• Title/Summary/Keyword: 상반정리

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Tellegen의 정리에 대하여

  • 고명삼
    • 전기의세계
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    • v.23 no.1
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    • pp.46-48
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    • 1974
  • 회로망정리에는 Kirchhoff의 법칙을 바탕으로 한 Tellegen의 정리[T-1]를 비롯하여 치환정리, 중첩정리, Thevenin-Norton의 정리 및 상반정리 등이 있다. 이들 제정리들은 실제 우리 전기공학자 및 기술자들이 실제문제 또는 현장에서 작업하는 과정에서 자주 부딛치게 되는 각종 회로망이 광범위하게 적용될 수 있을 뿐만 아나라, 그 결론이 매우 간단하므로 그 유용성은 매우 크다. 그러나 이들 제정리들이 지니고 있는 일반성과 간이성을 잘못 인식하여, 실제 응용에서 맛볼 수 있는 통쾌감을 제대로 느끼지 못하는 사람들이 비교적 많다. 본 해설에서는 상기한 제정리중 비교적 최근에 발표된 (1952년) Tellegen의 정리에 대하여 설명하며, 이 정리가 어떻게 유용하게 이용될 수 있는가를 보기를 통하여 설명하고저 한다.

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A Study on Scattered Wave Amplitude Closed-Form Solution Calculation of Torsional Wave Mode by Reciprocity Theorem (배관에서 상반 정리를 활용한 비틀림 파의 산란 신호 진폭의 닫힘 해 계산 연구)

  • Lee, Jaesun;Cho, Younho;Achenbach, Jan D.
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.40 no.7
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    • pp.647-652
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    • 2016
  • Guided waves can be used for the inspection of long range pipelines. Surface corrosion is often found as a major defect type in pipelines. The reciprocity relation is a well-established theorem by which one can simplify complicated mathematical expressions. The approach has been already applied to plate and half-space structures to obtain the closed-form solutions of scattered amplitude. However, results for the case of cylindrical structures have not been reported yet. In this paper, the scattering of torsional waves, which is widely used in commercial applications, is explored by the reciprocity theorem approach. Obtaining closed-form solutions of the amplitudes of propagating waves is much simplified by using the reciprocal relation. The scattered amplitudes for elliptical and rectangular defect shapes are calculated with respect to defect depth and width, at frequencies between 0 and 500 kHz. The amplitude shows the periodic result as a function of frequency. The derived closed-form solutions can play a significant role in quantitative signal interpretation.

일반화 볼록공간에서의 평형문제들

  • 박세희
    • Communications of the Korean Mathematical Society
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    • v.15 no.2
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    • pp.197-231
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    • 2000
  • 평형문제들에서의 기본적인 정리들이 일반화 볼록공간에서 어떻게 확장되는가를 보인다. KKM 이론의 중요한 정리들 대부분이 위상벡터공간에서의 선형성을 가정하지 않아도 위상적인 성질만으로 성립한다. 이같은 정리들의 예로는 KKM정리, von Neumann의 최소최대정리와 교차정리, Nash의 평형정리, 여러 가지 부동점정리, 극대원정리, Ky Fan의 최소최대부등식, 변분부등식들, 최량근사정리, 일반화 의사평형문제들의 해의 존재정리들이 있다.

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New Balancing Method of a Flexible Rotor Without Trial Weights (彈性回轉體의 평형잡이에 관한 연구)

  • 양보석;암호탁삼
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.3
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    • pp.409-418
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    • 1988
  • Steam turbines, gas turbines, multistage centrifugal compressors are operated over the range of the first critical speed. In these rotors flexible rotor balancing technique is necessary. In such balancing, influence coefficients are measured by rotating a rotor with trial weight. But for the large rotor, the measurement of influence coefficient takes much time and it reduces the cost efficiency. In this paper the new influence coefficient with rotation of rotor is proposed. First the theoretical background of the method is presented and it is applied to the simple flexible rotor model. Then the experiments are performed and the results of presented method are compared with those of analytical method. By using the obtained influence coefficient, balancing of the flexible rotor is performed.

Imaging of Seismic Sources Using Time Reversal Wave Propagation (지진파 역행 전파를 이용한 지진원 영상화)

  • Sheen, Dong-Hoon;Baag, Chang-Eob;Hwang, Eui-Hong;Ryoo, Yong Gyu;Youn, Yong-Hoon
    • 한국지구물리탐사학회:학술대회논문집
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    • 2006.06a
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    • pp.181-186
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    • 2006
  • An imaging method of seismic sources using time-reversal wave propagation is presented. The method is based on the time-reversal invariance and the spatial reciprocity of the wave equation. Time-reversal wave propagation has been used to image anomalous features of a midium in medical imaging, non destructive testing and waveform tomography. Seismogram is the record whose energy is propagated from the seismic source. If time-reversed seismogram propagates back into the medium, seismic energy is concentrated at the origin time of the event and at the source location. In this work, a staggered-grid finite-difference method of the elastic wave equation is parallelized for 3-D wave propagation simulation. With numerical experiments, we show that the time-reversal imaging will enable us to explore the spatio-temporal history of complex earthquake.

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Investigation on Vibration Characteristics and Structural Reciprocity of Heunginjimun (흥인지문의 진동특성 및 상반성 분석)

  • Choi, Jae-Sung;Lee, Sung-Kyung;Min, Kyung-Won;Yoon, Weon-Kyu;Kim, Derk-Moon
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.20 no.4
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    • pp.338-347
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    • 2010
  • Heunginjimun designated as a Treasure No.1 is a two-story wooden structure with 5 bay and 2 bay in its front and side views, respectively. This paper presents an investigation on vibration characteristics of Heunginjimun through both ambient vibration and impact hammer tests. Ambient vibration test was performed to identify the natural frequency of Heunginjimun from the spectrum analysis of time history. Impact hammer test was undertaken to find the frequency of Heunginjimun which is affected by the surrounding traffics and to verify the reciprocal principle for the wooden structural system. Ambient vibration test results of Heunginjimun showed that the natural frequencies in two principal axes 1.5 Hz and 1.1 Hz, respectively. It was confirmed from impact hammer tests for a ground that the frequency of 4.2 Hz is caused by the traffics surrounding Heunginjimun. It was also observed that from the impact hammer test results between two locations in Heunginjimun that the transfer functions measured from two corresponding locations coincided well with each other. This result shows that the wooden structural system is globally linear, and the reciprocal principle is established.

Calculation of weight functions in single edge notched specimen (SEN시편에서의 무게함수 계산)

  • 안득만
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.2
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    • pp.604-610
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    • 1991
  • In this paper, the weight functions for the Mode I and Mode II in SEN(single edge notched) specimen are obtained by superposition of the displacement in the singular field of the Buckner type and the displacements by opposite tractions induced by the singular field. The stress intensity factors, $K_{I}$ and $K_{II}$ are calculated by the weight function theory in SEN specimen under the loading equivalent to uniform tension and shear at infinity in Griffith crack. And the results are compared with the exact solutions.s.

Weight Function Theory for a Mode III Crack In a Rectilinear Anisotropic Material (가중함수이론을 이용한 선형이방성재료에서의 Mode III 균열해석)

  • An, Deuk-Man;Kwon, Sun-Hong
    • Journal of Ocean Engineering and Technology
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    • v.23 no.1
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    • pp.146-151
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    • 2009
  • In this paper, a weight function theory for the calculation of the mode III stress intensity factor in a rectilinear anisotropic body is formulated. This formulation employs Lekhnitskii's formalism for two dimensional anisotropic materials. To illustrate the method used for the weight function theory, we calculated the mode III stress intensity factor in a single edge-notched configuration.

Noise Estimation in a Passenger Compartment and Trunk Coupled System by Using the Vibro-Acoustic Reciprocity (진동-음향 상반성을 이용한 차실-트렁크 연성계의 소음평가)

  • 이진우;이장무;김석현;박동철
    • Transactions of the Korean Society of Automotive Engineers
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    • v.9 no.6
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    • pp.178-185
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    • 2001
  • This paper describes the correlation between the interior noise and the trunk wall vibration. Using the vibro-acoustic reciprocity, effect of the trunk wall vibration on the compartment noise is investigated on a medium size car. In the low frequency range, vehicle interior noise is dominated by several acoustic modes of the passenger compartment and the vibration modes of the surrounding shell parts. Especially, vibration of the trunk wall radiates sound and it is transferred through holes on the package tray into the passenger compartment. This paper experimentally reveals that sound can be well produced at some particular vibration modes of the trunk lid and it strongly influences the compartment noise through package tray holes. Contributions of the trunk walls to the interior noise are estimated by measuring the acoustic-structural transfer function, based on the vibro-acoustical reciprocity theorem.

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