1,720,961 research outputs found
A Prototype NIRS Device to Increase Safety of Diving
No full textA simple prototype device that may become part of the standard divers’ safety equipment is designed, constructed, and tested in order to prove the practicability of the underlying idea. The device is based on near-infrared spectroscopy (NIRS) and can detect drops in oxyhemoglobin and rises in deoxyhemoglobin concentrations in the blood. The proposed device not only collects biometric data, but can also autonomously identify and promptly notify anomalies so as to warn and speed up appropriate rescue activities. Easiness of use and low costs are important requirements in order to make the device suitable for everyday use by most divers. The first demonstration tests, carried out in laboratory conditions, are illustrated and discussed
A 4g robotic platform for shallow water operations
No full textA prototypal robotic platform that consists of a small autonomous surface vehicle (ASV) and of a micro-ROV, connected by an umbilical, is described. 4G/internet connection makes it possible to operate the platform from remote location. The operator can concentrate on guiding the micro-ROV by means of visual data, while the surface vehicle automatically coordinates its movements with those of the micro-ROV. Small dimensions, low costs and easiness of use make the platform an effective tool for low-budget survey in shallow water. The mechatronic characteristics of the platform are illustrated and discussed, together with the results of functional tests
Disturbance decoupling and model matching problems for discrete-time systems with time-varying delays
Full text linkIn this paper, the disturbance decoupling problem and the model matching problem for discrete-time linear systems with time-varying delays are considered. Solvability of the above problems is characterized by means of structural necessary and sufficient conditions that can be checked by algorithmic procedures. The basic method used to analyze the considered problems consists in representing the discrete-time linear systems with time-varying delays as switching linear systems, whose properties can be studied by a powerful structural approach. In this way, the considered control problems can be reduced to the corresponding problems for switched linear systems, whose solvability has been recently characterized
Output regulation of discrete-time systems with time-varying delays
No full textIn this paper the output regulation problem for discrete-time linear systems with time-varying delays is considered. Solvability of the above problem is completely characterized in structural geometric terms and a sufficient condition that can be practically checked, together with a procedure to construct solutions, if any exists, is given. The basic method used to analyze the considered problem consists in representing the discrete-time linear systems with time-varying delays as switching linear systems, whose properties can be studied by a powerful structural approach. In this way, the considered problem can be reduced to the corresponding problem for switched linear systems, whose solvability has been recently characterized
Synchronization and Sub-synchronization Problems for Switching Max-Plus Systems: Structural Solvability Conditions
Full text linkSwitching linear systems over the max-plus algebra can be used to model production plants where different choices in resource allocation are possible. In such case, internal and external variables represent the time instants at which internal or external events occur. In particular, output variables represent the time instants at which lots of manufactured goods are released to the market. Here, we consider the problems of system synchronization and sub-synchronization, which consist in forcing the output of a system to equal or to anticipate the output of a given model. Their solution in the max-plus framework provides a viable strategy to control a given production plant in such a way to comply with a desired production time schedule. Using structural methods and introducing novel structural notions, necessary and sufficient solvability conditions are given. Practical methods to construct solutions are illustrated and discussed
The Model Matching Problem for Max-Plus Linear Systems: a Geometric Approach
Full text linkLinear systems over the max-plus algebra provide a suitable formalism to model discrete event systems where synchronization, without competition, is involved. In this paper, we consider a formulation of the model matching problem for systems of such class, in which the output of a given system, called the plant, is forced, by a suitable input, to track exactly that of a given model. A necessary and sufficient condition for its solvability is obtained by making a suitable use of geometric methods in the framework of systems over the max-plus algebra
The Model Matching Problem for Switching Max-Plus Systems: a Geometric Approach
No full textLinear systems over the max-plus algebra can model discrete event systems where synchronization, without competition, is involved. The lack of competition can be partly circumvented by considering multiple linear models, each representing a possible choice in resource allocation, and a switching mechanism, thus obtaining a switching linear max-plus system. We propose a formulation of the model matching problem for systems of such kind. The aim is to force a given plant to match exactly the output of a given model. A sufficient condition for the solvability of the problem is obtained by extending the geometric approach to switching systems over the max-plus algebra
The Model Matching Problem for Periodic Max-Plus Systems
No full textMax-plus linear systems are suitable to model discrete event systems with synchronization phenomena, but not competition. In specific situations, competition can be introduced by considering event-varying periodic parameters, which allow us to model shared resources allocated in accordance to a periodic schedule, thus obtaining a periodic max-plus linear system. In this paper, we propose an extension of the geometric approach to systems of such class. The new results can be used to solve the model matching problem, so as to force a given plant to match the output of a given model exactly. A geometric, structural, necessary and sufficient condition for the solvability of such problem 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
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