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Mengchu Zhou - One of the best experts on this subject based on the ideXlab platform.
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deadlock prevention for flexible manufacturing systems via controllable Siphon basis of petri nets
Systems Man and Cybernetics, 2015Co-Authors: Huixia Liu, Mengchu Zhou, Keyi Xing, Hailin ZouAbstract:Siphons are a kind of special structural objects in a Petri net, and plays a key role in synthesizing a live Petri net controller for flexible manufacturing systems. In order to obtain a small size Petri net controller, this paper introduces the concept of a controllable Siphon basis. It then proves that a live Petri net controller can be established by adding a control place and related arcs to each strict minimal Siphon (SMS) in a controllable Siphon basis. The initial markings of control places are determined by an integer linear program. The number of control places in the obtained controllers is the same as the number of SMSs in the controllable Siphon basis, while the latter is no more than that of the activity places in a Petri net model. An algorithm for constructing a controllable Siphon basis is proposed, and a new deadlock prevention policy based on it is established. A few examples are provided to demonstrate the proposed concepts and policy and used to compare them with the state-of-the-art methods.
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resource transition circuits and Siphons for deadlock control of automated manufacturing systems
Systems Man and Cybernetics, 2011Co-Authors: Keyi Xing, Mengchu Zhou, Feng Wang, Feng TianAbstract:The resource-transition circuit ( RTC) and Siphon are two different structural objects of Petri nets and used to develop deadlock control policies for automated manufacturing systems. They are related to the liveness property of Petri net models and thus used to characterize and avoid deadlocks. Based on them, there are two kinds of methods for developing deadlock controllers. Such methods rely on the computation of all maximal perfect RTCs and strict minimal Siphons (SMSs), respectively. This paper concentrates on a class of Petri nets called a system of simple sequential processes with resources, establishes the relation between two kinds of control methods, and identifies maximal perfect RTCs and SMSs. A graph-based technique is used to find all elementary RTC structures. They are then used to derive all RTCs. Next, an iterative method is developed to recursively construct all maximal perfect RTCs from elementary ones. Finally, a one-to-one correspondence between SMSs and maximal perfect RTCs and, hence, an equivalence between two deadlock control methods are established.
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on Siphon computation for deadlock control in a class of petri nets
Systems Man and Cybernetics, 2008Co-Authors: Mengchu ZhouAbstract:As a structural object, Siphons are well recognized in the analysis and control of deadlocks in resource allocation systems modeled with Petri nets. Many deadlock prevention policies characterize the deadlock behavior of the systems in terms of Siphons and utilize this characterization to avoid deadlocks. This paper develops a novel methodology to find interesting Siphons for deadlock control purposes in a class of Petri nets, i.e., a system of simple sequential processes with resources . Resource circuits in an are first detected, from which, in general, a small portion of emptiable minimal Siphons can be derived. The remaining emptiable ones can be found by their composition. A polynomial-time algorithm for finding the set of elementary Siphons is proposed, which avoids complete Siphon enumeration. It is shown that a dependent Siphon can always be controlled by properly supervising its elementary Siphons. A computationally efficient deadlock control policy is accordingly developed. Experimental study shows the efficiency of the proposed Siphon computation approach.
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control of elementary and dependent Siphons in petri nets and their application
Systems Man and Cybernetics, 2008Co-Authors: Mengchu ZhouAbstract:The importance of Siphons is well recognized in the analysis and control of deadlocks in a Petri net. To minimize the number of Siphons that have to be explicitly controlled, Siphons in a net are divided in a net into elementary and dependent ones. The concepts of token-rich, token-poor, and equivalent Siphons are newly presented. More general conditions under which a dependent Siphon can be always marked are established. The existence of dependent Siphons in a Petri net is investigated. An algorithm is developed to find the set of elementary Siphons in a net system for deadlock control purposes. The application of the proposed elementary Siphon concept to the existing deadlock control policies is discussed. A few different-sized manufacturing examples are used to demonstrate the advantages of elementary Siphon-based policies. The significant value of the proposed theory via a particular deadlock control policy is shown. Finally, some interesting and open problems are discussed.
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a maximally permissive deadlock prevention policy for fms based on petri net Siphon control and the theory of regions
IEEE Transactions on Automation Science and Engineering, 2008Co-Authors: Zhiwu Li, Mengchu Zhou, Muder JengAbstract:This paper addresses the deadlock problems in flexible manufacturing systems (FMS) by using a Petri net Siphon control method and the theory of regions. The proposed policy consists of two stages. The first one, called Siphons control, is to add, for every Siphon that we identify, a monitor to the original net model such that it is optimally invariant controlled. In the second stage, the theory of regions is utilized to derive the net supervisors such that deadlocks can be prevented. The first-stage work significantly lowers the computational cost compared with the approach where the theory of regions is used alone. An FMS example is presented to illustrate the technique. By varying the markings of given net structures, this paper shows its computational advantages.
William R Jeffery - One of the best experts on this subject based on the ideXlab platform.
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closing the wounds one hundred and twenty five years of regenerative biology in the ascidian ciona intestinalis
Genesis, 2015Co-Authors: William R JefferyAbstract:Summary This year marks the 125th anniversary of the beginning of regeneration research in the ascidian Ciona intestinalis. A brief note was published in 1891, reporting the regeneration of the Ciona neural complex and Siphons. This launched an active period of Ciona regeneration research culminating in the demonstration of partial body regeneration: the ability of proximal body parts to regenerate distal ones, but not vice versa. In a process resembling regeneration, wounds in the Siphon tube were discovered to result in the formation of an ectopic Siphon. Ciona regeneration research then lapsed into a period of relative inactivity after the purported demonstration of the inheritance of acquired characters using Siphon regeneration as a model. Around the turn of the present century, Ciona regeneration research experienced a new blossoming. The current studies established the morphological and physiological integrity of the regeneration process and its resemblance to ontogeny. They also determined some of the cell types responsible for tissue and organ replacement and their sources in the body. Finally, they showed that regenerative capacity is reduced with age. Many other aspects of regeneration now can be studied at the mechanistic level because of the extensive molecular tools available in Ciona. genesis 53:48–65, 2015. © 2014 Wiley Periodicals, Inc.
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regeneration of oral Siphon pigment organs in the ascidian ciona intestinalis
Developmental Biology, 2010Co-Authors: Helene Auger, William R Jeffery, Yasunori Sasakura, Jeanstephane JolyAbstract:Ascidians have powerful capacities for regeneration but the underlying mechanisms are poorly understood. Here we examine oral Siphon regeneration in the solitary ascidian Ciona intestinalis. Following amputation, the oral Siphon rapidly reforms oral pigment organs (OPO) at its distal margin prior to slower regeneration of proximal Siphon parts. The early stages of oral Siphon reformation include cell proliferation and re-growth of the Siphon nerves, although the neural complex (adult brain and associated organs) is not required for regeneration. Young animals reform OPO more rapidly after amputation than old animals indicating that regeneration is age dependent. UV irradiation, microcautery, and cultured Siphon explant experiments indicate that OPOs are replaced as independent units based on local differentiation of progenitor cells within the Siphon, rather than by cell migration from a distant source in the body. The typical pattern of eight OPOs and Siphon lobes is restored with fidelity after distal amputation of the oral Siphon, but as many as 16 OPOs and lobes can be reformed following proximal amputation near the Siphon base. Thus, the pattern of OPO regeneration is determined by cues positioned along the proximal distal axis of the oral Siphon. A model is presented in which columns of Siphon tissue along the proximal–distal axis below pre-existing OPO are responsible for reproducing the normal OPO pattern during regeneration. This study reveals previously unknown principles of oral Siphon and OPO regeneration that will be important for developing Ciona as a regeneration model in urochordates, which may be the closest living relatives of vertebrates.
Mi Zhao - One of the best experts on this subject based on the ideXlab platform.
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extraction of elementary Siphons in a class of generalized petri nets using graph theory
Engineering Computations, 2014Co-Authors: Yifan Hou, Mi Zhao, Ding LiuAbstract:Purpose – Siphon-based deadlock control in a flexible manufacturing system (FMS) suffers from the problems of computational and structural complexity since the number of Siphons grows exponentially with respect to the size of its Petri net model. In order to reduce structural complexity of a supervisor, a set of elementary Siphons derived from all strict minimal Siphons (SMS) is explicitly controlled. The purpose of this paper is through fully investigating the structure of a class of generalized Petri nets, WS3PR, to compute all SMS and a compact set of elementary Siphons. Design/methodology/approach – Based on graph theory, the concepts of initial resource weighted digraphs and restricted subgraphs are proposed. Moreover, the concept of augmented Siphons is proposed to extend the application of elementary Siphons theory for WS3PR. Consequently, the set of elementary Siphons obtained by the proposed method is more compact and well suits for WS3PR. Findings – In order to demonstrate the proposed method, a...
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extended elementary Siphon based deadlock prevention policy for a class of generalised petri nets
International Journal of Computer Integrated Manufacturing, 2014Co-Authors: Yifan Hou, Mi Zhao, Ding LiuAbstract:This paper develops a novel deadlock prevention policy for a class of generalised Petri nets, namely S4PR that can well model flexible manufacturing systems FMS. The analysis of generalised Petri nets leads us to characterise deadlock situations in terms of insufficiently marked Siphons. The theory of elementary Siphons guides our efforts towards the development of structurally simple liveness-enforcing supervisors. Therefore, insufficiently marked Siphons can be classified into elementary ones and dependent ones. The controllability of a dependent Siphon can be ensured by properly supervising its elementary ones. In order to find a compact and proper set of elementary Siphons for S4PR, the concept of augmented Siphons is proposed. Then, the concept of max′-controlled Siphons is employed, which can relax the Siphon controllability condition. By explicitly controlling elementary Siphons via adding monitors, a liveness-enforcing controlled system can be found. In addition, the liveness-enforcing supervisor with more permissive behaviour is obtained through the rearrangement of the output arcs of the monitors. Finally, an FMS case study is utilised to demonstrate the proposed method.
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on controllability of dependent Siphons for deadlock prevention in generalized petri nets
Systems Man and Cybernetics, 2008Co-Authors: Mi ZhaoAbstract:A fair amount of research has shown the importance of Siphons in the analysis and control of deadlocks in a variety of resource allocation systems by using a Petri net formalism. In this paper, Siphons in a generalized Petri net are classified into elementary and dependent ones, as done for ordinary nets in our previous work. Conditions are derived under which a dependent Siphon is controlled by properly supervising its elementary Siphons, which indicates that the controllability of dependent Siphons in an ordinary Petri net is a special case of that in a generalized one. The application of the controllability of dependent Siphons is shown by considering the deadlock prevention problem for a class of resource allocation systems, namely, G-system that allows multiple resource acquisitions and flexible routings in a flexible manufacturing system with machining, assembly, and disassembly operations. We develop a monitor-based deadlock prevention policy that first adds monitors for elementary Siphons only to a G-system plant model such that the resultant net system satisfies the maximal controlled-Siphon property (maximal cs-property). Then, by linear programming, initial tokens in the additional monitors are decided such that liveness is enforced to the supervised system. Also, a simplified live marking relationship for a G-system between the initial tokens of the source places and those of the resource places is derived. Finally, the proposed deadlock prevention methods are illustrated by using an example.
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liveness enforcing supervisor design for a class of generalised petri net models of flexible manufacturing systems
Iet Control Theory and Applications, 2007Co-Authors: Jincheng Zhang, Mi ZhaoAbstract:The importance of Siphons is well recognised in the analysis and control of deadlocks in Petri nets. Deadlock prevention problems are considered for S4PR, a class of generalised Petri nets, that can model well a large class of flexible manufacturing systems (FMS). Siphons in a plant net model are divided into elementary and dependent ones. Deadlock prevention is achieved by adding monitors (control places) to make every elementary Siphon satisfy the maximal controlled-Siphon property. Conditions are developed under which a dependent Siphon is maximally controlled when its elementary Siphons are so. The max-controllability of a dependent Siphon is ensured by properly supervising the control depth variables of its elementary Siphons via linear integer programming techniques. Compared with existing methods, this policy requires a much smaller number of supervisory monitors. Finally, the application of this approach is illustrated by an FMS example.
Charles H Peterson - One of the best experts on this subject based on the ideXlab platform.
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control of foraging behavior of individuals within an ecosystem context the clam macoma balthica and interactions between competition and Siphon cropping
Oecologia, 1994Co-Authors: Gregory A Skilleter, Charles H PetersonAbstract:Macoma balthica (L.) is a common clam of the estuarine seafloor, belonging to an important group of invertebrates possessing the capacity to choose between the two fundamental modes of feeding available, using its Siphon to inhale either suspended food particles from the water or food particles deposited on the sediment surface. Field experiments demonstrate that intraspecific competition, effects of other competing benthic invertebrates, and complex interactions between competition and partial predation (Siphon cropping by fishes) modify the foraging behavior of Macoma. When protected by caging from Siphon nipping by fishes, Macoma demonstrated greater Siphon regeneration at lower density, indicating the importance of competition for limited resources. In the absence of Siphon croppers, these same clams also exhibited more deposit feeding at the lower density either because of improved ability to deposit-feed with longer Siphons or because deposited foods become more rapidly depleted than suspended foods on local spatial scales. Addition of Siphon-nipping fishes caused greater reductions in Siphon size of clams at lower density, presumably because the intensity of nipping per clam was greater where clam targets were fewer and because deposit feeding, which was more intense at lower densities, confers a greater risk of cropping from greater Siphon extension and activity than characterize suspension feeding. Deposit feeding by Macoma was reduced in the presence of Siphon croppers at both high and low density of clams, but the intensity of deposit-feeding activity at low density was substantially higher than predicted by additive effects of clam density and cropping. This suggests operation of a balancing strategy in Macoma whereby it is accepting greater risks of partial predation when rewards of greater food harvest are larger. The surprising failure to adopt a risk-averse stratery may be explained by the non-lethal nature of partial predation, which renders Siphon loss an energetic penalty replacable through regeneration. The presence of a bed of suspension-feeding Rangia cuneata also altered foraging behavior of Macoma by inducing a switch to more intense deposit feeding, in response either to the documented near-bottom depletion of suspended foods or to likely enhanced biodeposition from feces and pseudofeces. The induction of greater deposit feeding by the presence of this competing suspension feeder led to greater Siphon losses during exposure to croppers because Macoma was practicing more risky feeding behavior. This enhanced loss of Siphon tissues to croppers in the presence of the suspension-feeding Rangia induced an interaction between the effects of Siphon croppers and Rangia, such that Macoma exhibited a larger switch away from deposit feeding in the presence of Siphon croppers when Rangia were also present. Clearly, the foraging decisions made by individuals can only be understood in a broad holistic context of population, community, and ecosystem processes.
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control of foraging behavior of individuals within an ecosystem context the clam macoma balthica flow environment and Siphon cropping fishes
Oecologia, 1994Co-Authors: Charles H Peterson, Gregory A SkilleterAbstract:Macoma balthica (L.), an abundant clam, ubiquitous in temperate estuaries across the North Atlantic, is known to practice both alternative basic modes of feeding available to seafloor invertebrates. It either holds its feeding organ, the Siphon, at a fixed position just above the sediment surface to filter out food particles suspended in the overlying water or else extends and moves its Siphon around to vacuum up deposited food particles on the sediment surface. Previous laboratory experiments have established an understanding of the role of current flow in dictating the choice of whether suspension or deposit feeding will be used by marine invertebrates with the facultative flexibility to choose. Faster flows imply greater fluxes of suspended particles so that the energetic rewards of suspension feeding are enhanced. Slower flows imply reduced renewal rates of suspended foods in the bottom boundary layers and enhanced deposition of food particles on the seafloor so that a switch to deposit feeding is favored. Like early optimal foraging theory, this understanding is based on energetic considerations alone without incorporation of broader implications of how population interactions such as predation and competition influence individual foraging behavior. Feeding behavior of Macoma balthica is influenced in the Neuse River estuary by both hydrodynamics and Siphon-cropping by juvenile demersal fishes. Under conditions of identical concentrations of suspended particulates in the water column and organic contents of surface sediments, Macoma exhibited much higher levels of deposit feeding where currents were slower. In addition, exclosure and fish inclosure experiments demonstrated that juvenile demersal fishes influence feeding behavior of Macoma by cropping exposed Siphons and inducing reduction in deposit-feeding activity. Effects of croppers were substantial in early to midsummer, when juvenile fish abundances were greatest in trawl samples from this estuarine nursery and before the growing fish exhibited ontogenetic changes in diet away from early concentration on bivalve Siphons. Field experiments in which Siphon-cropping fish were caged at varying distances off the bottom failed to detect any effective behavioral avoidance by Macoma of cropping in response to proximity of fish. One might have hypothesized that under high risk of cropping, Macoma would switch to suspension feeding and away from deposit feeding, the feeding method entailing more risk of losses to croppers because of greater Siphon activity and greater extension of Siphons on the sediment surface. Consequently, partial predation by Siphon-cropping fishes greatly reduces deposit-feeding activity by Macoma balthica during summer as an apparent direct effect of disfigurement and reduction of Siphons, the organ required for efficient deposit feeding. Information on current flows alone would not suffice to predict feeding behavior of this marine invertebrate: the influence of partial predation must also be included.
Gregory A Skilleter - One of the best experts on this subject based on the ideXlab platform.
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control of foraging behavior of individuals within an ecosystem context the clam macoma balthica and interactions between competition and Siphon cropping
Oecologia, 1994Co-Authors: Gregory A Skilleter, Charles H PetersonAbstract:Macoma balthica (L.) is a common clam of the estuarine seafloor, belonging to an important group of invertebrates possessing the capacity to choose between the two fundamental modes of feeding available, using its Siphon to inhale either suspended food particles from the water or food particles deposited on the sediment surface. Field experiments demonstrate that intraspecific competition, effects of other competing benthic invertebrates, and complex interactions between competition and partial predation (Siphon cropping by fishes) modify the foraging behavior of Macoma. When protected by caging from Siphon nipping by fishes, Macoma demonstrated greater Siphon regeneration at lower density, indicating the importance of competition for limited resources. In the absence of Siphon croppers, these same clams also exhibited more deposit feeding at the lower density either because of improved ability to deposit-feed with longer Siphons or because deposited foods become more rapidly depleted than suspended foods on local spatial scales. Addition of Siphon-nipping fishes caused greater reductions in Siphon size of clams at lower density, presumably because the intensity of nipping per clam was greater where clam targets were fewer and because deposit feeding, which was more intense at lower densities, confers a greater risk of cropping from greater Siphon extension and activity than characterize suspension feeding. Deposit feeding by Macoma was reduced in the presence of Siphon croppers at both high and low density of clams, but the intensity of deposit-feeding activity at low density was substantially higher than predicted by additive effects of clam density and cropping. This suggests operation of a balancing strategy in Macoma whereby it is accepting greater risks of partial predation when rewards of greater food harvest are larger. The surprising failure to adopt a risk-averse stratery may be explained by the non-lethal nature of partial predation, which renders Siphon loss an energetic penalty replacable through regeneration. The presence of a bed of suspension-feeding Rangia cuneata also altered foraging behavior of Macoma by inducing a switch to more intense deposit feeding, in response either to the documented near-bottom depletion of suspended foods or to likely enhanced biodeposition from feces and pseudofeces. The induction of greater deposit feeding by the presence of this competing suspension feeder led to greater Siphon losses during exposure to croppers because Macoma was practicing more risky feeding behavior. This enhanced loss of Siphon tissues to croppers in the presence of the suspension-feeding Rangia induced an interaction between the effects of Siphon croppers and Rangia, such that Macoma exhibited a larger switch away from deposit feeding in the presence of Siphon croppers when Rangia were also present. Clearly, the foraging decisions made by individuals can only be understood in a broad holistic context of population, community, and ecosystem processes.
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control of foraging behavior of individuals within an ecosystem context the clam macoma balthica flow environment and Siphon cropping fishes
Oecologia, 1994Co-Authors: Charles H Peterson, Gregory A SkilleterAbstract:Macoma balthica (L.), an abundant clam, ubiquitous in temperate estuaries across the North Atlantic, is known to practice both alternative basic modes of feeding available to seafloor invertebrates. It either holds its feeding organ, the Siphon, at a fixed position just above the sediment surface to filter out food particles suspended in the overlying water or else extends and moves its Siphon around to vacuum up deposited food particles on the sediment surface. Previous laboratory experiments have established an understanding of the role of current flow in dictating the choice of whether suspension or deposit feeding will be used by marine invertebrates with the facultative flexibility to choose. Faster flows imply greater fluxes of suspended particles so that the energetic rewards of suspension feeding are enhanced. Slower flows imply reduced renewal rates of suspended foods in the bottom boundary layers and enhanced deposition of food particles on the seafloor so that a switch to deposit feeding is favored. Like early optimal foraging theory, this understanding is based on energetic considerations alone without incorporation of broader implications of how population interactions such as predation and competition influence individual foraging behavior. Feeding behavior of Macoma balthica is influenced in the Neuse River estuary by both hydrodynamics and Siphon-cropping by juvenile demersal fishes. Under conditions of identical concentrations of suspended particulates in the water column and organic contents of surface sediments, Macoma exhibited much higher levels of deposit feeding where currents were slower. In addition, exclosure and fish inclosure experiments demonstrated that juvenile demersal fishes influence feeding behavior of Macoma by cropping exposed Siphons and inducing reduction in deposit-feeding activity. Effects of croppers were substantial in early to midsummer, when juvenile fish abundances were greatest in trawl samples from this estuarine nursery and before the growing fish exhibited ontogenetic changes in diet away from early concentration on bivalve Siphons. Field experiments in which Siphon-cropping fish were caged at varying distances off the bottom failed to detect any effective behavioral avoidance by Macoma of cropping in response to proximity of fish. One might have hypothesized that under high risk of cropping, Macoma would switch to suspension feeding and away from deposit feeding, the feeding method entailing more risk of losses to croppers because of greater Siphon activity and greater extension of Siphons on the sediment surface. Consequently, partial predation by Siphon-cropping fishes greatly reduces deposit-feeding activity by Macoma balthica during summer as an apparent direct effect of disfigurement and reduction of Siphons, the organ required for efficient deposit feeding. Information on current flows alone would not suffice to predict feeding behavior of this marine invertebrate: the influence of partial predation must also be included.
