1,722,022 research outputs found
A coloured Petri net model for automated storage and retrieval systems serviced by rail-guided vehicles: A control perspective
No full textAn Automated Storage and Retrieval System (AS/RS) automatically stores incoming material and retrieves stored parts with no direct human handling. This paper proposes a modular and unified modelling framework for heterogeneous automated storage and retrieval systems, comprising rail guided vehicles and narrow aisle cranes. We employ coloured timed Petri nets, representing a concise and computationally efficient tool for modelling the system dynamic behaviour, particularly suitable for real-time control implementation. Indeed, the model can be utilized in a discrete event simulation to apply control policies in order to solve scheduling problems, as well as to avoid deadlock and collision occurrences
Deadlock Control Methods in Automated Manufacturing Systems
No full textAs more and more producers move to use flexible
and agile manufacturing as a way to keep them with a competitive
edge, the investigations on deadlock resolution in automated
manufacturing have received significant attention for a decade.
Deadlock and related blocking phenomena often lead to catastrophic
results in automated manufacturing systems. Their
efficient handling becomes a necessary condition for a system to
gain high productivity. This paper intends to present a tutorial
survey of state-of-the art modeling and deadlock control methods
for discrete manufacturing systems. It presents the updated
results in the areas of deadlock prevention, detection and recovery,
and avoidance. It focuses on three modeling methods: digraphs,
automata, and Petri nets. Moreover, for each approach, the main
and relevant contributions are selected enlightening pros and
cons. The paper concludes with the future research needs in this
important area in order to bridge the gap between the academic
research and industrial needs
A Generalized Stochastic Petri Net Model for Management of Distributed Manufacturing Systems
No full textA Distributed Manufacturing System (DMS) is a collection of independent companies possessing complementary skills and integrated with transportation and storage systems. This paper deals with the issues of modeling and managing a DMS. The system is modeled as a timed discrete event dynamical system by generalized stochastic Petri nets. Moreover, two well known broad policies are considered to manage the DMS: make-to-stock and make-to-order. In order to compare the two management techniques and to show the effectiveness of each method, a case study is presente
Performance-Based Comparison of Control Policies for Automated Storage and Retrieval Systems Modelled by Coloured Petri Nets
No full textThe industrial manufacturing environment is nowadays characterized by fierce global competition, rapid market changes and short product life cycles. Such a complex scenario originated a vast demand for sophisticated techniques guaranteeing adequate planning and control of warehouses. A widely used solution is to adopt Automated Storage and Retrieval Systems (AS/RSs). A typical AS/RS comprises a number of parallel aisles with storage racks, serviced by automated stacker cranes and rail guided vehicles. This paper compares several management strategies addressing the system operational control, i.e., dealing with the AS/RS real time behaviour. A common coloured timed Petri net models the system and the controlled AS/RS operation is highlighted by way of several discrete event simulations carried out in the Matlab-Stateflow software environment. The proposed control policies are compared and discussed on the basis of appropriate performance indices
Silis (Silis) boninoi FANTI & M. G. PANKOWSKI 2022, sp. nov.
No full textSilis (Silis) boninoi FANTI & M. G. PANKOWSKI sp. nov. (Fig. 1) Description. Adult, winged, male. Body length: 2.7 mm; elytra: approximately 2.4 mm long, and 1.0 mm wide at apex. Entirely blackish-dark brown. Head large, slightly narrower than pronotum, smooth, equipped with several long setae, largely covered by pronotum. Eyes rounded and protruded, wide, inserted in upper and lateral part of the head. Maxillary palpi 4- segmented, unequal in length with last palpomere very elongated and securiform. Labial palps 3-segmented with last palpomere securiform. Antennal insertions and eyes not juxtaposed, antennae surpassing two-thirds of the elytra, 11-segmented, filiform, each antennomere covered with several setae; scape elongated, slightly club-shaped; antennomere II (pedicel) short, about 2.1 times shorter than scape; antennomeres III–V subequal in length, longer than antennomere II, rather robust; antennomeres VI–IX subequal in length, slightly longer than antennomeres III–V; antennomere X very slightly shorter and more slender than previous ones; antennomere XI filiform, oblong with extremely thin and pointed apex. Pronotum strongly transverse, surface undulating with concavities (pores) and equipped with sparse long setae, apparently without punctuation; anterior margin curved and protruding in the middle; sides strongly sinuous, with two very short processes on each side: Posterior processes are thicker and wider than anterior ones and rounded apically; anterior processes are shorter than posterior ones and rounded apically; posterior margin irregular and sinuous with two expansions in the middle. Scutellum triangular with rounded apex. Elytra wider than pronotum, elongated and surpassing last abdominal segments, enlarged at humeri and apex, restricted in middle, apex strongly rounded, surface with very superficial punctation and several very long setae. Posterior wings transparent, completely covered by elytra but just barely shorter than them. Metasternum very elongated with a strongly rounded posterior margin, abdominal segments transverse and pubescent. Legs relatively short, robust and strongly pubescent; coxae massive; trochanters elongated and triangular-shaped with rounded apex; femora enlarged and slightly curved; tibiae cylindrical, with one apical and robust spur, protibiae as long as profemora, mesotibiae slightly shorter than mesofemora, metatibiae just slightly shorter than metafemora. Tarsal formula 5-5-5; first tarsomere elongated; second tarsomere about 1.2 times shorter than first; third tarsomere triangular and shorter than tarsomere II; fourth tarsomere deeply bilobed at sides; fifth tarsomere very elongated, slender, flat and curved; claws simple without basal tooth. Note. Female unknown. The specimen is a male, defined on the basis of long antennae and lateral sides of pronotum toothed. Sexual dimorphism is supposed because females of the genus Silis are characterized by a pronotum with sides without appendages or with very small teeth, and have shorter antennae and a wider abdomen than males. Etymology. Named in honor of Enrico Bonino for donating the described specimen, photographing it and kindly giving us access to it. Holotype. Male, in Baltic amber, deposited at the Back to the Past Museum, Cancún, Mexico with accession no. BPM-1111. Type locality. Yantarny mine, Sambian Peninsula, Kaliningrad Region, Russia. Type horizon. Middle Eocene: Bartonian-Priabonian (45.0–38.0 Mya). Syninclusions. A few botanical fragments (trichomes). Systematic placement. The specimen is clearly a new species belonging to the subfamily Silinae and to the genus Silis (Brancucci 1980; Kazantsev 1997) based on its maxillary palpi sub-equal in length with their last palpomere securiform, elytra elongated, tarsomeres IV wider than other tarsomeres, pores on the anterior part of the pronotum, the internal claw simple, tibial spurs conspicuous and the lateral section of its pronotum having two lobes on each side. Genera that appear most similar to Silis are distinguished by a few different characters. The genus Podosilis has a complex pronotal armature at the sides and a cleft outer claw in males (Kazantsev 1997, 2019, 2020). Autosilis features the anterior half of its mesonotum smooth without clear pores, and the anal ring in the male has a tergite and sternite that are roughly equally wide (Kazantsev 1997). Differential diagnosis. Silis boninoi sp. nov. differs from Silis lombardii Parisi & Fanti, 2019 (from Baltic amber) based on the new species’ pronotum that is much more transverse and with shorter pronotal lobes on its sides, and by the new species’ significantly smaller size: 2.7 mm vs. 5.2 mm for S. lombardii (Parisi & Fanti 2019). In addition, Silis chiapasensis Wittmer, 1963 (found in Mexican Chiapas amber) differs based on its pronotum that is deeply incised at the sides and its lobes that are more curved and longer than on the new species (Wittmer 1963). Finally, Silis curleri Fanti & M. G. Pankowski 2021 and Silis hegnai Fanti & M. G. Pankowski 2021 (both from Dominican amber) have a very different pronotal shape, with lobes that are longer and more curved, and a less transverse pronotum (Fanti & Pankowski 2021). The living and widely distributed species Silis ruficollis (Fabricius, 1775) has a pronotum with a lateral margin that is less toothed and indented compared to the new fossil species described here. Remarks. The yellow amber piece has an elongated drop shape and measures approximately 22x 11 mm. The inclusion is complete and well visible. Once trapped, the specimen struggled to get out of the sticky resin and thus created characteristic ripples (“fringes”) in the amber. A photo of this new species is included in Enrico Bonino’s forthcoming book on amber (Bonino, 2022), expected to be published in 2022.Published as part of Fanti, Fabrizio & Pankowski, Maximilian G., 2022, A new fossil Silis Charpentier, 1825 from Baltic amber (Cantharidae, Silinae, Silini), pp. 87-91 in Zootaxa 5195 (1) on pages 88-90, DOI: 10.11646/zootaxa.5195.1.5, http://zenodo.org/record/718066
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
Fuzzy rule-based models for home energy consumption prediction
No full textPredicting energy demands based on the past energy consumption can allow a reasonable allocation of energy resource to avoid waste and improve utilization. To this end, linear or nonlinear forecasting models are applied. Some researchers use support vector regression models to deal with the energy consumption prediction problem as they can handle with nonlinear problems through their kernel function. However, using fuzzy rule-based models based on the granulation-degranulation mechanism to predict energy consumption can better deal with the nonlinear data and further improve the robustness and the accuracy of prediction compared with the support vector regression models. In this paper we apply a first-order fuzzy rule-based model to predict the energy data. Firstly, the data is granulated in the input space, and then the number of rules is determined according to the error value between the estimated value and the actual value. The prediction task can be completed based on a small amount of input data. It has good interpretability and delivers superior predictive performance. The experimental results show that the improvement of performance index MAE of the first-order fuzzy rule-based model is 18.59%, 37.58%, 25.82% and 8.43% better than that of the Lasso model, support vector regression, zero-order fuzzy rule-based model and LSTM-RNN model, respectively, on the testing data. (c) 2022 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
Structurally fixed modes of systems described by Rosenbrock's polynomial matrices
No full textA full characterization of structurally fixed modes for systems described by Rosenbrock's polynomial matrices is given. The constraints imposed on the feedback structure are quite general, so that the decentralized-control problem can be viewed as a particular case. The results are obtained in the digraph-theory framework and provide computationally efficient test
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