The paper analyzes the problems of carbon stocks variation in the pool of cropland mineral soils at the regional scale of the Russian Federation. The carbon stock balance of cropland soils was ...evaluated by estimating carbon gains and losses, and then the components of the carbon footprint were measured as a ratio of soil organic carbon balance to crop production quantity in terms of grain equivalent (t C/t grain eq.). The estimates for the period 2011–2020 have revealed that there is generally a small net gain of carbon on cropland in Russia, mainly due to the intake of carbon from plant residues. Most of the steppe region of Russia suffers from net losses of carbon at levels from –0.15 t C/t grain eq. up to –0.69 t C/t grain eq. In other regions, such as the Central Chernozem and Black Sea Coast regions, net carbon gain is observed in the range of 0.1–0.3 t C/t grain eq. due to the intake of significant biomass of crop and root residues as a consequence of intensive crop production.
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Cooling of a melt with the composition Bi
2
O
3
·SiO
2
and the metastable phase Bi
2
SiO
5
under various conditions has been studied by computer simulation with ProCAST software. Using previously ...reported thermophysical characteristics (thermal conductivity, heat capacity, and density) of the melt and metastable phase and the experimentally determined thermal diffusivity of the metastable Bi
2
SiO
5
compound in the range 299–700°C, we have evaluated the cooling rate, which has been shown to agree well with the experimentally determined one, confirming that the assumptions made in our simulations are quite adequate.
The possibility of modeling the processes of cooling of the metastable Bi
2
GeO
5
compound in the ProCAST software package is demonstrated. Despite a number of assumptions that are made in the ...modeling, the calculated data are shown to be in good agreement with the real melt cooling rates and can be used in the development of modeling in the Bi
2
O
3
–GeO
2
system to obtain metastable materials with a desired set of properties and a microstructure.
ULTRAFAST TRANSMISSION ELECTRON MICROSCOPY Ischenko, A. A.; Tarasov, Yu. I.; Ryabov, E. A. ...
Fine Chemical Technologies,
02/2017, Letnik:
12, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Ultrafast laser spectral and electron diffraction methods complement each other and open up new possibilities in chemistry and physics to light up atomic and molecular motions involved in the primary ...processes governing structural transitions. Since the 1980s, scientific laboratories in the world have begun to develop a new field of research aimed at this goal. “Atomic-molecular movies” will allow visualizing coherent dynamics of nuclei in molecules and fast processes in chemical reactions in real time. Modern femtosecond and picosecond laser sources have made it possible to significantly change the traditional approaches using continuous electron beams, to create ultrabright pulsed photoelectron sources, to catch ultrafast processes in the matter initiated by ultrashort laser pulses and to achieve high spatio-temporal resolution in research. There are several research laboratories all over the world experimenting or planning to experiment with ultrafast electron diffraction and possessing electron microscopes adapted to operate with ultrashort electron beams. It should be emphasized that creating a new-generation electron microscope is of crucial importance, because successful realization of this project demonstrates the potential of leading national research centers and their ability to work at the forefront of modern science.
Technologies for the 3D printing of metallic powders are being increasingly extensively used around the world as alternatives to casting and machining to manufacture components of complex shapes and ...prototypes. Silicon-alloyed aluminum alloys are the most widely used materials in the selective laser melting technologies, which is caused by the price of these alloys and their high manufacturability for the layer-by-layer fused deposition, owing to their low susceptibility to hot cracking under thermal and shrinkage stresses. High rates of cooling the melt facilitate the formation in the material of ultradispersed silicon-containing phases, which results in increased strength. In the article, exemplified by two cast alloys (AK7ch and AK9ch), the speeds of the process of building up the products by the selective laser melting technology have been determined at a laser-beam power of 300 and 325 W and an energy density within the range 89–32 J/mm
3
. It is shown that, for the AK9ch alloy, lower porosity values are achieved within the investigated energy density range when compared with the AK7ch alloy and better mechanical properties of the alloy with a higher silicon content are achieved within the range of lower laser-beam energy densities than for the alloy with a lower silicon content. The mechanical properties of the materials produced under the optimal selective laser melting conditions comply with the most stringent requirements for the mechanical characteristics of the castings of the AK7ch alloy upon heat treatment.
It is well known that during the propagation of a noise wave in a nonlinear medium the spectral composition of the field as well as the higher statistical characteristics of the wave (multipoint ...probability distribution, higher moments, and cumulants) change. The object of the present study also is a numerical analysis of the spectral and bispectral functions of the intense regular and random signals propagating in nondispersive nonlinear media. LabVIEW environment is extremely simple in use, and provides good results as compared to traditional programming techniques. For example, internal libraries make it easy to take direct and inverse Fourier transform, as well as regular and random signals. The possibility of recovering the input spectrum from the measured spectrum and bispectrum at the output of the nonlinear medium is discusses. The analytical estimations are supported by numerical simulation. For two different types of primary spectrum evolution of flat random waves were numerically simulates at a short distance and assayed bispectrum and a spectrum analysis of the signals. This model is a virtual instrument which can solve some diagnosis problems using spectral and bispectral processing tools.
The crystallographic characteristics of YNi3-x Mnx pseudobinary compounds are determined by the methods of X-ray diffraction analysis. It is shown that the partial substitution of nickel for ...manganese occurs mainly in the layers with CaCu5-type structure but not in the layers with Mg Zn2-type structure, as was reported for A3B8X compounds. All synthesized samples are efficient absorbers of hydrogen and their hydrogen-absorption capacity monotonically decreases as the concentration of the alloying element increases. At the same time, this type of alloying substantially decreases the absorption-desorption pressure of hydrogen, which makes the developed alloys quite promising as hydrogen-storage materials. All investigated materials have good charging-discharging characteristics in KOH solutions. The best electrochemical parameters are observed for the Y Ni2.67Mn0.33 alloy (C max = 305 mA * h/g).
We have developed a new computerized PGStat-8 device for the high-cycle charge-discharge of electrodes under galvanostatic or potentiostatic conditions and, with its help, have investigated the ...charge-discharge characteristics of metal-hydride electrodes based on Ti2Ni-type alloys. We show the effect of partial replacement Ti - > Zr or V and Ni - > Co or Cu, modification with oxygen, homogenizing annealing, polymeric addition, and metallic binder on the discharge capacity and cyclic stability of the prepared metal-hydride electrodes.
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