The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Jason M Reese - One of the best experts on this subject based on the ideXlab platform.
-
a volume based hydrodynamic approach to Sound Wave propagation in a monatomic gas
Physics of Fluids, 2010Co-Authors: Kokou S Dadzie, Jason M ReeseAbstract:We investigate Sound Wave propagation in a monatomic gas using a volume-based hydrodynamic model. In Dadzie et al. [Physica A 387, 6079 (2008)], a microscopic volume-based kinetic approach was proposed by analyzing molecular spatial distributions; this led to a set of hydrodynamic equations incorporating a mass-density diffusion component. Here we find that these new mass-density diffusive flux and volume terms mean that our hydrodynamic model, uniquely, reproduces Sound Wave phase speed and damping measurements with excellent agreement over the full range of Knudsen number. In the high Knudsen number (high frequency) regime, our volume-based model predictions agree with the plane standing Waves observed in the experiments, which existing kinetic and continuum models have great difficulty in capturing. In that regime, our results indicate that the “Sound Waves” presumed in the experiments may be better thought of as “mass-density Waves,” rather than pressure Waves.
-
a volume based hydrodynamic approach to Sound Wave propagation in a monatomic gas
arXiv: Fluid Dynamics, 2009Co-Authors: Kokou S Dadzie, Jason M ReeseAbstract:We investigate Sound Wave propagation in a monatomic gas using a volume-based hydrodynamic model. In Physica A vol 387(24) (2008) pp6079-6094, a microscopic volume-based kinetic approach was proposed by analyzing molecular spatial distributions; this led to a set of hydrodynamic equations incorporating a mass-density diffusion component. Here we find that these new mass-density diffusive flux and volume terms mean that our hydrodynamic model, uniquely, reproduces Sound Wave phase speed and damping measurements with excellent agreement over the full range of Knudsen number. In the high Knudsen number (high frequency) regime, our volume-based model predictions agree with the plane standing Waves observed in the experiments, which existing kinetic and continuum models have great difficulty in capturing. In that regime, our results indicate that the "Sound Waves" presumed in the experiments may be better thought of as "mass-density Waves", rather than the pressure Waves of the continuum regime.
Kokou S Dadzie - One of the best experts on this subject based on the ideXlab platform.
-
a volume based hydrodynamic approach to Sound Wave propagation in a monatomic gas
Physics of Fluids, 2010Co-Authors: Kokou S Dadzie, Jason M ReeseAbstract:We investigate Sound Wave propagation in a monatomic gas using a volume-based hydrodynamic model. In Dadzie et al. [Physica A 387, 6079 (2008)], a microscopic volume-based kinetic approach was proposed by analyzing molecular spatial distributions; this led to a set of hydrodynamic equations incorporating a mass-density diffusion component. Here we find that these new mass-density diffusive flux and volume terms mean that our hydrodynamic model, uniquely, reproduces Sound Wave phase speed and damping measurements with excellent agreement over the full range of Knudsen number. In the high Knudsen number (high frequency) regime, our volume-based model predictions agree with the plane standing Waves observed in the experiments, which existing kinetic and continuum models have great difficulty in capturing. In that regime, our results indicate that the “Sound Waves” presumed in the experiments may be better thought of as “mass-density Waves,” rather than pressure Waves.
-
a volume based hydrodynamic approach to Sound Wave propagation in a monatomic gas
arXiv: Fluid Dynamics, 2009Co-Authors: Kokou S Dadzie, Jason M ReeseAbstract:We investigate Sound Wave propagation in a monatomic gas using a volume-based hydrodynamic model. In Physica A vol 387(24) (2008) pp6079-6094, a microscopic volume-based kinetic approach was proposed by analyzing molecular spatial distributions; this led to a set of hydrodynamic equations incorporating a mass-density diffusion component. Here we find that these new mass-density diffusive flux and volume terms mean that our hydrodynamic model, uniquely, reproduces Sound Wave phase speed and damping measurements with excellent agreement over the full range of Knudsen number. In the high Knudsen number (high frequency) regime, our volume-based model predictions agree with the plane standing Waves observed in the experiments, which existing kinetic and continuum models have great difficulty in capturing. In that regime, our results indicate that the "Sound Waves" presumed in the experiments may be better thought of as "mass-density Waves", rather than the pressure Waves of the continuum regime.
Ying Wei - One of the best experts on this subject based on the ideXlab platform.
-
a reconfigurable Sound Wave decomposition filterbank for hearing aids based on nonlinear transformation
IEEE Transactions on Biomedical Circuits and Systems, 2016Co-Authors: Shaoguang Huang, Lan Tian, Ying WeiAbstract:Hearing impaired people have their own hearing loss characteristics and listening preferences. Therefore hearing aid system should become more natural, humanized and personalized, which requires the filterbank in hearing aids provides flexible Sound Wave decomposition schemes, so that patients are likely to use the most suitable scheme for their own hearing compensation strategy. In this paper, a reconfigurable Sound Wave decomposition filterbank is proposed. The prototype filter is first cosine modulated to generate uniform subbands. Then by non-linear transformation the uniform subbands are mapped to nonuniform subbands. By changing the control parameters, the nonlinear transformation changes which leads to different subbands allocations. It provides four different Sound Wave decomposition schemes without changing the structure of the filterbank. The performance of the proposed reconfigurable filterbank was compared with that of fixed filerbanks, fully customizable filterbanks and other existing reconfigurable filterbanks. It is shown that the proposed filterbank provides satisfactory matching performance as well as low complexity and delay, which make it suitable for real hearing aid applications.
-
a reconfigurable digital filterbank for hearing aid systems with a variety of Sound Wave decomposition plans
IEEE Transactions on Biomedical Engineering, 2013Co-Authors: Ying Wei, Debao LiuAbstract:Current hearing-aid systems have fixed Sound Wave decomposition plans due to the use of fixed filterbanks, thus cannot provide enough flexibility for the compensation of different hearing impairment cases. In this paper, a reconfigurable filterbank that consists of a multiband-generation block and a subband-selection block is proposed. Different subbands can be produced according to the control parameters without changing the structure of the filterbank system. The use of interpolation, decimation, and frequency-response masking enables us to reduce the computational complexity by realizing the entire system with only three prototype filters. Reconfigurability of the proposed filterbank enables hearing-impaired people to customize hearing aids based on their own specific conditions to improve their hearing ability. We show, by means of examples, that the proposed filterbank can achieve a better matching to the audiogram and has smaller complexity compared with the fixed filterbank. The drawback of the proposed method is that the throughput delay is relatively long (>20 ms), which needs to be further reduced before it can be used in a real hearing-aid application.
M. Murakami - One of the best experts on this subject based on the ideXlab platform.
-
Three dimensionality of pulsed second-Sound Waves in He II
Physical Review B, 2006Co-Authors: Peng Zhang, M. MurakamiAbstract:Three dimensionality of three-dimensional (3D) pulsed second-Sound Waves in He II emitted from a finite size heater is experimentally investigated and theoretically studied based on the two-fluid model in this study. The detailed propagation of the 3D pulsed second-Sound Wave is presented and reasonable agreement between the experimental and theoretical results is obtained. Heater size has a big influence on the profile of the 3D second-Sound Wave. The counterflow between the superfluid and normal fluid components becomes inverse in the rarefaction of the 3D second-Sound Wave. The amplitude of rarefaction decreases due to the interaction between second-Sound Wave and quantized vortices, which explains the experimental results about the second-Sound Wave near ${T}_{\ensuremath{\lambda}}$ [L. C. Krysac, Phys. Rev. Lett. 73, 2480 (1994)]. The accumulation of dense quantized vortices in the vicinity of heater surface leads to the formation of a thermal boundary layer, and further increase of heating duration results in the occurrence of boiling phenomena.
Eok Kyun Lee - One of the best experts on this subject based on the ideXlab platform.
-
molecular hydrodynamics vortex formation and Sound Wave propagation
Journal of Chemical Physics, 2018Co-Authors: Kyeong Hwan Han, Changho Kim, Peter Talkner, George Em Karniadakis, Eok Kyun LeeAbstract:In the present study, quantitative feasibility tests of the hydrodynamic description of a two-dimensional fluid at the molecular level are performed, both with respect to length and time scales. Using high-resolution fluid velocity data obtained from extensive molecular dynamics simulations, we computed the transverse and longitudinal components of the velocity field by the Helmholtz decomposition and compared them with those obtained from the linearized Navier–Stokes (LNS) equations with time-dependent transport coefficients. By investigating the vortex dynamics and the Sound Wave propagation in terms of these field components, we confirm the validity of the LNS description for times comparable to or larger than several mean collision times. The LNS description still reproduces the transverse velocity field accurately at smaller times, but it fails to predict characteristic patterns of molecular origin visible in the longitudinal velocity field. Based on these observations, we validate the main assumptio...
-
molecular hydrodynamics vortex formation and Sound Wave propagation
arXiv: Fluid Dynamics, 2017Co-Authors: Kyeong Hwan Han, Changho Kim, Peter Talkner, George Em Karniadakis, Eok Kyun LeeAbstract:In the present study, quantitative feasibility tests of the hydrodynamic description of a two-dimensional fluid at the molecular level are performed, both with respect to length and time scales. Using high-resolution fluid velocity data obtained from extensive molecular dynamics simulations, we computed the transverse and longitudinal components of the velocity field by the Helmholtz decomposition and compared them with those obtained from the linearized Navier-Stokes (LNS) equations with time-dependent transport coefficients. By investigating the vortex dynamics and the Sound Wave propagation in terms of these field components, we confirm the validity of the LNS description for times comparable to or larger than several mean collision times. The LNS description still reproduces the transverse velocity field accurately at smaller times, but it fails to predict characteristic patterns of molecular origin visible in the longitudinal velocity field. Based on these observations, we validate the main assumptions of the mode-coupling approach. The assumption that the velocity autocorrelation function can be expressed in terms of the fluid velocity field and the tagged particle distribution is found to be remarkably accurate even for times comparable to or smaller than the mean collision time. This suggests that the hydrodynamic-mode description remains valid down to the molecular scale.