• 한국의학물리학회지:의학물리
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• 제27권4호
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• pp.175-179
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• 2016

In this study, we evaluated the reusable leuco malachite green (LMG) micelle gel properties dependent on various components of chemical concentration and compared with leuco crystal violet (LCV). The gels were delivered to 10, 20, 30, 40 and 50 Gy at 6 MV photon beam from linear accelerator and analyzed using spectrophotometry. We confirmed that the reusable LMG and LVC absorbance wavelength peak were made up at 630 nm and 600 nm respectively. The transparency of reusable LMG decreased with higher amount of trichloroacetic acid (TCAA) and lower reusable LMG dyes. 1 mM reusable LMG was the lowest transparency. The sensitivity was increased depending on lower trichloroacetic acid (TCAA) concentrations and the amount of suitable surfactant (Triton X-100), which was found to be 7 mM. However, we were not able to investigate sensitivity effects factor from reusable LMG dyes. The gel dosimeter containing 16 mM TCAA, 7 mM Triton X-100 gel dosimeter showed the highest sensitivity at $0.0021{\pm}0.0001cm^{-1}.Gy^{-1}$. The sensitivity of LCV was found to be higher than reusable LMG at $0.0037{\pm}0.0005cm^{-1}.Gy^{-1}$. The reusable LMG and LCV dose responses were shown to be $R^2=0.997$, $R^2=0.999$ respectively, as stable measurement results. Future research is necessary to improve dose sensitivity, dose rate dependency and gel fading with extensive chemical formulations.

• 한국지열·수열에너지학회논문집
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• 제12권4호
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• pp.40-46
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• 2016

In order to improve air quality of indoor environment, studies of the underfloor air distribution (UFAD) system for application in buildings are actively in progress based on temperature and air flow distribution. However, although the age of air is the major evaluation parameter, there has been very little study on this parameter for the UFAD system. In this study, we investigated the age of air to reach the air diffuser, which is installed at the bottom of the interior by the UFAD system. Computational fluid dynamics simulations showed no regular pattern to the maximum value of the age of air in accordance with air flow rate and the velocity at air diffuser. These factors can be deduced from air movement by considering that air emitted from air conditioners was rotated according to the bottom shape of the floor, and then, the age of air in the rotation center was increased. The average age of air of internal interior was reduced considerably as the flow velocity at the underfloor air diffuser was increased from 0.5 m/s to 1.0 m/s However, the age of air was not substantially affected with change in the air volume. Moreover, when the flow velocity at the underfloor air diffuser was higher than 1.0 m/s, the age of air showed no significant difference with change in air volume or height of measurement. These results imply that indoor air quality is more substantially influenced by flow velocity than air volume, and the appropriate flow velocity is 1 m/s or more.

• 산업경영시스템학회지
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• 제22권51호
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• pp.175-187
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• 1999

The notion of productivity has been extended from the quantitative change of input factors to the efficiency change meaning efficient use of resources, and to the technical change meaning the qualitative improvement of input resources. In this way, the technical change is termed as total factor productivity in the individual businesses or the manufacturing industries. They should efficiently respond to the variations of economic environment and at the same time, have to make the efforts to improve productivity by increasing managerial efficiency and rasing the level of technology change for the continuous growth. Considering the growing importance of productivity, this study closely examines the factors influctuation on the productivity, fluctuation using total factor productivity in korean manufacturing industries. For the objective this study investigates the methods of measurement about total factor productivity, establishes the hypotheses based on the preceding research and finding. The results are obtained through the examination on the outcoms of regression analysis and related data. The results can be summarized as follows, First, in the progress of korean industrialization, the qualitative growth does not depend on the total factor productivity of the technical advance, and does not lead to the industry expansion. That is, the contribution of total factor productivity turns out to be relatively low. Second, it is necessary for the manufacturing industry to improve the level of technology and to emphasize the innovation of business, since the capital investment does not completely become fixed in the growth rate of productivity. Finally, continuous R&D investment should be made to increase total factor productivity. Namely, the regulation of industrial structure with an intensive technical development is essential and should be based on scientific and technical knowledge.

• 한국의학물리학회지:의학물리
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• 제29권2호
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• pp.53-58
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• 2018

This paper evaluates patient-specific quality assurance (PSQA) in the treatment of small and multiple tumors by the CyberKnife system with fixed collimators, using an ion chamber and EBT3 films. We selected 49 patients with single or multiple brain tumors, and the treatment plans include one to four targets with total volumes ranging from 0.12 cc to 3.74 cc. All PSQA deliveries were performed with a stereotactic dose verification phantom. The A16 microchamber (Standard Imaging, WI, USA) and Gafchromic EBT3 film (Ashland ISP Advanced Materials, NJ, USA) were inserted into the phantom to measure the point dose of the target and the dose distribution, respectively. The film was scanned 1 hr after irradiation by a film digitizer scanner and analyzed using RIT software (Radiological Imaging Technology, CO, USA). The acceptance criteria was <5% for the point dose measurement and >90% gamma passing rate using 3%/3 mm and relative dose difference, respectively. The point dose errors between the calculated and measured dose by the ion chamber were in the range of -17.5% to 8.03%. The mean point dose differences for 5 mm, 7.5 mm, and 10 mm fixed cone size was -11.1%, -4.1%, and -1.5%, respectively. The mean gamma passing rates for all cases was 96.1%. Although the maximum dose distribution of multiple targets was not shown in the film, gamma distribution showed that dose verification for multiple tumors can be performed. The use of the microchamber and EBT3 film made it possible to verify the dosimetric and mechanical accuracy of small and multiple targets. In particular, the correction factors should be applied to small fixed collimators less than 10 mm.

• 융합신호처리학회논문지
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• 제13권3호
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• pp.119-129
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• 2012

의료분야에서 조직의 경화는 진단 또는 질환의 진행상황의 파악에 이용되는 중요한 정보의 한 가지이며, 객관적인 진단을 위해서는 경화의 정량적 계측법이 중요하다. 경화의 지표인 점탄성 정수를 비침습적으로 계측하는 방법으로 MRE(Magnetic Resonance Elastography) 법이 제안되고 있다. MRE 법에서는 전파파(propagating wave)의 국소 파장과 국소 감쇠율로부터 점탄성 정수를 구하는데 MRE 화상은 S/N 비가 낮아지므로, 잡음의 영향을 감소시키기 위하여 다중 위상 MRE 화상을 이용한 방법이 검토되고 있다. 본 연구에서는 다중 위상 MRE 화상에 함수를 적용하여 점탄성 정수를 측정하는 방법을 제안한다. 제안 방법은 다중 위상 MRE 화상에 점탄성파를 적용시키지만, 점탄성 정수의 공간방향으로의 변화율이나 화상에 포함된 잡음에 따라 측정값의 공간분해능을 임의적으로 설정할 수 있다는 장점이 있다. 시뮬레이션 화상을 이용한 실험과 silicone-gel phantom을 이용한 실험에 의하여 제안된 방법의 유효성을 확인하였다.

• 한국가스학회지
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• 제2권3호
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• pp.49-53
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• 1998

온라인 가스 크로마토그래피와 같은 실시간 분석기기는 데이터 채취 및 분석과정의 시간이 오래 걸려 측정 신뢰성이 낮으며 또한 설치 및 보수비용이 많이 들어서, 실제 가스 산업 공정에서는 온도, 압력과 같은 공정의 운전 변수들을 이용하여 간접적으로 가스의 성분 및 양을 감지하는 소프트 센서에 관한 연구가 활발하게 진행 중이다. 본 연구에서는 데이터 기반 소프트 센서의 설계에 있어서 공정 데이터가 갖는 패턴을 잘 반영하여 추정 능력을 높이는 내적 조합모델 PLS를 제안하고, 이를 산업체의 농도 추정 목적으로 적용하였다. 제안된 PLS모델은 기존에 제시된 모델들보다 뛰어난 추정 능력을 보였다.

• 한국의학물리학회지:의학물리
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• 제28권1호
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• pp.33-38
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• 2017

Creating individualized build-up material for superficial photon beam radiation therapy at irregular surface is complex with rice or commonly used flat shape bolus. In this study, we implemented a workflow using 3D printed patient specific bolus and describe our clinical experience. To provide better fitted build-up to irregular surface, the 3D printing technique was used. The PolyLactic Acid (PLA) which processed with nontoxic plant component was used for 3D printer filament material for clinical usage. The 3D printed bolus was designed using virtual bolus structure delineated on patient CT images. Dose distributions were generated from treatment plan for bolus assigned uniform relative electron density and bolus using relative electron density from CT image and compared to evaluate the inhomogeneity effect of bolus material. Pretreatment QA is performed to verify the relative electron density applied to bolus structure by gamma analysis. As an in-vivo dosimetry, Optically Stimulated Luminescent Dosimeters (OSLD) are used to measure the skin dose. The plan comparison result shows that discrepancies between the virtual bolus plan and printed bolus plan are negligible. (0.3% maximum dose difference and 0.2% mean dose difference). The dose distribution is evaluated with gamma method (2%, 2 mm) at the center of GTV and the passing rate was 99.6%. The OSLD measurement shows 0.3% to 2.1% higher than expected dose at patient treatment lesion. In this study, we treated Mycosis fungoides patient with patient specific bolus using 3D printing technique. The accuracy of treatment plan was verified by pretreatment QA and in-vivo dosimetry. The QA results and 4 month follow up result shows the radiation treatment using 3D printing bolus is feasible to treat irregular patient skin.

• 대한전자공학회논문지
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• 제27권10호
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• pp.106-112
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• 1990

다공질 실리콘을 열산화할 때 산화의 온도 의존성과 IR흡수 스펙트럼을 조사하여 다공질 실리콘외 산화특성을 조사하였다. PSL(porous silicon layer)을 $700^{\circ}C$에서 1시간, $1100^{\circ}C$에서 1시간으로 2단계 습식산화시켜 bulk 실리콘의 열산화막과 같은 성질의 수십 ${\mu}m$두께의 OPSL(oxidized porous silicon layer)을 짧은 시간에 형성시킬 수 있으며, 식각율과 항복전계는 산화온도와 산화 분위기에 크게 의존하는 것으로 나타났다. 이때 PSL의 산화율은 약 390nm/s이고, 항복전계는 1.0MV/cm~2.0MV/cm의 분포를 갖는다. 웨이퍼 휨을 측정하여 고온 열산화시 발생하는 산화막의 stress를 조사하였다. $1000^{\circ}C$ 이상의 고온에서 건식산화할 경우 발생하는 stress는 ${10^2}dyne/{cm^2}~{10^10}dyne/{cm^2}$로 측정되었다.

• 한국초전도ㆍ저온공학회논문지
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• 제14권2호
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• pp.24-27
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• 2012

The superconducting coil system is one of the most important components in Korea Superconducting Tokamak Advanced Research (KSTAR), which has been operated since 2008. $Nb_3Sn$ and NbTi superconductors are being used for cable-in-conduit conductors (CICCs) of the KSTAR toroidal field (TF) and poloidal field (PF) coils. The CICCs are cooled by forced-flow supercritical helium about 4.5 K. The temperature, pressure and mass flow rate of the supercritical helium in the CICCs are interacting with each other during the operation of the coils. The complicate behaviors of the supercritical helium have an effect on the operation and the efficiency of the helium refrigeration system (HRS) by means of, for instance, pressure drop. The hydraulic characteristics of the supercritical helium have been monitored while the TF coils have stably achieved the full current of 35 kA. In other hands, the PF coils have been operated with various pulsed or bipolar mode, so the drastic changes happen in view of hydraulics. The heat load including AC loss on the coils has been analyzed according to the measurement. These activities are important to estimate the temperature margin in various PF operation conditions. In this paper, the latest hydraulic behaviors of PF coils during KSTAR operation are presented.

• 한국컴퓨터정보학회논문지
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• 제19권2호
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• pp.133-142
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• 2014

의료 정보 시스템의 발달로 인해 환자들의 진료 시간이 짧아지고 그에 따라 진료 받는 환자들의 수가 증가하여 진료 데이터 양이 급속도로 증가하고 있으며, 증가하는 환자들의 데이터를 효율적으로 저장, 관리하기 위해 다양한 압축 방법에 대한 연구가 진행 중이다. 그러나 기존 방법들은 측정값을 원시 데이터로 압축하여 저장하기 때문에 압축률이 떨어지는 단점이 있다. 이러한 문제를 해결하기 위해 본 논문에서는 비트 단위로 압축 가능한 감마 코딩 기법을 이용하여 측정값과 정상범위 값과의 편차를 부호화하여 압축하는 방법을 제안한다. 또한 측정값과 편차가 가장 작은 과거 데이터를 기준치로 삼아 그 편차를 부호화하여 압축하는 방법을 제안한다. 제안하는 방법은 매우 간단하며 편차를 압축하기 때문에 기존 방법보다 압축률이 높은 장점이 있다. 성능평가를 통하여 제안한 방법이 기존 압축방법보다 우수하다는 것을 검증한다.