• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.6
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• pp.55-62
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• 2008

This paper reports the effect of replacement levels of silica fume on the resistance to magnesium sulfate attack. Mortar specimens incorporating silica fume were exposed to 5% magnesium sulfate solution for 360 days at ambient temperature. The main variable was the replacement levels of silica fume(0, 5, 10 and 15% of cement by mass). The resistance of mortar specimens incorporating silica fume against magnesium sulfate attack was regularly monitored by measuring compressive strength and expansion. In addition, in order to investigate the reactants formed by magnesium sulfate attack, various instrumental analyses such as XRD, SEM and DSC were used. Results demonstrated that the formation of gypsum, thaumasite and brucite led to a significant deterioration due to magnesium sulfate attack in cement matrix incorporating silica fume.

• The Korean Journal of Ceramics
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• v.6 no.2
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• pp.172-176
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• 2000

Solid solutions of Ti$_{0.5}$Zr$_{0.5}$B$_2$were successfully synthesized and densified simultaneously from elemental reactants by the use of a field-activated, pressure-assisted synthesis method. The method involves the application of an electric current and mechanical pressure across reactant compacts to achieve combustion synthesis. Dense solid solutions with relative densities of up to 99% were produced and characterized by XRD, SEM, and EPMA methods. With a maximum measured temperature of 145$0^{\circ}C$ under a load of 86 MPa for 30 min, the desired dense solid solution wad synthesized.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2015-2020
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• 2007

Diesel is an excellent candidate fuel for fuel cell applications due to its high hydrogen density and well-established infrastructure. But, it is hard to guarantee desirable performance of diesel reformer because diesel reforming has several problems such as sulfur poisoning of catalyst and carbon deposition. We have been focusing on diesel autothermal reforming(ATR) for substantial period. It is reported that ATR of diesel has several technical advantages such as relatively high efficiency and fuel conversion compared to steam reforming(SR) and partial oxidation(POX). In this paper, we investigate characteristics of diesel reforming under various ratios of reactants(oxygen to carbon ratio, steam to carbon ratio) for improvement of reforming performances(high reforming efficiency, high fuel conversion, low carbon deposition). We also exhibit calculated heat balance of autothermal reformer at each condition to help thermal management of SOFC system.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.06a
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• pp.223-228
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• 1997

The gas dynamics in a stagnation point upflow OMVPE reactor were studied by Raman spectroscopy. The gas temperature was measured as a function of inlet gas velocity and aspect ratio for both H$_2$ and N$_2$ carrier gases. The centerline temperature gradient was latger at higher inlet velocities and with the use of N$_2$, and only weakly dependent on the aspect ratio. a tracer molecule, CH$_4$, was used to investigate the steady state behavior of reactants in the reactor, and the use of a sweeping flow was found to be a suitable method for preventing wall deposition. The transient switching response of the gas manifold was also investigated. Under certain conditions (low velocities, unmatched flows) recirculation flows were apparent. Numerical calculations of the reactor gas dynamics gave reasonable agreement with experimental results when detailed thermal boundary conditions were included.

• Bulletin of the Korean Chemical Society
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• v.31 no.3
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• pp.595-598
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• 2010

Ab initio and DFT molecular orbital calculations predict that acetyl radical reacts with acetylene through interactions primarily involving the SOMO of the radical and the in-plane ${\pi}$-bond of acetylene. An energy barrier (${\Delta}E_1$) of 39.6 kJ $mol^{-1}$ is predicted for the preferred anti arrangement of reactants at the CCSD(T)/cc-pVDZ//BHandHLYP/cc-pVDZ level of theory. NBO analysis reveals additional interactions between the radical SOMO and the nearby C-H ${\sigma}$-bond in acetylene worth about 10% of the total transition state interaction energy. This type of orbital interaction has not previously been observed in radical addition reactions involving C-C ${\pi}$-bonds.

• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1699-1702
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• 2012

$TiO_2$ nanostructures with various morphologies like cubes, spheres, hexahedral pillars and spherical tubes were synthesized by microwave-assisted hydrothermal process. Each structure was obtained by changing the relative concentrations of titanium tetraisoproxide (TTIP), tetrabutylammonium hydroxide (TBAH) and ethanol. Scanning electron microscopy (SEM), transmission electoron microscopy (TEM), X-ray diffraction and Brunauer-Emmett-Teller (BET) surface area analysis were used to characterize the synthesized $TiO_2$ nanostructures. From these results, it has been proved that $TiO_2$ structure could be controlled to have specific morphology, size, surface area, pore volume and pore size distribution.

• Journal of Korean Society for Atmospheric Environment
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• v.30 no.4
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• pp.339-349
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• 2014

$CO_2$ emission has been gradually increased due to rising fossil fuel use. A gliding arc plasma scrubber (GAPS) was proposed to destruct $CO_2$. For optimum design of GAPS, a CFD analysis has been conducted in different configuration for the system. The parameters considered included gas injection velocity at the nozzle and gas flow rate to gap between electrodes. The reactor configuration affected velocity fields which caused changes in the mixture fraction and the retention time. The mixing effect of $CO_2$ and supplied gas ($CH_4$ and steam) was enhanced by installing a orifice baffle. This revealed that the orifice baffle is effective in $CO_2$ conversion by positioning the reactants in the gas into the center of plasma discharge.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.527-530
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• 2002

In the present study, immersion test using artificial seawater was performed to evaluate the resistance of mortar specimens with or without ground granulated blast-furnace slag (SG) and fly ash (FA). Another variable was the fineness levels of SG (4,450, 6,000 and 8,000 ㎠/g). From the results of the immersion test for 270 days of exposure, the excellent resistance to seawater attack for SG mortar mixtures, especially in a high fineness levels, was confirmed. However, the reductions in compressive strength of FA mortar specimens was similar to those of OPC mortar specimens irrespective of replacement of FA.. In order to understand the deterioration mechanism due to seawater attack, X-ray diffraction (XRD) analysis were also carried out. Some reactants such as ettringite, gypsum, brucite and Friedel's salt were possibly detected through XRD technique.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.305-308
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• 1997

The on-line calculation method is developed to obtain the temperature trajectory that brings the reactants to the desired state in batch styrene polymerization reactor. The temperature trajectory is obtained by applying the moments of the polymer concentration to the 2-step calculation method. The computer simulation is also carried out to verify the superiority of the on-line method to the off-line one. When a temperature disturbance of constant size is introduced, the off-line results shows considerable deviation from the target degree of polymerization. The on-line strategy set up a new trajectory to reach the desired state by using the current state of the reactor. Therefore, the on-line strategy deals with the changes of the system more adequately than the off-line strategy.

• Journal of the Korean Chemical Society
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• v.55 no.5
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• pp.824-829
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• 2011

In Fischer-Tropsch Synthesis, because of few reactants ($H_2$, CO), scarce operating parameters affected on efficiency especially the selectivity of products. In this research, effect of operating parameters on the selectivity of Co-Mn-$TiO_2$ Fischer-Tropsch synthesis catalyst were studied by design of experimental procedure and Taguchi method. According to this research, interactions between operating factors have a crucial effect on light products selectivity. Among these interactions, (temperature${\times}$feed ratio) has the main influence on light hydrocarbons selectivity. It was concluded that temperature and feed ratio ($H_2$/CO) were the most integral operating parameters for much greater selectivity of light hydrocarbons.