Regular boundary integral formulation for the analysis of opendielectric/optical waveguides

A regular boundary element method is employed for the variational formulation of the Helmholtz equation that governs waveguiding problems. The problems are defined on the boundary as usual, but as in the charge simulation method, the source points associated with the fundamental solutions are allocated outside the domain so that the singular integrals which occur in the standard boundary element procedure can be avoided. First, the formulation is developed for the two-dimensional (2-D) scalar Helmholtz problem, solving for the axial components of either electric or magnetic fields. Then the formulation is extended for the analysis of dielectric waveguides of the open type incorporating axial components of both electric and magnetic fields, for the solution of the propagating modes which are generally of hybrid types. Very close agreements have been found when the solutions obtained by the present formulation are compared with the ones obtained by different methods. One merit of the extended formulation is that it has been fixed to suppress the spurious solutions     

Pulse frequency modulation based CMOS image sensor for subretinal stimulation

We have developed a CMOS image sensor based on pulse frequency modulation for subretinal implantation. The sensor chip forms part of the proposed intraocular retinal prosthesis system where data and power transmission are provided wirelessly from an extraocular unit. Image sensing and electrical stimulus are integrated onto the same chip. Image of sufficient resolution has been demonstrated using 16/spl times/16 pixels. Biphasic current stimulus pulses at above threshold levels of the human retina (500 /spl mu/A) at varying frame rates (4 Hz to 8 kHz) have been achieved. The implant chip was fabricated using standard CMOS technology.     

Effects of intermediate semiconductor layers on carrier transport mechanisms through p-ZnSe/metals interfaces

The effects of formation of intermediate semiconductor layers at p-ZnSe/metals interfaces on carrier transport mechanisms were studied by comparing contacts prepared by the deposition and annealing (DA) technique or the molecular beam epitaxy (MBE) technique. Current density vs voltage (J-V) curves of the MBE contact with a p-ZnSe/p-ZnTe superlattice intermediate layer showed ohmic behavior. However, J-V curves of the DA contact with a ZnTe intermediate layer showed rectifying behavior. The difference of the electrical properties between these two contacts was due to existence of a highly resistive intermediate layer with highly dense defects in the DA contact and a low resistance p-type conductive intermediate layer with relatively small densities of crystalline defects in the MBE contacts. From the present results, it was concluded that formation of the highly resistive semiconductor layer with dense crystalline defects prevented the DA contact to transit from non-ohmic J-V behavior to ohmic.     

Dissolution theory of gold in alkaline thiourea solution(Ⅲ) ——Thermodynamics on dissolution of gold in alkaline thiourea solution containing Na _2SO_3

１　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｍｅｃｈａｎｉｓｍａｎｄｃｈｅｍｉｃａｌｐｒｏｃｅｓｓｆｏｒｄｉｓｓｏｌｖｉｎｇｇｏｌｄｉｎａｃｉｄｉｃｔｈｉｏｕｒｅａｓｏｌｕｔｉｏｎｗｅｒｅｓｔｕｄｉｅｄｂｙｍａｎｙｒｅｓｅａｒｃｈｅｒｓ［１～５］，ｗｈｏｇｅｎｅｒａｌｌｙｔｈｏｕｇｈｔｔｈａｔｔｈｉｏｕｒｅａａｓａｓｔｒｏｎｇｌｉｇａｎｄｃｏｍｐｌｅｘｅｓｓｅｌｅｃｔｉｖｅｌｙｗｉｔｈｇｏｌｄｉｏｎｔｏｆｏｒｍｓｔａｂｌｅｃｏｍｐｌｅｘｉｏｎＡｕ［ＣＳ（ＮＨ２）２］＋２，ａｎｄｓｏｍｅｏｘｉｄａｎｔｓ…     

Electromagnetic wave absorption potential of SiC-based ceramic woven fabrics in the GHz range

This article investigates the electromagnetic wave-absorbing properties of SiC-based ceramic woven fabrics. The electrical conductivity of ceramic woven fabrics was modified by heat treatment in air, resulting in oxidation, and the electromagnetic wave absorption potential of single- and double-layer ceramic woven fabrics were determined in the 17–40 GHz frequency range using the free-space method. The absorption potentials of ceramic woven fabrics of different chemical composition and weave were correlated with their material properties through X-ray diffraction, scanning electron microscopy, and electrical resistance measurement. The effect of the different arrangements of fabrics in multilayer forms, and how oxidation affects the electromagnetic wave absorption potential of the fabrics are discussed. Various double-layer combinations of SiC-based woven fabrics revealed promising potentials for both reduced reflection and transmission, resulting in ~90% absorption in the GHz range, which makes them powerful candidate materials for electromagnetic wave absorption applications.     

In vitro fertilization and polyspermy in the pig: factors affecting fertilization rates and cytoskeletal reorganization of the oocyte

Polyspermy is a common phenomenon in the pig. Extensive information has become available from in vitro studies on not only the quality of oocytes but also the quality of spermatozoa. However, little information is available on the relative penetration rates of fresh and frozen spermatozoa from the same ejaculate from boars of different breeds. The present results, based on a total of 15 boars of three different breeds, revealed that the inter-breed variation in fertilization and polyspermic rates is larger than intra-breed variation. It was also shown that the incidence of polyspermy as well as penetration rate was greatly decreased by freezing and thawing, even if a higher number of sperm was coincubated with cumulus-free oocytes for a longer period compared to fresh sperm of the same ejaculate. This study focuses on the cytoskeletal organization of the oocyte with respect to the status of cumulus investment, and monospermic and polyspermic fertilization. The status of cumulus cells correlated with the density of transzonal cumulus-cell processes and with the maturation rate of oocytes and, to some degrees, the incidence of polyspermy. Polyspermic zygotes formed multiple microtubule domains in association with individual male pronuclei (PN), but in a high degree of polyspermy (more than trispermy), the pronuclear apposition did not proceed. The effect of multiple PN of paternal and maternal origin on the cytoskeletal reorganization is also discussed.     

Atomic hydrogen emission induced by TEA CO(2) laser bombardment on solid samples at low pressure and its analytical application

Hydrogen emission has been studied in laser plasmas by focusing a TEA CO(2) laser (10.6 microm, 500 mJ, 200 ns) on various types of samples, such as glass, quartz, black plastic sheet, and oil on copper plate sub-target. It was found that H(alpha) emission with a narrow spectral width occurs with high efficiency when the laser plasma is produced in the low-pressure region. On the contrary, the conventional well-known laser-induced breakdown spectroscopy (LIBS), which is usually carried out at atmospheric air pressure, cannot be applied to the analysis of hydrogen as an impurity. By combining low-pressure laser-induced plasma spectroscopy with laser surface cleaning, a preliminary quantitative analysis was made on zircaloy pipe samples intentionally doped with hydrogen. As a result, a good linear relationship was obtained between H(alpha) emission intensity and its concentration.     

Preparation of Ultrafine MgO by the Spray-ICP Technique

Ultrafine MgO with uniform shape and particle size was prepared by spraying a solution of magnesium nitrate into an inductively coupled plasma (ICP) of Ar. The formation of the uniform particles seems to result from the complete decomposition of the nitrate to its component atoms in the ICP flame, followed by the precipitation of the oxide occurring just outside the flame.