Co-Degeneracy and Co-Treewidth: Using the Complement to Solve Dense Instances

Clique-width and treewidth are two of the most important and useful graph parameters, and several problems can be solved efficiently when restricted to graphs of bounded clique-width or treewidth. Bounded treewidth implies bounded clique-width, but not vice versa. Problems like Longest Cycle, Longest Path, MaxCut, Edge Dominating Set, and Graph Coloring are fixed-parameter tractable when parameterized by the treewidth, but they cannot be solved in FPT time when parameterized by the clique-width unless FPT = W[1], as shown by Fomin, Golovach, Lokshtanov, and Saurabh [SIAM J. Comput. 2010, SIAM J. Comput. 2014]. For a given problem that is fixed-parameter tractable when parameterized by treewidth, but intractable when parameterized by clique-width, there may exist infinite families of instances of bounded clique-width and unbounded treewidth where the problem can be solved efficiently. In this work, we initiate a systematic study of the parameters co-treewidth (the treewidth of the complement of the input graph) and co-degeneracy (the degeneracy of the complement of the input graph). We show that Longest Cycle, Longest Path, and Edge Dominating Set are FPT when parameterized by co-degeneracy. On the other hand, Graph Coloring is para-NP-complete when parameterized by co-degeneracy but FPT when parameterized by the co-treewidth. Concerning MaxCut, we give an FPT algorithm parameterized by co-treewidth, while we leave open the complexity of the problem parameterized by co-degeneracy. Additionally, we show that Precoloring Extension is fixed-parameter tractable when parameterized by co-treewidth, while this problem is known to be W[1]-hard when parameterized by treewidth. These results give evidence that co-treewidth is a useful width parameter for handling dense instances of problems for which an FPT algorithm for clique-width is unlikely to exist. Finally, we develop an algorithmic framework for co-degeneracy based on the notion of Bondy-Chvátal closure.publishedVersio

Evolution of hybrid robotic controllers for complex tasks

We propose an approach to the synthesis of hierarchical control systems comprising both evolved and manually programmed control for autonomous robots. We recursively divide the goal task into sub-tasks until a solution can be evolved or until a solution can easily be programmed by hand. Hierarchical composition of behavior allows us to overcome the fundamental challenges that typically prevent evolutionary robotics from being applied to complex tasks: bootstrapping the evolutionary process, avoiding deception, and successfully transferring control evolved in simulation to real robotic hardware. We demonstrate the proposed approach by synthesizing control systems for two tasks whose complexity is beyond state of the art in evolutionary robotics. The first task is a rescue task in which all behaviors are evolved. The second task is a cleaning task in which evolved behaviors are combined with a manually programmed behavior that enables the robot to open doors in the environment. We demonstrate incremental transfer of evolved control from simulation to real robotic hardware, and we show how our approach allows for the reuse of behaviors in different tasks.info:eu-repo/semantics/acceptedVersio

Anaerobic digestion experiment using Cynara cardunculus L. stalks

RAMIRAN International ConferenceAnaerobic digestion is an industrial process applied to organic wastes treatment with several environmental and energetic advantages over other forms of treatment and specially when is integrated in the agriculture sector (Möller, 2009; Prochnow, 2009; Chynoweth, 1987). In addition to the organic wastes treatment there is an emerging interest in the production of biomethane as a biocombustible through anaerobic digestion of biomass and / or energy crops (IEA, 2010; Chanakya, 2009; CONCAWE, 2008; Tilche, 2008; Yadvika, 2004; Gunaseelan, 1997; Chynoweth, 1987). Cynara cardunculus L. or commonly known as cardoon is a perennial herb or herbaceous crop native to Mediterranean region, grown since ancient times as a wild plant or as vegetable using intensive management techniques (Ortega, 2007; Fernández, 2006). The average biomass annual production varies from 15 to 20 tons of biomass/ha depending on soil and rainfall with 11% of moisture content and the following biomass partitioning: 40 % stalks, 25% leaves and 35 % capitula (Gominho, 2001 and 2008). Different studies have been shown the high potential of this plant as energy crop: the aerial biomass used as a solid biofuel and the oil from seeds used for the production of biodiesel (Fernández, 2006). However, the interest in their use in the production of biomethane has never been investigated. Different studies show that the addition of biomass or energy crops to the anaerobic digestion of cattle dung or the anaerobic digestion of energy crops residues with the addition of partially digested cattle dung or sewage digested sludge enhanced biogas production and methane yield (Chanakya, 2009; Yadvika, 2004). The goal of the research performed on Cynara cardunculus L. was to increase the knowledge about the use of this promising industrial crop for biogas production in Mediterranean countries or countries with similar edaphoclimate condition

Beyond onboard sensors in robotic swarms: Local collective sensing through situated communication

The constituent robots in swarm robotics systems are typically equipped with relatively simple, onboard sensors of limited quality and range. When robots have the capacity to communicate with one another, communication has so far been exclusively used for coordination. In this paper, we present a novel approach in which local, situated communication is leveraged to overcome the sensory limitations of the individual robots. In our approach, robots share sensory inputs with neighboring robots, thereby effectively extending each other’s sensory capabilities. We evaluate our approach in a series of experiments in which we evolve controllers for robots to capture mobile preys. We compare the performance of (i) swarms that use our approach, (ii) swarms in which robots use only their limited onboard sensors, and (iii) swarms in which robots are equipped with ideal sensors that provide extended sensory capabilities without the need for communication. Our results show that swarms in which local communication is used to extend the sensory capabilities of the individual robots outperform swarms in which only onboard sensors are used. Our results also show that in certain experimental configurations, the performance of swarms using our approach is close to the performance of swarms with ideal sensors.info:eu-repo/semantics/acceptedVersio

Phylogenetic Grouping by PCR Analyses of \u3ci\u3eSinorhizobium meliloti\u3c/i\u3e Strains Isolated from Eutrophic Soil

This study evaluated the ability of Sinorhizobium meliloti strains (SEMIA-116, SEMIA- 134 and SEMIA-135) to persist in eutrophic soils after three complete growing cycles of alfalfa. PCR fingerprinting using primers for the nifH, Eric, Rep, RP genes and P25 RAPD-PCR performed the phylogenetic grouping of the three commercial strains and 39 field isolates. These analyzes were sufficiently sensitive to discriminate and group the strains and isolate. Our preliminary studies were based upon Eric primers and RP01 RAPD-PCR

Glazing-related problems due to high temperatures in double skin façades

The thermal behaviour of a double skin façade building is modelled using the DOE-2 building energy simulation program. Maximum temperatures of glazed components of the double skin façade are determined to assess the occurrence of glazing-related problems, such as reduced thermal and aesthetic performance, increased maintenance costs and even injury hazards. The importance of detailed thermal modelling of double skin façades and of its glazed componentes is concluded

Evolving controllers for robots with multimodal locomotion

Animals have inspired numerous studies on robot locomotion, but the problem of how autonomous robots can learn to take advantage of multimodal locomotion remains largely unexplored. In this paper, we study how a robot with two different means of locomotion can effective learn when to use each one based only on the limited information it can obtain through its onboard sensors. We conduct a series of simulation-based experiments using a task where a wheeled robot capable of jumping has to navigate to a target destination as quickly as possible in environments containing obstacles. We apply evolutionary techniques to synthesize neural controllers for the robot, and we analyze the evolved behaviors. The results show that the robot succeeds in learning when to drive and when to jump. The results also show that, compared with unimodal locomotion, multimodal locomotion allows for simpler and higher performing behaviors to evolve.info:eu-repo/semantics/acceptedVersio

Design and development of an inexpensive aquatic swarm robotics system

Swarm robotics is a promising approach characterized by large numbers of relatively small and inexpensive robots. Since such systems typically rely on decentralized control and local communication, they exhibit a number of interesting and useful properties, namely scalability, robustness to individual faults, and flexibility. In this paper, we detail the design and development process of a swarm robotics platform composed of autonomous surface robots, which was designed in order to study the use of robotic swarms in real-world environments. Our aquatic surface robots where manufactured using digital fabrication techniques, such as 3D printing and CNC milling, and all hardware and software has been made available as open-source, thus allowing third-parties to customize and further improve our platform.info:eu-repo/semantics/acceptedVersio