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  • Articles  (2,812)
  • 1975-1979  (2,812)
  • 1945-1949
  • 1979  (2,812)
  • Electrical Engineering, Measurement and Control Technology  (2,812)
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  • Articles  (2,812)
Years
  • 1975-1979  (2,812)
  • 1945-1949
Year
Journal
  • 1
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A simple method is suggested for calculation of reflection, radiation and transmission coefficients for the distributed feedback structure in the second diffraction order. The method is based on a slight difference between coefficients of reflectionR and radiationI of the surface wave for λ=λ∞ (where λ∞ is the light wavelength corresponding to a precise resonance for the grating length I→∞) and those for λ=λl (where λl is the light wavelength corresponding to the resonance for the finite grating length). The simplicity of the method makes it possible to use it for optimization of the distributed feedback structure by a number of parameters. The technique can be used in the case of thin-film and diffused waveguides for both TE and TM modes.
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  • 2
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    Optical and quantum electronics 11 (1979), S. 43-59 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Curvature of a single-mode optical fibre gives rise to two principal forms of additional transmission loss, namely transition loss and pure bend loss. The transition loss and the associated ray radiation, which have been observed at the beginning of a bend, can be satisfactorily explained by a modified coupled-mode theory. The radiation modes are represented by a quasi-guided mode having an average propagation constantβ e. The introduction of a gradual change of curvature reduces the transition loss much more than the pure bend loss. Analysis of the microbending loss shows that the transition component is a maximum at a given correlation length which can be simply expressed in terms ofβ e. The contributions of both transition and bend components to the total microbend loss have been derived for the case of a randomly-curved fibre for several autocorrelation and density functions.
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  • 3
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    Optical and quantum electronics 11 (1979), S. 109-117 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A theoretical assessment is presented based on a modification of Baraff's theory in order to compare the temperature dependence of several characteristics, including breakdown voltage, excess noise factor, effective ionization rate ratio and efficiency in Ge, Si and GaAs PIN avalanche photodiodes. The temperature coefficient of avalanche breakdown voltage in a high field region is studied. Finally the response time of a PIN APD in these materials is discussed.
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  • 4
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    Optical and quantum electronics 11 (1979), S. 141-146 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The transmission of high power laser radiation through optical fibres is limited by the onset of stimulated Raman scattering (SRS). The possibility of improved transmission through the use of selective doping is discussed.
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  • 5
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    Optical and quantum electronics 11 (1979), S. 133-140 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Detection of binary images in noise is considered in the light of statistical detection theory, with particular reference to information storage systems. The different disturbances are classified into system noise and transparency noise. The receiver operating characteristics (ROC) have been obtained when the scanned binary image is corrupted by additive white Gaussian noise and multiplicative speckle. It is shown that improvement in ROC with signal-to-noise ratio (SNR) is less pronounced in the presence of speckle.
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  • 6
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    Optical and quantum electronics 11 (1979), S. 287-295 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The effect of the coherence properties of pumping and input radiations on parametric up conversion (PUC) is treated in this paper. It is shown here that the PUC depends essentially upon the coherence properties of the pumping radiation whilst it is hardly affected by the coherence properties of the input radiation. It has been found that for chaotic (Gaussian) pumping radiation with an extremely high degree of coherence the total conversion efficiency is one half of that for coherent (Poisson) pumping radiation, whilst for chaotic pumping radiation with a very low degree of coherence the PUC is much more effective. The influence of the coherence properties of pumping radiation upon the PUC is explained by the intermodal correlation effects in the nonlinear interaction.
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  • 7
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    Optical and quantum electronics 11 (1979), S. 276-277 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 8
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    Optical and quantum electronics 11 (1979), S. 283-286 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract This report summarizes the activities at the 3rd International Workshop on Optical Waveguide Theory, held at the Scuola Superiore Guglielmo Reiss Romoli, L'Aquila, Italy, on 9–11 September, 1978.
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  • 9
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    Optical and quantum electronics 11 (1979), S. 297-304 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract In the technique for measuring pulse width by two-photon absorption fluorescence, theoretical calculations indicate that one can hope to obtain a maximum contrast ratio of three between the point at which the two peaks overlap and the point at which there is no superposition. Nevertheless, this calculation has been carried out assuming that the pulse is not attenuated as it traverses the fluorescent medium. In this paper it will be shown that this attenuation gives rise to a decrease in the contrast ratio. As the fluorescence intensity is proportional to the absorption, an increase in the former will be to the detriment of the contrast ratio. We will attempt to give a criterion for the selection of experimental conditions which lead to maximum intensity without an appreciable decrease in the contrast ratio.
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  • 10
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    Optical and quantum electronics 11 (1979), S. 319-327 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The analysis of the heat spreading in the single-heterostructure GaAs-Ga1-x Al x As laser diode supplied with short current pulses (in the case, however, when the adiabatic approximation is no longer valid) at room temperature is presented in this paper. Relations are derived, describing the time-dependent temperature rise within the volume of the laser diode. The calculations are carried out for a typical SH laser diode. It turns out that in the duration of the short current pulses (t I=200 ns,j=1.5 × 104A cm−2) the increase in junction temperature of the typical SH laser diode amounts to about 6.1 K. This increase leads to an increase of about 9% in the threshold current, to a decrease of about 18% in the laser radiation intensity, and to a shift of the spontaneous radiation band and of the stimulated radiation modes of about 1.9 nm and 0.22 nm, respectively, during each current pulse.
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  • 11
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    Optical and quantum electronics 11 (1979), S. 370-372 
    ISSN: 1572-817X
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  • 12
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    Optical and quantum electronics 11 (1979), S. 373-376 
    ISSN: 1572-817X
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  • 13
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    Optical and quantum electronics 11 (1979), S. 485-495 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The correlation functions of the intensity fluctuations are calculated by use of a linearization procedure for the equations of motion which include the coupling of the counter-rotating travelling waves of the ring laser in the cases of Doppler broadening, of homogeneous broadening with a self-induced population-inversion grating, and in intermediate cases. Depending on the strength of the mode competition various stable stationary solutions exist for the amplitudes. The transition between these stable states shows phenomena closely resembling phase transitions such as critical fluctuations, critical slowing down, etc. In particular, when the system passes from the state where both modes are above threshold to the state where one mode is below threshold, the negative cross-correlation of the fluctuations also becomes critical. In the case of the transient behaviour of the ring laser in the unstable region the time development of the amplitudes and the correlation functions are described in a short-time approximation.
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  • 14
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    Optical and quantum electronics 11 (1979), S. 517-523 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Cumulative attenuation and dispersion were measured along a 11.7 km fibre link consisting of 10 spliced fibres and compared to measurements on the individual fibres. Four different procedures were used for the loss measurements, and the effect of transient losses has been investigated. Good agreement was obtained between predicted and measured losses in the link provided transient losses due to high-order modes were eliminated in the individual measurements. Pulse dispersion measurements were made without the use of any mode scrambler. The cumulative dispersion measurements clearly showed a significant correlation between non-adjoining fibres, and the observed pulse width exhibited more of a linear than a square root dependence on length.
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  • 15
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    Optical and quantum electronics 11 (1979), S. 541-550 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The problem of pulse shaping and sensitivity to timing errors in optical fibre data communication is considered. The performance of the overall transmission system is the average probability of error, which is computed for intersymbol interference, thermal noise, and shot noise in avalanche photodiodes. An analysis of the immunity to small sampling errors of various Nyquist pulses indicates useful design criteria.
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  • 16
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    Optical and quantum electronics 11 (1979), S. 558-560 
    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 17
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    Optical and quantum electronics 11 (1979), S. 103-108 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The dependence of quadratic nonlinear optical processes on intermodal correlations is treated in this paper. It is shown here that the bunching or antibunching between individual modes can considerably affect the rate of the nonlinear process. This is demonstrated by two examples, namely second harmonic generation and parametric generation from quantum noise.
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  • 18
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    Optical and quantum electronics 11 (1979), S. 71-86 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A combined pulse amplitude modulation (PAM) and pulse position modulation (PPM) technique is proposed and investigated as a feasible solution of the problem of line encoding in optical fibre communication systems. The basic idea is that of exploiting PAM and PPM jointly, to give rise to three different waveforms in one signalling period, without resorting to more than two signal levels. Some evaluations of the behaviour of this signalling format are reported in terms of coding efficiency, spectral density, timing information, and error probability. Alternative receiving schemes are also devised to improve system performance.
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  • 19
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    Optical and quantum electronics 11 (1979), S. 97-101 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A diode laser system for automatic monitoring of SO2 along a 60 m atmospheric path is reported. The laser is wavelength modulated and is used to obtain i.r. absorption spectra from the measurement path. These spectra are automatically correlated with reference spectra obtained simultaneously from a calibration cell. The minimum detectable SO2 concentration is at present around 100 ppb.
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  • 20
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    Optical and quantum electronics 11 (1979), S. 119-132 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The evolution of ultra-short pulses from noise in a passively mode-locked solid-state laser is treated. The statistical properties of the laser field, such as correlation functions, the mean pulse shape and its fluctuations, are investigated. The maximum intensity and the width of the pulse train are estimated taking account of the amplification saturation. As an example of the application of the results to non-linear optics, TPF traces are calculated.
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  • 21
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    Optical and quantum electronics 11 (1979), S. 147-151 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A simple perturbation theory has been used to study the characteristics of low-V, step-index optical fibres with a dip in the centre of the refractive index profile. Analytical expressions have been derived for the cut-off frequency and propagation constant of an arbitrary mode on such a fibre. In particular, it has been shown that even when the dip is quite large, the perturbation theory results for the propagation constant of the fundamental mode and cut-off frequency of the second mode are virtually indistinguishable from exact numerical results calculated by series expansion techniques.
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  • 22
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    Optical and quantum electronics 11 (1979), S. 173-183 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We present a straightforward geometric optics method to calculate the power attenuation induced by a circular bend in the axis of a multimode optical waveguide. The method involves tracing of rays and use of generalized power transmission coefficients. Both slab and fibre waveguides (with either step-index or parabolic core profiles) have been considered; the source has been assumed to be Lambertian.
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  • 23
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    Optical and quantum electronics 11 (1979), S. 197-203 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Both bound and tunnelling rays exist in multimode graded fibres which do not have circular symmetry; however, the fraction of energy in the tunnelling rays is generally less than that in a similar circular fibre, especially for near-parabolic profiles. For a large class of non-symmetric profiles, no tunnelling rays can propagate.
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  • 24
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    Optical and quantum electronics 11 (1979), S. 237-251 
    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The cross-sections of practical optical fibres do not have perfect circular symmetry. The appropriate mathematical representation of the refractive index profile is discussed and it is shown that the basic power law profile in circular fibres should be replaced by a grading functionF which is a homogeneous function of thex andy coordinates. Multimode optical fibres of this type are analysed using geometric optics. General properties of ray paths are described. The fundamental quantities of interest in fibre optics (power acceptance, ray transit time, impulse response) are shown to depend on the degree of homogeneity ofF but not on its specific form. Thus, fibres need not have circular symmetry in order to retain the desirable properties of the circular power law fibres. Ray paths and classifications are analysed in detail for elliptical, parabolic-index fibres. Splicing losses are examined and are shown to be not drastically dependent on deviations from circular symmetry.
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  • 25
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    Optical and quantum electronics 11 (1979), S. 253-264 
    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The use of differential lidar for measuring SO2 in plumes from fossil fuelled power stations is examined. The potential of the technique is investigated for the measurement of SO2 close to power station stacks and in situations where the long range transport of emissions is important. Detection limits are discussed as a function of range and spatial resolution and it is shown theoretically that concentrations as low as 10 ppb at a range of 2 km should be measurable. Details of a prototype, computer controlled, differential lidar based on a tunable dye laser are given and its mode of operation described. Results from field experiments carried out at Drax power station in Yorkshire (UK) and Fawley Power Station in Hampshire (UK) are presented. For plumes of small diameter a deconvolution technique has been applied to obtain better spatial resolution of the plume structure.
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  • 26
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    Optical and quantum electronics 11 (1979), S. 305-317 
    ISSN: 1572-817X
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    Notes: Abstract Differential mode delay measurements have been performed, both for step-index and for graded-index fibres, using a sinusoidally modulated optical source. From a differential mode delay measurement, it is possible to get all the information on the fibre baseband response with or without the effect of skew rays, and in particular of leaky rays. A theoretical model of mode coupling is developed and is used for computing the baseband response for fibres where mode coupling is not negligible.
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  • 27
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    Optical and quantum electronics 11 (1979), S. 345-352 
    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We examine the statistical properties of speckle patterns in and near the far-field, produced by an ordinary optical system having a hard-edged pupil. By applying Fresnel diffraction theory, expressions for the contrast in terms of the statistical parameters of rough surfaces and the geometry of the optical system are derived and discussed. It is shown that the contrast of speckle has maxima and minima in the focal plane and also along the axis of the optical system.
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  • 28
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    Optical and quantum electronics 11 (1979), S. 353-358 
    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Pulse-code modulation of a 0.6328μm He-Ne laser by simultaneous mode-locking and coupling modulation is achieved at a bit-rate of 150 Mbits−1 using a single modulation element. Both modelocking techniques, loss modulation and phase modulation are used and compared. The phase of the output signal is stabilized by means of a phase-locked loop. The influence of the coupling modulation on the resonator energy causes a time-dependent decrease of the output signal amplitude. This effect can be compensated by controlling the coupling voltage. A calculation of the maximum available bitrate for a 2 mm bore He-Ne laser tube is given.
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  • 29
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    Optical and quantum electronics 11 (1979), S. 329-344 
    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Mode propagation characteristics of parabolic-index fibres with a homogeneous cladding are studied by using vector wave analysis. By investigating the asymptotic behaviour of the eigenvalue equations and the field components at cut-off and far from cut-off, a comprehensive and consistent scheme for the designation of the various modes is established. Strong similarities with step index fibres are found for both the mode designation schemes and the degeneracy properties among the hybrid modes as well as the TE0m and TM0m modes. This suggests that the technique employed in this paper can be applied to other types of graded-index fibres. In addition, numerical results obtained by solving the eigenvalue equations for a wide range of parameters are presented, which verify the theoretical predictions. Comparisons with the infinite-core approximation (ICA) and the field decomposition technique (FDT) are given. It is shown that neither the ICA nor FDT are applicable for modes near cut-off.
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  • 30
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    Optical and quantum electronics 11 (1979), S. 413-418 
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    Notes: Abstract We show that if the first order probability density function of height on a rough surface is assumed to be symmetrical, it can be calculated from measurements of scattered coherent light made in and near the centre of the far-field. We derive the theory of the method and present some experimental results obtained for ground glass surfaces.
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  • 31
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    Optical and quantum electronics 11 (1979), S. 419-439 
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    Notes: Abstract The generation of amplitude and phase gratings in an absorbing medium is discussed, including the effects of light polarization, population kinetics and orientational relaxation. A theory is given which describes light diffraction by a combination of an amplitude and a phase grating. It is shown that the coherent coupling effect in transient absorption measurements is solely due to the amplitude grating. Weak absorption and a low triplet yield favour diffraction of the probing beam by the phase grating in triple-beam experiments. Phase grating experiments can be performed with highly soluble absorber dyes, the absorption maximum of which is far away from the laser wavelength. Due to photoselection, diffraction by an amplitude grating depends on the polarization of the probing beam while phase grating diffraction is insensitive to this. Perpendicular polarization of the two exciting pulses prevents the buildup of a phase grating and results in light diffracted by the amplitude grating that is proportional to the transient dichroism signal as known from the common absorption relaxation.
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  • 32
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    Optical and quantum electronics 11 (1979), S. 461-463 
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  • 33
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    Optical and quantum electronics 11 (1979), S. 407-412 
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    Notes: Abstract When a rough surface is viewed in an interference microscope with tilt fringes introduced, the effect of the roughness is to reduce the average visibility of the tilt fringes. The relationship between the standard deviation of surface height and the average visibility of the tilt fringes is derived, and experimental results are presented of measurements made on ground glass surfaces using a Linnik interference microscope.
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  • 34
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    Optical and quantum electronics 11 (1979), S. 441-446 
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    Notes: Abstract The concept of the reference range, a parameter used to characterize the ranging capability of radar systems, is applied to atmospheric backscatter lidar employing direct detection and optical heterodyne receivers. Use of the reference range is suggested for system evaluation in this area.
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  • 35
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    Optical and quantum electronics 11 (1979), S. 458-460 
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  • 36
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    Optical and quantum electronics 11 (1979), S. 447-457 
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    Notes: Abstract By using a Gaussian field approximation to the fundamental mode in a single-mode fibre, a very simple formula is derived for the splice loss in the two fibres when transverse, longitudinal and angular misalignments exist simultaneously. It is shown that the effects of the three misalignments on the splice loss are more significant for step-index fibres than for parabolic-index fibres, and also that matching oil in the gap between the fibres is effective for the end separation, but produces a reverse effect for the tilt. Calculated coupling efficiency between step-index fibres is compared with the experimental data reported so far, and good agreement between them is observed.
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    Optical and quantum electronics 11 (1979), S. 464-466 
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  • 38
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    Optical and quantum electronics 11 (1979), S. 23-27 
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    Notes: Abstract Experimental and theoretical results of the determination of the quadratic electro-optic coefficients in noncentrosymmetric KH2PO4(KDP) and KD2PO4(DKDP) monocrystals are presented. The coefficientR c=R 1122-R 1111 for the X-cut crystals has been measured by a dynamic method in the a.c. electric field. The theoretical value of the coefficient has been calculated by the Kurtz-Robinson model. It has been found that the coefficientR c was less than 10×10−20m2V−2.
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    Optical and quantum electronics 11 (1979), S. 29-42 
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    Notes: Abstract The description of hologram reconstruction in the scalar Born approximation reveals that a volume hologram reconstructed outside Bragg incidence acts as a bandpass filter for the recorded spatial frequencies of the object field. The bandwidth of such a filtering arrangement as well as the band shape drawn in the spatial frequency plane are not fixed, but can be controlled by the reconstruction parameters. Using the angular spectrum representation of the fields involved, the influence of the recording and reconstruction parameters on the filtering effect is discussed. For some parameter combinations the amplitude profile of the transfer function is plotted versus spatial frequency and the corresponding spatial frequency bands are calculated.
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    Optical and quantum electronics 11 (1979), S. 61-70 
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    Notes: Abstract A high-reliability diffraction-limited atomic iodine photodissociation laser is described. It is shown that a diffraction-limited output beam is obtained when the laser pulse is extracted before the onset of gain-medium inhomogeneities caused by non-uniform deposition of the pump radiation. No degradation of the beam focusability is observed for intensities at which the final amplifier is heavily saturated.
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    Optical and quantum electronics 11 (1979), S. 87-96 
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    Notes: Abstract In this paper we investigate the possibility of using thick holograms as diffraction gratings. We compare the well-known parameters of the plane diffraction grating such as dispersion, efficiency, resolution, and others, with those for volume holograms. The calculations for the case of volume holograms are based on the theory of coupled waves. Experiments were performed with volume-phase holograms in transmission, stored in dichromated gelatine layers. The investigations show that the volume hologram fulfills two functions simultaneously. It acts as a spectral predecomposer and also as a high-resolving spectral apparatus.
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    Optical and quantum electronics 11 (1979), S. 205-215 
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    Notes: Abstract Scattering of the light beam propagating through a dielectric-slab optical waveguide occurs due to refractive index inhomogeneities of the thin film region and due to boundary irregularities of the filmsubstrate and the film-air interfaces. The quantity and direction of the scattered light are evaluated by means of a perturbation method together with the use of a stationary phase method, for a variety of correlation lengths and variances and the thin film thicknesses. The results show that for a slab waveguide of t/λ=10.0,t and λ being the thickness of thin film and the wavelength of light, the effect of refractive index inhomogeneities is pronounced in comparison with that of waveguide wall irregularities. In this case, therefore, the scattering pattern is determined mainly by the correlation length of refractive index inhomogeneities.
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    Optical and quantum electronics 11 (1979), S. 223-228 
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    Notes: Abstract The attenuation of ultrashort laser pulses by two-photon absorption is theoretically described when a dye is used as the absorbing medium. It is shown that two-photon absorption also yields an intensity stabilization of low repetition rate laser emissions without a significant loss of power. Consequently this technique is proposed for pulse attenuation and stabilization near the damage threshold of second harmonic generator crystals, and its performance is theoretically compared with other attenuation methods.
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    Optical and quantum electronics 11 (1979), S. 274-275 
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    Optical and quantum electronics 11 (1979), S. 265-273 
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    Notes: Abstract The stability of optical-fibre delay lines is assessed by means of measurements of pulse transit times in unjacketed silica-based fibres. Data obtained for the effect of longitudinal stress and temperature are used to interpret the time delays found in jacketed fibres. It is shown that the application of close-fitting plastic cabling materials results in a residual fibre stress which is both temperature and humidity dependent.
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    Optical and quantum electronics 11 (1979), S. 278-281 
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    Optical and quantum electronics 11 (1979), S. 367-369 
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    Optical and quantum electronics 11 (1979), S. 377-384 
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    Notes: Abstract A theoretical assessment is presented based on a modification of Baraff's theory in order to compare the temperature dependence of several characteristics, including breakdown voltage, excess noise factor, effective ionization rate ratio and efficiency in Ge, Si and GaAs reach-through avalanche photodiodes (RAPD). The temperature coefficient of avalanche breakdown voltage in a depletion region is studied. The response time of a reach-through APD in these materials is also discussed. Finally a comparison of the characteristics between PIN APD and RAPD is presented. The theoretical data have also been substantiated experimentally by Kanedaet al.
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    Optical and quantum electronics 11 (1979), S. 393-405 
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    Notes: Abstract Both a displacement of axis and a change in the refractive index distribution function cause mode coupling to occur between two multimode parabolic-index optical waveguides. This coupling is investigated by the coherent states method and the method of the dynamical symmetry group. Expressions for the mode coupling coefficients are obtained and their relationship to the Franck-Condon factors is emphasized. Recurrence relations for the mode overlap integrals and sum rules for the mode coupling coefficients are presented. An analogue of the Franck-Condon principle for the mode coupling coefficients is formulated. A simple geometric method for finding the most intensively coupled modes is also proposed.
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    Optical and quantum electronics 11 (1979), S. 359-366 
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    Notes: Abstract Based on a holographic approach an analysis of the ‘chirped’ grating coupler is performed. Relations for the location of a focal line of a coupled out cylindrical wave for general construction parameters are obtained. Results of the analysis have been verified experimentally.
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    Optical and quantum electronics 11 (1979), S. 1-9 
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    Notes: Abstract The quantum mechanical Langevin equations of a cavity where laser action takes place both by ordinary population inversion and stimulated Raman scattering is discussed for both single mode and multimode oscillation of the pump and Raman laser. Expressions for amplitude correlation and linewidth due to phase diffusion are obtained both for homogeneous and inhomogeneous broadening.
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    Optical and quantum electronics 11 (1979), S. 153-160 
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    Notes: Abstract The operating characteristics of an unstable resonator Q-switched Nd-YAG laser are reported and its suitability for a number of applications has been tested. At repetition rates up to 50 Hz, output energies of 150–200 mJ are obtained with a beam divergence of 0.25 mrad half-angle. Single longitudinal mode operation has been achieved either with passive Q-switching or with an active slow Q-switch.
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    Optical and quantum electronics 11 (1979), S. 161-172 
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    Notes: Abstract The intensity of coherent anti-Stokes resonance Raman scattering (CARRS) is calculated taking into account the resonant absorption of laser and anti-Stokes waves and changes in the molecule population. The resonant absorption causes an alteration of the phase of the laser wave leading to a decrease and periodic behaviour of the anti-Stokes intensity. This phase change can be compensated by the choice of a definite wave vector mismatchΔK, which determines the optimum condition for the CARRS. The optimum angle between the Stokes and the laser propagation direction and the optimum cell length are calculated. The line shape of the CARRS is discussed and used for the explanation of the observed dependence of the CARRS spectra on the laser intensity and the frequency and on the molecule number density. In the case of a O-O excitation the vibrational frequencies of the ground and the excited level are generated simultaneously in the CARRS spectra.
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    Optical and quantum electronics 11 (1979), S. 185-196 
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    Notes: Abstract Both the theoretical basis and experimental realization of the refracted near-field technique for the direct measurement of optical fibre profiles are presented. The technique requires minimal sample preparation, no computation and is applicable to both single and multimode fibres. Both the core and the cladding are profiled. After outlining the problems associated with other techniques, the use of this method for the measurement of fibre profile, numerical aperture and geometry is discussed. Leaky mode rejection and resolution are treated in detail. A fitting procedure for determining theα-value of a profile is given. The experimental apparatus is fully discussed. Results are presented to illustrate both the applicability of the technique to single and multimode fibres and also the rejection of leaky modes. The experimental sensitivity is shown sufficient to reveal an index fluctuation having a wavelength 〈 1μm and an amplitude of 〈 0.0001.
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    Optical and quantum electronics 11 (1979), S. 217-222 
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    Notes: Abstract The effect of phase and amplitude fluctuations of the pump wave on second harmonic generation and parametric amplification has been considered. Expressions for the intensity and linewidth have been obtained. In the incoherent regime, the second harmonic intensity is directly proportional to the interaction length (L) and its linewidth Δω2∼1/L. A noise pump is more effective in parametric amplification. The linewidth of the generated signal and idler waves decrease with increasing interaction length.
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    Optical and quantum electronics 11 (1979), S. 229-236 
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    Notes: Abstract We report the first experimental measurement and theoretical estimation of seventh χ eff (7) and ninth χ eff (9) order effective nonlinear susceptibilities. The correlation of ninth, seventh and fifth harmonic signal efficiencies in various phase-matched mixtures of Ar (or Xe) and sodium atoms, is experimentally investigated. Using direct and cascade processes of harmonic generation, the modulus ratio is measured for the higher nonlinearities, which allows an estimation of χ eff (7) and χ eff (9) from the lower order optical susceptibilities. Results from numerical calculations of atomic nonlinear susceptibilities up to the ninth order, accounting for the discrete spectrum and the continuum, are presented.
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    Optical and quantum electronics 11 (1979), S. 385-391 
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    Notes: Abstract A laser absorption spectrometer is described which employs a wavelength tunable diode laser in conjunction with a multipass White cell. The instrument uses absorption lines in theν 3 band of SO2 to monitor atmospheric SO2 concentrations with sensitivities as high as 0.2 parts per billion (ppb) in a laboratory system. A portable instrument with a fast response time and a sensitivity of 1 ppb is described, and the development of a highly practical field instrument, based on pyroelectric detectors, is discussed.
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    Optical and quantum electronics 11 (1979), S. 467-469 
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    Optical and quantum electronics 11 (1979), S. 479-484 
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    Notes: Abstract An approximate formula is given for the probability distribution of integrated speckle pattern that results from a mixture of coherent and diffused light. This is a modified version of a formula originally used by Horáket al. in the context of photoelectron counting theory. The modification is based on introducing a new parameter that accounts for the lack of perfect mixing between the two waves due to temporal or spatial misalignments.
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    Optical and quantum electronics 11 (1979), S. 471-478 
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    Notes: Abstract The behaviour of light beams in nonlinear media (self-focussing of optical beams as well as self-modulation and transmission of optical pulses) is considered in the case when the nonlinear polarization contains susceptibilities of third- and fifth-order. The soliton solutions are obtained for the nonlinear equations deduced.
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    Optical and quantum electronics 11 (1979), S. 497-505 
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    Notes: Abstract This paper describes an experimental method to detect quantitative changes of both refractive index and diameter of unclad dielectric fibres, such as fused silica fibre and nylon 6 fibre, due to tensile stress. The technique employed here is based on the variation in the position of a fringe in back-scattered light, which is generated when a laser beam is incident at a right angle to the axis of the fibre. This procedure makes it possible to measure refractive index, diameter and ellipticity to within an accuracy of 0.048%, 2.6% and 0.05%, respectively.
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    Optical and quantum electronics 11 (1979), S. 507-516 
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    Notes: Abstract The characteristics of various models of refractive-index profile are examined. Four models are considered: (1) power-law profile, (2) truncated even polynomial profile, (3) truncated all-term polynomial profile, (4) Gauss-Chebychev approximation. The characteristics of the various models are examined with particular reference to the ray-delay times and the shape of the impulse response. The results show that models (1) and (2) are limited in their usefulness in representing practical profiles, while the approximation (4) is easily applied to a variety of practical profiles.
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    Optical and quantum electronics 11 (1979), S. 525-539 
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    Notes: Abstract Fields in the cores of graded non-circular optical fibres are analysed using a new method. It is shown that the scalar wave equation in elliptical co-ordinates can be separated for many realistic non-circular profiles, thus allowing calculation of fields by a double WKB method, The boundaries separating oscillatory and evanescent regions are found by simple analysis of algebraic equations, This method supports and further explains previous analysis which used geometric optics.
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    Optical and quantum electronics 11 (1979), S. 551-554 
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    Notes: Abstract Limiting currents were measured for the electropolishing of horizontal copper electrodes facing downwards in phosphoric acid solution under natural convection conditions. The electrode diameter was varied from 1–6 cm and the phosphoric acid concentration between 8–12 M. The limiting current was found initially to decrease with electrode diameter and then to remain constant with further increase. Within the concentration range of phosphoric acid used, the limiting current was found to decrease with phosphoric acid concentration. Mass transfer data was found to agree closely with the equation $$(Sh) = 0 \cdot 18[(Sc)(Gr)]^{0 \cdot 33} for 1 \cdot 1 \times 10^9〈 (Sc)(Gr)〈 2 \cdot 46 \times 10^{11} .$$
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    Journal of applied electrochemistry 9 (1979), S. 7-13 
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    Notes: Abstract An experimental programme in which aluminium-copper alloys were electroplated from alkyl benzene/ AlBr3 electrolytes is described. The investigation showed that Al-Cu alloys (0–3.5 wt% Cu) can be plated onto steel and that the resulting coatings are bright, adherent and less porous than equivalent coatings of pure aluminium. The composition of the cathode deposits can be readily controlled by using Al-Cu anodes of specified copper content. About half the copper dissolved from the anodes is transferred to the cathode, the remainder being precipitated from the electrolyte as CuBr. Coating composition varies with current density and this parameter can also be used to control the process. In a parallel investigation, potential differences between aluminium and a number of other metals (Zn, Pb, Cd, Sn, Cu, Ag) were measured. Potential differences in the alkyl benzene electrolytes were found to be 10–30 times less than in aqueous electrolytes which indicates that the alkyl benzenes should be useful for plating other alloys in addition to those of aluminium and copper.
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    Journal of applied electrochemistry 9 (1979), S. 29-35 
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    Notes: Abstract The investigation is concerned with the drop of current efficiency (CE) of copper deposition under pulsed current conditions. A mathematical model which is based on different charge transfer rates between the following two reactions, (1) $$Cu^{2 + } + e \to Cu^ + $$ and (2) $$Cu^ + + e \to Cu$$ has been formulated to describe the behaviour of a Cu/CuSO4 system under pulsed current conditions on a rotating disc electrode. The results indicate that the CE drops continuously as the difference between the exchange current densities of the two reactions increases. The exchange current densities of Reactions 1 and 2 were estimated to be 0.034 mA cm−2 and 0.024 mA cm−2, respectively. Prediction of CE using the mathematical model agreed to within 3.5% with experimental data over a range 80.4–93.7%.
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    Journal of applied electrochemistry 9 (1979), S. 37-41 
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    Notes: Abstract Rates of mass transfer for the cathodic reduction of potassium ferricyanide at a particulate bed of graphite supported on a horizontal nickel disc were studied under H2-evolving conditions. Variables studied were: H2 discharge rate, particle size and bed height. The rate of mass transfer was found to increase to a maximum in the presence of the bed which was about 4.5 times compared to that of the supporting disc. The rate of mass transfer was found to increase with H2 discharge rate, particle size and bed height. Polarization was measured for beds of different particle size and it was found that the presence of the bed increased polarization especially at relatively high current densities, the increase in polarization was independent of particle size of the bed. Comparison with an O2-evolving particulate electrode was made and possible practical applications were pointed out.
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    Notes: Abstract Zinc deposits contaminated with lead were found to have characteristic morphologies and orientations which were dependent on the amount of lead present in the zinc deposits and to a lesser extent on the presence of other impurities such as antimony and glue in the deposits. Increasing lead in the zinc deposits progressively changed the orientations from (1 1 2) to (1 0 1) to (1 0 0) to finally a poorly crystalline (0 0 2) structure. The lead content of the zinc deposits was dependent on both the concentration and chemical composition of lead added to the electrolyte, the current density and also on the presence of antimony or glue in the electrolyte. A relationship was shown to exist between the effect of lead contamination on zinc deposit morphology and orientation and on the overpotentials associated with zinc electrodeposition in the presence of lead.
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    Journal of applied electrochemistry 9 (1979), S. 15-20 
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    Notes: Abstract A comparison of calculated and experimental parameters for the packed-bed reactor working with recirculation of the electrolyte is given. A simple mathematical model was applied and the applicability of the relation $$c = c^0 {\text{ exp(}} - k_1 At/V{\text{) for }}V_c \ll V_R $$ was tested. For the investigated reactor a dimensionless relation has been established from experimentalI-E curves for the single pass mode $$(Sh) = 0 \cdot 5(Re)^{0 \cdot 7} (Sc)^{0 \cdot 33} .$$ For pure practical engineering requirements these two equations together give us a satisfactory way of predicting the concentration-time dependence.
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    Journal of applied electrochemistry 9 (1979), S. 21-27 
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    Notes: Abstract The voltage drop and current distribution in a chlorine-caustic cell using an anode with a titanium substrate was estimated for several geometric arrangements of the titanium mesh and associated supports and conducting elements. The cell was modelled with a three-dimensional grid network and Kirchoff's law applied to each node. Results were applied to the design of anodes for a full-scale cell which was put in operation and showed the anticipated voltage improvement.
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    Journal of applied electrochemistry 9 (1979), S. 43-53 
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    Notes: Abstract The electrode kinetics of spongy and dendritic zinc deposition were studied in the presence of three inhibitors (lead acetate, tetrabutylammonium bromide and benzalacetone). It was shown that these additives increase the cathodic overvoltage, decrease the current efficiency, eliminate multiple steady states in acid electrolytes, and modify the impedance diagrams. Such changes in electrode kinetics were interpreted in terms of weaker autocatalytic adsorption of metal cations and enhanced hydrogen adsorption. It was also shown that a pH decrease had a similar effect on these reaction rates. It was concluded from very low frequency impedance measurements that the additives give rise to an accelerated nucleation rate ensuring a faster renewal of active growth sites.
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    Journal of applied electrochemistry 9 (1979), S. 147-153 
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    Notes: Abstract Poly(4-vinyl pyridine-co-methyl methacrylate), which is soluble in water in its protonated form and insoluble as a neutral molecule, has been synthesized and introduced into an acid bath for copper deposition. Potential-sweep investigations have shown that the copolymer affects the electrocrystallization of copper on graphite by delaying nucleation even before conditions for codeposition of the polymer are reached. At overpotentials at which the diffusion limiting current of copper is reached and hydrogen evolution starts, alkalinity at the electrode surface causes precipitation of the polymer. This is found to affect the resistivity of the deposit. Electron microscopy revealed that under such conditions copper is deposited in the form of globular particles, the size of the globules being in the micron range and decreasing with increasing overpotential.
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    Journal of applied electrochemistry 9 (1979), S. 171-181 
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    Notes: Abstract The influence of HCl on the anodic behaviour of Fe and Ni in DMSO/1 M H2SO4 depends on the water content of the solution. In completely anhydrous solutions the current density at the same voltage is in no case enlarged and pittings are certainly not observed. At water contents in the range 2–50% the two metals show pitting corrosion, but the current density at the same voltage is much lower than in aqueous solutions. The true anodic polarization measured with an interrupting potentiostat is very high and probably caused by a salt layer. It may be the source of the inhibition effect of DMSO. Fe in DMF/1 M H2SO4 has a similar anodic behaviour depending on the HCl concentration, but the polarization in this anhydrous solvent is much lower. The inhibition effect also seems to be lower.
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    Journal of applied electrochemistry 9 (1979), S. 191-199 
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    Notes: Abstract Available data are assembled on the critical potentials for various metal-environment systems below which stress corrosion cracking (SCC) does not occur. Such data can be used practically to avoid SCC by use of cathodic polarization, inhibiting ions or by employing galvanic couples. The slow drift of the corrosion potential before coincidence with the critical potential explains in part the observed induction times for SCC. The relative positions of the two potentials with respect to each other explains the susceptibility or resistance to SCC of various metals in a variety of chemical media. Several models proposed to explain the SCC mechanism are reviewed in the light of the present evidence.
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    Journal of applied electrochemistry 9 (1979), S. 141-141 
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    Journal of applied electrochemistry 9 (1979), S. 117-123 
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    Notes: Abstract A trickle bed electrochemical reactor has been developed for the production of dilute alkaline peroxide solutions by reduction of oxygen. Oxygen gas and sodium hydroxide flow concurrently downward through a cell which consists of a thin packed cathode bed of graphite particles separated from the anode plate by a porous diphragm. Current flows perpendicular to the flow of electrolyte. The effects of current density, oxygen pressure and flow rate, electrolyte concentration and flow rate, graphite particle size, bed thickness and length were investigated. In 2 M NaOH peroxide solutions of 0.8 M have been produced at 60% efficiency with current densities of 1200 A m−2 and cell voltages of 1.8 V. A bipolar cell stack consisting of five cells has been tested.
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    Journal of applied electrochemistry 9 (1979), S. 155-160 
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    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The quantitative analysis of the morphology of dislocation-free {211} iron surfaces during electrochemical dissolution and measurements of distances and directions of monatomic steps provide information about the rates and potential dependences of three different elementary processes involving iron atoms bound to the lattice in three geometrically and energetically different states. The interaction of the three elementary processes explains the well-known anomalies of the kinetics of the iron electrode. A statistical analysis of the step distances is given.
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    Journal of applied electrochemistry 9 (1979), S. 161-169 
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    Notes: Abstract The influence of underpotential Pb- and Tl-adsorbates at rotating disc silver single crystal surfaces (111), (100), and (110) on the kinetics of ‘outer-sphere’ and ‘inner-sphere’ redox reactions was studied in 0.5 M NaClO4 and 0.5 M Na2SO4 solutions (2 〈 pH 〈 4) containing Fe3+, Ce4+ or NO 3 − ions. While the reduction of Fe3+ and Ce4+ under limiting diffusion conditions was not affected by the metal adsorbates, a strong inhibition effect correlated to the degree of Pb- or Tl-adsorbate coverages was observed in the case of the reduction process in the presence of NO 3 − ions. The results are interpreted in terms of a strong chemical interaction between the reactant or a reaction intermediate and the silver substrate, taking into account the previously proposed superlattice structures of the metal adsorbates, depending on the orientation of the silver single crystal surfaces and on the underpotential range.
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    Journal of applied electrochemistry 9 (1979), S. 183-189 
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    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The electrochemical reaction Ni(OH)2=NiOOH+H++e occurring under potentiodynamic conditions in 1 N KOH using complex triangular potential sweep revealed the existence of non-equilibrium effects of both reactant and products which cause the splitting of the anodic current peak already known. By a suitable choice of the perturbation variables, the rate of the chemical change the Ni(OH)2 species undergoes can be estimated. The reaction presenting the nickel hydroxide electrode is interpreted as two parallel electron transfer steps coupled to two chemical reactions through a square-type reaction model.
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    Journal of applied electrochemistry 9 (1979), S. 201-207 
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    Notes: Abstract The inhibition effect of normal aliphatic acids with 6–10 carbon atoms in the molecule has been investigated in aerated solutions of 0·05m sodium sulphate at 6–12 pH. It was found that the depolarization of oxygen is not the only factor responsible for the passivation of iron in aerated solution containing a critical concentration of the inhibitor. The inhibiting ability of aliphatic acids in Na2 SO4 solutions is brought about by a synergistic action of dissolved oxygen and of molecules (or anions) of the aliphatic acid.
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    Journal of applied electrochemistry 9 (1979), S. 219-232 
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    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The electrodeposition of hard gold in layers of 2 μm was investigated. The electrolyte was an acid citrate bath (pH 3·5) with cobalt as an additive. A flow cell allowed a controlled variation of the hydrodynamic conditions. The following features were examined quantitatively in the experiments: the current efficiency for gold deposition (10–30%), the carbon and cobalt content, as well as the porosity of the deposits, and the morphology [by scanning electron microscope (SEM)]. Above 50 mA cm−2 the deposition of gold and to a minor extent the incorporation of cobalt become mass transport limited (with certain complications resulting from the complex nature of the diffusion layer). The influence observed below 50 mA cm−2 seems to be due to the synergic effect of the transport controlled reduction of dissolved oxygen. A simple qualitative model for the incorporation of carbon is proposed. The substantial decrease in current efficiency observed upon the addition of cobalt to the bath is probably causedboth by a decrease of the hydrogen overpotential and by an increase of the overpotential for gold deposition. From the viewpoint of technical application, the most relevant result, is the substantial decrease in porosity at decreasing current density (c.d.) and increasing flow rate.
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    Journal of applied electrochemistry 9 (1979), S. 243-253 
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    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Flow-dependent corrosion phenomena can be studied in the laboratory and on a pilot plant scale by a number of methods, of which the rotating disc, the rotating cylinder, the coaxial cylinder and the tubular flow test are the most important. These methods are discussed with regard to mass transfer characteristics and their applicability to flow-dependent corrosion processes and erosion corrosion. To exemplify the application of such methods to materials selection for seawater pumps, corrosion data of non-alloyed and low alloy cast iron are presented.
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    Journal of applied electrochemistry 9 (1979), S. 321-327 
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    Notes: Abstract The square-type reaction scheme proposed to interpret the behaviour of the nickel hydroxide electrode in KOH solutions under non-equilibrium conditions must include electrochemical as well as chemical crossed reactions between the different transient species. These reactions are evidenced by means of the triangularly-modulated triangular potential sweep technique. The contribution of the crossed reactions in the square-type reaction scheme becomes more relevant as the KOH concentrations decreased in the presence of K2SO4 supporting electrolyte.
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    Journal of applied electrochemistry 9 (1979), S. 291-299 
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    Notes: Abstract The efficiency of laboratory type sodium-sulphur cells, especially the utilization of reactants, is critically dependent upon the design of the sulphur electrode. The satisfactory rechargeability of a new design, based on a graduated electronic resistance inside the carbon fibre matrix is analysed in terms of two models: (a) predominant influence of potential distribution, (b) predominant influence of free flow in open spaces. Experimental results in favour of model (a) are discussed. The potential distribution of the new design is computed using appropriate assumptions for the one-phase region and compared with that in the absence of a graduated electronic resistance. It appears that the improved rechargeability can be explained by the different potential distribution.
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    Journal of applied electrochemistry 9 (1979), S. 301-305 
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    Notes: Abstract OH radicals, produced in aqueous acid media by the electrogenerated system Fe(II)/H2O2, promote the oxidation of polymethylated benzenes. Under our experimental conditions only one -CH3 group was oxidized to -CHO. A reduction of aldehyde to alcohol by.OOH radicals was shown to occur when H2O2 was produced in excess over Fe(II). In hydrochloric acid or in perchloric acid with Cl− ions added, a remarkable increase of the yields was observed. The results are discussed on the basis of the kinetic parameters of the reactions involved in the process.
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    Journal of applied electrochemistry 9 (1979), S. 315-320 
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    Notes: Abstract The behaviour of copper silicide and of some iron silicides with different silicon contents to lithium deposited electro chemically from organic solvents is investigated. The silicide phases show marked differences. Whereas with copper silicide a time-dependent alloy formation with lithium is observed, the iron silicides exhibit a behaviour ranging from no alloy formation to very rapid alloy formation (depending on the silicon content). The alloyed lithium may be recovered during oxidation with high yields. If some lithium is deposited at the supporting grid of iron silicide electrodes with high silicon content, a rapid surface diffusion with alloy formation is observed.
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    Description / Table of Contents: Abstract The study of the electrochemical reduction of CuS and CuO membrane electrodes in 20 vol% propylene carbonate/80 vol% 1, 2-dimethoxyethane shows that the reaction proceeds via insertion of electrons and lithium ions into the crystalline lattice of the two materials. In the case of CuS, the overall reaction in the solid phase is CuS+2e+xLi+ → CuSLi x . At low discharge rates Cu2S is formed but at high rates of discharge the reaction proceeds through to Cu metal. With CuO the reaction is CuO+xe+xLi+ → CuOLi x but the formation of Cu2O never occurs; the reaction goes to Cu under all discharge conditions.
    Notes: Résumé L'étude de la réduction électrochimique d'électrodes membranaires de CuS et de CuO dans le mélange de solvant constitué par 20% en volume de carbonate de propylène et 80% de 1, 2-diméthoxyéthane, nous a conduits à admettre un mécanisme de réduction par insertion progressive d'électrons et d'ions Li+ dans le réseau cristallin de ces deux matériaux. En ce qui concerne CuS, cette insertion correspond à la réaction élémentaire en phase solide CuS+xe+xLi+ → CuSLi x . L'espèce formée à l'issue de cette réaction évoluerait alors soit vers la formation de Cu2S dans le cas des faibles régimes de décharge, soit directement vers la formation de cuivre dans le cas des forts régimes de décharge. En ce qui concerne CuO, cette insertion correspondrait à la réaction CuO+xe+xLi+ → CuOLi x mais dans ce cas la formation de Cu2O ne serait jamais possible, l'espèce intermédiaire formée évoluerait directement vers la formation de cuivre quels que soient les régimes de décharge.
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    Journal of applied electrochemistry 9 (1979), S. 361-367 
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    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Mass and momentum transfer at a wall in liquid-particle systems are studied with a two-dimensional model which consists of fixed spherical turbulence promoters arranged in a simple cubic lattice in a rectangular channel. Local values of the mass transfer coefficient and shear stress at a wall of the channel have been measured at identical locations. The results show that there are large differences between the local values but their distribution along the transfer surface is reproduced identically. The dependence of these local values on each other allows one to obtain a general relationship between overall mass and momentum transfer as well as a correlation of mass transfer results for exchange between a wall and a flowing liquid in a fixed bed of particles.
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    Journal of applied electrochemistry 9 (1979), S. 381-387 
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    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The results are presented of a study of the fundamental and technological aspects of a new process for the production of Planté cells. In this process the classical use of the perchlorate ion is replaced by the nitrate ion.
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    Journal of applied electrochemistry 9 (1979), S. 389-393 
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    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The electrical resistance per unit deposition charge per unit area (p,ΩC−1 cm−2) has been calculated from current-time data for the anodic deposition of polymers in the following systems: (a) resin deposition on mild steel and copper coated mild steel, (b) rubber deposition on mild steel and aluminium, and (c) two resin systems of two concentrations on mild steel and brass. The values ofp are analyzed in detail and it is concluded thatp can be qualitatively related to the electrical conductivity of the electrode material and the adhesion of the electrodeposits, taking into consideration the different mechanism for the stability of rubber latex and the resin system. For a given value ofp, electrodeposits on aluminium are 40% more adherent than those on mild steel. Further, for the same adhesion, values ofp are lower by about 20% when aluminium is used instead of mild steel as the anode. It has also been concluded that the study ofp versus the current density during the electrodeposition of the resins is a convenient and useful method of approach to the study of electrophoresis in its practical application to the preparation of electro-coatings of industrial value.
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    Journal of applied electrochemistry 9 (1979), S. 533-536 
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    Notes: Abstract The critical overpotential for zinc dendrite growth is determined as 173 mV by the method described by Popovet al. [1]. It was shown that this procedure can be applied successfully to metal deposition processes when there is a large codeposition of hydrogen.
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    Journal of applied electrochemistry 9 (1979), S. 537-543 
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    Notes: Abstract This paper is concerned with mass transfer to a rotating disc electrode (RDE) under pulsed potential and pulsed current conditions. For the case of pulsed potential, a numerical solution is presented to calculate the instantaneous current density for intermediate and large cycle times and an asymptotic solution for short cycle times. The special case of applying a step potential is then presented. The magnitude of the step current for a given transition time is calculated from the numerical solution by Viswanathanet al. for the pulsed current case. Comparison is made between the present results and various approximate solutions from the literature.
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    Journal of applied electrochemistry 9 (1979), S. 555-562 
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    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The influence of PbO modification on the formation of 4PbO·PbSO4 paste is determined by X-ray diffraction analysis and scanning electron microscopy. The paste was prepared from tetragonal PbO, orthorhombic PbO and several mixtures of both oxides at 80° C and a H2SO4/PbO ratio of 6 wt%. The reaction scheme of 4PbO·PbSO4 formation depends on the PbO modification. When tetragonal PbO is used, 3PbO·PbSO4·H2O crystals are obtained first and then 4PbO·PbSO4. If the initial oxide is orthorhombic PbO, PbSO4, PbO·PbSO4 and 3PbO·PbSO4·H2O are formed successively. When the correct ratio of 3PbO·PbSO4·H2O, orthorhombic PbO and tetragonal-PbO is achieved in the paste then 4PbO·PbSO4 formation begins. This ratio is reached most quickly if tetragonal PbO is present at 30–60wt% in the initial mixture of both modifications.
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    Journal of applied electrochemistry 9 (1979), S. 567-572 
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    Notes: Abstract Rates of electrochemical mass transfer were measured between finned rotating cylinders and solutions containing drag-reducing polymers. Variables studied were: Reynolds number, polymer concentration and fin height. Polyox and carboxymethyl cellulose (CMC) were used as drag-reducing polymers with concentrations ranging from 10–100 ppm for polyox and from 10–500 ppm for CMC. Cylinders with longitudinal fins ofe/d ranging from 0·0185–0·075 were used. Reynolds number was varied between 1000–10000. It was found that the presence of fins on the cylinder surface reduces the adverse effect of the polymer on the rate of mass transfer, the higher the fin height the lower is the ability of the polymer to reduce the rate of mass transfer. Mass transfer data for solutions containing polyox were correlated by the equation: (St) = 0.765(Re)♪-0.36(Sc)−0.669(e/d)0.36 Mass transfer data for solutions containing CMC were correlated by the equation: (St) = 1.704(Re)−0.36(Sc)−0.75(e/d)0.315
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    Journal of applied electrochemistry 9 (1979), S. 595-601 
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    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The electrochemical preparation of cobaltic sulphate has been studied and we have found that the reaction is best effected in 40 wt% H2SO4 in the presence of silver ions as the catalyst, using PbO2 as the anode, with a low current density and a low conversion.
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    Journal of applied electrochemistry 9 (1979), S. 615-621 
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    Notes: Abstract At low rotation speeds of a rotating disc electrode the diffusion-controlled inhibition of zinc deposition by lead acetate or tetrabutylammonium bromide emphasizes the existence of multiple steady states. With both zinc and nickel deposition, low frequency impedance measurements reveal an additional inductive loop associated with a diffusion-controlled inhibition of electrodeposition. From the relaxation time constant it has been concluded that this loop arises from a coupling between the inhibitor diffusion and interfacial processes slower than diffusion and involving, at least for zinc deposition, the slow renewal of active growth sites.
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    Journal of applied electrochemistry 9 (1979), S. 603-613 
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    Notes: Abstract Zinc deposits electrowon from synthetic zinc chloride electrolyte were characterized by a morphology which featured clusters of large platelets with rounded edges and by a preferred crystallographic orientation, namely (0 0 2) (1 0 3) (1 0 5). These deposit characteristics persisted over a wide range of experimental conditions which included variations in the current density and changes in anode material, cell design, and the zinc and hydrochloric acid concentrations. Although the addition of HCl to the electrolyte improved the physical characteristics of the deposit, it did not alter the deposit morphology or orientation. The addition of animal glue or tetrabutylammonium chloride resulted in smooth, compact deposits having a (1 1 0) orientation at 0·24 M H+. Jaguar C-13 additions gave a (1 1 2) orientation, while gum arabic and tetraethylammonium chloride only affected the grain size. The various deposit morphologies and orientations obtained showed only some correspondence to changes occurring in the zinc deposition polarization voltages. The presence of metallic impurities, Cu, Co, Fe, and Sb, caused the morphology and orientation of the deposits to become more basal and the current efficiency to decrease. The presence of Cd resulted in a (1 1 2) (1 1 4) orientation and Pb gave a (1 0 1) orientation.
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    Journal of applied electrochemistry 9 (1979), S. 641-642 
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    Notes: Abstract It is established that the absorbance of the SOCl2/LiAlCl4 electrolyte solutions at 2800 cm−1 is due the HCl, generated in the solution as a result of the hydrolysis reaction of SOCl2. A slow ‘self-desiccation’ reaction of the hydrated AlOHCl2 is also postulated to occur in these solutions.
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