We present a logic for stating properties such as, "after a request for service there is at least a 98% probability that the service will be carried out within 2 seconds". The logic extends the temporal logic CTL by Emerson, Clarke and Sistla with time and probabilities. Formulas are interpreted over discrete time Markov chains. We give algorithms for checking that a given Markov chain satisfies a formula in the logic. The algorithms require a polynomial number of arithmetic operations, in size of both the formula and This research report is a revised and extended version of a paper that has appeared under the title "A Framework for Reasoning about Time and Reliability" in the Proceeding of the 10 th IEEE Real-time Systems Symposium, Santa Monica CA, December 1989. This work was partially supported by the Swedish Board for Technical Development (STU) as part of Esprit BRA Project SPEC, and by the Swedish Telecommunication Administration. the Markov chain. A simple example is inc...

The design and analysis of routing protocols is an important issue in dynamic networks such as packet radio and ad-hoc wireless networks. Most conventional protocols exhibit their least desirable behavior for highly dynamic interconnection topologies. We propose a new methodology for routing and topology information maintenance in dynamic networks. The basic idea behind the protocol is to divide the graph into a number of overlapping clusters. A change in the network topology corresponds to a change in cluster membership. We present algorithms for creation of clusters, as well as algorithms to maintain them in the presence of various network events. Compared to existing and conventional routing protocols, the proposed cluster-based approach incurs lower overhead during topology updates and also has quicker reconvergence. The effectiveness of this approach also lies in the fact that existing routing protocols can be directly applied to the network -- replacing the nodes by clusters. 1 ...

Pajek is a program, for Windows, for analysis and visualization of large networks having some ten or houndred of thousands of vertices. In Slovenian language pajek means spider.

Coloured Petri nets (CP-nets or CPNs) provide a framework for the design, specification, validation, and verification of systems. CP-nets have a wide range of application areas and many CPN projects have been carried out in industry, e.g., in the areas of communication protocols, operating systems, hardware designs, embedded systems, software system designs, and business process re-engineering. Design/CPN is a graphical computer tool supporting the practical use of CP-nets. The tool supports the construction, simulation, and functional and performance analysis of CPN models. The tool is used by more than four hundred organisations in forty different countries -- including one hundred commercial companies. It is available free of charge, also for commercial use. This paper provides a comprehensive road map to the practical use of CP-nets and the Design/CPN tool. We give an informal introduction to the basic concepts and ideas underlying CP-nets. The key components and facilities of the Design/CPN tool are presented and their use illustrated. The paper is self-contained and does not assume any prior knowledge of Petri nets and CP-nets nor any experience with the Design/CPN tool.

Memory-System Design Considerations for Dynamically-Scheduled Microprocessors Keith Istvan Farkas Doctor of Philosophy Graduate Department of Electrical and Computer Engineering University of Toronto 1997 Dynamically-scheduled processors challenge hardware and software architects to develop designs that balance hardware complexity and compiler technology against performance targets. This dissertation presents a first thorough look at some of the issues introduced by this hardware complexity. The focus of the investigation of these issues is the register file and the other components of the data memory system. These components are: the lockup-free data cache, the stream buffers, and the interface to the lower levels of the memory system. The investigation is based on software models. These models incorporate the features of a dynamically-scheduled processor that affect the design of the data-memory components. The models represent a balance between accuracy and generality, and ar...

In this article we examine the problem of dynamic self-reconfiguration of a class of modular robotic systems referred to as metumorpkic systems. A metamorphic robotic system is a collection of mechatronic modules, each of which has the ability to connect, disconnect, and climb over adjacent modules. A change in the macroscopic morphology results from the locomotion of each module over its neighbors. Metamorphic systems can therefore be viewed as a large swarm of physically connected robotic modules that collectively act as a single entity. What distinguishes metamorphic systems from other reconfigurable robots is that they possess all of the following properties: (1) a large number of homogeneous modules; (2) a geometry such that modules fit within a regular lattice; (3) self-reconfigurability without outside help; (4) physical constraints which ensure contact between modules. In this article, the kinematic constraints governing metamorphic robot self-reconfiguration are addressed, and lower and upper bounds are established for the minimal number of moves needed to change such systems from any initial to any final specified configuration. These bounds are functions of initial and final configuration geometry and can be computed very quickly, while it appears that solving for the precise number of minimal moves cannot be done in polynomial time. It is then shown how the bounds developed here are useful in evaluating the performance of heuristic motion planning/reconfiguration algorithms for metamorphic systems. 0 2996 Iohn Wiky 6 Sons, rnc. *To whom all correspondence should be addressed

We consider the problem of representing trees (undirected, cycle-free graphs) in Genetic Algorithms. This problem arises, among other places, in the solution of network design problems. After comparing several commonly used representations based on their usefulness in genetic algorithms, we describe a new representation and show it to be superior in almost all respects to the others. In particular, we show that our representation covers the entire space of solutions, produces only viable offspring, and possesses locality, all necessary features for the effective use of a genetic algorithm. We also show that the representation will reliably produce very good, if not optimal, solutions even when the problem definition is changed. I. Introduction In this paper, we consider the problem of representing trees in genetic algorithms. A tree is an undirected graph which contains no closed cycles. There are many optimization problems which can be phrased in terms of finding the optimal tree wit...

While questions about social cohesion lie at the core of our discipline, definitions are often vague and difficult to operationalize. We link research on social cohesion and social embeddedness by developing a conception of structural cohesion based on network nodeconnectivity. Structural cohesion is defined as the minimum number of actors who, if removed from a group, would disconnect the group. A structural dimension of embeddedness can then be defined through the hierarchical nesting of these cohesive structures. We demonstrate the empirical applicability of our conception of nestedness in two dramatically different substantive settings and discuss additional theoretical implications with reference to a wide array of substantive fields. "...social solidarity is a wholly moral phenomenon which by itself is not amenable to exact observation and especially not to measurement." (Durkheim, (1893 [1984], p.24) "The social structure [of the dyad] rests immediately on the one and on the other of the two, and the secession of either would destroy the whole. ... As soon, however, as there is a sociation of three, a group continues to exist even in case one of the members drops out." (Simmel (1908 [1950], p. 123)

xiv Chapter 1 Introduction 1 Chapter 2 DNA structure and manipulation 6 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2 The structure and manipulation of DNA . . . . . . . . . . . . . . . . 7 2.3 Operations on DNA . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.3.1 Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.3.2 Denaturing, annealing and ligation . . . . . . . . . . . . . . . 10 2.3.3 Hybridisation separation . . . . . . . . . . . . . . . . . . . . . 10 2.3.4 Gel electrophoresis . . . . . . . . . . . . . . . . . . . . . . . . 11 2.3.5 Primer extension and PCR . . . . . . . . . . . . . . . . . . . 13 iii 2.3.6 Restriction enzymes . . . . . . . . . . . . . . . . . . . . . . . 14 2.3.7 Cloning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Chapter 3 Models of DNA computation 21 3.1 Introduction . . . . . . . . . . ....

In this paper, we introduce the power-efficient design space for multicast wavelength-routed networks. The power-efficient design space is based on the impact of power on the overall design of wavelength-routed networks. Two cross-connect architectures on this design concept are investigated. One is an existing architecture called splitter-and-delivery (SaD). The other is a new architecture called multicast-only splitter-and-delivery (MOSaD). The MOSaD architecture uses power splitters for multicast connections only, allowing unicast connections to pass without enduring unnecessary power losses. Our cross-connect design provides a strictly nonblocking service for unicast connections while eliminating unnecessary power loss of the SaD cross-connect. Experimental results demonstrate...