142 research outputs found
Padding Ain't Enough: Assessing the Privacy Guarantees of Encrypted DNS – Web Scans
No full textThis dataset contains the main data set of our FOCI 2020 paper "Padding Ain’t Enough: Assessing the Privacy Guarantees of Encrypted DNS".
https://www.usenix.org/conference/foci20/presentation/bushart
You can find the source code for this project on GitHub: https://github.com/jonasbb/padding-aint-enough
When using this software or our dataset, please cite our FOCI 20 paper.
@inproceedings {PaddingAintEnough,
author = {Jonas Bushart and Christian Rossow},
booktitle = {10th {USENIX} Workshop on Free and Open Communications on the Internet ({FOCI} 20)},
month = aug,
publisher = {{USENIX} Association},
title = {Padding Ain{\textquoteright}t Enough: Assessing the Privacy Guarantees of Encrypted {DNS}},
year = {2020},
Padding Ain't Enough: Assessing the Privacy Guarantees of Encrypted DNS – Subpage-Agnostic Domain Classification Tor Browser
No full textThis dataset contains the second part of the "Subpage-Agnostic Domain Classification" section of our FOCI 2020 paper "Padding Ain’t Enough: Assessing the Privacy Guarantees of Encrypted DNS".
https://www.usenix.org/conference/foci20/presentation/bushart
You can find the source code for this project on GitHub: https://github.com/jonasbb/padding-aint-enough
When using this software or our dataset, please cite our FOCI 20 paper.
@inproceedings {PaddingAintEnough,
author = {Jonas Bushart and Christian Rossow},
booktitle = {10th {USENIX} Workshop on Free and Open Communications on the Internet ({FOCI} 20)},
month = aug,
publisher = {{USENIX} Association},
title = {Padding Ain{\textquoteright}t Enough: Assessing the Privacy Guarantees of Encrypted {DNS}},
year = {2020},
Padding Ain't Enough: Assessing the Privacy Guarantees of Encrypted DNS – Subpage-Agnostic Domain Classification Firefox
No full textThis dataset contains one part for the "Subpage-Agnostic Domain Classification" section of our FOCI 2020 paper "Padding Ain’t Enough: Assessing the Privacy Guarantees of Encrypted DNS".
https://www.usenix.org/conference/foci20/presentation/bushart
You can find the source code for this project on GitHub: https://github.com/jonasbb/padding-aint-enough
When using this software or our dataset, please cite our FOCI 20 paper.
@inproceedings {PaddingAintEnough,
author = {Jonas Bushart and Christian Rossow},
booktitle = {10th {USENIX} Workshop on Free and Open Communications on the Internet ({FOCI} 20)},
month = aug,
publisher = {{USENIX} Association},
title = {Padding Ain{\textquoteright}t Enough: Assessing the Privacy Guarantees of Encrypted {DNS}},
year = {2020},
The role of collective motion in examples of coarsening and self-assembly
No full textThe simplest prescription for building a patterned structure from its constituents is to add particles, one at a time, to an appropriate template. However, self-organizing molecular and colloidal systems in nature can evolve in much more hierarchical ways. Specifically, constituents (or clusters of constituents) may aggregate to form clusters (or clusters of clusters) that serve as building blocks for later stages of assembly. Here we evaluate the character and consequences of such collective motion in a set of prototypical assembly processes. We do so using computer simulations in which a system's capacity for hierarchical dynamics can be controlled systematically. By explicitly allowing or suppressing collective motion, we quantify its effects. We find that coarsening within a two dimensional attractive lattice gas (and an analogous off-lattice model in three dimensions) is naturally dominated by collective motion over a broad range of temperatures and densities. Under such circumstances, cluster mobility inhibits the development of uniform coexisting phases, especially when macroscopic segregation is strongly favored by thermodynamics. By contrast, the assembly of model viral capsids is not frustrated but is instead facilitated by collective moves, which promote the orderly binding of intermediates consisting of several monomers
Script companion to: A note on the modelling of lubrication forces in unresolved simulations
No full textScript companion to:A note on the modelling of lubrication forces in unresolved simulationsTim M.J. Nijssen, Marcel Ottens, Johan T. PaddingPowder Technology, 2022contact: [email protected] (Tim M.J. Nijssen)Tested with: MATLAB R2021b and GNU Octave 6.4.0Delft University of Technology (NL), 09-03-2022</div
Fluidization of elongated particles—Effect of multi-particle correlations for drag, lift, and torque in CFD-DEM
No full textHaving proper correlations for hydrodynamic forces is essential for successful CFD-DEM simulations of a fluidized bed. For spherical particles in a fluidized bed, efficient correlations for predicting the drag force, including the crowding effect caused by surrounding particles, are already available and well tested. However, for elongated particles, next to the drag force, the lift force, and hydrodynamic torque also gain importance. In this work, we apply recently developed multi-particle correlations for drag, lift and torque in CFD-DEM simulations of a fluidized bed with spherocylindrical particles of aspect ratio 4 and compare them to simulations with widely used single-particle correlations for elongated particles. Simulation results are compared with previous magnetic particle tracking experimental results. We show that multi-particle correlations improve the prediction of particle orientation and vertical velocity. We also show the importance of including hydrodynamic torque.Complex Fluid Processin
On the orientational dependence of drag experienced by spheroids
No full textThe flow around different prolate (needle-like) and oblate (disc-like) spheroids is studied using a multi-relaxation-time lattice Boltzmann method. We compute the mean drag coefficient CD,ϕ at different incident angles ϕ for a wide range of Reynolds numbers ( Re ). We show that the sine-squared drag law CD,ϕ=CD,ϕ=0∘+(CD,ϕ=90∘−CD,ϕ=0∘)sin2ϕ holds up to large Reynolds numbers, Re=2000 . Further, we explore the physical origin behind the sine-squared law, and reveal that, surprisingly, this does not occur due to linearity of flow fields. Instead, it occurs due to an interesting pattern of pressure distribution contributing to the drag at higher Re for different incident angles. The present results demonstrate that it is possible to perform just two simulations at ϕ=0∘ and ϕ=90∘ for a given Re and obtain particle-shape-specific CD at arbitrary incident angles. However, the model has limited applicability to flatter oblate spheroids, which do not exhibit the sine-squared interpolation, even for Re=100 , due to stronger wake-induced drag. Regarding lift coefficients, we find that the equivalent theoretical equation can provide a reasonable approximation, even at high Re , for prolate spheroids.Accepted Author ManuscriptIntensified Reaction and Separation System
Coarse-grained simulations of entangled star polyethylene melts
No full textIn this paper, a previous coarse-grain model [J. T. Padding and W. J. Briels, J. Chem. Phys. 117, 925 (2002)]10.1063/1.1481859 to simulate melts of linear polymers has been adapted to simulate polymers with more complex hierarchies. Bond crossings between highly coarse-grained soft particles are prevented by applying an entanglement algorithm. We first test our method on a virtual branch point inside a linear chain to make sure it works effectively when linking two linear arms. Next, we apply our method to study the diffusive and rheological behaviors of a melt of three-armed stars. We find that the diffusive behavior of the three-armed star is very close to that of a linear polymer with the same molecular weight, while its rheological properties are close to those of a linear chain with molecular mass equal to that of the longest linear sub-chain in the star
Drag, lift and torque acting on a two-dimensional non-spherical particle near a wall
No full textGas-solid granular flows with non-spherical particles occur in many engineering applications such as fluidized beds. Such flows are usually contained by solid walls and always some particles move close to a wall. The proximity of a wall considerably affects the flow fields and changes the hydrodynamic forces and torque acting on particles moving near the wall. In this paper, we numerically investigate the drag, lift and torque acting on a non-spherical particle in the vicinity of a planar wall by means of lattice Boltzmann simulations. To gain an exhaustive understanding of the complex hydrodynamics and study the influence of various geometrical and flow parameters, a single 2D elliptical particle is selected as our case study. In the simulations, the effect of particle Reynolds number, distance to the wall, orientation angle and aspect ratio on drag, lift and torque is studied. Our study shows that the presence of a wall causes significant changes in hydrodynamic forces, with increasing or decreasing drag and lift forces, depending on the distance from the wall. Even the direction of lift and torque may change, depending on both the distance from the wall and particle orientation angle. Also, an ellipse with higher AR experiences larger hydrodynamic forces and torque whatever the gap size and orientation angle
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