Application of the Fast Fourier Transform to Impedance Analysis of Nitrogen - Titanium-Dioxide and Lanthanum-Trifluoride Electrodes.

A study is presented of the utility of pulse derived waveforms for use in impedance analysis of electrochemical systems. Factors to be considered in optimization of pulse duration and also in the proper implementation of the FFT are discussed. Impedance results are presented for model circuits and for two nonfaradaic electrochemical systems--n-TiO\sb2 electrode in aqueous Na\sb2SO\sb4 and LaF\sb3 electrode in aqueous fluoride solution. The techniques developed were applied to model circuits composed of aperiodic elements in order to quantify the decrease in precision with increasing frequency associated with pulse type waveforms. Using 8 bit digital sampling resolution and 512 point double precision Fourier transformation, model circuit results showed a relative standard deviation of approximately 0.5% for the first 20 harmonics and less than 2.5% for all harmonics up to the 50th. Modification of the waveform by analog high-pass filtering extended the useful range to almost 2 decades. Impedance measurements by pulse-Fourier transformation agreed with steady state a.c. results to within 1% at frequencies up to 100 kHz. The technique was used to study the n-TiO\sb2/electrolyte interface via Mott-Schottky analysis. Reliable estimates were obtained for donor densities in n-TiO\sb2 crystals. Investigation of the shift in flatband potentials with pH showed nernstian behavior although the data showed a high degree of scatter. Impedance studies were made of the fluoride selective LaF\sb3 membrane electrode in order to investigate reported concentration dependent conductance. Conductance was measured over frequencies between 500 Hz and 50 kHz. Studies were made using a standard addition method and an electrode immersion method. For the standard addition method, an apparent concentration dependence was seen in the frequency regime corresponding to a hydrated surface film on the membrane. Such concentration dependence was not seen for the immersion method. Relative standard deviations obtained for conductance values were on the order of 0.5% for frequencies up to 25 kHz

Role of the Navy in a Future War

For the purposes of this discussion, it makes a great dif­ference which segment of the future we contemplate. Fortunately, the problems of the very immediate future solve themselves: We simply use what we have to cope with the initial conditions im­posed upon us by the aggressor

Logistical Planning for War

Elsewhere, you will read or hear competent discussions on the various special­ized aspects of logistical planning; so, today, I shall content myself with acquainting you with some of the broad problems which con­stitute a challenge to those who must shape logistical policies in the national military establishment

Evolutionary Aspects of Command

If our country is to place justified reliance in its Armed Services, the proven standards of military character can never be relaxed. If Service-wide emphasis on leadership and Command is diluted, our Services will find it difficult, if not impossible, to live up to the proud record of the past

In My View

I read with interest the thoughtful article by Capt. Mark Light on “The Navy’s Moral Compass” (Naval War College Review, Summer 2012). Indeed it is a mystery to me why so many commanding officers, knowing what is at stake, hazard their careers by indulging in unprofessional behaviour

The Foundations of Future Navy Planning

Much has been written about planning, and there is good machinery now in existence at all levels for its accomplishment. Workable formats, techniques, procedures, and organizations for planning have evolved under the pressures of war and in the at­mosphere of joint effort