1,720,965 research outputs found
Robotic surgery: formal verification of plans
No full textIn this paper we discuss the introduction of formal methods for the verification of properties of control systems designed for autonomous robotic systems
Automating Numerical Parameters Along the Evolution of a Nonlinear System
No full textWhen analysing cyber-physical systems for runtime verification purposes, reachability analysis can be used to identify whether the set of reached points stays within given safe bounds. If the system dynamics exhibits nonlinearity, approximate numerical techniques (with rigorous numerics) are often necessary when dealing with system evolution. Since the error involved in numerical approximation should be kept low to perform verification successfully, the associated processing and memory costs become relevant especially when runtime verification is considered. Given a reachability analysis tool, the issue of controlling its numerical accuracy is not trivial from the user’s perspective, due to the complex interaction between the configuration parameters of the tool. As a result, user intervention in the tuning of a specific problem is always required. This paper explores the problem of automatically choosing numerical parameters that drive the computation of the finite-time reachable set, when the configuration parameters of the tool are specified within bounds or lists of values. In particular, it is designed to be performed along evolution, in order to adapt to local properties of the dynamics and to reduce the setup overhead, essential for runtime verification
HermesBDD: A Multi-Core and Multi-Platform Binary Decision Diagram Package
No full textBDDs are representations of a Boolean expression in the form of a directed acyclic graph. BDDs are widely used in several fields, particularly in model checking and hardware verification. There are several implementations for BDD manipulation, where each package differs depending on the application. This paper presents HermesBDD: a novel multi-core and multi-platform binary decision diagram package focused on high performance and usability. HermesBDD supports a static and dynamic memory management mechanism, the possibility to exploit lock-free hash tables, and a simple parallel implementation of the IF-THEN - ELSE procedure based on a higher-level wrapper for threads and futures. HermesBDD is completely written in C++ with no need to rely on external libraries and is developed according to software engineering principles for reliability and easy maintenance over time. We provide experimental results on the n-Queens problem, the de-facto SAT solver benchmark for BDDs, demonstrating a significant speedup of 18.73x over our non-parallel baselines, and a remarkable performance boost w.r.t. other state-of-the-art BDDs packages
Computing the evolution of hybrid systems using rigorous function calculus
No full textHybrid systems exhibit all the complexities of finite automata, nonlinear dynamic systems and differential equations, and are extremely difficult to analyze. A rigorous mathematical approach is needed to achieve provable approximation bounds along the computations.
In this paper we describe a rigorous numerical calculus for working with functions that can be used for computing the evolution of nonlinear hybrid systems, and the implementation in the tool Ariadne for reachability analysis of hybrid systems. The method is based around expressing the sets attained during the evolution in terms of functions, and computing approximations to these functions, and allows highly accurate approximations for the evolved sets to be computed. An example of the control of the water level in a tank is presented
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
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