30,623 research outputs found
Performance Analysis of Best Relaying Protocol Selection with Interferences at Relays
In this paper, we investigate the performance of selecting the best protocol between amplify and forward (AF) and decode and forward (DF) in multiple relay networks with multiple interferences at relays. In the selection scheme, the best protocol between AF and DF is selected depending on the comparisons of signal-to-interference and noise ratio (SINR) for all source-relay links. All relays measure the received SINR to decide forwarding signal or not. When SINR is above a certain threshold then DF is used otherwise AF is used. Particularly, we develop an accurate mathematical model for best relaying protocol by considering the effect of interferences to our scheme. Firstly, we derive the asymptotic closed form expression for the symbol error rate (SER) for the system under study. Also we derive an upper and lower bound of symbol error rate and show how they were tight with exact SER. Furthermore an approximate expression for the outage probability is derived. Numerical results are finally presented to validate the theoretical analysis with a different number of relays
Crystal field effects on spin pumping
"Spin pumping" is the injection of spin angular momentum by a time-dependent
magnetization into an adjacent normal metal proportional to the spin mixing
conductance. We study the role of electrostatic interactions in the form of
crystal fields on the pumped spin currents generated by insulators with
exchange-coupled local moments at the interface to a metal. The crystal field
is shown to render the spin currents anisotropic, which implies that the spin
mixing conductance of insulator|normal metal bilayers depends on crystal cut
and orientation. We interpret the interface "effective field" (imaginary part
of the spin mixing conductance) in terms of the coherent motion of the
equilibrium spin density induced by proximity in the normal metal.Comment: 8 pages+, 7 figure
Voltage control of interface rare-earth magnetic moments
The large spin orbit interaction in rare earth atoms implies a strong
coupling between their charge and spin degrees of freedom. We formulate the
coupling between voltage and the local magnetic moments of rare earth atoms
with partially filled 4f shell at the interface between an insulator and a
metal. The rare earth-mediated torques allow power-efficient control of
spintronic devices by electric field-induced ferromagnetic resonance and
magnetization switching
Seismicity along the western part of the Eurasia-Nubian plate boundary
The seismicity along the western part of the Eurasia-Nubian plate boundary is characterized by a very complex
pattern. In average, the motion is transtensional in the Azores, dextral along the Gloria transform zone and convergent
between the SW Portuguese Atlantic margin and the Ibero-Maghrebian zone. To constraint the factors
controlling the seismicity, we provide a new seismotectonic synthesis using several significant seismic events. We
show that the studied area can be divided into six different regions, each one characterized by a coherent seismicity
pattern. The total seismic moment tensor and the average slip velocities are provided for each one of them. To
understand the spatial distribution of the seismicity, we compute for each event from the focal mechanism the slip
vector and compare it to the relative velocity between the Eurasia and Nubia plates, deduced from global kinematics
models. Despite local departures in the Alboran Sea and in the proximity of the Mid Atlantic Ridge, we find
a good correlation between these two independent vectors sets. Quantitatively, the slip velocities display a linear,
non-affine correlation with the norms of the relative kinematics velocities. The norm of the slip velocities seems to
also depend on the tectonic regime and on the morphology of the platesâ boundary
Weak-Field Thermal Hall Conductivity in the Mixed State of d-Wave Superconductors
Thermal transport in the mixed state of a d-wave superconductor is considered
within the weak-field regime. We express the thermal conductivity,
, and the thermal Hall conductivity, , in terms of
the cross section for quasiparticle scattering from a single vortex. Solving
for the cross section (neglecting the Berry phase contribution and the
anisotropy of the gap nodes), we obtain and
in surprisingly good agreement with the qualitative features
of the experimental results for YBaCuO. In particular, we
show that the simple, yet previously unexpected, weak-field behavior,
, is that of thermally-excited nodal
quasiparticles, scattering primarily from impurities, with a small skew
component provided by vortex scattering.Comment: 5 pages, 2 figures; final version as published in Phys Rev Let
Memory, space and time: Researching children's lives
This article discusses the research approach in 'Pathways through Childhood', a small qualitative study drawing on memories of childhood. The research explores how wider social arrangements and social change influence children's everyday lives.The article discusses the way that the concepts of social memory, space and time have been drawn on to access and analyse children's experiences, arguing that attention to the temporal and spatial complexity of childhood reveals less visible yet formative influences and connections. Children's everyday engagements involve connections between past and present time, between children, families, communities and nations, and between different places. Children carve out space and time for themselves from these complex relations. © The Author(s) 2010
Sensitivity to new supersymmetric thresholds through flavour and CP violating physics
Treating the MSSM as an effective theory below a threshold scale Lambda, we
study the consequences of having dimension-five operators in the superpotential
for flavour and CP-violating processes. Below the supersymmetric threshold such
terms generate flavour changing and/or CP-odd effective operators of dimension
six composed from the Standard Model fermions, that have the interesting
property of decoupling linearly with the threshold scale, i.e. as 1/(Lambda
m_soft), where m_soft is the scale of soft supersymmetry breaking. The
assumption of weak-scale supersymmetry, together with the stringent limits on
electric dipole moments and lepton flavour-violating processes, then provides
sensitivity to Lambda as high as 10^7-10^9 GeV. We discuss the varying
sensitivity to these scales within several MSSM benchmark scenarios and also
outline the classes of UV physics which could generate these operators.Comment: 28 pages, 9 figure
Improving Productivity of Multiphase Flow Aerobic Oxidation Using a Tube-in-Tube Membrane Contactor
The application of flow reactors in multiphase catalytic reactions represents a promising approach for enhancing the efficiency of this important class of chemical reactions. We developed a simple approach to improve the reactor productivity of multiphase catalytic reactions performed using a flow chemistry unit with a packed bed reactor. Specifically, a tube-in-tube membrane contactor (sparger) integrated in-line with the flow reactor has been successfully applied to the aerobic oxidation of benzyl alcohol to benzaldehyde utilizing a heterogeneous palladium catalyst in the packed bed. We examined the effect of sparger hydrodynamics on reactor productivity quantified by space time yield (STY). Implementation of the sparger, versus segmented flow achieved with the built in gas dosing module (1) increased reactor productivity 4-fold quantified by space time yield while maintaining high selectivity and (2) improved process safety as demonstrated by lower effective operating pressures
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