63,336 research outputs found
Ionization effects due to solar flare on terrestrial ionosphere
Sudden frequency deviation ionospheric disturbances related to the flares of May 18 and 19, 1973 were observed from the NASA/MSFC high frequency Doppler sounder array system in Huntsville, Alabama. The results are compared with those observed at Table Mountain near Boulder, Colorado and at the University of Hawaii
Valley filter in strain engineered graphene
We propose a simple, yet highly efficient and robust device for producing
valley polarized current in graphene. The device comprises of two distinct
components; a region of uniform uniaxial strain, adjacent to an out-of-plane
magnetic barrier configuration formed by patterned ferromagnetic gates. We show
that when the amount of strain, magnetic field strength, and Fermi level are
properly tuned, the output current can be made to consist of only a single
valley contribution. Perfect valley filtering is achievable within
experimentally accessible parameters.Comment: 4 pages, 3 figures; minor corrections, updated Figs. 2 and 3, added
reference
Non-equilibrium spatial distribution of Rashba spin torque in ferromagnetic metal layer
We study the spatial distribution of spin torque induced by a strong Rashba
spin-orbit coupling (RSOC) in a ferromagnetic (FM) metal layer, using the
Keldysh non-equilibrium Green's function method. In the presence of the s-d
interaction between the non-equilibrium conduction electrons and the local
magnetic moments, the RSOC effect induces a torque on the moments, which we
term as the Rashba spin torque.
A correlation between the Rashba spin torque and the spatial spin current is
presented in this work, clearly mapping the spatial distribution of Rashba Spin
torque in a nano-sized ferromagnetic device. When local magnetism is turned on,
the out-of-plane (Sz) Spin Hall effect (SHE) is disrupted, but rather
unexpectedly an in-plane (Sy) SHE is detected. We also study the effect of
Rashba strength (\alpha_R) and splitting exchange (\Delta) on the
non-equilibrium Rashba spin torque averaged over the device. Rashba spin torque
allows an efficient transfer of spin momentum such that a typical switching
field of 20 mT can be attained with a low current density of less than 10^6
A/cm^2
Student Preferences for Lecturers' Personalities
The present study set out to examine students’ preferences for lecturers’ personality as a function of their classroom behaviour, core self-evaluations and self-rated character strengths. Various hypotheses were tested: first, students’ Big Five traits would significantly predict corresponding personality preferences for lecturers (the matching hypothesis); second, students’ core self-evaluation scores would significantly predict preferences for extraverted, agreeable and conscientious lecturers; and third, self-rated character strengths would also significantly predict extraverted, agreeable and conscientious lecturers. We also investigated difference in preferences among two ethnic groups (South East Asian/Chinese versus Caucasian/British). In all, 264 British students completed four questionnaires. Conscientiousness was the most desired trait in lecturers, followed by agreeableness, extraversion and openness; neuroticism was the least desired trait. Preference for agreeable lecturers was best predicted by all individual difference variables. Caucasian students had a stronger dislike for neurotic lecturers, while Asians had higher preferences for extraverted, open and agreeable lecturers. There was some evidence of the student–lecturer personality match. Limitations and further research options were discussed
Implementation of Design Changes Towards a More Reliable, Hands-off Magnetron Ion Source
As the main ion source for the accelerator complex, magnetron ion
sources have been used at Fermilab since the 1970s. At the offline test stand,
new R&D is carried out to develop and upgrade the present magnetron-type
sources of ions of up to 80 mA and 35 keV beam energy in the context of
the Proton Improvement Plan. The aim of this plan is to provide high-power
proton beams for the experiments at FNAL. In order to reduce the amount of
tuning and monitoring of these ion sources, a new electronic system consisting
of a current-regulated arc discharge modulator allow the ion source to run at a
constant arc current for improved beam output and operation. A solenoid-type
gas valve feeds gas into the source precisely and independently of
ambient temperature. This summary will cover several studies and design changes
that have been tested and will eventually be implemented on the operational
magnetron sources at Fermilab. Innovative results for this type of ion source
include cathode geometries, solenoid gas valves, current controlled arc pulser,
cesium boiler redesign, gas mixtures of hydrogen and nitrogen, and duty factor
reduction, with the aim to improve source lifetime, stability, and reducing the
amount of tuning needed. In this summary, I will highlight the advances made in
ion sources at Fermilab and will outline the directions of the continuing R&D
effort.Comment: 4 pp. arXiv admin note: substantial text overlap with
arXiv:1701.0175
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