The drying of a cellulosic fibrous material by acoustic-convective and thermal-convective methods under different conditions has been studied. Using the thermal-vacuum drying method, the weight of an ...absolutely dry sample of the starting material was determined and used to calculate the initial absolute and relative moisture contents, which were 12.38% and 10.96%, respectively. The dynamics of capillary impregnation and sorption wetting of samples was determined. The limiting values of the absolute and relative moisture content of cellulose fibers were found to be 862.16% and 89.47%, respectively. The kinetic curves of moisture extraction obtained in acoustic-convective and thermal-convective drying under different conditions were constructed, analyzed, and compared. It is shown that the acoustic-convective extraction of moisture has an advantage over the thermal-convective method.
The design, properties, and applications of transparent glass-ceramics are reviewed. Interference effects in light scattering by transparent glass-ceramics are discussed. The scattering coefficient ...of transparent glass-ceramics is found to be significantly less than that for the case of independent Rayleigh scattering by nanocrystals; its wavelength dependence is qualitatively different. A reduction in interference effects achieved by precipitation of nanocrystals of different crystalline phases with different scattering properties results in glass-ceramics with high diffuse reflection. The origin of the low coefficient of thermal expansion of glass-ceramics is discussed based on the temperature dependence of the unit cell parameters of β-quartz solid solutions measured by in situ high-temperature x-ray diffraction. Transparent glass-ceramics doped with Co2+ and Ni2+ ions for thermal shock-resistant color filters, for broadband near-infrared (IR) optical amplifiers, and for passive Q-switching of eye-safe Er lasers are presented. Glass-ceramics with rare-earth titanates, titanates-zirconates, and niobates in dual roles of nucleators and active crystals are reviewed.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The purpose of this study is to determine the influence of the diameter of a subsonic conical nozzle on the generation of acoustic waves in a two-channel system. Three-dimensional numerical ...simulation of flow in the duct of an actual device was performed. A complete picture of the flow generated in the acoustic-convective drying system of the Institute of Theoretical and Applied Mechanics, SB RAS, was obtained. The results of the study show that to maintain the amplitude-frequency characteristics of the workflow with increasing diameter of the subsonic conical nozzle, it is necessary to reduce the settling chamber pressure. The numerically simulated amplitude-frequency characteristics of the acoustic flow generated in the working section of the drying system are in satisfactory agreement with the results of physical experiments.
The need to increase the precision with which the form of the pulse of the rapidly varying current of powerful plasma radiation is recorded under the conditions of powerful electromagnetic induction ...is considered. It is suggested that that a polarimetric fiber-optic current sensor based on a Spun-type light guide should be used to record powerful pulsed discharges. With the use of this type of current sensor it becomes possible to implement a technique of recording powerful pulse discharges of a plasma radiator in a regime of time profiling of the current pulse of two high-voltage capacitative storage devices with total energy up to 1800 kJ. The discharge chamber, power circuit, and evolution of the plasma discharge are described. The design and operating principle of a prototype of a two-pass polarimetric fiber-optic sensor with Spun-type optical cable and Faraday compensator that exhibits mutual optical anisotropy are presented. The general scheme of current measurements and the calibration circuit of the sensor are presented and experience gained from the use of a prototype of a sensor for measurement of powerful current pulses is described. Features of pre-calibration of the sensor are discussed. Results of a measurement of current by optical and traditional methods of recording based on the use of a Rogowski coil and Hall sensors are compared and a significant increase in the precision of reproduction of the shape of the current pulse by the optical method of recording is noted. Different modes of modernization of a fiber-optic sensor for expanding the range of recording current are considered.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This paper is devoted to an experimental study of the characteristics of the operating flow in a two-channel system of an acoustic-convective dryer (ACD), developed at the Institute of Theoretical ...and Applied Mechanics (ITAM) SB RAS. A parametric study of cylindrical resonator depth and pressure in settling chamber influence on amplitude-frequency characteristics (AFC) of the formed flow is carried out. The influence of pressure in settling chamber and geometry of resonant cavity on AFC are considered. A tendency toward a decrease in Hartmann effect existence region with a decrease in cavity depth was found. A satisfactory agreement was obtained between the frequencies registered in the experiments and calculated using the Helmholtz formula for the natural frequency of resonant cavity.
The results of numerical simulation of gas-dynamic flow in the channel of a technical device with a resonant cavity are presented. One period of gas-dynamic loading of structural elements of the ...resonant cavity has been studied in detail. A complete picture of pressure and temperature field distribution along the resonant cavity channel has been obtained. The maximum and minimum values of pressure and temperature, achieved when the gas flow moves along the resonator channel, have been determined.
Full text
Available for:
EMUNI, FZAB, GEOZS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NUK, OILJ, PNG, SAZU, SBCE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Abstract
With using the mechanics of multiphase media, the process of extraction of moisture from a dead pore is considered. The study was carried out by numerical simulation. Two-dimensional ...approach of interaction of the air flow with droplets without taking into account the processes of heat and mass transfer was considered.
Absorption and luminescence of nickel-containing ZnO–Al2O3–SiO2 glasses and glass–ceramics nucleated by TiO2 and ZrO2 were investigated for variable NiO content and heat-treatment conditions. Ni2+ ...ions in the as-cast glasses are predominately five-fold coordinated. Heat-treatment of glasses containing 1–3mol.% NiO at 730–800°C results in precipitation of nickel titanate–zirconate xNiO·yTiO2·zZrO2 nanocrystals with Ni2+ ions entering octahedral sites. Optical absorption of samples treated at 800–1100°C is determined by precipitation of gahnite nanophase with Ni2+ ions entering both octahedral and tetrahedral sites and minor fraction of ions remaining in the residual glass phase. These samples are characterized by strong near-IR luminescence associated with 3T2g(3F)→3A2g(3F) transition of 6Ni2+ ions (FWHM more than 200nm, centered at ~1.2μm) in gahnite nanocrystals. Luminescence intensity increases substantially with the increase of heat-treatment temperature due to increase of volume fraction of gahnite nanophase and size of gahnite nanocrystals (which in turn causes decrease of relative fraction of Ni2+ ions located near the nanocrystal surface and suppresses the non-radiative relaxation path), the second factor is the dominant one. Concentration of NiO has dramatic effect on the luminescence efficiency of glass–ceramics due to a strong temperature and concentration quenching.
•Nickel-containing ZnO–Al2O3–SiO2 glass and glass–ceramics nucleated by TiO2 and ZrO2•Influence of heat-treatment and NiO content on absorption and luminescence spectra•Structural state of Ni2+ in gahnite and titanate–zirconate crystalline nanophase•Discussion of physical mechanisms governing photoluminescence intensity
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The influence of NiO addition (from 0.1 up to 3mol%) on structure and phase transformations of zinc aluminosilicate glasses nucleated by a mixture of TiO2 and ZrO2 has been studied using small angle ...X-ray scattering (SAXS), X-ray diffraction (XRD) analysis, Raman scattering and optical absorption spectroscopy. All parent glasses were X-ray amorphous and according to SAXS data inhomogeneous. Though SAXS intensity increased with increasing the NiO content in parent glasses, the distance between the inhomogeneous regions was independent of the NiO content implying that NiO does not play a role of additional nucleating agent. The processes of phase transformations were different for glasses doped with 0–0.1 and 1–3mol% NiO. In glasses containing 0–0.1mol% NiO, ZrTiO4 and Ni,Ti-doped gahnite crystals precipitated simultaneously starting from heat-treatment at above 730°C; traces of ZrO2 tetragonal crystals were found in glass-ceramics prepared at 1000–1200°C. In glasses doped with 1–3mol% NiO, metastable nickel titanate-zirconate crystals with fluorite-type structure and size of 4–5nm appeared during heat-treatments in the temperature range of 730–800°C, the fraction of this phase increased with the increase of the NiO content in the parent glass. Nickel titanate-zirconate crystals with fluorite structure decomposed during annealing at above 800°C. Ni,Ti-doped gahnite crystals precipitated starting from heat-treatment at 800°C; ZrO2 tetragonal crystals were formed at 900–1200°C.
•Zinc-aluminosilicate glass-ceramics based on Ni,Ti-doped gahnite nanosized crystals•Inhomogeneity of parent glasses according to SAXS and Raman spectroscopy•Metastable nickel titanate-zirconate nanophase with fluorite-type structure•Sequence of phase transformations in glasses doped with low and high concentrations of NiO
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
PDF
