• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2679-2683
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• 2014

Mechanisms underlying the impacts of interactions between carbon nanoparticles (CNPs) and ionic liquids (ILs) on the physicochemical behavior of CNPs need to be more full worked out. This manuscript describes a theoretical investigation at multiple levels on the interactions of fullerene $C_{60}$ with 21 imidazolium-based ILs of varying alkyl side chain lengths and anionic types and their impacts on $C_{60}$ dispersion behavior. Results show that ${\pi}$-cation interaction contributed to mechanism of the $C_{60}$-IL interaction more than ${\pi}$-anion interaction. The calculated interaction energy ($E_{INT}$) indicates that $C_{60}$ can form stable complex with each IL molecule. Moreover, the direction of charge transfer occurred from IL to $C_{60}$ during the $C_{60}$-IL interaction. Quantitative models were developed to evaluate the self-diffusion coefficient of $C_{60}$ ($D_{fullerene}$) in bulk ILs. Three interpretative molecular descriptors (heat of formation, $E_{INT}$, and charge) that describe the $C_{60}$-IL interactions and the alkyl side chain length were found to be determinants affecting $D_{fullerene}$.

• Bulletin of the Korean Chemical Society
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• v.23 no.2
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• pp.267-270
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• 2002

Photodissociations of o-, m-, and p-iodotoluene radical cations were investigated by using Fourier-transform ion cyclotron resonance (FT-ICR) spectrometry. Iodotoluene radical cations were prepared in an ICR cell by a photoionization charge-transfer method. The time-resolved one-photon dissociation spectra were obtained at 532 nm and the identities of $C_7H_7^+$ products were determined by examining their bimolecular reactivities toward toluene-$d_8$. The two-photon dissociation spectra were also recorded in the wavelength range 615-670 nm. The laser power dependence, the temporal variation, and the identities of $C_7H_7^+$ were examined at 640 nm. The mechanism of unimolecular dissociation of iodotoluene radical cations is elucidated: the lowest barrier rearrangement channel leads exclusively to the formation of the benzyl cation, whereas the direct C-I cleavage channel yields the tolyl cations that rearrange to both benzyl and tropylium cations with dissimilar branching ratios among o-, m-, and p-isomers. With a two-photon energy of 3.87 eV at 640 nm, the direct C-I cleavage channel results in the product branching ratio, [tropylium cation]/[benzyl cation], in descending order, 0.16 for meta >0.09 for ortho >0.05 for para.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1201-1206
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• 2004

Sonoluminescence (SL) characteristics such as pulse shape, radiance and spectrum radiance from submicron bubbles were investigated. In this study, a set of analytical solutions of the Navier-Stokes equations for the gas inside bubble and equations obtained from mass, momentum and energy equations for the liquid layer adjacent the bubble wall were used to estimate the gas temperature and pressure at the collapse point, which are crucial parameters to determine the SL characteristics. Heat transfer inside the gas bubble as well as at the liquid boundary layer, which was not considered in the most of previous studies on the sonoluminescence was taken it into account in the calculation of the temperature distribution inside the bubble. It was found that bremsstrahlung is a very possible mechanism of the light emission from either micron or submicron bubbles. It was also found that the peak temperature exceeding $10^{6}$ K in the submicron bubble driven at 1 MHz and 4 atm may be due to the rapid change of the bubble wall acceleration near the collapse point rather than shock formation.

• Environmental Engineering Research
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• v.19 no.4
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• pp.363-367
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• 2014

One chambered sediment microbial fuel cell (SMFC) was equipped with Fe, brass (Cu/Zn), Fe/Zn, Cu, Cu/carbon cloth and graphite felt anode. Graphite felt was used as common cathode. The SMFC was membrane-less and mediator-less as well. Order of anodic performance on the basis of power density was Fe/Zn ($6.90Wm^{-2}$) > Fe ($6.03Wm^{-2}$) > Cu/carbon cloth ($2.13Wm^{-2}$) > Cu ($1.13Wm^{-2}$) > brass ($Cu/Zn=0.24Wm^{-2}$) > graphite felt ($0.10Wm^{-2}$). Fe/Zn composite anode have twisted 6.73% more power than Fe alone, Cu/carbon cloth boosted power production by 65%, and brass (Cu/Zn) produced 65% less power than Cu alone. Graphite felt have shown the lowest electricity generation because of its poor galvanic potential. The estuarine sediment served as supplier of oxidants or electron producing microbial flora, which evoked electrons via a complicated direct microbial electron transfer mechanism or making biofilm, respectively. Oxidation reduction was kept to be stationary over time except at the very initial period (mostly for sediment positioning) at anodes. Based on these findings, cost effective and efficient anodic material can be suggested for better SMFC configurations and stimulate towards practical value and application.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.8
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• pp.768-772
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• 2008

Today's microprocessor normally includes several processing cores to reduce the energy consumption without losing performance. In this paper, data transfer ordering mechanism can be efficiently used for cache coherence solution in unidirectional ring interconnect. RING-DATA ORDER combines the simplicity of GREEDY-ORDER and the performance of RING-ORDER. RING-DATA ORDER can be easily applicable to multicore processor with unidirectional ring interconnect.

• Bulletin of the Korean Chemical Society
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• v.34 no.3
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• pp.907-911
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• 2013

Numbers of matrix- and analyte-derived ions and their sum in matrix-assisted laser desorption ionization (MALDI) of a peptide were measured using 2,5-dihydroxybenzoic acid (DHB) as matrix. As for MALDI with ${\alpha}$-cyano-4-hydroxy cinnamic acid as matrix, the sum was independent of the peptide concentration in the solid sample, or was the same as that of pure DHB. This suggested that the matrix ion was the primary ion and that the peptide ion was generated by matrix-to-peptide proton transfer. Experimental ionization efficiencies of $10^{-5}-10^{-4}$ for peptides and $10^{-8}-10^{-7}$ for matrices are far smaller than $10^{-3}-10^{-1}$ for peptides and $10^{-5}-10^{-3}$ for matrices speculated by Hillenkamp and Karas. Number of gas-phase ions generated by MALDI was unaffected by laser wavelength or pulse energy. This suggests that the main role of photo-absorption in MALDI is not in generating ions via a multi-photon process but in ablating materials in a solid sample to the gas phase.

• Journal of the Korean Ceramic Society
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• v.38 no.2
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• pp.107-111
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• 2001

Sr$_{(1-x)}$Ca$_{x}$TiO$_3$: Pr$^{3+}$ , Ga$^{3+}$ (0$\leq$x$\leq$1) 형광체의 여기 및 발광 스펙트럼과 분광 반사율을 조사하여 발광 메커니즘을 규명하고자 하였다. 발광 스펙트럼에서는 611~614nm 사이에서 peak을 가지는 하나의 적색 발광 밴드가 관찰되었으며, 조성에 따라 발광밴드의 모양이 달랐다. 이는 조성에 따른 모체의 결정 구조 변화 때문으로 생각된다. 여기 스펙트럼 끝단과 분광 반사율 스펙트럼의 흡수단은 서로 일치하였으며, 이 결과로부터 모체에 흡수된 에너지가 Pr$^{3+}$ 에 전달되어 적색광을 방출하는 것이 주된 메커니즘으로 생각된다. 한편 120$0^{\circ}C$에서 4시간동안 열처리하여 합성한 Sr$_{0.4}$Ca$_{0.6}$TiO$_3$:(0.1 mol%)Pr$^{3+}$ , (0.2 mol%)Ga$^{3+}$ 는 우수한 색순도와 휘도를 나타내었다.다.

• Journal of computational fluids engineering
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• v.21 no.3
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• pp.110-117
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• 2016

It is a essential to minimize production of by-products for economically effective petrochemical process. In order to find key factor to achieve the effective process, 2-dimensional computational fluid dynamics considering a variety of physics such as convective and radiative heat transfer and thermal cracking of ethane are carried out. The reactor is modeled as an isothermal tube, whose length is 1.2 m and radius is 0.01 m, respectively. At first, the axial distribution of representative by-products in ethane thermal cracking are investigated in each inner wall temperature conditions. Then the comparison between concentration of propene($C_3H_6$) and ethane conversion is discussed with respect to inner wall temperature conditions too. Finally, both reaction rate and turbulent kinetic energy are used to identify the production mechanism of $C_3H_6$ under the intersection point in the plot for $C_3H_6$ molar concentration and ethane conversion.

• Journal of the Korean Applied Science and Technology
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• v.25 no.4
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• pp.418-428
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• 2008

Transesterification of fat of Tra catfish with methanol in the presence of the KOH catalyst yields fatty acid methyl esters (FAME) and glycerol (GL). The effects of the reaction temperature and reaction time on rate constants and kinetic order were investigated. Three regions were observed. In the initial stage, the immiscibility of the Tra fat and methanol limited the reaction rate, hence this region was controlled by the mass transfer. Subsequent to this region, produced FAME like a co-solvent made the reaction mixture homogeneous, therefore the conversion rate increased rapidly so it was controlled by the kinetic parameters of the reaction until the equilibrium was approached in the final slow region. A second-order kinetic mechanism was proposed involving second regions for the forward reaction. The rate determining step for the overall KOH catalyzed-methanolysis of Tra fat was the conversion of triglycerides (TG) to diglycerides (DG). This rate constant was increased from 0.003 to $0.019min^{-1}$ when the reaction temperature was increased from 35 to $60^{\circ}C$. Its calculated activation energy was 14.379 ($kcal.mol^{-1}$).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.7 s.178
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• pp.1650-1660
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• 2000

Continuous casting process has been adopted increasingly in recent years to save both energy and labor. It has experienced a rapid development in the production of semi-finished steel products, rep lacing the conventional route of ingot casting and rolling. In order to achieve this merit, however, more studies about the mechanism between roll and slab are needed. In this paper, a dynamic bulging in steel cast slabs was simulated by considering the solidification and heat transfer. This study is to prevent internal cracks of a slab in a bending and unbending zone. The value of moving strand shell bulging between two supporting rollers under the ferrostatic pressure and slab-self weight has been calculated in terms of creep and elasto-plasticity. The strain and strain rate distributions in solidified shell undergoing a series of bulging are calculated with working boundary conditions.