26,825 research outputs found
Detection of a Spin Accumulation in Nondegenerate Semiconductors
Electrical detection of a spin accumulation in a nondegenerate semiconductor using a tunnel barrier and ferromagnetic contact is shown to be fundamentally affected by the energy barrier associated with the depletion region. This prevents the ferromagnet from probing the spin accumulation directly, strongly suppresses the magnetoresistance in current or potentiometric detection, and introduces nonmonotonic variation of spin signals with voltage and temperature. Having no analogue in metallic systems, we identify energy mismatch as an obstacle for spin detection, necessitating control of the energy landscape of spin-tunnel contacts to semiconductors
The stack resource protocol based on real time transactions
Current hard real time (HRT) kernels have their timely behaviour guaranteed at the cost of a rather restrictive use of the available resources. This makes current HRT scheduling techniques inadequate for use in a multimedia environment where one can profit by a better and more flexible use of the resources. It is shown that one can improve the flexibility and efficiency of real time kernels and a method is proposed for precise quality of service schedulability analysis of the stack resource protocol. This protocol is generalised by introducing real time transactions, which makes its use straightforward and efficient. Transactions can be refined to nested critical sections if the smallest estimation of blocking is desired. The method can be used for hard real time systems in general and for multimedia systems in particular
Kondo effect and impurity band conduction in Co:TiO2 magnetic semiconductor
The nature of charge carriers and their interaction with local magnetic moments in an oxide magnetic semiconductor is established. For cobalt-doped anatase TiO2 films, we demonstrate conduction in a metallic donor-impurity band. Moreover, we observe a clear signature of the Kondo effect in electrical transport data with remarkably high Kondo temperatures of up to 120 K. This indicates a strong coupling between local Co moments and delocalized electrons in the impurity band
The PHMC algorithm for simulations of dynamical fermions: II - Performance analysis
We compare the performance of the PHMC algorithm with the one of the HMC
algorithm in practical simulations of lattice QCD. We show that the PHMC
algorithm can lead to an acceleration of numerical simulations. It is
demonstrated that the PHMC algorithm generates configurations carrying small
isolated eigenvalues of the lattice Dirac operator and hence leads to a
sampling of configuration space that is different from that of the HMC
algorithm.Comment: Latex2e file, 6 figures, 31 page
How the PHMC algorithm samples configuration space
We show that in practical simulations of lattice QCD with two dynamical light
fermion species the PHMC algorithm samples configuration space differently from
the commonly used HMC algorithm.Comment: 3 pages, 2 figures, LATTICE98 (Algorithms
Sign of tunnel spin polarization of low-work-function Gd/Co nanolayers in a magnetic tunnel junction
Magnetic tunnel junctions having a low-work-function Gd/Co nanolayer at the interface with an Al2O3 tunnel barrier are shown to exhibit both positive and negative values of the tunnel magnetoresistance. The sign of the tunnel spin polarization of the Gd/Co nanolayer electrode depends on the thickness of the Gd and Co layers, temperature, and applied voltage. This reflects the nature of the interaction between the conduction electrons of the rare-earth and transition metals. \u
Effects of liquid and vapor cesium on structural materials
Literature survey on corrosive effects of liquid and vapor cesium on structural materials, and compatibility of cesium as working fluid for Rankine cycle space power plan
Non-perturbative running of the average momentum of non-singlet parton densities
We determine non-perturbatively the anomalous dimensions of the second moment
of non-singlet parton densities from a continuum extrapolation of results
computed in quenched lattice simulations at different lattice spacings. We use
a Schr\"odinger functional scheme for the definition of the renormalization
constant of the relevant twist-2 operator. In the region of renormalized
couplings explored, we obtain a good description of our data in terms of a
three-loop expression for the anomalous dimensions. The calculation can be used
for exploring values of the coupling where a perturbative expansion of the
anomalous dimensions is not valid a priori. Moreover, our results provide the
non-perturbative renormalization constant that connects hadron matrix elements
on the lattice, renormalized at a low scale, with the experimental results,
renormalized at much higher energy scales.Comment: Latex2e file, 6 figures, 25 pages, Corrected errors on linear fit in
table 2 and discussion on anomalous dimension of f_
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