Preparation of Aluminum Oxynitride and Nitride Spherical Powders Via Flame Synthesis Assisted by DC Arc Plasma

Spherical powders of aluminum oxynitride/nitride are directly prepared by flame synthesis in which oxygen serves as an indispensable reactant. Nonoxide powders are commonly nonspherical, and the particle sizes of these powders are less than submicrometers. The major limiting factors for the synthesis are the free energy, reaction temperature, and reaction rate. The innovative issue related to this flame technology that is assisted by plasma is the ambivalence of the reducing gas atmosphere over 1500 K. The chemical equilibrium calculated indicates that the plasma heating compensates for the lack of reaction temperature under a low-oxygen condition. This burner realizes a high-speed reaction with the help of the reactive species in the arcs.     

Performance of Micro-fabricated Magnetic Calorimeters Arrays for X-Ray Spectroscopy

We have been developing array technology for fabricating magnetic calorimeters for X-ray astronomy. The magnetization change in each pixel of the paramagnetic sensor material due to the heat input of an absorbed X-ray is sensed by a meander shaped coil. With this geometry it is possible to obtain excellent energy sensitivity, low magnetic cross-talk and large format arrays fabricated on wafers that are separate from the SQUID read-out. A magnetic bias field for each pixel is generated by the use of a persistent current that is stored. We report on the results from our prototype arrays, which are coupled to low noise DC-SQUIDs. The first test results are presented and the sensitivity is compared with calculations.     

Photocatalytic activities of CdS crystallites embedded in TiO2 gel as a stable semiconducting matrix

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Computational fluid dynamics simulation and statistical procedure for estimating wide-area distributions of airborne sea salt considering local ground conditions

Steel corrosion under atmospheric conditions is a critical issue in the maintenance of structures such as electric transmission towers and bridges during their long-term operation, which are generally located at many places over a wide area. Since a major factor causing corrosion is airborne salt particles coming from the sea, wide-area distributions of the long-term cumulative amount of sea salt deposited on surfaces are needed. Moreover, since the amount of airborne sea salt varies locally with the topography, it is also important to consider the effects of topography. In this paper, a method combining a computational fluid dynamics model and a statistical procedure is proposed to efficiently estimate wide-area distributions of the cumulative amount of airborne sea salt by considering the local topography. The predicted amount of airborne sea salt decreases with increasing distance from the coast and varies with the topography and the offshore wind. A comparison between predicted and observed amounts revealed that: (1) this method appropriately estimates topographical effects on sea-salt transport and enables the estimation of deposited sea salt on structure surfaces, and (2) consideration of the trapping efficiency of sea-salt particles on structure surfaces improves the prediction accuracy.     

Elevated plasma bile acids in hypergalactosaemic neonates: a diagnostic clue to portosystemic shunts

To determine whether plasma levels of total bile acids may provide a useful index for hypergalactosaemia due to porto-systemic shunts, these levels were determined in hypergalactosaemic neonates. Increased levels were found in all cases with portohepatic venous or portocaval shunts. The levels of both total bile acids and galactose were normalized when the shunts disappeared on the echograms. Both bile acids and galactose are almost completely absorbed by the liver via the first portal blood passage. Portosystemic shunts contribute to elevated levels of bile acids and galactose. CONCLUSION: Increased plasma levels of total bile acids serve as a diagnostic clue to the presence of portosystemic shunts in neonates with hypergalactosaemia.     

A control method for the matrix converter based on virtual AC/DC/AC conversion using carrier comparison method

This paper proposes a novel control method based on the virtual AC/DC/AC conversion for the matrix converter. The virtual AC/DC/AC conversion method is a very simple strategy to control the input current and the output voltage for the matrix converter. There are two new topics proposed in this paper. First, this paper proposes the minimum switching loss modulation on the virtual rectifier. In our proposed modulation, only two arms switching in the virtual rectifier using DC link current control by the virtual inverter can obtain clean sinusoidal input current. Second, a novel lean controlled carrier modulation on the virtual inverter is proposed. The leans of the triangle carrier are controlled by the duty ratio of the rectifier side pulse. The lean controlled carrier reduces harmonic distortion of the input current by avoiding interference between the rectifier control and the inverter control. These new proposals are confirmed by simulation and experimental results. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(3): 65–73, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20144