The paper presents the results of a study of a number of key optical characteristics of some highly porous thermal protection materials based on amorphous SiO
2
fibers in the near and mid IR ranges. ...In the optical part of the statistical simulation model of such materials, based on the rigorous Mie theory, its application requires the introduction of cooperative corrections to the results of interaction with electromagnetic radiation of individual fragments. These corrections are introduced into the model in the form of an additional multiplier (
C
s
) of the scattering and absorption Mie efficiencies, which was usually used as a model tuning parameter when interpreting the experimental results of thermophysical studies. In this work, using the example of TZM-23M materials (Russia), made of a relatively thick (~9 μm) silica fiber PS-23 (Belarus), for the first time, data were obtained that make it possible to study the
C
s
parameter as a spectral quantity. The study is based on the results of experimental determination of the spectral hemispherical reflectivity of layers of material of two or more optical thicknesses in the wavelength range 0.83–16.65 μm. These data and Zege’s asymptotic formulas were used to estimate the values of the absorption and scattering coefficients. The spectral parameter
C
s
is determined from the value of the scattering coefficient in the process of solving the inverse optical problem. The data obtained are compared with the results calculated on the basis of classical approximations of the optical constants. The results of this work can be useful for specialists in the field of radiation heat transfer and the interaction of electromagnetic radiation with complex partially transparent media with high spectral albedo scattering values.
A method for solving the problem of nonlinear diffraction on two-dimensional periodic gratings of graphene ribbons has been developed. The third-order nonlinear conductivity of graphene under the ...action of two waves is taken into account, which is determined by the field of the pump wave, for which we use the field on graphene ribbons obtained by solving the linear diffraction problem. Numerical analysis shows the efficiency of nonlinear frequency conversion in the terahertz and infrared ranges when the frequencies of the incident pump and signal waves coincide with the resonant frequencies of the fundamental and higher order modes of surface plasmon polaritons in graphene ribbons.
Abstract
The processes of ordering and structuring of particles in a magnetic fluid (MF) arise in three cases: interactions of magnetic particles, internal forces of liquid and an external magnetic ...field of constant or variable magnitude. Processes of magnetic particles ordering in a magnetic fluid by interaction an external field are considered, and threshold of occurrence of a periodic lattice from particles with different size is established.
In addition to its use in the fertilizer and chemical industries1, ammonia is currently seen as a potential replacement for carbon-based fuels and as a carrier for worldwide transportation of ...renewable energy2. Implementation ofthis vision requires transformation of the existing fossil-fuel-based technology for NH3 production3 to a simpler, scale-flexible technology, such as the electrochemical lithium-mediated nitrogen-reduction reaction3,4. This provides a genuine pathway from N2 to ammonia, but it is currently hampered by limited yield rates and low efficiencies4-12. Here we investigate the role of the electrolyte in this reaction and present a high-efficiency, robust process that is enabled by compact ionic layering in the electrode-electrolyte interface region. The interface is generated by a high-concentration imide-based lithium-salt electrolyte, providing stabilized ammonia yield rates of 150 ± 20 nmol s-1 cm-2 and a current-to-ammonia efficiency that is close to 100%. The ionic assembly formed at the electrode surface suppresses the electrolyte decomposition and supports stable N2 reduction. Our study highlights the interrelation between the performance of the lithium-mediated nitrogen-reduction reaction and the physicochemical properties of the electrode-electrolyte interface. We anticipate that these findings will guide the development of a robust, high-performance process for sustainable ammonia production.
•The homogeneity ranges for the Ba1−xPrxFe1−yCoyO3−δ solid solutions were evaluated.•Crystal structure for the Ba1−xLnxFe1−yCoyO3−δ solid solutions was refined.•The values of oxygen content in ...Ba1−xPrxFe1−yCoyO3−δ were determined.•The pseudo-phase diagram has been constructed for the room temperature conditions.
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The study of 96 samples of various compositions (x, y) in the Ba1−xPrxFe1−yCoyO3−δ system, prepared in air by the glycerol-nitrate method, made it possible to establish the compositional boundaries of stability for three types of crystal structure: 1) layered 112-type PrBaCo2−yFeyO5+δ (x = 0.5; 0 ≤ y ≤ 0.6) A-site ordered perovskite, 2) cubic perovskite phase (SG Pm-3m) within 0 ≤ x ≤ 0.6 and for which y depends on the Pr (x) content, and 3) orthorhombic phase (SG Pbnm) within 0.7 ≤ x ≤ 1. The unit cell parameters for the cubic and orthorhombic perovskites were refined by the Le-Bail or Rietveld analysis. The values of oxygen content, determined by the iodometric titration and TGA, are found to increase with Pr and Fe contents. The stability ranges for all three types of complex oxides, together with the multi-phase fields, were outlined for the room temperature conditions in a form of pseudo-phase diagram.
A numerical–analytical method is developed for mathematical simulation of nonlinear effects in multilayer plasmonic structures (PSs) based on nanostructured graphene. A nonlinear effect of the ...third-harmonic generation in multilayer PSs based on 2D periodic lattices of rectangular graphene microribbons on dielectric layers is numerically simulated in the terahertz frequency range. It is shown that the efficiency of nonlinear interaction (third-harmonic generation) in multilayer graphene PSs increases by several orders of magnitude at the resonance frequencies of the fundamental and higher modes of surface plasmon polaritons and can be increased in comparison with single-layer PSs due to an increase in the number of layers and packing density of the lattices of graphene microribbons, as well as application of multilayer substrates (dielectric mirrors). A decrease in the chemical potential leads to a decrease in the plasmon resonance frequency whereas the amplitude of the generated third harmonic significantly increases.
We report here studies of the important connection between the state of body systems and their organization as self-similar fractal structures. Morphogenesis at all hierarchical levels — from a ...protein molecule to a whole organism — obeys general laws of structural self-organization. Creation of effective computer algorithms for processing biosignals based on nonlinear dynamic models of the biosystems of the human body is a valuable task in monitoring the state of the cardiovascular system, as biological processes are nonlinear in nature and fractal in structure. Detailed information on the state of the biological networks of the human body can be obtained during topical diagnostics by using wavelet analysis of biological signals (wavelet introscopy). Wavelet introscopy provides for visualization of the cryptic elements of the cardiac neural conducting system (CNCS), in particular its amplitude-phase characteristics and the presumptive intermittent nature of the operation of nerve endings between adjacent heart cycles.
The lithium mediated reduction of N2 is one of the only available approaches to electrochemical ammonia production at significant yields under ambient conditions. However, much remains to be ...investigated about the various electrochemical processes and side reactions that are involved. Herein, we have examined the effects of parameters including electrode potential, convection, N2 pressure, and water content to refine and control the process. We demonstrate that a closely linear ammonia yield can be maintained during experiments up to 60 h in length, with approximately constant faradaic efficiency. This steady state operation appears to be preceded by a coating of the electrode surface with the products of the reductive electrolyte decomposition, such as LiF. We demonstrate ammonia yield rates above 1 nmol s–1 cm–2 and faradaic efficiencies as high as 60% through the improved control of the reaction conditions.
The effect of air humidity on the transport properties of the La2-xAxNi1-yFeyO4+δ (A=Ca, Sr; x = 0.5, 0.6 and y = 0.4, 0.5) oxides was studied in the temperature range of 25–950 °C. Total ...conductivity of the samples decreased with increasing relative humidity (RH), most significantly in the range of 250–550 °C. Thermogravimetric analysis in dry and wet air indicated that the observed changes in conductivity could be attributed to the hydration of the samples. The high-temperature X-ray powder diffraction (HT-XRPD) results for La1.4Sr0.6Ni0.5Fe0.5O4+δ (LSNF0605) suggested that the hydration led to the insertion of hydroxide ions into the interstitial sites resulting in the expansion of the rock-salt type layers and shrinkage of the perovskite layers. The Electrochemical Impedance Spectroscopy (EIS) measurements for the LSNF0605/Ce0.8Sm0.2O2-δ (SDC) and LSNF0605/La28−zW4+zO54+1.5z (LWO) symmetrical cells showed that the hydration affected the surface exchange process in LSNF0605. The activation energy of surface exchange decreased with the increase in RH for the LSNF0605/LWO cell indicating that water could participate in the surface exchange. The activation energy of the charge transfer – ionic diffusion process in the LSNF0605 electrode for the LSNF0605/LWO cell possessed smaller values compared to that for the LSNF0605/SDC cell in wet air, suggesting the presence of proton conduction.
•Effect of air humidity on properties of La2-xAxNi1-yFeyO4+δ was observed at T ≤ 700 °C.•Thermogravimetric analysis suggested hydration of the samples in wet air below 700 °C.•(La/A)O layer of La2-xAxNi1-yFeyO4+δ expanded with increasing air humidity.•The impedance studies showed that hydration affected the surface exchange process.•The results indicated the presence of proton conduction in La1.4Sr0.6Ni0.5Fe0.5O4+δ.
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