1,704 research outputs found
Frequency and power dependence of spin-current emission by spin pumping in a thin film YIG/Pt system
This paper presents the frequency dependence of the spin current emission in
a hybrid ferrimagnetic insulator/normal metal system. The system is based on a
ferrimagnetic insulating thin film of Yttrium Iron Garnet (YIG, 200 nm) grown
by liquid-phase-epitaxy (LPE) coupled with a normal metal with a strong
spin-orbit coupling (Pt, 15 nm). The YIG layer presents an isotropic behaviour
of the magnetization in the plane, a small linewidth, and a roughness lower
than 0.4 nm. Here we discuss how the voltage signal from the spin current
detector depends on the frequency [0.6 - 7 GHz], the microwave power, Pin, [1 -
70 mW], and the in-plane static magnetic field. A strong enhancement of the
spin current emission is observed at low frequencies, showing the appearance of
non-linear phenomena.Comment: 7 pages, 5 figure
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When enough is not enough: information overload and metacognitive decisions to stop studying information
People are often exposed to more information than they can actually remember. Despite this frequent form of information overload, little is known about how much information people choose to remember. Using a novel âstopâ paradigm, the current research examined whether and how people choose to stop receiving newâpossibly overwhelmingâinformation with the intent to maximize memory performance. Participants were presented with a long list of items and were rewarded for the number of correctly remembered words in a following free recall test. Critically, participants in a stop condition were provided with the option to stop the presentation of the remaining words at any time during the list, whereas participants in a control condition were presented with all items. Across five experiments, we found that participants tended to stop the presentation of the items to maximize the number of recalled items, but this decision ironically led to decreased memory performance relative to the control group. This pattern was consistent even after controlling for possible confounding factors (e.g., task demands). The results indicated a general, false belief that we can remember a larger number of items if we restrict the quantity of learning materials. These findings suggest people have an incomplete understanding of how we remember excessive amounts of information
Shell-Model Effective Operators for Muon Capture in ^{20}Ne
It has been proposed that the discrepancy between the partially-conserved
axial-current prediction and the nuclear shell-model calculations of the ratio
in the muon-capture reactions can be solved in the case of ^{28}Si by
introducing effective transition operators. Recently there has been
experimental interest in measuring the needed angular correlations also in
^{20}Ne. Inspired by this, we have performed a shell-model analysis employing
effective transition operators in the shell-model formalism for the transition
. Comparison of
the calculated capture rates with existing data supports the use of effective
transition operators. Based on our calculations, as soon as the experimental
anisotropy data becomes available, the limits for the ratio can be
extracted.Comment: 9 pages, 3 figures include
Modeling and performance evaluation of the eICIC/ABS in H-CRAN
International audienceIn this paper, we propose mathematical models to evaluate the performance of the interference remediation technique eICIC/ABS (enhanced Inter-Cell Interference Coordination / Almost Blank Sub-frame) in the context of Heterogeneous Cloud based Radio Access Networks (H-CRAN) architecture and 5G networks. The objective is to propose a dynamic resource management tool to ease decisions on the activation/deactivation of micro-cells as well as on the distributions of subframes among macro and micro cells. First, we propose a Markov chain based model that fits the behavior of the considered scheme and allows the analysis of the cell throughput according to traffic load, radio conditions and the distribution of available resources among macro and micro cells. Then, we propose an approximation model with a closed form formula. The two models are validated and evaluated in terms of accuracy and computation time. Numerical results are compared to matlab simulations that reproduce realistic radio conditions. Results show that both models are accurate. However, the closed form approximation is less complex and provides faster results
Systematics of g factors of 2_1^+ states in even-even nuclei from Gd to Pt: A microscopic description by the projected shell model
The systematics of g factor of first excited 2^+ state vs neutron number N is
studied by the projected shell model. The study covers the even-even nuclei of
all isotopic chains from Gd to Pt. g factors are calculated by using the
many-body wavefunctions that reproduces well the energy levels and B(E2)'s of
the ground-state bands. For Gd to W isotopes the characteristic feature of the
g factor data along an isotopic chain is described by the present model.
Deficiency of the model in the g factor description for the heavier Os and Pt
isotopes is discussed.Comment: 9 pages, 5 figure
Dominant g(9/2)^2 neutron configuration in the 4+1 state of 68Zn based on new g factor measurements
The factor of the state in Zn has been remeasured with
improved energy resolution of the detectors used. The value obtained is
consistent with the previous result of a negative factor thus confirming
the dominant neutron nature of the state. In addition, the
accuracy of the factors of the , and states has been
improved an d their lifetimes were well reproduced. New large-scale shell model
calculations based on a Ni core and an model space
yield a theoretical value, . Although the calculated value
is small, it cannot fully explain the experimental value, . The magnitude of the deduced B(E2) of the and
transition is, however, rather well described. These results demonstrate again
the importance of factor measurements for nuclear structure determination s
due to their specific sensitivity to detailed proton and neutron components in
the nuclear wave functions.Comment: 7 pages, 3 figs, submitted to PL
High Precision CTE-Measurement of SiC-100 for Cryogenic Space-Telescopes
We present the results of high precision measurements of the thermal
expansion of the sintered SiC, SiC-100, intended for use in cryogenic
space-telescopes, in which minimization of thermal deformation of the mirror is
critical and precise information of the thermal expansion is needed for the
telescope design. The temperature range of the measurements extends from room
temperature down to 10 K. Three samples, #1, #2, and #3 were
manufactured from blocks of SiC produced in different lots. The thermal
expansion of the samples was measured with a cryogenic dilatometer, consisting
of a laser interferometer, a cryostat, and a mechanical cooler. The typical
thermal expansion curve is presented using the 8th order polynomial of the
temperature. For the three samples, the coefficients of thermal expansion
(CTE), \bar{\alpha}_{#1}, \bar{\alpha}_{#2}, and \bar{\alpha}_{#3} were
derived for temperatures between 293 K and 10 K. The average and the dispersion
(1 rms) of these three CTEs are 0.816 and 0.002 (/K),
respectively. No significant difference was detected in the CTE of the three
samples from the different lots. Neither inhomogeneity nor anisotropy of the
CTE was observed. Based on the obtained CTE dispersion, we performed an
finite-element-method (FEM) analysis of the thermal deformation of a 3.5 m
diameter cryogenic mirror made of six SiC-100 segments. It was shown that the
present CTE measurement has a sufficient accuracy well enough for the design of
the 3.5 m cryogenic infrared telescope mission, the Space Infrared telescope
for Cosmology and Astrophysics (SPICA).Comment: in press, PASP. 21 pages, 4 figure
Chiral three-nucleon interaction and the carbon-14 dating beta decay
We present a shell model calculation for the beta decay of 14-C to the 14-N
ground-state, treating the relevant nuclear states as two 0p-holes in an 16-O
core. Employing the universal low-momentum nucleon-nucleon potential V(low-k)
only, one finds that the Gamow-Teller matrix element is too large to describe
the known (very long) lifetime of 14-C. As a novel approach to the problem, we
invoke the chiral three-nucleon force (3NF) at leading order and derive from it
a density-dependent in-medium NN interaction. Including this effective
in-medium NN interaction, the Gamow-Teller matrix element vanishes for a
nuclear density close to that of saturated nuclear matter. The genuine
short-range part of the three-nucleon interaction plays a particularly
important role in this context, since the medium modifications to the pion
propagator and pion-nucleon vertex (due to the long-range 3NF) tend to cancel
out in the relevant observable. We discuss also uncertainties related to the
off-shell extrapolation of the in-medium NN interaction. Using the off-shell
behavior of V(low-k) as a guide, we find that these uncertainties are rather
small.Comment: 22 pages, 11 figure
Competition in rotation-alignment between high-j neutrons and protons in transfermium nuclei
The study of rotation-alignment of quasiparticles probes sensitively the
properties of high-j intruder orbits. The distribution of very high-j orbits,
which are consequences of the fundamental spin-orbit interaction, links with
the important question of single-particle levels in superheavy nuclei. With the
deformed single-particle states generated by the standard Nilsson potential, we
perform Projected-Shell-Model calculations for transfermium nuclei where
detailed spectroscopy experiment is currently possible. Specifically, we study
the systematical behavior of rotation-alignment and associated band-crossing
phenomenon in Cf, Fm, and No isotopes. Neutrons and protons from the high-j
orbits are found to compete strongly in rotation-alignment, which gives rise to
testable effects. Observation of these effects will provide direct information
on the single-particle states in the heaviest nuclear mass region.Comment: 9 pages, 5 figure
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