Finite-element analysis of edge resonance in a semi-infinite elastic plate

A finite-element analysis is presented for reflection of the fundamental symmetric Lamb wave at the free edge of a semi-infinite elastic plate. It is shown that the edge resonance phenomenon is very sensitive to the value of Poisson's ratio. For a smaller value of Poisson's ratio, this phenomenon occurs at a lower frequency and the solutions vary more rapidly with frequency.     

Acrylamide content of commercial frying oil

After Swedish researchers reported that heated foods such as potato chips and French fries contain acrylamide, the potential for health damage resulting from the consumption of these foods became a widespread concern. Used frying oils collected from food manufacturing companies were subjected to acrylamide determination using GC/MS-SIM, but the compound was not detected. Thus, we conclude that frying oil used in deep frying would not contaminate foodstuffs with acrylamide and that the recovered oil, much of which is used as a component of animal feeds, would be safe for livestock. Model experiments heating oil at 180 degrees C suggested that no acrylamide was formed either from a mixture of major amino acids exuded from frying foodstuffs and carbonyl compounds generated from oxidized oil, or from oil and ammonia generated from amino acids.     

Tunable light propagation in photonic Crystal coupler filled with liquid Crystal

We propose a new photonic crystal coupler-type optical switch which consists of a triangular lattice of air holes filled with liquid crystal (LC). This switch utilizes the decoupling nature. In order to utilize a large refractive index change of LC, /spl pi/ phase-shifted larger air holes are introduced into the core region, compared to the cladding region. In our structure, all air holes are filled with LC and selective injection of LC is not required. By changing the orientation of the applied field, the coupling state changes decoupling from perfect coupling, and switching operation is realized. Switching operation of the present switch is confirmed by the two-dimensional finite-element method (FEM), and also preliminary three-dimensional calculations confirm the two-dimensional FEM results.     

Chloride ion influencing potential oscillation generated by formaldehyde oxidation

The effect of chloride ions (10⁻⁷ to 10⁻¹ M) on the potential oscillation generated by the oxidation of formaldehyde is investigated with polycrystalline platinum at 315 K in a sulfuric acid solution containing 0.1 M formaldehyde. When the chloride ion concentration is 10⁻⁵ M or lower, between the two current regions for the appearance of relaxational oscillations, a large-amplitude trapezoidal oscillation appears, which is alternately accompanied by a relaxational one at a lower current. At a still lower current, the relaxational oscillation changes to a sinusoidal one, which then produces a well-known chaos. When the chloride ion concentration is between 10⁻⁴ and 3 × 10⁻⁴ M, the relaxational oscillations disappear and the alternating oscillation shows chaos, the properties of which are different from those of the chaos already stated. When the chloride ion concentration is 10⁻³ M or greater, a simple large-amplitude trapezoidal oscillation prevails without alternation with the relaxational one, along with much less chaos. The surface adsorption state during the various observed oscillations is discussed on the basis of voltammograms measured at various chloride ion concentrations.     

Virtual boundary method for the analysis of elliptically cross-sectional photonic-crystal fibers with elliptical pores

This paper introduces a new semianalytical method for the analysis of propagation characteristics of elliptically cross-sectional photonic-crystal fibers (PCFs) with elliptical pores. This method known as a virtual boundary method (VBM) is based on the equivalency between an actual PCF and a three-layered, transversely inhomogeneous waveguide. The complicated refractive-index profile of the PCF is written as a double Fourier series, and an approximate separable wave equation is found in an elliptical coordinate system for the longitudinal field components. The exact solution to the derived equation is expressed in terms of higher order transcendental functions, such as regular and irregular Coulomb-wave functions and Mathieu functions. After having expressed all the field components, boundary conditions are imposed on the boundaries, and then, a transcendental equation for the propagation constant is derived, which is solved numerically. The validity of the method is ensured by comparing various quantities, such as effective indexes, modal birefringences, and electromagnetic field distributions, with those from an accurate full-vector finite-element method (FEM) simulator, showing relatively good agreement between the results. The method correctly confirms some of the unique PCFs' properties, such as strong localization of light within the fiber and enhancement of modal birefringence as a function of the topology of hole arrangement.     

Cobalt-based bulk glassy alloy with ultrahigh strength and soft magnetic properties

Bulk metallic glasses--formed by supercooling the liquid state of certain metallic alloys--have potentially superior mechanical properties to crystalline materials. Here, we report a Co(43)Fe(20)Ta(5.5)B(31.5) glassy alloy exhibiting ultrahigh fracture strength of 5,185 MPa, high Young's modulus of 268 GPa, high specific strength of 6.0 x 10(5) Nm kg(-1) and high specific Young's modulus of 31 x 10(6) Nm kg(-1). The strength, specific strength and specific Young's modulus are higher than previous values reported for any bulk crystalline or glassy alloys. Excellent formability is manifested by large tensile elongation of 1,400% and large reduction ratio in thickness above 90% in the supercooled liquid region. The ultrahigh-strength alloy also exhibited soft magnetic properties with extremely high permeability of 550,000. This alloy is promising as a new ultrahigh-strength material with good deformability and soft magnetic properties.     

Compact effector optics for processing in limited physical access situations

A major advantage of fiber-optic beam delivery in laser materials processing is the ability to guide the laser power to the location where it is needed, leaving the laser itself remote and protected from the process. This is of special importance if the processing is to be performed in a hazardous environment. Particular problems are faced by the nuclear industry where weld repair and surface treatment work are required inside radioactive installations. By use of fiber beam delivery, only part of the delivery system and effector optics become contaminated, but the expensive laser system does not. However, in many cases the region where repair is required is not only radioactive but has only limited physical access, e.g., inside tubes or into corners, which prevents use of standard effector optics. We present a new design to deal with such constraints of a 2-mm outer diameter employing a hollow waveguide and gas shielding. This design is optically characterized and its performance assessed in welding and surface treatment applications. The potential of this compact effector optics in limited physical access situations is clearly demonstrated.