• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.266-266
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• 2010

Ion beam sputtering(IBS)을 이용한 pattern 형성은 대상 물질의 제한이 적고 물리적 변수의 조절에 의해 쉽게 nano 구조의 형태와 크기를 조절할 수 있다는 점에서 관심을 받아오고 있다. 하지만 IBS를 이용한 pattern 형성이 어려운 물질들도 있어 다양한 기판에서의 nano pattern 형성에 관련된 많은 연구가 보고되고 있다. 본 연구발표에서는 유용한 반도체인 Si 표면에서의 IBS를 이용한 nano 구조 형성이 가능함과 그 과정에 대해 말하고자 한다. Ru을 100nm 두께로 증착시킨 Si(100)을 sputter 했을 때, Ru 표면에 잘 order된 nano pattern이 형성되었다. Sputter 시간이 증가하면서 pattern은 유지된 채 Ru이 깎여 나가다가 pattern의 가장 낮은 부분부터 Si기판이 드러나게 된다. 이 때 노출된 Si은 sputtering에 의해 깎여나가고 아직 Ru이 덮여있는 부분의 Si은 그대로 유지되어, Ru이 모두 sputter 되면서 보여지는 Si의 pattern은 Ru의 그것과 동일한 형태를 띄게 된다. 그 결과, Ru의 pattern이 Si으로 transfer되었음을 AFM과 SAM을 통해 확인할 수 있었다. 또한 IBS를 이용해 pattern 형성이 힘든 metallic glass에도 같은 방식으로 Ru을 쌓아 sputter 해봄으로써 pattern transfer를 확인해 볼 계획이다. 이러한 pattern transfer는 sputtering을 통한 pattern 형성이 어려웠던 다른 물질들에 그 가능성이 있음을 보여주고 있어 sputtering의 응용 폭이 넓어질 것을 기대한다.

• 전력전자학회논문지
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• 제24권4호
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• pp.279-285
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• 2019

This study proposes an enhanced switching pattern that can improve energy transfer efficiency in an active cell-balancing circuit using a multiwinding transformer. This balancing circuit performs cell balancing by transferring energy stored in a specific cell with high energy to another cell containing low energy through a multiwinding transformer. The circuit operates in flyback and buck-boost modes in accordance with the energy transfer path. In the conventional flyback mode, the leakage inductance of the transformer and the stray inductance component of winding can transfer energy to an undesired path during the balancing operation. This case results in cell imbalance during the cell-balancing process, which reduces the energy transfer efficiency. An enhanced switching pattern that can effectively perform cell balancing by minimizing the amount of energy transferred to the nontarget cells due to the leakage inductance components in the flyback mode is proposed. Energy transfer efficiency and balancing speed can be significantly improved using the proposed switching pattern compared with that using the conventional switching pattern. The performance improvements are verified by experiments using a 1 W prototype cell-balancing circuit.

• Tribology and Lubricants
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• 제22권5호
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• pp.243-251
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• 2006

Molecular dynamics simulations of nanoimprint lithography NIL) are performed in order to investigate effects of process parameters, such as stamp shape, imprinting temperature and adhesive energy, on nanoimprint lithography process and pattern transfer. The simulation model consists of an amorphous $SiO_{2}$ stamp with line pattern, an amorphous poly-(methylmethacrylate) (PMMA) film and an Si substrate under periodic boundary condition in horizontal direction to represent a real NIL process imprinting long line patterns. The pattern transfer behavior and its related phenomena are investigated by analyzing polymer deformation characteristics, stress distribution and imprinting force. In addition, their dependency on the process parameters are also discussed by varying stamp pattern shapes, adhesive energy between stamp and polymer film, and imprinting temperature. Simulation results indicate that triangular pattern has advantages of low imprinting force, small elastic recovery after separation, and low pattern failure. Adhesive energy between surface is found to be critical to successful pattern transfer without pattern failure. Finally, high imprinting temperature above glass transition temperature reduces the imprinting force.

• 대한교통학회지
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• 제24권7호
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• pp.53-62
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• 2006

본 연구는 대구시 대중교통체계 개편 후 이용자 의식조사를 토대로 대중교통체계 개편 전후의 이용자 통행패턴의 변화 및 환승통행, 서비스 만족도에 대한 분석을 실시하였다. 그 결과 대중교통체계 개편으로 환승통행 수요가 증가하였으며, 특히 버스를 이용한 통행패턴에서 버스와 지하철간의 환승을 통한 통행패턴으로의 변화가 높은 것으로 나타났다. 이는 환승요금 무료할인제 실시로 환승에 대한 경제적 부담감의 감소와 버스노선체계 개편으로 대중교통이용자의 통행패턴이 다양화되었기 때문이다 환승에 대해서는 전반적으로 개선된 것으로 나타났지만, 무환승 희망비율이 높게 나타난 환승에 대해서는 여전히 많은 부담을 느끼는 것으로 나타났다

• Tribology and Lubricants
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• 제21권4호
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• pp.177-184
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• 2005

The molecular dynamics simulation of nanoimprint lithography (NIL) using $SiO_2$ stamp and amorphous poly-(methylmethacrylate) (PNMA) film is performed to study pattern transfer in NIL. Force fields including bond, angle, torsion, van der Waals and electrostatic potential are used to describe the intermolecular and intramolecular force of PMMA molecules and $SiO_2$ stamp. Nose-Hoover thermostat is used to control the system temperature and cell multipole method is adopted to treat long range interactions. The deformation of PMMA film is observed during pattern transfer in the NIL process. For the detail analysis of deformation characteristics, the distributions of density and stress in PMHA film are calculated. The adhesion and friction forces are obtained by dividing the PMMA film into subregions and calculating the interacting force between subregion and stamp. Their effects on the pattern transfer are also discussed as varying the indentation depth and speed.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.198-198
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• 2012

Graphene has been the subject of intense study in recent years owing to its good optoelectronic properties, possibility for stretchable electronics, and so on. Especially, many research groups have studied about graphene nanostructures with various sizes and shapes. Graphene needs to be fabricated into useful devices with controllable electrical properties for its successful device applications. However, this been far from satisfaction owing to a lack of reliable pattern transfer techniques. Photolithography, nanowire etching, and electron beam lithography methods are commonly used for construction of graphene patterns, but those techniques have limitations for getting controllable GNRs. We have developed a novel nanoscale pattern transfer technique based on an electro-hydrodynamic lithography providing highly scalable versatile pattern transfer technique viable for industrial applications. This technique was exploited to fabricate nanoscale patterned graphene structures in a predetermined shape on a substrate. FE-SEM, AFM, and Raman microscopy were used to characterize the patterned graphene structures. This technique may present a very reliable high resolution pattern transfer technique suitable for graphene device applications and can be extended to other inorganic materials.

• 설비공학논문집
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• 제8권1호
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• pp.140-150
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• 1996

CFC-12, which has been used most widely in automobile air conditioners and household refrigerators is scheduled to be phased out soon because of its high ozone depletion potential. Now HFC-134a is suggested as an alternative refrigerant for CFC-12. In this Study, we intended to investigate how PAG oil influence evaporation heat transfer and flow pattern, using R-134a and PAG oil influences evaporation heat transfer and flow pattern, using R-134a and PAG oil in the horizontal miro-fin evaporation tube. Experiments were conducted under the flowing est conditions : mass velocity 86-250kg/$m^2$s, heat flux 5-30 ㎾/$m^2$, oil concentration 0-21 wt.% and saturation temperature 5$^{\circ}C$. Local evaporation heat transfer coefficients were found to be higher at the top, side and bottom of the tube in this order. Average heat transfer coefficients turned out to increase with oil concentration increment up to 3 wt.% oil concentration, whereas heat transfer coefficients gradually decreased over 3 wt.% oil concentration, because of oil-rich liquid film was formed on the heat transfer surface. Flow patterns were rapidly transitioned to annular regimes up to 3 wt.% oil concentration. In case of pure refrigerant, measured heat transfer coefficients in the experiments were similar to those of Kandlikar＇s correlation.

• 한국광학회지
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• 제9권6호
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• pp.396-402
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• 1998

광학계의 결상성능평가는 optical transfer function(OTF)을 측정하는 것이 표준적인 방법으로 사용되고 있다. 그러나, 대량 생산되는 광학계의 경우에서는 측정의 편리함 때문에 test pattern을 투영하여 contrast를 검사하는 방법도 많이 사용되고 있다. 본 연구에서는 회절결상이론을 사용하여 주기적 line-space pattern에 대한 contrast transfer function(CTF)을 계산하는 프로그램을 개발하고, C­계수와 Zernike 다항식으로 표현되는 3차 파면수차에 의한 광학계의 modulation transfer function (MTF)과 CTF 변화를 비교, 분석하였다.

• 한국의류산업학회지
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• 제8권5호
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• pp.562-570
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• 2006

Knit industry requires versatile knit designers who have to control whole process such as material select, color, type of machine, technique, structure and shape. In other words, knit designers urgently need to interplay between technology and design aesthetics. It becomes essential to learn and master basic principles of knitting in order to design and develop effectively for innovative knitwear design. The main purpose of this study is to show fresh methodology through examining the various applications of 'Stitch transfer knitting structure' used in women's knitwear design development. Stitch transfer knitting structure is one of the most popular techniques among various basic knitting methods. Eight knitwears were designed and produced with various types of formative applications which differ from existent stitch transfer knitwears of flat and simple style in the market. These are produced by computer knitting machine 'Shima Seiki 122S' and programmed by 'Knit CAD' software. Among various basic stitch transfer pattern, 'Leaf' pattern is selected as a most effective example for this study. This fabric applied to collar, sleeves, body pattern and accessories as formative decoration. It is expected that this study of methodology helps to get open mind and to indicate possibility to develop and show creative and innovative knitwear and knitted textile design.

• 대한기계학회논문집
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• 제12권4호
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• pp.833-846
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• 1988

본 연구에서는 후래시현상과 가열이 동시에 존재하면서 증발을 일으키는 수직 증발관내에서의 유동양식에 대해서, 우선 전기 프로우브를 이용하여 관내의 유동양식 에 따른 전기적 신호를 얻고, 시진실험 방법(photographic experimental method)을 통 하여 이를 확인한다. 또한, 전기 프로우브를 통하여 얻은 신호는 적절한 해석과정을 통해 수직 증발관내의 유동에 따른 기공률을 측정하는데 적용된다.