1,720,958 research outputs found
An analytical model for optimizing the combination of energy sources in a single power transmission network
Full text linkThe increasing amount of renewable energy currently being added to distribution networks presents new challenges and opportunities to system operators. This situation further complicates the operators’ tasks in dealing with changing net loads and balancing. The current work provides an analytical model to assist systems operators in stabilizing power generation and lowering total costs, through optimization of choices in the combination of programmable fossil sources and nonprogrammable renewable sources. The study first examines the various programmable and renewable energy sources that appear broadly suitable and economically appealing for combination. Next we identify the most important factors determining the potential integration of the sources in the system. Based on this introductory information we then develop the model for the selection of the appropriate mix of sources to achieve stable production. In developing the model we define indicators to evaluate and select the best configurations of the sources included in a particular combination. Next we apply the model to a specific case study and finally reexamine the interdependencies among all the variables of the model, to provide a better understanding of its dynamics and results
Integrating Capacity and Logistics of Large Additive Manufacturing Networks
No full textAmong future manufacturing systems, we are going to see networks of intelligent and autonomous entities sharing manufacturing resources, knowledge and information. Possible advantages are relevant, such as increasing overall production efficiency and product variety as well as reducing responsiveness and lead times. This paper focuses on the architectures and dynamics of productive-demanding nodes in a Scattered Manufacturing (SM) Network, with an application in Additive Manufacturing scenarios. SM allows launching production orders everywhere anytime inside the domain of the network. These autonomous nodes can rely on on-demand manufacturing services by sharing resources in a geographically distributed network. One possible approach is the introduction of a platform to coordinate the dynamics along the network according to principles of sustainability, equated shared resources and transparency by managing communication activities among nodes. To identify variables/factors that affect the system, a unique model is proposed by combining different perspectives, which focus on: a) decomposition and localization of demanding node’s order into subtasks of variable size; b) tasks allocation criteria among geographically distributed nodes; c) logistics issues related to the localization of productive nodes. In particular, the model, with the aim of optimizing the overall manufacturing and logistics costs, suggests either logistics paths along the sub-network or tasks assignment criteria and scheduling in geographically distributed nodes
Designing a multi-agent system architecture for managing distributed operations within cloud manufacturing
No full textCloud manufacturing (CM) is a challenging scenario in the fourth stage of industrial production (i.e. Industry 4.0). In this context, the fusion of physical and virtual worlds in cyber-physical production systems transforms manufacturing resources into homogeneous services that can be shared and distributed in collaborative environments. CM systems are characterized by intelligent capability management and manufacturing cloud service-management. An interesting research topic in these areas is the production planning with a decentralized pool of homogeneous resources. The distributed Task Scheduling Problem in CM has been partially tackled in the current literature, but some issues, such as the dynamic task arrival, the downtime of machines, the anomalous tasks identification, have not been addressed. Armed with such a vision, we discuss the design of a multi-agent system for managing and monitoring homogeneous manufacturing services in a CM system based on Additive Manufacturing Technologies
Negotiating and Sharing Capacities of Large Additive Manufacturing Networks
No full textThis paper focuses on dynamics of productive and demanding nodes for Scattered Manufacturing Networks within 3D Printings contexts. The various nodes issue orders or sell production slots in order to achieve their own aims. An orchestrator coordinates the dynamics along the network according to principles of sustainability, equated shared resources and transparency by managing communication activities among nodes. In particular, suitable tradeoffs occur by a unique framework that, with the aim of optimizing the overall costs, suggests either logistics paths along the network or negotiation policies among nodes in order to reallocate resources. Numerical examples present the proposed approach
A Queueing Networks-Based Model for Supply Systems
No full textIn this paper, a stochastic approach, based on queueing networks, is analyzed in order to model a supply system, whose nodes are working stations. Unfinished goods and control electrical signals arrive, following Poisson processes, at the nodes. When the working processes at nodes end, according to fixed probabilities, goods can leave the network or move to other nodes as either parts to process or control signals. On the other hand, control signals are activated during a random exponentially distributed time and they act on unfinished parts: precisely, with assigned probabilities, control impulses can move goods between nodes, or destroy them. For the just described queueing network, the stationary state probabilities are found in product form. A numerical algorithm allows to study the steady state probabilities, the mean number of unfinished goods and the stability of the whole network
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
Situation Awareness and Environmental Factors: The EVO Oil Production
No full textThe paper considers simulation results for a supply network, that deals
with Extra Virgin Olive (EVO) oil production, an activity that is typical of Southern
Italy. The phenomenon is studied by differential equations, that focus on goods on
arcs and queues for the exceeding goods. Different numerical schemes are used for
simulations. A strategy of Situation Awareness allows defining a possible choice
of the input flow to the supply network. The achieved results indicate that Situa-
tion Awareness permits to find good compromises for the modulation of production
queues and the optimization of the overall system features
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