• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.242-243
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• 2006

NiTiZrSiSn bulk metallic glass powder was produced using inert gas atomization and then was sprayed onto a SS 41 mild steel substrate using the kinetic spraying process. Through this study, the effects of thermal energy of in-flight particle and crystallization degree by powder preheating temperature were evaluated. The deformation behavior of bulk metallic glass is very interesting and it is largely dependent on the temperature. The crystalline phase formation at impact interface was dependent on the in-flight particle temperature. In addition, variations in the impact behavior need to be considered at high strain rate and in-flight particle temperature.

• 한국응용곤충학회지
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• 제42권4호
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• pp.367-381
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• 2003

곤충의 분산다형성이란 비상능력과 관련된 다형성으로 그 구체적 내용으로는 시다형성, 비상근다형성 그리고 비상행동변이성 등과 이들과는 별개로 개체군 밀도의존적인 상변이성이 있다. 분산다형성은 시간적으로나 공간적으로 이질적인 서식처 환경에 대응하기 위하여 이동형인 “유시형이나 장시형”과 정주형인 “무시형이나 단시형”을 생활사에 적절히 짜넣은 적응적 형질이다. 점변태곤충류에서는 유충과 성충의 생태학적지위가 중복되여 있어 유충과 성충이 생활공간과 그 밖의 요구조건을 달리하고 있는 완전변태류나 반변태류에 비하여 분산다형성의 예가 대단히 많다. 무시형 또는 단시형곤충은 같은 종의 유시형 또는 장시형곤충에 비하면 초산연령이 빠르고 총산란수도 많은 것이 보통이여서 자연증가율(r)이 크다. 단시형과 관련된 환경요인으로는 서식처의 시간적 영속성이나 공간적 이질성, 먹이조건, 개체군밀도, 온도, 일장 기타 여러 가지가 알려지고 있다 서식처의 환경조건에 대한 분산다형성발현상은 종에 따라 다를 뿐 아니라 암수간에도 차가 있고 같은 종에서도 계통간에 차가 있는 극히 탄력적인 현상이다. 분산다형성의 문제는 생리학, 유전학 그리고 생태학등에 걸친 폭넓은 학문분야로 특히 생태유전학이나 정량유전학분야치 연구는 분산다형성의 유전적본질 구명에 중요하다 하겠다.

• Journal of Mechanical Science and Technology
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• 제14권3호
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• pp.320-330
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• 2000

It is desirable to perform nondestructive evaluation (NDE) to assess material properties and part homogeneity because the manufacturing of carbon/carbon brake disks requires complicated and costly processes. In this work several ultrasonic techniques were applied to carbon/carbon brake disks (322mm ad, 135mm id) for the evaluation of spatial variations in material properties that are attributable to the manufacturing process. In a large carbon/carbon disk manufactured by chemical vapor infiltration (CYI) method, the spatial variation of ultrasonic velocity was measured and found to be consistent with the densification behavior in CYI process. Low frequency (e.g., 1-5MHz) through-transmission scans based on both amplitude and time-of-flight of the ultrasonic pulse were used for mapping out the material property inhomogeneity. Images based on both the amplitude and the time-of-flight of the transmitted ultrasonic pulse showed significant variation in the radial direction. The radial variations in ultrasonic velocity and attenuation were attributed to a density variation caused by the more efficient densification of pitch impregnation near the id and od and by the less efficient densification away from the exposed edged of the disk. Ultrasonic velocities in the edges of the disk. Ultrasonic velocities in the thickness direction were also measured as a function of location using dry-coupling transducers ; the results were consistent with the densification behavior. However, velocities in the in-plane directions (circumferential and radial) seemed to be affected more by the relative contents of fabric and chopped fiber, and less by the void content.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 C
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• pp.1385-1387
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• 1995

The Monte Carlo method for studying the steady-state behavior of electrons under the influence of a electric field is described. In this simulation used a Free Flight Time technique based on determination of the increase in kinetic energy between two collisions. The electron behavior in the cathode region of a corona discharge has been analysed using this method; spatial variations of the energy and excitation, ionization, and the multiplication of electrons were discussed.

• Journal of Mechanical Science and Technology
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• 제16권12호
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• pp.1652-1663
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• 2002

It is desirable to perform nondestructive evaluation to assess material properties and part homogeneity because manufacturing of carbon/carbon (C/C) composites requires complicated and costly processes. In this work several ultrasonic techniques were applied to carbon/carbon composites for the evaluation of spatial variations in material properties that are attributable to the manufacturing process. In a large carbon/carbon composite manufactured by chemical vapor infiltration (CVI) method, the spatial variation of ultrasonic velocity was measured and found to be consistent with the densification behavior in CVI process in order to increase the density of C/C composites. Ultrasonic velocity and attenuation depend on a density variation of materials. Low frequency through-transmission scans based on both amplitude and time-of-flight of the ultrasonic pulse were used for mapping out the material property inhomogeneity These results were compared with that obtained by dry-coupling ultrasonics. Pulse-echo C-scans was used to image near-surface material property anomalies such as the placement of spacers between disks during CVI. Also, optical micrograph had been examined on the surface of C/C composites using a destructive way.