• 한국분말재료학회지
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• 제29권1호
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• pp.34-40
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• 2022

Recently, high-entropy carbides have attracted considerable attention owing to their excellent physical and chemical properties such as high hardness, fracture toughness, and conductivity. However, as an emerging class of novel materials, the synthesis methods, performance, and applications of high-entropy carbides have ample scope for further development. In this study, equiatomic (Hf-Ti-Ta-Zr-Nb)C high-entropy carbide powders have been prepared by an ultrahigh-energy ball-milling (UHEBM) process with different milling times (1, 5, 15, 30, and 60 min). Further, their refinement behavior and high-entropy synthesis potential have been investigated. With an increase in the milling time, the particle size rapidly reduces (under sub-micrometer size) and homogeneous mixing of the prepared powder is observed. The distortions in the crystal lattice, which occur as a result of the refinement process and the multicomponent effect, are found to improve the sintering, thereby notably enhancing the formation of a single-phase solid solution (high-entropy). Herein, we present a procedure for the bulk synthesis of highly pure, dense, and uniform FCC single-phase (Fm3m crystal structure) (Hf-Ti-Ta-Zr-Nb)C high-entropy carbide using a milling time of 60 min and a sintering temperature of 1,600℃.

• 디지털정책학회지
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• 제2권4호
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• pp.17-23
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• 2023

본 논문에서는 중소 규모의 정밀 가공 기업에 대한 생산 가공의 개선을 위하여 기존 공정 방식에 제조 실행 시스템을 적용하고 정밀가공의 데이터를 통합하였다. 이에 따른 기업 내 공정 관리 시스템의 강화, 장비 운용 효율의 증대, 불량률 감소를 통한 생산성 향상 및 작업 공수 감소에 따른 원가 절감률의 차이를 비교 분석하였다. 그 결과 제조 실행 시스템 도입으로 인해 생산 업무 생산성이 7.0% 향상되었고, 제품 불량률은 0.1%p 개선되었다. 제조원가 절감은 10.0%, 납기 준수율은 1.1% 개선되었음을 확인하였다. 추후 본 연구에서 제안한 제조 실행 시스템을 기반으로 추가적인 스마트팩토리 기술을 적용하는 경우 PQCD 지표의 상승으로 인한 가공 산업의 매출 및 이익 증대가 예상된다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 춘계학술대회 논문집
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• pp.113-114
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• 2009

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.376-381
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• 1987

There are many kinds of intelligent devices on the factory floor nowadays. Standardized communication methods became a necessity for efficient flow of production information among various systems. MAP (Manufacturing Automation Protocol) based on ISO (International Standard Organization) OSI (Open Systems Interconnection) is gaining acceptance of major industries worldwide.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 1998년도 추계학술대회 및 정기총회
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• pp.142-146
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• 1998

In this paper, we suggests a WIP(work in process) of FMS analysis methods based on the Genetic algorithm. We conjoined both the assignment and the scheduling problem in order to create a new representation scheme for a chromosome and a mutation operators.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.135-137
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• 2009

After setting the gold standard for both industrial dropon-demand inkjet printheads and R&D printers for functional materials printing, FUJIFILM Dimatix has developed a printhead with the highest jetting frequency ever obtained. Operating at 100 kHz, the MEMS fabricated SAMBA printhead expands the capabilities of fabrication methods for display applications.

• 한국산업보건학회지
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• 제6권1호
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• pp.17-27
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• 1996

This study was designed to survey exposure levels of formaldehyde among workplaces in some plywood industries and to compare three sampling methods including the impinger method(IM, NIOSH method No. 3500), the solid sorbent tube method(SS, NIOSH method No. 2541), and the passive bubbler monitor method(PB, SKC). The survey was conducted in seven particle board manufacturing factories, two resin manufacturing factories and two plywood manufacturing factories in Incheon area during the period from March 6 to April 20, 1995. The workplaces included were the hot/cold press, the roller/spreader, the soaking/drying, and the reaction/mixing areas. The results were as follows; 1. The average(GM, GSD) concentrations of formaldehyde by sampling methods were 0.11(4.43) ppm by IM, 0.27(2.03) ppm by SS, and 0.29(2.04) ppm by PB, respectively. The concentrations by 1M method were statistically very significantly lower than those of SS and PB methods, particularly at low air borne concentrations of formaldehyde (p<0.001). 2. The area average concentrations of formaldehyde by workplaces measured with PB bubblers were 0.23(2.08) ppm from the press, 0.23(1.77) ppm from the spreader, 0.24(1.51) ppm from the soaking, and 0.46(1.96) ppm from the reaction areas, respectively. The personal average concentrations of formaldehyde by workplaces measured with PB bubblers were 0.30(1.77) ppm from the press, 0.33(1.54) ppm from the spreader, 0.36(1.46) ppm from the soaking, and 0.84(1.19) ppm from the reaction areas, respectively. 3. No statistically significant differences of formaldehyde concentrations among workplaces except the reaction area(p<0.001) were found. 4. Formaldehyde concentrations from personal samples were higher than those of from area sam pies in all workplaces studied. But no statistically significant differences of formaldehyde concentrations both area and personal samples were found. In conclusion, this study found that although formaldehyde concentrations in some plywood industries in Incheon area were below the regulatory limit of 1 ppm, they were over the limits recommended by NIOSH and ACGIH. This study also suggests that the impinger method may underestimate true formaldehyde concentrations. It implies that there will be more workplaces not meeting current regulatory limit if either the solid sorbent or passive bubbler methods were used instead of the impinger method. It is suggested that passive monitors will be a reasonable alternative for area and personal sampling of formaldehyde if the accuracy and validity of passive monitors be verified before use.

• 한국산업보건학회지
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• 제16권2호
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• pp.131-144
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• 2006

For the purpose of preparing the fundamental data on working environment of small scale manufacturing industries and preventing the occupational diseases of workers in these industries, authors surveyed the status of working environment to several chemical substances and physical agents by types of industry and types of process in the small scale manufacturing industries with less than five workers in Gimhae including 235 workplaces, 14 types of industry and 25 types of process from January 2002 to December 2004. This measurement method was work environment measurement method (established in Ministry of Labor, Korea), analytical methods (2nd Ed.) of Occupational Safety and Health Administration (OSHA) and manual of analytical methods (4th Ed.) of National Institute for Occupational Safety and Health (NIOSH) and collected data was analyzed by using SPSS 10.0 for windows, the results were as follows: 1. Noise generated in 14 types of industry and 22 types of process. an actual level of mean exposure (90.7 dB(A)) exceeded threshold limit values (TLVs) in manufacture of other transport equipment. An actual level of mean exposure (90.2dB) exceeded TLVs in the process of wire-drawing and 90.4dB in the process of wire-stranding. 2. Dusts of type I, II, III were generated in 9 types of industry and 8 types of process. Its mean concentration did not exceed TLVs. 3. Heavy metals (Pb, Mn, Cr, Ni) were generated in 7 types of industry and 7 types of process. Its mean concentration did not exceed TLVs. 4. 16 kinds of organic solvents were generated in 11 types of industry and 6 types of process. Its mean concentration did not exceed TLVs. As the above results, chemical substances and physical agents were generated in the several different types of industry and process of the manufacturing industry with less than five workers, and only mean level of noise was exceeded TLVs. In case of exceeding threshold limit values, improvement of work environment is actively needed, and work environment management should be performed continuously for prevention of an occupational diseases and work related diseases.

• 자원리싸이클링
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• 제27권1호
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• pp.3-13
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• 2018

3D 적층가공(3D Additive manufacturing, AM) 기술은 기존산업의 패러다임을 혁신하는 새로운 비즈니스 모델로 자리매김하고 있다. 2000년대 초 선보인 건축용 3D 프린팅(3D printed building) 기술 또한 미국과 유럽을 중심으로 기계/전자 기술과 연계하여 빠르게 발전하고 있다. 그러나 건축용 3D 프린터 시스템의 경우 기존 전통적인 건설공법에 사용되는 시멘트/콘크리트 원료 제품과는 다른 기계적 특성을 요구한다. 이에 따라 시멘트 산업과 자원리사이클링 산업에서 생산되는 소재원료의 활용도를 높이기 위해서는 건축용 3D 프린팅 기술의 특성을 반영하기 위한 소재가공 및 활용기술 개발, 새로운 물성평가 및 테스트 방법의 확보, 환경적 안정성과 관련된 장기간의 데이터베이스 확보가 필요하다.

• Current Optics and Photonics
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• 제4권1호
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• pp.9-15
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• 2020

Fresnel zone plates have been widely used in many applications, such as x-ray telescopes, microfluorescence, and microimaging. To obtain an x-ray Fresnel zone plate, many fabrication methods, such as electron-beam etching, ion-beam etching and chemical etching, have been developed. Fresnel zone plates fabricated by these methods will inevitably lead to some nonideal factors, which have an impact on the focusing characteristics of the zone plate. In this paper, the influences of these nonideal factors on the focusing characteristics of the zone plate are studied systematically, by numerical simulations based on scalar diffraction theory. The influence of the thickness of a Fresnel zone plate on the absolute focusing efficiency is calculated for a given incident x-ray's wavelength. The diffraction efficiency and size of the focal spot are calculated for different incline angles of the groove. The simulations of zone plates without struts, with regular struts, and with random struts are carried out, to study the effects of struts on the focusing characteristics of a zone plate. When a Fresnel zone plate is used to focus an ultrashort x-ray pulse, the effect of zone-plate structure on the final pulse duration is also discussed.