An MPC approach to the design of two-layer hierarchical control systems

A methodology for the design of two-layer hierarchical control systems is presented. The high layer corresponds to a system with slow dynamics, whose control inputs must be provided by subsystems with faster dynamics placed at the low layer. Model Predictive Control laws are synthesized for both layers and overall convergence properties are established. The use of different control configurations is also considered by allowing the switching on/off of the subsystems at the low layer. A simulation example is reported to witness the potentialities of the proposed solution.     

Ontogenetic development of migration: Lagrangian drift trajectories suggest a new paradigm for sea turtles

Long distance migration occurs in a wide variety of taxa including birds, insects, fishes, mammals and reptiles. Here, we provide evidence for a new paradigm for the determinants of migration destination. As adults, sea turtles show fidelity to their natal nesting areas and then at the end of the breeding season may migrate to distant foraging sites. For a major rookery in the Mediterranean, we simulated hatchling drift by releasing 288 000 numerical particles in an area close to the nesting beaches. We show that the pattern of adult dispersion from the breeding area reflects the extent of passive dispersion that would be experienced by hatchlings. Hence, the prevailing oceanography around nesting areas may be crucial to the selection of foraging sites used by adult sea turtles. This environmental forcing may allow the rapid evolution of new migration destinations if ocean currents alter with climate change.     

Comparative analysis of Rac1 binding efficiency with different classes of ligands: morpholines, flavonoids and imidazoles

The focal adhesion pathway has a great impact on cellular growth and survival. Its disregulation is correlated with the loss of cellular mechanical properties. Such modifications are, in many cases, associated with pathologies such as cancer and cardiovascular diseases. Actin remodeling is a critical reaction cascade embedded in focal adhesion pathway, and Rac1 is one of the proteins involved in actin remodeling. In order to design highly selective pharmacophores against this target, it is necessary to maximize the binding affinity of chemical entities against Rac1. To this purpose we propose an integrative chemo-bioinformatics tool to screen ligand specificity for a target protein. Our integrative workflow includes chemo-informatics data mining (Chemical System), structural bioinformatics and combined exploratory data analysis. We have applied this integrative chemo-bioinformatics workflow to a comparative analysis of three different classes of ligands (morpholines, flavonoids and imidazoles) against the Rac1 protein. Our analysis emphasizes the presence of several ligands that preferentially dock Rac1 in the domain that seems to be responsible for Rac1-phospholipase C gamma 1 interaction. Recent studies have highlighted the Rac1 and PLC interactions in platelet adhesion. Our study has highlighted the role of Rac1-PLC gamma1 interaction in cytoskeleton remodeling associated with cardiovascular diseases. Rac1 PLC interaction is Calcium dependent. This suggest that some of the analysed ligands, could be used to control the Calcium dependent cytoskeleton remodeling since they dock Rac1 in the switch 2 domain. Our results, in a nanotechnology perspective, also endorse the use Rac1's switch 2 domain suitable for new highly specific biosensors.     

Reference architectures modelling and compliance checking

Software and Systems Modeling - Reference architectures (RAs) are successfully used to represent families of concrete software architectures in several domains such as automotive, banking, and the...     

Application of high resolution shear-wave seismic methods to a geotechnical problem

Applied geophysical techniques in underground exploration can be useful in defining the subsoil geometry and the spatial relationships of the physico–mechanical properties of the materials. An example is presented to demonstrate how high-resolution seismic techniques using shear waves can assist with a geotechnical issue. The survey has been carried out to elucidate the subsoil geometry and characterize lithotypes in terms of physico-mechanical parameters, useful in the geotechnical study of an historic monument in which fractures developed following a downslope excavation.     

Global adaptive learning control of robotic manipulators by output error feedback

This paper addresses the problem of designing a global, output error feedback based, adaptive learning control for robotic manipulators with revolute joints and uncertain dynamics. The reference signals to be tracked are assumed to be smooth and periodic with known period. By developing in Fourier series expansion the input reference signals of every joint, an adaptive, output error feedback, learning control is designed, which ‘learns’ the input reference signals by identifying their Fourier coefficients: global asymptotic and local exponential stability of the tracking error dynamics are obtained when the Fourier series expansion of each input reference signal is finite, while arbitrary small tracking errors are achieved otherwise. The resulting control is not model based and depends only on the period of the reference signals and on some constant bounds on the robot dynamics. Copyright © 2008 John Wiley & Sons, Ltd.     

The mechanical properties of a nanocrystalline Al2O3/a-Al2O3 composite coating measured by nanoindentation and Brillouin spectroscopy

In this work, ellipsometry, Brillouin spectroscopy and nanoindentation are combined to assess the mechanical properties of a nanocrystalline Al₂O₃/a-Al₂O₃ composite coating with high accuracy and precision. The nanocomposite is grown by pulsed laser deposition at either room temperature or 600 °C. The adhesive strength is evaluated by nanoscratch tests. In the room temperature process the coating attains an unusual combination of compactness, strong interfacial bonding, moderate stiffness (E = 195 ± 9 GPa and ν = 0.29 ± 0.02) and significant hardness (H = 10 ± 1 GPa), resulting in superior plastic behavior and a relatively high ratio of hardness to elastic modulus (H/E = 0.049). These features are correlated to the nanostructure of the coating, which comprises a regular dispersion of ultrafine crystalline Al₂O₃ nanodomains (2–5 nm) in a dense and amorphous alumina matrix, as revealed by transmission electron microscopy. For the coating grown at 600 °C, strong adhesion is also observed, with an increase of stiffness and a significant enhancement of hardness (E = 277 ± 9 GPa, ν = 0.27 ± 0.02 and H = 25 ± 1 GPa), suggesting an outstanding resistance to wear (H/E = 0.091).     

Perceptual aspects in data hiding

In this paper, a new methodology for the secure embedding of data in a video sequence is presented. To guarantee the imperceptibility of the embedded data, we propose a novel method for selecting the frame regions that may be considered perceptually non relevant. For each frame of the video, a saliency analysis is performed based on features that are thought to be relevant to the Human Vision System. In particular, the local contrast, the color, and the motion information have been considered. By weighting all these features, an importance map is built to drive the embedding procedure. Subjective experiment results show that the artifacts caused by this localized embedding procedure are considered by the subjects to be less annoying than if the data hiding is performed on the whole frame. Nevertheless robustness is achieved.     

POPEYE: providing collaborative services for ad hoc and spontaneous communities

Next generation collaborative systems will offer mobile users seamless and natural collaboration amongst a diversity of agents, within distributed, knowledge-rich and virtualized working environments. This ambitious goal faces numerous challenges from the underlying communication infrastructure to the high level application services, with the aim to provide services with the appropriate quality (such as persistence, synchronization, and security). Most currently available tools supporting collaboration address either rather traditional and rigid intra-organizational collaboration scenarios or, at the opposite, completely free and unstructured open communities’s interactions. Emerging dynamic, flexible and ad hoc collaboration schemes are hardly or not supported at all. The POPEYE framework offers collaborative services for applications that aim to enable spontaneous collaboration over P2P wireless ad hoc groups, where fixed infrastructure is not a prerequisite, where virtual communities can emerge spontaneously and share data with the appropriate quality of service for business applications (persistence, synchronization, security, etc.).