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>

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.

생쥐 중이와 상기도 점막의 섬모세포운동

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

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.

敎育大學 實科 實驗實習의 效率化를 위한 資料開發 硏究

鄭原圭,尙貞基,鄭模根,李時元 釜山敎育大學 1987 부산교육대학 논문집 Vol.23 No.1

This study is to research the better ways of management in the practical arts-education in primary schools. The primary school teachers' concrete experiences are made use of to improve their teaching methods in teachers college, a teacher training institute. Therefore this research is supposed to be able to fix on the aim of practical arts-education. Accordingly the questionaires of the problems caused on the scene of education are given to the present teachers in the seasonal system of Pusan Teachers College and Jinju Teachers College. The aim of this research is to develop the materials to improve the educational effectiveness in the practical art-education of teachers college. The result is as follows : 1. According to the questionaires, the problems in the education of the practical course for elementry schools are mainly due to the deficiency of its materials. On the other hand, the teaching methods depending on experiment and practice together should be applied to the class. 2. In the current practical textbook, experiment, practice and observation are shown in the units separately in the contents. The Fifth Educational Revised Plan compared to the current educational curriculum, the units of computer and life are newly showed in the life function scope of the sixth grade textbook. Besides the contents of teaching and the factors of teaching are revised a little. The current educational curriculum, therefore, should be supplied more faithfully. 3. In order to develop the textbook of the practical arts-education of the teachers college, the contents of practical arts-education textbook mainly by experiment and practice are made up of the five scopes of the departments of agriculture, commerce, fishing, household management, etc... 4. To get rid of the formal procedures of abstraction and theory, the practical arts-education of the teachers college quickly needs to make the practical application of audiovisual aids and to introduce the manufactured mechanical apparatus helpful to developing the practical materials by itself. 5. At the departments of practical arts-education of the nation-wide Teachers Colleges, the facilities and equipments of experiment and practice are now as follows : The Ministry of Education shows the standard of equipments, that is, the 7 kinds of laboratories and 179 kinds of experimental apparatus, but the average rates of laboratories of 11 Teachers Colleges is 10.37 percent. So the Ministry of Education should reconsider the standard of its equipments. 6. To develop the practical arts-education of the teachers college, the general institute of practical arts-education should be set up. The kinds of laboratory and its structure (or scale) are shown on each scope.

EZW를 적용한 영상압축에 관한 연구

具元謨,金昌錫 明知大學校 産業技術硏究所 2002 産業技術硏究所論文集 Vol.21 No.-

The EZW algorithm is encoded by zerotree coding technique using serif-similarity of wavelet coefficients. If the coefficient is larger than the threshold a POS coded, if the coefficients is smaller than minus the threshold a NEG is coded. If the coefficient is the root of a zerotree than a ZTR is coded and finally, if yhe coefficient is smaller then the threshold but it is not the root of a zerotree, than an IZ is coded. This process is repealed until all the wavelet coefficients have been encoded compleatly. This paper was compared to EZW algorithm and a widely available version of JPEG. As the results of compare, it is shown that the PSNR of the EZW algorithm is bettor than JPEG.

광 인터넷을 위한 광 제어 패킷 처리 모듈 구현

연삼모,정원일 한밭대학교 2004 한밭대학교 논문집 Vol.21 No.-

네트워크에서 전기적인 병목현상을 제거시키기 위한 노력으로, IP가 전부 광인 WDM 계층에서 동작하는 새로운 광 라우터(router)/스위치(하드웨어)가 차세대 광 인터넷용으로 구축되고있다. 앞으로 광 인터넷은 광 플로우 단위의 교환방식을 거쳐 광 패킷(packet) 교환망으로 발전하게 될 것으로 전망하고 있다. 본 논문에서는 WDM 광패킷 라우팅/스위칭 기술에 광패킷 Label 스위칭 기술을 접목시키기 위하여 고속으로 광 헤더패킷을 처리하는 모듈을 개발하는 것이다. 이를 위하여 입력포트로부터 수신된 IP 패킷 헤더를 분석하여 IP 룩업(lookup)을 제어하는 룩업 제어기, 그리고 헤더(header) 패킷을 처리하고, 이 헤더 패킷에 해당하는 버스트(burst) 데이터를 포워딩하는데 필요한 자원을 예약하는 역할을 수행하고, 이에 필요한 정보(광 스위치상의 파장 채널 지정, 지정된 파장 채널 셋업, 유지 및 복구 Timing 정보)를 전달해 주는 스케줄러가 구현된다. 룩업제어기와 스케쥴러(schedulor)는 VHDL과 관련 기술을 이용하여 구현된다. As the effort to remove the electrical bottleneck in network, newoptical router and switch for next generation Internet to operate IP on optical WDM layer has been installing. In the future, Optical Internet will be the optical packet switched network using switching method based on optical flow. In This paper, to connect WDM optical packet routing/switching to the optical packet label switching technology, the module for processing the optical header packet will be developed. For this, IP lookup controller, which analyzes IP packet header received from the input port, and then control IP lookup, will be developed. And also the Scheduler, which processes the header packet, reserves the resources necessary to forward the burst data according to this header packet, and deliveries information(assignment of wavelength channel on optical switch, timing information according to setup, maintenance, and recovery of the assigned wavelength channel) necessary for this, will be developed. Lookup controller and scheduler will be developed using VHDL and its related technology.

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.

데페록사민 전처치가 토끼 심근경색 크기의 감소에 미치는 효과

양관모,오동렬,박승현,박규남,이원재,김형국,황두영,최승필,채장성 대한응급의학회 1998 대한응급의학회지 Vol.9 No.4

Background: Reperfusion of ischemic myocardium has been postulated to result in a specific oxygen radical mediated tissue injury. Iron may liberate during ischemia and we hypothesized that administration of the iron chelator, deferoxamine during ischemia would result in improved recovery after postischemic reperfusion. Purpose: To test whether iron-catalyzed processes contribute to myocardial necrosis during ischemia and reperfusion, deferoxamine was administered to block iron catalyzed hydroxyl radical formation in rabbits. Methods: Eleven rabbits were divided into two groups : control group (n=5) and deferoxamine pretreatment group (n=6). The left circumflex coronay artery was ligated for 30 minutes and reperfused for 180 minutes. Area at risk (AR) was measured by non-stained area with methylene blue injection into left atrium after left circumflex coronary artery ligation. Infarct size was measured by weighing after triphenyltetrazolium chloride staining. Heart rate was measured using electrocardiographic recording and systemic blood pressure was monitored by pressure transducer connected to the catheter in the left ventricle. Results: 1. There was no significant difference of heart rate and blood pressure in deferoxamine pretreatment group compared with control group. 2. There was significant decrease of serum iron concentration after continuous infusion of deferoxamine compared with serum iron concentration before ligation of coronary artery(P<0.05). 3. There was no significant difference of area at risk between control and deferoxamine pretreatment group. 4. Area at necrosis to area at risk was significantly reduced in deferoxamine pretreatment group compared with control group(P<0.05). The results suggest that deferoxamine infusion prior to coronary artery occlusion has a significant benefit in reducing infarct size in this model.