Parametric investigations of target normal sheath acceleration experiments

One of the most important challenges related to laser-driven ion acceleration research is to actively control some important ion beam features. This is a peculiar topic in the light of future possible technological applications. In the present work we make use of one theoretical model for target normal sheath acceleration in order to reproduce recent experimental parametric studies about maximum ion energy dependencies on laser parameters. The key role played by pulse energy and intensity is enlightened. Finally the effective dependence of maximum ion energy on intensity is evaluated using a combined theoretical approach, obtained by means of an analytical and a particle-in-cell numerical investigation.     

An alternative analytical formulation for the Voigt function applied to resonant effects in nuclear processes

The Voigt function H(a,v) is defined as the convolution of the Gaussian and Lorentzian functions. Recent papers puplished in different areas of physics emphasize the importance of the fast and accurate calculation of the Voigt function for different orders of magnitude of variables a and v. An alternative analytical formulation for the Voigt function is proposed in this paper. This formulation is based on the solution of the non-homogeneous ordinary differential equation, satisfied by the Voigt function, using the Frobenius and parameter variation methods. The functional form of the Voigt function, as proposed, proved simple and precise. Systematic tests are accomplished demonstrating some advantages with other existent methods in the literature and with the numeric method of reference.     

Impact of inelastic phonon scattering in the OFF state of Tunnel-field-effect transistors

We study the impact of electron–phonon interaction on the subthreshold operation region of Tunnel-FETs by means of full-quantum simulations. Our approach is based on the nonequilibrium Green’s function method, where acoustic and optical phonon scatterings are taken into account through the self-consistent Born approximation. Two device architectures are analyzed: InAs nanowire longitudinal Tunnel-FETs, and 2D vertical Tunnel-FETs based on either an GaSb/AlSb/InAs heterostructure or a MoS\(_2\)/WTe\(_2\) van der Waals heterojunction. In InAs nanowire Tunnel-FETs with interface traps, electron–phonon interaction deteriorates the subthreshold swing by allowing trap-assisted tunneling at energies higher than the valence-band edge in the source. In vertical heterojunction Tunnel-FETs, optical phonon scattering increases the OFF current by inducing inelastic transition in the overlap region even in the absence of traps.     

From objects to services: toward a stepwise migration approach for Java applications

Migrating legacy applications toward service-oriented systems is a hard task complicated by the lack of appropriate approaches and tools. In this paper, a stepwise approach is proposed to migrate a Java application into an equivalent application composed of a set of Web services invoked by an orchestrator. In each migration step, a portion of the target application is identified and migrated into a Web service. In this approach, the role of testing is central since after each migration step the new service-oriented application is tested with the aim of checking “its equivalence” with the original version. An experiment based on four Java applications has been conducted to tune the approach and evaluate applicability and effort involved in the migration process. The obtained results confirm the viability of the proposed approach and highlight some encountered SOA migration difficulties.     

Microplane Model M5f for Multiaxial Behavior and Fracture of Fiber-Reinforced Concrete

Despite impressive advances, the existing constitutive and fracture models for fiber-reinforced concrete (FRC) are essentially limited to uniaxial loading. The microplane modeling approach, which has already been successful for concrete, rock, clay, sand, and foam, is shown capable of describing the nonlinear hardening–softening behavior and fracturing of FRC under not only uniaxial but also general multiaxial loading. The present work generalizes model M5 for concrete without fibers, the distinguishing feature of which is a series coupling of kinematically and statically constrained microplane systems. This feature allows simulating the evolution of dense narrow cracks of many orientations into wide cracks of one distinct orientation. The crack opening on a statically constrained microplane is used to determine the resistance of fibers normal to the microplane. An effective iterative algorithm suitable for each loading step of finite element analysis is developed, and a simple sequential procedure for identifying the model parameters from test data is formulated. The model allows a close match of published test data on uniaxial and multiaxial stress–strain curves, and on multiaxial failure envelopes.     

Analytical Model for Geometric and Material Nonlinear Analysis of Externally Prestressed Beams

The analysis of beams prestressed by external slipping tendons involves various difficulties related to the coupling between the local strain of the tendons and the global deformation of the beam. The structural behavior of the beam–tendon system at collapse is ruled both by the nonlinearity of materials and by geometric nonlinear effects. Recent scientific papers have shown the relevance of the geometric effects in evaluating the failure load of externally prestressed beams by considering the tendon eccentricity variation. The change of eccentricity is however only one of the geometric nonlinear effects. In this work the writers present a complete geometric and mechanical nonlinear analytical model based on the theory of small strains and moderate rotations deduced from the finite deformation theory.     

Diffusion coefficient measurements in consolidated clay by RBS micro-scale profiling

The determination of radionuclide diffusion coefficients is necessary for performance assessment of clay formations as a geological barrier for deep geological repositories for high-level radioactive waste.Diffusion coefficients of elements that are retained by the clay and have short diffusion lengths are quite difficult to measure over reasonable time spans, by conventional techniques.This paper presents a novel application of the Rutherford Backscattering Spectrometry (RBS) technique to determine solute diffusion coefficients in consolidated clays. The RBS technique was selected because it allows the measurement of concentration profiles at short range distances (μm).The proposed methodology was tested on the Opalinus clay (OPA) from the Swiss Jura, where the Mont Terri underground laboratory is located. The diffusion of four elements with different adsorption behaviors onto the clay was analyzed: Eu and U as adsorbing elements, Sr as low adsorbing, and Re as a non-adsorbing element with anionic behavior.Apparent diffusion coefficients (D_a) could be experimentally determined for Re, Eu and U after a few days of diffusion time, while for Sr it was only possible to estimate a lower limit for the diffusion coefficient. The uncertainties of the proposed methodology are discussed on the basis of sensitivity studies.     

Model checking for action-based logics

A model checker is described that supports proving logical properties of concurrent systems. The logical properties can be described in different action-based logics (variants of Hennessy-Milner logic). The tools is based on the EMC model checker for the logic CTL. It therefore employs a set of translation functions from the considered logics to CTL, as well as a model translation function from labeled transition systems (models of the action-based logics) to Kripke structures (models for CTL). The obtained tool performs model checking in linear time complexity, and its correctness is guaranteed by the proof that the set of translation functions, coupled with the model translation function, preserves satisfiability of logical formulae.     

Robust frame synchronization for the DVB‐S2 system with large frequency offsets

This paper tackles the problem of frame synchronization design for the Digital Video Broadcasting standard via Satellite (DVB‐S2) system. In particular, the design of a novel frame detection scheme exhibiting robustness against large frequency errors is proposed. Post‐detection integration (PDI) is exploited to provide coarse frame alignment with limited complexity with respect to classical approximate maximum likelihood (ML) solutions. The novel scheme, denoted as differential generalized post‐detection integration, derives from a pragmatic adaptation of the well‐known generalized PDI scheme (IEEE Trans. Commun. 2007; 55 (11):2159–2171), which eliminates its inherent source of weakness in the presence of large frequency offsets, i.e. its non‐differential component given by non‐coherent PDI. The proposed approach manages to reduce the remarkable performance gap with respect to approximate ML techniques available in the literature (IEEE Trans. Commun. 2002; 50 (7):1062–1065), providing the designer with an interesting performance/complexity trade‐off. Performance is numerically evaluated in terms of receiver operating characteristics and mean acquisition time (MAT), handling the acquisition procedure according to a single‐dwell approach. Both threshold crossing and MAX criterion are contrasted to identify the best design solution. Copyright © 2008 John Wiley & Sons, Ltd.     

Effect of mobilizing agents on mycoremediation and impact on the indigenous microbiota

BACKGROUND: Mobilizing agents (MAs) have been suggested to improve the fungal degradation of polycyclic aromatic hydrocarbons (PAHs) in soil. Three different MAs (Tween 20, Tween 80 and soybean oil) were investigated for their ability to stimulate contaminant degradation by either Phlebia sp. DABAC 9 or Allescheriella sp. DABAC1 in a soil spiked with a mixture of PAHs. RESULTS: Phlebia sp. and Allescheriella sp. markedly differed in their growth capabilities under non‐sterile conditions and without MAs (3.0 versus 0.1 µg ergosterol g^?1 soil, respectively). However, soybean oil led to a 35‐fold increase of Allescheriella sp. growth. Contaminant degradations by Phlebia sp. DABAC 9 and Allescheriella sp. DABAC 1 were best supported by soybean oil and Tween 20, respectively. Enumeration of cultivable bacteria and denaturing gradient gel electrophoresis (DGGE) analysis of PCR‐amplified 16S rRNA showed that microbial density and biodiversity were positively affected by the mycoremediation especially with Allescheriella sp., the use of which led to an evident detoxification. CONCLUSIONS: Allescheriella sp. DABAC 1 appears to be a promising strain in the remediation of PAH‐contaminated soils. The different response of the two fungi to MAs addition confirms the stringent need for a preliminary lab‐scale assessment of fungus/MA combinations prior to application. Copyright © 2009 Society of Chemical Industry