• 한국자동차공학회논문집
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• 제15권4호
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• pp.154-160
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• 2007

The experimental system, developed in this research, is a teaching material that trains and practices automobile electric circuit in technical high school. This system consists of a textbook, 15 kinds of instruments and 62 kinds of 'Flash' animations. Textbook includes automobile electric circuits and experimental process. Instruments have 23 kinds of drills. Its is composed of electrical relays, motors, switches, light bulbs, electrical lines and power unit so on. 'Flash' animation displays an electrical current flow on circuits actually. Both Dacum method and ISD skill have been conducted to analysis job and design syllabus. The experimental system have been implemented on technical high school class to evaluate its objectivity and effect. It is expected that this system can contribute to studying of car service.

• 한국재료학회지
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• 제31권12호
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• pp.665-671
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• 2021

A 1.8 ㎛ thick polycrystalline diamond (PCD) thin film layer is prepared on a Si(100) substrate using hot-filament chemical vapor deposition. Thereafter, its thermal conductivity is measured using the conventional laser flash analysis (LFA) method, a LaserPIT-M2 instrument, and the newly proposed light source thermal analysis (LSTA) method. The LSTA method measures the thermal conductivity of the prepared PCD thin film layer using an ultraviolet (UV) lamp with a wavelength of 395 nm as the heat source and a thermocouple installed at a specific distance. In addition, the microstructure and quality of the prepared PCD thin films are evaluated using an optical microscope, a field emission scanning electron microscope, and a micro-Raman spectroscope. The LFA, LaserPIT-M2, and LSTA determine the thermal conductivities of the PCD thin films, which are 1.7, 1430, and 213.43 W/(m·K), respectively, indicating that the LFA method and LaserPIT-M2 are prone to errors. Considering the grain size of PCD, we conclude that the LSTA method is the most reliable one for determining the thermal conductivity of the fabricated PCD thin film layers. Therefore, the proposed LSTA method presents significant potential for the accurate and reliable measurement of the thermal conductivity of PCD thin films.

• 한국정보과학회논문지:시스템및이론
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• 제36권5호
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• pp.422-428
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• 2009

플래시 메모리는 부피가 작고, 가볍고, 소비전력이 낮으며 입출력이 빨라 최근 소형기기의 저장 장치로 널리 사용이 되고 있다. 그러나 플래시 메모리는 지움 연산을 수반하는 가비지 컬렉션을 수행해야 한다. 지움 연산은 속도가 느리고, 각 블록마다 지움 연산 횟수가 제한이 있다. 따라서 본 논문에서는 지움 연산 횟수와 각 블록의 지움 횟수 편차를 줄이는데 초점을 맞춘 균등화 정책을 제안한다. 따라서 플래시 메모리의 페이지 사용률에 기반을 둔 두 가지 가비지 컬렉션 수행 모드를 정의하고 그리고 각 모드에 대해 다른 지움 비용을 계산하여 전체 지움 연산 횟수와 각 블록의 지움 횟수 편차를 최소화하는 가비지 컬렉션 기법을 제안한다. 추가로 가비지 컬렉션 연산 시간을 최소화하기 위해 그룹 관리 기법을 제안해 보다 빠른 수행 시간을 가질 수 있도록 한다. 실험 결과 제안하는 정책은 기존의 Greedy 와 CAT 기법의 장점들을 동시에 나타내었고, 지움 횟수 편차를 평균 85% 감소 시켰고 가비지 컬렉션 수행 시간을 최대 6% 단축 시켰다

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제15권9호
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• pp.617-625
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• 2009

NAND 플래시 메모리는 부피가 작고, 가볍고, 소비전력이 낮으며 입출력이 빠르고 집적도가 높아 최근 임베디드 기기들에 널리 사용되고 있다. 그러나 NAND 플래시 메모리는 지움 연산을 수반하는 가비지 컬렉션 연산을 수행해야 한다. 게다가 지움 연산은 속도가 느리고, 각 블록마다 지움 연산 횟수가 제한이 있다. 따라서 제안하는 가비지 컬렉션 기법은 전체 지움 연산 횟수와 각 블록의 지움 횟수 편차를 감소시키고, 가비지 컬렉션 수행 시간을 최소화하는데 초점을 맞춘다. NAND 플래시 메모리는 유효 페이지, 무효 페이지, 빈 페이지로 구성되어 있다. 제안하는 기법은 페이지들의 비율을 이용해 가비지 컬렉션의 수행 시기를 결정하고 대상 블록을 선택한다. 그리고 할당 기법과 그룹 관리기법을 추가적으로 구현하였다. 실험 결과 제안한 정책은 기존의 Greedy나 CAT 기법에 비해 전체 지움 횟수를 최소화 하면서, 최대 82% 지움 횟수 편차를 감소시켰고, 최대 75%의 가비지 컬렉션 수행 시간을 단축시켰다.

• 한국재료학회지
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• 제29권7호
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• pp.443-450
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• 2019

Thermal management is a critical issue for the development of high-performance electronic devices. In this paper, thermal conductivity values of mild steel and stainless steel(STS) are measured by light flash analysis(LFA) and dynamic thermal interface material(DynTIM) Tester. The shapes of samples for thermal property measurement are disc type with a diameter of 12.6 mm. For samples with different thickness, the thermal diffusivity and thermal conductivity are measured by LFA. For identical samples, the thermal resistance($R_{th}$) and thermal conductivity are measured using a DynTIM Tester. The thermal conductivity of samples with different thicknesses, measured by LFA, show similar values in a range of 5 %. However, the thermal conductivity of samples measured by DynTIM Tester show widely scattered values according to the application of thermal grease. When we use the thermal grease to remove air gaps, the thermal conductivity of samples measured by DynTIM Tester is larger than that measured by LFA. But, when we did not use thermal grease, the thermal conductivity of samples measured by DynTIM Tester is smaller than that measured by LFA. For the DynTIM Tester results, we also find that the slope of the graph of thermal resistance vs. thickness is affected by the usage of thermal grease. From this, we are able to conclude that the wide scattering of thermal conductivity for samples measured with the DynTIM Tester is caused by the change of slope in the graph of thermal resistance-thickness.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.952-957
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• 2001

The objectives of this investigation were to obtain an excellent spray by cavitation under the low injection pressure. When cavitation occurs in the nozzle hole, the atomization of the liquid jet enhanced considerably. In this experiments, a acrylic nozzle made the gap and installed the bypass in the nozzle hole was used to enhance the atomization of the liquid jet at the low injection pressure. The liquid flow in the nozzle hole was photographed by a transmitted light using a micro flash. The spray angle was measured macroscope images of PMAS and the Sauter mean diameter was measured PDA system. To measure the pressure of the nozzle hole, pressure transducer was used. The results of this study indicated that enhanced atomization of the liquid jet at the low injection pressure was obtained by making the gap and installing the bypass at the single hole nozzle.

• 한국분무공학회지
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• 제7권1호
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• pp.36-42
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• 2002

The objective of this investigation was to obtain an excellent spray at the low injection pressure. When cavitation occurred in the nozzle hole the atomization of the liquid jet enhanced considerably. In this experiments, a acrylic nozzle which was installed the gap and installed the bypass in the nozzle hole was used to enhance the atomization of the liquid jet at the few injection pressure. The liquid flow in the nozzle hole was photographed by a transmitted light using a micro flash. The spray angle was measured by macroscope images of PMAS and the Sauter mean diameter was measured by PDA system. The pressure of the notate hole was measured by pressure transducer. It was found that enhanced atomization of the liquid jet at the low injection pressure was obtained by installing the gap and the bypass at the single hole nozzle.

• 전기의세계
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• 제25권1호
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• pp.87-94
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• 1976

The characteristic of flashover electric discharge has been brought to light in this paper for the situation in which the space and creeping gaps are laid out in series. The result of this study has disclosed the facts that the over all flashover characteristics have three kind of features such as unilateral increase after increase, and increase after decrease in compliance with varied layout method and relative magnitude of gap length, and accordingly there exist a ratio among the magnitudes of gap length and a proper layort method through which the over all flashover voltage reaches the highest. Also involved with this study is the theoretic analysis of flashover characteristics even in the case of creeping electric discharge from hand tip of the gauge, where the over all value of flashover voltage can be estimated from the peculiar value of flashover voltage and flicker voltage for the space and creeping gap within the extent of 5% error.

• 대한기계학회논문집B
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• 제30권5호
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• pp.413-421
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• 2006

The bubble dynamics induced by direct laser heating is experimentally analyzed as a first step to assess the technical feasibility of laser-based ink-jet technology. To understand the interaction between laser light and ink, the absorption spectrum is measured for various ink colors and concentrations. The hydrodynamics of laser-generated bubbles is examined by the laser-flash photography. When an Ar ion laser pulse (wavelength 488 nm) with an output power up to 600 mW is incident on the ink solution through a transparent window, a hemispherical bubble with a diameter up to ${\sim}100{\mu}m$ can be formed with a lifetime in a few tens of microsecond depending on the laser power and the focal-spot size. Parametric study has been performed to reveal the effect of laser pulse width, output power, ink concentration, and color on the bubble dynamics. The results show that the bubble generated by a laser pulse is largely similar to that produced by a thin-film heater. Consequently, the present work demonstrates the feasibility of developing a laser-actuated droplet generation mechanism for applications in ink-jet print heads. Furthermore, the results of this work indicate that the droplet generation frequency is likely to be further increased by optimizing the process parameters.

• 한국콘텐츠학회논문지
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• 제6권8호
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• pp.57-67
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• 2006

애니메이션은 제작에 있어 수용자의 지각에 반응하는 의도된 프레임 수(명멸현상)를 이용함으로써 움직임의 효과를 극대화 할 수 있다. 그러나 특정의 효과(경찰차의 경광등이나, 신호등의 점멸을 확대한 장면에서 빠른 점멸을 의도적으로 계획한 프레임 수)나 지나친 시각적 자극을 주기 위하여 배색에 있어서 채도의 대비를 높이는 경우는 매우 위험한 상황을 초래할 수도 있다. 일본의 '포켓몬스터' 방영에서 일어난 피해로 문제의 심각성이 대두된 명멸현상의 위험성은 의학용어로 '빛과민성 발작증세'로 정의되고 있다. 애니메이션의 제작에 있어서 컬러의 품질관리도 중요하지만 색채가 미치는 심리적인 요인을 분석한 컬러설정이라든가, 영상효과에 있어서 섬광과 패턴의 연속적인 점멸이 미치는 위험성을 제작단계에서 체크할 필요가 있음을 시사하고 있다. 연구자는 일본에서 사용 중인 영상 애니메이션 등의 제작기법에 관한 가이드라인을 포함, 국외의 관련규정들을 종합 검토하고 피험자를 대상으로 한 실험과 비교하여 명멸현상의 위험성에 대한 해결방안을 마련하였다.