272 research outputs found
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Recursive least squares semi-blind beamforming for MIMO using decision directed adaptation and constant modulus criterion
A new semi-blind adaptive beamforming scheme is proposed for multi-input multi-output (MIMO) induced and space-
division multiple-access based wireless systems that employ high order phase shift keying signaling. A minimum number of training
symbols, very close to the number of receiver antenna elements, are used to provide a rough initial least squares estimate of the
beamformer0s weight vector. A novel cost function combining the constant modulus criterion with decision-directed adaptation is
adopted to adapt the beamformer weight vector. This cost function can be approximated as a quadratic form with a closed-form
solution, based on which we then derive the recursive least squares (RLS) semi-blind adaptive beamforming algorithm. This semi-blind
adaptive beamforming scheme is capable of converging fast to the minimum mean-square-error beamforming solution, as demonstrated
in our simulation study. Our proposed semi-blind RLS beamforming algorithm therefore provides an e±cient detection scheme for the
future generation of MIMO aided mobile communication systems
Coherent diffraction of single Rice Dwarf virus particles using hard X-rays at the Linac Coherent Light Source
Single particle diffractive imaging data from Rice Dwarf Virus (RDV) were recorded using the Coherent X-ray Imaging (CXI) instrument at the Linac Coherent Light Source (LCLS). RDV was chosen as it is a wellcharacterized model system, useful for proof-of-principle experiments, system optimization and algorithm development. RDV, an icosahedral virus of about 70 nm in diameter, was aerosolized and injected into the approximately 0.1 mu m diameter focused hard X-ray beam at the CXI instrument of LCLS. Diffraction patterns from RDV with signal to 5.9 angstrom ngstrom were recorded. The diffraction data are available through the Coherent X-ray Imaging Data Bank (CXIDB) as a resource for algorithm development, the contents of which are described here.11Ysciescopu
Superconductivity at 31 K in 111 type iron arsenide superconductor NaxFeAs induced by pressure
The effect of pressure on superconductivity of 111 type NaxFeAs is
investigated through temperature dependent electrical resistance measurement in
a diamond anvil cell. The superconducting transition temperature (Tc) increases
from 26 K to a maximum 31 K as the pressure increases from ambient to 3 GPa.
Further increasing pressure suppresses Tc drastically. The behavior of pressure
tuned Tc in NaxFeAs is much different from that in LixFeAs, although they have
the same Cu2Sb type structur
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