• Progress in Medical Physics
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• v.23 no.4
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• pp.317-325
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• 2012

The Varian PORTALVISION (Varian Medical Systems, US) shows significant overresponses as the off-center distance increases compared to the predicted dose. In order to correct the dose discrepancy, the off-axis correction is applied to VARIAN iX linear accelerators. The portal dose for $38{\times}28cm^2$ open field is acquired for 6 MV, 15 MV photon beams and also are predicted by PDIP algorithm under the same condition of the portal dose acquisition. The off-axis correction is applied by modifying the $40{\times}40cm^2$ diagonal beam profile data which is used for the beam profile calibration. The ratios between predicted dose and measured dose is modeled as a function of off-axis distance with the $4^{th}$ polynomial and is applied to the $40{\times}40cm^2$ diagonal beam profile data as the weight to correct measured dose by EPID detector. The discrepancy between measured dose and predicted dose is reduced from $4.17{\pm}2.76$ CU to $0.18{\pm}0.8$ CU for 6 MV photon beam and from $3.23{\pm}2.59$ CU to $0.04{\pm}0.85$ CU for 15 MV photon beam. The passing rate of gamma analysis for the pyramid fluence patten with the 4%, 4 mm criteria is improved from 98.7% to 99.1% for 6 MV photon beam, from 99.8% to 99.9% for 15 MV photon beam. IMRT QA is also performed for randomly selected Head and Neck and Prostate IMRT plans after applying the off-axis correction. The gamma passing rare is improved by 3% on average, for Head and Neck cases: $94.7{\pm}3.2%$ to $98.2{\pm}1.4%$, for Prostate cases: $95.5{\pm}2.6%$, $98.4{\pm}1.8%$. The gamma analysis criteria is 3%, 3 mm with 10% threshold. It is considered that the off-axis correction might be an effective and easily adaptable means for correcting the discrepancy between measured dose and predicted dose for IMRT QA using EPID in clinic.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2005.11a
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• pp.189-191
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• 2005

전국매립지 중 수도권, 울산, 대구 세 매립지의 침출수를 채수하여 Photobacterium을 이용한 독성 test와 Yeast Two-hybride Based Assay을 이용하여 에스트로겐성을 측정하였다. 독성도 값은 대구에서 145로 가장 높은 값을 나타냈다. 에스트로겐성은 울산이 hER 3.2ppt, mER 210ppt로 가장 높게 나타났으며, 채수지점 모두 industrial hormones에 반응성이 좋은 mER 값이 높게 나타났다. 특히 대구지점은 독성도 값은 높으나 에스트로겐성은 낮은 값을 나타내는 것으로 보아 호르몬 영향을 억제하는 antangonist chemicaldml 존재 가능성이 시사된다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.324-325
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• 2012

반도체 소자의 미세화가 진행됨에 따라 고품질의 절연막, 즉 낮은 두께에서 높은 밀도와 낮은 누설 전류를 필요로 하게 되었다. 이를 위해 기존의 화학 기상 증착법을 이용한 절연막 증착의 공정 압력을 낮추어 1 Pa 이하의 공정 압력에서 절연막 증착 공정이 필요로 하게 되었다. 본 연구에서는 화학 기상 증착법을 이용하여 최저 0.1 mtorr의 극 저압에서 SiO2 절연막증착 공정을 구현하였고, 증착된 박막의 특성을 평가하였다. Fig. 1은 공정 압력의 변화에 따른 화학 기상 증착 장비의 플라즈마 상태를 나타낸 결과이다. 1.5 mtorr의 공정 압력 까지는 플라즈마의 상태가 균일하게 나타나지만, 그 이하의 압력에서는 플라즈마 균일도가 떨어지는 결과가 나타났다. 이는 기존의 플라즈마 공정을 이용하여 절연막 증착 공정이 어려움을 제시하는 결과이며, 이의 해결을 위해 새로운 형태의 플라즈마 장치가 필요함을 시사한다. Fig. 2는 각각의 공정 압력에 다른 $SiO_2$ 박막의 증착 결과를 AFM을 이용하여 측정한 결과이다. 박막의 표면 거칠기 값은 0.9 mTorr까지는 3 nm 수준이며, 0.1 mTorr에서는 0.4 nm로 측정되었다. 플라즈마 상태가 균일하지 않은 0.1 mTorr에서도 비교적 균일한 박막을 얻을 수 있었으나, 높은 공정 업력에 비해 전체적인 균일도도 낮은 결과이며, 이는 플라즈마 상태를 보완함으로서 해결 가능하다. 측정된 박막의 밀도는 2.311~2.59 g/$cm^3$의 수준으로 벌크 상태의 밀도 값에 근접한 결과를 얻었으며 이는 저압에서 증착한 $SiO_2$ 박막의 품질이 높음을 시사한다. 절연막의 증요한 특성 중 하나인 누설 전류 값은 MIM 구조를 이용하여 측정하였다. 측정된 누설 전류 값은 10~12 A 수준으로 기존 반도체 소자 공정에 적용 가능한 수준이다. 고 품질의 절연체 박막 증착을 위해서는 플라즈마 구조를 보완할 필요가 있으며, 이를 이용하면 반도체 소자 제작에 요구되어 지는 절연막 증착이 가능할 것으로 예상된다.

• Journal of the Korean Society of Radiology
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• v.14 no.6
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• pp.781-790
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• 2020

Tract-Based Spatial Statics (TBSS) after obtaining the image by examining a diffusion tensor image that can determine the presence or absence of damage to the cerebral white matter and gray matter for middle-aged men aged 30 to 50 with the starting age of drinking as a variable. As a result of measuring and analyzing the FA (fractional anisotropy) value of the brain gray matter region to the hippocampal region nerve fibers, the lower the alcohol start age in all regions, the lower the anisotropy measurement value, but the FA value was statistically significant. The study results indicated by the FA results measured in this study are that the earlier the drinking start age, the more severe the morphological changes in all neurological and anatomical brain regions in the hippocampal region of the brain gray matter and seriously affect the nerve fiber tissue. It can be said to harm and damage nerve fibers and affect functional morphological variations associated with alcohol.

• Composites Research
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• v.16 no.3
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• pp.58-67
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• 2003

To perform the realtime strain and fracture monitoring of the smart composite structures, two optical fiber sensor systems are proposed. The two types of the coherent sources were used for fracture signal detection - EDFA with FBG and EDFA with Fabry-Perot filter. These sources were coupled to EFPI sensors imbedded in composite specimens. To understand the characteristics of matrix crack signals, at first, we performed tensile tests using surface attached PZT sensors by changing the thickness and width of the specimens. This paper describes the implementation of time-frequency analysis such as short time Fourier transform (STFT) and wavelet transform (WT) for the quantitative evaluation of fracture signals. The experimental result shows the distinctive signal features in frequency domain due to the different specimen shapes. And, from the test of tensile load monitoring using optical fiber sensor systems, measured strain agreed with the value of electric strain gage and the fracture detection system could detect the moment of damage with high sensitivity to recognize the onset of micro-crack fracture signal.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.3
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• pp.23-30
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• 1985

When a digital filter implementation is based on a difference equation, the frequency characteristics cannot be obtained by direct computation, but be obtained by experiment or analogized by Z-transform. In this paper, the method to compute the frequency magnitude response of the function expressed in a difference equation is derived from PARSEVAL's relation. To verify the validity of this new method two types of digital filters are implemented. Both filters' characteristics are measured and their values are compared with the value obtained by a Z-transform and with the value by a difference equation. The result shows that the measured values and the values obtained by the difference equaton are more closer than the values by a Z-transform. And the difference-equaton-based filters' showed sharper roll off characteristics than the Z-transform-based filters. Therefore when a digital filter implementation is based on a difference equation, the characteristics computation by a difference equation predicts better practical results than based on Z-transform.

• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.535-544
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• 2012

Filtration on horizontal filter medium facing upward is accompanied by sedimentation. When sedimentation phenomenon is not considered, the average specific cake resistance by filtration could be in error more than two times. In the previous paper on this subject, it was insisted that the solid mass fraction of suspension changes in filtration period by sedimentation. But we could not find out the degree of change. At the first half of this paper, the average specific cake resistance measured by permeation will be proved to be exact in several means. The average specific cake resistance conventionally measured by filtration does not give correct results because it uses initial solid mass fraction of suspension. Then we calculated the changed solid mass fraction of suspension due to sedimentation during filtration by the experimental values obtained "filtration-permeation" method. We also determined the solid mass fraction at a certain moment of filtration from the suspension height and a new equation derived in this study. The two results were compared and proven that they almost matched.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.30 no.2
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• pp.141-145
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• 2004

This study was pursued to measure skin feeling of cosmetics by mechanical methods. For this attempt, skin feeling of cosmetics such as spreading properties, tackiness, and residual greasy feeling after skin application was explored with the amount and kinds of cosmetic compositions-emulsifiers, waxes, thickeners, polyols, and oils. Furthermore, the relationship between these cosmetic compositions and viscometry of cosmetic products was studied. In case of emulsifiers, waxes, and thickeners, they showed strong correlation with both skin feeling and the value of phase angle, the property of viscometry, respectively, while polyols and oils were observed a special tendency neither skin feeling nor the property of viscometry. It leads to the conclusion that skin feeling may be corresponded to not values of a mechanical measure completely but a function of several properties. We expect that a better correlation can be discovered with additionally measured properties such as friction, volatility, etc.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.2 no.2
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• pp.9-14
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• 2009

This study was conducted to develop a electronic circuit of primary color reaction for urine analyzer for measuring color response of urine strip. A primary color reaction system is equipped with the computer, electronic circuit, tray, detecting assembly and software. The determination of coefficient($R^2$) between reagent and color sensor were 0.9801(R), 0.9868(G) and 0.9837(B). To evaluate the system verification, we measured the primary color reaction of erythrocytes, Bilirubin, Urobilinogen, Ketones and Protein. We concluded that it is possible to use the developed the primary color reaction system for urine analyzer using u-health.

• Journal of radiological science and technology
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• v.33 no.4
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• pp.355-362
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• 2010

This study determines a range of CT parameter values in Brain CT which are minimizing patient absorption dose without compromising the image quality and optimal exposure condition. We measured dose and image noise using conventional CT parameters in Brain CT. In additon, we evaluated dose, SNR and PSNR of head phantom images while changing kVp and rotation time. In this study, effectiveness of dose that was achieved from dose reproducible experiments in conventional head CT condition is determined by changing kVp and rotation time. Dose and PSNR is related to low dose-high resolution condition. In conclusion, we suggest that using proposed conditions is effective for imaging to compare with conditions proposed by the manufacturer.