Cooperation in Swarms of Robots without Communication

Swarm robotics aims to use a large group of relatively simple robots to solve tasks that can hardly be achieved by a single robot in the group. Compared to single robot systems with increased capability, a swarm robotic system may have advantages in robustness, flexibility and scalability. However, designing cooperative behaviors for a swarm robotic system is a challenging problem, especially when the robots may not have communication capabilities and thus only know local information. For a swarm of miniature mobile robots that cannot communicate explicitly, this thesis studies fully decentralized solutions of two problems. For the problem of cooperative transport, the thesis presents a strategy to push an object that is large enough to occlude the robots' perception of the goal of the transportation. For the problem of pattern formation, the thesis investigates algorithms based on the Brazil nut effect that can organize the swarm of robots into an annular formation. These problems are studied using physics-based computer simulations as well as experimental implementations based on the e-puck robotic platform. The simplicity of the solutions make them suitable for applications that require the individual robots to be as simple as possible. Example application scenarios could be micro robot swarms working in the human body

The Terentius Frieze in Context

As the sun set on James Henry Breasted’s single day of field work at Dura-Europos in 1920 he and his team stood in front of the north wall of the pronaos of the Temple of the Palmyrene Gods, Although paintings covered the entire extant wall, they had only one film plate left and chose to photograph the painting of Julius Terentius with his troops, on the right hand side of the wall (pl. 37). When Franz Cumont returned in the season of 1922 through 1923, he re-exposed the decoration on the north wall, took pictures, made illustrations, and noted graffiti. Cumont also had a protective wall built in front of the paintings. This wall was dismantled eight years later, when most of the paintings adorning the temple were removed and transported to the National Museum in Damascus and the Yale University Art Gallery." Although scholars who work at Dura-Europos know when the paintings were removed and, generally, where they went, the current location of the remainder of the north wall of the pronaos is a mystery. In his description of the removal process, field director Maurice Fillet mentions only three in particular: the painting of Terentius; the painting of Lysias, Apollodorus, and Zenodotus on the south wall of the pronaos; and the painting of Conon and his family on the south wall of the naos. It is certain, however, that other paintings were removed and transported that day, for the mythological scene on the east wall of the pronaos went to Yale along with the Terentius painting. The remainder of the north wall has not resurfaced and its disappearance has contributed to the trend that began on that fateful day in 1920, with the painting of Terentius and his troops being studied as an independent tableau. The purpose of this essay is to place the painting back into its artistic context in order to understand better the function of mural adornment in the temple

A Polyhedral Study of Mixed 0-1 Set

We consider a variant of the well-known single node fixed charge network flow set with constant capacities. This set arises from the relaxation of more general mixed integer sets such as lot-sizing problems with multiple suppliers. We provide a complete polyhedral characterization of the convex hull of the given set

Swarming Reconnaissance Using Unmanned Aerial Vehicles in a Parallel Discrete Event Simulation

Current military affairs indicate that future military warfare requires safer, more accurate, and more fault-tolerant weapons systems. Unmanned Aerial Vehicles (UAV) are one answer to this military requirement. Technology in the UAV arena is moving toward smaller and more capable systems and is becoming available at a fraction of the cost. Exploiting the advances in these miniaturized flying vehicles is the aim of this research. How are the UAVs employed for the future military? The concept of operations for a micro-UAV system is adopted from nature from the appearance of flocking birds, movement of a school of fish, and swarming bees among others. All of these natural phenomena have a common thread: a global action resulting from many small individual actions. This emergent behavior is the aggregate result of many simple interactions occurring within the flock, school, or swarm. In a similar manner, a more robust weapon system uses emergent behavior resulting in no weakest link because the system itself is made up of simple interactions by hundreds or thousands of homogeneous UAVs. The global system in this research is referred to as a swarm. Losing one or a few individual unmanned vehicles would not dramatically impact the swarms ability to complete the mission or cause harm to any human operator. Swarming reconnaissance is the emergent behavior of swarms to perform a reconnaissance operation. An in-depth look at the design of a reconnaissance swarming mission is studied. A taxonomy of passive reconnaissance applications is developed to address feasibility. Evaluation of algorithms for swarm movement, communication, sensor input/analysis, targeting, and network topology result in priorities of each model\u27s desired features. After a thorough selection process of available implementations, a subset of those models are integrated and built upon resulting in a simulation that explores the innovations of swarming UAVs

Traitement des arythmies cardiaques par ablation micro-onde

A comparative study of four open-ended coaxial probe models for permittivity measurements of lossy dielectric/biological materials at microwave frequencies -- Experimental setup for dielectric measuremetns -- Modeling of the open-ended coaxial probe -- Experimental results on saline solutions -- Sensitivity to the calibration media of the virtual line model and the capacitive model -- Correction des discontinuités lors des mesures de la permittivité complexe à l'aide d'une sonde coaxiale -- Catheter ablation : infarcted myocardium has a higher electrical conductivity at rf frequencies but the same complec permittivity at microwave frequencies in comparison with normal cardiac tissue -- A microwave ablation system to treat cardiac arrhythmia