Vaughn College of Aeronautics and Technology

About: Vaughn College of Aeronautics and Technology is a education organization based out in New York, New York, United States. It is known for research contribution in the topics: Gravitational microlensing & Planetary system. The organization has 727 authors who have published 708 publications receiving 14082 citations. The organization is also known as: College of Aeronautics.

Computation of shock wave structure using a simpler set of generalized hydrodynamic equations based on nonlinear coupled constitutive relations

Abstract: Generalized hydrodynamic equations were originally proposed to describe the rarefied non-equilibrium flows beyond the Navier–Stokes–Fourier (NSF) equations by constructing a non-equilibrium canonical distribution function for the mesoscopic Boltzmann equation. Subsequently, nonlinear coupled constitutive relations (NCCR) were developed under the adiabatic assumption, the Eu’s closure, and Myong’s simplification. NCCR+ was also proposed to include the omitted terms in Myong’s simplification. The goal of this paper is to assess the improvements in the accuracy due to NCCR+ and the influence of the bulk viscosity in one-dimensional steady shock wave structure for monatomic and diatomic gases. In order to solve NCCR+ equations, a coupled solution process based on the time-independent method for non-conserved variables is employed, which is different from the previous uncoupled solution process used for the NCCR equations. Shock structures in argon and nitrogen are calculated up to Mach 50, where the shock profile, inverse shock thickness, asymmetry parameter, and temperature–density separation distance are validated by DSMC and available experimental measurements. The results show that NCCR+ could not provide much improvement in accuracy compared to NCCR but adds to the computational cost, suggesting that Myong’s simplification used in NCCR is satisfactory. Both NCCR and NCCR+ perform better than NSF in computing the one-dimensional shock wave structure at high Mach numbers. It is also shown that the bulk viscosity has significant influence on the accuracy of prediction of the shock wave structure in a diatomic gas using both NSF and NCCR. Stokes’ hypothesis in conventional NSF is valid only for flows in a monatomic gas and for very low Mach number flows in a diatomic gas. Additionally, it is also found that the viscosity exponent s = 0.81 in variable-hard-sphere model provides a good fit with the experimental data for shock wave in argon using NCCR.

Reinforcement Learning for Emotional Text-to-Speech Synthesis with Improved Emotion Discriminability

Abstract: Emotional text-to-speech synthesis (ETTS) has seen much progress in recent years. However, the generated voice is often not perceptually identifiable by its intended emotion category. To address this problem, we propose a new interactive training paradigm for ETTS, denoted as i-ETTS, which seeks to directly improve the emotion discriminability by interacting with a speech emotion recognition (SER) model. Moreover, we formulate an iterative training strategy with reinforcement learning to ensure the quality of i-ETTS optimization. Experimental results demonstrate that the proposed i-ETTS outperforms the state-of-the-art baselines by rendering speech with more accurate emotion style. To our best knowledge, this is the first study of reinforcement learning in emotional text-to-speech synthesis.

Non-linear Flight Dynamics at High Angles of Attack

Abstract: The methods of non-linear dynamics are applied to the longitudinal motion of a vectored thrust aircraft, in particular the behaviour at high angles-of-attack. The model contains analytic non-linear aerodynamic coefficients based on Nasa windtunnel tests on the F-18 high alpha research vehicle (Harv). The equilibrium surfaces are plotted against thrust magnitude and thrust deflection and are used to explain the behaviour. When the aircraft is forced with small thrust deflections whilst in poststall equilibrium, chaotic motion is observed at certain frequencies. At other frequencies, several limiting states coexist, e.g. a chaotic attractor and a limit cycle, or two limit cycles. The steady state behaviour then depends on the initial conditions

3-D particle image velocimetry of the flow field around a sphere sedimenting near a wall: Part 2. Effects of distance from the wall

Abstract: Through the use of stereoscopic 3-D particle image velocimetry (3-D PIV), the flow field surrounding a sphere sedimenting at a distance of one, two and three ball diameters from the wall is measured. A Newtonian (constant shear viscosity, inelastic) fluid, a Boger (constant shear viscosity, elastic) fluid and a shear-thinning (variable shear viscosity, elastic) fluid are used to study the effects of shear-thinning and elasticity. There are significant differences in the flow fields that can be observed for the different types of fluids and the different distances from the wall from which the sphere is dropped. We find that the structure of the flow field and the motion perpendicular to the wall are dependent on the distance from the wall at which the sphere sediments.