40,747 research outputs found
Trajectory and stability of Lagrangian point in the Sun-Earth system
This paper describes design of the trajectory and analysis of the stability
of collinear point in the Sun-Earth system. The modified restricted three
body problem with additional gravitational potential from the belt is used as
the model for the Sun-Earth system. The effect of radiation pressure of the Sun
and oblate shape of the Earth are considered. The point is asymptotically
stable upto a specific value of time correspond to each set of values of
parameters and initial conditions. The results obtained from this study would
be applicable to locate a satellite, a telescope or a space station around the
point .Comment: Accepted for publication in Astrophysics & Space Scienc
Geometry-induced pulse instability in microdesigned catalysts: the effect of boundary curvature
We explore the effect of boundary curvature on the instability of reactive
pulses in the catalytic oxidation of CO on microdesigned Pt catalysts. Using
ring-shaped domains of various radii, we find that the pulses disappear
(decollate from the inert boundary) at a turning point bifurcation, and trace
this boundary in both physical and geometrical parameter space. These
computations corroborate experimental observations of pulse decollation.Comment: submitted to Phys. Rev.
How can we demonstrate the economic value of Precision Agriculture (PA) practices to New Zealand Agriculture service providers and arable farmers?
The amount of data collected has become a major challenge to the uptake of PA practices in New Zealand.
There is a lack of clear value propositions around some PA practices, e.g. variable rate seeding (VRS).
The importance of calibrating yield monitors, collecting yield data and mapping results has not been realised by farmers.
The goal of the study is to provide economic evidence through yield data mining to encourage the adoption of PA
Electron spin relaxation in bulk III-V semiconductors from a fully microscopic kinetic spin Bloch equation approach
Electron spin relaxation in bulk III-V semiconductors is investigated from a
fully microscopic kinetic spin Bloch equation approach where all relevant
scatterings, such as, the electron--nonmagnetic-impurity, electron-phonon,
electron-electron, electron-hole, and electron-hole exchange (the
Bir-Aronov-Pikus mechanism) scatterings are explicitly included. The
Elliot-Yafet mechanism is also fully incorporated. This approach offers a way
toward thorough understanding of electron spin relaxation both near and far
away from the equilibrium in the metallic regime. The dependence of the spin
relaxation time on electron density, temperature, initial spin polarization,
photo-excitation density, and hole density are studied thoroughly with the
underlying physics analyzed. In contrast to the previous investigations in the
literature, we find that: (i) In -type materials, the Elliot-Yafet mechanism
is {\em less} important than the D'yakonov-Perel' mechanism, even for the
narrow band-gap semiconductors such as InSb and InAs. (ii) The density
dependence of the spin relaxation time is nonmonotonic and we predict a {\em
peak} in the metallic regime in both -type and intrinsic materials. (iii) In
intrinsic materials, the Bir-Aronov-Pikus mechanism is found to be negligible
compared with the D'yakonov-Perel' mechanism. We also predict a peak in the
temperature dependence of spin relaxation time which is due to the nonmonotonic
temperature dependence of the electron-electron Coulomb scattering in intrinsic
materials with small initial spin polarization. (iv) In -type III-V
semiconductors, ...... (the remaining is omitted here due to the limit of
space)Comment: 25 pages, 17 figure
Thermal conductance of Andreev interferometers
We calculate the thermal conductance of diffusive Andreev
interferometers, which are hybrid loops with one superconducting arm and one
normal-metal arm. The presence of the superconductor suppresses ; however,
unlike a conventional superconductor, does not vanish as the
temperature , but saturates at a finite value that depends on the
resistance of the normal-superconducting interfaces, and their distance from
the path of the temperature gradient. The reduction of is determined
primarily by the suppression of the density of states in the proximity-coupled
normal metal along the path of the temperature gradient. is also a
strongly nonlinear function of the thermal current, as found in recent
experiments.Comment: 5 pages, 4 figure
Federating distributed clinical data for the prediction of adverse hypotensive events
The ability to predict adverse hypotensive events, where a patient's arterial blood pressure drops to abnormally low (and dangerous) levels, would be of major benefit to the fields of primary and secondary health care, and especially to the traumatic brain injury domain. A wealth of data exist in health care systems providing information on the major health indicators of patients in hospitals (blood pressure, temperature, heart rate, etc.). It is believed that if enough of these data could be drawn together and analysed in a systematic way, then a system could be built that will trigger an alarm predicting the onset of a hypotensive event over a useful time scale, e.g. half an hour in advance. In such circumstances, avoidance measures can be taken to prevent such events arising. This is the basis for the Avert-IT project (http://www.avert-it.org), a collaborative EU-funded project involving the construction of a hypotension alarm system exploiting Bayesian neural networks using techniques of data federation to bring together the relevant information for study and system development
Single spin measurement using spin-orbital entanglement
Single spin measurement represents a major challenge for spin-based quantum
computation. In this article we propose a new method for measuring the spin of
a single electron confined in a quantum dot (QD). Our strategy is based on
entangling (using unitary gates) the spin and orbital degrees of freedom. An
{\em orbital qubit}, defined by a second, empty QD, is used as an ancilla and
is prepared in a known initial state. Measuring the orbital qubit will reveal
the state of the (unknown) initial spin qubit, hence reducing the problem to
the easier task of single charge measurement. Since spin-charge conversion is
done with unit probability, single-shot measurement of an electronic spin can
be, in principle, achieved. We evaluate the robustness of our method against
various sources of error and discuss briefly possible implementations.Comment: RevTeX4, 4 pages, some figs; updated to the published versio
Hot-electron effect in spin dephasing in -type GaAs quantum wells
We perform a study of the effect of the high in-plane electric field on the
spin precession and spin dephasing due to the D'yakonov-Perel' mechanism in
-type GaAs (100) quantum wells by constructing and numerically solving the
kinetic Bloch equations. We self-consistently include all of the scattering
such as electron-phonon, electron-non-magnetic impurity as well as the
electron-electron Coulomb scattering in our theory and systematically
investigate how the spin precession and spin dephasing are affected by the high
electric field under various conditions. The hot-electron distribution
functions and the spin correlations are calculated rigorously in our theory. It
is found that the D'yakonov-Perel' term in the electric field provides a
non-vanishing effective magnetic field that alters the spin precession period.
Moreover, spin dephasing is markedly affected by the electric field. The
important contribution of the electron-electron scattering to the spin
dephasing is also discussed.Comment: 11 pages, 11 figures, accepted for publication in Phys. Rev.
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