Preparation of polymer brush-type cellulose β-ketoesters using LiCl/1,3-dimethyl-2-imidazolidinone as a solvent

Cellulose β-ketoesters with branched alkenyl chains were prepared using cis-9-octadecenyl ketene dimer (OKD) and LiCl/1,3-dimethyl-2-imidazolidinone (DMI) as the esterifying reagent and cellulose solvent, respectively. Relationships between degree of substitution (DS) of the cellulose/OKD β-ketoesters and reaction conditions were studied in detail. The results showed that DS values of the products were controllable up to 2.1 by selecting the reaction conditions. Solution- and solid-state ¹³C-NMR analyses revealed that cellulose backbones of the cellulose/OKD β-ketoesters with DS 2.1 behave like solid in chloroform owing to strong restriction on movement of cellulose chains by the long and branched alkenyl substituents introduced. Size-exclusion chromatographic analysis showed that little depolymerization occurred on cellulose during β-ketoesterification at room temperature, and that molecules of the cellulose/OKD β-ketoesters with DS 2.1 had semi rigid-rod conformation in tetrahydrofuran. Thus, cellulose β-ketoesters with densely substituents like polymer brushes or comb-shaped polymers were prepared in this study.     

Ultrasonic reflectivity computed tomography with small number of transmitter/receiver transducers for carotid diagnosis

We developed an ultrasound reflectivity computed tomography (CT) system with only a small number of transmitter/receiver transducers for carotid diagnosis. To this end, a ring array system with eight element transducers was fabricated with center frequency 10 MHz. The present CT technique assures the image with high resolution on the order of 0.1 mm over the entire imaging region. In addition, the reduction of the number of transducer element enables fast data acquisition and lower cost hardware system. With appropriate combinations of the dual and/or separate transmitter and receiver pairs, 21 backscattering projection data were observed. To comply with the ill‐posed inverse problem due to the lack of angular view data, the conjugate gradient method was applied for the solution of the matrix observation equation. Both experiment and simulation examinations were made using the cylindrical shell object as a carotid phantom. As a result, it is demonstrated that the image with greater resolution compared with the conventional B‐mode method can be obtained by using only eight element transducers. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(4): 58–66, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20301     

Photocatalytic inactivation and removal of algae with TiO<Subscript>2</Subscript>-coated materials

The capabilities of TiO₂-coated materials for the inactivation and removal of algae were investigated. As supports for TiO₂, non-woven fabric and Ni foam were chosen. To evaluate the ability of noble metal cocatalyst additions to facilitate the photocatalytic algal inhibition of TiO₂-coated materials, Pd nanoparticles were deposited on non-woven fabric-supported TiO₂ by photoelectrochemical deposition. The fabric-supported Pd/TiO₂ showed higher inhibition activity for algal growth compared to the fabric-supported TiO₂ without Pd. In addition, Ni foam-supported TiO₂ also showed high inhibition activity, both in laboratory-scale tests and open-air tests. Therefore, TiO₂-coated materials with suitable coating methods such as the use of cocatalysts or large surface area can substantially inhibit algal growth. The ability of the TiO₂-coated materials to inhibit algae correlated well with their activity for the photocatalytic decolorization of methylene blue, suggesting a nonspecific mechanism in the breakdown of cellular structures.     

Adaptive Control of Partially Known Systems and Application To Active Suspensions

In this paper, an adaptive control method is proposed for systems whose structures can be divided into a known part and an unknown part. A non‐adaptive control design, such as H∞ control design can be introduced into the known part of the system, and adaptive control can cope with the unknown part to realize the property designed by non‐adaptive control. This is achieved by means of backstepping. This method is applied to the control design of an active suspension system for a railway vehicle, which is divided into two parts: a main car body part and an actuator part. Some simulation results of the control system designed using H∞ control for the body part and adaptive control for the actuator part are provided.     

Microstructure and Mechanical Properties of ZrO2(2Y)-Toughened Al2O3 Ceramics Fabricated by Spark Plasma Sintering

Spark plasma sintering (SPS) has been performed for 5 min at 1500°C and 30 MPa using submicrometer-sized Al₂O₃/ZrO₂(2Y) composite powders in the Al₂O₃-rich region. Dense ZrO₂-toughened Al₂O₃ (ZTA) ceramics show excellent mechanical strength; the strength of 1620 MPa is achieved in the ZTA with 50 mol% ZrO₂. The grain size of Al₂O₃ in ZTA decreases from 1.5 to 0.6 m with increased ZrO₂ content. Almost all the ZrO₂ grains (0.3 m) are located in the boundaries of the Al₂O₃ grains. Mechanical properties are discussed, with an emphasis on the relation between t-/m-ZrO₂ ratios and microstructures of ZTA.     

An Approach to Flux Control of Induction Motors Operated with Variable-Frequency Power Supply

A new speed control system for induction motors has been developed which is capable of controlling with quick field weakening and superior response and stability. This method is to control the stator current as a vector quantity on the basis of slip frequency control. More specifically, it is designed to calculate the commanded stator current of the induction motor by corresponding to flux and torque commands on the basis of motor constants and use the calculated commands to control the stator current.     

Experimental fluid dynamics of particles in a dielectric barrier discharge plasma-enhanced spouted bed

This study proposed the fluidized particles with dielectric barrier discharge (DBD) plasma in a slot-rectangular divergent-base spouted bed and focused on the dynamics of solid particles with the plasma irradiation. Two bed materials (Polypropylene (PP) particles and Polyamide (PA) particles) with same diameter (3 mm) were fluidized in this study. Fluidization parameters included gas velocity (7.4–14.9 m/s), particle amount (100–500), and plasma parameter (apply voltage, 0 and 7 kV) as the applied voltage were investigated here. Particle velocity profiles were analyzed through the methods of particle image velocimetry (PIV) and particle tracking velocimetry (PTV). Results show that the particle velocity was increased with the plasma irradiation, mainly by the enhancement in the vertical direction. The location of the highest particle velocity area related to the fluidization behavior of particles. With the increase of superficial gas velocity, the location of the highest particle velocity area raised along the central line but not reached the top of the solid bed. While the electron temperature of Ar plasma decreased with the addition of particles. Two electric fields (external electric field and surface charge electric field) presenting in the system were assumed to give the reason for the changes of the particle fluid dynamics.     

Room-temperature synthesis of γ-Ga2O3 nanoparticles from gallium metal via ultrasound irradiation

In this study, gallium oxide (Ga₂O₃) nanoparticles were synthesized by sonochemical techniques at room temperature. We investigate the ultrasound irradiation conditions and the solvent type to synthesize Ga₂O₃ nanoparticles. γ-Ga₂O₃ nanoparticles were synthesized by irradiating gallium metal with ultrasound in hydrazine monohydrate solvent. The irradiation of hydrazine with ultasound suppresses the generation of ·OH, and GaOOH was not formed, and gallium metal directly oxidized. When the synthesized γ-Ga₂O₃ nanoparticles were heat-treated, a transition to β-Ga₂O₃ was observed. The heat-treated Ga₂O₃ nanoparticles showed excellent photocatalytic activity for the decomposition of RhB under UV irradiation.     

The detailed analysis of the vinylidene structure of metallocene-catalyzed polypropylene

The vinylidene structures in polypropylenes produced by ethylenebis(indenyl)zirconiumdichloride (En(Ind)₂ZrCl₂), 1, and isopropyl(cyclopentadienyl)(fluorenyl)zirconiumdichloride (iPr(Cp)(Flu)ZrCl₂), 2, were analyzed by ¹H NMR. The vinylidene group adjacent to the chain end was clearly distinguished from other internal vinylidene structures for the first time using 1,2-dichlorobenzene as solvent. The polypropylene produced by 2 had much internal vinylidene groups compared with one by 1.     

Three-way two-dimensional alternating finite automata with rotated inputs

The authors have introduced an automaton on a two-dimensional tape, which decides acceptance or rejection of an input tape by scanning the tape from various sides by three-way (deterministic and nondeterministic) finite automata, and have investigated the accepting powers. This paper continues the investigation of this type of automata, which consists of four three-way two-dimensional alternating finite automata (tr2-afa’s). We first investigate a relationship between the accepting powers of ∨-type automata (obtained by combining tr2-afa’s in ‘or’ fashion) and ∧-type automata (obtained by combining tr2-afa’s in ‘and’ fashion), and show that they are incomparable. Then, we investigate a hierarchy of the accepting powers based on the number of tr2-afa’s combined. Finally, we briefly describe a relationship between the accepting powers of automata obtained by combining three-way two-dimensional nondeterministic and alternating finite automata.