Upper and lower critical solution temperatures in poly (ethylene glycol) solutions

Upper and lower critical solution temperatures have been determined for solutions of poly(ethylene glycol) in t-butyl acetate and water over the molecular weight range of M_η = 2.18 × 10³ to ～1020 × 10³. The phase diagram for solutions of poly(ethylene glycol) (M_η = 719 × 10³) in t-butyl acetate was expressed as the ‘hour glass’ type, while the phase diagram for solution of poly(ethylene glycol) (M_η = 2.18 × 10³ to ～2.29 × 10³) in water was expressed as the ‘closed loop’ type. The value of the pressure dependence of the lower critical solution temperature $\text{(}\text{d}\text{T}\text{d}\text{P}\text{)}{}_{\mathrm{c}}$ in the poly(ethylene glycol) (M_η = 1020 × 10³)/water system over the pressure range of 0 to ～50 atm was negligibly small and positive.     

Molecular weights and molecular weight distributions of irradiated cellulose fibers by gel permeation chromatography

Radiation degradation of cellulose fibers was investigated by gel permeation chromatography (GPC). Scoured cotton of Mexican variety (cellulose I), Polynosic rayon (cellulose II), and their microcrystalline celluloses obtained by hydrolysis of the original fibers were irradiated by Co-60 γ-rays under vacuum or humid conditions. The irradiated samples were then nitrated under nondegradative conditions. The molecular weights and molecular weight distributions were measured by GPC using tetrahydrofran as solvent. The relationship between molecular weight and elution count was obtained with cellulose trinitrate standards fractionated by preparative GPC. The degree of polymerization of the fibers decreased with increasing irradiation dose, but their microcystalline celluloses were only slightly degraded by irradiation, especially in microcrystalline cellulose from cellulose I. Degradation of the fibers irradiated under humid conditions was less than that irradiated under vacuum. It was found that the G-values for main-chain scission for the irradiated cellulose I, cellulose II, microcrystalline cellulose I, and microcrystalline cellulose II were 2.8, 2.9, less than 1, and 2.9, respectively, but the G-value for main-chain scission for the irradiated cellulose II was increased to 11.2 at irradiation doses above 3 Mrad. Consequently, it is inferred that cellulose molecules in the amorphous regions are degraded more readily, and the well-aligned molecules in crystalline regions are not as easily degraded by irradiation.     

Comparison of the SiH4---C2H4 and SiH2Cl2---C2H4 systems during the synthesis of silicon carbide ultrafine particles by laser-induced gas-phase reaction

The synthesis conditions of SiC ultrafine particles from SiH₄ and C₂H₄ using a CO₂ laser were studied and a comparison was made between SiH₄---C₂H₄ and SiH₂Cl₂---C₂H₄ systems. Ultrafine SiC particles were synthesized by irradiating a SiH₄ and C₂H₄ gas mixture with a CO₂ laser at atmospheric pressure. SiC particles were obtained at a laser power of more than 0·92 kW/cm².

The behavior of the reaction flame temperature and the extent of the laser light absorption by SiH₄---C₂H₄ was different from that of SiH₂Cl₂---C₂H₄, although an abrupt temperature increase was observed in both cases. In the case of SiH₄---C₂H₄ an abrupt increase in the laser light absorption was not observed, whilst it was observed in the case of SiH₂Cl₂---C₂H₄. This difference resulted from the difference in liability to form solid carbon particles.     

Evaluation of cost and reliability of power systems with large numbers of distributed generators

The authors have proposed the Flexible, Reliable and Intelligent ENergy Delivery System (called “FRIENDS”), which is a new concept for future power distribution systems. Also, a “micro grid” which is a similar concept to FRIENDS has been developed. In a micro grid, an independent distribution system can be constituted by a number of distributed generators. In this paper, FRIENDS, Micro grid, and conventional distribution systems are compared quantitatively in supply reliability and system cost through time sequential Monte Carlo simulations. In addition, for cost evaluation, interruption costs are included to show risk incurred by unsupplied energy. Finally, the authors search for preferable form with install and operation of distributed generators and network composition according to social cost including interruption cost and system cost. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(2): 28–37, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20659     

Synergistic effect of Pt or Pd and perovskite oxide for water gas shift reaction

The water gas shift (WGS) reaction over Pt and Pd catalysts supported on various perovskite oxides has been investigated at 573 K without catalyst pretreatment. The Pt and Pd catalysts on LaCoO₃ support showed high catalytic activity. Interaction between Pt or Pd and the support is considered to promote the WGS reaction: Pt/LaCoO₃ had high initial activity but deactivated immediately; Pd/LaCoO₃ was less active than Pt/LaCoO₃, but had superior stability. Catalysts were characterized using XRD, STEM, XPS, and H₂-temperature programmed reduction (TPR). Results of this study showed that reduction of the support decreased the CO conversion on Pt/LaCoO₃. On the other hand, Pd/LaCoO₃ showed stable activity for the WGS reaction. Therefore, Pd was added to Pt/LaCoO₃ for stabilizing the catalyst activity, and 0.5 wt.% Pd/1 wt.% Pt/LaCoO₃ catalyst showed higher activity and stability.     

Transmission line tower models in frequency domain

This paper proposes a transmission line tower model in frequency domain for back-flashover analysis, which has a uniform characteristic impedance and a uniform propagation constant. Most conventional tower models are constructed as a constant and uniform parameter transmission line that is independent of frequency. However, the authors' models have the frequency dependency of the characteristic impedance and the propagation constant to express the frequency characteristic of the transmission line tower. Two models, a cylinder model and a four-frames model, were investigated to simulate the tower. Their surge responses were computed by numerical electromagnetic field analysis based on the moment method. From the results, the two-port circuit constants were calculated in the frequency domain, and the characteristic impedance and the propagation constant are derived from them. The complex artificial oscillations appeared in frequency dependency of the parameters because the parameters were calculated numerically. The equations with analytical form were obtained by approximating with a smooth curve to the oscillations. It is possible for the equations to represent the transmission line constants as a function of geometrical parameters such as the tower height and the radius. Close agreement was found between the surge response computed by the numerical electromagnetic field analysis and the result calculated by inverse Laplace transformation of the analytical equations. To prove the model, the experimental results were compared with the computed ones of the cylinder model that has arms, and it was shown that the new model agrees closer with the experiment than conventional transmission line models.     

Remarkable enhancement in durability of Pd/H-ZSM-5 zeolite catalysts for CH4-SCR

Effect of second components on the catalytic performance of Pd/H-ZSM-5 zeolite (Pd: 0.4 wt.%) was evaluated by a durability test of NO reduction with CH₄ at a relatively high temperature of 500°C in the presence of water vapor for a prolonged period. The Pd/H-ZSM-5 showed high stable activity for this reaction without H₂O in the reactant feed, while immediate and irreversible deactivation was observed in the presence of H₂O, resulting in no activity after 7 h. The second components such as Co, Rh, Ag, Ce, and Fe introduced individually to the Pd/H-ZSM-5 enhanced the durability, and in particular the addition of 3.3 wt.% Co led to a stable NO conversion for more than 40 h in the presence of H₂O.