• 소음진동
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• 제5권1호
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• pp.117-122
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• 1995

The transfer matrix method is proposed to compensate the attachment effect of a piezo-electric impedance head. To validate the proposed method, an experiment is carried out for axial vibration of a uniform rod for which an analytical solution is known. The impedance head is attached to the test rod by a stud and is connected to the exciter. The frequency response function is mesured by applying random excitation from the electro-magnetic exciter. The frequency response function compensated by the method proposed in this research shows good agreement with the analytical solution.

• Smart Structures and Systems
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• 제17권1호
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• pp.107-122
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• 2016

We propose an effective methodology using electromechanical impedance characteristics for estimating the remaining tensile force of tendons and simultaneously detecting damages of the anchorage blocks. Once one piezoelectric patch is attached on the anchor head and the other is bonded on the bearing plate, impedance responses are measured through these two patches under varying tensile force conditions. Then statistical indices are calculated from the impedances, and two types of relationship curves between the tensile force and the statistical index (TE Curve) and between statistical indices of two patches (SR Curve) are established. Those are considered as database for monitoring both the tendon and the anchorage system. If damage exists on the bearing plate, the statistical index of patch on the bearing plate would be out of bounds of the SR curve and damage can be detected. A change in the statistical index by damage is calibrated with the SR curve, and the tensile force can be estimated with the corrected index and the TE Curve. For validation of the developed methodology, experimental studies are performed on the scaled model of an anchorage system that is simplified only with 3 solid wedges, a 3-hole anchor head, and a bearing plate. Then, the methodology is applied to a real scale anchorage system that has 19 strands, wedges, an anchor head, a bearing plate, and a steel duct. It is observed that the proposed scheme gives quite accurate estimation of the remaining tensile forces. Therefore, this methodology has great potential for practical use to evaluate the remaining tensile forces and damage status in the post-tensioned structural members.

• 한국농공학회지
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• 제32권3호
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• pp.20-22
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• 1990

• 전자공학회논문지SC
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• 제46권5호
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• pp.38-43
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• 2009

본 논문에서는 자기 벡터 포텐셜 해석을 통해 3-코일 구조를 갖는 금속 검출기 헤드가 수신 코일에 미치는 유도 전압을 구하고, 금속 물체의 특성이 송신 코일의 임피던스에 미치는 영향을 유도하였다. 이러한 해석을 통하여 최적의 검출 성능을 위한 송신 코일과 수신 코일 간의 거리를 구하였고, 최대 유도 전압을 출력하는 금속의 위치를 유도하였다. 또한 기존의 수식과 비교하여 본 논문의 자기 벡터 포텐셜 해석에 대한 타당성을 입증하였다.

• 상하수도학회지
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• 제37권6호
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• pp.437-446
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• 2023

We propose a transient evaluation scheme using a pressure measurement in a complicate pipeline systems. Conservation of mass and momentum equations in time domain can be transformed into a pressure head and flowrate relationship between upstream and downstream point in frequency domain. The impedance formulations were derived to address measured pressure at downstream to evaluate of flowrate or pressure head at any point of system. Both branched pipeline element and looped pipeline element can be generally addressed in the platform of the basic reservoir pipeline valve system. The convolution of time domain response function with measured pressure head from a downstream point provides flowrate or pressure head response in any point of the designated pipeline system. The proposed method was validated through comparison between traditional method of characteristics and the proposed method in several hypothetical systems.

• 한국ITS학회 논문지
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• 제8권2호
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• pp.45-52
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• 2009

본 논문에서는 기존의 전구방식 신호등과 비교하여 LED신호등의 교통신호기 간 신호 안전성 측면의 연계 호환성을 실험 검토하고 보완 방안을 설계하여 제안하였다. 실험 분석 결과 신호의 안전성을 향상하기 위하여, 교통신호기의 출력 누설전류에 따른 LED신호등의 OFF 상태 누설전압의 과다로 인한 문제와, 누전상황 대응에 대한 문제에 대하여 보완이 필요한 것으로 나타났다. 보완을 위한 교통신호기 규격의 개선 방안은 220V 전원을 기준으로 출력 누설전류 허용 값을 기존의 8mA사양에서 3mA로 변경하고, 출력전압 평가의 기준을 기존의 25-45V에서 65-75V로 변경하는 것이며, LED신호등 규격의 개선 방안은 기존과 동일하게 95V이하에서 OFF상태를 유지하도록 함에 더하여 OFF상태에서 10Kohm이내의 임피던스를 유지하도록 하는 내용을 추가하는 것이다.

• 상하수도학회지
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• 제36권4호
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• pp.219-228
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• 2022

In this study, we propose a flow velocity evaluation scheme based on pressure measurement in pressurized pipeline systems. Conservation of mass and momentum equations can be decomposed into mean and perturbation of pressure head and flowrate, which provide the pressure head and flowrate relationship between upstream and donwstream point in pressurized pipeline system. The inverse impedance formulations were derived to address measured pressure at downstream to evaluation of flow velocity or pressure at any point of system. The convolution of response function to pressure head in downstream valve provides the flow velocity response in any point of the simple pipeline system. Simulation comparison between traditional method of characteristics and the proposed method provide good agreements between two distinct approaches.

• 소음진동
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• 제6권6호
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• pp.749-754
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• 1996

In this paper, a design method of matching layers is presented for the sandwich type broad band underwater acoustic vibrators. The characteristic impedances of matching layers are determined to be matched to the characteristic impedance of head mass material. For the dynamic characteristic analysis of the sandwich type transducers, one dimensional FEM technique is also introduced. A test vibrator with the quarter wave matching layers has been designed to verify the proposed method. And the wide band characteristics of the input impedance and transmitting voltage response (TVR) are investigated.

• 한국전자파학회논문지
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• 제16권5호
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• pp.534-540
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• 2005

휴대전화 안테나와RF회로간의 임피던스 정합과 본체에서 복사되는 전자파의 상관관계를 측정, 분석하였다. 수납형과 고정형 안테나를 갖는 두 종류의 휴대전화를 이용하여, 총 16가지의 다양한 사용 조건 하에서 임피던스와 복사 전자파를 측정하였다. 임피던스 정합이 잘 이루어질수록 본체에서의 복사가 감소하여, 휴대전화는 모노폴 안테나와 동일한 복사 패턴을 갖게 되었으며, 이 경우 두부 방향으로의 복사를 감소시킬 수 있음을 확인하였다.

• 대한조선학회논문집
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• 제42권2호
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• pp.136-141
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• 2005

An experiment method has been developed to analyse the vibration characteristics of marine propeller blades, and vibration tests have been carried out on the model scale propeller in air and in water. The driving point transfer function(acceleration/excitation force) has been measured and modified by compensating the attachment effect of the impedance head. The measured natural frequencies in air have been compared with the theoretical results by an in-house FEM code PROSTEC. The added masses have been derived by comparing the measured natural frequencies in air and in water, and the results have been compared to the results using existing formula based on experience.