On state representations of nonlinear implicit systems

This work considers a semi-implicit system A, that is, a pair (S, y), where S is an explicit system described by a state representation (x)over dot(t) = f(t, x(t), u(t)), where x(t) is an element of R(n) and u(t) is an element of R(m), which is subject to a set of algebraic constraints y(t) = h(t, x(t), u(t)) = 0, where y(t) is an element of R(l). An input candidate is a set of functions v = (v(1),.... v(s)), which may depend on time t, on x, and on u and its derivatives up to a Finite order. The problem of finding a (local) proper state representation (z)over dot = g(t, z, v) with input v for the implicit system Delta is studied in this article. The main result shows necessary and sufficient conditions for the solution of this problem, under mild assumptions on the class of admissible state representations of Delta. These solvability conditions rely on an integrability test that is computed from the explicit system S. The approach of this article is the infinite-dimensional differential geometric setting of Fliess, Levine, Martin, and Rouchon (1999) (`A Lie-Backlund Approach to Equivalence and Flatness of Nonlinear Systems`, IEEE Transactions on Automatic Control, 44(5), (922-937)).

THE VANISHING DISCOUNT APPROACH FOR THE AVERAGE CONTINUOUS CONTROL OF PIECEWISE DETERMINISTIC MARKOV PROCESSES

This work is concerned with the existence of an optimal control strategy for the long-run average continuous control problem of piecewise-deterministic Markov processes (PDMPs). In Costa and Dufour (2008), sufficient conditions were derived to ensure the existence of an optimal control by using the vanishing discount approach. These conditions were mainly expressed in terms of the relative difference of the alpha-discount value functions. The main goal of this paper is to derive tractable conditions directly related to the primitive data of the PDMP to ensure the existence of an optimal control. The present work can be seen as a continuation of the results derived in Costa and Dufour (2008). Our main assumptions are written in terms of some integro-differential inequalities related to the so-called expected growth condition, and geometric convergence of the post-jump location kernel associated to the PDMP. An example based on the capacity expansion problem is presented, illustrating the possible applications of the results developed in the paper.

Reachability of the synchronous state in a mutually connected PLL network

Second-order phase locked loops (PLLs) are devices that are able to provide synchronization between the nodes in a network even under severe quality restrictions in the signal propagation. Consequently, they are widely used in telecommunication and control. Conventional master-slave (M-S) clock-distribution systems are being, replaced by mutually connected (MC) ones due to their good potential to be used in new types of application such as wireless sensor networks, distributed computation and communication systems. Here, by using an analytical reasoning, a nonlinear algebraic system of equations is proposed to establish the existence conditions for the synchronous state in an MC PLL network. Numerical experiments confirm the analytical results and provide ideas about how the network parameters affect the reachability of the synchronous state. The phase-difference oscillation amplitudes are related to the node parameters helping to design PLL neural networks. Furthermore, estimation of the acquisition time depending on the node parameters allows the performance evaluation of time distribution systems and neural networks based on phase-locked techniques. (c) 2008 Elsevier GmbH. All rights reserved.

Singular Perturbation for the Discounted Continuous Control of Piecewise Deterministic Markov Processes

This paper deals with the expected discounted continuous control of piecewise deterministic Markov processes (PDMP`s) using a singular perturbation approach for dealing with rapidly oscillating parameters. The state space of the PDMP is written as the product of a finite set and a subset of the Euclidean space a""e (n) . The discrete part of the state, called the regime, characterizes the mode of operation of the physical system under consideration, and is supposed to have a fast (associated to a small parameter epsilon > 0) and a slow behavior. By using a similar approach as developed in Yin and Zhang (Continuous-Time Markov Chains and Applications: A Singular Perturbation Approach, Applications of Mathematics, vol. 37, Springer, New York, 1998, Chaps. 1 and 3) the idea in this paper is to reduce the number of regimes by considering an averaged model in which the regimes within the same class are aggregated through the quasi-stationary distribution so that the different states in this class are replaced by a single one. The main goal is to show that the value function of the control problem for the system driven by the perturbed Markov chain converges to the value function of this limit control problem as epsilon goes to zero. This convergence is obtained by, roughly speaking, showing that the infimum and supremum limits of the value functions satisfy two optimality inequalities as epsilon goes to zero. This enables us to show the result by invoking a uniqueness argument, without needing any kind of Lipschitz continuity condition.

Linear minimum mean square filter for discrete-time linear systems with Markov jumps and multiplicative noises

In this paper we obtain the linear minimum mean square estimator (LMMSE) for discrete-time linear systems subject to state and measurement multiplicative noises and Markov jumps on the parameters. It is assumed that the Markov chain is not available. By using geometric arguments we obtain a Kalman type filter conveniently implementable in a recurrence form. The stationary case is also studied and a proof for the convergence of the error covariance matrix of the LMMSE to a stationary value under the assumption of mean square stability of the system and ergodicity of the associated Markov chain is obtained. It is shown that there exists a unique positive semi-definite solution for the stationary Riccati-like filter equation and, moreover, this solution is the limit of the error covariance matrix of the LMMSE. The advantage of this scheme is that it is very easy to implement and all calculations can be performed offline. (c) 2011 Elsevier Ltd. All rights reserved.

On state representations of time-varying nonlinear systems

This work considers a nonlinear time-varying system described by a state representation, with input u and state x. A given set of functions v, which is not necessarily the original input u of the system, is the (new) input candidate. The main result provides necessary and sufficient conditions for the existence of a local classical state space representation with input v. These conditions rely on integrability tests that are based on a derived flag. As a byproduct, one obtains a sufficient condition of differential flatness of nonlinear systems. (C) 2009 Elsevier Ltd. All rights reserved.

Floristic composition of seasonal riparian forests in Mato Grosso do Sul State, Brazil

(Floristic composition of seasonal riparian forests in Mato Grosso do Sit] State, Brazil). This Study aimed to characterize the floristic composition in two stretches of seasonal semideciduous forest associated with the Formoso River, Bonito, Mato Grosso do Sul State, and in three stretches of seasonal deciduous and semideciduous forests associated with the Salobra, Salobrinha and Perdido rivers in Bodoquena Plateau National Park (76,481 ha) - the only Federal Conservation unit with Integral Protection in the state of Mato Grosso do Sul. The floristic survey was carried out monthly from October/2004 to March/2006, where flowering and fruiting phanerogams were collected by the method of evaluation time. The floristic survey resulted in 56 families, 184 genera and 307 species. Of the total number of species, 68% were trees, 17% shrubs, 14% lianas and only 1% palms. The Fabaceae family (Leguminosae), represented by 51 (16.6%) species, was the most species-rich. These results increase our knowledge of the Mato Grosso do Sul flora and its geographic distribution, thus emphasizing the need for conservation of these riparian forests and providing subsidies for restoration projects of the degraded areas around the conservation unit and permanent protection areas (APPs) of regional rivers.

Forest restoration in an indigenous land considering a forest remnant influence (Avai, Sao Paulo State, Brazil)

The expansion of agricultural and pasture areas over native forest areas has been broadly documented and represents the main cause of deforestation that has occurred for the last decades. Such reality is not different in indigenous lands, and has been considered as an important obstacle for individuals who directly depend upon the appropriate management of natural resources to maintain their traditions. We investigated the seed rain, seed bank and natural regeneration of native woody species within a degraded pasture land in different distances from an adjacent seasonal semideciduous forest fragment to define methodological procedures based on ecological processes that might subsidize forest restoration in an indigenous land. Most seeds and seedlings picked from the seed rain and seed bank belonged to anemochoric and autochoric dispersing shrubby and herbaceous species originated in the pasture land. The woody species regeneration, on the other hand, reached higher levels, in terms of abundance and richness, as the forest fragment became closer. Zoochoric dispersal was predominant among such species and was mainly detected closer to the forest fragment. Several woody species picked in the forest fragment were also found in the pasture land, thus reinforcing their important role in supplying propagules and easing the successional process. (c) 2007 Elsevier B.V. All rights reserved.

SELF-SIMILARITY AND LAMPERTI CONVERGENCE FOR FAMILIES OF STOCHASTIC PROCESSES

We define a new type of self-similarity for one-parameter families of stochastic processes, which applies to certain important families of processes that are not self-similar in the conventional sense. This includes Hougaard Levy processes such as the Poisson processes, Brownian motions with drift and the inverse Gaussian processes, and some new fractional Hougaard motions defined as moving averages of Hougaard Levy process. Such families have many properties in common with ordinary self-similar processes, including the form of their covariance functions, and the fact that they appear as limits in a Lamperti-type limit theorem for families of stochastic processes.

The effectiveness of Eucalyptus barrier in containing the edge effect on a subtropical forest fragment in the state of Sao Paulo, Brazil

Edge effects resulting from isolation and subsequent microclimatic changes are one of the most important threats to the forest fragments conservation. The efficiency of maintaining a barrier formed by three rows of Eucalyptus along the edge of a subtropical seasonal semi deciduous forest fragment, surrounded by Eucalyptus monoculture, was evaluated as a way of softening the microclimatic changes (light intensity, temperature and relative humidity) and the impacts of eucalypt mechanized harvesting on the native vegetation along the contact zone between the forest fragment and the plantation. The Eucalyptus barrier was effective in softening the microclimate. Light intensity was 35% lower in the presence of the barrier. The barrier also provided a reduction of 1 C in air temperature and increased in 3.4% in relative humidity throughout the year. The barrier was also effective in preventing the impact on native vegetation, avoiding damage to adult trees and preserving the regenerating forest stratum near the border, which was reduced to less than 20% in density and 50% in richness, with no such barrier. The barrier of Eucalyptus may, therefore, be recommended as an effective method to minimize the impacts of mechanized forest harvesting operations and mitigate the microclimatic conditions along the edge of forest fragments.

Sugar and ethanol production as a rural development strategy in Brazil: Evidence from the state of Sao Paulo

Sugar and ethanol production are key components of Brazil`s rural development and energy strategies, yet in recent years sugar production has been widely criticized for its environmental and labor practices. This study examines the relationship between rural development and sugarcane, ethanol, and cattle production in the state of Sao Paulo. Our results suggest that the value added components of sugarcane production, which include sugar refining and ethanol production, may have a strong positive affect on local human development in comparison to primary agricultural production activities and other land uses. These results imply that sugar production, when accompanied by a local processing industry can stimulate rural development. However, this paper also highlights the significant environmental and social harms generated by the sugar industry at large, which may undermine its development benefits if not addressed. (C) 2011 Elsevier Ltd. All rights reserved.

New species of Anastrepha Schiner (Diptera, Tephritidae) from remnant area of the Atlantic Rain Forest and surroundings in the state of Espirito Santo, Brazil

Four new species of Anastrepha Schiner were collected in McPhail-type traps hung in trees in a natural reserve and in commercial papaya orchards in Linhares, Espirito Santo state, Brazil. They are described and named herein as follows: Anastrepha atlantica n. sp., Anastrepha glochin n. sp., Anastrepha linharensis n. sp. and Anastrepha martinsi n. sp. Only the latter was collected in traps hung in papaya orchards. The classification of these species in species groups of Anastrepha is also discussed.

Rhodacaridae mites (Acari: Mesostigmata: Rhodacaroidea) from the state of Sao Paulo, Brazil, with descriptions of a new genus and three new species

- This paper reports the occurrence of five species of Rhodacaridae mites collected in the State of Sao Paulo, Brazil. One of these corresponds to a new genus and a new species, Binodacarus brasiliensis n. gen. n. sp.; two correspond to new species of kno

Fruit flies (Diptera, Tephritidae) and their associations with native host plants in a remnant area of the highly endangered Atlantic Rain Forest in the State of Espirito Santo, Brazil

The results presented in this paper refer to a host survey, lasting approximately three and a half years (February 2003-july 2006), undertaken in the Vale do Rio Doce Natural Reserve, a remnant area of the highly endangered Atlantic Rain Forest located in Linhares County, State of Espirito Santo, Brazil. A total of 330 fruit samples were collected from native plants, representing 248 species and 51 plant families. Myrtaceae was the most diverse family with 54 sampled species. Twenty-eight plant species, from ten families, are hosts of ten Anastrepha species and of Ceratitis capitata (Wiedemann). Among 33 associations between host plants and fruit flies, 20 constitute new records, including the records of host plants for A. fumipennis Lima and A. nascimentoi Zucchi. The findings were discussed in the light of their implications for rain forest conservation efforts and the study of evolutionary relationships between fruit flies and their hosts.

Economic feasibility of cowpea irrigation in Piaui State

The objective of this work was to evaluate the economic feasibility of cowpea irrigation in Piaui State Brazil. Water balances were carried out on a daily basis using the Thornthwaite and Mather (1955) method, for 165 sites, considering twelve sowings dates and available water capacity in the soil of 20, 40 and 60 mm. The net revenues were estimated with a probability of occurrence of 75%, later being spatialized to Piaui State. Cowpea irrigation was shown to economically viable for all sowing dates, irrespective of the available water capacity. Net revenues varied among several regions of the State, in function of the sowing date and available water capacity in the soil. Considering a planning strategy for Piaui State, sowing on February, I was shown to be most favorable, because it enabled higher net revenue values, covering larger areas of the State.