Dynamical Casimir effect with Robin boundary conditions in a three dimensional open cavity

We consider a massless scalar field in 1+1 dimensions inside a cavity composed by a fixed plate, which imposes on the field a Robin BC, and an oscillating one, which imposes on the field a Dirichlet BC. Assuming that the plate moves for a finite time interval, and considering parametric resonance, we compute the total number of created particles inside the cavity. We generalize our results to the case of two parallel plates in 3+1 dimensions.Comment: This work was presented in the Conference QFEXT09, held at the University of Oklahoma, Norman, OK, USA, September 21-25, 2009, and will appear in the proceedings of this conference. It contains 4 figure

Estimative for the size of the compactification radius of a one extra dimension Universe

In this work, we use the Casimir effect to probe the existence of one extra dimension. We begin by evaluating the Casimir pressure between two plates in a $M^4\times S^1$ manifold, and then use an appropriate statistical analysis in order to compare the theoretical expression with a recent experimental data and set bounds for the compactification radius

Decoupled Sampling-Based Motion Planning for Multiple Autonomous Marine Vehicles

There is increasing interest in the deployment and operation of multiple autonomous marine vehicles (AMVs) for a number of challenging scientific and commercial operational mission scenarios. Some of the missions, such as geotechnical surveying and 3D marine habitat mapping, require that a number of heterogeneous vehicles operate simultaneously in small areas, often in close proximity of each other. In these circumstances safety, reliability, and efficient multiple vehicle operation are key ingredients for mission success. Additionally, the deployment and operation of multiple AMVs at sea are extremely costly in terms of the logistics and human resources required for mission supervision, often during extended periods of time. These costs can be greatly minimized by automating the deployment and initial steering of a vehicle fleet to a predetermined configuration, in preparation for the ensuing mission, taking into account operational constraints. This is one of the core issues addressed in the scope of the Widely Scalable Mobile Underwater Sonar Technology project (WiMUST), an EU Horizon 2020 initiative for underwater robotics research. WiMUST uses a team of cooperative autonomous ma- rine robots, some of which towing streamers equipped with hydrophones, acting as intelligent sensing and communicat- ing nodes of a reconfigurable moving acoustic network. In WiMUST, the AMVs maintain a fixed geometric formation through cooperative navigation and motion control. Formation initialization requires that all the AMVs start from scattered positions in the water and maneuver so as to arrive at required target configuration points at the same time in a completely au- tomatic manner. This paper describes the decoupled prioritized vehicle motion planner developed in the scope of WiMUST that, together with an existing system for trajectory tracking, affords a fleet of vehicles the above capabilities, while ensuring inter- vehicle collision and streamer entanglement avoidance. Tests with a fleet of seven marine vehicles show the efficacy of the system planner developed.Peer reviewe

Finding non-dominated bicriteria shortest pairs of disjoint simple paths

http://www.sciencedirect.com/science/article/B6VC5-4VBDKNX-1/2/b7e59602a9fb4eb885f498b0d8c779c

Plant / Controller Optimization with applications to Integrated Surface Sizing and Feedback Controller Design for Autonomous Underwater Vehicles (AUVs)

This paper describes a solution to the following plant controller optimization (PCO) problem: given an autonomous underwater vehicle (AUV) - with a fixed baseline body configuration - that is required to operate over a finite number of representative trimming conditions in the vertical plane, determine the optimal size of the bow and stern control surfaces so that a weighted average J of the power required at trimming is minimized, subject to the conditions that: i) a given set of open loop requirements are met, and ii) stabilizing feedback controllers can be designed to meet desired time and frequency closed loop performance requirements about each trimming point. The solution proposed is rooted in the theory of Linear Matrix Inequalities (LMIs) and leads to efficient PCO algorithms that build on a recently released LMI Toolbox.The work of C. Silvestre and A. Pascoal was partially supported by the Portuguese PRAXIS XXI Programme under the INFANTE project. The work of the first author was also supported by NATO Scholarship 17/A/94/PO The second author benefited from a NATO Fellowship during his 1996-98 sabbatical at the Naval Postgraduate School

Mobile pervasive augmented reality systems the role of user preferences in perceived quality of experience

This work addresses reasons and aspects required to boost the acceptance and use of mobile pervasive augmented reality systems - MPARS - for outdoor applications and the need to develop context-aware close to- real-time feedback mechanisms that take into consideration a continuous measurement of Quality of Experience. For this purpose, we delve into how user preferences can be integrated in context-aware feedback systems, proposing a Quality of Experience theoretical model derived from an analysis on technology adoption models and user preferences. The how and why such model can be integrated into future solutions is also addressed.info:eu-repo/semantics/acceptedVersio

The University of Lisbon’s cultural heritage survey (2010–2011)

In this paper, a survey of the cultural heritage of the University of Lisbon (2010–2011) will be presented, with a focus on the methodological approach. Main results will be discussed, as well as future perspectives regarding management, preservation and access of the university’s scientific and artistic collections, and buildings of artistic, architectonic and historical significance

Urethanes and polyurethanes from suberin 2: synthesis and characterization

Polyurethanes based on suberin from cork of Quercus suber L. and conventional isocyanate monomers were prepared and fully characterized in terms of both structure (FTIR and 1 H NMR spectroscopy) and thermal properties (differential scanning calorimetry and thermogravimetric analysis). Two fractions were systematically isolated, namely (i) methylene-chloride soluble products, which corresponded to linear and branched macromolecules and (ii) methylene-chloride insoluble products, representing the crosslinked material. The structures of these polymers were regular and no appreciable side reactions were detected. DSC analyses provided information about the glass transition temperature of both fractions and this parameter was correlated with the stiffness of the isocyanate used. The TGA of these polyurethanes showed that they started to degrade at about 175°C and that the residue at 400°C was around 50%. The highest amounts of insoluble fractions, as well as the highest Tgs, were reached when an initial [NCO]/[OH] of unity was used.info:eu-repo/semantics/publishedVersio

Particle creation in a Robertson-Walker Universe revisited

We reanalyze the problem of particle creation in a 3+1 spatially closed Robertson-Walker space-time. We compute the total number of particles produced by this non-stationary gravitational background as well as the corresponding total energy and find a slight discrepancy between our results and those recently obtained in the literatur

Cork suberin as a new source of chemicals.: 1. isolation and chemical characterization of its composition

Extractive-free cork from Quercus suber L. was submitted to a solvolysis treatment with methanolic NaOH which yielded 37% (o.d. cork) of suberin. This mixture of compounds was thoroughly characterized by FTIR, 1 H- and 13C-NMR, gas chromatogra phy coupled with mass spectrometric (GC–MS) analysis, vapour pressure osmometry (VPO), mass spectrography (MS) and gel permeation chromatography (GPC). After derivatization, the main components of the volatile fraction, representing less than half of the total, were found to be v-hydroxymonocarboxylates, a,v-dicarboxylates, simple alkanoates and 1-alkanols, all with chain lengths ranging from C16 to C24. A second fraction, with an average molecular weight about three times higher, was detected by VPO, MS and GPC. The presence of this important fraction in cork suberin had not been recognized in earlier studies. Both fractions constitute interesting precursors for the elaboration of new materials.info:eu-repo/semantics/publishedVersio