1,300 research outputs found
Numerical and experimental analysis of vortex sheets behind lifting surfaces
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77273/1/AIAA-1992-409-534.pd
Temporal response of mountain drainage basins in Taiwan to earthquake and typhoon perturbation.
In tectonically-active mountain belts, earthquake-triggered landslides deliver large amounts of sediment to rivers. In previous work, we have quantified the geomorphic impact of the 1999 Mw 7.6 Chi-Chi earthquake in Taiwan, which triggered >20,000 landslides and elevated suspended sediment loads in rivers by up to a factor of four. At the time, many coseismic landslides remained confined to hillslopes and, on the basis of four years of hydrometric data, we predicted that downslope transport of sediment would continue to occur during later storms. During the seven years since the Chi- Chi earthquake, several major typhoons storms have hit Taiwan (e.g., Typhoons Bilis, Toraji, Nari, Mindulle, Aere) and the Water Resources Agency of Taiwan has contin- ued to monitor water discharge and suspended sediment concentration. Here we use these new data to refine the spatial and temporal pattern of the decaying geomorphic response to the Chi-Chi earthquake in the face of several large typhoons. Our results indicate that the broad pattern of exponential decay in sediment concentration for a given river discharge (prevalent in winter seasons without typhoons) is punctuated by markedly elevated periods associated with typhoon storms. However, our analyses show that the change in unit sediment concentration (i.e., suspended sediment concen- tration for a unit water discharge) associated with each storm depends more strongly on the length of time elapsed since the earthquake than it does on the magnitude of the storm itself
Transcritical flow of a stratified fluid over topography: analysis of the forced Gardner equation
Transcritical flow of a stratified fluid past a broad localised topographic
obstacle is studied analytically in the framework of the forced extended
Korteweg--de Vries (eKdV), or Gardner, equation. We consider both possible
signs for the cubic nonlinear term in the Gardner equation corresponding to
different fluid density stratification profiles. We identify the range of the
input parameters: the oncoming flow speed (the Froude number) and the
topographic amplitude, for which the obstacle supports a stationary localised
hydraulic transition from the subcritical flow upstream to the supercritical
flow downstream. Such a localised transcritical flow is resolved back into the
equilibrium flow state away from the obstacle with the aid of unsteady coherent
nonlinear wave structures propagating upstream and downstream. Along with the
regular, cnoidal undular bores occurring in the analogous problem for the
single-layer flow modeled by the forced KdV equation, the transcritical
internal wave flows support a diverse family of upstream and downstream wave
structures, including solibores, rarefaction waves, reversed and trigonometric
undular bores, which we describe using the recent development of the nonlinear
modulation theory for the (unforced) Gardner equation. The predictions of the
developed analytic construction are confirmed by direct numerical simulations
of the forced Gardner equation for a broad range of input parameters.Comment: 34 pages, 24 figure
Selective interlayer ferromagnetic coupling between the Cu spins in YBa Cu O grown on top of La Ca MnO
Studies to date on ferromagnet/d-wave superconductor heterostructures focus
mainly on the effects at or near the interfaces while the response of bulk
properties to heterostructuring is overlooked. Here we use resonant soft x-ray
scattering spectroscopy to reveal a novel c-axis ferromagnetic coupling between
the in-plane Cu spins in YBa Cu O (YBCO) superconductor when it
is grown on top of ferromagnetic La Ca MnO (LCMO) manganite
layer. This coupling, present in both normal and superconducting states of
YBCO, is sensitive to the interfacial termination such that it is only observed
in bilayers with MnO_2but not with La Ca interfacial
termination. Such contrasting behaviors, we propose, are due to distinct
energetic of CuO chain and CuO plane at the La Ca and
MnO terminated interfaces respectively, therefore influencing the transfer
of spin-polarized electrons from manganite to cuprate differently. Our findings
suggest that the superconducting/ferromagnetic bilayers with proper interfacial
engineering can be good candidates for searching the theorized
Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state in cuprates and studying the
competing quantum orders in highly correlated electron systems.Comment: Please note the change of the title. Text might be slightly different
from the published versio
Speeding up Simplification of Polygonal Curves using Nested Approximations
We develop a multiresolution approach to the problem of polygonal curve
approximation. We show theoretically and experimentally that, if the
simplification algorithm A used between any two successive levels of resolution
satisfies some conditions, the multiresolution algorithm MR will have a
complexity lower than the complexity of A. In particular, we show that if A has
a O(N2/K) complexity (the complexity of a reduced search dynamic solution
approach), where N and K are respectively the initial and the final number of
segments, the complexity of MR is in O(N).We experimentally compare the
outcomes of MR with those of the optimal "full search" dynamic programming
solution and of classical merge and split approaches. The experimental
evaluations confirm the theoretical derivations and show that the proposed
approach evaluated on 2D coastal maps either shows a lower complexity or
provides polygonal approximations closer to the initial curves.Comment: 12 pages + figure
Spontaneous Crystallization of Skyrmions and Fractional Vortices in the Fast-rotating and Rapidly-quenched Spin-1 Bose-Einstein Condensates
We investigate the spontaneous generation of crystallized topological defects
via the combining effects of fast rotation and rapid thermal quench on the
spin-1 Bose-Einstein condensates. By solving the stochastic projected
Gross-Pitaevskii equation, we show that, when the system reaches equilibrium, a
hexagonal lattice of skyrmions, and a square lattice of half-quantized vortices
can be formed in a ferromagnetic and antiferromagnetic spinor BEC, respetively,
which can be imaged by using the polarization-dependent phase-contrast method
A study on using genetic niching for query optimisation in document retrieval
International audienceThis paper presents a new genetic approach for query optimisation in document retrieval. The main contribution of the paper is to show the effectiveness of the genetic niching technique to reach multiple relevant regions of the document space. Moreover, suitable merging procedures have been proposed in order to improve the retrieval evaluation. Experimental results obtained using a TREC sub-collection indicate that the proposed approach is promising for applications
Cenderitide, a novel dual GC-A and GC-B receptor activator, is a potent chronic cardiorenal fibroinhibiting peptide which suppresses aldosterone and reduces proteinuria in models of ardiorenal fibrosis
Targeting the ALS/FTD-associated A-DNA kink with anthracene-based metal complex causes DNA backbone straightening and groove contraction
The use of a small molecule compound to reduce toxic repeat RNA transcripts or their translated aberrant proteins to target repeat-expanded RNA/DNA with a G4C2 motif is a promising strategy to treat C9orf72-linked disorders. In this study, the crystal structures of DNA and RNA-DNA hybrid duplexes with the -GGGCCG- region as a G4C2 repeat motif were solved. Unusual groove widening and sharper bending of the G4C2 DNA duplex A-DNA conformation with B-form characteristics inside was observed. The G4C2 RNA-DNA hybrid duplex adopts a more typical rigid A form structure. Detailed structural analysis revealed that the G4C2 repeat motif of the DNA duplex exhibits a hydration shell and greater flexibility and serves as a 'hot-spot' for binding of the anthracene-based nickel complex, NiII(Chro)2 (Chro = Chromomycin A3). In addition to the original GGCC recognition site, NiII(Chro)2 has extended specificity and binds the flanked G:C base pairs of the GGCC core, resulting in minor groove contraction and straightening of the DNA backbone. We have also shown that Chro-metal complexes inhibit neuronal toxicity and suppresses locomotor deficits in a Drosophila model of C9orf72-associated ALS. The approach represents a new direction for drug discovery against ALS and FTD diseases by targeting G4C2 repeat motif DNA
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