SHS 공정에 의해 제조된 Mo_xW_1-xSi₂ 발열체의 열화메커니즘

이동원,이상헌,김용남,이성철,구상모,오종민,Lee, Dong-Won,Lee, Sang-Hun,Kim, Yong-Nam,Lee, Sung-Chul,Koo, Sang-Mo,Oh, Jong-Min 한국전기전자재료학회 2017 전기전자재료학회논문지 Vol.30 No.10

The degradation mechanism of $Mo_xW_{1-x}Si_2$ ultrahigh-temperature heating elements fabricated by self-propagating high-temperature synthesiswas investigated. The $Mo_xW_{1-x}Si_2$ specimens (with and without post-annealing) were subjected to ADTs (accelerated degradation tests) at temperatures up to $1,700^{\circ}C$ at heating rates of 3, 4, 5, 7, and $14^{\circ}C/min$. The surface loads of all the specimen heaters were increased with the increase in the target temperature. For the $Mo_xW_{1-x}Si_2$ specimens without annealing, many pores and secondary-phase particles were observed in the microstructure; the surface load increased to $23.9W/cm^2$ at $1,700^{\circ}C$, while the bending strength drastically reduced to 242 MPa. In contrast, the $Mo_xW_{1-x}Si_2$ specimens after post-annealing retained $single-Mo_xW_{1-x}Si_2$ phases and showed superior durability after the ADT. Consequently, it is thought that the formation of microcracks and coarse secondary phases during the ADT are the main causes for the degraded performance of the $Mo_xW_{1-x}Si_2$ heating elements without post-annealing.

Effect of post annealing on the microstructure, mechanical properties, and failure of Mo_xW_1-xSi₂ heaters produced by self-propagating high-temperature synthesis

Cho, Myung-Yeon,Lee, Sung-Chul,Park, Chulhwan,Lee, Daeseok,Koo, Sang-Mo,Moon, Kyoung-Sook,Lee, Dong-Won,Oh, Jong-Min Elsevier 2019 INTERMETALLICS Vol.110 No.-

<P><B>Abstract</B></P> <P>High-performance tungsten molybdenum disilicide (Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB>) heating elements were prepared using a self-propagating high temperature synthesis process. The effect of post annealing on the degradation behavior of the alloy was experimentally investigated. Increasing the attrition milling time up to 20 min during powder preparation resulted in Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB> heaters with the highest density, which increased the fracture strength compared to samples with shorter attrition times. Such samples were annealed and evaluated as heating elements using accelerated degradation tests and failure analysis in order to compare their structural characteristics and flexural strength with as-fabricated samples. The annealed Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB> heater showed a relatively dense structure with few pores and no secondary phases, apart from a SiO<SUB>2</SUB> layer. This favorable structure prevented bubble formation, which can result in fracturing of the heater, as revealed by evaluation at high temperatures with various heating rates. The flexural strength of the annealed specimen was 2.5-times higher than that of the as-fabricated specimen, which was attributed to removal of secondary phases during annealing. Failure time and surface load analyses were used to investigate the fracture mechanism of the Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB> heaters in detail at 1790 °C by quantifying bubble formation and the presence of secondary phases.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Self-propagating high temperature synthesis of Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB> heaters demonstrated. </LI> <LI> Post-annealed Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB> heaters were highly dense, with good flexural strength. </LI> <LI> Bubble formation (the main cause of fracture) suppressed at ultra-high temperature (above 1700 °C). </LI> <LI> Surface load, failure time, and bubble formation used to study fracture mechanisms. </LI> </UL> </P>

SHS 공정으로 제조된 Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si₂ 발열체의 가속수명시험과 고장분석

이동원(Dong-Won Lee),이상헌(Sang-Hun Lee),김용남(Yong-Nam Kim),이희수(Heesoo Lee),이성철(Sung-Chul Lee),구상모(Sang-Mo Koo),오종민(Jong-Min Oh) 한국전기전자학회 2017 전기전자학회논문지 Vol.21 No.3

고온자전합성과 후열처리 공정으로 MoxW1-xSi₂ 발열체를 제조하였다. MoxW1-xSi₂ 발열체의 신뢰성을 검증하기 위해 가속수명시험을 수행하였으며, 수명시간을 Minitab 프로그램으로 추정하였다. 또한, 가속수명시험 후의 MoxW1-xSi₂ 발열체의 고장분석을 전기적과 구조적 특성으로부터 수행하였다. 그 결과, MoxW1-xSi₂ 발열체의 지배적인 고장 유형은 발열체 내부의 크랙 형성과 SiO₂ 보호층의 박리임을 확인하였다. MoxW1-xSi₂ heaters were fabricated by self-propagating high-temperature synthesis (SHS) process and post sintering process. To validate the reliability of the MoxW1-xSi₂ heaters, the accelerated life test (ALT) was conducted, and then lifetime to MoxW1-xSi₂ heaters was estimated by using Minitab programs. Also, the failure analysis of MoxW1-xSi₂ heaters after ALT was performed through electrical and structural properties. As the results, it was confirmed that the dominant failure mode of MoxW1-xSi₂ heaters is the crack formation in heaters and the delamination of protective SiO₂ layers.

상주 및 인근지역 단체급식소의 다량조리 실태연구 : 식단분석 및 다량조리 실태

박모라,김귀영,박필숙,강우원 동아시아식생활학회 1998 동아시아식생활학회지 Vol.8 No.1

The purpose of this study was to investigate quantity food production practices in foodservices by analysing the menus of April, 1996. The questionnaire was developed and responded to by 96 dietitians in Sangju, Munkyung, Gumee, Kimchun, and Andong during November, 1996. The survey was performed by simple random samplings. The results were as follows; 1. Hospitals and industry served food for thirty days and schools for twenty days. Kimchi was a select-menu for hospitals and one side dish for industry and schools. The type of menu was a single use menu which consisted of cooked rice, soups and three side dishes. 2. The most frequently used ingredients were green onions, rice, carrots, onions, Korean radish roots, pork, eggs, glutinous rice, and milk. Kimchis were served most frequently in all food-services and cooked rices and soups were next. 3. The age of most of the respondents was 26 to 30. 54.2% of subjects were junior college graduates and 77.1% were single. Fifty-seven point three percent of the dietitians lived with family, relatives, or friends. 87.5% of the dietitians had been working for 1 to 5 years. 4. Most foodservices were self-operated. The number of meals served was determined by meal coupon counting in hospitals(37.5%), meal board counting in industry(29.2%), and attendance card counting in schools(41.1%). The cost of sales per meal was approximately 2,450 won in hospitals and was approximately 1,100 won in industry and schools. The average number of days per menu cycle was 7.4 in hospitals, 10.3 in industry and 25.5 in schools. Hospitals, industry, and schools held about 118, 265, and 263 recipes, respectively. The average number of dietitians was 2.6 in hospitals and 1.0 in industry and schools. Except for the number of recipes, the general practices of foodservices were significantly different(P<0.05). 5. In the general quantity food production, food and seasonings measuring was hardly done. The percentage of foodservices using chemical seasonings was higher in hospitals and industry than in schools. The most important concern was taste. Registered cooks were employed in 75% of schools but only 50.0% in hospitals and 20.8% in industry. Most of the dietitians responded that their cooks skill was not bad. The education of unregistered cooks was performed once or two times a month in hospitals and industry, and in schools performed everyday. The problem when educating cooks was the lack of cooking skill of the dietitians in schools, and the lack of time in hospitals, and the negative attitude toward education in industry. The method for improving cooking in all foodservices was OJT, or the extension of education facilities and the development and dissemination of standard recipes. The frequency of throwing away leftovers was higher in hospitals. But in industry, the frequency of saving leftovers was higher. 6. Though all foodservices have standard recipes, the number that used them was low. Another problem is that standard recipes resulted in leftovers. The inconveniences of using standard recipes were the difficulty of applying standard recipes to various numbers of customers the complication of use, or facility insufficiency.

통풍형 방음벽 개발 및 적용에 관한 연구

윤제원(Je-Won Yoon),김영찬(Young-Chan Kim),김금모(Keum-Mo Kim),장강석(Kang-Seok Jang),구본성(Bon-Sung Ku),엄주용(Joo-Yong Eom) 한국소음진동공학회 2011 한국소음진동공학회 학술대회논문집 Vol.2011 No.10

The purpose of this study is to develop an air-passing soundproofing panel with more improved structure to reduce the CO2 emission and installation cost. To reduce the emission of CO2 ; it is suggested to choose low CO2 emission material relative to the aluminum and to reduce the materials by developing a specially designed air-passing soundproofing panel structure. First of all, we performed the flow analysis to predict the wind pressure according to the open angle of the air-passing soundproofing panel and the noise level analysis at the receiver point. To verify the simulation, a prototype of the soundproofing panel was made. The flow test in the wind tunnel and load test were performed. The economic evaluation for the installation of the air-passing soundproofing panel was performed and specifications of the installation was prepared. As the results of this research, it was verified that the wind load was reduced about 40% to that of the conventional one at 25m/s wind speed in the wind tunnel test. By applying the 4m span soundproofing wall with air-passing soundproofing panel and under the cost of 250 thousand won/m2 instead of the conventional 2m span panel, the installation cost will always be lowered than the conventional one in the combination of (60:40~50:50) conventional to air-passing soundproofing panel from the economic evaluation. The 20% reduction of CO2 was found by changing the 50% of aluminum soundproof panel to air-passing soundproofing panel.

완화환율의 장기구매력평가 : 정수차분과 분수차분

모수원(Soo Won Mo),박석호(Seok Ho Park) 한국국제경영학회 1999 國際經營硏究 Vol.10 No.1

구매력평가(PPP)는 국제금융이론에서 중요한 비중을 차지하고 있다. 초기 환율의 화폐적 모형인 신축물가모형은 지속적인 구매력평가의 성립을 전제로 하고 있으며, 경직물가모형은 환율의 구매력평가로부터의 단기적 괴리를 허용하나 장기에서는 균형이 이루어짐을 상정하고 있다. 이러한 PPP의 중요성에도 불구하고 단기에서 PPP가 성립하지 않는다는 데에는 일반적으로 견해가 일치하고 있으나, 장기에서의 PPP 타당성에 대해서는 많은 논란이 되고 있다. 이러한 결과는 저자에 따라 물가지수, 자료의 빈도 또는 이용하는 검정기법상의 차이가 있기 때문이다. 일반적으로 장기PPP검정에는 흔히 공적분기법이 주로 이용되고 있다. 그러나 많은 문헌들이 사용하는 정수차분에 근거를 두는 기존의 Dickey-Fuller류의 공적분기법은 충격효과가 즉시 소멸하는가 아니면 영구히 지속되는가 하는 양 극단의 경우만을 다룰 수 있을 뿐이다. 즉 시계열의 특성이 I(0)인가 흑은 I(1)인가를 식별하는 데 그치고 있다. 이에 따라 정상성과 추세회귀성향을 구분할 수 있는 장점을 지닌 분수차분에 의한 검정이 이루어져야 한다. 이러한 분수차분에 의한 GPH검정을 통해 한국의 원화환율은 장기에 있어서 PPP를 지지하지 않음을 밝힌다.

무역수지와 환율의 변이성 : 한국의 경우

모수원(Soo Won Mo),조우길(Woo Kil Cho) 한국국제통상학회 1998 국제통상연구 Vol.3 No.1

In this paper, we investigate GARCH and ARCH models to examine the relationship between nominal exchange rate volatility and trade balances. We find that the ARCH(GARCH) conditional variance has a statistically significant impact on the trade balance. This study also provides an empirical overview of the trade account and Korean won-dollar exchange rate using integer and fractional cointegration approach. The analysis of fractional cointegration which integrates the notions of cointegration and of fractional differencing allows the equilibrium error to follow a fractionally integrated process and avoids the stringent Ⅰ(1) and Ⅰ(0) distinction maintained in previous empirical work. This paper shows that all the fractional estimates of d not only lie between 0 and 1, but are greater than 0, suggesting a mean-reverting bahaviors.

한국인의 연, 망간, 알루미늄 및 실리콘의 혈중 농도

김정만,안정모,김원술,김정일,신해림,정갑열,김준연 동아대학교 산업의학연구소 2000 산업의학연구소 논총 Vol.- No.5

Blood Lead, Manganese, Aluminium and Silicon Concentrations in Korean Adults Jung Man Kim, Jung Mo Ahn, Won Sul Kim1), Jung Il Kim2), Hai Rim Shin, Kap Yeol Jung2), Joon Youn Kim Department of Preventive Medicine, College of Medicine and Industrial Medicine Research Institute. Dong-A University Department of Health Care, Handong University Sunlin Presbyterian Hotpital1) Department of Occupational Medicine, College of Medicine, Dong-A University2) 0bjectives : This study was performed to determine the reference values of blood lead, manganese, aluminium, and silicon in healthy adults. Methods : The subjects were 132 (67 male and 65 female), and classified to three age groups (≤39,40∼49, and 50≤). Hood lead, manganese and aluminium were analyzed by atomic absorption spectrophotometer, and blood silicon was analyzed by direct current plasma optical omission spectrometer. Results : Blood lead levels(geometric mean, S.D) were (3.49, 1.70) ㎍/dL in male auld (3.04, 1.65) ㎍/dL in female, but the difference is not significant, and there was no significant difference between age groups. Mean blood manganese level was 0.99±0.41㎍/dL, and there was no significant difference between sex or age groups. Mean blood aluminium level was 0.59±0.35㎍/dL and there was no significant difference between sex or age groups. Mean blood silicon level was 54.41±27.64㎍/dL in male and 43.34±23.51㎍/dL in female, and the level in male was significantly higher than that in female (p〈0.05). There was significant difference between age groups, and the oldest showed the highest level in male (p〈0.05), but no significant difference between age groups in female. Conclusions : Authors hope that this study would provide basic data for determininig reference values and evaluating health effects.

석탄 가스화를 통한 전력 생산과 DME 병산 공정에 대한 기초 경제성 분석

유영돈 ( Young Don Yoo ),김수현 ( Su Hyun Kim ),조원준 ( Won Jun Cho ),모용기 ( Yong Gi Mo ),송용택 ( Tae Kyong Song ) 한국화학공학회 2014 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.52 No.6

석탄가스화를 기반으로 한 발전(IGCC 발전) 및 화학원료 제조공정의 상업화 관건은 화석연료인 원유 또는 천연가스를 기반으로 생산되는 경우와 비교하여 경제성을 확보할 수 있는지 여부이다. 경제성 확보를 위한 가장 현실적인 방법으로는 석탄 가스화를 통해 얻어진 합성가스로부터 2개 이상의 생산물(예: 발전과 화학원료를 동시 생산)을 병산(coproduction또는 poly-generation)하는 것이다. 본 연구에서는 석탄 가스화를 기반으로 하여 발전과 수송용, 발전용 및 가정용 연료로 사용이 가능한 DME(dimethyl ether)를 병산하는 공정에 대한 경제성 분석을 실시하였다. 경제성 분석을 위한 병산 공정에서는 250 MW 전력생산 연간 30만 톤의 DMZ 생산을 기준으로 하였다. 병산 공정에서 DME 판매가격이 50만원/ton인 경우, 전기 생산원가는 34.8~58.4원/kWh으로 SMP(계통한계가격) 가중평균인 150.69원/kwh(2013년 1월~12월까지의 평균값)의 33~58% 수준으로 산정되었다. 따라서, DME 판매가격이 적정하게 유지될 경우 석탄IGCC+DME 병산공정은 IGCC 단독 발전과 비교하여 경제성을 확보할 수 있을 것으로 판단된다. 현재 중국에서 DME판매가격이 900,000원/톤 내외이므로, 전력과 DME를 병산할 경우, IGCC 단독으로 전력을 생산할 경우와 비교하여 전력 생산 원가를 월등하게 낮출 수 있음을 알 수 있다. 이와 같이 석탄 가스화를 기반으로 한 병산 공정을 통해 전력과 DME를 병산하는 시스템에서, 시장 여건에 따라 전력과 DME 생산비율 제어가 가능하고, 석탄 가스화기 및 정제 시스템을 공통 설비로 활용함으로써, 개별적으로 생산하는 것보다 생산 원가를 낮출 수 있다는 결과를 얻었다. The key for the commercial deployment of IGCC power plants or chemical (methanol, dimethyl ether, etc.) production plants based on coal gasification is their economic advantage over plants producing electricity or chemicals from crude oil or natural gas. The better economy of coal gasification based plants can be obtained by co-production of electricity and chemicals. In this study, we carried out the economic feasibility analysis on the process of co-producing electricity and DME (dimethyl ether) using coal gasification. The plant’s capacity was 250 MW electric and DME production of 300,000 ton per year. Assuming that the sales price of DME is 500,000 won/ton, the production cost of electricity is in the range of 33~58% of 150.69 won/kwh which is the average of SMP (system marginal price) in 2013, Korea. At present, the sales price of DME in China is approximately 900,000 won/ton. Therefore, there are more potential for lowering the price of co-produced electricity when comparing that from IGCC only. Since the co-production system can not only use the coal gasifier and the gas purification process as a common facility but also can control production rates of electricity and DME depending on the market demand, the production cost of electricity and DME can be significantly reduced compared to the process of producing electricity or DME separately.

생쥐 중이와 상기도 점막의 섬모세포운동

정하원,오승하,유원석,이강수,모지훈,전상준,김인상,김종선 대한이비인후과학회 1999 대한이비인후과학회지 두경부외과학 Vol.42 No.9