Evaluation of a benchmark on dynamic reliability via Fluid Stochastic Petri Nets

The paper presents the evaluation of a benchmark on dynamic reliability. Such system consists of a tank containing some liquid, two pumps and one valve to renew the liquid in the tank, a heat source warming the liquid, and a controller acting on the state of the components. Three failure conditions are possible: the dry out, the over\ufb02ow or the high temperature of the liquid. Due to the presence of continuous variables, such as the liquid level and temperature, the system is modelled as a Fluid Stochastic Petri Net which is the object of simulation obtaining the unreliability evaluation of the system

Modelling dynamic reliability via Fluid Petri Nets

Combinatorial models for reliability analysis (like fault-trees or block diagram) are static models that cannot include any type of component dependence. In the CTMC (Continuous Time Markov Chain) framework, the transition rates can depend on the state of the system thus allowing the analyst to include some dependencies among components. However, in more general terms, the system reliability may depend on parameters or quantities that vary continuously in time (like temperature, pressure, distance, etc.). Systems whose behavior in time can be described by discrete as well as continuous variables, are called hybrid systems. In the dependability literature, the case in which the reliability characteristics vary continuously versus a process parameter, is sometimes referred to as dynamic reliability [1]. The modelling and analysis of hybrid dynamic systems is an open research area. The present paper discusses the evaluation of a benchmark on dynamic reliability proposed in [1] via a modelling framework called Fluid Stochastic Petri Net (FSPN)

The convergence of the disciplines for stage in high schools

The scientific discoveries gained over the last 70 years now allow us to build a unitary history of the universe that gathers the contributions of many disciplines. These new vision assigns to the Earth Sciences a new and important role to promote the convergence of many disciplines in order to build a unified history of the universe and of man in it. An example of this new role can be found in the Alternanza Scuola-Lavoro ASL (combined experience of study and work). For the Liceo the ASL, is a challenge. It risks becoming another activity that is added to citizenship education, assessment by skills, university orientation. The teachers see this set of activities as an already inadequate subtraction of time. Interesting opportunities are created by engaging students and the whole class council in activities of contextualization of knowledge. Students, with a precise responsibility in a working group, experience some of the typical dynamics of a work situation. From the observation, guided by indicators, and from the evaluation of the products, the teachers can obtain useful indications for inserting the students in the business realities. The Big History Project in Earth\u2019s Science context can be the solution. The students, in groups, study the history of the Universe according, they will have the task of creating a product of their choice. \u201cAvogadro Institute\u201d of Biella has produced videos with Sony Vegas Pro. One has engaged in a History of the Universe in 8 minutes, the other has presented the geological history of Biella. This job could be preparatory to a subsequent ASL in a geopark. In the \u201cA. Banfi\u201d Liceo in Vimercate (MI) it was decided to let the whole class work in the realization of a single product as 30-minute documentary that obtained almost 1500 views on Youtube. An educational trip to the Geological Observatory of Coldigioco has introduced students to the complexity of the geological history of Italy and the international interest it raises. A subsequent inspection in Val d\u2019Ossola, led by the Department of Earth Sciences of the University of Milan, provided the necessary information to relate the remote history of the valley with the recent one. The online attendance of a coding course allowed students to design and implement an application for mobile phones with App Inventor. From the set of evaluative elements such as group work observation tables, the daily report of the progress of the activities on a dedicated platform and the evaluation of the realized products, a profile of the student\u2019s skills can emerge, useful for a subsequent ASL insertion in a company real and also for orientation at the end of high school studies

Analysis of new control applications

This document reports the results of the activities performed during the first year of the CRUTIAL project, within the Work Package 1 "Identification and description of Control System Scenarios". It represents the outcome of the analysis of new control applications in the Power System and the identification of critical control system scenarios to be explored by the CRUTIAL project

Methodologies synthesis

This deliverable deals with the modelling and analysis of interdependencies between critical infrastructures, focussing attention on two interdependent infrastructures studied in the context of CRUTIAL: the electric power infrastructure and the information infrastructures supporting management, control and maintenance functionality. The main objectives are: 1) investigate the main challenges to be addressed for the analysis and modelling of interdependencies, 2) review the modelling methodologies and tools that can be used to address these challenges and support the evaluation of the impact of interdependencies on the dependability and resilience of the service delivered to the users, and 3) present the preliminary directions investigated so far by the CRUTIAL consortium for describing and modelling interdependencies

Solving Dynamic Reliability Problems by means of Ordinary and Fluid Stochastic Petri Nets

A benchmark on dynamic reliability taken from Marseguerra & Zio (1996) is considered; though the behaviour of this system is dynamic and is described by continuous variables, we show that the system is suitable to an analytical solution, instead of simulation. The system consists of a tank containing some liquid whose level is monitored by a controller acting on two pumps and one valve, in order to avoid the liquid dry out or overflow. The reliability evaluation of the system is obtained by resorting to Generalized Stochastic Petri Nets (GSPN) and Fluid Stochastic Petri Nets (FSPN). FSPNs are hybrid models and differ from GSPNs by the presence of both fluid places (modelling continuous variables) and discrete places (containing a discrete number of tokens). GSPNs are used for the analytical solution of the benchmark, while the simulation on the FSPNs, is run with the aim of validating the analytical results

Compiling Dynamic Fault Trees into Dynamic Bayesian Networks: the RADYBAN Tool

In this paper, we present Radyban (Reliability Analysis with DYnamic BAyesian Networks), a software tool which allows to analyze systems modeled by means of Dynamic Fault Trees (DFT), by relying on automatic conversion into Dynamic Bayesian Networks (DBN). The tools aims at providing a familiar interface to reliability engineers, by allowing them to model the system to be analyzed with quite a standard formalism (i.e. DFT) based on specic extensions to the well-known methodology of Fault Trees; however, the tool also implements a modular algorithm for automatically translating a DFT into the corresponding DBN, without any explicit intervention from the end user. In fact, when the computation of specic reliability measures is requested, the tool exploits classical algorithms for the inference on Dynamic Bayesian Networks, in order to compute the requested parameters. This is performed in a totally transparent way to the user, who could in principle be completely unaware of the underlying Bayesian Network. However, the use of DBNs allows the tool to be able to compute measures that are not directly computable from DFTs, but that are naturally obtainable from DBN inference. After having described the basic features of the tool, we show how it operates on a real world example and we compare the unreliability results it generates with those returned by other methodologies, in order to verify the correctness and the consistency of the results obtained