Monolithic four-channel photodiode/amplifier receiver array integrated on a GaAs substrate

A four-channel optoelectronic integrated receiver array operating at the wavelength near 850 nm has been fabricated on a single GaAs substrate by using metal-semiconductor-metal (MSM) photodiodes (PD's) and metal-semiconductor field-effect transistors (MESFET's). The largest integration scale for a monolithic receiver and uniform characteristics among circuit channels have been achieved due to the structural simplicity and the process-compatibility of this array. Also, an extremely small capacitance of MSM-PD, 0.10 pF, has lead us to obtain a high-speed operation up to a bit rate of 1.5 Gbit/s, NRZ, and a low noise characteristic exhibiting an equivalent input noise current as small as 5 pA/Hz^1/2. These results have indicated the suitability of MSM-PD/MESFET's circuits for large-scale multichannel optoelectronic integration of receivers.     

Solving constraint-satisfaction problems by a genetic algorithm adopting viral infection

Several approximate algorithms have been reported to solve large constraint-satisfaction problems (CSPs) within a practical time. While those papers discuss techniques to escape from local optima, this paper describes a method that actively performs global searches. The present method improves the rate of search of genetic algorithms by using viral infection instead of mutation. Partial solutions of a CSP are considered to be viruses, and a population of viruses is created, as well as a population of candidate solutions. The search for a solution is conducted by crossover and infection. Infection substitutes the gene of a virus for the locus decided by the virus. Experimental results using randomly generated CSPs prove that the proposed method is faster that usual genetic algorithms at finding a solution when the constraint density of a CSP is low.     

220,000‐r/min, 2‐kW PM motor drive for turbocharger

This paper describes an ultrahigh‐speed permanent‐magnet synchronous motor drive, which is embedded in a turbocharger of an internal‐combustion engine. The electrical drive makes it possible to enhance output power of the turbocharger in a motoring mode and to retrieve combustion energy from exhaust gas in a regenerating mode. Computer simulations and experimental tests are conducted to examine various operation characteristics of a prototype. The experimental data demonstrate 220,000‐r/min operation at 2.2‐kW inverter output power, in good agreement with the simulation results and proving the feasibility of the proposed system. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(3): 31–40, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20408     

A comparison of the hydrolysis of sweet potato starch with β-amylase and infrared radiation allows prediction of reducing sugar production

The apparent reaction rate constants (k) of the reaction that generates reducing sugar (presented as mg maltose equivalents) from raw sweet potato starch by using β‐amylase were determined by varying enzyme concentration, starch concentration and pH. The Arrhenius plot of the k‐value reached a peak at approximately 86 °C; the activation energy and frequency factor were also determined. Moreover, the amount of reducing sugar produced in sweet potato heated by infrared irradiation was estimated by using the values of k and the kinetic parameters. The calculated amounts of reducing sugar produced generally agreed with the experimental values. These results indicate that the amount of reducing sugar produced in heat‐treated sweet potato can be predicted by the methodology described in this study.     

Analysis of annotations on documents for recycling of information

In order to make collaborative business activities fruitful, it is essential to know characteristics of organizations and persons in more details and to gather information relevant to the activities. In this paper, we describe a notion of “information recycling” that actualizes these requirements by analyzing documents. The key of recycling information is to utilize annotations on documents as clues for generating user profiles and for weighting contents in the context of the activities. We also propose a method of extracting annotations on paper documents just by pressing one button with the help of techniques of camera‐based document image analysis. Experimental results demonstrate that it is fundamentally capable of acquiring annotations on paper documents on the condition that their electronic versions without annotations are available for the processing. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(2): 60–68, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20516     

Design methodology for a braided cylinder

In this study, the design methodology for a braided cylinder was presented. The concept of an analytical model which involved both micro model and macro model was proposed. The analytical method was applied to estimate the rigidity and elastic limit of a braided cylinder subjected to bending and torsional load independently and as combined load. Using the analysis method, the design of a braided cylinder would be carried out in consideration of the factors that decide the mechanical properties of braided cylinder. This method has the possibility to be useful for structural design of braided composites and can be included as a unit in CAE systems for braided composites.     

A new superleak to remove He for UCN experiments

The production of superleaks to remove He³ in helium for UCN experiments is described. Using one of these superleaks, He³/He⁴ ratio was found to be less than 3 × 10⁻⁹ as indicated by the UCN storage lifetime.     

Advanced fabrication technologies of integrated-type structure for a-Si solar cells

This paper proposes a new advanced fabrication technology for a low-cost integrated-type a-Si solar cell. Integrated-type cells provide many advantages and have been industrialized with a laser patterning method. However, a higher throughput and more efficient patterning method was required for applying a-Si solar cells to a power generating system. Plasma CVM (Chemical Vaporization Machining) was first applied to advanced patterning because of its advantages of high speed and selectivity. In this method, a plasma generated under high pressure localizes near the wire electrode and concentrates reactive radicals. As a result, we achieved an etching rate of more than 1 μm/s and selective patterning of a 200 μm-wide a-Si layer in 1 s multiline patterning was also developed for large-area modules.