1,696 research outputs found
Type IIA Orientifold Limit of M-Theory on Compact Joyce 8-Manifold of Spin(7)-Holonomy
We show that M-theory compactified on a compact Joyce 8-manifold of
-holonomy, which yields an effective theory in with = 1
supersymmetry, admits at some special points in it moduli space a description
in terms of type IIA theory on an orientifold of compact Joyce 7-manifold of
-holonomy. We find the evidence in favour of this duality by computing the
massless spectra on both M-thory side and type IIA side. For the latter, we
compute the massless spectra by going to the orbifold limit of the Joyce
7-manifold.Comment: 26 pages, 2 eps figures, Latex file, two references and one footnote
added, corrected some typo
Elevated-temperature impact toughness of Mg–(Gd, Y)–Zr alloy
The Charpy impact results for Mg–10Gd–3Y–0.5Zr and Mg–11Y–5Gd–2Zn–0.5Zr alloys at various temperatures showed that Mg–10Gd–3Y–0.5Zr was more sensitive to temperature. The increase in impact toughness with temperature was related to the blunt crack-tip at high temperatures. The delamination and local melt of matrix were responsible for the brittle-to-ductile transition of GW103 alloy. The branch and bridging of cracks resulting from ordered phases played an import role in the change in fracture mode from cleavage fracture to quasi-cleavage and dimple-fracture for WGZ1152 alloy
Thermally-activated biochemically-sustained reactor for soft fluidic actuation
Soft robots have shown remarkable distinct capabilities due to their high deformation. Recently increasing attention has been dedicated to developing fully soft robots to exploit their full potential, with a recognition that electronic powering may limit this achievement. Alternative powering sources compatible with soft robots have been identified such as combustion and chemical reactions. A further milestone to such systems would be to increase the controllability and responsiveness of their underlying reactions in order to achieve more complex behaviors for soft robots. In this paper, we present a thermally-activated reactor incorporating a biocompatible hydrogel valve that enables control of the biochemical reaction of sugar and yeast. The biochemical reaction is utilized to generate contained pressure, which in turn powers a fluidic soft actuator. Experiments were conducted to evaluate the response time of the hydrogel valves with three different crosslinker concentrations. Among the tested concentrations, we found that the lowest crosslinker concentration yielded the fastest response time of the valve at an ambient temperature of 50â—¦C. We also evaluated the pressure generation capacity of the reactor, which can reach up to 0.22 bar, and demonstrated the thermoresponsive behavior of the reactor to trigger a biochemical reaction for powering a fluidic soft actuator. This work opens up the possibility to power and control tetherless and fully soft robots
Energy Level Statistics of the U(5) and O(6) Symmetries in the Interacting Boson Model
We study the energy level statistics of the states in U(5) and O(6) dynamical
symmetries of the interacting boson model and the high spin states with
backbending in U(5) symmetry. In the calculations, the degeneracy resulting
from the additional quantum number is eliminated manually. The calculated
results indicate that the finite boson number effect is prominent. When
has a value close to a realistic one, increasing the interaction strength of
subgroup O(5) makes the statistics vary from Poisson-type to GOE-type and
further recover to Poisson-type. However, in the case of , they
all tend to be Poisson-type. The fluctuation property of the energy levels with
backbending in high spin states in U(5) symmetry involves a signal of shape
phase transition between spherical vibration and axial rotation.Comment: 38 pages, 13 figure
In-situ epitaxial growth of superconducting La-based bilayer cuprate thin films
We investigate the epitaxial growth of bilayer cuprate La2CaCu2O6+\delta
using pure ozone as an oxidant, and find that even the crystal with parent
composition without cation substitution can show metallic behavior with the aid
of epitaxial strain effect. The hole concentration is controlled simply by
excess-oxygen doping, and the films grown under the optimum conditions exhibit
superconductivity below 30 K. This is the first result on the superconductivity
of bilayer La2CaCu2O6+\delta induced purely by the excess oxygen.Comment: 5 pages, 3 figures, To appear in Phys. Rev. B, Rapid Communication
Striped antiferromagnetic order and electronic properties of stoichiometric LiFeAs from first-principles calculations
We investigate the structural, electronic, and magnetic properties of
stoichiometric LiFeAs by using state-of-the-arts first-principles method. We
find the magnetic ground-state by comparing the total energies among all the
possible magnetic orders. Our calculated internal positions of Li and As are in
good agreement with experiment. Our results show that stoichiometric LiFeAs has
almost the same striped antiferromagnetic spin order as other FeAs-based parent
compounds and tetragonal FeSe do, and the experimental fact that no magnetic
phase transition has been observed at finite temperature is attributed to the
tiny inter-layer spin coupling
Influence of Carbon Concentration on the Superconductivity in MgCxNi3
The influence of carbon concentration on the superconductivity (SC) in
MgCNi has been investigated by measuring the low temperature specific
heat combined with first principles electronic structure calculation. It is
found that the specific heat coefficient of the
superconducting sample () in normal state is twice that of the
non-superconducting one (). The comparison of measured
and the calculated electronic density of states (DOS) shows that the
effective mass renormalization changes remarkably as the carbon concentration
changes. The large mass renormalization for the superconducting sample and the
low (7K) indicate that more than one kind of boson mediated
electron-electron interactions exist in MgCNi.Comment: 4 pages, 4 figure
Private-label use and store loyalty
The authors develop an econometric model of the relationship between a household’s private-label (PL) share and its behavioral store loyalty. The model includes major drivers of these two behaviors and controls for simultaneity and nonlinearity in the relationship between them. The model is estimated with a unique data set that combinescomplete purchase records of a panel of Dutch households with demographic and psychographic data. The authorsestimate the model for two retail chains in the Netherlands the leading service chain with a well-differentiatedhigh-share PL and the leading value chain with a lower-share PL. They find that PL share significantly affects all three measures of behavioral loyalty in the study: share of wallet, share of items purchased, andshare of shopping trips. In addition, behavioral loyalty has a significant effect on PL share. For the service chain, the authors find that both effects are in the form of an inverted U. For the value chain, the effects are positive and nonlinear, but they do not exhibit nonmonotonicity, because PL share has not yet reached high enough levels. The managerial implications of this research are important. Retailers can reap the benefits of a virtuous cycle; greater PL share increases share of wallet, and greater share of wallet increases PL share. However, this virtuous cycle operates only to a point because heavy PL buyers tend to be loyal to price savings and PLs in general, not to the PL of any particular chain.pre-prin
Oscillations of a solid sphere falling through a wormlike micellar fluid
We present an experimental study of the motion of a solid sphere falling
through a wormlike micellar fluid. While smaller or lighter spheres quickly
reach a terminal velocity, larger or heavier spheres are found to oscillate in
the direction of their falling motion. The onset of this instability correlates
with a critical value of the velocity gradient scale
s. We relate this condition to the known complex rheology of wormlike
micellar fluids, and suggest that the unsteady motion of the sphere is caused
by the formation and breaking of flow-induced structures.Comment: 4 pages, 4 figure
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