• Bulletin of the Korean Chemical Society
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• v.18 no.8
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• pp.856-860
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• 1997

The arene epoxides from naphthalene, 1β,2α-dihydroxy-3α,4α-epoxy- (1) and 1β,2α-dihydroxy-3β,4β-epoxy-1,2,3,4-tetrahydronaphthalene (2) (anti- and syn-diol epoxide), 1,2-epoxy-1,2,3,4-tetrahydronaphthalene (3), and 1,2-epoxy-l,2-dihydronaphthalene (4), are model compounds of the ultimate carcinogenic metabolites of polycyclic aromatic hydrocarbons, ubiquitous environmental pollutants which may be causal in several human cancers. The product distribution in the hydrolysis of 1-4 have been studied by HPLC analysis of reaction mixtures. The yields of the trans product from the hydronium-ion-catalyzed and pH-independent hydrolysis in 9 : 1 (v/v) 20 mM buffer-dioxane at 25 ℃, respectively, were; 1: 98, 100; 2: 74, 87, 3: 95, 97, 4:100, 100. The results were rationalized by conformational equilibria of the epoxides and the carbocationic and zwitterionic intermediates from the epoxides.

• Bulletin of the Korean Chemical Society
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• v.20 no.8
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• pp.939-942
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• 1999

The tie lines delineating ion-exchange equilibria between NiFe2O4-NiCr2O4 spinel solid solution and Fe2O3-Cr2O3 corundum solid solution were determined at 900, 1000, and 1200 ℃ by electron microprobe and energy dispersive X-ray analysis of oxide phases, using the flux growth technique. Activities of the spinel components were calculated from the tie lines, assuming Temkin's ideal mixing in the corundum solid solution. The spinel phase could be expressed by a regular solution with negative deviations from ideality. The Gibbs free energies of mixing for spinel solid solution were discussed in terms of the cation distribution model, based on site preference energies and assuming random mixing on both tetrahedral and octahedral sites.

• Bulletin of the Korean Chemical Society
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• v.18 no.9
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• pp.965-972
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• 1997

An approximate molecular theory of classical fluids based on the nonrandom lattice statistical-mechanical theory is presented. To obtain configurational Helmholtz free energy and equation of state (EOS), the lattice-hole theory of the Guggenheim combinatorics is approximated by introducing the nonrandom two-fluid theory. The approximate nature in the derivation makes the model possible to unify the classical lattice-hole theory and to describe correctly the configurational properties of real fluids including macromolecules. The theory requires only two molecular parameters for a pure fluid. Results obtained to date have demonstrated that the model correlates quantitatively the first- and second-order thermodynamic properties of real fluids. The basic simplicity of the model can readily be generalized to multicomponent systems. The model is especially relevant to (multi) phase equilibria of systems containing molecularly complex species.

• Bulletin of the Korean Chemical Society
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• v.10 no.5
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• pp.434-437
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• 1989

The pH dependence of the absorption and fluorescence of 4-hydroxy-2-methyl-1,2-benzothiazinenecarboxylat es, piroxicam and HMBDC have been measured and compared with the solvent dependence of the spectra reported previously. Four different prototropic species are observed in both ground and excited states of piroxicam ; the cation, the neutral, the anion and the dianion, while three different species such as the cation, the neutral and the anion are observed in HMBDC. The $pK_a$ and $pK_a^{\ast}$ have been determined by absorptiometric titration and Forster cycle method, respectively. The probable structure of each species has been proposed on the basis of the intramolecular phototautomerism.

• Bulletin of the Korean Chemical Society
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• v.13 no.6
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• pp.680-683
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• 1992

The electrochemistry of benzidine and hydrazobenzene was studied in water-acetonitrile mixed solutions at various pHs and the results are reported. The cyclic voltammetric peak for the oxidation of benzidine shows a pH dependency of -62 mV/pH in the pH range of 0-3.5, no pH dependency between pH values of 3.5 and about 10.5, and of about -50 mV/pH between pH=10.50 and 14.0, indicating that oxidation mechanisms differ depending on the pH of the medium. However, the CV peak for the hydrazobenzene oxidation is shown to be independent of pH of the medium, suggesting that the proton is not involved in the rate limiting step of the electrochemical oxidation of hydrazobenzene to azobenzene. Results of in situ spectroelectrochemical experiments indicate that the oxidation products obtained during the oxidation of benzidine and hydrazobenzene depend on the result of dynamic equilibria taking place at various pHs.

• Communications of the Korean Mathematical Society
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• v.34 no.2
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• pp.685-699
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• 2019

This research is focused on a continuous epidemic model of transmission of Plasmodium vivax malaria with a time delay. The model is represented as a system of ordinary differential equations with delay. There are two equilibria, which are the disease-free state and the endemic equilibrium, depending on the basic reproduction number, $R_0$, which is calculated and decreases with the time delay. Moreover, the disease-free equilibrium is locally asymptotically stable if $R_0<1$. If $R_0>1$, a unique endemic steady state exists and is locally stable. Furthermore, Hopf bifurcation is applied to determine the conditions for periodic solutions.

• International Journal of Internet, Broadcasting and Communication
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• v.13 no.1
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• pp.238-242
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• 2021

Game theory has been regarded as a useful theoretical tool for modeling the interactions between distinct entities and thus it has been harnessed in various research field. In particular, research attention has been shown to how to apply game theory to modeling the interactions between malign and benign entities in the field of wireless networks. Although various game theoretic modeling work have been proposed in the field of wireless networks, our proposed work is disparate to the existing work in the sense that we focus on mobile malign node detection problem in static wireless sensor networks. More specifically, we propose a Bayesian game theoretic modeling for mobile malign node detection problem in static wireless sensor networks. In our modeling, we formulate a two-player static Bayesian game with imperfect information such that player 1 is aware of the type of player 2, but player 2 is not aware of the type of player 1. We use four strategies in our static Bayesian game. We obtain Bayesian Nash Equilibria with pure strategies under certain conditions.

• Journal of the Mineralogical Society of Korea
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• v.21 no.4
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• pp.425-434
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• 2008

Arsenic contamination in soil and groundwater has recently been one of the most serious environmental concerns. This arsenic contamination can be originated from natural or anthropogenic sources. It has been well known that arsenic behavior in geo-environmental is controlled by various oxides or hydroxides, such as those of iron, manganese, and aluminum, and clay minerals. Among those, particularly, iron (oxy)hydroxides are the most effective scavengers for arsenic. For this reason, this study characterized arsenic adsorption of magnetite which is a kind of iron oxide in nature. The physicochemcial features of the magnetite were investigated to evaluate adsorption of arsenite [As(III)] and arsenate [As(V)] onto magnetite. In addition to experiments on adsorption equilibria, kinetic experiments were also conducted. The point of zero charge (PZC) and specific surface area of the laboratory-synthesized magnetite used as an arsenic adsorbent were measured 6.56 and $16.6\;g/m^2$, which values seem to be relatively smaller than those of the other iron (oxy)hydroxides. From the results of equilibria experiments, arsenite was much more adsorbed onto magnetite than arsenate, indicating the affinity of arsenite on magnetite is larger than arsenate. Arsenite and arsenate showed adsorption maxima at pHs 7 and 2, respectively. In particular, adsorption of arsenate decreased with increase in pH as a result of electrical repulsion caused by anionic arsenate and negatively-charged surface of magnetite. These results indicate that the surface charge of magnetite and the chemical speciation of arsenic should be considered as the most crucial factors in controlling arsenic. The results of kinetic experiments show that arsenate was adsorbed more quickly than arsenite and adsorption of arsenic was investigated to be mostly completed within the duration of 4 hours, regardless of chemical speciation of arsenic. When the results of kinetic experiments were fitted to a variety of kinetic models proposed so far, power function and elovich model were evaluated to be the most suitable ones which can simulate adsorption kinetics of two kinds of arsenic species onto magnetite.

• Korean Chemical Engineering Research
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• v.49 no.3
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• pp.367-371
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• 2011

TBAB (tetra-n-butyl ammonium bromide) forms a semi-clathrate with water under atmospheric pressure conditions and recently has attracted great attention due to its usage as a thermodynamic promoter in gas storage and separation process using gas hydrate formation. In this study, we measured the three-phase (hydrate (H) - liquid water ($L_{w}$)-vapor (V)) equilibria of the ternary $CH_{4}$+TBAB+water and $CO_{2}$+TBAB+water mixtures at the TBAB concentrations of 5 and 32 wt% to investigate promoting characteristics of TBAB. The greater promotion effect of TBAB was observed at 32 wt% than at 5 wt%. This result was in good agreement with that from pure TBAB semi-clathrate phase diagram under atmospheric pressure conditions. Through $^{13}C$ NMR analysis of the $CH_{4}$+TBAB semi-clathrate, it was found that $CH_{4}$ molecules are enclathrated in the cages of the double semi-clathrate and the position of resonance peak from encaged $CH_{4}$ molocules in the double semi-clathrate is the same as that from encaged $CH_{4}$ molocules in the pure $CH_{4}$ hydrate of structure I.

• Journal of Korean Society of Forest Science
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• v.54 no.1
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• pp.36-40
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• 1981

with the chemical equilibrium formula by Hailwood and Horrobin, $$m=a{\cdot}((k_1k_2h)(1+k_1k_2h)^{-1}+(k_2h)_n-k_2h)^{-1})$$, based on absorption theory, monthly equilibrium moisture content(EMC) variations in southern Korea were predicted. The results were as follows: $$k_1=47370272{\cdot}10^{-7}+477345{\cdot}10^{-7}t-502775{\cdot}10^{-8}t^2$$ $$k_2=705940864{\cdot}10^{-9}+16979472{\cdot}10^{-10}t-555336{\cdot}10^{-11}t^2$$ $$w=2233848{\cdot}10^{-4}+694242{\cdot}10^{-6}+185328{\cdot}10^{-7}t^2$$ Here, it is temperature degrees in Celsius, k is the equilibria between hydrate water and dissolved water, k is the equilibria between dissolved water and the water vapour pressure surrounding atmosphere, w is the molecular weight of the polymer unit that forms the hydrate, h is the relative vapour pressure, And the formula was well agreed with the data when the constant values ${\alpha}$ were given to be 2200 in January, February, October, November and December, 1850 in March, April and May, 1920 June, July, August, and September seasonally.