Study on the supported Cu-based catalysts for the low-temperature water–gas shift reaction

This paper presents a study on the influence of support (Al₂O₃, MgO, SiO₂-Al₂O₃, SiO₂-MgO, β-zeolite, and CeO₂) of Cu-ZnO catalysts for the low-temperature water–gas shift reaction. Supported Cu-ZnO catalysts were prepared by the conventional impregnation method, followed by the H₂ reduction. The activity of Cu-ZnO catalysts for the water–gas shift (WGS) reaction was largely influenced by the kind of support; Cu-ZnO catalysts supported on Al₂O₃, MgO, and CeO₂ showed high activity, while those on SiO₂-Al₂O₃, SiO₂-MgO and β-zeolite showed less activity in the temperature range 423–523 K. XRD analysis demonstrated that the copper species were highly dispersed on the supports used in the present study, except for a MgO support. TPR results of a series of supported CuO-ZnO catalysts suggest that the reducibility of CuO is one of the important factors controlling the activity of the WGS reaction over the supported catalysts.     

Inevitability of spiral-shape in DNA

Cyto-fluid dynamic theory, which clarifies the inevitability of the size ratio of purine and pyrimidine in the base-pairs, is extended to reveal the inevitability of the spiral-shape in DNA, i.e., the double-strand of bases-pairs. First, we will define the cluster consisting of a nitrogenous base and water molecules as continuum flexible column. Then, the differential equation describing deformation motions of the columns having spiral-shapes is derived based on the momentum conservation law. The stability theory, which is based on the concept of the quasistability weaker than the neutral stability, clarifies the inevitability of the spiral shape of B-DNA. It is stressed that the other mode corresponding to A-DNA or C-DNA is also predicted by the present approach. (until March 31, 2008) This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Enhancement of catalytic activity of alumina by copper addition for selective reduction of nitrogen monoxide by ethene in oxidizing atmosphere

The catalytic activity of alumina for the title reaction has been found to be greatly improved by the loading of copper. The addition of copper resulted in lowering the active temperature region, the higher maximum activity, and the enhancement of the reaction rate. The maximum effect was observed at 0.3 wt% of the loading amount of copper. A similar enhancement was also confirmed on SiO₂-Al₂O₃.     

Crystallographic orientation contrast associated with Ga+ ion channelling for Fe and Cu in focused ion beam method

In this study, Cu and Fe single crystals are used to examine the change in secondary electron intensity associated with Ga(+) ion channelling in a focused ion beam (FIB) system. The single crystals having three different orientations are tilted with respect to the beam incidence and the resulting variation in the secondary electron intensity is measured through the variation in brightness of the crystals. It is shown that intensity minima appear at the beam directions normal to the lower indices of the crystal orientations. The appearance of the intensity minima including the magnitude of the minima is consistent with the prediction based on the event of ion channelling in the crystal and is affected by the crystal structure. The effect of background on the intensity minima is discussed in this study. It is suggested that the presence of the intensity minima may be used to identify a crystal orientation including a crystal structure.     

Robust PD Control Using Adaptive Compensation for Completely Restrained Parallel-Wire Driven Robots: Translational Systems Using the Minimum Number of Wires Under Zero-Gravity Condition

A parallel-wire driven mechanism uses flexible wires instead of heavy rigid links. In this paper, we propose a robust point-to-point (PTP) position control method in the task-oriented coordinates for completely restrained parallel wire-driven robots, which are translational systems using the minimum number of wires under zero-gravity conditions. In the cases where parallel-wire driven robots are disassembled/assembled and used outdoors (also applied in space), actuator positions would be uncertain or contain some errors. The error of internal force among wires that results from such uncertainty of actuator positions deteriorates positioning performance. To overcome such a difficulty, adaptive compensation is employed for robust PD control against the error of internal force, in this paper. It is necessary for the adaptive compensation to separate the internal force term linearly into a regressor matrix and a parameter vector concerned with the errors of actuator positions. The internal force term, however, possesses the nonlinear characteristic concerned with the errors of actuator position. Noting the structure of the internal force term, this paper shows that measuring both the position of an end-effector and wire length in real time enables the linear separation. Not only does this robust PD control method ensure precise positioning using external sensors; it enhances the robustness for uncertainty of the Jacobian matrix, which results from the error of actuator installation. First, we explain the linearization of the internal force term. Next, the robust PD control for the parallel-wire driven system using the uncertain Jacobian matrix is proposed; then, we prove the motion convergence to desired points and discuss its robustness based on Lyapunov stability analysis. Finally, the usefulness of the proposed control method is demonstrated through experiments and simulations.