• 대한화학회지
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• 제34권3호
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• pp.232-238
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• 1990

Zn의 생화학적 역할을 연구하기 위하여, 간단한 모델시스템을 설정하였다. 즉, Zn가 리간드인 $OH_2나 NH_3$와 배위결합을 이루거나 carboxypeptidase A (CPA)의 기질에 해당하는 펩티드의 O=C-와 배위결합을 할 때, 그 기하학적 구조 및 net atomic charge의 변화를 조사하였다. Double Zeta basis set를 사용한 ab initio HF-SCF 계산에 의하면, Zn는 이들 리간드의 O-H, N-H, O=C-를 매우 polar하게 만든다. 특히, 펩티드의 탄소는 친전자성이 매우 증가하여, nucleophile의 공격을 용이하게 받을 수 있을 것으로 예측되었다. 또한, CPA에서 Zn 주위에 있는 리간드의 분자배위 상태를 조사하기 위하여, CPA+glycyltyrosine complex에 관한 molecular mechanics방법을 적용하였다. 이 결과를 X-ray 결과와 비교하였을 때, Zn는 4배위 결합 이외에 물분자도 관여할 것으로 예측된다.

• 한국자기학회지
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• 제13권6호
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• pp.251-256
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• 2003

컴퓨터, TV, 의료용기기 등의 모니터로 사용되는 브라운관의 자기장 영향에 따른 특성을 분석하기 위한 자기장 발생 및 측정장치를 개발하였다. 한 변의 길이가 2 m인 정육각형 형태의 3-축 자기장 발생장치, 컴퓨터, 전원공급기 및 자기장 측정기 등을 이용하여 전세계 각 나라별 지구자기장(Earth Magnetic Field, EMF)을 발생시킬 수 있는 대형 3-축 코일 시스템을 설계하고 제작하였다. 각 코일의 코일상수는 X축(E-W)는 30.31 $\mu$T/A, Y축(Ver)는 29.73 $\mu$T/A 및 Z축(N-S)는 30.51 $\mu$T/A이고, 자기장 분해능은 0.01 $\mu$T이었다. 자기장 균일도는 사용되는 편향요크(Deflection York, DY)의 크기를 고려하여 중심에서 12 cm 이내의 공간에서 측정하였고, 균일도는 1 % 내외 이었다.

• Korean Chemical Engineering Research
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• 제46권1호
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• pp.189-193
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• 2008

본 연구는 zinc aluminate 촉매를 사용한 고압연속식 고정층 반응시스템에서의 대두유와 메탄올의 transesterification에 관한 것이다. 바이오디젤 제조를 위한 고압 연속식 고정층 촉매 반응에서 반응 조건이 메틸에스터 생성에 미치는 영향이 주로 조사되었다. 촉매가 없는 경우, 거의 모든 반응 조건에서 메틸에스터의 수율이 4.5% 이하로 매우 낮았지만, $300^{\circ}C$, 1,200 psi 조건에서는 19%의 메틸에스터 수율을 보여 주었다. 이는 반응 조건이 메탄올의 초임계점에 근접하였기 때문으로 보인다. 촉매 반응에서는 무촉매 반응과 비교하여 비교적 낮은 온도와 압력에서도 높은 메틸에스터 수율을 보여주었다. 또한 수율에 미치는 반응 조건의 영향을 살펴본 결과, 반응온도, 압력, 반응물에서 메탄올 몰비가 높을수록 높은 메틸에스터 수율을 보여주었다. 반응 변수 중에서도 반응온도가 메틸에스터 수율에 가장 큰 영향을 미치는 것으로 확인되었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.380-381
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• 2007

This paper reports on the deposition conditions and properties of ITO films used as electrode layer in a organic light emitting diodes on a PET substrate. The deposition technique employed was specially designed roll-to-roll sputtering. The oxide was deposited at room temperature in an argon and oxygen plasma on a transparent conducting ITO layer on a PET film. The influence of deposition parameters such as DC power, working pressure and oxygen partial pressure has been investigated, in order to obtain the best compromise between a high deposition rate and adequate electro-optical properties. Electrical and optical properties of ITO films were analyzed by Hall measurement examinations with van der pauw geometry at room temperature and UV/Vis spectrometer analysis, respectively. In addition, the structural properties and surface smoothness were measured by x-ray diffraction and scaning electron microscopy, respectively. From optimized ITO films grown by roll-to-roll sputter system, good electrical$(6.44{\times}10^{-4}\;{\Omega}-cm)$ and optical(above 86 % at 550 nm) properties were obtained. Also, the ITO films exhibited amorphous structure and very flat surface beacause of low deposition temperature.

• 폴리머
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• 제26권5호
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• pp.680-690
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• 2002

골 재흡수 치료를 목적으로 파미드로네이트를 지속적으로 방출하는 제형으로 제조하기 위하여 락타이드-글리콜라이드 공중합체 (PLGA, 락타이드 : 글리콜라이드 몰비 = 75 : 25, 분자량 20000 g/mole 및 90000 g/mole)를 이용하여 직접압축 성형방법으로 생분해성 웨이퍼를 제조하였다. 약물과 고분자의 함량비 웨이퍼의 두께, PLGA 분자량 등을 조절하여 PLGA 웨이퍼를 제조하였고 이들의 형태학적 특성과 방출거동 및 분해거동을 살펴보았다. 웨이퍼의 제조는 혼합된 분말을 웨이퍼 제작용 몰드에 넣은 후 프레스를 이용하여 일정 압력으로 일정시간 동안 상온에서 가압하여 제조하였다. 제조된 웨이퍼는 약물의 초기함량이 증가할수록 방출속도가 빠르게 나타났으며, 제형의 두께가 두꺼워질수록 시간이 경과함에 따라 약물의 방출속도가 증가하였다. 또한 고분자의 분자량이 큰 것이 작은 것에 비해 상대적으로 초기 약물 방출량이 적고 방출되는 속도 또한 느려져. 저분자보다 오랫동안 약물이 방출되었다. 이러한 약물전달 시스템은 압축성형방법에 의해 제조하므로 제조가 간단하고 약물방출속도를 정확하게 제어할 수 있으므로 이식을 위한 제형으로 제조시 유용하게 쓰일 것으로 예상되었다.

• Tribology and Lubricants
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• 제31권2호
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• pp.42-49
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• 2015

Because of the growing need for high-speed transport options such as trains and aircraft, there is increasing demand for technology related to high-speed trains. Among them, braking systems are important in high-speed trains in terms of reliability. Especially, the disk brake system, in use in most high-speed trains, transforms kinetic energy into thermal energy and noise. Therefore, the material properties of both the friction materials and disks are expected to influence the tribological characteristics. In this paper, the tribological characteristics depend on the hardness of the brake disks between the Cu-based sintered metallic friction material and the heat-treated heat-resisting steel disks. A lab-scale dynamometer used to perform braking tests at a variety of braking speeds using dry conditions. The test results revealed that the hardness of the disks affects the friction coefficients, friction stabilities, and wear rates. Thus, the brake system using the heat-resisting steel disk requires proper heat-treatment. These differences are considered to be caused by the change in tribological mechanisms and the generation of an oxide layer on the friction surfaces. The oxide layers on the friction surfaces are confirmed to Fe₂O₃ by x-ray diffraction (XRD) and scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) analysis.

• 한국재료학회지
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• 제18권1호
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• pp.32-37
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• 2008

The electrical, optical, structural and surface properties of an indium tin oxide (ITO) film grown on a flexible PET substrate using a specially designed roll-to-roll (R2R) sputtering system as a function of the DC power, $Ar/O_2$ flow ratio, and rolling speed is reported. It was observed that both the electrical and optical properties of the ITO film on the PET substrate were critically dependent on the $Ar/O_2$ flow ratio. In addition, x-ray diffraction examination results showed that the structure of the ITO film on the PET substrate was an amorphous structure regardless of the DC power and the $Ar/O_2$ flow ratio due to a low substrate temperature, which was maintained constant by a main cooling drum. Under optimized conditions, ITO film with resistivity of $6.44{\times}10^{-4}{\Omega}-cm$ and transparency of 86% were obtained, even when prepared at room temperature. Furthermore, bending test results exhibited that R2R-grown ITO film had good flexibility which would be applicable to flexible displays and solar cells.

• 대한방사선기술학회지:방사선기술과학
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• 제42권1호
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• pp.25-30
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• 2019

Whole Spine Scanography (WSS) using the Digital Radiography (DR) system is an examination that requires whole body X-ray exposure, which involves more exposure to radiation for patients than other general radiographies. This can affect the occurrence of breast cancer. This research measured radiation dose when breasts were shield and not shield using the Auto Exposure Control (AEC) mode. The radiation dose without a shield was 1.540 mGy, and that using a collimator was measured 0.506 mGy. Moreover, 0.733 mGy was measured when 1 shield (0.3 mm) was used, and $0.523{\mu}Gy$ when 5 of them (1.5 mm) were used. The results showed that the radiation dose with 5 shields and the radiation dose with a collimator were similar. Moreover, 0.233 mGy was measured when 8 shields (2.4 mm) were used. The standard deviation were 0.081 when using collimator and 0.014 when 5 shields were used. Also, when 8 shields were used, it was found to be 0.002. Most patients who go under a scoliosis test are children or young people who are highly sensitive to radiation. In the research results, the case where the organs sensitive to radiation, women's breasts, were shielded showed more distinct differences compared to without shields. It is considered that using shields can provide more constant shield than using a collimator and lower the risk of breast cancer caused by exposure to radiation.

• 대한방사선기술학회지:방사선기술과학
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• 제41권6호
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• pp.567-572
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• 2018

Radiation therapy is one of the beneficial choices in the treatment of cancer. This is a comparison of TPS(Treatment Planning System) and GEANT4-DICOM, which should be preceded by the best radiation therapy. A treatment plan for prostate cancer was established with Eclipse and the point doses 366.1 cGy, 189.1 cGy, 213.4 cGy, 127 cGy, 105.7 cGy of any five prostate, bladder, rectum, right femoral head and left femoral head were identified. GEANT4-DICOM simulation showed that the results of Eclipse and ${\pm}2%$ dose error were confirmed. The monthly X-ray output agreement management value recommended by TG-142 is ${\pm}2%$, which means that the experimental results can be meaningful. In conclusion, GEANT4-DICOM is an infinite way to obtain more extended dose information once the time constraints are overcome in the simulation.

• 대한금속재료학회지
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• 제50권8호
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• pp.605-611
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• 2012

ZnO nanostructures were grown on R-plane sapphire substrates with seed layers annealed at different temperatures ranging from 600 to $800^{\circ}C$. The properties of the ZnO nanostructures were investigated by scanning electron microscopy, high-resolution X-ray diffraction, UV-visible spectrophotometer, and photoluminescence. For the as-prepared seed layers, ZnO nanorods and ZnO nanosheets were observed. However, only ZnO nanorods were grown when the annealing temperature was above $700^{\circ}C$. The crystal qualities of the ZnO nanostructures were enhanced when the seed layers were annealed at $700^{\circ}C$. In addition, the full width at half maximum (FWHM) of near-band-edge emission (NBE) peak was decreased from 139 to 129 meV by increasing the annealing temperature to $700^{\circ}C$. However, the FWHM was slightly increased again by a further increase in the annealing temperature. Optical transmittance in the UV region was almost zero, while that in the visible region was gradually increased as the annealing temperature increased to $700^{\circ}C$. The optical band gap of the ZnO nanostructures was increased as the annealing temperature increased to $700^{\circ}C$. It is found that the optical properties as well as the structural properties of the rod-shaped ZnO nanostructures grown on R-plane sapphire substrates by hydrothermal method are improved when the seed layers are annealed at $700^{\circ}C$.