Optimal frequency tracking method for phase‐shift PWM inverter

This paper proposes a new resonant frequency tracking control method for full‐bridge‐type high‐frequency inverters. Whereas the ordinary phase‐locked loop (PLL) based frequency control method uses a current sensor and a voltage sensor, the proposed technique can achieve the same purpose with a single current sensor. In high‐frequency power supply systems using a PLL, it is impossible to perform power control with an inverter. Therefore, an active converter must be used for power control, and the system grows larger. On the other hand, high‐frequency inverters using the proposed control system simultaneously enable power control and achieve the same resonant frequency tracking as a PLL, and thus high‐frequency power supply systems become extremely simple. This paper explains in detail the principle underlying the control method, and presents an example of a circuit to realize it. The theory is backed up by using a prototype high‐frequency power supply system which actually employs the proposed control system, thereby demonstrating its practical utility in industry. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Software Defined Radio Technology for Highly Reliable Wireless Communications

This paper introduces the concept of highly dependable wireless communications for wireless robotics based on software defined radio (SDR) technologies. The features and advantages of SDR technologies are initially explained, whereupon the research and development activities of KDDI R&D Laboratories are presented. Advanced applications of SDR for telerobotic control, which require highly reliable wireless communications and for multi-mode wireless sensor networks are proposed as potential markets for wireless robotics and machine to machine communication. Finally, the current status and research issues of SDR are summarized and this paper is concluded.     

Benzopyrazine-fused tetracene derivatives: Thin-film formation at the crystalline mesophase for solution-processed hole transporting devices

Benzopyrazine-fused tetracene (TBPy) and its disulfide (TBPyS) bearing alkoxy groups (OCH₃, OC₈H₁₇) were designed and synthesized to obtain π-expanded tetracene derivatives. These derivatives are featured with long-wavelength light absorption property (λ_onset: up to 820 nm), photooxidative stability (half-lives (τ_1/2): 11 times longer than tetracene), and solubility for solution process. The methoxy compounds (TBPy-C1 and TBPyS-C1) were used for single-crystal X-ray crystallographic analysis and single-crystal organic field-effect transistor (OFET) devices showing relationship between packing structures and hole mobilities. The octyloxy compounds (TBPy-C8 and TBPyS-C8) were investigated on solution-processed thin-film formation and hole transport property in thin-film OFET devices. Crystalline mesophase of TBPy-C8 and TBPyS-C8 was characterized by differential scanning calorimetry analysis showing endothermic peaks at 98 and 198 °C on its second heating process and exothermic peaks at 177 and 76 °C on its second cooling process for TBPyS-C8, and played crucial roles in thin-films formation. Hole mobility of 1.7 × 10^?2 cm²/V s (with V_th = ?30 V and I_ON/I_OFF = 10⁴) was obtained for the thin-film OFET device of TBPyS-C8.     

Fabrication of novel composites of ZnO-nanoparticles and magadiite

Novel composites of ZnO-nanoparticles and magadiite were successfully prepared by a simple ion-exchange technique in an aqueous suspension of magadiite (Na₂Si₁₄O₂₉·nH₂O) and Zn(NO₃)₂. The TEM and STEM measurements showed that the composites have a structure in which ZnO-nanoparticles with relatively uniform particle sizes are well dispersed within the interlaminar spaces of the magadiite matrix. The particle sizes of the ZnO-nanoparticles were found to depend on the heat-treatment temperature; the average particle sizes are ~ 2.6, ~ 2.8, ~ 4.4 and ~ 4.6 nm, respectively, for the temperatures of 40, 180, 300 and 600 °C. It was also found that the ZnO nanoparticles crystallize and form a single-crystalline particle when the temperature exceeds ~ 300 °C.     

The Effect of Ethanol on Disassembly of Amyloid-β1-42 Pentamer Revealed by Atomic Force Microscopy and Gel Electrophoresis

The most common type of dementia, Alzheimer’s disease, is associated with senile plaques formed by the filamentous aggregation of hydrophobic amyloid-β (Aβ) in the brains of patients. Small oligomeric assemblies also occur and drugs and chemical compounds that can interact with such assemblies have attracted much attention. However, these compounds need to be solubilized in appropriate solvents, such as ethanol, which may also destabilize their protein structures. As the impact of ethanol on oligomeric Aβ assembly is unknown, we investigated the effect of various concentrations of ethanol (0 to 7.2 M) on Aβ pentameric assemblies (Aβp) by combining blue native-PAGE (BN-PAGE) and ambient air atomic force microscopy (AFM). This approach was proven to be very convenient and reliable for the quantitative analysis of Aβ assembly. The Gaussian analysis of the height histogram obtained from the AFM images was correlated with band intensity on BN-PAGE for the quantitative estimation of Aβp. Our observations indicated up to 1.4 M (8.3%) of added ethanol can be used as a solvent/vehicle without quantitatively affecting Aβ pentamer stability. Higher concentration induced significant destabilization of Aβp and eventually resulted in the complete disassembly of Aβp.     

Thermodynamics of iron oxide in Fe x O-dilute CaO+Al2O3+Fe x O fluxes at 1873 K

The distribution of iron between Fe _x O-dilute CaO+Al₂O₃+Fe _x O fluxes and Pt+Fe alloys, as well as the redox equilibrium of iron ions in these fluxes, was experimentally investigated in pressure-controlled CO₂/CO gas at 1873 K. Total iron content in flux (pct Fe ^T ) and the ratio of (pct Fe²⁺) to (pct Fe ^T ) in fluxes with constant can be related to the activity of iron, α _Fe, and the partial pressure of oxygen, a _Fe, using the following equation:

Probing the Nature and the Structure of Pores in Silica Xerogels by Water Sorption: The Tetramethyl Orthosilicate-Hydrogen Chloride/Fluoride System

A series of silica xerogels were synthesized in a closed system by hydrolyzing tetramethyl orthosilicate (TMOS) with various concentrations of hydrochloric acid solution but without the addition of alcohol. The molar ratio of H₂O to TMOS was fixed at 4.96. The gels were characterized by water and nitrogen sorption measurements. The gelation time peaked at 50 to 80 h with 5 × 10⁻² to 10⁻¹ M HCl, apparently a consequence of the isoelectric point of silica. Surface area, pore size, and sorption capacity were, however, at a minimum for samples prepared with 5 × 10⁻² to 10⁻¹ M HCl. The BET c constant and hence the net heats of sorption were at a maximum for these samples. Although water sorption of all the samples prepared with HCl exhibited moderate Type I isotherms, the concavity of the isotherms to the P/P ₀ axis increased with increasing concentrations of HCl up to 10⁻¹ M in accordance with the decreased pore size and increased heat of sorption. Addition of F⁻ ions (HF or NaF) in the presence of 10⁻¹ M HCl steadily decreased the gelation time. Addition of F⁻ in the absence of HCl, however, caused rapid gelation and an increase in pore size, nitrogen BET surface area, and hydrophobicity. Consequently, the shape of water isotherms gradually converted to Type IV and/or Type V. Adsorption and desorption measurements on differently activated gels exhibited various types of hystereses as a result of development of hydrophobie sites at as low as 200°C, inelastic distortion induced by adsorption, and chemical reaction and aging of gels when exposed to water vapor.     

Reliability Considerations for a 2-Unit Redundant System with Erlang-Failure and General Repair Distributions

This paper considers the case of a 2-identical-unit redundant system with Erlang-failure and general repair distributions. Two cases are considered: 1) the failure of each unit is independent of the other; 2) when one unit fails, the failure distribution in the other unit changes. The Laplace transforms of the distribution of time to system failure and the explicit formula for the mean time to system failure are derived.     

Characterization of gangliosides of porcine erythrocyte membranes: Occurrence of ganglioside GD3 as major ganglioside

Four major ganglioside species were isolated from porcine erythrocyte membranes by DEAE-Sephadex and Iatrobeads column chromatography. Treatment of the lipids with graded neuraminidase and β-galactosidase, gas chromatographic analysis of their carboyhydrates, sphingosine bases and molecular species of sialic acid revealed that the structure of these gangliosides were G_M3(NeuAc), G_M3(NeuGc), G_D3(NeuAc) and G_D3(NeuGc), each of which was 16±2 μg, 304±42 μg, 30±3 μg and 240±26 μg, respectively, per gram of the dry erythrocyte stroma. The amount of G_M3 and G_D3 accounted for more than 95% of total gangliosides of the erythrocytes. Porcine erythrocytes may provide a good source for large scale preparation of ganglioside G_D3 which recently was identified as a human melanoma-associated antigen. Gangliosides are named according to Svennerholm (1) and the recommendation of the IUPAC-IUB Commission on Biochemical Nomenclature (2).     

Water resources development and management

This paper examines the maximum available water resources in Japan, nationally and by region, and describes the present balance of demand and supply. The major existing mechanisms of water development and control ‐ dam construction and pricing structures ‐ are reviewed. Finally a classification of various stages of water resource and irrigation development is presented. These stages are identified as reliance on natural river discharge, the construction of reservoirs, restrictions on water use, inter‐basin planning, and the construction of reservoirs for perennial water regulation.