• Design & Manufacturing
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• 제11권3호
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• pp.29-34
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• 2017

Increased demand for parts with micro-pattern structure made of metals, ceramics, and composites in various fields such as medical ultrasonic sensors, CT collimators, and ultra-small actuator parts. Micro powder injection molding (PIM) is a technology for manufacturing micro size, high volume, complex, precision, net-shape components from either metal or ceramic powder. In the present study, a standard mold with a variable insert core capable of producing various micro patterns was investigated. An injection molding test was performed on a standard mold using a line type micro-pattern core having an aspect ratio of 2, a slenderness ratio of 70, a pattern size of $200{\mu}m$, and a pattern spacing of $150{\mu}m$. During the filling process, the deformation of the mold with large aspect ratio and slenderness ratio was analyzed by the experiment and the numerical simulation according to the position of the gate. We proposed a mold structure that minimizes mold deformation by gate modification and enables uniform pattern filling behavior.

• Journal of Information Display
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• 제2권3호
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• pp.54-59
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• 2001

The role of $NH_3$ for vertical alignment of CNTs was investigated. The direct cause of the alignment was a dense distribution of catalytic metal particles, but which was kept catalytically active during the growth process by $NH_3$. This allows a dense nucleation of the CNTs, and consequently, assists vertical alignment through entanglement and mechanical leaning among the tubes. The CNTs grow in a base growth mode. Several evidences were presented including a direct cross-sectional TEM observation. Since Ni is consumed both by silicide reaction and by capture in the growing tube, the growth stops when Ni is completely depleted. This occurs faster for smaller particles, and thus a longer growth results in thin bottom with poor adhesion.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.159-162
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• 1999

All solid state thin film micro-batteries consisting of lithium metal anode, an amorphous LiPON electrolyte and cathode of vanadium oxide have been fabricated and characterized, which were fabricated with cell structure of Li/LiPON/V$_2$O$\sub$5/Pt. The vanadium oxide thin films were formed by d.c. reactive sputtering on Pt current collector. After deposition of vanadium oxide films, in-situ growths of lithium phosphorus oxynitride film were conducted by r.f. sputtering of Li$_3$PO$_4$ target in mixture gas of N$_2$ and O$_2$. The pure metal lithium film was deposited by thermal evaporation on thin film LiPON electrolyte. The cell capacity was about 45${\mu}$Ah/$\textrm{cm}^2$ $\mu\textrm{m}$ after 200 cycle. No appreciable degradation of the cell capacity could be observed after 50 cycles .

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2395-2397
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• 2005

A low voltage operated piezoelectric RF MEMS in-line switch has been realized by using silicon bulk micromachining technologies for advanced mobile/wireless applications. The developed RF MEMS in-line switches were comprised of four piezoelectric cantilever actuators with an Au contact metal electrode and a suspended Au signal transmission line above the silicon substrate. The measured operation dc bias voltages were ranged from 2.5 to 4 volts by varying the thickness and the length of the piezoelectric cantilever actuators, which are well agreed with the simulation results. The measured isolation and insertion loss of the switch with series configuration were -43dB and -0.21dB (including parasitic effects of the silicon substrate) at a frequency of 2GHz and an actuation voltage of 3 volts.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2005년도 종합학술발표회 논문집 Vol.15 No.1
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• pp.371-374
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• 2005

This paper presents the design and fabrication of a cost effective and broad band 8$\times$8 stacked patch array antenna which are backed by a metal cavity operating at 400Hz based on 4 layers LTCC technology. Gain of antenna can be enhanced by using a metal cavity, which can be easily implemented by using LTCC substrates and vias. The broadband performance can be obtained by varying the dimension of patch and the number of layers. Furthermore, to keep the feeding network as smal1 as possible and reduce radiation from feeding network a mirrored patch orientation and embedded micro strip line are adopted, The fabricated antenna is $40\times45\times0.4$ $mm^3$in size. It shows gain 20.4dBi, beam width 10.7deg and impedance bandwidth of l0dE return loss 3.35GHz (40.9$\sim$44.25 GHz), which is about 8% of a center frequency.

• 대한기계학회논문집
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• 제11권6호
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• pp.953-962
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• 1987

본 연구에서는 국산 구조용강의 SM 45C 와 SUS 304 재를 최고 강도치가 나타 나는 압접조건하에서 압접하여 우재료의 용착금속부, 열영향부, 각 모재부 소정의 장 소에 미소원공을 가공한 시험편을 토대로 피로크랙의 발생 및 전파거동을 응력 레벨의 고저를 고려하여 고찰하였다.

• Nuclear Engineering and Technology
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• 제52권3호
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• pp.589-596
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• 2020

Many components in the assembly section of Sodium-cooled Fast Reactor are made of good corrosionresistant 316 LN Stainless Steel material. To avoid self-welding of the components with the coolant sodium at elevated temperature, hardfacing is inevitable. Ni-based colmonoy-5 is used for hardfacing due to its lower dose rate by Plasma Transferred Arc process due to its low dilution. Since Ni-Cr-B-Si alloy becomes very fluidic while depositing, the major height of the weld overlay rests inside the groove. Hardfacing is also done over the plain surface where grooving is not possible. Therefore, grooved and ungrooved hardfaced specimens were prepared at different travel speeds. Fe content at every 100 ㎛ of the weld overlay was studied by Energy Dispersive Spectroscopy and also the micro hardness was determined at those locations. A correlation between iron dilution from the base metal and the micro hardness was established. Therefore, if the Fe content of the weld overlay is known, the hardness at that location can be obtained using the correlation and vice-versa. A new correlation between micro hardness and dilution coefficient is obtained at different locations. A comparative study between those specimens is carried out to recommend the optimum travel speed for lower dilution.

• 한국기계가공학회지
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• 제20권10호
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• pp.88-94
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• 2021

Machining operations require the removal of chips to keep the water-soluble cutting oil clean and fresh throughout the operation time. Water-soluble cutting oil for metal processing is diluted using a 3-8% solution in water which is generally replaced every three to six months. This study aims to develop multiple purification devices to efficiently remove fine contaminating particles from water-soluble cutting oil. The 2D concept designs were created using AutoCAD. The designs were drawn using the 3D modelling feature of CATIA. Flow analysis was performed in a bubble purifier using Ansys computational fluid dynamics (CFD). This analysis has aided in improving the design and structure of the device to create the final prototype. Experiments were conducted to check the prototype's performance. Comparisons of the effects of each process variable on the experiment was carried out using ANOVA.

• 한국방사선학회논문지
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• 제6권2호
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• pp.93-98
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• 2012

미세단층촬영기법은 전임상 동물실험 분석시 고해상도의 혈관 영상화를 위한 중요한 수단이다. 이는 조직 분석과 같이 샘플 훼손이 예상되는 분석 작업 이전에 비파괴적인 방법으로 2차원 또는 3차원 이미지 재구성할 수 있는 장점이 있다. 본 연구에서는 생체 이식용 의료기기인 스텐트를 동물모델에서 전임상 분석을 하는데 있어 미세단층촬영기법의 활용방법을 제시하고 금속 스텐트(BMS)와 약물(paclitaxel)이 코팅된 스텐트(DES)의 스텐트 내 재협착정도(ISR)를 토끼 모델을 이용하여 평가하고자 하였다. BMS와 DES를 무작위적으로 토끼의 장골동맥에 식립하고 4주 후에 스텐트가 식립된 주위 혈관을 적출한 다음 스텐트 내강에 조영제를 투여하였다. 미세단층촬영기를 이용하여 50kV/200${\mu}A$의 X-ray 조사량으로 샘플을 스캔하였다. 정량적 분석을 위해 CTAN 소프트웨어를 이용하여 관심영역을 지정하여 정량적 분석을 수행하였다. 피폭 대상에 따라 각기 다른 CT값(Hounsfied Unit)을 획득할 수 있었으며(스텐트 영역; 약 1.2, 조영제 영역; 0.12~0.17, X-ray 비흡수 영역; 0~0.06), 이를 이용하여 2차원, 3차원적 영상을 획득하고 스텐트내 재협착 면적을 산출하였다. 조직병리학적 분석의 염증지수에 해당할 수 있는 확장된 스텐트의 크기를 측정하였을 때 BMS와 DES간의 유의한 차이가 나타나지 않았다. 또한 BMS 그룹의 ISR($1.52{\pm}0.48mm2$)이 DES의 ISR($0.94{\pm}0.42mm2$)에 비해 약 1.6배 높은 것으로 확인되었다. 이는 DES에 코팅된 paclitaxel이 세포 증식을 억제하여 스텐트 내강으로 증식하는 것을 저해하였기 때문으로 판단된다. 2차원적 분석 결과 BMS의 재협착 분포는 스텐트 중간 영역에서 전면부와 후면부에 비해 비교적 높은 것으로 확인되었다. 이러한 연구 결과로 볼 때 미세단층촬영기법은 비파괴적인 방법으로 분석이 가능하며 정량적 분석을 위한 기존의 복잡한 조직병리학적 분석법의 보조적인 수단으로 활용될 수 있을 것이다.

• 한국기계가공학회지
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• 제20권3호
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• pp.122-128
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• 2021

Machining operations require removal of chips to keep the coolant clean and fresh throughout the operation time. In this study, microchip removal equipment was developed using AutoCAD and CATIA programs for 3D modeling and 2D draft. In addition, the flow analysis and electromagnetic field analysis of the equipment were performed using the COMSOL Multiphysics program. The flow design of the coolant oil tank was realized on the basis of fluid analysis results. Further, on the basis of magnetic density analysis, a conveyer was designed for effectively removing metal microchips in the tank by using arrays of neodymium permanent magnets.