Impact of Obstacles on the Degree of Mobile Ad Hoc Connection Graphs

What is the impact of obstacles on the graphs of connections between stations in Mobile Ad hoc Networks? In order to answer, at least partially, this question, the first step is to define both an environment with obstacles and a mobility model for the stations in such an environment. The present paper focuses on a new way of considering the mobility within environments with obstacles, while keeping the core ideas of the well-known Random WayPoint mobility model (a.k.a RWP). Based on a mesh-partitioning of the space, we propose a new model called RSP-O-G for which we compute the spatial distribution of stations and analyse how the presence of obstacles impacts this distribution compared to the distribution when no obstacles are present. Coupled with a simple model of radio propagation, and according to the density of stations in the environment, we study the mean degree of the connection graphs corresponding to such mobile ad hoc networks

GraphStream: A Tool for bridging the gap between Complex Systems and Dynamic Graphs

The notion of complex systems is common to many domains, from Biology to Economy, Computer Science, Physics, etc. Often, these systems are made of sets of entities moving in an evolving environment. One of their major characteristics is the emergence of some global properties stemmed from local interactions between the entities themselves and between the entities and the environment. The structure of these systems as sets of interacting entities leads researchers to model them as graphs. However, their understanding requires most often to consider the dynamics of their evolution. It is indeed not relevant to study some properties out of any temporal consideration. Thus, dynamic graphs seem to be a very suitable model for investigating the emergence and the conservation of some properties. GraphStream is a Java-based library whose main purpose is to help researchers and developers in their daily tasks of dynamic problem modeling and of classical graph management tasks: creation, processing, display, etc. It may also be used, and is indeed already used, for teaching purpose. GraphStream relies on an event-based engine allowing several event sources. Events may be included in the core of the application, read from a file or received from an event handler

DynamicScore: a Novel Metric for Quantifying Graph Dynamics

This study introduces a new metric called ''DynamicScore'' to evaluate the dynamics of graphs. It can be applied to both vertices and edges. Unlike traditional metrics, DynamicScore not only measures changes in the number of vertices or edges between consecutive time steps, but also takes into account the composition of these sets. To illustrate the possible contributions of this metric, we calculate it for increasing networks of preferential attachment (Barab{\'a}si-Albert model) and Edge-Markovian graphs. The results improve our understanding of the dynamics inherent in these generated evolving graphs

Dynamic Graphs Generators Analysis : an Illustrative Case Study

In this work, we investigate the analysis of generators for dynamic graphs, which are defined as graphs whose topology changes over time. We introduce a novel concept, called ''sustainability,'' to qualify the long-term evolution of dynamic graphs. A dynamic graph is considered sustainable if its evolution does not result in a static, empty, or periodic graph. To measure the dynamics of the sets of vertices and edges, we propose a metric, named ''Nervousness,'' which is derived from the Jaccard distance.As an illustration of how the analysis can be conducted, we design a parametrized generator, named D3G3 (Degree-Driven Dynamic Geometric Graphs Generator), which generates dynamic graph instances from an initial geometric graph. The evolution of these instances is driven by two rules that operate on the vertices based on their degree. By varying the parameters of the generator, different properties of the dynamic graphs can be produced.Our results show that in order to ascertain the sustainability of the generated dynamic graphs, it is necessary to study both the evolution of the order and the Nervousness for a given set of parameters

Decentralized High Level Controller for Formation Flight Control of UAVs

International audienceThe main contribution of this paper is the design of a decentralized and tuning-less high level controller able to maintain without tracking errors a Leader-Follower (LF) configuration in case of lack or degraded communications (latencies, loss…) between the leader and followers UAVs. The high level controller only requires simple tunings and rests on a predictive filtering algorithm and a first order dynamic model to recover an estimation of the leader UAV velocities and avoid the tracking errors

A Semi-Autonomous Multi-Vehicle Architecture for Agricultural Applications

The ageing population, climate change, and labour shortages in the agricultural sector are driving the need to reevaluate current farming practices. To address these challenges, the deployment of robot systems can help reduce environmental footprints and increase productivity. However, convincing farmers to adopt new technologies poses difficulties, considering economic viability and ease of use. In this paper, we introduce a management system based on the Robot Operating System (ROS) that integrates heterogeneous vehicles (conventional tractors and mobile robots). The goal of the proposed work is to ease the adoption of mobile robots in an agricultural context by providing to the farmer the initial tools needed to include them alongside the conventional machinery. We provide a comprehensive overview of the system’s architecture, the control laws implemented for fleet navigation within the field, the development of a user-friendly Graphical User Interface, and the charging infrastructure for the deployed vehicles. Additionally, field tests are conducted to demonstrate the effectiveness of the proposed framework.publishedVersio

A Decentralized Interactive Architecture for Aerial and Ground Mobile Robots Cooperation

This paper presents a novel decentralized interactive architecture for aerial and ground mobile robots cooperation. The aerial mobile robot is used to provide a global coverage during an area inspection, while the ground mobile robot is used to provide a local coverage of ground features. We include a human-in-the-loop to provide waypoints for the ground mobile robot to progress safely in the inspected area. The aerial mobile robot follows continuously the ground mobile robot in order to always keep it in its coverage view.Comment: Submitted to 2015 International Conference on Control, Automation and Robotics (ICCAR

Overproduction and properties of the mannuronate alginate lyase AlxMB

peer reviewedIn previous studies (Malissard et al., FEMS Microbiol. Lett. (1993) 110, 101-106), the alginate lyase AlxM of the marine bacterium ATCC 433367 was produced in Escherichia coli TC4/pAL-A3 with a yield of 50 mu g per litre of culture. The polypeptide chain was cleaved between two cysteine residues, C169 and C183, themselves linked by a disulphide bridge. AlxM has now been overproduced in E. coli BL21(DE3)/pAL-Sur/pLysS. Under conditions in which formation of inclusion bodies can be avoided, the enzyme is synthesized as a catalytically active, water-soluble, unnicked polypeptide with a yield of 32 mg per litre of culture. It has been purified to protein homogeneity using a one-step procedure. The nicked ALxM(A) and unnicked ALxM(B) alginate lyases have identical alginate-degrading activities at high salt concentrations