The erosion of dust by an airflow

Fletcher, B.

doi:10.1088/0022-3727/9/6/005

Cited by 36 publications

(24 citation statements)

References 9 publications

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“…For NH 3 and SO 2 , SFIE is 25.1 and 21.16 eV, respectively. [33,34] This is higher than that of other atoms and molecules such as Ar (11.87 eV), Xe (9.08 eV), [7] diatomic hydrogen molecules (0.824), [12] and triatomic water molecules (1.88 eV). [18] This is reflected in the increased laser energy required for the electron tunnelling ionization.…”

Section: Simulation Modelmentioning

confidence: 80%

“…Hence, these energies are implemented in the XOOPIC code for both NH 3 and SO 2 molecules. [33,34] Each cycle of the PIC-MCC simulation is described schematically in Figure 1. The time step of this procedure should be smaller than the shortest characteristic timescale of the problem (such as inverse of plasma frequency, maximum collision frequency, and incident laser frequency or pulse duration).…”

Section: Simulation Modelmentioning

confidence: 99%

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THz radiation generation via the interaction of two‐colour ultra‐short laser pulses with SO₂ and NH₃ gases

Gishini

Ganjovi

2017

Contrib. Plasma Phys

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In this work, using a two‐dimensional particle‐in‐cell Monte Carlo collision computation method, terahertz (THz) radiation generation via the interaction of two‐colour, ultra‐short, high‐power laser pulses with the polyatomic molecular gases sulphur dioxide (SO2) and ammonia (NH3) is examined. The influence of SO2 and NH3 pressures and two‐colour laser pulse parameters, i.e., pulse shape, pulse duration, and beam waist, on the THz radiation generation is studied. It is shown that the THz signal generation from SO2 and NH3 increases with the background gas pressure. It is seen that the THz emission intensity for both gases at higher laser pulse durations is higher. Moreover, for these polyatomic gases, the plasma current density increases with increase in the laser pulse beam waist. A more powerful THz radiation intensity with a larger time to peak of the plasma current density is observed for SO2 compared to NH3. In addition, many THz signals with small intensities are observed for both polyatomic gases. It is seen that for both SO2 and NH3 the generated THz spectral intensity is higher at higher gas pressures.

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Section: Simulation Modelmentioning

confidence: 80%

Section: Simulation Modelmentioning

confidence: 99%

THz radiation generation via the interaction of two‐colour ultra‐short laser pulses with SO₂ and NH₃ gases

Gishini

Ganjovi

2017

Contrib. Plasma Phys

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“…For more details see Ref. . In VSVB, each orbital is expanded in a subset of the basis functions on the molecule,

φ_{i} = \sum_{μ}^{M_{i}} C_{μi} ζ_{μi}

where C μi , ζ μi , and M i are the expansion coefficients, basis functions, and number of basis functions, for i th orbital.…”

Section: Theorymentioning

confidence: 99%

“…This article describes Valence , a quantum chemistry program designed for performing ab initio electronic‐structure calculations based on the variational subspace valence bond (VSVB) method . The key idea that sets VSVB apart is the use of multicenter orbitals that are required to be linearly independent but not orthogonal.…”

Section: Introductionmentioning

confidence: 99%

Valence: A Massively Parallel Implementation of the Variational Subspace Valence Bond Method

et al. 2019

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This work describes the software package, Valence, for the calculation of molecular energies using the variational subspace valence bond (VSVB) method. VSVB is an ab initio electronic structure method based on nonorthogonal orbitals. Important features of practical value include high parallel scalability, wave functions that can be constructed automatically by combining orbitals from previous calculations, and ground and excited states that can be modeled with a single configuration or determinant. The open‐source software package includes tools to generate wave functions, a database of generic orbitals, example input files, and a library build intended for integration with other packages. We also describe the interface to an external software package, enabling the computation of optimized molecular geometries and vibrational frequencies. © 2019 Wiley Periodicals, Inc.

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“…By fitting a group of studies from decades ago to recent time (Bagnold 1937;Chepil 1945;Fletcher 1976aFletcher , 1976bGreeley et al 2003;Mazurak et al 1953;Shao and Klose 2016;Shao and Lu 2000), u * t can be estimated with a curve that has a valley around 70 µm using equation 5:…”

Section: Us Environmental Protection Agencymentioning

confidence: 99%

Amplification factors to estimate wind erosion of piles of soil with different heights: Numerical simulation and structure-from-motion photogrammetry verification

Liu¹,

Qu²,

Ning³

2018

Journal of Soil and Water Conservation

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Abstract:In this study, we propose amplification factors of single conical piles with different heights and sizes to describe wind erosion acceleration effects of piles compared to flat erodible surfaces. It is not difficult using traditional wind erosion models to estimate wind erosion of flat agricultural land or pastoral surfaces. However, in the current form these models cannot be used for elevated surfaces such as dunes or piles, which may lead to more serious dust emission and air pollution. A computational fluid dynamics simulation was used to refine a wind erosion estimation method of pile from the US Environmental Protection Agency (USEPA) by dividing the pile surface into multiple subareas with constant wind speed for each subarea and then obtaining ratios of pile erosion to the corresponding flat surface by calculating the total erosion rate of the pile and that of a flat surface with the same floor area. The ratios as amplification factors, E amp , for six pile sizes (from 1 to 12 m) and five wind speed scenarios covering most erosive daily wind speeds from 824 stations throughout China were analyzed and fitted to equations to enable consideration of other heights and wind speed conditions. The changing patterns of the factors were verified using experimental surveys of two plots via the structure-from-motion photogrammetry method, which generated high-resolution digital elevation maps and detected detailed erosion changes. The erosion from a stockpile surface was found to be 2.52 to 7.16 times that from a flat surface with the same floor area, and the influence of pile height on amplification factor could be expressed by a logarithmic equation. These factors can be easily applied to estimate pile erosion by multiplying them by wind erosion results for flat surfaces obtained from other indexes or models. The procedure described in this paper can be extended to consider amplification or reduction effects of dunes, hills, piles, pits, and gullies with different shapes or configurations in relation to wind erosion. Furthermore, the reliability of wind erosion estimation over complex surfaces can be improved to implement specific soil conservation practices.Key words: computational fluid dynamics-Dunhuang-pile-structure-from-motion photogrammetry-wind erosion Wind erosion produces suspended particles from erodible surfaces and causes air pollution, land degradation, and human health problems. The impact of wind erosion is significant in areas severely affected by poor air quality, such as northern China. The effects of terrain obstructions like dunes or piles on modifying wind speed and wind erosion have long been identified (Bagnold 1941; Stunder and Arya 1988;Sullivan and Ajwa 2011). Several models have been developed and improved to estimate wind erosion from agricultural, pastoral, and, sometimes, human disturbed surfaces (Alfaro and Gomes 2001;Hagen 2001;Tatarko et al. 2016;Wagner 2013;Zhang et al. 2017). However, there are no models capable of estimating wind erosion from elevated surfaces because ...

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The erosion of dust by an airflow

Cited by 36 publications

References 9 publications

THz radiation generation via the interaction of two‐colour ultra‐short laser pulses with SO₂ and NH₃ gases

THz radiation generation via the interaction of two‐colour ultra‐short laser pulses with SO₂ and NH₃ gases

Valence: A Massively Parallel Implementation of the Variational Subspace Valence Bond Method

Amplification factors to estimate wind erosion of piles of soil with different heights: Numerical simulation and structure-from-motion photogrammetry verification

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The erosion of dust by an airflow

Cited by 36 publications

References 9 publications

THz radiation generation via the interaction of two‐colour ultra‐short laser pulses with SO2 and NH3 gases

THz radiation generation via the interaction of two‐colour ultra‐short laser pulses with SO2 and NH3 gases

Valence: A Massively Parallel Implementation of the Variational Subspace Valence Bond Method

Amplification factors to estimate wind erosion of piles of soil with different heights: Numerical simulation and structure-from-motion photogrammetry verification

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THz radiation generation via the interaction of two‐colour ultra‐short laser pulses with SO₂ and NH₃ gases

THz radiation generation via the interaction of two‐colour ultra‐short laser pulses with SO₂ and NH₃ gases