Date: December 5, 2003  download  
 Speaker: Boleslaw Mikolajczak
 Title: Study of Structural and Behavioral Petri net Properties with respect to Operations of Abstraction and Refinement and their Role in Development of Concurrent Systems
 Abstract:

We discuss a role of Petri net morphisms in conceptual modeling of concurrent
computing systems with several levels of abstractions and/or refinements. We study
structural and behavioral properties of concurrent systems that are modeled by Petri nets.
These properties, particularly liveness, boundedness and safety, are important in
assuring correctness of design for complex concurrent systems. Examples
are also provided to illustrate significance and applications of Petri net morphisms
in development of concurrent systems.

Date: September 26, 2003  
 Speaker: Dr. Ramprasad Bala
 Title: Visualization, Detection and Tracking of Mesoscale Oceanic Features in an Ocean Circulation Model
 Abstract:

The process of identifying and tracking oceanic eddies over space and time, and their relationship to the net poleward heat transport are of fundamental importance for Climate studies. The visualization of heat flux in the numeric motivates the detection and tracking of mesoscale features to understand their role in poleward heat transport. The numeric model MICOM for the North Atlantic is used. Methods developed to automatically detect, locate and track mesoscale eddies spatially and temporally are presented. Using structuring elements based on velocity information eddy centers are detected and streamline plots used to eliminate false positives. Additional visualization, based on the detected eddy centers provides information about eddies temporally and spatially.

Date: April 18,2003  -  download
 Speaker: Boleslaw Mikolajczak
 Title: Integrating Object-Oriented Design and High-level Petri Nets in Software Development of Concurrent Systems
 Abstract:

A method of designing concurrent systems, based on integration of Object-Oriented Design and High-level Petri nets, is presented. Object-Oriented technology has well established design techniques but lacks analysis, verification and validation methods of the designed system and formal specification of concurrency and conflict. All these features are extremely important from practical point of view, especially in terms of rapid prototyping of parallel and distributed systems. On the other hand, Petri net is a well defined formalism of parallel and distributed systems wrt modeling, verification, validation (including conflict resolution and resource allocation) that lacks clear and effective design techniques. The method takes advantages of both Object-Oriented Design and High-level Petri nets by using Object-Oriented methodology on the design stage and High-level Petri nets on the analysis, verification and validation stages. Petri net modeling of classes with inheritance and solution to inheritance anomaly are central to achieve executable specification of the OO system. The method utilizes specialized CASE software tools that effectively support modeling, verification, and validation of high-level Petri nets, such as Design/CPN and SYROCO.
 

Date: April 04,2003  -  download
 Speaker: Xiaqin Shelley Zhang
 Title: Integrative Negotiation In Complex Organizational Agent Systems
 Abstract:

Agents are autonomous, intelligent, computational entities that pursue goals or carry out tasks in order to meet their designed objectives. A multi-agent system (MAS) consists of a group of agents that can take specific roles within organizational structures. Computers are no longer stand-alone devices; they are tightly connected to each other and their users. Researchers have applied the technology of autonomous agents and multi-agent systems in many applications, such as airport management, traffic control and transport logistics, and distributed electricity management. These applications require a number of agents to work together, given the complexity of these problems, also the distribution of the data and resources. Organization structures are necessary for large-scale agent-based systems to operate efficiently. Meanwhile, organizational structures in a large-scale agent society are not static. Agents from different, separate organizational entities will come together to dynamically form virtual organizations for solving specific problems that are relevant to each of their organizational entities. This presentation addresses the problem of negotiation in a complex organizational context and tries to bridge the gap between self-interested negotiation and cooperative negotiation. An integrative negotiation mechanism is introduced, which enables agents to choose any attitude from the extremes of self-interested and cooperative to those that are partially self-interested and partially cooperative. This mechanism is based on and also extends the motivational qualities (MQ) framework for evaluating which task an agent should pursue at each time point. Experimental work verifies this mechanism and explores the question whether it always improves the social welfare to have an agent be completely cooperative.

 Date: March 28,2003  -  download
 Speaker:Emad Aboelela
 Title: Quality-of-Service Provision For Multimedia Networking
 Abstract:

For many years, packet-switched networks have offered the promise of supporting multimedia applications, that is, those that combine audio, video, and data. Audio and video applications are examples of real-time applications. The best-effort model, in which the network tries to deliver your data but makes no promises and leaves the "cleanup operation" to the edges, is not sufficient for real-time applications. What we need is a new service model; one in which applications that need better assurances can request such service from the network. The network may then respond by providing an assurance that it will do better or perhaps by saying that it cannot promise anything better at the moment. A network that can provide different levels of service is often said to support Quality of Service (QoS). In this seminar different developed approaches to provide a range of QoS will be illustrated. An optimal routing model will be presented. The routing model is formulated as a fuzzy optimization model, that takes into consideration bandwidth allocation to avoid link saturation and hence the possibility of congestion. A management-dependent margin is used for bandwidth allocation. A path is considered attractive to incoming calls as long as its available bandwidth is around that margin. This greatly reduces the fragmentation problem of the load-balancing techniques and avoids packing some paths with heavy loads (with the benefit of decreasing the likelihood of congestion)