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  • 2010-2014  (24,908)
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  • 1977  (2,761)
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  • Electrical Engineering, Measurement and Control Technology  (28,352)
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  • 2010-2014  (24,908)
  • 1980-1984
  • 1975-1979  (2,761)
  • 1950-1954  (683)
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  • 1
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    Springer
    Optical and quantum electronics 9 (1977), S. 1-13 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Electro-optic waveguide modulators utilizing phase retardation of two orthogonally polarized optical modes in LiNbO3 and LiTaO3 waveguides have been designed taking into consideration the optical field distribution in the waveguides and the electrical properties of the electrodes. The analysis has revealed that a driving-voltage to frequency-bandwidth ratio of 1 V/GHz is attainable at the wavelength of 1.05 μm using presently available embedded and ridge waveguides. Improvement in waveguide fabrication techniques may reduce the ratio by at least a half. Thus, LiNbO3 and LiTaO3 waveguide modulators are considered to be promising candidates for practical application to single-mode optical-fibre transmission systems of higher than 1 Gbit/s.
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  • 2
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    Optical and quantum electronics 9 (1977), S. 15-32 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Weak perturbations from various refractive index distributions have been introduced into the central layer of the three layered dielectric slab optical waveguide model and solutions of the wave equation in this guide for TE modes have been compared with the results published for the unperturbed mode. The perturbations in general introduce quadrature components in the transverse modes and a mode width dependent amplitude. The mode position within the guide can be shifted and the mode width increased or decreased. With increasing parabolic perturbation there is increasing waveguide discrimination against higher order modes.
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  • 3
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    Optical and quantum electronics 9 (1977), S. 33-42 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Optical transmission systems, using extremely low-loss fibres in the 1.0–1.4μm wavelength region are proposed. Possibilities and expected performances are reviewed for optical components in the low-loss band, such as optical oscillators, modulators, detectors, isolators and fibre connectors. Basic considerations for the systems are described. These systems will have advantages such as a reduction in the number of repeaters and in the system costs by expanding the repeater spacing up to several tens of kilometers. Reliability requirements for repeaters, power supply and maintenance problems will be relaxed by accommodating repeaters in stations instead of manholes.
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  • 4
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    Optical and quantum electronics 9 (1977), S. 121-133 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The well-known stepped-index representation for graded-core fibre analysis is extended to cover all aspects of fibre propagation on a rigorous electromagnetic basis. Calculations are implemented on a large digital computer system, and a new, very efficient formulation is used, so that the resulting program package turns out to be a very general and powerful tool for fibre description. It can be used to establish on a quantitative basis the merits and limitations of well-known approximate procedures (e.g., the WKBJ method) and, at the same time, to get considerably deeper insight into the exact mode pattern of the graded-core fibre than provided by existing approximations.
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  • 5
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    Optical and quantum electronics 9 (1977), S. 135-141 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract On the basis of ray model solutions, the response of a lossless multimode graded-index fibre to a modulated source is calculated. The results demonstrate great sensitivity of the bandwidth of the fibre to small variations in index profile.
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  • 6
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    Optical and quantum electronics 9 (1977), S. 153-165 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The excitation characteristics and spatial coherence of partially coherent optical waves in gradient fibres are demonstrated for incident light waves radiated from semiconductor lasers and light emitting diodes. Lower modes are efficiently excited in the case of coherent laser beams, while incident waves of low coherence such as lightwaves of LEDs excite higher modes. Pulse propagation of partially coherent optical waves in dispersive gradient fibres is also discussed for random index fluctuations. Mode coupled equations for temporal correlation functions of the electric field that are generalizations of coupled power equations are found. Mode filtering and pulse improvement with a lossy inhomogeneous cladding are described.
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  • 7
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    Optical and quantum electronics 9 (1977), S. 167-175 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The microbending loss in single-mode or quasi-single-mode fibres is approximately determined from a calculation of the fundamental mode field in a fibre with constant curvature. The result of the microbending loss essentially depends on the spot size of the fundamental mode, only. The approximations are verified by studying a statistical model and by comparing the approximations with exact calculations in the case of W fibres.
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  • 8
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    Optical and quantum electronics 9 (1977), S. 143-152 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract This paper presents a new method for investigating the effects of mode conversion due to microbends on the transmission characteristics (attenuation, frequency response ...) of multimode optical fibres. The method applies to both step-index and graded-index fibres and takes into account any dependence of the mode coupling coefficient upon propagation angle. The general theory of propagation with mode coupling is developed and we introduce the concept ofθ modes. The propagation problem is then simplified by using hypotheses based on exerpimental results and the solution is obtained with the help of a computer. Practical results concerning the increase of attenuation due to microbends are presented, from which the precautions to be taken when cabling fibres are deduced. It is also shown that in every practical case encountered, the prediction of the total attenuation and of the frequency response of a given fibre, when the launching conditions are specified is obtained from analytical expressions which approximate well with the exact results obtained from the computer. All these results make the method powerful and very useful for system designers when evaluating the effect of introducing an optical fibre into a transmission system.
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  • 9
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    Optical and quantum electronics 9 (1977), S. 411-418 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A high resolution infra-red PbSe diode laser spectrometer has been developed for application in air pollution monitoring and mineral prospecting. This instrument possesses three cells for measurement and calibration. Correlation techniques have been applied to increase the sensitivity. SO2 concentrations of around 5 ppm have been monitored at 7.3μm with the diode operating at 77 K.
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  • 10
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    Optical and quantum electronics 9 (1977), S. 419-425 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We investigate in this paper the results yielded by a rigorous application of second order spatial coherence theory to a Gaussian TEM-multimode laser beam. Formulae for a qualitative discussion and a quantitative evaluation of the second order spatial coherence properties of a laser oscillator with an arbitrary number of longitudinal and/or transverse Gaussian TEM-modes of oscillation are derived and considered for some practically important cases.
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  • 11
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    Optical and quantum electronics 9 (1977), S. 519-525 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Very low threshold current laser sources are desirable for a number of potential applications including optical fibre telecommunications systems. Conventional proton-isolated stripe geometry (GaAl)As lasers can be designed to give threshold currents in the range 10–50 mA by proper optimization of device geometry. Experimentally, it is shown that such devices can be easily fabricated and bonded and that their characteristics are not adversely affected by the optimization procedure.
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  • 12
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    Optical and quantum electronics 9 (1977), S. 532-535 
    ISSN: 1572-817X
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  • 13
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    Optical and quantum electronics 9 (1977), S. 536-538 
    ISSN: 1572-817X
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  • 14
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    Optical and quantum electronics 9 (1977), S. 539-539 
    ISSN: 1572-817X
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  • 15
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    Optical and quantum electronics 9 (1977), S. 383-391 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The problem of timing recovery in optical data communication is considered using the maximum likelihood (ML) estimation. Assuming negligible intersymbol interference, the structure of the ML estimator is first obtained and some approximations of it are suggested both in the form of decision-directed tracking loops and in the form of data-independent trackers. Comparisons are made with other synchronization schemes discussed in the literature.
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  • 16
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    Optical and quantum electronics 9 (1977), S. 373-382 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A general partially coherent source field on the end of an optical fibre has been represented by a characteristic angular spectrum of independent plane waves. The launching of both trapped and tunnelling (leaky) power is investigated for both step and graded-index fibres by considering the effect of one component of the angular spectrum, using geometric optics acceptance theory. The effect of the degree of coherence on the pulse response of the fibres is briefly discussed.
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  • 17
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    Optical and quantum electronics 9 (1977), S. 399-409 
    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Refractive index versus composition data are presented for three silica based binary glass systems SiO2-B2O3, SiO2-P2O5 and SiO2-GeO2. Using a near-field scanning method refractive index measurements were made on graded-index optical fibres, of known composition, fabricated by the chemical vapour deposition technique. The experimental data for each glass system is also compared with theoretical predictions of refractive index versus composition made from a single oscillator, Sellmeier model involving an oscillator energy and a dispersion energy term.
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  • 18
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    Optical and quantum electronics 9 (1977), S. 393-397 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract To realize the low-loss connection of two optical fibres intended as a transmission medium for optical signals, very tight tolerances have to be observed on account of the small geometrical dimensions involved. The present work describes a fully automatic system for the alignment of optical fibres in thex-y planes relative to a light source, which has only a single intensity peak, so that maximum optical power is launched into the fibre. The light source can be, for instance, the radiating end of a fibre, a semi-conductor laser or a light-emitting diode. The optical power coupled into the fibre serves as the control signal. Three precision displacement stages driven by stepping motors serve to align the fibres. Various sequential control algorithms for optimal coupling are investigated with reference to theory. Two algorithms are tested with the aid of a computer with reference to the alignment accuracy and speed requirements which have to be met and the one shown by theoretical simulation to be the more favourable is selected for technical realization. The resulting system was used for numerous alignment operations for the coupling of two graded-index fibres. The alignment time is below 1 s and the coupling efficiency compared with manual coupling alignment efficiency (= 100%) is above 99%, corresponding to an additional loss of 〈0.05 dB.
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  • 19
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    Optical and quantum electronics 9 (1977), S. 509-518 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Stimulated electronic Raman scattering (SERS) in atomic vapours provides a simple method of extending the tuning ranges of pulsed dye lasers well into the infrared region. The special advantages of this technique in comparison with other types of tunable infrared lasers are discussed, and are illustrated by describing a SERS system which uses a modest nitrogen laser-pumped dye laser (∼ 20 kW). This produces infrared radiation tunable from 2.67 to 3.47μm by SERS in caesium vapour, which is contained in a heat pipe oven. Photon conversion efficiencies of up to 50% are obtained. The design of the heat pipe oven, operation of the system and optimization of experimental parameters are described in detail.
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  • 20
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    Optical and quantum electronics 9 (1977), S. 527-531 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We inv estigate the problem in which a volume hologram is produced by two waves of arbitrary amplitude and phase distribution (the only restriction being that they must obey the rules of geometrical optics), and the developed hologram is illuminated by one of the waves having the same phase distribution but not necessarily the same amplitude distribution. Coupled partial differential equations are derived and solved in the form of an infinite series valid for both transmission and reflection holograms. For transmission holograms a simple approximate solution is given for the amplitude of the reconstructed wave in the immediate vicinity of the input surface.
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  • 21
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    Optical and quantum electronics 9 (1977), S. 43-50 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Optical diffusion coefficients, computed from ray-tracing in step-index slab guides with small continuous width perturbations, show an angular dependence which does not in general correspond well with the mechanical deformation spectrum. This contrasts with assumptions of a one-to-one correspondence in earlier reports. The results indicate that, in a fibre having a steep cut-off in the perturbation spectrum at high mechanical frequencies, the corresponding diffusion coefficient will have a significantly less pronounced cut-off. It is also shown that, in a cylindrical guide with diameter perturbations, the effect of skew rays is to further reduce the cut-off rate in the diffusion coefficient. An immediate consequence of these findings is that, in a perturbed fibre without appreciable cladding loss, the loss penalty (due to radiation) may be much higher than would be predicted by the mechanical spectrum alone. As a prelude to the above ray-tracing studies, a derivation of the optical diffusion equation is given from the analogy with Brownian motion.
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  • 22
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    Optical and quantum electronics 9 (1977), S. 51-60 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Wave propagation in a step-index optical fibre with a curved section is treated theoretically. Mode conversion and radiation take place. The mode coupling coefficients which depend on the polarization of the incident mode are calculated. Radiation losses at the transition between a straight and a curved fibre section and total losses including the continuous radiation loss due to a uniform bend are evaluated. Comparisons are also made between singly and doubly clad fibres. It is shown that the doubly clad fibre can tolerate a sharper bend.
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  • 23
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    Optical and quantum electronics 9 (1977), S. 289-297 
    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The transfer function of a multimode step-index fibre has been calculated by means of geometrical optics taking into account mode coupling and leaky rays. The light source may have axial symmetry (light emitting diode) or be line shaped (semiconductor laser). Radial displacement of the line source relative to the fibre axis is allowed. Calculations performed for a large numerical aperture fibre (N.A.=0.475) with a coupling length of 2 km show that leaky rays and radial displacement of the line source are significant for fibre lengths shorter than 200m. The influence of the width of the entrance beam is significant for lengths up to 5 km. Varying coupling length and steady state angle for a fibre length of 150 m calculations show that the bandwidth varies between 15 and 95 MHz for penalty losses between 8 and 18 dB. Calculations have been compared with direct baseband frequency measurements for a high-loss fibre with a large numerical aperture and excellent agreement has been found.
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    Optical and quantum electronics 9 (1977), S. 305-313 
    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The gain calculated for a laser with ring and Fabry-Perot resonators respectively is given in a general formulation which shows clearly the influence of the spatially inhomogeneous saturation due to the standing wave pattern and the resulting Bragg scattering. When selecting a single mode in a Fabry-Perot resonator, the losses necessary to quench the modes are equal to those losses which the selected mode suffers due to the self-induced Bragg grating in the active medium. In a unidirectional ring laser, the losses only need exceed the gain of additional separate gain reservoirs of the modes. Also possible reasons are dealt with which cause stable bidirectional operation in a ring laser with homogeneously broadened gain.
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    Optical and quantum electronics 9 (1977), S. 353-353 
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  • 26
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    Optical and quantum electronics 9 (1977), S. 315-349 
    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Light continua extending from the i.r. to the u.v. are generated with picosecond laser pulses in liquids and solids. It is demonstrated that the light spectra in water are produced by stimulated parametric fourphoton interactions, which are resonantly enhanced by single and difference frequency resonances of the non-linear susceptibilityχ (3). A theory of the various parametric four-photon interaction processes is developed and the resonant structure ofχ (3) is discussed. The experimental results are compared with theoretical calculations. The generation of light continua by other nonlinear optical processes is briefly discussed.
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    Optical and quantum electronics 9 (1977), S. 354-356 
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    Optical and quantum electronics 9 (1977), S. 357-359 
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    Optical and quantum electronics 9 (1977), S. 360-360 
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    Optical and quantum electronics 9 (1977), S. II 
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    Optical and quantum electronics 9 (1977), S. 361-371 
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    Notes: Abstract This paper is devoted to a comparison of two electromagnetic models of junction lasers — the dielectric slab and the Epstein layer. The main emphasis is on the discussion of possible methods of matching the parameters appearing in both models. The threshold condition for active layer thickness and mode frequency at a given gain and mode number is solved numerically. It is shown that the discrepancies between both models become reasonably small when a proper method, involving averaging of the dielectric constant over the active and passive regions, is applied. The cases of the three lowest order TE transverse modes of homojunction, single-, and double-heterojunction lasers are considered. The obtained results suggest that the Epstein-layer model can approximate experimental data as well as the dielectricslab model does.
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    Optical and quantum electronics 9 (1977), S. 445-447 
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  • 34
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    Optical and quantum electronics 9 (1977), S. 448-450 
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    Optical and quantum electronics 9 (1977), S. 427-436 
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    Notes: Abstract Signal distortion noise in volume phase holograms is analysed for the case in which the object beam consists of two plane waves. It is shown that, for a given (on-Bragg) signal diffraction efficiency, the magnitude of the signal distortion noise is inversely proportional to the square of crystal thickness. Furthermore, as a function of the angular position of the reconstruction beam, the signal distortion noise has two peaks: one at the Bragg angle and the other at a deviation Δθ 0 from the Bragg angle, where Δθ 0 is a function of relative angles between the components of the object beam and the reference beam. The on-Bragg peak of the signal distortion noise is experimentally located for volume phase holograms recorded in Fe-doped LiNbO3. The measured angular position is found to be in accord with the calculated value.
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    Optical and quantum electronics 9 (1977), S. 437-444 
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    Notes: Abstract Based on the differential equations of [1] a general solution in closed form is obtained for the amplitudes of the transmitted and diffracted beams for Bragg angle incidence in a lossless, transmission type volume hologram. Numerical solutions are plotted for Gaussian input beams. For the range of parameter values investigated it is shown that complete power transfer into the diffracted beam is not possible.
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    Optical and quantum electronics 9 (1977), S. 451-453 
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    Optical and quantum electronics 9 (1977), S. 455-458 
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    Notes: Abstract An optical analogue system is described for performing the complex Hilbert transformation of a phase object.
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    Optical and quantum electronics 9 (1977), S. 459-464 
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    Notes: Abstract It is shown in this paper that the near field and far field power distributions corresponding to any distribution of rays in an arbitrary graded fibre, reach a steady state along the fibre. This steady state is usually a function of the input distribution of rays and of the refractive index profile of the fibre. The case of parallel beam injection is considered and an analytical expression for the near field power distributions for any arbitrary profile is found. This suggests a new method of refractive index profile measurement which is free of leaky ray corrections and can be very sensitive near the optimum profile for time dispersion.
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    Optical and quantum electronics 9 (1977), S. 61-74 
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    Notes: Abstract Simple analytical results are obtained for the mode distribution and impulse response of graded index fibres under a variety of excitation conditions relevant to practical systems. It is found that the choice of an optimum refractive index profile depends quite strongly on the source distribution of or, that one can significantly improve the impulse response of a particular profile by appropriate choice of launching conditions. Furthermore the r.m.s. pulse width is not necessarily reduced simply by partially filling the numerical aperture of the fibre.
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    Optical and quantum electronics 9 (1977), S. 75-78 
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    Optical and quantum electronics 9 (1977), S. 83-83 
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    Optical and quantum electronics 9 (1977), S. 79-82 
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    Optical and quantum electronics 9 (1977), S. 83-83 
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    Optical and quantum electronics 9 (1977), S. 84-86 
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    Optical and quantum electronics 9 (1977), S. 111-119 
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    Notes: Abstract A simple closed-form expression is given for the index profile of multimode fibres with arbitrary dispersion providing transmission capacities as large as 1.6/Δ 2 Mbit/s km, whereΔ≡Δn/n. Our result reduces to a previous result of Marcatili for the special case of circularly symmetric fibres. A transmission capacity of 150 Mbit/s over a 10 km long fibre appears possible with LED sources operating at optimum wavelengths for the medium.
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    Optical and quantum electronics 9 (1977), S. 87-109 
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    Notes: Abstract The methods of geometric optics are applied to light acceptance and propagation in graded index fibres. The symmetry of the basic ray equations reveals ray path invariants. Rays are classified into bound, tunnelling and refracting rays. The role of source properties in exciting different ray types is analysed. Pulses are considered in terms of absolute widths, r.m.s. widths and complete shape detail. Optimization formulae are obtained. The incorporation of attenuation mechanisms is described and the effects of an absorbing core are analysed in detail.
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    Optical and quantum electronics 9 (1977), S. 189-195 
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    Notes: Abstract The global properties of modal ray fields and the local properties of source-excited ray fields are discussed within the context of propagation in optical fibres. The importance of bounded beams is stressed for unambiguous determination of local energy transport, reflection, refraction and tunnelling.
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    Optical and quantum electronics 9 (1977), S. 177-188 
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    Notes: Abstract In this paper the different loss mechanisms of light in multimode fibres are analysed from the point of view of the extinction of leaky skew rays. First, the intrinsic loss mechanism of leaky rays due to optical tunnel effect is fully investigated by means of a quasi-classical approach and a well approximated form of the relative extinction coefficient is derived. Second, the influence of other loss phenomena, due to imperfections or impurities in the fibre such as core and cladding absorption and scattering, on the relative contribution of leaky rays is analysed. Finally some phenomena of failed excitation of leaky rays are also examined. The phenomena are analysed both qualitatively and quantitatively and a comparative analysis of various effects referring to actual fibres is made.
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    Optical and quantum electronics 9 (1977), S. 197-202 
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    Notes: Abstract Formulae are derived giving the flight time of a ray impinging on a nearly-parabolic fibre whose core index profile includes a fourth order perturbation term in addition to the usual second order term of parabolic profiles. The method is applied to the case of parallel beam injection to calculate the impulse responses of nearly parabolic fibres characterized either by a fourth order term or by an ‘α value’ very close to 2. Numerical results are given for parameters typical of silica fibres made by the CVD technique.
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    Optical and quantum electronics 9 (1977), S. 203-208 
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    Notes: Abstract Impulse responses are calculated for parallel-beam injection into fibres havingα-type profiles with a varying from 1 to 8. The responses obtained exhibit characteristic features which can guide the interpretation of experimental investigations of such fibres. The ray model is used and leaky-mode attenuation is taken into account. Finally, the dependence of the transmitted power on the injection angle is investigated, suggesting a possible functional relation to the index profile.
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    Notes: Abstract The elements of the scattering matrix of the junction between two circular monomode dielectric waveguides with different diameters and/or different refractive indices are calculated using the mode matching method. The theory is evaluated numerically for a wide range of parameters and simplified considerably for two important cases of weakly guiding waveguides. The radiation pattern of the junction is calculated using the Huygens-Kirchhoff theory of diffraction and shown to be reducible to the weighted difference of the radiation patterns of the ends of the primary and secondary waveguide. Simple approximations are derived for weakly guided waves. The theory is verified experimentally by measuring the scattering parameters, the far-field radiation pattern and the near-field distribution of abrupt changes in diameter of microwave dielectric rod transmission lines.
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    Optical and quantum electronics 9 (1977), S. 223-232 
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    Notes: Abstract Eigenvalues and field distributions for optical waveguides obtained from the WKB approximation have been compared with those found from geometrical optics and from more rigorous weakly-guiding LP mode theories in the cases of the step-index and parabolic-index profiles. In all cases it is found that the zero-order WKB approximation yields very accurate eigenvalues provided care is taken in the choice of phase factors in the eigenvalue equation. Expressions are deduced for the required phase factors for guides of arbitrary index profile in both two- and three-dimensions, and physical interpretations are given in terms of ray optics. The first-order WKB field distributions are found to give good agreement with the mode fields everywhere except in the vicinity of the caustics.
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    Optical and quantum electronics 9 (1977), S. 233-239 
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    Notes: Abstract The dependence of the intrinsic random intensity noise spectrum of the radiation from CW DH GaAIAs diode multimode lasers on optical wavelength has been investigated for the first time in a wide frequency range 30 MHz to 3 GHz. It was generally observed, that a lasing mode which is optically isolated from the rest of the radiation, shows much stronger intensity fluctuations as compared to the fluctuations of the total output, particularly in the frequency range below the intrinsic natural resonance frequency of the laser. The magnitude of the fluctuations decreases when the number of modes in the detected radiation increases. Our experimental results are compared to computer solutions which were obtained with a simple, analytical laser noise model. Good qualitative agreement between theory and experiment is demonstrated.
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    Optical and quantum electronics 9 (1977), S. 241-248 
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    Description / Table of Contents: Résumé Des expériences de détection hétérodyne ont été effectuées, dans l'infrarouge, avec trois montages optiques différents un interféromètre de Michelson modifié et deux montages utilisant l'amplification de la puissance rétrodiffusée dans la cavité laser. A partir de la rétrodiffusion sur un disque en rotation, on étudie la réponse du système en fonction de la fréquence de battement. L'évolution du signal n.est pas linéaire. Cette non linéarité provient de l'interaction de l'onde diffusée avec le milieu laser. A partir de ces résultats, on présente un prototype d'anémomètre à laser capable de mesurer des vitesses de vent jusqu'à 40 km/h à une distance de 500 mètres.
    Notes: Abstract Some infrared heterodyne detection experiments have been performed with a modified Michelson interferometer and two systems of back-scattered radiation amplified in the laser cavity. The frequency responses have been studied using the radiation scattered from a rotating wheel. The evolution is nonlinear with the frequency and seems to originate in the interaction of the back-scattered wave with the laser itself. Taking into account these results, a laser anemometer is presented, capable of detecting aerosols as far as 500 metres away.
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    Optical and quantum electronics 9 (1977), S. 259-261 
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    Optical and quantum electronics 9 (1977), S. 263-264 
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    Optical and quantum electronics 9 (1977), S. 265-267 
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    Optical and quantum electronics 9 (1977), S. 249-258 
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    Notes: Abstract The coupling between bound modes of a corrugated dielectric-slab waveguide and modes of the radiation continuum is analysed by a perturbation method. Loss coefficients that account for the power coupled into radiation modes by any Bragg order of corrugations with an arbitrary profile are determined for the bound modes. Agreement is found with published results for sinusoidal profiles. The proportion of power coupled out through each dielectric interface of the slab waveguide is also determined. When the corrugation has an asymmetric (blazed) profile and coupling to radiation modes is by the first Bragg order, more power can be coupled out through one interface than the other, even if the refractive indices of the cladding regions are equal. If the coupling is by a higher Bragg order, then the division of power can be considerably more unequal than for first-order coupling, with the greater proportion leaving the side of the waveguide opposite to that for first-order coupling. The ratio of the power coupled out the two sides varies cyclically with radiation wavelength.
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    Optical and quantum electronics 9 (1977), S. 269-287 
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    Notes: Abstract The relations between surface statistics and the near- and far-field scattered light statistics are surveyed, mainly using scalar diffraction theory. The methods which have been proposed and used are grouped and described according to whether they operate in the near-field or the far-field and whether they use monochromatic or polychromatic light. Several methods emerge as promising for practical application to non-contacting and non-destructive testing. Deterministic methods such as interference microscopy are not discussed.
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    Optical and quantum electronics 9 (1977), S. 299-304 
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    Notes: Abstract A simple model is used to evaluate the power penalty accruing from nearest neighbour Intersymbol Interference (ISI) in a digital optical communications system using an integrate- and -dump decision process. The results compare closely with those obtained by Personick in a frequency domain analysis. An analysis of the effects of drift in the transmission bandwidth in the cable and of imperfect equalization indicates a simple design criterion for a fixed equalizer link.
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    Optical and quantum electronics 9 (1977), S. 465-471 
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    Notes: Abstract The true focal spot of a focusing system may be defined as either the location of the maximum on-axis intensity or the location of the minimum beam diameter that contains a certain fraction of the power. Diffraction causes this true focus to be shifted from the ideal geometrical optics prediction, the effect being greatest at largeF-numbers. Specifically, a theoretical and experimental study is made of the largeF-number focusing properties of a thin lens in contact with a uniformly illuminated aperture. The results are clarified by a comparison to the focal spot shift for a Gaussian beam.
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    Optical and quantum electronics 9 (1977), S. 473-485 
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    Notes: Abstract In this paper volume hologram reconstruction is considered as an electromagnetic scattering problem that leads to a characteristic integral equation. Our main attempt is the calculation of diffraction efficiency for attenuated gratings, that is compared with those of unattenuated gratings, to point out the influence of grating attenuation. In this respect the solution in the first Born approximation is found to be sufficient for diffraction efficiency calculations of attenuated gratings.
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    Optical and quantum electronics 9 (1977), S. 487-491 
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    Notes: Abstract In this paper the effect of anomalous absorption of the direct wave in thick hologram gratings at Bragg incidence is considered. The description of this effect is possible by the solution, in the second order approximation, of the basic integral equation introduced in Part I [1] which describes the holographic reconstruction process.
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    Optical and quantum electronics 9 (1977), S. 493-498 
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    Notes: Abstract A technique is described by which an optical fibre may be packaged in a loose fitting tube of oriented polypropylene. This structure offers substantial improvements in resistance to microbending. The linear expansion coefficient of the material is very small and can be varied about zero, allowing matching to the fibre so that temperature variations do not cause fibre buckling.
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    Optical and quantum electronics 9 (1977), S. 499-507 
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    Notes: Abstract Phase compensation can lead to a significant improvement in the intensity characteristics of high order laser beam modes. Optimal design procedures for phase compensation structures are described, and the behaviour of the higher order spatial harmonics is considered in detail. The effects of possible phase errors are also derived analytically.
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    Optical and quantum electronics 9 (1977), S. 540-544 
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    Journal of applied electrochemistry 7 (1977), S. 1-29 
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    Notes: Abstract To the end of 1974 the scientific literature contained over 1200 articles on electrochemical machining (ECM) [1]. Additionally approximately 100 papers appeared in 1975. Although a large number of those references appeared in what might be described as ‘non-learned’ journals, this still leaves the potential student with a difficult task if he wishes to review the state of the art. This is the first attempt to review thoroughly the literature in this field, although only a small proportion of those contributions are considered pertinent. The review will take the following form: after an introductory chapter there will be two chapters on dissolution kinetics, the second concerned with the kinetics as affected by the physical characteristics of the electrolyte; this will be followed by a section on the effects of electrochemically machined surface on the physical properties of a metal. Chapters 5 and 6 will deal with tool design and the optimizing of process parameters, after which will be a review of topics concerned with the application of ECM.
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    Journal of applied electrochemistry 7 (1977), S. 37-43 
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    Notes: Abstract A solid electrolyte cell has been developed using a high copper ion conductivity solid electrolyte, 7CuBr·C6H12N4CH3Br, a copper anode, and a chalcogen cathode. The open-circuit voltages of the cells with sulphur, selenium, and tellurium as cathode materials were 0·448, 0·373, and 0·258 V, respectively, at 25° C. These cells yielded a current of several tens of microamperes at room temperature and several milliamperes at 114° C without appreciable polarization. An energy density of 4.5 Wh kg−1 at room temperature was evaluated from the weights of the electrolyte and electrode materials for the cell using a selenium cathode in the discharge current density range 60–150μA cm−2.
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    Journal of applied electrochemistry 7 (1977), S. 51-55 
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    Notes: Abstract The kinetic parameters for the hydrogen evolution reaction on a stainless steel substrate have been obtained from a study of the steady-state polarization curves as well as the galvanostatic transients. The high Tafel slope obtained in the steady-state polarization measurements was ascribed to the presence of an oxide film present on the surface of the stainless steel electrode.
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    Journal of applied electrochemistry 7 (1977), S. 77-80 
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    Notes: Abstract The possibility of electrodepositing copper powder by pulsating overpotential is shown. These powders are compared to the powders obtained by constant overpotential electrodeposition. It is also shown that the grain size and the morphology of deposited powder is a function of overpotential, and of amplitude and frequency of pulsation in constant and pulsating overpotential deposition respectively.
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    Journal of applied electrochemistry 7 (1977), S. 93-93 
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    Journal of applied electrochemistry 7 (1977), S. 91-92 
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    Journal of applied electrochemistry 7 (1977), S. 31-35 
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    Notes: Abstract In order to examine the conduction behaviour in the sintered oxides of MoO3-doped Bi2O3, the electrical conductivity in air and the EMF of oxygen gas concentration cell were measured with respect to the phase relation determined by X-ray diffraction. The tetragonal single phase oxide containing 22 mol% MoO3 was found to be a high oxide ion conductor, the conductivity of which was comparable to those of stabilized zirconias. The partial electronic conduction in this phase was negligibly small at relatively high oxygen pressure. The oxide ion conduction was considered to be attributable to an appreciable amount of oxygen vacancies present in the crystal. In the monoclinic compound 3Bi2O3·2MoO3, the oxide ion conduction was also observed. Although the conductivity of this phase was somewhat lower than that of the tetragonal phase, the activation energy for conduction (53·5 kJ mol−1) was much lower than the values for usual oxide ion conductors.
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    Journal of applied electrochemistry 7 (1977), S. 175-179 
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    Notes: Abstract A laboratory-scale cell for the continuous electrolytic reduction of chalcopyrite contained in copper concentrate is described. Dry concentrate is fed into one end of the cell and forms a particulate bed electrode, with fluidized properties, resting on the copper cathode constituting the cell base. At the opposite end, the reduced product containing copper sulphide of composition Cu1.8S to Cu2S flows over a weir. The feed rate determines the coulombic efficiency and extent of reduction of the sulphide. A copper extraction process incorporating slurry electrolysis is proposed and scale-up problems discussed
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    Notes: Abstract Trifluoromethanesulphonic acid monohydrate CF3SO3H.H2O and its aqueous solutions have been evaluated as an electrolyte for methanol electro-oxidation. The performances of conventional noble metal catalysts in the pure monohydrate are very poor compared with those in 3 M sulphuric acid. This is contrary to previously published literature data, and possible reasons for the discrepancy are given. In aqueous solutions of CF3SO3H at concentrations between 10 and 50%wt. considerably improved performance is obtained and at 60° C the activities of the catalysts are in most cases slightly higher than in 3 M H2SO4. In addition the poisoning effect of acid radicals is considerably less in CF3SO3H than in H2SO4 solutions. Above 60° C, however, the aqueous CF3SO3 anion decomposes to produce sulphur, which poisons the noble metal catalysts. Carbon-13 NMR studies of the CF3SO3H/H2O/CH3OH system were carried out at 20 and 37° C. From the results it was concluded that no significant ester formation occurred between CH3OH and CF3SO3H.H2O at these temperatures. Earlier published data on1H NMR studies of these solutions had indicated that 100% of the methanol was involved in ester formation with the acid. A critical analysis of this1H NMR work is given. Cyclic voltammetric characterization of catalysts in 10 and 25%wt. aqueous CF3SO3H solutions gave similar results to those in 3 M H2SO4; however, at concentrations of 50% wt. the acid decomposed at 0.0 V to produce a sulphur species that poisoned the catalyst. The conclusion of the work was that while aqueous CF3SO3H solutions produced promising catalyst performance up to 60° C the slight improvement in performance over 3 M H2SO4 would not offset the greater expense of the CF3SO3H. In addition, it was suspected that the long-term stability of the aqueous solutions even at 60° C might be poor.
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    Journal of applied electrochemistry 7 (1977), S. 185-188 
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    Notes: Abstract The porosity of copper deposits on steel obtained by constant and pulsating overpotential electrolysis has been investigated and determined as a function of the overpotential of deposition. Optimal conditions for copper plating on steel from pyrophosphate baths have been established.
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    Journal of applied electrochemistry 7 (1977), S. 211-214 
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    Notes: Abstract The galvanostatic method has been employed for following the time change of the ATA potential in 0.5 N H2SO4. On the basis of the experimental data it is proposed that the loss of ATA activity results from the formation of a non-conductive oxide film at the titanium-active layer interface.
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    Journal of applied electrochemistry 7 (1977), S. 235-238 
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    Notes: Abstract The enhancing effect of gas bubbles generated at an anode, on the ionic mass transport rate at the associated cathode is analysed by means of an experimental laboratory-scale copper electrowinning cell in which the bubbles were (a) permitted to rise freely in the entire cell and (b) restricted in their motion by a copper baffle-plate placed between the two electrodes. The improvement in mass transfer observed in the unrestricted case has been correlated via statistical regression analysis to the intensity of bubble motion and pertinent cell parameters.
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    Journal of applied electrochemistry 7 (1977), S. 247-252 
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    Notes: Abstract High rate anodic dissolution of nickel in sodium nitrate electrolytes was studied under controlled hydrodynamic conditions in order to investigate the influence of electrolyte concentration, pH and temperature on surface brightening under conditions comparable to electrochemical machining. Dissolution experiments were performed on a rectangular flow channel cell through which the electrolyte was pumped at a constant linear velocity of 1000 cm s−1. Results show that the onset of surface brightening depends on concentration and temperature of the electrolyte but is little affected by pH. The data are consistent with a previously described salt precipitation model for surface brightening.
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    Journal of applied electrochemistry 7 (1977), S. 267-270 
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    Journal of applied electrochemistry 7 (1977), S. 271-273 
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    Notes: Abstract Confirmatory evidence is provided that at the point of passivation of solid zinc in alkali there is no free OH− in the reaction layer at the electrode.
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    Journal of applied electrochemistry 7 (1977), S. 277-286 
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    Notes: Abstract The temperature of the flowing electrolyte solution within the inter-electrode gap has been measured by means of miniature bead-thermistors. For NaCl solution the temperatures recorded within the gap are higher than those outwith the gap. As the flow-rate is reduced the temperature within the gap increases to a maximum which corresponds closely to the boiling state of the electrolyte. These results are consistent with measurements in a region of increased resistivity within the gap such as that provided by the hydrogen bubble-electrolyte layer adjacent to the cathode. Similar tests with NaNO3 solution have shown that the temperatures within the gap are much lower with that electrolyte than with NaCl solution. These effects follow previous observations that substantially less hydrogen gas is evolved with NaNO3 than with the NaCl electrolyte.
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    Journal of applied electrochemistry 7 (1977), S. 299-302 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The cathodic current blackening of Bi2O3-based oxide ion conductors was examined for the Bi2O3-Y2O3 electrolyte at low oxygen pressure. In air, more than 500 mA cm−2 d.c. could be passed at 600° C without causing changes in the electrolyte itself. However, in argon gas, a limiting current of 3 mA cm−2 was observed and the electrolyte was blackened at the cathode side. The limiting current was ascribed to control by the diffusion of oxygen gas at the cathode. The blackened oxide was found to consist of a mixture of Bi metal and Bi2O3-Y2O3 solid solution and to exhibit the equilibrium oxygen partial pressure almost corresponding to that of the Bi, Bi2O3 mixture.
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    Journal of applied electrochemistry 7 (1977), S. 309-314 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Metal powders have been obtained continuously from dilute feedstocks (about 10−3 mol 1−1 metal) in an unoptimized electrochemical pump cell at an electrolysis cost of about 1·8 kWh kg−1. Particle sizes ranged from about 10 to 250 μm depending on metal and conditions. Good quality copper, tin, copper/ tin (‘bronze’), and zinc powders have been obtained.
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  • 86
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    Journal of applied electrochemistry 7 (1977), S. 315-321 
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    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract A new method of investigating photoactive pigment particles, based on electrochemical measurements on suspended particles in a dielectric fluid containing an indifferent electrolyte is discussed. This technique provides information on the absolute valence and conduction energy levels and band gaps of organic pigments as well as the distribution of states in these solids. The voltammetric oxidations and reductions of theα,β andx-forms of metal-free phthalocyanine (H2Pc) suspended in methylene chloride were examined on the surface of a hanging mercury drop electrode (HMDE) and a Pt disc electrode (PDE). One of the more significant aspects of the electrochemical studies of these suspensions is that substances of identical chemical composition but different solid state structure, such asα,β andx-H2Pc, could be examined under the same experimental conditions to give detailed electrochemical information which could be related to the valence and conduction levels.
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  • 87
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    Notes: Abstract Phosphoric acid and sulphuric acid have been compared as potential electrolytes for methanol-air fuel cells. The performances of typical electro-oxidation catalysts were measured in both electrolytes over a range of concentrations. With all catalysts the activity falls with increasing acid concentration. While this is to some extent due to the decrease in water activity at higher concentrations it seems that with both acids there is significant poisoning of the catalyst. The results can be explained for both electrolytes by assuming that adsorption of undissociated acid poisons the catalyst surfaces and that the reaction rate on the poisoned surfaces is proportional to the water activity.
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    Journal of applied electrochemistry 7 (1977), S. 181-182 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Electrodes for the sulphide/sulphur (polysulphide) redox system are described which show low polarization when operated under conditions to be expected in a practical photo-electrochemical cell (P. E. C.)-These electrodes are composed of Teflon-bonded high surface area carbon, loaded with electrocatalysts, the best results having been obtained using cobalt as electrocatalyst.
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  • 89
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    Journal of applied electrochemistry 7 (1977), S. 183-183 
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    Journal of applied electrochemistry 7 (1977), S. 379-382 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The photoelectrochemical behavior ofn-type TiO2 in aqueous solutions was investigated. Current-potential characteristics of polycrystalline TiO2 and single crystals of TiO2 of two different surface orientations (perpendicular and parallel to the ‘C’ axis) were measured in the dark and under irradiation of a 150 W Xenon lamp with an intensity of 20% of one Sun. The rate of photo-induced oxygen evolution on TiO2 anodes increased in the following order: polycrystal TiO2〈single crystal TiO2 (⊥)〈single crystal TiO2 (∥). Photo-induced hydrogen evolution onp-type single crystal GaAs was obtained with photocurrents associated with hydrogen evolution over an order of magnitude larger than those obtained for oxygen evolution on illuminated TiO2. The wavelengths at the maxima in the spectral photoresponse of TiO2 were as follows: polycrystal TiO2, 3100 A: single crystal TiO2 (⊥), 3250 A; single crystal TiO2 (∥), 3450 A. The maximum in the spectral photoresponse of GaAs was at 6650 A. A photoelectrolysis cell which consisted of an illuminated polycrystal TiO2 anode and a Pt cathode developed photocurrents equivalent to about 0.1 mA cm−2 for an incident radiant power of one Sun.
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  • 91
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    Description / Table of Contents: Abstract It is demonstrated through the example of the electrochemical reduction of oxygen on nickel manganites doped with copper, Ni1-x Cu x Mn2O4, that the electrocatalysis occurs through adsorption on active sites formed by Mn4+ ions associated, in octahedral sites, with Mn3+ ions.
    Notes: Résumé On montre, en étudiant la réduction électrochimique de l'oxygène sur les manganites de nickel dopés en cuivre, Ni1-x Cu x Mn2O4, que lélectrocatalyse se produit par adsorption sur des sites actifs constitués par des ions Mn4+ associés, en sites octaédriques, à des ions Mn3+.
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  • 92
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    Description / Table of Contents: Abstract Oxygen is electrochemically reducible in slightly acidic medium (pH=6.6) on copper manganites, Cu x Mn3−x O4, of the spinel type. The reduction is likely to occur on active sites created by the tetravalent Mn4+ ions. These ions act as acceptors of electrons from the solid and as donors to the adsorbed-oxygen molecules or atoms. The rate of the electrochemical reduction depends on the surface concentration of active sites, which itself is a function of copper content. The nature and, concentration of the anions of the supporting electrolyte influence the rate of reduction.
    Notes: Résumé L'oxygène peut être réduit électrochimiquement, en milieu légèrement acide (pH=6.6) sur les manganites de cuivre, Cu x Mn3−x O4, de type spinelle. La réduction se fait probablement sur les sites actifs créés par les ions manganèse tétravalents, Mn4+, jouant le rôle d'accepteur des électrons vis à vis du solide et celui de donneur vis à vis des molécules ou atomes d'oxyène adsorbés. La vitesse de la réduction électrochimique de l'oxygène dépend de la concentration des sites actifs superficiels qui varie en fonction des proportions de cuivre ajoutées. La nature et la concentration des anions de l'électrolyte support influence la vitesse de réduction.
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  • 93
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    Journal of applied electrochemistry 7 (1977), S. 437-443 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Hypobromite and propylene oxide have been generated in an electrochemical pump cell and the production rates have been related to the space-time histories of the species within the cell. Production rates are typically 0.15 and 0.11 mol h−1 dm−2 (depending on current density) and energy yields 1.4 and 2.7 kW h kg−1 respectively. Other figures of merit are given.
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    Journal of applied electrochemistry 7 (1977), S. 445-450 
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Preliminary attempts to develop inexpensive, protective conducting coatings on mild steel for use as insoluble anodes are described. From the consideration that a mixture of acid resistant semiconducting oxide and glass might form a satisfactory coating when heated on a steel substrate, Sb-SnO2 and Ti-Fe2O3 were selected as conducting oxide materials for evaluation. With 3–30 wt.% glass added to the oxides, Sb-SnO2 was found to be unsuitable as pellets of the glass-oxide mixture did not densify on heating up to 1400° C. 3% Ti-Fe2O3 plus 20% glass pellets fired at 1250° C showed low resistivity and porosity. An oxide-glass mixture of this composition fired on a mild steel substrate at 1250° C gave a coating with a porosity of ∼ 0.5%, on which chlorine could be evolved in HCl solution. The Ti-Fe2O3 oxides were very acid resistant under conditions of chlorine evolution. A reduction in the porosity of the coating, or the use of an acid resistant metal substrate, would be required to make the oxide-glass coating a practicable proposition.
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  • 95
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    Journal of applied electrochemistry 7 (1977), S. 463-471 
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract This paper deals with an experimental study of copper deposition in fluidized bed electrodes from acidified aqueous solutions containing copper. Overpotential distributions are determined and the amount of copper deposited at various levels within the electrodes is also measured. Experiments with long duration times allow the variations of current efficiency for recovery to be obtained as a function of current density and fixed bed thickness. These variations could be explained by the existence of dissolution zones within the electrodes.
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  • 96
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    Journal of applied electrochemistry 7 (1977), S. 473-484 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Many electrochemical processes suffer in varying degrees from mass transfer limitations. These limitations may require operation at considerably less than economic optimum current densities. Mass transfer to a surface may be considerably enhanced by insertion of turbulence promoters in the fluid flow path near the affected surface. An instrument was developed to measure local current densities in the hydrodynamically very difficult region near the turbulence promoter. A general method for the relative evaluation of hydrodynamic conditions has been developed. Generalization of the data permits optimization of hydrodynamic cell design using the promoter shapes investigated.
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    Journal of applied electrochemistry 7 (1977), S. 501-504 
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    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract A simple procedure for the oxidation of benzyl alcohols to aldehydes is described. The oxidizing agent is hypobromite generated by the anodic oxidation of aqueous bromide and the reactions are carried outin situ in an undivided cell in an amyl acetate/water emulsion containing 2% tetrabutylammonium bisulphate.
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    Journal of applied electrochemistry 7 (1977), S. 505-510 
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    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract It is shown that the inhibiting effect of an additive (lead acetate) on the irregular growth of zinc electrodeposits is connected with a change in the kinetics of the reaction. In both alkaline and acid electrolytes, the range of current densities leading to compact deposits is widened by the additive. Simultaneously a shift of the current-potential curves towards more cathodic voltages is observed, and this inhibition rises with an increase of the additive concentration. In addition, the disappearance of the multiple steady states and the change observed at low frequencies in the impedance diagrams prove that the additive modifies the rates of some of the elementary reactions taking place at the interface and seems to decrease the importance of the autocatalytic step in the reaction mechanism.
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    Journal of applied electrochemistry 7 (1977), S. 539-544 
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    Journal of applied electrochemistry 7 (1977), S. 517-530 
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The kinetics for the hydrothermal decomposition of sodium amalgam was studied in the presence of water and caustic soda on graphite electrodes containing iron. Regression analysis of over 1000 data points in a linear regression analysis yielded the following rate expression, explaining 89% of the variance in the data, leaving 11% of the variance unexplained: r=−d(Na)/dt=187.8 (T)−2/3 exp (− 196.9/RT) (Na)3/4 (NaOH)−1/5. The decomposition rate of sodium amalgam is strongly limited by the rate of diffusion of sodium metal atoms in the mercury, and also the activity of water at the active cathodic sites on the catalyst. The activation energy for charge transfer for this process is low at 196.9 cal mol−1 or 8.5 mV. The range of variables studied was: temperature −25, 50 and 85° C; caustic concentration −10, 30 and 50 wt.%; amalgam concentration −0.1,0.2 and 0.3 mol.%, and finally with iron concentrations in the graphite matrix of − 215.9, 929.5 and 6180 ppm.
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