, we use IMAGE J to evaluate the program. Quantitative evaluation with CT attenuation coefficient and the noise measurement, the uniformity measurement, the slice thickness measurement, contrast resolution of the measurement, a phantom image of the spatial resolution determined by the evaluation program is evaluated as self-extracting the result after processing the image, CT uniformity measurement for the evaluation that was smaller and the standard deviation of a video image processing more uniform slice thickness measurements it is difficult to evaluate due to the difference of the ratio of the measured value of the phantom image. Contrast resolution was measured cylindrical diameter 6th evaluate the shape of a circle obtained a mean value and a standard deviation of diameters, the spatial resolution of the group of source, including acceptance criteria automatically extracted result as a result of both the number of the extracted circularIt appeared. Evaluate the source image and video processing, and video to qualitative evaluation by gross were processed video image is shown excellent results. If the evaluators in order to minimize the errors of subjective judgment based on the results of the above should be done with a quantitative evaluation and qualitative evaluation utilizes a computerized assessment program is considered that further evaluation be made more efficient.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.154.2-154.2
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• 2011

행성 및 타이탄과 같은 태양계 내의 면천체(extended source)를 관측하기 위해서는 공간분해능이 높은 대형망원경과 파장분해능이 높은 분광기가 필요하다. 특히 분광 관측 자료를 이용하면 행성 및 타이탄의 대기 구성 성분 및 그 성분비, 온도 분포, 구름과 연무 등의 수직 구조 등을 알 수 있다. 최근 연구에서는 구름, 연무, 비 등의 생성 과정에 불포화/초과포화 상태의 메탄, 에탄, 에틸렌 등이 관여하는 것이 새롭게 알려져 보다 활발한 후속 연구가 필요하다. 현재 개발 중인 IGRINS는 적외선 영역의 H band($1.49{\sim}1.8{\mu}m$)와 K band($1.96{\sim}2.46{\mu}m$)를 동시에 관측할 수 있고, McDonald 2.7m 망원경에 부착할 때 R~40,000의 높은 분해능을 가지는 장비로서 태양계 천체를 관측하는 데에 매우 적합하다. 따라서 향후 IGRINS가 본격적으로 가동될 때 얻을 수 있는 자료에 대한 사전 연구가 필요하며, 이는 대형 망원경 및 고분산 분광기를 이용한 관측, 자료 처리 및 분석 등의 경험에 기반을 두어 진행되어야 한다. 이에 NIFS/Gemini에 의해 관측된 타이탄 분광 자료와 TEXES/IRTF에 의해 획득된 목성극지방의 분광 자료를 분석하는 사전 연구를 진행하고 있다. 목성에 대해서는, 극지방에서 관측되는 hotspot, warm, normal 지역의 근적외선 영역 분광선 분석을 통해 기존에 결정되어 있지 않은 극지방 성층권의 고도에 따른 온도분포를 알아본다. 타이탄에 대해서는, 근적외선 영역의 메탄흡수밴드에서 관측된 주연증광(Limb brightening) 현상을 복사전달모델로 구현함으로써 어떤 기작이 이 현상에 가장 큰 영향을 미치는지에 대해 알아본다. 이런 태양계 천체 자료에 대한 연구는 향후 mission 및 rover 작업을 수행함에 있어 기본적인 정보로서 활용될 수 있다.

• Geophysics and Geophysical Exploration
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• v.2 no.1
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• pp.43-53
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• 1999

Numerical modeling and inversion for electromagnetic exploration methods are essential to understand behaviour of electromagnetic fields in complex subsurface. In this study, a finite element method was adopted as a numerical scheme for the 2.5-dimensional forward problem. And a finite element equation considering linear conductivity variation was proposed, when 2.5-dimensional differential equation to couple eletric and magnetic field was implemented. Model parameters were investigated for near-field with large source effects and far-field with responses dominantly by homogeneous half-space. Numerical responses by this study were compared with analytic solutions in homogeneous half-space. Blocky inversion model was modified to be applied to the forward calculation in this study and it was also adopted in the inversion algorithm. Resolution for isolated bodies were investigated to confirm possibility and limitation of inversion for electromagnetic exploration data.

• Journal of Korea Multimedia Society
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• v.5 no.4
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• pp.426-433
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• 2002

In this paper, we have studied the images which have been reconstructed by using combination of images acquired by the variation of operating frequency. When inner images have been reconstructed, they have been superposed by the surface state effect. In this case, the images of the phase object can be enhanced by the contrast of inner images. In this experiment, there are two kinds of specimens, one is a reference block haying 1/4T, 1/2T, 3/4T side drilled holes as main run piping material 111 the steam generator in NPP(Neuclear Power Plant)s and the another is a part of a hemisphere type specimen having about 1-2㎜ distance gap. It has been shown that the two results of defect shapes have better than before in this processing and phase contrast grow about twice. And we have constructed the acoustic microscope by using a quadrature detector that enables to acquire the amplitude and phase of the reflected signal simultaneously Further more ore have studied the reconstruction method of the amplitude and phase images and the enhancement method of the defect images contrast.

• Journal of Astronomy and Space Sciences
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• v.14 no.2
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• pp.312-319
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• 1997

The magnetometer is one of the most important payloads for scientific satellite to monitor the near-earth space environment. The electromagnetic variations of the space environment can be observed with the electric and magnetic field measurements. In practice, it is well known that the measurement of magnetic fields needs less technical complexities than that of electric fields in space. Therefore the magnetometer has long been recognized as one of the basic payloads for the scientific satellites. In this paper, we discuss the scientific fluxgate magnetometer which will be on board the KITSAT-3. The main circuit design of the present magnetometer is based on that of KITSAT-1 and -2 but its facilities have been re-designed to improve the resolution to about 5nT for scientific purpose. The calibration and noise level test of this circuit have been performed at the laboratory of the Tierra Tecnica company in Japan.