272,484 research outputs found
Low-Complexity Reduced-Rank Beamforming Algorithms
A reduced-rank framework with set-membership filtering (SMF) techniques is
presented for adaptive beamforming problems encountered in radar systems. We
develop and analyze stochastic gradient (SG) and recursive least squares
(RLS)-type adaptive algorithms, which achieve an enhanced convergence and
tracking performance with low computational cost as compared to existing
techniques. Simulations show that the proposed algorithms have a superior
performance to prior methods, while the complexity is lower.Comment: 7 figure
Galaxy Formation Through Filamentary Accretion at z=6.1
We present ALMA observations of the dust continuum and [C II] 158um line
emission from the z=6.0695 Lyman Break Galaxy WMH5. These observations at 0.3"
spatial resolution show a compact (~3kpc) main galaxy in dust and [C II]
emission, with a 'tail' of emission extending to the east by about 5kpc (in
projection). The [C II] tail is comprised predominantly of two distinct
sub-components in velocity, separated from the core by ~100 and 250km/s, with
narrow intrinsic widths of about 80km/s, which we call 'sub-galaxies'. The
sub-galaxies themselves are extended east-west by about 3kpc in individual
channel images. The [C II] tail joins smoothly into the main galaxy velocity
field. The [C II] line to continuum ratios are comparable for the main and
sub-galaxy positions, within a factor 2. In addition, these ratios are
comparable to z~5.5 LBGs. We conjecture that the WMH5 system represents the
early formation of a galaxy through the accretion of smaller satellite
galaxies, embedded in a smoother gas distribution, along a possibly filamentary
structure. The results are consistent with current cosmological simulations of
early galaxy formation, and support the idea of very early enrichment with dust
and heavy elements of the accreting material.Comment: 10 pages, 9 figures, Accepted for publication in Ap
Improving the applicability of radar rainfall estimates for urban pluvial flood modelling and forecasting
This work explores the possibility of improving the applicability of radar rainfall estimates (whose accuracy is generally insufficient) to the verification and operation of urban storm-water drainage models by employing a number of local gauge-based radar rainfall adjustment techniques. The adjustment techniques tested in this work include a simple mean-field bias (MFB) adjustment, as well as a more complex Bayesian radar-raingauge data merging method which aims at better preserving the spatial structure of rainfall fields. In addition, a novel technique (namely, local singularity analysis) is introduced and shown to improve the Bayesian method by better capturing and reproducing storm patterns and peaks. Two urban catchments were used as case studies in this work: the Cranbrook catchment (9 km2) in North-East London, and the Portobello catchment (53 km2) in the East of Edinburgh. In the former, the potential benefits of gauge-based adjusted radar rainfall estimates in an operational context were analysed, whereas in the latter the potential benefits of adjusted estimates for model verification purposes were explored. Different rainfall inputs, including raingauge, original radar and the aforementioned merged estimates were fed into the urban drainage models of the two catchments. The hydraulic outputs were compared against available flow and depth records. On the whole, the tested adjustment techniques proved to improve the applicability of radar rainfall estimates to urban hydrological applications, with the Bayesian-based methods, in particular the singularity sensitive one, providing more realistic and accurate rainfall fields which result in better reproduction of the urban drainage system’s dynamics. Further testing is still necessary in order to better assess the benefits of these adjustment methods, identify their shortcomings and improve them accordingly
Enhanced Magnetization from Proton Irradiated Bulk van der Waals Magnet CrSiTe3
Van der Waals (vdWs) crystals have attracted a great deal of scientific
attention due to their interesting physical properties and widespread practical
applications. Among all, CrSiTe3 (CST) is a ferromagnetic semiconductor with
the Curie temperature (TC) of ~32 K. In this letter, we study the magnetic
properties of bulk CST single-crystal upon proton irradiation with the fluence
of 1x1018 protons/cm2. Most significantly, we observed an enhancement (23%) in
the saturation magnetization from 3.9 {\mu}B to 4.8 {\mu}B and is accompanied
by an increase in the coercive field (465-542 Oe) upon proton irradiation.
Temperature-dependent X-band electron paramagnetic resonance measurements show
no additional magnetically active defects/vacancies that are generated upon
proton irradiation. The findings from X-ray photoelectron spectroscopy and
Raman measurements lead us to believe that modification in the spin-lattice
coupling and introduction of disorder could cause enhancement in saturation
magnetization. This work demonstrates that proton irradiation is a feasible
method in modifying the magnetic properties of vdWs crystals, which represents
a significant step forward in designing future spintronic and
magneto-electronic applications
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