• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.1
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• pp.27-35
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• 2009

In this paper, we study the classification of steam generator tube defects using an improved feature extraction. We consider 4 axisymmetric defect patterns of tube: I-In type, I-Out type, V-In type, and V-Out type. Through numerical analysis program based on finite element modeling, 400 ECT signals are generated by varying width and depth of each defect type. From those generated ECT signals, we propose new feature vectors that include an angle between the two points where the Maximum impedance and half the Maximum impedance, and angles between Maximum impedance point and 10%, 20%, 30%, 40% of Maximum impedance points. Also, multi-layer perceptron with one hidden layer is used to classify the defect patterns. Through the computer simulation study, it is shown that the proposed method achieves an improved defect classification performance in terms of Maximum Error and mean square Error.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.2
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• pp.85-90
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• 2010

The infrared energy is emitted in the infrared wavelength range that corresponds to the surface temperature of a object which has temperature that is over the absolute the temperature(OK). The infrared thermography (IRT) is a non-destrnctive testing method that provides thermal video for the user in real-time by converting the infrared quantity that is detected by the infrared detector into temperature. The pipes of nuclear power plant(NPP) could be thinned by the corrosion and fatigue and the defect could lead to a big accident. For this reason, the effective non-destructive testing method is necessary. In this study, the relationship between the measured temperature and the defect depth or size of NPP pipes were recognized and that was applied to detect the wall thinning defects of NPP pipes.

• Journal of the Korea Convergence Society
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• v.11 no.11
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• pp.249-255
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• 2020

This study developed the health monitoring method of press process using the acoustic emission (AE) sensor and high-pass filter. Also, the AE parameters such as ring-down count and peak amplitude are used. Based on this AE signal, the AE parameters were acquired and was utilized to detect the crack of the specimen. Since the defect detection is difficult due to noise and low magnitude of signal, the signal noise and press operation frequency were checked through the Short Time Fourier Transform(STFT) and damped. High-pass Filtering data was applied to AE parameters to select effective parameters. By using this signal processing techniques, the proposed AE parameters could improve the performance of defect detection in the press process.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.3
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• pp.91-94
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• 2007

Single-crystalline $SnO_2$ nanowires were successfully grown on Si(001) substrates via vapor-liquid-solid mechanism in a thermal chemical vapor deposition. Large quantity of $SnO_2$ nanowires were synthesized at temperature ranges of $950{\sim}1000^{\circ}C$ in Ar atmosphere. It was found that the grown $SnO_2$ nanowires are of a tetragonal rutile structure and single crystalline by diffraction and transmission electron microscopy measurements. Broad emission located at about 600 m from the grown nanowires was clearly observed in room temperature photoluminescence measurements, indicating that the emission band originated from defect level transition into $SnO_2$ nanowires.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.5
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• pp.694-700
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• 1999

In this paper, we studied the design of power divider using the slow-wave effect of Photonic Bandgap structure, which is etched on the ground plane. The proposed PBG structure can provides the changing of the characteristic impedance of the transmission line and the group delay velocity characteristic. Therefore we can make wider width than the width of conventional transmission line and decrease the length of transmission line. We presented the application for power divider using the characteristic impedance and electrical length extracted from scattering parameter. As adding proposed defect units, the effect of defect is studied. The experimental results show good agreements with the simulated results.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.11
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• pp.1720-1728
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• 2022

The industrial 4.0 era has been opened with the development of artificial intelligence technology, and the realization of smart farms incorporating ICT technology is receiving great attention in the livestock industry. Among them, the quality management technology of livestock products and livestock operations incorporating computer vision-based artificial intelligence technology represent key technologies. However, the insufficient number of livestock image data for artificial intelligence model training and the severely unbalanced ratio of labels for recognizing a specific defective state are major obstacles to the related research and technology development. To overcome these problems, in this study, combining oversampling and adversarial case generation techniques is proposed as a method necessary to effectively utilizing small data labels for successful defect detection. In addition, experiments comparing performance and time cost of the applicable techniques were conducted. Through experiments, we confirm the validity of the proposed methods and draw utilization strategies from the study results.

• Advances in nano research
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• v.15 no.1
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• pp.59-65
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• 2023

In this present article, the mechanical behavior of single-walled black phosphorene nanotubes (SW-αPNTs) is simulated using molecular dynamics (MD). The proposed model is subjected to the axial loading and the effects of morphological parameters, such as the mono-vacancy defect and strain rate on the tensile behavior of the zigzag and armchair SW-αPNTs are studied as a pioneering work. In order to assess the accuracy of the MD simulations, the stress-strain response of the current MD model is successfully verified with the efficient quantum mechanical approach of the density functional theory (DFT). Along with reproducing the DFT results, the accurate MD simulations successfully anticipate a significant variation in the stress-strain curve of the zigzag SW-αPNTs, namely the knick point. Predicting such mechanical behavior of SW-αPNTs may be an important design factor for lithium-ion batteries, supercapacitors, and energy storage devices. The simulations show that the ultimate stress is increased by increasing the diameter of the pristine SW-αPNTs. The trend is identical for the ultimate strain and stress-strain slope as the diameter of the pristine zigzag SW-αPNTs enlarges. The obtained results denote that by increasing the strain rate, the ultimate stress/ultimate strain are respectively increased/declined. The stress-strain slope keeps increasing as the strain rate grows. It is worth noting that the existence of mono-atomic vacancy defects in the (12,0) zigzag and (0,10) armchair SW-αPNT structures leads to a drop in the tensile strength by amounts of 11.1% and 12.5%, respectively. Also, the ultimate strain is considerably altered by mono-atomic vacancy defects.

• Korean Journal of Construction Engineering and Management
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• v.20 no.6
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• pp.3-10
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• 2019

The entire duration of the long-term continuous construction contract project cannot be expected when calculating the initial budget as the construction of the contract is carried out annually according to the budget composition. In addition, the statutes related to the defect liability and execution of contracts have not been established systematically in relation to the contract. Therefore, there are many problems at the actual construction site with regard to the defect liability or the performance of the contract in relation to the contract. In this study, the following improvement directions were presented for the efficient operation of the contracts: First, the defect liability is legal and should be specified in an Act rather than an enforcement decree. Second, if the parties to the contract vary in the following order in the contract, the special agreement should be specified in the enforcement decree. Third, in the event of an indirect cost due to the extension of the period of the long-term continuous work, the contingency items of the total project cost management policy should be utilized. Fourth, in the case of general construction contract conditions, clauses related to the purchase of the premium of the CAR, inspection, taking over, defect repair, and defect inspection shall be supplemented.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.35 no.1
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• pp.13-17
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• 2013

Purpose: This study evaluated the capability of bone formation of silk fibroin particles coated with hydroxyapatites (HA/SF), as bone graft material when put into the calvarial defect of rats. Methods: Twenty Sprague Dawley rats were used for this study and round shaped defects were formed in the center of parietal bones (diameter: 8.0 mm). The defect was filled with (1) HA/SF (experimental group), or (2) left as a vacant space (control group). The animals were sacrificed at 4 or 8 weeks, postoperatively. The specimens were decalcified and stained with Masson's trichrome for histomorphometric analysis. Results: The average of new bone formation was $33.18{\pm}3.10%$ in the experimental group and $20.49{\pm}5.79%$ in the control group at 4 weeks postoperatively. That was $42.52{\pm}7.74%$ in the experimental group and $25.50{\pm}7.31%$ in the control group at 8 weeks postoperatively. The difference between the groups was significantly higher at both 4 weeks and 8 weeks postoperatively (P<0.05). Conclusion: The rat calvarial defect was successfully repaired by HA/SF graft. The HA/SF graft showed more new bone formation compared with the unfilled control.

• Journal of Navigation and Port Research
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• v.28 no.1
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• pp.43-49
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• 2004

Defects inspection of commodities are very important with those design and manufacturing process and essential to strengthen the competitiveness of those. If on-line automatic defects detection is performed without damaging to products, the production cost shall be curtailed through the reducing man-power, economical management of Q.C(Quality Control). In this paper, it is suggested three spatial filtering methods which can extract the necessary information in case of defects being on the surface of object like iron plate. In addition, the dependence of filtering characteristics on parameters such as the pitch and width of slits is analyzed and the surface defect detection system is constructed. Several experiments were carried out for determining the adequate spatial filtering method through comparing and analyzing effects of parameters like defect's size and shape, intensity of light, noise of coherent source and slit number.