• 한국소음진동공학회논문집
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• 제23권2호
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• pp.152-159
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• 2013

A structural health monitoring(SHM) technique for locating impact position in a composite plate is presented in this paper. The technique employs a single sensor and spatial focusing properties of time reversal(TR) and inverse filtering(IF). We first examine the focusing effect of back-propagated signal at the impact position and its surroundings through simulation. Impact experiments are then carried out and the localization images are found using the TR and IF signal processing, respectively. Both techniques provide accurate impact location results. Compared to existing techniques for locating impact or acoustic emission source, the proposed methods have the benefits of using a single sensor and not requiring knowledge of material properties and geometry of structures. Furthermore, it does not depend on a particular mode of dispersive Lamb waves that is frequently used in the SHM of plate-like structures.

• 비파괴검사학회지
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• 제25권2호
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• pp.87-94
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• 2005

최근 램파를 비파괴검사에 이용하고자 하는 연구가 활발히 진행되고 있다. 그 중에서도, 레이저에 의해 집속형 램파를 발생시키는 방법은 비접촉식 검사의 장점과 함께 높은 공간분해능을 기대할 수 있다 이 방법에서 레이저는 원호배열슬릿을 통하여 판재 표면에 조사되는데, 발생된 램파의 에너지가 원호배열의 초점에 집속되는 효과를 갖게 된다. 이 때 공간분해능의 향상은 램파의 집속도를 높임으로써 가능하다. 본 논문에서는 높은 집속도의 램파를 발생시키도록 원호형 슬릿을 설계하기 위해 슬릿의 형상인자와 램파의 집속도 사이의 관계를 분석하였다. 그 결과, 레이저조사반경과 원호각, 원호수를 증가시키거나 원호반경과 파장을 감소시킴으로써 집속도를 높일 수 있다는 것을 알 수 있었으며, 본 연구의 결과는 적절한 원호형 슬릿의 설계기준으로 활용될 수 있을 것으로 기대 된다.

• 한국게임학회 논문지
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• 제7권2호
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• pp.73-82
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• 2007

이 연구는 "모차르트 이펙트"를 통해 밝혀진 모차르트 음악이 지능향상에 효과가 있다는 연구결과와 비교하여 온라인 게임 이용자의 게임 후 시 공간 능력에 어떤 영향이 나타나는지 알아보고자 한다. 10대 후반에서 20대 초반의 대학생을 대상으로 한 이번 연구에서 게임 이용 시 시공간 인지 능력의 차이는 공간 인지 능력의 차이에서 두드러지는 것으로 나타났다. 음악, 애니메이션, 온라인 게임(카트라이더)을 이용한 세 집단의 공간인지 능력의 차이를 분석한 결과, 온라인게임을 선호하는 집단이 '모양맞추기' 점수가 높아 온라인게임 이용이 이용자의 시 공간 능력 향상에 도움이 된다는 연구결과를 도출하였다.

• 한국GIS학회:학술대회논문집
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• 한국GIS학회 2003년도 공동 춘계학술대회 논문집
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• pp.629-636
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• 2003

• 한국수학교육학회지시리즈C:초등수학교육
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• 제9권2호
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• pp.119-134
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• 2005

The goals of this study is to analyze develop the materials which help students develop spatial sense in elementary school and to investigate its effects. To accomplish those goals, the 7th National Curriculum was analyzed to identify the contents of spatial sense. After analyzing the 7th National Curriculum, the principle for developing the teaching aids focusing the realization of the contents in the spatial sense was set up. And then various teaching materials which can enhance students' spatial sense was developed. It is consist of 17 kinds of concretely operating materials, 7 kinds of tangram papers, one web-material. To verify the effect of the materials, surveyed the usability of the materials and two classes was selected and tests were administered before and after the treatment. Through this application, several conclusion were drawn. First, a survey result says that teachers thought materials developed would be effective in developing spatial sense. Second, the materials developed were effective to develop spatial sense. The score gained by the experiment group after the treatment was statistically meaningfully higher than the control group. This means that the materials developed helped children to develop spatial sense.

• 비파괴검사학회지
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• 제32권4호
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• pp.355-361
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• 2012

This paper presents an experimental study on the detection and location of nonlinear scattering source due to the presence of fatigue crack in a laboratory specimen. The proposed technique is based on a combination of nonlinear elastic wave spectroscopy(NEWS) and time reversal(TR) focusing approach. In order to focus on the nonlinear scattering position due to the fatigue crack, we employed only one transmitting transducer and one receiving transducer, taking advantage of long duration of reception signal that includes multiple linear scattering such as mode conversion and boundary reflections. NEWS technique was then used as a pre-treatment of TR for spatial focusing of reemitted second harmonic signal. The robustness of this approach was demonstrated on a cracked specimen and the nonlinear TR focusing behavior is observed on the crack interface from which the second harmonic signal was originated.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1992년도 학술논문발표회 논문집 제11권 1호
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• pp.123-126
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• 1992

A new class of data transformation matri is introduced for estimation of angles of arrivals by the rank reduction of multiple wideband sources. The proposed unitary focusing matri minimizes the average of the squared norm of focusing error over the angles of interest without a priori knowledge of source locations. The merit that result as a consequence is a lower resolution threshold. These matrices can be applied to the case of the multigroup sources. Simulations and the comparison of statistical performance are compared with the algorithms (especially, spatial resampling method) which does not require the pre-estimation.

• 한국실내디자인학회논문집
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• 제36호
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• pp.30-36
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• 2003

The purpose of this study is to analyze the contextual cognition of space in architecture focusing on Aldo Rossi and Michael Graves, the representative architects of spatial cognition in contextual architecture. This study on the contextual cognition of architectural space can be connected with linguistics and aesthetics's approaches. The conclusions of the study as per the above mentioned aims and intentions are as follows : The concept of spatial analysis in Aldo Rossi's contextual cognition in architecture is described the Analogical Space of Speculative Aesthetics by Diachronie Restoration That of Michael Graves' contextual cognition Is defined Semiotics Space of Empirical Aesthetics by Synchronie Repeatition.

• 한국수학교육학회지시리즈D:수학교육연구
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• 제16권2호
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• pp.107-123
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• 2012

A group of twenty-nine high school student-teachers were given a set of mathematical propositions focusing on shape-to-shape transformations. Their task was to determine through hands-on manipulation and use of dynamic software that each shape be transformed into an area equivalent rectangular region. This paper reports on a classroom-based research.

• 한국환경보건학회지
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• 제37권1호
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• pp.1-11
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• 2011

Recent advances in Geographic Information Systems and spatial statistical and analytical methods, along with the availability of spatially referenced health and environmental data, have created unique opportunities to investigate spatial associations between environment exposures and health outcomes at multiple spatial scales and resolutions. However, the increased use of spatial data also faces challenges, one of which is to ensure certainty and accuracy of locational data that meets the needs of a study. This article critically reviews the use of spatially referenced data in epidemiologic studies, focusing on the issue of locational uncertainty generated from the process of geocoding health and environmental data. Primarily, major issues involving the use of spatially referenced data are addressed, including completeness and positional accuracy, potential source of bias and exposure misclassification, and implications for epidemiologic studies. The need for critical assessment and caution in designing and conducting spatial epidemiology studies is briefly discussed.