• Title/Summary/Keyword: Equation of State

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Instantaneous Deflection calculation Incorporated with Internal Force State Factor In RC short beams(a/d<2.5) (RC 짧은보(a/d<2.5)의 순간처짐 산정에 대한 연구)

  • Oh, Hyun-Chul;Jeong, Jae-Pyong;Kim, Woo
    • Proceedings of the Korea Concrete Institute Conference
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    • 2001.11a
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    • pp.713-718
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    • 2001
  • This paper describes an attempt to develop a new equation to calculate deflection for reinforced concrete deep beams(a/d<2.5). The main idea incorporated with this equation is the internal force state factor($\alpha$)which is able to express global state of internal force flow in cracked reinforced concrete beams subjected to shear and bending. A new equation for deflection calculation using internal force state factor($\alpha$)provides more exact result of deflection in reinforced concrete deep beams than the equation predicted by the current code provisions.

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A Computational Analysis of Air Entrainment with a Nip Roller

  • Lee, Jae-Yong;Chang, Young-Bae;Shelton, John J.
    • Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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    • 2002.11a
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    • pp.81-90
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    • 2002
  • Air entrainment of a winding roll with a nip roller was studied numerically. The amount of air entrainment between two rotating rollers was obtained by solving lubrication equation, Reynolds equation, which neglect the existence of a web. However, the numerical model of this study included the web existence, therefore it considered the two lubricating air films between a winding roll and a web and also between a nip roller and the web. The pressure profiles and gap profiles of the two films were obtained by solving lubrication equation for the two air films and force balance equation of the web. Ballooning phenomenon was examined in terms of nip force, wrap angle, web stiffness, web speed, and web tension. This ballooning phenomenon caused by the back flow of the air film blocked by the nip roller. Air entrainment of the two numerical models was compared.

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Comparative Study on Classical Control and Modern Control via Analysis of Circuit-based Time Response (회로망 기반의 시간응답 해석에 따른 고전제어와 현대제어의 비교 연구)

  • Min, Yong-Ki
    • The Journal of the Korea institute of electronic communication sciences
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    • v.12 no.4
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    • pp.575-584
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    • 2017
  • It is suggested the circuit network to analyze the time response of control system. And it is analyzed the interrelation for classical control and modern control by the transfer function and the state equation. Without complicated integration of state transition equation, it is suggested to possible time response by combining the state transition matrix and the transfer function. A source program is coded to display the time response according to the unit-step and the sinusoidal input. Transient response is analyzed in the unit-step input and phase difference between current and voltage is analyzed in sinusoidal input. As writing the suggested contents in transient response or state-space analysis, it is improved the understanding for control engineering and ability for system design.

Estimation of Thermodynamic Properties of Refrigerant Mixtures Using a Modified Carnaha-Starling Equation of State (수정된 Carnahan-Starling 상태방정식을 이용한 혼합냉매의 물성계산)

  • 김민수;김동섭;노승탁
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.6
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    • pp.2189-2205
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    • 1991
  • Thermodynamic properties of binary nonazeotropic refrigerant mixtures are estimated by using a modified Carnhan-Starling equation of state. In this study, pure component refrigerants such as R14, R23, R13, R13 B1, R22, R12, R134a, R152a, R142b, RC318, R114, R11, R123 and R113 are chosen and the thermodynamic properties of enthalpy and entropy are calculated in terms of relevant variables. The modified Carnahan-Starling equation of state is compared with the carnahan-Staring-De Santis equation of sate. Results show that the relative errors become slightly smaller with the equation of state proposed in this study. Correlations are obtained for the mixtures of which the vapor liquid equilibruim data are available to us in the literature. Those mixtures are R14/R23, R23/R12, R13/R12, R13/R11, R13B1/R22, R13B1/RC318, R12/RC138, R12/R114 and R12/R11. The binary interaction coefficients are found under the condition of minimizing the pressure deviations at the vapor liquid equiblibrium state and the estimation of the vapor liquid equilibrium for the refrigerant mixtures is done. Pressure-enthalpy and temperature-entropy diagrams are plotted for the refrigerant mixtures of specific composition.

A New Model and Equation Derived From Surface Tension and Cohesive Energy Density of Coagulation Bath Solvents for Effective Precipitation Polymerization of Acrylonitrile

  • Zhou, You;Xue, Liwei;Yi, Kai;Zhang, Li;Ryu, Seung Kon;Jin, Ri Guang
    • Carbon letters
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    • v.13 no.3
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    • pp.182-186
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    • 2012
  • A new model and resultant equation for the coagulation of acrylonitrile monomers in precipitation polymerization are suggested in consideration of the surface tension (${\gamma}$) and cohesive energy density ($E_{CED}$). The equation was proven to be quite favorable by considering figure fittings from known surface tensions and cohesive energy densities of certain organic solvents. The relationship between scale value of surface tension (${\gamma}$/M) and cohesive energy density of monomers can be obtained by changing the coagulation bath component for effective precipitation polymerization of acrylonitrile in wet spinning.

The Construction of Semi-diabatic Potential Energy Surfaces of Excited States for Use in Excited State AIMD Studies by the Equation-of-Motion Coupled-Cluster Method

  • Baeck, Kyoung-Koo;Martinez, Todd J.
    • Bulletin of the Korean Chemical Society
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    • v.24 no.6
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    • pp.712-716
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    • 2003
  • The semi-diabatic potential energy surfaces (PESs) of the excited states of polyatomic molecules can be constructed for use in ab initio molecular dynamics (AIMD) studies by relying on the continuity of the electronic energy, oscillator strength, and spherical extent of an excited state along with first derivatives of these quantities as computed by using the equation-of-motion coupled-cluster (EOM-CC) method. The semidiabatic PESs of both the π → $π^*$ valence excited state and the 3s-type Rydberg state of ethylene are presented and discussed in this paper, in conjunction with some of the AIMD results we obtained for these states.

Improvement of the Spectral Reconstruction Process with Pretreatment of Matrix in Convex Optimization

  • Jiang, Zheng-shuai;Zhao, Xin-yang;Huang, Wei;Yang, Tao
    • Current Optics and Photonics
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    • v.5 no.3
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    • pp.322-328
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    • 2021
  • In this paper, a pretreatment method for a matrix in convex optimization is proposed to optimize the spectral reconstruction process of a disordered dispersion spectrometer. Unlike the reconstruction process of traditional spectrometers using Fourier transforms, the reconstruction process of disordered dispersion spectrometers involves solving a large-scale matrix equation. However, since the matrices in the matrix equation are obtained through measurement, they contain uncertainties due to out of band signals, background noise, rounding errors, temperature variations and so on. It is difficult to solve such a matrix equation by using ordinary nonstationary iterative methods, owing to instability problems. Although the smoothing Tikhonov regularization approach has the ability to approximatively solve the matrix equation and reconstruct most simple spectral shapes, it still suffers the limitations of reconstructing complex and irregular spectral shapes that are commonly used to distinguish different elements of detected targets with mixed substances by characteristic spectral peaks. Therefore, we propose a special pretreatment method for a matrix in convex optimization, which has been proved to be useful for reducing the condition number of matrices in the equation. In comparison with the reconstructed spectra gotten by the previous ordinary iterative method, the spectra obtained by the pretreatment method show obvious accuracy.

Characteristics Analysis of a Forward Converter by Finite Element Method and State Variables Equation (유한요소법과 상태방정식을 이용한 포워드 컨버터의 동작 특성 해석)

  • Park, Seong-Jin;Gwon, Byeong-Il;Park, Seung-Chan
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.48 no.9
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    • pp.467-475
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    • 1999
  • This paper presents an analysis method of a forward converter, using both the finite element method considering the external circuit and a state variables equation. The converter operates at 50kHz and its one period is divided into two modes for the simplicity of the analysis. In the first mode, the switching transistor turns on and an input power is transferred into the load by the electromagnetic conversion action of a ferrite transformer. In the second mode, the switching transistor turns off and the stored energy in an inductor is delivered to the load, and the transformer core is demagnetized by the reset winding current. In this paper, time-stepping finite element method taking into account the on-state electrical circuit of the converter in used to analyze both the electrical circuit and electromagnetic field of the magnetic device during the first mode and the demagnetization period of the transformer core. Then a state variables equation for the circuit which the inductor current flows is constituted and solved during the second mode. As a result, the simulation results have been good agreement with the results obtained form experiment.

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Prediction of partial molar volumes of solutes in supercritical CO2 using the Peng-Robinson equation of state with various mixing rules and Kirkwood-Buff solution theory (3차 상태방정식과 여러 혼합법칙 및 Kirkwood-Buff용액이론을 이용한 초임계유체내에서의 용질의 무한희석 부분몰부피의 계산)

  • Jeon, Young-Pyo;Park, Jong-Seon;Kwon, Yong-Jung
    • Journal of Industrial Technology
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    • v.19
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    • pp.253-260
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    • 1999
  • Two thermodynamic models were used to predict the partial molar volumes of solutes in supercritical carbon dioxide at infinite dilution: (1) the Peng-Robinson equation of state with various mixing rules including those based on $EOS/G^E$ (2) the Kirkwood Buff fluctuation integral with the hard sphere expansion (HSE) method. The Kirkwood-Buff fluctuation integral method, in which an equation of state for pure component and molecular parameters are required, produced better results especially near the critical point than the Peng-Robinson equation of state with the several mixing rules based an $EOS/G^E$. When the $EOS/G^E$ mixing rules were used, poorer results were obtained compared with the classical mixing rule and Kirkwood-Buff model.

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State-Space Equation Model for Motion Analysis of Floating Structures Using System-Identification Methods (부유식 구조체 운동 해석을 위한 시스템 식별 방법을 이용한 상태공간방정식 모델)

  • Jun-Sik Seong;Wonsuk Park
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.37 no.2
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    • pp.85-93
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    • 2024
  • In this paper, we propose a method for establishing a state-space equation model for the motion analysis of floating structures subjected to wave loads, by applying system-identification techniques. Traditionally, the motion of floating structures has been analyzed in the time domain by integrating the Cummins equation over time, which utilizes a convolution integral term to account for the effects of the retardation function. State-space equation models have been studied as a way to efficiently solve floating-motion equations in the time domain. The proposed approach outlines a procedure to derive the target transfer function for the load-displacement input/output relationship in the frequency domain and subsequently determine the state-space equation that closely approximates it. To obtain the state-space equation, the method employs the N4SID system-identification method and an optimization approach that treats the coefficients of the numerator and denominator polynomials as design variables. To illustrate the effectiveness of the proposed method, we applied it to the analysis of a single-degree-of-freedom model and the motion of a six-degree-of-freedom barge. Our findings demonstrate that the presented state-space equation model aligns well with the existing analysis results in both the frequency and time domains. Notably, the method ensures computational accuracy in the time-domain analysis while significantly reducing the calculation time.