620 research outputs found
Experimental Study of Magnetic Slurries Regarding Magnetic Properties
Abstract-The aim of this study was to assess the basic magnetic properties of a mixture composed of a commercial lubricant and soft magnetic iron particles, where the particle content is significantly higher than in conventional magnetic fluids, due to the fact that the particles verge on the sedimentation level. This so called magnetic slurry can, then, be regarded as a highly ductile magnetic conductin material for tentative use in magnetic circuit that can cgange shape under operation. The high particle content results in high saturation field densities that extend the application field towards electric power en ineering. This paper, therefore, focuses on properties life relative permeability, losses, the Q-factor and the efficiency for the power fre uencies 50 and 400 Hz. It shows that the relative permea%ilities are low (below 10). The values of the efficiency and the Q-factor decrease considerably above 0.5 T. That limit$ the application of the studied slurry in electric power engineering. In such applications, the powder properties must be improved
Are megaquakes clustered?
We study statistical properties of the number of large earthquakes over the
past century. We analyze the cumulative distribution of the number of
earthquakes with magnitude larger than threshold M in time interval T, and
quantify the statistical significance of these results by simulating a large
number of synthetic random catalogs. We find that in general, the earthquake
record cannot be distinguished from a process that is random in time. This
conclusion holds whether aftershocks are removed or not, except at magnitudes
below M = 7.3. At long time intervals (T = 2-5 years), we find that
statistically significant clustering is present in the catalog for lower
magnitude thresholds (M = 7-7.2). However, this clustering is due to a large
number of earthquakes on record in the early part of the 20th century, when
magnitudes are less certain.Comment: 5 pages, 5 figure
Density and Pâwave velocity structure beneath the ParanĂĄ Magmatic Province: Refertilization of an ancient lithospheric mantle
We estimate density and Pâwave velocity perturbations in the mantle beneath the southeastern South America plate from geoid anomalies and Pâwave traveltime residuals to constrain the structure of the lithosphere underneath the ParanĂĄ Magmatic Province (PMP) and conterminous geological provinces. Our analysis shows a consistent correlation between density and velocity anomalies. The Pâwave speed and density are 1% and 15 kg/m3 lower, respectively, in the upper mantle under the Late Cretaceous to Cenozoic alkaline provinces, except beneath the GoiĂĄs Alkaline Province (GAP), where density (+20 kg/m3) and velocity (+0.5%) are relatively high. Underneath the PMP, the density is higher by about 50 kg/m3 in the north and 25 kg/m3 in the south, to a depth of 250âââ300 km. These values correlate with highâvelocity perturbations of +0.5% and +0.3%, respectively. Profiles of density perturbation versus depth in the upper mantle are different for the PMP and the adjacent Archean SĂŁo Francisco (SFC) and Amazonian (AC) cratons. The Paleoproterozoic PMP basement has a highâdensity root. The density is relatively low in the SFC and AC lithospheres. A reduction of density is a typical characteristic of chemically depleted Archean cratons. A more fertile Proterozoic and Phanerozoic subcontinental lithospheric mantle has a higher density, as deduced from density estimates of mantle xenoliths of different ages and composition. In conjunction with ReâOs isotopic studies of the PMP basalts, chemical and isotopic analyses of peridodite xenoliths from the GAP in the northern PMP, and electromagnetic induction experiments of the PMP lithosphere, our density and Pâwave speed models suggest that the densification of the PMP lithosphere and flood basalt generation are related to mantle refertilization. Metasomatic refertilization resulted from the introduction of asthenospheric components from the mantle wedge above Proterozoic subduction zones, which surrounded the ParanĂĄ lithosphere. The highâdensity PMP lithosphere is presently gravitationally unstable and prone to delamination.Key Points:Density and Pâwave velocity in the lithospheric mantle beneath the ParanĂĄ Magmatic Province are highHigh density precludes a depleted cratonic lithosphere and indicates refertilized lithospheric mantleBasalt magmatism suggests refertilized mantle with asthenospheric components from mantle wedgePeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134193/1/ggge21079-sup-0003-2016GC006369-fs02.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134193/2/ggge21079-sup-0004-2016GC006369-fs03.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134193/3/ggge21079-sup-0002-2016GC006369-fs01.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134193/4/ggge21079_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134193/5/ggge21079.pd
Magnetostrictive and magnetoelectric behavior of Feâ20âat.â% Ga/Pb(Zr,Ti)O3 laminates
The magnetostrictive and magnetoelectric (ME) properties of laminate composites of Feâ20âat.â%âGa and Pb(Zr,Ti)O3 (PZT) have been studied for laminates of different geometries. The results show that (i) a long-type magnetostrictive Feâ20âat.â%âGa crystal plate oriented along ă001ăc and magnetized in its longitudinal (or length) direction has higher magnetostriction than a disk-type one; and consequently (ii) a long-type Feâ20âat.â%âGa/PZT laminate has a giant ME effect, and is sensitive to low-level magnetic fields
A QUASI-STATIC MODELLING APPROACH OF AIRBORNE POWER SYSTEMS
Abstract Modelling the whole power system of an airborne system requires very high computational capacity. This paper presents a possible approach to overcome this obstacle when considering new technology and topologies in airborne systems. Using Step-down and step-up voltage converters are described as fictive DC/DC transformers. This approach makes it possible to reduce the complexity of power system models of tentative systems to such extent that the resulting computational tool can be used for studies of the system performance during entire flight missions and/or for optimisation
The Importance of Boundary Conditions in Quantum Mechanics
We discuss the role of boundary conditions in determining the physical
content of the solutions of the Schrodinger equation. We study the
standing-wave, the ``in,'' the ``out,'' and the purely outgoing boundary
conditions. As well, we rephrase Feynman's prescription as a
time-asymmetric, causal boundary condition, and discuss the connection of
Feynman's prescription with the arrow of time of Quantum
Electrodynamics. A parallel of this arrow of time with that of Classical
Electrodynamics is made. We conclude that in general, the time evolution of a
closed quantum system has indeed an arrow of time built into the propagators.Comment: Contribution to the proceedings of the ICTP conference "Irreversible
Quantum Dynamics," Trieste, Italy, July 200
FeâGa/Pb(Mg1/3Nb2/3)O3âPbTiO3 magnetoelectric laminate composites
We have found large magnetoelectric (ME) effects in long-type laminate composites of Feâ20%Ga magnetostrictive alloys and piezoelectric Pb(Mg1/3Nb2/3)O3âPbTiO3 single crystals. At lower frequencies, the ME voltage coefficient of a laminate with longitudinally magnetized and longitudinally polarized (i.e., L-L mode) layers was 1.41âV/Oe (or1.01âV/cmâOe). Near the natural resonant frequency ( ⌠91âkHz) of the laminate, the ME voltage coefficients were found to be dramatically increased to 50.7âV/Oe (36.2âV/cmâOe)for the L-L mode. In addition, the laminate can detect a minute magnetic field as low as ⌠2Ă10â12âT at resonance frequency, and ⌠1Ă10â10âT at lower frequencies
Direct inversion of S-P differential arrival-times for Vp/Vs ratio in SE Asia
Open Access via Jisc Wiley agreementPeer reviewedPublisher PD
Microseismicity of the Mid-Atlantic Ridge at 7°S-8°15âČS and at the Logatchev Massif oceanic core complex at 14°40âČN-14°50âČN
Lithospheric formation at slow spreading rates is heterogeneous with multiple modalities, favoring symmetric spreading where magmatism dominates or core complex and inside corner high formation where tectonics dominate. We report microseismicity from three deployments of seismic networks at the Mid-Atlantic Ridge (MAR). Two networks surveyed the MAR near 7 degrees S in the vicinity of the Ascension transform fault. Three inside corner high settings were investigated. However, they remained seismically largely inactive and major seismic activity occurred along the center of the median valley. In contrast, at the Logatchev Massif core complex at 14 degrees 45N seismicity was sparse within the center of the median valley but concentrated along the eastern rift mountains just west of the serpentine hosted Logatchev hydrothermal vent field. To the north and south of the massif, however, seismic activity occurred along the ridge axis, emphasizing the asymmetry of seismicity at the Logatchev segment. Focal mechanisms indicated a large number of reverse faulting events occurring in the vicinity of the vent field at 3-5 km depth, which we interpret to reflect volume expansion accompanying serpentinization. At shallower depth of 2-4 km, some earthquakes in the vicinity of the vent field showed normal faulting behavior, suggesting that normal faults facilitates hydrothermal circulation feeding the vent field. Further, a second set of cross-cutting faults occurred, indicating that the surface location of the field is controlled by local fault systems
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Older people as equal partners in creative design
Active older people want to be actively engaged by contributing their experiences to design better services and products. This paper demonstrates the importance of older peoples engagement in the creative design process in a small study where older people were engaged together with designers in the design of digital devices. Three creative workshops were conducted: the first with designers, the second with designers and older people, and the third with older people only. During the illumination stage of the creative process flexibility and flow were measured with topics and turns. Results show that when older people were working with designers more topics and a higher total number of turns were developed than by older people or designers working on their own, which indicates that they had the highest flexibility of ideas and possibly also the greatest flow
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