• 한국분말재료학회지
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• 제24권6호
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• pp.494-507
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• 2017

A three-dimensional physical part can be fabricated from a three-dimensional digital model in a layer-wise manner via additive manufacturing (AM) technology, which is different from the conventional subtractive manufacturing technology. Numerous studies have been conducted to take advantage of the AM opportunities to penetrate bespoke custom product markets, functional engineering part markets, volatile low-volume markets, and spare part markets. Nevertheless, materials issues, machines issues, product issues, and qualification/certification issues still prevent the AM technology from being extensively adopted in industries. The present study briefly reviews the standard classification, technological structures, industrial applications, technological advances, and qualification/certification activities of the AM technology. The economics, productivity, quality, and reliability of the AM technology should be further improved to pass through the technology adoption lifecycle of innovation technology. The AM technology is continuously evolving through the introduction of PM materials, hybridization of AM and conventional manufacturing technologies, adoption of process diagnostics and control systems, and enhanced standardization of the whole lifecycle qualification and certification methodology.

• 한국분말재료학회지
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• 제25권5호
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• pp.435-440
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• 2018

In the present study, we develop a conductive copper/carbon nanomaterial additive and investigate the effects of the morphologies of the carbon nanomaterials on the conductivities of composites containing the additive. The conductive additive is prepared by mechanically milling copper powder with carbon nanomaterials, namely, multi-walled carbon nanotubes (MWCNTs) and/or few-layer graphene (FLG). During the milling process, the carbon nanomaterials are partially embedded in the surfaces of the copper powder, such that electrically conductive pathways are formed when the powder is used in an epoxy-based composite. The conductivities of the composites increase with the volume of the carbon nanomaterial. For a constant volume of carbon nanomaterial, the FLG is observed to provide more conducting pathways than the MWCNTs, although the optimum conductivity is obtained when a mixture of FLG and MWCNTs is used.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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• pp.917-919
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• 2003

The effect of conducting carbon layer on the performance of AC thin film EL display was examined. It was found that incorporation of small amount of carbon nano-tube and conducting additive greatly improve the luminance of the inorganic EL compared to the one with only conducting carbon black.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2001년도 춘계학술발표회 초록집
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• pp.19-20
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• 2001

• 한국분말재료학회지
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• 제24권3호
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• pp.187-194
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• 2017

Selective laser melting (SLM) can produce a layer of a metal powder and then fabricate a three-dimensional structure by a layer-by-layer method. Each layer consists of several lines of molten metal. Laser parameters and thermal properties of the materials affect the geometric characteristics of the melt pool such as its height, depth, and width. The geometrical characteristics of the melt pool are determined herein by optical microscopy and three-dimensional bulk structures are fabricated to investigate the relationship between them. Powders of the commercially available Fe-based tool steel AISI H13 and Ni-based superalloy Inconel 738LC are used to investigate the effect of material properties. Only the scan speed is controlled to change the laser parameters. The laser power and hatch space are maintained throughout the study. Laser of a higher energy density is seen to melt a wider and deeper range of powder and substrate; however, it does not correspond with the most highly densified three-dimensional structure. H13 shows the highest density at a laser scan speed of 200 mm/s whereas Inconel 738LC shows the highest density at 600 mm/s.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2019년도 춘계학술대회
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• pp.133-136
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• 2019

최근 많은 산업용 기기들은 외부 모니터링과 제어 시스템에 프로토콜 호환성 문제에 직면하고 있다. 본 논문은 다층 통신 모듈을 사용하여 산업 통신 프로토콜 변환을 지원할 수 있는 산업용 통신 게이트웨이를 설계하였다. 산업용 통신 게이트웨이는 rs485 시리얼 통신을 이용하는 개별 통신 모듈을 다층으로 연결하는 구조를 가지고 있다. 각각의 통신 모듈은 analog data card, digital data card LAN 및 CAN 지원 카드로 구성하였다. 메인 보드 프로세서는 Atmega micro-processor를 사용하였고, rs485 시리얼 슬롯을 배치하여 다층의 통신 모듈 구조를 가지도록 하였다. 이러한 통신 모듈 적층형을 이용하여 아날로그 및 디지털 I/O 기능과 LAN과 CAN을 지원하여 산업용 통신 제어 및 모니터링에 폭넓게 사용할 수 있다.

• 한국통신학회논문지
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• 제26권11A호
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• pp.1803-1811
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• 2001

본 논문에서는 미국의 유선 케이블 모뎀 규격인 MCNS(Multimedia Cable Network System) DOCSIS(Data Over Cable Service Interface Specification)를 만즉하는 하향 채널의 64/256-QAM 수신부 FEC(Forward Error Correction)를 분석하였다. FEC는 기본적으로 RS(Reed-Solomon) 계층과 TCM(Trellis Coded Modulation) 계층으로 구분되며, 여기에 추가적으로 interleaving과 randomizer 계층들이 결합되어 있다. AWGN(Additive White Gaussian Noise) 환경에서의 BER(Bit Error Rate) 성능평가를 통해 수신부 연판정 비터비 복호기(soft Viterbi decoder)의 추적 깊이(trace-back depth)와 양자화 레벨(quantization level)의 크기에 따라 부호화 이득이 변함을 확인하였다.

• 펄프종이기술
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• 제42권4호
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• pp.71-77
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• 2010

To utilize modified pulp fibers in papermaking system, it is necessary to evaluate the interaction between modified fibers and papermaking additives. Fluorescent whitening agent (FWA) is an important additive which has been widely used for production of writing and printing paper. We modified pulp fiber surface by Layer-by-Layer multilayering of polyelectrolytes, and investigated the interaction between these fibers and FWA used in internal addition or surface treatment. Pulp fiber with cationic surface charge showed a good affinity to internal FWA. For FWA in surface sizing agent, whiteness and brightness of paper was dependent on pickup weight and polyelectrolyte type. Pulp fibers with C-starch/PSS multilayer showed better optical properties than poly-DADMAC/PSS treatment. It indicated that polyelectrolyte type in Layer-by-Layer multilayering as well as a good affinity to FWA is important to get better whiteness and brightness.

• 한국산업융합학회 논문집
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• 제4권1호
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• pp.61-69
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• 2001

Polycarbonate(PC) membranes for oxygen enrichment from air were prepared by the wet phase inversion method. In order to improve oxygen separation performances of the PC membrane, the effect of the added ethanol(nonsolvent) and $CuCl_2$(metal salt) concentration in the casting solution on morphology, oxygen permeability ami $O_2/N_2$ separation factor of the membrane was studied. In addition, tensile strength and elongation at break of the membrane were investigated. An asymmetric membrane with a dense top layer and a porous sublayer was obtained. The thickness of the dense top layer decreased with increasing amount of nonsolvent additive. Compared with pure PC membrane without additive(metal salt), the oxygen permeability and $O_2/N_2$ separation factor of the $PC/CuCl_2$ membrane are significantly improved. The oxygen permeability and $O_2/N_2$ separation factor is $5.25{\times}10^{-9}cm^3(STP){\cdot}cm/cm^2{\cdot}sec{\cdot}cmHg$ and 4.5, respectively. This improvement might be due to good interaction between metal salt and oxygen.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.155-156
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• 2006

UV-NIL is a promising technology for the fabrication of sub-100 nm features. Due to non-uniformity of the residual layer thickness (RLT) and a strong possibility of defects, many UV-NIL processes have been developed and some are commercially available at present, most are based on the 'step-and-repeat' nanoimprint technique, which employs a small-area stamp, much smaller than the substrate. This is mainly because, when a large-area stamp is used, it is difficult to obtain acceptable uniform residual layer thickness and/or to avoid defects such as air entrapment. As an attempt to enable UV_NIL with a large-area stamp for high throughput, we propose a new UV-NIL tool that is able to imprint 4 inch wafer in a low vacuum environment at a single step.