• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.673-676
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• 2004

Fast and high-quality document clustering algorithms play an important role in providing data exploration by organizing large amounts of information into a small number of meaningful clusters. In particular, hierarchical clustering provide a view of the data at different levels, making the large document collections are adapted to people's instinctive and interested requires. Many papers have shown that the hierarchical clustering method takes good-performance, but is limited because of its quadratic time complexity. In contrast, K-means has a time complexity that is linear in the number of documents, but is thought to produce inferior clusters. Think of the factor of simpleness, high-quality and high-efficiency, we combine the two approaches providing a new system named CONDOR system [10] with hierarchical structure based on document clustering using K-means algorithm to "get the best of both worlds". The performance of CONDOR system is compared with the VIVISIMO hierarchical clustering system [9], and performance is analyzed on feature words selection of specific topics and the optimum hierarchy depth.

• Smart Media Journal
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• v.8 no.2
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• pp.39-45
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• 2019

As deep learning has become popular, researches which can help explaining the prediction results also become important. Superpixel based multi-scale combining technique, which provides the advantage of visual pleasing by maintaining the shape of the object, has been recently proposed. Based on the principle of prediction difference, this technique computes the saliency map from the difference between the predicted result excluding the superpixel and the original predicted result. In this paper, we propose a new technique of both excluding and including super pixels. Experimental results show 3.3% improvement in IoU evaluation.

• Explosives and Blasting
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• v.37 no.3
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• pp.25-33
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• 2019

Controlling the blast-induced damage zone(BDZ) in mining excavation is a significant issue for the safety of employees and the maintenance of facilities. Numerous studies have been conducted to accurately predict the BDZ in underground mining. This study employed the dynamic fracture process analysis (DFPA) to estimate the BDZ from a single hole blasting. The estimated BDZ were compared with the results obtained by Swedish empirical equation. The DFPA was also used to investigate the control mechanism of BDZ and fracture plane formation around perimeter holes for underground mining blasting.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.11
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• pp.78-86
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• 2020

A stress analysis was performed to verify the stability of the digging part of a garlic harvester. A finite element analysis was performed to examine the distribution and concentrated loads on the digging part of the blade and contact plate. Moreover, the stability and maximum deformation of the digging part were determined. Under a distributed load, the maximum principal stress, total deformation, and minimum safety factor ranged from 64-128 MPa, 0.35-0.70 mm, and 2.9-5.7, respectively. The analysis results for the distribution load indicated that the maximum stress occurred at the center of the blade. In contrast, under the concentrated load, the maximum principal stress, total deformation, and minimum safety factor ranged from 66-247 MPa, 0.35-0.79 mm, 1.48-5.53, respectively. The analysis results for the concentrated load indicated that stress and deformation were larger toward the edge and center, respectively.

• Korean Journal of Metals and Materials
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• v.48 no.5
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• pp.417-423
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• 2010

A dense nanostructured MoSi$_{2}$-SiC composite was synthesized by a pulsed current activated combustion synthesis method within 2 min of one step from mechanically activated powders of Mo$_{2}$C and Si. Simultaneous combustion synthesis and consolidation were accomplished under the combined effects of a pulsed current and mechanical pressure. Highly dense MoSi$_{2}$-SiC with a relative density of up to 98% was produced under simultaneous application of an 80 MPa pressure and pulsed current. The average grain size and mechanical properties of the composite were investigated.

• Korean Journal of Metals and Materials
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• v.49 no.9
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• pp.715-719
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• 2011

Nanopowders of $Fe_3N$ and Si were fabricated by high-energy ball milling. A dense nanostructured $12Fe-Si_3N_4$ composite was simultaneously synthesized and consolidated using a high-frequency induction-heated sintering method for 2 minutes or less from mechanically activated powders of $Fe_3N$ and Si. Highly dense $12Fe-Si_3N_4$ with a relative density of up to 99% was produced under simultaneous application of 80 MPa pressure and the induced current. The microstructure and mechanical properties of the composite were investigated.

• Korean Journal of Metals and Materials
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• v.47 no.11
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• pp.754-758
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• 2009

Dense $5Cu_{0.6}Fe_{0.4}-Al_{2}O_{3}$ composite was consolidated from mechanically synthesized powders by high frequency induction heating method within 2 min. Consolidation was accomplished under the combined effects of a induced current and mechanical pressure. Dense $5Cu_{0.6}Fe_{0.4}-Al_{2}O_{3}$ with relative density of up to 95% was produced under simultaneous application of a 80 MPa pressure and the pulsed current. Fracture toughness and hardness of the composite are $7.6MPa{\cdot}m^{1/2}$ and $844kg/mm^{2}$ respectively.

• Journal of Powder Materials
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• v.28 no.6
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• pp.478-482
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• 2021

The effect of the process conditions of high-velocity oxygen fuel (HVOF) thermal spray coating on the porosity of the coating layer is investigated. HVOF coating layers are formed by depositing amorphous FeMoCrBC powder. Oxygen pressure varies from 126 to 146 psi and kerosene pressure from 110 to 130 psi. The Microstructural analysis confirms its porosity. Data analysis is performed using experimental data. The oxygen pressure-kerosene pressure ratio is found to be a key contributor to the porosity. An empirical model is proposed using linear regression analysis. The proposed model is then validated using additional test data. We confirm that the oxygen pressure-kerosene pressure ratio exponentially increases porosity. We present a porosity prediction model relationship for the oxygen pressure-kerosene pressure ratio.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.2
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• pp.172-177
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• 2022

The quench voltage of the second-generation superconducting wire is affected by the resistivity characteristics of the stabilization layer. The specific resistance of the stabilization layer can be changed by the deposition process using RF magnetron sputtering. In this paper, a thin film made of a homogeneous material (Ag) and a dissimilar material (Cu) was deposited on the stabilization layer of the second-generation superconducting wire through RF magnetron sputtering. We found that the specific resistance was reduced by increasing the thickness of the stabilization layer. The reduction in the resistivity of the stabilization layer led to a decrease in the quench voltage of the second-generation superconducting wire. We suggest that various characteristic changes of the second-generation superconducting wire can be expected through the successful change in the resistivity of the stabilization layer of the proposed deposition process.

• Journal of Powder Materials
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• v.29 no.6
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• pp.517-522
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• 2022

We investigate the austenite stability in nanocrystalline Fe-7%Mn-X%Mo (X = 0, 1, and 2) alloys fabricated by spark plasma sintering. Mo is known as a ferrite stabilizing element, whereas Mn is an austenite stabilizing element, and many studies have focused on the effect of Mn addition on austenite stability. Herein, the volume fraction of austenite in nanocrystalline Fe-7%Mn alloys with different Mo contents is measured using X-ray diffraction. Using a disk compressive test, austenite in Fe-Mn-Mo alloys is confirmed to transform into strain-induced martensite during plastic deformation by a disk d. The variation in austenite stability in response to the addition of Mo is quantitatively evaluated by comparing the k-parameters of the kinetic equation for the strain-induced martensite transformation.