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  • Articles  (4,207)
  • Springer  (4,207)
  • National Academy of Sciences
  • 1995-1999
  • 1975-1979  (4,207)
  • 1978  (4,207)
  • Energy, Environment Protection, Nuclear Power Engineering  (3,125)
  • Electrical Engineering, Measurement and Control Technology  (1,082)
Collection
  • Articles  (4,207)
Years
  • 1995-1999
  • 1975-1979  (4,207)
Year
Journal
  • 1
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    Optical and quantum electronics 10 (1978), S. 83-93 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract An analysis of the role of tunnelling rays in pulse propagation in graded-index fibres is presented. Tunnelling ray attenuation is handled by using the generalized parameter technique which allows attenuation coefficients to be dispensed with and relevant families of tunnelling rays to be identified. Results are given for impulse response pulse widths and shapes. Incorporation of tunnelling ray pulse contributions into the formalism for determining optimum refractive-index profiles is presented. For most cases, tunnelling ray effects are small, but significant corrections may be necessary when measurements are made on short lengths of fibre.
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  • 2
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    Optical and quantum electronics 10 (1978), S. 131-138 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Fifth order non-linear processes produced by a focused beam in metal vapour have been investigated experimentally. Evidence of saturation of fifth harmonic generation by picosecond laser pulses is reported.
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  • 3
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    Optical and quantum electronics 10 (1978), S. 107-117 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract In this paper power coupling between two multimode optical fibres is investigated. A formalism (based on a geometrical approach) suitable for analysing any coupling configuration between fibres with any index profile and any radiance distribution is presented. The model is applied to obtain coupling losses both in uniformly excited parabolic- and step-index fibres, in the presence of all kinds of coupling errors. Numerical results of extensive utility are shown and useful asymptotic expressions of coupling efficiency, valid for small values of coupling error parameters, are derived together with some practical rules for error combination. Mention is also made of some experimental results we have obtained, which corroborate some previous assertions. The work can supply a useful tool in the design of joints and connectors between single fibres or optical cables.
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  • 4
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    Optical and quantum electronics 10 (1978), S. 153-161 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The photon drag and optical rectification response fromn-type gallium phosphide containing 2.4×1016 electrons cm−3 has been studied using laser sources at 10.61 and 2.83μm. By using different contact configurations, the existence of an additional electric field term in the propagation direction has been deduced. This field is shown to arise from the spatial derivatives of the photon drag and optical rectification field components caused by absorption of the radiation. The importance of this effect in detector design is considered.
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  • 5
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    Optical and quantum electronics 10 (1978), S. 171-178 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract On the basis of the theory of coupled waves the amplitudes of the first-order diffracted waves and the diffraction efficiency is calculated for sequentially superposed phase gratings stored in dielectric reflection holograms. The investigations are restricted to the case of a fixed reference wave during recording and Bragg-angle incidence. By analogy to the transmission volume grating the coupling effects which appear between incident beams and diffracted waves give the possibility of building up beam-couplers and -splitters with certain coupling parameters determined by the recording process. Moreover, reflection gratings allow a favourable combination between coupling and reflecting properties and avoid the diffraction efficiency oscillations that are characteristic of transmission gratings. The performance of the reconstruction process with several waves simultaneously allows the tuning of the intensities of diffracted waves with dependence on amplitude or phase differences between incident beams.
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  • 6
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    Optical and quantum electronics 10 (1978), S. 181-183 
    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 7
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    Optical and quantum electronics 10 (1978), S. 9-15 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The optical processor proposed here consists basically of a coherent light source and two liquid crystal light valves, of which the first converts incoherent input patterns into coherent ones; the second operates entirely on coherent signals. It is shown that, if the valve operating point is correctly chosen and its transfer characteristic linearized, negative feedback is implemented around the second valve. The valves perform as active system components, because they modulate the source power by their driving signals. The linear dynamic range, modulation transfer function, and time transient behaviour of the system are briefly studied.
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  • 8
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    Optical and quantum electronics 10 (1978), S. 31-40 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The propagation of electromagnetic waves along a radially-inhomogeneous single-mode optical fibre with small index difference between core and cladding is studied. As in the case of the step-index fibre the propagation modes are weakly guided and their transverse fields are essentially polarized in one direction. The simple field descriptions and characteristic equation obtained here enable mode spot size and bending loss to be determined and are useful for practical design work of radially-inhomogeneous single-mode optical fibres.
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  • 9
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    Optical and quantum electronics 10 (1978), S. 17-29 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A two-dimensional real waveguide having a parabolic distribution of dielectric permittivity in the core region, flanked by cladding layers of constant refractive index is proposed as a model for a class of stripe-geometry injection lasers. The model is analysed by a series-solution method and results are given in terms of plots of normalized propagation constant, near-field filling factor, and far-field half-angle, all versus normalized frequency. These results are compared with those for the alternative models of (a) a homogeneous core waveguide, and (b) a medium whose dielectric permittivity varies quadratically with position throughout the whole of space. Apart from the series-solution method which was employed, a survey is included of other techniques available for analysing this waveguide model. These include perturbation theory, variational analysis, an exact solution of the scalar wave equation, and the WKB approximation.
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  • 10
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    Optical and quantum electronics 10 (1978), S. 53-60 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A ray theory based on the time-independent Fokker-Planck equation and the integration of time along ray trajectories provides analytical expressions for the average arrival time and spread of optical pulses propagating in randomly distorted, multimode, optical fibres. A clear physical picture emerges from the theory. The analytical expressions obtained for 〈t〉 and 〈t 2〉 coincide with the ones obtained by Olshansky from coupled-mode theory. The 〈t 3〉 and 〈t 4〉 moments of the impulse response are also calculated. Simple closed-form formulae are given for the step-index slab. The coupling between all modes is effectively taken into account in our ray theory.
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  • 11
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    Optical and quantum electronics 10 (1978), S. 61-82 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract If light comes from a fixed direction and is to be collected onto an absorbing body which is approximately a point or a straight line, it is well known that a mirror of parabolic profile serves the purpose efficiently. If the light is diffuse, or its direction of incidence variable, or if the absorber is not approximately a point or a straight line, the parabola is less useful. This paper describes various particular collecting problems of this more general sort, together with efficient solutions for them, mainly by means of mirrors. The subject represents a corner of geometric optics little explored until recently, in which the notion of image formation scarcely appears. A unifying principle is the invariance of the ‘Lagrange-Helmholtz’ invariant, which is related to Liouville's theorem of Hamiltonian mechanics, and there is a unifying method of construction of the mirror profiles by means of string.
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  • 12
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    Optical and quantum electronics 10 (1978), S. 119-129 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Frequency stabilization using ‘mobile’ resonances is compared with that employing frequency modulation. Analogy with radio-frequency experiments leads to an optimization of the error signal. Offsets occuring in each case are discussed and additional offsets due to asymmetry are evaluated.
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  • 13
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The influence of bulk losses and bulk dispersion on the propagation properties of surface waves in a radially inhomogeneous optical fibre is investigated numerically. The fibre is assumed to consist of a homogeneous cladding of either infinite or finite extent and a radially inhomogeneous core of higher permittivity. Bulk losses and dispersion in the core and cladding materials are presented by frequency-dependent complex permittivities. Power series expansions for the electromagnetic field quantities in the core have been used and the attenuation and the phase coefficients for the lower order modes have been calculated numerically. Results are presented for two different permittivity profiles, viz. the parabolic profile and the cubic spline profile, the cladding being of infinite extent in this case. Also, the influence of a finite cladding diameter on the numerical results is discussed.
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  • 14
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    Optical and quantum electronics 10 (1978), S. 139-151 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A simple model for the description of intracavity measurements of narrow absorption lines, developed in a previous paper [5], is generalized to include the effect of an inhomogeneous, in addition to the homogeneous, contribution to the laser line. Moreover, the standing wave effect which was previously treated only near threshold, is now properly studied well above threshold. It is shown that mode competition increases strongly, in the case of a large number of standing waves falling within the homogeneous laser line width, when one passes from the near threshold region to a high excitation level. The enhancement factor, however, is nearly independent of the intensity. Consideration is also given to the case of running waves.
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  • 15
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    Optical and quantum electronics 10 (1978), S. 163-170 
    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A composition-dependent single Sellmeier oscillator model, developed for predicting the refractive index against composition behaviour for the three binary glass systems, SiO2-B2O3, SiO2-P2O5 and SiO2-GeO2, is extended to a double Sellmeier oscillator model. The inclusion of both composition-dependent u.v. and i.r. terms in the Sellmeier equation has enabled the wavelength dispersive properties of optical glass fibres; refractive index, material dispersion and profile dispersion, to be computed for any composition, in any one of these three binary glasses. Theoretical calculations, for particular compositions, of material and profile dispersions are compared with experimental measurements on fibres of the same compositions, fabricated by chemical vapour deposition.
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  • 16
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    Optical and quantum electronics 10 (1978), S. 179-180 
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  • 17
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    Optical and quantum electronics 10 (1978), S. 184-185 
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  • 18
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    Optical and quantum electronics 10 (1978), S. 186-187 
    ISSN: 1572-817X
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  • 19
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    Optical and quantum electronics 10 (1978), S. 195-203 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract In the present paper the two-photon fluorescence (TPF) quenching produced by ruby lasers in dye is calculated on the basis of an electronic energy level system adapted for the special conditions of Rhodamine 6G. The model used here takes into consideration the action of competing one-photon processes. It will be shown that the reversed profile of TPF quenching in the overlap region is produced by the superposition of pulses with a time-dependent fluctuating phase as well as with a determinate quadratically time-dependent phase.
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  • 20
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    Optical and quantum electronics 10 (1978), S. 211-221 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A simplified theory for the performance of a digital optical receiver is developed. The receiver sensitivity is calculated in terms of circuit parameters, received and equalized pulse shapes, photodiode parameters and bit-rate. An excellent agreement between this theory and a more complicated analysis by Personick [4] is demonstrated. It is shown that the receiver sensitivity may be improved by launching reduced-width pulses into the fibre, particularly if fibre bandwidth is a significant limitation. Reduced-width pulses bring benefits in source power consumption and lifetime, and in timing recovery.
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  • 21
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    Optical and quantum electronics 10 (1978), S. 233-242 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The influence of the spectral width on the modulation behaviour of semiconductor injection lasers has been investigated theoretically on the basis of multimode rate equations. Analytical expressions are derived yielding an effective rate of spontaneous emission for a suitable description of dynamic characteristics of injection lasers. This effective emission rate may drastically exceed the total rate of spontaneous emission into the lasing modes. In the case of large signal modulation it has been shown that a large modulation depth as required for PCM-transmission also yields a considerable spectral broadening.
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  • 22
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    Optical and quantum electronics 10 (1978), S. 270-272 
    ISSN: 1572-817X
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  • 23
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    Optical and quantum electronics 10 (1978), S. 273-276 
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  • 24
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    Optical and quantum electronics 10 (1978), S. 279-282 
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    Optical and quantum electronics 10 (1978), S. 283-291 
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    Notes: Abstract A novel method is proposed for selecting a single longitudinal mode in lasers with homogeneously broadened gain medium. Mode selection is achieved by the interaction of the standing cavity wave between the gain medium and a spatially saturated absorber. The theory is treated in detail for various geometric configurations including examples of important laser systems under continuous-wave operation, such as dye lasers.
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  • 26
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    Optical and quantum electronics 10 (1978), S. 323-330 
    ISSN: 1572-817X
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    Notes: Abstract Mode coupling coefficients and coupling lengths are determined for multimode fibres with general index distributions in the case where random bending is the main cause of mode coupling. It is shown that the product of the coupling length and the coupling-induced loss is determined only by the shape of the index distribution, and that the coupling length of the focusing fibre is about four times longer than that of the step-index fibre when the coupling-induced losses of both fibres are equal.
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    Optical and quantum electronics 10 (1978), S. 341-351 
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    Notes: Abstract A single expression is presented for the power transmission coefficient of both step- and graded-index fibres, which is uniformly valid for all weakly tunnelling and refracting rays. Its accuracy is demonstrated in a comparison of the corresponding power attenuation coefficient for the step-index fibre with solutions to the electromagnetic boundary value problem.
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  • 28
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    Optical and quantum electronics 10 (1978), S. 361-363 
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  • 29
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    Optical and quantum electronics 10 (1978), S. 367-381 
    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The progress of ultra high-speed photography using electron-optical devices is surveyed with special reference to recent work in the USSR. In some applications time resolutions of better than 1 ps are obtainable. The ultimate limits of streak camera techniques are discussed. Finally, systems for X-ray chronography are described.
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    Optical and quantum electronics 10 (1978), S. 353-360 
    ISSN: 1572-817X
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    Notes: Abstract A detailed analysis of a symmetric cladded slab waveguide having a parabolic refractive-index profile in the core is carried out. Two techniques, one based on the step-index approximation and the other on the WKB approximation, are used to obtain the dispersion curves and the field plots for both the even and odd TE and TM-modes. An example of the practical relevance of the structure studied is given.
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    Optical and quantum electronics 10 (1978), S. 331-340 
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    Notes: Abstract Through numerical solution of the Schrödinger equation we illustrate the influence of laser modulation upon the excitation of anN-level system irradiated by simultaneous laser pulses. We show that amplitude modulation, applied to a Gaussian statistical distribution of detunings, creates a sideband structure to the excitation-reaction profile which can enhance the excitation over that for monochromatic excitation.
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  • 32
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    Optical and quantum electronics 10 (1978), S. 364-366 
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  • 33
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    Optical and quantum electronics 10 (1978), S. 441-444 
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    Optical and quantum electronics 10 (1978), S. 475-482 
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    Notes: Abstract The characteristics of graded-index optical fibres with power-law core profile and homogeneous cladding have been studied using perturbation theory. Analytical expressions are derived for the cut-off frequency, propagation constant and, in the case of leaky modes, the attenuation coefficient of an arbitrary mode on such a fibre. For the case of monomode fibres, excellent agreement is found with existing theoretical results for the propagation constant of the HE11 mode and cut-off frequency of the TE01 mode.
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    Optical and quantum electronics 10 (1978), S. 459-474 
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    Notes: Abstract The field problem for DH stripe lasers is solved, using a two-dimensional model; the field variation perpendicular to the junction plane is found from a slab model, whereas the transverse variation is calculated using a method applicable to any complex permittivity profile. The origin of transverse variations in the permittivity is described by including current spreading, temperature variations and the carrier profile. The permittivity is used directly and not fitted by a parabola or a step. The fact that a large fraction of the intensity may be propagating in then-andp-layers, is taken into account by introduction of an effective permittivity. The model is applied to a practical example, and the threshold current is found as a function of active-layer thickness and stripe width. It is described how the model can be used both below and above the threshold.
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    Optical and quantum electronics 10 (1978), S. 483-493 
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    Notes: Abstract A technique is described for obtaining deep spatial modulation of laser beams. A phase modulator at one plane in the beam path can yield amplitude modulation at a later plane with little loss in power. Explicit formulae are derived for the field distributions of the modulated beams, and applications are considered.
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    Optical and quantum electronics 10 (1978), S. 1-8 
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    Notes: Abstract This paper points out that, in impulse response calculations by the method of Gloge and Marcatili, the condition that the equal propagation constant lines and the equal group delay lines coincide is not satisfied except for a power law index profile. The group delay time is derived in this paper, by a perturbation method. The optimum index profile is determined from the measured refractive indices data of several doped silica glasses. It is found that (1) the optimum value of the fourth order coefficient is not so different from the value which minimizes the modal dispersion, except in the short wavelength region, (2) the wavelength which minimizes the total dispersion is near 1.30μm and (3) a B2O3 doped fibre has a small profile dispersion and a small total r.m.s. width.
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    Optical and quantum electronics 10 (1978), S. 41-51 
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    Notes: Abstract A model for the analysis of the bandwidth along an optical transmission line is suggested and tested on the Post Office experimental link. It is found that optical equalization is a real effect that has been observed in practice and that the degree of equalization is affected by only two major factors. These are the degree of mode coupling in the route and the functional relationship between mode delay and mode number. Finally a procedure for the optimization of the bandwidth of a link is suggested and tested.
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    Optical and quantum electronics 10 (1978), S. 503-507 
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    Notes: Abstract The properties of a volume-phase hologram of the reflection type are studied in the case when the reference and object waves are beams of finite width. Numerical results are obtained by considering a sufficiently large number of terms in a previously derived infinite series solution. The results reproduce Kogelnik's one-dimensional theory [1] when the thickness of the hologram is small in comparison with the widths of the beams but otherwise the finiteness of the recording beams leads to significant variations in the amplitude of the reconstructed beam.
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    Optical and quantum electronics 10 (1978), S. 515-520 
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    Notes: Abstract High intensity laser irradiation of a plasma can accelerate the electrons to relativistic velocities. For circularly polarized light the refractive index,n, of the collisionless plasma is then a time-independent function of laser and plasma frequency as well as laser peak intensity; but for linearly polarized light,n (i.e., the wave or phase velocity of the wave in units of the speed of light in vacuum) also becomes a periodic function of time. The deeper the wave penetrates the plasma the higher becomes the multiplicity of values ofn. This means that the laser radiation transforms inside the plasma into several nonlinear waves with periodically changing phase velocities.
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    Optical and quantum electronics 10 (1978), S. 521-526 
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    Notes: Abstract Impulse responses of a wide class of multimode optical fibres with near-optimum index profiles are investigated. The index profile is described by three parameters: the power law exponentα, the magnitude and the width of a dip at the centre of the core. It is found that for overcompensated profiles (α〈α opt) a moderate dip decreases the r.m.s. dispersion. Leaky modes are found to improve the dispersion characteristics for fibres with a dip in the index profile. Impulse response measurements are interpretated to give information about the index profile.
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    Optical and quantum electronics 10 (1978), S. ii 
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    Optical and quantum electronics 10 (1978), S. II 
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    Optical and quantum electronics 10 (1978), S. 189-194 
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    Notes: Abstract The effect of self-focusing of the pump laser beam on the temporal growth of a parametric excitation has been investigated in the paraxial region. The two equations for the signal and idler modes have been decoupled by assuming the near self-trapping condition and a linearly varying phase mismatch. By employing the WKBJ approximation, it is found that the growth rate is a strong function of the radial intensity inhomogeneity of the pump laser beam. The condition for validity of the first-order approximate theory employed here has been derived.
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    Optical and quantum electronics 10 (1978), S. 205-210 
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    Notes: Abstract A low drive-voltage optical modulator using a Ti-diffused UNbO3 optical waveguide has been fabricated. Stabilization against ambient temperature change was realized by using a miniature halfwave plate. The halfwave voltage, 3 dB bandwidth, optical insertion loss and extinction ratio were 3·8 V (at 1·06μm wavelength), 850 MHz, 10 dB and 13 dB, respectively. A reduction scheme for the optical absorption caused by metallic electrodes, and an analysis of the modulator high frequency response are also reported.
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    Optical and quantum electronics 10 (1978), S. 223-231 
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    Notes: Abstract We present quantitative results for the effect of cladding absorption on the transmitted power and impulse response of a typical multimode, graded-index fibre that is excited by a Lambertian source. Power attenuation is due to the absorbing cladding material and the radiation loss of the tunnelling rays. Graded-index fibres are shown to be far less susceptible to the effect of cladding absorption than step-index fibres.
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    Optical and quantum electronics 10 (1978), S. 266-269 
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    Optical and quantum electronics 10 (1978), S. 243-252 
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    Notes: Abstract A steerable laser radar suitable for a wide range of atmospheric studies is described. The system incorporates a flashlamp-pumped dye laser and a receiving telescope with a 0.3 m mirror. The steering capability is provided by the use of a 0.61 m by 0.46 m plane mirror for both transmission and reception. Manual and automatic control of the mirror drive is provided, with its angular position being recorded. Digital counting is used in the recording electronics. The performance of the system in measurements over a large range of heights in the atmosphere is illustrated.
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    Notes: Abstract This paper reports the transmission measurements made on 40 km of graded-index fibre which have been cabled and installed in operational ducts for use in 8 and 140 Mbits−1 systems. Extensive loss and bandwidth measurements were made at all stages of the programme, both before and after cabling and also in the field using two mobile test vehicles. The problems of obtaining meaningful and reproducible measurements are discussed and the stability of the measurements between the various cabling and installation stages is assessed. The results have been analysed in conjunction with additional laboratory measurements and a number of important propagation effects have been brought to light.
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    Optical and quantum electronics 10 (1978), S. 277-278 
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    Optical and quantum electronics 10 (1978), S. 293-300 
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    Notes: Abstract The effects of photodiode bulk leakage current and amplifier noise on receiver sensitivity are analysed using a model described previously [4]. The sensitivity of a receiver using a PIN photodiode can be greatly improved by employing a high-performance microwave FET in the input stage, to the point where its remaining technical disadvantage in comparison with a silicon APD receiver at 800–900 nm may be offset by economic and operational attractions. In systems operating at the optimum transmission wavelength beyond 1.1 μm, the PIN-FET hybrid receiver may offer better technical performance than an APD receiver.
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    Optical and quantum electronics 10 (1978), S. 301-309 
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    Notes: Abstract A theoretical study has been carried out on propagation in single-mode fibres having a dip in the refractive index at the centre of the core. The energy of the mode gradually spreads from the centre of the core with increase of the degree of the dip. Nevertheless the near and far-field distributions of such single-mode fibres are very nearly Gaussian in shape. A simple method of estimating the limit of the single-mode region for any kind of index profile is presented. For a particular class of profiles, dip widths up to 30% have a negligible effect on the propagation characteristics.
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    Optical and quantum electronics 10 (1978), S. 311-322 
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    Notes: Abstract Repetitive self-pulsations under CW operation in the frequency range of 200 MHz–2 GHz are observed in many (GaAl)As double-heterostructure injection lasers. About 100 lasers of both low-mesa stripe geometry and with proton-implanted structures have been studied and about half of them exhibited more or less pronounced self-induced pulsations. The experimental results on three typical lasers are discussed more in detail on the basis of existing theories. Self-induced pulsations have often been observed in the non-linear region of the laser light output characteristic. The most probable reason for the instabilities appears to be a repetitive Q-switching process.
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    Optical and quantum electronics 10 (1978), S. 393-398 
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    Notes: Abstract Using a Y3Fe5O12 crystal as a Faraday rotator material, a samarium cobalt permanent magnet and two iron yokes, a compact optical isolator was constructed at 1.153μm for optical transmission systems. The developed isolator is 13 mm in diameter and 25 mm in length, including two polarizers. The isolator characteristics are 1.3 dB forward loss and greater than 30 dB backward loss. A broadband isolator is realized by inserting a 45 degree Faraday rotator and an optically active 45 degree quartz rotator between the two polarizers set at 90 degrees in relation to each other.
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    Optical and quantum electronics 10 (1978), S. 425-433 
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    Notes: Abstract An optical ring resonator with asymmetric three-layered dielectrics is shown to have an anomalously highQ-factor compared with the conventional symmetric three-layered ring resonator by several orders of magnitude for suitably chosen parameters. A new leaky mode which can propagate on the asymmetric structure is found having an extremely small attenuation loss near the cut-off frequency of the guided mode, but which does not exist in the symmetric structure. Optimum values of the normalized frequency for a single-mode operation to suppress the undesired leaky modes are discussed. It is also shown that the size of the ring resonator using the asymmetric structure can be reduced considerably from that of the ordinary symmetric resonator.
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    Optical and quantum electronics 10 (1978), S. 383-392 
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    Notes: Abstract A multi-layered graded or step-index optical waveguide of slab or cylindrical geometry and composed of slightly lossy core and cladding materials is regarded as a superposition of separate layers. The ray power loss within each layer can be summed to determine the total power loss and the power attenuation coefficient along the guide. This building-block approach accounts for losses due to both tunnelling and absorption. In general, for practical waveguides, the total loss can be written down by inspection as a combination of six basic terms. Power loss along the ray path, in the neighbourhood of caustics and in the evanescent regions associated with the ray fields are all included in the description.
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    Optical and quantum electronics 10 (1978), S. 399-423 
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    Notes: Abstract The amplified spontaneous emission in dye solutions excited with intense picosecond light pulses is studied theoretically. A multi-level model is applied to take into account the effects of the various dye parameters such as ground-state absorption, stimulated emission, excited-state absorption, reabsorption and relaxations from populated excited levels. The influence of the pump laser duration and intensity and of the dye concentration and sample length is investigated. Optimum situations are derived for the generation of intense picosecond light pulses at new frequencies by amplified spontaneous emission. On the other hand, conditions are found where amplification of spontaneous emission may be neglected. The analysis allows the determination of unknown dye parameters by comparing the calculations with the experiment.
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    Optical and quantum electronics 10 (1978), S. 435-439 
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    Notes: Abstract A scanning optical microscope in which an image is produced from the generation of optical second harmonics within the specimen has been constructed. Pictures have been obtained from various crystals which show high contrast levels and detail not visible with the conventional microscope.
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    Optical and quantum electronics 10 (1978), S. 445-458 
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    Notes: Abstract The variance of the jitter in a timing recovery circuit for fibre optical digital transmission is computed. The timing circuit is simply a narrow-band filter, tuned to the pulse repetition frequency. It is found that, if the time dispersion of the fibre is limited, this circuit provides satisfactory timing information.
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    Optical and quantum electronics 10 (1978), S. 495-501 
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    Notes: Abstract Multiplicity of the output frequency of a spin-flip laser, caused by the simultaneous multiline operation of the CO pump laser, is identified. This multiplicity is shown to arise from a four-wave mixing process for which only a single input threshold intensity exists for oscillation. Experimental data are presented together with a determination of the interdependence of the input and output frequency power ratio.
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    Optical and quantum electronics 10 (1978), S. 509-514 
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    Notes: Abstract Exact equations are derived for mode cut-off frequencies on a W-fibre enabling the range of monomode operation of such a fibre to be accurately determined. Solutions are presented for a variety of parameters showing the influence of the refractive index and thickness of the inner cladding on the propagation characteristics of the fibre.
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    Optical and quantum electronics 10 (1978), S. 527-528 
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    Optical and quantum electronics 10 (1978), S. 529-532 
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    Optical and quantum electronics 10 (1978), S. 533-535 
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    Power technology and engineering 12 (1978), S. 12-19 
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    Notes: Conclusion Protection of the Sayano-Shushenskoe spillway from cavitation erosion is achieved by an aeration sill behind the radial gate and an aeration groove at elevation 35.25 m. The air content in the near-bottom layer (without consideration of its increase in the prototype) will be at least 6–8%, which is sufficient to eliminate cavitation erosion. As a consequence it seems possible to reduce the grade of concrete in the spillway with a strength of 400 kgf/ cm2 to grade 300 kgf/cm2. Protection of the upper concrete-hauling trestle from splashes is provided by deflectors.
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    Power technology and engineering 12 (1978), S. 26-26 
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    Power technology and engineering 12 (1978), S. 51-60 
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    Power technology and engineering 12 (1978), S. 71-72 
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    Power technology and engineering 12 (1978), S. 61-64 
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    Notes: Conclusions 1. When comparing alternatives of hydroelectric stations which differ with respect to the magnitude of hydraulic losses, the introduction of supplementary outlays for thermal-electric stations, corresponding to the “lost power,” leads to an unjustified increase in the volume of work and in the cost of structures and equipment for hydroelectric stations. 2. If the change in availability of the design head caused by hydraulic losses is small and does not give rise to a perceptible effect on the power indexes of the hydroelectric station, then the effect of hydraulic losses on the power generation of the station can be ignored. 3. Where it is necessary to preserve the availability of the design head and hydroelectric-station output, this should be allowed for by a corresponding change in the value of the design head, introducing supplementary capital outlays only into turbine equipment and the structural part of the power-station building, which should be determined in accordance with actual indexes. 4. Taking into account the great importance that a correct allowance for hydraulic losses has in engineering-economic substantiations of alternatives for hydroelectric stations, appropriate recommendations for standards should be developed.
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    Power technology and engineering 12 (1978), S. 46-50 
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    Notes: Conclusions 1. In order to increase the operating period and service life of axial pumps transferring liquids with a high content of hard particles, they should be operated at maximum efficiency, at all installation angles of impeller blades. 2. Superimposition of isolines of hydroabrasive wear onto the universal characteristic diagram enables optimal operational regimes for pumps to be selected on a well-founded basis, and also makes it possible to make engineering-economic comparisons of alternative pumping-station arrangements which differ in the number of units. 3. The data obtained regarding changes in the zones of hydroabrasive wear on components of the flow-through parts of axial pumps, which occurs as their operating conditions are varied, enables design measures to be taken for their protection. 4. The protective effect of cavitation, which is based on the damping properties of the cavitation zone, when traced experimentally over a wide range of change in the concentration of the turbidity current and the operational pump parameters, enables, within certain limits, the intensity of total cavitational-abrasive wear to be reduced.
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    Power technology and engineering 12 (1978), S. 82-84 
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    Power technology and engineering 12 (1978), S. 80-81 
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    Notes: Conclusions In the author's opinion, the installation of drains by drilling holes from galleries should be considered the only valid and progressive method that makes it possible to install drainage from galleries working from bottom to top as the dam rises, irrespective of the procedure adopted for placing concrete in the dam.
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    Power technology and engineering 12 (1978), S. 98-99 
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    Power technology and engineering 12 (1978), S. 107-107 
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    Power technology and engineering 12 (1978), S. 998-1001 
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    Notes: Conclusions 1. At existing hydroelectric plants it is essential to carry out not only equipment repairs, with replacement of the rapidly wearing subassemblies, but also reconstruction work, including major jobs, which will improve quality indexes to meet modern demands on the operation of power systems and to ensure prolonged reliable equipment operation. At the same time there should be careful inspection and study of the maintenance documentation and the condition of the equipment. 2. Equipment reconstruction should be carried out as a combined project, bearing in mind that unreliable performance of any particular subassembly leads to unreliable operation of the whole turbogenerator. 3. In resolving the question of equipment reconstruction, it is essential to take into account the real prospects of long-term operation of the structures and equipment, not only under design conditions but also with the possible changes in such conditions.
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    Power technology and engineering 12 (1978), S. 995-997 
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    Power technology and engineering 12 (1978), S. 1006-1010 
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    Notes: Conclusions 1. As shown by foreign experience, the reconstruction of old hydroelectric plants may be an economical way of improving the use of hydropower resources and upgrading the role of hydroelectric plants in the load regulation of power systems. 2. There is experience with reconstruction of hydroelectric plants, ranging from the very large (Grand Coulee) to the very small. At low-head plants wide use is made of horizontal units when reconstructing. 3. In several countries, attention is paid to reconstruction of low-capacity hydroelectric plants) not only the equipment is modernized, but also use is made of automation, including computer complexes which increase the control reliability and reduce the need for operating personnel. 4. The increase in fuel prices in the world market has encouraged the reconstruction and modernization of old hydroelectric plants, which were formerly considered unprofitable. 5. To increase the hydroelectric plant capacity and improve streamflow regulation, hydraulic structures are being widely reconstructed; another factor resulting from reconstruction of hydraulic structures is the increase in their safety factor.
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    Power technology and engineering 12 (1978), S. 1033-1039 
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    Power technology and engineering 12 (1978), S. 1017-1020 
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    Power technology and engineering 12 (1978), S. 1021-1028 
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    Power technology and engineering 12 (1978), S. 1042-1043 
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    Power technology and engineering 12 (1978), S. 1057-1060 
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    Power technology and engineering 12 (1978), S. 1069-1070 
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    Power technology and engineering 12 (1978), S. 1120-1122 
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    Power technology and engineering 12 (1978), S. 1105-1112 
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    Notes: Conclusions In the core of the river-channel dam of the Ust-Khantaika hydroelectric plant rewetted, weakly compacted moraine soils and soil mixes were placed, which during the construction period were frozen, a very nonuniform core structure being formed with interbedding of thawed and frozen soils, which substantially differ in water content and density in the different zones: from hard to flowing (17%) and from loose (with γdr.d.≤1.4–1.5 g/cm3) to overcompacted (with γdr.d.≥1.8–1.9 g/cm3). 2. Control drilling permitted determining the actual core structure and the soil state as regards water content, density, and temperature, at the start of dam operation. The soil decompression regions under the upper frozen zone in the river-channel portion of the core were determined. 3. From field observations and controlled drilling data it was found that despite the nonuniform structure, composition, and state of the core soils, in the dam of the Ust-Khantaika plant there were no dangerous deformations or concentrated seepage centers during the first years after start of operation under the reservoir water pressure, and that thawing of the frozen zones and deformation of the dam take place very slowly. 4. Taking into account the unsteady temperature and seepage regimes of the core and the dam on the whole, as well as the established soil decompression zones, it is necessary to intensify the field observations on the unique river-channel dam of the Ust-Khantaika plant and to increase the control-measurement equipment and the frequency of the measurements. 5. In order to generalize and analyze the behavior of the river-channel dam during the first years of its operation and to determine the changes in the state and properties of the core soils, it is necessary to repeat control drilling and core inspection during 1979–1980. 6. The factual data on the structure, composition, and properties of the soils in the core of the Ust-Khantaika dam should be used in design practice for earth dams in the Far North, to improve their design features and the techniques for constructing their antiseepage components, as well as to work out long-term predictions of the behavior of such dams for operating under severe climatic conditions.
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    Power technology and engineering 12 (1978), S. 1135-1140 
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    Notes: Conclusions 1. The system developed for the field observations made it possible reliably to control the safety of the spillway dam during construction of the Dneproges-2 plant. 2. Analysis of the field-observation data indicated the absence of adverse changes in the state of the Dneprovsk spillway dam, which for a long period was subjected to the action of the special conditions caused by construction of the Dneprogés-2 plant. 3. In the construction joints and the foundation of the gravity dam, significant seasonal changes in the uplift pressure may occur. In this case, the stability and strength characteristics of the dam may periodically decrease during the winter, which must be taken into account for operating the structure.
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    Power technology and engineering 12 (1978), S. 1149-1150 
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    Power technology and engineering 12 (1978), S. 1151-1151 
    ISSN: 1570-1468
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
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    Power technology and engineering 12 (1978), S. 1170-1172 
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    Power technology and engineering 12 (1978), S. 1186-1189 
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Conclusions Standardization of the turbogenerators for the Lower Kama and Cheboksary plants is an effective measure which enables: a) the capital expenditure on the two plants to be reduced by about 3.4 million rubles; b) the labor input to be reduced and the utilization of equipment to be improved at the works engaged in the manufacture of the standardized units; c) identical scroll casings to be designed for both plants, the service cranes in the machine halls and the auxiliary-equipment systems to be standardized; d) practically equivalent overall dimensions and arrangements to be adopted for the hydrotechnical parts of the power-station building blocks, and of the layouts of the turbogenerator units, thus reducing the design effort on the two stations. Standardization of the hydropower equipment can be recommended for hydroelectric plants which have nearly the same head and are on rivers with comparable flow characteristics.
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    Power technology and engineering 12 (1978), S. 1219-1224 
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    Power technology and engineering 12 (1978), S. 1215-1218 
    ISSN: 1570-1468
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Conclusions 1. The choice of components and composition of concrete should be based on consideration of all factors of both the environment and the concrete that can have an effect on its cavitation resistance, including the climatic factor and degree of corrosiveness and erosiveness of the water. 2. Concrete should be of high strength and uniformity and the concrete mix should be plastic for the placement method used. Evidently we can consider correct the suggestions of the “Methodological Recommendations” that the concrete grade should be 400 at 28 days. Higher grades can be recommended only if this does not involve a considerable increase in the cement content. 3. The frost resistance of concrete, especially in the surface layer, should be high. To increase it, it is recommended to use the additive hydropolysiloxane GKZh-94 at a rate of 0.2% of the weight of cement, which has shown good results. The use of other additives after conducting appropriate investigations is also possible. 4. To establish more confidence and to check the quality of concrete undergoing cavitation, it is necessary to develop a new criterion of frost resistance of the surface layers exposed to cavitation and to provide an appropriate method for determining it. 5. Both gravel and stone not containing weathered rocks, clean, and of good granular composition (with respect to the State Standard) can be used equally well as the coarse aggregate in cavitation-resistant concrete. 6. The surface of the concrete should be compact, smooth, and well streamlined to the flowing jet.
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    Power technology and engineering 12 (1978), S. 1232-1232 
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    Power technology and engineering 12 (1978), S. 1251-1260 
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    Power technology and engineering 12 (1978), S. 1261-1261 
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    Power technology and engineering 12 (1978), S. 141-146 
    ISSN: 1570-1468
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Conclusions 1. The data obtained should be used when modernizing turbines at existing low-head stations; analogous investigations of other types of turbines with higher heads should be carried out. 2. To create improved and more economical large high-speed turbines and to determine the conditions of applicability of vertical and horizontal bulb units, it is required to conduct comprehensive investigations for optimization and technicoeconomic comparison of units with consideration of all factors determining the reliability and economy of the hydrodevelopment as a whole and operating stability of the power system.
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