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1
Content available Effect of Trace Elements (Co, Cr) on the Microstructure and Physical Properties of Al-Si-Cu-Mg-Fe Extruded Alloy
Ahn S. S., Sharief P., Lee C. H., Son H. T., Kim Y. H., Kim Y. C., Hong S., Hong S. J.
Archives of Metallurgy and Materials
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2019
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Vol. 64, iss. 3
857--862
EN
Trace elements Co, Cr were added to investigate their influence on the microstructure and physical properties of Al-Si extruded alloy. The Co, Cr elements were randomly distributed in the matrix, forms intermetallic phase and their existence wereconfirmed by XRD, EDS and SEM analysis. With addition of trace elements, the microstructure was modified, Si particle size was reduced and the growth rate of β-(Al5 FeSi) phase limited. Compared to parent alloy, hardness and tensile strength were enhanced while the linear coefficient of thermal expansion (CTE) was significantly reduced by 42.4% and 16.05% with Co and Cr addition respectively. It is considered that the low CTE occurs with addition of Co was due to the formation of intermetallic compound having low coefficient of thermal expansion. The results suggested that Co acts as an effective element in improving the mechanical properties of Al-Si alloy.
2
Content available Effect of Milling Time Parameter on the Microstructure and the Thermoelectric Properties of n-Type Bi2Te2.7Se0.3 Alloys
Sharief P., Madavali B., Koo J. M., Kim H. J., Hong S., Hong S.-J.
Archives of Metallurgy and Materials
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2019
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Vol. 64, iss. 2
585-590
EN
Nanostructured thermoelectric materials receiving great attention for its high thermoelectric performance. In this research, nanostructured n-type Bi2 Te2.7 Se0.3 alloys have prepared using high energy ball milling and followed by spark plasma sintering. Also, we have varied ball milling time to investigate milling time parameter on the thermoelectric properties of n-type Bi2 Te2.7 Se0.3 powder. The powders were discrete at 10 min milling and later particles tend to agglomerate at higher milling time due to cold welding. The bulk fracture surface display multi-scale grains where small grains intersperse in between large grains. The maximum Seebeck coefficient value was obtained at 20-min milling time due to their lower carrier density. The κ values were decreased with increasing milling time due to the decreasing trend observed in their κL values. The highest ZT of 0.7 at 350 K was observed for 30-min milling time which was ascribed to its lower thermal conductivity. The Vickers hardness values also greatly improved due to their fine microstructure.
3
Content available remote Orthogonal Experiment Design Algorithm of a Distribution Network Reconfiguration
Yanli L., Dexiang Z., Hong S., Xue G.
Przegląd Elektrotechniczny
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2013
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R. 89, nr 4
120-122
EN
According to the operation characteristics of the power distribution network with tree structure and the reconfiguration power distribution network, this paper proposes the orthogonal experiment design algorithm of power distribution network reconfiguration by mending the switch of the ring net presented by the orthogonal table.
PL
W artykule przedstawiono propozycję algorytmu rekonfiguracji sieci dystrybucji energii. W metodzie zastosowano projektowanie ortogonalnego eksperymentu. Wykonanie operacji polega na przełączaniu (łączeniu) odpowiednich łączników w pierścieniu sieci, która zapisana jest w tablicy ortogonalnej.
4
Content available Parametric study simulation of axially loaded ored pile using finite element ode—Plaxis Software on subsurface soils Khartoum area-Sudan
Ibrahim A. M., Widodo S., Hong S.
Challenges of Modern Technology
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2012
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Vol. 3, no. 3
33--38
EN
The diversity and complexity of subsurface soil in studied area consisting of alluvial deposits cause many diffi culties for foundation engineering. Therefore, a solution is needed for foundation in this problematic soil. In Sudan, raft foundation represents the basic and most widespread shallow foundation method for engineering structure except for bridges where the pile foundation is used. In recent years, after the discovery of petroleum in Sudan, a major advance in piling technology is needed due to intensive building of large numbers of precast high-rise tower. This paper used Plaxis software to understand the behavior of axially loaded bored pile using different loads, lengths and diameters of piles. In this paper a comprehensive analytical study using fi nite element analysis is presented and parametric study of pile under vertical load is performed. The analytical and quantitative analysis in this study shows useful understanding of the behavior of bored pile.
5
Content available Analysis of different equations of undrained shear strength estimations using Atterberg Limits on Pontianak Soft Clay
Widodo S., Ibrahim A., Hong S.
Challenges of Modern Technology
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2012
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Vol. 3, no. 3
46--50
EN
Many researchers have done study to estimate the value of undrained shear strength for fine grained soils like clay or silt. Determining of undrained shear strength and compressibility parameters in laboratory are really tedious and time consuming. Therefore, a correlation between undrained shear strength and Atterberg limits is useful for restraint of testing number and costs. Central tendency parameters such as an average, deviation standard and coeffi cient of variation are performed to analyze the data of soft clay in Pontianak, Indonesia. Based on analysis that undrained shear strength coincides with 50 percentile of distribution data meanwhile undrained compressive strength is around twice of cohesion for testing using unconfi ned pressure. This relationship is the most familiar equation. Moreover, undrained shear strength using mean value is more realistic for correlation between undrained shear strength and Atterberg limits on some equations from previous findings.
6
Content available remote Collision Scenario-based Cognitive Performance Assessment for Marine Officers
Kim H., Kim H. J., Hong S.
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
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2010
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Vol. 4, no. 1
73--77
EN
The overall aim of this paper is to determine a fatigue factor that can be applied to human performance data as a part of a software program that calculates total cognitive performance. This program enables us to establish the levels of cognitive performance in a group of marine pilots in order to test a decision-making task based on radar information. This paper addresses one of the factors that may contribute to the determination of various fatigue factors: the effects of different work patterns on the cognitive performance of a marine pilot.
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