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      • SCOPUSKCI등재

        Microstructure and Tensile Properties in Low Pressure Cast Al-Si Alloy through Cooling Rate Control

        Suh,,Jun-Young,Park,,Sung,Jin,Lee,,Hee-Kwon,Chang,,Si,Young Materials Research Society of Korea 2020 한국재료학회지 Vol.30 No.2

        In this study, three kinds of metal chills such as SS400, AC4CH and brass, with different thicknesses of 40 ~ 80 mm, were applied for low pressure casting of Al-Si alloy to control cooling rate. The microstructural characteristics with increasing cooling rate were represented using factors including D<sub>1</sub>, D<sub>2</sub>, size of primary α phases and shape factor and size of eutectic Si. The tensile properties were investigated and additionally analyzed based on the microstructural characteristics. As the cooling rate increased, D<sub>1</sub>, D<sub>2</sub>, and sizes of primary α phases and eutectic Si apparently decreased and the shape factor of eutectic Si increased to over 0.8. The ultimate tensile strength (UTS) and yield strength (YS) increased with decreasing D<sub>1</sub>, D<sub>2</sub>, and size of primary α phases, while elongation increased with decreasing size of eutectic Si and concurrently increasing shape factor of eutectic Si. This indicated that the primary α phases and eutectic Si in Al-Si alloy were refined with increasing cooling rate, resulting in improvement of UTS and YS without sacrificing elongation. After the tensile test, preferential deformation of primary α phases was observed in the Al-Si alloy produced at higher cooling rates of more than 0.1 K/s.

      • KCI등재

        전자기 듀오캐스팅으로 제조한 Al-Mn/Al-Si 하이브리드 알루미늄합금의 미세조직과 인장 특성

        박성진,김종호,박준표,장시영,Park,,Sung-Jin,Li,,Tingju,Kim,,Chong-Ho,Park,,Jun-Pyo,Chang,,Si-Young 한국재료학회 2012 한국재료학회지 Vol.22 No.2

        The microstructure and tensile properties of Al-Mn/Al-Si hybrid aluminum alloys prepared by electromagnetic duocasting were investigated. Only the Al-Mn alloy showed the typical cast microstructure of columnar and equiaxed crystals. The primary dendrites and eutectic structure were clearly observed in the Al-Si alloy. There existed a macro-interface of Al-Mn/Al-Si alloys in the hybrid aluminum alloys. The macro-interface was well bonded, and the growth of primary dendrites in Al-Si alloy occurred from the macro-interface. The Al-Mn/Al-Si hybrid aluminum alloys with a well-bonded macro-interface showed excellent tensile strength and 0.2% proof stress, both of which are comparable to those values for binary Al-Mn alloy, indicating that the strength is preferentially dominated by the deformation of the Al-Mn alloy side. However, the degree of elongation was between that of binary Al-Mn and Al-Si alloys. The Al-Mn/Al-Si hybrid aluminum alloys were fractured on the Al-Mn alloy side. This was considered to have resulted from the limited deformation in the Al-Mn alloy side, which led to relatively low elongation compared to the binary Al-Mn alloy.

      • 전립선암에 대한 초음파 영상유도 방사선치료의 Setup 오차 분석을 통한 재현성 평가

        박성용,임승규,시명근,이지해,김종열,조은주,Park,,Sung,Yong,Lim,,Seung,Kyu,Si,,Myoung,Geun,Lee,,Ji,Hae,Kim,,Jong,Yeol,Cho,,Eun,Joo 대한방사선치료학회 2017 대한방사선치료학회지 Vol.29 No.2

        목 적: 전립선암 환자에 대한 비침습적이고 피폭선량에 대한 부담이 없는 초음파를 이용한 영상유도방사선치료의 Setup 오차 분석을 통해 치료의 재현성을 평가해 보고자 한다. 대상 및 방법: 치료가 종료된 전립선암 환자 26명의 1,105영상에 대하여 앞-뒤(anterior-posterior, AP), 좌-우(right-left, RL), 위-아래(superior-inferior, SI) 방향의 Setup 오차에 대해 평균, 표준편차와 3D-error을 분석하였다. 또한 오차범위 0-1 mm, 1-3 mm, 3-5 mm, 5 mm 이상에 대한 각 오차 빈도수(frequency, %) 분석을 통하여 AP, RL, SI 방향에 대한 방향성을 확인 하였다. 결 과: Setup 오차는 AP, RL, SI 방향에 대하여 평균과 표준편차는 $1.87{\pm}1.36mm$, $1.73{\pm}1.22mm$, $2.01{\pm}1.40mm$였다. 3D-error는 평균 $3.63{\pm}1.63mm$였다. 각 방향에 대한 Setup 오차값의 빈도(frequency, %)는 AP 방향에 대한 오차범위 0-1 mm에서 29 %, 1-3 mm에서 50.2 %, 3-5 mm에서 19.6 %, 5 mm 이상에서 1.3 %였다. RL 방향에 대하여 오차범위 0-1 mm에서 31.3 %, 1-3 mm에서는 52.5 %, 3-5 mm에서는 15.8 %, 5 mm 이상에서 0.5 %였다. 마지막으로 SI 방향에 대한 오차범위 0-1 mm에서 26.3 %, 1-3 mm에서 50.2 %, 3-5 mm에서 22.4 %, 5 mm 이상에서 1.1 %였다. 결 론: Setup error는 SI 방향에서 $2.01{\pm}1.40mm$로 가장 컸으며 오차 빈도는 모든 방향에서 50 % 이상 오차 범위 1-3 mm에 들어온 것으로 확인되었다. $Clarity^{TM}$ Auto scan을 이용한 초음파영상유도 방사선치료는 치료 전에 방광의 전처치 상태, target의 구조 등을 관찰이 가능하고, 치료 중 target의 움직임을 실시간으로 monitoring하여 빠른 repositioning이 가능하다. 결과적으로 초음파를 이용한 실시간 영상유도방사선치료는 치료의 재현성을 높일 수 있을 것으로 사료된다. Purpose: To evaluate the reproducibility of image-guided radiotherapy using ultrasonography which is non-invasive, without radiation exposure for prostate cancer patients. Materials and Methods: We analyzed the setup variation of 1,105 images for 26 prostate cancer patients and the mean, standard deviation and 3D-error in AP, RL and SI directions. Setup variations were classified 0-1 mm, 1-3 mm, 3-5 mm, 5 mm and more. Results: The mean and standard deviation of setup variation in AP, RL and SI directions was $1.87{\pm}1.36mm$, $1.73{\pm}1.22mm$ and $2.01{\pm}1.40mm$. The 3D-error in AP, RL and SI directions was $3.63{\pm}1.63mm$. The frequency of setup variation in AP direction was 29 % in the range from 0 mm to 1 mm, 50.2 % in the range from 1 mm to 3 mm, 19.6 % in the range from 3 mm to 5 mm and 1.3 % in the range of 5 mm or more. In RL direction, the frequency was 31.3 % in the range from 0 mm to 1 mm, 52.5 % in the range from 1 mm to 3 mm, 15.8 % in the range from 3 mm to 5 mm and 0.5 % in the range of 5 mm or more. SI direction, the frequency of errors in the range from 0 mm to 1 mm was 26.3 %, 50.2 % in the range from 1 mm to 3 mm, 22.4 % in the range from 3 mm to 5 mm, and 1.1 % in the range of 5 mm or more. Conclusion: The setup error was highest in the SI direction of $2.01{\pm}1.40mm$. The frequency in each direction was the highest in more than 50 % in the range from 1 mm to 3 mm. $Clarity^{TM}$ Auto scan is possible to monitoring the motion of the prostate during the treatment and to repositioning the patient. In conclusion real-time image-guided radiotherapy using ultrasonography will be increase the reproducibility of radiation therapy.

      • KCI등재SCOPUS

        Controlled infiltration profile of SiC coating layer on graphite by Si vapor deposition reaction

        Kuk-Jin,Hwang,Si-Young,Bae,Kyoung-Ho,Kim,Yoon-Cheol,Lee,Jung-Tae,Hwang,Heesoo,Lee,Seong,Min,Jeong,Myung-Hyun,Lee 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.2

        SiC-coated graphite was successfully fabricated at different temperatures (1300-1600 oC) through a silicon vapor depositionreaction (Si-VDR) process. Si powder was used for the Si source of the SiC coating layers. When Si powder was evaporatedat high temperature near the melting point of bulk Si, Si gases are moved and changed into Si liquid at the surface of thegraphite. The high-temperature process facilitated the formation of SiC coating layers on the graphite. The microstructural,mechanical, and thermal oxidation properties of the coated graphite were investigated.

      • KCI등재

        LiF:Mg,Cu,Na,Si TL 소자의 선량계적 특성

        남영미,김장렬,장시영 대한방사선 방어학회 2001 방사선방어학회지 Vol.26 No.1

        최근 개발된 방사선량 측정용 LiF:Mg,Cu,Na,Si TL 소자의 글로우 곡선, 방출스펙트럼, 광자에 대한 선량의존성, 에너지의존성 및 페이딩 등과 같은 물리적 및 선량계적 특성들을 연구하였다. LiF:Mg,Cu,Na,Si TL 소자는 LiF:Mg,Cu,Na,Si TL 분말에 압력을 가한 후 소결하는 방법으로 제조되었다. 방사선에 대한 특성을 알아보기 위하여 광자선 조사는 한국원자력연구소의 X선 발생 장치 및 137Cs γ선 원격조사장치를 이용하였으며, 사용된 광자선 에너지 범위는 20-662keV, 선량 범위는 10-6-102 Gy이었다. 글로우 곡선은 수동형의 TLD 판독장치 (System 310, Teledyne)로 질소를 흘리면서 선형적인 가열률로 측정하였으며, TL 강도는 글로우 곡선을 전체 적분한 면적으로 평가하였다. 5℃·s-1의 선형적인 가열률로 측정한 글로우 곡선은 5개의 피그들로 분리되었으며, 234℃에 나타나는 주피크의 활성화에너지는 2.34 eV, 진동수인자는 1.00×1023이고, 방출스펙트럼은 410nm를 중심으로한 단일한 분포로 나타났다. 선량의존성은 100Gy 이상까지 선형성을 나타내었으며, 137Cs에 대한 저에너지 광자의 상대적인 에너지 반응값은 20% 범위 이내였다. 또한 실온에서 1년간 보관하였을 때, 시간경과에 따른 TL 감도의 감소가 거의 없는 좋은 페이딩 특성을 보였다. Sintered LiF:Mg,Cu,Na,Si thermoluminescence (TL) pellets were developed for application in radiation dosimetry. In the present study, the TL dosimetric properties of LiF:Mg,Cu,Na,Si TL pellets have been investigated for emission spectrum, dose response, energy response, and fading characteristics. LiF:Mg,Cu,Na,Si TL pellets were made by using a sintering process, that is, pressing and heat treatment from TL powders. Photon irradiations for the experiments were carried out using X-ray beams and a 137Cs gamma source at the Korea Atomic Energy Research Institute(KAERI). The average energies and the dose were in the range of 20-662 keV and 10-6- 102 Gy, respectively. The glow curves were measured with a manual type TLD reader(System 310, Teledyne) at a constant nitrogen flux and a linear heating rate. For a constant heating rate of 5℃·s-1, the main dosimetric peak of glow curve appeared at 234℃, the activation energy was 2.34eV and frequency factor was 1.00×1023. TL emission spectrum is appeared at the blue region centered at 410 nm. A linearity of photon dose response was maintained up to 100 Gy. The photon energy responses relative to 137Cs response were within ±20% at overall photon energy region. The fading of TL sensitivity of the pellets stored at the room temperature was not found for one year.

      • KCI등재SCIESCOPUS

        New fabrication process of silicon quantum dots using external laser irradiation

        Jung,Yup,Yang,Jin,Pyo,Hong,Chae,Ok,Kim,Eun,Kyu,Kim,Hyun,Jung,Kim,Kap,Soo,Yoon,Seong,Ki,Min,Si,Ok,Shon,Young,Ho,Do,Young,Ju,Park 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.1

        We present an ecient technique for the formation of silicon quantum dots (Si QDs) by exposing a Nd: YAG laser (wavelength = 355 nm) onto amorphous Si lm. Primary emphasis is placed on the simple and direct fabrication of the Si QDs without performing any micro or nano-patterning process. The scanned laser irradiation of low power causes localized segregation of as-deposited lm by the laser-induced heat, resulting in the fabrication of Si QDs. Observations in scanning electron microscope and atomic force microscope system clearly conrm highly uniform and controllable nanoscale Si QDs in our case. The average size and density of the Si QDs were about 4 nm and 1.5 1012/cm2, respectively. In addition, optical and electrical properties of the Si QDs were investigated by photoluminescence and C-V measurements. The experimental results suggest that our new process can lead to very stable optical and electrical devices, with well controllable and reproducible Si QDs.

      • KCI등재

        논문 : 듀오캐스트 Al-Mg-Si/Al 하이브리드 합금의 미세조직과 기계적 변형 특성

        한지민 ( Ji Min Han ), 김종호 ( Chong Ho Kim ), 박준표 ( Jun Pyo Park ), 장시영 ( Si Young Chang ) 한국주조공학회 2012 한국주조공학회지 Vol.32 No.6

        Al-Mg-Si/Al hybrid alloy was prepared by Duo-casting and the mechanical behavior was evaluated based on their microstructure and mechanical properties. The hybrid aluminum alloy included the Al-Mg-Si alloy with fine eutectic structure, pure Al with the grains in pure Al occurred from the macro-interface existing between Al-Mg-Si/ alloy and pure Al. The growth of columnar grains in pure Al occurred from the macro-interface. The tensile strength, 0.2% proof stress and bending strength of the hybrid aluminum alloy were almost similar to those of pure Al, and the elongation was much higher than the Al-Mg-Si alloy. The fracture of the hybrid alloy took place in pure Al side, indicating that the macro-interface was bonded and the mechanical behavior strongly depends on the limited deformation in pure Al side.

      • 플라즈마를 이용한 Si (100) 기판위에 Ge 결정성장

        최시영,박명기 경북대학교 전자기술연구소 1989 電子技術硏究誌 Vol.10 No.1

        Ge layers were grown on Si(100) by thermal evaporation and plasma-assisted epitaxy at various substrate temperatures. We studied the structural properties of Ge layer on Si substrate by XRD and back reflection Laue pattern. In hydrogen plasma, we were able to obtain good quality Ge crystal layer by means of removal of native oxide and enhancement of surface atom migration on Si substrate. Removal of native oxide near Ge-Si interface by plasma was, confirmed by AES depth profile. Also, enhancement of surface atom migration on substrate was verified through SEM observations. Ge layer deposited on Si substrate by plasma-assisted epitaxy in hydrogen plasma of 10mTorr at a substrate temperature of 450℃, showed surface like mirror face and good crystal quality.

      • SCOPUSKCI등재

        Electrical Analysis of Bottom Gate TFT with Novel Process Architecture

        Pak,,Sang-Hoon,Jeong,,Tae-Hoon,Kim,,Si-Joon,Kim,,Kyung-Ho,Kim,,Hyun-Jae The Korean Infomation Display Society 2008 Journal of information display Vol.9 No.2

        Bottom gate thin film transistors (TFTs) with microcrystalline and amorphous Si (a-Si) double active layers (DAL) were fabricated. Since the process of DAL TFTs can use that of conventional a-Si TFTs, these DAL TFT process has advantages, such as low cost, large substrate, and mass production capacity. In order to analyze the degradation characteristics in saturation region for driving TFTs of active matrix organic light emitting diode, three different dynamic stresses were applied to DAL TFTs and a-Si TFTs. The threshold voltage shift of DAL TFTs and a-Si TFTs during 10,000 second stress is 0.3V and 2V, respectively. DAL TFTs were more reliable than a-Si TFTs.

      • SCOPUSKCI등재

        적외선 분광법에 의한 양이온 교환된 Faujasite 의 T - O 결합특성

        김명철,이시훈,김종택 한국화학공학회 1989 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.27 No.5

        양이온 교환된 faujasite에 대하여 적외선 분광법, X선 회절분석 및 X선 형광분석법을 이용하여 연구하였다. 적외선 흡수띠의 이동이나 Si/Al비 및 결정성의 정도를 고찰하였다. 양이온 교환된 faujasite에 대한 적외선 흡수띠를 분해하먼 T-O(T : Al 또는 Si)의 진동파수가 940-1051㎝^(-1)(띠 A), 1000-1100㎝^(-1)(띠 B), 1097-1190㎝^(-1)(띠 C), 680-730㎝^(-1)(띠 D), 748-780㎝^(-1)(띠 E) 영역에서 나타났다. 띠 A와 E는 각각 Al-O의 비대칭 신축진동(υ_1) 및 대칭 신축진동(υ_2)에 의한 것으로 볼 수 있다. 띠 C와 D는 Si-O의 비대칭 신측진동(υ_3)과 대칭 신축진동(υ_2)에 의한 것으로 각각 보여진다. 띠 B는 Si-O의 비대칭 신축진동(υ_1)과 Al-O의 비대칭 신축진동(υ_3)의 띠가 겹쳐져서 나타난 것으로 볼 수 있다. The cation-exchanged faujasite were characterized and studied by infrared spectrometer, X-ray fluorescence spectrometer and X-ray diffractometer. The shift of i.r. absorption band, Si/Al ratio and degree of crystallinity were studied respectively. The deconvoluted bands of spectra for the cation-exchanged faujasite corresponding T-O vibration frequency appeared at 940-1050 ㎝^(-1) (band A), 1000-1100 ㎝^-1 (band B), 1097-1190 ㎝^-1 (band C), 680-730 ㎝^-1 (band D), and 748-780 ㎝^-1 (band E). The bands A and E were assigned to the asymmetric stretching(υ_1) and symmetric stretching (υ_2) of Al-O respectively. The bands C and D were assigned to the asymmetric stretching (υ_3) and symmetric stretching (υ_2) of Si-O respectively. The band B was assigned to the overlapping of asymmetric stretching (υ_1) of Si-O and asymmetric stretching (υ_3) of Al-O.

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