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See detailIdentification method of an advanced constitutive law for nickel-based alloy Haynes 230 used in solar receivers
Morch, Hélène ULiege; Duchene, Laurent ULiege; Habraken, Anne ULiege

in Journal of Physics. Conference Series (2018, August), 1063

A model to study panels of thin tubes of Haynes 230 nickel alloy used in solar receivers has been developed. The thermo-mechanical behavior of these tubes is simulated using an advanced model capable of ... [more ▼]

A model to study panels of thin tubes of Haynes 230 nickel alloy used in solar receivers has been developed. The thermo-mechanical behavior of these tubes is simulated using an advanced model capable of representing specific characteristics such as viscosity, kinematic and cyclic hardening, static recovery, or dynamic recovery. The constitutive law implemented is a finite-element visco-plastic model based on the work of Chaboche. Due to its complexity, the model uses a significant number of parameters that need to be identified at several temperatures. The aim of this article is to define an efficient method for the identification of the parameters of this Chaboche model adapted to cyclic thermo-mechanical loading. [less ▲]

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See detailMachine Learning in High Energy Physics Community White Paper
Albertsson, Kim; Altoe, Piero; Anderson, Dustin et al

in Journal of Physics. Conference Series (2018), 1085

Machine learning is an important research area in particle physics, beginning with applications to high-level physics analysis in the 1990s and 2000s, followed by an explosion of applications in particle ... [more ▼]

Machine learning is an important research area in particle physics, beginning with applications to high-level physics analysis in the 1990s and 2000s, followed by an explosion of applications in particle and event identification and reconstruction in the 2010s. In this document we discuss promising future research and development areas in machine learning in particle physics with a roadmap for their implementation, software and hardware resource requirements, collaborative initiatives with the data science community, academia and industry, and training the particle physics community in data science. The main objective of the document is to connect and motivate these areas of research and development with the physics drivers of the High-Luminosity Large Hadron Collider and future neutrino experiments and identify the resource needs for their implementation. Additionally we identify areas where collaboration with external communities will be of great benefit. [less ▲]

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See detailThermomechanical simulations of blanking process operated over a wide range of punch velocities
Canales Cardenas, Cristian ULiege; Boman, Romain ULiege; Ponthot, Jean-Philippe ULiege

in Journal of Physics. Conference Series (2018), 1063

numerical model based on the finite element method has been developed to simulate the blanking process. Thanks to this model we analyse the influence of punch velocities during blanking on the quality of ... [more ▼]

numerical model based on the finite element method has been developed to simulate the blanking process. Thanks to this model we analyse the influence of punch velocities during blanking on the quality of the sheared edge and the characteristic parameters governing the process (maximum punch force and displacement, temperature increase). In this model, inertia, viscous and thermal effects are properly considered by means of a unified thermomechanical framework. A full remeshing approach is adopted to overcome the high distortion of elements due to large deformations, prior to fracture. The material strain-rate sensitivity is introduced by means of an extension of elasto-viscoplastic constitutive equations for the large strain regime. The inertial effects are considered thanks to an implicit time integration scheme. Crack propagation during the process is tracked using the element deletion method driven by an uncoupled damage criterion. Finally, the coupled thermomechanical problem is solved by an isothermal staggered scheme. Experimental and numerical results are compared for the entire range of punch velocities under consideration. Good agreement between both results has been found. [less ▲]

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See detailLi4Ti5O12 powders by spray-drying: influence of the solution concentration and particle size on the electrochemical properties
Jamin, Claire; Jungers, Thomas ULiege; Piffet, Caroline ULiege et al

in Journal of Physics. Conference Series (2018), 1081

The lithium battery electrode compound Li4Ti5O12 was synthesized by calcination of precursor powders obtained through spray-drying of solutions prepared with titanium isopropoxide and lithium nitrate. X ... [more ▼]

The lithium battery electrode compound Li4Ti5O12 was synthesized by calcination of precursor powders obtained through spray-drying of solutions prepared with titanium isopropoxide and lithium nitrate. X-ray diffraction and thermal analysis coupled to mass spectrometry show that single phase crystalline Li4Ti5O12 particles can be obtained after calcination at 800 °C for 2 hours. Decreasing the solution concentration leads to smaller particle sizes but also to an unexpected decrease of the electrochemical capacity, probably related to the presence of residual Li2TiO3. On the contrary, the capacity of the Li4Ti5O12 powder prepared with the high concentration solution can be increased from 150 mAh/g to 165 mAh/g (C/4 rate) by grinding. These results highlight the fact that smaller particles do not systematically display better performances for Li+ intercalation/desintercalation and confirm the need for a comprehensive approach including parameters such as crystallinity, phase purity or agglomeration. [less ▲]

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See detailHexaferrite multiferroics: From bulk to thick films
Koutzarova, T.; Ghelev, C.; Peneva, P. et al

in Journal of Physics. Conference Series (2018), 992(1),

We report studies of the structural and microstructural properties of Sr3Co2Fe24O41 in bulk form and as thick films. The precursor powders for the bulk form were prepared following the sol-gel auto ... [more ▼]

We report studies of the structural and microstructural properties of Sr3Co2Fe24O41 in bulk form and as thick films. The precursor powders for the bulk form were prepared following the sol-gel auto-combustion method. The prepared pellets were synthesized at 1200 °C to produce Sr3Co2Fe24O41. The XRD spectra of the bulks showed the characteristic peaks corresponding to the Z-type hexaferrite structure as a main phase and second phases of CoFe2O4 and Sr3Fe2O7-x. The microstructure analysis of the cross-section of the bulk pellets revealed a hexagonal sheet structure. Large areas were observed of packages of hexagonal sheets where the separate hexagonal particles were ordered along the c axis. Sr3Co2Fe24O41 thick films were deposited from a suspension containing the Sr3Co2Fe24O41 powder. The microstructural analysis of the thick films showed that the particles had the perfect hexagonal shape typical for hexaferrites. © Published under licence by IOP Publishing Ltd. [less ▲]

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See detailStructural and morphological properties of sol-gel ZnO:Ni films
Ivanova, T.; Harizanova, A.; Koutzarova, T. et al

in Journal of Physics. Conference Series (2018), 992(1),

Ni doping induces modifications and considerable changes in the optical, electrical and magnetic properties of ZnO films. In this work, the influence is discussed of Ni-doping (two nickel concentrations ... [more ▼]

Ni doping induces modifications and considerable changes in the optical, electrical and magnetic properties of ZnO films. In this work, the influence is discussed of Ni-doping (two nickel concentrations) and annealing temperature (ranging from 300 ° C to 800 °C) on the structural and optical properties of sol-gel derived ZnO:Ni films. Uniform and smooth films were obtained by spin-coating on quartz and Si substrates. The ZnO:Ni films were crystallized in wurtzite phase with no impurity phases found for annealing temperatures up to 600 °C. The size of the crystallites was strongly affected by the Ni content and the heat treatment. Furthermore, the Ni doping improved the optical transparency of the sol-gel films, while the AFM studies showed that the film morphology and the roughness were influenced by the nickel doping. © Published under licence by IOP Publishing Ltd. [less ▲]

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See detailMonitoring of comets activity and composition with the TRAPPIST-North telescope
Moulane, Youssef ULiege; Benkhaldoun, Zouhair; Jehin, Emmanuel ULiege et al

in Journal of Physics. Conference Series (2017, July), 869

TRAPPIST-North (TRAnsiting Planets and PlanetesImals Small Telescope) is a 60-cm robotic telescope that was installed in May 2016 at the Oukaimeden Observatory. The project is led by the University of ... [more ▼]

TRAPPIST-North (TRAnsiting Planets and PlanetesImals Small Telescope) is a 60-cm robotic telescope that was installed in May 2016 at the Oukaimeden Observatory. The project is led by the University of Liège (Belgium) and the Caddi Ayad University of Marrakech (Morocco). This telescope is a twin of the TRAPPIST-South telescope, which was installed at the ESO La Silla Observatory in 2010. The TRAPPIST telescopes are dedicated to the detection and characterization of planets orbiting stars other than our Sun (exoplanets) and the study of comets and other small bodies in our solar system. For the comets research, these telescopes have very sensitive CCD cameras with complete sets of narrow band filters to measure the production rates of several gases (OH, NH, CN, C3 and C2) and the dust. With TRAPPIST-North we can also observe comets that would not be visible in the southern hemisphere. Therfore, with these two telescopes, we can now observe continuously the comets around their orbit. We project to study individually the evolution of the activity, chemical composition, dust properties, and coma morphology of several comets per year and of different origins (New comets and Jupiter Family comets) over a wide range of heliocentric distances, and on both sides of perihelion. We measure the production rates of each daughter molecules using a Haser model, in addition to the Afρ parameter to estimate the dust production in the coma. In this work, we present the first measurements of the production rates of comet C/2013 X1 (PANSTARRS) observed with TN in June 2016, and the measurements of comet C/2013 V5 (Oukaimeden) observed in 2014 with TRAPPIST-South. [less ▲]

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See detailPrompt atmospheric neutrino flux in perturbative QCD and its theoretical uncertainties
Jeong, Yu Seon; Bhattacharya, Atri ULiege; Enberg, Rikard et al

in Journal of Physics. Conference Series (2017), 888(1), 012117

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See detailThe Role of Super-Atom Molecular Orbitals in Doped Fullerenes in a Femtosecond Intense Laser Field
Berrah, N.; Xiong, H.; Mignolet, Benoît ULiege et al

in Journal of Physics. Conference Series (2017), 875(4),

The photoionization of complex targets, such as endohedral fullerenes, in strong laser fields has been studied experimentally and theoretically. We used the prototype Ho3N@C80 interacting with intense (0 ... [more ▼]

The photoionization of complex targets, such as endohedral fullerenes, in strong laser fields has been studied experimentally and theoretically. We used the prototype Ho3N@C80 interacting with intense (0.1-5×1014 W/cm2), short (30 fs), 800 nm laser pulses giving rise to multiply charged parent ions. The power law dependence of Ho3N@C80 q+, q=1-2, was found to be different from that of C60. Time-dependent density functional theory computations suggest that the fast ionization of the SAMO states in Ho3N@C80 is responsible for the different power law behavior. [less ▲]

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See detailEvaluation of the Antiproton Flux from the Antineutrino Electron Scattering
Alekseev, V. V.; Belotsky, K. M.; Bogomolov, Yu V. et al

in Journal of Physics. Conference Series (2016), 675(3), 032004

Recent experiments in high enegry cosmic ray physics, PAMELA and AMS-02, excite a new interest to the mechanisms of generation of galactic antiparticles. In spite of the fact that global picture coincides ... [more ▼]

Recent experiments in high enegry cosmic ray physics, PAMELA and AMS-02, excite a new interest to the mechanisms of generation of galactic antiparticles. In spite of the fact that global picture coincides with the predictions of the standard model, there are some black spots stimulating scientists to involve into research a particularly new physics like dark matter. In the present work, we make an attempt to estimate the impact of standard neutrino processes into the total flux of secondary antiprotons detected by contemporary experiments. [less ▲]

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See detailOptical characterization of Sol-Gel ZnO:Al thin films
Ivanova, T; Harizanova, A; Koutzarova, T et al

in Journal of Physics. Conference Series (2016), 700

This paper presents a sol-gel technological process for preparing thin films of ZnO and ZnO:Al. The effect of annealing treatments (500, 600, 700 and 800 oC) on their properties was studied. The ... [more ▼]

This paper presents a sol-gel technological process for preparing thin films of ZnO and ZnO:Al. The effect of annealing treatments (500, 600, 700 and 800 oC) on their properties was studied. The structural evolution with the temperature was investigated by using X-Ray diffraction (XRD). Fourier Transform Infrared (FTIR) and UV-VIS spectrophotometry were applied to characterizing the films’ vibrational and optical properties. The ZnO and ZnO:Al films possessed a polycrystalline structure. The films studied are highly transparent in the visible spectral range. The optical band gap values and the haze parameter were also determined. [less ▲]

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See detailInvestigation of sol-gel yttrium doped ZnO thin films: structural and optical properties
Ivanova, T; Harizanova, A; Koutzarova, T et al

in Journal of Physics. Conference Series (2016)

Nanostructured metal oxide films are extensively studied due to their numerous applications such as optoelectronic devices, sensors. In this work, we report the Y–Zn–O nanostructured films prepared by sol ... [more ▼]

Nanostructured metal oxide films are extensively studied due to their numerous applications such as optoelectronic devices, sensors. In this work, we report the Y–Zn–O nanostructured films prepared by sol-gel technology from sols with different concentration of yttrium precursor, followed by post-annealing treatment. The Y doped ZnO thin films have been deposited on Si and quartz substrates by spin coating method, then treated at températures ranging from 300-800°C. XRD analysis reveals modification of the film structure and phases in the doped ZnO films. [less ▲]

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See detailHigh-energy cosmic antiparticle excess vs. isotropic gamma-ray background problem in decaying dark matter Universe
Alekseev, V. V.; Belotsky, K. M.; Bogomolov, Yu V. et al

in Journal of Physics. Conference Series (2016), 675(1), 012023

We are going to show that any conventional decaying dark matter model, providing an explanation of cosmic antiparticle excess observed by PAMELA and AMS-02, inevitably faces the contradiction with ... [more ▼]

We are going to show that any conventional decaying dark matter model, providing an explanation of cosmic antiparticle excess observed by PAMELA and AMS-02, inevitably faces the contradiction with isotropic diffuse gamma-ray background, measured by FERMI/LAT. [less ▲]

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See detailOn a possible solution to gamma-ray overabundance arising in dark matter explanation of cosmic antiparticle excess
Alekseev, V. V.; Belotsky, K. M.; Bogomolov, Yu V. et al

in Journal of Physics. Conference Series (2016), 675(1), 012026

As we are going to show, some self-interacting dark matter models may provide an intriguing solution to the ”cosmic antiparticle excess vs. isotropic diffuse gamma-ray background” problem (an ... [more ▼]

As we are going to show, some self-interacting dark matter models may provide an intriguing solution to the ”cosmic antiparticle excess vs. isotropic diffuse gamma-ray background” problem (an overproduction of diffuse gamma rays, arising in any reasonable decaying or annihilating dark matter model explaining high-energy charged cosmic antiparticles anomalous abundance). [less ▲]

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See detailInfluence of crossed fields in structures combining large grain, bulk (RE)BCO superconductors and soft ferromagnetic discs
Philippe, Matthieu ULiege; Fagnard, Jean-François ULiege; Wera, Laurent ULiege et al

in Journal of Physics. Conference Series (2016), 695

Bulk (RE)BCO superconductors are able to trap record magnetic fields and can be used as powerful permanent magnets in various engineering applications such as rotating machines and magnetic bearings. When ... [more ▼]

Bulk (RE)BCO superconductors are able to trap record magnetic fields and can be used as powerful permanent magnets in various engineering applications such as rotating machines and magnetic bearings. When such superconducting (SC) “trapped field magnets” are combined to a ferromagnetic (FM) disc, the total magnetic moment is increased with respect to that of the superconductor alone. In the present work, we study experimentally the magnetic behaviour of such hybrid FM/SC structures when they are subjected to cycles of applied field that are orthogonal to their permanent magnetization, i.e. a “crossed-field” configuration. Experimental results show that the usual “crossed-field demagnetization” caused by the cycles of transverse field is strongly reduced in the presence of the ferromagnet. [less ▲]

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See detailShell structure and few-nucleon removal in intranuclear cascade
Mancusi, Davide; Boudard, Alain; Carbonell, Jaume et al

in Journal of Physics. Conference Series (2015), 580

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See detailAnomaly-free chiral fermion sets and gauge coupling unification
Da Silva Simoes, Catarina ULiege

in Journal of Physics. Conference Series (2015)

In this work we search for minimal sets of chiral fermions, with arbitrary quantum numbers, beyond the Standard Model that are anomaly-free and lead to vector-like particles under SU(3) and U(1)_em after ... [more ▼]

In this work we search for minimal sets of chiral fermions, with arbitrary quantum numbers, beyond the Standard Model that are anomaly-free and lead to vector-like particles under SU(3) and U(1)_em after symmetry breaking. We further study which of these anomaly free sets lead to unification of the gauge couplings at energy scales higher that 5.0×10^15 GeV in order to be consistent with proton decay bounds. A similar study is performed in the context of the SU(5) gauge group; for some of the anomaly-free sets found it is possible to obtain unification of the gauge couplings with the extra fermions decoupling at high intermediate scales. [less ▲]

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See detailCommensurate - Incommensurate vortex phase in a nanopatterned superconductor
Shaw, Gorky ULiege; Banerjee, S. S.; Tamegai, T. et al

in Journal of Physics. Conference Series (2015), 638(1), 012009

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See detailEffect of different technological approaches on the optical properties of ZnO sol-gel thin films
Ivanova, T.; Harizanova, A.; Koutzarova, T. et al

in Journal of Physics. Conference Series (2014), 514

The work presents a sol-gel approach with two types of solvents for ZnO films deposition in view of varying the films' structural and optical properties. The ZnO films were characterized by X-Ray ... [more ▼]

The work presents a sol-gel approach with two types of solvents for ZnO films deposition in view of varying the films' structural and optical properties. The ZnO films were characterized by X-Ray diffraction (XRD) and found to have a polycrystalline wurtzite phase structure. The grain sizes and the lattice parameters were determined; it was established that the ZnO crystallites' size increases with the annealing temperatures from 25 nm to 36 nm. The ZnO films possess high transmittance in the visible spectral range. Further, the optical band gap values were estimated. The material's vibration properties were analyzed by Fourier Transform Infrared (FTIR) spectroscopy. The two technological sol-gel approaches for deposition of ZnO films, using two different solvents, proved to be successful in producing structures with different structural and optical properties. The thin films fabricated were very smooth and uniform and exhibited a high transparency in the visible spectral range. [less ▲]

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See detailSome features of bulk melt-textured high-temperature superconductors subjected to alternating magnetic fields
Vanderbemden, Philippe ULiege; Molenberg, Isabel ULiege; Simeonova, Pavlina et al

in Journal of Physics. Conference Series (2014), 558

Monolithic, large grain, (RE)Ba2Cu3O7 high-temperature superconductors (where RE denotes a rare-earth ion) are known to be able to trap fields in excess of several teslas and represent thus an extremely ... [more ▼]

Monolithic, large grain, (RE)Ba2Cu3O7 high-temperature superconductors (where RE denotes a rare-earth ion) are known to be able to trap fields in excess of several teslas and represent thus an extremely promising competing technology for permanent magnet in several applications, e.g. in motors and generators. In any rotating machine, however, the superconducting permanent magnet is subjected to variable (transient, or alternating) parasitic magnetic fields. These magnetic fields interact with the superconductor, which yields a reduction of the remnant magnetization. In the present work we quantify these effects by analysing selected experimental data on bulk melt-textured superconductors subjected to AC fields. Our results indicate that the non-uniformity of superconducting properties in rather large samples might lead to unusual features and need to be taken into account to analyse the experimental data. We also investigate the evolution of the DC remnant magnetization of the bulk sample when it is subjected to a large number of AC magnetic field cycles, and investigate the experimental errors that result from a misorientation of the sample or a mispositioning of the Hall probe. The time-dependence of the remnant magnetization over 100000 cycles of the AC field is shown to display distinct regimes which all differ strongly from the usual decay due to magnetic relaxation. [less ▲]

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