• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.1738-1741
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• 1997

This paper addresses the issue fo target classification and localization with a SONAR for mobiler robot indoor navigation. In particular, multiple refetions of SONAR sound are used actively and interntionally. As for the SONAR sensor, the multiple reflection has been generally considered as one of the noisy phenomena, which is inevitable in the indoor environments. However, these multiple reflections can be a clue for classifying and localizing targets in the indoor environment if those can be controlled and used well. This paper develops a new SONAR sensor module with a reflection plane which can actively create the multiple refection. This paper also intends to suggest a new target classification emthod which uses the multiple refectiions. We approximate the world as being two dimensional and assume that the targets consisting of the indoor environment are pland, corner, and edge. Multiple reflection paths of an acoustic bean by a SONAR are analyzed, by simulations and the patterns of the TOPs (Time Of Flight) and angles of multiple reflections from each target are also analyzed. In addition, a new algorithm for target classification and localization is proposed.

• 전기학회논문지
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• 제59권6호
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• pp.1136-1142
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• 2010

In this study, an efficient removal algorithm for specular reflections in a tooth color image is proposed to minimize the artefact interrupting color image segmentation. The pixel values of RGB color channels are initially reversed to emphasize the features in reflective regions, and then those regions are automatically detected by utilizing perceptron artificial neural network model and those prominent intensities are corrected by applying a smoothing spatial filter. After correcting specular reflection regions, multiple seeds in the tooth candidates are selected to find the regional minima and MCWA(Marker-Controlled Watershed Algorithm) is applied to delineate the individual tooth region in a CCD tooth color image. Therefore, the accuracy in segmentation for separating tooth regions can be drastically improved with removing specular reflections due to the illumination effect.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2000년도 종합학술발표회 논문집 Vol.10 No.1
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• pp.158-161
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• 2000

In this paper, we propose a new technique to compensate for the VCO nonlinearity using only the returned beat signal whose spectrum contains the internal reflections and the targets simultaneously. In the case of a distance measurement system using single antenna, the reflections from the circulator and the antenna are much larger than the return signal from target. The beat signal by these reflections is at much lower frequency than that of the target, and the VCO nonlinearity can be compensated leer using these signals. Indoor experiments were carried out and the results show marked improvement in the shape of range profile arid the range resolution.

• 아동학회지
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• 제27권6호
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• pp.13-34
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• 2006

The study analyzed reflections on parenting and its meaning represented on mothers' self-reports of filial therapy sessions. The filial therapy program consisted of understanding of child development and parental role, practicing new parenting skill, feedback from the play therapist, lectures on child-centered play therapy, supervision of mother's play therapy sessions, and writing journals. Through repeated meta-parenting experiences during the sessions, four mothers who had relationship problems with their children improved awareness of themselves as parents, authentic understanding of the mother-child relationship and development, and reflections of their parental abilities despite individual differences.

• 한국정밀공학회지
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• 제12권4호
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• pp.78-87
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• 1995

Specular reflection appears with metals, plastics, glasses and many other solid objects which are required to be inspected, assembled, moved, or processed automatically. Recongnizing such shiny objects with specular reflections is a hard problem for computer vision, since specular reflections appear, disappear, or change their shapes abruptly, due to tiny movements of the view. Traditionally, such specular reflections are discarded as annoying noise for recongnition purposes. In this paper a technique is represented for obtaining shapes of specular objects. The ring illumin- ation system employes a ring source which is positioned on the axis of the camera. The concept of the proposed method is that if specular objects are illuminated by the ring they show their own dis- tinctive specularity features in surface from which we can infer the shape of the object. A series of experiments are performed to evaluate the performance of this system.

• 한국수학교육학회:학술대회논문집
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• 한국수학교육학회 2010년도 제44회 전국수학교육연구대회
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• pp.205-212
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• 2010

Reflection has been of interest to educators as Dewey discussed it. Information about how teachers interpret and analyze their students' learning would help us understand difficulties in teaching and learning. Moreover, it can be useful for teacher education by improving teaching methods. In this study, I investigated four U.S.A. mathematics teachers in a middle school. In this paper, I discussed Assess instances among the teachers' reflections on their students' thinking and changes of the reflections as time went by.

• Educational Technology International
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• 제6권2호
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• pp.1-9
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• 2005

Starting with analyzing the development of cyber-education in China, this article discusses experiences and lessons acquired through making reflections on the following aspects: technology vs. pedagogy, the degree education vs. non-degree education, resource exclusivism vs. resource inclusivism, mono-service system vs. multi-service system, and educational quality vs. economic profit. Finally, the paper puts forward some suggestions on the future development of cyber-education in China.

• 지구물리와물리탐사
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• 제21권1호
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• pp.41-53
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• 2018

전통적인 탄성파 탐사 자료처리 분야에서 겹반사파(multiple)는 잡음으로 취급되어 제거한 후 자료처리를 수행한다. 그러나 최근 겹반사파를 잡음이 아닌 하나의 신호로 인식하고 이를 영상화에 이용하는 연구가 많이 이루어지고 있다. 겹반사파는 일차 반사파(primary reflection)가 도달하지 못하는 지점까지 도달할 수 있어 적은 수의 송신원과 수신기로도 더 넓은 범위를 영상화 할 수 있다. 이를 검증하기 위해 본 연구에서는 영상화 기법 중 하나인 거꿀시간 참반사 보정(reverse-time migration)을 이용하여 겹반사파 자료를 영상화한 후 일차 반사파를 사용한 전통적인 거꿀시간 참반사 보정 결과와 비교하였다. 겹반사파를 독립적으로 사용하기 위해 자유면 기인 겹반사파 제거(surface-related multiple elimination; SRME)기법을 사용해 탄성파 자료에서 겹반사파를 분리하였다. 수치 예제를 통해 겹반사파를 이용한 참반사 보정 결과가 일차 반사파를 이용한 전통적인 참반사 보정 결과보다 더 넓은 범위를 영상화 할 수 있음을 확인하였고, 특히 천부 지층에서 두드러진 효과가 나타나는 것을 알 수 있었다. 또한 겹반사파를 이용한 참반사 보정은 자료취득 흔적(acquisition footprint)에 의한 영상 왜곡이 제거됨을 확인할 수 있었다.

• 정보처리학회논문지B
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• 제16B권3호
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• pp.203-214
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• 2009

본 연구에서는 모니터, 카메라 및 눈동자 좌표계간의 복잡한 3차원 관계를 고려하지 않고, 동공의 중심 위치와 모니터의 구석에 설치된 적외선 조명에 의한 네 개의 조명 반사광 사이의 관계를 사용하여 2차원적인 변환 방법으로 사용자의 시선 위치를 파악한다. 동공중심과 조명 반사광을 정확하게 추출하고, 이를 통해 계산된 시선 위치 계산의 정확도에 영향을 줄 수 있는 오차 요소들을 보정하는 것이 본 연구의 목적이다. 이를 위하여, 동공 중심을 통해 계산된 시선위치와 실제 시선 축이 이루는 카파에러를 초기 1회의 사용자 캘리브레이션을 통해 보정하였다. 또한, 칼만 필터를 기반으로 눈의 급격한 움직임 변화에도 각막 조명 반사광을 안정적으로 추적하여 시선 위치를 정확하게 추적한다. 실험 결과, 제안한 연구방법의 시선 위치 추출 오차는 눈의 급격한 움직임 변화에 상관없이 약 1.0$^\circ$ 를 나타냈다.

• Smart Structures and Systems
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• 제21권2호
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• pp.195-205
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• 2018

Research on Lamb wave-based damage identification in plate-like structures depends on precise knowledge of dispersive wave velocity. However, boundary reflections with the same frequency of interest and greater amplitude contaminate direct waves and thus compromise measurement of Lamb wave dispersion in different materials. In this study, non-reflecting boundaries were proposed in both numerical and experimental cases to facilitate time-frequency characterization of Lamb wave dispersion. First, the Lamb wave equations in isotropic and laminated materials were analytically solved. Second, the non-reflecting boundaries were used as a series of frames with gradually increased damping coefficients in finite element models to absorb waves at boundaries while avoiding wave reflections due to abrupt property changes of each frame. Third, damping clay was sealed at plate edges to reduce the boundary reflection in experimental test. Finally, the direct waves were subjected to the slant-stack and short-time Fourier transformations to calculate the dispersion curves of phase and group velocities, respectively. Both the numerical and experimental results suggest that the boundary reflections are effectively alleviated, and the dispersion curves generated by the time-frequency analysis are consistent with the analytical solutions, demonstrating that the combination of non-reflecting boundary and time-frequency analysis is a feasible and reliable scheme for characterizing Lamb wave dispersion in plate-like structures.