6,572 research outputs found
Rapid Changes of Photospheric Magnetic Field after Tether-Cutting Reconnection and Magnetic Implosion
The rapid, irreversible change of the photospheric magnetic field has been
recognized as an important element of the solar flare process. This Letter
reports such a rapid change of magnetic fields during the 2011 February 13 M6.6
flare in NOAA AR 11158 that we found from the vector magnetograms of the
Helioseismic and Magnetic Imager with 12-min cadence. High-resolution
magnetograms of Hinode that are available at ~-5.5, -1.5, 1.5, and 4 hrs
relative to the flare maximum are used to reconstruct three-dimensional coronal
magnetic field under the nonlinear force-free field (NLFFF) assumption. UV and
hard X-ray images are also used to illuminate the magnetic field evolution and
energy release. The rapid change is mainly detected by HMI in a compact region
lying in the center of the magnetic sigmoid, where the mean horizontal field
strength exhibited a significant increase by 28%. The region lies between the
initial strong UV and hard X-ray sources in the chromosphere, which are
cospatial with the central feet of the sigmoid according to the NLFFF model.
The NLFFF model further shows that strong coronal currents are concentrated
immediately above the region, and that more intriguingly, the coronal current
system underwent an apparent downward collapse after the sigmoid eruption.
These results are discussed in favor of both the tether-cutting reconnection
producing the flare and the ensuing implosion of the coronal field resulting
from the energy release.Comment: 7 pages, 5 figures, accepted to the Astrophysical Journal Letter
Integration of magnetic residuals,derivates and located euler deconvolution for structural and geologic mapping of parts of the precambrian gneisses of Ago-Iwoye, Southwestern Nigeria
Ground based magnetic survey conducted between longitude 06O 55I 51IIN –06O 55I 54IIN and latitude 03O 52I 06IIE –03O 52I 4.8IIE (Olabisi Onabanjo University) remarkably revealed a consistent subsurface NW -SE structural azimuth of localized discontinuities within the shallowly buried heterogeneous basement rocks, which at exposed locations are composed of strongly foliated granite gneiss and migmatite-gneiss with veins and veinlets principally orientated in NNW –SSE direction.Magnetic survey of the area was preceded by site inspection to avoid metallic objects interferences. Field procedure in the area involved Cartesian gridding, base station establishment, data acquisition at gridded points, and repeated bihourly diurnal checksat the base station. At the processing stage, diurnal variation effect was aptly removed before subjection to Kriging (gridding). The gridded data was then prepared as input for Forward Fourier Filter Transform (FFT), which upon definition and implementation enabled Butterworth filtering of isolated ringing effects, reduction to the equator (RTE) for geomagnetic correction, and the use of Gaussian and Upward Continuation filtering for regional magnetic intensity trend determination. Removal of the regional magnetic intensity (RMI) from the total magnetic intensity (TMI) resulted in the derivation of the residual anomaly. Enhancement filters adopted for better resolution of the residual magnetic gradient include analytical signal (AS), tilt-angle derivative (TDR), vertical derivative deconvolution (VDD), and the first vertical derivatives (FVD).TMI and RMI values range between 32925nT –33050nT and 32935nT –333050nT respectively, while the residual gradient ranges between 15nT/m and10nT/m; AS ranges between 0.28nT/m and4.1nT/m; and TDR ranges from-1.4nT/m to 1.4nT/m. Source depth calculation estimated from power spectrum analysis and Euler deconvolution ranges between 1m and15m. Composite overlay of magnetic maps revealed jointed and faulted zones within the area; exhibiting a NW-SE principal azimuth of Liberian orogenic impress, which are in consistence with the foliation direction of the jagged foliated bedrock with an estimated maximum overburden of about 15m.The structural significance of this area as a prospective hydro-geological centre, and as an undesirable spot for high-rise building has been accurately evaluated from research findings. Application of integrated geophysical approach, complemented by detailed geological studies may furnish greater information about the subsurface structural architecture.Keywords:Gneisses; Ground Magnetic Surveying;RTE;Structural discontinuities;TDR.1INTRODUCTIONStructuralmapping is an integral part of geologic surveys. It involves measurements, analyses, interpretation and recognition of geometrical features (structures) generated by rock deformations [1]. These structures often serve as fountains of environmental challenges or unparalleled opportunities depending on their modesof occurrences, which in most cases are imminently controlled by the dynamic interplay of differential stress distributions within the earth interior. In line with the principle of uniformitarianism, a broad understanding about Earth’s paleo processes and internal workingsare deductible from the various deformation types for diverse applications. Deductible inferences from brittle deformationsinclude the kinematics of crustal blocks, orientation of principal axes of regional and local stresses, and geometry. Deeper insights indeep seated stresses, regional movements and block motions are obtainable from ductile deformations
Recycling process of permanent magnets by polymer binder using injection molding technique
Seltene Erden-Elemente (REE) werden aufgrund ihrer technologischen Bedeutung und geopolitischen Versorgungskriterien als kritische Metalle eingestuft. Sie werden in einem breiten Spektrum von Anwendungen eingesetzt, einschließlich der Herstellung von Magneten, Batterieelektroden, Katalysatoren und Polierpulver. Viele dieser Anwendungen sind wichtig für die sog. „grünen“ Technologien. Dauermagneten sind hinsichtlich der Marktgröße die wichtigste Anwendung insbesondere für Neodym-, Praseodym-, Dysprosium- und Terbium-Magnete, die in NdFeB-Magneten verwendet werden. Die Nachfrage nach Seltenerdelementen für die Herstellung von Magneten nimmt zu und es wird erwartet, dass sich dieser Trend in den kommenden Jahren fortsetzt. Um die mit der Nachfrage verbundenen Risiken zu verringern, wurden Maßnahmen zur Entwicklung von Recyclingtechnologien zur Wiederverwendung von NdFeB aus Magneten ergriffen. Während der industrielle NdFeB-Schrott bereits zurückgewonnen wird, ist das Recycling von Magneten aus Altprodukten noch weitergehend auf Labor- und Pilotprojekte beschränkt. Diese Abhandlung stellt die Ergebnisse der Materialanalyse vor, die die Möglichkeit bestätigen, magnetische Materialien durch die Einarbeitung in eine Polymermatrix zu recyceln und mittels Spritzgussprozess vorzubereiten.
Kern der vorliegenden Dissertation ist die Frage, wie der geschlossene Kreislauf und das Recyclingverfahren von Neodynium Magneten aus Elektroschrott gestattet sein soll. Um diese Frage zu beantworten, sind folgende Aspekte relevant:
• Die Wahl der Technologien/Prozesse, die für das Recycling eingesetzt werden.
• Nachweis der Wiederverwendung von Neodym-Magneten, die aus WEEE (Waste of Electrical and Electronic Equipment) gewonnen sind.
• Herstellung und Analyse von Polymer/Magnet- Compound.
• Einfluss der Magnetpartikel, abhängig von ihrer Anzahl und Größe, auf die Viskosität und Fließverhalten des Materials während des Spritzgussprozess.
• Analyse des Einflusses der Restmagnetisierung auf das Fließverhalten und einer gezielten Anordnung von magnetischen Partikeln im Bauteil.
• Technisch-ökonomische Analyse, die entscheidend dazu beitragen wird, ob und in welchem Ausmaß die Einführung des Prozesses erreichbar ist und damit geschlossene Kreisläufe möglich sind.
Auf der Grundlage einer umfangreichen Analyse wurden die optimalen Prozessparameter und die Spritzgussmöglichkeiten des verwendeten Materials vorgestellt. Die Nachfrage nach NdFeB-Magneten in Motoranwendungen wächst und wird in den nächsten Jahren voraussichtlich noch zunehmen. Vor allem die Nachfrage nach E-Bike und E-Autos gewinnt an Bedeutung. Infolgedessen wird die Nachfrage nach schweren Seltenen Erden steigen, was die Entwicklung von Recyclingsystemen für diese Materialien erforderlich macht.Rare earth elements (REE) are classified as critical metals due to their technological importance and geopolitical supply criteria. They are used in a wide range of applications, including the manufacture of magnets, battery electrodes, catalysts, and polishing powders. Many of these applications are important for so-called "green" technologies. Permanent magnets are the most important application in terms of market size, particularly for neodymium, praseodymium, dysprosium, and terbium magnets used in NdFeB magnets. The demand for rare earth elements for the production of magnets is increasing and this trend is expected to continue in the coming years (Langkau S. 2020; Li J. 2020; Goodenough K.M. et al. 2018). To mitigate the risks associated with that demand, have been taken to develop recycling technologies to reuse NdFeB magnets. While industrial scrap is already being recovered, recycling of magnets from end-of-life products is still further limited to laboratory and pilot projects. The following work presents the results of the material analysis, which confirm the possibility to recycle magnetic materials by using a polymer matrix.
The main goal of this dissertation is the question of how the closed-loop and recycling process of neodymium magnets from electronic waste should be designed. To answer this question, the following aspects are relevant:
• The choice of technologies/processes used for recycling and processing.
• Evidence of reuse of neodymium magnets obtained from WEEE (Waste of Electrical and Electronic Equipment).
• Process flow analysis and final product evaluation (polymer/magnet compound).
• The effect of magnetic particles characteristics (size, distribution, and contribution) on the viscosity and flow behavior of the material during the injection molding process.
• Analysis of residual magnetization on the flow behavior and a targeted arrangement of magnetic particles in the component.
• Technical-economic analysis, which decisively contributes to whether and to what extent the introduction of the process is achievable.
Based on an extensive analysis, the optimal process parameters and the maximum injection possibilities of the material used is discussed along the whole processing line. The demand for NdFeB magnets in motor applications is growing and is expected to increase in the coming years. In particular, the demand for e-bikes and e-vehicles is gaining importance (Kampker A. et al. 2021; Pollák F. 2021; Flores P.J 2021). As a result, the demand for heavy rare earths will increase, necessitating the development of recycling systems for these materials, where this thesis is one basic concept to close the loop
Magnetism, FeS colloids, and Origins of Life
A number of features of living systems: reversible interactions and weak
bonds underlying motor-dynamics; gel-sol transitions; cellular connected
fractal organization; asymmetry in interactions and organization; quantum
coherent phenomena; to name some, can have a natural accounting via
interactions, which we therefore seek to incorporate by expanding the horizons
of `chemistry-only' approaches to the origins of life. It is suggested that the
magnetic 'face' of the minerals from the inorganic world, recognized to have
played a pivotal role in initiating Life, may throw light on some of these
issues. A magnetic environment in the form of rocks in the Hadean Ocean could
have enabled the accretion and therefore an ordered confinement of
super-paramagnetic colloids within a structured phase. A moderate H-field can
help magnetic nano-particles to not only overcome thermal fluctuations but also
harness them. Such controlled dynamics brings in the possibility of accessing
quantum effects, which together with frustrations in magnetic ordering and
hysteresis (a natural mechanism for a primitive memory) could throw light on
the birth of biological information which, as Abel argues, requires a
combination of order and complexity. This scenario gains strength from
observations of scale-free framboidal forms of the greigite mineral, with a
magnetic basis of assembly. And greigite's metabolic potential plays a key role
in the mound scenario of Russell and coworkers-an expansion of which is
suggested for including magnetism.Comment: 42 pages, 5 figures, to be published in A.R. Memorial volume, Ed
Krishnaswami Alladi, Springer 201
Determination and emulation of motor-like flux conditions for loss characterization by means of a single tooth geometry
High quantities and a demand on low costs in automotive drives result in new production methods of electrical machines. Besides, the electric drive train efficiency is improved to offer long ranges. Referring to this relationship the loss models of electrical machines are improved more and more. Focusing on iron losses, remarkable influences on the loss characteristics are attributed to the manufacturing processes. In this publication, a new approach of measuring the losses of a single stator tooth of an electrical machine considering motor-like flux conditions is introduced. Derivation of motor-like flux conditions is described, transfer to the test bench is defined and measurements are shown - concluding with a comparison of simulation and measurement as well as the identified tooth losses of the investigated machine. This gives the possibility to improve iron loss models in case of additional losses due to manufacturing influences
Holocene Varved Lake Sediments as Records of Palaeoenvironmental Change and Geomagnetic Palaeosecular Variation in Eastern Finland
This dissertation discusses Holocene palaeoenvironmental and palaeomagnetic secular variation (PSV) records reconstructed from sediments preserved in Lake Lehmilampi (63º37´N, 29º06´E) and Lake Kortejärvi (63º37´N, 28º56´E) in eastern Finland. Several piston and freeze cores were obtained from both lakes for varve and magnetic analyses. Sediment samples were impregnated in low-viscosity epoxy and physical parameters of varves, including varve thickness and relative grey-scale values, were recorded using x-ray densitometry combined with semiautomatic digital image analysis. On average, varve records of Lehmilampi and Kortejärvi cover 5122 and 3902 years, respectively. Past solar activity, as estimated by residual 14C data, compares favourably with varve thicknesses from Lehmilampi during the last 2000 years. This indicates the potential of clastic-organic varves to record sensitively climatic variations. Bulk magnetic parameters, including magnetic susceptibility together with natural, anhysteretic and isothermal remanent magnetizations, were measured to describe mineral magnetic properties and geomagnetic palaeosecular variation recorded in the sediments. Main stages in the development of the investigated lakes are reflected in the variations in the mineral magnetic records, sediment lithology and composition. Similar variations in magnetic parameters and sediment organic matter suggest contribution of bacterial magnetite in the magnetic assemblages of Lehmilampi. Inclination and relative declination records yielded largely consistent results, attesting to the great potential of these sediments to preserve directional palaeosecular variation in high resolution. The PSV data from Lehmilampi and Kortejärvi were stacked into North Karelian PSV stack, which may be used for dating homogenous lake sediments in the same regional context. Reconstructed millennial variations in relative palaeointensity results are approximately in agreement with those seen in the absolute palaeointensity data from Europe. Centennial variations in the relative palaeointensity, however, are influenced by environmental changes. Caution is recommended when using varved lake sediments in reconstructing relative palaeointensity.Siirretty Doriast
Magnetic phases and reorientation transitions in antiferromagnetically coupled multilayers
In antiferromagnetically coupled superlattices grown on (001) faces of cubic
substrates, e.g. based on materials combinations as Co/Cu, Fe/Si, Co/Cr, or
Fe/Cr, the magnetic states evolve under competing influence of bilinear and
biquadratic exchange interactions, surface-enhanced four-fold in-plane
anisotropy, and specific finite-size effects. Using phenomenological
(micromagnetic) theory, a comprehensive survey of the magnetic states and
reorientation transitions has been carried out for multilayer systems with even
number of ferromagnetic sub-layers and magnetizations in the plane. In
two-layer systems (N=2) the phase diagrams in dependence on components of the
applied field in the plane include ``swallow-tail'' type regions of
(metastable) multistate co-existence and a number of continuous and
discontinuous reorientation transitions induced by radial and transversal
components of the applied field. In multilayers (N \ge 4) noncollinear states
are spatially inhomogeneous with magnetization varying across the multilayer
stack. For weak four-fold anisotropy the magnetic states under influence of an
applied field evolve by a complex continuous reorientation into the saturated
state. At higher anisotropy they transform into various inhomogeneous and
asymmetric structures. The discontinuous transitions between the magnetic
states in these two-layers and multilayers are characterized by broad ranges of
multi-phase coexistence of the (metastable) states and give rise to specific
transitional domain structures.Comment: Manuscript 34 pages, 14 figures; submitted for publicatio
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