• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.856-859
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• 2005

The OPMT(Orientation-adjustable Patch-type Magnetostrictive Transducer) was proposed as a tool for generating and measuring the ultrasonic Lamb wave in plate type structures. This sensor has a lot of new features compared to the traditional piezo-type ultrasonic transducers. As an example, it does not need any kind of wiring for lunching or measuring ultrasonic waves. But it has also definite limitation for practical usage as a nondestructive testing tool in that it cannot help rotating the direction of ultrasonic wave manually. The idea for 'scanning OPMT' is proposed in this respect. Two kinds of basic ideas for rotating the wave direction not manually but electrically are proposed. The fabrication of the transducer and the testing for Identifying the primary characteristics are done for one of the proposed transducers. The results says that there are the possibilities as a new tool for NDE in that the proposed transducer follows well the characteristics of the traditional OPMT. But there are also the 1imitations to overcome.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.2
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• pp.208-216
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• 2009

In this paper, we present the equations of motion by which the natural vibration of a rotating annular disk can be analyzed accurately. These equations are derived from the theory of finite deformation and the principle of virtual work. The radial displacements of annular disk at the steady state where the disk is rotating at a constant angular velocity are determined by non-linear static equations formulated with 1-dimensional finite elements in radial direction. The linearlized equations of the in-plane vibrations at the disturbed state are also formulated with 1-dimensional finite elements in radial direction along the number of nodal diameters. They are expressed as in functions of the radial displacements at the steady state and the disturbed displacements about the steady state. In-plane static deformation modes of an annular disk are used as the displacement functions for the interpolation functions of the 1-dimensional finite elements. The natural vibrations of an annular disk with different boundary conditions are analyzed by using the presented model and the 3-dimensional finite element model to verify accuracy of the presented equations of motion. Its results are compared and discussed.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.14 no.1
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• pp.7-13
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• 2021

This paper proposes a method to minimize the target's direction detection error using RADAR. The radar system cannot accurately detect the target direction due to the phase error of he received signal. The proposed method of this study obtains a phase by applying an root mean square to each antenna incident signal, and reduces the phase error by using an optimal signal to noise ratio. In the simulation result, the probability of detecting the target direction is the best when the antenna spacing is half wavelength. The conventional method of direction detection probability 10-1.7 and the proposed method is 10-3.3. The target detection direction of the existing method represents [-8°,8°] with an error of 2 degrees. The target detection direction of the proposed method is shown in [-10°,10°], and all target directions are accurately detected. In the future, There is need for a method to reduce the phase error even though the resolution decrease.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.763-768
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• 2012

Active window system which can reduce the environmental noises, such as traffic noise and construction noise, from an open window into a room was proposed in the previous works. The key idea of the proposed active window system was that the control sources are approximately collocated with the primary noise source in terms of the acoustic power for global noise reduction throughout the interior room. Moreover, because it is important not to intrude into the living space in the building environment, no error sensors were used and an open-loop control method using control sources at the window frame and the reference sensors outside the room was used for the proposed system. The open-loop control gain was calculated by the interior room model assumed as the semi-infinite space, and the interior sound field was estimated by Rayleigh integral equation under the baffled window model assumption. However, windows with a finite thickness should were considered for the calculation of the open-loop control gain of the active window system since these are representative of most window cases. Therefore, the finite thickness window model based on the Sgard's model was derived and the open-loop control gain using the interior sound field estimated by that model was calculated for active window system. To compare the performance of these two models, a scale-model experiment was performed in an anechoic chamber according to noise source directions. Experimental results showed that the performance for the thickness window model is better than the baffled window model as the angle with respect to the perpendicular direction is larger.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.4
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• pp.854-860
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• 2004

The result of fingerprint matching is different as the quality or the state of input fingerprint image. We can extract the false direction information when the quality of fingerprint is degraded by the noise or the scars of the ridges. The information of the direction is very important for the elimination of the false minutia, the measurement of the ridge distance, matching, finding of cores and deltas. We need the method which can compensate or correct the false information of directions because the false directions include serious errors in the fingerprint recognition. We propose a method which can compensate or correct the false direction of fingerprint with a \alpha$-trimmed mean filter followed by LPF to reconstruct the false direction information when fingerprints are corrupted by scars.

• Journal of Information Processing Systems
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• v.16 no.1
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• pp.49-60
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• 2020

To solve the edge ringing or block effect caused by the partial differential diffusion in image enhancement domain, a new image enhancement algorithm based on bidirectional diffusion, which smooths the flat region or isolated noise region and sharpens the edge region in different types of defect images on aviation composites, is presented. Taking the image pixel's neighborhood intensity and spatial characteristics as the attribute descriptor, the presented bidirectional diffusion model adaptively chooses different diffusion criteria in different defect image regions, which are elaborated are as follows. The forward diffusion is adopted to denoise along the pixel's gradient direction and edge direction in the pixel's smoothing area while the backward diffusion is used to sharpen along the pixel's gradient direction and the forward diffusion is used to smooth along the pixel's edge direction in the pixel's edge region. The comparison experiments were implemented in the delamination, inclusion, channel, shrinkage, blowhole and crack defect images, and the comparison results indicate that our algorithm not only preserves the image feature better but also improves the image contrast more obviously.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.4
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• pp.497-502
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• 2010

The accurate estimation of position and direction of the mobile robot is essential for preparing precise movement and works in the inner complex environment. In this paper, we propose a robust estimation method of location and direction using the velocity of mobile robot in the inner GPS environment. The estimation using the inner GPS with ultrasonic sensors have to consider with various acoustic noise and sensor errors. We design a robust estimation method using a membership function based on uncertainty of the obtained information and robot velocity. The simulation results of the proposed method show effectiveness in the contaminated environment with position errors.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.6
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• pp.809-818
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• 2019

Since January 1, 2020, the International Maritime Organization (IMO) has put in place strong regulations to reduce air pollution caused by ships by lowing the upper limit of ship fuel oil sulfur content from 3.5% to 0.5% for ships passing through all sea areas around the world. Although it is important to reduce air pollutants by using fuel oil with low sulfur content, reducing the amount of energy waste through the economic operation of a ship can also help reduce air pollutants. Ships can follow designated routes accurately even under the influence of noise using autopilot systems. However, regardless of their quality, the performance of these systems is af ected by noise; heading angles with added measurement noise from the gyroscope are input into the autopilot system and degrade its performance. A technique to solve these problems reduces noise effects through the application of a Kalman filter, which is widely used in condition estimation. This method, however, cannot completely eliminate the effects of noise. Therefore, to further improve noise removal performances, in this study we propose a better denoising method than the Kalman filter technique by applying a multi-layer perceptron (MLP) in forward direction motion and a Kalman Filter in rotation motion. Simulations show that the proposed method improves forward direction motion by preventing the malfunction of a rudder more so than merely using a Kalman Filter.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.3
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• pp.345-355
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• 2008

This paper presents a design of a tuned liquid mass damper(TLMD) for controlling bi-directional response of high-rise building structure subjected to windload. The proposed damper behaves as a tuned mass damper(TMD) of which mass is regarded as the mass of a tuned liquid column damper(TLCD) and the case wall of the TLCD itself in one direction and the TLCD in the other direction. Because the proposed device has coupled design parameter along two orthogonal directions, it is very important to select designing components by optimal fine tuning. In the designing TLMD, for easy maintenance, the rubber-bearing with small springs was applied in TMD direction. In this study, the Songdo New City Tower 1A in Korea, which has been designed and constructed two TLCDs in order to control bi-directional response, was chosen as the model building structure. The results of rotation test proved the effectiveness of bi-directional behavior of TLMD.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.12
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• pp.1322-1329
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• 2004

End-milling has been used widely in industrial system because it is effective to a material manufacturing with various shapes. Recently the end-milling processing is needed the high-precise technique with good surface roughness and rapid time in precision machine part and electronic part. The optimum mechanical vibration of main spindle, surface roughness and cutting temperature have an effect on end-milling condition such as, cutting direction, revolution of spindle, feed rate and depth of cut, etc. Therefore, this study carried to decide the working condition for optimum mechanical vibration of main spindle, surface roughness and cutting temperature using design of experiments, ANOVA and characteristic function. From the results of experimentation, mechanical vibration has an effect on revolution of spindle, radial depth of cut, and axial depth of cut. The surface roughness has an effect on cutting direction, revolution of spindle and depth of cut. And then the optimum condition used design of experiments is upward cutting In cutting direction, 600 rpm in revolution of spindle, 240 mm/min in feed rate, 2 mm in axial depth of cut and 0.25 mm in radial depth of cut. By design of experiments and characteristic function, it is effectively represented shape characteristics of mechanical vibration, surface roughness and cutting temperature in end-milling.