The Experts below are selected from a list of 243 Experts worldwide ranked by ideXlab platform
Shanhwei Ou - One of the best experts on this subject based on the ideXlab platform.
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laboratory flume studies on Monochromatic Wave fine sandy bed interactions part 2 sediment suspensions
Coastal Engineering, 2009Co-Authors: Shiawyih Tzang, Shanhwei OuAbstract:Abstract As reported in preceding paper (Part 1. Soil Fluidization), the observed phenomena of sediment suspensions above a fluidized sandy bed of Sand II ( d 50 = 0.092 mm) under Monochromatic Wave actions are quantitatively investigated. The suspended sediment concentration (SSC) at a single point within 5 cm above the bed was synchronously measured with water Waves and bed soil's pore pressures with an intrusive optical sediment-concentration probe. The measurements show that SSC initiates several Wave cycles after initiation of bed soil's fluidized response and grows to a peak value mainly in the post-fluidization phase. Under similar Wave loadings in the same test series, SSC is usually higher over a resonantly fluidized (RF) bed than over a non-resonantly fluidized (NRF) bed. On the contrary, only relatively low SCC can be identified above an unfluidized bed. The analyses illustrate that to certain extent, peak values of SSC are directly proportional to the thickness of fluidized soil layer d f . Values of d f usually decrease with repeated fluidized response, longer consolidation periods, and in deeper water depths. Once the fluidized responses initiate, pore pressures are generally much significantly amplified in both shallow fluidized soil layers and near below the fluidized layer, especially during the resonance event. The resulting depth gradients of dynamic pore pressure amplitudes in shallow layers are likely to have caused higher initial rises of SSC in a RF bed than in the subsequent NRF bed. Those in deeper layer should have contributed to sustain the fluidization state for further SSC increments. Immediately after termination of Wave loading, re-deposited suspended sediments always result in a typical flat bed form. For a pre-fluidized bed, Wave-induced drastic sediment suspensions are still obtainable very near above the bed with even a rather thin fluidized surface soil layer.
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laboratory flume studies on Monochromatic Wave fine sandy bed interactions part 1 soil fluidization
Coastal Engineering, 2006Co-Authors: Shiawyih Tzang, Shanhwei OuAbstract:Abstract Tests on two fine sandy soils (d50 = 0.134 mm and 0.092 mm) under Monochromatic Wave actions were conducted in a Wave flume of 37 m (L) by 1.2 m (H) by 1 m (W) to investigate characteristics of fluidized responses. The pore pressure measurements demonstrate only an unfluidized response in the coarser sandy bed, while in the finer one, two more feature fluidized responses. Fluidized responses are similarly classified into resonantly and non-resonantly fluidized according to Foda and Tzang [Foda, M.A., Tzang, S.-Y., 1994. Resonant fluidization of silty soil by water Waves. J. Geophys. Res., 99-C10: 20463–20475.]. At a given depth, they are in principle defined by magnitude of fluidization ratio between excess pore pressure and static soil stresses and by the occurrence of a resonance event in the same test series. Inside the sandy bed, the excess pore pressures of a fluidized response are almost initiated simultaneously. Their magnitudes are essentially in static balance to the integrated weight of overlaying fluidized soil layers. Comparisons with previously reported data from a silty bed (d50 = 0.05 mm) by Foda and Tzang have immediately indicated the importance of grain fraction. With less fine constituents, surface layers of the two sandy soils are less susceptible to fluidization. Resonance mechanism is evidently diminishing in a resonantly fluidized response, and re-fluidization becomes less potential in the subsequent tests. In a resonantly fluidized response, pore pressures at a given depth would start to resonantly grow from a fluidization ratio of 7–14%. In a few Wave cycles, resonant growth subsides at a fluidization ratio of greater than 50%, which value increases with depth. The analyses clearly illustrate that fluidization tends to be initiated in surface layers and fast spreads into lower layers. Fluidization is dependent on finer constituting grains, smaller shear modulus G and permeability k and thinner boundary layers in bed soils. Measurements of previous silt tests are analyzed to show that lower limits of Wave steepness on resonantly fluidizing a soil bed increase linearly with relative water depth ranging from 0.13 to 0.23. Data of present fine sand tests have preliminarily confirmed the linear trend. Over a fluidized sandy bed, similar vivid sediment suspensions were observed during Wave generations as had been reported in silt tests.
G C Ho - One of the best experts on this subject based on the ideXlab platform.
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reconnection remnants in the magnetic cloud of october 18 19 1995 a shock Monochromatic Wave heat flux dropout and energetic ion beam
Journal of Geophysical Research, 2001Co-Authors: M R Collier, A Szabo, W M Farrell, J A Slavin, R P Lepping, R J Fitzenreiter, B J Thompson, D C Hamilton, G Gloeckler, G C HoAbstract:Evidence is presented that the Wind spacecraft observed particle and field signatures on October 18–19, 1995, due to reconnection near the foot points of a magnetic cloud (i.e., between 1 and 5 solar radii). These signatures include (1) an internal shock traveling approximately along the axis of the magnetic cloud, (2) a simple compression of the magnetic field consistent with the foot point magnetic fields being thrust outward at speeds much greater than the solar wind speed, (3) an electron heat flux dropout occurring within minutes of the shock, indicating a topological change resulting from disconnection from the solar surface, (4) a very cold 5 keV proton beam, and (5) an associated Monochromatic Wave. We expect that given observations of enough magnetic clouds, Wind and other spacecraft will see signatures similar to the ones reported here indicating reconnection. However, these observations require the spacecraft to be fortuitously positioned to observe the passing shock and other signatures and will therefore be associated with only a small fraction of magnetic clouds. Consistent with this, a few magnetic clouds observed by Wind have been found to possess internal shock Waves.
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Reconnection remnants in the magnetic cloud of October 18–19, 1995: A shock, Monochromatic Wave, heat flux dropout, and energetic ion beam
Journal of Geophysical Research, 2001Co-Authors: M R Collier, A Szabo, W M Farrell, J A Slavin, R P Lepping, R J Fitzenreiter, B J Thompson, D C Hamilton, G Gloeckler, G C HoAbstract:Evidence is presented that the Wind spacecraft observed particle and field signatures on October 18–19, 1995, due to reconnection near the foot points of a magnetic cloud (i.e., between 1 and 5 solar radii). These signatures include (1) an internal shock traveling approximately along the axis of the magnetic cloud, (2) a simple compression of the magnetic field consistent with the foot point magnetic fields being thrust outward at speeds much greater than the solar wind speed, (3) an electron heat flux dropout occurring within minutes of the shock, indicating a topological change resulting from disconnection from the solar surface, (4) a very cold 5 keV proton beam, and (5) an associated Monochromatic Wave. We expect that given observations of enough magnetic clouds, Wind and other spacecraft will see signatures similar to the ones reported here indicating reconnection. However, these observations require the spacecraft to be fortuitously positioned to observe the passing shock and other signatures and will therefore be associated with only a small fraction of magnetic clouds. Consistent with this, a few magnetic clouds observed by Wind have been found to possess internal shock Waves.
Shiawyih Tzang - One of the best experts on this subject based on the ideXlab platform.
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laboratory flume studies on Monochromatic Wave fine sandy bed interactions part 2 sediment suspensions
Coastal Engineering, 2009Co-Authors: Shiawyih Tzang, Shanhwei OuAbstract:Abstract As reported in preceding paper (Part 1. Soil Fluidization), the observed phenomena of sediment suspensions above a fluidized sandy bed of Sand II ( d 50 = 0.092 mm) under Monochromatic Wave actions are quantitatively investigated. The suspended sediment concentration (SSC) at a single point within 5 cm above the bed was synchronously measured with water Waves and bed soil's pore pressures with an intrusive optical sediment-concentration probe. The measurements show that SSC initiates several Wave cycles after initiation of bed soil's fluidized response and grows to a peak value mainly in the post-fluidization phase. Under similar Wave loadings in the same test series, SSC is usually higher over a resonantly fluidized (RF) bed than over a non-resonantly fluidized (NRF) bed. On the contrary, only relatively low SCC can be identified above an unfluidized bed. The analyses illustrate that to certain extent, peak values of SSC are directly proportional to the thickness of fluidized soil layer d f . Values of d f usually decrease with repeated fluidized response, longer consolidation periods, and in deeper water depths. Once the fluidized responses initiate, pore pressures are generally much significantly amplified in both shallow fluidized soil layers and near below the fluidized layer, especially during the resonance event. The resulting depth gradients of dynamic pore pressure amplitudes in shallow layers are likely to have caused higher initial rises of SSC in a RF bed than in the subsequent NRF bed. Those in deeper layer should have contributed to sustain the fluidization state for further SSC increments. Immediately after termination of Wave loading, re-deposited suspended sediments always result in a typical flat bed form. For a pre-fluidized bed, Wave-induced drastic sediment suspensions are still obtainable very near above the bed with even a rather thin fluidized surface soil layer.
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laboratory flume studies on Monochromatic Wave fine sandy bed interactions part 1 soil fluidization
Coastal Engineering, 2006Co-Authors: Shiawyih Tzang, Shanhwei OuAbstract:Abstract Tests on two fine sandy soils (d50 = 0.134 mm and 0.092 mm) under Monochromatic Wave actions were conducted in a Wave flume of 37 m (L) by 1.2 m (H) by 1 m (W) to investigate characteristics of fluidized responses. The pore pressure measurements demonstrate only an unfluidized response in the coarser sandy bed, while in the finer one, two more feature fluidized responses. Fluidized responses are similarly classified into resonantly and non-resonantly fluidized according to Foda and Tzang [Foda, M.A., Tzang, S.-Y., 1994. Resonant fluidization of silty soil by water Waves. J. Geophys. Res., 99-C10: 20463–20475.]. At a given depth, they are in principle defined by magnitude of fluidization ratio between excess pore pressure and static soil stresses and by the occurrence of a resonance event in the same test series. Inside the sandy bed, the excess pore pressures of a fluidized response are almost initiated simultaneously. Their magnitudes are essentially in static balance to the integrated weight of overlaying fluidized soil layers. Comparisons with previously reported data from a silty bed (d50 = 0.05 mm) by Foda and Tzang have immediately indicated the importance of grain fraction. With less fine constituents, surface layers of the two sandy soils are less susceptible to fluidization. Resonance mechanism is evidently diminishing in a resonantly fluidized response, and re-fluidization becomes less potential in the subsequent tests. In a resonantly fluidized response, pore pressures at a given depth would start to resonantly grow from a fluidization ratio of 7–14%. In a few Wave cycles, resonant growth subsides at a fluidization ratio of greater than 50%, which value increases with depth. The analyses clearly illustrate that fluidization tends to be initiated in surface layers and fast spreads into lower layers. Fluidization is dependent on finer constituting grains, smaller shear modulus G and permeability k and thinner boundary layers in bed soils. Measurements of previous silt tests are analyzed to show that lower limits of Wave steepness on resonantly fluidizing a soil bed increase linearly with relative water depth ranging from 0.13 to 0.23. Data of present fine sand tests have preliminarily confirmed the linear trend. Over a fluidized sandy bed, similar vivid sediment suspensions were observed during Wave generations as had been reported in silt tests.
D I Kamenev - One of the best experts on this subject based on the ideXlab platform.
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stability of the ground state of a harmonic oscillator in a Monochromatic Wave
Chaos, 2001Co-Authors: G P Berman, Daniel F. V. James, D I KamenevAbstract:The stability of the ground state of a harmonic oscillator in a Monochromatic Wave is studied. This model describes, in particular, the dynamics of a cold ion in a linear ion trap, interacting with two laser fields with close frequencies. The stability of the “classical ground state”—the vicinity of the point (x=0,p=0)—is analyzed analytically and numerically. For the quantum case, a method for studying a stability of the quantum ground state is developed, based on the quasienergy representation. It is demonstrated that stability of the ground state may be substantially improved by increasing the resonance number, l, where l=Ω/ω+δ, Ω and ω are, respectively, the Wave frequency and the oscillator frequency, l=1,2,…, |δ|<1; or by detuning the system from exact resonance, so that δ≠0. The influence of a large-amplitude Wave (in the presence of chaos) on the stability of the ground state is analyzed for different parameters of the model in both the quantum and classical cases.
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Stability of the ground state of a harmonic oscillator in a Monochromatic Wave.
Chaos, 2001Co-Authors: G P Berman, Daniel F. V. James, D I KamenevAbstract:The stability of the ground state of a harmonic oscillator in a Monochromatic Wave is studied. This model describes, in particular, the dynamics of a cold ion in a linear ion trap, interacting with two laser fields with close frequencies. The stability of the “classical ground state”—the vicinity of the point (x=0,p=0)—is analyzed analytically and numerically. For the quantum case, a method for studying a stability of the quantum ground state is developed, based on the quasienergy representation. It is demonstrated that stability of the ground state may be substantially improved by increasing the resonance number, l, where l=Ω/ω+δ, Ω and ω are, respectively, the Wave frequency and the oscillator frequency, l=1,2,…, |δ|
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quantum chaos a harmonic oscillator in Monochromatic Wave
2001Co-Authors: D I Kamenev, G P BermanAbstract:A review on transition from regular dynamics to quantum chaos in a quantum degenerate system - a harmonic oscillator perturbed by a Monochromatic Wave. It explains how the transition to quantum chaos occurs and how the theoretical predictions can be tested in experiments.
M R Collier - One of the best experts on this subject based on the ideXlab platform.
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reconnection remnants in the magnetic cloud of october 18 19 1995 a shock Monochromatic Wave heat flux dropout and energetic ion beam
Journal of Geophysical Research, 2001Co-Authors: M R Collier, A Szabo, W M Farrell, J A Slavin, R P Lepping, R J Fitzenreiter, B J Thompson, D C Hamilton, G Gloeckler, G C HoAbstract:Evidence is presented that the Wind spacecraft observed particle and field signatures on October 18–19, 1995, due to reconnection near the foot points of a magnetic cloud (i.e., between 1 and 5 solar radii). These signatures include (1) an internal shock traveling approximately along the axis of the magnetic cloud, (2) a simple compression of the magnetic field consistent with the foot point magnetic fields being thrust outward at speeds much greater than the solar wind speed, (3) an electron heat flux dropout occurring within minutes of the shock, indicating a topological change resulting from disconnection from the solar surface, (4) a very cold 5 keV proton beam, and (5) an associated Monochromatic Wave. We expect that given observations of enough magnetic clouds, Wind and other spacecraft will see signatures similar to the ones reported here indicating reconnection. However, these observations require the spacecraft to be fortuitously positioned to observe the passing shock and other signatures and will therefore be associated with only a small fraction of magnetic clouds. Consistent with this, a few magnetic clouds observed by Wind have been found to possess internal shock Waves.
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Reconnection remnants in the magnetic cloud of October 18–19, 1995: A shock, Monochromatic Wave, heat flux dropout, and energetic ion beam
Journal of Geophysical Research, 2001Co-Authors: M R Collier, A Szabo, W M Farrell, J A Slavin, R P Lepping, R J Fitzenreiter, B J Thompson, D C Hamilton, G Gloeckler, G C HoAbstract:Evidence is presented that the Wind spacecraft observed particle and field signatures on October 18–19, 1995, due to reconnection near the foot points of a magnetic cloud (i.e., between 1 and 5 solar radii). These signatures include (1) an internal shock traveling approximately along the axis of the magnetic cloud, (2) a simple compression of the magnetic field consistent with the foot point magnetic fields being thrust outward at speeds much greater than the solar wind speed, (3) an electron heat flux dropout occurring within minutes of the shock, indicating a topological change resulting from disconnection from the solar surface, (4) a very cold 5 keV proton beam, and (5) an associated Monochromatic Wave. We expect that given observations of enough magnetic clouds, Wind and other spacecraft will see signatures similar to the ones reported here indicating reconnection. However, these observations require the spacecraft to be fortuitously positioned to observe the passing shock and other signatures and will therefore be associated with only a small fraction of magnetic clouds. Consistent with this, a few magnetic clouds observed by Wind have been found to possess internal shock Waves.