A secure, constraint-aware role-based access control interoperation framework

With the growing needs for and the benefits of sharing resources and information among different organizations, an interoperation framework that automatically integrates policies to facilitate such cross-domain sharing in a secure way is becoming increasingly important. To avoid security breaches, such policies must enforce the policy constraints of the individual domains. Such constraints may include temporal constraints that limit the times when the users can access the resources, and separation of duty (SoD) constraints. Existing interoperation solutions do not address such cross-domain temporal access control and SoDs requirements. In this paper, we propose a role-based framework to facilitate secure interoperation among multiple domains by ensuring the enforcement of temporal and SoD constraints of individual domains. To support interoperation, we do not modify the internal policies, as most of the current approaches do. We present experimental results to demonstrate our proposed framework is effective and easily realizable. © 2011 IEEE

Finite element structural model of a large, thin, completely free, flat plate

A finite element structural model of a 30.48 m x 30.48 m x 2.54 mm completely free aluminum plate is described and modal frequencies and mode shape data for the first 44 modes are presented. An explanation of the procedure for using the data is also presented. The model should prove useful for the investigation of controller design approaches for large flexible space structures

Mappings preserving locations of movable poles: a new extension of the truncation method to ordinary differential equations

The truncation method is a collective name for techniques that arise from truncating a Laurent series expansion (with leading term) of generic solutions of nonlinear partial differential equations (PDEs). Despite its utility in finding Backlund transformations and other remarkable properties of integrable PDEs, it has not been generally extended to ordinary differential equations (ODEs). Here we give a new general method that provides such an extension and show how to apply it to the classical nonlinear ODEs called the Painleve equations. Our main new idea is to consider mappings that preserve the locations of a natural subset of the movable poles admitted by the equation. In this way we are able to recover all known fundamental Backlund transformations for the equations considered. We are also able to derive Backlund transformations onto other ODEs in the Painleve classification.Comment: To appear in Nonlinearity (22 pages

Sub-femtosecond electron bunches created by direct laser acceleration in a laser wakefield accelerator with ionization injection

In this work, we will show through three-dimensional particle-in-cell simulations that direct laser acceleration in laser a wakefield accelerator can generate sub-femtosecond electron bunches. Two simulations were done with two laser pulse durations, such that the shortest laser pulse occupies only a fraction of the first bubble, whereas the longer pulse fills the entire first bubble. In the latter case, as the trapped electrons moved forward and interacted with the high intensity region of the laser pulse, micro-bunching occurred naturally, producing 0.5 fs electron bunches. This is not observed in the short pulse simulation.Comment: AAC 201

On the genericity of spacetime singularities

We consider here the genericity aspects of spacetime singularities that occur in cosmology and in gravitational collapse. The singularity theorems (that predict the occurrence of singularities in general relativity) allow the singularities of gravitational collapse to be either visible to external observers or covered by an event horizon of gravity. It is shown that the visible singularities that develop as final states of spherical collapse are generic. Some consequences of this fact are discussed.Comment: 19 pages, To be published in the Raychaudhuri Volume, eds. Naresh Dadhich, Pankaj Joshi and Probir Ro

Analysis and simulation of a magnetic bearing suspension system for a laboratory model annular momentum control device

A linear analysis and the results of a nonlinear simulation of a magnetic bearing suspension system which uses permanent magnet flux biasing are presented. The magnetic bearing suspension is part of a 4068 N-m-s (3000 lb-ft-sec) laboratory model annular momentum control device (AMCD). The simulation includes rigid body rim dynamics, linear and nonlinear axial actuators, linear radial actuators, axial and radial rim warp, and power supply and power driver current limits

QQˉQ\bar Q (Q∈{b,c}Q\in \{b, c\}) spectroscopy using Cornell potential

The mass spectra and decay properties of heavy quarkonia are computed in nonrelativistic quark-antiquark Cornell potential model. We have employed the numerical solution of Schr\"odinger equation to obtain their mass spectra using only four parameters namely quark mass ($m_c$, $m_b$) and confinement strength ($A_{c\bar c}$, $A_{b\bar b}$). The spin hyperfine, spin-orbit and tensor components of the one gluon exchange interaction are computed perturbatively to determine the mass spectra of excited $S$, $P$, $D$ and $F$ states. Digamma, digluon and dilepton decays of these mesons are computed using the model parameters and numerical wave functions. The predicted spectroscopy and decay properties for quarkonia are found to be consistent with available experimental observations and results from other theoretical models. We also compute mass spectra and life time of the $B_c$ meson without additional parameters. The computed electromagnetic transition widths of heavy quarkonia and $B_c$ mesons are in tune with available experimental data and other theoretical approaches