• Journal of Advanced Navigation Technology
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• v.18 no.4
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• pp.304-311
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• 2014

In this paper, we propose a ultra sound inspection technique for automatic defect detection and classification in aircraft composite materials. Using local maximum values of ultra sound wave, we choose peak values for defect detection. Distance data among peak values are used to construct histogram and to determine surface and back-wall echo from the floor of composite materials. C-scan image is then composed through this method. A threshold value is determined by average and variance of the peak values, and defects are detected by the values. PCA(principal component analysis) and QDA(quadratic discriminant analysis) are carried out to classify the types of defects. In PCA, 512 dimensional data are converted into 30 PCs(Principal Components), which is 99% of total variances. Computational cost and misclassification rate are reduced by limiting the number of PCs. A decision boundary equation is obtained by QDA, and defects are classified by the equation. Experimental result shows that our proposed method is able to detect and classify the defects automatically.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.25 no.5
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• pp.383-392
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• 2007

This study focuses on co-registration and band selection, which are one of the pre-processing steps to apply the change detection technique using hyperspectral images. We carried out automatic co-registration by using the SIFT algorithm which performance was already established in the computer vision fields, and selected the bands fur change detection by estimating the noise of image through the PIFs reflecting the radiometric consistency. The EM algorithm was also applied to select the band objectively. Hyperion images were used for the proposed techniques, and non-calibrated bands and striping noises contained in Hyperion image were removed. Throughout the results, we could develop the reliable co-registration procedure which coincided with accuracy within 0.2 pixels (RMSE) for change detection, and verified that band selection depending on the visual inspection could be objective by extracting the PIFs.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.4 s.97
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• pp.57-63
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• 1999

A thin metal plate such as detent spring has the shape deformation due to the phenomenon of spring back after press machining and heat treatment process. This requires the correction of spring shape and force in final inspection process. To do correction of the shape deformation the impact force is manually applied to the bended part of detent spring after measuring the shape deformation and spring force. To develop the automatic spring force correction system, applied force of occurring plastic deformation must be derived from the experimental method. But frequent change of spring shape and material makes it difficult to accomplish the experimental method to be applied. This paper describes the analytical method for detent spring force correction system is to be substituted for the experimental method. FEM(Finite Element Method) is used to find the boundary value between elastic and plastic deformation in the analytical method. To confirm the validity of the analytical method, the result of two methods is compared each other at various applied force conditions. It shows that the simulation result of the analytical method is consistent with the result of the experimental method within the error bound ${\pm}$5%. The result of this paper is useful for development of the automatic spring correction system and reduction of the complicated and tedious processes involved in experimental method.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.2
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• pp.70-77
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• 2010

This study proposed an auto focusing method for a multi-focus image in assembling lens modules in digital camera phones. A camera module in a camera phone is composed of a lens barrel, an IR glass, a lens mount, a PCB board and aspheric lenses. Alignment among the components is one of the important factors in product quality. Auto-focus is essential to adjust image quality of an IR glass in a lens holder, but there are two focal points in the captured image due to thickness of IR glass. So, sharpness, probability and a scale factor are defined to find desired focus from a multi-focus image. The sharpness is defined as clarity of an image. Probability and a scale factors are calculated using pattern matching with a registered image. The presented algorithm was applied to a lens assembly machine which has 5 axes, two vacuum chucks and an inspection system. The desired focus can be determined on the local maximum of the sharpness, the probability and the scale factor in the experiment.

• Nuclear Engineering and Technology
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• v.44 no.4
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• pp.421-428
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• 2012

Analog instrument and control systems in nuclear power plants have recently been replaced with digital systems for safer and more efficient operation. Digital instrument and control systems have adopted various fault-tolerant techniques that help the system correctly and safely perform the specific required functions regardless of the presence of faults. Each fault-tolerant technique has a different inspection period, from real-time monitoring to monthly testing. The range covered by each faulttolerant technique is also different. The digital instrument and control system, therefore, adopts multiple barriers consisting of various fault-tolerant techniques to increase the total fault detection coverage. Even though these fault-tolerant techniques are adopted to ensure and improve the safety of a system, their effects on the system safety have not yet been properly considered in most probabilistic safety analysis models. Therefore, it is necessary to develop an evaluation method that can describe these features of digital instrument and control systems. Several issues must be considered in the fault coverage estimation of a digital instrument and control system, and two of these are addressed in this work. The first is to quantify the fault coverage of each fault-tolerant technique implemented in the system, and the second is to exclude the duplicated effect of fault-tolerant techniques implemented simultaneously at each level of the system's hierarchy, as a fault occurring in a system might be detected by one or more fault-tolerant techniques. For this work, a fault injection experiment was used to obtain the exact relations between faults and multiple barriers of faulttolerant techniques. This experiment was applied to a bistable processor of a reactor protection system.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.49 no.1
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• pp.80-87
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• 2012

We have developed the ATE(Automatic Test Equipment) system for the performance test of pre-amplifier of thermal imaging devices. The device regenerates the electronic signals of photon detection module which is normally in weak energy, for the image signals processing. Previous ATE system was primarily and actively developed in the field of semiconductor devices quality parts inspection. Recently, it has been studied in the field of performance testing of equipment. In the field of thermal performance test equipment, however, it lacks the study of ATE compared to other areas, which causes the maintenance related to the core of military thermal imaging system maintenance to be limited. In this paper, a new study of ATE in the field of thermal imaging system is done. It is designed to be used universally for the ATE system with different types of circuit card of thermal imaging system by adopting matrix relays. Using the developed ATE measuring the pre-amplifier amplitude, an average amplified amplitude of 2.71Vpp was measured which confirms that it is within the range of theoretical analysis and also verifies the good performance of the developed ATE.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.363-366
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• 2001

The present process of grading leather quality by the rare eyes is not reliable. Because inconsistency of grading due to eyes strain for long time can cause incorrect result of grading. Therefore it is necessary to automate the process of grading quality of leather based on objective standard for it. In this paper, leather automatic classification system consists of the process obtaining the information of leather and the process grading the quality of leather from the information. Leather is graded by its information such as texture density, types and distribution of defects. This paper proposes the algorithm which sorts out leather information like texture density and defects from the gray-level images obtained by digital camera. The density information is sorted out by the distribution value of Fourier spectrum which comes out after original image is converted to the image in frequency domain. And the defect information is obtained by the statistics of pixels which is relevant to Window using searching Window after sort out boundary lines from preprocessed images. The information for entire leather is used as standard of grading leather quality, and the proposed algorithm is practically applied to machine vision system.

• Fire Science and Engineering
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• v.24 no.1
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• pp.134-139
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• 2010

According to the "Yearbook of disaster response, fire safety and fire statistics (NEMA: National Emergency Management Agency)", approximately 34% of all fire is interior fire such as hotel, restaurant and residence and more than 53% of which is occurring in the kitchen. The evaluation of fire extinguishing system in the kitchen is performed in accordance with the "Korea Fire Equipment Inspection Standard (KOFEIS 0101-1)" which is using one environmental condition. However, only using one environmental condition is not enough to evaluate the performance of the automatic fire extinguisher in kitchen fire. So the study of fire detecting characteristic about various environmental condition needs. In this study, the numerical analysis is carried out about detecting time characteristic for various range's surrounding environment. As a result, it showed up to 100 s difference in the detection time depending on the position of the range. And detecting time also showed difference for on-off hood operation. From this results, it can be verify and improve the evaluation standard for the fire extinguishing system in kitchen fire.

• Journal of radiological science and technology
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• v.42 no.1
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• pp.19-24
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• 2019

For general radiological examinations, even in the same area and the same test, the test conditions must be set differently according to the patient. However, since it is impossible to consider the body shape and conditions of patients every time in medical institutions where various patients visit, the tests are conducted by setting the AEC which automatically sets the test conditions. AEC is most commonly used in chest radiography. Therefore, the purpose of this study is to propose the improvement plans for using AEC by measuring the exposure dose and evaluating the image quality according to whether the AEC is used or not, and to provide basic data for AEC research. In the present study, images were acquired while varying tube voltage and test distance according to the use of AEC in chest radiography. The radiation dose was measured by placing the dosimeter in front of the chest phantom, and the CNR and SNR of acquired images were analyzed using Image J. The t-test was conducted for the statistical analysis and the significance was determined at the level of 95%(p<.05). As a result of this study, in the inspection distance (100cm, 140cm, 180cm) according to the use of AEC, high doses were observed when the AEC was used and there was statistically significant difference(p<.05). In the t-test to determine the difference between CNR and SNR depending on whether AEC was used or not, there was no significant difference according to the use of AEC(p>.05). Therefore, when performing chest radiography, if the radiologist establishes the appropriate examination conditions and conducts the examination by not just relying solely on AEC, it may be possible to reduce unnecessary radiation exposure to the patient.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.903-909
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• 2018

In this paper, performance analysis of machine vision techniques is presented to improve the convenience and speed of automatic inspection in the industrial field when machine vision is applied to the image not taken in the stationary state, but in the moving state on a conveyer. When the length of cylindrical rods used for automobiles was measured using the edge detection method, the conveying speed increased, and the uncertainty of the boundary between the background and the part image increased, which resulted in a shorter image of the object taken. This paper proposes a linear compensation method to predict the biased errors of the length measurements after examining the pattern of biased and random errors, respectively, with 6 different types of specimens and 7 velocity stages. The length measurement corrected by the linear compensation method had the same accuracy as the stationary state within the speed range of 30 cm/s and could enhance the application capability in automatic inspections.