Simple method of measuring propagation properties of integrated optical waveguides: an improvement

In this paper we report a simple method of measuring mode propagation losses of integrated optical waveguides with small scattering. The basic technique, reported previously, uses a microcomputer-assisted video camera; here we have improved our observation scheme by coating the optical waveguide with a thin film of fluorescent dye (Nile Blue A perchlorate) thus permitting observation of the optical fields. The Nile Blue A perchlorate absorbs light centered at 0.63 microm and emits light centered at 0.69 microm. We have measured a mode propagation loss of the order of 0.1 dB/cm of a potassium ion-exchanged glass waveguide and confirmed the damped oscillatory behavior of the attenuation vs a slightly lossy thin-film thickness curve for the ion-exchanged waveguide coating with an indium tin oxide film.     

Preparation and Sintering of Monosized Al2O3-TiO2 Composite Powder

An unagglomerated, monosized Al₂O₃TiO₂ composite powder was prepared by the stepwise hydrolysis of titanium alkoxide in an Al₂O₃ dispersion. Particle size was controlled by selecting the particle size of the starting Al₂O₃ powder; TiO₂ content was determined by the amount of alkoxide hydrolyzed. A composite-powder compact containing 50 mol% TiO₂, when fired at 1350°C for 30 min, showed nearly theoretical density with aluminum titanate phase formation.     

Surgical and interventional robotics: Part II

A large family of medical interventions can be represented by a model that is analogous to industrial manufacturing systems. If the right information is available, they can be planned ahead of time and executed in a reasonably predictable manner. We, therefore, have classified them as surgical computer-aided design (CAD)-computer-aided manufacturing (CAM) systems, having three key concepts: 1) surgical CAD, in which medical images, anatomical atlases, and other information are combined preoperatively to model an individual patient; the computer then assists the surgeon in planning and optimizing an appropriate intervention 2) surgical CAM, in which real-time medical images and other sensor data are used to register the preoperative plan to the actual patient and the model and the plan are updated throughout the procedure; the physician performs the actual surgical procedure with the assistance of the computer, using appropriate technology (robotics, mechatronics, optical guidance, perceptual guidance, etc.) for the intervention 3) surgical total quality management (TQM), which reflects the important role that the computer can play in reducing surgical errors and in promoting more consistent and improved execution of procedures. Successful procedures are also included in procedural statistical atlases and fed back into the system for pre- and intraoperative planning. This article, primarily concerned with robotics and mechatronics, concentrates on the surgical action (surgical CAM), although for the sake of completeness, major issues in surgical planning (surgical CAD) and postoperative data analysis (surgical TQM) are also included. This article is the second installment of a three-part series on surgical and interventional robotics.     

Ionic graft copolymerization. VIII. Homopolymerization of β-propiolactone by radical catalysts in the presence of electron acceptors and application to graft copolymerization

The polymerization of β-propiolactone (βPL) induced by radiation and by radical catalysts, the influences of radical inhibitors and electron acceptors on this polymerization, and graft copolymerization were studied. It was found that βPL was polymerized by benzoyl peroxide in the presence of electron acceptors such as maleic anhydride and acrylonitrile. This polymerization method was applied to graft copolymerization. The electron donative trunk polymer containing ether groups was heated with benzoyl peroxide or was irradiated by γ-rays from Co⁶⁰ in the presence of maleic anhydride as the electron acceptor. βPL was added subsequently to form the graft copolymer.     

Ferroelectric and magnetic properties of multiferroic BiFeO(3)-based composite films

BiFeO(3)-based composite films were fabricated onto the Pt/Ti/SiO(2)/Si(100) substrates by a chemical solution deposition (CSD) method using the precursor solutions with various excess iron composition followed by annealing at 923 K for 30 minutes under oxygen gas flow. Coexistence of spontaneous magnetization and remanent polarization could be obtained in the BiFeO(3)-based composite films with high excess iron composition. The remanent magnetization of almost 20 emu/cm(3) and the magnetic coercive field of 1.5 kOe were obtained at the iron composition ratio of Fe/Bi = 1.25. In this specimen, the remanent polarization at 90 K was approximately 10 microC/cm(2) at the electric field of 1500 kV/cm. Structural analysis suggested that the remanent polarization has a possibility to increase by suppressing the formation of the secondary phases of Bi(2)Fe(4)O(9) and alpha-Fe(2)O(3), these are the nonferroelectric material as well as antiferromagnetic phase.     

Image quality improvement of digital holography by superposition of reconstructed images obtained by multiple wavelengths

A method to improve the image quality of a digital holographic reconstructed image by means of speckle reduction is proposed. The size and position of the speckles are changed according to the wavelengths to record a digital hologram. By superposing reconstructed images with different wavelengths, the effect of speckle is reduced so that the image quality is improved. Optical experiments are given to confirm the proposed method.     

Oxidation Behavior of Si-C-O Fibers (Nicalon) under Oxygen Partial Pressures from 102 to 105 Pa at 1773 k

Polycarbosilane-derived SiC fibers (Nicalon) were oxidized at 1773 K under oxygen partial pressures from 10² to 10⁵ Pa. The effect of oxygen partial pressure on the oxidation behavior of the Nicalon fibers was investigated by examining mass change, surface composition, crystal phase, morphology, and tensile strength. The Nicalon fibers were passively oxidized under oxygen partial pressures of >2.5 ×10² Pa and actively oxidized under an oxygen partial pressure of 10² Pa. Under oxygen partial pressures from 2.5 × 10² to 10³ Pa, active oxidation occurred at the earliest stage of oxidation, resulting in the formation of both a silica film and a carbon intermediate layer. Although the unoxidized core retained considerable levels of strength under the passive-oxidation condition, fiber strength was lost under the active-oxidation condition.     

Catalytic hydrogenation of linoleic acid on nickel,copper, and palladium

The catalytic activity and selectivity for hydrogenation of linoleic acid were studied on Ni, Cu, and Pd catalysts. A detailed analysis of the reaction product was performed by a gas-liquid chromatograph, equipped with a capillary column, and Fourier transform-infrared spectroscopy. Geometrical and positional isomerization of linoleic acid occurred during hydrogenation, and many kinds of linoleic acid isomers (trans-9,trans-12; trans-8,cis-12 orcis-9,trans-13; cis-9,trans-12; trans-9,cis-12 andcis-9,cis-12 18∶2) were contained in the reaction products. The monoenoic acids in the partial hydrogenation products contained eight kinds of isomers and showed different isomer distributions on Ni, Cu, and Pd catalysts, respectively. The positional isomers of monoenoic acid were produced by double-bond migration during hydrogenation. On Ni and Pd catalysts, the yield ofcis-12 andtrans-12 monoenoic acids was larger than that ofcis-9 andtrans-9 monoenoic acids. On the contrary, the yield ofcis-9 andtrans-9 monoenoic acids was larger than that ofcis-12 andtrans-12 monoenoic acids on Cu catalyst. From these results, it is concluded that the double bond closer to the methyl group (Δ12) and that to the carboxyl group (Δ9) show different reactivity for hydrogenation on Ni, Cu, and Pd catalysts. Monoenoic acid formation was more selective on Cu catalyst than on Ni and Pd catalysts.