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Open Access Publishing Costs in Spain : Implementing openCost for DSpace Repositories
No full textThe Institutional Repositories Working Group of the Spanish Network of University and CSIC Li-braries (REBIUN, https://www.rebiun.org/grupos-trabajo/repositorios) is working on implementingthe openCOST metadata schema as there is an interest in showing information about open accesspublishing costs in a commonly agreed way. The analysis and beta implementation of the metadataschema is being advanced by the DSpace repositories subgroup and ongoing work has focused onidentifying the most relevant metadata given the data model in place in such repositories as wellas the type and granularity of OA publishing cost information collected by their institutions. Theposter gives an overview of progress so far and next steps
Arc-based additive manufacturing of Cu-Al-Mn shape memory alloys: microstructure, tensile behavior and superelastic properties
No full textCu-based shape memory alloys (SMA) are a class of materials with high potential industry adoption due to theirintrinsic shape memory and superelastic properties. The application of this material has been studied for years inthe as-cast and heat treated conditions. Additive Manufacturing (AM) of these alloys is only sparsely reported forlaser powder bed fusion with no reports for the successful application of high deposition rate processes, such asarc-based ones, found in the literature. Thus, this work presents, for the first time, the successful fabrication ofCu-17Al-11.4Mn (at. %) SMA components via arc-based additive manufacturing using a gas metal arc weldingsystem. The deposition process yielded a structurally defect-free wall with homogeneous microstructure. Opticaland electron microscopy, and synchrotron X-ray diffraction confirmed the presence of columnar grainsmorphology due to the associated thermal cycling effects, and a primarily FCC phase. Tensile tests in bothhorizontal and vertical directions showed high strength and ductility with minimal anisotropy, while superelasticcyclic testing revealed stable hysteresis behavior up to 100 load-unload cycles, indicating high functional fatigueresistance. Further, a stress-induced transformation observed via in situ synchrotron X-ray diffraction duringtensile loading underscores the material’s suitability for superelastic applications. The present findingsdemonstrate the feasibility and advantages of employing arc-based additive manufacturing for processing CubasedSMA, opening new pathways for cost-effective fabrication of functional components
Impact of ionization potential depression on single particle imaging
No full textUltraintense and ultrashort x-ray free-electron laser (XFEL) pulses promise single particle imaging (SPI) via enabling collection of diffraction data for nanocrystals, or nano-size nonperiodic objects before the destruction of the sample. Photoionization and subsequent processes lead to plasma generation within the sample in such experiments. The continuum energy levels of electrons for atoms and atomic ions are lowered due to plasma screening, also known as ionization potential depression (IPD). We theoretically investigate the plasma formation and the effect of IPD in the context of SPI with calculations performed on bulk glycine, mimicking the interior of irradiated biological macromolecules, e.g., proteins or viruses. To simulate the plasma formation dynamics, we employ a nonequilibrium, hybrid quantum-classical approach, combined with the evaluation of the transient IPD from first-principles electronic structure calculations considering the time-dependent microscopic environment, which in earlier work was applied to a solid-density plasma consisting of a single atomic species [Phys. Rev. E 106, 015206 (2022)]. Here, this approach is extended to more than one atomic species for applications to biological macromolecules in SPI studies. Our work quantifies the effect and importance of IPD in XFEL-based imaging of biological systems and provides further guidance for simulations of electronic radiation damage dynamics toward successful SPI experiments
Soft-unclustered-energy patterns from quirks
No full textWe propose searching for physics beyond the Standard Model in the low-transverse-momentum tracks accompanying hard-scatter events at the LHC. TeV-scale resonances connected to a dark QCD sector could be enhanced by selecting events with anomalies in the track distributions. As a benchmark, a quirk model with microscopic string lengths is developed, including a setup for event simulation. For this model, strategies are presented to enhance the sensitivity compared to inclusive resonance searches: a simple cut-based selection, a supervised search, and a model-agnostic weakly supervised anomaly search with the CATHODE method. Expected discovery potentials and exclusion limits are shown for 140 fb of 13 TeV proton-proton collisions at the LHC
MirrorCBO: A consensus-based optimization method in the spirit of mirror descent
No full textIn this work we propose MirrorCBO, a consensus-based optimization (CBO) method which generalizes standard CBO in the same way that mirror descent generalizes gradient descent. For this we apply the CBO methodology to a swarm of dual particles and retain the primal particle positions by applying the inverse of the mirror map, which we parametrize as the subdifferential of a strongly convex function . In this way, we combine the advantages of a derivative-free non-convex optimization algorithm with those of mirror descent. As a special case, the method extends CBO to optimization problems with convex constraints. Assuming bounds on the Bregman distance associated to , we provide asymptotic convergence results for MirrorCBO with explicit exponential rate. Another key contribution is an exploratory numerical study of this new algorithm across different application settings, focusing on (i) sparsity-inducing optimization, and (ii) constrained optimization, demonstrating the competitive performance of MirrorCBO. We observe empirically that the method can also be used for optimization on (non-convex) submanifolds of Euclidean space, can be adapted to mirrored versions of other recent CBO variants, and that it inherits from mirror descent the capability to select desirable minimizers, like sparse ones. We also include an overview of recent CBO approaches for constrained optimization and compare their performance to MirrorCBO
Non-monotonic fluctuation of structural heterogeneity in metallic glass due to cyclic rapid heat treatment
No full textFlash-annealing (FA) of metallic glasses (MGs) allows one to modulate their disordered structure. Here, we have flash-annealed a CuZr-based MG below the glass transition temperature at different cycles and generated MGs with various heterogeneous structures. We quantified the glassy structure via the relaxation enthalpy, ΔrelH, which did not significantly change for MGs flash-annealed at a low number of cycles. Their hardness monotonically reduced. However, when more than ten FA cycles were applied, ΔrelH, perceivably decreased, while corresponding hardness increased. High-energy x-ray diffraction analysis revealed that the medium-range ordering of the corresponding structure initially rose and then decreased with an increasing number of FA cycles. This structural change is accompanied by first a hardness decrease followed by an increase. Molecular dynamics simulations showed that throughout the shift from low to high cycles, the structural non-uniformity changed from being non-uniform to more uniform. Through a combination of experiments and simulations, we have shown the non-monotonic relationship between the structural heterogeneity of MGs and cyclic treatments, contributing to a better understanding of the relationship between structural control techniques, microstructure, and properties
High-entropy alloy mapping in the Co-Cr-Fe-Mo-Ni-W compositional library using a combinatorial thin film
No full textExperiments were conducted to study the structure and mechanical behavior of high-entropy alloys (HEAs) in the Co-Cr-Fe-Mo-Ni-W compositional library. This investigation was performed on a 3 μm thick combinatorial thin film deposited on a single crystal silicon (c-Si) substrate by magnetron sputtering technique. The chemical composition for each element varied in the range of about 5–40 at%. The mapping of the structure was carried out by synchrotron X-ray diffraction while the mechanical behavior was studied by nanoindentation. A complementary transmission electron microscopy investigation at some selected compositions was also performed. Most of the studied compositions formed an amorphous structure while nanocrystalline body-centered cubic (bcc) and hexagonal close-packed (hcp) phases were detected in the vicinity of W/Mo and Co/Ni elemental sources, respectively. The hcp structure contained a very high density of stacking faults on the basal planes. The variation of the phase composition can be related to the change of valence electron concentration. The lattice constants in the crystalline regions of the combinatorial sample changed in accordance with the variation of the average atomic radius. The combinatorial sample contained pores which significantly reduced the hardness. The highest hardness values (7.8 ± 0.3 GPa) were detected in the bcc region for the compositions of 8.1 % Co – 25.6 % Cr – 6.9 % Fe – 16.4 % Mo – 9.1 % Ni – 33.9 % W (at%)
In-situ synchrotron HEXRD study on the stress relaxation behavior and internal stress evolution mechanism of a PM nickel-base superalloy
No full textFGH96 is a powder metallurgy nickel-base superalloy used for turbine disk of aero-engines. In this study, theevolution of micro-lattice stress and strain of FGH96 alloy during stress relaxation and thermal deformation wasinvestigated by employing in-situ high-energy synchrotron radiation techniques. Results indicate that therelaxation of macroscopic compressive stress is closely related to the increased lattice strain in grains of differentorientations. During high-temperature relaxation, the lattice stress of the (111)γ/γ′ and (220)γ/γ′ planes decreasesrapidly in the initial relaxation phase and then stabilizes, while the lattice stress of the (200)γ/γ′ planeremain uniformly relaxed throughout, suggesting minimal load transfer between different grains. During thehigh-temperature compression and holding process, dynamic recrystallization partially releases the internalstress generated by work hardening. During the holding stage, different stress relaxation mechanisms wereobserved for grains of varying orientations, with (311) oriented grains primarily achieving this through dislocationrearrangement and sub-grain nucleation, while (220) oriented grains tend to migrate grain boundariesbased on existing recrystallization nucleation
Nanoscale Inhomogeneity and Epitaxial Strain Control Metallicity in Single Crystalline Thin Films of High Entropy Oxide
No full textUnderstanding the electronic transport properties of thin films of high-entropy oxide (HEO), having multiple elements at the same crystallographic site, is crucial for their potential electronic applications. However, very little is known about the metallic phase of HEOs even in bulk form. This work delves into the interplay between global and local structural distortion and electronic properties of single crystalline thin films of (La0.2Pr0.2Nd0.2Sm0.2Eu0.2)NiO3, which exhibit metal-insulator transition under tensile strain. Employing electron microscopy and elemental resolved electron energy loss spectroscopy, we provide direct evidence of nanoscale chemical inhomogeneities at the rare-earth site, leading to a broad distribution of Ni–O–Ni bond angles. However, the octahedral rotation pattern remains the same throughout. The metallic phase consists of insulating patches with more distorted Ni–O–Ni bond angles, responsible for higher resistance exponents with increased compositional complexity. Moreover, a rare, fully metallic state of HEO thin film is achieved under compressive strain. We further demonstrate a direct correlation between the suppression of the insulating behavior and increased electronic hopping. Our findings provide a foundation for exploring Mott-Anderson electron localization physics in the high-entropy regime