열전달 효과를 고려한 비행체 낫셀의 엔진 부품 전산해석 연구

원성식,우상무,안형진,박원규 한국전산유체공학회 2017 한국전산유체공학회지 Vol.22 No.4

In a certain flight envelope, the surface of engine of aircraft has very high temperature and the heat is delivered to the linear replacement units in a form of complex of convection and radiation. This kind of mixed heat transfer should be seriously considered, because it may not adjust the limit temperature condition of several linear replacement units inside Nacelle and it can cause mechanical failure or fire. This thesis is about whether the linear replacement units of the engine with mixed heat transfer made from high temperature of the engine surface in each different flight envelopments with different speed conditions adjust the limit temperature condition.

무연계 Bi_0.5(Na_1-xK_x)_0.5TiO₃ 박막의 강유전 특성

원성식,채송아,안창원,김일원 한국물리학회 2012 새물리 Vol.62 No.4

PZT계 물질은 환경에 유해한 납 (Pb)이 60 wt% 이상 포함되어 있어인체에 유해하므로 산업계에서 납이 함유되지 않는 친환경 무연 강유전물질의 개발이 요구되고 있다. Bi_(0.5)(Na_(1-x)K_x)_(0.5)TiO_3 (BNKT) 세라믹은 K 치환량이 증가함에 따라 rhombohedral에서 tetragonal 상으로상전이하며, K 치환량이 0.16 ≤ x ≤ 0.20 영역에서 두 개의 상이공존하는 상경계 영역 (Morphotropic Phase Boundary)이 존재한다는 선행연구로부터 BNKT 박막을 Pt(111)/TiO_2/SiO_2/Si 기판위에 Sol-Gel 방법으로 증착한 후 750 ℃에서 O_2 분위기로 후열 처리하였다. BNKT-0.18 박막은 페로브스카이트 구조를 나타내었으며, 기공들이상대적으로 적고 낱알 크기가 증가하여 낱알 경계면이 감소하였다. 인가전기장이 200 kV/cm일 때 BNKT-0.18 박막에서 가장 큰잔류분극(P_r)값 23.1 μC/㎠ 을 나타내었으며항전기장(E_c)은 63.3 kV/cm 이었다. Ferroelectric materials are primarily Pb(Zr,Ti)O_3 (PZT)-based materials, which contain more than 60 wt\% lead. Lead is a very toxic substance that can affect the kidney, brain, and nervous system. Therefore, lead-free ferroelectric materials must be developed to replace PZT-based materials. Bi_(0.5)(Na_(1-x)K_x)_(0.5)TiO_3 (BNKT) is one of those lead-free candidates which is showing strong ferroelecticity. The Bi_(0.5)(Na_(1-x)K_x)_(0.5)TiO_3 (BNKT) ceramics have received a great deal of attention due to their excellent ferroelectric and piezoelectric properties in the rhombohedral-tetragonal morphotropic phase boundary (MPB) at optimal compositions in the range 0.16 ≤ x ≤ 0.20. We fabricated BNKT ferroelectric films on Pt/TiO_2/SiO_2/Si substrates by using a sol-gel technique and post-annealed them in an oxygen ambient at 750 ℃. The films exhibit a perovskite structure without secondary phases. The Porosity and the grain boundaries are reduced due to the increase of grain size in the BNKT-0.18 film. The remanent polarization and the coercive field of BNKT-0.18 film were 23.1 μC/㎠ and 63.3 kV/cm, respectively, at an applied electric field of 200 kV/cm.

The Effect of Annealing Temperature on the Piezoelectric and Dielectric Properties of Lead-free Bi0.5(Na0.85K0.15)0.5TiO3 Thin Films

원성식,안창원,김일원 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.6

We fabricated Bi<SUB>0.5</SUB>(Na<SUB>0.85</SUB>K<SUB>0.15</SUB>)<SUB>0.5</SUB>TiO<SUB>3</SUB> (BNKT) lead-free thin films on Pt(111)/TiO<SUB>2</SUB>/SiO<SUB>2</SUB>/Si(100) substrate using a chemical solution deposition method. The BNKT thin films were annealed at 650, 700, 750, or 800 ℃ in an O<SUB>2</SUB> atmosphere. X-ray diffraction patterns revealed a pure perovskite structure at annealing temperatures from 650 to 800 ℃. A field emission electron microscope study revealed an increase in grain size with increasing annealing temperature. BNKT thin films annealed at 700 ℃ had a high remnant piezoelectric coefficient <I>d</I><SUB>33,<I>f </I></SUB>value of 63.6 pm/V and a low leakage current density of 5.15 10<SUP>-6</SUP> A/cm<SUP>2</SUP>.

Pt와 ITO 상부전극에 따른 강유전체 Pb(Zr0.3Ti0.7)O3 박막의 광전류 특성

원성식,안창원,김일원 한국물리학회 2012 새물리 Vol.62 No.8

In materials without a center of symmetry, such as ferroelectric materials, photocurrent can be produced in a homogeneous medium under uniform illumination, which is called the ferroelectric photovoltaic effect (FPE). We have fabricated Pb(Zr0.3Ti0.7)O3 (PZT) ferroelectric thin films with Pt and ITO electrodes on Pt/Ti/SiO_2/Si substrates by using a sol-gel technique and investigated the photocurrent behaviors. The photocurrent of the Pt/PZT/Pt capacitor, which depended on the direction of polarization, exhibited a symmetric behavior, but that of the ITO/PZT/Pt capacitor, which also depended on the direction of polarization, exhibited an asymmetric behavior. The effects of the difference between the top electrode materials on the photocurrent behaviers of the Pt/PZT/Pt and ITO/PZT/Pt capacitors are discussed. 결정구조 상 대칭중심을 가지지 않는 강유전 물질에 빛이 입사되면광전류가 발생되는데 이 현상을 강유전체 광기전력 효과 (ferroelectric photovoltaic effect, FPE)라 한다. 졸-겔 방법으로 Pt/Ti/SiO_2/Si 기판 위에 Pb(Zr0.3Ti0.7)O3 강유전체 박막을 제조후 서로 다른 Pt와 ITO 상부전극을 사용하여 광전류 특성을 조사하였다. 분극 방향에 따른 Pt/PZT/Pt 캐패시터의 광전류는 대칭적이었으나ITO/PZT/Pt 캐패시터의 광전류는 비대칭적이었다. 상부전극 물질 차이에따른 Pt/PZT/Pt와 ITO/PZT/Pt 캐패시터의 광전류 특성 변화에 관하여논의하였다.

폴리에틸렌 글리콜 첨가에 따른 Bi_0.5(Na_0.85K_0.15)_0.5TiO₃ 박막의 강유전 특성

원성식,채송아,석해진,안창원,김일원 한국물리학회 2012 새물리 Vol.62 No.4

With PEG (polyethylene glycol) solutions, We have fabricated Bi_(0.5)(Na_(0.85)K_(0.15))_(0.5)TiO_3 (BNKT) and BNKT thin films on Pt(111)/TiO_2/SiO_2/Si substrates by using a chemical solution deposition (CSD) method. A presence of PEG decreased pores on the surfaces of the BNKT thin films and enhanced the ferroelectric properties. The BNKT thin film with PEG exhibited a perovskite structure without any secondary phases. The remanent polarization (2P_r) and the coercive field (2E_) of the BNKT thin film with PEG were 20.3 μC/㎠ and 191 kV/cm,respectively, at an applied electric field of 950 kV/cm. The leakage current density of the BNKT thin film with PEG was 4.0 ×10^-5A/㎠ at 500 kV/cm. Bi_(0.5)(Na_(0.85)K_(0.15))_(0.5)TiO_3 (BNKT)와 폴리에틸렌글리콜 (polyethylene glycol : PEG)을 첨가한 BNKT 용액 졸을 화학 용액증착(chemical solution deposition : CSD) 방법으로 제작하여Pt(111)/TiO_2/SiO_2/Si 기판위에 박막을 증착하였다. PEG의 첨가는박막 표면의 기공을 감소시켰으며, 강유전 특성을 향상 시켰다. PEG가첨가된 BNKT 박막은 페로브스카이트 구조를 나타내었으며 2차상은존재하지 않았다. 인가전기장이 950 kV/cm일 때 PEG를 첨가한 BNKT 박막에서 큰 잔류분극(2P_r)값 20.3 μC/㎠을 나타내었으며,항전기장(2E_c)은 191 kV/cm 이었다. 인가전기장이 500 kV/cm 일 때PEG를 첨가한 BNKT 박막의 누설전류밀도는 4.0 × 10^-5A/㎠ 이었다.

풍력 터빈을 이용한 상용 차량의 항력 저감과 에너지 활용 방안 연구

원성식(Sungsik Won),박원규(Warnkyu Park) 한국신재생에너지학회 2017 한국신재생에너지학회 학술대회논문집 Vol.2017 No.5

Large piezoresponse of lead-free Bi0.5(Na0.85K0.15)0.5TiO3 thin film

안창원,원성식,Aman Ullah,이선영,이수대,이지혜,조윌렴,김일원 한국물리학회 2012 Current Applied Physics Vol.12 No.3

0.85Bi0.5Na0.5TiO3-0.15Bi0.5K0.5TiO3 (BNKT15) lead-free thin films were prepared on Pt(111)/TiO2/SiO2/Si(100) substrates by the chemical solution deposition method. BNKT15 are MPB composition in the Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3 (BNTeBKT) system. The maximum piezoelectric coefficient (d33,f) value of BNKT15 thin film is approximately 75 pm/V, which is comparable to that of polycrystalline PZT thin films. These results suggest that BNKT15 thin film can be used as an alternative for PZT films in piezoelectric micro-electromechanical systems.

강유전체 Pb(Zr_0.3Ti_0.7)O₃ 박막의 광전도 특성

김성철,진병문,원성식,안창원,박정민,석해진,채송아,김일원,김영수 한국물리학회 2012 새물리 Vol.62 No.1

In materials without a center of symmetry, such as ferroelectric materials, a photocurrent can be produced in a homogeneous medium under uniform illumination, the so called ferroelectric photovoltaic effect (FPE). The FPE is an effect that has an extremely large photovoltage (> kV) and a photocurrent proportional to the magnitude of the polarization and the charge carrier separation. We fabricated Pb(Zr_0.3Ti_0.7)O_3 (PZT) ferroelectric thin films on Pt/Ti/SiO_2/Si substrates by using a sol-gel technique and investigated the photocurrent properties. In the measurement of the photocurrent, the maximum photocurrent density of the PZT films was obtained at a wavelength of 350 nm. The band gap energy of the PZT film was 3.5 eV, which is consistent with that of the bulk PZT material. From the I-V measurement, the Schottky barriers between the Pt (top electrode)/PZT film and the PZT film/Pt (bottom electrode) were symmetric. 결정구조 상 대칭중심을 가지지 않는 강유전 물질에 빛이 입사되면광전류가 발생되는데 이 현상을 강유전체 광기전 효과 (ferroelectric photovoltaic effect, FPE)라 한다. FPE는 매우 큰 광전압(>kV)을 발생할 수 있는 장치로 이때 생성되는 광전류는 강유전체의 분극과전하운반체의 분리에 기인한다. 졸-겔 방법으로 Pt/Ti/SiO_2/Si 기판위에 Pb(Zr_0.3Ti_0.7)O_3 (PZT) 강유전체 박막을 제조하여광전류 특성을 조사하였다. 입사광의 파장에 따른 PZT 박막의 광전류측정결과 파장 350 nm에서 최대 광전류밀도 --93.3 nA/cm^2을나타내었으며 밴드갭 에너지는 3.5 eV 이었다. I-V 측정으로부터상부전극/PZT박막과 하부전극/PZT박막 사이의 두 경계면에 형성되는쇼트키 장벽은 대칭을 이루었다.

Pure Ferroelectric Polarization of Lead-free Na0.5K0.5NbO3 Thin Films by Using the Double Wave Method

이해준,안창원,원성식,Achiri Tange,박봉찬,석해진,김일원 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.9

Na0.5K0.5NbO3 (NKN) thin films were grown on Pt(111)/Ti/SiO2/Si substrates by using RFmagnetron sputtering. We investigated the behavior of the ferroelectric polarization. Well-saturated P-V hysteresis loops were observed, but the P-V hysteresis loops were sometimes distorted and consisted of three roughly parallel components, such as ferroelectric, dielectric and conductive components. Correction methods were proposed to identify the undesirable components and the pure ferroelectric polarization components from the observed P-V hysteresis loops. A new polarization hysteresis loop measurement technique, the double wave method (DWM), was applied to NKN thin films to obtain pure ferroelectric polarization and elucidate the behaviors of the polarization components.

한국인 남성에서 자폐스펙트럼장애와 DLX6 유전자 단일염기다형성간 연관성 연구

김현근(Hyoun Geun Kim),원성식(SeongSik Won),이승구(Seung Ku Lee),남민(Min Nam),방희정(Hee Jung Bang),박현정(Hyun Jung Park),윤진영(Jin Young Yoon),최경식(Kyung-Sik Choi),홍미숙(Mee Sook Hong),정주호(Joo-Ho Chung),곽규범(KyuBum Kwack 대한소아청소년정신의학회 2010 소아청소년정신의학 Vol.21 No.1

Objectives:Autism spectrum disorder (ASD) is a neurodevelopmental disorder that is characterized by abnormalities of social functioning, communication and behavior. The association of the 7q21-34 region with ASD has been reported. The DLX6 gene, which is located at the 7q22 region, is one of the positional and functional candidate genes for ASD. We found that there is no association between DLX6 polymorphisms and ASD in the Korean male population. Methods:We selected three single nucleotide polymorphisms (SNPs) that might be implicated in the change of the DLX6 gene expression. The genomic DNA was collected from the venous blood of 147 male controls and 179 male patients with ASD. The genotypes of the selected SNPs were determined using the Illumina GoldenGate assay, and the statistical analyses were performed using HapAnalyzer software and SAS Enterprise. Results:We found no association of the three SNPs in the DLX6 gene with ASD in the Korean male population. Conclusion:Our study suggests that the three SNPs in the DLX6 gene are not associated with ASD, and we need to analyze the previously reported regions for their associations with ASD.