• The Journal of the Petrological Society of Korea
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• v.9 no.4
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• pp.205-210
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• 2000

Measurements of phase identification and degree of orientation for fine-grained (about 0.3 mm in diameter) minerals in rock samples performed by micro-area X-ray diffractometer.$Al_{2}SiO_{5}$ polymorphs (andalusite, kyanite and sillimanite) were chosen for the measurements and target minerals were existed on thin sections. Micro-area X-ray diffractometer is composed of 3(${\omega}\;{\chi}\;{\phi}$)-circle oscillating goniometer and position sensitive proportional counter (PSPC). $CuK_{\alpha}$ radiation was used as X-ray source and a pin hole ($50\;\mu\textrm{m}$$ in diameter) collimator was selected to focus radiation X-ray onto the target minerals. Phase identification and diffracted X-ray peak indexing were carried out by 3(${\omega}\;{\chi}\;{\phi}$)-circle oscillation measurement. Then, 2(${\omega}\;{\phi}$)-circle oscillation measurement was made for the purpose of searching the prevailing lattice plane of the minerals on thin section surface. Finally, for a selected peak by 2-circle oscillation measurement, X-ray pole figure measurement was executed for the purpose of check the degree of orientation of the single lattice direction and examine its pole distribution. As a result of 3-circle oscillation measurement, it was possible that phase identification among $Al_{2}SiO_{5}$ polymorphs. And from the results of 2-circle oscillation measurement and X-ray pole figure measurement, we recognized that poles of andalusite (122), kyanite (200) and sillimanite (310) lattice plances were well developed with direction normal to each mineral surface plane respectively. Therfore, the measurements used with micro-area X-ray diffractometer in this study will be a useful tool of phase identification and degree of orientation measurement for fine-grained rock forming minerals.

• Journal of the Korean Society of Radiology
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• v.15 no.1
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• pp.71-78
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• 2021

When continuous X-ray are used when acquiring and X-ray image, even the same material may not be accurately represented in the image according to the thickness due to various X-ray energies. To solve this problem, the X-ray energy spectrum was changed to improve the image quality. Using SPEKTR v3.0, an X-ray energy spectrum with an additional filter added and a general X-ray energy spectrum using only a unique filter were obtained. Simulation was performed using the obtained X-ray energy spectrum as a radiation source for Geant4 Application for Tomographic Emission (GATE). Using GATE data, an X-ray image with an additional filter and an image reconstructed from and X-ray image without an additional filter were compared and analyzed through a mono energy image of 74 keV. In the case of using the X-ray energy spectrum without using an additional filter, the amount of X-rays transmitted according to the thickness of the same material is different from the amount that decreases according to the thickness of the material. Similar results were obtained as the amount decreased with the material thickness. In other words, a similar result was obtained when the reduced dose was used with a mono energy. When an X-ray image is obtained by changing an X-ray energy spectrum using an additional filter, a more accurate result of transmission of X-rays may be obtained. In radiological examination, it was confirmed that the appropriate use of the additional filter has a great effect on improving the image quality.

• Electronics and Telecommunications Trends
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• v.34 no.5
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• pp.71-80
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• 2019

Gallium nitride (GaN) can be used in high-voltage, high-power-density/-power, and high-speed devices owing to its characteristics of wide bandgap, high carrier concentration, and high electron mobility/saturation velocity. In this study, we investigate the technology trends for X-/Ku-band GaN RF power devices and MMIC power amplifiers, focusing on gate-length scaling, channel structure, and power density for GaN RF power devices and output power level and output power density for GaN MMIC power amplifiers. Additionally, we review the technology trends in gallium arsenide (GaAs) RF power devices and MMIC power amplifiers and analyze the technology trends in RF power devices and MMIC power amplifiers based on both GaAs and GaN. Furthermore, we discuss the current direction of national research by examining the national and international technology trends with respect to X-/Ku-band power devices and MMIC power amplifiers.

• Journal of Radiation Protection and Research
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• v.19 no.3
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• pp.189-198
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• 1994

An angular dependence experiment was made and a performance test of the Teledyne dosimetry system was done in accordance with the ANSI N13.11-1992. The angular dependence experiment was performed with $^{137}Cs$ and low energy X-ray beam. Teledyne dosimetry system performed well at the $0^{\circ}$ angle of incidence for all dosimeters in both vertical and horizontal irradiations. It would have easily passed the 0.5 tolerance limit. But the dosimetry system was not performed well at the ${\pm}60^{\circ}$ angle of incidence for low energy X-ray beam. The accuracy for $^{137}Cs$ beam at all angles of incidence was within the 0.5 tolerance limit. Therefore performance of the dosimetry system could be considered acceptable in case that the dosimeter is irradiated to $^{137}Cs$ beam. However, it could not be acceptable for the dosimeter irradiated to low energy X-ray, especially at more than ${\pm}40^{\circ}$

• Journal of Radiation Protection and Research
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• v.2 no.1
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• pp.38-46
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• 1977

오늘날 에너지 공급(供給)을 위한 새로운 해결책(解決策)의 하나로서 등장(登場)한 원자력발전소(原子力發電所), 재래(在來)의 X선(線) 진료(診療) 이외(以外)에 의학계(醫學界)에 도입(導入)된 방사선원(放射線源), 그리고 각종(各種) 전자생산품(電子生産品) 등(等)의 증가현상(增加現象)은 방사선(放射線) 방어(防禦) 문제(問題)와 관련(關聯)하여 보건의학분야(保健醫學分野)에서 종사(從事)하는 사람들에게 지대(至大)한 관심(關心)거리가 되고있다. 그래서, 우선(于先) 방사선(放射線)에 관(關)한 사항(事項)중에서 가장 기초(基礎)가되는 방사선량계측(放射線量計測)에 있어서 그 양(量)과 단위(單位) 문제(問題)가 체계적(體系的)으로 서술(敍述)되었다. 즉(卽) 방사선(放射線)이 인체(人體)에 끼칠 수 있는 해(害)로운 영향(影響)에 그 주안점(主眼點)을 두어 조사선량(照射線量), 흡수선량(吸收線量), 선량당량(線量當量), 그리고 그들의 관계(關係) 및 방사능등(放射能等)에 관(關)하여 토론(討論)되었다. 특(特)히 조사선량률(放射線量率), X는 비(比)감마선선상수(線常數), ($\Gamma$)를 포함(包含)하는 함수(函數)로 표현(表現)되었고, 끝으로 인체(人體) 내부(內部)에 축적(蓄積)된 방사능(放射能)으로부터의 영향(影響)에 의(依)한 이른바 생물학적효과(生物學的效果) (Somatic or Genetic Effects)와 관련(關聯)되는 내부흡수선량율(內部吸收線量率)은 평형흡수선량상수(平衡吸收線量常數)($\Delta_i$)와 흡수율($F_i$)를 포함(包含)하는 수학적(數學的) 모델로 소개(紹介)되었다. 한편 방사능(放射能)은 방사선원(放射線源) 물질(物質)의 자연붕괴율(自然崩壞率)이므로 다른 방사선량(放射線量)들 즉(卽) 조사선량(照射線量), 흡수선량(吸收線量)그리고 선량당량(線量當量)과는 별도(別途)로 취급(取扱)하였음을 부언(附言)한다.

• Journal of Radiation Protection and Research
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• v.11 no.1
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• pp.57-64
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• 1986

This paper described an improved technical method required for proper evaluation of personnel exposures by means of the photographic dosimeter developed by KAERI in lower gamma or X-ray energy regions, with which response of the dosimeter varies significantly. With calibration of the dosimeter in the energy range from 30 to 300 keV, the beam spectrum was carefully selected and specified it adequately. The absorber combinations and absorber thickness used to obtain the specified X-ray spectra from a constant potential X-ray machine were determined theoretically and also experimentally. A correlation between the density and exposure for the four separate energies, such as $49\;keV_{eff},\;154\;keV_{eff}\;250\;keV_{eff}\;and\;662\;keV$, is experimentally determined. As a result, it can be directly evaluated the exposure from the measured response of dosimeter.

• Progress in Medical Physics
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• v.9 no.4
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• pp.195-200
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• 1998

Purpose: When an elongated x-ray field is used for treating a patient, the equivalent- field method is commonly used for the output calculation. This study is intended for investigating potential factors such as, beam quality, field elongation ratio, and depth of measurement, which might effect on the applicability of the equivalent square technique for output calculation. The derivation of a 'rule of thumb' for the application criteria of the equivalent-field method is also aimed. Materials and Methods: Three x-ray beams, 4-, 6- and 10-MV, were employed for this study. Width of the rectangular field was ranged from 5-40 cm and the elongation ratio (length/width) 1:0 to 10:0. An elongation effect was measured in a water phantom at three different depths, dmax, 5-cm, and 10-cm. For an elongated field and its equivalent square field, the output factor was measured and the difference in the output factor were examined between two fields. Results and Discussions: As the elongation ratio increases, a larger discrepancy in outputs is observed between the elongated rectangular field and its corresponding equivalent square field. Output was measured larger for an elongated field than for its corresponding equivalent square field and the maximal difference over 10 % was found. The difference was found larger for the smaller field with the same elongation ratio. The effect of the beam quality and the depth of measurement on the output difference was minimal. Conclusion: Based on the study, there is criteria for the application of the method for output calculation. For the combination of long axis and elongation ratio whose relationship satisfies Elongation ratio < (0.48) (Long axis) - 0.5, the equivalent-field method is valid for output calculation within 2 % for the field whose long axis < 25-cm. For other combinations, instead of using the equivalent-field method, direct output measurement is recommended. This criteria can be applied for 4-10 MV x-ray beams up to 10-cm depth.

• Progress in Medical Physics
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• v.1 no.1
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• pp.51-60
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• 1990

Dose distributions around Co- 60 moving source in high dose rate remote afterloading unit, Buchler 3K unit, were experimented with X-omat V films and calculations. In our experiments, film dosimetries have achieved to evaluated the axial dose distributions for source oscillations were 0, 3.5, 5.0 and 6.0 cm in periodically, In results, the dose distributions in axial of source movement showed apparently higher than in transverse direction caused by source locations, dwelling time and air gap in the applicator. In the calculations, the dose rate was derived by using the inverse square law, filteration corrections and Meisberger constant for scatter corrections as source movings. In our experiments and calculations, the average dose uncertainties were showed -2.1$\pm$1.9% in fixed sourdce, -2.9$\pm$1.8%, -7.4$\pm$6.1% and -6.7$\pm$4.6% at 3.5 cm, 5.0 cm and 6.0 cm source oscillations, but the calculations have showed very close to experimental dose rate within 4 cm distance from source.

• Proceedings of the KIEE Conference
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• 2007.04b
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• pp.121-123
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• 2007

광변환 물질을 사용하여 X-선이나 감마방사선을 가시 광으로 변환한 다음 CCD 카메라를 통하여 광량을 측정하면 방사선의 양을 간접적으로 측정할 수 있다. 본 연구에서는 CCD형 비상대응 로봇용 고속 삼차원 방사선 위치 탐지장치에서 방사선 위치 센싱의 핵심 역할을 수행하는 CCD 방사선 탐지부를 간접 방사선 측정 방법을 응용하여 고안하고 구현한 다음 이에 대한 방사선 특성시험 및 거리측정을 수행하였다. 시험 결과로부터 구현한 CCD형 방사선 센서가 방사선 위치 및 선량 탐지장치로 활용 가능성이 충분함 확인하였다.

• Radiation Oncology Journal
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• v.10 no.2
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• pp.147-153
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• 1992

It is ideal thing to compensate tissue deficit without skin contamination in curvatured irradiation field of high energy photon beam. The 3-dimensional compensating technique utilizing tissue equivalent materials to ensure an adequate dose distribution and skin sparing effect was described. This compensator was made of paraffin ($70\%$) and stearin wax ($30\%$) compound. The parameters for evaluation of the effect on skin dose in application of compensator were considered in the size of the field, the thickness of the compensator and the source-to-axis distance. The results are as follows; the skin doses were not changed even though application of the compensator, but depended on the field size and the source-to-axis distance, and the skin doses were only slightly changed within $1\%$ relative errors as increasing the thickness of the compensator in these experiments.