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"Sol, H."
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Controlling superconducting spin flow with spin-flip immunity using a single homogeneous ferromagnet
Spin transport via electrons is typically plagued by Joule heating and short decay lengths due to spin-flip scattering. It is known that dissipationless spin currents can arise when using conventional superconducting contacts, yet this has only been experimentally demonstrated when using intricate magnetically inhomogeneous multilayers, or in extreme cases such as half-metals with interfacial magnetic disorder. Moreover, it is unknown how such spin supercurrents decay in the presence of spin-flip scattering. Here, we present a method for generating a spin supercurrent by using only a single homogeneous magnetic element. Remarkably, the spin supercurrent generated in this way does not decay spatially, in stark contrast to normal spin currents that remain polarized only up to the spin relaxation length. We also expose the existence of a superconductivity-mediated torque even without magnetic inhomogeneities, showing that the different components of the spin supercurrent polarization respond fundamentally differently to a change in the superconducting phase difference. This establishes a mechanism for tuning dissipationless spin and charge flow separately and confirms the advantage that superconductors can offer in spintronics.
Journal Article
Bending-strain effects in conventional superconductors and superconducting junctions
We consider the effect of bending-strain in thin films of clean, conventional superconductors (S), and the proximity-induced effect of this strain in SN bilayers with a normal metal (N), and SNS junctions with equal curvatures in each superconductor. We find that the effective spin-orbit coupling due to strain in the superconductor induces both spin-polarized and unequal-spin even-frequency p-wave triplet pairings throughout the superconductor. When interfaced with a normal metal, additional odd-frequency pairings are induced, and their magnitudes can be tuned with the strain. In SNS junctions, the strain alone can induce a superconducting spin current in the junction. The spin-polarized current can undergo a 0 −
π
-transition, resulting in an in-plane, strain-induced magnetization that switches sign as a function of the strain. We discuss the underlying physics and its implications for superconducting spintronics.
Journal Article
Direct Ink Writing of Anisotropic Luminescent Materials
Luminescent solar concentrators are relatively inexpensive devices proposed to collect, convert, and redirect incident (sun)light for a variety of potential applications. In this work, dichroic dyes are embedded in a liquid crystal elastomer matrix and used as feedstock for direct ink writing. Direct ink writing is a promising and versatile application technique for arbitrarily aligning the dichroic dyes over glass and poly(methyl methacrylate) lightguide surfaces. The resulting prints display anisotropic edge emissions, and suggest usage as striking visual objects, combining localized color and intensity variations when viewed through a polarizer.
Journal Article
Identification of Mechanical Material Behavior Through Inverse Modeling and DIC
Inverse methods offer a powerful tool for the identification of the elasto-plastic material parameters. One of the advantages with respect to classical material testing is the fact that those inverse methods are able to deal with heterogeneous deformation fields. The basic principle of the inverse method that is presented in this paper, is the comparison between experimentally measured strain fields and those computed by the finite element (FE) method. The unknown material parameters in the FE model are iteratively tuned so as to match the experimentally measured and the numerically computed strain fields as closely as possible. This paper describes the application of an inverse method for the identification of the hardening behavior and the yield locus of DC06 steel, based on a biaxial tensile test on a perforated cruciform specimen. The hardening behavior is described by a Swift type hardening law and the yield locus is modeled with a Hill 1948 yield surface.
Journal Article
The central dusty torus in the active nucleus of NGC 1068
Active galactic nuclei (AGNs) display many energetic phenomena—broad emission lines, X-rays, relativistic jets, radio lobes—originating from matter falling onto a supermassive black hole. It is widely accepted that orientation effects play a major role in explaining the observational appearance of AGNs. Seen from certain directions, circum-nuclear dust clouds would block our view of the central powerhouse
1
,
2
. Indirect evidence suggests that the dust clouds form a parsec-sized torus-shaped distribution. This explanation, however, remains unproved, as even the largest telescopes have not been able to resolve the dust structures. Here we report interferometric mid-infrared observations that spatially resolve these structures in the galaxy NGC 1068. The observations reveal warm (320 K) dust in a structure 2.1 parsec thick and 3.4 parsec in diameter, surrounding a smaller hot structure. As such a configuration of dust clouds would collapse in a time much shorter than the active phase of the AGN
3
, this observation requires a continual input of kinetic energy to the cloud system from a source coexistent with the AGN.
Journal Article
Decision enhancement services : rehearsing the future for decisions that matter
Decision Enhancement (DE) is a field of practice aimed at extending lessons, principles and tools built up over a thirty year period, largely under the term 'Decision Support'. Enhancement goes beyond support which has mostly focused on helping managers make use of interactive computer models and methods. DE substantially adds to the opportunities, especially in the use of the Internet as both an information resource and communications base for collaboration between groups but it also goes well beyond it in two important regards: a focus on enhancement of the processes that influence the quality of decisions that really matter in an organization; the ones that are most consequential, complex, and uncertain, and a shift from the design of computer- and telecommunications-based tools to a far more comprehensive 'studio' approach to the integration of change management, collaborative development and use, and a new generation of visual technology. DE is a lens that focuses on stakeholders in decision arenas and their decisions that matter. It continues with its invitation to bring stakeholders, domain experts and suite designers into its studios. The invitation extends to experts in domains relevant to making DE studios effective, as well as to the suite designers and providers of technology capabilities needed to provide the tools within the studio. DE provides services to guide a journey where executives, their advisors, change management specialists, experts in multi-disciplinary fields and technology developers can come together to make a substantive new impact on effective decision making in any organization. This book will add to the old - the proven lessons and expertise of these fields - and to their innovation. It is in this sense that it is an invitation and written to encourage reflection and discussion within and across them.
eBook
Full-Field Deformation Measurements of Aluminum Plates Under Free Air Blast Loading
Assessment of the structural dynamic response caused by an explosion is complex due to the high velocity impact, the transient nature of the deformation and the interactions between the structure and the pressure wave. This paper deals with full-field measurements of aluminum plates under free air blast loading conditions. Forty grams of explosive material C4 is detonated at a stand-off-distance of 250 mm and two synchronized high-speed cameras in a stereoscopic setup are used to capture the plate response with an inter frame rate of 6,000 fps. The transient deformation fields are calculated using a three-dimensional digital image correlation technique. The observations appeared to be interesting and somewhat counter intuitively. Results show that a free air blast load induces a highly localized, rapid material response which can be essentially divided in two different stadia. First, when the shock impulse occurs, all particles are forced to move out-of-plane and provided with initial velocities. Secondly, when the pressure wave has vanished, the deformation is further driven by this imparted momentum. This paper shows that a 3D high-speed DIC system is a powerful tool for the assessment of the dynamic response of a structure subjected to extreme loading conditions such as explosions and that this system is capable of accurately measuring surface displacement and deformation data at high rates. Moreover, a free air blast load makes it possible to load a plate specimen at different strain rates in different zones. This makes the test suitable for future material identification using inverse methods, which profit from heterogeneous displacement and strain fields.
Journal Article
The Pulsed Ultrasonic Backscatter Polar Scan and its Applications for NDT and Material Characterization
In a conventional ultrasonic polar scan (UPS) experiment, the amplitude or time-of-flight-diffraction (TOFD) values of the transmitted and/or reflected acoustic pulse are recorded for a wide range of incidence angles, in view of gaining knowledge about the elastic properties at the insonified material spot. Here we apply the pulsed UPS technique and investigate the backscattered signal, resulting in the ultrasonic backscatter polar scan (UBPS). It is shown that a UPBS contains a blueprint of geometrically related features of the insonified material spot which can be of particular interest for various industrial applications. We applied the UBPS for (i) the determination of the stacking sequence of a cross-ply composite laminate, (ii) the semi-quantification of a multidirectional microscopic surface corrugation, (iii) the detection of corrosion in an early stage as well as (iv) the detection and the localization of a closed surface breaking crack.
Journal Article