• Title, Summary, Keyword: directivity

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Directivity Analysis for Optimal Design of Ultrasonic Angle Beam Transducer (초음파 사각 트랜스듀서의 최적설계를 위한 지향성 해석)

  • Nam, Young-Hyun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.32 no.9
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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.

Propagation Characteristic of Ultrasonic on Slit Defect in Butt Joint (맞대기 용접부내의 인공 결함에서 초음파의 전파특성)

  • 남영현
    • Journal of Welding and Joining
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    • v.14 no.6
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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.

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A New Directional Coupler Design with High Directivity for PCS and IMT-2000

  • Ji, Il-Gu;Chong, Jong-Wha
    • ETRI Journal
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    • v.27 no.6
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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.

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A Study on Epistemological Critique between Philosophy and Architecture (건축과 철학의 인식론적 논의에 관한 연구)

  • Lee, Yong-Jae
    • Korean Institute of Interior Design Journal
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    • v.21 no.1
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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).

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Directivity Pattern Simulation of the Ears with Two Pairs' Hearing Aid Microphone Arrays by BEM

  • Jarng Soon Suck;Kwon You Jung
    • The Journal of the Acoustical Society of Korea
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    • v.24 no.2E
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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.

Effects of revolutional leadership of manager at private security service organization members learning directivity and organizational innovation behavior (민간경비 경영자의 변혁적리더십이 구성원의 학습지향성 및 조직혁신 행동에 미치는 영향)

  • Kang, Minwan
    • Journal of the Society of Disaster Information
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    • v.10 no.2
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    • pp.264-273
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    • 2014
  • The purpose of the study is to demonstrate the effects of revolutional leadership of manager at private security organization on members' learning directivity and organizational innovation behavior. The results attained from studying method and procedure as mentioned above are in the following. First, the revolutional leadership of manager at private security service organization influence learning directivity. That is, the more he or she shows revolutional leadership, the more enhanced the learning directivity of members. Second, the revolutional leadership of manager at private security service organization has effects on organizational innovation behavior. Thatis, the more he or she shows revolutional leadership the more enhanced organizational innovation behavior. Third, learning directivity of manager at private securitys service organization influences organizational innovation behavior. Thatis, the more he or she shows learning directivity, the more enhanced organizational innovation behavior. Taken all, revolutional leadership of manager at private security service organization affects organizational innovation behavior through learning directivity. It is shown that learning directivity is a key variable connecting revoultional leadership with organization al innovation behavior.

A Study on the Design of Directional Coupler with high Directivity (높은 지향성을 갖는 방향성 결합기 설계에 관한 연구)

  • 지일구;정정화
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.11A
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    • pp.921-928
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    • 2003
  • This paper propose a new design of directional couplers with the high directivity. The directional coupler is used to check and verify the power, frequency and antenna reflection of a signal at transmission station for the mobile communications. The performance index of the directional coupler is to which the coupling is strong to reduce the effect on the transmitted power and the directivity is high to suppress the interference of the reflected signals and reduce the nor in the communication. Then, the architectures to gain the high directivity and the studies to get the strong coupling have been proposed However, the conventional architectures lot the high directivity and strong coupling have the directivity by about 20㏈ and the difficulty to achieve the higher directivity than 40㏈ suitable for IMT-2000 [1]. This paper proposes an architecture of the directional coupler which is based on the grounding composed of the strip lines and the comparison results with the conventional directional couplers. The comparison results show that the proposed directional coupler has the directivity more than 40 ㏈ and is adequate for the 2.05GHz IMT-2000

Optimal Directivity Synthesis of Linear array Sources (선형배열음원의 최적 지향성합성)

  • Jeong, Eui-Cheol;Kim, Sang-Yun;Kim, On;Cho, Ki-Ryang
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.37 no.4A
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    • pp.250-259
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    • 2012
  • This paper compared and investigated the choice of optimal algorithm affects on the directivity synthesis of linear array in the satisfaction to the design specification of the desired directivity, convergence characteristic, and adaptability. Optimal algorithms use a quasi-Newton method(DFP and BFGS method) for realizing the desired directivity, used a quasi-ideal beam, steering beam, and a multi-beam, chosen as desired directivity. In the numerical result, this paper verified the effectiveness of the quasi-Newton method to the directivity synthesis, and offered a solving approach of occurred problems in the numerical simulation process.

A Study on the Relationship between Temperament and Mathematics Academic Achievement

  • Li, Mingzhen;Pang, Kun
    • Research in Mathematical Education
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    • v.11 no.3
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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.

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The Directivity Measurement of Angle Probe by Photoelastic Visualization Method (광탄성가시화법에 의한 사각탐촉자의 지향성 평가에 관한 연구)

  • Nam, Y.H.;Date, K.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.14 no.2
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    • pp.83-89
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    • 1994
  • It is important for an ultrasonic testing to know the sound pressure field and the directivity of ultrasonic waves propagating in a solid. The directivity of ultrasonic wave is closely related to the sensitivity, the scanning pitch, the arrangement of angle probe, and the defect kind in ultrasonic testing. This paper describes on the directivity measurement of ultrasonic wave using ultrasonic wave visualization method. The directivity of the shear wave emitted from the angle probes were constant during propagation. The difference of directivity was existed between 2MHz and 4MHz angle probes. The centers of directivity were located backward from the incident poing and inside of the angle probe and were not changed during the wave propagation.

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