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Basal and prismatic slips induced by thermoelastic stresses during the growth of 4H-SiC are investigated by using the finite element method (FEM) and considering factors such as the crystal diameter, temperature, and off-axis angle. It is found that with the increase of the crystal diameter from 6 to 8 inches, the prismatic slip more likely occurs, leading to a higher density of basal plane dislocations (BPDs). However, the basal slip hardly changes. The temperature difference, rather than the growth temperature, is the primary factor contributing to the increase in the slip stresses. The stresses of the basal slip are significantly affected by a small off-axis angle, whereas those of the prismatic slip are not unaffected until the off-axis angle reaches 30 degrees. The mechanism for the decrease of the density of BPDs along the growth direction in an 8 inch 4H-SiC crystal is elucidated. We verify that the prismatic slip in an 8 inch 4H-SiC crystal contributes more to the BPD formation than the basal slip. [ABSTRACT FROM AUTHOR]

Gob is one of the most serious areas of coal spontaneous combustion. With the continuous increase of mining depth, the residual coal in gob bears increased axial stress, the rise of ground temperature, and the degree of fragmentation of mining coal and rock continues to increase, the external water in the mining process changes the water content of broken residual coal, under the influence of multiple factors, the prevention and control situation of coal spontaneous combustion in gob is becoming more serious. Based on the actual accumulation environment of residual coal in gob, this paper carried out the oxidation and temperature rise experiment of broken coal under the condition of water bearing and pressure. The variation laws of oxidation characteristic parameters such as outlet oxygen concentration, oxidation derived gas, oxygen consumption rate and heat release intensity were obtained. It is found that with the increase of water content of coal sample, the water content first promotes and then inhibits the oxidation process of coal. It is found that after water molecules form a relatively stable hydrogen bond with oxygen-containing functional groups, the total energy of the two-phase materials decreases, and the reason for the decrease of wetting heat release is analyzed. The influence mechanism of axial stress loading on coal spontaneous combustion oxidation process is studied. It is found that the increase of axial stress first promotes and then inhibits the process of coal spontaneous combustion. [ABSTRACT FROM AUTHOR]

The primary challenge for preparing SiC crystals during the PVT process is the fractures, especially with the increase in diameter (≥8 inches). In this study, the elastic–plastic behaviors of the azimuthal component (σφφ) of primary stress causing SiC crystal fractures have been investigated to research the fracture mechanism. It is concluded that the plastic deformations caused by prismatic plane slips contribute positively to σφφ. Besides, the magnitude of the plastic component of σφφ is determined by the magnitude of resolved shear stresses (RSS) on each prismatic slip system over the same period, according to the Alexander–Haasen (AH) model. Further, the evolution of the magnitude of RSS (‖RSS‖) during the cooling process has been simulated, and the effects of the experimental conditions on the elastic–plastic behaviors of σφφ have been investigated qualitatively. Control experiments of SiC crystal growth have been carried out simultaneously, and our conclusions have been verified by the experimental results. Lastly, the maximum ‖RSS‖ can be a criterion for the fracture of SiC crystal, giving a critical value near 30 MPa under our experimental conditions. The analysis of the relation between the growth conditions and fractures guides the growth of perfect 8-inch SiC crystals. [ABSTRACT FROM AUTHOR]

Simple Summary: This study examines how altitude affects the fatty acid composition of pasture grass, yak milk, and yak ghee on the Qinghai–Tibet Plateau. It aims to understand how environmental factors, particularly altitude, influence the nutritional quality of these products. The results indicate that higher altitudes correlate with a greater presence of beneficial unsaturated fatty acids, such as oleic acid (C18:1) and linoleic acid (C18:2n6c), suggesting that yaks adapt to their high-altitude surroundings. These adaptations positively impact the quality of yak milk and yak ghee, essential food sources for local communities. By emphasizing the connection between altitude and fatty acid profiles, this research offers insights that can enhance dairy production practices. Ultimately, it aims to improve nutrition and food security for residents in high-altitude regions, ensuring access to nutritious food options. This study investigates the effect of altitude on the fatty acid composition of pasture grass, yak milk, and yak ghee on the Qinghai–Tibet Plateau, aiming to understand how environmental factors influence the nutritional quality of these products. Samples were collected from four different altitudes and analyzed for fatty acid profiles using gas chromatography. The analysis reveals that higher altitudes are associated with an increased prevalence of beneficial unsaturated fatty acids, such as oleic acid (C18:1) and linoleic acid (C18:2n6c). These findings highlight the significant influence of altitude on yak lipid metabolism, ultimately enhancing the nutritional value of dairy products. This adaptation not only supports the health and resilience of yaks, but also provides vital nutritional benefits to residents in high-altitude regions. The research underscores the importance of further investigations to optimize dairy production practices, ensuring improved food security and health outcomes for residents of the plateau. [ABSTRACT FROM AUTHOR]

An efficient, environmentally friendly, and economical polyphosphate/nitrogen-containing composite inhibitor (APNI) has been developed to prevent coal spontaneous combustion (CSC) disasters. Using temperature rise experiments during coal spontaneous combustion, mercury pressure experiments, and Fourier transform infrared spectroscopy (FTIR), the samples treated with the APNI were compared with those treated with MgCl2 and NH4H2PO4 inhibitors, and the inhibitory effects of the three inhibitors on CSC were studied. The results showed that the APNI effectively limited the reactions between the coal and oxygen, reduced the amount of CO gas generated, sealed most of the cracks, large pores and mesopores in the coal, and reduced the number of active functional groups in the coal. The APNI was more effective in preventing CSC than MgCl2 and NH4H2PO4. [ABSTRACT FROM AUTHOR]

Free radicals and metal ions are key factors causing coal spontaneous combustion. In order to effectively suppress coal spontaneous combustion, experiments were conducted using luteolin as an inhibitor, luteolin is abbreviated as LUT. The influence of different concentrations of LUT on the spontaneous combustion heat characteristics of coal was tested using a C600 high-precision microcalorimeter, and the inhibition mechanism was inferred by FTIR. The experimental results show that LUT is an effective coal oxygen inhibitor, under the same action conditions, different concentrations of LUT can absorb heat to different degrees, delay the initial exothermic temperature of coal, prolong the heat absorption phase of coal. Compared with raw coal, 6 wt% LUT absorbs the most heat, the starting exothermic temperature is delayed by 46°C, and the activation energy is increased by 47.89 kJ/mol, the functional group -OH content decreased by 43.4%, -CH3 decreased by 32.1%, -CH2-decreased by 37.76%. Based on this, the mechanism of inhibition is inferred, LUT not only removes free radicals (ROO•) during the chain initiation stage and captures free radicals (•OH) in the reaction chain but also chelates metal ions to inhibit the catalytic effect of metal ions during the free radical reaction, which can play a dual role in preventing free radical generation and interrupting the free radical chain reaction. The results of the study can provide a novel, environmentally friendly and effective way to prevent the spontaneous combustion of coal. [ABSTRACT FROM AUTHOR]

Partial discharge in oil paper insulation is an important reason for insulation breakdown. The study of partial discharge in transformer oil is of great significance for ensuring the reliability of transformers. In this paper, a comprehensive observation platform of partial discharge with needle plate electrode and oil-paper insulation is built, and the original shape image set of partial discharge is collected and established. Through multi-channel convolution processing of the true color image, gray level equivalent distribution of 3D section, segmentation stretching of threshold interval and binary neighborhood search, a general technical method suitable for processing a series of low brightness discharge images with background interference is finally obtained. [ABSTRACT FROM AUTHOR]

Single‐crystal silicon carbide (SiC) is an important semiconductor material for the fabrication of power and radio frequency (RF) devices. The major technique for growing single‐crystal SiC is the so‐called physical vapor transport (PVT) method, in which not only the thermal field but also the fluid‐flow field and the distribution of gas species can be hardly measured directly. In this study, a multi‐component flow model is proposed that includes the inside and outside of a growth chamber and a joint between the seed crystal holder and crucible which allows exchanges of the gas species. The joint is simulated as a thin porous graphite sheet. The Hertz‐Knudsen equation is used to describe the sublimation and deposition. The convection and diffusion are described by the Navier–Stokes equations and mixture‐averaged diffusion model, in which the Stefan flow is taken into account. The numerical simulations are conducted by the finite element method (FEM) with a multi‐physics coupled model, which is able to predict the fluid flow field, species distribution field, crystal growth rate, and evolution of the molar concentration of dopant gas. Using this model, the effects of several experimental conditions on the transport of gas species and the growth rate of single‐crystal SiC are analyzed. [ABSTRACT FROM AUTHOR]