This comprehensive book provides the first unified framework for stability and dissipativity analysis and control design for nonnegative and compartmental dynamical systems, which play a key role in ...a wide range of fields, including engineering, thermal sciences, biology, ecology, economics, genetics, chemistry, medicine, and sociology. Using the highest standards of exposition and rigor, the authors explain these systems and advance the state of the art in their analysis and active control design.
Tropical reefs have been impacted by thermal anomalies caused by global warming that induced coral bleaching and mortality events globally. However, there have only been very few recordings of ...bleaching within the Red Sea despite covering a latitudinal range of 15° and consequently it has been considered a region that is less sensitive to thermal anomalies. We therefore examined historical patterns of sea surface temperature (SST) and associated anomalies (1982–2012) and compared warming trends with a unique compilation of corresponding coral bleaching records from throughout the region. These data indicated that the northern Red Sea has not experienced mass bleaching despite intensive Degree Heating Weeks (DHW) of >15°C‐weeks. Severe bleaching was restricted to the central and southern Red Sea where DHWs have been more frequent, but far less intense (DHWs <4°C‐weeks). A similar pattern was observed during the 2015–2016 El Niño event during which time corals in the northern Red Sea did not bleach despite high thermal stress (i.e. DHWs >8°C‐weeks), and bleaching was restricted to the central and southern Red Sea despite the lower thermal stress (DHWs < 8°C‐weeks). Heat stress assays carried out in the northern (Hurghada) and central (Thuwal) Red Sea on four key reef‐building species confirmed different regional thermal susceptibility, and that central Red Sea corals are more sensitive to thermal anomalies as compared to those from the north. Together, our data demonstrate that corals in the northern Red Sea have a much higher heat tolerance than their prevailing temperature regime would suggest. In contrast, corals from the central Red Sea are close to their thermal limits, which closely match the maximum annual water temperatures. The northern Red Sea harbours reef‐building corals that live well below their bleaching thresholds and thus we propose that the region represents a thermal refuge of global importance.
(1) Tropical reefs have been impacted by thermal anomalies that have induced coral bleaching; however, there are only few recordings of bleaching across the Red Sea. (2) Historical and contemporary mass bleaching appears to be restricted to the central and southern Red Sea, and the northern region remains bleaching‐free despite experiencing intensive thermal anomalies. (3) Heat stress experiments demonstrated that corals in the north are thermally tolerant and exist within a region where ambient and anomalous temperatures are lower than their physiological thermal maximum and we therefore propose that the northern region is thermal refugia with global significance.
Le but de cette étude est d’évaluer les gestes techniques d’utilisation des lecteurs de glycémie en pratique courante. Matériel et méthode Il s’agit d’une étude prospective descriptive incluant ...369 diabétiques depuis plus d’un an. Un questionnaire a été établi utilisant plusieurs items. Résultats Sur les 369 diabétiques nous avons retrouvé 17 % de type 1 et 83 % de type 2, sex-ratio à 1, l’âge moyen est de 52,6 ± 15,5 ans, avec une ancienneté du diabète de 10,3 ± 8 ans. Plus de la moitié sont traités par insuline. Leur HbA1c moyen est de 8,25 ± 1,8 %. Les patients disposent de plus de deux lecteurs dans 33,9 % des cas, les options du lecteur ne sont utilisées que par un tiers des patients. Parmi les patients, 22,36 % des patients ne se lavent pas systématiquement les mains avant la glycémie capillaire, et l’utilisation de l’alcool ou un autre antiseptique est observé chez 32,5 % des patients, 59,2 % utilisent les sites recommandés pour la piqûre, le changement régulier des lancettes est observé dans 2/3 des cas et l’élimination de ces dernières se fait avec les déchets ménagers dans 86 % des cas. Discussion À travers ces résultats, on note que l’accessibilité et l’attribution du lecteur est facilitée ; nos patients en disposent de deux ou plus dans un tiers des cas, ses options ne sont malheureusement utilisées que par une infime partie de notre population, témoignant du manque d’information complémentaire. Contrairement à ce qui est recommandé la lancette n’est pas à usage unique chez nos patients, et leur élimination s’avère problématique.
Severe insect declines make headlines, but they are rarely based on systematic monitoring outside of Europe. We estimate the rate of change in total butterfly abundance and the population trends for ...81 species using 21 years of systematic monitoring in Ohio, USA. Total abundance is declining at 2% per year, resulting in a cumulative 33% reduction in butterfly abundance. Three times as many species have negative population trends compared to positive trends. The rate of total decline and the proportion of species in decline mirror those documented in three comparable long-term European monitoring programs. Multiple environmental changes such as climate change, habitat degradation, and agricultural practices may contribute to these declines in Ohio and shift the makeup of the butterfly community by benefiting some species over others. Our analysis of life-history traits associated with population trends shows an impact of climate change, as species with northern distributions and fewer annual generations declined more rapidly. However, even common and invasive species associated with human-dominated landscapes are declining, suggesting widespread environmental causes for these trends. Declines in common species, although they may not be close to extinction, will have an outsized impact on the ecosystem services provided by insects. These results from the most extensive, systematic insect monitoring program in North America demonstrate an ongoing defaunation in butterflies that on an annual scale might be imperceptible, but cumulatively has reduced butterfly numbers by a third over 20 years.
While adaptive control has been used in numerous applications to achieve system performance without excessive reliance on dynamical system models, the necessity of high-gain learning rates to achieve ...fast adaptation can be a serious limitation of adaptive controllers. This is due to the fact that fast adaptation using high-gain learning rates can cause high-frequency oscillations in the control response resulting in system instability. In this note, we present a new adaptive control architecture for nonlinear uncertain dynamical systems to address the problem of achieving fast adaptation using high-gain learning rates. The proposed framework involves a new and novel controller architecture involving a modification term in the update law. Specifically, this modification term filters out the high-frequency content contained in the update law while preserving asymptotic stability of the system error dynamics. This key feature of our framework allows for robust, fast adaptation in the face of high-gain learning rates. Furthermore, we show that transient and steady-state system performance is guaranteed with the proposed architecture. Two illustrative numerical examples are provided to demonstrate the efficacy of the proposed approach.
Impulsive and hybrid dynamical systems Haddad, Wassim M; Chellaboina, VijaySekhar; Nersesov, Sergey G
2014., 20140908, 2006, 2006-01-01, Letnik:
15
eBook
This book develops a general analysis and synthesis framework for impulsive and hybrid dynamical systems. Such a framework is imperative for modern complex engineering systems that involve ...interacting continuous-time and discrete-time dynamics with multiple modes of operation that place stringent demands on controller design and require implementation of increasing complexity--whether advanced high-performance tactical fighter aircraft and space vehicles, variable-cycle gas turbine engines, or air and ground transportation systems.
Impulsive and Hybrid Dynamical Systemsgoes beyond similar treatments by developing invariant set stability theorems, partial stability, Lagrange stability, boundedness, ultimate boundedness, dissipativity theory, vector dissipativity theory, energy-based hybrid control, optimal control, disturbance rejection control, and robust control for nonlinear impulsive and hybrid dynamical systems. A major contribution to mathematical system theory and control system theory, this book is written from a system-theoretic point of view with the highest standards of exposition and rigor. It is intended for graduate students, researchers, and practitioners of engineering and applied mathematics as well as computer scientists, physicists, and other scientists who seek a fundamental understanding of the rich dynamical behavior of impulsive and hybrid dynamical systems.
In this article, we address finite time stability in probability of discrete-time stochastic dynamical systems. Specifically, a stochastic comparison lemma is constructed along with a scalar system ...involving a generalized deadzone function to establish almost sure convergence and finite time stability in probability. This result is used to provide Lyapunov theorems for finite time stability in probability for Itô-type stationary nonlinear stochastic difference equations involving Lyapunov difference conditions on the minimum of the Lyapunov function itself along with a fractional power of the Lyapunov function. In addition, we establish sufficient conditions for almost sure lower semicontinuity of the stochastic settling-time capturing the average settling time behavior of the discrete-time nonlinear stochastic dynamical system. Furthermore, a stochastic finite-time optimal control framework is developed by exploiting connections between Lyapunov theory for finite time stability in probability and stochastic Bellman theory. In particular, we show that finite time stability in probability of the closed-loop nonlinear system is guaranteed by means of a Lyapunov function that can clearly be seen to be the solution to the steady state form of the stochastic Bellman equation, and hence, guaranteeing both stochastic finite time stability and optimality.
Thermodynamics Haddad, Wassim M; Haddad, Wassim M; Chellaboina, VijaySekhar ...
2005., 20090110, 2005, 2009, 2005-01-01, c2005, Letnik:
12
eBook
This book places thermodynamics on a system-theoretic foundation so as to harmonize it with classical mechanics. Using the highest standards of exposition and rigor, the authors develop a novel ...formulation of thermodynamics that can be viewed as a moderate-sized system theory as compared to statistical thermodynamics. This middle-ground theory involves deterministic large-scale dynamical system models that bridge the gap between classical and statistical thermodynamics. The authors' theory is motivated by the fact that a discipline as cardinal as thermodynamics--entrusted with some of the most perplexing secrets of our universe--demands far more than physical mathematics as its underpinning. Even though many great physicists, such as Archimedes, Newton, and Lagrange, have humbled us with their mathematically seamless eurekas over the centuries, this book suggests that a great many physicists and engineers who have developed the theory of thermodynamics seem to have forgotten that mathematics, when used rigorously, is the irrefutable pathway to truth.
This paper focuses on semistability and finite-time stability analysis and synthesis of systems having a continuum of equilibria. Semistability is the property whereby the solutions of a dynamical ...system converge to Lyapunov stable equilibrium points determined by the system initial conditions. In this paper, we merge the theories of semistability and finite-time stability to develop a rigorous framework for finite-time semistability. In particular, finite-time semistability for a continuum of equilibria of continuous autonomous systems is established. Continuity of the settling-time function as well as Lyapunov and converse Lyapunov theorems for semistability are also developed. In addition, necessary and sufficient conditions for finite-time semistability of homogeneous systems are addressed by exploiting the fact that a homogeneous system is finite-time semistable if and only if it is semistable and has a negative degree of homogeneity. Unlike previous work on homogeneous systems, our results involve homogeneity with respect to semistable dynamics, and require us to adopt a geometric description of homogeneity. Finally, we use these results to develop a general framework for designing semistable protocols in dynamical networks for achieving coordination tasks in finite time.
Global modeling of nature's contributions to people Chaplin-Kramer, Rebecca; Sharp, Richard P; Weil, Charlotte ...
Science (American Association for the Advancement of Science),
10/2019, Letnik:
366, Številka:
6462
Journal Article
Recenzirano
The magnitude and pace of global change demand rapid assessment of nature and its contributions to people. We present a fine-scale global modeling of current status and future scenarios for several ...contributions: water quality regulation, coastal risk reduction, and crop pollination. We find that where people's needs for nature are now greatest, nature's ability to meet those needs is declining. Up to 5 billion people face higher water pollution and insufficient pollination for nutrition under future scenarios of land use and climate change, particularly in Africa and South Asia. Hundreds of millions of people face heightened coastal risk across Africa, Eurasia, and the Americas. Continued loss of nature poses severe threats, yet these can be reduced 3- to 10-fold under a sustainable development scenario.
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