• 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.

• Ocean Systems Engineering
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• v.4 no.4
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• pp.263-278
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• 2014

The spudcan requires the suitable design considering the soil, platform, and environmental conditions. Its shape needs to be designed to secure sufficient reaction of soil so that it can prevent overturning accidents. Its shape also has to minimize the installation and extraction time. Even in the same soil condition, the reaction of soil may be different depending on the shape of spud can, mainly the slope of top and bottom plates. Therefore, in this study, the relation between the slope of plates and the reaction of soil with and without water jetting is analyzed to better understand their interactions and correlations. For the investigation, a wind turbine installation jack-up rig (WTIJ) is selected as the target platform and the Gulf of Mexico is considered as the target site. A multi layered (sand overlying two clays) soil profile is applied as the assumed soil condition and the soil-structure interaction (SSI) analysis is performed by using ANSYS to analyze the effect of the slope change of the bottom plate and water jetting on the reaction of soil. This kind of investigation and simulation is needed to develop optimal and smart spudcan with water-jetting control in the future.

• Journal of Internet Computing and Services
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• v.1 no.1
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• pp.63-72
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• 2000

Data mining means a process of nontrivial extraction of hidden knowledge or potentially useful information from data in large databases. Data mining algorithm is a multi-disciplinary field of research; machine learning, statistics, and computer science all make a contribution. Different classification schemes can be used to categorize data mining methods based on the kinds of tasks to be implemented and the kinds of application classes to be utilized, and classification has been identified as an important task in the emerging field of data mining. Since classification is the basic element of human's way of thinking, it is a well-studied problem in a wide varietyof application. In this paper, we propose a classifier system based on genetic algorithm with robust property, and the proposed system is evaluated by applying it to nDmC problem related to classification task in data mining.

• Applied Chemistry for Engineering
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• v.9 no.2
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• pp.232-237
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• 1998

This study was carried out to find the optimal operating conditions for separation of residual uranium from the simulated radwaste solution containing 19 elements, and to evaluate the validity of the process. The selected process was based on the solvent extraction with TBP(tributyl phosphate). As an extractor, two miniature mixer-settlers with a total of 18 stages were used. Extraction yield of U, Np and Tc was about 99.2%. 32.1%, and 99.9%, respectively. The other elements were coextracted in the range of 1~4%. Extraction yield of U exceeded those of the previous work performed with batch system, which resulted in the low extractability of U (about 80%) according to the coexisting element such as Nd and Fe. It was due to the characteristics of multi-stage extractor. On the other hand, low extractability of Np was caused by various oxidation states in the nitric acid medium. In the case of Tc, its high extractability may be attributed to the complex formation with Zr and U, which is not well proved yet. All elements extracted with TBP were stripped into aqueous phase more than 99% by 0.01M $HNO_3$. From the results, this process has no problem with respect to in the same step was required, because Np was distributed in the raffinate and U product, respectively.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.5
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• pp.383-392
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• 2007

In this paper, we study the prediction of depth and width of a defect in steam generator tube in nuclear power plant using neural network. To this end, we first generate eddy current testing (ECT) signals for 4 defect patterns of SG tube: I-In type, I-Out type, V-In type, and V-Out type. In particular, we generate 400 ECT signals for various widths and depths for each defect type by the numerical analysis program based on finite element modeling. From those generated ECT signals, we extract new feature vectors for the prediction of defect size, which include the angle between the two points where the maximum impedance and half the maximum impedance are achieved. Using the extracted feature vector, multi-layer perceptron with one hidden layer is used to predict the size of defects. Through the computer simulation study, it is shown that the proposed method achieves decent prediction performance in terms of maximum error and mean absolute percentage error (MAPE).

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.5
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• pp.44-53
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• 1999

This paper are reported a methodology and application for extracting parasitic capacitances in a multi-level interconnect semiconductor structure by a numerical technique. To calculate the parasitic capacitances between the interconnect lines, we employed finite element method (FEM) and calculated the distrubution of electric potential in the inter-metal layer dielecric(ILD) by solving the Laplace equation. The three-dimensional multi-level interconnect structure is generated directly from two-dimensional mask layout data by specifying process sequences and dimension. An exemplary structure comprising two metal lines with a dimension of 8.0$\times$8.0$\times$5.0$\mu\textrm{m}^3/TEX>, which is embedded in three dielectric layer, was simulated to extract the parasitic capacitances. In this calculation, 1960 nodes with 8892 tetrahedra were used in ULTRA SPARC 1 workstation. The total CPU time for the simulation was 28 seconds, while the memory size of 4.4MB was required.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.7
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• pp.16-25
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• 2002

This paper presents a methodology and application for extracting parasitic inductances in a multi-level interconnect semiconductor structure by a numerical technique. In order to calculate the parasitic inductances, the distrubution of electric potential and current density in the metal lines are calculated by finite element method (FEM). Thereafter, the magneto-static energy caused by the current density in metal lines was calculated. The result of simulation is compared with the result of Grover equation about analytic simple structures, and 4 bit ROM array with a dimension of $13{\times}10.25{\times}8.25{\mu}m^3$ was simulated to extract the parasitic inductnaces. In this calculation, 6,358 nodes with 31,941 tetrahedra were used in ULTRA 10 workstation. The total CPU time for the simulation was about 150 seconds, while the memory size of 20 MB was required.

• Economic and Environmental Geology
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• v.38 no.2 s.171
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• pp.101-111
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• 2005

The objectives of this study we to assess the extent and degree of environmental contamination and to draw general conclusions on the fate of toxic elements derived from mining activities in Korea. 인t abandoned mines with four base-metal mines and four Au-Ag mines were selected and the results of environmental surveys in those areas were discussed. In the base-metal mining areas, the Sambo Pb-Zn-barite, the Shinyemi Pb-Zn-Fe, the Geodo Cu-Fe and the Shiheung Cu-Pb-Zn mine, significant levels of Cd, Cu, Pb and Zn were found in mine dump soils developed over mine waste materials, tailings and slag. Furthermore, agricultural soils, stream sediments and stream water near the mines were severely contaminated by the metals mainly due to the continuing dispersion downstream and downslope from the sites, which was controlled by the feature of geography, prevailing wind directions and the distance from the mine. In e Au-Ag mining areas, the Kubong, the Samkwang, the Keumwang and the Kilkok mines, elevated levels of As, Cd, Cu, Pb and Zn were found in tailings and mine dump soils. These levels may have caused increased concentrations of those elements in stream sediments and waters due to direct dis-charge downstream from tailings and mine dumps. In the Au-Ag mines, As would be the most characteristic contaminant in the nearby environment. Arsenic and heavy metals were found to be mainly associated with sulfide gangue minerals, and mobility of these metals would be enhanced by the effect of oxidation. According to sequential extraction of metals in soils, most heavy metals were identified as non-residual chemical forms, and those are very susceptible to the change of ambient conditions of a nearby environment. As application of pollution index (PI), giving data on multi-element contamination in soils, over 1.0 value of the PI was found in soils sampled at and around the mining areas.