• 한국소음진동공학회논문집
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• 제15권4호
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• pp.382-387
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• 2005

For successful guided-wave damage inspection, the appropriate signal processing of measured wave signals is very important. The objective of this paper is to introduce an efficient signal processing technique especially suitable for the guided-waves used for damage detection. The key idea of this technique is to model guided-waves by chirp functions of special form considering the dispersion phenomenon. To determine the parameter of the chirp functions simulating guided-waves, the matching pursuit algorithm is employed. The damage information in waveguides can be extracted by pulse-characterizing parameters. The effectiveness of present method is checked with the guided wave-based damage inspection.

• 비파괴검사학회지
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• 제21권4호
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• pp.383-390
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• 2001

Long-range guided wave inspection is a new emerging technology for rapidly and globally inspecting a large area of a structure from a single test location. This paper describes a general overview of the guided wave properties and its application for long-range inspection of structures the principle and instrument system for a guided wave inspection technology called "magnetostrictive sensor (MsS)" that generates and detects guided waves electromagnetically in the material under testing, and examples of long-range guided wave inspection of structures that can be accomplished using the MsS.

• 비파괴검사학회지
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• 제29권6호
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• pp.525-533
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• 2009

Emphasis in the paper is placed on describing guided wave successes and challenges for applications in aircraft and composite materials inspection. Guided wave imaging methods discussed includes line of sight, tomography, guided wave C-scan, phased array, and ultrasonic vibration methods. Applications outlined encircles lap splice, bonded repair patch, fuselage corrosion, water loaded structures, delamination, and ice detection and de-icing of various structures.

• 비파괴검사학회지
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• 제24권2호
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• pp.125-135
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• 2004

This paper describes the calculation technique for guided wave propagation with a semi-analytical finite element method (SAFEM) and shows some results of numerical calculation and guided wave simulation for plates, pipes and railway rails. The SAFEM calculation gives dispersion curves and wave structures for bar-like structures. Dispersion curve software for a pipe is introduced, and also dispersion corves for a rail are given and experimentally verified. The mode conversions in a plate with a defect and in a pipe with an elbow or a defect are shown as examples of our guided wave simulations.

• 전기학회논문지P
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• 제57권3호
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• pp.209-214
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• 2008

A precision guided kit is a GPS/INS guided range extension system to improve the accuracy and availability of existing dumb bombs. The PSD(power supply device) installed in the GPS guided kit supplies electrical power to all electrical loads in the kit. In this paper, design process and test results of the PSD have been presented. Additionally, the performance results of the PSD during actual ground and flight tests have been described.

• Nuclear Engineering and Technology
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• 제47권2호
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• pp.196-203
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• 2015

The aim of this work is to demonstrate a method for exciting and receiving torsional and longitudinal mode guided waves with an electromagnetic acoustic transducer (EMAT) ring array. First of all, a three-dimensional guided wave simulator is developed in order to numerically analyze the propagation of the guided wave. The finite difference time domain method is used for the simulator. Second, two guided wave testing systems using an EMAT ring array are provided: one is for torsional mode (T-mode) guided wave and the other is for longitudinal mode (L-mode). The EMATs used in the both systems are the same in design. A method to generate and receive the T- and L-mode guided waves with the same EMAT is proposed. Finally, experimental and numerical results are compared and discussed. The results of experiments and simulation agree well, showing the potential of the EMAT ring array as a mode controllable guided wave transmitter and receiver.

• Journal of Korean Biological Nursing Science
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• 제8권1호
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• pp.15-21
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• 2006

Purpose: The purpose of this study was to test the effect of pleasant guided imagery on the vital signs of elderly. Method: The subjects of this study were 15 elderly women. Collecting data were blood pressure, pulse rate, body temperature, the degree of imagination and relaxation. Data were analyzed using SPSS PC+ program with percentage, paired t-test. Result: After practicing of pleasant guided imagery, systolic blood pressure and pulse rate were significantly lowered than before practicing of pleasant guided imagery. After practicing of pleasant guided imagery, Diastolic blood pressure and body temperature were not significantly changed. After practicing of pleasant guided imagery, the degree of imagination and relaxation were relatively higher in old women. Conclusion: Pleasant guided imagery can be used for elderly patients with hypertension. And it can be used to promote relaxation of elderly with stress.

• Journal of Welding and Joining
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• 제23권5호
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• pp.43-48
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• 2005

Conventional non-destructive techniques for inspection of the weld in pipelines require significant test time and high cost. Ultrasonic guided waves have been widely studied and successfully applied to various non-destructive tests with advantage of the long-range inspection. In this paper, a study on the application of ultrasonic guided waves to the long-range inspection of the pipeline is presented using a long-range guided wave inspection system, Wavemaker SE16, GUL. The characteristics and setup of the long-range guided wave inspection system and experimental results in pipes of with various diameter are introduced. The experimental results in mock-up pipes with cluster type detects show that the minimum detectable wall thickness reduction with this guided wave system is $2\~3\%$ in the pipe cross section area. And the wall thickness reduction of $5\%$ in cross section area can be detected when actual detection level is used. Therefore, the applicability of the guided wave systeme to long-range inspection of wall thickness reduction in pipes is verified.

• Smart Structures and Systems
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• 제30권6호
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• pp.639-648
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• 2022

This study aims at numerically and experimentally investigating torsional guided wave mixing with weak material nonlinearity under acoustoelastic effect in tubular structures. The acoustoelastic effect on single central frequency guided wave propagation in structures has been well-established. However, the acoustoelastic on guided wave mixing has not been fully explored. This study employs a three-dimensional (3D) finite element (FE) model to simulate the effect of stress on guided wave mixing in tubular structures. The nonlinear strain energy function and theory of incremental deformation are implemented in the 3D FE model to simulate the guided wave mixing with weak material nonlinearity under acoustoelastic effect. Experiments are carried out to measure the nonlinear features, such as combinational harmonics and second harmonics in related to different levels of applied stresses. The experimental results are compared with the 3D FE simulation. The results show that the generation combinational harmonic at sum frequency provides valuable stress information for tubular structures, and also useful for damage diagnosis. The findings of this study provide physical insights into the effect of applied stresses on the combinational harmonic generation due to wave mixing. The results are important for applying the guided wave mixing for in-situ monitoring of structures, which are subjected to different levels of loadings under operational condition.

• 대한치과보철학회지
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• 제26권1호
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• pp.133-151
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• 1988

The objectives of this study were to compare the position of centric relation guided by means of leaf gauges, bilateral manipulation, chin-point guidance with Lucia jig and self-guided method and the reproducibility, respectively. A Veri-check (Denar Co., Anaheim, California) was employed for examining, and the displacement of position and reproducibility were verified. The following results were obtained. 1. On the sagittal plane, the centric relation guided by means of leaf gauges showed greater posterior displacement than that by means of bilateral manipulation and less than that by means of chin-point guidance with Lucia jig, and self-guided centric relation showed least posterior displacement. The centric relation guided by means of bilateral manipulation showed greater superior displacement than that by means of chin-point guidance with Lucia jig and less than that by means of leaf gauges and self-guided centric relation showed least superior displacement. 2. On the horizontal plane, the centric relation guided by means of chin-point guidance with Lucia jig showed greater posterior displacement than that of bilateral manipulation and less than that leaf gauges, however the self-guided centric relation showed slightly anterior displacement. 3. The anteroposterior displacement measured on sagittal plane and horizontal plane were highly correlated. (p<0.05). 4. The reproducibility of centric relation guided by means of leaf gauges, bilateral manipulation and chin-point guidance with Lucia jig were similar and more reproducible than self-guided centric relation.