• Journal of the Korean institute of surface engineering
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• v.29 no.1
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• pp.15-25
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• 1996

자동차엔진의 피스톤-링에 응용할 목적으로 플라즈마 용사 기술로 피막한 몰리부덴늄 및 코발트 합금 피막 층의 마모성질을 비교 조사하였다. Ball-on-disc 형태의 마모기를 사용하여 상온 및 대기 중에서의 마모 및 마찰거동에 대하여 조사하였다. 용사 층의 미세경도 시험도 행하였으며, 용사층의 결정구조를 알기 위해 용사층을 x-선 회절 방법으로 분석하였다. 주사전자현미경을 사용하여 마모면의 표면 형상을 관찰하였다. 여러 용사조건으로 만든 용사층의 미세경도치와 마모거동과의 상관관계를 이해하려고 시도하였다. 주사전자현미경과 EDX를 사용하여 마모시 화학반응층과 마모기구를 규명하고자 하였다. 모리부덴늄 및 코발트 합금 분말을 각각 플라즈마 용사층의 단면을 관찰하여 마모기구을 비교하였다.

• Annual Conference on Human and Language Technology
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• 2023.10a
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• pp.563-567
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• 2023

본 연구는 한국 통계청이 수행하는 가계동향조사와 생활시간조사에서 자료처리 과정 및 방법을 혁신하려는 시도로, 기존의 통계 생산 방법론의 한계를 극복하고, 대규모 데이터의 효과적인 관리와 분석을 가능하게 하는 인공지능 기반의 통계 생산을 목표로 한다. 본 연구는 데이터 과학과 통계학의 교차점에서 진행되며, 인공지능 기술, 특히 자연어 처리와 딥러닝을 활용하여 비정형 텍스트 분류 방법의 성능을 검증하며, 인공지능 기반 통계분류 방법론의 확장성과 추가적인 조사 확대 적용의 가능성을 탐구한다. 이 연구의 결과는 통계 데이터의 품질 향상과 신뢰성 증가에 기여하며, 국민의 생활 패턴과 행동에 대한 더 깊고 정확한 이해를 제공한다.

• Journal of Drive and Control
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• v.13 no.1
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• pp.84-88
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• 2016

• Journal of the KSME
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• v.32 no.5
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• pp.429-440
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• 1992

공작기계와 측정기기류는 산업현장에서 점점 그 수요가 증대되고 있다. 초기 단순한 기능위주의 기계의 선택, 사용으로부터 고정도, 소형, 경량화, 다기능화의 세계적 추세에 비추어 볼 때, 측 정기기류와 공작기계에 있어서의 고정밀도 기술은 점점 그 수요가 증대되고 있다. 특히 현재 사용 또는 제작중인 기계의 정밀도를 측정하여 체계적으로 진단, 관리하는 정밀측정기술은 그 중의 핵심기술로서, 전통적으로 선진국의 산업현장에서 내려오는 현장기술이든 측정기술의 중 요성이 본격적으로 대두된 것은 선진국에서도 비교적 최근의 일이다. 최근 컴퓨터의 발달에 힘 입어, 종래의 측정기술들을 적용함에 있어서 측정자체의 온라인화, 측정해석의 정확성이 이루어 지게 되었다. 이 글에서는 현장 및 하계에서 정밀측정기술에 대해서 관심을 가진 분들을 위해서 공작기계 및 측정기기의 정밀도를 측정하는 방법 등을 소개하고, 또한 이와 관련하여 포항공대 정밀측정실에서 개발 또는 개발중인 측정방법 등과 측정의 컴퓨터화 등에 대해서 간략히 소개 하도록 한다.

• 연구논문집
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• s.27
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• pp.127-139
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• 1997

Two-for-one twister is a kind of textile machine and makes special fancy yarn which is twisted two times per one revolution in order to increase tensile strength and wear resis-tance of yarn. Spindle mechanism has to be stable and continuous motion in high speed revolution, and then optimal design is necessary to analyze dynamic characteristics of spindle unit. Spindle unit is consist of blade and rotary disc that are cylindrical body of revolution. For analysis of the dynamic characteristics of spindle unit, transfer matrix method is used and a numerical code SPINDLE also. Torsion and natural bending frequency of the spindle unit are examined. Its displacement mode is studied in function of variable revolutions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.8
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• pp.743-752
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• 2013

This is the second paper on the combustion characteristics of landfill gas in a constant volume combustion chamber for a large displacement volume commercial engine, and it discusses the combustion process on the basis of pressure measurements. The results show that the bimodal peak pressure phenomenon, which is caused by the interaction of the heat release and the heat transfer, is more apparent as the mixtures are more favorable to combustion, and the magnitudes of the pressures depend on the unburned fraction. In addition, there exist four main inflection points during heat release owing to variations in the heat transfer area related to flame propagation from the ignition point. Furthermore, the number of inflection points increases as the mixture quality worsens because of the extended burn duration. Consequently, the sophisticated interactions between the heat transfer area changing pattern due to flame propagation and transfer duration might cause very peculiar heat release patterns.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.2
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• pp.125-134
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• 2015

This is the third paper on the combustion characteristics of the landfill gas in a constant volume combustion chamber for a large displacement volume commercial engine. It is the first in this series to discuss the effects of the torch device on combustion. The results show that an optimum orifice ratio exists regardless of the torch volume, and a few adverse effects on the combustion are observed for an excessively small orifice ratio. In addition, the torch ignition decreases the initial burn duration, and the decrease in the heat transfer caused by this decreased duration contributes to an increase in the peak combustion pressure. Finally, the torch mostly plays a positive role in shortening the main burn duration when the combustion condition is worsened by a lower methane fraction. Yet, the torch decreases the initial burn duration rather than the main burn as the methane fraction increases.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.7
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• pp.727-734
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• 2014

This paper describes multi-scale based ductile fracture simulation using finite element (FE) damage analysis. The maximum and crack initiation loads of cracked components were predicted using proposed virtual testing method. To apply the local approach criteria for ductile fracture, stress-modified fracture strain model was adopted as the damage criteria with modified calibration technique that only requires tensile and fracture toughness test data. Element-size-dependent critical damage model is also introduced to apply the proposed ductile fracture simulation to large-scale components. The results of the simulation were compared with those of the tests on SA333 Gr. 6 full-scale pipes at $288^{\circ}C$, performed by the Battelle Memorial Institute.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.3
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• pp.237-243
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• 2010

In this study, the effect of the shape of a pintle(obstacle) on thrust-modulation performance and drag in a pintle rocket was investigated by a cold flow test and by computational fluid dynamics. Pintle movement caused a monotonic increase in the chamber pressure. Thrust generated by the pressure distribution on the pintle body was linearly changed to the chamber pressure, and this thrust was greater than that generated by the nozzle-wall pressure distribution. Because the shock pattern in the nozzle changes with the shape of the pintle body and pressure ratio, the thrust generated by the nozzle-wall pressure is not directly affected by chamber pressure. The drag due to the pintle(obstacle) can be minimized for a fully linear pintle shape, regardless of chamber pressure.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.1
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• pp.45-53
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• 2000

To analyze the photodegradation mechanism of materials for fisheries facilities which stand for considerable time immediately under or even partly above the water surface, such as cage collar, cage net, stationary fishing gear, egc. after 900 hours exposure, weathering experiments on 3 kinds of netting twines like dyed polyethylene(PE) and nylon, and non-treated high strength PE(Hi-PE) were carried out by using xenon light source. The results obtained are as follows : It was observed by scanning electron micrograph(SEM) that a good protection by pigments was obtained in PE and nylon specimen, while crack was rapidly progressed at the surface of Hi-PE one owing to etching by UVR. There was a little increase in density resulting from reorientation of polymer chain, chain scission, etc. in Hi-PE specimen. A wide angle X-ray diffraction showed that 3 kinds of specimens had no fundamental changes in polymer crystalline structure considering each 2$\theta$ of diffraction peak. Remaining tenacity of netting twines was in order of PE, nylon, and Hi-PE after having been exposed to the effect of 900 hours. PE and nylon treated with stuffs were shown to be more resilient than non-treated Hi-PE as confirmed by SEM.