癸未銘 高麗鍾의 鑄造法에 대한 考察

羅亨用 龍仁大學校 傳統文化硏究所 1999 丹豪文化硏究 Vol.- No.4

We have had many temple bells temple bells in Korea, which were cast during Koryo dynasty. But unfortunately there are no remains of documentary evidences about the casting techniques of the temple bells, so it is so difficult to find out the real techniques, how to make the temple bell. However we can assume and presume the techniques form the casting defects and traces remained on the bell surface. In this paper, the casting techniques and processes of temple bell, which was cast in Gemi-year(A.D. 1233 or A.D. 1282) in Koryo dynasty, are reasoned and summed as follows after investigation the casting defects and traces, remained on the bell surface. 1) The bell is cast of lead bronze, Cu-10.5wt%Sn-9.9wt%Pb and total 84.1㎏ weight. 2) The bell is satisfies with all the traditional requisites of the Korean bell and the size of bell are as follows Dia. bottom : 445㎜ Dia. upper : 290㎜ height : 574㎜ thickness of bottom wall : 45㎜ 3) The melt is poured into the mold which are divided into three parts, cope, drag and bottom flask through the two top gates, and molded by the lost-wax process. 4) The blister defects appear on the parts of the dragon head and top of the sound pipe of the bell. These are caused by the gas which are formed by the combustion of wax remained in the mold.

급냉 응고된 Al-Li-Cu합금의 열처리, 미세조직 및 기계적 성질에 관한 연구(I)

許明日,南勝義,李範圭,羅亨用,金錫胤 弘益大學校 1988 弘大論叢 Vol.20 No.2

Effect of aging condition on the microstructure and hardness properties of Al-3Li, Al-3Li-2Cu, Al-3Li-2Cu-0.3Zr have been studied. The alloy ribbons have been prepared by means of Single Roll Melt Spinning by rapid solidification technique. In rapidly solidified Al-3Li-2Cu, Al-3Li-2Cu-0.3Zr alloy ribbons show the icosahedral intermetallic compound of five-fold symmetry which is placed in cell-bound-ary and matrix. In the matrix precipitated fine δ'(Al₃Li) phase. Heat-treated at 250℃ 1hr. In this condition, δ'(Al₃Li) phase started decompose. The icosahedral intermetallic compound has been grown. When heat-treated at 300℃ 1 hr, the δ' phase has been decomposed all. In the matrix, icosahedral intermetallic compound has been grown greatly. The micro-hardness has been obtained more high Al-Li-Cu-(Zr) alloy than Al-Li alloy. Strength-hardended phenomena showed to solution hardning by the addition of Cu. When the heat-treated at 250℃ 1 hr, in the alloy of Zr addition, delayed decomposed δ' phase. In the case, micro-hardness gradually decreased. When the heat-treatment have done at 300℃ 1 hr, the micro-hardness has been decreased because δ' phase decomposed all.

일과성전기억상실증의 국소 뇌혈류 변화 : Statistical Parametric Mapping을 이용한 Tc-99m ECD SPECT분석 Statistical Parametric Mapping analysis of Tc-99m ECD SPECT

이승재,양동원,손영민,김범생,정용안,손형선,주라형 대한치매학회 2003 Dementia and Neurocognitive Disorders Vol.2 No.1

Background & Objectives:Transient global amnesia (TGA) is a clinical syndrome characterized by sudden memory loss of recent events, transient inability to retain new information, and retrograde amnesia in the absence of other neurological signs and symptoms, resolving within 24 hours. This study investigated alterations in regional cerebral blood flow (rCBF) in patients with TGA by using statistical parametric mapping 99 (SPM99). Methods:5 patients with TGA and 9 age-matched normal control subjects were evaluated. Tc-99m-ethyl cysteinate dimer (ECD) SPECT were performed within 1 to 4 days of the event to measure the regional CBF, and SPM99 were applied to the objective analysis of SPECT data between two groups. Follow-up ECD SPECT was done at 49 to 107 days (mean 76.8) after the previous SPECT to evaluate the long term changes of the regional CBF. Results:The SPM analysis of SPECT images revealed significantly decreased rCBF in the left superior temporal gyrus, the left parietal supramarginal gyrus and the left thalamus (corrected p=0.01) and increased CBF in the contralateral mirror regions in patients with TGA. Follow-up SPECT showed persistent rCBF changes in the same regions. Conclusions:We demonstrate decreased perfusion in the left cerebral hemisphere and increased perfusion in the right cerebral hemisphere in patients with TGA. This reciprocal change of rCBF might suggest that imbalanced neuronal activity between two hemispheres may be important in the pathogenesis of the TGA. Also, the abnormal rCBF changes appeared to last long after the complete recovery of clinical manifestation of TGA.

A Study on the Melting Morphology of Graphite in Cast Iron

Ra,Hyung Yong,Lim,Chang Hee 한국주조공학회 1985 한국주조공학회지 Vol.5 No.4

Many authors have studied the solidification process of cast iron and the effect of grain boundaries in austenite shell on the growth of spheroidal graphite. But, the studies on the melting morphology of cast iron are rare and the effect of grain boundaries in austenite shell on the melting procedure of spheroidal graphite cast iron is unknown. Therefore, in this work, the melting procedure of cast iron and the role of grain boundaries in austenite shell on the melting of spheroidal graphite have been studied. The main results are summarized as follows. 1. In white cast iron containing silicon, melting initiates at the interface between austenite matrix and temper carbon which was decomposed from Fe₃C during heating. 2. In gray cast iron, melting initiates at the boundary of eutectic cell where elements with low melting temperature are condensed. The dissolution of kish graphite is difficult. 3. In spheroidal graphite cast iron containing little phosphor, melting initiates at the outer region of austenite shell in which silicon is condensed. In this case, grain boundaries in austenite shell give little effect on the melting procedure of spheroidal graphite. 4. In spheroidal graphite cast iron containing phosphor above 0.3wt%, its melting phenomena are changed with heating rate due to the existence of steadite. In this case, it can be concluded that liquid phase of steadite, which segregated on outer region of austenite shell, moves to spheroidal graphite-austenite interface along the grain boundaries in austenite shell.

가스 분무법에 대한 기초 연구

나형용 ( Hyung Yong Ra ) 대한금속재료학회 ( 구 대한금속학회 ) 1990 분말야금 Vol.2 No.-

성덕대왕 (聖德大王) 신종의 주조법에 (鑄造法) 대한 고찰

나형용 ( Hyung Yong Ra ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.4

범종 (梵鍾)

라형용 (Hyung Yong Ra) 대한금속재료학회 1999 大韓金屬學會會報 Vol.12 No.1

N/A

급속응고한 Al-Fe-Mo-Si 계 합금분말 압출재의 고온 성질에 관한 연구

나형용,최주태 대한금속재료학회(대한금속학회) 1993 대한금속·재료학회지 Vol.31 No.3

The microstructure and properties of the rapidly solidified Al-8Fe-2Mo-1.5Si alloy for elevated temperature applications were investigated. The effects of Mo on thermal stability and Si on fracture toughness through the observation of microstructure, hardness test and tensile test were described. The mechanical properties of extrudates with the variation of extrusion ratio and size distribution of powder were investigated. Hardness of smaller powder(50㎛) was superior to that of larger powder(150㎛). The extrudate consolidated with finer powder size distribution (10∼100㎛) yields higher strength than that with a coarse size distribution(100∼200㎛). The tensile strength of 2nd extruded bar which was consolidated with finer powders was 520MPa at 25℃, 310MPa at 275℃. The deterioration of mechanical properties at elevated temperature was due to the decomposition of Zone A and metastable phase Al_6Fe into stable phase Al₃Fe and the growth of needle-like Al₃Fe precipitates. Quarternary Mo and Si containing alloys showed uniform dispersion of fine cuboidal-polygonal precipitates, bcc Al_(12)(Fe,Mo)₃Si phase which displayed a remarkable resistance to coarsening.

스트립캐스팅한 구상흑연주철박판의 흑연화 과정에 대한 phase - field 모델링(1) : 고용도가 없는 상의 모델링 Modeling of Phases with Negligible Solubility

나형용,김성균 한국주조공학회 2000 한국주조공학회지 Vol.20 No.2

This study aims at the phase-field modeling of the phase transformation in graphitization of the cast iron. As the first step, we constructed a phase-field model including the phases with negligible solubility. Under the dilute regular solution approximation, a simplified version of the phase-field model was obtained, which can be used for the phase transformation related with the stoichiometric phases. The results from the numerical calculation of the phase-field model was in good agreement with the exact analytic solution. The compositional shift due to Gibbs-Thomson effect can be reproduced within 0.5% error in the numerical calculation. The interface velocity, whereas, in numerical calculation of phase-field model appeared to be 15% larger than that from the analytic solution. This error is due to the shift of the interface position in phase-field model from the position with ø=0.5.

기계적 합금에 의한 Fe (1-x) Bx 계의 비정질화

나형용,박현식,신관수부 대한금속재료학회(대한금속학회) 1990 대한금속·재료학회지 Vol.28 No.8

Mechanical alloying in the Fe(1-x)Bx system was performed by ball-Milling. The Mechanically alloyed powders were investigated by X-ray diffraction, differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). In case of Fe(1-x)Bx (x=0.2) specimen, the broad peak of x-ray diffraction and the exothermic peak of DSC indicated the characteristic behavior of amorphous alloy. However, TEM observation revealed the existence of fine bcc Fe phase. On the other hand, the boride of Fe₂B or FeB was formed by mechanical alloying in Fe(1-x) Bx (x>0.3) specimens.