• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.636-639
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• 2003

It is difficult to machine below 10 micrometers by conventional machining methods, such as micro-EDM. However, ultra micro machining using focused ion beam(FIB) is able to machine to 50 nanometers. In addition, 3 dimensional structures can be made by a combination of FIB and CVD to the level of 10 nanometers. Die ＆ moulds techniques are better than one-to-one machining techniques in the mass production of ultra size structures, in regards to production costs. In this case, the machining precision of die ＆ moulds affects produced parts. Also, it is advantageous to machine die ＆ moulds to the 10 micrometer level by FIB technique rather than other techniques. In this paper, the grooving characteristics for die ＆ mould materials by FIB were carried out experimentally in order to compare the machining characteristics of FIB with conventional machining methods. The results showed that the machining parameters and the scanning path of FIB affects the precision. The machined width and depth of the groove varied depending on the required depth due to the redeposition of the sputtered ion material accumulating on both the bottom and the side of the wall.

• JSTS:Journal of Semiconductor Technology and Science
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• 제14권6호
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• pp.733-740
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• 2014

A resistive micro Pirani gauge using amorphous silicon (a-Si) thin membrane is proposed. The proposed Pirani gauge can be easily integrated with the other process-compatible membrane-type sensors, and can be applicable for in-situ vacuum monitoring inside the vacuum package without an additional process. The vacuum level is measured by the resistance changes of the membrane using the low noise correlated double sampling (CDS) capacitive trans-impedance amplifier (CTIA). The measured vacuum range of the Pirani gauge is 0.1 to 10 Torr. The sensitivity and non-linearity are measured to be 78 mV / Torr and 0.5% in the pressure range of 0.1 to 10 Torr. The output noise level is measured to be $268{\mu}V_{rms}$ in 0.5 Hz to 50 Hz, which is 41.2% smaller than conventional CTIA.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.43-46
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• 2005

Micro molding technology is a promising mass production technology for polymer based microstructures. Mass production technologies such as the micro injection/compression molding, hot embossing, and micro reaction molding are already in use. In the present study, we have developed a numerical analysis system to simulate three-dimensional non-isothermal cavity filling for hot embossing, with a special emphasis on the free surface capturing. Precise free surface capturing has been successfully accomplished with the level set method, which is solved by means of the Runge-Kutta discontinuous Galerkin (RKDG) method. The RKDG method turns out to be excellent from the viewpoint of both numerical stability and accuracy of volume conservation. The Stokes equations are solved by the stabilized finite element method using the equal order tri-linear interpolation function. To prevent possible numerical oscillation in temperature Held we employ the streamline upwind Petrov-Galerkin (SUPG) method. With the developed code we investigated the detailed change of free surface shape in time during the mold filling. In the filling simulation of a simple rectangular cavity with repeating protruded parts, we find out that filling patterns are significantly influenced by the geometric characteristics such as the thickness of base plate and the aspect ratio and pitch of repeating microstructures. The numerical analysis system enables us to understand the basic flow and material deformation taking place during the cavity filling stage in microstructure fabrications.

• Nuclear Engineering and Technology
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• 제53권2호
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• pp.498-508
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• 2021

Micro reactors are increasingly being considered for utilization as distributed power sources. Hence, the probabilistic safety assessment (PSA) of a direct supercritical-CO₂-cooled fast reactor, called micro modular reactor (MMR), was performed in this study; this reactor was developed using innovative design concepts. It adopted a modular design and passive safety systems to minimize site constraints. As the MMR is in its conceptual design phase, design weaknesses and valuable safety insights could be identified during PSA. Level 1 internal event PSA was carried out involving literature survey, system characterization, identification of initiating events, transient analyses, development of event trees and fault trees, and quantification. The initiating events and scenarios significantly contributing to core damage frequency (CDF) were determined to identify design weaknesses in MMR. The most significant initiating event category contributing to CDF was the transients with the power conversion system initially available category, owing to its relatively high occurrence frequency. Further, an importance analysis revealed that the safety of MMR can be significantly improved by improving the reliability of reactor trip and passive decay heat removal system operation. The findings presented in this paper are expected to contribute toward future applications of PSA for assessing unconventional nuclear reactors in their conceptual design phases.

• 한국정보통신학회논문지
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• 제10권6호
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• pp.1045-1054
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• 2006

본 논문에서는 MIL-STD-1553 data bus 네트워크의 다중화를 위한 버스 인터페이스 모듈의 설계에 관하여 기술하였다. 일반적으로 MIL-STD-1553 네트워크는 단일 레벨의 버스 토플로지를 사용하지만 응용 시스템의 구조에 따라 데이터 버스의 다중화가 요구된다. 버스의 다중화를 위해서는 마이크로 프로세서가 사용되며, 시스템의 하드웨어와 소프트웨어의 추가 기능이 요구된다. 설계된 인터페이스 모듈은 마이크로 프로세서의 사용 없이 통신용 트랜시버와 간단한 전자회로로 구성되어 있다. 하드웨어 테스트 및 소프트웨어 시뮬레이션 통하여 설계 제작된 모듈의 성능을 검증하였다.

• 펄프종이기술
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• 제37권2호
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• pp.21-29
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• 2005

Increase in the utilization rate of recycled paper has significantly increased the problem associated with stickies. Despite the effort to eliminate contaminants from recycled furnishes, stickies are still the most serious obstacle in using recycled paper. The amount of micro stickies that are too small to be eliminated by screening, tends to increase significantly as the closure level of white water system is increased and the quality of raw material deteriorates. To establish a process efficient in removing micro stickies is strongly required. In this study, the surface characteristic of micro stickies was investigated with contact angle measurement. Surface energies of MCC, PSA film and model micro stickies were 53.37 mN/m, 29.75mN/m, and 29.63mN/m, respectively. This indicates that the surface characteristic of MMS is very similar to PSA. Thus, solvent coating of PSA and evaporation of the solvent provided excellent model micro stickies for flotation experiment.

• 한국재료학회지
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• 제20권12호
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• pp.640-644
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• 2010

Information technology devices, such as cellular phones, MP3s and so on, due to restrictions of space, require thin and small micro-speakers to generate sound. The reduction of the size of micro-speakers has resulted in the decrease of sound quality, due to such factors as frequency range and sound pressure level. In this study, the acoustical properties of oval microspeakers has been studied as a function of pattern shape on the diaphragm. The other conditions of micro-speakers, except for the pattern, was not changed. When the pattern is present on the diaphragm and the shape of pattern was a whirlwind, the resonance frequency was reduced due to the decrease of tensile strength of diaphragm. The patterns presented in the semi-minor axis of diaphragm did not effect a change of resonance frequency. However, increasing the number of patterns in the semimajor axis of diaphragm became a reason for the decrease of resonance frequency on edge side. When the depth of pattern on edge side was increased, the resonance frequency was decreased due to reduction of geometrical stiffness. If the height of edge and dome were increased, the resonance frequency and geometrical stiffness rapidly increased. After reaching the maximum values, they began to decrease with the continuous increase of height.

• 한국염색가공학회지
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• 제25권4호
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• pp.303-313
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• 2013

Alkali hydrolysis of sea-island PET 0.02denier microfiber were compared to those on the fabrics of the 0.06denier microfiber. In the dissolution of the sea component out of sea island type ultra-microfiber, it is important to determine the optimum division and divided material. Weight reduction of sea island ultra-micro sea island fiber was faster than regular PET about 10 times. Also 0.2denier sea-island ultra-micro sea island fiber has better color fastness (washing, friction, and daylight) than 0.06denier level sea-island ultra-microfiber. In this study, 0.2denier ultra-micro sea island fiber shows the possibility of high value product.

• 정보저장시스템학회:학술대회논문집
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• 정보저장시스템학회 2005년도 추계학술대회 논문집
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• pp.197-202
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• 2005

Current Optical Disk drive is dominating high share gradually in information storage device market through development of great skill. These technologies can achieve not only improvement of transmission speed but also elevation of recording/reproduction technology. However, these present state cause not only the increase of vibration in structural viewpoint but also problem of serious noise while the ODD becomes high speed/high performance. Specially, air-born noise is being bigger than structural-born noise as disk rotation speed increases gradually. The object of this research is that reduce the air-born noise in optical disk drive by reducing a quantity of flow by using a miniaturized muffler. The micro muffler is a miniaturized muffler. The muffler is used widely by solution to reduce air-born noise which is generated by flow. According to frequency band of the noise source, it can be applied by muffler of various forms. In this research, we examined the noise characteristics of the micro muffler and applied it by noise reduction solution of the ODD. It could get an excellent noise reduction in high frequency band by using the micro muffler than the opened case through the decrease of an inner flow. But it could not get a noise reduction in low frequency band through the decrease of an inner flow.

• 정보저장시스템학회논문집
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• 제2권1호
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• pp.50-55
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• 2006

As high performance and high speed have been accomplished by technology of optical disk drive. optical disk drives have gradually high percentage of the market share in market of storage devices. This technology helps to improve the quality of record/reproduction. However, simultaneously it causes various problems in the structural aspect and increases noise largely. Especially at high speed, dominant noise is more influenced by fluid noise than by structure-borne noise. The purpose of this study is that reduce the air-born noise in optical disk drive as it decreases a quantity of flow by using a micro muffler. The micro muffler is a miniaturized muffler. The muffler is used widely by solution to reduce air-borne noise which is generated by flow. According to frequency band of the noise source, it can be applied by muffler of various forms. In this study, we examined the acoustic characteristics of the micro muffler and applied it to reduction of the ODD noise. It could get an excellent noise reduction in high frequency band through the decrease of an inner flow. But it could not get a noise reduction in low frequency band.