• 설비공학논문집
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• 제18권10호
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• pp.819-825
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• 2006

In a SOFC/GT (solid oxide fuel cell/gas turbine) hybrid power generation system, the recuperator is an indispensible component to enhance system performance. Since the expansion ratio to the recuperator core is very large, generally, the effective header design to distribute the flow uniformly before entering the core is crucial to guarantee the required performance. In the present study, we focus on the design of a diffuser type recuperator header with a 90 degree turn inlet port. To reduce the flow separation and recirculation flows, multiple horizontal vanes are used. The number of horizontal vanes is varied from 0 to 24. The air flow velocity is measured at 40 points just behind the core outlet by using a hot wire anemometer. Then, the flow non-uniformity is evaluated from the measured flow velocity. The experimental results showed that inlet air velocity did not effect on relative flow non-uniformity. According to increasing the number of horizontal vanes, flow non-uniformity reduced about $40{\sim}50%$ than without using horizontal vanes.

• 한국항행학회논문지
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• 제25권3호
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• pp.185-193
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• 2021

항공기의 성능 개선이나 관련 법규의 요건 만족을 위해 항공기 시스템 개조는 필요하다. 이러한 개조를 위해 기술력이나 항공기의 감항성을 위한 설계 검증, 형식 증명에 대한 부가형식증명(STC)의 인증 절차는 적절한 표준이 요구된다. 본 연구는 국내 항공기 개조 현황과 수요를 분석하고 현재의 부가형식증명 절차를 검토하여 그 문제점을 진단한다. 또한 늘어난 항공기의 수명에 대하여 개조기술 및 인증 능력 향상방안을 연구한 결과 개조 조직의 인가와 분야별 전문 엔지니어 자격 임명 그리고 교육 체계 개선이 요구되었고 국내 부가형식증명 절차의 개선을 도출하였다.

• Journal of Mechanical Science and Technology
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• 제15권4호
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• pp.413-421
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• 2001

A simple procedure to add and remove material simultaneously along the boundary is developed to optimize the shape of a two dimensional elastic problems and to minimize the maximum von Mises stress. The results for the two dimensional infinite plate with a hole, are close to the theoretical results of an elliptical boundary and the stress concentration is reduced by half for the fillet problem. The proposed shape optimization method, when compared with existing derivative based shape optimization methods has many features such as simplicity, applicability, flexibility, computational efficiency and a much better control on stresses on the design boundary.

• 대한안전경영과학회지
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• 제11권4호
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• pp.153-159
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• 2009

This study was conducted in search of the acceptance level of air traffic services from domestic airlines pilot's perspective in comparison with male controllers and female controllers. Pilots responded to the questionnaire that female ATC controllers are of significance to male controllers in terms of pronunciation, accuracy of English grammar, attitude and kindness. Besides, The ICAO aviation English proficiency level four test revealed that female controllers were found superior to male controllers in terms of rating scales of holistic descriptors.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.11-15
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• 2002

This paper presents the thermal characteristic analysis of a high-speed HMC with spindle speed of 50,000rpm. The spindle is supported by two radial and axial magnetic bearings. and the built-in motor is located between the axial and rear radial magnetic bearings. The X-axis and Y-axis feeding systems are composed of linear motor and linear motion guides, and the Z-axis feeding system is composed of servo-motor, ballscrew and linear motion guide. The thermal analysis model of high-speed HMC is constructed by the finite element method, and the thermal characteristics in the design stage are estimated based on the temperature distribution and thermal deformation under the conditions related to the heat generation of built-in motor, magnetic bearings, linear motors, servo-motor, ballscrew, and so on.

• 한국항공운항학회:학술대회논문집
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• 한국항공운항학회 2015년도 추계학술대회
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• pp.50-54
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• 2015

구형무인비행체는 다중 모터를 이용한 무인항공기에 비행 소형화, 경량화, 경제화 등의 장점을 가지고 있다. 본 논문에서는 구형무인비행체의 경로 추종을 위한 제어기 설계 및 성능에 대한 내용을 다루고 있다. 먼저 구형무인비행체의 운동방정식이 제어기 설계를 위해 유도되었고, 유도된 운동방정식을 이용해 경로 추종 제어기를 설계하였다. 구형무인비행체의 자세제어는 무게중심을 변화하는 방법을 사용하였다. 요구 경로를 설정하여 설계된 제어기의 경로 추종 성능을 MATLAB 시뮬레이션을 통해 확인하였다. 시뮬레이션 결과, 제시된 제어기가 설정된 경로를 추종하고 있음을 확인하였다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1995년도 춘계학술대회
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• pp.15-18
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• 1995

Three-dimensional steady and pulsatile flow experiments and numerical simulations have conducted to investigate the flow characteristics in the aortic bifurcation model. In vitro velocity measurements were made using both laser Doppler anemometry and pulsed Doppler ultrasound velocimetry. In this study, flow phenomena in the aortic bifurcation model are discussed extensively and the numerical results are compared with experimental results.

• 항공우주시스템공학회지
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• 제7권4호
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• pp.55-61
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• 2013

In recent years, NASA, FAA and the aerospace industry, through MIL-HDBK-17 and the NASA-conceived AGATE(Advanced General Aviation Transport Experiments) program, have worked together to reduce the qualification burden imposed on individual aircraft manufacturers. AGATE is one of the most successful public/private cost-haring partnerships ever conceived, bringing together academia, the FAA, other government agencies and industry to develop affordable new technologies and accompanying industry standards and certification methods. In 2005, NASA established NCAMP(National Center for Advanced Materials Performance) with the purpose of refining and enhancing the AGATE process to a self-sustaining level to serve the entire aerospace industry in partnership with CMH-17, FAA, and SAE. In this paper, I will introduce briefly NCAMP process and explain its organization structure and core NCAMP documents. This paper can provide some help in establishing our certification system for composite materials where the NCAMP process is expected to be the most good model.

• Journal of Ceramic Processing Research
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• 제19권6호
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• pp.455-460
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• 2018

Chromium plating is a common surface treatment technique extensively applied in industry due its excellent properties which include substantial hardness, abrasion resistance, corrosion resistance, surface color, and luster. In this study, the effect of PTFE on corrosion behavior of Cr-P plating, low carbon steel substrates are electroplated in Cr(III) baths without and with PTFE. Trivalent chromium carbon plating was electroplated from trivalent chromium sulfate-based baths with different PTFE dispersion contents. The study focused on the microstructure, PTFE content, roughness, and corrosion resistance of the Cr-P-PTFE composite plating. Scanning electron microscopy and atomic force microscopy images showed a smoother plating and a decrease in the surface roughness of the electrodeposited. The results demonstrate that PTFE eliminates the cracks within plating by reducing internal stress. Therefore, the corrosion resistance of Cr-P-PTFE composite platings were better than that of Cr-P alloy platings.

• Journal of Ceramic Processing Research
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• 제20권5호
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• pp.464-469
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• 2019

In this study, the electrical conductivity of multi-walled carbon nanotubes (MWCNTs) and polyethylene synthesized by an extrusion process was evaluated. The MWCNTs used exhibited differences in their dispersion characteristics depending on the type of catalyst or synthesis gas used. Thus, the choice of catalyst or synthesis gas significantly affect the physicochemical state of the final MWCNTs and MWCNT-based composites. In this investigation, the characteristics of MWCNTs were analyzed in four cases by introducing ethylene and propylene gas to each catalyst synthesized using deposition precipitation and spray drying methods. The MWCNT-based composites synthesized using the catalyst prepared by deposition precipitation and the ethylene synthesis gas showed the best electrical conductivity. In principle, the morphologies of the MWCNTs indicate that the smaller the aggregate size and bundle thickness, the better the electrical conductivity of the MWCNT composites. This implies that the network is well-formed.