• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.10
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• pp.56-60
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• 2006

It is essential to predict thermodynamic properties of combustion gas with respect to a propellant mixture ratio for the development of a gas generator for a liquid rocket engine. The present study shows the temperature measurement of exit combustion gas as a function of a mixture ratio through the series of combustion tests of a fuel-rich gas generator with liquid oxygen and Jet A-1. The measurements of dynamic and static pressures, and combustion gas temperatures allowed the estimation of thermodynamic properties like a specific heat ratio, a gas constant, and a constant pressure specific heat of the combustion gas. The comparison of the experimental results with predictions made by interpolation parameters obtained from the modification of the chemical equilibrium code indicates that the interpolation method calibrated using the temperature measurements can be utilized as an effective tool for the initial design of a fuel-rich gas generator.

• Korean Journal of Materials Research
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• v.9 no.4
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• pp.341-344
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• 1999

We reported compositional separation(CS) into Co-enriched and Cri-enriched components inside the grains of Co-Cr based thin films prepared by rf sputtering. CS strongly depends on the sputtering conditions of substrate temperature and target composition. Tuning the microstructure of the Co-Cr films is important in order to employ the CS for high-density magnetic recording. We investigated the origin of CS from thermodynamic viewpoint. We employ a spinodal decomposition-like model to describe the origin of the CS in Co-Cr films. We consider the total free energy of the Co-Cr films as the sum of several free energies of; 1) thermodynamic mixing entropy of a binary solid solution, 2) magnetic ordering interaction(MOI) energy below the Curie temperature, and 3) excess interaction energy(XS) caused by the sputtering process as a function of temperature and composition. Those energies distorted the total free energy like the spinodal decomposition and caused the compositionally separated fine microstructure inside the grains. If the second derivative of the total free energy with respect to Cr composition becomes negative at a given substrate temperature, we may observe a metastable compositional separation inside the Co-Cr alloy films. We expect to exploit the microstructure of CS for ultra-high density magnetic recording.

• Journal of the Korean Ceramic Society
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• v.45 no.5
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• pp.280-284
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• 2008

In order to investigate residence time effect on the growth of ZrC film, the ZrC films grew with various system total pressure (P) and total flow rate (Q) by low pressure chemical vapor deposition because residence time is function of system total pressure and total flow rate. Thermodynamic calculations predict that the decomposition of source gases ($ZrCl_4$ and $CH_4$) would be low as increasing the residence time. Thermodynamic calculations results were proved by investigating deposition rate with various residence time. Deposition rate decreased with residence time of source gas increased. Besides, depletion effect accelerated diminution of deposition rate at high residence time. On the other hands, the deposition rated was increased as decreasing the residence time because fast moving of intermediate gas species decrease the depletion effect. The crystal structure was not changed with residence time. However, the largest size of faceted grain showed up to specific residence time and the size of grain was decreased whether residence time increase or not.

• Journal of the Korean Chemical Society
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• v.56 no.4
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• pp.416-423
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• 2012

Using time domain reflectometry, the complex dielectric spectra between 10 MHz to 20 GHz has been measured in the whole composition range at 10, 20, 30 and $40^{\circ}C$ for the binary mixtures of ethylene glycol and dimethyl sulfoxide. For all the mixtures, only one dielectric loss peak was observed in this frequency range. The relaxation in these mixtures can be described by a single relaxation time using the Debye model. A systematic variation is observed in dielectric constant (${\varepsilon}_0$) and relaxation time (${\tau}$). The excess permittivity (${\varepsilon}^E$), excess inverse relaxation time $(1/{\tau})^E$, Kirkwood correlation factor (g) and thermodynamic parameters viz. enthalpy of activation (${\Delta}H$) and Gibbs free energy of activation (${\Delta}G$) have been determined, to confirm the formation of hydrogen bonded homogeneous and heterogeneous cooperative domains, the dynamics of solute - solute interaction and the hindrance to molecular rotation in the hydrogen bonded glass forming ethylene glycol - dimethyl sulphoxide system.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.62-66
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• 2016

Tumor suppressor protein p53 loses its function upon binding with the HDM2 protein, and inhibiting the p53-HDM2 interaction is critical to suppress tumor cell growth. Recently, the cyclized helix-loop-helix peptide (cHLH) mimicking the ${\alpha}-helix$ part of the p53 protein has been designed and found to exhibit high binding affinity with HDM2. Here, we report the structural and thermodynamic characteristics of the bound complex of the cHLH peptide with the HDM2 protein. We performed molecular dynamics simulations to investigate the structural features of the cHLH peptide as well as its complex with the HDM2. The binding free energy calculation based on the integral equation theory was also executed to quantify the binding affinity for the cHLH/HDM2 complex and to understand the factors contributing to the binding affinity. We found a variety of factors for the helix stability of the cHLH peptide as well as in the complexation with the HDM2, which may provide an insight into the development of anti-cancer drug designs.

• Applied Chemistry for Engineering
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• v.30 no.3
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• pp.316-323
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• 2019

The adsorption of bisphenol A from an aqueous solution onto dried rice husk was investigated. Batch adsorption experiments were performed as a function of the pH, contact time, bisphenol A concentration, adsorbent dose and temperature. The concentration of Bisphenol A was measured by HPLC. The results showed that bisphenol A removal was highest at a solution pH value of 3, adsorbent dose of 4 g/L, and contact time of 75 min. The bisphenol A removal percentage decreased from 99.1 to 66.7%, when the bisphenol A concentration increased from 10 to 200 mg/L. The Langmuir isotherm and pseudo-second order kinetics provided the best fit for the experimental data. Thermodynamic parameters such as ${\Delta}G^0$, ${\Delta}H^0$ and ${\Delta}S^0$ were also evaluated and it was found that the sorption process was feasible, spontaneous and exothermic in nature. Overall, the studied absorbent can be used as an effective and low cost material to treat the industrial wastewater and aqueous solution containing phenolic compounds.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.3
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• pp.267-273
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• 2023

As the impacts of global climate change become increasingly apparent, the reduction of carbon emissions has emerged as a critical subject of discussion. Nuclear power has garnered attention as a potential carbon-free energy source; however, the rapidity of load following in nuclear power generation poses challenges in comparison to fossil-fueled methods. Consequently, power-to-gas systems, which integrate nuclear power and hydrogen, have attracted growing interest. This study presents a preliminary design of a very high temperature reactor (VHTR) integrated blue hydrogen production process utilizing DWSIM, an open-source process simulator. The blue hydrogen production process is estimated to supply the necessary calorific value for carbon capture through tail gas combustion heat. Moreover, a thermodynamic assessment of the main recuperator is performed as a function of the helium flow rate from the VHTR system to the blue hydrogen production system.

• Polymer(Korea)
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• v.25 no.4
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• pp.536-544
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• 2001

We investigate, in the viewpoint of mathematical stability, the validity of the time-strain separability hypothesis employed in polymer viscoelasticity on the basis of experimental results. There have been suggested two distinct stability criteria such as Hadamard related to quick response and dissipative stability conditions, and in the limit of high deformation rate we have proved that separable constitutive equations are either Hadamard or dissipative unstable. The fact that the separability is not valid in the short time region in stress relaxation experiments exactly coincides with the results of our analysis. Therefore, since the application of the separability hypothesis incurs thermodynamic inconsistency as well as mathematical instability, such application should be avoided in the formulation of constitutive equations. In addition, careful attention should be paid to the limit of its validity even in experiments. It is also proved that there is neither theoretical nor physical validity of using the damping function.

• Journal of the Korean Chemical Society
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• v.15 no.6
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• pp.285-293
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• 1971

The statistical thermodynamical properties of heavy water are calculated according to the transient state theory of significant liquid structure. The calculated values are shown to be in good agreement with the observed ones. The grand canonical ensemble partition function for the adsorbed phase of heavy water on graphite surface is derived using the theory. The adsorption isotherm, the surface pressure, the molar entropy and the molar internal energy for the adsorbed phase and then the molar heat of adsorption are calculated according to the derived partition function. The thermodynamic properties of the adsorbed water are also calculated and the results are compared with those of heavy water and discussed in view of the experimentally observed phenomena.

• Journal of the Korean Chemical Society
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• v.6 no.1
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• pp.36-46
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• 1962

The author assumes that pure liquid metal is composed of molecular oscillators whose energy states are classified into two subgroups, i.e., A and B states, each being accesible to either one of the two sorts of lattice sites. The partition function involves constants characteristic of substance, which are obtainable from the Debye characteristic temperature assigned to its solid state. Calculation has been made for the various thermodynamic properties such as the vapor pressure, the entropy, and the heat capacity of liquid metals of GroupⅠelements over the temperature range from the melting points to the boiling points. The theoretical values thus obtained are in good accordances with those observed, within experimental error, although a slight derivation is observed in the atomic heat capacity.