A novel electrochemical method for simultaneously measuring diffusion coefficient and ion transference number

This paper introduces a new method to estimate the diffusion coefficient and transference number of a salt or an electroactive ion in a solution with little or no supporting electrolyte. The above two parameters can be obtained from a single potential step experiment without previous knowledge of either one. It would appear that the method could also be used in the study of ion transport in a high viscosity solvent or a solid electrolyte. (C) 1998 Elsevier Science S.A.

Studies on the PTC/NTC effect of carbon black filled low density polyethylene composites

The positive temperature coefficient (PTC) and negative temperature coefficient (NTC) effect of carbon black (CB) filled low density polyethylene (LDPE) composites was studied using electrical resistivity spectra, DSC, tensile mechanical analysis (TMA) and small-angle X-ray scattering (SAXS) techniques. The three LDPEs used have a similar crystallinity and different melting index (MI). The experimental results indicate that the CB has no significant effect on the crystallinity and the long spacing of crystalline domains of LDPE. Based upon the TMA and dynamic elastic modulus spectra, it can be concluded that the PTC effect is related to the thermal expansion of the polymer matrix, and the NTC effect is caused by a decrease of the elastic modulus of the polymer at high temperatures. The NTC effect can be reduced by enhancing either the elastic modulus or the interaction between carbon black and matrix. (C) 1997 Elsevier Science Ltd.

Dependence of linear electro-optic coefficient on difference in the atomic sizes in zinc blende crystals

Covalent radii of the bonding elements have strong effects on the linear electro-optic coefficients of zinc blende crystals; these effects can be quantitatively determined by investigating the relation between the difference in the atomic sizes rho and the magnitude of the linear electro-optic tensor coefficient r(41). It is interesting to note that for the same cation Zn2+, Ga3+, or In3+ the magnitude of r(41) increases with increased covalent radius of the bonded anion r(beta). Especially with the increasing tendency of the parameter rho, the magnitude of r(41) of crystals that have a same cation will increase suddenly when the value of r(beta) becomes larger. (C) 1997 Academic Press.

Study on relationship between partition coefficient of compounds and topological indices

In this work, the A(m) indices and the molecular connectivity indices of fifty aromatic compounds have been calculated, and applied for studying on relationship between partition coefficient and structure of aromatic compounds. The results demonstrate that the property of compounds can be described better with revisionary A(m) indices.

Calculation of the nonlinear optical coefficient of the NdAl3(BO3)(4) crystal

For the first time, we present the calculation of the nonlinear optical coefficient of the NdAl3(BO3)(4) (NAB) crystal from a systematic and quantitative standpoint. Based on the dielectric theory of complex crystals and the Levine bond charge model, the method of calculation of the second-order nonlinear optical tensor coefficients of complex crystals has been given systematically. The chemical bond parameters and linear and nonlinear susceptibilities of the NAB crystal have been calculated in detail, and the calculated value of d(11)(NAB) is -5.81 x 10(-9) esu, which agrees with the measured value of 4.06 x 10(-9) esu.

Small angle X-ray scattering study of structural parameters of the aggregated state in polyamide 1010+BMI

The structural parameters of the aggregated state in the polyamide PA1010 and N,N'-bismaleimide-4,4'-diphenyl methane (BMI) system were computed by means of the desmearing intensity from SAXS and using the concept of the distance distribution function. The results revealed that the parameters Q, I(0), l(c) and L decreased with the increase BMI component, whereas O-s increased. The particle dimension Z for different BMI contents was less than 13.2 nm, and the maximum value of the distance distribution function P(Z) was found to be in the range Z = 6.5-7.0 nm.

SMALL-ANGLE X-RAY-SCATTERING STUDY ON THE INTERFACE IN BLOCK-COPOLYMERS WITH FRACTAL PROPERTIES

The interface thickness in two triblock copolymers were determined using small-angle x-ray scattering in the context of the theory proposed by Ruland. The thickness was found to be nonexistent for the samples at three different temperatures. By viewing th

STUDY ON MEASUREMENT OF DIFFUSION-COEFFICIENT OF LI ATOM IN LIQUID ALUMINUM

The tess potential-concentration curve was first applied to measure the concentration of an alloy. Attempt to use the V-c curve of Al-Li alloy in measuring the diffusion coeffictent of Li atom in liquid aluminium with anode chronopotentiometry at 720℃, was made and D_(Li/Al=4.94×10~(-5)cm~2·s~(-1) was obtained. The value is well consistent wish the theoretical value, D_(Li/Al)=4.85×10~(-5)cm~2·s~(-1) in terms of Stokes-Einstein equation.

The effects of random surface waves on the steady Ekman current solutions

The response of near-surface current profiles to wind and random surface waves are studied based on the approach of Jenkins [1989. The use of a wave prediction model for driving a near surface current model. Dtsch. Hydrogr. Z. 42,134-149] and Tang et al. [2007. Observation and modeling of surface currents on the Grand Banks: a study of the wave effects on surface currents. J. Geophys. Res. 112, C10025, doi:10.1029/2006JC004028]. Analytic steady solutions are presented for wave-modified Ekman equations resulting from Stokes drift, wind input and wave dissipation for a depth-independent constant eddy viscosity coefficient and one that varies linearly with depth. The parameters involved in the solutions can be determined by the two-dimensional wavenumber spectrum of ocean waves, wind speed, the Coriolis parameter and the densities of air and water, and the solutions reduce to those of Lewis and Belcher [2004. Time-dependent, coupled, Ekman boundary layer solutions incorporating Stokes drift. Dyn. Atmos. Oceans. 37, 313-351] when only the effects of Stokes drift are included. As illustrative examples, for a fully developed wind-generated sea with different wind speeds, wave-modified current profiles are calculated and compared with the classical Ekman theory and Lewis and Belcher's [2004. Time-dependent, coupled, Ekman boundary layer solutions incorporating Stokes drift. Dyn. Atmos. Oceans 37, 313-351] modification by using the Donelan and Pierson [1987. Radar scattering and equilibrium ranges in wind-generated waves with application to scatterometry. J. Geophys. Res. 92, 4971-5029] wavenumber spectrum, the WAM wave model formulation for wind input energy to waves, and wave energy dissipation converted to currents. Illustrative examples for a fully developed sea and the comparisons between observations and the theoretical predictions demonstrate that the effects of the random surface waves on the classical Ekman current are important, as they change qualitatively the nature of the Ekman layer. But the effects of the wind input and wave dissipation on surface current are small, relative to the impact of the Stokes drift. (C) 2008 Elsevier Ltd. All rights reserved.