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| 1.
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論文
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Higashi, Hidenori ; Iwai, Yoshio ; Nakamura, Yuji ; Yamamoto, Shinobu ; Arai, Yasuhiko
概要:
金沢大学大学院自然科学研究科生産プロセス<br />An equation proposed by Darken, including the thermodynamic factor and tracer diffusion coeffi
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cients of solvent and solute, was adopted to correlate the diffusion coefficients for naphthalene and dimethylnaphthalene (DMN) isomers in supercritical carbon dioxide and the correlated results were compared with the experimental data. IML equation of state with mixing rules and combining rules containing two adjustable interaction parameters were used for calculation of the thermodynamic factor. By using the interaction parameters adjusted to the solubility data, the concentration dependence of diffusion coefficients and their anomaly near the critical point of carbon dioxide can be quantitatively represented. In order to improve the reliability of experimental results, some re-measured diffusion coefficient data for naphthalene, 2,6- and 2,7-DMN at 308.2 K, and new data for naphthalene at 318.2 K and for 2,3-DMN at 308.2 K are presented.
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| 2.
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論文
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Higashi, Hidenori ; Iwai, Yoshio ; Oda, Tsuyoshi ; Murai, Kengo ; Arai, Yasuhiko
概要:
金沢大学大学院自然科学研究科生産プロセス<br />金沢大学工学部<br />The diffusion coefficients of cetyl alcohol in supercritical carbon dioxide were
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measured by the pseudo steady state solid dissolution method at 308.2 K. The Schmidt number correlation was applied to correlate with the experimental diffusion coefficients. Further, molecular dynamics simulation was performed to calculate the diffusion coefficients by an all atom model of solute. The correlated results by the Schmidt number correlation show good agreement with the experimental results. The calculated results by molecular dynamics simulation give fair estimation to the experimental data without adjustable parameters. Copyright © 2005 The Society of Chemical Engineers, Japan.
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| 3.
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論文
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Higashi, Hidenori ; Iwai, Yoshio ; Arai, Yasuhiko
概要:
金沢大学大学院自然科学研究科生産プロセス<br />NVT ensemble molecular dynamics simulation was performed to calculate the tracer diffusion coe
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fficients of naphthalene and dimethylnaphthalene isomers in supercritical carbon dioxide. Carbon dioxide was treated as a Lennard-Jones molecule (single site model) and solutes were treated as a rigid model of multi sites (united atom model) and a flexible model of all atoms (all atom model). The calculated results are compared with the experimental data and the calculated results by a single site model. The united atom model gives the best results to the experimental data among the three models. The calculated tracer diffusion coefficients by the all atom model show fairly good results without adjustable interaction parameters. © 2005 Elsevier B.V. All rights reserved.
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| 4.
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論文
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Iwai, Yoshio ; Higashi, Hidenori ; Uchida, Hirohisa ; Arai, Yasuhiko
概要:
金沢大学大学院自然科学研究科生産プロセス<br />NVT ensemble molecular dynamics simulation has been applied to calculate the diffusion coeffic
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ients of naphthalene and 2-naphthol in supercritical carbon dioxide in the pressure range from 8 to 40 MPa under infinite dilution conditions. The Lennard-Jones (12-6) potential function was used as the intermolecular potential. The calculation results showed good agreement with the experimental values, by using the intermolecular interaction parameters between unlike molecules which were determined by Monte Carlo simulation to give good representation for the solubilities of naphthalene and 2-naphthol in supercritical carbon dioxide.
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| 5.
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論文
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Higashi, Hidenori ; Oda, Tsuyoshi ; Iwai, Yoshio ; Arai, Yasuhiko
概要:
金沢大学大学院自然科学研究科生産プロセス<br />A non-equilibrium molecular dynamics simulation was adopted to calculate the diffusion coeffic
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ients for a pseudo-binary system of carbon dioxide and for a carbon dioxide + solute system at 308.2 and 318.2K. The calculated results were compared with the self- and tracer diffusion coefficients calculated by an equilibrium molecular dynamics simulation. The simulated results for the pseudo-binary system of carbon dioxide by the non-equilibrium molecular dynamics simulation are in good agreement with the results of self diffusion coefficients for pure carbon dioxide by the equilibrium molecular dynamics simulation. The simulated results of mutual diffusion coefficients for the carbon dioxide + solute system by the non-equilibrium molecular dynamics simulation are slightly lower than the results of the tracer diffusion coefficients by the equilibrium molecular dynamics simulation. The anomalous behavior of diffusion coefficients near the critical concentration was represented by the results of the non-equilibrium molecular dynamics simulation. © 2004 Elsevier B.V. All rights reserved.
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| 6.
論文 |
論文
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Higashi, Hidenori ; Iwai, Yoshio ; Oda, Tsuyoshi ; Nakamura, Yuji ; Arai, Yasuhiko
概要:
金沢大学大学院自然科学研究科生産プロセス<br />The concentration dependence of diffusion coefficients for naphthalene in supercritical carbon
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dioxide at 308.2K was measured by a pseudo steady-state solid dissolution method. The experimental diffusion coefficients were compared with the calculated results by the Darken equation including a thermodynamic factor and tracer diffusion coefficients of supercritical carbon dioxide and naphthalene. The thermodynamic factor in the Darken equation was determined by using several cubic equations of state. The calculated results by the Darken equation represent the concentration dependence of the experimental diffusion coefficients. © 2002 Elsevier Science B.V. All rights reserved.
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| 7.
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論文
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Tada, T. ; Seo, T. ; Higashimine, K. ; Monzen, Ryoichi
概要:
The coarsening behavior of rod-shaped α-Fe particles in Cu–1.0 wt.% Fe and Cu–1.0 wt.% Fe–1.2 wt.% Sb alloys during agin
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g at 700 °C has been studied by transmission electron microscopy and electric resistivity. The kinetics of the decay of supersaturation with aging time t for both alloys coincide with the t−1/3 law. The coarsening kinetics of the cylindrical radius of the Fe particles obey the t1/3 law. Using the Lifshitz–Slyozov–Wagner theory modified for the case of rod-shaped particles by Speich and Oriani, the maximum value of the Cu/α-Fe interfacial energy γ and the volume diffusivity D of Fe in Cu for the Cu−Fe alloy are independently derived to be 1.3 J/m2 and 3.9×10−16 m2/s. Adding Sb to the Cu−Fe alloy decreases the values of γ and D.
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| 8.
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論文
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李, 光洙 ; 山田, 敏郎 ; 多田, 薫 ; 勝尾, 憲一 ; 石原, 英昭
概要:
Segmented poly (urethane-urea) (SPUU) fibers such as spandex fibers are usually produced by dry spinning process. The pr
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ocessing conditions for dry spinning of SPUU can be optimized by computer simulation. In this work, a simulation model is proposed for the dry spinning process where the SPUU dope in the liquid state is first extruded from the nozzle in the shape of spinline, then the solvent in the spinline is removed by the blowing of hot gas while elongated, and finally a few spinlines come to a fiber in the solid state after they are twisted. The deformation behavior, solvent concentration, temperature of spinline and so on can be predicted with this model. Governing equations composed of the equations of continuity, motion, energy, rheology and deflection were derived under the assumption of Newtonian fluid. Simulations for dry spinning process were carried out with various diffusion coefficients previously reported for two kinds of solvents (dimethyl formamid (DMF), dimethyl acetamide (DMAc)) and three measurement methods of diffusion coefficients (Moiré pattern, Film and Dope methods), where Moiré pattern method gives the mutual diffusion coefficient for the liquid-liquid system, Film method gives the diffusion coefficient of solvent into the film which changes from the solid state to the semisolid state during measurement, and Dope method gives the diffusion coefficient of solvent from the dope which changes from the liquid state to the (semi-) solid state during measurement. The temperature distribution in the spinning chamber was linearly approximated in the distribution close to a practical plant. The simulation model can predict the residual solvent concentration, temperature, cross sectional area, spinning stress and deflection of spinline. The simulation results denoted that the change of solvent concentration is mainly determined in the hot gas zone even if the diffusion coefficients are different. Therefore, the deformation behavior of spinline is chiefly governed in the hot gas zone. And there is little change found in the interim zone and blowing zone.
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| 9.
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論文
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土成, 昭弘 ; 保木井, 利之 ; 下林, 修 ; 金岡, 千嘉男
概要:
In a permeable MgO ceramic containing TiO_2 and Al_2O_3 as matrix MgO ・ Al_2O_3-2MgO・TiO_2 solid solutions were detected
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and no Al_2O_3・TiO_2 was observed. Therefore, the solid state reaction among MgO, TiO_2 and Al_2O_3 with excess MgO was studied at various firing temperatures. The formation mechanism of MgO・Al_2O_3-2MgO・TiO_2 solid solutions was studied from the results of interface reactions between MgO-TiO_2 and MgO-Al_2O_3. MgO・Al_2O_3-2MgO・TiO_2 solid solutions were detected at 1573-1673 K and increased with the firing temperature. 2MgO・TiO_2 was formed in the system MgO-TiO_2, but was not produced in the system MgO-TiO_2-Al_2O_3, because the amount of Mg diffusion at the interface of aggregate and matrix additives was not enough due to the large aggregate size of MgO. MgO・Al_2O_3 and 2MgO・TiO_2 formed at the interface between MgO-TiO_2 and MgO-Al_2O_3 decreased with the firing time at 1873 K. On the other hand, MgO・Al_2O_3-2MgO・TiO_2 solid solutions increased. Mg was recognized in the matrix without addition of MgO as a matrix. Al diffused in the layer of MgO-TiO_2, in opposition Ti diffused in the layer of MgO-Al_2O_3 by EPMA analysis. From the above results, the formation mechanism of a MgO・Al_2O_3-2MgO・TiO_2 solid solution was proposed; (1) Mg diffusion at the interface of MgO aggregate and matrix additives, (2) formation of MgO・TiO_2 and MgO・Al_2O_3, (3) formation of 2MgO・TiO_2 due to the reaction with MgO・TiO_2 and MgO, (4) reaction of the solid solution with MgO・Al_2O_3 and 2MgO・TiO_2. In the reactions between MgO・TiO2 and MgO-Al_2O_3 the product layer of MgO・Al_2O_3-2MgO・TiO_2 solid solution increased as the firing time increased. The diffusion coefficient of Mg was about 4.8×10^<-7>(cm^2/s), in a good agreement with that of Mg which was reported.
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