30131271
A Simple and Fast Algorithm to Obtain All Invariants of a Generalized Petri Net
After a linear algebraic characterization of the minimal support invariant concept, it is proposed a very efficient algorithm to calculate all the minimal support invariants of Generalised and Capacity Petri Nets.
18072299
Petri nets and flexible manufacturing
The aim of this invited survey is to introduce Computer science/Petri nets specialists to the basic system level issues brought up by the development of Flexible Manufacturing and how Petri nets are used to aid the production engineers in their work. After some terminology concerning production engineering, the hierarchical decision and control level is briefly reviewed. Finally, the role and the presence of nets in CAE (Computer Aided Engineering) and in CAM (Computer Aided Manufacturing) for FMSs (Flexible Manufacturing Systems) are considered. From the design point of view, the use of nets have many advantages in modeling, qualitative analysis, performance evaluation and code generation. From the control of the plant perspective, scheduling on nets models, the coordination of the plant (global and partial) and the presence of nets in the local control level are discussed.
17241799
Basic Server Semantics and Performance Monotonicity of Continuous Petri Nets
Continuous Petri nets were introduced as an approximation to deal with the state explosion problem which can appear in discrete event models. When time is introduced, the flow through a fluidified transition can be defined in many ways. The most used in literature are constant and variable speed (David and Alla, Discrete, continuous and hybrid Petri nets, Springer-Verlag, 2005), which can be seen as some kind of finite and infinite server interpretations of the transitions behavior, and derived from stochastic (discrete) Petri nets (Silva and Recalde, Annu Rev Control 28(2):253–266, 2004). In this paper we will compare the results obtained with both relaxations for the broad class of mono-T-semiflow reducible nets, and prove that, under some frequently true conditions, infinite server semantics offers a throughput which is closer to the throughput of the discrete system in steady state. In the second part, it will be proved that the throughput of mono-T-semiflow reducible net systems is monotone with respect to the speed of the transitions and the initial marking of the net.
9463713
Structure Theory of Equal Conflict Systems
Abstract Equal conflict net systems are a weighted generalisation of the (extended) free choice subclass that keeps the total autonomy of choices. A substantial part of the analytical branch of the structure theory of free choice systems, including decomposition and duality, the rank theorem, characterisations of impartial sequences and prompt interfaces, and the existence of home states, is extended to the equal conflict case. In so doing, several familiar concepts and objects from the structure theory of place/transition net systems are revisited from a linear algebraic perspective, which is specially adequate to cope with weighted nets.
26560925
{SC}*ECS: A Class of Modular and Hierarchical Cooperating Systems
We introduce a new class of Place/Transition net systems, {SC}*ECS, a generalisation of Equal Conflict systems [13] and Deterministic Systems of Sequential Processes [7, 11, 9, 10, 6]. {SC}*ECS are modular and hierarchical by definition: An {SC}*ECS is made up of a set of {SC}*ECS modules that asynchronously communicate through buffers in a restricted way.
29997198
Liveness and Home States in Equal Conflict Systems
Structure theory is a branch of net theory devoted to investigate the relationship between the structure and the behaviour of net models. Many of its powerful results have been derived for some subclasses of ordinary (i.e. all weights one) Place/Transition net systems. Nevertheless, weights may be very convenient to properly model systems with bulk services and arrivals. They can be implemented by means of ordinary subnets, but then the original structure of the net becomes too complex, even in the simplest cases, to be amenable of some interesting structural analysis techniques.
30523521
Correction of Temperature Variations in Kinetic-Based Determinations by Use of Pruning Computational Neural Networks in Conjunction with Genetic Algorithms
The joint use of genetic algorithms and pruning computational neural networks is shown to be an effective means for selecting the number of inputs required to correct temperature variations in kinetic-based determinations. The genetic algorithm uses a pruning procedure based on Bayesian regularization and is highly efficient as a feature selector; it provides quite good results in the generalization process without the need to use a validation set. The fitness function is defined as the sum of two subfunctions: one controls the learning ability of the network and the other its complexity. The training, pruning, and generalization processes were initially tested with simulated data in order to acquire preliminary information for the ensuing work with real data. The performance of the proposed method was assessed by applying it to the determination of the amino acid L-glycine by its classical spectrophotometric reaction with ninhydrin. A straightforward network topology including temperature as input (40+T:2:1 with 19 connections after the pruning process) was used to estimate the L-glycine concentration from kinetic curves affected by temperature variations over the range 60-75 degrees C, using kinetic data acquired up to only 1.5 half-lives. The trained network estimates this concentration with a standard error of prediction for the testing set of ca. 8%, which is much smaller than those provided by a classical parametric method such as nonlinear regression (even if kinetic data acquired at longer half-lives are used). Finally, a kinetic interpretation of the pruning process is provided in order to better demonstrate its potential for kinetic analysis.
800062
Words avoiding repetitions in arithmetic progressions
Carpi constructed an infinite word over a 4-letter alphabet that avoids squares in all subsequences indexed by arithmetic progressions of odd difference. We show a connection between Carpi's construction and the paperfolding words. We extend Carpi's result by constructing uncountably many words that avoid squares in arithmetic progressions of odd difference. We also construct infinite words avoiding overlaps and infinite words avoiding all sufficiently large squares in arithmetic progressions of odd difference. We use these words to construct labelings of the 2-dimensional integer lattice such that any line through the lattice encounters a squarefree (resp. overlapfree) sequence of labels.
15093494
Developing Enterprise Sponsored Virtual Communities: The Case of a SME's Knowledge Community
This paper presents a case in the development of a knowledge community support system in the context of an industrial association group in the construction sector This system is a result of the Know-Construct project which aims at providing association sponsored SME communities of the construction sector with a sophisticated information management platform and community building tools for knowledge sharing The paper begins by characterizing the so-called construction industry knowledge community The Know-Construct system concept and the its general architecture are described, focusing on the semantic resources, in particular the ontologies structure The final part of the paper depicts the approach to the actual introduction of the system in the community An action-research approach was planned to obtain research results regarding the social acceptance of semantic resources such as the ontologies and technical classifications used in system.
34650038
Estimation of Parameters of Kinetic Compartmental Models by Use of Computational Neural Networks
A novel methodological approach to the estimation of parameters involved in multicomponent kinetic determinations from real kinetic data by use of computational or artificial neural networks (ANNs) is proposed. The ANN input data used are also estimates obtained by using the Levenberg−Marquardt method in the form of an approximate nonlinear function that is the sum of the two expressions associated with the pseudo-first-order kinetics of the two mixture components. The performance of the optimized network architecture, 2:4s:2l, was tested at variable rate constant ratios. The reduced dimensions of the network input space obtained using the Kolmogorov−Sprecher theorem result in improved limits of precision in estimating parameters at near-unity rate constant ratios. Experiments with real kinetic data provided a relative standard error of prediction of 2.47% and 4.23% for the two mixture components. These errors are much smaller than those obtained with existing alternative methods, particularly at the low ...
42029640
Computational Neural Networks for Resolving Nonlinear Multicomponent Systems Based on Chemiluminescence Methods
This paper proves that computational neural networks are reliable, effective tools for resolving nonlinear multicomponent systems involving synergistic effects by using chemiluminescence-based methods developed by continuous addition of reagent technique. Computational neural networks (CNNs) were implemented using a preprocessing of data by principal component analysis; the principal components to be used as input to the CNN were selected on the basis of a heuristic method. The leave-one-out method was applied on the basis of theoretical considerations in order to reduce sample size with no detriment to the prediction capacity of the network. The proposed approach was used to resolve trimeprazine/methotrimeprazine mixtures with a classical peroxyoxalate chemiluminescent system, such as the reaction between bis(2,4,6-trichlorophenyl)oxalate and hydrogen peroxide. The optimum network design, 9:5s:2l, allowed the resolution of mixtures of the two analytes in concentration ratios from 1:10 to 10:1 with very s...