• Computers and Concrete
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• v.33 no.5
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• pp.621-630
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• 2024

This study presents novel electromagnetic wave-based methods for evaluating the integrity of cement-based structures using time domain reflectometry (TDR). Two cement-based plates with embedded rebars are prepared under sound and defective conditions. TDR tests are carried out using transmission lines with various numbers of artificial joints, and electromagnetic waves are measured to assess the integrity of the plates. The experimental results show that the travel time of electromagnetic waves is consistently longer in sound plates than in defective ones, and an increase in the reflection coefficients is observed in the defect zone of the defective plates. Electromagnetic wave velocities are higher in the defective plates, especially when connectors are present in the transmission line. A novel approach based on the area of the reflection coefficient provides larger areas in the defective plates, and the attenuation effect of the electromagnetic waves induces a difference in the areas of the reflection coefficient between the two defect conditions. An alternative method using the centroid of the defect zone slightly overestimates the location of the defect zone. The length of the defect zone is estimated using the defect ratio and wave velocities of cement, air, and plate. The length of the defect zone can also be calculated using the travel times within the plate, total measured length of the plate, and wave velocities in the cement and air. Therefore, the electromagnetic wave-based methods proposed in this study may be useful for estimating the location and length of defect zones by considering attenuation effects.

• Journal of Chest Surgery
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• v.23 no.3
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• pp.430-437
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• 1990

We clinically evaluated 121 cases of ventricular septal defect which we operated from April, 1986 to December, 1989 at Inha General Hospital, Seong-Nam, Department of Thoracic and Cardiovascular Surgery, College of Medicine, Inha University. These patients were occupied 54.8% of all congenital heart diseases operated on its same period. Of the 121 patients, 63 patients were male[52.1%] and 58 patients were female[47.9i]. The two most common symptoms were frequent upper respiratory infection and dyspnea on exertion. By Kirklin s anatomical classification, type I constituted 34.7%, type II 61.98%, type III 0.03% and type IV not occupied. Associated cardiac anomalies were found in 34 cases, and PDA was most common associated anomaly, occupied in 22 cases. On the cardiac catheterization data, there were statistically significant correlation between VSD size[cm2 /BSAm2] and systolic pulmonary arterial pressure[sPAP], pulmonary to systemic flow ratio[Qp/Qs] & pulmonary to systemic pressure ratio[Pp/Ps] respectively, Type II [r=0.53, p<0.01] was more correlated than type I [r=0.49, p<0.05] between VSD size and Qp /Qs. We could not found the correlationship between age and Qp/Qs [Type I; r=0.16, Type II; r=-0.15] All cases were operated under cardiopulmonary bypass and 58 cases[46.3%] were operated through the right atrial approach, and 34 cases[28.1%] through the pulmonary arterial approach. Operative mortality rate was 4.13%[5 cases].

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.12
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• pp.2004-2011
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• 2004

The applicability of the ultrasonic C-scan inspection is restricted due to the deterioration of mechanical properties of specimen during the test. Therefore, the aim of this research is applied to Eddy Current (EC) test substitute for the C-scan inspection in CFRP tube containing defects. This research is to evaluate the EC signals for the inspection of CFRP tube containing various circular hole defects (20% to 100% depth to the specimen thickness) using the unloading specimen and radial loading specimen. This study was considered the following points; 1) Analysis of EC signals for the inspection of saw-cut defect and circular hole defect, 2) The evaluation of defect depths and EC signals relationship. 3) Variation of EC signal owing to the radial load. In conclusions, the high frequency such as 300∼500 kHz made it possible to the inspection of 40% to 100% defects. Particularly, in case of 20% defect, the EC signal was not detected due to the noise of micro-crack and delamination. While the depth of the hole defects were decreasing, the difference of the phase angle between unloading specimen and radial loading specimen was gradually increasing.

• Journal of KIISE:Computing Practices and Letters
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• v.10 no.6
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• pp.499-506
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• 2004

The copper foil surface inspection system is necessary for the factory automation and product quality. The developed system is composed of the high speed line scan camera, the image capture board and the processing computer. For the system resource utilization and real-time processing, multi-threaded architecture is introduced. There are one image capture thread, 2 or more defect detection threads, and one defect communication thread. To process the high-speed input image data, the I/O overlap is used through the double buffering. The defect is first detected by the predetermined threshold. To cope with the light irregularity, the compensation process is applied. After defect detection, defect type is classified with the defect width, eigenvalue ratio of the defect covariance matrix and gray level of defect. In experiment, for high-speed input image data, real-time processing is possible with multi -threaded architecture, and the 89.4% of the total 141 defects correctly classified.

• Journal of Environmental Science International
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• v.32 no.11
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• pp.821-831
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• 2023

Recently, landscaping construction has played a significant role in enhancing the quality of life for citizens by creating and maintaining outdoor spaces. However, landscaping projects vary in material procurement depending on the contracting method, and they also present various challenges in defect occurrence and defect rectification due to their specialized nature. In this study, we classified different types of projects based on material procurement ratios and conducted on-site assessments of defect status by specific processes. We also analyzed the itemization of material ratios and defect rectification costs. The results revealed it was found that projects with a higher proportion of government-provided materials had the poorest defect status in terms of planting works and also incurred the highest defect rectification costs. Moreover, conflicts concerning the responsibility for defects arose. Currently, there are no specific guidelines for setting standards for the proportion of government-provided materials in landscaping construction contracts. Furthermore, there is ambiguity in the management of defect rectification. Therefore, it is necessary to establish a systematic landscaping construction contracting framework by providing institutional guidelines tailored to local governments or the circumstances of contracting entities and to conduct thorough reviews of construction processes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.365-365
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• 2010

In this paper, silicon nitride thin films with different silane and ammonia gas ratios were deposited and characterized for the antireflection and passivation layer of high efficiency single crystalline silicon solar cells. As the flow rate of the ammonia gas increased, the refractive index decreased and the band gap increased. Consequently, the transmittance increased due to the higher band gap and the decrease of the defect states which existed for the 1.68 and 1.80 eV in the SiNx films. The reduction in the carrier lifetime of the SiNx films deposited by using a higher $NH_3/SiH_4$ flow ratio was caused by the increase of the interface traps and the defect states in/on the interface between the SiNx and the silicon wafer. The silicon and nitrogen rich films are not suitable for generating both higher carrier lifetimes and transmittance. These results indicate that the band gap and the defect states of the SiNx films should be carefully controlled in order to obtain the maximum efficiency for c-Si solar cells.

• Journal of Chest Surgery
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• v.28 no.1
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• pp.18-22
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• 1995

From January 1989 to December 1993, cardiac catheterization and open heart surgery for ventricular septal defect closure were performed in 115 pediatric patients who were selected as meeting the criteria for elective closure of restrictive ventricular septal defect. These criteria included age greater than 1 year and less than 15 years, no evidence of congestive heart failure, Qp/Qs 2.0, pulmonary artery systolic pressure 35mmHg, and no associated cardiac anomalies. Mean age of patients was 5.25$\pm$ 3.53, and 72 patients were male, 43 patients were female[male:female=1.9:1 . Mean systolic pulmonary artery pressure was 19.66$\pm$4.79mmHg, and mean pulmonary to systemic flow ratio was 1.27$\pm$ 0.28. Aortic cusp prolapse was present in 30 patients [26% , aortic insufficiency was present in 1 paient, and 1 patient had prior bacterial endocarditis. There were no instances of complete atrioventricular dissociation, reoperations for bleeding, or reoperations for recurrent ventricular septal defect, but wound infection was present in 1 patient, and there were 7 patients who had the hemodynamically insignificant remnant shunt. There were no early or late deaths or major morbidity.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.72-79
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• 2008

The weak point of the artificial neural network(ANN) is that it is easy to fall in local minima when it learns too much nonlinear data. Accordingly, the classification ratio must be low. To overcome this weakness, the hybrid method has been proposed. That is, the ANN learns data selectively after detecting the defect position by the support vector machine(SVM). First, the SVM has been used for determination of the defect position and then the magnitude of the defect has been measured by the ANN. In off-design condition, the operation region of the engine is wide and the nonlinearity of learning data increases. The module system, dividing the whole operating region into reasonably small-size sections, has been suggested to solve this problem. In this study, the proposed algorithm has diagnosed the defects of triple components as well as single and dual components of the gas turbine engine in off-design condition.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.23-27
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• 2008

In this study, Real Coded Genetic Algorithm(RCGA) and Artificial Neural Network(ANN) are used for developing the defect diagnostics of the aircraft turbo-shaft engine. ANN accompanied with large amount data has a most serious problem to fall in the local minima. Because of this weak point, it becomes very difficult to obtain good convergence ratio and high accuracy. To solve this problem, GA based ANN has been suggested. GA is able to search the global minima better than ANN. GA based ANN has shown the RMS defect error of 5% less in single and dual defect cases.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.42-45
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• 2002

General wheel mark in mono-crystalline silicon wafer finding is able to be expected because it depends on radius ratio and angular velocity ratio of wafer and wheel. The pattern is predominantly determined by the contour of abrasive grits resulting from a relative motion. Although such a wheel mark is made uniform pattern if the process parameters are fixed, sub-surface defect is expected to be distributed non-uniformly because of characteristic of mono-crystalline silicon wafer that has diamond cubic crystal. Consequently it is considered that this phenomenon affects the following process. This paper focused on kinematic analysis of wafer grinding process and simulation program was developed to verify the effect of process variables on wheel mark. And finally, we were able to predict sub-surface defect distribution that considered characteristic of mono-crystalline silicon wafer