• JSTS:Journal of Semiconductor Technology and Science
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• 제16권6호
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• pp.800-807
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• 2016

We propose a fast algorithm using Extreme Contour Point (ECP) to detect the angle of rotated images, is implemented by rotation feature of one covered frame image that can be applied to correct the rotated images like in image processing for real time applications, while CORDIC is inefficient to calculate various points like high definition image since it is only possible to detect rotated angle between one point and the other point. The two advantages of this algorithm, namely compatibility to images in preprocessing by using Sobel edge process for pattern recognition. While the other one is its simplicity for rotated angle detection with cyclic shift of two $1{\times}n$ matrix set without complexity in calculation compared with CORDIC algorithm. In ECP, the edge features of the sample image of gray scale were determined using the Sobel Edge Process. Then, it was subjected to binary code conversion of 0 or 1 with circular boundary to constitute the rotation in invariant conditions. The results were extracted to extreme points of the binary image. Its components expressed not just only the features of angle ${\theta}$ but also the square of radius $r^2$ from the origin of the image. The detected angle of this algorithm is limited only to an angle below 10 degrees but it is appropriate for real time application because it can process a 200 degree with an assumption 20 frames per second. ECP algorithm has an O ($n^2$) in Big O notation that improves the execution time about 7 times the performance if CORDIC algorithm is used.

• Wind and Structures
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• 제30권2호
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• pp.165-180
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• 2020

To determine tornadic wind loads, the wind pressure, forces and moments induced by tornadoes on civil structures have been studied. However, in most previous studies, only the individual building of interest was included in the wind field, which may be suitable to simulate the case where a tornado strikes rural areas. The statistical data has indicated that tornadoes induce more significant fatalities and property loss when they attack densely populated areas. To simulate this case, all buildings in the community of interest should be included in the wind field. However, this has been rarely studied. To bridge this research gap, this study will systematically investigate the influence of a community of buildings on tornadic wind fields by modeling all buildings in the community into the wind field (designated as "the Community case under tornadic winds"). For comparison, the case in which only a single building is included in the tornadic wind field (designated as "the Single-building case under tornadic winds") and the case where a community of buildings are included in the equivalent straight-line wind field (designated as "the Community case under straight-line winds") are also simulated. The results demonstrate that the presence of a number of buildings completely destroys the pattern of regular circular strips in the distribution of tangential velocity and pressure on horizontal planes. Above the roof height, the maximum tangential velocity is lower in the Community case under tornadic winds than that in the Single-building case under tornadic winds because of the higher surface friction in the Community case; below the roof height, greater tangential velocity and pressure are observed in the Community case under tornadic wind fields, and more unfavorable conditions are observed in the Community case under tornadic winds than under the equivalent straight-line winds.

• Journal of Mechanical Science and Technology
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• 제20권5호
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• pp.710-716
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• 2006

Micro-PIV system with a high speed CCD camera is used to measure the flow field near the advancing meniscus of a water slug in microchannels. Image shifting technique combined with meniscus detecting technique is proposed to measure the relative velocity of the liquid near the meniscus in a moving reference frame. The proposed method is applied to an advancing front of a slug in microchannels with rectangular cross section. In the case of hydrophilic channel, strong flow from the center to the side wall along the meniscus occurs, while in the case of the hydrophobic channel, the fluid flows in the opposite direction. Further, the velocity near the side wall is higher than the center region velocity, exhibiting the characteristics of a strong shear-driven flow. This phenomenon is explained to be due to the existence of small gaps between the slug and the channel wall at each capillary corner so that the gas flows through the gaps inducing high shear on the slug surface. Simulation of the shape of a static droplet inside a cubic cell obtained by using the Surface Evolver program is supportive of the existence of the gap at the rectangular capillary corners. The flow fields in the circular capillary, in which no such gap exists, are also measured. The results show that a similar flow pattern to that of the hydrophilic rectangular capillary (i.e., center-to-wall flow) is always exhibited regardless of the wettability of the channel wall, which is also indicative of the validity of the above-mentioned assertion.

• 대한기계학회논문집B
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• 제21권8호
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• pp.1009-1023
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• 1997

The breakup length of a liquid jet with flowrate, formed by releasing through a nozzle of circular cross-section into the atmosphere, was experimented and studied for 3 liquid nozzles of varying diameters. The experimental result was analyzed using the existing theoretical equation for predicting the breakup length. It was found that the breakup length of liquid jet depends on the velocity, and the breakup length increases with increasing of the liquid nozzle diameter. Also, the variation range of the breakup length for the same flowrate of liquid increased rapidly as velocity was increased for laminar flow, but in the turbulent flow region, it leveled off in the range of approximately 0.55-0.7 of the mean breakup length. Furthermore, when the longest smooth liquid jet was applied to the co-axial flow air blast atomizer, the effect of air flow on the flow pattern and breakup length was studied for 6 glass nozzles of different lengths and diameters. It was found that depending on the diameter of the mixing tube and liquid jet, it was possible to observe a wide range of flow patterns, such as liquid jet through flow, partial annular flow and annular flow. The liquid jet breakup length was more sensitive to the change in the length rather than the diameter of the mixing tube. As the length of the mixing tube shortens, the breakup length also shortens rapidly.

• Applied Microscopy
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• 제40권3호
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• pp.147-154
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• 2010

본 연구에서는 광학 및 전자현미경 관찰과 전자현미분석을 수행하여 쥐 치아의 미세구조, 화학 조성 및 hydroxyapatite의 결정구조를 파악하였다. 치아의 겉 표면을 둘러싸고 있는 법랑질은 막대들이 일정하게 배열된 구조이며 결정도가 높고 Ca이 많이 침착되어 있다. 그에 비해 상아질은 상아세관이 통과하는 원형의 구멍이 고루 분포되어 있는 스펀지 구조이며 유기질의 존재로 인해 Mg의 분포가 법랑질에 비해 상대적으로 높게 나타났다. Hydroxyapatite 결정들은 법랑질에서는 크기가 큰 막대 형태로 나타났으나 상아질에서는 크기가 작은 침상 형태로 나타났으며, 각 조직의 결정도와 유기질의 유무에 따라 전자회절패턴의 차이를 보였다.

• 한국통신학회논문지
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• 제25권5A호
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• pp.696-701
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• 2000

마이크로파 통신하는 여러 응용 장치들에서 송, 수신 장치들 사이의 전파경로에 따라 수신아테나에 수신되는 전압이 달라진다. 교통제어를 목적으로 하는 ETC(Electronic Toll Collection)시스템은 고속도로의 자동요금징수시스템으로 노변장치(Beacon)와 차량 탑재장치(On Board Unit) 등으로 구성되며 이 장치들 사이의 전파경로는 다중 경로이다. 따라서 수신안테나의 전압은 거리에 따라서 그 키기가 크게 감소되는 페이딩 현상이 발생된다. 본 연구에서는 모델화된 ETC 시스템의 전파 다중경로를 사용하여 주파수변화에 따른 효과, 환경 변화, 편파, 및 안테나 방사패턴 등의 영향들을 고려하여 페이딩 현성이 최소로 되는 조건을 구하였다. 분석결과, 강우 시 수직 편파의 경우 페이딩 효과가 크게 감소되며 일반적으로 원형 편파일 경우 페이딩 효과가 비교적 적었다. 큰 방향성의 안테나를 사용하면 근거리에서 페이딩 효과가 감소하였다. 공간과 주파수 다이버시티 기술을 적용하면 페이딩에 의한 영향을 감소시킬 수 있었다. 이러한 결과들을 차량 탑재장치에서 수신된 전압의 크기(dB)와 노변장치와 차량 사이거리로 도시하였으며 실험에 의한 결\ulcorner와 비교 검토하였다.

• 터널과지하공간
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• 제11권3호
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• pp.248-256
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• 2001

실린더 컷은 터널 굴착단면의 크기에 관계없이 널리 이용된다. 본 연구에서는 발파당 굴진장을 중대시키기 위하여 종래의 방법과 다른 새로운 방법을 제안하였다. 이 방법의 새로운 패턴은 그림과 같으며, 각 단계별로 상세한 저항선, 공간간격은 별도 그림과 같다. 새로운 실린더 컷 방법과 종래의 방법과의 결과는 다음과 같다. 종래 방법은 굴진장이 천공장의 90∼95%인데 비하여 새로운 방법은 대체로 99.5%이다. 비장약량이 1.363kg/㎥에서 1.297로 약 5% 감소되며, 비천공장이 2.393 m/㎥에서 2.130으로 약 8%o감소 된다. 그밖에 지반진동, 비산, 파쇄암의 크기 등이 종래 방법에 비하여 우수함을 확인하였다.

• 터널과지하공간
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• 제9권1호
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• pp.27-35
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• 1999

아치형 공동의 열원 경계에 대한 열전도 특성은 반무한평면이나 원형공동에 대한 열전도 특성과는 다른 양상을 나타낸다. 본 연구에서는 지하 냉동저장 pilot plant 의 운영을 통하여 계측된 저장공동 주위안반내 온도분포패턴의 분석을 통하여 아치형 공동의 열원 경계를 갖는 새로운 열전도식을 유도하였다. 계측된 암반온도 분포패턴은 선형적 변화와 로그함수적 변화의 중간적인 양상을 보였다. 열전파에 미치는 열물성 변수들의 영향도 분석 및 도출된 열전도식과 현장계측에 의한 암반온도 분포양상의 비교를 통하여 암반의 열물성을 추정하였다. 추정된 암반의 열전도도와 비열은 실내시험에 의한 무결 암석의 열물성과 비교해 20~25%의 차이를 보였다. 이는 암반내의 절리와 지하수의 영향에 기인한 것으로 판단되는데, 앞으로 현지암반에 대한 이들 영향요소의 조사와 열물성의 측정 및 비교분석을 통하여 정량적인 상관관계의 규명이 이루어져야 할 것이다.

• 한국수산과학회지
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• 제14권4호
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• pp.265-268
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• 1981

길이 250cm, 간격 10cm의 25개의 수동계 직선배열 hydrophone을 0, $\pm1$의 거형파 weighting을 부가하여 신호와 weighting과의 convolution을 구하고 이것을 동기가산하는 방법으로 얻는 방향검출과 spectrum분석은 그 실현방법을 증대시키고 정현파 weighting을 부가하는 것보다 3dB정 도 낮으나 지향성을 준 방향보다 타방향의 spectrum성분의 Power level을 적어도 16dB 정도 이상 억제할 수가 있었다. 또 신호까지 0, $\pm1$의 거형파로 바꾸는 경우는 전술한 성분을 적어도 8 dB 이상 억제할 수 있었다.

• Journal of Periodontal and Implant Science
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• 제39권2호
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• pp.167-176
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• 2009

Purpose: The purpose of this study is to histologically and histomorphometrically evaluate the effect of PLGA on bone regeneration compared with bone graft material. Methods: The experimental study was conducted in 10 rabbits with 2 different healing periods of 2 and 4 weeks. Following surgical exposure of the calvarium, 4 circular bone defects with a diameter of 4.6mm were formed. Rabbits were divided into control group, test groups I, and II. 10 defects assigned to the test group Ⅰ were grafted with Nu-oss and other 10 defects assigned to the test group II were grafted with PLGA. The rest of the defects were in the negative control group. At 2nd and 4th week after surgery, 10 rabbits were sacrificed through intracardiac perfusion and then specimens were obtained. Histological analysis was performed following staining with trichorme and transversal sectioning of the calvarial bone. Results: A group which used PLGA showed tissue reactions characterized by severe inflammation, rather than distinctive new bone formation. Conclusions: The present experimental investigations have failed to prove any beneficial effects of PLGA. PLGA used in this study exhibited foreign body reactions and a less favorable pattern of new bone formation in comparison to control group. Conclusion: PLGA did not function as scaffold. Further investigations of many types of micro PLGA that could improve its potential in GBR procedures are needed.