• Journal of the Mineralogical Society of Korea
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• v.23 no.2
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• pp.117-124
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• 2010

The sorption of $AsO_4,\;SeO_3,\;CrO_4$ on schwertmannite and thermal analysis of sorbed samples were carried out. The results of sorption experiments showed that sorption characteristics of those three oxyanions on schwertmannite can be divided into two groups. The extent of sorption of $AsO_4$ and $SeO_3$ were 100% at up to 1 mM solution concentration, and they increased no more significantly. This can be interpreted as $AsO_4$ and $SeO_3$ substituting $SO_4$ in schwertmannite strucure by the ratio of 1 : 1. The extent of the sorption of $CrO_4$ was much lower than those of other two oxyanions. Thermal analysis was performed using two kinds of sorbed samples at 0.1 and 1.25 mM concentrations. The results of the thermal analysis showed that the samples sorbed by three different oxyanions have different thermal characteristics. The samples sorbed by $AsO_4$ showed smaller weight loss around $600^{\circ}C$ than the original loss of pure schwertmannite, and it is attributed to the substitution of $AsO_4$ for $SO_4$, which was caused by the loss of $SO_4$, than pure schwertmannite due to the substitution of $SO_4$ by $AsO_4$. It also showed additional weight loss around $600^{\circ}C$ due to the decomposition of $AsO_4$ at that temperature. The weight loss of samples sorbed by $SeO_3$ started at slightly lower temperature than that sorbed by $SO_4$ and kept that loss at wider temperature range, probably indicating that the decomposition of $SeO_3$ occurs at slightly lower temperature. However, for the samples sorbed by $CrO_4$, the weight loss caused by the decomposition of $SO_4$ was also smaller and there was no additional weight loss at higher temperature due to the thermal stability of $CrO_4$, indicating that $SO_4$ was also substituted by $CrO_4$ in schwertmannite. Sorption experiment and thermal analysis indicate that $CrO_4$ sorbs on schwertmannite by substiuting $SO_4$, but the affinity to $SO_4$ or instability of $CrO_4$ in scwertmannite structure probably prohibit perfect 1 : 1 substitution.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.535-540
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• 2002

A satellite shipping container must afford the satellite a relatively benign thermal, vibration, and particle environment that is oblivious to the extreme temperatures, sand, dust, vibrations, and shock that can accompany the transportation. Korea Aerospace Research Institute has developed a new shipping container system that will be used to transport KOMPSAT-2(Korea Multi-Purpose SATellite) from Tae-jon to launch site. To verify the dynamic characteristics, a Finite Element Analysis model and a 1/3 scaled mockup of the container were developed before the fabrication of real one. After fabrication of real shipping container, experimental modal analysis was peformed to identify the dynamic characteristics. This paper presents a series of development process of KOMPSAT-2 shipping container.

• Steel and Composite Structures
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• v.27 no.6
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• pp.761-775
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• 2018

In the present work, the recently developed non-polynomial shear deformation theories are assessed for thermo-mechanical response characteristics of laminated composite plates. The applicability and accuracy of these theories for static, buckling and free vibration responses were ascertained in the recent past by several authors. However, the assessment of these theories for thermo-mechanical analysis of the laminated composite structures is still to be ascertained. The response characteristics are investigated in linear and non-linear thermal gradient and also in the presence and absence of mechanical transverse loads. The laminated composite plates are modelled using recently developed six shear deformation theories involving different shear strain functions. The principle of virtual work is used to develop the governing system of equations. The Navier type closed form solution is adopted to yield the exact solution of the developed equation for simply supported cross ply laminated plates. The thermo-mechanical response characteristics due to these six different theories are obtained and compared with the existing results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.599-604
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• 2000

Excessive vibration magnitude results in serious damage and economic losses in the turbine and generator system. Therefore, it is of importance to evaluate the accurate dynamic characteristics of the system in advance. In this paper, rotordynamic characteristics of both the shrunk-fit disc and welded drum rotors have been investigated to ensure an excellent running behavior of the system in which low-pressure(LP) turbines of a nuclear power plant were retrofitted to improve thermal efficiency and reliability. Analysis shows that the welded drum rotor has good torsional characteristics rather than the shrunk-fit disc rotor. In addition, verification testing of field test was performed to confirm the retrofit. Test results are good agreement with analysis ones.

• Korean Journal of Materials Research
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• v.15 no.5
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• pp.318-322
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• 2005

Ti-capped NiSi contacts were formed on $p^+/n$ junctions to improve the leakage problem and then Cu was deposited without removing the Ti-capping layer in an attempt to utilize as a diffusion barrier. The electrical characteristics of these $p^+/n$ diodes with Cu/Ti/NiSi electrodes were measured as a function of drive-in RTA(rapid-thermal annealing) and silicidation temperature and time. When drive-in annealed at $900^{\circ}C$, 10 sec. and silicided at $500^{\circ}C$, 100 sec., the diodes showed the most excellent I-V characteristics. Especially, the leakage current was $10^{-10}A$, much lower than reported data for diodes with NiSi contacts. However, when the $p^+/n$ diodes with Cu/Ti/NiSi contacts were furnace-annealed at $400^{\circ}C$ for 40 min., the leakage current increased by 4 orders. The FESEM and AES analysis revealed that the Ti-capping layer effectively prohibited the Cu diffusion, but was ineffective against the NiSi dissociation and consequent Ni diffusion.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.910-913
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• 2001

Rapid Prototyping(RP) techniques have unique characteristics according to their working principle: the stair-stepped surface of a part due to layer-by-layer stacking, low building speed, and additional post-processing to improve surface roughness. A new RP process, Variable Lamination Manufacturing by using expandable polystyrene foam(VLM-S), has been developed to overcome the unfavorable characteristics. The objective of this study is to investigate the thermal characteristics and skeleton size effects as the hotwire cuts EPS foam sheet in order to improve dimensional accuracy of the parts, which is produced by VLM-S. Empirical and analytical approaches are performed to find the relationship between cutting speed and heat input, and the relationship between maximum available cutting speed and heat input. In addition, empirical approaches are carried out to find the relationship between cutting error and skeleton size, and cutting deviation and skeleton size. Based on these results, the optimal hotwire cutting condition and available minimum skeleton size are derived. The outcomes of this study are reflecting in the enhancement of VLM-S input data generation S/W.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.75-79
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• 2008

In this study, the numerical process for analyzing the automotive louver fin heat exchanger was developed with a 3D microscopic and semi-microscopic analysis. In the microscopic analysis, the simulation with the detailed meshes was performed for obtaining the characteristics of the heat exchanger. From this simulation, the numerical correlations of the heat transfer and flow friction were obtained. In the semi-microscopic analysis, the Semi-microscopic Heat Exchanger (SHE) method, which is characterized by a conjugate heat transfer and porous media analysis was used with the numerical correlation from the microscopic analysis. This analysis predicted the flow and heat transfer characteristics of the louver fin heat exchanger in the wind tunnel and vehicle. In the design of the louver fin heat exchanger, this numerical process can predict the performance and characteristic of the louver fin heat exchanger.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.377-378
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• 2007

• Proceedings of the Korean Nuclear Society Conference
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• 2004.10a
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• pp.311-312
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• 2004

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.171-172
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• 2009