Дисертації: "Hybrid systems modeling and verification"

1

Mohammed, Ammar Mohammed [Verfasser]. "Hybrid multi-agent systems: modeling, specification and verification / Ammar Mohammed Mohammed." Koblenz : Universitätsbibliothek Koblenz, 2010. http://d-nb.info/1008134155/34.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

2

Becker, Basil, and Holger Giese. "Cyber-physical systems with dynamic structure : towards modeling and verification of inductive invariants." Universität Potsdam, 2012. http://opus.kobv.de/ubp/volltexte/2012/6243/.

Повний текст джерела

Анотація:

Cyber-physical systems achieve sophisticated system behavior exploring the tight interconnection of physical coupling present in classical engineering systems and information technology based coupling. A particular challenging case are systems where these cyber-physical systems are formed ad hoc according to the specific local topology, the available networking capabilities, and the goals and constraints of the subsystems captured by the information processing part. In this paper we present a formalism that permits to model the sketched class of cyber-physical systems. The ad hoc formation of tightly coupled subsystems of arbitrary size are specified using a UML-based graph transformation system approach. Differential equations are employed to define the resulting tightly coupled behavior. Together, both form hybrid graph transformation systems where the graph transformation rules define the discrete steps where the topology or modes may change, while the differential equations capture the continuous behavior in between such discrete changes. In addition, we demonstrate that automated analysis techniques known for timed graph transformation systems for inductive invariants can be extended to also cover the hybrid case for an expressive case of hybrid models where the formed tightly coupled subsystems are restricted to smaller local networks.
Cyber-physical Systeme erzielen ihr ausgefeiltes Systemverhalten durch die enge Verschränkung von physikalischer Kopplung, wie sie in Systemen der klassichen Igenieurs-Disziplinen vorkommt, und der Kopplung durch Informationstechnologie. Eine besondere Herausforderung stellen in diesem Zusammenhang Systeme dar, die durch die spontane Vernetzung einzelner Cyber-Physical-Systeme entsprechend der lokalen, topologischen Gegebenheiten, verfügbarer Netzwerkfähigkeiten und der Anforderungen und Beschränkungen der Teilsysteme, die durch den informationsverabeitenden Teil vorgegeben sind, entstehen. In diesem Bericht stellen wir einen Formalismus vor, der die Modellierung der eingangs skizzierten Systeme erlaubt. Ein auf UML aufbauender Graph-Transformations-Ansatz wird genutzt, um die spontane Bildung eng kooperierender Teilsysteme beliebiger Größe zu spezifizieren. Differentialgleichungen beschreiben das kombinierte Verhalten auf physikalischer Ebene. In Kombination ergeben diese beiden Formalismen hybride Graph-Transformations-Systeme, in denen die Graph-Transformationen diskrete Schritte und die Differentialgleichungen das kontinuierliche, physikalische Verhalten des Systems beschreiben. Zusätzlich, präsentieren wir die Erweiterung einer automatischen Analysetechnik zur Verifikation induktiver Invarianten, die bereits für zeitbehaftete Systeme bekannt ist, auf den ausdrucksstärkeren Fall der hybriden Modelle.

Стилі APA, Harvard, Vancouver, ISO та ін.

3

Aljarbouh, Ayman. "Accelerated simulation of hybrid systems : method combining static analysis and run-time execution analysis." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S033/document.

Повний текст джерела

Анотація:

Cette thèse apporte quatre principales contributions : une méthode d'éliminateur de phénomènes de ''chattering'' d'automates hybrides, par calcul d'une dynamique régulière équivalente à l'aide d'une convexification de Filippov ; une méthode d'accélération de la simulation de certains comportements Zénon, dits géométriques, pour certains automates hybrides ; des preuves de préservation par les méthodes ci-dessus d'une sémantique des automates hybrides à base d'analyse non-standard ; développement de trois logiciels prototypes, l'un sous la forme d'une bibliothèque Simulink, le second sous la forme d'un environnement de simulation de composants FMI, et le troisième étant une implémentation de la méthode de régularisation dans le langage de modélisation de systèmes hybrides Acumen
This thesis deals with Zeno behavior of hybrid systems, and it has four main contributions : a method of eliminating "chattering" phenomena of hybrid automata, by computing an equivalent dynamics using a new convexification approach ; a method for accelerating the simulation of geometric-Zeno behavior in which the solution converges to a Zeno limit point according to a geometric series ; a proof of preservation by the above methods of a semantics of hybrid automata based on non-standard analysis ; a development of three prototype software, one in the form of a Simulink library, the other in the form of an FMI simulation environment, and the third being an implementation of the regularization method in the Modeling and simulation tool Acumen

Стилі APA, Harvard, Vancouver, ISO та ін.

4

Bujorianu, Manuela-Luminita. "Stochastic hybrid system : modelling and verification." Thesis, University of Stirling, 2005. http://hdl.handle.net/1893/3451.

Повний текст джерела

Анотація:

Hybrid systems now form a classical computational paradigm unifying discrete and continuous system aspects. The modelling, analysis and verification of these systems are very difficult. One way to reduce the complexity of hybrid system models is to consider randomization. The need for stochastic models has actually multiple motivations. Usually, when building models complete information is not available and we have to consider stochastic versions. Moreover, non-determinism and uncertainty are inherent to complex systems. The stochastic approach can be thought of as a way of quantifying non-determinism (by assigning a probability to each possible execution branch) and managing uncertainty. This is built upon to the - now classical - approach in algorithmics that provides polynomial complexity algorithms via randomization. In this thesis we investigate the stochastic hybrid systems, focused on modelling and analysis. We propose a powerful unifying paradigm that combines analytical and formal methods. Its applications vary from air traffic control to communication networks and healthcare systems. The stochastic hybrid system paradigm has an explosive development. This is because of its very powerful expressivity and the great variety of possible applications. Each hybrid system model can be randomized in different ways, giving rise to many classes of stochastic hybrid systems. Moreover, randomization can change profoundly the mathematical properties of discrete and continuous aspects and also can influence their interaction. Beyond the profound foundational and semantics issues, there is the possibility to combine and cross-fertilize techniques from analytic mathematics (like optimization, control, adaptivity, stability, existence and uniqueness of trajectories, sensitivity analysis) and formal methods (like bisimulation, specification, reachability analysis, model checking). These constitute the major motivations of our research. We investigate new models of stochastic hybrid systems and their associated problems. The main difference from the existing approaches is that we do not follow one way (based only on continuous or discrete mathematics), but their cross-fertilization. For stochastic hybrid systems we introduce concepts that have been defined only for discrete transition systems. Then, techniques that have been used in discrete automata now come in a new analytical fashion. This is partly explained by the fact that popular verification methods (like theorem proving) can hardly work even on probabilistic extensions of discrete systems. When the continuous dimension is added, the idea to use continuous mathematics methods for verification purposes comes in a natural way. The concrete contribution of this thesis has four major milestones: 1. A new and a very general model for stochastic hybrid systems; 2. Stochastic reachability for stochastic hybrid systems is introduced together with an approximating method to compute reach set probabilities; 3. Bisimulation for stochastic hybrid systems is introduced and relationship with reachability analysis is investigated. 4. Considering the communication issue, we extend the modelling paradigm.

Стилі APA, Harvard, Vancouver, ISO та ін.

5

Mitra, Sayan. "A verification framework for hybrid systems." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42238.

Повний текст джерела

Анотація:

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.
Includes bibliographical references (p. 193-205) and index.
Combining; discrete state transitions with differential equations, Hybrid system models provide an expressive formalism for describing software systems that interact with a physical environment. Automatically checking properties, such as invariance and stability, is extremely hard for general hybrid models, and therefore current research focuses on models with restricted expressive power. In this thesis we take a complementary approach by developing proof techniques that are not necessarily automatic, but are applicable to a general class of hybrid systems. Three components of this thesis, namely, (i) semantics for ordinary and probabilistic hybrid models, (ii) methods for proving invariance, stability, and abstraction, and (iii) software tools supporting (i) and (ii), are integrated within a common mathematical framework. (i) For specifying nonprobabilistic hybrid models, we present Structured Hybrid I/O Automata (SHIOAs) which adds control theory-inspired structures, namely state models, to the existing Hybrid I/O Automata, thereby facilitating description of continuous behavior. We introduce a generalization of SHIOAs which allows both nondeterministic and stochastic transitions and develop the trace-based semantics for this framework. (ii) We present two techniques for establishing lower-bounds on average dwell time (ADT) for SHIOA models. This provides a sufficient condition of establishing stability for SHIOAs with stable state models. A new simulation-based technique which is sound for proving ADT-equivalence of SHIOAs is proposed. We develop notions of approximate implementation and corresponding proof techniques for Probabilistic I/O Automata. Specifically, a PIOA A is an E-approximate implementation of B, if every trace distribution of A is c-close to some trace distribution of B-closeness being measured by a metric on the space of trace distributions.
(cont.) We present a new class of real-valued simulation functions for proving c-approximate implementations, and demonstrate their utility in quantitatively reasoning about probabilistic safety and termination. (iii) We introduce a specification language for SHIOAs and a theorem prover interface for this language. The latter consists of a translator to typed high order logic and a set of PVS-strategies that partially automate the above verification techniques within the PVS theorem prover.
by Sayan Mitra.
Ph.D.

Стилі APA, Harvard, Vancouver, ISO та ін.

6

Livadas, Carolos. "Formal verification of safety-critical hybrid systems." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/42817.

Повний текст джерела

Анотація:

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.
Includes bibliographical references (p. 181-185).
This thesis investigates how the formal modeling and verification techniques of computer science can be used for the analysis of hybrid systems [7,14,22,37] - systems involving both discrete and continuous behavior. The motivation behind such research lies in the inherent similarity of the hierarchical and decentralized control strategies of hybrid systems and the communication and operation protocols used for distributed systems in computer science. As a case study, the thesis focuses on the development of techniques that use hybrid I/O automata [29,30] to model and analyze automated vehicle transportation systems and, in particular, their various protection subsystems - control systems that are used to ensure that the physical plant at hand does not violate its various safety requirements. The thesis is split into two major parts. In the first part, we develop an abstract model of a physical plant and its various protection subsystems - also referred to as protectors. The specialization of this abstract model results in the specification of a particular automated transportation system. Moreover, the proof of correctness of the abstract model leads to simple correctness proofs of the protector implementations for particular specializations of the abstract model. In this framework, the composition of independent protectors is straightforward - their composition guarantees the conjunction of the safety properties guaranteed by the individual protectors. In fact, it is shown that under certain conditions composition holds for dependent protectors also. In the second part, we specialize the aforementioned abstract model to simplified versions of the personal rapid transit system (PRT 200TM) under development at Raytheon Corporation. We examine overspeed and collision protection for a set of vehicles traveling on straight tracks, on binary merges, and on a directed graph of tracks involving binary merges and diverges. In each case, the protectors sample the state of the physical plant and take protective actions to guarantee that the physical plant does not reach hazardous states. The proofs of correctness of such protectors involve specializing the abstract protector to the physical plant at hand and proving that the suggested protector implementations are correct. This is done by defining simulations among the states of the protector implementations and their abstract counterparts.
by Carolos Livadas.
M.Eng.

Стилі APA, Harvard, Vancouver, ISO та ін.

7

Denman, William. "Automated verification of continuous and hybrid dynamical systems." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708809.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

8

Savicks, Vitaly. "Integrating formal verification and simulation of hybrid systems." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/400280/.

Повний текст джерела

Анотація:

An increasing number of today's systems can be characterised as cyber-physical, or hybrid systems that combine the concurrent continuous environment and discrete computational logic. In order to develop such systems as safe and reliable one needs to be able to model and verify them from the early stages of the development process. Current modelling technologies allow us to specify the abstractions of these systems in terms of the procedural or declarative modelling languages and visual notations, and to simulate their behaviour over a period of time for analysis. Other means of modelling are formal methods, which define systems in terms of logics and enable rigorous analysis of system properties. While the first class of technologies provides a natural notation for describing physical processes, but lacks the formal proof, the second class relies on mathematical abstractions to rationalise and automate the complex task of formal verification. The benefits of both technologies can be significantly enhanced by a collaborative methodology. Due to the complexity of the considered systems and the formal proof process it is critical that such a methodology is based on a top-down development process that fully supports abstraction and refinement. We develop this idea into a tool extension for the state of the art Rodin platform for system-level formal modelling and analysis in the Event-B language. The developed tool enables integration of the physical simulation with refinement-based formal verification in Event-B, thus enhancing the capabilities of Rodin with the simulation-based validation that supports refinement. The tool utilises the Functional Mock-up Interface (FMI) standard for industrial-grade model exchange and co-simulation and is based on a co-simulation principle between the discrete models in Event-B and continuous physical models of FMI. It provides a graphical environment for model import, composition and co-simulation, and implements a generic simulation algorithm for discrete-continuous co-simulation.

Стилі APA, Harvard, Vancouver, ISO та ін.

9

Carroll, Simon A. "Strategies for Improving Verification Techniques for Hybrid Systems." Case Western Reserve University School of Graduate Studies / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=case1212713593.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

10

Carter, Rebekah. "Verification of liveness properties on hybrid dynamical systems." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/verification-of-liveness-properties-on-hybrid-dynamical-systems(8817319c-a63f-4cf3-927d-a2ddf69139b4).html.

Повний текст джерела

Анотація:

A hybrid dynamical system is a mathematical model for a part of the real world where discrete and continuous parts interact with each other. Typically such systems are complex, and it is difficult to know how they will behave for general parameters and initial conditions. However, the method of formal verification gives us the ability to prove automatically that certain behaviour does or does not happen for a range of parameters in a system. The challenge is then to define suitable methods for proving properties on hybrid systems.This thesis looks at using formal verification for proving liveness properties on hybrid systems: a liveness property says that something good eventually happens in the system. This work presents the theoretical background and practical application of various methods for proving and disproving inevitability properties (a type of liveness) in different classes of hybrid systems. The methods combine knowledge of dynamical behaviour of a system with the brute-force approach of model checking, in order to make the most of the benefits of both sides. The work on proving liveness properties is based on abstraction of dynamical systems to timed automata. This thesis explores the limits of a pre-defined abstraction method, adds some dynamical knowledge to the method, and shows that this improvement makes liveness properties provable in certain continuous dynamical systems. The limits are then pushed further to see how this method can be used for piecewise-continuous dynamical systems. The resulting algorithms are implemented for both classes of systems.In order to disprove liveness properties in hybrid systems a novel framework is proposed, using a new property called deadness. Deadness is a dynamically-aware property of the hybrid system which, if true, disproves the liveness property by means of a finite execution: we usually require an infinite execution to disprove a liveness property. An algorithm is proposed which uses dynamical properties of hybrid systems to derive deadness properties automatically, and the implementation of this algorithm is discussed and applied to a simplified model of an oilwell drillstring.

Стилі APA, Harvard, Vancouver, ISO та ін.

11

Mover, Sergio. "Verification of Hybrid Systems using Satisfiability Modulo Theories." Doctoral thesis, Università degli studi di Trento, 2014. https://hdl.handle.net/11572/368887.

Повний текст джерела

Анотація:

Embedded systems are formed by hardware and software components that interact with the physical environment and thus may be modeled as Hybrid Systems. Due to the complexity the system,there is an increasing need of automatic techniques to support the design phase, ensuring that a system behaves as expected in all the possible operating conditions.In this thesis, we propose novel techniques for the verification and the validation of hybrid systems using Satisfiability Modulo Theories (SMT). SMT is an established technique that has been used successfully in many verification approaches, targeted for both hardware and software systems. The use of SMT to verify hybrid systems has been limited, due to the restricted support of complex continuous dynamics and the lack of scalability. The contribution of the thesis is twofold. First, we propose novel encoding techniques, which widen the applicability and improve the effectiveness of the SMT-based approaches. Second, we propose novel SMT-based algorithms that improve the performance of the existing state of the art approaches. In particular we show algorithms to solve problems such as invariant verification, scenario verification and parameter synthesis. The algorithms fully exploit the underlying structure of a network of hybrid systems and the functionalities of modern SMT-solvers. We show and discuss the effectiveness of the the proposed techniques when applied to benchmarks from the hybrid systems domain.

Стилі APA, Harvard, Vancouver, ISO та ін.

12

Schrammel, Peter. "Logico-Numerical Verification Methods for Discrete and Hybrid Systems." Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENM082/document.

Повний текст джерела

Анотація:

Cette thèse étudie la vérification automatique de propriétés de sûreté de systèmes logico-numériques discrets ou hybrides. Ce sont des systèmes ayant des variables booléennes et numériques et des comportements discrets et continus. Notre approche est fondée sur l'analyse statique par interprétation abstraite. Nous adressons les problèmes suivants : les méthodes d'interprétation abstraite numériques exigent l'énumération des états booléens, et par conséquent, ils souffrent du probléme d'explosion d'espace d'états. En outre, il y a une perte de précision due à l'utilisation d'un opérateur d'élargissement afin de garantir la terminaison de l'analyse. Par ailleurs, nous voulons rendre les méthodes d'interprétation abstraite accessibles à des langages de simulation hybrides. Dans cette thèse, nous généralisons d'abord l'accélération abstraite, une méthode qui améliore la précision des invariants numériques inférés. Ensuite, nous montrons comment étendre l'accélération abstraite et l'itération de max-stratégies à des programmes logico-numériques, ce qui aide à améliorer le compromis entre l'efficacité et la précision. En ce qui concerne les systèmes hybrides, nous traduisons le langage de programmation synchrone et hybride Zelus vers les automates hybrides logico-numériques, et nous étendons les méthodes d'analyse logico-numérique aux systèmes hybrides. Enfin, nous avons mis en oeuvre les méthodes proposées dans un outil nommé ReaVer et nous fournissons des résultats expérimentaux. En conclusion, cette thèse propose une approche unifiée à la vérification de systèmes logico-numériques discrets et hybrides fondée sur l'interprétation abstraite qui est capable d'intégrer des méthodes d'interprétation abstraite numériques sophistiquées tout en améliorant le compromis entre l'efficacité et la précision
This thesis studies the automatic verification of safety properties of logico-numerical discrete and hybrid systems. These systems have Boolean and numerical variables and exhibit discrete and continuous behavior. Our approach is based on static analysis using abstract interpretation. We address the following issues: Numerical abstract interpretation methods require the enumeration of the Boolean states, and hence, they suffer from the state space explosion problem. Moreover, there is a precision loss due to widening operators used to guarantee termination of the analysis. Furthermore, we want to make abstract interpretation-based analysis methods accessible to simulation languages for hybrid systems. In this thesis, we first generalize abstract acceleration, a method that improves the precision of the inferred numerical invariants. Then, we show how to extend abstract acceleration and max-strategy iteration to logico-numerical programs while improving the trade-off between efficiency and precision. Concerning hybrid systems, we translate the Zelus hybrid synchronous programming language to logico-numerical hybrid automata and extend logico-numerical analysis methods to hybrid systems. Finally, we implemented the proposed methods in ReaVer, a REActive System VERification tool, and provide experimental results. Concluding, this thesis proposes a unified approach to the verification of discrete and hybrid logico-numerical systems based on abstract interpretation, which is capable of integrating sophisticated numerical abstract interpretation methods while successfully trading precision for efficiency

Стилі APA, Harvard, Vancouver, ISO та ін.

13

Peters, Karsten. "Hybrid systems modeling manufacturing and front dynamics." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=971895147.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

14

Segala, Roberto. "Modeling and verification of randomized distributed real-time systems." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36560.

Повний текст джерела

Анотація:

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.
Includes bibliographical references (p. 267-274) and index.
by Roberto Segala.
Ph.D.

Стилі APA, Harvard, Vancouver, ISO та ін.

15

Alouffi, Bader. "Run time verifcation of hybrid systems." Thesis, De Montfort University, 2016. http://hdl.handle.net/2086/12490.

Повний текст джерела

Анотація:

The growing use of computers in modern control systems has led to the develop- ment of complex dynamic systems known as hybrid systems, which integrates both discrete and continuous systems. Given that hybrid systems are systems that operates in real time allowing for changes in continuous state over time periods, and discrete state changes across zero time, their modelling, analysis and verification becomes very difficult. The formal verifications of such systems based on specifications that can guar- antee their behaviour is very important especially as it pertains to safety critical applications. Accordingly, addressing such verifications issues are important and is the focus of this thesis. In this thesis, in order to actualise the specification and verification of hybrid systems, Interval Temporal Logic(ITL) was adopted as the underlying formalism given its inherent characteristics of providing methods that are flexible for both propositional and first-order reasoning regarding periods found in hardware and software system’s descriptions. Given that an interval specifies the behaviour of a system, specifications of such systems are therefore represented as a set of intervals that can be used to gain an understanding of the possible behaviour of the system in terms of its composition whether in sequential or parallel form. ITL is a powerful tool that can handle both forms of composition given that it offers very strong and extensive proof and specification techniques to decipher essential system properties including safety, liveliness and time projections. However, a limitation of ITL is that the intervals within its framework are considered to be a sequence of discrete states. Against this back- drop, the current research provides an extension to ITL with the view to deal with verification and other related issues that centres around hybrid systems. The novelty within this new proposition is new logic termed SPLINE Interval Temporal Logic (SPITL) in which not only a discrete behaviour can be expressed, but also a continuous behaviour can be represented in the form of a spline i.e. the interval is considered to be a sequence of continuous phases instead of a sequence of discrete states. The syntax and semantics of the newly developed SPITL are provided in this thesis and the new extension of the interval temporal logic using a hybrid system as a case study. The overall framework adopted for the overall structure of SPITL is based on three fundamental steps namely the formal specification of hybrid systems is expressed in SPLINE Interval Temporal Logic, followed by the executable subset of ITL, called Tempura, which is used to develop and test a hybrid system specification that is written in SPITL and finally a runtime verification tool for ITL called AnaTempura which is linked with Matlab in order to use them as an integrated tool for the verification of hybrid systems specification. Overall, the current work contributes to the growing body of knowledge in hybrid systems based on the following three major milestones namely: i. the proposition of a new logic termed SPITL; ii. executable subset, Tempura, integrated with SPITL specification for hybrid systems; and iii. the development of a tool termed Ana Tempura which is integrated with Matlab to ensure accurate runtime verification of results.

Стилі APA, Harvard, Vancouver, ISO та ін.

16

Siu, Daniel. "Stochastic Hybrid Dynamic Systems: Modeling, Estimation and Simulation." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4405.

Повний текст джерела

Анотація:

Stochastic hybrid dynamic systems that incorporate both continuous and discrete dynamics have been an area of great interest over the recent years. In view of applications, stochastic hybrid dynamic systems have been employed to diverse fields of studies, such as communication networks, air traffic management, and insurance risk models. The aim of the present study is to investigate properties of some classes of stochastic hybrid dynamic systems. The class of stochastic hybrid dynamic systems investigated has random jumps driven by a non-homogeneous Poisson process and deterministic jumps triggered by hitting the boundary. Its real-valued continuous dynamic between jumps is described by stochastic differential equations of the It\^o-Doob type. Existing results of piecewise deterministic models are extended to obtain the infinitesimal generator of the stochastic hybrid dynamic systems through a martingale approach. Based on results of the infinitesimal generator, some stochastic stability results are derived. The infinitesimal generator and stochastic stability results can be used to compute the higher moments of the solution process and find a bound of the solution. Next, the study focuses on a class of multidimensional stochastic hybrid dynamic systems. The continuous dynamic of the systems under investigation is described by a linear non-homogeneous systems of It\^o-Doob type of stochastic differential equations with switching coefficients. The switching takes place at random jump times which are governed by a non-homogeneous Poisson process. Closed form solutions of the stochastic hybrid dynamic systems are obtained. Two important special cases for the above systems are the geometric Brownian motion process with jumps and the Ornstein-Uhlenbeck process with jumps. Based on the closed form solutions, the probability distributions of the solution processes for these two special cases are derived. The derivation employs the use of the modal matrix and transformations. In addition, the parameter estimation problem for the one-dimensional cases of the geometric Brownian motion and Ornstein-Uhlenbeck processes with jumps are investigated. Through some existing and modified methods, the estimation procedure is presented by first estimating the parameters of the discrete dynamic and subsequently examining the continuous dynamic piecewisely. Finally, some simulated stochastic hybrid dynamic processes are presented to illustrate the aforementioned parameter-estimation methods. One simulated insurance example is given to demonstrate the use of the estimation and simulation techniques to obtain some desired quantities.

Стилі APA, Harvard, Vancouver, ISO та ін.

17

Branicky, Michael Stephen. "Studies in hybrid systems : modeling, analysis, and control." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11398.

Повний текст джерела

Анотація:

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.
Includes bibliographical references (p. 183-192) and index.
by Michael Stephen Branicky.
Sc.D.

Стилі APA, Harvard, Vancouver, ISO та ін.

18

Khlifi, Oussama [Verfasser]. "Modeling and formal verification of probabilistic reconfigurable systems / Oussama Khlifi." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2020. http://d-nb.info/1221129384/34.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

19

Soulat, Romain. "Synthesis of correct-by-design schedulers for hybrid systems." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2014. http://tel.archives-ouvertes.fr/tel-01062337.

Повний текст джерела

Анотація:

In this thesis, we are interested in designing schedulers for hybrid systems. We consider two specific subclasses of hybrid systems, real-time systems where tasks are competing for the access to common resources, and sampled switched systems where a choice has to be made on dynamics of the system to reach goals. Scheduling consists in defining the order in which the tasks will be run on the processors in order to complete all the tasks before a given deadline. In the first part of this thesis, we are interested in the scheduling of periodic tasks on multiprocessor architectures. We are especially interested in the robustness of schedulers, i.e., to prove that some values of the system parameters can be modified, and until what value they can be extended while preserving the scheduling order and meeting the deadlines. The Inverse Method can be used to prove the robustness of parametric timed systems. In this thesis, we introduce a state space reduction technique which allows us to treat challenging case studies such as one provided by Astrium EADS for the launcher Ariane 6. We also present how an extension of the Inverse Method, the Behavioral Cartography, can solve the problem of schedulability, i.e., finding the area in the parametric space in which there exists a scheduler that satisfies all the deadlines. We compare this approach to an analytic method to illustrate the interest of our approach In the second part of this thesis, we are interested in the control of affine switched systems. These systems are governed by a finite family of affine differential equations. At each time step, a controller can choose which dynamics will govern the system for the next time step. Controlling in this sense can be seen as a scheduling on the order of dynamics the system will have to use. The objective for the controller can be to make the system stay in a given area of the state space (stability) or to reach a given region of the state space (reachability). In this thesis, we propose a novel approach that computes a scheduler where the strategy is uniform for dense subsets of the state space. Moreover, our approach only uses forward computation, which is better suited than backward computation for contractive systems. We show that our designed controllers, systems evolve to a limit cyclic behavior. We apply our method to several case studies from the literature and on a real-life prototype of a multilevel voltage converter. Moreover, we show that our approach can be extended to systems with perturbations and non-linear dynamics.

Стилі APA, Harvard, Vancouver, ISO та ін.

20

Gokgoz, Nurgul. "Development Of Tools For Modeling Hybrid Systems With Memory." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12610003/index.pdf.

Повний текст джерела

Анотація:

Regulatory processes and history dependent behavior appear in many dynamical systems in nature and technology. For modeling regulatory processes, hybrid systems offer several advances. From this point of view, to observe the capability of hybrid systems in a history dependent system is a strong motivation. In this thesis, we developed functional hybrid systems which exhibit memory dependent behavior such that the dynamics of the system is determined by both the location of the state vector and the memory. This property was explained by various examples. We used the hybrid system with memory in modeling the gene regulatory network of human immune response to Influenza A virus infection. We investigated the sensitivity of the piecewise linear model with memory. We introduced how the model can be developed in future.

Стилі APA, Harvard, Vancouver, ISO та ін.

21

Farag, Wael. "Synthesis of intelligent hybrid systems for modeling and control." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0013/NQ30606.pdf.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

22

Jamroga, Wojciech [Verfasser]. "Modeling, verification, and strategic reasoning in multi-agent systems / Jamroga Wojciech." Clausthal-Zellerfeld : Universitätsbibliothek Clausthal, 2010. http://d-nb.info/1004774389/34.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

23

Sogokon, Andrew. "Direct methods for deductive verification of temporal properties in continuous dynamical systems." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/20952.

Повний текст джерела

Анотація:

This thesis is concerned with the problem of formal verification of correctness specifications for continuous and hybrid dynamical systems. Our main focus will be on developing and automating general proof principles for temporal properties of systems described by non-linear ordinary differential equations (ODEs) under evolution constraints. The proof methods we consider will work directly with the differential equations and will not rely on the explicit knowledge of solutions, which are in practice rarely available. Our ultimate goal is to increase the scope of formal deductive verification tools for hybrid system designs. We give a comprehensive survey and comparison of available methods for checking set invariance in continuous systems, which provides a foundation for safety verification using inductive invariants. Building on this, we present a technique for constructing discrete abstractions of continuous systems in which spurious transitions between discrete states are entirely eliminated, thereby extending previous work. We develop a method for automatically generating inductive invariants for continuous systems by efficiently extracting reachable sets from their discrete abstractions. To reason about liveness properties in ODEs, we introduce a new proof principle that extends and generalizes methods that have been reported previously and is highly amenable to use as a rule of inference in a deductive verification calculus for hybrid systems. We will conclude with a summary of our contributions and directions for future work.

Стилі APA, Harvard, Vancouver, ISO та ін.

24

Adimoolam, Santosh Arvind. "A Calculus of Complex Zonotopes for Invariance and Stability Verification of Hybrid Systems." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAM027/document.

Повний текст джерела

Анотація:

Le calcul des ensembles atteignables est une approche de facto utilisée dans de nombreuses méthodes de vérification formelles pour les systèmes hybrides. Mais le calcul exact de l'ensemble atteignable est un problème insurmontable pour de nombreux types de systèmes hybrides, soit en raison de l'indécidabilité ou de la complexité de calcul élevée. Alternativement, beaucoup de recherches ont été axées sur l'utilisation de représentations d'ensembles qui peuvent être manipulées efficacement pour calculer une surestimation suffisamment précise de l'ensemble atteignable. Les zonotopes sont une représentation utile de l'ensemble dans l'analyse de l'accessibilité en raison de leur fermeture et de leur faible complexité pour le calcul de la transformation linéaire et des opérations sommaires de Minkowski. Mais pour approximer les ensembles de temps non bornés atteignables par des invariants positifs, les zonotopes ont l'inconvénient suivant. L'efficacité d'une représentation d'ensemble pour calculer un invariant positif dépend de l'encodage efficace des directions de convergence des états vers un équilibre. Dans un système hybride affine, certaines des directions de convergence peuvent être codées par les vecteurs propres à valeur complexe des matrices de transformation. Mais la représentation zonotopique ne peut pas exploiter la structure propre complexe des matrices de transformation car elle n'a que des générateurs à valeur réelle.Par conséquent, nous étendons les zonotopes réels au domaine de valeur complexe d'une manière qui peut capturer la contraction le long de vecteurs évalués complexes. Cela donne une nouvelle représentation d'ensemble appelée zonotope complexe. Géométriquement, les zonotopes complexes représentent une classe plus large d'ensembles qui comprennent des ensembles non polytopiques ainsi que des zonotopes polytopiques. Ils conservent le mérite des zonotopes réels que nous pouvons effectuer efficacement la transformation linéaire et les opérations sommaires de Minkowski et calculer la fonction de support. De plus, nous montrons qu'ils peuvent capturer la contraction le long de vecteurs propres complexes. De plus, nous développons des approximations traitables par calcul pour la vérification d'inclusion et l'intersection avec des demi-espaces. En utilisant ces opérations sur des zonotopes complexes, nous développons des programmes convexes pour vérifier les propriétés d'invariance linéaire des systèmes hybrides affines à temps discret et la stabilité exponentielle des systèmes impulsifs linéaires. Nos expériences sur certains exemples de benchmarks démontrent l'efficacité des techniques de vérification basées sur des zonotopes complexes
Computing reachable sets is a de facto approach used in many formal verification methods for hybrid systems. But exact computation of the reachable set is an in- tractable problem for many kinds of hybrid systems, either due to undecidability or high computational complexity. Alternatively, quite a lot of research has been focused on using set representations that can be efficiently manipulated to com- pute sufficiently accurate over-approximation of the reachable set. Zonotopes are a useful set representation in reachability analysis because of their closure and low complexity for computing linear transformation and Minkowski sum operations. But for approximating the unbounded time reachable sets by positive invariants, zonotopes have the following drawback. The effectiveness of a set representation for computing a positive invariant depends on efficiently encoding the directions for convergence of the states to an equilibrium. In an affine hybrid system, some of the directions for convergence can be encoded by the complex valued eigen- vectors of the transformation matrices. But the zonotope representation can not exploit the complex eigenstructure of the transformation matrices because it only has real valued generators.Therefore, we extend real zonotopes to the complex valued domain in a way that can capture contraction along complex valued vectors. This yields a new set representation called complex zonotope. Geometrically, complex zonotopes repre- sent a wider class of sets that include some non-polytopic sets as well as polytopic zonotopes. They retain the merit of real zonotopes that we can efficiently perform linear transformation and Minkowski sum operations and compute the support function. Additionally, we show that they can capture contraction along complex valued eigenvectors. Furthermore, we develop computationally tractable approx- imations for inclusion-checking and intersection with half-spaces. Using these set operations on complex zonotopes, we develop convex programs to verify lin- ear invariance properties of discrete time affine hybrid systems and exponential stability of linear impulsive systems. Our experiments on some benchmark exam- ples demonstrate the efficiency of the verification techniques based on complex zonotopes

Стилі APA, Harvard, Vancouver, ISO та ін.

25

Corner, Sebastien Marc. "Modeling, Sensitivity Analysis, and Optimization of Hybrid, Constrained Mechanical Systems." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/82713.

Повний текст джерела

Анотація:

This dissertation provides a complete mathematical framework to compute the sensitivities with respect to system parameters for any second order hybrid Ordinary Differential Equation (ODE) and rank 1 and 3 Differential Algebraic Equation (DAE) systems. The hybrid system is characterized by discontinuities in the velocity state variables due to an impulsive forces at the time of event. At the time of event, such system may also exhibit a change in the equations of motion or in the kinematic constraints. The analytical methodology that solves the sensitivities for hybrid systems is structured based on jumping conditions for both, the velocity state variables and the sensitivities matrix. The proposed analytical approach is then benchmarked against a known numerical method. The mathematical framework is extended to compute sensitivities of the states of the model and of the general cost functionals with respect to model parameters for both, unconstrained and constrained, hybrid mechanical systems. This dissertation emphasizes the penalty formulation for modeling constrained mechanical systems since this formalism has the advantage that it incorporates the kinematic constraints inside the equation of motion, thus easing the numerical integration, works well with redundant constraints, and avoids kinematic bifurcations. In addition, this dissertation provides a unified mathematical framework for performing the direct and the adjoint sensitivity analysis for general hybrid systems associated with general cost functions. The mathematical framework computes the jump sensitivity matrix of the direct sensitivities which is found by computing the Jacobian of the jump conditions with respect to sensitivities right before the event. The main idea is then to obtain the transpose of the jump sensitivity matrix to compute the jump conditions for the adjoint sensitivities. Finally, the methodology developed obtains the sensitivity matrix of cost functions with respect to parameters for general hybrid ODE systems. Such matrix is a key result for design analysis as it provides the parameters that affect the given cost functions the most. Such results could be applied to gradient based algorithms, control optimization, implicit time integration methods, deep learning, etc.
Ph. D.

Стилі APA, Harvard, Vancouver, ISO та ін.

26

Cortés, Luis Alejandro. "A Petri Net based Modeling and Verification Technique for Real-Time Embedded Systems." Licentiate thesis, Linköping University, Linköping University, ESLAB - Embedded Systems Laboratory, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-5751.

Повний текст джерела

Анотація:

Embedded systems are used in a wide spectrum of applications ranging from home appliances and mobile devices to medical equipment and vehicle controllers. They are typically characterized by their real-time behavior and many of them must fulfill strict requirements on reliability and correctness.

In this thesis, we concentrate on aspects related to modeling and formal verification of realtime embedded systems.

First, we define a formal model of computation for real-time embedded systems based on Petri nets. Our model can capture important features of such systems and allows their representations at different levels of granularity. Our modeling formalism has a welldefined semantics so that it supports a precise representation of the system, the use of formal methods to verify its correctness, and the automation of different tasks along the design process.

Second, we propose an approach to the problem of formal verification of real-time embedded systems represented in our modeling formalism. We make use of model checking to prove whether certain properties, expressed as temporal logic formulas, hold with respect to the system model. We introduce a systematic procedure to translate our model into timed automata so that it is possible to use available model checking ools. Various examples, including a realistic industrial case, demonstrate the feasibility of our approach on practical applications.

Стилі APA, Harvard, Vancouver, ISO та ін.

27

Patti, Alessandro. "Molecular Modeling of Self-Assembling Hybrid Materials." Doctoral thesis, Universitat Rovira i Virgili, 2007. http://hdl.handle.net/10803/8551.

Повний текст джерела

Анотація:

Los surfactantes son moléculas anfifílicas, con una cabeza solvofílica y una cola solvofóbica. Cuando la concentración de surfactante en solución es suficientemente alta, las moléculas se agregan entre ellas para proteger las partes solvofóbicas del contacto con el medio. Tales agregados pueden tener forma y tamaño muy diferentes, dependiendo del surfactante y de las condiciones del sistema. La auto-organización de los surfactantes (self-assembly), debida a un compromiso energético y entrópico de su estructura molecular, es la clave que permite observar cristales líquidos muy ordenados. En presencia de un precursor inorgánico y dependiendo de las interacciones que este precursor establece con el surfactante, se puede observar la formación del material híbrido. Los materiales híbridos constituyen un paso intermedio fundamental para la síntesis de los materiales mesoporosos ordenados, los cuales se obtienen eliminando la matriz orgánica (surfactante) del substrato inorgánico.
El presente estudio tiene como principal objetivo estudiar bajo cuales condiciones los sistemas formados por un surfactante, un precursor inorgánico y un solvente, se auto-organizan para dar lugar a estructuras híbridas muy ordenadas. En particular nos proponemos individuar cuales son las características más importantes que los precursores inorgánicos deberían tener para poder observar la formación de materiales mesoporosos ordenados.
Simulaciones Monte Carlo en el colectivo canónico han sido utilizadas para analizar la agregación de los surfactantes en estructuras complejas, como micelas, cilindros organizados en forma hexagonal, o laminas, a partir de configuraciones totalmente desordenadas. Con particular interés hemos analizado el rango de condiciones que llevan a la formación de las estructuras cilíndricas, y estas mismas estructuras han sido comparadas en función de algunas importantes características morfológicas, como el tamaño de poro, el grosor de las paredes, la presencia y accesibilidad de los grupos funcionales en los poros. El modelo usado representa las moléculas de surfactante y de precursor inorgánico como cadenas de segmentos en una red tridimensional que discretiza el espacio en sitios de volumen unitario. Este modelo no entra en el detalle de las características físicas y químicas de las moléculas, pero permite reproducir su agregación en estructuras complejas en un tiempo de cálculo muy razonable. La separación de fase ha sido también evaluada recorriendo a una teoría de campo medio, la quasi-chemical theory, que, aunque no pueda predecir la formación de estructuras ordenadas, ha sido muy útil para confirmar los resultados de las simulaciones, sobretodo cuando no se observa formación de fases ordenadas.
El estudio de surfactantes distintos, uno modelado por una cadena lineal y otro con una cabeza ramificada, nos ha permitido evaluar algunas diferencias estructurales de los materiales obtenidos. La ramificación de la cabeza, que merecería un estudio más profundo del que hemos descrito en este trabajo, ha evidenciado unas interesantes consecuencias en el tamaño de los poros. Este mismo surfactante con cabeza ramificada ha sido elegido para la síntesis de agregados cilíndricos utilizados como templates en la formación, agregación, y condensación de una capa de sílica modelada a través de un modelo atomístico. En particular, hemos aislado uno de los cilindros presentes en los cristales líquidos de estructura hexagonal, y a su alrededor hemos simulado la formación de una capa de sílica utilizando un modelo atomístico. De esta forma, hemos obtenido un poro típico de una estructura mesoporosa más realista, sin necesidad de asumir una forma mas o menos cilíndrica del template, por ser este generado de la auto-agregación del surfactante.
Surfactants are amphiphilic molecules with a solvophilic head and a solvophobic tail. When the surfactant concentration in a given solution is high enough, the molecules aggregate between them to shield the solvophobic part from the contact with the solvent. Such aggregates can show very different sizes and shapes, according to the surfactant and the conditions of the system. The surfactants self-assembly, being due to an energetic and entropic compromise of their molecular structure, is fundamental to observe the formation of very ordered liquid crystals. In the presence of an inorganic precursor and depending on the interactions established between such a precursor and the surfactant, it is possible to synthesize a hybrid material. Hybrid materials are the key step for the formation of periodic ordered mesoporous materials, which can be obtained by eliminating the organic soft matter (the surfactants) from the inorganic framework. Periodic ordered mesoporous materials represent an important family of porous materials as they find a large number of applications in several industrial fields, such as separations, catalysis, sensors, etc. In the last decade, the range of potential applications has increased with the possibility of functionalizing the pore walls by incorporating organic groups during the synthesis, or with post-synthesis treatments.
In this work, we are interested in studying the formation of ordered materials when hybrid organic-inorganic precursors are used. Lattice Monte Carlo simulations in the NVT ensemble have been used to study the equilibrium phase behavior and the synthesis of self-assembling ordered mesoporous materials formed by an organic template with amphiphilic properties and an inorganic precursor in a model solvent. Three classes of inorganic precursors have been modeled: terminal (R-Si-(OEt)3) and bridging ((EtO)3-Si-R-Si-(OEt)3)) organosilica precursors (OSPs), along with pure silica precursors (Si-(OEt)4). Each class has been studied by analyzing its solubility in the solvent and the solvophobicity of the inorganic group.
At high surfactant concentrations, periodic ordered structures, such as hexagonally-ordered cylinders or lamellas, can be obtained depending on the OSPs used. In particular, ordered structures were obtained in a wider range of conditions when bridging hydrophilic OSPs have been used, because a higher surfactant concentration was reached in the phase where the material was formed. Terminal and bridging OSPs produced ordered structures only when the organic group is solvophilic. In this case, a partial solubility between the precursor and the solvent or a lower temperature favored the formation of ordered phases.
With particular interest, we have analyzed the range of conditions leaving to the formation of cylindrical structures, which have been evaluated according to the pore size distribution, the pore wall thickness, the distribution and the accessibility of the functional organic groups around the pores. The phase behavior has been also evaluated by applying the quasi-chemical theory, which cannot predict the formation of ordered structures, but was very useful to confirm the results of simulations, especially when no ordered structures were observed.
The study of the phase and aggregation behavior of two different surfactants, one modeled by a linear chain of head segments and the other modeled by a branched-head, permitted us to evaluate some structural differences of the materials obtained.

Стилі APA, Harvard, Vancouver, ISO та ін.

28

Assar, Rodrigo. "Modeling and simulation of Hybrid Systems and Cell factory applications." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2011. http://tel.archives-ouvertes.fr/tel-00635273.

Повний текст джерела

Анотація:

Les Fonctions biologiques sont le résultat de l'interaction de beaucoup de processus, avec differents objectives, complexités, niveaux d'hiérarchie, et changements de conditions que modi ent le comportement de systèmes. Nous utilisons des équations diferenciales ou dynamiques plus générales, et Stochastic Systèmes de Transition pour décrire la dynamique de changements des modèles. La composition, réconciliation et reutilisation des modèles nous permettent d'obtenir des descriptions de systèmes biologiques complètes et compatibles et leur combiner. Notre spéci cation de Systèmes Hybrides avec BioRica assures l'intégrité de modèles, et implement notre approche. Nous appliquons notre approche pour décrire in-silico deux systèmes: la dynamique de la fermentation du vin, et des décisions cellulaires associées à la formation de tissu d'os.

Стилі APA, Harvard, Vancouver, ISO та ін.

29

Assar, Cuevas Rodrigo. "Modeling and simulation of hybrid systems and cell factory applications." Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14335/document.

Повний текст джерела

Анотація:

Les fonctions biologiques sont le résultat de l'interaction de beaucoup de processus, avec différents objectifs, complexités, niveaux de hiérarchie, et changements de conditions que modifient le comportement de systèmes. Nous utilisons des équations différentielles ou dynamiques plus générales, et systèmes stochastiques de transition pour décrire la dynamique de changements des modèles. La composition, réconciliation et réutilisation des modèles nous permettent d'obtenir des descriptions de systèmes biologiques complètes et compatibles et leur combiner. Notre spécification de systèmes hybrides avec BioRica assure l'intégrité de modèles, et implémente notre approche. Nous appliquons notre approche pour décrire in-silico deux systèmes: la dynamique de la fermentation du vin, et des décisions cellulaires associées à la formation de tissu d'os
The main aim of this thesis is to develop an approach that allows us to describe biological systems with theoretical sustenance and good results in practice. Biological functions are the result of the interaction of many processes, that connect different hierarchy levels going from macroscopic to microscopic level. Each process works in different way, with its own goal, complexity and hierarchy level. In addition, it is common to observe that changes in the conditions, such as nutrients or environment, modify the behavior of the systems. So, to describe the behavior of a biological system over time, it is convenient to combine different types of models: continuous models for gradual changes, discrete models for instantaneous changes, deterministic models for completely predictable behaviors, and stochastic or non- deterministic models to describe behaviors with imprecise or incomplete information. In this thesis we use the theory of Composition and Hybrid Systems as basis, and the BioRica framework as tool to model biological systems and analyze their emergent properties in silico.With respect to Hybrid Systems, we considered continuous models given by sets of differential equations or more general dynamics. We used Stochastic Transition Systems to describe the dynamics of model changes, allowing cofficient switches that control the parameters of the continuous model, and strong switches that choose different models. Composition, reconciliation and reusing of models allow us to build complete and consistent descriptions of complex biological systems by combining them. Compositions of hybrid systems are hybrid systems, and the refinement of a model forming part of a composed system results in a refinement of the composed system. To implement our approach ideas we complemented the theory of our approach with the improving of the BioRica framework. We contributed to do that giving a BioRica specification of Hybrid Systems that assures integrity of models, allowing composition, reconciliation, and reuse of models with SBML specification.We applied our approach to describe two systems: wine fermentation kinetics, and cell fate decisions leading to bone and fat formation. In the case of wine fermentation, we reused known models that describe the responses of yeasts cells to different temperatures, quantities of resources and toxins, and we reconciled these models choosing the model with best adjustment to experimental data depending on the initial conditions and fermentation variable. The resulting model can be applied to avoid process problems as stuck and sluggish fermentations. With respect to cell fate decisions the idea is very ambitious. By using accurate models to predict the bone and fat formation in response to activation of pathways such as the Wnt pathway, and changes of conditions affecting these functions such as increments in Homocysteine, one can analyze the responses to treatments for osteoporosis and other bone mass disorders. We think that here we are giving a first step to obtain in silico evaluations of medical treatments before testing them in vitro or in vivo

Стилі APA, Harvard, Vancouver, ISO та ін.

30

Bagnato, Alessandra. "Modeling and verification in model-based software engineering : application to embedded systems." Thesis, Evry, Institut national des télécommunications, 2013. http://www.theses.fr/2013TELE0004.

Повний текст джерела

Анотація:

Les systèmes embarqués, y compris les dispositifs, l’intergiciel et le logiciel pour la création de sous-systèmes intelligents capables de gérer le contrôle d’appareils électroniques, font de plus en plus partie de nos vies quotidiennes : ils sont intégrés dans des infrastructures de base, (par exemple dans la gestion des routes et des chemins de fer) et sont désormais utilisés en tant que technologies-clés par des millions d'applications logicielles chaque jour. En outre, l'évolution rapide et continue des systèmes embarqués modernes a provoqué de nouveaux défis. Par exemple, la conception des processus complexes qui causent des retards dans le temps de commercialisation et la conséquente augmentation des coûts globaux. Ces systèmes sont plus enclins aux erreurs et par conséquence il devient prioritaire de fournir aux concepteurs des outils effectifs et efficaces pour les aider à surmonter les difficultés liées à la conception des systèmes globales, pour la vérification et pour la validation. Cette thèse est la définition et le développement d'une méthodologie de modélisation basée sur le profil de MARTE et sur le profil de SysML dans un contexte avionique, et orientée à la réutilisation des composantes logicielles et à leur vérification. Cette thèse vise à discuter et illustrer aussi l'efficacité d’une stratégie basée sur la combinaison d’UML, MARTE (Modeling and Analysis of Real Type and Embedded Systems) et des langages SysML sur des étapes différentes de la modélisation d'un système embarqué
Embedded Systems, including devices, middleware and software for the creation of intelligent sub-systems able of monitoring and controlling appliances, are more and more part of our world everyday lives; they are included in the basic infrastructure of society such as roads and railways and are key technologies used by millions of people every day. Moreover the continuous rapid evolution of modern embedded systems has given rise to new challenges: such as increasingly complex design processes that cause delays in time to market and cause escalation of overall design costs. Additionally, these systems are more prone to containing errors, and it becomes more relevant to provide designers with effective tools to aid them in overcoming the difficulties related to the overall system design, verification and validation. This thesis contributes to the definition and to the development of a model based methodology grounded on the OMG’s MARTE profile (Modeling and Analysis of Real Type and Embedded Systems) and on SysML profile to model requirements targeting an avionic case study, with a particular attention to the reuse of the modelled components and to the benefits of their verification. This thesis aims at discussing and illustrating the effectiveness of using a combination of UML, MARTE and SysML languages at the different steps of the embedded system modelling efforts and to provide within this thesis a set of methodological guidelines/steps and an approach to create design model, stores and verify them

Стилі APA, Harvard, Vancouver, ISO та ін.

31

Fippo, Fitime Louis. "Modélisation hybride, analyse et vérification quantitative des grands réseaux de régulation biologique." Thesis, Ecole centrale de Nantes, 2016. http://www.theses.fr/2016ECDN0016.

Повний текст джерела

Анотація:

Les Réseaux de Régulation biologique (RRB) sont couramment utilisés en biologie des systèmes pour modéliser, comprendre et contrôler les dynamiques des différentes fonctions biologiques (différenciation, synthèse protéique, apoptose) au sein des cellules. Ces réseaux sont enrichis des données expérimentales de plus en plus nombreuses et disponibles qui renseignent sur les dynamiques des composants des RRB. L’analyse formelle de tels modèles se heurte rapidement à l’explosion combinatoire des comportements engendrés malgré le fait que les RRB offrent une représentation abstraite des systèmes biologiques. Cette thèse traite de la modélisation hybride, de la simulation, de la vérification formelle et du contrôle des grands Réseaux de Régulation Biologique. Cette modélisation est effectuée grâce aux réseaux d’automates stochastiques, puis aux Frappes de Processus qui en sont une restriction, en intégrant des données de séries temporelles. En premier lieu, cette thèse propose un raffinement des dynamiques par l’estimation des paramètres stochastiques et temporels (délais) à partir des données de séries temporelles et l’intégration de ces paramètres dans les modèles en réseaux d’automates. Cette intégration permet de paramétrer les transitions entre les états du système. Puis, une analyse statistique des traces des simulations stochastiques est proposée afin de comparer les dynamiques des simulations à celles des données expérimentales. En deuxième lieu, cette thèse développe une analyse statique par interprétation abstraite dans les réseaux d’automates permettant des approximations inférieures et supérieures très efficaces des propriétés d’accessibilité d’un point de vue quantitatif (probabilité et délai). Cette analyse permet de faire apparaître des composants critiques pour la satisfaction de ces propriétés. Enfin, tirant avantage des analyses statiques développées pour l’accessibilité dans les réseaux d’automates, et de la puissance de la programmation logique (ASP), cette thèse aborde le domaine du contrôle des systèmes en proposant l’identification des transitions de bifurcation. Les bifurcations sont des transitions après lesquelles le système ne peut plus atteindre un état précédemment accessible
Biological Regulatory Networks (BRNs) are usually used in systems biology for modelling, understanding and controlling the dynamics of different biological functions (differentiation, proliferation, proteins synthesis, apoptose) inside cells. Those networks are enhanced with experimental data that are nowadays more available which give an idea on the dynamics of BRNs components. Formal analysis of such models fails in front of the combinatorial explosion of generated behaviours despite the fact that BRNs provide abstract representation of biological systems. This thesis handles hybrid modelling, the simulation, the formal verification and control of Large Biological Regulatory Networks. This modelling is done thanks to stochastic automata networks, thereafter to Process Hitting by integrating time-series data. Firstly, this thesis proposes a refining of the dynamics by estimation of stochastic and temporal (delay) parameters from time-series data and integration of those parameters in automata networks models. This integration allows the parametrisation of the transitions between the states of the system. Then, a statistical analysis of the traces of the stochastic simulation is proposed to compare the dynamics of simulations with the experimental data. Secondly, this thesis develops static analysis by abstract interpretation in the automata networks allowing efficient under- and over-approximation of quantitative (probability and delay) reachability properties. This analysis enables to highlight the critical components to satisfy these properties. Finally, taking advantage from the previous developed static analyses for the reachability properties in the qualitative point of view, and from the power of logic programming (Answer Set Programming), this thesis addresses the domain of control of system by proposing the identification of bifurcation transitions. Bifurcations are transitions after which the system can no longer reach a state that was previously reachable

Стилі APA, Harvard, Vancouver, ISO та ін.

32

Wu, Jialiang. "Hybrid modeling and analysis of multiscale biochemical reaction networks." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/47723.

Повний текст джерела

Анотація:

This dissertation addresses the development of integrative modeling strategies capable of combining deterministic and stochastic, discrete and continuous, as well as multi-scale features. The first set of studies combines the purely deterministic modeling methodology of Biochemical Systems Theory (BST) with a hybrid approach, using Functional Petri Nets, which permits the account of discrete features or events, stochasticity, and different types of delays. The efficiency and significance of this combination is demonstrated with several examples, including generic biochemical networks with feedback controls, gene regulatory modules, and dopamine based neuronal signal transduction. A study expanding the use of stochasticity toward systems with small numbers of molecules proposes a rather general strategy for converting a deterministic process model into a corresponding stochastic model. The strategy characterizes the mathematical connection between a stochastic framework and the deterministic analog. The deterministic framework is assumed to be a generalized mass action system and the stochastic analogue is in the format of the chemical master equation. The analysis identifies situations where internal noise affecting the system needs to be taken into account for a valid conversion from a deterministic to a stochastic model. The conversion procedure is illustrated with several representative examples, including elemental reactions, Michaelis-Menten enzyme kinetics, a genetic regulatory motif, and stochastic focusing. The last study establishes two novel, particle-based methods to simulate biochemical diffusion-reaction systems within crowded environments. These simulation methods effectively simulate and quantify crowding effects, including reduced reaction volumes, reduced diffusion rates, and reduced accessibility between potentially reacting particles. The proposed methods account for fractal-like kinetics, where the reaction rate depends on the local concentrations of the molecules undergoing the reaction. Rooted in an agent based modeling framework, this aspect of the methods offers the capacity to address sophisticated intracellular spatial effects, such as macromolecular crowding, active transport along cytoskeleton structures, and reactions on heterogeneous surfaces, as well as in porous media. Taken together, the work in this dissertation successfully developed theories and simulation methods which extend the deterministic, continuous framework of Biochemical Systems Theory to allow the account of delays, stochasticity, discrete features or events, and spatial effects for the modeling of biological systems, which are hybrid and multiscale by nature.

Стилі APA, Harvard, Vancouver, ISO та ін.

33

Bhattacharyya, Siddhartha. "HIERARCHICAL HYBRID-MODEL BASED DESIGN, VERIFICATION, SIMULATION, AND SYNTHESIS OF MISSION CONTROL FOR AUTONOMOUS UNDERWATER VEHICLES." UKnowledge, 2005. http://uknowledge.uky.edu/gradschool_diss/344.

Повний текст джерела

Анотація:

The objective of modeling, verification, and synthesis of hierarchical hybrid mission control for underwater vehicle is to (i) propose a hierarchical architecture for mission control for an autonomous system, (ii) develop extended hybrid state machine models for the mission control, (iii) use these models to verify for logical correctness, (iv) check the feasibility of a simulation software to model the mission executed by an autonomous underwater vehicle (AUV) (v) perform synthesis of high-level mission coordinators for coordinating lower-level mission controllers in accordance with the given mission, and (vi) suggest further design changes for improvement. The dissertation describes a hierarchical architecture in which mission level controllers based on hybrid systems theory have been, and are being developed using a hybrid systems design tool that allows graphical design, iterative redesign, and code generation for rapid deployment onto the target platform. The goal is to support current and future autonomous underwater vehicle (AUV) programs to meet evolving requirements and capabilities. While the tool facilitates rapid redesign and deployment, it is crucial to include safety and performance verification into each step of the (re)design process. To this end, the modeling of the hierarchical hybrid mission controller is formalized to facilitate the use of available tools and newly developed methods for formal verification of safety and performance specifications. A hierarchical hybrid architecture for mission control of autonomous systems with application to AUVs is proposed and a theoretical framework for the models that make up the architecture is outlined. An underwater vehicle like any other autonomous system is a hybrid system, as the dynamics of the vehicle as well as its vehicle level control is continuous whereas the mission level control is discrete, making the overall system a hybrid system i.e., one possessing both continuous and discrete states. The hybrid state machine models of the mission controller modules is derived from their implementation done using TEJA, a software for representing hybrid systems with support for auto code generation. The verification of their logical correctness properties has been done using UPPAAL, a software tool for verification of timed automata a special kind of hybrid system. A Teja to Uppaal converter, called dem2xml, has been created at Applied Reserarch Lab that converts a hybrid (timed) autonomous system description in Teja to an Uppaal system description. Verification work involved developing abstract models for the lower level vehicle controllers with which the mission controller modules interact and follow a hierarchical approach: Assuming the correctness of level-zero or vehicle controllers, we establish the correctness of level-one mission controller modules, and then the correctness of level-two modules, etc. The goal of verification is to show that any valid meaning for a mission formalized in our research verifies the safe and correct execution of actions. Simulation of the sequence of actions executed for each of the operations give a better view of the combined working of the mission coordinators and the low level controllers. So we next looked into the feasibility of simulating the operations executed during a mission. A Perl program has been developed to convert the UPPAAL files in .xml format to OpenGL graphic files. The graphic files simulate the steps involved in the execution of a sequence of operations executed by an AUV. The highest level coordinators send mission orders to be executed by the lower level controllers. So a more generalized design of the highest level controllers would help to incorporate the execution of a variety of missions for a vast field of applications. Initially, we consider manually synthesized mission coordinator modules. Later we design automated synthesis of coordinators. This method synthesizes mission coordinators which coordinate the lower level controllers for the execution of the missions ordered and can be used for any autonomous system.

Стилі APA, Harvard, Vancouver, ISO та ін.

34

Greenhut, Andrew David. "Modeling and analysis of hybrid geothermal-solar thermal energy conversion systems." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/58087.

Повний текст джерела

Анотація:

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, February 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 116-118).
Innovative solar-geothermal hybrid energy conversion systems were developed for low enthalpy geothermal resources augmented with solar energy. The goal is to find cost-effective hybrid power cycles that take advantage of the potential synergies of solar thermal and geothermal resources. One aspect is to determine the hybrid configuration that yields the highest annualized electricity generation. The levelized cost of electricity (LCOE) is estimated using equipment costing rules of thumb developed from Aspen HTFS and Aspen ICARUS software and from other sources. Detailed models for the hybrid solar-geothermal system were developed using Aspen Plus and Aspen Dynamics. Turbine flexibility relative to vapor flow rate, temperature and pressure variations was analyzed. In one scenario, a parametric steady-state study was carried out to examine the performance over the range of conditions resulting from diurnal and seasonal variations. The results of the diurnal and seasonal parametric studies were grossly weighted to approximate a typical year in Nevada, and these results led to an estimate of the annualized electricity generation. In another scenario, a dynamic model was selected from possible "greenfield" hybrid systems and used to examine the transient performance for a typical January day and a typical July day in Nevada. The dynamic model approximates the thermal inertial of the heat exchangers and the working fluids in the exchangers, solar collectors, piping and storage tanks. The dynamic model is driven with forcing functions for solar input and ambient temperature to approximate the typical winter and summer days.
(cont.) In all cases, solar energy was found to come at a higher cost per kW capacity than geothermal when the cost of geothermal wells was not considered. However, including well costs had an effect of evening out the levelized cost of electricity. Model complexity increased as more solar heat was added to existing geothermal systems, which suggests that moving a higher exergy heat source down to a lower exergy heat source is difficult, especially given the transient nature of the solar resource. The models developed in this thesis demonstrate the design decisions and complex dynamic behavior inherent in this type of hybrid system.
by Andrew David Greenhut.
S.M.

Стилі APA, Harvard, Vancouver, ISO та ін.

35

Ajib, Balsam. "Data-driven building thermal modeling using system identification for hybrid systems." Thesis, Ecole nationale supérieure Mines-Télécom Lille Douai, 2018. http://www.theses.fr/2018MTLD0006/document.

Повний текст джерела

Анотація:

Le secteur du bâtiment est un consommateur énergétique majeur, par conséquent, un cadre d’actions a été décidé au niveau international dans le but de limiter son impact. Afin de mettre en œuvre ces mesures, il est nécessaire d’avoir à disposition des modèles offrants une description fiable du comportement thermique des bâtiments. A cet effet, cette thèse propose l’application d’une nouvelle technique guidée par les données pour la modélisation thermique des bâtiments en se basant sur l’approche des systèmes hybrides, caractérisés par des dynamiques continues et événementielles. Ce choix est motivé par le fait qu’un bâtiment est un système complexe caractérisé par des phénomènes non-linéaires et l’apparition de différents événements. On utilise les modèles affines par morceaux ou PWARX pour l’identification de systèmes hybrides. C’est une collection de sous-modèles affines représentant chacun une configuration caractérisée par une dynamique particulière. Le manuscrit commence par un état de l’art sur les principales techniques de modélisation thermique des bâtiments. Ensuite, le choix d’une approche hybride est motivé par une interprétation mathématique basée sur les équations d’un circuit thermique. Ceci est suivi par une brève présentation des modèles hybrides et une description détaillée de la méthodologie utilisée. On montre ensuite comment utiliser la technique SVM pour classifier les nouvelles données. Enfin, l’intégration des modèles PWARX dans une boucle de contrôle hybride afin d’estimer le gain en performance énergétique d’un bâtiment après rénovation est présentée. La méthodologie est validée en utilisant des données issues de cas d’études variés
The building sector is a major energy consumer, therefore, a framework of actions has been decided on by countries worldwide to limit its impact. For implementing such actions, the availability of models providing an accurate description of the thermal behavior of buildings is essential. For this purpose, this thesis proposes the application of a new data-driven technique for modeling the thermal behavior of buildings based on a hybrid system approach. Hybrid systems exhibit both continuous and discrete dynamics. This choice is motivated by the fact that a building is a complex system characterized by nonlinear phenomena and the occurrence of different events. We use a PieceWise AutoRegressive eXogeneous inputs (PWARX) model for the identification of hybrid systems. It is a collection of sub-models where each sub-model is an ARX equation representing a certain configuration in the building characterized by its own dynamics. This thesis starts with a state-of-the-art on building thermal modeling. Then, the choice of a hybrid system approach is motivated by a mathematical interpretation based on the equations derived from an RC thermal circuit of a building zone. This is followed by a brief background about hybrid system identification and a detailed description of the PWARX methodology. For the prediction phase, it is shown how to use the Support Vector Machine (SVM) technique to classify new data to the right sub-model. Then, it is shown how to integrate these models in a hybrid control loop to estimate the gain in the energy performance for a building after insulation work. The performance of the proposed technique is validated using data collected from various test cases

Стилі APA, Harvard, Vancouver, ISO та ін.

36

Mashaba, Kobamelo. "Modeling, Control and Optimisation of Hybrid Systems in a Manufacturing Setting." Thesis, Curtin University, 2020. http://hdl.handle.net/20.500.11937/80113.

Повний текст джерела

Анотація:

This study comprises a body of work that investigates the performance of hybrid manufacturing systems. And we have provided a valuable insight into the development of the optimisation techniques for hybrid manufacturing system. With the primary objective of developing prac-tical mathematical algorithms that balance trade-o? cost between product quality and completion time. For sta-bility criterion, a sliding mode control was deployed.

Стилі APA, Harvard, Vancouver, ISO та ін.

37

Samuel, Durair Raj Kingsly Jebakumar. "Modeling, Control and Prototyping of Alternative Energy Storage Systems for Hybrid Vehicles." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1331140529.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

38

Xie, Gaoyan. "Fundamental studies on a decompositional and hybrid approach to automatic verification of component-based systems." Online access for everyone, 2005. http://www.dissertations.wsu.edu/Dissertations/Summer2005/g%5Fxie%5F072205.pdf.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

39

Friedel, Vincent. "MODELING AND SIMULATION OF A HYBRID WIND-DIESEL MICROGRID." Thesis, KTH, Elektriska energisystem, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-119251.

Повний текст джерела

Анотація:

Some communities in remote locations with high wind velocities and an unreliable utility supply, will typically install small diesel powered generators and wind generators to form a microgrid. Over the past few years, microgrid projects have been developed in many parts of the world, and commercial solutions have started to appear. Such systems face specific design issues, especially when the wind penetration is high enough to affect the operation of the diesel plant. The dynamic behavior of a medium penetration hybrid microgrid is investigated. It consists of a diesel generator set, a wind-generator and several loads. The diesel engine drives a 62.5 kVA synchronous generator with excitation control. The fixed-speed wind turbine drives a 60 kW cage rotor induction generator. The microgrid can be connected to the utility grid but can also run as an isolated system. The total load of the microgrid is about 100 kVA which varies during the day, and consists of static and dynamic loads, including an induction motor. The excitation controller and speed controller for the diesel’s synchronous generator are designed, as well as the power control of the wind turbine, and the controller for capacitor banks and dump load. The system is modeled and simulated using PSCAD. The study evaluates how the power generation is shared between the diesel generator set and the wind generator, the voltage regulation during load connections, and discusses the need of battery energy storage, the system ride- through-fault capability and frequency control, particularly at times when the utility is disconnected and the microgrid is run as an independent isolated power system. The results of several case studies are presented.

Стилі APA, Harvard, Vancouver, ISO та ін.

40

Ellis, Joshua Randolph. "Modeling, Dynamics, and Control of Tethered Satellite Systems." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/26456.

Повний текст джерела

Анотація:

Tethered satellite systems (TSS) can be utilized for a wide range of space-based applications, such as satellite formation control and propellantless orbital maneuvering by means of momentum transfer and electrodynamic thrusting. A TSS is a complicated physical system operating in a continuously varying physical environment, so most research on TSS dynamics and control makes use of simplified system models to make predictions about the behavior of the system. In spite of this fact, little effort is ever made to validate the predictions made by these simplified models. In an ideal situation, experimental data would be used to validate the predictions made by simplified TSS models. Unfortunately, adequate experimental data on TSS dynamics and control is not readily available at this time, so some other means of validation must be employed. In this work, we present a validation procedure based on the creation of a top-level computational model, the predictions of which are used in place of experimental data. The validity of all predictions made by lower-level computational models is assessed by comparing them to predictions made by the top-level computational model. In addition to the proposed validation procedure, a top-level TSS computational model is developed and rigorously verified. A lower-level TSS model is used to study the dynamics of the tether in a spinning TSS. Floquet theory is used to show that the lower-level model predicts that the pendular motion and transverse elastic vibrations of the tether are unstable for certain in-plane spin rates and system mass properties. Approximate solutions for the out-of-plane pendular motion are also derived for the case of high in-plane spin rates. The lower-level system model is also used to derive control laws for the pendular motion of the tether. Several different nonlinear control design techniques are used to derive the control laws, including methods that can account for the effects of dynamics not accounted for by the lower-level model. All of the results obtained using the lower-level system model are compared to predictions made by the top-level computational model to assess their validity and applicability to an actual TSS.
Ph. D.

Стилі APA, Harvard, Vancouver, ISO та ін.

41

Zhang, Jiafeng [Verfasser], and Georg [Akademischer Betreuer] Frey. "Modeling and verification of reconfigurable discrete event control systems / Jiafeng Zhang. Betreuer: Georg Frey." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2015. http://d-nb.info/1080521577/34.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

42

Ahmad, Manzoor. "Modeling and verification of functional and non functional requirements of ambient, self adaptative systems." Phd thesis, Université Toulouse le Mirail - Toulouse II, 2013. http://tel.archives-ouvertes.fr/tel-00965934.

Повний текст джерела

Анотація:

The overall contribution of this thesis is to propose an integrated approach for modeling and verifying the requirements of Self Adaptive Systems using Model Driven Engineering techniques. Model Driven Engineering is primarily concerned with reducing the gap between problem and software implementation domains through the use of technologies that support systematic transformation of problem level abstractions to software implementations. By using these techniques, we have bridged this gap through the use of models that describe complex systems at multiple levels of abstraction and through automated support for transforming and analyzing these models. We take requirements as input and divide it into Functional and Non Functional Requirements. We then use a process to identify those requirements that are adaptable and those that cannot be changed. We then introduce the concepts of Goal Oriented Requirements Engineering for modeling the requirements of Self Adaptive Systems, where Non Functional Requirements are expressed in the form of goals which is much more rich and complete in defining relations between requirements. We have identified some problems in the conventional methods of requirements modeling and properties verification using existing techniques, which do not take into account the adaptability features associated with Self Adaptive Systems. Our proposed approach takes into account these adaptable requirements and we provide various tools and processes that we developed for the requirements modeling and verification of Self Adaptive Systems. We validate our proposed approach by applying it on two different case studies in the domain of Self Adaptive Systems.

Стилі APA, Harvard, Vancouver, ISO та ін.

43

Fenning, David P. "Retrograde melting in transition metal-silicon systems : thermodynamic modeling, experimental verification, and potential application." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/62530.

Повний текст джерела

Анотація:

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 97-103).
A theoretical framework is presented in this work for retrograde melting in silicon driven by the retrograde solubility of low-concentration metallic solutes at temperatures above the binary eutectic. High enthalpy of formation of point defects in silicon leads to retrograde solubility for a number of solutes, including many 3d transition metals. The Ni-Si system is used to demonstrate that in silicon under supersaturated conditions, such solutes precipitate out into liquid droplets. Synchrotron-based Xray Absorption Microspectroscopy measurements provide experimental confirmation of such phase transitions and the underlying thermodynamics. Finally, the potential for using retrograde melting to improve the electronic minority carrier lifetime of low quality silicon solar cell materials is considered.
by David P. Fenning.
S.M.

Стилі APA, Harvard, Vancouver, ISO та ін.

44

Wang, Caisheng. "Modeling and Control of Hybrid Wind/Photovoltaic/Fuel Cell Distributed Generation Systems." Thesis, Montana State University, 2006. http://etd.lib.montana.edu/etd/2006/wang/WangC0806.pdf.

Повний текст джерела

Анотація:

Due to ever increasing energy consumption, rising public awareness of environmental protection, and steady progress in power deregulation, alternative (i.e., renewable and fuel cell based) distributed generation (DG) systems have attracted increased interest. Wind and photovoltaic (PV) power generation are two of the most promising renewable energy technologies. Fuel cell (FC) systems also show great potential in DG applications of the future due to their fast technology development and many merits they have, such as high efficiency, zero or low emission (of pollutant gases) and flexible modular structure. The modeling and control of a hybrid wind/PV/FC DG system is addressed in this dissertation. Different energy sources in the system are integrated through an AC bus. Dynamic models for the main system components, namely, wind energy conversion system (WECS), PV energy conversion system (PVECS), fuel cell, electrolyzer, power electronic interfacing circuits, battery, hydrogen storage tank, gas compressor and gas pressure regulator, are developed. Two types of fuel cells have been modeled in this dissertation: proton exchange membrane fuel cell (PEMFC) and solid oxide fuel cell (SOFC). Power control of a grid-connected FC system as well as load mitigation control of a stand-alone FC system are investigated. The pitch angle control for WECS, the maximum power point tracking (MPPT) control for PVECS, and the control for electrolyzer and power electronic devices, are also addressed in the dissertation. Based on the dynamic component models, a simulation model for the proposed hybrid energy system has been developed using MATLAB/Simulink. The overall power management strategy for coordinating the power flows among the different energy sources is presented in the dissertation. Simulation studies have been carried out to verify the system performance under different scenarios using a practical load profile and real weather data. The results show that the overall power management strategy is effective and the power flows among the different energy sources and the load demand is balanced successfully. The DG's impacts on the existing power system are also investigated in this dissertation. Analytical methods for finding optimal sites to deploy DG sources in power systems are presented and verified with simulation studies.

Стилі APA, Harvard, Vancouver, ISO та ін.

45

Zhao, Ruichen. "Analysis, Modeling, and Control of Highly-Efficient Hybrid DC-DC Conversion Systems." Thesis, The University of Texas at Austin, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3577697.

Повний текст джерела

Анотація:

This dissertation studies hybrid dc-dc power conversion systems based on multiple-input converters (MICs), or more generally, multiport converters. MICs allow for the integration of multiple distributed generation sources and loads. Thanks to the modular design, an MIC yields a scalable system with independent control in all sources. Additional characteristics of MICs include the improved reliability and reduced cost. This dissertation mainly studies three issues of MICs: efficiency improvement, modeling, and control.

First, this work develops a cost-effective design of a highly-efficient non-isolated MIC without additional components. Time-multiplexing (TM) MICs, which are driven by a time-multiplexing switching control scheme, contain forward-conducting-bidirectionalblocking (FCBB) switches. TM-MICs are considered to be subject to low efficiency because of high power loss introduced by FCBB switches. In order to reduce the power loss in FCBB switches, this work adopts a modified realization of the FCBB switch and proposes a novel switching control strategy. The design and experimental verifications are motivated through a multiple-input (MI) SEPIC converter. Through the design modifications, the switching transients are improved (comparing to the switching transients in a conventional MI-SEPIC) and the power loss is significantly reduced. Moreover, this design maintains a low parts-count because of the absence of additional components. Experimental results show that for output power ranging from 1 W to 220 W, the modified MIC presents high efficiency (96 % optimally). The design can be readily extended to a general n-input SEPIC. The same modifications can be applied to an MI-Ćuk converter.

Second, this dissertation examines the modeling of TM-MICs. In the dynamic equations of a TM-MIC, a state variable from one input leg is possible to be affected by state variables and switching functions associated with other input legs. In this way, inputs are coupled both topologically and in terms of control actions through switching functions. Coupling among the state variable and the time-multiplexing switching functions complicate TM-MICs’ behavior. Consequently, substantial modeling errors may occur when a classical averaging approach is used to model an MIC even with moderately high switching frequencies or small ripples. The errors may increase with incremental number of input legs. In addition to demonstrating the special features on MIC modeling, this dissertation uses the generalized averaging approach to generate a more accurate model, which is also used to derive a small-signal model. The proposed model is an important tool that yields better results when analyzing power budgeting, performing large-signal simulations, and designing controllers for TM-MICs via a more precise representation than classical averaging methods. Analyses are supported by simulations and experimental results.

Third, this dissertation studies application of a decentralized controller on an MISEPIC. For an MIC, a multiple-input-multiple-output (MIMO) state-space representation can be derived by an averaging method. Based on the averaged MIMO model, an MIMO small-signal model can be generated. Both conventional method and modern multivariable frequency analysis are applied to the small-signal model of an MI-SEPIC to evaluate open-loop and closed-loop characteristics. In addition to verifying the nominal stability and nominal performance, this work evaluates robust stability and robust performance with the structured singular value, μ . The robust performance test shows that a compromised performance may be expected under the decentralized control. Simulations and experimental results verify the theoretical analysis on stability and demonstrate that the decentralized PI controller could be effective to regulate the output of an MIC under uncertainties.

Finally, this work studies the control of the MIMO dc-dc converter serving as an active distribution node in an intelligent dc distribution grid. The unified model of a MIMO converter is derived, enabling a systematical analysis and control design that allows this converter to control power flow in all its ports and to act as a power buffer that compensates for mismatches between power generation and consumption. Based on the derived high-order multivariable model, a robust controller is designed with disturbance-attenuation and pole-placement constraints via the linear matrix inequality (LMI) synthesis. The closed-loop robust stability and robust performance are tested through the structured singular value synthesis. Again, the desirable stability and performance are verified by simulations and experimental results.

Стилі APA, Harvard, Vancouver, ISO та ін.

46

Promkam, Ratthaprom [Verfasser], and Sergey [Gutachter] Dashkovskiy. "Hybrid Dynamical Systems: Modeling, Stability and Interconnection / Ratthaprom Promkam ; Gutachter: Sergey Dashkovskiy." Würzburg : Universität Würzburg, 2019. http://d-nb.info/1199267163/34.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

47

Ogburn, Michael James. "Systems Integration, Modeling, and Validation of a Fuel Cell Hybrid Electric Vehicle." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/32124.

Повний текст джерела

Анотація:

The goals of the research documented in this thesis were the design, construction, modeling, and validation of a fuel cell hybrid electric vehicle based a conversion of a five-passenger production sedan. Over 60 engineering students working together as the Hybrid Electric Vehicle Team of Virginia Tech (HEVT), integrated a proton exchange membrane fuel cell system into a series hybrid electric vehicle. This design produced an efficient and truly zero-emission vehicle. This 1997 Chevrolet Lumina sedan, renamed ANIMUL H2, carries this advanced powertrain, using an efficient AC induction drivetrain, regenerative braking, compressed hydrogen fuel storage, and an advanced lead-acid battery pack for peak power load leveling. The vehicle weighed 2000 kg (4400 lb) and achieved a combined city/highway fuel economy of 9L/100 km or 26 mpgge (miles per gallon gasoline equivalent, charge depleting, state of charge corrected). A model of the vehicle was developed using ADVISOR, an Advanced Vehicle Simulator that tracks energy flow and fuel usage within the vehicle drivetrain and energy conversion components. The vehicle was tested using the Environmental Protection Agency city and highway driving cycles to provide data for validation of the model. Vehicle data and model results show good correlation at all levels and show that ADVISOR has the capability to model fuel cell hybrid electric vehicles. To make techniques proven by this work more versatile for real world application, VT worked with engineers at the National Renewable Energy Laboratory to develop a 'generic' version of this fuel cell system model that was released to the public in ADVISOR 2.2. This generic model correlates well to test data and incorporates both fuel cell stack and subsystem models. This feature allowed HEVT to predict the benefits of load following subsystem control, showing a 40% fuel economy improvement.
Master of Science

Стилі APA, Harvard, Vancouver, ISO та ін.

48

CASTIGLIA, VINCENZO JUNIOR. "Hybrid Energy Storage Modeling And Innovative Solutions For Energy Storage Management Systems." Doctoral thesis, Università degli Studi di Palermo, 2022. https://hdl.handle.net/10447/533479.

Повний текст джерела

Анотація:

La presente tesi riguarda la modellazione di diverse fonti di accumulo di energia elettrica, in particolare batterie e supercondensatori (SC), e di nuove configurazioni di metodi di gestione di sistemi di accumulo di energia ibridi . Il crescente bisogno di domanda di energia e il desiderio di raggiungere uno sviluppo sostenibile, si riflettono nell'uso di Generatori Distribuiti (DG) basati sulle Fonti energetiche Rinnovabili (FER). L'uso di un controllo di supervisione intelligente e il raggruppamento locale della domanda e della generazione possono portare a notevoli miglioramenti nell'efficienza, affidabilità e resilienza del sistema elettrico. Il problema principale della DG basata sulle FER è la variazione naturale di alcune fonti rinnovabili, come il vento e il sole. Per ridurre l'impatto della generazione intermittente delle FER, la soluzione più efficace e pratica è l'impiego di sistemi di stoccaggio dell'energia.
The present dissertation concerns about the modeling of different electrical energy storage sources, in particular batteries and supercapacitors (SCs), and of novel configurations of Hybrid Energy Storage Management Systems (HESMS). The growing need for energy demand and the desire to achieve sustainable development, are reflected in the use of Renewable Energy Sources (RESs)-based Distributed Generators (DG). The use of smart supervisory control and local clustering of demand and generation can lead to marked improvements in the efficiency, reliability, and resilience of the electrical system. The main problem of RESs-based DG is the natural variation of some renewable sources, such as wind and solar. To reduce the impact of intermittent RES generation, the most effective and practical solution is the employment of Energy Storage Systems (ESSs).

Стилі APA, Harvard, Vancouver, ISO та ін.

49

Chen, Minghan. "Stochastic Modeling and Simulation of Multiscale Biochemical Systems." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/90898.

Повний текст джерела

Анотація:

Numerous challenges arise in modeling and simulation as biochemical networks are discovered with increasing complexities and unknown mechanisms. With the improvement in experimental techniques, biologists are able to quantify genes and proteins and their dynamics in a single cell, which calls for quantitative stochastic models for gene and protein networks at cellular levels that match well with the data and account for cellular noise. This dissertation studies a stochastic spatiotemporal model of the Caulobacter crescentus cell cycle. A two-dimensional model based on a Turing mechanism is investigated to illustrate the bipolar localization of the protein PopZ. However, stochastic simulations are often impeded by expensive computational cost for large and complex biochemical networks. The hybrid stochastic simulation algorithm is a combination of differential equations for traditional deterministic models and Gillespie's algorithm (SSA) for stochastic models. The hybrid method can significantly improve the efficiency of stochastic simulations for biochemical networks with multiscale features, which contain both species populations and reaction rates with widely varying magnitude. The populations of some reactant species might be driven negative if they are involved in both deterministic and stochastic systems. This dissertation investigates the negativity problem of the hybrid method, proposes several remedies, and tests them with several models including a realistic biological system. As a key factor that affects the quality of biological models, parameter estimation in stochastic models is challenging because the amount of empirical data must be large enough to obtain statistically valid parameter estimates. To optimize system parameters, a quasi-Newton algorithm for stochastic optimization (QNSTOP) was studied and applied to a stochastic budding yeast cell cycle model by matching multivariate probability distributions between simulated results and empirical data. Furthermore, to reduce model complexity, this dissertation simplifies the fundamental cooperative binding mechanism by a stochastic Hill equation model with optimized system parameters. Considering that many parameter vectors generate similar system dynamics and results, this dissertation proposes a general α-β-γ rule to return an acceptable parameter region of the stochastic Hill equation based on QNSTOP. Different objective functions are explored targeting different features of the empirical data.
Doctor of Philosophy
Modeling and simulation of biochemical networks faces numerous challenges as biochemical networks are discovered with increased complexity and unknown mechanisms. With improvement in experimental techniques, biologists are able to quantify genes and proteins and their dynamics in a single cell, which calls for quantitative stochastic models, or numerical models based on probability distributions, for gene and protein networks at cellular levels that match well with the data and account for randomness. This dissertation studies a stochastic model in space and time of a bacterium’s life cycle— Caulobacter. A two-dimensional model based on a natural pattern mechanism is investigated to illustrate the changes in space and time of a key protein population. However, stochastic simulations are often complicated by the expensive computational cost for large and sophisticated biochemical networks. The hybrid stochastic simulation algorithm is a combination of traditional deterministic models, or analytical models with a single output for a given input, and stochastic models. The hybrid method can significantly improve the efficiency of stochastic simulations for biochemical networks that contain both species populations and reaction rates with widely varying magnitude. The populations of some species may become negative in the simulation under some circumstances. This dissertation investigates negative population estimates from the hybrid method, proposes several remedies, and tests them with several cases including a realistic biological system. As a key factor that affects the quality of biological models, parameter estimation in stochastic models is challenging because the amount of observed data must be large enough to obtain valid results. To optimize system parameters, the quasi-Newton algorithm for stochastic optimization (QNSTOP) was studied and applied to a stochastic (budding) yeast life cycle model by matching different distributions between simulated results and observed data. Furthermore, to reduce model complexity, this dissertation simplifies the fundamental molecular binding mechanism by the stochastic Hill equation model with optimized system parameters. Considering that many parameter vectors generate similar system dynamics and results, this dissertation proposes a general α-β-γ rule to return an acceptable parameter region of the stochastic Hill equation based on QNSTOP. Different optimization strategies are explored targeting different features of the observed data.

Стилі APA, Harvard, Vancouver, ISO та ін.

50

Zhu, Tao. "Extended cluster weighted modeling methods for transient recognition control." Diss., Montana State University, 2006. http://etd.lib.montana.edu/etd/2006/zhu/ZhuT0806.pdf.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Дисертації з теми "Hybrid systems modeling and verification"

Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями