• Title/Summary/Keyword: Phase potential

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Stability analysis of gas-liquid interface using viscous potential flow (점성포텐셜유동을 이용한 이상유동장의 표면안정성 해석)

  • Kim, Hyung-Jun;Kwon, Se-Jin
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.3033-3038
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    • 2007
  • In this research, Rayleigh instability of gas-liquid flow in annular pipe is studied in film boiling using viscous potential flow. Viscous potential flow is a kind of approximation of gas-liquid interface considering velocity field as potential including viscosity. A dispersion relation is obtained including the effect of heat and mass transfer and viscosity. New expression for dispersion relation in film boiling and critical wave number is obtained. Viscosity and heat and mass transfer have a stabilizing effect on instability and its effect appears in maximum growth rate and critical wave number. And the existence of marginal stability region is shown.

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Early Hydration of Tricalcium Silicate(III) (Tricalcium Silicate의 초기수화반응(III))

  • 오희갑;최상흘
    • Journal of the Korean Ceramic Society
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    • v.24 no.4
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    • pp.385-391
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    • 1987
  • Zeta potential according to the hydration time was studied during the early hydration of C3S with and without CO2 atmosphere. Zeta potential was low as a level of 20mV at the first and second exothermic peaks of heat evolution, but it was rapidly increased up to a level of 300mV. In the CO2 atmosphere, zeta potential was level of 60mV at 10 minutes hydration and it's value became a low gradually according to the hydration time. Zeta potential was also proportioned to the Ca2+ concentration in the liquid phase, i.e., there was positive correlation between zeta potential and Ca2+ concentration. The existence of silicate layer was not found out on the hydrated C3S in the CO2 atmosphere by SEM-EDAX.

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A Functional Representation of the Potential Energy Surface of Non-Identical $S_N2$ Reaction: F- … $CH_3Cl \rightarrow FCH_3$ … Cl-

  • 김정섭;김영훈;노경태;이종명
    • Bulletin of the Korean Chemical Society
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    • v.19 no.10
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    • pp.1073-1079
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    • 1998
  • The potential energy surface (PES) of the non-identical SN2 reactions, F- + CH3Cl → FCH3 + Cl and (H2O)F + CH3Cl → FCH3 + Cl-(H2O), were investigated with ab initio MO calculations. The ab initio minimum energy reaction path (MERP) of the F- + CH3Cl → FCH3 + Cl- was obtained and it was expressed with an intermediate variable t. The ab initio PES was obtained near around t. Analytical potential energy function (PEF) was determined as a function of the t in order to reproduce the ab initio PES. Based on Morse-type potential energy function, a Varying Repulsive Cores Model (VRCM) was proposed for the description of the bond forming and the bond breaking which occur simultaneously during the SN2 reaction. The MERP calculated with the PEF is well agreed with the ab initio MERP and PEF could reproduce the ab initio PES well. The potential parameters for the interactions between the gas phase molecules in the reactions and water were also obtained. ST2 type model was used for the water.

The thermal effect on electrical capacitance sensor for two-phase flow monitoring

  • Altabey, Wael A.
    • Structural Monitoring and Maintenance
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    • v.3 no.4
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    • pp.335-347
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    • 2016
  • One of major errors in flow rate measurement for two-phase flow using an Electrical Capacitance Sensor (ECS) concerns sensor sensitivity under temperature raise. The thermal effect on electrical capacitance sensor (ECS) system for air-water two-phase flow monitoring include sensor sensitivity, capacitance measurements, capacitance change and node potential distribution is reported in this paper. The rules of 12-electrode sensor parameters such as capacitance, capacitance change, and change rate of capacitance and sensitivity map the basis of Air-water two-phase flow permittivity distribution and temperature raise are discussed by ANSYS and MATLAB, which are combined to simulate sensor characteristic. The cross-sectional void fraction as a function of temperature is determined from the scripting capabilities in ANSYS simulation. The results show that the temperature raise had a detrimental effect on the electrodes sensitivity and sensitive domain of electrodes. The FE results are in excellent agreement with an experimental result available in the literature, thus validating the accuracy and reliability of the proposed flow rate measurement system.

Nerve Agents and Their Detection

  • Kim, Young Jun;Huh, Jae Doo
    • Journal of Sensor Science and Technology
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    • v.23 no.4
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    • pp.217-223
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    • 2014
  • Nerve agents are major chemical warfare agents with the "G series" and "V series" being the most widely known because of their lethal effect. Although not conspicuously used in major wars, the potential detrimental impact on modern society had been revealed from the sarin terror attack on Tokyo subway, which affected thousands of people. In this mini-review, major nerve agents of the "G series" and "V series" have been described along with various types of their detection methods. The physical properties and hydrolysis mechanisms of the major nerve agents are discussed since these are important factors to be considered in choosing detection methods, and specifying the procedures for sample preparations in order to enhance detection precision. Various types of extraction methods, including liquid-phase, solid-phase, gas-phase and solid-phase microextraction (SPME), are described. Recent development in the use of gas sensors for detecting nerve agents is also summarized.

Nondestructive Evaluation of Railway Bridge by System Identification Using Field Vibration Measurement

  • Ho, Duc-Duy;Hong, Dong-Soo;Kim, Jeong-Tae
    • Journal of the Korean Society for Nondestructive Testing
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    • v.30 no.6
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    • pp.527-538
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    • 2010
  • This paper presents a nondestructive evaluation approach for system identification (SID) of real railway bridges using field vibration test results. First, a multi-phase SID scheme designed on the basis of eigenvalue sensitivity concept is presented. Next, the proposed multi-phase approach is evaluated from field vibration tests on a real railway bridge (Wondongcheon bridge) located in Yangsan, Korea. On the steel girder bridge, a few natural frequencies and mode shapes are experimentally measured under the ambient vibration condition. The corresponding modal parameters are numerically calculated from a three-dimensional finite element (FE) model established for the target bridge. Eigenvalue sensitivities are analyzed for potential model-updating parameters of the FE model. Then, structural subsystems are identified phase-by-phase using the proposed model-updating procedure. Based on model-updating results, a baseline model and a nondestructive evaluation of test bridge are identified.

Influence of grain interaction on lattice strain evolution in two-phase polycrystals

  • Han, Tong-Seok
    • Interaction and multiscale mechanics
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    • v.4 no.2
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    • pp.155-164
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    • 2011
  • The lattice strain evolution within polycrystalline solids is influenced by the crystal orientation and grain interaction. For multi-phase polycrystals, due to potential large differences in properties of each phase, lattice strains are even more strongly influenced by grain interaction compared with single phase polycrystals. In this research, the effects of the grain interaction and crystal orientation on the lattice strain evolution in a two-phase polycrystals are investigated. Duplex steel of austenite and ferrite phases with equal volume fraction is selected for the analysis, of which grain arrangement sensitivity is confirmed in the literature through both experiment and simulation (Hedstr$\ddot{o}$m et al. 2010). Analysis on the grain interaction is performed using the results obtained from the finite element calculation based on the model of restricted slip within crystallographic planes. The dependence of lattice strain on grain interactions as well as crystal orientation is confirmed and motivated the need for more in-depth analysis.

Effects of Tungsten on the Precipitation Kinetics of Secondary Phases and the Associated Susceptibility to Pitting Corrosion in Duplex Stainless Steels

  • Park, Chan-Jin;Kwon, Hyuk-Sang
    • Corrosion Science and Technology
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    • v.5 no.6
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    • pp.189-195
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    • 2006
  • Effects of tungsten (W) on the precipitation kinetics of secondary phases and the associated resistance to pitting corrosion of 25%Cr duplex stainless steels were investigated through microstructural and electrochemical noise analyses. With the partial substitution of W for Mo in duplex stainless steel, the potential and current noises of the alloy were significantly decreased in chloride solution due to retardation of the ${\sigma}$ phase precipitation. The preferential precipitation of the $\chi$ phase in the W-containing alloy during the early period of aging contributed to retarding the precipitation of the $\sigma$ phase by depleting W and Mo along grain boundaries. In addition, the retardation of the nucleation and growth of the $\sigma$ phase in the W-containing alloy appears to be attributed to the inherently low diffusivity of W compared with that of Mo.

Biodegradation of Secondary Phase Particles in Magnesium Alloys: A Critical Review

  • Kannan, M. Bobby
    • Corrosion Science and Technology
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    • v.15 no.2
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    • pp.54-57
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    • 2016
  • Magnesium alloys have been extensively studied in recent years for potential biodegradable implant applications. A great deal of work has been done on the evaluation of the corrosion behaviour of magnesium alloys under in vitro and in vivo conditions. However, magnesium alloys, in general, contain secondary phase particles distributed in the matrix and/or along the grain boundaries. Owing to their difference in chemistry in comparison with magnesium matrix, these particles may exhibit different corrosion behaviour. It is essential to understand the corrosion behaviour of secondary phase particles in magnesium alloys in physiological conditions for implant applications. This paper critically reviews the biodegradation behaviour of secondary phase particles in magnesium alloys.

Molecular Dynamic Simulations of the Phase Transition of $\alpha-quartz$ and $\alpha-quartz-type$-type $GeO_2$ under High Pressure (고압력하에서의 $\alpha-quartz$$\alpha-quartz$$GeO_2$의 상전이에 관한 분자동력학시뮬레이션)

  • ;;;;河村雄;Zenbe-e Nakagawa
    • Journal of the Korean Ceramic Society
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    • v.34 no.7
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    • pp.713-721
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    • 1997
  • Molecular dynamic (MD) simulations with new interatomic potential function including the covalent bond were performed on the phase transition of $\alpha$-quartz-type GeO2 under high pressure. The optimized crystal structure and the pressure dependence of the lattice constant showed higher reproducibility than the previous models and were in very good agreement with the experimental data. A phase transition of $\alpha$-quartz and $\alpha$-quartz-type GeO2 by simulation was found approximately 24 GPa and 6-7 GPa, respectively. This phase transition involved an abrupt volume shrinkage and showed 4-6 coordination mixed structure with the increasing in the coordination number of cation.

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