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  • 2000-2004  (12)
  • 1995-1999  (36)
  • 1965-1969  (20)
  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 3122-3124 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using photoemission and inverse photoemission, we have been able to characterize the Cr2O3 oxide surface of CrO2 thin films. The Cr2O3 surface oxide exhibits a band gap of about 3 eV, although the bulk CrO2 is conducting. The thickness of this insulating Cr2O3 layer is twice the photoelectron escape depth which is about 2 nm thick. The effective Cr2O3 surface layer Debye temperature, describing motion normal to the surface, is about 370 K. From a comparison of CrO2 films grown by different techniques, with different Cr2O3 content, evidence is provided that the CrO2 may polarize the Cr2O3. © 2001 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 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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  • 3
    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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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 10189-10195 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Relaxation processes in polymethylmethacrylate were investigated using light scattering and mechanical relaxation techniques. The acoustic attenuation data cover the frequency range from 1 Hz to 17 GHz and the light scattering from 0.5 to 10 000 GHz. Analysis of the data in a broad temperature range (80–350 K) shows that the model of the asymmetric double-well potentials, traditionally used for description of the acoustic attenuation in glasses, cannot describe all the data consistently. It is shown that assuming an additional relaxation in GHz region with a constant loss spectrum provides a good agreement of the model with experimental data. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Optics and spectroscopy 89 (2000), S. 469-475 
    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Polarization aberrations (PAs) of laser radiation, defined as distortions of the wave-polarization characteristics, are considered within the framework of wave theory. The parameters describing these aberrations are introduced. It is established that PAs already appear in the paraxial region. PAs of a thin lens are calculated using the method of wave-polarization matrices. It is shown that, under certain conditions, the polarization state is modified at the axis of the laser beam.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The electronic structure of the strongly Coulomb correlated cuprate CuGeO3 has been calculated by the local-density-approximation method (LDA + U). The parameter U was varied from 0 to 8 eV. The results of the band-structure calculations are compared with experimental data obtained by means of X-ray photoelectron and resonant X-ray emission spectroscopy methods (Cu L $\alpha$ and O K $\alpha$ X-ray emission spectra). It is established that a LDA + U calculation with U = 4 eV reproduces well the X-ray photoelectron and X-ray resonant emission spectral data.
    Type of Medium: Electronic Resource
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  • 8
    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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  • 9
    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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  • 10
    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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