• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1996년도 춘계학술대회 논문집
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• pp.24-29
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• 1996

The seniconductor, which is precision product, requires many inspection processes. The surface conditions of the semiconductor chip effect on the functions of the semiconductors. The defects of the chip surface is crack or void. Because general inspection method requires many inspection processes, the inspection system which searches immediately and preciselythe defects of the semiconductor chip surface. We propose the inspection method by using the computer vision system. This study presents an image processing algorithm for inspecting the surface defects(crack, void)of the semiconductor test samples. The proposed image processing algorithm aims to reduce inspection time, and to analyze those experienced operator. This paper regards the chip surface as random texture, and deals with the image modeling of randon texture image for searching the surface defects. For texture modeling, we consider the relation of a pixel and neighborhood pixels as noncasul model and extract the statistical characteristics from the radom texture field by using the 2D AR model(Aut oregressive). This paper regards on image as the output of linear system, and considers the fidelity or intelligibility criteria for measuring the quality of an image or the performance of the processing techinque. This study utilizes the variance of prediction error which is computed by substituting the gary level of pixel of another texture field into the two dimensional AR(autoregressive model)model fitted to the texture field, estimate the parameter us-ing the PAA(parameter adaptation algorithm) and design the defect detection filter. Later, we next try to study the defect detection search algorithm.

• 제어로봇시스템학회논문지
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• 제17권10호
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• pp.983-988
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• 2011

This paper presents a robust method for ground plane detection in vision-based applications based on a monocular sequence of images with a non-stationary camera. The proposed method, which is based on the reliable estimation of the homography between two frames taken from the sequence, aims at designing a practical system to detect road surface from traffic scenes. The homography is computed using a feature matching approach, which often gives rise to inaccurate matches or undesirable matches from out of the ground plane. Hence, the proposed homography estimation minimizes the effects from erroneous feature matching by the evaluation of the difference between the predicted and the observed matrices. The method is successfully demonstrated for the detection of road surface performed on experiments to fill an information void area taken place from geometric transformation applied to captured images by an in-vehicle camera system.

• 한국전산구조공학회논문집
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• 제33권4호
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• pp.225-235
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• 2020

초음파 탐상은 다양한 콘크리트 구조물의 비파괴검사에서 활용된다. 본 연구에서는 골재형상을 고려한 골재-모르타르 모델 생성과 초음파 전파 해석을 수행하였다. 실제 골재형상을 반영하기 위해 이미지처리를 통한 골재-모르타르 단면으로부터 모르타르와 골재 영역을 파악하고, 영역 경계형상을 보존하면서 격자를 생성하는 기법을 개발하였다. 개발된 기법에서는 모든 격자가 4각형으로 생성된다. 골재-모르타르 모델을 통해 초음파 전파 해석을 수행하였고 모델을 반무한체로 간주하기 위해 CALM 기반 경계흡수 조건을 적용하였다. 골재 및 결함을 포함한 이미지로부터 격자를 생성한 뒤, 결함 영역에 포함된 격자를 제거하여 공극결함을 모사하였다. 본격적인 결함탐지 전 선행 해석을 통해 모델 동특성을 고려한 적절한 가진 주파수를 결정 및 가진 신호형상을 설계하였다. 이후 case 별초음파 전파 해석을 통해 신호를 획득하고 신호 에너지 맵핑 작업을 통해 내부 결함을 가시화 하였다. 가시화 결과, 골재에 의한 다수반사 및 산란현상이 관찰되지만 결함부에서 신호 에너지는 가장 높게 나타났으며 모든 해석 case에서 결함위치 추정이 가능하였다. 또한 균열의 경우 형상파악도 가능하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.783-788
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• 2001

Voids created with concrete construction or deterioration result in serious weakness from the aspects of both structural and durable function. Ultrasonic method using image processing technique was used for detecting pattern of voids in concrete in this study Experimental investigation was carried out for three types(patterns) of void in concrete. The effect of curing period of concrete and ultrasonic measurement method was also investigated. As a result it has been verified that the semi-direct measurement method is more effective than the other methods for detecting pattern of voids in concrete in ultrasonic method using image processing technique. The longer the curing period of concrete is, the better the detection accuracy of void pattern can be obtained.

• Smart Structures and Systems
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• 제1권2호
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• pp.217-233
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• 2005

Elastic and electromagnetic waves can be used to gather important information about particulate materials. To facilitate smart geophysical characterization of particulate materials, their fundamental properties are discussed and experimental procedures are presented for both elastic and electromagnetic waves. The first application is related to the characterization of particulate materials using shear waves, concentrating on changes in effective stress during consolidation, multi-phase phenomena with relation to capillarity, and microscale characteristics of particles. The second application involves electromagnetic waves, focusing on stratigraphy detection in layered soils, estimation of void ratio and its spatial distribution, and conduction in unsaturated soils. Experimental results suggest that shear waves allow studying particle contact phenomena and the evolution of interparticle forces, while electromagnetic waves give insight into the characteristics of the fluid phase and its spatial distribution.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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• pp.1261-1266
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• 2000

In the impact echo method, a stress pulse is introduced into an object at on accessible surface by a transmitter. The pulse propagates into the test object and is reflected by flaws or interfaces. In this paper, void and crack locations of concrete specimens were detected using impact echo method. In their modal identification procedures, the double least squares solution for Ibrahim Time Domain technique was used.

• 로봇학회논문지
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• 제17권2호
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• pp.172-177
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• 2022

In general, detection robots using ultrasonic sensors are equipped with sensors to protrude outward or to contact objects. However, in the case of a screw-propelled robot that detects the inside of a reactor tendon duct, if the ultrasonic sensor protrudes to the outside, resistance due to grease is generated, and thus the propulsion efficiency is reduced. In order to increase the propulsion efficiency, the screw must be sharp, and the sharper the screw, the more difficult it is to apply a high-performance ultrasonic sensor, and the detection efficiency decreases. This paper proposes a screw shape-changing mechanism that can improve both propulsion efficiency and detection efficiency. This mechanism includes an overlapped helical ring (OHR) structure and a magnetic clutch system (MCS), and thus the shape of a screw may be changed to a compact size. As a result, the Screw-propelled robot with this mechanism can reduce the overall length by about 150 mm and change the shape of the screw faster and more accurately than a robot with a linear actuator.

• 한국전기전자재료학회논문지
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• 제19권10호
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• pp.947-952
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• 2006

It has been confirmed that the inner defect of insulator and the perfect diagnosis for aging are closely related to safe electric power transmission system and that the detection of accident and diagnosis technique turn out to be very important issues. But perfect diagnosis is difficult because discharge pattern is irregular. Thus, we investigated discharge pattern using the new distribution statistical models with cross-inked polyethylene(XLPE) specimens. Voltage was applied to power frequency by step method, and calibration of discharge was set to 50 pC. After the voltage was applied, it measured the discharge occurring during 10s. We investigated discharge pattern using the K-means analysis and Weibull function. We also investigated variation of centroid and shape parameter due to variation of voltage. As a result of analyzing K-means, it was confirmed that cluster including many object numbers was formed by the presence of void. And result of Weibull distribution, it was confirmed that shape parameter of discharge varied from 1.28 to 1.62 in no void specimens, and that shape parameter of discharge number varied from 1.28 to 1.62. In the void, shape parameter of discharge varied from 5.66 to 6.43, and shape parameter of discharge number varied from 5.05 to 5.08.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권1호
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• pp.44-51
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• 2000

In this paper, using a wide-band AE sensor with the frequency range from 100[kHz] to 1.5[kHz], the frequency spectra of AE signals generated from the corona discharges of the needle-plane gap and from the partial discharges of an epoxy void were analyzed to determine the proper ultrasonic sensor with optimum frequency range according to the patterns of corona discharges. We also examined the propagation characteristics of AE signals in oil and the relationship between the magnitude of corona discharge and the magnitude of AE signals in peak-to-peak value under the application of 60[Hz] ac high-voltage. From these results, the main frequency spectra of AE signals emitted from the corona discharges of the needle-plane gap were about 130[kHz] by the fast fourier transform, but the main frequency spectra appeared to be 230[kHz] in the partial discharges of an epoxy void. The magnitude of AE signals was proportional to the magnitude of corona discharge and discharge current pulse with increasing the applied voltages.

• Smart Structures and Systems
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• 제24권6호
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• pp.803-812
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• 2019

Triplex composite is an epoxy-bonded joint structure, which constitutes the secondary barrier in a liquefied natural gas (LNG) carrier. Defects in the triplex composite weaken its shear strength and may cause leakage of the LNG, thus compromising the structural integrity of the LNG carrier. This paper proposes an autonomous triplex composite inspection (ATCI) system for visualizing and classifying hidden defects in the triplex composite installed inside an LNG carrier. First, heat energy is generated on the surface of the triplex composite using halogen lamps, and the corresponding heat response is measured by an infrared (IR) camera. Next, the region of interest (ROI) is traced and noise components are removed to minimize false indications of defects. After a defect is identified, it is classified as internal void or uncured adhesive and its size and shape are quantified and visualized, respectively. The proposed ATCI system allows the fully automated and contactless detection, classification, and quantification of hidden defects inside the triplex composite. The effectiveness of the proposed ATCI system is validated using the data obtained from actual triplex composite installed in an LNG carrier membrane system.