1,974,926 research outputs found
The March model applied to boron cages
No full textAbstract: The so-called March model of fullerene, in which a self-consistent spherical distribution of pi electrons is combined with the proper nuclear-nuclear potential energy for the correct structure, is here extended to boron cages. The Thomas-Fermi approximation of the initial studies is here replaced by Hartree-Fock calculations. Explicit results for B-2k and B-2k+1(+), with k ranging from 15 to 27, are discussed and compared with calculations on similar clusters found in the literature. (C) 2001 Elsevier Science B.V. All rights reserved
The application of high temperature superconducting materials to power switches
No full textSuperconducting switches may nd application in superconducting magnet systems that
require energy extraction. Such superconducting switches could be bypass-switches that
are operated in conjunction with a parallel resistor or dump-switches where all of the
energy is dissipated in the switch itself. Bypass-switches are more suited to higher energy
circuits as a portion of the energy can be dissipated in the external dump resistor. Dump-switches
require less material and triggering energy as a lower switch resistance is needed
to achieve the required total dump resistance.Both superconducting bypass-switches and superconducting dump-switches can be thermally
activated. Switching times that are comparable to those obtained with mechanical
bypass-switch systems can be achieved using a co-wound heater that is powered by a capacitor
discharge. Switches that have fast thermal diffusion times through the insulation
can be modelled as a lumped system whereas those with slow thermal diffusion times were
modelled with the full heat diffusion equation.Superconducting switches can be formed of either high temperature superconductors
(HTS) or low temperature superconductors (LTS). Switches based on HTS materials allow
operation at higher temperatures where the cost of cooling is less. Extracting the magnet
energy and depositing the heater energy at higher temperatures will also reduce the load on
the overall cryogenic system during switching and energy extraction. For magnet circuits
that are based on high temperature superconductors the switch must also be formed of
HTS material. Due to the approximately T3 dependence of specific heat capacity, switches
that operate at higher temperatures have slower heat diffusion times and require higher
triggering energies than those operating at low temperature. HTS based dump-switches
and HTS based bypass-switches were tested in liquid nitrogen to show that the required
switching time could be achieved at these high temperatures.The design and optimisation of superconducting switches that were formed of various
superconducting materials were performed for example magnet circuits to provide reference
designs of switches. These example circuits were based on selected Large Hadron Collider
600 A circuits that had a stored energy of 5.5 kJ. Superconducting switches may also nd
application in magnet circuits with higher transport currents and higher energies. The
scaling and suitability of the reference designs to higher energy circuits was also described
March to the Brazos - 125
No full textCorps of Cadets: March to the Brazosphotograph date: UnknownThe Corps made its annual March to the Brazos Saturday. The March is held each year to raise money for the March of Dimes. The march is about 14 miles long round trip. Once the cadets reach the river they spend the afternoon competing in games and activities
March to the Brazos - 123
No full textCorps of Cadets: March to the Brazosphotograph date: Unknown(newspaper caption) Outfit tug-of-wars and taking upperclassmen to the muddy 'grode hole' are some of the events held when the seven-mile jaunt to the Brazos River ends. A sophomore becomes a victim at the 'grode hole.' Underclassmen use it to get revenge on upperclassmen by catching them and dumping them in the hole, face-first. The march is an annual fundraiser for the March of Dimer
March to the Brazos - 114
No full textCorps of Cadets: March to the Brazosphotograph date: ca. 1989-1990A junior member of the A-2 outfit in the Corps of Cadets watches as fellow outfit members perform unusual push-ups along HW 60 during March to the Brazos
March to the Brazos - 115
No full textCorps of Cadets: March to the Brazosphotograph date: UnknownWing Commander and Senior in Squadron 8 talks to freshmen from Squadron 15 about "March to the Brazos" his freshman year. The Corps walks seven miles to the Brazos River each year to benefit "The March of Dimes.
Exposición de cajas, cofres y arquetas a través de la historia : Fundación Bartolomé March Servera : [Palma de Mallorca, mayo de 1979]
No full textCatàleg de l'exposició de caixes i arquetes de tot el món a través de la història, organitzada per la Fundació Bartolomé March Servera a l'any 1979. Aquesta exposició reunia materials de la col·lecció Bartolomé March amb aportacions d'altres col·leccions espanyoles i estrangeres. Conté làmines.Catalogue of the exhibition of boxes and chests from all over the world through history, organized by the Bartolomé March Servera Foundation in 1979. This exhibition brought together materials from the Bartolomé March collection with contributions from other Spanish and foreign collections. With prints.Catálogo de la exposición de cajas y arquetas de todo el mundo a través de la historia, organizada por la Fundación Bartolomé March Servera en 1979. Esta exposición reunía materiales de la colección Bartolomé March con aportaciones de otros co lecciones españolas y extranjeras. Contiene láminas
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