1,720,969 research outputs found
An MILP approach for persistent coverage tasks with multiple robots and performance guarantees
No full textMultiple robots are increasingly being considered in a variety of tasks requiring continuous surveillance of a dynamic area, examples of which are environmental monitoring, and search and rescue missions. Motivated by these applications, in this paper we consider the multi-robot persistent coverage control problem over a grid environment. The goal is to ensure a desired lower bound on the coverage level of each cell in the grid, that is decreasing at a given rate for unoccupied cells. We consider a finite set of candidate poses for the agents and introduce a directed graph with nodes representing their admissible poses. We formulate a persistent coverage control problem as a MILP problem that aims to maximize the coverage level of the cells over a finite horizon. To solve the problem, we design a receding horizon scheme (RHS) and prove its recursive feasibility property by introducing a set of time-varying terminal constraints to the problem. These terminal constraints ensure that the agents are always able to terminate their plans in pre-determined closed trajectories. A two-step method is proposed for the construction of the closed trajectories, guaranteeing the satisfaction of the coverage level lower bound constraint, when the resulting closed trajectories are followed repeatedly. Due to the special structure of the problem, agents are able to visit every cell in the grid repeatedly within a worst-case visitation period. Finally, we provide a computational time analysis of the problem for different simulated scenarios and demonstrate the performance of the RHS problem by an illustrative example.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Tamas Keviczk
Multi-Robot Path Planning for Persistent Coverage Tasks with Performance Guarantees
No full textRecent advances on the design of autonomous mobile agents have motivated the use of the latter in persistent surveillance tasks with applications in agriculture, information gathering and search and rescue missions. In these tasks the goal is to design agents’ paths so as every point in the area of interest is covered more than once. In literature the persistent surveillance problem has been addressed under two different frameworks: 1) the visitation frequency of a finite set of points (discrete spaces) and 2) the amount of coverage offered by the agents over the area of interest. In the first category agents aim at visiting a finite set of points in the area so as the time elapsed since a point was last visited is minimized over the set. Here, the environment is considered static and no information on the coverage condition of the points is available. In the second category the environment is characterized by a property that changes over time, called coverage level and the goal is to design agents’ paths so as the coverage level is maintained at a desired level over the area. In this approach the error between the actual and desired coverage level of the area is bounded. However, locally no information is available on the frequency at which each point gets covered. The novelty of this thesis lies in the integration of the aforementioned solution approaches so as complete coverage information is provided for a finite set of points. Here, the goal is to design the agents’ paths so as the coverage level of each point is bounded from below by a desired level. The paths are planned over a finite optimization horizon and found as a solution to a Mixed Integer Linear Program (MILP). Two formulations of the problem are proposed and their efficiency is validated in simulation. The recursive feasibility of the centralized problem is also guaranteed when a set of time-varying terminal constraints is introduced to the problem. These constraints force agents to move along a pre-defined set of closed paths designed in a way that the coverage level boundness constraint is always satisfied. A two-step method is proposed for their design that relies on the solution of a Linear Program (LP) when a set of closed paths violating the objective is given, found as a solution to a modified version of the proposed MILP at step 1. Finally, two distributed formulations of the problem are introduced in which agents solve in parallel a local path planning problem. The difference on these methods lies in the accuracy of the information available to the agents for planning. Despite this difference simulation tests show a difference of only 1.5% in the coverage level performance when various sized teams of agents are employed for the task.Mechanical Engineering | Systems and Contro
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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