3,019 research outputs found
Multi-objective optimisation of risk and business strategy in real-world supply networks in the presence of uncertainty
From Dumb Wireless Sensors to Smart Networks using Network Coding
The vision of wireless sensor networks is one of a smart collection of tiny,
dumb devices. These motes may be individually cheap, unintelligent, imprecise,
and unreliable. Yet they are able to derive strength from numbers, rendering
the whole to be strong, reliable and robust. Our approach is to adopt a
distributed and randomized mindset and rely on in network processing and
network coding. Our general abstraction is that nodes should act only locally
and independently, and the desired global behavior should arise as a collective
property of the network. We summarize our work and present how these ideas can
be applied for communication and storage in sensor networks.Comment: To be presented at the Inaugural Workshop of the Center for
Information Theory and Its Applications, University of California - San
Diego, La Jolla, CA, February 6 - 10, 200
Giant Carrier Mobility in Single Crystals of FeSb2
We report the giant carrier mobility in single crystals of FeSb2. Nonlinear
field dependence of Hall resistivity is well described with the two-carrier
model. Maximum mobility values in high mobility band reach ~10^5 cm^2/Vs at 8
K, and are ~10^2 cm^2/Vs at the room temperature. Our results point to a class
of materials with promising potential for applications in solid state
electronics.Comment: 5 pages, 3 figures. Applied Physics Letters (in press
Anomalous specific heat jump in the heavy fermion superconductor CeCoIn
We study the anomalously large specific heat jump and its systematic change
with pressure in CeCoIn superconductor. Starting with the general free
energy functional of the superconductor for a coupled electron boson system, we
derived the analytic result of the specific heat jump of the strong coupling
superconductivity occurring in the coupled electron boson system. Then using
the two component spin-fermion model we calculate the specific heat coefficient
both for the normal and superconducting states and show a good
agreement with the experiment of CeCoIn. Our result also clearly
demonstrated that the specific heat coefficient of a coupled electron
boson system can be freely interpreted as a renormalization either of the
electronic or of the bosonic degrees of freedom.Comment: 5 pages, 2 figure
Anisotropy in magnetic and transport properties of Fe1-xCoxSb2
Anisotropic magnetic and electronic transport measurements were carried out
on large single crystals of Fe1-xCoxSb2 (0<= x <=1). The semiconducting state
of FeSb2 evolves into metallic and weakly ferromagnetic by substitution of Fe
with Co for x<0.5. Further doping induces structural transformation from
orthorhombic Pnnm structure of FeSb2 to monoclinic P21/c structure of CoSb2
where semiconducting and diamagnetic ground state is restored again. Large
magnetoresistance and anisotropy in electronic transport were observed.Comment: 7 pages, 6 figure
Spin Fluctuation Induced Superconductivity Controlled by Orbital Fluctuation
A microscopic Hamiltonian reflecting the correct symmetry of -orbitals is
proposed to discuss superconductivity in heavy fermion systems. In the
orbitally degenerate region in which not only spin fluctuations but also
orbital fluctuations develop considerably, cancellation between spin and
orbital fluctuations destabilizes -wave superconductivity.
Entering the non-degenerate region by increasing the crystalline electric
field, -wave superconductivity mediated by antiferromagnetic
spin fluctuations emerges out of the suppression of orbital fluctuations. We
argue that the present scenario can be applied to recently discovered
superconductors CeTIn (T=Ir, Rh, and Co).Comment: 4 pages, 3 figure
On the origin of the zero-resistance anomaly in heavy fermion superconducting Ir: a clue from magnetic field and Rh-doping studies
We present the results of the specific heat and AC magnetic susceptibility
measurements of for x from 0 to 0.5. As x is increased
from 0 both quantities reflect the competition between two effects. The first
is a suppression of superconductivity below the bulk transition temperature of
T K, which is due to the pair breaking effect of Rh impurities. The
second is an increase in the volume fraction of the superconducting regions
above T, which we attribute to defect-induced strain. Analysis of the H-T
phase diagram for CeIrInobtained from the bulk probes and resistance
measurements points to the filamentary origin of the inhomogeneous
superconductivity at T K, where the resistance drops to
zero. The identical anisotropies in the magnetic field dependence of the
specific heat and the resistance anomalies in CeIrIn indicate that the
filamentary superconductivity is intrinsic, involving electrons from the part
of the Fermi surface responsible for bulk superconductivity.Comment: 4 page
Light elements in massive single and binary stars
We highlight the role of the light elements (Li, Be, B) in the evolution of
massive single and binary stars, which is largely restricted to a diagnostic
value, and foremost so for the element boron. However, we show that the boron
surface abundance in massive early type stars contains key information about
their foregoing evolution which is not obtainable otherwise. In particular, it
allows to constrain internal mixing processes and potential previous mass
transfer event for binary stars (even if the companion has disappeared). It may
also help solving the mystery of the slowly rotating nitrogen-rich massive main
sequence stars.Comment: 10 pages, 8 figures, to appear in proc. IAU-Symp. 268. C. Charbonnel
et al., eds
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