In this work, the powder and ceramic samples of gadolinium tantalum niobate (Gd(NbxTa1-x)O4) grown by the liquid-phase method were studied. Phase homogeneity and composition were determined by x-ray ...diffraction analysis and electron probe microanalysis. Luminescent properties were studied by local cathodoluminescence technique. All samples obtained a high phase homogeneity. It was found that the dependence of the monoclinic lattice parameters on the niobium content in the niobium-tantalum pair has monotonic character. The solid solutions were formed at synthesis temperatures from 1180 to 1400°C. The sample of pure gadolinium niobate (GdNbO4) showed the maximal cathodoluminescence intensity.
An upgraded version of the OGRAN—combined optical-acoustic gravitational wave detector has been investigated in a long-term operation mode. This installation, located at the Baksan Neutrino ...Observatory (BNO) INR RAS, is designed to work under the program for detecting collapsing stars in parallel with the neutrino detector: Baksan Underground Scintillation Telescope (BUST). Such joint search corresponds to the modern trend for a development of “multi-messenger astronomy”. In this work the effects of thermal relaxation OGRAN are experimentally investigated using passive and active thermal stabilization systems in the underground laboratory BNO PK-14.
•How to increase the efficiency of the gas-steam hybrid cycle using pulsed detonations?•We extract the kinetic energy of detonation products by a durable pulse turbine.•Calculations and experiments ...show that only 8–16% of the kinetic energy is utilized.•There exists the optimal value of the rotor blade blockage factor providing the maximum torque.•The torque is created by several reflections of the lead shock wave from rotor blades.•Flow oscillations in the exhaust duct of the pulse turbine are small.•This allows the use of conventional gas and/or steam turbines further downstream.
The possibility of utilizing the kinetic energy of detonation products by a pulse turbine of the simplest water-wheel-like design during the implementation of the Zel'dovich thermodynamic cycle with pulse detonation combustion of fuel is investigated computationally and experimentally. The coefficients of utilization of the momentum and kinetic energy of detonation products in the pulse turbine with unoptimized mass and dimensions are found to be as low as 8%–16%. To improve the efficiency of the pulse turbine, it is necessary to take measures for eliminating unnecessary reflections of shock waves, to select the optimal mass and dimensions of the turbine rotor and the number of blades, to profile the blades and to select the optimal angle of attack, to optimize the size of the lateral gap between the rotor and the housing, and to select the optimum location of the exhaust duct. It is expected that the efficiency of a combined cycle including the optimized pulse turbine and conventional gas and/or steam turbines attached to the exhaust duct could be higher than the efficiency of a conventional hybrid cycle by at most 9%.
For the first time, terbium-activated gadolinium tantalo-niobates were synthesized ((Gd
1‒
x
Tb
x
)Nb
y
Ta
1–
y
O
4
). The synthesis was carried out by the liquid-phase method. All studied materials ...had the main crystalline modification M GdNbO
4
. The content of impurity phases did not exceed 2–5%. The photo- and cathodoluminescence spectra were studied. Concentration quenching of the terbium ion luminescence for a series of solid solutions containing tantalum ((Gd
1–
x
Tb
x
)Nb
0.9
Ta
0.1
O
4
) occurs earlier than for pure gadolinium niobates ((Gd
1–
x
Tb
x
)NbO
4
). The obtained materials are promising for use as scintillators.
—
We have developed a technological scheme for the preparation of europium-activated gadolinium niobates and tantalates and related solid solutions by a sol–gel process. It has been shown that, ...during synthesis of crystalline powders, raising the calcination temperature from 1200 to 1400°C leads to a decrease in the concentration of impurity phases from 10–15 to 4–10 wt %. The Gd
x
Eu
1 –
x
TaO
4
samples have been shown to have different structural polytypes at these temperatures. The synthesized materials exhibit bright red luminescence under photoexcitation.
Detonability of fuel–air mixtures Frolov, S. M.; Zvegintsev, V. I.; Aksenov, V. S. ...
Shock waves,
11/2020, Letnik:
30, Številka:
7-8
Journal Article
Recenzirano
A new experimental method for evaluating the detonability of fuel–air mixtures (FAMs) based on measuring the deflagration-to-detonation (DDT) run-up distance and/or time in a standard pulse ...detonation tube (SDT) is used to rank gaseous premixed and non-premixed FAMs by their detonability under substantially identical thermodynamic and gasdynamic conditions. In the experiments, FAMs based on hydrogen, acetylene, ethylene, propylene, propane–butane, n-pentane, and natural gas of various compositions, as well as FAMs based on the gaseous pyrolysis products of polypropylene (PP), are used: from extremely fuel-lean to extremely fuel-rich at normal temperatures and pressures. The concept of
equivalent
FAMs exhibiting the same or similar detonability under the same conditions is proposed. Equivalent FAMs can be used for predictive physical modeling of detonation processes involving FAMs of other fuels. The ranking of FAMs in terms of their relative detonability allows choosing a propylene FAM for physical modeling of the operation process in the PP-fueled solid-fuel ramjets operating on detonative combustion.
Ductular reaction develops during liver regeneration, fibrosis, and carcinogenesis. However, the types, stages of formation, and topography of ductular profiles in various pathologies remain ...insufficiently studied. Using the model of common bile duct occlusion, we showed that the number and topography of ductular profiles are closely related to the duration of biliary obstruction. The ductular profiles can be located inside the portal tract, along the existing bile ducts, and/or intramurally, around the portal vein, periportally, inside the lobules, in the portocaval fibrous connections, in the adventitia of the hepatic veins, in the septs connecting the portal tracts, and also in the “portal plate” of the liver. The ductular profiles can be formed as a result of expansion of existing bile ducts, cholangiocyte proliferation, as well as transdifferentiation of hepatocytes and activation of mesenchymal stem cells.
The flora of silica-scaled algae of the orders Synurales, Paraphysomonadales, and Chromulinales in southern provinces of Vietnam (Binh Thuan and Đồng Nai) is studied. Forty-eight taxa (40 of which ...belong to the genus
Mallomonas
; 5 to the genus
Synura
; and 1 each from the genera
Paraphysomonas, Spiniferomonas
, and
Chrysosphaerella
) are identified in 37 studied water bodies. One taxon is found for the first time in Vietnam. Rare species endemic to Southeast Asia have also been found. Single scales of three species potentially new to science have been found. Forty-two taxa of silica-scaled algae are found in Bình Thuận province and 30 taxa are found in Đồng Nai province (taking into account earlier findings, 52).
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