• Advances in robotics research
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• 제2권2호
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• pp.141-149
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• 2018

In image processing and robotic applications, two-dimensional (2D) black and white patterned planar markers are widely used. However, these markers are not detectable in low visibility environment and they are not changeable. This research proposes an active and adaptive marker node, which displays 2D marker patterns using light emitting diode (LED) arrays for easier recognition in the foggy or turbid underwater environments. Because each node is made to blink at a different frequency, active LED marker nodes were distinguishable from each other from a long distance without increasing the size of the marker. We expect that the proposed system can be used in various harsh conditions where the conventional marker systems are not applicable because of low visibility issues. The proposed system is still compatible with the conventional marker as the displayed patterns are identical.

• 제어로봇시스템학회논문지
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• 제15권4호
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• pp.353-364
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• 2009

In this paper, a SLAM (Simultaneous Localization and Mapping) method using a single camera and planar fiducial markers is proposed. Fiducial markers are planar patterns that are mounted on the ceiling or wall. Each fiducial marker has a unique hi-tonal identification pattern with square outlines. It can be printed on paper to reduce cost or it can be painted using retro-reflective paint in order to make invisible and prevent undesirable visual effects. Existing localization methods using artificial landmarks have the disadvantage that landmark locations must be known a priori. In contrast, the proposed method can build a map and estimate robot location even if landmark locations are not known a priori. Hence, it reduces installation time and setup cost. The proposed method works good even when only one fiducial marker is seen at a scene. We perform computer simulation to evaluate proposed method.

• 한국정밀공학회지
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• 제32권2호
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• pp.191-198
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• 2015

In this paper, six-degree-of-freedom (DoF). Displacement measurement technique using a compact stereo-vision system is proposed. The measuring system consists of a camera, an optical prism, two plane mirrors, and a planar marker on a target. The target was attached on an object so that its six-DoF displacement can be calculated using a proposed coordinates estimating algorithm and stereo images of the marker. A prototype was designed and fabricated for performance test. From the test results, it can be confirmed that the proposed measuring technique can be applied to monitoring and control of various manipulators.

• 한국콘텐츠학회논문지
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• 제10권5호
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• pp.20-28
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• 2010

본 논문에서는 증강현실 환경에서 등장하는 3차원 공간상의 객체를 카메라와 손을 사용하여 조작할 수 있는 인터페이스를 제안한다. 일반적으로 3차원 움직임을 검출하기 위해서 마커를 사용하지만, 이러한 경우에는 객체를 등록하기 위해서 마커가 영상 내에 있어야 하며 추가적인 장비를 사용함으로서 몰입감의 저하를 초래한다. 이것을 극복하기 위해서 본 연구에서는 손을 하나의 평면으로 변환하고 손 모양의 변화를 검출하여 마커를 대체하는 방법을 제안한다. 또한 조명으로 인한 손의 색상 변화에 따른 객체의 등록 위치 변화를 칼만 필터를 적용하여 추적하였다. 실험결과, 제안한 알고리즘은 손의 원활한 움직임에 의한 객체의 3차원 조작이 가능함을 보였다.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제16권11호
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• pp.1131-1135
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• 2010

본 논문에서는 고정시킨 평면거울을 바라보는 단일 카메라에서 얻어진 영상을 이용하여 훈련자 양 하지의 자세를 3차원으로 추정하는 방법을 제안한다. 이를 위해, 카메라 입력영상으로부터 평면거울에 부착된 네 개의 적외선 마커를 탐색하여 단일 카메라의 자세를 추정한다. 추정된 카메라 자세를 통해 거울평면을 기준으로 하는 훈련공간을 정의하고, 압력 센서를 사용하여 공간 내의 훈련자의 양 하지 위치를 측정한다. 양 하지의 마커는 직접적으로, 또는 거울을 통해 카메라 영상으로 투영되고, 정의된 훈련 공간에서 3차원 위치로 변환된다. 변환된 마커들의 3차원 위치관계에 의해 최종적으로 양 하지의 자세를 얻고 연속적인 움직임에 대해 운동 상태를 추정한다.

• Smart Structures and Systems
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• 제20권4호
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• pp.397-413
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• 2017

Precast concrete (PC) members are currently being employed for general construction or partial replacement to reduce construction period. As assembly work in PC construction requires connecting PC members accurately, measuring the 6-DOF (degree of freedom) relative displacement is essential. Multiple planar markers and camera-based displacement measurement systems can monitor the 6-DOF relative displacement of PC members. Conventional methods, such as direct linear transformation (DLT) for homography estimation, which are applied to calculate the 6-DOF relative displacement between the camera and marker, have several major problems. One of the problems is that when the marker is partially hidden, the DLT method cannot be applied to calculate the 6-DOF relative displacement. In addition, when the images of markers are blurred, error increases with the DLT method which is employed for its estimation. To solve these problems, a hybrid method, which combines the advantages of the DLT and MCL (Monte Carlo localization) methods, is proposed. The method evaluates the 6-DOF relative displacement more accurately compared to when either the DLT or MCL is used alone. Each subsystem captures an image of a marker and extracts its subpixel coordinates, and then the data are transferred to a main system via a wireless communication network. In the main system, the data from each subsystem are used for 3D visualization. Thereafter, the real-time movements of the PC members are displayed on a tablet PC. To prove the feasibility, the hybrid method is compared with the DLT method and MCL in real experiments.

• 한국산학기술학회논문지
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• 제15권9호
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• pp.5854-5860
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• 2014

본 연구에서는 대표적인 토목구조물인 교량에서 영상 기반 변위 계측장치(VDMS)를 이용하여 변위를 측정하고, 고가의 변위측정장비인 LDV와의 비교를 통하여 그 현장 적용 성능을 평가하였다. 본 연구에서 사용한 VDMS는 카메라와 마커, 프레임 그래버, 노트북으로 구성되었으며, 마커를 구조물에 부착하여 그 영상을 촬영하고 평면 호모그래피 기법을 이용하여 마커가 부착된 구조물의 변위를 측정하는 장치이다. 개발된 VDMS의 성능 검증을 위하여 우선 소형 구조물을 이용한 간단한 실내 실험을 수행하였다. 다음으로 실제 철도교량에서 KTX를 다양한 조건으로 주행하고, 그에 의하여 발생한 변위를 VDMS과 LDV를 이용하여 계측한 뒤, 얻어진 두 변위를 비교하여 VDMS의 현장 적용 성능을 평가하였다.

• 대한전자공학회논문지SP
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• 제48권4호
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• pp.49-58
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• 2011

일반적으로 사용되는 마커 기반의 증강현실 시스템은 카메라 입력영상 내에 마커가 항상 존재해야 한다는 제한 때문에 사용자의 접근에 불편을 준다. 때문에 최근 배경 영상에서 취득할 수 있는 객체를 자연 마커로 생성한 시스템이나 배경 영상의 특징을 이용해 기하학적 지도를 작성하여 가상의 객체 정합에 이용한 증강현실 시스템들이 관심을 끌고 있다. 본 논문에서는 카메라 입력 영상에서 동일 평면상에 존재하는 특징들을 검출하고, 이를 추적함으로써 카메라 위치 정보를 추정하는 증강현실 시스템을 제안한다. 또한 특징점 추적에 사용된 추적 방법은 카메라에서 취득한 영상 밖으로 특징점이 벗어날 경우 더 이상 추적할 수 없는 문제점을 가지고 있어, 이를 보완하기 위해 새로운 특징점을 재검출하여 객체의 정합을 유지하는 방법도 제시한다. 제안된 방법은 미리 지정된 마커를 사용하지 않기 때문에 사용자의 접근이 편리하고, 특정한 형태의 마커를 사용하지 않는 다른 시스템보다 비교적 간단하게 구현할 수 있어 다양한 모바일 환경에서 유용하게 이용될 수 있다.

• 대한핵의학회지
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• 제27권2호
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• pp.218-222
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• 1993

Lung/heart uptake ratio (L/H R) in $^{201}Tl$ myocardial perfusion scan is a reliable marker for long-term prognosis in patients with coronary artery disease. However, the value of L/H R in $^{99m}Tc-MIBI$ myocardial perfusion scan is controversial in determining the prognosis and severity of the coronary artery disease. The purpose of this study was to determine the clinical implications of L/H R in $^{99m}Tc-MIBI$ myocardial perfusion scan. Forty five patients who received $^{99m}Tc-MIBI$ myocardial perfusion scan were divided into control group and coronary artery disease (CAD) group by their clinical findings, EKGs, and $^{99m}Tc-MIBI$ myocardial perfusion scans. Twenty five patients in CAD group were divided into ischemic group and infarct group according to their results from $^{99m}Tc-MIBI$ myocardial perfusion scan. L/H R was calculated on the anterior planar view, 60 minutes after infusion of dipyridamole. Two regions of interest (ROI) were placed on the left lung area 8 pixel above the left ventricle and on the myocardial area which had the highest radioactivity. In the control group, there were no significant differences of L/H R according to sex and age. No significant difference of L/H R was found between the control and CAD group ($0.26{\pm}0.06,\;0.29{\pm}0.05$, p>0.05). In the CAD group, there was also no significant difference of L/H R between the ischemic group and infarct group ($0.29{\pm}0.07,\;0.30{\pm}0.04$, p>0.05). L/H R in CAD group did not show correlations with the defect area of stress polar map (r=0.18, p >0.05) and with the sum of severity weighted extent score or reversibility score which represent severity and extent of myocardial perfusion defect area in stress (r=0.18, p>0.05). We conclude that it is difficult to use L/H R as a marker for severity of CAD in dipyridamole $^{99m}Tc-MIBI$ myocardial perfusion scan.

• Natural Product Sciences
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• 제26권3호
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• pp.230-235
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• 2020

A pregnane steroid, 3α-hydroxy-pregn-7-ene-6,20-dione (1), was isolated from a Hydractinia-associated Cladosporium sphaerospermum SW67 by repetitive column chromatographic separation and high-performance liquid chromatography (HPLC) purification. The planar structure of 1 was elucidated from the analysis of the spectroscopic data (1D and 2D NMR spectra) and LC-MS data. The absolute configuration of 1 was determined by interpretation of ROESY spectrum of 1, together with the comparison of reported spectroscopic values in previous studies. To the best of our knowledge, this is the first report of the identification of the pregnane scaffold from C. sphaerospermum, a natural source. Compound 1 was evaluated for its effects on lipid metabolism and adipogenesis during adipocyte maturation and showed that compound 1 substantially inhibited lipid accumulation compared to the control. Consistently, the expression of the adipocyte marker gene (Adipsin) was reduced upon incubation with 1. Further, we evaluated the effects of 1 on lipid metabolism by measuring the transcription of lipolytic and lipogenic genes. The expression of the lipolytic gene ATGL was significantly elevated upon exposure to 1 during adipogenesis, whereas the expression of lipogenic genes FASN and SREBP1 was significantly reduced upon treatment with 1. Thus, our findings provide experimental evidence that the steroid derived from Hydractinia-associated C. sphaerospermum SW67 is a potential therapeutic agent for obesity.