In high-purity GaN grown by hydride vapor phase epitaxy, the commonly observed yellow luminescence (YL) band gives way to a green luminescence (GL) band at high excitation intensity. We propose that ...the GL band with a maximum at 2.4 eV is caused by transitions of electrons from the conduction band to the 0/+ level of the isolated C sub(N) defect. The YL band, related to transitions via the -/0 level of the same defect, has a maximum at 2.1 eV and can be observed only for some high-purity samples. However, in less pure GaN samples, where no GL band is observed, another YL band with a maximum at 2.2 eV dominates the photoluminescence spectrum. The latter is attributed to the C sub(N)O sub(N) complex.
As the population grows, the need for mineral resources increases, resulting in an intensification of their extraction. This increases the amount of industrial waste and, thus, the human impact on ...the environment. Further accumulation and storage of industrial waste lead to irreversible changes in the ecosystem. The only correct vector of environmental protection is the utilization of industrial waste. Mining waste can be disposed by creating waste-free technologies that take into account the integrated development of deposits. The creation of an additional material resource base of a mining company by processing mineral waste will allow implementing the tasks of integrated development of deposits.
The impact of mining and metallurgical works on the ecosystem of the region is assessed. Significant conceptual issues of application of industrial waste in the closed cycle of mining and metallurgical works are considered. It is confirmed that waste-free production is possible with a system approach to the integrated development of mineral resources.
The impact of mining and metallurgical works on the environment is classified, with the physical and chemical principles of impact as the main classification feature. The ecological and economic efficiency of the use of industrial waste is assessed. A concept scheme of waste-free production is proposed, where the task of improving the efficiency of developing a mineral deposit is accomplished by rational, integrated use of mineral resources of the Earth.
Excitons in lead bromide perovskites exhibit high binding energy and high oscillator strength, allowing for a strong light‐matter coupling regime in the perovskite‐based cavities localizing photons ...at the nanoscale. This opens up the way for the realization of exciton‐polariton Bose–Einstein condensation and polariton lasing at room temperature – the inversion‐free low‐threshold stimulated emission. However, polariton lasing in perovskite planar photon cavities without Bragg mirrors has not yet been observed and proved experimentally. In this study, perovskite metasurface is employed, fabricated with nanoimprint lithography, supporting so‐called exceptional points to demonstrate the room‐temperature polariton lasing. The exceptional points in exciton‐polariton dispersion of the metasurface appear upon optically pumping in the nonlinear regime in the spectral vicinity of a symmetry‐protected bound state in the continuum providing high mode confinement with the enhanced local density of states beneficial for polariton condensation. The observed lasing emission possesses high directivity with a divergence angle of 1° over one axis. The employed nanoimprinting approach for solution‐processable large‐scale polariton lasers is compatible with various planar photonic platforms suitable for on‐chip integration.
A strong light‐matter coupling regime is observed at room temperature in the lead‐halide perovskite metasurface fabricated by nanoimprint lithography. Thanks to the high polariton nonlinearity under the non‐resonant pump, exceptional points appear providing enhanced local density of states and exciton‐polariton condensation with low‐threshold highly‐directive lasing.
Land cover changes following rewetting of 73 thousand hectares of peatland after the severe 2010 peat fires in Moscow Region (Russia) were monitored using multispectral remote sensing. The results ...revealed a reduction in the area of bare peat and dry grasslands, the rapid expansion of willow and birch vegetation, and a steady increase in wet grasslands and open water. Both the number and area of peat fires were clearly reduced compared to all wildfires in the region.
Monitoring large areas over longer periods generally implies using different satellites and sensors. The developed methodology enabled assessing the effectiveness of rewetting to reduce fire hazard as well as identifying areas that remain fire-prone and require additional restoration effort. The methodology proved to be robust for the long-term monitoring of the effect of rewetting large areas of peatlands, as required under the Paris Agreement.
Two yellow luminescence bands related to different defects have been revealed in undoped GaN grown by hydride vapor phase epitaxy (HVPE). One of them, labeled YL1, has the zero-phonon line (ZPL) at ...2.57 eV and the band maximum at 2.20 eV at low temperature. This luminescence band is the ubiquitous yellow band observed in GaN grown by metalorganic chemical vapor deposition, either undoped (but containing carbon with high concentration) or doped with Si. Another yellow band, labeled YL3, has the ZPL at 2.36 eV and the band maximum at 2.09 eV. Previously, the ZPL and fine structure of this band were erroneously attributed to the red luminescence band. Both the YL1 and YL3 bands show phonon-related fine structure at the high-energy side, which is caused by strong electron-phonon coupling involving the LO and pseudo-local phonon modes. The shapes of the bands are described with a one-dimensional configuration coordinate model, and the Huang-Rhys factors are found. Possible origins of the defect-related luminescence bands are discussed.
The temperature dependences of magnetic properties and magnetic field behavior of Co/Gd/Co thin-film three-layer systems obtained via ion-plasma magnetron sputtering are studied. The thickness of ...cobalt layers is 5.0 nm and of Gd layers (
t
Gd
) varies from 3.0 to 10.0 nm. The bulk magnetic characteristics of the samples were measured on a vibration magnetometer with an external magnetic field oriented parallel to the plane of the samples. The influence of the temperature and the thickness of a Gd layer on the shape of the hysteresis loops, the values of the magnetic moment m and the coercive force
H
C
are discovered. In particular, when the temperature changes from 100 to 300 K, the coercive force decreases, and the magnetic moment increases at a temperature above 150 K. The
m
value decreases with an increase in thickness of gadolinium.
This study shows the effect of strain-induced martensitic transformation (austenite (γ)–to–martensite (α′)) on the cavitation erosion resistance of a Fe-Cr-C-Al-Ti deposited layer with a high share ...of metastable austenite in the structure. For comparison, the cavitation erosion of a E308L-17 deposited layer and an AISI 316L stainless steel substrate was also evaluated. Cavitation tests were performed using a modified ultrasonic tester. X-ray diffraction (XRD) was used to examine martensitic phase transformation. An optical microscope (OM), a scanning electron microscope (SEM), and a 3D optical profilometer were utilized to evaluate the eroded specimens' surfaces. The chemical composition of the Fe-Cr-C-Al-Ti deposited layer was analyzed using an energy-dispersive microanalysis system (EDS). The cavitation results revealed that the Fe-Cr-C-Al-Ti specimen exhibited a resistance to cavitation erosion approximately 4 and 10 times higher than the E308L-17 and AISI 316L specimens, respectively. As shown, effects of γ → α′ transformation were mainly responsible for the results.
•The deposited layer of metastable Fe-Cr-C-Al-Ti steel shows superior cavitation erosion resistance.•γ–to–ά transformation of the deposited layer led to increasing cavitation erosion resistance.•Hardening the surface of Fe-Cr-C-Al-Ti layer contributed to improving cavitation resistance.
Contemporary rock mechanics is based on the principals of classical Continuum Mechanics theory. But new experimental results such as “zonal disintegration” around deep openings and “reversible ...deformations” of highly compressed rock samples cannot be described correctly from this viewpoint. A new approach to rock mechanics mathematical models consists of the application of non-Euclidian modelling to the problem of the description of anomalous experimental results. This leads to the formation of the “Geomechanics of Highly Compressed Rock and Rock Massifs” – a new branch of the existing theory of Geomechanics – in which framework a radical rise in geodynamical phenomena forecasting can be achieved. Principles of the geomechanics of highly compressed rock and rock massifs are discussed in this paper. The effectiveness of the application of non-Euclidian modelling to the anomalous experimental effects observed in research is demonstrated on two hierarchical geomedia block levels such as rock samples and rock massif around underground openings.
Methods of mathematical modeling and qualitative analysis of geotextile nonwoven creep processes using computer programming of these processes are described. Qualitative analysis of geotextile ...nonwoven creep processes is the foundation for enhancing their competitiveness.
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