Deriving the performance indices in product-form stochastic Petri nets: Open problems and simulation

Stochastic Petri nets are an important formalism used for the performance evaluation of computer and communication systems as well as other fields like bioin-formatics and logistics. Despite its high flexibility and modelling power, one of the problems of quantitative analyses based on stochastic Petri nets is the state space explosion, i.e., the high cardinality reached by the state space of even a structurally small SPN. As a consequence a direct analysis of the Markovian processes underlying the models is not feasible. Product-form Petri nets are a class of stochastic Petri nets whose invariant measure can be expressed as a product of functions, each of which depends only on a marking of a single place. Nevertheless, for the effective computation of the performance indices the computation of the stationary distribution is required. In this paper we propose a classification of product-form stochastic Petri nets based on the availability of algorithms for the computation of their stationary performance indices. Moreover, in case simulation is required, we introduce two stopping criteria that exploit the product-form property of the nets

Identifying the Optimal transmission range in Depth-Based Routing For UWSN

Routing in Underwater Wireless Sensor Networks (UWSNs) is a challenging problem because of the intrinsic characteristics of this class of wireless networks (long propagation delay, mobility of nodes, etc.) and because of the performance indices that must be taken into account, such as the network throughput, the packet delivery ratio and the energy cost. In particular, routing algorithms must grant a low energy cost in order to maximize the lifetime of the network's nodes. In this study, we focus on a popular routing protocol for UWSNs, namely the Depth-Based Routing (DBR). Specially, we study the impact of the transmission range of the nodes on the network performance indices, with particular attention to its energy efficiency. The study is based on an extensive set of simulations performed in AquaSim-NG using a library that has been developed with the aim of providing an accurate estimation of the nodes' energy consumption. The main outcome of our work is showing the relation between transmission range providing the optimal DBR energy efficiency and the density of the nodes in a UWSN

Diagnosis, treatment and prevention of pediatric obesity: consensus position statement of the Italian Society for Pediatric Endocrinology and Diabetology and the Italian Society of Pediatrics

The Italian Consensus Position Statement on Diagnosis, Treatment and Prevention of Obesity in Children and Adolescents integrates and updates the previous guidelines to deliver an evidence based approach to the disease. The following areas were reviewed: (1) obesity definition and causes of secondary obesity; (2) physical and psychosocial comorbidities; (3) treatment and care settings; (4) prevention.The main novelties deriving from the Italian experience lie in the definition, screening of the cardiometabolic and hepatic risk factors and the endorsement of a staged approach to treatment. The evidence based efficacy of behavioral intervention versus pharmacological or surgical treatments is reported. Lastly, the prevention by promoting healthful diet, physical activity, sleep pattern, and environment is strongly recommended since the intrauterine phase

Decomposability for General Markovian Networks

The conditions under which queueing networks with general service times enjoy the property of near complete decomposability are discussed, and the expression is given (in terms of the network topology) of a new condition for network decomposability

Simulation modeling of UML software architectures

Quantitative analysis of software systems is being recognized as an important issue in the software development process. Performance analysis can help to address quantitative system analysis from the early stages of the software development life cycle, e.g., to compare design alternatives or to identify system bottlenecks. Modeling software systems by simulation allows the analyst to represent detailed characteristics of the system. We consider simulation for performance evaluation of software architectures specified by UML. We derive a simulation model for annotated UML software architectures. First we propose the annotation for some UML diagrams to describe performance parameters. Then we derive the simulation model by automatically extracting information about Use Case and Activity Diagrams from the XMI descriptions of UML diagrams. This information is used to build a discrete-event simulation model, which is finally executed. Simulation results are inserted back into the original UML diagrams as tagged values to provide feedback at the software architectural design level