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61.
M. V. Avdeev N. M. Blagoveshchenskii V. M. Garamus A. G. Novikov A. V. Puchkov 《Crystallography Reports》2011,56(7):1090-1095
The characteristics of the tripoli porous structure have been investigated by small-angle neutron scattering (SANS). Tripoli is a finely porous sedimentary rock formed by small spherical opal particles. Its main component is aqueous silica SiO2 · nH2O (80–90%). Tripoli is widely used in practice as a working medium for sorption filters and in some other commercial and construction technologies. The shape of the experimental SANS curves indicates the presence of small and large pores in tripoli. The small-pore size was estimated to be ~100 Å. The size of large pores turned out to be beyond the range of neutron wave vector transfers Q that are available for the instrument used; however, their size was indirectly estimated to be ~(2000–2500) Å. The pores of both groups behave as surfacetype fractal scatterers with the fractal dimension D ~ 2.2‐2.6. The densities of pores of these two groups differ by approximately three orders of magnitude (~1016 and ~1013 cm?3 for small and large pores, respectively); the fraction of large pores amounts to 70–80% of the total pore volume. The found pore characteristics (their densities, sizes, and relative volumes) are in satisfactory agreement (when a comparison is possible) with the absorption data. 相似文献
62.
63.
Maxim Avdeev Andrei Kholkin 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(12):e539-e540
The crystal structure of the low-temperature Na4Ti5O12 (tetrasodium pentatitanium dodecaoxide) phase has been solved and refined from X-ray and neutron powder diffraction data at 295 K. The structure is trigonal, space group P3, with Z = 1, although it is pseudo-centrosymmetric. The O and Na atoms form a distorted close-packed structure, where Ti atoms occupy octahedral sites. 相似文献
64.
Alexander V. Avdeev Eldar V. Goriounov Mikhail M. Lavrentiev Jr. Renato Spigler 《Applied Mathematical Modelling》2009
A behavior-oriented diffusion model, governing the time evolution of the cross-shore position of coastal profiles, is studied. Here, two time-independent, space-varying coefficients, which embody the relevant physical properties, are identified simultaneously. Two sets of real data, the first measured over 10 years at Duck, in NC (USA), the second obtained over 39 years measurements at Delfland (Holland), have been processed numerically by a suitable “inversion algorithm”, earlier developed by the authors. This is based on the minimization of a certain cost functional in order to identify both coefficients. The numerical results, obtained by solving the diffusion equation with the so-determined coefficients, favorably agree with the real data, which fact validates and calibrates somehow the diffusion model under investigation. A short-term prediction is finally obtained for coastal profiles, using such a model. 相似文献
65.
66.
Georgi E. Chernev Borislava V. Borisova Lyudmila V. Kabaivanova Isabel M. Salvado 《Central European Journal of Chemistry》2010,8(4):870-876
This work reports the sol-gel synthesis of silica hybrids. We determined the effect of the type and quantity of silica precursors
and organic compounds on the resulting structure, surface area, nanostructure design and size, and potential applications.
The structure of the synthesized hybrids was analyzed using FT-IR, XRD, BET-Analysis, SEM, and AFM. We demonstrate the immovilization
of whole living thermophilic bacterial cells with cyanocompound degradation activity in the synthesized silica hybrid biomaterials
by entrapment, chemical binding, and adsorption. 相似文献
67.
Georgi Vodev 《Mathematische Annalen》1991,291(1):39-49
Partially supported by Bulgarian Ministry of Science and Education under grant No. 52 相似文献
68.
Barrier-discharge excilamps operating in homonuclear chlorine, bromine, and iodine and their mixtures with inert gases have been studied. The spectral and energy characteristics of the barrier-discharge plasma have been obtained. The conditions have been determined at which the band D′ → A′ predominates in the spectra of molecules I*2 (342 nm), Cl*2 (257.8 nm), and Br*2 (291 nm). The efficiencies of I2, Cl2, and Br2 excilamps were found to be 1.6, 2, and 3.8%. 相似文献
69.
Heat transfer with steam condensation under moderate pressure on the surface of a horizontal tube immersed in a bubbling layer was experimentally investigated. A copper test section 16 mm in outer diameter and 400 mm in length was placed in a bubbling column 455 mm in diameter. Experiments were made under pressures of 0.14–0.8 MPa, with void fraction 0.04–0.23, vapor superficial velocities 0.05–0.42 m/s, liquid-wall temperature differences 47–105 K, and heat flux densities 0.12–0.8 MW/m2. The heat transfer process in the bubbling layer is shown to be of a high intensity: with moderate values of steam content, heat transfer coefficients reach 12–14 kW/(m2 · K). Data obtained showed that the known correlations do not consider the influence of pressure on heat transfer. For the first time, data on radial steam content distribution under pressures higher than atmospheric were obtained by an electroprobe method. A table of experimental data is presented. 相似文献
70.
An original experimental investigation of heat transfer with steam condensation on a surface of a horizontal cooled tube immersed in a bubbling layer was carried out. A copper test section 16 mm in diameter and 285 mm in length was placed in a bubbling column 295 mm in diameter. Experiments were made under a pressure of 0.72-3.8 MPa with volume steam content 0-0.18, steam superficial velocities 0-0.18 m/s, and liquid-wall temperature difference 38–106 K. The heat transfer process in a bubbling layer under high pressures is shown to be of considerably intensity; with moderate values of steam content heat transfer coefficients reach 10–12 kW/(m2·K). The use of the known correlations assumed for the case of air bubbling under atmospheric pressure results in systematically underestimating heat transfer by 30–80%. Data were obtained on heat transfer with film condensation of steam and natural convection of subcooled water at high temperature differences outside the range investigated earlier. Experimental data table is appended. 相似文献