Institute for Systems Research
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Item Automated Network Fault Management(1997) Baras, John S.; Ball, Michael O.; Gupta, Sonjai K.; Viswanathan, P.; Shah, P.; ISR; CSHCNFuture military communication networks will have a mixture of backbone terrestrial, satellite and wireless terrestrial networks. The speeds of these networks vary and they are very heterogeneous. As networks become faster, it is not enough to do reactive fault management. Our approach combines proactive and reactive fault management . Proactive fault management is implemented by dynamic and adaptive routing. Reactive fault management is implemented by a combination of a neural network and an expert system. The system has been developed for the X.25 protocol. Several fault scenarios were modeled and included in the study: reduced switch capacity, increased packet generation rate of a certain application, disabled switch in the X.25 cloud, disabled links. We also modeled occurrence of alarms including severity of the problem, location of the event and a threshold. To detect and identify faults we use both numerical data associated with the performance objects (attributes) in the MIB as well as SNMP traps (alarms). Simulation experiments have been performed in order to understand the convergence of the algorithms, the training of the neural networks involved and the G2/NeurOn-Line software environment and MIB design.Item The Acts Experiments program at the Center for Satellite and Hybrid Communication Networks(1997) Friedman, Daniel E.; Gupta, Sonjai K.; Zhang, C.; Ephremides, Anthony; ISR; CSHCNThis paper describes experiments conducted over ACTS and the associated T1~VSAT terminal. The experiments were motivated by the commercial potential of low-cost receive-only satellite terminals that can operate in a hybrid network environment, and by the desire to demonstrate frame relay technology over satellite networks. The first experiment tested highly adaptive methods of satellite bandwidth allocation in an integrated voice- data service environment. The second involved comparison of FEC and ARQ methods of error control for satellite communication with emphasis on the advantage that a hybrid architecture provides, especially in the case of multicasts. Finally, the third experiment demonstrated hybrid access to databases through the use of Mosaic and compared the performance of internetworking protocols for interconnecting LANs via satellite. A custom unit termed Frame Relay Access Switch (FRACS) was developed by COMSAT Laboratories for these experiments; the preparation and conduct of these experiments involved a total of twenty people from the University of Maryland, the University of Colorado, and COMSAT Laboratories, from late 1992 through 1995.Item Experiments in Hybrid Networking with the Advanced Communications Technology Satellite(1996) Friedman, Daniel E.; Gupta, Sonjai K.; Zhang, C.; Ephremides, Anthony; ISR; CSHCNThis paper describes experiments conducted over ACTS that were motivated by the commercial potential of low-cost receive-only satellite terminals operating in a hybrid network environment. The first experiment tested highly adaptive methods of satellite bandwidth allocation in an integrated voice-data service environment. The second involved comparison of FEC and ARQ methods of error control for satellite communication with emphasis on the advantage that a hybrid architecture provides especially in the case of multicasts. Finally, the third experiment demonstrated hybrid access to databases through the use of Mosaic and compared the performance of internetworking protocols for interconnecting LANs via satellite.Item Review of the VSAT ACTS Experiments at the Center for Satellite & Hybrid Communication Networks(1996) Friedman, Daniel E.; Gupta, Sonjai K.; Zhang, C.; Ephremides, Anthony; ISR; CSHCNThis paper describes experiments conducted over ACTS and the associated TI VSAT terminal. The experiments were motivated by the commercial potential of low-cost receive-only satellite terminals that can operate in a hybrid network environment, and by the desire to demonstrate frame relay technology over satellite networks. A custom unit termed Frame Relay Access Switch (FRACS) was developed by COMSAT Laboratories for these experiments; the preparation and conduct of these experiments involved a total of twenty people from the University of Maryland, the University of Colorado, and COMSAT Laboratories, from late 1992 through 1995.Item Design for Manufacture by Multi-Enterprise Partnerships(1994) Nau, D.; Ball, Michael O.; Gupta, Sonjai K.; Minis, Ioannis; Zhang, G.; ISRRecent world-wide political and financial events have intensified the need to renew the competitiveness of the US manufacturing industry. The means for enabling competitiveness include fast response to the market needs for new designs and re-designs, and the ability to manufacture products at the right quality and at competitive costs. To pursue market and technology opportunities effectively, US commercial and defense industries will be relying increasingly on multi-enterprise partnerships [12]. Vertical partnering combines the strengths of multiple firms in product design, manufacture, after sales support and customer service, in order to launch superior products in the global market.To support effective partnering, new approaches will be needed for integrating the activities of design, planning, and production. Furthermore, it is important to address both the fundamental modeling of design, process planning, and production planning in ways that account for the capabilities of potential manufacturing partners, and the development of optimization procedures to address the underlying decision problems. This paper elaborates on these issues and discusses approaches for addressing them.
Item Optimization of Injection Molding Operational Conditions(1987) Pandelidis, I.; Smith, T.; Azarm, Shapour; Gupta, Sonjai K.; ISRA major goal of the injection molding process is to produce complex parts to a relatively high degree of accuracy. To do this, one must be able to control the warpage that often occurs in injection molded products. We have developed a methodology to minimize product deformation. Pressure and temperature distributions obtained from flow simulation software are used as an indirect measure of the quality of the molded product. Optimization theory is then used to determine the optimal molding conditions to minimize product deformation.