• 대한기계학회논문집A
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• 제39권12호
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• pp.1245-1249
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• 2015

본 연구에서는 나노스케일 박막의 표면주름 형성에 의한 산란반사도 향상을 평가하였다. 실리콘 기판 위에 120 nm 두께의 Poly(methyl metacrylate) 층을 스핀코팅(spin-coating)한 후, 20 nm 의 알루미늄 박막을 증착하여 시편을 제작하였다. 이를 오븐에서 $95^{\circ}C$의 온도로 2 시간 동안 풀림처리하여 표면주름을 형성하였다. 분광광도계로 가시광선 영역의 산란반사도를 측정한 결과 400 nm 파장에서 40%의 증가를 보였으며, 표면주름 위에 100 nm 의 은박막을 추가적으로 증착한 경우 산란반사도가 50%까지 향상되는 것을 확인하였다. 본 연구는 산란반사도의 증대를 요구하는 박막형 소자에 표면주름을 활할 수 있음을 제시한다.

• 대한기계학회논문집B
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• 제33권10호
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• pp.757-766
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• 2009

In the present study, the effect of delta-wing vortex generators(DWVG) on the local heat transfer of the plate fin-oval tube was experimentally analyzed for Reynolds numbers for 2000, 2500 and 3200. The local heat transfer coefficient of the fin surface for four type DWVGs was measured by the naphthalene sublimation technique. As the results, the distribution of the heat transfer coefficient at rear of DWVGs showed longitudinal contours for common flow down DWVGs and wavy contours for common flow up DWVGs. The distribution showed many cell type contours at near wall and downstream for all DWVGs. Compared to case without DWVGs in present experimental tests, all DWVGs showed the best enhancement of heat transfer at Re=2000. Of 4 cases of DWVGs, D type showed the best enhancement of heat transfer.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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• pp.156-156
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• 2000

Recently, the surface electronic states have attracted much attention since their standing wave patterns created around steps, defects, and adsorbates on noble metal surfaces such as Au(111), Ag(110), and Cu(111) were observed by scanning tunneling microscopy (STM). As a typical example, a striking circular pattern of "Quantum corral" observed by Crommie, Lutz, and Eigler, covers a number of text books of quantum mechanics, demonstrating a wavy nature of electrons. After the discoveries, similar standing waves patterns have been observed on other metal and demiconductor surfaces and even on a side polane of nano-tubes. With an expectation that the surface states could be utilized as one of ideal cases for studying two dimensionakl (sD) electronic system, various properties, such as mean free path / life time of the electronic states, have been characterized based on an analysis of standing wave patterns, . for the 2D electron system, electron density is one of the most importnat parameters which determines the properties on it. One advantage of conventional 2D electron system, such as the ones realized at AlGaAs/GaAs and SiO2/Si interfaces, is their controllability of the electrondensity. It can be changed and controlled by a factor of orders through an application of voltage on the gate electrode. On the other hand, changing the leectron density of the surface-state 2D electron system is not simple. On ewqy to change the electron density of the surface-state 2D electron system is not simple. One way to change the electron density is to deposit other elements on the system. it has been known that Pd(111) surface has unoccupied surface states whose energy level is just above Fermi level. Recently, we found that by depositing Pd on Cu(111) surface, occupied surface states of Cu(111) is lifted up, crossing at Fermi level around 2ML, and approaches to the intrinsic Pd surface states with a increase in thickness. Electron density occupied in the states is thus gradually reduced by Pd deposition. Park et al. also observed a change in Fermi wave number of the surface states of Cu(111) by deposition of Xe layer on it, which suggests another possible way of changing electron density. In this talk, after a brief review of recent progress in a study of standing weaves by STM, I will discuss about how the electron density can be changed and controlled and feasibility of using the surface states for a study of 2D electron system. One of the most important advantage of the surface-state 2D electron system is that one can directly and easily access to the system with a high spatial resolution by STM/AFM.y STM/AFM.

• 대한수의학회지
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• 제34권2호
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• pp.219-227
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• 1994

The development of abomasum in fetuses between 60, 90, 120 days of gestation and neonates of Korean native goats was investigated by light, scanning and transmission electron microscopy. The results obtained were summarized as follows ; 1. The abomasum wall appeared to be differentiated into the epithelium, lamina propria, muscle layer, and serosa at 60 days of gestation. The epithelium was stratified columnar and these nuclei were located near the apical two thirds portion of the cell at 60 days of gestation, and then transformed into simple columnar epithelium with the flat basal nuclei. 2. The inner circular and outer longitudinal muscle layers were observed at 90 days of gestation and the blood vessels had become quite well developed as various arterioles, venules and capillaries of different size during this age. 3. Gastric pits were seen at 90 days of gestation and continued gradually to increase depth during gestation. 4. The mucous, parietal and chief cells appeared in epithelium at 90 days of gestation and continued gradually to increase in number during gestation. In 120 days fetuses and neonates, muscle layer had become very thickeness. 5. Scanning electron microscopically, the inner surface of the abomasum already consisted of wavy spiral folds which had many fine wrinkles at 60 days of gestation. In 90 day old fetuses, each spiral fold was enlarged and its surface was tended to be split into many straight longitudinal ridges and among these ridge were found shallow grooves, At 120 days, the subdivided swellings of ridges were progressively complicated in shape. In the neonates, the inner surface was flat and holed with many gastric pits. 6. Transmission electron microscopically, the epithelium was straified columnar and these nuclei were irregular shape at 60 days fetus. The parietal, chief and mucous cells were observed in 90 day old fetuses and continued gradually to increase in number during gestation. 7. The development of the abomasum was relatively slow at early stages, it was accelerated greatly in the last of gestation.

• 패션비즈니스
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• 제11권4호
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• pp.101-110
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• 2007

Since cotton fabrics with ripple finish treatment form wavy furrows on the surface or bumpy patterns, air circulation during wearing is good and the fabric is cool to the touch. The finishing principle is based on the mercerization, which utilizes the fact that cotton fibers contract in a concentrated NaOH solution. In this study, as fabric specimens, cotton fabrics with yarn counts of 40's, 60's and 80's were used. Concentrations of the NaOH solutions were 15%, 25%, and 35%. After dyeing fabrics using Rubia akane nakai, color and other properties were measured. As the concentration of the NaOH solution increased, the fabric became thicker and denser, and the number of occurrence of the prominence and depression per unit length became larger. The color of the region contracted by ripple finish became darker after dyeing, while the color of the untreated region became lighter, which enhanced the cubic effect of the ripple finish. As the count of the cotton yarn increased, the dyeability became better. As the concentration of the NaOH solution increased, the air permeability became lower.

• Applied Microscopy
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• 제42권3호
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• pp.129-135
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• 2012

In this study, the changes in hair quality before and after Magic straight perm have been evaluated through a hair damage measurement method. For this, a healthy high school student's (age18 years) wavy hair was selected and permed on the left and right sides. Then, the changes caused by physical methods which were applied during the fl at iron-based Magic straight perm were evaluated based on the hair damage measurement method before and after the Magic straight perm. According to the protein release test after the Magic straight perm, 1.26% in average and 0.14% was observed in Cool Magic straight perm sample. In a field emission scanning electron microscopy (FE-SEM) test, saw teeth-shaped partial desquamation of cuticle cells and impurities were observed in the warm-treated hair sample. In atomic force microscope (AFM), line-profile is a method to represent roughness data on hair. According to analysis on 3-dimensional (3D) images, the hair with Cool Magic straight perm was lower than the hair with Warm Magic perm in terms of the color change of 3D images. In addition, vertical changes were observed in the hair with Cool Magic perm. As a result, irregular surface roughness was observed. This study proposed a method to minimize hair damage by cooling down the heat with the cool hair straightener as soon as the Warm Magic was finished.

• Nuclear Engineering and Technology
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• 제26권1호
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• pp.108-118
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• 1994

긴 수평관에서 공기와 물의 역성층류시 적용할 수 있는 단열계면 마찰계수에 대한 준 실험식을 개발하였다. 둥근관과 사각관으로 된 단열 역성층류 실험장치를 사용하여 물의 수위 및 공기의 속도를 변화시키면서 일련의 실험을 수행하였다. 수평으로 된 원형 및 사각형 실험관속으로 흐르는 유체의 주요 유동 변수들을 동시에 측정한 실험치들과 계면이 물결파에 의해 거칠어진다는 새로운 개념을 도입하여 성층류영역의 계면마찰 계수에 대한 준 실험식을 개발하였다. 이 해석에는 다른 연구자들의 병류실험치 15개를 포함하여 총 201개의 실험치들을 사용하였다. 이 실험치들과 여기서 제안한 준 실험식의 예측치와 비교하면 오차 범위는 $\pm$30% 정도이다.

• ETRI Journal
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• 제18권4호
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• pp.339-346
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• 1997

Good quality a-axis oriented thin films of $YBa_2Cu_3O_{7-x}$ may be grown by the use of a $PrBa_2Cu_3O_{7-x}$ (PBCO) layer as a template. Here we present a detailed study of the nucleation of the PBCO layer, explaining the orientations observed. It is determined that the wavy surface of a $LaSrGaO_4$ (LSGO) (100) substrate consists of the {101} planes by observing cross-sectional transmission electron microscopy images of the interface between the PBCO film and the substrate. The images and selected area diffraction patterns show that a mixed c-and b-axis oriented PBCO layer was initially grown on the substrate, followed by pure b-axis oriented PBCO growth. We explain that the c-axis oriented growth is the result of the growth of the PBCO (019) planes on the LSGO (101) planes. We conclude that the nucleation and growth of the PBCO films at the initial stages depends on the crystallographic plane of the substrate surfaces, however, as the film grows further, the kinetics of the deposition process favors b-axis oriented growth.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1995년도 추계학술발표회논문집(1)
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• pp.450-455
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• 1995

A three-dimensional numerical tool is developed to calculate the potential distribution, electric field, and conductance for any types of conductance probes immersed in the wavy liquid film with various shapes of its free surface. The tool is validated against various analytical solutions. It is applied to find out the characteristics of the wire-wire probe, the flush-wire probe and the flush-flush probe in terms of resolution, linearity, and sensitivity. The wire-wire probe shows high resolution and excellent linearity for various film thickness, but comparably low sensitivity for low film thickness fixed. The flush-wire probe shows good linearity and high sensitivity for varying film thickness, but resolution degrading with an increase in film thickness. In order to check the applicability of the three types of probes in the real situation, the Korteweg-de Vries(KdV) two-dimensional solitary wave is simulated. The wire-wire probe is strongly affected by the installation direction of the two wires; when the wires are installed perpendicularly to the flow direction, the wire-wire probe shows large distortion of the solitary wave. In order to measure the transverse profile of waves, the wire-wire probes and the flush-wire probes are required to be separately installed 2mm and 2mm, respectively.

• 천문학회보
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• 제43권1호
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• pp.73.1-73.1
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• 2018

We investigated shock history of three achondrite meteorites: NWA 3117, a howardite from asteroid Vesta, NWA 2727, a breccia from the Moon, and NWA 856, a shergottite from Mars. Shock histories were evaluated from deformation of plagioclase feldspars. Feldspar grains were classified based on observations in cross-polarized light as undulatory, mosaic, mosaic-recrystallized or maskelynite. This sequence represents increasing deformation of original feldspar crystals. Undulatory crystals have wavy extinction, mosaic crystals have patchy extinction, and mosaic-recrystallized grains appear as if they were originally coarse-grained and have recrystallized to mosaics of small equant crystals. Maskelynite grains are isotropic, indicating transformation to glass. Based on feldspar deformation, the degrees of impact processing are NWA 856 > NWA 3117 > NWA 2727. The high deformation of NWA 856 is expected because this sample is from Mars, which is a large parent body and requires a powerful impact to accelerate a rock to escape velocity. In contrast, the parent body of NWA 3117 (Vesta) is smaller than that of NWA 2727 (the Moon), yet NWA 3117 appears more highly deformed than NWA 2727. One possible explanation is that NWA 2727 is from a relatively young part of the Moon, which has not been exposed to impacts as long as the surface of Vesta.