• 대한기계학회논문집A
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• 제32권9호
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• pp.796-803
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• 2008

Ultrasonic testing uses the directivity of the ultrasonic wave, which propagates in on direction. The directivity is expressed as the relationship between the propagate direction and its sound pressure. The directivity of an ultrasonic wave is related to the choice of probe arrangement, testing sensitivity and scanning pitch and correct measurement of defect size and location. This paper describes on the directivity measurement of ultrasonic wave using the visualization method. The directivity of shear wave emitted from the angle beam transducer were constant during propagation. The difference of directivity was existed between 2 MHz and 4 MHz angle beam transducers. When these experimental results were compared with the theory which was based on the continuous wave, it showed good agreement with theoretical directivity on the principal lobe.

• Journal of Welding and Joining
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• 제14권6호
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• pp.37-47
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• 1996

An ultrasonic testing uses the directivity of the ultrasonic wave which propagates in one direction. The directivity is expressed as the relationship between the propagate direction and its sound pressure. The directivity of ultrasonic wave is related to determination of testing sensitivity, scanning pitch and defect location. This paper investigated the directivity of ultrasonic wave, which scattered from slit defect located in heat-affected zone (HAZ) in butt joint using visualization method. The directivity of shear waves scattered from slit defect were different according to probe direction (far defect, near defect) and probe position (forward movement, maximum echo position, backward movement). The difference of directivity of reflection wave was existed between 2 MHz and 4 MHz angle probes. In the case of 2 MHz angle probe, the directivity of reflection wave was appeared sharp form because of the relation wave length and defect size.

• ETRI Journal
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• 제27권6호
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• pp.697-707
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• 2005

This paper proposes a new design of directional couplers with high directivity for personal communication services (PCS) and International Mobile Telecommunications-2000 (IMT-2000). The directional coupler is used to check and verify the power, frequency, and antenna reflection of a signal at transmission stations for mobile communications. The performance requirements of directional couplers are a strong coupling to reduce the effect on the transmitted power and high directivity to suppress the interference of the reflected signals and reduce the errors in communication. So far, various architectures have been proposed to gain high directivity, and there have been many studies used to obtain a strong coupling. However, conventional architectures for high directivity and strong coupling have a directivity of only about 20 dB, and there have been difficulties to achieve the higher directivity of 30 dB suitable for PCS and IMT-2000. This paper proposes a new architecture of directional couplers based on a grounding composed of strip lines, and compares the test results of this directional coupler with conventional ones. The results show that the proposed directional coupler has a directivity of more than 30 dB and is adequate for PCS and IMT-2000.

• 한국실내디자인학회논문집
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• 제21권1호
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• pp.111-118
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• 2012

The purpose of this study is to classify the epistemological critique between philosophy and architecture. Although there are various interpretations and criticism about the architecture, the fundamental critique of architecture is difficult. It is necessary to approach by the philosophic paradigm rather than architectural one. Therefore the procedure and method of study is to define the epistemology within philosophy and architecture, and present the classification viewpoint and the architecture case. The conclusions of this study based on purpose and process are as follows : The First, the philosophic epistemology is to mean the unity of subjective and objective. And the epistemological viewpoint of architectural philosophy is to define the construction's universality. The second, the architectural philosophy is a kind of the philosophy of art, and It is associated with the basis of aesthetics. Thus, the category of architectural philosophy like the aesthetics is classified with function directivity and form directivity, content directivity. The Last, epistemological critiques between philosophy and architecture are as follows ; 1) subject-object-integrated recognition critique (function directivity), 2) object-oriented recognition critique (form directivity), 3) subject-oriented recognition critique (content directivity).

• The Journal of the Acoustical Society of Korea
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• 제24권2E호
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• pp.38-45
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• 2005

The noise reduction of the In-The-Ear (ITE) hearing aid (HA) can be achieved by arrays of microphones. Each of the right and the left ears was assumed to have two HA microphones. These arrays of HA microphones produce particular patterns of directivity by some time delay between two microphones. The directivity pattern geometrically increase the S/N ratio. The boundary element method (BEM) was used for the three dimensional simulation of the HA directivity pattern with the two pairs' microphone arrays. The separation between two microphones was fixed to 10 mm. The time delay between the two microphones was calculated to produce the most narrow directivity pattern in the fore front of the head. The variation of the time delay was examined in accordance with input frequencies. This numerical analysis may be then applied for the calculation of the time delay parameter of the digital hearing aid DSP chip.

• 한국통신학회논문지
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• 제28권11A호
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• pp.921-928
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• 2003

본 논문은 높은 지향성을 갖는 방향성 결합기 설계에 관한 연구이다. 이동통신 기지국의 송신단에서는 신호의 크기나 주파수 혹은 안테나에서의 반사등을 확인하기 위해 방향성 결합기를 사용한다 즉. 통신에 간섭을 줄여 에러 발생을 막고 원활한 통신 성능 시험을 하기 위해서는 높은 지향성이 요구된다. 지금까지 높은 지향성을 얻기 위한 많은 구조가 제시되었고, 지향성과 관련한 분석과 연구가 있었다. 그러나 현재 지향성은 일반적으로 20㏈정도가 구현되고 있으며. 40㏈이상과 같은 높은 지향성을 구현하는데 어려움이 있다. [1] 따라서 본 논문에서는 40㏈와 같은 높은 지향성을 구현하기 위하여 스트립선로 구조로 시도하였으며, 50$\Omega$ 전송선과 만나는 접합부분의 밴드에서 야기되는 불연속으로 인한 리액턴스 성분을 줄이기 위하여 케패시턴스 성분을 추가하였다. 여기에서는 케패시턴스 성분을 대신하여 접지면을 추가한 새로운 구조의 방향성결합기를 제안하고 이를 설계하여 실험하였다 그리고 이 새로운 구조를 이용한 방향성 결합기와 기존의 방향성 결합기와의 지향성 측정 실험(시뮬레이션) 결과 값을 비교 검토하였다. 실험에 사용한 측정 주파수의 중심주파수는 2.05㎓(IMT-2000용)로 하였으며 $\pm$50MHz의 범위를 갖도록 실험하였다. 실험(시뮬레이션) 결과 약 43㏈ 정도의 높은 지향성을 보였으며 기존 방향성 결합기의 지향성(약 20㏈)보다 약 23㏈ 개선을 구현하였다.

• 한국재난정보학회 논문집
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• 제10권2호
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• pp.264-273
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• 2014

이 연구의 목적은 민간경비조직 경영자의 변혁적리더십이 구성원의 학습지향성 및 조직혁신행동에 미치는 영향을 규명하는데 있다. 이 연구에서 얻은 결론은 다음과 같다. 첫째, 민간경비 조직 경영자의 변혁적 리더십은 학습지향성에 영향을 미친다. 즉, 변혁적 리더십을 보일수록 학습지향성은 강화된다. 둘째, 민간경비 조직 경영자의 변혁적 리더십은 조직혁신행동에 영향을 미친다. 즉, 변혁적 리더십을 보일수록 조직혁신행동은 강화된다. 셋째, 민간경비 조직 경영자의 학습지향성은 조직혁신행동에 영향을 미친다. 즉, 학습지향성을 보일수록 조직혁신행동은 강화된다. 종합해보면, 민간경비 조직 경영자의 변혁적 리더십은 학습지향성을 통하여 조직혁신행동에 영향을 미치고 있음을 알 수 있다. 학습지향성은 변혁적 리더십과 조직혁신행동의 관계를 연결하는 중요한 변수라 할 수 있다.

• 비파괴검사학회지
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• 제14권2호
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• pp.83-89
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• 1994

고체내를 전파하는 초음파의 지향성과 음압 분포를 아는 일은 초음파탐상시험에 있어서 대단히 중요하다. 초음파의 지향성은 초음파탐상시험에 있어 감도, 주사 간격, 탐촉자의 배치, 결함의 종류 등을 판단하는 지침이 되고 있다. 본 논문에서는 초음파가시화법을 이용해 초음파의 지향성을 측정했다. 사각탐촉자로부터 나온 횡파의 지향성은 초음파의 전파 거리에 따라 변하지 않았다. 2MHz와 4MHz의 사각탐촉자에는 지향성의 차이가 있었다. 지향성의 중심 위치는 사각탐촉자의 입사점으로부터 뒤쪽 및 탐촉자의 내부에 위치하고 있었으며, 초음파의 전파 거리에 따라 변하지 않았다.

• 한국통신학회논문지
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• 제37권4A호
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• pp.250-259
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• 2012

본 논문에서는 반복계산에 따라 비선형 최소점을 탐색하는 최적화 알고리즘의 선택이 선형배열음원의 지향성합성에 미치는 영향을 목적지향성의 설계사양에 대한 만족도, 수렴성, 그리고 적응성의 면에서 비교 검토하였다. 지향성합성은 최적화 알고리즘인 DFP(Davidon-Fletcher-Powell)법과 BFGS (Broyden-Fletcher-Goldfarb-Shanno)법을 이용하였으며, 준이상 빔과 회전 빔, 그리고 멀티 빔을 목적지향성으로 설정하였다. 수치계산 결과, 지향성합성에 대한 준뉴톤법의 유효성 확인과 함께 수치계산 과정에서 발생된 문제점에 대한 해결 방법도 제시하였다.

• 한국수학교육학회지시리즈D:수학교육연구
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• 제11권3호
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• pp.197-207
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• 2007

Based on a survey on 1620 students in primary school and secondary school., by adopting Eysenck Personality Questionnaire (EPQ), we got the following findings : 1. There is close relationship between emotionality characteristics of temperament and mathematics academic achievement of the subjects at Grade 5 (Primary 5), Grade 8 (Junior Secondary 2), and Grade 10 (Senior Secondary 2). Also there is close relationship between internal-external directivity characteristics of temperament and mathematics academic achievement at Grade 5 and Grade 8. While there is not close relationship between internal-external directivity characteristics of temperament and mathematics academic achievement at Grade 10; 2. There is close relationship between temperament types and mathematics academic achievement of the subjects from the three grades. Superior temperament, which benefit learning mathematics, are sanguine, sanguine-phlegmatic and phlegmatic; While inferior temperament types, which don't benefit learning mathematics, are choleric, melancholic and choleric-melancholic. With the rising of grade, temperament types of benefiting learning mathematics converts from external directivity emotion balance to balance of internal-external directivity emotion stability. While temperament of no benefiting learning mathematics converts from internal directivity emotion balance to balance of internal-external directivity emotion instability; 3. In mathematics education, students' temperament difference, which affects learning mathematics, should be recognized. Mathematics teachers should find out the best teaching ways, forms and methods which are suitable for student's temperament type, so that the students with different temperament types can gain better mathematics academic achievement.