강유전 고분자 박막의 상전이 특성

박철우,정치섭,Park, Chul-Woo,Jung, Chi-Sup 한국전기전자재료학회 2014 전기전자재료학회논문지 Vol.27 No.2

Phase transition properties of the copolymer films of polyvinylidene fluoride (PVDF) and trifluoroethylene(TrFE), P(VDF-TrFE), were studied with X-ray diffraction (XRD) and polarization modulated ellipsometry (PME). XRD studies on both Langmuir-Blodgett (LB) films and spin coated films exhibit conversions from ferroelectric phase to paraelectric phase at $108{\pm}2^{\circ}C$ on heating and paraelectric phase to ferroelectric phase at $78{\pm}2^{\circ}C$ on cooling. The presence of the ferroelectric-paraelectric phase transition is also confirmed by the PME technique for the first time in this study. PME was proved to be a very sensitive tool in the measurement of the structural changes at the nano-thickness films.

산업부산물의 사용성 확대를 위한 기초연구: 숏크리트의 강도특성

박철우,권승준,심종성,강태성,이현기,심재원,Park, Cheol-Woo,Kwon, Seung-Joon,Sim, Jong-Sung,Kang, Tae-Sung,Lee, Hyeon-Gi,Sim, Jae-Won 한국건설순환자원학회 2009 한국건설순환자원학회지 Vol.4 No.3

The industrial by-products market has increased at a geometric rate worldwide with the rapid economic growth. Among the wide variety of industrial by-products, fly ash which is generated by the combustion of coal is one of the more troublesome industrial wastes because they entail substantial disposal cost and also cause a shortage of disposal sites. In Korea alone, fly ash generation is expected to increase to 5.8 million tons by 2009, and to 6 million tons by 2010. Given the accelerated industrial development in developing countries, the amount of fly ash generation is predicted to reach enormous levels throughout the world. An increasing number of studies have currently focused on the feasibility of recycling industrial wastes i.e., fly ash in terms of environmental advantages. In this study, the optimized mix proportion of high performance shotcrete using fly ash was determined for the purpose of promoting recycling and reuse of resources. 최근 국제적으로 급속한 경제성장으로 인한 산업부산물이 기하급수적으로 늘어가고 있다. 산업부산물중 석탄의 연소과정에서 발생하는 폐석탄회는 산업폐기물로서 막대한 처리비용과 함께 매립장 부족 등 여러 가지 많은 문제점을 발생 시키고 있다. 한국의 경우 2009년에는 580만톤 2010년 이후에는 600만톤 으로 증가될 것으로 전망되고 있으며, 개발도상국의 선진화에 따른 폐석탄회 발생량은 세계적으로 볼 때 엄청난 양이 발생될 것으로 전망 된다. 이에 따라 세계적으로 산업폐기물 재활용 및 환경을 고려한 폐석탄회를 재활용 연구가 활발히 진행되고 있으며, 이 연구에서도 자원재활용을 목적으로 폐석탄회를 이용한 고성능 숏크리트용 최적 배합비를 도출하고자 한다.

고 에너지 광자선의 조사선량 측정 시 전리함의 스템효과 보정계수

박철우,이재승,권대철,차동수,김진수,김경근,Park, Cheol-Woo,Lee, Jae-Seung,Kweon, Dae-Chel,Cha, Dong-Soo,Kim, Jin-Soo,Kim, Kyoung-Keun 대한디지털의료영상학회 2010 대한디지털의료영상학회논문지 Vol.12 No.1

Ionization chambers often exhibit a stem effect, caused by interactions of radiation with air near the chamber end, or with dielectric in the chamber stem or cable. In this study measured stem effect correction factor for length of ionization chamber from medical linear accelerator recommend to with the use of stem correction method. For a model of the Farmer-type chamber, were used to calculate the beam quality correction factor. These interactions contribute to the apparent measured exposure. Additionally, it needs to consider ionization chamber use of small volume and stem effect of cable by a large field. Linear accelerator generated photons energy and increased dose repeatedly measured by using stem correction method. Stem effect was dependence of the energy and increases with photon energy conditions improved of beam quality. In conclusion, stem effect correction factor was measured within 0.4% calculated according to the exposures stem length and also supposed to determined below 1% of another stem correction method.

대기경계층 내에 놓인 실린더의 자유단 형상변화가 후류유동에 미치는 영향에 관한 연구

박철우,이상준,Park, Cheol-Woo,Lee, Sang-Joon 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.1

The flow structure around the free end of a finite circular cylinder (FC) embedded in an atmospheric boundary layer (ABL) over open terrain was investigated experimentally with varying the free end shape. The experiments were carried out in a closed-return type subsonic wind tunnel. A finite cylinder with an aspect ratio (L/D) of 6 was mounted vertically on a long flat plate. The Reynolds number based on the cylinder diameter is about Re=7,500. The velocity fields near the FC free end were measured using the single-frame double-exposure PIV method. As a result, for the FC with a right-angled free end, there is a peculiar vortical structure, showing counter-rotating twin vortices near the FC free end. It is caused by the interaction between the entrained irrotational fluids from both sides of FC and the downwash flow from the FC free-end.

EDISON Co-rotational Plane Beam-Dynamic Tip Load를 이용한 가진주파수 변화에 따른 외팔보의 자유단 진동 연구

박철우,주현식,류한열,신상준,Park, Chul-Woo,Joo, Hyun-Shig,Ryu, Han-Yeol,Shin, Sang-Joon 한국전산구조공학회 2015 한국전산구조공학회논문집 Vol.28 No.5

본 논문에서는 Euler-Bernoulli Beam(EB-beam) 및 신속 Fourier 변환을 이용하여 수치분석적 빔 모델 및 Co-rotational plane beam EDISON program(CR-beam)을 이용한 빔 모델의 가진주파수 변화에 따른 외팔보의 자유단 진동 연구를 수행하였다. 위의 두 빔 모델에서의 끝단에서는 진동이 시간이 지남에 따라 감소하다가 정상상태에 이르는 것을 확인하였다. 끝단에서 가진주파수가 증가함에 따라 구조적 감쇠에 의해 변위이 감소하는 경향을 보인다. 감쇠를 고려한 EB-beam과 CR-beam가 정상상태로 진입하는 경향이 비슷하나, 가진주파수는 정상상태가 나타나는 시간과 독립적임을 제시한다. In this paper, Euler-Bernoulli beam theories(EB-beam) are used, and Fast Fourier Transformation(FFT) analysis is then employed to extract their natural frequencies using both analytical approach and Co-rotational plane beam(CR-beam) EDISON program. EB-beam is used to analyze a spring-mass system with a single degree of freedom. Sinusoidal force with various frequencies and constant magnitude are applied to tip of each beam. After the oscillatory tip response is observed in EB-beam, it decreases and finally converges to the so-called 'steady-state.' The decreasing rate of the tip deflection with respect to time is reduced when the forcing frequency is increased. Although the tip deflection is found to be independent of the excitation frequency, it turns out that time to reach the steady state response is dependent on the forcing frequency.

한국인 모유와 조제분유 중의 공액리놀레산

박철우,반경녀,이영남,김정옥,김민석,하영래,Park, Cherl-Woo,Bahn, Kyeong-Nyeo,Lee, Young-Nam,Kim, Jeong-Ok,Kim, Min-Seok,Ha, Yeong-Lae 한국식품영양과학회 2007 한국식품영양과학회지 Vol.36 No.3

The concentrations of conjugated linoleic acid (CLA) in twelve Korean mothers' milk samples collected in October 2006 and four infant formula samples produced by Korean manufacturers were determined. CLA detected from both mothers' milk and infant formula samples was only cis-9, trans-11 CLA isomer. The amount of cis-9, trans-11 CLA in Korean mothers' milk (100 mL) ranged from 4.32 to 10.12 mg ($6.27{\pm}0.28\;mg$). Infant formula (13 g), which is the manufacturers' recommended amount to make up 100 mL with water, contained cis-9, trans-11 CLA isomer in amounts ranging from 1.61 to 2.97 mg ($2.27{\pm}0.31\;mg$). 한국인 모유에는 cis-9, trans-11 CLA 이성체만 동정되었고, 그 함량은 $4.32{\sim}10.12\;mg/100\;mL$(평균 $6.27{\pm}0.28\;mg/100\;mL$)이었고, 지방함량 중에는 $1.35{\sim}3.13\;mg/g$(평균 $1.96{\pm}0.06\;mg/g$)으로 개인에 따라 큰 차이가 있었다. 한국인 모유에 함유된 CLA의 함량은 외국의 CLA 함량에 비해 낮았고, 그 이유는 식사의 차이 때문인 것으로 추정되었다. 국내에서 제조된 조제분유에서도 cis-9, trans-11 CLA만 동정되었는데, 그 함량은 $2.35{\sim}22.82\;mg/100\;g$으로 평균치는 $17.45{\pm}1.24\;mg/100\;g$이었고, 지방에 함유된 cis-9, trans-11 CLA 함량은 $0.45\;mg/g{\sim}0.85\;mg/g$으로 그 평균치는 $0.65{\pm}0.02\;mg/g$이었다. 영유아가 조제분유 제조사의 지시된 13% 조제분유를 섭취할 경우 cis-9, trans-11 CLA를 2.27 mg 섭취하는 것으로 모유 100 mL에 함유되어 있는 양에 비해 낮다. 따라서 조제분유를 조제할 때 모유와 동일한 cis-9, trans-11 CLA를 섭취할 수 있도록 조제분유를 제조하는 것이 바람직하다.

새 정부에 바란다 - '신성장동력을 중심으로'

박철우,Park, Cheol-Woo 한국과학기술단체총연합회 2013 과학과 기술 Vol.526 No.-

루프형 낙석방지안전시설의 구조적 안전성 검토 연구

박철우,이학용,Park, Cheol-U,Lee, Hak-Yong 한국건설안전협회 2009 建設 安全技術 Vol.50 No.-

Road is typically constructed along ridge area of mountain because of topographical and economic reasons. Therefore, road may face lots of open cut slope which can easily cause rock falling. This study evaluates the structural safety of newly developed falling rock protection system which has a roof deck plate. The structural performance under self-weight, snow load and load from failing rock was investigated using a finite element numerical analysis method. From the analysis results, the H-beam space was limited not to exceed 2.2m. The deck plate was also safe under the examined loading condition. A hinge and connection in the system were investigated through detailed modelling and analysis. The results showed that the hinge was safe enough and that the connection should strengthened with appropriate stiffeners.

볼나사 그루브 상사비 결정에 관한 연구

박철우,김대은,이상조,Park, Cheol-U,Kim, Dae-Eun,Lee, Sang-Jo 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.1

Ball screws are commonly used in linear motion feeding systems of various machine tools and automated systems. They are known to have relatively little backlash, high precision and efficiency compared to ordinary lead screws. Furthermore, the effectiveness of ball screw has made it the preferred choice of many newly developed high speed precision feeding units. The motivation of this work is to establish the groove edsigh basis of ball screws for the reduction of contact fatigue failure. In most instances, fatigue failure between ball and shaft groove is due to excessive contact pressure. Especially, the excessive load is causative of plastic flow below the contact surface, which can contribute to surface failure. But, in spite of small load, if groove conformity rate is large, contact pressure is increased and internal shear stress reach the yield value of the material. In such a point, the authors deal with design procedure for deciding the permissible conformity rate of a ball screw groove with the computational evaluation of contact pressure and maximum shear stress.

다공성 방풍펜스가 대기경계층내에 놓인 삼각프리즘 표면압력에 미치는 영향에 관한 연구

박철우,성승학,Park, Cheol-U,Seong, Seung-Hak 대한기계학회 1996 大韓機械學會論文集B Vol.20 No.8

Effeccs of porous wind fence on surface-pressure around 2-dimensional prism model of triangular cross-section were investigated experimentally. The pressure data were obtained at a Reynolds number based on the model height of Re=2.1*10$^{5}$ . Flow visualization also carried out to investigate the flow structure qualitatively. The mean velocity and turbulent intensity profiles measured at fence location were well fitted to the neutral atmospheric surface boundary layer over the open terrain. Various fences with different porosity and height were tested to investigate their effects on the surface pressure acting on a prism model at different locations. As the results, porous fence with porosity 40 ~ 50% is most effective for abating wind erosion. With decreasing porosity of the fence, pressure fluctuations on the model surface are increased. The mean pressure coefficients are decreased only when the fence height is greater than the model height. The effect of distance between wind fence and triangular prism was not significant, compared to that of the fence porosity and height.