Frequency response function of magnetic bearings using high-temperature superconductor

A high-temperature superconductor YBa₂Cu₃O_7-x with strong pinning force has allowed stable magnetic suspension with no control to be developed. Two types of superconducting magnetic bearings (SMB) using YBCO and permanent magnet were assembled. The two types are radial and axial. The dynamic stiffness of each SMB as it was cooled down under a magnetic field by liquid nitrogen was measured both radially and axially. As a result, it was found that the spring constants of these SMBs were almost as large as a practically desirable value; however, their damping coefficients were lower than the practical level. These findings are useful as one of the data bases for development of an optimum SMB design to support the weight of rotors in an axial direction.     

An optically clocked transistor array with dual serial-to-parallel and parallel-to-serial conversion capability for optical label swapping

We propose an optically clocked transistor array optoelectronic integrated circuit (OEIC) for both serial-to-parallel and parallel-to-serial conversion (demux/mux), enabling an interface between high-speed asynchronous burst optical labels and CMOS circuitry for optical label swapping. Dual functionality of the OEIC reduces size, power, and cost of the optical label swapper. The capability for greater than 20-Gb/s conversion operation is demonstrated.     

Measurement of gain saturation coefficients in strained-layermultiple quantum-well distributed feedback lasers

Gain saturation coefficients of unstrained- and strained-layer multiple-quantum-well lasers were measured experimentally. These coefficients were higher in lasers that had compressive strain in their active-layer wells: 2.45×10^-17 cm³ with unstrained wells and 12.6×10^-17 cm³ with strained wells. The higher gain saturation coefficient in lasers with strained active-layer wells is related to their higher linear TE mode gain coefficient. The linearity factor (K factor) between a laser's damping constant and the square of the laser's resonant frequency decreased slightly with the introduction of the strain in the laser's active layer wells. This factor, however, took the value of about 0.2×10^-9 s for each of these lasers     

A method of single-phase PWM for an independent power supply in photovoltaic power generation systems

We propose a method of single-phase PWM for an independent power supply in photovoltaic power generation systems. This new PWM is derived by comparing levels of signal waves with one of carrier waves which have bipolar swing different from unipolar swing in the conventional PWM. In this PWM, we can use a battery with lower voltage in combination with the photovoltaic power generation; fundamental level of output voltage is raised by about 11%, though poor in quality of waveforms. © 1998 Scripta Technica. Electr Eng Jpn, 122(4): 55–62, 1998     

Fabrication of nanograined silicon by high-pressure torsion

This paper describes fabrication of Si nanograins through allotropic phase transformation by concurrent application of high pressure and intense straining using high-pressure torsion (HPT). Single-crystalline Si(100) wafers were processed by HPT under a pressure of 24 GPa at room temperature. X-ray diffraction and Raman analysis revealed that the HPT-processed samples were composed of metastable Si-III and Si-XII phases and amorphous phases in addition to the original diamond-cubic Si-I phase. It was found that nanograins formed because the Si-I diamond phase had transformed to high-pressure phases (Si-II, Si-XI, and Si-V) having metallic nature, and it then became easier to generate a high density of dislocations to form grain boundaries. The high-pressure phases were further transformed to the Si-XII and Si-III phases via the Si-II phase upon unloading and they existed as metastable phases at ambient pressure. Subsequent annealing at 873 K gave rise to reverse transformation to Si-I but with nanograin sizes. Although no appreciable photoluminescence (PL) peak was observed from the HPT-processed sample, a broad PL peak centered around 600 nm was detected from the annealed sample due to quantum confinement in the Si-I nanograins.     

Quantitative risk assessment of noroviruses in drinking water based on qualitative data in Japan

Noroviruses are one of the major causes of viral gastroenteritis in Japan. A quantitative risk assessment was conducted to evaluate the health risk caused by this virus in drinking water. A Monte Carlo analysis was used to calculate both the probability of infection and the disease burden using disability-adjusted life years (DALYs). The concentration of noroviruses in tap water was estimated based on qualitative data and a most probable number (MPN) method with an assumed Poisson lognormal distribution. This numerical method was evaluated using two sets of available count data of Cryptosporidium: that collected from a river and that found in tap water in Japan. The dose-response relationships for noroviruses were estimated using assumed ID50 (10 or 100). The annual risk was higher than the US-EPA acceptable level (10(-4) [infection/ person-year]) but around the WHO level (10(-6) [DALYs/ person-year]). As suggested by others, since microbial concentrations are generally lognormally distributed, the arithmetic mean was directly related to the annual risk, suggesting that the arithmetic mean is more useful in representing the degree of microbial contamination than the geometric mean.     

Antifungal activity of the fermentation product of herbs by lactic acid bacteria against tinea

The fermentation product of herbs by lactic acid bacteria (FHL), in which Enterococcus faecalis TH10 predominated, was assayed for antifungal activity against tinea. The antifungal activity of FHL was as high as that of a synthetic fungicide. Autoclaving FHL did not reduce its antifungal activity, whereas neutralizing it did. The results suggested that nonproteinaceous compounds or organic acids in FHL could inhibit the growth of the dermatophyte tinea under low-pH conditions, and that malonic acid and acetic acid could have especially high antifungal activity against tinea.     

Evaluation of immunochromatographic test kits for food allergens using processed food models

It has been mandatory to label five allergenic substances (AS; egg, milk, wheat, buckwheat and peanut) in all processed foods, since April 2002 in Japan. Two kinds of ELISA kits have been provided as screening test kits for the Japanese official method. The kits have many advantages but some disadvantages, i.e., the kits are not necessarily suitable for daily monitoring in food manufacturing plants, because they require various analytical equipments and the use of complicated procedures. To overcome these drawbacks, we have developed other diagnostic kits based on immunochromatography that should enable more rapid and simple screening for food allergens. Then we examined the performance of these immunochromatographic test kits (IC kits) in terms of sensitivity, repeatability and cross-reactivity to AS proteins in 11 kinds of food models with various heating conditions and physical properties. We also examined processed food models including AS protein of constant concentration, using the IC kits and ELISA kits, and compared the results. The IC kits detected AS proteins at 5 microg/g in the extracts from processed food models, and provided highly reproducible results. Cross-reactivity among the AS proteins was not observed. The results obtained using the IC kits showed performance equivalent to that of the ELISA kits we examined in unheating processed food models including AS proteins of constant concentration. The IC kits should be more suitable for daily monitoring in food manufacturing plants.     

Respiration-deficient mutants of Zymomonas mobilis show improved growth and ethanol fermentation under aerobic and high temperature conditions

Respiration-deficient mutant (RDM) strains of Zymomonas mobilis were isolated from antibiotic-resistant mutants. These RDM strains showed various degrees of respiratory deficiency. All RDM strains exhibited much higher ethanol fermentation capacity than the wild-type strain under aerobic conditions. The strains also gained thermotolerance and exhibited greater ethanol production at high temperature (39°C), under both non-aerobic and aerobic conditions, compared with the wild-type strain. Microarray and subsequent quantitative PCR analyses suggest that enhanced gene expression involved in the metabolism of glucose to ethanol resulted in the high ethanol production of RDM strains under aerobic growth conditions. Reduction of intracellular oxidative stress may also result in improved ethanol fermentation by RDM strains at high temperatures.     

Locomotion Control of MEMS Microrobot Using Pulse‐Type Hardware Neural Networks

This paper presents the locomotion control of a microelectromechanical system (MEMS) microrobot. The MEMS microrobot demonstrates locomotion control by pulse‐type hardware neural networks (P‐HNN). P‐HNN generate oscillatory patterns of electrical activity like those of living organisms. The basic component of P‐HNN is a pulse‐type hardware neuron model (P‐HNM). The P‐HNM has the same basic features as biological neurons, such as the threshold, the refractory period, and spatiotemporal summation characteristics, and allows the generation of continuous action potentials. P‐HNN has been constructed with MOSFETs and can be integrated by CMOS technology. Like living organisms, P‐HNN has realized robot control without using software programs or A/D converters. The size of the microrobot fabricated by MEMS technology was 4 × 4 × 3.5 mm. The frame of the robot was made of a silicon wafer, equipped with rotary actuators, link mechanisms, and six legs. The MEMS microrobot emulated the locomotion method and the neural networks of an insect by rotary actuators, link mechanisms, and the P‐HNN. We show that the P‐HNN can control the forward and backward locomotion of the fabricated MEMS microrobot, and that it is possible to switch its direction by inputting an external trigger pulse. The locomotion speed was 19.5 mm/min and the step size was 1.3 mm. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(3): 43–50, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22473