Pictures from Mongolia. Extracting the Top Elements from a Partially Ordered Set

You are back from that very long, marvellous journey. You have a thousand pictures, but your friends and relatives will stand just a few dozens. Choosing is a painful process, in particular when you cannot decide between the silent vastness of that desert and the idyllic picture of that tranquil, majestic lake. We are going to help. A preliminary version of this paper appeared in [1].     

Performance of different simple linearizing techniques in SiGe LNA at 1900 MHz

Five different linearizing methods were implemented to improve the linearity of a low noise amplifier (LNA). Obtaining a very good performance concerning output and input third-order intercept point without significant degradation of the noise figure. Moreover, high 1 dB-gain compression point was succeeded, obtaining a very high linear amplifier operating at 1900 MHz and biased with 2.4 V and 10 mA of collector current.     

Posidonia oceanica genetic and biometry mapping through high-resolution satellite spectral vegetation indices and sea-truth calibration

In the framework of Posidonia oceanica (PO) preservation activities, a small-scale restoration pilot project was implemented in 2005 at a Santa Marinella site to replace the loss of this important species of seagrass in this zone of the central Tyrrhenian coast via an innovative transplantation approach. In this context, taking into account the recent advances in the fields of high-resolution (HR) satellite/airborne remote-sensing and genetics laboratory analysis techniques, we propose this integrated methodology for monitoring changes in transplanted meadows in regard to perspective to provide support in the assessment of the entire local PO and seagrass population dynamic. According to specific information requirements in terms of radiometric and spectral/spatial resolution, the multispectral data currently available from the QuickBird polar satellite’s four-band (red, green, blue visible and near-infrared) HR sensor were exploited for methodology implementation using a practical ‘image-based’ approach to account for atmospheric and water column turbidity typical of this mid-coastal Mediterranean region. First, the extents and types of seagrass cover were suitably mapped, and then also the distributions of specific vegetation parameters related to PO dynamics and health were assessed by exploiting the remotely sensed satellite-derived radiance signals and point sea-truth calibration measurements of the bio-genetic parameters. In particular, we implemented maps of leaf area index, genetic similarity, and density Giraud indices corresponding to distributions of PO patches using multivariate and data-mining models (artificial neural network) based on appropriately preprocessed radiometric and auxiliary (bathymetry) input variables.     

Knowledge-based interaction protocols for intelligent interactive environments

Intelligent interactive environments are systems whose main features are related to intelligence, interactivity and location. Intelligent interactive environments are implemented in a variety of platforms, such as distributed sensors, actuators and processors for ambient intelligence; distributed and mobile reasoning entities in virtual worlds and augmented reality; and distributed, multiuser information systems such as social networks and service-oriented systems directed to the dissemination of public services and retailing. In the present article, we introduce JamSession, a tool to specify and execute workflow choreographies, as well as to monitor and control heterogeneous resources, which can be specially useful for the specification and implementation of the coordination of real-time, multimodal and multimedia activities. JamSession is used to specify and execute knowledge-based interaction protocols, which are formally grounded and can be formally analysed and verified using a straightforward and user-friendly graphical language. A knowledge-based interaction protocol determines how disparate resources can work cooperatively to build complex behaviour in intelligent interactive environments.     

Spatial Networks of Hybrid I/O Automata for Modeling Excitable Tissue

We propose a new biological framework, spatial networks of hybrid input/output automata (SNHIOA), for the efficient modeling and simulation of excitable-cell tissue. Within this framework, we view an excitable tissue as a network of interacting cells disposed according to a 2D spatial lattice, with the electrical behavior of a single cell modeled as a hybrid input/ouput automaton. To capture the phenomenon that the strength of communication between automata depends on their relative positions within the lattice, we introduce a new, weighted parallel composition operator to specify the influence of one automata over another.The purpose of the SNHIOA model is to efficiently capture the spatiotemporal behavior of wave propagation in 2D excitable media. To validate this claim, we show how SNHIOA can be used to model and capture different spatiotemporal behavior of wave propagation in 2D isotropic cardiac tissue, including normal planar wave propagation, spiral creation, the breakup of spirals into more complex (potentially lethal) spatiotemporal patterns, and the recovery of the tissue to the rest via defibrillation.     

On Performance Congruences for Process Algebras

Based on the hypothesis of durational actions and process synchronization with “busy waiting” mechanism,performance equivalencehas been proposed to introduce a simple form of performance evaluation in process algebras. This equivalence enjoys many of the pleasant properties of those in the untimed setting but it is not a congruence for parallel composition with synchronization. In this paper we give a bisimulation-based characterization of the coarsest congruence contained within performance equivalence (and discuss alternative formulations). This problem was left open in several papers. We study how the new equivalence, calledperformance congruence, relates with other closed equivalences in the literature and show that, unlike other proposals, it is a natural extension of those standard in the untimed setting. The weak version of performance congruence, which abstracts from internal details, is also studied. A number of examples of processes related or taken apart by performance congruence, and its weak version, are provided. A nontrivial one is also presented to illustrate the utility of the new congruences. The paper concludes with further observations concerning performance congruence and with a discussion on related and further interesting work.     

Adaptive output feedback control of a class of non-linear systems using neural networks

This paper presents tools for the design of a neural network based adaptive output feedback controller for a class of partially or completely unknown non-linear multi-input multi-output systems without zero dynamics. Each of the outputs is assumed to have relative degree less or equal to 2. A neural network based adaptive observer is designed to estimate the derivatives of the outputs. Subsequently, the adaptive observer is integrated into a neural network based adaptive controller architecture. Conditions are derived which guarantee the ultimate boundedness of all the errors in the closed loop system. Stability analysis reveals simultaneous learning rules for both the adaptive neural network observer and adaptive neural network controller. The design approach is illustrated using a fourth order two-input two-output example, in which each output has relative degree two.     

Tile-Packing Tomography Is \mathbb{NP}-hard

Discrete tomography deals with reconstructing finite spatial objects from their projections. The objects we study in this paper are called tilings or tile-packings, and they consist of a number of disjoint copies of a fixed tile, where a tile is defined as a connected set of grid points. A row projection specifies how many grid points are covered by tiles in a given row; column projections are defined analogously. For a fixed tile, is it possible to reconstruct its tilings from their projections in polynomial time? It is known that the answer to this question is affirmative if the tile is a bar (its width or height is 1), while for some other types of tiles $\mathbb {NP}$ -hardness results have been shown in the literature. In this paper we present a complete solution to this question by showing that the problem remains $\mathbb {NP}$ -hard for all tiles other than bars.