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This work investigates quantitative supervisory control of discrete event systems modeled with Petri nets under the fixed‐initial‐credit energy objective. A weight function referred to as an energy function is defined on a Petri net to characterize the energy level of a transition. The proposed fixed‐initial‐credit energy problem aims to design a supervisor such that the energy level of a transition sequence in a supervised system is higher than 0 under a given initial energy level. The problem is eventually transformed into a two‐player game between a system and a supervisor; supervisor synthesis is reduced to finding a winning strategy in the two‐player game. Instead of enumerating the complete state space of the underlying Petri net, two information structures are utilized, namely the conventional basis reachability graph and the newly proposed essential marking graph, to construct two‐player games based on each of them. It is shown that a winning strategy for a supervisor decoded from the game based on the basis reachability graph of the Petri net is a solution to the problem but is in general restrictive. Further, it is shown that the set of strategies for a supervisor in the game based on the essential marking graph is consistent with that from the game based on the reachability graph of a Petri net. The two developed approaches do not require an exhaustive exploration of the state space of a plant, thus achieving higher efficiency. [ABSTRACT FROM AUTHOR]

Dealloying is a powerful technology to fabricate nanoporous materials with tunable structures and compositions for battery applications. Meanwhile, electrochemical dealloying is an intrinsic process for metal anodes that exhibits fundamental correlations with electrode morphologies and structures. In this work, Li‐Ag composites are fabricated as a case study to understand the spontaneous structural evolution and the in situ formation of nanoporosity during a reversible lithiation/delithiation process. The rationally designed nanoporous AgLi (NPAgLi) framework with limited Li capacity (10 mAh cm−2) enables a dendrite‐free anode with marginal volume variation upon long‐term cycling, which can be attributed to the spatially confined reaction pattern along with efficient Li alloying/dealloying. Furthermore, full cell tests reveal the NPAgLi anode remains stable under practical conditions such as lean electrolyte (15 µL), large areal capacity (1.6 mAh cm−2), and high‐loading cathode (12 mg cm−2). This work provides new perspectives on the in situ structural evolution of Li‐rich alloy electrodes and the results are expected to contribute to the development of alkali metal anodes. [ABSTRACT FROM AUTHOR]

Research on traffic forecasting in transportation has received worldwide concern over the past three decades. While there are comprehensive review studies on traffic forecasting, few of them explore the research advancement in this field from a visual perspective. With the help of CiteSpace and VOSviewer, this study uses scientometric review to identify the evolution and emerging trends of the research in the field. Totally, 1536 bibliographic records with references are extracted from Web of Science and used as the datasets to form the author network, institutional network, keyword network, and co‐citation network. The visualization of the results characterizes the research progress in the field. It can be found that Eleni I. Vlahogianni receives the highest citation frequency, China and the United States contribute most of the journal articles. Some influential institutions and articles are also identified. With the author keyword network, the words "recurrent neural network", "convolutional neural network", "spatio‐temporal correlation", "traffic pattern", and "feature selection" are identified as the emerging trends. Also, the document citation bursts reveal that the applications of combined models and the study of traffic flow forecasting in atypical situations are becoming the emerging trends. This study provides a valuable reference for the research community in this field. [ABSTRACT FROM AUTHOR]

The exploration of advanced electrode materials with appropriate structures and compositions is the primary task for nonaqueous potassium ion batteries (PIBs). Herein, 3D nanoporous CuBi anodes are fabricated through a facile chemical dealloying process. The ligaments of this nanoporous alloy are composed of interconnected Bi serving as the active material and Cu decoration as a highly conductive matrix. Such a typical bicontinuous ligament‐channel structure is beneficial to overcome the slow K‐ion diffusion kinetics as well as electrode expansion on cycling, as evidenced by the high discharge capacity and good rate capability in PIBs. Potassium storage mechanisms in the Bi anodes are investigated through combined techniques to identify the multiple step postassiation process and the charge/discharge products at each stage. Furthermore, it is the first time to report the irreversible phase transition of KBi2→Bi upon charge, which seems associated with the ligament pulverization process. These results provide critical insights into the capacity degradation mechanisms of Bi anodes in PIBs. Also, dealloying is proved to be an efficient technology for the rational design of metal/alloy materials for high performance PIBs. [ABSTRACT FROM AUTHOR]

Power transmission lines of traditional power transmission systems (PTSs) may suffer from some faults that can lead to blackouts. This work proposes a methodology to construct hierarchical distributed control systems (DCSs) for the automatic fault detection and restoration of PTSs using colored Petri nets (CPNs). If faults occur in power transmission lines, they can be detected by supervisors, and local solutions can be computed to restore the faults. Each supervisor is coordinated by a coordination protocol to perform the computation of local solutions. The structures of traditional PTSs are simplified and defined by CPNs, and the derivation processes of fault detection and restoration based on the proposed coordination protocol are verified by the mathematical methods of CPNs. Finally, the complexity of the proposed hierarchical DCS and coordination protocol is discussed and an example is given to illustrate the proposed method. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

Abstract: This paper develops an approach to the design of an optimal Petri net supervisor that enforces liveness to flexible manufacturing systems. The supervisor contains a set of observer places with weighted inhibitor arcs. An observer place with a weighted inhibitor arc is used to forbid a net from yielding an illegal marking by inhibiting the firing of a transition at a marking while ensuring that all legal markings are preserved. A marking reduction technique is presented to decrease the number of considered markings, which can dramatically lower the computational burden of the proposed approach. An integer linear program is presented to simplify the supervisory structure by minimizing the number of observer places. Finally, several examples are used to shed light on the proposed approach which can lead to an optimal supervisor for the net models that cannot be optimally controlled via pure Petri net supervisors. [ABSTRACT FROM AUTHOR]

As a type of process plant, a refinery is characterized by the interaction of discrete events and continuous processes. To schedule crude oil operations in a refinery, it is necessary to define and schedule the jobs simultaneously such that heuristics and meta-heuristics cannot be directly applied. It is very challenging to schedule crude oil operations. To solve this problem, it is decomposed into two subproblems hierarchically. At the upper level, a refining schedule is found, while at the lower level a detailed schedule is obtained to realize the refining schedule. Given a refining schedule at the upper level, this paper studies the detailed scheduling problem at the lower level. Based on a control-theoretic perspective, the problem is innovatively transformed to a problem of assigning charging tanks to distillers such that meta-heuristic methods can be applied. Then, a genetic algorithm (GA) approach is developed to solve the problem. In realizing the proposed GA, based on a set of existence conditions of a feasible schedule, methods are presented to guarantee that each chromosome corresponds to a feasible schedule. An industrial case study is used to show the application of the proposed method. It shows that the method works well and is applicable to real-life problems. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

Nondeterministic firing of concurrent transitions in Petri nets (PNs) may lead to the disappearance of conflicts. The disappearance implies that the partial conflicting transitions in a conflict become disabled before the resolution of the conflict. The phenomenon is called confusions that are caused by the interlacement of conflicting and concurrent transitions in PNs, which generates incomplete and faulty system conflicting behavior such that conflicts cannot be correctly resolved. In this paper, conflict-increasing confusions (CICs) and conflict-decreasing confusions (CDCs) in a PN are investigated. The relation graph of conflicts and confusions (RGC²) in a PN is proposed to detect the structure of confusions. To avoid the occurrence of confusions in a PN, an algorithm based on generalized mutual exclusion constraints (GMECs) is proposed, which can generate confusion-avoidance supervisors such that the occurrence of conflicts can be ensured in a PN. Finally, an example of confusion detection and avoidance in a flexible assembly system is presented. [ABSTRACT FROM AUTHOR]