• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 춘계학술발표대회
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• pp.31.1-31.1
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• 2009

Carbon nanotubes (CNTs) are attractive material because of their superior electrical, mechanical, and chemical properties. Furthermore, their geometric features such as a large aspect ratio and a small radius of curvature at tip make them ideal for low-voltage field emission devices including backlight units of liquid crystal display, lighting lamps, X-ray source, microwave amplifiers, electron microscopes, etc. In field emission devices for display applications, the phosphor anode is positioned against the CNT emitters. In most case, light generated from the phosphor by electron bombardment passes through the anode front plate to reach observers. However, light is produced in a narrow depth of the surface of the phosphor layer because phosphor particles are big as much as several micrometers, which means that it is necessary to transmit through the phosphor layer. Hence, a drop of light intensity is unavoidable during this process. In this study, we fabricated a transparent cathode back plate by depositing an ultra-thin film of single walled CNTs (SWCNTs) on an indium tin oxide (ITO)-coated glass substrate. Two types of phosphor anode plates were employed to our transparent cathode back plate: One is an ITO glass substrate with a phosphor layer and the other is a Cr-coated glass substrate with phosphor layer. For the former case, light was radiated from both the front and the back sides, where luminance on the back was ~30% higher than that on the front in our experiments. For the other case, however, light was emitted only from the cathode back side as the Cr layer on the anode glass rolled as a reflecting mirror, improving the light luminance as much as ~60% compared with that on the front of one. This study seems to be discussed about the morphologies and field emission characteristics of CNT emitters according to the experimental parameters in fabricating the lamps emitting light on the both sides or only on the cathode back side. The experimental procedures are as follows. First, a CNT aqueous solution was prepared by ultrasonically dispersing purified SWCNTs in deionized water with sodium dodecyl sulfate (SDS). A milliliter or even several tens of micro-liters of CNT solution was deposited onto a porous alumina membrane through vacuum filtration. Thereafter, the alumina membrane was solvated with the 3 M NaOH solution and the floating CNT film was easily transferred to an ITO glass substrate. It is required for CNT film to make standing CNTs up to serve as electron emitter through an adhesive roller activation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.943-945
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• 2002

This paper presents conceptual design and 3-D electromagnetic analysis of 1MVA transformer with BSCCO-2223 High Tc Superconducting (HTS) tapes. The rated voltages of each sides of the transformer are 22.9 kV and 6.6 kV, and double pancake windings were adopted. High voltage and Low voltage sides were composed of several double pancake windings. Four HTS tapes were wound in parallel for the windings of low voltage side and were transposed in order to distribute the currents equally in each conductor. The transformer core was designed as a shell type core made of laminated silicon steel plates and the core is separated with the windings by a cryostat with Fiberglass Reinforced Plastics(FRP). A sub-cooling system using $LN_2$ were designed to maintain the coolant temperature of 65K. Finally perpendicular components of magnetic field applied to tapes were calculated 0.24T in the rated operation using 3-D analysis. A real 1MVA HTS transformer will be manufactured in near future based on the design parameters presented in this paper.

• Korean Chemical Engineering Research
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• 제50권4호
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• pp.738-742
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• 2012

본 연구에서는 알루미나 나노 템플레이트(anodic alumina oxide; AAO)를 이용하여 신속하면서도 효과적으로 나노입자 및 바이오물질을 분리, 농축할 수 있는 나노필터 소자를 개발하였다. 본 연구에서 사용한 나노필터 소자는 유체의 주입 및 흐름이 가능한 미세유체채널(microfluidic channel)을 PDMS에 패터닝하였다. 위아래로 형성된 PDMS 미세유체채널 사이로, 다양한 크기의 나노 다공을 형성하고 있는 AAO 막을 삽입하여 크기에 따른 나노입자 및 바이오 물질을 분리할 수 있었다. 위아래로 PDMS 유체채널과 AAO 분리막을 집적하고, 최종적으로 아크릴레이트 플락스틱(acrylic plastic)으로 전체 소자를 고정하여 나노필터유체소자를 제작하였다. 완성된 나노필터소자를 이용하여 나노입자의 농축효율 및 은나노입자가 뭉쳐져있는 필터존(filtration zone)으로부터 뎅기 바이러스(dengue virus)를 표면증강라만(surface enhanced Raman scattering)분석법에 의해 검출할 수 있었다.

• Journal of Welding and Joining
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• 제27권5호
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• pp.74-80
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• 2009

The membrane of the LNG carriers consists of thin strips of INVAR(Fe-36%Ni) steel plates, and the junction between INVAR strips is fabricated by welding. Thousands of the raised edge joints, regularly spaced, are located around all the side of the tank corner near the transverse bulkhead, and TIG welding is manually made on the top of the raised edges. Since the thickness of all the laminated edge plies is extremely thin and the weld position is under a bad accessibility, highly skilled workers are required to perform welding relatively for a long welding time. An alternative scheme for the corner membrane fabrication is proposed in the study to improve the installation workability and thus productivity. The scheme replaces the welded edges with the preformed corrugation ones. A panel strip with regularly-spaced corrugations is installed at the corner instead of the individual flat strip of which edge is vertically raised to be welded with the adjacent strip. In the study, a series of the evaluation on the corrugated edge members was performed to assess the applicability to the real LNG carrier fabrication. Opening displacement at the raised edge was experimentally examined. Elastic stiffness regressed from the displacement was nearly same in both edge types. Edge displacement and local stresses were calculated under hydrostatic pressure and temperature change due to liquefied cargo. Fatigue test was performed on both corrugated and welded edge specimens consisting of two or five plies of invar strips. Fatigue strength of the corrugated specimens was not less than that of the welded specimens.

• Journal of Periodontal and Implant Science
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• 제24권2호
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• pp.238-254
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• 1994

Cyclosporine A is an immunosuppressant commonly used for patients receiving organ transplants. Gingival overgrowth is an adverse side-effect seen in about 8-26% of patients taking cyclosporine A which have been shown to increase the DNA synthesis of gingival fibroblast at the concentration of $10^{-9}g/ml$ in vitro. Glycyrrhetinic acid is the active pharmacological ingredients of licorice which exerts steroid-like action and anti-viral activity. Oleanolic acid, which were isolated from Glechoma hederacea, has been shown to act as inhibitors of tumor promotion in vivo and to be less cytotoxic retinoic acid. This study has been performed to evaluate the effects of glycyrrhetinic acid and oleanolic acid on cyclosporine A induced cell activity in vitro. Human gingival fibroblasts were isolated from explant cultures of healthy gingiva of orthodontic patients. Gingival fibroblasts were trypsinized and transferred to the walls of microtest plates. Fibroblasts were cultured in growth medium added $10^{-9}g/ml$ cyclosporineA and $50{\mu}l/ml$ lipopolysaccharides. Cells between the 4th and 6th transfer in culture were used for this study. The morphology of gingival fibroblst were examined by inverted microscope. The effects of cyclosporine A on the time course of DNA sythesis by human gingival fibroblasts were assessed by $[^3H]-thymidine$ uptake assays. Cyclosporine A was found to stimulate DNA synthesis of human gingival fibroblast at a concentration of $10^{-9}g/ml$. In the presence of lipopolysaccharide derived from Fusobacterium nucleatum, addition of cyclosporine A results in reversal of inhibition at the concentration which normally inhibits gingival fibroblast proliferation. The cell acitivities in the presence of glycyrrhetinic acid and oleanolic acid were decreased, and increased cell acitivities by cyclosporine A were decreased by glycyrrhetinic acid and oleanolic acid at the concentration of $200{\mu}g/ml$. These results suggested that the increased cell activities by cyclosporine A modulated by glycyrrhetinic acid and oleanolic acid.

• Journal of Periodontal and Implant Science
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• 제26권3호
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• pp.669-679
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• 1996

Gingival overgrowth is a well known side effect of several drugs, including nifedipine, phenytoin, cyclosporin, dilitiazem, verapamil. A number of studies have been performed to investigate the mechanism by which nifedipine(a calcium channel blocking agent) affects the gingival tissue. The aim of the present work was to investigate the effect of nifedipine on healthy gingival fibroblasts with special emphasis on determining the changes in cellular proliferation and protein and collagen synthesis. Gingival fibroblasts were obtained from the explants of healthy gingiva of extracted 3rd molars or premolar teeth extracted from the patients for orthodontic treatment. To evaluate the effect of nifedipine on cell proliferation, the cells were seeded at a cell density of $1{\times}10^4$cells/well in 24-well culture plates and treated with 100 and 200ng/ml of nifedipine for 10days. After trypsinization, the cells were counted with a haemocytometer on 1st, 3rd, 5th, 7th and 10th days. Then, MTT assay was carried out. For total protein and percent collagen synthesis, $3{\mu}Ci/ml$ $^3H-proline$ was added to each well for the final 4 hours of the incubation period. The results indicate that nifedipine does not influence cell proliferation in healthy gingival fibroblast in vitro and has a specific effect in reducing total protein and percent collagen synthesis. On the above the findings, exogenous nifedipine does not influence on healthy human gingival fibroblast proliferation and protein and collagen synthesis.

• Journal of Advanced Marine Engineering and Technology
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• 제37권6호
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• pp.589-595
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• 2013

본 논문은 플라즈마 절단 면 특성이 I Groove 서브머지드 아크 용접 용락 현상에 미치는 영향과 용락 현상을 감소시키는 방법에 대하여 연구하였다. 조선해양 구조물의 주판은 대부분 후판으로 설계되고 깊은 용입을 얻기 위하여 고 전류를 사용하게 된다. 용접부의 절단 품질에 따라서 서브머지드 아크용접 진행 시 용락 현상이 자주 발생되고 이는 용접부의 품질 저하와 수정 작업을 유발시킨다. 본 연구의 플라즈마 절단 실험에서 나타난 특성으로 I형상 그루브 직각 절단 시 상,하면에 플라즈마 열원에 의한 녹음 현상과 함께 하면 한 방향에 약 2~4도 정도의 각 변형 베벨이 형성됨을 확인하였다. 이는 맞대기 이음에서 용락 현상의 주된 원인이며 모재 절단 시 상면 방향에 I 그루브 형상에 가깝도록 한 방향 기준으로 V형상 그루브 4도 베벨을 시공하여 서브머지드 아크 용접을 실시한 결과 용락 현상을 현저히 저감시키는 결과를 얻을 수 있었다.

• Archives of Plastic Surgery
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• 제37권3호
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• pp.309-312
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• 2010

Purpose: An osteoma is one of the common benign tumors that penetrate the nasal portion, paranasal and frontal sinus. This tumor is mostly found by radiation test accidentally, however in rare cases; it can be found to be touched or with its symptoms as the tumor grows. We report this case since we found and healed the benign tumor which was affecting orbit and the both sides of fronal sinus. Methods: A 19 year old female patient visited to our hospital due to the mass on her forehead. The symptoms began 3 years ago but no special symptom was found except for touchable mass. She was diagnosed as the osteoma of superior orbital parts and both sides of frontal sinus using X-ray and CT scanning. The size of osteoma was $5{\times}2.5{\times}3.5\;cm$ and indicated the patterns penetrated to the right side of orbital region. The osteoma excision was conducted with coronal incision and wide area of defect part in frontal sinus and superior orbital part were reconstructed by cranial bone graft and resorbable fixation plates. Results: The patient recovered without any postoperative infections or complications and symptoms. Dysaesthesia was found on her frontal area but improved in 1 month after the surgery. Conclusion: The occurrences of osteoma in frontal sinus are rare and can be treated with conservative methods if there are no infections and symptoms. We report this case since we found the benign tumor, which was affecting orbit and the both sides of fronal sinus and healed it with coronal resectomy without any complications.

• Journal of Advanced Marine Engineering and Technology
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• 제38권7호
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• pp.900-908
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• 2014

본 연구는 상류측에 작은 수직평판을 가진 정방형주의 유동장 특성을 양 항력측정 실험과 PIV를 이용한 가시화 실험으로 파악한 것이다. 실험파라메터는 정방형주 한 변의 길이에 대한 수직평판의 폭비(H/B=0.2~0.6) 및 정방형주 전면에서부터 수직평판까지의 거리 (G/B=0~3) 로 했다. 수직평판의 폭비를 고정시킨 경우 정방형주의 항력감소율은 간격비가 증가할수록 증가하다 감소하는 특성을 보였다. 또한 같은 간격비에서는 수직평판의 폭비가 클수록 정방형주의 항력감소율이 컸다. 정방형주의 양력감소율은 수직평판의 폭비 및 간격비에 거의 영향을 받지 않았으며, 양력감소율의 평균치는 48.1% 정도였다. 수직평판을 설치한 경우 정방형주 상류측과 하류측에 정체영역이 나타났다.

• Journal of Advanced Marine Engineering and Technology
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• 제34권5호
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• pp.711-717
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• 2010

본 논문에서는 플라스틱 평판에 핀 홀을 생성하여 문자나 이미지를 표현하는 디스플레이 보드를 자동으로 제작하는 펀칭시스템을 개발하였다. 핀 홀을 생성한 평판은 가장자리에 설치한 다양한 색상의 발광다이오드 빛을 반사하여 미려한 디스플레이 보드에 사용된다. 펀칭시스템은 정밀한 위치 및 깊이 생성을 위해 총 4개의 엑추에이터를 사용하였다. 디스플레이 보드 상의 글자나 이미지의 반사효과와 빠른 생산성을 위하여 정밀한 구동 기구부를 개발하고 PID 제어 알고리즘을 적용하였다. 그리고 사용자가 반사되는 글자의 모양이나 이미지를 구성하는데 도움을 줄 수 있는 GUI 프로그램과 PC기반의 제어시스템을 구성하였다. 또한 펀칭속도와 생성된 핀 홀의 깊이를 검사하여 본 시스템의 성능을 검증하였다.