• Title, Summary, Keyword: Thermodynamic model

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Thermodynamic Assessment of the $ZrO_2-TiO_2$ System

  • Park, Jeong-Ho;Ping Liang;Seifert, Hans-Jurgen;Fritz Aldinger;Koo, Bon-Keup;Kim, Ho-Gi
    • The Korean Journal of Ceramics
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    • v.7 no.1
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    • pp.11-15
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    • 2001
  • A thermodynamic assessment for the ZrO$_2$-TiO$_2$ system has been conducted. An optimal thermodynamic data set for this system is evaluated by the CALPHAD(CALculation of PHAse Diagram) method applied to experimental phase diagram and thermodynamic data. The liquid is described by ionic liquid model with two sublattices. The solubilities of the solid phases, tetragonal ZrO$_2$ and TiO$_2$(rutile), were described by subregular substitutional model with one sublattice. Two compounds, ZrTiO$_4$ and ZrTi$_2$O$_6$, are modeled as stoichiometric compounds.

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A REVIEW FOR DEVELOPING THERMODYNAMIC MODEL OF COMS CPS

  • Chae, Jong-Won;Han, Cho-Young;Yang, Koon-Ho
    • Proceedings of the KSRS Conference
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    • pp.179-182
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    • 2007
  • COMS (Communication, Ocean and Meteorological Satellite) is a geosynchronous satellite and has been developing by KARI and Astrium for Ka-band communication, ocean observation and meteorological observation. COMS Chemical Propulsion System (CPS) uses a bipropellant propulsion subsystem, which is applied for transferring COMS from GTO to GEO (mission orbit) and implementing station-keeping manoeuvres. In this paper COMS CPS is briefly introduced for understanding. A few of mathematical thermodynamic modelings of bipropellant propulsion system in literatures are reviewed and authors has studied those models for developing a computer program, which predicts variations of thermodynamic properties such as temperature and pressure histories in the helium pressurant tank, MMH propellant tank and NTO propellant tank during LAE firing and on-orbit manoeuvrings. The CPS thermodynamic model may be used to compute pressurant and propellant masses and to size tank volumes.

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A Constitutive Model for Plastic Damage of Ductile Materials

  • Nho, In-Sik;Yim, Sahng-Jun;Shin, Jong-Gye
    • Selected Papers of The Society of Naval Architects of Korea
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    • v.2 no.1
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    • pp.106-128
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    • 1994
  • An elasto-plastic-damage constitutive model for ductile materials is proposed within the framework of a thermodynamic approach of continuum damage mechanics (CDM) in which internal irreversible thermodynamic changes of micro-structure of materials such as plastic deformation and damage evolution are considered as thermodynamic state variables. The new constitutive model can predict not only the elasto-plastic behaviors but also the sequential stiffness degradation process of ductile materials more rationally.

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Thermodynamic Analysis of Vapor Explosion Phenomena (증기폭발 현상의 열역학적 해석)

  • Bang, Kwang-Hyun
    • Nuclear Engineering and Technology
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    • v.25 no.2
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    • pp.265-275
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    • 1993
  • A vapor explosion has been a concern in nuclear reactor safety due to its potential for a destructive mechanical energy release. In order to properly assess the hazard of a vapor explosion, it is necessary to accurately estimate the conversion efficiency of the thermal energy to mechanical energy. In the absence of a complete model to determine the explosive energy yield, one may have to rely on a simpler upper bound estimate such as a thermodynamic model. This paper discusses various thermodynamic models and presents a clarification of each model in their mathematical formulation and the thermodynamic work conversion. It is shown that the work release in the shock adiabatic model of Board and Hall is essentially equal to that of Hicks-Menzies thermodynamic model. The effect of coolant void fraction on the explosion efficiency is also predicted based on these thermodynamic models. Finally, the Hicks-Menzies model is modified to account for the chemical reaction between a metallic fuel and water and the resultant effects on the explosion expansion work are discussed.

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Thermodynamic Assessment of the PbO-ZrO2 System

  • Koo, Bon-Keup;Ping Liang;Hans Jiirgen Seifert;Fritz Aldinger
    • The Korean Journal of Ceramics
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    • v.5 no.3
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    • pp.205-210
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    • 1999
  • The thermodynamic properties and phase diagram of the$ PbO-ZrO_2$ system have been critically assessed using the Thermo-Calc program. Excess Gibbs energies were expressed by Redlich-Kister polynomials for the solid phases, by the two-sublattice ionic liquid model for the liquid phase and by the compound energy model for the solid solution phase. All solid phases were treated as stoichimetric compounds.

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Development of a three dimensional circulation model based on fractional step method

  • Abualtayef, Mazen;Kuroiwa, Masamitsu;Sief, Ahmed Khaled;Matsubara, Yuhei;Aly, Ahmed M.;Sayed, Ahmed A.;Sambe, Alioune Nar
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.2 no.1
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    • pp.14-23
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    • 2010
  • A numerical model was developed for simulating a three-dimensional multilayer hydrodynamic and thermodynamic model in domains with irregular bottom topography. The model was designed for examining the interactions between flow and topography. The model was based on the three-dimensional Navier-Stokes equations and was solved using the fractional step method, which combines the finite difference method in the horizontal plane and the finite element method in the vertical plane. The numerical techniques were described and the model test and application were presented. For the model application to the northern part of Ariake Sea, the hydrodynamic and thermodynamic results were predicted. The numerically predicted amplitudes and phase angles were well consistent with the field observations.

Study on Kinetic and Thermodynamic for Adsorption of As Ion by CTABr-Impregnated Anthracite (CTABr로 표면처리된 Anthracite에 의한 비소(As) 이온의 흡착에 대한 동력학 및 열역학에 관한 연구)

  • Kim, Hak-Yoon;Kim, Jeung-Bea
    • Journal of Korean Society of Water Science and Technology
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    • v.25 no.2
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    • pp.47-60
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    • 2017
  • The removal characteristics of As ion from aqueous solution by CTABr impregnated anthracite(CTAB-AT) was investigated under various conditions of contact time, pH and temperature. When the pH is 6, the zeta potential value of anthracite(AT) is -30 mV and on the other hand, the zeta potential value of the CTAB-AT is +40 mV. It can be seen that the overall increase of about 70 mV. The kinetic study shows that As ion was adsorbed onto the CTAB-AT within the first 80 min, while equilibrium was arrived within 2 h for As ion. The experimental data was analyzed using equilibrium isotherm, kinetic and thermodynamic models. The isotherm data was well described by Langmuir isotherm model and Temkin model. The maximum adsorption capacity was found to be 7.81 mg/g for As ion from the Langmuir isotherm model at $298^{\circ}K$. The kinetic data was tested using pseudo first and second order models. The results indicated that adsorption fitted well with the pseudo-second order kinetic model. The mechanism of the adsorption process showed that adsorption was dependent on intra particle diffusion model according to two step diffusion. The thermodynamic parameters(${\Delta}G^o$, ${\Delta}H^o$, and ${\Delta}S^o$) were also determined using the equilibrium constant value obtained at different temperatures. The thermodynamic parameters indicated that the adsorption process was physisorption, and also an endothermic and spontaneous process.

Theoretical Analysis of a Spark Ignition Engine by the Thermodynamic Engine Model

  • Han, Sung Bin
    • Journal of Energy Engineering
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    • v.24 no.3
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    • pp.55-60
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    • 2015
  • Recent engine development has focused mainly on the improvement of engine efficiency and output emissions. The improvements in efficiency are being made by friction reduction, combustion improvement and thermodynamic cycle modification. Computer simulation has been developed to predict the performance of a spark ignition engine. The effects of various cylinder pressure, heat release, flame temperature, unburned gas temperature, flame properties, laminar burning velocity, turbulence burning velocity, etc. were simulated. The simulation and analysis show several meaningful results. The objective of the present study is to develop a combustion model for a spark ignition engine running with isooctane as a fuel and predicting its behavior.

Finite Element Analysis of Elasto-Plastic Large Deformation considering the Isotropic Damage (the 1st Report) -Development of Elasto-Plastic Damage Constitutive Model- (등방성 손상을 고려한 탄소성 대변형 문제의 유한요소해석(제1보) -탄소성 손상 구성방정식 개발-)

  • 노인식
    • Journal of Ocean Engineering and Technology
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    • v.14 no.2
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    • pp.70-75
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    • 2000
  • In this paper a new constitutive model for ductile materials was proposed. This model can describe the material degradation due to the evolution of isotropic damage during elasto-platic deformation. The plastic flow rule was derived under the framework of thermodynamic approach of continuum damage mechanics(CDM) in which plastic strain hardening parameters and isotropic damage were taken as thermodynamic state variables. And the process to determine material constants for constitutive model using an experimental data was presented.

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Molecular Dynamics Simulation of Liquid Alkanes. Ⅰ. Thermodynamics and Structures of Normal Alkanes : n-butane to n-heptadecane

  • 이송희;이홍;박형석;Jayendran C. Rasaiah
    • Bulletin of the Korean Chemical Society
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    • v.17 no.8
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    • pp.735-744
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    • 1996
  • We present results of molecular dynamic (MD) simulations for the thermodynamic and structural properties of liquid n-alkanes, from n-butane to n-heptadecane, using three different models Ⅰ-Ⅲ. Two of the three classes of models are collapsed atomic models while the third class is an atomistically detailed model. Model Ⅰ is the original Ryckaert and Bellemans' collapsed atomic model [Discuss. Faraday Soc. 1978, 66, 95] and model Ⅱ is the expanded collapsed model which includes C-C bond stretching and C-C-C bond angle bending potentials in addition to Lennard-Jones and torsional potentials of model Ⅰ. In model Ⅲ all the carbon and hydrogen atoms in the monomeric units are represented explicitly for the alkane molecules. Excellent agreement of the results of our MD simulations of model Ⅰ for n-butane with those of Edberg et al.[J. Chem. Phys. 1986, 84, 6933], who used a different algorithm confirms the validity of our algorithms for MD simulations of model Ⅱ for 14 liquid n-alkanes and of models Ⅰ and Ⅲ for liquid n-butane, n-decane, and n-heptadecane. The thermodynamic and structural properties of models Ⅰ and Ⅱ are very similar to each other and the thermodynamic properties of model Ⅲ for the three n-alkanes are not much different from those of models Ⅰ and Ⅱ. However, the structural properties of model Ⅲ are very different from those of models Ⅰ and Ⅱ as observed by comparing the radial distribution functions, the average end-to-end distances and the root-mean-squared radii of gyrations.

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