Technical Note: Regularization performances with the error consistency method in the case of retrieved atmospheric profiles

International audienceThe retrieval of concentration vertical profiles of atmospheric constituents from spectroscopic measurements is often an ill-conditioned problem and regularization methods are frequently used to improve its stability. Recently a new method, that provides a good compromise between precision and vertical resolution, was proposed to determine analytically the value of the regularization parameter. This method is applied for the first time to real measurements with its implementation in the operational retrieval code of the satellite limb-emission measurements of the MIPAS instrument and its performances are quantitatively analyzed. The adopted regularization improves the stability of the retrieval providing smooth profiles without major degradation of the vertical resolution. In the analyzed measurements the retrieval procedure provides a vertical resolution that, in the troposphere and low stratosphere, is smaller than the vertical field of view of the instrument

Optimal oblivious routing under linear and ellipsoidal uncertainty

In telecommunication networks, a common measure is the maximum congestion (i.e., utilization) on edge capacity. As traffic demands are often known with a degree of uncertainty, network management techniques must take into account traffic variability. The oblivious performance of a routing is a measure of how congested the network may get, in the worst case, for one of a set of possible traffic demands. We present two models to compute, in polynomial time, the optimal oblivious routing: a linear model to deal with demands bounded by box constraints, and a second-order conic program to deal with ellipsoidal uncertainty, i.e., when a mean-variance description of the traffic demand is given. A comparison between the optimal oblivious routing and the well-known OSPF routing technique on a set of real-world networks shows that, for different levels of uncertainty, optimal oblivious routing has a substantially better performance than OSPF routing. © Springer Science+Business Media, LLC 2007

Probing the Evaporation Dynamics of Ethanol/Gasoline Biofuel Blends Using Single Droplet Manipulation Techniques

Peer reviewedPublisher PD

A Gray-Box Approach for Curriculum Learning

Curriculum learning is often employed in deep reinforcement learning to let the agent progress more quickly towards better behaviors. Numerical methods for curriculum learning in the literature provides only initial heuristic solutions, with little to no guarantee on their quality. We define a new gray-box function that, including a suitable scheduling problem, can be effectively used to reformulate the curriculum learning problem. We propose different efficient numerical methods to address this gray-box reformulation. Preliminary numerical results on a benchmark task in the curriculum learning literature show the viability of the proposed approach

Extended Formulations in Mixed-integer Convex Programming

We present a unifying framework for generating extended formulations for the polyhedral outer approximations used in algorithms for mixed-integer convex programming (MICP). Extended formulations lead to fewer iterations of outer approximation algorithms and generally faster solution times. First, we observe that all MICP instances from the MINLPLIB2 benchmark library are conic representable with standard symmetric and nonsymmetric cones. Conic reformulations are shown to be effective extended formulations themselves because they encode separability structure. For mixed-integer conic-representable problems, we provide the first outer approximation algorithm with finite-time convergence guarantees, opening a path for the use of conic solvers for continuous relaxations. We then connect the popular modeling framework of disciplined convex programming (DCP) to the existence of extended formulations independent of conic representability. We present evidence that our approach can yield significant gains in practice, with the solution of a number of open instances from the MINLPLIB2 benchmark library.Comment: To be presented at IPCO 201

OSPF routing with optimal oblivious performance ratio under polyhedral demand uncertainty

We study the best OSPF style routing problem in telecommunication networks, where weight management is employed to get a routing configuration with the minimum oblivious ratio. We consider polyhedral demand uncertainty: the set of traffic matrices is a polyhedron defined by a set of linear constraints, and a routing is sought with a fair performance for any feasible traffic matrix in the polyhedron. The problem accurately reflects real world networks, where demands can only be estimated, and models one of the main traffic forwarding technologies, Open Shortest Path First (OSPF) routing with equal load sharing. This is an NP-hard problem as it generalizes the problem with a fixed demand matrix, which is also NP-hard. We prove that the optimal oblivious routing under polyhedral traffic uncertainty on a non-OSPF network can be obtained in polynomial time through Linear Programming. Then we consider the OSPF routing with equal load sharing under polyhedral traffic uncertainty, and present a compact mixed-integer linear programming formulation with flow variables. We propose an alternative formulation and a branch-and-price algorithm. Finally, we report and discuss test results for several network instances. © 2009 Springer Science+Business Media, LLC

Provisioning virtual private networks under traffic uncertainty

We investigate a network design problem under traffic uncertainty that arises when provisioning Virtual Private Networks (VPNs): given a set of terminals that must communicate with one another, and a set of possible traffic matrices, sufficient capacity has to be reserved on the links of the large underlying public network to support all possible traffic matrices while minimizing the total reservation cost. The problem admits several versions depending on the desired topology of the reserved links, and the nature of the traffic data uncertainty. We present compact linear mixed-integer programming formulations for the problem with the classical hose traffic model and for a less conservative robust variant relying on the traffic statistics that are often available. These flow-based formulations allow us to solve optimally medium-to-large instances with commercial MIP solvers. We also propose a combined branch-and-price and cutting-plane algorithm to tackle larger instances. Computational results obtained for several classes of instances are reported and discussed. © 2006 Wiley Periodicals, Inc

Engineering robust next-generation networks

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ESDA2008-59395 LIFECYCLE MONITORING FOR THE AUTOMOTIVE ECO-SUSTAINABILITY

ABSTRACT The growth sustainability requires dramatic changes to lower the natural resources consumption and the surroundings pollution, by recovery/remediation processes. The EU policy aims at the extended producers/suppliers responsibility, with effective charges on the products allowed to be put on the market, used and called-back, in view of the properly small impact and transparent lifecycle acknowledgement. This leads to «extensions» in designing the new offers with integrated monitoring and service functions. The design for the lifecycle eco-effectiveness is accomplishment, better qualifying the far-seeing companies according to the EU eco-policy. The idea is to reach the duty visibility, by the extended plug-and-play concept, based on series of integrated design options, assigning the structural and functional modules, for the operation monitoring, the reliability assessment and the impact appraisal. This instrumental setting includes intangible information/communication aids, to confer ambient intelligence abilities. This way, the on-process visibility is assured, and exploited for on-duty servicing and end-of-life processing. The example case chosen deals with the critical situation of the parts manufactured in plastics, which are deemed to represent most relevant portion in the cars to come. The following recovery options are possible: -the reuse of the reconditioned items, according to suitably assessed life-extension opportunities; -the recycling of the warn-out components, with the regeneration and reusing of the materials; -the thermal recovery of residual stuffs, within careful handling and pollution-safe warnings ; -the reduction to registered ASR, automobile shredding residue, within the EU directives limits. The on-board information system includes, as innovative feature, the resort to identifying tags or labels, to be read and written through wireless links. The technology exploits cheap and compact supports, allowing the labelling of the component, from production, to lifecycle, with an identifying code. The RFID, Radio Frequency Identification Device, is privileged, as ideal means for the component traceability and the history, use modes/styles and cumulated issues storing. ACRONYMS ASR, Automobile Shredding Residue. ELV, End-of-Life Vehicle

Symmetrical anatomical variant of the anterior belly of the digastric muscle: clinical implicat

The digastric muscle is an important surgical landmark. Several anatomical variants of the digastric muscle are reported in literature and, in particular, the presence of accessory anterior bellies of the muscle is not uncommon. Here, an unreported symmetrical variant of the digastric muscle was found during a dissection of the suprahyoid region. The dissection showed digastric muscles with an accessory anterior belly, which originated from the anterior belly of muscles in proximity and anteriorly to the intermediate tendon. The accessory bellies were fused together on the midline and were attached with a unique tendon to the inner surface of the mental symphysis. These muscles completely filled the submental triangle. This unreported anatomical variant could be considered an additional contribution to description of the anatomical variants of the digastric muscle, with several implications in head and neck pathology, diagnosis and surgery.