1,721,258 research outputs found
A Strategy for Parallel Simulation of Declarative Object-Oriented Models of Generalized Physical Networks
Full text linkFor several years now, most of the growth of comput-
ing power has been made possible by exploiting paral-
lel CPUs on the same chip; unfortunately, state-of-the-art
software tools for the simulation of declarative, object-
oriented models still generate single-threaded simulation
code, showing an increasingly disappointing performance.
This paper presents a simple strategy for the efficient com-
putation of the right-hand-side of the ordinary differen-
tial equations resulting from the causalization of object-
oriented models, which is often the computational bottle-
neck of the executable simulation code. It is shown how
this strategy can be particularly effective in the case of gen-
eralized physical networks, i.e., system models built by the
connection of components storing certain quantities and of
components describing the flow of such quantities between
them
Efficient Computation of State Derivatives for Multi-Rate Integration of Object-Oriented Models
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Il ruolo della simulazione dinamica nell'ingegneria di processo: stato dell'arte e prospettive
Full text linkLa modalità tradizionale di progetto degli impianti a fluido (ad. es. impianti per l'energia, condizionamento e raffrescamento aziendale, chimico e petrolchimico) si pone normalmente
il problema del sistema di controllo nelle ultime fasi del progetto; spesso, la verifica delle prestazioni dinamiche avviene direttamente sul campo, durante la messa in servizio. In
particolare nel caso di impianti innovativi, questo tipo di procedura non è soddisfacente, perché le possibili criticità sia a livello di processo che di strategie di controllo si evidenziano
quando è ormai troppo tardi per attuare interventi correttivi.
La simulazione dinamica di sistema può accompagnare l'intero arco della progettazione dell'impianto, dal progetto di massima (in cui possibilmente si valutano alternative
progettuali), passando per l'ingegneria di dettaglio, fino alla messa in opera, all'esercizio, e possibilmente al revamping. In questo modo si ha sempre chiaro quali sono le prestazioni attese dell'impianto accoppiato al suo sistema di controllo, ed è possibile ottenere prestazioni ottimali senza sgradite sorprese.
A tale scopo risultano particolarmente adatte le moderne metodologie e strumenti di modellazione e simulazione orientata agli oggetti. Nella memoria vengono riassunte le caratteristiche salienti di tali ambienti, con una panoramica delle attività di ricerca passate, presenti e future presso il Dipartimento di Elettronica e Informazione del Politecnico di Milano
Modeling, simulation, control, and optimization of a geothermal power plant
No full textThe main results of the simulation study of a double-flash geothermal plant, including a steam-CO2 reboiler-based separation process, are presented. Dynamic models of two-phase, H2O-CO2 components are derived, and their use for dynamic simulation and operating point optimization is discussed. Control system issues are then considered. On one hand,
the simulator is used as an aid to design and test standard level and pressure control loops, whose actual performance would otherwise be difficult to predict due to the high degree of interconnection of the plant components. On the other hand, the control concept for the innovative part of the plant is discussed, recognizing that the control problem and the operating point optimization problems have to be tackled simultaneously. A simple, yet effective, solution for this problem is propose
Can the COVID-19 epidemic be controlled on the basis of daily test reports?
Full text linkThis letter studies if and to which extent COVID-19 epidemics can be controlled by authorities taking decisions on public health measures on the basis of daily reports of swab test results, active cases and total cases. A suitably simplified process model is derived to support the controllability analysis, highlighting the presence of very significant time delay; the model is validated with data from several outbreaks. The analysis shows that suppression strategies can be effective if strong enough and enacted early on. It also shows how mitigation strategies can fail because of the combination of delay, unstable dynamics, and uncertainty in the feedback loop; approximate conditions based on the theory of limitation of linear control are given for feedback control to be feasible
On the Formulation of Steady-State Initialization Problems in Object-Oriented Models of Closed Thermo-Hydraulic Systems
Full text linkThe object-oriented formulation of steady-state initialization for models of closed thermo-hydraulic systems yields singular problems; due to system-wide structural issues. The paper proposes how to solve this problem in an object-oriented fashion; by means of an additional component that helps to uniquely determine the initial conditions of the system. A method based on the analysis of the null space of the Jacobian of the initialization problem and on suitable annotations is also proposed to provide the end user with meaningful; high-level; context-relevant diagnostic messages; in case the singular problem arises. This diagnostic method can also be applied to other cases; such as closed systems with constant density fluid and electrical circuits lacking a ground connection
Simulation of Large-Scale Models in Modelica: State of the Art and Future Perspectives
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