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.-

한국 전통 금속 공업 : 범종 (梵鍾)

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

성덕대왕 (聖德大王) 신종의 주조법에 (鑄造法) 대한 고찰

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

가스분무한 Al-Si-Fe 합금분말 압출재의 기계적 성질

나형용,최이식 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.4

Al-(20,30wt%)Si-(3,5,8wt%)Fe alloy powders were consolidated by hot extrusion and the change powder microstructure during extrusion was investigated. The effects of Fe addition to Al-Si alloy on the mechanical properties, wear and heat resistance of extruded bars were examined, too. During extrusion of Al-Si-Fe alloy powders, primary Si is broken into fragments from 10∼20 ㎛ size to size less than 10 ㎛ and intermetallic compound from 20∼50 ㎛ size to size less than 5 ㎛. The intermetallic compound in matrix is broken finely, too. Additionally, during extrusion metastable δ phase(Al₄FeSi₂) intermetallic compound disappears and the equilibrium β phase(Al_5FeSi) is formed. Al-Si-Fe alloys showed better mechanical properties, wear and heat resistance than Al-Si binary alloys, resulting from the composite like hardening and matrix hardening by finely distributed primary and eutectic intermetallic compound. Especially, Al-20Si-8Fe alloy showed best physical properties in this work

가스 분무법으로 제조한 Fe-Cr-C 합금분말의 소결성에 미치는 영향

나형용,손광석 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.7

The Fe-Cr-C alloys having high hardness and good wear resistance have been used as the wear resistance materials, valve seat, tappet, etc. mainly made by sintering of powder. For the examination of the role of P that is added with gas atomized Fe-Cr-C alloy powder which has a finer microstructure than chemical reduction powder in view of liquid phase and phase sta ilization, this study was carried out. In this study, Fe-14wt%Cr-1.77wt%C alloy powder compact was sintered for 1 hr at 1170℃ in H2 atmosphere. The effects of P were examined by OM, SEM, EDS, DSC and micro Vickers hardness of quenched specimen. During sintering, P was diffused throughout Fe(γ) matrix, and changed it from FCC to BCC structure and the sintering rate was increased by rapid self-diffusivity, but the hardness of quenched specimen decreased because the amount of FCC phase which carried out martensitic transformation decreased. And liquid phase (Fe3P + Fe matrix) asisted that P diffused to matrix, but the excess liquid phase hampered densification for increasing swelling effect.

Al-Li-Cu-Mg-Zr 계 합금분말의 응고조직과 압출재에서의 석출물에 대한 고찰

나형용,이동수,이성의 대한금속재료학회(대한금속학회) 1993 대한금속·재료학회지 Vol.31 No.9

AL-Li-Cu-Mg-Zr alloy powders were manufactured by gas atomizer and then extruded. The microstructures and mechanical properties of alloy powders and extruded bars were studied. The microstructures were typical cellular structure and icosahedral phases were crystallized out on the cell boundaries in Al-3Li-3Cu-1Mg-0.3Zr, Al-3Li-3Cu-1Mg-0.1Zr and Al-4Li-3Cu-1Mg-0.1Zr alloy powders. But increasing Li/Cu ratio, icosahedral phase and T_B, phase were crystallized out simultaneously. In Al-3Li-3Cu-Mg-Zr alloy extruded bars, almost the precipitates were icosahedral phase and Type 1 phase appeared. In Al-3Li-1.5Cu-Mg-Zr alloy extruded bars, the precipitates were almost R phase. In Al-3Li-1Cu-Mg-Zr alloy extruded bars, the precipitates were almost C phase. Therefore, In AI-Li-Cu-Mg-Zr alloy extruded bars, precipitation mode is Icosahedral phase → Type 1 → Type 2 → R → C phase appeared according to increasing Li/Cu ratio.