An enhanced time-frequency-spatial approach for motor imagery classification.

Human motor imagery (MI) tasks evoke electroencephalogram (EEG) signal changes. The features of these changes appear as subject-specific temporal traces of EEG rhythmic components at specific channels located over the scalp. Accurate classification of MI tasks based upon EEG may lead to a noninvasive brain-computer interface (BCI) to decode and convey intention of human subjects. We have previously proposed two novel methods on time-frequency feature extraction, expression and classification for high-density EEG recordings (Wang and He 2004; Wang, Deng, and He, 2004). In the present study, we refined the above time-frequency-spatial approach and applied it to a one-dimensional "cursor control" BCI experiment with online feedback. Through offline analysis of the collected data, we evaluated the capability of the present refined method in comparison with the original time-frequency-spatial methods. The enhanced performance in terms of classification accuracy was found for the proposed approach, with a mean accuracy rate of 91.1% for two subjects studied.     

Identification of phenolic compound in manuka honey as specific superoxide anion radical scavenger using electron spin resonance (ESR) and liquid chromatography with coulometric array detection

Apitherapy has become the focus of attention as a form of folk and preventive medicine for treating certain conditions and diseases as well as promoting overall health and well‐being. In apitherapy, honey is the therapeutic agent used for dressing surgical wounds, burns or skin ulcers, as well as for dyspepsia, peptic ulcer, etc., because of its antioxidant activity. Therefore, it is important to determine the antioxidants in honey by analytical techniques. In the present study, the antioxidant activities of honeys from different floral sources were investigated by electron spin resonance (1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) and H₂O₂/NaOH/DMSO scavenging systems), liquid chromatography with coulometric array detection (LC‐ED), and liquid chromatography with electrospray mass spectrometry (LC‐MS). The antioxidant activities of some unifloral honeys (acacia, Chinese milk vetch, buckwheat and manuka) were evaluated using the radical scavenging systems. It was shown that DPPH radical scavenging activity was significantly different among the honeys, with buckwheat and manuka honeys having significantly higher scavenging activity than acacia honey. In addition, only manuka honey had specific scavenging activity for superoxide anion radicals. The compound responsible for this activity in manuka honey was identified by LC‐ED and LC‐MS. Careful examination of the LC‐ED chromatographic patterns of manuka and other honey samples revealed a distinct peak in the chromatogram of manuka honey to be methyl syringate (MSYR). The radical scavenging activity of MSYR was specific for superoxide anion radicals, similar to the case of manuka honey. Copyright © 2005 Society of Chemical Industry     

Crosstalk reduction in arrayed-waveguide grating multiplexer/demultiplexer using cascade connection

This paper proposes a cascade-connected arrayed-waveguide grating (AWG) as a solution to the problem of crosstalk accumulation in a large-scale AWG multiplexer/demultiplexer (MUX/DEMUX) and demonstrates a 64-channel cascaded AWG module with a very low background crosstalk of less than -80 dB and a total crosstalk of about -34 dB. In this paper, the authors densely integrate 64 additional compactly designed crosstalk-suppressing AWGs whose bandwidths were carefully optimized and directly attach them to a conventional 64-channel AWG. Consequently, in addition to a very low crosstalk, a low insertion loss and a compact size without passband shape distortion are achieved with this module. Based on the performance of the cascaded AWG module, it is then estimated that it is possible to realize a 1000-channel AWG MUX/DEMUX that is free from the problem of crosstalk accumulation.     

Sensorless salient‐pole PM synchronous motor drive in all speed ranges

This paper presents a position sensorless drive of salient‐pole PM synchronous motors in all speed ranges including zero speed. Two position and speed estimation algorithms using the current differences between the actual and the estimated currents are proposed. One is based on the back emf estimation in the medium‐ and high‐speed ranges. Another is based on the position dependency of the winding inductances in the low‐speed ranges including zero speed. The effectiveness of the proposed algorithm has been verified with a six‐pole, 1.5‐kW, 1500‐rpm test motor. Stable sensorless speed control from zero to 3000 rpm within ±100% load torque range was achieved. © 2001 Scripta Technica, Electr Eng Jpn, 135(3): 64–73, 2001     

Optical qubit generation by state truncation using an experimentally feasible scheme

Generation of arbitrary superposition of vacuum and one-photon states using a quantum scissors device (QSD) is studied. The device allows the preparation of states by truncating an input coherent light. Optimum values of the intensity of the coherent light for the generation of any desired state using the experimentally feasible QSD scheme are found.     

Noncontact energy transfer system using immittance converter

Noncontact energy transfer systems are widely used in industrial material handling systems. This paper proposes a new noncontact energy transfer system using a tuned pickup coil and an immitance converter inductively coupled to a parallel transmission line excited by a high‐frequency constant‐current source. In a noncontact energy transfer system which supplies continuous energy to movers by electromagnetic induction, the efficiency is low owing to low excitation impedance because of the wide air gap of the magnetic core in the pickup coil. The excitation impedance can be increased by the resonance with a capacitor connected parallel to the pickup coil. The resonant pickup coil works as a high‐frequency constant‐current source for the load. We propose using an immittance converter to transform the high‐frequency constant‐current source into a high‐frequency constant‐voltage source. Then, the high‐frequency constant‐voltage source is rectified into a constant‐voltage dc source, and supplies power to an inverter for motor driving. In this paper, the configuration of this new noncontact energy transfer system and its characteristics are described. The experimental results and simulation waveforms are also described. © 2001 Scripta Technica, Electr Eng Jpn, 136(4): 58–64, 2001     

Sensorless control of SRM using magnetizing curves

Among various variable speed drives, switched reluctance motors (SRMs) have been found to be competitive with traditional ac and dc motors because of their simple construction and drive electronics. However, the necessity of using a shaft‐mounted position sensor is one of the drawbacks of the SRM from the standpoint of cost, size, and reliability. Position sensorless SRM drives are expected to solve these problems. This paper presents a method of position sensorless control based on a simple fuzzy model of nonlinear position‐dependent magnetizing curves. The sensors needed for the drive are one voltage sensor and one current sensor. Experimental studies using a 1.5‐kW, 5400‐rpm SRM with a 6/4 tooth configuration show that the maximum error of rotor position estimation is less than three mechanical degrees in the 1:20 speed range under any load conditions. © 2001 Scripta Technica, Electr Eng Jpn, 135(2): 60–68, 2001     

Stacked polypyrrole-coated non-woven fabric sheets for absorbing electromagnetic waves with extremely high frequencies

Conductive non-woven fabric sheets coated with polypyrrole nanoparticles and having resistivity from 1.5 × 10⁵ to 3.0 Ω cm were prepared by immersing non-woven fabric sheets in solutions containing various concentrations of oxidizing agent and dopant and then exposing the sheets to pyrrole vapor. A stack of ten treated sheets could absorb more than 95% of electromagnetic waves in the frequency range of 75–110 GHz and more than 99% in the range of 85–105 GHz, irrespective of the resistivity of the sheet. This absorption was achieved even though the thickness of the stack was less than 10 mm. Furthermore, a conductive non-woven fabric sheet with resistivity of 7.5 Ω cm and thickness of only 0.5 mm could absorb about 90% of electromagnetic waves in the range of 75–110 GHz. These results clearly demonstrate that the stacked conductive non-woven fabric sheets prepared in this study are a new material that effectively absorbs electromagnetic waves with extremely high frequencies in the millimeter band.     

Structural Relaxation, Glass Transition, Viscous Formability, and Crystallization of Zr-Cu–Based Bulk Metallic Glasses on Heating

In this article, we summarize our recent findings on relaxation, glass transition, viscous flow, and crystallization of Zr-Cu?Cbased metallic glasses on heating. At least two processes related to the diffusivities of different alloying elements take place in the glass-transition region of a Zr-Cu-Al-Ni glassy alloy. Also, we report an unusual solidification behavior of the bulk glassy alloy produced using low-purity Zr in which both primary and eutectic-type structural constituents were formed simultaneously during solidification of the melt. In addition, viscous flow and structure changes in the Zr-Cu-Al-Ag glassy alloy are examined in both the glass-transition and supercooled liquid regions. This alloy is found to exhibit localized phase separation leading to nanocrystallization before massive crystallization of the entire sample.