1,720,956 research outputs found
Constructive analysis and computer-certified formal proofs for selected control-theoretical aspects
No full textNowadays, computers are indispensable devices in the daily work of scientists. Specifically, control engineers use the computers in the design, evaluation, simulation and optimization of complex control systems of different kind. Notably, the advances in numerical methods and computer hardware significantly impacted the application of the control theory on a wide range of real-world problems. It is well-known within the computer science community that computers are capable not only to work with numerical problems, but are also general information processing devices. This means that the computation can be applied to a wide range of different non-numeric data types: strings, lists, graphs, logical premises, computer programs themselves and even mathematical statement and their proofs. In context of the mathematical proofs, this phenomenon is also known as the so-called proofs-as-programs paradigm - a direct correspondence between computer programs and mathematical proofs. The idea is pretty simple: by the appropriate encoding of the mathematical statements, axioms and assumptions, derive a finite sequence of steps such that this sequence gets accepted by a certain computational device. The paradigm can be used for conceptional correctness, software verification and certification. This are undoubtedly desirable properties of any controller and/or controlled real-world system. Unfortunately, the classical model of the mathematics most commonly used for this purpose is not well-suitable, especially when dealing with the real numbers and continuous quantities, several issues regarding undecidability, non-computability and uncertainty arise. In contrast, this present work addresses the reasoning within the constructive analysis, which is a model of mathematics which is very close to computational devices and is valid within the framework of classical mathematics. This theoretical framework is applied to selected control-theoretical aspects, such as asymptotical stability of dynamical systems in sense of Lyapunov, existence of the solutions of ordinary differential equations, sliding-mode control and controller's verification. The work is motivated by various examples of different sources of the so-called computational uncertainty, i.e. a discrepancy between theoretical results and their computer realization, which might arise in the control theoretical applications. It demonstrates the principle possibility of deriving formal and computer-assisted proofs for the control theoretical purposes and thus contributing towards the so-called algorithmic control theory. The application of the derived theorems were demonstrated on several examples from control theory
Analysis of control system stability under algorithmic uncertainty
Get PDFStability of control systems is one of the central subjects in control theory. The classical asymptotic stability theorem states that the norm of the residual between the state trajectory and the equilibrium is zero in limit. Unfortunately, it does not in general allow computing a concrete rate of convergence particularly due to algorithmic uncertainty which is related to numerical imperfections of floating-point arithmetic. This work proposes to revisit the asymptotic stability theory with the aim of computation of convergence rates using constructive analysis which is a mathematical tool that realizes equivalence between certain theorems and computation algorithms. Consequently, it also offers a framework which allows controlling numerical imperfections in a coherent and formal way. The overall goal of the current study also matches with the trend of introducing formal verification tools into the control theory. Besides existing approaches, constructive analysis, suggested within this work, can also be considered for formal verification of control systems. A computational example is provided that demonstrates extraction of a convergence certificate for example dynamical systems
Constructive analysis and computer-certified formal proofs for selected control-theoretical aspects
No full textNowadays, computers are indispensable devices in the daily work of scientists. Specifically, control engineers use the computers in the design, evaluation, simulation and optimization of complex control systems of different kind. Notably, the advances in numerical methods and computer hardware significantly impacted the application of the control theory on a wide range of real-world problems. It is well-known within the computer science community that computers are capable not only to work with numerical problems, but are also general information processing devices. This means that the computation can be applied to a wide range of different non-numeric data types: strings, lists, graphs, logical premises, computer programs themselves and even mathematical statement and their proofs. In context of the mathematical proofs, this phenomenon is also known as the so-called proofs-as-programs paradigm - a direct correspondence between computer programs and mathematical proofs. The idea is pretty simple: by the appropriate encoding of the mathematical statements, axioms and assumptions, derive a finite sequence of steps such that this sequence gets accepted by a certain computational device. The paradigm can be used for conceptional correctness, software verification and certification. This are undoubtedly desirable properties of any controller and/or controlled real-world system. Unfortunately, the classical model of the mathematics most commonly used for this purpose is not well-suitable, especially when dealing with the real numbers and continuous quantities, several issues regarding undecidability, non-computability and uncertainty arise. In contrast, this present work addresses the reasoning within the constructive analysis, which is a model of mathematics which is very close to computational devices and is valid within the framework of classical mathematics. This theoretical framework is applied to selected control-theoretical aspects, such as asymptotical stability of dynamical systems in sense of Lyapunov, existence of the solutions of ordinary differential equations, sliding-mode control and controller's verification. The work is motivated by various examples of different sources of the so-called computational uncertainty, i.e. a discrepancy between theoretical results and their computer realization, which might arise in the control theoretical applications. It demonstrates the principle possibility of deriving formal and computer-assisted proofs for the control theoretical purposes and thus contributing towards the so-called algorithmic control theory. The application of the derived theorems were demonstrated on several examples from control theory
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
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