• Composites Research
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• 제22권1호
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• pp.9-14
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• 2009

본 논문에서는 탄소섬유 복합재료의 균열의 위치 및 성장을 감지하기 위하여 브리지 회로 개념이 적용된 전기 전위법을 제안하였다. 중앙 관통 균열을 가진 복합재료 박판 시험편에 두 쌍의 전극을 생성하였으며, 브리지 회로 개념을 적용하여 한 쌍의 전극에 외부 전압을 인가하고 다른 한 쌍의 전극으로부터 출력 전압 변화를 관찰하였다. 실험과 유한요소해석을 통하여 전극의 크기와 간격, 균열의 위치와 크기 및 성장 방향의 영향을 고찰하였다. 검출 가능한 균열의 크기는 전극의 크기 보다는 전극의 간격에 의한 영향이 더 컸으며, 전극의 크기와 간격이 작을수록 균열의 검출 능력이 우수하였다. 또한, 균열 크기가 증가할 수록, 입력 전극과 가까울수록 출력 전압의 변화가 큼을 관찰할 수 있었다.

• Journal of Acupuncture Research
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• 제18권6호
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• pp.151-160
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• 2001

Objective : Assuming that the characteristic of meridian system has been similar to this of electric potentials in human body and that measurements of electric potential at well(井穴) and sea(合穴) points in branches of the twelve meridians will be representative of measurements of the twelve meridians, to measure the electric potentials in twenty aged and fifty aged healthy volunteers groups at sleeping(SG) and awakening(AG), and then to find out the characteristic of meridian system among 2 groups. Methods : We selected who thirty healthy volunteers were diagnosed by a blood test, urine examination and differentiation of syndromes by five viscera(五臟辨證) among volunteers. Their electric potential of well and sea points in the meridians were simultaneously measured by physiograph. Results : Measurements were analyzed by statistical factor analysis, we obtained that the both left and right side electric potential of well and sea points in branches of the twelves meridians were unclearly divided into four factors according to age and whether sleeping or not, which were the three Yin meridians of the hand, the three Yang channels of the hand, the three Yin meridians of the foot, and the three Yin meridians of the foot. Conclusion : In conclusion, using the sequently measuring method, we obtained that electrical potentials of well and sea points in branches of the twelves meridians were divided into two factors, but the simultaneously measuring method, those were divided into four factors. The latter result means that the electrical potentials of twelve meridians were reflected by the function of the viscera and bowels.

• 한국산학기술학회논문지
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• 제12권11호
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• pp.5123-5127
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• 2011

증가 추세인 지중 전력설비의 사고 예방과 유지 보수를 위한 기술 연구 개발 요구가 증가하고 있다. 지중선로의 경우 누전 불량의 점유율이 높고 보수도 어려워 정확한 누전점 위치의 탐지가 중요하다. 교류 송신파를 누전점을 가지는 지중선로에 인가하여 발생시킨 교류 대지전위를 측정하여 누전점의 위치를 찾는 방법은 송신파 특정 극성반주기에 교류 대지전위를 동기화하여 비교 판단하여야 한다. 송신파의 특정 극성의 반주기와 동기화하는 기존 방법을 설명하고, 송신파 반주기 변조된 대지 전위 측정 방식을 제안하고 소개하였다. 실험을 통하여 제안한 방식이 구현 가능함을 확인하였다.

• 대한기계학회논문집A
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• 제32권11호
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• pp.918-923
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• 2008

Since crack detection for laminated composites in-service is effective to improve the structural reliability of laminated composites, it have been tried to detect cracks of laminated composites by various nondestructive methods. An electric potential method is one of the widely used approaches for detection of cracks for carbon fiber composites, since the electric potential method adopts the electric conductive carbon fibers as reinforcements and sensors and the adoption of carbon fibers as sensors does not bring strength reduction induced by embedding sensors into the structures such as optical fibers. However, the application of the electric method is limited only to electrically conductive composite materials. Recently, a piezoelectric method using piezoelectric characteristics of epoxy adhesives has been successfully developed for the adhesive joints because it can monitor continuously the damage of adhesively bonded structures without producing any defects. Polymeric materials for the matrix of composite materials have piezoelectric characteristics similarly to adhesive materials, and the fracture of composite materials should lead to the fracture of polymeric matrix. Therefore, it seems to be valid that the piezoelectric method can be applied to monitoring the damage of composite materials. In this research, therefore, the feasibility study of the damage monitoring for composite materials by piezoelectric method was conducted. Using carbon fiber epoxy composite and glass fiber composite, charge output signals were measured and analyzed during the static and fatigue tests, and the effect of fiber materials on the damage monitoring of composite materials by the piezoelectric method was investigated.

• Journal of Mechanical Science and Technology
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• 제14권8호
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• pp.845-850
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• 2000

We consider the problem of determining the singular stresses and electric fields in a piezoelectric ceramic strip containing a Griffith crack under in-plane normal loading within the framework of linear piezoelectricity. The potential theory method and Fourier transforms are used to reduce the problem to the solution of dual integral equations, which are then expressed to a Fredholm integral equation of the second kind. Numerical values on the field intensity factors are obtained, and the influences of the electric fields for PZT-6B piezoelectric ceramic are discussed.

• Structural Engineering and Mechanics
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• 제53권6호
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• pp.1167-1182
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• 2015

In this study, the stresses and electric potential redistributions of a cylinder made from functionally graded piezoelectric material (FGPM) are investigated. All the mechanical, thermal and piezoelectric properties are modeled as power-law distribution of volume fraction. Using the coupled electro-thermo-mechanical relations, strain-displacement relations, Maxwell and equilibrium equations are obtained including the time dependent creep strains. Creep strains are time, temperature and stress dependent, the closed form solution cannot be found for this constitutive differential equation. A semi-analytical method in conjunction with the Mendelson method of successive approximation is therefore proposed for this analysis. Similar to the radial stress histories, electric potentials increase with time, because the latter is induced by the former during creep deformation of the cylinder, justifying industrial application of such a material as efficient actuators and sensors.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 B
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• pp.828-830
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• 2000

This paper describes BIEM(Boundary Integral Equation Method) for computation of three dimensional electric field distribution and numerical method that an equivalent charge density is unknown variable. After computing numerically the surface charge distribution. the distribution of both potential and electric field are obtained. Finally, this numerical method is applied to the concentric sphere and the coaxial cylindrical model and numerical result is compared to the analytic solution.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 A
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• pp.79-82
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• 1999

So far, The methods for identifying the parameters of some region or material have been developed. This paper describes a new method for electric resistivity reconstruction using multi-resolution property of wavelet. The outputs of the potential electrodes are computed using two dimensional FEM in the wave number space by Fourier transforming the governing equation. The resistance distribution in the region of interests, which makes the computed potential distribution coincide with the measured potential, is found by minimizing the objective function using an optimization method. Multi-resolution analysis introduced in this paper will be proved to be the proper method in the viewpoint of effectivity and time-consuming by the numerical results.

• 한국정보통신학회논문지
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• 제11권12호
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• pp.2335-2342
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• 2007

최근에 레이저를 임상치료에 응용하는 사례가 증가하고 있다. 그러나 전기적 관점에서 레이저 자극이 경락에서 어떠한 전기적 반응을 유도할 수 있는지에 대한 연구가 미흡하고, 명확한 치료효과에 대한 임상보고가 발표되지 않고 있다. 본 논문에서는 레이저자극과 수기자극이 경락전위 형성에 미치는 영향을 비교 관찰하여 전기적 관점에서 침술과정 및 침술효과에 대한 객관적 근거를 제시하고자 하였다. 수양명대장경상의 삼간혈(LI3)을 각각 자극했을 경우, 삼간혈(LI3)과 합곡혈(LI4)에서의 전위변화를 측정하였다. 그 결과, 레이저 자극 시, 평균 피크전위는 $7.53{\pm}3.44{\mu}V$로 매우 낮게 나타났고, 자극전후 전위패턴에 차이가 없어서 레이저 자극에 대한 유효한 전기반응으로 간주하기 어렵다. 접지조건에 대한 수기자극에서는 평균피크전위가 $2.65{\pm}1.53mV$로 매우 높게 측정되었고, 개인별, 접지조건에 따라 전위크기와 패턴이 다양하게 나타나고 전위패턴은 주로 캐패시터의 충방전 전위와 매우 비슷하게 나타났다. 또한, 절연자침의 경우에서는 접지조건에 관계없이 평균 피크 전위가 $0.25{\pm}0.16mV$로 수기자극 전위에 비하여 매우 낮게 나타났으며, 이는 침자극에 대한 유효한 전기 반응으로 간주하기 어렵다. 따라서, 전기적 관점에서 침술과정과 침술효과는 시술자와 피시술자간의 생체이온전하의 이동에 의한 에너지 교감현상임을 확인하고, 수기자극은 경락의 전기반응을 유도하는 반면, 레이저 자극은 경락의 전기적 반응을 유도하기 어렵다는 것을 확인하였다.

• 기술사
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• 제42권6호
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• pp.36-41
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• 2009

Smart Grid is grafting IT(information technology) techniques on existing electric power network, supplier and the consumer to do real-time exchange of information lead to both direction and energy efficiency optimization, it is a next potential electric power network method. Because of applying various distributed electric power sources, the electric power network system will follow in size and it is dispersive and it will operate independently, and it become the intelligent electric power network, which in consumer demand reacts at real-time, because of using various sensors. In this article explain concept, features, and contemporary background of Smart Grid, and describe improve reliability of the electric power quality.