156 research outputs found
Extreme vortex pinning in the non-centrosymmetric superconductor CePtSi
We report on the vortex dynamics of a single crystal of the
non-centrosymmetric heavy-fermion superconductor CePtSi. Decays of the
remnant magnetization display a clean logarithmic time dependence with rates
that follow the temperature dependence expected from the Kim-Anderson theory.
The creep rates are lower than observed in any other centrosymmetric
superconductor and are not caused by high critical currents. On the contrary,
the critical current in CePtSi is considerably lower than in other
superconductors with strong vortex pinning indicating that an alternative
impediment on the flux line motion might be at work in this superconductor.Comment: 4 pages, 5 figure
Vortex avalanches in the non-centrosymmetric superconductor Li2Pt3B
We investigated the vortex dynamics in the non-centrosymmetric superconductor
Li_2Pt_3B in the temperature range 0.1 K - 2.8 K. Two different logarithmic
creep regimes in the decay of the remanent magnetization from the Bean critical
state have been observed. In the first regime, the creep rate is
extraordinarily small, indicating the existence of a new, very effective
pinning mechanism. At a certain time a vortex avalanche occurs that increases
the logarithmic creep rate by a factor of about 5 to 10 depending on the
temperature. This may indicate that certain barriers against flux motion are
present and they can be opened under increased pressure exerted by the
vortices. A possible mechanism based on the barrier effect of twin boundaries
is briefly discussed
Connected Bike-smart IoT-based Cycling Training Solution
The Connected Bike project combines several technologies, both hardware and software,
to provide cycling enthusiasts with a modern alternative solution for training. Therefore, a trainer
can monitor online through a Web Application some of the important parameters for training, more
specifically the speed, cadence and power generated by the cyclist. Also, the trainer can see at every
moment where the rider is with the aid of a GPS module. The system is built out of both hardware and
software components. The hardware is in charge of collecting, scaling, converting and sending data
from sensors. On the software side, there is the server, which consists of the Back-End and the MQTT
(Message Queues Telemetry Transport) Broker, as well as the Front-End of the Web Application that
displays and manages data as well as collaboration between cyclists and trainers. Finally, there is the
Android Application that acts like a remote command for the hardware module on the bike, giving
the rider control over how and when the ride is monitored
Possible re-entrant superconductivity in EuFe2As2 under pressure
We studied the temperature-pressure phase diagram of EuFe2As2 by measurements
of the electrical resistivity. The antiferromagnetic spin-density-wave
transition at T_0 associated with the FeAs-layers is continuously suppressed
with increasing pressure, while the antiferromagnetic ordering temperature of
the Eu 2+ moments seems to be nearly pressure independent up to 2.6 GPa. Above
2 GPa a sharp drop of the resistivity, \rho(T), indicates the onset of
superconductivity at T_c \approx 29.5 K. Surprisingly, on further reducing the
temperature \rho(T) is increasing again and exhibiting a maximum caused by the
ordering of the Eu 2+ moments, a behavior which is reminiscent of re-entrant
superconductivity as it is observed in the ternary Chevrel phases or in the
rare-earth nickel borocarbides
Coupled SDW and Superconducting Order in FFLO State of CeCoIn
The mechanism of incommensurate (IC) spin-density-wave (SDW) order observed
in the Flude-Ferrell-Larkin-Ovchinnikov (FFLO) phase of CeCoIn is discussed
on the basis of new mode-coupling scheme among IC-SDW order, two
superconducting orders of FFLO with B () symmetry
and -pairing of odd-parity. Unlike the mode-coupling schemes proposed by
Kenzelmann et al, Sciencexpress, 21 August (2008), that proposed in the present
Letter can offer a simple explanation for why the IC-SDW order is observed only
in FFLO phase and the IC wave vector is rather robust against the magnetic
field.Comment: 3pages, 1 figure, accepted for publication in J. Phys. Soc. Jpn.,
Vol.77 (2008), No.1
A Portable Implementation on Industrial Devices of a Predictive Controller Using Graphical Programming
This paper presents an approach for developing an Extended Prediction Self-Adaptive Controller employing graphical programming of industrial standard devices, for controlling fast processes. For comparison purposes, the algorithm has been implemented on three different FPGA (Field Programmable Gate Arrays) chips. The paper presents research aspects regarding graphical programming controller design, showing that a single advanced control application can run on different targets without requiring significant program modifications. Based on the time needed for processing the control signal and on the application, one can efficiently and easily select the most appropriate device. To exemplify the procedure, a conclusive case study is presented
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