• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.687-690
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• 2002

Multimode boundary-layer transition on a NACA0012 airfoil is experimentally investigated under periodically passing wakes and the moderate level of free-stream turbulence. The periodic wakes are generated by rotating circular cylinders clockwise or counterclockwise around the airfoil. The free-stream turbulence is produced by a grid upstream of the rotating cylinder, and its intensity(Tu) at the leading edge of the airfoil is $0.5\;or\;3.5\;{\%}$. The Reynolds number ($Re_c$) based on chord length (C) of the alrfoil is $2.0{\times}10^5$, and Strouhal number ($St_c$) of the passing wake is about 0.7. Time- and phase-averaged streamwise mean velocities and turbulence fluctuations are measured with a single hot-wire probe, and especially, the corresponding wall skin friction is evaluated using a computational Preston tube method. The wake-passing orientation changes pressure distribution on the airfoil in a different manner irrespective of the free-stream turbulence. Regardless of free-stream turbulence level, turbulent patches for the receding wakes propagate more rapidly than those for the approaching wake because adverse pressure gradient becomes larger. The patch under the high free-stream turbulence ($Tu=3.5{\%}$) grows more greatly in laminar-like regions compared with that under the low background turbulence ($Tu=0.5{\%}$) in laminar regions. The former, however, does not greatly change the original turbulence level in the very near-wall region while the latter does it. At further downstream, the former interacts vigorously with high environmental turbulence inside the pre-existing transitional boundary layer and gradually lose his identification, whereas the latter keep growing in the laminar boundary layer. The calmed region is more clearly observed under the lower free-stream turbulence level and for the receding wakes. The calmed region delays the breakdown further downstream and stabilizes more the boundary layer.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1668-1670
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• 2002

Since more than two decades, the conventional PD detecting systems have been employed in order to detect the partial discharges occurring inside the HV power apparatus for their diagnosis by use of different type of detection such as acoustic and UHF detection method. Regardless of their wide on-site application, a certain number of technical inconveniences have been disclosed as follows : multistage amplification. large volume, susceptible to external noise and high price. In this respect, the optical measurement techniques are widely proposed in these days in this concerned field ascribed to the following advantages : immune to external EMI noise and broad band response of the Pockels cell covering from DC to GHz. However, the reliability of several proposed techniques enabling to measure the electric field inside the large high power apparatus has not yet been well approved In this work, an optical measuring system, based on the Pockels effect, has been developed for measuring the field variation due to the corona discharges occurring in air and in oil. This system consists of He-Ne laser, single mode optical fiber, multi mode optical fiber, polarizing film, Y-cut LiNbO3 cell, photo detector, digital oscilloscope and personal computer with GPIB. For this purpose, optical probe has been specially designed and realized and put into the needle-plane electrode. Afterward, same measurement is carried out in oil. We demonstrate the characteristic of the optical measuring system and the measurement results.

• 대한기계학회논문집B
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• 제30권9호
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• pp.921-928
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• 2006

Wake-induced boundary-layer transition on a NACA0012 airfoil with zero angle of attack is experimentally investigated in periodically passing wakes under the moderate level of free-stream turbulence. The periodic wakes are generated by rotating circular cylinders clockwise or counterclockwise around the airfoil. The free-stream turbulence is produced by a grid upstream of the rotating cylinder, and its intensities $(Tu_{\infty})$ at the leading edge of the airfoil are 0.5 and 3.5%, respectively. The Reynolds number (Rec) based on chord length (C) of the airfoil is $2.0{\times}10^5$, and Strouhal number (Stc) of the passing wake is about 1.4. Time- and phase-averaged streamwise mean velocities and turbulence fluctuations are measured with a single hot-wire probe, and especially, the corresponding wall skin friction is evaluated using a computational Preston tube method. The patch under the high free-stream turbulence $(Tu_{\infty}=3.5%)$ grows more greatly in laminar-like regions compared with that under the low turbulence $(Tu_{\infty}=0.5%)$ in laminar regions. The former, however, does not greatly change the turbulence level in very near-wall region while the latter does it. At further downstream, the former interacts vigorously with high environmental turbulence inside the pre-existing transitional boundary layer and gradually loses its identification, whereas the latter keeps growing in the laminar boundary layer. The calmed region is more clearly observed under the lower free-stream turbulence level and with the receding wakes.

• Journal of Microbiology and Biotechnology
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• 제11권3호
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• pp.508-514
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• 2001

A stuructural gene (ycl) encoding novel yeast cell wall hydrolase, YCL, was cloned from alkalophilic Bacillus alcalophilus subsp. YB380 by PCR, and transformed into E. coli JM83. Based on the N-terminal and internal amino acid sequences of the enzyme, primers were designed for PCr. The positive clone that harbors 1.8 kb of the yeast cell wall hydrolase gene was selected by the colony hybridization method with a PCR fragment as a probe. According to the computer analysis, this gene contained a 400-base-paired N-terminal domain of the enzyme. Based on nucletide homology of the cloned gene, a 850 bp fragment was amplified and the C-terminal domain of the enzyme was sequenced. With a combination of the two sequences, a full nucleotide sequence for YCL was obtained. This gene, ycl, consisted of 1,297 nucleotides with 27 nucleotides with 27 amino acids of signal sequence, 83 redundant amino acids of prosequence, and 265 amino acids of the mature protein. This gene was then cloned into the pJH27 shuttle vector and transformed into the Bacillus subtilis DB104 to express the enzyme. It was confirmed that the expressed cell wall hydrolase that was produced by Bacillus subtilis DB104 was the same as that of the donor strain, by Western blot using polyclonal antibody (IgY) prepared from White Leghorn hen. Purified yeast cell wall hydrolase and expressed recombinant protein showed a single band at the same position in the Western blot analysis.

• Transactions on Electrical and Electronic Materials
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• 제5권5호
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• pp.204-207
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• 2004

In this work, we present the electrochemical properties of Al bipolar plate, which can be re-searched for the application of PEMFC system. Bulk resistance of the plate was measured with a four-point probe method. The electrical conductivity of noble metal coated Al plate was 4.40 x 10$^4$ S/cm. On the other hand, the electrical interfacial resistance of the noble metal coated Al plate valued at 0.15 mΩ-$\textrm{cm}^2$ and that of graphite was 0.26 mΩ-$\textrm{cm}^2$ under the holding pressure of 140 N/$\textrm{cm}^2$ at the applied current of 5 A. And the performance of Al bipolar plate for PEMFC was evaluated at various conditions. The single cell performance was more than 0.43 W/$\textrm{cm}^2$ (0.47 Wig) for noble metal coated Al bipolar plate at 5$0^{\circ}C$ under atmospheric pressure in external humidified hydrogen and oxygen condition. As the present results, we could show the results that the noble metal coated Al bipolar plates were favorable in the aspect of electrical properties compared with those of the commercialized resin-impregnated graphite plates.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.111.1-111.1
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• 2012

Interest in flexible transparent conducting films (TCFs) has been growing recently mainly due to the demand for electrodes incorporated in flexible or wearable displays in the future. Indium tin oxide (ITO) thin films, which have been traditionally used as the TCFs, have a serious obstacle in TCFs applications. SWNTs are the most appropriate materials for conductive films for displays due to their excellent high mechanical strength and electrical conductivity. In this work, the fabrication by the spraying process of transparent SWNT films and reduction of its sheet resistance on PET substrates is researched Arc-discharge SWNTs were dispersed in deionized water by adding sodium dodecyl sulfate (SDS) as surfactant and sonicated, followed by the centrifugation. The dispersed SWNT was spray-coated on PET substrate and dried on a hotplate. When the spray process was terminated, the TCF was immersed into deionized water to remove the surfactant and then it was dried on hotplate. The TCF film was then was doped with Au-ionic doping treatment, rinsed with deionized water and dried. The surface morphology of TCF was characterized by field emission scanning electron microscopy. The sheet resistance and optical transmission properties of the TCF were measured with a four-point probe method and a UV-visible spectrometry, respectively. This was confirmed and discussed on the XPS and UPS studies. We show that 87 ${\Omega}/{\Box}$ sheet resistances with 81% transmittance at the wavelength of 550nm. The changes in electrical and optical conductivity of SWNT film before and after Au-ionic doping treatments were discussed. The effect of Au-ion treatment on the electronic structure change of SWNT films was investigated by Raman and XPS.

• 융합신호처리학회논문지
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• 제16권4호
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• pp.156-161
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• 2015

본 논문에서는 GPS(Global positioning System)-Bluetooth-DSRC(Dedicated short range communication) 대역의 신호를 동시에 수신할 수 있는 차량용 이중편파 다중대역 안테나를 적층형으로 설계하였다. 안테나는 다층 구조(Multi-Layer)이고, 유전율이 4.4이고, 두께가 1.6mm 인 FR4-epoxy 기판을 사용하였다. GPS와 DSRC 대역은 원형편파(Circular Polarization) 특성을 가지고, 블루투스 대역은 선형편파(Linear Polarization) 특성을 가지며, 이들 안테나는 단일 프루브 급전하였다. 안테나는 Ansys HFSS v11로 시뮬레이션 하였고, 측정결과와 비교하면서 크기가 $67mm{\times}67mm{\times}4.8mm$인 안테나를 설계하였다. 최적 설계된 안테나는 -10dB 대역폭이 각 대역에서 82MHz, 127MHz, 862MHz로 측정되었고, GPS 및 DSRC 대역의 3dB 축비 대역폭은 12MHz와 112MHz로 시뮬레이션 되었다. 이 결과는 시스템이 요구하는 사양을 만족하고 있음을 확인하였다.

• 융합정보논문지
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• 제11권8호
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• pp.137-150
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• 2021

본 연구는 대학부설 평생교육원 콘텐츠를 활용한 가정 내 온라인 평생교육이 발달장애인들의 조리직무기술 습득 및 일반화에 미치는 효과를 알아보는 데에 목적을 두어 실시되었다. 연구 대상은 학교 졸업 후 미취업의 상태로 가정 내에서 부모와 함께 거주하는 발달장애인 세 명으로 구성되었으며, 연구 설계 및 방법은 단일대상연구 중 대상자간 중다 간헐 기초선 설계의 기법이 사용되었다. 연구 결과, 연구 대상으로 참여한 세 명의 발달장애인은 대학부설 평생교육원 콘텐츠를 활용한 가정 내 온라인 평생교육을 통하여 조리직무기술을 효과적으로 습득하였으며, 가정이 아닌 실제 식당환경에서 역시 조리직무기술의 수행을 일반화한 것으로 나타났다.

• 대한의용생체공학회:의공학회지
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• 제43권4호
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• pp.271-279
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• 2022

Functional cosmetics containing various ingredients that improve skin health are currently being developed. In addition, technologies that help increase the absorption rate of such cosmetics have recently gained significant attention. Sonophoresis is a method to increase the transdermal absorption of cosmetics using ultrasound. A skin-mimicking phantom was fabricated using polydimethylsiloxane, Strat-M^TM membrane, and thermochromic pigments. Gel-type cosmetics used in skin mask packs and epidermal-growth-factor-based nano-cosmetics were tested for their absorption rates at ultrasound frequencies of 1, 3, and 10 MHz in the single frequency mode, and 1/3 and 3/10 MHz in the dual frequency mode. The gel-type cosmetics and epidermal-grow-factor-based nano-cosmetics showed the highest absorption rate at 3/10MHz dual frequency. The size of the cosmetic particles decreased by 5-9 %. Furthermore, the temperature rise caused by ultrasound could be visually recognized by the thermochromic pigment in the phantom turning white. We presented a skin-mimicking phantom. The device can be customized according to the size of the ultrasound probe and has the advantage of quantitatively evaluating the transdermal permeability of cosmetics at a low cost. The development of the skin-mimicking phantom will be useful for determining the suitable conditions required to increase the absorption rate of cosmetics using ultrasound.

• 한국콘텐츠학회논문지
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• 제10권3호
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• pp.204-214
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• 2010

본 연구는 지적장애인의 직업능력 향상을 위한 보조공학의 활용에 대한 국외의 단일대상연구 논문을 분석하여 지적장애인의 직업능력 향상을 위한 보조공학의 활용 연구에 대한 기초자료를 제시하는데 목적이 있다. 본 연구는 문헌연구로써, 관련 단일대상연구 논문을 분석하여 연구의 특성, 연구방법의 내용, 연구 설계의 질적 수준을 알아보았다. 분석결과는 다음과 같았다: 첫째, 연구의 특성을 분석한 결과, 실험환경은 분리된 환경에서의 연구가 대부분이었으며 중다간헐 설계가 대부분이었다; 둘째, 연구 방법의 내용을 분석한 결과, 대상자의 선정기준에 대해서는 모든 논문에서 언급하였으나 대상자와 관련한 내용을 기술한 논문의 비율이 낮게 나타났다. 기초선 측정시의 행동통제방법과 외부변수 통제방법에 대한 기술의 빈도가 낮았다; 셋째, 연구 설계의 질적 수준을 분석한 결과, 대부분의 논문에서 독립변수를 측정하고 중재충실도를 제시하고 있으나 사회적 타당도를 제시한 논문의 비율은 낮게 나타났다. 직업재활 분야에서 보조공학의 효과적인 활용을 위해서는 직업재활에 있어 보조공학의 활용이 근거기반의 실제라는 것에 대한 결과의 축적이 필요하며, 이를 위해 앞으로의 연구에서는 연구방법의 내용이나 연구 설계의 질적 수준에 대한 보완이 필요할 것이라 생각된다.