• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05a
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• pp.61-65
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• 2001

The conventional tracking testing as IEC-60587 is widely used in surface aging measurement of outdoor insulator because those testing can carry out very short time in Lab-testing. Also IEC-60587 testing is able to offer the standard judgement of relative degradation level of outdoor HV machine/system. Therefore it is very useful method compare to previous conventional tracking testing method and effective Lab-testing method. But surface discharges(SD) have very complex characteristics of discharge pattern so it is required estimation research to development of precise analysis method. In recent, the study of IRR-camera is carrying out discover of temperature of power equipment through condition diagnosis and system development of degradation diagnosis. In this study, SD occurred from procelain insulator, used 22.9[KV] distribution, is measured with partial temperature distribution in real time, the degradation grade of SD is analyzed through produced patterns in SD concentration according to applied time.

• Journal of the Korean institute of surface engineering
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• v.29 no.4
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• pp.268-277
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• 1996

Boronizing treatment of Microalloyed steel has been investigated by mean of Boronizing paste mainly consisted of $B_4C$ at various temperatures and times. The micro hardness of the boride layers were about HV 1200~1500. The thickness of the boride layer were increased with an increase of square root of treatment time at constant temperature. The activation energy for diffusion of boron in the specimen obtained from the slope of Arrhenius plots was 254 kJ/mol, but 197 kJ/mol for the induction heated specimen. The boride layer had a good corrosion resistance in solutions of 20% HCl and 20% $H_2SO_4$, solution. In 20% $HNO_3$ solution, however, its corrosion resistance increased. The boride layer had a good high temperature oxidation resistance at below $800^{\circ}C$, but at temperature above $900^{\circ}C$, the oxidation resistance decreased as the oxidation temperature.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.5
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• pp.36-41
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• 1999

Although the problems of defects and nonmetallic inclusion in metal fatigue are very complicated it is particularly important to view these problems from the perspective that defects and inclusions are virtually equivalent to small cracks. This concept will help us to understand various fatigue phenomena caused by graphite of Ductile cast iron. Therefore in this study different ferrite-pearlite matrix structure and pheroidal ratio of graphite of 70%, 80% and 90% GCD40 , GCD45-2 series have been carried out rotary bending fatigue test estimated the maxi-mum size of graphite investigated correlation. It was concluded as follows : (1) in ductile cast iron which have various spheroidal ratio of graphite the fatigue limit C series of 90% spheroidal ratio of graphite is the highest. While A series of 70% spheroidal ratio of graphite is the lowest (2) fatigue limit was predicted by vickers hardness(Hv) of matrix {{{{ SQRT {area } }}}} of maximum size graphite inputting Murakami and Endo's formula.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2016.06a
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• pp.275-277
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• 2016

본 논문은 human visual system(HVS)에 따른 주파수 민감도와 공간에서 다양한 특성들을 구현하기 위한 신호처리 방법을 개발하였다. 인간의 눈은 주파수 성분에 따라 민감도가 다르며 초점에서 멀수록 인지 가능한 해상도가 떨어진다. 주파수 민감도를 구현하기 위해서 본 논문은 영상 신호의 에너지 스펙트럼 모양이 contrast sensitivity function(CSF)의 모양이 되도록 하여 영상 신호의 에너지를 증가시켰으며 신호 방향에 적응적인 multiband energy scaling 방법을 개발하였다. 기존의 시스템에서 능률만을 향상시키는 기존의 분석 모델과 비교하면 개발한 방법은 HVS에 좀 더 적절하고 선호되게 영상 신호를 처리할 수 있다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.201.1-201.1
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• 2016

전주된 Invar (Fe-35%Ni) 박판 위에 증착된 Cu 박막은 스퍼터 전력량이 증가할수록 증착속도가 증가하였다. Cu/Invar 박판이 Invar 박판보다 면저항 값이 34%로 작았다. Invar 박판 위에 Cu가 증착되면 최대자화와 투자율은 각각 40.3, 65.0 [%] 감소하였다. Cu 박막의 탄성하강강성도, 마찰계수, 피로한계는 각각 45, 0.130, 0.093 이었다. 동적 나노 압침법으로 얻은 Invaar/Cu 박막의 하중-시간-변위 곡선의 가장 큰 차이는 탄성하강강성도(elastic stiffness) 이었다. 미세경도와 나노경도의 실험적 관계식은 $Y[GPa]=9.18{\times}10^{-3}X[Hv]$ 이었다. 나노압침선단의 하중분포를 이차원 선형 및 비선형 유한요소해석을 통하여 1.0 [mN] 의 정적하중을 가한 Cu 박막은 486 [mN] 으로 예측되었다. 이는 표면탐침현미경으로 관찰한 압흔의 변형정도와 유사한 경향을 보였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.456-459
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• 2005

The setting of a presintering temperature is carried out on the basis of the Vickers hardness of the presintered compact in the method for producing a ceramic sintered compact comprising presintering a formed compact composed of a ceramic powder and a sintering assistant, then machining the presintering compact and subsequently sintering the machined compact. The Presintering temperature is preferably set at a temperature so as to provide 213-230 Hv Vickers hardness of the compact for presintering. Furthermore, the presintering temperature is preferably within the range of 1,300-1,450$^{\circ}C$.

• Transactions of Materials Processing
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• v.24 no.4
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• pp.272-279
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• 2015

The characteristics of the laser metal deposition parameters were studied to enhance the deposition efficiency using a diode pumped disk laser. STD61 hot tool steel plate and Fe based AISI M2 alloy were used as a substrate and powder for the laser metal deposition, respectively. Among the laser metal deposition parameters the laser power, track pitch and powder feed rate were used to estimate the deposition efficiency. From the experimental results, the deposition efficiency was shown to be excellent when 1.8kW laser power 500um track pitch and 10g/min of the powder feed rate were used. For this optimal condition the average hardness of the deposition track was approximately 830HV, and this value is 30~50% better than the hardness of the commercially produced tool steel after heat treatment.

• Korean Journal of Materials Research
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• v.5 no.4
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• pp.405-411
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• 1995

급냉응고된 Al-3.51wt%Li-0.34wt%Zr 합금의 시효거동을 시차주사열량계(DSC)에 의한 열분석 방법으로 조사하였다. DSC에 의한 비열측정 결과 $\delta$’의 석출에 의한 발열반응과 $\delta$, $\beta$ 및 복합석출상의 석출에 의한 발열반응을 확인하였으며 $\delta$’ 및 $\delta$의 재고용에 의한 2개의 흡열반응을 확인하였다. 7$0^{\circ}C$ 저온시효시 $\delta$’의 석출에 의한 발열반응 이전에 흡열반응이 나타났으며 이것은 $\delta$’ 석출 이전에 $\delta$’ 전구생성물이 형성되었음을 의미한다. DSC 곡선상에 나타난 발열과 흡열곡선을 해석하여 얻은 $\delta$’상 석출과 재고용의 활성화에너지값은 각각 83KJ/mol과 98KJ/mol로서 Al-Li 2원계 및 Al-Li-Mg에 비해 높은 값을 나타내엇으며, 시효에 의한 강화가 일어나 DSC에 의한 비열변화 조사결과 나타난 $\delta$’상 석출 완료 시효조건점 (21$0^{\circ}C$, 1시간)에서 최고경도값(Hv 160)을 나타내었다.

• Korean Journal of Materials Research
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• v.11 no.11
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• pp.1001-1005
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• 2001

In this study, the surface of 40Cr steel was hardened by $CO_2$Laser, and then the microstructural transformations and the hardness distributions of the laser surface hardened layer were observed. The experimental results showed the surface hardening layer was consisted of three parts, which is outmost surface layer of needle martensite, middle layer of martensite and remained pearlite, and transitory boundary layer. In hardness distributions, the surface hardeness of the surface hardening layer had Hv 800~1000, that was 2 to 4 times of matrix's hardness. The hardeness distribution of laser hardening layer that of surface layer hardened by general heat treatment.

• Proceedings of the KSRS Conference
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• 1999.11a
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• pp.154-157
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• 1999

Microwave polarimetric backscattering from a wet soil surface had been measured using a Ku-band polarimetric scatterometer at the incidence angles ranging from 10$^{\circ}$ to 70$^{\circ}$ Since the accurate target parameters as well as the radar parameters are necessary for radar scattering modeling, a complete and accurate set of ground truth data were also collected, from which accurate measurements were made of the rms height, correlation length, and dielectric constant. The measured polarimetric backscattering coefficients (vv-, hh-, vh-, hv-polarizations) were compared with theoretical models and empirical models. A new semi-empirical model for microwave polarimetric radar backscattering from bare soil surfaces was developed using polarimetric radar measurements and the knowledge based on the theoretical and numerical solutions. The model was found to yield very good agreement with the backscattering measurements of this study.