Potentiometric sensor for sulfur oxides using NASICON as a solid electrolyte

The ac conductivity of NASICON is higher by two orders of magnitude than that of Na₂SO₄ at 1000 K. The dc polarization measurement reveals that NASICON shows sodium ion conduction even at the temperature of about 1200 K, and that the electronic transference number is of the order of 10^?5. The SO₂-O₂-SO₃ concentration cell using NASICON electrolyte gives essentially the same electromotive force as in the cell using Na₂SO₄ electrolyte because a thin layer of Na₂SO₄ if formed on NASICON at the electrodes. The high sinterability of NASICON offers a dense electrolyte without permeation of gases. The SO_x sensor using NASICON electrolyte exhibits good response and excellent selectivity against CO₂ and NO₂.     

Oxygen nonstoichiometry in high-Tc superconductor HoBa2Cu3O6+x and application of coulometric tritration

Nonstoichiometry in the perovskite-type compound, HoBa₂Cu₃O_6+x, was determined as a function of oxygen partial pressure (5 × 10⁻¹ 1 × 10⁵ Pa) in the temperature range of 8631173 K by coulometric titration using a stabilized zirconia electrolyte. Electromotive force of the cell, EMF, was measured as a function of oxygen content at constant temperature, and as a function of temperature at constant oxygen content. The perovskite-type compound was found to have a tendency to decompose into Ho₂O₃, BaO, CuO and some double-oxides at low oxygen partial pressures. Defect equilibria are discussed on the basis of the dependence of nonstoichiometry on oxygen partial pressure. Variation of the relative partial molar entropy with composition is explained in terms of a well-known defect model. A new technique which was developed for measuring the electrical conductivity of a non-stoichiometric oxide, in situ, at constant oxygen content as a function of temperature in the coulometric titration cell, is presented.     

Development of an ultrasonic inspection robot using an electromagnetic acoustic transducer for a Lamb wave and an SH-plate wave

For inspection of a storage tank and pipeline in service, the application of an automatic inspection system (nondestructive inspection robot) is desirable, because manual inspection is difficult to perfectly and exactly perform due to the enormous amount of inspection needed. However, an ultrasonic nondestructive inspection robot with a piezoelectric oscillator needs to touch only the material surface to be directly inspected using a coupling medium. That is, the material surface and the sensor must always be held by constant pressure in the vertical direction on the material side. Actually, it is difficult to overcome these problems; thus an ultrasonic inspection robot could not be widely applied. We then tried to develop an ultrasonic inspection robot with an electromagnetic acoustic transducer (EMAT) which did not require a coupling medium to inspect the circumferential pipe parts. We developed a special EMAT that could transmit and receive alternately a Lamb wave with high sensitivity and a SH-plate wave without influence by the welded part. The method by which the inspection robot turned around the direction of the steel pipe surroundings was executed by observing the tape pasted in the direction of the steel pipe surroundings with an installed CCD camera. In this report, the basic mechanism of this inspection robot and an examination of results are described.     

Global minimization of a generalized convex multiplicative function

This paper discusses an algorithm for generalized convex multiplicative programming problems, a special class of nonconvex minimization problems in which the objective function is expressed as a sum ofp products of two convex functions. It is shown that this problem can be reduced to a concave minimization problem with only 2p variables. An outer approximation algorithm is proposed for solving the resulting problem.     

A Polyhedral Approach for Nonconvex Quadratic Programming Problems with Box Constraints

We apply a linearization technique for nonconvex quadratic problems with box constraints. We show that cutting plane algorithms can be designed to solve the equivalent problems which minimize a linear function over a convex region. We propose several classes of valid inequalities of the convex region which are closely related to the Boolean quadric polytope. We also describe heuristic procedures for generating cutting planes. Results of preliminary computational experiments show that our inequalities generate a polytope which is a fairly tight approximation of the convex region.     

Permeation of high-pressure gases in poly(ethylene-co-vinyl acetate)

A previously proposed theoretical treatment to elucidate the pressure dependence of gas permeability is improved in order to apply it to polymer-gas systems in which gas dissolution follows the Flory-Huggins equation. Permeation rates of N₂, CH₄, and CO₂ in poly(ethylene-co-vinyl acetate) are measured in the pressure range below 90 atm at 10–40°C, and the effect of pressure on permeability is found for each gas. The data are analyzed using the improved method to estimate the contributions of concentration and hydrostatic pressure to the pressure dependence of permeability. The concentration effect decreases with increasing temperature, whereas the hydrostatic-pressure effect is almost independent of temperature. Crystallinity dependence of the concentration effect is discussed in connection with high-pressure permeation data of other semicrystalline polymers reported elsewhere. © 1993 John Wiley & Sons, Inc.     

Sorption,diffusion, and partial molar volumes of C4 hydrocarbons in rubbery polymers

Sorption and dilation isotherms and diffusion coefficients for seven hydrocarbons (n-butane, isobutane, 1-butene, cis-2-butene, trans-2-butene, isobutylene, and 1,3-butadiene) in two rubbery polymers, 1,2-polybutadiene (PB) and poly(ethylene-co-vinyl acetate) (EVAc), were measured at 25°C. Dissolution parameters (Henry's law coefficient and Flory-Huggins interaction parameter), partial molar volumes, and diffusion coefficients were determined. PB exhibited greater affinity and lower diffusivity than EVAc to the C₄ gases, although the gases showed nearly the same partial molar volumes in the two polymers. The diffusivity of such elongated molecules as trans-2-butene in both polymers was higher than that of bulky molecules with similar partial molar volume, such as cis-2-butene and isobutylene. Pressure-dependent permeabilities of PB and EVAc films to the hydrocarbons were predicted and discussed based on the dissolution parameters and the diffusivities. © 1995 John Wiley & Sons, Inc.