• Title/Summary/Keyword: thermodynamic properties

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Studies on the Surfactants of the N-Acyl Amino Acid(part 9) -The Effect of Temperature and Electrolytes on the Micellization of Sodium N-Lauroyl-N-Methyl-Taurate- (N-아실 아미노산계 계면활성제에 관한 연구(제9보) -Sodium N-Lauroyl-N-methyl-taurate의 미셀형성에 대한 온도 및 전해질의 영향-)

  • Kim, Jin-Hyun;Kim, Tae-Young;Ju, Myung-Jong;Nam, Ki-Dae
    • Applied Chemistry for Engineering
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    • v.7 no.3
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    • pp.401-409
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    • 1996
  • The effect of temperature on the cmc of sodium N-lauroyl-N-methyl taurate was examined. The cmc values were found to be decreased initially but increased further with the increase of temperature. From the temperature dependence of cmc, various thermodynamic properties were calculated. The effects of various electrolytes on the cmc of sodium N-lauroyl-N-methyl-taurate were also examined. The free energy of hydrophobic bond formation and the degree of dissociation of the micelles were calculated from log cmc vs. log counter ion concentration plots. The ${\Delta}H_m$ values were decreased with increasing the temperature and changed their signs from plus to minus at $40^{\circ}C{\sim}50^{\circ}C$. The ${\Delta}G_m$ values were decreased with the increase of electrolyte concentration and temperature.

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Analysis on the Langmuir adsorption isotherm at the $Pt/H_2SO_4$ electrolyte interface using the ac impedance measurement and phase-shift method ($Pt/H_2SO_4$ 전해질 계면에서 교류임피던스 측정과 위상이동 방법에 의한 Langmuir 흡착등온식 해석)

  • Chun Jang Ho;Cho Sung Chil;Son Kwang Chul
    • Journal of the Korean Electrochemical Society
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    • v.2 no.1
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    • pp.23-26
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    • 1999
  • The Langmuir adsorption isotherm at the $(Pt)/0.1M\;H_2SO_4$ electrolyte interface has been qualitatively analyzed using the ac impedance measurement and phase-shift method. The phase shift $(\phi)$ depends on both the cathode potential (E<0) and frequency (f) and is inversely proportional to the factional surface coverage $(\theta)$. At an intermediate frequency band (ca. $1\~100$ Hz), the phase-shift profile $(\phi\;vs.\;E)$ can be related to the fractional surface coverage $(\theta\;vs.\;E)$. The phase-shift profile $(\phi\;vs.\;E)$ can be used as an experimental method to estimate and analyze the Langmuir adsorption isotherm $(\theta\;vs.\;E)$. The equilibrium constant (K) and the standard free energy $({\Delta}G_{ads})$ of the adsorbed hydrogen atom $(H_{ads})\;and\;3\times10^{-4}$ and 20.1 kJ/mol, respectively.

Development of a Dynamic Model for Double-Effect LiBr-$H_2O$ Absorption Chillers and Comparison with Experimental Data. (이중효용 흡수식 냉온수기 동특성 모델 개발 및 실험결과 비교)

  • Shin, Young-gi;Seo, Jung-A;Cho, Hyun-Wook;Nam, Sang-Chul;Jeong, Jin-Hee
    • Proceedings of the SAREK Conference
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    • 2008.06a
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    • pp.109-114
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    • 2008
  • A dynamic model has been developed to simulate dynamic operation of a real double-effect absorption chiller. Dynamic behavior of working fluids in main components was modeled in first-order nonlinear differential equations based on heat and mass balances. Mass transport mechanisms among the main components were modeled by valve throttling, 'U' tube overflow and solution sub-cooling. The nonlinear dynamic equations coupled with the subroutines to calculate thermodynamic properties of working fluids were solved by a numerical method. The dynamic performance of the model was compared with the test data of a commercial medium chiller. The model showed a good agreement with the test data except for the first 5,000 seconds during which different flow rates of the weak solution caused some discrepancy. It was found that the chiller dynamics is governed by the inlet temperatures of the cooling water and the chilled water when the heat input to the chiller is relatively constant.

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Pressure Effect on the Dissociation Reactions of Some Weak Acids (약산의 해리반응에 미치는 압력의 영향)

  • J. U. Hwang;J. J. Chung;Y. T. Park;J. G. Jee;E. S. Park
    • Journal of the Korean Chemical Society
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    • v.27 no.5
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    • pp.311-319
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    • 1983
  • The dissociation constants of anilinium ion, o-toluidinium ion, phenol and o-chlorophenol were measured spectroscopically in aqueous solution over the temperature range of 10∼40$^{\circ}C$ and at the pressures up to 2,000 bars. The effects of temperature and pressure on the dissociation of the phenols are the same as those of the ordinary weak acids. Meanwhile the dissociation constants of anilinium ions are increased with temperature raising and decreased with pressure elevation. The effects of pressure on the constants can be explained by taking account of change of charge during dissociation reaction; there are increase in charge in the dissociation of phenols but anilinium ions are not. Several thermodynamic properties, ${\Delta}H^{circ}$,${\Delta}G^{circ}$, ${\Delta}S^{circ}$,${\Delta}V^{circ}$ and ${\beta}$ are calculated from those constants, and the dissociation reactions are discussed by them.

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Three-dimensional Analysis of Heavy Rainfall Using KLAPS Re-analysis Data (KLAPS 재분석 자료를 활용한 집중호우의 3차원 분석)

  • Jang, Min;You, Cheol-Hwan;Jee, Joon-Bum;Park, Sung-Hwa;Kim, Sang-il;Choi, Young-Jean
    • Atmosphere
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    • v.26 no.1
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    • pp.97-109
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    • 2016
  • Heavy rainfall (over $80mm\;hr^{-1}$) system associated with unstable atmospheric conditions occurred over the Seoul metropolitan area on 27 July 2011. To investigate the heavy rainfall system, we used three-dimensional data from Korea Local Analysis and Prediction System (KLAPS) reanalysis data and analysed the structure of the precipitation system, kinematic characteristics, thermodynamic properties, and Meteorological condition. The existence of Upper-Level Jet (ULJ) and Low-Level Jet (LLJ) are accelerated the heavy rainfall. Convective cloud developed when a strong southwesterly LLJ and strong moisture convergence occurring around the time of the heavy rainfall is consistent with the results of previous studies on such continuous production. Environmental conditions included high equivalent potential temperature of over 355 K at low levels, and low equivalent potential temperature of under 330 K at middle levels, causing vertical instability. The tip of the band shaped precipitation system was made up of line-shaped convective systems (LSCSs) that caused flooding and landslides, and the LSCSs were continuously enhanced by merging between new cells and the pre-existing cell. Difference of wind direction between low and middle levels has also been considered an important factor favouring the occurrence of precipitation systems similar to LSCSs. Development of LSCs from the wind direction difference at heights of the severe precipitation occurrence area was also identified. This study can contribute to the identification of production and development mechanisms of heavy rainfall and can be used in applied research for prediction of severe weather.

Kinetic Analysis of Rate Limiting Step in the Metabolic Process -[Part I.] A Modified Emzymatic Method- (대사과정(代謝過程)에 있어서 율속단계(律速段階)의 속도론적(速度論的) 해석(解析) -[제1보(第一報)] 수정된 효소적 방법에 대하여-)

  • Shin, Kui-Nam;Koh, Ik-Bai
    • Applied Biological Chemistry
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    • v.19 no.3
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    • pp.162-171
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    • 1976
  • The determination of rate limiting step in the metabolic process is of great importance to understand the metabolic properties. In this paper the authors propose a modified enzymatic method instead of thermodynamic method. This method is based on the assumption that the over-all rate increment would be larger than by any other steps to which the individual enzyme are added respectively, provided that the enzyme participated in the rate limiting step is added to the reactions composed of n steps of metabolic process with which n kind of enymes are concerned. The present paper deals with analysis and discussion about some factors having influence on the proposed process, mainly about the metabolic process constituted with homogeneous steps. The results show that the determination of rate limiting step by a modified enzymatic method is feasible, provided that some restrictions are added in any type of mechanisms.

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Electrocatalytic Effect on the Oxygen Reduction and Electrochemical Properties of Co(Ⅱ)-dimethyl Bipyridine Perchlorate (Co(Ⅱ)$(dimethyl bipyridine)_3(ClO_4)_2$의 전기화학적 성질과 산소환원에 대한 전극 촉매 효과)

  • Kim, Il Kwang;Park, Chong Sool;Han, Wan Soo;Kim, Youn Keun;Jeon, Il Cheol
    • Journal of the Korean Chemical Society
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    • v.41 no.8
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    • pp.385-391
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    • 1997
  • Diffusion Coefficient$(D_0)$ and electrode reaction rate Constant$(K_0)$ of Co$(dimethyl bipyridine)_3(ClO_4)_2$ were determined by cyclic voltammetry and chronoamperometry. It was also investigated that the effects of solvent, concentration, and scan rate, etc. on the diffusion coefficient and the temperature effect on the rate constant. The peak currents and diffusion coefficients were dcreased as increasing the viscosity of solvent. Diffusion coefficient was $5.54{\times}10^{-6 }cm^2/sec$ and the reaction rate constant was $2.39{\times}10^{-3 }/s$ at 25$^{\circ}C$. The thermodynamic parameters such as ${\Delta}G^{\neq},\;{\Delta}H^{\neq},\;and\;{\Delta}S$ were calculated from plotting the reaction rate constants versus the solution temperatures. This compound was shown the catalytic effect on the oxygen reduction that the reduction peak current of oxygen was greatly enhanced and the peak potential was shifted to +0.2 volt.

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On Numerical Modeling of Kerosene/Liquid Oxygen Coaxial Swirl Injectors (케로신/액체산소 동축 와류형 분사기에 대한 수치해석 모델 고찰)

  • Kim, Seong-Ku;Choi, Hwan-Seok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2010.11a
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    • pp.729-732
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    • 2010
  • The present study has been motivated by the development of a reliable numerical methodology for simulation of kerosene/LOx coaxial swirl injectors. To deal with thermodynamic non-ideality and anomalies of transport properties pronounced at supercritical pressures, a set of subroutine libraries has been constructed based on the cubic equations of state, and applied to an existing flamelet analysis code. For computational efficiency, two-dimensional axisymmetric RANS formulation with swirl was adopted and validated successfully against an isothermal coaxial swirling jet. For the actual problem with high pressure combustion, however, numerical results show that the RANS models yield excessive production of turbulence probably due to high density gradient magnitude in the vicinity of mixing layer of swirling film flow, and imply strongly further improvement of the turbulence models.

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Development of a Dynamic Model for Double-Effect LiBr-$H_{2}O$ Absorption Chillers and Comparison with Experimental Data (이중효용 흡수식 냉온수기 동특성 모델 개발 및 실험결과 비교)

  • Shin, Young-Gy;Seo, Jung-A;Cho, Hyun-Wook;Nam, Sang-Chul;Jeong, Jin-Hee
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.20 no.12
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    • pp.781-788
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    • 2008
  • A dynamic model has been developed to simulate dynamic operation of a real double-effect absorption chiller. Dynamic behavior of working fluids in main components was modeled in first-order nonlinear differential equations based on heat and mass balances. Mass transport mechanisms among the main components were modeled by valve throttling, 'U' tube overflow and solution sub-cooling. The nonlinear dynamic equations coupled with the subroutines to calculate thermodynamic properties of working fluids were solved by a numerical method. The dynamic performance of the model was compared with the test data of a commercial medium chiller. The model showed a good agreement with the test data except for the first 5,000 seconds during which different flow rates of the weak solution caused some discrepancy. It was found that the chiller dynamics is governed by the inlet temperatures of the cooling water and the chilled water when the heat input to the chiller is relatively constant.

Thermal Analysis of Prelaunch Transients in Cryogenic Oxidizer Tank of Liquid Propulsion Rocket (발사대기 중인 액체추진 로켓의 극저온 산화제 탱크 내 비정상 열해석)

  • Kim, Kyoung-Hoon;Ko, Hyung-Jong;Kim, Kyoung-Jin;Cho, Kie-Joo;Oh, Seung-Hyub
    • Journal of the Korean Society of Propulsion Engineers
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    • v.12 no.4
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    • pp.33-41
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    • 2008
  • The prelaunch thermal transients in the cryogenic oxidizer tank of liquid propulsion rocket subjected to uniform heat flux from outside are numerically analyzed through thermodynamic equations and heat and mass transfer relations. The prelaunch stage is assumed to be composed of five idealized sub-stages including pressurization process by helium gas injection. The Peng-Robinson equation of state is utilized in the lumped analysis of ullage gas. The liquid region is divided into a number of horizontal layers of uniform properties to account for the thermal stratification. The computational result for the typical case shows that the temperature rise of liquid oxidizer is less than 1K and the adsorbed helium into the liquid is approximately 10g.