1,721,127 research outputs found
Replication vs erasure coding in data centric storage for wireless sensor networks
No full textIn-network storage of data in wireless sensor networks contributes to reduce the communications inside the network and to favor data aggregation. In this paper, we consider the use of n out of m codes and data dispersal in combination to in-network storage. In particular, we provide an abstract model of in-network storage to show how n out of m codes can be used, and we discuss how this can be achieved in five cases of study. We also define a model aimed at evaluating the probability of correct data encoding and decoding, we exploit this model and simulations to show how, in the cases of study, the parameters of the n out of m codes and the network should be configured in order to achieve correct data coding and decoding with high probability
AOI cast by Tolerance Based Compass Routing in Distributed Virtual Environments
No full textThis paper presents an Area of Interest(AOI)-cast
strategy for P2P Distributed Virtual Environment (DVE) which
exploits a Delaunay Triangulation of the DVE to define a
compass-based routing algorithm. A set of formal results for
circular AOI is presented. Inconsistencies between local views
of different peers due to the network latency are faced by
introducing a tolerance threashold in the compass routing
VoRaQue: Range Queries on Voronoi Overlays
No full textThis paper presents VoRaQue, a software layer supporting range queries on Voronoi P2P overlays. VoRaQue maps data in a 2-dimensional space. The P2P overlay is defined by links connecting nodes that are close in the 2-dimensional space and by a set of long-range links which guarantee a poly-logarithmic routing. When a query is submitted, VoRaQue finds out a node belonging to the region defined by the query. A multicast spanning tree covering that region is then built by applying compass routing, a distributed protocol to embed a spanning tree into a Delaunay Triangulation. The paper presents the basic VoRaQue protocol, then introduces a set of optimizations and finally presents some experimental results
Hivory: Range Queries on Hierarchical Voronoi Overlays
No full textThe problem of defining a support for multidimensional range queries on P2P overlays is currently an active field of research. Several approaches based on the extension of the basic functionalities offered by Distributed Hash Tables have been recently proposed. The main drawback of these approaches is that the locality required for the resolution of a range query cannot be guaranteed by uniform hashing. On the other way, locality preserving hashing functions do not guarantee a good level of load balancing. This paper presents Hivory, a P2P overlay based on a Voronoi tessellation defined by the objects published by peers. Each object is mapped to a site of the Voronoi tessellation and the corresponding Delaunay Triangulation defines the P2P overlay. A hierarchy of Voronoi diagrams is defined by exploiting clusters of objects paired with the same site of the Voronoi diagram. A new Voronoi diagram including the peers of the cluster is created so that the query resolution may be refined by a top down visit of the Voronoi hierarchy. The paper presents the proposed solution, analyses its complexity, and provides a set of experimental results
Multidimensional range queries on hierarchical Voronoi overlays
No full textThe definition of a support for multi-attribute range queries is mandatory for highly distributed systems. Even if several solutions have been proposed in the last decade, most of them do not meet the requirements of recent platforms, like IoT or smart cities. The paper presents an approach that builds a multidimensional Voronoi graph by exploiting the attributes of the objects published by a node. Our solution overcomes the curse of dimensionality issue affecting Voronoi Tessellations in high dimensional spaces by defining a Voronoi hierarchy. The paper formally defines the structure, analysis the complexity of the operations and presents experimental results
Hierarchical P2P Overlays for DVE: An Additively Weighted Voronoi Based Approach
No full text—This paper presents a support for the development
of Distributed Virtual Environments (DVEs) on P2P architectures.
A hierarchical overlay is defined by pairing each peer with a
weight which is proportional to its networking bandwidth. Peers
characterized by higher weights are assigned a greater workload,
in terms of connections with other peers and of number of
passive objects they manage, and can act as superpeers that offer
a set of services to peers characterized by lower bandwidth.
Additively Weighted Voronoi (AWV) Diagrams are exploited to
define a partition of the DVE that assigns to each peer a region
whose size is dependent on the peer’s weight. Superpeers are
modeled by sites of the tessellation that have absorbed at least
the Voronoi region of another site. A set of experimental results
shows that this approach can be a load balancing mechanism for
peer-to-peer networks, that does not impair usual properties of
Voronoi-based peer-to-peer network
A Model-Checking Static Analysis of Task-Based Energy Neutrality for Energy Harvesting IoT
No full textWe address the problem of energy neutrality in energy harvesting IoT devices by means of a model checking approach, aiming at analyzing the dynamics of the battery charge in energy-neutral IoT devices. Our approach allows to compute the best task schedule and to study the maximum utility when operating on other parameters such as the initial battery charge, the number and structure of the available tasks, the size of the photo-voltaic panel that recharges the device, the day of the year, and the variable weather conditions that affect the energy production. The simulations confirm the state space explosion typical of model checking, but also hint that a small number of alternative tasks can achieve an overall utility very close to a large number of tasks. This conjecture has a strong practical relevance since it can pave the way to the wider adoption of energy neutrality concept in low-power IoT devices
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
The future of Maintenance
Get PDFThe Big Data and data science revolution, internet of things, advances in machine learning, improvements in wireless connectivity, sensor technologies and available computing power. This final chapter takes a step back and presents some views towards the future. Whether one deals with PM on a manufacturing process or a fleet of machines, in logistics or construction, the potential gains from improving the maintenance policies can be substantial. The chapter focuses on the following provocative questions: Is it cybernetic or is it human? Real-time communication in maintenance? How to determine granularity in space and time? Open or closed maintainability? Insourcing or outsourcing? Explicit modeling or data-driven pragmatics? How to apply Virtual Reality and Augmented Reality? Service robotics for maintenance? Today manufacturing companies are very keen on developing maintenance service businesses for the equipment they have sold.<br/
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