Robust dynamic state feedback for underactuated systems with linearly parameterized disturbances

This article investigates the control problem for underactuated port‐controlled Hamiltonian systems with multiple linearly parameterized additive disturbances including matched, unmatched, constant, and state‐dependent components. The notion of algebraic solution of the matching equations is employed to design an extension of the interconnection and damping assignment passivity‐based control methodology that does not rely on the solution of partial differential equations. The result is a dynamic state‐feedback that includes a disturbance compensation term, where the unknown parameters are estimated adaptively. A simplified implementation of the proposed approach for underactuated mechanical systems is detailed. The effectiveness of the controller is demonstrated with numerical simulations for the magnetic‐levitated‐ball system and for the ball‐on‐beam system.     

Secure communication via quantum illumination

In the quantum illumination protocol for secure communication, Alice prepares entangled signal and idler beams via spontaneous parametric downconversion. She sends the signal beam to Bob, while retaining the idler. Bob imposes message modulation on the beam he receives from Alice, amplifies it, and sends it back to her. Alice then decodes Bob’s information by making a joint quantum measurement on the light she has retained and the light she has received from him. The basic performance analysis for this protocol—which demonstrates its immunity to passive eavesdropping, in which Eve can only listen to Alice and Bob’s transmissions—is reviewed, along with the results of its first proof-of-principle experiment. Further analysis is then presented, showing that secure data rates in excess of 1 Gbps may be possible over 20-km-long fiber links with technology that is available or under development. Finally, an initial scheme for thwarting active eavesdropping, in which Eve injects her own light into Bob’s terminal, is proposed and analyzed.     

An analysis of parameter adaptation in reactive tabu search

On‐line parameter adaptation schemes are widely used in metaheuristics. They are sometimes preferred to off‐line tuning techniques for two main reasons. First, they promise to achieve good performance even on new instance families that have not been considered during the design or the tuning phase of the algorithm. Second, it is assumed that an on‐line scheme could adapt the algorithm's behaviour to local characteristics of the search space. This paper challenges the second hypothesis by analysing the contribution of the parameter adaptation to the performance of a state‐of‐the‐art reactive tabu search () algorithm for the maximum clique problem. Our experimental analysis shows that this on‐line parameter adaptation scheme converges to good instance‐specific settings for the parameters, and that there is no evidence that it adapts to the local characteristics of the search space. The insights gained from the analysis are confirmed by further experiments with an algorithm for the quadratic assignment problem. Together, the results of the two algorithms shed some new light on the reasons behind the effectiveness of .     

A Layered Alumina Composite Tested at High Temperature in Air

An oxidation-resistant interphase for layered alumina composites was prepared by aerosol spray deposition of submicrometer alumina powder. A model composite specimen was made by placing the interphase between thin layers of monolithic alumina. The composite sandwich was hot-pressed to control the interphase fracture resistance for successful crack deflection. Specimens were tested under four-point bending in air at two crosshead speeds at ambient temperature, 1000°C, and 1200°C. The fracture behavior was temperature dependent, with a higher work of fracture at higher temperatures. Interphase delamination and composite toughening behavior were very pronounced at all temperatures. At the highest temperature, the transition to multiple widely distributed cracks and increased crack deflection may be related to inelastic deformation in the alumina.     

Cooperative topological accumulation of vacancies in honeycomb lattices

Present topological study focuses on the formation mechanism of clusters of vacancies in graphenic layers. An original effect that explains both accumulation and self-healing of vacancies represents the original outcome of our investigation whose results, based on the long-range topological properties of the honeycomb lattices, are applicable to defective graphene sheets and general honeycomb lattices when other elements other than carbon are present. Some speculations about the role of long-range bondonic states in such a kind of lattices contribute to the understanding of electronic and transport properties in graphenic nanomaterials.     

Biological characterization of a new silicon based coating developed for dental implants

Taking into account the influence of Si in osteoblast cell proliferation, a series of sol–gel derived silicon based coating was prepared by controlling the process parameters and varying the different Si-alkoxide precursors molar rate in order to obtain materials able to release Si compounds. For this purpose, methyltrimethoxysilane (MTMOS) and tetraethyl orthosilicate (TEOS) were hydrolysed together and the sol obtained was used to dip-coat the different substrates. The silicon release ability of the coatings was tested finding that it was dependent on the TEOS precursor content, reaching a Si amount value around ninefolds higher for coatings with TEOS than for the pure MTMOS material. To test the effect of this released Si, the in vitro performance of developed coatings was tested with human adipose mesenchymal stem cells finding a significantly higher proliferation and mineralization on the coating with the higher TEOS content. For in vivo evaluation of the biocompatibility, coated implants were placed in the tibia of the rabbit and a histological analysis was performed. The evaluation of parameters such as the bone marrow state, the presence of giant cells and the fibrous capsule proved the biocompatibility of the developed coatings. Furthermore, coated implants seemed to produce a qualitatively higher osteoblastic activity and a higher number of bone spicules than the control (uncoated commercial SLA titanium dental implant).     

A service-based architecture for dynamically reconfigurable workflows

In the last few years, business process management systems have been employed for handling information systems of ever increasing complexity. As a consequence, the adoption of modelling languages enabling smooth and seamless transitions among the various phases of the process lifecycle, the ability of exploiting coordination schema over distributed execution contexts and the support for dynamic evolution and reconfiguration have become software engineering issues of great importance. This paper proposes the use of PN-Engine, a decentralized Petri nets execution engine, as a business process enactment engine. PN-Engine, which is based on the Jini service architecture, supports the decentralized execution of process models specified as Petri nets (PNs) enhanced with modular constructs and offers suitable mechanisms for dealing with the aforementioned design issues. PN-Engine allows to deploy and enact a new version of an existing process model without requiring the stopping/removal of older instances that are still running. The paper presents a novel approach enabling a decentralized migration procedure where concurrent portions of older instances migrate asynchronously to the new process model. Advantages of the proposed approach are demonstrated by means of an example concerning a workflow for a wine-production process.     

Thermoelectric Transport Properties of a Quantum Wire,Coupled to a Quantum Dot: Finite Band Effects

We study the thermoelectric transport properties through a quantum wire, modeled on a tight-binding linear chain, with an embedded gate-defined quantum dot. We obtain the thermopower, thermal conductance and electrical conductance with a lateral Fano resonance, linked to a many-body renormalized quantum dot resonant level at the edge of the conduction band strongly hybridized with the van Hove singularity of the one-dimensional density of states of the lead; this resonance appears above the Kondo temperature and is due to a quantum interference thermally activated. We discuss the possibility of practical application of the system to a mesoscopic cooling process and thermopower generators, based on the thermoelectric figure of merit and thermal conductance values. Our results for the thermal transport properties are consistent with those obtained previously for electronic transport.