• Smart Structures and Systems
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• v.4 no.4
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• pp.391-406
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• 2008

This study attempts to develop a real-time debonding monitoring system for carbon fiber-reinforced polymer (CFRP) strengthened structures by continuously inspecting the bonding condition between the CFRP layer and the host structure. The uniqueness of this study is in developing a new concept and theoretical framework of nondestructive testing (NDT), in which debonding is detected without relying on previously-obtained baseline data. The proposed reference-free damage diagnosis is achieved based on the concept of time reversal acoustics (TRA). In TRA, an input signal at an excitation point can be reconstructed if the response signal measured at another point is reemitted to the original excitation point after being reversed in the time domain. Examining the deviation of the reconstructed signal from the known initial input signal allows instantaneous identification of damage without requiring a baseline signal representing the undamaged state for comparison. The concept of TRA has been extended to guided wave propagations within the CFRP-strengthened reinforced concrete (RC) beams to improve the detectibility of local debonding. Monotonic and fatigue load tests of large-scale CFRP-strengthened RC beams are conducted to demonstrate the potential of the proposed reference-free debonding monitoring system. Comparisons with an electro-mechanical impedance method and an inferred imaging technique are provided as well.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.475-478
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• 2001

In performing the three-level SVPWM, it is nearly impossible to control the neutral-point potential exactly to the half of the dc-link voltage at all times. Therefore the inverter would produce an erroneous output voltage by this voltage unbalance. So the voltage unbalance has to be compensated in doing PWM, when the voltage unbalance occurs whether it is small or large, to make the inverter output voltage follow the reference voltage exactly the same. In this paper, a new compensating method for the neutral-point potential variation in a three-level inverter space vector PWM (SVPWM) is presented. By using the proposed method, the output voltage of the inverter can be made same as the reference voltage and thus the current and torque ripple of the inverter driven motor can be greatly improved even if the voltage unbalance is quite large. The proposed method is verified experimentally with a 3-level IGBT inverter.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.3
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• pp.209-219
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• 2004

In order to implement a real time hardware for keyword spotting, we propose a Single-End-Point DTW(SEP-DTW) algorithm which is simple and less complex for computation. The SEP-DTW algorithm only needs a single end point which enables efficient applications, and it has a small wont of computations because the global search area is divided into successive local search areas. Also, we adopt new local constraints and a new distance measure for a better performance of the SEP-DTW algorithm. Besides, we make a normalization of feature same vectors so that they have the same variance in each frequency bin, and each frame has the same energy levels. To construct several reference patterns for each keyword, we use a clustering algorithm for all training patterns, and mean vectors in every cluster are taken as reference patterns. In order to detect a key word for input streams of speech, we measure the distances between reference patterns and input pattern, and we make a decision whether the distances are smaller than a pre-defined threshold value. With isolated speech recognition and keyword spotting experiments, we verify that the proposed algorithm has a better performance than other methods.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.8
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• pp.807-814
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• 2014

In this paper, we proposed a haptic navigation system which used the tactile data for the user guides of the mobile robot to the reference point via tele-operation in unknown blind environment. This navigation system can enable a mobile robot to avoid obstacles and move to the reference point, according to the direction provided by the device guides through a haptic device consisting of a vibration motor in a blind environment. There are a great deal of obstacles in real environments, and so mobile robots can avoid obstacles by recognizing the exact position of each obstacle through the superposition of an ultrasonic sensor. The navigation system determines the direction of obstacle avoidance through an avoidance algorithm that uses virtual impedance, and lets users know the position of obstacles and the direction of the avoidance through the haptic device consisting of 5 vibration motors. By letting users know intuitionally, it lets the mobile robot precisely reach the reference point in unknown blind environment. This haptic device can implement a haptic navigation system through the tactile sensor data.

• Journal of Digital Convergence
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• v.18 no.2
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• pp.73-81
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• 2020

The purpose of this study is to analyze the current status of expected cadastral coordinate maps by type of district boundary surveying and the problems of non-coincidence with the surrounding land parcels, and to suggest ways to improve them in the future. Currently, the expected cadastral coordinate maps are drawn using various methods such as reference point adjust adjustment, reference point adjust adjustment and present condition, reference point and present condition. As a result, there was a problem of non-coincidence such as overlapping or blanking in expected cadastral coordinate maps for cadastral confirmation surveying and surrounding individual parcels. In addition, detailed unified standards for minimizing the occurrence of non-coincidence problems are lacking. In order to improve the problems analyzed, the study suggested the acquisition and management of digital coordinates for the parcels around the district boundary, the preparation and dissemination of cadastral surveying results determination standard manual for the preparation of expected cadastral coordinate maps, and the preparation of educational programs for cadastral surveying results determination.

• Journal of Korean Society for Geospatial Information Science
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• v.22 no.2
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• pp.17-24
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• 2014

This paper proposes an automatic extraction method of control point based on Geospatial Web Service. The proposed method consists of 3 steps. 1) The first step is to acquires reference data using the Geospatial Web Service. 2) The second step is to finds candidate control points in reference data and the target image by SURF algorithm. 3) By using RANSAC algorithm, the final step is to filters the correct matching points of candidate control points as final control points. By using the Geospatial Web Service, the proposed method increases operation convenience, and has the more extensible because of following the OGC Standard. The proposed method has been tested for SPOT-1, SPOT-5, IKONOS satellite images and has been used military standard data as reference data. The proposed method yielded a uniform accuracy under RMSE 5 pixel. The experimental results proved the capabilities of continuous improvement in accuracy depending on the resolution of target image, and showed the full potential of the proposed method for military purpose.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.22 no.1
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• pp.63-69
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• 2000

Le fort II osteotomy is much useful technique to correct the midfacial hypoplasia including nasomaxillary complex especilly in patient with dish face appearance. Not in simple orthognathic surgery but in Le Fort II osteotomy, the standardization of prognostic value is essential in treatment planning to achieve satisfactory postoperative results. According to pervious reports, the ratio of soft tissue change to hard tissue movements varies as to different surgical methods and different facial regions. But there are few report about the ratio of soft tissue change to hard tissue movement following Le Fort II osteotomy. So we tried to develop standarized soft tissue surgical treatment objective. We have followed up 16 patients, who had received Le Fort II osteotomy by one operator from 1990 to 1996, one year postoperatively. In cephalometrics, we used Frankfort line as horizontal reference line, and vertical reference line as one drawn from Sella to horizontal line perpendicularly. The landmarks are G to soft tissue G, N on reference line to soft tissue N, ANS to Pn and A to Sn. The results are as follows. 1. The value of soft tissue change to hard tissue movement showed positive correlation, having statistical significancy at G, N2, N3 point. 2. At G, N2, N3 point, the ratio of soft tissue change to hard tissue movement was 0.51, 0.98 and 0.80 respectively and showed statistical significancy, while at N1, ANS, A point, that was 0.72, 0.49 and 0.26 but didn't showed statistical significance. 3. This result shows much the same change of the soft tissue change to hard tissue movement on the upper nasomaxilla, and less the same change on the lower maxilla and so the Le Fort II osteotomy can be recommended as a reliable effective operation method for correction of nasomaxillary retrusion.

• Journal of the Optical Society of Korea
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• v.18 no.5
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• pp.523-530
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• 2014

Machine material and structural strain are critical factors for appraising mechanical properties and safety. Particularly in three and four-point bending tests, which appraise the deflection and flexural strain of an object due to external force, measurements are made by the crosshead movement or deflection meter of a universal testing machine. The Digital Image Correlation (DIC) method is one of the non-contact measurement methods. It uses the image analyzing method that compares the reference image with the deformed image for measuring the displacement and strain of the objects caused by external force. Accordingly, the advantage of this method is that the object's surface roughness, shape, and temperature have little influence. However, its disadvantage is that it requires extensive time to compare the reference image with the deformed image for measuring the displacement and strain. In this study, an algorithm is developed for DIC that can improve the speed of image analysis for measuring the deflection and strain of an object caused by a three-point bending load. To implement this algorithm for improving the speed of image analysis, LabVIEW 2010 was used. Furthermore, to evaluate the accuracy of the developed fast correlation algorithm, the deflection of an aluminum specimen under a three-point bending load was measured by using the universal test machine and DIC measurement system.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.901-904
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• 2000

A direct authentication from gray-scale image, instead of the conventional multi-step preprocessing, is proposed using Gabor filter-based features from the gray-scale fingerprint around core point. The core point is located as a reference point for the translation invariant matching. And its principal symmetry axis is detected for the rotation invariant matching from its neighboring region centered at the core point. And then fingerprint is divided into non-overlapping blocks with respect to the core point and features are directly extracted form the blocked gray level fingerprint using Gabor filter. The proposed fingerprint authentication is based on the Euclidean distance between the corresponding Gabor features of the input and the template fingerprints. Experiments are conducted on 300${\times}$300 fingerprints obtained from a CMOS sensor with 500 dpi resolution, and the proposed method could lower the False Reject Rate(FRR) to 18.2% under False Acceptance Rate(FAR) of 0%.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.3
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• pp.310-315
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• 2011

General portal machine represents a distinct weak spot concerning their structural behavior because of long protruding structure components, such as saddles and rams. The weak point causes the deformation of the machine tool and consequently rises a severe machining error. The purpose of this study is to improve the structural design of crossrail in order to minimize it's distortion. Tool Center Point (TCP) was chosen as a reference point for evaluating the distortion effect of a crossrail and topological optimization was adopted as a method of structural design improvement. The displacements of TCP according to the machining positions were investigated by structural analyses for both of original crossrail design and the improved one. The comparing results showed that the displacement of TCP could be reduced about 55% maximum.