16,026 research outputs found
Strain Effect in MgB2/Stainless Steel Superconducting Tape
The influence of mechanical strain on the critical current (Ic) is
investigated for MgB2/stainless steel (SUS316) superconducting tapes. The tapes
are fabricated by using 'powder in tube' method and deformation process without
any heat treatment. The tensile axial strain along tape length is successfully
induced to the sample by using a U-shape holder made of stainless steel
(SUS304). Two samples are examined at 4.2 K in 5 T (B is applied perpendicular
to the tape surface). While the initial Ic at zero external strain state (Ic0)
varies (30.4 and 33.3 A), normalized Ic (Ic/Ic0) vs. external strain relations
fall on the same curve. Linear increase of Ic is observed from zero external
strain state to 0.5% strain (107% of Ic0). Rapid and large degradation occurs
at the strain exceeding 0.4-0.5%. High durability against stress can be
expected for MgB2/stainless steel superconducting tapes.Comment: 3 pages including 2 figures, submitted to Physica
Competitive Pressure on China: Factor Rewards Migration
Our objective is to assess personal income under perfect competition, when factors are rewarded according to their productivities, and to contrast the ensuing distribution with the status quo.Competition will yield winners and losers, both in terms of factor claims and in terms of regions or provinces. Income differences will press people to migrate.To analyze this, we divide China into 30 input-output sectors and 27 provinces; we maximize domestic final demand, while preserving its proportions in each province, subject to material balances and factor constraints.The shadow prices to the constraints represent competitive commodity prices and factor rewards.Unskilled labor would stand to lose and, therefore, inequality would mount.The pressure on interprovincial migration would be enormous with 10 to 20% of the people on the road.The flipside is the great potential for improvement of the average standard of living.competition;income distribution;migration
Competitive pressures on income distribution in China
competition;income distribution
Oxidative coupling of methane in a mixed-conducting perovskite membrane reactor
Ionic-electronic mixed-conducting perovskite-type oxide La0.6Sr0.4Co0.8Fe0.2O3 was applied as a dense membrane for oxygen supply in a reactor for methane coupling. The oxygen permeation properties were studied in the pO2-range of 10Âż3Âż1 bar at 1073Âż1273 K, using helium as a sweeping gas at the permeate side of the membrane. The oxygen semi-permeability has a value close to 1 mmol mÂż2 sÂż1 at 1173 K with a corresponding activation energy of 130Âż140 kJ/mol. The oxygen flux is limited by a surface process at the permeate side of the membrane. It was found that the oxygen flux is only slightly enhanced if methane is admixed with helium. Methane is converted to ethane and ethene with selectivities up to 70%, albeit that conversions are low, typically 1Âż3% at 1073Âż1173 K. When oxygen was admixed with methane rather than supplied through the membrane, selectivities obtained were found to be in the range 30Âż35%. Segregation of strontium was found at both sides of the membrane, being seriously affected by the presence of an oxygen pressure gradient across it. The importance of a surface limited oxygen flux for application of perovskite membranes for methane coupling is emphasized
Conceptual Design of a New Large Superconducting Toroid for IAXO, the New International AXion Observatory
The International AXion Observatory (IAXO) will incorporate a new generation
detector for axions, a hypothetical particle, which was postulated to solve one
of the puzzles arising in the standard model of particle physics, namely the
strong CP problem. The new IAXO experiment is aiming at achieving a sensitivity
to the coupling between axions and photons of one order of magnitude beyond the
limits of the current state-of-the-art detector, represented by the CERN Axion
Solar Telescope (CAST). The IAXO detector relies on a high-magnetic field
distributed over a very large volume to convert solar axions into x-ray
photons. Utilizing the designs of the ATLAS barrel and end-cap toroids, a large
superconducting toroidal magnet is currently being designed at CERN to provide
the required magnetic field. The new toroid will be built up from eight, one
meter wide and 20 m long, racetrack coils. The toroid is sized about 4 m in
diameter and 22 m in length. It is designed to realize a peak magnetic field of
5.4 T with a stored energy of 500 MJ. The magnetic field optimization process
to arrive at maximum detector yield is described. In addition, force and stress
calculations are performed to select materials and determine their structure
and sizing. Conductor dimensionality, quench protection and the cryogenic
design are dealt with as well.Comment: 5 pages, 5 figures. To be published in IEEE Trans. Appl. Supercond.
23 (ASC 2012 conference special issue
The Superconducting Toroid for the New International AXion Observatory (IAXO)
IAXO, the new International AXion Observatory, will feature the most
ambitious detector for solar axions to date. Axions are hypothetical particles
which were postulated to solve one of the puzzles arising in the standard model
of particle physics, namely the strong CP (Charge conjugation and Parity)
problem. This detector aims at achieving a sensitivity to the coupling between
axions and photons of one order of magnitude beyond the limits of the current
detector, the CERN Axion Solar Telescope (CAST). The IAXO detector relies on a
high-magnetic field distributed over a very large volume to convert solar
axions to detectable X-ray photons. Inspired by the ATLAS barrel and end-cap
toroids, a large superconducting toroid is being designed. The toroid comprises
eight, one meter wide and twenty one meters long racetrack coils. The assembled
toroid is sized 5.2 m in diameter and 25 m in length and its mass is about 250
tons. The useful field in the bores is 2.5 T while the peak magnetic field in
the windings is 5.4 T. At the operational current of 12 kA the stored energy is
500 MJ. The racetrack type of coils are wound with a reinforced Aluminum
stabilized NbTi/Cu cable and are conduction cooled. The coils optimization is
shortly described as well as new concepts for cryostat, cold mass, supporting
structure and the sun tracking system. Materials selection and sizing,
conductor, thermal loads, the cryogenics system and the electrical system are
described. Lastly, quench simulations are reported to demonstrate the system's
safe quench protection scheme.Comment: To appear in IEEE Trans. Appl. Supercond. MT 23 issue. arXiv admin
note: substantial text overlap with arXiv:1308.2526, arXiv:1212.463
New Superconducting Toroidal Magnet System for IAXO, the International AXion Observatory
Axions are hypothetical particles that were postulated to solve one of the
puzzles arising in the standard model of particle physics, namely the strong CP
(Charge conjugation and Parity) problem. The new International AXion
Observatory (IAXO) will incorporate the most promising solar axions detector to
date, which is designed to enhance the sensitivity to the axion-photon coupling
by one order of magnitude beyond the limits of the current state-of-the-art
detector, the CERN Axion Solar Telescope (CAST). The IAXO detector relies on a
high-magnetic field distributed over a very large volume to convert solar
axions into X-ray photons. Inspired by the successful realization of the ATLAS
barrel and end-cap toroids, a very large superconducting toroid is currently
designed at CERN to provide the required magnetic field. This toroid will
comprise eight, one meter wide and twenty one meter long, racetrack coils. The
system is sized 5.2 m in diameter and 25 m in length. Its peak magnetic field
is 5.4 T with a stored energy of 500 MJ. The magnetic field optimization
process to arrive at maximum detector yield is described. In addition,
materials selection and their structure and sizing has been determined by force
and stress calculations. Thermal loads are estimated to size the necessary
cryogenic power and the concept of a forced flow supercritical helium based
cryogenic system is given. A quench simulation confirmed the quench protection
scheme.Comment: Accepted for publication in Adv. Cryo. Eng. (CEC/ICMC 2013 special
issue
Longitudinal propagation velocity of the normal zone in superconducting wires
The longitudinal propagation of the normal zone in superconducting wires was experimentally investigated in order to evaluate existing analytical expressions which attempt to describe the propagation velocity in a more or less simple manner. The availability of a reliable expression is important for application in computer codes that calculate quench evolutions in superconducting magnets. We measured the propagation velocity as function of transport current and magnetic field in five different insulated NbTi superconductors having a copper, a copper-nickel or a mixed matrix. The comparison to calculated velocities using five existing models showed that large quantitative and qualitative differences exist
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