Numerical study of the low-frequency atomic dynamics in a Lennard-Jones glass

Abstract This paper constructs and analyzes a reduced nonlinear stochastic model of extratropical low-frequency variability. To do so, it applies multilevel quadratic regression to the output of a long simulation of a global baroclinic, quasigeostrophic, three-level (QG3) model with topography; the model's phase space has a dimension of O(104). The reduced model has 45 variables and captures well the non-Gaussian features of the QG3 model's probability density function (PDF). In particular, the reduced model's PDF shares with the QG3 model its four anomalously persistent flow patterns, which correspond to opposite phases of the Arctic Oscillation and the North Atlantic Oscillation, as well as the Markov chain of transitions between these regimes. In addition, multichannel singular spectrum analysis identifies intraseasonal oscillations with a period of 35–37 days and of 20 days in the data generated by both the QG3 model and its low-dimensional analog. An analytical and numerical study of the reduced model starts with the fixed points and oscillatory eigenmodes of the model's deterministic part and uses systematically an increasing noise parameter to connect these with the behavior of the full, stochastically forced model version. The results of this study point to the origin of the QG3 model's multiple regimes and intraseasonal oscillations and identify the connections between the two types of behavior.

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Numerical Study on Hydrodynamic Responses of a Two-Body System in Side-by-Side Operation

Volume 7: Ocean Engineering ◽

10.1115/omae2016-54625 ◽

2016 ◽

Author(s):

Shaowu Ou ◽

Shixiao Fu ◽

Wei Wei ◽

Tao Peng ◽

Xuefeng Wang

Keyword(s):

Numerical Study ◽

Low Frequency ◽

Optimal Operation ◽

Hydrodynamic Interactions ◽

Irregular Waves ◽

Mooring System ◽

Time Varying ◽

Body System ◽

The Time Domain ◽

Two Bodies

Typically, in some side-by-side offshore operations, the speed of vessels is very low or even 0 and the headings are manually maneuvered. In this paper, the hydrodynamic responses of a two-body system in such operations under irregular seas are investigated. The numerical model includes two identical PSVs (Platform Supply Vessel) as well as the fenders and connection lines between them. A horizontal mooring system constraining the low frequency motions is set on one of the ships to simulate maneuver system. Accounting for the hydrodynamic interactions between two bodies, 3D potential theory is applied for the analysis of their hydrodynamic coefficients. With wind and current effects included, these coefficients are further applied in the time domain simulations in irregular waves. The relevant coefficients are estimated by experiential formulas. Time-varying loads on fenders and connection lines are analyzed. Meanwhile, the relative motions as well as the effects of the hydrodynamic interactions between ships are further discussed, and finally an optimal operation scheme in which operation can be safely performed is summarized.

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Numerical Study of Crosshole Electromagnetic Tunnel Detection

Geophysics ◽

10.1190/geo2020-0376.1 ◽

2021 ◽

pp. 1-68

Author(s):

John W. Neese ◽

David R. Jackson ◽

Yingcai Zheng ◽

Leon A. Thomsen

Keyword(s):

Fresh Water ◽

Numerical Study ◽

Low Frequency ◽

Open Circuit ◽

Infinite Cylinder ◽

Optimum Frequency ◽

Low Frequencies ◽

Tunnel Detection ◽

Lossy Medium ◽

Water Saturated

Electromagnetic tunnel detection is studied numerically using a 3D analytic infinite lossy homogeneous space solution to magnetic dipole radiation and scattering from an infinite cylinder, in a crosshole context. At low frequencies this serves as a model for a transmit coil radiating a time-varying magnetic field that is then detected from the open-circuit voltage induced on a receive coil. Numerical simulations illustrate how various parameters influence the signal strength and the ability to discern the scattered signal. Tunnel detection is achieved at relatively high frequencies (but below typical GPR frequencies) for fresh water saturated sand and for weathered granite, which are lower loss media; for the coil and tunnel parameters used here, optimum frequencies appear to be between 100 kHz and 1 MHz. Tunnel detection for fresh water saturated clay, a much more lossy medium, can be achieved at a quite low frequency, with an optimum frequency between 1 and 10 kHz. These results suggest that, when a resonant coil system is employed, tunnel detection may be possible in a wider range of earth media than previously reported, when the best-suited choice of frequency is employed.

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Numerical study for increasement of low frequency sound insulation of double-panel structure using sonic crystals with distributed Helmholtz resonators

International Journal of Modern Physics B ◽

10.1142/s0217979219501388 ◽

2019 ◽

Vol 33 (14) ◽

pp. 1950138

Author(s):

Myong-Jin Kim

Keyword(s):

Free Space ◽

Transmission Loss ◽

Numerical Study ◽

Low Frequency ◽

Helmholtz Resonator ◽

Sound Insulation ◽

The Finite Element Method ◽

Helmholtz Resonators ◽

Sonic Crystal ◽

Sonic Crystals

Numerical simulations of the sound transmission loss (STL) of a double-panel structure (DPS) with sonic crystal (SC) comprised of distributed local resonators are presented. The Local Resonant Sonic Crystal (LRSC) consists of “C”-shaped Helmholtz resonator columns with different resonant frequencies. The finite element method is used to calculate the STL of such a DPS. First, the STLs of LRSC in free space and the DPS with LRSC are calculated and compared. It is shown that the sound insulations of the local resonators inserted in the double panel are higher than that in free space for the same size of the SCs and the same number of columns. Next, STL of the DPS in which the SC composed of three columns of local resonators having the same outer and inner diameters but different slot widths are calculated, and a reasonable arrangement order is determined. Finally, the soundproofing performances of DPS with distributed LRSC are compared with the case of insertion of general cylindrical SC for SC embedded in glass wool and not. The results show that the sound insulation of the DPS can be significantly improved in the low frequency range while reducing the total mass without increasing the thickness.

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The numerical study of viscous drag force influence on low-frequency surge motion of a semi-submersible in storm sea states

Ocean Engineering ◽

10.1016/j.oceaneng.2020.107511 ◽

2020 ◽

Vol 213 ◽

pp. 107511 ◽

Cited By ~ 1

Author(s):

Shan Ma ◽

De-kang Xu ◽

Wen-yang Duan ◽

Ji-kang Chen ◽

Kang-ping Liao ◽

...

Keyword(s):

Drag Force ◽

Numerical Study ◽

Low Frequency ◽

Viscous Drag ◽

Viscous Drag Force

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A Numerical Study on Conductivity Estimation of the Human Head in the Low Frequency Domain Using Induced Current MR Phase Imaging EIT With Multiple Gradients

IEEE Transactions on Magnetics ◽

10.1109/tmag.2013.2250985 ◽

2013 ◽

Vol 49 (9) ◽

pp. 5004-5010 ◽

Cited By ~ 9

Author(s):

Nele De Geeter ◽

Guillaume Crevecoeur ◽

Luc Dupre

Keyword(s):

Frequency Domain ◽

Numerical Study ◽

Low Frequency ◽

Human Head ◽

Phase Imaging ◽

Induced Current

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Numerical study of magnetic particles mixing in waste water under an external magnetic field

Journal of Water Supply Research and Technology—AQUA ◽

10.2166/aqua.2020.090 ◽

2020 ◽

Vol 69 (3) ◽

pp. 266-275 ◽

Cited By ~ 4

Author(s):

Christos Liosis ◽

Evangelos G. Karvelas ◽

Theodoros Karakasidis ◽

Ioannis E. Sarris

Keyword(s):

Magnetic Field ◽

Magnetic Particles ◽

Numerical Study ◽

Low Frequency ◽

Water And Wastewater Treatment ◽

Novel Approach ◽

Optimal Value ◽

Frequency Optimum ◽

Combined Action ◽

Aligned Magnetic Field

Abstract The combination of nanotechnology and microfluidics may offer an effective water and wastewater treatment. A novel approach combines the use of magnetic particles which can capture heavy metal impurities in microfluidic ducts. The purpose of this study is to investigate the mixing mechanism of two water streams, one with magnetic particles and the other with wastewater. The optimum mixing is obtained when particles are uniformly distributed along the volume of water in the duct for the combined action of a permanent, spatially and temporally aligned magnetic field. Results showed that mixing is enhanced as the frequency of the magnetic field decreases or its amplitude increases, while magnetic gradient is found to play an insignificant role in the present configuration. Moreover, for simulations with low frequency, the mean concentration of particles is found to be twice as high as compared to the cases with higher frequency. Optimum distribution of particles inside the micromixer is observed for the combination of 0.6 T, 8 T/m and 5 Hz for the magnetic magnitude, gradient and frequency, respectively, where concentration reaches the optimal value of 0.77 mg/mL along the volume of the duct.

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