Different support effect of M/ZrO2 and M/CeO2 (M = Pd and Pt) catalysts on CO adsorption: A periodic density functional study

CO adsorption over Pd₄ and Pt₄ cluster supported by c-ZrO₂(1 1 1) and CeO₂(1 1 1) catalyst systems was investigated using periodic density functional method in order to clarify the support effect on CO activation. We found that the support increases the CO activation for bridge and three-fold sites but decreases for the atop site. Moreover, it was found that the support changes the site preference for the CO adsorption. Bridge site on both the Pt₄/c-ZrO₂ and Pt₄/CeO₂ show larger CO adsorption energies than those on the other sites while the atop site is energetically preferable on isolated Pt₄ cluster. c-ZrO₂ supported Pd shows the largest CO activation with large charge transfer from the catalyst to the CO molecule. This reveals that ZrO₂ supported Pd can be a good catalyst for CO activation because of its higher probability to the three-fold site CO adsorption. We also found that positively charged M₄ clusters on the support keep their strong electron-donating properties and have enough charge density to contribute to the activation of an adsorbed CO molecule by a charge transfer.     

Unsteady flow field numerical calculations of a ship’s rotating Weis-Fogh-type propulsion mechanism with the advanced vortex method

The Weis-Fogh mechanism, found in the hovering flight of a small bee, is a unique and efficient lift generation. In this study, we proposed a rotating type propulsion model that applies the principle of the Weis-Fogh mechanism and calculated the unsteady flow field of the propulsion model with the advanced vortex method. The wing (NACA0010 airfoil) and channel are approximated by source and vortex panels, and free vortices are introduced away from the body surfaces. The viscous diffusion of fluid is represented using the core-spreading model to the discrete vortices. We investigated the thrust and drag coefficients, pressure field, vorticity field, velocity vector field, and average propulsive efficiency of the propulsion model by changing the rotating angle velocity. The force acting on the wing depended heavily on the directions of the thrust and drag and the thrust and drag coefficients largely fluctuated with the change in the rotating angles. The average thrust increased as the rotating angle velocity increased. The maximum propulsive efficiency was 27.9% at a calculated angle velocity. The flow field of this rotating type propulsion mechanism is unsteady and very complex because the wing rotates and moves unsteadily in the channel. However, using the advanced vortex method, it could be calculated accurately.     

A modularized framework for solving an economic–environmental power generation mix problem

This paper presents a modularized simulation modelling framework for evaluating the impacts on economic cost and CO₂ emissions resulting from the introduction of a solid oxide fuel cell (SOFC) system into the existing mix of centralized power generation technologies in Japan. The framework is comprised of three parts: a dual‐objective linear programming model that solves the generation best‐mix problem for the existing power generation technologies; a nonlinear SOFC system model in which the economic cost and CO₂ emissions by the SOFC system can be calculated; and the Queuing Multi‐Objective Optimizer (QMOO), a multi‐objective evolutionary algorithm (MOEA) developed at the EPFL in Switzerland as the overall optimizer of the combined power supply system. Thus, the framework integrates an evolutionary algorithm that is more suitable for handling nonlinearities with a calculus‐based method that is more efficient in solving linear programming problems. Simulation experiments show that the framework is successful in solving the stated problem. Moreover, the three components of the modularized framework can be interconnected through a platform‐independent model integration environment. As a result, the framework is flexible and scalable, and can potentially be modified and/or integrated with other models to study more complex problems. Copyright © 2004 John Wiley & Sons, Ltd.     

Improvement in Oxidation Resistance of Stainless Steel by Molten-Salt Electrodeposition of La

Improvement in the oxidation resistance of SUS304 stainless steel was accomplished by electrodeposition of La in a molten salt. The electrolysis of La was conducted using a potentiostatic-polarization method in an equimolar NaCl–KCl melt containing 3.5 mol. LaF ₃ at 1023 K. Observation of the specimen surface after polarization at –1.8 V (vs. Ag/Ag⁺ (0.1)) for 0.18 ks showed that La particles were uniformly dispersed on the surface. The oxidation resistance of the electrodeposited stainless steel was significantly improved as compared with the untreated stainless steel. The scale formed on the untreated stainless steel after oxidation was thick and consisted of Fe₂O₃ and Fe₃O₄, whereas the scale formed on the elecrodeposited stainless steel was extremely thin, and mainly consisted of Cr₂O₃.     

Deformation behavior of polytetrafluoroethylene films under tensile stress at various temperatures

Deformation behavior of polytetrafluoroethylene (PTFE) films was investigated by thermomechanical analysis (TMA) under various tensile stresses (σ) up to 1.15 MPa in the temperature range from room temperature to 360°C. In the heating process above σ ≈ 0.25 MPa, a contraction of the PTFE film occurs in the melting temperature region. In the cooling process above σ ≈ 0.05 MPa, an elongation occurs in the crystallization temperature region, and above σ ≈ 0.5 MPa, it reaches 20–30% of the original length of the film. The PTFE films in the melt state above σ ≈ 0.5 MPa contract with increasing temperature up to 360°C and elongate with decreasing temperature. For the films that underwent deformation in the TMA, the crystalline orientation and the surface morphology were investigated by wide-angle X-ray diffraction and scanning electron microscopy, respectively. The degree of crystalline orientation in the deformed films increases with increasing σ and approaches a plateau at σ ≈ 0.4 MPa. On the surface of the deformed films, alignment of the bands and deformation of granules, which are formed by heat treatment above the melting point, are observed. © 1994 John Wiley & Sons, Inc.     

Numerical analysis of a weak shock wave propagating in a medium using lattice boltzmann method (LBM)

This study introduced a lattice Boltzmann computational scheme capable of modeling thermo hydrodynamic flows with simpler equilibrium particle distribution function compared with other models. The equilibrium particle distribution function is the local Maxwelian equilibrium function in this model, with all the constants uniquely determined. The characteristics of the proposed model is verified by calculation of the sound speeds, and the shock tube problem. In the lattice Boltzmann method,a thermal fluid or compressible fluid model simulates the reflection of a weak shock wave colliding with a sharp wedge having various angles θ_w. Theoretical results using LBM are satisfactory compared with the experimental result or the TVD.     

Development of “STORK”, a watermelon-harvesting robot

Recently, the production of heavy fruit and vegetables has been decreasing in Japan because strenuous labor is require to harvest them. A robot would allow them to be harvested more easily. We have developed the robot “STORK” to harvest watermelons. STORK has a low mass and a long working range. The position accuracy and repeatability of the manipulator, the required vacuum, and the allowance for position error of the vacuum pad were tested.     

Numerical simulation of sound generation in a mixing layer by the finite difference lattice Boltzmann method

We simulated aerodynamic sound in a two-dimensional mixing layer using the finite difference lattice Boltzmann method (FDLBM). We introduced a finite difference scheme, called the dispersion relation preserving (DRP) scheme, into the FDLBM to carry out an accurate simulation of aerodynamic problems. The scheme is designed such that the dispersion relation of the finite difference scheme is the same as that of the original partial differential equations and is useful for acoustic simulations. A turbulent flow field was simulated by large-eddy simulation (LES), using the Smagorinsky model, and the results were compared with those from a direct simulation based on the Navier–Stokes equations to confirm the usefulness of this method. The combination of the FDLBM and the DRP scheme was shown to be very effective for direct simulations of aerodynamic sound.     

Design and control of a heavy material handling manipulator for agricultural robots

In this paper, we propose a manipulation system for agricultural robots that handle heavy materials. The structural systems of a mobile platform and a manipulator are selected and designed after proposing new knowledge about agricultural robots. Also, the control systems for these structural systems are designed in the presence of parametric perturbation and uncertainty while avoiding conservative results. The validity of both the structural and control systems is confirmed by conducting watermelon harvesting experiments in an open field. Furthermore, an explicit design procedure is confirmed for both the structural and control systems and three key design tools are clarified.