Mining is a high-risk industry, and mine accidents occur frequently. To better understand the characteristics and trends of current coal mine accidents, 29 cases of significant accidents occurred in ...China in 2016 are introduced first in this manuscript; then, the accident types, occurrence time, occurrence locations, and direct causes were analyzed for these accidents. Finally, according to the analysis results, coal mine accident prevention and control suggestions are presented. This data analysis not only plays a positive role in the prevention and control of mine accidents in China but also has reference significance for the safe production of coal mines in other countries of the world.
In this paper, using the charge-plasma concept, we propose an effective technique to implement a graded channel (GC) nanoscale MOSFET without the need for a separate implantation. The characteristics ...are demonstrated and compared with conventional dopingless, junctionless, and underlap inversion-mode MOSFET. The results show that the proposed GC device exhibits reduced drain-induced barrier lowering, improved intrinsic gain (A V ), cutoff frequency (f T ), and maximum oscillation frequency (f MAX ). Our approach overcomes the difficulty of creating a narrow GC doping profile and, thus, makes the GC MOSFET more attractive in carrying on with the scaling trend. The possible fabrication process flow of GC-double-gate (DG) FET is also proposed.
Fake news impacts individuals' behavior and decision-making while also disrupting political processes, perceptions of medical advice, and societal trends. Improving individuals' ability to accurately ...assess fake news can reduce its harmful effects. However, previous research on media literacy interventions designed for improving fake news credibility assessments has yielded inconsistent results. We systematically collected 33 independent studies and performed a meta-analysis to examine the effects of media literacy interventions on assessing fake news credibility (
= 36,256). The results showed that media literacy interventions significantly improved fake news credibility assessments (Hedges'
= 0.53, 95% confidence interval 0.29-0.78,
< 0.001). Gaming interventions were the most effective intervention form. Conversely, the intervention channel, outcome measurement, and subject characteristics (age, gender, and country development level) did not influence the intervention effects.
Magnetorheological fluids (MRF) are regarded as a novel 'intelligent' material because they show the ability to respond to external stimuli. However, with the extension of working time, the ...agglomeration and sedimentation of magnetic particles become a serious problem, which has a great impact on the magnetorheological performance. Many methods have been proposed to overcome the particle settling problem, including magnetic particle modification and carrier liquid modification, but they all show negative effects on the magnetorheological performance of MRF. A new method to prepare the magnetic liquid crystal (LC) composites PEA-COOHSO
3
H@Fe
3
O
4
series, with Fe
3
O
4
nanoparticles as core and side-chain supramolecular LC polymers with different mesogen contents as coating, were reported. The chemical structure, magnetic property and LC properties were investigated by a variety of techniques. In order to study the effects of the mesogen content and LC phase state of magnetic LC composites on magnetorheological performance and sedimentation stability, MRF based on silicone oil carrier liquid and PEA-COOHSO
3
H@Fe
3
O
4
dispersed phase were prepared. It was found that dynamic yield stress, plastic viscosity and the sedimentation ratio increased slightly with increasing mesogen content in the magnetic LC composites. What's more, MRF prepared by magnetic LC composites annealed in LC state exhibited better magnetorheological performance and sedimentation stability than those in glassy state and isotropic state. These results indicated that the synergetic effects of LC orientation and magnetic field-induced arrangement of Fe
3
O
4
magnetic particles can improve the magnetorheological performance and sedimentation stability of MRF.
The Hypersonic Precooled Combined Cycle Engine (HPCCE), which introduces precooler into traditional hypersonic engine, is regarded as the most promising propulsion system for realizing a ...single-stage-to-orbit vehicle. The unique demands lead to the application of the compact heat exchangers, which can realize high thrust-to-weight ratio, sufficient specific impulse and high compression ratio. However, it is challenging to accurately manufacture the compact heat exchanger due to its extremely high heat dissipation capacity, remarkable compactness, superior adaptability and harsh operating condition. This review summarizes the precooling schemes of combined cycle propulsions and describes the demands and key issues in the fabrication of a compact heat exchanger for HPCCE. The investigation focuses on the application of various micromanufacturing methods of heat exchangers constructed from tubes of less than 1 mm in diameter and microchannels of less than 200 micrometers. Various micromanufacturing processes, which include microforming, micromachining, stereolithography, chemical etching, 3D printing, joining and other advanced microfabricating processes, were reviewed. In addition, the technologies are compared in terms of dimensional tolerance, material compatibility, and process applicability. Furthermore, the boundaries of the micromanufacturing constraints are specified as references for the design of compact heat exchangers. Ultimately, the technological difficulties and development trends are discussed for the fabrication of compact heat exchangers for HPCCE.
The deformation process of metal foils is usually under a complex stress status, and the size effect has an obvious influence on the microforming process. To study the effect of grain orientation and ...grain size distribution on the yield loci evolution of SUS304 stainless steel foils, three representative volume element (RVE) models were built based on the open source tools NEPER and MTEX. In addition, the yield loci with different grain sizes are obtained by simulation with Duisseldorf Advanced Material Simulation Kit (DAMASK) under different proportional loading conditions. The initial yield loci show a remarkable difference in shape and size, mainly caused by the distinct texture characteristics. By comparing the crystal plasticity simulation with the experimental results, the model with normal grain size distribution and initial texture based on Electron Back-scattered Diffraction (EBSD) data can more accurately describe the influence of the size effect on the shape and size of yield loci, which is the result of the interaction of grain size distribution and texture. However, the enhancement of grain deformation coordination will weaken the impact of the size effect on yield loci shape if the grain size distribution is more uniform.
The issue of global environmental contamination of microplastics has recently been receiving widespread attention. However, the effects of polystyrene nanoparticles (Nano-PS) on the female ...reproductive system remain unclear. We investigated the toxicity and explored the potential underlying mechanisms of Nano-PS in both mouse ovarian tissue in vivo and human ovarian granulosa cell lines in vitro. In vivo experiments: Mice were fed different concentrations of Nano-PS for 8 weeks. In vitro experiments: COV434 cells were treated with increasing concentrations of Nano-PS. In the present study, ovarian reserve was found to decrease significantly, while oxidative stress and apoptosis levels increased. Nano-PS increased the proportion of metestrum and diestrus periods, and decreased the proportion of estrous period. The implantation rates and the number of pups per litter decreased. In COV434 cells, Nano-PS reduced cell viability and mitochondrial membrane potential, increased the expression of apoptotic and oxidative stress markers and led to subsequent cell cycle arrest. Specifically, Nano-PS exert their toxic effects on mouse ovarian tissue and COV434 cells by inducing oxidative stress. A potential strategy to overcome this could be to activate the nuclear factor-E2-related factor 2 (Nrf2) signaling pathway to mitigate Nano-PS-induced oxidative stress.
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•Nano-PS exposure reduces the growing follicle number and fertility in mice.•Nano-PS exposure on mice affects sex hormone and oxidation-antioxidant status.•Nano-PS exposure inhibited Nrf2 expression and increase apoptosis in mouse ovaries.•Nrf2 plays a protective role against Nano-PS-induced oxidative stress.
In this work, the single-event burnout (SEB) and degradation behaviors induced by heavy-ion irradiation were investigated in an 80-V-rated SEB-hardened split-gate trench (SGT) power U-shaped ...metal-oxide-semiconductor field-effect transistor (UMOSFET). After SEB hardening, the SEB failure threshold voltage of the sample device was measured to be 90 V; furthermore, a permanent degradation of the drain leakage or gate leakage was found after irradiation when the reverse voltage exceeded 60 V. The simulation results demonstrate that the heavy-ion-induced transient high temperature is a common mechanism responsible for the severe degradation and the catastrophic SEB. In addition, an effective method to improve the degradation and SEB tolerances, which enhances the rated breakdown voltage of a device, was proven through simulations.
In this article, a method of single-event burnout (SEB) hardening at high linear energy transfer (LET) value range is proposed and investigated by the 2-D numerical simulations. The improved MOSFET ...using this method and the conventional MOSFET are analyzed and compared to evaluate the effectiveness of this method. Simulation results show that, compared with the conventional MOSFET, the improved MOSFET using this method can effectively and quickly reduce the internal high electric field, thereby reducing the temperature. Under the condition of a LET value of 0.5 pC/<inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> and a drain voltage of 1200 V, the maximum drain current is 0.168 A, and the maximum global device temperature is 1724 K, which is much lower than the melting down temperature of silicon carbide (SiC) (3100 K). The hardening method in this article can be applied to different breakdown voltages by adjusting structure parameters.
In this article, we investigate Schottky diodes with pure W and W-C alloy metal electrodes. The electrical characteristics of samples were analyzed by comparing the current density-voltage ...(<inline-formula> <tex-math notation="LaTeX">{J} - {V} </tex-math></inline-formula>) and capacitance-voltage (<inline-formula> <tex-math notation="LaTeX">{C} - {V} </tex-math></inline-formula>) curves at different annealing temperatures from 400 °C to 900 °C. The ideality factor of W-C alloy diodes annealed at 400 °C was 1.162. When W-C alloy diodes were annealed at 500 °C-900 °C, the range of <inline-formula> <tex-math notation="LaTeX">\emptyset _{B}^{I-{V}} </tex-math></inline-formula> was merely 0.08 eV, the ideality factors were below 1.15, and the difference between <inline-formula> <tex-math notation="LaTeX">\emptyset _{B}^{I-{V}} </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">\emptyset _{B}^{C-{V}} </tex-math></inline-formula> was smaller compared to the pure W diodes. For W-C alloy diodes annealed at 500 °C, the barrier height fluctuated only slightly, and the leakage current was suppressed effectively as the operating temperature increased. These results show that the new structure has better electrical characteristics and thermal stability. Meanwhile, transmission electron microscope (TEM) and energy-dispersive X-ray (EDX) images also verify that W-C alloy diodes reduce the interface reaction between the metal and silicon carbide (SiC), which improves the barrier inhomogeneity of W-based Schottky diodes effectively.
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