150 research outputs found
Development of a Respirable Dust Mitigation System for a High Longwall Face at Sihe Colliery in China â a Case Study
Dust is a major hazard in underground coal mines that threatens the work health and safety of coal miners. The dust issue becomes increasingly significant with the development of highly mechanized coal mining. This issue is particularly serious at the high longwall faces of the Sihe colliery in China as the concentration of dust, in particular respirable dust, at these faces far exceeds the regulatory dust limits. Field testing and computational fluid dynamics (CFD) simulations were conducted to understand the sources of dust generation and its dynamic movement in the #5301 longwall face of high-cutting height at the colliery. The investigation results showed that shearer generated dust was minimal during the coal cutting operation; that face spalling and chock movement were the main dust generating sources, causing significant contamination to the walkway; and that the majority of dust particles from the face (regardless of source) eventually disperse into the main gate, where the dust concentration was greater than 500 mg/m3. These findings were used to develop an effective coal dust mitigation system involving the installation of dust scrubbers, curtains, and venture and crescent sprays. The results of CFD modeling indicate that the dust concentration could be significantly reduced by adopting the new dust mitigation system
2-(4-Carboxypiperidinium-1-yl)pyridine-3-carboxylate
The title compound, C12H14N2O4, crystallizes as a zwitterion. A negative charge is delocalized in the deprotonated carboxyl group attached to the pyridine ring. The piperidine N atom accepts a proton and the ring is transformed into a piperidinium cation. There is an intramolecular N—H⋯O hydrogen bond between the protonated NH and a carboxylate O atom. In the crystal, an O—H⋯O hydrogen bond between the carboxyl group and the carboxylate O atom of another molecule generates a helix along the b axis
Acoustic diagnostics of femtosecond laser filamentation
The promising application of femtosecond laser filamentation in atmospheric
remote sensing brings imperative demand for diagnosing the spatiotemporal
dynamics of filamentation. Acoustic emission (AE) during filamentation opens a
door to give the insight into the dynamic evolution of filaments in air. In
particular, the frequency features of the acoustic emission provide relevant
information on the conversion of laser energy to acoustic energy. Here, the
acoustic emission of femtosecond laser filament manipulated by energy and the
focal lengths was measured quantitatively by a broadband microphone, and the
acoustic parameters were compared and analyzed. Our results showed that the
acoustic power presents a squared dependence on the laser energy and the
bandwidth of the acoustic spectrum showed a significant positive correlation
with laser energy deposition. It was found that the spectrum of the acoustic
pulse emitted from the middle of the filament has a larger bandwidth compared
to those emitted from the ends of the filament and the spectrum of the acoustic
pulse is also an indicator of the filament intensity distribution. These
findings are helpful for studying the plasma filament properties and complex
dynamic processes through acoustic parameters and allow the optimization of
remote applications.Comment: 8 pages,5 figure
Effects of impurity gases on interfaces of the hydrogen-water-decane three-phase system: A square gradient theory investigation
The effects of impurity gases on interfacial characteristics of hydrogen-water-oil three-phase systems are critical to underground H2 storage in depleted oil fields but have not been investigated yet. The square gradient theory calculations with Perturbed-chain statistical associating fluid theory equation of state are carried out to understand the effects of impurity gases (N2, CH4, and CO2) on interfaces of the H2-H2O-n-decane three-phase system under reservoir conditions. Our results obtained from the four-component three-phase systems are compared to the corresponding system without impurity gases. It is found that the all three interfaces (H2-H2O, H2O-C10H22, and H2-C10H22) are greatly influenced by impurity gases. The impurity gases accumulate in all three interfacial regions and have positive surface excesses, which leads to smaller interfacial tensions. The reduction of interfacial tensions depends on the type of impurity gas following this order: CO2 ≥ CH4 > N2. In general, the adsorption of impurity gases weakens the adsorption of other species. However, the adsorption of decane in the H2-H2O interface can be enhanced by impurity gases, which also contributes to the decrease of interfacial tensions. Moreover, the spreading coefficients are mostly negative over the studied temperature and pressure conditions indicating the existence of three-phase contact in the N2/CH4/CO2-hydrogenwater- oil three-phase systems.Document Type: Original articleCited as: Yang, Y., Wan, J., Li, J., Zhu, W., Zhao, G., Shang, X. Effects of impurity gases on interfaces of the hydrogen-water-decane three-phase system: A square gradient theory investigation. Capillarity, 2023, 9(1): 9-24. https://doi.org/10.46690/capi.2023.10.0
Finite-time lag projective synchronization of delayed fractional-order quaternion-valued neural networks with parameter uncertainties
This paper discusses a class issue of finite-time lag projective synchronization (FTLPS) of delayed fractional-order quaternion-valued neural networks (FOQVNNs) with parameter uncertainties, which is solved by a non-decomposition method. Firstly, a new delayed FOQVNNs model with uncertain parameters is designed. Secondly, two types of feedback controller and adaptive controller without sign functions are designed in the quaternion domain. Based on the Lyapunov analysis method, the non-decomposition method is applied to replace the decomposition method that requires complex calculations, combined with some quaternion inequality techniques, to accurately estimate the settling time of FTLPS. Finally, the correctness of the obtained theoretical results is testified by a numerical simulation example
Radio pulsar B095008: Radiation in Magnetosphere and Sparks above Surface
The nearby radio pulsar B095008 with full duty cycle is targeted by the
Five-hundred-meter Aperture Spherical radio Telescope (FAST, 110 minutes
allocated), via adopting polarization calibration on two ways of baseline
determination, in order to understand its magnetospheric radiation geometry as
well as the polar cap sparking. % The radiation of the main pulse could not be
informative of magnetic field line planes due to its low linear polarization
() and the position angle jumps, and the polarization position angle in
the pulse longitudes whose linear fractions are larger than is
thus fitted in the classical rotating vector model (RVM). % The best RVM fit
indicates that the inclination angle, , and the impact angle, ,
of this pulsar are and , respectively,
suggesting that the radio emission comes from two poles. % Polar cap sparking
in the vacuum gap model, either the annular gap or the core gap, is therefore
investigated in this RVM geometry, resulting in a high-altitude magnetospheric
emission at heights from to , with
the light cylinder radius. % It is evident that both sparking
points of the main and inter pulses are located mainly away from the magnetic
pole, that is meaningful in the physics of pulsar surface and is even relevant
to pulsar's inner structure.Comment: 13 pages, 9 figures, submitte
Coupled air lasing gain and Mie scattering loss: aerosol effect in filament-induced plasma spectroscopy
Femtosecond laser filament-induced plasma spectroscopy (FIPS) demonstrates
great potentials in the remote sensing for identifying atmospheric pollutant
molecules. Due to the widespread aerosols in atmosphere, the remote detection
based on FIPS would be affected from both the excitation and the propagation of
fingerprint fluorescence, which still remain elusive. Here the physical model
of filament-induced aerosol fluorescence is established to reveal the combined
effect of Mie scattering and amplification spontaneous emission, which is then
proved by the experimental results, the dependence of the backward fluorescence
on the interaction length between filament and aerosols. These findings provide
an insight into the complicated aerosol effect in the overall physical process
of FIPS including propagation, excitation and emission, paving the way to its
practical application in atmospheric remote sensing.Comment: 7 pages, 4 figure
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