320,749 research outputs found
Reinforcement learning for efficient network penetration testing
Penetration testing (also known as pentesting or PT) is a common practice for actively assessing the defenses of a computer network by planning and executing all possible attacks to discover and exploit existing vulnerabilities. Current penetration testing methods are increasingly becoming non-standard, composite and resource-consuming despite the use of evolving tools. In this paper, we propose and evaluate an AI-based pentesting system which makes use of machine learning techniques, namely reinforcement learning (RL) to learn and reproduce average and complex pentesting activities. The proposed system is named Intelligent Automated Penetration Testing System (IAPTS) consisting of a module that integrates with industrial PT frameworks to enable them to capture information, learn from experience, and reproduce tests in future similar testing cases. IAPTS aims to save human resources while producing much-enhanced results in terms of time consumption, reliability and frequency of testing. IAPTS takes the approach of modeling PT environments and tasks as a partially observed Markov decision process (POMDP) problem which is solved by POMDP-solver. Although the scope of this paper is limited to network infrastructures PT planning and not the entire practice, the obtained results support the hypothesis that RL can enhance PT beyond the capabilities of any human PT expert in terms of time consumed, covered attacking vectors, accuracy and reliability of the outputs. In addition, this work tackles the complex problem of expertise capturing and re-use by allowing the IAPTS learning module to store and re-use PT policies in the same way that a human PT expert would learn but in a more efficient way
Bianchi type I universes with dilaton and magnetic fields
We consider the dynamics of a Bianchi type I spacetime in the presence of
dilaton and magnetic fields. The general solution of the Einstein-Maxwell
dilaton field equations can be obtained in an exact parametric form. Depending
on the numerical values of the parameters of the model there are three distinct
classes of solutions. The time evolution of the mean anisotropy, shear and
deceleration parameter is considered in detail and it is shown that a
magnetic-dilaton anisotropic Bianchi type I geometry does not isotropize, the
initial anisotropy being present in the universe for all times.Comment: 10 pages, 4 figure
On Optimum End-to-End Distortion in MIMO Systems
This paper presents the joint impact of the numbers of antennas,
source-to-channel bandwidth ratio and spatial correlation on the optimum
expected end-to-end distortion in an outage-free MIMO system. In particular,
based on an analytical expression valid for any SNR, a closed-form expression
of the optimum asymptotic expected end-to-end distortion valid for high SNR is
derived. It is comprised of the optimum distortion exponent and the
multiplicative optimum distortion factor. Demonstrated by the simulation
results, the analysis on the joint impact of the optimum distortion exponent
and the optimum distortion factor explains the behavior of the optimum expected
end-to-end distortion varying with the numbers of antennas, source-to-channel
bandwidth ratio and spatial correlation. It is also proved that as the
correlation tends to zero, the optimum asymptotic expected end-to-end
distortion in the setting of correlated channel approaches that in the setting
of uncorrelated channel. The results in this paper could be performance
objectives for analog-source transmission systems. To some extend, they are
instructive for system design.Comment: 35 pages, 10 figures, submitted to EURASIP Journal on Wireless
Communications and Networkin
Non-analyticity of the groud state energy of the Hamiltonian for Hydrogen atom in non-relativistic QED
We derive the ground state energy up to the fourth order in the fine
structure constant for the translation invariant Pauli-Fierz
Hamiltonian for a spinless electron coupled to the quantized radiation field.
As a consequence, we obtain the non-analyticity of the ground state energy of
the Pauli-Fierz operator for a single particle in the Coulomb field of a
nucleus
Simple models of the hydrofracture process
Hydrofracturing to recover natural gas and oil relies on the creation of a fracture network with pressurized water. We analyze the creation of the network in two ways. First, we assemble a collection of analytical estimates for pressure-driven crack motion in simple geometries, including crack speed as a function of length, energy dissipated by fluid viscosity and used to break rock, and the conditions under which a second crack will initiate while a first is running. We develop a pseudo-three-dimensional numerical model that couples fluid motion with solid mechanics and can generate branching crack structures not specified in advance. One of our main conclusions is that the typical spacing between fractures must be on the order of a meter, and this conclusion arises in two separate ways. First, it arises from analysis of gas production rates, given the diffusion constants for gas in the rock. Second, it arises from the number of fractures that should be generated given the scale of the affected region and the amounts of water pumped into the rock.Shell UTNational Science FoundationPhysic
Low frequency electrical noise across contacts between a normal conductor and superconducting bulk YBa2Cu3O7
Virtually every device that makes use of the new ceramic superconductors will need normal conductor to supercondutor contacts. The current-voltage and electrical noise characteristics of these contacts could be become important design considerations. I-V and low frequency electrical noise measurements are presented on contacts between a normal conductor and superconducting polycrystalline YBa2Cu3O7. The contacts were formed by first sputtering gold palladium pads onto the surface of the bulk superconductor and then using silver epoxy to attach a wire(s) to each pad. Voltage across the contacts was found for small current densities. The voltage spectral density, S sub v(f), a quanity often used to characterize electrical noise, very closely followed an empirical relationship given by, S sub v(f) = C(VR)sq/f, where V is the DC voltage across the contact, R is the contact resistance, F is frequency, and C is a contant found to be 2 x 10(exp -10)/Omega sq at 78 K. This relationship was found to be independent of contact area, contact geometry, sample fabrication technique, and sample density
Low frequency electrical noise across contacts between a normal conductor and superconducting bulk YBa2Cu3O7
Virtually every device that makes use of the new ceramic superconductors will need normal conductor to superconductor contacts. The current-voltage and electrical noise characteristics of these contacts could become important design considerations. I-V and low frequency electrical noise measurements are presented on contacts between a normal conductor and superconducting polycrystalline YBa2Cu3O7. The contacts were formed by first sputtering gold palladium pads onto the surface of the bulk superconductor and then using silver epoxy to attach a wire(s) to each pad. Voltage across the contacts was found for small current densities. The voltage spectral density, S sub v(f), a quantity often used to characterize electrical noise, very closely followed an empirical relationship given by S sub v(f) = C(VR)sq/f, where V is the DC voltage across the contact, R is the contact resistance, F is frequency, and C is a contant found to be 2 x 10(exp -10)/Omega sq at 78 K. This relationship was found to be independent of contact area, contact geometry, sample fabrication technique, and sample density
Enhanced collimated GeV monoenergetic ion acceleration from a shaped foil target irradiated by a circularly polarized laser pulse
Using multi-dimensional particle-in-cell (PIC) simulations we study ion
acceleration from a foil irradiated by a circularly polarized laser pulse at
1022W/cm^2 intensity. When the foil is shaped initially in the transverse
direction to match the laser intensity profile, the center part of the target
can be uniformly accelerated for a longer time compared to a usual flat target.
Target deformation and undesirable plasma heating are effectively suppressed.
The final energy spectrum of the accelerated ion beam is improved dramatically.
Collimated GeV quasi-mono-energetic ion beams carrying as much as 18% of the
laser energy are observed in multi-dimensional simulations. Radiation damping
effects are also checked in the simulations.Comment: 4 pages, 4 figure
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