An experimental study on changes in sound absorption capability of spruce (Picea sitchensis), Douglas fir (Pseudotsuga menziesii), and larch (Larix kaempferi) after microwave treatment

This study investigated changes in the sound absorption coefficients of three anatomical sections of cubed spruce (Picea sitchensis), Douglas fir (Pseudotsuga menziesii), and larch (Larix kaempferi) after microwave treatment. Microwave treatment at 1000 W and 2.4 GHz for 20 min increased the sound absorption coefficients (at 2000–5000 Hz) of spruce by 6.9% in the transverse section, 20.0% in the radial section, and 31.7% in the tangential section. The sound absorption coefficients of Douglas fir increased by 28.9% in the transverse section, 19.1% in the radial section, and 50.0% in the tangential section. Larch coefficients increased by 16.7% in the transverse section, 37.2% in the radial section, and 38.8% in the tangential section. The sound absorption coefficients of the softwoods differed according to species and anatomical plane after microwave treatment. It was concluded that changes in the measured sound absorption coefficient indicate alteration in the pore structure of wood, which can affect in turn wood permeability and impregnation. These data will be helpful for predicting the permeability and impregnation of wood after microwave treatment.

Infrared Absorption and Its Sources of CdZnTe at Cryogenic Temperature

To reveal the causes of infrared absorption in the wavelength region between electronic and lattice absorptions, we measured the temperature dependence of the absorption coefficient of p-type low-resistivity ($$\sim 10^2~ \Omega \mathrm{cm}$$ ∼ 10 2 Ω cm ) CdZnTe crystals. We measured the absorption coefficients of CdZnTe crystals in four wavelength bands ($$\lambda =6.45$$ λ = 6.45 , 10.6, 11.6, 15.1$$~\mu $$ μ m) over the temperature range of $$T=8.6$$ T = 8.6 -300 K with an originally developed system. The CdZnTe absorption coefficient was measured to be $$\alpha =0.3$$ α = 0.3 -0.5 $$\mathrm{cm}^{-1}$$ cm - 1 at $$T=300$$ T = 300 K and $$\alpha =0.4$$ α = 0.4 -0.9 $$\mathrm{cm}^{-1}$$ cm - 1 at $$T=8.6$$ T = 8.6 K in the investigated wavelength range. With an absorption model based on transitions of free holes and holes trapped at an acceptor level, we conclude that the absorption due to free holes at $$T=150$$ T = 150 -300 K and that due to trapped-holes at $$T<50$$ T < 50 K are dominant absorption causes in CdZnTe. We also discuss a method to predict the CdZnTe absorption coefficient at cryogenic temperature based on the room-temperature resistivity.

Application of the medical linear accelerator ELEKTA AXESSE in the study of sorption properties of impurities and absorption coefficients of medium and heavy chemical elements

In this article, the authors propose a new technique for measuring linear attenuation coefficients on the medical linear accelerator Elekta Axesse. Linear attenuation coefficients were obtained for four samples at different concentrations of substances at a gamma-ray energy of 6 MeV. A unified ionization chamber was used as a detector to register the transmitted gamma-ray beam through the samples under study. Linear absorption coefficients were obtained for elements B, C, O, S, Fe, Ba taking into account their concentration, as well as taking into account the different mass inclusion of paraffin in the samples under study, which is acyclic hydrocarbons CnH2n+2. The measurement results showed that taking into account certain components in impurities leads to relatively small, but quite noticeable differences in the determination of the total absorption coefficients. This is especially important to take into account for determining the concentration of light elements in samples. To determine the content of medium and heavy chemical elements, taking into account the content of light elements can be neglected. The use of a 6 MeV gamma-ray beam made it possible to reduce the errors in determining the absorption coefficients, since their dependence on energy in the region of applicable gamma-ray energies is not so great in comparison with the low-energy region, in which the shell effects for heavy elements will introduce significant contribution.

Chlorophyll-a concentrations inversion based on the modified Quasi-Analytical Algorithm and Sentinel-3 OLCI in Daihai Lake, China

The Quasi-Analytical Algorithm (QAA) is effective in retrieving water inherent optical properties (IOPs) from remote sensing spectral reflectance and has wider applications in studies of the open ocean and coastal waters than of inland waters. This research aimed to modify the QAA model based on measured field spectral reflectance and absorption coefficients to render it applicable to studies of Daihai Lake, China. The improvements mainly included the reference wavelength selection, the power index of the particle backscattering coefficient and the exponential slope of the absorption coefficient of the colored detrital matter estimation. The average relative error between the inversed and measured absorption coefficients was less than 20%. A linear model was established between the phytoplankton absorption coefficient at a wavelength of 674 nm (aph(674)) and the chlorophyll-a (Chl-a) concentration, with a determination coefficient of 0.88. Additionally, the modified Quasi-Analytical Algorithm (MQAA) model was applied to the Ocean and Land Color Instrument (OLCI) data aboard the Sentinel-3 satellite. Finally, a spatial distribution map for the Chl-a concentrations in Daihai Lake on August 10, 2017 was drawn and the mid-eutrophication area was found to occur in the north and border.

ECOLOGICAL AND GEOCHEMICAL SPECIFICS OF SOIL AND PLANT COVERING OF URBAN LANDSCAPES (IN THE TOWN OF BROVARY AS AN EXAMPLE)

The results of the pollutants content research in urbanized landscapes soils of Ukraine (on the example of Brovary city, Kyiv region) were shown. The total and mobile contents data of chemical elements (Ni, Co, Zn, V, Pb, Cr, Cu) were obtained and analyzed using the methods of landscape-geochemical studies, analytical and statistical methods. The dependences of the vegetation resistance in cities to the level of soil cover contamination and the degree of heavy metals income have been established. The geochemical characteristics (such as the value of the accumulation coefficients; concentration of soil and vegetation cover; index of biogeochemical activity of the species within Brovary city) were analyzed. Throughout most of the city territory, the level of soil contamination is above average. Soils are characterized by the following association of heavy metals: Cu> Pb> Zn> Co> Cr> V> Mo> Mn> Ni. The dominant association is distributed heterogeneous throughout the city, forming geochemical anomalies depending on the source of contamination. The maximum technogenic load was recorded in urban soils areas within zones of transport infrastructure, production and communal-warehouse facilities.Woody vegetation is the most actively absorbed copper, manganese from the soil, and the least intensively absorbed chromium, vanadium and nickel. The biogeochemical activity coefficient of the research species is the following: Acer platanoides - 7,26, Betula pendula Roth. - 7,07, and Populus deltoides - 7,05, Pínus sylvestris - 1.32 and Alnus incana - 3.37. The biological absorption coefficients of manganese and copper are high because these metals have the ability to form strong complexes with organic matter. Biological absorption coefficients of vanadium and chromium is low for the researched plant species because these chemical elements are immobile in soils. For the city of Brovary, the presence of polyelemental contamination of soil and vegetation has been established. According to the indicators of the gross content of VM, the main pollutants are Cu, Zn, Pb and Mn. Concentrations of gross and mobile forms of VM exceed background values ​​and maximum concentration limits in 17-28 times. The maximum of man-caused load was recorded in the urban soils of the transport infrastructure zone and the zone of production and communal-warehouse facilities. Regularities of formation of elemental composition of plants of urban areas undergo significant changes in comparison with natural conditions, which is due to the strengthening of the role of foliar absorption of pollutants from the air and their high content in soils. The greatest ability to bioaccumulate has a male thyroid (Dryopteris filix-mas Schott) and birch (Convolvulus arvensis). The highest coefficient of biogeochemical activity of the studied species is Acer platanoides - 7.26, hanging birch (Betula pendula Roth.) - 7.07 and Canadian poplar (Populus deltoides) - 7.05, the lowest - Scots pine (Pínus sylvеstris ) - 1.32 and gray alder (Alnus incana) - 3.37. Weakly and very weakly, most of the studied plant species capture vanadium and chromium, which are relatively sedentary in the soil. Further research is needed to analyze the physicochemical parameters of soils, the coefficients of transition of metals to plants relative to their content in organic and mobile form in order to establish the relationships that characterize the process of translocation of chemical elements. Keywords: landscape-geochemical conditions, heavy metals, soils, vegetation.

Structural stabilities, electronic structures, photocatalysis and optical properties of γ-GeN and α-SnP monolayers: a first-principles study

Exploring two-dimensional materials with excellent photoelectricity properties is of great theoretical significance and practical value for developing new photocatalysts, electronics and photonic devices. Here, using first-principle calculations, we designed and analyzed systematically a series of α, β and γ phase structures of two-dimensional group IV-V monolayers (IV-V, IV = C, Si, Ge, Sn, Pb；V = N, P, As, Sb, Bi), most of them are semiconductors. Among them, γ-GeN and α-SnP monolayers with thermodynamic and kinetic stability (at 300K) have been further studied due to their wide range of energy band gaps (γ-GeN: 2.54 eV, α-SnP:1.34 eV). The two band gaps are greater than the free energy for water splitting (1.23 eV), which are crucial for photocatalytic decomposition of water. The γ-GeN and α-SnP monolayers present excellent photocatalystics properties in PH=0/7 and PH=10 environments, respectively. Moreover, both of the monolayers show strong light absorption coefficients greater than 105 cm-1 in the visible and ultraviolet regions. In addition, it is found that the band edge positions and band gap sizes of γ-GeN and α-SnP monolayers can be regulated by biaxial strain. Benefitting from the wide selection of energy band gaps and high absorption coefficients, the γ-GeN and α-SnP monolayers are the next generation of promising candidate materials for photocatalysts, nanoelectronics and optoelectronics.