On the ring loading problem with demand splitting

In this paper, we improve the rerouting step of Myung, Kim and Tcha's algorithm for the ring loading problem with demand splitting and achieve a better running time. We also conduct a computational study to evaluate the practical performance of the proposed algorithm.     

Effective bandwidths: Call admission,traffic policing and filtering for ATM networks

In this paper we review and extend the effective bandwidth results of Kelly [28], and Kesidis, Walrand and Chang [29, 6]. These results provide a framework for call admission schemes which are sensitive to constraints on the mean delay or the tail distribution of the workload in buffered queues. We present results which are valid for a wide variety of traffic streams and discuss their applicability for traffic management in ATM networks. We discuss the impact of traffic policing schemes, such as thresholding and filtering, on the effective bandwidth of sources. Finally we discuss effective bandwidth results for Brownian traffic models for which explicit results reveal the interaction arising in finite buffers.     

Flocks and Formations

Given a large number (the “flock”) of moving physical objects, we investigate physically reasonable mechanisms of influencing their orbits in such a way that they move along a prescribed course and in a prescribed and fixed configuration (or “in formation”). Each agent is programmed to see the position and velocity of a certain number of others. This flow of information from one agent to another defines a fixed directed (loopless) graph in which the agents are represented by the vertices. This graph is called the communication graph. To be able to fly in formation, an agent tries to match the mean position and velocity of his neighbors (his direct antecedents on the communication graph) to his own. This operation defines a (directed) Laplacian on the communication graph. A linear feedback is used to ensure stability of the coherent flight patterns. We analyze in detail how the connectedness of the communication graph affects the coherence of the stable flight patterns and give a characterization of these stable flight patterns. We do the same if in addition the flight of the flock is guided by one or more leaders. Finally we use this theory to develop some applications. Examples of these are: flight guided by external controls, flocks of flocks, and some results about flocks whose formation is always oriented along the line of flight (such as geese). In Honor of Mitchell Jay Feigenbaum’s 60’th Birthday     

Communication, complexity, and evolutionary stability

In games with costless preplay communication, some strategies are more complex than others in the sense that they induce a finer partition of the set of states of the world. This paper shows that if the concept of evolutionary stability, which is argued to be a natural solution concept for communication games, is modified to take lexicographic complexity preferences into account, then for a class of games of common interest only communication strategies that induce payoff-dominant Nash outcomes of the underlying game are stable. Received April 1998/Final version September 1998     

Simultaneous demultiplexing and clock recovery using a single electroabsorption modulator in a novel bi-directional configuration

A single electroabsorption modulator was used to demultiplex a 10 Gbit/s channel from a 40 Gbit/s OTDM data stream, whilst simultaneously recovering the 10 GHz electrical clock. This was achieved using a new bi-directional operation of the EA modulator, combined with a simple phase-locked loop feedback circuit. Excellent system performance was achieved, indicating that operation up to and beyond 100 Gbit/s is possible using current technology.     

Chemical communication between solids placed at distance: Sol-gel entrapped acids and bases

Chemical reactions between “far-away” components are quite common in the living world and in geological processes, and are affected by communicating shuttling molecules and ions. Surprisingly, there has been little attention in the chemical literature to model these natural processes by bench-laboratory heterogeneous reactions. Towards that goal we report the study of chemical communication between solid acids and bases placed at distance. The porous solids were prepared by entrapping various acids and bases in silica sol-gel matrices. We recall that while, of course, dissolved acids and bases titrate each other, when solid acids and bases are placed in the same pot, titration can be affected only through an ion-exchange process. This property is used here to cause the two distantly placed solids to communicate with each other. In particular, we use here the entrapped acids as senders of messenger-hydronium ions and as receivers of hydroxyl ions, and entrapped bases as senders of messenger-hydroxyls. We demonstrate the possibility to control the parameters of the communication between these solids.     

The epistemic gossip problem

In the gossip problem information (‘secrets’) must be shared among a certain number of agents using the minimum number of calls. We extend the gossip problem to arbitrary epistemic depths. For example, we may require not only that all agents know all secrets but also that all agents know that all agents know all secrets. We give optimal protocols for various versions of this epistemic gossip problem, depending on the graph of communication links, in the case of two-way communication, one-way communication and parallel communication. We show, among other things, that increasing epistemic depth from 1 (all agents know all secrets) to 2 (so that all agents know that all agents know all secrets) does not double the required number of calls but increases this number by $3∕2$ (for a complete graph). We also show that the following counter-intuitive result generalises to the epistemic gossip problem: asymptotically the same number of calls are required whether calls are two-way or one-way.     

Overlapping and communication policies in product development

Shorter product life cycles in many industries impel firms to accelerate the product development process. Overlapping development stages, combined with frequent information exchange, is commonly regarded as a core technique for faster product development. However, overlapping and communication require additional resources and can be costly. We investigate the time-cost tradeoffs involved in concurrent product development to determine the optimal overlapping and communication strategies. The methodology was applied to a refrigerator development process in order to illustrate its utility.