• 한국가시화정보학회지
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• 제6권1호
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• pp.53-58
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• 2008

We carried out the experiments which controled the periodic jet in front of the fence to alter the fence wake. The experiments were performed in circulating water channel and the vertical fence was submerged in the boundary layer. The frequency, jet nozzle distance and speed of jet passing the slit were investigated. Each case divided into 20 phases and phase-averaged results were compared with uncontrolled fence flow. From the results, we found the specific frequency and nozzle distance which were good for reducing the reattachment length. In this case, the reattachment length was decreased 35% compared with the uncontrolled fence flow.

• Applied Microscopy
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• 제17권1호
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• pp.47-64
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• 1987

Morphological difference of the renal glomerulus at different age groups have been studied in young (three month-old), adult (twelve month-old) and old (thirty month-old) Fisher strain 344 rats. Pieces of the tissues were taken from renal corticies prefixed with 2.5% glutaraldehyde-1.5% paraformaldehyde (0.1 M Millonig's phosphate buffer, pH 7.3), following by post-fixation with 1% osmium tetroxide (0.1 M Millonig's phosphate buffer, pH 7.3) and embedded within Araldite. The ultrathin sections contrasted with uranyl acetate and lead citrate were observed under a JEM 100CX electron microscope. The mean thickness of glomerular basal lamina and Bowman's capsule were determined by measuring the thinnest portion of basal lamina, and by taking the average of 50 readings from electron micrographs at different ages. The numerical changes of the slit pores were compared based upon the numbers over the length of 10um of glomerular basal lamina. The results were as follow: 1. The thickness of glomerular basal lamina is increased during aging; 140.4 nm in young rats, 270.0 nm in adult ones, and 437.8 nm in old ones. 2. The thickness of basal lamina of parietal cells of Bowman's capsule is 187.5 nm in young rats, 914.0 nm in adult ones, and 2850.0 nm in old ones. 3. The numbers of the slit pores of basal lamina are reduced during aging, 30.3 slit pores/$10{\mu}m$ in adult ones, and 24.2 slit pores/$10{\mu}m$ in old ones. 4. Accumulation of dense intracytoplasmic filamentous material in the parietal cells of Bowman's capsule is increased in the vicinity of the basal lamina during aging. The proximal tubule-like epithelial cell in Bowman's capsule is observed at one glomerulus in a young rat. 5. The endothelial cells are edematous and form balloon-like structure protruding into capillary lumen in young and old rats. 6. Cytoplasm of the podocyte shows a variety of alteration during aging, such as swelling of mitochondria and of endoplasmic reticulum, and increase of microtubules, microfilaments, lysosomes and lamellated myelin structures, etc. Accumulation of dense intracytoplasmic material in the foot processes is increased in the vicinity of the basal lamina during aging. The podocytic membrane-like structures are seen in young and o]d rats. 7. The mesangial matrices and mesangial cells are increased during aging, and slight swelling of endoplasmic reticulum and Golgi cisternae in young and old rats.

• 대한기계학회논문집
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• 제18권2호
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• pp.446-455
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• 1994

An experimental study is conducted for the turbulent recirculating flow behind a backward-facing step when the oscillating jet is issued sinusoidally through a thin slit at the separation edge. Two key parameters are dealt with in the present experiment, i.e., the amplitude of forcing and the forcing frequency. The Reynolds number based on the step height is varied from 25,000 to 35,000. In order to investigate the effect of local forcing, turbulent structures are scrutinized for both the flow of forcing and the flow of no forcing. The growth of shear layer with a local forcing is larger than that of no forcing. The influence of a local forcing brings forth the decrease of reattachment length and the particular frequency gives a minimum reattachment length. The most effective frequency depends on the non-dimensional frequency, St/sub .theta./, based on the momentum thickness at the separation point. A comparative study leads to the conclusion that the large-scale vortical structure is strongly associated with the forcing frequency and the natural flow instability.

• 대한기계학회논문집B
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• 제26권3호
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• pp.423-431
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• 2002

An experimental study is conducted to investigate the effect of two-frequency forcing on turbulent flow behind a backward-facing step at the Reynolds number of 27000 based on the step height. The forcing is provided from a thin slit located at the edge of the backward-facing step to increase mixing behind the backward-facing step and consequently to reduce the reattachment length. With single frequency forcing, the minimum reattachment length is obtained at the non-dimensional forcing frequency (F) of St$\_$h/ = 0.29. With two-frequency forcing, a subharmonic frequency (F/2) or biharmonic frequency (2F) is combined with the fundamental frequency (F), i.e. (F, F/2) or (F, 2F) forcing is applied. In the case of (F, F/2) forcing, the reattachment length is not much sensitive to the phase difference between F and F/2. However, the reattachment length significantly depends on the phase difference between F and 2F in the case of (F, 2F) forcing. At a certain range of the phase difference, the reattachment length becomes smaller than that of the single frequency forcing.

• 대한전자공학회논문지SP
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• 제41권3호
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• pp.139-146
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• 2004

본 논문에서는 솔더페이스트의 이차원 및 삼차원 자동검사를 함께 할 수 있는 복합 검사 광학계와 그 구동유닛을 단일 프로브 시스템으로 구현하고, 그를 위한 효과적인 비젼검사 알고리즘을 제안하였다. 솔더페이스트의 이차원 검사에는 One-pass Run Length 레이블링 알고리즘을 제안하여 입력 영상으로부터 솔더 페이스트 형상을 효과적으로 추출하도록 하였고, 고속 검사를 위한 프로브의 최적 이동 경로도 구하였으며, 삼차원 검사에는 기존의 레이져 슬릿빔(slit-beam) 방식 대신 격자 투영식 모아레 간섭계에 기반한 위상이동 알고리즘을 도입하여 고정밀 검사가 가능토록 하였다. 전체 소프트웨어 구현에는 MMX 병렬처리기법도 적용함으로써 더욱 고속화 하였다. 10㎜×10㎜의 단위 측정영역(field of view: FOV)에 대하여 x, y 축으로 10㎛ Z축으로 l ㎛의 분해능을 가지는 이차원 및 삼차원 복합 광학 검사 시스템을 제작하여 실험한 결과, 한 FOV에 대한 솔더페이스트의 이차원 및 삼차원 검사를 영상포착 후 각각 평균 11msec와 15msec의 짧은 시간에 처리할 수 있었고, ±1㎛의 두께 측정 정밀도를 얻을 수 있었다.

• 한국의류학회지
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• 제27권12호
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• pp.1390-1396
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• 2003

본 연구는 타이트 스커트의 트임의 개수가 왼쪽 옆선에 1개 있을 때와 왼쪽 옆선, 오른쪽 옆선에 각각 1개씩 모두 2개 있을 때 평지 보행, 계단 승강, 버스 승강 등과 같은 일상동작에 잘 적응할 수 있는 타이트 스커트의 적정 트임 길이를 설정하는 것을 목표로 하였다. 아울러 각 동작시의 트임 길이에 따른 생리적인 반응을 의복압, 산소 섭취량을 통해 알아보고자 하였다. 평균보폭은 4m 구간을 평상시대로 걸을 때의 발자국간 평균거리를 이용하였으며 국민표준체위조사보고서(1997)에 의한 평균체형을 가진 9명의 피험자를 정하였다. 스커트의 형태는 무릎길이인 타이트 스커트로 정하였다. 스커트의 트임은 왼쪽 옆선에 1개 있는 경우와 왼쪽 옆선, 오른쪽 옆선에 각각 1개씩 있는 경우의 2종류이다. 트임이 1개인 스커트는 2cm 간격으로, 트임이 2개인 스커트는 1cm 간격으로 트임 위치를 표시하여 길이를 조정하였다. 적정 트임 길이는 Likert 척도에 의한 만족도 평가로 측정하였으며 의복압은 air-bag system으로, 산소 섭취량은 Quark $B^2$ 으로 측정하였다. 본 연구의 결과는 다음과 같다. 1. 스커트의 최소 적정 트임 길이는 트임 1개일 때 평지 보행시 4cm, 계단 승강시 12cm ,버스 승강시 18cm이며, 트임 2개일 때 평지 보행시 2cm, 계단 승강시 8cm, 버스 승강시 15cm로 나타났다. 2. 의복압의 경우, 동일 트임 길이에서 트임 1개의 의복압이 트임 2개의 의복압보다 높았지만 트임 개수에 따른 전체 트임 길이로 보면 트임 1개의 의복압이 트임 2개의 의복압 보다 낮게 나타났다. 동작별로는 버스 승강의 의복압이 가장 높고 계단 승강, 평지 보행 순으로 낮아졌다. 3. 산소 섭취량의 경우, 동일 트임 길이에서 트임 1개와 트임 2개의 산소 섭취량은 거의 비슷하였다. 트임 개수에 따른 전체 트임 길이로 보면 트임 1개의 산소 섭취량이 트임 2개의 산소 섭취량보다 낮게 나타났다. 동작별로는 버스 승강의 산소 섭취량이 가장 높고 계단 승강, 평지 보행 순으로 낮아졌다.

• ALGAE
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• 제25권4호
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• pp.173-182
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• 2010

Four Rhizosolenia species of marine diatom were appeared at 30 sites in Korean coastal waters from September 2008 to February 2010. The cell shape, diameter, length of pervalvar axis, external process, segment and areolation characters of the species were examined. All four species were cylindrically shaped, but the external processes differed. Segment striations were regularly straight, and velum showed hexagonal, circular pore and narrow slit. Rhizosolenia formosa and R. hyalina were only occurred in September 2008 from the Yellow Sea, R. bergonii was appeared throughout the year from Korea Strait and Yangyang coasts, and R. setigera was abundantly showed in all seasons from all site. R. formosa is a newly recorded species in Korean coastal waters.

• Steel and Composite Structures
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• 제28권4호
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• pp.495-508
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• 2018

In this paper, the effect of matrix cracks on the buckling of a hybrid laminated plate is investigated. The plate is composed of carbon nanotube reinforced functionally graded (CNTR-FG) layers and conventional fiber reinforced composite (FRC) layers. Different distributions of single walled carbon nanotubes (SWCNTs) through the thickness of layers are considered. The cracks are modeled as aligned slit cracks across the ply thickness and transverse to the laminate plane, and the distribution of cracks is assumed statistically homogeneous corresponding to an average crack density. The first-order shear deformation theory (FSDT) is employed to incorporate the effects of rotary inertia and transverse shear deformation, and the meshless kp-Ritz method is used to obtain the buckling solutions. Detailed parametric studies are conducted to investigate the effects of matrix crack density, CNTs distributions, CNT volume fraction, plate aspect ratio and plate length-to-thickness ratio, boundary conditions and number of layers on buckling behaviors of hybrid laminated plates containing CNTR-FG layers.

• Animal Systematics, Evolution and Diversity
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• 제28권4호
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• pp.308-311
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• 2012

A single specimen (134.3 mm standard length) of a snailfish, Careproctus notosaikaiensis was collected from a fish trap in Goseong-gun, Gangwon-do, East Sea, Korea. It is characterized by having the teeth strongly trilobed; dorsal fin rays 52; anal fin rays 47; pectoral fin rays 35; caudal fin rays 10; vertebrae 58; ribs 2 pairs; cephalic pores, 2-6-7-2; gill slit extending to the fifth pectoral fin ray; chin pores paired and equal in size; dorsal and anal fins with distinct reddish margins. We describe this species as the first record to Korea, and proposed the new Korean name, "Dong-hae-bun-hong-ggom-chi" for this species.

• 천문학회지
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• 제4권1호
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• pp.9-16
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• 1971

The asymmetry of received intensity pattern within the bandwidth is derived from the analogy of the intensity distribution of two-slit interference. This suggests that the length of $\frac{1}{2}{\lambda}$ delay line should be adjusted to the slightly upper frequency than the central frequency of the radio telescope with a wide bandwith. Some strange communication signals and man-made noises prevented us from obtaining the discernible information from the observed data for the sun. To overcome this difficulties, it is necessary to alter the operating frequency and site. It will be fo1lowed to measure the angular dimensions of the superposed radio sources by changing the distance between two antennas.