Evaluation of Corba for use in distributed control systems

The Common Object Request Broker Architecture (CORBA)-based Simulator was a Laboratory Directed Research and Development (LDRD) project that applied simulation techniques to explore critical questions about advanced distributed control system architectures. A three-prong approach comprised of a study of object-oriented distribution tools, computer network modeling, and simulation of key control system scenarios was used in the LDRD project. This input report describes the first of the three approaches Ñ the study of object-oriented distribution tools together with measurements, and predictions of use within the National Ignition Facility (NIF) and some aspects of CORBA which remain to be resolved. For the ICCS, the completeness of suitable functionality, the speed of performance and utilization of machine and network resources, and the developing nature of the commercial CORBA products themselves, presented a certain risk. This LDRD thus evaluated CORBA in general, and a particular implementation, to determine its features, performance, and scaling properties, and to optimize its use within the ICCS. Both UNIX and real-time operating systems were studied

CORBA: a middleware for an heterogeneous cooperative system

Two kinds of heterogeneities interfere with the integration of different information sources, those in systems and those in semantics. They generate different problems and require different solutions. This paper tries to separate them by proposing the usage of a distinct tool for each one (i.e. CORBA and BLOOM respectively), and analizing how they could collaborate. CORBA offers lots of ways to deal with distributed objects and their potential needs, while BLOOM takes care of the semantic heterogeneities. Therefore, it seems promising to handle the system heterogeneities by wrapping the components of the BLOOM execution architecture into CORBA objects.Postprint (published version

An NMR Study of Helium-3 Adsorbed on Hexagonal Boron Nitride

A Pulse-NMR study of helium-3 adsorbed on hexagonal boron-nitride (BN) powder has been performed. Structurally very similar to graphite, the exposed basalplanes present a very smooth, ideal adsorbing surface and lack its undesirable strong anisotropic diamagnetism. The relaxation times T1 and T2 of helium-3 have been measured as a function of coverage, temperature and frequency. A variety of two dimensional phases have been observed including: a fluid, commensurate solid, incommensurate solid plus a separate crystallite edge film. 2D melting in the incommensurate solid and an order-disorder transition in the commensurate solid have been observed. Evidence for a low temperature, low coverage fluid+commensurate solid coexistence which transforms to a single phase at higher temperatures plus a possible domain-wall phase at higher coverages has been identified. Coupled magnetic relaxation between the helium-3 film and substrate boron-11 spins has been noted. Boron-11 relaxation times have been measured against coverage and temperature. Heteronuclear relaxation is particularly important in the commensurate phases where it can dominate homonuclear spin-lattice relaxation, providing a powerful new probe of the low coverage phases. Based on the detailed theory of coupled magnetic dipolar relaxation a model has been developed which quantitatively describes all the important features of the data many of which are unique to the BN/3He system. Presented separately in chapter 8, it concludes the magnetic properties of registered helium 3 spins are dominated by 14N�� 3He cross relaxation processes, mediated by the €14N quadrupole splitting at FQ(14N) and driven by exchange motion in the film. Using a computer for unattended, real-time experimental control has allowed substantial quantities of high quality relaxation data to be taken. Off-line, automated, numerical analysis of raw spin-echo and processed data has been extensively used. Modelling relaxation data with a stretched-exponential function, h(t) = h(0) exp(ta/T1,2) has provided a exceptionally sensitive indicator of physical changes in the film

The design and application of an extensible operating system

Tanenbaum, A.S. [Promotor

Second Annual Conference on Astronomical Data Analysis Software and Systems. Abstracts

Abstracts from the conference are presented. The topics covered include the following: next generation software systems and languages; databases, catalogs, and archives; user interfaces/visualization; real-time data acquisition/scheduling; and IRAF/STSDAS/PROS status reports

Master/worker parallel discrete event simulation

The execution of parallel discrete event simulation across metacomputing infrastructures is examined. A master/worker architecture for parallel discrete event simulation is proposed providing robust executions under a dynamic set of services with system-level support for fault tolerance, semi-automated client-directed load balancing, portability across heterogeneous machines, and the ability to run codes on idle or time-sharing clients without significant interaction by users. Research questions and challenges associated with issues and limitations with the work distribution paradigm, targeted computational domain, performance metrics, and the intended class of applications to be used in this context are analyzed and discussed. A portable web services approach to master/worker parallel discrete event simulation is proposed and evaluated with subsequent optimizations to increase the efficiency of large-scale simulation execution through distributed master service design and intrinsic overhead reduction. New techniques for addressing challenges associated with optimistic parallel discrete event simulation across metacomputing such as rollbacks and message unsending with an inherently different computation paradigm utilizing master services and time windows are proposed and examined. Results indicate that a master/worker approach utilizing loosely coupled resources is a viable means for high throughput parallel discrete event simulation by enhancing existing computational capacity or providing alternate execution capability for less time-critical codes.Ph.D.Committee Chair: Fujimoto, Richard; Committee Member: Bader, David; Committee Member: Perumalla, Kalyan; Committee Member: Riley, George; Committee Member: Vuduc, Richar

Techniques and countermeasures of TCP/IP OS fingerprinting on Linux Systems

Thesis (M.Sc. - Computer)-University of KwaZulu-Natal, Durban, 2007.Port scanning is the first activity an attacker pursues when attempting to compromise a target system on a network. The aim is to gather information that will result in identifying one or more vulnerabilities in that system. For example, network ports that are open can reveal which applications and services are running on the system. How a port responds when probed with data can reveal which protocol the port utilises and can also reveal which implementation of that protocol is being employed. One of the most valuable pieces of information to be gained via scanning and probing techniques is the operating system that is installed on the target. This technique is called operating system fingerprinting. The purpose of this research is to alert computer users of the dangers of port scanning, probing, and operating system fingerprinting by exposing these techniques and advising the users on which preventative countermeasures to take against them. Analysis is performed on the Transmission Control Protocol (TCP), User Datagram Protocol (UDP), Internet Protocol (IPv4 and IPv6), and the Internet Control Message Protocol (ICMPv4 and ICMPv6). All the software used in this project is free and open source. The operating system used for testing is Linux (2.4 and 2.6 kernels). Scanning, probing, and detection techniques are investigated in the context of the Network Mapper and Xprobe2 tools