Numerical models for the simulation of currents in naples gulf

Two numerical hydrodynamic models of wind-driven water circulation in a basin are considered.Some results from their application to the Gulf of Naples are described.     

Reports of the DAS02 working groups

This document is a collection of four working group reports in the areas of digital libraries, document image retrieval, layout analysis, and Web document analysis. These reports were the outcome of discussions by participants at the Fifth IAPR International Workshop on Document Analysis Systems held in Princeton, NJ on 19-21 August 2002.Published online: 16 March 2004     

Quasiparticle correction for electronic transport in molecular wires

In this paper we present calculations of ballistic transport in molecular wires. The calculations are performed using an approximated version of the GW correction in the plasmon-pole framework, which is used to improve the starting Density Functional Theory energy spectrum of the molecule between metallic leads. We show that this correction reduces the error of the correlation part for the electron energy. Finally a model with complex bands is implemented in order to get the damping regime for long polymers.     

A plug-in approach to sparse and robust principal component analysis

We propose a method for sparse and robust principal component analysis. The methodology is structured in two steps: first, a robust estimate of the covariance matrix is obtained, then this estimate is plugged-in into an elastic-net regression which enforces sparseness. Our approach provides an intuitive, general and flexible extension of sparse principal component analysis to the robust setting. We also show how to implement the algorithm when the dimensionality exceeds the number of observations by adapting the approach to the use of robust loadings from ROBPCA. The proposed technique is seen to compare well for simulated and real datasets.     

“Collapsible” lightweight aggregate concrete. Part II: characterization under static and dynamic loadings

In this work a granular cementitious composite has been developed, tailoring its performance to a low compressive strength and high deformation and energy dissipation capacity, which can be required to the material when employed in post-installed screeds for protection of structures and infrastructures against accidental actions such as impact and blast. The required level of performance can be achieved by uniform grain size distribution, paste content as low as minimum theoretical void ratio and low paste strength: it is believed that the synergy between the aforementioned three requirements can allow for energy dissipation capacity after paste cracking due to both rearrangement of grain meso-structure and, in case, grain crushing. After the mix design concept and optimization of the material composition, illustrated in the first part of this companion paper study, the mechanical performance of the composite under static and impact compressive loadings has been thoroughly characterized, as affected by mix-design variables, such as paste volume fraction, water to cement ratio and aggregate size. The reliability will thus be thoroughly checked, of the employed material concept, and the influence will also be investigated, if any, of specimen shape, size and boundary conditions.     

Quantised control of nonlinear systems: analysis of robustness to parameter uncertainty,measurement errors,and exogenous disturbances

We propose a variant of the recently introduced strategy for stabilisation with limited information by D. Liberzon and J.P. Hespanha and analyse its robustness properties. We show that, if the nominal plant can be made input-to-state stable with respect to measurement errors, parameter uncertainty and exogenous disturbances, then this robustness is preserved with this quantised feedback. More precisely, if a sufficient bandwidth is available on the communication network, then the resulting closed loop is shown to be semiglobally input-to-state practically stable.     

A study of heat distribution and dissipation in a micromachined chemoresistive gas sensor

A micromachined chemoresistive gas sensor was studied from the point of view of heat distribution and thermal dissipation: this innovative device for environmental pollutant gas monitoring, is based on a sensitive film of semiconductor metal oxides, kept in temperature by a platinum resistor. In order to avoid electrical interactions between the film heater and the contacts for the film reading, the heater is driven by a square wave, and the film is read when no voltage is provided. Since the working temperature of the film is extremely important for its operation, it is crucial to maintain the temperature fluctuations within few degrees; to this end, in this work we study the heat distribution and dissipation of such a device, aiming to set a proper heating frequency, which will assure a right stability of the working temperature.     

Bisorbicillinoids Produced by the Fungus <Emphasis Type="Italic">Trichoderma citrinoviride</Emphasis> Affect Feeding Preference of the Aphid <Emphasis Type="Italic">Schizaphis graminum</Emphasis>

We report the effects of some bisorbicillinoids isolated from biomass of the fungus Trichoderma citrinoviride on settling and feeding preference of the aphid Schizaphis graminum. Purification of the fungal metabolites was carried out by a combination of column chromatography and thin-layer chromatography using direct and reverse phases. Chemical identification was performed by spectroscopic methods including nuclear magnetic resonance and mass spectrometry. The identified bisorbicillinoids appeared to be bislongiquinolide, its 16,17-dihydro derivative, trichodimerol, and dihydrotrichodimerol. A feeding preference test with alate morphs of S. graminum was used to identify the active fractions. Among the four bisorbicillinoids, dihydrotrichodimerol and bislongiquinolide influenced aphid feeding preference, restraining specimens from settling on leaves treated with metabolites. Taste neurons sensitive to these compounds, particularly to bislongiquinolide, were located on tarsi of the S. graminum alate morphs.