Formation of asymmetric separated flow past slender bodies of revolution at large angles of attack

The paper examines the problem of determining stationary positions of pairs of vortices of unequal intensity in the flow behind a cylinder modeling the axisymmetric separated flow past a slender body at large angles of attack. The possible asymmetric stationary positions of two vortices are calculated, and their stability with respect to small perturbations is determined. Bifurcations of the flow field with changes in vortex intensity are analyzed

General Cause of Sheath Instability Identified for Low Collisionality Plasma in Devices with Secondary Electron Emission

A condition for sheath instability due to secondary electron emission (SEE) is derived for low collisionality plasmas. When the SEE coefficient of the electrons bordering the depleted loss cone in energy space exceeds unity, the sheath potential is unstable to a negative perturbation. This result explains three different instability phenomena observed in Hall thruster simulations including a newly found state with spontaneous ~20MHz oscillations. When instabilities occur, the SEE propagating between the walls becomes the dominant contribution to the particle flux, energy loss and axial transport

Aerodynamic Modeling for Post-Stall Flight Simulation of a Transport Airplane

The file attached to this record is the author's final peer reviewed version.open access articleThe principles of aerodynamic modeling in the extended flight envelope, which is characterized by the development of separated flow, are outlined and illustrated for a generic transport airplane. The importance of different test techniques for generating wind tunnel data and the procedure for blending the obtained experimental data for aerodynamic modeling are discussed. Complementary use of computational fluid dynamics simulations reveals a substantial effect of the Reynolds number on the intensity of aerodynamic autorotation, which is later reflected in the aerodynamic model. Validation criteria for an extended envelope aerodynamic model are discussed, and the important role of professional test pilots with post-stall flying experience in tuning aerodynamic model parameters is emphasized. The paper presents an approach to aerodynamic modeling that was implemented in the project Simulation of Upset Recovery inAviation (2009–2012), funded by the EuropeanUnion under the seventh framework programme. The developed post-stall aerodynamic model of a generic airliner configuration for a wide range of angles of attack, sideslip, and angular rate was successfully validated by a number of professional test pilots on hexapod and centrifuge-based flight simulator platforms

DruGAN: An Advanced Generative Adversarial Autoencoder Model for de Novo Generation of New Molecules with Desired Molecular Properties in Silico

© 2017 American Chemical Society. Deep generative adversarial networks (GANs) are the emerging technology in drug discovery and biomarker development. In our recent work, we demonstrated a proof-of-concept of implementing deep generative adversarial autoencoder (AAE) to identify new molecular fingerprints with predefined anticancer properties. Another popular generative model is the variational autoencoder (VAE), which is based on deep neural architectures. In this work, we developed an advanced AAE model for molecular feature extraction problems, and demonstrated its advantages compared to VAE in terms of (a) adjustability in generating molecular fingerprints; (b) capacity of processing very large molecular data sets; and (c) efficiency in unsupervised pretraining for regression model. Our results suggest that the proposed AAE model significantly enhances the capacity and efficiency of development of the new molecules with specific anticancer properties using the deep generative models

Absence of Debye Sheaths Due to Secondary Electron Emission

A bounded plasma where the electrons impacting the walls produce more than one secondary on average is studied via particle-in-cell simulation. It is found that no classical Debye sheath or space-charge limited sheath exists. Ions are not drawn to the walls and electrons are not repelled. Hence the plasma electrons travel unobstructed to the walls, causing extreme particle and energy fluxes. Each wall has a positive charge, forming a small potential barrier or "inverse sheath" that pulls some secondaries back to the wall to maintain the zero current condition.Comment: 4 pages, 3 Figure

Reconstructing CMEs with Coordinated Imaging and In Situ Observations: Global Structure, Kinematics, and Implications for Space Weather Forecasting

See the pdf for detailsComment: 45 pages, 16 figures, ApJ, in pres

The cornucopia of meaningful leads: Applying deep adversarial autoencoders for new molecule development in oncology

Recent advances in deep learning and specifically in generative adversarial networks have demonstrated surprising results in generating new images and videos upon request even using natural language as input. In this paper we present the first application of generative adversarial autoencoders (AAE) for generating novel molecular fingerprints with a defined set of parameters. We developed a 7-layer AAE architecture with the latent middle layer serving as a discriminator. As an input and output the AAE uses a vector of binary fingerprints and concentration of the molecule. In the latent layer we also introduced a neuron responsible for growth inhibition percentage, which when negative indicates the reduction in the number of tumor cells after the treatment. To train the AAE we used the NCI-60 cell line assay data for 6252 compounds profiled on MCF-7 cell line. The output of the AAE was used to screen 72 million compounds in PubChem and select candidate molecules with potential anticancer properties. This approach is a proof of concept of an artificially-intelligent drug discovery engine, where AAEs are used to generate new molecular fingerprints with the desired molecular properties

Interplay of unsteady aerodynamics and flight dynamics of transport aircraft in icing conditions

Airframe icing causes significant degradation of aerodynamic characteristics and influences the flight safety. Wind tunnel study of longitudinal steady and unsteady aerodynamic characteristics of a transport aircraft in icing conditions is carried out in order to develop mathematical model of aerodynamics in the extended flight envelope. The wind tunnel results are validated through flight tests conducted for the real aircraft. Large, glaze-horn ice shapes, corresponding to holding flight phase, are considered. Influence of an ice protection system as well as its failure is examined. Effect of icing on the unsteady aerodynamics characteristics is studied not only through wind tunnel tests but also via analysis of subsequent influence on the flight dynamics of the aircraft. The conducted study shows that the ice shapes of the holding phase leads to reduced stall angle of attack (AoA), maximum lift, and longitudinal damping. Flight dynamics analysis demonstrates that dangerous aircraft behaviour in the form of high AoA departure and limit cycle oscillations (LCO) can be observed at smaller elevator deflections for the iced aircraft. Taking into account icing influence on the unsteady aerodynamics in the flight dynamics simulations revealed degradation of the dynamic response and deterioration of phase portraits of the system. Even for small AoA and elevator deflection the aircraft might be trapped into the basin of attraction of high-AoA LCO. In addition, incorporating icing effects in unsteady aerodynamics manifest larger amplitude of LCO