A Small Angle Scattering Sensor System for the Characterization of Combustion Generated Particulate

One of the critical issues for the US space program is fire safety of the space station and future launch vehicles. A detailed understanding of the scattering signatures of particulate is essential for the development of a false alarm free fire detection system. This paper describes advanced optical instrumentation developed and applied for fire detection. The system is being designed to determine four important physical properties of disperse fractal aggregates and particulates including size distribution, number density, refractive indices, and fractal dimension. Combustion generated particulate are the primary detection target; however, in order to discriminate from other particulate, non-combustion generated particles should also be characterized. The angular scattering signature is measured and analyzed using two photon optical laser scattering. The Rayleigh-Debye-Gans (R-D-G) scattering theory for disperse fractal aggregates is utilized. The system consists of a pulsed laser module, detection module and data acquisition system and software to analyze the signals. The theory and applications are described

Guardat: {Enforcing} Data Policies at the Storage Layer

In today’s data processing systems, both the policies protecting stored data and the mechanisms for their enforcement are spread over many software components and con-figuration files, increasing the risk of policy violation due to bugs, vulnerabilities and misconfigurations. Guardat ad-dresses this problem. Users, developers and administrators specify file protection policies declaratively, concisely and separate from code, and Guardat enforces these policies by mediating I/O in the storage layer. Policy enforcement relies only on the integrity of the Guardat controller and any external policy dependencies. The semantic gap between the storage layer enforcement and per-file policies is bridged using cryptographic attestations from Guardat. We present the de-sign and prototype implementation of Guardat, enforce ex-ample policies in a Web server, and show experimentally that its overhead is low