치과주조용 저카라트 금합금의 시효경화

김형일,김종렬,안호경,장명익,설효정,김교한 대한치과기재학회 1997 대한치과재료학회지 Vol.24 No.2

The age-hardening behavior of a commercial dental casting low-carat gold alloy was investigated by means of differential thermal analysis, hardness test, optical microscopic observation and X-ray diffraction study. The following results were obtained. 1. By the isothermal aging of this alloy at 300∼400℃, the hardness increased markedly at the initial stage and continued to increased gradually for the time, and then decreased dractically after longer aging time. 2. The hardening was attributed to the formation of the metastable AuCu I' ordered phase from the α matrix. 3. The overaging with softening was attributed to the precipitation of the fine lamellar structure which was composed of the Ag-rich α1 and AuCu I ordered phases.

치과용 Au-Ag-Cu-Pd 합금의 시효경화특성

김형일,김영근,장명익,김교한 대한치과기재학회 1997 대한치과재료학회지 Vol.24 No.1

The relationship between the isothermal age-hardening behavior and the phase transformation process in a dental casting Au-Ag-Cu-Pd alloy was investigated by means of hardness test, X-ray diffraction study. 1. The isothermal age-hardening behavior in the 350∼450℃ temperature range showed a similar tendency in the changes. However, the initial hardening was faster and the maximum hardness was higher and the overaging with softening was slower on aging at the lower temperature. 2. By the isothermal aging at 350∼450℃, the metastable Ag-rica α₁’and AuCu Ⅰ’orderd phases were formed from the supersaturated α phase prior to the final formation of the equilibrium Ag-rich α₁’and AuCu Ⅰordered phases. 3. By aging at 450℃, the age-hardening was attributed to the lattice strains of the parent phases resulting from the transformation of the αphase resulting from the transformation to the metastable phases. The X-ray diffraction peaks of the αphase showed a distinct shift toward both the high and low diffraction angles during transformation.

수술의 함정 : 중심성 신경세포종 2례 2 Cases of Central Neurocytoma

김범태,주교성,장채칠,신원한,최순관,변박장 대한신경외과학회 1999 Journal of Korean neurosurgical society Vol.28 No.3

석탄폐석의 골재자원화에 관한 연구

이재장,김교선 강원대학교 석재복합신소재제품연구센터 1996 석재연 논문집 Vol.1 No.-

석탄폐석의 골재 자원화에 필요한 폐석 정제 기술에 수반되는 전처리 단위공정에 대하여 전반적으로 살펴보고 각 단위공정의 종류, 이론적 배경, 특성 및 장단점 등에 대하여 알아보았다. 특히 석탄페석의 전처리 단위 공정으로 사분공정, 분쇄공정, 혼합 공정 등에 대하여 자세히 알아보았다. 사북(동원)지역 상부의 폐석은 휴발분 4.6%, 고정탄소 2.7%, 황 0,26%이고, 하부의 폐석은 휴발분 5.7%, 고정탄소 6.4%, 황 0,25%이었다. 상부의 폐석은 10cm이하 크기로 구성되어 있으며 3메시 이하의 입단은 25.2%이었고, 하부폐석의 3메시 이하 입단은 53.2% 이었다. 예비혼합조의 기본설계를 위한 예비실험으로써 실험실용 도우넛형 저장조를 아크릴로 제작하여 모래, 석탄,소금 등을 시료로 하여 예비혼합실험을 하였다. 실험방법은 소금을 tracer로하여 모래 또는 석탄을 예비혼합조에 계단입력 또는 충격입력을 가하여 예비혼합조 출구에서의 응답특성을 관찰하였으며 출구에서의 전기전도도 변화를 측정하였다. 실험실용 도우넛형 저장조의 실험결과 충분한 혼합효과를 얻고 있었으며 특히 시간에 따른 석탄 폐석질의 변화를 급격히 감소시킬 수 있음을 알 수 있었다. 본 실험에서 예비저장조 중앙부분의 유량이 바깥 쪽에 비해 대체로 많은 편이었으며 그 결과로 계단입력의 응답특성이 이론적 예측보다 원만히 증가하고 있었다. 앞으로의 연구에서는 예비혼합조의 벽면 각도, baffle의 각도, 간격 및 너비 등을 사용하는 분체의 물성에 관련시켜 체계적으로 설계하는 연구가 필요하다. In this study, we investigated several unit processes to pretreat coal mine wastes to produce aggregates. We also analysed the kinds, theoretical backgrounds, characteristics, merits and demerits of each unit process. The process of screening, crushing and mixing were analyzed, more specifically, to pretreat the coal mine wastes. It is found that the congromerates, sandstone, shale, coal shale and clay are included in coal mine wastes and the carbonates and sulfates are required to be eleminated from coal mine wastes to produce aggregates. The coal wastes from the upper part of coal mine in Sabuk(Dongwon) are observed to have the content of volatile matter, 4.6%, fixed carbon, 2.7% and sulfur, 0.26%, respectively, while the coal wastes from the lower part of coal mine waste pile have the content of volatile matter, 5.7%, fixed carbon, 6.4% and sulfur, 0.25%. The size fraction of sample under 3 mesh size is 25.2% for fresh samples from upper part of coal waste pile and is 53.2% for coal wastes from lower part. The doughnut-type preblending storage tank were made of acryl and the preliminary experiments were performed with sand, coals and salts to get the basic data to design the preblending storage tank. The sands or coals were introduced into the preblending storage tank with step input or impulse input of salts as tracer and the response characteristics of storage tank were at the outlet of storage tank by measuring the change of electrical conductivities. We could observe the sufficient preblending effects by these experiments of doughnut-type storage tank and, especially, we could reduce the change of coal waste quality as a function of time. In these experiments, we observed the higher flow rates of powder at the center of blending tanks than in the region near the wall of storage tank and, as a result, the response characteristics of step input was increasing more slowly than that expected theoretically. Further systematic studies in preblending storage tank are required about the angle of surface wall, and the angles, spaces and widths of baffles in correlation with the properties of powders being treated.

민간부문 건설사업관리 활성화방안

이정희,장홍진,구교진,김옥규,현창택,김양현 대한건축학회 2004 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.24 No.1

Since, korean government introduced Construction Management system by the law in 1997, only a few public construction projects have been adopted the system Nevertheless there are many laws which are related in public construction projects, Construction Management is positively carried out by non-government. About the activation plan of Construction Management questionnaire was inquired by experts in construction. The purpose of this study is to give a solution by finding out the problem of the laws, reconstructions remodelings.

자발성 뇌실내출혈 환자에서 임상적 -전산화단층촬영상소견의 상관관계

황선철,김범태,장재칠,주교성,신원한,최순관,변박장 대한신경외과학회 1998 Journal of Korean neurosurgical society Vol.27 No.6

온실재배와 노지재배한 금산 깻잎의 품질 특성과 향기성분

현광욱,구교철,장정호,이재곤,김미리,이종수 한국식품저장유통학회 ( 구 한국농산물저장유통학회 ) 2004 한국식품저장유통학회지 Vol.11 No.1

깻잎을 이용한 건강 식품을 개발하고자 먼저 깻잎의 주산지인 금산에서 5월 온실재배한 깻잎과 8월 노지재배한 깻잎들의 품질특성과 향기성분을 조사하였다. 시료깻잎 모두 4.0%의 조단백질과 0.8%의 조지방을 함유하고 있었고, 플라보노이드의 함량은 온실재배 깻잎 25.2%, 노지재배 깻잎 26.5%로 시료깻잎간에 큰 차이는 나타나지 않았으며 조사포닌 함량도 2,7%와 2,8%로 비슷하였다. 시료깻잎의 효소 활성은 오직 알칼리성 단백질 분해효소 활성만이 8월 노지재배 깻잎에서만 물 추출물 7.1 unit, 에탄올 추출불 11.8 unit을 보였고 기타 효소 활성은 없었다. 8월 노지재배 깻잎의 조직감 특성으로 먼저 견고성과 탄력성 등은 잎의 상층부와 중층부 보다 잎받침을 포함하는 하층부에서 높았고 응집성은 하층부가 약간 약하였으며 5월 온실재배 깻잎은 씹힘성이 다서 낮았을 뿐 노지재배 깻잎과 비슷하였다. 5월 온실재배와 8월 노지재배 깻잎에는 1-octen-3-ol, linalool, β-caryorhyllene, α-caryophyllene, α-famesene, perilla ketone, nerolidol, eugenol. α-cadinol 등 14종∼15종의 향기성분을 함유하고 있었고 주요한 향기성분은 perilla ketone 이었다. Quality and flavor compounds of perilla leaves cultivated in greenhouse(May) and field (August) in Geumsan province were investigated and compared. All perilla leaves contained 4.0% crude protein and 0.8% crude lipid. C겨de flavonoid contents of perilla leaves cultivated in greenhouse and field showed 25.2% and 26.5%, respectively and each crude saponin content was cultivated in field. Hardness and chewness of bottom parts of field-perilla leaves were higher than those of top and middle part, whereas the cohesiveness of top parts and middle parts of perilla leaves were higher than that of bottom part. Furthermore, texture properties of greenhouse-perilla leaves were similar with those of field-perilla leaves except chewness. Nine kind of flavor compounds such as 1-octen-3-ol, linalool, β-caryophyllene, α-caryophylene, α-franesene, perilla ketone, nerolidol, eugennl, α-cadinol were identified in greenhouse-perilla and field-perilla leaves, showing that main flavor compound was perilla ketone.

요추간판탈출증에서 현미경 수술과 경피적 자동수핵제거술에 대한 비교연구

신원한,장재칠,주교성,김범태,최순관,변박장 순천향의학연구소 1997 Journal of Soonchunhyang Medical Science Vol.3 No.1

A retrospective study of operative results were carried out in a series of 164 patients who were performed microdiscectomy and 57 patients performed automated percutaneous lumbar discectomy (APLD) for herniated lumbar discs between January 1, 1990 and June 30, 1996 at the Department of Neurosurgery, Soonchunhyang University Hospital. The operative results were analysed, and the correlation between preoperative clinicoradiological factors and postoperative clinical results were statistically assessed. The major results were as follows : 1. Of 164 microdiscectomy cases, 102 were males and 62 were females, mean age was 42.4 years and incidence was the highest in the 5th decade, and of 57 APLD cases, 43 were male and 14 female, mean age was 32.2 years and incidence was the highest in the 3rd decade. 2. The preoperative symptoms and signs were lumbago(98.2%), radiating pain(96.3%), positive straight leg raising test(77.4%), motor weakness(27.4%), claudication(13.4%) & voiding difficulty(2.4%) in microdiscectomy cases, and lumbago(98.2%), radiating pain(98.2%), positive straight leg raising test(70.2%) & motor weakness(17.5%) in APLD cases. 3. Number of operated levels were performed 226 in microdiscectomy and 74 in APLD. The most commonly operated levels of two groups were L4-5 level. 4. Operative results 1) The overall success rates by Prolo's scale were 87.1% in microdiscectomy and 80.7% in APLD, respectively. 2) In younger age group (below 30 years) and in non-compensatory group, success rates were significantly higher in microdiscectomy. 3) As to protrusion and degeneration on MRI, clinical results of moderate protrusion and degeneration of discs in microdiscectomy were statistically significant, and those of mild protrusion and degeneration of discs in APLD were also statistically significant. 4) The most common cause of failure was inappropriate removal of disc material in microdiscectomy and sequestered discs in APLD. According to the above results, there were no differance in overall success rates between microdiscectomy and APLD. But clinical results seem to be influenced by the age, existence of compensation, and by the degree of protrusion and degeneration of discs as prognostic factors. If the selection of operative procedure between microdiscectomy and APLD for herniated lumbar disc is carefully done with clinical and radiologic findings of patients, good outcome might be achieved.

中學 科學敎育의 探究學習에 대한 評價問項 開發 (Ⅱ)

閔庚德,楊洪準,李善行,鄭遠佑,이병교,金裕漢,羅長薰 경북대학교 과학교육연구소 1985 科學敎育硏究誌 Vol.9 No.-

This study was accomplished to develope the evaluation items for inquiry learning in the 2nd grade Middle School Science for the consecutive study of the evaluation items for inquiry learning in the 1st grade Middle School Science(U-Hang Ki et al, 1984). In this study, paper and pencil test items and performance test items are made by analyzing the abilities of inquiry according to the contents and four basic experiments from each unit in the 2nd grade Middle school science. These evaluation items were applied to tke five classes of the 2nd grade of middle school to test their validity. It is desirable that performance test schuld be used for the evaluation for the abilities of inquiry which can not be evaluated by paper and pencil test. In the evaluation methods of performance test, tester evaluation, peer evaluation and self-evaluation can be applied to the science class in a multi-student class. In higher grade, however tester evaluation is more desirable than peer and self evaluation. It is found that peer evaluation and self-evaluation make possible the perfect study by feedback.

Highly Conductive and Fracture-Resistant Epoxy Composite Based on Non-oxidized Graphene Flake Aerogel

Kim, Jin,Han, Ne Myo,Kim, Jungmo,Lee, Jinho,Kim, Jang-Kyo,Jeon, Seokwoo American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.43

<P>Graphene aerogel (GA) has shown great promise as reinforcement of polymeric composites with exceptional electrical and mechanical characteristics. Although there has been significant progress in controlling the structure of GAs, no studies have appeared on the enhanced properties of GAs by employing high-quality precursor graphene flakes (GFs). However, the assembly of high-quality GFs is particularly challenging due to their highly hydrophobic and agglomerative nature in aqueous media, and of the few methods available to synthesize high-quality GFs, most produce flakes with very small lateral sizes. Herein, we report the fabrication of highly crystalline GAs using large nonoxidized graphene flakes (NOGFs) prepared by a novel graphite intercalation compound-based method. Bidirectional freeze casting is utilized for aligning NOGFs in two orthogonal directions, vertically and laterally, where the NOGF walls individually function as effective conductive pathways. The as-prepared nonoxidized graphene aerogel (NOGA) exhibits a defect concentration as low as 1.4% of impurity oxygen with an excellent electrical conductivity of 202.9 S/m at a low density of 5.7 mg/cm<SUP>3</SUP>. The corresponding NOGA-epoxy composite shows a remarkable electrical conductivity of 122.6 S/m and a fracture toughness of 1.74 MPa·m<SUP>1/2</SUP> at a low filler content of 0.45 vol %.</P> [FIG OMISSION]</BR>