CSGNet: Neural Shape Parser for Constructive Solid Geometry

We present a neural architecture that takes as input a 2D or 3D shape and outputs a program that generates the shape. The instructions in our program are based on constructive solid geometry principles, i.e., a set of boolean operations on shape primitives defined recursively. Bottom-up techniques for this shape parsing task rely on primitive detection and are inherently slow since the search space over possible primitive combinations is large. In contrast, our model uses a recurrent neural network that parses the input shape in a top-down manner, which is significantly faster and yields a compact and easy-to-interpret sequence of modeling instructions. Our model is also more effective as a shape detector compared to existing state-of-the-art detection techniques. We finally demonstrate that our network can be trained on novel datasets without ground-truth program annotations through policy gradient techniques.Comment: Accepted at CVPR-201

Modifications Of Fluid Flow About Bodies And Surfaces With Synthetic Jet Actuators

The present invention involves a system for altering the aerodynamic shape and/or fluid flow field about a solid body. The preferred embodiment comprises a synthetic jet actuator embedded in a solid body, with the jet orifice built into the body surface. The synthetic jet actuator generates a series of fluid vortices emanating from the orifice so as to entrain fluid external to the actuator chamber and form a synthetic jet stream. A recirculating flow region is formed along the solid body surface about the synthetic jet orifice. As a result the apparent aerodynamic shape of the body is altered. Consequently, if the solid body is placed in a fluid flow field, the entire fluid flow field is altered by the operation of the synthetic jet actuator.Georgia Tech Research Corporatio

3D numerical simulation of Circulating Fluidized Bed: comparison between theoretical results and experimental measurements of hydrodynamic

This work was realized in the frame of the European GAYA project supported by ADEME. This paper presents a description of the hydrodynamic into a CFB according to experimental measurements of gas pressure and solid mass flux. These experimental data are compared to three dimensional numerical simulation with an Eulerian approach. The obtained numerical results show that the applied mathematical models are able to predict the complex gas-solid behavior in the CFB and highlight the large influence of the particle wall boundary condition. Indeed, it is shown that free slip wall boundary condition gives a good prediction a solid mass flux profile in comparison with experimental measurements nevertheless a convex shape. Moreover, the numerical solid hold-up is underestimated compared to the experimental data. On the contrary, a no-slip boundary condition improves the profile shape of solid mass flux but highly overestimates its intensity and the solid hold-up. A compromise appears to be a friction particle-wall boundary condition such as Johnson and Jackson (1) but the model parameters have to be chosen very carefully especially the restitution coefficient

Non-universal equilibrium crystal shape results from sticky steps

The anisotropic surface free energy, Andreev surface free energy, and equilibrium crystal shape (ECS) z=z(x,y) are calculated numerically using a transfer matrix approach with the density matrix renormalization group (DMRG) method. The adopted surface model is a restricted solid-on-solid (RSOS) model with "sticky" steps, i.e., steps with a point-contact type attraction between them (p-RSOS model). By analyzing the results, we obtain a first-order shape transition on the ECS profile around the (111) facet; and on the curved surface near the (001) facet edge, we obtain shape exponents having values different from those of the universal Gruber-Mullins-Pokrovsky-Talapov (GMPT) class. In order to elucidate the origin of the non-universal shape exponents, we calculate the slope dependence of the mean step height of "step droplets" (bound states of steps) using the Monte Carlo method, where p=(dz/dx, dz/dy)$, and represents the thermal averag |p| dependence of , we derive a |p|-expanded expression for the non-universal surface free energy f_{eff}(p), which contains quadratic terms with respect to |p|. The first-order shape transition and the non-universal shape exponents obtained by the DMRG calculations are reproduced thermodynamically from the non-universal surface free energy f_{eff}(p).Comment: 31 pages, 21 figure

Nanoparticle shape and thermal radiation on Marangoni Water, Ethylene Glycol and Engine Oil Based Cu, Al2O3 and SWCNTs

The aim of this paper is to investigate the relationship between particle shape and radiation effects on Marangoni boundary layer flow and heat transfer of water, ethylene glycol and engine oil based Cu, Al2O3 and SWCNTs. There are three types of nanoparticle shapes are considered in this research such as sphere, cylinder and lamina. The governing nonlinear partial differential equations are reduced into a set of nonlinear ordinary differential equations by applying similarity transformation which is solved using shooting technique in conjunction with Newton’s method and Runge Kutta algorithm. Temperature profiles are graphically and tabularly provided for the effects of solid volume fraction parameter, radiation parameter and empirical shape factor. The result shows that solid volume fraction and radiation energy gives a good impact on thermal boundary layer. Sphere nanoparticle shape predicts a better result on heat transfer rather than other nanoparticle shapes

Topology and shape optimization of induced-charge electro-osmotic micropumps

For a dielectric solid surrounded by an electrolyte and positioned inside an externally biased parallel-plate capacitor, we study numerically how the resulting induced-charge electro-osmotic (ICEO) flow depends on the topology and shape of the dielectric solid. In particular, we extend existing conventional electrokinetic models with an artificial design field to describe the transition from the liquid electrolyte to the solid dielectric. Using this design field, we have succeeded in applying the method of topology optimization to find system geometries with non-trivial topologies that maximize the net induced electro-osmotic flow rate through the electrolytic capacitor in the direction parallel to the capacitor plates. Once found, the performance of the topology optimized geometries has been validated by transferring them to conventional electrokinetic models not relying on the artificial design field. Our results show the importance of the topology and shape of the dielectric solid in ICEO systems and point to new designs of ICEO micropumps with significantly improved performance.Comment: 18 pages, latex IOP-style, 7 eps figure