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  • 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
    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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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Powder metallurgy and metal ceramics 33 (1995), S. 431-436 
    ISSN: 1573-9066
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A sintered composite material consisting of a two-component mixture of powders with different particle sizes was investigated. It was assumed that a layer with different mechanical properties formed at the component interfaces. A structural model and method of calculating the linear elastic modulus of the composite was proposed. Calculated results were compared with experimental data. It is shown that the properties of this class of materials can be predicted using the proposed model and method of calculation.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Biomedical engineering 29 (1995), S. 116-118 
    ISSN: 1573-8256
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Metal science and heat treatment 37 (1995), S. 53-55 
    ISSN: 1573-8973
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The use of titanium alloys for parts that operate under contact friction conditions is possible if the alloy's tribological characteristics are substantially improved. This paper concerns the investigation of technological, high-temperature, diffusion saturation with boron and phosphorus coatings on titanium alloy surfaces by the chemical precipitation of nickel.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Radiophysics and quantum electronics 38 (1995), S. 538-545 
    ISSN: 1573-9120
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We present the results of a study of the space-frequency energy distribution of the near acoustic field of noise radiation from a moving source. Dynamic spectrograms of the received signal of noise radiation in the frequency range of 0–2.0 kHz at distances of up to 1300 m are given. It is shown that the variation in the levels of spectral components of the signal due to interference modulation in the near field can attain 12 dB. The interference pattern is shown to occur over the entire range of considered distances of 100–1300m. Within the framework of ray theory, using hydrological data for C(z) in the region of measurements, we calculate the near field for a lumped noise source. The calculation results are in good agreement with the results of field experiments. It is shown that the sound velocity profile C(z) in the region of measurements has a pronounced influence on the interference pattern of the near field. Allowance for C(z) in the calculations of the near acoustic field within the framework of the existing theory allows one to predict the interference pattern and choose optimal distances for measurements under near-field conditions.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Metal science and heat treatment 37 (1995), S. 339-340 
    ISSN: 1573-8973
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Piano wire is a specific elastic element, which in most musical instruments is a source of sound vibrations of a specific frequency. In the production of such wire much attention is paid to an analysis of technological methods providing high functional properties for it. The present work concerns the effect of steel purity with respect to nonmetallic inclusions on the parameters of the acoustic properties of wire used for the production of strings of musical instruments.
    Type of Medium: Electronic Resource
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  • 8
    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
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  • 9
    ISSN: 1573-8221
    Keywords: laser radiation ; rate ; exposure ; irradiation site ; ischemic arrhythmia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Acute experiments on cats narcotized with nembutal using the same model of ischemic disturbances of cardiac rhythm reveal that the antiarrhythmic effect of laser depends on the rate and duration of exposure, while its degree of expression depends on the site exposed to radiation.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-9031
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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