• Progress in Medical Physics
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• v.22 no.4
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• pp.190-197
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• 2011

Currently, the dose distribution calculation used by commercial treatment planning systems (TPSs) for high-dose rate (HDR) brachytherapy is derived from point and line source approximation method recommended by AAPM Task Group 43 (TG-43). However, the study of Monte Carlo (MC) simulation is required in order to assess the accuracy of dose calculation around three-dimensional Ir-192 source. In this study, geometry factor was calculated using segmented sources integration method by dividing microSelectron HDR Ir-192 source into smaller parts. The Monte Carlo code (MCNPX 2.5.0) was used to calculate the dose rate $\dot{D}(r,\theta)$ at a point ($r,\theta$) away from a HDR Ir-192 source in spherical water phantom with 30 cm diameter. Finally, anisotropy function and radial dose function were calculated from obtained results. The obtained geometry factor was compared with that calculated from line source approximation. Similarly, obtained anisotropy function and radial dose function were compared with those derived from MCPT results by Williamson. The geometry factor calculated from segmented sources integration method and line source approximation was within 0.2% for $r{\geq}0.5$ cm and 1.33% for r=0.1 cm, respectively. The relative-root mean square error (R-RMSE) of anisotropy function obtained by this study and Williamson was 2.33% for r=0.25 cm and within 1% for r>0.5 cm, respectively. The R-RMSE of radial dose function was 0.46% at radial distance from 0.1 to 14.0 cm. The geometry factor acquired from segmented sources integration method and line source approximation was in good agreement for $r{\geq}0.1$ cm. However, application of segmented sources integration method seems to be valid, since this method using three-dimensional Ir-192 source provides more realistic geometry factor. The anisotropy function and radial dose function estimated from MCNPX in this study and MCPT by Williamson are in good agreement within uncertainty of Monte Carlo codes except at radial distance of r=0.25 cm. It is expected that Monte Carlo code used in this study could be applied to other sources utilized for brachytherapy.

• Progress in Medical Physics
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• v.24 no.3
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• pp.171-175
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• 2013

Applicator of various kind of number ten kinds is used to raise from efficiency of brachytherapy to maximum. The compatibility of radiation source and applicator is very important subject for safety brachytherapy. Developed high dose rate brachytherapy source through Hanaro nuclear reactor in Korea Atomic Energy Research Institute and improve compatibility with using equipment in present. In this research, we wished to evaluate stability mechanical safety of radiation source and we developed phantom for evaluate several quality about Ir-192 sealed source that improve newly in Korea Atomic Energy Research Institute and is improved. The result for suitability of Ir-192 HDR source with brachytherapy tools that did normal operation in 2.2~2.7 cm extent about change of equal curvature and consider change of sudden curvature that did normal operation in radius 1.5~1.8 cm extent.

• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.487-494
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• 2020

The distance between the source and the detector, the diameter of the detector, and the volume effect of the radiation source result in a change in solid angle at the detector entrance, which affects the determination of detection efficiency by causing a difference in path length within the detector. A typical analysis method for calculating solid angles was useful only for a source (⁶⁰Co) with a simple geometric structure, so in this experiment, the distance between the detector and the source was measured by switching on for up to 25 cm with the reference point of window cap 0.5 cm. In addition, 450 and 1000 ㎖ Marinelli beaker of standard volumetric sources were closely adhered to the detector. For circular point sources co-axial with the detector, the change in the solid angle to the distance from the detector window is equal to half the square radius of the source versus the square radius of the detector, if the resulting relationship of the calculation analysis results in the detector being less than the radius of the source. Since the solid angular difference is 0.5 the result of Monte Carlo is acceptable. The relationship between detector and source distance is shown. Solid angles have been verified to decrease rapidly with distance. Measurement and simulation results for a volumetric source show a difference of ±1.01% from a distance of 0 cm and less than 4 % when the distance is reduced to 5 and 10 cm. It can be seen that the longer distance, the smaller efficiency angle, and the exponential increase in attenuation as the energy decreases, is reflected in the calculation of efficiency. Thus, the detection efficiency has proved sufficient for the use of solid angle and Monte Carlo codes.

• Journal of radiological science and technology
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• v.36 no.4
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• pp.291-297
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• 2013

This study is aimed to evaluate the effect of $T_{1/2}$ upon count rates in the analysis of dynamic scan using NaI (Tl) scintillation camera, and suggest a new quality control method with this effects. We producted a point source with $^{99m}TcO_4^-$ of 18.5 to 185 MBq in the 2 mL syringes, and acquired 30 frames of dynamic images with 10 to 60 seconds each using Infinia gamma camera (GE, USA). In the second experiment, 90 frames of dynamic images were acquired from 74 MBq point source by 5 gamma cameras (Infinia 2, Forte 2, Argus 1). There were not significant differences in average count rates of the sources with 18.5 to 92.5 MBq in the analysis of 10 to 60 seconds/frame with 10 seconds interval in the first experiment (p>0.05). But there were significantly low average count rates with the sources over 111 MBq activity at 60 seconds/frame (p<0.01). According to the second analysis results of linear regression by count rates of 5 gamma cameras those were acquired during 90 minutes, counting efficiency of fourth gamma camera was most low as 0.0064%, and gradient and coefficient of variation was high as 0.0042 and 0.229 each. We could not find abnormal fluctuation in $x^2$ test with count rates (p>0.02), and we could find the homogeneity of variance in Levene's F-test among the gamma cameras (p>0.05). At the correlation analysis, there was only correlation between counting efficiency and gradient as significant negative correlation (r=-0.90, p<0.05). Lastly, according to the results of calculation of $T_{1/2}$ error from change of gradient with -0.25% to +0.25%, if $T_{1/2}$ is relatively long, or gradient is high, the error increase relationally. When estimate the value of 4th camera which has highest gradient from the above mentioned result, we could not see $T_{1/2}$ error within 60 minutes at that value. In conclusion, it is necessary for the scintillation gamma camera in medical field to manage hard for the quality of radiation measurement. Especially, we found a tendency that count rate changes over time at this study, and we proved that it can effect $T_{1/2}$. And also, there is need of appropriate phantoms and the method of quality management like this study, because there are not any advice or limitation degrees for domestic medical purpose scintillation camera.

• Journal of radiological science and technology
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• v.30 no.2
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• pp.147-151
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• 2007

AAPM TG43 report has recommended to measure air kerma strength with the strength of source. Main purpose of this study is to verify the accuracy of air kerma strength provided by manufacturer. Materials for this study were MAX-4001 Electrometer, HDR 1000 Plus of the corporation of standard imaging, and 6 french bronchial Applicator with 1000 mm. we measured ionization current in 10-90 mm range from the bottom of the central axis of chamber. The reference point of calibration displayed by the maximum ionization current in the ionization current curve was measured, and air kerma strength was computed from the maximum ionization current. we acquired 50 mm distance to correspond with the maximum ionization current in the ionization current curve. Its distance has perfectly fitted to the source reference point of calibration certificate of UW-ADCL. Air kerma strength computed value has measured about 0.5% more than calibration value provided by manufacturer. Air kerma strength of calibration certificate provided by manufacturer has acquired reliable results. This study shows that considering the move error of dwell position of source and the dead space length in well-type chamber is a good way to get an accurate result.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.4
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• pp.389-394
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• 2023

In recent years, use of machine automation is rising in the industry. Ships also obtain machine condition information from sensor as digital information. However, on ships, crew members regularly surveil the engine room to check the condition of equipment and their information through analog gauges. This is a time-consuming and tedious process and poses safety risks to the crew while on surveillance. To address this, engine room surveillance using an autonomous mobile robot is being actively explored as a solution because it can reduce time, costs, and the safety risks for crew. Analog gauge reading using an autonomous mobile robot requires digitization for the robot to recognize the gauge value. In this study, image processing techniques were applied to achieve this. Analog gauge images were subjected to image preprocessing to remove noise and highlight their features. The center point, indicator point, minimum value and maximum value of the analog gauge were detected through image processing. Through the straight line connecting these points, the angle from the minimum value to the maximum value and the angle from the minimum value to indicator point were obtained. The obtained angle is digitized as the value currently indicated by the analog gauge through a formula. It was confirmed from the experiments that the digitization of the analog gauge using image processing was successful, indicating the equivalent current value shown by the gauge. When applied to surveillance robots, this algorithm can minimize safety risks and time and opportunity costs of crew members for engine room surveillance.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2021.11a
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• pp.195-197
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• 2021

한국의 현대 해운업이 불과 반세기 만에 세계적인 수준으로 성장하는 데 해기사가 주도적인 역할을 했음은 주지의 사실이다. 이는 1960년대 중반에 시작된 해외취업과 외화획득, 선원송출업, 해운대리점업, 선박소유 등의 연관 산업의 발전을 통해 해운산업의 성장에 '내부 '파급효과'와 '외부경제 효과'를 미쳤기 때문이다. 그 중에서도 해외취업선원의 외화획득은 경제발전 초창기에 절대적으로 필요했던 외화를 제공했다는 점에서 그 경제적 의의가 컸다고 할 수 있다. 1965년부터 1999년까지 해외취업 선원들은 82억 6178달러를 벌어들인 데 반해, 파독 근로자들은 1963년부터 1977년까지 1억 15만달러를 국내로 송금한 데 그쳤다. 이 연구에서는 1978년에서 1992년까지 미국선사인 Lasco에 취업했던 해기사의 월급여명세서를 분석해 해기사의 평생 임금수입액을 계산해 볼 것이다. 분석 결과, 11년 5개월간 승선기간 동안 24만 3230달러(1억 6606만 7839원)을 벌어들인 것으로 나타났다. 이는 승선기간 월평균 120만 5282원의 수입을 올린 것으로 우리나라 제조업 월평균임금의 약 3.8배에 상당하는 것이고, 1963-1977년까지 파독근로자 1인의 평균외화송금액 5273달러에 비해 46배에 상응하는 것이다.

• Korean Architects
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• no.3 s.335
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• pp.53-63
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• 1997

"제가 하고 싶은 비평은 우리 건축물의 좋은 점이 무엇이고 그것이 왜 좋은지를 먼저 찾아보는 것입니다. 저는 아직 연구가 부족해서인지 지금까지 우리의 건축이 (진심으로) 어떤 점에서 잘됐다는 얘기를 들어본 적이 별로 없습니다. 그런데 제가 아는 원로 건축가들은 어려운 중에 무척 열심히 살아오신 분들로 알고 있습니다. 아무리 여건이 나쁘다 하여도 그들의 작품 안에 좋은 점이 하나도 없으리라고는 생각지 않습니다. 그런데 아무도 그 좋은 점을 찾아내려하지 않으면, 그 건물이 사라지고(좋은 건물이 아니라고 생각하니까 언젠가는 헐리겠죠.) 도면도 기억도 사라진 후 우리는 계속 우리를 한심하게 생각하고 있을 것입니다. 우리가 우리의 좋은 점을 찾지 않는데 누가 우리의 좋은 점을 찾아주겠습니까? 한국 건축의 자부심(개혁?)은 건축가에 의해서가 아니라 건축 비평가에 의해서 먼저 이루어져야 합니다. 잘 팔리는 신파극 뒤에는 잘나가는 변사가 있듯이 말입니다. 물론 배우도 잘 나가야하지만. 그리고 저는 제가 모르는(건축가나 사용자나 같이 모르는) 서양철학에 비추어 이 건물을 이해하지 않겠습니다. 또 건축가가 건축역사의 어느 부분에 속할 것을 목표하여 설계하지 않은 이상, 건축사에 비추어 특히 세계건축사에 비추어 이 건물을 보지 않겠습니다. 저는 이 건물을 설계하는 이의 입장에서 또 사용하는 이의 입장에서 이해하려 노력하겠습니다.

• Journal of Navigation and Port Research
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• v.33 no.8
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• pp.531-537
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• 2009

As the Port State Control Inspection recognized that almost marine casualties are caused by human faults rather than vessel's defaults, it has put more emphasis on the qualification of ships' crew and the education required. Accordingly, for shipping companies it is an urgent task to operate effective crew education system that can meet the standards of international agreements and domestic laws. Therefore, this study aims at deriving the attitude of crews of 'S' shipping company on the education and some implication for the effective crew education systems. For this questionnaire survey has been carried out and the data analysed by the respondent groups.

• Journal of the Korean Vacuum Society
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• v.20 no.6
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• pp.403-408
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• 2011

To develop the MFX (Micro-Focus X-ray) tube, the trajectories of electrons emitted from the field emission cathode was simulated using SIMION program. Regardless of starting position of the electron in emitter, we found out the fact that there is the optimum extractor voltage Ve, which can focus the electron beam on one place. Extractor voltage Ve varies depending on the source voltage Vs, but the ratio of two voltages (Ve/Vs) is always constant, its value was 99.4%. When the ratio of two voltages (Ve/Vs) was 99.4%, the beam diameter in the cross-over point was $1.2{\mu}m$. Because the focal spot size in MFXG (Micro-Focus X-ray Generator) can not be less than the cross-over diameter within MFX tube, it is important to find out the conditions that can make a smaller beam diameter. Therefore, the above results is considered to be a very important ones in the development of the MFXG.