접촉각이 유하액막 특성에 미치는 영향에 관한 실험적 연구

김경희,강병하,이대영 대한설비공학회 2006 설비공학 논문집 Vol.18 No.11

Vertical falling liquid film is extensively used in heat and mass transfer processes of many applications, such as evaporative coolers, cooling towers, and absorption chillers. In such cases, it is required that the falling film spreads widely in the surface forming thin liquid film to enlarge contact surface. An addition of surface active agent to a falling liquid film or hydrophilic surface treatment affects the fluid physical properties of the film. Surfactant addition not only decreases contact angle between the liquid and solid surface but also changes the surface from hydrophobicity to hydrophilicity. In this study, the effects of contact angle on falling film characteristics over a vertical surface have been investigated experimentally. The contact angle is varied either by an addition of surfactant to the liquid or by hydrophilic surface treatment. It is found that the wetted area is increased and film thickness is decreased by the hydrophilic treatment as compared with those of other surfaces. With this hydrophilic treatment, the falling liquid film spreads out widely in the surface. As surfactant concentration is increased, wetted area is also increased and the film thickness is substantially decreased.

Atomically flat single terminated oxide substrate surfaces

Biswas, Abhijit,Yang, Chan-Ho,Ramesh, Ramamoorthy,Jeong, Yoon H. Elsevier 2017 Progress in surface science Vol.92 No.2

<P><B>Abstract</B></P> <P>Scientific interest in atomically controlled layer-by-layer fabrication of transition metal oxide thin films and heterostructures has increased intensely in recent decades for basic physics reasons as well as for technological applications. This trend has to do, in part, with the coming post-Moore era, and functional oxide electronics could be regarded as a viable alternative for the current semiconductor electronics. Furthermore, the interface of transition metal oxides is exposing many new emergent phenomena and is increasingly becoming a playground for testing new ideas in condensed matter physics. To achieve high quality epitaxial thin films and heterostructures of transition metal oxides with atomically controlled interfaces, one critical requirement is the use of atomically flat single terminated oxide substrates since the atomic arrangements and the reaction chemistry of the topmost surface layer of substrates determine the growth and consequent properties of the overlying films. Achieving the atomically flat and chemically single terminated surface state of commercially available substrates, however, requires judicious efforts because the surface of as-received substrates is of chemically mixed nature and also often polar. In this review, we summarize the surface treatment procedures to accomplish atomically flat surfaces with single terminating layer for various metal oxide substrates. We particularly focus on the substrates with lattice constant ranging from 4.00Å to 3.70Å, as the lattice constant of most perovskite materials falls into this range. For materials outside the range, one can utilize the substrates to induce compressive or tensile strain on the films and explore new states not available in bulk. The substrates covered in this review, which have been chosen with commercial availability and, most importantly, experimental practicality as a criterion, are KTaO<SUB>3</SUB>, <I>RE</I>ScO<SUB>3</SUB> (<I>RE</I> =Rare-earth elements), SrTiO<SUB>3</SUB>, La<SUB>0.18</SUB>Sr<SUB>0.82</SUB>Al<SUB>0.59</SUB>Ta<SUB>0.41</SUB>O<SUB>3</SUB> (LSAT), NdGaO<SUB>3</SUB>, LaAlO<SUB>3</SUB>, SrLaAlO<SUB>4</SUB>, and YAlO<SUB>3</SUB>. Analyzing all the established procedures, we conclude that atomically flat surfaces with selective A- or B-site single termination would be obtained for most commercially available oxide substrates. We further note that this topmost surface layer selectivity would provide an additional degree of freedom in searching for unforeseen emergent phenomena and functional applications in epitaxial oxide thin films and heterostructures with atomically controlled interfaces.</P>

PIXEL-BASED CORRECTION METHOD FOR GAFCHROMIC^®EBT FILM DOSIMETRY

Jeong, Hae-Sun,Han, Young-Yih,Kum, O-Yeon,Kim, Chan-Hyeong,Ju, Sang-Gyu,Shin, Jung-Suk,Kim, Jin-Sung,Park, Joo-Hwan Korean Nuclear Society 2010 Nuclear Engineering and Technology Vol.42 No.6

In this paper, a new approach using a pixel-based correction method was developed to fix the non-uniform responses of flat-bed type scanners used for radiochromic film dosimetry. In order to validate the method's performance, two cases were tested: the first consisted of simple dose distributions delivered by a single port; the second was a complicated dose distribution composed of multiple beams. In the case of the simple individual dose condition, ten different doses, from 8.3 cGy to 307.1 cGy, were measured, horizontal profiles were analyzed using the pixel-based correcton method and compared with results measured by an ionization chamber and results corrected using the existing correction method. A complicated inverse pyramid dose distribution was made by piling up four different field shapes, which were measured with GAFCHROMIC$^{(R)}$EBT film and compared with the Monte Carlo calculation; as well as the dose distribution corrected using a conventional method. The results showed that a pixel-based correction method reduced dose difference from the reference measurement down to 1% in the flat dose distribution region or 2 mm in a steep dose gradient region compared to the reference data, which were ionization chamber measurement data for simple cases and the MC computed data for the complicated case, with an exception for very low doses of less than about 10 cGy in the simple case. Therefore, the pixel-based scanner correction method is expected to enhance the accuracy of GAFCHROMIC$^{(R)}$EBT film dosimetry, which is a widely used tool for two-dimensional dosimetry.

평판 유리로 봉인된 다층 무기 박막을 갖는 OLED 봉지 방법

박민경,주성후,양재웅,백경갑,Park, Min-Kyung,Ju, Sung-Hoo,Yang, Jae-Woong,Paek, Kyeong-Kap 한국전기전자재료학회 2011 전기전자재료학회논문지 Vol.24 No.11

To study encapsulation method for large-area organic light emitting diodes (OLEDs), red emitting OLEDs were fabricated, on which LiF and Al were deposited as inorganic protective films. And then the OLED was attached to flat glass by printing method using epoxy. In case of direct coating of epoxy onto OLED by printing method, luminance and current efficiency were remarkably decreased because of the damage to the OLED by epoxy. In case of depositing LiF and Al as inorganic protective films and then coating of epoxy onto OLED, luminance and current efficiency were not changed. OLED lifetime was more increased through inorganic protective films between OLED and flat glass than that without any encapsulation (8.8 h), i.e., 47 (LiF/Al/epoxy/glass), 62 (LiF/Al/LiF/epoxy/glass), and 84 h (LiF/Al/Al/epoxy/glass). The characteristics of OLED encapsulated with inorganic protective films (attached to flat glass) showed the possibility of application of protective films.

계면활성제의 농도가 유하액막의 열전달 특성에 미치는 영향에 관한 실험적 연구

김경희(Kyung Hee Kim),강병하(Byung Ha Kang),이대영(Dae-Young Lee) 대한설비공학회 2006 대한설비공학회 학술발표대회논문집 Vol.2006 No.6

Effect of honeycomb-patterned structure on electrical and magnetic behaviors of poly(@?-caprolactone)/capped magnetic nanoparticle composite films

Kim, J.K.,Basavaraja, C.,Umashankar, M.,Huh, D.S. IPC Science and Technology Press 2016 Polymer Vol.87 No.-

Novel biocompatible poly(@?-caprolactone) (PCL) was synthesized via in situ ring-opening polymerization of @?-caprolactone under different concentrations (10, 20, and 30 wt%) of capped magnetic nanoparticles (CMPs). The prepared PCL/CMP composites were characterized using Fourier transform infrared, UV-vis spectra, and X-ray photoelectron spectroscopy to demonstrate the interaction between PCL and CMP. X-ray diffraction patterns, scanning electron microscopy with energy dispersive X-ray spectroscopy, and thermogravimetric analysis were used to understand the structural nature and thermal stability of the polymer composites. Honeycomb-patterned thin films were fabricated by casting the composite solutions under humid conditions. The I-V characteristics and magnetic behavior of the honeycomb-patterned films were observed and compared with those of the flat thin composite films. The honeycomb-patterned PCL/CMP composite films revealed higher conductivity than the flat films and showed a hysteresis loop in the magnetization plotted against the applied magnetic field for magnetic behavior.

Silicon TFTs at the Dawn of FPD Technology

Setsuo Usui 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.1

This article reviews the research and development of crystalline Si films of early days (1980s∼) conducted in laboratories. Thin film transistors (TFTs) for large-area devices, such as contact-type image sensors and flat panel displays, were extensively investigated using ZMR (zone melting recrystallization) or Ar-ion laser annealing. In search of SOI (silicon on insulator) on glass substrates, the excimer laser annealing method was introduced to manufacture LTPS (low temperature poly-Si) TFTs on low-cost glass substrates and TFTs with good characteristics emerged as a result of using LTPS. This technology still has many problems and issues, but is pushed forward aiming at the realization of LTSS (low temperature single-crystalline silicon) films.

비정질 셀레늄을 이용한 평판 Digital X선 검출기 개발

박지군,최장용,강상식,차병열,장기원,최준영,남상희,Park, J.K.,Choi, J.Y.,Kang, S.S.,Cha, B.Y.,Jang, G.W.,Choi, J.Y.,Nam, S.H. 대한디지털의료영상학회 2003 대한디지털영상기술학회지 Vol.6 No.1

Flat-panel detector(FPD) is the driving force for realizing the next gene ration of x-ray system. In this study, we developed amorphous selenium(a-Se) based flat-panel digital X-ray detector(DXD) for radiography. The prototype detector consists of an amorphous selenium layer and a thin-film transistor(TFT) array. Comparing to other papers1)-4), optimization of amorphous selenium and progress of evaporation were similar. The pixel pitch of fabricated detector was $139{\mu}m$, fill factor was 86%, and the size was 14"${\times}$8.5". Hand and test bar pattern images were acquired. A high modulation transfer function(MTF) factor was obtained: 58% at 3.0 lp/mm. 평판 digital x-선 검출기는 차세대 x-ray system으로 최근 연구와 개발이 활발하게 진행되고 있는 system이다. 본 연구는 환자의 피폭 및 작업 종사자의 피폭을 최소화 할 수 있고 의료장비의 디지털화에 발맞추어 PACS 등에 사용 가능한 a-Se을 이용한 직접방식의 digital x-선 검출기 구현에 관한 것이다. Prototype digital x-선 검출기는 TFT층과 a-Se층으로 이루어져 있다. Digital x-선 검출기센서 증착과 정의 최적화 수행 결과를 참고문헌1)-4)과 비교했을 때 매우 유사함을 확인하였다. 제작된 검출기의 pixel pitch는 $139{\mu}m$였고, fill factor는 86%, 전체 검출기의 검출면적은 14"${\times}$8.5"였다. Digital 영상의 해상력을 고려하기 위해 손과 test 패턴영상을 얻었고, 58%, 3.0lp/mm의 높은 MTF를 얻을 수가 있었다. 이러한 결과로 a-Se 기반의 Digital X선 검출기가 구현되었으며 본 연구결과를 토대로 향후 digital X선 검출기 개발기술의 발전과 성능향상을 가져올 것으로 기대된다.

비정질 셀레늄을 이용한 평판 Digital X선 검출기 개발

남상희,문치웅,이형원,김재형 인제대학교 백병원 2002 仁濟醫學 Vol.23 No.1S

Flat-panel detector(FPD) is the driving force for realizing the next generation of x-ray system. In this study, we developed amorphous selenium(a-Se) based flat-panel digital X-ray detector(DXD) for radiography. The prototype detector consists of an amorphous selenium layer and a thin-film transistor(TFT) array. Comparing to other papers, optimization of amorphous selenium and progress of evaporation were similar. The pixel pitch of fabricated detector was 139㎛. fill factor was 86%, and the size was 14"×8.5". Hand and test bar pattern images were acquired. A high modulation transfer function(MTF) factor was obtained: 58% at 3.01p/㎜.

Investigation of Wafer Warpage Induced by Multi-layer Films

Byung-Wook Nam,Jea-Gun Park 대한전자공학회 2018 Journal of semiconductor technology and science Vol.18 No.1

Oxide/poly-Si films were repeatedly grown on one side of 300 mm silicon wafers to induce bending, the extent of which was quantified by warp and bow changes. Bending was affected by crystal properties, wafer shape, and local stress, as well as by oxide layer thickness and heat treatment temperature, being less pronounced for wafers with high boron and oxygen impurity concentrations and those with low initial warp, especially, in the case of negative (concave shape) initial bow. Additionally, we investigated the effect of wire-saw cut bending on site flatness and demonstrated that local area damage such as soft laser marking induced a sudden deterioration of edge flatness.