X射线激励下介质中气隙放电的研究

针对油-纸绝缘系统中的局部放电问题,提出在X射线激励条件下的局部放电检测和定位新方法。实验表明,X射线照射可以电离气体原子,为气隙放电提供必需的初始电子,减小放电的统计时延,从而降低放电的起始电压、增加放电脉冲的次数,这一结果有利于局部放电的检测和定位。     

Single Gold Nanorod Detection Using Confocal Light Absorption and Scattering Spectroscopy

Gold nanorods have the potential to be employed as extremely bright molecular marker labels for fluorescence, absorption, or scattering imaging of living tissue. However, samples containing a large number of gold nanorods usually exhibit relatively wide spectral lines. This linewidth limits the use of the nanorods as effective molecular labels, since it would be rather difficult to image several types of nanorod markers simultaneously. In addition, the observed linewidth does not agree well with theoretical calculations, which predict significantly narrower absorption and scattering lines. The discrepancy could be explained by apparent broadening because of the contribution of nanorods with various sizes and aspect ratios. We measured native scattering spectra of single gold nanorods with the confocal light absorption and scattering spectroscopy system, and found that single gold nanorods have a narrow spectrum as predicted by the theory, which suggests that nanorod-based molecular markers with controlled narrow aspect ratios, and to a lesser degree size distributions, should provide spectral lines sufficiently narrow for effective biomedical imaging.     

Quantitative Evaluation of Corrosive Sulfur in Electrical Insulating Oil

This paper presents quantitative evaluation method of corrosive sulfur in insulating oil. The level of corrosion on copper strip which was aged in insulating oil is expressed numerically by the amount of sulfur on it. Since X‐ray strength by wave length dispersive X‐ray (WDX) and measurement value of sulfur on copper strip by titration show good correlation, the amount of sulfur can be obtained rapidly only by WDX. The performance of passivator such as BTA or Irgamet39 was quantitatively evaluated by WDX. The evaluation of life of passivator was also achieved. Copyright © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Photoemission study on natural oxidation of Cu3Au with synchrotron radiation

We report the results of a study of the natural oxidation of Cu₃Au(110) with high‐resolution X‐ray photoemission spectroscopy in conjunction with synchrotron radiation. The clean surface of Cu₃Au(110) is terminated with 50% Au and 50% Cu atoms. After natural oxidation in the air, Cu atoms segregate on the surface and produce Cu‐oxide. As a result, Au atoms move into the bulk. Au atoms below the oxide reduce the diffusion of O atoms farther into bulk and limit the oxide thickness. The face dependence of natural oxidation indicates that the diffusion of Cu atoms also contributes to oxide formation. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 175(4): 43–47, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21149     

Noise removal for medical X‐ray images in wavelet domain

Many important problems in engineering and science are well‐modeled by Poisson noise, and the noise of medical X‐ray images is Poisson noise. In this paper, we propose a method for noise removal for degraded medical X‐ray images using improved preprocessing and an improved BayesShrink (IBS) method in the wavelet domain. First, we preprocess the medical X‐ray image. Second, we apply the Daubechies (db) wavelet transform to medical X‐ray images to acquire scaling and wavelet coefficients. Third, we apply the proposed IBS method to process wavelet coefficients. Finally, we compute the inverse wavelet transform for the threshold coefficients. Experimental results show that the proposed method always outperforms traditional methods. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(3): 37– 46, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20486     

Investigating the optical NOR gate using plasmonic nanorods

In this paper, a coherent perfect absorption‐type NOR gate based on plasmonic nano particles is proposed. It consists of two plasmonic nanorod arrays on top of two serial arms with quartz substrate. The operation principle is based on the absorbable formation of a conductive path in the dielectric layer of a plasmonic nanoparticle waveguide. Because the coherent perfect absorption efficiency depends strongly on the number of plasmonic nanorods and the locations of nanorods, an efficient binary optimization method based the Particle Swarm Optimization algorithm is used to design an optimized array of the plasmonic nanorods in order to achieve the maximum absorption coefficient in the ‘off’ state and the minimum absorption coefficient in the ‘on’ state. In Binary Particle Swarm Optimization, a group of birds consists a matrix with binary entries, control the presence (‘1’) or the absence (‘0’) of nanorods in the array. Copyright © 2016 John Wiley & Sons, Ltd.     

Silicon nanorods‐based all‐dielectric waveguides with long decay‐length at the telecommunication band

We investigate subwavelength waveguides composed of silicon nanorods array in straight and nonstraight regimes deposited on a silica (SiO₂) substrate. It is shown that using all‐dielectric nanorods with high permittivity to design an all‐dielectric optical waveguide provides several advantages such as low‐dissipation coefficient and long decay length for the distributed fields. Exploiting silicon arrays in touching and nontouching arrangements, we examined the optical response of the structure to the guiding of magnetic and electric fields with transverse and longitudinal polarization modes. We studied the decay length for all propagated modes in both nanochain orientations numerically. Simulation results for straight arrays showed that the averaged decay length for the structure with dielectric particles in touching regime is 1.6 µm (for the waveguide with the length of 2.2 µm), and for the nontouching array is 2.2 µm (for the array with the length of 3.1 µm). Calculating transmission loss factors and considering decay length of the proposed waveguide, we verified the strong potential of the proposed structure to design all‐dielectric photonic devices to operate at telecommunication spectra (λ~1310 nm and 1550 nm). Also, we computed bending losses [dB] for the examined structures based on the bends degree. Copyright © 2015 John Wiley & Sons, Ltd.     

Automated X‐ray inspection method for fillet‐less mounted chip components

Chip components mounted on the printed circuit board are rapidly being miniaturized. Furthermore, the fillet‐less chip soldering technique, which does not use a solder fillet, is widely used in portable products such as mobile phones. However, there is no method to inspect the soldering of fillet‐less chip mounting. In this paper, we propose an automated X‐ray inspection technique for fillet‐less chip mounting. It extracts three inspection parameters from the X‐ray image. In the experiments, we evaluate the repeatability and inspecting ability of the technique and confirm that sufficient information for failure detection is obtained. An automated X‐ray inspection system using this technique is now in operation at some factories, so in conclusion our automated method would be useful in practice. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

NO2 sensing characteristics of ZnO nanorods prepared by hydrothermal method

ZnO nanorods were prepared via a hydrothermal reaction in a solution containing Zn(NO₃)₂⋅6H₂O, NaOH, cyclohexylamine, ethanol and water, and their NO₂ and CO sensing behaviors were investigated. The morphology and agglomeration of ZnO nanorods could be manipulated by controlling the amount of water in the solution, which was explained by the variation in the [OH⁻] due to an interaction between the water and cyclohexylamine. Sea-urchin-like and well-dispersed ZnO nanorods were prepared at low and high water content, respectively. Well-dispersed ZnO nanorods showed 1.8 fold change in resistance at 1 ppm NO₂ while there was no significant change in resistance at 50 ppm CO. The present ZnO nanorods can be used in automated car ventilation systems to detect NO₂ in the presence of CO. Presenting author in conference: PYEONG-SEOK CHO     

A novel micromixer with three‐dimensionally cross‐linked capillary array structure fabricated by deep X‐ray lithography

A novel micromixer was proposed, fabricated and verified. The new concept of the micromixer is to cross‐link many capillaries in a three‐dimensional structure. The characteristic flow behaviors were simulated by using the “FLUENT” computational fluid dynamics (CFD) software. The results of the CFD showed unique mixing behavior in three‐dimensionally cross‐linked capillaries. The mixing performance of the micromixer is strongly influenced by controlling the three‐dimensional crossing conditions. The micromixer was fabricated by deep X‐ray lithography with multistep exposure. The cross‐linked capillary structures were successfully fabricated while controlling the cross‐link conditions. The performance of the micromixer was evaluated by using an enzyme reaction. By comparing the mixtures produced with a cross‐linked fluid filter and with a fluid filter without cross‐linked capillaries, we found that the reaction was accelerated by using the new micromixer. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 177(1): 26–31, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21157     

Assembling tin dioxide nanorods on carbon nanotubes by a chemical solution method

Nanocomposites have significant potential in development of advanced materials and nanotechnology applications. Here, multi-walled carbon nanotubes (MWCNTs) sheathed with tin dioxide (SnO₂) nanorods by a two-step chemical solution route are reported. Hydrolyzing of MWCNTs and SnCl₄·5H₂O at a near room temperature followed by alkali-assisted hydrothermal process resulted in perfect SnO₂ coating on MWCNTs. Based on the XRD and TEM results, we found the nanoscale SnO₂ rods covered densely on MWCNTs.     

Development of a 3‐dimensional LIGA process and application to fabricate a spiral microcoil

LIGA process has been developed in the 2.5‐dimensional world. We introduced new technologies of a 3D X‐ray lithography and a worm injection molding with an unscrewing de‐molding mechanism, and succeeded in the deployment of a 3D LIGA process. Furthermore, we fabricated a spiral microcoil using the 3D‐LIGA process and a metallization technique combining flat and smooth electroplating and isotropic chemical etching. The microcoil diameter was 0.5 mm and the length was 1 mm. The width of coil lines was 10µm and the pitch was 20µm. Characteristics of this microcoil as an inductor combine the inductance of 91 nH and the quality factor of 5.8 at the frequency of 1 GHz. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(1): 43–51, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20679     

Preparation of sputtered SrAl2O4:Eu films and their thermoluminescence properties

SrAl₂O₄ activated with Eu, a new fluorescent material having a long decay time, was deposited on Si substrates using an RF sputtering technique with facing targets. The as‐deposited films did not show any peaks in the X‐ray diffraction spectra and no photoluminescence was observed. However, X‐ray diffraction peaks and a photoluminescent peak at about 520 nm were observed after annealing in a reducing Ar+H₂ gas and an inert Ar gas. The structure of the sputtered films was investigated using EDS and SEM. The thermoluminescence peaks were observed, and the lifetime of the fluorescence and the activation energies were calculated from the peaks. The results in this work are useful for future applications. © 2000 Scripta Technica, Electr Eng Jpn, 132(1): 7–14, 2000     

Structural change induced in LaAlO3 by ion implantation

Ion implantation is used for various purposes in manufacturing semiconductor devices such as MOS‐FETs. In the present study, the effects of implantation of P⁺ or B⁺ ions on the structural change of single‐crystal LaAlO₃ were examined. The optical absorption edge located at ∼5.6 eV, which seems to correspond to the bandgap energy of LaAlO₃, is hardly affected by the ion implantation. The X‐ray diffraction peak intensity at 2θ_χ=23.5° is decreased by the ion implantation. The intensities of three sharp photoluminescence (PL) peaks detected at 1.62, 1.65, and 1.69 eV, which appear only when the samples are crystalline, become smaller by ion implantation. However, the intensity of a broad PL peak at ∼2.8 eV due to the oxygen vacancy, which is detectable in both amorphous and crystalline samples, hardly changes after the ion implantation. These results indicate that the ion implantation degrades the crystallinity of LaAlO₃. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Propagation and radiation field characteristics of nanometer electromagnetic waves in x‐ray dielectric waveguides with random media

X‐rays in the nanometer electromagnetic region are useful for nanospace fabrication, information and high‐energy transmission and control techniques of angstrom‐size structures in biomedical sciences and technology. In this paper, the electromagnetic fields in X‐ray gradient fiber with random refractive index media are studied. Statistical mode conversion of beam propagation, beam broadening, and beam center are investigated by the stochastic process theory of electromagnetic fields. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 139(3): 53–61, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.10002/eej.1160     

Surface evaluation of LiNbO3 and LiTaO3 crystals etched using fluorine system gas plasma reactive ion etching

The etching characteristics of LiNbO₃ and LiTaO₃ single crystals have been investigated by performing plasma reactive ion etching (RIE) with CF₄/Ar, CF₄/H₂, and CF₂/Ar/H₂ gas mixtures. The etched surface was evaluated by atomic force microscopy and X‐ray diffraction. The in situ surface temperature of the sample was measured during RIE. F atoms exist in the contamination layer on the surface etched using mixtures of CF₄, Ar, and H₂ gases. The etch rate was dependent on the crystal orientation. The etch rate of LiTaO₃ was less than that of LiNbO₃. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(2): 18–24, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10365     

Effect of Ni addition on PNZT tungsten bronze structure

Lead niobate zirconate titanate (PNZT) with general formula 0.5PbNb₂O₆–0.5Pb(Zr_xTi_1-x)O₃ (where x?=?0.15, 0.25, 0.35) and lead nickel niobate zirconate titanate (PNNZT) with general formula Pb(Ni_xNb_0.5-xZr_0.25Ti_0.25)O₃ (where x?=?0.167, 0.250, 0.333) have been prepared by conventional solid state reaction. The phase formation has been studied by X – ray diffraction analysis. Raman investigations have been carried out in the 200–1000 cm^?1 wave number range. The structural changes observed in the X – ray diffraction pattern has been further confirmed by Raman analysis. The major changes in the E(1TO), A₁(1TO) and E?+?B₁ phonon modes suggest the structural change from cubic to rhombohedral with increase in Ni concentration in PNNZT. The optical band gap has been calculated from UV – Vis absorption spectra.     

Changes of Cu electrode surface conditions and prebreakdown current characteristics caused by repetitive breakdowns in a vacuum

To clarify factors influencing the conditioning effect produced by repetitive breakdowns of a vacuum gap, changes of electrode surface conditions before and after 500 breakdowns caused by impulse voltage application were investigated. Changes of prebreakdown current characteristics were also investigated. The electrode material was copper. The electrode surfaces were analyzed by X‐ray photoelectron spectroscopy (XPS). XPS analysis revealed that the electrode surfaces were completely cleaned by repetitive breakdowns. Prebreakdown characteristics were classified into three patterns: (1) displacement current alone, (2) field emission current as well as displacement current, (3) explosive current increase. Patterns (1) and (4) were observed mainly in the early stage of repetitive breakdowns, while pattern (2) was found in the later stage. It has been concluded that the breakdown mechanism changes during conditioning by repetitive breakdowns. © 2000 Scripta Technica, Electr Eng Jpn, 133(1): 11‐18, 2000     

Growth and magnetic properties of Mn and MnSn-doped ZnO nanorods

ZnO nanorods synthesized at 700^∘C by heating the mixture of solution processed Zn precursor with NaCl−Li₂CO₃ salt were examined. The size of the nanorods was in the range of 15–100 nm in diameter and 0.5–5 μm in length. The nanorods show the single crystal structure being free from second phases. The Mn and MnSn-doped nanorods by demonstrated ferromagnetic properties and unique luminescence properties due to doping and charge carrier confinement effects. Magnetic susceptibility of the samples as a function of temperature shows Curie–Weiss behavior. Hysteresis with the coercive field <200 Oe was clearly observed in magnetization versus field curves at 5 and 300 K. Increasing the Mn concentration increases significantly the magnetic hysteresis.