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  • 1995-1999  (36)
  • 1990-1994  (47)
  • 1965-1969  (20)
  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 4691-4698 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A model of the low-frequency Raman scattering intensity in glasses is proposed, which describes the spectrum in the region of the boson peak, typical of glasses. The model considers the boson peak as a result of first-order light scattering by harmonic quasilocalized vibrations. The amplitude, frequency, and polarization dependence of the light on the vibrational coupling coefficient C(ω) are estimated. The model predicts a linear frequency dependence of C(ω) in the region of the boson peak and the depolarization ratio as a function of the relative contribution of the longitudinal and transverse-type motions which comprise these quasilocal vibrational modes. Low-frequency Raman and Brillouin measurements have been made on SiO2 glass in order to check the predictions of the model regarding the amplitude and integrated intensity of the boson peak. The estimated ratio of these values to those of the Brillouin lines are in good agreement with experiment. Comparison of the theoretical and experimental values of the depolarization ratio for the boson peak shows a predominance of the transverse-type atomic motions in the low-frequency quasilocalized vibrational modes in glasses. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 1057-1065 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Quasielastic light scattering (QLS) in the frequency interval 100–1000 GHz is measured in some polymers: polycarbonate, polybutadiene, polystyrene, and poly(methyl methacrylate). To describe the spectra, a model of the fast picosecond relaxation processes responsible for the QLS, which is based on the damping of the boson peak vibrations by the dynamic hole volume fluctuations, is used. Within the frame of the model, the intensity of the fast relaxation process is proportional to the fractional dynamic hole volume (which above the glass transition temperature Tg is known as the fractional free volume). The hole volumes can be measured using the positron annihilation lifetime spectroscopy (PALS). The comparison of the literature PALS data in the four polymers with the QLS shows an apparent correlation between the relaxation strength and the fractional dynamic hole volume in good agreement with the predictions of the model. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 7053-7057 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Inelastic neutron scattering spectra of DNA-fibers are analyzed using ideas formulated recently in the field of the glass transition. The analysis reveals two temperatures, namely, T∼180–200 K and T∼230 K, at which the dynamics of DNA exhibits qualitative changes. The former is similar to the glass transition temperature, whereas the latter is similar to the crossover temperature recognized now as an important point for the dynamics of the glass transition. Exactly in this temperature range many other hydrated biopolymers show some dynamic transition and strong slowing down of their functions. The crossover temperature appears to be close to the crossover temperature of bulk water. A possible relation of the dynamic transition to functions of biomolecules and also to the dynamic transition in the hydration shell is discussed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Power technology and engineering 26 (1992), S. 551-556 
    ISSN: 1570-1468
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Power technology and engineering 29 (1995), S. 483-489 
    ISSN: 1570-1468
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Conclusions 1. During the physical modeling of the hydrothermal regime of cooling basins, processes of diffusion transfer may play a major role in shaping the temperature distribution. Estimation of the turbulent- and convective-diffusion coefficients under model and field conditions therefore assumes critical significant for determination of the quality, of the modeling. 2. For the actual conditions under which laboratory experiments are conducted, distortion of geometric scales of the hydrothermal model may be necessary both to ensure a turbulent flow regime, and to fulfill the self-similarity condition with respect to the thermal criterion-heat-exchange parameter. 3. Forcing of the flow of water in the model within limits established by corresponding standard documents, as well as a certain deviation in the difference between the densities of the cold, and hot water and the Chezy coefficient from those calculated from similitude conditions (in the example under consideration, by a factor of four and two, respectively), have virtually no reflection in the results of the modeling. The conclusions drawn may not lay claim to universality, since we examined only one of the characteristic schemes for which cooling basins are used. In addition to this, the example that we cited for calculating the hydrothermal regime of a cooling basin under model and field conditions illustrates greater potential use of mathematical models in estimating the effect of parameters of the physical model and the results of modeling. In the future, it is proposed to continue a series of numerical experiments dealing with study of problems associated with the hydrothermal modeling of cooling basins. In that case, it is submitted that basic attention be focused on the modeling of weather conditions, which are some of the basic factors defining the temperature regime.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Power technology and engineering 30 (1996), S. 257-266 
    ISSN: 1570-1468
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Conclusions 1. The proposed mathematical model of phytoplankton primary production and destruction permits estimating the dynamics of production and destruction processes both in operating and planned reservoirs as applied to the problem of calculating (predicting) the water quality and oxygen regime of these reservoirs. 2. A necessary condition of the practical use of this model is a preliminary determination of a number of its parameters on an operating reservoir-analog, the selection of which is not limited by any certain conditions related to its size, level of pollution, and trophic state, although, of course, it is advisable that it be close in these indices to the reservoir for which it serves as an analog. 3. The result of using this model for calculating phytoplankton primary production and destruction on an operating reservoir show that it reflects with less accuracy the dynamics of production and destruction during the growing season and with greater accuracy their annual values. 4. When using the given model for predicting phytoplankton primary production and destruction on operating or planned reservoirs it is advisable to calculate them in several variants with the use of various approaches to a determination of various parameters of the model so that the most preferable of the variants is selected in accordance with the purposes and tasks of predicting the water quality and oxygen regime of these reservoirs.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Power technology and engineering 32 (1998), S. 618-624 
    ISSN: 1570-1468
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Conclusions A mathematical model is proposed for the oxygen regime of a stratified reservoir. A model is based on representation of the reservoir on the whole or its layers individually as an ideal mixer. The thermal regime of a stratified reservoir is schematized by a two-layer model-epilimnion and hypolimnion, which provide the plane with a pronounced variation in water temperature (thermocline). In calculating the oxygen regime, the epilimnion and hypolimnion are considered individual reservoirs with their own water balance, which is linked, however, to the water balance of the reservoir on the whole. Characteristic features of the aeration and reaeration of the epilimnion and hypolimnion, and also the selectivity of water intake from the reservoir are considered here. Practical use of the model is illustrated in an example of the calculation of the oxygen regime of a hypothetical stratified reservoir, the characteristics of which are determined on the basis of field data derived from observations on the water bodies of the Zagorsk water-storage power plant. The proposed model can be used to predict the oxygen regime of stratified reservoirs and the ecological feasibility of nature-conserving measures directed toward improving the quality of their water and conserving fauna.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Power technology and engineering 30 (1996), S. 222-228 
    ISSN: 1570-1468
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Conclusions 1. The results of using the model of an ideal mixer for calculating one of the integral hydrochemical indices of water quality — the annual BOD5 dynamics observed on reservoirs of the Zagorsk PSS in 1989 — permit concluding the correspondence of this mode to the on-site observation data. 2. The methods of calculating the water self-purification coefficients developed on the basis of the model of an ideal mixer permit determining these coefficients by solving the inverse problem on the basis of the data of on-site observations of the actual water, hydrochemical, and hydrobiological regimes of an operating reservoir-analog (for conditions of a steady regime) and recalculating them theoretically for any given regime (steady and transient) of an operating or planned reservoir. 3. An evaluation of the accuracy of various methods of calculating the self-purification coefficients and water quality in a reservoir (main and simplified) for the example of calculating the actual annual BOD5 dynamics of the Zagorsk PSS reservoirs during 1989 showed that they give results close among themselves and to the observed BOD5. This permits recommending both methods for practical use jointly or independently of one another.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Power technology and engineering 30 (1996), S. 392-399 
    ISSN: 1570-1468
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Conclusions 1. The developed dynamic model of the oxygen regime of the reservoir is in essence the next modification of the classical steady-state Streeter-Phelps model proposed for describing the interaction between dissolved oxygen and BOD on the river stretch. 2. Underlying the given modification is the use, in the Streeter-Phelps model, of a dynamic ideal mixer model for describing the process of movement of water in the reservoir, unlike a river stretch, on a steady-state ideal displacement model and consideration of certain additional oxygen sources and sinks having a determining effect on the oxygen regime of the reservoir and related mainly to the production and destruction (mineralization) of phytoplankton as well as to the inflow of river and wastewaters and oxygen consumption by bottom deposits. 3. The proposed dynamic model includes the main (numerical) and simplified (analytical) methods of calculating the oxygen regime of a reservoir, the practical use of which for calculating and predicting this regime in particular operating and planned reservoirs showed that they give similar results and, consequently, can be used jointly or independently of one another.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1570-1468
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
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