13,453 research outputs found
Temperature dependence of the spin and orbital magnetization density in around the spin-orbital compensation point
Non-resonant ferromagnetic x-ray diffraction has been used to separate the
spin and orbital contribution to the magnetization density of the proposed
zero-moment ferromagnet . The alignment of the
spin and orbital moments relative to the net magnetization shows a sign
reversal at 84K, the compensation temperature. Below this temperature the
orbital moment is larger than the spin moment, and vice versa above it. This
result implies that the compensation mechanism is driven by the different
temperature dependencies of the spin and orbital moments. Specific heat
data indicate that the system remains ferromagnetically ordered throughout
The Application of MIMO to Non-Orthogonal Multiple Access
This paper considers the application of multiple-input multiple-output (MIMO)
techniques to non-orthogonal multiple access (NOMA) systems. A new design of
precoding and detection matrices for MIMO-NOMA is proposed and its performance
is analyzed for the case with a fixed set of power allocation coefficients. To
further improve the performance gap between MIMO-NOMA and conventional
orthogonal multiple access schemes, user pairing is applied to NOMA and its
impact on the system performance is characterized. More sophisticated choices
of power allocation coefficients are also proposed to meet various quality of
service requirements. Finally computer simulation results are provided to
facilitate the performance evaluation of MIMO-NOMA and also demonstrate the
accuracy of the developed analytical results
Anisotropic Diamagnetic Response in Type-II Superconductors with Gap and Fermi-Surface Anisotropies
Effects of anisotropic gap structures on a diamagnetic response are
investigated in order to demonstrate that the field-angle-resolved
magnetization () measurement can be used as a spectroscopic method
to detect gap structures. Our microscopic calculation based on the
quasiclassical Eilenberger formalism reveals that in a
superconductor with four-fold gap displays a four-fold oscillation reflecting
the gap and Fermi surface anisotropies, and the sign of this oscillation
changes at a field between and . As a prototype of
unconventional superconductors, magnetization data for borocarbides are also
discussed.Comment: 5 pages, 4 figure
Programmable physiological infusion
A programmable physiological infusion device and method are provided wherein a program source, such as a paper tape, is used to actuate an infusion pump in accordance with a desired program. The system is particularly applicable for dispensing calcium in a variety of waveforms
Programmed physiological infusion system
Infusion system delivers incremental volumes from a reservoir with a piston pump at a rate that varies in time and follows the envelope of a preprogrammed curve
Chemisorption and reactions on clusters of nickel atoms
The nucleation and growth of metallic clusters on a substantially amorphous substrate are discussed with emphasis on the geometrical and electronic structure of the clusters. Several clusters of different symmetry containing five to nine nickel atoms were studied. It was found that the energy range of primary d-like states is not significantly different from the width of the d-band states in nickel metal, as long as the interatomic distance is comparable to that in the bulk metal. The approach of one or more molecules to the cluster is examined using at the hydrogenation of acetylene and the dehydrogenation of ethylene as examples
Magnetic-field effects on the charge-spin stripe order in La-214 high-Tc cuprates
Magnetic-field effects on the charge-spin stripe order in La-214 high-Tc
cuprates have been investigated from measurements of the in-plane
electrical-resistivity, Rho_ab_. In La_2-x_Ba_x_CuO_4_ with x=0.10 and
La_2-x_Sr_x_CuO_4_ with x=0.115 where the incommensurate charge peaks are weak
and unobservable in zero field in elastic neutron-scattering measurements,
respectively, the normal-state value of Rho_ab_ at low temperatures markedly
increases with increasing field up to 27 T. For La_2-x_Ba_x_CuO_4_ with x=0.11
and Zn-substituted La_2-x_Sr_x_Cu_1-y_Zn_y_O_4_ with x=0.115 and y=0.02 where
the charge stripe order is fairly stabilized in zero field, on the other hand,
the increase in Rho_ab_ with increasing field is negligibly small. In
conclusion, when the charge-spin stripe order is not fully stable in zero
field, magnetic field operates to stabilize the charge-spin stripe order. The
value of Rho_ab_ increases with increasing field depending on the stability of
the charge stripe order.Comment: 4 pages, 2 figures, Proceedings of Yamada Conference LX on Research
in High Magnetic Fields (RHMF2006) (Satellite of ICM2006
Approach to a Stable Field Emission Electron Source
Field emission occurs at the sharp apex of a metal needle, so that it can be considered as providing a point electron source, which is a desirable feature for a fine focused electron beam. The disadvantage is its low stability. It is shown that the current fluctuations occur mainly due to the interaction with the residual gas in the vacuum; thus reduction of the interaction with the residual gas is essential for a stable field electron source. The stringency of the vacuum requirement has prevented wide application of the field emission electron source. New materials which have low work functions and high melting points are examined in the view of a stable field electron emitter, and it is shown that carbides of transition metals have potential as a stable field emitter. Very stable field emission has been reported for TiC single crystals. Operation in the thermal-field emission mode is examined and it is shown that ZrO/W(100) emitter gives stable emission, whose fluctuation is less than 0.23% in the frequency interval 1 to 5000 Hz. The only disadvantage of the ZrO/W thermal field emitter is its rather high level of instability at very low frequencies. This paper reviews the development of field electron emission as it is applied to electron sources
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