• 폴리머
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• 제32권4호
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• pp.322-327
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• 2008

본 연구에서 제조한 다중층 펠렛은 수팽윤성 고분자를 포함하는 시드층, 모델 약물인 독사조신을 함유한 약물층, 약물의 방출을 제어하는 다공성막 그리고 지질층으로 구성되어 있으며, 유동층 코팅 방법을 이용하여 제조하였다. 펠렛을 구성하는 각각의 층에 다양한 특성을 가지는 고분자들의 블렌딩에 따른 독사조신의 약물방출 거동을 확인하기 위하여 히드록시프로필메틸셀룰로오스(HPMC)와 에틸셀룰로오스(EC)의 양을 달리하여 약물층을 제조하였고, 셀룰로오스 아세테이트(CA)와 $Eudragit^{(R)}$ RS의 비율을 달리하여 다공성막을 제조하였다. 그리고 지질층에 의한 방출 거동을 확인하고자 피마자유의 두께를 다르게 하여 펠렛을 제조한 결과, 대략 $1500{\mu}m$의 균일한 크기를 가지는 구형의 펠렛을 얻었다. 수용액에서 용출시험을 통하여 시간에 따른 약물방출량을 확인한 결과, 약물층에 첨가된 고분자 중, EC의 비율과 다공성막에서 CA의 비율이 증가하고, 피마자유층의 두께가 두꺼워지면 약물의 방출이 감소함을 알 수 있었다. 그리고 약물방출을 제어하는데 가장 큰 역할을 하는 다공성막의 다공형성거동 역시 SEM을 통해 확인하였다.

• 한국재료학회지
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• 제17권4호
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• pp.185-191
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• 2007

The purpose of this study is to evaluate the thin fihn dielectric made of hybrid sol, which consist of barium titanate powder, polymeric sol and other polymers. This sol will be used dielectric applied to small, thin electric passive components such as MLCC(Multi Layer Ceramic Condenser), resister, inductor. This sol is composed of mixed fine barium titanate powder and polymeric sol including Ba, Ti-precursor, solvent, chelating agent, chemical reaction catalyst, the additive sols to improve fired densification and temperature reliability. First at all, we mixed hybrid sol to be dispersed and be stabilized by ball milling for 24hrs. By spin coating method, we makes thin film dielectric on the convectional green sheet for MLCC. After heat treatments, we analyzes the structure morphology, physical, electrical properties and X5R Temperature properties.

• 전기전자학회논문지
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• 제24권1호
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• pp.238-242
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• 2020

본 논문에서는 구축함에 탑재되는 통합 마스트의 RCS(Radar Cross Section) 값을 저감시키기 위해 다층 구조로 되어있는 유전체 코팅을 이용한 기법을 제시한다. 제시된 다층 구조는 특별히 고유전율을 요구하거나 전자기파 흡수 차단에 많이 사용되는 자성체성분을 포함하지 않은 일반적인 유전체를 사용할 수 있도록 유전율의 범위를 정했기 때문에 제작에 용이하다는 장점이 있다. 제시된 다층 유전체 구조를 통합 바스트 형상에 적용시킨 후 시뮬레이션을 진행한 결과 다층 구조가 없는 구조물과 비교하여 6GHz에서 10.9dB, 12GHz에서 11.95dB, 18GHz에서 11.63dB의 RCS 저감 성능이 있는 것을 확인하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.224-224
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• 2012

For decades, carbon fiber has expanded their application fields from reinforced composites to energy storage and transfer technologies such as electrodes for super-capacitors and lithium ion batteries and gas diffusion layers for proton exchange membrane fuel cell. Especially in fuel cell, water repellency of gas diffusion layer has become very important property for preventing flooding which is induced by condensed water could damage the fuel cell performance. In this work, we fabricated superhydrophobic network of carbon fiber with high aspect ratio hair-like nanostructure by preferential oxygen plasma etching. Superhydrophobic carbon fiber surfaces were achieved by hydrophobic material coating with a siloxane-based hydrocarbon film, which increased the water contact angle from $147^{\circ}$ to $163^{\circ}$ and decreased the contact angle hysteresis from $71^{\circ}$ to below $5^{\circ}$, sufficient to cause droplet roll-off from the surface in millimeter scale water droplet deposition test. Also, we have explored that the condensation behavior (nucleation and growth) of water droplet on the superhydrophobic carbon fiber were significantly retarded due to the high-aspect-ratio nanostructures under super-saturated vapor conditions. It is implied that superhydrophobic carbon fiber can provide a passage for vapor or gas flow in wet environments such as a gas diffusion layer requiring the effective water removal in the operation of proton exchange membrane fuel cell. Moreover, such nanostructuring of carbon-based materials can be extended to carbon fiber, carbon black or carbon films for applications as a cathode in lithium batteries or carbon fiber composites.

• 펄프종이기술
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• 제40권5호
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• pp.60-69
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• 2008

The principal reasons for applying a pigment coating to paper are to improve appearance and printability. The pigment coating provides a surface that is more uniform and more receptive to printing ink than are the uncoated fibers and, in turn, both facilitates the printing process and enhances the graphic reproduction. The improvement in print quality is readily apparent, especially in image areas or when multiple colors are involved. Although pigment coating of paper is to improve the printability, coated paper is not completely free from printing defects. Actually there are a number printing defects that are observed only with the coated papers. Among the printing defects that are commonly observed for coated papers, print mottle during multi-color offset printing is one of the most concerned defects, and it appears not only on solid tone area but also half dot print area. There are four main causes of print mottle ranging from printing inks, dampening solution, paper, and printing press or its operation. These indicates that almost every factors associated with lithographic printing can cause print mottle. Among these variation of paper quality influences most significantly on print mottle problems in multicolor offset printing, and this indicates that paper is most often to be blamed for its product deficiency as far as print mottle problems are concerned. Furthermore, most of the print mottle problems associated with paper is observed when coated papers are printed. Uncoated papers rarely show mottling problems. This indicates that print mottle is the most serious quality problems of coated paper products. Overcoming the print mottle is becoming more difficult because the operating speeds of coating and printing machines are increasing, coating weights are decreasing, and the demands on high-quality printing are increasing. Print mottle in offset printing is caused by (a) nonuniform back trap of ink caused by a nonuniform rate of ink drying, referred as "back trap mottle, and (b) nonuniform absorption of the dampening solution. Furthermore, both forms of print mottle have some relationship to the structure of the coated layer. The surest way of eliminating ink mottling is to eliminate unevenness in the base paper. Coating solutions, often easier to put into practice, should, however, be considered. In this paper the principal factors influencing print mottle of coated papers will be discussed. Especially the importance of base paper roughness, binder migration, even consolidation of coating layers, control of the drying rate, types of binders, etc. will be described.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 1994년도 춘계학술대회강연 및 발표대회 강연및 발표논문 초록집
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• pp.6-6
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• 1994

Har dmaterials such as cemented carbides with or without coated layer, cermets, ceramics and diamond or c-BN high pressure sintered compact are used for cutting tools, wear -resistant parts, rock drilling bits and/or high pressure vessels. These hardmaterials contain not only hard phase, but also second consituent as the element for forming ductile phase and/or sintering aid, and the mechanical properties of each material depend on (1) the amount of the second constituent as well as (2) the grain size of the hard phase. The hardness of each material mainly depends on these two factors. The fracture strength, however, largely depends on other microstructur a1 factors as well as the above two factors. For all hardmaterials, the fracture strength is consider ably affected by (3) the size of microstructur a1 defect which acts as the fracture source. In cemented carbides, the following factors which are generated mainly due to the addition of the second constituent are also important; (4) the variation of the carbon content in the normal phase region free from V-phase and graphite phase, (5) the precipitation of $Co_3$ during heating at about $800^{\circ}C$,(6) the domain size of binder phase, and (7) the formation of ${\beta}$-free layer or Co-rich layer near the surface of sintered compacts. For cemented carbides coated with thin hard substance, the important factors are as follows; (8) the kind of coated substance, (9) the formation of ${\eta}$-phase layer at the interface between coated layer and substrate, (10) the type of residual stress (tension or compression) in the coated layer which depends on the kind of coating method (CVD or PVD), and (11) the properties of the substrate, and (12) the combination, coherency and periodicity of multi-layers. In the lecture, the details of these factors and their effect on the strength will be explained.

• 한국균학회소식:학술대회논문집
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• 한국균학회 2015년도 추계학술대회 및 정기총회
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• pp.14-14
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• 2015

Cellular aspects of sooty mold on walnut leaves were investigated by using light and electron microscopy. A black coating developed on the adaxial leaf surface of a walnut tree. No infestations were found on the abaxial leaf surface with peltate glandular trichomes. Light microscopy showed that fungal complexes from the leaf surface were composed of brown conidia and hyphae. Conidia, with longitudinal and transverse septa, were variable in length ranging from 10 to $30{\mu}m$, and commonly found in clusters, forming microsclerotia. Neither epidermal penetration nor hyphal entrance to host tissues was observed. Based on their morphological characteristics, the fungal complexes were assumed to be Capnodium species. An electron-dense melanized layer was present on the cell wall of multi-celled conidia. Concentric bodies in the fungal cytoplasm had an electron-translucent core surrounded by an electron-dense margin with a fibrillar sheath. Chloroplasts without starch granules in the palisade mesophyll cells of sooty leaves had electron-dense stromata and swollen plastoglobuli. These results suggest that the epiphytic growth of fungal complexes can be attributed to the melanized layer and concentric bodies against a water-deficient environment on the leaf surface. Ultrastructural characteristics of the sooty leaves indicate typical features of dark-adapted and non-photosynthetic shade leaves.

• 한국초전도ㆍ저온공학회논문지
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• 제21권1호
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• pp.1-5
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• 2019

The pulsed field magnetization of the short-circuited soldered double pancake coil made of stabilized commercial high-Tc superconductor (HTS) tape is experimentally studied. The evolution of the shielding current induced by the pulsed field and the trapped field after the pulsed magnetization was measured at 77 K. It is shown that the trapped field in the coil is close to the value reached in the field cooling process and reduces weakly at 5-fold increasing of pulsed field amplitude. The current relaxation at t~2 ms after the pulse is defined by the current sharing between the tape's copper coating and the $YBa_2Cu_3O_{7-d}$ layer. In the intermediate time scale (1 s < t < 100 s) the flux creep in HTS layer dominates. At t > 100 s the current's relaxation is defined by the resistance of soldered joint between tapes.

• 한국의류학회지
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• 제39권2호
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• pp.247-256
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• 2015

This study prepared fabric-heating elements of carbon nanofiber composite to characterize morphologies and electrical properties. Carbon nanofiber composite was prepared with 15wt% PVDF-HFP/acetone solution, and 0, 1, 2, 4, 8, and 16wt% carbon nanofiber. Dispersion of solution was conducted with stirring for a week, sonification for 24 hours, and storage for a month, until coating. Carbon nanofiber composite coated fabrics were prepared by knife-edge coating on nylon fabrics with a thickness of 0.1mm. The morphologies of carbon nanofiber composite coated fabrics were measured by FE-SEM. Surface resistance was determined by KS K0555 and worksurface tester. A heating-pad clamping device connected to a variable AC/DC power supply was used for the electric heating characteristics of the samples and multi-layer fabrics. An infrared camera applied voltages to samples while maintaining a certain distance from fabric surfaces. The results of morphologies indicated that the CNF content increased specifically to the visibility and presence of carbon nanofiber. The surface resistance test results revealed that an increased CNF content improved the performance of coated fabrics. The results of electric heating properties, surface temperatures and current of 16wt% carbon nanofiber composite coated fabrics were $80^{\circ}C$ and 0.35A in the application of a 20V current. Carbon nanofiber composite coated fabrics have excellent electrical characteristics as fabric-heating elements.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1995년도 춘계학술대회 논문집
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• pp.187-191
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• 1995

Thin film of the (Pb$\_$1-x/La.sub x/)(Zr$\_$0.25/Ti/Sub 0.48/) O$_3$(x=0~13[at%]) were prepared by Sol - Gel method. Multi-layer PLZT thin films were fabricated by spin-coating on Pt/Ti/SiO$_2$/Si substrate. The crystallinity and microstructure of the films were investigated with the sintering condition. At the sintering temperature of of 600[$^{\circ}C$], the perovskite phase was dominat. PLZT(11/52/48)thin films sintered at 600[$^{\circ}C$], 1[hr] had good dielectric constant (1236), dielectric loss (2.2[%]), remanent polarization (1.38[${\mu}$C/$\textrm{cm}^2$] and coercive field(16.86[ kV/cm]) respectively.