플라즈마 표지소자의 제작

이상윤,라병욱,박동수,황인헌,이덕동,신영남,박성배,이동욱,박용석,박형근,손상호,권태근,채경락,정경득 慶北大學校 自然科學大學 1986 自然科學論文集 Vol.4 No.-

An Ac-type Plasma Display Panel (PDP) operating with Ne-Ar(0.1%) Penning mixture gas is fabicated. The characterics of the panel with electrodes covered with thin and thick dielectric layers are studied. The brightness of the Neon-orange light emitted by the panel measured as function of applied voltage and frequency. As an application, a graphic display system equipped with PDP showing still and moving pictures is made.

부등각 엔드밀 가공시 음향방출신호와 절삭력 거동에 관한 연구

김영수,김원일,이윤경,왕덕현 한국공작기계학회 2002 한국공작기계학회 춘계학술대회논문집 Vol.2002 No.-

This study shows how the change of helix angle for different helix angle end mill affects machining accuracy. It was verified that cutting forces are remarkably low when endmill has helix angle of different helix angle 25°, 31°, 37° and AE signals have less relationship with the change of helix angle Moreover, as the number of rotations are increased, the AE signals are increased with the proportion to the number but cutting forces are inversely proportional to the rotation.

알루미나-탄화티타늄 복합체 방전가공의 정상상태 수치해석

안영철,정영습,왕덕현,우정윤,윤존도,고철호 경남대학교 신소재연구소 1996 論文集 Vol.7 No.-

알루미나와 탄화티타늄이 혼합된 세라믹 복합체의 방전가공 현상에 대하여 방전열량이 연속적으로 공급되는 정상상태를 가정하여 갤러킨 방법으로 유한요소 해석을 수행하였다. 해석결과 방전열속이 3.710×10^(7) cal/s·㎡인 경우 반경 20㎛, 깊이 5㎛정도의 홈이 파일 것으로 예측되었다. 방전열속을 5,565×10^(7) cal/s·㎡로 1.5배 정도 높인 경우에는 관심영역 안의 모든 알루미나가 녹았으며 탄화티타늄도 반경 30㎛. 깊이 25㎛에 상당하는 범위까지 녹는 것을 알 수 있었고, 방전흔은 적어도 반경 30㎛ 이상이 될 것으로 예측되었다. 방전역속이 7,420×10^(7) cal/s·㎡ 이상이 되면 피가공물이 완전히 녹아 가공표면이 거칠어질 수 있으므로 방전열속을 이 값 이상 올리지 않는 것이 바람직하다. A finite element analysis has been performed for the electro-discharge machining of an alumina-titanium carbide(Al₂O₃-TiO₂) composite, assuming that the electro-discharge system is in steady-state. A discharge heat flux of 3.710X l0^{7} cal/s·m²is shown to possibly make a crater with radius of 20 μm and depth of 5 μm. When a discharge heat flux of 5.565× l0^{7} cal/s·m²is used, all of the alumina particles in the domain of intrest melts while the titanium carbide particles within the radius of 30 urn and the depth of 25 μm reach the melting point, thus the size of the crater formed becomes larger than 30 μm in radius. It is not recommended to use a discharge heat flux of greater than 7.42O×10^{7} cal/s·m², because it may deteriorate the surface roughness.

Fluoride, Bisphosphonate 및 Gallium이 상아질 흡수 억제에 미치는 영향

백은영,유윤정,노병덕,최윤정,이승종 大韓齒科保存學會 1997 Restorative Dentistry & Endodontics Vol.22 No.2

Replacement resorption is followed by the delayed replantation of an avulsed tooth. Currently no effective treatment is substantiated for replacement resorption. The purpose of this study was to investigate the effect of stannous fluoride, bisphosphonate(etidronate disodium) and gallium nitrate, which have been shown to reduce dentin resorption, on human dentin. Osteoclasts were collected from tibeas of chich embryo. The cells were well agitated to prevent adhesion and seeded onto the sliced human dentin wafers which had been soaked in either culture media(control), or several different concentrations of stannous fluoride, etidronate disodium(1-hydroxyethylidene-1, 1-bisphosphonate disodium), and gallium nitrate. Resorption was measured by counting the number of resorptive pit produced by the cells. Results are ad follows. Stannous fluoride and etidronate disodium showed statistically significant reduction of dentin resorption(p<0.05) but the effect of stannous fluoride seemed to be its high cytotoxicity. Etidronate disodium did not show cytotoxicities in all experimented concentrations. Gallium nitrate did not show differences in resorption either between different concentrations of from the control group.

탄화규소/알루미늄 금속계 복합재료의 형상방전가공

왕덕현,이윤경,우정윤,허보영 한국공작기계학회 1998 한국생산제조학회지 Vol.7 No.1

Conductive metal matrix composite(MMC) material of 30% silicon carbide particulate based on aluminum matrix was machined by die sinking electrical discharge machining(EDM) process according to different current and duty factor for reverse polarity of electrode. Material removal rate(MRR) was examined by process under various operating conditions. The surface morphology was evaluated by surface roughness parameter and scanning electron microscopy(SEM) research. The MRR was suddenly increased over 11 ampere of current, and it was slightly changed over 0.3 of duty factor. The maximum surface roughness of EDMed surface was affected by the duty factor. The SEM photographs of EDMed surface showed wide recast distribution region of melting materials as increased of current and duty factor.

산화알루미늄-탄화티타늄(Al₂O₃-TiC) 세라믹 복합체의 방전가공

왕덕현,우정윤,윤존도,고철호,안영철,정영습 경남대학교 신소재연구소 1996 論文集 Vol.7 No.-

도전성 탄화티타늄 33무게%를 포함하는 산화알루미늄基 세라믹 복합체에 대한 방전가공을 시도하고 최적조건과 방전메카니즘을 조사하였다. 방전조건으로 전류 7-15A, 듀티팩터 0.24-0.45, 인가전압 40V를 사용하여 방전가공을 실시하였는데, 전류가 7A이하, 듀티팩터가 0.30이하일 때 가공이 잘 되었으며, 그 이상에서는 표면 파괴가 일어났다. 방전전류와 듀티팩터가 증가하면 공작물 제거속도는 증가하나 표면 거칠기도 역시 증가하는 것으로 나타났다. 방전가공 표면에 대한 미세구조 분석을 통하여 방전가공 메카니즘은 용융증발기구로 분석이 되었다. Alumina ceramic matrix composite containing electro-conductive titanium carbide of 33 weight % was machined by electrical discharge machining (EDM) method. The machining condition was 7-15A of current, 0.24-0.45 of duty factor, and 40V of applied voltage. When the current and duty factor were 7A and 0.30 or lower, respectively. the specimen were machined successfully. When the current and duty factor were higher. the specimen showed surface damage and fracture after machining. As the current and duty factor increased. the material removal rate(MRR) and maximum surface roughness increased. implying that the machining condition would be selected according to the requirement whether high speed machining or good surface finish is needed. By the microstructure analysis on the machined surface, the mechanism of machining was determined to be melting and evaporation.

연쇄상구균을 실험감염시킨 넙치치어의 병리조직학적 관찰

조성환,류시윤,김현수,박배근,김덕환,손화영,윤원기,신창호 충남대학교 수의과대학 동물의과학연구소 1999 動物醫科學硏究誌 Vol.7 No.-

Pathological observations were examined after abdominal inoculation in 7∼8㎝ sized flounder (Paralichthys olivaceus) with 1X10^7 cfu/㎖ of Streptococcus faecalis. The infected flounder were clinically observed and weighed a fish body at 0, 5, 10, 15, 20, 25, 30 days post inoculation. In infected group, mortality were 70% and feed efficiency were 7.2%. In non-infected group, mortality were 10% and feed efficiency were 18.2%. Macroscopically, the significant lesions were characterized by protrusions and opacity of the eyes and ulcer of the caudal pecuncle. Histopathologically, the lesions were observed a degeneration. necrosis and inflammatory cells in muscle of the caudal peduncle and a degeneration and necrosis of the rod cells and detached retina from the black pigmented layer

개에서 관찰된 모기질세포종의 증례보고

조성환,손화영,김혜성,최종윤,류시윤,박배근,윤원기,홍성혁,김덕환 충남대학교 수의과대학 동물의과학연구소 2002 動物醫科學硏究誌 Vol.10 No.-

Pilomatricoma was histopathologically diagnosed in a 2.5-year-old male Alaskan malamute. The patient was referred to Chungnam National University, Veterinary Medical Teaching Hospital with solitary, firm and well-circumscribed mass at shoulder. Grossly, the mass was dome shaped to tumor like and 10 x 8 x 5㎝ in size. Some lesions had gritty or bony consistency and was chalky when sectioned Histopathologic feature included mumerous clusters of tightly arranged, basaloid cells with evenly distributed chromatin and ghost cells were characterized by a central unstained zone. The ghost cells often become calcified and osseous metaplasia was also present.

High-frequency micromechanical resonators from aluminium–carbon nanotube nanolaminates

Bak, Jung Hoon,Kim, Young Duck,Hong, Seung Sae,Lee, Byung Yang,Lee, Seung Ran,Jang, Jae Hyuck,Kim, Miyoung,Char, Kookrin,Hong, Seunghun,Park, Yun Daniel Nature Publishing Group 2008 NATURE MATERIALS Vol.7 No.6

At micro- and nanoscales, materials with high Young’s moduli and low densities are of great interest for high-frequency micromechanical resonator devices. Incorporating carbon nanotubes (CNTs), with their unmatched properties, has added functionality to many man-made composites. We report on the fabrication of ≤100-nm-thick laminates by sputter-deposition of aluminium onto a two-dimensional single-walled CNT network. These nanolaminates—composed of Al, its native oxide Al<SUB>2</SUB>O<SUB>3</SUB> and CNTs—are fashioned, in a scalable manner, into suspended doubly clamped micromechanical beams. Dynamic flexural measurements show marked increases in resonant frequencies for nanolaminates with Al–CNT laminae. Such increases, further supported by quasi-static flexural measurements, are partly attributable to enhancements in elastic properties arising from the addition of CNTs. As a consequence, these nanolaminate micromechanical resonators show significant suppression of mechanical nonlinearity and enhanced strength, both of which are advantageous for practical applications and analogous to biological nanocomposites, similarly composed of high-aspect-ratio, mechanically superior mineral platelets in a soft protein matrix.

심한 낙타혹(Hump)의 형성을 동반한 제 2 형 막증식성 사구체신염(Dense Deposit Disease) 1예

오희정,유민아,이영숙,김미연,김승정,강덕희,윤견일,최규복,성순희 이화여자대학교 의과대학 2004 EMJ (Ewha medical journal) Vol.27 No.1

Dense deposit disease (DDD), known as type Ⅱ MPGN, is an uncommon form of glomerulonephritis. It is an acquired primary glomerular disease, characterised by electron microscopic evidence of a continous, dense membrane deposition replacing the lamina densa. There is associated alternative pathway complement activation and a C3 nephritic factor maybe present. Patients with dense deposit disease tend to be young at clincal onset and more commonly have persistent nephrotic syndrome, gross hematuria, and acute nephritis episode and persistent depression of the serum complement level. The prognosis of dense deposit disease is worse than that of typeⅠMPGN. We experienced a patient with dense deposit disease that presenting persistent nephrotic syndrome, gross hematuria and having subepithelial hump. It is a first report of dense deposit disease having subepithelial hump in Korea, therefore we report this case with the review of relevant literatures.