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  • 1
    Electronic Resource
    Electronic Resource
    A model of low-frequency Raman scattering in glasses: Comparison of Brillouin and Raman data (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 4691-4698 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.469517
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  • 2
    Electronic Resource
    Electronic Resource
    Use of a numerical model to assess certain positions of a procedure for the hydrothermal modeling of cooling basins (1995)
    Springer
    Power technology and engineering 29 (1995), S. 483-489 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02446553
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  • 3
    Electronic Resource
    Electronic Resource
    Mathematical modeling of primary production and destruction of phytoplankton in operating and planned reservoirs (1996)
    Springer
    Power technology and engineering 30 (1996), S. 257-266 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02443099
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  • 4
    Electronic Resource
    Electronic Resource
    Use of a model of an ideal mixer for calculating hydrochemical water-quality indices of a reservoir (1996)
    Springer
    Power technology and engineering 30 (1996), S. 222-228 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02443081
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  • 5
    Electronic Resource
    Electronic Resource
    Dynamic model of the oxygen regime of a reservoir (1996)
    Springer
    Power technology and engineering 30 (1996), S. 392-399 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02446420
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  • 6
    Electronic Resource
    Electronic Resource
    Characterization of vacancy-related defects introduced into silicon during heat treatment by deep-level transient spectroscopy and gamma-ray diffraction techniques (1996)
    Springer
    Applied physics 62 (1996), S. 259-262 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 61.72.Cc; 61.72.Ji; 73.61.Cw
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract.  Vacancy-related defects introduced into n-Si during annealing or aluminium diffusion at high temperatures (1000–1250 °C) have been studied. Different ambients (argon, nitrogen, vacuum and chlorine-containing atmosphere) were used to create a vacancy supersaturation during heat treatments. Three deep-level centers whose formation is governed by the presence of vacancies have been identified. They were characterized by the following temperature dependences of the thermal emission rate: e 3=7.92×107 T 2×exp(−0.455/kT), e 5= 2.64×106 T 2×exp(−0.266/kT), e 7=7.26×106 T 2×exp (−0.192/kT). The influence of different factors, such as heat-treatment conditions, concentration of oxygen and doping level in initial crystals, on center formation was studied. An asymmetric diffuse γ-ray scattering was observed near the surface of a crystal irradiated by thermal neutrons and annealed in a chlorine-containing atmosphere. This scattering is related to the formation of structural defects of the vacancy type. In the same region of the crystal, the concentration of the E7 center was one order of magnitude higher than that of other deep-level centers. Comparison of the γ-ray diffraction and deep-level transient spectroscopy (DLTS) data suggests that the formation of the center occurs under the conditions of Si supersaturation with vacancies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01575091
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  • 7
    Electronic Resource
    Electronic Resource
    Characterization of vacancy-related defects introduced into silicon during heat treatment by deep-level transient spectroscopy and gamma-ray diffraction techniques (1996)
    Springer
    Applied physics 62 (1996), S. 259-262 
    Details
    ISSN: 1432-0630
    Keywords: 61.72.Cc ; 61.72.Ji ; 73.61.Cw
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Vacancy-related defects introduced into n-Si during annealing or aluminium diffusion at high temperature (1000–1250°C) have been studied. Different ambients (argon, nitrogen, vacuum and chlorine-containing atmosphere) were used to create a vacancy supersaturation during heat treatments. Three deep-level centers whose formation is governed by the presence of vacancies have been identified. They were characterized by the following temperature dependences of the thermal emission rate:e3 = 7.92 × 107 T 2 × exp(− 0.455/kT),e 5 = 2.64 × 106 T 2 × exp( − 0.266/kT),e 7 = 7.26 × 106 T 2 × exp (− 0.192/kT). The influence of different factors, such as heat-treatment conditions, concentration of oxygen and doping level in initial crystals, on center formation was studied. An asymmetric diffuseγ-ray scattering was observed near the surface of a crystal irradiated by thermal neutrons and annealed in a chlorine-containing atmosphere. This scattering is related to the formation of structural defects of the vacancy type. In the same region of the crystal, the concentration of the E7 center was one order of magnitude higher than that of other deep-level centers. Comparison of theγ-ray diffraction and deeplevel transient spectroscopy (DLTS) data suggests that the formation of the center occurs under the conditions of Si supersaturation with vacancies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01575091
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  • 8
    Electronic Resource
    Electronic Resource
    Linear low-temperature dependence of the surface impedance of a Ba0.6K0.4BiO3 single crystal (1996)
    Springer
    JETP letters 64 (1996), S. 832-838 
    Details
    ISSN: 1090-6487
    Keywords: 84.37.+q ; 74.72.Yg ; 74.72.Bk ; 74.72.Hs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The temperature dependences of the real part R s and the imaginary part X s of the surface impedance Z s =R s +iX s of the superconductor Ba0.6K0.4BiO3 (T c ≃30 K) are measured at a frequency of 9.4 GHz. Its temperature dependence Z s (T) and that of the complex conductivity σ s (T) can be described on the basis of a two-fluid model under two assumptions: The density of superconducting carriers increases linearly, and the relaxation time increases as a power law (∝1/T 5), with decreasing temperature T〈T c . This model also describes well the curves Z s (T) and σs (T) recently measured for YBa2Cu3O6.95 and Bi2Sr2CaCu2O8 single crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.567255
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  • 9
    Electronic Resource
    Electronic Resource
    Application of technetium-99m hexamethylpropylene amine oxime single-photon emission tomography to neurologic prognosis in patients undergoing urgent carotid surgery (1995)
    Springer
    European journal of nuclear medicine 22 (1995), S. 132-138 
    Details
    ISSN: 1619-7089
    Keywords: Acute cerebral ischaemia ; Carotid endarterectomy ; Technetium-99m hexamethylpropylene amine oxime ; Single-photon emission tomography ; Discriminant analysis ; Prognosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In this study we aimed to work out a quantitative prognostic index for preoperative assessment of brain technetium-99m hexamethylpropylene amine oxime (HMPAO) single-photon emission tomography (SPET) in patients referred for urgent carotid endarterectomy due to acute obstructive disease of the internal carotid artery (ICA) and neurological deficit. To this end we compared data from preoperative SPET studies with the postinterventional changes in neurological status in 20 patients (17 males, three females; mean age 53 years, SD 4 years) with acute ischaemic cerebral disorders induced by obstruction of the ICA. Carotid obstruction was diagnosed by ultrasound B-mode study. All patients underwent urgent carotid endarterectomy from the ICA. Patients were divided into two groups in accordance with the results of postoperative follow-up: group A comprised patients with significant (more than 3 points) postoperative improvement in neurological condition as quantified by the Canadian Neurological Scale (11 patients); group B consisted of patients with minimal improvement or deterioration (nine, three of whom died). All patients were studied preoperatively by99mTc-HMPAO SPET. The volume of nonperfused tissue (VS, cm3) was quantified using the Mountz technique. Hypoperfused volume (V hypoperf, cm3) in the affected hemisphere was calculated as the total volume of voxels with99mTc-HMPAO uptake 〈90% of the contralateral symmetric voxels. Discriminant prognostic function was calculated by discriminant analysis as:PF = 0.072×VS + 29.46×(VS/V hypoperf). Patients with preoperativePF values 〈8.20 demonstrated postoperative improvement in neurological status, while the group withPF〉8.90 comprised patients who demonstrated minimal improvement or deterioration. PF values in the range 8.20–8.90 carried an indefinite prognosis. We conclude that the preoperative99mTc-HMPAO SPET can be used for the selection of patients in whom improvement in neurological status may be expected after urgent surgical correction of acute extracranial obstruction of the ICA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00838943
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  • 10
    Electronic Resource
    Electronic Resource
    Comparative assessment of the indications of different types of radon meters (1996)
    Springer
    Atomic energy 81 (1996), S. 479-488 
    Details
    ISSN: 1573-8205
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02415731
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