173,560 research outputs found
Charge pumping in monolayer graphene driven by a series of time-periodic potentials
We applied the Floquet scattering-matrix formalism to studying the electronic
transport properties in a mesoscopic Dirac system. Using the method, we
investigate theoretically quantum pumping driven by a series of time-periodic
potentials in graphene monolayer both in the adiabatic and non-adiabatic
regimes. Our numerical results demonstrate that adding harmonic modulated
potentials can break the time reversal symmetry when no voltage bias is applied
to the graphene monolayer. Thus, when the system is pumped with proper dynamic
parameters, these scatterers can produce a nonzero dc pumped current. We also
find that the transmission is anisotropic as the incident angle is changed.Comment: 8 pages, 6 figure
The effect of supernova heating on cluster properties and constraints on galaxy formation models
Models of galaxy formation should be able to predict the properties of
clusters of galaxies, in particular their gas fractions, metallicities, X-ray
luminosity-temperature relation, temperature function and mass-deposition-rate
function. Fitting these properties places important constaints on galaxy
formation on all scales. By following gas processes in detail, our
semi-analytic model (based on that of Nulsen & Fabian 1997) is the only such
model able to predict all of the above cluster properties. We use realistic gas
fractions and gas density profiles, and as required by observations we break
the self-similarity of cluster structure by including supernova heating of
intracluster gas, the amount of which is indicated by the observed
metallicities. We also highlight the importance of the mass-deposition-rate
function as an independent and very sensitive probe of cluster structure.Comment: 5 pages, 4 figures, accepted for publication in MNRAS as a lette
Analysis of a single-fold deployable truss beam preloaded by extension of selected face diagonal members
A technique for preloading a deployable box truss beam by extension of one face diagonal per bay was studied to determine if it would result in uniform loading of truss joints without causing excessive truss deformations. Results indicate that it is possible to accomplish uniform loading in the beam region way from beam boundaries, whereas in the regions near boundaries the member loading becomes non-uniform with magnitudes greater than those in the uniform load region. Also, the type of deformation which results in the beam depends on the pattern of preloaded members
Ionospheric sounder as a means of monitoring ground moisture
Ionospheric sounding for monitoring effective reflection coefficient of ground moistur
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