• Applied Microscopy
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• 제39권1호
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• pp.79-83
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• 2009

We report a useful method to estimate the electron dose rate which may be a decisive factor to characterize sample properties. Even though most mircoscopes have their own exposure meters, there are several practical concerns when such exposure meters are used to measure the electron dose rate: 1) Specimen should be avoided within the entire area of exposure meter; 2) beam current has to be always recorded whenever the operation mode is changed; 3) the electron dose rate can not be calculated for the beam current beyond the detectable range. To overcome these limitations, we suggest a useful method which utilize a CCD (charge coupled device) camera which is now a popular detector to obtain the final electron micrographs. We have evaluated the CCD sensitivity using the linear relationship between electron current on the exposure meter and counter ratio on the CCD camera which are built in KBSI-HVEM (high voltage electron microscope). Applying the new method, we obtained the CCD sensitivity which are approximately 0.039 counts/$e^-$ and 1.37 counts/$e^-$ for the Top-TV and the HV-GIF CCD cameras, respectively.

• 전기전자학회논문지
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• 제23권2호
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• pp.739-742
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• 2019

본 논문에서는 성능이 향상된 면적선량계(DAP)를 제안한다. 본 논문에서 제안한 성능이 향상된 면적선량계는 기존에 개발되었던 면적선량계를 최적화하였다. 성능이 향상된 면적선량계는 전하 적분기 및 ADC 회로의 최적화 설계, RS-485 통신용 Line transceiver의 최적화 설계, Display 회로의 최적화 설계, 연동 및 에이징을 위한 PC 기반 제어 프로그램 최적화 등을 수행하였다. 제안된 시스템의 성능을 평가하기 위하여 공인시험기관에서 실험한 결과는 Radiation dose dependence와 Radiation quality dependence는 4.2%의 측정 불확도가 측정되어 국제 표준인 ${\pm}15%$ 이하에서 정상동작 됨이 확인되었다. Energy range/Tube voltage는 30~150kV 구간에서 반응이 확인되었다. 센서필드간 감도차이와 센서필드간 면적선량 감도차이는 4.3%의 측정 불확도가 측정되어 국제 표준인 ${\pm}15%$ 이하에서 정상동작 됨이 확인되었다. 면적선량계의 재현성을 측정하기 위하여 10회 반복하여 측정한 결과 0%로 확인되어서 IEC60580 권고 사항인 2% 이하에서 정상동작 됨이 확인되었다. Digital resolution은 시간당 기준선량에 대해 오차 범위 내에서 $0.01{\mu}Gy{\cdot}m^2$의 최소단위로 측정되는 것을 확인되었다.

• 한국콘텐츠학회논문지
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• 제14권2호
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• pp.457-466
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• 2014

고 에너지 전자선 치료에 있어서 차폐물질은 종양조직 외 정상조직이나 주요장기를 보호하기 위해 사용된다. 하지만 이러한 물질에서 발생되어지는 산란선은 심부선량에 영향을 줄 수 있으며, 물질원자번호에 따라 다르게 나타난다. 이에 차폐물질로써 사용가능한 알루미늄, 구리, 납 등의 다양한 원자번호 물질을 전하 감약율 95% 되는 두께로 하여 측정과 MCNPX 모의계산으로 산란율을 비교분석하였다. 산란선 영향을 많이 받는 표면의 선량변화율은 최대 물질두께에서 +0.88%, 원자번호에서 +0.43%의 영향을 받으며, 전하 감약율 95% 되는 두께의 알루미늄, 구리, 납 물질은 측정에서 +19.70%, +15.20%, +12.40% 계산에서 +25.00%, +15.10%, +13.70%를 보였다. 이로 인해 산란율은 물질두께가 원자번호보다 많은 영향을 주며, 산란전자가 광자보다 많은 기여를 하고 있음을 알 수 있었다. 이에 임상에서의 적절한 차폐물질은 두께영향 산란선이 적게 방출되는 고 원자번호물질이 적당하다고 사료된다.

• 한국의학물리학회지:의학물리
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• 제11권2호
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• pp.147-155
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• 2000

Patient dose verification is one of the most important parts in quality assurance of the treatment delivery for radiation therapy. The dose distributions may be meaningfully improved by modulating two dimensional intensity profile of the individual high energy radiation beams In this study, a new method is presented for the pre-treatment dosimetric verification of these two dimensional distributions of beam intensity by means of a charge coupled device video camera-based fluoroscopic device (henceforth called as CCD-VCFD) as a radiation detecter with a custom-made software for dose calculation from fluorescence signals. This system of dosimeter (CCD-VCFD) could reproduce three dimensional (3D) relative dose distribution from the digitized fluoroscopic signals for small (1.0$\times$1.0 cm$^2$ square, ø 1.0 cm circular ) and large (30$\times$30cm$^2$) field sizes used in intensity modulated radiation therapy (IMRT). For the small beam sizes of photon and electron, the calculations are performed In absolute beam fluence profiles which are usually used for calculation of the patient dose distribution. The good linearity with respect to the absorbed dose, independence of dose rate, and three dimensional profiles of small beams using the CCD-VCFD were demonstrated by relative measurements in high energy Photon (15 MV) and electron (9 MeV) beams. These measurements of beam profiles with CCD-VCFD show good agreement with those with other dosimeters such as utramicro-cylindrical (UC) ionization chamber and radiographic film. The study of the radiation dosimetric technique using CCD-VCFD may provide a fast and accurate pre-treatment verification tool for the small beam used in stereotactic radiosurgery (SRS) and can be used for verification of dose distribution from dynamic multi-leaf collimation system (DMLC).

• Environmental Engineering Research
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• 제22권4호
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• pp.356-362
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• 2017

This study investigates the use of methyl-esterified eggshell membranes (MESM) for the harvesting of microalgae species under various conditions. Eggshell membranes were esterified with HCl to impact polycationic characteristics. After methyl esterification, the negative surface charge property of eggshell membrane was changed from negative to positive for all pH values to improve microalgae sorption capacity. The harvesting efficiency of microalgae by MESM reached 78-99% for all pH ranges evaluated. In addition, a 150 mesh particle size and $10mg\;L^{-1}$ MESM dose were found to yield up to 98% microalgae harvesting. These results indicate that the high cationic charge of MESM strongly adsorbs the negatively-charged microalgae. MESM is biocompatible and can be applied to the harvest of microalgae.

• Bulletin of the Korean Chemical Society
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• 제26권7호
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• pp.1083-1089
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• 2005

Most experimental studies available in the literature on filtration are based on observed average zeta potential of particles (usually 10 measurements). However, analyses of data using the average zeta potential alone can lead to misleading and erroneous conclusions about the attachment behavior because of the variation of particle zeta potentials and the heterogeneous distribution of the collector surface charge. To study characteristics of zeta potential, zeta potential distributions (ZPDs) of silica particles under 9 different chemical conditions were investigated. Contrary to many researchers’ assumptions, most of the ZPDs of silica particles were broad. The solids concentration removal was better near the isoelectric point (IEP) as many researchers have noticed, thus proper destabilization of particles is very important to achieve better particle removal in particle separation processes. While, the mean zeta potential of silica particles at a given coagulant dose was a function of particle concentration; the amount of needed coagulant for particle destabilization was proportional to the total surface charge area of particles in the suspension.

• 전자공학회논문지
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• 제50권12호
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• pp.247-253
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• 2013

본 연구의 목적은 Direct DR(Digital Radiography), Indirect DR, I.I(Image Intensifier) DR에서 X선 광자 검출 방식에 따른 선량측정 및 획득된 영상을 정량적이고 객관적인 측정을 통해 DR System을 비교 평가 하는 것이다. Rando phantom을 사용하여 입사표면선량을 측정하였으며, 측정된 입사표면선량 값을 통해 PCXMC 프로그램을 사용하여 유효선량과 방사선 조사로 인한 위험을 평가하였다. 21cm 아크릴 phantom을 사용하여 SNR(Signal to Noise Ratio), NPS(Noise Power Spectrum), CNR(Contrast to Noise Ratio)을 측정하였으며, 측정값은 통계학적 분석기법을 사용하여 유의성을 평가하였다. 입사표면선량, 주요장기선량, 유효선량 모두 direct DR이 가장 낮게 측정되었으며, direct DR 선량을 기준으로 I.I type DR은 약 1.3배, indirect DR은 약 2.4배 높은 선량 비율로 측정되었다. 방사선량에 따른 위험도 역시 동일한 비율로 측정되었다. SNR 측정 결과 direct DR측정값을 기준으로 I.I DR은 약 7.25배, indirect DR이 약 1.48배 낮은 비율로 측정되었다. CNR 측정 결과 direct DR 측정값을 기준으로 I.I DR은 약 1.16배 높고, indirect DR이 약 0.87배 낮은 비율로 측정되었다. 따라서 a-selenium 검출소자를 사용하여 X선 광자를 검출하는 방식인 direct DR은 적은 선량으로 우수한 화질의 영상을 구현함으로써 선량에 민감한 소아나 생식선이 포함된 검사 등에 유용할 것으로 사료된다. 또한 많은 진단 정보를 위한 영상 평가가 요구되는 경우에는 indirect DR이 유용할 것으로 판단된다.

• Environmental Engineering Research
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• 제10권4호
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• pp.155-164
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• 2005

This study investigated the possibility of reducing the residual aluminum (Al) in the treated water using polymers. Two raw waters (lake and river water) and three kinds of polymers (coagulant, flocculant, and filtration aids) were used for this purpose. This study found that coagulation at the high dose did not necessarily lead to the high concentration of the residual Al in the treated water. The coagulation efficacy was found more important in determining the residual Al than the coagulant dose. The use of a polymer enhanced the removal of turbidity as well as the residual Al. The coagulant aid removed the dissolved Al as well as the particulate Al by helping the coagulation and the solid-liquid separation. The flocculant aid and the filtration aid preferentially removed the particulate Al while helping the solid-liquid separation. The filtration aid reduced the residual Al substantially more effectively than the flocculant aid. The polyamine-based coagulant aid (FL) showed the better performance in reducing the residual Al and turbidity than DADMAC (WT). The cationic flocculant aid with weak charge density and the medium molecular weight (SC-020) showed the best performance in reducing the residual Al.

• Environmental Analysis Health and Toxicology
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• 제19권2호
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• pp.201-206
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• 2004

Recently, waste plastic recycling technology is transforming from Incineration system to pyrolysis gasification system which can derive the resources from environmental waste and charge no more environmental burden to nature. The present study was carried out to investigate the potential acute toxicity of derived product of pyrolysis gasifications system for recycling of waste plastic by a single oral dose in Sprague-Dawley Rats. In order to evaluate the hepatotoxic effects of derived product of pyrolysis gasification system, activities of serum transaminase were measured in rats. No related changes in survivals, clinical signs and the ratio of the liver to body weights of rats were monitored. The results showed that the single oral administration of material of pyrolysis system for recycling of waste plastic did not induce any toxic effect at orally single dose level of 0 and 100, 200, 400, 800mg/kg body weight in rats. We could not find out any significant tocxicity induced by single oral administrate of material of pyrolysis system for recycling of waste plastic.

• ETRI Journal
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• 제31권5호
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• pp.604-606
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• 2009

The primary dose effects on an insulated gate bipolar transistor (IGBT) irradiated with a $^{60}Co$ gamma-ray source are found in both of the components of the threshold shifting due to oxide charge trapping in the MOS and the reduction of current gain in the bipolar transistor. In this letter, the IGBT macro-model incorporating irradiation is implemented, and the electrical characteristics are analyzed by SPICE simulation and experiments. In addition, the collector current characteristics as a function of gate emitter voltage, VGE, are compared with the model considering the radiation damage of different doses under positive biases.