15,013 research outputs found
Switching control for incremental stabilization of nonlinear systems via contraction theory
In this paper we present a switching control strategy to incrementally
stabilize a class of nonlinear dynamical systems. Exploiting recent results on
contraction analysis of switched Filippov systems derived using regularization,
sufficient conditions are presented to prove incremental stability of the
closed-loop system. Furthermore, based on these sufficient conditions, a design
procedure is proposed to design a switched control action that is active only
where the open-loop system is not sufficiently incrementally stable in order to
reduce the required control effort. The design procedure to either locally or
globally incrementally stabilize a dynamical system is then illustrated by
means of a representative example.Comment: Accepted to ECC 201
Ratiometric control for differentiation of cell populations endowed with synthetic toggle switches
We consider the problem of regulating by means of external control inputs the
ratio of two cell populations. Specifically, we assume that these two cellular
populations are composed of cells belonging to the same strain which embeds
some bistable memory mechanism, e.g. a genetic toggle switch, allowing them to
switch role from one population to another in response to some inputs. We
present three control strategies to regulate the populations' ratio to
arbitrary desired values which take also into account realistic physical and
technological constraints occurring in experimental microfluidic platforms. The
designed controllers are then validated in-silico using stochastic agent-based
simulations.Comment: Accepted to CDC'201
Reconstructing directed and weighted topologies of phase-locked oscillator networks
The formalism of complex networks is extensively employed to describe the
dynamics of interacting agents in several applications. The features of the
connections among the nodes in a network are not always provided beforehand,
hence the problem of appropriately inferring them often arises. Here, we
present a method to reconstruct directed and weighted topologies (REDRAW) of
networks of heterogeneous phase-locked nonlinear oscillators. We ultimately
plan on using REDRAW to infer the interaction structure in human ensembles
engaged in coordination tasks, and give insights into the overall behavior
Optimization of Stone Cutting Techniques for the Seismic Protection of Archaeological Sites
Since the beginning of civilization, history tells of the movement of art pieces, monuments and manufacts from site to site. The causes are multiple: the displacements due to the "spoils of war", ordered by kings and emperors, the movements caused by the need for reuse, especially in the early Christian period, and so forth. Considerations about the events of the past, yield a possible strategy to transform this concept into a technique for earthquake prevention of archaeological sites. The seismic safety retrofits have often proven to be scarcely effective, because of the difficulties involved in complex sites. The aim of this study is to analyze an "alternative" method of preventing natural disaster like floods, eruption and earthquakes, through the movimentation of the most representative structural elements of archaeological sites by decomposition of the masonry and marbles [1]. The procedure considers a process of "cutting optimization," calibrated on the characteristics of the specific material that has to be cut and then displaced in safer places (i.e., MEP, "manufact evacuation plan"). This process should not create excessive problems to the structure, and aims to reassembly the manufact in contexts able to guarantee safety through advanced earthquake-resistant expedients. From these considerations, the work develops a procedure to safeguard the archaeological site of Pompei (Naples), through an appropriate analysis of representative portions of the site, aimed to a careful handling and to a proper reconstruction in a safe location, from the seismic point of vie
On complex power nonnegative matrices
Power nonnegative matrices are defined as complex matrices having at least
one nonnegative integer power. We exploit the possibility of deriving a Perron
Frobenius-like theory for these matrices, obtaining three main results and
drawing several consequences. We study, in particular, the relationships with
the set of matrices having eventually nonnegative powers, the inverse of M-type
matrices and the set of matrices whose columns (rows) sum up to one
Observer design for piecewise smooth and switched systems via contraction theory
The aim of this paper is to present the application of an approach to study
contraction theory recently developed for piecewise smooth and switched
systems. The approach that can be used to analyze incremental stability
properties of so-called Filippov systems (or variable structure systems) is
based on the use of regularization, a procedure to make the vector field of
interest differentiable before analyzing its properties. We show that by using
this extension of contraction theory to nondifferentiable vector fields, it is
possible to design observers for a large class of piecewise smooth systems
using not only Euclidean norms, as also done in previous literature, but also
non-Euclidean norms. This allows greater flexibility in the design and
encompasses the case of both piecewise-linear and piecewise-smooth (nonlinear)
systems. The theoretical methodology is illustrated via a set of representative
examples.Comment: Preprint accepted to IFAC World Congress 201
The Evolution of Primate Societies - Chapter 3
Compared with other primates, New World monkeys display relatively limited ecological variability. New World monkey anatomy and social systems, however, are extremely diverse. Several unique morphological features (e.g., claws, prehensile tails) and uncommon patterns of social organization (e.g., paternal care, cooperative breeding, female dispersal) have evolved in some platyrrhine species. Social organization and mating patterns include typical harem- like structures where mating is largely polygynous, and large multimale, multifemale groups with promiscuous mating and fi ssion- fusion societies. In addition, some species are socially monogamous and polyandrous. Even closely related species may exhibit strikingly different social organizations, as the example of the squirrel monkeys demonstrates (Mitchell et al. 1991; Boinski et al. 2005b). New World monkey behavior varies within species as well as between them. While the behavior of many species is known from only one study site, intriguing patterns of intraspecific variation are beginning to emerge from observations of populations that sometimes live in close proximity. For example, spider monkeys are often described as showing sex- segregated ranging behavior. Several studies show that males range farther, travel faster, and use larger areas than females, who tend to restrict their habitual ranging to smaller core areas within a group’s large territory (Symington 1988; Chapman 1990; Shimooka 2005). In at least one well- studied population in Yasuní National Park, Ecuador, however, males and females both travel over the entire community home range, and different females within the community show little evidence of occupying distinct core areas (Spehar et al. 2010). Similarly, in most well- studied populations of spider monkeys, females disperse and the resident males within a group are presumed to be close relatives—a suggestion corroborated by genetic data for one local population of spider monkeys in Yasuní. Still, in a different local population, males are not closely related to one another, an unexpected pattern if signifi cant male philopatry were common (Di Fiore 2009; Di Fiore et al. 2009). While the causes of this local variation in group genetic structure are not clear, it may be signifi cant that the groups examined likely had different histories of contact with humans. For longlived animals who occupy relatively small social groups, the loss of even a handful of individuals to hunting, or to any other demographic disturbance, can have a dramatic impact on a group’s genetic structure. Intragroup social relationships, in turn, are likely to be infl uenced by patterns of intragroup relatedness and by the relative availability of social partners of different age or sex class (chapter 21, this volume). Thus, historical and demographic contingencies are likely to create conditions where considerable local, intrapopulation variation in social systems exists. Slight changes in ecological conditions may also contribute to variation in the behavior of individuals living in a single population over time. For example, some authors have hypothesized that howler monkey populations may undergo dramatic fluctuations in size and composition in response to several ecological factors, including resource abundance, parasite and predation pressure, and climate (Milton 1982; Crockett & Eisenberg 1986; Crockett 1996; Milton 1996; Rudran & Fernandez- Duque 2003). This variability, not only among populations, but also within populations across time highlights the need for long- term studies. In sum, our understanding of the behavior of New World monkeys has increased dramatically over the past 25 years. This understanding highlights how their behavior varies within populations over time and among populations or species across space. As our knowledge of platyrrhine behavior continues to unfold and is enriched via additional long- term studies, a central challenge will be to explain how these variations arise. It will be important to entertain adaptive explanations while acknowledging that some differences may emerge via stochastic changes in demography (Struhsaker 2008) or nongenetic, relatively short- term, nonadaptive responses to sudden ecological change
Contraction analysis of switched Filippov systems via regularization
We study incremental stability and convergence of switched (bimodal) Filippov
systems via contraction analysis. In particular, by using results on
regularization of switched dynamical systems, we derive sufficient conditions
for convergence of any two trajectories of the Filippov system between each
other within some region of interest. We then apply these conditions to the
study of different classes of Filippov systems including piecewise smooth (PWS)
systems, piecewise affine (PWA) systems and relay feedback systems. We show
that contrary to previous approaches, our conditions allow the system to be
studied in metrics other than the Euclidean norm. The theoretical results are
illustrated by numerical simulations on a set of representative examples that
confirm their effectiveness and ease of application.Comment: Preprint submitted to Automatic
The role of R/D expenditure: a critical comparison of the two (R&S and CIS) sources of data
The paper explores the relation between two data sources (R&D and CIS surveys) in the aim of better representing the roles of R/D activity in relation with innovation processes. This paper starts with controlling the relation between the R/D expenditure in the two surveys (R&D and CIS) for a same group of firms and for the same year (2000) and deals with the question of how much we know at present of the different components of the industrial R/D activity and how we can use the frame of the two surveys for arriving to gain this knowledge. The final aim is that of getting finest grained indicators for studies on the impact of industrial investment on R/D.Industrial R/D, R/D survey, CIS survey
What industry incumbents need to know about platform models before it’s too late
Platform companies have already disrupted some industries and will inevitably disrupt more, writes Alessandro Di Fior
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