Niobic acid, Nb(2)O(5)·nH(2)O, has been studied as a heterogeneous Lewis acid catalyst. NbO(4) tetrahedra, Lewis acid sites, on Nb(2)O(5)·nH(2)O surface immediately form NbO(4)-H(2)O adducts in the presence of water. However, a part of the adducts can still function as effective Lewis acid sites, catalyzing the allylation of benzaldehyde with tetraallyl tin and the conversion of glucose into 5-(hydroxymethyl)furfural in water.

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In a mixed-valence polyoxometalate, electrons are usually delocalized within the cluster anion because of low level of inter-cluster interaction. Herein, we report the structure and electrical properties of a single crystal in which mixed-valence polyoxometalates were electrically wired by cationic π-molecules of tetrathiafulvalene substituted with pyridinium. Electron-transport characteristics are suggested to represent electron hopping through strong interactions between cluster and cationic π-molecules.

To investigate the effect of the network structure on the mechanical properties of a polymer network formed from a certain polymer, we should prepare polymer networks with clearly different network structures made of the same polymer and compare the mechanical properties of these polymer networks. If a living radical polymerization method is applied to the same monomer constituting the polymer network with a nonuniform network structure obtained by conventional free-radical polymerization, it is possible to obtain a polymer network with a uniform network structure in which the molecular weights of the polymer chains bonded to the cross-linking points are uniform and the number of chains bonded to the cross-linking points is constant. In this study, we worked on the synthesis of a polymer network with a uniform network structure by combining two different types of star-shaped polymer synthesis methods using living radical polymerization, i.e., the core-first method and the linking method. In the core-first method, it was possible to synthesize a star-shaped polymer with a narrow molecular weight distribution in a state with a molecular weight corresponding to the charging ratio of the initiator with four initial groups and the monomer. We confirmed that the polymer network obtained by binding the star-shaped polymers by the linking method had a uniform structure, even when swollen with a good solvent or dried, from small-angle X-ray scattering. Depending on the molecular weight of the star-shaped polymer obtained by the core-first method and the amount of the cross-linking agent added for the linking method, the mesh size of the network could be changed while having a uniform network structure. The dried polymer network with uniform network structures exhibited significantly higher values of fracture extensibility and energy than those with nonuniform network structures via conventional free-radical polymerization, when compared at the same monomer and cross-linker concentration.

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This paper proposes a robust controller for sinusoidal pulse width modulation (PWM) inverters, which can track a sinusoidal reference with zero steady-state error. A closedloop system for single-phase full-bridge inverters is constructed on the basis of the internal model principle. The appropriate control gains of the constructed closed-loop system are determined using a state-feedback controller design method via linear matrix inequalities. The proposed controller can adapt to the uncertain variations in the load conditions. It is also shown that the pole-placement constraints and control performance indexes based on the H 2 and H ∞ norms as well as a standard quadric performance index in optimal control can be applied to the proposed robust controller. Digital computer simulation is implemented to confirm the validity of the proposed robust controller with the internal model principle. A prototype experimental model is constructed and tested. Experimental results demonstrate that an excellent and practical robust controller for sinusoidal PWM inverters is realized under uncertain and fluctuating load conditions, including the nonlinear loads such as diode rectifiers. C⃝ 2014 Wiley Periodicals, Inc. Electr Eng Jpn, 187(2): 44-52, 2014; Published online in Wiley Online Library (wileyonlinelibrary.com).

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