Fast Discrete Consensus Based on Gossip for Makespan Minimization in Networked Systems

In this paper we propose a novel algorithm to solve the discrete consensus problem, i.e., the problem of distributing evenly a set of tokens of arbitrary weight among the nodes of a networked system. Tokens are tasks to be executed by the nodes and the proposed distributed algorithm minimizes monotonically the makespan of the assigned tasks. The algorithm is based on gossip-like asynchronous local interactions between the nodes. The convergence time of the proposed algorithm is superior with respect to the state of the art of discrete and quantized consensus by at least a factor O(n) in both theoretical and empirical comparisons

A new approach for diagnosability analysis of Petri nets using Verifier Nets

In this paper, we analyze the diagnosability properties of labeled Petri nets. We consider the standard notion of diagnosability of languages, requiring that every occurrence of an unobservable fault event be eventually detected, as well as the stronger notion of diagnosability in K steps, where the detection must occur within a fixed bound of K event occurrences after the fault. We give necessary and sufficient conditions for these two notions of diagnosability for both bounded and unbounded Petri nets and then present an algorithmic technique for testing the conditions based on linear programming. Our approach is novel and based on the analysis of the reachability/coverability graph of a special Petri net, called Verifier Net, that is built from the Petri net model of the given system. In the case of systems that are diagnosable in K steps, we give a procedure to compute the bound K. To the best of our knowledge, this is the first time that necessary and sufficient conditions for diagnosability and diagnosability in K steps of labeled unbounded Petri nets are presented

Some New Results on Supervisory Control of Petri Nets with Decentralized Monitor Places

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Stealthy Sensor Attacks for Plants Modeled by Labeled Petri Nets

The problem of stealthy sensor attacks for labeled Petri nets is considered. An operator observes the plant to establish if a set of critical markings has been reached. The attacker can corrupt the sensor channels that transmit the sensor readings, making the operator incapable to establish when a critical marking is reached. We first construct the stealthy attack Petri net that keeps into account the real plant evolutions observed by the attacker and the corrupted plant evolutions observed by the operator. Starting from the reachability graph of the stealthy attack Petri net, an attack structure is defined: it describes all possible attacks. The supremal stealthy attack substructure can be obtained by appropriately trimming the attack structure. An attack function is effective if the supremal stealthy attack substructure contains a state whose first element is a critical marking and the second element is a noncritical marking

Fault Diagnosis of Timed Discrete Event Systems

In this paper, we consider partially observable timed discrete event systems (DES) endowed with a single clock that is reset at each event occurrence. A time interval with integer bounds is associated with each transition specifying at which clock values it may occur. This work deals with the fault diagnosis problem of such timed DES, assuming that faulty behaviours are described by means of timed transitions. We present a zone automaton that provides a purely discrete event description of the behaviour of the timed DES with faults and construct a fault recognizer as the parallel composition of the zone automaton with a fault monitor that recognizes the occurrence of faults. The diagnosis approach allows one to compute the diagnosis state for each timed observation, which consists in a timed sequence of observed events

Dermatitis in community pharmacies: a survey on italian pharmacists’ management and implications on corticophobia

Community pharmacists represent an important resource for the promotion of a safer and more effective self-management of common skin diseases, as well as the provision of educational support on therapies prescribed by clinicians, ultimately improving patients’ adherence. In this study, a semi-structured survey was administered to 154 Italian community pharmacists, in order to acquire information on their counseling activity on dermatological disorders. Collected data provide an overview on the frequency and methodology of counseling offered in Italian community pharmacies, identifying knowledge gaps and misbeliefs. In particular, an overall negative opinion on topical corticosteroid therapy emerged among pharmacists, unveiling a phenomenon previously described as corticophobia. Starting from this observation, we discuss the risks for patients’ adherence, associated with corticophobia among pharmacists. Lastly, we briefly report on the main tools desired by pharmacists to improve their education on dermatology, envisioning their implementation with the aim of a more effective counseling

The effect of sucralfate-containing ointment on quality of life in people with symptoms associated with haemorrhoidal disease and its complications: The results of the emocare survey

Background and aim: A rectal ointment containing 3% of sucralfate and herbal extracts (calendula, witch hazel leaf (hamamelis), chamomile), became available in Italy in 2019 for the treatment of symptoms associated with haemorrhoidal disease. This survey evaluated the effect of the mentioned sucralfate ointment, on quality of life (QoL) and symptom frequency in participants seeking treatment for haemorrhoidal disease from community pharmacies in Italy. Methods: EMOCARE was a multicentre prospective survey conducted at community pharmacies in Italy. Eligible participants (≥18 years) were those with haemorrhoidal symptoms in the last 7 days and were willing to initiate a treatment with the sucralfate ointment and herbal extracts (calendula, witch hazel leaf (hamamelis), chamomile). A survey was administered by the investigating pharmacists at the beginning and end (~14 days) of treatment. The primary endpoint was the change in HEMO-FISS-QoL scores. Results: Of the 290 (mean age 53.1 years old; 58.3% female) enrolled, 287 attended the follow-up visit. After a mean duration of 13 days, the sucralfate ointment significantly improved total HEMO-FISS-QoL scores (mean change from baseline: -10.41; 95%CI -11.95, -8.86; P<0.001) and mean scores for all domains of the HEMO-FISS-QoL scale (-11.13 [95%CI -12.95, -9.30] for physical disorders, -6.14 [95%CI -7.42, -4.85] for psychology, -18.79 [95% CI -21.67, -15.90] for defaecation, and -6.46 [95%CI -8.40, -4.51] for sexuality; all P<0.001 versus baseline). At the end of treatment, 39.4% of participants reported that they no longer had haemorrhoidal symptoms and the frequency of all assessed symptoms were reduced significantly from baseline (all P<0.05). Conclusions: After a mean 13 days of treatment  the sucralfate ointment with herbal extracts improved HEMO-FISS-QoL scores and reduced symptoms in people with haemorrhoidal disease

Supervisor Synthesis for Discrete Event Systems under Partial Observation and Arbitrary Forbidden State Specifications

In this paper, we consider the forbidden state problem in discrete event systems modeled by partially observed and partially controlled Petri nets. Assuming that the reverse net of the uncontrollable subnet of the Petri net is structurally bounded, we compute a set of weakly forbidden markings from which forbidden markings can be reached by firing a sequence of uncontrollable/unobservable transitions. We then use reduced consistent markings to represent the set of consistent markings for Petri nets with structurally bounded unobservable subnets. We determine the control policy by checking if the firing of a certain controllable transition will lead to a subsequent reduced consistent marking that belongs to the set of weakly forbidden markings; if so, we disable the corresponding controllable transition. This approach is shown to be minimally restrictive in the sense that it only disables behavior that can potentially lead to a forbidden marking. The setting in this paper generalizes previous work by studying supervisory control for partially observed and partially controlled Petri nets with a general labeling function and a finite number of arbitrary forbidden states. In contrast, most previous work focuses on either labeling functions that assign a unique label to each observable transition or forbidden states that are represented using linear inequalities. More importantly, we demonstrate that, in general, the separation between observation and control (as considered in previous work) may not hold in our setting