Construction of Lyapunov function for power system based on solving linear matrix inequality

This paper presents construction of Lyapunov functions for power systems based on solving the Linear Matrix Inequality (LMI) derived from the Lyapunov stability theorem considering the dynamics of load characteristic and AVR control system. The proposed Lyapunov function is constructed as a quadratic form of state variables and an integral term which satisfies the curl equation and the sector condition. An induction machine and a synchronous machine are considered as load characteristics. One‐machine one‐load infinite bus system is considered taking into account the flux decay effects and AVR with one time constant of the generator. To verify the proposed Lyapunov function, the transient stability assessment is shown. The critical clearing times given by the proposed Lyapunov function are compared with those obtained by the numerical integration method, and they are shown to be practical. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 158(4): 42– 50, 2007; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20328     

High‐precision positioning control for hard disk drives: 1st report: High‐precision simulator using differential iteration method

The paper proposes a high‐precision simulator for the following mode system design in hard disk drives (HDDs). The simulator is composed of two models: one is a precise mechanical plant which includes numerous high‐frequency vibration modes, and the other is a disturbance signal model which is separated into various disturbances. In the proposed approach, a differential iteration method is applied to identify the precise mechanical plant, providing accurate experimental model analyses. The effectiveness of the synthesized simulator was verified by the comparative studies for experiments and numerical simulations. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(1): 54–61, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20457     

Synergetic toughening of poly(phenylene sulfide) by poly(phenylsulfone) and poly(ethylene-ran-methacrylate-ran-glycidyl methacrylate)

Poly(phenylene sulfide) (PPS) is a high-performance super-engineering plastic, but is brittle. In this study, super-tough PPS-based blends were successfully generated by melt blending PPS with poly(ethylene-ran-methacrylate-ran-glycidyl methacrylate) (EGMA) and poly(phenylsulfone) (PPSU) at (56/14/30) PPS/EGMA/PPSU composition, and their toughening mechanisms were investigated in detail. It was demonstrated the interfacial reaction between PPS and EGMA and partial miscibility between PPS and PPSU, both play important synergistic roles on the toughening. The interfacial reaction between PPS and EGMA contributes to the reduction of the PPSU domain size by the increased viscosity of the PPS matrix containing EGMA, and the increased mobility of EGMA chains by negative pressure effect. The partial miscibility between PPS and PPSU contributes to the increased interfacial adhesion between PPS and PPSU, resulting in effective propagation of the impact to the domains, and the increased mobility of not only PPSU chains but also PPS chains, causing a reduction in crystallization.     

Simulation of isolated operation in fault condition by loop power flow controller

6.6 kV overhead distribution systems are currently constructed in Japan as radial networks. The load imbalance of each feeder therefore has a negative impact on voltage stability. On the other hand, disconnecting distributed generators with faults causes line overload or under-voltage. Therefore, controlling line voltage and line power flow on the distribution system is critical for the open access of indefinite numbers of distributed generators. We are investigating a new loop or mesh structure distribution system to maximise network capacity. This paper describes a control method for a loop power flow controller (LPC) focusing on 1 line-to-ground (LG) fault states.     

Alkene selectivity enhancement in the oxidation of propane on calcium-based catalysts

The oxidation of propane has been investigated in the presence and absence of tetrachloromethane (TCM) on calcium hydroxyapatite (CaHAp), Ca₃(PO₄)₂, CaSO₄ and CaO at 723 K. In the absence of TCM, the conversion of C₃H₈ on CaHAp was 7.7–9.2% during 6 h on-stream while that on Ca₃(PO₄)₂, CaSO₄ and CaO was 0.6, 0 and 0.2–0.4%, respectively. The principal products on all catalysts in the absence of TCM were CO and CO₂ with small selectivities to C₃H₆ and C₂H₄ (both 5–6%) observed on CaHAp. Upon addition of TCM, the selectivity to C₃H₆ on all catalysts and the conversion of C₃H₈ on CaSO₄ increased while, with increasing time-on-stream, the changes in the conversion and selectivity were dependent upon the nature of the catalysts. XPS and XRD analyses provide evidence for the presence of chlorine in the surface and/or bulk of three of the catalysts, suggesting that chlorinated species on the solids play a role in the selectivity enhancement, but the absence of chlorine from the sulphate demonstrates the dissimilarities of the catalysts in their abilities to sorb and decompose TCM. This revised version was published online in July 2006 with corrections to the Cover Date.     

Stereoselective reduction of (±)-bicyclo[3.3.1]nonane-2,6-dione by microorganisms

The biotransformation of (±)-bicyclo[3.3.1]nonane-2,6-dione by Aspergillus niger and Glomerella cingulata was investigated. The diketone was reduced to the ketoalcohol 2-endo-hydroxy-bicyclo[3.3.1]nonane-6-one and the diol endo,endo-bicyclo[3.3.1]nonane-2,6-diol respectively. Endo,endo-bicyclo[3.3.1]nonane-2,6-diol and ketoalcohols produced by G. cingulata had high optical purity, on the other hand, reduction by A. niger yielded optically active (-)-(1R, 2S, 5R, 6S)-bicyclo[3.3.1]nonane-2,6-diol(99·9% e.e.). © 1998 SCI     

Effect of Tetrachloromethane on Redox Behaviors of Copper(II) Oxide in the Oxidative Dehydrogenation of Propane

The oxidative dehydrogenation of propane on CuO has been investigated at 723 K in the presence and absence of tetrachloromethane (TCM). Under oxygen-limiting conditions, the conversion of propane and the selectivity to propylene were enhanced by the introduction of TCM. The catalyst converted to metallic Cu during the oxidation in the absence of TCM while no conversion of CuO was observed in the sample used in the presence of TCM. In contrast, the conversion of propane dramatically decreased upon addition of TCM into the feedstream for the oxidation of propane under the oxygen-excess conditions. The catalyst used under the oxygen-excess conditions was not reduced to metallic Cu, regardless of the addition of TCM. It is suggested that an abstraction of lattice oxygen from the catalyst is strongly influenced by the concentration of oxygen in the feed, resulting in the different effect of TCM on the oxidative dehydrogenation of propane.     

Biological enantioselective reduction of methylcyclohexanones by Glomerella cingulata

Biological reduction of alkylcyclohexanones by Glomerella cingulata was studied. With this organism regioisomeric 2-, 3- or 4-methylcyclohexanone gave the corresponding cis- and trans-methylcyclohexanols. The major metabolites of (±)-2- and (±)-3-methylcyclohexanone were cis-2- and cis-3-methylcyclohexanol. On the other hand, 4-methylcyclohexanone yielded mainly the trans-4-methylcyclohexanol. In addition, the metabolites from (±)-2- and (±)-3-methylcyclohexanone indicated enantioselective reduction by specific optical rotation of the products. The enantiomeric excesses of the microbiological reduction products were determined by NMR spectra of (+)-MTPA-esters of the alcohols produced. The reduction of (±)-2-methylcyclohexanone was stereospecific, with the (2R)-ketone being converted to the corresponding (+)-cis-2-methylcyclohexanol (1S-2R); absolute configuration, 92% e.e. On the other hand, the enantiomeric excess of the major metabolite of (±)-3-methylcyclohexanone was (−)-cis-3-methylcyclohexanol (1S-3R); absolute configuration, 33% e.e.     

Prediction of slippage onset condition between web and steel roller

This paper describes the theoretical modeling for the prediction of slippage onset condition between the paper web and steel roller with experimental verifications. For the first step of modeling, the occurrence of slippage is observed for the cases of uncoated paper (newsprint) and coated paper, and the relation between the slip ratio and roller velocity is measured by changing web tension. Two kinds of theoretical model are proposed, and the applicability of the models is confirmed experimentally.     

Comparison of nutrient removal efficiency between pre- and post-denitrification wastewater treatments.

A shortage of organic substances (COD) may cause problems for biological nutrient removal, that is, lower influent COD concentration leads to lower nutrient removal rates. Biological phosphorus removal and denitrification are reactions in which COD is indispensable. As for biological simultaneous nitrogen and phosphorus removal systems, a competition problem of COD utilisation between polyphosphate accumulating organisms (PAOs) and non-polyphosphate-accumulating denitrifiers is not avoided. From the viewpoint of effective utilisation of limited influent COD, denitrifying phosphorus-removing organisms (DN-PAOs) can be effective. In this study, DN-PAOs activities in modified UCT (pre-denitrification process) and DEPHANOX (post-denitrification process) wastewater treatments were compared. In conclusion, the post-denitrification systems can use influent COD more effectively and have higher nutrient removal efficiencies than the conventional pre-denitrification systems.