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>

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.

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.

한우에 있어 황토 첨가급여가 면역기능에 미치는 영향

조원모,기광석,정하연,강수원,김준식,오성종,김용국 한국국제농업개발학회 2003 韓國國際農業開發學會誌 Vol.15 No.2

본 연구는 한우 육성우에 대한 황토 첨가급여가 항병성에 미치는 효과를 구명하고자 혈액성상변화를 규명한바 아래와 같은 결과를 얻었다. 대조구 및 처리구에서 전체적인 혈액성상의 변화는 없었으나 백혈구수치가 대조구 및 처리구에서 각각 15.35K/㎕ 및 13.37K/㎕이였으며, 적혈구에 있어서도 정상수치인 5~10M/㎕보다 대조구 10.03M/㎕, 처리구 11.35M/㎕로 모두 높은 수치를 보였다. 황토첨가에 따른 혈액성상의 변화는 처리간에 유의한 차이는 보이지 않았다. The study was conducted to investigate the effect of dietary supplements of reddish clay on the immunity of growing Hanwoo steers. A total of 8 calves were divided into 2 feeding groups, control(basal diet) and treatment(basal diet plus ad libitu reddish clay) for Hanwoo steers. This study was carried out for 5 months using 8 calves. The results obtained by the present study are summarized as follows : The proportion of WBC, NE as well as LY(15.35, 6.85, 6.86K/??) was higher in the control group than in the Reddish clay-supplemented group. But no statistical differences were found in blood substances among treatment calves.

원貨의 對美달러換率은 예측이 가능한가?

모수원,구희조 木浦大學校 企業經營硏究所 1997 企業經營硏究 Vol.1 No.1

Abstract This paper examines forecasting performance of two structureal models and the random walk model for the recent period in Korea. This essay also evaluates the forecasting accuracy of monetary models of the exchange rate determination. It is found that the performance of the two error-correction structural models of the flexible-price and the sticky-price version is superior to that of the random walk medel.

황토 급여가 거세한우의 발육에 미치는 영향

조원모,기광석,정하연,강수원,김준식,백봉현,김용국 한국국제농업개발학회 2003 韓國國際農業開發學會誌 Vol.15 No.1

본 연구는 거세한우 육성우에 대한 황토 첨가급여가 발육에 미치는 효과를 구명하고자 발육능력, 사료섭취량을 규명한 바 아래와 같은 결과를 얻었다. 전 시험기간 동안의 평균 일당증체량은 대조구와 황토급여구가 각각 0.91㎏과 0.87㎏/day로 대조구가 높은 것으로 나타났지만 유의성은 인정되지 않았다. 사료섭취량은 대조구와 황토급여구 모두 평균 일일 두당 농후사료 섭취량이 2.42㎏이었으나, 건초섭취량에 있어서는 각각 3.02와 3.14㎏으로 황토급여구가 다소 높은 경향으로 나타났다. The study was conducted to investigate the effect of dietary supplements of reddish clay on the growth performance in growing Hanwoo steers. A total of 8 calves was allocated into 2 feeding groups, control(basal diet) and treatment(basal diet plus ad libitim Reddish clay) for Hanwoo steers. This study was carried out for 5 months with a total of 8 calves. The results obtained in the present studies are summarized as follows : Average daily gains throughout the experimental period of 4 months to 9 months of age were 0.91 and 0.87㎏ for control group and reddish clay-supplemented group, respectively, however, no statistical significances were found. Average daily intake of concentrates was 2.42㎏ for each group, while that of hay tended to be higher in reddish clay-supplemented group(3.14㎏) than in control group(3.02㎏).

팽이 톱밥 人工栽培時 培地微生物相의 經時的인 密度變化

배태웅,文炳周,辛元敎,宋模烈,李鉉旭,曺東進 東亞大學校生命資源科學大學附設 農業資原硏究所 1996 農業生命資援硏究 Vol.5 No.1

팽이 재배에 있어 가장 큰 문제 중의 하나는 雜菌에 대한 汚染, 특히 細菌에 의한 피해가 극심하므로 作業段階와 栽培過程 전반에 걸쳐 培地徵生物相의 經時的인 密度變化에 따른 雜菌의 培地內 流入時期를 조사하여 汚染菌의 發生消長을 알아보기 위해 現地農家에서 시험해 본 결과 接種후 培養室에서 菌絲培養을 시작한 5일후부터 細菌이 檢出되기 시작하여 菌긁기전까지 약 25일간 0.5∼3.1×10⁴cfu/g의 密度를 보였으나 經時的인 密度增加는 없었고, 菌絲培養이 끝난 뒤 菌긁기직후부터 細菌의 密度는 118.3×10⁴cfu/g으로 급격히 높아졌으며 子實體生育 기간동안에 시간이 경과함에 따라 密度가 현저하게 증가되는 경향을 나타냈다. 이는 培養室 안으로 흐르는 空氣를 통하여 甁內로 細菌이 流入되고 또한 菌긁기 직후 培地表面에 灌注하는 물과 加濕機에서 噴霧되는 물粒子가 細菌의 密度增加에 절대적으로 영향을 미치는 것으로 판단되므로 이때가 細菌性褐斑病菌에 感染되기 가장 용이한 시기로 생각된다. 眞菌은 菌긁기후 子實體生育 기간동안 1.17∼7.87×10⁴/g의 密度로서 菌絲培養 기간동안의 密度보다 다소 높게 檢出되었으나 대체로 經時的인 密度增加는 보이지 않았으며, 放線菌은 거의 검출되지 않거나 菌絲培養 후 5일째부터 다소 검출되기 시작했으나 밀도가 매우 낮았고 經時的으로도 증가되지 않았다. One of the most serious problem on the Enoki mushroom cultivation is the infection by pathogenicitic microorganisns, especially bacterial diseases causing serious economical losses in the mushroom production. It was carried out to find the tendency of the development of mushroom diseases by temporal changes and variation of the densities of media microflora through the cultivation periods and working stages in a mushroom farm. According to the results, several bacteria were detected from the fifth day after the inoculation and incubation of mycelium in the incubation room, and the density of bacterium was 0.5∼3.1×10⁴cfu/g media for 25 days before the inoculum-removing, although there was no increment of the density. Since the inoculum-removing after the spawn run, the density of bacterium was rapidly increased as 118.3×10⁴cfu/g media, and was significantly increased by time during the growth period of fruitbodies. It was hypothesized that it is the most suitable period for the pathogen infection because the bacterium might be introduced by the air in the incubation-room, and the increment of bacterium density might be affected by moisture supplied through watering or humidifier in the growing room after the inoculum-removing. Fungi were detected as the density as 1.17∼7.87×10⁴/g media and the density was slightly higher than that during the incubation period of hyphae, although there was no significant increment. Generally, the density of Actinomycetes was disregardfully low, or Actinomycetes were hardly ever found, although there was found some 5 days after incubation hyphae in few cases.

Productivity Loss of Rheumatoid Arthritis Patients according to the Their Stages of the Disease Activity Score

( Sang-Cheol Bae ),( Jin-Hye Cha ),( Jung-Yoon Choe ),( Sung Jae Choi ),( Soo-Kyung Cho ),( Won-Tae Chung ),( Chung-Il Joung ),( Young-Ok Jung ),( Young Mo Kang ),( Dong-Wook Kim ),( Jinseok Kim ),( Y 대한류마티스학회 2018 대한류마티스학회지 Vol.25 No.2

Objective. Productivity loss was compared by 3-stage of disease activity and associations between higher disease activity and high productivity loss were identified. Methods. Data were extracted from Rheumatoid Arthritis (RA) Patient-reported Outcomes Research, which enrolled 2,000 RA patients (>20-year) on disease-modifying-antirheumatic-drugs (DMARDs) (≥ 6-month) from December 2012 to June 2013. This included 1,457 RA patients with the disease activity score (DAS-28-ESR) in their medical charts. Productivity loss in time and indirect cost was estimated using The World Health Organization Health and Work Performance Questionnaire (HPQ). Baseline characteristics and productivity loss outcomes were compared according to DAS-28-ESR groups. Results. 84.4% were females, 54.2% had low DAS-28-ESR (<3.2), and 38.2% and 7.6% had moderate (3.2∼5.1) and high DAS-28-ESR (>5.1). Patients with moderate to high DAS-28-ESR had higher lost productivity time (LPT) and monthly costs of LPT than those with low DAS-28-ESR (time in hours: 110.0±58.4 vs. 132.4±57.2 vs. 71.5±52.0, p<0.0001; monthly costs of LPT in 1,000 Korean won: 1,097±607 vs. 1,302±554 vs. 741±531, p<0.0001). Multiple regression analyses revealed significant associations with high LPT in high (adjusted odds ratio [OR]=3.87, 95% confidence interval [CI]: 2.18∼6.87) and moderate DAS-28-ESR (adjusted OR=1.88, 95% CI: 1.41∼2.52) compared to low DAS-28-ESR. In addition, positive associations with high monthly costs of LPT were observed in high (adjusted OR=3.45, 95% CI: 1.98∼5.99) and moderate DAS-28-ESR (adjusted OR=1.93, 95% CI: 1.43∼2.54) compared to low DAS-28-ESR. Conclusion. Timely therapeutic strategies should be taken into consideration given that the RA patients with moderate to high DAS-28-ESR showed strong associations with high productivity loss for effective management of RA. (J Rheum Dis 2018;25:122-130)

자동착유시스템 설치농가의 설치 후 만족도에 관한 실태조사

기광석,김종형,정영훈,김윤호,박성재,김상범,이왕식,이현준,조원모,백광수,김현섭,권응기,김완영,여준모,Ki, Kwang-Seok,Kim, Jong-Hyeong,Jeong, Young-Hun,Kim, Yun-Ho,Park, Sung-Jai,Kim, Sang-Bum,Lee, Wang-Shik,Lee, Hyun-June,Cho, Won-Mo,Baek, Kwang- 한국축산환경학회 2011 축산시설환경학회지 Vol.17 No.1

본 시험은 국내에 도입되기 시작한 AMS에 대하여 설치 동기, 설치 후 우유생산량과우유품질, AMS 설치계기 및 설치 후 만족도, AMS 운영상 애로점 및 건의사항 등을 조사 분석하였다. 설치 계기가 무엇인가에 대한 응답비율은 노동력 부족 44%, 체험목장으로 전환 25%, 소들의 고능력화에 대응 19% 순이었으며 기타 6%였다. AMS 설치농가의 사육경력은 평균 24.9년, 평균 연령은 53.2세로 나타났으며 가족노동력만으로 경영하는 목장이 조사농가의 38%, 고용+자가노동력 형태의 목장이 63%로 나타났다. 목장의 산유능력은 두당 평균 유량은 1일 $30.9{\ell}$, 평균 유지율 3.9%, 세균수는 9.1천개/$m{\ell}$ 수준이었다. 후계자 육성에 대한 질문에 매우 그렇다라고 응답한 비율은 68%였으며, 보통 18%, 아니다와 매우 아니다라고 응답한 비율은 18%로 나타났다. 시스템 운영현황 및 애로사항을 파악하기 위하여 AMS의 프로그램 주운영자에 대한 질문에 본인 44%, 부인 6%, 자녀 또는 후계자사람이 44%, 기타 6%나 되었다. AMS 운영상 가장 어려운 점에 대한 조사결과, 기기 작동 및 복잡한 프로그램 운영이 각각 31%로 가장 많았다. 그 외 기계 에러 및 고장에 대한 애로사항이 25%이였다. 도태원인에 대하여 유방염 28%, 번식장애 20%, 발굽질환 19%, AMS에 부적합한 유두 배열 12%, 분만 후 대사성질병 7%, 노산 등 기타 14%였다. 시스템 설치 후 유지보수 계약 체결유무 및 비용에 대하여 유지보수 계약 56%, 유지 보수 계약 미체결 44%이었다. 유지보수 계약 평균 계약비용은 연간 658만원 정도였다. 시스템 설치 후 항목별 만족도에 대하여 5점 만점에 3.9점이었으며, 노동력 절감 3.7점, 업체의 A/S 3.6점, 산유량 증가 3.2점, 원유의 체세포 수 저감 2.8점이었다. 시스템 설치 시 고려사항 및 건의사항에 대하여 고가의 장비를 효율적으로 사용하기 위하여 젖소의 유방과 유두 배열이 적합하도록 젖소를 선발하는 것, 시스템을 운용할 수 있는 능력, 적합한 환경, 재정적 능력과 부지 확보, 지속적인 관찰 등이 권장되어야 할 것으로 나타났으며, 설치 업체에 대해서는 컨설팅이 체계화될 필요가 가장 높게 나타났으며 이어서 보다 저렴한 설치와 서비스의 체계화를 요구하는 결과를 보였다. The present survey was conducted to provide basic information on automatic milking system (AMS) in relation to purchase motive, milk yield and quality, customer satisfaction, difficulties of operation and customer suggestions, etc. Purchase motives of AMS were insufficient labor (44%), planning of dairy experience farm (25%), better performance of high yield cows (19%) and others (6%), respectively. Average cow performance after using AMS was 30.9l/d for milk yield, 3.9% for milk fat, 9,100/ml for bacterial counts. Sixty-eight percentage of respondents were very positive in response to AMS use for their successors but 18% were negative. The AMS operators were owner (44%), successor (44%), wife (6%) and company worker (6%), respectively. The most difficulty (31%) in using AMS was operating the system and complicated program manual. The rate of response to system error and breakdown was 25%. The reasons for culling cow after using AMS were mastitis (28%), reproduction failure (19%), incorrect teat placement (12%), metabolic disease (7%) and others (14%), respectively. Fifty-six percentages of the respondents made AMS maintenance contract and 44% did not. Average annual cost of the maintenance contract was 6,580,000 won. Average score for AMS satisfaction measurement (1 to 5 range) was 3.2 with decrease of labor cost 3.7, company A/S 3.6, increase of milk yield 3.2 and decrease of somatic cell count 2.8, respectively. Suggestions for the higher efficiency in using AMS were selecting cows with correct udder shape and teat placement, proper environment, capital and land, and attitude for continuous observation. Systematic consulting was highly required for AMS companies followed by low cost for AMS setup and systematization of A/S.

한우 비육우 전업농가 시설투자한계 분석

김재환,김상우,조원모,강희설,조영무,Kim, Jae-Hwan,Kim, Sang-Woo,Cho, Won-Mo,Kang, Hee-Seol,Cho, Young-Moo 한국축산환경학회 1996 축산시설환경학회지 Vol.2 No.2

The objective of this study was to estimate the investment limit in equipment capital by Capital Recovery Method. The data used was collected from 23 Hanwoo(Korean Native Cattle) farms in 1994. The necessary time for herd size expansion was average 5 years from opening(9.7 heads) to 50 heads, 4 years from 50 to 100heads, 3 years from 100 to 150 heads, and 2 years from 150 to 200 heads, respectively. It took 14 years from opening to 200 heads of herd size. The debts for fattening cattle farms were 15.2million won for the size of 50 heads, 37.1 million won for the size of 100 heads and 89.0 million won for the size 200 heads, respectively. Average rates of debt interest were 5.1 % 7.2 and 10.8, correspendingly. As the hear size increased, debt interest rates also increased due to government funds limit. The investment limits in equipment capital perfarm household were 77.7 million won for 50 heads, 135.1 for 100 heads, and 294.3 for 200 heads for 5,500 won per kg liveweight, 70.7 million won for 50 heads, 122.6 for 100 heads and 269.3 for 200 heads for 5,000 won per kg liveweight, 63.6 million won for 50 heads 110.0 for 100 heads and 244.2 for 200 heads for 4,500 won per kg liveweight.