• 대한기계학회논문집A
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• 제26권4호
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• pp.617-624
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• 2002

An equation of J-integral for a penny-shaped crack at the end of the fiber embedded in rubber matrix is proposed. The values of J-integral for the specimens with various crack and specimen radius are obtained by FEA(Finite Element Analysis). The dimensional analysis is applied to derive an equation of J-integral as a nonlinear elastic energy release rate. The geometry and deformation calibration function in an equation of J can be expressed in a separated form. The geometry calibration function characterizing the effects of cord and specimen size is expressed in a polynomial form of fourth order. The deformation calibration function characterizes the effect of the overall level of strain. As approaching the infinitesimal strain, the value of the deformation calibration function approaches the results of LEFM(Linear Elastic Fracture Mechanics).

• 한국방사선학회논문지
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• 제16권5호
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• pp.537-543
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• 2022

본 연구의 목적은 이중에너지 CT를 이용한 유효원자번호 정보를 통한 췌장 검출 가능성 연구이다. 10개의 다양한 인체 등가 물질의 유효원자번호를 Stoichiometric calibration을 통해 추정하였다. Stoichiometric calibration을 위해 저에너지와 고에너지에 해당하는 10개 인체 등가 물질에 대한 HU값을 이용하였다. 이를 바탕으로 반복 알고리즘을 통해 인체 등가 물질에 대한 유효원자번호 영상을 추출하였다. 연구결과에 따르면, 유효원자번호에 따른 감약의 비는 R²값이 0.9999로 추정되었고, Pancreas, water, Liver, Blood, Spongiosa, Cortical bone의 유효원자번호는 이론값과 비교하여 전체적으로 1% 이내의 정확도를 보였다. 췌장암 검사는 조영제를 사용하므로 잠재적인 조영제 부작용 가능성이 있다. 이를 해결하기 위해 조영 증강 없는 이중에너지를 이용한 유효원자번호 추출을 통해 정확하고 안전한 검사에 기여할 수 있을 것으로 사료된다. 본 연구를 바탕으로 향후 연구에서는 임상 영상을 바탕으로 췌장암의 HU값을 이용하여 췌장암 검출에 대한 연구를 수행할 것이다.

• Nuclear Engineering and Technology
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• 제40권5호
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• pp.419-428
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• 2008

During the overhaul period of nuclear power plants in Korea, an ROV(Remotely Operated Vehicle) enters the cold-leg pipes connected with the reactor to examine the state of the thermal sleeves and their positions in the safety injection nozzles. To measure the positions of the thermal sleeves or scratches with video images recorded during the examination, time-varying camera parameters should be known, such as the focal length and principal points used for the capturing each video image. In this paper, we propose a camera calibration and measurement scheme by using a single image containing two circular grooves of a cylindrical nozzle whose radius and distance are known.

• Nuclear Engineering and Technology
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• 제53권4호
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• pp.1297-1303
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• 2021

Most thickness measurement techniques using X-ray radiation are unsuitable in field processes involving fast-moving organic films. Herein, we propose a Compton scattering X-ray radiation method, which probes the light elements in organic materials, and a new simple, non-destructive, and non-contact calibration-free real-time film thickness measurement technique by setting up a bench-top X-ray thickness measurement system simulating a field process dealing with thin flexible organic films. The use of X-ray fluorescence and Compton scattering X-ray radiation reflectance signals from films in close contact with a roller produced accurate thickness measurements. In a high-thickness range, the contribution of X-ray fluorescence is negligible, whereas that of Compton scattering is negligible in a low-thickness range. X-ray fluorescence and Compton scattering show good correlations with the organic film thickness (R² = 0.997 and 0.999 for X-ray fluorescence and Compton scattering, respectively, in the thickness range 0-0.5 mm). Although the sensitivity of X-ray fluorescence is approximately 4.6 times higher than that of Compton scattering, Compton scattering signals are useful for thick films (e.g., thicker than ca. 1-5 mm under our present experiment conditions). Thus, successful calibration-free thickness monitoring is possible for fast-moving films, as demonstrated in our experiments.

• 한국재료학회지
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• 제29권5호
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• pp.336-341
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• 2019

The gas adsorption isotherm requires accurate measurement for the analysis of porous materials and is used as an index of surface area, pore distribution, and adsorption amount of gas. Basically, adsorption isotherms of porous materials are measured conventionally at 77K and 87K using liquid nitrogen and liquid argon. The cold volume calibration in this conventional method is done simply by splitting a sample cell into two zones (cold and warm volumes) by controlling the level sensor in a Dewar filled with liquid nitrogen or argon. As a result, BET measurement for textural properties is mainly limited to liquefied gases (i.e. $N_2$ or Ar) at atmospheric pressure. In order to independently investigate other gases (e.g. hydrogen isotopes) at cryogenic temperature, a novel temperature control system in the sample cell is required, and consequently cold volume calibration at various temperatures becomes more important. In this study, a cryocooler system is installed in a commercially available BET device to control the sample cell temperature, and the automated cold volume calibration method of temperature variation is introduced. This developed calibration method presents a reliable and reproducible method of cryogenic measurement for hydrogen isotope separation in porous materials, and also provides large flexibility for evaluating various other gases at various temperature.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2001년도 추계학술발표회요약집
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• pp.364.1-364
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• 2001

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2001년도 추계학술발표회요약집
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• pp.318.1-318
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• 2001

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1516-1519
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• 2004

A tele-operated robot should be used to maintain and inspect nuclear power plants to reduce the radiation exposure to the human operators. During an overhaul of the nuclear power plants in Korea, a ROV(Remotely Operated Vehicle) may enter a cold-leg connected to the reactor to examine the state of the thermal sleeve and it's position in the safety injection nozzle. To measure the positions of the thermal sleeve or scratches from the video images captured during the examination, the camera parameters should be identified. However, the focal length of the CCD camera could be increased to a close up of the target and the aspect ratio and the center of the image could also be varied with capturing devices. So, it is desired to self-calibrated the intrinsic parameters of the camera and capturing device with the video images captured during the examination. In the video image of the safety injection nozzle, two or more circular grooves around the nozzle are shown as ellipse contours. In this paper, we propose a camera self-calibration method using a single image containing two circular grooves which are the greatest circles of the cylindrical nozzle whose radius and distance are known.

• Nuclear Engineering and Technology
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• 제53권9호
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• pp.3018-3025
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• 2021

The authors developed a volumetric dosimetry detector system using in-house 3D-printable plastic scintillator resins. Three tumor model scintillators (TMSs) were developed using magnetic resonance images of a tumor. The detector system consisted of a TMS, an optical fiber, a photomultiplier tube, and an electrometer. The background signal, including the Cherenkov lights generated in the optical fiber, was subtracted from the output signal. The system showed 2.1% instability when the TMS was reassembled. The system efficiencies in collecting lights for a given absorbed energy were determined by calibration at a secondary standard dosimetry laboratory (k_SSDL) or by calibration using Monte Carlo simulations (k_sim). The TMSs were irradiated in a Gamma Knife® Icon^TM (Elekta AB, Stockholm, Sweden) following a treatment plan. The energies absorbed to the TMSs were measured and compared with a calculated value. While the measured energy determined with k_SSDL was (5.84 ± 3.56) % lower than the calculated value, the energy with k_sim was (2.00 ± 0.76) % higher. Although the TMS detector system worked reasonably well in measuring the absorbed energy to a tumor, further improvements in the calibration procedure and system stability are needed for the system to be accepted as a quality assurance tool.

• Bulletin of the Korean Chemical Society
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• 제29권1호
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• pp.127-129
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• 2008

EPR spectroscopic technique was applied for a quantitative analysis of Eu(II) for a speciation of europium in a LiCl-KCl eutectic melt. By adopting the first absorption line of each isotopes (151Eu and 153Eu), a calibration plot was obtained. The calibration of the EPR intensity shows a good linearity according to the amount of Eu(II). The EPR intensity was identified to increase proportionally with a decrease of the attenuation parameter for EPR microwave power. The fluorescence technique was used qualitatively to find whether either of Eu(II) or Eu(III) ions exists in a molten salt sample. The ICP-AES technique was also adopted to determine the total concentration of europium in the sample, since EPR is only sensitive for detecting the Eu(II) ion. The extent of the reduction of Eu(III) in the LiCl-KCl eutectic melt at 723 K was determined by using this technique.