Effects of Cooling Rate on the Microstructure and Tensile Properties of Wire-Arc Additive Manufactured Ti–6Al–4V Alloy

Hui‑Jun Yi,Jin‑Woo Kim,Young‑Lak Kim,Sangyong Shin 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.8

Wire-arc additive manufacturing has emerged as a technology that could replace the conventional manufacturing processof titanium alloys. However, it produces a coarse β grain, which can accumulate via several deposited materials, resulting isstrong texture and anisotropy. To investigate potential solutions, the effects of the cooling rate on the resulting microstructureand tensile properties were studied. The cooling rate of the deposited materials was adjusted by interpass temperaturecontrol. Under rapid cooling, fine α + α′ grain with a low aspect ratio were observed and tensile and hardness propertieswere also improved.

A Study on Characteristics of Wet Oxide Gate and Nitride Oxide Gate for fabrication of NMOSFET

Yi, Jae-Young,Lee, Young-Hui,Yi, Cheon-Hee 청주대학교 산업과학연구소 2005 産業科學硏究 Vol.23 No.1

이 논문에서는 HP 4145 소자 테스터를 사용하여 핫 케리어 효과와 트래핑차지, SILC의 특성을 비교하기 위하여 질화 산화막 게이트와 습식게이트 산화막을 가지고 0.26㎛ NMOSFET를 테스트하고 생성시켰다. 그 결과로 습식게이트 산화막소자보다 질화 산화막 게이트의 특성이 더 좋다는 것을 알게 되었고 특히 핫 케리어 라이트 타임이 (질화 산화막 게이트 소자는 30년이나 습식 게이트 산화막은 10년) 길고 Vg의 변화 및 항복전압이나 트래핑의 충전 등이 좋음을 알 수 있었다. In this paper we fabricated and tested the 0.26㎛ NMOSFET with wet gate oxide and nitride oxide gate to compare that the characteristics of hot carrier effect, charge to breakdown, transistor Id_Vg curve, charge trapping, and SILC(Stress Induced Leakage Current) using the HP4145 device tester. As a result we find that the characteristics of nitride oxide gate device better than wet gate oxide device, especially hot carrier lifetime (nitride oxide gate device satisfied 30years, but the lifetime of wet gate oxide was only 0.1year), variation of Vg, charge to breakdown and charge trapping etc.

합금의 종류와 지대주 성분이 바형 유지 장치의 변연 적합도에 미치는 영향

이윤희,송영균,이준석 대한치과보철학회 2012 대한치과보철학회지 Vol.50 No.2

Purpose: The object of this study was to determine if the low-priced alloy and metal UCLA abutment could be available for manufacturing bar-retained framework of implant prosthesis. Materials and methods: Bar structure was classified into 4 groups, The specimen of group 1 and 2 were based on casting high noble metal alloys and noble metal alloys with gold UCLA abutment. The specimen of group 3 and 4 were based on casting noble metal alloys and base metal alloys with metal UCLA abutment. Cast bar structure was installed in an acrylic resin model and only the screw on the hexed abutment side was tightened to 20 Ncm. On the opposite side, vertical discrepancy was measured with stereo microscope from front, back, and lateral side of the implant-abutment interface. One-way ANOVA was performed to analyze the marginal fit discrepancy. Results: One-way ANOVA test showed significant differences among all groups (P<.05) except for Group 1 and 3. Among them, difference between Group 1 and 2 was noticeable. Measured vertical discrepancies were all below 70 ㎛ except to Group 2. Conclusion: Base metal alloy and metal UCLA abutment could be used as an alternative to high-priced gold alloy for implant bar-retained framework. 연구 목적: 합금의 종류와 지대주의 재질의 차이가 변연적합도에 미치는 영향을 비교 분석하고자 한다. 연구 재료 및 방법: 2개의 임플란트 유사체를 평행하게 위치시킨 후 아크릴릭 레진으로 포매하여 연구모형을 제작하였다. 바 구조물은 gold UCLA 지대주에 고귀금속 합금(high noble metal alloy)과 귀금속 합금(noble metal alloy)을, 그리고 metal UCLA 지대주에 고귀금속 합금과 비귀금속 합금(base metal alloy)을 이용하여 총 4 종류의 바 구조물을 7개씩 시편을 제작하였다. 주조된 바 구조물을 레진 모형에 장착하고 한쪽 지대나사를 조인 후, 반대쪽 임플란트-지대주 간극의 수직 거리를 앞, 뒤, 측면 3부위에서 입체 광학 현미경으로 관찰하여 기록하였다. 결과: 각 군들의 변연오차 평균값은 gold UCLA 지대주에 고귀금속 합금과 귀금속 합금을 사용했을 때 각각 13.69 ± 6.74 ㎛와 267.26 ± 65.85 ㎛이었으며, metal UCLA 지대주에 고귀금속 합금과 비귀금속 합금을 사용했을 때 26.19 ± 8.14 ㎛와 61.90 ± 33.65 ㎛이었다. One-way ANOVA를 이용하여 변연 적합도의 차이를 분석했을 때 고귀금속 함금을 사용한 군들을 제외하고, 모든 군간에 유의한 차이가 존재하였다(P<.05). Gold UCLA 지대주-귀금속 합금 조합을 제외하고 모두 70 ㎛ 이하의 수직오차를 보였다. 결론: 임플란트 바 유지 장치의 제작에 있어서 고귀금속 합금 대신 비귀금속 합금과 metal UCLA 지대주를 사용하는 것은 임상적 타당성이 있다고 판단된다.

[논문]직렬형 2배수 권선비 변압비를 이용한 HBML PWM 인버터

고희영,김철우 釜山大學校生産技術硏究所 2005 生産技術硏究所論文集 Vol.64 No.-

본 논문에서는 고조파를 저감하고 출력 파형을 개선하기 위하여 H-Bridge 인버터와 변압기 조합을 이용한 다중레벨 인버터를 구성함에 있어 변압기 출력 전압의 조합을 이용한 새로운 하이브리드형 멀티레벨 인버터를 제안한다. 제안한 다중 레벨 인버터는 THD을 저감하기 위해 변압기의 권션비가 1배,2배,4배인 3대를 사용하여 출력전압을 기존의 9 레벨에서 15 레벨로 증가 하였다. 또한 PWM 인버터 스위칭 패턴을 변경하여 스위칭 소자수를 10개에서 8개로 저감하고,변압기를 4개에서 3개로 저감할 수 있는 방법을 제안한다. 제안된 다중레벨 PWM 인버터의 전력회로 및 제어신호의 타당성을 입증하기 위해 프로토 타입 15레벨 언버터에 대하여 실험을 행하였다.

인터넷을 중심으로 한 ICT 기반 수업 전략

김영환,김광휘 釜山大學校 敎育硏究所 2001 敎育硏究 Vol.11 No.1

For an ideal ICT education, the development of alternative and strategies toward internet based instructions will be needs. However, the essential factor of instructions is that there should be more considerations and cares for learners, and thus more improved quality of instructions. Internet based instruction is part of those attempts. The basic condition for internet based instructions is the fulfillment of various factors for good instructions. Strategically, they are effectiveness for better instructions, efficiency between teacher’s and student’s performances, attractiveness for exiting learners’ and teachers’ interactions, and morality in means and contents. They are microscopic factors. The example of macroscopic factors is the reliance and empathy between teachers and students. A good teacher will be free from external restrictions and steadily use the internet or other ICT environments to make the best ICT based instructions.

우리나라 시외통신망의 과부하 통화량 관리 방안에 관한 연구

서영태,박상희 연세대학교 산업기술연구소 1991 논문집 Vol.23 No.2

When the traffic performance begins to decline, to assure the adequate call processing of the toll network, efficient management of overload traffic is needed. In this paper, the generated patterns and managing methods of overload traffic in Korean toll network have been studied and the traffic performance has been analyzed by the result of applying overload traffic managing methods and compared with a traffic performance without this method. When the overload traffic managing method, the obtained results are as follows. 1. When the busy traffic performance is 700,000 houses, good processing of the traffic performance over 95% is obtained, which is the operation target of an automatic trunk call operator. 2. If the busy traffic performance increases above 700,000 houses, the trunk call performance goes down abruptly. 3. When the number of trunk call is 700,000, 665,000 calls are connected and 35,000 calls are not connected.

칼슘급원과 섭취수준의 노령 암컷흰쥐의 혈청 및 대퇴골에 미치는 영향

유영상,김희정,구재옥 동아시아식생활학회 1996 동아시아식생활학회지 Vol.6 No.2

This study was performed to investigate the effect of dietary dried anchovy and non-fat dried milk on serum and femur. Ten months old female rats were divieded into 6 groups(ST. A-middle, A-high, M-middle, M-high, A+M), and fed the diet containing different level of food calcium for 8 weeks. The results obtained were summarized as follow : 1. The rats' weight gain were not significantly different from the fed groups, but food intake were significantly higher or lower level in the group of A-high than the other groups. 2. Serum calcium concentration was significantly increased in the A-middle group, the M-high group were significantly decreased. Serum phosphorous contents of M-high group were increased significantly higher than ST group. The serum magnesium contents were increased significantly higher than in the A-middle group. Serum iron contents of other experimental groups were significantly higher than ST group. All experimental groups were significantly lower copper contents in serum than ST group. 3. The more rats took dried anchovy and non-fat dried milk, the longer the length of femur. But this trend is not statistically difference. In the breaking force of left femur, most of all experimental group were stronger than ST group. 4. The calcium, phosphorous contents of ash, dry, wet weight of right femur in A+M group were higher than any other groups.

서울시내 유아기 어린이의 간식실태 및 기호도에 대한 조사 연구

유영상,김희정 동아시아식생활학회 1998 동아시아식생활학회지 Vol.8 No.1

This study estimate the amount of snack intake of 290 children from ages 3 to 6 living in Seoul, to provide some basic information for a nutrition education program for the promotion of health. Average height and weight of the children were 110.5㎝ and 19.7㎏, respectively. Their body mass index was 16.2 ㎏/㎡ and obesity index was 6.5%. Calorie intake from snacks was 294㎉, and protein, fat, carbohydrate were 11.3g, 9.3g and 40.6g, respectively. The 117(40.3%) boys prefered boiled-eggs and 112(38.6%) girls prefered fruits. The 133(45.9%) mothers of the children were in their thirties, and 123(42.4%) of them had a college degree. One hundred and thirty-one(45.2%) mothers were house keepers, and they had been givins snacks to their children 1 or 2 times daily(245, 84.5%). The daily snack budget was 1,500 won(109, 37.6%). The person who served the snack was a mother(141, 48.6%). As a result, snack intake of pre-school children showed very good but partially showed a potential problem. We hope that the results of this study can be helpful for the nutrition education program for the health and nutrition of pre-school children.

유아교육기관의 운영관리 현황연구 : 서부경남 지역을 중심으로 around West Kyung Sang Nam-do

천희영 진주여자전문대학 1988 論文集 Vol.10 No.-

The purpose of this study was to assess the general situation of preschool management according to type and region of preschool. The subject preschools of this study included 33 private preschools, 33 primary school's coexistent preschools, 33 saemaul nursery schools. For data analysis, this study used percentage, one-way ANOVA by SPSS/PC computer program and content analysis. The following couclusion could be drawn. 1. Physical setting ; Most of preschools in West Kyung Sang Nam-do were managed in corporation, opened early 1980 decade. Among subsettings for children, child s rest room and observational room were rare. Such kinds of equipment in and out door were plentiful, for example, music instrument, primary materials for art, blocks, traffic toy, sand play box, playing house materials, books, puzzle, outdoor macroequipment and indoor ornaments. But it was insufficient such as wheel toy, water play equipments, pretend play materials, woodworking materials, indoor macroequipment and nature observational equipment. 2. Educational program ; Most of preschools collected children with the guide paper, grouping them by homogeneous age, chose half day program. There were 36.2 children a class and the ratio of child to teacher was 33.6 : 1 in an average. Most of preschools chose 'education for whole child' as the goal of education and used reference book published by a public institution for planning the curriculum. 3. Health management ; As a rule child s case history was kept, but not the family history in many preschools. There were many preschools which hold a vaccination and a physical examination, a tooth examination, health education, figuring the developmental chart, keeping the firstaid medicine and health guide. Mainly it was teacher who took charge of the health management. Preschool didn't sterilized bowls and equipment of play room. Teachers were not examined periodically and they prepared the food service. 4. Parent education program; There were not various types of parent education program, though the half of subject preschools took the periodical interview and patial parent involvement. 5. Personnel management ; Teachers including the director were mostly female and their educational background was equal to or higher than technical college graduate. The age of director was higher than 40 years, but that of teacher and assistant teacher was lower than 40 years. Experience of teaching children was not longer than 10 years in case of director, 3 years in case of teacher and assistant teacher. The director had monthly income more than 170000 won, teacher and assistant teacher less than 100000 won. It was rare to employ the staffs, most of them were female and had no licence, no experience of teaching children. 6. Evaluation management ; Half of the subject preschools didn't evaluate the curriculum including teacher and child development. In the case of evaluation, there were two or three times evaluations a semester. 7. Private preschool and preschool situated in city region were managed well rather than those of other type or other region.

解放神學과 暴力

朴永烋 명지대학교 인문과학연구소 1996 인문과학연구논총 Vol.14 No.-