• Applied Microscopy
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• v.40 no.2
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• pp.81-88
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• 2010

The fine structural characteristics of the apoptotic cells in the cutaneous epithelium of the anuran tadpole of the black-spotted frog, Rana nigromaculata was examined using the TUNEL (Terminal deoxynucleotidyl transferase-mediated biotinylated d-Uridine triphosphate Nick End Labeling) staining technique and TEM (transmission electron microscopy) observations. The cutaneous epithelium of the tadpole was composed of stratified cuboidal cells and the apoptotic cell death was observed continuously during the tail degeneration stages from the Shumway stage number 31 to 33. The early apoptotic cells shown in the epithelium demonstrated condensation and margination of the chromatin material at the nuclear periphery, and nuclear breakdown and cytoplasmic condensation were followed. Subsequent cytoplasmic degeneration of the apoptotic cell were produced by membrane-bounded cell fragments with relatively well preserved organelles. Following the processes of autophagic degradation, the late apoptotic cells being phagocytosed by other surrounding cells. These nearby cells, presumptive intraepithelial macrophages, contain a variety of lysosomal residual bodies which fuses with other cell organelles or other cytoplasmatic material to form secondary lysosomes. They are soon transformed into lamellar shaped vesicles and finally disappeared during the process of degradation.

• The Korean Journal of Zoology
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• v.33 no.1
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• pp.22-27
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• 1990

The gastro-endocrine cells were examined in the fundic region of stomach of the frog, Rana rugosa, by transmission electron microscope. In the present paper, at least three kinds of cell type distributed in this region were idendfted according to their morphological charactedstics based on the size, shape and electron density of the secretory granules. Type I cells were characterized by the presence of round or oval granules (300-5OOnm in diameter) with high electron density. The granules showed a wide lucent between the contents and the limiting membrane. This cell was reminiscent of the ECL cell in the human alimentary mucosa. Type II cells were characterized by the presence of spherical or oval granules (11O-230nm in diameter) with low or high electron density. The granules showed a clear halo between the homogenous contents and the limiting membrane. This cell was reminiscent of the G cell in the human alimentary mucosa. Type Ill cells were characterized by the presence of elongated oval or pheomorphic granules (50-2OOnm in diameter) with low or moderate electron density and abundant microfilament bundles in the cytoplasm. The granules contained a very thin halo.

• The Korean Journal of Malacology
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• v.29 no.2
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• pp.129-137
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• 2013

This study was conducted to find out the changes of survivorship, respiration and organ structure of Mactra veneriformis exposed to copper (Cu). Experimental period was four weeks. Experimental groups were composed of one control condition and three copper exposure conditions (0.025, 0.050 and 0.100 mg/L). The results of the study confirmed that copper induces reduction of survival rate and respiration rate and histopathology of organ structure of the bivalve. In the copper concentration of 0.100 mg/L, mortality was 100% after Cu exposure of 3 weeks. Respiration rate was observed exposure groups lower than control decline by 75%. Histological analysis of organ system illustrated expansion of hemolymph sinus, disappearance of epidermal layer and degeneration of connective tissue layer of the mantle. Also, histological degenerations as epithelial necrosis and hyperplasia of mucous cells are recognized in the gill and it was observed expansion of hemolymph sinus, disruption of epithelial layer, decrease of mucous cell and degeneration of connective tissue layer in the foot. In the digestive diverticulum, it was showed atrophy of basophilic cell and degeneration of epithelial cell in the digestive tubules, and as the concentration of copper increased the accumulation of lipofuscin increased.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.646-646
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• 2013

그래핀은 이차원의 탄소 원자들이 벌집구조를 이루는 탄소 원자 한 층의 물질이다. 우수한 기계적, 전기적, 광학적 특성으로 인해 투명전극, 가스 센서, 트랜지스터 등과 같이 다양한 응용이 가능하고 연구가 행해지고 있다. 최근 몇 년 동안, 그래핀의 우수한 특성을 이용해서 마이크로센서나 신축성 있는 전자소자를 위한 전도막과 같은 응용이 시도되고 있다. 본 연구에서는 화학기상증착법 (CVD)으로 합성한 그래핀을 이용해서 암모니아 가스 센서 소자를 제작, 센서 특성을 관찰하였다. 구리 기판을 이용하여 화학기상증착법으로 그래핀을 합성하였으며 진공로에서 수소(H2)와 메탄(CH4) 가스를 사용하였다. 그래핀 합성 온도, 가스 유량 등을 변화시키며 그래핀을 합성하고, 합성된 그래핀을 구리기판을 식각용액을 이용해 제거하는 방법으로 그래핀을 전사시키는 공정거쳐 Au/Ni 전극패턴 위에 전사시킴으로 가스 센서 소자를 제작하였다. 제작된 센서 소자를 이용해 상온에서 암모니아(NH3) 가스의 유량을 변화시키며 실험하였다. 암모니아 가스가 흐를 때 그래핀에 암모니아 분자가 흡착되어 그래핀의 전기저항을 증가시켜 이를 이용해서 암모니아 가스를 감지할 수 있었다. 본 연구에서 제작한 소자는 상온에서 암모니아 가스에 민감하게 반응했으며 이는 기존의 금속산화물을 이용한 암모니아 센서는 대부분 고온에서 작동하는 점과 비교 하였을 때 가스 센서 소자로써 큰 장점이라고 할 수 있다.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.387-390
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• 1999

누설탄성표면파(Leaky Surface Acoustic Wave : LSAW) 측정에 사용하는 것을 목적으로 PVBF 압전막을 이용하여 직선집속 초음파트랜스듀서를 제작하고 그 특성을 평가하였다. 제작은 한쪽 면이 원통형 구조를 갖는 구리, 알루미늄, 3mmPVC-에폭시 3가지 재료를 배면층으로 사용하여 각각에 PVDF를 부착시켜서 수중에 음파를 방사하도록 구성하였고, 특성평가는 임펄스응답 특성과 음장 특성으로 나누어서 평가하였다. 임펄스응답 특성은 제작한 3종류의 집속 초음파트랜스듀서에 대해 실험적으로 측정하고, Mason 등가회로1)를 이용한 이론적 해석결과와 비교하였다. 음장특성 측정실험은 구리를 배면체로 하여 제작한 집속 초음파트랜스듀서에 대해서 실시하였고, 그 이론적인 계산결과는 Raylelgh-Somme-rfeld 회 절이론2)을 도입하여 초점면에 형성되는 음압분포를 계산하는 것으로 얻어졌다. 실험은 펄스 초음파 송수기 및 $2{\mu}m/step$으로 이동하는 정밀 x-y-z 스테이지를 컴퓨터에 연결하여 자동 측정하는 것으로 수행되었는데, 그 결과는 이론 해석결과와 비교적 잘 일치하였다.

• Journal of Advanced Navigation Technology
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• v.12 no.6
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• pp.653-658
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• 2008

The automotive environment is particularly demanding on connector performance, and is characterized by large temperature changes, high humidity and corrosive atmospheres. Fretting is a contact damage process that occurs between two contact surfaces. Fretting corrosion refers to corrosion damage at the asperities of contact surfaces. This damage is induced under load and in the presence of repeated relative surface motion, as induced for example by vibration. This paper critically reviews the works published previously on fretting corrosion of electrical connectors. Various experimental approaches such as testing machines, material selection, testing environments, acceleration testing techniques and preventing methods are addressed. Future research prospects arc suggested.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.5
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• pp.78-84
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• 2007

In the regeneratively cooled combustion chambers of liquid rocket engine using hydrocarbon fuels, coking occurs as the wall temperature increases which results in compounds deposition on the wall of cooling channels. This phenomenon reduces cooling capability of the coolant which finally causes damage to the combustor by overheating of the chamber wall. In this paper, experiment results using an electrical heating equipment to simulate the regeneratively cooled channel are introduced and based on the results the compatibility of copper alloy with hydrocarbon fuel Jet A-1 is investigated.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.1
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• pp.34-46
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• 2004

Copper films were prepared by using ECR-MOCVD(Electron Cyclotron Resonance Metal Organic Chemical Vapor Deposition) coupled with a DC bias system. The DC bias is connected to the electrode which placed 1∼3cm above the polymer substrate. The pulse electrical field around the electrode attracts the positive charged copper ions generated from the dissociation of copper precursor, $Cu(hfac)_2$, under ECR plasma. Condensation of supersaturated copper ions in the space between the electrode and substrate, makes it possible to deposit copper film on the polymer substrate even at room temperature. In this study, optimization of the electrode configuration was carried out in order to obtain the uniform films. The uniformity of the deposited films were closely related to the parameters of electrode geometry such as electrode shape, thickness, grid size and the spacing between electrodes. The most uniform copper film was observed with the electrode that enabled uniform electrical field distribution across the whole dimension of electrode.

• Membrane Journal
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• v.29 no.6
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• pp.308-313
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• 2019

In this study, the Fe₃O₄/porous carbon composite was synthesized by hydrothermal method for removal of Cu²⁺ ions and the characteristic of Cu²⁺ ions removal was performed. The Fe₃O₄/porous carbon composite was investigated via using SEM, XRD for its morphology and structure. BET analysis was conducted to conform a specific area and pore size distribution of the composite. For the investigation of the performance for removal of Cu²⁺ ions in the solution, UV-vis spectrometer was used. It suggests that a synergetic effect between magnetic Fe₃O₄ and porous carbon shows an improvement for removal of Cu²⁺ ions.

• Land and Housing Review
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• v.4 no.1
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• pp.119-124
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• 2013

Generally, the characteristic of nanofiltration membranes were catagorized into charged membrane, sieve effect, interaction between membarnes and target solutes. This study aims to investigate the effect item of heavy metal separation with view of charge nanofiltration membranes. The experiments of nanofiltration were conducted by nanofiltration set-up with operational pressure of 0.24 MPa at $25^{\circ}C$ by using synthetic wastewater containing 0.1mg/L of Cr, Fe, Cu, Zn, As, Sn, Pb. Nanofiltration membranes rejected heavy metals much better than chloride, sulfate and TOC, of which concentration in synthetic wastewater was higher than that of heavy metals. To consider rejection characteristics of various metals by nanofiltration membranes, separation coefficient, which is the molar conductivity ratio of the metal permeation rate to the chloride ion or TOC permeation rate, was introduced. In spite of different materials and different nominal salt rejection of nanofiltration membrane used, the separation coefficients of metals were nearly the same. These phenomena were observed in the relationship between the molar conductivity and the separation coefficient for heavy metals.