Auto‐detection of partial discharges in power cables by discrete wavelet transform

One of the serious problems that can occur in power XLPE cables is destruction of insulator. The best and conventional way to prevent this is ascertaining partial corona discharges occurring at small voids in organic insulators. However, there are some difficulties in detecting those partial discharges due to the existence of external noise in detected data, whose patterns are hardly identified at a glance. For this reason, there have been a number of researches into detecting partial discharges by employing a neural network (NN) system, which is widely known as a system for pattern recognition. We have been developing an NN system for auto‐detection of partial discharges, and have input numerical data of the waveform itself and obtained appropriate performance. In this paper, we employed the discrete wavelet transform (DWT) to acquire more detailed transformed data in order to use them in the NN system. Employing the DWT, we were able to express the waveform data in time–frequency space, and achieved effective detection of partial discharges by the NN system. We present herein the results using DWT analysis for partial discharges and noise signals which we obtained. Moreover, we present results out of the NN system which dealt with those transformed data. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(1): 24–30, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10315     

A 10-GHz Optoelectronic Oscillator at 850 nm Using a Single-Mode VCSEL and a Photonic Crystal Fiber

We demonstrate an optoelectronic oscillator using a gain-switched single-mode vertical cavity surface-emitting laser and a single-mode photonic crystal fiber. A 10-GHz optical pulse train at 850 nm with a timing jitter of 1.2 ps was successfully generated.     

Parasympathetic activity is a major modulator of the circadian variability of heart rate in healthy subjects and in patients with coronary artery disease or diabetes mellitus

Autonomic heart rate control was assessed by power spectral analysis of heart rate variability in 24-hour ambulatory electrocardiographic recordings from 23 healthy subjects, 14 patients with coronary artery disease without cardiac dysfunction, and 14 patients with diabetes mellitus. The log value of the ratio of the low-frequency component (LF = 0.04 to 0.15 Hz) to the high-frequency component (HF = 0.15 to 0.5 Hz) and logHF were employed as indexes of sympathetic and parasympathetic activity, respectively. Diurnal and nocturnal logLF, logHF, and log(LF/HF) values were calculated for heart rates of 60, 70, and 80 beats/min. Intergroup differences among these three variables were not significant at any heart rate. Although a heart rate-related decrease in logHF was generally observed, the relationship between log(LF/HF) and heart rate was not consistent. The correlation between diurnal and nocturnal logHF values was significant at all three heart rates (r = 0.63, 0.87, and 0.59), whereas the diurnal log(LF/HF) was correlated with the nocturnal value only at 70 beats/min (r = 0.77). These results suggest that the heart rate during normal daily activities is a reliable indicator of parasympathetic tone, if not sympathetic tone, in healthy subjects and patients with coronary artery disease or diabetes mellitus.     

Modeling and designing aircraft taxiing patterns for a large airport

At large airports, aircraft takeoff and land simultaneously on multiple runways. As a result, taxiing is a complex and, at times, lengthy process. Planning for aircraft taxiing is an essential design element for the expansion of runways, taxiways, and terminals. Unnecessary taxiing should be reduced. In this study, we develop a taxiing model and calculate the taxiing time. We observed aircraft traffic patterns and listened to the communication of air traffic controllers (ATCs) in order to develop a taxiing model. The developed model was applied to Narita International Airport. We begin by estimating the time required for taxiing at Narita International for 2014. Next, we propose two strategies to reduce the taxiing time. The first strategy involves changes in departure times with controlled intervals between them. In this strategy, the average taxiing time is reduced by 16.5%. The other strategy requires adjustments in the time from the aircraft departure from the terminal to the start of taxiing. In this strategy, the maximum taxiing time is reduced by 11.5%, and the intervals between the terminal departures and taxiing were more uniform.     

Densely packed organic nanocrystals ultrathin film using a liquid–liquid interface

We report a fabrication of densely packed polydiacetylene nanocrystal film using a liquid–liquid interface. Polydiacetylene (pDCHD) nanocrystals was dispersed into water solution by reprecipitation method from a good solvent. Then, hexane was added to the water dispersion to create the liquid–liquid interface. pDCHD nanocrystals were assembled at the interface, when ethanol was added to the pDCHD water dispersion–hexane solution. The assembled film was transferred onto a solid substrate and the film morphology was observed by scanning electron microscope (SEM). With addition of 10 vol% of ethanol to 2.5 mM of pDCHD water dispersion–hexane solution, a densely packed pDCHD film is fabricated. Optical and electrical properties of the pDCHD film are discussed by UV–vis spectroscopy and current–voltage measurement.     

Quick change of ion species of heavy-ion microbeam by cocktail beam acceleration technique with the JAEA AVF cyclotron

A heavy-ion microbeam with hundreds of MeV energy is utilized for research in biotechnology and materials science at the JAEA AVF cyclotron facility. Beam users need microbeams providing a wide range of the LET. We have to change ion species and/or energy in order to vary the LET widely. However, it takes much time to develop a new microbeam of different ion species step by step using a flat-top acceleration system. A cocktail beam acceleration technique is frequently used to change the ion species and energy quickly. The cocktail beam acceleration has been first applied to the microbeam formation for quick change of the ion species. As a result, we have succeeded to reduce considerably microbeam changing time to within 30 min between a 520 MeV ⁴⁰Ar¹⁴⁺ and a 260 MeV ²⁰Ne⁷⁺. No deterioration of the microbeam spot size has been confirmed using a SE image of a copper grid.     

Development of a real-time beam current monitoring system for microbeam scanning-PIXE analysis using a ceramic channel electron multiplier

Microbeam scanning-PIXE (micro-PIXE) analysis is a useful method for obtaining information of multi-elemental distribution in samples by two-dimensional images of sample surfaces such as mammalian cells, tissues, and other environmental monitoring species. In addition to elemental distribution information, quantitative analysis is in demand for further investigations of environmental and biomedical studies concerning heavy metals accumulated in terms of cells and sub-cellular organelles. To make quantitative analysis possible, a real-time beam monitoring system that gives a precise number of ions, and an output independent from a sample that enables one to keep a beam resolution of micrometer size is required. In this paper, we report on the development of beam current monitoring. The beam current was monitored using a ceramic channel electron multiplier (CEM) to detect secondary electrons induced from a 50 nm thick carbon film (10 μg/cm²). This carbon film was attached to a sample holder, which was set at the targeted sample position. The output value of the CEM was proportional to the Faraday cup installed just after the sample position. The beam resolution was measured using off-axis STIM by scanning a copper grid, and was estimated at 1.79 and 1.72 μm for the horizontal and vertical directions, respectively, sufficient for routine micro-PIXE analysis.     

Fabrication of nanowires by varying energy microbeam lithography using heavy ions at the TIARA

In TIARA facility of Japan Atomic Energy Agency (JAEA) Takasaki, we have produced three-dimensional micro/nano-structures with high aspect ratio using cross linking process based on negative resist such as SU-8 by a technique of mask less ion beam lithography. By bombarding high energy heavy ions such as 450 MeV Xe²³⁺ to SU-8, on the other hand, it appeared that a nanowire could be produced just with a single ion hitting. Then we tried to produce nanowires, of which both ends were fixed in the three-dimensional structure. This paper shows a preliminary experiment for this purpose using a combination of 15 MeV Ni⁴⁺ ion microbeam patterning and the 450 MeV ¹²⁹Xe²³⁺ hitting on SU-8.     

Counter-doped MOSFETs of 4H-SiC

In this paper, we investigate the effect of counter-doping of nitrogen at the channel region of epitaxial n-channel 4H-SiC MOSFETs on the channel mobility and the threshold voltage. From this study, we have found that the channel mobility steeply improves as the nitrogen dose increases. At a dose of 2× or 2.5×10¹² cm^-2 the enhancement MOSFET has achieved an effective channel mobility of 20 cm²/Vs or a field effect mobility of 38 cm²/Vs at a peak     

Co41Ni33Al26合金的再结晶、马氏体相变和铁磁特性

研究了Co41Ni33Al26铁磁性形状记忆合金的再结晶行为和组织变化规律,采用振动磁力计（VSM）和示差热分析仪（DSC）分析了合金磁性和马氏体相变特点。结果表明,经43．65％的大压下量冷轧变形的Co41Ni33Al26合金在低于1000℃发生再结晶,随着淬火温度的升高,合金中β相体积分数不断增加。冷轧组织中在β／γ相界面上有很多微裂纹,这是由于两相变形不协调而形成的,微裂纹的形成有利于合金的塑性变形,在高于1200℃处理时微裂纹消失,表现出“自愈合”能力。该合金的马氏体相变温度和居里点都随着淬火温度的升高而升高,居里点始终高于马氏体相变温度,且马氏体相的磁晶各向异性高于β母相的,说明该合金是很好的铁磁性形状记忆合金的候选材料。