• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.255.2-255.2
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• 2014

Electrode erosion is indispensable for atmospheric plasma systems, as well as for switching devices, due to the high heat flux transferred from arc plasmas to contacts, but experimental and theoretical works have not identified the characteristic phenomena because of the complex physical processes. Our investigation is concerned with argon free-burning arcs with anode erosion at atmospheric pressure by computational fluid dynamics (CFD) analysis. We are also interested in the energy flux and temperature transferring to the anode with a simplified unified model of arcs and their electrodes. In order to determine two thermodynamic quantities such as temperature and pressure and flow characteristics we have modified Navier-Stokes equations to take into account radiation transport, electrical power input and the electromagnetic driving forces with the relevant Maxwell equations. From the simplified self-consistent solution the energy flux to the anode can be derived.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1677-1681
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• 2002

A computational approach of the arc quenching process in GCB was developed. it is capable to calculates the thermodynamic quantities of the gas as a function of time taking into account of all spaces concerned with the arc quenching. Basically using so-called FLIC method, this program adoptes 'Simplified Enthalpy Arc Model', which is somewhat modified. And, to examine whether our works were done properly, it was simulated the whole process of the arc quenching that is based on self-flow generation phenomena/current interruption in a thermal expansion type circuit breaker. This program was verified by experiments, both showed fairly good agreement.

• Journal of the Korean Chemical Society
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• v.10 no.3
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• pp.129-132
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• 1966

It is known that almost all cyclohexane molecules are chair form in liquid state. Therefore, only chair form is considered in formulating the partition function for liquid cyclohexane, according to the Transient State Theory of Significant Liquid Structure proposed by Pak, Ahn and Chang. The thermodynamic quantities such as molar volume, vapor pressure, entropy of vaporization and compressibility of the liquid are calculated. The results are in good agreement with experimental values.

• Bulletin of the Korean Chemical Society
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• v.2 no.3
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• pp.90-96
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• 1981

The significant structure theory of liquids has been successfully applied to the sodium ammonia solution. In applying the theory to sodium ammonia solution, we assumed there were four species in solution, i.e., sodium cation, solvated electron, triple ion, and free electron and equilibria existed between them. Based on these assumptions, we set up the model explaining the anomalous properties of sodium ammonia solution. The partition function for sodium ammonia solution is composed of the partition functions for the above four species and also for the Debye-Huckel excess free energy term. Agreements between calculated and experimental values of the thermodynamic quantities, such as molar volume, vapor pressure, partial molar enthalpy and entropy, and chemical potential as well as viscosity are quite satisfactory.

• Bulletin of the Korean Chemical Society
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• v.20 no.3
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• pp.345-351
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• 1999

The structures, the energetics, and the spectra of K+(H2O)3 have been studied at HF and MP2 levels with the basis set of triple-zeta plus two sets of polarization functions (TZ2P) for water molecules. Two structures considered are 3+0 (D3), and 2+1 (C2v). The 2+1 (C2v) has two hydrogen bonds between the primary hydration and the secondary hydration shell water molecules. They have similar binding energy and enthalpy. The most stable conformation of K+(H2O)3 is entropy driven as shown in Na+(H2O)5 and in Na+(H2O)6 cases. The 3+0 (D3) conformation is the most stable at 298 K and at 1 atm, based on Gibbs free energy changes (ΔGr). The thermal contributions to the enthalpy and the Gibbs free energy are corrected for the low frequency modes. The corrected ΔGr is in good agreement with the experimental value. Vibrational frequencies of two conformations are revealed as their characteristics.

• Korean Journal of Environmental Agriculture
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• v.40 no.4
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• pp.239-247
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• 2021

BACKGROUND: Enormous amounts of the wood biomass wastes have been produced through various wood processing. This study characterizes the surface characteristics of biomass powders of Cornus controversa (CC) and Quercus mongolica (QM) and investigates their removal efficiency and mechanism for Pb (II) in aqueous solution on which to base potential recycling alternative of the wood biomass. METHODS AND RESULTS: Batch experiments were conducted under different conditions of Pb concentrations, temperatures, time and solid/solution ratios. Adsorption isotherm of Pb by CC and QM biomass was explained significantly by the Langmuir model, indicating Pb was likely adsorbed on the monolayer of the surfaces. The adsorption kinetics were fitted significantly to the double first-order model consisting of rapid and slow steps. The respective rate constants (k1) of CC and QM for the rapid adsorption kinetic steps were 0.051 and 0.177 min^-1, and most of the sorption reactions proceeded rapidly within 6-20 minutes. The maximum adsorption quantities (q_max) of Pb were 17.25 and 23.47 mg/g for CC and QM, respectively. Thermodynamic parameters revealed that adsorption of Pb on the biomass of CC and QM was a spontaneous endothermic reaction. CONCLUSION(S): Results demonstrate that biomass wastes of CC and QM can be used as Pb adsorbents judging from adsorption isotherm, kinetics, and thermodynamic parameters.

• Journal of the Korean Chemical Society
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• v.9 no.4
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• pp.215-221
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• 1965

The significant liquid structure theory is extended to binary mixture, benzene-ethylenechloride system. The partition function, applicable throughout the temperature range in which Raoult's law is satisfied is derived. The thermodynamic quantities such as total and partial pressures, molar volumes and mixing entropies are calculated from the partition function at the temperatures $293.15^{\circ},\;323.14^{\circ}\;and\;357.15^{\circ}K.$ The theoretical values, thus calculated, are found to agree with the experimental data in the literatures.

• Transactions of Materials Processing
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• v.33 no.1
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• pp.18-35
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• 2024

In the present work, the evolution rules for the internal variables including continuum damage factors are obtained using the thermodynamic framework, which are in turn facilitated to derive the elastic-plastic constitutive relation for the particulate composites. Using the Mori-Tanaka scheme, the homogenization on state and internal variables such as back-stress and damage factors is carried out to procure the rate independent plasticity relations. Moreover, the degradation of mechanical properties of constituents is depicted by the distinctive damages such that the phase and interfacial damages are treated individually accordingly, whereas the kinematic hardening is depicted by combining the Armstrong-Frederick and Phillips' back-stress evolutions. On the other hand, the present constitutive relation for each phase is expressed in terms of the respective damage-free effective quantities, then, followed by transformation into the damage affected overall nominal relations using the aforementioned homogenization concentration factors. An emphasis is placed on the qualitative analyses for strain localization by observing the perturbation growth instead of the conventional bifurcation analyses. It turns out that the proposed constitutive model offers a wide range of strain localization behavior depending on the evolution of various internal variable descriptions.

• Tunnel and Underground Space
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• v.21 no.6
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• pp.518-525
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• 2011

In this study, the natural ventilation pressure resulting from the large altitude difference which is a characteristic of high radioactive waste repository and the caloric value of the heat emitted by wastes was calculated and based on the results, natural ventilation quantities were calculated. A high radioactive waste repository can be considered as being operated through closed cycle thermodynamic processes similar to those of thermal engines. The heat produced by the heating of high radioactive wastes in the underground repository is added to the surrounding air, and the air goes up through the upcast vertical shaft due to the added heat while working on its surroundings. Part of the heat added by the work done by the air can be temporarily changed into mechanical energy to promote the air flow. Therefore, if a sustained and powerful heat source exists in the repository, the heat source will naturally enable continued cyclic flows of air. Based on this assumption, the quantity of natural ventilation made during the disposal of high radioactive wastes in a deep geological layer was mathematically calculated and based on the results, natural ventilation pressure of $74{\sim}183$Pa made by the stack effect was identified along with the resultant natural ventilation quantity of $92.5{\sim}147.7m^3/s$. The result of an analysis by CFD was $82{\sim}143m^3/s$ which was very similar to the results obtained by the mathematical method.

• Journal of the Korean Chemical Society
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• v.31 no.3
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• pp.207-214
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• 1987

Rates of solvblysis of benzyl chloride in ethanol-water mixtures have been measured at 30 and $40^{\circ}C$ under various pressures up 1.6 kbar. The plots of 1n k as a function of pressure are fitted to a second order function in p, and values of ${\Delta}V^{\neq}$and ${\Delta}{\beta}^{\neq}$ are obtained from the results. Also the values of various pseudo thermodynamic quantities were evaluated from the rate constants. The relationships of the 1n k to $Q_w$ or 1n $C_w$ indicate that the reaction proceeds through $S_N1$ mechanism. A comparison between the present and the previous results gives that the increasing order of ${\mid}{{\Delta}V_0}^{\neq}{\mid}$ and n-values are $p-Cl>p-H>p-CH_3$ and $p-CH_3>p-H.p-Cl$, respectively. From these results, it is believed substituent such as the $p-CH_3$group favors the $S_N1(1)$ character, while the p-Cl group leads to the $S_N1(2)$ character.