10,580 research outputs found
Implementable Wireless Access for B3G Networks - III: Complexity Reducing Transceiver Structures
This article presents a comprehensive overview of some of the research conducted within Mobile VCE’s Core Wireless Access Research Programme,1 a key focus of which has naturally been on MIMO transceivers. The series of articles offers a coherent view of how the work was structured and comprises a compilation of material that has been presented in detail elsewhere (see references within the article). In this article MIMO channel measurements, analysis, and modeling, which were presented previously in the first article in this series of four, are utilized to develop compact and distributed antenna arrays. Parallel activities led to research into low-complexity MIMO single-user spacetime coding techniques, as well as SISO and MIMO multi-user CDMA-based transceivers for B3G systems. As well as feeding into the industry’s in-house research program, significant extensions of this work are now in hand, within Mobile VCE’s own core activity, aiming toward securing major improvements in delivery efficiency in future wireless systems through crosslayer operation
Induced antiferromagnetism and large magnetoresistances in RuSr2(Nd,Y,Ce)2Cu2O10-d ruthenocuprates
RuSr2(Nd,Y,Ce)2Cu2O10-d ruthenocuprates have been studied by neutron
diffraction, magnetotransport and magnetisation measurements and the electronic
phase diagram is reported. Separate Ru and Cu spin ordering transitions are
observed, with spontaneous Cu antiferromagnetic order for low hole doping
levels p, and a distinct, induced-antiferromagnetic Cu spin phase in the 0.02 <
p < 0.06 pseudogap region. This ordering gives rise to large negative
magnetoresistances which vary systematically with p in the
RuSr2Nd1.8-xY0.2CexCu2O10-d series. A collapse of the magnetoresistance (MR)
and magnetisation in the pre-superconducting region may signify the onset of
superconducting fluctuations.Comment: 22 pages, 11 figure
Phase Mixing of Alfvén Waves Near a 2D Magnetic Null Point
The propagation of linear Alfvén wave pulses in an inhomogeneous plasma near a 2D coronal null point is investigated. When a uniform plasma density is considered, it is seen that an initially planar Alfvén wavefront remains planar, despite the varying equilibrium Alfvén speed, and that all the wave collects at the separatrices. Thus, in the non-ideal case, these Alfvénic disturbances preferentially dissipate their energy at these locations. For a non-uniform equilibrium density, it is found that the Alfvén wavefront is significantly distorted away from the initially planar geometry, inviting the possibility of dissipation due to phase mixing. Despite this however, we conclude that for the Alfvén wave, current density accumulation and preferential heating still primarily occur at the separatrices, even when an extremely non-uniform density profile is considered
K-shell x-ray spectroscopy of atomic nitrogen
Absolute {\it K}-shell photoionization cross sections for atomic nitrogen
have been obtained from both experiment and state-of-the-art theoretical
techniques. Due to the difficulty of creating a target of neutral atomic
nitrogen, no high-resolution {\it K}-edge spectroscopy measurements have been
reported for this important atom. Interplay between theory and experiment
enabled identification and characterization of the strong
resonance features throughout the threshold region. An experimental value
of 409.64 0.02 eV was determined for the {\it K}-shell binding energy.Comment: 4 pages, 2 graphs, 1 tabl
Molecular dynamics simulations of an anomalous response of diamond to shock compression
We performed molecular dynamics simulations of shock wave propagation in diamond in the [110] crystallographic direction and observed an anomalous response of the material. This regime is characterized by absence of plastic deformation in the intermediate interval of shock wave intensities between shear-deformation and overdriven rehybridization shock wave regimes
A flight investigation with a STOL airplane flying curved, descending instrument approach paths
A flight investigation using a De Havilland Twin Otter airplane was conducted to determine the configurations of curved, 6 deg descending approach paths which would provide minimum airspace usage within the requirements for acceptable commercial STOL airplane operations. Path configurations with turns of 90 deg, 135 deg, and 180 deg were studied; the approach airspeed was 75 knots. The length of the segment prior to turn, the turn radius, and the length of the final approach segment were varied. The relationship of the acceptable path configurations to the proposed microwave landing system azimuth coverage requirements was examined
Photoionization of tungsten ions: experiment and theory for W
Experimental and theoretical results are reported for single-photon single
ionization of the tungsten ion W. Absolute cross sections have been
measured employing the photon-ion merged-beams setup at the Advanced Light
Source in Berkeley. Detailed photon-energy scans were performed at 200~meV
bandwidth in the 40 -- 105~eV range. Theoretical results have been obtained
from a Dirac-Coulomb R-matrix approach employing basis sets of 730 levels for
the photoionization of W. Calculations were carried out for the
, =2, ground level and the
associated fine-structure levels with =3 and 4 for the W ions. In
addition, cross sections have been calculated for the metastable levels
. Very satisfying agreement of theory and experiment is
found for the photoionization cross section of W which is remarkable
given the complexity of the electronic structure of tungsten ions in low charge
states.Comment: 15 pages, 3 figures, to appear in the Journal of Physics B: Atomic,
Molecular and Optical Physic
Association Between a Directly Translated Cognitive Measure of Negative Bias and Self-reported Psychiatric Symptoms
BACKGROUND: Negative interpretation biases are thought to be core symptoms of mood and anxiety disorders. However, prior work using cognitive tasks to measure such biases is largely restricted to case-control group studies, which cannot be used for inference about individuals without considerable additional validation. Moreover, very few measures are fully translational (i.e., can be used across animals and humans in treatment-development pipelines). This investigation aimed to produce the first measure of negative cognitive biases that is both translational and sensitive to individual differences, and then to determine which specific self-reported psychiatric symptoms are related to bias. METHODS: A total of 1060 (n = 990 complete) participants performed a cognitive task of negative bias along with psychiatric symptom questionnaires. We tested the hypothesis that individual levels of mood and anxiety disorder symptomatology would covary positively with negative bias on the cognitive task using a combination of computational modeling of behavior, confirmatory factor analysis, exploratory factor analysis, and structural equation modeling. RESULTS: Participants with higher depression symptoms (β = −.16, p = .017) who were older (β = −.11, p = .001) and had lower IQ (β = .14, p < .001) showed greater negative bias. Confirmatory factor analysis and structural equation modeling suggested that no other psychiatric symptom (or transdiagnostic latent factor) covaried with task performance over and above the effect of depression, while exploratory factor analysis suggested combining depression/anxiety symptoms in a single latent factor. Generating groups using symptom cutoffs or latent mixture modeling recapitulated our prior case-control findings. CONCLUSIONS: This measure, which uniquely spans both the clinical group-to-individual and preclinical animal-to-human generalizability gaps, can be used to measure individual differences in depression vulnerability for translational treatment-development pipelines
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