Discrete-time dynamic modeling for software and services composition as an extension of the Markov chain approach

Discrete Time Markov Chains (DTMCs) and Continuous Time Markov Chains (CTMCs) are often used to model various types of phenomena, such as, for example, the behavior of software products. In that case, Markov chains are widely used to describe possible time-varying behavior of “self-adaptive” software systems, where the transition from one state to another represents alternative choices at the software code level, taken according to a certain probability distribution. From a control-theoretical standpoint, some of these probabilities can be interpreted as control signals and others can just be observed. However, the translation between a DTMC or CTMC model and a corresponding first principle model, that can be used to design a control system is not immediate. This paper investigates a possible solution for translating a CTMC model into a dynamic system, with focus on the control of computing systems components. Notice that DTMC models can be translated as well, providing additional information

The Weaker Voice in Asymmetric Alliances. How voice opportunities affect weaker partners' choice for alliance persistence or termination

Diplomatic history provides several examples of weaker allies that take themselves out of military agreements with major powers in charge of guarantying for their security. Unfortunately, alliance theorists have barely been focusing on this empirical puzzle, assuming widely that weaker sides in asymmetric relationships take on a passive attitude. Still, we can find many cases of unsatisfied minor allies that prefer to terminate military agreements instead of continuing to benefit from the stronger side's protection. To solve this puzzle, I argue that the effectiveness of a minor ally\u2019s voice affects its preference for the persistence or termination of an asymmetric alliance

Automating Dynamic Decoupling in Object-Oriented Modelling and Simulation Tools

Abstract This manuscript presents a technique that allows Equationbased Object-Oriented Modelling Tools (EOOMT) to exploit Dynamic Decoupling (DD) for partitioning a complex model into "weakly coupled" submodels. This enhances simulation efficiency, and is naturally keen to parallel integration or co-simulation. After giving an overview of the problem and of related work, we propose a method to automate DD by means of a novel structural analysis of the system -called "cycle analysis" -and of a mixed-mode integration method. Also, some considerations are exposed on how the presented technique can be integrated in EOOMT, considering as representative example a Modelica translator. Simulation tests demonstrate the technique, and the realised implementation is released as free software

Lightweight adaptive filtering for efficient learning and updating of probabilistic models

Adaptive software systems are designed to cope with unpredictable and evolving usage behaviors and environmental conditions. For these systems reasoning mechanisms are needed to drive evolution, which are usually based on models capturing relevant aspects of the running software. The continuous update of these models in evolving environments requires efficient learning procedures, having low overhead and being robust to changes. Most of the available approaches achieve one of these goals at the price of the other. In this paper we propose a lightweight adaptive filter to accurately learn time-varying transition probabilities of discrete time Markov models, which provides robustness to noise and fast adaptation to changes with a very low overhead. A formal stability, unbiasedness and consistency assessment of the learning approach is provided, as well as an experimental comparison with state-of-the-art alternatives

User Behavior Clustering Based Method for EV Charging Forecast

The increasing adoption of electric vehicles poses new problems for the electrical distribution network. For this reason, proper electric vehicle forecasting will be of fundamental importance for a predictive energy management system, which could greatly help the operation of the grid. This paper proposes a comprehensive novel methodology to forecast single charging sessions of electric vehicle and the resulting cumulative energy forecast of the charging infrastructure. Historical charging sessions are first clustered on the basis of similar user characteristics and their respective probability density functions are defined. From this, every charging session is predicted with a triplet of parameters, namely the arrival time, the charging duration and the average power expected during the process. The proposed method has been evaluated by considering a real case study. The results showed the ability to greatly improve the accuracy with respect to the chosen benchmark, both in terms of energy required by the station and the predicted number of charging sessions. The overall performance measured by Skill Score is 0.37 for the year 2019

HOT-SPOT PHENOMENON IN PV SYSTEMS WITH OVERHEAD LINES PARTIAL SHADING

This paper deals with the occurrence of hot-spot phenomenon in photovoltaic systems under PV partial shadowing. In an experimental campaign, the hot-spot phenomenon was revealed on a PV installation in Italy, caused my medium voltage overhead lines shadowing the PV cells. Starting from these practice case studies, at the SolarTech laboratory of Politecnico di Milano, the conditions for hot-spot phenomenon occurrence due to the overhead lines shading the PV cells were reproduced. Two experimental campaigns were carried out to investigate the current-voltage and power-voltage characteristics, and the energy production. In each experimental campaign, the built shadowing structure was considered fixed, and different shadowing conditions were created based on the natural displacement of the sun. Still, for occurring the hot- spot phenomenon during the laboratory tests, more PV modules must be connected in parallel

La moltiplicazione del melo con la tecnica della micropropagazione. Variazione del pH in substrati diversi durante la fase di moltiplicazione

10 páginas, 2 figuras, 5 tablas, 9 referencias.-- Esta revista es continuación de Rivista della Societa Toscana di Orticoltura y continuada por Advances in horticultural science.I numerosi studi condotti in questi ultimi 20 anni sulla applicazione della coltura in vitro a diverse specie coltivate, hanno focalizzato principalmente la messa a punto dei terreni nutritivi, il ruolo dei fitoregolatori nelle diverse fasi di crescita ed il controllo ormonale sulla morfogenesi. Quasi del tutto trascurata, come appare dai lavori riportati in bibliografia, sono state invece le indagini su altri fattori che probabilmente esercitano un ruolo di primo piano sulla crescita e sui processi morfogenetici che avvengono in vitro.Peer reviewe

On consistency of physical and DEVS models in control-targeted DTs: an industrial case study

The DT-based design and control of modern production assets requires simulation models with different viewpoints, purposes, and nature. Most notably, component-level design and control require detailed physical models, while plant-level automation and production management mostly need DEVS-type ones. Inconsistencies among the said models can have significant impacts on decision processes related e.g. to (re-)configuration, diagnostics and maintenance—in one word, on the ultimate outcome of an asset. However, given their heterogeneous nature, making physical and DEVS models consistent requires new methods and tools, in fact starting with the definition itself of what “consistent” has to mean. We here present a methodology to state and address such consistency problems, and support our statements with a case study taken from the cosmetics industry

Characterization of Bifacial Photovoltaic Modules Based on I-V Curves Outdoor Measurement

Photovoltaic (PV) systems are well known for their simplicity of design, environmental friendliness, and low maintenance. Among the PV technologies, the behaviour of bifacial PV modules was studied in this research. Measurements of the I-V curves were carried out in the SolarTechLAB test facility at the Department of Energy of Politecnico di Milano, Italy, to detect the bifacial PV module behaviour, mainly in terms of power performance. In particular, I-V and power-voltage curves were measured at different tilt angles to consider several irradiance and cell temperature levels with both sides uncovered as well as with the back side covered. This last configuration was tested to evaluate the contribution of the rear face in the overall photoelectric conversion process. The comparison between the bifacial and monofacial operations highlighted that the power at the maximum power point of the bifacial operation can increase up to 13%. At the same time, leaving the rear face free allows for reducing the bifacial cell temperature up to about 6°C