• 한국방사선학회논문지
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• 제14권4호
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• pp.477-486
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• 2020

본 연구는 디지털 단층영상합성장치에서 재구성 필터, X-선원 이동궤적 및 이동간격이 화질에 미치는 영향을 평가하고 임상적 검증을 수행하는 것을 목적으로 한다. 필터링후역투영법 재구성 시 Ramp, Shepp-Logan, Cosine, Hamming, Hann 및 Blackman 필터를 사용하였고, X-선원 이동궤적의 변화를 위해 1 × 36, 2 × 18, 3 × 12, 4 × 9 및 6 × 6 배열 형태의 이동궤적을 모사하였다. X-선원 이동간격에 따른 영향을 평가하기 위해 X-선원간 거리를 5, 10, 20, 30 및 40 mm로 변화시켰다. 재구성 영상의 깊이분해능, 공간분해능 및 잡음을 평가하기 위해 인공물확산함수, 반치폭 및 신호대잡음비를 측정하였다. 연구결과 Ramp 및 Blackman 필터를 사용하였을 때 각각 공간분해능 및 잡음 특성이 최대화 되었으며, X-선원 이동궤적의 형태가 1 × 36일 때 깊이분해능과 잡음 특성이 가장 우수하였다. 또한 X-선원 이동간격이 증가함에 따라 깊이분해능 및 잡음 특성은 향상되었고, 공간분해능은 저하되었다. 따라서 디지털 단층영상합성장치를 통한 3차원 영상획득 시 재구성 필터, X-선원 이동궤적 및 이동간격이 화질에 미치는 영향은 각기 다르며, 진단 목적에 부합하는 조건 설정이 필요하다.

• Current Optics and Photonics
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• 제4권1호
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• pp.9-15
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• 2020

Fresnel zone plates have been widely used in many applications, such as x-ray telescopes, microfluorescence, and microimaging. To obtain an x-ray Fresnel zone plate, many fabrication methods, such as electron-beam etching, ion-beam etching and chemical etching, have been developed. Fresnel zone plates fabricated by these methods will inevitably lead to some nonideal factors, which have an impact on the focusing characteristics of the zone plate. In this paper, the influences of these nonideal factors on the focusing characteristics of the zone plate are studied systematically, by numerical simulations based on scalar diffraction theory. The influence of the thickness of a Fresnel zone plate on the absolute focusing efficiency is calculated for a given incident x-ray's wavelength. The diffraction efficiency and size of the focal spot are calculated for different incline angles of the groove. The simulations of zone plates without struts, with regular struts, and with random struts are carried out, to study the effects of struts on the focusing characteristics of a zone plate. When a Fresnel zone plate is used to focus an ultrashort x-ray pulse, the effect of zone-plate structure on the final pulse duration is also discussed.

• 농업과학연구
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• 제16권1호
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• pp.102-110
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• 1989

가열조건(加熱條件)을 달리한 감자 전분(澱粉) 호화액(糊化液)의 X-ray diffractogram과 표면구조(表面構造)를 SEM으로 촬영(撮影)하여 관찰(觀察)한 결과(結果), 전분입자(澱粉粒子)의 모양은 계란형(鷄卵形) 이었으며, 호화시간(糊化時間)과 호화온도(糊化溫度)가 증가(增加)할수록 전분입자(澱粉粒子)는 파괴(破壞)되었고, 완전(完全) 호화시(糊化時)에는 전분(澱粉)의 구조(構造)를 나타내지 않았다. 시료(試料)감자 전분(澱粉)의 구성(構成)을 검토(檢討)하기 위하여, Amylose 함량(含量)과 Blue Value를 측정(測定)한 결과(結果), 각각(各各) 23.5%, 0.49%였다. X-ray diffractogram으로 호화도(糊化度)를 측정(測定)한 결과(結果), $70^{\circ}C$에서 90 %의 호화도(糊化度)를 보였고, 동일(同一)한 온도(溫度)에서 가열시간(加熱時間)에 따른 변화(變化)는 크지 않았으며, 인산염(燐酸鹽)의 농도(濃度)가 증가(增加)할수록 호화도(糊化度)도 증가(增加)하였다.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.411-414
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• 2002

The CdTe semiconductor detector has a higher detection efficiency for x-rays and $\square$amma rays and a wider energy band gap compared with Si and Ge semiconductor detectors. Therefore, the size of the detector element can be made small, and can be operated at room temperature. The interaction between a CdTe detector and incident x-rays is mainly photoelectric absorption in the photon energy range of up to 100 keV. In this energy range, Compton effects are almost negligible. We have developed a 256 channel CdTe array detector system for monochromatic x-ray CT using synchrotron radiation. The CdTe array detector system, the element size of which is 1.98 mm (h) x 1.98 mm (w) x 0.5 mm (t), was operated in photon counting mode. In order to improve the spatial resolution, we tilted the CdTe array detector against the incident parallel monochromatic x-ray beam. The experiments were performed at the BL20B2 experimental hutch in SPring-8. The energy of incident monochromatic x-rays was set at 55 keV. Phantom measurements were performed at the detector angle of 0, 30 and 45 degrees against the incident parallel monochromatic x-rays. The linear attenuation coefficients were calculated from the reconstructed CT images. By increasing the detector angle, the spatial resolutions were improved. There was no significant difference between the linear attenuation coefficients which were corrected by the detector angle. It was found that this method was useful for improving the spatial resolution in a parallel monochromatic x-ray CT system.

• 한국입자에어로졸학회지
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• 제5권2호
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• pp.53-62
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• 2009

In this study, the continuous monitoring of the concentration of PM-10 atmospheric particulate matter using beta ray attenuation method was compared with gravimetric method from September, 2006 to August, 2007. On the effects of the PM-10 concentration and mass difference by relative humidity and precipitation were considered. The result showed that the measurement error between beta ray method and gravimetric method are within -3~6% in average, which means PM-10 concentration data with beta ray method are relatively comparable. The current study also shows that the high PM-10 concentration events are mainly due to haze, Asian dust, and high relative humidity and the PM-10 mass concentration is closely related with relative humidity and precipitation events. Based on daily mean data, the PM-10 increases as relative humidity increases up to 70~80%, then decreases over 80% due to the precipitation. However, the distinct measurement discrepancy was not shown between beta ray method and gravimetric method based on current results. Consequently, this study shows that the collocated measurement in different instrument is essential in order to quantify the accuracy of PM-10. Furthermore, the more comprehensive and spatially distributed comparison is needed and this is remained for future study.

• 대한소아치과학회지
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• 제11권1호
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• pp.131-143
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• 1984

150 rats weighting about 150gm were devided into control group of 80 and experimental group of 70. Control group was subdivided into the irradiated vitamin D injection group and X-ray irradiated group. Experimental group was given 2.0mg ergocalciferol by four intramuscular injection prior to X-ray irradiation with single 800 rads and 1,500 rads respectively. Experimental animals from each group was sacrificed after 1, 3, 7, 14, and 28 days and their incisors were investigated by histopathological examination. The results were as follows; 1. In the irradiated groups, it showed dentin hypoplasia and formation of dentinoid substance caused by degeneration of odontoblast at the early stage. Especially, 1,500 rads group which was severely effected showed formation of osteoid dentin at the apical portion and severe injuries of dental papilla at the first week. 2. In the vitamin D2 administration group, it showed thinned dentin layer at the early stage but, taking time, predentin and dentin layer was thickened. At the fourth week, dentin was chiefly composed of interglobular dentin, especially in the lingual portion. 3. Using in combination of overdose vitamin D2 administration and X-ray irradiation, it effected severely odontoblast, undifferentiated mesenchymal cells around tooth germ and pulp tissue. At the early stage, dentin layer was thinned but, taking time, it was thickened and composed of interglobular dentin caused by calcification of predentin layer. 4. In 800 rads irradiation after the overdose vitamin D2 administration, it showed formation of osteoid dentin in the lingual portion at the first week. In the 1,500 rads irradiation after the overdose vitamin D2 administration, it showed formation of osteoid dentin and degeneration of ameloblast in both buccal and lingual portion at the first week, and enamel hypoplasia caused by edema and loss of polarity of ameloblasts at the second week. 5. By the entire experiment, the overdose vitamin D2 administration and X-ray irradiation effected severely odontoblasts, undifferentiated mesenchymal cells of dental papilla, and primitive cells of tooth germ among the dental tissue. Especially using combination of overdose vitamin D2 administration and X-ray irradiation also effected ameloblasts, resulting in enamel hypoplasia.

• KSBB Journal
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• 제19권2호
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• pp.159-163
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• 2004

$\AA$의 분해능을 가진 Bacillus macerans에서 분리 정제한 cyclodextrin glucanotransferase의 결정 구조를 X-ray를 이용하여 분자 대치법을 사용하여 밝혔다. 정확한 구조는 16.6% ( $R_{free}$ = 20.5%)의 결정학적 R-factor를 가지고 있다. 두 개의 $Ca^{2+}$$_{-}$/ 이온이 점유된 새로운 금속 결합자리는 활성 자리의 도달 채널에서 발견되었다. $Ca^{2+}$$_{-}$/ 이온에 결합하는 음의 하전을 띤 아미노산 잔기들이 많이 밀집되어 있고 이 때, domain A ($\alpha$H에서 아미노산 잔기 283-297)의 중심부에 연결 부분은 $\beta$ 13-$\alpha$G 이었다. $\beta$13-$\alpha$G 부분은 활성 자리의 입구에 위치한 subsite 1에서 -1 과 Tyr260 (subsite 2)사이에 있는 촉매 부위 Glu258을 포함하고 있다. 비록 $\alpha$-CGTase 부류에서 잘 보존되어 있지는 않으나, 새로운 $Ca^{2+}$$_{-}$/ 자리 3a,b가 이 $\alpha$-CGTase의 활성도와 생성물의 특이성에 중요한 역할을 하리라 추측된다.다.

• 대한의용생체공학회:의공학회지
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• 제25권6호
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• pp.623-628
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• 2004

본 논문에서는 원적외선 온열효과가 자율 신경계에 미치는 영향을 심박변동(HRV)을 이용하여 평가 하였다. 측정된 심박변동신호를 FFT 의한 전력스펙트럼을 구함으로써 자율 신경계의 반응 특성을 고찰하고 Poincare plot 분석 방법을 이용하여 결과를 비교 분석하였다. 실험을 통해 심박변동 신호분석해보면 원적외선 온열에 노출되기 전에 비해 노출된 후에 매우 복잡한 모습임을 관찰 할 수 있었는데 이것은 자율신경계가 관여하는 심혈관계 제어 메커니즘이 원적외선 온열에 노출되기 전보다 노출된 후에 더욱 복잡함을 반영하는 것으로 분석된다.

• 한국방사선학회논문지
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• 제15권5호
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• pp.705-713
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• 2021

엑스선 영상 시스템으로부터 획득한 영상의 공간주파수에 대한 해상도를 분석하기 위해 변조전달함수(modulation-transfer function, MTF)를 계산한다. 일반적으로 검출기의 응답함수는 슬릿-카메라를 사용하여 선분포함수(line-spread function, LSF)를 획득하고, 푸리에 변환을 거쳐 변조전달함수를 도출한다. 엑스선이 항상 슬릿-카메라 중심에 입사해야 된다는 조건 때문에 실험자에 의해 발생하는 검출기와 슬릿-카메라의 기울임은 검출기 성능에 영향을 미치게 된다. 이와 더불어 기울임에 확대율이 더해진다면 엑스선 영상 시스템의 성능평가에 문제가 발생할 것이다. 본 연구에서는 실험적 오차에 기인하여 이를 변조전달함수, 즉 푸리에 도메인에서 실험과 분석모델을 해석하였고, 공간주파수에 미치는 영향을 분석하였다. 나아가 다양한 엑스선 영상 시스템에 있어 성능평가가 실시되어야 할 것이고, 실험적 오차는 불가결하게 발생하며 이를 허용할 수 있는 범위에 대한 검토가 이루어져야 한다.

• 방사선산업학회지
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• 제18권1호
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• pp.53-61
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• 2024

This study explores the effects of X-ray irradiation for biological control and high-temperature degradation on dye stability in dyed textiles with Gardenia. To evaluate this study, optimal extraction solvents for these textiles were identified by comparing them with a crocin standard solution. Extraction using pyridine closely matched crocin. The study then assessed the stability of X-ray irradiation and high-temperature degradation on these textiles. Transparent yellow dyes were observed in all samples. Color differences were found to increase at higher irradiation doses and longer degradation periods. While UV spectroscopy spectra showed broadening and lowering trends with higher irradiation doses and longer degradation periods, suggesting a reduction in colorant transition, mass spectrometry revealed minimal chemical changes. In conclusion, both X-ray irradiation and high-temperature degradation induced spectral changes without complete dye decomposition. Major colorants were consistently detected.