We propose theoretically that the reactivity of O2-bound Cu-ZSM-5 toward methane is enhanced by the presence of one water molecule near a dinuclear copper site inside a 10-membered ring of the zeolite cavity. The current study employed density functional theory (DFT) calculations with the B3LYP functional to elucidate reaction intermediates during dioxygen activation by Cu-ZSM-5 in the presence of one water molecule attached to a dicopper site. The initial event is the formation of a hydroperoxo species bridged by the dicopper site via an H atom transfer from an attached water to the bound dioxygen. After the formation of the intermediate, the hydroperoxo O–O bond is completely cleaved to form radical oxygen containing intermediates, such as a Cu–O–Cu species bound by two OH groups (HO–Cu–O–Cu–OH), as well as a copper oxyl group containing intermediate (HO–Cu–OH–CuO). The radical oxygen containing intermediates can cleave a methane C–H bond in a homolytic fashion. Examining the barrier for the C–H bond activation obtained from DFT calculations, we found that the two types of intermediates have the power to more effectively cleave methane C–H bonds than the Cu–O–Cu intermediate that has been proposed to be formed in the absence of a water molecule. The current DFT findings propose that O2-bound Cu-ZSM-5 in the presence of one water molecule is a potential candidate for catalysts desired for methane to methanol conversion under mild conditions. Recently, techniques for controlling the number of water molecules near the active site of a ZSM-5 zeolite have been developed, and therefore the DFT findings should stimulate experimental efforts for constructing catalysts for direct methane hydroxylation.

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A theoretical and experimental investigation was conducted into the spatial behavior of a flexible pipe through which fluid flows and which is built-in at one end and has an asymmetric spring-support at the other end. Planar, non-planar and beating type vibrations occur in such a system and depend on the flow velocity and spring coefficients. Equations governing amplitudes and the phase were derived and used to clarify numerically the above specific cases. Corresponding actual pipe displacements were then measured experimentally using an image processing system employing two CCD cameras. Qualitative agreement was demonstrated between the experimental and theoretical results.

La むeral vibrations of a cantilevered pipe ， which is hung ver もicall γ with an end mass and collveys Huid ， are experimentally and theoretically examined when the 且ow velocity is constant ． We are interes し