• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.796-799
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• 2002

The stress of the rotating disc with several types of hole was investigated in detail in this paper. Maximum circumferential stress of rotating disc by changing hole shape with same area, were studied using FEM. The results obtained were as follows: 1. The disc which rotates at high speed is subjected to circumferential stress remarkably. 2. When the number of circular holes in rotating disc is four, stress reduction effect is maximum. 3. When shape of holes in rotating disc is cylindrical elongated hole, maximum circumferential stress of the rotating disc decreased most.

• 한국항공우주학회지
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• 제48권4호
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• pp.243-254
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• 2020

한국 전통 지연은 장방형으로 그 가운데 방구멍을 가진 특이한 형태를 갖고 있다. FLUENT 코드를 사용하여, 가로세로비 1:1.5인 한국 전통 지연에 작용하는 공기역학적 힘들을 수치적으로 계산하였다. 다양한 직경의 방구멍에 대하여 연의 비행을 시뮬레이션하여, 방구멍의 역할과 방구멍 크기에 따른 영향을 조사하였다. 방구멍은 연싸움에서 연실의 빠른 되감기로 인한 장력의 급격한 상승을 완화시켜 주는 역할을 함으로써, 연실을 더 빨리 되감을 수 있게 한다. 방구멍의 적절한 직경은 가로 폭의 1/3이다.

• 대한기계학회논문집B
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• 제20권4호
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• pp.1406-1415
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• 1996

Several recent studies have revealed that boiling heat transfer may be considerably enhanced in a narrow restricted region. In his study, the narrow restricted region was formed by attaching a perforated plate on top of a boiling surface. Through systematic experiments, effects of the hole size, hole pattern, gap width between the perforated plate and the boiling surface were investigated using water or R-113. Results show that perforated plates considerably enhance the boiling of water or R-113. For water, especially, they have outperformed commercial enhanced tubes, which confirms that boiling enhancement mechanism of the perforated plate (thin film evaporation beneath the elongated bubble) is very effective to the boiling of high surface tension liquids such as water. Optimum configuration was found - 3.0 mm hole diameter, 15 mm * 15 mm hole pattern, 0.3 ~ 0.5 mm gap width for water, and 2.0 mm hole diameter, 3.5 mm * 3.5 mm hole pattern, O.5 mm gap width for R-113. A correlation which correlates most of the data within .+-. 30% was also developed.

• 대한치과의사협회지
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• 제22권11호통권186호
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• pp.961-971
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• 1984

The purpose of this study was designed to evaluate the existence of the junctional epithelia on the tooth surface in periodontal pocket, and what were the morphologic differences between the junctional epithelia on the healthy and advanced periodontitis tooth. Fifteen premolar teeth from patients of Yon Sei University, Dental Infirmary were selected for this study. After extration, the teeth were prepared and examined in Scanning electro microscope. The results were as follows. 1. The junctional epithelia from healthy tooth surface were irreguraly round, oval, polygonal and slightly elongated while those from periodontal pocket were so elongated that difficult to distinguished the individual cell boundary. 2. There were a lot of round space so called 'HOLE or WHORL' which seemed tunnel in periodontal pocket with advanced periodontitis. 3. Microvilli were going to destructed and disappeared on surfaces of junctional epithelia in periodontal pocket with advanced periodontitis. 4. There were a lot of Filopodia on Junctional epithelia from healthy surfaces. %. Junctional epithelia from periodontal pocket with advanced periodontitis contained more inflammatory cells than healthy junctional epithelia did.

• 한국생산제조학회지
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• 제7권2호
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• pp.9-14
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• 1998

One of the areas in the continuous casting process that up to this point, has not been definitively instrumented is a method of reliably locating the part of a continuously cast strand that remains liquid for a period after the outer portion has solidified. To solve the problem. Electromagnetic Trandsducers(EMAT) which operate across an air gap without the need for a coupling medium has been developed. The system was designed to employ a through transmission technique which enhanced the signal-to-noise ratio. The Al 75$\times$75mm and 75$\times$100mm simulators with 2, 4, 8, 16, 32 mm hole respectively has been produced in order to verify the developed EMAT system and to measure to liquid core in continuous casting strand. The system developed can be employed for the optimization of torch cutting speed and for the final cut length of the bloom as well as calculation of average bloom temperature.

• 한국추진공학회지
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• 제20권3호
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• pp.54-62
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• 2016

이단 마이크로 할로우 음극 방전(MHCD) 플라즈마를 사용하는 마이크로 플라즈마 추력기(${\mu}PT$)에 대한 실험 연구가 수행되었다. 40 sccm의 아르곤 유량과 10 W 미만의 전력으로 보다 더 직진성 있고 긴 침투 길이를 가진 배기 플룸을 만드는 정전기적 가속이 이단 MHCD에 의해 발생되었다. 전압-전류 특성에서는 이단 운전 시 두 번째 단의 가속 전압이 일정하게 되는 최적 영역이 있음을 보였다. 추정된 배기 플룸의 길이가 가속 전압으로 추산된 이론적 배출 속도와 비슷한 증가 경향을 보였다. 다중 채널을 가진 마이크로 플라즈마 추력기는 동일한 총 전력량에 대하여 단일 채널 추력기와 비슷한 특성을 보여, 이는 채널 당 허용 전력량을 낮춰 전체 전력량을 높일 수 있음을 의미한다. 아르곤 원자 분광선의 볼츠만 그래프에서 배기 플룸의 평균 전자 여기 온도는 약 2.6 eV(=약 30,170 K)임이 확인되었다.

• 한국기계가공학회지
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• 제15권2호
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• pp.118-124
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• 2016

In this study, experiments are conducted to improve spray coating uniformity by using second and third electrodes based on the electrospray atomization mechanism. The uniformity of fabricated thin films can be improved by adjusting the design of the second electrode. The implementation of the second electrode with an elongated hole and a bending angle of $90^{\circ}$ results in highly uniform films. In addition, induced area to substrate is increased by lowering the applied voltage using the third electrode with a round rod shape. A linear correlation between applied voltage and induced area is confirmed. Thin film thickness and surface roughness are measured after the fabrication of thin films through the electrospray process. It is confirmed that a thin film is formed having an average thickness of 273.44 nm, a thickness uniformity of less than 10%, and a surface roughness of 3 nm.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.237-244
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• 2002

Televiewer is a logging tool capable of scanning the borehole wall. The tool uses a rotating acoustic beam generator that acts as both a transmitter and receiver. The beams are sent toward the wall. The amplitude of a returning signal from the wall has nearly a linear relationship with the reflection coefficient R of the borehole wall, when the wall is smooth. As R depends only on rock impedance for fixed water impedance, the amplitude is directly associated with mass density and seismic velocity of rock. Meanwhile, the amplitude can be further reduced by wall roughness that may be caused by drilling procedures, differences in rock hardness, because the rough surface can easily scatter the acoustic energy and sometimes the hole becomes elongated in all directions according to the degree of weathering. In this sense, the amplitude is related to the hardness of rocks. For convenience of analysis, the measured amplitude image(2-D data(azimuth ${\times}$ depth)) is converted, with an appropriate algorithm, to the 1-D data(depth), where the amplitude image values along a predetermined fracture signature(sinusoid) are summed up and averaged. The resulting values are subsequently scaled simply by a scalar factor that is possibly consistent with a known strength. This scaled Televiewer reflectivity is named, as a matter of convenience,“Televiewer rock strength”. This paper shows, based on abundant representative case studies from about 8 years of Televiewer surveys, that Televiewer rock strength might be regarded, on a continuous basis with depth, as a quitely robust indicator of rock classification and in most cases as an approximate uniaxial strength that is comparable to the rebound value from Schmidt hammer test.