2,878 research outputs found
MgB2 tunnel junctions and 19 K low-noise dc superconducting quantum interference devices
Point contact junctions made from two pieces of MgB2 can be adjusted to
exhibit either superconductor-insulator-superconductor (SIS) or
superconductor-normal metal-superconductor (SNS) current-voltage
characteristics. The SIS characteristics are in good agreement with the
standard tunneling model for s-wave superconductors, and yield an energy gap of
(2.02 +/- 0.08) meV. The SNS characteristics are in good agreement with the
predictions of the resistively-shunted junction model. DC Superconducting
QUantum Interference Devices made from two SNS junctions yield magnetic field
noise as low as 35 fT/Hz^{1/2} at 19 K.Comment: 4 pages, 4 figure
Weak turbulence theory of the non-linear evolution of the ion ring distribution
The nonlinear evolution of an ion ring instability in a low-beta
magnetospheric plasma is considered. The evolution of the two-dimensional ring
distribution is essentially quasilinear. Ignoring nonlinear processes the
time-scale for the quasilinear evolution is the same as for the linear
instability 1/t_ql gamma_l. However, when nonlinear processes become important,
a new time scale becomes relevant to the wave saturation mechanism. Induced
nonlinear scattering of the lower-hybrid waves by plasma electrons is the
dominant nonlinearity relevant for plasmas in the inner magnetosphere and
typically occurs on the timescale 1/t_ql w(M/m)W/nT, where W is the wave energy
density, nT is the thermal energy density of the background plasma, and M/m is
the ion to electron mass ratio, which has the consequence that the wave
amplitude saturates at a low level, and the timescale for quasilinear
relaxation is extended by orders of magnitude
The Effect of Large Amplitude Fluctuations in the Ginzburg-Landau Phase Transition
The lattice Ginzburg-Landau model in d=3 and d=2 is simulated, for different
values of the coherence length in units of the lattice spacing , using
a Monte Carlo method. The energy, specific heat, vortex density , helicity
modulus and mean square amplitude are measured to map the phase
diagram on the plane . When amplitude fluctuations, controlled by the
parameter , become large () a proliferation of vortex
excitations occurs changing the phase transition from continuous to first
order.Comment: 4 pages, 5 postscript (eps) figure
Role of twin boundaries on the vortex dynamics in YBaCuO
By means of a novel technique of rotating the applied current we have
directly measured the influence of twin boundaries on the vortex motion in a
YBaCuO single crystal. The results indicate that the effect of twin
planes on the vortex dynamics starts to develop below a certain temperature,
being responsible for an anisotropic viscosity in the vortex liquid state and a
guided motion in the solid state.Comment: 4 pages, 4 figure
Data work: how energy advisors and clients make IoT data accountable
We present fieldwork findings from the deployment of an interactive sensing system that supports the work of energy advisors who give face-to-face advice to low-income households in the UK. We focus on how the system and the data it produced are articulated in the interactions between professional energy advisors and their clients, and how they collaboratively anticipate, rehearse, and perform data work. In addition to documenting how the system was appropriated in advisory work, we elaborate the ‘overhead cost’ of building collaborative action into connected devices and sensing systems, and the commensurate need to support discrete workflows and accountability systems to enable the methodical incorporation of the IoT into collaborative action. We contribute an elaboration of the social, collaborative methods of data work relevant to those who seek to design and study collaborative IoT systems
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