1,721,074 research outputs found
Distributed synthesis is simply undecidable
No full textAbstractThe distributed synthesis problem of safety and reachability languages is known to be undecidable. In this article, we establish that this is the case for very simple languages, namely for safety and reachability specifications in the intersection of LTL and ACTL
Detecting Operational Adversarial Examples for Reliable Deep Learning
Full text linkThe utilisation of Deep Learning (DL) raises new challenges regarding its
dependability in critical applications. Sound verification and validation
methods are needed to assure the safe and reliable use of DL. However,
state-of-the-art debug testing methods on DL that aim at detecting adversarial
examples (AEs) ignore the operational profile, which statistically depicts the
software's future operational use. This may lead to very modest effectiveness
on improving the software's delivered reliability, as the testing budget is
likely to be wasted on detecting AEs that are unrealistic or encountered very
rarely in real-life operation. In this paper, we first present the novel notion
of "operational AEs" which are AEs that have relatively high chance to be seen
in future operation. Then an initial design of a new DL testing method to
efficiently detect "operational AEs" is provided, as well as some insights on
our prospective research plan.Comment: Preprint accepted by the fast abstract track of DSN'2
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
Hidden Probabilistic One-Counter Automata
Full text linkThis thesis furthers the ongoing study of devising faster algorithms for the learning problem of infinite-state systems. We examine the Hidden Probabilistic One-Counter Machine (HP1CA) model, a natural extension of both Probabilistic One-Counter Automata (P1CA) and Hidden Markov Model (HMM) in this thesis. HP1CAs allow for the quadratic time complexity of learning the parameters of the model based on observational data. This gives them a big advantage over other infinite-state systems, e.g., probabilistic pushdown automata for which the same task requires cubic time.
An HP1CA is a P1CA where both the control states and the counter values are hidden, but the output sequence is not (note that there is no input sequence). Such a model has a non-negative counter whose value can change by at most one during a transition. The probability of a transition depends only on the current control state and whether the counter value is zero or not. The probability of a given output symbol depends on the current control state, but not on the value of the counter. A sequence of transitions is valid only if it starts and ends in a special initial control state and final control state, respectively, with the counter value equal zero.
After introducing the model, we adapt Baum-Welch algorithm, which is a special case of the Expectation-Maximization algorithm used in unsupervised learning in HMM, to update the parameters of an HP1CA. Furthermore, we also adopted two dynamic programming algorithms which are called Forward algorithm and Backward algorithm, respectively to our new model. Our adapted algorithms have worst-case quadratic time complexity as compared to the linear time for HMM. At the same time, its complexity is linear if the maximum value of the counter is assumed to be bounded by a constant (as it is commonly in practice).
After that, we look at other possible HP1CA models that differ depending on the semantic of what a valid transition sequence is. This can depend on the initial and final terminal state conditions as follows. First, an HP1CA can either start in (1) a fixed control state with counter zero or (2) have multiple initial control states, and some fixed probability distribution specifies the likelihood of starting in a given control state (with a counter value zero). Second, an HP1CA may be required to end with (A) a unique final control state with counter value zero, (B) a unique final control state with arbitrary counter value, (C) multiple final control states with zero counter value. This gives rise to six possible semantics, and only (1-A) semantic studied by us earlier. We adapt the learning and dynamic programming algorithms to the remaining five models.
In the end, we demonstrate that our HP1CA model leads to better accuracy and lower fit error of observation sequences as compared to HMMs through an implementation
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
Optimisation in multi-mode systems
Full text linkWe study cost optimisation in multi-mode systems with discrete costs. We first solve the problem in one dimension and next we study it in multiple dimensions. As a motivating example, we study the temperature control in buildings using heating, ventilation and air-conditioning system HVAC while paying the minimal cost as possible. By optimising the behaviour of the HVAC systems, lots of energy could be saved. We are interested in finding optimal solutions as well as approximate solutions with guarantees
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