Identification of task model using piecewise affine systems with variable switching points and its application

This paper considers a human‐operated task model based on identification techniques using switched systems expressed by mixed logical dynamical systems. In the system, each subsystem is expressed by a piecewise affine system. For a model to be identified, it is not easy to determine a number of subsystems in advance. In this paper, we propose a simultaneous identification technique which takes into account both a number of subsystems and parameters, so that a piecewise affine model of a human operation can be obtained. In addition, the obtained model is applied to automation. The effectiveness of the proposed method is illustrated by simulations and experiments. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(1): 46–54, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21079     

Direct observation of internal structure in spray-dried yttria-doped zirconia granule

Spray-dried yttria-doped zirconia granules were made transparent by immersion in a liquid and the internal structure was characterized using an optical microscope. This unique technique was found to be applicable for this system by using an immersion liquid with appropriate refractive index, and it enabled observation of the internal structure to be made over the entire volume of granules, in clear contrast to conventional SEM observation. Distinct features, which were considered to be agglomerates, were found in the granules. This was supported by SEM observation.     

Numerical Modeling of an Earthquake-Induced Landslide Considering the Strain-Softening Characteristics at the Bedding Plane

The damage caused by an earthquake-induced landslide can generally be classified as either a limited deformation or a catastrophic failure. From an engineering point of view, the latter can be much more dangerous because the sliding mass may continue moving until it collides with another object. If a catastrophic failure occurs near a river, the debris may block the river, causing serious damage to the adjacent area. Therefore, examination of the mechanism of such catastrophic slope failures is important with respect to the mitigation of earthquake disasters in mountainous districts, although numerical modeling of such phenomena is rather difficult. In the present study, a new numerical model is developed to simulate an earthquake-induced catastrophic landslide that occured at a typical dip slope, namely, the Yokowatashi Landslide in Japan. In this case, the upper part of the bedrock on the planer tectonic dip surface slid more than 70 m. Only shear-strength degradation at the bedding plane could cause such a long-distance traveling failure. To investigate the strain-softening characteristics of the materials that filled the bedding plane, a series of laboratory tests involving undisturbed block samples was performed. The measured stress-displacement relationships under cyclic loading were numerically modeled as a newly proposed elasto-plastic constitutive model to be used in numerical simulations of landslide, based on the dynamic finite element method. The observed phenomena were appropriately simulated by the proposed method. The mechanism of catastrophic failure is discussed in detail in this paper in order to clarify the relationships between the strain-softening characteristics and the global slope stability. Our newly proposed method to evaluate the possibility of a catastrophic failure was applied to the landslide, and the moment when the slope becomes unstable was able to be predicted. The results confirm that the proposed method can predict the catastrophic failure of a slope.     

Ethanol Conversion on MCM-41 and FSM-16, and on Ni-Doped MCM-41 and FSM-16 Prepared without Hydrothermal Conditions

MCM-41 and FSM-16 were both prepared using no hydrothermal conditions, and nickel was doped into these catalysts (Ni-MCM-41 and Ni-FSM-16) using a template ion exchange method. FSM-16 and Ni-FSM-16 had greater catalytic activity for the conversion of ethanol than MCM-41 and Ni-MCM-41, indicating that FSM-16 has potential as a catalyst for the conversion of ethanol to propylene.     

Rapid erasing of wettability patterns based on TiO2-PDMS composite films

TiO₂-polydimethylsiloxane (TiO₂-PDMS) composite films are prepared using the sol–gel method from a Ti(OBu)₄–benzoylacetone solution containing PDMS. The prepared films are cured by irradiation with ultraviolet (UV) light. Structural changes in the films after UV irradiation are confirmed by UV–vis absorption experiments, which show that an absorption band characteristic of the benzoylacetonate chelate rings disappears. This finding is ascribed to structural changes associated with the dissociation of the chelate rings. The IR spectra of the thin films exhibit a broad absorption band after UV irradiation, indicating that a Ti–O–Ti network forms in the thin film. Contact angles are measured for the TiO₂-PDMS thin films, showing wettability conversion from hydrophobic to superhydrophilic states by irradiation with oxygen plasma for 1 s. This phenomenon is explained by XPS experiments which reveal that the number of carbon atoms decreases, whereas the number of oxygen atoms increases on the surface of the TiO₂-PDMS composite films. Finally, hydrophobic–superhydrophilic patterns are fabricated based on a patterned TiO₂-PDMS composite film. The film displays a rapid change to superhydrophilicity over the whole film surface upon plasma irradiation for 1 s, which means that the wettability patterns are rapidly erasable.     

On the high-temperature corrosion of Fe-Cr alloys in sulfur vapor

The mechanism of sulfidation of Fe-Cr alloys ranging from 8 to 97 wt.% chromium was determined from studies of scale structures, surface morphologies of scale, and reaction kinetics. Although the kinetics of sulfidation were quite similar to those previously determined by Mrowec et al., the structures in the present work were different, being triplex in nature. The growth mechanism of each layer was determined, and the overall sulfidation behavior was compared to the oxidation behavior. Many similarities between the two corrosion processes were observed.     

Drag reduction of aqueous suspensions of fine solid matter in pipe flows

It is well known that drag reduction properties of polymer solutions in pipe flows are classified into two categories, based on the relationship between the friction factor and the Reynolds number. The degree of drag reduction either increases with an increase in the Reynolds number or is independent of the Reynolds number. In the latter case, the drag reduction behavior is referred to as type B behavior. In this study, the pressure losses of aqueous suspensions of biofibers and graphene oxide flat particles in pipe flows were measured to clarify the effect of the shape of suspended fine solid matter on the friction factor. The experimental results demonstrated that the behavior of the friction factor corresponded with the type B behavior of drag reduction. The mean velocity profile in the range of the turbulent flow was also estimated from the friction factor data.     

Preparation and characterization of membranes with positively charged main chain from polyethylenimine

A membrane, which has positively charged groups in the polymer main chain, was prepared from polyethylenimine by crosslinking and successive alkylation. Dibromoalkane was used as a crosslinking agent. The crosslinked membrane was alkylated using methyl iodide under several conditions. Elemental and ICP emission analyses were introduced to measure the rates of alkylation and quaternization. From the membrane potential measurement, the effective charge density was estimated. The highest value was about 1.0 M, which was obtained by a prolonged alkylation time. This value was larger than that of some commercial ion exchange membranes. The effective charge density, which was obtained by the last alkylation procedure, was 10 times larger than that of the former one, though the rate of quaternizing increased by less than a factor of two. This implies that the activity constant in the membrane increased when the charge density is increased. © 1993 John Wiley & Sons, Inc.